JP2008274520A - Sizing agent for carbon fiber and carbon fiber bundle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sizing agent for carbon fibers, a carbon fiber bundle, and carbon short fibers which provide a carbon-fiber reinforced composite material having excellent high-order processability such as handleability or resin impregnating properties in FW (filament winding), PT (pultrusion), and molding of an SMC (sheet molding compound), and excellent adhesive strength to a matrix resin. <P>SOLUTION: The sizing agent for the carbon fibers includes a urethane-modified epoxy resin (A) represented by formula (1) and a polyether being a bisphenol compound (B) in which 10-50 mol of an alkylene oxide is added in a mass ratio (A)/(B) within the range of 2-10. In the carbon fiber bundle, the sizing agent is applied in an amount of 0.2-4 mass% based on the unit mass of the carbon fiber bundle, 10,000-150,000 filaments composes the carbon fiber bundle, and the cross-section of the fiber bundle has a flatness (width/thickness) of 20 to 200. In the carbon short fibers, the sizing agent is applied in an amount of 1-10 mass% based on the unit mass of the carbon fibers, the fiber length is 2 to 60 mm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sizing agent for carbon fibers excellent in high-order processability such as handling property and resin impregnation property and filament reinforced composite material properties in filament winding and pultrusion molding of composite materials, and the sizing agent. The present invention relates to a carbon short fiber having excellent dispersibility, resin impregnation property, and the like, and excellent short fiber reinforced composite material properties in adhering carbon fiber bundle and sheet molding (SMC) molding.

  Since carbon fibers have the characteristics of high mechanical properties, particularly specific strength and specific elastic modulus, they are widely used in aerospace applications, leisure applications, general industrial applications, and the like.

  Various molding methods such as prepreg / layup molding, hand layup molding, filament winding molding, pultrusion molding, pullwinding molding, fiber placement molding, resin transfer molding (RTM) molding, sheet molding compound molding, etc. are used. ing. Among these, the filament winding (hereinafter abbreviated as FW) molding method, the pultrusion (hereinafter abbreviated as PT) molding method, and the sheet molding compound (hereinafter abbreviated as SMC) molding method are methods that have been originally applied to glass fibers. However, it can be widely applied to carbon fibers by taking advantage of its excellent productivity, molding cost, high design flexibility when using short fibers, and high mechanical properties of the resulting composite materials. It is becoming.

  The current carbon fiber applied to these molding methods is a thick carbon fiber bundle having a filament number of 10,000 or more from the merit of productivity, but when molded under the same conditions, Formed products using thick carbon fiber bundles are compared to formed products using thin carbon fiber bundles with a fine number of filaments of about several thousand in terms of the quality of molded products such as surface irregularities and void formation. Since it is inferior, it has been dealt with by slightly reducing the molding speed. Furthermore, these molding methods draw a carbon fiber bundle from a bobbin at a high speed, and handle and handle it through a large number of rollers. Friction with a roller and fluffing are likely to occur, and it has been dealt with by slightly reducing the molding speed. In other words, in molding using a thick carbon fiber bundle, surface unevenness, void formation, etc. can be suppressed by improving the spreadability of the thick carbon fiber bundle, resin impregnation, etc., and handling properties can be improved. If possible, further improvement in productivity is possible. In addition, in the case of short carbon fibers cut from a thick carbon fiber bundle, convergence as a thick carbon fiber bundle in handling before entering the cutting process, and appropriate cracking occurs during cutting in the cutting process By improving the dispersibility and resin impregnation property as short carbon fibers by the surface, surface irregularities, void formation, etc. can be suppressed, and excellent short fiber reinforced composite material properties can be expected.

  The need to produce high-performance fuel cylinders such as those used in natural gas vehicles with high productivity is increasing day by day. With this increase in handling properties and resin impregnation properties suitable for FW or PT molding. The demand for thickened carbon fiber bundles is increasing, and the productivity is high and the degree of freedom in design is high. For example, resin impregnation properties suitable for SMC molding, fluidity during molding, etc. The demand for excellent carbon short fibers is also increasing.

  As a method for improving the handleability, a method of applying a sizing agent having excellent scratch resistance to a carbon fiber bundle has been proposed (see Patent Document 1 and Patent Document 2). Further, a sizing agent for FW molding has been proposed (see Patent Document 3). Patent Document 4 proposes a substantially untwisted thick carbon fiber bundle having a combined yarn cracking rate of 40% or less. Patent Documents 5 and 6 disclose carbon fiber bundles that define the flatness of the fiber bundle and the solid epoxy-based resin viscosity.

  However, sizing agents for carbon fibers and carbon fibers suitable for FW molding methods that can exhibit excellent composite material properties with various matrix resins, although all have excellent processability such as handling properties and resin impregnation properties in FW molding. At present, no bundle has been obtained.

On the other hand, in general, in SMC, a reinforcing fiber is cut into several to several tens of millimeters. Therefore, a fiber-reinforced thermoplastic resin having a matrix resin as a thermoplastic resin that is also used by cutting the reinforcing fiber. The composite material (hereinafter abbreviated as FRTP) may be treated in the same manner as the chopped strand. As an example of the carbon fiber chopped strand, use of a urethane resin as a sizing agent is disclosed (see Patent Documents 7 and 8). However, in SMC and FRTP, in addition to the different characteristics of the matrix resin used, the molding method is also completely different, so the characteristics required for the carbon fiber bundle are naturally different, and carbon fibers suitable for SMC and FRTP are used. Need to design. Patent Document 9 discloses the use of a reactive urethane resin as a sizing agent for SMC. However, at present, carbon short fibers satisfying the dispersibility of the short carbon fibers in the cutting process, the resin impregnation property in the SMC molding process, and the mechanical properties of the SMC molded product have not been obtained.
Japanese Patent Publication No. 01-046636 Japanese Unexamined Patent Publication No. 01-314785 JP 58-013781 A Japanese Patent Laid-Open No. 08-158163 JP 2002-294568 A JP 2002-317383 A JP-A-10-001877 Japanese Patent Laid-Open No. 10-073350 JP 2006-144168 A

  An object of the present invention is to provide a carbon fiber sizing agent and a carbon fiber bundle that are excellent in high-order processing such as FW or PT molding and have excellent adhesion strength with a matrix resin, and SMC molding. Another object of the present invention is to provide a short carbon fiber that is excellent in moldability and gives high short fiber reinforced composite material properties.

