JP6893638B2 - Surface-treated carbon fiber, its manufacturing method and carbon fiber reinforced resin composite - Google Patents

Description

The present invention relates to a surface-treated carbon fiber and a method for producing the same, which can be used for a carbon fiber reinforced resin composite. More specifically, the present invention relates to carbon fibers capable of imparting affinity to a resin having a low affinity for carbon fibers, and a method for easily producing such carbon fibers.

Carbon fiber reinforced resin composite (CFRP) has advantages such as light weight and excellent strength, so it is used as a molding material in a wide range of fields such as aerospace, transportation machinery (automobiles, ships), civil engineering and construction, industrial equipment, and sports. Has been done. About 90% of the resin used as a matrix in CFRP is epoxy resin. In the glass fiber reinforced resin composite (GFRP), unsaturated polyester resin and vinyl ester resin are often used along with epoxy resin, but in CFRP, unsaturated polyester resin and vinyl ester resin are hardly used.

The main factor is the low adhesion between carbon fiber and unsaturated polyester resin and vinyl ester resin. Therefore, even if the resin composite is produced in the same manner as the glass fiber, sufficient strength cannot be obtained because peeling is likely to occur at the interface between the carbon fiber and the resin. However, unsaturated polyester resins and vinyl ester resins have a faster molding cycle than epoxy resins and can reduce manufacturing costs. Therefore, various studies have been conducted on applying these resins to CFRP.

As an attempt to improve the adhesion between carbon fiber and unsaturated polyester resin and vinyl ester resin, a method of oxidizing carbon fiber to generate hydroxyl groups on the surface and adhering resin etc. as a sizing agent on it has been actively studied. (Patent Documents 1 to 4 etc.). However, this method has not been sufficiently successful.

It has also been proposed to modify the surface of carbon fibers by metal plating the carbon fibers (Patent Documents 5 and 6). Further, several methods have been proposed for the pretreatment of the plating (Patent Documents 7 and 8).
However, in each case, the carbon fiber processing process is complicated, and it cannot be said that it is sufficient to achieve a reduction in the production cost of the complex.

Japanese Patent No. 3860169 Japanese Patent No. 3971664 Japanese Patent No. 4856292 Japanese Patent No. 4420712 Tokukousho No. 48-25065 Japanese Unexamined Patent Publication No. 58-71954 Special Publication No. 62-15637 Japanese Unexamined Patent Publication No. 3-199666

An object of the present invention is a surface-modified carbon fiber that can also be used for a carbon fiber reinforced resin composite (CFRP) using an unsaturated polyester resin or vinyl ester resin having insufficient adhesion to carbon fibers as a matrix. , And a method for easily producing the carbon fiber thereof. Another object of the present invention is to provide a carbon fiber reinforced resin composite containing the carbon fibers.

