JP7468608B2 - Carbon fiber reinforced resin material and its manufacturing method - Google Patents

Description

The present invention relates to a carbon fiber reinforced resin material exhibiting excellent compression properties and a method for producing the same .

Various carbon fiber resin composite materials have been proposed as lightweight, high-strength structural components for automobiles and electrical equipment. In general, structural components used in industrial applications are strongly required to be lightweight and have high mechanical properties, especially compressive strength and compressive modulus.

Metal materials have often been used for such structural members in the past, but in recent years, the use of carbon fiber resin composites (CFRP), which are lighter and stronger than metal materials, has been considered. Various materials can be used as the matrix resin for carbon fiber resin composites, but CFRP (CFRTP) made of thermoplastic resin, which has a shorter molding cycle than thermosetting resins, is industrially useful.
As the matrix resin of carbon fiber resin composite materials, polypropylene resin (PP) excellent in cost and light weight, polyamide resin (PA) excellent in mechanical strength, polyphenylene sulfide resin (PPS) excellent in heat resistance, etc. are generally considered. In addition, polycarbonate resin (PC) is relatively easy to mold and maintains stable physical properties in the usage environment of structural members for automobiles, etc., but has poor chemical resistance, so there are problems in terms of joint strength when assembling by adhesion and maintaining strength in the usage environment. As a technique for improving the chemical resistance of PC, alloying with other crystalline resins such as polyester is widely known, and a technique for using it as the matrix resin of CFRTP has also been devised.

Literature 1 describes a fiber-reinforced resin composition that has improved impact resistance, warpage, electromagnetic shielding, and thin-wall flame retardancy by mixing polycarbonate resin, liquid crystal polyester, and carbon fiber. Literature 2 describes a technology for obtaining a fiber-reinforced resin laminate that has excellent mechanical strength, heat resistance, electrical insulation, and chemical resistance by using a graft copolymer consisting of an acid-modified polyacrylate backbone and polyacrylate side chains to obtain a highly uniform resin composition of polycarbonate and polyester. However, according to the inventors' investigations, the resin compositions produced by these technologies were not suitable for the application of the present invention because no investigations were conducted into improving the compression properties.

JP 2000-226508 A Japanese Patent Application Laid-Open No. 6-287428

The present invention aims to solve the problems associated with the conventional techniques described above, and aims to provide a resin composition that exhibits excellent compression properties.

As a result of intensive research, the inventors of the present invention have found that the problem can be solved by using a crystalline thermoplastic resin, controlling the crystalline state in the resin portion, and setting the content of carbon fiber relative to the resin within a specific range, and have completed the present invention. That is, the gist of the present invention resides in the following (1) to (7).
(1) A carbon fiber reinforced resin material comprising the following components (A) and (B): wherein the crystalline resin in the component (A) has a crystallinity χc of 40% or more when melted, and a recrystallization rate of less than 70%.
Component (A): Resin composition containing 5 weight percent or more of crystalline resin Component (B): Carbon fiber <Degree of crystallinity χc and recrystallization rate>
Crystallinity χc=ΔHm/ΔHo/w×100(%)
Recrystallization rate = |ΔHc/ΔHm| × 100 (%)
ΔHm: melting enthalpy of the crystalline resin contained in the component (A). ΔHo: equilibrium melting enthalpy of the crystalline resin contained in the component (A). ΔHc: recrystallization enthalpy of the crystalline resin contained in the component (A). w: mass fraction of the crystalline resin in the component (A). (2) The carbon fiber reinforced resin material according to (1) above, containing 30 to 200 parts by weight of the component (B) when the component (A) is 100 parts by weight.
(3) The carbon fiber reinforced resin material according to any one of (1) to (2) above, wherein the component (A) is a resin containing a polycarbonate resin and a polyester resin in a total amount of 80 weight percent or more.
(4) The carbon fiber reinforced resin material according to the above (3), in which the mixed mass ratio of the polycarbonate resin and the polyester resin in the component (A) is PC/PEs, is 1 or more and PC/PEs is 19 or less.
(5) The carbon fiber reinforced resin material according to the above (3) or (4), wherein the polyester resin in the component (A) is polybutylene terephthalate.
(6) A stampable sheet made of the carbon fiber reinforced resin material according to any one of (1) to (5) above.
(7) A molded product of the stampable sheet described in (6) above.

The present invention provides a carbon fiber reinforced resin material that exhibits excellent compression properties.

The carbon fiber reinforced resin material of the present invention is described in detail below, but is not limited to the details as long as they do not go against the spirit of the present invention.

The carbon fiber reinforced resin material of the present invention is a carbon fiber reinforced resin material containing the components (A) and (B) described below, in which the crystallinity χc of the crystalline resin in the component (A) when melted is 40% or more, and the recrystallization rate is less than 70%.

Component (A): Resin composition containing 5 weight percent or more of crystalline resin Component (B): Carbon fiber <Degree of crystallinity χc and recrystallization rate>
Crystallinity χc=ΔHm/ΔHo/w×100(%)
Recrystallization rate = |ΔHc/ΔHm| × 100 (%)
ΔHm: melting enthalpy of the crystalline resin contained in component (A); ΔHo: equilibrium melting enthalpy of the crystalline resin contained in component (A); ΔHc: recrystallization enthalpy of the crystalline resin contained in component (A); w: mass fraction of the crystalline resin in component (A). The carbon fiber resin material of the present invention is obtained by using a crystalline resin, setting the content of carbon fiber relative to the resin within a specific range, and controlling the crystalline state in the resin portion.
The structure of the carbon fiber resin composite material will be described in detail below.

<Crystalline Resin>
The crystalline resin used in the present invention may be polyethylene, polypropylene, polyamide, polyacetal, polyester, polyphenylene sulfide, polyether ether ketone, polyether ketone ketone, polytetrafluoroethylene, etc., and may be used alone or in combination. Of these, it is preferable to use polyester from the standpoint of moldability and chemical resistance.
The polyester resin used in the present invention is a polymer or copolymer obtained by a condensation reaction of aromatic dicarboxylic acid or its reactive derivative and diol or its ester derivative as the main components.

As the aromatic dicarboxylic acid, terephthalic acid, isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-biphenyletherdicarboxylic acid, 4,4'-biphenylmethanedicarboxylic acid, 4,4'-biphenylsulfonedicarboxylic acid, 4,4'-biphenylisopropylidenedicarboxylic acid, 1,2-bis(phenoxy)ethane-4,4'-dicarboxylic acid, 2,5-anthracenedicarboxylic acid, 2,6-anthracenedicarboxylic acid, 4,4'-p-terphenylenedicarboxylic acid, 2,5-pyridinedicarboxylic acid, and other aromatic dicarboxylic acids are preferably used, with terephthalic acid and 2,6-naphthalenedicarboxylic acid being particularly preferred.

Two or more aromatic dicarboxylic acids may be used in combination. In addition, it is also possible to use small amounts of aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and dodecane diacid, and alicyclic dicarboxylic acids such as cyclohexane dicarboxylic acid in combination with the dicarboxylic acids.

The diols that are components of the aromatic polyester of the present invention include aliphatic diols such as ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, neopentyl glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol, 2-methyl-1,3-propanediol, diethylene glycol, and triethylene glycol; alicyclic diols such as 1,4-cyclohexanedimethanol; diols containing aromatic rings such as 2,2-bis(β-hydroxyethoxyphenyl)propane; and mixtures thereof. In addition, one or more long-chain diols having a molecular weight of 400 to 6,000, such as polyethylene glycol, poly-1,3-propylene glycol, and polytetramethylene glycol, may be copolymerized in small amounts.

The aromatic polyester of the present invention can be branched by introducing a small amount of a branching agent. There are no limitations on the type of branching agent, but examples include trimesic acid, trimellitic acid, trimethylolethane, trimethylolpropane, and pentaerythritol.

Specific examples of aromatic polyester resins include polyethylene terephthalate (PET), polypropylene terephthalate, polybutylene terephthalate (PBT), polyhexylene terephthalate, polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polyethylene-1,2-bis(phenoxy)ethane-4,4'-dicarboxylate, and copolymer polyesters such as polyethylene isophthalate/terephthalate, polybutylene terephthalate/isophthalate, and the like. Of these, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and mixtures thereof, which have well-balanced mechanical properties, can be preferably used.

The end group structure of the resulting aromatic polyester resin is not particularly limited, and the ratio of hydroxyl groups and carboxyl groups in the end groups may be approximately equal, or one may be greater than the other. The end groups may be blocked by reacting them with a compound that is reactive to the end groups.

The method for producing such aromatic polyester resins is carried out according to the usual method by polymerizing a dicarboxylic acid component and the diol component while heating in the presence of a polymerization catalyst containing titanium, germanium, antimony, etc., and discharging the by-product water or diol from the system. For example, germanium-based polymerization catalysts include germanium oxides, hydroxides, halides, alcoholates, phenolates, etc., and more specifically, germanium oxide, germanium hydroxide, germanium tetrachloride, tetramethoxygermanium, etc.

Preferred specific examples of the polymerization catalyst for the organic titanium compound include titanium tetrabutoxide, titanium isopropoxide, titanium oxalate, titanium acetate, titanium benzoate, titanium trimellitate, and the reaction product of tetrabutyl titanate and trimellitic anhydride. The amount of the organic titanium compound used is preferably such that the titanium atoms account for 3 to 12 mg atomic % of the acid component that constitutes the polyester resin.

In addition, in the present invention, compounds such as manganese, zinc, calcium, and magnesium that are used in the transesterification reaction, which is a step prior to polycondensation, can be used in combination, and after the transesterification reaction is completed, such catalysts can be deactivated with a compound of phosphoric acid or phosphorous acid, and then polycondensation can be performed.

The aromatic polyester resin can be produced by either a batch method or a continuous polymerization method.
The molecular weight of the aromatic polyester resin is not particularly limited, but the intrinsic viscosity measured at 35° C. using a phenol/tetrachloroethane (50:50) mixed solvent is 0.5 to 1.4, preferably 0.7 to 1.2.

If the intrinsic viscosity of the polyester resin is less than 0.5, sufficient chemical resistance is not ensured. If the intrinsic viscosity of the polyester resin is more than 1.4, it becomes difficult to impregnate the carbon fiber bundles, which is undesirable.

<Component (B): Carbon Fiber>
The carbon fiber used in the present invention may be any carbon fiber known as a reinforcing fiber, and is not particularly limited. The average fiber diameter of the carbon fiber is preferably 1 to 50 μm, and more preferably 5 to 20 μm. The average single fiber fineness of the carbon fiber is preferably 0.5 dtex or more, more preferably 0.6 dtex or more, and preferably 3.0 dtex or less, and more preferably 2.5 dtex or less. In terms of handling, it is usually desirable to use such single carbon fibers in the form of a carbon fiber bundle in which 1,000 to 60,000 single fibers are bundled together.

The single fibers constituting the carbon fiber bundles can be obtained by fiberizing and carbonizing, for example, acrylonitrile-based polymers (PAN-based polymers), pitch obtained from petroleum or coal, rayon, lignin, etc. In particular, PAN-based carbon fibers made from PAN-based polymers are preferred because of their excellent productivity on an industrial scale and excellent mechanical properties.
The PAN-based polymer has an acrylonitrile unit in its molecular structure, and can be a homopolymer of acrylonitrile or a copolymer of acrylonitrile and another monomer (e.g., methacrylic acid, etc.).

Although it is preferable to use carbon fiber alone, other reinforcing fibers such as inorganic fibers, organic fibers, metal fibers, or hybrid fibers combining these may be included.
Examples of inorganic fibers include graphite fibers, silicon carbide fibers, alumina fibers, tungsten carbide fibers, boron fibers, and glass fibers.
Examples of organic fibers include aramid fibers, high density polyethylene fibers, and other common nylon fibers, polyester fibers, and the like.
The metal fibers include stainless steel, iron, and the like, and may also be metal-coated carbon fibers.
The content of carbon fibers in the reinforcing fibers is preferably 50 to 100 mass %, more preferably 80 to 100 mass %, and most preferably 100 mass %.

<Component (A): Resin composition containing 5 weight percent or more of crystalline resin>
The present invention uses a resin part in which crystalline resin is mixed at 5 weight percent or more as a matrix resin. The present invention has a configuration in which a specific amount of carbon fiber is dispersed in this resin part. In addition to the crystalline resin, the resin part may contain an amorphous resin, an ester exchange reaction inhibitor, an antioxidant, etc. In the resin part, the total content of the crystalline resin is 5 weight percent or more, preferably 10 weight percent or more, and more preferably 15 weight percent. Within the above range, excellent compression characteristics can be exhibited when made into a carbon fiber reinforced resin material.

<Method of producing component (A)>
The method for producing the resin part of the present invention uses a conventionally known melt kneading method. That is, the raw material resin is supplied in bulk or in portions to a twin-screw extruder, a single-screw extruder, a batch kneader, or the like to obtain a resin part in which the raw material resins and the like are mixed. Among these, a twin-screw extruder is preferably used, and a vacuum vent can be used in combination as necessary to reduce deterioration of the resin during kneading.
The temperature during kneading is appropriately changed depending on the type and molecular weight of the resin, etc. The screws of the twin-screw extruder are preferably provided with one or more kneading disks in order to obtain high kneading efficiency.
After the kneading step, the resin is usually pelletized in a granulation step and then subjected to the next step. In the granulation step, either a cold cutter or a hot cutter may be used.

When carbon fibers are added as short fibers to obtain a resin composition, a good resin composition that maintains the fiber length can be obtained by side-feeding chopped carbon fibers in the downstream region of the twin-screw extruder during the kneading process of the resin section. When side-feeding chopped carbon fibers, the average length of the carbon fibers can be controlled by appropriately changing the feed position.

<Amorphous Resin>
The resin portion used in the carbon fiber resin composite composition of the present invention may contain a predetermined amount of amorphous resin. The amorphous resin used in the present invention may be polystyrene, polyvinyl chloride, AS resin, ABS resin, acrylic resin, polycarbonate, polyamideimide, polyethersulfone, polyetherimide, polysulfone, etc., and may be used alone or as a mixture. Of these, it is preferable to use polycarbonate, which has an excellent balance of strength, elastic modulus, and moldability.

The polycarbonate resin used in the present invention includes aromatic homo- or copolycarbonates obtained by reacting an aromatic dihydric phenol compound with phosgene or a carbonic acid diester. The aromatic homo- or copolycarbonate resin has a glass transition temperature of about 130 to 160° C. and a viscosity average molecular weight in the range of 8,000 to 25,000, preferably 10,000 to 20,000. Polycarbonate resins with different viscosity average molecular weights may be used in combination as long as the viscosity average molecular weight of the mixture is in the range of 8,000 to 25,000. The viscosity average molecular weight is measured by the following procedure. First, a solution with a resin concentration C=0.5 g/dl is prepared using methylene chloride as a solvent, and the specific viscosity η _sp is measured at a solution temperature of 20° C. using an Ubbelohde capillary viscometer. The measured reduced viscosity is used to calculate the specific viscosity η sp according to the Huggins formula [η]={(1+1.8×η _sp ) ^1/2 −1}/0.45
The intrinsic viscosity [η] is calculated using the Mark-Houwing-Sakurada formula [η] = 1.23 × 10 ^-4 × Mv0.83
The viscosity average molecular weight Mv can be obtained by substituting [η] into the viscosity average molecular weight M. If the viscosity average molecular weight is 8000 or less, the excellent mechanical properties of the present invention are impaired, which is not preferable, and if the viscosity average molecular weight is 25000 or more, the impregnation property may deteriorate when the continuous carbon fiber is impregnated with the resin to prepare a prepreg, and the flowability is impaired when the stampable sheet made of the resin composition is molded into an industrial part, which is not preferable.

As the aromatic dihydric phenol compound, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxy-3,5-diphenyl)butane, 2,2-bis(4-hydroxy-3,5-diethylphenyl)propane, 2,2-bis(4-hydroxy-3,5-diethylphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1-phenyl-1,1-bis(4-hydroxyphenyl)ethane, etc. can be used alone or in mixtures.

When phosgene is used as the carbonate precursor, the reaction is usually carried out in the presence of an acid binder and a solvent to produce an aromatic polycarbonate resin.
As the acid binder, for example, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, or an amine compound such as pyridine is used. As the solvent, for example, a halogenated hydrocarbon such as methylene chloride or chlorobenzene is used. To accelerate the reaction, a catalyst such as a tertiary amine or a quaternary ammonium salt may be used. The reaction temperature is usually 0 to 40°C, and the reaction time is several minutes to 5 hours.

When using a carbonic acid diester as a carbonate precursor and producing an aromatic polycarbonate resin by an ester exchange reaction, a specified ratio of aromatic dihydroxy component and carbonic acid diester are heated and stirred in an inert gas atmosphere, and the resulting alcohol or phenol is distilled off.

In this case, the reaction temperature varies depending on the boiling point of the produced alcohol or phenol, but is usually in the range of 120 to 300° C. The pressure of the reaction system is reduced from the initial stage of the reaction, and the reaction is completed while distilling off the alcohol or phenol.
In order to promote the reaction, a catalyst usually used in transesterification reactions may be used, and a suitable molecular weight regulator may also be used as appropriate.

When a polycarbonate resin is used as the crystalline resin and a polyester resin is used as the amorphous resin, the preferred mixing mass ratio PC/PEs of the polycarbonate resin (PC) and the polyester resin (PEs) is 1 or more and 19 or less. If PC/PEs is less than 1, the strength and elastic modulus are significantly reduced, which is not preferred. If PC/PEs exceeds 19, sufficient chemical resistance cannot be obtained. The more preferred composition ratio of PC/PEs is 1 or more and 15 or less.
The composition ratio of PC/PEs is more preferably 3 or more and 10 or less.

<Transesterification Reaction Inhibitor>
In producing the resin part, further blending a small amount of an acidic phosphate ester is useful for suppressing the transesterification reaction between the aromatic polycarbonate resin and the thermoplastic polyester, and is effective for maintaining the crystallinity of the polyester resin during high dispersion. The acidic phosphate ester is a general term for partial ester compounds of alcohols and phosphoric acid.

Specific examples of the acidic phosphate esters include monomethyl acid phosphate, monoethyl acid phosphate, monoisopropyl acid phosphate, monobutyl acid phosphate, monolauryl acid phosphate, monostearyl acid phosphate, monododecyl acid phosphate, monobehenyl acid phosphate, dimethyl acid phosphate, diethyl acid phosphate, diisopropyl acid phosphate, dibutyl acid phosphate, lauryl acid phosphate, distearyl acid phosphate, didodecyl acid phosphate, dibehenyl acid phosphate, trimethyl acid phosphate, triethyl acid phosphate, and mixtures of the above mono and di, mixtures of mono, di and tri, or mixtures of one or more of the above compounds. Preferred examples of the acidic phosphate esters include long-chain alkyl acid phosphate compounds such as a mixture of mono and distearyl acid phosphate. A commercially available product is "ADEKA STAB" AX-71 manufactured by ADEKA Corporation.

In addition, the amount of the acidic phosphate ester is 0.05 to 2 parts by mass, preferably 0.1 to 1 part by mass, per 100 parts by mass of the polycarbonate resin/polyester resin composition, in terms of heat distortion temperature and mechanical properties.

<Antioxidants>
The resin portion used in the carbon fiber resin composite composition of the present invention may contain a predetermined amount of an antioxidant.
As the antioxidant, it is preferable to use a phenol-based antioxidant as a primary antioxidant and a phosphorus-based antioxidant as a secondary antioxidant in combination.

<Phenol-based antioxidants>
Phenol-based antioxidants include 3,5-di-t-butyl-4-hydroxyphenyl)-propionate, n-octadecyl-3-(3-methyl-5-t-butyl-4-hydroxyphenyl)-propionate, n-tetradecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate, 1,6-hexanediol-bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate], 1,4-butanediol-bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate], 2,2'-methylenebis-(4-methyl-t-butylphenol), triethylene glycol-bis-[3-(3-t-butyl -5-methyl-4-hydroxyphenyl)-propionate], tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, 3,9-bis[2-{3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane, N,N'-bis-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionylhexamethylenediamine, N,N'-tetramethylene-bis-3-(3-methyl-5-t-butyl-4-hydroxyphenol)propionyldiamine, N,N'-bis-[3-(3,5-di-t-butyl-4 3-(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid, and the like. Preferred are triethyl esters. ethylene glycol-bis-[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)-propionate], tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, 1,6-hexanediol-bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], N,N'-hexamethylene bis-(3,5-di-t-butyl-4-hydroxy-hydrocinnamide, 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid. Specific trade names of the hindered phenol compounds include "ADEKA STAB AO-20", "AO-30", "AO-40", "AO-50", "AO-60", "AO-70", "AO-80", and "AO-330" manufactured by ADEKA Corporation, and "Irganox 245", "259", "565", "1010", "1035", "1076", and " Examples of such compounds include "1098", "1222", "1330", "1425", "1520", "3114", "5057", "Sumilizer BHT-R", "MDP-S", "BBM-S", "WX-R", "NW", "BP-76", "BP-101", "GA-80", "GM", and "GS" manufactured by Sumitomo Chemical Co., Ltd., and "Cyanox CY-1790" manufactured by Sun Chemical Co., Ltd.

<Phosphorus-based antioxidants>
Examples of phosphorus compounds include phosphite compounds and phosphate compounds. Specific examples of such phosphite compounds include tetrakis[2-t-butyl-4-thio(2-methyl-4-hydroxy-5-t-butylphenyl)-5-methylphenyl]-1,6-hexamethylene-bis(N-hydroxyethyl-N-methylsemicarbazide)-diphosphite, tetrakis[2-t-butyl-4-thio(2-methyl-4-hydroxy-5-t-butylphenyl)-5-methylphenyl]-1,10-decamethylene-dicarboxylic acid-dihydroxyethylcarbonylhydrazide-diphosphite, tetrakis[2-t-butyl-4-thio(2-methyl-4-hydroxy-5-t-butylphenyl)-5-methylphenyl]-1,10-decamethylene-dicarboxylic acid-dihydroxyethylcarbonylhydrazide-diphosphite, tetrakis[2-t-butyl-4-thio(2-methyl-4-hydroxy-5-t-butylphenyl)-5-methylphenyl]-N,N'-bis(hydroxyethyl)oxamide-diphosphite, and the like, but at least one P-O bond is bonded to an aromatic group. are more preferred, and specific examples thereof include tris(2,4-di-t-butylphenyl)phosphite, tetrakis(2,4-di-t-butylphenyl)4,4'-biphenylene phosphonite, bis(2,4-di-t-butylphenyl)pentaerythritol-diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol-diphosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octylphosphite, 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl)phosphite, 1,1,3-tris(2-methyl-4-ditridecyl) Phosphite-5-t-butyl-phenyl)butane, tris(mixed-mono- and di-nonylphenyl)phosphite, tris(nonylphenyl)phosphite, 4,4'-isopropylidenebis(phenyl-dialkylphosphite), etc. can be mentioned, and tris(2,4-di-t-butylphenyl)phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octylphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol-di-phosphite, tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylenephosphonite, etc. can be preferably used. Specific trade names of phosphite compounds include "ADEKA STAB C,""PEP-4C,""PEP-8,""PEP-11C,""PEP-24G,""PEP-36,""HP-10,""2112,""260,""522A,""329A,""1178,""1500,""135A,""3010," and "TPP" manufactured by ADEKA CORPORATION, "IRGAFOS 168" manufactured by Ciba Specialty Chemical Co., Ltd., "SUMIRAIZER P-16" manufactured by Sumitomo Chemical Co., Ltd., "Sandstab PEPQ" manufactured by Clariant Co., Ltd., and "WESTON 618,""619G," and "624" manufactured by GE.

<Method of producing carbon fiber resin composite composition>
In addition to the above-mentioned method of adding carbon fibers as short fibers, the method of manufacturing the carbon fiber resin composite composition of the present invention preferably includes a method of impregnating unidirectionally aligned carbon fiber bundles with a molten thermoplastic resin. This method makes it possible to manufacture a prepreg containing carbon fibers as long fibers, which is advantageous in manufacturing structural members with high elastic modulus and high strength.

The carbon fibers used in producing the prepreg are continuous fibers, supplied from one or more bobbins, opened before contacting with the molten resin, and supplied as sheet-like carbon fiber bundles to an apparatus for impregnating the molten resin. Known techniques such as bar opening and air opening can be used to open the carbon fibers. The sheet-like carbon fiber bundles may be heated before contacting with the molten resin.

The method of supplying the molten resin is not particularly limited, but for example, a method in which a resin portion that has been melt-kneaded and granulated in advance is supplied to a single-screw extruder, and a film of molten resin is allowed to flow down onto the carbon fiber bundle from a T-die attached to the tip of the extruder is suitably used. In addition, a twin-screw extruder can be used as the extruder to directly manufacture prepregs without going through the aforementioned resin mixing and granulation processes.

As another method, a pre-formed film of resin may be supplied onto a heated roll that is heated to the melting point or softening point of the resin or higher, and then contacted with the carbon fiber bundle.

The carbon fiber bundles are preferably impregnated with resin by sandwiching the carbon fiber bundles and molten resin between opposing heated rolls and pressurizing the resin for impregnation. From the viewpoint of impregnation efficiency, it is preferable that the heated rolls are at a temperature equal to or higher than the melting point or softening point of the resin. However, when using a resin with a particularly low melt viscosity or when the carbon fiber bundles have a low basis weight, it is also possible to simultaneously supply the carbon fiber bundles and molten resin to opposing heated rolls at a temperature equal to or lower than the melting point or softening point of the resin, and simultaneously cool and solidify the resin during impregnation.

It is possible to peel the molten resin directly from the hot roll, but in this case a certain amount of molten resin remains on the surface of the hot roll, which is likely to cause thermal degradation of the resin. From the viewpoint of material properties and productivity, a method in which the hot roll and cooling roll are connected by a seamless belt, the carbon fiber bundle is impregnated with the resin in the melting zone, and the resin is then solidified in the cooling zone is preferably used. Another method that is preferably used is to insert release paper between the hot roll and the molten resin, and then cool the resin together with the release paper on the cooling roll.

In addition, a method in which molten resin is allowed to flow like a curtain onto the carbon fiber bundle and then squeezed with an impregnation blade to impregnate the bundle with resin can also be suitably used. Compared to methods using seamless belts or release paper, this method has the advantages of reduced capital investment, easy operation management, and being suitable for high speed operation.

The mass parts of carbon fiber relative to the resin part in the carbon fiber resin composite composition of the present invention is 30 parts by mass or more, preferably 45 parts by mass or more, more preferably 60 parts by mass or more, and 200 parts by mass or less, preferably 150 parts by mass or less, more preferably 100 parts by mass or less, relative to 100 parts by mass of the resin part. If the mass parts of carbon fiber relative to 100 parts by mass of the resin part is 200 parts by mass or less, sufficient fluidity can be ensured during molding, and the lower the value of the mass parts of carbon fiber, the better the fluidity. If the mass parts of carbon fiber relative to 100 parts by mass of the resin part is 30 parts by mass or more, the mechanical properties required for structural members can be obtained. The content of carbon fiber in the resin composition can be measured by a method conforming to JIS K7075.

The carbon fiber resin composite prepreg thus obtained can be used alone as a tape-like reinforcing material, or can be laminated and used as a stampable sheet (sheet for compression molding).
Carbon fiber resin composite prepregs usually have a thickness of 50 to 200 μm, and a carbon fiber resin composite sheet can be obtained by laminating multiple sheets of these. When laminating, the fiber axes can be aligned to form a unidirectional material, but the anisotropy of strength and elastic modulus can be controlled by arbitrarily combining the fiber axes.

To obtain a stampable sheet with isotropic mechanical properties, for example, a method can be used in which a prepreg is slit along the fiber axis, then cut to any length, and the resulting micro-pieces are randomly stacked and heated and pressed. In this case, the slitting width is preferably 2 to 50 (mm). More preferably, it is 4 to 30 (mm). If the slitting width is less than 2 (mm), the moldability of the stampable sheet is deteriorated, and the sheet becomes bulky when stacked, resulting in poor productivity. If the slitting width exceeds 50 (mm), the mechanical strength of the stampable sheet varies greatly, which is undesirable.

In order to obtain a stampable sheet with isotropic mechanical properties, it is also preferable to laminate prepregs aligned in one direction, making cuts to cut the carbon fibers as necessary, and laminating them so that the fiber direction divides the plane (360°) equally. For example, laminating with the fiber axis at [0°, 90°] can divide the plane into two. Laminating with the fiber axis at [0°, 60°, 120°] can divide the plane into three. To divide it into four, use [0°, 45°, 90°, 135°], and to divide it into six, use [0°, 30°, 60°, 90°, 120°, 150°].

Generally, the longer the carbon fibers contained in a carbon fiber resin composite, the better the mechanical properties, but the lower the flowability during stamping molding. In order to improve the flowability during stamping molding, it is effective to cut the carbon fibers to a certain length, which makes it possible to obtain a carbon fiber resin composite that can flow into complex three-dimensional shapes such as ribs and bosses. Note that "cuts to cut the carbon fibers" means cuts that are deep enough to cut the carbon fibers and extend in a direction different from the orientation direction of the carbon fibers.

When the carbon fiber resin composite has a cut that cuts the carbon fiber, the length of the cut carbon fiber is not particularly limited, but is usually 5 mm or more, preferably 10 mm or more, more preferably 20 mm or more, and usually 100 mm or less, preferably 50 mm or less, more preferably 40 mm or less. Within the above range, sufficient mechanical properties and flow into thin-walled parts such as ribs during stamping can be achieved at the same time. In the present invention, long fibers refer to those with a number average fiber length of 5 mm or more.

It is preferable to make such cuts in the prepreg before it is made into a laminate. The cuts in the prepreg can be at any angle to the fibers, but from the perspective of the balance between fluidity and mechanical strength, it is preferable to make the cuts at an angle of 30 to 60 degrees to the fiber direction. The cuts can be continuous or discontinuous.

The stampable sheet can be produced, for example, by laminating multiple sheets of the above prepreg and performing hot press molding at a temperature equal to or higher than the melting point of the resin part. After hot pressing, the resin part may be held at a temperature below the melting point for a certain period of time in order to promote crystallization of the resin part. After hot pressing or holding at a temperature below the melting point for a certain period of time, a cold press may be performed at a temperature below the glass transition point of the resin part in order to maintain the shape of the molded body. In addition, pressure may be reduced during hot pressing and cold pressing in order to remove voids in the molded body.

The unidirectional, isotropic, or quasi-isotropic stampable sheets obtained by these methods may be used alone or in combination of one or more types of sheets.
When stampable sheets are laminated, a resin composition layer, a resin-filler composite material layer, a foamed resin layer, or the like may be sandwiched between the sheets.

The mechanical strength of carbon fiber resin composites containing such long fibers can be measured as compressive strength and compressive modulus based on ASTM D6641. For carbon fiber resin composite molded bodies obtained by the manufacturing method of the present invention, in the case of unidirectional materials, the compressive strength is 550 MPa or more, preferably 560 MPa or more, and more preferably 570 MPa or more. The compressive modulus is 72 GPa or more, preferably 76 GPa or more, and more preferably 80 GPa or more.

The present inventors have focused on the heat of crystal fusion of the crystalline resin component in thermal analysis measurements, and have found that when the carbon fiber resin composite material is made, high compressive strength and compressive modulus can be achieved when the value ΔHm/ΔHo of the thermal energy (melting enthalpy) ΔHm absorbed during crystal fusion of the crystalline resin component contained in the resin portion relative to the equilibrium melting enthalpy ΔHo theoretically calculated from the amount of crystalline resin contained is 40% or more, preferably 42% or more, and more preferably 45% or more. If ΔHm/ΔHo is less than 40%, the resin has few crystalline portions, making it impossible to achieve sufficient compressive strength and compressive modulus when made into a carbon fiber resin composite material.

Furthermore, the inventors have improved the compression properties by lowering the recrystallization rate of the crystalline resin. When the recrystallization enthalpy of the crystalline resin contained in the resin portion is ΔHc, it is preferable that the recrystallization rate |ΔHc/ΔHm| is less than 70%, preferably less than 60%, and more preferably less than 55%. When |ΔHc/ΔHm| is less than 70%, it is possible to achieve high compressive strength and elastic modulus when made into a carbon fiber resin composite material.

Specific embodiments of the present invention will be described in detail below with reference to examples, but the present invention is not limited to the embodiments of the examples.
(Example Unidirectional Laminate)
<Ingredients>
<Component (A)>
T: Polycarbonate resin, Mitsubishi Engineering Plastics Co., Ltd., Iupilon H3000
U: Polyester resin, Novaduran 5008, manufactured by Mitsubishi Engineering Plastics
V: Core-shell type graft copolymer, Metablen S2006, manufactured by Mitsubishi Rayon Co., Ltd.
W: Ester exchange inhibitor Adeka STAB AX-71 [octadecyl phosphate] manufactured by Adeka Corporation
X: Antioxidant Phenol-based antioxidant: Adeka STAB AO-50 [octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] manufactured by Adeka Corporation
Y: Phosphorus-based antioxidant: Adeka STAB 2112 [tris(2,4-di-t-butylphenyl)phosphite] manufactured by Adeka Corporation

<Component (B)>
Z: Carbon fiber, Pyrofil TR50S15L AD, manufactured by Mitsubishi Rayon Co., Ltd.

<Manufacturing of Resin Parts>
The resin part was produced by kneading the (T), (U), (V), (W), (X), and (Y) components shown in Table 1 using a co-rotating twin-screw extruder (PCM-30, manufactured by Ikegai Corporation). The extruded strands were cooled in a water tank and granulated (pelletized) using a pelletizer. The (T), (U), (V), (W), (X), and (Y) components were fed to the extruder from the main feeder. The kneading conditions were as follows:
Cylinder temperature C1: 230°C, C2: 250°C, C3 to C8: 270°C
Screw formation: Two kneading zones were installed.
Decompression vent: Installed at C7 Screw rotation speed: 200 rpm
Discharge rate: 15 kg/hr

<Production of long fiber resin composition>
(Production of resin film)
The above-mentioned resin part was supplied to a PMS30-32 single-screw extruder manufactured by IKG Co., Ltd., extruded from a 350 mm wide T-die attached to the extruder, and passed through a sheet cooling and winding device 705-FA082 manufactured by GSI Creos Co., Ltd. to form a resin part film having a thickness of about 40 μm.

(Prepreg Production)
A unidirectionally oriented carbon fiber sheet was prepared by a drum winding method using carbon fibers to adjust the fiber basis weight to 100 g/ ^m2 . Appropriate tension was then applied to the carbon fiber sheet, and the carbon fiber sheet was sandwiched between the resin film, a fluororesin film (manufactured by Nitto Denko Corporation, product name: Nitoflon Film 970-4UL), and an aluminum plate (thickness 10 mm) in that order from both sides of the carbon fiber sheet. The sheet was preheated at 270°C without pressure for 5 minutes on the heating plate of a heating/cooling press, pressure molded at 20 kPa for 5 minutes, and pressure-cooled at 25°C and 30 kPa for 5 minutes on a cooling plate to obtain a resin composition prepreg having a fiber content of about 34 vol% and a thickness of 0.13 mm.

(Manufacturing of unidirectional laminates)
Sixteen prepregs thus obtained were placed in a 100 mm square, 2.0 mm deep ingot mold with the fiber axis direction aligned, and pressure molded on the heating plate of a hot press at 260°C and 20 kPa for 10 minutes. After that, the temperature of the heating plate was set to 100°C and held at 20 kPa for 30 minutes while maintaining the pressure at 20 kPa. Next, the mixture was cooled under pressure at 25°C and 40 kPa for 5 minutes on a cooling plate to obtain a unidirectional resin composition laminate (long fiber resin composition) with a fiber content of about 34 vol% and a thickness of 2 mm.

(Comparative example unidirectional laminate)
Sixteen prepregs obtained in the same manner as in the examples were placed in a 100 mm square, 2.0 mm deep ingot mold with the fiber axis direction aligned, and pressure molded on the heating plate of a hot press at 260°C and 20 kPa for 10 minutes. Next, the prepregs were pressure-cooled on the cooling plate at 25°C and 40 kPa for 5 minutes to obtain a unidirectional resin composition laminate (long fiber resin composition) with a fiber content of about 34 vol% and a thickness of 2 mm.

<Evaluation of the crystalline state in the resin portion of the carbon fiber resin composite composition>
From the carbon fiber resin composite composition obtained above, a sample of about 10 mg was cut out with nippers, and the sample was enclosed in an aluminum open pan and a pan cover. The sample was heated from 0° C. to 250° C. at a rate of 10° C./min in a nitrogen stream using a differential scanning calorimeter ("DSC Q-1000" manufactured by TA Instruments), and the recrystallization heat value ΔHc of the polyester resin and the endothermic heat value ΔHm of crystalline melting observed during the process were measured.

ΔHc was calculated from the area of the exothermic peak observed between 100 and 190° C. during the above measurement, and ΔHm was calculated from the area of the endothermic peak observed between 180 and 250° C. In either case, when multiple peaks were observed, the sum of the multiple peaks was calculated.
The degree of crystallinity of the polyester resin component of the resin part was calculated from the ratio of the theoretical equilibrium fusion enthalpy calculated from the above-mentioned ΔHm and the amount of polyester resin added. That is, the degree of crystallinity χc was calculated by the following formula using the equilibrium fusion enthalpy ΔHo of PBT = 145 J/g.
χc=ΔHm/ΔHo/w×100 (%)

The recrystallization rate of the polyester resin component of the resin portion was calculated from the above-mentioned ΔHc and ΔHm according to the following formula.
Recrystallization rate = ΔHc / ΔHm × 100 (%)
χc: Crystallinity (%) of resin in pellet
w: mass fraction of polyester resin component relative to the entire resin portion; ΔHc: recrystallization heat value of the resin portion (J/g);
ΔHm: melting heat absorption amount of the resin part (J/g)
ΔHo: Theoretical equilibrium fusion enthalpy of polyester resin (J / g)

In addition, since the measurement sample contains carbon fiber,
ΔHc=ΔHcs/wA
ΔHm = ΔHms / wA
ΔHcs: Recrystallization heat value (J/g) of the measurement sample (molded body)
ΔHms: melting endotherm of the measurement sample (molded body) (J/g)
Note that wA is the mass fraction of component (A) in the measurement sample (molded product).

<Evaluation of compression properties in the fiber direction of carbon fiber resin composite composition>
(Preparation of test specimens)
From the obtained flat carbon fiber resin unidirectional laminate, a test piece having a length of 137 mm and a width of 10 mm was cut in a direction parallel to the fiber direction (0°).
(Evaluation of compression test properties)
The cut-out bending test pieces were subjected to a compression test at room temperature with a support distance of 10 mm and a crosshead speed of 1.0 mm/min in accordance with the test method specified in ASTM D6641 to measure strength and elastic modulus. The test machine used was Shimadzu Corporation's "Autograph AG-X 100kN." The average values of the measured values obtained (n=5) were recorded as the compressive strength and the compressive elastic modulus.

Claims (7)

A tape- or sheet-shaped carbon fiber reinforced resin material comprising the following components (A) and (B), wherein the crystalline resin in the component (A) has a crystallinity χc of 40% or more when melted, and a recrystallization rate of less than 70%.
Component (A): A resin composition containing 5 weight percent or more of a polyamide resin, a polyester resin, a polyphenylene sulfide resin, a polyether ether ketone resin, or a polyether ketone ketone resin as a crystalline resin. Component (B): Carbon fiber. <Degree of crystallinity χc and recrystallization rate>
Crystallinity χc=ΔHm/ΔHo/w×100(%)
Recrystallization rate = |ΔHc/ΔHm| × 100 (%)
ΔHm: melting enthalpy of the crystalline resin contained in the component (A); ΔHo: equilibrium melting enthalpy of the crystalline resin contained in the component (A); ΔHc: recrystallization enthalpy of the crystalline resin contained in the component (A); w: mass fraction of the crystalline resin in the component (A); 2. The carbon fiber reinforced resin material according to claim 1, wherein the component (A) contains an acrylic resin, a polycarbonate resin, a polyamideimide resin, a polyethersulfone resin, or a polyetherimide resin as an amorphous resin . 3. The carbon fiber reinforced resin material according to claim 1, wherein the component (A) contains a polycarbonate resin and a polyester resin in a total amount of 80 weight percent or more . 4. The carbon fiber reinforced resin material according to claim 3, wherein the mixed mass ratio of the polycarbonate resin and the polyester resin in the component (A) is PC/PEs, which is 1 or more and 19 or less . A method for producing a carbon fiber reinforced resin material containing the following components (A) and (B), comprising: maintaining the carbon fiber reinforced resin material at a temperature below the melting point of the resin such that the crystallinity χc of the crystalline resin in the component (A) when melted is 40% or more and the recrystallization rate is less than 70%.
Component (A): A resin composition containing an amorphous resin and a crystalline resin, the crystalline resin being 5 weight percent or more of a polyamide resin, a polyester resin, a polyphenylene sulfide resin, a polyether ether ketone resin, or a polyether ketone ketone resin.
(B) Component: Carbon fiber
<Crystallization degree χc and recrystallization rate>
Crystallinity χc=ΔHm/ΔHo/w×100(%)
Recrystallization rate = |ΔHc/ΔHm| × 100 (%)
ΔHm: fusion enthalpy of the crystalline resin contained in component (A)
ΔHo: Equilibrium fusion enthalpy of the crystalline resin contained in component (A)
ΔHc: recrystallization enthalpy of the crystalline resin contained in component (A)
w: mass fraction of the crystalline resin in component (A) The method for producing a carbon fiber reinforced resin material according to claim 5, wherein the carbon fibers have a number average fiber length of 5 mm or more. The method for producing a carbon fiber reinforced resin material according to claim 5 or 6, which is for compression molding.