  In view of the current situation, the present inventors have intensively studied sizing agents for carbon fibers, carbon fiber bundles and carbon short fibers suitable for FW, PT, and SMC molding methods, and have reached the present invention.

  The present invention employs the following configuration in order to solve the above problems. Specifically, a urethane-modified epoxy resin (A) having a structure represented by the following formula (1) and a polyether (B) that is an adduct of 10 to 50 mol of alkylene oxide of a bisphenol compound represented by the following formula (2): The sizing agent for carbon fiber, wherein the mass ratio (A) / (B) is contained at a ratio in the range of 2 to 10.

[Wherein, R 1 represents a saturated aliphatic hydrocarbon group or unsaturated aliphatic hydrocarbon group having 1 to 18 carbon atoms, and X represents an aromatic, alicyclic, or aliphatic divalent linking group. . m is 1 or 2, and n is 5-20. ]

[Wherein, R 2 and R 3 each independently represents a hydrogen atom or a saturated aliphatic hydrocarbon group having 1 to 4 carbon atoms. ]
Moreover, the carbon fiber bundle of the present invention has the sizing agent of the present invention attached to 0.5 to 4% by mass per unit mass of the carbon fiber bundle, and the number of filaments constituting the carbon fiber bundle is 10,000 to 150, It is a carbon fiber bundle having a flatness ratio (width / thickness) of 20 to 200 and 000 fibers.

Moreover, the carbon short fiber of the present invention is a carbon short fiber in which the sizing agent of the present invention is attached in an amount of 1 to 10% by mass per unit mass of the carbon fiber and the fiber length is 2 to 60 mm.

In the present invention, the carbon fiber or carbon fiber bundle refers to a carbon fiber or carbon fiber bundle provided with a sizing agent, and the carbon fiber or carbon fiber bundle before sizing is applied. In order to distinguish from this, it is referred to as a sizing-treated carbon fiber or a sizing-treated carbon fiber bundle.

  According to the present invention, a sizing agent for carbon fiber that is excellent in handling property, resin impregnation property, moldability, and can exhibit physical properties of a fiber reinforced composite material excellent in adhesive strength with a matrix resin, and carbon to which the sizing agent is attached. Fiber bundles and short carbon fibers can be obtained, and can be suitably used for FW molding or PT molding for producing cylinders and the like, and SMC molding with a high degree of design freedom.

  As a result of intensive studies, the present inventors have added 10 to 50 mol of alkylene oxide of a urethane-modified epoxy resin (A) having a structure represented by the following formula (1) and a bisphenol compound represented by the following formula (2). A sizing agent for carbon fiber containing a polyether (B) as a product and having a mass ratio (A) / (B) in the range of 2 to 10, and 0.5% of the sizing agent per unit mass of the carbon fiber bundle. A carbon fiber bundle that is attached to ˜4 mass%, has a number of filaments constituting the carbon fiber bundle of 10,000 to 150,000, and a flatness (width / thickness) of the fiber bundle cross section is 20 to 200, and The present inventors have investigated that the above problems can be solved at once by using carbon short fibers having 1 to 10% by mass of the sizing agent per unit mass of carbon fiber and having a fiber length of 2 to 60 mm.

[Wherein, R 1 represents a saturated aliphatic hydrocarbon group or unsaturated aliphatic hydrocarbon group having 1 to 18 carbon atoms, and X represents an aromatic, alicyclic, or aliphatic divalent linking group. . m is 1 or 2, and n is 5-20. ]

[Wherein, R 2 and R 3 each independently represents a hydrogen atom or a saturated aliphatic hydrocarbon group having 1 to 4 carbon atoms. ]
In this invention, the sizing agent for carbon fibers which contains the urethane modified epoxy resin (A) which has a structure represented by Formula (1), and the polyether (B) represented by Formula (2) in a specific ratio in a sizing agent Although the mechanism of action relating to the compatibility of the high-order processability and the adhesive strength with the matrix resin is not clear, it is considered as follows.

  To obtain high adhesive strength at the interface between various matrix resins and carbon fibers, such as epoxy resins, vinyl ester resins and unsaturated polyester resins, which are usually used as matrix resins in FW molding, PT molding and SMC molding, a sizing agent Ingredients need an epoxy group or urethane skeleton. On the other hand, a low-viscosity resin used in FW molding, PT molding, and SMC molding is impregnated into a thick carbon fiber bundle, and in order to improve high-order workability by each molding method, an alkylene oxide is used as a sizing agent component. The introduction of chains and aliphatic hydrocarbon groups is effective, but the introduction of such a skeleton into the sizing agent component simultaneously reduces the bond strength between the matrix resin and the carbon fiber interface (ie, the surface of the carbon fiber and the matrix resin). Let

  Therefore, in the present invention, as the composition of the sizing agent, the resin-impregnated property and the resin-impregnated property are obtained by introducing a relatively low molecular weight ethylene oxide chain having a terminal aliphatic hydrocarbon group into the urethane-modified epoxy to suppress a decrease in adhesive strength with the matrix resin. By improving the high-order processability and adding a small amount of a relatively low molecular weight polyether (B) as a separate component simultaneously, the affinity between the surface of the carbon fiber and the urethane-modified epoxy resin (A) is synergistic. It is considered that a sizing agent excellent in resin impregnation property and high-order processability was obtained without lowering the adhesive strength between the carbon fiber surface and the matrix resin.

