AU5422290A

AU5422290A - Polypropylene-polyester graft copolymer and production method thereof

Info

Publication number: AU5422290A
Application number: AU54222/90A
Authority: AU
Inventors: Kikuo Inamori; Akira Kobayashi; Tadashi Sezume
Original assignee: Tonen Corp
Current assignee: Tonen General Sekiyu KK
Priority date: 1989-04-12
Filing date: 1990-04-11
Publication date: 1990-11-05
Also published as: WO1990012054A1; JPH0347844A; EP0467958A1; KR920701312A; EP0467958A4; CA2050283A1

Description

POLYPROPYLENE-POLYESTER GRAFT COPOLYMER AND PRODUCTION METHOD THEREOF

Field of the Invention The present invention relates to a polypropylene-polyester graft copolymer which is effective as a compatibilizing agent for both of ingredients in a resin composition comprising a polycarbonate and a polyolefin, in particular, a polypropylene, and a production process for the graft copolymer. More in particular, it relates to a graft copolymer of a polyester having specific intrinsic viscosity and concentration of terminal carboxyl group and a modified polypropylene having a specific melt flow rate (MFR), as well as a production process thereof. 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 poor, it has been attempted to add various 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 ethyl ene-propylene copolymer and/or ethyl ene-propylene-diene copolymer, and Japanese Patent Laid Open Sho 57-111351 discloses an isoprene rubber and/or methyl pentene polymer. There is, thus, a continuing need for an improved compatibilizing agent for the polycarbonate resin and the polyolefin, in particular, polypropylene, wherein the impact resistance of the molding product is not reduced and the problem of surface peeling as the amount of the polyolefin is increased is diminished. 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 [ η] of 0.30 and 1.2 and a concentration of terminal carboxyl group of 15 to 200 meg/ g, and from 85 to 15 parts by weight of a modified polyolefin containing 0.2 to 5 moll 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 63-258883). However, in the course of further studies, it has been found that when a polypropylene is used as a polyolefin in a blend of a polyolefin and a polycarbonate, the affinity is not sufficient between the polyethylene-polyester graft copolymer obtained by the process described above and polypropylene and that reaction less occurs between high M_W molecules of the modified polypropylene and the polyester even when it is intended to produce the polypropylene-polyester copolymer by the process described above. It is, accordingly, an object of the present invention to provide a polypropylene-polyester graft copolymer capable of functioning as a compatibilizing agent for a polycarbonate resin and a polyolefin, particularly, a polypropylene. Another object of the present invention is to provide a process for producing such a propylene-polyester graft copolymer. SUMMARY OF THE INVENTION The present inventors have made earnest studies for attaining the foregoing objects and, as a result, have accomplished the present invention based on the finding that a graft copolymer of a polyester and a functional group-containing modified polypropylene is effective as a compatibilizing agent for a polycarbonate resin and a polyolefin, particularly, a polypropylene and that a desired polypropylene-polyester graft copolymer can be obtained through grafting reaction by defining the intrinsic viscosity and the concentration of the terminal carboxyl group of the polyester and the functional group content and the melt flow rate (MFR) of the modified polypropylene to respective specific ranges. That is, a polypropylene-polyester graft copolymer according to the present invention comprises from 10 to 90 parts by weight of a polyester having an intrinsic viscosity [ η] of 0.5 to 1.8 and a concentration of terminal carboxyl group of 10 to 1000 meq/Kg, and 90 to 10 parts by weight of a modified polypropylene containing 0.2 to 5.0 % by weight of functional groups and a melt flow rate (MFR) measured at 230°C under the load of 2160 g) of 0.5 to 80 g/10 min. Further, a process for producing a polypropylene- polyester graft copolymer according to the present invention comprises reacting:

