JP2002067070A - Molded article of fiber reinforced plastic and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molded article 20 of a fiber reinforced plastic being excellent in mechanical characteristics of strength, rigidity, etc., and electromagnetic wave shielding characteristics and applicable also to a smooth surface decorating process such as high-brightness coating and having an outward appearance of the smooth surface free of indentation and exposure of fibers, and also provide a manufacturing method therefor. SOLUTION: The molded article 20 of the fiber reinforced plastic is constituted of a thermoplastic resin containing reinforcing carbon fibers 7, and it has the following conditions [A], [B], [C] and [D] concurrently. [A] The weight- average fiber length of the carbon fibers contained in the molded article 20 is within the range of 0.1-1.0 mm. [B] The section of the molded article 20 is within the range of 0.6-5.0 mm and the bending strength based on ASTM-D790 is 100 MPa or above. [C] The arithmetic mean roughness (Ra) of the surface of the molded article 20 based on JIS B 0601 is 2 μm or below. [D] The maximum height (Ry) of the surface of the molded article 20 based on JIS B 0601 is 10 μm or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a housing for accommodating electronic devices therein, for example, in a notebook personal computer, a digital camera, a portable telephone and the like.
More specifically, the present invention relates to a fiber-reinforced plastic molded article having a smooth outer surface that can withstand surface painting and a method for producing the same.

[0002]

2. Description of the Related Art As is well known, as a housing material for housing electronic equipment such as a notebook personal computer,
Fiber reinforced plastics have been widely used. The fiber reinforced plastic has an advantage that a molding method excellent in productivity and design freedom such as injection molding can be performed, and a molded product excellent in mechanical properties such as rigidity and strength can be obtained.

[0003] In particular, when carbon fiber is used as a reinforcing fiber, rigidity and strength are further improved. In addition, since carbon fiber is a conductive material, the carbon fiber exhibits a conductive property as a molded product, and a high electromagnetic wave shielding property is obtained. Demonstrate the characteristics. When using long fiber type carbon fiber as the reinforcing fiber,
Its performance is further improved as compared with the case where a conventional short fiber material is used.

[0004] By the way, a housing for accommodating an electronic device such as a notebook personal computer is a part that can be seen by the user and directly touched by the user's hand, so that design and appearance quality of the surface are regarded as important. For this purpose, the casing is generally decorated by exterior painting, and the surface quality is managed according to strict appearance standards.

[0005] In recent years, design diversification such as clear metallic paint and pearl clear paint has been diversified, and advanced coating techniques have been required to satisfy surface quality.
The quality required on the surface of molded products is becoming severer.
Specifically, the level required for the surface quality of a molded product in order to correspond to a clear paint which is difficult to satisfy the appearance quality is Ra (arithmetic average roughness) of 1 μm or less and Rz (ten-point average). (Roughness) is 6 μm or less. Ra is 2 μm or less and Rz is 10 μm even in a grain-like paint containing resin beads, etc.
The following are required:

[0006] The surface quality of a molded article using fiber-reinforced plastic as a molding material is often inferior after molding as compared with the case of using non-reinforced plastic. This is because the reinforcing fibers are partially exposed on the surface and become uneven, which causes a poor appearance after painting. In particular, when a long fiber pellet such that the reinforcing fiber has a length of 1 to 20 mm is used as a molding material, when compared with a case where a short fiber pellet such that the reinforcing fiber has a length of 1 mm or less is used. While the mechanical properties and the electrical properties are greatly improved, if the reinforcing fibers are not well dispersed, they are likely to be exposed on the surface of the molded product, which is likely to cause poor appearance after painting. Further, depending on the shape, unevenness due to a difference in material shrinkage called sink mark may occur, or in the case of an injection molded product, unevenness may occur along a weld line, which may cause a poor appearance after painting. In particular, when long fiber pellets are used, unevenness is large due to the influence of the orientation of the reinforcing fibers, which tends to cause a poor appearance after painting, as compared with the case where short fiber pellets are used.

Originally, the purpose is to obtain a desired surface quality only by a general injection molding process. For this purpose, the composition of the molding material has been improved, but the appearance quality is maintained while maintaining the performance and moldability. Not enough to be satisfied.

