In-mold foamed resin core material for composite structural member, method for manufacturing the same, and composite structural member

Abstract

To provide a method for easily forming a groove in a core material without requiring a groove forming step by cutting.SOLUTION: There is provided a method for manufacturing an in-mold foamed resin core material for a composite structural member, and the method is configured in that: the core material has a groove portion on a surface to be combined with a skin material; an in-mold foam-molding step of filling foam particles into a mold having a shape corresponding to a shape of the groove portion and foaming the foam particles to obtain a core material is provided; the groove portion is composed of a bottom surface and side surfaces 1 and 2; and in a cross section perpendicular to a longitudinal direction of the groove, the bottom surface, the side surface 1, and the side surface 2 all include curves.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an in-mold foamed resin core material for a composite structural member, a manufacturing method thereof, and a composite structural member. [Background technology]

[0002] In-mold foam molding has been widely used as a method for producing foamed molded articles. In-mold foam molding is a molding method including a step of filling a mold with foamed resin particles, and a step of heating the foamed resin particles filled in the mold with a heat medium such as steam to cause secondary foaming, and heat-fusing and integrating the secondary foamed particles together to produce an in-mold foamed article having a desired shape.

[0003] Furthermore, for the purposes of adding further functions to a foam molded article or improving its appearance, it has been reported that a composite structural member can be produced by adhering a skin material such as a film or prepreg to the surface of the foam molded article and heating the skin material to laminate and integrate the foam molded article (Patent Document 1, Patent Document 2, Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-080022 A [Patent Document 2] JP 2015-098587 A [Patent Document 3] International Publication No. 2021 / 166951 Summary of the Invention [Problem to be solved by the invention]

[0005] A composite structural member is manufactured, for example, by laminating a skin material onto the surface of a foamed molded body used as a core material, supplying liquid resin to the surface of the foamed molded body, and heating and pressurizing it. At this time, in order to facilitate the supply of the liquid resin, the foamed molded body used as the core material is cut to provide grooves (flow paths for the liquid resin).

[0006] However, the present inventors found that when grooves are formed by cutting, the inside of the molten foamed particles (also called secondary foamed particles) is exposed, and the resin penetrates into the exposed molten foamed particles, resulting in an increase in the weight of the core material. Although one of the advantages of using a foamed molded body as the core material is its light weight, an increase in the weight of the core material can diminish this advantage. [Means for solving the problem]

[0007] The inventors have discovered that by using a mold having a portion shaped to correspond to the groove portion during in-mold foam molding of the foamed molded body that serves as the core material, it is possible to easily and without the need for a groove formation process by cutting, produce a core material having a groove portion in which the bottom surface, side surface 1 and side surface 2 all include curves in a cross section perpendicular to the longitudinal direction of the groove portion (also referred to simply as the "cross section of the groove portion" in this specification).

[0008] Representative aspects of the present invention are as follows. Section 1. A method for producing an in-mold foamed resin core material for a composite structural member, comprising the steps of: the core material has a groove on a surface to be combined with the skin material, an in-mold foam molding step of filling foam particles into a mold having a shape corresponding to the shape of the groove portion and foaming the foam particles to obtain a core material; The groove portion is composed of a bottom surface and side surfaces 1 and 2, In a cross section perpendicular to the longitudinal direction of the groove, the bottom surface, the side surface 1, and the side surface 2 all include curves. A method for producing in-mold foamed resin core material for composite structural members. Section 2. The manufacturing method of the in-mold foamed resin core material for a composite structural member according to claim 1, wherein the groove portion is formed in a shape extending in one direction of the core material or in a lattice shape. Item 3. The manufacturing method of the in-mold foamed resin core material for a composite structural member according to claim 1 or 2, wherein the bottom surface, side surface 1, and side surface 2 are all composed of only curves. Item 4. The manufacturing method of the in-mold foamed resin core material for a composite structural member according to any one of claims 1 to 3, wherein in the cross-section, all the curves included in the bottom surface, side surface 1, and side surface 2 include at least one arc. Item 5. The manufacturing method of the in-mold foamed resin core material for a composite structural member according to any one of claims 1 to 3, wherein in the cross-section, all the curves included in the bottom surface, side surface 1, and side surface 2 include at least one arc. When the radius of curvature of the arc included in the bottom surface is R1, the radius of curvature of the arc included in side surface 1 is R2, and the radius of curvature of the arc included in side surface 2 is R3, they have the relationship of R1≦R2 and R1≦R3. Item 6. The manufacturing method of the in-mold foamed resin core material for a composite structural member according to any one of claims 1 to 5, wherein when the average particle diameter of the foamed particles is r1 and the maximum width of the groove portion is r2, they have the relationship of r1 < r2. Item 7. The manufacturing method of the in-mold foamed resin core material for a composite structural member according to any one of claims 1 to 6, wherein the average bubble diameter of the foamed particles on the surface where the core material is to be composite with the skin material is 50 to 300 μm. Item 8. The manufacturing method of the in-mold foamed resin core material for a composite structural member according to any one of claims 1 to 7, wherein the in-mold foamed resin core material contains a polyester-based resin. Item 9. An in-mold foamed resin core material for a composite structural member having a groove portion on the surface to be composite with the skin material, wherein the core material is a fused body of foamed particles, the core material has a groove portion on the surface to be composite with the skin material, the groove portion is composed of a bottom surface, side surface 1, and 2, In a cross-section orthogonal to the longitudinal direction of the groove portion, the bottom surface, side surface 1, and side surface 2 all include curves. In-mold foamed resin core material for composite structural members. Item 10. The in-mold foamed resin core material for composite structural members according to item 9, wherein the groove portion is formed in a shape extending in one direction of the core material or in a lattice shape. Item 11. The in-mold foamed resin core material for composite structural members according to item 9 or 10, wherein the bottom surface, side surface 1, and side surface 2 all consist only of curves. Item 12. The in-mold foamed resin core material for composite structural members according to any one of items 9 to 11, wherein in the cross-section, all the curves included in the bottom surface, side surface 1, and side surface 2 include at least one arc. Item 13. The in-mold foamed resin core material for composite structural members according to any one of items 9 to 11, wherein in the cross-section, all the curves included in the bottom surface, side surface 1, and side surface 2 include at least one arc. When the radius of curvature of the arc included in the bottom surface is R1, the radius of curvature of the arc included in side surface 1 is R2, and the radius of curvature of the arc included in side surface 2 is R3, they have the relationship of R1≦R2 and R1≦R3. Item 14. The in-mold foamed resin core material for composite structural members according to any one of items 9 to 13, wherein when the average particle diameter of the foamed particles is r1 and the maximum width of the groove portion is r2, they have the relationship of r1 < r2. Item 15. The in-mold foamed resin core material for composite structural members according to any one of items 9 to 14, wherein the average bubble diameter of the foamed particles on the surface planned to be compounded with the skin material of the core material is 50 to 300 μm. Item 16. A composite structural member including the in-mold foamed resin core material according to any one of items 9 to 15 and at least one skin material.

