JP2018080230A - Fiber-reinforced thermoplastic resin molded body and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber-reinforced thermoplastic resin molded body which can be molded without causing large thickness unevenness even in a large-sized member and a complicated shape, and keeps a fixed value even in elastic modulus and strength of an overlapped portion.SOLUTION: There is provided a fiber-reinforced thermoplastic resin molded body in which two or more base material sheets are partially overlapped without formation of butt portions and the overlapped portion is bonded by melt-boding, where the base material sheet is a fiber-reinforced thermoplastic resin sheet which contains 30-85 mass% of a reinforced fiber and 70-15 mass% of a thermoplastic resin, the reinforced fiber has a fiber length of 10-100 mm and forms a fiber bundle and a length axis of the fiber bundle is randomly oriented in a sheet surface, and a boundary portion derived from the base material sheet is provided on the surface of the molded body.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fiber reinforced thermoplastic resin molded body having a boundary portion derived from a raw material base sheet on the surface of the molded body, and a method for producing the same.

  In recent years, fiber reinforced resins with high rigidity, high strength, and high lightening effect have attracted attention from the viewpoint of energy problems and environmental problems. In particular, a fiber reinforced thermoplastic resin using a thermoplastic resin as a matrix resin is excellent in processability and impact resistance, and application to the field of vehicles such as automobiles and the field of construction is being studied.

  In the fiber reinforced thermoplastic resin molded body, it is desirable to be molded from a single base material from the viewpoint of strength and the like. However, in the case of molding a relatively large molded body such as an automobile member, a single base material is used. Is limited in size that can be manufactured in terms of weight, ease of handling, and cost. Therefore, a method of arranging a plurality of small base materials side by side to obtain a molded body may be used. Further, even when a molded body having a complicated shape is molded, a method of obtaining a molded body using a plurality of base materials instead of a single base material may be used.

  However, in the molded body formed by arranging a plurality of base materials side by side, the fibers are divided at the boundary between the base materials, so that the mechanical properties of the joint portion are reduced as compared with other portions. There is a problem.

  In Patent Document 1, in order to obtain a relatively large fiber-reinforced resin molded article, a reinforcing fiber base is partially overlapped before the resin is impregnated to produce a larger base material, A technique for forming a molded body by impregnating a material with a resin is described. However, at the stage of molding by resin impregnation, a large molding apparatus is required, which causes a problem that the manufacturing cost is increased.

  Patent Document 2 describes a technique for preventing a joint from becoming a strong singularity or a defect by needle punching and joining the ends of a mixed fiber mat composed of reinforcing fibers and thermoplastic resin fibers. Has been. However, since the fibers in the joint portion are entangled with each other by needle punching, the fluidity at the time of molding is lowered, and it is difficult to mold a molded body having a complicated shape.

  In Patent Document 3, a thermoplastic resin reinforced with randomly oriented discontinuous reinforcing fiber mats is molded so that the bonded cross section has an inclined structure, thereby maintaining a large-sized molded body while maintaining the mechanical characteristics of the bonded portion. The method of obtaining is described. However, in order to form an inclined structure, it is necessary to increase the joining length when the substrate thickness increases, and the discontinuous reinforcing fiber mat with many fiber entanglements does not have sufficient fluidity, and the thickness variation of the molded body There was a problem that would become larger. Further, in this bonded cross section, since the surface-side bonded surface is nearly vertical, there is a problem that becomes a drawback when a bending force is applied.

JP 2010-150368 A JP 10-325072 A JP 2014-177117 A

  The present invention has been made against the background of such prior art problems. That is, the object of the present invention is a molded body formed by overlapping the base material and having a boundary portion derived from the base material sheet on the surface, and can be formed without large thickness unevenness even in a large member or a complicated shape. An object of the present invention is to provide a fiber reinforced thermoplastic resin molded body that can maintain a constant value in the elastic modulus and strength of the overlap portion.

