KR20190084580A - Sizing agent for carbon fiber and method of preparing carbon fiber using the same - Google Patents

Abstract

The present invention relates to a sizing agent for carbon fiber and a carbon fiber manufacturing method using the same. According to the present invention, the sizing agent for carbon fiber comprises: an epoxy compound (A) with two or more epoxy functional groups; unsaturated polyester resin (B); and a modified epoxy compound (C) with two or more urethane modified functional groups. Accordingly, a hard sizing agent is coated on a surface of carbon fiber and thus, variance in an inter-fiber interval is decreased when the carbon fiber is immersed in resin, a running state of a carbon fiber bundle is good, and an inter-fiber interval of the wound carbon fiber is not changed to prevent twisting of the carbon fiber. Moreover, urethane modified epoxy on a surface of the carbon fiber is changed into a semi-solid state by heating at an inlet of a carding cleaner, thereby increasing processing properties of an opening process. Moreover, a carbon fiber composite material with excellent physical properties and high surface strength is provided, thereby manufacturing a pressure container with uniform explosion pressure.

Description

Technical Field [0001] The present invention relates to a sizing agent for carbon fibers and a method for producing carbon fibers using the same.

The present invention relates to a sizing agent for carbon fibers and a method for producing carbon fibers using the same. More particularly, the present invention relates to a sizing agent for carbon fibers, And then coated with a modified epoxy compound having two or more urethane-denatured functional groups having a large molecular weight to reduce the fluctuation in width upon resin impregnation and to manufacture a pressure vessel having a high explosion pressure due to stable running, And a method for producing carbon fiber using the same.

Carbon fibers produced from acrylonitrile (PAN) polymers are very strong and widely used as raw materials for carbon fibers. More recently, more than 90% of the total carbon fibers are PAN-based carbon fibers. As is well known, as a method of producing carbon fibers, precursor fibers (precursors) such as polyacrylonitrile are subjected to chlorination treatment at 200 to 310 占 폚 in an oxidizing atmosphere to obtain raw chlorinated fibers And then carbonizing the carbon fiber at 350 to 2000 ° C in an inert gas atmosphere to obtain carbon fibers.

Carbon fibers that are excellent in light weight and strength / elastic modulus are composited with various types of matrix resin to become carbon fiber composite material (CFRP). Recently, CFRP has been applied to various fields as it has widened in industrial use. (High strength, high elasticity), light weight (reduction of fiber weight and fiber content), improvement of physical properties of composites (carbon fiber) in sports / leisure field, aerospace field, automobile field, Improvement of fiber surface / interfacial characteristics) is actively being researched and developed. It is known that the physical properties of such a composite material vary depending on the surface functional group, sizing agent, chemical structure and affinity of the matrix resin functional group, and reactivity of the carbon fiber. In particular, The characteristics are different.

On the other hand, pressure vessels generally refer to structures which, under pressure, can contain fluids, such as liquids, liquefied gases, condensed gases, and combinations thereof. These pressure vessels are produced by the filament winding method, which is very useful because it is suitable for the manufacture of cylindrical or spherical shaped articles and also facilitates the automatic manufacturing process. In the filament winding method, generally, the reinforcing fiber, that is, the reinforcing fiber is dipped in the impregnation tank containing the low-viscosity resin to remove the excessive resin, and the reinforcing fiber is wound around the mandrel or the form to produce a pressure vessel or a tubular body. The reinforcing fibers are generally impregnated into the matrix resin and wound or laminated to a plastic liner. Traditionally metal was used in this filament winding method. However, the conventional pressure vessel made of a metallic liner has a problem that it is heavy in weight, very weak in corrosion, and high in manufacturing cost. To solve this problem, the use of pressure vessels in which reinforcing fiber such as carbon fiber or glass fiber is wound or laminated on the outside of plastic liner is increasing. If the viscosity of the resin used for the filament winding is low when carbon fiber is used as the reinforcing fiber, there is a problem that the width of the carbon fiber is varied during the carbon fiber impregnation and the explosion pressure of the pressure vessel is uneven .

It is an object of the present invention to provide a sizing agent for carbon fibers which can improve the problem of width variation during resin impregnation.