Advantages of the Invention

[0009] According to the present invention, the flow rate of the liquid resin is improved during compounding, which shortens the compounding time and enables the use of a resin that is more likely to gel as the liquid resin (generally also called a binder resin).

[0010] According to the present invention, a groove forming step by cutting is not required, which makes it possible to prevent liquid resin from penetrating into the cut surface, and as a result, to prevent an increase in the weight of the core material. [Brief description of the drawings]

[0011] [Figure 1] 1A is a perspective view of a foam molded article having a conventional groove formed by cutting, and FIG. 1B is a cross-sectional view of the groove. [Diagram 2] 1A is a perspective view of a foam molded article according to one embodiment of the present invention, and FIG. 1B is a cross-sectional view of a groove portion. [Diagram 3] FIG. 1 is a schematic diagram showing an example of a cross section of a conventional groove portion formed by cutting. [Figure 4] This is a schematic diagram showing an example of a cross section of a groove of the present invention. In this diagram, imaginary circles A1 to A3, their center points X1 to X3, and their radii R1 to R3 are also shown to show that the curves constituting the bottom surface, side surface 1, and side surface 2 are circular arcs. In one embodiment, R1 to R3 are all 1 mm, the linear distance between ce is 1.73 mm, and the linear distance between bj is 3.46 mm. [Diagram 5] FIG. 1 is a schematic perspective view of the foam molded product (400 mm×300 mm×10 mm) produced in Example 1. Grooves are formed on the upper and lower surfaces, with a pitch of 40 mm. [Figure 6] FIG. 1 is a schematic perspective view of an embodiment of the present invention in which grooves are arranged in a lattice pattern. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] As used herein, the phrase "comprising" is intended to encompass the phrases "consisting essentially of" and "consisting of."

[0013] (In-mold foam resin core material) The in-mold foamed resin core material of the present invention is a core material for composite structural members, and is obtained by filling a mold with foamed particles and heating the mold to cause foaming and thermal fusion. Therefore, the core material is a foamed molded body composed of a fused body of foamed particles. Composite structural members having such a core material are excellent in terms of light weight, heat insulation, and sound insulation.

[0014] A skin material may be laminated on the surface of the core material, and the surface may be composited by various composite methods to form a composite structural member. In this specification, the surface on which the skin material is laminated is referred to as the surface to be composited with the skin material. The core material may have one or two or more surfaces to be composited with the skin material, preferably one to four, and more preferably one or two.

[0015] In the core material, the average bubble diameter of the expanded particles on the surface to be combined with the skin material may be 50 to 300 μm, preferably 100 to 250 μm, and more preferably 150 to 220 μm. If the average bubble diameter is within the above range, it is advantageous in terms of improving the expanding power or the fusion power of the secondary expanded particles.