As a result of intensive studies, the present inventors have found that the above problems can be solved by the following means, and have reached the present invention. That is, the present invention is as follows.
(1) A fiber-reinforced thermoplastic resin molded body in which two or more base material sheets do not form a butted portion, partially overlap, and the overlap portion is joined by fusion joining, The sheet contains 30 to 85% by mass of reinforcing fibers and 70 to 15% by mass of thermoplastic resin, and the reinforcing fibers have a fiber length of 10 to 100 mm to form a fiber bundle. The length axis of the fiber bundle Is a fiber-reinforced thermoplastic resin sheet that is randomly oriented in the sheet plane, and has a boundary portion derived from the base sheet on the surface of the molded body. .
(2) The fiber-reinforced thermoplastic resin molded article according to (1), wherein the length of the overlap portion of the molded article is 30 mm or more.
(3) The fiber reinforced thermoplastic resin molded article has a bending elastic modulus and bending strength of the overlap portion of 70% or more compared to the elastic modulus and bending strength of the portion other than the overlap portion, respectively. The fiber-reinforced thermoplastic resin molded article according to (1) or (2).
(4) Two or more base material sheets are arranged so as to partially overlap each other without forming a butt portion, and are stamped and integrated into any one of (1) to (3) Of manufacturing a fiber-reinforced thermoplastic resin molded article.

  The molded body of the present invention is a molded body having a boundary portion derived from the base sheet on the surface of the molded body, and is formed by overlapping the base sheet. Therefore, the effect of facilitating the molding of a large-sized member having a unit area or more of the base sheet can be obtained, and further the effect of preventing the elastic modulus and strength of the overlap portion from being reduced can be obtained. Is also very small.

It is an example (schematic figure seen from the top) of the overlap of a base material sheet in the molded object of the present invention. It is the schematic which showed the arrangement | positioning method (E) of the base material sheet for shape | molding the molded object in an Example, and the molded object (F) after shaping | molding. It is the schematic which showed the arrangement | positioning method (G) of the base material sheet for shape | molding the molded object in a comparative example, and the molded object (H) after shaping | molding. It is the schematic (top view (I), side view (J)) which showed the position which cut out the bending test piece from the molded object in an Example, and the indenter contact part of the bending test. It is the schematic (top view (K), side view (L)) which showed the position which cut out the bending test piece from the molded object in a comparative example, and the indenter contact part of the bending test.

  The fiber-reinforced thermoplastic resin molded body of the present invention is a molded body having a base material sheet on the surface of the molded body, that is, a boundary derived from the fiber-reinforced thermoplastic resin sheet, and has two or more base material sheets in the mold. It is obtained by overlapping and arranging so that a butt portion does not occur and integrally molding.

The boundary part derived from the base material sheet on the surface of the molded body in the present invention is the boundary of the end of the base material sheet that is overlapped on the surface side of the molded body among the overlapped base material sheets. A point where the surface appears discontinuous. A similar boundary portion is also provided on the opposite surface (back surface side) of the molded body.
When the base sheet is partially overlapped and integrally molded, the part where the base sheet overlaps melts and flows, and the surface of the molded body is flat. The surface of the molded body of the present invention does not have a step due to overlapping the base sheet, but the boundary portion can be visually confirmed.

  The base sheet used in the present invention contains 30 to 85% by mass of reinforcing fibers and 70 to 15% by mass of thermoplastic resin, and the reinforcing fibers have a fiber length of 10 to 100 mm and form a fiber bundle. A fiber reinforced thermoplastic resin sheet in which the length axis of the fiber bundle is randomly oriented in the sheet surface.

