JPH06157687A - Highly clear rubber-modified styrenic resin composition and clear container - Google Patents

Abstract

PURPOSE:To obtain the subject composition having high-level rigidity and impact resistance and excellent clearness (contact-clearness). CONSTITUTION:The objective composition is prepared by grafting a vinyl aromatic monomer onto polybutadiene and has the following properties (a) to (f): (a) the polybutadiene used has a vinyl bond content of 8-30wt.% and a solution viscosity of 300-2000cP as measured in a 5wt.% styrene solution at 25 deg.C, (b) the polybutadiene content of the resin composition is 3-5wt.%, (c) the median particle diameter of the polybutadiene particles in the resin composition is 1.8mum or above, (d) the particle diameter distribution of the polybutadiene particles in the resin composition has a D75/D25 ratio of 1.8 or below (wherein D25 is the particle diameter at which the cumulative weight of smaller particles in the weight distribution of particle diameters is 25wt.%, and D75 is the particle diameter at which the cumulative weight is 75wt.%), (e) the degree of swelling of the polybutadiene particles in the resin composition is 5-15, and (f) the grafting ratio is 2.5-4.0.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a highly transparent rubber-modified styrene resin composition and a transparent container. More specifically, the present invention is a highly transparent rubber-modified styrene that maintains rigidity and impact resistance at a high level and is excellent in transparency (contact clear property), and is therefore particularly suitable for a packaging container for food or the like. The present invention relates to a resin composition and a transparent container using the resin composition.

[0002]

2. Description of the Related Art A rubber-modified styrenic resin composition comprising a styrenic resin and a rubber-like polymer is known as high-impact polystyrene (High Impact Polystyrene).
ren: HIPS). Such impact-resistant polystyrene is useful as a resin which has improved impact resistance while maintaining the rigidity of ordinary polystyrene.

By the way, in addition to the requirement that the container for food including various beverages has sufficient rigidity and impact resistance, it is required that the contents can be seen well, that is, the so-called contact clear property is excellent. To be This is an important requirement from the viewpoint of safety and health, in addition to the viewpoint of display effect as a store product.

Conventionally, in a rubber-modified styrenic resin composition, by making the rubber component particles a so-called capsule type having a particle size of about 0.2 μ (also called a single occlusion structure), the contact clear property is enhanced. The method is known. However, in this method, a large amount of rubber component particles must be contained in order to maintain the impact resistance at a high level, and in this case, there is a problem that the contact clear property is deteriorated. Further, a method of improving the contact clear property by using a copolymer of styrene and a vinyl monomer as a matrix is also known. However, in this method, the cost of the rubber-modified styrenic resin composition obtained is increased due to the use of the relatively expensive copolymer.
It was not a preferable method from an industrial viewpoint.

[0005]

In view of the above situation, the problem to be solved by the present invention is to maintain rigidity and impact resistance at a high level and to be excellent in transparency (contact clear property). It is an object to provide a highly transparent rubber-modified styrene-based resin composition and a transparent container using the resin composition, which is most suitable for a packaging container for food and the like.

[0006]

The present inventors have arrived at the present invention as a result of intensive studies to solve the above problems.

That is, one of the inventions is a rubber-modified styrene resin composition obtained by graft polymerization of a vinyl aromatic monomer in the presence of polybutadiene, which comprises the following (a) to ( The present invention relates to a highly transparent rubber-modified styrene resin composition having the characteristics of f). (A) The vinyl content of the polybutadiene used is 8 to 30% by weight, and its solution viscosity (value at 25 ° C. in 5% by weight styrene solution) is 300 to 2000 centipoise. (B) In the resin composition The polybutadiene content is 3 to 5% by weight. (C) The median particle size of the polybutadiene particles in the resin composition is 1.8 μm or more. (D) In the particle size distribution of the polybutadiene rubber in the resin composition, The value of D ₇₅ / D ₂₅ is 1.8 or less (however, D ₂₅ is the particle size when the cumulative weight from the smaller particle size distribution is 25% by weight, D
₇₅ is the particle size when the cumulative weight is 75% by weight. (E) The degree of swelling of the polybutadiene particles in the resin composition is 5
15 to 15 (f) Graft ratio is 2.5 to 4.0

Another aspect of the present invention relates to a transparent container using the above-mentioned highly transparent rubber-modified styrene resin composition.