[0016] The average cell diameter is determined as follows. (average bubble diameter) A cross section of an expanded bead roughly divided in two at the center was photographed at 100x magnification using a scanning electron microscope, SU1510, manufactured by Hitachi High-Technologies Corp. The area photographed was a region within 20% of the expanded bead's radius from the surface. The captured microscopic images are arranged so that two images are side-by-side on one A4 sheet of paper in landscape orientation, and then printed on A4 paper. For each image of the cross section of the printed foamed particles, three arbitrary straight lines (60 mm long) parallel to the vertical and horizontal directions are drawn. That is, for each two microscopic images, six arbitrary straight lines are drawn in the vertical direction and six in the horizontal direction. The lines are drawn so that they do not come into contact with the bubbles only at their points of contact, as much as possible. The number of bubbles that the straight lines pass through is then counted. If a bubble comes into contact with the line only at its points of contact, this bubble is also included in the count. The number of bubbles counted for the six arbitrary straight lines in each of the vertical and horizontal directions is calculated as the number of bubbles in each direction. The average chord length t of the bubbles is calculated from the magnification of the image on which the number of bubbles was counted and this number of bubbles using the following formula. Average chord length t(mm)=60 / (number of bubbles x image magnification) The image magnification is calculated by measuring the scale bar on the image to the nearest 1 / 100 mm using a Mitutoyo Digital Caliper and using the following formula: Image magnification = Scale bar actual value (mm) / Scale bar display value (mm) Then, the bubble diameters in the vertical and horizontal directions are calculated using the following formula. Vertical or horizontal bubble diameter D(mm)=t / 0.616 Furthermore, the square root of the product of the air bubble diameter D in the vertical direction and the air bubble diameter D in the horizontal direction is defined as the air bubble diameter. Bubble diameter (μm) = 1000 x (D length x D width) 1 / 2 The above procedure is carried out with an N number of 10, and the average value is taken as the average bubble diameter.

[0017] The size and shape of the core material can be appropriately selected depending on the size, shape, etc. of the desired composite structural member. The thickness of the core material is preferably 1 mm to 40 mm from the standpoints of strength, weight, and impact resistance.

[0018] (Groove) The surface to be combined with the skin material has one or more grooves, which serve as flow paths for the liquid resin used to combine the skin material with the core material.

[0019] The groove portion is composed of a bottom surface and a pair of side surfaces (side surfaces 1 and 2).

[0020] The groove will be described with reference to Figures 3 and 4. Figure 3 shows a cross section of an example of a conventional groove. This cross section is composed of side surface 1 (c' to e'), bottom surface (e' to g'), and side surface 2 (g' to i'). a' to c' and i' to k' are surfaces.

[0021] 4 shows a cross section of an example of a groove of the present invention. This cross section is composed of side surfaces 1 (b to c), a bottom surface (c to e), and side surfaces 2 (e to f). a to b and f to g are surfaces. The arc ce is a part of the arc of the imaginary circle A1. The arc bc is a part of the arc of the imaginary circle A2. The arc ef is a part of the arc of the imaginary circle A3. The radius of the imaginary circle A1 is R1. The radius of the imaginary circle A2 is R2. The radius of the imaginary circle A3 is R3. In one embodiment, R1 to R3 are 1 mm, the linear distance between bf (the maximum width of the groove portion (r2)) is 3.46 mm, the linear distance between ce is 1.73 mm, and the groove depth is 1.0 mm. In the cross section perpendicular to the longitudinal direction of the groove, the core material may include curved lines on the bottom surface, side surface 1, and side surface 2, and preferably consists of only curved lines. In addition, by making the transition portion between the surface of the core material and the side surface of the groove, the transition portion between the side surface of the groove and the bottom surface of the groove, and the bottom surface rounded, the flow rate of the liquid resin used during compounding is improved compared to a groove whose cross section is composed of only straight lines.

[0022] A groove having such a shape can be formed by using a mold (preferably a metal mold) having a shape corresponding to the shape of the groove in the in-mold foam molding process for manufacturing the core material. Forming the groove in the in-mold foam molding process is advantageous in that it does not require a groove forming process by cutting, and it is possible to prevent resin from entering the cut surface, thereby preventing an increase in the weight of the core material.

[0023] The arrangement of the grooves on the surface of the core material is not particularly limited. The grooves may be arranged along one direction of the core material (for example, the arrangement shown in FIG. 5) or in a lattice pattern (for example, the arrangement shown in FIG. 6). For example, the core material may have one or more grooves extending in the longitudinal direction of the core material, one or more grooves extending in the lateral direction (also referred to as the width direction) of the core material, or one or more grooves extending in the longitudinal direction and one or more grooves extending in the lateral direction of the core material.

[0024] The grooves may be provided on at least one surface that is to be combined with the skin material. For example, when the upper and lower surfaces of the core material are to be combined with the skin material, the grooves may be provided on the upper and lower surfaces. The surface of the core material on which the grooves are provided may be flat or curved, or may be irregular in shape as long as the core material can be combined with the skin material.

[0025] The length of the groove is not limited as long as the skin material and the core material are combined, and can be appropriately selected depending on the size, shape, etc. of the desired combined structural member.

[0026] The depth of the groove (the distance corresponding to R1 in the groove shown in FIG. 4) is not limited as long as the skin material and the core material are combined. The depth of the groove can be, for example, 0.5 to 5.0 mm, preferably 1.0 to 5 mm, and more preferably 1.5 to 5.0 mm.

