JPS5835536B2 - resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resin composition that is well-balanced in moldability, mechanical properties, and electrical properties.

It has been known to mix carbon black as a filler into a thermoplastic resin to produce a semiconductive resin.

However, when a large amount of carbon black is mixed, the mechanical properties tend to deteriorate, and in particular, brittle fracture tends to occur, which is a major problem.

Like polyethylene polypropylene and polyvinyl chloride, polystyrene, which is versatile as a polymer for bottom shapes, is one of the materials that should be used as a semiconductive resin, but this polymer suffers from brittle fracture when a large amount of carbon black is mixed in. is particularly remarkable.

Therefore, it has been considered to incorporate glass fiber, for example, to reinforce mechanical strength, or polyolefins such as polyethylene and polypropylene to facilitate the incorporation of carbon black, but the physical properties have not been sufficiently improved. In fact, problems such as making the molding process complicated or difficult, deteriorating other physical properties, or making the product expensive, make it difficult to use carbon black on polystyrene from a practical point of view. At present, the amount of colorant mixed in is limited to about 0.5% by weight.

It is also known to mix large amounts of carbon black into synthetic rubber to obtain semiconductive molded products, but in this case vulcanization is always performed, and the molded products obtained also have rubber elastic properties. It is limited to products such as automobile tires that utilize this technology.

By the way, in recent years in the electronics industry, parts, storage cases, etc. that were traditionally made of metal have been replaced with semiconductive plastics due to the remarkable progress in plastic molding technology. It is desirable to use general-purpose resins that are as cheap as possible, but the physical properties (
(mechanical properties, electrical properties, etc.) are extremely demanding.

An example of an electronic component storage case is a container for integrated circuits (hereinafter referred to as an IC container).

), in the case of IC containers, the resistance value is 10-2 to 10-2 to prevent damage or deformation of the container due to impact or temperature rise during transportation, and troubles due to static electricity.
An aluminum container with a resistance of 10-4 ohms was used.

In recent years, as an alternative to such aluminum products, there have been products with metal plating, metal vapor deposition film, or conductive paint applied to the plastic surface, but these have problems in processing, are expensive, and the coating tends to peel off, making it impossible to use them permanently. It had drawbacks such as being difficult and was not satisfactory.

On the other hand, some hard vinyl chloride molded products coated with an antistatic agent are known to have a resistance value of about 108 to 1013Ω, but the antistatic agent does not have sufficient effect when dry, and also over time. The use of antistatic agents has also not been sufficient, as their effectiveness is diminished over time.

Furthermore, hard vinyl chloride products have a heat distortion temperature of about 60°C, so they are susceptible to deformation due to rising temperatures during summer transportation.
In addition, there was a problem with the toxicity of the stabilizer used, and in any case it could not be said to be sufficient.

The inventors of the present invention conducted intensive research to use polystyrene, which is relatively inexpensive, has good moldability, and is versatile, as a semiconductive resin, and found that impact-resistant polystyrene, carbon black, and a certain type of resin were combined with certain limitations. The inventors have discovered that a semiconductive resin composition with well-balanced moldability, mechanical properties, and electrical properties can be obtained by blending them in the above proportions, and have completed the present invention.

That is, the present invention includes (a) 100 parts by weight of impact-resistant polystyrene, (b) 10 to 70 parts by weight of carbon black, and (C) butadiene, which has good affinity for both carbon black and impact-resistant polystyrene. At least 15 to 80 parts by weight of a synthetic rubber or rubbery olefin copolymer as a component, with a Rockwell hardness (R scale) of 55 degrees or more and a heat distortion temperature of 1 cm/cr? The above is a resin composition characterized by having a resistance value of 5 x 104 to I x 1010 Ω.

In the present invention, impact-resistant polystyrene refers to high-impact polystyrene (HI-PS), which is already well-known in which polystyrene is graft-polymerized to synthetic rubber, or general-purpose polystyrene (GP-PS), which is physically mixed with this. The content of graft-polymerized synthetic rubber is 2% by weight or more.

