JPH10193380A - Heat-generating molding of thermoplastic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a molding having specific volume resistivity value, thermal conductivity, high conductivity without anisotropy, uniformly heating surface, light weight and much processability by molding resin to be granulated by extrusion covering carbon fiber roving after surface treating with predetermined emulsion with graphite-added thermoplastic resin. SOLUTION: Carbon fiber roving manufactured by polyacrylonitrile as raw material is dipped in thermoplastic resin or styrene-butadiene resin emulsion compatible with thermoplastic resin, then dried, extrusion covered with thermoplastic resin such as graphite-added general polystyrene, and cut to granulate pellets. The resin containing the carbon fiber and graphite is injection molded or extrusion molded. As a result, a molding having volume resistivity value of 0.01 to 100Ωcm, thermal conductivity of 0.15kcal/m.Hr. deg.C or more, high conductivity without anisotropy, uniformly heating surface, light weight and easy processability can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin molded article containing a conductive material in a thermoplastic resin and having excellent conductivity and heat conductivity. More specifically, using a thermoplastic resin containing graphite and carbon fibers of long fibers,
The present invention relates to a lightly heat-formed thermoplastic resin molded article having high conductivity, good thermal conductivity and uniform heat generation on the surface.

[0002]

2. Description of the Related Art Thermoplastic resins have been used in various fields because of their excellent moldability. Among them, styrene resins are widely used in housings of electric / electronic equipment and OA equipment, daily necessities, toys, automobile parts and the like. Used in the field. In recent years, resin compositions having excellent conductivity have been obtained by adding a conductive material to a thermoplastic resin which is such a non-conductive substance. Floor heaters, tank heaters, etc. have been used as planar heating elements. It has begun to be widely used as an industrial and household heating element.

[0003] However, when a metal foil or a metal fiber such as aluminum, stainless steel, brass or the like is used as a conductive material, the effect of improving conductivity is excellent, but a large amount of metal is added to impart a uniform conductivity improving effect. However, there is a disadvantage that the weight of the molded product is increased. On the other hand, carbon black is used favorably because it has a low specific gravity and requires a small amount of addition per weight.However, since it is a very fine powder, there is a problem in workability. , And the mechanical properties of the molded article are reduced.

[0004] Therefore, for example, Japanese Patent Application Laid-Open No. 60-1845.
No. 34 proposes a conductive plastic composition in which carbon black and carbon fibers are combined with a polymer component composed of a polyolefin resin and a thermoplastic elastomer. JP-A-62-42402 proposes a molded article of a conductive resin composition using both carbon black and graphite. Japanese Patent Application Laid-Open No. Sho 60-202154 discloses a method using long fiber carbon fibers.
JP-A-5725 and JP-A-1-300914 propose a method of adding short metal fibers and carbon black. JP-A-5-217711 proposes a composition to which inorganic nitride particles or magnesium oxide particles are added in order to increase the thermal conductivity and the heat generation unevenness with the conductive particles.

[0005]

However, in a conductive plastic composition in which carbon black and carbon fiber are combined, it is necessary to add a conductive material of 30 wt% or more in order to obtain a conductivity of about 10 Ω · mm. Moreover, anisotropy occurs in the conductivity of the molded product. Even in the case where carbon black and graphite are used in combination, a high concentration of addition is required to obtain high conductivity, so that the processability of the composition is reduced and the mechanical properties of the molded product are reduced.

