|Title of Invention||
A METHOD FOR IMPROVING THE WETTABILITY OF AN OPTHALMIC DEVICE
|Abstract||A method comprising the steps of (a) mixing reactive components comprising 15-25 wt% of high molecular weight hydrophilic polymer having molecular wt between 100,000 to 150,000 Daltons and an effective amount of a compatibilizing component and (b) curing the product of step (a) at or above a minimum gel time, to form a ophthalmic lens wherein the said lens has an advancing dynamic contact angle of 80° or less.|
RELATED PATENT APPLICATIONS
This patent application claims priority of a provisional application, U.S.
Ser. No. 60/318,536 which was filed on September 10,2001.
FIELD OF THE INVENTION
This invention relates to silicone hydrogels that contain internal wetting
agents, as well as methods for their production and use.
BACKGROUND OF THE INVENTION
Contact lenses have been used commercially to improve vision since
at least the 1950s. The first contact lenses were made of hard materials and
as such were somewhat uncomfortable to users. Modem lenses have been
developed that are made of softer materials, typically hydrogels and
particularly silicone hydrogels. Silicone hydrogels are water-swollen polymer
networks that have high oxygen permeability and surfaces that are more
hydrophobic than hydrophilic. These lenses provide a good level of comfort to
many lens wearers, but there are some users who experience discomfort and
excessive ocular deposits leading to reduced visual acuity when using these
lenses. This discomfort and deposits has been attributed to the hydrophobic
character of the surfaces of lenses and the interaction of those surfaces with
the protein, lipids and mucin and the hydrophilic surface of the eye.
Others have tried to alleviate this problem by coating the surface of
silicone hydrogel contact lenses with hydrophilic coatings. For example, it has
been disclosed that silicone hydrogel lenses can be made more compatible
with ocular surfaces by applying plasma coatings to the lens surface.
However, uncoated silicone hydrogel lenses having low incidences of surface
deposits have not been disclosed.
Incorporating internal hydrophilic agents (or wetting agents) into a
macromer containing reaction mixture has been disclosed. However, not all
silicone containing macromers display compatibility with hydrophilic polymers.
Modifying the surface of a polymeric article by adding polymerizable
surfactants to a monomer mix used to form the article has also been
disclosed. However, lasting in vivo improvements in wettability and
reductions in surface deposits are not likely.
Polyvinylpyrrolidone (PV?) or poly-2-ethyl-2-oxazoline have been
added to a hydrogel composition to form an interpenetrating network which
shows a low degree of surface friction, a low dehydration rate and a high
degree of biodeposit resistance. However, the hydrogel formulations
disclosed are conventional hydrogels and there is no disclosure on how to
incorporate hydrophobic components, such as siloxane monomers, without
losing monomer compatibility.
While it may be possible to incorporate high molecular weight polymers
as internal wetting agents into silicone hydrogel lenses, such polymers are
difficult to solubilize in reaction mixtures which contain silicones. In order to
solubilize these wetting agents, silicone macromers or other prepolymers
must be used. These silicone macromers or prepolymers must be prepared
in a separate step and then subsequently mixed with the remaining
ingredients of the silicone hydrogel formulation. This additional step (or steps)
increases the cost and the time it takes to produce these lenses.
Therefore it would be advantageous to find a lens formulation that does
not require the use of surface treatment to provide on eye wettability and
resistance to surface depositions.
SUMMARY OF THE INVENTION
The present invention relates to a wettable silicone hydrogel
comprising the reaction product of at least one siloxane containing macromer;
at least one high molecular weight hydrophilic polymer; and at least one
The present invention further relates to a ethod comprising the steps of
(a) mixing reactive components comprising at least one high molecular weight
hydrophilic polymer, at least one siloxane containing macromer and an
effective amount of at least one compatibilizing component and (b) curing the
product of step (a) to form a biomedical device.
The present invention further comprises a method comprising the steps of (a)
mixing reactive components comprising a high molecular weight hydrophilic
polymer and an effective amount of a compatibilizing component and (b)
curing the product of step (a) at or above a minimum gel time, to form a
wettable biomedical device.
The present invention yet further relates to an ophthalmic lens
comprising a silicone hydrogel which has, without surface treatment, a tear
film break up time of at least about 7 seconds
The present invention still further relates to a silicone hydrogel contact
lens comprising at least one oxygen permeable component, at least one
compatibilizing component and an amount of high molecular weight
hydrophilic polymer sufficient to provide said device, without a surface
treatment, with tear film break up time after about one day of wear of at least
about 7 seconds.
A device comprising a silicone hydrogel contact lens which is substantially
free from surface deposition without surface modification.
DETAILED DESCRIPTION OF THE INVENTION
A biomedical device formed from a reaction mixture comprising,
consisting essentially of, or consisting of a silicone containing macromer, at
least one high molecular weight hydrophilic polymer and a compatibilizing
amount of a compatibilizing component.
It has been surprisingly found that biomedical devices, and particularly
ophthalmic devices having exceptional in vivo or clinical wettability, without
surface modification may be made by including an effective amount of a high
molecular weight hydrophilic polymer and a compatibilizing amount of a
compatibilizing component in a silicone hydrogel formulation. By exceptional
wettability we mean a decrease in advancing dynamic contact angle of at
least about 10% and preferably at least about 20% in some embodiments at
least about 50% as compared to a similar formulation without any hydrophilic
polymer. Prior to the present invention ophthalmic devices formed from
silicone hydrogels either had to be surface modified to provide clinical
wettability or be formed from at least one silicone containing macromer having
As used herein, a "biomedical device" is any article that is designed to
be used while either in or on mammalian tissues or fluid and preferably on or
in human tissues or fluid. Examples of these devices include but are not
limited to catheters, implants, stents, and ophthalmic devices such as
intraocular lenses and contact lenses. The preferred biomedical devices are
ophthalmic devices, particularly contact lenses, most particularly contact
lenses made from silicone hydrogels.
As used herein, the terms "lens" and "opthalmic device" refer to
devices that reside in or on the eye. These devices can provide optical
correction, wound care, drug delivery, diagnostic functionality or cosmetic
enhancement or effect or a combination of these properties. The term lens
includes but is not limited to soft contact Senses, hard contact lenses,
intraocular lenses, overlay lenses, ocular inserts, and optical inserts.
As used herein the term "monomer" is a compound containing at least
one polymerizable group and an average molecular weight of about less than
2000 Daltons, as measure via gel permeation chromatography refractive
index detection.. Thus, monomers, include dimers and in some cases
oligomers, including oligomers made from more than one monomeric unit.
As used herein, the phrase "without a surface treatment" means that
the exterior surfaces of the devices of the present invention are not separately
treated to improve the wettability of the device. Treatments which may be
foregone because of the present invention include, plasma treatments,
grafting, coating and the like. However, coatings which provide properties
other than improved wettability, such as, but not limited to antimicrobial
coatings may be applied to devices of the present invention.
Various molecular weight ranges are disclosed herein. For compounds
having discrete molecular structures, the molecular weights reported herein
are calculated based upon the molecular formula and reported in gm/mol. For
polymers molecular weights (number average) are measured via gel
permeation chromatography refractive index detection and reported in Daltons
or are measured via kinematic viscosity measurements, as described in
Encyclopedia of Polymer Science and Engineering, N-Vinyl Amide Polymers,
Second edition, Vol 17, pgs. 198-257, John Wiley & Sons Inc. and reported in
High Molecular Weight Hvdrophilic Polymer
As used herein, "high molecular weight hydrophilic polymer" refers to
substances having a weight average molecular weight of no less than about
100,000 Daltons, wherein said substances upon incorporation to silicone
hydrogel formulations, improve the wettability of the cured silicone hydrogels.
The preferred weight average molecular weight of these high molecular
weight hydrophilic polymers is greater than about 150,000 Daltons; more
preferably between about 150,000 to about 2,000,000 Daltons, more
preferably still between about 300,000 to about 1,800,000 Daltons, most
preferably about 500,000 to about 1,500,000 Daltons (all weight average
Alternatively, the molecular weight of hydrophilic polymers of the
invention can be also expressed by the K-value, based on kinematic viscosity
measurements, as described in Encyclopedia of Polymer Science and
Engineering, N-Vinyl Amide Polymers, Second edition, Vol 17, pgs. 198-257,
John Wiley & Sons Inc. When expressed in this manner, hydrophilic
monomers having K-values of greater than about 46 and preferably between
about 46 and about 150. The high molecular weight hydrophilic polymers are
present in the formulations of these devices in an amount sufficient to provide
contact lenses, which without surface modification remain substantially free
from surface depositions during use. Typical use periods include at least
about 8 hours, and preferably worn several days in a row, and more
preferably for 24 hours or more without removal. Substantially free from
surface deposition means th at, when viewed with a slit lamp, at least about
80% and preferably at least about 90%, and more preferably about 100% of
the lenses worn in the patient population display depositions rated as none or
slight, over the wear period.
Suitable amounts of high molecular weight hydrophilic polymer include
from about 1 to about 15 weight percent, more preferably about 3 to about 15
percent, most preferably about 5 to about 12 percent, all based upon the total
weight of all reactive components.
Examples of high molecular weight hydrophilic polymers include but
are not limited to polyamides, polylactones, polyimides, polylactams and
functionalized polyamides, polylactones, polyimides, polylactams, such as
DMA functionalized by copolymerizing DMA with a lesser molar amount of a
hydroxyl-functional monomer such as HEMA, and then reacting the hydroxyl
groups of the resulting copolymer with materials containing radical
polymerizable groups, such as isocyanatoethylmethacrylate or methacryloyl
chloride. Hydrophilic prepolymers made from DMA or N-vinyl pyrrolidone with
glycidyl methacrylate may also be used. The glycidyl methacrylate ring can
be opened to give a diol which may be used in conjunction with other
hydrophilic prepolymer in a mixed system to increase the compatibility of the
high molecular weight hydrophilic polymer, hydroxyl-functionalized silicone
containing monomer and any other groups which impart compatibility. The
preferred high molecular weight hydrophilic polymers are those that contain a
cyclic moiety in their backbone, more preferably, a cyclic amide or cyclic
imide. High molecular weight hydrophilic polymers include but are not limited
to poly-N-vinyl pyrrolidone, poly-N-vinyl-2- piperidone, poly-N-vinyl-2-
caprolactam, poly-N-vinyl-3-methyi-2- caprolactam, poly-N-vinyl-3-methyl-2-
piperidone, poly-N-viny!-4-methyl-2- piperidone, poly-N-vinyl-4-methyl-2-
caprolactam, poly-N-vinyl-3-ethyl-2- pyrrolidone, and poly-N-vinyl-4,5-
dimethyl-2-pyrrolidone, polyvinylimidazole, poly-N-N-dimethylacrylamide,
polyvinyl alcohol, polyacrylic acid, polyethylene oxide, poly 2 ethyl oxazoline,
heparin polysaccharides, polysaccharides, mixtures and copolymers
(including block or random, branched, multichain, comb-shaped or star
shaped) thereof where poly-N-vinylpyrrolidone (PVP) is particularly preferred.
Copolymers might also be used such as graft copolymers of PVP.
The high molecular weight hydrophilic polymers provide improved
wettability, and particularly improved in vivo wettability to the medical devices
of the present invention. Without being bound by any theory, it is believed
that the high molecular weight hydrophilic polymers are hydrogen bond
receivers which in aqueous environments, hydrogen bond to water, thus
becoming effectively more hydrophilic. The absence of water facilitates the
incorporation of the hydrophilic polymer in the reaction mixture. Aside from
the specifically named high molecular weight hydrophilic polymers, it is
expected that any high molecular weight polymer will be useful in this
invention provided that when said polymer is added to a silicone hydrogel
formulation, the hydrophilic polymer (a) does not substantially phase separate
from the reaction mixture and (b) imparts wettability to the resulting cured
polymer. In some embodiments it is preferred that the high molecular weight
hydrophilic polymer be soluble in the diluent at processing temperatures.
Manufacturing processes which use water or water soluble diluents may be
preferred due to their simplicity and reduced cost. In these embodiments high
molecular weight hydrophilic polymers which are water soluble at processing
temperatures are preferred.
