Foamed resin sheets and molded resin products

Abstract

To provide lightweight foamed resin sheets and vacuum-formed products made from foamed resin sheets that offer excellent impact resistance and resilience. [Solution] The foamed resin sheet 1 comprises a core layer 2 made of foamed resin, a skin layer 3 made of non-foamed resin laminated on one main surface of the core layer 2, and a skin layer 4 laminated on the other main surface of the core layer 2. The core layer 2 contains amorphous engineering plastic. Each of the skin layers 3 and 4 contains thermoplastic polyester elastomer. The foamed resin sheet has a density of 0.4 to 0.9 g / cm³. 3 It has a density and satisfies the equation "0.1 ≤ (t1 + t2) / T ≤ 0.5". In this equation, t1 represents the thickness of skin layer 3, t2 represents the thickness of skin layer 4, and T represents the thickness of foamed resin sheet 1.

Description

[Technical Field]

[0001] This disclosure relates to foamed resin sheets and resin molded products. [Background technology]

[0002] In recent years, foamed resins have attracted attention because they can improve convenience by making resin molded products lighter, and also reduce carbon dioxide emissions.

[0003] In recent years, there has been a demand for lighter interior and exterior materials for automobiles from the perspective of improving fuel efficiency. In response to this, various interior and exterior materials using lightweight resins have been offered. However, interior and exterior materials using resins (especially exterior materials) have presented problems such as reduced impact strength and secondary damage caused by fragments scattered in the event of an accident.

[0004] To further reduce the weight of automotive interior and exterior materials, foam molding of resins has been considered. Foam molding allows for increased thickness and improved rigidity by expanding the resin, while also contributing to weight reduction by reducing the amount of resin used.

[0005] Japanese Patent Publication No. 2024-058068 (Patent Document 1) discloses a laminated foam sheet having a non-slip surface, excellent heat resistance, and excellent thermoformability. The laminated foam sheet has a foamed layer and a first non-foamed layer located on one side of the foamed layer. The resin constituting the foamed layer is a polyester resin, and the non-foamed layer contains a polyester elastomer. The degree of crystallinity of the foamed polyester resin is 20% or less, and the durohardness D of the first non-foamed layer is 70 or less.

[0006] Japanese Patent Publication No. 2023-152225 (Patent Document 2) discloses a co-extruded sheet that can suppress surface bulging and cracking during thermal shaping such as vacuum forming, and can obtain excellent mechanical strength. The co-extruded sheet comprises a core layer made of foamed resin containing polycarbonate resin, and a first skin layer and a second skin layer made of non-foamed resin. The first skin layer is laminated on one main surface of the core layer, and the second skin layer is laminated on the other main surface of the core layer. The co-extruded sheet has a density of 0.4 to 0.9 g / cm³. 3 It has a density of . The co-extruded sheet has a thickness of 1 to 5 mm and satisfies formula (1) {0.10 ≤ (t1 + t2) / T ≤ 0.5}. In formula (1), t1 is the thickness of the first skin layer, t2 is the thickness of the second skin layer, and T is the thickness of the co-extruded sheet. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2024-058068 [Patent Document 2] Japanese Patent Publication No. 2023-152225 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The objective of this disclosure is to provide foamed resin sheets and resin molded products that are lightweight while exhibiting excellent impact resistance and resilience. [Means for solving the problem]

[0009] To solve the above problems, this disclosure employs the following solutions. Specifically, the foamed resin sheet according to this disclosure comprises a core layer made of foamed resin, a first skin layer made of non-foamed resin laminated on one main surface of the core layer, and a second skin layer laminated on the other main surface of the core layer. The core layer contains amorphous engineering plastic. The first skin layer and the second skin layer each contain thermoplastic polyester elastomer. The foamed resin sheet has a viscosity of 0.4 to 0.9 g / cm³. 3 It has a density and satisfies the following equation. 0.1 ≤ (t1 + t2) / T ≤ 0.5 In the above formula, t1 represents the thickness of the first skin layer, t2 represents the thickness of the second skin layer, and T represents the thickness of the foamed resin sheet.