Attempts have been made to improve the appearance quality by a special injection molding process.
In Japanese Patent No. 109637, by rapidly heating a mold, injection molding and then rapidly cooling the mold,
Although a method of preventing the reinforcing fiber from being exposed to the surface of the molded article is disclosed, it is difficult to apply the method because it has an adverse effect on reducing sink marks and unevenness of a weld line. Further, there has been an attempt to improve the surface quality in a secondary processing step after molding, and the method has been partially applied as a mass production step. In this method, the surface of a molded product is polished manually using a polishing tool made of abrasive paper or nonwoven fabric and using an electric or pneumatic driving type polishing tool. As a result, the unevenness on the surface of the molded article becomes smooth, but it requires a large amount of time in the polishing step due to manual operation, and there is a problem that the polishing amount and the surface smoothness vary greatly.

[0009]

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the prior art, the present invention provides a molded product used for a housing of electronic equipment made of fiber reinforced plastic while maintaining a good surface while maintaining the performance and moldability. It is an object of the present invention to provide a molded article having an appearance quality and a method for producing the same.

[0010]

The present invention employs the following means in order to solve the above problems. That is, the fiber-reinforced plastic molded article of the present invention is a fiber-reinforced plastic molded article in which a thermoplastic resin contains reinforcing fibers made of carbon fiber, and the following [A],
A molded article made of fiber-reinforced plastic, which simultaneously satisfies the conditions of [B], [C] and [D].

[A] The weight-average fiber length of the carbon fibers contained in the molded article is in the range of 0.1 to 1.0 mm.

[B] The thickness of the molded product is 0.6 to 5.0 mm
And the bending strength based on ASTM-D790 is 100 MPa or more.

[C] JIS B 0601 on the surface of the molded product
The arithmetic average roughness (Ra) based on is not more than 2 μm.

[D] JIS B 0601 on the surface of the molded product
The maximum height (Ry) based on is not more than 10 μm.

The method for producing a fiber-reinforced plastic molded article according to the present invention has a weight average fiber length of 0.1 to 20 mm.
The carbon fiber in the range of (1) is coated with a thermoplastic resin as a reinforcing fiber, impregnated or kneaded to form a molding material, and the weight average fiber length of the carbon fiber is in the range of 0.1 to 1 mm and the content is 5
After injection molding of a molded product within the range of ４０40% by weight,
The surface of the molded product is polished so that the arithmetic average roughness (Ra) based on JIS B0601 is 2 μm or less and the maximum height (Ry) is 10 μm or less.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a partial cross-sectional view of a fiber-reinforced plastic molded product 20 (external surface 6) according to the present invention. For convenience of explanation, the figure shows a fiber-reinforced plastic molded product 20 of the present invention. Including weld line 3 and sink 4
Shows the molded product 30 immediately after the injection step in which remains.

The fiber-reinforced plastic molded article 2 of the present invention
0 is the core layer 1 in which the reinforcing fibers 7 are oriented at a high density and has high strength and high elasticity, and the skin layer 2 in which the density of the resin component with respect to the reinforcing fibers 7 is higher than that of the core layer 1 and which becomes the appearance surface. The skin layer 2 is laminated on both sides of the core layer 1 in a sandwich shape. Reference numeral 3 denotes a weld line, which has three irregularities formed on the external surface of the skin layer 2 when resin flow ends collide with each other inside the mold during injection molding. Reference numeral 4 denotes sink marks, which are caused by differences in the amount of resin shrinkage at locations where there is a difference in the thickness of the molded product. In the present invention, the irregularities due to the weld line 3 and the irregularities due to the sink mark 4 are removed and smoothed by mechanical polishing, so that a fiber-reinforced plastic molded product 20 having the surface 6 which is the appearance surface is obtained.
Each of the core layer 1 and the skin layer 2 includes a matrix resin containing reinforcing fibers made of carbon fibers.

