JPH0433944A - Flame-retardant impact-resistant polymer composition - Google Patents

Abstract

PURPOSE:To obtain the title composition suitable as parts of household electric appliances, parts of office automation devices, etc., having excellent heat stability during processing, heat resistance, solvent resistance, etc., by blending a vinyl chloride-based graft copolymer with specific two rubber-like graft copolymers. CONSTITUTION:(A) 40-80pts.wt. vinyl chloride-based graft copolymer comprising A1: 51-100wt.% vinyl chloride-based polymer linked to >=1wt.% aromatic vinyl polymer or copolymer of an aromatic vinyl compound and a methacrylic ester by graft bond and A2: 0-49wt.% aromatic vinyl polymer or copolymer of an aromatic vinyl compound and a methacrylic ester having 0.3-1dl/g reducing viscosity is blended with (B) 10-50pts.wt. graft polymer of a rubber-like polymer having <=25 deg.C glass transition point and an aromatic vinyl compound and (C) 5-20pts.wt. graft copolymer of a rubber-like polymer having <=25 deg.C glass transition point, an aromatic vinyl compound and a methacrylic ester.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel flame-retardant and impact-resistant polymer composition, and more particularly, it relates to a novel flame-retardant and impact-resistant polymer composition, and more particularly, to a novel flame-retardant and impact-resistant polymer composition. This invention relates to a flame-retardant and impact-resistant polymer composition.

[Conventional technology] Styrene resins have excellent moldability and dimensional stability, as well as rigidity and electrical insulation properties, so they are used in a wide variety of fields including home appliance parts and OA equipment parts. However, the easy flammability of polystyrene limits its use.

To make styrene resin flame retardant, a method of adding a flame retardant or a method of blending a flame retardant resin is used. As the former method, it is known to add a halogenated organic compound, but in order to have sufficient flame retardancy, a large amount is required, resulting in discoloration during molding and This is problematic because it often has an adverse effect or reduces the heat resistance and weather resistance of the polymer composite acid. On the other hand, the latter method involves blending polystyrene with vinyl chloride resin, which is a typical flame-retardant resin. The strength of the resulting polymer composition is also low. (Refer to Comparative Example 1 described later) As an example of compatibilization of vinyl chloride resin and styrene resin,
-48209, vinyl chloride polymer or
An extruded foam comprising a vinyl chloride copolymer and a vinyl aromatic polymer polymerized in the resin with a vinyl aromatic monomer adsorbed to the resin is disclosed, which does not contain a rubbery component. It is different from the impact resistant polymer compositions of the present invention.

Furthermore, Japanese Patent Publication No. 54-44023 discloses (1) a vinyl chloride graft copolymer obtained by graft copolymerizing a monomer mixture such as an aromatic vinyl monomer in the presence of a vinyl chloride polymer; and (2) a styrene graft copolymer obtained by graft copolymerizing a monomer mixture of styrene, methyl methacrylate, and acrylonitrile in the presence of a styrene-butadiene copolymer. has been disclosed, but when the vinyl chloride-based graft copolymer is reinforced with the styrene-based graft copolymer, there is an effect of improving impact resistance, but the heat resistance and rigidity are significantly reduced, making it difficult for industrial use. The purpose of use is narrowed.

[Problems to be Solved by the Invention] In view of the current situation, the present invention aims to provide a flame retardant material that does not have the above-mentioned problems, that is, has thermal stability during processing, heat resistance, solvent resistance, and rigidity. An object of the present invention is to provide an impact-resistant polymer composition.

[Means for Solving the Problems] As a result of intensive research to solve the above-mentioned problems, the present inventor has discovered that a vinyl chloride-based graft copolymer is combined with two specific types of rubber-like graft copolymers. It was discovered that this is effective, leading to the present invention.

[Means for Solving the Problems] That is, the present invention provides A (a) vinyl chloride to which 1% by weight or more of an aromatic vinyl polymer or a copolymer of an aromatic vinyl compound and a methacrylic acid ester is graft-bonded; 51 to 100% by weight of the system polymer, and (b) reduced viscosity ηsp/c
40 to 80 parts by weight of an aromatic vinyl polymer having an OJ of ~1.0 dl/g, or a vinyl chloride graft copolymer consisting of 0 to 49% by weight of a copolymer of an aromatic vinyl compound and a methacrylic acid ester. , B glass transition point (Tg) is 2
10 to 50 parts by weight of a graft polymer of a rubbery polymer and an aromatic vinyl compound at a temperature of 5°C or lower, and a glass transition point (T
Graft copolymer 5 of g) a rubbery polymer having a temperature of 25° C. or less, an aromatic vinyl compound and a methacrylic acid ester
A flame retardant impact resistant polymer composition comprising 20 parts by weight is provided.

