JPS63165580A - Surface electrolytic 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] [Industrial Application] The present invention relates to a surface electrolytic treatment method for carbon fiber. [Prior Art] Carbon fiber, which has recently attracted attention as a structural material, can be used in various matrices. For example, it is used as a composite material with each of the 11 resins, such as thermosetting resins such as epoxy resins, unsaturated polyester resins, and phenol resins, and thermoplastic resins such as polyamide resins, polyacetal resins, and polysulfone resins.

Normally, surface treatment of carbon fibers is required to improve the adhesion between carbon fibers and these resins, and various methods have been proposed. Among these, the so-called electrolytic surface treatment method, in which carbon fibers are energized in an aqueous electrolyte solution such as sodium hydroxide, potassium hydroxide, sulfuric acid, or phosphoric acid, is considered useful from an economic standpoint. These are known from Publications No. 40//9 and Hakokosho 5R-Aozz.

Among these electrolytes, sodium hydroxide in particular has high conductivity, and therefore 1! It is widely used because it has the advantage that solution processing can be performed at low voltage and in a short time.

[Problem that the invention seeks to solve]

However, sodium hydroxide tends to remain in carbon fibers after electrolytic treatment, and although it is usually removed by washing with water, it is said to be difficult to completely remove, and the removal of residual electrolyte may be insufficient. , 7+2. The heat oxidation resistance of carbon fiber is poor. Problems have been pointed out, such as deactivation of the catalyst used to cure the resin matrix, resulting in poor curing, and deterioration of the physical properties of the resulting bonding material. Furthermore, there is the problem of how to treat the large amount of wastewater that comes out of the washing process.

According to the prior art, various methods have been proposed for removing the tFM substance remaining in carbon fibers after such electrolytic treatment, but these methods cannot necessarily be said to be favorable.

For example, Tokko Sho Data 2 Data 01-1! The publication describes a method in which carbon fibers containing an electrolyte solution are passed through a cathode and/or a cathode in a cleaning solution to remove the electrolyte.

However, in this method, in addition to applying electricity for electrolytic treatment, it is necessary to apply electricity further for removing the electrolyte, which has the disadvantage of increasing power consumption.

In addition, in a method in which carbon fibers are subjected to electrolytic surface treatment and then dried with hot air, Hokaisho To-4toer Publication No. 1 describes that in the electrolytic surface treatment process, carbon fibers are dispersed or decomposed and disappear as melted snow during drying. 1 by using something that
A method of reducing residual solute deposition is disclosed. However, this method also requires a washing process, treatment of washing wastewater, and in some cases treatment of decomposed gas during drying, and decomposition at high temperatures requires extra energy, making it uneconomical. Not.

In addition, Kimiaki Sae! ! - Ori J'da Publication describes ammonium bicarbonate, etc., which can be used as snow melt when electrolytically surface-treating graphite fibers, and can be heated at temperatures below 250°C and decomposed to produce gaseous products. Although a method has been disclosed in which the residual electrolyte is removed from the fiber by heat-treating the electrolytically treated fiber at a temperature of 200° C. or less using an ammonium compound of 35 to 60 When heated to ℃, it decomposes into ammonia, carbon dioxide gas, and water.Ammonia is a highly corrosive and highly toxic substance, so it is necessary to take measures to prevent corrosion on equipment, and to take environmental measures for exhaust gas. This poses problems in terms of equipment and cost, such as having to take steps to do so.

From this point of view, Akira Narukai Turf o 07 t a
``Y'''' proposes a method of energizing carbon fibers in water that does not substantially contain electrolytes, such as river water, well water, industrial water, or tap water. However, this method does not require a water washing process and has the advantage of not emitting harmful gases during drying.
H4+, Na+, K+, Ca2+, Mg2+, aco3
-1C'l-1s04'- There are temporal or seasonal changes in the concentration and type of ions, and the electrical conductivity of water changes accordingly, so the surface electrical debris of cryocarbon fibers This causes variations in the treatment effect, and therefore carbon fiber and 7
The problem was that the adhesion with the Trix resin varied, causing quality problems.

