Resin foam

Abstract

The present application provides a foamed body having excellent punchability. The resin foamed body of the present application has a bubble structure, and has an apparent density of 0.02 g / cm 3 ~ 0.30 g / cm 3 25% compression load of 0.1 kPa to 80 kPa, and has a bubble aspect ratio of 1.5 or more. In one embodiment, the average bubble diameter of the above resin foamed body is 10 μm to 200 μm.

Description

Technical Field

[0001] This invention relates to resin foams. Background Technology

[0002] Foam is commonly used as a cushioning material for purposes such as screen protection, substrate protection, and protection of electronic components in electronic devices. In recent years, in line with the trend towards thinner electronic devices, there has been a demand to narrow the gaps between the parts where cushioning materials are placed. Furthermore, with the miniaturization and multifunctionality of electronic devices, the electronic components used are also trending towards miniaturization, sometimes requiring even smaller cushioning materials (foam).

[0003] Typically, to obtain a foam body of the desired shape, the foam roll is punched. During punching, high pressure is applied to the foam body using a die to achieve the desired shape. However, with existing foam bodies, the thickness reduced by the punching process is not fully recovered afterward, sometimes resulting in thickness variations. This phenomenon is particularly problematic when manufacturing foam bodies for applications with narrow gaps.

[0004] Patent Document 1 discloses a resin foam with excellent impact absorption. However, this document does not disclose or teach anything regarding processability during die-cutting. Patent Document 2 discloses a thin-layer resin foam with excellent impact absorption. However, this document does not disclose any information regarding resilience or damage after die-cutting.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2017-186504

[0008] Patent Document 2: Japanese Patent Application Publication No. 2015-034299 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] The objective of this invention is to provide a resin foam with excellent die-cutting processability.

[0011] Problem Solving Methods

[0012] The resin foam of the present invention has a bubble structure and an apparent density of 0.02 g / cm³. 3 ~0.30g / cm 3 The 25% compressive load is 0.1 kPa to 80 kPa, and the length-to-diameter ratio of the air bubbles in the resin foam is 1.5 or higher.

[0013] In one embodiment, the average bubble diameter of the resin foam is 10 μm to 200 μm.

[0014] In one embodiment, the bubble rate of the above-mentioned resin foam is 30% or more.

[0015] In one embodiment, the variation coefficient of the bubble diameter of the above-mentioned resin foam is 0.5 or less.

[0016] In one embodiment, the thickness of the bubble wall of the resin foam is 0.1 μm to 10 μm.

[0017] In one embodiment, the tensile modulus of the resin foam at 25°C is 1.5 MPa or higher.

[0018] In one embodiment, the resin foam comprises a polyolefin resin.

[0019] In one embodiment, the polyolefin resin is a mixture of a polyolefin elastomer and a polyolefin other than a polyolefin elastomer.

[0020] In one embodiment, the resin foam has a hot-melt layer on one or both sides.

[0021] According to another aspect of the present invention, a foamed component may be provided having a resin foam layer and an adhesive layer disposed on at least one side of the resin foam layer, the resin foam layer being the aforementioned resin foam body.

[0022] The effects of the invention

[0023] According to the present invention, by using bubbles with a specific shape, it is possible to provide a foam with minimal thickness change before and after punching, and excellent punching processability. Attached Figure Description

[0024] Figure 1 This is a cross-sectional schematic diagram of a foamed component according to one embodiment of the present invention.

[0025] Symbol Explanation

[0026] 100 foamed components

[0027] 10. Resin foam layer (resin foam body)

[0028] 20 Adhesive layers Detailed Implementation

[0029] A. Resin foam

[0030] The apparent density of the resin foam of the present invention is 0.02 g / cm³. 3~0.30g / cm 3 The 25% compressive load is 0.1 kPa to 80 kPa. The resin foam of the present invention has a bubble structure (pore structure). Examples of bubble structures (pore structures) include independent bubble structures, continuous bubble structures, and semi-continuous semi-independent bubble structures (bubble structures containing both independent and continuous bubble structures). Preferably, the bubble structure of the resin foam is a semi-continuous semi-independent bubble structure. Typically, the resin foam of the present invention can be obtained by foaming a resin composition. The aforementioned resin composition is a composition containing at least the resin constituting the resin foam.

[0031] The resin foam described above has bubbles with an aspect ratio of 1.5 or higher. In this invention, by constructing the resin foam from bubbles with a high aspect ratio, the deformation of the bubbles during compression is small, and the bubbles deform in a manner that does not exceed the yield point of the bubble wall (pore wall). Therefore, the bubble structure is less prone to buckling, and as a result, the resin foam easily recovers to its shape before compression. If the resin foam is constructed in this way, even when it is intended for punching, shape changes (especially thickness changes) before and after processing can be suppressed. The aspect ratio of the bubbles constituting the resin foam is preferably 2.0 or higher, more preferably 2.5 or higher. If it is within this range, the above-mentioned effect becomes significant. Furthermore, the upper limit of the aspect ratio of the bubbles constituting the resin foam is preferably 5, more preferably 4, and even more preferably 3.5. If it is within this range, a resin foam with excellent impact absorption can be obtained.

[0032] It should be noted that, in this specification, "the aspect ratio of the air bubbles in the resin foam" refers to a given area (3mm²) in the cross-section of the resin foam at a randomly selected location. 2 The average aspect ratio of all bubbles present within the range is given below. The specific method for determining the aspect ratio of bubbles in the resin foam is as follows.

[0033] • Cut the resin foam using a die-cutting mold, and observe the cut section at 100x magnification using a microscope (e.g., Keyence "VHX-2000") to determine the area (3 mm²). 2 Range. Measure the length of a bubble in the thickness direction and its transverse length.

