JP6982784B2 - A method for producing a sizing agent-coated carbon fiber and a sizing agent-coated carbon fiber, and a carbon fiber reinforced resin composition. - Google Patents

Description

INDUSTRIAL APPLICABILITY The present invention relates to a sizing agent-coated carbon fiber coated with a sizing agent and a sizing agent-coated carbon fiber, which exhibits high adhesiveness to a thermoplastic resin and exhibits good fiber-opening property in the fiber-spreading step of the sizing agent-coated carbon fiber. It relates to a manufacturing method and a carbon fiber reinforced resin composition.

Since carbon fiber is lightweight but has excellent strength and elastic modulus, many of the composite materials combined with various matrix resins include aircraft members, spacecraft members, automobile members, ship members, civil engineering and building materials, and sporting goods. It is used in the field of. As a typical form of a composite material using carbon fiber, a molded product obtained by press-molding (a molding method of defoaming and shaping under a pressing force) obtained by laminating prepregs can be mentioned. This prepreg is generally produced by impregnating a carbon fiber base material in which continuous carbon fibers are arranged in one direction with a resin. Composite materials using discontinuous carbon fibers (chopped, web, etc.) that have excellent shape followability to complex shapes and can be molded in a short time have also been proposed. In terms of stability, prepreg is excellent in practical performance as a structural material.

In recent years, carbon fiber composite materials have been required to have excellent moldability, handleability, and mechanical properties of the obtained molded product, and industrially higher economic efficiency and productivity have been required. ing. As one of the answers to this demand, the development of prepregs using thermoplastic resin as the matrix resin is underway.

In order to take advantage of the excellent properties of carbon fiber, it is important to improve the adhesiveness between the carbon fiber and the matrix resin. In order to improve the interfacial adhesion between the carbon fiber bundle and the matrix resin, a method is usually performed in which the carbon fiber bundle is subjected to an oxidation treatment such as vapor phase oxidation or liquid phase oxidation to introduce an oxygen-containing functional group on the carbon fiber surface. It has been. For example, Patent Document 1 proposes a method of improving the interlayer shear strength, which is an index of interfacial adhesiveness, by subjecting a carbon fiber bundle to an electrolytic treatment.

If sufficient interfacial adhesiveness cannot be obtained only by surface modification of carbon fibers, an attempt is made to add a sizing treatment. For example, Patent Documents 2 to 4 propose a method for improving interfacial adhesiveness by using a compound having an epoxy group as a sizing agent. Further, Patent Documents 5 and 6 propose a method of improving the compatibility between the carbon fiber coated with the sizing agent and the thermoplastic resin which is a matrix resin by using a sizing agent having an amino group and an amide group. ..

Japanese Unexamined Patent Publication No. 04-361619 Japanese Unexamined Patent Publication No. 63-14114 Japanese Unexamined Patent Publication No. 7-279040 Japanese Unexamined Patent Publication No. 8-113876 Japanese Unexamined Patent Publication No. 2013-166922 Japanese Unexamined Patent Publication No. 2006-89734

As described above, in the field of composite materials using discontinuous carbon fibers, studies on improving adhesiveness are being conducted. On the other hand, in the case of a prepreg using a thermoplastic resin as a matrix resin using the above technique, the defibration property of the carbon fiber bundle coated with the sizing agent and the matrix resin can be obtained from the three viewpoints of carbon fiber, sizing agent, and resin. There was no idea of suppressing the generation of uneven impregnation and voids by achieving both high adhesiveness and improving the impregnation property of the highly viscous thermoplastic resin. It is an object of the present invention to provide a sizing agent-coated carbon fiber bundle that exhibits a high level of adhesiveness to a thermoplastic resin and exhibits good fiber opening property in the fiber opening process.

In the present invention for solving the above-mentioned problems, when the carbon fiber cross section is detected by energy dispersion type X-ray spectroscopy, the composition ratio of oxygen to all elements is 2% or more in the cross section perpendicular to the longitudinal direction of the carbon fiber. The sizing agent-coated carbon fiber has a layer of 10 nm or more and is coated with a sizing agent satisfying the following (a), (b), and (c1) or (c2).
(A) The weight average molecular weight Mw determined by gel permeation chromatography is 650 ≦ Mw ≦ 1900.
(B) γ _Sz > 35 mJ / m ² (γ _Sz : surface free energy of the sizing agent).
(C1) Includes either a compound having an amino group or a compound having an amide group.
(C2) Contains a compound having a trifunctional or higher functional epoxy group.

Further, in the method for producing the sizing agent-coated carbon fiber of the present invention, the weight average molecular weight Mw of the sizing agent before being applied to the carbon fiber, which is obtained by gel permeation chromatography, is 650 or more, or the sizing agent is used. The BET adsorption area of the carbon fiber before coating is 0.5 m ² / g or more.

Further, the carbon fiber reinforced resin composition of the present invention contains a thermoplastic resin having a reactive functional group amount of 30 μmol / g or more, or is a carbon fiber reinforced resin when observed by energy dispersion type X-ray spectroscopy. In the cross section perpendicular to the longitudinal direction of the carbon fiber in the composition, the layer in which the element derived from the thermoplastic resin is infiltrated by 25% or more is 5 nm or more, or the surface free energy γ _r of the thermoplastic resin and the sizing agent. The surface free energy γ _Sz of the following equations (e) and (f)
(E) γ _r > 38 mJ / m ² (γ _r : surface free energy of the thermoplastic resin).
_{^{(F) 2 (γ p r}} · γ p Sz) 0.5 +2 (γ d r · γ d Sz) 0.5> 95 mJ / m 2.

γ ^p _r : Polar component of surface free energy of thermoplastic resin γ ^d _r : Dispersion component of surface free energy of thermoplastic resin γ ^p _Sz : Polar component of surface free energy of ^{sizing agent γ d} _Sz : Surface free of sizing agent In the cross section perpendicular to the longitudinal direction of the carbon fiber in the carbon fiber reinforced resin composition when satisfying the energy dispersion component or detecting the carbon fiber cross section by energy dispersion type X-ray spectroscopy, nitrogen with respect to all elements There is a layer having a composition ratio of 0.5% or more higher than the composition ratio of nitrogen inside the carbon fiber or a layer having an oxygen composition ratio of 3% or more higher than the composition ratio of oxygen inside the carbon fiber of 5 nm or more. It is characterized by.

According to the present invention, it is possible to obtain a sizing agent-coated carbon fiber bundle which has a high level of adhesiveness to a thermoplastic resin and exhibits good fiber opening property in the fiber opening process. As a result, the fibers in the thermoplastic resin molded product can be made uniform, and the mechanical properties of the molded product are also improved.

Hereinafter, embodiments for carrying out the present invention will be described.

In the sizing agent-coated carbon fiber of the present invention, when the carbon fiber cross section is detected by energy dispersion type X-ray spectroscopy, the composition ratio of oxygen to all elements is 2% or more in the cross section perpendicular to the longitudinal direction of the carbon fiber. It is a sizing agent-coated carbon fiber having a layer of 10 nm or more and being coated with a sizing agent satisfying the following (a), (b), and (c1) or (c2).
(A) The weight average molecular weight Mw determined by gel permeation chromatography is 650 ≦ Mw ≦ 1900.
(B) γ _Sz > 35 mJ / m ² (γ _Sz : surface free energy of the sizing agent).
(C1) Includes either a compound having an amino group or a compound having an amide group.
(C2) Contains a compound having a trifunctional or higher functional epoxy group.