On the other hand, in the method using long-fiber carbon fibers, high conductivity can be obtained by adding a small amount, but there is anisotropy in conductivity. The method of adding short metal fibers and carbon black increases the weight of the molded product and wears the screws and cylinders of the molding machine. Further, the composition to which inorganic nitride particles or magnesium oxide particles are added in order to increase the thermal conductivity has significantly reduced conductivity. The present invention has been made in view of the above circumstances, has high conductivity by adding a small amount of conductive material, has no anisotropy in conductivity, generates heat uniformly on the surface, and is light and easily processed. It is an object of the present invention to provide a heat-molded thermoplastic resin product.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that a carbon fiber roving surface-treated with a specific emulsion is extrusion-coated with a thermoplastic resin to which graphite is added. By molding a granular resin, a thermoplastic resin extruded product that has high conductivity with a small amount of conductive material added, has no anisotropy in conductivity, generates heat uniformly on the surface, and is light and easy to process and mold. They have found that they can be provided, and have completed the present invention. That is, the present invention provides a method for extruding and coating a carbon fiber roving with a thermoplastic resin or a resin emulsion compatible with the thermoplastic resin, drying, extruding with a thermoplastic resin to which graphite is added, and granulating. Injection molding or extrusion molding of a thermoplastic resin containing carbon fiber and graphite, having a volume resistivity of 0.01 to 100 Ω · cm and a thermal conductivity of 0.15 Kca.
The present invention relates to an exothermic molded article of a thermoplastic resin having a temperature of 1 / m · Hr · ° C or more.

The thermoplastic resin used herein is not particularly limited, and any one can be selected from those conventionally used as molding materials. Examples of the thermoplastic resin include a styrene resin, a polyphenylene ether resin, a polyolefin resin, a polyvinyl chloride resin, a polyamide resin, a polyester resin, a polyacetal resin, and an acrylic resin.

Examples of the styrene-based resin include homopolymers such as styrene and α-methylstyrene, copolymers thereof, and copolymers thereof with unsaturated monomers copolymerizable therewith. Specifically, general-purpose polystyrene (GPPS), impact-resistant polystyrene (HIP)
S), heat-resistant polystyrene (α-methylstyrene polymer), acrylonitrile-butadiene-styrene copolymer (ABS), acrylonitrile-butadiene-styrene-α-methylstyrene copolymer (α-methylstyrene-based heat-resistant ABS), Acrylonitrile-butadiene-styrene-phenylmaleimide copolymer (phenylmaleimide-based heat-resistant ABS), acrylonitrile-styrene copolymer (AS), acrylonitrile-chlorinated polyethylene-
Styrene copolymer (ACS), acrylonitrile-ethylene propylene rubber-styrene copolymer (AES), acrylic rubber-acrylonitrile-styrene copolymer (A
AS) and the like. It can also be made of a polymer blend.

[0010] Polyphenylene ether resin (PPE)
Are, for example, poly (2,6-dimethyl-1,4phenylene) ether, poly (2-methyl-6-ethyl1,
Homopolymers such as 4-phenylene) ether and the like can be used, and those obtained by modifying this with a styrene resin can be used. Typical polyolefin resins include ethylene, propylene, butene-1,3-methylbutene-
1,3-methylpentene-1,4-methylpentene-1
And the like, or a copolymer of these with another copolymerizable unsaturated monomer, or the like. Typical examples are high density,
Medium density, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polyethylene such as ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, atactic, syndiotactic, isotactic polypropylene And polypropylenes such as a propylene-ethylene block copolymer or a random copolymer, and poly-4-methylpentene-1 and the like.

Examples of the polyvinyl chloride resin include a vinyl chloride homopolymer and a copolymer of vinyl chloride with an unsaturated monomer copolymerizable with vinyl chloride. Specifically, vinyl chloride-acrylate copolymer, vinyl chloride-methacrylate copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-propylene copolymer, vinyl chloride-vinyl acetate copolymer, And vinyl chloride-vinylidene chloride copolymer. Further, those obtained by chlorinating these polyvinyl chloride resins to increase the chlorine content can also be used.

Examples of the polyamide resin (PA) include those obtained by ring-opening polymerization of a cyclic aliphatic lactam such as 6-nylon or 12-nylon, 6.6-nylon, or 6-10-nylon.
Examples thereof include those obtained by polycondensation of an aliphatic diamine and an aliphatic dicarboxylic acid such as nylon and 6,12-nylon, and those obtained by polycondensation of an amine acid such as 11-nylon.

Examples of the polyester resin include those obtained by condensation polymerization of an aromatic dicarboxylic acid and an alkylene glycol. Specific examples include polyethylene terephthalate and polybutylene terephthalate. Examples of the polyacetal-based resin (POM) include a polyoxymethylene homopolymer or a formaldehyde-ethylene oxide copolymer obtained from trioxane and ethylene oxide.