[0010] Furthermore, the resin molded product relating to this disclosure consists of the foamed resin sheet described above. [Effects of the Invention]

[0011] The foamed resin sheet and resin molded product relating to this disclosure can be made lightweight while achieving excellent impact resistance and resilience. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a perspective view showing a foamed resin sheet according to an embodiment. [Figure 2] Figure 2 is a cross-sectional view showing the foamed resin sheet shown in Figure 1. [Modes for carrying out the invention]

[0013] The inventors further studied the impact resistance and resilience of interior and exterior automotive materials. Generally, as described above, the hard plastics used for interior and exterior automotive materials have a concern about safety because their impact strength decreases. For example, when cracks occur in the interior and exterior materials due to impact, the fracture surfaces of the fragments become sharp, and secondary damage caused by the fragments can occur. In addition, when a dent occurs in the interior and exterior materials of an automobile (e.g., bumper, etc.) due to impact, it is difficult to restore it to its original shape, and repair or replacement is inevitable.

[0014] Patent Document 1 aims to provide a laminated foam sheet with a surface that is difficult to slip and excellent heat resistance and thermoformability, and does not propose a configuration of a laminated foam sheet for obtaining impact resistance and resilience. Further, although Patent Document 2 forms the thicknesses of the core layer and the skin layer in a predetermined ratio in order to obtain formability such as vacuum forming and excellent mechanical strength, it does not propose a configuration of a coextruded sheet excellent in resilience, which is an object of the present disclosure.

[0015] In order to achieve both excellent impact resistance and resilience of the foamed resin sheet, the inventors considered a foamed resin sheet in which a core layer (foamed layer) and a skin layer (non-foamed layer) are laminated. The core layer is formed by foaming with a resin excellent in impact resistance, and the skin layer is formed by a resin excellent in flexibility and flexural resistance characteristics. The skin layer made of a non-foamed resin excellent in flexibility and flexural resistance characteristics contributes not only to resilience but also to an improvement in impact resistance. However, it is not easy to achieve both impact resistance and resilience while simply reducing the weight of the foamed resin sheet by this method. As a result of intensive studies, the inventors considered the balance between the thickness of the core layer made of a foamed resin and the thickness of the skin layer made of a non-foamed resin excellent in flexibility and flexural resistance characteristics, and formed the foamed resin sheet to have a predetermined density and the thickness ratio of the skin layer to be within a predetermined range. It has been found that both excellent resilience and impact resistance of the foamed resin sheet can be achieved while reducing the weight by foam molding of the core layer. The present disclosure has been completed by the inventors based on such findings.

[0016] Here, in the present disclosure, the term "resilience" refers to a state where when the foamed resin sheet is deformed beyond the yield strain point obtained by a three-point bending test (conforming to "JIS K7171"), no cracks or fractures occur in the foamed resin sheet, and no cracks or fractures occur even when the foamed resin sheet is restored to its original shape. For example, when an iron array weighing 4 kg is freely dropped from a height of 1 m or more onto the main surface of the foamed resin sheet, the foamed resin sheet temporarily dents and deforms. At this time, by applying pressure with finger pressure or a tool from the back side of the main surface that has received the impact, it means that the foamed resin sheet can be restored to its original shape without cracks or fractures occurring.

[0017] (Configuration 1) The foamed resin sheet according to an embodiment of the present disclosure is a foamed resin sheet including a core layer made of a foamed resin, a first skin layer made of a non-foamed resin and laminated on one main surface of the core layer, and a second skin layer laminated on the other main surface of the core layer. The core layer contains an amorphous engineering plastic. Each of the first skin layer and the second skin layer contains a thermoplastic polyester elastomer. The foamed resin sheet has a density of 0.4 to 0.9 g / cm 3 and satisfies the following formula. 0.1 ≦ (t1 + t2) / T ≦ 0.5 In the above formula, t1 represents the thickness of the first skin layer, t2 represents the thickness of the second skin layer, and T represents the thickness of the foamed resin sheet.

[0018] Thus, by controlling the thicknesses of the first skin layer and the second skin layer with respect to the density of the foamed resin sheet and the thickness of the foamed resin sheet in a well-balanced manner, the foamed resin sheet can achieve excellent resilience and impact resistance while achieving weight reduction. Furthermore, it can be easily processed into an arbitrary shape by thermoforming such as vacuum forming or pressure-air forming.

