JP2011208324A - Sizing agent for reinforced fiber, carbon fiber bundle, manufacturing method thereof, thermoplastic resin composition, and molded article thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sizing agent for a reinforced fiber which is inexpensive and can express interfacial adhesion preferable for both a matrix resin and a carbon fiber bundle.SOLUTION: The sizing agent for the reinforced fiber comprises a polymer (A) which has a unit derived from a monomer (a) represented by general formula (1) and a unit derived from a monomer (b) represented by general formula (2), wherein Rand Rare hydrogen or a methyl group respectively, Rand Rrepresent an alkyl group having a linear or branched structure, and they may be identical or different mutually.

Description

  The present invention relates to a sizing agent for reinforcing fibers, a carbon fiber bundle used as a reinforcing material for thermoplastic resins, and a method for producing them. The present invention also relates to a thermoplastic resin composition using the carbon fiber bundle and a molded product thereof.

  A carbon fiber bundle is a form in which a plurality of single fibers made of carbon are combined, and is used as a reinforcing material such as a thermoplastic resin. A composite material containing this is a fiber-reinforced composite material. Called.

  In general, carbon fiber bundles are subjected to a sizing treatment in which a sizing agent mainly composed of a water-soluble or water-dispersible epoxy resin is attached for the purpose of improving the handleability and the physical properties of the composite material. . It is indispensable to attach these sizing agents to the carbon fiber bundle because fluff and fly are easily generated in the carbon fiber bundle, and the carbon fiber bundle obtained by the off-line method is easily broken and difficult to handle.

  Carbon fiber bundles for fiber-reinforced composites that use thermoplastic resin as a matrix resin are usually provided in the form of chopped carbon fiber bundles that are cut to a length of 5 to 15 mm. However, in order to impart convergence, a process of attaching a sizing agent that is compatible with the matrix resin is performed.

  Here, in producing pellets by kneading a chopped carbon fiber bundle and a thermoplastic resin, it is necessary that the chopped carbon fiber bundle is quantitatively provided in the extruder. For that purpose, the chopped carbon fiber is required. The morphological stability of the bundle is important. If the form is not appropriate, ejection spots may occur and cause carbon fiber content spots. Further, since a constant extrusion speed cannot be obtained, strand breakage may occur, and the productivity of pellets may be significantly reduced.

  As the thermoplastic resin used as the matrix resin, polycarbonate resin, nylon resin, polyester resin, and the like are often used. Recently, polyolefin resins, particularly polypropylene resins, have attracted attention because of their recyclability and economy. However, since the polyolefin-based resin is basically nonpolar, the interfacial adhesiveness with the carbon fiber or the glass fiber is very poor, and the effect of improving the mechanical properties as a reinforcing material is often not sufficiently exhibited.

  As a method for solving this problem, a method of sizing carbon fibers and glass fibers with a sizing agent composed of a polyolefin resin and a silane coupling agent (for example, Patent Document 1), an acid-modified polyolefin resin is added to a matrix resin. There are known methods for improving adhesion (for example, Patent Document 2) and methods for sizing carbon fibers and glass fibers with a sizing agent containing acid-modified polypropylene as an essential component (for example, Patent Document 3).

  Further, in Patent Document 4, a modified polyolefin resin obtained by graft-modifying a polyolefin resin with a vinyl monomer having a (meth) acrylic acid ester monomer in which a (meth) acryloyloxy group is bonded to a secondary or tertiary carbon atom. It has been proposed to improve the interfacial adhesion between the matrix resin and the fiber by a sizing treatment method. In Patent Document 5, a matrix resin and a fiber are treated by a method of treating with a sizing agent containing a polymer having a (meth) acrylic acid ester monomer in which a (meth) acryloyloxy group is bonded to a secondary or tertiary carbon atom. It has been proposed to improve interfacial adhesion.

JP-A-7-309979 JP 2005-213478 A JP-A-6-107442 JP 2005-226193 A JP 2005-146431 A

  However, in the case of the method described in Patent Document 1, in the case of carbon fiber, since there are not so many hydroxyl groups present on the surface as compared with glass fiber, the effect of improving the interfacial adhesion is considerably low. In the case of the method described in Patent Document 2, it is necessary to add a large amount of acid-modified polyolefin-based resin, which is not excellent in recyclability and economy. In the case of the method described in Patent Document 3, relatively good interfacial adhesion with a polyolefin-based resin can be realized, but the effect in the case of carbon fiber is not sufficient.

  Although the method of performing the treatment with the sizing agent described in Patent Documents 4 and 5 shows good interfacial adhesion with both the matrix resin and the carbon fiber, (meth) acrylic acid is a monomer to be used Since the ester is expensive, there remains a problem in terms of the cost of manufacturing the sizing agent.

  The present invention has been made in view of such a background, and an object thereof is to provide a sizing agent for reinforcing fibers that is inexpensive and can exhibit good interfacial adhesion with both a matrix resin and a carbon fiber bundle. And

  The first gist of the present invention has a unit derived from the monomer (a) represented by the following general formula (1) and a unit derived from the monomer (b) represented by the following general formula (2). A sizing agent for reinforcing fibers containing the polymer (A).

(Here, R ¹ represents hydrogen or a methyl group. R ² and R ³ represent a linear or branched alkyl group, and may be the same or different from each other.)

(Here, R ⁴ represents hydrogen or a methyl group.)
The second gist of the present invention is a method for producing the sizing agent for reinforcing fibers, wherein the monomer (a) and the monomer (b) are emulsion-polymerized using a surfactant. And a method for producing a reinforcing fiber sizing agent for synthesizing the polymer (A).

  The third gist of the present invention is a carbon fiber bundle that is sized by the sizing agent for reinforcing fibers.

