Sandwich panel and method for preparing same

Abstract

The sandwich panel of the present invention comprises: a foamed molded body; a first thermoplastic continuous fiber reinforced woven body fused to an upper portion of the foamed molded body; a second thermoplastic continuous fiber reinforced woven body fused to a lower portion of the foamed molded body; and one or more composite material bars embedded in the foamed molded body. The sandwich panel exhibits excellent rigidity (flexural strength, flexural rigidity, and maximum deflection), lightweight properties, and the like.

Description

Sandwich panel and method for manufacturing the same

[0001] The present invention relates to a sandwich panel and a method for manufacturing the same. More specifically, the present invention relates to a sandwich panel having excellent rigidity (flexural strength, flexural rigidity, and maximum deflection) and light weight, and a method for manufacturing the same.

[0002]

[0003] Automotive interior components such as luggage boards, headliners, and seat back panels, as well as the body shells and floor structures of buses and trams, are manufactured using a sandwich structure in which a core layer made of expanded plastic foam is bonded to a reinforcing layer made of fiber-reinforced composite material on both sides. Sandwich panels with this sandwich structure are lightweight and have excellent rigidity, and are easy to manufacture in large-area plate form, so they are mainly applied to products in the form of panels with large areas.

[0004] In order to meet the continuously strengthening demands for lightweight and eco-friendly products in the automobile industry, sandwich panel components are also becoming lighter, and there is a strong trend to introduce thermoplastic resins, especially polypropylene (PP), instead of using environmentally harmful substances such as thermosetting resins as the material. Recent sandwich panel components use EPP (expanded polypropylene) sheets as the core layer, and a glass fiber-reinforced thermoplastic composite material called felt, which is a sheet-shaped material in which glass fibers with a length of about 100 to about 150 mm are mixed with polypropylene fibers without any direction, is bonded to both sides to introduce polypropylene materials. However, due to the use of glass fiber-reinforced composite material (felt) as the reinforcing layer, the weight and rigidity of the sandwich panel have not been significantly improved.

[0005] For example, a luggage board has been developed that uses EPP as the core material and glass fiber reinforced sheets or natural fiber reinforced sheets as the reinforcement material. The luggage board is formed by manufacturing an EPP board having the same shape as the final product, preheating the EPP board and the reinforcement material to a temperature of about 150 to about 220°C, laminating, and cold pressing the product. This method enables molding without the generation of odor or volatile organic compounds (VOCs) by bonding the core and reinforcement layers through a process of preheating and cold pressing without the use of a separate adhesive. However, the process of preheating the EPP board and the reinforcement layer requires a heating device that consumes a lot of power to heat the material to a high temperature for a long time, which requires significant production costs and process time. In addition, the cold pressing process also requires expensive molds and press equipment, resulting in high initial investment costs.

[0006] As another example, in order to improve the moisture resistance and strength of sandwich structures for automotive interior materials, a sandwich structure was developed in which a moisture-curable isocyanate was added to a natural fiber reinforcing layer, a curing reaction was performed, the sheet was manufactured, and this was then bonded to both sides of a thermoplastic foam sheet using a thermal lamination process. The sandwich structure uses environmentally friendly natural fibers and recyclable thermoplastic resins, but since the reinforcing layer and the core layer are bonded by heating after being manufactured, the bonding process time is longer than that of the existing adhesive-using bonding process, which reduces productivity. In addition, the natural fibers that make up the reinforcing layer have lower mechanical properties than the existing glass fibers, which is disadvantageous in securing product performance and reducing weight.

[0007] Therefore, it is necessary to develop a sandwich panel that can be applied in an economical way that reduces production time and cost, and has excellent rigidity (flexural strength, flexural stiffness and maximum deflection) and light weight.

[0008] The background technology of the present invention is disclosed in Korean Patent Publication No. 10-2017-0116793, Korean Patent Registration No. 10-1619977, etc.

[0009]

[0010] The purpose of the present invention is to provide a sandwich panel having excellent rigidity (flexural strength, flexural rigidity and maximum deflection), light weight, etc.

[0011] Another object of the present invention is to provide a method for manufacturing the sandwich panel.

[0012] The above and other objects of the present invention can all be achieved by the present invention described below.

[0013]

[0014] 1. One aspect of the present invention relates to a sandwich panel. The sandwich panel comprises: a foam molded body; a first thermoplastic continuous fiber reinforced woven body fused to an upper portion of the foam molded body; a second thermoplastic continuous fiber reinforced woven body fused to a lower portion of the foam molded body; And at least one composite material bar embedded inside the foamed molded body; wherein the first thermoplastic continuous fiber reinforced woven fabric and the second thermoplastic continuous fiber reinforced woven fabric are woven fabrics in which a continuous fiber composite material in the form of a tape in which continuous glass fibers are impregnated with polypropylene resin is used as warp and weft yarns, and a void space of about 3 to about 30 mm × about 3 to about 30 mm in size is formed between the warp and warp yarns and between the weft and the weft yarns, and the composite material bar includes at least one continuous fiber composite material in the form of a tape in which continuous glass fibers are impregnated with polypropylene resin and a discontinuous fiber composite material surrounding the continuous fiber composite material, and the discontinuous fiber composite material is characterized in that it includes a polypropylene resin and discontinuous glass fibers.

