JPH0365311A - Carbon fiber chop - Google Patents

Abstract

PURPOSE:To obtain chops with high binding properties and excellent dispersibilities by binding carbon fibers with a solution having the specific content of a polyimine resin. CONSTITUTION:A polyimine resin, for example, polyethylene-imine is dissolved in water in the range of 0.1 to 10 wt. %, and the roving of carbon fibers is continuously dipped into this resultant solution to allow 0.1 to 10wt.% of the pllyethylene-imine to adhere to the carbon fibers. Thereafter, the roving of carbon fibers is dried by blowing hot air to obtain a strand, and, by cutting this strand, chops can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a carbon fiber tip made of carbon fibers bundled with a polyimine resin. More specifically, the present invention relates to a carbon fiber chop that can be directly injection molded into a carbon fiber reinforced resin and has excellent moldability, carbon fiber dispersibility, mechanical strength, and electrical conductivity.

[Conventional technology]

Fiber-reinforced molding materials made by mixing and dispersing carbon fibers in various matrices have the excellent properties of carbon fibers, such as high strength, high rigidity, low specific gravity, high electrical conductivity, low coefficient of thermal expansion, and high wear resistance. Because of this, it is expected to have a wide range of uses and is attracting attention as an industrially important material.

Generally, in order to obtain a fiber-reinforced molding material by mixing and dispersing carbon fibers in various thermoplastic resins, carbon fibers consisting of hundreds to hundreds of tensile strength are used as a sizing agent, such as polyolefin, polyester, etc., which are usually used in fiber-reinforced molding materials. , polyamide (Japanese Patent Publication No. 62-7225), acrylic resin, epoxy resin (Japanese Patent Application Laid-open No. 61-66615), and phenol resin, cut into 1~loan to make carbon fiber chops, which are then made into thermoplastic fibers. The strands are melt-kneaded together with resin pellets or powder in an extruder, and the resulting strands are pelletized to produce a carbon fiber-reinforced molding material.

A commonly used method is to injection mold the carbon fiber-reinforced molding material thus obtained to obtain a product.

Conventionally, in order to obtain a carbon fiber-reinforced molded product, it was necessary to melt and knead the thermoplastic resin and carbon fiber chops in an extruder in advance to uniformly disperse the carbon fibers in the matrix. However, this caused the carbon fibers to break (shorten fibers) during melt-kneading in an extruder, resulting in a significant decrease in mechanical properties, electrical conductivity, etc. Additionally, since the carbon fiber reinforced molding material is manufactured using an extruder, productivity is low.

[The problem that the invention aims to solve]

The purpose of the present invention is 1. In the production of carbon t1iIiw, reinforced shaped articles, carbon fiber chops and thermoplastic resin are directly bonded to each other without using a carbon fiber reinforced molding material obtained by melt-kneading in an extruder. It is an object of the present invention to provide a carbon fiber chop that can be injection molded with the carbon fibers to obtain a product with a long carbon fiber weave length and excellent physical properties.

At this time, if the convergence of the fiber chops is insufficient, the chops will open and clog the supply port of the injection molding machine, making it impossible to uniformly control the carbon fiber content in the carbon fiber reinforced molded product. In addition, there are times when the raw material itself cannot be used and molding cannot be performed.

Therefore, in order to directly injection mold carbon fiber chops,
It is necessary to impart high cohesiveness to the fibers and to prevent the opening of the chops from becoming fat.

On the other hand, since the extrusion process is omitted and the carbon fiber chopped thermoplastic resin is directly injection molded, the reinforcing fibers must be easily and uniformly dispersed in the plasticization zone of the injection molding machine. Poor dispersion of carbon fibers in the resulting molded product will result in poor appearance.
Physical properties vary widely and strength is inferior. Therefore, it is necessary to use a sizing agent with excellent dispersibility.

In this way, since the fiber chop is directly injection molded,
The chop must have both high convergence and excellent dispersion.

In addition, when manufacturing carbon fiber reinforced molded products, in the conventional method, it is necessary to once melt and knead the carbon fibers in an extruder to improve the dispersion of the carbon fibers, which inevitably shortens the fiber length of the carbon fibers and reduces the required mechanical strength. It was difficult to obtain the physical properties of conductivity.

Therefore, there has never been a fiber chop that satisfies both of the long fiber length of the carbon fibers in the molded article and the excellent dispersibility.

[Means to solve the problem]

The present inventors have solved the conflicting problem of the focusing power and dispersibility of chopping, and have achieved high focusing ability (c) that allows short carbon fibers to be directly formed, and that they can be uniformly dispersed in the 7-tricks.
The present invention was developed as a result of research into a sizing agent that maintains long fiber length and has excellent physical properties.

That is, the present invention is a carbon fiber chop characterized in that carbon fibers are bundled with a polyurethane resin content of 0.1 to 100% by weight.