The present inventors have developed a sizing agent-coated carbon fiber bundle when the weight average molecular weight of the sizing agent is large even when a compound having a strong interaction with the matrix resin and having high adhesiveness is used as the sizing agent. It was found that there is a problem that the properties tend to deteriorate and impregnation unevenness and void generation easily occur during prepreg production. To solve this problem, it was found that high adhesiveness and high fiber openness can be achieved at the same time by controlling the thickness of the layer having a high oxygen composition ratio on the carbon fiber surface, the molecular weight of the sizing agent, and the surface free energy. rice field.

In the sizing agent-coated carbon fiber according to the present invention, a layer having an oxygen composition ratio of 2% or more (hereinafter, oxidation) when the cross section perpendicular to the longitudinal direction of the carbon fiber is observed by energy dispersive X-ray spectroscopy. It is necessary that the layer (abbreviated as layer) is present at 10 nm or more. The sizing agent-coated carbon fiber obtained by applying the sizing agent to the carbon fiber having a thickness of the oxide layer of 10 nm or more exhibits excellent adhesiveness to the thermoplastic resin. Although the mechanism is not clear, it is considered that the sizing agent and the resin permeate the oxide layer and bond with each other to develop excellent adhesiveness.

In the sizing agent-coated carbon fiber according to the present invention, it is necessary that the weight average molecular weight Mw of the sizing agent applied to the carbon fiber is 650 ≦ Mw ≦ 1900. The weight average molecular weight Mw is measured by a gel permeation chromatograph (hereinafter abbreviated as GPC) method, and polystyrene, pullulan, or the like can be obtained as a standard substance. Since the viscosity of the sizing agent increases as the Mw increases, a large force is required to separate the carbon fibers adhering to each other via the sizing agent. By setting Mw to 1900 or less, the viscosity, which is an index of the mobility of the sizing agent, is lowered, and the force for restraining the carbon fibers is weakened, so that the openness of the carbon fiber bundle is improved. It is more preferable that Mw is 1300 or less. On the other hand, in terms of decomposition, the larger the Mw, the more the volatilization and decomposition of the sizing agent at high temperature can be suppressed. Therefore, the lower limit of the Mw of the sizing agent after being applied to the carbon fiber is preferably 650 or more, preferably 700 or more. It is more preferable to have. Since the sizing agent has a higher Mw than before the sizing coating due to the volatilization of low molecular weight components and the cross-linking between the sizing agents in the drying step at the time of sizing coating, carbon used for producing the sizing agent coated carbon fiber of the present invention. The weight average molecular weight Mw of the sizing agent before being applied to the fibers is preferably 650 or more.

The sizing agent constituting the present invention _{needs to have a surface free energy γ Sz} of the sizing agent larger than 35. When the surface free energy is 35 or more, the adhesiveness is improved, preferably 45 or more.

The sizing agent constituting the present invention needs to either contain a compound having an amino group or a compound having an amide group, or contain a compound having a trifunctional or higher functional epoxy group. Adhesion is improved by containing either a compound having an amino group, a compound having an amide group, or a compound having a trifunctional or higher functional epoxy group. Although the mechanism is not clear, compounds having amino groups and amide groups have high polarity and strongly interact with oxygen-containing functional groups such as carboxyl groups and hydroxyl groups on the surface of carbon fiber bundles and resins, such as hydrogen bonds. Therefore, it is considered that excellent adhesiveness is exhibited. The reason why a compound having a trifunctional or higher functional epoxy group tends to have high adhesiveness is that the sizing agent crosslinks the oxide layers with each other as the amount of the functional group increases, and a strong oxide layer film is formed on the surface of the carbon fiber. By forming the above, it is considered that the adhesiveness with the thermoplastic resin tends to be high due to the anchor effect. The sizing agent constituting the present invention may contain the above-mentioned compound having an amino group or a compound having an amide group, and a compound having a trifunctional or higher functional epoxy group as a mixture of two or more kinds, respectively. It may be contained as a compound having more than one kind of functional group.

The sizing agent constituting the present invention preferably contains a compound having an amino group, and the amino group value thereof is preferably 2 to 200 mmol / g. When the carbon fiber bundle coated with the sizing agent containing the compound having an amino group has an amino base value of 2 mmol / g or more, the affinity with the surface of the reinforcing fiber becomes large and sufficient interfacial adhesiveness can be obtained. There is no particular upper limit on the amino base value, but the adhesiveness may be saturated at 100 mmol / g or more. A more preferable range of the amino base value is 15 mmol / g or more, and more preferably 20 mmol / g or more.

The amino base value is an index indicating the total amount of 1, 2 and tertiary amines measured according to ASTM D2074, and indicates the number of moles of potassium hydroxide corresponding to the amount of hydrochloric acid required to neutralize 1 g of compound (A).

Examples of the above-mentioned compound having an amino base value of 2 to 200 mmol / g include an aliphatic amine compound and an aromatic amine compound. Of these, an aliphatic amine compound is preferable from the viewpoint of exhibiting high adhesiveness. The reason why the aliphatic amine compound has high adhesiveness is considered to be that the polarity is very high as compared with other compounds having an amino group or an amide group.

Specific examples of aliphatic amine compounds include diethylenetriamine, triethylenetetramine, dicyandiamide, tetraethylenepentamine, diproprendamine, piperidine, N, N-dimethylpiperazine, triethylenediamine, polyamideamine, octylamine, and laurylamine. Adipose monoamines such as myristylamine, stearylamine, cocoalkylamine, beef alkylamine, oleylamine, hardened beef alkylamine, N, N-dimethyllaurylamine, N, N-dimethylmyristylamine; polyethyleneimine, polypropireimin, poly Butylene imine, 1,1-dimethyl-2-methylethyleneimine, 1,1-dimethyl-2-propylethyleneimine, N-acetylpolyethyleneimine, N-propionylpolyethyleneimine, N-butylylpolyethyleneimine, N-paleryl Examples thereof include polyalkylene amines such as polyethyleneimine, N-hexanoylpolyethyleneimine, N-stearoylpolyethyleneimine; and derivatives thereof, and mixtures thereof.

Among the aliphatic amine compounds, a compound having a functional group amount of 2 or more contained in one molecule is preferably used because it tends to have high adhesiveness. In particular, polyalkyleneimine is preferably used because it is easy to increase the amount of functional groups contained in one molecule and it is easy to improve the adhesiveness. It is considered that the reason why the adhesiveness of the compound containing 2 or more functional groups in one molecule tends to increase is that the polarity of the molecule tends to increase as the amount of functional groups increases.

Specific examples of aromatic amines include 1,2-phenylenediamine, 1,3-phenylenediamine, 1,4-phenylenediline, benzidine, triaminophenol, triglycidylaminocresol, 2,4,6-tri. Aminophenol, 1,2,3-triaminopropane, 1,2,3-triaminobenzene, 1,2,4-triaminobenzene, 1,3,5-triaminobenzene and its derivatives, and mixtures thereof. And so on.

The sizing agent constituting the present invention preferably contains a compound having an amino group or a compound having an amide group, and the surface free energy γ _{Sz of the} sizing agent is preferably larger than 50. When the surface free energy γ _Sz is 50 or more, the adhesiveness is improved, preferably 55 or more.

The carbon fiber coated with the sizing agent containing the compound having an amino group or the compound having an amide group is characterized in that the oxide layer and the sizing agent form an amide bond. Since the oxide layer and the sizing agent form an amide bond, the sizing agent crosslinks the oxide layers with each other, and a strong oxide layer film is formed on the surface of the carbon fiber. It is considered that the adhesiveness with is improved.

