JPH0747680B2 - Rubber modified polystyrene composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an improved rubber-modified polystyrene composition having excellent impact resistance, good gloss and heat resistance. The rubber-modified polystyrene composition of the present invention is AB
Widely used as a substitute for S resin in light electrical appliances and audio equipment.

[Prior Art] Conventionally, a rubber-modified polystyrene-based resin having physical properties comparable to that of an ABS resin has not yet been obtained as an alternative to the ABS resin. If the dispersed particles are made finer to increase the gloss, the impact resistance, particularly the drop weight strength, is notably reduced, and even if a certain kind of additive is used, it is not always satisfactory in terms of overall quality balance.

For example, a rubber-modified polystyrene composition having a specified rubber type and a rubber particle size and a rubber-modified polystyrene composition containing polydimethylsiloxane and a zinc salt of a higher fatty acid as an additive are known (Japanese Patent Publication No. 61-
No. 50488 and Japanese Patent Application Laid-Open No. 61-183339) both have the drawback that the impact resistance, especially the falling weight strength, is insufficient.

On the other hand, it is also known to use a combination of a fatty acid ester of a polyhydric alcohol and a higher fatty acid zinc salt as an additive for the resin composition. For example, it is known that the ABS resin composition is added in an amount of 4.0 to 6.0% by weight in order to prevent static electricity (Japanese Patent Publication No. 51-8981). There is a drawback that the stability decreases and yellowing occurs. In addition, there has been proposed one in which a combination of glycerin monostearate and a higher fatty acid zinc salt is added to polystyrene (JP-A-54-132650), but this product has poor gloss and impact resistance. Is insufficient. It is also known that ester waxes of higher fatty acids and higher alcohols can be used in combination with higher fatty acid zinc salts as additives for other polyesters, but gloss, impact resistance,
There is a problem in heat resistance. Further, although it is known to use an ester of a divalent saturated aliphatic alcohol and a carboxylic acid and a higher fatty acid zinc salt (Japanese Patent Publication No. 60-37138), there is a drawback that the heat resistance is remarkably lowered. is there.

As described above, the conventional rubber-modified polystyrene is not always satisfactory because it has difficulty in the overall physical properties.

[Problems to be Solved by the Invention] The present invention overcomes the drawbacks of the conventional rubber-modified polystyrene resin, and is excellent in a comprehensive quality balance such as impact resistance, gloss and heat resistance. It is intended to provide.

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to develop a rubber-modified polystyrene composition having excellent quality, and as a result, in the rubber-modified polystyrene composition, a rubber-like elastic body is specified. Having a microstructure and a melt viscosity, and being present as dispersed particles having a specific average particle size, by further including each specific amount of a zinc salt of a higher fatty acid and a sorbitan fatty acid ester, the overall balance is achieved. It was found that a rubber-modified polystyrene of excellent quality can be obtained, and the present invention has been completed based on this finding.

That is, the present invention relates to a rubber-modified polystyrene composition containing 5 to 12% by weight of a rubber-like elastic material as dispersed particles, wherein (A) the rubber-like elastic material has a 1,2-vinyl bond of 8 to 15 mol%, 25-45 mol% 1,4-cis bond, 1,4-trans bond
Dispersed particles having an average particle size of 0.5 to 1.2 μm, having a microstructure of 30 to 67 mol% and a solution viscosity of 20 to 200 centipoise, and further comprising (B) a higher fatty acid in the composition. The present invention provides a rubber-modified polystyrene composition characterized by containing 0.2 to 2.0% by weight of zinc salt and 0.01 to 1.0% by weight of (C) sorbitan fatty acid ester.

The rubber-modified polystyrene composition used as the main component of the present invention can be produced by a bulk polymerization method or a bulk suspension polymerization method in which a styrene-based monomer is polymerized in the presence of a rubber-like elastic material. At this time, the average particle diameter of the dispersed particles can be adjusted by controlling the stirring state in the polymerization step, the mixing state when the rubber particles are produced, and the like. For example, if the stirring speed is increased, the average particle diameter is decreased, and if the stirring speed is decreased, the average particle diameter is increased. Therefore, a desired average particle diameter can be obtained by appropriately selecting the stirring speed.

