JPH08157545A - Rubber-modified styrene resin composition and molded article obtained therefrom - Google Patents

Abstract

PURPOSE: To provide a low-cost rubber-modified styrene resin composition excellent in transparency while retaining high rigidity and impact resistance. CONSTITUTION: This composition is obtained by polymerizing a styrene monomer or its mixture with a compound copolymerizable therewith in the presence of a rubbery polymer and contains 5-40wt.% nonrigid component particles having a mean particle diameter Dp of 0.1-1μm, wherein the rubbery polymer comprises an AB block copolymer (wherein A is a styrene/butadiene random copolymer having a styrene content of 5-40wt.%; and B is a styrene polymer and accounts for 20-50wt.% of the AB block copolymer).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a rubber-modified styrene resin composition and a molded article thereof. More specifically, the present invention maintains high rigidity and impact resistance,
The present invention also relates to a rubber-modified styrene resin composition which is excellent in transparency and is inexpensive, and a molded article using the composition.

[0002]

2. Description of the Related Art A rubber-modified styrene resin composition comprising styrene resin and soft component particles is known as so-called high impact polystyrene (HIPS). Such impact-resistant polystyrene is useful as a resin having improved impact resistance while maintaining the rigidity of ordinary polystyrene. However,
Since the refractive index of the matrix styrenic polymer for visible light and the refractive index of the soft component particles dispersed in the matrix for visible light are different, the light incident on the molded article using the rubber-modified styrene resin composition Are scattered in all directions and the part looks white. Therefore, the container using the rubber-modified styrene-based resin composition usually has low transparency and the contents cannot be seen well.

By the way, food containers such as various beverages must have sufficient rigidity and impact resistance. Moreover, the contents of the container must be clearly visible from the viewpoint of display effect as an over-the-counter product and from the viewpoint of health and safety. Therefore, the container is required to have high transparency.

Conventionally, in order to give a rubber-modified styrene resin composition a high transparency, its soft component particles have a particle size of about 0.2 μm.
A structure having a particle size of about m and composed of a core portion which is a single continuous phase consisting only of a styrene polymer and a shell portion consisting of a rubber-like polymer encapsulating the core portion, a so-called core A method of forming a shell structure is used (Japanese Patent Publication No. 60-57443, Japanese Patent Publication No. 6-3550).
No. 0 publication). However, as a rubber-like polymer, a method of forming a rubber-modified styrenic resin composition obtained by using a polystyrene-polybutadiene block copolymer into a core-shell structure has a high transparency enough to meet the recent severe requirements. I can't get it.

Also known is a method of improving the transparency while maintaining the impact resistance by using a copolymer of styrene and a vinyl monomer as the matrix. However, this method cannot be said to be a preferable method from an industrial viewpoint since the cost of the rubber-modified styrene resin composition obtained is increased because the above-mentioned copolymer is relatively expensive.

[0006]

The problem to be solved by the present invention is to provide a rubber-modified styrene resin composition which is excellent in transparency and inexpensive while maintaining sufficient rigidity and impact resistance, and the resin composition. The point is to provide a molded product using the product.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a rubber-modified styrene resin composition obtained by using a specific block copolymer as a rubber-like polymer. However, the present invention has been completed on the basis of the finding that, while maintaining sufficient rigidity and impact resistance, it is remarkably excellent in transparency and is inexpensive. That is, the present invention is a rubber-modified styrene resin composition obtained by polymerizing a styrene monomer or a styrene monomer and a compound copolymerizable with the styrene monomer in the presence of a rubber-like polymer. A rubber-modified styrene-based resin, wherein the average particle diameter Dp of the soft component particles in the resin composition is 0.1 to 1 μm, and the weight ratio of the soft component particles in the resin composition is 5 to 40% by weight. In the resin composition, the rubber-like polymer has the following (a) to
It is intended to provide a rubber-modified styrene resin composition, which is an AB block copolymer having the constitution (c). (A) A is a styrene-butadiene random copolymer having a styrene content of 5 to 40% by weight. (B) B is a styrene polymer. (C) The weight ratio of B in the AB block copolymer is 20 to 50% by weight. The present invention also provides a molded product using the above rubber-modified styrene resin composition.

The present invention will be described in detail below. The A of the AB block copolymer used in the present invention has a styrene content of 5 to 5.
40% by weight of styrene-butadiene random copolymer. As the styrene content in A is increased, the difference between the refractive index of the matrix for visible light and the refractive index of the soft component particles for visible light becomes smaller, and the scattering of incident light is reduced, so only transparency is considered. If so, a highly transparent resin can be obtained. However, if the styrene content exceeds 40% by weight, the soft component particles become hard, and a large amount of soft component particles must be contained in order to maintain high impact resistance, and the transparency eventually decreases. On the other hand, when the styrene content is less than 5% by weight, there is a large difference in the refractive index between the matrix and the styrene polymer, and sufficient transparency cannot be obtained.

