JPH0832422B2 - Sheet for forming conductive plastic and method for producing conductive plastic molded product - Google Patents

Description

Detailed Description of the Invention TECHNICAL FIELD OF THE INVENTION

The present invention relates to a conductive plastic molding sheet and a method for producing a conductive plastic molded product. The conductive plastic molding sheet of the present invention (hereinafter, simply “sheet”)
May be used) for producing a conductive plastic molded product (hereinafter sometimes simply referred to as “molded product”). The molded product produced by the method of the present invention is a radio wave reflector, an electromagnetic wave shield material, an antistatic material, a conductive required material,
It is used for applications such as heat ray reflectors and soundproofing materials.

[Prior art]

Conventionally used plastics do not have any function such as a radio wave reflection function, an electromagnetic wave shield function, an antistatic function, a conductive function, and a heat ray reflection function. Therefore, conventionally, in order to impart such a function to a plastic molded product, a conductive paint is applied to the surface of the plastic molded product, a metal foil is attached, or the surface of the plastic molded product is plated. It has been proposed to impart conductivity by doing so.

[Problems to be Solved by the Invention]

However, in the case of applying the conductive paint, a laborious coating process is required, and there is a problem that productivity is reduced by a total of two processes including the molding process. Further, the state of the conductive film formed by coating is greatly affected by the adhesive force of the coating material, and therefore often poses a problem in terms of durability. Further, in the case of the method of sticking a metal foil, it is difficult to manufacture a product having a complicated shape because the elongation rate of the metal foil is low. For example, when a thin film such as aluminum is placed in a mold and filled with a plastic material, the thin film can be shaped by the filling pressure of the plastic material if the molded product has a simple shape, but the molded product has a complicated shape. If so, the thin film cannot be stretched along the shape, and therefore the thin film is cut and a molded product cannot be obtained. In addition, an adhesive is required to attach the metal foil to the surface of the plastic to integrate it, but various adhesives must be selected depending on the type of the plastic material. If this selection is incorrect, the resulting molded article will be totally unusable. In addition, plastic materials with large shrinkage and difficult to adhere, such as polyethylene, polypropylene, polyacetal, and polybutylene terephthalate, cannot successfully bond the metal foil and the plastic with any adhesive. There is a big drawback. In addition, the method of plating the surface of a plastic molded product increases the cost, and there is a problem with the adhesion between the plastic and the plating film, so if the adhesion is poor, the heat resistance and durability of the molded product will be significantly reduced. Will be reduced to. The object of the present invention is to solve these problems of the prior art, namely, to easily and integrally form a conductive film on the surface of a plastic having a complicated shape, to perform the conductive film forming step simultaneously with molding, It is to solve the problems that a conductive film can be integrally formed on plastic without using an agent and that the production cost is low.

[Means for Solving the Problems]