The polyimine resin used as the sizing agent and L7 in the present invention preferably has a molecular weight of 11,500,000 and is solid at room temperature. Examples of such polyimine resins include polyethyleneimine, polyethyleneimine,
polybutyleneimine, 1.1 dimethylethyleneimine,
1.1-dimethyl-2methylethyl-imine, 1゜1
-dimethyl-2propylethyleneimine, N-acetylpolyethyleneimine, N-probionylpolyethyleneimine, N-7'tyrylpolyethyleneimine, N-valerylpolyethyleneimine, N-hexanoylpolyethyleneimine, Examples include polyamines such as N-stearoyl polyethyleneimine and polybenzaldoimimine, derivatives thereof, mixtures thereof, and modified and copolymerized polyene resins. Particularly preferably,
Examples include polyethyleneimine and N-probionyl polyethyleneimine.

In the present invention, as a sizing agent for the carbon fiber assembly, polyimine resin is added to the carbon fibers in an amount of 0.1 to 100% by weight, preferably 2.
Contain ~6%. If this amount is less than 0.1 weight, the convergence will be insufficient and the fluidity in the Horapal supplied to the injection molding machine will be poor, so the carbon fiber content in the molded product will not be uniform and the chops will open. Then, the supply port gets clogged and molding cannot be performed.

Moreover, if it exceeds 100 weight, problems will arise in the mechanical properties such as tensile strength and bending strength of the molded product obtained using it.

The carbon fiber chop of the present invention (゛, bulk density is 300g/
42 or more, preferably 350g/42 or more.

If the bulk density is less than 300g/ff, it cannot be said to be completely concentrated and the fluidity in the supply popper of the injection molding machine will be poor, resulting in poor supply to the injection molding machine scruff and - and damage to the matrix resin. Uniform dispersion occurs, making continuous production difficult and making it impossible to fully achieve the purpose of the present invention.

The method for manufacturing carbon fiber chops of the present invention involves first continuously immersing an appropriate number of continuous carbon fiber bundles in a polyimine resin solution with a concentration of 0.5 to 10% by weight, and then soaking the carbon fibers at 200''C. The carbon fiber chops bundled with polyimine resin are then obtained by cutting into desired lengths, for example, 1 to 10 mm.

Furthermore, the carbon fiber-reinforced molded product can be produced by supplying the carbon fibers and thermoplastic resin of the present invention into the hopper of an injection molding machine, melting them in the plasticizing cylinder, and injecting them into the injection mold. It is obtained by cooling and solidifying and taking out the molded product. In order to make the molded product more uniform, preliminary mixing may be performed using a high-speed tumbler or a mixer or the like before molding with an injection molding machine.

In the present invention, the carbon fiber used as a material is not particularly limited, and there are various known carbon fibers, such as carbon fibers manufactured using rayon, polyacrylonitrile, pitch, lignin, hydrocarbon gas, etc., and graphite fibers. Any material can be selected from among fibers and metal-coated carbon fibers obtained by coating these fibers with metal.

Examples of matrices used to produce fiber-reinforced molded products using the carbon fiber chop of the present invention include polycarbonate, polyamide, polyester, polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyether/etherketone, polyolefin, Examples include thermoplastic resins such as polyphenylene sulfone, acrylic resins, and styrene resins, with polycarbonate resins being particularly suitable.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

The methods for measuring various physical properties are as follows.

<Bulk density of carbon fiber chops> After filling a 50 d measuring cylinder with carbon fiber chops, apply vertical impact vibration to the graduated cylinder, and calculate by dividing the weight by the volume of the carbon fiber chops that has reached equilibrium.

<Dispersibility of carbon fiber chops> The dispersibility of carbon fiber chops is as follows:
Based on the appearance observation of the plate-shaped molded product of ms, the quality of dispersibility is evaluated in three grades from 1 to 3. 3 is the best value.

<Fiber length of carbon fiber in molded product> Place the molded product in a crucible and bake the resin in an electric furnace. The remaining carbon fibers are magnified with a microscope, an image is captured with a camera, and the length of the carbon fibers is measured with an image processor. The number of fibers to be measured is about 1,500, and the average value of the fibers is calculated as the fiber length of the carbon fiber.

Mechanical properties> The mechanical properties of the short carbon fiber reinforced molded product are as per JISK681.
Measured according to 0.

<Conductivity> The conductivity of the short carbon fiber-reinforced molded product is determined by applying a conductive silver paste on a plate-shaped molded product obtained in exactly the same manner as the dispersion of the carbon fiber chops described above in parallel squares of 50 squares on each side. It was applied on two sides, and the electrical resistance value between them was defined as the surface resistivity (Ω).

Example 1 Evomin P-1000 (manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd., polyethyleneimine, molecular weight approximately 70,000) was dissolved at 5% by weight in water, and carbon fiber (Hycarboro 712kf, manufactured by Asahi Nippon Carbon Fiber Co., Ltd.) was dissolved in this solution. The rovings were continuously dipped to adhere 5% by weight of polyethyleneimine to the carbon fibers, and dried with hot air at 140°C for 5 minutes to obtain strands. The strand was cut into a length of 6 mm using a guillotine cutter manufactured by Onouchi Seisakusho.
Bulk density 380g/j! Got a chop.