B of the AB block copolymer used in the present invention
Is a styrene polymer, and the weight ratio of B is 20
~ 50% by weight. Within this range, the soft component particles in the rubber-modified styrene-based resin composition have a particle size of 0.1 to 1 μm, and the core portion is a single continuous phase consisting of only the styrene-based polymer and the core. It has a core-shell structure composed of a shell made of a rubber-like polymer that encloses the part, and can achieve high transparency and maintain high impact resistance. If the proportion of the styrenic polymer exceeds 50% by weight, the soft component particles become stiff and the impact resistance decreases. If it is less than 20% by weight, the soft component particles do not have a core / shell structure and the transparency decreases. . The structure of the soft component particles can be confirmed by observing an ultrathin section of the resin composition with a transmission electron microscope. Examples of the styrene-based polymer include styrene,
Examples of the polymer include at least one monomer selected from alkyl-substituted styrenes such as α-methylstyrene, m-methylstyrene, and p-methylstyrene.
Specific examples thereof include polystyrene, α-methylstyrene-based polymer, m-methylstyrene-based polymer, p-methylstyrene-based polymer and the like. Of these, polystyrene is preferred.

The AB block copolymer used in the present invention preferably has a 5 wt% styrene solution viscosity of 30.
~ 40 cps. What is the 5 wt% styrene solution viscosity?
The AB block copolymer was dissolved in styrene so that the concentration of the copolymer would be 5% by weight, and the viscosity of the solution (25
(° C) is a value measured according to JIS K7117.

The AB block copolymer used in the present invention is
It can be produced by a known living anion polymerization method. That is, first, the A component is polymerized, and then the B component
An AB block copolymer is produced by polymerizing the components.

Styrene is generally used as the styrene-based monomer in the present invention, but alkyl-substituted styrenes such as α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, etc. Kinds are also included. Further, with the styrene-based monomer, a compound copolymerizable with the styrene-based monomer such as acrylonitrile, methacrylonitrile, methacrylic acid, methyl methacrylate, maleic anhydride, and maleimide may be used in combination.

The rubber-modified styrenic resin composition of the present invention uses the above-mentioned AB block copolymer instead of the conventionally used polystyrene-polybutadiene block copolymer, and uses the above-mentioned styrene-based monomer or The resin composition is obtained by polymerizing a styrene monomer and a compound copolymerizable with the styrene monomer, and is a resin composition in which soft component particles are dispersed in a matrix composed of a styrene polymer.

The rubber-modified styrenic resin composition of the present invention comprises a styrenic polymer as a matrix and a soft component having particles dispersed therein. The average particle size of the soft component particles is 0.1 to 1 μm, preferably 0.1.
It is 15 to 0.5 μm. If the average particle size is too small, the impact strength is poor, whereas if the average particle size is too large, the transparency and surface appearance properties are poor. The average particle diameter is obtained by taking a transmission electron micrograph of an ultrathin section of the rubber-modified styrene resin composition, measuring the particle diameter of 200 to 500 soft component particles in the photograph, and calculating by the following equation. It is the assigned value. Average particle size Dp = Σn _i D _i / Σn _i Here, n _i is the number of soft component particles having an average particle size D _i , and Σ means the sum for i. When the particles are not perfectly circular, the average value of the maximum diameter and the minimum diameter is used as the particle diameter.

The weight ratio of the soft component particles of the rubber-modified styrenic resin composition of the present invention is 5 to 40% by weight, preferably 8 to 35% by weight. If the weight ratio of the soft component particles is too small, the impact resistance is poor, while if the weight ratio of the soft component particles is too large, the transparency, rigidity or elastic modulus is lowered, which is not preferable in practice. The weight ratio of the soft component particles is determined by the following method. That is, 0.5 g of the resin composition is dissolved in 50 ml of a methylethylketone / methanol mixed solvent (volume ratio = 10/1) at room temperature. The obtained solution is subjected to a centrifuge (10000 rpm × 30 minutes), and the insoluble matter is isolated by decantation. The insoluble matter is dried with a vacuum dryer (70 ° C x 3 hours).
Let it. If the dry weight of insoluble matter is a, then a ÷ 0.5 ×
100 is the weight ratio of the soft component particles.

The swelling degree of the soft component particles in the present invention is
It is preferably 3 to 30, more preferably 8 to 20. The degree of swelling is determined by the following method. That is, about 1.0 g of the resin composition is dissolved in 50 ml of toluene at room temperature and left for one day. The obtained toluene solution is centrifuged (10000 rpm × 1 hour) to separate the insoluble matter. The supernatant liquid is discarded, the insoluble matter is weighed, and the weight is defined as a. Next, the insoluble matter is dried by a vacuum dryer (70 ° C. × 3 hours), and the weight after drying is represented by b. The degree of swelling is (ab) / b.