As used herein a "compatibilizing component" is a compound having a
number average molecular weight of about less than 5000 Daltons, and
preferably less than about 3000 Daltons, and containing at least one
polymerizable group, which is capable of solubilizing the selected reactive
components. Without a compatibilizing component the high molecular weight
hydrophilic polymer and oxygen permeable components are insufficiently
miscible, and cannot, with reasonable processing conditions, form an optically
transparent ophthalmic device. The compatibilizing component of the present
invention solubilizes the oxygen permeable components) and high molecular
weight hydrophilic polymer via hydrogen bonding, dispersive forces,
combinations thereof and the like. Thus any functionality which reacts in any
of these ways with the hydrophilic polymer may be used as a compatibilizing
component. Macromers (number average molecular weights of between
about 5000 and about 15,000 Daltons) may also be used so long as they
have the compatibilizing functionality described herein. If a compatibilizing
macromer is used it may still be necessary to add an additional
compatibilizing component to get the desired level of wettability in,the
resulting ophthalmic device.
One suitable class of compatibilizing components of the present
invention comprise at least one active hydrogen and at least one siloxane
group. An active hydrogen has the ability to hydrogen bond with the
hydrophilic polymer and any hydrophilic monomers present. Hydroxyl groups
readily participate in hydrogen bonding and are therefore a preferred source
of active hydrogens. Thus, in one embodiment, the compatibilizing
components of the present invention beneficially comprise at least one
hydroxyl group and at least one "-Si-O-Si-"group. It is preferred that silicone
and its attached oxygen account for more than about 10 weight percent of
said compatibilizing component, more preferably more than about 20 weight
The ratio of Si to OH in the compatibilizing component is also important
to providing a compatibilzing component which will provide the desired degree
of compatibilization. If the ratio of hydrophobic portion to OH is too high, the
compatibilizing component may be poor at compatibilizing the hydrophilic
polymer, resulting in incompatible reaction mixtures. Accordingly, in some
embodiments, the Si to OH ratio is less than about 15:1, and preferably
between about 1:1 to about 10:1. In some embodiments primary alcohols
have provided improved compatibility compared to secondary alcohols.
Those of skill in the art will appreciate that the amount and selection of
compatibilizing component will depend on how much hydrophilic polymer is
needed to achieve the desired wettability and the degree to which the silicone
containing monomer is incompatible with the hydrophilic polymer.
Examples of compatibilizing components include monomers of
Formulae I and II
n is an integer between 3 and 35, and preferably between 4 and 25;
R1 is hydrogen, C1-6alkyl,;
R2,R3, and R4, are independently, C1-6alkyl, triC1-6alkylsiloxy, phenyl, naphthyl,
substituted C1-6allkyl, substituted phenyl, or substituted naphthyl
where the alkyl substitutents are selected from one or more members
of the group consisting of C1-6alkoxycarbonyl, C1-6alkyI, C1-6alkoxy,
amide, halogen, hydroxyl, carboxyl, C1-6alkylcarbonyl and formyl, and
where the aromatic substitutents are selected from one or more
members of the group consisting of C1-6alkoxycarbonyl, C1-6alkyl,
C1-6alkoxy, amide, halogen, hydroxyl, carboxyl, C1-6alkylcarbonyl and
R5 is hydroxyl, an alkyl group containing one or more hydroxyl groups, or
(CH2(CR9R10)yO)x)-R11 wherein y is 1 to 5, preferably 1 to 3, x is an integer of
1 to 100, preferably 2 to 90 and more preferably 10 to 25; R9 - R11 are
independently selected from H, alkyl having up to 10 carbon atoms and alkyls
having up to 10 carbon atoms substituted with at least one polar functional
R6 is a divalent group comprising up to 20 carbon atoms;
R7 is a monovalent group that can undergo free radical and/or cationic
polymerization comprising up to 20 carbon atoms; and
R8 is a divalent or trivalent group comprising up to 20 carbon atoms.
Reaction mixtures of the present invention may include more than one
For monofunctional compatibilizing components the preferred R1 is
hydrogen, and the preferred R2,R3, and R4, are C1-6allkyl and triC1-6alkylsiloxy,
most preferred methyl and trimethylsiloxy. For multifunctional (difunctional or
higher) R1-R4 independently comprise ethylenically unsaturated polymerizable
groups and more preferably comprise an acrylate, a styryl, a C1-6alkylacrylate,
acrylamide, C1-6alkylacrylamide, N-vinyllactam, N-vinylamide,, C2-12alkenyl,
C2-12alkenylphenyl, C2-12alkenylnaphthyl, or C2-6alkenylphenyl C1-6 alkyl.
The preferred R5 is hydroxyl, -CH2OH or CH2CHOHCH2OH, with
hydroxyl being most preferred..
The preferred R6 is a divalent C1-6allkyl, C1-6alkyloxy,
C1-6alkyloxyC1-6alkyl, phenylene, naphthalene, C1-12cycloalkyl,
C1-6alkoxycarbonyl, amide, carboxy, C1-6alkylcarbonyl, carbonyl, C1-6alkoxy,
substituted C1-6alkyl, substituted C1-6alkyloxy, substituted C1-6alkyloxyC1-6alkyl,
substituted phenylene, substituted naphthalene, substituted C1-12cycloalkyl,
where the substituents are selected from one or more members of the group
consisting of C1-6alkoxycarbonyl, C1-6allkyl, C1-6alkoxy, amide, halogen,
hydroxyl, carboxyl, C1-6alkylcarbonyl and formyl. The particularly preferred R6
is a divalent methyl (methylene).
The preferred R7 comprises a free radical reactive group, such as an
acrylate, a styryl, vinyl, vinyl ether, itaconate group, a C1-6alkylacrylate,
acrylamide, C1-6alkylacrylamide, N-vinyllactam, N-vinylamide, C2-12alk.enyl,
C2-12alkenylphenyl, C2-12alkenylnaphthyl, or C2-6alkenylphenylC1-6alkyl or a
cationic reactive group such as vinyl ether or epoxide groups. The particular/
preferred R7 is methacrylate.
The preferred R8 is is a divalent C1-6allkyl, C1-6alkyloxy,
C1-6alkyloxyC1-6alkyl, phenylene, naphthalene, C1-12cycloalkyl,
C1-6alkoxycarbonyl, amide, carboxy, C1-6alkylcarbonyl, carbonyl, C1-6alkoxy,
substituted C1-6allkyl, substituted C1-6alkyloxy, substituted C1-6alkyloxyC1-6alkyl,
substituted phenylene, substituted naphthalene, substituted C1-12cycloalkyl,
where the substituents are selected from one or more members of the group
consisting of C1-6alkoxycarbonyl, C1-6alkyl, C1-6alkoxy, amide, halogen,
hydroxyl, carboxyl, C1-6alkylcarbonyl and formyl. The particularly preferred R8
Examples of compatibilizing component of Formula I that are
particularly preferred are 2-propenoic acid, 2-methyl-2-hydroxy-3-[3-[1,3,3,3-
tetramethyl-1-[trimethylsilyl)oxy]disiloxanyl]propoxy]propyl ester (which can
also be named (3-methacryloxy-2-
The above compound, (3-methacryloxy-2-
hydroxypropyloxy)propylbis(trimethylsiloxy)methylsilane is formed from an
epoxide, which produces an 80:20 mixture of the compound shown above and
In the present invention the 80:20 mixture is preferred over pure (3-
some embodiments of the present invention it is preferred to have some
amount of the primary hydroxyl present, preferably greater than about 10 wt%
and more preferably at least about 20 wt%
Other suitable hydroxyl-functionalized silicone containing monomers include
The reaction products of glycidyl methacrylate with amino-functional
poiydimethylsiloxanes may also be used as a compatibilizing components.
Other suitable compatibilizing components include those disclosed in columns
6,7 and 8 of US 5,994,488, and monomers disclosed in 4,259,467; 4,260,725;
4,261,875; 4,649,184; 4,139,513,4,139,692; US 2002/0016383; 4,139,513
and 4,139,692. These and any other patents or applications cited herein are
incorporated by reference.
Still additional structures which may be suitable compatibilizing
components include those similar to the compounds disclosed in Pro. ACS
Div. Polym. Mat. SC1- Eng., April 13-17,1997, p. 42, and having the following
where n = 1 -50 and R independently comprise H or a polymerizable
unsaturated group), with at least one R comprising a polymerizable group,
and at least one R, and preferably 3-8 R, comprising H.
A second suitable class of compatibilizing components include those
having the structure given in Formula III, below:
Wherein x is 1 to 10;
IWA is a difunctional hydrophilic polymer as defined below, but having
a number average molecular weight of between about 1000 and about 50,000
HB is a difunctional moeity comprising at least one N which is capable
of hydrogen bonding with active hydrogens in the hydrophilic polymer and any
other component having active hydrogens.
Preferred IWA groups may be derived from a,io-hydroxyl terminated
PVP and α,ω-hydroxyl terminated polyoxyalkylene glycols having number
average molecular weights between about 1,000 and about 50,000 Daltons.
Preferred HB groups include difunctional amides, imides, carbamates
and ureas, combinations thereof and the like.
Compatibilizing components of Formula III may be made by amine
terminated polyoxyalkyleneglycols (Jeffamines) reacted with isocyanates,
chloroformates or acyl chlorides or anhydrides.
Additional suitable compatibilizing components are disclosed in U.S.
Patent 4,235,985 which is hereby incorporated by reference.
Suitable compatibilizing components may also comprise silicone
containing macromers which have been modified to include compatibilizing
functionality as defined above. Such macromers comprise substantial
quantities of both Si and HB groups as defined, above, or active hydrogen
functionality, such as hydroxyl groups. One class of suitable macromers
include hydroxyl functionalized macromers made by Group Transfer
Polymerization (GTP), or styrene functionalized prepolymers of hydroxyl
functional methacrylates and silicone methacrylates and are disclosed in
US6,367,929, which is incorporated herein by reference. In the present
ivention, these macromers are preferably used with another compatibilizing
component, such as a siloxane containing monomer. Other macromers, such
as those made by radical polymerization or condensation reaction may also
be used independently or in combination with other compatibilizing
components so long as the Si to hydrogen molar ratio (OH) of the macromer
is less than about 15:1, and preferably between about 1:1 to about 10:1 or the
Si to HB molar ratio is less than about 10:1 and preferably between about 1:1
and about 8:1. However, those of skill in the art will appreciate that including
difluoromethylene groups will decrease the molar ratio suitable for providing
Suitable monofunctional compatibilizing components are commercially
available from Gelest, Inc. Morrisville, PA. Suitable multifunctional
compatibilizing components are commercially available from Gelest, Inc.
Morrisville, PA or may be made using the procedures disclosed in 5,994,488
and 5,962,548. Suitable PEG type monofunctional compatibilizing
components may be made using the procedures disclosed in
Suitable compatibilizing macromers may be made using the general
procedure disclosed in US 5,760,100 (material C) or US 6,367,929.
While compatibilizing components comprising hydroxyl functionality
have been found to be particularly suitable for providing compatible polymers
for biomedical devices, and particulalrly ophthalmic devices, any
compatibilizing component which, when polymerized and/or formed into a final
article is compatible with the selected hydrophilic components may be used.
Compatibilizing components may be selected using the following monomer
compatibility test. In this test one gram of each of mono-3-methacryloxypropyl
terminated, mono-butyl terminated polydimethylsiloxane (mPDMS MW 800-
1000) and a monomer to be tested are mixed together in one gram of 3,7-
dimethyl-3-octanol at about 20°C. A mixture of 12 weight parts K-90 PVP and
60 weight parts DMA is added drop-wise to hydrophobic component solution,
with stirring, until the solution remains cloudy after three minutes of stirring.
The mass of the added blend of PVP and DMA is determined in grams and
recorded as the monomer compatibility index. Any compatibilizing component
having a compatibility index of greater than 0.5 grams, more preferably
greater than about 1 grams and most preferably greater than about 1.5 grams
will be suitabie for use in this invention. Those of skill in the art will appreciate
that the molecular weight of the active compatibilizing component will effect
the results of the above test. Compatibilizing components having molecular
weights greater than about 800 daltons may need to mix for longer periods of
time to give representative results.
An "effective amount" of the compatibilizing component of the invention
is the amount needed to compatibilize or dissolve the high molecular weight
hydrophilic polymer and the other components of the polymer formulation.
