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Polyesters whose polycondensation is catalyzed by titanium-containing catalysts and which are susceptible to acetaldehyde formation during polycondensation or subsequent molding operations are prepared with low finished acetaldehyde content and reduced acetaldehyde generation by adding an ammonium o

Polyesters whose polycondensation is catalyzed by titanium-containing catalysts and which are susceptible to acetaldehyde formation during polycondensation or subsequent molding operations are prepared with low finished acetaldehyde content and reduced acetaldehyde generation by adding an ammonium or amine salt of an oxyphosphorus-acid. Polyesters, especially polyethylene terephthalate, may be produced with high inherent viscosity in reduced processing time, without the necessity of further polymerization in the solid state.

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What is claimed is: 1. A process for reducing the acetaldehyde content of polyesters susceptible to generation of acetaldehyde during their preparation or subsequent use, comprising preparing said polyester by a continuous melt polymerization process comprising polycondensing a polyester melt in th

What is claimed is: 1. A process for reducing the acetaldehyde content of polyesters susceptible to generation of acetaldehyde during their preparation or subsequent use, comprising preparing said polyester by a continuous melt polymerization process comprising polycondensing a polyester melt in the presence of one or more titanium polycondensation catalysts, and after the It.V. of the melt reaches at least 0.45 dL/g, adding to said polyester melt in said continuous melt polymerization process at least one additive comprising an ammonium salt of an oxyphosphorus acid compound containing an oxyphosphorus group, an amine salt of an acid compound containing an oxyphosphorus group, or mixture thereof, wherein said polyester has a final It.V. after solidification from the melt, and prior to optional solid state polymerization, of from 0.7 to 1.2 dL/g, and wherein said polyester comprises a polyethyleneterephthalate polyester. 2. The process of claim 1, wherein addition of said additive takes place following the polyester reaching an It.V. of at least 0.60dL/g during melt polymerization. 3. The process of claim 1, wherein addition of said additive takes place following the polyester reaching an It.V. of at least 0.68 dL/g during melt polymerization. 4. The process of claim 1, wherein addition of said additive takes place following the polyester reaching an It.V. of at least 0.72 dL/g during melt polymerization. 5. The process of claim 1, wherein addition of said additive takes place following the polyester reaching an It.V. of at least 0.76 dL/g during melt polymerization. 6. The process of claim 1, wherein the polyester melt is polycondensed in more than one reactor and is cut with a cutter, and the addition of said additive takes place at a location near or at the end of a final reactor. 7. The process of claim 1, wherein said polyethyleneterephthalate polyester contains not more than 10 mole percent of diol residues of diols other than ethylene glycol, and no more than 10 mole percent of diacid residues other than residues of terephthalic acid, where the mole % of other diol residues are based on 100 mole % of total glycol residues in the polyester and where the mole % of other diacid residues are based on 100 mole % of total diacid residues in the polyester. 8. The process of claim 1, wherein said polyester is a polyethyleneterephthalate polyester, said titanium catalyst is present in an amount of from 3 ppm to 35 ppm calculated as titanium relative to the weight of the polyester, and the addition of said additive causes a reduction of at least 20% in the content of acetaldehyde in the polyester relative to the amount of acetaldehyde in an otherwise identical polyester prepared in an identical fashion but without addition of the additive. 9. The process of claim 8 wherein the titanium catalyst comprises a titanium alkoxide. 10. The process of claim 8 wherein the titanium catalyst is present in an amount of from 3 ppm to 20 ppm calculated as titanium relative to the weight of the polyester. 11. The process of claim 1, wherein an amine salt is employed, said amine salt being a salt of one or more acid compounds containing an oxyphosphorus group selected from the group consisting of hypophosphorous acid, phosphorous acid, phosphoric acid, and polyphosphoric acid. 12. The process of claim 1, wherein said salt is a phosphorous acid salt, a phosphoric acid salt, or mixture thereof. 