JPH0319063B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a synthetic resin molded article having electrical conductivity.

Conductive synthetic resin molded products are often used as storage containers or bags for storing semiconductor elements such as ICs and LSIs, electronic equipment parts, and precision equipment parts, or as packaging sheets or films containing these. It plays the role of preventing dust from adhering to parts and preventing static electricity. Conventionally, conductive sheets, which are the materials for these molded products, have been produced by bonding nonwoven fabrics containing conductive fibers to a base material made of thermoplastic synthetic resin sheets or films by means such as thermocompression bonding or heat fusion. It had been. However, in this manufacturing method, when the nonwoven fabric is attached to the base material using the roll press method, the temperature and pressure are lower than with the hot platen press method, so the nonwoven fabric does not adhere completely to the base material, and Some of the conductive fibers constituting the nonwoven fabric stood up from the surface of the nonwoven fabric in a fuzzy state. Therefore, when such a conductive sheet is used as a molding material, the fluffy portions of the conductive fibers break and become loose from the sheet surface during use, which not only reduces the conductivity but also causes the loose fiber fragments to become dust. This led to environmental deterioration. Furthermore, when a molded product such as a container is manufactured using a conductive sheet with fluff as described above, fiber bridges occur on the inside corners of the molded product, and the fluff of the fibers becomes even more noticeable on the flat parts. The molded product could no longer be used for the above-mentioned purposes.

An object of the present invention is to provide a method for manufacturing a conductive synthetic resin molded article that can solve the above-mentioned problems.

The method for producing a conductive synthetic resin molded article according to the present invention includes: a base material made of a thermoplastic resin sheet;
Nonwoven fabrics made of conductive fibers are bonded together, and a synthetic resin liquid for fiber attachment is applied to the surface of the nonwoven fabric side of the obtained nonwoven fabric sheet so that the fluffed portions of the fibers are attached to the same surface, and dried. The conductive sheet thus prepared is set in a molding device so that its non-woven surface faces the mold, and the sheet is molded into a desired shape.

Examples of thermoplastic resins that make up the base material include vinyl chloride resin, acrylonitrile, butadiene,
Styrene copolymer resin, acrylic resin, ethylene/
Examples include vinyl acetate copolymer resin, and the thickness of the base material is usually 0.1 to 3.0 mm. If the base material is thick,
A base material containing carbon black inside may also be used.

The nonwoven fabric is made of conductive fibers alone or conductive fibers mixed with low softening point thermoplastic fibers, and the thermoplastic fibers are thermally fused or a binder is used to combine the fibers to form a web. It is manufactured by conventional methods such as the needle punching method, in which the fibers are stitched onto the web using needles without using a binder. Examples of conductive fibers include copper-adsorbing fibers, metal-plated fibers, carbon composite fibers, metal-deposited fibers, thin metal wires, and the like.
Further, the thermoplastic fiber with a low softening point is made of a resin that is compatible with the base material, and examples thereof include various fibers such as polyethylene fiber, nylon fiber, polyester fiber, and acrylic fiber.

The base material and the nonwoven fabric are bonded together by a roll press method. The pressing temperature is usually around 70°C, but this is set appropriately depending on the resin of the base material.

The synthetic resin liquid for fiber attachment is a solution prepared by dissolving a resin compatible with the base material resin in a solvent, or an emulsion containing the same resin, whose viscosity is adjusted to 5 to 300 centipoise. used. If the viscosity of the synthetic resin liquid is less than 5 centipoise, even if the fluffed portion of the fibers is pressed against the surface of the nonwoven fabric, the elastic repulsive force of the fibers overcomes the adhesive force of the liquid, causing the fibers to stand up again. Also, if the viscosity of the synthetic resin liquid exceeds 300 centipoise,
The conductivity of the conductive sheet decreases below the required value, and the workability of the coating operation deteriorates.

The molding process is carried out by a conventional method using a vacuum molding machine, a pressure molding machine, or the like. However, unless the surface of the nonwoven fabric is directed toward the mold, the desired molded product cannot be obtained.

As described above, according to the present invention, since the synthetic resin liquid for fiber attachment is applied to the surface of the nonwoven fabric side of the nonwoven fabric pasted sheet, the fluffed portions of the fibers constituting the nonwoven fabric can be pressed and attached to the surface of the sheet. Therefore, there is no risk of problems such as a decrease in conductivity or generation of dust due to fiber fragments as explained at the beginning, and the conductivity of the product sheet is reduced due to the application of the synthetic resin liquid. Not at all. The reason for this is not certain, but even after the conductive fibers are attached to the surface of the sheet, at least the non-attached side of the fluffed portion is exposed, and the entire part is not covered with the coating solution. It is thought that there is no such thing. Furthermore, since the nonwoven fabric side surface of the conductive sheet faces the mold in the molding process, it is possible to eliminate the formation of bridges on the inside corners of the molded product and the fluffing on the flat parts as described at the beginning.

