Gel compositions
View Patent ↗Disclosed are four gel compositions that have improved properties over the prior art. These gels include elastosols, solid rubbery gels, UV cured gels and chemically cured gels. The gels are formed from selectively hydrogenated styrene/diene block copolymers, unhydrogenated styrene/diene block copolymers, and selectively hydrogenated styrene/diene block copolymers that have been maleated.
1. A method for preparing an elastosol, comprising the steps of:
(a) mixing 5 to 50 parts by weight of a block copolymer and 95 to 50 parts by weight of a benzoate ester having a melting point between about 70° C. and about 170° C. at a mixing temperature above the melting point of the ester, wherein said block copolymer is a solid selectively hydrogenated block copolymer having the general configuration A-B-A, (A-C) n X or mixtures thereof, where n is an integer from 2 to about 4, and X is coupling agent residue, and wherein:
(i) prior to hydrogenation each A block is a mono alkenyl arene polymer block and each B block and C block is a conjugated diene block having a vinyl content between 30 weight percent and 70 weight percent;
(ii) subsequent to hydrogenation about 0-10% of the arene double bonds have been reduced, and at least about 90% of the conjugated diene double bonds have been reduced;
(iii) each A block having a number average molecular weight between about 25,000 and about 35,000; each B block having a number average molecular weight between about 100,000 and about 150,000; and each C block having a number average molecular weight between about 50,000 and about 75,000; and
(iv) the total amount of mono alkenyl arene in the hydrogenated block copolymer is about 30 percent weight to about 35 percent weight;
(b) cooling the block copolymer/benzoate ester mixture below the melting point of the ester and turning it into a powder having a particle size of less than 800 micron;
(c) mixing the block copolymer/benzoate ester powder with an oil and a tackifying resin at room temperature to form a dispersion wherein the percent weight of the block copolymer/benzoate ester powder mixture is between 15 and 50 wt. %, the weight percent of oil is between zero and 30 wt. %, and the weight percent of tackifying resin is between 85 and 30 wt. %;
(d) heating the dispersion of the block copolymer/benzoate ester powder to a temperature higher than the melting point of the ester to form a hot fluid mixture; and
(e) cooling the fluid mixture to form a solid elastic composition.
2. The method of claim 1 , wherein the block copolymer/benzoate ester mixture is turned into a powder by cryogenic milling.
3. The method of 1 , wherein the block copolymer/benzoate ester mixture is turned into a powder by spraying.
4. The method of claim 2 , wherein said block copolymer is a selectively hydrogenated A-B-A polymer where the B block prior to hydrogenation is a 1,3-butadiene block having a vinyl content of between 35 and 45 weight percent.
5. The method according to claim 4 , wherein said benzoate ester is 1,4-cyclohexane dimethanol dibenzoate.
6. The method of claim 5 , wherein the heated dispersion of step (d) is applied to a substrate.