  Further, in a thick carbon fiber bundle having more than 10,000 filaments, the sizing agent is attached in a specific amount, and the cross section of the fiber bundle is made to have a specific flattening rate so that the matrix resin is contained inside the carbon fiber bundle. It is considered that a carbon fiber reinforced composite material with a sufficient adhesion, no voids, and high mechanical strength at the same time as the adhesive strength with the matrix resin was obtained.

  Moreover, by attaching the sizing agent adhering amount in a specific amount, due to the convergence of the carbon fiber bundle necessary for handling before entering the cutting process of the thick carbon fiber bundle and the impact at the time of cutting in the cutting process It is considered that a split carbon short fiber having excellent dispersibility was obtained by causing an appropriate crack in the thick carbon fiber bundle.

  The urethane-modified epoxy resin (A) that can be used in the sizing agent of the present invention has a structure represented by the above formula (1) and can be obtained as follows. First, the terminal hydroxyl group of polyethylene oxide monoalkyl ether is reacted with a polyvalent isocyanate having a reaction equivalent to the amount of the hydroxyl group, and then the isocyanate residue of the obtained reaction product is reacted with the hydroxyl group in the polyvalent epoxy resin. Obtainable.

  Here, as the polyvalent isocyanate used, 2,4-tolylene diisocyanate, metaphenylene diisocyanate, paraphenylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, norbornane diisocyanate, triphenylmethane triisocyanate, biphenyl-2, Examples include 4,4′-triisocyanate.

  The polyethylene oxide monoalkyl ether preferably has a long chain alkyl group and polyethylene oxide structure from the viewpoint of scratch resistance. However, the bond strength with the matrix resin used in the FW molding method, PT molding method and SMC molding In view of the above, for the alkyl group, R1 must be a saturated aliphatic hydrocarbon or unsaturated aliphatic hydrocarbon group having 1 to 18 carbon atoms, and the polyethylene oxide structure has n in the range of 5 to 20. It is necessary to be. Specific examples of the alkyl group include a methyl group, an ethyl group, a butyl group, a lauryl group, a stearyl group, and an oleyl group. From the viewpoint of adhesive strength with a matrix resin, a methyl group, an ethyl group, and a butyl group are exemplified. More preferably, it is a group. The polyethylene oxide structure is preferably n in the range of 5 to 15 from the balance of adhesion strength with the matrix resin and scratch resistance.

  Further, the polyvalent epoxy resin to be reacted with the isocyanate residue of the reaction product of the polyvalent isocyanate and polyethylene oxide monoether needs to be a polyvalent epoxy resin having a plurality of hydroxyl groups and epoxy groups. Specifically, it is a reaction product of bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, resorcinol type epoxy resin, bisphenol S type epoxy resin, polyhydric alcohols and the above halogen-containing epoxides. Examples thereof include a polyethylene glycol type epoxy resin and a polypropylene glycol type epoxy resin. Of these, aromatic epoxy resins are preferred from the viewpoint of imparting affinity to the surface of the carbon fiber and converging properties. Specifically, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, and the like are preferably used.

  The urethane-modified epoxy resin of the present invention preferably has an epoxy equivalent of 500 to 2000 and more preferably 600 to 1500 from the viewpoint of obtaining high adhesive strength with the matrix resin. When the epoxy equivalent is less than 500, the adhesive strength with the matrix resin can be obtained, but the sizing agent itself becomes more sticky, so that the single fiber is easily wound around the metal roller during the FW molding process, and the processability in the FW molding is improved. Deteriorate. On the other hand, when the epoxy equivalent exceeds 2000, the affinity between the surface of the carbon fiber and the sizing agent becomes low, and the adhesive strength with the matrix resin becomes insufficient. This epoxy equivalent is measured according to JIS-K-7236 (1986).

  The polyether (B) that can be used in the sizing agent of the present invention is an alkylene oxide 10 to 50 mol adduct of the bisphenol compound represented by the formula (2). When the added number of moles of alkylene oxide is less than 10 moles, the resin impregnation property may be deteriorated due to scratch resistance and insufficient affinity with the urethane-modified epoxy resin (A). When the added mole number exceeds 50 moles, the matrix Since the adhesive strength with the resin is lowered, it is necessary to be in such a range, and a 10 to 40 mol adduct is preferable. The polyether (B) specifically includes, for example, an alkylene oxide adduct of bisphenol A represented by the following formula (3), and the alkylene oxide is not particularly limited, but ethylene oxide, propylene oxide, ethylene oxide / propylene oxide. The block polymer of these is mentioned.