The sizing agent constituting the present invention preferably contains a compound having a trifunctional or higher functional epoxy group, and the epoxy equal amount of the sizing agent is preferably 50 to 1000 g / eq. When the equal amount of epoxy is 1000 or less, the adhesiveness is improved, and the physical properties of the thermoplastic resin molded product using the same are also improved. When the epoxy equal amount is larger than 50, the thermal stability of the compound becomes high, and it becomes difficult to decompose by heating.

Further, the sizing agent containing the above-mentioned compound having a trifunctional or higher functional epoxy group preferably contains a polyether type or a polyol type aliphatic epoxy.

The carbon fiber bundle coated with the sizing agent containing the polyether type or polyol type aliphatic epoxy exhibits excellent adhesion to the thermoplastic resin. As a result, the mechanical properties of the thermoplastic resin molded product using the carbon fiber bundle coated with the sizing agent are improved. Although the mechanism is not clear, the polyether-type or polyol-type aliphatic epoxy groups are highly reactive and form strong chemical bonds with oxygen-containing functional groups such as carboxyl groups and hydroxyl groups on the surface of carbon fiber bundles and resins. , It is considered to exhibit excellent adhesiveness.

In the present invention, specific examples of the polyether type or polyol type aliphatic epoxy include, for example, a glycidyl ether type epoxy compound derived from a polyol.

Examples of the glycidyl ether type epoxy compound include a glycidyl ether type epoxy compound obtained by reaction with epichlorohydrin. Further, as glycidyl ether type epoxy compound, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polypropylene glycol, trimethylene glycol, 1, 2 -Butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, polybutylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,4 -Cyclohexanedimethanol, hydrogenated bisphenol A, hydrogenated bisphenol F, glycerol, diglycerol, polyglycerol, trimethylolpropane, pentaerythritol, sorbitol, and arabitol and glycidyl ether type epoxy obtained by reaction with epichlorohydrin. Compounds are also exemplified. Further, as the glycidyl ether type epoxy compound, a glycidyl ether type epoxy compound having a dicyclopentadiene skeleton is also exemplified.

The sizing agent constituting the present invention preferably contains a compound having a trifunctional or higher functional epoxy group, and the surface free energy γ _{Sz of the} sizing agent is preferably larger than 40. When the surface free energy γ _Sz is 40 or more, the adhesiveness is improved, preferably 45 or more.

In the method for producing carbon fiber coated with a sizing agent according to the present invention, it is preferable that ^{the BET adsorption area α of the carbon fiber before sizing is applied is 0.5 m 2 / g.} When the BET adsorption area α is 0.5 m ² / g, the surface area of the carbon fiber is increased and the adhesiveness is improved.

The thermoplastic resin contained in the carbon fiber reinforced resin composition according to the present invention preferably has a reactive functional group amount of 30 μmol / g or more in the resin. When the amount of the reactive functional group is 30 μmol / g or more, the interaction with the oxide layer and the sizing agent becomes strong, and the adhesiveness is improved.

The carbon fiber reinforced resin composition according to the present invention contains 25 thermoplastic resin-derived elements in a cross section perpendicular to the longitudinal direction of the carbon fibers in the carbon fiber reinforced resin composition when observed by energy dispersion type X-ray spectroscopy. It is preferable that the layer infiltrating% or more is 5 nm or more. By penetrating into the elemental oxide layer derived from the thermoplastic resin, the interaction between the oxide layer or the sizing agent and the resin becomes stronger, and the adhesiveness is improved.

The surface free energy γ _r of the thermoplastic resin and the surface free energy γ _Sz of the sizing agent according to the present invention preferably satisfy the following formulas (e) and (f).
(E) γ _r > 38 mJ / m ² (γr: surface free energy of thermoplastic resin).
_{^{(F) 2 (γ p r}} · γ p Sz) 0.5 +2 (γ d r · γ d Sz) 0.5> 95 mJ / m 2.

γ ^p _r : Polar component of surface free energy of thermoplastic resin γ ^d _r : Dispersion component of surface free energy of thermoplastic resin γ ^p _Sz : Polar component of surface free energy of ^{sizing agent γ d} _Sz : Surface free of sizing agent Dispersive component of energy.

The thermoplastic resin constituting the present invention preferably has a surface free energy γ _r larger than 38. When the surface free energy γ _r is larger than 38, the interaction with the oxide layer and the sizing agent becomes stronger, and the adhesiveness is improved. In order to further improve the adhesiveness, it is more preferable that _{the surface free energy γ r is larger than 40.}

The left side of the formula (f) is the bonding work Wa of the sizing agent and the thermoplastic resin, which is the energy required to separate the two adhered phases. When it exceeds 95 mJ / m ² , the interaction between the sizing agent and the thermoplastic resin becomes strong. It is more preferably 100 mJ / m ^{2 or more.}

_{^{Here, γ p r, γ d r}} , γ p Sz, γ d Sz polar component of the surface free energy of each thermoplastic resin, the dispersion component of the surface free energy of the thermoplastic resin, the polarity of the surface free energy of the sizing agent The components and the dispersion components of the surface free energy of the sizing agent are shown. The polar component of the surface free energy is a component of the interaction acting on the electric dipole acting between the polar functional groups, and the dispersion component is a component of the interaction acting on the van der Waals force. At the interface where the solid and the liquid adhere, it is considered that an interaction acts between the same components of the two phases. Therefore, in order to strengthen the interaction and improve the adhesiveness, the carbon fiber bundle and the sizing agent having a large polar component of the surface free energy, or the carbon fiber bundle and the sizing agent having a large dispersion component of the surface free energy. It is important to use a sizing agent-coated carbon fiber bundle in which the agents are combined from the viewpoint of enhancing the adhesiveness.

Adhesive work Wa is calculated by the following method.

If the contact angle between the solid 1 and the liquid 2 adhering to each other is θ _1/2 , the Young's equation shown in the equation (1) is established.
cosθ _1/2 = (γ _{1 −} γ _1/2 ) _/ γ ₂ ... (1).

Here, γ _{1 and} γ ₂ indicate the surface free energy of the solid 1 and the liquid 2, respectively, and γ _1/2 indicates the interfacial free energy in the state where the solid 1 and the liquid 2 are adhered to each other. Here, the surface free energy γ can be represented by the sum of the ^{polar component γ p} and the dispersion component γ ^d.
γ ₁ = γ ^p ₁ + γ ^d ₁ ... (2)
γ ₂ = γ ^p ₂ + γ ^d ₂ ... (3).

Further, the bonding work Wa between the solid 1 and the liquid 2 bonded to each other is defined by the difference between the energy before bonding and the energy after bonding, and can be expressed by Dupre's equation (4).
Wa = γ ₁ + γ _2- γ _1/2 ... (4)
From the equations (1) and (3), the Young-Dupre equation (5) is established.
Wa = γ ₂ (1 + cos θ _1/2 ) ... (5).

When the geometric mean rule (6) of each component of the surface free energy is applied to this Wa, the equation (7) is established, and the solid 1 is used as a carbon fiber bundle and the liquid 2 is used as a sizing agent to disperse the respective surface free energies. By obtaining the component and the polar component, the adhesive work Wa specified in the present invention can be calculated.
γ _{1/2 = γ 1 +} γ ₂ -2 (γ ^p _1, γ ^p ₂ ) ^0.5 -2 (γ ^d _1, γ ^d ₂ ) ^0.5 ... (6)
Wa = 2 (γ ^p _1, γ ^p ₂ ) ^0.5 + 2 (γ ^d _1, γ ^d ₂ ) ^0.5 ... (7).

In the present invention, the surface free energy of the thermoplastic resin and the sizing agent can be calculated by using the approximate formula of Owens.