[0027] The width of the upper end of the groove, i.e., the distance between the upper end of side surface 1 and the upper end of side surface 2 (the linear distance between b and f in the groove shown in FIG. 4), is not limited as long as the skin material and the core material are combined. The width of the upper end of the groove can be, for example, 3.0 to 10.0 mm, and preferably 3.4 to 10.0 mm.

[0028] The width of the bottom of the groove, i.e., the distance between the bottom ends of side 1 and side 2 (the linear distance between c e in the groove shown in FIG. 4), is not limited as long as the skin material and the core material are combined. The width of the bottom of the groove can be, for example, 1.0 to 3.0 mm, and preferably 1.4 to 3.0 mm.

[0029] It is preferable that the width of the upper end of the groove is wider than the width of the bottom surface.

[0030] In the cross section of the groove, one or more of the bottom surface, side surface 1 and side surface 2 may include a straight line, so long as the bottom surface, side surface 1 and side surface 2 all include a curved line. From the viewpoint of improving the fluidity of the liquid resin, it is preferable that the bottom surface, side surface 1, and side surface 2 of the groove are all made up of curved lines in the cross section of the groove. Thus, none of the bottom surface, side surface 1, and side surface 2 include straight lines.

[0031] In the cross section of the groove, each of the curves included in the bottom surface, side surface 1, and side surface 2 may include at least one arc. Each of the curves may be composed of one arc or multiple arcs. From the viewpoint of improving the fluidity of the liquid resin, it is preferable that each of the curves included in the bottom surface, side surface 1, and side surface 2 includes one arc, and it is more preferable that each of the bottom surface, side surface 1, and side surface 2 is composed of only one arc.

[0032] When the cross section of the groove includes curves on the bottom surface, side surface 1, and side surface 2 that all include at least one arc, it is preferable that the relationships R1≦R2 and R1≦R3 are satisfied, where R1 is the radius of curvature of the arc included on the bottom surface, R2 is the radius of curvature of the arc included on side surface 1, and R3 is the radius of curvature of the arc included on side surface 2. When these relationships are satisfied, the fluid resin on the bottom surface flows first, which is advantageous in that air is less likely to remain in the groove.

[0033] In the cross-section of the groove portion, when the bottom surface, side surface 1, and side surface 2 are all composed of only curves, it is preferable that the curve consists of only one arc. In the cross-section of the groove portion, when the bottom surface, side surface 1, and side surface 2 are all composed of only curves and all of the curves include arcs, when the radius of curvature of the arc included in the bottom surface is R1, the radius of curvature of the arc included in side surface 1 is R2, and the radius of curvature of the arc included in side surface 2 is R3, it is preferable to have the relationships of R1≦R2 and R1≦R3. When having these relationships, since the flowing resin on the bottom surface flows first, it is advantageous in that air is less likely to remain.

[0034] The number of arcs included in the bottom surface can be 1 to 3, 1 or 2, and 1 is preferable. The number of arcs included in side surface 1 can be 1 to 3, 1 or 2, and 1 is preferable. The number of arcs included in side surface 2 can be 1 to 3, 1 or 2, and 1 is preferable.

[0035] In the cross-section of the groove portion, it is preferable in terms of improving the fluidity of the liquid resin that the bottom surface is composed of one arc, side surface 1 is composed of one arc, and side surface 2 is composed of one arc. The radii of curvature (R1 to R3) of these arcs can all be the same.

[0036] The average particle diameter (r1) of the foamed particles used in the manufacture of the core material and the length (r2) of the largest width in the groove portion in the cross-section of the groove portion can have the relationship of r1 < r2. When having this relationship, since the cross-section of the groove portion is formed by a plurality of foamed particles, it is advantageous in terms of good shape accuracy during molding.

[0037] (Foamed resin) The resin constituting the core material may be a thermoplastic resin. The thermoplastic resin is not particularly limited, and examples thereof include thermoplastic polyester resins such as aromatic polyester resins and polylactic acid resins, polycarbonate resins, acrylic resins, polymethacrylimide resins, polyamide resins, modified polyphenylene ether resins, cyclic olefin resins, and styrene-methacrylic acid-methyl methacrylate copolymers. Thermoplastic polyester resins are preferred, and aromatic polyester resins are more preferred. The thermoplastic resins may be used alone or in combination of two or more. The thermoplastic resin may be a recycled material recovered and regenerated from used PET bottles or the like.

[0038] Specific examples of aromatic polyester resins include polyethylene terephthalate, polybutylene terephthalate, copolymers of terephthalic acid, isophthalic acid and ethylene glycol, copolymers of terephthalic acid, ethylene glycol and neopentyl glycol, copolymers of terephthalic acid, ethylene glycol and cyclohexane dimethanol, etc., with polyethylene terephthalate being preferred. The aromatic polyester resins may be used alone or in combination of two or more.

[0039] As the polylactic acid resin, a resin in which lactic acid is polymerized through an ester bond can be used, and from the viewpoints of commercial availability and imparting expandability to the polylactic acid resin expanded particles, a copolymer of D-lactic acid (D-form) and L-lactic acid (L-form), a homopolymer of either D-lactic acid or L-lactic acid, or a ring-opening polymer of one or more lactides selected from the group consisting of D-lactide, L-lactide and DL-lactide are preferred. The polylactic acid resins may be used alone or in combination of two or more kinds.

