Copolymers of dicarboxylic acids and salicylic acids

Abstract: A composition and method of making copolymers of salicylic acid and dicarboxylic acid by reacting at least one salicylic acid with at least one dicarboxylic acid and at least one acetic anhydride for every salicylic and dicarboxylic acid present. The composition is useful for functionalizing polyphenylene ethers that are capable of forming copolymers useful for compatibilizing blends of polyphenylene ethers and polyamides.

Description: This invention relates to copolymers of dicarboxylic acids and salicylic acid. EP-A-0055527 discloses a melt-processable aromatic polyester anhydride characterised in that from 5 to 80% of the units linking the reactant residues in the polymer chain have the formula -C(O)-O-C(O)-, the remaining linkages between the residues and the reactants being of the formula C(O)O-; optionally together with linkages of the formula -C(O)NH-; substantially all of the remaining linkages being disposed in coaxial or parallel and oppositely directed manner with respect to the residues to which they are linked, the polyester anhydride having a solubility of less than 5% by weight in dimethyl sulphoxide at room temperature. Chemical Abstracts, Vol 79, No 24, 1973, Abstract No 137595y and JP-A-7303716 disclose polyester-anhydrides having good heat resistance and solubility which are obtained by polymerising p-hydroxybenzoic acid or p-acetoxybenzoic acid with terephthalic or isophthalic acid in acetic anhydride, optionally in the presence of a catalyst. US-A-4988775 discloses polyphenylene ethers capped by reaction in the melt, with application of vacuum, with at least one trimellitic anhydride salicylate ester, preferably the 4-(phenyl salicylate)ester. The preferred melt processing method is extrusion with vacuum venting. By this method, the polyphenylene ether is capped with reactive dicarboxylate groups and also with salicylate groups, improving its thermal stability. The capped polyphenylene ether is capable of forming copolymers with polyamides, and said copolymers are useful as compatibilizers for polyphenylene ether-polyamide blends. US-A-4760118 discloses polyphenylene ethers capped by reaction in the melt with an ester of salicylic acid, anthranilic acid or a substituted derivative thereof. Esters of salicylic acid, and especially salicylic carbonate and linear polysalicylates, are preferred. The capping reaction typically takes place at a temperature in the range of about 225°-325°C, employing about 5-12% by weight of the ester based on polyphenylene ether. The present invention provides a polymer having structural units of the formula : wherein R is (CH₂)m or trans -CH=CH-, wherein m is at least four, and each of x and y is independently at least 1. The present invention also provides a method of preparing copolymers of dicarboxylic acid and salicylic acid. The copolymers of the present invention may be produced by contacting salicylic acid, at least one dicarboxylic acid and acetic anhydride in equimolar amount with respect to the salicylic and dicarboxylic acid present at a temperature and pressure sufficient to distill off the acetic acid and any excess acetic anhydride if any excess is used. In accordance with the method of the present invention reaction is preferably heated at reflux at about 140°C for about 10 to about 20 hours and then the acetic acid is distilled off under vacuum conditions. A suitable amount of salicylic acid present in accordance with the present invention ranges from 25 percent to 75 percent of the reaction mixture. A suitable amount of dicarboxylic acid present in accordance with the present invention ranges from 75 percent to 25 percent of the reaction mixture. Preferably the amount of salicylic acid and dicarboxylic acid present in the reaction mixture is about 50 percent respectively. Dicarboxylic acids preferable for use in the present invention include isophthalic acid, terephthalic acid, fumaric acid and aliphatic acids having at least 6 carbon atoms. Salicylic acids useful in the present invention are are commercially available from Monsanto. These copolymers of salicylic acid and dicarboxylic acid are of great use as capping agents for polyphenylene ether. Such capped polyphenylene ethers are disclosed and claimed in commonly assigned and copending application EP-A-0 498 282. To produce the above mentioned capped polyphenylene ethers a preformed copolymer made from salicylic acid and dicarboxylic acid described hereinabove is reacted with at least one polyphenylene ether. The polyphenylene ether may be prepared by pre-extrusion with vacuum venting to remove amines and other impurities that can react with the capping agent. The preferred polyphenylene ether is poly(2,6-dimethyl-1,4-phenylene enter). To produce the capped polyphenylene ethers of EP-A-0 498 282 the salicylic acid/dicarboxylic acid copolymer is preferably contacted under reactive conditions with the polyphenylene ether or optionally the pre-extruded polyphenylene ether. The reactive conditions preferably include extrusion. While not critical, the amount of dicarboxylic acid salicylic acid copolymer present is generally about 1% to about 10% based on weight of the polyphenylene ether present. The molar ratio of salicylic acid to dicarboxylic acid usually ranges from 3:1 to 1: 3. The reaction occurs at a temperature ranging from 250°C to 350°C. In order that those skilled in the art may be better able to practice the present invention, the following examples are given as illustrations of the preparation of the dicarboxylic acid/salicylic acid copolymers of the present invention. It should be noted that the invention is not limited to the specific details embodied in the examples. Example 1 Salicylate/Isophthalate