JPS63314258A - High-impact polystyrene resin composition - Google Patents

Abstract

PURPOSE:To obtain the title composition having good gloss, rigidity and heat resistance and high impact resistance, especially, falling dart impact strength, by mixing a PS resin containing a rubber-like substance dispersed therein as particles with polydimethylsiloxane and a sorbitan fatty acid ester. CONSTITUTION:A rubber-like PS resin composition formed by mixing a PS resin containing 1-15wt.% rubber-like substance (e.g., low-cis polybutadiene rubber of a cis-1,4-isomer content of 25-45%, obtained by solution-polymerizing butadiene by using a Li catalyst) dispersed therein as particles of an average particle diameter of 0.5-1.2mu with 0.005-0.8pt.wt. polydimethylsiloxane and 0.3-3.0pts.wt. sorbitan fatty acid ester (e.g., mono- or di-stearate) per 100pts.wt. said resin. This composition has good gloss, high impact strength, especially, falling dart impact resistance and further good rigidity and heat resistance. This composition can be produced at low cost without any expensive materials, and can be suitably used as a material for weak-current electrical appliances, acoustic apparatuses and automobile parts.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rubber-modified polystyrene resin composition that has good gloss, rigidity and heat resistance, and also has high impact resistance, particularly high falling weight impact strength. It is something.

[Prior Art] Polystyrene resin compositions containing rubber-like substances dispersed in the form of particles have good impact resistance, moldability, and gloss, and are therefore used as materials for various electrical parts, office supplies, and containers. ,
It is widely used as a material for automobile parts.

By the way, among this type of resin composition, ABS resin can be cited as one that exhibits the most excellent physical properties, but since this resin contains an acrylic component, it is inevitably expensive. It is extremely disadvantageous to use it as a general-purpose material. In order to solve these problems, many rubber-modified polystyrene-based resin compositions that omit the acrylic component have been proposed, but each has advantages and disadvantages, and none that have physical properties comparable to ABS resins are yet known. do not have.

For example, in order to improve the gloss that would be damaged by omitting the acrylic component, a rubbery substance with a particle size of 0.5
A rubber-modified polystyrene resin composition formulated with a microstructure of ~1.5 pya (Japanese Patent Publication No. Sho H-50488) is a high-grade polystyrene resin composition formulated to improve moldability and appearance while maintaining excellent impact resistance Rubber-modified polystyrene resins containing tertiary amines have been proposed (Japanese Patent Application Laid-Open No. 61-209245), but when the rubbery substance is made fine and dispersed, the impact resistance, especially the falling weight impact strength, decreases. Furthermore, even those containing higher tertiary amines do not necessarily give satisfactory results in terms of improving impact resistance.

On the other hand, rubber-modified polystyrene resins to which polysiloxane is added (JP-A-53-12456, JP-A-55-3494, JP-A-57-1873)
No. 45, JP-A-57-1!17346) and those to which sorbitan fatty acid ester is added (JP-A No. 57-1!17346)
No. 89H) has also been proposed, but even if polysiloxane is added, the impact resistance and gloss are not sufficiently improved, and the addition of sorbitan fatty acid ester improves impact resistance but does not improve thermal stability. It has a tendency to lose its properties and turn yellow.

[Problems to be solved and attempted by the invention] The present invention overcomes the drawbacks of conventional rubber-modified polystyrene resins, and provides excellent impact resistance, particularly drop weight impact strength, as well as good gloss, rigidity, and heat resistance. The purpose of this invention was to provide a novel rubber-modified polystyrene resin composition having the following properties.

[Means for Solving the Problems] As a result of intensive research to develop a rubber-modified polystyrene resin with excellent physical properties comparable to ABS resin, the present inventors have found that the rubber-like substance has a particle size of 0. .5-1.2μm
When a combination of polydimethylsiloxane and sorbitan fatty acid ester is added to a polystyrene resin dispersed as fine particles, it not only shows excellent impact resistance but also improves gloss, rigidity, and heat resistance. Based on this finding, the present invention has been completed.

That is, in the present invention, polydimethylsiloxane is added per 100 parts by weight of a polystyrene resin in which 1 to 15% by weight of a rubbery substance is dispersed and blended into particles with an average particle size of 0.5 to 1.2 μm. The present invention provides an impact-resistant polystyrene resin composition characterized by containing 0.005 to 0.8 parts by weight and 0.3 to 3.0 parts by weight of sorbitan fatty acid ester.

The polystyrene resin of the present invention includes styrene monomers such as styrene, σ-methylstyrene, 0-methylstyrene, p-methylstyrene, 0-methylstyrene, 2.4
- It is obtained by polymerizing at least one selected from dimethylstyrene, p-ethylstyrene, p-tert-butylstyrene, α, p-dimethylstyrene, and the like.

Further, the rubbery substance to be blended into this polystyrene resin can be arbitrarily selected from among the rubbery substances used in conventional rubber-modified polystyrene resins. An example of such a rubbery substance is obtained by solution polymerizing butadiene using a lithium-based catalyst.

