Title of Invention

"A LATEX COMPOSITION AND PROCESS FOR PREPARATION THEREOF"

Abstract The formation of a nanocomposite by emulsion polymerization is described. The invention includes the nanocomposite latex, a solid nanocomposite of a layered silicate mineral intercalated with an emulsion polymer and blends of the solid nanocomposite with other polymers.
Full Text Field of the Invention
This invention relates to composite materials having reduced permeability to small molecules, such as air, and which has enhanced mechanical properties. More particularly this invention relates to layered silicates intercalated with an emulsion polymer.
Background of the Invention
Layered clay minerals such as montmorillonite are composed of silicate layers with a thickness of about 1 nanometer. Dispersions of such layered materials in polymers are frequently referred to as nanocomposites.
Recently, there has been considerable interest in forming nanocomposites as a means to improve the mechanical properties of polymers. Incorporating clay minerals in a polymer matrix, however, does not always result in markedly improved mechanical properties of the polymer. This may be due to the lack of affinity between the layered silicate materials and the organic polymers. Thus it has been proposed to use ionic interactions as a means of incorporating clay minerals in a polymer. In this regard, see for example U.S. Patent 4,889,885 and U.S. Patent 4,810,734. This type of approach, unfortunately, has limited usefulness. Indeed, a more direct, simple, and economic approach to preparing nanocomposites is highly desirable.
One object of the present invention is to provide a latex comprising a layered silicate intercalated with an emulsion polymer.
Another object of the present invention is to provide a composite material formed from a dispersion latex of a layered silicate and an emulsion polymer which material has reduced permeability to small molecules such as air, and improved mechanical properties.
These and other objects, features and advantages of the present invention will become more apparent from the description which follows.
Summary of the Invention
In one embodiment of the present invention, a latex is provided comprising water and a layered mineral intercalated with a polymer emulsion.
Another embodiment of the present invention provides a nanocomposite comprising a layered mineral intercalated with an emulsion polymer.
Another aspect of the present invention comprises a blend of a first polymer with a nanocomposite composed of a layered mineral intercalated with an emulsion polymer.
The process for producing the latex of the present invention comprises forming a dispersion of a layered mineral in water including a swelling agent such as an onium salt, adding a polymerizable monomer or monomers, such as an olefin or diene, with a polymerization initiator to the dispersion, and thereafter polymerizing the monomer or monomers to form a latex comprising water and a polymer nanocomposite. The preparation of this latex comprises yet another embodiment of the present invention.
A composite material formed from the latex of the present invention has improved mechanical properties and reduced air permeability to small molecules such as air making it particularly useful in a range of applications, particularly as a tire liner and as inner tubes, barriers, films, coatings and the like.
Accordingly, the present invention relates to a latex composition comprising 100 grams of water and 0.01 to 80 grams of a layered mineral intercalated with an emulsion polymer or copolymer.
The invention also relates to a process for producing a latex composition as claimed in any of the preceding claims comprising the steps of
dispersing in a known manner 0.01 to 80 grams of a layered mineral of the kind such as herein described in 100 grams of water to form a dispersion;
adding in a known manner a swelling agent of the kind such as herein described to the said dispersion;
polymerizing in a known manner a free radical polymerizable olefinic monomer or monomers of the kind such as herein described in the presence of the said dispersion under emulsion polymerization conditions , wherein the polymerization is conducted in the presence of an emulsifying agent at a temperature in the range of 5°C to 100° C for a time sufficient to form the latex including the said nanocomposite material and optionally adding a coagulating agent to said latex to coagulate solid nanocomposite and thereafter separating the said soild nanocomposite therefrom.
DETAILED DESCRIPTION OF THE INVENTION:
Any natural or synthetic layered mineral capable of being intercalated may be employed in the present invention, however,
layered silicate minerals are preferred. The layered silicate minerals that may be employed in the present invention include natural and artificial minerals capable of forming intercalation compounds. Nonlimiting examples of such minerals include smectite clay, mont-morillonite, saponite, beidellite, montronite, hectorite, stevensite, vermiculite, and hallosite. Of these montmorillonite is preferred.
The swelling agent used in the practice of the present invention is any compound capable of intercalating the layered mineral and thereby increasing the distance between the layers. Particularly preferred swelling agents are hydrocarbyl onium salts represented by the formulae A~M+R1R2R3R4 and A~Py+R4 where A- denotes an anion such as halide, OH", NO3-, SO4- and the like; M denotes N, S, P; Rl, R2, R3 and R4 independently denote hydrogen alkyl, aryl or allyl groups, which may be the same or different, provided at least one of which is other than hydrogen; and Py denotes the pyridinium or alkyl substituted pyridinium group.
It will be readily appreciated that some of the above mentioned swelling agents are also emulsifying agents. However, in those instances when the swelling agent is not an emulsifying agent preferably an emulsifying agent will be employed in carrying out the polymerization. Optionally, of course, another emulsifying agent may be used even when the swelling agent has emulsifying properties. In either event, the emulsifying agent will be one typically used in emulsion polymerization processes. Cationic emulsifying agents and non-ionic emulsifying agents are preferred.