[0015] 2. In the above 1 specific example, the foamed molded article may be formed by filling a foamable resin composition in the form of foamed particles, which is manufactured by foaming a resin composition including a polypropylene resin so that the foaming ratio is about 5 to about 50 times and the average cell size is about 50 to about 400 ㎛, into a mold, and heating and fusing the foamed resin composition.

[0016] 3. In the above two specific examples, the polypropylene resin may include at least one of a propylene homopolymer, a propylene-ethylene random copolymer, and an ethylene-propylene copolymer.

[0017] 4. In the above 2 or 3 specific examples, the foaming is performed by mixing a dispersion medium including water and a dispersant into the resin composition to prepare a mixture, adding a foaming agent to the mixture, and then heating the mixture with the foaming agent added thereto under temperature conditions of about 130 to about 160°C and pressure of about 15 to about 60 kgf / cm. 2 It may be heated and pressurized to achieve pressure conditions, and then exposed to room temperature and atmospheric pressure conditions.

[0018] 5. In the above specific examples 1 to 4, the continuous fiber composite material may include about 20 to about 80 wt% of the continuous glass fiber and about 20 to about 80 wt% of the polypropylene resin.

[0019] 6. In the above 1 to 5 specific examples, the continuous fiber composite material may be in the form of a tape having a thickness of about 0.3 to about 1.2 mm and a width of about 5 to about 25 mm.

[0020] 7. In the above specific examples 1 to 6, the composite material bar can be manufactured by simultaneously injecting the continuous fiber composite material into a mold into which the discontinuous fiber composite material, which is melted and extruded from an extruder, is injected, and drawing the composite material bar that is pushed out from the end of the mold.

[0021] 8. In the above specific examples 1 to 7, the composite material bar may have one or more cross-sectional shapes of “ㅁ”, “L”, “T”, and “I”.

[0022] 9. In the above 1 to 8 specific examples, the sandwich panel may be in a form in which the foam molded body is filled and fused into the empty space of the first thermoplastic continuous fiber reinforced woven body and the second thermoplastic continuous fiber reinforced woven body, and one or more of the composite material bars are embedded inside the foam molded body.

[0023] 10. In the above specific examples 1 to 9, the sandwich panel may be in a form in which two or three sandwich panels are connected by hinges and can be folded.

[0024] 11. In the above 1 to 10 specific examples, the sandwich panel may have a flexural strength of about 12 MPa or more in a four-point flexural test of a 350 mm × 50 mm × 12 mm sized specimen measured by applying a flexural load at a rate of 5 mm / min under conditions of a lower span of 300 mm and an upper span of 100 mm in accordance with ASTM D7249.

[0025] 12. In the above specific examples 1 to 11, the sandwich panel may have a flexural rigidity of about 3 GPa or more in a four-point flexural test of a 350 mm × 50 mm × 12 mm sized specimen measured by applying a flexural load at a rate of 5 mm / min under conditions of a lower span of 300 mm and an upper span of 100 mm in accordance with ASTM D7249.

[0026] 13. Another aspect of the present invention relates to a method for manufacturing a sandwich panel. The method comprises the steps of: fixing a first thermoplastic continuous fiber-reinforced woven fabric and a second thermoplastic continuous fiber-reinforced woven fabric to the surfaces of both molds, respectively; inserting at least one composite bar into the mold; filling the mold with a foamable resin composition so that the foamable resin composition is positioned between the first thermoplastic continuous fiber-reinforced woven fabric and the second thermoplastic continuous fiber-reinforced woven fabric and the composite bar is embedded therein; And a step of manufacturing a sandwich panel including a foamed molded body formed from the foamed resin composition by supplying saturated steam to the mold, thereby heating and fusing the foamed resin composition, the first thermoplastic continuous fiber reinforced woven body, the second thermoplastic continuous fiber reinforced woven body, and the composite material bar, the first thermoplastic continuous fiber reinforced woven body fusing to the upper portion of the foamed molded body, the second thermoplastic continuous fiber reinforced woven body fusing to the lower portion of the foamed molded body, and at least one composite material bar embedded inside the foamed molded body; wherein the first thermoplastic continuous fiber reinforced woven body and the second thermoplastic continuous fiber reinforced woven body utilize a tape-shaped continuous fiber composite material in which continuous glass fiber is impregnated with polypropylene resin as warp and weft, and are woven so that a void space of about 3 to about 30 mm × about 3 to about 30 mm in size is formed between the warp and warp and between the weft and the weft. A woven body, wherein the composite material bar comprises at least one continuous fiber composite material in the form of a tape in which continuous glass fibers are impregnated with polypropylene resin and a discontinuous fiber composite material surrounding the continuous fiber composite material, wherein the discontinuous fiber composite material comprises polypropylene resin and discontinuous glass fibers.

[0027] 14. In the above 13 specific examples, the foamable resin composition may be foam particles manufactured by foaming a resin composition including a polypropylene resin so that the foaming ratio is about 5 to about 50 times and the average cell size is about 50 to about 400 ㎛.