[0019] (Configuration 2) The foamed resin sheet of composition 1 may be a block copolymer having a hard segment made of aromatic polyester and a soft segment made of aliphatic polyester. This improves bending resistance and provides fatigue resistance against repeated impact loads.

[0020] (Composition 3) The foamed resin sheet has a composition of 1 or 2, and the amorphous engineering plastic may be polycarbonate. This improves the heat resistance of the foamed resin sheet, making it easier to use the foamed resin sheet 1 even at high temperatures. In other words, it is possible to mold a resin molded product that has excellent heat resistance and can be used even at high temperatures using the foamed resin sheet.

[0021] (Composition 4) The foamed resin sheet, comprising any one of the three components (1-3), may have a load deflection temperature of 125°C or higher. This improves the heat resistance of the foamed resin sheet, making it easier to use even at high temperatures. In other words, it is possible to mold resin products with excellent heat resistance that can be used even at high temperatures using the foamed resin sheet.

[0022] (Composition 5) In any one of the four components, the foamed resin sheet, in which the resin material forming the core layer, may have an amorphous engineering plastic content of 90% by weight or more. This makes it easier to process the foamed resin sheet into various shapes by heat molding such as vacuum forming.

[0023] (Composition 6) In a foamed resin sheet comprising any one of the configurations 1 to 5, the content of thermoplastic polyester elastomer in the resin material forming the first skin layer and the second skin layer may be 90% by weight or more. This makes it easier to improve the resilience of the foamed resin sheet.

[0024] (Composition 7) The foamed resin sheet is one of the compositions 1 to 6, and the thermoplastic polyester elastomer may be a block copolymer having a hard segment made of polybutylene terephthalate and a soft segment made of polyether. This improves the bending resistance and provides fatigue resistance against repeated impact loads.

[0025] (Composition 8) The resin molded product according to this embodiment consists of one of the foamed resin sheets from components 1 to 7. This allows the resin molded product to achieve excellent resilience and impact resistance while being lightweight. The resin molded product may be formed, for example, by heat shaping such as vacuum forming or pressure forming from a foamed resin sheet.

[0026] Hereinafter, embodiments of the foamed resin sheet 1 of this disclosure will be specifically described with reference to Figures 1 and 2. In the figures, the same and corresponding components are denoted by the same reference numerals, and the same explanation will not be repeated. In order to make the explanation easier to understand, the components in the drawings referred to below are shown in a simplified or schematic manner, and some components are omitted.

[0027] [Foamed resin sheet] As shown in Figure 1, the foamed resin sheet 1 has a core layer 2, a skin layer 3 laminated on one main surface of the core layer 2, and a skin layer 4 laminated on the other main surface of the core layer 2.

[0028] [Core Layer] Core layer 2 is a foamed layer made of foamed resin. That is, core layer 2 is foamed and has a large number of air bubbles. In this disclosure, foamed resin refers to a resin having an average porosity of 5% to 95%. That is, core layer 2 can also be said to have an average porosity of 5% to 95%.

[0029] Core layer 2 contains amorphous engineering plastic. The content of amorphous engineering plastic in the resin material forming core layer 2 is preferably 90% by weight or more, preferably 95% by weight or more, and more preferably 98% by weight or more. However, core layer 2 is more preferably formed using a single resin material, amorphous engineering plastic. That is, the content of thermoplastic polyester elastomer in the resin material forming core layer 2 may be 100% by weight.

[0030] In this disclosure, amorphous engineering plastics are amorphous resins having a deflection temperature of 100°C to 200°C. Examples of amorphous engineering plastics include polycarbonate (PC), acronitrile butadiene styrene (ABS), and polyethylene terephthalate (PET). The amorphous engineering plastics contained in core layer 2 may include one or more selected from the group consisting of these various amorphous engineering plastics. The deflection temperature can be measured in accordance with JIS K7191-1.

[0031] The deflection temperature under load of the amorphous engineering plastic contained in the core layer 2 is preferably 125°C or higher. An amorphous engineering plastic having a deflection temperature under load of 125°C or higher is, for example, polycarbonate. This improves the heat resistance of the foamed resin sheet 1, making it easier to use the foamed resin sheet 1 even at high temperatures.

