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
2002-04-05
2004-04-13
Harlan, Robert DeShon (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...
C525S328600, C525S329200, C525S329500, C525S329800, C525S330300, C526S318000, C526S319000, C526S324000, C526S329700, C526S330000, C526S331000
Reexamination Certificate
active
06720390
ABSTRACT:
FIELD OF THE INVENTION
Copolymers of acrylic esters are crosslinked by converting some of the ester groups to ester or amide groups which contain unsaturation and then sulfur or peroxide curing the resulting polymers.
TECHNICAL BACKGROUND
Crosslinking (also sometimes termed vulcanization or curing) of polymers yields products which often have improved properties for their intended uses. This is particularly true when the polymer is an elastomer, and curing of elastomers is very commonly done, for instance using sulfur or peroxide curing. For sulfur cures, generally speaking the polymer contains olefinic unsaturation, while for peroxide curing the presence of olefinic unsaturation is often preferable, see for instance H. Mark, et al., Ed., Encyclopedia of Polymer Science and Engineering, Vol. 17, McGraw-Hill Book Co., New York, 1989, p. 666-698.
However, some types of elastomers do not contain olefinic unsaturation, and so are not generally sulfur cured, and/or cured by peroxides with some difficulty. These elastomers are cured using other curing systems. For example, elastomeric ethylene/acrylic copolymers may be crosslinked by the use of primary diamines, which form crosslinks, see for instance H. Mark, et al., Ed., Encyclopedia of Polymer Science and Engineering, Vol. 1, McGraw-Hill Book Co., New York, 1985, p. 325-334. In order to aid in such crosslinking to more readily form crosslinks and/or form more stable crosslinks curesite monomers, such as carboxylic acids or half acid esters may be copolymerized into the polymer, see for instance U.S. Pat. Nos. 3,883,472 and 3,904,588. In another example, polyacrylate elastomers are typically crosslinked through curesites containing chlorine, epoxy, and/or carboxylic acid groups. These curesites may be obtained from curesite monomers which are copolymerized into the polymer, for example, 2-chloroethyl vinyl ether, vinyl chloroacetate, p-vinylbenzyl chloride, or glycidyl acrylate, see for instance Kirk-Othmer Encyclopedia of Chemical Technology, 4th edition, Vol. 8, John Wiley and Sons, New York, 1993 p. 927 and Polymeric Materials Encyclopedia, Vol. 1, CRC Press, New York, 1996, p.74.
However, it is often desirable to crosslink such polymers using conventional sulfur or peroxide curing systems such as are widely employed in the art, because such cures are already in use in many factories for a wide variety of common elastomers, and/or the curing agents are less expensive and/or less toxic. In order to make such types of polymers curable with those peroxide or sulfur cure systems, it is desirable to introduce into them olefinic unsaturation containing groups. These groups should be introduced in such a way so as not to harm the basic polymer properties, so that the polymers may be readily and/or economically cured, and/or the resulting crosslinks are stable, so as to give good vulcanizate properties.
In order to form polyacrylate elastomers it is known to introduce olefinic unsaturation by copolymerization with comonomers such as butadiene, isoprene, allyl maleate, dicyclopentenyl acrylate, 5-ethylidene-2-norbornene, or tetrahydrobenzyl acrylate. These monomers are expensive and in some cases may cause the polymer to prematurely crosslink in the polymerization reaction, see for instance Kirk-Othmer Encyclopedia of Chemical Technology, 4th edition, Vol. 8, John Wiley and Sons, New York, 1993, p. 928.
It is also possible to introduce olefinic unsaturation containing groups by chemical modification of the polymer after the polymerization. Japanese Patent Application 62-121746 describes the esterification of a polymer made from ethylene, an acrylic ester and maleic anhydride and/or a maleic half acid ester which is “modified” with an olefinically unsaturated amine or alcohol, and then cured using a sulfur or peroxide cure. No mention is made of polymers containing acrylic ester repeat units.
