JP6458589B2 - Sheet material, integrated molded product, and integrated molded product manufacturing method - Google Patents

Description

  The present invention relates to a sheet material composed of discontinuous carbon fibers and a thermoplastic resin, an integrated molded product obtained by combining and integrating the sheet material, and a method for manufacturing the integrated molded product, particularly in a preheating step. The present invention relates to a sheet material that is excellent in handling properties and bonding strength when integrally formed.

  In recent years, industrial parts such as automobiles, electrical / electronic devices, home appliances, etc. that have been manufactured with metal materials have been replaced by thermoplastic FRP materials consisting of reinforcing fibers and thermoplastic resins. Yes. Among them, thermoplastic CFRP using carbon fiber that is lightweight and has excellent mechanical properties as a reinforcing fiber is attracting attention from the market because it is excellent in specific strength and specific rigidity and has a large lightening effect.

  However, in accordance with the required characteristics of the member, a plurality of small members are prepared, preheated to a temperature higher than the melting temperature of the matrix resin to be plasticized, and supplied between molds consisting of a pair of males and females for pressure cooling. Although an integrated molding method is widely known to form into a desired shape, when components with different material prescriptions such as thickness and Vf are combined, the heating efficiency differs for each member. Resin is not easily melted or thermally decomposed, and there are problems such as a decrease in bonding strength of the obtained integrally molded product and a decrease in surface quality.

  Patent Document 1 discloses a molded product composed of discontinuous carbon fibers and a thermoplastic resin, in which a chopped strand of carbon fibers is partially opened to mix a carbon fiber bundle and a carbon fiber single yarn. ing.

  According to this technique, since the weight ratio of the fiber bundle having the carbon fiber single yarn of the specified number or more is large, it is possible to increase the volume content of the carbon fiber and improve the tensile strength. However, in the molding of an integrally molded product using this technology, the carbon fiber is densely arranged and the specific heat is high, so that the molding material can be preheated in a short time, while a plurality of preheated members are placed in the mold. There was a problem that the temperature drop was large and the joint strength of the obtained molded product was inferior.

  Therefore, Patent Document 2 discloses a molded body in which a thermoplastic FRP member in which discontinuous reinforcing fibers are randomly oriented is bonded and integrated with high bonding strength and a manufacturing method thereof.

  According to such a technique, a high joint strength is realized by processing the cross section of the joint portion of the joint member into an inclined structure, but in addition to the cost of cross-section processing, the preheated member is accurately placed on the mold. There is a need. Furthermore, it does not improve the heat resistance of the material in the preheating process, and does not provide a fundamental solution to market demand.

Japanese Patent No. 5627803 JP 2014-177117 A

  Accordingly, an object of the present invention relates to a sheet material composed of discontinuous carbon fibers and a thermoplastic resin, an integrated molded product obtained by combining the sheet materials, and a method for manufacturing the integrated molded product. An object of the present invention is to provide a sheet material that eliminates this point and has excellent handling strength in the preheating process and excellent bonding strength when integrally molded.

In order to solve the above-described problems, the present invention employs one of the following configurations.
(1) A sheet material in which a discontinuous carbon fiber base material is impregnated with a thermoplastic resin, the number average fiber length of carbon fibers of the sheet material is 10 mm or more and less than 50 mm, and the carbon fibers of the sheet material are single. It consists of yarns and fiber bundles, and the weight ratio of the single yarn and the fiber bundle having a single yarn number of less than 50 is 60 wt% or more and less than 85 wt%, and the weight proportion of the fiber bundle having a single yarn number of 50 or more and less than 300 to the entire carbon fiber. A sheet material, wherein the weight ratio of the fiber bundle having a single yarn number of 300 or more is 3 wt% or more and less than 10 wt%.
(2) The carbon fiber of the sheet material is composed of a single yarn and a fiber bundle, and the weight ratio of the single yarn and the fiber bundle having a number of single yarns of less than 50 is 70 wt% or more and less than 85 wt% with respect to the entire carbon fiber, and the number of single yarns (1), wherein the weight ratio of fiber bundles of 50 or more and less than 300 is less than 27 wt% and 10 wt% or more, and the weight ratio of fiber bundles of 300 or more single yarns is 3 wt% or more and less than 5 wt%. Sheet material.
(3) The sheet material according to (1) or (2), wherein the thermoplastic resin is polypropylene, polyamide, or polyphenylene sulfide.
(4) The sheet material according to any one of (1) to (3), wherein a volume ratio of carbon fibers of the sheet material is 10 vol% or more and 50 vol% or less.
(5) The sheet material according to any one of (1) to (4), wherein a thickness of the sheet material at 23 ° C is 0.1 to 10 mm.
(6) The ratio tb / ta of the thickness (ta) of the sheet material at 23 ° C. and the thickness (tb) of the thermoplastic resin above the melting temperature and below the pyrolysis temperature is 4 or more and 12 or less, (1) -Sheet material in any one of (5).
(7) A sheet material obtained by laminating a plurality of sheet materials according to any one of (1) to (6).
(8) The first sheet material (i) and the second sheet material (ii), which are the sheet materials according to any one of (1) to (7), are partially bonded to each other through melting. It is an integrally molded product obtained by bonding, and the thickness (ti) of the first sheet material (i) at 23 ° C. and the thickness of the second sheet material (ii) at 23 ° C. (tii). ) Is an integral molded product having an absolute value of a difference (ti-tii) of 0.1 mm or more and less than 6 mm.
(9) A method for producing an integrated molded product, wherein the integrated molded product according to (8) is obtained by sequentially performing the following steps (A) to (D).
Step (A): The first sheet material (i) and the second sheet material (ii) are simultaneously conveyed into the heater furnace, and the thermoplastic resin impregnated in the sheet material is heated to the melting point or higher to melt. Process.
Step (B): A step of conveying and arranging the first sheet material (i) and the second sheet material (ii) in the mold.
Step (C): A step in which the first sheet material (i) and the second sheet material (ii) are pressurized and cooled in a mold to form a molded product.
Step (D): A step of taking out the integrally molded product from the mold.