A rubber-like elastic material 5 was added to the rubber-modified polystyrene composition.
.About.12% by weight, preferably 6 to 11% by weight. If the content is less than 5% by weight, impact resistance is lowered, and if it exceeds 12% by weight, gloss is lowered.

Styrene-based monomers include styrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, 2,4
-Nuclear alkyl-substituted styrenes such as dimethyl styrene, ethyl styrene and p-tert-butyl styrene, and α-alkyl substituted styrenes such as α-methyl styrene and α-methyl-p-methyl styrene are used.

The rubber-like elastic material is composed of 1,2-vinyl bonds 8 to 15 mol% and 1,4-vinyl bonds.
It is necessary to have a microstructure defined by 25-45 mol% cis bonds, 30-67 mol% 1,4-trans bonds, and a solution viscosity of 20-200 centipoise. Even if such a rubber-like elastic material occupies only about 70% by weight with respect to the entire rubber-like elastic material, there is no practical problem.

Rubber-like elastic bodies outside this range, such as cis 1,4-bonds of 90
High cis-polybutadiene of mol% or more, polybutadiene having a solution viscosity of less than 20 centipoise or more than 200 centipoise, styrene-butadiene copolymer rubber (SBR or SBS), etc. as a rubber-like elastic body, when an amount exceeding 30% by weight is used , The gloss and impact resistance of the composition are reduced.

That is, when the 1,2-vinyl bond is less than 8 mol%, the gloss is decreased, and when it exceeds 15 mol%, the impact resistance is decreased, and when the 1,4-cis bond is less than 25 mol%, the impact resistance is decreased. Deteriorates, and when it exceeds 45 mol%, the gloss decreases. Also,
If the solution viscosity is less than 20 centipoise, the impact resistance will decrease,
When it exceeds 200 centipoise, the gloss decreases.

The microstructure of such a rubber-like elastic material is determined by measuring its infrared absorption spectrum and using the Morello method or the like. The solution viscosity is 2.5 g of rubber-like elastic material
The product dissolved in 47.5 g is obtained by measuring with an Ubbelohde viscometer at 25 ° C.

The dispersed particles present dispersed in the rubber-modified polystyrene composition, which is the main component of the present invention, have an average particle diameter of 0.5 to 1.2.
.mu.m, preferably 0.6-1.1 .mu.m. If the average particle size is less than 0.5 μm, the impact resistance decreases and 1.2 μm
If it exceeds, gloss and heat resistance decrease.

The average particle size referred to here is a transmission electron micrograph (enlargement magnification 10,000
2 times), and the particle size of 800 to 2,000 dispersed particles in the photograph was measured as follows. Since the dispersed particles shown in the electron micrograph are not necessarily perfect circles, the diameter a in the longitudinal direction and the diameter b in the short width direction of the dispersed particles are measured and calculated by the following formula.

Average particle diameter Ds (micron) = ΣniDi ³ / ΣniDi ² (where ni is the number of dispersed particles having a particle diameter Di) The higher fatty acid zinc salt used in the present invention is a higher fatty acid C _{12 to} C _32. The above-mentioned salts of straight-chain saturated monocarboxylic acid and zinc are collectively referred to, and representative examples thereof include zinc laurate, zinc palmitate, zinc stearate, zinc behenate, and zinc montanate. These may be used alone or in combination of two or more. Metal salts other than higher fatty acid zinc salt, such as potassium, magnesium,
Higher fatty acid metal salts such as calcium do not show a preferable effect for improving gloss.

The content of zinc salt of higher fatty acid in the composition of the present invention is 0.
It must be in the range of 2 to 2.0% by weight. If this amount is less than 0.2% by weight, the effect of the present invention will not be exhibited, and if it exceeds 2.0% by weight, adhesion of oily substances to the molded product is observed, which is not preferable. A particularly preferred range is 0.3 to 1.5% by weight. If it exceeds 1.5% by weight, the heat distortion temperature decreases,
It is not preferable for molded products that require heat resistance.

In the composition of the present invention, as the sorbitan fatty acid ester used in combination with the zinc salt of higher fatty acid, a monoester of sorbitan and a higher fatty acid having 12 to 20 carbon atoms, a diester, for example, a mono- or di-stearic acid sorbitan ester, Examples include mono- or di-palmitic acid sorbitan ester, mono- or di-lauric acid sorbitan ester, mono- or di-oleic acid sorbitan ester, or a mixture thereof.

