Title of Invention

POLYETHYLENE MOLDING POWDER AND PORUS ARTICLE MADE THEREFROM

Abstract A molding powder comprising a polyethylene polymer, wherein the polyethylene polymer has a molecular weight in the range of from 800,000 g/mol to 1,800,000 g/mol as determined by ASTM 4020, an average particle size in the range of from 5 microns to 1000 microns, and a powder bulk density in the range of from 0.10 to 0.30 g/cc.
Full Text POLYETHYLENE MOLDING POWDER AND
POROUS ARTICLES MADE THEREFROM
Priority Claim
This application is based upon United States Provisional Application Serial
No. 60/578,005 titled "Polyethylene Resin and Porous Articles Made Therefrom,"
filed June 7, 2004, the priority of which is hereby claimed.
Field of Invention
The invention relates to the field of synthetic polymer materials for
molding porous articles. In particular, the invention is directed to a new
polyethylene molding resin which can be shped and sintered to form articles
having high porosity.
Background
Ultra-high-molecular weight polyethylene (UHMW-PE), standard high-
density polyethylene (HDPE) and low-density polyethylene (LDPE) have all been
used as polymeric materials for producing different types of molded porous
articles. Such articles include filter funnels, immersion filters, filter crucibles,
porous sheets, pen tips, marker nibs, aerators, diffusers and light weight molded

parts. However, the polyethylene formulations used in these applications arc all
associated with various disadvantages.
LDPE and standard HDPE, which include polyethylene of molecular
weight up to 250,000 g/mol, yield good part strength but their melt behavior
results in a narrow processing window with respect to both time and temperature.
As result, there is a strong tendency toward reduced porosity and an increased
quality inconsistency in the molded product. Furthermore, with LDPE or standard
HDPE as the molding powder, the non-uniformity of heating within molds having
complex geometric conduits tends to result in non-uniformity in the porosity of the
product part.

In contrast to LDPE and standard HDPE, UHMW-PE formulations with an
average molecular weight above 2,500,000 g/mol exhibit excellent processing
forgiveness. Specifically, it is known in the art that UHMW-PE molding powders
are characterized by a wide time and temperature processing window. However,
these UHMW-PE formulations are known to result in rather weak molded
products. Moreover, regional weak spots tend to be formed when UHMW-PE is
used with molds having a complex geometric conduit. To maintain or improve the
strength of porous articles made from UHMW-PE, US 4,925,880 to Stein discloses
the addition of a polyethylene wax to the UHMW-PE particles. Stein teaches to
add the wax in an amount between 5-60% to improve strength and porosity.
However, the use of polyethylene wax in this manner restricts the time and
temperature processing window and is thus associated with the same disadvantages
as using LDPE and standard HDPE.
High molecular weight polyethylenes are valued for properties such as
chemical resistance, abrasion resistance, strength, water absorption, energy
absorption, heat deflection, and sound-dampening capabilities. Processes for
preparing high molecular weight polyethylenes are known in the art. United States
Patent No. 4,962,167 to Shiraishi et at. discloses a process for making
polyethylene powder by polymerizing ethylene using a solid catalyst component
and an organometallic compound. According to the '167 patent the polyethylene
powder is reported to have bulk densities from 0.30 g/cc to 0.34 g/cc with particle
diameters ranging from 195 to 245 microns.
Another process for making high molecular weight polyethylene is
disclosed by United States Patent No. 4,972,035 to Suga et al., whereby
polymerization is carried out in the presence of a Ziegler catalyst and the
polyethylene is subjected to a high-speed shearing treatment. The morphologies of
the particles in Suga et al. are stated to be substantially spherical, with elliptical or
cocoon-like shapes.