The sheet according to the present invention and the method for producing a molded article using the sheet will be described with examples. The sheet according to the present invention is a fiber made of only a non-metal material, for example, a glass fiber, a woven fabric or a non-woven fabric produced by using an organic fiber, a metal having a melting point of 47 to 300 ° C. (hereinafter referred to as “low melting point metal”). Is applied by a suitable amount using, for example, a metal spray gun. At the time when the sheet is produced, the applied low-melting-point metal remains temporarily adhered to the surface of the fibrous material in the form of particles or flakes. For example, by adhering this to a mold for thermoplastic resin molding and filling the molding material melted at high temperature,
The applied low melting point metal is pressed against the surface of the mold and is instantaneously softened by the heat of the high temperature material. Furthermore, in injection molding of thermoplastic resin, it is a general condition to apply a high material filling pressure of 300 to 2000 kg / cm ² , so the melted and softened low melting point metal and fibrous material can be applied to the mold wall at high pressure depending on the material. As a result, the low melting point metal becomes a metal thin film (conductive film) and is cooled on the mold surface. As a result, the metal thin film can be instantly molded in the molding die on the surface of the plastic. The outer surface of the metal thin film formed by molding has a metallic tone and is reinforced by the fiber material used. In addition, many irregularities and voids remain in the fibrous material, but this portion is filled with a plastic material, and a strong bond can be made between the plastic and the sheet without using any adhesive. Be seen. In addition, it can be firmly joined to any plastic material, and polyethylene, polypropylene, acetal resin, which has been impossible to join with metals without finding an appropriate adhesive in the past,
An integrated electric conductive film can be formed on polybutylene terephthalate, polystyrene-modified polyphenylene oxide, and the like. Other plastics such as polystyrene, polycarbonate, polyurethane, polyimide, polyamide, vinyl chloride, ABS resin, AS resin, acrylic resin, fibrous plastic, other so-called polymer alloy resin, super engineering resin, etc. The invention can be applied. A thermosetting resin can also be used as the plastic material. For example, the sheet of the present invention is placed in a heated mold for molding BMC, SMC, epoxy resin molding material, diaryl phthalate resin, etc., which are mainly composed of unsaturated polyester resin, and the thermosetting resin is placed thereon. A molded product that shows a uniform and beautiful appearance on the surface of the molded product even after the process of placing a molding material made of resin, clamping the mold with high pressure, and taking out the molded product after the material hardens, that is, by compression molding. Is obtained. The fibers used in the present invention are, for example, polyester fibers, rayon fibers, glass fibers, cotton fibers, carbon fibers and the like. A woven or non-woven fabric is produced using these fibers. In the case of a woven fabric, its weave method, in the case of a non-woven fabric, by adjusting the fiber length and the binder,
It is also possible to have a large elongation rate that cannot be obtained with a metal thin film, for example, an elongation rate of 100% or more. For this reason, a conductive layer (electrically conductive layer) can be formed even on a product having a complicated shape, and no matter how the sheet is stretched, the metal is applied by the material filling pressure and temperature finally applied. Since the particles become a metal thin film, a uniform and defect-free conductive film can be formed on the surface of the plastic. The low melting point metal used in the present invention is not particularly limited,
It is used as a metal or an alloy depending on the purpose of use. The criteria for selection are the plasticizing temperature of the plastic material used, the mold temperature at the time of molding, the amount of heat from the molding material, the required heat resistance, the characteristics required for the metal thin film, and the like. As an example of the low melting point metal, tin-bismuth-indium-lead alloy (melting point 47 ° C), bismuth-lead-tin alloy (melting point 96 ° C), tin-indium alloy (melting point 117 ° C), bismuth-tin alloy ( Melting point 138 ° C), tin-lead-cadmium alloy (melting point 145 ° C), tin-zinc alloy (melting point 199 ° C), cadmium-antimony alloy (melting point 292 ° C), and other single-component metals such as tin, lead, and bismuth. A metal having a melting point of 300 ° C. or lower can be used.