Thus, the amount of compatibilizing component will depend in part on the
amount of hydrophilic polymer which is used, with more compatibilizing
component being needed to compatibilize higher concentrations of high
molecular weight hydrophilic polymer. Effective amounts of compatibilizing
component in the polymer formulation include about 5% (weight percent,
based on the total weight of the reactive components) to about 90 %,
preferably about 10% to about 80%, most preferably, about 20% to about
In addition to the high molecular weight hydrophilic polymers and the
compatibilizing components of the invention other hydrophilic monomers,
oxygen permeability enhancing components, crosslinkers, additives, diluents,
polymerization imitators may be used to prepare the biomedical devices of the
Oxygen Permeable Component
The compositions and devices of the present invention may further
comprise additional components which provide enhanced oxygen permeability
compared to a conventional hydrogel. Suitable oxygen permeable
components include siloxane containing monomers, macromers and reactive
prepolymers, fluorine containing monomers, macromers and reactive
prepolymers and carbon-carbon triple bond containing monomers, macromers
and reactive prepolmers and combinations thereof, but exclude the
compatibilizing component. For the purposes of this invention, the term
macromer will be used to cover both macromers and prepolymers. Preferred
oxygen permeable components comprise siloxane containing monomers,
macromers, and mixtures thereof
Suitable siloxane containing monomers include, amide analogs of TRIS
described in U.S. 4,711,943, vinylcarbamate or carbonate analogs decribed in
U.S. Pat. 5,070,215, and monomers contained in U.S. Pat. 6,020,445 are
useful and these aforementioned patents as well as any other patents
mentioned in this specification are hereby incorporated by reference. More
specifically, 3-methacryloxypropyltris(trimethylsiloxy)silane (TRIS),
monomethacryloxypropyl terminated polydimethylsiloxanes,
methacryloxypropylpentamethyl disiloxane and combinations thereof are
particularly useful as siloxane containing monomers of the invention.
Additional siloxane containing monomers may be present in amounts of about
0 to about 75 wt%, more preferably of about 5 and about 60 and most
preferably of about 10 and 40 weight%.
Suitable siloxane containing macromers have a number average
molecular weight between about 5,000 and about 15,000 Daltons. Siloxane
containing macromers include materials comprising at least one siloxane
group, and preferably at least one dialkyl siloxane group and more preferably
at least one dimethyl siloxane group. The siloxane containing macromers
may include other components such as urethane groups, alkylene or alkylene
oxide groups, polyoxyalkalene groups, arylene groups, alkyl esters, amide
groups, carbamate groups, perfluoroalkoxy groups, isocyanate groups,
combinations thereof of and the like. A preferred class of siloxane containing
macromers may be formed via the polymerization of one or more siloxanes
with one or more acrylic or methacrylic materials. Siloxane containing
macromers may be formed via group transfer polymerization ("GTP"), free
radical polymerization, condensation reactions and the like. The siloxane
containing macromers may be formed in one or a series of steps depending
on the components selected and using conditions known in the art. Specific
siloxane containing macromers, and methods for their manufucture, include
those disclosed in US 5,760,100 as materials A-D (methacrylate
functionalized, silicone-fluoroether urethanes and methacrylate functionalized,
silicone urethanes), and those disclosed in US 6,367,929 (styrene
functionalized prepolymers of hydroxyl functional methacrylates and silicone
methacrylates), the disclosures of which are incorporated herein by reference.
Suitable siloxane containing reactive prepolymers include vinyl
carbamate functionalized polydimethylsiloxane, which is further disclosed in
US 5,070215 and urethane based prepolymers comprising alternating "hard"
segments formed from the reaction of short chained diols and diisocyantes
and "soft" segments formed from a relatively high molecular weight polymer,
which is α,ω endcapped with two active hydrogens. Specific examples of
suitable siloxane containing prepolymers, and methods for their manufacture,
are disclosed in US 5,034,461, which is incorporated herein by reference.
The hydrogels of the present invention may comprise at least one
siloxane containing macromer. The siloxane containing macromer may be
present in amounts between about 5 and about 50 weight%, preferably
between about 10 and about 50 weight% and more preferably between about
15 and about 45 weight%, all based upon the total weight of the reactive
Suitable fluorine containing monomers include fluorine-containing
(meth)acrylates, and more specifically include, for example, fluorine-
containing C2-C12alkyl esters of (meth)acrylic acid such as 2,2,2-trifluoroethyl
(meth)acrylate, 2,2,2,2' ,2',2'-hexafJuoroisopropyl (meth)acrylate, 2,2,3,
hexadecafluorononyl (meth)acrylate and the like. Fluorine containing
macromers and reactive prepolymers include macromers and prepolymers
which include said flurorine containing monomers.
It has been found that wettability of macromer containing silicone
hydrogels may be improved by including at least one hydrophilic polymer and
a compatibilizing component. Improved wettability includes a decrease in
advancing dynamic contact angle of at least about 10%, and preferably at
least about 20% and in some embodiment a decrease of at least about 50%.
In certain embodiments it may be preferred to use mixtures of siloxane
containing monomers or mixtures of siloxane containing monomers with
siloxane containing macromers or prepolymers.
Additionally, reactive components of the present invention may also
include any hydrophiiic monomers used to prepare conventional hydrogels.
For example monomers containing acrylic groups (CH2=CROX, where R is
hydrogen or C1-6alkyl an X is 0 or N) or vinyl groups (-C=CH2) may be used.
Examples of additional hydrophiiic monomers are N,N-dimethylacrylamide,
2-hydroxyethyl methacrylate, glycerol monomethacrylate, 2-hydroxyethyl
methacrylamide, polyethyleneglycol monomethacrylate, methacrylic acid,
acrylic acid, N-vinyl pyrrolidone, N-vinyl-N-methyl acetamide, N-vinyl-N-ethyl
acetamide, N-vinyl-N-ethyl formamide, N-vinyl formamide and and
Aside the additional hydrophiiic monomers mentioned above,
polyoxyethylene polyols having one or more of the terminal hydroxyl groups
replaced with a functional group containing a polymerizable double bond may
be used. Examples include polyethylene glycol, as disclosed in US
5,484,863, ethoxylated alkyl glucoside, as disclosed in US 5,690,953, US
5,304,584, and ethoxylated bisphenol A, as disclosed in US5,565,539,
reacted with one or more molar equivalents of an end-capping group such as
isocyanatoethyl methacrylate, methacrylic anhydride, methacryloyl chloride,
vinylbenzoyl chloride, and the like, produce a polyethylene polyol having one
or more terminal polymerizable olefinic groups bonded to the polyethylene
polyol through linking moieties such as carbamate, urea or ester groups.
Still further examples include the hydrophiiic vinyl carbonate or vinyl
carbamate monomers disclosed in U.S. Pat. Nos. 5,070,215, the hydrophiiic
oxazolone monomers disclosed in U.S. Pat. No. 4,910,277, and polydextran.
The preferred additional hydrophiiic monomers are N,N-
dimethylacrylamide (DMA), 2-hydroxyethyl methacrylate (HEMA), glycerol
methacrylate, 2-hydroxyethyl methacrylamide, N-vinylpyrrolidone (NVP),
polyethyleneglycol monomethacrylate, methacrylic acid, acrylic acid and
combinations thereof, with hydrophiiic monomers comprising DMA being
particularly preferred. Additional hydrophiiic monomers may be present in
amounts of about 0 to about 70 wt%, more preferably of about 5 and about 60
and most preferably of about 10 and 50 weight%, based upon the total weight
of the reactive components.
Suitable crosslinkers are compounds with two or more polymerizable
functional groups. The crosslinker may be hydrophilic or hydrophobic and in
some embodiments of the present invention mixtures of hydrophilic and
hydrophobic crosslinkers have been found to provide silicone hydrogels with
improved optical clarity (reduced haziness compared to a CSI Thin Lens®).
Examples of suitable hydrophilic crosslinkers include compounds having two
or more polymerizable functional groups, as well as hydrophilic functional
groups such as polyether, amide or hydroxyl groups. Specific examples
include TEGDMA (tetraethyleneglycol dimethacrylate), TrEGDMA
(triethyleneglycol dimethacrylate), ethyleneglycol dimethacylate (EGDMA),
ethylenediamine dimethyacrylamide, glycerol dimethacrylate and
combinations thereof Examples of suitable hydrophobic crosslinkers include
multifunctional compatibilizing component, multifunctional polyether-
polydimethylsiloxane block copolymers, combinations thereof and the like.
Specific hydrophobic crosslinkers include acryloxypropyl terminated
polydimethylsiloxane (n= 10 or 20) (acPDMS), hydroxylacrylate functionalized
siloxane macromer, methacryloxypropyl terminated PDMS, butanediol
dimethacrylate, divinyl benzene, 1,3-bis(3-
methacryloxypropyl)tetrakis(trimethylsiloxy) disiloxane and mixtures thereof.
Preferred crosslinkers include TEGDMA, EGDMA, acPDMS and combinations
thereof. The amount of hydrophilic crosslinker used is generally about 0 to
about 2 weight% and preferably from about 0.5 to about 2 weight % and the
amount of hydrophobic crosslinker is about 0 to about 0 to about 5 weight %
based upon the total weight of the reactive components, which can
alternatively be referred to in mol% of about 0.01 to about 0.2 mmole/gm
reactive components, preferably about 0.02 to about 0.1 and more preferably
0.03 to about 0.6 mmole/gm.
Increasing the level of crosslinker in the final polymer has been found
to reduce the amount of haze. However, as crosslinker concentration
increases above about 0.15 mmole/gm reactive components modulus
increases above generally desired levels (greater than about 90 psi). Thus, in
the present invention the crosslinker composition and amount is selected to
provide a crosslinker concentration in the reaction mixture of between about 1
and about 10 mmoles crosslinker per 100 grams of reactive components.
Additional components or additives, which are generally known in the
art may also be included. Additives include but are not limited to ultra-violet
absorbing compounds and monomer, reactive tints, antimicrobial compounds,
pigments, photochromic, release agents, combinations thereof and the like.
The reactive components (compatibilizing component, hydrophilic
polymer, oxygen permeable components, hydrophilic monomers,
crosslinker(s) and other components) are mixed and reacted in the absence
of water and optionally, in the presence of at least one diluent to form a
reaction mixture. The type and amount of diluent used also effects the
properties of the resultant polymer and article. The haze and wettability of the
final article may be improved by selecting relatively hydrophobic diluents
and/or decreasing the concentration of diluent used. As discussed above,
increasing the hydrophobicity of the diluent may also allow poorly compatible
components (as measured by the compatibility test) to be processed to form a
compatible polymer and article. However, as the diluent becomes more
hydrophobic, processing steps necessary to replace the diluent with water will
require the use of solvents other than water. This may undesirably increase
the complexity and cost of the manufacturing process. Thus, it is important to
select a diluent which provides the desired compatibility to the components
with the necessary level of processing convenience. Diluents useful in
preparing the devices of this invention include ethers, esters, alkanes, alkyl
halides, silanes, amides, alcohols and combinations thereof. Amides and
alcohols are preferred diluents, and secondary and tertiary alcohols are most
preferred alcohol diluents. Examples of ethers useful as diluents for this
invention include tetrahydrofuran, tripropylene glycol methyl ether,
dipropylene glycol methyl ether, ethylene glycol n-butyl ether, diethylene
glycol n-butyl ether, diethylene glycol methyl ether, ethylene glycol phenyl
ether, propylene glycol methyl ether, propylene glycol methyl ether acetate,
dipropylene glycol methyl ether acetate, propylene glycol n-propyl ether,
dipropylene glycol n-propyl ether, tripropylene glycol n-butyl ether, propylene
glycol n-butyl ether, dipropylene glycol n-butyl ether, tripropylene glycol n-
butyl ether, propylene glycol phenyl ether dipropylene glycol dimetyl ether,
polyethylene glycols, polypropylene glycols and mixtures thereof. Examples
of esters useful for this invention include ethyl acetate, butyl acetate, amyl
acetate, methyl lactate, ethyl lactate, i-propyl lactate. Examples of alkyl
halides useful as diluents for this invention include methylene chloride.