13. The process of claim 1, wherein the amount of said ammonium salt or amine salt of an acid phosphorus-containing compound added to said polyester is an amount sufficient to supply from 3 ppm to 250 ppm phosphorus based on the weight of the polyester. 14. The process of claim 13, wherein the amount of said ammonium salt or amine salt of an acid phosphorus-containing compound added to said polyester is an amount sufficient to supply from 7 ppm to 150 ppm phosphorus based on the weight of the polyester. 15. The process of claim 1, wherein said amine is a cyclic amine or hindered amine. 16. The process of claim 15, wherein said hindered amine is selected from the group consisting of: wherein R1 and R2 are independently selected from hydrogen, C1-C22-alkyl, substituted C1-C22-alkyl, C3-C8-cycloalkyl, substituted C3-C8-cycloalkyl, heteroaryl, and aryl; R3, R4, and R5 are independently selected from hydrogen, C1-C22-alkyl, substituted C1-C22-alkyl, C3-C8-cycloalkyl, and substituted C3-C8-cycloalkyl wherein at least one of R3, R4, and R5 is a substituent other than hydrogen; R3 and R4 or R4 and R5 collectively may represent a divalent group forming a ring with the nitrogen atom to which they are attached, e.g., morpholino, piperidino and the like; R6, R7, R8, and R9 are independently selected from hydrogen, C1- C22-alkyl, substituted C1- C22-alkyl, C3-C8-cycloalkyl, substituted C3-C8-cycloalkyl, heteroaryl, aryl; R10 is selected from hydrogen, —OR6, C1-C22-alkyl, substituted C1-C22-alkyl, C3-C8-cycloalkyl, substituted C3-C8-cycloalkyl; R11 is selected from hydrogen; C1-C22-alkyl, substituted C1-C22-alkyl, C3-C8-cycloalkyl, substituted C3-C8-cycloalkyl, heteroaryl, aryl, —Y1-R3 or a succinimido group having the formula R12 is selected from hydrogen, C1-C22-alkyl, substituted C1-C22-alkyl, C3-C8-cycloalkyl, substituted C3-C8-cycloalkyl, heteroaryl, aryl and may be located at the 2, 3 or 4 positions on the aromatic ring; the —N(R3)(R4) group may be located at the 2, 3 or 4 positions on the pyridine ring of nitrogen compound (5); the —CO2R3 and R1 groups may be located at any of the 2, 3, 4, 5, 6 positions of the pyridine ring of nitrogen compound (6); L1 is a divalent linking group selected from C2-C22-alkylene; —(CH2CH2—Y1)1-3—CH2CH2—; C3-C8-cycloalkylene; arylene; or —CO—L2—OC—; L2 is selected from C1-C22-alkylene, arylene, —(CH2CH2—Y1)1-3—CH2CH2—and C3—C8-cycloalkylene; Y1 is selected from —OC(O)—, —NHC(O)—,—O—, —S—, —N(R1)—; Y2 is selected from —O—or —N(R1)—; R13 and R14 are independently selected from —O—R2, and —N(R2)2; Z is a positive integer of up to about 20; m1, is selected from 0 to about 10; n1 is a positive integer selected from 2 to about 12; R15, and R16 are independently selected from hydrogen, C1-C22-alkyl, substituted C1-C22-alkyl, C3-8-cycloalkyl, substituted C3-C8-cycloalkyl, heteroaryl, aryl, and radical A wherein radical A is selected from the following structures: 17. The process of claim 15, wherein said amine salt is a phosphorous acid salt of a hindered amine comprising units of the formula 18. The process of claim 15, wherein said amine salt is a phosphoric acid salt of a hindered amine comprising units of the formula 19. The process of claim 15, wherein said amine salt is a salt of N- methylpiperidine with at least one of phosphorous acid or phosphoric acid. 20. The process of claim 1, wherein said amine salt is a salt of an amino acid with at least one of phosphorous acid or phosphoric acid. 21. The process of claim 1, wherein said amine salt is a salt of alanine with at least one of phosphorous acid or phosphoric acid. 22. The process of claim 1, wherein said amine salt is added in an amount sufficient to supply from 20 ppm to 100 ppm phosphorus based on the weight of the polyester. 23. the process of claim 1, the process comprising: a) selecting as a polymerizable diol component ethylene glycol and not more than 20 mole percent of diol residues other than ethylene glycol based on 100 mole % of total moles of diol residues in the polyester; b) selecting as a polymerizable diacid component terephthalic acid and not more than 20 mole percent of diacid residues other than terephthalic acid based on 100 mole % of total moles of diacid residues in the polyester; c) esterifying and polyesterifying said diol component and said diacid component to a weight-average molecular weight of at least 1000 grams per mole, d) polycondensing, in one or a plurality of stages, the product of step c) to a polyester of said target ItV in the presence of at least one titanium catalyst in an amount of from 3 ppm to 35 ppm titanium based on the total weight of polyester; and e) adding said additive to step d) when the ItV of the polyester is at least 0.50 dL/g, in an amount ranging from 5 ppm to 250 ppm phosphorus based on the weight of the polyester; and f) following steps d) and e), solidifying molten polyester to a solid polyester product. 