JPH04198233A - Molding of conductive composite resin - Google Patents

Abstract

PURPOSE:To obtain the title molding of an improved appearance by forming a coating film made from an acrylic resin coating material containing dispersed resin beads on the surface of a substrate made from a conductive composite resin prepared by dispersing specified conductive fibers in a thermoplastic resin. CONSTITUTION:A conductive composite resin obtained by adding 2-20wt.% conductive fibers of a length of 1-15mm and an aspect ratio of 100-2000 to a thermoplastic resin (e.g. polycarbonate) is molded into a substrate. 1-30wt.% resin beads (acrylic beads) of a bead diameter of 10-600mum are dispersed in an acrylic coating material to obtain a coating material containing dispersed beads, which is adhered to the surface of the substrate and dried to form a coating film comprising the coating material.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a conductive composite resin molded product suitable as an electromagnetic shielding material, an antistatic material, etc. The present invention relates to a molded product made of a conductive composite resin that has conductivity imparted to the entire body, and whose appearance has been improved by forming a coating film on the surface.

[Prior Art] In recent years, metals have been replaced as casing materials and housing materials for electronic devices, especially household electronic devices and office electronic devices, due to their light weight, productivity, corrosion resistance, and low cost. Plastics or glass fiber reinforced plastics are often used.

When plastics or glass fiber reinforced plastics (hereinafter simply referred to as plastics) are used as casing materials or housing materials (hereinafter simply referred to as housing materials) for electronic devices, these housing materials do not have shielding properties against electromagnetic waves. Therefore, unnecessary electromagnetic waves emitted by this electronic device are radiated to the outside and act as interference waves on nearby electronic devices, causing electromagnetic interference such as noise and malfunction. Conversely, electromagnetic waves radiated from the outside enter the interior of electronic devices whose housing material is made of plastic, and electromagnetic interference similarly occurs.

For this reason, many plastic molded products used as housing materials for electronic devices are given conductivity in order to provide electromagnetic shielding properties.
There is a conductive composite resin molded product that uses a thermoplastic resin as a matrix resin and imparts conductivity by dispersing and blending conductive fibers such as metal fibers into the matrix resin, thereby providing electromagnetic shielding properties. There is also a conductive composite resin molded product whose appearance is further improved by coating the conductive composite resin base.

[Problems to be Solved by the Invention] However, when coating is applied to a substrate made of a conductive composite resin that has been given conductivity by dispersing and blending conductive fibers such as metal fibers into a thermoplastic resin, the paint Because the substrate surface is eroded and the conductive fibers are exposed, it is necessary to go through a complicated painting process such as multiple coats of paint and surface polishing, which leads to problems such as low productivity and increased costs, as well as paint There were concerns about negative effects on the substrate.

Therefore, the object of the present invention is to provide a conductive composite resin whose appearance is improved by coating a conductive composite resin substrate which is imparted with conductivity by blending conductive fibers such as metal fibers into a thermoplastic resin. An object of the present invention is to provide a conductive composite resin molded product that can be manufactured with a simple coating process during manufacturing and with high productivity.

[Means for Solving the Problems] The present invention has been made to achieve the above object, and the conductive composite resin molded product of the present invention has a length of 1 to 15 mm using a thermoplastic resin as a matrix resin. , a base made of a conductive composite resin containing at least conductive fibers with an aspect ratio of 100 to 2000, and a coating film formed on the surface of the base made of an acrylic resin paint in which resin beads are dispersed. It is characterized by:

The present invention will be explained in detail below.

As described above, the base of the conductive composite resin molded article of the present invention is made of a conductive composite resin having a thermoplastic resin as a matrix resin. There are no particular restrictions on the thermoplastic resin used here, and it can be appropriately selected from those conventionally used as molding materials and (-) depending on the purpose.

Examples of the thermoplastic resin include polyolefin resins, polyvinyl chloride resins, polyamide resins, polyimide resins, polyester resins, polyacetal resins, polycarbonate resins, polyaromatic ether or thioether resins, and polyaromatic resins. group ester resin,
Examples include polysulfone resins, styrene resins, acrylate resins, fluorine resins, and the like.

Examples of polyolefin resins include homopolymers of α-olefins such as ethylene, propyne, butene-1,3-methylbutene-1,3-methylpentene-1,4-methylpentene-1, and copolymers thereof. or copolymers of these and other copolymerizable unsaturated monomers. Typical examples include high-density, medium-density, and low-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, polyethylenes such as ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and atactic polyethylene. , syndiotactic, isotactic polypropylene, polypropylenes such as propylene-ethylene block copolymers or random copolymers, and poly4-methylpentene-1.