Next, a method for producing the rubber-modified styrene resin composition of the present invention will be described. The method for producing the rubber-modified styrenic resin composition of the present invention includes the styrene monomer or the styrene monomer in the presence of the AB block copolymer by the bulk polymerization method or the bulk / suspension two-step polymerization method. To polymerize the above compound which is copolymerizable with the polymer and the styrene monomer. Furthermore, the rubber-modified styrene-based resin composition of the present invention is prepared by mixing two or more rubber-modified styrene-based resin compositions or styrene-based resin compositions.
A rubber-modified styrene-based resin composition that satisfies the requirements of the present invention can also be used.

The rubber-modified styrenic resin composition of the present invention contains, if necessary, a plasticizer such as silicone oil or mineral oil which imparts an impact strength improving effect, a lubricant, an antistatic agent, an antioxidant, and an ultraviolet ray. Absorbent, heat stabilizer, pigment,
You may add dye etc.

The rubber-modified styrene resin composition of the present invention can be molded using a molding machine that is generally used. Examples of the molding machine include an injection molding machine, an extrusion molding machine, a blow molding machine, and an injection blow molding machine.

The rubber-modified styrenic resin composition of the present invention has outstanding transparency while maintaining rigidity and impact resistance, is inexpensive, and can be used in a wide range of fields utilizing its excellent characteristics. It is preferably used for molded articles such as various beverage and food containers, cosmetic containers, and pharmaceutical containers.

[0021]

EXAMPLES The present invention will be described below based on examples.
The present invention is not limited to these examples. The data shown in the examples and comparative examples are measured based on the following method. (1) Transparency (total light transmittance, parallel light transmittance) Using an injection molded sheet with a thickness of 0.7 mm, JIS K
It measured based on 6714. (2) Haze value Using an injection-molded sheet with a thickness of 0.7 mm, JIS K
It measured based on 6714. (3) Izod impact strength (impact resistance) Measured according to JIS K7110. In addition, 6.4
mm (thickness), notched, and measurement temperature 23 ° C. (4) Flexural modulus (rigidity) The flexural modulus was measured according to JIS K7203. The measurement temperature was 23 ° C.

Example 1 A fully mixed type autoclave with a stirrer having an internal volume of 20 liters. 2.2 parts by weight of mineral oil was added to 100 parts by weight of styrene to prepare an AB block having the following structures (1) to (4). 10.5 parts by weight of the polymer was dissolved, 0.06 parts by weight of n-dodecyl mercaptan was added at the start of bulk polymerization, and bulk polymerization was carried out at 120 ° C. for 4 hours while stirring at 220 rpm, so that the polymerization rate of styrene was 30% by weight. did. With 100 parts by weight of this polymerization liquid, 100 parts by weight of water, 1.2 parts by weight of calcium triphosphate, 45 ppm by weight of sodium dodecylbenzenesulfonate, 0.3 parts by weight of benzoyl peroxide, and t-butylperoxy were added to the polymerization liquid. Add 0.075 parts by weight of benzoate and mix at 90 ° C. for 3 hours 3
Suspension polymerization was carried out for 0 minutes at 140 ° C. for 1 hour and 30 minutes while stirring at 220 rpm. Hydrochloric acid was added to the obtained suspension polymerization solution, which was filtered, washed with water, dried, and pelletized with an extruder to obtain a rubber-modified styrene resin composition. The soft component particles in the resin composition had a core / shell structure. Table 1 shows the measurement results and the evaluation results. (1) A is a styrene-butadiene random copolymer having a styrene content of 28%. (2) B is polystyrene. (3) The proportion of B in the AB block copolymer is 28% by weight. (4) 5 wt% styrene solution viscosity is 36 cps. The AB block copolymer having the above structure was produced as follows. The stainless steel polymerization reactor having an internal volume of 20 liters was replaced with dry nitrogen, and 1,3-butadiene 1032 g, styrene 406 g, cyclohexane 15 liters, tetrahydrofuran 55 mmol, n-butyl lithium (n-hexane solution) 7.1 mmol were charged, The polymerization reaction was carried out at 75 ° C. for 3 hours with stirring. Next, 562 g of styrene was added to the polymerization solution, and while stirring, 1
React for a time, then add 10 ml of methanol,
Stir for a further 5 minutes. Next, the contents of the polymerization reactor were taken out, 10 g of 2,6-di-t-butyl-p-cresol (Sumitomo Chemical Co., Ltd. Sumilizer BHT) was added, and most of cyclohexane was removed by steam stripping. After evaporating, it was dried under reduced pressure at 50 ° C. for 20 minutes to obtain a copolymer.