Copolymer Salicylic acid (276 g, 2 mol), isophthalic acid (332 g, 2 mol) and 800 mL acetic anhydride were charged into a flask and heated under nitrogen at reflux for 17 hrs to form a clear solution. A vacuum (13.34 mbar) (⁻10 mm Hg) was applied and ⁻150 mL acetic acid/acetic anhydride was removed. The vacuum was increased to less than 1.334 mbar (1 mm Hg) and additional acetic acid was removed over a period of 2 hrs. During this time the temperature of the reaction mixture increased to 240°C. The clear melt was poured onto Teflon coated aluminum foil and allowed to cool to form a transparent, light colored glass (weight: 512 g) which was then ground up into a powder. NMR spectra were measured on a General Electric QE-300 NMR Spectrometer. A ¹H NMR analysis showed only a trace of acetate or acetic acid, no starting materials. A ¹³C NMR analysis revealed 22 weak to strong resonances at 123-134 ppm, 8 weak to medium resonances at 150-151 ppm, 26 weak resonances at 150-167 ppm. DSC: Tg at 85°C, Tm at 255°C (second heat), 240°C (third heat). Infrared spectra for the copolymers were measured in chloroform solution and in KBr pellets on a GE FTIR spectrometer. The IR analysis revealed (in CHCl₃): 1773 (weak), 1752 (strong), 1695 (medium) cm-1. The procedure was repeated with 1 mole of salicylic acid and 3 moles of isophthalic acid to produce 520g of a light colored, translucent glassy product. DSC: Tg at 100°C (second heat), 132°C (third heat). Example 2 Salicylate/Terephthalate Copolymer The procedure described in Example 1, above, was used on the same scale with terephthalic acid instead of isophthalic acid using a 1 to 1 ratio of reactants. The final product was a light colored, translucent glass which after grinding to a powder weighed 486 g. NMR spectra indicated very little acetate and no starting materials were present. Example 3 Salicylate/Suberate Copolymer The procedure described in Example 1, above, was used with suberic acid (315 g, 1.8 mol), salicylic acid (250 g, 1.8 mol) and 725 mL acetic anhydride. The reaction mixture formed a clear solution and then a clear melt and the final product was a light colored, transparent, slightly fluid glass which weighed 489 g. NMR spectra indicated very little acetate and no starting materials were present. Example 4 Salicylate/Sebacate Copolymer The procedure described in Example 1, above was used with sebacic acid (50g, 0.5 mol), salicylic acid (69g, 0.5 mol) and 200 mL acetic anhydride. The reaction mixture formed a clear solution and then a clear melt and the final product was a dark colored, transparent, slightly fluid glass which weighed 127 g. NMR spectra indicated very little acetate and no starting materials were present. Example 5 Salicylate/Fumarate Copolymer The procedure described in Example 1, above, was used with fumaric acid (58 g, 0.5 mol), salicylic acid (69 g, 0.5 mol) and 200 mL acetic anhydride. The reaction mixture formed a clear solution and then a clear melt and the final product was a dark colored, transparent glass which weighed 70.5 g NMR spectra indicated very little acetate and no starting materials were present. Table 1 describes products prepared from mixtures of salicylic acid and various dicarboxylic acids. The preparation of the capped polyphenylene ether is illustrated by the following example. Example 6 Salicylate/Isophthalate Cappped Polyphenylene Ether A dry blended mixture of 2020 g polyphenylene ether (commercial resin with an intrinsic viscosity of 0.46 dL/g) and 202g of salicylate/isophthalate (1:1 molar ratio) copolymer was extruded in a Werner-Pfleider 28 mm twin screw extruder equipped with a vacuum venting port and a devolatilizing screw (zones 1 - 5: 180°C/290°C/300°C/310°C/310°C; die: 320°C) and the extrudate was pelletized with a mechanical chopper. The feed rates for the extrusions were about 4.08 kg/h (9 pounds per hour). A portion of the extrudate (~40 g) was stirred in chloroform and the solution filtered to remove any trace of insoluble material. Addition of methanol to the filtrate caused the polymer to precipitate. It was washed with methanol and dried at 70°C in a vacuum oven for 20 hours. Infrared spectra were measured on a General Electric QE FTIR spectrometer using carbon disulfide to dissolve the functionalized polyphenylene ethers. IR analysis at 3610 cm-1 showed 0.003 wt % OH, which corresponded to 97% capping. These capped polyphenylene ethers are useful in compatibilizing blends of polyphenylene ethers and such materials as polyamides, polycarbonates, and polyesters. Compositions comprising copolymers of these capped polyphenylene ethers and polyamides are disclosed and claimed in commonly assigned EP-A-0 498 284.

Claims: A polymer comprising structural units of the formula wherein R is (CH₂) m or trans -CH=CH-, m is at least 4; and each of x and y is independently at least 1. A method of making the copolymer of Claim 1 comprising : a contacting under reactive conditions salicylic acid, at least one dicarboxylic acid of the formula R(COOH)₂ wherein R has the same meaning as in Claim 1, and acetic anhydride wherein the acetic anhydride is in a molar ratio of about 1:1 with respect to the salicylic and dicarboxylic acid present; and b distilling off the acetic acid and any excess acetic anhydride. A method according to Claim 2 wherein the molar ratio of salicylic acid to dicarboxylic acid present ranges from 1:3 to 3:1. A method according to any one of Claims 2 or 3 wherein the molar ratio of dicarboxylic acid to salicylic acid present is about 1:1.

Inventors: SOCHA LAURA ANN, WHITE DWAIN MONTGOMERY, SOCHA, LAURA ANN, WHITE, DWAIN MONTGOMERY
Applicants: GEN ELECTRIC, GENERAL ELECTRIC COMPANY
Application year: 1992
Main classification: C08G67
IPC codes: C08L71, C08G63, C08G67, C08G65