The present invention will be explained in detail below.

The polymer composition of the present invention is a vinyl chloride-based graft copolymer (hereinafter abbreviated as polymer A) and a graft polymer of a rubbery polymer and an aromatic vinyl compound (hereinafter abbreviated as polymer B). and a graft copolymer of a rubbery polymer, an aromatic vinyl compound, and a methacrylic acid ester (hereinafter referred to as polymer C).
(abbreviated)) produces surprising advantages.

First, Polymer A is produced by impregnating a polymerization initiator with an aromatic vinyl compound and/or a methacrylic acid ester in the presence of a vinyl chloride polymer, and then grafting the polymer. It consists of a graft polymer in which an aromatic vinyl compound and/or a methacrylic acid ester is graft-polymerized to an aromatic vinyl polymer and a vinyl chloride polymer. Here, the aromatic vinyl polymer refers to an aromatic vinyl polymer or a copolymer of an aromatic vinyl compound and a methacrylic acid ester.

The vinyl chloride polymer used in polymer A is a vinyl chloride homopolymer or a vinyl chloride polymer containing at least 70% of vinyl chloride.
It is a copolymer containing at least % by weight. Here, it is important that the vinyl chloride polymer (a) in which an aromatic vinyl compound and/or a methacrylic acid ester is graft-polymerized to this polymer accounts for 51% by weight or more in the polymer A. If it is less than 51% by weight, the flame retardance of the polymer composition will be poor. Furthermore, the above (
Component a) usually includes a vinyl chloride polymer to which an aromatic vinyl compound and/or methacrylic acid ester is not grafted, but we focused on the vinyl chloride polymer component regardless of the presence or absence of grafting. When this is done, the total amount of the polymer A is preferably 50 to 80% by weight. 50
If it is less than 80% by weight, the flame retardance of the polymer composition will be poor;
If it exceeds % by weight, mechanical strength and thermal stability during processing will decrease.

The aromatic vinyl compound used in polymer A is styrene, α-methylstyrene, vinyltoluene, halogenated styrene, etc., and the methacrylate ester is methyl methacrylate, ethyl methacrylate, propyl methacrylate, etc. Alternatively, it may be a mixture of the aromatic vinyl compound and a copolymerizable hetamine, such as an unsaturated nitrile compound or an acrylic ester. The aromatic vinyl compound and/or methacrylic acid ester polymer polymerized here is classified into two types. One is an aromatic vinyl polymer grafted onto a vinyl chloride polymer, and the other is a single aromatic vinyl polymer (b).

The aromatic vinyl polymer grafted onto the vinyl chloride polymer must account for 1% or more by weight of the entire vinyl chloride polymer (a) to which the aromatic vinyl polymer is grafted. If it is less than 1% by weight, the compatibility between the vinyl chloride polymer and the aromatic vinyl polymer decreases, and the mechanical strength of the polymer composition decreases. Further, the amount of the aromatic vinyl polymer graft-bonded to the vinyl chloride polymer is preferably 49% by weight or less in component (a). If it exceeds 49% by weight, the processability of the polymer composition will be poor.

The presence of the aromatic vinyl polymer grafted onto the vinyl chloride polymer of polymer A means that the vinyl chloride polymer is insoluble;
This is confirmed because the absorption of aromatic vinyl and/or methacrylic acid ester was detected in the infrared absorption spectrum of the solvent-insoluble matter obtained by extraction using a solvent that dissolves the aromatic vinyl polymer. Further, the amount of the grafted aromatic vinyl polymer is calculated from the difference between the percentage of the solvent-insoluble component in the entire polymer A and the percentage of the vinyl chloride polymer in the entire polymer composition. Ru.

