JPH02169661A - Production of lowly resistant molding resin article - Google Patents

Abstract

PURPOSE:To prepare a lowly resistant molded resin article which has antistatic properties without using any conductive filler by compounding a thermoplastic polyester molding material with an olefinic molding material in a specified ratio and then injection molding the resulting compound. CONSTITUTION:A thermoplastic polyester molding material is dry blended with an olefinic molding material and injection molded. Examples of the thermoplastic polyester molding material are polyethylene terephthalate polybutylene terephthalate and polycarbonate; examples of the olefinic molding material, polyethylene and polypropylene. Thus, a lowly resistant molded resin article with a volume resistivity of not more than 10<10>OMEGA.cm is produced without using any conductive filler.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing low-resistance resin molded parts or molding materials thereof, which are required to have an antistatic function in casings and mechanical parts of electrical equipment.

[Conventional technology]

Electrical equipment parts that are required to have an antistatic function are required to have a volume resistivity in a low resistance range of 100-V or less. This type of low-resistance molding materials include conventional general-purpose plastics such as ABS resin (acrylonitrile-loose-styrene-styrene turbopolymer) and polyethyl methacrylate resin (PMMA), polybutylene terephthalate resin (PBT), and polycarbonate resin ( PBT) and other general-purpose enserializing resins are molding materials that include metal fibers such as brass, aluminum, and stainless steel alloys, as well as carbon black, carbon 7 ipa,
It is known that the conductive material (hereinafter referred to as conductive filler) is added to form a suitable amount of conductive material such as graphite.The conductive fillers come into contact with each other and exhibit low resistance.

[Problem to be solved by the invention]

Conventional low-resistance resin molding materials (hereinafter abbreviated as molding materials)
In particular, when adding a conductive filler to a polyester resin to make a molding material, there are limited types of conductive filler that can be used, and some fillers are expensive depending on the type. In addition, it may adversely affect moldability during injection molding,
There are various problems with adding conductive fillers, such as deterioration of the mechanical properties of molded products. Also,
Low-resistance molding materials are usually supplied with conductive fillers added by their manufacturers, and molders can select and add conductive fillers on their own to make the molding material grade v4!1. There is a problem in that it is difficult to select forest materials, and the degree of freedom in selecting forest materials is restricted.

On the other hand, the volume resistivity of the polyester resin itself is generally on the order of 10130 mm, which is a high level of electrical insulation. When static electricity is generated on the surface of a molded product, leakage and diffusion of the charged static electricity is inhibited by high insulation resistance, resulting in a so-called charging phenomenon in which the static charge on the surface of the molded product continues for a long time. Since the static charge on the surface of the molded product has the property of adsorbing dust and the like in the atmosphere, a problem arises in that the surface of the molded product is contaminated. In addition, when a grounded conductor comes close to a charged molded product, static electricity discharge often occurs, and in recent years electronic equipment has become a problem where semiconductor circuits such as ICs are damaged by surge voltage caused by static electricity discharge. This has occurred and improvements are required.

An object of the present invention is to obtain a low-resistance resin molded product or molded material having an antistatic function and having a volume resistivity of 1010 Ω or less without using a conductive filler.

[Means to solve the problem]

In order to solve the above problems, according to the method of the present invention, an olefin-based molding material is dry-blended with a polyester-based thermoplastic molding material at a ratio of 1 to 20% by weight, and then injection molding is performed.

[Effect]

In the above means, polybutylene terephthalate is used as a polyester-based thermoplastic molding material.

Polyethylene terephthalate, polyoxybenzoyl (
Aromatic polyester) or bisphenol-based amorphous polyester material such as polycarbonate is mixed with an olefin molding material such as polyglopylene or polyethylene at a ratio of 1% by weight to 20'1iilX in a hopper of an injection molding machine or the like. Due to the structure in which injection molding is performed after blending, the polyolefin material has conjugated double bonds in the process of injection molding in the presence of the polyester material, even though both materials are insulating materials. It is thought that it changed to an organic conductive material, such as polyacetylene, and developed low resistance characteristics.
The volume resistivity of the obtained molded product decreases by several orders of magnitude when only 1% by weight of the polyolefin material is added, and by up to 10 orders of magnitude when the addition ranges from a few percent to a dozen percent. In addition to providing the function of preventing electrification and electrostatic discharge, the compatibility with the image molding material is good, and homogeneous molded products can be easily obtained without impairing moldability and properties.

