JPH06299024A - Thermoplastic resin composition - Google Patents

Abstract

PURPOSE:To provide a thermoplastic resin compsn. which has water absorption capacity lower than that of a polyamide resin and a good balance among heat resistance, impact strength, and stiffness. CONSTITUTION:The compsn. is produced by mixing 1-99wt.% methyl methacrylate-alpha-methylstyrene-maleic anhydride terpolymer comprising 10-40mol% alpha-methylstyrene units, 30-89.9mol% methyl methacrylate units, and 0.1-30mol% maleic anhydride units and having a wt. average mol.wt. of 30,000-200,000, 1-99wt.% polyamide resin, and 10-40wt.% maleic anhydride-modified ethylene- propylene random copolymer mainly comprising ethylene units and contg. 0.01-10wt.% maleic anhydride units.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin composition obtained from a methyl methacrylate copolymer and a polyamide resin, which is excellent in heat resistance and impact resistance.

[0002]

2. Description of the Related Art Polyamide resins represented by nylon 6, nylon 66 and the like are conventionally known as general-purpose engineering plastics because of their good mechanical properties, heat resistance, solvent resistance and abrasion resistance, It has been used as a molding material for parts, electrical equipment parts, machine parts and the like.

[0003]

However, compared with other resins, the polyamide resin has a high water absorption and is inferior in dimensional stability such as warping or sinking in the molded product due to the water absorption after the molding process. It has drawbacks. For this reason, the polyamide resin is unsuitable as a molding material for a large-sized molded product that requires dimensional accuracy.

A method of melting and kneading a polyamide resin and a polystyrene resin has been proposed for the purpose of reducing the water absorption of the polyamide resin (Japanese Patent Publication No. 40-7380). However, with this resin mixture, although the water absorbency of the polyamide resin is improved, the miscibility between the two resins is poor, and a resin mixture having excellent properties such as heat resistance and mechanical strength could not be obtained.

In Japanese Patent Application No. 3-47302, for the purpose of improving miscibility with a polyamide resin and maintaining heat resistance, a methyl methacrylate-α-methylstyrene-maleic anhydride copolymer and a polyamide are used. A thermoplastic resin composition prepared by melt-kneading with a resin is proposed. The thermoplastic resin described in this specification was superior to the conventional polyamide resin-polystyrene resin composition in mechanical properties such as water absorbency, heat resistance, tensile strength, and tensile modulus. However, this thermoplastic resin composition impairs the toughness and impact resistance of the polyamide resin, like the resin composition of the polyamide resin and the polystyrene resin.

On the other hand, in order to improve the impact resistance represented by the Izod impact strength of polyamide resin, a method of incorporating an elastomer component has been proposed. For example, when a polyamide and an ethylene-vinyl acetate copolymer having a vinyl acetate unit content of 42% by weight are melt-kneaded using a screw extruder or the like, the resin composition obtained has an Izod impact strength of a polyamide resin. It has already been reported that it will be about twice as much as a single unit (L.D'ORAZIO, C.MANCARELLA, E.
MARTUSCELLI, JOURNAL OF MATERIALS SCIENCE, 22 (198
7)). In Japanese Patent Publication No. 4-14138, an ethylene-α-olefin-diene copolymer obtained by graft-copolymerizing a polyamide resin and an unsaturated carboxylic acid or a derivative component thereof, and a polar vinyl monomer-containing ethylene-based random copolymer are disclosed. A polyamide composition consisting of is proposed.
Further, in JP-B-4-14139, a polyamide comprising a polyamide resin, an ethylene-α-olefin-diene copolymer graft-copolymerized with an unsaturated carboxylic acid or a derivative component thereof, and an ethylene-vinyl acetate copolymer. A resin composition is proposed.

