JPH06184400A - Resin composition - Google Patents

Abstract

PURPOSE:To improve both of rigidity and impact resistance, which are contradictory to each other, while maintaining a high degree of transparency. CONSTITUTION:This resin composition comprises 95-99.7wt.% thermoplastic copolymer (a) which is a vinylaromatic hydrocarbon/conjugated diene block copolymer having a vinylaromatic hydrocarbon content of 65-85wt.% and 0.3-5wt.% high-impact polystyrene (b) obtained by graft-polymerizing styrene with a butadiene rubber and having an average rubber particle diameter of 1.5mum or larger. It may further contain at least one compound (c) selected from polystyrene and vinylaromatic hydrocarbon/(meth)acrylic ester copolymers, with the amounts of the components (b) and (c) being 0.3-5wt.% and 5-60wt.%, respectively, based on the sum of the components (a), (b), and (c). The composition containing the component (c) has further improved rigidity, moldability, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent resin composition having an improved surface impact property, and a container, a housing, a case, a cover obtained by injection molding, and a sheet obtained by extrusion molding. The present invention relates to a resin composition suitable for a film or a transparent molded article which requires high transparency and surface impact resistance such as a container and a case obtained by further performing vacuum molding, bending molding, press molding and the like.

[0002]

Block copolymer resins composed of vinyl aromatic hydrocarbons and conjugated dienes are resins having excellent transparency and impact resistance, and are widely used in sheets, films, injection molded products and the like. However, there is a trade-off relationship in that the resin that has excellent impact resistance has low rigidity, and the resin that has high rigidity has low impact resistance. In particular, both block impact resistance and surface rigidity are excellent. The actual situation is that a combined resin has not been obtained yet.

An attempt to improve the Izod impact strength as impact resistance is disclosed in Japanese Examined Patent Publication No. 52-16496. When rubber-modified polystyrene is blended in an amount of 15% or more, impact strength is improved, but transparency is significantly reduced. In addition, 0.
When the blending amount is 5%, the impact resistance, strength and rigidity are equivalent to the blending amount of 0%, and no improvement effect is recognized. Japanese Patent Office Sho 5
JP-A-9-25821 has an impact resistance composed of a rubber-modified impact-resistant styrene polymer modified with a block copolymer having a specific structure and a block copolymer comprising a vinyl aromatic hydrocarbon and a conjugated diene. And a polymer composition having good transparency is disclosed. However, the disclosed rubber-modified impact-resistant styrene polymer has a lower Izod impact strength than that of the conventional rubber-modified impact-resistant styrene polymer and does not reach sufficient impact resistance.

JP-A-51-895550 discloses a transparent impact-resistant styrenic polymer composition comprising a block copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene, a rubber-modified styrene polymer and a styrene polymer. The thing is disclosed. However, no composition having satisfactory transparency and impact resistance has been found in this composition either.

[0005]

An injection-molded article or extruded sheet such as a cover, a case or a housing, which requires high transparency, rigidity and surface impact resistance as described above, and further vacuum molding, press molding or bending molding. The present invention provides a composition in which rigidity and impact resistance, which are in a trade-off relationship, are simultaneously improved while maintaining a high degree of transparency in the container and case.

[0006]

According to the present invention, a thermoplastic block copolymer comprising a vinyl aromatic hydrocarbon and a conjugated diene is blended with a rubber-modified high impact polystyrene having a specific particle size in a very small amount. In a molded product that maintains the original transparency of the block copolymer and has high rigidity,
We have found that surface impact can be dramatically improved.

That is, the present invention is a thermoplastic block copolymer (a) comprising a vinyl aromatic hydrocarbon and a conjugated diene, the block having a vinyl aromatic hydrocarbon content of 65% by weight or more and 85% by weight or less. 95% by weight or more of copolymer 9
9.7 wt% or less and (b) a rubber-modified impact-resistant polystyrene in which rubber particles obtained by graft-polymerizing styrene to a butadiene rubber-like polymer are rubber particles having an average particle diameter of 1.5 μm or more. From 0.3% by weight or more and 5% by weight or less of the resin composition, and (C) polystyrene, vinyl aromatic hydrocarbon- (meth) acrylic acid ester copolymer, and the above-mentioned compositions (a) and (b) A resin composition comprising one or more resins selected from (a) + (b) +
(C) = 100% by weight, (b) is 0.3% by weight or more and 5% by weight or less, and (c) is 5% by weight or more and 70% by weight or less.