The details will be described below. The polybutadiene used in the present invention has a vinyl content of 8 to 30% by weight, preferably 10 to 20% by weight, and a solution viscosity (value of 25 ° C. in 5% by weight styrene solution) of 300 to 2%.
It should be 000 centipoise, preferably 300-1000 centipoise. If the vinyl content is too low, a sufficient graft ratio cannot be obtained and the impact resistance is poor. on the other hand,
If the vinyl content is too high, the particle size of the polybutadiene particles will be small and the transparency will be poor. Even if the solution viscosity is too low, the particle size of the polybutadiene particles will be small and the transparency will be poor. On the other hand, polybutadiene having an excessively high solution viscosity has poor solubility with a vinyl aromatic monomer, resulting in reduced production efficiency when obtaining a resin composition.

As the vinyl aromatic monomer used in the present invention, styrene is generally used, but alkyl-substituted styrenes such as o-methylstyrene, m-methylstyrene and p-methylstyrene can also be used.

The resin composition of the present invention is obtained by graft-polymerizing the above vinyl aromatic monomer in the presence of the above polybutadiene rubber, and particles of polybutadiene in a matrix composed of the vinyl aromatic resin. Are dispersed. Here, the structure of the polybutadiene particles is not particularly limited, so-called capsule type,
Various types such as salami type may be used.

The content of polybutadiene in the resin composition is 3 to 5% by weight. If the content is too small, impact resistance is poor, and if the content is too large, transparency and rigidity are poor. The content of polybutadiene in the resin composition can be calculated by dividing the charged weight of polybutadiene in the polymerization by the final conversion rate during the polymerization. In addition, a titration method using iodine monochloride (for example, Polymer Handbook, edited by Amane Kambara, N. Fujiwara, published by Asakura Shoten, Showa 45)
It may be obtained by measuring according to (year). The final conversion rate is calculated as follows. That is, a small amount (weight a) of resin is collected from the polymerization tank at the end of the polymerization, the resin is vacuum dried (70 ° C., 3 hr + 130 ° C., 1 hr), and the weight (b) after drying is measured. Final conversion rate is b / a x 1
It is calculated by 00%.

The median particle size of the polybutadiene particles in the resin composition must be 1.8 μm or more, preferably 2.5 μm or more. If the medium particle size is too small, the transparency is poor. The medium particle size is obtained by the following method. That is, the resin composition was dissolved in a solution of ammonium thiocyanate (4% by weight) in dimethylform, and the obtained sample was measured by a particle size distribution measuring device (for example, Coulter Multisizer manufactured by Nikkaki Co., Ltd.) on a weight basis. The median particle size in the particle size distribution curve of 1 is defined as the median particle size of the present invention.

In the particle size distribution of the polybutadiene particles in the resin composition, the value of D ₇₅ / D ₂₅ must be 1.8 or less. Here, D ₂₅ is a particle size when the cumulative weight from the smaller particle size is 25% by weight in the weight distribution of the particle size, and D ₇₅ is a particle size when the cumulative weight is 75% by weight. The particle size. If the value of D ₇₅ / D ₂₅ is too large, the transparency is poor. The values of D ₇₅ and D ₂₅ are obtained from the above particle size distribution.

The degree of swelling of the polybutadiene particles in the resin composition must be 5 to 15, preferably 8 to 15. If the degree of swelling is too small, the impact resistance is poor, whereas if the degree of swelling is too large, the transparency is poor. 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 overnight. The obtained toluene solution was centrifuged (10000r).
(pm × 30 minutes) to separate 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 x 3 hours),
Let the weight after drying be b. Swelling degree is (ab) / b × 1
00.

The graft ratio should be 2.5 to 4.0, preferably 2.7 to 3.5. If the graft ratio is too low, impact resistance and transparency are poor, while if the graft ratio is too high, rigidity is poor. The graft ratio is determined by the following method. That is, the resin composition is dissolved in a methyl ethyl ketone / methanol mixed solvent (volume ratio 10/1) at room temperature (23 ° C.) (provided that the resin composition /
The mixed solvent is 0.01 g / ml. ), The value obtained by dividing the dry weight of the insoluble matter at that time by the polybutadiene content is taken as the graft ratio.

The highly transparent rubber-modified styrene resin composition of the present invention is basically a conventional method for obtaining impact-resistant polystyrene, that is, a method in which a vinyl aromatic monomer is graft-polymerized in the presence of polybutadiene. Can be obtained by Here, examples of the polymerization reaction method include a bulk polymerization method and a bulk-suspension two-stage polymerization method. The highly transparent rubber-modified styrene-based resin composition satisfying the requirements of the present invention can be obtained by adjusting the stirring speed, temperature, etc. during the polymerization reaction. Furthermore, a highly transparent rubber-modified styrene-based resin composition satisfying the requirements of the present invention can be obtained by mixing two or more rubber-modified styrene-based resin compositions or styrene-based resin compositions.