The present invention provides the following.
[1] The carbon fiber surface is contacted with an aqueous solution containing ^{Sn 2+ and then with an aqueous solution containing Pd 2+} , or by contacting the carbon fiber with a colloidal solution containing ^{Sn 2+} and Pd ^2+. Step 1 of adhering tin and palladium to the carbon fiber surface, and step 2 of binding the silane coupling agent to tin and palladium adhering to the carbon fiber surface.
A method for producing surface-treated carbon fibers, which comprises.
[2] an aqueous solution containing the Sn ²⁺ is, Sn ²⁺ concentration is at 0.01 to 5 mol / l, pH of 4 or less, an aqueous solution containing the Pd ²⁺ is, Pd ²⁺ concentration 0.5 The production method according to 1 above, wherein the pH is ~ 3 mmol / liter and the pH is 4 or less.
[3] The ^{aqueous solution containing Sn 2+} is the sensitizing liquid used in the sensitizer / activator method, and the ^{aqueous solution containing Pd 2+} is the activating liquid used in the sensitizer / activator method. The manufacturing method described in.
[4] The colloidal solution containing ^{Sn 2+} and Pd ^{2+ has a Sn 2+} concentration of 0.01 to 5 mol / liter, a Pd ²⁺ concentration of 0.5 to 3 mmol / liter, and a pH of 4 or less. The production method according to 1 above.
[5] The production method according to 1 above, wherein the colloidal liquid containing ^{Sn 2+} and Pd ^{2+ is a catalyzing liquid used in the catalyzer / accelerator method.}
[6] Between the step 1 and the step 2, the carbon fiber having tin and palladium adhered to the surface obtained in the step 1 is heated or energized to transfer tin and palladium to the carbon fiber surface. The production method according to any one of 1 to 5 above, which comprises a step of fixing, wherein the step 2 is a step of binding a silane coupling agent to tin and palladium fixed on the surface of carbon fibers.
[7] The above-mentioned 6 in which the heating is carried out in an inert gas at 250 ° C. to 1000 ° C. for 30 seconds or more, and the energization is carried out in an electrolytic solution with carbon fibers as a cathode and 1 to 1000 coulombs / g is energized. Production method.
[8] The production method according to any one of 1 to 7 above, wherein the surface-treated carbon fiber is for a carbon fiber reinforced resin composite.
[9] The production method according to 8 above, wherein the resin for the carbon fiber reinforced resin composite is a thermoplastic resin or a thermosetting resin.
[10] The production method according to 9 above, wherein the thermosetting resin is an unsaturated polyester resin or a vinyl ester resin.
[11] A method for producing a carbon fiber reinforced resin composite molded product, which comprises a step of combining and molding the surface-treated carbon fiber obtained by the method according to any one of 1 to 10 and a resin.
[12] A method for producing a sheet-shaped prepreg, which comprises a step of impregnating the surface-treated carbon fiber obtained by the method according to any one of 1 to 10 with a resin.
[13] A carbon fiber characterized in that tin and palladium adhere to the surface of the carbon fiber, and a silane coupling agent is bonded to the tin and palladium.
[14] The carbon fiber according to 13 above, wherein the total amount of tin and palladium is 0.02 to 2 parts by mass with respect to 100 parts by mass of the carbon fiber.
[15] The carbon fiber according to 13 or 14, which is used for a carbon fiber reinforced resin composite.
[16] A carbon fiber reinforced resin composite containing the carbon fiber and the resin according to any one of 13 to 15.
[17] The carbon fiber reinforced resin composite according to 16, wherein the resin is an unsaturated polyester resin or a vinyl ester resin.

According to the present invention, carbon fibers that can be particularly preferably used for a carbon fiber reinforced resin composite (CFRP) using an unsaturated polyester resin or vinyl ester resin having insufficient adhesion to carbon fibers as a matrix can be easily produced. be able to. Since this carbon fiber has excellent adhesion to a resin, CFRP using this carbon fiber has excellent physical properties. Moreover, since these resins have a faster molding cycle than epoxy resins, it is possible to reduce the manufacturing cost as compared with CFRP using epoxy resins.

SEM image of a fracture test of a resin complex using carbon fibers of Example 1. SEM image of a fracture test of a resin complex using carbon fibers of Example 2. SEM image of a fracture test of a resin complex using carbon fibers of Example 3. SEM image of a fracture test of a resin complex using carbon fibers of Example 4. An SEM image of a fracture test of a resin complex using the carbon fibers of Comparative Example 1. An SEM image of a fracture test of a resin complex using carbon fibers of Comparative Example 2. An SEM image of a fracture test of a resin complex using carbon fibers of Comparative Example 3.

The method for producing a surface-treated carbon fiber that can be preferably used for the carbon fiber reinforced resin composite in one embodiment of the present invention has the following steps.
(Step 1) Carbon fibers are contacted with an aqueous solution containing ^{Sn 2+ and then with an aqueous solution containing Pd 2+} , or by contacting the carbon fibers with a colloidal solution containing ^{Sn 2+} and Pd ^2+. The process of adhering tin and palladium to the surface.
(Step 2) A step of binding a silane coupling agent to tin and palladium adhering to the surface of carbon fibers.

In step 1, tin and palladium are attached to the surface of the carbon fiber.
In a preferred embodiment of the method, the carbon fibers are contacted with an aqueous solution containing ^{Sn 2+ and then with an aqueous solution containing Pd 2+} , or the carbon fibers are brought into contact with a colloidal solution containing ^{Sn 2+} and Pd ^2+. ..

Examples of the aqueous solution containing Sn ²⁺ include an aqueous solution having a Sn ²⁺ concentration of 0.01 to 5 mol / liter and a pH of 4 or less. Contains acetic acid and the like. Examples of the aqueous solution containing Pd ²⁺ include aqueous solutions having a Pd ²⁺ concentration of 0.5 to 3 mmol / liter and a pH of 4 or less, such as palladium chloride, palladium sulfate, palladium acetate and the like, and hydrochloric acid, sulfuric acid, acetic acid and the like. including. The pH of each solution is preferably 2 or less.
The Sn ²⁺ concentration can be measured by the iodine titration method, and the Pd ²⁺ concentration can be measured by the atomic absorption method or ICP emission spectrometry. The pH is measured at room temperature using a commercially available measuring meter. The specific measurement method is as described in the column of Examples.

