JP2018196937A - Method for producing molded article - Google Patents

Abstract

In a molding material including a carbon fiber bundle, the inside of the carbon fiber bundle included in the molding material may not be wetted with a thermoplastic resin in order to improve manufacturing efficiency. In this case, it is difficult to obtain a molded article having high mechanical properties by a normal molding method. Then, the provision of the manufacturing method which can improve the adhesive force of carbon fiber and a thermoplastic resin, and can manufacture a molded object with higher mechanical strength.
A method of manufacturing a molded body by injection molding a molding material containing a carbon fiber bundle and a thermoplastic resin, and measuring an injection capacity of 400 to 2000 with respect to a mold cavity volume 100 Molded body with high mechanical strength to be molded.
[Selection] Figure 1

Description

  The present invention relates to a method for producing a molded body using a molding material containing a carbon fiber bundle and a thermoplastic resin.

  As a means for obtaining a resin material having high strength and suppressed brittle fracture, it is known that the resin is a composite material reinforced with carbon fibers. In particular, a composite material in which a thermoplastic resin reinforced with a carbon fiber as a matrix resin is excellent in easy processability and recyclability as a molding material, and is expected to be applied in various fields.

  For example, Patent Document 1 proposes a molding material in which carbon fiber is easily dispersed during melt-kneading in injection molding by coating a polycarbonate resin on a carbon fiber bundle to which an impregnation aid is attached and cutting it into pellets. Has been. Patent Document 2 proposes a molding material in which a carbon fiber bundle to which a phenol resin is attached is coated with a polycarbonate resin.

International Publication No. 2013/137246 Pamphlet JP 2014-159560 A

  However, in a molding material containing a carbon fiber bundle, the carbon fiber bundle inside the molding material may not be wetted with a thermoplastic resin in order to improve manufacturing efficiency (Patent Document 1). In this case, in the conventional injection molding method, even if the carbon fiber and the thermoplastic resin are mixed with each other in the kneading step, the functional group on the surface of the carbon fiber and the thermoplastic resin are not sufficiently acting (sufficiently It is difficult to use for applications where a molded product with higher mechanical properties is required.

  Therefore, an object of the present invention is to provide a manufacturing method for solving the conventional problems, improving the adhesive force between the carbon fiber and the thermoplastic resin, and manufacturing a molded article having higher mechanical strength. is there.

In order to solve the above problems, the present invention provides the following means.
1. A method for producing a molded body by injection molding a molding material containing a carbon fiber bundle and a thermoplastic resin,
A method for manufacturing a molded body, in which a molding cavity volume 100 is molded by measuring an injection capacity of 400 to 2000.
2. A core-sheath structure in which a thermoplastic resin is coated around a carbon fiber bundle, and the length L1 in the axial direction of the carbon fiber bundle and the length L2 of the molding material are 0.9 <L1 / L2 <1. The method for producing a molded article according to claim 1, which is 0.0.
3. 3. The method for producing a molded article according to 2 above, wherein the thermoplastic resin contained in the molding material is not impregnated inside the carbon fiber bundle.
4). The manufacturing method of the molded object of any one of said 1-3 whose weight ratio of a thermoplastic resin is 150 to 900 mass parts with respect to 100 mass parts of carbon fibers.
5. The manufacturing method of the molded object of any one of said 1-4 whose solubility parameter SP value (unit: (J / cm < ³ >) < ^1/2 >) of a thermoplastic resin is 18-21.
6). 6. The method for producing a molded article according to any one of 1 to 5, wherein the thermoplastic resin is polycarbonate.
7). The method for producing a molded body according to any one of 1 to 6, wherein the time for the molding material to pass through the cylinder is 1 min or more and less than 10 min.
8). The manufacturing method of the molded object of any one of said 1-7 whose surface oxygen concentration ratio [O / C] of the carbon fiber which comprises a carbon fiber bundle is 0.1-0.5.

  If the manufacturing method body of a molded object in the present invention is used, the functional group on the carbon fiber surface and the thermoplastic resin can sufficiently act, and a molded object with high mechanical strength can be manufactured.

An example of the molding material in this invention.