(a) from 10 to 90 parts by weight of a polyester having an intrinsic viscosity [η ] of 0.5 to 1.8 and a concentration of terminal carboxyl groups of from 10 to 100 meq/Kg, and (b) from 90 to 10 parts by weight of a modified polypropylene containing 0.1 to 2.0% by weight of functional group and a melt flow rate (MFR, measured at 230°C under the load of 2160 g) of 0.5 to 80 g/10 min, by using a twin screw extruder at 240 - 300°C. 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, polytetramethylene terephthalate (polybutylene terephthalate), polyhexamethylene 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 [η ] (dl/g) is determined from a solution viscosity measured in an o-chlorophenol solvent at 25°C. If the intrinsic viscosity [ η] of the polyester is less than 0.5, 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, the intrinsic viscosity [η ] is from 0.5 to 1.0 and the concentration of the terminal carboxyl group is from 10 to 100 meq/kg. If the intrinsic viscosity [η] exceeds 1.0, the m melt viscosity of the graft polymer is increased to cause gelation. Further, the terephthalic acid ingredient in the polyethylene terephthalate may be substituted with alkyl group, halogen group, etc., and the glycol ingredient may contain, in addition to ethyl ene 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 [ η ] 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, up to about 50% by weight of other glycol, for example, ethylene glycol, propylene glycol and hexamethylene glycol. Furthermore, the modified polypropylene used in the present invention is a polypropylene containing an unsaturated monomer having a functional group. The functional group contained in the modified polypropylene is at least one such group that is reactive with the terminal carboxyl group or hydroxyl group of the polyester and it can include for example carboxyl group, epoxy group, hydroxyl group and amino group. The unsaturated monomer having carboxyl group is an unsaturated carboxyl ic 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 itanconic acid, dicarboxylic acid anhydride such as maleic acid anhydride or itaconic acid anhydride, the 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 or glycidyl ester of acrylic acid. Other unsaturated monomers, including those having hydroxyl or amino groups, are known in the art and will be effective within the scope of this invention where reactive as described. The backbone for the functional group-containing modified polypropylene may be any of block copolymer, graft copolymer, random copolymer or intercopolymer of, e.g., propylene and it is, particularly preferably, a propylene random copolymer containing a non-conjugated diene comonomer represented by the general formula: where R₁ - R₄ each represents H or an alkyl group with 1 to 6 carbon atoms and n represents an integer of 1 to 20. As the non-conjugated diene, there can be mentioned, for example, 1,4-hexadiene, 7-methyl-1,6-octadiene, 5-methyl- 1,4-hexadiene, 1,9-decadiene, 4-methyl-1,4-heptadiene, 4-ethyl- 1,4-hexadiene and 1,13-tetradecadiene. Among them, 1,4-hexadiene, 7-methyl-1,6-octadiene, 5-methyl-1,4-hexadiene and 1,9 decadiene are particularly preferred. Two or more of the non-conjugated diene comonomers may be used in admixture. For the random copolymerization of propylene and the non-conjugated diene comonomer, usual copolymerization process using a Ziegler-Natta catalyst may be applied. In this case, it is desirable that the ratio of the non-conjugated diene is from 0.05 to 10 mol%. If the content of the non-conjugated diene is less than 0.05 mol%, high grafting rate can not be obtained in the subsequent grafting reaction. On the other hand, if it exceeds 10 mol%, crystal Unity of the copolymer is remarkably reduced. More preferred content of the non-conjugated diene is from 0.1 to 3 mol%. Further, propylene copolymerized with the unsaturated monomer having the functional group as described above may be incorporated as required, with less than 10% by weight of olefin such as ethylene, butene-1 or pentene-1, monomers such as vinyl acetate, isoprene, chloroprene or butadiene. The unsaturated monomer having the functional group may be reacted with the polypropylene-non conjugated diene random copolymer by the following methods. That is, it is possible to employ methods such as solution method of dissolving a random copolymer into an organic solvent such as xylene or toluene, and adding to react a monomer and a radical generator to the solution, or a melt-kneading method of melt-kneading a random copolymer, a monomer and a radical generator using an extruder or the like thereby causing reaction, etc. Particularly, the melt-kneading method is suitable since the continuous reaction is easy. In the case of the melt-kneading method, the reaction time is preferably from 10 sec to 20 min. As the radical generator (reaction initiator), peroxides such as benzoyl peroxide, lauroyl peroxide, ditertiary butylperoxide, acetyl peroxide, tertiary butyl peroxybenzoic acid, dicumyl peroxide, peroxybenzoic acid, peroxyacetic acid, tertiary butyl peroxypivalate, or diazo compounds such as azobisisobutylonitrile are preferred. The blending ratio is desirably within a range from 0.1 to 10 parts by weight based on 100 parts by weight of the radical polymerizable monomer. It is also possible to cause grafting reaction by kneading under heating without using the radical generator. It is necessary that the melt flow rate (MFR) of the modified polypropylene be from 0.5 to 80 g/10 min and the amount of the functional group in the modified polypropylene be from 0.1 to 2.0% by weight. The melt flow rate (MFR) was measured at 230ºC under the load of 2160 g and represented by the unit of g/10 min. The functional group content was determined from the analytical value for elemental oxygen. If the melt flow rate (MFR) exceeds 80 g/10 min (that is, if the molecular weight is too low), reaction with polyester minimally occurs, bringing about a difficulty in the snythesis of the graft copolymer. If it is less than 0.5 g/10 min (if the molecular weight is excessively high), the melt viscosity is increased such that moldability properties are adversely affected. Generally, the average molecular weight (Mw) of the modified polypropylene having MFR from 0.5 to 80 g/10 min is about from 70,000 to 300,000. Further, if the functional group is less than 0.1% by weight, the reactivity with the polyester is so poor that graft copolymer is minimally formed. On the other hand, if it exceeds 2.0% by weight, the melt viscosity of the reaction product is increased due to the excess reaction, tending to result in gel-like material. For graft reacting the polyester and the modified polyolefin, both of them are dry blended and then melt-kneaded at 240 - 300ºC, for polypropylene, and at 260 - 320ºC for other polyolefins. The melt-kneading is preferably conducted in an extruder, particularly, in a twin screw extruder. If the reaction temperature is lower than described, the grafting is not sufficient. On the other hand, if it exceeds that described, excess reaction occurs and the melting temperature of the reaction product is increased, tending to cause blocking in the extruder. Further, the modified polypropylene adversely tends to be degraded more easily. The time for the grafting reaction is typically from about 0.5 to 15 min although it may vary depending on the reaction conditions. The blending amount of the polyester and the modified polypropylene is from 10 to 90 parts by weight, preferably, from 20 to 80 parts by weight from 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. The thus obtained polypropylene-polyester graft copolymer is useful as a compatibilizing agent for a polycarbonate resin and a polyolefin, particularly a polypropylene and, generally, it is added at a ratio of 1 to 30 parts by weight based on 100 parts by weight of the sum of both of them. By defining the intrinsic viscosity [ η ] and the concentration of the terminal carboxyl group of the polyester, and the functional group content, and the melt flow rate (MFR) of the modified polypropylene used in the graft polymerizing reaction to respective specific ranges, the grafting reaction proceeds easily, a graft copolymer of sufficient grafting ratio can be obtained and formation of gel due to excess reaction can be prevented. Thus providing a satisfactory compatibilizing agent. Exampl es The present invention is to be described more in details referring to the following examples. In each of the examples and comparative examples, characteristics values were measured as described below. (1) Intrinsic viscosity [η]:

determined from a solution viscosity measured in an o-chlorophenol solvent at 25ºC. (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) Melt flow rate (MFR):

determined at 230ºC under the load of 2160 g. (4) Grafting rate:

grafting rate was determined by isolating ingredients insoluble to both of m-cresol (100°C) and xylene (100ºC). (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 mm at a discharge amount of 30 kg/hr. Examples 1 - 6. Comparative Examples 1 - 3 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 polypropylene (graft copolymer of propylene non-conjugated diene random copolymer and maleic acid anhydride or glycidyl methacrylate) having various functional group contents and melt flow rates (MFR) at a ratio of 20/80 (by weight), they were supplied to a twin screw extruder of 45 mmΦ and a melt-kneaded at 280°C at 200 rpm to proceed grafting reaction. The residence time in the extruder was about 1 min. The grafting rates of the reacting products were as shown in Table 1. In the examples, neither the gel formation nor the clogging of the extruder was observed. Example 7 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 [ ] of 0.72 and a concentration of terminal carboxyl group of 30 meq/Kg, and 50% by weight of a polybutylene terephthalate having an intrinsic viscosity [η] of 0.85 and a concentration of terminal carboxyl group of 52 meq/Kg. The results are also shown in Table 1. Also in this example, neither the gel formation nor the clogging of the extruder was observed. Examples 8, 9 Copolymers were produced in the same manner as in Example 1 except for changing the ratio (by weight) of the polybutylene

Note: (1) Polyethylene terephthalate (TR 455OBH, manufactured by Teijin Co.)