As the matrix resin, a thermoplastic resin excellent in impact resistance and capable of being injection molded with high productivity is preferable. For example, in addition to polyesters such as polyethylene terephthalate, polybutylene terephthalate, and liquid crystal polyester, polyolefins such as polyethylene, polypropylene, and polybutylene, polyoxymethylene, polyamide, polycarbonate, polystyrene, styrene / acrylonitrile copolymer, and acrylonitrile / butadiene styrene copolymer Polymer, acrylate / styrene / acrylonitrile copolymer, polymethylene methacrylate, polyvinyl chloride, polyphenylene sulfide, polyphenylene ether, polyimide, polyamideimide, polyetherimide, polysulfone, polyethersulfone,
Polyether ketone, polyether ether ketone and the like can be used. Also, these copolymers, modified products, and blended resins of two or more types can be used. Further, in order to further improve impact resistance, a resin obtained by adding an elastomer or a rubber component to the above resin can be used.

The type of the reinforcing fiber 7 is not particularly limited, and two or more types of fibers such as glass fiber, aramid fiber, and carbon fiber may be used in combination. In order to obtain electrical characteristics, it is preferable that at least a part thereof is carbon fiber. As the carbon fiber, a polyacrylonitrile (PAN) -based carbon fiber can be used, and a pitch-based carbon fiber can also be used. In order to obtain good mechanical properties, the tensile strength of carbon fiber alone is in the range of 2,000 to 6,000 MPa,
The tensile modulus is preferably in the range of 100 to 800 GPa. The carbon fiber in the molded product may be a continuous fiber or a discontinuous fiber, but in order to obtain good mechanical and electrical properties, the carbon fiber has a weight average fiber length of 0.1 to 1.0.
mm. If the thickness is less than 0.1 mm, the excellent properties of carbon fiber such as high strength, high elasticity and high conductivity cannot be sufficiently exhibited, and if it exceeds 1.0 mm, the fiber is easily exposed to the surface of the molded product. Also, when the surface of the molded article is polished, the fibers may fall off the molded article, making it difficult to control the surface roughness of the molded article with high precision, and forming the molded article with a good surface appearance. Unsatisfactory products cannot be obtained.

The thickness of the molded product is 0.6 to 5.0 mm.
Is preferably within the range. When the wall thickness is less than 0.6 mm, the fibers are easily exposed to the surface of the molded product, and sufficient rigidity cannot be obtained.
It becomes a fragile structure and is unsuitable. When the wall thickness is more than 5.0 mm, sufficient strength and rigidity can be obtained, but irregularities on the surface of the molded product due to the difference in the amount of resin shrinkage become remarkable, making it difficult to obtain a good surface appearance. . Further, it is preferable that the bending strength of the molded product is in the range of 100 MPa or more. If the bending strength is less than 100 MPa, even if the thickness of the molded product is set to be large, the molded product may be broken by an external force during the secondary processing step or during use of the product, which is not preferable. In particular, when the surface of the molded article is processed by mechanical polishing, the load pressure of the polishing head on the molded article is directly transmitted to the molded article through the abrasive, and the molded article may be broken, which is not preferable.

The carbon fiber content in the molded article is preferably 5 to 40% by weight in order to sufficiently exhibit the mechanical and electrical properties of the molded article while maintaining the moldability. When the content is less than 5% by weight, the mechanical properties and electrical properties, which are excellent properties of carbon fibers, cannot be sufficiently exhibited. If the content is more than 40% by weight, the flowability of the fiber-reinforced resin is reduced, adversely affecting the moldability, and the exposure of the reinforcing fibers to the surface of the molded article becomes conspicuous, and the molding having a good appearance is obtained. It becomes difficult to obtain goods.

The weld line 3 and the sink mark 7 were mechanically polished and removed from the material after the injection molding. As a result, the outer surface, which is the surface 6, had an arithmetic average roughness Ra within a range of 2 μm or less. The surface has a height Ry within a range of 10 μm or less and a ten-point average roughness Rz within a range of 10 μm or less.

