THERMALLY STABLE POLYESTERS CONTAINING TRANS-4,4'-STILBENEDICARBOXYLIC ACID

Abstract: Melt processable copolyesters having improved thermal stability are prepared from 1,4-butanediol, minor amounts of trans-4,4'-stilbenedicarboxylic acid and trans- or cis-1,4-cyclohexanedicarboxylic acid.

Description: THERMALLY STABLE POLYESTERS CONTAINING TRANS-4.4'-STILBENEDICARBOXYLIC ACID Field of the Invention The present invention relates to isotropic polyesters containing repeating units prepared from trans— or cis—1,4—cyclohexanedicarboxylic acid, 1,4- butanediol, and minor amounts of trans—4,4'— stilbenedicarboxylic acid. Background of the Invention U.S. 4,459,402 discloses copolyesters of 20—80 mol % trans—4,4'—stilbenedicarboxylic acid, 80—20 mol % terephthalic acid and/or 80-20 mol % 2,6-naphthalene- dicarboxylic acid and 100 mol % 1,4-butanediol having exceptionally high tensile strength. U.S. 4,414,382 discloses polyesters based on 90—55 mol % 2,6— naphthalenedicarboxylic acid, 10-45 mol % trans—4,4'- stilbenedicarboxylic acid, and 100 mol % ethylene glycol. U.S. 4,526,822 discloses a polyester of terephthalic acid and ethylene glycol modified with 10-40 mol % trans-4,4'—stilbenedicarboxylic acid. Japanese Kokai 72348/74 discloses blends of poly(1,4—butylene terephthalate) and a polyester having an aromatic dicarboxylic acid content that has at least 55 mol % trans-4,4'—stilbenedicarboxylic acid. Heretofore, copolyesters prepared from 1,4- butanediol, minor amounts of trans—4,4'—stilbene— dicarboxylic acid and trans- or cis-1,4- cyclohexanedicarboxylic acid were not known. Summary of the Invention The present invention is directed to a copolyester having improved thermal stability comprising: (A) acid repeating units from (1) a major portion of an acid component of trans— or cis—1,4— cyclohexanedicarboxylic acid, and (2) greater than 0 but less than 20 mol % acid component of trans—4,4'— stilbenedicarboxylic acid; and (B) glycol repeating units from 1,4- butanediol, wherein the total mol % of acid repeating units and glycol repeating units are each 100 mol %; said copolyester having an inherent viscosity greater than 0.2, determined at 25°C in 25/35/40 (wt./wt./wt.) phenol, tetrachloroethanexp—chlorophenol at a concentration of 0.1 g/100 mL. Detailed Description of the Invention The copolyesters of the present invention are useful in molding plastics, fibers, and films and have unexpectedly improved thermal stability in the melt. The polyesters of the present invention prepared from 1,4—butanediol, and trans— or cis—1,4— cyclohexanedicarboxylic acid or its esters have greatly enhanced melt stability when modified with up to 20 mol % of trans—4,4'—stilbenedicarboxylic acid (SDA) . Minor amounts, i.e., as little as 5 mol % and below, of SDA component in the copolyester of the present invention reduce thermal degradation, i.e. thus improve the thermal degradation rate constant compared to the unmodified homopolymer of 1,4— cyclohexanedicarboxylic acid and 1,4—butanediol. At 260°C, as little as 2 mol % of SDA results in a copolyester with a thermal degradation rate constant one—half that of the unmodified homopolymer. Increasing the SDA content to 10 mol % further reduces the thermal degradation rate constant compared to the unmodified homopolymer. However, increasing the SDA content to greater than 10 mol % begins to reduce the polymer melting point, and above 20 mol % the melting point is at an unacceptably low temperature for injection molding into useful parts. The copolyesters of the present invention generally comprise (A) acid repeating units from (1) at least 80 mol % of an acid component of