[0028]

[0029] The present invention has the effect of providing a sandwich panel having excellent rigidity (flexural strength, flexural rigidity and maximum deflection), light weight, etc., and a method for manufacturing the same.

[0030]

[0031] Figure 1 is a perspective view of a sandwich panel according to one specific example of the present invention.

[0032] Figure 2 is a cross-sectional view of a sandwich panel according to one specific example of the present invention.

[0033] FIG. 3 is a plan view of the first and second thermoplastic continuous fiber reinforced woven fabrics according to one specific example of the present invention.

[0034] Figure 4 is a photograph of a composite bar manufactured according to one specific example of the present invention.

[0035]

[0036] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. However, the following embodiments are provided to enable those skilled in the art to fully understand the present invention, and may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0037] In order to clearly express the components in the drawings, the sizes of the components, such as their widths and thicknesses, are somewhat enlarged. In addition, although only a portion of the components is illustrated for convenience of explanation, those skilled in the art will be able to easily understand the remaining portions of the components. Furthermore, those skilled in the art will be able to implement the concept of the present invention in various other forms without departing from the technical spirit of the present invention. Overall, the drawings have been described from the observer's perspective, and the terms "upper," "lower," "left," "right," "front," and "back" are based on the drawings. Furthermore, those skilled in the art will be able to implement the concept of the present invention in various other forms without departing from the technical spirit of the present invention. In addition, the same reference numerals in multiple drawings indicate substantially the same elements.

[0038] In addition, singular expressions should be understood to include plural expressions unless the context clearly indicates otherwise, and terms such as "comprises", "have", etc. should be understood to specify the presence of a described feature, number, step, operation, component, part, or combination thereof, but not to exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0039] In this specification, “a to b” indicating a numerical range is defined as “≥a and ≤b”.

[0040]

[0041] FIG. 1 is a perspective view of a sandwich panel according to one embodiment of the present invention, and FIG. 2 is a cross-sectional view of a sandwich panel according to one embodiment of the present invention. As shown in FIGS. 1 and 2, a sandwich panel (100) according to one embodiment of the present invention includes a foam molded body (110) as a core layer; a first thermoplastic continuous fiber reinforced woven body (120) fused to an upper portion of the foam molded body (110) as a reinforcing layer; and a second thermoplastic continuous fiber reinforced woven body (130) fused to a lower portion of the foam molded body (110); and one or more composite material bars (140) embedded in the interior of the foam molded body (110) as a reinforcing material.

[0042] A foamed molded article (110) according to one specific example of the present invention may be formed by filling a foamable resin composition in the form of foamed particles, which is manufactured by foaming a resin composition including a polypropylene resin so that the foaming ratio is about 5 to about 50 times and the average cell size is about 50 to about 400 ㎛, into a mold and heating and fusing the foamed resin composition.

[0043] In a specific example, the resin composition may be in the form of pellets obtained by mixing the above components and melt-extruding them at about 150 to about 240°C, for example, about 160 to about 230°C, using a conventional single-screw or twin-screw extruder.

[0044] In a specific example, the foamable resin composition (foam particles) may have a foaming ratio of about 5 to about 50 times, for example, about 10 to about 40 times, and an average cell size of about 50 to about 400 ㎛, for example, about 70 to about 300 ㎛. In the above range, the foaming moldability (adhesion) and mechanical properties of the foam particles may be excellent. Here, the foaming ratio of the foam particles may be measured by a direct immersion method, and specifically, the weight and volume of the dried foam particles are measured using a graduated cylinder and a scale, and the density of the particles is calculated, and then the density of the resin composition particles before foaming is 0.9 g / cm3 This is a value converted to 1 times the standard, and the average cell size is a value obtained by cooling the foam particles with liquid nitrogen, cutting the cross-section, measuring the cell diameter (size) of three or more foam particles using a SEM (Scanning Electron Microscope), and calculating the average value.

[0045] In a specific example, the polypropylene resin is a base resin for forming a foamable resin composition and a foamed molded article, and may include a propylene homopolymer; a propylene-ethylene random copolymer; an ethylene-propylene copolymer in which a propylene homopolymer portion and an ethylene-propylene copolymer portion are stepwise polymerized in a reactor; or a combination thereof. For example, a propylene-ethylene random copolymer may be used.

[0046] In a specific example, the polypropylene resin may have a melt flow index of about 1 to about 50 g / 10 min, for example, about 5 to about 30 g / 10 min, measured under conditions of 230°C and 2.16 kg according to ASTM D1238. Within this range, the mechanical strength, molding processability, and foaming properties of the foamable resin composition (foam particles) may be excellent.

[0047] In a specific embodiment, the foamable resin composition may further include additives used in conventional foamable resin compositions, as long as they do not impede the purpose and effects of the present invention. Examples of the additives include, but are not limited to, antioxidants, light stabilizers, heat stabilizers, flame retardants, colorants, plasticizers, slip agents, and combinations thereof. When the additives are used, the content thereof may be about 0.001 to about 40 parts by weight, for example, about 0.1 to about 10 parts by weight, based on about 100 parts by weight of the polypropylene.

[0048] In a specific example, the foamable resin composition can be manufactured according to a known foam particle manufacturing method. For example, a mixture can be manufactured by mixing a dispersion medium including water and a dispersant with the resin composition; and a foaming agent can be added to the mixture, followed by foaming to obtain the foaming ratio and the average cell size.