The polymers and copolymers referred to herein as emulsion polymers are those formed by emulsion polymerization techniques. Included are polymers based on one or more water immiscible, free radical polymerizable, monomers such as olefinic monomers and especially styrene or paramethyl styrene, butadiene, isoprene, chloroprene, and acrylonitrile. Particularly preferred are styrene rubber copolymers, i.e., copolymers of styrene and butadiene, isoprene chloroprene and acrylonitrile. Especially preferred, in the practice of the present invention are homopolymers and copolymers having a glass transition temperature less than about 25°C, a number average
molecular weight above 5,000g/mole and especially above 15,000g/mole. Also, the preferred polymer will contain some unsaturation or other reactive sites for vulcanization.
The latex of an intercalatable mineral having an emulsion polymer intercalated in the mineral is prepared by forming a dispersion of the layered mineral in water and including the swelling agent. Typically, the mineral is first dispersed in water by adding from about 0.01 to about 80 grams of mineral to 100 grams of water and preferably, about 0.1 to about 10.0 g of mineral to 100 g of water, and then vigorously mixing or shearing the mineral and water for a time sufficient to disperse the mineral in the water. Then the hydrocarbyl onium salt is added to the dispersion, preferably as a water solution, and with stirring.
The amount of the onium salt used in the process of the present invention depends on the type of layered material and monomers used as well as process conditions. In general, however, the amount of onium salt used will be in the range of the cation co-exchange capacity of the layered mineral to about 10% to about 2,000% of the cationic exchange capacity of the layered mineral.
Next, the polymer latex is formed by adding to the mineral dispersion an emulsifying agent, if desired or necessary, the appropriate monomer or monomers, and free a radical initiator under emulsion polymerization conditions. For example, styrene and isoprene are polymerized in the mineral dispersion using a free radical polymerization initiator while stirring the reactants. The copolymeri-zation typically is conducted at a temperature in the range of about 25°C to about 100°C and for a time sufficient to form the polymer latex, followed by termination of the reaction.
The latex described above can be used to form coatings or films following standard techniques employed for forming such materials. Additionally, the nanocomposite of the layered silicate mineral and the polymer may be recovered by coagulating the latex, and drying the solid composite. The solid composite can then be formed into tire
inner-liners or inner tubes using conventional processing techniques such as calendaring or extrusion followed by building the tire and molding.
In one embodiment of the present invention the nancomposite is dispersed with another polymer, such as a styrene-rubber copolymer by blending on a rubber mill or in an internal mixer. Preferably the nanocomposite will be blended with a polymer formed from the same monomer or monomers used in forming the nanocomposite. The amount of the nanocomposite in the polymer typically will be in the range of about 0.1 to about 70 wt.%.
In producing tire inner liners the polymer blended with the nanocomposite of this invention preferably will have a molecular weight of greater than about 10,000 and some unsaturation or other reactive sites so that it can be vulcanized or cross-linked in the bulk state.
The invention will be more clearly understood by reference to the following examples.
Example 1
A layered silicate, montmorillonite clay (18g), was slurried with water (450g) which had been degased by sparging with nitrogen. The slurry was stirred overnight at 23°C. The clay was dispersed in the water in a Waring blender for three minutes and then degased further. Dodecyl trimethyl ammonium bromide (25.7g) was dissolved in degassed water (250g) and added to the clay slurry. Isoprene (35g), styrene (15g), and azobisisobutyronitrile (AIBN) (0.25g) as initiator were blended and then added to the clay slurry. The mixture was mechanically stirred for 20 hours at 23°C and for 26 hours at 65°C at which time polymerization was terminated with a 5g aliquot of a mixture of (0.24g) 2,6-di-tert-butyl -4-methylphenol, (1.6g) hydro-quinone, (0.8g) tetrakis [methylene(3,5-di-tert-butyl-4-hydroxy-hydrocinnamate)] methane and 200 ml methanol. The net result was the
formation of an emulsion containing a layered silicate having a styrene-isoprene copolymer latex intercalated in the layered mineral.
Example 2
A solid nanocomposite was formed from the latex of Example 1 by adding an excess of methanol to the latex, separating the solid from the liquid aqueous phase and washing the solid six times with methanol, followed by drying for about 18 hours at 60°C under vacuum and for 48 hours at 23°C in vacuum.
Example 3
A portion of the solid nanocomposite (20 grams) of Example 2 was then melt blended at 130°C in a Brabender mixer for 5 minutes with a styrene-isoprene copolymer (20 grams) that was synthesized identically but had no clay. The blend of nanocomposite and the clay-free styrene-isoprene copolymer was cross-linked by roll milling the blend with stearic acid (1 phr), zinc oxide (3.9 phr), and tetramethyl thiuram disulfide (accelerator) (1 phr) at 558C for ten minutes. Then the blend was hot pressed into 20 mil films and cured for 20 minutes at 130°C. The films were tested on a Mocon 2/20 for oxygen transmission at 30°C. The results are given in Table I below. Also shown in Table 1 were the results obtained with a film formed from a styrene-isoprene copolymer that had been synthesized identically but had no clay. (Comparative Example 1)
Uniaxial tensile properties were also measured on mini-tensile film specimens using an Instron tester. The stress-strain measurements were performed at room temperature and at an extension rate of 0.51 mm/min and the results are shown in Table 2 below. Also shown in Table 2 and labeled as Comparative Example 1 are the tensile properties obtained for a polystrene-isoprene copolymer that was synthesized identically to that in Example 1 but had no clay.
TABLE 1 (Table Removed)