United States Patent No. 5,587,440 to Ehlers el al. discloses a method for
making high molecular weight polyethylene powder with bulk densities ranging
from 350 to 460 g/liter using Ziegler type catalysts.
Methods for producing porous articles from high molecular weight
polyethylene powders are likewise known. United States Patent No. 3,024,208, to
Goethel et al. discloses a process for forming porous bodies by placing the
polyethylene powder into containers and heating it under slight pressure. The
porous articles produced by the process in Goethel et al. are reported to have
densities ranging from 0.33 g/cc to 0.66 g/cc and porosities between 32 and 67 %.
Still further processes for making polyethylene articles are noted below.
PCT Application Publication No. WO 85/04365 discloses a sintering
process whereby high molecular weight polyethylene powder is pre-compacted
under pressure and heat to increase its bulk density. The compacted powders are
reported to have bulk densities that are greater than 0.4 g/cc. The bulk density is
increased by altering the particles' morphologies (removing the "fine structure")
by passing the powder through a pellet or roll mill. The particle morphology of
high molecular weight polyethylene can affect the compaction and sintering
behavior of the powder. See, Sangeeta Hambir and J P Jog, Sintering of Ultra
High Molecular Weight Polyethylene, Bull. Mater. Sci., v. 23, No. 3 (June 2000).
United States Patent No. 5,977,229 to Barth et al. and United States Patent
No. 3,954,927, discloses porous articles, particularly filters, which are sintered
from high molecular weight polyethylene.
Copending U.S. patent application serial no. 10/640,830 discloses a process
for forming a porous article using a molding powder comprising a polyethylene
polymer having a molecular weight in the range of about 800,000 to about
3,500,000 as determined by ASTM-D 4020, and a particle size distribution in the

range of about 10 microns to about 1,000 microns. The particles are spherical in
shape. Commercial examples of resins which can be successfully used in this
process are GUR® 4012 and 4022, produced by Ticona LLC (Florence, KY).
These materials have a powder bulk density in the range of 0.38 to 0.55 gm/cc.
Although GUR® 4012 and 4022 can be shaped and sintered to yield articles having
good porosity! there is still a need for improved polyethylene resins for preparation
of articles having well-controlled porosity and good mechanical strength.
Summary of the Invention
According to one aspect of the present invention, a molding powder
comprising polyethylene polymer particles is provided. The polyethylene polymer
has a molecular weight within the range of about 600,000 g/mol to about
2,7.00,000 g/mol as determined by ASTM 4020. The polyethylene polymer has an
average particle size that is within the range of about 5 microns to about 1000
microns, and the polyethylene has a powder bulk density in the range of about 0.10
to about 0.30 g/cc.
The polyethylene polymer typically has a molecular weight ranging from
about 750000 g/mol to about 2,400,000 g/mol, and is preferably in between about
800,000 and about 1,800,000 g/mol. A particularly preferred range is from about
900,000 to about 1,500,000 g/mol. Generally, the polyethylene has a powder bulk
density of from about 0.12 to 0.26 grams per cubic centimeter.
The molding powders of the present invention have especially good
strength characteristics. The powder exhibits a characteristic flexural strength
(defined hereinafter) of at least about 0.7 MPa (megapascals). Preferably the
inventive molding powder exhibits a characteristic flexural strength of at least
about 0.9 MPa, or at least about 1.1 MPa.
In some embodiments of the present invention the molding powder
comprises a polyethylene with a molecular weight of about 1,000,000 g/mol to

about 2,600,000; a particle size of about 5 to about 800 microns; and a powder
bulk density ranging from about 0.12 to 0.29 g/cc. Alternatively, the polymer may
have a molecular weight that ranges from about 1,000,000 g/mol to about
1,800,000 g/mol and have an average particle size that is between about 10 and
200 microns.
In another aspect of the present invention, there is provided a process for
preparing a porous article from the inventive resin powder. The molding powder
comprises polyethylene with a molecular weight between about 600,000 and
2,700,000 g/mol; an average particle size ranging from about 5 to about 1000
microns; and a powder bulk density between about 0.10 and 0.30 g/cc. The
powder is formed into the desired shape and heated to a temperature of between
140°C and 300°C for a sufficient time to permit the polymer to expand and soften.
The powder is preferably heated to temperatures of between about 150°C to about
280°C, and even more preferably to about 170 °C to about 260°C. The porous
article is subsequently cooled.
In still another yet another aspect of the present invention there is provided
a porous article that is prepared from a polyethylene powder which has a
molecular weight of between about 600,000 g/mol to about 2,700,000 g/mol; an
average particle size in the range of about 5 microns to about 1,000 microns, and a
powder bulk density in the range of about 0.1 to about 0.3 g/cc. Generally, the
porous article has an average pore size of between about 5 µm and 100 µm and,
even more typically, between about 50 µm and 80 µm. Also, the porous article
usually has a porosity of between about 30 to 85 percent; preferably between about
60 and 75 percent.
Further features and advantages of the present invention will become
apparent from the discussion that follows.