The sizing agent of the present invention contains the urethane-modified epoxy resin (A) and the polyether (B) as essential components in a ratio in which the mass ratio (A) / (B) is in the range of 2 to 10. . That is, the mass ratio in the dry state of the urethane-modified epoxy resin (A) and the polyether (B) used in the present invention is 2 to 10, preferably 3 to 8. When the mass ratio in the dry state is less than 2, fluffing occurs due to insufficient focusing of the carbon fiber bundle and insufficient abrasion resistance, and cannot withstand friction caused by a metal guide passing through when forming FW, PT, and SMC. It becomes easy and a single yarn is wound around a metal guide or the like, and at the same time, the adhesive strength between the carbon fiber bundle and the epoxy resin matrix may be insufficient. On the other hand, when the dry mass ratio exceeds 10, the affinity between the surface of the carbon fiber and the sizing agent is reduced, and the carbon fiber bundle is excessively focused, so that the matrix resin is used in the FW molding, PT molding and SMC molding processes. In addition, the matrix resin is not impregnated inside the carbon fiber bundle, and voids are easily generated in the resulting composite material. The mass ratio of the urethane-modified epoxy resin (A) and the polyether (B) in the dry state is determined by preparing the treatment liquid from the solid content mass of the urethane-modified epoxy resin (A) and the mass calculated value of the polyether (B). Other components that can make up the sizing agent can be adjusted by improving the handleability, scratch resistance and fluff resistance of the carbon fiber bundles or short carbon fibers, and improving the impregnation of the matrix resin. Therefore, if necessary, a polyether resin, a polyester resin, a polyurethane resin, etc., a dispersant, a surfactant, and the like can be added. The surfactant is not particularly limited. However, when an ionic surfactant is used, when an epoxy resin is used as a matrix resin in the FW molding, PT molding, and SMC molding processes, the epoxy resin and the surfactant on the surface of the carbon fiber. The nonionic surfactant is preferred because the carbon fiber bundle becomes hard and the epoxy resin does not impregnate the carbon fiber bundle and may cause void formation.

  In the carbon fiber bundle of the present invention, the number of filaments constituting the carbon fiber bundle is 10,000 to 150,000, and the sizing agent is within a range of 0.5 to 4% by mass per unit mass of the carbon fiber bundle. The carbon fiber bundle having a flatness (width / thickness) of the fiber bundle cross section of 20 to 200 attached to the sizing treated carbon fiber bundle.

  In the present invention, the number of filaments constituting the carbon fiber bundle is 10,000 to 150,000, preferably 20,000 to 100,000. If it is less than 10,000, good resin impregnation can be obtained even within the range of the prior art, but there is a limit to improving the productivity of the molded product. If it exceeds 150,000, the surface of FW molded product and PT molded product Smoothness may not be obtained. Moreover, the adhesion amount of the said sizing agent is 0.5-4 mass% per unit mass, and if it exists in the range of 0.4-2.5 mass%, it is more preferable. If the amount of sizing agent attached is less than 0.5% by mass, the carbon fiber bundles will not be able to withstand the friction caused by metal guides passing through when forming FW or PT due to insufficient focusing and abrasion resistance. It becomes easy to do so, and a single yarn is wound around a metal guide or the like. On the other hand, when the adhesion amount of the sizing agent exceeds 4% by mass, the carbon fiber bundles are excessively focused, and the matrix resin is not impregnated with the matrix resin inside the carbon fiber bundles in the FW molding and PT molding processes, and thus obtained composite Voids are easily generated in the material, and the mechanical properties are lowered at the same time as the quality of the composite material is lowered.

  Further, the carbon fiber bundle of the present invention requires that the flatness (width / thickness) of the cross section of the fiber bundle is in a specific range. The flatness of the cross section of the fiber bundle in the present invention is based on the fiber bundle thickness and the fiber bundle width of the carbon fiber bundle wound on a bobbin and used as a package. In the present invention, the flatness of the cross section of the fiber bundle needs to be in the range of 20 to 200, and more preferably in the range of 30 to 150. When the flatness of the cross section of the fiber bundle is less than 20, a carbon fiber bundle having more than 10,000 filaments cannot sufficiently impregnate the matrix resin inside the carbon fiber bundle when filament winding at high speed, and the resulting composite material In some cases, voids are generated at the same time, and the mechanical properties are lowered simultaneously with the deterioration of the quality of the composite material. Also, when the flatness of the fiber bundle cross section exceeds 200, the end of the bobbin around which the carbon fiber bundle is wound is broken or twisted, and the width of the fiber bundle is narrowed. In addition to the unevenness of the spread and widening properties of the resin, which may cause the impregnation of the matrix resin and the generation of fluff during the process, the surface of the FW molded product may be uneven and the smoothness may be reduced. .

  The short carbon fiber of the present invention is a short carbon fiber having a fiber length of 2 to 60 mm, wherein the sizing agent is attached to the sizing-treated carbon fiber within a range of 1 to 10% by mass per unit mass of the short carbon fiber. is there.

  In this invention, the adhesion amount of the said sizing agent is 1-10 mass% per unit mass, and if it exists in the range of 1-5 mass%, it is more preferable. If the amount of sizing agent attached is less than 1% by mass, the carbon fiber bundles before cutting will be insufficiently focused and the scuff resistance will be insufficient, and fluff will be generated during the cutting process, and the carbon short fibers will be too finely divided after cutting. As a result, the dispersibility and fluidity in the SMC molding process are lowered, voids are easily generated in the obtained composite material, and the mechanical properties are lowered at the same time as the quality of the composite material is lowered. On the other hand, when the adhesion amount of the sizing agent exceeds 10% by mass, the carbon fiber bundle before cutting is excessively focused, and the short carbon fibers after cutting are less likely to be split, resulting in low fluidity in the SMC molding process. The bundle of short carbon fibers is not impregnated with the matrix resin, and voids are easily generated in the resulting composite material.

