COPOLYESTERS OF TEREPHTHALIC ACID, PHENYLHYDROQUINONE AND HYDROQUINONE

Abstract: Copolyesters are prepared from terephthalic acid, phenylhydroquinone and 30 to 50 mole percent hydroquin­ one based on total moles of diol. These copolyesters are characterized by chemical resistance.

Description: COPOLYESTERS OF TEREPHTHALIC ACID, PHENYL HYDROQUINONE AND HYDROQUINONE This invention relates to high molecular weight copolyesters of terephthalic acid, phenylhydroquinone and hydroquinone having a critical ratio of phenylhydroquinone to hydroquinone. These copolyesters have good melt processability, high heat resistance, high oxidative stability and high chemical resistance. These copolyesters are valuable for the manufacture of plastics, fibers, films and other shaped objects. U.S. Patent 4.159,365 discloses copolyesters of phenylhydroquinone and terephthalic acid containing up to 10 mole percent (based on the total moles of units) of other aromatic or cycloaliphatic polyesterforming units, including hydroquinone. Ten mole percent of the "other aromatic polyester-forming units" above, if an aromatic diol, corresponds to 20 mole percent based on the total moles of aromatic diols combined. In column 2, lines 29-31, the above patent discloses: "The presence of comonomer unit depresses the melting point as would be expected." The copolyesters of this invention prepared from terephthalic acid, 50-70 mole percent phenylhydroquinone dipropionate, and 30-50 mole percent hydroquinone dipropionate melt similar to or higher than the homopolymer prepared from terephthalic acid and phenylhydroquinone dipropionate. In addition, they have unexpected chemical resistance. U.S. Patent 3,160,602 discloses a process for the preparation of aromatic polyesters from dihydric phenols and aromatic carbonyl halides while dissolved in certain solvents. The use of phenylhydroquinone is disclosed (column 6, line 12), but there is no disclosure concerning which of the numerous copolyesters can be prepared which are sufficiently soluble in the solvents for useful molecular weights to be attained. The copolyesters of this invention contain the following divalent radicals EMI2.1 wherein (B) is present in the amount of 50 to 70 mole percent and (C) is present in the amount of 50-30 mole percent based on total moles of (B) and (C). According to the disclosure in U.S. Patent 4,159,365 the presence of 50-30 mole percent of (C), based on the total moles of (B) and (C), should depress the melting point of the copolyester. Unexpectedly, the melting points of the copolyesters of this invention are not lower than similar copolyesters containing 20 mole percent of (C), based on the total moles of (B) and (C). The melting points of the Co- polyesters of this invention are at least as high as the copolyesters containing 20 mole percent of (C), and the melting points of the copolyesters of this invention can be substantially higher. The diacyl derivative of hydroquinone used to prepare the copolyesters of this invention contain 2 to 8 carbon atoms in the acyl group. The acetyl and propionyl derivatives are preferred, but the butyryl, isobutyryl or benzoyl derivatives are examples of others which may also be used. Up to 20 mole percent of aromatic dicarboxylic acids other than terephthalic acid may be used in the preparation of the copolyesters of this invention provided the properties of the copolyesters are not substantially altered. Examples of such acids are 2,6-naphthalenedicarboxylic acid, 4,4'-oxydibenzoic acid, monochloroterephthalic acid, dichloroterephthalic acid, methylterephthalic acid, dimethylterephthalic acid, 4,4'-diphenyldicarboxylic acid, isophthalic acid, or methylisophthalic acid. Preferably, terephthalic acid is the only acid used. The copolyesters of this invention are made by conventional techniques, such as by acidolysis of phenylhydroquinone diacetate and hydroquinone diacetate with terephthalic acid. The reactants are heated at about 3000C. until most of the monocarboxylic acid has evolved. The temperature of the melt is then increased to about 380-3900C., a vacuum of about 0.5 millimeter is applied and stirring is continued until a high melt viscosity polymer is obtained. If the polymer solidifies, its molecular weight may be increased to a sufficient value by heating particles of the polymer in an inert atmosphere or under reduced pressure at a temperature just below the softening point of the polymer. The molecular weights are high enough for the polymer to be used to form fiber and film. Higher tenacities can be obtained by heating melt-spun fibers in an inert atmosphere or under reduced pressure at 300-3300C. for several hours. Tough films are obtained by pressing or by