On the other hand, it is important that the aromatic vinyl polymer (b) alone accounts for 49% by weight or less in the polymer A. If it exceeds 49% by weight, the flame retardancy of the polymer composition will decrease. or,
The reduced viscosity η sp/c (0.5 g/d in methyl ethyl ketone at 25°C) is an indicator of the molecular weight of the aromatic vinyl polymer.
1 solution), it should be in the range 0.3-1.0 dl/g.

Below 0.3 dl/g, the mechanical strength of the polymer composition is low, and above 1°0 dl/g, during extrusion operations,
Since the melt viscosity is high, the vinyl chloride polymer deteriorates due to heat generation, making it impossible to obtain a good molded product.

Moreover, as a polymerization initiator used when performing graft polymerization, a normal radical initiator can be used.

For example, tert-butyl peroxy (2-ethylhexanoate), tert-butyl perbenzoate, di-tert-butyl peroxide, benzoyl peroxide, lauroyl peroxide, tert-butyl peracetate, tert-butyl peroxide,
2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t
ert -butylperoxy)hexane-3, tert
Examples include peroxides such as -butyl hydroperoxide and cumene hydroperoxide, and azo compounds such as azobisisobutyronitrile.

Furthermore, a chain transfer agent may be added together with the aromatic vinyl compound and/or methacrylic acid ester and a polymerization initiator. For example, butyl mercaptan, octyl mercaptan, ter
alkyl mercaptans such as t-dodecyl mercaptan;
α-Methylstyrene dimer Triethylamine, dimethylacetamide, dimethylformamide, etc. can be used.

In the presence of a vinyl chloride polymer, the polymer A of the present invention is
After impregnating the polymerization initiator with an aromatic vinyl compound and/or methyl methacrylate, the method is then subjected to known bulk polymerization.
It is manufactured by performing solution polymerization, suspension polymerization, emulsion polymerization, etc.

The polymerization temperature is preferably 60 to 150°C.

On the other hand, polymer B is obtained by graft polymerizing an aromatic vinyl compound in the presence of a rubbery polymer.

Here, the aromatic vinyl compound is styrene, α-methylstyrene, vinyltoluene, halogenated styrene, etc., and the content thereof in the polymer B is preferably 70 to 95% by weight. If it is less than 70% by weight, fluidity decreases, and if it exceeds 95% by weight, impact resistance decreases.

Rubber-like polymers with a glass transition point (Tg) of 25°C or less include polybutadiene rubber, styrene-butadiene copolymer rubber, ethylene-propylene-butadiene copolymer rubber, etc. It is preferably 5 to 30% by weight in Combined B.

If it is less than 5% by weight, impact resistance will decrease, and if it exceeds 30% by weight, heat resistance, fluidity, and rigidity will decrease.

Regarding the production method of polymer B, publicly known bulk polymerization, bulk suspension polymerization, emulsion polymerization, etc. can be adopted, but rubber-like polymers,
Generally, a bulk polymerization method is used in which a homogeneous polymerization stock solution consisting of an aromatic vinyl compound and a polymerization solvent is supplied to a continuous multistage bulk polymerization reactor equipped with a stirrer, and is continuously polymerized and devolatilized.

Moreover, the polymer C is obtained by graft polymerizing an aromatic vinyl compound and a methacrylic acid ester in the presence of a rubbery polymer.

Here, the aromatic vinyl compound is styrene, α-methylstyrene, vinyltoluene, halogenated styrene, etc., and the methacrylate ester is methyl methacrylate, ethyl methacrylate, propyl methacrylate, etc. The total amount of monomers is preferably 10 to 60% by weight of the polymer C. If it is less than 10% by weight, fluidity decreases, and if it exceeds 60% by weight, impact resistance decreases.

Furthermore, the rubber-like polymers having a glass transition point (Tg) of 25°C or less include polybutadiene rubber, styrene-butadiene copolymer rubber, ethylene-propylene-butadiene copolymer rubber, etc., and the content thereof is as low as that of the polymer. Among C, 40 to 90% by weight is preferable.

If it is less than 40% by weight, impact resistance will decrease, and if it exceeds 90% by weight, heat resistance, fluidity, and rigidity will decrease.

As for the method for producing the polymer C, known bulk polymerization, bulk suspension polymerization, emulsion polymerization, etc. can be employed.

- Numerically, an emulsion polymerization method is chosen, in which the monomers are emulsion-grafted in the presence of a latex in which a rubbery polymer is dispersed in an aqueous medium.