The block copolymer of the component (a) used in the present invention is a polymer obtained by anionically polymerizing a vinyl aromatic hydrocarbon and a conjugated diene in a hydrocarbon solvent, and substantially contains at least two vinyl aromatic compounds. A mainly composed of group hydrocarbons
A polymer having a segment and a B segment mainly composed of at least one conjugated diene, which can be represented by the following general formula, in which one vinyl aromatic hydrocarbon-based A segment and one or two A polymer composed of B segment mainly composed of one conjugated diene may be contained in an amount of 30% by weight or less.

A- (B-A) _n , B-A- (B-A) _n , (
A−B) − _J X− (B−A−B) _k (where n, j, and k are integers from 1 to 5, and j,
k represents an integer satisfying 2 ≦ j + k ≦ 6, and X represents a coupling agent residue or a polyanion initiator residue. Further, the polymer which may be contained in an amount of 30% by weight or less is AB
Alternatively, it can be represented by B-A-B. ) A segment mainly composed of vinyl aromatic hydrocarbon is a vinyl aromatic hydrocarbon homopolymer and / or a copolymer segment of vinyl aromatic hydrocarbon and conjugated diene containing 50% by weight or more of vinyl aromatic hydrocarbon. The B segment mainly containing a conjugated diene is a homopolymer of a conjugated diene and / or a copolymer segment of a vinyl aromatic hydrocarbon and a conjugated diene having a conjugated diene content of 50% by weight or more. The boundary between the segment A and the segment B does not have to be clear, and the distribution of each monomer in the copolymerized portion may be uniform random or tapered.

The vinyl aromatic hydrocarbons constituting the block copolymer include, for example, styrene, o-methylstyrene,
p-methylstyrene, p-tert-butylstyrene,
Examples include α-methylstyrene, vinylnaphthalene, vinylanthracene, and 1,1-diphenylethylene. These may be used alone or in combination of two or more. When importance is attached to heat resistance, it is preferable to use 1,1-diphenylethylene together as a copolymerization monomer.

Therefore, the content of vinyl aromatic hydrocarbon in the block copolymer is 65% by weight or more and 85% by weight or less, preferably 70% by weight or more and 80% by weight or less.
When the vinyl aromatic hydrocarbon content is less than 65% by weight or exceeds 85% by weight, the transparency of the composition is significantly lowered, which is not preferable. A block copolymer having a large content of a polymer present as a vinyl aromatic hydrocarbon homopolymer in the block copolymer has excellent rigidity but low impact resistance, and conversely, the content of the homopolymer is A small number of block copolymers are excellent in impact resistance but low in rigidity. Therefore, it is necessary to select the composition ratio of the vinyl aromatic hydrocarbon and the conjugated diene according to the performance of the final composition, and at the same time, select the content of the polymer existing as the vinyl aromatic hydrocarbon homopolymer. is there. The preferred content of polymer present as a vinyl aromatic hydrocarbon homopolymer is 60.
It is at least 80% by weight. The content of the polymer existing as the vinyl aromatic hydrocarbon homopolymer can be measured by decomposing the block copolymer with osmic acid and then reprecipitating it in methanol.

Examples of the conjugated diene constituting the block copolymer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-hexadiene, which may be used alone or in combination. You can use it. The content of these conjugated diene monomers in the block copolymer is 15% by weight or more and 35% by weight or less, and preferably 20% by weight or more and 30% by weight or more from the transparency of the composition.
It is less than or equal to wt.

These block copolymers can be prepared by a known polymerization technique, for example, in a hydrocarbon solvent such as n-hexane, cyclohexane or toluene, in which organic lithium compounds or organic sodium compounds such as n-butyllithium, sec-butyllithium, Polymerization can be carried out by a method in which monomers are sequentially added with an initiator such as butadienyldilithium, and if necessary, after coupling with a polyfunctional coupling agent such as tin tetrachloride or a polyepoxy compound, alcohol or It can be obtained by adding water to stop the polymerization and removing the solvent. Further, in order to control the polymerization rate and molecular weight distribution, the microstructure such as the vinyl structure of the conjugated diene portion in the polymer, an appropriate amount of an ether compound such as tetrahydrofuran or tetramethylethylenediamine, a polar compound represented by an amine compound is added. It can also be polymerized.