Another object of the present invention is to provide a method of manufacturing a carbon fiber capable of producing a pressure vessel having a reduced explosion pressure due to reduced sag width variation during resin impregnation.

Another object of the present invention is to provide a method of manufacturing a pressure vessel in which unevenness of explosion pressure is improved by using a carbon fiber composite material having excellent physical properties and high interfacial strength.

One aspect of the present invention for attaining the above object is to provide a sizing agent for carbon fiber comprising an epoxy compound having at least two epoxy functional groups, an unsaturated polyester resin and a modified epoxy compound having at least two urethane-modified functional groups .

According to another aspect of the present invention for achieving the above object,

Subjecting a precursor fiber bundle containing a polyacrylonitrile polymer to a chlorination process, a preliminary carbonization process, and a carbonization process to obtain a carbon fiber bundle; The carbon fiber bundle is impregnated into a first sizing bath in which a first sizing agent comprising an epoxy compound (A) having two or more epoxy functional groups and an unsaturated polyester resin (B) is dispersed in water, Coating the agent; And

The carbon fiber bundle coated with the epoxy compound is passed through a second sizing bath in which a second sizing agent containing a modified epoxy compound (C) having two or more urethane-modified functional groups is passed through a water-dispersed second sizing bath, And coating the second sizing agent.

According to another aspect of the present invention for achieving the above object,

A sizing agent-coated carbon fiber bundle to which a sizing agent is applied to a carbon fiber bundle, wherein a first sizing agent comprising an epoxy compound (A) having at least two epoxy functional groups on the surface of the carbon fiber bundle and an unsaturated polyester resin (B) Coated carbon fiber bundle coated with a second sizing agent comprising a modified epoxy compound (C) having at least two urethane-modified functional groups on the surface of a carbon fiber bundle coated with the first sizing agent.

According to another aspect of the present invention for achieving the above object,

And a method of manufacturing a pressure vessel using the composite material containing the sizing agent-coated carbon fiber bundle.

The carbon fiber produced by the present invention has a hard sizing agent coated on the surface of the carbon fiber to reduce the variation in width at the time of impregnation with the resin, the running condition of the carbon fiber bundle is good, There is no kink. In addition, since the urethane-modified epoxy on the surface of the carbon fiber is heated to a semi-solid state by heating at the opening of the can opener, the processability of the carding process is improved, and the carbon fiber composite material having excellent physical properties and high interfacial strength is used. A pressure vessel can be manufactured.

1 is a view showing a step of providing a first sizing agent containing an epoxy compound (A) having at least two epoxy functional groups and an unsaturated polyester resin (B) on the surface of a bundle of carbon fibers passing through a first sizing bath according to the present invention FIG.
2 is a schematic view showing a step of providing a second sizing agent containing a modified epoxy compound (C) having two or more urethane-modified functional groups on the surface of the carbon fiber bundle passing through the second sizing bath according to the present invention.

Hereinafter, a sizing agent according to the present invention and a method for producing carbon fiber produced using the sizing agent will be described with reference to the accompanying drawings and examples. Although the terms used in the present invention have been selected as general terms that are widely used at present, there are some terms selected arbitrarily by the applicant in a specific case. In this case, the meaning described or used in the detailed description part of the invention The meaning must be grasped.

Like reference numerals refer to like elements throughout the specification. The use of the terms " lower " and " upper " herein is based on the direction of the gravitational direction.

First, a carbon fiber precursor fiber including a polyacrylonitrile polymer is prepared, and a carbon fiber bundle is obtained by subjecting the precursor fiber to a chlorination process, a preliminary carbonization process, and a carbonization process.

At this time, the carbon fiber precursor fibers are obtained from the acrylonitrile-based polymer, and the properties of the carbon fiber precursor basically vary depending on the composition of the acrylonitrile-based polymer. The main component of the acrylonitrile-based polymer used in the present invention is an acrylonitrile unit, and the content of the acrylonitrile unit is preferably 90% by weight or more, more preferably 95% by weight or more based on the total acrylonitrile- %, For example, 95 to 99 wt%. Here, if the content of the acrylonitrile unit is too small, the strength of the carbon fiber obtained by the firing process is lowered, and the mechanical properties of the carbon fiber may be deteriorated.