The compositions proposed in these prior art documents all have improved impact resistance, but the elastic modulus decreases, and a molded article having high rigidity and high impact resistance cannot be obtained. It has drawbacks. Furthermore, ethylene-vinyl acetate copolymer and ethylene-α blended with polyamide
-Elastomer components such as olefin-diene copolymers all exhibit rubber-like elasticity even at room temperature or lower, so that the heat resistance of the resin composition obtained when blended with the polyamide resin is higher than that of the polyamide resin alone. The molded product had an unfavorable change in physical properties, such as a remarkable decrease.

The inventors of the present invention have conducted studies to develop a thermoplastic resin composition having no such problems and having excellent properties. As a result, the methyl methacrylate-α-methylstyrene-maleic anhydride copolymer A polymer, a polyamide resin, and a melt-kneaded product of a maleic anhydride-modified ethylene-propylene copolymer have a low water absorption and a good balance of impact resistance and rigidity without impairing the excellent heat resistance of polyamide. The inventors have found that it is a resin and completed the present invention. Therefore, an object of the present invention is to provide a thermoplastic resin composition having a lower water absorption rate than a polyamide resin and having a good balance of heat resistance, impact resistance and rigidity.

[0009]

Means for Solving the Problems That is, the present invention provides a methyl methacrylate-α-methylstyrene-maleic anhydride copolymer 1-89% by weight, a polyamide resin 1-89% by weight, and a maleic anhydride-modified ethylene. A thermoplastic resin composition obtained by mixing 10 to 40% by weight of a propylene copolymer.

The present invention will be described in detail below.

Methyl methacrylate used in the present invention
α-Methylstyrene-maleic anhydride copolymer (A)
(Hereinafter, simply referred to as “copolymer (A)”) may be polymerized by any method of bulk polymerization, solution polymerization, emulsion polymerization or suspension polymerization. It may be polymerized by either initiator polymerization using an azo compound or the like as a polymerization initiator or thermal polymerization without using an initiator. Preferably, bulk polymerization in which impurities are not mixed in the copolymer is used. In addition, when the viscosity of the copolymer is high, it is possible to add a small amount of a solvent to carry out the polymerization in order to reduce the viscosity. In this case, the solvent is preferably an inert solvent used in ordinary radical polymerization, such as benzene, toluene or ethylbenzene.

As the copolymer (A), those having a weight average molecular weight of 30,000 to 200,000 can be used.
It is preferably 50,000 to 150,000, more preferably 70,000 to 130,000. At this time, if the weight average molecular weight is less than 30,000, mechanical strength will not be exhibited, and if it exceeds 200,000, thermal decomposition will occur during molding and the resulting monomer components will reduce heat resistance.

The composition of this copolymer (A) is α-
The methylstyrene unit is preferably 10 to 40 mol%, the methyl methacrylate unit is 30 to 89.9 mol%, and the maleic anhydride unit is preferably 0.1 to 30 mol%, more preferably the α-methylstyrene unit is 10 to 10. Two
5 mol%, methyl methacrylate unit 60 to 89 mo
1%, and the maleic anhydride unit is preferably 1 to 30 mol%.
When the α-methylstyrene unit is less than 10 mol%, the heat resistance is impaired, and when it exceeds 40 mol%, thermal decomposition tends to occur during molding. When the thermal decomposition occurs, a monomer is generated, so that the heat resistance is lowered as described above. Further, when the maleic anhydride unit is less than 0.1 mol%, the miscibility between the copolymer and the polyamide resin is poor, and the amount is 30 mo.
If it exceeds 1%, the coloring during molding becomes remarkable.

The copolymer (A) contains a small amount of a fourth component (eg, styrene, acrylonitrile, 10 mol% or less) as a constituent unit as long as its properties are retained.
Methacrylonitrile, N-phenylmaleimide, N-phenylmethacrylamide, methacrylic acid, acrylic acid,
Methacrylic acid esters such as ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, Acrylic acid esters such as n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, cyclohexyl acrylate and benzyl acrylate. ) May be entered.