Brief Description of Drawings
The invention is described in detail below with reference to the various
figures wherein like numerals designate similar parts and wherein:
Figure 1 illustrates a filter element according to the present invention;
Figure 2 shows a section through the filter element at the position marked
II-II in Figure l;and
Figure 3 shows a section through the filter element at the position marked
III—III in Figure 1.
Detailed Description
The present invention is described in detail below with reference to the
various examples and appended Figures. Modifications to particular examples
within the spirit and scope of the present invention, set forth in the appended
claims, will be readily apparent to those of skill in the art.
Unless otherwise indicated, terms are to be construed in accordance with
their ordinary meaning. Following are some exemplary definitions of terms used
in this specification and the appended claims.
The present invention provides a new and improved molding powder
comprising polyethylene polymer particles. Specifically, the polyethylene
polymer has a molecular weight within the range of about 600,000 g/mol to about
2,700,000 g/mol. The particle size distribution of the polyethylene polymer
particles is within the range of about 5 microns to about 1000 microns, and the
polymer particles have a powder bulk density in the range of about 0.10 to about
0.30 g/cc.

In accordance with more particular embodiments of the invention, the
molecular weight of the polyethylene polymer may fall within any of the following
molecular weight ranges as determined by ASTM 4020: from about 750,000 g/mol
■+.
to about 2,400,000 g/mol; and from about 800,000 g/mol to about 1,750,000
g/mol. In further embodiments of the invention, the powder bulk density may be
in the range of from about 0.12 to 0.26 g/cc or, preferably, from about 0.18 to
about 0.26 g/cc.
The production of high molecular weight polyethylene is typically
achieved by the catalytic polymerization of ethylene monomer with a
heterogeneous catalyst and Aluminium Alkyl as cocata|yst. The ethylene is
usually polymerized in gaseous phase or slurry phase at relatively low
temperatures and pressures. The polymerization reaction may be carried out at a
temperature of between 50°C and 100°C and pressures in the range of 0,02 and
2MPa.
The molecular weight of the polyethylene can be adjusted by adding
hydrogen. Altering the temperature or the Aluminium alkyl (type and
concentration) may also be used to fine tune the molecular weight. Additionally,
the reaction may occur in the presence of antistatic agents to avoid wall fouling
and product contamination.
Preferred catalysts include Ziegler-Natta type catalysts. Ziegler type
catalysts are typically halides of transition metals from Groups IV-VIII react with
alkyl derivatives of metals or hydrides from Groups I-III. Exemplary Ziegler
catalysts include those based on the reaction products of aluminium and
magnesium alkyls and titanium tetrahalides. Magnesium Chloride and porous fine
grained materials, like silica, may also be used as support. Specifically the
reaction product of Titaniumtetrachloride and Isoprenylaluminium is preferred.

The solid catalyst component results as the reaction product of a diluted Ti
(IV)-chloride and diluted Isoprenylaluminium. The mole ratio (Ti:Al) is between
1:0.01 and 1:4 at a reaction temperature between -40°C and 100°C. The feed of
titaniumtetrachloride is between 0.5 min and 60 min. An aliphatic solvent is used,
which is purified through distillation and mole sieve treatment.
Preferred reaction conditions are a temperature in the range of-20°C and
50°C, most preferred is the range of 0°C and 30°C. The concentration of
titaniumtetrachloride is in the range of 0.1 and 9.1 mole/1, preferred 0.2 and 5
mole/1. The concentration of aluminiumalkyl is in the range 0.02 and 0.2 mol/l.
The titanium component is added to the aluminium component. The dosing time is
in the range of 0.1 min and 60 min, preferred l min to 30 min. The reaction
mixture is cooled or heated to ambient temperature. The amount of Ti (III) is at
least 95% after 10h. The isorenyl is supplied from Crompton; the
titaniumtetrachloride from Akzo. The particle morphology is controlled through
concentration of reactants, reaction temperature and agitation speed.
The polymerization is carried out in suspension at low pressure and
temperature in one or multiple steps, continuous or batch. The polymerization
temperature is in the range of 30°C and 130°C, preferred is the range of 50°C and
90°C. The ethylene partial pressure is in the range of less than 10 MPa, preferred is
the range of 0.05 and 5MPa. Isoprenyl aluminium is used as cocatalyst. The ratio
of Al:Ti is in the range of 1 and 30:1, more preferred is the range of 2:1 and 20:1.
The solvent is an inert organic solvent as typically used for Ziegler type
polymerizations. Examples are butane, pentane, hexane, cyclohexene, nonane,
decane, higher homologous pure or as mixture of these. The polymer molecular
mass is controlled through feeding hydrogen. The ratio ethylene partial pressure
and hydrogen partial pressure is in the range of 5 to 100, preferred is the range of
10 and 50. The polymer is isolated and dried in a fluidized bed drier under
nitrogen. The solvent may be removed through steam distillation in case of using