Examples of the polyvinyl chloride resin include vinyl chloride homopolymers and copolymers of vinyl chloride and unsaturated monomers copolymerizable. Examples of this copolymer include vinyl chloride-acrylic acid ester copolymer, vinyl chloride-methacrylic acid ester copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-propylene copolymer, and vinyl chloride-vinyl acetate copolymer. Examples include copolymers, vinyl chloride-vinylidene chloride copolymers, and the like. Furthermore, these polyvinyl chloride resins can be post-chlorinated to increase the chlorine content.

Examples of polyamide resin include 6-nylon and 1
Ring-opening polymerization of cycloaliphatic lactams such as 2-nylon, 6,6-nylon, 6゜10-nylon, 6,1
Condensation polymerization of an aliphatic diamine and an aliphatic dicarboxylic acid, such as 2-nylon, and a condensation polymerization product of an aromatic diamine and an aliphatic dicarboxylic acid, such as a condensation product of m-xylene diamine and adipic acid. 11-Nylon Examples include those produced by condensation polymerization of amino acids such as .

Polyimide resins include polyimides and polyamideimides, and specific examples of polyimides include:
Pyromellitic anhydride and diaminodiphenyl ether, 3
．． 4. Examples include those obtained from combinations of 3', 4'-benzophenone tetracarboxylic acid anhydride and diaminodiphenyl ether, bismaleimide and diaminodiphenylmethane, and the like. On the other hand, specific examples of polyamideimides include those obtained from a combination of trimellitic anhydride and diaminophenyl ether.

Examples of polyester resin include those obtained by condensation polymerization of aromatic dicarboxylic acid and alkylene glycol,
Specific examples include polyethylene terephthalate and polybutylene terephthalate.

Examples of the polyacetal resin include a homopolymer of polyoxymethylene and a formaldehyde-ethylene oxide copolymer obtained from trioxysan and ethylene oxide.

Examples of polycarbonate resins include 4,4'-dihydroxydiarylalkane polycarbonates, particularly those obtained by the phosgene method in which bisphenol A and phosgene are reacted, or the transesterification method in which bisphenol A is reacted with a carbonic acid diester such as diphenyl carbonate. Bisphenol A polycarbonate is preferably used.

In addition, a part of bisphenol A was added to 2,2'-bis(4
Modified bisphenol A polycarbonate substituted with -hydroxydi-3,5-dimethylphenyl)propane or 2,2-bis(4-hydroxy-3゜5-dibromophenyl)propane, flame-retardant bisphenol A polycarbonate, etc. are also used. be able to.

Polyaromatic ether or thioether resins have ether bonds or thioether bonds in their molecular chains, and examples of such resins include polyphenylene oxide, styrene-grafted polyphenylene oxide, polyetheretherkene, Examples include polyphenylene sulfide.

Examples of polyaromatic ester resins include polyoxybenzoyl obtained by condensation polymerization of p-hydroxybenzoic acid, polyarylate obtained by condensation polymerization of bisphenol A and aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, etc. can be mentioned.

Polysulfone resins have sulfone groups in their molecular chains, such as polysulfones obtained by condensation polymerization of bisphenol A and 4,4'-dichlorodiphenylsulfone, phenylene groups, or ether groups. Examples include polyether sulfone having a structure in which the sulfone group is linked to the p-position via a sulfone group, and polyallyl sulfone having a structure in which diphenylene groups and diphenylene ether groups are alternately linked to each other via a sulfone group.

Examples of the styrenic resin include homopolymers of styrene and α-methylstyrene, copolymers thereof, and copolymers of these with unsaturated monomers copolymerizable with them. Typical examples include general purpose polystyrene, impact-resistant polystyrene, heat-resistant polystyrene (α-methylstyrene polymer), acrylonitrile-butadiene-styrene copolymer (ABS), and methyl methacrylate-butadiene-styrene copolymer (MBS). , acrylonitrile-styrene copolymer (AS), acrylonitrile-chlorinated polyethylene-styrene copolymer (Ac1), acrylonitrile-ethylenepropylene rubber-styrene copolymer (AES), acrylic rubber-acrylonitrile-styrene copolymer (AAS) , styrene-maleic anhydride copolymer (SMA), and the like.

