JPH07266462A - Carbon fiber chopped strand - Google Patents

Abstract

PURPOSE:To provide a carbon fiber chopped strand used in the production of a fiber reinforced molding material excellent in dynamical strength and conductivity and capable of being directly subjected to injection molding. CONSTITUTION:A carbon fiber chopped strand is obtained by bundling carbon fibers by polyallylamine. When this strand and a thermoplastic resin are subjected to injection molding, an extrusion process can be omitted and a carbon fiber reinforced molded product having excellent characteristics can be obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to carbon fiber chopped strands. More specifically, the present invention relates to a carbon fiber chopped strand capable of producing a carbon fiber reinforced molded article having excellent mechanical strength and conductivity.

[0002]

2. Description of the Related Art When carbon fibers are mixed and dispersed in a matrix, a fiber-reinforced molding material having various properties can be obtained.
This material has excellent properties derived from carbon fiber such as high strength, high rigidity, and high electrical conductivity. Therefore, a wide range of applications are expected. However, usually, in order to disperse the carbon fibers in the matrix, it is necessary to melt-knead with an extruder. Therefore, it takes time and labor to manufacture the material, and the productivity is low. Further, during melt-kneading, there is a problem that the carbon fiber is broken and mechanical properties and conductive properties are significantly reduced.

On the other hand, a method is also known in which pellets of a thermoplastic resin and carbon fiber chopped strands are directly injection-molded to produce a fiber-reinforced molding material. This has the advantage of omitting the extrusion process. However, if the carbon fibers in the obtained molded product are not well dispersed, the physical properties are greatly varied and the strength is poor. Further, if the fiber chopped strands have poor focusing properties, the chopped strands may be cleaved and molding may not be possible. Therefore, the properties and manufacture of fiber reinforced molding materials are highly dependent on the carbon fiber chopped strands used.

JP-A-3-65311 describes a carbon fiber chopped strand obtained by bundling carbon fibers with polyethyleneimine. The fiber-reinforced molding material produced from this carbon fiber chopped strand and various resins showed improved carbon fiber dispersion. However, this fiber-reinforced molding material is, from the viewpoint of mechanical strength and conductivity,
It does not take full advantage of the excellent features of carbon fiber.

Therefore, it is possible to produce a fiber-reinforced molding material having further excellent characteristics, and to perform direct injection molding,
There is a need to develop superior carbon fiber chopped strands.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an excellent carbon fiber chopped strand capable of producing a fiber-reinforced molding material excellent in mechanical strength and conductivity and capable of direct injection molding. To provide.

[0007]

The excellent characteristics of carbon fibers are the high mechanical strength such as tensile strength and the magnitude of conductivity. The present inventor has conducted extensive studies on carbon fiber chopped strands for obtaining a reinforced resin molded product that makes use of these characteristics. As a result, surprisingly,
It has been discovered that using carbon fiber chopped strands focused with an allylamine polymer, the resulting reinforced resin has excellent properties in terms of mechanical strength and conductivity.
The present invention has been achieved based on such findings. That is, the present invention is a carbon fiber chopped strand obtained by bundling carbon fibers with an allylamine polymer.

The allylamine polymer used as a sizing agent in the present invention has a molecular weight of usually 3000 to 5,000,000, preferably 10,000 to 500,000. When the molecular weight is small, the focusing ability becomes weak. On the other hand, when the molecular weight is large, the solubility becomes poor and it is difficult to operate. The allylamine polymer is preferably solid at room temperature.

The allylamine polymer of the present invention is a polymer compound obtained by using an allylamine monomer as a polymerization component. The allylamine-based monomer is at least 1
An amine or ammonium salt having two allyl groups, and specific examples thereof include monoallylamine; N-alkylallylamine such as methylallylamine and ethylallylamine; N, N-dialkyl such as dimethylallylamine, diethylallylamine and methylethylallylamine. Allylamine; N-arylallylamine such as benzylallylamine; N, N-diarylallylamine such as dibenzylallylamine; N-alkyl-N-arylallylamine such as methylbenzylallylamine and ethylbenzylallylamine; N, N-diallylamine; methyldiallylamine; N-alkyldiallylamine such as ethyldiallylamine; N-aryldiallylamine such as benzyldiallylamine; dimethyldiallylammonium Id, methyl ethyl diallyl ammonium halides, N, such as diethyl diallyl ammonium halide, N- dialkyl diallyl ammonium salts and the like.