Examples of silanes useful as diluents for this invention include
Examples of alcohols useful as diluents for this invention include those
having the formula
wherein Where R, R' and R" are independently selected from H, a linear,
branched or cyclic monovalent alkyl having 1 to 10 carbons which may
optionally be substituted with one or more groups including halogens, ethers,
esters, aryls, aminos, amides, alkenes, alkynes, carboxylic acids, alcohols,
aldehydes, ketones or the like, or any two or all three of R, R and R" can
together bond to form one or more cyclic structures, such as alkyl having 1
to10 carbons which may also be substituted as just described, with the
proviso that no more than one of R, R' or R" is H.
It is preferred that R, R' and R" are independently selected from H or
unsubstituted linear, branched or cyclic alkyl groups having 1 to 7 carbons. It
is more preferred that R, R', and R" are independently selected form
unsubstituted linear, branched or cyclic alkyl groups having 1 to 7 carbons. In
certain embodiments, the preferred diluent has 4 or more, more preferably 5
or more total carbons, because the higher molecular weight diluents have
lower volatility, and lower flammability. When one of the R, R' and R" is H, the
structure forms a secondary alcohol. When none of the R, R' and R" are H,
the structure forms a tertiary alcohol. Tertiary alcohols are more preferred
than secondary alcohols. The diluents are preferably inert and easily
displaceable by water when the total number of carbons is five or less.
Examples of useful secondary alcohols include 2-butanol, 2-propanol,
menthol, cyclohexanol, cyclopentanol and exonorbomeol, 2-pentanol, 3-
pentonal, 2-hexanol, 3-hexanol, 3-methyl-2-butanol, 2-heptanol, 2-octanol, 2-
nonanol, 2-decanol, 3-octanol, norbomeol, and the like.
Examples of useful tertiary alcohols include tert-butanol, tert-amyl,
alcohol, 2-methyl-2-pentanol, 2,3-dimethyl-2-butanol, 3-methyl-3-pentahol, 1-
methylcyclohexanol, 2-methyl-2-hexanol, 3,7-dimethyl-3-octanol, 1-chloro-2-
methyl-2-propanol, 2-methyl-2-heptanol, 2-methyl-2-octanol, 2-2methyl-2-
nonanol, 2-methyl-2-decanol, 3-methyl-3-hexanol, 3-methyl-3-heptanol, 4-
methyl4-heptanol, 3-methyl-3-octanol, 4-methyl-4-octanol, 3-methyl-3-
nonanol, 4-methyl-4-nonanol, 3-methyl-3-octanol, 3-ethyl-3-hexanol, 3-mehtyl-
3-heptanol, 4-ethyl-4-heptanol, 4-propyl-4-heptanol, 4-isopropyl-4-heptanol,
2,4-dimethyl-2-pentanol, 1-methylcyclopentanol, 1-ethylcyclopentanol, 1-
ethylcyclopentanol, 3-hydroxy-3-methyl-1 -butene, 4-hydroxy-4-methyl-1 -
cyclopentanol, 2-phenyl-2-propanol, 2-methoxy-2-methyl-2-propanol 2,3,4-
trimethyl-3-pentanol, 3,7-dimethyl-3-octanol, 2-phenyl-2-butanol, 2-methyl-1-
phenyl-2-propanol and 3-ethyl-3-pentanol, and the like.
A single alcohol or mixtures of two or more of the above-listed alcohols or
two or more alcohols according to the structure above can be used as the
diluent to make the polymer of this invention.
In certain embodiments, the preferred alcohol diluents are secondary and
tertiary alcohols having at least 4 carbons. The more preferred alcohol
diluents include tert-butanol, tert-amyl alcohol, 2-butanol, 2-methyl-2-pentanol,
2,3-dimethyl-2-butanol, 3-methyl-3-pentanol, 3-ethyl-3-pentanol, 3,7-dimethyl-
Presently, the most preferred diluents are hexanol, heptanol, octanol,
nonanol, decanol, tert-butyl alcohol, 3-methyl-3-pentanol, isopropanol, t amyl
alcohol, ethyl lactate, methyl lactate, i-propyl lactate, 3,7-dimethyl-3-octanol,
dimethyl formamide, dimethyl acetamide, dimethyl propionamide, N methyl
pyrrolidinone and mixtures thereof. Additional diluents useful for this invention
are disclosed in US patent 6,020,445, which is incorporated herein by
In one embodiment of the present invention the diluent is water soluble
at processing conditions and readily washed out of the lens with water in a
short period of time. Suitable water soluble diluents include 1-ethoxy-2-
propanol, 1-methyl-2-propanol, t-amyl alcohol, tripropylene glycol methyl
ether, isopropanol, 1-methyl-2-pyrrolidone, N,N-dimethylpropionamide, ethyl
lactate, dipropylene glycol methyl ether, mixtures thereof and the like. The
use of a water soluble diluent allows the post molding process to be
conducted using water only or aqueous solutions which comprise water as a
In one embodiment, the amount of diluent is generally less than about
50 weight % of the reaction mixture and preferably less than about 40
weight% and more preferably between about 10 and about 30 weight %
based upon the total weight of the components of the reaction mixture.
The diluent may also comprise additional components such as release
agents. Suitable release agents are water soluble and aid in lens deblocking
The polymerization initiators includes compounds such as lauryl
peroxide, benzoyl peroxide, isopropyl percarbonate, azobisisobutyronitrile,
and the like, that generate free radicals at moderately elevated temperatures,
and photoinitiator systems such as aromatic alpha-hydroxy ketones,
alkoxyoxybenzoins, acetophenones, acyl phosphine oxides, and a tertiary
amine plus a diketone, mixtures thereof and the like. Illustrative examples of
photoinitiators are 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-
phosphine oxide (DMBAPO), bis(2,4,6-trimethylbenzoyl)-
phenylphosphineoxide (Irgacure 819), 2,4,6-trimethylbenzyldiphenyl
phosphine oxide, 2,4,6-trimethylbenzyoyl diphenylphosphine oxide, benzoin
methyl ester.and a combination of camphorquinone and ethyl 4-(N,N-
dimethylamino)benzoate. Commercially available visible light initiator
systems include Irgacure 819, Irgacure 1700, Irgacure 1800, Irgacure 1850
(all from Ciba Specialty Chemicals) and Lucirin TPO initiator (available from
BASF). Commercially available UV photoinitiators include Darocur 1173 and
Darocur 2959 (Ciba Specialty Chemicals). The initiator is used in the reaction
nvxture in effective amounts to initiate photopolymerization of the reaction
mixture, e.g., from about 0.1 to about 2 parts by weight per 100 parts of
reactive monomer. Polymerization of the reaction mixture can be initiated
using the appropriate choice of heat or visible or ultraviolet light or other
means depending on the polymerization initiator used. Alternatively, initiation
can be conducted without a photoinitiator using, for example, e-beam.
However, when a photoinitiator is used, the preferred initiator is a combination
of 1-hydroxycyclohexyl phenyl ketone and bis(2,6-dimethoxybenzoyl)-2,4-4-
trimethylpentyl phosphine oxide (DMBAPO), and the preferred method of
polymerization initiation is visible light. The most preferred is bis(2,4,6-
trimethylbenzoyl)-phenylphosphineoxide (Irgacure 819).
The preferred range of all silicone containing components (oxygen
permeable components and compatibilizing components) is from about 5 to
99 weight percent, more preferably about 15 to 90 weight percent, and most
preferably about 25 to about 80 weight percent, based upon the total weight of
the reactive components. A preferred range of compatibilizing components is
about 5 to about 90 weight percent, preferably about 10 to about 80, and most
preferably about 20 to about 50 weight percent. A preferred range of
hydrophilic monomer is from about 5 to about 80 weight percent, more
preferably about 5 to about 60 weight percent, and most preferably about 10
to about 50 weight percent of the reactive components in the reaction mixture.
A preferred range of high molecular weight hydrophilic polymer is about 1 to
about 15 weight percent, more preferably about 3 to about 15 weight percent,
and most preferably about 5 to about 12 weight percent. A preferred range of
macromer is from about 5 to about 50 weight%, preferably from about 10 to
about 50 weight % and more preferably from about 15 to about 45 weight %.
All of the foregoing ranges are based upon the total weight of all reactive
A preferred range of diluent is from about 0 to about 70 weight percent,
more preferably about 0 to about 50 weight percent, and still more preferably
about 0 to about 40 weight percent and in some embodiments, most
preferably between about 10 and about 30 weight percent based upon the
weight of all components in the total reaction mixture. The amount of diluent
required varies depending on the nature and relative amounts of the reactive
The invention further comprises, consists and consists essentially of a
silicone hydrogel, biomedical device, ophthalmic device and contact lenses of
the formulations shown below:
Thus, the present invention includes silicone hydrogel,
biomedical device, ophthalmic device and contact lenses having each of the
composition listed in the table, which describes 261 possible compositional
ranges. Each of the ranges listed above is prefaced by the word "about". The
foregoing range combinations are presented with the proviso that the listed
components, and any additional components add up to 100 weight%.
In a preferred embodiment, the reactive components comprise about
28 wt.% SiGMA; about 31 wt.% 800-1000 MW monomethacryloxypropyl
terminated mono-n-butyl terminated polydimethylsiloxane, "mPDMS", about
24 wt.% N,N-dimethylacrylamide, "DMA", about 6 wt.% 2-hydroxyethyl
methacryate, "HEMA", about 1.5 wt% tetraethyleneglycoldimethacrylate,
"TEGDMA", about 7 wt.% polyvinylpyrrolidone, "K-90 PVP"; with the balance
comprising minor amounts of additives and photoinitiators. The polymerization
is most preferably conducted in the presence of about 23% (weight % of the
combined monomers and diluent blend) 3,7-dimethyl-3-octanol diluent.
In a second preferred embodiment the reactive components comprise
about 30 wt.% SiGMA, about 23 wt.% mPDMS, about 31 wt% DMA, about 0.5
to about 1 wt.% ethyleneglycoldimethacrylate, "EGDMA", about 6 wt.% K-90
PVP; and about 7.5 wt% HEMA, with the balance comprising minor amounts
of additives and photoinitiators. The polymerization is most preferably
conducted fn the presence of tert-amyl-alcohol as a diluent comprising about
29 weight percent of the reaction mixture. The diluent may also comprise
about 11 weight % low molecular weight PVP (less than about 5,000 and
preferably less than about 3,000 Mn.
In a third preferred embodiment, the reactive components comprise
about 11-18 wt % macromer (the GTP reaction product of about 24 wt.%
HEMA; about 3wt% MMA; about 33wt.%
methacryloxypropyltris(trimethylsiloxy)silane and about 32wt.% mono-
methacryloxypropyl terminated mono-butyl terminated polydimethylsiloxane
functionalized with 8 wt % 3-isopropenyl- a,a-dimethylbenzyl isocyanate);
about 18-30 wt.% mPDMS, about 2-10 wt% acPDMS, about 27-33 wt.%
DMA, about 13-15 wt.% TRIS, about 2-5 wt.% HEMA, and about 5-7 wt.% K-
90 PVP; with the balance comprising minor amounts of additives and
photoinitiators. The polymerization is most preferably conducted in the
presence of 25-30% (weight % of the combined monomers and diluent blend)
a diluent comprising 3,7-dimethyl-3-octanol.
In a fourth preferred embodiment, the reactive components comprise
between about 15 to about 40 wt.% macromer (formed from perfluoroether
having a mean molecular weight of about 1030 g/mol and a, u/-hydroxypropyl-
terminated polydimethylsiloxane having a mean molecular weight of about
2000 g/mol, isophorone diisocyanate and isocyanatoethyl methacrylate);
about 40 to about 52% SiGMA, about 0 to about 5 wt% 3-
tris(trimethylsiloxy)silylpropyl methacrylate, "TRIS", about 22 to about 32 wt.%
DMA, about 3 about 8 wt% K-90 PVP with the balance comprising minor
amounts of additives and photoinitiators. The polymerization is most
preferably conducted in the presence of about 15 to about 40, and preferably
beiween about 20 and about 40% (weight % of the combined monomers and
diluent blend), diluent, which may, in some emobodiments preferably be
The biomedical devices of the invention are prepared by mixing the
high molecular weight hydrophilic polymer, the compatibilizing component,
plus one or more of the following: the oxygen permeability enhancing
component, the hydrophilic monomers, the additives ("reactive components"),
and the diluents ("reaction mixture"), with a polymerization initator and curing
by appropriate conditions to form a product that can be subsequently formed
into the appropriate shape by lathing, cutting and the like. Alternatively, the
reaction mixture may be placed in a mold and subsequently cured into the
Various processes are known for curing the reaction mixture in the
production of contact lenses, including spincasting and static casting.