The approximate equation of Owens is the surface free energy γ _L of the liquid, the polar component γ ^p _{L of} the surface free energy, the dispersion component γ ^d _L of the surface free energy, and the contact angle θ obtained by the measurement. Substitute in 10) and plot in X and Y. The square of the slope a of the approximate expression linearly approximated by the least squares method of the plot prepared using the liquid in which the polar component and the dispersion component of two or more kinds of surface free energies are known is γ ^p _{CF and the} intercept b squared. Can be obtained as γ ^d _CF.
Y = a ・ X + b ・ ・ ・ (8)
X = (γ ^p _L ) ^0.5 / (γ ^d _L ) ^0.5 ... (9)
Y = (1 + cosθ) · (γ _L ) / 2 (γ ^d _L ) ^0.5 ... (10).

The surface free energy of the thermoplastic resin is based on the contact angle measured from the shape of the prepared droplet by dropping a liquid whose polar component and dispersion component of the surface free energy are known on a flat plate of the thermoplastic resin. squaring the gamma ^{p r} of the slope a from the approximate expression of the aforementioned _Owens, the square of the intercept b can be obtained as gamma ^d _r.

The surface free energy of the sizing agent is the above-mentioned formula (8) based on the contact angle measured from the shape of the prepared droplet by dropping the sizing agent on the thermoplastic resin flat plate whose surface free energy is calculated by the above method. ^{) ~ Gamma p} _{L and} γ ^d _L in the equation (10) can be changed to ^{γ p} _{s and} γ ^d _{s, respectively.}
The carbon fiber reinforced resin composition according to the present invention has a composition ratio of nitrogen to all elements in a cross section perpendicular to the longitudinal direction of the carbon fibers in the carbon fiber reinforced resin composition when observed by energy dispersion type X-ray spectroscopy. It is preferable that there is a layer having a composition ratio of 0.5% or more higher than that of nitrogen inside the carbon fiber or a layer having an oxygen composition ratio of 3% or more higher than the composition ratio of oxygen inside the carbon fiber of 5 nm or more. .. It is considered that the permeation of the sizing agent into the oxide layer increases the composition ratio of the nitrogen element and oxygen element derived from the sizing agent, and strengthens the interaction between the oxide layer and the sizing agent and the resin to improve the adhesiveness. ..

Next, the components constituting the sizing agent-coated carbon fiber bundle used in the present invention will be described.

The carbon fiber bundle used in the present invention is not particularly limited, but polyacrylonitrile-based carbon fibers are preferably used from the viewpoint of mechanical properties. The polyacrylonitrile-based carbon fiber bundle used in the present invention is obtained by subjecting a carbon fiber precursor fiber made of a polyacrylonitrile-based polymer to a flame-resistant treatment at a maximum temperature of 200 to 300 ° C. in an oxidizing atmosphere and then in an inert atmosphere. It is obtained by performing a preliminary carbonization treatment at a maximum temperature of 500 to 1200 ° C., and then carbonizing at a maximum temperature of 1200 to 2000 ° C. in an inert atmosphere.

In the present invention, in order to improve the adhesiveness between the carbon fiber bundle and the thermoplastic resin, it is preferable to introduce an oxygen-containing functional group into the surface by subjecting the carbon fiber bundle to an oxidation treatment. As the oxidation treatment method, gas phase oxidation, liquid phase oxidation and liquid phase electrolytic oxidation are used, but liquid phase electrolytic oxidation is preferably used from the viewpoint of high productivity and uniform treatment.

In the present invention, examples of the electrolytic solution used in the liquid phase electrolytic oxidation include an acidic electrolytic solution and an alkaline electrolytic solution. Examples of the acidic electrolytic solution include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, boric acid, and carbonic acid, organic acids such as acetic acid, butyric acid, oxalic acid, acrylic acid, and maleic acid, or ammonium sulfate and ammonium hydrogensulfate. And other salts. Of these, sulfuric acid and nitric acid, which are strongly acidic, are preferably used. Specific examples of the alkaline electrolytic solution include an aqueous solution of a hydroxide such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide and barium hydroxide, sodium carbonate, potassium carbonate, magnesium carbonate and calcium carbonate. An aqueous solution of carbonate such as barium carbonate and ammonium carbonate, an aqueous solution of hydrogen carbonate such as sodium hydrogen carbonate, potassium hydrogen carbonate, magnesium hydrogen carbonate, calcium hydrogen carbonate, barium hydrogen carbonate and ammonium hydrogen carbonate, ammonia, tetraalkylammonium hydroxide. And an aqueous solution of hydrazine.

Next, a method for producing the sizing agent-coated carbon fiber according to the present invention will be described.

First, a means for applying (applying) the sizing agent constituting the present invention to carbon fibers will be described.

In the present invention, the sizing agent is preferably diluted with a solvent and used as a uniform solution. Examples of such a solvent include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, dimethylformamide, dimethylacetamide and the like, but among them, they are easy to handle and are advantageous from the viewpoint of safety. Therefore, water is preferably used.

As the coating means, for example, a method of immersing the carbon fiber bundle in the sizing agent solution via a roller, a method of contacting the carbon fiber bundle with the roller to which the sizing agent solution is attached, and a method of atomizing the sizing agent solution into a carbon fiber bundle. Although there are methods such as spraying, in producing the sizing agent-coated carbon fiber bundle of the present invention, the method of immersing the carbon fiber bundle in the sizing agent solution via a roller is preferably used. Further, the means for applying the sizing agent may be either a batch type or a continuous type, but a continuous type that has good productivity and can reduce the variation is preferably used. It is also a preferred embodiment to vibrate the carbon fiber bundle with ultrasonic waves when the sizing agent is applied.

In the present invention, it is preferable to obtain a sizing agent-coated carbon fiber bundle by, for example, contacting a heated roller with a carbon fiber bundle by a contact-type drying means after applying the sizing agent solution. The carbon fiber bundle introduced into the heated roller is pressed against the heated roller by tension and dried rapidly, so that the flat form of the carbon fiber bundle widened by the heated roller is easily fixed by the sizing agent. Since the contact area between the single fibers of the carbon fiber bundle having a flat morphology is small, the fibrous opening property tends to be high.

Further, in the present invention, after passing through a heated roller as a preliminary drying step, further heat treatment may be added as a second drying step. For the heat treatment as the second drying step, either a contact method or a non-contact heating method may be adopted. By performing the heat treatment, the diluting solvent remaining in the sizing agent can be further removed and the viscosity of the sizing agent can be stabilized, so that the fiber opening property can be stably enhanced.

Further, the heat treatment can be performed by microwave irradiation and / or infrared irradiation.

In the present invention, it is preferable that the carbon fiber bundle coated with the sizing agent is composited with the thermoplastic resin (B) to form a carbon fiber reinforced resin composition. Examples of the thermoplastic resin (B) constituting the present invention include a polyketone resin, a polyether ketone resin, a polyether nitrile resin, a polyimide resin, a polyamide imide resin, a polyetherimide resin, a polysulfone resin, a polyether sulfone resin, and a polyarylene. At least one selected from the group consisting of sulfide resin, polyether ether Kenton resin, polyphenylene ether resin, polyoxymethylene resin, polyamide resin, polyester resin, polycarbonate resin, fluororesin, styrene resin and polyolefin resin. Thermoplastic resin is preferred.

Next, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

<Measurement method of weight average molecular weight Mw>
The weight average molecular weight of the sizing agent can be measured by a known method using polystyrene as a standard substance using GPC. In the present invention, the following conditions are adopted as the measurement conditions of GPC.