In addition, a polymer that can be used with impact-resistant polystyrene and carbon black to improve moldability, mechanical properties, and electrical properties contains butadiene as a component, which has good affinity for both carbon black and impact-resistant polystyrene. Synthetic rubber or rubbery olefin polymer that
All of them are already known.

Specifically, for example, butadiene rubber (BR), styrene-butadiene rubber (5BR), acrylonitrile-
Synthetic rubber such as butadiene rubber (NBR), or olefin-based graft copolymer with a small amount grafted with ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), vinyl acetate, acrylic acid, etc. Examples of combinations include the trade names rDEXONJ (manufactured by Esso Chemical Co., Ltd.) and rADMERJ (manufactured by Mitsui Petrochemical Co., Ltd.).

Preferably BR, SBR. NBR, EVA, EEA, and most preferably SBR.

There are no particular limitations on the carbon black used in the present invention, but if the average surface area is relatively small, a large amount of carbon black will be used, resulting in poor fluidity during molding and an extreme drop in impact strength. For work purposes, it is recommended to use surfaces with an average surface area of 30m”/9 or more, as this may cause problems such as
It is preferable from the viewpoint of physical properties, and those having an average surface area of 100 m/.9 or more are particularly preferable.

In the present invention, (a) polystyrene for impact resistance, (b)
The proportion of carbon black and (C) synthetic rubber or rubbery olefin copolymer containing butadiene as a component, which has good affinity for both carbon black and impact-resistant polystyrene, is (a) 100 parts by weight. b)
10 to 70 parts by weight and (c) 15 to 80 parts by weight,
Preferably, the concentration of carbon black is 6 to 25% by weight within the above-mentioned usage ratio range.

If the proportion of carbon black used is less than the above range, sufficient semiconductivity will not be provided, and if it is mixed in beyond the range, disadvantages such as a decrease in fluidity during molding and a decrease in impact strength will occur. So I don't like it.

Even if the amount of carbon black used is within the above range, (C) synthetic rubber or rubbery olefin copolymer containing butadiene, which has good affinity for both carbon black and impact-resistant polystyrene, may be used. If the amount used is less than 15 parts by weight, it will cause poor sizing during molding, deterioration of moldability such as warpage and deformation of the molded product, and decrease in impact strength, and if it exceeds 80 parts by weight, the resulting molded product will The surface condition of the molded product deteriorates, and the heat deformation temperature also becomes 60° C. or less, which causes the molded product to become easily deformed when the temperature rises.Furthermore, the hardness decreases, making it impossible to obtain a rigid molded product.

. That is, when the three components a, b, and C are within the above ranges, the flowability during molding, sizing properties, warp, deformation of the molded product, moldability such as heat distortion temperature, hardness, impact strength, etc., and mechanical This provides a resin composition with well-balanced physical and electrical properties.

Furthermore, the resin composition of the present invention can be sufficiently applied to applications that require even more severe physical properties in terms of electrical and mechanical properties, such as storage cases for electronic components.

When receiving particularly severe electrical and mechanical property requirements such as for IC containers, find the relationship between carbon concentration and resistance value for carbon blacks with each average surface area, and calculate the resistance value 5X10' from each graph. , Q and l
Xl010/? It is further necessary to set the carbon black component within the shaded area of Figure 1, which is a graph of the relationship between the average surface area and concentration of carbon black.

In the present invention, other ingredients may be added in addition to the above-mentioned components a, b, and C depending on the intended use.

Examples of substances that can be used include stabilizers such as anti-aging agents and antioxidants, lubricants (slip agents) such as fatty acid esters, fatty acid amides, paraffins, and hydrocarbon resins, and substances that are compatible with polystyrene and rubber-like substances. Examples include softening agents such as coumaron indene resin, terpene/phenol resin, process oil, and various plasticizers that reduce viscosity during processing.

