JPH04122751A - Thermoplastic resin composition - Google Patents

Abstract

PURPOSE:To prepare the title compsn. excellent in impact resistance, mechanical strengths, and moldability and prevented from the surface delamination of a molded article by compounding a mixture of a PP resin with a PS resin with a specific styrene-based thermoplastic elastomer. CONSTITUTION:100 pts.wt. mixture comprising 5-99wt.% PP resin and 95-1wt.% PS resin is compounded with 1-40 pts.wt. styrene-based thermoplastic elastomer contg. 40-95wt.% PS part to give a thermoplastic resin compsn., which is excellent in impact resistance, mechanical strengths, and moldability and prevented from the surface delamination of a molded article.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a thermoplastic resin composition containing a polypropylene resin and a polystyrene resin. The present invention relates to a thermoplastic resin composition containing a polypropylene resin with improved physical strength and a polystyrene resin.

[Conventional technology]

Polypropylene resin has excellent mechanical strength, moldability, chemical resistance, etc., and is widely used in various industrial fields such as inner and outer layer parts of automobiles, home appliance parts, and housings. However, since polypropylene is a non-polar polymer, it has difficulties in secondary processability, especially in solid phase adhesion and paintability. As a method for improving polypropylene,
Blending polystyrene-based resins with good paintability into polypropylene has been attempted, but since polypropylene and polystyrene-based resins are not compatible, there is a problem that the physical properties are significantly deteriorated.

Therefore, various compositions have been proposed in which a compatibilizer is added to a composition of polypropylene and polystyrene resin for the purpose of improving the compatibility thereof (Japanese Patent Application Laid-open No. 87645/1983). JP-A No. 1-174550).

[Problem to be solved by the invention]

However, all of the above compositions contain a styrene-nonconjugated diene block copolymer or the like as a compatibilizing agent between the polypropylene resin and the polystyrene resin, and the compatibilizing agent contains polypropylene and polystyrene. Since it is difficult to sufficiently make these components compatible with each other, there is a problem that the impact resistance, mechanical strength, and surface peeling resistance of the molded product are not necessarily sufficient.

Therefore, an object of the present invention is to provide a thermoplastic resin composition of polypropylene resin/polystyrene resin that is excellent in impact resistance, mechanical strength, and moldability, and in which surface peeling of molded products is suppressed. That's true.

[Means to solve the problem]

As a result of intensive research in view of the above problems, the present inventors found that by adding a styrenic thermoplastic elastomer with a high polystyrene content as a compatibilizer between polypropylene resin and polystyrene resin, the resulting composition It was discovered that surface peeling of the molded product was suppressed and it exhibited excellent mechanical properties, and the present invention was conceived.

That is, the thermoplastic resin composition of the present invention comprises (a) 5 to 99% by weight of a polypropylene resin, (b) 95 to 1% by weight of a polystyrene resin, the (a) polypropylene resin, and (bl polystyrene). (c) contains 1 to 40 parts by weight of a styrene thermoplastic elastomer to a total of 100 parts by weight of the system resin, and the content of the polystyrene portion in the (c) styrene thermoplastic elastomer is 40 to 95 parts by weight. %, and the weight average molecular weight (Ikun) is 3 x 104 ~ 50 x 10'
It is characterized by

The present invention will be explained in detail below.

In the present invention, (a) polypropylene resin includes:
There is no particular restriction as long as the polymer is polymerized with propylene monomer as the main component, and up to about 20% by weight of ethylene,
It may also be copolymerized with other α-olefins such as butene and 4-methylpentene.

The copolymer may be either a random copolymer or a block copolymer. Furthermore, copolymer rubbers of two or more α-olefins such as ethylene, propylene, l-butene, 1-hexene, and 4-methyl-pentene, or copolymer rubbers of lead olefins and other monomers, etc. The olefinic thermoplastic elastomer may be contained up to about 40% by weight.

The copolymer rubber of two or more lead olefins is typically ethylene-propylene copolymer rubber (EPR) or ethylene-butene copolymer rubber (EBR).
and ethylene-propylene-diene copolymer rubber (EP
DM).

The melt flow rate (MFR, 230°C, 2,16 kg load) of such polypropylene resin is 0.
5 to 60 g/10 minutes is preferred. If the melt flow rate is less than 0.5 g/10 minutes, the moldability of the resulting thermoplastic resin composition will deteriorate, and if it exceeds 60 g/10 minutes, the impact resistance will decrease, which is not preferable.