For the contact of the carbon fibers with the aqueous solution, it is preferable to immerse the carbon fibers in the aqueous solution. As a specific dipping method, for example, in an environment of 10 to 50 ° C., preferably 20 to 30 ° C., the carbon fiber is ^{immersed in an aqueous solution containing Sn 2+} for about 20 seconds to 10 minutes, and then the carbon fiber is used from the aqueous solution. Can be immersed in an aqueous solution containing Pd ²⁺ in the same environment for about 10 seconds to 5 minutes. After pulling up the carbon fiber from the aqueous solution containing Sn ^{2+, it may be washed lightly with water.}

Further, as the aqueous solution containing ^{Sn 2+} , the sensitizing solution used in the sensitizer / activator method can be used, and as the aqueous solution containing ^{Pd 2+, the activator used in the sensitizer / activator method can be used.} A ting liquid can be used. Commercially available sensitizing liquids and activating liquids can be used without particular limitation. The contact method with the carbon fiber is also not limited, and can be performed in the same manner as described above, for example.

The colloidal solution containing ^{Sn 2+} and Pd ^{2+ has a Sn 2+} concentration of 0.01 to 5 mol / liter, a Pd ²⁺ concentration of 0.5 to 3 mmol / liter, and a pH of 4 or less. Liquids are mentioned, and for example, hydrochloric acid, sulfuric acid, and acetic acid can be used for pH adjustment.

For the contact of the carbon fiber with the colloidal liquid, it is preferable to immerse the carbon fiber in the colloidal liquid. As a specific method of immersion, the carbon fibers can be immersed in the colloidal solution for about 2 to 5 minutes in an environment of, for example, 10 to 60 ° C., preferably 30 to 40 ° C.

Further, as the colloidal liquid, a catalyzing liquid used in the catalyzer / accelerator method can be used. Commercially available catalyzing liquid can be used without particular limitation. The contact method with the carbon fiber is also not limited, and can be performed in the same manner as described above, for example. In the catalyzer / accelerator method, the accelerator treatment is performed after contact with the catalyzing liquid, but the main purpose of the accelerator treatment is to dissolve and remove excess tin ions, and the treatment is performed with a silane coupling agent in the next step. Accelerator processing is not always necessary in the present invention.

As the carbon fiber as a raw material used in one embodiment of the present invention, PAN (polyacrylonitrile) -based carbon fiber, pitch-based carbon fiber and the like can be used without limitation, and these can also be used in combination.
Those that are easy to perform surface treatment are filaments (toe, filament), and may be processed into cloth or chops after surface treatment. Commercially available carbon fiber yarns are supplied by bundling 300 to 1000 single carbon fibers having a diameter of 5 μm to 20 μm into one unit yarn, and supplying several km to several hundred km as one roll. It is also possible to prevent fluffing and thread breakage by performing a sizing treatment after processing.
When a commercially available product is used, it can be used in the process of the present invention after the sizing agent has been removed from the product that has been subjected to a sizing treatment or the like. The sizing agent is removed by, for example, washing with a solvent such as acetone or methyl ethyl ketone (MEK), or heating to 350 to 600 ° C. in an inert gas (nitrogen, argon, etc.) to decompose the sizing agent.

In step 1, since the surface modification effect of the carbon fiber changes according to the amount of tin and palladium components attached as the catalyst metal, the amount of tin and palladium components attached is adjusted so as to meet the desired modification effect. To do. This adjustment can be performed by selecting each solution, immersion time, etc., but can also be performed by performing surface pretreatment of carbon fibers prior to this step 1.
The total amount of tin and palladium adhering to the surface of the carbon fiber is preferably 0.02 to 2 parts by mass, more preferably 0.05 to 1 part by mass with respect to 100 parts by mass of the carbon fiber. The total amount of tin and palladium attached can be measured by immersing the carbon fibers to which tin and palladium are attached in sulfuric acid and nitric acid to dissolve the attached metal, and then analyzing the obtained solution by ICP emission analysis. ..