German Patent Application 3,715,027 A1 describes various copolymers of ethylene and acrylic acids and/or esters, and optionally other monomers such as maleic anhydride, their reaction with olefinic alcohols, including those with polyunsaturation, and their subsequent crosslinking by oxidation, e.g., reaction with air, often in the presence of an oxidation catalyst. The polymers are useful as thermosetting melt adhesives. No mention is made of sulfur or peroxide curing. U.S. Pat. No. 5,736,616 is similar to German Patent Application 3,715,027, in that a polymer containing pendant unsaturation is used as an oxygen scavenger (react with oxygen). The polymer is made by polymerizing ethylene and acrylic esters and/or acids and then esterifying or transesterifying the resulting polymer with an unsaturated alcohol. No mention is made of curing such a polymer using a sulfur or peroxide cure.
U.S. Pat. No. 5,093,429 describes the preparation of a polymer containing olefinic unsaturation by direct copolymerization of ethylene, an acrylic ester, and a copolymerizable monomer containing unsaturation which survives the polymerization (for example has a copolymerizable double bond and a double bond which is unreactive in the polymerization), or by copolymerization of ethylene, and acrylic ester, and another copolymerizable monomer which may then be reacted with an unsaturated alcohol or amine to attach such unsaturation to the polymer. The polymer containing unsaturation may then be crosslinked using a sulfur or peroxide curing system. No mention is made of using the acrylic ester as a site to attach the olefinic unsaturation.
In some instances the crosslinks that result from curesite monomers present in some of the above references are not as stable as desired because linkages between the crosslinkable groups (e.g., olefinic unsaturation) are not as stable as desired. U.S. Pat. No. 4,399,263, for example, mentions that at temperatures above 160° C. ethylene/alkyl acrylate/maleic acid ester polymers form anhydride moieties by internal reaction at the acid-ester curesite. The crosslinks may not be sufficiently stable because the curesite monomers and/or polymer-modifying reagents, which attach curable functionalities onto the polymer, introduce groups into the composition which catalyze unwanted reactions.
SUMMARY OF THE INVENTION
This invention concerns a process for crosslinking a polymer, comprising:
(a) transesterifying or amidating a first polymer consisting essentially of about 60 or more mole percent of
and up to about 40 mole percent of one or more comonomers selected from the group consisting of aromatic hydrocarbon olefins, acrylonitrile, olefinic monomers containing one or more functional groups selected from the group consisting of chlorine, epoxy, and carboxylic acid, and cyanoalkyl acrylates wherein alkyl comprises 2-8 carbons, with an alcohol or a primary amine which contains one or more olefinic bonds, to form a second polymer having side chains containing said olefinic bonds; and
(b) crosslinking said second polymer using a sulfur or peroxide cure system; and wherein:
R
1
is methyl or hydrogen; and
R
2
is hydrocarbyl, substituted hydrocarbyl, or a mixture thereof.
Also disclosed herein is a composition comprising:
(a) a second polymer made by transesterifying or amidating a first polymer consisting essentially of about 60 or more mole percent of
and up to about 40 mole percent of one or more comonomers selected from the group consisting of aromatic hydrocarbon olefins, acrylonitrile, olefinic monomers containing one or more functional groups selected from the group consisting of chlorine, epoxy, and carboxylic acid, and cyanoalkyl acrylates wherein alkyl comprises 2-8 carbons, with an alcohol or a primary amine which contains one or more olefinic bonds; and
(b) a sulfur or peroxide cure system; and wherein:
R
1
is methyl or hydrogen; and
R
2
is hydrocarbyl, substituted hydrocarbyl, or a mixture thereof.
Another composition disclosed herein comprises:
(a) a polymer consisting essentially of about 60 or more mole percent of
and up to about 40 mole percent of one or more comonomers selected from the group consisting of aromatic hydrocarbon ol
Cohen Gordon Mark
Deyrup Edward Johson
Harrell Jerald Rice
E. I. du Pont de Nemours and Company
Harlan Robert DeShon
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