The allylamine polymer may be a homopolymer of any one of the above-mentioned allylamine-based monomers or a copolymer of two or more types thereof, or at least one of the above-mentioned allylamine-based monomers and the other one.
It may be a copolymer with one or more kinds of cationic monomers or nonionic monomers. Examples of cationic or nonionic monomers that can be used for copolymerization with an allylamine-based monomer are as follows.

Examples of the cationic monomer include dialkylaminoalkyl acrylates such as dimethylaminoethyl acrylate, dialkylaminoalkyl (alkyl) acrylates such as dimethylaminoethyl methacrylate, dialkylaminoalkylacrylamides such as dimethylaminoethylacrylamide, dimethylaminoethylmethacrylamide, and the like. Dialkylaminoalkyl (alkyl) acrylamides, trialkylacryloxyalkylammonium salts such as trimethylacryloxyethylammonium chloride, trialkyl (alkyl) acryloxyalkylammonium salts such as trimethylmethacryloxyethylammonium chloride,
Examples thereof include trialkylacryloylaminoalkylammonium salts such as trimethylacryloylaminoethylammonium chloride and trialkyl (alkyl) acryloylaminoalkylammonium salts such as trimethylmethacryloylaminoethylammonium chloride.

As the nonionic monomer, sulfur dioxide (which becomes a nonionic group by copolymerization), acrylamide,
Methacrylamide, methylacrylamide, methylmethacrylamide, dimethylacrylamide, dimethylmethacrylamide, ethylacrylamide, ethylmethacrylamide, diethylacrylamide, diethylmethacrylamide, methylethylacrylamide, methylethylmethacrylamide, methyl acrylate, methyl methacrylate, acrylic acid Examples thereof include ethyl, ethyl methacrylate, vinyl acetate and the like.

When a copolymer of an allylamine-based monomer and another monomer is used, the molar ratio of the allylamine-based monomer is usually 20% or more, preferably 40 mol%.
That is all. When this ratio is small, the focusing property becomes poor.

When the allylamine polymer is used, one of the above homopolymers or copolymers may be an aqueous solution or a mixed aqueous solution of two or more thereof. As long as the solvent dissolves the allylamine polymer and does not adversely affect the carbon fiber, and even if there is a small amount of residue that does not completely volatilize in the drying step, it does not adversely affect the matrix resin. Other than water, it can be appropriately used.

Particularly preferred allylamine polymers for use in the present invention are polyallylamine which is a homopolymer of monoallylamine, polydiallylamine which is a homopolymer of diallylamine, a copolymer of monoallylamine and diallylamine, and dimethyldiallylammonium. Examples thereof include polydimethyldiallylammonium chloride which is a homopolymer of chloride, and polyamine sulfone which is a copolymer of dimethyldiallylammonium chloride and sulfur dioxide at a molar ratio of 1: 1. The above-mentioned allylamine polymer is also effective when used in the form of a neutralized salt such as hydrochloride.

In the present invention, the carbon fiber used as a raw material varies depending on the molded product to be manufactured, but is not particularly limited. Generally, various known carbon fibers such as rayon, polyacrylonitrile, pitch, lignin, carbon fibers produced using graphite gas, graphite fibers, and metal-coated carbon fibers obtained by coating these with metals can be used. It is preferable to use polyacrylonitrile-based or pitch-based carbon fiber.

However, when a carbon fiber having a high affinity with the sizing agent is required, when the use of the sizing agent is intended to be kept low, the surface of the carbon fiber is oxidized by heating in the gas phase or electrolysis. It is better to use the carbon fiber.

In the carbon fiber chopped strand of the present invention, the allylamine polymer as the carbon fiber sizing agent is 0.1.
The content should be 1-10% by weight, preferably 1-6% by weight. If the content is less than 0.1% by weight, the chopped strands are opened because of insufficient binding, which causes poor flow in the feed hopper of the injection molding machine, clogging the feed port.
It tends to cause poor uniformity of the carbon fibers in the molded product. On the other hand, if it exceeds 10% by weight, the tensile strength and bending strength of the molded product obtained using this will be poor. The bulk density of the carbon fiber chopped strands of the present invention is usually 280 g / l or more, preferably 330 g / l or more. If the bulk density is less than 280 g / l, poor flow tends to occur in the feed hopper of the injection molding machine due to opening of chopped strands due to insufficient focusing. As a result, defective supply to the screw part of the injection molding machine and poor uniformity of the carbon fibers in the molded product occur, making continuous production difficult.