[0040] The polylactic acid resin may contain, as a monomer component other than lactic acid, for example, aliphatic hydroxycarboxylic acids such as glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, and hydroxyheptanoic acid; aliphatic polycarboxylic acids such as succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedicarboxylic acid, succinic anhydride, adipic anhydride, trimesic acid, propanetricarboxylic acid, pyromellitic acid, and pyromellitic anhydride; and aliphatic polyhydric alcohols such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, decamethylene glycol, glycerin, trimethylolpropane, and pentaerythritol, so long as the monomer components do not affect the foamability and the physical properties of the resulting composite foam.

[0041] The polylactic acid resin may contain other functional groups such as alkyl groups, vinyl groups, carbonyl groups, aromatic groups, ester groups, ether groups, aldehyde groups, amino groups, nitrile groups, nitro groups, etc., so long as they do not affect the foaming step and the physical properties of the resulting composite foam. The polylactic acid resin may be crosslinked with an isocyanate crosslinking agent or the like, and may be bonded by bonds other than ester bonds.

[0042] The thermoplastic resin may be crosslinked by a crosslinking agent. As the crosslinking agent, a known one is used, for example, a compound having an acid anhydride group, a multifunctional epoxy compound, an oxazoline compound, an oxazine compound, etc., and a compound having an acid anhydride group is preferable. The crosslinking agent may be used alone or in combination of two or more kinds.

[0043] The compound having an acid anhydride group is not particularly limited, and may be, for example, any of aromatic, alicyclic, and aliphatic, and may be a halogenated acid anhydride.The compound having an acid anhydride group may be, for example, pyromellitic anhydride, benzophenonetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, diphenylsulfonetetracarboxylic dianhydride, etc.The compound having an acid anhydride group may be used alone or in combination of two or more.

[0044] When the thermoplastic resin is crosslinked by a crosslinking agent, for example, the crosslinking agent may be fed to an extruder together with the thermoplastic resin. If the amount of the crosslinking agent fed to the extruder is too small, the melt viscosity of the thermoplastic resin when melted may be small, and the expansion ratio of the thermoplastic resin expanded particles may not be increased. If the amount of the crosslinking agent fed to the extruder is too large, the melt viscosity of the thermoplastic resin when melted may be too large, and extrusion foaming may be difficult. Therefore, the amount of the crosslinking agent fed to the extruder is preferably 0.010 to 5.0 parts by mass, more preferably 0.10 to 1.0 parts by mass, relative to 100 parts by mass of the thermoplastic resin.

[0045] The foamed resin (preferably foamed polyester resin) content in the core material may be 70% by mass or more, 80% by mass or more, or 90% by mass or more, preferably 95% by mass or more, more preferably 97% by mass or more, and even more preferably 98% by mass or more.

[0046] (Method of manufacturing the core material) The in-mold foamed resin core material for composite structural members of the present invention is produced by filling a mold with foamed particles and foaming them to produce a foamed molded product having a shape corresponding to the shape of the mold. The mold (preferably a metal mold) used in this case has a shape corresponding to the shape of the groove portion of the core material. In the present invention, the groove portion is formed during in-mold foam molding, so that the groove portion can be easily formed without requiring a groove portion forming step by cutting.

[0047] The method for producing the core material may include an in-mold foam molding step of filling the inside of a mold having a shape corresponding to the shape of the groove with foamed particles and foaming them to obtain the core material. The in-mold foam molding step can be carried out in accordance with a conventional in-mold foam molding method, except that a mold having a shape corresponding to the shape of the groove is used.

[0048] (foam particles) The expanded beads can be produced by a known method, for example, a method including a step of supplying a raw material resin (which is also the resin constituting the core material) and, if necessary, a crosslinking agent to an extruder and melt-kneading them in the presence of a foaming agent to prepare a molten kneaded product, a step of extruding and foaming the molten kneaded product to prepare an extruded foam, and a cutting step of cutting the extruded foam to prepare expanded beads.

[0049] (Composite structural members) The composite structural member of the present invention can be produced by integrally laminating a skin material onto the surface of the core material of the present invention.

[0050] The skin material is mainly used to protect the surface of the core material and to obtain more excellent properties than the core material alone. For example, the use of the skin material can further increase heat resistance and mechanical strength. The skin material may be laminated on the entire surface of the core material, or on only a part of the surface.

[0051] Examples of the skin material include fiber reinforced materials, metal sheets, resin films, etc. Among these, fiber reinforced materials are preferred.

[0052] The fibers constituting the fiber reinforcement material are not particularly limited, and examples thereof include carbon fibers, glass fibers, aramid fibers, boron fibers, and metal fibers. Carbon fibers, glass fibers, and aramid fibers are preferred because of their excellent heat resistance and mechanical strength, and carbon fibers are more preferred. The fiber reinforcement material may be impregnated with a thermosetting resin or a thermoplastic resin. In other words, the skin material may be a prepreg.