[Carbon fiber]
The carbon fiber contained in the molding material of the present invention may be any carbon fiber such as polyacrylonitrile (PAN), petroleum / petroleum pitch, rayon, and lignin. In particular, PAN-based carbon fibers using PAN as a raw material are preferable because they are excellent in productivity and mechanical properties on a factory scale.

  Carbon fibers having an average diameter of 5 to 10 μm can be preferably used. A general carbon fiber is a carbon fiber filament in which 1000 to 50000 single fibers are bundled. The carbon fiber bundle in the present invention includes such general carbon fiber filaments, and the carbon fiber filaments are further overlapped and combined, or the combined yarn is twisted into a twisted yarn. Is also included. As the carbon fiber contained in the molding material of the present invention, one in which an oxygen-containing functional group is introduced to the surface by a surface treatment is preferable in order to improve the adhesion between the carbon fiber and the thermoplastic resin.

  In addition, when making an easily impregnable carbon fiber bundle by including an impregnation aid in the carbon fiber bundle, the carbon fiber bundle is converged to stabilize the process of uniformly attaching the impregnation aid to the carbon fiber bundle. It is preferable that it is what was processed with the sizing agent for giving property. As the sizing agent, those known for producing carbon fiber filaments can be used. Further, as the carbon fiber bundle, even if the oil agent used for increasing the slipping property at the time of production remains, it can be used without any problem in the present invention.

[Carbon fiber bundle]
The carbon fiber bundle contained in the molding material in the present invention means that the carbon fibers are present in a bundle rather than in a single yarn form. As described above, the carbon fiber generally has 1000 to 50000 short fibers as a fiber bundle, and it is preferable that the carbon fiber is included in the molding material as it is. That is, the molding material in the present invention is not obtained by kneading carbon fiber and a thermoplastic resin.

[Core-sheath structure and impregnated state of thermoplastic resin inside carbon fiber bundle]
When the molding material contains a carbon fiber bundle (especially when the molding material has a core-sheath structure in which a thermoplastic resin is coated around the carbon fiber bundle), the carbon fiber inside the carbon fiber bundle is partially absorbed by the impregnation aid. Even if it is wet, it is hardly in contact with the thermoplastic resin. Therefore, many functional groups present on the surface of the carbon fiber are not in a state of exhibiting high adhesive force with the thermoplastic resin.

  Therefore, the surface functional group of the carbon fiber needs to act with the thermoplastic resin in the kneading step before injection molding. However, in the case of the conventional molding method, the time for the kneading process is short, and many of the surface functional groups possessed by the carbon fibers inside the carbon fiber bundle remain in a state where they do not sufficiently function with the thermoplastic resin and often become molded bodies. It was.

  On the other hand, in the present invention, since the injection capacity is measured from 400 to 2000 with respect to the mold cavity volume 100, the molding material passes through the cylinder for a longer time than before. Yes. Therefore, even when a molding material containing a carbon fiber bundle (preferably a molding material in which the thermoplastic resin contained in the molding material is not impregnated inside the carbon fiber bundle) is used, many carbon fiber surface functional groups are used. Can work with thermoplastics.

  Moreover, in this invention, it is preferable that the thermoplastic resin contained in a molding material is not impregnated inside a carbon fiber bundle from a viewpoint of the manufacturing efficiency of a molding material. Here, the carbon fiber bundle is not impregnated with a thermoplastic resin means a core-sheath structure in which a thermoplastic resin is coated around the carbon fiber bundle, and the molding material is cut in the axial direction and observed. It means that the penetration thickness of the thermoplastic resin into the carbon fiber bundle is 50 μm or less. Note that the axial direction is the direction toward the center of the axis, which is the Z-axis direction in FIG. When the thermoplastic resin is not impregnated inside the carbon fiber bundle, many of the functional groups on the surface of the carbon fiber inside the carbon fiber bundle remain in a state where they do not sufficiently function with the thermoplastic resin. Appears.

[Surface oxygen concentration ratio [O / C]]
The carbon fiber constituting the carbon fiber bundle in the present invention has a surface oxygen concentration ratio [O / C] which is a ratio of the number of atoms of oxygen (O) and carbon (C) on the fiber surface measured by X-ray photoelectron spectroscopy. Is preferably from 0.1 to 0.5.

