JPH0247331B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing molded products such as injection molded products and blow molded products that have excellent electrical conductivity (antistatic properties and conductivity).

In parts, cabinets, housings, etc. of electronic and electrical equipment incorporating magnetic tapes, magnetic disks, semiconductors, etc., static electricity generated due to friction and other causes significantly impairs the performance of the equipment. For example, in the case of audio cassettes, video cassettes, computers, etc., paper impregnated with an antistatic agent is pasted on the inside of the cabinet or housing or on the side of the reel, or metal plating is applied. However, in the case of the former, the surface to which it is attached is required to be flat, and the antistatic effect inevitably decreases over time, reducing its effectiveness by half in about a year. However, the disadvantage is that the cost increases significantly due to post-processing called plating. Also parts, cabinets,
A large amount of carbon black is sometimes mixed in when molding housings, etc., but adding a large amount of carbon black not only significantly increases costs but also makes molding conditions difficult, and since only black products can be obtained, color There is also the drawback that it is impossible to

The present invention solves the conventional difficulties as described above,
The object of the present invention is to provide an industrially advantageous method for obtaining molded products having excellent antistatic properties and conductive properties.

The present invention involves inserting a cloth-like material made of a fibrous material consisting of 0.1 to 90% by weight of conductive fibers and 99.9 to 10% by weight of heat-melting fibers into the inner surface of a mold, and injecting molten resin into the mold. , which is characterized in that a resin melt or softened body is pressed onto the mold to obtain a molded article in which conductive fibers are integrally fixed to the surface and heat-fusible fibers have apparently disappeared due to melting, This produces excellent effects as listed below.

(1) In ordinary injection molding, blow molding, etc., the target object can be obtained all at once by simply adding an insert process, which is extremely advantageous in terms of industrial production and economy. In other words, the production speed does not decrease, there is no need for post-processing such as pasting or plating after molding, and no special thermal energy is required.

(2) Since the obtained molded product has conductive fibers fixed and integrated on its surface like a mesh, it has excellent static electricity removal action and electrical conductivity. Even when this molded product is rubbed, it is difficult to be charged due to conduction and self-discharge from the tips of the fibers, and even if it is temporarily charged, the static electricity is quickly removed.

(3) The conductive performance of the obtained molded product is semi-permanent.

(4) Since the conductive fibers are only very thinly adhered to the surface of the molded product, they do not impair the physical properties of the molded product itself.

(5) Even if the molded product is transparent or colored, the transparency or coloring will not be significantly impaired.

(6) Even if the surface of the molded product is curved, has unevenness, grooves, or through holes, the conductive fibers will freely wrap around and adhere to the surface shape.

Since the heat-fusible fibers forming the cloth-like material apparently disappear due to melting, the binding force of the conductive fibers fixed to the surface of the molded product becomes extremely strong due to the binder action of the heat-fusible fibers. The surface smoothness and appearance of the molded product are favorable.

In the present invention, a cloth-like material formed from a fibrous material containing at least a portion of conductive fibers is used.

Examples of conductive fibers include copper adsorption fibers, metal-plated fibers, carbon fibers, carbon composite fibers, metal-deposited fibers,
Examples include thin metal wires. The copper-adsorbing fiber refers to a fiber having a cyano group that is adsorbed with copper ions and then reduced.

The cloth-like material refers to non-woven fabric, woven fabric, knitted fabric, net, or anything similar thereto.

Both the conductive fiber (a) and the thermofusible fiber (a) are used to form the cloth-like article, and by using both in combination, a conductive molded article of excellent quality can be obtained. This is because when the fabric formed from this is pressed against the melted or softened resin, (a ₂ ) melts or softens and plays the role of a binder that firmly fixes (a ₁ ) to the surface of the molded product. be. When a cloth-like article is formed using (a ₁ ) and (a ₂ ), the proportion of (a ₁ ) in the fibrous material is preferably 0.01 to 99% by weight, particularly 0.1 to 90% by weight.

The heat-melting fibers ( _A2 ) include polyolefin fibers, nylon fibers, polyester fibers,
Various fibers including acrylic fibers can be mentioned.

In addition to the above (a ₁ ) and (a ₂ ), other fibers (a ₃ ) having a high melting point or showing no meltability may be included. This fiber (a ₃ ) plays a reinforcing material and other roles during fabric production.