Example 2 Bulk polymerization was carried out exactly as in Example 1. With 100 parts by weight of this polymerization solution, 100 parts by weight of water, 1.2 parts by weight of calcium triphosphate, 45 ppm by weight of sodium dodecylbenzenesulfonate, 0.28 parts by weight of benzoyl peroxide, t-butylperoxy were added to the polymerization solution. 0.15 parts by weight of benzoate was added, and the mixture was added at 90 ° C. for 3 hours and 30 minutes.
Suspension polymerization was carried out at 0 ° C. for 1 hour and 45 minutes while stirring at 220 rpm. Hydrochloric acid was added to the obtained suspension polymerization solution, which was filtered, washed with water, dried, and pelletized with an extruder to obtain a rubber-modified styrene resin composition. The soft component particles in the resin composition had a core / shell structure. Table 1 shows the measurement results and the evaluation results.

Comparative Example 1 The procedure of Example 1 was repeated except that 9.0 parts by weight of polystyrene-polybutadiene block copolymer (NS312SC manufactured by Nippon Zeon Co., Ltd.) was used in place of the AB block copolymer of Example 1. A rubber-modified styrene resin composition was obtained. The amount of polystyrene-polybutadiene block copolymer was set so that the amount of butadiene in the resin composition was the same as in Example 1. The soft component particles in the resin composition had a core / shell structure. Table 1 shows the measurement results and the evaluation results.

Comparative Example 2 In place of the AB block copolymer of Example 1, 7.0 parts by weight of an AB block copolymer (Soaprene 1205 manufactured by Asahi Kasei) having the following characteristics (1) to (3) was used. A rubber-modified styrene resin composition was obtained in the same manner as in Example 1 except that the above was used. The amount of the AB block copolymer was set so that the amount of butadiene in the resin composition was the same as in Example 1. The soft component particles in the resin composition had a so-called salami structure in which a plurality of small particles of styrene resin were dispersed in a continuous phase composed of a rubber-like polymer. Table 1 shows the measurement results and the evaluation results. (1) A is a styrene-butadiene random copolymer having a styrene content of 8%. (2) B is polystyrene. (3) The proportion of B in the AB block copolymer is 17% by weight.

[0026]

[Table 1] ─────────────────────────────────── Example 1 Example 2 Comparative Example 1 Comparative Example 2 ─────────────────────────────────── Rubber characteristics type AB-BLOCK AB-BLOCK AB-BLOCK AB- Styrene content in BLOCK A (wt%) 28 28 0 8 Ratio of B in the AB copolymer (wt%) 28 28 40 17 Structure average particle size (μm) 0.13 0.15 0.15 3.0 Amount of soft component (wt%) 18.4 19.6 17.7 12.1 Swelling degree 18.9 16.8 16.1 30.4 Butadiene content (wt%) * 4.8 4.8 4.9 4.9 Evaluation Total light transmittance (%) 73.7 73.8 70.1 66.7 Parallel light transmittance (%) 51.6 51.7 41.7 24.6 Haze value 29.9 29.9 40.6 63.4 Izod Impact strength 3.5 3.7 4.1 4.0 (kgcm / cm) Flexural modulus (kg / cm ² ) 23500 23300 22900 23400 ────────────────────────── ─────────── * Butadiene content It was calculated from the structure of the rubber content and rubber.

[0027]

As described above, according to the present invention,
It is possible to provide an inexpensive rubber-modified styrene-based resin composition which is excellent in transparency while maintaining high rigidity and impact resistance, and a molded article using the resin composition.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Shin 1-5-1, Anesaki Kaigan, Ichihara-shi, Chiba Sumitomo Chemical Co., Ltd.

Claims (3)

[Claims] 1. A rubber-modified styrene resin composition obtained by polymerizing a styrene monomer or a styrene monomer and a compound copolymerizable with a styrene monomer in the presence of a rubber-like polymer. And a rubber-modified styrene resin in which the average particle diameter Dp of the soft component particles in the resin composition is 0.1 to 1 μm and the weight ratio of the soft component particles in the resin composition is 5 to 40% by weight. In the composition, a rubber-modified styrene-based resin composition, wherein the rubber-like polymer is an AB block copolymer having the following constitutions (a) to (c). (A) A is a styrene-butadiene random copolymer having a styrene content of 5 to 40% by weight. (B) B is a styrene polymer. (C) The weight ratio of B in the AB block copolymer is 20 to 50% by weight. 2. A rubber-modified styrenic resin composition according to claim 1, wherein the AB block copolymer has a 5 wt% styrene solution viscosity of 30 to 40 cps. 3. A molded product using the rubber-modified styrene resin composition according to claim 1.