  Although the manufacturing method of the base material sheet used for this invention is not specifically limited, For example, the manufacturing method which passes through the following processes is preferable. A thermoplastic resin and an optional stabilizer are premixed at a predetermined ratio and supplied to a hopper of a screw type extruder whose temperature is controlled to be equal to or higher than the melting point of the thermoplastic resin. The molten resin is measured at the number of revolutions of the gear pump and supplied upstream of the impregnation extruder whose temperature is adjusted to be equal to or higher than the melting point of the resin. On the other hand, roving-like reinforcing fibers are expanded and supplied downstream of the impregnation extruder. Reinforced fiber roving is impregnated and defoamed with resin pressure in an extruder for impregnation equipped with a slit die with an opening at the downstream end, and predetermined reinforcing fibers and thermoplastics discharged from the downstream opening. A tape-shaped reinforcing fiber composed of a resin mass ratio and a prepreg composed of a thermoplastic resin are cooled, and the tape-shaped prepreg is cut into a predetermined length of 10 mm or more and 100 mm or less. Tape-shaped prepregs (strip-shaped prepregs) cut to a predetermined length are randomly scattered and laminated in a flat shape, and compressed using a compression molding machine in which a mold whose temperature has been adjusted above the melting point of the thermoplastic resin in advance is set. Those manufactured by a method of cooling the mold and then opening the mold to obtain a plate-like substrate sheet are preferable.

In the base sheet, the reinforcing fibers form a fiber bundle. The fiber bundle in the base sheet has a strip shape. Here, a fiber bundle having a single fiber surface interval of 30 μm or less and a difference in azimuth of the length axes of the single fibers of 15 degrees or less is referred to as a fiber bundle. When the base sheet is produced by the above preferred production method, the reinforcing fibers form a fiber bundle. The fiber bundle in the base sheet can also be confirmed by incinerating the thermoplastic resin at about 500 ° C. and measuring the number of single fibers from the remaining fiber bundle.
In the base sheet, the length axis of the fiber bundle is randomly oriented in the sheet plane. When the base sheet is manufactured by the above preferable manufacturing method, the length axis of the fiber bundle is randomly oriented in the sheet plane. The length axis of the fiber bundle is randomly oriented in the sheet plane. The base sheet is magnified about 100 times with a microscope, and the orientation angle is obtained for the fiber bundle observed in an arbitrary field of view. It can also be confirmed from the fact that the orientation angle is random.

  The above base sheet retains its laminated structure even when it is laminated, so that the decrease in elastic modulus and strength is suppressed, and it flows while causing slippage between strip-shaped prepreg layers, so that it has fluidity. It is also preferable from the viewpoint of good, that is, excellent moldability.

Although the magnitude | size of the base material sheet used for this invention is not restrict | limited in particular, It is preferable that it is a projection area of 0.25 m < ² > or less from viewpoints, such as a weight, ease of handling, and cost.

  The thickness of the base sheet used in the present invention is preferably 1 mm or more. If it is less than 1 mm, the number of laminated tapes is small, and it is not preferable because the reinforcing effect of the reinforcing fibers is difficult to obtain and the fluidity at the time of molding is lowered. The upper limit of the thickness of the substrate sheet is not particularly limited, but is preferably 10 mm or less from the viewpoint of weight and ease of handling.

  The fiber length of the reinforcing fibers in the base sheet used in the present invention is 10 mm or more, and more preferably 15 mm or more. If it is less than 10 mm, the mechanical properties are lowered, which is not preferable. In view of mechanical properties, continuous fibers are preferable, but fluidity in the mold at the time of molding is necessary, so that a tape-shaped prepreg cut into shorter lengths (strip-shaped prepreg) is used. Therefore, the fiber length of the reinforcing fiber corresponds to the length of the strip-shaped prepreg, and the upper limit of the fiber length is preferably about 100 mm.