It is essential that the polymer composition of the present invention contains 40 to 80 parts by weight of polymer A, 10 to 50 parts by weight of polymer B, and 5 to 20 parts by weight of polymer C.

In addition, impact resistance and rigidity are achieved only when the three polymers are combined, and the reason for this is that in polymer A, the vinyl chloride polymer and the aromatic vinyl polymer are mutually bonded by graft bonding. This is because, although the polymer A is dissolved, the vinyl chloride polymer is reinforced by the polymer C, and the aromatic vinyl polymer is reinforced by the polymer B. Here, if the polymer A is less than 40 parts by weight, the flame retardancy will decrease, and if it exceeds 80 parts by weight, the impact resistance will decrease.

On the other hand, if Polymer B is less than 10 parts by weight, it will not have the reinforcing effect of Polymer A, and if it exceeds 50 parts by weight, rigidity, fluidity, and heat resistance will decrease. Furthermore, if the amount of polymer C is less than 5 parts by weight, the reinforcing effect of polymer A will not be achieved, and if it exceeds 20 parts by weight, the rigidity, fluidity, and heat resistance will decrease.

When heating and melting mixing Polymer A and BSC in an extruder,
Known tin-based heat stabilizers, lubricants such as stearic acid and zinc stearate, light stabilizers such as ultraviolet absorbers, antioxidants such as BHT, flame retardant aids such as antimony oxide, colorants, etc. may be added. can.

[Example] Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples. The methods for measuring each physical property used in the present invention are as follows.

(1) Composition ratio of vinyl chloride polymer and aromatic vinyl polymer in the graft polymer: Amount of aromatic vinyl polymer determined from the polymerization rate of aromatic vinyl and/or methacrylic acid ester and charged vinyl chloride Calculated from the amount of system polymer.

(2) Amount of aromatic vinyl polymer grafted onto vinyl chloride polymer: 25 times the amount of a solvent (e.g. toluene) that is insoluble in vinyl chloride polymer but dissolves aromatic vinyl polymer based on the sample. In addition, after shaking the sample for 2 hours at room temperature and removing the supernatant using a centrifuge three times, the percentage of the weight ratio of the dried sample to that of the initial sample was calculated as the solvent. It is called insoluble content (%). The amount of aromatic vinyl polymer grafted onto vinyl chloride polymer is the solvent-insoluble content (%)
and the percentage of vinyl chloride polymer in the entire polymer A.

(3) Thermogravimetric balance test: Using Shimabara thermal analyzer DT-40, under nitrogen flow, 10
The temperature was increased at a rate of °C/min and the temperature at which the weight decreased by 5% by weight was taken as a measure of thermal stability.

(4) Reduced viscosity ηsp/c of aromatic vinyl polymer:
The polymer precipitated from the upper liquid obtained during the solvent-insoluble content measurement in (2) is an aromatic vinyl homopolymer, and a solution of the polymer in methyl ethyl ketone (concentration 0.5 g/
dl) was placed in a viscometer, and the falling seconds t was measured in a constant temperature bath at 25°C. On the other hand, the falling seconds to of pure methyl ethyl ketone was measured separately using the same viscometer, and calculated using the following formula.

ηsp/c-t/l o-1 (C: polymer concentration g/d
l)-1-17------- (5) Tensile strength, tensile elongation Measured by a method based on ASTM-D63g. (1/
8' test piece) (6) Bending strength and flexural modulus Measured by a method based on ASTM-D790. (1/
8' test piece) The flexural modulus was used as a measure of the rigidity of the polymer.

(7) Izot impact strength Measured in accordance with ASTM-D256 and used as a measure of impact resistance. (1/8' test piece V notch) (8) Flammability V B (Vertical B) based on UL-94
urntng) method. (1/8' test piece)
(9) Solvent resistance A 1/8' test piece was immersed in gasoline at room temperature for 24 hours, and its appearance was observed.

(10) Observation of morphology of polymer composition Ultra-thin sections of 0.5 mm square or less are prepared from the polymer composition, and the surfaces are cut and finished using a diamond knife. This sample was immersed in an osmic acid aqueous solution and stained.
Observation was made using a transmission electron microscope with an accelerating voltage of 100 KV.