Measuring device: Shimadzu detector: Refractometer (Shimadzu)
(When a sizing agent other than the following (A-2, A-3) is used)
Column used: TSKgel HXL-L + TSKgel α-3000 manufactured by TOSOH BIOSCIENCE
Eluent: Dimethylformamide 0.01 mol / L Lithium bromide solution Standard substance: Polystyrene (manufactured by Tosoh)
(When the following (A-2, A-3) are used as the sizing agent)
Column used: Showa Denko Shodex Asahipac GF-710HQ + GF-510HQ + GF-310HQ
Eluent: 0.2 mol% -monoethanolamine aqueous solution (adjusted to pH 5.1 by adding acetic acid)
Standard substance: Pullulan (manufactured by Sigma-Aldrich).

<Measuring method of sizing adhesion amount>
After weighing 2.0 ± 0.5 g of sizing-coated carbon fiber bundle (W ₁ ) (reading to the 4th place in the minority), an electric furnace (capacity) set to a temperature of 450 ° C. in a nitrogen stream of 50 ml / min. Leave in 120 cm ³ ) for 15 minutes to completely pyrolyze the sizing agent. Then, the carbon fiber bundles are transferred to a container in a dry nitrogen stream of 20 liters / minute, cooled for 15 minutes, weighed (W ₂ ) (read to the fourth decimal place), and sized and adhered by _{W 1-} W _2. Find the amount. The value obtained by converting this sizing adhesion amount into a mass part with respect to 100 parts by mass of the carbon fiber bundle (rounded to the third decimal place) was taken as the adhesion amount (mass part) of the adhered sizing agent. The measurement was performed twice, and the average value was taken as the amount of the sizing agent adhered.

<Measurement method of interfacial shear strength>
A single yarn is extracted from the carbon fiber bundle, sandwiched from above and below with a resin film laminated so as to have a thickness of 0.4 mm or more, heated and pressed by a heat press device, and then heated to room temperature while maintaining the pressurized state. After cooling, a molded plate in which a single carbon fiber yarn was embedded was obtained. A dumbbell-shaped test piece for IFSS measurement was punched out from this molded plate using an SD type lever cutting machine.

Both ends of the dumbbell-shaped sample were sandwiched, and a tensile force was applied in the fiber axial direction (longitudinal direction) to generate 12% of strain at a speed of 2.0 mm / min. Then, 20 mm of the central portion of the test piece was cut out and heated to a temperature equal to or higher than the melting point of the thermoplastic resin while being sandwiched between glass plates on a hot plate. The fragmented fiber length inside the sample made transparent by heating was observed under a microscope. Further, the critical fiber length lc was calculated from the average broken fiber length la by the formula of lc (μm) = (4/3) × la (μm). The strand tensile strength σ and the diameter d of the carbon fiber single yarn were measured, and the interface shear strength (IFSS), which is an index of the adhesive strength between the carbon fiber and the resin interface, was calculated by the following equation. In the examples, the average of the number of measurements n = 5 was used as the test result.
IFSS (MPa) = σ (MPa) × d (μm) / (2 × lc) (μm)
In the present invention, the preferable range of IFSS was evaluated on a four-point scale based on different criteria for each of the following resins, and ⊚ and ◯ were accepted.
-Resin: Polyphenylene sulfide
⊚: IFSS is greater than 26 ○: IFSS is 24 or more and 26 or less Δ: IFSS is 22 or more and less than 24 ×: IFSS is less than 22.
-Resin: Polyvinylidene fluoride
⊚: IFSS is greater than 18 ○: IFSS is 15 or more and 18 or less Δ: IFSS is 10 or more and less than 15 ×: IFSS is less than 10.

<Measuring method of spreadability (spread retention rate)>
Prepare three carbon fiber bundles cut to a length of 380 mm, and arrange the three evenly on a cardboard (width 300 mm, length 430 mm) placed on a horizontal work table. Next, the upper 1/3 of both ends of the thread bundle protruding in the width direction are fixed with tape. Then, pinch the lower 1/3 of the lower ends of the thread bundle protruding in the width direction with both hands, pull it in parallel toward the lower part for 3 seconds, and release the hand. The thread width of the thread bundle having good fiber opening property remains 80 mm, but the thread width of the thread bundle having poor fiber opening property is shortened. After repeating this three times, the yarn width of each yarn bundle was measured and the average value was obtained. Finally, the spread retention rate was calculated by dividing the average value of the yarn width by 80 mm.
The spread retention rate was evaluated on a 4-point scale according to the following criteria, and ◎ and ○ were judged as acceptable.

⊚: Open fiber retention rate is 0.95 or more ○: Open fiber retention rate is 0.90 or more and less than 0.95 Δ: Open fiber retention rate is 0.80 or more and less than 0.90 ×: Open fiber retention rate is Less than 0.80.

<Measurement method of BET adsorption specific surface area>
The BET adsorption area of carbon fiber can be measured by a known method using krypton gas. In the present invention, the following conditions are adopted for measuring the BET adsorption area.

Measuring device: BELSORP-max made by Nippon Bell
Adsorbent: Kr
Measurement temperature: 77K (liquid nitrogen temperature)
Saturated vapor pressure: 0.331 kPa
Pretreatment temperature / time: 300 ° C / 5 hours Decompression degassed specific surface area analysis method: BET multipoint method.

<Method of measuring the thickness of the oxide layer, the composition ratio of the elements, and the degree of penetration of the resin into the oxide layer>
The thickness of the region (oxide layer) having a high oxygen concentration on the surface of the carbon fiber was measured by the following method.

A slice of carbon fiber having a thickness of about 100 nm was prepared by using a focused ion beam (FIB) in the cross-sectional direction. In addition, the surface of the carbon fiber was protected with amorphous carbon. Arbitrary three points were measured with an atomic resolution analysis electron microscope device with a spot diameter of 0.2 nm or less using energy dispersive X-ray spectroscopy as a detector. The ratio of the element concentration was measured in a width of 80 nm toward the protective film, with the inside of the carbon fiber as the measurement start point in the direction perpendicular to the circumference of the carbon fiber. The thickness at which the oxygen concentration was 2% or more in the line profile was defined as the thickness of the region where the oxygen concentration was high on the surface of the carbon fiber.

The ratio of the concentration of each element inside the carbon fiber was obtained from the average value at any five points between the measurement start point and the point where the oxygen concentration started to increase. Further, in the above line profile, when the composition ratio (%) of nitrogen inside the carbon fiber is N ₁ and the composition ratio of nitrogen inside the oxide layer is N ₂ , the portion Z where _{N 1} + 0.5 ≦ N _{2 is satisfied. When} the composition ratio (%) of oxygen inside the carbon fiber is O ₁ and the composition ratio of oxygen inside the oxide layer is O ₂ , the following criteria are used for the portion Z ₂ where O ₁ + 3 ≦ O _2. Was evaluated on a two-point scale using, and ○ was regarded as a pass.

◯: Z ₁ or Z ₂ is 5 nm or more.

X: Both Z ₁ and Z ₂ are less than 5 nm.

The permeation thickness of the thermoplastic resin-derived element into the oxide layer was measured by the following method.

A slice of carbon fiber having a thickness of about 100 nm was prepared by using a focused ion beam (FIB) in the cross-sectional direction. Arbitrary three points were measured with an atomic resolution analysis electron microscope device with a spot diameter of 0.2 nm or less using energy dispersive X-ray spectroscopy as a detector. Crystal lattice fringes derived from the crystal structure inside the carbon fiber were observed from the BF (bright field) image, and superimposed on the element mapping image obtained from the EDX image in the same field of view. The part where the crystal lattice fringes were not observed and the oxygen concentration was concentrated was defined as the oxide layer. Subsequently, the ratio of the element concentration was measured with a width of 80 nm toward the thermoplastic resin in the direction perpendicular to the circumference of the carbon fiber, with the inside of the carbon fiber as the measurement start point. In the line profile, of the ratio of element concentration specific element X in the thermoplastic resin, the proportion of X in the boundary of the carbon fibers inside the oxide layer W _3, at the border of the oxide layer and the thermoplastic resin When the ratio of X was W ₄ , the _{partial Y in which (W 3} + W ₄ ) / 4 ≦ Y ≦ W ₄ was evaluated in two stages using the following criteria, and ◯ was regarded as acceptable.