Examples of acrylate resins include methacrylic ester polymers and acrylic ester polymers, and examples of these monomers include methacrylic acid and acrylic acid methyl, ethyl, n-propyl, isopropyl,
Although butyl ester and the like are used, methyl methacrylate resin is a typical example of an industrial molding material.

Examples of fluororesins include homopolymers such as tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, and vinyl fluoride, copolymers of these, and unsaturated monomers that can be copolymerized with these. Examples include copolymers of. Specifically, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-vinylidene fluoride copolymer, hexafluoropropylene-vinylidene fluoride copolymer, tetrafluoroethylene Examples include fluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer.

Only one type of these thermoplastic resins may be used, or two types may be used.
You may use combinations of more than one species. In particular, it is preferable to use styrene resin and/or polycarbonate resin from the viewpoint of adhesion of the coating film.

The substrate constituting the conductive composite resin molded article of the present invention is made of a conductive composite resin in which the above-mentioned thermoplastic resin contains at least conductive fibers having a length of 1 to 15 mm and an aspect ratio of 100 to 2000.

The conductive fiber used here may be composed of a single fiber or a fiber bundle, as long as it has a length of 1 to 15 mm and an aspect ratio of 100 to 2000. Furthermore, it may be made of a fibrous material. Furthermore, when using single fibers or fibrous substances, they may be bundled and used as a fiber bundle.

The conductive fiber material has good conductivity, and when made into a single fiber, a fiber bundle, or a fiber, the length is 1 to 15 m.
It is not particularly limited as long as it can lead to m and aspect ratio of 100 to 2000. Examples of materials for such conductive fibers include aluminum,
Highly conductive metals or alloys such as copper, iron, steel, stainless steel, and brass, carbon fibers, coatings made of carbon fibers, glass fibers, natural fibers, or synthetic fibers coated with highly conductive metals or alloys, and conductive materials such as polyacetylene. Examples include organic compounds, with stainless steel being particularly suitable.

Among these conductive fibers, those made of single fibers, including single fibers that serve as the base material for coatings, can be produced by melt spinning, stretching, drawing, extrusion, drawing, etc., depending on the material. It can be obtained by producing short fibers, long fibers, continuous fibers, or fibrous materials by known methods such as rolling methods and cutting methods, and then cutting them into lengths within the above-mentioned range as necessary.

Among conductive fibers, fiber bundles, including fiber bundles that serve as the base material for coatings, can be processed into short fibers, long fibers, continuous fibers, or fibrous materials by the above-mentioned method, for example, depending on the material. After manufacturing, it can be obtained by converging it by a known method such as a resin impregnation method or a resin coating method, and cutting it into the above-mentioned length range if necessary.

The coating is applied to the surface of the fiber before or after cutting obtained by the above method, or the surface of the fiber bundle before or after cutting, for example, by electroless plating method, electrolytic plating method, physical vapor deposition method (vacuum plating method), etc. It can be obtained by coating with a highly conductive metal or alloy by a known method such as a vapor deposition method, a sputtering method, an ion blating method, etc.), a chemical vapor deposition method, a thermal spraying method, a coating method, or the like.

Here, the reason why the length of the conductive fiber is limited to 1 to 15 mm and the aspect ratio is limited to 100 to 2000 is as follows.

If the length of the conductive fiber is less than 11 mm, the resulting resin molded product will have insufficient conductivity, and if it exceeds 15 mm, molding workability will deteriorate and it will be difficult to stably obtain a molded product. In addition, if the aspect ratio is less than 100, the effect of improving the conductivity in the resin molded product obtained will be insufficient unless the blending amount of the conductive fiber is increased. On the other hand, the aspect ratio is 200
If it exceeds 0, agglomerates of conductive fibers will occur, which will deteriorate the appearance of the resulting resin molded product, or the conductive fibers will be easily cut, resulting in insufficient conductivity of the resulting resin molded product. Become.

The proportion of the conductive fiber formed in this way in the base is
Although it cannot be specified because it varies depending on the shape and conductivity of the conductive fiber, the use of the final conductive composite resin molded product, and the characteristics required of this molded product, it should be approximately 2 to 20 νt%. is preferred.

In addition to the above-mentioned conductive fibers, the substrate constituting the conductive composite resin molded product of the present invention may optionally contain an inorganic filler, an organic filler, a chemically modified material, an antistatic agent, and an antioxidant. It may contain additives and reinforcing materials conventionally used as components of housing materials, such as additives, light stabilizers, heat stabilizers, flame retardants, plasticizers, lubricants, and colorants.

