PROCESS FOR PRODUCTION OF POLYOLEFIN-POLYESTER GRAFT COPOLYMER

Abstract: A process for producing a polyolefin-polyester graft copolymer by melt-kneading, in the presence of a minor part of water, a polyester having both an intrinsic viscosity of 0.5 to 1.8 and a concentration of terminal carboxyl group of 10 to 100 meq/Kg with a polyolefin containing 0.2 to 5 mol % carboxyl or epoxy group and having a weight average molecular weight of 8,000 to 140,000.

Description: PROCESS FOR PRODUCTION OF POLYOLEFIN-POLYESTER GRAFT COPOLYMER Field of the Invention The present invention relates to a process for producing a polyolefin-polyester graft copoly er which is effective as a compatibilizing agent for both of ingredients in a resin composition comprising an engineering plastic such as a polycarbonate and a polyolefin. More in particular, it relates to a method of preventing gel formation upon producing a graft copolymer of a polyester having specific intrinsic viscosity and concentration of terminal carboxyl group and a modified polyolefin containing epoxy or carboxyl groups. Description of the Related Art Aromatic polycarbonates have excellent impact resistance, heat resistance, rigidity and dimensional stability, but they involve a drawback of insufficient solvent resistance and moldability. For obtaining a composition of well-balanced mechanical properties while compensating these drawbacks, various studies have been made on blends with polyolefin. However, since the compatibility between a polyolefin and a polycarbonate is not so good, it has been attempted to add third ingredients for improving the compatibility. As the third ingredient added to the composition of a polycarbonate resin and a polyolefin resin, Japanese Patent Laid Open Sho 57-108151 discloses a butyl rubber, Japanese Patent Laid Open Sho 57-108152 discloses an ethylene-propylene copolymer and/or ethylene-propylene-diene copolymer, and Japanese Patent Laid Open Sho 57-111351 discloses an isoprene rubber and/or methyl pentene polymer. However, none of the ingredients is sufficient as the compatibilizing agent for the polycarbonate resin and the polyolefin, and not only the impact resistance of the molding product is rapidly reduced but also there is a problem of surface peeling as the amount of the polyolefin is increased. In view of the above, the present inventors have previously proposed a process for producing a polyolefin-polyester graft copolymer that can be used as a satisfactory compatibilizing agent for a polycarbonate resin and a polyolefin by reacting from 15 to 85 parts by weight of a polyester having an intrinsic viscosity [ ] of 0.30 and 1.2 and a concentration of terminal carboxyl group of 15 to 200 meq/Kg, and from 85 to 15 parts by weight of a modified polyolefin containing 0.2 to 5 mol 1 of epoxy groups and having a weight average molecular weight of 8,000 to 140,000 in a twin screw extruder at 260 - 320°C (Japanese Patent Application Sho 63-25BB83). Hov/€ver, in the course of further studies, it has been found that a problem results in the above-mentioned process in that a gel is easily formed due to excess reaction and, accordingly, an extruder is clogged to bring about a difficulty in the stable production of a polyolefin-polyester graft copolymer which is effective as a compatibilizing agent. It is, accordingly, an object of the present invention to provide a process for stably producing a polyolefin-polyester graft copolymer which is a satisfactory compatibilizing agent for an engineering plastic such as a polycarbonate resin and a polyolefin, without clogging the extruder while preventing gel formation. SUMMARY OF THE INVENTION T e present inventors have made earnest studies for attaining the foregoing object and, as a results, have found that it can be attained by the reaction while defining the intrinsic viscosity and the concentration of the terminal carboxyl group of a polyester and the functional group content and the molecular weight of a modified polyolefin to respective predetermined ranges and by adding water to the reaction system thereby accomplishing the present invention. That is, a process for producing a polyolefin-polyester graft polymer according to the present invention resides in melt-kneading to react: (a) from 10 to 90 parts by weight of a polyester having a intrinsic viscosity [* ] of 0.50 to 1.8 and a concentration of terminal carboxyl group of 10 to 100 meq/Kg, and (b) from 90 