Foam crystallization of condensation polymers

Claim 2

A process for crystallizing a crystallizable linear polyester which comprises dispersing a chemical blowing agent in the molten polyester, extruding the molten polyester to form a solid closed cell foam and maintaining the solid foam at a temperature above the glass transition temperature of the polyester until crystallization occurs and the crystallized polyester has a heat of fusion in the range of about 12 to about 40 J/g.

Claim 3

The process of claim 1 wherein the crystallized polyester has a heat of fusion of about 16 to about 30 J/g.

Claim 4

The process of claim 1 or 2 wherein the chemical blowing agent has a decomposition temperature above the glass transition temperature of the polymer.

Claim 5

The process of claim 1 or 2 wherein the chemical blowing agent and its products of decomposition are inert to the polymer.

Claim 6

The process of claim 1 or 2 wherein the quantity of blowing agent dispersed in the molten polyester is in the range of about 0.02 to about 1.5 parts per 100 parts by weight of polymer.

Claim 7

The process of claim 1 or 2 wherein the quantity of blowing agent dispersed in the molten polyester is in the range of about 0.1 to about 0.5 part per 100 parts by weight of polymer.

Claim 8

The process of claim 1 or 2 wherein the blowing agent is selected from the group consisting of tetrazoles, hydrazides, hyrazines, semicarbazides, carbazates and dinitrosoamides.

Claim 9

The process of claim 1 or 2 wherein the crystallizable linear polyester is the polyester condensate of a diphenol and an aromatic dicarboxylic acid.

Claim 10

The process of claim 1 or 2 wherein the crystallizable linear polyester is a polyester of 2,2-bis(4-hydroxyphenyl)propane and a mixture of isophthalic and terephthalic acids containing from 100-75 mole percent isophthalic acid and from 0 to 25 percent terephthalic acid.

Claim 11

The process of claim 1 or 2 wherein the crystallizable linear polyester is a polyester of 2,2-bis(4-hydroxyphenyl)propane and isophthalic acid of inherent viscosity in the range of about 0.15 to about 0.7 dl/g.

Claim 12

A process for crystallizing a crystallizable linear polyester which comprises dispersing a chemical blowing agent in the molten polyester, extruding the molten polyester to form a solid closed cell foam, and maintaining the solid foam at a temperature above the glass transition temperature of the polyester until crystallization occurs and the crystallized polyester has a heat of fusion in the range of about 16 to about 30 J/g., wherein the polyester is a condensate of a diphenol and an aromatic dicarboxylic acid, wherein the quantity of blowing agent dispersed in the molten polyester is in the range of about 0.2 to about 0.5 part per 100 parts by weight of polyester, wherein the chemical blowing agent has a decomposition temperature above the glass transition temperature of the polyester and wherein the chemical blowing agent and its products of decomposition are inert to the polyester.

Claim 13

A process for crystallizing a crystallizable linear polyester which comprises dispersing a chemical blowing agent in the molten polyester, extruding the molten polyester to form a solid closed cell foam, and maintaining the solid foam at a temperature above the glass transition temperature of the polyester until crystallization occurs and the crystallized polyester has a heat of fusion in the range of about 16 to about 30 J/g., wherein the polyester is a condensate of a diphenol and an aromatic dicarboxylic acid, wherein the quantity of blowing agent dispersed in the molten polyester is in the range of about 0.2 to about 0.5 part per 100 parts by weight of polyester, wherein the chemical blowing agent has a decomposition temperature above the glass transition temperature of the polyester and wherein the chemical blowing agent and its products of decomposition are inert to the polyester.

Claim 14

The process of claim 11 wherein the chemical blowing agent is selected from the group consisting of tetrazoles, hydrazides, hydrazines, semicarbazides and carbazates.

Claim 15

The process of claim 11 wherein the chemical blowing agent is selected from the group consisting of 5-phenyltetrazole, 5-tolyltetrazole and 5-cyclohexyltetrazole.

Claim 16

The process of claim 11, 12 or 13 wherein the polyester is a condensate of 2,2-bis(4-hydroxyphenyl)propane.

Claim 17

The process of claim 11, 12 or 13 wherein the polyester is a condensation product of 2,2-bis(4-hydroxyphenyl)propane and isophthalic acid of inherent viscosity in the range of about 0.15 to about 0.7 dl/g.

Claim 18

A process for solid state polymerization of a crystallizable linear polyester which comprises melting the polyester, dispersing a chemical blowing agent in the molten polyester, extruding the molten polyester to form a solid closed cell foam, maintaining the solid foam at a temperature above the glass transition temperature of the polyester to crystallize the polyester and develop a heat of fusion in the range of about 12 to about 40 J/g and increasing the degree of polymerization of the polyester by heating the crystallized solid foam at a temperature below its sticking temperature.