[0053] The thermosetting resin is not particularly limited, and examples thereof include epoxy resin, unsaturated polyester resin, phenol resin, melamine resin, polyurethane resin, silicone resin, maleimide resin, vinyl ester resin, cyanate ester resin, and resin obtained by prepolymerizing maleimide resin and cyanate ester resin. Epoxy resin or vinyl ester resin is preferable because of excellent heat resistance, elastic modulus, and chemical resistance. Only one type of thermosetting resin may be used, or two or more types may be used in combination.

[0054] The thermoplastic resin is not particularly limited, and examples thereof include polyolefin resin, polyester resin, thermoplastic epoxy resin, polyamide resin, thermoplastic polyurethane resin, sulfide resin, acrylic resin, etc. Polyester resin and thermoplastic epoxy resin are preferred because they have excellent adhesion between the skin material and the core material or between the fibers constituting the fiber reinforcement material. Only one type of thermoplastic resin may be used, or two or more types may be used in combination.

[0055] The metal sheet is not particularly limited, and examples thereof include aluminum sheets, stainless steel sheets, iron sheets, steel sheets, titanium sheets, etc. Aluminum sheets are preferred because they are both lightweight and have excellent mechanical strength. Aluminum sheets also include aluminum alloy sheets containing 50% by mass or more of aluminum.

[0056] The resin film is not particularly limited, and examples thereof include polyolefin-based resin films, polyester-based resin films, acrylic-based resin films, etc. Examples of the polyolefin-based resin films include polyethylene-based resin films, polypropylene-based resin films, etc. Examples of the polyester-based resin films include polyethylene terephthalate films.

[0057] The skin material is preferably integrally laminated with the core material. The method for laminating and integrating the skin material onto the surface of the core material is not particularly limited, and examples thereof include (1) a method of laminating and integrating the skin material onto the surface of the core material via an adhesive, (2) a method of laminating a skin material (preferably a fiber-reinforced material) impregnated with a thermoplastic resin onto the surface of the core material, and laminating and integrating the skin material onto the surface of the core material using the thermoplastic resin impregnated in the skin material as a binder, (3) a method of laminating a skin material (preferably a fiber-reinforced material) impregnated with an uncured thermosetting resin onto the surface of the core material, and laminating and integrating the skin material onto the surface of the core material using the thermosetting resin impregnated in the skin material as a binder, by curing the thermosetting resin, (4) a method of disposing a skin material in a heated and softened state on the surface of the core material, and pressing the skin material against the surface of the core material to deform the skin material along the surface of the core material as necessary, and (5) other methods generally applied in the molding of fiber-reinforced resin sheets. For example, there are an autoclave method, a hand lay-up method, a spray-up method, a PCM (Prepreg Compression Molding) method, an RTM (Resin Transfer Molding) method, a VaRTM (Vacuum assisted Resin Transfer Molding) method, etc. In these methods, it is preferable to mold a skin material (preferably a fiber reinforced material) not impregnated with a binder resin into a mold, place a core material in the mold, and impregnate the skin material with the binder resin by an injection machine or the like, since this makes it possible to utilize the effect of increasing the flow rate of the binder resin due to the grooves in the core material. The RTM method and the VaRTM method are preferable methods for laminating and integrating the skin material and the core material.

[0058] In addition to the inherent lightness, soundproofing, heat insulation, vibration-damping properties, etc. of the core material, the composite structural member is integrated with the skin material to add various functions (heat resistance, abrasion resistance, abrasion resistance, beautiful appearance, chemical resistance, water resistance, oil resistance, stain resistance, etc.), so in addition to the applications in which aromatic polyester-based resin core materials have traditionally been used, it can be used in the fields of architecture, transportation equipment (automobiles, motorcycles, buses, trains, aircraft, ships, etc.), space, energy technology (for example, rotors of wind power generators), sports (various exercise equipment, etc.), electrical industry, electronics industry, etc. Examples of such applications include aircraft equipment structures (helicopter blades, etc.), interior and exterior materials for various vehicles, sports equipment materials, leisure equipment materials, sandwich structure materials, wind power generation blades, etc. Examples of automotive parts include door panels, door inners, bumpers, fenders, fender supports, engine covers, roof panels, trunk lids, floor panels, instrument panels, center clusters, center tunnels, crash boxes, etc. For example, by using a composite structural member for a door panel that was previously made of steel plate, the door panel can be made significantly lighter while having roughly the same rigidity as a steel door panel, and its thermal insulation and soundproofing properties can be improved. EXAMPLES

[0059] Hereinafter, an embodiment of the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. Methods for determining various physical properties in the examples will be described below.

[0060] (Resin flow completion time) The time from when the VaRTM molding resin started to be injected into the bagging film from the resin supply line to when the impregnation of the VaRTM molding resin was confirmed at the end of the laminate on the vacuum line side was measured with a timer, and this was taken as the resin flow completion time.