to 10 parts by weight of a modified polyolefin containing 0.2 to 5 mol % of carboxyl group or epoxy group and having a weight average molecular weight of 8,000 to 140,000, at 250 - 320°C, wherein from 0.05 to 2.0 parts by eigtrt of water is added to 100 parts by weight of the sum of the polyester and the modified polyolefin. DESCRIPTION OF THE PREFERRED EMBODIMENTS The polyester used in the present invention is, generally, a thermoplastic resin comprising a saturated dicarboxylic acid and a saturated difunctional alcohol and there can be mentioned, for example, polyethylene terephthalate, polypropylene terephthalate, polytetra ethylene terephthalate (polybutylene terephthal te), polyhexa ethylene terephthalate, polycyclohexane-1 ,4-dimethylol terephthalate and polyneopentyl terephthalate. Among them, polyethylene terephthalate and polybutylene terephthalate are particularly preferred. It is necessary that the polyester has an intrinsic viscosity [^ ] of 0.5 to 1.8 and a concentration of terminal carboxyl group of 10 to 100 meq/Kg. The intrinsic viscosity [^ ] (dl/g) is determined from a solution viscosity measured in an o-chlorophenol solvent at 25°C. If the intrinsic viscosity [^ ] of the polyester is less than 0.50, the effect for improving the compatibility is insufficient. On the other hand, if it exceeds 1.8, the melt viscosity of the reaction product is increased to bring about a difficulty in fabrication. Meanwhile, if the concentration of the terminal carboxyl group is less than 10 meq/Kg, reactivity with the modified polypropylene is poor. On the other hand, if it exceeds 100 meq/Kg, the reactivity with the modified polypropylene is excessively high tending to form a gel. Particularly, in the case of polyethylene terephthalate, it is preferred that the intrinsic viscosity [ • * ] is from 0.50 to 1.0 and the concentration of the terminal carboxyl group is from 10 to 100 meq/Kg. If the intrinsic viscosity [^ ] exceeds 1.0, the melt viscosity of the graft polymer is increased to cause gelation. Further, ttie tereptittvalic acid ingredient in the polyethylene terephthalate may be substituted with alkyl group, halogen group, etc., and the glycol ingredient may contain, in addition to ethylene glycol, up to about 50% by weight of other glycol, for example, 1,4-butylene glycol, propylene glycol, hexamethylene glycol, etc. in the case of polybutylene terephthalate, it is sufficient that the intrinsic viscosity i~^ ] is from 0.5 to 1.8 and the concentration of the terminal carboxyl group is from 10 to 100 meq/Kg. Also in this case, the terephthalic acid ingredient may be substituted with alkyl group, halogen group, etc. Further, the glycol ingredient may contain, in addition to 1,4 butylene glycol, up to about 50% by weight of other glycol, for example ethylene glycol, propylene glycol and hexamethylene glycol. Furthermore, the modified polyolefin used in the present invention is a polyolefin copolymerized with an unsaturated monomer having a functional group. The unsaturated monomer having the carboxyl group is an unsaturated carboxylic acid or anhydride thereof and it can include, for example, monocarboxylic acid such as acrylic acid or methacrylic acid, dicarboxylic acid such as maleic acid, humaric acid or itaconic acid, dicarboxylic acid anhydride such as maleic acid anhydride or itaconic acid anhydride, dicarboxylic acid and anhydride thereof being particularly preferred. Further, as the unsaturated monomer having epoxy group, there can be mentioned glycidyl ester of metacrylic acid. Further, as the olefin copoly erized with the unsaturated monomer having the epoxy group, there can be mentioned olefins such as ethylene, propylene, butene-1 and pentene-1. These olefins may be used alone or as a mixture of two or more of them. Further, the olefins may be incorporated, as required, with less than 10% by weight of other copoly erizable monomers, for example, vinyl acetate, isoprene, chloroprene and butadiene. Among the modified polyolefins, copolymers of glycidyl acrylate or methacrylate and ethylene are particularly preferred. The modified polyolefin containing carboxyl group of epoxy group may be any of block copolymer, graft copolymer, andom copolymer or intercopolymer. It is necessary that the weight average molecular weight of the modified polyolefin is from 8,000 to 140,000 and the content of the carboxyl group or epoxy group in the modified polyolefin is from 0.2 to 5 mol %. The