The acrylonitrile-based polymer may contain, if necessary, one or more copolymerizable components (auxiliary components other than acrylonitrile), and the content thereof is preferably 10% by weight or more, , More preferably less than 5 wt%, for example, 1 to 5 wt%. Examples of the copolymerization component include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, citraconic acid, maleic acid, alkyl esters (such as methyl acrylate), diamine compounds and triamine compounds.

In order to produce a carbon fiber precursor from such an acrylonitrile-based polymer, the acrylonitrile-based polymer is dissolved in an organic solvent to prepare a dope stock solution, the dope stock solution is spun, the coagulated fiber formed by spinning the dope stock solution is washed , Drawing, drying, emulsion application, and winding. Generally, the process for producing carbon fiber precursor fibers is roughly divided into wet and dry wet spinning processes. As a solvent for preparing the dope solution, dimethyl sulfoxide (DMSO), dimethyl acetate, zinc chloride aqueous solution , Nitric acid, and the like can be used. The amount of the solvent to be used is usually 10 to 30 parts by weight based on 100 parts by weight of the acrylonitrile-based polymer. Here, if the amount of the organic solvent used is too small or too large, it may be difficult to spin the polymer, or void removal may be performed inefficiently.

As a non-solvent for the coagulation bath, a solvent compatible with the organic solvent of the polymer solution but capable of solidifying the polymer without dissolving the polymer can be used without limitation. The non-solvent may be water, preferably a mixture of water and an organic solvent, and if necessary, a solution of three or more components may be used. When an organic solvent is used for the non-solvent, it is preferable that the content thereof is uniformly maintained at about 35 to 85% by weight. The temperature of the non-solvent of the coagulating bath can be adjusted, for example, in the range of 5 to 85 ° C, preferably in the range of 30 to 33 ° C. If the temperature setting is out of the above range, the spinning of the polymer solution is not performed smoothly, the efficiency of the spinning process is lowered and the operation is uneconomical.

The coagulated fiber that has passed through the coagulation bath is washed with water through a washing bath. Further, a squeezing roller can be used to compress the spun solidified fibers, and the pressure of the compression roller is usually 1 to 5 kgf / cm2, preferably 2 to 3 kgf / cm2. When the step of washing and stretching and drying the coagulated fiber is completed, an emulsion is provided. After the emulsion is treated with an aqueous solution containing 0.01 to 5.0% by weight of an emulsion containing an amino-modified silicone emulsion, fine particles and an ammonium compound, Lt; RTI ID = 0.0 > high-temperature < / RTI > The total draw ratio of the prepared precursor fibers is generally 7 to 35 times, and the single fiber fineness is 0.5 to 2.0 dtex. Carbon fibers having uniform physical properties can be produced by subjecting the spun carbon fiber precursor to a chlorination treatment in an oxygen atmosphere and at a temperature of 200 to 310 占 폚 and a carbonization treatment at 350 to 2000 占 폚 in an inert atmosphere according to a conventional method .

A sizing agent is added to the carbon fiber carbon fiber bundle thus produced. The sizing agent according to the present invention is characterized by comprising an epoxy compound (A) having at least two epoxy functional groups, an unsaturated polyester (B) and a modified epoxy compound (C) having at least two urethane-modified functional groups.

The epoxy compound (A) having two or more epoxy functional groups in the molecule can be semi-solid at room temperature to facilitate wetting with the epoxy resin contained in the matrix and to participate in the epoxy curing reaction, Lt; / RTI > The epoxy compound (A) having two or more epoxy functional groups in the molecule may be at least one selected from the group consisting of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol alkylene oxide addition epoxy resin, phenol novolac epoxy resin, But are not limited to, resins, biphenyl-type epoxy resins, hydrogenated bisphenol epoxy resins, alkylene oxide-added epoxy resins of hydrogenated bisphenols, and naphthalene-type epoxy resins.

In the present invention, the unsaturated polyester resin is solid at room temperature and can maintain its shape stability when impregnated with an epoxy resin by a solid phase component. In addition, it participates in the reaction with the vinyl ester sizing agent of the glass fiber which is mixed in the production of the pressure vessel, thereby contributing to the improvement of the physical properties at the glass fiber / carbon fiber interface. Thus, the cycle test of the pressure vessel (repetitive pressure charging and discharging test ) Of the carbon fiber composite material layer and the glass fiber composite material layer.