  In general, when the surface oxygen concentration ratio is 0.1 or more, a sufficient amount of functional groups can be secured on the carbon fiber surface, and (C) a stronger bond with the thermoplastic resin can be obtained. The impact strength of the product can be further improved. In the conventional manufacturing method, when a molding material containing a carbon fiber bundle is used, even if carbon fibers having a large surface oxygen concentration ratio are used, it is difficult to cause all surface functional groups to act on the thermoplastic resin. In the present invention, even if a molding material containing a carbon fiber bundle having a relatively high surface oxygen concentration ratio [O / C] is used, almost all surface functional groups can act on the thermoplastic resin. it can. This is because the injection volume is set to 400 to 2000 with respect to the mold cavity volume 100 and is measured and molded. The surface oxygen concentration ratio [O / C] is more preferably 0.15 or more, and further preferably 0.2 or more.

On the other hand, the upper limit of the surface oxygen concentration ratio is not particularly limited, but is generally preferably 0.5 or less, more preferably 0.4 or less, and more preferably 0.3 or less, from the balance of carbon fiber handleability and productivity. Further preferred.
In addition, the surface oxygen concentration ratio of the carbon fiber in the present invention is a value in a state where no sizing agent or impregnating aid is attached.

[Impregnation aid]
The impregnation aid used in the present invention is not particularly limited, and may be one kind or may contain plural kinds of impregnation aids. Specifically, US Patent Application No. 14/384857, name “Material for Molding, Shaped Product Thefrom, and Method for Manufacturing the Shaped Product ”.

  The impregnation aid used in the present invention is preferably at least one selected from the group consisting of phosphate esters and aliphatic hydroxycarboxylic acid polyesters, and of course, phosphate esters and aliphatic hydroxycarboxylic acid based resins. It may contain both polyesters.

  Although there is no limitation in particular in the quantity of the impregnation adjuvant contained in a carbon fiber bundle, 3-15 mass parts is preferable with respect to 100 mass parts of carbon fibers, and 5-12 mass parts is more preferable.

[Thermoplastic resin]
Examples of the thermoplastic resin used in the present invention include polyolefin resin, polystyrene resin, polyamide resin, polyester resin, polyacetal resin (polyoxymethylene resin), polycarbonate resin, (meth) acrylic resin, polyarylate resin, polyphenylene ether resin. , Polyimide resin, polyether nitrile resin, phenoxy resin, polyphenylene sulfide resin, polysulfone resin, polyketone resin, polyether ketone resin, thermoplastic urethane resin, fluorine resin, thermoplastic polybenzimidazole resin, vinyl resin, etc. Can do.

  Examples of the polyolefin resin include polyethylene resin, polypropylene resin, polybutadiene resin, and polymethylpentene resin. Examples of the vinyl resin include vinyl chloride resin, vinylidene chloride resin, vinyl acetate resin, and polyvinyl alcohol resin. Examples of the polystyrene resin include polystyrene resin, acrylonitrile-styrene resin (AS resin), acrylonitrile-butadiene-styrene resin (ABS resin), and the like. Examples of the polyamide resin include polyamide 6 resin (nylon 6), polyamide 11 resin (nylon 11), polyamide 12 resin (nylon 12), polyamide 46 resin (nylon 46), polyamide 66 resin (nylon 66), and polyamide 610. Resin (nylon 610) etc. can be mentioned. Examples of the polyester resin include polyethylene terephthalate resin, polyethylene naphthalate resin, boribylene terephthalate resin, polytrimethylene terephthalate resin, and liquid crystal polyester. Examples of the (meth) acrylic resin include polymethyl methacrylate. Examples of the polyphenylene ether resin include modified polyphenylene ether. Examples of the polyimide resin include thermoplastic polyimide, polyamideimide resin, polyetherimide resin, and the like. Examples of the polysulfone resin include a modified polysulfone resin and a polyethersulfone resin. Examples of the polyetherketone resin include polyetherketone resin, polyetheretherketone resin, and polyetherketoneketone resin.