trans— or cis—1,4—cyclo¬ hexanedicarboxylic acid , preferably having greater than 90 mol % of the trans isomer content, more preferably greater than 95 mol % with a constent greater than 98% of the trans isomer being most preferred, and (2) less than 20 mol %; preferably less than 10 mol %, acid repeating units of trans—4,4'—stilbenedicarboxylic acid; and (B) glycol repeating units up to 100 mol % 1,4- butanediol. The repeating units of the copolyesters of the present invention preferably comprise 81 to 98 mol % trans- or cis-1,4-cyclohexanedicarboxylic acid, 2 to 19 mol % trans—4,4'—stilbenedicarboxylic acid and 100 mol % 1,4-butanediol. The repeating units of the copolyesters of the present invention more preferably comprise 90 to 95 mol % trans- or cis-1,4—cyclohexanedicarboxylic acid, 5 to 10 mol % trans—4,4'—stilbenedicarboxylic acid and 100 mol % 1,4-butanediol. Dicarboboxylic acids or diesters of the dicarboxylic acids may be used to prepare the polymer esters of the present invention. Suitable esters include the esters of methyl, ethyl, propyl, butyl, phenyl and mixed esters thereof. Copolyesters of the present invention can be prepared by conventional melt processes. In the copolyester of the present invention, the acid repeating units of (A) above can be substituted with up to 10 mol %, preferably no more than 5 mol % of an additional aromatic dicarboxylic acid. Examples of suitable aromatic dicarboxylic acids include 4,4'— biphenyldicarboxylic acid. 1,5—, 2,6—, 2,7— naphthalenedicarboxylic, or 4,4'—oxydibenzoic acid. The 1,4- utanediol, i.e., glycol portion of the copolyesters of the present invention can be substituted with up to 10 mol % of another glycol containing 2—16 carbon atoms. Examples of suitable glycols include 1,3— propanediol, neopentyl glycol, trans— or cis—2,2,4,4— tetramethyl—1,3-cyclobutanediol, 1,5—pentanediol, 1,6— hexanediol, trans— or cis—1,4—cyclohexanedimethanol and p— ylene. These copolyesters can also be modified by the incorporation of units from polyethylene glycols or polytetramethylene glycols to enhance elastomeric behavior. The copolyesters of the present invention preferably have an inherent viscosity of at least 0.2, determined at 25°C in 25/35/40 (wt./wt./wt.) phenol/ tetrachloroethane/p-chlorophenol at a concentration of O.l g/100 mL, more preferably at least 0.6 or more. The copolyesters of the present invention also preferably have a degradation rate constant less than 3.8 x 10~ 4 at 260 β C. The copolyesters of the present invention can be further modified by the incorporation of blend modifiers. This composition can comprise: (i) 95 to 5 weight percent of the copolyester and (ii) 5 to 95 weight percent of at least one property modifier. Preferably (i) is present in an amount of 90 to 10 weight percent, and (ii) is present in an amount of 10 to 90 weight percent. Examples of suitable blend or property modifiers include polyamides such as Nylon 6,6 from DuPont, poly(ether-imides) such as ϋltem Brand poly(ether—imide) from General Electric, polyphenylene oxides, such as poly(2,6-dimethylphenylene oxide) or poly(phenylene oxide)/polystyrene blends such as the Noryl Brand resins from General Electric, other polyesters, polyphenylene sulfides, polyphenylene sulfide/sulfones, poly(ester- carbonates) , polycarbonates such as Lexan Brand polycarbonate from General Electric, polysulfones, polysulfone ethers, and poly(ether—ketones) of aromatic dihydroxy compounds. Suitable dihydroxy compounds used to prepare these modified polyesters are disclosed in U.S. Patents 3,030,335 and 3,317,466. The copolyesters of the present invention can also contain conventional flame