high boiling solvents. Salts of long chain fatty acids may be added as a stabilizer.
Typical examples are calcium- magnesium or zink-Stearate.
Optionally, other catalysts such as Phillips catalysts, metallocenes and post
metallocenes may be employed, metallocene and postmetallocene catalysts are
also well known. Generally a cocatalyst such as alumoxane is also employed.
United States Patent Application No. 2002/0040113 to Fritzsche et al, the entirety
of which is incorporated herein by reference, discusses several catalyst systems for
producing ultra-high molecular weight polyethylene. The selection of particularly
active catalysts may enable the fluidized bet process to be made continuous.
As stated, the powders of the present invention preferably have molecular
weights between 600,000 g/ mol and 2,700,000 g/mol and a relatively low bulk
density. The powders have a lower bulk density, in part, due to their unique
porous particle morphology. The polyethylene particles of the present invention
typically have a characteristic microglobular appearance. The particles have
irregular geometries with uneven surface features. The particles also have porous
surface features. The porous particle morphology of the polyethylene powder is a
significant factor in contributing to the high porosity of the molded articles made
according to the present invention. In contrast, many conventional high molecular
weight polyethylenes have a relatively spherical particle morphology. Spherical
particles typically have an elliptical shape with relatively smooth surface features.
The morphology of the polymer develops as the particle grows. The break-
up of the catalyst may determine the final particle morphology. The size of the
catalyst particles may also determine the particle size of the polymer. The final
polymer particle is typically 10-50 times as large as the original catalyst particle.
Factors such as particle size, particle morphology, particle size distribution, and
bulk density are significant properties of the powder because they affect the
porosity characteristics of articles which are molded from the powder.

United States Patent No. 5,300,470 to Cuffiani et al. discloses catalysts
used in the production of high molecular weight polyethylene. Cuffiiani notes that
the morphology of the polymer particle substantially replicates that of the catalyst
particle, i.e., morphologic replica. And, the morphology of the catalyst can be
controlled, for example, by precipitating the catalyst components from a liquid
phase under particular conditions. (Cuffiani at col. 1, lines 45-60). EP 1124860 to
Ehlers et al., noted above, discloses Ziegler type catalysts used in the production
of high and ultra high molecular weight polyethylene. The solid catalyst
component is the reaction product of titanium tetrachloride and an aluminium
alkyl. The catalyst morphology is controlled through dosing rate, reaction
temperature, concentration and the ratio of educts.
Additional materials may be added to the molding powder, depending on
the desired properties of the molded article. For example, it may be desirable to
combine the polyethylene powder with activated carbon for filtering applications.
The powder may also contain additives such as lubricants, dyes, pigments,
antioxidants, fillers, processing aids, light stabilizers, neutralizers, antiblock, or the
like. Preferably, the molding powder consists essentially of polyethylene polymer,
such that additional materials do not alter the basic and novel characteristics of the
powder, i.e., processing flexibility and being suitable for forming articles with
superior porosity and mechanical strength.
According to another aspect of the present invention, a process for forming
a porous article is provided. The process involves molding a shape from a
molding powder comprising polyethylene polymer particles. The polyethylene
polymer typically has a single modal molecular weight distribution. Here again,
the molecular weight of the polyethylene polymer is within the range of about
600,000 g/mol to about 2,700,000 g/mol as determined by ASTM. The particle
size distribution of the particles of the polyethylene polymer is within the range of
about 5 microns to about 1000 microns. The polymer particles have a powder bulk
density in the range of about 0.10 to about 0.30 g/cc. Advantageously, the process