  The thermoplastic resin used in the present invention may be only one type or two or more types. In the present invention, as an aspect of using two or more types of thermoplastic resins in combination, for example, an aspect in which thermoplastic resins having different softening points or melting points are used in combination, an aspect in which thermoplastic resins having different average molecular weights are used in combination, etc. This is not a limitation.

[Solubility parameter SP value of thermoplastic resin]
The solubility parameter SP value (unit: (J / cm ³ ) ^1/2 ) of the thermoplastic resin in the present invention is preferably 18 or more and 21 or less.

Conventionally, the thermoplastic resin has a solubility parameter SP value (unit: (J / cm ³ ) ^1/2 ) in the range of 18 or more and 21 or less, and the surface oxygen concentration ratio [O / C] described above. When molding is performed using a molding material containing carbon fibers, all the surface functional groups of the carbon fibers are difficult to act because the time for mixing the carbon fibers and the thermoplastic resin in the cylinder is short.

On the other hand, the present invention relative to the mold cavity volume 100, since the 400 to 2,000 injection capacity, solubility parameter SP value of the thermoplastic resin ^{(unit: (J / cm 3) 1/2} ) is 18 or more Even when molded using a molding material containing a thermoplastic resin in a range of 21 or less and carbon fibers having the above-mentioned surface oxygen concentration ratio [O / C], many of the surface functional groups of the carbon fibers Is easy to act. As a result, mechanical properties when formed into a molded body are improved.
A preferable solubility parameter SP value (unit: (J / cm ³ ) ^1/2 ) is 19.5 or more and 20.5 or less.

[Polycarbonate]
The thermoplastic resin in the present invention is preferably a polycarbonate. The solubility parameter SP value of polycarbonate (unit: (J / cm ³ ) ^1/2 ) is 20.2.

  In this case, the kind of polycarbonate is not particularly limited, and examples thereof include those obtained by reaction of various dihydroxyaryl compounds with phosgene, or those obtained by transesterification reaction of dihydroxyaryl compounds and diphenyl carbonate. A typical example is 2,2'-bis (4-hydroxyphenyl) propane, a polycarbonate obtained by reacting so-called bisphenol A with phosgene or diphenyl carbonate.

  Examples of the dihydroxyaryl compound used as a raw material for polycarbonate include bis (4-hydroxyphenyl) methane, 1,1′-bis (4-hydroxyphenyl) ethane, 2,2′-bis (4-hydroxyphenyl) propane, 2, 2'-bis (4-hydroxyphenyl) butane, 2,2'-bis (4-hydroxyphenyl) octane, 2,2'-bis (4-hydroxy-3-methylphenyl) propane, 2,2'-bis (4-hydroxy-3-tert-butylphenyl) propane, 2,2′-bis (3,5-dimethyl-4-hydroxyphenyl) propane, 2,2′-bis (4-hydroxy-3-cyclohexylphenyl) Propane, 2,2′-bis (4-hydroxy-3-methoxyphenyl) propane, 1,1′-bis (4-hydroxyphenyl) Cyclopentane, 1,1′-bis (4-hydroxyphenyl) cyclohexane, 1,1′-bis (4-hydroxyphenyl) cyclododecane, 4,4′-dihydroxyphenyl ether, 4,4′-dihydroxy-3, 3'-dimethylphenyl ether, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfide, 4,4'-dihydroxydiphenyl sulfoxide, 4,4'-dihydroxydiphenyl sulfone, Examples include bis (4-hydroxyphenyl) ketone. These dihydroxyaryl compounds can be used alone or in combination of two or more.

  Preferred dihydroxyaryl compounds include bisphenols that form highly heat-resistant aromatic polycarbonates, bis (hydroxyphenyl) alkanes such as 2,2′-bis (4-hydroxyphenyl) propane, and bis (4-hydroxyphenyl) cyclohexane. Bis (hydroxyphenyl) cycloalkane, dihydroxydiphenyl sulfide, dihydroxydiphenyl sulfone, dihydroxydiphenyl ketone and the like. Particularly preferred dihydroxyaryl compounds include 2,2'-bis (4-hydroxyphenyl) propane which forms bisphenol A type aromatic polycarbonate.

