Amorphous foamed resin sheet

Abstract

The present invention provides an amorphous foamed resin sheet that can improve strength even in a non-crystallized state. [Solution] The amorphous 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 is made of amorphous thermoplastic resin. Skin layers 2 and 4 contain amorphous thermoplastic resin and crystalline elastomer. The content of crystalline elastomer in each of skin layers 3 and 4 is 20% to 50% by weight.

Description

Technical Field

[0001] The present disclosure relates to an amorphous foamed resin sheet that is in a state not crystallized by heat treatment or the like.

Background Art

[0002] In recent years, foamed resins have attracted attention because they can improve convenience by reducing the weight of resin molded bodies and can also reduce carbon dioxide emissions. Also, thermoplastic elastomers have attracted attention because they can improve various properties of resin products.

[0003] Japanese Patent Application Laid-Open No. 2002-019065 (Patent Document 1) discloses a resin molded body excellent in heat resistance, productivity, fracture resistance, and light reflection performance. The resin molded body is composed of 35 to 75% by weight of an aromatic polycarbonate resin (A), 5 to 45% by weight of a thermoplastic resin other than the aromatic polycarbonate resin or / and a thermoplastic elastomer (B), 0 to 35% by weight of a flame retardant (C), and 0 to 15% by weight of a white pigment (D) (however, (A)+(B)+(C)+(D)=100% by weight). On the back surface of the mixed resin layer, a back surface layer made of a synthetic resin or a synthetic resin composition having an Izod impact value of at least 5 kJ / m 2 is integrally adhered.

[0004] Japanese Patent No. 5158836 (Patent Document 2) discloses a thermoplastic resin foam. The thermoplastic resin foam is composed of 100 parts by mass of a thermoplastic resin (A) selected from polyester and polycarbonate, and 0.1 to 10 parts by mass of a thermoplastic elastomer (B) having a functional group having an affinity with the thermoplastic resin (A), and has a plurality of pores with an average bubble diameter of 10 μm or less inside.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] The objective of this disclosure is to provide an amorphous foamed resin sheet that can improve strength even when it is not crystallized. [Means for solving the problem]

[0007] To solve the above problems, this disclosure employs the following solutions. Specifically, the amorphous 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 first skin layer and the second skin layer contain amorphous thermoplastic resin and crystalline elastomer. The content of crystalline elastomer in each of the first and second skin layers is 20% to 50% by weight. [Effects of the Invention]

[0008] According to the amorphous foamed resin sheet described herein, it is possible to improve strength even in a non-crystallized state. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a perspective view showing an amorphous foamed resin sheet according to an embodiment. [Figure 2] Figure 2 is an enlarged cross-sectional view of the skin layer shown in Figure 1. [Figure 3] Figure 3 is a graph showing the tensile modulus of the examples and comparative examples. [Modes for carrying out the invention]

[0010] Normally, crystalline polymers harden and gain strength when crystallized. However, crystallizing crystalline polymers requires a predetermined heat treatment, such as heating. As a result of diligent research, the inventors have discovered that even in an uncrystallized state, when a crystalline polymer (crystalline elastomer) is blended with an amorphous thermoplastic resin at a predetermined concentration, the strength may actually improve. This invention was completed by the inventors based on this finding. It should be noted that the aforementioned Patent Documents 1 and 2 do not propose any improvement in strength in an uncrystallized state.

[0011] (Composition 1) An amorphous foamed resin sheet according to the embodiment of 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 first skin layer and the second skin layer contain an amorphous thermoplastic resin and a crystalline elastomer. The content of the crystalline elastomer in each of the first and second skin layers is 20% to 50% by weight.

[0012] This makes it possible to improve the strength, particularly the tensile modulus, of the foamed resin sheet, even when it is not crystallized.

[0013] (Configuration 2) In the amorphous foamed resin sheet of configuration 1, the tensile modulus of the amorphous foamed resin sheet may be greater than the tensile modulus of the amorphous foamed resin sheet when it is crystallized. This makes it possible to improve the strength of the amorphous foamed resin sheet.