extrusion. Molding plastics having very high tensile strength, modulus and heat deflection temperatures are obtained by injection-molding at about 360-14000C. In addition to exhibiting melt processability and heat resistance, the copolymers of this invention have unexpected chemical resistance. The following table summarizes the melting points and chemical resistance data of pressed, quenched films (5-7 mils thick) of poly(phenyl-1,4- phenylene terephthalate) modified with 0, 20, 30, 35, 40, and 50 mole percent hydroquinone and exemplifies the unexpected chemical resistance. The solubility was determined by stirring the films in a 60/40 ±by weight) solution of phenol/tetrachloroethane at 1000C. for one hour. The solubility of the films was also determined in an even more potent solvent, 65/35 (by volume) solution of methylene chloride/trifluoroacetic acid, at room temperature. Solubility Hydroquinone, Melting 60/40 Phenol/ 65/35 Methylene Chloride/ Mole Percent Point, C.a Tetrachloroethaneb Trifluoroacetic Acidc 0 340 Soluble Soluble 20 330 Soluble Soluble 30 333 Insoluble Soluble 35 359 Insoluble Partially soluble 40 372 Insoluble Insoluble 50 420 Insoluble Insoluble aDetermined with a Perkins-Elmer DSC-2 differential scanning calorimeter. bDetermined at 100 C. cDetermined at 25 C. In view of the melting points and solubility characteristics, the preferred copolyesters contain 35-40 mole percent of hydroquinone. In addition to plastics, films and fibers, the copolyesters of this invention may be fabricated to give other types of shaped objects, such as foamed plastics, extruded shapes and coatings. The copolyesters of this invention also may contain nucleating agents, pigments, glass fibers, asbestos fibers, antioxidants, stabilizers, plasticizers, lubricants and other additives. The following examples illustrate the Co- polyesters of this invention. EXAMPLE 1 This example illustrates the preparation of a copolyester from terephthalic acid, 30 mole percent hydroquinone dipropionate and 70 mole percent 2phenylhydroquinone dipropionate. A mixture of 11.6 g. (0.70 mole) terephthalic acid, 4.7 g. (0.021 mole) hydroquinone dipropionate and 14.6 g. (0.049 mole) phenylhydroquinone dipropionate was placed in a 100 ml. flask equipped with a stirrer, a short distillation column and an inlet for nitrogen. The flask was evacuated and purged three times with nitrogen before being lowered into a metal bath maintained at 1400C. The mixture was heated under a nitrogen atmosphere with stirring to a temperature of 2950C. at which point propionic acid began to distill rapidly from the flask. After the reaction mixture was maintained with stirring at this temperature for 90 minutes, the temperature of the bath was increased to 3600C. A vacuum of 0.5 millimeter of mercury was then applied over a period of 5 minutes. After stirring was continued under 0.5 millimeter of mercury at 3600C. for 5 minutes, a medium melt viscosity, opaque, light tan polymer was obtained. The polymer had a crystalline melting point at 3330C. and an inherent viscosity of 1.9. Fibers melt spun from this polymer at 3700C. were heated in a nitrogen atmosphere at 1250C. for one hour, heated to 3600C. over a period of 45 minutes and then heated at 3600C. for 15 minutes. The fibers had the following properties: 2.6 denier per filament, tenacity 17.3 grams per denier, elongation 3.2% and elastic modulus 730 grams per deftier. EXAMPLE 2 A copolyester was prepared with 0.50 mole (100 mole percent) terephthalic acid, 0.20 mole (40 mole percent) hydroquinone dipropionate and 0.30 mole (60 mole percent) phenylhydroquinone dipropionate by the procedure of Example 1, except the maximum temperature was 3950C. A light tan, opaque, fibrous polymer was obtained. The polymer had a crystalline melting point of 3720C. Bars molded at 3800C. from this polymer were smooth and tough. Tensile bars (2-1/2 x 3/8 x 1/16inch) had a tensile strength of 16,400 psi. at 230C. and 5,400 psi. at 2600C. Flexure bars (5 x 1/2 x 1/8-inch) had a flexural modulus of 18.9 x 105 psi. at 230C. and 2.9 x 105 psi. at 2600C.

Claims: Claims: 1. Copolyesters having a film- and fiberforming molecular weight and consisting essentially of the following divalent radicals EMI8.1 wherein (B) is present in the amount of 50 to 70 mole percent and (C) is present in the amount of 50-30 mole percent based on total moles of (B) and (C). 2. Copolyesters of Claim 1 wherein (B) is present in the amount of 65 to 60 mole percent and (C) is present in the amount of 35 to 40 mole percent based on (B) and (C).

Inventors: JACKSON, WINSTON JEROME, JR., KUHFUSS, HERBERT FRED
Applicants: EASTMAN KODAK COMPANY
Application year: 1980
Main classification: C08G63
IPC codes: D01F6, C08G63