◯: Y is 5 nm or more.

X: Y is less than 5 nm.
The following equipment was used for sample preparation.

Sample preparation: FIB method SIINT SMI3200SE
Hitachi FB-2000A-2 Micro Sampling System FEI Strata400S
Analytical device: Atomic resolution analysis electron microscope JEM-ARM200F manufactured by JEOL
EDX detector Centurion made by JEOL (100mm ² silicon drift (SDD) type)
Measurement conditions: Acceleration voltage 200 kV.

<Evaluation method of surface free energy of thermoplastic resin>
The surface free energy of the thermoplastic resin was determined according to the following procedure.

2 μl of the solvent was gently dropped onto a flat plate of the thermoplastic resin. At this time, the contact angle was calculated from the shape of the water droplet using the θ / 2 method. For the contact angle, the average value of each 10 points was used. Purified water as the solvent, ethylene glycol, and using the tricresyl phosphate, following the surface free energy by using the approximate expression of Owens gamma _r, surface free polar component energy gamma ^{p _r,} and the surface free dispersion component of energy gamma ^d _r was calculated.

The approximate expression of Owens was obtained by substituting the surface free energy component and contact angle peculiar to each solvent, plotting them on X and Y, and then calculating the slope a and the intercept b when linearly approximated by the least squares method. ..
Y = a ・ X + b
X = (γ ^p _L ) ^0.5 / (γ ^d _L ) ^0.5
Y = (1 + cosθ) · (γ _L ) / 2 (γ ^d _L ) ^0.5 .

Here, γ _L, γ ^p _L , and γ ^d _L are the surface free energy, the polar component, and the dispersion component of the solvent whose contact angle is measured, respectively.
γ ^p _r = ^{a 2}
γ ^d _r = ^{b 2}
γ _r = a ² + b ² .

The following eigenvalues were used for the polar component and the dispersion component of the surface free energy of the liquid used.

-Purified water surface free energy 72.8 mJ / m ² , polar component 51 mJ / m ² , dispersion component 21.8 mJ / m ² .

Ethylene glycol surface free energy 48.0 mJ / m ² , polar component 19.0 mJ / m ² , non-polar component 29.0 mJ / m ² .

Tricresyl phosphate surface free energy 40.9 mJ / m ² , polar component 1.7 mJ / m ² , non-polar component 39.2 mJ / m ² .

<Surging agent surface free energy>
2 μl of the sizing agent was gently dropped onto the thermoplastic resin flat plate for which the surface free energy was obtained above. At this time, the contact angle was calculated from the shape of the water droplet using the θ / 2 method. For the contact angle, the average value of each 10 points was used. Using polyetherimide, polypropylene, and polyphenylene sulfide as flat plates, the surface free energy γ _Sz , the polar component γ ^p _{Sz of} the surface free energy, and the dispersion component γ ^d _Sz of the surface free energy were calculated using the approximate formula of Owens. ..

<Calculation method of adhesive work>
Adhesion work Wa is a polar component gamma ^{p r} of the surface free energy of the thermoplastic resin obtained _above, the dispersion component of the surface free energy of the thermoplastic resin gamma ^{d _r,} polar component gamma ^p _Sz of the surface free energy of the sizing _agent, It was calculated by the following formula using ^{the dispersion component γ d} _Sz of the surface free energy of the sizing agent.
_{^{Wa = 2 (γ p r ·}} γ p Sz) 0.5 +2 (γ d r · γ d Sz) 0.5
<Measuring method of resin functional group amount>
(When the following (B-1) is used as the thermoplastic resin)
The sample was weighed in a platinum crucible and heated and incinerated in a burner and an electric furnace. The ash was decomposed by heating with sulfuric acid and nitric acid, and then heated and dissolved with dilute nitric acid to give a constant volume. Na was measured for this solution by atomic absorption spectrometry, and the amount of sodium carboxylate group (μmol / g) in the sample was calculated.
Equipment: Atomic absorption spectrometer Z-2300 manufactured by Hitachi High-Technologies Corporation.

(When the following (B-2) is used as the thermoplastic resin)
About 50 mg of the sample was weighed in a sample bottle, 7.5 g of 1-chloronaphthalene and a 1% phenolphthalein ethanol solution were added, heated to 250 ° C., and the sample was dispersed in the solution while stirring. A sample bottle was placed on a hot stirrer heated to 250 ° C., and a 0.02 mol / L KOH / ethanol solution was added dropwise using a micro burette while rotating the stirrer, and the 1-chloronaphthalene solution turned light purple. At that point, the dropping was completed. The amount of carboxyl groups (μmol / g) was calculated from the amount of dropping.

(When the following (B-3) is used as the thermoplastic resin)
About 50 mg of the sample was weighed in a sample bottle, 7.5 g of N-methyl-2-pyrrolidone and a 1% phenolphthalein ethanol solution were added, heated to 100 ° C., and the sample was dispersed in the solution with stirring. A sample bottle was placed on a hot stirrer heated to 100 ° C., a 0.02 mol / L KOH / ethanol solution was added dropwise using a micro burette while rotating the stirrer, and the N-methyl-2-pyrrolidone solution was light purple. When the color changed to, the dropping was completed. The amount of carboxyl groups (μmol / g) was calculated from the amount of dropping.

The materials and components used in each Example and each Comparative Example are as follows.

(A) Ingredient: Sizing agent A-1: Polyglycerol polyglycidyl ether (γ _s = 51 mJ / m ² )
("Denacol (registered trademark)" Ex-521 manufactured by Nagase ChemteX Corporation)
A-2: Polyethyleneimine (γ _s = 61 mJ / m ² )
(“Lupasol®” G20 Waterfree manufactured by BASF Japan Ltd.)
A-3: Polyethyleneimine (γ _s = 62 mJ / m ² )
(“Lupasol®” FG manufactured by BASF Japan Ltd.)
A-4: Bisphenol A ethylene oxide adduct (γ _s = 49 mJ / m ² )
A-5: Amino ethylated acrylic polymer (γ _s = 36 mJ / m ² )
("Polyment (registered trademark)" NK-350 manufactured by Nippon Shokubai Co., Ltd.).
A-6: Diglycerol polyglycidyl ether (γ _s = 50 mJ / m ² )
("Denacol (registered trademark)" Ex-421 manufactured by Nagase ChemteX Corporation)
A-7: glycerol polyglycidyl ether (γ _s = 50 mJ / m ² )
("Denacol (registered trademark)" Ex-313 manufactured by Nagase ChemteX Corporation)
A-8: Polyethylene glycol diglycidyl ether (γ _s = 50 mJ / m ² )
("Denacol (registered trademark)" Ex-832 manufactured by Nagase ChemteX Corporation).
A-9: Polyglycidyl methacrylate (γ _s = 44 mJ / m ² )
(Prototype manufactured by Toray Fine Chemicals Co., Ltd.).

(B) Component: Thermoplastic resin B-1: Polyphenylene sulfide ("Durafide (registered trademark)" PPS W-540 manufactured by Polyplastics Co., Ltd.)
B-2: Polyphenylene sulfide (“Trelina®” M2888 manufactured by Toray Industries, Inc.).
B-3: Polyvinylidene fluoride (“Soref (registered trademark)” 9009 manufactured by Solvay Specialty Polymers Japan Co., Ltd.).