[0014] (Composition 3) In an amorphous foamed resin sheet of composition 1 or 2, the first skin layer and the second skin layer may have a sea-island structure in which the amorphous thermoplastic resin forms the sea and the crystalline elastomer forms the islands. This can improve the strength of the amorphous foamed resin sheet.

[0015] (Composition 4) In any one of the amorphous foamed resin sheets of composition 1 to 3, the amorphous thermoplastic resin may include at least one selected from the group consisting of polycarbonate, polyolefin, and polyamide. These amorphous thermoplastic resins have poor compatibility with crystalline elastomers. Therefore, they can be easily used to form the aforementioned sea-island structure.

[0016] Hereinafter, embodiments of the amorphous foamed resin sheet 1 (hereinafter sometimes simply referred to as "foamed resin sheet") in 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.

[0017] The foamed resin sheet 1 according to this embodiment mainly consists of an amorphous thermoplastic resin. Examples of amorphous thermoplastic resins include polycarbonate (PC), polyvinyl chloride (PVC), polystyrene (PS), polymethyl methacrylate (PMMA), acrylonitrile butadiene styrene (ABS), modified polyphenylene ether (m-PPE), polyethersulfone (PES / PESU), polyetherimide (PEI), and polyamideimide (PAI). The amorphous thermoplastic resin forming the foamed resin sheet 1 may be at least one or more alloy resins selected from the group consisting of these various amorphous thermoplastic resins. However, from the viewpoint of improving the heat resistance or strength of the foamed resin sheet 1, the amorphous thermoplastic resin is preferably polycarbonate.

[0018] The resin material of the foamed resin sheet 1 can contain various additives as long as it does not significantly affect the effects of the present disclosure. The types of additives are not particularly limited. For example, they include cell nucleating agents, crystal nucleating agents, lubricants, surfactants, surface tension modifiers, anti-shrinkage agents, fluidity modifiers, impact modifiers, fillers, reinforcing agents, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, plasticizers, lubricants, mold release agents, antistatic agents, colorants (pigments, dyes, etc.), surface effect additives, infrared absorbers, radiation stabilizers, drip-proof materials, and anti-aging agents. The addition amount of the additives can be appropriately selected within a range that does not impair the formation of bubbles, etc., and the addition amount used in the molding of ordinary thermoplastic resins can be adopted.

[0019] As shown in FIG. 1, the foamed resin sheet 1 has a core layer 2, a skin layer 3, and a skin layer 4. The skin layer 3 is laminated on one main surface of the core layer 2. The skin layer 4 is laminated on the other main surface of the core layer 2. The foamed resin sheet 1 can include such a three-layer laminated structure. The foamed resin sheet 1 can be formed, for example, by coextrusion foam molding. The foamed resin sheet 1 may have a thickness of, for example, 1 to 5 mm.

[0020] The core layer 2 is made of a foamed resin. That is, the core layer 2 is foam molded and has a large number of bubbles. In the present disclosure, the foamed resin refers to a resin having an average porosity of 5% to 95%. That is, it can also be said that the core layer 2 has an average porosity of 5 to 95%. The core layer 2 is made of the above-mentioned amorphous thermoplastic resin.

[0021] The skin layer 3 and the skin layer 4 are made of a non-foamed resin. That is, the skin layer 3 and the skin layer 4 are not foam molded and do not have a large number of bubbles. In the present disclosure, the non-foamed resin refers to a resin having an average porosity of 0% or more and less than 5%. That is, it can also be said that the skin layer 3 and the skin layer 4 have an average porosity of 0% or more and less than 5%.

[0022] 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.

[0023] Skin layer 3 and skin layer 4 contain the amorphous thermoplastic resin described above. Skin layer 3 and skin layer 4 also contain a crystalline elastomer at a predetermined content. Examples of crystalline elastomers include styrene-based crystalline elastomers, olefin-based crystalline elastomers, ester-based crystalline elastomers, amide-based crystalline elastomers, and urethane-based crystalline elastomers. The crystalline elastomer has a hard segment and a soft segment in its molecule, and from the viewpoint of improving the strength of the foamed resin sheet 1, an aromatic polyester crystalline elastomer in which the hard segment is an aromatic polyester is preferred. An example of an aromatic polyester crystalline elastomer is "Hytrel®" from Toray Celanese Co., Ltd. Furthermore, it is preferable that the soft segment of the aromatic polyester crystalline elastomer is an aliphatic polyether or an aliphatic polyester.