Of these, a methyl methacrylate-α-methylstyrene-maleic anhydride-styrene copolymer containing styrene as the fourth component is a methyl methacrylate unit, an α-methylstyrene unit, and a maleic anhydride unit. Since it has better fluidity than a copolymer consisting of three components,
The load on the polymerization device and the kneader is reduced. Further, the methyl methacrylate-α-methylstyrene-maleic anhydride-styrene copolymer has less undesired coloring compared to the copolymer containing the fourth component other than styrene. Will be excellent.
Therefore, styrene is the most preferable as the fourth component.

The polyamide resin (B) used in the present invention includes nylon 6, nylon 66, nylon 610,
Nylon 46, nylon 11, nylon 12, metaxylene diamine type nylon, etc. are used. Of these, nylon 6 is preferable because it can be melt-kneaded at a relatively low temperature and is less likely to cause thermal deterioration of other copolymers.

The maleic anhydride-modified ethylene-propylene copolymer (C) used in the present invention is an ethylene-propylene random copolymer containing ethylene as a main component.
The content of maleic anhydride in the maleic anhydride-modified ethylene-propylene copolymer is preferably 0.01 to 10% by weight. More preferably, it is 0.1 to 2.0% by weight. When the content of maleic anhydride is less than 0.01% by weight, the miscibility of the maleic anhydride-modified ethylene-propylene copolymer with the polyamide resin phase becomes poor and the phase separation becomes severe, resulting in a thermoplastic resin composition obtained. The impact resistance of is poor.

The maleic anhydride-modified ethylene-propylene copolymer has a test temperature of 230 ° C. and a test load of 2.1.
Melt flow rate at 6 kgf is 0.05 to 50
What is g / min is used. If the melt flow rate of the maleic anhydride-modified ethylene-propylene copolymer is less than 0.05 g / min, the fluidity during melt kneading will be reduced, and the moldability will be poor. In addition, unfavorable results such as a decrease in impact resistance of the molded product may occur. On the other hand, when the melt flow rate is more than 50 g / min, the impact resistance is lowered, which is not preferable.

Copolymer (A) and polyamide resin (B)
Although various known methods can be applied as a method for mixing the ethylene glycol with the maleic anhydride-modified ethylene-propylene copolymer (C), melt kneading is preferable. The kneading machine used for melt kneading is
Various internal mixers such as rolls and Banbury mixers,
Various screw type extruders and other mixers.

When blending is carried out by the melt-kneading method, the kneading temperature varies depending on the blending ratio of both resins and the copolymer composition of the copolymer, but it is carried out at 210 to 280 ° C, preferably 220 to 270 ° C, more preferably 220-250
It is performed at ℃. When the kneading temperature is lower than 210 ° C, when the polyamide (B) is nylon 6, the nylon 6 does not melt, and when it exceeds 280 ° C, thermal decomposition or coloring of the copolymer occurs. Also, nylon 66 is used as the polyamide resin.
When using, the melting temperature is preferably 260 to 280 ° C. When using other polyamide resins, it is necessary to carry out melt-kneading at a temperature not lower than the melting point of the polyamide resin used. The melt-kneading time is 0.5 to 20 minutes, preferably 1 to 10 minutes, more preferably 3 to 5 minutes.
If this time is less than 0.5 minutes, the kneading will not be sufficient and 20
If it exceeds the minute, thermal decomposition and coloring become remarkable.

When this melt-kneading is performed, the polyamide resin (B) and the copolymer (A) partially react with each other during the melt-kneading, and the polyamide resin (B) and the copolymer (A).
A graft copolymer with is produced. Further, during the melt-kneading, a part of the polyamide resin (B) and the maleic anhydride-modified ethylene-propylene copolymer (C) also react, and the polyamide resin (B) and the maleic anhydride-modified ethylene-propylene copolymer are reacted. A graft copolymer with the polymer (C) is produced. Therefore, the thermoplastic resin composition obtained by melt-kneading includes the polyamide resin (B), the copolymer (A),
Maleic anhydride-modified ethylene-propylene copolymer (C), polyamide resin (B) and copolymer (A) graft copolymer, and polyamide resin (B) and maleic anhydride-modified ethylene-propylene copolymer It is a mixture of a graft copolymer with (C).