WE CLAIM:
1. A process for producing a latex composition comprising the steps
of
dispersing in a known manner 0.01 to 80 grams of a layered mineral of the kind such as herein described in 100 grams of water to form a dispersion;
adding in a known manner a swelling agent of the kind such as herein described to the said dispersion;
polymerizing in a known manner a free radical polymerizable olefinic monomer or monomers of the kind such as herein described in the presence of the said dispersion under emulsion polymerization conditions , wherein the polymerization is conducted in the presence of an emulsifying agent of the kind such as herein described at a temperature in the range of 5°C to 100° C for a time sufficient to form the latex including the said nanocomposite material and optionally adding a coagulating agent known in the art to said latex to coagulate solid nanocomposite and thereafter separating in a manner such as herein described the said soild nanocomposite therefrom.
2. The process as claimed in claim 1, wherein the said two monomers are co-polymerized , one being a styrene or paramethylstryne monomer and the other being butadiene, isoprene, chloroprene or acrylonitrile.
3. The process as claimed in claim 1, wherein the said swelling agent is a hydrocarbyl onium salt.
4. The process as claimed in claim 3, wherein the said hydrocarbyl onium salt has the formula A-M+ R1 R2 R3 R4, or APy+R4, wherein
or A- is an anion, M is N, S or P; R1R2R3 and R4 independently denotes the same or different hydrogen, alkyl, aryl or allyl groups and Py denotes a pyridinium or an alkyl substituted pyridinium group.
5. A process for producing a latex composition substantially as herein described with reference to the forgoing examples.

Documents:

1280-del-1996-abstract.pdf

1280-del-1996-claims.pdf

1280-del-1996-complete specification (granted).pdf

1280-del-1996-correspondence-others.pdf

1280-DEL-1996-Correspondence-PO.pdf

1280-del-1996-description (complete).pdf

1280-del-1996-form-1.pdf

1280-del-1996-form-13.pdf

1280-del-1996-form-2.pdf

1280-del-1996-form-3.pdf

1280-del-1996-form-4.pdf

1280-del-1996-form-6.pdf

1280-del-1996-pa.pdf

1280-del-1996-petition-137.pdf

1280-del-1996-petition-138.pdf

1280-del-1996-petition-others.pdf


Patent Number 196961
Indian Patent Application Number 1280/DEL/1996
PG Journal Number 29/2008
Publication Date 26-Sep-2008
Grant Date 30-Mar-2007
Date of Filing 11-Jun-1996
Name of Patentee EXXON RESEARCH AND ENGINEERING COMPANY, a Delaware corporation
Applicant Address P.O. BOX 390, FLORHAM PARK, NEW JERSEY 07932, USA.
Inventors:
# Inventor's Name Inventor's Address
1 DONG-TSAI HSEIH 6803 TEMPLE CITY BLVD., ARCADIA, CALIFORNIA, USA.
2 CHESTER WILLIAM ELSPASS 496 FRANKLIN STREET, ALPHA, NEW JERSEY, USA.
3 EDWARD N KRESGE 68 PARLIN LANE, WATCHUNG, NEW JERSEY, USA.
4 DENNIS GEORGE PEIFFER 33 JOHN DRIVE, ANNANDALE, NEW JERSEY, USA.
5 JAMES JOSEPH CHLUDZINSKI 31 CASPENBERGER ROAD, WHITEHOUSE, NEW JERSEY, U.S.A.
PCT International Classification Number B01F 3/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 494,208 1995-06-23 U.S.A.