When Ra is within the above range, the surface of the molded article becomes smooth, and even when a high-brightness and smooth decoration such as metal coating or pearl clear coating is applied thereon, the surface of the molded article is smooth. It is possible to obtain an appearance quality having a good surface appearance, in which minute irregularities hardly appear. In addition, when Ry is within the above range, the undulating irregularities on the surface of the molded product are suppressed, and the molded product can be subjected to high-brightness and smooth decorative processing such as metal coating or pearl clear coating. Irregularities due to weld lines and sink marks on the surface hardly appear, and a good surface appearance quality can be obtained. When Rz is within the above range, the same effect as when Ra is within the above range can be expected. When each surface roughness is out of the above range, fine irregularities and undulating irregularities can be confirmed on the decorative film, and when a smooth external surface is required, it causes poor appearance. As a method of adjusting Ra and Rz, a desired surface roughness can be obtained by optimizing the type and count of the abrasive used in the polishing step, and controlling the polishing direction, the polishing load, and the polishing rate. As a method of adjusting Ry,
Polishes weld lines and sink marks that appear on the material surface.
In order to remove it, it is necessary to have a sufficient amount of polishing at a sufficient depth. For that purpose, it is important to optimize the type and number of the abrasive used in the polishing process and control the polishing direction, polishing load, polishing rate It is. The surface roughness of the above molded product is measured according to JIS
It is measured by a stylus type surface roughness measuring instrument specified in B0651. The surface roughness of the decorative film surface when the coating process is performed on the polished surface of the molded product is measured in the same manner, and when measuring the surface roughness of the molded product under the decorative film, metal In plating, reverse plating is performed or the plating film is physically peeled off, and in coating, the coating film is peeled off using a methylene chloride solvent. Measure with a measuring instrument.

Although not described in FIG. 1, the surface of the molded article 20 of the present invention is usually coated with a metal by a method such as plating or vapor deposition, or spray-coated with a solvent or a powdery paint. Electrostatic coating is applied to form a so-called decorative film. As the material of the metal coating, any one of copper, nickel, chromium, zinc, gold, silver, aluminum, titanium and the like, or a metal alloy thereof is used. As the coating material, various resin coating materials or coating materials obtained by adding an inorganic filler or metal particles to a resin are used. The thickness of the decorative film is usually processed in the range of 1 to 100 μm. In the molded article of the present invention, a decorative film such as a metal coating or a coating as described above is formed on a smooth surface appearance surface, and the appearance quality is further improved. As described above, since the molded product 20 of the present invention has the surface roughness of the above-described precision, even if a decoration process such as painting is performed after polishing, the obtained molded product is polished through the decorative film. An excellent quality is obtained in which the eyes and a part of the reinforcing fibers are not exposed, and the unevenness of the appearance surface does not occur.

Next, a method for producing a fiber-reinforced plastic molded article of the present invention will be described in the order of steps. 1. Molding Step First, the content of carbon fiber in the whole molding material is 5 to 4%.
Pellets of a molding material are prepared by coating, impregnating, or kneading a thermoplastic resin on a reinforcing fiber having a fiber length within a range of 0% by weight and a fiber length of 1 to 20 mm. Then, the pellets are charged as a molding material into an injection molding machine, melted and kneaded, and the kneaded molding material is preliminarily formed into a desired molded article 40 having a rib 9 and a boss 10 of FIG. Into the mold cavity machined to obtain
After solidification, the mold is released to obtain a desired molded product 30. The cross section of the molded product 30 immediately after molding has a sandwich structure in which the skin layers 2 are laminated on both surfaces of the core layer 1 as shown in the figure. In addition, irregularities due to weld lines 3 and sink marks 4 are generated on the surface. 2. Surface Polishing Step Next, as shown in FIG. 2, the surface 5 of the molded product 30 immediately after the injection molding is applied to a surface 5 of the molded product 30 by a grindstone grinder having a grindstone 8.
Polishing is performed to a depth d in the range of １００100 μm. For this polishing, in addition to a grindstone device, for example, a polishing device such as a belt polishing machine or a buff polishing device may be used. The purpose is to smooth the weld lines 3 and the sink marks 4, and the polishing amount d is 100
If it is larger than μm, the effect of smoothing the irregularities of weld lines and sink marks is high, but the thickness of the molded product will be reduced, deviating from the specified dimensions, and reducing the rigidity and strength of the molded product. It becomes a factor. Such an excessive amount of polishing will scrape off the skin layer of the molded product, exposing the core layer in which the reinforcing fibers are oriented at a high density to the surface, and performing plating, vapor deposition, ion plating in the subsequent steps. After the steps of sputtering, film coating, electric flocking and painting, it causes suction and roughness on the surface. Conversely, if it is less than 5 μm, the effect of smoothing the irregularities of weld lines and sink marks is small. Further, in the main polishing step, polishing is performed so that the arithmetic average roughness Ra of the polished surface after polishing is 2 μm or less. In this case, Ra is 2
If it exceeds μm, it will appear as fine irregularities on the surface after painting, which will cause poor painting. As a processing condition for achieving such polishing accuracy, the number of abrasives is # 180.
~ # 2000, the rotation speed of the abrasive is 50 at the outer periphery of the abrasive.
It is preferred to be within the range of ２０００2000 m / min.

