JPS61209120A - Manufacture of electrically conductive termoplastic resin molding - Google Patents

Abstract

PURPOSE:To enable to easily obtain a molding with excellent electrical conductivity by a method wherein thermoplastic resin and condensed metallic short fibers are blended and molded by means of a molding machine equipped with a static mixing nozzle. CONSTITUTION:Thermoplastic resin and paralleled metallic short fibers are blended and molded by means of a molding machine equipped with a static mixing nozzle, or the so-called direct molding is compulsory. The nozzle of a molding machine having so-called Konigs type static mixing elements, each of which consists in twists in twisting a rectangular plate through 180 deg., is exampled for the static mixing nozzle. The number of static mixing elements is enough if the dispersion of metallic short fibers is fully done or preferably lies with in the range of 3-15. Further, the extrusion molding or injection molding is available for the molding method. The rotational frequency of the screw of the molding machine is enough, if thermoplastic resin is filled in a cylinder and plasticized at said rotational frequency. Excessive kneading may be avoided. Furthermore, the size of the metallic short fiber is enough if its supply from a hopper and its molding are possible or preferably lies within the ranges of 2-100mum in fiber diameter, of 2-20mm in fiber length and of 50-3,000 in the aspect ratio of fiber.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention has a conductive property suitable for use as a surface heating element or as a shielding component for unnecessary electromagnetic waves emitted from various electronic and electrical devices incorporating ICs and LSIs. This invention relates to a method for manufacturing thermoplastic resin molded products.

(Prior Art) A method of imparting conductivity by blending a conductive filler such as short metal fibers to a thermoplastic resin is widely known. When obtaining a conductive resin by mixing short metal fibers, it is known that the larger the aspect ratio, the better the conductivity. This makes it difficult to mix and mix wires into the thermoplastic resin, and even if blending and wires occur, there is a problem that the short metal fibers are damaged and the conductivity is lowered. As a method to solve this problem, a method has been proposed in which a bundle of short metal fibers and a thermoplastic resin are mixed and kneaded to form pellets for molding, and then molded using an injection molding machine or the like. (Unexamined Japanese Patent Publication No. 58-12
9081, JP-A-58-176220). However, although this method facilitates blending and avoids the fiber ball phenomenon, breakage of the short metal fibers during the kneading process cannot be avoided. On the other hand, it has been proposed to bundle long metal fibers, cover them with resin, and then cut them to create so-called high-concentration master pellets, and then mix and mold these master pellets with natiniral pellets (Japanese Patent Application Laid-Open No. 5-11913).
8-150208). However, the production of master pellets requires a complicated process that increases costs, and also has the disadvantage that the short metal fibers in the molded product are not uniformly dispersed.

(Problems to be Solved by the Invention) The present invention solves the problems of breakage and poor dispersion of short metal fibers that occur during the process of blending short metal fibers with thermoplastic resin and molding, and the problem of mixing and kneading of short metal fibers and thermoplastic resin. Solved the problem of increased costs due to manufacturing process or master pellet manufacturing process.

(Means for Solving the Problem) The present invention provides a conductive thermoplastic resin molded product characterized by blending and molding a thermoplastic resin and focused short metal fibers using a molding fa equipped with a static mixing nozzle. This relates to a manufacturing method.

The present invention will be explained in detail below.

The thermoplastic resin used in the present invention can be any thermoplastic resin depending on the purpose, but in particular polyamide, polyester, polycarbonate, polyolefin, polyacetal, polyphenylene oxide, polyphenylene sulfide, polyurethane, vinyl chloride resin, polystyrene, ABS. Resins, AS resins, acrylic resins, and modified products or blends thereof are preferred, and the shape may be pellets, granules, or powders.

The short metal fibers used in the present invention include iron, stainless steel,
Examples include copper, brass, aluminum, nickel, and short fibers of these alloys, or glass fibers and carbon fibers coated with nickel or aluminum, and iron, copper, aluminum, and alloys containing these are particularly preferred. . In addition, the size of the short metal fibers may be as long as it can be fed from a hopper and formed, and in particular, the fiber diameter is 2 to 100 μm.
.

Fiber length 2-20mm, aspect ratio 50-aoo.

A range of is preferred. The blending ratio of the short metal fibers to the thermoplastic resin can be arbitrarily selected as required, but it is preferable that the blending ratio does not exceed 1O capacity so as not to significantly impair the physical properties.

The sizing agent used in the present invention includes a thermoplastic resin solution,
There are emulsions and melts, such as vinyl resin, vinyl acetate resin, polyvinyl alcohol, acrylic resin, polyolefin, polystyrene, polyamide, polyester, and polyurethane, and the sizing agent and base polymer may be the same or different. It can also be used as long as it does not impede the properties of the pace polymer. Further, the proportion of the sizing agent may be any amount that can substantially bundle the short metal fibers to the extent that they can be supplied from the hopper during molding, and is preferably 2 to 40% by weight of the total amount of the sizing agent and short metal fibers.