The viscosity of the unsaturated polyester resin of the present invention is not particularly limited, but it is preferably from 5 to 25 mg KOH / g in terms of V to W (Gardner viscosity), an acid value of from 25 to 25, a gelation time of from 4 to 5 minutes, 10 minutes, and a peak temperature of 175 to 185 ° C can be used. The peak time refers to the time from the transition from gel to solid when ascertaining the gelation time of the resin to the temperature reaching the peak (peak temperature).

The unsaturated polyester resin may include an aliphatic dicarboxylic acid or an anhydride thereof having (a) an aromatic dicarboxylic acid and (b) an unsaturated carbon-carbon double bond as polymerized units. Although not particularly limited, examples of the aromatic dicarboxylic acid (a) include benzene dicarboxylic acid, naphthalene dicarboxylic acid and isophthalic acid. (b) The aliphatic dicarboxylic acid or its anhydride having an unsaturated carbon-carbon double bond may be selected from maleic acid, fumaric acid, gluconic acid, tromatin acid and an anhydride thereof.

In the present invention, the modified epoxy compound (B) having two or more urethane-modified functional groups is solid at room temperature and has at least one ring structure. The cyclic structures such as oxazolidone structure form hydrogen-hydrogen bond between oxygen and epoxy curing structure, and the energy generated by many hydrogen bonds prevents the cracking of the composite material, thereby improving the impact resistance of the composite material Contributing. The modified epoxy compound (C) having two or more urethane-modified functional groups at a room temperature at room temperature has a property that the urethane-modified epoxy on the surface of the carbon fiber is changed into a semi-solid state by heating at the inlet of the can body, It is possible to manufacture a pressure vessel of excellent quality without the use of the above-mentioned method.

The modified epoxy compound (C) having two or more urethane-modified functional groups is obtained by reacting a polyepoxy compound and a polyurethane having an isocyanate content of 0.1 to 10% by mass obtained from a polyhydroxy compound and an excessive polyisocyanate compound have. Examples of the polyisocyanate used herein include, but are not necessarily limited to, hexamethylene diisocyanate, isophorone diisocyanate, norbornadiisocyanate, and the like.

The first sizing agent and the second sizing agent may contain, in addition to the epoxy compound (A) having two or more epoxy functional groups, the unsaturated polyester resin (B) and the modified epoxy compound (C) having two or more urethane- And an accelerator for enhancing the adhesiveness of the fiber and the sizing agent. Thus, convergence or flexibility is imparted to the sizing agent-coated carbon fiber bundle, whereby the handling property, the scratch resistance and the resistance to infiltration can be enhanced, and the impregnation property of the matrix resin can be improved. Further, for the purpose of stability of the sizing agent, an auxiliary component such as a dispersant and a surfactant may be further included.

The sizing pick-up (SPU) of the first sizing agent is 0.3 to 2.8 wt%, and the SPU of the second sizing agent is 0.2 to 2.7 wt%. If the size sizing pick-up of the first sizing agent is less than 0.3 wt%, the thickness of the carbon fiber can be increased due to friction during the process. If the size sizing pick-up of the second sizing agent is less than 0.2 wt% it's difficult.

In the carbon fiber bundle according to the present invention, the produced carbon fiber short fibers are bundled into a bundle of fibers. The number of the staple fibers is preferably 3000 to 43500, more preferably 10000 to 20,000. The total fineness of the sizing agent-coated carbon fiber bundle according to the present invention is preferably 310 to 3000 tex.

Hereinafter, the step of providing a sizing agent comprising an epoxy compound (A) having two or more functional groups in a carbon fiber bundle, an unsaturated polyester (B) and a modified epoxy compound (C) having two or more urethane- The following is an explanation.

1 is a view showing a step of providing a first sizing agent containing an epoxy compound (A) having at least two epoxy functional groups and an unsaturated polyester resin (B) on the surface of a bundle of carbon fibers passing through a first sizing bath according to the present invention FIG. 2 is a schematic view showing a step of providing a second sizing agent containing a modified epoxy compound (C) having two or more urethane-modified functional groups on the surface of the carbon fiber bundle passing through the second sizing bath according to the present invention FIG.