[0049] In a specific embodiment, the dispersant may include one or more of a higher fatty acid, a higher fatty acid ester, and a higher fatty acid amide.

[0050] In a specific example, the resin composition may be introduced into a reactor in which a dispersion medium is present, or the dispersion medium may be introduced into the reactor together with the resin composition to form a mixture.

[0051] In a specific example, the foaming agent may be a foaming agent used in conventional foam particles, and for example, carbon dioxide, propane, butane, hexane, pentane, heptane, cyclobutane, cyclohexane, methyl chloride, ethyl chloride, methylene chloride, dimethyl ether, diethyl ether, methyl ethyl ether, nitrogen, argon, etc. may be used alone or in combination of two or more.

[0052] In a specific example, the foaming is carried out under temperature conditions of about 130 to about 160°C, for example, about 135 to about 155°C, and about 15 to about 60 kgf / cm of the mixture into which the foaming agent is added. 2 , for example, about 20 to about 50 kgf / cm 2 After heating and pressurizing to achieve the pressure conditions, it can be performed by exposing to room temperature and atmospheric pressure conditions. Under the above temperature and pressure conditions, foam particles (foamable resin composition) having a foaming ratio of about 5 to about 50 times and an average cell size of about 50 to about 400 ㎛ can be obtained.

[0053] In a specific example, the foam particles (foamable resin composition) may have an average particle diameter of about 1 to about 7 mm, for example, about 2 to about 6 mm, as measured by a vernier caliper, but is not limited thereto. Within this range, the foaming moldability, etc., may be excellent.

[0054] In a specific example, the foamed molded body (110) can be formed by filling the foamable resin composition (foam particles) into a mold and fusing them, and can be easily manufactured by a person having ordinary skill in the art to which the present invention pertains. For example, the foamed molded body (110) can be a foamed molded body manufactured by filling (introducing) the foamed particles into a non-airtight mold, supplying saturated steam (e.g., saturated steam at a pressure of about 2.0 to about 3.5 bar) to the mold for about 30 seconds, fusing the foamed particles to each other, and drying the same.

[0055] FIG. 3 is a plan view of first and second thermoplastic continuous fiber reinforced woven fabrics according to one embodiment of the present invention. As illustrated in FIG. 3, the first thermoplastic continuous fiber reinforced woven fabric (120) according to one embodiment of the present invention; and the second thermoplastic continuous fiber reinforced woven fabric (130); are characterized in that they are woven fabrics in which a tape-shaped continuous fiber composite material in which continuous glass fibers are impregnated with polypropylene resin is used as warp yarns (122, 132) and weft yarns (124, 134), and a void space (126, 136) having a size of about 3 to about 30 mm × about 3 to about 30 mm is formed between the warp yarns (122, 132) and the warp yarns (122, 132) and between the weft yarns (124, 134) and the weft yarns (124, 134).

[0056] In a specific example, the first thermoplastic continuous fiber reinforced woven fabric (120) and the second thermoplastic continuous fiber reinforced woven fabric (130) are configured to allow the introduction of saturated steam for heating and fusing into the mold through empty spaces (126, 136), and further, the same polypropylene resin as the polypropylene resin, which is the base resin of the foamed molded body (110, foamable resin composition), is applied to ensure excellent adhesion between similar materials during the heating and fusing process.

[0057] In a specific example, the continuous fiber composite material may include about 20 to about 80 wt%, for example, about 40 to about 50 wt%, of the continuous glass fiber and about 20 to about 80 wt%, for example, about 50 to about 60 wt%, of the polypropylene resin. Within this range, the rigidity, etc., of the sandwich panel may be excellent.

[0058] In a specific example, the continuous fiber composite material may have a thickness of about 0.3 to about 1.2 mm, for example, about 0.4 to about 1.1 mm, and may be in the form of a tape having a width of about 5 to about 25 mm, for example, about 7 to about 20 mm. Within the above range, the rigidity of the sandwich panel may be excellent.

[0059] In a specific example, the continuous fiber composite material can be manufactured by a known manufacturing method, and for example, can be manufactured using a manufacturing device disclosed in Korean Patent Publication No. 10-2018-0035064.

[0060] In addition, as illustrated in FIG. 2, a composite material bar (140) according to one specific example of the present invention includes at least one continuous fiber composite material (142) in the form of a tape in which continuous glass fibers are impregnated with polypropylene resin; and a discontinuous fiber composite material (144) surrounding the continuous fiber composite material. For example, the composite material bar (140) may be manufactured by simultaneously injecting the continuous fiber composite material (142) into a mold into which the discontinuous fiber composite material (144) melted and extruded from an extruder is injected, and drawing a bar-shaped composite material bar (140) that is pushed out from the end of the mold, according to a known extrusion and drawing molding method.

[0061] In a specific example, the continuous fiber composite material (142) may be a continuous fiber composite material used in the first thermoplastic continuous fiber reinforced woven fabric (120) and the second thermoplastic continuous fiber reinforced woven fabric (130).