The surface pretreatment of the carbon fiber performed prior to the step 1 includes a treatment for increasing the hydrophilicity of the surface of the carbon fiber, a treatment for imparting irregularities on the surface of the carbon fiber, and the like. Examples of this treatment include an etching treatment with an oxidizing solution such as chromic acid and hydrogen peroxide, and an electrolytic oxidation treatment in which a fiber is used as an anode in an electrolytic solution to conduct electricity. Above all, the electrolytic oxidation treatment using an acid aqueous solution such as hydrochloric acid or nitric acid or an alkaline aqueous solution such as an ammonium compound as an electrolytic solution is preferable because it is efficient and contains a small amount of residual ionic substances.

The carbon fibers having tin and palladium attached to the surface in step 1 can be used as they are in step 2, but tin and palladium are attached to the surface obtained in step 1 between the steps 1 and 2. It is also possible to provide a step of fixing tin and palladium to the surface of the carbon fiber by heating or energizing the carbon fiber. In this case, the step 2 is a step of binding the silane coupling agent to tin and palladium fixed on the surface of the carbon fiber.

Here, fixing means a state in which tin and palladium are not dissolved in an acid aqueous solution or an alkaline aqueous solution of about 1 M and are fixed to such an extent that they do not come off when rubbed.
The case where the carbon fiber reinforced resin composite is produced by using the obtained carbon fiber by bonding with the silane coupling agent which is the step 2 described later in the adhered state by the step 1, and the case where the carbon fiber reinforced resin composite is manufactured by the above step, will be described later. In the latter case, the adhesion between the resin and the carbon fiber is better than in the case where the carbon fiber reinforced resin composite is produced by performing the bonding with the silane coupling agent in step 2 and using the obtained carbon fiber. It is preferable because it is further improved. Adhesion can be seen in electron microscopic observations in fracture tests on each complex (see Examples).

The heating performed for immobilization can be performed, for example, by maintaining the temperature at 250 to 1000 ° C. for 30 seconds or longer. The preferred temperature is 300 to 900 ° C., more preferably 300 to 500 ° C., and the preferred time is 40 seconds to 5 minutes, more preferably 1 to 2 minutes. Fixation may not be sufficient if the temperature is too low or the time is too short. If the time is too long, the attached tin and palladium may permeate into the carbon fiber or, conversely, scatter and the metal may not be present on the surface of the carbon fiber. Further, if the temperature is too high, the crystallinity of the carbon fiber may change, and the performance such as the tensile strength and elastic modulus of the carbon fiber may change, resulting in a carbon fiber different from the performance of the target carbon fiber. The heating is preferably performed in the presence of an inert gas such as nitrogen gas or argon gas.

The energization can be performed in the electrolytic solution by connecting the carbon fibers to the cathode. Carbon, tungsten, titanium or the like can be used as the anode. As the electrolytic solution, either an acid aqueous solution or an alkaline aqueous solution can be used, but an alkaline aqueous solution in which attached tin and palladium are less likely to elute is preferable, and an ammonium hydrogen carbonate aqueous solution and an ammonium carbonate aqueous solution in which no metal residue is generated by energization are particularly preferable. preferable. The concentration is not particularly limited as long as it is within an appropriate range for energization, but is, for example, 0.1 to 5 M, preferably 0.3 to 1 M.
The energization amount can be 1 to 1000 coulombs / g, more preferably 10 to 500 coulombs / g (electric energy (coulombs) = voltage (ampere) x time (seconds)).

In step 2, the silane coupling agent is bound to tin and palladium attached or fixed to the surface of the carbon fiber. By binding the silane coupling agent, the affinity and adhesion between the carbon fiber and the resin can be enhanced via the silane coupling agent.
The silane coupling agent has a high affinity for glass fibers, and by binding the silane coupling agent to the glass fibers, the adhesion between the glass fibers and the resin is improved, and the physical properties of the fiber reinforced resin composite are improved. It is possible to make it. However, the silane coupling agent has a very low effect on carbon fiber (graphite) (Monthly Plastic Sage, April 2014, pp. 72-76), and even if it is treated in the same manner as glass fiber, it is a fiber reinforced resin composite. It is difficult to improve the physical properties of.