  The sheet material of the present invention is excellent in handleability in the preheating process. Furthermore, by combining and combining the sheet materials, an integrally molded product having excellent bonding strength and surface quality can be obtained.

FIG. 1 is an example of a carding apparatus used in the present invention. FIG. 2 is a perspective view showing an example of carbon and a thermoplastic resin attached to the single yarn when the sheet material of the present invention is preheated. FIG. 3 is a perspective view showing an example of a fiber bundle having 50 to 300 single yarns and a thermoplastic resin attached to the fiber bundle when the sheet material of the present invention is preheated. FIG. 4 is a perspective view showing an example of a fiber bundle having 300 or more single yarns and a thermoplastic resin attached to the fiber bundle when the sheet material of the present invention is preheated. FIG. 5 is a perspective view showing an example of an integrally molded product in the present invention. FIG. 6 is a perspective view showing tensile test pieces used in Examples and Comparative Examples of the present invention. FIG. 7 is a simplified diagram of a lower die (concave die) for a molding die used in Examples and Comparative Examples. FIG. 8 is a simplified diagram of the upper mold (convex mold) of the molding mold used in the examples and comparative examples.

  The sheet material of the present invention is a sheet material obtained by impregnating a discontinuous carbon fiber base material with a thermoplastic resin, and the number average fiber length of carbon fibers of the sheet material is 10 mm or more and less than 50 mm, The carbon fiber is composed of a single yarn and a fiber bundle, and the weight ratio of the single yarn and the fiber bundle having a number of single yarns less than 50 is 60 wt% or more and less than 85 wt% with respect to the entire carbon fiber, and the fiber bundle having a number of single yarns of 50 or more and less than 300 The weight ratio is less than 37 wt% and 5 wt% or more, and the weight ratio of the fiber bundle having 300 or more single yarns is 3 wt% or more and less than 10 wt%.

  The components of the sheet material of the present invention will be described below.

  The discontinuous carbon fiber substrate of the present invention is a form in which single yarns and fiber bundles of discontinuous carbon fibers are dispersed in a planar shape, and examples thereof include a papermaking mat, a carding mat, and an airlaid mat. By setting it as the form of this discontinuous carbon fiber base material, since it is excellent in the shaping property to the shape used as the parameter | index of moldability, shaping | molding of a complicated shape becomes easy.

  A general manufacturing process of the carding mat can be used. For example, as shown in FIG. 1, the carding apparatus 1 includes a cylinder roll 2, a take-in roll 3 provided on the upstream side near the outer peripheral surface, and a downstream side opposite to the take-in roll 3. And a plurality of worker rolls provided close to the outer peripheral surface of the cylinder roll 2 between the take-in roll 3 and the doffer roll 4. 5, a stripper roll 6 provided close to the worker roll 5, a feed roll 7 and a belt conveyor 8 provided close to the take-in roll 3.

  A carbon fiber bundle 9 cut to a certain length is supplied to the belt conveyor 8, and the carbon fiber bundle 9 is introduced onto the outer peripheral surface of the cylinder roll 2 through the outer peripheral surface of the feed roll and then the outer peripheral surface of the take-in roll 3. Is done. Up to this stage, the carbon fiber bundle is unwound and becomes an aggregate of cotton-like carbon fiber bundles. A part of the aggregate of the cotton-like carbon fiber bundle introduced on the outer peripheral surface of the cylinder roll 2 is wound around the outer peripheral surface of the worker roll 5, and this cotton-like carbon fiber bundle is peeled off by the stripper roll 6. Then, it is returned to the outer peripheral surface of the cylinder roll 2 again. A large number of needles and protrusions are present on the outer peripheral surface of each of the feed roll 7, the take-up roll 3, the cylinder roll 2, the worker roll 5 and the stripper roll 6, and the carbon fiber is The bundle is opened to a carbon fiber bundle consisting of a predetermined number of single yarns by the action of the needle, and is oriented to some extent. Through such a process, the fiber bundle is opened up to a predetermined carbon fiber bundle, and moves onto the outer peripheral surface of the doffer roll 4 as a sheet-like web 10 which is one form of a carbon fiber nonwoven fabric sheet.

  As the carbon fiber constituting the sheet material of the present invention, polyacrylonitrile (PAN) -based, rayon-based, lignin-based, pitch-based carbon fiber, or graphite fiber is preferably used. Of these, it is more preferable to use PAN-based carbon fibers. Moreover, the surface treatment may be given to these fibers. Examples of the surface treatment include a treatment with a sizing agent, a treatment with a binding agent, and an additive adhesion treatment.

  It is important that the number average fiber length of the carbon fibers constituting the sheet material of the present invention is 10 mm or more and less than 50 mm. When the number average fiber length is less than 10 mm, there is little entanglement between the carbon fibers, so that the strength of the discontinuous carbon fiber substrate is low, and the handleability may be inferior in the preform laminating process or conveying / molding process. Furthermore, when the number average fiber length is 50 mm or more, the sheet material may be greatly expanded in the preheating step, and the handleability may be impaired.