Next, embodiments of the present invention will be specifically described based on the drawings.

In FIG. 1, the base material 2 extruded by the sheet extrusion molding device 1 is transferred to a pair of pressure rolls 4 together with the conductive nonwoven fabric 3 fed out from the roll 13 while it is still in a thermally softened state. The nonwoven fabric 3 is pasted on one side of the base material 2 by being passed through the base material 2 in an overlapping manner. The base material 2 is made of vinyl chloride resin and has a thickness of 0.4 mm. The nonwoven fabric 3 is manufactured by a binder method from acrylic fibers adsorbed with copper and polyethylene fibers. The temperature of the pressure roll 4 is adjusted to about 70°C. The high-temperature sheet 5 emerging from between the pair of rolls 4 is then passed through a plurality of cooling rolls 6 in a zigzag manner and wound up into a roll. In this way, a roll of nonwoven fabric-covered sheet 7 is obtained.

Next, as shown in FIG. 2, the nonwoven fabric pasted sheet 7 is fed out from this roll, passed between a plurality of pinch rolls 8 with the nonwoven fabric side down, and then passed between a pair of upper and lower application rolls 9. be done. The lower coating roll 9 is in close contact with a coating liquid supply roll 10, and the lower half of the roll 10 is coated with a synthetic resin liquid 11 for adhering fibers.
It is immersed in. The synthetic resin liquid is a solution prepared by diluting an acrylic resin solution (manufactured by Mitsubishi Rayon Co., Ltd., product name Acrynal, product number H-004) with methyl ethyl ketone at a ratio of 6:4 to adjust the viscosity to 10 centipoise. . By passing the nonwoven fabric-covered sheet 7 between the pair of application rolls 9 in this manner, approximately 20 g/m ² of the synthetic resin liquid is applied to the surface of the sheet 7 on the nonwoven fabric side. The sheet 7 is then dried while passing through a plurality of take-up rolls 12,
The obtained conductive sheet 13 with a thickness of 0.4 mm is wound into a roll.

When the surface of the nonwoven fabric side of this conductive sheet 13 was observed with a magnifying glass, no fluffing of the conductive fibers was observed, and the conductivity of the sheet 13 was completely different from the conductivity of the nonwoven fabric pasted sheet 7 before the coating process. Nakatsuta.

Next, the conductive sheet is cut to the required length,
As shown in FIG. 3, the nonwoven fabric side surface of the sheet piece 14 faces the male mold 15, and both ends of the sheet piece 14 are connected to a pair of clamps 1 of the molding device 16.
7. Then, the sheet piece 14 is attached to the heater 1
8 from above at 170°C for 20 seconds.
Then, the sheet piece 14 in a softened state is formed by vacuum forming.
It is molded into a 300mm x 300mm x 10mm container.

When the inside corners and flat parts of the obtained container were observed with a magnifying glass, no fiber bridging or fuzz was observed, and the conductivity of the container was no different from the conductivity of the sheet piece 14 before molding. .

Comparative Example The operation of the example is repeated, except that the nonwoven side surface of the sheet piece is oriented in the opposite direction of the mold. However, in this case, the mold is a female mold. As a result of observation using a magnifying glass, it was found that fiber bridges were formed on the inside corners of the container, and fiber fluff was formed on the flat portions.

[Brief explanation of the drawing]

1 and 2 are process diagrams showing an embodiment of the present invention, and FIG. 3 is a vertical sectional view of a vacuum forming apparatus. 2...Base material, 3...Nonwoven fabric, 4...Pressure roll, 7...Nonwoven fabric pasted sheet, 9...Coating roll, 11...Synthetic resin liquid for fiber attachment, 13...
Conductive sheet, 14... Sheet piece, 15... Molding mold, 16... Molding device, 17... Clamp, 18
……heater.

Claims (1)

[Claims] 1. On one side of a base material made of a thermoplastic resin sheet,
Nonwoven fabrics made of conductive fibers are bonded together, and a synthetic resin liquid for fiber attachment is applied to the surface of the nonwoven fabric side of the obtained nonwoven fabric sheet so that the fluffed portions of the fibers are attached to the same surface, and dried. 1. A method for manufacturing a conductive synthetic resin molded article, which comprises setting the conductive sheet in a molding device so that the surface of the nonwoven fabric side faces a mold, and molding the sheet into a desired shape. 2. The method according to claim 1, wherein the resin of the synthetic resin liquid is compatible with the resin of the base material. 3. The method according to claim 1 or 2, wherein the synthetic resin liquid has a viscosity of 5 to 300 centipoise.