If desired, various additives can be used in the highly transparent rubber-modified styrene resin composition of the present invention. As the additive, for example, an antioxidant,
Examples thereof include heat stabilizers, ultraviolet absorbers, lubricants, antistatic agents, mineral oils and silicone oils.

The highly transparent rubber-modified styrene resin composition of the present invention can be molded using a molding machine that is generally used. For example, in addition to injection molding, extrusion molding and blow molding, injection blow molding is particularly suitable.

The highly transparent rubber-modified styrene resin composition of the present invention thus obtained maintains rigidity and impact resistance at a high level and is excellent in transparency (contact clear property). A wide range of fields,
For example, it is preferably used for various beverages such as lactic acid drinks and containers for foods, cosmetics containers, pharmaceutical containers and the like.

[0021]

EXAMPLES Next, the present invention will be explained with reference to examples. Regarding the polybutadiene content in the resin composition, the median particle diameter of the polybutadiene particles, the D ₇₅ / D ₂₅ value of the polybutadiene particles, the swelling degree of the polybutadiene particles and the graft ratio,
It was measured by the method described above. The other evaluation items were evaluated as follows. (1) Impact strength (Izod impact strength) Measured in accordance with JIS K7110. (2) Rigidity (flexural modulus) It was measured according to JIS K7203. (3) Transparency (total light transmittance) Using an injection molded sheet with a thickness of 0.7 mm, JIS K
It measured based on 6714.

Example 1 Middle cis polybutadiene (1271SL, manufactured by Nippon Zeon Co., vinyl content 12% by weight) was added to a stirring and mixing type polymerization tank.
Solution viscosity (value at 25 ° C in 5% by weight styrene solution) 70
0 centipoise) 2.9% by weight, styrene 90% by weight,
A mixture consisting of 5% by weight of ethylbenzene, 0.02% by weight of t-dodecylmercaptan and 2.1% by weight of mineral oil was fed, and the temperature was 138 ° C. and the stirring rotation speed was 60 r.
Polymerization was performed at a conversion rate of 23% under the condition of pm. Subsequently, the obtained polymerization mixture was polymerized to a conversion of 80% using a full-filling type polymerization tank, and then volatile components were removed in a degassing tank at 250 ° C. to obtain pellet-shaped highly transparent rubber-modified styrene resin. A composition was obtained. The measurement results and evaluation results are shown in Table 1.

Example 2 Example 1 was repeated except that the content of middle cis polybutadiene was 3.6% by weight and the content of styrene was 89.4% by weight.

Example 3 As a middle cis polybutadiene, Diene 7 manufactured by Asahi Kasei Corporation
Example 1 was repeated except that 0 (vinyl content 13% by weight, solution viscosity 300 centipoise) was used.

Example 4 12 manufactured by Nippon Zeon Co., Ltd. as middle cis polybutadiene
Example 1 was repeated except that 71S (vinyl content 13% by weight, solution viscosity 1000 centipoise) was used.

Comparative Example 1 5.8% by weight of middle cis polybutadiene (the same as in Example 3), 87.1% by weight of styrene, 5% by weight of ethylbenzene, 0.02 of t-dodecyl mercaptan were placed in a stirring and mixing type polymerization tank. A mixture consisting of 1% by weight and 2.1% by weight of mineral oil was fed, the temperature was 137 ° C., and the stirring rotation speed was 6
Polymerization was performed at a conversion rate of 23% under the condition of 0 rpm. Subsequently, the obtained polymerization mixture was polymerized to a conversion of 80% using a liquid-filled polymerization tank, and then the volatile matter was removed in a degassing tank at 250 ° C. to obtain a pelletized rubber-modified styrene resin composition. Obtained.

Comparative Example 2 The procedure of Comparative Example 1 was repeated except that the content of middle cis polybutadiene was 3.6% by weight, the content of styrene was 89.3% by weight, and the temperature of the degassing tank was 220 ° C.

Comparative Example 3 Instead of middle cis polybutadiene, high cis polybutadiene (Ubepol 22H manufactured by Ube Industries, Ltd., vinyl content 1.
Example 1 was repeated except that 4% by weight and a solution viscosity of 200 centipoise) were used.