The fourth gist of the present invention is as follows.
(I) Using an aqueous emulsion in which the polymer (A) contained in the sizing agent for reinforcing fibers according to claim 1 or 2 is dispersed in water, the adhesion amount of the polymer (A) is a carbon fiber bundle. Sizing the carbon fiber bundle so as to be 1 to 30% by mass or less of the weight;
(II) adjusting the water content of the carbon fiber bundle subjected to sizing treatment to 20 to 60% by mass, and cutting to a predetermined length;
(III) A method for producing a carbon fiber bundle having the steps of drying the carbon fiber bundle cut into a predetermined length in this order.

  The fifth gist of the present invention is a thermoplastic resin composition containing a thermoplastic resin and the carbon fiber bundle, wherein the mass ratio of the carbon fiber bundle is 3 to 60% by mass. It is a resin composition.

  Moreover, the 6th summary of this invention is a molded article formed by shape | molding said thermoplastic resin composition.

  According to the present invention, it is an object to provide a sizing agent that is inexpensive and can exhibit good interfacial adhesion with both a matrix resin and a carbon fiber bundle. By using the sizing agent for reinforcing fibers according to the present invention, good interfacial adhesion with polyolefin resins, particularly polypropylene resins, can be developed.

<Sizing agent for reinforcing fibers>
The sizing agent for reinforcing fibers according to the present invention is a unit derived from the monomer (a) represented by the following general formula (1) and a unit derived from the monomer (b) represented by the following general formula (2). A polymer (A) having

[Monomer (a)]
The monomer (a) has a structure represented by the following general formula (1).

Here, R ¹ represents hydrogen or a methyl group. R ² and R ³ represent a linear or branched alkyl group and may be the same or different from each other.

  Specific examples of the monomer (a) include isobutyl (meth) acrylate, 2-methylbutyl (meth) acrylate, 2-ethylbutyl (meth) acrylate, 2-methylpentyl (meth) acrylate, (Meth) acrylic acid-2-ethylhexyl, (meth) acrylic acid-2-methylheptyl, (meth) acrylic acid-2-ethylheptyl, (meth) acrylic acid-2-methyloctyl, (meth) acrylic acid-2 -Ethyloctyl, (meth) acrylic acid-2-methylnonyl, (meth) acrylic acid-2,4-dimethylpentyl and the like. Among these, in view of availability, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, or 2,4-dimethylpentyl (meth) acrylate is preferable. In the present specification, the expression “(meth) acrylic acid” means acrylic acid or methacrylic acid. A monomer (a) may be used individually by 1 type, and may use 2 or more types together.

  The monomer (a) can be appropriately selected depending on the required glass transition temperature (Tg) of the polymer (A). From the viewpoint of process stability after adhering to the carbon fiber bundle and drying, the polymer (A) It is preferable to select and use the monomer (a) so that the Tg of) is -80 ° C to 60 ° C.

[Monomer (b)]
The monomer (b) is glycidyl (meth) acrylate having a structure represented by the following general formula (2).

Here, R ⁴ represents hydrogen or a methyl group. The monomer (b) may be used alone or in combination of two. The monomer (b) can be appropriately selected depending on the required glass transition temperature (Tg) of the polymer (A).

[Monomer (c)]
In addition to the unit derived from the monomer (a) and the unit derived from the monomer (b), the polymer (A) is another monomer different from the monomer (a) and the monomer (b). A copolymer having a unit derived from (c) may be used.

  The monomer (c) is a monomer that is different from the monomer (a) and the monomer (b), and can be copolymerized with the monomer (a) and the monomer (b). If it is a body, it will not specifically limit. Specific examples of the monomer (c) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and isoamyl (meth) acrylate. (Meth) acrylate esters such as lauryl (meth) acrylate, dodecyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acrylic acid-t-butylcyclohexyl; Α, β-insoluble such as acid, acrylic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, bicyclo [2.2.1] -5-heptene-2,3-dicarboxylic acid anhydride Saturated carboxylic acids; maleimides such as N-phenylmaleimide, N-cyclohexylmaleimide, Nt-butylmaleimide; Vinyl esters such as nyl, vinyl laurate, vinyl stearate, vinyl trifluoroacetate; nitrogen-containing monomers such as (meth) acrylamide, (meth) acrylonitrile, diacetone acrylamide, dimethylaminoethyl methacrylate; (meth) 2-hydroxyethyl acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, (meth) 4-hydroxybutyl acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, “Placcel FM or FA” [Daicel Chemical Industries, Ltd. Name; Capro Kuton addition monomer], "FM-1 or FM-2" [trade name, manufactured by Daicel Chemical Industries, Ltd .; 1- or 2-molecule addition product of ε-caprolactone of 2-hydroxyethyl methacrylate], "CHDMMA" [Nippon Kasei. Examples include hydroxyl group-containing various (meth) acrylic esters such as 1,4-cyclohexanedimethanol acrylate; and allyl group-containing monomers such as allyl glycidyl ether and allyl (meth) acrylate.

  Among the above-described monomers (c), n-butyl (meth) acrylate, lauryl (meth) acrylate, () from the viewpoint of availability, compatibility with polyolefin, and adhesion to carbon fiber (Meth) acrylic acid esters such as dodecyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acrylic acid-t-butylcyclohexyl; α, β-unsaturated carboxylic acids; hydroxyl group Containing various (meth) acrylic acid esters; allyl group-containing monomers are preferable, n-butyl (meth) acrylate, lauryl (meth) acrylate, dodecyl (meth) acrylate, cyclohexyl (meth) acrylate, ( (Meth) acrylic acid-t-butylcyclohexyl, methacrylic acid, acrylic acid, maleic acid, fumaric acid, itaconic acid, anhydrous Maleic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, “FM-1 or FM- 2 ”[trade name made by Daicel Chemical Industries, Ltd .; 1- or 2-molecule adduct of ε-caprolactone of 2-hydroxyethyl methacrylate],“ CHDMMA ”[manufactured by Nippon Kasei Co., Ltd .; 1,4-cyclohexanedimethanol acrylic acid] Allyl glycidyl ether and allyl (meth) acrylate are more preferred.

