Low viscosity high solids copolymer

1. A reaction mixture containing a copolymer having a number average molecular weight less than about 4,000 amu and a polydispersity less than about 3 formed in the presence of a free radical initiator and a heated liquid reaction mixture fed with one or more added olefinic monomers, the reaction mixture otherwise consisting essentially of non-homopolymerizable olefinic monomer.

2. A reaction mixture according to claim 1 wherein the non-homopolymerizable olefinic monomer has the formula:

or is an anhydride thereof, wherein each X moiety may independently be hydrogen, halogen, or an organic group and at least two X moieties are selected from R 1 , COOR 2 , and Ar, wherein R 1 is an organic group; R 2 is hydrogen, halogen, or an organic group; and Ar is an aromatic group.

3. A reaction mixture according to claim 1 wherein the non-homopolymerizable olefinic monomer consists essentially of fumaric acid, maleic acid, maleic anhydride, trans-beta-methylstyrene, alpha-ethylstyrene, diethyl fumarate, diethyl maleate, cis-stilbene or trans-stilbene.

4. A reaction mixture according to claim 1 wherein the non-homopolymerizable olefinic monomer consists essentially of alpha-methylstyrene.

5. A reaction mixture according to claim 1 wherein the added olefinic monomer comprises a homopolymerizable (meth)acrylate, vinyl, vinyl ether, alkene or mixture thereof.

6. A reaction mixture according to claim 1 wherein the added olefinic monomer comprises styrene, vinyl toluene, vinyl acetate, (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxypropyl (meth)acrylate, glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidylether, 2-acetoacetoxy)ethyl methacrylate, diacetone acrylamide, methylol (meth)acrylamide, acrylonitrile, allyl methacrylate, or mixture thereof.

7. A reaction mixture according to claim 1 having a solids level of at least about 50 wt. % based on the total copolymer weight.

8. A reaction mixture according to claim 1 having a solids level of at least about 70 wt. % based on the total copolymer weight and little or no added solvent.

9. A reaction mixture according to claim 1 wherein the copolymer is an acrylic copolymer.

10. A reaction mixture according to claim 1 wherein the copolymer is an acrylic polyol.

11. A reaction mixture according to claim 1 wherein the copolymer has a polydispersity less than about 2.5.

12. A reaction mixture according to claim 1 wherein an added olefinic monomer imparts reactive unsaturation into the copolymer.

13. A reaction mixture according to claim 1 wherein the non-homopolymerizable olefinic monomer serves as a reactive diluent in which the copolymer is formed without an early increase in viscosity as copolymerization proceeds.

14. A reaction mixture according to claim 1 wherein the reaction mixture is at a temperature of at least about 140° C.

15. A reaction mixture according to claim 1 wherein the non-homopolymerizable olefinic monomer comprises alpha-methylstyrene and the reaction mixture is at a temperature of at least about 160° C.

16. A reaction mixture according to claim 1 wherein the non-homopolymerizable olefinic monomer represents about 10 to about 40 wt. % of the total copolymer weight and the one or more added olefinic monomers represent about 60 to about 90 wt. % of the total copolymer weight.

17. A reaction mixture according to claim 1 wherein the copolymer is water soluble or water dispersible.

18. A reaction mixture according to claim 1 wherein the copolymer has reactive oxirane groups.

19. A reaction mixture according to claim 1 wherein the copolymer has reactive acidic groups.

20. A reaction mixture according to claim 1 wherein the copolymer has condensable crosslinkable groups.