Solvent resistant polyurethane adhesive compositions
View Patent ↗A solvent resistant adhesive obtained by the crosslinking of a hydroxyl or urea or hydrocarbon terminated unsaturated polyurethane or polyurethane-urea polymer with a peroxide or a silicone hydride. The adhesive is useful as a component in pressure sensitive adhesives.
1. A solvent resistant adhesive composition comprising:
(i) a hydroxyl terminated or urea terminated or hydrocarbon terminated unsaturated polyurethane derived from a hydroxyl-terminated vinyl-containing branched butadiene polymer, wherein the butadiene polymer has a molecular weight (Mn) of from 500 to 10,000, an average content of copolymerized additional monomer of from 0 to 50 weight percent, hydroxyl groups per polymer of from 2.4 to 2.8 and terminal hydroxyl groups bonded to carbon atoms adjacent to double bonded carbon atoms, and a polyisocyanate and,
(ii) a peroxide capable of generating free radicals or a silicone hydride providing SiH, wherein components (i) and (ii) are present in an amount sufficient to provide a molar ratio of unsaturated sites of component (i) relative to SiH or free radicals of component (ii) between 514 and 824,
wherein the silicone hydride is a substantially linear hydrogen siloxane having a formula selected from the group consisting of MD e D′ f M, MD′ f M′, M′D e D′ f M′ and M′D e M′, wherein
M is defined as R 3 SiO 1/2
M′ is defined as H g R 3-g SiO 1/2
D=RRSiO 2/2, and
D′=RHSiO 2/2
where each R is independently a monovalent hydrocarbon radical of from about 1 to 40 carbon atoms, the subscripts e and f may be zero or positive wherein the sum of e and f ranges from about 10 to about 100, with the proviso that the sum of f and g is at least 2; and
wherein the peroxide is one or more compound selected from the groups consisting of di-tert-butyl peroxide, dicumyl peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, tert-butyl perbenzoate, tert-butyl per-3,5,5-trimethylhexanoate, tert-butyl per-2-ethylhexanoate, and benzoyl peroxide.
2. The composition of claim 1 wherein the unsaturated polyurethane or polyurethane-urea is hydroxyl terminated.
3. The composition of claim 1 wherein the unsaturated polyurethane or polyurethane-urea is urea terminated.
4. The composition of claim 1 wherein the unsaturated polyurethane or polyurethane-urea is hydrocarbon terminated.
5. The composition of claim 1 wherein the unsaturated polyurethane or polyurethane-urea is crosslinked with a peroxide.
6. The composition of claim 1 wherein the unsaturated polyurethane or polyurethane-urea is crosslinked with the silicone hydride in the presence of a hydrosilylation catalyst.
7. The solvent resistant adhesive composition of claim 1 wherein the unsaturated polyurethane or polyurethane-urea is crosslinked with the silicone hydride in the presence of a hydrosilylation catalyst and a hydrosilylation inhibitor.
8. The composition of claim 1 wherein the hydroxyl-terminated polybutadiene contains copolymerizable additional comonomer.
9. The composition of claim 8 wherein the comonomer is selected from the group consisting of ethylene, propylene, 1-butene, isoprene, chloroprene, 2,3-methyl-1,3-butadiene, 1,4-pentadiene, acrylonitrile, methacrylonitrile, methylstyrene, methyl acrylate, methyl methacrylate, vinyl acetate, 1,2-epoxides and ε-caprolactone.
10. The composition of claim 1 wherein the polyisocyanate is selected from the group consisting of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4′ diphenyl-methanediisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4′-diisocyanate and liquid diphenylmethane-diisocyantes containing a mixture of 2,4- and 4,4′ isomers.
11. The composition of claim 1 wherein R includes substituted or unsubstituted aryl, alkaryl or alkyl radicals.
12. The composition of claim 1 containing at least one additional component selected from the group consisting of filler, tackifier, adhesion promoter, plasticizer, solvent, thixotropic agent, UV stabilizer and antioxidant.
13. The composition of claim 1 further including a tackifier comprising one or more compounds selected from the group consisting of MQ silicone resins, terpene oligomers, coumarone/indene resins, aliphatic petrochemical resins and modified phenolic resins.
14. The composition of claim 1 further including a filler selected from the group consisting of one or more compounds selected from the group consisting of fumed silica, precipitated silica and calcium carbonates.
15. A method for making a cured solvent resistant adhesive composition comprises:
a) providing a mixture of
(i) a hydroxyl urea- or hydrocarbon-terminated unsaturated polyurethane derived from a hydroxyl-terminated vinyl-containing branched butadiene polymer, wherein the butadiene polymer has a molecular weight (Mn) of from 800 to 5,000 gram/mole, a primary hydroxyl group content of from 0.3 to 1.8 meq/g, an average content of copolymerizable additional monomer of from 0 to 50 weight percent, hydroxyl groups per polymer of from 2.4 to 2.8 and terminal hydroxyl groups bonded to carbon atoms adjacent to double bonded carbon atoms, and a polyisocyanate; and,
(ii) a peroxide capable of generating free radicals or a silicone hydride providing SiH, wherein components (i) and (ii) are present in an amount sufficient to provide a molar ratio of unsaturated sites of component (i) relative to SiH or free radicals of component (ii) between 514 and 824, and,
b) crosslinking the mixture of step (a) at elevated temperatures,
wherein the silicone hydride is a substantially linear hydrogen siloxane having a formula selected from the group consisting of MD e D′ f M, MD′ f M, MD e D′ f M′, M′D e D′ f M′ and M′D e M′, wherein
M is defined as R 3 SiO 1/2
M′ is defined as H g R 3-g SiO 1/2
D=RRSiO 2/2 and
D′=RHSiO 2/2
where each R is independently a monovalent hydrocarbon radical of from about 1 to 40 carbon atoms, the subscripts e and f may be zero or positive wherein the sum of e and f ranges from about 10 to about 100, with the proviso that the sum off and g is at least 2; and
wherein the peroxide is one or more compound selected from the groups consisting of di-tert-butyl peroxide, dicumyl peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, tert-butyl perbenzoate, tert-butyl per-3,5,5-trimethylhexanoate, tert-butyl per-2-ethylhexanoate, and benzoyl peroxide.
16. The method of claim 15 wherein the unsaturated polyurethane or polyurethane-urea is hydroxyl terminated and prepared by the reaction of a polyisocyanate with a stoichiometric excess of hydroxyl terminated butadiene polymer.
17. The method of claim 15 wherein the unsaturated polyurethane or polyurethane-urea is urea terminated and prepared by the reaction of a hydroxyl terminated butadiene polymer with a stoichiometric excess of polyisocyanate and primary or secondary organic amines.
18. The method of claim 15 wherein the unsaturated polyurethane or polyurethane-urea is hydrocarbon terminated and prepared by the reaction of a hydroxyl terminated butadiene polymer with a stoichiometric excess of a monoisocyanate.
19. The method of claim 15 wherein the unsaturated polyurethane or polyurethane-urea is crosslinked with a peroxide.
20. A cured composition provided by the method of claim 15 .