Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-03-02
2001-01-23
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S264000, C525S265000, C525S288000
Reexamination Certificate
active
06177519
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to curable silane-grafted isomonoolefin/vinyl aromatic copolymers particularly useful in sealants, caulks, adhesives and coating compositions.
2. Description of Related Art
Curable copolymers comprising at least one alphamonoolefin and styrene or para-alkylstyrene are known in the prior art. For example, U.S. Pat. No. 5,162,445 discloses curable random copolymers containing a C
4
to C
7
isomonoolefin, e.g., isobutylene, and para-alkylstyrene, e.g., para-methylstyrene prepared by cationic polymerization of the monomer mixture in the presence of a Lewis acid catalyst, followed by halogenation, e.g., bromination, of the resultant copolymer to introduce benzylic halogen into the polymer molecules. The resultant halogenated copolymer is curable in a variety of ways, including by means of zinc oxide or promoted zinc oxide curing systems normally used to cure halogenated butyl rubber. These halogenated copolymers may also be further functionalized by reaction with a nucleophilic reagent capable of displacing benzylic halogen to provide copolymers containing ester, hydroxyl, carboxy, nitrile, quaternary ammonium, mercapto and other functionality as described in the aforementioned U.S. Pat. No. 5,162,445.
Analogous copolymers prepared by copolymerization of C
2
to C
12
monoolefin, e.g., ethylene or propylene, and para-alkylstyrene, e.g., para-methylstyrene, using a metallocene catalyst, and functionalized derivatives thereof, are disclosed in U.S. Pat. No. 5,543,484.
Copolymers such as described above exhibit many outstanding properties after curing, such as improved resistance to oils and greases, resistance to oxygen and ozone degradation, excellent impermeability to air, water vapor and many organic solvents as well as resistance to aging and sunlight. These properties render these materials, particularly curable elastomeric copolymers where the olefin component comprises at least 50 mole % of C
4
to C
7
isomonoolefin such as isobutylene, as ideal candidates for applications such as sealants, caulking and coatings. However, in many of these applications, particularly outdoor applications, the material must be in pliable form for use and must be curable in-situ under ambient conditions without the need to apply excessive amounts of heat.
It is known in the prior art that amorphous polyolefins such as copolymers of ethylene and propylene can be rendered cross-linkable by reaction of the polyolefin with a free radical generating compound and an unsaturated hydrolyzable silane, as disclosed in U.S. Pat. No. 3,646,155. However, such materials usually have a relatively high glass transition temperature and are not sufficiently pliable at ambient temperature to serve as polymeric components in sealant or caulking compositions.
Attempts to apply such modification techniques to polyisobutylene-based polymers have not been successful because polyisobutylene-based polymers tend to degrade in the presence of free radical initiators. An attempt to overcome this problem is disclosed in U.S. Pat. No. 4,245,060, which describes silane-functionalized terpolymers of isobutylene, alkylstyrene and a third monomer which is an unsaturated cyclic diene, e.g., cyclopentadiene. In U.S. Pat. No. 4,524,187, copolymers of isobutylene and a triene containing two conjugate double bonds are silylated to provide cross-linkable compositions. In each of these cases, polymer modification takes place by the addition of a silylradical to residual double bonds present in the polymer molecules; however, the presence of residual unsaturation in the polymer molecules severely detracts from the normally good chemical and heat stability of polyisobutylene polymers.
Other methods for introducing silane functionality into binary copolymers of isobutylene and an alkylstyrene are disclosed in U.S Pat. No. 5,426,167, which suggests the reaction of brorninated isobutylene/para-methylstyrene copolymers with an N,N-dimethyl-3-aminopropylsilane. This reaction is a nucleophilic displacement of bromide ion by the tertiary amine and is thus a two-step functionalization process involving both halogenation and nucleophilic displacement reactions.
SUMMARY OF THE INVENTION
The present invention provides a silylated copolymer which is the reaction product of: a) an olefin copolymer comprising at least 50 mole % of at least one C
4
to C
7
isomonoolefin; b) a silane of the general formula RR′SiY
2
wherein R represents a monovalent olefinically unsaturated hydrocarbon or hydrocarbonoxy radical, each Y represents a hydrolyzable organic radical and R′ represents an alkyl or aryl radical or a Y radical; and c) a free radical generating agent.
The invention also provides a process for producing a silylated copolymer which comprises the steps of contacting: a) an olefin copolymer comprising at least 50 mole % of at least one C
4
to C
7
isomonoolefin and at least one vinyl aromatic monomer; and b) a silane of the general formula RR′SiY
2
wherein R represents a monovalent olefinically unsaturated hydrocarbon or hydrocarbonoxy radical, each Y represents a hydrolyzable organic radical and R′ represents an alkyl or aryl radical or a Y radical; said contact being made in the presence of a free radical generating agent at reaction conditions in a reaction zone.
The silylated copolymers of the invention are readily curable by contact with water (moisture) and a silanol condensation catalyst and are particularly useful as a polymeric component in sealant, caulking, adhesive and coating formulations.
DETAILED DESCRIPTION OF THE INVENTION
The silylated copolymers of the invention may be characterized as the addition product of an olefin copolymer radical created by contact of the copolymer with a free radical generating agent and an olefinically unsaturated, hydrolyzable silane wherein the silane adds to the polymer backbone to produce a silane grafted or silane modified copolymer product.
Olefin copolymers suitable for modification in accordance with this invention comprise copolymers containing at least 50 mole % of at least one C
4
to C
7
isomonoolefin and from about 0.1 up to 50 mole % of at least one vinyl aromatic monomer. Preferred vinyl aromatic monomers are mono-vinyl aromatics such as styrene, alpha-methylstyrene, alkyl-substituted styrenes such as t-butylstyrene and para-alkyl substituted styrenes wherein the alkyl group contains from 1 to 4 carbon atoms, more preferably para-methylstyrene. Suitable isomonoolefin monomers include isobutylene and the like. Preferably, 100% of the isomonoolefinic content of the copolymer comprises isobutylene.
Preferred olefin copolymers include elastomeric copolymers comprising isobutylene and para-methylstyrene and containing from about 0.1 to 20 mole % of para-methylstyrene. These copolymers (hereinafter referred to as IPMS) have a substantially homogeneous compositional distribution such that at least 95% by weight of the polymer has a para-methylstyrene content within 10% of the average para-methylstyrene content of the polymer. They are also characterized by a narrow molecular weight distribution (Mw/Mn) of less than about 5, more preferably less than about 3.5, a glass transition temperature (T
g
) of below about −50° C. and a number average molecular weight (Mn) in the range of about 2,000 to 1,000,000, and even more preferably from 10,000 to 50,000.
These copolymers may be prepared by conventional cationic polymerization of the monomer mixture using a Lewis Acid catalyst and are more particularly disclosed in U.S. Pat. No. 5,162,445, the complete disclosure of which is incorporated herein by reference.
Another class of olefin copolymers which are useful in the present invention are the metallocene-catalyzed copolymers comprising at least one C
4
to C
7
isomonoolefin and an alkylstyrene, particularly a C
1
to C
4
para-alkylstyrene and most preferably para-methylstyrene, as disclosed in U.S. Pat. No. 5,543,484, the complete disclosure of which is incorporated herein by reference. These co
Chung David Yen-Lung
Saxena Anil Kumar
Suzuki Toshio
Tabler Raymond Lee
Wang Hsien-Chang
Exxon Chemical Patents Inc.
Lipman Bernard
Peebles Brent M.
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