It is necessary that these sorbitan fatty acid esters are contained in the polystyrene-based resin modified with a rubber-like elastic material in an amount of 0.01 to 1.0% by weight, preferably 0.05 to 0.9% by weight. If the content is less than 0.01% by weight, the impact resistance cannot be sufficiently improved, and if it exceeds 1.0% by weight, the rigidity and the impact resistance are unavoidably deteriorated.

In the composition of the present invention, it is necessary to use a zinc salt of a higher fatty acid and a sorbitan fatty acid ester in combination, and if either one is omitted, the impact resistance and the gloss are not improved. That is, according to the present invention, the lack of impact resistance, which is a drawback of the rubber-modified polystyrene-based resin having a specific microstructure, is improved only by the combined use of both without impairing the good gloss, rigidity, etc. You can do it.

To prepare the composition of the present invention, any method commonly used for preparing a rubber-modified polystyrene-based composition can be used. For example, it is also possible to form a resin composition by adding a required amount of a higher fatty acid zinc salt and a sorbitan fatty acid ester to a styrene-based monomer, adding a rubber-like substance prepared in advance thereto, and polymerizing while stirring. Alternatively, a required amount of higher fatty acid zinc salt and sorbitan fatty acid ester may be added to a rubber-modified polystyrene-based resin prepared in advance, and the mixture may be melt-mixed to obtain a resin composition. In this case, since the sorbitan fatty acid ester has low thermal stability and is easily yellowed, it is advantageous to melt-mix the sorbitan fatty acid ester in a short time using an extruder or the like. In addition, a master pellet having a higher zinc salt concentration of higher fatty acid can be produced from a zinc salt of higher fatty acid and polystyrene, and the master pellet and rubber-modified polystyrene can be mixed to obtain a composition. It is also possible to mix the master pellets and rubber modified polystyrene to obtain the composition.

If desired, conventional additives such as colorants, lubricants, fillers, release agents, plasticizers and antistatic agents can be added to the composition of the present invention.

Examples of this lubricant include higher fatty acids, higher fatty acid amides, paraffins, waxes, polyhydric alcohols, and silicone-based substances.

[Effects of the Invention] The rubber-modified polystyrene composition of the present invention has the remarkable effects of being excellent in impact resistance, particularly drop weight impact strength, having good gloss and heat resistance, and being excellent in overall quality balance.

The composition of the present invention can be used as a substitute molded article such as expensive ABS resin in the fields of light electric appliances such as home electric appliances, audio equipment, sundries, and cancer tools.

EXAMPLES Next, the present invention will be described in more detail with reference to examples.

The physical properties in each example were measured as follows.

(1) Gloss Compliant with JIS Z 8741 (incident angle 60 ° C) (2) Compliant with Izod impact strength JIS Z 7110 (with notch) (3) Drop weight impact strength 1/2 inch φ using DuPont impact tester 1.0
Test piece (width 70mm, length 270mm, thickness 3
mm) shows the energy at which 50% of the test pieces break when hit at a point 125 mm from the gate.

(4) Heat distortion temperature Measured in accordance with JIS K 6871 Reference example Production of rubber-modified polystyrene resin Polybutadiene rubber (Asahi Kasei
Product name Jien , NF35AS; 1,2-vinyl bond
Total: 13 mol%, solution viscosity: 85 centipoise) 7.5 parts by weight,
Consists of 87.5 parts by weight of styrene and 5.0 parts by weight of ethylbenzene.
100 parts by weight of the mixture of 1,1-bis (tertiary butylperoxy)
Si) 0.040 parts by weight of 3,3,5-trimethylcyclohexane and n
− 0.030 parts by weight of dodecyl mercaptan and antioxidant (
Made by Bageigie, product name; Irganox 1076) 0.070
1 part weight of volume 13 which was added with parts by weight and maintained at a temperature of 117 ° C
Polymerization is carried out by continuously supplying to the mixing tank. Here
While stirring at a mixing speed of 100 to 450 rpm, a rubber-like material
Adjust the average rubber particle size of quality.