The molecular weight of the block copolymer varies depending on the intended use, but MI (G condition) is 1 to 20 g / min.
Is preferable, and if it is less than 1, workability is poor, and if it exceeds 20, the strength of the product is lowered, which is not preferable. The rubber-modified impact-resistant polystyrene of the component (b) used in the present invention is polymerized under the condition that styrene is polymerized after dissolving the butadiene rubber-like polymer in styrene and then styrene is graft-polymerized to the rubber-like polymer. The rubber-modified impact-resistant polystyrene in which the average particle diameter of the rubber particles formed by the grafted rubber-like polymer is 1.5 μm or more.

The average particle size referred to herein is a transmission electron micrograph of a rubber-modified impact-resistant polystyrene obtained by an ultrathin section method, and the particle size of about 500 rubber particles in the photo is measured. It is calculated by a formula. Average particle size = ΣniDi ⁴ / ΣniDi ³ (where ni is the number of particles whose major axis of the rubber particles is Di.) These rubber particles have a so-called salami structure in which a polystyrene part is incorporated inside, It has a core / shell structure.

A rubber-modified impact-resistant polystyrene having an average particle size of less than 1.5 μ is not preferable because the effect of improving the surface impact property is small. A more preferable average particle size is 1.8 μm or more. To control the average particle size of the rubber particles, the composition of the rubber-like polymer that dissolves in styrene, the degree of polymerization, the stirring state when polymerizing styrene, the polymerization initiator, the chain transfer agent, the graft ratio and cross-linking of the rubber particles. It is possible by changing the degree appropriately.

The rubber-like polymer used for obtaining the rubber-modified impact-resistant polystyrene includes polybutadiene, styrene-butadiene random polymer, styrene-butadiene block copolymer and the like. Polybutadiene is preferable for enhancing impact resistance, and styrene-butadiene copolymer obtained by copolymerizing styrene is preferable for transparency. The amount of the rubber-modified impact-resistant polystyrene as the component (b) compounded in the transparent resin composition of the present invention is used within a range that does not impair the original transparency of the block copolymer. As a standard, a haze value of 3 mm or less with a molded plate of 2 mmt is preferable, and a sheet also has a haze value of 3% or less in the thickness of the final product. The specific compounding amount of the rubber-modified impact-resistant polystyrene is 0.3 in the composition with the block copolymer.
It is used in an amount of 5% by weight or more and 5% by weight or less, preferably 0.5% by weight or more and 3% by weight or less.

When the content of the rubber-modified impact-resistant polystyrene is less than 0.3% by weight, the transparency is good, but the effect of improving the impact resistance is small, and when it exceeds 5% by weight, the impact resistance is improved. However, the transparency of the product becomes extremely poor. In the present invention, in order to further improve the rigidity, surface hardness, heat resistance (heat distortion temperature), or to improve the moldability (c)
As a component, one or more resins selected from polystyrene and vinyl aromatic hydrocarbon- (meth) acrylic acid ester copolymer can be blended.

The blending amounts of component (c) are (a), (b),
It is 5% by weight or more and 70% by weight or less, preferably 10% by weight or more and 60% by weight or less, and more preferably 10% by weight or more and 50% by weight or less based on 100% by weight of the total of each component (c). If the blending amount of the component (c) is less than 5% by weight, the rigidity is
The effect of improving heat resistance is poor, and if it exceeds 70% by weight, the rigidity is increased but the impact resistance is lowered. When the block copolymer of the component (a) is a block copolymer having a high content of a polymer present as a vinyl aromatic hydrocarbon homopolymer in the block copolymer, the content of the component (c) should be adjusted. If the amount of the block copolymer is small, on the contrary, the amount of the component (c) can be increased to balance the impact resistance and the rigidity.

