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
1995-04-18
2001-04-03
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S123000, C525S303000
Reexamination Certificate
active
06211292
ABSTRACT:
This invention relates to isocyanate-cured block copolymers. Further, it relates to coatings, sealants, adhesives and modified asphalts made from such block copolymers.
BACKGROUND OF THE INVENTION
Conventional A-B-A block copolymers are known to be useful in coatings, sealants, adhesives and modified asphalts but their usefulness in such products is not as great as it could be if these polymers did not suffer from deficiencies in certain physical properties such as creep resistance and solvent resistance. For instance, U.S. Pat. No. 3,792,005 disclosed that coatings can be made using block copolymers of A—B—A type where A is a monovinyl aromatic polymer block, usually polystyrene (S), and B is a rubber polymer block, usually hydrogenated polybutadiene (EB) or hydrogenated polyisoprene (EP). These polymers could be especially useful in elastomeric coatings because they can be formulated to have good flexibility and therefore, will not crack during thermal cycling, an important requirement for roof coatings for example, or during metal forming, where the coating becomes stretched as the metal is bent. However, coatings based on conventional A—B—A type block copolymers are deficient in that they lack strong adhesion and in applications in which the coating will contact organic liquids such as gasoline, the coatings will merely dissolve off of the substrate.
It would be advantageous to provide block polymers of this type which had increased creep and solvent resistance. By functionalizing these conventional block polymers, they can then be crosslinked to give polyurethane and polyurea structures which perform better at high temperatures and are thus more useful than the conventional block polymers in many coatings, sealants, adhesives and modified asphalt applications.
SUMMARY OF THE INVENTION
The present invention provides isocyanate cured hydroxy, acid or amine functionalized selectively hydrogenated block copolymers of vinyl aromatic hydrocarbons and conjugated dienes. The polymers are produced by selectively hydrogenating the block copolymer, grafting thereon a hydroxy, acid or amine functional monomer and then curing the polymer through the functionalization with isocyanate. Such polymers are useful for coatings, adhesives, sealants and modified asphalts, among other things.
The present invention demonstrates that both the creep and solvent resistance limitations can be overcome by using such crosslinked functionalized polymers while maintaining the many advantages of conventional block copolymers in adhesives, coatings, sealants and modified asphalts. Specifically, the cured functionality on the polymer improves these properties.
According to the present invention, there is provided a process and corresponding product for coating substrates which comprises coating at least one surface of a substrate with an isocyanate-cured selectively hydrogenated functionalized block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene. The functional groups, which are hydroxy, acid or amine, are grafted on to the polymer in an amount from about 0.1 to about 10 weight percent and then are cured with isocyanate to improve the physical properties of the copolymer.
DETAILED DESCRIPTION OF THE INVENTION
Selectively Hydrogenated Block Copolymers
Block copolymers have been produced which comprise primarily those having a general structure
(A—B)
n
—A or (A—B)
n
wherein the polymer blocks A comprise thermoplastic polymer blocks of vinylarenes such as polystyrene, wherein block B is a polymer block of a selectively hydrogenated conjugated diene and wherein n is 1 or greater. The proportion of the thermoplastic terminal blocks to the center elastomeric polymer block and the relative molecular weights of each of these blocks is balanced to obtain a rubber having an optimum combination of properties such that its behavior resembles that of a vulcanized rubber without requiring the actual step of vulcanization. Moreover, these block copolymers can be designed not only with this important advantage but also so as to be handled in thermoplastic processing equipment and are soluble in a variety of relatively low cost solvents.
The process by which the block copolymers are prepared is not critical to this invention. However, the block copolymers may be produced by any well known block polymerization or copolymerization procedures including the well known sequential addition of monomer techniques, incremental addition of monomer technique or coupling technique as illustrated in, for example, U.S. Pat. Nos. 3,251,905; 3,390,207; 3,598,887 and 4,219,627. As is well known in the block copolymer art, tapered copolymer blocks can be incorporated in the multiblock copolymer by copolymerizing a mixture of conjugated diene and vinyl aromatic hydrocarbon monomers utilizing the difference in their copolymerization reactivity rates. Various patents describe the preparation of multiblock copolymers containing tapered copolymer blocks including U.S. Pat. Nos. 3,251,905; 3,265,765; 3,639,521 and 4,208,356. The disclosures of all of the patents listed in this paragraph are incorporated herein by reference.
Conjugated dienes which may be utilized to prepare the polymers and copolymers are those having from 4 to 8 carbon atoms and include 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.
Vinyl aromatic hydrocarbons which may be utilized to prepared selectively hydrogenated block copolymers include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, alpha-methylstyrene, vinylnaphthalene, vinylanthracene and the like. The preferred vinyl aromatic hydrocarbon is styrene.
While these block copolymers have a number of outstanding technical advantages, one of their principal limitations lies in their sensitivity to oxidation. This was due to their unsaturated character which can be minimized by hydrogenating the copolymer, especially in the center section comprising the polymeric diene block. Hydrogenation may be effected selectively as disclosed in U.S. Pat. No. Re 27,145 which is incorporated by reference herein. These polymers are hydrogenated block copolymers having a configuration, prior to hydrogenation, of (A—B)
n
—A or (A—B)
n
wherein each of the A's is an alkenyl-substituted aromatic hydrocarbon polymer block and B is either a butadiene polymer block wherein 30-55 mol percent of the condensed butadiene units in the butadiene polymer block have the 1,2 configuration, or B is an isoprene polymer block having predominately 1,4 configuration. Other dienes can also be used.
The hydrogenation of these polymers and copolymers may be carried out by a variety of well established processes including hydrogenation in the presence of such catalysts as Raney Nickel, noble metals such as platinum, palladium and the like, soluble transition metal catalysts and titanium catalyts. Suitable hydrogenation processes which can be used are ones wherein the diene-containing polymer or copolymer is dissolved in an inert hydrocarbon diluent such as cyclohexane and hydrogenated by reaction with hydrogen in the presence of a soluble hydrogenation catalyst. Such processes are disclosed in U.S. Pat. Nos. 3,113,986 and 4,226,952, the disclosures of which are incorporated herein by reference. The polymers and copolymers are hydrogenated in such a manner as to produce hydrogenated polymers and copolymers having a residual unsaturation content in the polydiene block of from about 0.05 to about 20 percent of their original unsaturation content prior to hydrogenation, and above about 50 percent of the original unsaturation in the alkenyl-substituted aromatic hydrocarbon block.
Functionalized Block Copolymer
The selectively hydrogenated (A—B)
n
—A or (A—B)
n
block copolymers are deficient in many applications in which adhesion is required due to their hydrocarbon nature. However, the placement onto the block copolymers of the hydrox
Dawson Robert
Haas Donald F.
Shell Oil Company
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