Non-aqueous solvent-free process for making UV curable adhesive and sealants from expodized monohydroxylated diene polymers
View Patent ↗This invention is a process for making UV curable adhesives, sealants, coatings, ink, flexible printing plates, laminating adhesives, fibers, gaskets, and related compositions, films, and thin parts, wherein an epoxidized monohydroxylated polydiene polymer comprised of at least two different diene monomers wherein at least one is a diene monomer which yields unsaturation suitable for epoxidation is used as the binder for the composition. The preferred epoxidized monohydroxylated polymers are block copolymers of isoprene and butadiene wherein a hydroxyl group is attached at one end of the polymer molecule. These polymers may be hydrogenated or unhydrogenated. The process involves mixing the above polymer or the polymer with one or more other formulating ingredients together with and insoluble photoinitiator which is preferably selected from the group consisting of triaryl sulfonium salts. The mixture is then subjected to mixing conditions in a high speed mixer, preferably a high speed disk disperser, at a blade tip speed of from 200 to 2000 cm/sec at a temperature from 25 to 130° C., preferably from 40 to 100° C. This process is highly suited for making stable cationic photoinitiator concentrations that can be added to adhesive, coating, or sealant formulations to effect rapid UV cure.
1. A process, which does not utilize a non-aqueous solvent, for producing a ultraviolet curable adhesive, coating, or sealant composition comprising a monohydroxylated epoxidized polydiene block copolymer comprised of at least, two different diene monomers wherein at least one is a diene monomer which yields unsaturation suitable for epoxidation and wherein the polymer contains from 0.5 to 4.0 milliequivalents of epoxy per gram of polymer, and, optionally, other formulating ingredients, said process comprising mixing the epoxidized polymer and optional formulating ingredients with a photoinitiator which is insoluble in the polymer in a high speed mixer under mixing conditions of a blade tip speed of from 200 to 2000 centimeters per second at a temperature from 25 to 130° C.
2. The process of claim 1 wherein the blade tip speed is from 300 to 1500 cm/sec.
3. The process of claim 1 wherein the blade tip speed is from 800 to 1200 cm/sec.
4. The process of claim 1 wherein the temperature is from 40 to 100° C.
5. The process of claim 4 wherein the temperature is from 50 to 80° C.
6. The process of claim 1 wherein the polymer is a diblock polymer of isoprene and butadiene wherein the isoprene block contains most of the epoxidation and the hydroxyl group is on the end of the butadiene block.
7. The process of claim 6 wherein the polymer has a number average molecular weight of 2500 to 14,000.
8. The process of claim 7 wherein the polymer has a number average molecular weight of 3000 to 7000.
9. The process of claim 7 wherein the polymer has from 1 to 3 milliequivalents of epoxy per gram of polymer.
10. The process of claim 9 wherein the polymer has a number average molecular weight of 5400 to 6600 and from 1.4 to 2.0 milliequivalents of epoxy per gram of polymer.
11. The process of claim 1 wherein the insoluble photoinitiator is a triaryl sulfonium salt.
12. The process of claim 1 wherein the mixing equipment is comprised of a high speed disk disperser.