Claim 19

A process for solid state polymerization of a crystallizable linear polyester which comprises melting the polyester, dispersing a chemical blowing agent in the molten polyester, extruding the molten polyester to form a solid closed cell foam, maintaining the solid foam at a temperature above the glass transition temperature of the polyester to crystallize the polyester and develop a heat of fusion in the range of about 12 to about 40 J/g and increasing the degree of polymerization of the polyester by heating the crystallized solid foam at a temperature below its sticking temperature.

Claim 20

The process of claim 16 wherein the crystallized polyester has a heat of fusion in the range of about 16 to about 30 J/g.

Claim 21

The process of claim 16 or 17 wherein the chemical blowing agent has a decomposition temperature above the glass transition temperature of the polyester.

Claim 22

The process of claim 16 or 17 wherein the chemical blowing agent and its products of decomposition are inert to the polyester.

Claim 23

The process of claim 16 or 17 wherein the quantity of blowing agent dispersed in the molten polyester is in the range of about 0.02 to about 1.5 parts per 100 parts by weight of polyester.

Claim 24

The process of claim 16 or 17 wherein the quantity of blowing agent dispersed in the molten polyester is in the range of about 0.1 to about 0.5 part per 100 parts by weight of polyester.

Claim 25

The process of claim 16 or 17 wherein the crystallizable linear polyester is the polyester condensate of a diphenol and an aromatic dicarboxylic acid.

Claim 26

The process of claim 16 or 17 wherein the blowing agent is selected from the group consisting of tetrazoles, hydrazides, hydrazines, semicarbazides, carbazates and dinitrosoamides.

Claim 27

The process of claim 16 or 17 wherein the crystallizable linear polyester is a polyester of 2,2-bis(4-hydroxyphenyl)propane.

Claim 28

The process of claim 16 or 17 wherein the crystallizable linear polyester is a polyester of 2,2-bis(4-hydroxyphenyl)propane and isophthalic acid of inherent viscosity in the range of about 0.15 to about 0.7 dl/g -1 .

Claim 29

The process of claim 25 wherein the blowing agent is selected from the group consisting of 5-phenyltetrazole, 5-tolyltetrazole and 5-cyclohexyltetrazole.

Claim 30

The process of claim 16 wherein the polyester foam is extruded in sheets or strands.

Claim 31

The process of claim 26 wherein the extruded polyester is chopped into small particles.

Claim 32

A process for solid state polymerization of a crystallizable linear polyester which comprises dispersing a chemical blowing agent in the molten polyester, extruding the molten polyester to form a solid foam, maintaining the solid foam at a temperature above the glass transition termperature of the polyester to crystallize the polyester and develop a heat of fusion in the range of about 16 to about 30 J/g, and increasing the degree of polymerization of the polyester by heating the crystallized solid foam at a temperature below its sticking temperture, wherein the polyester is a condensate of a diphenol and an aromatic dicarboxylic acid, wherein the quantity of blowing agent dispersed in the molten polyester is in the range of about 0.2 to about 0.5 part per 100 parts by weight of polyester, wherein the chemical blowing agent has a decomposition temperature above the glass transition temperature of the polyester and wherein the chemical blowing agent and its products of decomposition are inert to the polyester.

Claim 33

A process for solid state polymerization of a crystallizable linear polyester which comprises dispersing a chemical blowing agent in the molten polyester, extruding the molten polyester to form a solid foam, maintaining the solid foam at a temperature above the glass transition termperature of the polyester to crystallize the polyester and develop a heat of fusion in the range of about 16 to about 30 J/g, and increasing the degree of polymerization of the polyester by heating the crystallized solid foam at a temperature below its sticking temperture, wherein the polyester is a condensate of a diphenol and an aromatic dicarboxylic acid, wherein the quantity of blowing agent dispersed in the molten polyester is in the range of about 0.2 to about 0.5 part per 100 parts by weight of polyester, wherein the chemical blowing agent has a decomposition temperature above the glass transition temperature of the polyester and wherein the chemical blowing agent and its products of decomposition are inert to the polyester.

Claim 34

The process of claim 29 wherein the chemical blowing agent is selected from the group consisting of tetrazoles, hydrazides, hydrazines, semicarbazides, carbazates and dinitrosoamides.

Claim 35

The process of claim 29 or 30 wherein the polyester is a condensation product of 2,2-bis(4-hydroxyphenyl)propane and iosphthalic acid of inherent viscosity in the range of about 0.15 to about 0.7 dl/g -1 .

Claim 36

The process of claim 29 or 30 wherein the polyester foam is extruded in sheets or strands.

Claim 37

The process of claim 32 wherein the extruded polyester is chopped into small particles.

Claim 38

The process of claim 29 or 30 wherein the polymerization step is carried out while the crystallized solid foam is subjected to reduced pressure.

Claim 39

The process of claim 29 or 30 wherein the polymerization step is carried out while a stream of inert gas flows over the crystallized solid foam.