The shape of the base body is not particularly limited, and can take various shapes depending on the intended use of the conductive composite resin molded article, and the molding method thereof can also be injection molding, extrusion molding, Known molding methods such as compression molding, calendar molding, blow molding, and vacuum molding can be applied.

The conductive composite resin molded article of the present invention is one in which a coating film made of an acrylic resin paint in which resin beads are dispersed is provided on the surface of the substrate formed as described above.

The acrylic paint used as the dispersion medium is preferably one that is less corrosive to the thermoplastic resin described above, such as an acrylic lacquer. Paints other than acrylic paints, such as urethane paints, are highly corrosive to thermoplastic resins,
This is not preferable because the conductive fibers become more prominent.

As for the thinner for dissolving this acrylic paint, it is preferable to use an alcohol-based thinner that has low corrosivity to thermoplastic resins. The use of ester or aromatic thinners is undesirable because they are highly corrosive to thermoplastic resins and cause the conductive fibers to protrude to a large extent.

The resin beads dispersed in such an acrylic paint are resins that are insoluble in the acrylic paint as a dispersion medium and have a specific gravity close to that of the acrylic paint as a dispersion medium, such as acrylic resin, nylon resin, urethane resin, Preferred are polyethylene resins, polyester resins, epoxy resins, and phenol resins. If the specific gravity is too heavy, the resin beads will sink into the coating film, making it easy for the conductive fibers to stand out. Furthermore, if the specific gravity is too light, it will be difficult to disperse and mix it into paints.

The bead diameter of the resin beads is 10 to 600 μm, especially 40 μm.
It is preferable that it is 150 micrometers. Bead diameter is 10μ
If it is smaller than m, the protrusion of the conductive fibers becomes more noticeable. On the other hand, if the diameter is larger than 600 μm, the adhesion will be reduced and the coating will be rough and the appearance will deteriorate.

The amount of resin beads added to acrylic paint is as follows:
It is preferably 1 to 30 wt%, particularly 5 to 20 wt% in the paint. If the blending amount is less than 1 wt%, the conductive fibers will stand out easily. On the other hand, if it is blended in an amount exceeding 30 wt%, the coating workability and adhesion will decrease, and the coating will become rough and the appearance will deteriorate.

A coating film made of an acrylic resin paint in which resin beads are dispersed is prepared by applying the paint onto the surface of the conductive composite resin substrate described above by a known method such as a coating method, a spraying method, or a dipping method. After being attached, it can be formed by drying.

[Example j Examples of the present invention will be described below.

Example 1 First, as a raw material thermoplastic resin for matrix resin, 5
0 parts by weight of polycarbonate (molecular weight 20,000, hereinafter abbreviated as PC) and 35 parts by weight of styrene-maleic anhydride copolymer [maleic anhydride content: 14 mol%,
MI (230℃, under 2.16kg load): 1.3g
/10 minutes, hereinafter abbreviated as SMA] and 15 parts by weight of methyl methacrylate-butadiene-styrene copolymer (
Butadiene content (nearly 0 wt%, hereinafter abbreviated as MBS) was used, and 15 parts by weight of a brominated flame retardant (trade name: Pratherm EC-20, manufactured by Dainippon Ink ■) and 5 parts by weight of antimony trioxide were used. These were triblended using a 2-screw mixer, and then pelletized using a twin-shaft mixer to obtain a thermoplastic resin composition.

Next, a stainless steel fiber bundle made of 1000 continuous stainless steel (SUS304) fibers with a fiber diameter of 15 μm as a conductive fiber material was coated with the above thermoplastic resin composition using a wire coating device, and cut into 6 mm lengths. , a pellet-shaped conductive composite resin with a diameter of about 5 mm (conductive fiber content: 10 wt%, conductive fiber aspect ratio 400)
) was obtained.

Next, the obtained conductive composite resin was pre-dried and then injection molded at 260° C. to obtain a square plate with a size of 140×140×3 mm. By this injection molding, the stainless steel fiber bundle was broken up, and each of the single fibers constituting the stainless steel fiber bundle was dispersed into the rectangular plate.

After this, the obtained square plate was used as a base, and after degreasing this base with isopropyl alcohol, 100 parts by weight of acrylic lacquer (trade name Nibraslac #1800, manufactured by Cashew Paint Co., Ltd.) and 130 parts by weight of alcohol-based thinner were added. (
A paint containing 10 parts by weight of acrylic beads (bead diameter = 50 to 60 μm, product name Nyacrycon, manufactured by Mitsubishi Rayon Co., Ltd.) dispersed in an acrylic paint consisting of a mixture with Nibla Slack #165 (trade name, manufactured by Cashew Paint Co., Ltd.). Spraying is applied once to a film thickness of 10 to 20 μm and heated at 60°C.
was dried for 10 minutes to form a coating film, thereby obtaining a conductive composite resin molded article of the present invention.