  The carbon fiber constituting the sheet material of the present invention comprises a single yarn and a fiber bundle. In the preheating process of the sheet material, the single fiber and the fiber bundle having a number of single yarns of less than 50 contribute to the expansion of the sheet material and have a heat insulating effect. It is possible to prevent the temperature increase in the preheating process and to prevent the temperature decrease in the conveying process after preheating. On the other hand, the expanded thermoplastic resin is attached so as to cover the surface of the single yarn or fiber bundle as shown in FIG. 2, and since the surface area is large, there are many opportunities for contact with air, and oxidative degradation tends to occur. Preheating characteristics may be degraded.

  As shown in FIG. 3, the fiber bundle having a single yarn number of 50 or more and less than 300 includes a thermoplastic resin impregnated therein, and these thermoplastic resins are less likely to come into contact with air, hardly undergo oxidative degradation, and have preheating characteristics. Can be improved. Moreover, the thermoplastic resin adhering to the surface of the fiber bundle has a relatively small surface area and is moderately oxidatively deteriorated.

  As shown in FIG. 4, fiber bundles having 300 or more single yarns contain more resin impregnated inside, and these resins have less chance of contact with air, are less susceptible to oxidative degradation, and improve preheating characteristics. Can be made.

  The carbon fiber constituting the sheet material of the present invention comprises a single yarn and a fiber bundle, and the weight ratio of the single yarn and the fiber bundle having a number of single yarns of less than 50 is 60 wt% or more and less than 85 wt% with respect to the entire carbon fiber. is important. If it is less than 60 wt%, there are many bundled carbon fibers, there are few entanglement points between the carbon fibers, the strength of the discontinuous fiber base material is low, and the handleability may be poor. Moreover, in the conveyance process after preheating a sheet | seat base material, a temperature fall is large and there exists a possibility that it may be inferior to the joint strength of the obtained integrated molded product. Moreover, when it is 85 wt% or more, in the preheating process of the sheet material, there is a possibility that the thickness expansion increases and the handling property is impaired. Preferably, the weight ratio of the single yarn and the fiber bundle having a number of single yarns of less than 50 is 70 wt% or more and less than 85 wt%. By satisfying this range, the sheet material is excellent in mechanical properties and the thickness expansion is performed in the preheating step and the conveying step. Small and easy to handle.

  Of the carbon fiber bundles constituting the sheet material of the present invention, it is important that the weight ratio of the fiber bundles having 50 or more and less than 300 single yarns is less than 37 wt% and 5 wt% or more with respect to the entire carbon fiber. In the case of 37 wt% or more, a large number of bundled carbon fibers are present, and the area of the carbon fiber-matrix resin interface in the sheet material is reduced, which may reduce the mechanical properties and the bonding strength. Moreover, when it is less than 5 wt%, the preheating characteristic of the sheet material may be deteriorated. Preferably, the weight ratio of the fiber bundle having a single yarn number of 50 or more and less than 300 is less than 27 wt% and 10 wt% or more, and is excellent in the mechanical properties and preheating properties of the sheet material.

  Of the carbon fiber bundles constituting the sheet material of the present invention, it is important that the weight ratio of the fiber bundle having 300 or more single yarns is 3 wt% or more and less than 10 wt% with respect to the entire carbon fiber. If it is less than 3 wt%, the preheating characteristics of the sheet material may be reduced. In the case of 10 wt% or more, a large number of bundled carbon fibers exist, and the area of the carbon fiber / matrix resin interface in the sheet material decreases, which may reduce the mechanical properties and bonding strength. Preferably, the weight ratio of the fiber bundle having 300 or more single yarns is 3 wt% or more and less than 5 wt%, which is excellent in the bonding strength and preheating characteristics of the sheet material.

  Examples of the thermoplastic resin constituting the sheet material of the present invention include polyolefin resins such as polyethylene (PE) resin and polypropylene (PP) resin, polyethylene terephthalate (PET) resin, polyamide (PA) resin, polyphenylene sulfide ( PPS) resin, these copolymer resins, modified resins, alloys, and the like. Among these, a polypropylene resin is preferable from the viewpoint of lightness of the obtained molded product, and a polyamide resin is preferable from the viewpoint of mechanical characteristics. From the viewpoint of heat resistance, polyphenylene sulfide resin is preferably used.

  The sheet material of the present invention preferably has a carbon fiber volume content (Vf) of 10 to 50%, more preferably 20 to 40%. By adjusting within this range, a sheet with few voids and excellent bonding strength can be obtained. Moreover, the strength utilization rate of the fiber is excellent, and the sheet material is also excellent in the effect of reducing the weight for the price.

  The sheet material of the present invention preferably has a thickness (ta) at 23 ° C. of 0.1 mm to 10 mm. By setting the thickness to 0.1 mm or more, it is easy to control the thickness at the time of molding, and it can be manufactured inexpensively with a general-purpose molding apparatus. Moreover, by setting it as 10 mm or less, the expansion | swelling in a preheating process is restrict | limited and it is excellent in handleability.

  In the sheet material of the present invention, the ratio tb / ta of the thickness (ta) at 23 ° C. and the thickness (tb) between the melting temperature of the thermoplastic resin and the pyrolysis temperature is preferably 4 or more and 12 or less. By adjusting within this range, the expansion of the sheet material is small in the preheating step, and the preheating efficiency is excellent. When the thickness ratio tb / ta is less than 4, the thickness (tb) between the melting temperature of the thermoplastic resin and the thermal decomposition temperature is smaller than the thickness (ta) at 23 ° C. Specifically, a state in which the ratio of fiber bundles having 50 or more single yarns and less than 300 single fibers or fiber bundles having 300 or more single yarns is increased is exemplified. In such a sheet material, there is no sufficient expansion at the time of heating, and the heat insulation effect is low, so the temperature drop in the conveying process after preheating is large, and the mechanical properties of the molded product and the fluidity may be lowered. is there. On the other hand, when the thickness ratio tb / ta exceeds 12, the sheet material is excessively expanded in the preheating step. Specifically, the ratio of the fiber bundles of the single yarn and the fiber bundle of less than 50 single yarns. A state in which increases is exemplified. In such a sheet material, since the preheating efficiency is low, it takes a long time to heat the thermoplastic resin to a temperature higher than the melting temperature, resulting in a decrease in productivity, a decrease in surface quality and a decrease in mechanical properties due to resin burning. May happen. More preferably, tb / ta is 5 or more and 10 or less, which is excellent in the mechanical properties and preheating properties of the molded product.