〔Example〕

The method of this invention will be explained below based on examples.

Using polybutylene terephthalate (PBT) as a polyester-based thermoplastic molding material and polypropylene (PP) as an olefin-based molding material, the mixing ratio of both in the hopper of an injection molding machine is significantly changed to produce plate-shaped or box-shaped molding materials. A molded article was injection molded, and its volume resistance was measured.

FIG. 1 is a characteristic diagram showing a typical example of the volume resistivity of the obtained molded product, and Table 1 is a data formula of the main parts thereof.

Table 1 By adding only 1% by weight of polypropylene (PP), the volume resistivity ρ rapidly decreases to the order of 10'Ω-Ω, and PP
As the amount of addition increases, the resistivity ρ further decreases, and when the amount added is between 8 and 16% by weight, the resistivity ρ becomes 1.
06 to 10'Ω-flaw order (minimum lX10Ω-
c1n). If the amount added is further increased, 18
108Ω at 1%, 1×10 at 201E
The 0-wetting order and volume resistivity increase, and when the addition amount is 30 to 40 or more, the insulation property is almost restored. In other words, there is a clear correlation between the volume resistivity ρ of the injection molded product and the mixing ratio of the polyester molding material and the olefin molding material. % range from 10' to 1
The volume resistivity is reduced to 0 Ω, and a molded article having an antistatic function can be obtained.

In addition, the molding conditions are not particularly different from the injection molding conditions for 9 molded products using the main material, polyester molding side slope, and since it does not contain conductive filler, it is easy to obtain molded products with good surface condition, and 1. No adverse effects were observed on physical strength or thermal properties.

The mechanism by which resistance decreases due to the combination of 2m@ insulating materials is not clear at present.In the process of injection molding of carbon olefin materials in the presence of polyester materials, organic materials such as polyacetylene, which have conjugated double bonds, It is presumed that this is due to the change to an organic conductive material, and it is thought that the volume resistivity changes depending on the proportion of the organic conductive material in the insulating material and the state of its dispersion.

In addition, this manufacturing method is effective as a method for manufacturing molded parts that require electrical conductivity, such as covers and mechanical parts for electrical equipment, and it is also possible to use conductive resin molding materials rather than injecting molded products into pellets, for example. It is also easy to produce a homogeneous, low-resistance resin molded product that does not contain conductive fillers etc. by injection molding or compression in the same way as using polyester molding materials. Can be molded.

〔Effect of the invention〕

As described above, the present invention is configured such that an olefin molding material is dry blended with a polyester thermoplastic molding material in a range of 1 to 20% by weight in the hopper of an injection molding machine, and then injection molding is performed. As a result, although the two types of molding materials are insulating materials, the volume resistivity of injection molded products or molding materials is 1.
To provide a new low-resistance resin molding material and a molded product thereof, which has a significantly lower resistance from 0'Ω-era to 1010Ω-era and has a composition different from conventional molding materials or molded products using conductive fillers. Can be done.

In addition, the manufacturing method is simple: two types of molding materials of stable quality are dry blended in a hopper, and then immediately injection molded. Molded products with antistatic properties can be obtained by a simple operation. This eliminates the negative effects on moldability and deterioration of the mechanical properties of molded products caused by blending, making it easy to obtain molded products with a homogeneous and good surface condition. Compared to this, the degree of freedom in material selection increases,
Advantages such as economical advantages can be obtained.

Furthermore, by providing a pellet-shaped low-resistance resin molding material using the method of the invention, it is possible to contribute to expanding the scope of application of molded products that require antistatic function, and by devising molding conditions, the internal It is also possible to obtain a molded product having an insulating property on the resistive 2 surface, or a molded product having the opposite configuration.

[Brief explanation of the drawing]

Claims (1)

[Claims] 1) A method for producing a low-resistance resin molding material, which comprises dry blending an olefin molding material with a polyester thermoplastic molding material at a ratio of 1 to 20% by weight, and then performing injection molding.