  The monomer (c) may be used alone or in combination of two or more. In the case where maleic anhydride is used as the monomer (c), further copolymerization of an aromatic vinyl monomer such as styrene or α-methylstyrene can increase the efficiency of introduction into the copolymerization of maleic anhydride. To preferred.

[Polymer (A)]
The mass proportion of the unit derived from the monomer (a) in the polymer (A) is preferably 50 to 99 mass%, and preferably 80 to 95 mass%, from the viewpoint of adhesion to the polyolefin resin. More preferred.

  The mass ratio of the unit derived from the monomer (b) in the polymer (A) is preferably 1 to 50% by mass, and more preferably 5 to 20% by mass. When the mass ratio of the unit derived from the monomer (b) is less than 1% by mass, adhesion to the carbon fiber bundle may not be sufficiently exhibited. On the other hand, when the mass ratio of the unit derived from the monomer (b) exceeds 50 mass%, the mass ratio of the monomer (a) is relatively decreased, and the adhesion to the polyolefin resin may be insufficient. is there.

  The sum of the mass ratio of the unit derived from the monomer (a) and the mass ratio of the unit derived from the monomer (b) in the polymer (A) is compatible with the polyolefin resin and adheres to the carbon fiber bundle. From the viewpoint, it is preferably 60 to 100% by mass, more preferably 65 to 100% by mass, and particularly preferably 70 to 100% by mass. That is, the mass ratio of the unit derived from the monomer (c) in the polymer (A) is preferably 0 to 40% by mass, more preferably 0 to 35% by mass, and 0 to 30% by mass. It is more preferable that

  When the polymer (A) is a copolymer comprising a unit derived from the monomer (a) and a unit derived from the monomer (b), the polymer structure is a random copolymer, a graft copolymer, It may have any polymer structure such as a block copolymer.

[Synthesis Method of Polymer (A)]
As a method for synthesizing the polymer (A), a method of copolymerizing the monomer (a) and the monomer (b) by an emulsion polymerization method is preferable from the viewpoints of safety and economy. When a copolymer having a unit derived from the monomer (c) is synthesized, the monomer (a), the monomer (b) and the monomer (c) may be copolymerized by an emulsion polymerization method. .

  In carrying out the emulsion polymerization, a surfactant is used as an emulsifier for the purpose of uniformly dispersing the constituent components in water. As an emulsifier, an anionic surfactant, a cationic surfactant, a nonionic surfactant, etc. can be used. Among these, an anionic or nonionic surfactant is preferable from the viewpoint of emulsification performance and low cost.

  Anionic surfactants include carboxylate type (potassium oleate, sodium oleate, etc.), sulfonate type (sodium dodecylbenzenesulfonate, sodium dioctylsulfosuccinate, etc.), sulfate salt type (sodium lauryl sulfate, etc.) ) And the like. Neutralizing agents include potassium hydroxide, sodium hydroxide, magnesium hydroxide, calcium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, calcium carbonate, calcium bicarbonate, magnesium carbonate, magnesium bicarbonate, mono Examples include laurylamine, trimethylamine, dimethylmonoethanolamine, triethanolamine, ethylenediamine, and ammonia. Examples of the reducing agent include sodium sulfite.

  Nonionic surfactants include polyethylene glycol type (higher alcohol ethylene oxide adduct, alkylphenol ethylene oxide adduct, fatty acid ethylene oxide adduct, polypropylene glycol ethylene oxide adduct, etc.), polyhydric alcohol type (glycerin fatty acid ester) Sorbitol fatty acid ester, fatty acid alkanolamide, etc.). However, the HLB of the nonionic surfactant is usually 8-20. If a nonionic surfactant having an HLB outside this range is used, a stable aqueous emulsion may not be obtained.

  The radical polymerization initiator used for emulsion polymerization is not particularly limited as long as it is used for radical polymerization. Radical polymerization initiators include oil-soluble ones used in polymerization in organic solvents and water-soluble ones used in polymerization in aqueous solutions such as emulsion polymerization. In this polymerization, an oil-soluble radical polymerization initiator can also be used.

  Specific examples of the radical polymerization initiator include cumene hydroperoxide, t-butyl peroxide, benzoyl peroxide, t-butyl peroxyisopropyl carbonate, di-t-butyl peroxide, t-butyl peroxylaurate, lauroyl. Organic peroxides such as peroxide, succinic peroxide, cyclohexanone peroxide, acetylacetone peroxide; inorganic peroxides such as potassium persulfate and ammonium persulfate; 2,2′-azobisisobutyronitrile, 2,2 Examples include azo compounds such as' -azobis-2,4-dimethylvaleronitrile. Of these, organic peroxides or inorganic peroxides are particularly preferred because of their high reactivity. When an organic peroxide or an inorganic peroxide is used, a reducing agent can be used in combination. Specific examples of the reducing agent include ferrous sulfate / glucose / sodium pyrophosphate, ferrous sulfate / dextrose / sodium pyrophosphate, or a mixture of ferrous sulfate / sodium formaldehyde sulfoxylate / ethylenediamine acetate. It is done. Use of a reducing agent in combination is particularly preferred because the polymerization temperature can be lowered.

  The amount of the radical polymerization initiator used is preferably 0.005 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, and still more preferably 0.02 to 2 parts by mass with respect to 100 parts by mass of the monomer. . The lower limits of these ranges are significant in terms of polymerization rate and production efficiency. The upper limit is significant in terms of increasing the molecular weight of the polymer, impact resistance, and powder characteristics.

  Although superposition | polymerization temperature is not specifically limited, The range of -50-200 degreeC is preferable, and the range of 0-150 degreeC is more preferable. Furthermore, in a polymerization method using water as a medium called emulsion polymerization, a range of 40 to 120 ° C. is preferable. In addition, in superposition | polymerization of 100 degreeC or more, superposition | polymerization under pressurization may be sufficient.