  The sheet material of the present invention can be obtained by impregnating and integrating a thermoplastic resin into a discontinuous carbon fiber substrate. There is no restriction | limiting in particular as a method of impregnating a discontinuous carbon fiber base material with a thermoplastic resin, It can select from a desired method. For example, a plurality of discontinuous carbon fiber base materials and thermoplastic resin films are prepared, and the laminated body is alternately heated to melt the thermoplastic resin, and then pressurize the thermoplastic resin to the carbon fiber mat. The method of impregnation and integration is exemplified. The method for heating and pressurizing the laminate is not particularly limited, and examples thereof include a method of applying high temperature and pressure in a mold press or an autoclave. Another example is a method in which an element such as a double belt press or a calender roll is used to feed the elements constituting the sheet material into a crimping zone that can be subjected to a desired temperature and pressure. In this way, a sheet material can be produced by operating a continuous or semi-continuous process.

  There is no restriction | limiting in particular as a laminated structure of a laminated body, A desired laminated structure can be selected from viewpoints, such as a mechanical characteristic, impact resistance, a shaping property, or designability. For example, multiple sheets of thin carbon fiber mat and thin layer thermoplastic resin are prepared and laminated alternately, so that the thermoplastic resin is sufficiently impregnated in the heating and pressurizing process, and has excellent mechanical properties. Can be obtained. Moreover, the sheet | seat material which is excellent in the surface external appearance can be obtained by shape | molding the laminated body which has arrange | positioned the thermoplastic resin in the outermost layer. From the viewpoint of warping of the obtained sheet material, a method of laminating so as to be symmetric with respect to the thickness direction can be preferably exemplified.

  The sheet material of the present invention can be used by laminating a plurality of sheet materials. There is no restriction | limiting in particular as a laminated structure, A desired laminated structure can be selected from viewpoints, such as a mechanical characteristic of the obtained molded article, a shaping property, or designability.

  A molded product can be obtained by molding the sheet material of the present invention.

  Although there is no restriction | limiting in particular about the shaping | molding method of a molded article, Stamping press molding is illustrated. The type of press molding can be selected according to the shape of the molded product. Here, press molding refers to a molded product by applying deformation such as bending, shearing, compression, etc. to a laminate of a preform or a sheet material using a processing machine and a die, a tool, or other molding jigs or auxiliary materials. Is the way to get. Examples of the forming form include drawing, deep drawing, flange, call gate, edge curling, stamping and the like. In addition, as a method of press molding, a metal mold is used from the viewpoint of energy consumption in equipment and molding process, simplification of jigs and auxiliary materials used, molding pressure, and flexibility of temperature. It is more preferable to use a die press method in which molding is performed.

  As the mold pressing method, a preform or sheet material is placed in a mold in advance, pressed and heated together with mold clamping, and then the preform or sheet is cooled by mold cooling. Heat and cool method to obtain a molded product by cooling the material, or heating the preform or sheet material in advance to the melting temperature of the matrix resin or more, such as far infrared heater, heating plate, high temperature oven, dielectric heating, etc. Stamping, which is a method of heating with an apparatus, placing the thermoplastic resin on the mold that will be the lower surface of the molding die in a state where the thermoplastic resin is melted and softened, then closing the die and clamping, and then pressurizing and cooling The law can be adopted.

  In the molded product of the present invention, a filler, a conductivity imparting material, a flame retardant, a pigment, a dye, a lubricant, a release agent, a compatibilizing agent, a dispersant, a crystal nucleating agent, a plasticizer, Add heat stabilizer, antioxidant, anti-coloring agent, UV absorber, fluidity modifier, foaming agent, antibacterial agent, vibration control agent, deodorant, slidability modifier, antistatic agent, etc. Also good.

  The integrally molded product of the present invention is obtained by heating the first sheet material (i) and the second sheet material (ii) made of the sheet material, melting the matrix resin, and joining a part thereof to each other. It is done. Large-scale molded products can be obtained without increasing the device width due to capital investment, and cost effectiveness is great.

  The integral molded product of the present invention is a difference in thickness between the thickness (ti) of the first sheet material (i) at 23 ° C. and the thickness (tii) of the second sheet material (ii) at 23 ° C. It is important that the absolute value of (ti-tii) is 0.1 mm or more and less than 6 mm. When the absolute value of the thickness difference is 6 mm or more, when two sheet materials are preheated, it is difficult to preheat sufficiently to the inside, and the bonding strength may be reduced. In addition, the integrally molded product may be warped and have poor dimensional stability. If the thickness is less than 0.1 mm, the entire integrally molded product has a substantially uniform thickness, and therefore, the reinforcing effect of a member having high mechanical characteristics may be inferior.

  This invention is a manufacturing method of the integrated molded product which obtains the said integrated molded product by passing through the following processes in order of (A)-(D).