[0032] The glass transition temperature of the amorphous engineering plastic contained in the core layer 2 is preferably 120°C or higher, more preferably 140°C or higher. An amorphous engineering plastic having a glass transition temperature of 140°C or higher is, for example, polycarbonate. This improves the heat resistance of the foamed resin sheet 1, making it easier to use the foamed resin sheet 1 even at high temperatures.

[0033] [Skin layer] Skin layer 3 and skin layer 4 are non-foamed layers made of non-foamed resin. That is, skin layer 3 and skin layer 4 are not foamed and do not have a large number of air bubbles. In this disclosure, non-foamed resin means a resin having an average porosity of 0% or more and less than 5%. That is, skin layer 3 and skin layer 4 can also be said to have an average porosity of 0% or more and less than 5%.

[0034] Here, the average porosity (%) of core layer 2, skin layer 3, and skin layer 4 can be determined from the ratio of the cross-sectional area of ​​foam cells per unit cross-sectional area in the foamed resin sheet 1. More specifically, the average porosity is calculated as follows. First, the foamed resin sheet 1 is cut in the thickness direction, and the cross-section is photographed at 25x magnification using a scanning electron microscope (Hitachi, Ltd., model number "Miniscope(registered trademark), TM4000Plus2"). In the captured cross-sectional image, the foamed resin sheet 1 is divided into 10 equal parts with a width of 1 mm in the thickness direction, and 10 sections arranged in a row along the thickness direction of the foamed resin sheet 1 are extracted at three locations: the center and both ends in the width direction of the foamed resin sheet 1. Next, the closed cells contained in each section are extracted, and the cross-sectional area of ​​these closed cells is calculated using the cell diameter that maximizes the cell size of these closed cells, and assuming that the closed cells are circular. The average value of the cross-sectional area of ​​the closed cells contained in each section is calculated, and the porosity for each section is calculated by dividing this average value by the cross-sectional area of ​​the section. Next, the average value of the porosity of the three sections in the same thickness region in the three columns mentioned above is calculated. This average value of the porosity of the three sections in the same thickness region is called the average porosity. In order to calculate the average porosity in more detail in the thickness direction, the foamed resin sheet 1 may be divided into 11 or more equal parts.

[0035] Skin layer 3 and skin layer 4 contain thermoplastic polyester elastomer. The content of thermoplastic polyester elastomer in the resin material forming each of skin layer 3 and skin layer 4 is preferably 90% by weight or more, more preferably 95% by weight or more, and more preferably 98% by weight or more. However, each of skin layer 3 and skin layer 4 is more preferably formed using a single resin material, which is thermoplastic polyester elastomer. That is, the content of thermoplastic polyester elastomer in the resin material forming each of skin layer 3 and skin layer 4 may be 100% by weight.

[0036] Thermoplastic polyester elastomers include, for example, "Hytrel®" from Toray Celanese Co., Ltd. Thermoplastic polyester elastomers are block copolymers consisting of hard segments and soft segments.

[0037] The hard segment is made of aromatic polyester. Alternatively, the hard segment may be made of polybutylene terephthalate (PBT). In the thermoplastic polyester elastomer, the hard segment content is 40 to 85% by mass, preferably 50 to 80% by mass. This makes it easier to heat-process the skin layer 3 and skin layer 4 and the core layer.

[0038] The soft segment is made of an aliphatic polyether. Alternatively, the soft segment may be made of a polyether. In the thermoplastic polyester elastomer, the content of the soft segment (L1) is 15 to 60% by mass, and the content of the soft segment (L) is 20 to 50% by mass. This improves the flexibility of the skin layer 3 and skin layer 4, and consequently, the foamed resin sheet 1.

[0039] Thus, by forming a thermoplastic polyester elastomer using a block copolymer having a hard segment made of aromatic polyester (or polybutylene terephthalate) and a soft segment made of aliphatic polyether (or polyether), the bending resistance of the foamed resin sheet 1 can be improved, and fatigue resistance to repeated impact loads can be obtained.

