JPS59100762A - Surface treatment of carbon fiber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a method for surface treatment of carbon fibers.

Composite materials made of carbon fiber and various resin matrices are used in aerospace structural materials, automobiles, industrial machinery parts, sporting goods, etc. due to their outstanding properties such as light weight, high strength, and high elasticity. However, when carbon A...P fibers are used as these composite materials, the strength of carbon 1f, N#(li) itself is important, but it also improves the adhesion with matrices such as other resins, and increases the strength of the composite material. , it is extremely important to improve interlaminar shear strength.

In order to improve this adhesion, methods such as vapor phase oxidation, liquid phase oxidation, and electrolytic oxidation of the carbon fiber surface have been proposed. Among these, an electrolytic treatment method in which carbon fibers are energized in an electrolyte aqueous solution such as sodium hydroxide, sulfuric acid, or phosphoric acid is considered to be useful.
It is disclosed in Japanese Patent Publication No. 48-12444. However, the disadvantage of electrolytic surface treatment is that the electrolyte adheres to the carbon fibers, which adversely affects subsequent processing steps. In other words, the adhering ions cannot be completely removed by washing with water for a short time, and recently, for example,
A method using a decomposable electrolyte has been proposed as seen in Japanese Patent Application Laid-open No. 91 or 157697/1983. However, this method also requires a washing process, and it is necessary to treat washing wastewater and, in some cases, to treat decomposed gas during drying.Additionally, decomposition at high temperatures requires extra energy and generates dust. At present, this method is not necessarily satisfactory in terms of product quality and economic efficiency, such as being uneconomical.

Under such circumstances, the present inventors developed a carbon fiber matrix.
As a result of extensive research into a surface treatment method that has excellent adhesion to IJ Lux resin, is economical, and has excellent productivity, the present invention has been achieved.

That is, the present invention provides a method for surface treatment of carbon fibers, which is characterized in that carbon fibers are continuously supplied as anodes into water substantially free of electrolyte, and electricity is passed between the carbon fibers as anodes and the cathodes in the water. It is in.

According to the method of the present invention, carbon fibers having high strength and interlaminar shear strength with excellent adhesion to matrix resins can be obtained, and can be usefully used in applications such as aerospace structural materials and automobile parts. Furthermore, since the method of the present invention does not substantially use an electrolyte, there is no need for a washing step, no need to treat washing waste water, and the process is extremely simple and generates harmful gases during drying, which improves productivity and economic efficiency. However, it is an extremely excellent and useful process, and the filli value for nib j'14 is large.

The method of the present invention requires only a tank containing water (current-carrying tank) equipped with a copper plate and a graphite plate as cathodes. This is an extremely simple method in which the carbon fibers that come out of the energizing tank pass through a water squeezing roller and are immediately coated with a sizing agent to form a product. .

In the present invention, the water used in the energized tank is water that does not substantially contain electrolytes, and! ' = Includes water from ordinary rivers with a small amount of suspended solids, well water, industrial water, soft water partially treated with industrial water, tap water, etc.

Furthermore, in order to fully achieve the purpose of the present invention, NH4+ Na +, which is the main ion contained in the water, +,
Ca”, My”, HCO;”, Ct + SO
, ' + is more preferably 500 mV t or less.

In the method of the present invention, the method of energizing the continuously running carbon fiber glue as an anode may be carried out in a contact manner, for example through a carbon roller, or by a conventionally known method such as non-contact energization. good. Further, the 51 electrifications may be performed at two locations before and after the energizing tank, but may be performed at one location or three or more locations depending on the case.

In the method of the present invention, the amount of air to be added varies depending on the type of carbon fiber, processing speed, degree of processing, etc., but usually the current is about 10 mA to 5 A 4
'4 with n'i-te '1l-i; pressure is about 1.
5 ■ 200V, 0. If it is less than this, it will not be possible to improve the contact 2'i with the matrix resin and the object of the present invention will not be met. In addition, if it is more than this, it is not practical because just adding extra energy to the carbon% Q'i fiber causes damage to the carbon fjλ navy blue.

Next, the present invention will be explained by examples, but the present invention is not limited thereto.

Example 1 Carbon fiber obtained by finally firing acrylic stock fiber at 13500c (strength ass Ky/mr!, elastic modulus 2
3.5 T/mrr1', single 19. Diameter 7゜5
μ) using a bundle of 12,000 filaments at a yarn speed of 1.
The surface was treated continuously for 5 ml/min.

Fish @ Pour industrial water into a 1 m long energized tank with frf & electrode plates, and add 1 m of carbon via carbon rollers before and after this energized tank! , t=Ill is used as an anode, graphite in the current-carrying tank is used as a cathode, and a current of 5 100 mA is applied/c:. The carbon fibers were squeezed with water, then coated with a conventional sizing agent and dried. The tensile strength of the carbon fiber thus prepared is 383 Kg/m i and the elastic modulus is 23.5 T/m i
It was mrII'. Furthermore, in order to check the adhesion with the resin, a unidirectional prepreg was prepared by impregnating an epoxy resin (Epicor) 82B (100 parts by weight) and boron trifluoride monomethylamine (3 parts by weight) in a methyl ethyl ketone solution. This unidirectional prepreg is laminated in one direction and 130
'CX 10 minutes, 175℃ x 2 hours to heat up to v1,
A flat composite village with a fiber content of 60 ml was created. Then, the interlaminar shear strength (1, L) was measured using an Instron.

S, S) were rectangularly measured using the three-point bending short beam method under the condition of L/D=4. The resulting convodine had no voids and was cured satisfactorily, with an ILSS of 8.6 Kg/rnrl.
For comparison, carbon wafer 4.1 without surface treatment was used.
A similar experiment using fibers yielded a good value of 6.1Kf/n.
111j was clearly found to be more adhesive than lni'.

Example 2 Using a method similar to Example 1, the tensile strength was 392 h/m I+12 as carbon water W・ef, and the elastic modulus was 26.5 T/
Using mn1', and using soft water in the energizing tank lol
I tried it. The tensile strength of the surface-treated carbon fiber is 395 knots/111 to', and the elastic modulus is 26.4 T/mn? So, 1
．． L, S, and S were 8.4 Kg/m (), which was clearly superior to the value of 5.9 Ky/mn without surface treatment.

Comparative Example Using the carbon fiber of Comparative Example 1, in the same manner,
Electrolytic treatment was performed with a 5-module aqueous solution using caustic soda and ammonium carbonate as electrolytes in a 4"+'l current. The two types of carbon fibers obtained were used to create a unidirectional brig leg and a composite material by the method of Example 1. Caustic soda The sample treated with the liquid caused curing failure and a good molded product could not be obtained. Also, samples using ammonium carbonate tended to have voids in the molded product, and the ILSS was measured to be 6.5 to 7. 6
1 (7/rr+ro), but one good data was not recorded.It is believed that these are the negative effects of IW quality addition 71'f.

In view of the above embodiments, the present invention has a matrix ((
I] It can be seen that this is a simple and excellent method that improves the contact with fat and does not require a water washing step, and has excellent pileability.

Claims (1)

[Claims] A method for surface treatment of carbon fibers, characterized in that carbon fibers are continuously supplied as anodes into water that does not substantially contain electrolyte, and electricity is passed between the carbon fibers as anodes and the cathodes in the water.