[0062] In a specific example, the discontinuous fiber composite material (144) includes a polypropylene resin and discontinuous glass fibers, and uses the same polypropylene resin as the base resin of the foamed molded body (110, foamable resin composition), so that excellent adhesion between similar materials is realized during the heating and fusing process of the foamable resin composition (foam particles).

[0063] In specific embodiments, the discontinuous glass fibers may include short glass fibers having an average diameter of about 14 to about 17 μm and an average length of about 0.1 to about 2 mm, and / or long glass fibers having an average diameter of about 14 to about 17 μm and an average length of about 8 to about 12 mm.

[0064] In a specific example, the discontinuous fiber composite material (144) may include about 20 to about 80 wt%, for example, about 30 to about 70 wt%, of the polypropylene resin and about 20 to about 80 wt%, for example, about 30 to about 70 wt%, of the discontinuous glass fiber. Within this range, the rigidity, etc., of the sandwich panel may be excellent.

[0065] In a specific example, the composite bar (140) may have one or more cross-sectional shapes of "ㅁ", "L", "T", and "I". This cross-sectional shape can be adjusted according to the shape of the mold used in the extrusion and drawing molding. In addition, the composite bar (140) can be arranged in the longitudinal direction of the sandwich panel (100), and in the case of a discontinuous sandwich panel (100) with hinges connected, arranging the composite bar (140) around the hinges can help improve the rigidity of the sandwich panel (100). In addition, in the composite material bar (140), manufacturing the continuous fiber composite material (142) so that it is positioned in the thickness direction of the sandwich panel (100) (the vertical direction of the first thermoplastic continuous fiber reinforced woven fabric (120) and the second thermoplastic continuous fiber reinforced woven fabric (130)) can help improve the rigidity of the sandwich panel (100).

[0066] In a specific example, the thickness of the cross-section of the composite material bar (140) may be about 1 to about 10 mm, for example, about 2 to about 8 mm. Within this range, the sandwich panel may have excellent rigidity, lightness, etc.

[0067]

[0068] According to one specific example of the present invention, the sandwich panel (100) may be formed in such a manner that the foam molded body (110) is filled and fused into the empty spaces (126, 136) of the first thermoplastic continuous fiber reinforced woven body (120) and the second thermoplastic continuous fiber reinforced woven body (130), and at least one composite material bar (140) is embedded inside the foam molded body (110). Here, the foam molded body (110) may be formed in such a manner that it fills the empty spaces (126, 136) and covers part or all of the upper portion of the first thermoplastic continuous fiber reinforced woven body (120) and part or all of the lower portion of the second thermoplastic continuous fiber reinforced woven body (130), but is not limited thereto. In addition, the foamed molded body (110) may cover the entire first thermoplastic continuous fiber reinforced woven fabric (120) and the second thermoplastic continuous fiber reinforced woven fabric (130), so that the first and second thermoplastic continuous fiber reinforced woven fabrics (120, 130) are not exposed to the surface of the sandwich panel (100).

[0069] In a specific example, the sandwich panel (100) may be foldable in a form in which two or three sandwich panels (100) are connected by a hinge (not shown).

[0070] In a specific example, the sandwich panel (100) comprises: a step of fixing the first thermoplastic continuous fiber reinforced woven fabric (120) and the second thermoplastic continuous fiber reinforced woven fabric (130) to the surfaces of both molds, respectively; a step of inserting one or more composite material bars (140) into the mold; a step of filling the mold with the foamable resin composition so that it is positioned between the first thermoplastic continuous fiber reinforced woven fabric (120) and the second thermoplastic continuous fiber reinforced woven fabric (130) and the composite material bars (140) are embedded therein; And a step of supplying saturated steam (for example, saturated steam at a pressure of about 2.0 to about 3.5 bar) to the mold for about 30 seconds to heat and fuse the foamable resin composition, the first thermoplastic continuous fiber reinforced woven fabric (120), the second thermoplastic continuous fiber reinforced woven fabric (130), and the composite material bar (140), thereby manufacturing a sandwich panel (100) including a foamed molded body (110) formed from the foamable resin composition, the first thermoplastic continuous fiber reinforced woven fabric (120) fused to the upper portion of the foamed molded body (110), the second thermoplastic continuous fiber reinforced woven fabric (130) fused to the lower portion of the foamed molded body (110), and one or more composite material bars (140) embedded inside the foamed molded body (110).

[0071] The above manufacturing method is an insert foam molding process that adds only the step of fixing a first thermoplastic continuous fiber reinforced woven fabric (120) and a second thermoplastic continuous fiber reinforced woven fabric (130) to the surfaces of both molds, respectively, and inserting a composite material bar (140) to the existing foam molding manufacturing method, and is an economical method that reduces production time and cost, etc., without a separate bonding process for bonding a reinforcing layer and reinforcing material to a core layer.

[0072] In a specific example, the sandwich panel may have a flexural strength of about 12 MPa or more, for example, about 12.5 to about 15 MPa, as measured by applying a flexural load at a rate of 5 mm / min under the conditions of a lower span of 300 mm and an upper span of 100 mm in a four-point flexural test of a 350 mm × 50 mm × 12 mm specimen according to ASTM D7249.