[0040] Furthermore, the resin materials of core layer 2 and skin layers 3 and 4 may contain various types of additives, provided that they do not significantly affect the thermal shaping and mechanical properties. The types of additives are not particularly limited, but examples include bubble nucleating agents, crystal nucleating agents, lubricants, surfactants, tension modifiers, shrinkage inhibitors, flow modifiers, impact modifiers, fillers, reinforcing agents, antioxidants, heat stabilizers, light stabilizers, UV absorbers, plasticizers, lubricants, mold release agents, antistatic agents, colorants (pigments, dyes, etc.), surface effect additives, infrared absorbers, radiation stabilizers, anti-drip agents, and anti-aging agents. The amount of additives can be appropriately selected within a range that does not impair bubble formation, and the amounts used in the molding of ordinary thermoplastic resins can be adopted.

[0041] [Density of foamed resin sheet] The foamed resin sheet 1 has a density of 0.4 to 0.9 g / cm². 3 The density of the foamed resin sheet 1 is preferably 0.6 g / cm³. If the density of the foamed resin sheet 1 is too low, although it is possible to reduce the weight of the foamed resin sheet 1, the impact strength will decrease significantly, making the foamed resin sheet 1 or the molded resin product made from the foamed resin sheet 1 more susceptible to cracking and breakage when subjected to impact. On the other hand, if the density of the foamed resin sheet 1 is too high, it becomes difficult to reduce its weight. From this viewpoint, the density of the foamed resin sheet 1 is preferably 0.6 g / cm³. 3 More than 0.85g / cm 3 It is preferable to keep it below a certain value. Furthermore, from the viewpoint of achieving greater weight reduction and resilience, the density of the foamed resin sheet 1 is preferably 0.7 g / cm³. 3 g / cm³ or more, less than 0.85 g / cm³ 3 It is best to do so. In other words, the density of foamed resin sheet 1 is 0.4 g / cm³.3 Preferably, it is 0.6 g / cm or more 3 or 0.7 g / cm or more 3 and preferably 0.9 g / cm or less 3 Preferably, it is 0.85 g / cm or less. The density of the foamed resin sheet 1 can be measured with an automatic specific gravity meter (DSG-1 (water displacement type density specific gravity meter) manufactured by Toyo Seiki). 3

[0042] [Thickness ratio of the skin layer] The foamed resin sheet 1 satisfies the following formula. 0.1 ≦ (t1 + t2) / T ≦ 0.5 As shown in FIG. 2, in the above formula, t1 represents the thickness of the skin layer 3, t2 represents the thickness of the skin layer 4, and T represents the thickness of the foamed resin sheet 1. That is, in the above formula, "(t1 + t2) / T" represents the thickness ratio of the skin layer to the total thickness of the foamed resin sheet 1. The foamed resin sheet 1 can have a thickness T of, for example, 1 to 5 mm.

[0043] ​If the thickness ratio of the skin layer is too small, the thickness of the skin layer, i.e., the layer made of thermoplastic polyester elastomer, becomes small relative to the total thickness of the foamed resin sheet 1, which tends to reduce resilience. On the other hand, if the thickness ratio of the skin layer, i.e., the non-foamed layer made of non-foamed resin, is too large, it becomes difficult to reduce weight. From the viewpoint of achieving both resilience and weight reduction, the thickness ratio of the skin layer "(t1+t2) / T" should be 0.1 to 0.5, preferably 0.15 to 0.5 (or 0.45), and more preferably 0.25 to 0.5 (or 0.45). In other words, the thickness ratio of the skin layer should be 0.1 or more, preferably 0.15 or more, more preferably 0.25 or more, and 0.5 or less, preferably 0.45 or less. Furthermore, the resin molded product made from the foamed resin sheet 1 is formed by vacuum forming or pressure forming, as described later. The resin molded product may be thinned during vacuum forming or pressure forming. Considering the case where the thickness is reduced, the skin layer thickness ratio is preferably 0.15 or more, more preferably 0.2 or more, and preferably 0.3 or less.