When a silane coupling agent is applied to carbon fibers, if the surface of the carbon fibers is metal-plated, the metal can be bonded to the silane coupling agent, thereby improving the affinity for the resin. However, the metal plating process on carbon fibers is complicated and leads to high cost. In one embodiment of the present invention, by performing step 1 or step 1 and the subsequent immobilization treatment of tin or palladium on the carbon fibers, the binding force (affinity, adhesion) of the silane coupling agent to the carbon fibers. Etc.) is greatly increased. The treatment of step 1 is also known as plating pretreatment, but in the present invention, plating itself is not performed, so that there is an advantage that the operation is simple.

Examples of the silane coupling agent include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-methacryloxypropyl. Methyldiethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3 − Glycydoxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, polyfunctional acrylicsilane, polyfunctional group epoxysilane, etc., which may be used alone or in combination of two. The above can be used in combination. Preferred silane coupling agents include, for example, 3-acryloxypropyltrimethoxysilane and polyfunctional acrylic silane.
To bond the silane coupling agent, a method of immersing the carbon fiber in an alcohol or a water-alcohol mixed solution to which 1 to 10% by mass of the silane coupling agent is added and then drying the carbon fiber for 1 minute to 1 day, or a method of drying the above solution with the carbon fiber. There is a method of spraying the silane to allow it to adhere sufficiently and then drying it. As the alcohol, lower alcohols such as methanol and ethanol can be preferably used. The amount of the silane coupling agent bonded to the carbon fibers is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 2 parts by mass with respect to 100 parts by mass of the carbon fibers.

The obtained carbon fiber can be preferably used for producing a composite with a resin (carbon fiber reinforced resin composite). As the resin, either a thermoplastic resin or a thermosetting resin can be used. These can also be mixed and used.
As the thermoplastic resin, polycarbonate, polyethylene terephthalate, nylon, polyolefin, polyetheretherketone, polyphenylene sulfide and the like are preferably used. As the thermosetting resin, an epoxy resin, a vinyl ester resin, an MMA resin (methyl methacrylate resin), an unsaturated polyester resin, a phenol resin and the like are preferably used. These can be used alone or in combination of two or more.
The amount of carbon fibers in the complex is preferably 10 to 90% by mass, more preferably 20 to 60%, and the amount can be appropriately selected depending on the use and form of the complex.

Since the carbon fiber in one embodiment of the present invention has a silane coupling agent firmly bonded to its surface, carbon is particularly carbon when it is formed into a composite with a resin having an affinity for the silane coupling agent. Even when a composite is formed with a resin having a low affinity for fibers, the composite has excellent adhesion between the resin and carbon fibers and has good physical properties. Examples of such resins include thermosetting resins such as unsaturated polyester resins and vinyl ester resins.

As a method for producing a composite of carbon fiber and resin, a conventionally known method is used without particular limitation. The carbon fiber and the resin may be melt-kneaded or molded into a prepreg, and a manufacturing method and a molding method suitable for the intended use may be selected. Specific molding methods include filament wind molding, drawing molding, hand lay-up molding, resin transfer molding, resin injection molding, press molding, autoclave molding, spray-up molding, etc. , Cross-processed or chopped. It is also possible to prepare the prepreg first and provide it to these molding methods.

The carbon fiber in one embodiment of the present invention comprises tin and palladium attached to the surface of the carbon fiber, and a silane coupling agent bonded to the tin and palladium. Although it is difficult for the silane coupling agent to directly bond to the carbon fiber, the silane coupling agent adheres well to the carbon fiber surface by binding via tin and palladium attached to the carbon fiber surface.
The total amount of tin and palladium adhering to the surface of the carbon fiber is preferably 0.02 to 2 parts by mass, more preferably 0.05 to 1 part by mass with respect to 100 parts by mass of the carbon fiber. The method for measuring the total amount of attached tin and palladium can be measured by the same method as described above.
The amount of the silane coupling agent bonded is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 2 parts by mass with respect to 100 parts by mass of the carbon fiber.
Such carbon fibers can be produced, for example, by the above method, and can be used as carbon fibers for a carbon fiber reinforced resin composite in the same manner as described above.

Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited by these descriptions.
^{The Sn 2+} concentration, Pd ²⁺ concentration and pH of the reagents used, and the amount of tin and palladium adhered to each other were measured as follows.
(1) Sn ²⁺ concentration To ^{5 ml of an aqueous solution containing Sn 2+} , 20 ml of a 6 mol / L hydrochloric acid solution and 100 ml of pure water are added. A 1% starch solution is added as an indicator to this, and titration is performed with a 0.05 mol / L iodine standard solution. The end point is the point where the color of the solution changes from translucent brown to turbid dark blue. ^{The amount of Sn 2+} is quantified from the amount of iodine dropped, and the ^{Sn 2+} concentration is calculated.
(2) Pd ²⁺ concentration 20 ml of a 6 mol / L hydrochloric acid solution is added to 5 ml of an aqueous solution containing ^{Pd 2+ and the mixture is sufficiently stirred, and then 50 ml of pure water is further added and stirred.} Then, 5 ml of 35% hydrogen peroxide solution is added and stirred. The mixture is heated until the volume of the mixture reaches 50 ml to evaporate the water content, cooled to room temperature, and then diluted with pure water to 100 ml. ^{The Pd 2+} concentration is measured by atomic absorption spectrometry or ICP emission spectrometry using the obtained solution.
(3) pH
Measure at room temperature (23 ° C) with a multi-water quality meter (MM-60R: manufactured by DKK-TOA CORPORATION).

Example 1
A 15 cm (about 0.1 g) carbon fiber (T-700SC 12K; manufactured by Toray Industries, Inc.) was heated at 500 ° C. for 1 hour in a nitrogen gas atmosphere to remove the sizing agent. Then, in a 0.5 M NH ₄ HCO ₃ aqueous solution, the carbon fiber was used as an anode and electrolyzed by energizing the carbon fiber to 30 coulon / g, and the obtained carbon fiber was washed with water to pretreat the surface of the carbon fiber. Was done.
The obtained carbon fiber is immersed in 100 ml of a sensitizing solution (sensitizer; manufactured by Okuno Pharmaceutical Co., Ltd.) in 1 L of purified water at 25 ° C. for 3 minutes, rinsed thoroughly with water, and then activated. Sn and Pd were adhered to the carbon fiber surface by immersing 50 ml of a liquid (activator; manufactured by Okuno Pharmaceutical Co., Ltd.) in 1 L of purified water at 30 ° C. for 1 minute and rinsing thoroughly with water.
The sensitizer (manufactured by Okuno Pharmaceutical Industry Co., Ltd.) used as the ^{sensitizing liquid had a Sn 2+} concentration of 0.05 mol / L and a pH of 0.8, and the activator (Okuno) used as the activating liquid. ^{The Pd 2+} concentration of (manufactured by Pharmaceutical Industry Co., Ltd.) was 0.9 mmol / L, and the pH was 0.12.
The total amount of attached tin and palladium was 0.3 parts by mass with respect to 100 parts by mass of carbon fiber. The measurement was carried out by immersing the carbon fiber to which tin and palladium were attached in sulfuric acid and nitric acid to dissolve the attached metal, and then performing ICP emission analysis of the obtained solution.
Example 1 was obtained by immersing the obtained carbon fibers in an ethanol solution containing 3% by mass of a silane coupling agent (KBM-503; manufactured by Shin-Etsu Chemical Co., Ltd.) and then drying at 110 ° C. for 15 minutes. Carbon fiber was obtained.

Example 2
The carbon fibers from which the sizing agent was removed, electrolytically oxidized, and washed with water in the same manner as in Example 1 were mixed with 20 ml of a catalyst solution (Catalist C-7; manufactured by Okuno Pharmaceutical Industry Co., Ltd.) and 200 ml of 35% hydrochloric acid with purified water. It was immersed in 1 L of the solution at 32 ° C. for 3 minutes. The obtained carbon fibers were thoroughly rinsed with water to allow Sn and Pd to adhere to the surface of the carbon fibers.
^{The Sn 2+} concentration of Catalyst C-7 (manufactured by Okuno Pharmaceutical Industry Co., Ltd.) used as the catalyst solution was 0.03 mol / L, the Pd ²⁺ concentration was 0.8 mmol / L, and the pH was 0.5. there were.
Next, the carbon fibers of Example 2 were obtained by immersing the carbon fibers in a 10% by mass silane coupling agent (KBM-5103; manufactured by Shin-Etsu Chemical Co., Ltd.) ethanol solution and then drying at 110 ° C. for 15 minutes. Obtained.