DETAILED DESCRIPTION OF THE INVENTION

According to various aspects of the sheet and manufacturing method of the present invention,
Sheets obtained by applying metal materials having various melting points to the surface of various fiber base materials using an appropriate method such as a metal spraying device are inserted into a mold used for injection molding, compression molding, transfer molding, etc. , The heat of the plastic material, the mold temperature, or the pressure is used to melt and soften the granular or scaly metal to form a uniform and highly conductive conductive thin film on the plastic surface in one step. can do. Example 1 A woven fabric and a non-woven fabric made of polyester fiber, rayon fiber, glass fiber, cotton fiber, and carbon fiber, respectively, were prepared, and tin-bismuth-indium-lead having a melting point of 47 ° C. was prepared on the surface thereof. Alloy, bismuth-lead-tin alloy with a melting point of 96 ° C, tin-lead-cadmium alloy with a melting point of 145 ° C, using metal spray guns, so that the amount of metal per square meter is 300g, 500g, 800g. Each was applied to prepare a sheet. On the other hand, the mold clamping pressure is
An injection molding machine of 100 tons was prepared, and a mold capable of molding a curved surface molded product having a curvature of 200 mm and a diameter of 80 mm was attached to it. The molding materials used were polypropylene, ABS and polycarbonate, respectively. The molding die was adjusted to 80 ° C., and the sheet was sandwiched between the opened dies to perform molding under standard molding conditions. The appearance of the obtained molded product, the adhesion between the metal layer and the plastic, the electromagnetic shielding property, etc. were tested. 1. Appearance test Fiber type (woven fabric) Melting point of metal Appearance of molded product Polyester 47 ° C Good Rayon 47 Good Cotton 47 Good Glass 47 Edge break Carbon fiber 47 Edge break Fiber type (nonwoven) Metal melting point Appearance Polyester 96 ° C Good Rayon 96 Good Cotton 96 Good Glass 96 Good Carbon fiber 96 Edge break Fiber type (nonwoven) Metal melting point Molded product appearance Polyester 145 ° C Good rayon 145 Good Cotton 145 Good Glass 145 Good Carbon fiber 145 Edge Breakage The above results were obtained when polycarbonate was used as the plastic material, but similar results were obtained when ABS and polypropylene were used. Further, the above results are the results when a sheet having a metal coating amount of 500 g / m ² was used. When the coating amount of the metal was small (300 g / m ² ), the metallic luster was slightly lost, and when it was large (800 g / m ² ), the appearance was extremely smooth. 2. Adhesion test (90 ° peeling) Fiber type (woven fabric) Melting point of metal Adhesive strength Polyester 47 ° C Material destruction Rayon 47 Material destruction Cotton 47 Material destruction Glass 47 Material destruction Carbon fiber 47 Material destruction Fiber type (nonwoven) Metal Melting point Adhesive strength Polyester 96 ℃ Material destruction Rayon 96 Material destruction Cotton 96 Material destruction Glass 96 Material destruction Carbon fiber 96 Material destruction Fiber type (nonwoven) Metal melting point Adhesion strength Polyester 145 ℃ Material destruction Rayon 145 Material destruction Cotton 145 Material Destruction Glass 145 Material destruction Carbon fiber 145 Material destruction The above results were obtained when ABS was used as the molding material and a sheet with a metal coating amount of 500 g / m ² was used. 3. Electromagnetic wave shielding test Measurement material Fiber type (nonwoven) Melting point of metal Amount applied Polyester 96 ℃ 300g b. Rayon 96 500 Ha. Cotton 96 500 d. Glass 96 300 e. Carbon fiber 96 100 Molding material: Polycarbonate Sample name Attenuation rate (dB) a. 55 b. 55 c. 55 d. 55 E. 55 (Measurement frequency: 500 MHz) [Example 2] In Example 2, a thermosetting resin was used as the molding material. The specifications of the sheet used are as follows. Fiber type (nonwoven) Melting point of metal Coating weight Polyester 145 ℃ 300g Rayon 145 300 Cotton 145 300 Glass 145 300 Carbon fiber 145 300 The molding materials used are as follows. SMC Unsaturated polyester resin 30% Glass fiber (mat) 30% Calcium carbonate 10% Talc 20% Thickening material 9% Hardening material 0.5% Pigment 0.5% Compression molding gold that can mold molded products with a diameter of 100 mm and a thickness of 3 mm. The mold was attached to a compression molding machine and the mold temperature was adjusted to 150 ° C. The above 5 types of sheets were placed in this mold, the weighed SMC was placed thereon, and the mold was clamped at a pressure of 150 kg / cm ² , and the material was cured in 5 minutes. Then, the mold was opened, the molded product was taken out, and various tests were conducted. Appearance test: Gloss of the mirror surface Adhesion: Completely integrated and destroyed material Electromagnetic Shielding property: Attenuation of 60 decibels at 500 MHz Heat resistance: 150 ° C, no change in 24 hours Conductivity: 10 mOhm Less than

【The invention's effect】

According to the present invention, the conductive film can be easily and integrally formed on the surface of the plastic, and the conductive film forming step can be performed simultaneously with the molding. Further, the conductive film can be integrally formed on most plastics without using an adhesive. Furthermore, the non-metallic material is used as the material of the fiber,
Since a large extensibility can be obtained by appropriately selecting the material, it can be applied to a deep drawing shape product which cannot be achieved by the conventional metal, and a molded product having a complicated shape can be manufactured. Further, the production cost is low and the cost of the molded product can be reduced due to the fact that the process is simple in industrial production, a large-scale device is not required, and the productivity is excellent.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H05K 9/00 WD // B29L 9:00

Claims (2)

[Claims] 1. A conductive plastic molding sheet used for forming an electrically conductive layer on the surface of a molded product that is plastic molded using a mold, the non-metal having no metal layer on the surface. A conductive plastic molding sheet, characterized in that a woven or non-woven fabric made of fibers is coated with a metal having a melting point of 47 ° C to 300 ° C. 2. The conductive plastic molding sheet according to claim 1, which is arranged along the mold surface of a mold of a molding machine, is melted in the mold at a temperature higher than the melting point of the metal. Filling with a plastic material, melting and rolling the metal by heat and filling pressure of the plastic material, and molding the plastic material integrally with the conductive plastic molding sheet. For producing flexible plastic molded products.