retardants, such as phosphorus or halogen compounds; fillers, such as talc, or mica; reinforcing agents such as glass fiber, Kevlar Brand fiber from DuPont, carbon fibers, and the like. The following examples are to illustrate the present invention but should not be interpreted as a limitation thereof. Examples These examples illustrate the unobvious thermal stabilization of aliphatic dicarboxlic acid/aliphatic glycol polyesters of 1,4—cyclohexanedicarboxylic acid and 1,4-butanediol with a minor amount of trans—4,4'— stilbenedicarboxylic acid (See Table 1) . Example 1 This example illustrates the preparation and determination of melt stability of the homopolyester containing 100 mol % trans—1,4—cyclohexanedicarboxylic acid units and 100 mol % 1,4-butanediol units. A mixture of 100 g (0.50 mol) dimethyl trans—1,4— cyclohexanedicarbox late and 90 g (1.00 ols) 1,4- butanediol (100 mol % excess) and 0.07 g titanium tetraisopropoxide was placed in 500— L flask equipped with an inlet for nitrogen, a metal stirrer, and a short distillation column. The flask was placed in a Wood's metal bath already heated at 200 β C for 3.5 hours and then the temperature was raised to 260°C for 15 minutes. A vacuum of 0.5 mm was gradually applied over the next 5—10 minutes. Full vacuum was maintained for 2.5 hours. A high melt viscosity, crystalline polymer was obtained with and I.V. of 1.20 and a melting endotherm measured by DSC at 160°C. The polymer was ground to pass a 3—mm screen, dried and the thermal degradation rate constant was determined to be 1.77 x 10 4 (poise) •JΛ *sec- 1 [(dyne/cm2)- 2 - 9 *sec" 1 ) ] at 240°C and 3.72 x 10* (poise)" M «*βec- 1 [(dyne/cm2)' 294 *sec- 1 ) ] at 260°C. Example 2 This example illustrates the preparation and determination of melt stability of the copolyester containing 90 mol % 1,4—cyclohexanedicarboxylic acid (99 % trans) units, 10 mol % trans—4,4'—stilbenedicarboxylic acid units, and 100 mol % 1,4-butanediol units. A mixture of 90 g (0.45 mol) dimethyl 1,4— cyclohexanedicarboxylate (98 % trans), 14.8 g (0.05 mol) dimethyl trans-4, '—stilbenedicarboxylate, and 90 g (1.00 mols) 1,4-butanediol (100 mol % excess) and 0.07 g titanium tetraisopropoxide was placed in a 500 mL flask equipped with an inlet for nitrogen, a metal stirrer, and a short distillation column. The flask was placed in a Wood's metal bath already heated at 200°C for 4.75 hours and then the temperature was raised to 260°C for 15 minutes. A vacuum of 0.5 mm was gradually applied over the next 5—10 minutes. Full vacuum was maintained for 2 hours. A high melt viscosity, crystalline polymer was obtained with an I.V. of 1.36 and a melting endotherm measured by DSC at 156°C. The polymer was ground to pass a 3—mm screen, dried and the thermal degradation rate constant was determined to be —3.9 x 10 5 (poise) •JΛ *sec" 1 [ (dyne/cm2)" 29 *sec" 1 ) ] at 240°C and -1.21 x 10 4 (poise) •2 - 94 *sec- 1 [ (dyne/cm2)- 294 *sec- ~ ) ] at 260°C. TABLE I Effect of trans-4,4'-Stilbenedicarboxylic Acid on the Thermal Degradation Rate Constant of Polyesters of Trans—Cis—1,4—Cyclohexanedicarboxylic Acid and acid 1,4 butanediol SDA Thermal Degradation Content, Rate Constant, x 10—4* Mol % 240°C @ 260 e C 0 1.77 3.72 10 -0.39 -1.21 A A A negative degradation constant suggests a positive slope for the curve of the degradation rate constant indicating the polymer has been thermally stabilized and is not thermally degrading. * [ (dyne/cm2)- 94 *sec'. 