[0061] Example 1 Manufacturing of core material (in-mold foam molding process) An in-mold foam molding machine equipped with molds (male and female molds) was prepared. The mold had inside dimensions of 300 mm length x 400 mm width x 10 mm height, and was used to manufacture a rectangular parallelepiped foam molded body, but had seven shapes corresponding to the grooves. The shapes corresponding to the grooves were formed such that grooves were formed at a pitch of 40 mm in the longitudinal direction (400 mm direction) with a depth of 1 mm, a maximum width of 3.46 mm, and R1 to R3 of 1.0 mm, connected by a fillet of R1 from the main surface of the mold (two surfaces having a size of 300 mm x 400 mm). This 40 mm pitch means that the distance between the center line of a groove in the longitudinal direction and the center line of the adjacent groove in the longitudinal direction is 40 mm. The mold was filled with foamed particles (average particle diameter 2.5 mm) with a gap (cracking) between the male and female dies of 1 mm. After the male and female dies were closed to eliminate cracking, steam was introduced from the female mold for 60 seconds so that the inside of the cavity was 0.30 MPa (gauge pressure) (one-sided heating), then steam was introduced from the male mold for 45 seconds so that the inside of the cavity was 0.30 MPa (gauge pressure) (reverse one-sided heating), and then steam was supplied from both the male and female molds for 60 seconds so that the inside of the cavity was 0.33 MPa (gauge pressure) (double-sided heating), heating and foaming the foamed particles to heat-seal and integrate the secondary foamed particles. After that, the introduction of steam into the cavity was stopped and the state was maintained for 110 seconds (heat retention process), and finally, a cooling liquid was supplied into the cavity to cool the foamed molded body in the mold, and the cavity was opened to take out the foamed molded body (core material). The groove in the core material was formed with its longitudinal direction aligned 400 mm horizontally (Fig. 5). The depth of the groove was 1 mm, and its maximum width (the straight-line distance between bj in Fig. 4) was 3.46 mm. In the cross section of the groove, the radius of curvature of the bottom arc, the arc of side 1, and the arc of side 2 were all 1 mm (Fig. 4).

[0062] Composite structural component manufacturing (Lamination process) Carbon fiber reinforcement material (CHOMARAT "C-WEAVE 200TX 3KHS X100CM50ME", plain weave cloth, 200g / m 2) was cut into a size of 200 mm × 120 mm to prepare a skin material. Four skin materials were prepared. 3 A core material was prepared by cutting out a piece of 200mm x 120mm x 10mm thick plastic (material: polyester resin) from a sheet of acrylic resin. The longitudinal direction of the grooves was aligned with the 200mm direction of the cut core material, and the core material contained three grooves. Two sheets of the prepared skin material were laminated on the main surface of the core material (a surface measuring 200mm x 120mm), and two sheets were also laminated on the other main surface. As a result, a laminate was obtained with two skin materials on top of the core material and two skin materials underneath.

[0063] (compounding process) VaRTM molding was performed. First, the obtained laminate was placed on a glass plate for molding. One end of a flow media (DIATEX's "DRAIKO") was connected to one end of the longitudinal direction of the groove on the surface of the core material. As a result, the flow media was placed from the end of the core material to the outside of the edge by 10 mm. A spiral tube (φ6 mm) was connected to the other end of the flow media as a resin supply line. A spiral tube (φ6 mm) was connected as a pressure reduction line to the other end of the groove on the surface of the core material in the longitudinal direction. An air tube was connected to both spiral tubes. The laminate was covered with a peel ply ("Peel Ply PA85" manufactured by DIATEX). The laminate, resin supply line, and vacuum line were covered with bagging film (Airtech; W17400-.002"-27"-1000'-LFT), and the edges of the bagging film and the mold surface, as well as the spaces between the air tubes on the resin supply line side and the vacuum line side, were sealed with sealing tape (AIRTECH; AT-200Y). The air tubes were connected to a vacuum pump via a vacuum container connected to a vacuum pressure gauge.

[0064] The air tube on the resin supply side was blocked with vice pliers, the vacuum pump was operated, and the airtightness between the molding glass plate and the bagging film was confirmed, with the reduced pressure gauge maintaining a pressure of 10 kPa or less. While maintaining the above-mentioned degree of vacuum, 100 parts by mass of VaRTM molding resin (Japan U-Pica Co., Ltd. "CBZ 500LM-AS", urethane acrylate resin), 0.3 parts by mass of hardening accelerator (Japan U-Pica Co., Ltd. "PR-CBZ01"), 3.0 parts by mass of polymerization initiator (NOF Corp. "Permec N"), and 0.05 parts by mass of polymerization retarder (Japan U-Pica Co., Ltd. "ST-A") were uniformly mixed and transferred into the resin tank. After inserting the air tube on the resin supply side into the resin, the vice pliers were released and the injection of resin into the carbon fiber reinforcement between the mold and the film was started. After the resin impregnation into the carbon fiber reinforcement was completed, the resin supply hose and the vacuum hose were blocked with the vice pliers. The mixture was left at room temperature for 12 hours to obtain a composite structural member. The resin flow completion time of this composite structural member was 380 seconds, and the mass was 82 g.

[0065] Example 2 Except for changing the groove pitch of the foam molded body to 20 mm, a composite structural member was obtained in the same manner as in Example 1. The resin flow completion time of this composite structural member was 300 seconds, and the mass was 84 g.