provides a desirable processing window for producing articles with excellent
porosity and strength.
Molded articles may be formed in accordance with the invention by a free
sintering process which involves introducing the molding powder comprising the
polyethylene polymer particles into either a partially or totally confined space, e.g.,
a mold, and subjecting the molding powder to heat sufficient to cause the
polyethylene particles to soften, expand and contact one another. Suitable
processes include compression molding and casting. The mold can be made of
steel, aluminum or other metals.
Sintering processes are well-known in the art. The mold is heated to the
sintering temperature, which will vary depending upon individual circumstances.
In one embodiment, this temperature is in the range of about 100°C and 300°C.
The sintering temperature may also be within the following ranges: 140°C to
300°C and 140°C to 240°C. The mold is typically heated in a convection oven,
hydraulic press or infrared heaters. The heating time will vary and depend upon
the mass of the mold and the geometry of the molded article. Typical heating time
will lie within the range of about 5 to about 300 minutes. In more particular
embodiments, the heating time may be in the range of about 25 minutes to about
100 minutes. The mold may also be vibrated to ensure uniform distribution of the
powder. As noted in Goethel el al., higher temperatures generally produce molded
articles that have higher densities and are harder. Also, the strength of the desired
article correlates with the length of heating time. The optimum temperatures and
heating times depend on the molecular weight of the polymer.
A molding pressure may be applied, if desired. In cases requiring porosity
adjustment, a proportional low pressure can be applied to the powder. Subjecting
the particles to pressure causes them to rearrange and deform at contact points
until the material is compressed. The molding powders of the present invention,
however, are preferably not compacted either before or during the sintering

process. Generally, a powder that is compacted will yield articles with lower
porosities.
During sintering, the surface of individual polymer particles fuse at their
contact points forming a porous structure. The polymer particles coalesce together
at the contact points due to the diffusion of polymer chains across the interface of
the particles. The interface eventually disappears and mechanical strength at the
interface develops. Subsequently, the mold is cooled and the porous article
removed. The cooling step may be accomplished by conventional means, for
example it may be performed by blowing air past the article or the mold, or
contacting the mold with a cold fluid. Upon cooling, the polyethylene typically
undergoes a reduction in bulk volume. This is commonly referred to as
"shrinkage." A high degree of shrinkage is generally not desirable as it can cause
shape distortion in the final product.
Advantageously, parts made in accordance with the process of the
invention and with the polyethylene powder of the described molecular weight
range have an improved strength and porosity relative to other HMW-PE and
UHMW-PE grades. The polyethylene molding powder of the invention provides
excellent processing flexibility and low pressure drop, high porosity through much
lower porosity reduction than standard HDPE and LDPE. The articles obtained in
accordance with the claimed invention have exceptionally high porosity, excellent
porosity uniformity, and good strength for porous and porous filtration
applications. Other applications include sound-dampening, absorbent wicking,
fluidizing sheets or membranes, analytical equipment, venting and aeration. The
molding powder of the present invention is particularly suitable for forming
sintered air and liquid filters.
A porous element for a fluid filter made in accordance with the present
invention can be seen in Figures 1-3. Figure 1 illustrates a filter element 10 as
seen in the viewing direction of a first porous side wall 12. Narrower, second

porous side walls 14 laterally join the first side walls 12 to each other so as to form
a box like structure. The porous side walls of filter element 10 are sintered from
the molding powder of the present invention. A partition 16 separates an
unfiltered gas side 18 from a filtered gas side 20. When the filter is operating, the
medium to be filtered is sucked through an opening, not shown, and flows from the
unfiltered gas side 18 through the porous side walls 12,14 into the hollow interior
of filter element 10. The solid particles to be separated from the medium are
retained on the surface of filter element 10 and may be cleaned off periodically.
Referring to Figure 2, the medium is further sucked through a flow passage 22 in
head 24 to the clean gas side 20. From there it is discharged through an opening,
not shown, to the outside of the apparatus. The space 26 between sidewalls 12,
continues in flow passage 22 and extends through head 24 to clean gas side 20.
Figure 3 illustrates two first sidewalls 12 and a narrow, second side wall 14. It
can be seen that filter element 10 comprises two halves 28 and 30 coupled along
their longitudinal axis 32. The halves are also connected along wall portions 34
and 36, thereby creating individual cells and increasing the strength of the entire
filter element 10. Further discussion of sintered filter elements appears in United
States Patent No. 6,331,197 to Herding et al., the entirety of which is incorporated
herein by reference.
Additional sintered fillers can be seen in United States Patent No.
6,770,736 and copending United States Patent Application Serial no. 10/855,749,
which disclose activated carbon filters using high molecular weight polyethylene
as a binder. The filter unit is produced by mixing finely divided activated carbon
with the polyethylene and molding the powder by thermoplastic sintering.
Procedures
In the following examples, polyethylene molding powder was prepared
using a Ziegler-Natta catalyst.