  Moreover, the short carbon fiber of the present invention has a fiber length of 2 to 60 mm and is more preferably within a range of 4 to 40 mm. When the fiber length is less than 2 mm, the reinforcing effect tends to be reduced. On the other hand, when the fiber length is longer than 60 mm, the flowability of the short carbon fibers at the time of molding is lowered and the formability may be deteriorated. As a cutting means, it can be cut by a known method such as a guillotine cutter or a rotary cutter such as a roving cutter.

  As the carbon fiber bundle of the present invention, for example, a known carbon fiber filament such as polyacrylonitrile (PAN), rayon, or pitch is bundled from several thousand to several tens of thousands, and particularly, a reinforcing effect is obtained. Above all, a PAN-based carbon fiber bundle from which a high-strength carbon fiber bundle can be easily obtained is preferable.

In addition, the strand tensile strength of the carbon fiber bundle of the present invention is appropriately selected depending on the use of the molded body and is not particularly limited, but is preferably 1 to 10 GPa, more preferably 5 to 8 GPa. The strand tensile elastic modulus of the carbon fiber bundle is preferably 100 to 1000 GPa, more preferably 200 to 600 GPa. Here, the strand tensile strength / tensile modulus is measured as follows. Obtained by impregnating a carbon fiber bundle with a resin consisting of “Bakelite (registered trademark)” ERL 4221 / boron trifluoride monoethylamine (BF ₃ .MEA) / acetone = 100/3/4 parts manufactured by Union Carbide Corp. After the resin-impregnated strand was cured by heating at 130 ° C. for 30 minutes, it was measured according to JIS-R-7601 (1986).

  Next, taking the case of using a PAN-based carbon fiber bundle as an example, the method for producing the carbon fiber bundle of the present invention will be described in detail.

  As a spinning method for obtaining a precursor fiber for producing a carbon fiber bundle, a spinning method such as a wet type, a dry type or a dry type can be adopted, but a wet type or a dry type wet type in which high-strength fibers are easily obtained. Spinning is preferred, and dry and wet spinning is particularly preferred. As the spinning dope, a polyacrylonitrile homopolymer or copolymer solution or suspension can be used.

  The spinning solution is spun through a base, solidified, washed with water, and drawn into a precursor fiber. The precursor fiber is subjected to flameproofing treatment, carbonization treatment, and, if necessary, graphitization treatment to obtain a sizing-treated carbon. Use fiber bundles. The obtained fiber bundle is subjected to surface oxidation treatment such as electrolytic surface treatment as necessary in order to improve the adhesive strength with the matrix resin to be combined when it is made into a composite material.

  A sizing agent is attached to such a sizing-treated carbon fiber bundle. In order to attach a sizing agent to a sizing-treated carbon fiber bundle, a method of using a sizing solution in which a sizing agent is dissolved or dispersed in a solvent, applying the sizing solution to the fiber bundle, and drying and removing the solvent Is simple.

  Moreover, in the drying process of the carbon fiber bundle after sizing agent provision, the method of air-drying a carbon fiber bundle in the state which provided the tension | tensile_strength moderately between rollers can be taken. If the carbon fiber bundle is dried in a state of pressing the carbon fiber bundle on the roller, the carbon fiber bundle is fixed in an expanded state, and the flatness of the cross section of the fiber bundle may become larger than 200. The air bundle is dried in the air in a squeezed state (that is, in a state where the fiber bundle width is smaller than that in the case of no tension), so that the flatness of the cross section of the fiber bundle is maintained at 200 or less. It can be done. At this time, it is preferable to apply a tension within a range of 500 to 3000 g. When the tension is less than 500 g, the fiber bundle may be loosened and the fiber bundle may be uneven. Moreover, if tension exceeding 3000 g is applied, thread pain and fluff may occur.

  The concentration of the sizing agent needs to be adjusted as appropriate by adjusting the sizing liquid application method and adjusting the amount of squeezing out the excess sizing liquid after the application, but is usually within the range of 0.5% by mass to 5% by mass. It can be.

  In the present invention, a roller sizing method, a roller dipping method, a spray method, and the like can be used as means for applying the sizing liquid to the sizing-treated carbon fiber bundle. Among them, the sizing treatment carbon fiber bundle having a large number of filaments per bundle can be uniformly applied with a sizing agent, so that the roller dipping method is preferably used, and after applying the sizing liquid, the excess sizing liquid is squeezed. By adjusting the drawing amount to be taken, the sizing agent can be uniformly applied in the carbon fiber bundle. The treatment for drying and removing the solvent is preferably a treatment at a temperature of 120 to 300 ° C. for 10 seconds to 10 minutes, and more preferably a treatment at a temperature of 150 to 250 ° C. for 30 seconds to 4 minutes.

  Although it does not specifically limit as matrix resin used for shaping | molding which applied the carbon fiber bundle of this invention, Usually, the epoxy resin used for FW shaping | molding, PT shaping | molding, and SMC shaping | molding, vinyl ester resin, unsaturated A polyester resin can be suitably used because of its high adhesive strength.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. The measuring method and evaluation method of each physical property used in this example are as shown below.

<Sizing agent adhesion amount>
About 2 g of carbon fiber bundles are weighed (W1) and then heated in an electric furnace (capacity 120 cm ³ ) set at a temperature of 450 ° C. in a nitrogen stream of 50 liters / minute for 15 minutes to completely thermally decompose the sizing agent. . And the carbon fiber bundle after cooling for 15 minutes in a dry nitrogen stream at 20 liters / minute is weighed (W2), and the sizing agent adhesion amount is obtained by the following formula.
Sizing adhesion amount (%) = [W1 (g) −W2 (g)] / [W1 (g)] × 100
<Flatness of fiber bundle cross section>
The flatness of the cross section of the fiber bundle is expressed as a ratio of the fiber bundle width W to the fiber bundle thickness T of the carbon fiber bundle wound on the bobbin and in a packaged state, that is, W / T. Here, the fiber bundle thickness T is determined by unwinding the carbon fiber bundle from the package so that its form does not collapse, and using a high-precision laser light displacement meter Z300 manufactured by OMRON Co., Ltd. The thickness was measured and determined as an average value of n number 10. Further, the fiber bundle width W was measured by applying a scale to the carbon fiber bundle located on the surface of the package, and obtained as an average value of n number 10.