10 parts by weight of this chop and 90 parts by weight of polycarbonate resin were triblended using a V-type mixer.

A test piece for evaluation was obtained from this triblend product using a Toshiba Model 1575E injection molding machine. The results are shown in Table 1.
The dispersibility evaluation of the obtained molded product was 3, and the fiber length was 0.3.
5 mm, tensile strength was 1500 kg/c4°, and surface electrical resistance was 2×10 3 Ω.

Comparative Example 1 In Example 1, the concentration of Evan P-1000 was changed to 0.
05 layered and attached to carbon fiber! Carbon fiber chops were obtained under exactly the same conditions as in Example 1, except that the amount of carbon fiber was 0.05% by weight.

The bulk density of the obtained carbon fiber chop was 200 g/4. Furthermore, when the injection molding machine was in operation, the supply port was clogged and raw materials were not supplied, resulting in frequent interruptions in operation. The dispersibility evaluation of the obtained molded product was 1, and the tensile strength was 1.
100 kg/crl, surface electrical resistance is 1500X
It was 103Ω.

Comparative Example 2 A triblend obtained in the same manner as in Example 1 was kneaded and extruded using a twin-screw extruder equipped with a screw feeder, and the resulting strands were pelletized to obtain a fiber-reinforced material. Next, a test piece for evaluation was obtained using a Toshiba Model 1575E injection molding machine. The dispersibility evaluation of the obtained molded product was 3, the fiber length was o, 23 mm, and the tensile strength was 1300 kg.
/cU, and the surface electrical resistance was 500×10 3 Ω.

Comparative Example 3 Carbon fiber chops were obtained under the same conditions as in Example 1 except that a solution of bisphenol A type epoxy resin with a molecular reservation of 1800 dissolved in methyl ethyl ketone was used instead of the aqueous solution of Evo-Yumin. The results are shown in Table 1.

Comparative Example 4 Carbon fibers were prepared under exactly the same conditions as in Example 1, except that an alcohol-soluble nylon solution manufactured by Teikoku Kagaku Sangyo Co., Ltd. (grade name: F3350E, methoxymethylated nylon resin) was used instead of Evomin. Got the chop. The results are shown in Table 1.

Comparative Example 5 Carbon fiber chops were obtained under the same conditions as in Example 1, except that polyvinylpyrrolidone (trade name Nilviscol 90) manufactured by BASF Japan Co., Ltd. was used instead of Evomin. The results are shown in Table 1.

Comparative Example 6 Carbon fiber chops were obtained under the same conditions as in Example 1, except that instead of Evomin, a solution of polyurethane resin (Grisbon 6216S L) manufactured by Dainippon Ink and Chemicals Co., Ltd. dissolved in methyl ethyl ketone was used. . The results are shown in Table 1.

Table 1 (blank below) Note) Used 7F Wax: Pc (blank below) Example 2 Example 1 except that polybutylene terephthalate resin was used instead of the polycarbonate resin used in Example 1.
Carbon fiber chops were obtained under the same conditions. The results obtained are shown in Table 2.

Comparative Examples 7 to 10 Carbon fiber chops were obtained under the same conditions as Comparative Examples 3 to 6, except that polybutylene terephthalate resin was used instead of polycarbonate resin. The results obtained are shown in Table 2.

(Space below) (4) Matrix used: PBT Example 3 A carbon fiber chop was obtained under the same conditions as in Example 1, except that polyphenylene oxide resin was used instead of the polycarbonate resin used in the example process. The results obtained are shown in Table 3.

Comparative Examples 11 to 15 Carbon fiber chops were obtained under the same conditions as Comparative Examples 3 to 6 except that polyphenylene oxide resin was used instead of polycarbonate resin. The results obtained are shown in Table 3.

(Hereinafter in the margin) Matrix used: polyphenylene oxide (hereinafter in the margin) [Effects of the invention] The carbon fiber chops bundled with the Bolikun resin of the present invention have excellent binding properties and dispersibility that can be directly injection molded. , when producing a carbon fiber reinforced molded product using this, the chop has good fluidity in the injection molding machine hopper, is stably supplied to the injection molding machine screen 1-, and is also used in the plasticizing cylinder. It is easily dispersed, and the appearance of the obtained molded product is also very good.

Therefore, the extrusion process can be omitted when producing carbon fiber reinforced molded products, and productivity is greatly improved. Furthermore, since the carbon fiber chop can be directly injection molded, the length of the carbon fibers in the resulting molded product is maintained long and exhibits excellent mechanical strength and electrical conductivity.

Claims (1)

[Claims] 1. A carbon fiber chop characterized by being made by bundling carbon fibers with a polyimine resin content of 0.1 to 10% by weight.