[0073] In a specific example, the sandwich panel may have a flexural rigidity of about 3 GPa or more, for example, about 3 to about 4 GPa, as measured by applying a flexural load at a rate of 5 mm / min under conditions of a lower span of 300 mm and an upper span of 100 mm in accordance with ASTM D7249, in a four-point flexural test of a 350 mm × 50 mm × 12 mm specimen.

[0074]

[0075] Hereinafter, the present invention will be described in more detail through examples; however, these examples are for the purpose of explanation only and should not be construed as limiting the present invention.

[0076]

[0077] Example

[0078] Manufacturing example: Manufacturing of composite bars

[0079] Composite bars manufactured through a general extrusion process only use discontinuous fiber composites, and the molten material discharged from the extruder nozzle passes through a mold of a specific shape to continuously produce bars with a cross-section of a certain shape. Composite bars have the advantage of high productivity and a variety of cross-sectional shapes, but because they are composed only of discontinuous fibers without continuous fibers, their physical properties are low. To compensate for this, a tape-shaped continuous fiber composite material (the black part in Fig. 4), in which continuous glass fibers are impregnated with polypropylene resin, is simultaneously injected into the mold into which the molten discontinuous fiber composite material (including polypropylene resin and discontinuous glass fiber, the white part in Fig. 4) from the extruder is injected, and the composite bar that is extruded from the mold outlet is drawn and manufactured. Since the continuous fiber composite material is manufactured in tape form, it is easy to insert into a mold, and since the same resin as the discontinuous fiber composite material is used, interfacial adhesion occurs naturally, and the continuous fiber composite material is automatically oriented and drawn in the longitudinal direction as it passes through the mold along the discontinuous fiber composite material being extruded. A photograph of the manufactured composite material bar is shown in Fig. 4.

[0080]

[0081] Example 1: Manufacturing of sandwich panels

[0082] A resin composition (in the form of pellets with a diameter of approximately 0.8 mm × a length of approximately 1.1 mm, each pellet weighing approximately 1.2 mg) was prepared by extruding a propylene-ethylene random copolymer (manufacturer: Lotte Chemical, product name: SEP-550) at 220°C. The extrusion was performed using a single-screw extruder (screw rotation speed: approximately 700 rpm) with an L / D of 34 and a diameter of 40 mm.

[0083] Next, 100 parts by weight of the resin composition was placed in an autoclave together with 300 parts by weight of a dispersion medium (water with a dispersant added). After adding carbon dioxide (CO2), a foaming agent, to the autoclave, the temperature and pressure inside the autoclave were adjusted to about 147°C and about 40 kg / cm while stirring. 2 Next, the contents of the autoclave were exposed to the atmosphere to produce foam particles (foamable resin composition, foaming ratio of about 20 times, average cell size of about 200 ㎛), which were dried at room temperature for about 24 hours, then placed in a pressurized tank and pressurized from atmospheric pressure (1 bar) to 3 bar for about 10 hours.

[0084] Next, a first thermoplastic continuous fiber reinforced woven fabric (a woven fabric manufactured by Sambak LFT Co., Ltd. using a tape-shaped continuous fiber composite material (continuous fiber reinforced composite material (CFT)) with a thickness of about 0.4 mm and a width of about 11 mm as weft and warp yarns, and a woven fabric manufactured so that a void of about 4 mm × about 4 mm is formed between the continuous fiber reinforced composite materials) and a second thermoplastic continuous fiber reinforced woven fabric (a woven fabric manufactured by Sambak LFT Co., Ltd. using a tape-shaped continuous fiber composite material (continuous fiber reinforced composite material (CFT)) with a thickness of about 0.4 mm and a width of about 11 mm as weft and warp yarns, and a woven fabric manufactured so that a void of about 4 mm × about 4 mm is formed between the continuous fiber reinforced composite materials) are fixed to the mold surface, and the composite material bar of the above manufacturing example is inserted, and then the mold is closed and the foam particles are formed. It was filled into the mold. Here, pins were created in the mold to fix the thermoplastic continuous fiber reinforced woven fabric to the surface of the foam mold so that the woven fabric could be inserted and fixed. A circular hole with the same diameter as the pin on the mold surface was created in the woven fabric so that it could be fixed after being inserted into the pin.

[0085] After this, saturated steam of about 2.5 bar was supplied to the mold for about 30 seconds to fuse the foam particles, the first thermoplastic continuous fiber reinforced woven fabric, the second thermoplastic continuous fiber reinforced woven fabric, and the composite material bar, and after cooling and taking it out, it was dried in a convection oven at about 70°C for about 12 hours, thereby manufacturing a sandwich panel including a foam molded body, a first thermoplastic continuous fiber reinforced woven fabric fused to the upper part of the foam molded body, a second thermoplastic continuous fiber reinforced woven fabric fused to the lower part of the foam molded body, and a composite material bar embedded inside the foam molded body. The physical properties of the manufactured sandwich panel were evaluated by the following method, and the results are shown in Table 1 below.

[0086]

[0087] Comparative Example 1: Manufacturing of sandwich panels

[0088] The same foam particles were filled into the luggage board mold used in Example 1, and saturated steam of about 2.5 bar was supplied to the mold for about 30 seconds to fuse the foam particles together, cool them, take them out, and dry them in a convection oven at about 70°C for about 12 hours to produce a foam molded body.