(2) Polybutylene terephthalate

(TRB-K, manufactured by Teijin Co.)

(3) 2160 g load (230ºC)

(4) Maleic acid anhydride

(5) Glycidyl methacrylate terephthalate and the modified polypropylene to 50/50 (in Example 8) and 80/20 (in Example 9). The results are also shown in table 1. Also in this example, neither the gel formation nor the clogging in the extruder was observed. As apparent from the results of Table 1, the polypropylene-polyester copolymer according to the present invention has high grafting ratio and, in addition, formation of gel due to excess reaction can be prevented and resin clogging in the extruder can also be prevented. On the other hand, it can be seen that the grafting ratio is 0 and grafting reaction did not proceed in the copolymers of the Comparative Examples. As has been described above in the present invention, since polyester having an intrinsic viscosity [ η ] and a concentration of terminal carboxyl group each within a predetermined range, and a modified polypropylene having a functional group content and a melt flow rate (MFR) each in a predetermined range are reacted, a copolymer can be obtained at a high grafting ratio. The polypropylene-polyester graft copolymer according to the present invention thus obtained is extremely effective as a compatibilizing agent for a polycarbonate resin and a polyolefin, particularly, a polypropylene. 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 devised without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

CLAIMS :

1. A polypropylene-polyester graft copolymer comprising from 10 to 90 parts by weight of a polyester having an intrinsic viscosity of 0.5 to 1.8 and a concentration of terminal carboxyl group of 10 to 100 meq/kg, and from 90 to 10 parts by weight of a modified polypropylene containing 0.1 to 2.0 % by weight of functional groups and a melt flow rate measured at 230ºC under the load of 2160 g of 0.5 to 80 g/10 min.

2. A polypropylene-polyester graft copolymer as defined in claim 1, wherein the modified polypropylene is a propylene random copolymer containing a non-conjugated diene comonomer represented by the general formula:

CH₂ = C(CH₂)_n C = C - R₄

R₁ R₂ R₃ where R₁ - R₄ each represents H or an alkyl group with 1 to 6 carbon atoms and n represents an i nteger of 1 to 20.

3. A polypropylene-polyester graft copolymer as defined in claim 1 or 2, wherein the polyester is a polyethylene terephthalate having an intrinsic viscosity of 0.5 to 1.0 and a concentration of terminal carboxyl group of 10 to 100 meq/Kg, polybutylene terephthalate having an intrinsic viscosity of 0.5 to 1.8 and a concentration of terminal carboxyl group of 10 to 100 meq/kg, or a blend thereof.

4. A polypropylene-polyester graft copolymer as defined in any one of claims 1 to 3, wherein the functional group of the modi fi ed polypropylene is carboxyl, acid anhydride or epoxy group.

5. A process of producing a polypropylene-polyester graft copolymer comprised of reacting:

(a) from 15 to 85 parts by weight of a polyester having an intrinsic viscosity of 0.5 to 1.8 and a concentration of terminal carboxyl group of 10 to 100 meq/kg; and

(b) from 85 to 15 parts by weight of a modified polypropylene containing 0.1 to 2.0% by weight of functional groups and a melt flow rate measured at 230ºC under the load or 2160 g of 0.5 to 80 g/10 min.

6. The process as defined in claim 5, wherein the polyester is a polyethylene terephthalate having an intrinsic viscosity of 0.5 to 1.0 and a concentration of terminal carboxyl group of 10 to 100 meq/kg, a polybutylene terephthalate having an intrinsic viscosity of 0.5 to 1.8 and a concentration of terminal carboxyl group of 10 to 100 meq/kg, or a blend thereof.

7. The process as defined in claim 5 or 6, wherein the functional group of the modified polypropylene is carboxyl group, acid anhydride or epoxy group.

8. The process defined in claim 5 wherein said reacting is accomplished in a twin-screw extruder at 240-300°C.

9. The use of the graft copolymer of claim 1 as a compatibilizing agent for blend compositions comprising polycarbonate resin and polypropylene wherein said graft co-polymer is present in a weight ratio of 1 to 30 parts to 100 parts of said polycarbonate resin plus said polypropylene.