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
2002-11-21
2003-11-25
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...
C525S332800, C525S332900, C525S333800, C525S333200, C525S370000
Reexamination Certificate
active
06653408
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to compositions comprising a functionalized block copolymer crosslinked aluminum acetylacetonate. More particularly, the present invention relates to novel compositions comprising a maleated, hydrogenated tri-block copolymer crosslinked with aluminum acetylacetonate.
2. Background of the Related Art
Compositions based on block copolymers having poly-vinyl-aromatic blocks such as polystyrene, and polydiene blocks such as polybutadiene or polyisoprene, or hydrogenated polydiene blocks such as polyethylene/butylene have a broad utility in commercial applications. Extensive work has been done to crosslink these copolymer blocks to increase upper service temperature and solvent resistance Much of this work has been done to develop pressure sensitive adhesives (PSA) which may be applied as hot melts and subsequently crosslinked by exposure to ultraviolet light or electron beam radiation via a free radical reaction in the unsaturated polydiene blocks. Free radical chemistry has proven to be acceptable for crosslinking ethylenically unsaturated multi-block copolymers containing polydiene blocks, however, free radical chemistry is not desirable for crosslinking saturated block copolymers containing hydrogenated polydiene blocks.
Compositions based on block copolymers having poly-vinyl-aromatic blocks and hydrogenated polydiene blocks are physically crosslinked through the well known domain structure formed by association of the poly-vinyl-aromatic blocks. As a result, compositions based on these physically crosslinked block copolymers may be advantageously processed as solvent-free thermoplastic compositions or as high solids solutions.
One disadvantage associated with compositions based on physically crosslinked multi-block copolymers is that the uses of these compositions are severely limited. Uses of the compositions may include adhesives, sealants, modified asphalt, and oil gels, for example. The domain structure formed by association of the poly-vinyl-aromatic blocks looses integrity when the composition is heated above the glass transition temperature of the poly-vinyl-aromatic blocks. As a result, the upper service temperature of compositions based on these physically crosslinked multi-block copolymers are limited to less than about 100° C. Furthermore, the domain structure formed by association of the poly-vinyl-aromatic blocks looses integrity when the poly-vinyl-aromatic blocks are plasticized with solvent or a compatible plasticizer. As a result, compositions based on physically crosslinked multi-block copolymers weaken in the presence of solvents. Also, an adhesive composition based on these block copolymers is not suitable for use with plasticized polyvinylchloride (PVC) substrates because plasticizers, such as dioctylphthalate (DOP), which are typically used to soften PVC migrate into the adhesive and weaken the adhesive severely.
Therefore, there has been a long felt but unresolved need for a PSA based on crosslinked block copolymers which provides an increase in upper service temperature and improved solvent resistance. There is also a need for a PSA which may be used with PVC plasticized with DOP as a film backing for tapes, labels, and decals. There is further a need for sealants which do not slump out of a joint at higher temperatures. There is still further a need for oil gels which can maintain their shape at higher temperatures. There is yet further a need for modified asphalts which have higher softening points.
BRIEF SUMMARY OF THE INVENTION
In one embodiment, this invention provides a composition comprising a functionalized block copolymer crosslinked with acetylacetonate. The crosslinked block copolymer has improved solvent resistance and improved cohesive strength at high temperatures. The crosslinked block copolymer comprises preferably an acid functionalized, hydrogenated block copolymer having an ABA or similar structure wherein the A block comprises at least 80 wt % of a vinyl-aromatic hydrocarbon, preferably styrene, and wherein the B block comprises at least 80 wt % of a hydrogenated conjugated diene, preferably butadiene, isoprene, or a mixture thereof.
In another embodiment, this invention provides an adhesive, sealant, oil gel, asphalt composition, or wax composition comprising the acid functionalized, hydrogenated block copolymer.
DETAILED DESCRIPTION OF THE INVENTION
The present invention generally provides functionalized, hydrogenated-block copolymers crosslinked with aluminum acetylacetonate (AlAcAc). The copolymers are typically prepared by grafting maleic anhydride (MA) onto the block copolymer in an extruder grafting process. The acid groups grafted onto the copolymer form a reactive site which is then useful in a crosslinking reaction with the AlAcAc. Pressure sensitive adhesives comprising the block copolymers crosslinked with AlAcAc surprisingly exhibit an increased upper service temperature and improved solvent resistance. The adhesives can also prevent shrinkage of a DOP plasticized PVC film decal upon aging. Oil gels, modified asphalt, and modified waxes comprising the block copolymers crosslinked with AlAcAc surprisingly exhibit a very high softening point. Sealants comprising the block copolymers crosslinked with AlAcAc surprisingly exhibit good slump resistance at high temperatures.
The block copolymers, prior to hydrogenation, have both ethylenic and/or aromatic unsaturation, and may be prepared by copolymerizing one or more olefins, particularly a diolefin, with one or more alkenyl aromatic hydrocarbon monomers. The copolymers may be prepared using anionic initiators or polymerization catalysts using bulk, solution, or emulsion techniques.
In general, when solution anionic techniques are used, conjugated diolefin polymers and copolymers of conjugated diolefins and alkenyl aromatic hydrocarbons are prepared by contacting the monomer or monomers to be polymerized simultaneously or sequentially with an anionic polymerization initiator such as a Group IA metal or its alkyl, amide, silanolate, napthalide, biphenyl or anthracenyl derivative. It is preferred to use an organoalkali metal such as a sodium or potassium compound, for example, in a suitable solvent at a temperature within the range from about −100° C. to about 200° C., preferably at a temperature within the range from about 0° C. to about 100° C.
Particularly effective anionic polymerization initiators are organolithium compounds having the general formula:
RLi
n
,
wherein R is an aliphatic, cycloaliphatic, aromatic or alkyl-substituted aromatic hydrocarbon radical having from 1 to about 20 carbon atoms; and n is an integer of 1 to 4.
Conjugated diolefins useful in preparing the block copolymers include conjugated diolefins containing from 4 to about 8 carbon atoms such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene and the like. Mixtures of such conjugated dienes may also be used. The preferred conjugated diene is 1,3-butadiene.
Alkenyl aromatic hydrocarbons useful in preparing the block copolymers include vinyl aryl compounds such as styrene, various alkyl-substituted styrenes such as p-methylstyrene, p-tert-butylstyrene, and alpha-methylstyrene, alkoxy-substituted styrenes, vinyl naphthalene, alkyl-substituted vinyl naphthalenes, and the like. The preferred vinyl aromatic hydrocarbon is styrene.
Any of the inert hydrocarbon solvents known in the prior art to be useful in the preparation of such polymers may be used. In particular, suitable solvents may include straight- and branched-chain hydrocarbons such as pentane, hexane, heptane, octane and the like, as well as, alkyl-substituted derivatives thereof; cycloaliphatic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane and the like, as well as, alkyl-substituted derivatives thereof; aromatic and alkyl-substituted aromatic hydrocarbons such as benzene, naphthalene, toluene, xylene, and the like; hydrogenated aromatic hydrocarbons such as tetralin decalin, and the
Kraton Polymers U.S. LLC
Lipman Bernard
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