Catalyst Preparation
The catalyst is prepared in a 600 1 reactor using 13mol isoprenylaluminium
in 2521 Exxsol D30 (Exxon solvent grade). Titaniumtetrachloride (3000 mol/I)
was fed within 180 sec at a starting temperature of 10 - 15°C. The final Ti:Al ratio
was 0.78. The agitation was stopped after 2h post reaction at 25°C. The upper
solvent layer was removed after 15h. The catalyst solid component was used for
polymerization after diluting with 200 1 Exxsol D30.
Polymerization
The polymerization was performed in a single step continuous process.
Exxsol D30 was used as solvent. The reactor volume was 401, the reaction
temperature 85°C at ethylene partial pressure in the range of 0.11 MPa and 0.2
MPa.
Polymer Powder Preparation
The polymer powder was separated from the solvent which was eliminated
through a steam distillation. The resulting powder was dried in a fluidized bed
under nitrogen. 500ppm Ca-Stearate was added as an acid scavenger and blended
in a Hentschel mixer in order to destroy agglomerates.
Sintered samples were made according to the following procedure:
The porous test samples were prepared by forming porous plaques with a
diameter of 140mm and a thickness of 6.0 - 6.5 mm in a suitable mold. The mold
is filled with the polymer powder and the sides are tapped to settle the powder for
uniformity and to improve packing. The top of the mold is leveled, the mold is
covered and placed into the convection oven. The sintering temperature and time
are reported in the tables for each example and specimen. The mold was then
removed from the press and cooled quickly. The sample was removed from the
mold and allowed to air cool for 40 minutes.

The characteristic flexural strength of a powder is determined by preparing
a 140 mm diameter disk having a thickness of about 6.25 mm by way of the above
procedure, sintering the part for about 25 minutes at 220°C, and measuring the
flexural strength of the disk in accordance with DIN TSO 178.
The shrinkage (in %) is defined as the diameter of the porous plaque in
reference with the diameter of the mold.
The polymer powder and the porous plaques were analyzed for various
properties according to the following procedures:
Property Method
Molecular weight ASTM D-4020
Average Particle size Laser Scattering
Bulk density DIN 53 466
Average pore size DIN ISO 4003
Porosity DIN 661332
Flexural strength DIN ISO 1783
Pressure Drop Internal4
Properties of the tested powders are summarized in Table 1. Sinter
conditions and properties of porous parts are summarized in Tables 2 -5.
1 Helos, Sympatec with Rodos SR
2 Hg-Porosimeter, AutoPore IV Series 9500, Micromeretics
3 UTS Type 10T Universal Testing Machine (UTS Testsysteme GmbH)
4 Porous plaque with diameter: 140 mm, thickness: 6,2-6,5 mm ; airflow: 7,5 m3 / h


Examples 1-5
Porous plaques were produced by the free sintering process discussed
above from the polyethylene powders of Polymer ]. The polyethylene powder
was introduced into a mold, and the mold was heated according to the temperature
listed in Table 2, below. The mold was held at the temperature for the time
indicated. The shrinkage of the powder is indicated in the table below, as well as
results for the porosity of the filter, the strength of the filter, and the pressure drop.



Comparative Examples
Sintered parts were also made from polyethylene powders A, B, and C.
These samples represent different powder morphology and molecular weight.
These articles were prepared and tested according to the same procedures as in
Examples 1-5.







As can be seen from comparing Tables 2-5, the polyethylene molding
powder of the present invention exhibits excellent porosity characteristics while
still maintaining good mechanical strength. Porous articles made from the
comparative polymers exhibited lower flexural strength, higher pressure drops and
so forth as is appreciated from the data.
Alternative Embodiments
In general, the present invention provides a new and improved molding
powder comprising polyethylene polymer particles. Specifically, the polyethylene
polymer has a single modal molecular weight distribution, and a molecular
weight, broadly, within the range of about 600,000 g/mol to about 3,000,000
g/mol as determined by ASTM. The particle size distribution of the polyethylene
polymer particles is within the range of about 5 microns to about 1000 microns,
and the polymer particles have a powder bulk density in the range of about 0.10 to
about 0.35 g/cc. In cases where the molecular weight exceeds about 2,500,000,
the powder exhibits a characteristic flexural strength of at least about 0.7.
According to another aspect of the present invention, a process for forming
a porous article is provided. The process involves molding a shape from a
molding powder comprising polyethylene polymer particles. The polyethylene
polymer has a single modal molecular weight distribution. The molecular weight
of the polyethylene polymer is, broadly, within the range of about 600,000 g/mol
to about 3,000,000 g/mol as determined by ASTM. The particle size distribution
of the particles of the polyethylene polymer is within the range of about 5 microns
to about 1000 microns. The polymer particles have a powder bulk density in the
range of about 0.10 to about 0.35 g/cc. Advantageously, the process provides a
desirable processing window for producing articles with excellent porosity and
strength. In cases where the molecular weight exceeds about 2,500,000, the
powder exhibits a characteristic flexural strength of at least about 0.7.

