JPS5975927A - Production of conductive composition material - Google Patents

Abstract

PURPOSE:To obtain a composite material which is easy to handle and excellent in moldability, heat resistance, and toughness and has high electrical conductivity, by sandwiching a specified resin coat film having an intermediate layer comprising an aluminum fiber/glass fiber mixture between films and then effecting impregnation and deforming. CONSTITUTION:A film is coated with a composition of an unsaturated polyester or vinyl ester resin. Then, 2.5-25mm.-long aluminum fiber and 10-100mm.-long glass fiber in amounts to provide an aluminum fiber content >=5%, and a glass fiber content >=10%, a content of fibers <=60% and an aluminum fiber/glass fiber ratio of 0.2-1 are scattered over the surface of the coat film so that the both of the fibers may be mixed uniformly and randomly. Then, thereupon another film coated with the above composition is laid thereupon with its coat composition side situated down, and the impregnation and defoaming are effected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a thermosetting resin molding material having high strength and high conductivity.

The purpose is to provide a molding composite material that is easy to handle, has excellent moldability, heat resistance, and toughness, and has a high degree of electrical conductivity.

In recent years, metals have been actively replaced by plastic materials in order to reduce weight, rationalize manufacturing processes, and reduce costs, but plastics lack electrical and thermal conductivity.

Therefore, new problems such as electromagnetic interference are occurring due to this. Countermeasures such as metal spraying and coating with conductive paint have been taken to counter this problem, but since it is secondary processing and there is a risk of peeling off, composite materials with metals that do not require secondary processing are used. Various proposals have been made.

A typical example is a molding material in which metal fibers are mixed with thermoplastic resin. However, this method does not take full advantage of its characteristics because of crosstalk and severe breakage of the metal fibers during the molding process.

Sheet molding compounds (hereinafter referred to as SMC) and bulk molding compounds (hereinafter referred to as BMC) containing aluminum coated glass fibers are also known, but aluminum coated glass fibers are expensive and have poor adhesion to resin. , it lacks reinforcing effect.

A method of mixing metal fibers into SMC and BMC has been proposed, but relatively long metal fibers tend to harden into a ball shape, have poor impregnation of the resin into the metal fibers, and have problems with flow within the mold. Implementation was not easy due to problems such as severe sexual harassment.

The present inventors have found that it is easy to handle, has good moldability, heat resistance,
As a result of intensive studies to obtain a composite material for molding that has excellent toughness and high conductivity, the present invention has been completed.

The present invention involves applying a blend of unsaturated polyester or vinyl ester resin onto the film and applying 2.5 to 25
The proverbial aluminum fiber and 10-100m of glass fiber can be combined into 5 cases where the aluminum fiber content is 5% or more, the glass fiber content is 10% or more, and the total fiber content is 60% or less. , the aluminum fibers/glass fibers were spread so that the ratio was 0.2 to IK, and both were mixed randomly and uniformly, and another film-like composition coated with the above composition was placed on the bottom. and overlap it from above,
It is characterized by impregnation and defoaming.

The unsaturated polyester or vinyl ester resin formulation may be of a formulation commonly used in SMC.

The film may also be of any material as long as it is easy to peel off after curing.

Preferably, the aluminum fibers are manufactured by a chatter vibration cutting method and have non-smooth surfaces. Compared to fibers with smooth surfaces, the fibers are more likely to become entangled with each other, that is, the fibers are more likely to come into contact with each other to form a conductive path, which is advantageous for obtaining a high degree of conductivity.

However, if the aluminum fibers are too short, workability is improved, but the formation of conductive paths due to contact between the fibers is reduced, and a high degree of conductivity cannot be obtained. Even if long aluminum fibers are used, they are cut during the process of forming a molded product, and even if the fibers are shortened, high conductivity cannot be obtained.

On the other hand, if the length is too long, the intertwining of the fibers will become strong, making it difficult to unravel and significantly reducing workability. Uniform dispersion is difficult and fluidity within the mold is significantly inhibited.

The length of the aluminum fiber is 2.5 to 251111. Preferably, those with a concentration of 3 to 20 M tend to harden into lumps, but when placed on a sieve and subjected to vibration, they loosen at a certain rate, which is rather convenient for uniform dispersion.

The thickness of the aluminum fiber is preferably about 10 to 200 μm.

The content of aluminum fibers is preferably 5% by weight or more, preferably 7% by weight or more. If it is too small, the conductivity will decrease.

If the amount is too large, the impregnating properties of the resin will be poor, and the fluidity within the mold will also be significantly reduced, resulting in dense areas where aluminum fibers are intertwined with each other and areas with no aluminum fibers, resulting in extremely non-uniformity. Further, even if the amount is too large, the conductivity will not be improved. This is limited by the upper limit of the total fiber content and the aluminum fiber/glass fiber ratio.

Aluminum fiber is a conductive material, but it has a poor reinforcing effect on mechanical strength such as tensile strength and bending strength. In order to obtain high strength and toughness, it is essential to use glass fiber in combination.

The glass fibers may be those commonly used in SMC.

Of course, it is preferable to use a surface treatment to improve adhesion to unsaturated polyester or vinyl ester resin.