In the present invention, the polystyrene resin (b) includes those obtained by homopolymerizing styrene monomers, or those obtained by copolymerizing 5 to 50% by weight of other monomers. Examples of comonomers for copolymerization include α-methylstyrene, acrylonitrile, maleic anhydride, and methyl methacrylate. It is also possible to use rubber-modified polystyrene obtained by emulsion polymerizing about 10 to 30% by weight of a rubbery polymer such as polybutadiene or butadiene-styrene copolymer to styrene.

Furthermore, it is also possible to use a material containing 100% by weight of polystyrene and about 1 to 99% by weight of polyphenylene ether resin (PPO).

The above polyphenylene ether resin has the following general formula (1
).

(In the formula, R1 and R2 are an alkyl group having 1 to 4 carbon atoms, an aryl group having 4 to 8 carbon atoms, a halogen atom, or a hydrogen atom, and may be the same or different, and n is 50 to 5
Indicates the number of 00. ) Examples of such polyphenylene ether resins include poly(2,6-simethyl-1,4-phenylene) ether and poly(2,6-ethyl-1,4-phenylene).
Ether, poly(2-methyl-6-ethyl, 4-phenylene) ether, poly(2-methyl-6-itubrovir, 4-phenylene) ether, poly(2-methyl, 4-phenylene) ether, poly (2,6-nochrome-1,4-phenylene)ether, poly(2-ethyl-
6-bromo-1,4-phenylene)ether, poly(2
-phenyl, 4-phenylene) ether, and the like.

The melt index (Ml: 190°C, 2,16 kg load) of polystyrene resin as described above is 0.5 to
Approximately 20g and 710 minutes is preferable.

As mentioned above (aj polypropylene resin and (bl
The blending ratio of the polystyrene resin is 5 to 99% by weight, preferably 10 to 98% by weight of (a), excluding 100% by weight of (a) and (b), and 95 to 1% by weight of (b). ,
Preferably it is 90 to 2% by weight. (a) If the polypropylene resin is less than 5% by weight ((b) if it exceeds 95% by weight), the characteristics of polypropylene such as mechanical strength, moldability, chemical resistance, etc. will decrease, and (a) If the polypropylene resin exceeds 99% by weight ((b) less than 1% by weight), the effect of improving the elastic strength of the posttyrene resin is not sufficient.

In the present invention, the styrenic thermoplastic elastomer (c) is an elastomer copolymer with a polystyrene portion as a heart segment. Depending on the type of soft segment, polystyrene-polyphtadiene-polystyrene (SBS), polystyrene-polyisoprene-polystyrene (S'lS), hydrogenated polystyrene-polyisoprene-polystyrene (SEPS), hydrogenated polystyrene-polybutadiene-polystyrene ( SEBS) etc.

Among the above styrene thermoplastic elastomers, hydrogenated polystyrene-polyisoprene-polystyrene (SEPS) is particularly preferred in terms of weather resistance.

The hydrogenated polystyrene-polyisoprene-polystyrene (SEPS) is represented by the following general formula (1).

(S-EP7...(2) (wherein, S
represents the polystyrene part, EP represents the hydrogenated polyisoprene part (ethylene/propylene part), and n is 1.
-20 integer, m is O or 1. ) The above-mentioned hydrogenated polystyrene-polyisoprene-polystyrene block copolymer is a two-block type one (
For m-0, 5EP), 3 block type (n
21 and m=o), multi-block type (
In the case of n-2 to 20), any of them can be used in the present invention.

The hydrogenated polystyrene-polyisoprene-polystyrene block copolymer is a polystyrene-polyisoprene-polystyrene block copolymer.
By hydrogenating a polystyrene block copolymer at a temperature of 25 to 175°C in the presence of a catalyst prepared by reducing a cobalt or nickel alkoxide with an alkyl aluminum compound, selectively hydrogenating the polyisoprene portion. The structure corresponds to that of an ethylene-propylene copolymer.

In the hydrogenated polystyrene-polyisoprene-polystyrene block copolymer, it is not necessary that all of the polyisoprene portion be hydrogenated, as long as 5% or more of the polyisoprene portion is hydrogenated. The preferred hydrogenation ratio is 50% or more, more preferably 80% or more.

In the present invention, the content of the polystyrene portion of such a styrenic thermoplastic elastomer is 40 to 95% by weight, preferably 40 to 80% by weight.

If the polystyrene portion is less than 40% by weight, the effect of improving the compatibility between (a) polypropylene resin and (b) polystyrene resin is not sufficient, while if it exceeds 95% by weight, brittleness decreases. The content of styrene in a styrenic thermoplastic elastomer is usually about 15 to 35% by weight, and in the present invention, a high content of 40% by weight or more is used.