In accordance with more particular embodiments of the invention, the
molecular weight of the polyethylene polymer may fall within any of the
following molecular weight ranges as determined by ASTM: from about
1,000,000 g/mol to about 2,600,000 g/mol; and from about 1,000,000 g/mol to
about 1,500,000 g/mol. In further embodiments of the invention, the powder bulk
density may be in the range of from about 0.15 to about 0.30 g/cc, or in the range
of from about 0.20 to about 0.28 g/cc.
It is understood that the above described embodiments of the invention are
illustrative only and that modification throughout may occur to one skilled in the
art. Accordingly, this invention is not regarded as limited to the embodiments
disclosed herein. In view of the foregoing discussion, relevant knowledge in the
art and references discussed above in connection with the Background and
Detailed Description, the disclosures of which are all incorporated herein by
reference, further description is deemed unnecessary.

WE CLAIM:
1. A molding powder comprising a polyethylene polymer, wherein
the polyethylene polymer has a molecular weight in the range of
from 800,000 g/mol to 1,800,000 g/mol, an average particle size in
the range of from 5 microns to 1000 microns, and a powder bulk
density in the range of from 0.10 to 0.30 g/cc.
2. The molding powder as claimed in claim 1, wherein the
polyethylene polymer has a molecular weight within the range of
from 900,000 g/mol to 1,500,000.
3. The molding powder as claimed in claim 1, wherein the
polyethylene polymer has a powder bulk density in the range of from
0.12 to 0.26 g/cc.
4. The molding powder as claimed in claim 1, wherein the powder
exhibits a characteristic flexural strength of at least 0.7 MPa.

5. The molding powder as claimed in claim 1, wherein the powder
exhibits a characteristic flexural strength of at least 0.9 MPa.
6. The molding powder as claimed in claim 1, wherein the powder exhibits
a characteristic flexural strength of at least 1.1 MPa.

7. The molding powder as claimed in claim 1, wherein the polyethylene
polymer has an average particle size in the range of from 5 microns
to 800 microns and a powder bulk density in the range of from 0.12 to
0.29 g/cc.
8. The molding powder as claimed in claim 6, wherein the polyethylene
polymer has a molecular weight within the range of from 1,000,000
g/mol to 1,800,000 g/mol.
9. The molding powder as claimed in claim 1, wherein the average particle
size is in the range of from 10 microns to 200 microns.

10. A process for forming a porous article comprising:
(a) providing a molding powder comprising polyethylene polymer particles
having porous particle morphology and porous surface features, wherein
the polyethylene polymer has a molecular weight within the range of
from 600,000 g/mol to 1,800,000 g/mol; the average particle size of the
polyethylene polymer particles is within the range of from 5 microns to
1000 microns; and the polymer particles have a powder bulk density in
the range of from 0.10 to 0.30 g/cc;
(b) forming the molding powder into a desired shape;
(c) heating the shape to a temperature of 140°C to 300°C for a period of
time sufficient to permit the polyethylene polymer to expand and soften,
while maintaining a porosity of at least about 30%, and optionally
maintaining the shape under pressure; and
(d) thereafter cooling and recovering the porous article having a porosity of
between about 30% and about 85%.

11. The process as claimed in claim 10, wherein the temperature is in the
range of from 150°C to 280°C.
12. The process as claimed in claim 10, wherein the temperature is in the
range of from 170°C to 260°C.
13. A porous article prepared from a polyethylene powder, wherein the
polyethylene powder comprises particles having porous particle
morphology and porous surface features has a molecular weight within
the range of from 600,000 g/mol to 1,800,000 g/mol, an average particle
size in the range of from 5 microns to 1000 microns, and a powder bulk
density in the range of from 0.10 to 0.30 g/cc and the porous article has
a porosity of between about 30% and about 85%, wherein the article
has an average pore size of from about 50 urn to about 80 urn.
14. The porous article as claimed in claim 13, wherein the article has an
average pore size of from 5 pm to 100 pm.