  By using the polymer (A), which is an essential component of the sizing agent for reinforcing fibers, the (meth) acrylic acid ester monomer (a) is used when the fiber bundle is combined with a matrix resin such as a polyolefin resin. ) -Derived units and the matrix resin are compatible with each other, and adhesion can be improved. On the other hand, the unit derived from the monomer (b) of the polymer (A) is a component that acts as an effective coupling agent to cause a strong bond with the fiber bundle surface.

  When sizing the fiber bundle with such a sizing agent for reinforcing fibers, an aqueous emulsion in which the polymer (A) contained in the sizing agent for reinforcing fibers is dispersed in water may be used. For example, emulsion polymerization Can be used as it is. Moreover, the density | concentration of an aqueous emulsion can be adjusted suitably, For example, it can dilute with water so that the density | concentration of the sizing agent for reinforcing fibers may be 5-60 mass%.

  As the reinforcing fiber to be sized, either organic fiber or inorganic fiber may be used. For example, glass fiber, carbon fiber, aramid fiber, ceramic fiber, zonotlite, wollastonite, slag fiber, sepiolite, dosonite, gypsum fiber and the like can be mentioned. Among these, a carbon fiber bundle in which single fibers of carbon fibers are converged is preferable from the viewpoint of improving the elastic modulus of the matrix resin. Hereinafter, the carbon fiber bundle suitably used in the present invention will be described in detail.

<Carbon fiber bundle>
The carbon fiber bundle preferably has a form in which about 1000 to 100,000 single fibers having an average diameter of about 4 μm to 8 μm are collected. As the single fiber constituting the carbon fiber bundle, one obtained by fiberizing and carbonizing an acrylonitrile polymer, a pitch obtained from petroleum, coal, or the like can be used. The carbon fiber bundle before sizing treatment with the sizing agent for reinforcing fibers is the one after carbonization treatment, the one with oxygen-containing functional groups introduced by wet electrolytic acid value treatment, and the one pretreated Etc. can be used.

  In the carbon fiber bundle, a plurality of carbon single fibers each having a plurality of wrinkles having a height difference of 40 nm or more between the highest part and the lowest part in an area of 2 μm in the circumferential direction × 1 μm in the fiber axis direction are converged on the surface. It is preferable. Moreover, it is preferable that the height difference of the highest part and the lowest part in the area | region of the circumferential direction length 2 micrometer x fiber axial direction length 1 micrometer in a carbon single fiber is 10% or less of the diameter of a carbon single fiber.

  The depth of the wrinkles present on the surface of the single fiber of the carbon fiber bundle is defined by the difference in height between the highest part and the lowest part in the region of 2 μm in the circumferential direction × 1 μm in the length in the fiber axis direction. The wrinkle on the surface of a single fiber refers to the form of irregularities having a length of 1 μm or more in a certain direction. The direction is not particularly limited, and the direction may be parallel to or perpendicular to the fiber axis direction. Due to a general method for producing carbon fiber bundles, wrinkles that are substantially parallel to the fiber axis direction exist on the surface of ordinary carbon fibers. The height difference can be estimated as follows based on the surface shape obtained by scanning the surface of a single fiber using a scanning atomic force microscope (AFM).

  Several single fibers of a carbon fiber bundle are put on a sample stage, both ends are fixed, and dotite (trade name, manufactured by Fujikura Kasei Co., Ltd.) is applied around the periphery to obtain a measurement sample. Using an atomic force microscope (Seiko Instruments Inc., SPI3700 / SPA-300 (trade name)), using a silicon nitride cantilever, a range of 2-7 μm in the circumferential direction of the single fiber in AFM mode, The scanning is repeated while gradually shifting over a length of 1 μm in the fiber axis direction. The obtained measurement image is cut by low-frequency components by two-dimensional Fourier transform, and then inversely transformed. From the planar image of the cross section obtained by removing the curvature of the single fiber thus obtained, the difference in height between the highest part and the lowest part in the region of 2 μm in the circumferential direction × 1 μm in the length in the fiber axis direction is read.

  Examples of the carbon fiber bundle formed of a single fiber having a plurality of wrinkles include TR50S, TR30L (trade name) manufactured by Mitsubishi Rayon Co., Ltd., and the like.

  The single fiber of the carbon fiber bundle preferably has a ratio of the major axis to the minor axis (major axis / minor axis) of 1.03 or more and 1.20 or less. If the ratio of major axis / minor axis is small, the adhesion between single fibers is strong after sizing treatment, and the dispersion property to single fibers at the time of mixing and impregnation with resin deteriorates, making it difficult to obtain a uniformly dispersed molded product. The carbon fiber bundle is weak in that the single fibers are weakly bonded and easily broken, and the stability of the cutting process of a predetermined length and the stability of the shape of the carbon fiber bundle after cutting are disadvantageous. It is disadvantageous in that it tends to be inferior. Particularly preferably, it is 1.05 or more and 1.15 or less. The major axis / minor axis value can be measured as follows.

  After passing a carbon fiber bundle for measurement through a tube made of vinyl chloride resin having an inner diameter of 1 mm, this is cut into a sample with a knife and used as a sample. Next, the sample was adhered to the SEM sample stage with the cross section facing upward, and Au was sputtered to a thickness of about 10 nm, and then a scanning electron microscope (PHILIPS, XL20 (trade name)) Thus, the cross section is observed under the conditions of an acceleration voltage of 7.00 kV and a working distance of 31 mm, and the major axis and minor axis of the single fiber section are measured.

  The single fiber of the carbon fiber bundle preferably has an Si content measured by ICP emission analysis of 500 ppm (mass basis) or less. A large amount of Si is disadvantageous in that the wettability with the matrix resin and the interfacial adhesion tend to be poor. Particularly preferably, it is 350 ppm or less. The amount of Si can be measured as follows. The carbon fiber bundle is put in a known platinum crucible, ashed in a muffle furnace set at 600 to 700 ° C., and the mass of the crucible is measured to determine the ash content. Next, a prescribed amount of sodium carbonate is added, melted with a burner, and fixed in a 50 ml volumetric flask while dissolving with DI water (ion exchange water). This sample is quantified by Si by ICP emission analysis.