  In addition, when manufacturing bisphenol A type aromatic polycarbonate within a range not impairing heat resistance and mechanical strength, a part of bisphenol A may be substituted with another dihydroxyaryl compound. In addition, various polymers, fillers, stabilizers, pigments, etc. are blended within the range that does not impair the mechanical strength in order to increase fluidity, appearance gloss, flame retardancy, thermal stability, weather resistance, impact resistance, etc. May be. In addition, it is also possible to mix | blend a phosphoric acid ester with a polycarbonate as a flame retardant for the purpose of improving a flame retardance.

[Molding materials]
The shape of the molding material in the present invention is not particularly limited, and examples thereof include a columnar shape, a plate shape, a granular shape, a lump shape, a thread shape (string shape), a net shape, and the like, and it is possible to mold using a plurality of types of molding materials having different shapes. is there.

  The molding material has a core-sheath structure in which a thermoplastic resin is coated around the carbon fiber bundle, and the length L1 in the axial direction of the carbon fiber bundle and the length L2 of the molding material are 0.9 <L1. It is preferable that /L2<1.0, and it is more preferable that L1 and L2 are substantially the same. At this time, the carbon fiber bundle is the core and the thermoplastic resin is the sheath.

  That is, it is a pellet with a core-sheath type structure obtained by cutting a coated body in which the periphery of a carbon fiber bundle is coated with a thermoplastic resin with a cutter, etc., and having a carbon fiber bundle as a core component and a thermoplastic resin as a sheath component. More preferably (sometimes referred to as a core-sheath pellet).

  Further, in such a granular molding material, the length of the carbon fiber bundle in the axial direction is preferably 1 to 30 mm, more preferably 2 to 10 mm, and even more preferably 2 to 5 mm. There is no particular limitation on the diameter of the core-sheath pellet (for example, the core-sheath pellet described in FIG. 1), but it is preferably 1/10 or more and twice or less the pellet length, and 1/4 of the pellet length. More preferably, it is equal to or less than the pellet length.

[Mass ratio]
In the manufacturing method of the molded object in this invention, it is preferable to use the molding material whose weight ratio of a thermoplastic resin is 150 to 900 mass parts with respect to 100 mass parts of carbon fibers. The lower limit of the weight ratio of the more preferable thermoplastic resin is 200 parts by mass or more.

  On the contrary, the upper limit of the mass ratio of the thermoplastic resin is preferably 900 parts by mass or more with respect to 100 parts by mass of the carbon fibers. A more preferable upper limit of the mass ratio of the thermoplastic resin is 700 parts by mass or less.

[Method of manufacturing molding material]
There is no limitation in particular in the manufacturing method of the molding material in this invention, For example, what is necessary is just to use the method as described in international publication 2013/137246 pamphlet.

  Specifically, a method of coating the surface of the carbon fiber bundle with a molten thermoplastic resin, a method of casting and laminating the molten thermoplastic resin using a T-die or the like after arranging the carbon fiber bundles And a method of laminating and laminating a film-like thermoplastic resin on the aligned carbon fiber bundles, and a method of spraying a powdery thermoplastic resin after aligning the carbon fiber bundles. Instead of the carbon fiber bundles arranged continuously, an aggregate of carbon fiber bundles cut to a predetermined length can be used in the same manner.

  The molding material of the present invention preferably has a core-sheath structure in which a carbon fiber bundle is a core component and a thermoplastic resin is a sheath component, and in particular, a strand in which a carbon fiber bundle is coated with a thermoplastic resin is a strand. More preferably, it is a pellet of a core-sheath type structure obtained by cutting with a cutter, etc., using a carbon fiber bundle as a core component and a thermoplastic resin as a sheath component.

[Method for producing molded article]
1. Injection Capacity The method for producing a molded body according to the present invention is a method for producing a molded body by injection molding a molding material containing a carbon fiber bundle and a thermoplastic resin, and the injection volume for the mold cavity volume 100 Is molded to 400 to 2000.