[0044] The thickness t1 of skin layer 3 and the thickness t2 of skin layer 4 can be measured as follows. Observe the cross-section obtained by cutting the foamed resin sheet 1 in the thickness direction along the width direction using a microscope. In this disclosure, for example, a KEYENCE model VHX-6000 microscope is used. The magnification of the microscope should be such that the diameter of the bubbles at the interface between skin layer 3 and core layer 2 of the foamed resin sheet 1 can be confirmed. In the cross-sectional view of the foamed resin sheet 1, from among the many bubbles present, select 15 bubbles that are close to the surface of the foamed resin sheet 1 on each virtual boundary line obtained by dividing the cross-section of the foamed resin sheet 1 into 16 equal parts in the width direction, and identify the bubble that is closest to the surface of the foamed resin sheet 1. Draw a virtual line that passes through the upper edge of this closest bubble and is perpendicular to the thickness direction. At this time, the area inside the virtual line in the thickness direction can be defined as core layer 2, and the area outside the virtual line in the thickness direction can be defined as skin layer 3. The boundary between core layer 2 and skin layer 4 can be defined similarly, and the thickness t1 of skin layer 3 and the thickness t2 of skin layer 4 can be measured. Furthermore, the thickness t1 of skin layer 3 and the thickness t2 of skin layer 4 are preferably 0.050 mm or more, for example, from the viewpoint of making the thickness T of the foamed resin sheet 1 as uniform as possible during co-extrusion molding, as described later.

[0045] In this way, by controlling the density of the foamed resin sheet 1 and the thickness ratio of the skin layer, it is possible to achieve excellent impact resistance and resilience while reducing weight.

[0046] [Method for manufacturing foamed resin sheets] Here, we will briefly explain the manufacturing method of the foamed resin sheet 1. For example, the foamed resin sheet 1 can be manufactured by co-extrusion molding.

[0047] More specifically, amorphous engineering plastic (e.g., polycarbonate) is introduced into the screw cylinder of the main extruder and sheared and kneaded while being heated at a predetermined temperature. Then, a foaming agent is introduced into the screw cylinder under a predetermined pressure, and the molten resin mixed with the foaming agent is discharged from the die outlet to foam it. This forms the core layer 2.

[0048] Simultaneously, thermoplastic polyester elastomer is introduced into the screw cylinders of two auxiliary extruders and heated to a predetermined temperature to obtain molten resin. Of the two molten resins, one is extruded from the die outlet to form skin layer 3. The other is extruded from the die outlet to form skin layer 4.

[0049] The molten resin forming the core layer 2, skin layer 3, and skin layer 4 is combined in dies connected to the main extruder and two sub-extruders, and is extruded from the dies such that skin layer 3 is laminated on one main surface of core layer 2 and skin layer 4 is laminated on the other main surface of core layer 2.

[0050] The foamed resin sheet 1 extruded from the die is cooled while being taken up by a take-up machine and cut into the desired shape by a cutting machine. However, the method of manufacturing the foamed resin sheet 1 is not limited to this, and the core layer 2 and skin layers 3 and 4 may be molded separately, and then the skin layers 3 and 4 may be bonded to one main surface and the other main surface of the core layer 2, respectively, or the resin material that will become the skin layers 3 and 4 may be printed so as to be applied to one main surface and the other main surface of the core layer 2, respectively.

[0051] [Resin molded products] The resin molded product (not shown) is a molded product formed into various shapes by heat shaping, such as vacuum forming or pressure forming, of a foamed resin sheet 1. The various shapes of the resin molded product are determined by the purpose for which the resin molded product is used. For example, these include mobility materials such as signs or interior and exterior materials for automobiles where relatively high strength is required, wide products and parts such as flooring materials, bathtubs, partitions, and building panels, products and parts that require heat resistance such as trays for heating elements used in batteries or manufacturing processes involving heating, lighting covers and housings, or products and parts that require impact resistance and lightweight design such as sports equipment such as shin guards and protectors, and trays for food manufacturing. The foamed resin sheet 1 is useful as a material for molding these products and parts because it is lightweight while possessing excellent impact resistance and resilience.

[0052] Products and parts made from the foamed resin sheet 1 can reduce the amount of resin used. As a result, the foamed resin sheet 1 according to this embodiment can contribute to improved resource utilization efficiency, reduced transportation burden, reduced energy consumption, and reduced CO2 emissions. By providing the foamed resin sheet 1 to society, it is possible to contribute to achieving three of the 17 Sustainable Development Goals (SDGs) established by the United Nations: Goal 7 (Affordable and Clean Energy), Goal 9 (Industry, Innovation and Infrastructure), and Goal 11 (Sustainable Cities and Communities). Furthermore, since the foamed resin sheet 1 according to this embodiment can be melted and reused, it is possible to contribute to achieving Goal 12 (Responsible Consumption and Production).