24. The process of claim 23, wherein said additive is added during step d) at a point where the polyester ItV is at least 0.68 dL/g. 25. The process of claim 1, wherein the polyester melt is polycondensed in more than one reactor and is cut with a cutter, and the addition of said additive takes place at a location near the end of a final reactor. 26. The process of claim 1, wherein the additive is added when at least 95% of the polycondensation time has elapsed. 27. The process of claim 23, wherein said amine salt is added to a finisher in an amount sufficient to supply from 20 ppm to 100 ppm phosphorus. 28. The process of claim 23, wherein said additive is added at a point when the It. V. of the polyester polymer is at least 0.72 dL/g. 29. The process of claim 23, wherein at least one titanium catalyst is added in an amount of from 5 ppm to 20 ppm titanium based on the total weight of polyester. 30. The process of claim 23, wherein said hindered amine is selected from the group consisting of: wherein R1 and R2 are independently selected from hydrogen, C1-22-alkyl, substituted C1-C22-alkyl, C3-C8-cycloalkyl, substituted C3-C8-cycloalkyl, heteroaryl, and aryl; R3, R4, and R5 are independently selected from hydrogen, C1-C22-alkyl, substituted C1-C22-alkyl, C3-C8-cycloalkyl, and substituted C3C8-cycloalkyl wherein, at least one of R3, R4, and R5 is a substituent other than hydrogen; R3 and R4 or R4 and R5 collectively may represent a divalent group forming a ring with the nitrogen atom to which they are attached, e.g., morpholino, piperidino and the like; R6, R7, R8, and R9 are independently selected from hydrogen, C1-C22-alkyl, substituted C1-C22-alkyl, C3-C8-cycloalkyl, substituted C3-C8-cycloalkyl, heteroaryl, aryl; R10 is selected from hydrogen, —OR6, C1-C22-alkyl, substituted C1-C22-alkyl, C3-C8-cycloalkyl, substituted C3-C8-cycloalkyl; R11 is selected from hydrogen; C1-C22-alkyl, substituted C1-C22-alkyl, C3-C8-cycloalkyl, substituted C3-C8-cycloalkyl, heteroaryl, aryl, —Y1-R3 or a succinimido group having the formula R12 is selected from hydrogen, C1-C22-alkyl, substituted C1-C22-alkyl, C3-8-cycloalkyl, substituted C3-C8-cycloalkyl, heteroaryl, aryl and may be located at the 3, 4 or 5 positions on the aromatic ring; the —N(R3)(R4) group may be located at the 3, 4 or 5 positions on the pyridine ring of nitrogen compound (5); the —CO2R3 and R1 groups may be located at any of the 2, 3, 4, 5, 6 positions of the pyridine ring of nitrogen compound (6); L1 is a divalent linking group selected from C2-C22-alkylene; —(CH2CH2—Y1)1-3—CH2CH2—; C3-C8-cycloalkylene; arylene; or —CO—L2—OC—; L2 is selected from C1-C22-alkylene, arylene, —(CH2CH2—Y1)1-3—CH2CH2—and C3-C8-cycloalkylene; Y1 is selected from —OC(O)—, —NHC(O)—, —O—, —S—, —N(R1)—; Y2 is selected from —O—or —N(R1)—; R13 and R14 are independently selected from —O—R2, and —N(R2)2; Z is a positive integer of up to about 20; m1, is selected from 0 to about 10; n1 is a positive integer selected from 2 to about 12; R15, and R16 are independently selected from hydrogen, C1-C22-alkyl, substituted C1-C22-alkyl, C3-C8-cycloalkyl, substituted C3-C8-cycloalkyl, heteroaryl, aryl, and radical A wherein radical A is selected from the following structures: 31. The process of claim 23, wherein said acetaldehyde-reducing compound is an amine salt of one or more of phosphorous acid and phosphoric acid, and said amine is 32. The process of claim 23, wherein said amine salt is a salt of an optionally substituted piperidine with one or more of phosphorous acid or phosphoric acid. 33. The process of claim 23, wherein said amine salt is a salt of an amino acid with one or more of phosphorous acid or phosphoric acid. 34. The process of claim 23, wherein said amine salt is a salt of ammonia or its derivative with one or more of phosphorous acid or phosphoric acid. 35. The process of claim 23, further comprising subjecting the solid polyester product to solid state polymerization for a time sufficient to obtain a polymer It.V.higher than said final It.V. of the polymer exiting the melt phase process. 36. The process of claim 1, wherein the salt is added when at least 75% of the polycondensation time has elapsed. 37. The process of claim 1, wherein the salt is added when at least 90% of the polycondensation time has elapsed. 38. The process of claim 1, wherein the salt is added when at least the polyester melt in the melt phase process at a point within 0.05 dL/g of the final It.V. exiting the melt phase process. 39. The process of claim 38, wherein the point is within 0.03 dL/g. 40. The process of claim 38, wherein the point is within 0.015 dL/g. 41. The process of claim 1, wherein the salt is added at a point within 10 minutes of less of solidifying the melt.