Referring to FIGS. 1 and 2, a carbon fiber bundle 20 having passed through a first turn-guide 30 which carries a carbonized bundle of carbon fibers 20 has two or more epoxy functional groups Is impregnated in a first sizing bath (10) containing a first sizing agent (11) having a water-dispersed epoxy compound (A) and an unsaturated polyester (B) dispersed therein. A second turn-guide 31 is provided in the first sizing bath 10 so that the carbon fiber bundle 20 passing through the first turn-guide 30 passes through the second turn- The surface of the carbon fiber bundle 20 is coated with an epoxy compound. The carbon fiber bundle 20 having passed through the second turn-guide 31 in the first sizing bath 10 passes through the third turn-guide 32 provided at the rear end of the first sizing bath 10, And travels toward the bathtub 40.

The second sizing bath 40 is spaced apart at regular intervals in the running direction of the carbon fiber bundle 20 and includes a lower bath 41 and a lower bath 42 positioned opposite to each other with the carbon fiber bundle 20 as a center, ). The second sizing agent 43 in which the modified epoxy compound (C) having two or more urethane-modified functional groups is dispersed is placed in the lower bath 41 and the upper bath 42.

A modified epoxy compound C having two or more urethane-modified functional groups is coated on one surface of the carbon fiber bundle 20 in the lower bath 41 and the other side surface of the carbon fiber bundle 20 in the upper bathtub 42 (C) having two or more urethane-modified functional groups is coated. Specifically, a fourth turn-guide 33 is provided in the lower bath 41 so that when the carbon fiber bundle 20 passes through the fourth turn-guide 33, A modified epoxy compound (C) having two or more urethane-modified functional groups is coated. The carbon fiber bundle 20 is then spaced apart from the upper portion of the lower tub 41 and passes through the upper tub 42 located opposite the lower tub 41 about the carbon fiber bundle 20, A turn-guide 34 is installed in the upper bath 42 to allow the carbon fiber bundle 20 to pass through the fifth turn-guide 34 to form two urethane- The modified epoxy compound (C) having a functional group of the above-mentioned formula is coated.

Since the fourth turn-guide 33 is partially submerged in the lower tub 41, when the carbon fiber bundle 20 contacts the fourth turn-guide 33 while passing through the fourth turn-guide 33, A second sizing agent 43 applied to the surface of the fourth turn-guide 33 is coated on one surface of the carbon fiber bundle 20 and similarly a fifth turn-guide 34 is coated on the surface of the upper tub 42 The carbon fiber bundle 20 is applied to the surface of the fifth turn-guide 34 when it contacts the fifth turn-guide 34 while passing through the fifth turn-guide 34 A modified epoxy compound (C) having two or more urethane-modified functional groups on both surfaces of the carbon fiber in a so-called kissing type in which the second sizing agent (43) is coated on the other surface of the carbon fiber bundle (20) Coated.

The carbon fiber bundle 20 having passed through the upper bath 42 passes through the sixth turn-guide 35 and is dried in a drier (not shown) provided at the rear end of the second sizing bath 40, A carbon fiber bundle is obtained. In this case, the drying temperature is preferably 110 to 250 ° C, more preferably 210 ° C or less. If the drying temperature is lower than 110 deg. C, drying may not be performed properly. If the drying temperature is higher than 250 deg. C, the functional groups existing on the outermost surface of the carbon fiber tend to disappear due to thermal decomposition. .

In addition, the carbon fiber bundle 20 may be dried in a dryer (not shown) before passing through the first sizing bath 10 and then through the second sizing bath 10. The drying temperature is preferably 110 to 250 ° C, more preferably 210 ° C or less. If the drying temperature is lower than 110 deg. C, drying may not be performed properly. If the drying temperature is higher than 250 deg. C, the functional groups existing on the outermost surface of the carbon fiber tend to disappear due to thermal decomposition. .