For example, if we express the above fluctuations in electrical conductivity for a certain industrial water, the fluctuations with respect to the average value are ±6θ to 10% over time (2 g hours), and the fluctuations with respect to the average value are seasonal (1 year). is reported to be ±7Q to 0%. In the first report, M! Not only electrical conductivity, but also total sharpness,
It has also been shown that iron content and oxygen consumption vary greatly over time and season [author: Shizuo Suzuki;
Industrial water treatment, July 1920! Published by Uchida Rokakuba Shinsha, see pages Z to 2r [Kth means for solving the reference quantity problem] Therefore, the present invention Nagisa et al. solved the problems of the conventional technology regarding the surface electrolytic treatment of carbon fibers. We conducted research to find an industrially advantageous method.

In particular, in the case of an aqueous electrolyte solution with a concentration of several orders of magnitude, which is commonly used in conventional technology, there is the problem of removing electrolyte adhering to carbon fibers, and the electrical conductivity of the aqueous electrolyte solution is extremely higher than that of carbon fibers. big. The current flowing between the carbon fiber (anode) running through the surface electrolytic treatment device and the cathode reaches an excessive value at the inlet of the device, thereby considerably reducing the strength of the carbon fiber.

On the other hand, in the case of a low-concentration electrolyte aqueous solution, since the absolute value of the concentration is small, it has been found that fluctuations in the concentration have a large influence on the electrolytic surface treatment effect of carbon fibers.

As a result of conducting extensive research focusing on the above points, we found that carbon fibers were produced by using an aqueous solution prepared by adding an inorganic salt to water that does not substantially contain electrolytes to a certain low concentration as an electrolyte solution. By subjecting it to surface electrolytic treatment, we found that it is possible to easily and economically obtain carbon fibers that have excellent adhesion to matrix resins, high strength and interlaminar shear strength, and have very little variation in quality. Completed the invention.

That is, the purpose of the present invention is to provide high strength and glabellar shear strength with excellent adhesion to matrix resin, and to reduce quality fluctuations by employing a simple and economical method for surface electrolytic treatment of carbon fibers. The purpose of the present invention is to provide a surface electrolytic treatment method for obtaining bare fibers with very little amount of oxidation. The purpose is to add inorganic salts to water that does not substantially contain electrolytes as an electrolyte solution to increase the inorganic salt concentration to 10 to 10θ0.
(This can be achieved more easily by setting the range of p, adjusting the range of variation with respect to the concentration setting value to less than θ, and subjecting the carbon fibers to surface electrolytic treatment using a water running solution.

The present invention will be explained in detail below.

The carbon fibers used in the present invention can be manufactured from various known mild materials, such as coal tar pitch, petroleum pitch, liquefied coal, polyacrylonitrile, cellulose,
Manufactured from polyvinyl alcohol etc., 1ooo~20
Carbon fiber after carbonization treatment at about 00C or 2000C
Any fiber that is graphitized at temperatures above ℃ or higher and then graphitized can be used.

1! used when surface electrolytically treating these carbon fibers. The solute solution is prepared by adding inorganic salts to water that does not substantially contain electrolytes, setting the inorganic salt concentration from a range of 10 to 1,000 p%, and adjusting the fluctuation range f from the concentration setting value to -20 cm or less. It is a hydrotactic solution.

Specifically, water that does not substantially contain electrolytes is water that substantially contains electrolytes such as acids, alkalis, S salts, and organic salts, such as demineralized water, distilled water, and condensed water. , ion exchange treated water, etc. Since this water is the basis for adjusting the concentration in the electrolyte solution, it is desirable that its electrical conductivity be as low as possible. The electrical conductivity of this water is 1
0 μB/car or less, and the electrolyte concentration is preferably 10 P or less. If the electrical conductivity of this water exceeds 10 μ8/F or the concentration of electrolyte exceeds 10 pp, this water becomes an inorganic salt-modulated base, to which an inorganic salt is added to Even if an attempt is made to adjust the concentration, it may be difficult to keep the concentration to such a low level, or it may cause concentration fluctuations.

As the inorganic salt added to water that does not substantially contain electrolytes, seven or a mixture of two or more of alkaline earth metal or alkali metal halides, sulfates, or phosphates are used. Magnesium chloride, sodium chloride, potassium chloride, calcium sulfate, magnesium sulfate, sodium sulfate, potassium sulfate,
Calcium phosphate, magnesium phosphate, sodium phosphate, potassium phosphate, and mixtures thereof are used.

In the present invention, instead of inorganic salts, it is not possible to use acid or alkaline salts such as organic salts. When using electrolytes such as acid or alkali, carbon fiber can be made easily! The running electrolyte that adheres to the fibers is difficult to remove even when washed with water, and is likely to cause deactivation of the resin curing catalyst when used as a composite wing with a matrix resin.