<Interlaminar shear strength>
(1) A vinyl ester (VE) resin carbon fiber bundle wound in one direction, a 350 mm long and 50 mm wide metal frame is set in a 6 mm wide groove and 200 mm long mold, and vinyl ester resin (Showa Polymer) 100 parts of "Lipoxy (registered trademark)" R806) manufactured by Co., Ltd., 0.5 parts of cobalt naphthenate, 1.0 part of methyl ethyl ketone peroxide ("Permec (registered trademark) N" manufactured by NOF Corporation) as a mold And press-molded (room temperature × 24 hours). Subsequently, it was post-cured at 120 ° C. for 2 hours to obtain a test piece. A unidirectional CFRP test piece of 2.5 mm thickness × 6 mm width × 16 mm length is set to a support span of 14 mm using a normal three-point bending test jig (indenter 10 mmφ, fulcrum 4 mmφ), and strain rate is 2.0 mm. The fracture load was measured at / min, and the interlaminar shear strength was calculated according to JIS-K-7078 (1991), which was used as an index of the adhesive strength with the matrix resin.

(2) An epoxy (EP) resin carbon fiber is wound in one direction, a 350 mm long and 50 mm wide metal frame is set in a 6 mm wide groove and 200 mm long mold, and epoxy resin (Japan Epoxy Resin Co., Ltd.) “JER (registered trademark)” 828) 100 parts / boron trifluoride monoethylamine 3 parts kneaded material was poured into a mold, vacuum degassed, and press-molded (170 ° C. × 1 hour). Subsequently, it was post-cured at 170 ° C. for 2 hours to obtain a test piece. A unidirectional CFRP test piece of 2.5 mm thickness × 6 mm width × 16 mm length is set to a support span of 14 mm using a normal three-point bending test jig (indenter 10 mmφ, fulcrum 4 mmφ), and strain rate is 2.0 mm. The fracture load was measured at / min, and the interlaminar shear strength was calculated according to JIS-K-7078 (1991), which was used as an index of the adhesive strength with the matrix resin.

<High-order workability>
A bobbin around which a carbon fiber bundle is wound is placed on a creel, and after pulling the fiber bundle from the creel and impregnating with an epoxy resin, a tank-shaped metal mandrel (92 mm in diameter, hemispherical at both ends, capacity 2000 liters) The yarn was wound at a yarn speed of 30 m / min and a tension of 2 kg by the FW method. The orientation angle of the fibers was a combination of ± 10 / ± 45/90. During this molding, the number of yarn breaks that occurred and the fluff accumulated in the resin impregnation tank and the yarn path guides were collected and weighed. The fluff in the resin impregnation tank was weighed as fluff only by burning off the remaining resin at a temperature of 450 ° C. The number of yarn breaks obtained, the amount of fluff, and the appearance of the molded product were used as indicators of high-order workability. (The appearance of the molded product was evaluated in the following three stages: A: good, B: slightly uneven, C: uneven).

<Resin impregnation>
After polishing the cross section of the FW molded product produced by the above high-order workability evaluation with sandpaper and alumina powder, take a picture with an optical microscope at 25 magnification, and calculate the area ratio where a void of 1 mmΦ or more exists. The void formation status was used as an index for resin impregnation. (A: less than 1%, B: 1 to 5%, C: 5% or more).

<SMC molding>
100 parts by weight of vinyl ester resin (manufactured by Ashland Specialty Chemical Co., Ltd., “Delakane (registered trademark)” 790) as a matrix resin, and tert-butyl peroxybenzoate (manufactured by Nippon Oil & Fats Co., Ltd., “ 1 part by weight of perbutyl (registered trademark) “Z”, 2 parts by weight of zinc stearate (manufactured by Sakai Chemical Industry Co., Ltd., SZ-2000) as an internal mold release agent, and magnesium oxide (Kyowa Chemical Industry ( Using 4 parts by weight of MgO # 40), they were sufficiently mixed and stirred to obtain a resin paste. The resin paste was applied on a polypropylene release film using a doctor blade so that the weight per unit area was 400 g / m ² . From there, the carbon fiber bundle cut to a length of 25 mm was uniformly dropped and dispersed. Further, the resin paste was sandwiched with the other polypropylene film coated with the resin paste so that the weight per unit area was 400 g / m ² . The content of carbon fiber in the SMC sheet was 50% by weight. The obtained sheet was allowed to stand at 40 ° C. for 24 hours, thereby sufficiently thickening the resin paste to obtain a carbon fiber reinforced SMC sheet. Next, the obtained SMC sheet is charged into the mold so that the charging rate (the ratio of the area of the SMC sheet to the mold area when the mold is viewed from above) is 50%, and the heating mold press molding is performed. A flat carbon fiber reinforced composite material of 30 cm × 30 cm × 3 mm was obtained by curing with a machine under conditions of 150 ° C. × 5 minutes under a pressure of 588.4 kPa. The appearance of the molded product was evaluated in the following three stages. A: Good, B: Slightly uneven, C: Uneven.