This polymerization product is further sent to a second polymerization tank having a capacity of 19, and subsequently to a third polymerization tank having a capacity of 20, and after continuing the polymerization at a temperature of 120 to 180 ° C., a volatile component is removed by a devolatilization device, A rubber-modified polystyrene resin in pellet form was obtained.

Thus, the average particle diameters of dispersed particles having a polybutadiene content of 8.2% by weight are 0.42 μm, 0.61 μm and 0.73, respectively.
Six types of rubber-modified polystyrene resins having μm, 0.85 μm, 1.08 μm and 1.35 μm were obtained.

Examples 1 to 4 and Comparative Examples 1 and 2 To 6 types of rubber-modified polystyrene resins obtained in Reference Examples, 1.0% by weight of zinc stearate and 0.10% by weight of sorbitan monostearate were added, and the mixture was mixed with an extruder. The resin composition was prepared by kneading. This was injection-molded and the physical properties of the molded product were measured. The results are shown in Table 1.

Examples 5 to 8 and Comparative Examples 3 to 5 In the reference examples, the polybutadiene rubber was replaced with various commercially available polybutadiene rubbers shown in Table 2, and rubber-modified polystyrene resins obtained by using as shown in Table 3 were used. In contrast,
A resin composition was prepared by adding 1.0% by weight of zinc stearate and 0.10% by weight of sorbitan monostearate and kneading with an extruder. This was injection-molded and the physical properties of the molded product were measured. The results are shown in Table 3.

In Examples 9 and 10 and Comparative Examples 6 and 7, the rubber content in the rubber-modified polystyrene resin was changed as shown in Table 4, and the rubber-modified polystyrene resin was prepared in the same manner as in Example 1, A resin composition was prepared by adding 1.0% by weight of zinc stearate and 0.10% by weight of sorbitan monostearate and kneading with an extruder. This was injection-molded and the physical properties of the molded product were measured. The results are shown in Table 4.

Examples 11 to 17 and Comparative Examples 8 to 12 Zinc stearate and sorbitan acid monostearate were added to the rubber-modified polystyrene resins having an average rubber particle diameter of 0.73 μm obtained in Reference Examples at the addition amounts shown in Table 5, A resin composition was prepared in the same manner as in Example 2. The physical properties of this injection-molded product were measured, and the results are shown in Table 5. In Comparative Example 9 among them, the secondary processability (colorability,
Printability and paintability) were low.

As is clear from the results of Comparative Examples 10 and 11, the zinc stearate alone or the sorbitan monostearate alone does not improve the impact resistance, and it is preferable to use the combination of zinc stearate and the sorbitan monostannate. For the first time, the impact resistance is greatly improved, the gloss is also improved, and well-balanced physical properties are obtained.

Examples 18 and 19 The same experiment as in Example 2 was repeated except that sorbitan monopalmitate or sorbitan monolaurate was used instead of sorbitan monostearate. The results obtained are shown in Table 6.

Example 20 The same experiment as in Example 2 was repeated except that stearic acid (0.07% by weight) was also used as a lubricant. The results obtained are shown in Table 6.

Comparative Examples 13 and 14 The same experiment as in Example 1 was repeated using glycerin monostearate and polydimethylsiloxane instead of sorbitan stearate. The results obtained are shown in Table 7.

Comparative Examples 15 and 16 As stearic acid metal salt, calcium stearate,
The same experiment as in Example 1 was repeated using magnesium stearate. The results obtained are shown in Table 7.

Claims (1)

[Claims] 1. A rubber-modified polystyrene composition containing 5 to 12% by weight of a rubber-like elastic material as dispersed particles,
(A) The rubber-like elastic material has 1,2-vinyl bonds of 8 to 15 mol%, 1,4-cis bonds of 25 to 45 mol%, and 1,4-trans bonds of 30.
Dispersed particles having an average particle size of 0.5 to 1.2 μm, having a microstructure of ˜67 mol% and a solution viscosity of 20 to 200 centipoise, and further comprising (B) a zinc of a higher fatty acid in the composition. A rubber-modified polystyrene composition comprising 0.2 to 2.0% by weight of salt and 0.01 to 1.0% by weight of (C) sorbitan fatty acid ester.