JP2013177560A - Method for producing carbon fiber reinforced molded product, and carbon fiber reinforced molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an effective method for producing a carbon fiber reinforced molded product having excellent mechanical characteristics, conductivity and electromagnetic wave-shielding properties.SOLUTION: In a method for producing a carbon fiber reinforced molded product, a molding material including a thermoplastic resin (A) and a carbon fiber (B) subjected to sizing treatment with a sizing agent (a) having SP value difference of larger than 3.5 from the thermoplastic resin (A) and having an aspect ratio calculated from fiber length/fiber diameter of 250-10,000 is molded in a condition that a mold temperature is higher by 5-50°C than a heat distortion temperature of the thermoplastic resin (A).

Description

  The present invention relates to a method for producing a carbon fiber reinforced molded product, and more specifically, a method for producing a carbon fiber reinforced molded product that is lightweight and excellent in mechanical properties, electrical conductivity (low volume resistance), and electromagnetic wave shielding properties. And a carbon fiber reinforced molded product obtained by the production method thereof.

  Molded articles made of reinforcing fibers and thermoplastic resins are widely used in sports equipment applications, aerospace applications, and general industrial applications because they are lightweight and have excellent mechanical properties. These reinforcing fibers include metal fibers such as aluminum fibers and stainless fibers, organic fibers such as aramid fibers and polyparaphenylene benzoxazole (PBO) fibers, and inorganic fibers such as silicon carbide fibers and carbon fibers. However, carbon fiber is preferable from the viewpoint of the balance of specific strength, specific rigidity, and lightness, and among them, polyacrylonitrile (PAN) carbon fiber is preferably used.

  A molded article reinforced with carbon fiber has excellent electromagnetic shielding properties because carbon fiber has excellent conductivity. Therefore, it can shield the cause of noise and electromagnetic waves that adversely affect other electronic components, and is particularly suitable for electronic and information equipment such as personal computers, televisions, audio equipment, and EV / HEV related members of automobiles. Can be used.

  The present applicant has proposed a fiber-reinforced propylene resin composition having a reinforcing fiber, a terpene resin having a specific SP value, and a propylene resin in Patent Document 1. With such a resin composition, it is possible to obtain a molded article having excellent moldability, good interfacial adhesion between the reinforcing fiber and the propylene-based resin, and excellent mechanical properties. However, no mention is made of volume resistivity and electromagnetic shielding properties.

Patent Document 2 discloses a propylene having a molecular weight of 10 ⁶ or more in a propylene resin for the purpose of obtaining a carbon fiber reinforced molded article having uniform conductivity and excellent surface appearance. A resin-based molded article is disclosed. However, although it has been shown to exhibit an excellent volume resistance value, it is difficult to adapt to other commercially available thermoplastic resins.

  Patent Document 3 discloses a resin comprising an ethylene-based polymer and a thermoplastic resin that can be dispersed in islands for the purpose of obtaining a highly conductive resin molded article that has excellent corrosion resistance and can impart high conductivity. A highly conductive resin molded article formed by molding a conductive thermoplastic resin composition containing carbon black, carbon fiber, and / or flake graphite in its components is disclosed. However, the addition of carbon black and / or scaly graphite contained in the molded product may lead to a decrease in mechanical properties. Furthermore, the range in which the amount of carbon fiber is 60 to 400 parts by weight and the content is large with respect to 100 parts by weight of the resin component is specified, and if the amount of carbon fiber contained in the molded product is less than this range, the conductivity is reduced. Therefore, it is difficult to adapt to general carbon fiber reinforced molded products.

  As described above, in the conventional technology, in a carbon fiber reinforced molded article using a thermoplastic resin as a matrix, excellent conductivity (low volume resistance value) and electromagnetic wave shielding properties are expressed by a simple method. It has been desired to develop a carbon fiber reinforced molded product that can achieve both.

JP 2010-248482 A JP 2005-290021 A JP 2004-168897 A

  In view of the problems of the prior art, an object of the present invention is to provide an effective production method for obtaining a carbon fiber reinforced molded article having excellent mechanical properties, electrical conductivity (low volume resistance value), and electromagnetic wave shielding properties. And

In order to solve the above problems, the present invention has the following configuration.
(1) A sizing treatment in which the SP value difference between the thermoplastic resin (A) and the thermoplastic resin (A) is larger than 3.5 is calculated from the fiber length / fiber diameter. A carbon fiber, which is formed by molding a molding material containing carbon fiber (B) having an aspect ratio of 250 to 10,000 under a condition that the mold temperature is 5 to 50 ° C. higher than the thermal deformation temperature of the thermoplastic resin (A). A method of manufacturing a reinforced molded product.
(2) The method for producing a carbon fiber reinforced molded product according to (1), wherein an average fiber length of the carbon fiber (B) contained in the molding material is 1.5 to 40 mm.
(3) The carbon fiber reinforced molded product according to (1) or (2), wherein the molding material contains 5 to 50 parts by weight of the carbon fiber (B) with respect to 100 parts by weight of the thermoplastic resin (A). Manufacturing method.
(4) The method for producing a carbon fiber reinforced molded product according to any one of (1) to (3), wherein the form of the molding material is a long fiber pellet.
(5) A carbon fiber reinforced molded product satisfying the following requirements [1] and [2] obtained by the method for producing a carbon fiber reinforced molded product according to any one of (1) to (4).
[1] The relationship between the average interfiber distance D [μm] of the carbon fibers (B) dispersed in the molded product and the fiber content weight fraction Wf [%] of the carbon fibers (B) is represented by the following formula. Is done.
0 <D <83 × Wf ^−1.10
[2] The variation coefficient of the number of the carbon fibers (B) per unit area on the cut surface of the molded product is 15% or less.
(6) The carbon fiber reinforced molded product according to (5), wherein an average fiber length of the carbon fiber (B) dispersed in the molded product is 0.3 to 10 mm.

  The carbon fiber reinforced molded product obtained by the production method of the present invention is a molded product having excellent electrical properties (low volume resistance value) and electromagnetic wave shielding properties and excellent mechanical properties such as bending properties. Moreover, since the thermoplastic resin is used as a matrix, it also has light weight. The carbon fiber reinforced molded product of the present invention is extremely useful for electrical / electronic devices, OA devices, home appliances, housings, or automobile parts.

  The present invention will be described in detail. The carbon fiber reinforced molded product of the present invention (hereinafter sometimes simply referred to as “molded product”) and the molding material used in the production method thereof are composed of at least a thermoplastic resin (A) and a carbon fiber (B). The First, these constituent components will be described in detail. In the present invention, the “molding material” refers to a material that can be directly used in various molding methods without changing the form.

  In the present invention, the thermoplastic resin (A) is preferably one that can be molded at a molding temperature (melting temperature) of 200 to 450 ° C., polyolefin, polystyrene, polyamide, halogenated vinyl resin, polyacetal, saturated polyester, polycarbonate, polyarylsulfone. , Polyaryl ketone, polyphenylene ether, polyphenylene sulfide, polyaryl ether ketone, polyether sulfone, polyphenylene sulfide sulfone, polyarylate, liquid crystal polyester, fluororesin, and the like, all of which correspond to an electrical insulator. A thermoplastic resin selected from such a group can be used alone, or two or more thermoplastic resins can be used in combination as a polymer alloy.

  Among the above thermoplastic resins, polyolefin resin, polyamide resin, and polycarbonate resin that are lightweight and have a good balance of mechanical properties and moldability are more preferable for use as electrical / electronic equipment and automotive parts, and have chemical resistance and moisture absorption. Polypropylene resin is more preferable because of its excellent properties. Hereinafter, polypropylene resins, polyamide resins, and polycarbonate resins that are suitable thermoplastic resins will be described.

  The polypropylene resin referred to here includes both unmodified and modified ones.

  The unmodified polypropylene resin is specifically a homopolymer of propylene or a copolymer of propylene and at least one α-olefin, conjugated diene, non-conjugated diene or the like. Examples of the α-olefin include ethylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-hexene, and 4,4 dimethyl. Examples include α-olefins having 2 to 12 carbon atoms excluding propylene such as -1-hexene, 1-nonene, 1-octene, 1-heptene, 1-hexene, 1-decene, 1-undecene and 1-dodecene. . Examples of the conjugated diene and non-conjugated diene include butadiene, ethylidene norbornene, dicyclopentadiene, 1,5-hexadiene, and the like. Two or more of these may be used. As the skeleton structure of the unmodified polypropylene resin, a homopolymer of propylene, a random or block copolymer of propylene and the other monomer, or a random or block copolymer of propylene and another thermoplastic monomer Etc. For example, polypropylene, ethylene / propylene copolymer, propylene / 1-butene copolymer, ethylene / propylene / 1-butene copolymer, and the like are preferable. A propylene homopolymer is preferable from the viewpoint of further improving the rigidity of the molded product, and a random or block copolymer of propylene and the other monomers is preferable from the viewpoint of further improving the impact strength of the molded product.

  The modified polypropylene resin is preferably an acid-modified polypropylene resin, and more preferably a polypropylene resin having a carboxylic acid and / or salt group bonded to a polymer chain. The acid-modified polypropylene resin can be obtained by various methods, for example, whether the polypropylene resin is neutralized or a monomer having a non-neutralized carboxylic acid group, and / or saponified. A monomer having an unsaponified carboxylic acid ester can be obtained by graft polymerization.

  Here, as a monomer having a neutralized or non-neutralized carboxylic acid group, and a monomer having a saponified or unsaponified carboxylic acid ester group, for example, Examples thereof include ethylenically unsaturated carboxylic acids, anhydrides thereof, and esterified products thereof. Furthermore, the compound etc. which have unsaturated vinyl groups other than an olefin are also mentioned.

  Examples of the ethylenically unsaturated carboxylic acid include (meth) acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, and the like. Examples thereof include (endocis-bicyclo [2,2,1] hept-5-ene-2,3-dicarboxylic acid), maleic anhydride, citraconic anhydride and the like.

  Examples of esterified products of ethylenically unsaturated carboxylic acids include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl ( (Meth) acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) Acrylate, octadecyl (meth) acrylate, stearyl (meth) acrylate, tridecyl (meth) acrylate, lauroyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, (Meth) acrylic acid such as nyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate Esters, hydroxyethyl acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl acrylate, lactone-modified hydroxyethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl acrylate, etc. Hydroxyl group-containing (meth) acrylic acid esters, glycidyl (meth) acrylate, epoxy group-containing (meth) acrylic acid esters such as methyl glycidyl (meth) acrylate N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dipropylaminoethyl (meth) acrylate, N, Examples include aminoalkyl (meth) acrylates such as N-dibutylaminoethyl (meth) acrylate and N, N-dihydroxyethylaminoethyl (meth) acrylate.

  Monomers having unsaturated vinyl groups other than olefins include isocyanate groups-containing vinyls such as vinyl isocyanate and isopropenyl isocyanate, and aromatics such as styrene, α-methylstyrene, vinyltoluene, and t-butylstyrene. Vinyl, acrylamide, methacrylamide, N-methylol methacrylamide, N-methylol acrylamide, diacetone acrylamide, vinyl esters containing maleic acid amide, vinyl esters such as vinyl acetate and vinyl propionate, styrene sulfonic acid, Unsaturated sulfonic acids such as sodium styrene sulfonate and 2-acrylamido-2-methylpropane sulfonic acid, mono (2-methacryloyloxyethyl) acid phosphate, mono (2-acryloyloxyethyl) acid phosphate Unsaturated phosphoric acids, etc. and the like.

  Two or more of these may be used. Among these, ethylenically unsaturated carboxylic acid anhydrides are preferable, and maleic anhydride is more preferable.

  Here, in order to improve the mechanical properties of the molded article, particularly the bending strength, it is preferable to use both the unmodified polypropylene resin and the modified polypropylene resin, and particularly from the viewpoint of the balance between flame retardancy and mechanical properties, It is preferable that the weight ratio of the modified polypropylene resin is 95/5 to 75/25. More preferably, it is 95 / 5-80 / 20, More preferably, it is 90 / 10-80 / 20.

  The polyamide resin is a resin mainly composed of amino acid, lactam, or diamine and dicarboxylic acid. Representative examples of the main raw materials include amino acids such as 6-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid and paraaminomethylbenzoic acid, lactams such as ε-caprolactam and ω-laurolactam, tetramethylenediamine, Hexamethylenediamine, 2-methylpentamethylenediamine, nonamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4- / 2,4,4-trimethylhexamethylenediamine, 5-methylnonamethylenediamine, etc. Aromatic diamines such as aliphatic diamine, metaxylylenediamine, paraxylylenediamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, 1-amino-3-aminomethyl- 3,5,5-trimethyl Cyclohexane, bis (4-aminocyclohexyl) methane, bis (3-methyl-4-aminocyclohexyl) methane, 2,2-bis (4-aminocyclohexyl) propane, bis (aminopropyl) piperazine, aminoethylpiperazine, etc. Aliphatic diamine, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid and other aliphatic dicarboxylic acids, terephthalic acid, isophthalic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid , Aromatic dicarboxylic acids such as 5-sodium sulfoisophthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, fats such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid Cyclic dicarboxylic acid Etc., and the like. Two or more of these may be used.

  In the present invention, a polyamide resin having a melting point of 200 ° C. or higher is particularly useful from the viewpoint of excellent heat resistance and strength. Specific examples thereof include polycaproamide (nylon 6), polyhexamethylene adipamide (nylon 66), polycaproamide / polyhexamethylene adipamide copolymer (nylon 6/66), polytetramethylene adipa Midon (nylon 46), polyhexamethylene sebamide (nylon 610), polyhexamethylene dodecamide (nylon 612), polyhexamethylene terephthalamide / polycaproamide copolymer (nylon 6T / 6), polyhexamethylene adipamide / Polyhexamethylene terephthalamide copolymer (nylon 66 / 6T), polyhexamethylene adipamide / polyhexamethylene isophthalamide copolymer (nylon 66 / 6I), polyhexamethylene adipamide / polyhexamethylene terephthalamide Polyhexamethylene isophthalamide copolymer (nylon 66 / 6T / 6I), polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (nylon 6T / 6I), polyhexamethylene terephthalamide / polydodecanamide copolymer (nylon 6T / 12) , Polyhexamethylene terephthalamide / poly (2-methylpentamethylene) terephthalamide copolymer (nylon 6T / M5T), polyxylylene adipamide (nylon XD6), polynonamethylene terephthalamide (nylon 9T) and their co-polymers Examples include coalescence. Two or more of these may be used. Among these, nylon 6 and nylon 66 are more preferable.

  The degree of polymerization of these polyamide resins is not particularly limited, and the relative viscosity measured at 25 ° C. of a solution of 0.25 g of polyamide resin in 25 ml of 98% concentrated sulfuric acid is in the range of 1.5 to 5.0, particularly 2. A polyamide resin in the range of 0 to 3.5 is preferred.

  The polycarbonate resin is obtained by reacting a dihydric phenol and a carbonate precursor. The copolymer obtained using 2 or more types of dihydric phenols or 2 or more types of carbonate precursors may be sufficient. Examples of the reaction method include an interfacial polymerization method, a melt transesterification method, a solid phase transesterification method of a carbonate prepolymer, and a ring-opening polymerization method of a cyclic carbonate compound. Such polycarbonate resins are known per se, and for example, the polycarbonate resins described in JP-A-2002-129027 can be used.

  Examples of the dihydric phenol include 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, bis (4-hydroxyphenyl) alkane (such as bisphenol A), 2,2-bis {( 4-hydroxy-3-methyl) phenyl} propane, α, α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene, 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, and the like. . Two or more of these may be used. Among these, bisphenol A is preferable, and a polycarbonate resin excellent in impact resistance can be obtained. On the other hand, a copolymer obtained using bisphenol A and another dihydric phenol is excellent in terms of high heat resistance or low water absorption.

  As the carbonate precursor, for example, carbonyl halide, carbonic acid diester, haloformate or the like is used, and specific examples include phosgene, diphenyl carbonate, dihaloformate of dihydric phenol, and the like.

  In producing a polycarbonate resin from the dihydric phenol and the carbonate precursor, a catalyst, a terminal terminator, an antioxidant for preventing the oxidation of the dihydric phenol, and the like may be used as necessary.

  Further, the polycarbonate resin in the present invention is copolymerized with a branched polycarbonate resin copolymerized with a trifunctional or higher polyfunctional aromatic compound, an aromatic or aliphatic (including alicyclic) difunctional carboxylic acid. The polyester carbonate resin, the copolymer polycarbonate resin which copolymerized bifunctional alcohol (an alicyclic group is included), and the polyester carbonate resin which copolymerized both such bifunctional carboxylic acid and bifunctional alcohol are included. These polycarbonate resins are also known. Two or more of these polycarbonate resins may be used.

  The molecular weight of the polycarbonate resin is not specified, but those having a viscosity average molecular weight of 10,000 to 50,000 are preferred. When the viscosity average molecular weight is 10,000 or more, the strength of the molded product can be further improved. 15,000 or more is more preferable, and 18,000 or more is more preferable. On the other hand, if the viscosity average molecular weight is 50,000 or less, the moldability is improved. It is more preferably 40,000 or less, and further preferably 30,000 or less. When using 2 or more types of polycarbonate resin, it is preferable that at least 1 type of viscosity average molecular weight exists in the said range. In this case, it is preferable to use a polycarbonate resin having a viscosity average molecular weight of more than 50,000, preferably more than 80,000 as the other polycarbonate resin. Such polycarbonate resin has high entropy elasticity and is advantageous when used in combination with gas-assist molding, as well as improved properties such as anti-drip characteristics, draw-down characteristics, and improved jetting properties derived from high entropy elasticity. Exhibiting properties).

The viscosity average molecular weight (M) of the polycarbonate resin is obtained by inserting the specific viscosity (ηsp) obtained at 20 ° C. from a solution of 0.7 g of the polycarbonate resin in 100 ml of methylene chloride into the following equation.
ηsp / c = [η] + 0.45 × [η] 2c (where [η] is the intrinsic viscosity)
[Η] = 1.23 × 10 ⁻⁴ M ^0.83
c = 0.7

  The carbon fiber (B) used in the present invention is obtained by adding the sizing agent (a) to the carbon fiber (b) before the sizing treatment. It is preferable because it can be improved and the occurrence of fluff and yarn breakage can be suppressed in the high-order processing step, and the high-order workability can be improved as a so-called paste or bundling agent.

  Here, examples of the carbon fiber (b) in the present invention include PAN-based, pitch-based, and rayon-based, and PAN-based carbon fibers are preferable from the viewpoint of the balance between strength and elastic modulus of the obtained molded product.

  Further, as the carbon fiber (b), the surface oxygen concentration ratio [O / C] which is the ratio of the number of atoms of oxygen (O) and carbon (C) on the fiber surface measured by X-ray photoelectron spectroscopy is 0.05. What is -0.5 is preferable, More preferably, it is 0.08-0.4, More preferably, it is 0.1-0.3. When the surface oxygen concentration ratio is 0.05 or more, the amount of functional groups on the surface of the carbon fiber can be secured, and stronger adhesiveness can be obtained. From the viewpoint of improving the mechanical properties, a higher surface oxygen concentration ratio is preferable because high adhesiveness can be obtained. Moreover, although there is no restriction | limiting in particular in the upper limit of surface oxygen concentration ratio, Generally it can be illustrated to 0.5 or less from the balance of the handleability of carbon fiber, and productivity.

The surface oxygen concentration ratio of the carbon fiber (b) is determined by X-ray photoelectron spectroscopy according to the following procedure. First, after cutting the carbon fiber bundle from which the sizing agent and the like adhering to the carbon fiber surface with a solvent was cut to 20 mm and spreading and arranging on a copper sample support base, using A1Kα1,2 as the X-ray source, The sample chamber is kept at 1 × 10 ⁻⁸ Torr. The kinetic energy value (KE) of the main peak of C1s is adjusted to 1202 eV as a peak correction value associated with charging during measurement. The C1s peak area is expressed as K.S. E. Is obtained by drawing a straight base line in the range of 1191 to 1205 eV. The O1s peak area is expressed as K.I. E. Is obtained by drawing a straight base line in the range of 947 to 959 eV.

  Here, the surface oxygen concentration ratio is calculated as an atomic ratio by using a sensitivity correction value unique to the apparatus from the ratio of the O1s peak area to the C1s peak area. As an X-ray photoelectron spectroscopy apparatus, model ES-200 manufactured by Kokusai Electric Inc. is used, and the sensitivity correction value is set to 1.74.

  The means for controlling the surface oxygen concentration ratio [O / C] to 0.05 to 0.5 is not particularly limited. For example, in the step of performing the surface treatment on the carbon fiber (b), the treatment amount The method of increasing / decreasing is mentioned. As the surface treatment method, methods such as electrolytic oxidation treatment, chemical solution oxidation treatment, and gas phase oxidation treatment can be employed, and among them, electrolytic oxidation treatment is preferable.

  Moreover, there is no restriction | limiting in particular in the number of single yarns when carbon fiber (b) is made into a carbon fiber bundle, and it can be used within the range of 100 to 350,000, especially 1,000 to 250,000. It is preferable to use within the range. Further, from the viewpoint of productivity of the carbon fiber (b), those having a large number of single yarns are preferable, and it is preferable to use them within the range of 20,000 to 100,000.

  In the present invention, the compound is not particularly limited as the sizing agent (a) to be imparted to the carbon fiber (b), but the SP value difference between the sizing agent (a) and the thermoplastic resin (A) is larger than 3.5. It is preferable that it is 20 or less. More preferably, it is 4.0 or more and 10 or less.

  Here, in the present invention, the SP value is a solubility parameter, and it has been empirically obtained that the solubility increases as the SP values of the two components are closer. In the present invention, the carbon fiber (B) provided with the sizing agent (a) is selected by selecting the thermoplastic resin (A) and the sizing agent (a) so that the SP value is larger than 3.5. In the molding process, the resin tends to re-aggregate after being dispersed by shearing or flowing during molding in the resin. For this reason, an electroconductive network is formed by the carbon fiber (B) mentioned later, As a result, the average inter-fiber distance D becomes small, volume resistance value can be reduced, and electroconductivity can be improved.

  On the other hand, when the SP value difference is 3.5 or less, the wettability between the thermoplastic resin (A) and the carbon fiber (B) increases, and the thermoplastic resin (A As a result, the average inter-fiber distance D of the carbon fibers (B) is increased, a conductive network is not formed by the carbon fibers (B), and the volume resistance value is increased, which is not preferable.

  Note that several methods for determining the SP value are known, but the same determination method may be used for comparison. Specifically, it is desirable to use the Fedors method. (Reference SP Value Basics / Applications and Calculations, March 31, 2005, 1st edition, publisher Akitoshi Taniguchi, published by Information Organization Co., Ltd., pages 66-67)

  In the present invention, specific examples of the sizing agent (a) include epoxy resin, phenol resin, polyethylene glycol, polyurethane, polyester resin, polyamide resin, terpene resin, emulsifier, or surfactant. Of these, polyester resins are preferred. When kneading the thermoplastic resin matrix and the carbon fiber (B), it works to improve the dispersibility of the short carbon fibers and improve the electrical characteristics of the composition. In addition, polyester resin is suitable as a sizing agent that enhances the sizing properties of short carbon fibers because of its film properties. Further, water solubility or water dispersibility is preferable because of good wettability with the carbon fiber and good permeability into the carbon fiber bundle. These may be used alone or in combination of two or more.

  Examples of such polyester resins include polycondensates of dicarboxylic acids and glycols, ring-opening polymerization products of cyclic lactones, polycondensates of hydroxycarboxylic acids, polycondensates of dibasic acids and glycols, and the like. Specifically, polyethylene terephthalate resin, polypropylene terephthalate resin, polytrimethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, polybutylene naphthalate resin, polycyclohexanedimethylene terephthalate resin, polyethylene-1,2-bis (phenoxy) ) Ethane-4,4′-dicarboxylate resin, polyethylene-1,2-bis (phenoxy) ethane-4,4′-dicarboxylate resin, polyethylene isophthalate / terephthalate resin, polybuty Terephthalate / isophthalate resin, a copolymer of polybutylene terephthalate / decane carboxylate resin and polycyclohexanedimethylene terephthalate / isophthalate resin can be typically used. Two or more of these may be used in combination. Among these, a polyester resin which is a polycondensate of dicarboxylic acid and glycol is preferable, and at least one selected from the group consisting of aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid and derivatives thereof is used as the dicarboxylic acid component. A polycondensate of the dicarboxylic acid contained and a glycol containing at least one selected from the group consisting of ethylene glycol, propylene glycol, propanediol and derivatives thereof is preferred as the glycol component. In particular, the dicarboxylic acid component is preferably an aromatic dicarboxylic acid such as terephthalic acid or isophthalic acid, or a derivative thereof. In the total dicarboxylic acid component, 30 mol% or more (more preferably 50 mol% or more, more preferably 70 mol% or more). Of terephthalic acid and / or isophthalic acid. On the other hand, the glycol component is preferably ethylene glycol or a derivative thereof, and preferably contains 30 mol% or more (more preferably 50 mol% or more, more preferably 70 mol% or more) of ethylene glycol in the total glycol component.

  When these polyester resins are used as a sizing agent, they are preferably water-soluble, partially water-soluble, or water-dispersible. Water-soluble, partially water-soluble, or water-dispersible polyester resins introduce, for example, polyalkylene oxide chains, sulfonic acid groups or salts thereof, carboxyl groups or salts thereof, amino groups or salts thereof, in the molecular chain or at terminal groups. Among them, introduction of a polyalkylene oxide chain and / or introduction of a sulfonic acid group or a salt thereof is preferred, and an alkali metal salt is preferred as the salt thereof.

  The adhesion amount of the sizing agent (a) is not particularly limited, but is preferably 0.01 to 10% by weight, more preferably 0.05 to 5% by weight, based on the mass of the carbon fiber (b) alone, 0.1% More preferred is ˜2% by weight. Adhesion can be further improved by setting the amount of sizing agent (a) to be 0.01% by weight or more, and the physical properties of the thermoplastic resin (A) can be effectively expressed by setting it to 10% by weight or less. can do.

  Although it does not specifically limit as a sizing processing method, For example, the method of immersing carbon fiber (b) in a sizing liquid via a roller, the method of contacting carbon fiber (b) to the roller to which the sizing liquid adhered, sizing liquid And spraying the carbon fiber (b). Moreover, although either a batch type or a continuous type may be sufficient, the continuous type which has good productivity and small variations is preferable. At this time, it is preferable to control the sizing solution concentration, temperature, yarn tension, and the like so that the amount of the active component of the sizing agent (a) attached to the carbon fiber (b) is uniformly attached within an appropriate range. Moreover, it is more preferable to vibrate the carbon fiber (b) with ultrasonic waves during the sizing treatment.

  The drying temperature and drying time should be adjusted according to the amount of the compound attached, but the complete removal of the solvent used for applying the sizing agent (a) and the time required for drying are shortened, while the heat of the sizing agent (a) From the viewpoint of preventing the deterioration and preventing the sizing-treated carbon fiber (B) from becoming hard and spreading property, the drying temperature is preferably 150 ° C. or higher and 350 ° C. or lower, and 180 ° C. or higher and 250 ° C. or higher. It is more preferable that it is below ℃.

  Examples of the solvent used for diluting the sizing agent (a) include water, methanol, ethanol, dimethylformamide, dimethylacetamide, acetone and the like, but water is preferable from the viewpoint of easy handling and disaster prevention. Therefore, when using a compound insoluble or hardly soluble in water as a sizing agent, it is preferable to add an emulsifier and a surfactant and disperse in water. Specifically, as an emulsifier and a surfactant, styrene-maleic anhydride copolymer, olefin-maleic anhydride copolymer, formalin condensate of naphthalene sulfonate, anionic emulsifier such as sodium polyacrylate, Nonionic emulsifiers such as cationic emulsifiers such as polyethyleneimine and polyvinylimidazoline, nonylphenol ethylene oxide adducts, polyvinyl alcohol, polyoxyethylene ether ester copolymers, sorbitan ester ethyl oxide adducts, etc. can be used. A nonionic emulsifier having a small size is preferable because it hardly inhibits the adhesive effect of the polyfunctional compound.

  Next, the molding material used for the manufacturing method of the carbon fiber reinforced molded product of this invention mentioned later is demonstrated. This molding material is sizing-treated with a sizing agent (a) in which the SP value difference between the thermoplastic resin (A) and the thermoplastic resin (A) is larger than 3.5, and the fiber length / fiber The carbon fiber (B) whose aspect ratio calculated from a diameter is 250-10,000 is included. Here, in this invention, fiber length and a fiber diameter point out the below-mentioned average fiber length and average fiber diameter, respectively.

  The aspect ratio calculated from the fiber length / fiber diameter of the carbon fiber (B) contained in the molding material is preferably 50 to 50,000, and 250 to 10,000 in the present invention. When considering the breakage of the carbon fiber (B) at the time of molding, within this range, the aspect ratio of the carbon fiber (B) dispersed in the molded product is expressed with a good balance of mechanical properties, volume resistance, and electromagnetic shielding properties. And it is preferable because it can be adjusted to a suitable value capable of obtaining a good surface appearance. Here, when the aspect ratio is smaller than 250, the volume resistance value increases, and the electromagnetic wave shielding property may not be sufficiently obtained. The aspect ratio is preferably 400 or more, more preferably 500 or more. In addition, when the aspect ratio is greater than 10,000, the carbon fiber (B) may not be uniformly dispersed macroscopically at the time of molding, and the volume resistance value may not increase or electromagnetic wave shielding may not be exhibited. In addition, the moldability also decreases. The aspect ratio is preferably 8,000 or less, and more preferably 6,000 or less.

  In the present invention, the average fiber length of the carbon fibers (B) contained in the molding material is preferably 1.5 to 40 mm. As with the aspect ratio, when the breakage of the carbon fiber (B) at the time of molding is taken into consideration, the fiber length of the carbon fiber (B) dispersed in the molded product is determined within the above range in terms of mechanical properties, electrical conductivity, and electromagnetic shielding properties. Can be adjusted to a suitable value that can be expressed in a balanced manner. When the average fiber length is 1.5 mm or more, particularly excellent electromagnetic shielding properties can be exhibited. The average fiber length is more preferably 3 mm or more, and further preferably 4 mm or more. Moreover, if average fiber length is 40 mm or less, the carbon fiber (B) in a molded article can be fully disperse | distributed macroscopically, and electromagnetic wave shielding can be expressed more effectively. The average fiber length is more preferably 20 mm or less, and further preferably 15 mm or less.

Here, the “average fiber length” in the present invention is a method of calculating the weight average molecular weight applied to the calculation of the fiber length, not simply taking the number average, but from the following formula that takes into account the contribution of the fiber length: Refers to the calculated average fiber length. However, the following formula is applied when the fiber diameter and density of the carbon fiber (B) are constant.
Average fiber length = Σ (Mi ² × Ni) / Σ (Mi × Ni)
Mi: Fiber length (mm)
Ni: Number of carbon fibers having a fiber length Mi

  The average fiber length can be measured by the following method. The molding material is incinerated at 500 ° C. for 2 hours, the carbon fibers in the molding material are taken out, and the carbon fibers are uniformly dispersed in water. The dispersed water in which carbon fibers are uniformly dispersed is sampled in a petri dish, dried, and observed with an optical microscope (50 to 200 times). The length of 1000 carbon fibers (B) selected at random is measured, and the average fiber length is calculated from the above formula.

  Further, the average fiber diameter of the carbon fiber (B) used in the present invention is not particularly limited, but from the viewpoint of electromagnetic wave shielding properties, mechanical properties and surface appearance of the obtained molded product, the aspect ratio is within the range of 1 to 20 μm. It is preferable to select from the ratio and the fiber length, and it is more preferable to be within the range of 3 to 15 μm.

  The average fiber diameter can be measured by the following method. Observe the cross section of the carbon fiber (b) with a scanning electron microscope (5,000 times), measure the fiber diameter of 400 carbon fibers (b) selected at random, and calculate the number average value. calculate.

  In this invention, it is preferable that the said molding material contains 5-50 weight part of carbon fibers (B) with respect to 100 weight part of thermoplastic resins (A). In such a range, in the obtained carbon fiber reinforced molded product, the average inter-fiber distance D of the carbon fiber (B) described later is a suitable value, and both a low volume resistance value and excellent electromagnetic shielding properties can be achieved. More preferably, it is 10-40 weight part, More preferably, it is 15-30 weight part.

  As the form of the molding material in the present invention, pellets, stampable sheets, prepregs, SMC, BMC and the like can be used, but the most desirable form is pellets used for injection molding. The pellet is generally obtained by kneading a desired amount of thermoplastic resin (A) and chopped yarn or continuous fiber of carbon fiber (B) in an extruder, and extruding and pelletizing. Point to. In such a pellet, the fiber length in the pellet is shorter than the length in the longitudinal direction of the pellet, but the pellet in the present invention includes a long fiber pellet and can be particularly preferably used.

  Such a long fiber pellet is, as shown in Japanese Patent Publication No. 63-37694, in which fibers are arranged substantially parallel to the longitudinal direction of the pellet, and the fiber length in the pellet is equal to or longer than the pellet length. It points to something.

  In the long fiber pellet, the resin may be impregnated in the fiber bundle or may be coated on the fiber bundle. In particular, in the case of long fiber pellets coated with a resin, the fiber bundle may be impregnated in advance with a resin having the same viscosity as that of the coated fiber or a resin having a lower viscosity (or lower molecular weight) than the coated resin.

  When long fiber pellets are used for molding, the carbon fiber length in the molded product is longer than the pellets in which the fiber length in the pellet is shorter than the length in the longitudinal direction of the pellet. Are more preferably used.

  Next, the carbon fiber reinforced molded product obtained by the method for producing the carbon fiber reinforced molded product of the present invention described later will be described in detail.

In the carbon fiber reinforced molded product of the present invention, the volume resistance value and the electromagnetic wave shielding properties are expressed in a well-balanced manner, so that the average interfiber distance D [μm] of the carbon fibers (B) dispersed in the molded product and the carbon fiber ( It is preferable that the relationship between B) and the fiber-containing weight fraction Wf [%] satisfies the following formula.
0 <D <83 × Wf ^−1.10

  In the present invention, “the average interfiber distance D of the carbon fibers (B) dispersed in the molded product” means other carbons closest to the respective fibers with respect to the carbon fibers (B) dispersed in the molded product. It is a value representing the number average value of the shortest distance from the fiber (B).

  In general, as the value of the fiber-containing weight fraction is larger, the carbon fiber (B) is densely packed in a molded product having a constant volume, and therefore the value of the average interfiber distance tends to be smaller. Then, the cohesive force between the carbon fibers (B) tends to work, and the carbon fibers (B) come into contact with each other to form a conductive path, so that the volume resistance value can be reduced and the conductivity can be further improved. On the other hand, the smaller the value of the fiber-containing weight fraction, the greater the value of the average interfiber distance of the carbon fiber (B). Then, the influence of the dispersibility of the carbon fiber (B) on the electromagnetic wave shielding becomes large, and a gap in which the carbon fiber (B) does not exist is generated due to a slight deviation of the dispersion, and the electromagnetic wave shielding property is deteriorated and the mechanical properties are reduced. It will cause a decline. This invention pays attention to the fiber content weight fraction and average fiber distance of carbon fiber (B), and discovered the relationship of the said formula calculated | required in order to make a mechanical characteristic, electroconductivity, and electromagnetic shielding property compatible. . Note that the values of the coefficient and the exponent in the above formula are values obtained experimentally from a plurality of measurement results. In the present invention, the affinity between the thermoplastic resin (A) and the carbon fiber (B) is adjusted by the SP value of the sizing agent imparted to the carbon fiber (B), and the thermoplasticity between the carbon fibers (B). Since the resin (A) can be interposed, even when the value of the fiber-containing weight fraction is large, a certain value of the average interfiber distance can be ensured.

  A specific method for calculating the average inter-fiber distance D is a method of observing a cross section of a molded product with an optical microscope (200 to 400 times), image processing / analysis of the obtained microscopic image, A method of directly measuring the distance and obtaining the number average value, obtaining an image of the carbon fiber (B) dispersed in the molded product by X-ray CT in a three-dimensional manner, and using the obtained three-dimensional data with dedicated analysis software The method of calculating by analysis etc. is mentioned. Here, when calculating by cutting out a specific region two-dimensionally, depending on the orientation angle in the molded product of the carbon fiber (B), the measured inter-fiber distance may not be the closest distance, It is preferable to measure a plurality of cross sections to obtain more three-dimensional data. Specifically, it is preferable to measure about five or more cross sections, and it is more preferable to measure about ten or more cross sections. Moreover, when measuring the distance between fibers directly, it is preferable to measure about 400 or more randomly selected carbon fibers per cross section.

Further, the fiber-containing weight fraction Wf is a value indicating the proportion of the weight (W _B ) of the carbon fiber (B) in the weight (W _A ) of the entire molded product, and is represented by the following formula. .

The W _A, the specific measuring method of W _B, W _A is cutting out a portion of the molded article, and weighed. Also it is preferable to select a suitable method depending on the type of W the thermoplastic resin measured using the _B (A), for example, when using a polypropylene resin or polyamide resin, molded product pieces used for measurement of the W _A of Ashing treatment is performed at 500 ° C. for 15 minutes, the carbon fiber (B) in the molded product is taken out, and the weight is measured. In the case of using the polycarbonate resin in the thermoplastic resin (A), tetrahydrofuran was added to the molded product pieces used for measurement of the W _A, to dissolve the 45 minute ultrasound shaking to polycarbonate resins. This is suction filtered to take out the carbon fiber (B), and the weight is measured.

Here, when the average inter-fiber distance D is 83 × Wf ^−1.10 or more, there are few places where the carbon fibers (B) are in contact with each other, and a conductive network is not formed, so that the volume resistance value increases. This is not preferable. On the other hand, the average interfiber distance is generally greater than zero.

  In addition, when the average inter-fiber distance D [μm] and the fiber-containing weight fraction Wf [%] satisfy the above relational expression, the reason why such an effect appears is not necessarily clear, but the present inventors have It is estimated that. That is, by bringing the conductive carbon fibers (B) closer to each other, a conductive network is formed, and the electrical insulation inherently possessed by the thermoplastic resin (A) can be improved, while the carbon fibers (B) have It is presumed that the electromagnetic loss energy is converted into heat energy by the dielectric loss characteristic, and high electromagnetic shielding properties are exhibited.

  In the carbon fiber reinforced molded product of the present invention, the carbon fiber (B) is uniformly dispersed and exhibits excellent electromagnetic shielding properties and mechanical properties. Therefore, the carbon fiber (B) per unit area on the cut surface of the molded product The variation coefficient of the number is preferably 15% or less. More preferably, it is 10% or less.

  In the present invention, “the coefficient of variation of the number of carbon fibers (B) per unit area on the cut surface of the molded product” refers to the average value and standard deviation of the number of fibers present per unit area in the cross section of a certain molded product. Is a factor indicating the uniform dispersibility of the carbon fiber (B) in the molded product, calculated from The smaller the value of the coefficient of variation, the smaller the dispersion variation, indicating that the carbon fibers (B) are uniformly present in the molded product. As a specific calculation method, for example, a method of observing a cross section of a molded product with an optical microscope (50 to 200 times), counting the number of fibers per unit area for 40 or more observation sites, and calculating a coefficient of variation. Can be mentioned.

  Here, when the variation coefficient of the number of carbon fibers (B) per unit area on the cut surface of the molded product is 15% or less, the carbon fibers (B) in the molded product are sufficiently dispersed, The mechanical properties can be further improved.

  In this invention, it is preferable that the average fiber length of the said carbon fiber (B) disperse | distributed in a molded article is 0.1-10 mm. If the average fiber length is 0.1 mm or more, the electromagnetic wave shielding property can be expressed more effectively. The average fiber length is more preferably 0.2 mm or more, more preferably 0.3 mm or more, further preferably 0.4 mm or more, and further preferably 0.5 mm or more. Further, if the average fiber length is 10 mm or less, it is preferable because the dispersion failure in the molded product of the carbon fiber (B) can be reduced, the volume resistance value can be further reduced, and the electromagnetic wave shielding property can be expressed more effectively. . The average fiber length is more preferably 8 mm or less, and further preferably 6 mm or less. The average fiber length of the carbon fibers (B) dispersed in the molded product can be calculated in the same manner as the average fiber length of the carbon fibers (B) contained in the molding material.

  In addition, the carbon fiber reinforced molded product of the present invention may contain other fillers and additives as long as the object of the present invention is not impaired. Examples of these include inorganic fillers, crystal nucleating agents, antioxidants, damping agents, antibacterial agents, insect repellents, deodorants, anti-coloring agents, heat stabilizers, mold release agents, plasticizers, lubricants, and coloring agents. , Pigments, dyes, foaming agents, antifoaming agents, or coupling agents. In addition, when carbon black or scaly graphite is contained, the content is preferably less than 10% by weight in the carbon fiber reinforced molded product from the viewpoint of mechanical properties of the carbon fiber reinforced molded product.

  Subsequently, the method for producing the carbon fiber reinforced molded product of the present invention is described in detail.

  In the method for producing a carbon fiber reinforced molded article of the present invention, the molding temperature of the thermoplastic resin (A) and the carbon fiber (B) is determined from the heat distortion temperature of the thermoplastic resin (A). It is characterized in that it is molded under a condition that is 5 to 50 ° C. higher. A preferable mold temperature range is a condition that is higher by 10 ° C. to 30 ° C. than the heat distortion temperature. The heat distortion temperature in the present invention is measured for a molded article composed only of the thermoplastic resin (A) in accordance with ISO 75 under flat-wise test conditions with a test load of 0.45 MPa. It refers to the deflection temperature under load of the thermoplastic resin (A).

  By setting the mold temperature within such a range, the thermoplastic resin (A) in which the carbon fibers (B) are dispersed is cooled and cured in the mold to obtain a molded product. Due to the affinity of the interface between (A) and carbon fiber (B), carbon fiber (B) can form a stable dispersion state while maintaining a distance between fibers that can exhibit excellent conductivity. it can. Thereby, carbon fiber (B) can be disperse | distributed uniformly and the average inter-fiber distance D in a molded article, fiber content weight fraction Wf, and a coefficient of variation can be easily controlled to the said preferable range.

  Here, the affinity of the interface between the thermoplastic resin (A) and the carbon fiber (B) is related to the affinity between the sizing agent (a) present on the surface layer of the carbon fiber (B) and the thermoplastic resin (A). Dependent. Therefore, by making these SP value differences larger than 3.5, the thermoplastic resin (A) and the carbon fiber (B) show a low affinity, and as a result, the thermoplasticity between the carbon fibers (B). The state in which the carbon fibers (B) are in contact with each other is more stable than the state in which the resin (A) is interposed, and a conductive network is formed by the carbon fibers (B). It is preferable because the distance D and the fiber-containing weight fraction Wf can be easily controlled within the above preferable range and the volume resistance value can be reduced. On the other hand, when the SP value difference between the sizing agent (a) and the thermoplastic resin (A) is 3.5 or less, the wettability between the thermoplastic resin (A) and the carbon fiber (B) increases, and the carbon fiber ( B) The thermoplastic resin (A) is interposed between the carbon fibers (B), and the average interfiber distance D of the carbon fibers (B) is increased. As a result, a conductive network is not formed by the carbon fibers (B), and the volume resistance value is increased. Increase.

  Further, when the mold temperature is less than 5 ° C. higher than the thermal deformation temperature of the thermoplastic resin (A), the thermoplastic resin (A) in the molten state has a constant fiber distance between the carbon fibers (B). Since it is cooled and hardened before forming a stable dispersion state that is maintained, conductivity is lowered. Also, if the mold temperature exceeds the heat distortion temperature of the thermoplastic resin (A) + 50 ° C, it takes time for cooling and curing, the molding cycle is reduced, and the molded product is successfully removed from the mold. In some cases, it may not be possible to reduce the moldability. Furthermore, the thermoplastic resin (A) as a matrix may be thermally deteriorated and mechanical properties may be reduced.

  In the present invention, the method for producing a carbon fiber reinforced molded product is not particularly limited as long as it is a molding method using a mold having the above temperature, and various known methods such as injection molding, extrusion molding, and press molding are used. However, injection molding is preferred from the viewpoint of excellent molding efficiency.

  The carbon fiber reinforced molded product of the present invention can be suitably used for automobile parts such as various modules such as instrument panels, door beams, under covers, lamp housings, pedal housings, radiator supports, spare tire covers, and front ends. Furthermore, home / office electrical product parts such as telephones, facsimiles, VTRs, copiers, televisions, microwave ovens, audio equipment, toiletries, laser discs (registered trademarks), refrigerators, air conditioners, and the like are also included. Further, there are a housing used for a personal computer, a mobile phone and the like, and a member for electric / electronic equipment represented by a keyboard support which is a member for supporting a keyboard inside the personal computer. Especially because of its excellent balance between lightness, mechanical properties, electrical conductivity, and electromagnetic wave shielding, it is especially suitable for use as portable electrical / electronic equipment parts and electrical parts storage containers for electric vehicles, such as battery cases, inverter cases, and ECU cases. Is suitable.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, the following Example does not limit this invention.

[Material Evaluation Method]
(1) Thermal deformation temperature of thermoplastic resin According to ISO 75, the thermal deformation temperature (deflection temperature under load) of the thermoplastic resin was measured flat-wise under test conditions of a test load of 0.45 MPa.

(2) SP value calculation method The SP value was calculated from the molecular formula of the compound using the formula shown below.
σ (SP value) = (ΣE _coh / ΣV) ^1/2
Here, E _coh is the cohesive energy density, and V is the molar volume of the molecule. All values were proposed by Fedors as constants depending on the functional group, and this value was adopted.

(3) Average fiber length of carbon fibers in the molded product The center part of the molded ISO-type tensile dumbbell test piece was cut into 20 mm × 10 mm (4 mmt), ashed at 500 ° C. for 2 hours, and carbon in the test piece. The fiber was removed. This carbon fiber was put into a beaker together with 3 L of water, and the carbon fiber was uniformly dispersed in water using an ultrasonic cleaner. 1 mL of dispersed water in which carbon fibers are uniformly dispersed with a dropper having a tip diameter of 8 mm was sucked and sampled in a petri dish having a 10 mm × 10 mm recess, and then dried. The carbon fiber after drying was observed with an optical microscope (50 to 200 times), 1000 randomly selected lengths were measured, and the average fiber length was calculated from the following formula.
Average fiber length = Σ (Mi ² × Ni) / Σ (Mi × Ni)
Mi: Fiber length (mm)
Ni: Number.

(4) Average interfiber distance of carbon fiber After cutting with a diamond cutter at the center of the formed ISO type tensile dumbbell test piece and at four locations at 10 mm intervals from the center to both ends, the cross section was polished, A total of 5 samples were made. The carbon fibers in the five 10 mm × 4 mm cut surfaces were observed with an optical microscope (200 to 400 times), and the microscopic images obtained for the respective cut surfaces were subjected to image processing to measure 400 interfiber distances. The average interfiber distance was calculated by calculating the number average value.

(5) Coefficient of variation of the number of carbon fibers After cutting the center part of the formed ISO type tensile dumbbell test piece with a diamond cutter, the cross section was polished to prepare a sample. The cut surface of 10 mm × 4 mm was divided into 1 mm × 1 mm sections (40 sections in total) and observed with an optical microscope (50 to 200 times). From the obtained microscopic images of each section, the number of carbon fibers was counted by image processing, and the variation coefficient of the number of fibers was calculated.

(6) Bending strength Based on ISO 178, the fulcrum distance was set to 64 mm using a three-point bending test jig (indenter radius 5 mm), and the bending strength was measured under the test conditions of a test speed of 2 mm / min. As a testing machine, an “Instron (registered trademark)” universal testing machine type 5566 (manufactured by Instron) was used.

(7) Volume Resistance Value An ISO type tensile dumbbell test piece was cut and polished to a size of 80 mm × 10 mm (4 mmt) with a diamond cutter to obtain a test piece for measuring volume resistance value. In accordance with JIS K 6271, the volume resistance value was measured by a four-terminal method using an ohmmeter HIOKI3541.

(8) Electromagnetic wave shielding properties Using an evaluation device manufactured by Microwave Factory, electromagnetic wave shielding properties were measured in the vicinity of an electric field of 10 MHz to 1 GHz in accordance with the KEC method. The electromagnetic wave shielding property was calculated by the following formula. For the test piece, a conductive paste (Dotite manufactured by Fujikura Kasei Co., Ltd.) was applied to four sides of a 150 mm × 150 mm (3 mmt) square plate, and the conductive paste was sufficiently dried.
_{SE = 20 × logE 0 / E} X
SE: Electromagnetic wave shielding property (dB)
E ₀ : Spatial electric field strength when there is no shielding material E _X : Spatial electric field strength when there is a shielding material

(9) Fiber-containing weight fraction Wf
Cut out pieces of 10mm × 10mm (4mmt) from the central portion of the molded ISO type tensile dumbbell was a _{W A} by measuring the weight of the pieces. Further, the piece subjected to 15 minutes ashing at 500 ° C., the weight measured by taking out the carbon fibers in the molded article (B) was W _B. The resulting _W A, with _{W B,} was calculated Wf from the following equation.

[Reference Example 1-1] Production of carbon fiber (b-1) Spinning, baking treatment, and surface oxidation treatment were carried out from a copolymer containing polyacrylonitrile as a main component, the total number of single yarns was 24,000, and the single fiber diameter was 7 μm. Carbon fiber (b) having a mass per unit length of 1.6 g / m, a specific gravity of 1.8 g / cm ³ and a surface oxygen concentration [O / C] of 0.06 was obtained. The carbon fiber (b) had a strand tensile strength of 4880 MPa and a strand tensile elastic modulus of 225 GPa.

[Reference Example 1-2] Production of carbon fiber (b-2) Spinning, baking treatment and surface oxidation treatment were carried out from a copolymer containing polyacrylonitrile as the main component, the total number of single yarns was 24,000, and the single fiber diameter was 7 μm. A carbon fiber (b) having a mass per unit length of 1.6 g / m, a specific gravity of 1.8 g / cm ³ and a surface oxygen concentration [O / C] of 0.12 was obtained. The carbon fiber (b) had a strand tensile strength of 4880 MPa and a strand tensile elastic modulus of 225 GPa.

[Reference Example 2] Application of sizing agent (a) A sizing agent mother liquor in which sizing agent (a) is dissolved or dispersed in water so as to be 2% by weight is prepared, and the adhesion amount becomes 1.0% by weight. Thus, the sizing agent (a) was applied to the carbon fiber (b) by an immersion method and dried at 230 ° C.

Example 1
As thermoplastic resin (A), a polypropylene resin (Prime Polymer Co., Ltd. Prime Polypro J105G) and maleic acid-modified polypropylene resin (Mitsui Chemicals Co., Ltd. Admer QE840) are pellet blended at a weight ratio of 85/15 (A -1), using an SE75DUZ-C250 injection molding machine manufactured by Sumitomo Heavy Industries, Ltd., injection time: 10 seconds, holding pressure: molding lower limit pressure + 10 MPa, holding pressure time: 10 seconds, cylinder temperature: 230 ° C., Mold temperature: A test piece for characteristic evaluation was molded at 60 ° C. Next, the thermal deformation temperature of the thermoplastic resin (A-1) alone was measured for the obtained test piece according to the evaluation method shown in (1) above.

  Moreover, the evaluation method which showed SP value of aromatic polyester resin (DIC Corporation ES2200) (a-1) as said thermoplastic resin (A-1) and the sizing agent (a) in said (2). Respectively, and the SP value difference was calculated.

  Then, said sizing agent (a-1) is provided to the carbon fiber (b-1) obtained from Reference Example 1-1 by the method shown in Reference Example 2, and carbon fiber (B-1) is obtained. It was.

  Using a long fiber reinforced resin pellet manufacturing apparatus with a molten resin coating die port at the discharge tip of a single screw extruder, the extruder cylinder temperature was set to 220 ° C., and the thermoplastic resin (A- 1) is supplied from the main hopper, melted at a screw speed of 200 rpm, and the carbon fiber (B-1) is supplied to a die port (3 mm in diameter) for discharging the molten resin to cool the resin-coated strand. Thereafter, the pellet length was cut to 10 mm with a pelletizer to obtain long fiber pellets. Here, the fiber length of the carbon fiber (B) in the molding material was handled as being substantially equivalent to the pellet length. Further, the take-up speed of the carbon fiber (B-1) was adjusted so that the carbon fiber (B-1) was 30 parts by weight with respect to 100 parts by weight of the thermoplastic resin (A-1).

  The long fiber pellets thus obtained were used, using an SE75DUZ-C250 injection molding machine manufactured by Sumitomo Heavy Industries, Ltd., injection time: 10 seconds, holding pressure: molding lower limit pressure + 10 MPa, holding pressure time: 10 seconds, cylinder A test piece for characteristic evaluation (molded product) was molded under the conditions of a temperature of 230 ° C. and a mold temperature of 110 ° C. The obtained test piece was subjected to characteristic evaluation after being left in a constant temperature and humidity chamber adjusted to a temperature of 23 ° C. and 50% RH for 24 hours. Next, the obtained test pieces for characteristic evaluation (molded products) were evaluated according to the evaluation methods shown in the above (3) to (9). A series of evaluation results are summarized in Table 1.

(Example 2)
When producing long fiber pellets, molding evaluation was performed in the same manner as in Example 1 except that carbon fiber (B-1) was 5 parts by weight with respect to 100 parts by weight of thermoplastic resin (A-1). Went. The evaluation results are collectively shown in Table 1.

(Example 3)
When producing long fiber pellets, molding evaluation was performed in the same manner as in Example 1 except that carbon fiber (B-1) was 50 parts by weight with respect to 100 parts by weight of thermoplastic resin (A-1). Went. The evaluation results are collectively shown in Table 1.

Example 4
Except having obtained carbon fiber (B-2) using water-soluble nylon (AQ nylon P70 by Toray Industries, Inc.) (a-2) as a sizing agent (a) to be imparted to carbon fiber (b) Molding evaluation was performed in the same manner as in Example 1. The evaluation results are collectively shown in Table 1.

(Example 5)
Molding evaluation was performed in the same manner as in Example 1 except that the mold temperature at the time of injection molding at the time of molding the obtained long fiber pellets was 145 ° C. The evaluation results are collectively shown in Table 1.

(Example 6)
As the thermoplastic resin (A), nylon 6 (“Amilan” (registered trademark) CM1007 manufactured by Toray Industries, Inc.) (A-2) is used, and the carbon fiber (B) is used as a sizing agent (a). A carbon fiber (B-3) obtained using a polyolefin aqueous dispersion (Chemical S75N manufactured by Mitsui Chemicals, Inc.) (a-3) was used.

  Further, the cylinder temperature of the injection molding machine is 280 ° C., the mold temperature at the time of molding the test piece for measuring the heat distortion temperature is 80 ° C., the mold temperature at the time of molding the long fiber pellet is 190 ° C. Molding evaluation was performed in the same manner as in Example 1 except that the extruder cylinder temperature was set to 250 ° C. The evaluation results are collectively shown in Table 1.

(Example 7)
As carbon fiber (b) to which sizing agent (a) is applied, carbon fiber (b-2) obtained from Reference Example 1-2 was used, and (B-4) was used. Molding evaluation was performed. The evaluation results are collectively shown in Table 1.

(Example 8)
Molding evaluation was performed in the same manner as in Example 1 except that the long fiber pellet was cut so that the pellet length was 2 mm. The evaluation results are collectively shown in Table 1.

Example 9
Molding evaluation was performed in the same manner as in Example 1 except that the long fiber pellet was cut so that the pellet length was 40 mm. The evaluation results are collectively shown in Table 1.

(Comparative Example 1)
Molding evaluation was performed in the same manner as in Example 1 except that the sizing agent (a) was not applied to the carbon fiber (b-1). Many thread slips out of the long fiber pellets, bridging occurred in the hopper of the injection molding machine, and it was difficult to obtain a molded product.

(Comparative Example 2)
As a sizing agent (a) to be imparted to the carbon fiber (b), 41.2% by weight of bisphenol A type epoxy resin having an average molecular weight of 370 (Japan Epoxy Resin Co., Ltd., Epicoat 828), POA-tristyrenated phenyl ether Was evaluated in the same manner as in Example 1 except that a carbon fiber (B-5) was obtained using a sizing agent (a-4) containing 17.6% by weight and 41.2% by weight of an unsaturated polyester resin. went. The evaluation results are collectively shown in Table 2.

(Comparative Example 3)
Molding evaluation was performed in the same manner as in Example 1 except that the mold temperature at the time of injection molding at the time of molding the obtained long fiber pellets was set to 60 ° C. The evaluation results are collectively shown in Table 2.

(Comparative Example 4)
Although molding was attempted in the same manner as in Example 1 except that the mold temperature at the time of injection molding at the time of molding the obtained long fiber pellets was set to 170 ° C., the molded product could be removed from the mold. It was impossible to evaluate.

(Comparative Example 5)
Carbon fiber obtained by applying aromatic polyester resin (a-1) as a sizing agent (a) to the carbon fiber (b-1) obtained from Reference Example 1-1 by the method shown in Reference Example 2 ( B-1) was cut with a cartridge cutter to obtain a carbon fiber chopped strand having a length of 6 mm. Next, a thermoplastic resin (A-1) obtained by pellet blending polypropylene resin (Prime Polypro J105G manufactured by Prime Polymer Co., Ltd.) and maleic acid-modified polypropylene resin (Admer QE840 manufactured by Mitsui Chemicals Co., Ltd.) at a weight ratio of 85/15; The carbon fiber chopped strand was dry blended so that the carbon fiber (B-1) was 30 parts by weight with respect to 100 parts by weight of the thermoplastic resin (A-1). This was melt-kneaded using a JSW TEX-30α type twin screw extruder (screw diameter 30 mm, die diameter 5 mm, barrel temperature 220 ° C., screw rotation speed 150 rpm) to obtain melt-kneaded pellets, which were used as molding materials. Here, in the evaluation method of (3) above, the average fiber length of the carbon fibers (B) in the melt-kneaded pellets was the same as that of the melt-kneaded pellets except that 1 g of the melt-kneaded pellets was used instead of the ISO type tensile dumbbell test piece. Was measured.

  The melt-kneaded pellets thus obtained were injected using a SE75DUZ-C250 injection molding machine manufactured by Sumitomo Heavy Industries, Ltd., injection time: 10 seconds, holding pressure: molding lower limit pressure + 10 MPa, holding pressure time: 10 seconds, cylinder temperature: A test piece for characteristic evaluation (molded product) was molded at 230 ° C. and mold temperature: 110 ° C. The obtained test piece was subjected to characteristic evaluation after being left in a constant temperature and humidity chamber adjusted to a temperature of 23 ° C. and 50% RH for 24 hours. Next, the obtained test pieces for characteristic evaluation (molded products) were evaluated according to the evaluation methods shown in the above (3) to (9). A series of evaluation results are summarized in Table 2.

(Comparative Example 6)
Molding evaluation was performed in the same manner as in Example 1 except that the long fiber pellet was cut so that the length of the pellet was 100 mm. The fluidity was extremely low, and a molded product could not be obtained.

  The materials of Examples 1 to 5 and Examples 7 to 9 all showed excellent mechanical properties, conductivity, and electromagnetic shielding properties. Further, as shown from the material of Example 6, even when the matrix resin was changed, high mechanical properties, electrical conductivity, and electromagnetic shielding properties were similarly exhibited.

  On the other hand, in Comparative Example 1, since the sizing agent was not applied, yarn threading frequently occurred from the long fiber pellets, bridging occurred in the hopper of the injection molding machine, and it was difficult to obtain a molded product. In Comparative Example 2, although the mechanical properties were satisfactory, the volume resistance value increased because the interfacial adhesion between the carbon fibers and the matrix resin inhibited the formation of a conductive network between the carbon fibers. In Comparative Example 3, the mechanical properties were satisfactory, but as in Comparative Example 2, the volume resistance value was increased and the electromagnetic wave shielding property was also reduced. In Comparative Example 4, the mold temperature was high, the molded product could not be removed from the mold, and evaluation was impossible. In Comparative Example 5, since the aspect ratio of the carbon fiber (B) in the molding material was small, the volume resistance value was increased and the electromagnetic wave shielding property was also lowered. In Comparative Example 6, since the fiber length of the carbon fiber (B) in the molding material was long and the aspect ratio was large, the fluidity was remarkably lowered and a molded product could not be obtained.

  Since the carbon fiber reinforced molded product of the present invention has excellent mechanical properties and excellent electrical conductivity and electromagnetic wave shielding properties, it is suitably used for electric / electronic devices, OA devices, home appliances, and housings.

Claims (6)

Aspect ratio calculated from fiber length / fiber diameter by sizing treatment with a sizing agent (a) having a SP value difference between the thermoplastic resin (A) and the thermoplastic resin (A) larger than 3.5. A carbon fiber reinforced molded article formed by molding a molding material containing carbon fiber (B) having a thickness of 250 to 10,000 under a condition that the mold temperature is 5 to 50 ° C. higher than the thermal deformation temperature of the thermoplastic resin (A). Manufacturing method. The manufacturing method of the carbon fiber reinforced molded product of Claim 1 whose average fiber length of the said carbon fiber (B) contained in the said molding material is 1.5-40 mm. The manufacturing method of the carbon fiber reinforced molded product of Claim 1 or 2 with which the said molding material contains 5-50 weight part of said carbon fibers (B) with respect to 100 weight part of said thermoplastic resins (A). The manufacturing method of the carbon fiber reinforced molded article in any one of Claims 1-3 whose form of the said molding material is a long fiber pellet. A carbon fiber reinforced molded product that satisfies the following requirements [1] and [2], which is obtained by the method for producing a carbon fiber reinforced molded product according to claim 1.
[1] The relationship between the average interfiber distance D [μm] of the carbon fibers (B) dispersed in the molded product and the fiber content weight fraction Wf [%] of the carbon fibers (B) is represented by the following formula. Is done.
0 <D <83 × Wf ^−1.10
[2] The variation coefficient of the number of the carbon fibers (B) per unit area on the cut surface of the molded product is 15% or less. The carbon fiber reinforced molded product according to claim 5, wherein an average fiber length of the carbon fiber (B) dispersed in the molded product is 0.3 to 10 mm.