JPS6360152B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to carbon fibers for composite materials. In recent years, carbon fibers have been mixed with matrix materials such as resins, metals, and ceramics and used as composite materials in fields ranging from the aviation and space industries to sporting goods, and have excellent mechanical strength. The drawback is that the interlaminar shear strength of the fibers is relatively low. In order to improve this, there is a conventional method of subjecting the surface of carbon fiber to nitric acid oxidation and air oxidation treatment, but the oxidation treatment process is difficult to manage, the process is complicated, and the surface of carbon fiber is It comes with disadvantages such as damage. The present invention provides a method for producing carbon fibers for composite materials with increased interlaminar shear strength that can be easily obtained by coating with a conditioning liquid, and in which the alkoxy groups of titanium alkoxide are partially replaced with acetylacetone on the surface of the carbon fibers. The method is characterized by forming a film of a solution of a titanium compound formed by the method, and leaving or heating the film. Next, embodiments of the present invention will be described. Titanium compounds in which the alkoxy groups of titanium alkoxide are partially substituted with acetylacetone on the surface of carbon fibers are the following compounds in which the alkoxy groups of titanium alkoxide are partially substituted with acetylacetone, such as titanium ethoxide, titanium isopropoxide, and titanium normal butoxide. Including any of the general formulas () to (), in other words,
It is an alkoxy titanium acetylate.

【formula】

【formula】

In the formula, R represents an alkyl group such as an ethyl group, an i-propyl group, or an n-butyl group, and X represents an acetylacetone substituent. Any of the alkoxytitanium acetylates () to () above can be used. The reason for substituting a part of the alkoxy group of titanium alkoxide with acetylacetone is that if it is not replaced, titanium alkoxide will hydrolyze at a very high rate and be easily affected by moisture in the air, making workability extremely poor and difficult. This is to prevent inconveniences such as inconsistent quality of the film, and to enable the preparation of the next alcohol solution and a good coating solution using the acetylacetone substituent. Next, add this alkoxy titanium acetylate to alcohol,
Preferably ethanol, i-propanol, n
- Dissolve in butanol, etc. and apply the solution to carbon fiber to form a film on its surface. Incidentally, in order to adjust the viscosity of the solution, ether such as diethyl ether may be added. The coating may be formed by any method including immersing the carbon fibers in the solution in batches or continuously, or by spray coating. The thickness of the coating can be freely controlled by adjusting the time for which the carbon fibers are immersed in the solution, the amount of alcohol as a solvent, the presence or absence of addition of ether, the drying time, etc., but the thickness of the dried coating is preferably 1 μm or less. If it exceeds 1 μm, the coating tends to deteriorate. When the carbon fibers are passed through the solution, a speed of 1 to 50 mm/sec is preferred; if the speed exceeds 50 mm/sec, the coating tends to become non-uniform. Next, after a coating treatment such as immersion in the solution, the product is made by drying naturally or by heating at a temperature below 100°C, or further heated at a temperature above 100°C to oxidize the coating to produce a product. After the formation of the titanium compound film, the titanium compound film is brought into contact with moisture in the air during natural or relatively low-temperature heat drying to cause hydrolysis, resulting in hydration of titanium acetylate, titanium hydroxide, etc. Evaporation of the solvent that partially forms a film of decomposition products results in a dry film. By heating at 100° C. or higher, the above-produced hydrolyzate film of the titanium compound film is oxidized to partially or entirely form a titanium oxide film. Incidentally, it is also possible to omit the natural drying process and immediately heat the material, gradually heating it, and then raising the temperature to 100° C. or higher to form a titanium oxide film. In this way, the manufactured carbon fibers with a dry coating of a titanium compound or the carbon fibers with a titanium oxide coating can be either synthetic resin materials, metal materials,
It is applied to composite material products with inorganic materials such as ceramics, and in this case, the titanium compound coating, its hydrolyzed coating, or the titanium oxide coating improves the adhesion between the two and improves the interlaminar shear strength. Bringing you composite products. Incidentally, in the production of the composite material, a coupling agent such as titanium, borane, silane, etc. can be used in combination.
Next, detailed examples will be described. Example 1 Carbon fibers with a diameter of 7 μm and 6000 filaments were heated at a speed of 1 mm/sec in a V-shaped glass tube with an inner diameter of 20 mm and a length of 150 mm and open at both ends, containing a prepared solution having the components and composition ratios shown in Table 1 below. The carbon fibers coated with the titanium compound solution are then left in the air for 1 to 24 hours to allow the titanium compound to be hydrolyzed by the moisture in the air. After performing the reaction and simultaneously removing volatile components contained in the film to form a dry film, further
Drying by heating at a temperature range of 130 to 150°C for 2 hours, then further heating at a temperature range of 280 to 300°C for 0.5 to 1 hour,
Carbon fiber for composite materials with a titanium oxide coating on its surface was manufactured.

