High functionality number, low molecular weight polymers and methods of making same
View Patent ↗The present invention provides novel low molecular weight, high functionality number, polymers. The polymers may be made, for example, by heating (preferably, to a temperature of between about 130° C. and 180° C.) one or more ethylenically unsaturated monomers in the presence of a substantially aprotic solvent system; and maintaining the temperature for a time sufficient to polymerize the monomers to a preferred monomer to polymer conversion percentage of at least about 95 percent by weight. In a presently preferred embodiment, the polymer has a weight average molecular weight between about 900 and 7,000 Dalton and a functionality number of at least 100. The process is also preferably substantially free of chain transfer agents.
1. A process for preparing low molecular weight, high functionality number polymers, comprising:
heating to a temperature between 130° C. and 180° C. a mixture comprising:
one or more ethylenically unsaturated monomers;
an initiator system comprising a compound selected from the group consisting of persulfates, peroxides, di-azos, and combinations thereof; and
a substantially aprotic solvent system, and
maintaining the temperature of the mixture for a time sufficient to polymerize the monomers to a monomer to polymer conversion percentage of at least about 95 percent by weight,
wherein the polymer has a weight average molecular weight between about 900 and 7,000 Dalton, a hydroxyl number of at least 240 and an acid number of greater about 240.
2. The process of claim 1 , wherein the process is substantially free of chain transfer agents.
3. The process of claim 1 , wherein the process is substantially free of mercaptan chain transfer agents.
4. The process of claim 1 , wherein the polymer has an acid number between 320 and 600.
5. The process of claim 1 , wherein the polymer has an acid number between 320 and 600 and a weight average molecular weight between about 1,500 and 5,000 Dalton.
6. The process of claim 1 , wherein the polymer has a weight average molecular weight between about 1,500 and 5,000 Dalton.
7. The process of claim 1 , wherein the polymer has a number average molecular weight between about 1,000 and 2,500 Dalton.
8. The process of claim 1 , wherein the process comprises maintaining the temperature for a time sufficient to polymerize the monomers to a monomer to polymer conversion percentage of at least about 99 percent by weight.
9. The process of claim 1 , wherein the process comprises maintaining the temperature for a time sufficient to polymerize the monomers to a monomer to polymer conversion percentage of at least about 99.5 percent by weight.
10. The process of claim 3 , wherein the process is essentially completely mercaptan-free.
11. The process of claim 1 , wherein the process comprises eating the monomers in the presence of an essentially completely aprotic solvent system.
12. The process of claim 1 , wherein the monomers include acidic- or anhydride-functional monomer selected from the group of acrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleic acid, cinnamic acid, 2-methyl maleic acid, itaconic acid, 2-methyl itaconic acid, α,β-methyleneglutaric acid, anhydrides of the aforementioned acids, and mixtures thereof.
13. The process of claim 9 , wherein the process results in less than 20% of the acidic functionality being lost to esterification side reactions.
14. A polymer prepared by the process of claim 1 .
15. A coating composition, comprising: a polymer prepared by the process of claim 1 .
16. A coating composition, comprising: a low molecular weight, high acid number polymer, wherein the polymer has a weight average molecular weight between about 900 and 7,000 Dalton a hydroxyl number of at least 240 and an acid number of greater than about 240.