1 ) ] The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Claims: Claims 1. A copolyester having improved thermal stability comprising: (A) acid repeating units from (1) a major portion of an acid component of dimethyl tran- or cis- 1,4-cyclohexanedicarboxylie acid, and (2) greater than 0 but less than 20 mol % acid component of trans—4,4'- stilbenedicarboxylic acid; and (B) glycol repeating units from 1,4- butanediol, wherein the total mol % of acid repeating units and glycol repeating units are each 100 mol %; said copolyester having an inherent viscosity greater than 0.2, determined at 25°C in 25/35/40 (wt./wt./ t. ) phenol, tetrachloroethane/p-chlorophenol at a concentration of 0.1 g/100 mL and a melting point of at least 200°C. 2. The copolyester of Claim 1 wherein the acid repeating units from trans- or cis-1,4- cyclohexenedicarboxylic acid are present in the amount of 81 to 98 mol % at a trans isomer content of a least 90 mol % and the acid repeating units from trans—4,4,'— stilbenedicarboxylic acid are present in the amount of 2 to 19 mol %. 3. The copolyester of Claim 2 wherein the acid repeating units from trans— or cis—1,4—cyclohexene— dicarboxylic acid component (1) are present in the amount of 90 to 95 mol % and the repeating units from trans—4,4'—stilbenedicarboxylic acid are present in the amount of 10 to 5 mol %. 4. The copolyester of Claim 1 wherein the glycol repeating units from 1,4-butanediol are present in the amount of 100 mol %. 5. The copolyester of Claim 1 wherein said acid repeating units are from trans— or cis—1,4— cyclohexenedicarboxylic acid, trans—4,4'— stilbenedicarboxylic acid, and up to 10 mol % of at least one other aromatic dicarboxylic acid. 6. The copolyester of Claim 5 wherein said other aromatic dicarboxylic acid is selected from 4,4'—biphenyldicarboxylic, 1,5—, 1,6—, 2,7—naphtha— lenedicarboxylic, and 4,4'—oxydibenzoic acid. 7. The copolyester of Claim 1 wherein said glycol repeating units are from 1,4-butanediol and up to 10 mol % of at least one other glycol having 2 to 16 carbon atoms. 8. The copolyester of Claim 7 wherein said other glycol is selected from 1,3—propanediol, neopentyl glycol, cis—2,2,4,4—tetramethyl—1,3—cyclobutanediol, trans—2,2,4,4—tetramethyl—1,3—cyclobutanediol, trans— . 1,5—pentanediol, 1,6—hexanediol, cis—1,4—cyclohexane¬ dimethanol, trans-l,4-cyclohexanedimethanol, p-xylene glycol, polyethylene glycols, and polytetra ethylene glycols. 9. A composition comprising : (i) 95 to 5 weight percent of the polyester of Claim 1, and (ii) 5 to 95 weight percent of at least one property modifier. 10. The composition according to Claim 9 wherein (i) is present in an amount of 90 to 10 weight percent, and (ii) is present in an amount of 10 to 90 weight percent. 11. The composition according to Claim 9 wherein the property modifier is selected from nylon 6,6, poly(ether-imides) , polyphenylene oxides, poly(phenylene oxide)/polystyrene blends, other polyesters, polyphenylene sulfides, polyphenylene sulfide/sulfoneε, poly(ester—carbonates) , polycarbonates, polysulfones, polysulfone ethers, and poly(ether—ketones) of aromatic dihydroxy compounds. 12. The composition according to Claim 9 wherein the property modifier is selected from flame retardants, fillers, and reinforcing agents. 13. The composition according to Claim 9 wherein the property modifier is selected from flame retardant phosphorus compounds, flame retardant halogen compounds, talc, mica, glass fibers, Kevlar fibers, and carbon fibers. 14. A fiber comprising the polyester of Claim l. 15. A film comprising the polyester of Claim 1. 16. A molded object comprising the polyester of Claim 1.

Inventors: MORRIS JOHN CRAFT, MORRIS, JOHN, CRAFT
Applicants: EASTMAN KODAK CO, EASTMAN KODAK COMPANY
Application year: 1993
Main classification: C08G63
IPC codes: C08G63, C08L67, C08L101