  Step (A) is a step in which the first sheet material (i) and the second sheet material (ii) are simultaneously carried into a heater furnace, and the matrix resin is heated to a melting point or higher to melt. . In general, when preheating a plurality of materials, a preheating time is set for each material according to Vf and thickness, and the timing of charging into the heater furnace is shifted, but in step (A), two sheets are used. Process management can be facilitated by requiring the materials to be simultaneously introduced into the heater furnace. Furthermore, since the number of times of opening and closing the heater furnace door at the time of loading and unloading the sheet material can be reduced and the furnace temperature can be stably maintained at a high temperature, the sheet material can be efficiently preheated.

  Although there is no restriction | limiting in particular about a heater furnace, A far-infrared heater can be preferably used from the ease of control of a heating state.

  In the step (B), the first sheet material (i) and the second sheet material (ii), which have been heated to the plasticizing temperature of the matrix resin, are taken out from the heater furnace and are opened under the opened mold. This is a process of placing the mold. When transporting, a manpower or a robot is appropriately selected in consideration of the safety of the work place and the placement accuracy of the sheet material on the mold.

  Step (C) is a step of obtaining an integrated molded product by pressurizing and cooling the two sheet materials by clamping the mold. In the process of pressure cooling, press molding is used, and the type can be selected according to the obtained integrally molded product.

  Step (D) is a step of releasing the mold after cooling and taking out the integrally molded product from the mold.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

<Materials used>
[Carbon fiber (CF)]
CF-1: Carbon fiber Spinning and firing were performed from a polymer containing polyacrylonitrile as a main component to obtain a continuous carbon fiber having a total filament number of 12,000. Further, the continuous carbon fiber was subjected to electrolytic surface treatment and dried in heated air at 120 ° C. to obtain carbon fiber (CF-1). The characteristics of this carbon fiber (CF-1) were as follows.
Density: 1.8 g / cm ³
Single yarn diameter: 7μm
Tensile strength: 4.9 GPa
Tensile modulus: 230 GPa
Fineness: 800g / 1000m
Number of filaments: 12,000

[Polyamide short fiber]
PA-1: Polyamide short fiber A polyamide resin (“Amilan” (registered trademark) CM1001 manufactured by Toray Industries, Inc.) was melt-spun to obtain a polyamide short fiber (PA-1) having the following characteristics.
Short fiber fineness: 1.7 dtex
Cut length: 51mm
Number of crimps: 12 mountains / 25mm
Crimp rate: 15%

[Polypropylene short fiber]
PP-1: Polypropylene short fiber Unmodified polypropylene resin (Prime Polymer Co., Ltd., “Prime Polypro” (registered trademark) J707G) was melt-spun to produce a polypropylene short fiber (PP-1) having the following characteristics. Obtained.
Short fiber fineness: 1.7 dtex
Cut length: 51mm
Number of crimps: 12 mountains / 25mm
Crimp rate: 15%

[Carbon fiber mat 1 (CFM-1)]
After carbon fiber (CF-1) is widened to a width of 25 mm with a vibrating rod that vibrates at 10 Hz, it is slit at intervals of 0.5 mm using a disk-shaped split blade and then cut to a fiber length of 15 mm. The chopped strand 1 was obtained.

  A chopped strand 2 was obtained in the same manner as the chopped strand 1 except that the widened carbon fiber (CF-1) was cut to a fiber length of 15 mm without slitting.

  A mixture obtained by mixing chopped strand 1, chopped strand 2 and polyamide short fiber (PA-1) in a mass ratio of 40:40:20 is put into a carding apparatus, and a sheet-like carbon fiber mat having a basis weight of 125 g / cm 2. 1 was obtained.

[Carbon fiber mat 2 (CFM-2)]
Carbon fiber mat 2 was obtained in the same manner as carbon fiber mat 1 except that chopped strand 1, chopped strand 2 and polyamide short fiber (PA-1) were mixed at a mass ratio of 28:52:20.

[Carbon fiber mat 3 (CFM-3)]
Carbon fiber mat 3 was obtained in the same manner as carbon fiber mat 1 except that chopped strand 1, chopped strand 2 and polyamide short fiber (PA-1) were mixed at a mass ratio of 52:28:20.

[Carbon fiber mat 4 (CFM-4)]
A carbon fiber mat 4 was obtained in the same manner as the carbon fiber mat 1 except that polypropylene short fibers (PP-1) were used instead of the polyamide short fibers (PA-1).

[Carbon fiber mat 5 (CFM-5)]
A chopped strand 7 was obtained in the same manner as the chopped strand 1 except that the widened carbon fiber (CF-1) was slit at intervals of 5 mm.

  A mixture obtained by mixing chopped strand 1, chopped strand 7 and polyamide short fiber (PA-1) at a mass ratio of 52:28:20 is put into a carding apparatus, and a sheet-like carbon fiber mat having a basis weight of 125 g / cm 2. 6 was obtained.

[Carbon fiber mat 6 (CFM-6)]
Carbon fiber mat 7 was obtained in the same manner as carbon fiber mat 7 except that chopped strand 2 and polyamide short fiber (PA-1) were mixed at a mass ratio of 80:20.

[Carbon fiber mat 7 (CFM-7)]
Carbon fiber (CF-1) was cut into 6 mm with a cartridge cutter to obtain chopped fiber. 60 liters of a dispersion medium having a concentration of 0.1% by weight made of water and a surfactant (manufactured by Nacalai Tesque Co., Ltd., polyoxyethylene lauryl ether (trade name)) was prepared, and the dispersion medium was put into a papermaking apparatus. The papermaking apparatus comprises an upper papermaking tank (capacity 50 liters) equipped with a stirrer with rotary blades and a lower water storage tank (capacity 10 liters), and a porous support is provided between the papermaking tank and the water tank. . First, a chopped fiber whose mass was adjusted so as to obtain a desired basis weight was put into a dispersion medium. Next, the dispersion was stirred for 3 minutes with a stirrer to obtain a slurry in which carbon fibers were dispersed. And the slurry was attracted | sucked from the water storage layer, it spin-dry | dehydrated through the porous support body, the binder (B-1) was provided, and it was set as the carbon fiber mat which consists of discontinuous carbon fiber. The carbon fiber mat was dried in a hot air dryer at 150 ° C. for 2 hours to obtain a carbon fiber mat 8 made of discontinuous carbon fibers having a basis weight of 100 g / m ² .