Low-cis polybutadiene rubber with a cis-1,4-isomer content of 25 to 45%, high-cis polybutadiene rubber with a cis-1,4-isomer content of 90% or more obtained by solution polymerizing butadiene using a Ziegler catalyst, etc. There is. These rubbery substances may be used alone or in combination of two or more.

In the composition of the present invention, this rubbery substance has an average rubber particle diameter of O, S ~ 1.2 μm, preferably 0.6 ~ 1.1 μm.
It is necessary to disperse the above-mentioned styrenic monomer in the presence of a rubber-like substance prepared in advance in the form of particles of m in a polystyrene resin. This can be done by polymerization.

The average particle size in this case is determined by a transmission electron micrograph (magnification: 10.000 times) according to the ultrathin section method of the obtained resin.
The dispersed particles in the photo range from 800 to 2. Go.

It is determined by measuring the particle size of individual particles. At this time, since the dispersed particles seen in the electron micrograph are usually not perfectly circular, the diameter in the longitudinal direction and the diameter in the width direction are measured, and the average rubber particle diameter Ds (μm
) is calculated.

Particle size (D) - JT77 Average rubber particle size (Ds) - Σn1Di"/ΣaiDi2
In the composition of the present invention, if the average rubber particle diameter of the rubbery substance is less than 0.5 μm, the impact resistance will be reduced, and if it is larger than 1 or 2 μm, the gloss, rigidity and heat resistance will be reduced.

This rubbery substance is contained in polystyrene resin from 1 to 15
It is blended in a proportion in the range of % by weight. If this amount is less than 1% by weight, the impact resistance will be insufficient;
If the temperature is exceeded, rigidity, heat resistance, etc. will deteriorate.

Next, the polydimethylsiloxane added to the composition of the present invention is a silicon compound having a chemical structure represented by the general formula.

In the present invention, among these polydimethylsiloxanes, those having a relatively low molecular weight with a viscosity of 10 to IQ and about 1,000 centistokes at 25°C are preferably used.

In the present invention, it is necessary to use this polydimethylsiloxane; if other polysiloxanes such as polydiethylsiloxane and polymethylethylsiloxane are used, the impact resistance will be insufficient.

This polydimethylsiloxane is 0.005 to 100 parts by weight of polystyrene resin blended with a rubbery substance.
0.8 parts by weight, preferably 0.8 parts by weight. It is necessary to add it at a ratio of OI to 0.7 parts by weight. If the amount is less than this, the impact resistance will be insufficient, and if the amount is more than this, the rigidity, heat resistance, and secondary processability (adhesiveness, printability, paintability, etc.) will decrease.

In the composition of the present invention, the sorbitan fatty acid ester used in combination with the above-mentioned polydimethylsiloxane includes a monoester of sorbitan and a higher fatty acid having 12 to 20 carbon atoms;
Diesters such as sorbitan di- or di-stearate, sorbitan di-valmitate, sorbitan di-laurate, sorbitan di-oleate, or mixtures thereof.

These sorbitan fatty acid esters are used in an amount of 0.3 to 100 parts by weight of polystyrene resin containing a rubbery substance.
It is necessary to add it in a proportion of 3.0 parts by weight, preferably 0.5 to 2.8 parts by weight. If the amount is smaller than this, sufficient improvement in resistance and impact resistance cannot be obtained, and if the amount is larger than this, the rigidity and impact resistance are inevitably reduced.

In the composition of the present invention, it is necessary to use polydimethylsiloxane and sorbitan fatty acid ester together,
If either one is missing, no improvement in impact resistance or gloss will be observed. That is, according to the present invention, the lack of impact resistance, which is a drawback of rubber-modified polystyrene resins having a specific microstructure, can be overcome without impairing their advantages, such as good gloss and rigidity, by using both together. It can be scattered.

To prepare the composition of the present invention, any method commonly used for preparing rubber-modified polystyrene compositions can be used. For example, a resin composition can be formed by adding required amounts of polydimethylsiloxane and sorbitan fatty acid ester to a styrene monomer, adding a previously prepared rubbery substance thereto, and polymerizing while stirring. Alternatively, the required amount of polydimethylsiloxane and sorbitan fatty acid ester may be added to a rubber-modified polystyrene resin prepared in advance and melt-mixed to obtain a resin composition. In this case, sorbitan fatty acid ester has low thermal stability and tends to yellow, so
It is advantageous to melt and mix in a short time using an extruder or the like. In addition, a composition may be obtained by manufacturing master pellets with a high concentration of polydimethylsiloxane from polydimethylsiloxane and polystyrene and mixing the master pellets with rubber-modified polystyrene, or similarly, master pellets with a high concentration of sorbitan fatty acid ester and rubber. A composition can also be obtained by mixing modified polystyrene.

The resin composition of the present invention may further include a coloring agent, if desired.
Customary additives such as lubricants, fillers, mold release agents, plasticizers, antistatic agents and the like can be added.