weight average molecular weight was measured by a gel permeation chromatography (GPC) and converted as the not-modified polyolefin. Further, the carboxyl group content was determined based on the elemental analysis value. The epoxy group content was determined based on the analysis value for elemental oxygen. If the weight average molecular weight is less than 8,000, the effect of improving the compatibility is insufficient. On the other hand, if it exceeds 140,000, the melt viscosity is increased to worsen the moldability. Further, if the carboxyl group or the epoxy group is less than 0.2 mol %, reactivity with the polyester is poor in which graft copolymer is less formed. On the other hand, if it exceeds 5 mol %, melt viscosity of the reaction product is increased due to excess reaction with the polyester, tending to form gel-like material easily. For graft polymerizing the polyester and the modified polyolefin, both of them are dry blended and then melt-kneaded at 260 - 320 β C for 0.5 to 15 in. The melt-kneading is preferably conducted in an extruder, particularly, in a twin screw extruder. If the reaction temperature is lower than 260 C C, grafting is to sufficient. On the other hand, if it exceeds 320°C, excess reaction occurs to cause blocking in the extruder due to the gel formation. Also, the resin tends to be degraded easily. The blending amount of the polyester and the modified polyolefin is from 10 to 90 parts by weight, preferably, from 20 to 80 parts by weight for the former and from 90 to 10 parts by weight and, preferably, from 80 to 20 parts by weight for the latter. If the polyester is less than 10 parts by weight or greater than 90 parts by weight, the amount of the graft copolymer formed is reduced. Further, in the present invention, the polyester and the modified polyolefin are reacted under melt-kneading, wherein from 0.05 to 2.0 parts by weight of water is added based on 100 parts by weight of the sum of the polyester and the modified polyolefin. If the addition amounts of the water is less than 0.05 parts by weight, gel formation can not be prevented sufficiently. If it exceeds 2.0 parts by weight, the molecular weight of the graft copolymer is too low to sufficiently attain the improving effect for the compatibility. In the case of using an extruder for melt-kneading, water is continuously supplied to the inside of the extruder by means of a pump. Particularly, the addition of water to the downstream side of a kneading zone of the extruder is preferred. The thus obtained polyolefin-polyester graft copolymer is satisfactory as a compatibilizing agent for a polycarbonate resin and a polyolefin, and, generally, it is added at a ratio of 1 to 30 parts by weight based on 100 parts by weight of the sum for both of them. By defining the intrinsic viscosity [^ ] and the concentration of the terminal carboxyl group of the polyester, and the carboxyl group or epoxy group content and the weight average molecular weight of the modified polyolefin used in the grafting reaction to respective specific ranges, and adding water upon grafting reaction, the grafting reaction can be controlled easily, and gel formation due to excess reaction can be prevented. In particular, by the addition of water, the polyester chain portion in the graft copolymer is hydrolized to reduce the molecular weight. As a result, it is possible to suppress the gel formation due to increased molecular weight by excess reaction and prevent clogging in the extruder. In addition, grafting ratio is not reduced. Examples The present invention is to be described more in details referring to the following examples. In each of the examples and comparative examples, characteristic values were measured as described below. (1) Intrinsic viscosity [7 : determined from a solution viscosity measured in an o-chlorophenol solvent at 25°C. (2) Concentration of terminal carboxyl group: determined by diluting a benzyl alcohol solution of a polyester with chloroform and titrating with a solution of 0.1 N sodium hydroxide benzyl alcohol using a 0.1% alcohol solution of phenol red as an indicator. (3) Weight average molecular weight: measured by 6PC method and determined as a polyethylene-converted valued. (4) MFR : determined at 280°C under the load of 2160 g or 216 Kg. (5) Gel formation: a film of about 100 urn thickness was prepared by press-molding and presence or absence of gel was judged with naked eyes. (6) Clogging of