Examples of the monomer constituting the vinyl aromatic hydrocarbon- (meth) acrylic acid ester copolymer as the component (c) include the following. Vinyl aromatic hydrocarbons are styrene, α-methylstyrene, p-methylstyrene, pt-butylstyrene, etc., and (meth) acrylic acid esters are methyl esters of methacrylic acid,
Ethyl ester, n-butyl ester, i-butyl ester, t-butyl ester, 2-ethylhexyl ester, acrylic acid methyl ester, ethyl ester, n
-Butyl ester, 2-ethylhexyl ester, etc.,
It is an ester of (meth) acrylic acid and an alcohol having 1 to 8 carbon atoms.

Rigidity among the polymers of component (c),
To improve heat resistance, styrene-methyl methacrylate copolymer is preferable, but if a large amount is blended, the transparency becomes slightly inferior, and in order to maintain high transparency and improve processability at the same time. A styrene-butyl acrylate copolymer is preferred. In the styrene-methyl methacrylate copolymer and the styrene-butyl acrylate copolymer, the copolymerization composition ratio of methyl methacrylate or butyl acrylate is 10 to 30% by weight, preferably 12 to 25% from the transparency of the final composition. It is a weight% but may contain 0.1 to 2% of another monomer.

The rubber-modified impact-resistant polystyrene as the component (b), the polystyrene as the component (c), and the MI (G) of the vinyl aromatic hydrocarbon- (meth) acrylic acid ester copolymer are determined in terms of processability and strength of the product. As with the block copolymer, 1 to
20 g / min is preferable. Various additives can be added to the transparent resin composition of the present invention, if necessary, within a range that does not impair transparency, rigidity and impact resistance. These additives include block copolymer elastomers of vinyl aromatic hydrocarbons having a vinyl aromatic hydrocarbon content of 50% by weight or less and conjugated dienes, antioxidants, antistatic agents, antifogging agents,
UV absorbers, lubricants, colorants, mineral oils, plasticizers, etc.

[0023]

EXAMPLES Examples of the present invention will be described below, but these do not limit the scope of the present invention. Production of Block Copolymer of Component (a) The block copolymers A-1 to A-5 in Table 1 were prepared by using n-butyllithium as an initiator in a cyclohexane solvent, and using styrene, a styrene-butadiene mixture, and styrene. A cyclohexane solution of a monomer was added in order to perform polymerization, and the polymerization was stopped with methanol, followed by 2- (2-hydroxy-3-
t-butyl-5-methylbenzyl) -4-methyl-6-
Obtained by adding 0.5 parts of t-butylphenyl acrylate and trisnonylphenyl phosphite as stabilizers to 100 parts of the block copolymer, respectively, and distilling off the solvent. The amount of block styrene was measured by decomposing the block copolymer with osmic acid and then reprecipitating it in methanol. Further, the addition amount of the styrene monomer was adjusted so that the GPC peak of the block styrene became one peak.
Melt flow (MI) was measured under G conditions.

[0024]

[Table 1]

Preparation of rubber-modified impact-resistant polystyrene of component (b) The rubber-modified impact-resistant polystyrene of Table 2 is prepared by dissolving the rubber shown in Table 2 in styrene monomer and polymerizing in a reaction vessel equipped with a stirring blade. Then, the unreacted monomers and the like were removed under reduced pressure to obtain the product. The average particle diameter of the rubber particles was adjusted by changing the rotation speed of the stirring blade.

[0026]

[Table 2]

Note 1) Polybutadiene rubber and styrene
Manufacture of component (c) with butadiene rubber used in a weight ratio of 1/1 (c) The component (c) used in Table 3 is shown below. C-1 and C-2 are commercially available components, C-3 and C. -4 was obtained by radical polymerization in the same manner as in the component (b).

[0028]

[Table 3]

Note 2) Asahi Kasei Corp. 666 3) Asahi Kasei Polystyrene 663 3) Nippon Steel Chemical Co., Ltd. Estyrene MS
The MS-200 evaluation method is as follows. [Transparency] The haze value was measured according to JIS K6714. [Impactability] For the DuPont impact value, a tester manufactured by Toyo Seiki Seisakusho Co., Ltd. was used, and the impact radius was 1/8 inch.