Spincasting methods are disclosed in U.S. Pat. Nos. 3,408,429 and
3,660,545, and static casting methods are disclosed in U.S. Pat. Nos.
4,113,224 and 4,197,266. The preferred method for producing contact lenses
comprising the polymer of this invention is by the direct molding of the silicone
hydrogels, which is economical, and enables precise control over the final
shape of the hydrated lens. For this method, the reaction mixture is placed in
a mold having the shape of the final desired silicone hydrogel, i.e., water-
swollen polymer, and the reaction mixture is subjected to conditions whereby
the monomers polymerize, to thereby produce a polymer/diluent mixture in the
shape of the final desired product. Then, this polymer/diluent mixture is
treated with a solvent to remove the diluent and ultimately replace it with
water, producing a silicone hydrogel having a final size and shape which are
quite similar to the size and shape of the original molded polymer/diluent
article. This method can be used to form contact lenses and is further
described in U.S. Pat. Nos. 4,495,313; 4,680,336; 4,889,664; and 5,039,459,
incorporated herein by reference.
Yet another feature of the present invention is a process for curing
silicone hydrogel formulations to provide enhanced wettability. It has been
found that the gel time for a silicone hydrogel may be used to select cure
conditions which provide a wettable ophthalmic device, and specifically a
contact lens. The gel time is the time at which a crosslinked polymer network
is formed, resulting in the viscosity of the curing reaction mixture approaching
infinity and the reaction mixture becoming non-fluid. The gel point occurs at a
specific degree of conversion, independent of reaction conditions, and
therefore can be used as an indicator of the rate of the reaction. It has been
found that, for a given reaction mixture, the gel time may be used to
determine cure conditions which impart desirable wettability. Thus, in a
process of the present invention, the reaction mixture is cured at or above a
gel time that provides improved wettability, or more preferably sufficient
wettability for the resulting device to be used without a hydrophilic coating or
surface treatment ("minimum gel time"). Preferably improved wettability is a
decrease in advancing dynamic contact angle of at least 10% compared to
formulation with no high molecular weight polymer. Longer gel times are
preferred as they provide improved wettability and increased processing
Gel times will vary for different silicone hydrogel formulations. Cure
conditions also effect gel time. For example the concentration of crosslinker
will impact gel time, increasing crosslinker concentrations decreases gel time.
Increasing the intensity of the radiation (for photopolymerization) or
temperature (for thermal polymerization), the efficiency of initiation (either by
selecting a more efficient initiator or irradiation source, or an initiator which
absorbs more strongly in the selected irradiation range) will also decrease gel
time. Temperature and diluent type and concentration also effect gel time in
ways understood by those of skill in the art.
The minimum gel time may be determined by selecting a given
formulation, varylng one of the above factors and measuring the gel time and
contact angles. The minimum gel time is the point above which the resulting
lens is generally wettable. Below the minimum gel time the lens is generally
not wettable. For a contact lens "generally wettable" is a lens which displays
an advancing dynamic contact angle of less than about 70 and preferably less
than about 60° or a contact lens which displays a tear film break up time equal
to or better than an ACUVUE® lens. Thus, those of skill in the art will
appreciate that minimum gel point as defined herein may be a range, taking
into consideration statistical experimental variability.
In certain embodiments using visible light irradiation minimum
gel times of at least about 30, preferably greater than about 35, and more
preferably greater than about 40 seconds have been found to be
Curing may be conducted using heat, ionizing or actinic radiation, for
example electron beams, Xrays, UV or visible light, ie. electromagnetic
radiation or particle radiation having a wavelength in the range of from about
150 to about 800 nm. Preferable radiation sources include UV or visible light
having a wavelength of about 250 to about 700 nm. Suitable radiation
sources include UV lamps, fluorescent lamps, incandescent lamps, mercury
vapor lamps, and sunlight. In embodiments where a UV absorbing compound
is included in the reaction mixture (for example, as a UV block or
photochromic) curing is conducting by means other than UV irradiation (such
as by visible light or heat). In a preferred embodiment the radiation source is
selected from UVA (about 315 - about 400 nm), UVB (about 280-about 315)
or visible light (about 400 -about 450 nm). In another preferred embodiment,
the reaction mixture includes a UV absorbing compound, is cured using
visible light. In many embodiments it will be useful to cure the reaction
mixture at low intensity to achieve the desired minimum gel time. As used
herein the term "low intensity" means those between about 0.1 mW/cm2 to
about 6 mW/cm2 and preferably between about 1 mW/cm2 and 3 mW/cm2.
The cure time is long, generally more than about 1 minute and preferably
between about 1 and about 60 minutes and still more preferably between
about 1 and about 30 minutes This slow, low intensity cure is one way to
provide the desired minimum gel times and produce ophthalmic devices which
display good wettability.
Initiator concentration also effects gel time. Accordingly, in some
embodiments it is preferred to have relatively low amounts of photoinitiator,
generally 1% or less and preferably 0.5% or less.
The temperature at which the reaction mixture is cured is also
important. As the temperature is increased above ambient the haze of the
resulting polymer decreases. Temperatures effective to reduce haze include
temperatures at which the haze for the resulting lens is decreased by at least
about 20% as compared to a lens of the same composition made at 25°C.
Thus, suitable cure temperatures include those greater than about 25°C,
preferably those between about 25°C and 70CC and more preferably those
between about 40°C and 70°C. The precise set of cure conditions
(temperature, intensity and time) will depend upon the components of lens
material selected and, with reference to the teaching herein, are within the
skill of one of ordinary skill in the art to determine. Cure may be conducted in
one or a muptiplicity of cure zones.
The cure conditions must be sufficient to form a polymer network from
the reaction mixture. The resulting polymer network is swollen with the diluent
and has the form of the mold cavity.
After the lenses have been cured they must be removed from the mold.
Unfortunately, the silicone components used in the lens formulation render the
finished lenses "sticky" and difficult to release from the lens molds. Lenses
can be deblocked (removed from the mold half or tool supporting the lens)
using a solvent, such as an organic solvent. However, in one embodiment of
the present invention at least one low molecular weight hydrophilic polymer is
added to the reaction mixture, the reaction mixture is formed into the desired
article, cured and deblocked in water or an aqueous solution comprising,
consisting essentially of and consisting of a small amount of surfactant. The
low molecular weight hydrophilic polymer can be any polymer having a
structure as defined for a high molecular weight polymer, but with a molecular
weight such that the low molecular weight hydrophilic polymer extracts or
leaches from the lens under deblocking conditions to assist in lens release
from the mold. Suitable molecular weights include those less than about
40,000 Daltons and preferably less than about 20,000 Daltons. Those of skill
in the art will appreciate that the foregoing molecular weights are averages,
and that some amount of material having a molecular weight higher than the
given averages may be suitable, so long as the average molecular weight is
within the specified range. Preferably the low molecular weight polymer is
selected from water soluble polyamides, lactams and polyethylene glycols,
and mixtures thereof and more preferably polyvinylpyrrolidone, polyethylene
glycols, poly 2 ethyl-2-oxazoline (available from Plymer Chemistry
Innovations, Tuscon, AZ), polymethacrylic acid, poly(1 -lactic acid),
polycaprolactam, polycaprolactone, polycaprolactone diol, polyvinyl alcohol,
polyhema, polyacrylic acid, poly(1-glycerol methacrylate), poly(2-ethyl-2-
oxazoline), poly(2-hydroxypropyl methacrylate), poly(2-vinylpyridine N-oxide),
polyacrylamide, polymethacrylamide and the like.
The low molecular weight hydrophilic polymer may be used in amounts
up to about 20 wt.% and preferably in amounts between about 5 and about 20
wt% of the reactive components.
Suitable surfactants include non-ionic surfactants including betaines,
amine oxides, combinations thereof and the like. Examples of suitable
surfactants include TWEEN® (ICI), DOE 120 (Amerchol/Union Carbide and
the like. The surfactants may be used in amounts up to about 10,000 ppm,
preferably between about 25 ppm and about 1500 ppm and more preferably
between about 100 and about 1200 ppm.
Suitable release agents are low molecular weight, and include 1-
methyl-4-piperidone, 3-morpholino-1,2-propanediol, tetrahydro-2H-pyran-4-ol,
glycerol formal, ethyl-4-oxo-1-piperidine carboxylate, 1,3-dimethyl-3,4,5,6-
tetrahydro-2(1H)-pyrimidinone and 1-(2-hydroxyethyl)-2-pyrrolidone
Lenses made from reaction mixtures without low molecular weight
hydrophilic polymer may be deblocked in an aqueous solution comprising at
least one organic solvent. Suitable organic solvents are hydrophobic, but
miscible with water. Alcohols, ethers and the like are suitable, more
specifically primary alcohols and more specifically isopropyl alcohol, DPMA,
TPM, DPM, methanol, ethanol, propanol and mixtures thereof being suitable
Suitable deblocking temperatures range from about ambient to about
100°C, preferably between about 70°C and 95°C, with higher temperatures
providing quicker deblocking times. Agitation, such as by sonication, may
also be used to decrease deblocking times. Other means known in the art,
such as vacuum nozzles may also be used to remove the lenses from the
Typically after curing the reaction mixture, the resulting polymer is
treated with a solvent to remove the diluent (if used), unreacted components,
byproducts, and the like and hydrate the polymer to form the hydrogel.
Alternatively, depending on the solubility characteristics of the hydrogel's
components, the solvent initially used can be an organic liquid such as
ethanol, methanol, isopropanol, TPM, DPM, PEGs, PPGs, glycerol, mixtures
thereof, or a mixture of one or more such organic liquids with water, followed
by extraction with pure water (or physiological saline). The organic liquid may
also be used as a "pre-soak". After demolding, lenses may be briefly soaked
(times up to about 30 minutes, preferably between about 5 and about 30
minutes) in the organic liquid or a mixture of organic liquid and water. After
the pre-soak, the lens may be further hydrated using aqueous extraction
In some embodiments, the preferred process uses an extraction
solvent that is predominately water, preferably greater than 90% water, more
preferably greater than 97% water. Other components may includes salts
such as sodium chloride, sodium borate boric acid, DPM, TPM, ethanol or
isopropanol. Lenses are generally released from the molds into this
extraction solvent, optionally with stirring or a continuous flow of the extraction
solvent over the lenses. This process can be conducted at temperatures from
2 to 121°C, preferably from 20 to 98 °C. The process can be conducted at
elevated pressures, particularly when using temperatures in excess of 100°C,
but is more typically conducted at ambient pressures. It is possible to deblock
the lenses into one solution (for example containing some release aid) and
then transfer them into another (for example the final packing solution),
although it may also be possible to deblock the lenses into the same solution
in which they are packaged. The treatment of lenses with this extraction
solvent may be conducted for a period of from about 30 seconds to about 3
days, preferably between about 5 and about 30 minutes. The selected
hydration solution may additional comprise small amounts of additives such
as surfactants and/or release aids. Suitable surfactants include include non-
ionic surfactants, such as betaines and amine oxides. Specific surfactants
include TWEEN 80 (available from Amerchol), DOE 120 (available from Union
Carbide), Pluronics, methyl cellulose, mixtures thereof and the like and may
be added in amounts between about 0.01 weight% and about 5% based upon
total weight of hydration solution used.
In one embodiment the lenses may be hydrated using a "step down"
method, where the solvent is replaced in steps over the hydration process.
Suitable step down processes have at least two, at least three and in some
embodiments at least four steps, where a percentage of the solvent is
replaced with water.
The silicone hydrogels after hydration of the polymers preferably
comprise about 10 to about 60 weight percent water, more preferably about
20 to about 55 weight percent water, and most preferably about 25 to about
50 weight percent water of the total weight of the silicone hydrogel. Further
details on the methods of producing silicone hydrogel contact lenses are
disclosed in U.S. Patents 4,495,313; 4,680,336; 4,889,664; and 5,039,459,
which are hereby incorporated by reference.
The cured biomedical device of the present invention displays excellent
resistance to fouling in vivo, even without a coating. When the biomedical
device is an ophthalmic device, resistance to biofouling may be measured by
measuring the amount of surface deposits on the lens during the wear period,
often referred to as "lipid deposits".