(Example 1)
This embodiment comprises the following steps 1 to 4.

-First step: Step of producing a carbon fiber bundle as a raw material Acrylonitrile copolymer obtained by copolymerizing itaconic acid is spun and fired, and has a total number of filaments of 12,000, a total fineness of 800 tex, and a strand tensile strength of 5. A carbon fiber bundle having a strand tensile elastic modulus of .1 GPa and a strand tensile modulus of 240 GPa was obtained. Next, the carbon fiber bundle was electrolytically surface-treated with an aqueous solution of ammonium hydrogencarbonate as an electrolytic solution and an electric amount of 80 couron per 1 g of the carbon fiber bundle. The carbon fiber bundles subjected to this electrolytic surface treatment were subsequently washed with water and dried in heated air at a temperature of 150 ° C. to obtain carbon fiber bundles as a raw material.

-Second step: Step of adhering the sizing agent to the carbon fiber bundle Using (A-1) as the compound (A), (A-1) and water are mixed to uniformly dissolve (A-1). The aqueous solution was obtained. This aqueous solution is used as a sizing agent aqueous solution, and the sizing agent is applied to the surface-treated carbon fiber bundle by the dipping method, and then heat-treated with a hot roller at a temperature of 120 ° C. for 15 seconds as a pre-drying step, followed by a second. As a drying step, heat treatment was performed for 90 seconds in heated air at a temperature of 210 ° C. to obtain a sizing agent-coated carbon fiber bundle. The amount of the sizing agent applied was adjusted to be 0.2 to 0.5 parts by mass with respect to 100 parts by mass of the total amount of the surface-treated sizing agent-coated carbon fibers.

-Third step: Preparation and evaluation of a sample for a fiber-opening test Using the carbon fiber bundle obtained in the second step, the fiber-spreading retention rate was determined based on the method for evaluating the fiber-opening property. As a result, it was found that the spread retention rate was 0.95 and the spreadability was very high.

Fourth step: Preparation and evaluation of test piece for IFSS measurement Using the carbon fiber bundle obtained in the previous step and (B-1) as the thermoplastic resin (B), based on the method for measuring the interfacial shear strength. , A test piece for IFSS measurement was prepared. The heating and pressurizing conditions of the hot press were 320 ° C. and 2.0 MPa.

Subsequently, IFSS was measured using the obtained test piece for IFSS measurement. As a result, it was found that the IFSS was 26 MPa and the adhesiveness was sufficiently high. The above results are summarized in Table 1.

(Example 2)
A sizing agent-coated carbon fiber bundle and a test piece for IFSS measurement were obtained in the same manner as in Example 1 except that (B-2) was used as the thermoplastic resin (B) in the fourth step, and various evaluations were performed. .. The results are as summarized in Table 1, and carbon fiber bundles with extremely high adhesiveness and openness were obtained.

(Example 3)
A sizing agent-coated carbon fiber bundle was obtained in the same manner as in Example 1 except that (A-2) was used as the compound (A) in the second step, and various evaluations were performed. The results are as summarized in Table 1, and carbon fiber bundles with extremely high adhesiveness and openness were obtained.

(Example 4)
A sizing agent-coated carbon fiber bundle was obtained in the same manner as in Example 1 except that (A-3) was used as the compound (A) in the second step, and various evaluations were performed. The results are as summarized in Table 1, and carbon fiber bundles with extremely high adhesiveness and openness were obtained.

(Example 5)
A sizing agent-coated carbon fiber bundle was obtained in the same manner as in Example 1 except that (A-6) was used as the compound (A) in the second step, and various evaluations were performed. The results are as summarized in Table 1, and a carbon fiber bundle having very high adhesiveness and openness was obtained, although the pyrolysis property was slightly high.

(Example 6)
A sizing agent-coated carbon fiber bundle and a test piece for IFSS measurement were obtained in the same manner as in Example 1 except that (B-3) was used as the thermoplastic resin (B) in the fourth step, and various evaluations were performed. .. The results are as summarized in Table 1, and carbon fiber bundles with high adhesiveness and openness were obtained.

(Example 7)
A sizing agent-coated carbon fiber bundle and a test piece for IFSS measurement were obtained in the same manner as in Example 3 except that (B-3) was used as the thermoplastic resin (B) in the fourth step, and various evaluations were performed. .. The results are as summarized in Table 1, and carbon fiber bundles with extremely high adhesiveness and openness were obtained.

(Example 8)
A sizing agent-coated carbon fiber bundle and a test piece for IFSS measurement were obtained in the same manner as in Example 4 except that (B-3) was used as the thermoplastic resin (B) in the fourth step, and various evaluations were performed. .. The results are as summarized in Table 1, and carbon fiber bundles with extremely high adhesiveness and openness were obtained.

(Comparative Example 1)
A carbon fiber bundle coated with a sizing agent was obtained in the same manner as in Example 1 except that the electrolytic surface treatment was not performed in the first step, and various evaluations were performed. The results are as summarized in Table 1, and a carbon fiber bundle having high fiber openness but low adhesiveness was obtained.

(Comparative Example 2)
A sizing agent-coated carbon fiber bundle was obtained in the same manner as in Example 1 except that the electrolytic solution was changed to a sulfuric acid aqueous solution and the amount of electricity was changed to 3 coulombs per 1 g of carbon fiber bundle in the first step, and various evaluations were performed. rice field. The results are as summarized in Table 1, and a carbon fiber bundle having high fiber openness but low adhesiveness was obtained.

(Comparative Example 3)
A sizing agent-coated carbon fiber bundle was obtained in the same manner as in Example 1 except that the drying temperature in the second drying step was changed to 240 ° C. in the second step, and various evaluations were performed. The results are as summarized in Table 2, and a carbon fiber bundle having very high adhesiveness but low fiber opening property was obtained.

(Comparative Example 4)
A sizing agent-coated carbon fiber bundle was obtained in the same manner as in Example 1 except that (A-4) was used as the compound (A) in the second step, and various evaluations were performed. The results are as summarized in Table 1, and a carbon fiber bundle having high fiber openness but low adhesiveness was obtained.

(Comparative Example 5)
A sizing agent-coated carbon fiber bundle was obtained in the same manner as in Example 1 except that (A-5) was used as the compound (A) in the second step, and various evaluations were performed. The results are as summarized in Table 1, and carbon fiber bundles with low adhesiveness and openness were obtained.

(Comparative Example 6)
A sizing agent-coated carbon fiber bundle was obtained in the same manner as in Example 1 except that (A-7) was used as the compound (A) in the second step, and various evaluations were performed. The results are as summarized in Table 1, and a carbon fiber bundle having very high fiber opening property but low adhesiveness was obtained.

(Comparative Example 7)
A sizing agent-coated carbon fiber bundle was obtained in the same manner as in Example 1 except that (A-8) was used as the compound (A) in the second step, and various evaluations were performed. The results are as summarized in Table 1, and a carbon fiber bundle having very high fiber opening property but low adhesiveness was obtained.

(Comparative Example 8)
A sizing agent-coated carbon fiber bundle was obtained in the same manner as in Example 1 except that (A-9) was used as the compound (A) in the second step, and various evaluations were performed. The results are as summarized in Table 1, and carbon fiber bundles with low fiber openness and adhesiveness were obtained.

(Comparative Example 9)
A sizing agent-coated carbon fiber bundle and a test piece for IFSS measurement were obtained in the same manner as in Comparative Example 2 except that (B-3) was used as the thermoplastic resin (B) in the fourth step, and various evaluations were performed. .. The results are as summarized in Table 1, and a carbon fiber bundle having high fiber openness but low adhesiveness was obtained.