  In the present invention, the mold cavity volume means the total volume of sprue, runner, gate, waste cavity, and molded body created in one shot. If there is no discarded cavity volume, the volume may be calculated as zero.

  When the injection capacity is set to 400 or more with respect to the mold cavity volume 100, the working time of the thermoplastic resin and the carbon fiber is sufficiently secured, and most of the functional groups on the surface of the carbon fiber can work with the thermoplastic resin. The lower limit of the volume of the injection volume is more preferably 500 or more, more preferably 600 or more, still more preferably 700 or more, and most preferably 800 or more.

  On the contrary, the upper limit of the volume of the injection capacity with respect to the mold cavity volume 100 is 2000 or less. When exceeding this, since the thermoplastic resin is kneaded for a long time, the thermoplastic resin deteriorates, and the physical properties of the molded article deteriorate. The upper limit of the volume of the preferable injection volume is more preferably 1800 or less, further preferably 1600 or less, still more preferably 1400, and most preferably 1200 or less. If it is this range, the effect of the mechanical property improvement by the effect | action of the surface functional group of carbon fiber will become large rather than the influence of deterioration of a thermoplastic resin.

2. Cylinder passage time In injection molding, a molding material is melt-plasticized in a cylinder, injected into a mold, and solidified in the mold to obtain a molded body. Note that the cylinder for plasticization is a portion that melts the molding material introduced from the hopper by applying heat, and is injected into the mold after being melt plasticized by the cylinder. As the injection molding machine, an in-line injection molding machine is preferable.
The time for the molding material to pass through the cylinder is preferably 1 min or more and less than 10 min.
Here, the time for passing through the cylinder can be calculated by the following equation.
Time to pass through the cylinder = (volume of injection volume ÷ mold cavity volume) x 1 shot cycle time

  In order to lengthen the interaction between the thermoplastic resin and the carbon fiber, it is preferable to increase the time for passing through the cylinder to some extent, but it is desired to improve the productivity by shortening the one-shot cycle time. Therefore, in the present invention, the injection capacity is increased, the time for passing through the cylinder is lengthened, and the interaction between the thermoplastic resin and the carbon fiber is lengthened.

When the time for passing through the cylinder is 1 min or longer, the surface functional group of the carbon fiber present inside the carbon fiber bundle is preferable because the time for acting with the thermoplastic resin is sufficiently long. The preferred transit time is 2 min or more, and more preferably 4 min or more.
On the contrary, the upper limit is preferably 10 min or less. When it is 10 min or less, the degree of deterioration of the thermoplastic resin can be suppressed.

[Molded body]
When using the molding material of the present invention to obtain a molded body by molding without adding other molding materials and additives, the amount and ratio of the molding material and carbon fiber of the molded body, that is, the mass The reference composition is naturally the same. Therefore, the amount of carbon fiber and thermoplastic resin contained in the molded article of the present invention and the preferred range thereof are preferably the same for the molding material and the molded article.

  In addition, when molding is performed without adding other molding materials and additives using the molding material of the present invention, the carbon fiber content (rate) of either the molding material or the obtained molded body is calculated. Measured and this can be regarded as the other carbon fiber content (rate). Further, even when molding is performed by adding other molding materials or additives to the molding material of the present invention, calculation is performed based on the amount of addition, and either the molding material or the molded body of the present invention is calculated. From the carbon fiber content (rate) of the other, the other carbon fiber content (rate) can be determined.

  In the molded body of the present invention, it is preferable that the carbon fiber in which the carbon fiber bundles are unwound in the molded body is dispersed with a weight average fiber length of 0.3 mm or more, and more preferably, the carbon fiber has a weight. The fiber is dispersed with an average fiber length of 0.4 mm or more. In the molded article of the present invention, the upper limit of the weight average fiber length of the remaining carbon fibers is not particularly limited, and depends on the application and the molding method employed.

[Use of molded body]
The method for producing a molded article of the present invention enables a molded article having excellent mechanical strength to be produced by a simple process, such as automobiles, ships, aircraft and other transportation equipment, electrical / electronic equipment, It is extremely useful in various industrial fields such as interior and exterior materials and parts of office equipment.