  The sizing treatment in the present invention is a treatment for attaching a sizing agent for reinforcing fibers containing the polymer (A) to the fiber bundle. By this sizing treatment, it is possible to increase the convergence of the fiber bundle, and at the same time, it is possible to increase the affinity between the fiber bundle and the matrix resin. From the viewpoint of improving the elastic modulus of the matrix resin, it is preferable to perform sizing treatment on the carbon fiber bundle.

  As a method of performing sizing treatment using an aqueous emulsion in which the polymer (A) contained in the sizing agent for reinforcing fibers is dispersed in water, for example, a part of a roll is immersed in the aqueous emulsion and surface transfer is performed. A touch roll system in which a carbon fiber bundle made of single fibers is brought into contact with a roll to adhere an aqueous emulsion, and a carbon fiber bundle made of single fibers is directly immersed in an aqueous emulsion, and then passed through a nip roll as necessary to form an aqueous emulsion. An immersion method for controlling the amount of adhering is mentioned. Among them, the touch roll method is preferable, and the method in which the carbon fiber bundle is brought into contact with a plurality of touch rolls and the aqueous emulsion is adhered in a plurality of stages is particularly preferable from the viewpoint of the adhesion amount of the reinforcing fiber sizing agent and the bundle width control. It is. Thereafter, preliminary drying and heat treatment are performed as necessary. Detailed conditions may be appropriately selected so that the carbon fiber bundle exhibits desired characteristics.

  The adhesion amount of the reinforcing fiber sizing agent to the carbon fiber bundle is preferably 1 to 30% by mass of the carbon fiber bundle, and more preferably 5 to 10% by mass. When the adhesion amount of the reinforcing fiber sizing agent is 1% by mass or less, the convergence is insufficient, and the shape stability of the cut bundle may be deteriorated. If the adhesion amount of the sizing agent for reinforcing fibers exceeds 30% by mass, the wettability in the mixing process with the resin and the looseness to single fibers may be remarkably deteriorated, and the strength of the composite material will be sufficiently developed. You may not get. In addition, the adhesion amount of the sizing agent in the carbon fiber bundle is defined as a component amount other than water with respect to the entire carbon fiber bundle, and is measured by a pyrolysis method in accordance with SACMA method SRM14-90. is there.

  The carbon fiber bundle of the present invention as described above may be in a continuous fiber state or in a state cut to a predetermined length.

  Moreover, it is preferable that the fiber bundle in the state cut | disconnected by the predetermined length is 0.4-15 g / m of fabric weights (mass per 1 m in length). If the basis weight of the fiber bundle is less than 0.4 g / m, it is economically inconvenient, and the fiber bundle introduction process passability in the pellet manufacturing process may be deteriorated. On the other hand, if it exceeds 15 g / m, it is difficult to completely penetrate the fiber bundle of the aqueous emulsion, and it may be difficult to produce a fiber bundle having a stable shape. More preferably, it is 0.6-10 g / m, Most preferably, it is 0.8-8 g / m.

  Although there is no restriction | limiting in particular as a cutting method of a fiber bundle, A rotary cutter system etc. are suitable. The cutting length (length of the fiber bundle) is 2 to 30 mm, preferably 4 to 24 mm, more preferably 6 to 20 mm. In the rotary cutter method, the cutting length can be adjusted by adjusting the tooth tip interval of the apparatus to be used.

  When cutting with the rotary cutter method, if the fiber bundle thickness becomes too thick, the fiber bundle thickness will be damaged, the fiber bundle will be wrapped around the rotor, making it impossible to operate, and shape defects after cutting will occur. Is more advantageous. Further, in the case of a fiber bundle with a thick fiber weight exceeding 1.5 g / m, it is important to open the fiber bundle as much as possible and to uniformly adhere the aqueous emulsion to the inside of the fiber bundle. Therefore, it is preferable to use a guide roll, a comb guide, a spreader bar, or the like to control the fiber bundle so that the width / thickness of the fiber bundle is increased and to make the fiber bundle substantially untwisted.

  However, if the fiber bundle cut into a predetermined length becomes wider, it tends to be longitudinally cracked along the fiber orientation direction, and it tends to be difficult to maintain its form during use after use or after manufacture. This is particularly noticeable in thick fiber bundles. Therefore, it is preferable to control the width of the fiber bundle by adjusting the width of the guide attached to the rotary cutter so that the ratio (width / thickness) of the width and thickness of the carbon fiber bundle is 3 to 10. Generation | occurrence | production of the miscut in the cutting process with a rotary cutter can be suppressed as width / thickness is 3 or more. Further, if the width / thickness exceeds 10, miscutting at the time of cutting becomes difficult to occur, but the thickness becomes too thin and the fiber bundle is liable to be longitudinally cracked after cutting, and the subsequent process passability may be deteriorated. There is. Also, in order to widen and cut thick fiber bundles as thin as a general-purpose type, the number of fibers that can be processed simultaneously decreases, and it is necessary to widen the cutter or increase the processing speed to compensate for the decrease. There is a risk of reducing the load on the equipment and the production efficiency.

  This cutting is preferably performed on the fiber bundle in a wet state after the aqueous emulsion is attached to the fiber bundle. This utilizes the convergence effect due to the surface tension of the aqueous emulsion and the prevention of fiber cracking by absorbing the impact shear force at the time of cutting in a wet and flexible state. At the time of this cutting, it is preferable that the moisture content of the fiber bundle is 20 to 60% by mass, particularly 25 to 50% by mass. If the moisture content is less than 20% by mass, there is a risk that fiber breakage and fluff are likely to occur during cutting. Also, if the water content exceeds 60% by mass, the surface of the single fiber is excessively attached to the surface of the single fiber, so that the single fiber converges in a round shape due to the surface tension of the water, resulting in miscutting and clogging of the blade. There is a risk of increasing the frequency. Moreover, in order to adjust a moisture content as needed, you may perform an additional process using water or an aqueous | water-based emulsion before cutting | disconnection.

  Examples of a method for drying the fiber bundle after cutting include a hot air drying method. When the hot air drying method is employed, it is preferable to perform drying while transporting in a vibrated state in order to improve moisture evaporation efficiency and prevent adhesion between fiber bundles. In addition, when the vibration at the time of drying is too strong, it becomes easy to generate | occur | produce a fiber crack and the ratio of the fiber bundle whose bundle width / thickness is less than 3 increases. On the other hand, if the vibration is too weak, pseudo-bonding between the fibers occurs, resulting in a dumpling shape. Therefore, it is necessary to set an appropriate vibration condition. Further, it is more preferable to vibrate and dry while transporting the mesh diaphragm in order to improve the flow of hot air as well as shake off the subdivided fiber bundle. In order to improve the drying efficiency, auxiliary means such as infrared radiation can be used in combination.

<Thermoplastic resin composition and molded product>
The carbon fiber bundle of the present invention as described above can be made into a thermoplastic resin composition by kneading a thermoplastic resin as a matrix resin. When kneading the carbon fiber bundle into the thermoplastic resin, it is preferable to supply the carbon fiber bundle in a state cut to a predetermined length to the extruder and knead it with the thermoplastic resin to form a pellet. Moreover, the thermoplastic resin composition of the present invention can provide a molded product (fiber reinforced composite molded product) having an arbitrary shape by molding by a known molding method such as an injection molding method.

  In preparing the thermoplastic resin composition of the present invention, the carbon fiber bundle of the present invention is preferably blended in an amount of 3 to 60% by mass, more preferably 5 to 50% by mass. By blending 3% by mass or more of the carbon fiber bundle, the effect of improving the mechanical properties of the molded product is remarkably exhibited. However, if the blending amount is too large, no further significant improvement effect can be obtained, the process stability at the time of pellet production is lowered, and the pellets are uneven, which may deteriorate the quality stability of the molded product. There is.

  The thermoplastic resin used as the matrix resin in the present invention is not particularly limited, but a polyolefin resin is optimal from the viewpoint of affinity with the reinforcing fiber sizing agent attached to the single fiber surface of the carbon fiber bundle. Others are selected from the group consisting of polycarbonate resin, ABS resin, AS resin, polyoxymethylene resin, nylon resin, polyphenylene sulfide resin, polyethersulfin resin, polyetherimide resin, polyester resin and these alloy resins. At least one is preferred.

  Hereinafter, the present invention will be described in detail by examples and comparative examples. In addition, the measurement and evaluation of various characteristics in this example were performed by the following methods.

“The depth of wrinkles present on the surface of a single fiber of a carbon fiber bundle”
The depth of the wrinkles present on the surface of the single fiber of the carbon fiber bundle is defined by the difference in height between the highest part and the lowest part in the region of 2 μm in the circumferential direction × 1 μm in the length in the fiber axis direction. The height difference was measured based on the surface shape obtained by scanning the surface of a single fiber using a scanning atomic force microscope (AFM). Specifically, it was performed as follows.

  Several single fibers of a carbon fiber bundle were placed on a sample stage, both ends were fixed, and dotite (trade name, manufactured by Fujikura Kasei Co., Ltd.) was applied to the periphery to prepare a measurement sample. Using an atomic force microscope (Seiko Instruments Inc., SPI3700 / SPA-300 (trade name)), using a silicon nitride cantilever, a range of 2-7 μm in the circumferential direction of the single fiber in AFM mode, Scanning was repeated while gradually shifting over a length of 1 μm in the fiber axis direction. The low frequency component was cut from the obtained measurement image by two-dimensional Fourier transform, and then inverse transform was performed. From the planar image of the cross section obtained by removing the curvature of the single fiber thus obtained, the difference in height between the highest part and the lowest part in the region of circumferential length 2 μm × fiber axis direction length 1 μm was read.

“Ratio of major axis to minor axis of single fiber cross section of carbon fiber bundle (major axis / minor axis)”
A carbon fiber bundle for measurement was passed through a tube made of a vinyl chloride resin having an inner diameter of 1 mm, and this was cut into a sample with a knife and used as a sample. Next, the sample was adhered to the SEM sample stage with the cross section facing upward, and Au was sputtered to a thickness of about 10 nm, and then a scanning electron microscope (PHILIPS, XL20 (trade name)) Thus, the cross section was observed under the conditions of an acceleration voltage of 7.00 kV and a working distance of 31 mm, and the long diameter and short diameter of the single fiber cross section were measured and evaluated.

"Strand strength and elastic modulus"
Evaluation was performed according to JIS R7601.

“Amount of sizing agent”
In accordance with SACMA method SRM14-90, the total amount of carbon fiber bundle sizing agent after sizing treatment was measured by a thermal decomposition method. Moreover, the adhesion amount of the presizing agent of the carbon fiber bundle after a presizing process and before a sizing process was measured by the same method. Then, the adhesion amount of the sizing agent was calculated by subtracting the adhesion amount of the presizing agent from the adhesion amount of the total sizing agent.

"Si amount"
The carbon fiber bundle was put in a known platinum crucible, ashed in a muffle furnace set to 600 to 700 ° C., and the mass of the crucible was measured to determine the ash content. Next, a prescribed amount of sodium carbonate was added, melted with a burner, and fixed in a 50 ml polymeas flask while dissolving with DI water. This sample was quantified for Si by ICP emission analysis.

"Evaluation of mechanical properties of molded products"
The bending strength and flexural modulus of the molded product were evaluated according to ISO 178. The measurement was performed at room temperature.