Comparative Example 4 As middle cis polybutadiene, Diene 5 manufactured by Asahi Kasei Corporation
Example 5 was repeated except that 5 (vinyl content 13% by weight, solution viscosity 170 centipoise) was used.

Comparative Example 5 The procedure of Comparative Example 4 was repeated, except that the stirring rotation speed of the stirring and mixing type polymerization tank was 130 rpm.

The results are shown in Tables 1-2. From these results, the following can be seen. Examples 1 to 3 according to the present invention are
Satisfactory results are shown for all evaluation items. On the other hand, Comparative Example 1 having an excessive polybutadiene content is inferior in transparency and rigidity. Comparative Example 2 in which the swelling degree of the polybutadiene particles is excessively inferior in transparency. Comparative Example 3 in which the vinyl content of polybutadiene is too small, the solution viscosity is too small, and the graft ratio is too small, is inferior in impact resistance. Comparative Example 4 in which the solution viscosity of polybutadiene is too small is inferior in transparency and impact resistance. Comparative Example 5 in which the median particle size of the polybutadiene particles is too small
Is inferior in transparency and impact resistance.

[0032]

[Table 1] ------------------ Example 1 2 3 4 PBR characteristics * 1 Vinyl content wt% 12 12 13 13 Solution viscosity cps * 2 700 700 300 1000 PBR Particles * 3 Content wt% 3.6 4.5 3.6 3.6 Medium particle size μ 3.3 4.2 2.7 3.0 D ₇₅ / D ₂₅ 1.6 1.7 1.5 1.6 Swelling degree 15 15 12 14 Graft ratio % 2.8 3.0 2.7 2.8 Evaluation result Total light transmittance% 71 65 64 72 Impact strength kg ・ cm / cm 5.4 6.0 4.7 4.6 Rigidity kg / cm ² 23000 21500 25000 24800 −−−−−−−−−−−−−− −−−−−−−−−−−−−−−−−

[0033]

[Table 2] ------------------------------------------ Ratio Comparative Example 1 2 3 4 5 PBR Characteristics * 1 Vinyl content wt% 13 13 1.4 13 13 Solution viscosity cps * 2 300 300 200 170 170 PBR Particles * 3 Content wt% 7.3 4.5 3.6 3.6 3.6 Medium particle size μ 3.6 3.1 3.4 2.9 1.7 D ₇₅ / D ₂₅ 1.9 1.7 1.9 2.0 1.6 Swelling degree 12 19 26 14 15 Graft ratio% 2.7 2.8 1.7 3.1 2.4 Evaluation result Total light transmittance% 48 59 63 57 59 Impact strength kg ・ cm / cm 7.3 6.7 3.8 4.3 4.2 Rigidity kg / cm ² 16500 22000 27500 24000 26500 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

* 1 PBR characteristics: characteristics of polybutadiene used * 2 Solution viscosity: value at 25 ° C. in a 5 wt% styrene solution (centipoise) * 3 PBR particles: polybutadiene particles in resin composition

[0035]

As described above, according to the present invention, the rigidity and impact resistance are maintained at a high level, and the transparency (contact clear property) is excellent. Therefore, the present invention is most suitable for a packaging container for food or the like. It was possible to provide a highly transparent rubber-modified styrene resin composition and a transparent container using the resin composition.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor ▲ Yoshi ▼ Shuji Mi 1 1-5 Anezaki Kaigan, Ichihara City, Chiba Sumitomo Chemical Co., Ltd.

Claims (2)

[Claims] 1. A rubber-modified styrene resin composition obtained by graft-polymerizing a vinyl aromatic monomer in the presence of polybutadiene, which is a highly transparent rubber having the following characteristics (a) to (f): Modified styrene resin composition. (A) The vinyl content of the polybutadiene used is 8 to 30% by weight, and its solution viscosity (value at 25 ° C. in 5% by weight styrene solution) is 300 to 2000 centipoise. (B) In the resin composition The polybutadiene content is 3 to 5% by weight. (C) The median particle size of the polybutadiene particles in the resin composition is 1.8 μm or more. (D) In the particle size distribution of the polybutadiene particles in the resin composition, The value of D ₇₅ / D ₂₅ is 1.8 or less (however, D ₂₅ is the particle size when the cumulative weight from the smaller particle size distribution is 25% by weight, D
₇₅ is the particle size when the cumulative weight is 75% by weight. (E) The degree of swelling of the polybutadiene particles in the resin composition is 5
15 to 15 (f) Graft ratio is 2.5 to 4.0 2. A transparent container using the highly transparent rubber-modified styrene resin composition according to claim 1.