extruder with resin: presence or absence of clogging in the die portion with gel was observed upon reaction for one hour by using a twin screw extruder of 45 mmo at a discharge amount of 30 Kg/hr. (7) Grafting rate: grafting rate was determined by isolating ingredients insoluble to both of m-cresol (100 β C) and xylene (100°C). Examples 1 - 8. Comparative Example 1 - 2 As shown in Table 1, after blending polyethylene terephthalate or a polybutylene terephthalate each having various intrinsic viscosities [^] and concentrations of terminal carboxyl group and modified polyethylene (graft copolymer of glycidyl methacrylate or acrylate and ethylene) having various contents of epoxy and carboxyl groups and number average molecular weights at a ratio of 30/70 (by weight), they were supplied to a twin screw extruder of 45 mmo and a melt-kneaded at 280 β C at 200 rpm to proceed grafting reaction. In this case, water was added at a ratio shown in Table 1 based on 100 parts by weight of the sum of the polyethylene terethalate and a modified polyethylene to the down- stream side of the kneading zone in a twin screw extruder. The residence time in the extruder was about 1 min. MFR, grafting ratio, occurrence of gel formation and occurrence of clogging in the extruder were as shown in Table 1. Exampl e 9 A copolymer was produced and measured in the same manner as in Example 1 except for using, as a polyester, a mixture of 50% by weight of a polyethylene terephthalate having an intrinsic viscosity i- t m of 0.70 and a concentration of terminal carboxyl group of 35 meq/Kg, and 50% by weight of a polyethylene terephthalate having an intrinsic viscosity i-*\ of 0.73 and a concentration of terminal carboxyl group of 60 meq/Kg. The results are also shown in Table 1. Examples 10. 11 Copolymers were produced in the same manner as in Example 1 except for changing the ratio (by weight) of the polyethylene terephthalate and the modified polyethylene to 50/50 (in Example 10) and 80/20 (in Example 11). The results are also shown in Table 1. As has been described above in the present invention, since polyester having an intrinsic viscosity [^ & nd a concentration of terminal carboxyl group each within a predetermined range, and a modified polyolefin having carboxylic group and epoxy group contents and melt flow rate (MFR) each in a predetermined range are reacted, and since water is added, it is possible to prevent the gel formation due to excess reaction and prevent resin clogging of the extruder while maintaining satisfactory fluidity without reducing the grafting ratio. The 'polyolefin-polyester graft copolymer according to the present invention thus obtained is extremely effective as a compatibilizing agent for an engineering resin such as a polycarbonate resin and a polyolefin. Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be Table 1 o I (1) Polyethylene terephthalate (TR 4550, manufactured by Teijin Co.) (2) Polybutylene terephthalate (TRB-K, manufactured by Teijin Co.) (3) Glycidyl methacrylate (4) Acrylic acid (5) Parts by weight based on 100 parts by weight of polyester + modified polyethylene. devised without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims: CLAIMS : 1. A process for producing a polyolefin-polyester graft copolymer, wherein (a) from 10 to 90 parts by weight of a polyester having an intrinsic viscosity of 0.50 to 1.8 and a concentration of terminal carboxyl group of 10 to 100 meq/Kg, and (b) from 90 to 10 parts by weight of a modified polyolefin containing 0.2 to 5 mol of carboxyl group or epoxy jroup and having a weight average molecular weight of 8,000 to 140,000. are reacted by melt-kneading at 260 - 320°C, in which from 0.05 to 2.0 parts by weight of water is added to 100 parts by weight of the sum of the polyester and the modified polyolefin. 2. A process as defined in claim 1, wherein the polyester is at least one of a polyethylene terephthalate having an intrinsic viscosity of 0.50 to 1.0 and a concentration of terminal carboxyl group of 10 to 100 meq/Kg and a polybutylene terephthalate having an intrinsic viscosity C^] of 0.50 to 1.8 and a concentration of terminal carboxyl groups of 10 to 100 meq/Kg.

Inventors: INAMORI KIKUO, OOSAWA MASAHIRO, SATO SHIGERU, SEZUME TADASHI, INAMORI, KIKUO, OOSAWA, MASAHIRO, SATO, SHIGERU, SEZUME, TADASHI
Applicants: TONEN CORP, TONEN CORPORATION
Application year: 1990
Main classification: C08G81
IPC codes: C08G81, C08L23, C08L69, C08L87