[0014] As the polycarbonate resin,
4'-dihydroxydiarylalkane-based polycarbonate is exemplified. Specifically, bisphenol A-based polycarbonate, modified bisphenol A-based polycarbonate, flame-retarded bisphenol A-based polycarbonate and the like can be used. Examples of the acrylic resin include methacrylic acid ester polymers and acrylic acid ester polymers. Examples of these monomers include methyl, ethyl, n-propyl, isopropyl, and butyl esters of methacrylic acid or acrylic acid. And a typical example is methyl methacrylate resin (PMMA).

[0015] Among these thermoplastic resins, styrene resin, PPE, polyethylene (PE), polypropylene (PP), PA, POM, and PMMA are preferable. Further, styrene resin and PPE, that is, GPPS, HIP
S, ABS, α-methylstyrene heat-resistant ABS, phenylmaleimide heat-resistant ABS, AES, AAS, AS and P
PE is most preferred. These thermoplastic resins may be used alone or in combination of two or more.

The carbon fiber roving as a component constituting the composition of the present invention is not particularly limited, and those produced from polyacrylonitrile, pitch or the like can be used. The single fiber diameter is preferably 2 μm or more from the viewpoint of dispersibility in a thermoplastic resin or the generation of pills, and the diameter is preferably 10 μm or less to maintain a long fiber length in a molded product. . The amount of addition is 1 to 20 from the viewpoint of volume resistivity and thermal conductivity.
wt%, preferably 3 to 15 wt%.

The thermoplastic resin or an emulsion of a resin compatible with the thermoplastic resin is a styrene-butadiene resin emulsion (SB latex) when the thermoplastic resin is a polystyrene or a modified polyphenylene ether resin, and a hydrogenated styrene-butadiene. It is a resin emulsion or the like. Thermoplastic resin is AS, ABS, PMMA, P
In the case of an ET or PC resin, an acrylic emulsion such as a styrene-acrylic acid copolymer and a styrene-methyl methacrylate copolymer is used. When the thermoplastic resin is a polyolefin resin or a polyacetal resin, examples thereof include an emulsion of vinyl acetate, an ethylene-vinyl acetate copolymer, an ethylene-methacrylic acid copolymer, and a partial metal salt. When the thermoplastic resin is a polyamide resin, it is a urethane emulsion.

The solid concentration (mainly resin) of the emulsion may be in the range of 30 to 70% which is generally commercially available, and it is not necessary to use a special emulsion. In order to surface-treat the carbon fiber roving with the emulsion, first, as a method of attaching the emulsion to the surface of the carbon fiber, a spray method of spraying the emulsion on the carbon fiber, a dipping method of dipping the carbon fiber in the emulsion solution, and the like can be adopted. If necessary, the excessively adhered emulsion can be appropriately squeezed using an appropriate method. Next, in order to obtain a good dispersion of the carbon fibers, it is necessary to dry the fibers to which the emulsion is attached at a temperature at which the resin does not deteriorate. When the resin is an amorphous resin, the glass transition temperature of the resin is + 20 ° C. or lower, and when the resin is a crystalline resin,
It is preferable to dry at a temperature not higher than the melting point of the resin plus 20 ° C.

From the viewpoint of compatibility with the thermoplastic resin, the amount of resin coating the fiber surface is 0.5% by weight or more on a dry basis.
From the viewpoint of workability and economy, 50 wt% or less is preferable,
More preferably, it is 5 to 20 wt%. As the graphite, natural graphite obtained by purifying and finely pulverizing natural products and artificial graphite which is graphitized at a temperature of 2000 ° C. or more from petroleum coke or the like can be used. Particularly preferred is fine graphite having an average particle diameter of 10 μm or less, which has good dispersibility in a thermoplastic resin and excellent mechanical strength. Most preferably, graphite is immersed in a strong oxidizing agent such as sulfuric acid, nitric acid, chloric acid or the like to form an intercalation compound, and the expanded graphite which is foamed at 500 ° C. or higher after water washing is pulverized. Although there is no particular limitation on the amount of addition, it is sufficient that the anisotropy of conductivity is eliminated, and 0.1 to 10% by weight is preferable.