Furthermore, even if an organic salt is used as an electrolyte, the adhesion with the matrix resin cannot be sufficiently improved, and ■ LBB (interlaminar shear strength)
It is difficult to hope for the effects of the present invention, as only low values can be obtained.

Add inorganic salts to virtually electrolyte-free water! ! I
It is undesirable that the concentration of the inorganic salt in the aqueous solution is neither too low nor too high. If this concentration is too low, high voltage will be required to anodize carbon fibers and fibers due to the low electrical conductivity of the aqueous solution, which may pose an operational hazard. It becomes necessary to unnecessarily increase the capacity of the surface treatment device by oxidation.On the other hand, if this concentration is too large, the electrical conductivity of the aqueous solution is high, causing current distribution in the direction of the carbon fibers in the surface treatment device.
If the current density is abnormally high near the entrance of the surface treatment device, it may cause deterioration of the strength of the carbon fibers, and it becomes necessary to wash away inorganic salts adhering to the carbon fibers. The concentration of the inorganic salt in the aqueous solution from the Hiko point is usually in the range of 10-10θO, preferably in the range of 100 to zooP.

The concentration of the inorganic salt in the aqueous solution may be arbitrarily selected from the above range depending on the properties of the carbon fibers to be subjected to the surface electrolytic treatment, the required properties of the carbon fibers, the intended use, etc.

In addition to selecting the inorganic salt concentration in the aqueous solution, it is important to control the inorganic salt concentration in the aqueous solution to a constant value of 120% or less without greatly changing it during the electrolytic surface treatment operation of carbon fibers. That's true. In other words, in the conventional technology, 1!
The electrolyte concentration in the aqueous solution in the present invention is relatively high, in other words, the inorganic salt concentration is small, so the fluctuation in the value is caused by the surface of the carbon fiber. Sensitive to the electrolytic treatment effect. Therefore, it is necessary to control the total inorganic salt concentration in the aqueous solution to a constant value, preferably with a fluctuation range of 10 - or less, as described above. This includes, for example, a sensor that detects the inorganic salt concentration in an aqueous solution or the electrical conductivity of an aqueous solution in a surface electrolytic treatment device, and a sensor that detects the inorganic salt concentration in an aqueous solution or the electrical conductivity of an aqueous solution, and, corresponding to the detected value, water that does not substantially contain electrolytes, such as demineralized water, or a predetermined concentration. The purpose can be easily achieved by attaching a supply tank or the like for supplying an aqueous solution with a slightly higher inorganic salt concentration.

In the present invention, as mentioned above, it is important to once create water that does not substantially contain electrolytes and use it as a base. Although it is possible to control industrial water, river water, well water, etc. to a predetermined electrical conductivity, fluctuations in other physical properties (total hardness, iron content, oxygen consumption 1, etc.) are unavoidable, and the anodization of the present invention Therefore, it is unsuitable as an electrolyte, and consistent effects cannot be expected.

Other conditions for anodizing include pressure, current density, speed, time, temperature, etc.These also vary depending on the type of carbon fiber, processing speed, degree of processing, etc. The heavy pressure is l~tOV, the current density is carbon W fiber/cm drawing θ, l~100mA, and the amount of current is 12 carbon fibers O0σj~! 00 coulombs, time from several seconds to several minutes, and temperature from normal temperature to rO<0>C.

〔Example〕

The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to the Examples unless it goes beyond the gist of the present invention.

(Example 1) Thread diameter 10 obtained by firing pitch fiber at λ, 300°C
μ carbon9. Using the equipment f11 shown in Figure 1 (material of anode ropes 3, 3' and cathode plate: graphite, length/m'), 3,000 tows of Usui were continuously used under the following conditions. Surface treated.

Electric jlJ [: Demineralized water (back air conductivity - μs/sub, inorganic salt concentration j p) K (1!ao12 @ J H2O added to CaC], 2 Co! Hydrotactic solution prepared to a concentration of 0p).

N Kiden Fudo is 37! A sensor that measures the electrical conductivity in the electrolyte during operation, a demineralized water supply system and CaCl2! 00 pp aqueous solution (1:! in demineralized water!
AC12 and COH20 were added to make a m-modulated water running solution) and automatically controlled by a thread running from the supply system.

Voltage: ? V Temperature: 30℃ Crucible flow: /j
mA time: 6θsec
-f): /, J' C/? -CF thread
The tensile strength of the carbon fiber resin-impregnated strands was measured at -16T in accordance with J Engineering 5-R-760/.
LeS (interlaminar shear strength) was measured according to ASTM D-23at, and the results #a are shown in Table 1.