[Evaluation and analysis method]
Examples are shown below, but the present invention is not limited thereto. In addition, each value in a present Example was calculated | required according to the following method.
1. Measurement of Tensile Strength Tensile strength was evaluated by a method according to JIS K 7161: 1994, using the molded article of the present invention in the shape of a dumbbell-shaped test piece. The dumbbell-shaped test piece has a parallel section having a length of 80 mm, a width of 10 mm, and a thickness of 2 mm.
2. Measurement of bending strength Compliant with JIS K 7171 using the molded body of the present invention in the form of a dumbbell-shaped test piece (compliant with JIS K 7162: 1994 or ISO 527-2: 1998 test piece 1A type) The method was evaluated.
3. Ratio of carbon fiber of 0.3 mm or more A sample of the molded body was placed in a crucible and heated at 550 ° C. for 1.5 hours in an aerobic atmosphere to remove the resin component by combustion. The remaining carbon fiber was put into water containing a surfactant and sufficiently stirred by ultrasonic vibration. The stirred dispersion was randomly collected with a measuring spoon to obtain a sample for evaluation, and the weight ratio of carbon fibers having a length of 0.3 mm or more was calculated with an image analyzer Luzex AP manufactured by Nireco.

[Preparation of raw materials]
The raw materials used in the present invention are as follows.
1. Production of carbon fiber bundle (1) Spinning, baking treatment and surface oxidation treatment are carried out from a copolymer mainly composed of polyacrylonitrile, the total number of single yarns is 24,000, the single fiber diameter is 7 μm, and the mass per unit length is 1. A homogeneous carbon fiber bundle (1) having a density of 1.6 g / m, a specific gravity of 1.8 g / cm ³ and a surface oxygen concentration [O / C] of 0.11 was obtained. This carbon fiber had a strand tensile strength of 4000 MPa and a strand tensile modulus of 240 GPa.

(2) Spinning, baking treatment, surface oxidation treatment from a copolymer containing polyacrylonitrile as a main component, total number of single yarns 24,000, single fiber diameter 7 μm, mass per unit length 1.6 g / m, A homogeneous carbon fiber bundle (2) having a specific gravity of 1.8 g / cm ³ and a surface oxygen concentration [O / C] of 0.23 was obtained. This carbon fiber had a strand tensile strength of 5000 MPa and a strand tensile modulus of 240 GPa.

2. Thermoplastic resin Polycarbonate: Teijin Limited: L-1225Y
Glass transition temperature: 150 degrees Solubility parameter ((J / cm ³ ) ^1/2 ): 20.2
3. Impregnation aid (1) Bisphenol A bis (diphenyl phosphate) (Daihachi Chemical Co., Ltd .; CR-741)

[Example 1]
1. Preparation of molding material As an impregnation aid, bisphenol A bis (diphenyl phosphate) (made by Daihachi Chemical Co., Ltd .; CR-741), which is an aromatic condensed phosphate, was used, and this was emulsified to a non-volatile content of 25% by mass. After the carbon fiber bundle (1) is passed through the solution, the excessively adhered solution is removed with a nip roll, and then further passed through a hot air drying furnace heated to 180 ° C. for 2 minutes to be dried. It was. The content of the carbon fiber bundle impregnation aid was 11.1 parts by mass per 100 parts by mass of the carbon fibers.

  Next, the carbon fiber bundle obtained above was covered with polycarbonate (manufactured by Teijin Limited: L-1225Y) using a crosshead die for covering the wire with an outlet diameter of 3 mm, and this was cut into a length of 3 mm. A molding material which is a core-sheath pellet suitable for injection molding having a carbon fiber content of 15% by mass (566 parts by mass of polycarbonate per 100 parts by mass of carbon fiber), a diameter of 3.2 mm, and a length of 3 mm was obtained. .

2. Manufacture of a molded body A cylinder is selected so that this molding material can be measured to a volume 880 of an injection capacity with respect to a mold cavity volume 100. Specifically, “all electric injection molding machine EC450SX i26” (cylinder capacity PE equivalent 842 g) manufactured by Toshiba Machine was selected for 96 g of mold cavity volume PE equivalent.