The carbon fiber roving is surface-treated with an emulsion, extruded with a thermoplastic resin, and granulated. The pellet length is preferably 1.5 mm or more from the viewpoint of maintaining conductivity. From the viewpoint of preventing a reduction in formability due to the occurrence of bridges in the above-described method, the thickness is preferably 15 mm or less. More preferably, it is 3 to 8 mm.
Further, it is also possible to add a heat stabilizer, an ultraviolet absorber, a light stabilizer, an antioxidant, a plasticizer, a release agent, a lubricant, a flame retardant, a colorant, etc. to the thermoplastic resin of the present invention. Other conductive materials and good heat conductive materials can be added to adjust the volume resistivity and the thermal conductivity.

As a molding method for obtaining the molded article of the present invention, a commonly used molding method, for example, extrusion molding, injection molding, blow molding and the like can be used. The molded article of the present invention can also be obtained by mixing a masterbatch pellet containing a high concentration of carbon fiber and graphite with a thermoplastic resin pellet.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail by way of examples. The materials and molding equipment used in Examples and Comparative Examples are as shown below. <Molded product appearance evaluation device> Injection molding machine-1: IS55EPN Toshiba Machine Co., Ltd. Injection molding machine-2: IP1050 Komatsu Ltd. <Thermoplastic resin> HIPS: Styron <Registered trademark> EXG11 Asahi Chemical Industry Co., Ltd. PMMA: Delpet <registered trademark> 80N Same as above AS: Styrac <registered trademark> AS783 Same as above ABS: Stylac <registered trademark> ABS100 Same as above PPE: Zylon <registered trademark> 100Z Same as above PE: Suntech <registered trademark> HD < Registered trademark> J340 Same as above POM: Tenac <Registered trademark> -C4510 Same as above PA: Leona <Registered trademark> 1300S Same as above <Emulsion material> SB emulsion: Styrene-butadiene resin latex (solid content = 40 wt%) AS 〃: Acrylonitrile-styrene Polymer Fat latex (AN = 25%, solid content = 50 wt%) EVA〃: Ethylene-vinyl acetate copolymer resin latex (vinyl acetate = 20%, solid content = 50 wt%) Urethane〃: Urethane resin latex (solid content = 40 wt%) <Conductive material> Carbon fiber roving (CF-R): HTA-W12K Graphite manufactured by Toho Rayon Co., Ltd .: ACP-1000 Expanded graphite (BG) manufactured by Nippon Graphite Industry Co., Ltd .: KEX Nippon Graphite Industry Co., Ltd. Chopped carbon fiber (C-CF): A6000 Carbon black (CB) manufactured by Mitsubishi Rayon Co., Ltd .: ECX manufactured by Lion Akzo Co., Ltd. <Measurement and evaluation method> (1) Measurement of thermal conductivity Injection molding machine-1 Set the cylinder temperature to a molding temperature suitable for each thermoplastic resin, and for resins that require drying, dry According cycles, forming a plate (width 50 mm × length 90 mm × thickness 2.5 mm).

This plate is sandwiched between two thick copper rods which are in close contact with a heating source and a cooling source, and the temperature gradient of the copper rod and the temperature gradient of the plate are measured to measure the thermal conductivity by the temperature gradient method. . (2) Measurement of Volume Specific Resistance Silver paste is applied to both sides of the plate in the length direction (the flow direction of the resin during molding), and after drying, the resistance value (RL) is measured with a tester, and R1 = RL. × AL / L (A
L: cross-sectional area, L: length) is used to calculate the volume resistivity R1. (3) Measurement of anisotropy of volume resistivity A silver paste is applied to both sides of the plate in the width direction (perpendicular to the flow of resin during molding), and after drying, the resistance value (RW) is measured with a tester. And R2 = RW × AW / W
(AW: sectional area, W: width) Volume resistance value R2 calculated from
And the ratio of the volume specific resistance R1 in the flow direction of the resin (R2
/ R1) is calculated. (4) Evaluation of pills of carbon fiber Using an injection molding machine-1, the molding temperature and drying were the same as described above, and 1 part by weight of titanium dioxide was added to 100 parts by weight of resin to facilitate evaluation. A plate is formed from the pellets added and colored in gray, and the presence or absence of pills on the carbon fiber is visually determined.
(Slight occurrence) was indicated by Δ, and (Many occurrences) was indicated by ×.