[Carbon fiber mat 8 (CFM-8)]
A chopped strand 8 was obtained in the same manner as the chopped strand 1 except that the widened carbon fiber (CF-1) was slit at intervals of 0.25 mm.

A mixture of chopped strand 1, chopped strand 8 and polyamide short fiber (PA-1) mixed at a mass ratio of 16:64:20 is deposited on a conveyor to obtain a carbon fiber mat 9 having a basis weight of 125 g / m ^2. It was.

[Carbon fiber mat 9 (CFM-9)]
A mixture in which the chopped strand 7 and the polyamide short fiber (PA-1) were mixed at a mass ratio of 80:20 was deposited on a conveyor to obtain a carbon fiber mat 10 having a basis weight of 125 g / m ² .

[Carbon fiber mat 10 (CFM-10)]
A chopped strand 9 was obtained in the same manner as the chopped strand 1 except that the widened carbon fiber (CF-1) was slit at intervals of 1 mm.

  A carbon fiber mat 11 was obtained in the same manner as the carbon fiber mat 1 except that the chopped strand 1, the chopped strand 9, and the polyamide short fiber (PA-1) were mixed at a mass ratio of 40:40:20.

[Thermoplastic resin film 1 (TPF-1)]
A polyamide resin (manufactured by Toray Industries, Inc., “Amilan” (registered trademark) CM1001) is quantitatively placed on a stainless steel plate, and another stainless steel plate is stacked on top of it, and a desired space between the plates is desired. A spacer with a thickness was inserted. The pressing temperature was 250 ° C., the pressure was 1 MPa, and the pressure was maintained for 5 minutes to obtain a thermoplastic resin film 1.

[Thermoplastic resin film 2 (TPF-2)]
90% by mass of unmodified polypropylene resin (manufactured by Prime Polymer Co., Ltd., “Prime Polypro” (registered trademark) J707G) and 10 mass of acid-modified polypropylene resin (manufactured by Mitsui Chemicals, Inc., “Admer” (registered trademark) QB510) A thermoplastic resin film 2 was produced in the same manner as the thermoplastic resin film 1 except that a master batch consisting of% was used.

<Mold>
(Mold 1) Flat plate mold A pair of opposed molds for obtaining the integrally molded product shown in FIG. 5 was prepared having the dimensions shown below. The dimensions of the lower mold (convex mold) and the upper mold (concave mold) shown in the schematic diagrams of FIGS. 7 and 8 are as follows.
・ W1: 300mm, W2: 296mm, W3: 148mm, H1: 14mm, H2: 12mm, H3: 10mm
(Mold 2) Mold for Integrated Molded Product A pair of opposed molds for obtaining the integrally molded product of FIG. The dimensions of the lower mold (convex mold) and the upper mold (concave mold) shown in the schematic diagrams of FIGS. 7 and 8 are as follows.
・ W1: 300mm, W2: 296mm, W3: 148mm, H1: 17mm, H2: 12mm, H3: 10mm

<Evaluation and measurement method>
(1) Volume ratio of discontinuous carbon fibers contained in sheet material (V _f )
After measuring the mass W0 of the sheet material, the CFRTP sheet is heated in air at 500 ° C. for 30 minutes to burn off the thermoplastic resin component, and the remaining discontinuous reinforcing fiber mass W1 is measured. Calculated.
Vf = (W1 / ρf) / {W1 / ρf + (W0−W1) / ρr} × 100 (unit: volume%)
Ρf: density of reinforcing fiber (g / cm ³ )
· Pr: density of thermoplastic resin (g / ^cm 3)

(2) Number average fiber length (L _n ) of discontinuous carbon fibers contained in the sheet material
A part of the sheet material was cut out, the binder and the matrix were sufficiently dissolved with a solvent for dissolving the binder and the matrix, and then separated from the discontinuous carbon fibers by a known operation such as filtration. When there was no solvent for dissolving the binder and the matrix, a part of the sheet material was cut out and heated at a temperature of 500 ° C. for 30 minutes, and the binder and the matrix were burned off to separate the discontinuous carbon fibers. The separated discontinuous carbon fibers, randomly 400 to extract, its length with an optical microscope to measure up to 1μm units, and the fiber length L _i. The number average fiber length (L _n ) and CV value were determined by the following formula.
L _n = ΣL _i / 400
L _i : measured fiber length (i = 1, 2, 3,... 400) (unit: mm)

(3) Weight ratio of fiber bundle for each number of single yarns A sample of 100 mm × 100 mm was cut out from the sheet material, heated at a temperature of 500 ° C. for 30 minutes, and the thermoplastic resin film components were burned off to separate discontinuous carbon fibers. Then, from the separated carbon fibers, taken out of carbon fiber bundle (A), up to 1/100 mg were determined using measurable balance, and the weight _{m i} of the carbon fiber bundle, a measurable caliper to 1/100 mm The number of single yarns _xn contained in one fiber bundle was calculated from the fiber length L _i measured by use. Furthermore, the number of single yarns _xn was calculated for all fiber bundles contained in the separated carbon fibers, and the weight ratio _Mn of the fiber bundles for each number of single yarns was obtained by the following equation.
x _n = m _i / (L _i × F)
M _n = M _i / (M ₁ + M ₂ + M ₃ ) × 100
M _i : measured weight (i = 1, 2, 3,...) (Unit: mg)
L _i : measured fiber length (i = 1, 2, 3,...) (Unit: mm)
F: Fineness (unit: g / 1000m)
M _i : Total weight of fiber bundles per number of single yarns (i = 1, 50, 300) (unit: mg)
M ₁ : Total weight of carbon fiber bundles having a single yarn number _xn of 1 to less than 50 (unit: mg)
M ₅₀ : total weight of carbon fibers having a single yarn number _xn of 50 or more and less than 300 (unit: mg)
M ₃₀₀ : total weight of carbon fibers having a single yarn number _xn of 300 to less than 12000 (unit: mg)