As the material of the belt and the grindstone, which are the abrasives of the above-mentioned polishing apparatus, alumina, silicon carbide, emery, garnet and the like can be used. The buff can be classified into a bias type, a disc type, a brush type, and the like. As the type of the buffing abrasive, an oily solid abrasive, a non-oily solid abrasive, an emulsion type liquid abrasive, or the like can be used. The polishing method may be either a dry method or a wet method, but a wet polishing method is preferred from the viewpoint that the polishing powder can be efficiently cleaned. In addition, as an apparatus used for the above-mentioned polishing,
A hand-held polishing method using a tool driven by electric or compressed air may be used, but for mass production, an apparatus capable of continuously performing line polishing is preferable. Specifically, the surface of the molded product flowing in the line is used alone or in combination with the contact wheel type belt polishing method, platen type belt polishing method, free wheel belt polishing method, whetstone grinding method, buff polishing method, etc. It is preferable to use a molded product subjected to polishing. This step is a pretreatment step for performing the next surface decoration step. 3. Surface Decorating Step Next, the surface 6 after polishing of the molded article 20 is subjected to surface decorating processing such as plating, vapor deposition, ion plating, sputtering, film coating, electric flocking or painting. The purpose is to obtain a better appearance. As a plating method, copper plating, nickel plating, chromium plating, zinc plating, gold plating, gold alloy plating, silver plating, multilayer plating, electroless plating, or the like can be used. As other metal coating materials, in addition to the above-mentioned metals, simple metals including aluminum and titanium and alloys thereof can be used. As the coating, a conductive paint for imparting conductivity or an appearance paint for improving appearance can be applied. As the conductive paint, a silver paint, a nickel paint, a nickel-coated copper paint, or the like can be applied.
Exterior paints include acrylic paints, acrylic urethane paints, polyester paints, unsaturated polyester paints,
Polyamide paint, enamel paint, epoxy paint,
Silicone paints, lacquer paints, fluorine paints and the like can be applied. In addition, fillers such as resin beads, metal particles, and mica may be added to these resin paints. The thickness of the surface decoration film is preferably 1 to 100 μm.

The use of the molded article 20 of the present invention or a molded article whose surface is further subjected to decoration processing is not particularly limited, but the excellent mechanical properties and electrical properties which are its characteristics are sufficiently exhibited. In order to do so, it is required to be applied to a housing that houses electronic devices such as notebook personal computers, digital cameras, and mobile phones that require characteristics such as impact resistance, high strength, high rigidity, and electromagnetic wave shielding. preferable. Further, since such a molded product has a smooth external surface, it is more preferably applied as a casing used for painting.