(Example-) CaCl2 dli degree/θθ as an electromagnetic liquid v! The test was carried out in the same manner as in Example 1, except that the 4-size precipitating solution was used and the voltage was set to 0.

The resin-impregnated strand tensile strength and IL8B of the obtained nine carbon fibers were measured in the same manner as in Example 1, and the results are also listed in Table 1.

(Example: An aqueous solution prepared by adding demineralized water K MgSO4.H2O to a concentration of Mg5o4 2!Oppe was used as the electrolyte, and the voltage was set to r V %CI!LO12j 00
Alternative to fpa aqueous solution supply system F) K Mg804!
The procedure was carried out in the same manner as in Example 1 except that the 0θ-aqueous solution supply system was used for automatic control.

The tensile strength and IL8B of the carbon fibers impregnated with resin were measured in the same manner as in Example 1, and the results are also listed in Table 1.

(Comparative Example 1) The tensile strength and mechanical strength of a carbon fiber resin-impregnated strand without surface electrolytic treatment were measured in the same manner as in Example 1, and the results are also listed in Table 1.

Comparative Example 1 is a blank for the example, and it is clear from Table 1 that although the strength and tensile strength are slightly higher, the strength of the IIS is smaller, and the adhesion of the carbon fibers to the matrix resin is better. It turns out that it is.

(Comparative Example C-2) The same procedure as in Example 1 was carried out except that filtered water (summer, winter), industrial water, river water (summer, winter), and well water were used as the electrolytic solution for several months. The electrical conductivity of each dissolved solution, the tensile strength of the resin-impregnated carbon fiber strands, and the ILS date were measured in the same manner as in Example/ for several months, and the lowest and highest values were taken as the fluctuation range. Also listed in Table 1.

As is clear from Table 1, the electrical conductivity values of these waters vary depending on the type and season, and the types of dissolved ions are also diverse, so overall the tensile strength is Even though the tensile strength and rL8B were low, and the tensile strength was relatively high, the tensile strength was quite low, and a carbon fiber with well-balanced properties could not be obtained. Also, comparative example-2~
It can be seen that in No. 7, the range of variation in electrical conductivity is large, but the range of variation in carbon fiber properties accompanying this is also large.

〔Effect of the invention〕

According to the present invention, after the surface electrolytic treatment, there is almost no need to wash the carbon fiber with water, and a stable quality carbon fiber with high interlaminar shear strength is produced with little strength loss and high interlaminar shear strength! # Can be built. This high-performance carbon fiber is extremely useful for various fiber-reinforced composite materials.

[Brief explanation of the drawing]

FIG. 1 shows an example of a surface electrolytic treatment apparatus used in the present invention. l: Carbon fiber co:'M, decomposition tank liquid tank 3': Anode roller lag: Cathode plate Applicant: Mitsubishi Chemical Industries, Ltd. Representative Patent attorney For necessity - (7 others) A1 Figure

Claims (6)

[Claims] (1) In a method of immersing carbon fibers in an electrolyte solution and performing surface treatment by electrolysis using the carbon fibers as anodes, an inorganic salt is added to water that does not substantially contain electrolyte as the electrolyte solution, Inorganic salt concentration 10-1000ppm
Set from the range of 20% of the variation range for the density setting value.
A method for surface electrolytic treatment of carbon fibers, characterized by using an aqueous solution prepared as follows. (2) The electrical conductivity of water that does not substantially contain electrolytes is 10
The surface electrolytic treatment method for carbon fibers according to claim 1, wherein the surface electrolytic treatment is μs/cm or less. (3) The concentration of electrolytes in water that does not substantially contain electrolytes is 1
The surface electrolytic treatment method for carbon fibers according to claim 1, wherein the surface electrolytic treatment method is 0 ppm or less. (4) The inorganic salt is one or two of alkaline earth metals or alkali metal halides, sulfates, or phosphates.
The method for surface electrolytic treatment of carbon fibers according to claim 1, wherein the method is a mixture of more than one species. (5) The surface electrolytic treatment method for carbon fibers according to claim 1, wherein the inorganic salt concentration is set in the range of 100 to 500 ppm. (6) The surface electrolytic treatment method for carbon fibers according to claim 1, wherein the variation range with respect to the concentration setting value is 10% or less.