In order to form a cloth-like article from the above-mentioned fibrous material, a method of obtaining a nonwoven fabric from a fibrous material containing at least a portion of a (a ₁ ) by a conventional method such as a binder method, a needle punching method, or a spun bonding method.

(b) A method of producing a spun yarn by spinning cut fibers containing at least a portion of (a ₁ ), and weaving the spun yarn using at least a portion of the warp or weft to obtain a woven fabric.

(c) A method of weaving using the filament yarn of (a ₁ ) as at least a part of the warp or weft to obtain a woven fabric.

D. A method of weaving using threads made by twisting (a ₁ ) and (a ₂ ) together to obtain a woven fabric.

(e) A method of obtaining a knitted fabric by knitting spun yarn, filament yarn, or twisted yarn as described in B to D above.

Any method such as this may be adopted.

Among these methods, it is industrially most advantageous to obtain a nonwoven fabric by employing method A in terms of cost, and it is also advantageous because it increases the number of fiber ends and improves static electricity removal performance.

Although there is no particular limitation on the thickness of the cloth material, sufficient conductivity can be obtained even if it is as thin as several g/m ² to as thin as several tens of g/cm ² .

In the present invention, as described above, a cloth-like material is inserted into the inner surface of a mold, and a molten resin is injected into the mold, or a molten or softened resin is pressed against the mold, whereby conductive fibers are integrated onto the surface. Obtain a molded product that is firmly fixed.

The first concrete molding method is injection molding, and the resins include styrene resin, ABS resin, polyethylene, polypropylene, and ethylene.
In addition to thermoplastic resins such as vinyl acetate copolymers, vinyl chloride resins, acrylic resins, nylon, polyesters, polycarbonates, polyacetals, polyimides, ethylene-vinyl alcohol copolymers, cellulose resins, and thermoplastic polyutanes, Thermoplastic resins can also be used, including phenolic resins, urea resins, melamine resins, guanamine resins, epoxy resins, diallyl phthalate resins, and unsaturated polyester resins.
A cloth-like material is previously supplied into the mold, and molten resin is injected into it.

When using the blow molding method, a cloth-like material is supplied into a mold in advance, and gas is blown into the parison formed by discharging the molten resin to press the expanded parison onto the inner surface of the mold. In this case, there is also a method in which the cold parison is softened by reheating and then expanded by blowing gas into it. As the resin, a thermoplastic resin as exemplified in the case of injection molding is used.

When employing the vacuum forming method, a cloth-like material is placed in a mold in advance, the air inside the mold is removed, and the heated and softened sheet is pressed onto the mold surface.

Other methods such as compression molding and transfer molding can also be used.

The molded product obtained by the method of the present invention can be
It is useful for a variety of applications, including parts, cabinets, and housings for electrical equipment, audio equipment, and precision equipment, transportation and storage containers for semiconductors, parts boxes and racks for electronic components, fixtures for computer rooms, clean rooms, and sterile rooms, and gasoline pumps. .

Next, the method of the present invention will be further explained with reference to Examples.

Example 1 A fiber mixture consisting of 10% acrylic copper-adsorbing fiber (A ₁ ) with a thickness of 3 denier and a length of 5 cm, and 90% of a low-melting point polyester fiber (A ₂ ) with a thickness of 3 denier and a length of 5 cm. The 20 g/m ² nonwoven fabric obtained was inserted into the mold of an injection molding machine, and injection molding of ABS resin was performed under the following conditions.

Cylinder temperature Rear 210℃ Center 230℃ Front 245℃ Nozzle 230℃ Mold temperature 60℃ Injection pressure 1400Kg/cm ^2- injection time 20 seconds Due to this molding, the size is 300mm x 200mm, thickness 3mm
A cabinet was obtained having dimensions of , and several projections and grooves. On the inner surface of the cabinet, including the protrusions and grooves, acrylic copper-adsorbing fibers (a ₁ ) are firmly fixed and integrated in a random mesh pattern, and the polyester fibers (a ₂ ) melt and appear to disappear. Also, due to the fixation of fibers (a ₁ ),
The color of the ABS resin molded product was not significantly lost.

Although the inner surface of this cabinet was strongly rubbed with a cloth, the fibers (a ₁ ) did not come off. Furthermore, the frictional voltage measured by a rotary static meter on the inside of the cabinet is less than 0.1kV at 20℃ and 40℃RH.
The specific resistance was 10 ⁰ to 10 ⁻² Ωcm.