[0029]

EXAMPLES Example 1 First, as a reinforcing fiber 7 of a molded article 20 of the present invention, a PAN long fiber carbon fiber bundle (having a tensile strength of 4) was used.
900 MPa, tensile modulus of 230 GPa, number of filaments of 12,000, fineness of 800 TEX, specific gravity of 1.8, volume resistivity of 1.6 × 10 ⁻³ Ω · cm) are passed through a coating die for covering electric wires, and are passed through an extruder for 250. Nylon 6 resin melted at ℃ (weight average molecular weight 15,000)
Was discharged to obtain resin-coated carbon fibers in which the periphery of the carbon fiber bundle was coated with nylon resin 6. Next, after cooling this resin-coated carbon fiber to room temperature, the strand-cutter was used for 7 mm.
To obtain a long fiber carbon fiber reinforced pellet for injection molding. The carbon fiber content in the pellets is 20% by weight, and the weight average carbon fiber length is 7 mm. The pellets were molded with an injection molding machine having a clamping force of 350 tf,
An injection molded product having a housing shape of FIG. 3 having a size of 50 mm × 200 mm and a thickness of 1.5 mm was obtained. In this molded product, two bosses 10 for press-fitting metal bits are installed at a pitch of 150 mm. The bending strength of this molded product is 250 MPa. The entire exterior surface 5 of the molded product is a wet automatic belt polishing machine T26MW manufactured by Kikukawa Iron Works Co., Ltd., and the polishing belt is “Trisact 3M” manufactured by Sumitomo 3M Limited.
Using a count A45 (equivalent to # 320) of No. 243WA ”, polishing was continuously performed so that the polishing amount d was 30 μm to obtain a desired molded product 20. The surface roughness of the polished molded product was measured according to JIS B. 0651, Ra was measured.
Was 0.6 μm, Rz was 5.0 μm, and Ry was 5.6 μm. The appearance was applied to the surface 6 of the polished molded product 20 to obtain a coated product. The paint used was made by Origin Electric Co., Ltd. Origin primer E-03 (two-part epoxy type) was used for the undercoat, and Origin Plate Z-MP (two-part acrylic urethane type) was used for the top coat. To make the total film thickness 40 μm. The appearance of this coated product is good. <Example 2> A housing-like injection molded product was obtained in the same manner as in Example 1. The injection-molded article was used in the same polishing apparatus as in Example 1, and the polishing belt was a count A16 (equivalent to # 600) of "Trisact 3M243WA" manufactured by Sumitomo 3M Limited.
And a desired molded product was obtained by polishing continuously so that the polishing amount d was 30 μm. As for the surface compatibility of the polished molded product, Ra was 0.3 μm, Rz was 3.0 μm, and Ry was 3.
It was 6 μm. The polished molded product was subjected to appearance coating in the same manner as in Example 1 to obtain a coated product. The appearance of this coated product is good. <Example 3> A casing-like injection-molded product was obtained in the same manner as in Example 1. The entire exterior surface of the injection-molded product was manufactured using an SV26-2 type orbital sander manufactured by Kikukawa Iron Works Co., Ltd., and a nonwoven fabric equivalent to # 320 was used as an abrasive, and the polishing amount d was 50.
It was polished continuously to a thickness of μm to obtain a desired molded product. The surface compatibility of this polished molded product is Ra 0.6 μm.
m and Rz were 6.0 μm and Ry was 9.5 μm. The polished molded product was subjected to appearance coating in the same manner as in Example 1 to obtain a coated product. The appearance of this coated product is good. <Comparative Example 1> A housing-like injection molded product was obtained in the same manner as in Example 1. The entire appearance surface of the injection molded article is not polished. The surface compatibility of this molded product was Ra 1.1 μm and Rz 1
0.2 μm and Ry were 13.2 μm. The appearance was applied to this molded product in the same manner as in Example 1 to obtain a coated product. The appearance of this painted product can clearly be confirmed with weld lines and sink marks. <Comparative Example 2> A housing-like injection molded product was obtained in the same manner as in Example 1. Using a double action sander as an electric tool, the entire appearance surface of the injection molded product was used as an abrasive and # 320