(Example 9)
In this example, the thermal stability of the sizing agent was evaluated by the following procedure.

Using a thermogravimetric analyzer, the weight loss rate ΔWr was measured under the following conditions.

Approximately 10 mg of (A-1) as a sizing agent (A) containing a polyether-type or polyol-type aliphatic epoxy is weighed, held at 30 ° C. for 1 minute, and then heated in air at a heating rate of 10 ° C./min to 30 ° C. The temperature was raised to 450 ° C. In the process of raising the temperature from 30 ° C. to 450 ° C., the weight loss rate ΔWr was calculated from _{the sample weight W 2} when reaching 250 ° C. _{using the formula (e) with the sample weight W 1 at 30 ° C. as a reference.}
ΔWr = (W ₁ − W ₂ ) / W ₁ × 100 (e).

Thermal stability was evaluated on a three-point scale according to the following criteria, and ◎ and ○ were judged as acceptable.

⊚: △ Wr is 15 or less ○: △ Wr is 15 or more and less than 30 ×: △ Wr is 30 or more The results are as summarized in Table 1, the weight reduction rate △ Wr is 12%, and high thermal stability. It turned out to have.

(Example 10)
The weight reduction rate ΔWr of the sizing agent was determined in the same manner as in Example 9 except that (A-6) was used as the sizing agent (A) containing the polyether type or polyol type aliphatic epoxy. The results are as summarized in Table 2, and it was found that they have high thermal stability.

(Comparative Example 10)
The weight reduction rate ΔWr of the sizing agent was determined in the same manner as in Example 9 except that (A-7) was used as the sizing agent (A) containing the polyether type or polyol type aliphatic epoxy. The results are as summarized in Table 2, and it was found that the thermal stability was low.

When (A-7) is used as a sizing agent, the sizing agent is thermally decomposed in the drying step, so that it is necessary to increase the concentration of the sizing solution in order to obtain the desired sizing adhesion amount. It was a disadvantage.

(Comparative Example 11)
The weight reduction rate ΔWr of the sizing agent was determined in the same manner as in Example 9 except that (A-8) was used as the sizing agent (A) containing the polyether type or polyol type aliphatic epoxy. The results are as summarized in Table 2, and it was found that the thermal stability was very low.

When (A-8) is used as a sizing agent, the sizing agent is thermally decomposed in the drying step, so that it is necessary to increase the concentration of the sizing solution in order to obtain the desired sizing adhesion amount. It was a disadvantage.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a sizing agent-coated carbon fiber bundle that exhibits good fiber-opening property in the fiber-spreading step of the sizing agent-coated carbon fiber even when it exhibits a high level of adhesion to a thermoplastic resin. can do. Since the thermoplastic resin composition of the present invention and its molded body are lightweight and have excellent strength, they are suitable for many fields such as aircraft members, spacecraft members, automobile members, ship members, civil engineering and building materials, and sporting goods. Can be used for.

Claims (13)

When the carbon fiber cross section is detected by energy dispersion type X-ray spectroscopy, there is a layer having an oxygen composition ratio of 2% or more with respect to all elements of 10 nm or more in the cross section perpendicular to the longitudinal direction of the carbon fiber, and the following A sizing agent-coated carbon fiber coated with a sizing agent satisfying (a), (b) and (c1).
(A) The weight average molecular weight Mw determined by gel permeation chromatography is 650 ≦ Mw ≦ 1900.
(B) γ _Sz > 35 mJ / m ² (γ _Sz : surface free energy of the sizing agent).
(C1) Includes either a compound having an amino group or a compound having an amide group. The sizing agent-coated carbon fiber according to claim 1, wherein the sizing agent contains a compound having an amino group, and the amino base value of the sizing agent is 2 to 200 mmol / g. The sizing agent-coated carbon fiber according to claim 1 or 2, wherein a sizing agent having a surface free energy γ _Sz of 50 mJ / m ^{2 or more is applied.} The sizing agent-coated carbon fiber according to any one of claims 1 to 3, wherein the layer having an oxygen composition ratio of 2% or more to all elements and the sizing agent form an amide bond. When the carbon fiber cross section is detected by energy dispersion type X-ray spectroscopy, there is a layer having an oxygen composition ratio of 2% or more with respect to all elements of 10 nm or more in the cross section perpendicular to the longitudinal direction of the carbon fiber, and the following A sizing agent-coated carbon fiber coated with a sizing agent satisfying (a), (b) and (c2).
(A) The weight average molecular weight Mw determined by gel permeation chromatography is 650 ≦ Mw ≦ 1900.
(B) γ _Sz > 35 mJ / m ² (γ _Sz : surface free energy of the sizing agent).
(C2) Contains a compound having a trifunctional or higher functional epoxy group. The sizing agent-coated carbon fiber according to claim 5, wherein the epoxy equal amount of the sizing agent is 50 to 1000 g / eq. The sizing agent-coated carbon fiber according to claim 5 or 6, wherein a sizing agent containing a polyether-type or polyol-type aliphatic epoxy is applied. The sizing agent-coated carbon fiber according to any one of claims 5 to 7, wherein the sizing agent satisfies the following (d).
(D) γ _Sz > 40 mJ / m ² The method for producing a sizing agent-coated carbon fiber according to any one of claims 1 to 8, wherein the weight average molecular weight Mw of the sizing agent before being applied to the carbon fiber, which is obtained by gel permeation chromatography, is 650 or more. A method for producing carbon fiber coated with a sizing agent. A carbon fiber reinforced resin composition comprising the sizing agent-coated carbon fiber according to any one of claims 1 to 8 and a thermoplastic resin having a reactive functional group amount of 30 μmol / g or more. A carbon fiber reinforced resin composition comprising the sizing agent-coated carbon fiber according to any one of claims 1 to 8 and a thermoplastic resin, when the carbon fiber cross section is detected by energy dispersion type X-ray spectroscopy. A carbon fiber reinforced resin composition in which a layer in which 25% or more of a thermoplastic resin-derived element permeates is 5 nm or more in a cross section perpendicular to the longitudinal direction of the carbon fiber in the carbon fiber reinforced resin composition. A carbon fiber reinforced resin composition comprising the sizing agent-coated carbon fiber according to any one of claims 1 to 8 and a thermoplastic resin, wherein the surface free energy γ _r of the thermoplastic resin and the surface free energy of the sizing agent are used. A _{carbon fiber reinforced resin composition in which γ Sz} satisfies the following formulas (e) and (f).
(E) γ _r > 38 mJ / m ² (γ _r : surface free energy of the thermoplastic resin).
_{^{(F) 2 (γ p r}} · γ p Sz) 0.5 +2 (γ d r · γ d Sz) 0.5> 95 mJ / m 2.
γ ^p _r : Polar component of surface free energy of thermoplastic resin γ ^d _r : Dispersion component of surface free energy of thermoplastic resin γ ^p _Sz : Polar component of surface free energy of ^{sizing agent γ d} _Sz : Surface free of sizing agent Dispersion component of energy A carbon fiber reinforced resin composition comprising the sizing agent-coated carbon fiber according to any one of claims 1 to 8 and a thermoplastic resin, when the carbon fiber cross section is detected by energy dispersion type X-ray spectroscopy. In the cross section perpendicular to the longitudinal direction of the carbon fiber in the carbon fiber reinforced resin composition, the composition ratio of nitrogen to all elements is 0.5% or more higher than the composition ratio of nitrogen inside the carbon fiber, or oxygen to all elements. A carbon fiber reinforced resin composition in which a layer having a composition ratio of 3% or more more than the composition ratio of oxygen inside the carbon fiber is present at 5 nm or more.