[0089] Next, the upper and lower portions of the foamed molded body were heated to a temperature of approximately 180 to 220°C, and then a separately prepared thermoplastic felt sheet was heat-sealed and bonded. At this time, the separately prepared thermoplastic felt sheet was also preheated to a temperature of approximately 180 to 220°C, and a sandwich panel was manufactured through heat fusion through cold press molding. The physical properties of the manufactured sandwich panel were evaluated using the following method, and the results are shown in Table 1 below.

[0090]

[0091] Comparative Example 2

[0092] Luggage boards of the same dimensions manufactured using the GM-PUR (Glass Mat-Polyurethane) process, one of the existing luggage board mass production processes, were purchased, and their physical properties were evaluated using the following method, and the results are shown in Table 1 below.

[0093]

[0094] Method of measuring physical properties

[0095] (1) Lightness evaluation: The weight of each luggage board product manufactured by connecting a sandwich panel of size 996 mm × 429 mm × 21 mm (width × length × thickness) manufactured according to Example 1 and Comparative Example 1 and a sandwich panel of size 996 mm × 384 mm × 21 mm (width × length × thickness) with a hinge made of PP material of size 996 mm × 20 mm × 2 mm (width × length × thickness) was measured, as well as a purchased luggage board product (Comparative Example 2) of the same dimensions.

[0096] (2) Evaluation of stiffness (flexural strength and flexural stiffness): After collecting specimens measuring 350 mm × 50 mm × 12 mm from luggage board products of the examples and comparative examples with the same dimensions, a 4-point flexural test was performed in accordance with ASTM D7249, and a flexural load was applied at a rate of 5 mm / min under the conditions of a lower span of 300 mm and an upper span of 100 mm, to measure the flexural strength (unit: MPa) and flexural stiffness (unit: GPa).

[0097] (3) Evaluation of stiffness (maximum deflection): Each luggage board product manufactured by connecting a sandwich panel of size 996 mm × 429 mm × 21 mm (width × length × thickness) manufactured according to Example 1 and Comparative Example 1 and a sandwich panel of size 996 mm × 384 mm × 21 mm (width × length × thickness) with a hinge made of PP material of size 996 mm × 20 mm × 2 mm (width × length × thickness) was placed on a fixture with an overlap of 30 mm along the perimeter of a purchased luggage board product (Comparative Example 2) of the same dimensions, and then a load of 80 kg was applied to a square area of ​​300 mm × 300 mm at the center of the hinge portion, and the maximum deflection (unit: mm) was measured.

[0098]

[0099] Example 1Comparative Example 1Comparative Example 2Product Weight (kg)2.13.32.2Flexural Strength (MPa)12.69.86.7Flexural Stiffness (GPa)3.22.31.6Maximum Deflection (mm)10.713.514.3

[0100]

[0101] From the above results, it can be seen that the sandwich panel of the present invention was manufactured in an economical manner, reducing production time and cost, by applying an insert foam molding process that only adds a step of fixing a first thermoplastic continuous fiber reinforced woven fabric and a second thermoplastic continuous fiber reinforced woven fabric to the surface of a mold and inserting a composite material bar into the mold to the existing foam molded body manufacturing process, without a separate bonding process for bonding a reinforcing layer and reinforcing material to the core layer. In addition, it can be seen that it has excellent lightness and rigidity, and is environmentally friendly because no adhesives are used.

[0102] On the other hand, in Comparative Example 1, which used felt instead of the first and second thermoplastic continuous fiber reinforced woven fabrics of the present invention and did not use a composite material bar, insert foam molding was not possible, so a separate bonding process was required, which resulted in reduced environmental friendliness and economic feasibility. In addition, it can be seen that Comparative Examples 1 and 2 lack structural performance, such as lightness and rigidity, compared to Example 1.

[0103]

[0104] The present invention has been described above, focusing on specific embodiments. Those skilled in the art will appreciate that the present invention can be implemented in modified forms without departing from its essential characteristics. Therefore, the disclosed embodiments should be considered illustrative rather than limiting. The scope of the present invention is set forth in the claims, not the foregoing description, and all differences within the scope equivalent thereto should be construed as being encompassed by the present invention.

Claims

1. Foam molded body; A first thermoplastic continuous fiber reinforced woven fabric fused to the upper portion of the foamed molded body; A second thermoplastic continuous fiber reinforced woven fabric fused to the lower portion of the foamed molded body; and comprising one or more composite material bars embedded within the foamed molded body; The first thermoplastic continuous fiber reinforced woven fabric and the second thermoplastic continuous fiber reinforced woven fabric are woven fabrics in which a continuous fiber composite material in the form of a tape in which continuous glass fibers are impregnated with polypropylene resin is used as warp and weft yarns, and a void space of about 3 to about 30 mm × about 3 to about 30 mm in size is formed between the warp and warp yarns and between the weft and weft yarns. The above composite material bar includes at least one continuous fiber composite material in the form of a tape in which continuous glass fibers are impregnated with polypropylene resin and a discontinuous fiber composite material surrounding the continuous fiber composite material. A sandwich panel characterized in that the above discontinuous fiber composite material includes polypropylene resin and discontinuous glass fiber.