In the styrene thermoplastic elastomer, the polystyrene portion is not limited to consisting only of styrene, but may also consist of substituted styrene such as methylstyrene.

The weight average molecular weight (units) of the styrene thermoplastic elastomer is preferably 3 x 104 to 50 x 104, particularly 5
×104 to 35×104 is preferred. Weight average molecular weight (
Mw) is less than 3 x 104, the melt viscosity is too low, while 5
If it exceeds 0x104, the melt viscosity will become too high and the moldability will deteriorate, which is not preferable.

The amount of the styrene thermoplastic elastomer (c) added is 1 to 40 parts by weight based on 100 parts by weight of the total amount of (a) polypropylene resin and (b) polystyrene resin. If the amount of the styrenic thermoplastic elastomer added is less than 1 part by weight, the addition will not have a sufficient effect of improving compatibility, resulting in insufficient impact resistance, surface peeling resistance, etc. Moreover, if it exceeds 40 parts by weight, fluidity and rigidity will decrease. The preferred amount of the styrene thermoplastic elastomer added is 3 to 30 parts by weight.

The thermoplastic resin composition of the present invention basically consists of the above-mentioned components, but an inorganic filler may be added for the purpose of improving the rigidity of the molded product.

As the inorganic filler, talc, calcium carbonate, calcium sulfite, magnesium sulfate, kaolin, titanium oxide, zinc oxide, alumina, etc. can be used, and talc and calcium carbonate are particularly preferred.

Further, the particle size is preferably 3 or less. If the particle size of the inorganic filler exceeds 3 mm, the effect of improving rigidity etc. will not be sufficient and the impact resistance will decrease, which is undesirable.

The blending amount of the inorganic filler is preferably 10 to 100 parts by weight, particularly 15 to 100 parts by weight, based on 100 parts by weight of the thermoplastic resin composition.
40 parts by weight is preferred.

The thermoplastic resin composition of the present invention may further contain other additives for the purpose of modifying it, such as reinforcing materials such as glass fibers and carbon fibers, heat stabilizers, antioxidants, light stabilizers,
Flame retardants, plasticizers, antistatic agents, mold release agents, foaming agents, etc. may be added.

The thermoplastic resin composition of the present invention as described above can be prepared using a single screw extruder, a twin screw extruder, or a Banbury mixer 1.
180 to 320 using a kneader such as a mixed roll, Brabender, kneader, etc. or a mixer such as Henschel mixer.
It can be obtained by heating and kneading in a molten state at 1°C, preferably 230 to 280°C.

[For production]

The thermoplastic resin composition of the present invention is composed of a polypropylene resin, a polystyrene resin, and a styrene thermoplastic elastomer containing a large amount of polystyrene as a compatibilizer for both, so that surface peeling of the molded product is suppressed. It also has excellent mechanical properties.

The reason why such an effect is obtained is not necessarily clear, but the content of polystyrene in ordinary styrene-based thermoplastic elastomers is about 15 to 35% by weight, and in the present invention, the polystyrene content is about 15 to 35% by weight. % by weight) is used. This styrenic thermoplastic elastomer with a high polystyrene content exists in a layered form in the composition and is easily localized at the interface between the polypropylene resin and the polystyrene resin, and has an excellent ability to improve the affinity between the two. It is believed that there is.

〔Example〕

The present invention will be explained in further detail by the following examples.

Note that the following resins were used as raw material resins in each of the Examples and Comparative Examples.