  Examples of the reinforcing fiber used in the present invention include a high elastic modulus fiber that is solid at the processing temperature of the thermoplastic resin used, and specifically includes glass fiber, carbon fiber, aramid fiber, steel fiber, polyphenylene. Sulfide fibers, kenaf, cotton, etc. can be used. Among these, glass fibers and carbon fibers having particularly high elastic modulus are preferable, and carbon fibers are particularly preferable. As the carbon fiber, its production method is not particularly limited, but a fiber such as polyacrylonitrile fiber or cellulose fiber is treated in air at 200 to 300 ° C. and then fired in an inert gas at 1000 to 3000 ° C. or more. Carbon fibers having a tensile strength of 2 GPa or more and a tensile elastic modulus of 200 GPa or more produced by carbonization are preferable. The diameter of the single fiber used in the present invention is not particularly limited, but is preferably 3 to 9 μm from the production line process of the composite. If it is less than 3 μm, impregnation and defoaming are difficult, and if it exceeds 9 μm, the specific surface area becomes small and the effect of combining may be reduced. The carbon fiber used in the present invention is preferably treated for improving adhesion by wet oxidation with air or nitric acid, dry oxidation, heat cleaning, whiskerizing, or the like. Moreover, it is preferable that the carbon fiber used for manufacture of the base material sheet in this invention is converged by the sizing agent which softens at 120 degrees C or less from the handleability of a work process.

  The content of the reinforcing fiber in the base sheet used in the present invention is 30% by mass to 85% by mass, and preferably 55% by mass to 70% by mass. If it is less than 30% by mass, the reinforcing effect of the reinforcing fibers becomes insufficient, which is not preferable. Conversely, when it exceeds 85 mass%, since impregnation with a thermoplastic resin becomes difficult, it is not preferable.

  The thermoplastic resin used in the present invention is not particularly limited, but representative examples include polyamide resins such as polyamide 6, polyamide 12, polyamide 66, and polyamide 46, and polyester resins such as polyethylene terephthalate and polybutylene terephthalate. , Polyolefin resins such as polyethylene and polypropylene, polyether ketone resins, polyphenylene sulfide resins, polyether imide resins, polycarbonate resins and the like. Moreover, the modified body of these each resin may be used, and multiple types of resin may be blended and used. Of these, polyamide resins and modified polyolefin resins are preferred from the viewpoint of ease of handling and cost. The modification of the modified polyolefin resin is preferably modification with an acid, epoxy, or isocyanate in order to increase the adhesive strength with the reinforcing fiber.

  The base sheet used in the present invention has additives such as a crystal nucleating agent, a lubricant, an antioxidant, and a flame retardant for the purpose of improving physical properties, moldability, and durability, together with the thermoplastic resin. Can be blended. The total amount of these components is preferably 5 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin.

  The overlap length of the molded body of the present invention is preferably 30 mm or more. When the overlap length is less than 30 mm, or when the molded body has a sheet butt portion, the bending elastic modulus and bending strength of the joint portion are not preferable.

  Here, as shown in FIGS. 2 and 4, the length of the overlap portion of the molded body is the length between the end portions of the boundary portion derived from the base material sheet, which occurs on the front surface and the back surface of the obtained molded body. Say (length shown by double-headed arrow). The length in this case is a distance in a projection view when the molded body is viewed from the upper surface.

  The molded body having the overlap length as described above does not have a butt portion and the base sheet may be stacked in any way as long as the overlap length of the molded body is 30 mm or more. For example, as shown in FIGS. 1 (A) and 1 (B), rectangular and trapezoidal base sheets may be overlapped so that the end faces of the respective bases are parallel, or FIG. 1 (C). As described above, one base sheet may be formed by overlapping one having a narrower width than the other base sheet. Moreover, as shown in FIG. 1D, one of the base material sheets may be disposed obliquely, and the overlap portion may have a triangular shape. The overlap length in this case refers to the minimum length between the boundary near the apex of the triangle and the boundary at the bottom. In (A) to (D) of FIG. 1, the length indicated by the double arrow is the length of the overlap portion.

  The molded body of the present invention can be obtained by arranging two or more substrate sheets and performing stamping molding or the like, as will be described later. Therefore, the joint portion of the molded body is melt-bonded. The two or more substrate sheets may be the same or different in raw material type and blending amount. From the viewpoint of obtaining a molded article having homogeneous characteristics, it is preferable that the two or more base sheet have the same raw material type and blending amount. The two or more substrate sheets may have the same shape or different shapes.