[0066] Comparative Example 1 A foam molded body (length 300 mm × width 400 mm × height 10 mm) was produced in the same manner as in Example 1 using the same mold as in Example 1, except that it did not have a shape corresponding to the groove portion. A core material was cut out from this foam molded body in the same manner as in Example 1, and a composite structural member was produced, but the resin hardened before the resin impregnation into the skin material was completed, resulting in parts of the skin material that were not impregnated with resin, and a composite structural member could not be obtained.

[0067] Comparative Example 2 A foam molded body (length 300 mm × width 400 mm × height 10 mm) was produced in the same manner as in Example 1 using the same mold as in Example 1 except that it did not have a shape corresponding to the groove portion. A groove similar to that in Example 1 was formed in this foam molded body by cutting (specifically, NC processing) to produce a foam molded body having a groove portion. A core material was cut out from this foam molded body in the same manner as in Example 1 to produce a composite structural member. The resin flow completion time of the obtained composite structural member was 380 seconds, and the mass was 90 g. The weight increased by about 10% compared to the composite structural member obtained in Example 1.

[0068] Details of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 1.

[0069] [Table 1]

Claims

1. A method for producing an in-mold foamed resin core material for a composite structural member, comprising the steps of: the core material has a groove on a surface to be combined with the skin material, an in-mold foam molding step of filling foam particles into a mold having a shape corresponding to the shape of the groove portion and foaming the foam particles to obtain a core material; The groove portion is composed of a bottom surface and side surfaces 1 and 2, In a cross section perpendicular to the longitudinal direction of the groove, the bottom surface, the side surface 1, and the side surface 2 all include a curve. A method for producing in-mold foamed resin core material for composite structural members.

2. The method for producing an in-mold foamed resin core material for a composite structural member according to claim 1 , wherein the groove portion is formed in a shape extending in one direction of the core material or in a lattice shape.

3. 2. The method for producing an in-mold foamed resin core material for a composite structural member according to claim 1, wherein the bottom surface, the side surface 1 and the side surface 2 are all formed only of curves.

4. 2. The method for manufacturing an in-mold foamed resin core material for composite structural members according to claim 1, wherein in the cross section, the curves included in the bottom surface, the side surface 1 and the side surface 2 all include at least one circular arc.

5. 2. A method for manufacturing an in-mold foamed resin core material for composite structural members as described in claim 1, wherein, in the cross section, the curves included in the bottom surface, side surface 1 and side surface 2 all include at least one arc, and when the radius of curvature of the arc included in the bottom surface is R1, the radius of curvature of the arc included in side surface 1 is R2, and the radius of curvature of the arc included in side surface 2 is R3, the relationships R1≦R2 and R1≦R3 are satisfied.

6. 2. The method for producing an in-mold foamed resin core material for composite structural members according to claim 1, wherein, when the average particle diameter of the foamed beads is r1 and the maximum width of the groove portion is r2, a relationship of r1 < r2 is satisfied.

7. 2. The method for producing an in-mold foamed resin core material for composite structural members according to claim 1, wherein the average bubble diameter of the foamed particles on the surface of the core material to be composited with the skin material is 50 to 300 μm.

8. 2. The method for producing an in-mold foamed resin core for a composite structural member according to claim 1, wherein the in-mold foamed resin core contains a polyester-based resin.

9. An in-mold foamed resin core material for a composite structural member, the in-mold foamed resin core material having a groove on a surface to be composited with a skin material, The core material is a fused body of foamed particles, the core material has a groove on a surface to be combined with the skin material, The groove portion is composed of a bottom surface and side surfaces 1 and 2, In a cross section perpendicular to the longitudinal direction of the groove, the bottom surface, the side surface 1, and the side surface 2 all include a curve. In-mold foamed resin core material for composite structural members.

10. 10. The in-mold foamed resin core material for a composite structural member according to claim 9, wherein the groove portion is formed in a shape extending in one direction of the core material or in a lattice shape.

11. 10. The in-mold foamed resin core material for composite structural members according to claim 9, wherein the bottom surface, the side surface 1 and the side surface 2 are all formed only of curves.

12. The in-mold foamed resin core material for composite structural members according to claim 9, wherein in the cross section, the curves included in the bottom surface, the side surface 1 and the side surface 2 all include at least one circular arc.

13. 10. An in-mold foamed resin core material for composite structural members as described in claim 9, wherein in the cross section, the curves included in the bottom surface, side surface 1 and side surface 2 all include at least one arc, and when the radius of curvature of the arc included in the bottom surface is R1, the radius of curvature of the arc included in side surface 1 is R2, and the radius of curvature of the arc included in side surface 2 is R3, the relationships R1≦R2 and R1≦R3 are satisfied.

14. 10. The in-mold foamed resin core material for composite structural members according to claim 9, wherein, when an average particle diameter of the foamed beads is r1 and a maximum width of the groove portion is r2, a relationship of r1<r2 is satisfied.

15. 10. The in-mold foamed resin core material for composite structural members according to claim 9, wherein the average bubble diameter of the foamed particles on the surface of the core material to be composited with the skin material is 50 to 300 μm.

16. A composite structural member comprising the in-mold foamed resin core material according to any one of claims 9 to 15 and at least one skin material.

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