Lens surface deposits are measured as follows: Lenses were put on
human eyes and evaluated after 30 minutes and one week of wear using a slit
lamp. During the evaluation the patient is asked to blink several times and the
lenses are manually "pushed" in order to differentiate between deposits and
back surface trapped debris. Front and back surface deposits are graded as
being discrete (i.e. jelly bumps) or filmy. Front surface deposits give a bright
reflection while back surface deposits do not. Deposits are differentiated from
back surface trapped debris during a blink or a push-up test. The deposits will
move while the back surface trapped debris will remain still. The deposits are
graded into five categories based upon the percentage of the lens surface
which is effected: none ( 6% to about 15%), moderate (about 16% to about 25%) and severe (greater
than about 25%). A 10% difference between the categories is considered
The ophthalmic devices of the present invention also display low haze,
good wettability and modulus.
Haze is measured by placing test lenses in saline in a clear cell above
a black background, illuminating from below with a fiber optic lamp at an angle
66° normal to the lens cell, and capturing an image of the lens from above
with a video camera. The background-subtracted scattered light image was
quantitatively analyzed, by integrating over the central 10 mm of the lens, and
then compared to a -1.00 diopter CSI Thin Lens®, which is arbitrarily set at a
haze value of 100, with no lens set as a haze value of 0.
Wettability is measured by measuring the contact angle or DCA,
typically with borate buffered saline, using a Wilhelmy balance at 23°C. The
wetting force between the lens surface and borate buffered saline is
measured using a Wilhelmy microbalance while the sample is being
immersed into or pulled out of the saline. The following equation is used
F = 2γpcosθ or θ = cos-1(F/2γp)
where F is the wetting force, γ is the surface tension of the probe liquid,
p is the perimeter of the sample at the meniscus and θ is the contact angle.
Typically, two contact angles are obtained from a dynamic wetting experiment
- advancing contact angle and receding contact angle. Advancing contact
angle is obtained from the portion of the wetting experiment where the sample
is being immersed into the probe liquid. At least 4 lenses of each composition
are measured and the values reported herein.
However, DCA is not always a good predictor of wettability on eye.
The pre-lens tear film non-invasive break-up time (PLTF-NIBUT) is one
measure of in vivo or "clinical" lens wettability. The PLTF-NIBUT is measured
using a slit lamp and a circular fluorescent tearscope for noninvasive viewing
of the tearfilm (Keeler Tearscope Plus). The time elapsed between the eye
opening after a blink and the appearance of the first dark spot within the tear
film on the front surface of a contact lens is recorded as PLTF-NIBUT. The
PLTF-NIBUT was measured 30-minutes after the lenses were placed on eye
and after one week. Three measurements were taken at each time interval
and were averaged into one reading. The PLTF-NIBUT was measured on
both eyes, beginning with the right eye and then the left eye.
Movement is measured using the "push up" test. The patient's eyes
are in the primary gaze position. The push-up test is a gentle digital push of
the lens upwards using the lower lid. The resistance of the lens to upward
movement is judged and graded according to the following scale: 1
(excessive, unacceptable movement), 2 (moderate, but acceptable
movement), 3 (optimal movement), 4 (minimal, but acceptable movement), 5
(insufficient, unacceptable movement).
The lenses of the present invention display moduli of at least about 30
psi, preferably between about 30 and about 90 psi, and more preferably
between about 40 and about 70 psi. Modulus is measured by using the
crosshead of a constant rate of movement type tensile testing machine
equipped with a load cell that is lowered to the initial gauge height. A suitable
testing machine includes an Instron model 1122. A dog-bone shaped sample
having a 0.522 inch length, 0.276 inch "ear" width and 0.213 inch "neck" width
is loaded into the grips and elongated at a constant rate of strain of 2 in/min.
until it breaks. The initial gauge length of the sample (Lo) and sample length
at break (Lf) are measured. Twelve specimens of each composition are
measured and the average is reported. Tensile modulus is measured at the
initial linear portion of the stress/strain curve.
The contact lenses prepared by this invention have O2 Dk values
between about 40 and about 300 barrer, determined by the polarographic
method. Lenses are positioned on the sensor then covered on the upper side
with a mesh support. The lens is exposed to an atmosphere of humified 2.1%
O2. The oxygen that diffuses through the lens is measured using a
polarographic oxygen sensor consisting of a 4 mm diameter gold cathode and
a silver ring anode. The reference values are those measured on
commercially available contact lenses using this method. Balafilcon A lenses
available from Bausch & Lomb give a measurement of approx. 79 barrer.
Etafilcon lenses give a measurement of 20 to 25 barrer. (1 barrer = 10.10 (cm3
of gas x cm2)/(cm3 of polymer x s x cm Hg).
Gel time was measured using the following method. The photo-
polymerization reaction was monitored with an ATS StressTech rheometer
equipped with a photo-curing accessory, which consists of a temperature-
controlled cell with a quartz lower plate and an aluminum upper plate, and a
radiation delivery system equipped with a bandpass filter. The radiation,
which originates at a Novacure mercury arc lamp equipped with an iris and
computer-controlled shutter, was delivered to the quartz plate in the
rheometer via a liquid light guide. The filter was a 420 nm (20 nm FWHM)
bandpass filter, which simulates the light emitted from a TL03 bulb. The
intensity of the radiation, measured at the surface of the quartz window with
an IL1400A radiometer, was controlled to ± 0.02 mW/cm2 with an iris. The
temperature was controlled at 45 ± 0.1 °C. After approximately 1 mL of the de-
gassed reactive mixture was placed on the lower plate of the rheometer, the
25 mm diameter upper plate was lowered to 0.500 ± 0.001 mm above the
lower plate, where it was held until after the reaction reached the gel point.
The sample was allowed to reach thermal equilibrium (~4 minutes, determined
by the leveling-off of the steady shear viscosity) before the lamp shutter was
opened and the reaction begun. During this time while the sample was
reaching thermal equilibrium, the sample chamber was purged with nitrogen
gas at a rate of 400 seem. During the reaction the rheometer continuously
monitored the strain resulting from an applied dynamic stress (fast oscillation
mode), where time segments of less than a complete cycle were used to
calculate the strain at the applied programmable stress. The computer
calculated the dynamic shear modulus (C), loss modulus (G"), and viscosity
(v*), as a function of exposure time. As the reaction proceeded the shear
modulus increased from 0.1 MPa, and tan 6 (=G7G') dropped from
near infinity to less than 1. For measurements made herein the gel time is the
time at which tan 6 equals 1 .(the crossover point when G'=G"). At the time
that G' reaches 100 Pa (shortly after the gel point), the restriction on the upper
plate was removed so that the gap between the upper and lower plates can
change as the reactive monomer mix shrinks during cure.
It will be appreciated that all of the tests specified above have a certain
amount of inherent test error. Accordingly, results reported herein are not to
be taken as absolute numbers, but numerical ranges based upon the
precision of the particular test.
In order to illustrate the invention the following examples are included.
These examples do not limit the invention. They are meant only to suggest a
method of practicing the invention. Those knowledgeable in contact lenses as
well as other specialties may find other methods of practicing the invention.
However, those methods are deemed to be within the scope of this invention.
The following abbreviations are used in the examples below:
SiGMA 2-propenoic acid, 2-methyl-2-hydroxy-3-[3-[1,3,3,3-tetramethyl-
HEMA 2-hydroxyethyl methacrylate
mPDMS 800-1000 MW (Mn) monomethacryloxypropyl terminated mono-
n-butyl terminated polydimethylsiloxane
CG11850 1:1 (wgt) blend of 1-hydroxycyclohexyl phenyl ketone and
PVP poly(N-vinyl pyrrolidone) (K value 90)
Blue HEMA the reaction product of Reactive Blue 4 and HEMA, as described
in Example 4 of U.S. Pat. no. 5,944,853
IPA isopropyl alcohol
mPDMS-OH mono-(3-methacryloxy-2-hydroxypropyloxy)propyl terminated,
mono-butyl terminated polydimethylsiloxane (MW 1100)
TEGDMA tetraethyleneglycol dimethacrylate
TrEGDMA triethyleneglycol dimethacrylate
TRIS-HEMA 2-trimethylsiloxyethyl methacrylate
MMA methyl methacrylate
TBACB tetrabutylammonium 3-chlorobenzoate
TMI 3-isopropenyl- DD-dimethylbenzyl isocyanate
IPL isopropyl lactate
CGI 819 2,4,6-trimethylbenzyldiphenyl phosphine oxide
Throughout the Examples intensity is measured using an IL1400A
radiometer, using an XRL 140A sensor.
The reaction components and diluent (D30) listed in Table 1 were
mixed together with stirring or rolling for at least about 3 hours at 23°C, until
all components were dissolved. The reactive components are reported as
weight percent of all reactive components and the diluent is weight percent of
reaction mixture. The reaction mixture was placed into thermoplastic contact
lens molds (made from Topas® copolymers of ethylene and norbomene
obtained from Ticona Polymers), and irradiated using Philips TL 20W/03T
fluorescent bulbs at 45°C for about 20 minutes N2. The molds were opened
and lenses were extracted into a 50:50 (wt) solution of IPA and H2O, and
soaked in IPA at ambient temperature for about 15 hours to remove residual
diluent and monomers, placed into deionized H2O for about 30 minutes, then
equilibrated in borate buffered saline for at least about 24 hours and
autoclaved at 122°C for 30 minutes. The properties of the resulting lenses
are shown in Tablet
The results of Examples 1-10 show that the reaction mixture
components and their amounts may be varied substantially, while still
providing uncoated lenses having an excellent balance of mechanical
properties and wettability. The contact angle (DCA) of Example 9 may be too
high to form a lens that would be clinically wettable, and the modulus may be
lower than desired to provide a mechanically robust lens. Example 9
contained the lowest concentration of SiGMA (20%). Because the SiGMA
had been reduced, less PVP could be added to the formulation and still
provide a compatible reaction mixture. Thus, these examples show that
SiGMA is effective in compatibilizing PVP and that when sufficient SiGMA and
PVP are present lenses with desirable wettability and other mechanical
properties can be made without any form of surface modification.
Lenses having the formulation of Example 1 were remade, without
controlling cure intensity. The mechanical properties are reported in Table 2,
below. These lenses were clinically evaluated using ACUVUE® 2 lenses as
controls. The test lenses were worn in one eye and an ACUVUE®2 lens was
worn on the contralateral eye. The lenses were worn by 6 patients in a daily
wear mode (nightly removal) for a period of one week. At one week the
PLTF-NIBUT was 3.6 (±3.0) seconds compared to 5.8 (±2.5) seconds for
ACUVUE® 2 lenses. The front surface deposition was graded none to slight
for 50% of the test lenses and 100% for the control lenses. The movement
was acceptable for both test and control lenses.
Example 11 was repeated except that the cure intensity was reduced
to 1.0 mW/cm2. The mechanical properties are reported in Table 2, below.
These lenses were clinically evaluated using ACUVUE® 2 lenses as controls.
The test lenses were worn by 15 patients in a daily wear mode (nightly
removal), in one eye for a period of one week and an ACUVUE® 2 lens was
worn in the contralateral eye. At one week the PLTF-NIBUT was 8.2 (±1.7)
seconds compared to 6.9 (±1.5) seconds for ACUVUE® 2 lenses. The front
surface deposition was graded none to slight for all of the patients for both
test and control lenses. The movement was acceptable for both test and
Generally the mechanical properties for Examples 1,11 and 12 are
consistent results for multiple runs of the same material. However, the clinical
results for Examples 11 (uncontrolled cure intensity) and 12 (low, controlled
cure intensity) are substantially different. The on eye wettability after one
week of wear for Example 11 (measured by PLTF-NIBUT) was worse that the
ACUVUE® 2 lenses (3.6 v. 5.8) and half the lenses had more than slight
surface depositions. The Example 12 lenses (controlled, low intensity cure)
displayed significantly improved on-eye wettability, which was measurably
better than ACUVUE® 2 lenses (8.2 v. 6.9) and no surface depositions. Thus,
using a low, controlled cure provides an uncoated lens having on-eye
wettability which is as good as, and in some cases better than conventional
Reaction mixtures described in Table 3 and containing low or no
compatibilizing component (in these Examples SiGMA) were mixed with
constant stirring at room temperature for 16 hours. Even after 16 hours each
of the reaction mixtures remained cloudy and some contained precipitates.