Copolymer (A) and polyamide resin (B)
And the mixing ratio of maleic anhydride-modified ethylene-propylene copolymer (C) is (A) = 1 to 89% by weight,
(B) = 1 to 89% by weight, (C) = 10 to 40% by weight, but copolymer (A) is 30 to 70% by weight, polyamide (B) is 30 to 70% by weight, maleic anhydride. The modified ethylene-propylene copolymer (C) is preferably 10 to 40% by weight, more preferably the copolymer (A).
Is 40 to 60% by weight, or polyamide (B)
Is 40 to 60% by weight, and the maleic anhydride-modified ethylene-propylene copolymer (C) is 20 to 30% by weight. When the above range is selected, the thermoplastic resin composition obtained has a good balance between heat resistance and mechanical properties.

Copolymer (A) and polyamide resin (B)
And the maleic anhydride-modified ethylene-propylene copolymer (C) are melt-kneaded, the thermoplastic resin compositions having different properties can be selected by arbitrarily selecting the mixing ratio thereof within the range of the above mixing ratio. Becomes That is, since heat resistance and mechanical properties of the resin composition obtained by melt-kneading differ when the mixing ratio is different, it is necessary to select the mixing ratio according to the physical properties required for the molded product obtained from the resin composition.

For example, when impact resistance is required for the resin composition, the mixing ratio of the maleic anhydride-modified ethylene-propylene copolymer is preferably 10 to 40% by weight.
When heat resistance is required, the mixing ratio of the polyamide resin is 40% by weight or more, more preferably 50% by weight or more, and the mixing ratio of the maleic anhydride-modified ethylene-propylene copolymer is 30% or more. It is desirable that the content be less than or equal to weight%. When rigidity is required, the mixing ratio of the copolymer must be 30% by weight or more.

Further, the thermoplastic resin composition of the present invention comprises
Various additives can also be added for various purposes. Examples of such additives include Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.) as a processing stabilizer and n-octadecyl-3- (3 ′, 5′-di-ter) as an antioxidant.
t-Butyl-4'-hydroxyphenyl) propionate, pentaerythrityl-tetrakis [3- (3,5-
Di-tert-butyl-4-hydroxyphenyl) propionate] and other hindered phenol compounds, tris (2,4-di-tert-butylphenyl) phosphite and other phosphite compounds, and tetrakis [methylene-3]. Examples include thioether compounds such as-(dodecylthio) propionate] methane, and examples of flame retardants include bromine compounds such as tetrabromobisphenol A and decabromodiphenyl oxide.
Electrostatic stopper series [Kao Corporation] and Dasper series [Miyoshi Yushi Co., Ltd.] as antistatic agents
], TB-123, TB-128 [manufactured by Matsumoto Yushi-Seiyaku Co., Ltd.] and the like. Further, an ultraviolet absorber such as a benzotriazole-based compound and a light stabilizer such as a hindered amine-based compound can also be used if necessary. Further, various improving agents, release agents, dyes, pastes, etc. can be added.

[0026]

EXAMPLES The present invention will be specifically described below based on Examples and Comparative Examples. The present invention is not limited to the examples and comparative examples.

In the following examples and comparative examples, the polyamide resin is nylon 6 [UBE Kosan Co., Ltd. UBE
1011FB] was used. As a maleic anhydride-modified ethylene-propylene copolymer, T7 manufactured by Nippon Synthetic Rubber Co., Ltd.
711SP was used. Melt kneading and injection molding of the copolymer, nylon 6 and the acid-modified ethylene-propylene copolymer were carried out using a Minimax injection molding machine [manufactured by Custom Scientific Enstrument Co.]. Also,
The copolymer (A) was produced as follows.