The length of the glass fiber is 10~IQ□w, preferably 12~
50 proverbs are good. If it is too short, the reinforcing effect will be lacking, and if it is too long, the fluidity within the mold will deteriorate and the molded product will likely become non-uniform.

The content of glass fiber is 10% by weight or more, preferably 15% by weight.
Weight % or higher is better.

If it is too small, the reinforcing effect will be lacking, and if it is too large, the impregnating property will be poor and the fluidity within the mold will also be reduced. The upper limit is limited by the total fiber content and the aluminum fiber/glass fiber ratio. The total content of aluminum fiber and glass fiber is 6
It is preferably 0% by weight or less, preferably 50% by weight or less.

In order to obtain a high degree of conductivity, it is desirable to form a uniform layer of aluminum fibers within the molded product, but aluminum fibers have poor impregnation properties compared to glass fibers and have very poor fluidity within the mold. .

As a result, the molded product has areas where the aluminum fibers are dense and areas where the aluminum fibers are absent, and the product tends to be extremely non-uniform.

However, by scattering the above materials so that the ratio of aluminum fiber/glass fiber is 0.2 to IK, preferably O73 to 0.8, and so that both are randomly and uniformly mixed, it is possible to This maintains uniform flow and prevents non-uniformity of the molded product.

If the aluminum fiber/glass fiber ratio is too small, the conductivity will decrease, and if it is too large, the fluidity will deteriorate, the molded product will become significantly heterogeneous, and voids will easily occur.

Metal fibers other than aluminum, such as fibers of copper, brass, nickel, stainless steel, etc., can also be used, but they are not preferred because their specific gravity increases when used alone.

The combined use of conductive powder, such as aluminum powder and carbon black, is desirable since it has the effect of hiding the surface exposure of the aluminum fibers.

The sheet impregnated and defoamed by the method of the present invention is used as a composite material for molding after curing, and is formed into a desired molded product by compression molding.

The moldable composite material obtained by the manufacturing method of the present invention is easy to handle and has good moldability.

Molded products using this material have excellent heat resistance, toughness, and heat conductivity.
It also has a high degree of conductivity and excellent electromagnetic shielding properties. Very useful for housings of various electronic devices.

In addition, B whose main components are the above-mentioned aluminum fibers, glass fibers, and unsaturated polyester or vinyl ester resins.
The MC formulation can also be mixed in a kneader and subjected to transfer molding or injection molding.

However, since the aluminum fibers and glass fibers are significantly shorter, both the electrical conductivity and the mechanical strength are lower than those of the present invention.

Next, a specific explanation will be given with reference to examples.

Examples 1 to 3 500 parts of a blend consisting of 100 parts of unsaturated polyester (Polylite PS-260M manufactured by Inu Nippon Ink), 100 parts of calcium carbonate, 1 part of t-butyl perbenzoate and 1 part of magnesium oxide was deposited on a polyethylene film.
El/rr? Then, silane-treated glass fibers and aluminum fibers (manufactured by Aisin Seiki, Aisin Metal Fiber) are simultaneously and randomly and uniformly scattered thereon. On top of that, another polyethylene film coated with the above formulation is placed on top with the formulation side down, impregnated,
It was degassed and cured at 40°C for 48 hours to obtain SMC.

Note that 20 parts of aluminum powder was further added to the formulation of Example 2.

Comparative Example 1 SMC was obtained according to Example IK except that the amounts of glass fiber and aluminum fiber were replaced.

Comparative Example 2 A BMC having the same composition as Example 3 was obtained by further mixing aluminum fibers and glass fibers with the formulation of Example 3 using a kneader.

Comparative Example 3 Premixture of 30 parts of low-shrinkage unsaturated polyester, 0.3 parts of t-butyl perbenzoate, 1 part of zinc stearate and 40 parts of calcium carbonate, 15 parts of silane-treated glass fibers, 15 parts of aluminum fibers were mixed in a kneader to obtain BMC.

The materials of Examples 1 to 3 and Comparative Examples 1 to 2 were molded by compression molding, and the material of Comparative Example 3 was molded by injection molding. Its performance is shown in Table 1.

The materials of Examples 1 to 3 have good formability and aluminum dispersibility, high strength, and low volume resistivity. That is, a high degree of conductivity is obtained.

The material of Comparative Example 1 had uneven and poor fluidity within the mold. Due to the poor dispersibility of aluminum, some parts may be lacking in material. The variation in characteristic values is also very large.

The materials of Comparative Examples 2 and 3 are inferior to Example 3 in both strength and conductivity.

Note that the materials of the examples also have excellent electromagnetic shielding properties and heat conductivity.

Claims (1)

[Claims] A blend of unsaturated polyester or vinyl ester resin is applied on the film, on which 2.5-25111 m of aluminum fibers and 10-ioom of glass fiber are applied, with the content of aluminum fibers being 5% or more. The glass fiber content is 10% or more, and the total fiber content is 60% or less.1 The aluminum fiber/glass fiber ratio is 0.2 to 1, and both are randomly uniform. of the conductive composite material for molding, which is characterized in that the film is coated with another film coated with the above-mentioned composition and is layered on top with the composition facing down, impregnated and defoamed. Production method.