Polyester compositions which crystallize rapidly

Claim 2

A thermoplastic composition which crystallizes rapidly, comprising (a) a high molecular weight polyalkylene terephthalate which has an intrinsic viscosity of at least about 0.4 dl/g (measured as a 0.5% strength by weight solution in a phenol/tetrachloroethane mixture in a weight ratio of 1:1 at 25° C.) and (b) about 0.5 to 30% by weight based on the weight of (a) and (b) of an oligomeric polyester having a minimum polymerization degree of 2 and a maximum number-average molecular weight of about 6000, said oligomer being free of any substituents which are substantially reactive with said high molecular weight polyalkylene terephthalate under injection molding conditions.

Claim 3

The composition of claim 1 containing at least about 4 wt. % of oligomer based on the weight of high molecular weight polymer and oligomer.

Claim 4

The composition of claim 1 in which the polyalkylene terephthalate has an intrinsic viscosity of at least about 0.8 dl/g.

Claim 5

The composition of claim 1 wherein the oligomer is based on sebacic acid, adipic acid or both.

Claim 6

A process for the production of a composition as claimed in claim 1, in which about 70 to 99.5% by weight of a high molecular weight polyalkylene terephthalate with an intrinsic viscosity of at least about 0.4 dl/g and about 0.5 to 30% by weight of an oligomeric polyester having a minimum polymerization degree of 2 and a maximum number average molecular weight of about 6000, said oligomer being free of substituents which are substantially reactive with said high molecular weight polyalkylene terephthalate are mixed together and homogenized in the melt.

Claim 7

A process according to claim 5 in which about 85 to 99.5% by weight of the polyalkylene terephthalate and about 0.5 to 15% by weight of the oligomer are mixed together and homogenized in the melt.

Claim 8

A process according to claim 5, in which the polyalkylene terephthalate has been produced by esterifying or transesterifying an acid component which is at least about 90 mol % of terephthalic acid and a dialkylterephthalate with 1.05 to 5.0 mols of a diol component, relative to 1 mol of the dicarboxylic acid component, in the presence of an esterication catalyst and/or transesterification catalyst and subjecting the product thus obtained to a polycondensation reaction in the presence of a polycondensation catalyst at between about 200° and 300° C. under reduced pressure.

Claim 9

A process according to claim 7, in which at least about 90 mol % of the diol component is selected from the group consisting of 1,3-propane diol; 1,4-butane diol; 1,5-pentane diol; 1,6-hexane diol; cyclohexane-1,4-dimethanol and ethylene glycol.

Claim 10

A process according to claim 5 in which the oligomer has been produced by esterifying adipic acid or sebacic acid with a diol selected from 2-ethylhexane-1,3-diol, 2,2,4-trimethylpentane-1,3-diol, butane-1,3-diol, hexane-1,6-diol and butane-1,4-diol and a mono-hydric alcohol selected from 2-ethylhexanol, 3,5,5-trimethylhexanol and n-butanol.

Claim 11

The product of the process of claim 9.

Claim 12

A process for increasing the rate of crystallization of a high molecular weight polyethylene terephthalate comprising incorporating therein sufficient oligomeric polyester having a minimum polymerization degree of 2 and a maximum number average molecular weight of about 6000, said oligomer being free of any substituents which are substantially reactive with said high molecular weight polyethylene terephthalate under injection molding conditions to ensure that the polyester when injection molded into molds held at less than about 120° C. will have at least about 70% of the crystallinity obtainable by injection molding the polyester alone into molds held at temperatures in excess of 140° C. with mold residence times in excess of sixty seconds.

Claim 13

A process for increasing the rate of crystallization of a high molecular weight polyethylene terephthalate comprising incorporating therein sufficient oligomeric polyester having a minimum polymerization degree of 2 and a maximum number average molecular weight of about 6000, said oligomer being free of any substituents which are substantially reactive with said high molecular weight polyethylene terephthalate under injection molding conditions to ensure that the polyester when injection molded into molds held at less than about 120° C. will have at least about 70% of the crystallinity obtainable by injection molding the polyester alone into molds held at temperatures in excess of 140° C. with mold residence times in excess of sixty seconds.

Claim 14

A highly crystalline thermoplastic composition which crystallizes rapidly comprising a blend of (a) a polyalkylene terephthalate based on an acid component of at least about 90 mol % terephthalic acid and a diol component of at least about 90 mol % ethylene glycol, said polymer having an intrinsic viscosity of at least about 0.8 dl/g as measured at 25° in a 1:1 phenol tetrachloroethane mixture, and (b) about 0.5 to 15 weight % based on the weight of (a) and (b) of an oligomer of sebacic or adipic acid with a diol selected from 2-ethylhexane-1,3-diol; 2,2,4-trimethylpentane-1,3-diol; and butane-1,3-diol, hexane-1,6-diol and butane-1,4-diol; and with a monohydric alcohol selected from 2-ethylhexanol, 3,5,5-trimethyl hexanol and n-butanol; said oligomer having a polymerization degree of at least 2 and having a number-average molecular weight of no more than about 6000, and being free of substituents which are substantially reactive with said polyalkylene terephthalate under injection molding conditions.