[11 Polypropylene resin HPP/propylene homopolymer (J-209, manufactured by Tonen Petrochemical ■, melt flow rate (MFR, 230°C 12, 16 kg load) 8.5 g/
10 minutes] BPP: Propylene-ethylene block copolymer (B
J-309, manufactured by Tonen Petrochemical ■, melt flow rate (
MFR, 230°C12, 16kg load) 9.0g/1
0 minutes, ethylene content 7.5% by weight] [21 Polystyrene resin PS (GP-666, manufactured by Asahi Kasei Corporation, MFR (2
00°C 15kg load) 7.5g/10 minutes] HIPS: [475D, manufactured by Asahi Kasei Corporation, rubber reinforced polystyrene, MFR (200°C 15kg load) 2g
/10 minutes] [3] Styrenic thermoplastic elastomer ■ Hydrogenated polystyrene-polyisoprene-polystyrene block copolymer 5EPS-1: C weight average molecular weight 12.6' x 10
4 Polystyrene content 50% by weight] 5EPS-2: (Weight average molecular weight 8.4 x 104
Polystyrene content 65% by weight] 5EPS-3: (Weight average molecular weight 29.4 x 1
0' Polystyrene content 50% by weight] 5EPS-4: C weight average molecular weight 6.7 x 104
Polystyrene content: 31% by weight] ■Hydrogenated polystyrene-polyisoprene block copolymer SEP: (Weight average molecular weight: 16.2 x 104
Polystyrene content: 37% by weight] ■Hydrogenated polystyrene-polybutadiene-polystyrene block copolymer 5EBS-1: C weight average molecular weight 8.8 x 104
Polystyrene content 31% by weight] 5EBS-2: (Weight average molecular weight 9.6XlO'
Polystyrene content 30% by weight] Examples 1 to 9 and Comparative Examples 1 to 5 Polypropylene (HPP or BPP), polystyrene (
PS or former PS), styrenic thermoplastic elastomer (SEPS, SEP, or 5EBS) resin pellets were mixed at room temperature using a Henschel mixer in the proportions shown in Table 1, and then mixed using a 45Mφ twin-screw kneader. 250°
Crosstalk was performed at CC1200 rp, and the discharged material was rapidly cooled in water to obtain pellets of the thermoplastic resin composition.

The melt flow rate, surface peeling resistance, elongation at break, Izot impact strength, and flexural modulus of each of the obtained thermoplastic resin compositions were measured.

The results are also shown in Table 1.

(1) Melt flow rate - Measured at 230°C, 12 kg load, in accordance with JIS K6758.

(2) Surface peeling resistance - 1 mm' on the surface of the molded product (70 mm x 120 concave x 3 injections) using a razor:
y.

100 1 mm squares were made, and Sellotape (manufactured by Chiban ■) was attached to the squares, and then peeled off. Out of 100 squares, the number of cellophane tape that remained on the surface of the molded product without adhering to it was counted.

(3) Elongation at break: Measured according to JIS K7113.

(4) Izot impact strength Measured at 23°C (notched) in accordance with JIS K7110.

(5) Flexural modulus Measured according to JIS K7203.

As is clear from Table 1, the thermoplastic resin compositions of Examples 1 to 8 had excellent surface peeling resistance, elongation at break, impact resistance, and flexural modulus.

On the other hand, the thermoplastic resin composition of Comparative Example 1, which was a two-component composition of polypropylene and polystyrene, had extremely poor surface peeling resistance, and also had poor elongation at break and poor impact resistance values. Moreover, the thermoplastic resin compositions of Comparative Examples 2 to 5, in which a styrene-based thermoplastic elastomer having a low content of polystyrene moieties were used, had only poor surface peeling resistance.

〔Effect of the invention〕

As detailed above, the thermoplastic resin composition of the present invention has
Since it is composed of a polypropylene resin, a polystyrene resin, and a styrene thermoplastic elastomer with a high polystyrene content, it has good mechanical strength, impact resistance, and surface peeling resistance.

Such a thermoplastic resin composition of the present invention is suitable for use as an engineering plastic material, particularly for parts of automobiles and home appliances.

Claims (5)

[Claims] (1) (a) 5 to 99% by weight of polypropylene resin;
(b) 95 to 1% by weight of polystyrene resin and the above (a)
) polypropylene resin and (c) 1 to 40 parts by weight of a styrene thermoplastic elastomer based on a total of 100 parts by weight of the (b) polystyrene resin; A thermoplastic resin composition characterized in that the content of the polystyrene portion is 40 to 95% by weight. (2) In the thermoplastic resin composition according to claim 1,
A thermoplastic resin composition, wherein the weight average molecular weight (@M@w) of the styrene thermoplastic elastomer (c) is 3 x 10^4 to 50 x 10^4. (3) The thermoplastic resin composition according to claim 1 or 2, wherein the (c) styrenic thermoplastic elastomer is
1. A thermoplastic resin composition comprising a hydrogenated polystyrene-polyisoprene-polystyrene block copolymer or a hydrogenated polystyrene-polyisoprene block copolymer. (4) In the thermoplastic resin composition according to claim 3,
A thermoplastic resin characterized in that the hydrogenated polyisoprene portion of the hydrogenated polystyrene-polyisoprene-polystyrene block copolymer or hydrogenated polystyrene-polyisoprene block copolymer has an ethylene/propylene ratio of 5% or more. Composition. (5) In the thermoplastic resin composition according to any one of claims 1 to 4, the sum of (a) + (b) + (c) is 1
1. A thermoplastic resin composition comprising 1 to 50 parts by weight of an inorganic filler per 00 parts by weight.