Furthermore, resins such as polyethylene, polypropylene, polyethylene terephthalate, and polybutylene terephthalate and/or fillers such as calcium carbonate, diatomaceous earth, talc, and glass fibers can also be used as long as the amount used is 10 weight φ or less.

Hereinafter, the present invention will be explained with reference to examples, and unless otherwise specified, parts indicate parts by weight.

Examples 1 to 14 and Comparative Examples 1 to 13 HI-PS (melt index 0.5, Izod impact strength 5.4), 5BR (containing styrene 40φ) and carbon black were added in the proportions shown in Table 1. The ingredients were kneaded in a Banbury mixer preheated to 150°C, and then kneaded in a vented extruder (L/D-Re, 4) at 210°C.
0 mmφ) and pelletized.

Furthermore, a 180°C non-vent type extruder (L/D=24,4
An IC container molded product in a visiting-type shape was extrusion-molded at a temperature of 0 (φ), and the fluidity and sizing properties during molding, as well as warpage and deformation of the molded product were observed.

In addition, a similar composition was melt-kneaded on two rolls heated to 170°C, and a sheet with a thickness of X inch was prepared using a hot press at 200°C. The strength was measured.

The results are summarized in Table 1, and the final evaluation of practicality was performed using the following three-level evaluation.

(1) Fluidity during molding, (2) Sizing property, and (3) Visual observation of warpage and deformation of molded product; ○...Good, △...Good, ×・・・
...Poor (4) Heat deformation temperature; ○...Completely 65℃ or higher, △...
・The temperature is about 65℃, ×... clearly 65
℃ or less (5) Rockwell hardness (R scale); ○...
・・・It is completely 55 degrees or more, △・・・・・・Habo 5
It is about 5 degrees, ×...It is clearly 55 degrees underground (6) Impact strength; ○...It is completely more than 1 kg-cm7'crtt2, △...・・Habo 1kg・crr4/cy
It is about i' ×... clearly 1 kg・cm
(7) Resistance value that is 7'cd or less; ○... completely within the range of 5X10' to lXl010β, △... is approximately 5X10'Ω or 1x
It is about 10108, ×... clearly 5XI
O', less than 17 or IXI O', greater than 2.

(8) Final evaluation of molded products; * * ◎・・・・・・Can be used. Ru.

×...Unable to use Examples 15 to 19 Comparative Example 14 GP-PS (melt index 0.5) was added to the HI-PS used in the above example at an appropriate ratio, and As rubbery polymers, 5BR (contains 40% styrene), BR,
EVA (containing vinyl acetate 60φ) and carbon black have an average surface area of 300m27? A W-shaped molded product containing 20 weight φ of carbon black was obtained.

The results are summarized in Table-2.

[Brief explanation of the drawings] Figure 1 shows the relationship between the average surface area and concentration of the carbon black used in the resistance value (5×10', 2 and 1×101°8
) is a diagram created from the plot of

Claims (1)

[Scope of Claims] 1 (a) 100 parts by weight of polystyrene for impact resistance, (b) 10 to 70 parts by weight of carbon black, and (C) butadiene which has good affinity for both carbon black and polystyrene for impact resistance. Contains 15 to 80 parts by weight of at least one synthetic rubber or rubbery olefin copolymer with a Rockwell hardness (R scale) of 55 degrees or more, a heat distortion temperature of 65 degrees C or more, and an impact strength of 1kg・c
rn/cit or more, resistance value is 5 x 10' to I x
A resin composition characterized by having a resistance of 1010Ω. 2 Synthetic combs or comb-like olefinic copolymers containing butadiene, which has good affinity for both carbon black and impact styrene, are used as butadiene rubber, styrene-butadiene rubber, T'7'J Ronito IJ /
The resin according to claim 1, which is at least one selected from l/-butadiene rubber, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and olefin graft copolymer. Composition.