In the method for producing carbon fiber chopped strands of the present invention, first, an appropriate number of continuous carbon fiber bundles are continuously immersed in a solution of an allylamine polymer having a concentration of 0.3-10% by weight, and then 200 ° C. By drying with moderate hot air, and then cutting to a desired length, for example, 1-10 mm, so that the particle size of the resin pellets used together with the chopped strands can be matched.
This gives carbon fiber chopped strands bundled with an allylamine polymer. Additives which are usually added may be added to the allylamine polymer solution of the sizing agent. For example, a trace amount of preservative, cation or nonionic surfactant, etc. may be added.

By injection-molding the carbon fiber chopped strand of the present invention and a thermoplastic resin, a carbon fiber reinforced molded article which takes advantage of the characteristics of carbon fiber can be produced. This carbon fiber reinforced molded article is usually supplied with a carbon fiber chopped strand and a thermoplastic resin in the hopper of an injection molding machine, melted and mixed in a plasticizing cylinder, and injected into an injection molding die, It is obtained by cooling and solidifying in a mold and taking out a molded product. In order to make the molded product more uniform, the carbon fiber chopped strands and the thermoplastic resin may be premixed by using a tumbler, a high speed mixer or the like before injection molding.

The thermoplastic resin used for producing the carbon fiber reinforced molded article of the present invention includes polycarbonate, nylon 6,6, aromatic nylon or nylon 6
Polyamide such as polyethylene, polyester such as polyethylene terephthalate or polybutylene terephthalate, polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyether ether ketone, acrylic resin such as polyolefin, polyphenylene sulfone, polyacrylate or polymethacrylate, polystyrene etc. . Especially polycarbonate,
Polyethylene terephthalate and aromatic nylon are preferred.

[0022]

The present invention will be described in more detail with reference to Examples. The methods for measuring various physical properties are as follows.

<Measurement of Bulk Density of Carbon Fiber Chopped Strands> After filling a 50 ml graduated cylinder with carbon fiber chopped strands, light vertical vibration is applied to the graduated cylinder, and the weight is divided by the volume of the carbon fiber chopped strands that have reached equilibrium. I will stop.

<Measurement of Mechanical Properties of Carbon Fiber Reinforced Molded Product> The mechanical properties of the carbon fiber reinforced molded product obtained by using the carbon fiber chopped strand of the present invention were measured according to JIS K6810.

<Measurement of Conductivity> The conductivity of the carbon fiber reinforced molded product was measured on a flat plate molded body of 50 mm × 90 mm × 2.5 mm molded by using M-200 AII-DM type injection molding machine manufactured by Meiki Seisakusho. The conductive silver paste was applied onto two parallel sides of a square of 50 mm on each side, and the electric resistance value between them was defined as the surface resistivity (Ω).

Example 1 PAA HCl 10S (manufactured by Nitto Boseki Co., Ltd., polyallylamine, molecular weight about 80,000) was made into a 5% by weight aqueous solution, and carbon fiber (Hikerboron 12kf manufactured by Asahi Nippon Carbon Fiber Co., Ltd. ) Is continuously dipped in the carbon fiber to add 5% by weight of polyallylamine to the carbon fiber.
It was made to adhere and dried with hot air at 140 ° C. for 5 minutes to obtain a strand.

This strand was cut into a length of 6 mm using a D-type guillotine cutter to obtain a chopped strand having a bulk density of 388 g / l. 10 parts by weight of this chopped strand and 90 parts by weight of a polycarbonate resin (manufactured by Teijin Kasei) were dry blended with a V-type mixer.

This dry blend was manufactured by Meiki Seisakusho
A flat plate molding for evaluation was obtained using a -200 AII-DM type injection molding machine. The results are shown in Table 1.

[Chemical 1] The molded body thus obtained had a tensile strength of 1550 kg / cm ² and a surface electric resistance of 1.5 × 10 ³ Ω.

Example 2 In Example 1, where PAA HCl 10S was used, Danfix 505 RE (manufactured by Nitto Boseki Co., copolymer of 95 mol% monoallylamine and 5 mol% diallylamine, molecular weight about 50,000, The polymer fiber was replaced with a polymer concentration of about 20% by weight, diluted 4 times with water, and otherwise obtained under the same conditions as in Example 1 to obtain a carbon fiber chopped strand. The bulk density of the obtained carbon fiber chopped strands is 383 g.
It was / l.