Example 3
The carbon fibers from which the sizing agent was removed, electrolytically oxidized, and washed with water in the same manner as in Example 1 were added to a solution prepared by adding 100 ml of the sensitizing solution (sensitizer; manufactured by Okuno Pharmaceutical Co., Ltd.) to 1 L of purified water. After immersing at ° C. for 3 minutes and rinsing thoroughly with water, 50 ml of the above-mentioned activating liquid (activator; manufactured by Okuno Pharmaceutical Co., Ltd.) was immersed in 1 L of purified water at 30 ° C. for 1 minute. By rinsing thoroughly with water, Sn and Pd were attached to the surface of the carbon fibers.
Then, in a 0.5 M _{aqueous solution of NH 4} HCO ₃ , the obtained carbon fibers were used as a cathode and energized to 100 coulombs / g (1 A, 10 seconds), and then the obtained carbon fibers were washed with water. As a result, Sn and Pd were immobilized on the surface of the carbon fiber.
Example 3 is obtained by immersing the obtained carbon fibers in an ethanol solution containing 3% by mass of a silane coupling agent (KR-513; manufactured by Shin-Etsu Chemical Co., Ltd.) and then drying at 110 ° C. for 15 minutes. Carbon fiber was obtained.
Moreover, when the total amount of attached tin and palladium was measured in the same manner as in Example 1, it was 0.3 parts by mass with respect to 100 parts by mass of carbon fibers.

Example 4
20 ml of the above-mentioned catalyst solution (Catalist C-7; manufactured by Okuno Pharmaceutical Industry Co., Ltd.) and 200 ml of 35% hydrochloric acid are purified from the carbon fibers obtained by removing the sizing agent, electrolytically oxidizing, and washing with water in the same manner as in Example 1. It was immersed in a solution made up of 1 L of water at 32 ° C. for 3 minutes. The obtained carbon fibers were thoroughly rinsed with water to allow Sn and Pd to adhere to the surface of the carbon fibers.
Then, it was heated at 600 ° C. for 1 minute in a nitrogen gas atmosphere and then cooled to immobilize Sn and Pd on the carbon fiber surface.
Next, the carbon fibers of Example 4 were obtained by immersing the carbon fibers in a 10% by mass silane coupling agent (KBM-5103; manufactured by Shin-Etsu Chemical Co., Ltd.) ethanol solution and then drying at 110 ° C. for 15 minutes. Obtained.

Comparative Example 1
The sizing agent was removed, electrolytically oxidized, and washed with water in the same manner as in Example 1 to obtain carbon fibers of Comparative Example 1.

Comparative Example 2
The same operation as in Example 3 was carried out except that the operation of immersing the silane coupling agent in the ethanol solution was not carried out to obtain the carbon fibers of Comparative Example 2.

Comparative Example 3
The sizing agent was removed, electrolytically oxidized, and washed with water in the same manner as in Example 1, and the obtained carbon fibers were immersed in a 3% by mass silane coupling agent (KBM-503; manufactured by Shin-Etsu Chemical Co., Ltd.) ethanol solution. Then, it was dried at 110 ° C. for 15 minutes to obtain carbon fibers of Comparative Example 3.

Evaluation of Adhesion between Carbon Fiber and Resin in Carbon Fiber Reinforced Resin Composite 100 parts by mass of vinyl ester resin (Lipoxy (registered trademark) R802; manufactured by Showa Denko Co., Ltd.), 55 mass% methyl ethyl ketone peroxide (MEKPO) as a curing agent 1.0 part by mass and 0.3 part by mass of cobalt N (manufactured by Showa Denko Co., Ltd.) as a curing accelerator were mixed with a glass rod to obtain a resin composition.
1 g of the obtained resin composition was impregnated with 0.1 g of carbon fibers obtained in Examples and Comparative Examples, cured at room temperature for 1 hour, cured after 2 hours at 130 ° C. to remove excess resin, and the thickness was 0. A carbon fiber reinforced resin composite having a length of about 3 mm, a length of 100 mm, and a width of about 10 mm was obtained. The amount of carbon fiber in the obtained carbon fiber reinforced resin composite is about 20% by mass. This resin complex was bent and broken, and the fracture surface was observed by SEM.
The SEMs when the carbon fibers of Examples 1 to 4 and Comparative Examples 1 to 3 are used are shown in FIGS. 1 to 7, respectively, and the evaluation of the adhesion between the carbon fibers and the resin by the SEM is shown in Table 1. In the evaluation in Table 1, ◯ indicates that the part where the resin is not peeled off on the surface of the carbon fiber can be observed because the carbon fiber and the resin are in close contact with each other in the fracture surface, and ◎ indicates that the part where the resin is not peeled off is equivalent to Indicates that most of the resin is peeled off on the surface of the carbon fiber.