<Dispersibility>
By observing the SMC sheet obtained by uniformly dropping and spreading the carbon fiber bundle cut to a length of 25 mm obtained by the above method, the state of fluff and cracking of the carbon short fibers was observed, and the dispersibility of the carbon short fibers was observed. It was used as an index. Dispersibility was evaluated in the following three stages. A: Almost no fluff and short carbon fibers are finely cracked, B: Fluff is present, carbon short fibers are slightly agglomerated, and C: A lot of fluff is present and massive carbon short fibers are observed.

<SMC molded product evaluation>
(1) Bending strength A bending strength test piece having a length of 130 ± 1 mm and a width of 25 ± 0.2 mm was cut out from the flat SMC molded plate obtained above. According to the test method specified in ASTM D-790, the support span was set to 100 mm using a three-point bending test jig (indenter diameter 10 mm, fulcrum diameter 10 mm), and the bending strength was measured at a crosshead speed of 5.3 mm / min. . In this example, “Instron (registered trademark)” universal testing machine 4201 type was used as a testing machine. The number of test pieces measured was n = 5, and the average value was the bending strength.

(2) Resin impregnation property By observing the cross section of the bending strength test piece with an optical microscope, the resin impregnation state in the carbon fiber bundle and between the bundles was observed and used as an index of the resin impregnation property. The resin impregnation property was evaluated in the following three stages. A: A state in which no unimpregnated part is observed in the carbon fiber bundle and between the bundles, B: a state in which a slight unimpregnated part is observed, and C: a state in which an unimpregnated part is observed.

Example 1
A sizing-treated carbon fiber comprising 99 mol% allylonitrile and 1 mol% itaconic acid spun, calcined, subjected to electrolytic surface treatment, 24,000 total filaments and no sizing agent added. Got a bunch.

  160 parts of 2,4-tolylene diisocyanate (TDI) is added to 60 parts of polyethylene glycol (ethylene oxide addition moles: 10) monomethyl ether, and stirred at 90 ° C. for 1 hour in a sealed container under a nitrogen atmosphere. Reacted. Next, 800 parts of an epoxy resin (“jER (registered trademark)” 1001 manufactured by Japan Epoxy Resin Co., Ltd.) was added, and the reaction was further advanced. The infrared absorption spectrum of this reaction product was measured, and the reaction was stopped when no isocyanate group was observed. The epoxy equivalent of the urethane-modified epoxy resin (A) thus obtained was 950.

  75% by mass of urethane-modified epoxy resin (A) and 25% by mass of bisphenol A ethylene oxide (16 mol) adduct as polyether (B) are dissolved in dimethylformamide, and mass ratio (A) / (B) = 3 A sizing solution having a concentration of 3% by mass was obtained. This sizing solution is impregnated into the above-mentioned sizing-treated carbon fiber bundle by the dipping method, and then a tension of 700 g is applied between the rollers, and the sizing solution is dried for 2 minutes at a temperature of 200 ° C. with a hot air dryer. A carbon fiber bundle having a mass ratio of 5% by mass and a fiber bundle cross-sectional area of 40 was obtained. The properties of this carbon fiber bundle were a total fineness of 1600 tex, a specific gravity of 1.8, a strand tensile strength of 6.2 GPa, and a strand tensile modulus of 300 GPa.

  Using this carbon fiber bundle, the adhesion strength between the epoxy resin and the vinyl ester resin is measured by the above method, and a FW molded product is prepared by the above method. The characteristics of the obtained carbon fiber bundle and the yarn cracking at the time of FW molding Table 1 shows various evaluation results such as the number of times, the number of yarn breaks, the amount of fluff, and the appearance of the FW molded product.

(Example 2)
A carbon fiber bundle was obtained in the same manner as in Example 1 except that the mass ratio (A) / (B) was set to 9. Table 1 shows various evaluation results such as adhesive strength with the matrix resin and characteristics of the carbon fiber bundle.

(Comparative Example 1)
A carbon fiber bundle was obtained in the same manner as in Example 1 except that the mass ratio (A) / (B) was 1.5. Table 1 shows various evaluation results such as adhesive strength with the matrix resin and characteristics of the carbon fiber bundle.

(Example 3)
In the same manner as in Example 1, urethane-modified epoxy resin (A): 70% by mass, polyether (B): 20% by mass, and bisphenol A type epoxy resin (“JER (registered trademark)” 828 manufactured by Japan Epoxy Resins Co., Ltd. ) 10% by mass was mixed to obtain a sizing agent having a mass ratio (A) / (B) = 3.5. Table 1 shows various evaluation results such as adhesive strength with the matrix resin and characteristics of the carbon fiber bundle.

  From the various evaluation results in Table 1, it can be seen that both the vinyl ester resin and the epoxy resin can obtain high adhesive strength if the ratio (A) / (B) is within a specific range.

Example 4
Using 60 parts of polyethylene glycol (ethylene oxide addition mole number: 20) monobutyl ether, 98 parts of 2,4-tolylene diisocyanate (TDI), and 500 parts of an epoxy resin (“jER (registered trademark)” 1001 manufactured by Japan Epoxy Resin Co., Ltd.) In the same manner as in Example 1, a urethane-modified epoxy resin (A) was obtained. Table 2 shows various evaluation results such as adhesive strength with the matrix resin and characteristics of the carbon fiber bundle.

(Practical example 5)
Implementation using 60 parts of polyethylene glycol (ethylene oxide addition moles: 10) monobutyl ether, 110 parts of hexamethylene diisocyanate (HMDI), 500 parts of epoxy resin (“jER (registered trademark)” 1001 manufactured by Japan Epoxy Resin Co., Ltd.) In the same manner as in Example 1, a urethane-modified epoxy resin (A) was obtained. Table 2 shows various evaluation results such as adhesive strength with the matrix resin and characteristics of the carbon fiber bundle.

