Method for producing enhanced solid state
View Patent ↗A method for enhancing solid state polymerization of polyethylene terephthalate is disclosed in which at least one monomeric unit of diacid and/or dimethyl ester comprising at least one pendant chemical side group is copolymerized with a diol and a diacid or a dimethyl ester. The at least one pendant chemical side group may include groups chosen from tertiary butyl, hexyl, pentyl, butyl, propyl, ethyl, methyl, nitrosyl (NO 2 ) and sulfonyl (SO 2 ) groups.
1. A method for increasing the rate of solid state polymerization for polyethylene terephthalate (PET), which comprises: (i) directly esterifying or transesterifying, then copolymerizing in the melt, at temperatures between 250° C. and 310° C., with the other PET precursor materials at least one monomeric unit selected from the group consisting of diols, diacids and dimethyl esters that contain at least one pendant side group selected from the group consisting of tertiary butyl, hexyl, pentyl, butyl, propyl, ethyl, methyl, nitrosyl (NO 2 ) and sulfonyl (SO 2 ) groups to form a polymer feedstock; and
(ii) solid state polymerizing the polymer feedstock under heated nitrogen and/or air at a temperature between 160° C. and 230° C.
2. The method of claim 1 , wherein said at least one pendant side group is selected from tertiary butyl groups.
3. The method of claim 1 , wherein said at least one pendant side group is selected from nitrosyl (NO 2 ) groups.
4. The method of claim 2 , wherein said at least one monomeric unit comprises tertiary butyl isophthalic acid in an amount from about 0.1 to about 8 mole percent of the total diacid content of the PET.
5. The method of claim 3 , wherein said at least one monomeric unit comprises 5-nitrosisoisophthalic acid in an amount from about 0.05 to about 8 mole percent of the total diacid content of the PET.
6. The method of claim 3 , wherein said at least one monomeric unit comprises dimethyl 5-nitroisophthalate.
7. The method of claim 1 , wherein the solid state polymerization is carried out at a temperature in the range of from about 200° C. to 230° C. and the intrinsic viscosity is increased at an average rate that is at least five percent greater than the average intrinsic viscosity rate increase for solid state polymerization of a PET feedstock in the absence of at least one monomeric unit that comprises at least one pendant side group.
8. The method of claim 7 , wherein the average intrinsic viscosity rate increase is at least about 0.03 dL/g per hour.