[0053] Although embodiments have been described above, this disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the disclosure. [Examples]

[0054] As shown in Table 1 below, test specimens for Examples 1-5 and Comparative Examples 1-3 were prepared. Each test specimen was vacuum-formed to produce vacuum-formed products (resin molded products), and their resilience and impact resistance were evaluated. This disclosure is not limited to these examples.

[0055] [Table 1]

[0056] (Example 1) First, polycarbonate (amorphous engineering plastic) was introduced into the screw cylinder of the main extruder and sheared and kneaded while heating at 270°C. Then, the foaming agent N2 was injected under a pressure of 4 MPa. The polycarbonate (Teijin L1225-L) and the foaming agent were heated and melted at 210°C, and a core layer was obtained with a die outlet temperature of 215°C. Simultaneously, thermoplastic polyester elastomer (Toray Celanese Co., Ltd. "4797B2") was introduced into the screw cylinder of the secondary extruder and sheared and kneaded while heating at 255°C, and two skin layers were obtained with a die outlet temperature of 210°C. These core layer and skin layer were merged and laminated in the die and extruded from the die outlet. In this way, a test specimen of Example 1 was obtained in which skin layers made of non-foamed resin were laminated on both main surfaces of a core layer made of foamed resin. In Example 1, the die exit gap was set so that the thickness T of the test piece was 3 mm, and the drawing speed was arbitrarily set to co-extrude one test piece.

[0057] (Examples 2-5) In Examples 2 and 3, the skin layer discharge rate was increased by increasing the rotation speed of the gear pump of the secondary extruder while keeping the equipment, temperature, and gas pressure constant as in Example 1. After extruding the co-extruded sheet to the skin layer thickness shown in Table 1 while adjusting the take-up speed so that the thickness of the co-extruded sheet was 3 mm, the thickness of the test piece and the thickness of the skin layer were checked with a microscope, and if any deviation occurred, the discharge rate of the secondary extruder was finely adjusted.

[0058] (Comparative Example 1) The test specimen for Comparative Example 1 was prepared using the same procedure as in Examples 1 to 5, with the thickness of the skin layer adjusted.

[0059] (Comparative Examples 2 and 3) The test specimens for Comparative Examples 2 and 3 were prepared by injecting the foaming agent using the same procedure as in Examples 1 to 3, but with different gas pressures. In Comparative Example 2, the gas pressure was set to 2 MPa, and in Comparative Example 3, it was set to 8 MPa.

[0060] (vacuum formed product) As described above, the test specimens of Examples 1-5 and Comparative Examples 1-3 were vacuum-formed to produce vacuum-formed products. Specifically, each test specimen was placed in a constant temperature bath and dried at a heating temperature of 100°C for more than 6 hours. Then, using a vacuum forming machine (Vaquform DT2 manufactured by System Create Co., Ltd.), the test specimen was dropped into a mold at the moment the temperature of the unheated surface of the test specimen reached 150°C to perform vacuum forming. At this time, a bowl-shaped resin mold with a width of approximately 100 mm, a length of approximately 200 mm, and a height of approximately 80 mm was used as the mold.

[0061] (Evaluation of resilience) Each of the bowl-shaped vacuum-formed products from Examples 1-5 and Comparative Examples 1-3 was placed on a 2mm thick rubber sheet, and a 4kg dumbbell was dropped from a height of 1.5m so as to hit the apex of the bowl shape. After the drop, the vacuum-formed product had a concave shape at the apex of the bowl, and the product was restored to its original shape by applying pressure with a finger from the opposite side of the impact surface. At this time, if the vacuum-formed product was restored to its original shape without cracks or fractures, it was evaluated as having "resilience" and was deemed to have "resilience". On the other hand, if the vacuum-formed product developed cracks or fractures at the stage of impact, or if cracks or fractures developed after it was restored to its original shape, it was evaluated as not having "resilience" and was deemed to have "resilience".

[0062] (Evaluation of impact resistance) Furthermore, each vacuum-formed product was subjected to multiple tests to evaluate its resilience, and the final number of times it broke was recorded. A rating of "D" was given if it broke less than 10 times, "C" if it broke between 10 and 15 times, "B" if it broke between 15 and 20 times, and "A" if it broke 20 times or more. For example, a vacuum-formed product that broke on the 11th attempt was rated "C," and one that broke on the 10th attempt was rated "D."