[0024] Each of skin layer 3 and skin layer 4 contains 20 to 50% by weight of crystalline elastomer. The content A of crystalline elastomer in each of skin layer 3 and skin layer 4 can be calculated using the formula "A = {C / (B + C)} × 100", where B is the weight of each of skin layer 3 and skin layer 4, and C is the weight of the crystalline elastomer. In addition, each of skin layer 3 and skin layer 4 may contain 50% to 80% by weight of amorphous thermoplastic resin. The total content of crystalline elastomer and amorphous thermoplastic resin may be 100% by weight.

[0025] In the amorphous state, from the viewpoint of improving the strength of the foamed resin sheet 1, the content of crystalline elastomer in each of the skin layer 3 and skin layer 4 should be 20% by weight or more, preferably 30% by weight or more, and 50% by weight or less, preferably 40% by weight or less. In other words, the content of crystalline elastomer in each of the skin layer 3 and skin layer 4 should be 20% by weight to 50% by weight, preferably 30% by weight to 40% by weight.

[0026] In this disclosure, the non-crystallized state, i.e., amorphous state, refers to a state in which the crystallinity of each of the skin layer 3 and skin layer 4 is 5% or less. The crystallinity can be measured using, for example, X-ray analysis, DSC, density method, infrared spectroscopy (transmission method), infrared spectroscopy (ATR method), infrared spectroscopy (diffuse reflectance method), and Raman spectroscopy. To obtain an amorphous foamed resin sheet 1, for example, it is preferable to rapidly cool the molten resin discharged from the die in the co-extrusion foaming molding method described above.

[0027] As a result, the foamed resin sheet 1 of this disclosure can have improved strength compared to a foamed resin sheet 1 in which the crystalline elastomers of the skin layer 3 and skin layer 4 have been crystallized. More specifically, the tensile modulus of the foamed resin sheet 1 can be improved in the non-crystallized state. That is, the tensile modulus (Ma) of the foamed resin sheet 1 having non-crystallized skin layer 3 and skin layer 4 can be made greater than the tensile modulus (Mc) of a foamed resin sheet in which the crystalline elastomers of the skin layer 3 and skin layer 4 have been crystallized (a foamed resin sheet in which the amorphous state of the foamed resin sheet 1 has been crystallized) (Ma>Mc, or Ma / Mc>1).

[0028] Here, the tensile modulus can be measured in accordance with "JIS K 7161".

[0029] Furthermore, in order to crystallize the crystalline elastomer of skin layer 3 and skin layer 4 in the amorphous foamed resin sheet 1, a predetermined heat treatment is applied to the foamed resin sheet 1, particularly skin layer 3 and skin layer 4. More specifically, for example, the crystalline elastomer can be crystallized by a heat treatment in which the material is heated at 120°C for 1 hour using a low-temperature dryer "DVS602" manufactured by Yamato Scientific Co., Ltd.

[0030] The crystallization of a crystalline elastomer can be confirmed by a crystallinity exceeding 5%. The crystallinity can be determined by measuring the X-ray intensity of a foamed resin sheet in which skin layer 3 and skin layer 4 have been crystallized by the heat treatment described above, using X-ray analysis, and then dividing the sum of the integrated intensities of each crystal peak originating from the crystallized crystalline elastomer by the sum of the integrated intensities of the amorphous peaks and each crystal peak originating from the crystallized crystalline elastomer, calculated from the X-ray analysis pattern of either skin layer 3 or skin layer 4 obtained from the measurement.

[0031] From the viewpoint of improving the strength of the foamed resin sheet 1 and reducing its weight, the total thickness of skin layer 3 and skin layer 4 is preferably 5% or more, more preferably 10% or more, and 30% or less, more preferably 20% or less, relative to the total thickness of the foamed resin sheet 1. In other words, it is preferably 5-30%, and more preferably 10-20%.