Accordingly, these reaction mixtures could not be used to produce lenses.
Examples 13 through 15 show that reaction mixtures without any
compatibilizing component (SiGMA or mPDMS-OH) are incompatible, and not
suitable for making contact lenses. Examples 16 and 17 show that
concentrations of compatibilizing component less than about 20 weight% are
insufficient to compatibilize signifincant amounts of high molecular weight
PVP. However, comparing Example 17 to Example 9, lesser amounts of high
molecular weight PVP (3 weight %) can be included and still form a
compatible reaction mixture.
A solution of 1.00 gram of D30,1.00 gram of mPDMS and 1.00 gram
of TRIS was placed in a glass vial (Ex. 18). As the blend was rapidly stirred at
about 20 to 23 'C with a magnetic stir bar, a solution of 12 parts (wt) PVP
(K90) and 60 parts DMA was added dropwise until the solution remained
cloudy after 3 minutes of stirring. The mass of the added DMA/PVP blend
was determined in grams and reported as the "monomer compatibility index".
This test was repeated using SiGMA (Ex. 19), MBM (Ex. 20), MPD (Ex. 21),
acPDMS, where n=10 (Ex. 22), acPDMS where n=20 (Ex. 23), iSiGMA-3Me
(Ex. 24) and TRIS2-HOEOP2 (Ex. 25) as test silicone monomers in place of
The results, shown in Table 4, show that SiGMA, acPDMS (where n= 10 and
20) and mPDMS-OH more readily incorporate into a blend of a diluent,
another silicone containing monomer, a hydrophilic monomer, and an high
molecular weight polymer (PVP) than alternative silicone-containing
monomers. Thus, compatibilizing silicone containing monomers having a
compatibility index of greater than about 0.5 are useful for compatibilizing high
molecular weight hydrophilic polymers like PVP.
Example 27 -35
Lenses were made using the reaction mixture formulation of Example
1. The plastic contact lens molds (made from Topas® copolymers of ethylene
and norbornene obtained from Ticona Polymers) were stored overnight in
nitrogen ( mixture. Molds were closed and lenses photocured using the times and cure
intensities indicated in Table 5. Lenses were formed by irradiation of the
monomer mix using visible light fluorescent bulbs, curing at 45°C. The
intensity was varied by using a variable balast or light filters, in two steps of
varied intensity and cure time. The step 2 time was selected to provide the
same total irradiation energy (about 830 mJ/cm2) for each sample.
The finished lenses were demolded use a 60:40 mixture of isopropyl
alcohol/DI water. The lenses were transferred to a jar containing 300 g 100%
isopropyl alcohol (IPA). The IPA was replaced every 2 hours for 10 hours. At
the end of about 10 hours, 50% of the IPA was removed and replaced with Dl
water and the jar was rolled for 20 minutes. After 20 minutes, 50% of the IPA
was removed and replaced with Dl water and the jar was rolled for another 20
minutes. The lenses were transferred to packing solution, rolled for 20
minutes and then tested.
The contact angles for Examples 27 through 232 are not significantly
different, indicating that step 1 cure intensities of less than about about 2
mW/cm2 provide improved wettability for this lens formulation regardless of
the step 1 cure time. However, those of skill in the art will appreciate that
shorter step 1 cure times (such as those used in Examples 28 and 31) allow
for shorter overall cure cycles. Moreover, it should be noted that even though
the contact angles for Examples 33 through 35 are measurably higher than
those of Examples 27-32, the lenses of Examples 33-35 may still provide
desirable on eye wettability.
The reaction components of Example 1, were blended with either 25%
or 40% D30 as diluent in accordance with the procedure of Example 1. The
resultant reaction mixtures were charged into plastic contact lens molds
(made from Topas® copolymers of ethylene and norbornene obtained from
Ticona Polymers) and cured in a glove box under a nitrogen atmosphere, at
about 2.5 mW/cm2 intensity, about 30 minutes and the temperatures shown in
Table 6, below. The lenses were removed from the molds, hydrated and
autoclaved as describe in Example 1. After hydration the haze values of the
lenses were determined. The results shown in Table 6 show that the degree
of haziness was reduced at the higher temperatures. The results also show
that as the concentration of diluent decreases the haze also decreases.
The results in Table 6 show that haze may be reduced by about 20%
(Example 41 v. Example 39) and up to as much as about 65% (Example 37 v.
Example 36) by increasing the cure temperature. Decreasing diluent
concentration from 40 to 25% decrease haze by between about 40 and 75%.
Lenses were made from the formulations shown in Table 8 using the
procedure of Example 1, with a 30 minute cure time at 25°C and an intensity
of about 2.5 mW/cm2. Percent haze was measured and is reported in Table
A comparison of the results for formulations having the same amount
of diluent and either TEGDMA or acPDMS (Examples 42 and 46 and
Examples 43 and 47) shows that acPDMS is an effective crosslinker and
provides lenses with properties which are comparable to those where
TEGDMA is used as a crosslinker. Examples 44 and 45 contain both
crosslinkers. Haze for these Examples decreased substantially compared to
the lenses made from either crosslinker alone. However, modulus and
elongation were negatively impacted (likely because the amount of crosslinker
was too great).
Reaction mixtures were made using the formulations shown in Table 8
with a mixture of 72.5% t-amyl alcohol and 27.5% PVP (Mw = 2500) as the
diluent. The reaction mixtures were placed into thermoplastic contact lens
molds, and irradiated using Philips TL 20W/03T fluorescent bulbs at 45°C, 0.8
mW/cm2 for about 32 minutes. The molds were opened and lenses were
released into deionized water at 95°C over a period of 20 minutes. The
lenses were then placed into borate buffered saline solution for 60 minutes
and autoclaved at 122°C and 30 minutes. The properties of the resulting
lenses are shown in Table 9.
B = t-amyl alcohol
C = 15/38/38% TMP/2M2P/ PVP (Mw = 2500)
D= 57/43 2M2P/TMP
NT - not tested
Thus, Examples 48, 51 show that formulations comprising both
hydrophilic (EGDMA or TEGDMA) and hydrophobic crosslinkers (acPDMS)
provide silicone hydrogel compositions which display an excellent balance of
properties including good water content, moderate Dk, wettabiltiy, modulus
The lenses of Example 48 were clinically evaluated. The lenses were
worn by 18 patients in a daily wear mode (nightly removal) for a period of one
week. At one week the PLTF-NIBUT was 8.4 (±2.9) seconds compared to 7.0
(±1.3) seconds for ACUVUE® 2 lenses. The front surface discrete deposition
was graded none to slight for 97% of the patients with the test lenses,
compared with 89% in control lenses. The movement was acceptable for
both test and control lenses.
The lenses of Example 49 were clinically evaluated. The lenses were
worn by 18 patients in a daily wear mode (nightly removal) for a period of one
week. At one week the PLTF-NIBUT was 8.4 (±2.9) seconds compared to 7
(±1.3) seconds for ACUVUE® 2 lenses. The front surface discrete deposition
was graded none to slight for 95% of the patients with the test lenses,
compared with 89% in control lenses. The movement was acceptable for
both test and control lenses.
The lenses of Example 51 were clinically evaluated. The lenses were
worn by 13 patients in a daily wear mode (nightly removal) for a period of one
week. At one week the PLTF-NIBUT was 4.3 (±1.9) seconds compared to 9.6
(±2.1) seconds for ACUVUE® 2 lenses. The front surface discrete deposition
was graded none to slight for 70% of the patients with the test lenses,
compared with 92% in control lenses. The movement was acceptable for
both test and control lenses. Thus, there is some correlation between contact
angle measurements (108° for Example 51 versus 52° for Example 48) and
clinical wettability as measure by PLTF-NIBUT (4.3 seconds for Example 51
versus 8.4 seconds for Example 48).
Silicone hydrogel lenses were made using the components listed in
Table 9 and the following procedure:
The components were mixed together in a jar to for a reaction mixture.
The jar containing the reaction mixture was placed on a jar mill roller and
The reaction mixture was placed in a vacuum desiccator and the
oxygen removed by applylng vacuum for 40 minutes. The desiccator was
back filled with nitrogen. Contact lenses were formed by adding
approximately 0.10 g of the degassed lens material to the concave front curve
side of TOPAS® mold cavities in a glove box with nitrogen purge. The molds
were closed with polypropylene convex base curve mold halves.
Polymerization was carried out under a nitrogen purge and was photoinitiated
with 5 mW cm2 of visible light generated using 20W fluorescent lights with a
TL-03 phosphor. After curing for 25 minutes at 45oC, the molds were opened.
The concave front curve portion of the lens mold was placed into a sonication
bath (Aquasonic model 75D) containing deionized water under the conditions
(temperature and amount of Tween) shown in Table 10. The lens deblock
time is shown in Table 10. The lenses were clear and of the proper shape to
be contact lenses.
The lenses of Example 59 which were deblocked in Example 66, were
further hydrated in deionized water at 65°C for 20 minutes. The lenses were
then transferred into borate buffered saline solution and allowed to equilibrate
for at least about 24 hours. The lenses were clear and of the proper shape to
be contact lenses. The lenses had a water content of 43%, a modulus of 87
psi, an elongation of 175%, and a Dk of 61 barriers. The lenses were found to
have an advancing contact angle of 57 degrees. This indicates the lenses
were substantially free of hydrophobic material.
The concave front curve portion of the lens mold from Example 61 was
placed into a sonication bath (Aquasonic model 75D) containing about 5%
DOE-120 in deionized water at about 75°C. The lenses deblocked from the
frame in 18 minutes.
Example 71 fuse of an organic solvent)
The concave front curve portion of the lens mold from example 61 was
placed into a sonication bath (Aquasonic 75D) containing about 10% of 2-
propanol an organic solvent in deionized water at 75°C. The lenses
deblocked form the frame in 15 minutes. When Tween was used as the
additive (Example 68) the deblock time was 18 minutes. Thus, the present
example shows that organic solvents may also be used to deblock lenses
comprising low molecular weight hydrophilic polymers.
EXAMPLE 72 fcontains no low molecular weight PVP)
Silicone hydrogel lenses wee made using the formulation and
procedure of Example 58, but without any low molecular weight PVP. The
following procedure was used to deblock the lenses.
The concave front curve portion of the lens mold was placed into a
sonication bath (Aquasonic model 75D) containing about 850ppm of Tween in
deionized water at about 65°C. The lenses did not release from the mold.
The deblock time for the formulation which contained low molecular weight
hydrophilic polymer (Example 58 formuation) under similar deblock conditions
(Example 62 - 850 ppm Tween and 75°C) was 10 minutes. Thus, the present
Example shows that deblocking cannot be accomplished in water only, in this
formulation without including low molecular weight hydrophilic polymer in the
The concave front curve portion of the lens mold from example 72 was
placed into a sonication bath (Aquasonic 75D) containing about 10% of 2-
propanol an organic solvent in deionized water at 75°C. The lenses
deblocked form the frame in 20 to 25 minutes. Thus, lenses of the present
invention which do not contain low molecular weight hydrophilic polymer may
be deblocked using an aqueous solution comprising an organic solvent.
Formulations were made according to Example 49, but with varylng
amounts of photoinitiator (0.23,0.38 or 0.5 wt.%), curing at 45°C with Philips
TL 20W/03T fluorescent bulbs (which closely match the spectral output of the
visible light used to measure gel time) irradiating the molds at 2.0 mW/cm2.
The advancing contact angles of the resulting lenses are shown in Table 11.
Gel times were measured for the formulation of Example 1 at 45°C at
1.0,2.5 and 5.0 mW/cm2. The results are shown in Table 12.
The results of Examples 74 through 76 and 77 through 79 compared
with Examples 27-35, show that as gel times increase, wettability improves.
Thus, gel points can be used, in coordination with contact angle
measurements, to determine suitable cure conditions for a given polymer
formulation and photoinitiator system.
Example 80 (Macromer Preparation)
To a dry container, which was housed in a dry box under nitrogen at
ambient temperature was added 30.0 g (0.277 mol) of
bis(dimethylamino)methylsilane (a water scavenger), a solution of 13.75 ml of
a 1M solution of TBACB (386.0 g TBACB in 1000 ml dry THF), 61.39 g (0.578
mol) of p-xylene, 154.28 g (1.541 mol) methyl methacrylate (1.4 equivalents
relative to initiator), 1892.13 (9.352 mol) 2-(trimethylsiloxy)ethyl methacrylate
(8.5 equivalents relative to initiator) and 4399.78 g (61.01 mol) of THF. This
mixture was charged to a dry, three-necked, round-bottomed flask equipped
with a thermocouple and condenser, all connected to a nitrogen source.