  Cylinder temperature C1 / C2 / C3 / C4 / N = 280 ° C./290° C./320° C./320° C./310° C. (C1 to C4 are cavities, N is a nozzle), one shot cycle time is 45 seconds, Dumbbells for tensile strength and bending strength were obtained. The time for the molding material to pass through the cylinder was 6.6 min. The results are shown in Table 1.

[Example 2]
A molded body was produced in the same manner as in Example 1 except that the carbon fiber content was 30% by mass (the polycarbonate was 233 parts by mass per 100 parts by mass of the carbon fiber). The results are shown in Table 1.

[Example 3]
Molding is performed in the same manner as in Example 1 except that the carbon fiber bundle (2) is used as the carbon fiber bundle and the carbon fiber content is 30% by mass (the polycarbonate is 233 parts by mass per 100 parts by mass of the carbon fiber). The body was manufactured. The results are shown in Table 1.

[Example 4]
A molded body was manufactured in the same manner as in Example 3 except that the injection capacity for the mold cavity volume 100 was adjusted to 617 and a mold and an injection molding machine were prepared. The time for the molding material to pass through the cylinder was 4.6 min. The results are shown in Table 1.

[Comparative Example 1]
A molded body was manufactured in the same manner as in Example 1 except that the injection capacity for the mold cavity volume 100 was adjusted to 350 and a mold and an injection molding machine were prepared. The time for the molding material to pass through the cylinder was 2.6 min. The results are shown in Table 1.

[Comparative Example 2]
A molded body was manufactured in the same manner as in Example 3 except that the injection capacity for the mold cavity volume 100 was adjusted to 350 and a mold and an injection molding machine were prepared. The time for the molding material to pass through the cylinder was 2.6 min. The results are shown in Table 1.

[Comparative Example 3]
A molded body was produced in the same manner as in Example 1, except that a core-sheath molding material was not used and pellets in which carbon fibers were dispersed in a single yarn shape were used in the molding material. Since the molding material was produced by kneading a carbon fiber bundle and a thermoplastic resin, the weight average fiber length of the carbon fibers contained in the molding material was 0.3 mm. The results are shown in Table 1.

[Comparative Example 4]
A molded body was manufactured in the same manner as in Comparative Example 3 except that the injection capacity for the mold cavity volume 100 was adjusted to 350 and a mold and an injection molding machine were prepared. The results are shown in Table 1.
It can be seen that when a molding material containing no carbon fiber bundle is used, the mechanical properties hardly change even when the injection capacity for the mold cavity volume 100 is changed.

101 carbon fiber bundle 102 thermoplastic resin

Claims (8)

A method for producing a molded body by injection molding a molding material containing a carbon fiber bundle and a thermoplastic resin,
A method for manufacturing a molded body, in which a molding cavity volume 100 is molded by measuring an injection capacity of 400 to 2000.   A core-sheath structure in which a thermoplastic resin is coated around a carbon fiber bundle, and the length L1 in the axial direction of the carbon fiber bundle and the length L2 of the molding material are 0.9 <L1 / L2 <1. The method for producing a molded article according to claim 1, which is 0.0.   The method for producing a molded body according to claim 2, wherein the thermoplastic resin contained in the molding material is not impregnated inside the carbon fiber bundle.   The manufacturing method of the molded object of any one of Claims 1-3 whose weight ratio of a thermoplastic resin is 150 to 900 mass parts with respect to 100 mass parts of carbon fibers. The manufacturing method of the molded object of any one of Claims 1-4 whose solubility parameter SP value (unit: (J / cm < ³ >) < ^1/2 >) of a thermoplastic resin is 18-21.   The manufacturing method of the molded object of any one of Claims 1-5 whose thermoplastic resin is a polycarbonate.   The manufacturing method of the molded object of any one of Claims 1-6 whose time for a molding material to pass the inside of a cylinder is 1 minute or more and less than 10 minutes. The manufacturing method of the molded object of any one of Claims 1-7 whose surface oxygen concentration ratio [O / C] of the carbon fiber which comprises a carbon fiber bundle is 0.1-0.5.

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