(5) Measurement of heat generation temperature unevenness Using an injection molding machine-2, the molding temperature and drying were the same as described above, and a strip-shaped plate (width 25 mm × length 550 m) was used.
m × 2.5 mm thick). A silver paste is applied to both ends of the plate and dried to form electrodes. A power of 40 W is applied to this with a sliderac, and a total of 10 surface temperatures are measured at 50 mm intervals.

[0025]

Comparative Examples 1 to 4 and Examples 1 to 11 As shown in Table 1 below, pellets of each size were prepared with combinations and compositions of thermoplastic resins, emulsions, and conductive materials. As a method for preparing pellets, in Comparative Examples 2, 3 and 4, ABS and an additive were mixed with a tumbler and extruded with a twin screw extruder.
It was cut into 7 mm pellets. Except for Comparative Examples 2, 3 and 4, carbon fiber rovings (CF-R) were immersed in the respective emulsions, dried, extruded with the respective thermoplastic resins, and cut into 5.5 mm.

Next, in the obtained pellets, the resin that needs to be dried is dried, molded according to each evaluation method, and the evaluation results are shown in Table 1. In Examples 1 to 4 in Table 1, the carbon fiber has a thermal conductivity of 0.2 Kcal / m · Hr · ° C. or more, a volume resistance value R1 of 14 Ω · mm or less, an anisotropy (R2 / R1) of 1.4 or less. It can be seen that a molded product having a temperature variation of the exothermic temperature within ± 5 ° C. with almost no generation of pills can be obtained. Comparing Comparative Example 1 with Example 3, it can be said that when CF-R is contained in a high concentration, pills are generated more frequently, and by adding graphite, the anisotropy is improved and the heat generation temperature unevenness is reduced. By comparing Comparative Examples 2 and 3 with Example 3, the long fiber of the present invention has significantly increased thermal conductivity and volume resistivity, low anisotropy, and low exothermic temperature even with the same amount of carbon fiber added. It can be said that unevenness is reduced. Also, from Comparative Example 4 and Example 4, it can be said that the present invention can provide a molded article having significantly increased thermal conductivity and volume specific resistance value by adding a small amount of a conductive material, and can improve heat generation temperature unevenness. Further, as shown in Examples 5 to 11, resins other than ABS, HIPS, PMMA, AS, PPE, PE, PO
It can be said that similar effects can be obtained for M and PA.

[0027]

[Table 1]

[0028]

As described above, according to the present invention, a molded article made of a thermoplastic resin which has high conductivity by adding a small amount of a conductive material, does not have anisotropy in conductivity, generates heat uniformly on the surface, and is light and can be easily processed. Can be manufactured. Therefore, the volume resistivity is 0.01 to 100 Ω · mm and the thermal conductivity is 0.15
There is an effect that a thermoplastic resin exothermic molded product having a Kcal / m · Hr · ° C. or more and a specific gravity of 2 or less can be obtained.

Claims (3)

[Claims] 1. A carbon fiber roving is coated in advance with a thermoplastic resin or a resin emulsion compatible with the thermoplastic resin to be extrusion-coated, dried, and extruded with a thermoplastic resin to which graphite is added, and granulated. Injection molding or extrusion molding of the thermoplastic resin containing the carbon fiber and graphite thus obtained has a volume resistivity of 0.01 to 100 Ω · cm and a heat conductivity of 0.1 to 100 Ω · cm.
Exothermic molded product of thermoplastic resin of 15 Kcal / m · Hr · ° C or higher. 2. Carbon fiber of 1 to 20% by weight and graphite of 0.1 to 0.2% by weight.
2. The composition according to claim 1, wherein the content is 1 to 10 wt%.
An exothermic molded article of the thermoplastic resin described. 3. The heat-molded thermoplastic resin article according to claim 1, wherein the thermoplastic resin comprises a styrene resin or a polyphenylene ether resin.