Adhesion test by microdroplet method One carbon monofiber was taken out from each of the carbon fibers obtained in Examples and Comparative Examples, and the same resin composition formulation as in SEM observation was adhered to the surface of the carbon monofiber in a spherical shape at 130 ° C. A microdroplet test piece was prepared by curing for 2 hours. Set the resin-attached single fiber in the microdroplet measuring device, sandwich the resin part of the resin-attached single fiber with a blade, pull out the attached resin from the single fiber at a speed of 0.06 mm / min, and measure the maximum withdrawal load Fmax. The interfacial strength τ was calculated from the formula.
(Equation) τ = Fmax / (dπL)
Fmax: maximum drawing load, d: carbon single fiber diameter, L: diameter in drawing direction of the adhered spherical resin were measured 20 times each, and the average value was adopted. The resin sphere diameter of the test pieces was as close to 50 μm as possible, but the minimum resin sphere diameter of the 20 test pieces was 20 μm and the maximum was 80 μm.

Claims (17)

By contacting the carbon fibers with ^{an aqueous solution containing Sn 2+ and then} with an aqueous solution containing Pd ²⁺ , or by contacting the carbon fibers ^{with a colloidal solution containing Sn 2+} and Pd ²⁺ , tin and tin and the surface of the carbon fibers can be contacted. Step 1 of adhering palladium and step 2 of bonding a silane coupling agent to tin and palladium adhering to the carbon fiber surface.
A method for producing surface-treated carbon fibers, which comprises. Aqueous solution containing the Sn ²⁺ is, Sn ²⁺ concentration is at 0.01 to 5 mol / l, pH of 4 or less, an aqueous solution containing the Pd ²⁺ is, Pd ²⁺ concentration 0.5 to 3 mmol The production method according to claim 1, wherein / liter and pH is 4 or less. The first aspect of the present invention, wherein the ^{aqueous solution containing Sn 2+} is a sensitizing solution used in the sensitizer / activator method, and the ^{aqueous solution containing Pd 2+} is an activating solution used in the sensitizer / activator method. Manufacturing method. The colloidal solution containing ^{Sn 2+} and Pd ^{2+ has a Sn 2+} concentration of 0.01 to 5 mol / liter, a Pd ²⁺ concentration of 0.5 to 3 mmol / liter, and a pH of 4 or less. The manufacturing method according to 1. The production method according to claim 1, wherein the colloidal liquid containing Sn ²⁺ and Pd ^{2+ is a catalyzing liquid used in the catalyzer / accelerator method.} A step of fixing tin and palladium to the surface of the carbon fiber by heating or energizing the carbon fiber having tin and palladium attached to the surface obtained in the step 1 between the step 1 and the step 2. The production method according to any one of claims 1 to 5, wherein the step 2 is a step of binding a silane coupling agent to tin and palladium fixed on the surface of the carbon fiber. The production method according to claim 6, wherein the heating is performed in an inert gas at 250 ° C. to 1000 ° C. for 30 seconds or more, and the energization is carried out by using carbon fibers as a cathode in an electrolytic solution and energizing 1 to 1000 coulombs / g. .. The production method according to any one of claims 1 to 7, wherein the surface-treated carbon fiber is for a carbon fiber reinforced resin composite. The production method according to claim 8, wherein the resin for the carbon fiber reinforced resin composite is a thermoplastic resin or a thermosetting resin. The production method according to claim 9, wherein the thermosetting resin is an unsaturated polyester resin or a vinyl ester resin. A method for producing a carbon fiber reinforced resin composite molded product, which comprises a step of combining and molding the surface-treated carbon fiber obtained by the method according to any one of claims 1 to 10. A method for producing a sheet-shaped prepreg, which comprises a step of impregnating a surface-treated carbon fiber obtained by the method according to any one of claims 1 to 10 with a resin. A carbon fiber characterized in that tin and palladium adhere to the surface of the carbon fiber, and a silane coupling agent is bonded to the tin and palladium. The carbon fiber according to claim 13, wherein the total amount of tin and palladium is 0.02 to 2 parts by mass with respect to 100 parts by mass of the carbon fiber. The carbon fiber according to claim 13 or 14, which is for a carbon fiber reinforced resin composite. A carbon fiber reinforced resin composite containing the carbon fiber and the resin according to any one of claims 13 to 15. The carbon fiber reinforced resin composite according to claim 16, wherein the resin is an unsaturated polyester resin or a vinyl ester resin.

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