[Table] A large number of the carbon fibers for composite materials thus obtained were mixed with 100 parts of epoxy resin (Epicote 828 manufactured by Ciel Chemical Co., Ltd.) and boron trifluoride BF ₃ as a hardening agent.
The fibers are impregnated into a resin matrix containing 2 to 5 parts of
After degassing for 5 minutes at a vacuum level of 10 mmHg, curing was performed at 120°C for 40 minutes and at 170°C for 70 minutes in an annealing furnace. The composite molded product obtained in this way is
A test piece of 12 mm, width 10 mm, and thickness 3 mm was processed, and the interlaminar shear strength was measured by a three-point bending test using the shot beam method. The span/thickness in this case is 4
The crosshead speed of the bending tester was 1 mm/min. The measurement results are shown in Table 2 below. Example 2 Using an adjustment liquid with the same components and composition ratio as in Example 1, passing the carbon fiber through the preparation liquid in the same manner,
Carbon fibers with a coating of the prepared solution formed on their surfaces were left in the air for 24 to 48 hours to hydrolyze the titanium compounds and volatilize the solvent, resulting in a coating with a thickness of 1μ (titanium compounds, titanium acetylate, We created carbon fibers for composite materials with a composite coating of titanium hydroxide. About this product
A composite molded article was made using the same epoxy resin matrix as used in Example 1, and for this,
A test piece similar to that described above was prepared and an interlaminar shear strength test was conducted. The results are shown in Table 2. Example 3 The carbon fiber for composite material obtained by the same treatment as in Example 1 was further treated with 99.2wt of titanium coupling agent, for example, 0.8wt% of tetraisopropyl bisdioctyl phosphite titanate.
% of isopropanol and apply it uniformly to the entire surface by soaking, spraying, etc.
The same composite molded product as in Example 1 was made by leaving it to dry for a period of time, and the interlaminar shear strength of the test piece was measured in the same manner. The results are shown in Table 2. Comparative Example 1 A composite molded article was immediately made using the same carbon fiber material as used in Example 1, which was not treated with the liquid preparation of the present invention, in the same manner as described in Example 1, and a similar test piece was made for this. , and its interlaminar shear strength was measured. The results are shown in Table 2.

[Table] *The commercially available product is a composite material of oxidized carbon fiber and epoxy resin.
In addition, Me ₁ (OR) ₄ and Me ₂ are added to the alkoxy titanium acetylate of the present invention at a ratio of 0.01 to 10 mol%.
(OR) ₃ , (Me ₁ is Si, Zr, Me ₂ is Al, R is
A similar effect was obtained by adding an alkoxide represented by CH ₃ , C ₂ H ₅ , C ₃ H ₇ ). As described above, according to the present invention, a film of a titanium compound solution in which the alkoxy groups of titanium alkoxide are partially substituted with acetylacetone is formed on the surface of carbon fibers, and the film is left to stand or is heated. Carbon fibers for composite materials having a coating made of titanium acetylate, its hydrolyzate, or titanium oxide are obtained, and when mixed with other composite materials in the production of composite materials, it is important to have excellent interlaminar shear strength. It also has the effect of making it easier to manufacture carbon fibers for the composite material without damaging the surface of the carbon fibers.

Claims (1)

[Claims] 1. Forming on the surface of carbon fiber a coating of a solution of a titanium compound made by partially substituting the alkoxy group of titanium alkoxide with acetylacetone,
A method for producing carbon fiber for composite materials, which comprises leaving the coating on or heating it. 2. The manufacturing method according to claim 1, wherein the thickness of the coating is 1 micron or less.