The impact resistance at 0 ° C. is a drop weight type graphic impact tester manufactured by Toyo Seiki Seisakusho Co., Ltd., using a hammer diameter of 1 inch, the energy [J] until the sheet breaks and the maximum stress at that time. [N] was determined. [Flexural Modulus] Measured in accordance with ASTM D790. [Tensile Elastic Modulus] Based on JIS K7113, the length and width of the sheet in the extrusion direction were measured, and the average was obtained.

[0031]

[Examples 1 to 3 and Comparative Examples 1 to 3] Compositions roll-kneaded using the components (a), (b) and (c) shown in Table 4 were press-molded to obtain test pieces having a thickness of 2 mmt. Create
The haze value was measured. The results are shown in Table 4.

[0032]

[Table 4]

[0033]

Examples 4 to 6 and Comparative Examples 4 to 6 Components (a) and (b) shown in Table 5 were pelletized with a 30 mmφ co-rotating twin-screw extruder, and then tested with an injection molding machine at a thickness of 2 mmt. Pieces were prepared and the DuPont impact value and haze value at room temperature were measured. The results are shown in Table 5. When the component (b) having an average particle diameter of less than 1.5 μ is used, the impact improving effect is poor and the transparency is deteriorated.

[0034]

[Table 5]

[0035]

Examples 7 to 11 and Comparative Examples 7 and 8 By the same method as in Example 4, the DuPont impact value and the haze value at room temperature of the compositions shown in Table 5 were measured. The results are shown in Table 5. If the content of the component (b) is less than 0.3%, the impact improving effect is poor,
If it exceeds 5.0%, the transparency is significantly reduced.

[0036]

Examples 12 to 25 and Comparative Examples 9 to 13 In the same manner as in Example 4, the compositions shown in Table 6 were measured for DuPont impact value at room temperature, haze value and flexural modulus. The results are shown in Table 6. If the content of the component (c) is less than 5% by weight, the effect of improving rigidity is poor, and if it exceeds 70% by weight, the rigidity is increased but the impact resistance cannot be improved.

[0037]

[Table 6]

[0038]

Examples 26 to 28 and Comparative Examples 14 to 16 The components (a), (b) and (c) shown in Table 7 were pelletized with a 30 mmφ co-rotating twin-screw extruder, and then the compositions were prepared. 25
A sheet with a thickness of 0.75 mm is extruded from a T-die having a width of 250 mm with a uniaxial extruder of mmφ, and a haze value,
The tensile modulus and the impact strength at 0 ° C. were measured.

[0039]

[Table 7]

[0040]

The composition obtained by blending a small amount of rubber-modified impact-resistant polystyrene in a block copolymer resin composed of a vinyl aromatic hydrocarbon and a conjugated diene has a surface impact resistance while maintaining excellent transparency of the block copolymer. Significantly improved. Furthermore, when a styrene resin is added, a transparent and transparent composition with a good balance of rigidity and surface impact properties can be obtained, which is suitable for housings, cases, and packaging materials whose contents are clearly visible. It is suitable for disposable medical materials such as, for example, artificial kidney containers.

Claims (2)

[Claims] 1. A thermoplastic block copolymer comprising (a) a vinyl aromatic hydrocarbon and a conjugated diene, wherein the vinyl aromatic hydrocarbon content is 65% by weight or more and 85% by weight or less. Is 95% by weight or more and 99.7% by weight
And (b) the average particle size of the rubber particles obtained by graft-polymerizing styrene to the butadiene rubber-like polymer is 1.
A resin composition comprising 0.3% by weight or more and 5% by weight or less of rubber-modified impact-resistant polystyrene, which is rubber particles of 5 μm or more. 2. A thermoplastic block copolymer comprising (a) a vinyl aromatic hydrocarbon and a conjugated diene, wherein the vinyl aromatic hydrocarbon content is 65% by weight or more and 85% by weight or less. And (b) a rubber-modified impact-resistant polystyrene in which rubber particles obtained by graft-polymerizing styrene onto a butadiene rubber-like polymer are rubber particles having an average particle diameter of 1.5 μm or more, and (c) polystyrene. A resin composition comprising one or more resins selected from vinyl aromatic hydrocarbon- (meth) acrylic acid ester copolymers, wherein (a) + (b) + (c) = 100% by weight. On the other hand, (b) is 0.3% by weight or more and 5% by weight or less, and (c) is 5% by weight or more and 70% by weight or less.