In the present invention, the vertical length between the lower bath 41 and the upper bath 42 is preferably set to 10 cm to 1000 cm. When the vertical length is less than 10 cm, the length from the lower bath 41 to the upper bath 42 is too short so that the modified epoxy compound (C) having two or more urethane- It is not sufficiently coated on the surface. When the vertical length exceeds 1000 cm, vibration occurs in the carbon fiber bundle 20 and the tension of the carbon fiber bundle 20 becomes unstable, making it impossible to express the carbon fiber of high quality / high uniformity.

It is preferable that the epoxy compound (A) having two or more epoxy functional groups and the unsaturated polyester (B) are contained in an amount of 40 to 80 mass% with respect to the total amount of the sizing agent applied to the surface of the carbon fiber bundle 20. When the content of the epoxy compound (A) and the unsaturated polyester (B) having two or more epoxy functional groups is less than 40 mass%, the adhesiveness decreases. When the content exceeds 80 mass%, the pressure The physical properties of the container deteriorate during long-term storage. The epoxy compound (A) having two or more epoxy functional groups and the unsaturated polyester (B) are contained in the same composition ratios or are contained in different composition ratios.

The modified epoxy compound (C) having two or more urethane-modified functional groups is preferably contained in an amount of 20 to 60 mass% based on the total amount of the sizing agent applied to the surface of the carbon fiber bundle 20.

According to the sizing agent imparting method of the present invention, the carbon fiber bundle is impregnated in a bath in which the epoxy compound (A) having two or more epoxy functional groups in the molecule and the unsaturated polyester (B) are dispersed in water, A dispersion in which a modified epoxy compound (C) having two or more urethane-denatured functional groups sequentially modified in solid phase is dispersed is coated on both surfaces of a carbon fiber running in a kissing type to prepare a carbon fiber bundle The morphological stability of silkworm is very good.

As described above, according to the present invention, the surface of a carbon fiber is first coated with an epoxy compound (A) having two or more epoxy functional groups and an unsaturated polyester (B) to concentrate the carbon fibers, The surface of the carbon fiber is coated with the modified epoxy compound (C) to prepare a carbon fiber having excellent shape stability. The composite material using the carbon fiber thus produced has excellent physical properties and high interfacial strength, so that a pressure vessel having uniform explosion pressure can be manufactured.

Hereinafter, a process for manufacturing a pressure vessel using the carbon fiber coated with the sizing agent according to the present invention will be described.

The composite material containing the carbon fiber bundle coated with the sizing agent prepared as described above was wound around a plastic liner by a dry filament winding method to produce a pressure vessel, and the pressure vessel thus prepared was placed in a curing furnace at about 100 to 120 ° C Lt; 0 > C for 2 to 3 hours to produce a composite pressure vessel.

The composite material may be formed by using a thermosetting resin such as an epoxy resin, an unsaturated polyester resin, a phenol resin or a diallyl phthalate resin, or a thermoplastic resin such as polyamide, polyolefin, polyacetal, polycarbonate, And then impregnating the matrix resin with carbon fibers.

The pressure vessel of the present invention manufactured as described above is suitably used in general industrial applications such as a storage tank for a fuel tank, a portable gas storage tank and the like, as well as a pipe and a hydraulic line which can be used to transfer a fluid by boosting.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, The facts will be apparent to those skilled in the art. Accordingly, the scope of protection of the present invention should be defined in the appended claims and their equivalents.

10: first sizing bath 11: first sizing agent
20: carbon fiber bundle 30: first turn-guide
31: second turn-guide 32: third turn-guide
33: fourth turn-guide 34: fifth turn-guide
35: Sixth turn - Guide 40: Second sizing bath
41: lower bathtub 42: upper bathtub

Claims (18)