Claim 15

A highly crystalline thermoplastic composition which crystallizes rapidly comprising a blend of (a) a polyalkylene terephthalate based on an acid component of at least about 90 mol % terephthalic acid and a diol component of at least about 90 mol % ethylene glycol, said polymer having an intrinsic viscosity of at least about 0.8 dl/g as measured at 25° in a 1:1 phenol tetrachloroethane mixture, and (b) about 0.5 to 15 weight % based on the weight of (a) and (b) of an oligomer of sebacic or adipic acid with a diol selected from 2-ethylhexane-1,3-diol; 2,2,4-trimethylpentane-1,3-diol; and butane-1,3-diol, hexane-1,6-diol and butane-1,4-diol; and with a monohydric alcohol selected from 2-ethylhexanol, 3,5,5-trimethyl hexanol and n-butanol; said oligomer having a polymerization degree of at least 2 and having a number-average molecular weight of no more than about 6000, and being free of substituents which are substantially reactive with said polyalkylene terephthalate under injection molding conditions.

Claim 16

A process for injection molding a thermoplastic polyester comprising (1) intimately blending (a) a polyester at least about 90 mol % of whose acid residues are derived from terephthalic acid and at least 90 mol % of whose alcohol residues are derived from ethylene glycol, said polyester having an intrinsic viscosity of at least about 0.4 dl/g in 1:1 phenol/tetrachloroethane at 25° C., with (b) an oligomeric polyester having a minimum polymerization degree of 2 and a maximum number-average molecular weight of about 6000, said oligomer being free of substituents substantially reactive with said polyester under injection molding conditions and (2) injection molding, said blend into molds held at temperatures less than about 120° C., a sufficient amount of said oligomer product being included in the blend to ensure a significant degree of crystallinity to the molded polyester.

Claim 17

A process for injection molding a thermoplastic polyester comprising (1) intimately blending (a) a polyester at least about 90 mol % of whose acid residues are derived from terephthalic acid and at least 90 mol % of whose alcohol residues are derived from ethylene glycol, said polyester having an intrinsic viscosity of at least about 0.4 dl/g in 1:1 phenol/tetrachloroethane at 25° C., with (b) an oligomeric polyester having a minimum polymerization degree of 2 and a maximum number-average molecular weight of about 6000, said oligomer being free of substituents substantially reactive with said polyester under injection molding conditions and (2) injection molding, said blend into molds held at temperatures less than about 120° C., a sufficient amount of said oligomer product being included in the blend to ensure a significant degree of crystallinity to the molded polyester.

Claim 18

The process of claim 13 wherein sufficient oligomer is used to ensure that the molded polyester has no less than about 70% of the crystallinity obtainable by injection molding the polyester alone into molds held at least about 140° C. with residence times of in excess of about 60 seconds.

Claim 19

The process of claim 14 wherein the polyester consists essentially of terephthalic acid residues and ethylene glycol residues.

Claim 20

The process of claim 13 wherein sufficient oligomer is used to ensure that the molded polyester has at heat of crystallization of no less than about 6 cal/g.

Claim 21

The composition of claim 1 in which the oligomeric polyester (b) consists essentially of structural units of the formula (I) ##STR5## or of a mixture of said structural units with structural units of the formula (II) ##STR6## wherein R 1 denotes a linear or branched aliphatic, cycloaliphatic or araliphatic divalent radical with 2-20 C-atoms, R 2 denotes a linear or branched aliphatic, cycloaliphatic, araliphatic or aromatic divalent radical of 2 to 20 C-atoms, x denotes an integer of at least 2, up to any value giving the oligomer a number-average molecular weight of 6000 or less, and y is an integer of 0 or 1.

Claim 22

The composition of claim 17 wherein the oligomeric polyester consists essentially of structural units of the formula I ##STR7## wherein R 1 , R 2 , x and y are as defined in claim 17.

Claim 23

An improved process for forming injection molded articles comprising (1) intimately blending (a) a polyester at least about 90 mol % of whose acid residues are derived from terephthalic acid and at least 90 mol % of whose alcohol residues are derived from ethylene glycol, said polyester having an intrinsic viscosity of at least about 0.4 dl/g in 1:1 phenol/tetrachloroethane at 25° C., with (b) an oligomeric polyester having a minimum polymerization degree of 2 and a maximum number-average molecular weight of about 6,000, said oligomer being free of any substituents which are substantially reactive with said high molecular weight polyalkylene terephthalate, under injection molding conditions and (2) injection molding said blend with mold temperatures less than about 120° C. and with mold residence times significantly less than those required when molding the same part from the polyester alone, the amount of oligomeric polyester and the residence time being sufficient to ensure at least about 70% of the crystallinity obtainable by molding the polyester alone with mold temperatures no less than about 140° C. and residence times in excess of 60 seconds.

Claim 24

An improved process for forming injection molded articles comprising (1) intimately blending (a) a polyester at least about 90 mol % of whose acid residues are derived from terephthalic acid and at least 90 mol % of whose alcohol residues are derived from ethylene glycol, said polyester having an intrinsic viscosity of at least about 0.4 dl/g in 1:1 phenol/tetrachloroethane at 25° C., with (b) an oligomeric polyester having a minimum polymerization degree of 2 and a maximum number-average molecular weight of about 6,000, said oligomer being free of any substituents which are substantially reactive with said high molecular weight polyalkylene terephthalate, under injection molding conditions and (2) injection molding said blend with mold temperatures less than about 120° C. and with mold residence times significantly less than those required when molding the same part from the polyester alone, the amount of oligomeric polyester and the residence time being sufficient to ensure at least about 70% of the crystallinity obtainable by molding the polyester alone with mold temperatures no less than about 140° C. and residence times in excess of 60 seconds.