Table 1 shows the evaluation and measurement results of the coating film adhesion, electromagnetic interference shielding properties (hereinafter referred to as EMI shielding properties), and appearance of this conductive composite resin molded product.

In addition, evaluation and measurement were performed in the following manner.

■Adhesion of the coating film After being left for 2 days after coating, a cross-cut adhesive tape peeling test was conducted on the substrate.

■EMI shielding property After leaving the coating for 2 days, a heat shock test was conducted under the conditions of holding at -20℃ for 2 hours and holding at 70℃ for 2 hours 8 times.After this, the atopane test method was applied. Accordingly, the shielding effect of electric field waves at 300 MHz was determined.

■Appearance After being left for two days after painting, the finished state of the surface was visually judged according to the following criteria.

○: No protrusion of the conductive fibers is observed.

Δ: Slight protrusion of the conductive fibers is observed.

x: Embossed conductive fibers are observed over 50% or more of the surface.

XX: Embossed conductive fibers are observed on the entire surface.

Examples 2 to 4 Each was carried out in the same manner as in Example 1, except that the thermoplastic resin shown in Table 1 was used as the raw material thermoplastic resin of the matrix resin, and the conductive fiber shown in Table 1 was used as the conductive fiber. A conductive composite resin molded article of the present invention was obtained.

In addition, 100 parts by weight of impact-resistant polystyrene [polybutadiene content: 9 wt%, MI
(200℃, under 5kg load): 4g/10min, below PS
The molding temperature in Example 2 using only 80 parts by weight of SMA and 20 parts by weight of MBS was 240°C.

Table 1 shows the evaluation and measurement results of the coating film adhesion, EMI shielding properties, and appearance of each conductive composite resin molded product, which were evaluated and measured in the same manner as in Example 1.

Comparative Examples 1 to 3 Conductive composite resin molded articles were obtained in the same manner as in Examples 1 to 3, except that acrylic beads were not dispersed in the acrylic paint.

The adhesion of the coating film, the EMI shielding property, and the appearance of each conductive composite resin molded article were evaluated and measured in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Examples 4 to 7 Instead of the acrylic paint, 90 parts by weight of polyurethane paint (trade name Nistron #100, polyol/isocyanate = 80/10, manufactured by Cashew Paint Co., Ltd.) and 60 parts by weight of ester thinner (trade name Nistron #100, manufactured by Cashew Paint Co., Ltd.) were used. The procedure was the same as in Example 1, except that a polyurethane paint consisting of a mixture of Neostron #6 (manufactured by Kashiny Paint Co., Ltd.) was used, and a coating film was formed under the coating conditions shown in Table 1. , conductive composite resin molded products were obtained.

The coating adhesion, EMI shielding properties, and appearance of each conductive composite resin molded article were evaluated and measured in the same manner as in Example 1, and the results are shown in Table 1.

(Hereinafter, blank space) As is clear from Table 1, the conductive composite resin molded product of the present invention shows no decrease in paint film adhesion or EMI shielding properties, and has an excellent appearance. was confirmed.

[Effects of the Invention] As explained above, the conductive composite resin molded product of the present invention exhibits an excellent appearance after just one turn of coating, and has excellent adhesion and EMI shielding properties of the coating film. However, no decline has been observed.

Therefore, by carrying out the present invention, it becomes possible to provide a practical conductive composite resin molded product having an excellent appearance with high productivity.

Applicant: Idemitsu Petrochemical Co., Ltd. Agent: Patent Attorney Shizuo Nakamura

Claims (3)

[Claims] (1) Using thermoplastic resin as matrix resin, length 1
A base made of a conductive composite resin containing at least conductive fibers with a diameter of ~15 mm and an aspect ratio of 100 to 2000, and a coating film formed on the surface of the base made of an acrylic resin paint in which resin beads are dispersed. A conductive composite resin molded product characterized by comprising: (2) Claim (1) wherein the conductive fiber is a stainless steel fiber.
) The conductive composite resin molded product described in ). (3) Claim (1) or (2) wherein the thermoplastic resin is a styrene resin and/or a polycarbonate resin.
) The conductive composite resin molded product described in ).