A sizing agent for carbon fibers comprising an epoxy compound (A) having at least two epoxy functional groups, an unsaturated polyester resin (B) and a modified epoxy compound (C) having at least two urethane-modified functional groups.
The sizing agent for carbon fibers according to claim 1, wherein the epoxy compound (A) is a semi-solid at room temperature.
The sizing agent for carbon fiber according to claim 1, wherein the unsaturated polyester resin (B) is solid at room temperature.
The unsaturated polyester resin composition according to claim 1, wherein the unsaturated polyester resin (B) is an aliphatic dicarboxylic acid or an anhydride thereof having (a) an aromatic dicarboxylic acid or (b) an unsaturated carbon- Sizing agent.
The sizing agent for carbon fiber according to claim 1, wherein the modified epoxy compound (C) is solid at room temperature and has at least one ring structure.
Subjecting a precursor fiber bundle containing a polyacrylonitrile polymer to a chlorination process, a preliminary carbonization process, and a carbonization process to obtain a carbon fiber bundle;
The carbon fiber bundle is impregnated into a first sizing bath in which a first sizing agent comprising an epoxy compound (A) having two or more epoxy functional groups and an unsaturated polyester resin (B) is dispersed in water, Coating the agent; And
The carbon fiber bundle coated with the epoxy compound is passed through a second sizing bath in which a second sizing agent containing an urethane-modified denatured epoxy compound (C) having two or more functional groups is dispersed in water, And coating a sizing agent.
[7] The apparatus as claimed in claim 6, wherein the second sizing bath is composed of an upper bathtub and a lower bathtub facing each other with respect to a traveling path of the carbon fiber bundle and spaced apart at regular intervals in the running direction of the carbon fiber bundle, , The second sizing agent is coated on one surface of the carbon fiber, and the second sizing agent is coated on the other surface of the carbon fiber in the upper bathtub.
7. The method of claim 6, wherein a fixed turn-guide is provided in the first sizing bath, and the first sizing agent is coated on the surface of the carbon fiber bundle while the carbon fiber bundle passes through the fixed turn- ≪ / RTI >
The carbon fiber bundle according to claim 7, wherein the carbon fiber bundle passes through a turn-guide partially immersed in the lower tub, while the second sizing agent applied to the surface of the turn-guide in the lower tub is applied to one surface of the carbon fiber bundle And the second sizing agent coated on the surface of the turn-guide in the upper bath while the carbon fiber bundle passes through the turn-guide partially immersed in the upper bath is coated on the other surface of the carbon fiber bundle By weight.
The method of claim 6, wherein the carbon fiber bundle is further dried at a temperature of 110 to 250 DEG C in a dryer before passing through the first sizing bath and the second sizing bath Of the carbon fibers.
The method according to claim 6, wherein the vertical length between the lower bath and the upper bath is 10 cm to 1000 cm.
7. The method of claim 6, wherein the sizing pick-up (SPU) of the first sizing agent is 0.3 to 2.8 wt%, and the SPU of the second sizing agent is 0.2 to 2.7 wt%. ≪ / RTI >
The epoxy resin composition according to claim 6, wherein the epoxy compound (A) having two or more epoxy functional groups and the unsaturated polyester (B) are contained in an amount of 40 to 80 mass% based on the total amount of the sizing agent applied to the surface of the carbon fiber bundle A method for producing a carbon fiber.
A sizing agent-coated carbon fiber bundle to which a sizing agent is applied to a carbon fiber bundle, wherein a first sizing agent comprising an epoxy compound (A) having at least two epoxy functional groups on the surface of the carbon fiber bundle and an unsaturated polyester resin (B) A sizing agent-coated carbon fiber bundle coated with a second sizing agent coated with a second sizing agent comprising a modified epoxy compound (C) having at least two urethane-denatured functional groups on the surface of the carbon fiber bundle to which the first sizing agent is applied.
15. The sizing agent-coated carbon fiber bundle according to claim 14, wherein the SPU of the first sizing agent is 0.3 to 2.8 wt% and the SPU of the second sizing agent is 0.2 to 2.7 wt%.
The epoxy resin composition according to claim 14, wherein the epoxy compound (A) having two or more epoxy functional groups and the unsaturated polyester (B) are contained in an amount of 40 to 80 mass% based on the total amount of the sizing agent applied to the surface of the carbon fiber bundle Sizing agent Coated carbon fiber bundle.
A process for producing a pressure vessel, comprising: winding a composite material comprising a sizing agent-coated carbon fiber bundle according to any one of claims 14 to 16 onto a plastic liner to produce a pressure vessel; And
And curing the pressure vessel in a curing furnace at a temperature of 100 to 120 ° C for 2 to 3 hours.
The method of manufacturing a pressure vessel according to claim 17, wherein the step of manufacturing the pressure vessel is performed by a dry filament winding method.

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