The initial mixture was cooled to 15 °C while stirring and purging with
nitrogen. After the solution reached 15 °C, 191.75 g (1.100 mol) of 1 -
trimethylsiloxy-1-methoxy-2-methylpropene (1 equivalent) was injected into
the reaction vessel. The reaction was allowed to exotherm to approximately
62 °C and then 30 ml of a 0.40 M solution of 154.4 g TBACB in 11 ml of dry
THF was metered in throughout the remainder of the reaction. After the
temperature of reaction reached 30 °C and the metering began, a solution of
467.56 g (2.311 mol) 2-(trimethylsiloxy)ethyl methacrylate (2.1 equivalents
relative to the initiator), 3636.6. g (3.463 mol) n-butyl
monomethacryloxypropyl-polydimethylsiloxane (3.2 equivalents relative to the
initiator), 3673.84 g (8.689 mol) TRIS (7.9 equivalents relative to the initiator)
and 20.0 g bis(dimethylamino)methylsilane was added.
This mixture was allowed to exotherm to approximately 3842 °C and
then allowed to cool to 30 °C. At that time, a solution of 10.0 g (0.076 mol)
bis(dimethylamino)methylsilane, 154.26 g (1.541 mol) methyl methacrylate
(1.4 equivalents relative to the initiator) and 1892.13 g (9.352 mol) 2-
trimethylsiloxy)ethyl methacrylate (8.5 equivalents relative to the initiator) was
added and the mixture again allowed to exotherm to approximately 40 °C.
The reaction temperature dropped to approximately 30 °C and 2 gallons of
THF were added to decrease the viscosity. A solution of 439.69 g water,
740.6 g methanol and 8.8 g (0.068 mol) dichloroacetic acid was added and
the mixture refluxed for 4.5 hours to remove the trimethylsiloxy protecting
groups on the HEMA. Volatiles were then removed and toluene added to aid
in removal of the water until a vapor temperature of 110 °C was reached.
The reaction flask was maintained at approximately 110 °C and a
solution of 443 g (2.201 mol) TMI and 5.7 g (0.010 mol) dibutyltin dilaurate
were added. The mixture was reacted until the isocyanate peak was gone by
IR. The toluene was evaporated under reduced pressure to yleld an off-white,
anhydrous, waxy reactive macromer. The macromer was placed into acetone
at a weight basis of approximately 2:1 acetone to macromer. After 24 hrs,
water was added to precipitate out the macromer and the macromer was
filtered and dried using a vacuum oven between 45 and 60 °C for 20-30 hrs.
Reaction mixtures were made in a nitrogen-filled glove box using the
formulations shown in Table 12 with a D30 and/or IPL as the diluent. The
reaction mixtures were placed into thermoplastic contact lens molds, and
irradiated using Philips TL 20W/03T fluorescent bulbs at 50°C, for about 60
minutes. The molds were opened and lenses were released IPA, leached
and transferred into borate buffered saline. The properties of the resulting
lenses are shown in Table 13.
The lenses of Example 83 were clinically evaluated. The lenses were
worn by 10 patients in a daily wear mode (nightly removal) for a period of 30
minutes. For each patient, the test lens was worn in one eye and an Bauch &
Lomb Purevision lens was worn in the contralateral eye. At thirty minutes the
PLTF-NIBUT was 7.5 (±1.6) seconds compared to 8.6 (+1.6) seconds for the
Bausch & Lomb Purevision lens. . The front surface discrete deposition was
graded none to slight for 100% of the patients with the test lenses, compared
with 100% in control lenses. The movement was acceptable for both test and
control lenses. The lenses of the present invention are comparable in
performance to the B&L lens, which has a plasma coating. Thus, the present
Example shows that lenses formed from a polymer network comprising a
siloxane containing macromer, high molecular weight hydrophilic polymer and
a compatibilizing component display good wettability and deposition
resistance without a coating.
Trifluoromethane sulfonic acid (2.3 ml) was added to 27.8 g 1,3-
bis(hydroxybutyl)tetramethyldisiloxane and 204.4 g
octamethylcyciotetrasiloxane. The resulting solution was stirred overnight.
17.0 g Na2C03 were added and the mixture was stirred for one hour. About
50 ml hexane was added and the mixture was stirred for about one hour, then
filtered. The hexane was evaporated under reduced pressure and cyclics
were removed by heating to 110°C at hydroxybutyl terminated polydimethylsiloxane.
In a separate flask 12.2 g CH2OH terminated Fluorolink® Polymer
Modifier D10 with an average equivalent weight of 500 (Ausimont USA,
equivalent to Fomblin® ZDOL) was combined with 11.8 mg dibutyltin
dilaurate. The resulting solution was evacuated to about 20 mBar twice, each
time refilling with dry N2. 5.0 ml isophorone diisocyanate was added and the
mixture was stirred overnight under N2 to produce a clear viscous product.
47.7 g of the hydroxybutyl terminated polydimethylsiloxane from above
was combined with 41.3 grams anhydrous toluene. This solution was
combined with the Fluorolink®-lsophorone diisocyanate product and the
resulting mixture was stirred under nitrogen overnight. The toluene was
evaporated from the product over about 5 hours at isocyanatoethyl methacrylate was added and the resulting mixture was stirred
under N2 for four days to produce a slightly opaque viscous liquid
2.60 g of the fluorosilicone macromer made in Example 90 was
combined with 1.12 g ethanol, 1.04 g TRIS, 1.56 g DMA, 32 mg Darocur 1173
to produce a slightly hazy blend containing 18% diluent (ethanol). Contact
lenses were made from this blend in plastic molds (Topas) curing 30 minutes
under fluorescent UV lamps at room temperature in a N2 atmosphere. The
muds were opened, and the lenses released (deblocked) into ethanol. The
lenses were leached with CH2Cl2 and then IPA for about 30 minutes each at
room temperature, then placed into borate buffered saline for about 2 hours
and then autoclave at 121 °C for 30 minutes. The resulting lenses were tacky
to the touch and had a tendency to stick to each other. The advancing DCA
of these lenses was measured and is shown in Table 14.
Reaction mixtures were made using the reactive components (amounts
based upon reactive components) shown in Table 14 and D30 as a diluent.
The amount of D30 is based upon the total amount of reactive components
and diluent. The reaction mixture and lenses were made using procedure of
Example 91. The resulting lenses were slippery to the touch and did not stick
to each other.
The advancing DCA of these lenses was measured and is shown in
Table 14, below.
Examples 92 through 94 clearly show that hydrophilic polymer may be
used to improve wettability. In these Examples contact angles are reduced by
up to about 50% (Example 93) and up to about 60% (Example 94).
Compositons comprising higher amounts of fluorosilicone macromer and
hydrophilic polymer can also be made by functionalizing the fluorosilicone
macromer to include active hydrogens.
Reaction mixtures were made using reactive components shown in
Table 15 and 29% (based upon all reactive components and diluent) t-amyl
alcohol as a diluent and 11% PVP 2,500 (based upon reactive components).
Amounts indicated are based upon 100% reactive components. The reaction
mixtures were placed into thermoplastic contact lens molds, and irradiated
using Philips TL 20W/03T fluorescent bulb at 60°C, 0.8 mW/cm2 for about 30
minutes under nitrogen. The molds were opened and lenses were released
into deionized water at 95°C over a period of 15 minutes. The lenses were
then placed into borate buffered saline solution for 60 minutes and autoclaved
at 122° C for 30 min. The properties of the resulting lenses are shown in
Table 15 shows that the addition of PVP dramatically decreases
contact angle. As little as 1% decreases the dynamic contact angle by about
10% and as little as 3% decreases dynamic contact angle by about 50%.
These improvements are consistent with those observed for macromer based
polymers, such as those in Examples 92-94.
Preparation of mPDMS-OH (used in Examples 3)
96 g of Gelest MCR-E11 (mono-(2,3-epoxypropyl)-propyl ether
terminated polydimethylsiloxane(1000 MW)), 11.6 g methacrylic acid, 0.10 g
triethylamine and 0.02 g hydroqiinone monomethylether were combined and
heated to 140°C with an air bubbler and with stirring for 2.5 hours. The
product was extracted with saturated aqueous NaHCO3 and CH2Cl2. The
CH2Cl2 layer was dried over Na2 SO4 and evaporated to give 94 g of product.
HPLC/MS was consistent with desired structure:
WE CLAIM :
1. A method comprising the steps of (a) mixing reactive components
comprising 15-25 wt% of high molecular weight hydrophilic polymer having
molecular wt between 100,000 to 150,000 Daltons and an effective amount of a
compatibilizing component and (b) curing the product of step (a) at or above a
minimum gel time, to form a ophthalmic lens wherein the said lens has an
advancing dynamic contact angle of 80° or less.
2. The method as claimed in claim 1, wherein said ophthalmic lens is a contact lens.
3. The method as claimed in claim 1, wherein said lens comprises an
advancing dynamic contact angle of 70° or lens.
4. The method as claimed in claim 1, wherein said lens comprises a tear film
break up time of at least 7 seconds.
5. The method as claimed in claim 1, wherein said reactive components
optionally comprises at least one initiator.
6. The method as claimed in claim 5, wherein said cure is conducted via
irradiation and said conditions comprise an initiator concentration and cure
intensity effective to provide said minimum gel time.
7. The method as claimed in claim 6, wherein said initiator is present in an
amount up to 1% based upon all reactive components.
8. The method as claimed in claim 6, wherein said initiator is present in an
amount less than 0.5% based upon all reactive components.
9. The method as claimed in claim 6, wherein said cure is conducted via
irradiation at an intensity of less than 5 mW/cm2 .
10. The method as claimed in claim 6, wherein said gel time is at least about
11. The method as claimed in claim 6, wherein said gel time is at least about
12. The method as claimed in claim 1, wherein said compatibilizing
component is not a hydroxyl functionalized macromer made by group transfer
13. The method as claimed in claim 1, wherein said reactive components
further comprise at least one macromer.
14. The method as claimed in claim 13, wherein said compatibilizing
component is not a hydroxyl functionalized macromer made by group transfer
15. A method for improving the wettability of an ophthalmic device formed
from a reaction mixture as defined in step (a) of claim 1, comprising adding at
least one high molecular hydrophilic weight polymer and a compatibilizing
effective amount of at least one compatibilizing component to said reaction
mixture, wherein said compatibilizing component is not a styrene
functionalized prepolymer made from hydroxyl functional methacrylates.
16. The method as claimed in claim 15, wherein said compatibilizing
component has a compatibility index of greater than 0.5.
17. The method as claimed in claim 15, wherein said compatibilizing
component has a compatibility index of greater than 1.
18. The method as claimed in claim 15, wherein said compatibilizing
component comprises at least one siloxane group.
19. The method as claimed in claim 18, wherein said compatibilizing
component further comprises hydroxyl functionality and has a Si to OH ratio of
less than 15:1.
20. The method as claimed in claim 18, wherein said compatibilizing
component has a Si to OH ratio of between 1:1 to 10:1.
Title: A METHOD FOR IMPROVING THE WETTABILITY OF AN OPTHALMIC DEVICE
A method comprising the steps of (a) mixing reactive components comprising
15-25 wt% of high molecular weight hydrophilic polymer having molecular wt
between 100,000 to 150,000 Daltons and an effective amount of a
compatibilizing component and (b) curing the product of step (a) at or above a
minimum gel time, to form a ophthalmic lens wherein the said lens has an
advancing dynamic contact angle of 80° or less.
|Indian Patent Application Number||337/KOLNP/2008|
|PG Journal Number||28/2013|
|Date of Filing||24-Jan-2008|
|Name of Patentee||JOHNSON & JOHNSON VISION CARE, INC.|
|Applicant Address||7500 CENTURION PARKWAY, SUITE 100, JACKSONVILLE, FL 32256, UNITED STATES OF AMERICA|
|PCT International Classification Number||A61L 27/18|
|PCT International Application Number||PCT/US2002/28614|
|PCT International Filing date||2002-09-09|