Production of Copolymer (A) In a reaction vessel, α-methylstyrene (αMSt), methyl methacrylate (MMA) and maleic anhydride (MA).
H), 25 mol%, 65 mol%, 10 m, respectively
Perkadox 12 as polymerization initiator
[Kayaku Akzo Co., Ltd.] was added at 6000 ppm each. The reaction solution was reacted at 120 ° C. for 16 hours, the obtained reaction product and the unreacted monomer mixture liquid were diluted with chloroform, and then poured into methanol to remove the unreacted monomer. The monomer-removed product was filtered and dried to obtain a powdery copolymer. Obtained copolymer 100
With respect to parts by weight, n-octadecyl-3- as an antioxidant
0.5 parts by weight of (3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) propionate was added. Hereinafter, the methyl methacrylate-α-methylstyrene-maleic anhydride copolymer produced in this manner and to which the antioxidant is added is referred to as a copolymer (A).

The physical properties of the molded articles in Examples and Comparative Examples were evaluated as follows.

(1) Water Absorption Rate A disc-shaped test piece having a diameter of 16 mm and a thickness of 2 mm was manufactured by injection molding, and the test piece was dried at 110 ° C. for 1 hour and then immersed in distilled water at 23 ° C. for 24 hours. Then, the water absorption rate was determined according to the following formula. Water absorption rate (%) = [(weight after immersion in distilled water-weight when dried) / weight when dried] x 100

(2) Tensile Elastic Modulus A rod-shaped test piece having a diameter of 1.6 mm and a length of 7.5 mm was manufactured by injection molding, and an autograph manufactured by Shimadzu Corporation was used as a tensile tester.

(3) Vicat Softening Temperature A molded article was manufactured by injection molding according to ASTM standard D1525, and the Vicat softening temperature was measured.

(4) Izod Impact Test An Izod impact test was conducted in accordance with ASTM standard D256.

Examples 1 to 4 Copolymer (A), nylon 6, and maleic anhydride-modified ethylene-propylene copolymer were melt-kneaded at a compounding ratio shown in Table 1 to form a test piece, and water absorption The rate, Vicat softening temperature, tensile test and Izod impact test were conducted.

Comparative Example 1 Nylon 6 alone was melt-kneaded at 240 ° C., and the water absorption, tensile elastic strength, Vicat softening temperature and Izod impact strength of the injection molded product were measured.

Comparative Examples 2 to 3 Nylon 6 and maleic anhydride-modified ethylene-propylene copolymer were melt-kneaded at the compounding ratio shown in Table 1 to form a test piece, and the water absorption rate, Vicat softening temperature and tensile test were conducted. And Izod impact test.

The results of each Example and Comparative Example are shown in Table 2.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

EFFECT OF THE INVENTION The thermoplastic resin composition of the present invention has a significantly lower water absorption than polyamide alone and is excellent in heat resistance, impact resistance and rigidity. Therefore, it can be suitably used as a molding material for industrial products such as electric equipment parts, housings, and automobile parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ikuo Yamaoka 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Inside Advanced Technology Research Laboratories, Nippon Steel Corporation (72) Masao Kimura 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Address Inside Nippon Steel Corporation Advanced Technology Research Laboratories

Claims (3)

[Claims] 1. A methyl methacrylate-α-methylstyrene-maleic anhydride copolymer (A) 1 to 89% by weight, a polyamide resin (B) 1 to 89% by weight, and a maleic anhydride-modified ethylene-propylene copolymer. A thermoplastic resin composition, which is obtained by mixing 10 to 40% by weight of a polymer (C). 2. The thermoplastic resin composition according to claim 1, wherein the polyamide resin is nylon 6. 3. A maleic anhydride-modified ethylene-propylene copolymer having a maleic anhydride modification rate of 0.01 to 10% by weight and a melt flow rate of 0.05 to 50 under a load of 2.16 kg at 230 ° C. The thermoplastic resin composition according to claim 1 or 2, which is