Example 2 A fiber mixture consisting of 6% acrylic copper-adsorbing fiber (A ₁ ) with a thickness of 3 deniers and a length of 5 cm, and 94% of low melting point nylon fibers (A ₂ ) with a thickness of 3 deniers and a length of 5 cm. The 25g/ ^m2 nonwoven fabric was inserted into the mold of an injection molding machine, and nylon-6 was molded under the following conditions.
injection molding was carried out.

Cylinder temperature: 235°C Mold temperature: 60-70°C Injection pressure: 1100 kg/cm ² Injection time: 20 seconds This molding yielded a reel for videotape with a diameter of 90 mm, width of 18 mm, and thickness of both side plates of 1.5 mm. On both sides of this reel, acrylic copper-adsorbing fibers (a ₁ ) were strongly fixed and integrated in a random mesh pattern, and the nylon fibers (a ₂ ) had apparently disappeared.

When this reel is used to wind up a tape at high speed, or when it is actually used in a video cassette, static electricity problems due to friction between the tape and the reel and friction at the points of contact between the reel and the cabinet are avoided. It did not occur at all.

Furthermore, the frictional charging voltage on the fixed surface (a ₁ ) of the above reel is
The resistivity was 0.1 kV or less, and the specific resistance was 10 ⁰ to ^{10 −2} Ωcm.

Examples 3 to 4, Reference Example The cloth-like material shown below was inserted into the mold of an injection molding machine, and injection molding of polypropylene was performed.
A disk of 90 mm and thickness of 2 mm was obtained.

Example 3 Cut acrylic copper adsorption fiber (a ₁ ) 3% and cut low melting point polypropylene fiber (a ₂ )
Moss No. 4 (30 x 30/60 x 52) obtained by weaving spun yarn made from a 97% fiber mixture.

Example 4 A thin knitted fabric obtained by knitting the spun yarn of Example 3.

Reference example: A 20 g/m ² nonwoven fabric made from acrylic copper adsorption fiber (a ₁ ) with a thickness of 3 denier and a length of 5 cm.

The fibers (a ₁ ) were fixed and integrated on the surface of the obtained disk in a regular network (Example 3, Example 4) or in a random network (Reference Example). In addition, in the case of the reference example, the adhesion of the fibers was slightly lower than that of Examples 3 and 4. The frictional charging voltage and specific resistance showed the same values as in Examples 1 and 2 in all cases.

Example 5 The nonwoven fabric in Example 1 was inserted into the mold of a blow molding machine, and polyethylene with a density of 0.960 and a melt index of 0.2 was extruded from the extruder, and the parison formed was sandwiched between the molds and air was pumped into the parison. A bottle with a capacity of 2 was formed by blowing. The molding conditions were as follows.

Cylinder temperature C ₁ = 150°C C ₂ = 165°C C ₃ = 170°C C ₄ = 180°C Die temperature 185°C Resin temperature 180°C Mold temperature 50°C Approximately 40% of the outer surface of the body of the resulting bottle is made of aryl. The adsorbed fibers (a ₁ ) were firmly adhered to each other in a random network pattern.

Example 6 The same procedure as in Example 6 was carried out, except that a 20 g/m ² nonwoven fabric made from a fiber mixture consisting of 5% nickel fiber, 65% low melting point nylon fiber, and 30% acrylic fiber was inserted into the mold. Blow molding was performed. Fibers were adhered to the outer surface of the resulting bottle in a random mesh pattern.

Example 7 The nonwoven fabric in Example 2 was placed in a mold, and a foamed polystyrene sheet was vacuum formed. The molding temperature was 140°C. Fibers were adhered to the bottom of the resulting square container in a random mesh pattern.

Claims (1)

[Claims] 1. 0.1 to 90% by weight of conductive fibers and thermofusible fibers
A cloth-like material made of a fiber material consisting of 99.9 to 10% by weight is inserted into the inner surface of a mold, and molten resin is injected into the mold, or a molten or softened resin is crimped onto the mold to make the surface conductive. 1. A method for producing a molded article having electrical conductivity, characterized by obtaining a molded article in which the thermofusible fibers are integrally fixed and the thermofusible fibers have apparently disappeared by melting. 2. The method according to claim 1, wherein the cloth-like material is a nonwoven fabric.