A desired molded product was obtained by manually polishing a considerable amount of nonwoven fabric so that the polishing amount d was 50 μm. The surface compatibility of the polished molded product was Ra 0.5 μm, Rz 4.0 μm,
Rmax was 4.5 μm. The polished molded product was subjected to appearance coating in the same manner as in Example 1 to obtain a coated product. Although the appearance of this coated product is almost satisfactory, a large amount of polishing time is required, and the individual coated products vary greatly. <Comparative Example 3> A housing-like injection molded product was obtained in the same manner as in Example 1. The injection molded product was continuously polished using the same polishing apparatus and polishing belt as in Example 1 so that the polishing amount d was 2 μm, to obtain a desired molded product. The surface compatibility of the polished molded product was Ra 0.9 μm, Rz 9.5 μm, and Ry.
Was 12.0 μm. The polished molded product was subjected to appearance coating in the same manner as in Example 1 to obtain a coated product. The appearance of this painted product can clearly be confirmed with weld lines and sink marks. Comparative Example 4 A housing-like injection-molded product was obtained in the same manner as in Example 1. The injection molded product was continuously polished using the same polishing apparatus and polishing belt as in Example 1 so that the polishing amount d was 150 μm, to obtain a desired molded product. The surface compatibility of this polished molded product was Ra 0.5 μm, Rz 5.0 μm, R
y was 5.2 μm. The polished molded product was subjected to appearance coating in the same manner as in Example 1 to obtain a coated product. In the appearance of the coated product, a part of the reinforcing fiber is exposed on the surface due to excessive shaving, and it is confirmed that the paint is sucked. Comparative Example 5 A housing-like injection-molded product was obtained in the same manner as in Example 1. The injection-molded product was used in the same polishing apparatus as in Example 1, and the polishing belt was manufactured using Sumitomo 3M Co., Ltd. “Trisact 3M243WA” with a count A100 (corresponding to # 180) so that the polishing amount d was 30 μm. The desired molded product was obtained by continuous polishing. The surface compatibility of this polished molded product was Ra 2.5 μm, Rz 15.0 μm, and Ry.
Was 17.8 μm. The polished molded product was subjected to appearance coating in the same manner as in Example 1 to obtain a coated product. In the appearance of this coated product, the unevenness of the weld line and the sink mark can be smoothed, but the polished eyes can be clearly confirmed from the coating film. Examples 1, 2, 3, and Comparative Examples 1, 2, 3, 4,
In order to evaluate the mechanical properties of No. 5, the following bending test was performed. The outer peripheral end of the polished molded product is supported by a fulcrum, and the amount of deflection of the central portion of the molded product when a certain concentrated load is applied to the central portion of the molded product is measured. Was. The flexure amounts of Examples 1, 2, and 3 are not different from the flexure amounts of the molded product of Comparative Example 1 without polishing, and a large decrease in mechanical characteristics (rigidity) is not recognized. Further, Examples 1, 2, and 3
In order to evaluate the electric characteristics of Comparative Examples 1, 2, 3, 4, and 5, the following electric resistance value measurement test was performed. After inserting a metal insert nut into two bosses of the polished molded product by hot pressing, the electrical resistance value between the two metal nuts was measured, and the results shown in Table 1 were obtained. The electrical resistance values of Examples 1, 2 and 3 were not different from the electrical resistance values of the molded product of Comparative Example 1 without polishing, and no significant decrease in electrical characteristics (conductivity) was observed.