(4) Measurement of thickness of sheet material The thickness (ta) of the sheet material in an atmosphere at 23 ° C. was measured with a micrometer. Moreover, after taking out the sheet | seat material after a heating and fully cooling by 23 degreeC and no load, thickness (tb) was measured with the micrometer and thickness ratio (tb / ta) was computed.

(5) Tensile strength of joint The tensile strength of the joint of the integrally molded product shown in FIG. 5 was evaluated according to the standard of ASTM D3039.

  From the integrally molded products obtained in Examples or Comparative Examples, tensile test pieces having a span interval of 150 ± 1 mm and a width of 25 ± 0.2 mm shown in FIG. 6 were cut out to prepare test pieces. The value obtained by dividing the measured breaking load by the area of the A-A ′ cross section of each test piece was taken as the tensile strength, and the average values of the number n = 5 were compared.

  “Instron” (registered trademark) universal testing machine 5565 type (manufactured by Instron) was used as a testing machine, and the tensile strength was measured using a tensile test jig. The test was performed under the conditions that the moisture content of the test piece was 0.1% by mass or less, the ambient temperature was 23 ° C., and the humidity was 50% by mass.

(6) Evaluation of surface appearance The appearance of the integrally molded product was visually observed and judged according to the following criteria. In each evaluation, A and B were acceptable and C was not.
A: The surface is glossy and has an excellent surface appearance of an integrally molded product.
B: Although there is no problem in practical use, a haze after the part is seen in a part of the integrally molded product.
C: Resin is perforated, burned, or entirely blurred and inferior.

Example 1
A preform in which carbon fiber mat 1 (CFM-1) and thermoplastic resin sheet 1 (TPF-1) are superimposed is set in a flat plate mold so that the thickness is 4 mm and the volume content of carbon fiber is 30%. Then, it was press-molded with a press machine at a press temperature of 260 ° C., a pressure of 5 MPa, for 5 minutes, and naturally cooled to a room temperature of 25 ° C. while being pressed with the press machine to obtain a sheet material 1.

  A sheet material 2 was obtained in the same manner as the sheet material 1 except that the carbon fiber mat 1 (CFM-1) and the thermoplastic resin sheet 1 (TPF-1) were superposed so as to have a thickness of 2 mm.

  The sheet material 1 and the sheet material 2 are each processed to a size of 300 × 200 × 4 mm, and are simultaneously disposed in an oven equipped with a far infrared heater, so that the thermoplastic resin content of the sheet material 2 is sufficiently melted. Until preheated. At this time, the preheating time was 360 seconds. Next, the sheet material 1 is placed along the first bottom surface of the mold 1 heated to 150 ° C., the sheet material 2 is placed along the second bottom surface, and the two sheet materials are overlapped by 50 mm. Arranged. Thereafter, the upper mold was immediately lowered at a speed of 20 mm / second, pressurized and cooled at 10 MPa for 50 seconds, and then the molding mold was opened to remove the surplus portion and obtain an integrated molded product (FIG. 5). . The thickness of the thickest part of the integrally molded product was adjusted to 4 mm by controlling the position of the press. The evaluation conditions and results are summarized in Table 1.

(Example 2)
The carbon fiber mat 1 (CFM-1) and the thermoplastic resin sheet 1 (TPF-1) were superposed so as to have a thickness of 6 mm, and a sheet material 3 was obtained in the same manner as the sheet material 1.

  An integrally molded product was obtained in the same manner as in Example 1 except that the sheet material 3 and the sheet material 2 were molded using the mold 2 and subjected to evaluation. The thickness of the thickest part of the integrally molded product was adjusted to 6 mm by controlling the position of the press. Table 1 summarizes the evaluation conditions and characteristics.

(Example 3)
An integrated molded product was obtained and evaluated in the same manner as in Example 1 except that carbon fiber mat 2 (CFM-2) was used instead of carbon fiber mat 1 (CFM-1). Table 1 summarizes the evaluation conditions and characteristics.

(Example 4)
An integrated molded product was obtained and evaluated in the same manner as in Example 1 except that carbon fiber mat 3 (CFM-3) was used instead of carbon fiber mat 1 (CFM-1). Table 1 summarizes the evaluation conditions and characteristics.

(Example 5)
Except for using carbon fiber mat 4 (CFM-4) and thermoplastic resin sheet 2 (TPF-2) instead of carbon fiber mat 1 (CFM-1) and thermoplastic resin sheet 1 (TPF-1). In the same manner as in Example 1, an integrally molded product was obtained and used for evaluation. Table 1 summarizes the evaluation conditions and characteristics.

(Comparative Example 1)
An integrated molded product was obtained and evaluated in the same manner as in Example 1 except that carbon fiber mat 5 (CFM-5) was used instead of carbon fiber mat 1 (CFM-1). Table 2 summarizes the evaluation conditions and characteristics.