(11) Vicat Softening Temperature Measured in accordance with ASTM-D1525 and used as a measure of heat resistance.

Example 1 ■Production into polymer Polyvinyl chloride with a degree of polymerization of 700 (manufactured by Shin-Etsu Chemical ■Part name T
K700) 80 parts by weight, 20 parts by weight of styrene,
After impregnating 0.2 parts by weight of the polymerization initiator tert-butylperoxy (2-ethylhexanony) in a reactor at room temperature for 30 minutes, 250 parts by weight of ion-exchanged water and o out part of polyvinyl alcohol were added. The mixture was reacted at 80° C. for 5 hours under a nitrogen atmosphere. After the reaction, the suspension was filtered, washed with water, and dried. The obtained polymer is referred to as Polymer A-1.

The polymerization rate of styrene was 93.1%, and the toluene insoluble content (%) of the polymer composition was 94.2%.

In addition, the polymer composition ratio of polyvinyl chloride/grafted polystyrene/single polystyrene was 81.9, respectively.
/12.3/5.8. The reduced viscosity of polystyrene alone was 0.63 dl/g.

■Production of Polymer B 10 parts by weight of polybutadiene rubber is dissolved in a mixed solution containing 90 parts by weight of styrene and a small amount of chain transfer agent, and the solution is continuously fed to a multi-stage reactor equipped with a stirrer equipped with a devolatilization device. Polymer B-1 with a rubber content of 12.2% by weight was obtained by thermal polymerization.
I got it. Further, according to electron microscopic observation, the average rubber particle diameter was 1.15 .mu.-.

■Production of Polymer C 70 parts by weight of polybutadiene rubber, 0.05 parts by weight of dihexyl sulfosuccinate, 0.6 parts by weight of ammonium persulfate
An aqueous emulsion containing 200 parts by weight of ion-exchanged water and 200 parts by weight of ion-exchanged water was charged into a reactor, and the internal temperature was controlled at 75°C. Next, 30 parts by weight of a monomer mixture of 50% by weight of methyl methacrylate and 50% by weight of styrene was added continuously over 2 hours, and after the addition was completed, polymerization was continued for another 2 hours. Polymer C-1 was obtained. The reaction rate was 98%. The weight ratio of methyl methacrylate units to styrene units in this polymer was 50/50. Further, according to electron microscopic observation, the average rubber particle diameter was 0.4 μm.

Next, polymers A-1, B-1 and C-1 were mixed in a weight ratio of 5.
0/40/10, and further added to this mixture as a heat stabilizer for 100 parts by weight of vinyl chloride resin, 3 parts by weight of an organotin malate stabilizer, 1 part by weight of an organotin sulfur-containing stabilizer, and After adding 1 part by weight of higher alcohol fatty acid ester as a lubricant, 20+wmφ2 at 200℃
It was extruded using a screw extruder to produce a pellet.

A test piece for evaluation was prepared by hot pressing this pellet using a compression molding machine.

Table 1 shows various measurement results.

When this polymer composition was observed using an electron microscope, it was found that
The vinyl chloride resin and styrene resin were dispersed to a thickness of 1 μm or less, and the rubber particles were also uniformly dispersed.

Further, according to Table 1, it can be seen that this polymer composition has thermal stability, impact strength, rigidity, solvent resistance, heat resistance, and flame retardancy.

Example 2 ■ Production of Polymer A In the production of Polymer A-1 of Example 1, styrene 20
The same experiment was conducted except that instead of parts by weight, a mixed monomer of 10 parts by weight of styrene and 10 parts by weight of methyl methacrylate was used. The obtained polymer is referred to as Polymer A-2.

The polymerization rate of the styrene/methyl methacrylate monomer mixture was 94.3%, and the toluene insoluble content (%) of the polymer was 94.3%.
It was 8.1%. The polymer composition ratios of polyvinyl chloride/grafted styrene-methyl methacrylate copolymer/single styrene-methyl methacrylate copolymer were 80.9/17.2/1.9, respectively. The reduced viscosity of the styrene-methyl methacrylate copolymer alone was 0.66 dl/g.

Next, polymers A-2, B-1 and C-1 were mixed at a weight ratio of 50.
/40/10, and the same experiment as in Example 1 was repeated and evaluated. Table 1 shows various measurement results.