A flat plate molding for evaluation was obtained under the same conditions as in Example 1 except that the above carbon fiber chopped strand was used. The tensile strength of the obtained compact is 1
It was 500 kg / cm ² , and the surface electric resistance was 2.5 × 10 ³ Ω.

The results are shown in Table 1.

Example 3 In Example 1, PAS-H 35S (PAS-H 35S, manufactured by Nitto Boseki Co., Ltd., polydimethyldiallylammonium chloride, molecular weight of about 50) was used.
Carbon dioxide chopped strands were obtained under the same conditions as in Example 1 except that the aqueous solution was replaced by 5% by weight. The bulk density of the obtained carbon fiber chopped strands was 380 g / l.

Using the above carbon fiber chopped strands, a flat plate molding for evaluation was obtained under the same conditions as in Example 1 except for the above. The tensile strength of the obtained compact is 1
The surface electric resistance was 550 kg / cm ² , and the electric resistance was 2.5 × 10 ³ Ω.
The results are shown in Table 1.

Example 4 In Example 1, the place where PAA HCl 10S was used was replaced with PAS-A 120S (manufactured by Nitto Boseki Co., Ltd., polyamine sulfone, molecular weight about 100,000) to prepare a 5% by weight aqueous solution, and otherwise. A carbon fiber chopped strand was obtained under exactly the same conditions as in Example 1. The bulk density of the obtained carbon fiber chopped strands was 380 g / l.

A flat plate molding for evaluation was obtained under the same conditions as in Example 1 except that the above carbon fiber chopped strands were used. The tensile strength of the obtained compact is 1
It was 500 kg / cm ² , and the surface electric resistance was 3.5 × 10 ³ Ω.
The results are shown in Table 1.

Comparative Example 1 In Example 1, the place where PAA HCl 10S was used was replaced with Epomine P-1000 (manufactured by Nippon Shokubai, polyethyleneimine, molecular weight about 70,000) to give a 5% by weight aqueous solution. A carbon fiber chopped strand was obtained under exactly the same conditions as in 1. The bulk density of the obtained carbon fiber chopped strands was 370 g / l.

Using the above carbon fiber chopped strands, a flat plate molding for evaluation was obtained under the same conditions as in Example 1 except for the above. The tensile strength of the obtained compact is 1
It was 400 kg / cm ² , and the surface electric resistance was 10.0 × 10 ³ Ω.
The results are shown in Table 1.

Example 5-8 A carbon fiber chopped strand was obtained under the same conditions as in Examples 1-4 except that a polyethylene terephthalate resin (manufactured by Teijin) was used instead of the polycarbonate resin. The obtained results are shown in Table 2.

[Chemical 2]

Comparative Example 2 A carbon fiber chopped strand was obtained under the same conditions as in Comparative Example 1 except that a polyethylene terephthalate resin (made by Teijin) was used instead of the polycarbonate resin. The obtained results are shown in Table 2.

Examples 9-12 Examples 1-4 except that an aromatic nylon resin (manufactured by Mitsui Petrochemical Industry Co., Ltd.) was used in place of the polycarbonate resin.
A carbon fiber chopped strand was obtained under the same conditions as above.
The results obtained are shown in Table 3.

[Chemical 3]

Comparative Example 3 A carbon fiber chopped strand was obtained under the same conditions as in Comparative Example 1 except that an aromatic nylon resin (manufactured by Mitsui Petrochemical Industry Co., Ltd.) was used instead of the polycarbonate resin. The results obtained are shown in Table 3.

[0042]

The carbon fiber chopped strand of the present invention and the thermoplastic resin are directly injection-molded to obtain a carbon fiber reinforced molded product. At this time, since it is not necessary to perform melt-kneading with an extruder, it does not take time and effort. Also,
The carbon fiber reinforced molded article is extremely excellent in mechanical strength and conductivity. Therefore, by applying the present invention, it is possible to easily manufacture mechanical parts, conductive electronic parts, and the like that are superior to the conventional ones.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // B29B 9/14 9350-4F B29K 105: 06 C08L 39:00

Claims (2)

[Claims] 1. A carbon fiber chopped strand comprising a carbon fiber bundled with an allylamine polymer. 2. A carbon fiber reinforced molded product obtained by injection-molding the carbon fiber chopped strand according to claim 1 and a thermoplastic resin.