(Comparative Example 2)
An integrated molded product was obtained and evaluated in the same manner as in Example 1 except that carbon fiber mat 6 (CFM-6) was used instead of carbon fiber mat 1 (CFM-1). Table 2 summarizes the evaluation conditions and characteristics.

(Comparative Example 3)
An integrated molded product was obtained and evaluated in the same manner as in Example 1 except that carbon fiber mat 7 (CFM-7) was used instead of carbon fiber mat 1 (CFM-1). Table 2 summarizes the evaluation conditions and characteristics.

(Comparative Example 4)
An integrated molded product was obtained and evaluated in the same manner as in Example 1 except that carbon fiber mat 8 (CFM-8) was used instead of carbon fiber mat 1 (CFM-1). Table 2 summarizes the evaluation conditions and characteristics.

(Comparative Example 5)
An integrated molded product was obtained and evaluated in the same manner as in Example 1 except that carbon fiber mat 9 (CFM-9) was used instead of carbon fiber mat 1 (CFM-1). Table 2 summarizes the evaluation conditions and characteristics.

(Comparative Example 6)
An integrated molded product was obtained and evaluated in the same manner as in Example 1 except that the carbon fiber mat 10 (CFM-10) was used instead of the carbon fiber mat 1 (CFM-1). Table 2 summarizes the evaluation conditions and characteristics.

  As described above, in Examples 1 to 5, an integrally molded product having excellent surface appearance and bonding strength could be obtained, and good results were obtained. This can be achieved by adjusting the volume ratio of the carbon fibers constituting the sheet material of the present invention, the number average fiber length, and the weight distribution of the fiber bundle for each number of single yarns to satisfy the specified range.

  On the other hand, Comparative Examples 1 to 6 were inferior in bonding strength, and Comparative Examples 1, 3 and 6 were also inferior in bonding strength.

  Since the integrally molded product molded using the sheet material of the present invention has excellent bonding strength and surface appearance, it can be developed for various uses. Among them, it can be suitably used for automobile / aircraft parts, electrical / electronic product parts.

DESCRIPTION OF SYMBOLS 1 Carding apparatus 2 Cylinder roll 3 Take-in roll 4 Doffer roll 5 Worker roll 6 Stripper roll 7 Feed roll 8 Belt conveyor 9 Discontinuous carbon fiber 10 Sheet-like web 11 Single yarn 12 Adhered to single yarn or fiber bundle Thermoplastic resin 13 Fiber bundle 14 having 50 or more and less than 300 single yarns Thermoplastic resin impregnated with fiber 15 Fiber bundle having 300 or more single yarns 16 Lower mold 17 for integrated molded product 17 First mold of lower mold for integrated molded product 1 bottom surface 18 second bottom surface of lower mold for integrally molded product

Claims (9)

A sheet material in which a discontinuous carbon fiber base material is impregnated with a thermoplastic resin, the number average fiber length of the carbon fibers of the sheet material is 10 mm or more and less than 50 mm, and the carbon fibers of the sheet material are single yarns and fibers It consists of bundles, and the weight ratio of the fiber bundles of the single yarn and the number of single yarns less than 50 is 60 wt% or more and less than 85 wt%, and the weight proportion of the fiber bundle of the number of single yarns 50 or more and less than 300 is less than 37 wt% with respect to the entire carbon fiber. A sheet material, wherein the weight ratio of a fiber bundle having a single yarn number of 300 or more is 3 wt% or more and less than 10 wt%. The carbon fiber of the sheet material is composed of a single yarn and a fiber bundle, and the weight ratio of the single yarn and the fiber bundle having less than 50 single yarns to the entire carbon fiber is 70 wt% or more and less than 85 wt%, and the number of single yarns is 50 or more and 300. 2. The sheet material according to claim 1, wherein a weight ratio of less than 27 wt% is less than 27 wt% and 10 wt% or more, and a weight ratio of fiber bundles having 300 or more single yarns is 3 wt% or more and less than 5 wt%. . The sheet material according to claim 1 or 2, wherein the thermoplastic resin is polypropylene, polyamide, or polyphenylene sulfide. The sheet material in any one of Claims 1-3 whose volume ratio of the carbon fiber of the said sheet material is 10 vol% or more and 50 vol% or less. The sheet material in any one of Claims 1-4 whose thickness (ta) in 23 degreeC of the said sheet material is 0.1-10 mm. The ratio tb / ta of the thickness (ta) at 23 ° C. of the sheet material and the thickness (tb) not lower than the melting temperature of the thermoplastic resin and not higher than the thermal decomposition temperature is 4 or more and 12 or less. The sheet material according to any one of the above. A sheet material obtained by laminating a plurality of the sheet materials according to claim 1. The first sheet material (i) and the second sheet material (ii), which are the sheet materials according to any one of claims 1 to 7, are partly bonded to each other through melting. The obtained integrally molded product, which is the difference (ti) between the thickness (ti) of the first sheet material (i) at 23 ° C. and the thickness (tii) of the second sheet material (ii) at 23 ° C. An integral molded article having an absolute value of -tii) of 0.1 mm or more and less than 6 mm. The manufacturing method of the integrated molded product which obtains the integrated molded product of Claim 8 by passing through the following processes (A)-(D) in order.
Step (A): The first sheet material (i) and the second sheet material (ii) are simultaneously conveyed into the heater furnace, and the thermoplastic resin impregnated in the sheet material is heated to the melting point or higher to melt. Process.
Step (B): A step of conveying and arranging the first sheet material (i) and the second sheet material (ii) in the mold.
Step (C): A step in which the first sheet material (i) and the second sheet material (ii) are pressurized and cooled in a mold to form a molded product.
Step (D): A step of taking out the integrally molded product from the mold.