  The structure of the cross section of the joint in the molded body of the present invention has a structure having an inclined portion derived from the flow of the overlapped portion near the boundary of the surface of the molded body and a horizontal portion near the center of the joint. Yes. During the molding such as stamping molding, the overlapped base sheet portion flows in a strip-shaped prepreg unit while causing slippage, so that it is considered that such a cross-sectional shape is obtained. The angle of the inclined portion in the vicinity of the boundary line on the surface of the molded body is preferably 15 degrees or less. If the inclined portion is close to vertical, it is not preferable because it becomes a defect of destruction when a bending load is applied.

  The bending elastic modulus and bending strength in the vicinity of the overlap portion of the molded article of the present invention are preferably 70% or more of the values of bending elastic modulus and bending strength of portions other than the overlap portion, and are 90% or more. Is more preferable. If it is less than 70%, the mechanical properties of the overlapped portion are not satisfactory, and it becomes the starting point of fracture, which is not preferable. Details of the measurement of the flexural modulus and the flexural strength are described in the section of Examples described later.

  The thickness of the overlap portion of the molded body of the present invention is preferably within ± 10% with respect to the thickness of the portion other than the overlap portion. When the thickness exceeds ± 10% with respect to the thickness other than the overlap portion, the variation in physical properties is increased, which is not preferable.

  Stamping molding is a suitable molding method for molding the fiber-reinforced thermoplastic resin molding of the present invention. For example, by infrared heating or high-frequency heating, the base sheet is heated and melted above the melting point of the thermoplastic resin, supplied to a mold adjusted to a temperature below the melting point, and after mold cooling, demolding, Molded. What is necessary is just to set suitably about molding conditions, such as metal mold | die temperature, the time to hold by compression, and pressure, with the thermoplastic resin to be used.

  The shape of the molded body of the present invention is not limited to a flat plate shape, and the same effect can be obtained even in a curved shape.

  Such fiber reinforced thermoplastic resin moldings are used for, for example, automotive parts such as front subframes, rear subframes, front pillars, center pillars, side members, cross members, side sills, roof rails, propeller shafts, and subsea oil fields. Used for pipes, electric cable cores, rolls and pipes for printing presses, robot forks, aircraft primary structural materials, secondary structural materials, etc.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, it is not restrict | limited by these Examples.

Example 1
A roving made of 12,000 carbon fibers (Mitsubishi Rayon TR50) was expanded and supplied to the die head of the impregnation table at a predetermined speed. On the other hand, an acid-modified polypropylene resin (G2H manufactured by Toyobo Co., Ltd., developed product) is put into a hopper of a screw type extruder controlled at 260 ° C., and a predetermined amount of the molten resin is measured by a gear pump. Supplied to. After pressure impregnation on the impregnation stand and defoaming, the tape-shaped prepreg coated with impregnation is extruded from a die having a width of 10 mm and a height of 0.2 mm, compression-molded and solidified, and then cut to obtain 67% by mass of carbon fiber and resin 33 A strip-shaped prepreg having a composition of mass% and having a width of 15 mm, a length of 35 mm, and a thickness of 0.1 mm was prepared.
The cut strip-shaped prepreg is dispersed in a flat shape so that the length axis of the fiber bundle is randomly oriented in the sheet surface in a mold, and is heated and pressed at a temperature of 230 ° C. while being laminated. After the resin was melted, a cooling press was performed in a 100 ° C. mold to obtain a 2 mm thick base sheet.
Thereafter, two sheets of 380 mm wide and 400 mm long were cut out from the obtained base sheet, heated to a temperature of 230 ° C. in advance with an IR heater, and the center of the molding die heated to a temperature of 130 ° C. Then, as shown in FIG. 2 (E), the base sheet is overlapped by 50 mm, stamping is performed at a molding pressure of 38.7 MPa, and the molded body surface has a boundary portion derived from the base sheet, a length of 750 mm, a thickness of 2 mm A fiber reinforced thermoplastic resin molded article was obtained. The length of the overlap part of this molded body was 75 mm.
A test piece having a width of 60 mm and a length of 100 mm was cut out from the obtained molded body, and a three-point bending test was performed. As shown in Fig. 4, the three-point bend test piece is cut out so that the flow end (boundary part) of the overlap part is exactly in the center of the surface of the test piece. Two types of evaluations were performed, which were cut out avoiding the lap portion. The average thickness of the test piece was 2.3 mm for the test piece having the boundary portion, and 2.3 mm for the test piece having no boundary portion. The three-point bending test was conducted at a distance between supporting points of 80 mm in accordance with JIS K7074 except for the test piece dimensions. About the test piece which has a boundary part, it applied so that an indenter might touch the back side of a boundary part, and it set so that a boundary part might become a tension | pulling side. As a result of the three-point bending test, the bending elastic modulus of the test piece without the boundary portion was 36 GPa and the bending strength was 340 MPa, whereas the bending elastic modulus of the test piece having the boundary portion was 36 GPa (retention rate 100%), The bending strength was 310 MPa (retention rate 91%).