(Example 6)
Polyethylene glycol (added moles of ethylene oxide: 20) monobutyl ether 60 parts, 2,4-tolylene diisocyanate (TDI) 98 parts, sorbitol polyglycidyl ether ("Denacol (registered trademark)" EX- manufactured by Nagase ChemteX Corporation) 614; epoxy equivalent 167) 500 parts of epoxy equivalent was used to obtain a urethane-modified epoxy resin (A) in the same manner as in Example 1. Table 2 shows various evaluation results such as adhesive strength with the matrix resin and characteristics of the carbon fiber bundle.

(Example 7)
Carbon fiber in the same manner as in Example 2 except that in the following formula (3), a polyether (B) having an ethylene oxide addition mole number (p + s): 30 and a propylene oxide addition mole number (q + r): 12 was used. Got. Table 2 shows various evaluation results such as adhesive strength with the matrix resin and characteristics of the carbon fiber bundle.

(Comparative Example 2)
75 parts by mass of an epoxy resin (“jER (registered trademark)” 1001 manufactured by Japan Epoxy Resin Co., Ltd.) and the number of moles of ethylene oxide added (p + s) in the above formula (3): 90, the number of moles of propylene oxide added (q + r): Carbon fibers were obtained in the same manner as in Example 1 except that 25 parts by mass of polyether (B) which was 0 was used. Table 2 shows various evaluation results such as adhesive strength with the matrix resin and characteristics of the carbon fiber bundle.

(Comparative Example 3)
Similarly to Example 1, a urethane-modified epoxy resin (A) was obtained in the same manner as Example 1 except that polyethylene glycol (number of moles of ethylene oxide added: 80) was used. Table 2 shows various evaluation results such as adhesive strength with the matrix resin and characteristics of the carbon fiber bundle.

  From the various evaluation results in Table 2, both the vinyl ester resin and the epoxy resin are high by making the urethane-modified epoxy resin (A) and the polyether (B) having the structure represented by the formula (1) essential. It can be seen that the adhesive strength with the matrix resin can be obtained, and at the same time, the scratch resistance and impregnation properties are excellent in the FW molding method.

(Examples 8 and 9, Reference Examples 1 and 2)
Roller that passes through the processing method of the carbon fiber bundle after the sizing liquid concentration is changed in the range of 0.5 mass% to 9 mass% and impregnated with the sizing liquid, the contact time of the heating roller having a surface temperature of 150 ° C. By changing the number and tension between the rollers, carbon fiber bundles having different sizing agent adhesion amounts and flatness ratios of fiber bundle cross sections were obtained in the same manner as in Example 1. Table 3 shows the results of various evaluation tests.

  From the various evaluation results in Table 3, it can be seen that if the sizing agent adhesion amount and the flatness of the fiber bundle cross section are within a specific range, the FW molding method has excellent scratch resistance and impregnation properties.

(Example 10)
A carbon fiber bundle obtained in the same manner as in Example 1 was cut to a length of 25 mm with a roving cutter to obtain carbon short fibers. The adhesion amount of the sizing agent was 1.5% by mass. Fuzz and fluff balls at the time of cutting were hardly observed.

  Table 4 shows various evaluation results such as evaluation of the obtained SMC molded product obtained by using the short carbon fibers and obtaining the SMC molded product by the above method.

(Example 11)
A carbon fiber bundle obtained in the same manner as in Example 9 was cut into a length of 25 mm with a roving cutter to obtain carbon short fibers. Fuzz and fluff balls at the time of cutting were hardly observed. Table 4 shows the results of various evaluations such as SMC molded product evaluation.

(Reference Example 5)
A carbon fiber bundle obtained in the same manner as in Example 8 was cut into a length of 25 mm with a roving cutter to obtain carbon short fibers. A lot of fluff was generated at the time of cutting, and some fluff balls were observed. Table 4 shows the results of various evaluations such as SMC molded product evaluation.

  The carbon fiber bundle of the present invention is excellent in high-order processability such as handling and resin impregnation in filament winding and pultrusion molding, and excellent in moldability such as dispersibility and resin impregnation in sheet molding. Moreover, it provides a carbon fiber reinforced composite material excellent in adhesive strength with a matrix resin, and is suitable for general industrial uses such as tanks, structural materials for aircraft, sports uses such as golf shafts and fishing rods, and the like.

Claims (3)

A polyether (B) which is an adduct of 10 to 50 mol of alkylene oxide of a bisphenol compound represented by the following formula (2) and a urethane-modified epoxy resin (A) having a structure represented by the following formula (1) A sizing agent for carbon fiber, wherein the ratio (A) / (B) is contained at a ratio in the range of 2 to 10.

[Wherein, R 1 represents a saturated aliphatic hydrocarbon group or unsaturated aliphatic hydrocarbon group having 1 to 18 carbon atoms, and X represents an aromatic, alicyclic, or aliphatic divalent linking group. . m is 1 or 2, and n is 5-20. ]

[Wherein, R 2 and R 3 each independently represents a hydrogen atom or a saturated aliphatic hydrocarbon group having 1 to 4 carbon atoms. ]   Carbon in which 0.5 to 4% by mass of the sizing agent according to claim 1 is adhered, the number of filaments is 10,000 to 150,000, and the flatness (width / thickness) of the fiber bundle cross section is 20 to 200. Fiber bundle.   A carbon short fiber having a fiber length of 2 to 60 mm, to which 1 to 10% by mass of the sizing agent according to claim 1 is attached.