Examples of the lubricant include higher fatty acids, lower fatty acids, and metal salts of higher fatty acids.

[Effects of the Invention] The rubber-modified polystyrene resin composition of the present invention has good gloss, high impact resistance, especially falling weight impact strength, and also has good rigidity and heat resistance, and has physical properties comparable to ABS resin. Moreover, it has the advantage that it can be produced at low cost because it does not use expensive raw materials.

Therefore, it is suitable as a material for light electrical appliances, audio equipment, and automobile parts.

[Example] The present invention will be explained in more detail with reference to Examples.

The physical properties on each side were measured as follows.

(1) Gloss Compliant with JIS l 8741 (incidence angle 60°C) (
2) Compliant with Izot impact strength JIS l 711G (with /yf) (
3) Falling weight impact strength Using a DuPont impact tester, a test piece (70 mm in diameter and 2
This shows the energy required to destroy 50% of the test piece when struck at a point 125 mm from the gate (70 mm, 3 mm thick).

(4) Flexural modulus in accordance with ASTM D 790 (5) Heat distortion temperature Measured in accordance with JIS K 6871 Reference example Production of rubber-modified polystyrene resin At a feed rate of 1 tl/hour, 7.5 parts by weight of polybutadiene rubber, 87.5 parts by weight of styrene, 25.0 parts by weight of ethylben
1,1-bis(
(tert-butylperoxy) 3,3.5-trimethylcyclohexane 0. 140 parts by weight of f1 and 0.0 parts by weight of n-dodecylmercaptan. 13 parts by weight of G1, an antioxidant (manufactured by Ciba Geigy, trade name: Irganox +076), and 0.07 parts by weight of G were added and continuously supplied to a first polymerization tank with a capacity of 13Q maintained at a temperature of 93°C, and polymerization was carried out. Let it happen. Next, this partially polymerized product was sent to a second polymerization tank with a capacity of 13ffi maintained at a temperature of 112°C, where the stirring speed was set at 100 to 450 r.
Polymerization is continued while stirring within the pm range, and the average rubber particle size of the rubbery substance is adjusted.

This polymer was further transferred to a third polymerization tank with a capacity of 19Q, and then
Send it to the fourth polymerization tank with a capacity of 20Q, and the temperature is 120~180
After continuing the polymerization at 'C, volatile components were removed using a devolatilization device to obtain a rubber-modified polystyrene resin in the form of pellets.

In this way, the average particle size of the dispersed rubber particles with a polybutadiene content of 8.2% by weight was 0.40 μm and 10.6 μm, respectively.
2μm, 0.76μm, 0.117μm, 1.06
Six kinds of rubber-modified polystyrene resins having diameters of 1.35 μm and 1.35 μm were obtained.

Example 1 Six types of rubber-modified polystyrene resins obtained in reference examples 100
To the weight part, 0.13 part by weight of polydimethylsiloxane and 0.75 part by weight of sorbitan monostearate were added and kneaded using an extruder to prepare a resin composition. This was injection molded and the physical properties of the molded product were measured. The results are shown in Table 1.

Example 2 Polydimethylsiloxane and sorbitan monostearate were added in the amounts shown in Table 2 to the rubber-modified polystyrene resin with an average rubber particle diameter of 0.76 μm obtained in Reference Example, and the resin was prepared in the same manner as in Example 1. A composition was prepared. The physical properties of this injection molded product were measured and the results are shown in Table 2. Among these, Comparative Example 6 has secondary processability of resin molded products (
Adhesion, printability, paintability) were low.

Example 3 Same as Example 1 except that polydimethylsiloxane and sorbitan monostearate were added in the amounts shown in Table 3 to the rubber-modified polystyrene resin with an average rubber particle diameter of 0.76 μm obtained in Reference Example. A resin composition was prepared. The physical properties of this injection molded product were measured and the results were
Shown in the table.

As is clear from the results of N0.5 in Table 2 and N0.7.6 in Table 3, using polydimethylsiloxane alone or sorbitan monostearate alone did not improve impact resistance, and polydimethylsiloxane alone or sorbitan monostearate alone did not improve impact resistance. By using a combination of siloxane and sorbitan monostearate, impact resistance is greatly improved, gloss is also improved, and balanced physical properties can be obtained.

Example 4 The same experiment as in Example 1 was repeated using sorbitan monostearate, sorbitan monopalmitate, or sorbitan monolaurate as the sorbitan fatty acid ester. The obtained results are shown in the fourth
Shown in the table.

Example 5 In Example 1, stearic acid was also used as a lubricant,
A similar experiment was repeated. The results obtained are shown in Table 4.

Claims (1)

[Claims] 1 1 to 15% by weight of rubbery material with an average particle size of 0.5 to 1.5% by weight.
Contains 0.005 to 0.8 parts by weight of polydimethylsiloxane and 0.3 to 3.0 parts by weight of sorbitan fatty acid ester per 100 parts by weight of polystyrene resin dispersed and blended into particles of 2 μm. An impact-resistant polystyrene resin composition characterized by: