JP2015074837A - Sizing agent for carbon fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon fiber for molding, a nonwoven fabric and a fabric which can improve composite properties of a composite material suitable for RIM molding and a carbon-fiber-reinforced molding of a thermoplastic resin usable in e.g. automobile parts.SOLUTION: A carbon fiber bundle, a nonwoven fabric and a fabric suitable for RIM molding are treated with a sizing agent of a copolymerized polyamide resin having no moisture or reactive groups which affect a hardening agent, improves adhesiveness to matrix resins when used as a reinforcing material and provides a carbon-fiber-reinforced molding of a polyamide resin usable in e.g. automobile parts.

Description

  The present invention relates to a sizing agent for carbon fiber and a carbon fiber obtained using the sizing agent for carbon fiber. The present invention also relates to a reinforced composite material obtained using the carbon fiber.

  In recent years, composite materials using carbon fibers as reinforcing fibers are light and have excellent mechanical properties such as high strength, and thus are increasingly used as members of aircraft, automobiles and the like. These composite materials are molded, for example, from a prepreg, which is an intermediate product in which a reinforcing fiber is impregnated with a matrix resin, through molding and processing steps such as heating and pressing. However, this method has a problem from the viewpoint of work efficiency and cannot be applied to a thermoplastic resin.

  Conventionally, reaction injection molding (hereinafter referred to as RIM molding) is known as a method for producing fiber reinforced plastic, and a matrix made of polyamide (nylon), epoxy, urethane, etc. with a fiber reinforcing material arranged in a mold. This is a molding method in which an unreacted raw material liquid of a resin is injected, and the reaction is caused to solidify while impregnating the raw material liquid into a fiber reinforcing material in a mold. Polyurethane, polyurea, polyamide, epoxy, unsaturated polyester, dicyclopentadiene, etc. are used as matrix resins in RIM molding. Among them, polyamide RIM (nylon RIM) is molded by an anionic polymerization method of ε-caprolactam. An anion catalyst which is a reaction product with an alkali metal, an alkaline earth metal, a Grineer reagent or the like is used as a catalyst.

  In order that the carbon fiber reinforced thermoplastic resin molding obtained by RIM molding has high mechanical properties and can be obtained efficiently, a woven fabric in which carbon fiber bundles having a large number of filaments are woven at a high density ( It is necessary to obtain a non-woven fabric blended with (cross) or crimped thermoplastic fibers. More importantly, it is important that these cloths and non-woven fabrics do not inhibit curing during the RIM molding process and that the process of removing moisture that affects the curing can be omitted.

  However, a sizing agent is applied to the commercially available carbon fiber bundle and its plain weave cloth during the manufacturing process. The effect of these sizing agents is mainly to prevent troubles during the production process such as improving the bundling property, handling property, and scratch resistance of the carbon fiber bundle. For this reason, most of the sizing agents have reactive groups that cause curing inhibition and cannot be used as reinforcing fiber materials for RIM molding.

  These sizing agents loosely bond the fibers together, keep the fibers difficult to separate from each other, improve the processability, and improve the wettability between the fibers and the matrix resin, and the adhesion at the interface The conflicting effect of improving the quality is required. Carbon fiber sizing agents used as FRP reinforcing fibers include those based on water-soluble epoxy resins and those based on polyamide resins.

  In the sizing agent of the epoxy resin, the epoxy group reacts with the catalyst in the raw material of the polyamide RIM, and the catalyst necessary for the polyamide polymerization is insufficient, resulting in deactivation. For this reason, the curing of the resin is hindered, resulting in poor moldability and physical properties.

  In order to prevent this formability defect and deterioration of physical properties, Patent Document 1 discloses that the epoxy sizing agent for carbon fiber is completely desized or the epoxy group of the sizing agent on the carbon fiber is completely cured to disappear. It has been proposed to reduce the curing failure at the time of RIM molding, but in any case, a fiber-reinforced molded product having the expected physical properties can be obtained due to insufficient adhesion to the matrix resin. There wasn't.

  On the other hand, a polyamide resin sizing agent is suitable for polyamide RIM molding because it does not deactivate the catalyst. However, the sizing-treated carbon fiber has a hard yarn quality and has a drawback that the weaving property is lowered.

  In order to solve this drawback, as proposed in Patent Document 2 and Patent Document 3, a technique of sizing the carbon fiber using a water-soluble polyamide having a polyethylene oxide structure or the like is employed. However, in any case, the water-soluble polyamide has a high saturated water absorption rate, which may cause the curing agent to be deactivated during RIM molding.

Japanese Patent Laid-Open No. 10-286841 Japanese Patent Laid-Open No. 9-3777 JP 2002-88656 A

  In view of the background of such prior art, the present invention provides a carbon fiber sizing agent suitable for RIM molding, and carbon fiber obtained by using the sizing agent, and is reinforced with carbon fiber that can be used for automobile parts and the like. An object of the present invention is to provide a molded product of a thermoplastic resin.

The present invention has been intensively studied on the above-mentioned problem, a sizing agent for carbon fiber that does not cause poor curing during RIM molding, and specific copolymerization as a sizing agent that does not have moisture and reactive groups that are affected by the curing agent during RIM molding. A sizing agent suitable for RIM molding can be obtained by a sizing agent for carbon fiber containing polyamide, and further, adhesion between a cut fiber, a woven fabric, a non-woven fabric, etc. of a carbon fiber bundle treated with the sizing agent and a matric resin Has also been found to be improved.
The present invention includes the following inventions.

(1) Two or more copolymerized polyamides composed of two or more monomer units selected from nylon 6, nylon 66, nylon 11, nylon 12 and nylon 610 dispersed in an aqueous medium, having a melting point A carbon fiber sizing agent comprising the copolyamide having a melting point of 70 to 160 ° C and a wet melting point of 50 to 120 ° C.
(2) Copolymer polyamide is a ternary copolymer polyamide composed of monomer units of nylon 6, nylon 66 and nylon 12, or a quaternary copolymer composed of monomer units of nylon 6, nylon 66, nylon 11 and nylon 12. The sizing agent for carbon fiber according to (1), which is a polymerized polyamide.
(3) The aqueous medium is contained in an amount of 70 to 10,000 parts by weight with respect to 100 parts by weight of the copolymerized polyamide, and the average particle diameter of the copolymerized polyamide resin is 0.1 to 20 μm. Carbon fiber sizing agent.

(4) Carbon fiber to which the sizing agent for carbon fiber according to any one of (1) to (3) is attached.
(5) The carbon fiber according to (4), wherein the adhesion amount of the sizing agent for carbon fiber is 0.3 to 20% by weight with respect to the carbon fiber.
(6) The carbon fiber according to (4) or (5), which is a cut fiber, a nonwoven fabric with a thermoplastic crimped fiber, or an opened woven fabric.

(7) A carbon fiber reinforced composite material obtained by reaction injection molding of the carbon fiber and polyamide resin of any one of (4) to (6).
(8) A method for producing a carbon fiber reinforced composite material comprising a step of mixing the carbon fiber and polyamide resin of any one of (4) to (6) and a step of reaction injection molding the mixture.

  According to the present invention, a sizing agent for carbon fiber suitable for RIM molding can be obtained, and further, a carbon fiber bundle for molding treated with the sizing agent, a nonwoven fabric with thermoplastic crimped fibers, and a well-opened fiber The molded carbon fiber woven fabric (cloth) can be stably provided, and a molded article of a thermoplastic resin reinforced with carbon fibers that can be used for automobile parts or the like can be provided.

[Carbon fiber sizing agent]
The sizing agent for carbon fiber of the present invention is a copolymer of two or more composed of two or more monomer units selected from nylon 6, nylon 66, nylon 11, nylon 12 and nylon 610 dispersed in an aqueous medium. Contains polyamide.

  The copolymerized polyamide contained in the sizing agent for carbon fiber of the present invention is a copolymer of two or more composed of two or more monomer units selected from nylon 6, nylon 66, nylon 11, nylon 12 and nylon 610. Polyamide, for example, a binary copolymer polyamide composed of two types of monomer units, a ternary copolymer polyamide composed of three types of monomer units, and a quaternary copolymer polyamide composed of four types of monomer units Preferably, a terpolymer polyamide comprising nylon 6, nylon 66 and nylon 12 monomer units, a quaternary polyamide comprising nylon 6, nylon 66, nylon 11 and nylon 12 monomer units, nylon 6, A terpolymer copolymer comprising nylon 12 and nylon 610 monomer units. Nylon 6 and Nylon 11 monomer units, and Nylon 6 and Nylon 12 monomer units, especially Nylon 6, Nylon 66 and Nylon 12 monomer units. Terpolymer copolymer polyamide and quaternary copolymer polyamide composed of monomer units of nylon 6, nylon 66, nylon 11 and nylon 12.

  The copolymer polyamide contained in the sizing agent for carbon fiber of the present invention preferably has a melting point of 70 to 160 ° C, more preferably 100 to 155 ° C, and particularly preferably 120 to 150 ° C. The copolymerized polyamide can be adjusted to have a target melting point by changing the composition ratio of the copolymerization components.

  Usually, in order to increase the bonding strength, it is desirable to increase the processing temperature when bonding, but due to the heat treatment during bonding processing, the material to be bonded undergoes a thermal history, causing deterioration and performance degradation. . For this reason, it is desirable that the melting point of the polymer serving as the adhesive component is low.

  Therefore, the melting point of the copolyamide of the sizing agent for carbon fiber of the present invention is 160 ° C. or less. Thereby, the heat processing temperature at the time of an adhesive process can be made low, and the quality change and performance fall of a to-be-adhered material can be reduced to the minimum. Further, from the viewpoint of energy consumption and cost, it is preferable that the heat treatment temperature during the bonding process is low.

  On the other hand, when the melting point of the copolymerized polyamide is less than 70 ° C., when it becomes a hot and humid environment during storage or transportation, the yarns of the carbon fiber yarns are fused with each other, resulting in poor unwinding and deterioration of the yarn quality. There is a fear. In addition, it is not preferable to heat-treat the material to be bonded that has been subjected to bonding processing because durability such as peeling becomes poor.

  The melting point of the copolyamide of the sizing agent for carbon fiber of the present invention is a differential scanning calorimeter Thermo plus DSC8230L manufactured by Rigaku Corporation in accordance with the method described in JIS-K7121, and the heating rate is 10 ° C. Measured at / min.

  It is known that curing is inhibited by an epoxy group of an epoxy sizing agent used as a carbon fiber sizing agent as a cause of inhibiting curing in the RIM molding process. Furthermore, it is known that it is greatly affected by moisture, and for this purpose, it is essential that the sizing agent used has a low saturated water absorption.

  For example, when a water-soluble polyamide having a polyethylene oxide structure is used, its high water-saturation rate makes it highly water-soluble and easy to use and process. As a result, the amount of water contained at the time of RIM molding increases and the curing agent at the time of RIM molding is deactivated.

  As a result, it has been found that it is preferable to use a copolymerized polyamide resin having a low saturated water absorption rate that does not cause curing inhibition in the RIM molding process as a sizing agent for carbon fibers.

  The melting point of the copolymerized polyamide of the present invention when wet is preferably 50 to 120 ° C, more preferably 65 to 110 ° C, and particularly preferably 68 to 106 ° C. When the melting point when wet is within this range, the copolymerized polyamide can be easily dispersed in an aqueous medium.

  When the copolymerized polyamide of the present invention is dispersed in an aqueous medium, a saturated water-absorbing body is formed at a temperature equal to or higher than the melting point of the copolymerized polyamide. Therefore, it is preferable that the copolymerized polyamide has a low melting point in the range of 70 to 160 ° C. However, the lower melting point of the copolyamide is advantageous. However, when the melting point is less than 70 ° C., when the carbon fiber is treated with a sizing agent, the carbon fiber yarns are not separated from each other during storage or transportation of the carbon fiber. There is a risk of causing fusing and poor unwinding or deterioration of yarn quality. On the other hand, when the melting point is higher than 160 ° C., the copolyamide may be deteriorated.

  Further, since the copolyamide is dispersed in an aqueous medium under heating and moist heat conditions, the copolyamide can be easily dispersed when the melting point when wet is low, and the melting point when wet is 120 ° C. or less. Preferably there is. If the melting point when wet is lower than 50 ° C., the copolymerized polyamide is softened in the aqueous medium, and the dispersion in which the copolymerized polyamide is dispersed in the aqueous medium becomes unstable.

  The melting point of the copolymerized polyamide of the present invention when wet is measured by the following method. A clip-shaped load having a fineness of 1/30 g is attached to the tip of the fibrous copolymer polyamide of the present invention (length 30 cm), and the load of the fibrous copolymer polyamide is attached to a water bath at a water temperature of 20 ° C. Suspended and suspended for 20 cm in length. Next, the water temperature is raised at 12 ° C./min, the fibrous copolymer polyamide is melted, and the water temperature at the time when the load is dropped is taken as the melting point when wet.

  The aqueous medium used for dispersing the copolymerized polyamide of the present invention is preferably water, and various waters such as tap water, industrial water, ion exchange water, deionized water, and pure water can be used. Deionized water and pure water are particularly preferable. In addition, a pH adjuster, a viscosity adjuster, an antifungal agent and the like may be appropriately added to the water as needed within a range that does not impair the object of the present invention.

  In the sizing agent for carbon fiber of the present invention, the amount of water used for dispersing the copolymerized polyamide of the present invention is usually 70 to 10,000 parts by weight, preferably 90 to 100 parts by weight based on 100 parts by weight of the copolymerized polyamide. 10,000 parts by weight. If the amount of water used is less than 70 parts by weight, the copolymerized polyamide may not be sufficiently dispersed in water, and the concentration of the aqueous copolymerized polyamide dispersion obtained even when used in excess of 10,000 parts by weight. It becomes thin and is not preferable in use.

  In the carbon fiber sizing agent of the present invention, the average particle diameter of the copolymerized polyamide particles dispersed in the aqueous medium is adjusted to 0.1 to 20 μm, more preferably 0.1 to 10 μm. If the average particle size of the copolymerized polyamide resin in the aqueous copolymerized polyamide dispersion is less than 0.1 μm, the particles are likely to agglomerate and gel easily, making it difficult to achieve a high resin concentration. If the average particle size of the copolymerized polyamide resin in the aqueous copolymerized polyamide dispersion exceeds 20 μm, a problem arises in the uniformity of the coating layer and the adhesive strength of the sizing agent is reduced. In the present invention, the average particle size is determined by a laser diffraction particle size distribution measurement method.

  The carbon fiber sizing agent of the present invention can be obtained, for example, by producing an aqueous dispersion of a copolymerized polyamide by dispersing the copolymerized polyamide in an aqueous medium.

  The method for dispersing the copolymerized polyamide in the aqueous medium is not particularly limited, and examples thereof include a method of stirring with a stirrer equipped with a stirring blade and applying a shear force and a method of melt-kneading using a twin screw extruder. Can do.

  In the above production method, the terminal carboxyl group of the copolymerized polyamide resin is treated with a basic substance, and the mixture is stirred at a temperature equal to or higher than the softening point of the copolymerized polyamide in an aqueous dispersion containing a surfactant or a dispersant as necessary. When a shearing force is applied and dispersed, a stable aqueous dispersion can be obtained.

  Examples of the basic substance include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, ammonia, and amine compounds. In particular, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide are preferably used in terms of dispersion effect.

  Examples of the surfactant include anionic surfactants such as rosinate, fatty acid salt and alkylbenzene sulfonate, ethylene oxide propylene oxide block copolymer, polyoxyethylene alkyl ether, glycerin fatty acid ester and polyoxyethylene fatty acid ethanolamide. And nonionic surfactants such as amphoteric surfactants.

  Examples of the dispersant include polyacrylates, polystyrene sulfonates, salts of styrene maleic anhydride copolymers, polymer dispersants such as polyvinyl alcohol and hydroxyethyl cellulose, and inorganic dispersants such as alumina sol, silica sol, and calcium phosphate. Can be mentioned.

[Carbon fiber with sizing agent attached]
The present invention also includes a carbon fiber to which the carbon fiber sizing agent is attached.
In the present invention, “carbon fiber” includes both individual carbon fibers and carbon fiber bundles that are aggregates thereof.

  It does not specifically limit as carbon fiber to be used, A well-known carbon fiber can be used. For example, the type is not particularly limited as long as it is fibrous, such as polyacrylonitrile-based carbon fiber, rayon-based carbon fiber, lignin-based carbon fiber, pitch-based carbon fiber, vapor-grown carbon fiber, and carbon nanotube. Polyacrylonitrile-based carbon fiber is preferably used in that it can realize an inexpensive cost and a carbon fiber reinforced composite material obtained from carbon fiber has good mechanical properties.

  The carbon fiber to which the sizing agent for carbon fiber of the present invention is attached is obtained by treating the carbon fiber with the sizing agent for carbon fiber and drying it.

  The sizing treatment is not particularly limited as long as it is a known sizing treatment performed using a carbon fiber sizing agent that is an aqueous dispersion, but for example, a normal method such as a dip method, a spray method or a roller method is used as the sizing agent. The method of sizing the carbon fiber can be mentioned. Although it does not specifically limit as a drying method, For example, the method of using heat media, such as a hot air, a hot plate, a roller, an infrared heater, can be selected.

  If the carbon fiber sized with the carbon fiber sizing agent of the present invention is woven while applying heat, the carbon fiber bundle can be processed relatively easily by fiber opening. Increasing the value may cause problems in terms of processing. Since the carbon fiber used in RIM molding is brittle, it is necessary to further improve the convergence and handle it as a bundle.

  Therefore, when using a carbon fiber bundle having a large number of filaments and giving priority to spreadability (expandability) and weaving, the amount of sizing agent is preferably 2% by weight or less, more preferably 1% by weight. Need to lower. On the other hand, when the amount of the sizing agent on the carbon fiber is small, the adhesion between the fibers is loose, the fibers are easily separated from each other, fluff and the like are easily generated, and a problem occurs in the processing process. Furthermore, the effect of improving the wettability between the fiber and the matrix resin and improving the adhesion at the interface cannot be exhibited.

  Therefore, in the present invention, the sizing treatment is preferably performed by a method of continuously sizing a non-woven fabric of carbon fibers and thermoplastic crimped fibers or a plain fabric of carbon fibers, possibly through a desizing step. .

  In this method, a carbon fiber and a thermoplastic crimped fiber nonwoven fabric or a carbon fiber plain fabric is immersed in a sizing bath, a sizing agent is attached by roll coating, and a nip roller pressure is adjusted by a movable mangle or the like. The predetermined sizing agent can be uniformly attached by controlling the amount of the sizing agent attached and continuously drying and winding.

  The adhesion amount of the carbon fiber sizing agent (excluding an aqueous medium) of the present invention is not particularly limited with respect to the carbon fiber before the treatment, but is preferably 20 wt% to 0.3 wt%, and more preferably 10 wt%. % By weight to 0.5% by weight. When the adhesion amount of the sizing agent is 20% by weight or less, the physical properties of the copolymerized polyamide itself do not affect the physical properties of the molded product. When the adhesion amount of the sizing agent is 0.3% by weight or more, sufficient bundling property can be imparted to the carbon fiber.

  The sizing agent for carbon fiber of the present invention is preferably used alone, and the sizing agent is sized by a usual method such as a dip method, a spray method or a roller method. The sized carbon fiber is dried at 100 ° C. or more and 250 ° C. or less. The adhesion rate of the copolymerized polyamide resin at this time is preferably controlled in the range of 20% by weight to 0.3% by weight in view of the hardness of the carbon fiber and the problem of deactivating the curing agent during RIM curing.

  The carbon fiber of the present invention is preferably a carbon fiber bundle having a large number of filaments in order to enhance the properties of the molded product obtained by RIM molding, specifically preferably 15,000 or more, more preferably Should have a filament count of 45,000 or more. The upper limit of the number of filaments is preferably at most 100,000, more preferably 70,000 or less, but is selected from the viewpoint of spreadability.

  The molding carbon fiber bundle of the present invention can be molded by, for example, converting the molding carbon fiber bundle into a cut fiber, mixing it with a molding resin, and putting it into a mold, regardless of the RIM molding. You can also. In such a case, a cut fiber of 3 to 20 mm is preferably used.

  In addition, the carbon fiber bundle of the present invention may contain a small amount of other fiber types as long as the object of the invention is not impaired. Examples of other fiber types include high-strength and high-modulus fibers such as glass fiber, aramid fiber, alumina fiber, silicon carbide fiber, boron fiber, and metal fiber, and one or more of these may be contained.

[Carbon fiber reinforced composite]
The present invention also relates to a carbon fiber reinforced composite material obtained by reaction injection molding of a carbon fiber (including a carbon fiber bundle) treated with the carbon fiber sizing agent of the present invention and a matrix resin. The present invention particularly relates to a carbon fiber reinforced composite material obtained by reaction injection molding of carbon fiber and polyamide resin treated with the above-described sizing agent for carbon fiber of the present invention. When the carbon fiber treated with the sizing agent for carbon fiber of the present invention and the polyamide resin as the matrix resin are subjected to reaction injection molding, the sizing agent reacts with the catalyst in the RIM raw material to prevent the resin from being hardened, thereby reinforcing the carbon fiber. Composite materials can be manufactured.

  In the present invention, a thermosetting resin and a thermoplastic resin can be selected as the matrix resin. A thermoplastic resin capable of press molding or injection molding with high mechanical properties and high molding efficiency of the obtained carbon fiber reinforced composite material is preferable.

  Thermoplastic resins include polyester (eg, polyethylene terephthalate, polybutylene terephthalate, etc.), polyolefin (eg, polyethylene, polypropylene, polybutylene, etc.), styrenic resin, polyoxymethylene, polyamide, polycarbonate, polymethylene methacrylate, polyvinyl chloride. , Polyphenylene sulfide, polyphenylene ether, polyimide, polyamideimide, polyetherimide, polysulfone, polyethersulfone, polyketone, polyetherketone, polyetheretherketone, polyarylate, polyethernitrile, phenolphenoxy resin, fluorine resin, etc. Furthermore, polystyrene, polyolefin, polyurethane, saturated polyester, polyamide, poly Tajien system, polyisoprene, thermoplastic elastomers and fluorine-containing resins and the like are also mentioned, but preferably, a polyamide resin which can be mechanical properties obtain good carbon fiber reinforced composite material is used. Also, these copolymers, modified products, and blends of two or more of these can be used as the thermoplastic resin. Here, the modified body means a derivative obtained by substituting a reactive functional group such as a carboxyl group in the molecular structure, or a derivative obtained by adding a diol such as an oxyethylene group in the molecular structure. Say.

  The carbon fiber reinforced composite material of the present invention is obtained by, for example, mixing carbon fiber (including a carbon fiber bundle) treated with the sizing agent for carbon fiber of the present invention and a matrix resin, and injection-molding the mixture in a mold. Can be obtained. The mixing ratio is not particularly limited. For example, the carbon fiber treated with the sizing agent for carbon fiber of the present invention is preferably 2.5 to 1000 parts by weight, more preferably 5 to 300 parts by weight with respect to 100 parts by weight of the matrix resin. Amount. For mixing the carbon fiber sizing agent and the matrix resin of the present invention, a known method capable of uniformly mixing them can be used. For example, a single screw extruder, a twin screw extruder, a press machine, a high speed mixer, an injection molding machine. Using a known apparatus such as a pultrusion machine, it can be carried out according to a conventional method. The mixture can be obtained in various forms such as a powdery mixture of matrix resin and carbon fiber, and a granulated product made of this mixture, depending on its composition, blending method, and the like. Other known additives may be used in combination with the mixture as necessary. Specific examples of the additive include an antioxidant, a heat stabilizer, a weathering agent, a release agent and a lubricant, a pigment, a dye, a plasticizer, an antistatic agent, a flame retardant, and a reinforcing material.

  The carbon fiber sizing agent of the present invention is a carbon fiber reinforced composite having good mechanical properties such as bending strength and bending elastic modulus without causing inhibition of resin curing in reaction injection molding using a polyamide resin as a matrix resin. Chemical materials can be provided.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not particularly limited to the examples.

(Copolymer polyamide sizing agent for carbon fiber)
Example 1
A terpolymerized polyamide resin composed of nylon 6, nylon 66, and nylon 12 monomer units in a pressure-resistant autoclave with a jacket having a diameter of 350 mm, an inner diameter of 1500 mm, a height of 1500 mm, and an internal volume of 450 L, equipped with a turbine-type stirring blade having a diameter of 350 mm. 150 kg (manufactured by Arkema, trade name: H005FA, melting point: about 120 ° C., melting point: 72 ° C. when wet) 150 kg, water 149.6 kg and sodium hydroxide 0.4 kg were charged and sealed. Next, the inside of the autoclave was heated up to around 150 ° C. while starting the stirrer and stirring at 150 rpm. The mixture was further stirred for 30 minutes while maintaining the internal temperature at 140 to 150 ° C., and then the contents were cooled to 50 ° C. to obtain an aqueous dispersion (copolymer sizing agent) of a copolymerized polyamide resin having a resin concentration of 50% by weight. It was.
When the median diameter of the sizing agent for carbon fiber of the obtained copolymerized polyamide resin was measured with a laser diffraction particle size distribution analyzer (LA-910, manufactured by Horiba, Ltd.), the median diameter was 1.6 μm.

Example 2
A quaternary copolymerized polyamide (manufactured by Arkema, trade name M2468, melting point) composed of monomer units of nylon 6, nylon 66, nylon 11 and nylon 12 from the upstream side of a twin-screw extruder (S-4KRC manufactured by Kurimoto Iron Works) 40 kg of a melting point of 105 ° C. and a melting point of 68 ° C. when wet) was charged and melt-kneaded at a cylinder temperature of 140 ° C. and a rotation speed of 450 rpm. After melt-kneading, 16 kg of a 0.9 wt% sodium hydroxide aqueous solution was supplied from the supply port.

  After changing the setting conditions at a cylinder temperature of 100 ° C. and a rotational speed of 450 rpm, 44 kg of pure water was gradually added from the supply port of the twin-screw extruder and kneaded, and then passed through the die part (die temperature of 100 ° C.) The product was discharged from a twin screw extruder. The switching valve was opened, and 1 L of the polyamide resin aqueous dispersion was charged into a 2 L stirring tank equipped with a propeller type stirrer. The liquid temperature immediately after charging was measured with a temperature sensor and found to be 95 ° C. Next, cooling was continued until the liquid temperature reached 35 ° C. while stirring. As soon as the temperature reached 35 ° C., the stirring was stopped and the mixture was allowed to cool to room temperature (25 ° C.) to obtain an aqueous polyamide resin dispersion (carbon fiber sizing agent) (effective concentration 40%) having a median diameter of 1.2 μm.

Example 3
Nylon 6, nylon 66, and nylon 12 terpolymer polyamide resin (manufactured by Arkema, trade name H005FA, melting point approximately 120 ° C., wet melting point 72 ° C.) is replaced with nylon 6, nylon 12 and nylon Resin in the same manner as in Example 1 except that it was changed to ternary copolymerized polyamide composed of 610 monomer units (Daicel Eponic, trade name: Diamide, melting point: about 130 ° C., wet melting point: 90 ° C.) An aqueous copolymer polyamide resin dispersion (carbon fiber sizing agent) having a concentration of 50% by weight was obtained.

Example 4
Nylon 6, nylon 66, and nylon 12 terpolymer polyamide resin (manufactured by Arkema, trade name H005FA, melting point approximately 120 ° C., wet melting point 72 ° C.) is a monomer of nylon 6 and nylon 11 A resin concentration of 50% by weight was obtained in the same manner as in Example 1 except that the unit was changed to a binary copolymer polyamide (manufactured by Arkema, trade name: M995, melting point: about 150 ° C., wet melting point: 106 ° C.). An aqueous copolymerized polyamide resin dispersion (carbon fiber sizing agent) was obtained.

Example 5
A terpolymer polyamide resin (manufactured by Arkema, trade name: H005FA, melting point: about 120 ° C., melting point when wet: 72 ° C.) composed of monomer units of nylon 6, nylon 66 and nylon 12 is a monomer of nylon 6 and nylon 12 A resin concentration of 50% by weight was obtained in the same manner as in Example 1 except that the copolymer was changed to a binary copolymer polyamide (manufactured by Arkema, trade name: M1186, melting point: approximately 140 ° C., wet melting point: 93 ° C.). An aqueous copolymerized polyamide resin dispersion (carbon fiber sizing agent) was obtained.

Comparative Example 1
Nylon 6, Nylon 66, Nylon 11, Nylon 12, and Nylon 610, an aqueous dispersion of nylon alone, all have a melting point of 170 ° C. or more as a simple nylon, so stable aqueous dispersions as in Examples 1-5 Could not get.

Comparative Example 2
Since the melting point of nylon 6 / nylon 66 = 60/40, which is the lowest in the binary copolymer polyamide composed of nylon 6 and nylon 66 monomer units, is 180 ° C., the stability as in Examples 1-5 An aqueous dispersion could not be obtained.

(Manufacture of carbon fiber bundles)
[Measurement of sizing agent adhesion]
About 2 g of carbon fiber bundles were dried at 105 ° C. for 30 minutes, then cooled to room temperature in a desiccator for 30 minutes and weighed (W1). Thereafter, the carbon fiber bundle was immersed in acetone to wash away the sizing agent. The washed sample was dried at 105 ° C. for 1 hour, cooled to room temperature in a desiccator for 30 minutes, and weighed (W2). And the sizing agent adhesion amount was calculated | required from following Formula.
Sizing agent adhesion amount (% by weight) = [W1 (g) −W2 (g)] / [W2 (g)] × 100

[Measurement of saturated water absorption of sizing agent]
According to JIS K 7209 A method, after drying the sizing agent at 120 ° C. for 24 hours, about 10 g of the dried resin is precisely weighed (weight A), and then the weighed dry resin is placed in water kept at 23 ± 2 ° C. After 24 ± 1 hour, the dried resin was taken out of the water, and the weight increase (weight B) of the resin at that time was precisely weighed and calculated by the following formula.
Saturated water absorption (%) = 100 × weight B / weight A

[RIM polymerization evaluation]
Test tube A
Under a nitrogen atmosphere, ε-caprolactam (15 g) and dicyclohexylcarbodiimide (0.55 g) were placed in a test tube, and 3 g of the carbon fiber bundle obtained in the examples or comparative examples was further added.
Test tube B
Under a nitrogen atmosphere, ε-caprolactam (15 g) and sodium hydride (0.07 g) were added to another test tube.

  Test tube A and test tube B were heated in an oil bath at 200 ° C. for 20 minutes to melt ε-caprolactam, the contents of test tube A and test tube B were mixed, and a polymerization reaction was performed at 150 ° C. Determination of polymerization reaction inhibition evaluated how much hardening time became long with respect to the hardening time in the system which added the carbon fiber bundle which has not coat | covered anything.

[RIM polymerization evaluation criteria]
For the curing time when using a carbon fiber bundle that does not give anything,
○: Cured with a curing time of less than 1.1 times Δ: Cured with a curing time of 1.1 to 1.5 times ×: Cured with a curing time of 1.5 times or more.

[Measurement of bending strength and bending elastic force of fiber reinforced moldings]
Measurement was performed according to JIS-7171.

Example 6
A PAN (polyacrylonitrile) -based carbon fiber yarn (Toray Industries, Inc .: Torayca T700SC) having a fiber diameter of 7 μm and the number of constituting fibers of 24,000 is continuously run on the yarn, and the second desizing step, second The sizing process of the process and the drying process of the third process were performed. First, the carbon fiber yarn is immersed in an acetone bath equipped with a stirrer as a desizing bath, further immersed in a ceramic guide in an acetone bath equipped with a stirrer, and then ceramic in a water tank filled with ion-exchanged water. The guide was immersed, and excess water was removed by a roller press to obtain a desized carbon fiber bundle. The obtained carbon fiber bundle is subjected to sizing treatment by adding ion-exchanged water to the sizing agent for copolymerized polyamide carbon fiber obtained in Example 1 and immersing it in a sizing agent water dispersion bath having an effective concentration of 4% by weight. The sizing agent adhesion amount on the carbon fiber was adjusted to a predetermined amount with a nip roller. Subsequently, secondary drying was performed by pressing and contacting a drying roller heated to 120 ° C. for 150 seconds and then blowing air heated to 180 ° C. for 100 seconds. The amount of the sizing agent deposited on the obtained carbon fiber bundle was 1% by weight.

Examples 7 and 8
Examples 7 and 8 were the same as Example 6 except that the effective concentration of the sizing agent for copolymerized polyamide carbon fiber was changed so that the amount of the sizing agent deposited on the carbon fiber was 2% by weight and 3% by weight, respectively. I went.

Example 9
As in Example 6, except that the sizing agent of Example 2 was used as the sizing agent for copolymerized polyamide carbon fiber, and the effective concentration of the sizing agent was changed to make the amount of sizing agent deposited on the carbon fiber 10% by weight. I went.

Example 10
As in Example 6, except that the sizing agent of Example 3 was used as a sizing agent for copolymerized polyamide carbon fiber, and the effective concentration of the sizing agent was changed so that the amount of the sizing agent deposited on the carbon fiber was 5% by weight. I went.

Example 11
As in Example 6, except that the sizing agent of Example 4 was used as a sizing agent for copolymerized polyamide carbon fibers, and the effective concentration of the sizing agent was changed so that the adhesion amount of the sizing agent on the carbon fiber was 5% by weight. I went.

Example 12
As in Example 6, except that the sizing agent of Example 5 was used as a sizing agent for copolymerized polyamide carbon fibers, and the effective amount of the sizing agent was changed to make the amount of sizing agent deposited on the carbon fiber 5% by weight. I went.

Example 13
To a sizing agent for copolymerized polyamide carbon fiber obtained in Example 1, a PAN-based carbon fiber yarn having a fiber diameter of 7 μm and constituting fibers of 24,000 (Toray Industries, Inc .: Torayca T700SC) was added to ionizing water. Then, a sizing agent water dispersion bath having an effective concentration of 4% by weight was roll-immersed and subjected to sizing treatment, and the amount of adhesion of the top coat sizing agent on the carbon fiber was controlled to a predetermined amount by a nip roller. Subsequently, secondary drying was performed by pressing and contacting a drying roller heated to 120 ° C. for 150 seconds and then blowing air heated to 180 ° C. for 100 seconds. The amount of sizing agent attached to the obtained carbon fiber bundle was 1% by weight.

Examples 14 and 15
Examples 14 and 15 are the same as Example 13 except that the effective concentration of the sizing agent for the copolymerized polyamide carbon fiber to be overcoated was changed so that the adhesion amount of the sizing agent on the carbon fiber was 2% by weight and 3% by weight, respectively. The same was done.

Comparative Example 3
In Comparative Example 3, a PAN-based carbon fiber yarn (Toray Industries, Inc .: TORAYCA T700SC-24000) was subjected to RIM polymerization evaluation without any treatment.

Comparative Example 4
In Comparative Example 4, the evaluation was performed using a polyether block amide copolymer (Pebax MV1074 manufactured by Arkema) (R-1) as a sizing agent.

Comparative Example 5
In Comparative Example 5, the evaluation was performed using a polyether block amide copolymer (Pebax MV3000 manufactured by Arkema) (R-2) as a sizing agent.

  RIM polymerization evaluation was implemented using the carbon fiber obtained in Examples 6-15 and Comparative Examples 3-5. The results are summarized in Table 1. Here, the adhesion amount of the sizing agent in Examples 13 to 15 indicates the adhesion amount of the overcoated sizing agent. In addition, the nominal value was employ | adopted for the adhesion amount of the sizing agent of the comparative example 3. FIG.

  As is apparent from Table 1, it was revealed that the carbon fiber bundles sized with the sizing agent of Examples 1 to 5 of the present invention did not cause curing inhibition in RIM molding using ε-caprolactam. Furthermore, from the results of Examples 13 to 15, it was shown that it is effective to resize the carbon fiber bundle and then perform resizing.

[Manufacture of carbon fiber nonwoven fabric]
Example 16
70% by weight of 50 mm chopped fiber of carbon fiber obtained by resizing the carbon fiber (Toray Industries, Ltd., TORAYCA T700SC-24000, adhesion amount of epoxy resin sizing agent: 1.0 to 1.2% by weight) Nylon 6 short fiber (manufactured by Toray Industries Inc., single fiber fineness 1.7 dtex, cut length 51 mm, number of crimps 12/25 mm, crimp rate 15%) blended with 30% by weight of OPNER, roller card, cross layer Copolymer polyamide resin obtained in Example 1 using a nonwoven fabric (width 110 cm, length 30 m, basis weight 250 g / m ² ) having a good balance of vertical and horizontal strength obtained through each process of roller carding and needle punching Ion exchange water is added to the sizing agent and immersed in a sizing bath of a sizing agent aqueous dispersion adjusted to an effective concentration of 3% by weight. After coating, adjust the amount of sizing agent by adjusting the pressure (squeezing) of the nip roller of the mangle, and continuously drying at 120 ° C for 200 seconds with a hot air dryer while adjusting the width with a pin type tender. Went and rolled up. The amount of the sizing agent deposited on the obtained nonwoven fabric was 1% by weight.

Examples 17 and 18
Examples 17 and 18 were carried out in the same manner as Example 16 except that the effective amount of the sizing agent was changed so that the amount of the sizing agent deposited on the carbon fiber was 5% by weight and 10% by weight, respectively.

Example 19
As in Example 16, except that the sizing agent of Example 2 was used as a sizing agent for copolymerized polyamide carbon fiber, and the effective amount of the sizing agent was changed so that the amount of sizing agent deposited on the carbon fiber was 3% by weight. I went.

Example 20
As in Example 16, except that the sizing agent of Example 3 was used as the sizing agent for copolymerized polyamide carbon fiber, and the effective concentration of the sizing agent was changed so that the adhesion amount of the sizing agent on the carbon fiber was 15% by weight. I went.

Example 21
As in Example 16, except that the sizing agent of Example 4 was used as a sizing agent for copolymerized polyamide carbon fiber, and the effective concentration of the sizing agent was changed so that the adhesion amount of the sizing agent on the carbon fiber was 5% by weight. I went.

Example 22
As in Example 16, except that the sizing agent of Example 5 was used as a sizing agent for copolymerized polyamide carbon fiber, and the effective concentration of the sizing agent was changed so that the adhesion amount of the sizing agent on the carbon fiber was 5% by weight. I went.
The physical properties of these carbon fiber nonwoven fabrics are summarized in Table 2.

[Manufacture of carbon fiber reinforced composites using nylon RIM]
After the mold was heated to a predetermined temperature, the inside of the mold was reduced from atmospheric pressure to -90 kPa by a vacuum pump. Next, the raw material A (ε-caprolactam + dicyclohexylcarbodiimide) and the raw material B (ε-caprolactam + sodium hydride) were heated to 110 ° C. and melted with a dryer. After melting, raw material A and raw material B are quickly mixed to form a monomer melt, and eight layers of 160 × 160 mm carbon fiber nonwoven fabric obtained in Example 16 are placed in a mold and heated to 160 ° C. The mold was poured into the mold and molded. The physical properties of these molded products are summarized in Table 2.

  Comparative Example 6 is a carbon fiber 50 mm chopped fiber obtained by sizing treatment of carbon fiber (Toray Industries, Ltd., TORAYCA T700SC-24000, adhesion amount of epoxy resin sizing agent: 1.0 to 1.2% by weight). 70% by weight of nylon and 30% by weight of nylon 6 short fiber (manufactured by Toray Industries Inc., single fiber fineness 1.7 dtex, cut length 51 mm, number of crimps 12/25 mm, crimp rate 15%) The evaluation was performed using a nonwoven fabric having an excellent balance of vertical and horizontal strength obtained through each process of roller card, cross layer, roller card and needle punching.

  In Comparative Example 7, similar RIM molding was performed using a nonwoven fabric obtained from chopped fibers of nylon fibers and carbon fibers (Toray Industries, Inc., TORAYCA T700SC-24000) treated with an epoxy resin sizing agent. However, a good molded product could not be obtained due to inhibition of curing.

  Comparative Example 8 using a sizing agent (R-1) of a polyether block amide copolymer (Pebax MV1074 manufactured by Arkema) and a sizing agent (R) of a polyether block amide copolymer (Pebax MV3000 manufactured by Arkema) RIM molding was performed in the same manner for Comparative Example 9 using -2), but a good molded product could not be obtained due to curing inhibition by moisture.

  Table 2 shows that non-woven fabrics obtained from sized carbon fibers can provide molded articles having better physical properties than non-woven fabrics obtained from non-sized carbon fibers. Furthermore, from the results of Examples 16 to 22 and Comparative Examples 8 and 9, the non-woven fabric sized with the sizing agent of Examples 1 to 5 was compared with the non-woven fabric sized with the epoxy sizing agent and water-soluble polyamide. Also good results.

[Manufacture of carbon fiber plain fabric (cloth)]
Example 23
Carbon fiber plain woven fabric (toho Tenax Co., Ltd .: W3101) desized with an acetone solvent is added to the copolymerized polyamide resin sizing agent obtained in Example 1 to an effective concentration of 5% by weight. Immerse the adjusted sizing agent water dispersion in a sizing bath, perform roller coating, and then adjust the amount of sizing agent applied by adjusting the pressure of the nip roller of the mangle while adjusting the width of the pin type tender. The film was continuously wound at 120 ° C. for 200 seconds with a hot air drier. The amount of the sizing agent deposited on the obtained nonwoven fabric was 1% by weight.

  Examples 24 and 25 were carried out in the same manner as in Example 23, except that the effective concentration of the sizing agent was changed to change the adhesion amount of the sizing agent of the carbon fiber nonwoven fabric to 5% by weight and 10% by weight, respectively. These physical properties are summarized in Table 3.

  Examples 26 to 29 were carried out in the same manner as in Example 24 except that the sizing agent was changed from that of Example 1 to that of Examples 2 to 5, respectively. These physical properties are summarized in Table 3.

[Manufacture of carbon fiber reinforced composites using nylon RIM]
After the mold was heated to a predetermined temperature, the inside of the mold was reduced from atmospheric pressure to -90 kPa by a vacuum pump. Next, the raw material A (ε-caprolactam + dicyclohexylcarbodiimide) and the raw material B (ε-caprolactam + sodium hydride) were heated to 110 ° C. and melted with a dryer. After melting, raw material A and raw material B are quickly mixed to form a monomer melt, and eight layers of 160 × 160 mm carbon fiber cloth obtained in Example 23 are placed in a mold and heated to 160 ° C. The mold was poured into the mold and molded. The physical properties of these molded products are summarized in Table 3.

  Comparative Example 10 was evaluated by using a desiccated carbon fiber plain fabric (Toho Tenax Co., Ltd .: W3101) as a reinforcing fiber fabric without resizing.

  Comparative Example 11 was evaluated using a carbon fiber plain fabric (manufactured by Toho Tenax Co., Ltd .: W3101) without any treatment.

  In Comparative Examples 12 and 13, the sizing agent was changed from the sizing agent of Example 1 to the polyether block amide copolymer (Pebax MV1074 manufactured by Arkema Co., Ltd.) and the polyether block amide copolymer (R-1). The same procedure as in Example 24 was performed except that the sizing agent (R-2) of Pevacs MV3000 manufactured by Arkema was used.

  Table 3 shows that a well-opened plain fabric sized with a copolymerized polyamide can provide a molded product with good physical properties without causing poor curing during RIM molding.

Claims (8)

  Two or more copolymerized polyamides composed of two or more monomer units selected from nylon 6, nylon 66, nylon 11, nylon 12 and nylon 610 dispersed in an aqueous medium, having a melting point of 70 to 160 A sizing agent for carbon fiber comprising the copolymerized polyamide having a melting point of 50 to 120 ° C when wetted.   The copolymerized polyamide is a ternary copolymer polyamide composed of monomer units of nylon 6, nylon 66 and nylon 12, or a quaternary copolymer polyamide composed of monomer units of nylon 6, nylon 66, nylon 11 and nylon 12. The sizing agent for carbon fibers according to claim 1.   The sizing agent for carbon fiber according to claim 1 or 2, wherein the aqueous medium is contained in an amount of 70 to 10,000 parts by weight with respect to 100 parts by weight of the copolymerized polyamide, and the average particle diameter of the copolymerized polyamide resin is 0.1 to 20 µm. .   Carbon fiber to which the sizing agent for carbon fiber according to any one of claims 1 to 3 is adhered.   The carbon fiber of Claim 4 whose adhesion amount of the sizing agent for carbon fibers is 0.3-20 weight% with respect to carbon fiber.   The carbon fiber according to claim 4 or 5, which is a cut fiber, a nonwoven fabric with a thermoplastic crimped fiber, or an opened woven fabric.   A carbon fiber reinforced composite material obtained by reaction injection molding of the carbon fiber according to any one of claims 4 to 6 and a polyamide resin.   The manufacturing method of a carbon fiber reinforced composite material including the process of mixing the carbon fiber and polyamide resin of any one of Claims 4-6, and the process of carrying out reaction injection molding of the mixture.