<Synthesis Example 1: Synthesis by emulsion polymerization of 2-ethylhexyl methacrylate (EHMA) / glycidyl methacrylate (GMA) random copolymer (A-1)>
To a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and dripping device, add 190 g of DI water and 0.1 g of an anionic emulsifier (Kao, Perex SS-L (trade name)), and purge with nitrogen Did. Thereafter, the temperature was raised to 80 ° C., from 0.0001 g of ferric sulfate heptahydrate (FeSO ₄ ), disodium ethylenediaminetetraacetate (EDTA), 0.3 g of Rongalite (CRO) and 5 g of DI water. An aqueous reducing agent solution was added. While maintaining the temperature in the reaction vessel at 80 ° C., a mixture of a mixed monomer consisting of 4.5 g of EHMA and 0.5 g of GMA and 0.015 g of t-butyl hydroperoxide (tBH) as an initiator was added, Hold at 80 ° C. for 5 minutes. Again, a reducing agent aqueous solution consisting of 0.0001 g of FeSO ₄ , 0.0003 g of EDTA, 0.3 g of CRO and 5 g of DI water was added and maintained at 80 ° C. for 5 minutes. Next, a mixed monomer composed of 85.5 g of EHMA and 9.5 g of GMA, 200 g of DI water, 0.5 g of an anionic emulsifier (manufactured by Kao, Perex O-TP (trade name)) and 0.285 g of tBH were pre-emulsified. Then, it was dripped in reaction container using the metering pump over 2 hours. After completion of the dropping, aging was performed at the same temperature for 1 hour.

  Next, the inside of the reaction vessel is cooled to 40 ° C., and the product is filtered through a 200 mesh nylon cloth, so that the average particle diameter is 224 nm, the number average molecular weight of the polymer is 117,000, and the ratio of the polymer is An aqueous emulsion composition of polymer (A-1) that was 20% by mass with respect to the total mass (total of polymer and water) was obtained.

<Synthesis Example 2: Synthesis by emulsion polymerization of isobutyl methacrylate (IBMA) / GMA random copolymer (A-2)>
To a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and dropping device, add 225 g of DI water and 0.21 g of an anionic emulsifier (manufactured by Kao, Perex O-TP (trade name)), and purge with nitrogen. Did. Thereafter, the temperature was raised to 80 ° C., and a monomer consisting of 13.5 g of IBMA and 1.5 g of GMA was added and held for 15 minutes. While maintaining the temperature in the reaction vessel at 80 ° C., an aqueous solution consisting of 0.3 g of potassium persulfate (KPS) and 15 g of DI water was added and maintained at 80 ° C. for 60 minutes. Subsequently, a mixture of 256.5 g of IBMA and 28.5 g of GMA, 150 g of DI water and 1.5 g of an anionic emulsifier (manufactured by Kao, Perex O-TP (trade name)) was pre-emulsified in advance, and then took 2 hours. Then, it was dropped into the reaction vessel using a metering pump. After completion of the dropping, aging was performed at the same temperature for 1 hour.

  Next, the inside of the reaction vessel is cooled to 40 ° C., and the product is filtered through a 200 mesh nylon cloth, so that the average particle diameter is 326 nm, the number average molecular weight of the polymer is 183,000, and the ratio of the polymer is An aqueous emulsion composition of the polymer (A-2) that was 43% by mass with respect to the total mass (total of the polymer and water) was obtained.

<Synthesis Example 3: Synthesis by emulsion polymerization of isobutyl acrylate (IBA) / GMA random copolymer (A-3)>
The average particle diameter was 335 nm, the number average molecular weight of the polymer was 38300, and the ratio of the polymer was the total mass (the polymer and the polymer), except that IBA was used instead of IBMA. An aqueous emulsion composition of the polymer (A-3) that was 20% by mass relative to the total amount of water was obtained.

<Synthesis Example 4: Synthesis by emulsion polymerization of methyl methacrylate (MMA) / GMA random copolymer (B-1)>
The average particle diameter is 224 nm, the number average molecular weight of the polymer is 64200, and the proportion of the polymer is the total mass (the polymer and the polymer), except that MMA is used instead of IBMA. The aqueous emulsion composition of the polymer (B-1) which was 20 mass% with respect to the sum total of water) was obtained.

<Synthesis Example 5: Synthesis by emulsion polymerization of IBMA homopolymer>
Example 1 except that 5 g of IBMA was used instead of 4.5 g of EHMA and 0.5 g of GMA as the monomer charged first, and 95 g of IBMA was used instead of 85.5 g of EHMA and 9.5 g of GMA as the monomer charged next. In the same manner, IBMA single weight having an average particle size of 236 nm, a number average molecular weight of the polymer of 110,000, and a ratio of the polymer of 20% by mass with respect to the total mass (total of the polymer and water). An aqueous emulsion composition of the union (B-2) was obtained.

<Preparation of carbon fiber bundle (raw material)>
A spinning stock solution in which acrylonitrile-based polymer was dissolved in dimethylacetamide was discharged into a first coagulation bath composed of a dimethylacetamide aqueous solution having a concentration of 50 to 70% by mass and a temperature of 30 to 50 ° C. to obtain a coagulated yarn. Next, the coagulated yarn is subjected to a predetermined amount of stretching in a second coagulation bath made of a dimethylacetamide aqueous solution having a concentration of 50 to 70% by mass and a temperature of 30 to 50 ° C., and further subjected to wet heat stretching of 4 times or more to obtain a carbon fiber. A precursor fiber bundle was obtained. The ratio of the major axis to the minor axis of the cross section of the carbon fiber precursor fiber bundle and the depth of wrinkles formed on the surface can be adjusted by changing the concentration and temperature of the second coagulation bath, and further the stretching conditions. . Thereafter, for the purpose of maintaining the stability of the carbon fiber precursor fiber bundle, a silicon-based oil was adhered.

  Next, a plurality of carbon fiber precursor fiber bundles are introduced into a flameproofing furnace in a state where they are aligned in parallel, and an oxidizing gas such as air heated to 200 to 300 ° C. is blown onto the carbon fiber precursor fiber bundles, The carbon fiber precursor fiber bundle was made flame resistant to obtain a flame resistant fiber bundle. Subsequently, this flame-resistant fiber bundle was introduced into a carbonization furnace, and carbonized at a temperature of 1200 to 2000 ° C. in an inert atmosphere to obtain a carbon fiber bundle (raw material). Thereafter, for the purpose of improving the affinity with the resin, oxygen-containing functional groups were introduced on the surface of the carbon fiber bundle (raw material) by wet electrolytic oxidation treatment.