(Example 2)
A base sheet having a thickness of 4 mm was prepared in the same manner as in Example 1, and two sheets having a width of 380 mm and a length of 400 mm were cut out and heated to a temperature of 230 ° C. in advance with an IR heater. At the center of the heated molding die, 50 mm of base material sheets are overlapped as shown in FIG. 2 (E), stamping is performed at a molding pressure of 38.7 MPa, and a boundary portion derived from the base material sheet is formed on the surface of the molded body. A fiber-reinforced thermoplastic resin molded article having a length of 750 mm and a thickness of 4 mm was obtained. The length of the overlap part of this molded body was 75 mm.
A test piece having a width of 60 mm and a length of 200 mm was cut out from the obtained molded body. As in Example 1, the test piece was cut out so that the flow end (boundary portion) of the overlap portion was just in the center of the surface of the test piece as shown in FIG. Two types of evaluations were performed, which were cut out avoiding the lap portion. The average thickness of the test piece was 4.1 mm for the test piece having no boundary portion and 4.3 mm for the test piece having the boundary portion. Using the cut out test piece, a three-point bending test was performed in the same manner as in Example 1 to evaluate the bending elastic modulus and bending strength. The three-point bending test was performed at a distance between fulcrums of 160 mm in accordance with JIS K7074 except for the test piece dimensions. As a result of the three-point bending test, the bending elastic modulus of the test piece without the boundary portion was 31 GPa and the bending strength was 250 MPa, whereas the bending elastic modulus of the test piece having the boundary portion was 30 GPa (retention rate 97%), The bending strength was 190 MPa (retention rate 76%).

(Comparative Example 1)
A base sheet having a thickness of 4.5 mm was prepared in the same manner as in Example 1, and a sheet A having a width of 215 mm and a length of 430 mm and a sheet B having a width of 215 mm and a length of 215 mm were cut out by two each. The cut sheet is preheated to a temperature of 230 ° C. with an IR heater, and placed in a molding die heated to a temperature of 130 ° C. with the sheet A and the sheet B facing each other as shown in FIG. A fiber-reinforced thermoplastic resin molded article having a length of 750 mm and a thickness of 4 mm having a boundary part on the surface of the molded article, stamped by a molding pressure of 38.7 MPa, arranged in two stages so that the butted parts do not become the same position Got.
A bending test piece having a width of 60 mm and a length of 200 mm was cut out from the obtained molded body in the same manner as in Example 2. Using the cut-out test piece, a three-point bending test was performed at a distance between supporting points of 160 mm in accordance with JIS K7074 except for the test piece size. As shown in FIG. 5, the test piece was evaluated by two types, one cut out so that the boundary portion was exactly at the center of the surface of the test piece and one cut out so as not to enter the boundary portion. The average thickness of the test piece was 4.0 mm for the test piece without the boundary portion and 4.2 mm for the test piece having the boundary portion. Using the cut out test piece, a bending test was performed in the same manner as in Example 1, and the bending elastic modulus and bending strength were evaluated. As a result of the bending test, the bending elastic modulus of the test piece without the boundary portion was 30 GPa and the bending strength was 240 MPa, whereas the bending elastic modulus of the test piece having the boundary portion was 20 GPa (retention rate 67%) and the bending strength. Was 100 MPa (retention rate 42%).