Examples of methods for producing bundled short metal fibers include a method in which a plurality of long metal fibers obtained by an elongation method are bundled, impregnated or coated with a binding agent, and then cut.

The static mixing nozzle used in the present invention is, for example, a molding machine nozzle having a so-called KEX-type static mixing element, which is a rectangular plate twisted by 180°C, and this type of nozzle is commercially available (Kenix). super nozzle).

Further, the number of static mixing elements may be one sufficient to disperse the short metal fibers, and is preferably in the range of 8 to 15 since excessive use may cause breakage of the short metal fibers or pressure loss during molding.

In addition, extrusion molding or injection molding can be used as the molding method, and normal molding conditions can be applied except for using a static mixing nozzle. It is sufficient as long as the rotation is sufficient, and it is better to avoid excessive crosstalk.

In particular, as an injection molding machine, it is preferable to use a system that can be supplied under starvation conditions, such as the famous Dynamelta system.

The method for manufacturing conductive thermoplastic resin molded products of the present invention involves so-called direct molding, in which thermoplastic resin and bundled short metal fibers are mixed and molded using a molding machine equipped with a static mixing nozzle. If short metal fibers are used, a fiber ball phenomenon will occur, making it difficult to blend the short metal fibers.On the other hand, if direct molding is performed with a molding machine that is not equipped with a static mixing nozzle, the short metal fibers will not be dispersed. However, the conductivity, appearance of the molded product, and other physical properties are poor, and only molded products of uneven quality can be obtained. Furthermore, in a method in which short metal fibers and a thermoplastic resin are kneaded in advance and then molded, the short metal fibers are damaged, resulting in a decrease in conductivity.

The molded product of the present invention may further contain a flame retardant, if necessary.

Flame retardant aids, inorganic fillers, crystallization promoters, antioxidants, mold release agents, small amounts of polyfunctional compounds, etc. can be blended.

(Example) The present invention will be further explained below using Examples.

Example 1 10,000 stainless steel fibers with a fiber diameter of 8 μm were bundled with a binding agent as short metal fibers made of polyethylene terephthalate (Belpet manufactured by Kanebo Gosen ■) EFG-6' in a thermoplastic resin (binding agent content: 12 μm). % by weight) cut into 5 pieces (manufactured by Nippon Hasen), mixed with stainless steel fibers at a ratio of 2 volumes, and then fitted with a static mixing nozzle with 12 static mixing elements to 8.8 oz. 200 W with Meiki Dynamelta injection molding machine (manufactured by Meiki Seisakusho ■)
A plate of 200×3×2 was directly molded, and its volume resistivity was measured. The composition, molding conditions, and volume resistivity are shown in Table-1.

Example 2 Thermoplastic resin and nylon-6 (MC- manufactured by Kanebo Gosen ■)
A plate was molded in the same manner as in Example 1 except that 102) was used. The results are shown in Table-1.

Comparative Examples 1 and 2 The thermoplastic resin and short metal fibers had the same composition as in Example 1, and in Comparative Example 1, molding was performed using an injection molding machine equipped with an ordinary open nozzle instead of a static mixing nozzle. In No. 2, the thermoplastic resin and short metal fibers were kneaded in advance using a 25-diameter single-screw extruder, and then molded using an injection molding machine equipped with an open nozzle.

(Effects of the Invention) As is clear from the examples, the conductive heat treatment method is characterized in that the thermoplastic resin of the present invention and bundled short metal fibers are blended and molded using a molding machine equipped with a static mixing nozzle. According to the method for producing a plastic resin molded product, a molded product with excellent conductivity can be easily obtained.

Kanebo Gosen Co., Ltd.

Claims (7)

[Claims] (1) A method for producing a conductive thermoplastic resin molded article, which comprises blending and molding a thermoplastic resin and bundled short metal fibers using a molding machine equipped with a static mixing nozzle. (2) The fiber diameter of short metal fibers is 2 to 100μ, and the fiber length is 2
~20mm, aspect ratio (ratio of fiber length to fiber diameter) is 5
0-3000. The method according to claim 1. (3) The method according to claim 1 or 2, wherein the short metal fibers are iron, copper, aluminum, or an alloy containing these. (4) The method according to claim 1, wherein the short metal fibers are bundled with 2 to 40% by weight of a binding agent. (5) The method according to claim 1, in which the blended amount of short metal fibers does not exceed 10% by volume based on the thermoplastic resin. (6) Thermoplastic resin is polyamide, polyester, polycarbonate, polyolefin, polyacetal, polyphenylene oxide, polyphenylene sulfide,
Polyurethane, vinyl chloride resin, polystyrene, ABS
The method according to claim 1, which is a resin, an AS resin, an acrylic resin, and a modified product or blend thereof. (7) Claim 1 in which the static mixing nozzle has 3 to 15 static mixing elements each having a shape of a rectangular plate twisted by 180 degrees.
The method described in section.