15. The porous article as claimed in claim 13, wherein the article has a
porosity of from 60 to 75 percent.


A molding powder comprising a polyethylene polymer, wherein the polyethylene polymer
has a molecular weight in the range of from 800,000 g/mol to 1,800,000 g/mol as
determined by ASTM 4020, an average particle size in the range of from 5 microns to 1000
microns, and a powder bulk density in the range of from 0.10 to 0.30 g/cc.

Documents:

03552-kolnp-2006-abstract.pdf

03552-kolnp-2006-claims.pdf

03552-kolnp-2006-correspondence others-1.1.pdf

03552-kolnp-2006-correspondence others.pdf

03552-kolnp-2006-description(complete).pdf

03552-kolnp-2006-drawings.pdf

03552-kolnp-2006-form-1.pdf

03552-kolnp-2006-form-2.pdf

03552-kolnp-2006-form-26.pdf

03552-kolnp-2006-form-3.pdf

03552-kolnp-2006-form-5.pdf

03552-kolnp-2006-international publication.pdf

03552-kolnp-2006-pct request form.pdf

3552-KOLNP-2006-(13-04-2012)-CORRESPONDENCE.pdf

3552-KOLNP-2006-ABSTRACT 1.1.pdf

3552-KOLNP-2006-AMANDED CLAIMS-1.1.pdf

3552-KOLNP-2006-AMANDED CLAIMS.pdf

3552-KOLNP-2006-CORRESPONDENCE 1.1.pdf

3552-KOLNP-2006-CORRESPONDENCE-1.2.pdf

3552-KOLNP-2006-CORRESPONDENCE.pdf

3552-KOLNP-2006-DESCRIPTION (COMPLETE) 1.1.pdf

3552-KOLNP-2006-DRAWINGS 1.1.pdf

3552-KOLNP-2006-EXAMINATION REPORT REPLY RECIEVED.pdf

3552-KOLNP-2006-EXAMINATION REPORT.pdf

3552-KOLNP-2006-FORM 1 1.1.pdf

3552-KOLNP-2006-FORM 18.pdf

3552-KOLNP-2006-FORM 2 1.1.pdf

3552-KOLNP-2006-FORM 26.pdf

3552-KOLNP-2006-FORM 3.pdf

3552-KOLNP-2006-FORM 5.pdf

3552-KOLNP-2006-GRANTED-ABSTRACT.pdf

3552-KOLNP-2006-GRANTED-CLAIMS.pdf

3552-KOLNP-2006-GRANTED-DESCRIPTION (COMPLETE).pdf

3552-KOLNP-2006-GRANTED-DRAWINGS.pdf

3552-KOLNP-2006-GRANTED-FORM 1.pdf

3552-KOLNP-2006-GRANTED-FORM 2.pdf

3552-KOLNP-2006-GRANTED-SPECIFICATION.pdf

3552-KOLNP-2006-OTHERS-1.1.pdf

3552-KOLNP-2006-OTHERS.pdf

3552-KOLNP-2006-OTHERS1.2.pdf

3552-KOLNP-2006-PETITION UNDER RULE 137-1.1.pdf

3552-KOLNP-2006-PETITION UNDER RULE 137.pdf

3552-KOLNP-2006-REPLY TO EXAMINATION REPORT.pdf


Patent Number 251842
Indian Patent Application Number 3552/KOLNP/2006
PG Journal Number 15/2012
Publication Date 13-Apr-2012
Grant Date 11-Apr-2012
Date of Filing 28-Nov-2006
Name of Patentee TICONA LLC
Applicant Address 8040 DIXIE HIGHWAY, FLORENCE, KY 41042, U.S.A.
Inventors:
# Inventor's Name Inventor's Address
1 WANG, LOUIS, C. 4 MELANIE COURT, RARITAN, NJ 08869, U.S.A.,
2 EHLERS,JENS KRUMMER WEG 18,46499 HAMMINKELN, GERMANY
PCT International Classification Number C08J 3/12
PCT International Application Number PCT/US2005/019770
PCT International Filing date 2005-06-06
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 60/578,005 2004-06-07 U.S.A.