  Furthermore, the pre-sizing process was performed with the water dispersion type sizing agent which consists of an epoxy compound. The characteristics of the obtained carbon fiber bundle (raw material) are shown in Table 1.

<Manufacture of carbon fiber bundles I to V>
A carbon fiber bundle (raw material) having the characteristics shown in Table 1 is alternately passed through a fiber opening bar and a carbon fiber width regulating bar a plurality of times to obtain a predetermined carbon fiber width, and then a sizing treatment with a predetermined sizing agent. Went. As the sizing agent, polymers shown in Table 2 were used. In carrying out the sizing treatment, an aqueous emulsion in which the amount of water in the aqueous emulsion composition obtained in Synthesis Examples 1 to 5 was adjusted and the sizing agent concentration was adjusted as shown in Table 3 was used. Moreover, the following touch roll system was employ | adopted as a system which makes aqueous emulsion adhere.

Touch Roll Method After a part of the touch roll was immersed in the aqueous emulsion tank and transferred to the surface of the touch roll, the aqueous emulsion was adhered by bringing a carbon fiber bundle (raw material) into contact with the surface of the touch roll. In addition, it implemented with respect to two front and back surfaces of a carbon fiber bundle (raw material) using two touch rolls.

  Next, the carbon fiber bundle is cut into a predetermined length (6 mm) using a rotary cutter, and finally, the carbon fiber bundle is dried by continuously feeding it into a floor vibration type hot air drying furnace set at 150 ° C. Bundles I-V were obtained.

  In addition, all the aqueous emulsions used had good emulsification stability, and both the permeability of the carbon fiber bundle during the sizing treatment and the cutting process were good. After drying, no cracks occurred in all the carbon fiber bundles. Table 3 shows the evaluation results of the produced carbon fiber bundles I to V.

(Examples 1-3, Comparative Examples 1-2)
<Manufacture of pellets and molded articles of thermoplastic resin composition>
80 parts by mass of polypropylene resin (polypropylene homopolymer, trade name: Novatec MA03, manufactured by Nippon Polychem Co., Ltd.) and 20 parts by mass of carbon fiber bundles shown in Table 3 are manufactured by Custom Scientific Instruments, Inc. Machine (Model: CS-183-MMX) was supplied, and a molded article was produced under the condition of a cylinder temperature of 200 ° C.

  Table 4 shows the mechanical properties of the obtained molded product. The molded products obtained in Examples 1 to 3 were superior in bending strength and flexural modulus compared to the molded products obtained in Comparative Examples 1 and 2. From this, it was found that the carbon fiber bundle of the present invention has good interfacial adhesion.

  A molded product obtained by molding the thermoplastic resin composition of the present invention is excellent in mechanical properties and productivity and economy. Such a molded product is suitable for a vehicle part, a housing part of a portable electrical appliance, a housing part of a general household appliance, and the like.

Claims (12)

Reinforcing fiber comprising a polymer (A) having a unit derived from the monomer (a) represented by the following general formula (1) and a unit derived from the monomer (b) represented by the following general formula (2) Sizing agent.

(Here, R ¹ represents hydrogen or a methyl group. R ² and R ³ represent a linear or branched alkyl group and may be the same or different from each other.)

(Here, R ⁴ represents hydrogen or a methyl group.)   The unit derived from the monomer (a) is 50 to 99% by mass with respect to 100% by mass of all monomer units of the polymer (A), and the unit derived from the monomer (b) is 1%. The sizing agent for reinforcing fibers according to claim 1, which is -50 mass%.   It is a manufacturing method of the sizing agent for reinforcing fibers of Claim 1 or 2, Comprising: The said monomer (a) and the said monomer (b) are emulsion-polymerized using surfactant, The said polymer The manufacturing method of the sizing agent for reinforcing fibers which synthesize | combines (A).   The method for producing a sizing agent for reinforcing fibers according to claim 3, wherein the surfactant is an anionic or nonionic surfactant.   A carbon fiber bundle that has been sized by the sizing agent for reinforcing fibers according to claim 1 or 2.   The single fiber constituting the carbon fiber bundle has a plurality of wrinkles having a height difference of 40 nm or more between a highest part and a lowest part in a region having a circumferential length of 2 μm and a fiber axial direction length of 1 μm. 5. The carbon fiber bundle according to 5.   The carbon fiber bundle according to claim 5 or 6, wherein the sizing agent is attached in an amount of 1 to 30% by mass of the carbon fiber bundle cut to a predetermined length.   The mass per 1 m length of the carbon fiber bundle is 0.4 to 15 g, and the ratio (width / thickness) of the width and thickness of the carbon fiber bundle is 3 to 10. The carbon fiber bundle according to item 1. (I) Using an aqueous emulsion in which the polymer (A) contained in the sizing agent for reinforcing fibers according to claim 1 or 2 is dispersed in water, the adhesion amount of the polymer (A) is a carbon fiber bundle. Sizing the carbon fiber bundle so as to be 1 to 30% by mass or less of the weight;
(II) adjusting the water content of the carbon fiber bundle subjected to sizing treatment to 20 to 60% by mass, and cutting to a predetermined length;
(III) A method for producing a carbon fiber bundle, comprising the steps of drying the carbon fiber bundle cut into a predetermined length in this order.   A thermoplastic resin composition comprising a thermoplastic resin and the carbon fiber bundle according to any one of claims 5 to 8, wherein a mass ratio of the carbon fiber bundle is 3 to 60 mass%. object.   The thermoplastic resin composition according to claim 10, wherein the thermoplastic resin is a polyolefin resin.   A molded product obtained by molding the thermoplastic resin composition according to claim 10 or 11.