2. A sandwich panel characterized in that, in the first paragraph, the foamed molded body is formed by filling a foamed resin composition in the form of foamed particles, which is manufactured by foaming a resin composition containing a polypropylene resin so that the foaming ratio is about 5 to about 50 times and the average cell size is about 50 to about 400 ㎛, into a mold, and heating and fusing the foamed resin composition.

3. A sandwich panel according to claim 2, characterized in that the polypropylene resin comprises at least one of a propylene homopolymer, a propylene-ethylene random copolymer, and an ethylene-propylene copolymer.

4. In the second or third paragraph, the foaming is performed by mixing a dispersion medium containing water and a dispersant with the resin composition to prepare a mixture, adding a foaming agent to the mixture, and then adding the foaming agent to the mixture under temperature conditions of about 130 to about 160°C and pressure of about 15 to about 60 kgf / cm. 2 A sandwich panel characterized in that it is heated and pressurized to achieve pressure conditions, and then exposed to room temperature and atmospheric pressure conditions.

5. A sandwich panel according to any one of claims 1 to 4, characterized in that the continuous fiber composite material comprises about 20 to about 80 wt% of the continuous glass fiber and about 20 to about 80 wt% of the polypropylene resin.

6. A sandwich panel according to any one of claims 1 to 5, wherein the continuous fiber composite material is in the form of a tape having a thickness of about 0.3 to about 1.2 mm and a width of about 5 to about 25 mm.

7. A sandwich panel characterized in that the composite material bar according to any one of claims 1 to 6 is manufactured by simultaneously injecting the continuous fiber composite material into a mold into which the discontinuous fiber composite material, which is melted and extruded from an extruder, is injected, and drawing the composite material bar that is pushed out from the end of the mold.

8. A sandwich panel according to any one of claims 1 to 7, characterized in that the composite material bar has at least one cross-sectional shape among “ㅁ”, “L”, “T”, and “I”.

9. A sandwich panel according to any one of claims 1 to 8, characterized in that the foam molded body is filled and fused into the empty space of the first thermoplastic continuous fiber reinforced woven body and the second thermoplastic continuous fiber reinforced woven body, and at least one composite material bar is embedded inside the foam molded body.

10. A sandwich panel according to any one of claims 1 to 9, characterized in that the sandwich panel is foldable with two or three sandwich panels connected by hinges.

11. A sandwich panel according to any one of claims 1 to 10, characterized in that the sandwich panel has a flexural strength of about 12 MPa or more in a four-point flexural test of a 350 mm × 50 mm × 12 mm sized specimen measured by applying a flexural load at a rate of 5 mm / min under the conditions of a lower span distance of 300 mm and an upper span distance of 100 mm in accordance with ASTM D7249.

12. A sandwich panel according to any one of claims 1 to 11, characterized in that the sandwich panel has a flexural rigidity of about 3 GPa or more in a four-point flexural test of a 350 mm × 50 mm × 12 mm sized specimen, measured by applying a flexural load at a rate of 5 mm / min under conditions of a lower span distance of 300 mm and an upper span distance of 100 mm, in accordance with ASTM D7249.

13. A step of fixing the first thermoplastic continuous fiber reinforced woven fabric and the second thermoplastic continuous fiber reinforced woven fabric to the surfaces of both molds, respectively; A step of inserting one or more composite material bars into a mold; A step of filling a mold with a foamable resin composition so that the foamable resin composition is positioned between the first thermoplastic continuous fiber reinforced woven fabric and the second thermoplastic continuous fiber reinforced woven fabric and the composite material bar is embedded therein; and A step of manufacturing a sandwich panel including a foamed molded body formed from the foamed resin composition by supplying saturated steam to the mold, thereby heating and fusing the foamed resin composition, the first thermoplastic continuous fiber reinforced woven body, the second thermoplastic continuous fiber reinforced woven body, and the composite material bar, the first thermoplastic continuous fiber reinforced woven body being fusing to the upper portion of the foamed molded body, the second thermoplastic continuous fiber reinforced woven body being fusing to the lower portion of the foamed molded body, and one or more composite material bars embedded inside the foamed molded body; The first thermoplastic continuous fiber reinforced woven fabric and the second thermoplastic continuous fiber reinforced woven fabric are woven fabrics in which a continuous fiber composite material in the form of a tape in which continuous glass fibers are impregnated with polypropylene resin is used as warp and weft yarns, and a void space of about 3 to about 30 mm × about 3 to about 30 mm in size is formed between the warp and warp yarns and between the weft and weft yarns. The above composite material bar includes at least one continuous fiber composite material in the form of a tape in which continuous glass fibers are impregnated with polypropylene resin and a discontinuous fiber composite material surrounding the continuous fiber composite material. A method for manufacturing a sandwich panel, characterized in that the above discontinuous fiber composite material includes polypropylene resin and discontinuous glass fiber.

14. A method for manufacturing a sandwich panel, characterized in that in claim 13, the foamable resin composition is a foam particle manufactured by foaming a resin composition including a polypropylene resin so that the foaming ratio is about 5 to about 50 times and the average cell size is about 50 to about 400 ㎛.

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