[0063] (Evaluation of lightness) Generally, the density of ABS resin and polypropylene, which are used in automotive interior and exterior materials, is approximately 1.0 g / cm³. 3 Therefore, in the test specimens of Examples 1-5 and Comparative Examples 1-3, the density was 1.0 g / cm³. 3 If the above conditions are met, it was evaluated as not achieving weight reduction.

[0064] (Evaluation results) All vacuum-formed products in Examples 1-5 were evaluated as having good resilience. However, the impact resistance evaluations differed. Specifically, in the impact resistance evaluation, Example 1 received a "C". This is thought to be because the thickness ratio of the skin layer, which has excellent flexibility and bending resistance, was relatively small at 0.1 in Example 1. In Example 2, the evaluation was "B", and in Examples 3, 4, and 5, the evaluation was "A". This is thought to be because the thickness ratio of the skin layer was larger in Example 2, and even larger in Examples 3, 4, and 5, resulting in higher density. The density of the test pieces in Examples 1-5 was 0.9 g / cm³ in all cases. 3 The results were as follows. Therefore, all of the test pieces in Examples 1 to 5 could be evaluated as having achieved weight reduction.

[0065] However, while the vacuum-formed product in Comparative Example 1 achieved weight reduction, it lacked resilience and received a "D" rating for impact resistance. This is likely due to the skin layer thickness ratio being too small. Furthermore, in the test specimen of Comparative Example 2, the density of the test specimen was 1.1 g / cm³. 3 As a result, weight reduction was not achieved. Furthermore, the test specimen in Comparative Example 3 lacked resilience, and its impact resistance was rated as "D". This was because the density of the test specimen was 0.3 g / cm³. 3 This is likely because it was too small.

[0066] As described above, in order to achieve excellent resilience and impact resistance while reducing weight, it was found that it is best to control the balance between the thickness ratio and density of the skin layer of the test specimen. Specifically, the thickness ratio of the skin layer of the test specimen should be 0.1 to 0.5, and the density of the test specimen should be 0.4 to 0.9 g / cm³. 3 I realized that this is what I should do. [Explanation of Symbols]

[0067] 1 Foamed resin sheet, 2 Core layer, 3 Skin layer, 4 Skin layer, t1 Thickness of skin layer, t2 Thickness of skin layer, T Thickness of foamed resin sheet

Claims

1. A core layer made of foamed resin, It consists of a non-foaming resin, and a first skin layer laminated on one main surface of the core layer, A foamed resin sheet comprising a second skin layer laminated on the other main surface of the core layer, The core layer comprises amorphous engineering plastic, Each of the first skin layer and the second skin layer comprises a thermoplastic polyester elastomer. The foamed resin sheet contains 0.4 to 0.9 g / cm². ３ A foamed resin sheet having a density and satisfying the following formula. 0.1≦(t1+t2) / T≦0.5 In the above formula, t1 represents the thickness of the first skin layer, t2 represents the thickness of the second skin layer, and T represents the thickness of the foamed resin sheet.

2. A foamed resin sheet according to claim 1, The thermoplastic polyester elastomer is a block copolymer having a hard segment made of aromatic polyester and a soft segment made of aliphatic polyester, and is a foamed resin sheet.

3. A foamed resin sheet according to claim 1, The amorphous engineering plastic is a foamed resin sheet of polycarbonate.

4. A foamed resin sheet according to claim 1, The amorphous engineering plastic is a foamed resin sheet having a load deflection temperature of 125°C or higher.

5. A foamed resin sheet according to claim 1, A foamed resin sheet in which the resin material forming the core layer has an amorphous engineering plastic content of 90% by weight or more.

6. A foamed resin sheet according to claim 1, A foamed resin sheet in which the resin material forming the first skin layer and the second skin layer has a thermoplastic polyester elastomer content of 90% by weight or more.

7. A foamed resin sheet according to claim 1, The aforementioned thermoplastic polyester elastomer is a foamed resin sheet, which is a block copolymer having a hard segment made of polybutylene terephthalate and a soft segment made of polyether.

8. A resin molded article comprising a foamed resin sheet according to any one of claims 1 to 7.

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