When this polymer composition was observed using an electron microscope, it was found to be well dispersed as in Example 1.

Further, according to Table 1, it can be seen that this polymer composition has thermal stability, impact strength, rigidity, solvent resistance, heat resistance, and flame retardancy.

Example 3 (1) Preparation of Polymer A The same experiment was carried out in the preparation of Polymer A-2 in Example 2 except that the polymerization initiator was changed to azobisisobutyronitrile. The obtained polymer is referred to as Polymer A-3.

The polymerization rate of styrene was 93.9%, and the toluene insoluble content (%) of the polymer was 83.4%. In addition, the polymer composition ratios of polyvinyl chloride/grafted styrene-methyl methacrylate copolymer/single styrene-methyl methacrylate copolymer were 81.0/2.4/1B, respectively.
[It was i. The reduced viscosity of the single styrene-methyl methacrylate copolymer was O.E 19 dl/g. Next, polymers A-3, B-1 and C-1 were mixed in a weight ratio of 50
/40/10, and the same experiment as in Example 1 was repeated and evaluated. Table 1 shows various measurement results.

When this polymer composition was observed using an electron microscope, it was found to be well dispersed as in Example 1.

Further, according to Table 1, it can be seen that this polymer composition has thermal stability, impact strength, rigidity, solvent resistance, heat resistance, and flame retardance.

Comparative Example 1 Polyvinyl chloride with a degree of polymerization of 700 (manufactured by Shin-Etsu Chemical) Part name T
K 700), B-1 and C-1 of Example 1 were mixed in a weight ratio of 40/50/10, and the same experiment as in Example 1 was repeated and evaluated. Table 1 shows various measurement results.

When this polymer composition was observed using an electron microscope, it was found that
Vinyl chloride resin and styrene resin are several micrometers to several tens of micrometers.
There was phase separation on the order of m.

Also, according to Table 1, it is found that mechanical strengths such as Izot impact strength and tensile strength are inferior.

Comparative Example 2 Polymers A-2 and B-1 of Example 2 in a weight ratio of 50/5
The same experiment as in Example 1 was repeated and evaluated. Table 1 shows various measurement results.

According to Table 1, it can be seen that the binary system of polymers A and B has a low Izod impact strength.

Comparative Example 3 Polymers A-2 and C-1 of Example 2 in a weight ratio of 50/5
The same experiment as in Example 1 was repeated and evaluated. Table 1 shows various measurement results.

According to Table 1, it can be seen that the binary system of polymers A and C has low rigidity and heat resistance.

Comparative Example 4 Polyvinyl chloride with a degree of polymerization of 700 (manufactured by Shin-Etsu Chemical) Part name T
The same heat stabilizer and lubricant as in Example 1 were added to K 700), and the same experiment was repeated and evaluated. Table 1 shows the results of each measurement.

According to Table 1, it can be seen that the Izot impact strength, heat resistance, and thermal stability are low.

Comparative Example 5 Example 10 Polymer B-1 was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

According to Table 1, it can be seen that the flammability and solvent resistance are poor.

[Effects of the Invention] As explained above, the polymer composition of the present invention is a flame-retardant and impact-resistant polymer composition that has thermal stability during processing, heat resistance, solvent resistance, and rigidity.

This polymer composition is suitable for home appliance parts, OA equipment parts, etc., and plays a large role in industry.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Scope of Claims] A (a) Vinyl chloride polymers 51 to 100 in which 1% by weight or more of an aromatic vinyl polymer or a copolymer of an aromatic vinyl compound and a methacrylic acid ester is graft-bonded.
weight% and (b) reduced viscosity ηsp/c of 0.3 to 1.0
dl/g aromatic vinyl polymer or copolymer of aromatic vinyl compound and methacrylic acid ester 0 to 49% by weight
40 to 80 parts by weight of a vinyl chloride-based graft copolymer consisting of B, 10 to 50 parts by weight of a graft polymer of a rubbery polymer having a glass transition point (Tg) of 25°C or less and an aromatic vinyl compound, and C A flame-retardant, impact-resistant polymer composition comprising 5 to 20 parts by weight of a rubbery polymer having a glass transition point (Tg) of 25° C. or lower, and a graft copolymer of an aromatic vinyl compound and a methacrylic acid ester.