(Comparative Example 2)
A base sheet having a thickness of 2 mm was prepared in the same manner as in Example 1, and two sheets of a sheet A having a width of 400 mm and a length of 430 mm and a sheet B having a width of 400 mm and a length of 270 mm were cut out. The cut sheet is preheated to a temperature of 230 ° C. with an IR heater, and placed in a molding die heated to a temperature of 130 ° C. with the sheet A and the sheet B facing each other as shown in FIG. A fiber-reinforced thermoplastic resin molded article having a length of 750 mm and a thickness of 4 mm having a boundary part on the surface of the molded article, stamped by a molding pressure of 38.7 MPa, arranged in two stages so that the butted parts do not become the same position Got.
A bending test piece having a width of 60 mm and a length of 200 mm was cut out from the obtained molded body in the same manner as in Example 2. Using the cut-out test piece, a bending test was carried out at a fulcrum distance of 160 mm according to JIS K7074 except for the test piece size. As shown in FIG. 5, the test piece was cut out so that the boundary portion was exactly in the center of the surface of the test piece, and the test piece was cut out so as not to enter the boundary portion, as in Comparative Example 1. Two types were evaluated. The average thickness of the test piece was 3.8 mm for the test piece without the boundary portion and 4.1 mm for the test piece having the boundary portion. Using the cut out test piece, a bending test was performed in the same manner as in Example 1, and the bending elastic modulus and bending strength were evaluated. As a result of the bending test, the bending elastic modulus of the test piece without the boundary portion was 35 GPa and the bending strength was 270 MPa, whereas the bending elastic modulus of the test piece having the boundary portion was 27 GPa (retention rate 77%) and the bending strength. Was 180 MPa (retention rate 67%).

  According to the present invention, it is possible to obtain a fiber-reinforced thermoplastic resin molded body having a boundary portion on the surface of the molded body, in which a decrease in flexural modulus and bending strength is suppressed, and larger than the unit area of the base material. It can be used for structural members and parts of equipment, and is expected to make a significant contribution to the industry from the viewpoint of weight reduction and energy saving.

DESCRIPTION OF SYMBOLS 1 Test piece which has boundary part 1-1 Indenter contact part of bending test 2 Test piece without boundary part 3 Test piece which has boundary part 3-1 Indenter contact part of bending test 4 Test piece without boundary part

Claims (4)

Two or more base material sheets do not form a butt portion, partly overlap, and the joined part of the overlap part is a fiber reinforced thermoplastic resin molded body,
The base sheet contains 30 to 85% by mass of reinforcing fibers and 70 to 15% by mass of thermoplastic resin, and the reinforcing fibers have a fiber length of 10 to 100 mm to form a fiber bundle. A fiber reinforced thermoplastic resin sheet whose length axis is randomly oriented in the sheet plane,
A fiber-reinforced thermoplastic resin molded article having a boundary portion derived from the base sheet on the surface of the molded article. The length of the overlap part of the said molded object is 30 mm or more, The fiber reinforced thermoplastic resin molded object of Claim 1 characterized by the above-mentioned. The fiber-reinforced thermoplastic resin molded article is characterized in that the bending elastic modulus and bending strength of the overlapping portion are maintained at 70% or more, respectively, compared to the elastic modulus and bending strength of the portion other than the overlapping portion. The fiber-reinforced thermoplastic resin molded article according to claim 1 or 2. The fiber reinforced thermoplastics according to any one of claims 1 to 3, wherein two or more substrate sheets are partly overlapped without forming a butt portion, and are stamped and integrated. Manufacturing method of resin molding.