Table 1 summarizes the above results.

[0031]

[Table 1]

From this table, as a coated product of a fiber-reinforced plastic molded product, in order to obtain a good surface appearance quality free from irregularities due to weld lines or sink marks, defects due to fiber exposure, defects due to polishing eye exposure, etc. The weight average fiber length of the reinforcing fibers contained in the molded product before coating is in the range of 0.1 to 1.0 mm, and the thickness of the molded product is in the range of 0.6 to 5.0 mm. And a bending strength of 10
It is necessary to be within the range of 0 MPa or more, and further, it is necessary that the arithmetic mean roughness Ra of the surface of the molded product is within the range of 2 μm or less and the maximum height Ry is within the range of 10 μm or less. I found it.

[0033]

【The invention's effect】

[Brief description of the drawings]

FIG. 1 is a partial sectional view of one embodiment of a fiber-reinforced plastic molded product according to the present invention.

FIG. 2 is an explanatory view showing one embodiment of a polishing step of a fiber-reinforced plastic molded product according to the present invention.

FIG. 3 is a perspective view of an embodiment of a fiber-reinforced plastic molded product according to the present invention.

[Explanation of symbols]

 1: Core layer 2: Skin layer 3: Weld line 4: Sink 5: Surface before polishing 6: Surface (appearance after polishing) 7: Reinforcing fiber 8: Grinding stone (polishing device) 9: Rib 10: Boss 20: Fiber Reinforced plastic molded product (molded product of the present invention) 30: Fiber reinforced plastic molded product (after injection molding)

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) C08L 101: 00 C08L 101: 00 F term (reference) 4F006 AA12 AA15 AA17 AA22 AA31 AA35 AA36 AA39 AA40 AA53 AB19 AB24 AB34 AB35 AB37 AB38 AB39 AB73 BA15 DA01 DA04 EA04 4F072 AA02 AA04 AA08 AB06 AB09 AB10 AD04 AD05 AD06 AD09 AD37 AD41 AD42 AD44 AD45 AD46 AH05 AK15 AL11 4F206 AA29 AB25 AD16 AH42 AM34 AM36 JA07 JW24

Claims (12)

[Claims] 1. A molded article made of a fiber-reinforced plastic comprising a thermoplastic resin containing reinforcing fibers made of carbon fibers, wherein the following conditions [A], [B], [C] and [D] are satisfied. A molded article made of fiber-reinforced plastic, which is provided at the same time. [A] The weight-average fiber length of the carbon fibers contained in the molded product is in the range of 0.1 to 1.0 mm. [B] The thickness of the molded product is in the range of 0.6 to 5.0 mm, and the bending strength based on ASTM-D790 is 10
0 MPa or more. [C] The arithmetic mean roughness (Ra) of the surface of the molded article according to JIS B 0601 is 2 μm or less. [D] The maximum height (Ry) of the molded product surface according to JIS B 0601 is 10 μm or less. 2. The fiber-reinforced plastic molded article according to claim 1, further comprising the following condition [E]. [E] The ten-point average roughness (Rz) of the surface of the molded product according to JIS B 0601 is within a range of 10 μm or less. 3. A molded article having a carbon fiber content of 5-4.
The fiber-reinforced plastic molded product according to claim 1 or 2, wherein the content is within a range of 0% by weight. 4. The fiber-reinforced plastic molding according to claim 1, wherein the surface roughness [C] to [E] of the molded product is obtained by polishing. Goods. 5. The fiber-reinforced plastic molded product according to claim 1, further comprising a decorative film formed on a surface of the molded product. 6. The arithmetic average roughness (Ra) of the surface of the decorative film.
The height and the maximum height (Ry) are within the range of 0.5 to 10 times the arithmetic average roughness (Ra) and the maximum height (Ry) of the surface of the molded article, respectively. A molded article made of fiber-reinforced plastic according to Crab. 7. A height of 1 to 100 mm, a width of 0.1 to 5 mm,
The molded article made of fiber reinforced plastic according to any one of claims 1 to 6, wherein there is at least one rib having a length in a range of 1 to 1000 mm. 8. The fiber-reinforced plastic molded article according to claim 1, wherein at least one boss having a height of 1 to 100 mm and an outer diameter of 1 to 50 mm is present. 9. The fiber-reinforced plastic molded article is obtained by injection molding using a long fiber pellet having a fiber length of 1 to 10 mm of the reinforcing fiber. A molded article made of a fiber-reinforced plastic according to item 1. 10. A fiber reinforced plastic housing, wherein an electronic device is accommodated inside the fiber reinforced plastic molded product according to any one of claims 1 to 9. 11. A carbon fiber having a weight average fiber length in the range of 0.1 to 20 mm as a reinforcing fiber, which is coated, impregnated or kneaded with a thermoplastic resin to form a molding material. After injection molding of a molded product having a length in the range of 0.1 to 1 mm and a content in the range of 5 to 40% by weight, the surface of the molded product is subjected to arithmetic average roughness based on JIS B 0601. A method for producing a fiber-reinforced plastic molded product, wherein (Ra) is 2 μm or less and the maximum height (Ry) is polished to a range of 10 μm or less. 12. The polished surface is further subjected to any one of plating, vapor deposition, ion plating, sputtering, film coating, electric flocking, and painting. 12. The method for producing a fiber-reinforced plastic molded article according to item 11.