Preparation of dicyclopentadiene-containing unsaturated polyesters
View Patent ↗A process for making dicyclopentadiene (DCPD)-containing polyesters is disclosed. The process comprises reacting 2-methyl-1,3-propanediol with maleic anhydride to form an acid terminated prepolymer and then reacting the prepolymer with a low grade DCPD to form DCPD-containing polyesters. The reaction of the prepolymer with DCPD is catalyzed by a transition metal triflate catalyst.
1. A process comprising
(a) reacting 1.0 equivalent of 2-methyl-1,3-propanediol with from about 1.1 to about 2.0 equivalents of maleic anhydride to form an acid terminated prepolymer; and
(b) reacting the prepolymer with a low grade dicyclopentadiene (DCPD) containing more than 0.1 wt % of cyclopentadiene trimers in the presence of a transition metal triflate catalyst to form a DCPD-containing unsaturated polyester.
2. The process of claim 1 wherein the triflate is zinc triflate.
3. The process of claim 1 wherein the triflate is present in an amount within the range of about 25 ppm to about 250 ppm of the prepolymer.
4. The process of claim 3 wherein the amount of triflate is within the range of about 50 ppm to about 200 ppm.
5. The process of claim 1 wherein the low grade DCPD contains more than 0.1 wt % up to about 2 wt % of trimers.
6. The process of claim 1 wherein the unsaturated polyester contains from about 10 wt % to about 50 wt % of the DCPD.
7. The process of claim 1 wherein the unsaturated polyester contains from about 15 wt % to about 45 wt % of the DCPD.
8. The process of claim 1 wherein the unsaturated polyester contains from about 20 wt % to about 40 wt % of the DCPD.
9. The process of claim 1 wherein the unsaturated polyester has a fumarate/maleate ratio greater than 90/10 and is essentially gel free in styrene solution.
10. The process of claim 1 wherein step (b) is performed in two stages: the first stage is performed at a temperature within the range of about 100° C. to about 140° C. and the second stage is performed at a temperature within the range of about 150° C. to about 200° C.
11. An unsaturated polyester comprising recurring units of 2-methyl-1,3-propanediol, maleate, fumarate, and a low grade DCPD containing more than 0.1 wt % of cyclopentadiene trimers, wherein the fumarate/maleate ratio is greater than 90/10.
12. The unsaturated polyester of claim 11 wherein the DCPD contains more than 0.1 wt up to 2 wt % of cyclopentadiene trimers.
13. The unsaturated polyester of claim 12 which contains from about 20 wt % to about 40 wt % of DCPD.
14. A thermosetting composition comprising the unsaturated polyester of claim 11 and a monomer selected from the group consisting of vinyl aromatics, acrylates, methacrylates, vinyl ethers, vinyl esters, and mixtures thereof.