[0032] It is preferable that the amorphous thermoplastic resin and crystalline elastomer contained in skin layer 3 and skin layer 4, respectively, have a sea-island structure. In skin layer 3 shown in Figure 2, the amorphous thermoplastic resin is the sea portion S, and the crystalline elastomer is the island portion I. The same applies to skin layer 4. In order to form such a sea-island structure, it is preferable to use an amorphous thermoplastic resin that has poor compatibility with crystalline elastomer as the main resin material for skin layer 3 and skin layer 4. Amorphous thermoplastic resins that have poor compatibility with crystalline elastomer include, for example, polyolefins such as polycarbonate, polyethylene, or polypropylene, or polyamides such as nylon.

[0033] 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).

[0034] 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]

[0035] As shown in Table 1 below, test specimens for Examples 1-4 and Comparative Examples 1-2 were prepared, and the tensile modulus (Ma) in the amorphous state and the tensile modulus (Mc) after crystallization were measured and compared. Crystallization of the test specimens was carried out by the method described above. In Table 1, "content" refers to the content (weight %) of crystalline elastomer contained in the skin layer of the test specimen. The common conditions for each test specimen are as follows. Furthermore, this disclosure is not limited to these examples. Sheet structure: 3-layer structure (core layer and two skin layers laminated on both sides of the core layer) Resin material: Core layer - Polycarbonate Skin layer: Polycarbonate and crystalline elastomer Crystalline elastomer: Hytrel (Toray Celanese Co., Ltd.) Thickness: Core layer 2.5mm Each skin layer is 0.25 mm thick.

[0036] [Table 1]

[0037] Comparing Examples 1-4 with Comparative Examples 1-2, as shown in the graph in Figure 3, in Examples 1-4, where the crystalline elastomer content was 20-50% by weight, the tensile modulus (Ma) of the uncrystallized specimen exceeded the tensile modulus (Mc) of the crystallized specimen. On the other hand, in Comparative Example 1, where the crystalline elastomer content was 10%, the low content of crystalline elastomer in the skin layer resulted in a small impact on the tensile modulus of the specimen. Furthermore, in Comparative Example 2, where the crystalline elastomer content was 60%, the high content of crystalline elastomer in the skin layer meant that the tensile modulus of the crystalline elastomer itself had an influence, resulting in a higher tensile modulus (Mc) even in the crystallized specimen.

[0038] Comparing Examples 1-4, Examples 2 and 3, which had crystalline elastomer content of 30% by weight and 40% by weight, showed a larger Ma / Mc value and a significant improvement in tensile modulus in the non-crystallized state. From this, it was confirmed that the crystalline elastomer content is preferably 20% to 50% by weight, and more preferably 30% to 40% by weight. [Explanation of Symbols]

[0039] 1 Amorphous foamed resin sheet, 2 Core layer, 3 Skin layer, 4 Skin layer, S Sea portion, I Island portion

Claims

1. A foamed resin sheet in an amorphous state, 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, The core layer comprises a second skin layer laminated on the other main surface of the core layer, The first skin layer and the second skin layer comprise an amorphous thermoplastic resin and a crystalline elastomer, An amorphous foamed resin sheet, wherein the content of the crystalline elastomer in each of the first and second skin layers is 20% to 50% by weight.

2. The amorphous foamed resin sheet according to claim 1, The amorphous foamed resin sheet wherein the tensile modulus of the amorphous foamed resin sheet is greater than the tensile modulus of the amorphous foamed resin sheet when it is crystallized.

3. The amorphous foamed resin sheet according to claim 1, In the first skin layer and the second skin layer, the amorphous thermoplastic resin and the crystalline elastomer have a sea-island structure, with the amorphous thermoplastic resin forming the sea and the crystalline elastomer forming the islands, in an amorphous foamed resin sheet.

4. An amorphous foamed resin sheet according to any one of claims 1 to 3, The amorphous thermoplastic resin is an amorphous foamed resin sheet comprising at least one selected from the group consisting of polycarbonate, polyolefin, and polyamide.

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