[0034] • Perform the same measurement on all bubbles present in a given area.

[0035] • The aspect ratio of the bubble is calculated by dividing the length in the horizontal direction by the length in the thickness direction. The same calculation is performed on all bubbles, and the average value is taken as the "aspect ratio of the bubbles in the resin foam".

[0036] As mentioned above, the apparent density of the resin foam is 0.02 g / cm³. 3 ~0.30g / cm 3 Within this range, a resin foam with excellent flexibility and stress dispersion can be obtained. The apparent density of the aforementioned resin foam is preferably 0.03 g / cm³. 3 ~0.28g / cm 3 More preferably 0.04 g / cm³ 3 ~0.25g / cm 3 The preferred value is 0.05 g / cm³. 3 ~0.20g / cm 3 The optimal value is 0.07 g / cm³. 3 ~0.15g / cm 3 If the range is such, the above effect becomes significant. The method for determining apparent density is described later.

[0037] As described above, the 25% compressive load of the resin foam is 0.1 kPa to 80 kPa. If the resin foam has a 25% compressive load within this range, the load on the applied component can be reduced. More specifically, when the resin foam is applied with slight compression in areas with narrow gaps, the resin foam according to the present invention can reduce the stress applied to other components. For example, when the resin foam is applied to a display component, the stress applied to that display component can be mitigated / dispersed, thus being useful from the viewpoint of reducing color unevenness and protecting the component. The 25% compressive load of the aforementioned resin foam is preferably 1 kPa to 75 kPa, more preferably 5 kPa to 70 kPa, further preferably 10 kPa to 75 kPa, and particularly preferably 20 kPa to 75 kPa. If it falls within this range, the above-mentioned effect becomes significant. The method for measuring the 25% compressive load is described later.

[0038] The elastic strain energy of the resin foam under compression is preferably 10 kPa or higher. "Elastic strain energy under compression" refers to the total amount of compressive rebound force when the resin foam is compressed by 10%. Specifically, when the compression ratio (%) and compressive rebound force (kPa) of the resin foam are determined by a compression test based on JIS K 6767 (test temperature: 23℃, sample size: 10mm × 10mm, compression speed: 10mm / min), the "elastic strain energy under compression" is calculated from a compression SS curve with the x-axis set to the compression ratio (%) and the y-axis set to the compressive rebound force (kPa). This "elastic strain energy under compression" is the area of ​​the region defined by the SS curve and the x-axis within the range of 0% to 10% compression ratio. If the elastic strain energy of the resin foam under compression is within the above range, a resin foam with excellent impact absorption can be obtained. More specifically, when an impact is applied, the deformation of the resin foam having the above-mentioned elastic strain energy consumes a large amount of energy, thus effectively absorbing even strong impacts. The elastic strain energy of the resin foam under compression is more preferably 20 kPa or more, further preferably 28 kPa or more, further preferably 35 kPa or more, further preferably 50 kPa or more, further preferably 80 kPa or more, particularly preferably 100 kPa or more, and most preferably 150 kPa or more. If it falls within this range, the aforementioned effect becomes significant. The upper limit of the elastic strain energy under compression of the resin foam is, for example, 500 kPa (preferably 800 kPa).

[0039] Resin foams with high aspect ratios of air bubbles can exhibit high thickness recovery rates. The thickness recovery rate of the resin foam is preferably 72% or more, more preferably 75% or more, and even more preferably 80% or more. It should be noted that the thickness recovery rate of the foam layer is defined by the following formula. This thickness recovery rate is measured by applying a load to the foam sheet over a certain area and compressing it, and is different from the so-called indentation recovery rate measured by applying a load locally and causing only a portion of the surface to indent.

[0040] Thickness recovery rate (%) = {(thickness 0.5 seconds after decompression) / (initial thickness)} × 100

[0041] Initial thickness: The thickness of the resin foam before the load is applied.

[0042] Thickness 0.5 seconds after decompression: When a 1000 g / cm³ pressure is applied to the resin foam. 2 The resin foam is kept under load for 120 seconds, then the compression is released, and the thickness of the resin foam is measured 0.5 seconds after the compression is released.

[0043] The thickness of the aforementioned resin foam is preferably 30 μm to 5000 μm, more preferably 35 μm to 4000 μm, further preferably 40 μm to 3000 μm, even more preferably 45 μm to 2000 μm, even more preferably 50 μm to 1000 μm, and particularly preferably 55 μm to 500 μm. As described above, although the resin foam of the present invention is a thin layer, it exhibits excellent impact resistance. Furthermore, if the thickness of the resin foam is within the above range, a fine and uniform bubble structure can be formed, which is advantageous in terms of exhibiting excellent impact absorption.

[0044] The average bubble diameter (average pore diameter) of the aforementioned resin foam is preferably 10 μm to 200 μm, more preferably 15 μm to 180 μm, further preferably 20 μm to 150 μm, particularly preferably 23 μm to 120 μm, especially preferably 25 μm to 100 μm, and most preferably 30 μm to 90 μm. Within this range, a resin foam with superior flexibility and stress dispersion can be obtained. Furthermore, a resin foam with excellent compression recovery and resistance to repeated impacts can be obtained. If the average bubble diameter is too small, there is a tendency for the apparent density to increase, potentially leading to higher compressive loads. As a result, when the resin foam is applied to display components, the stress applied to the display component cannot be adequately mitigated or dispersed, sometimes resulting in uneven color or component breakage. On the other hand, if the average bubble diameter is too large, dust and water can easily enter the resin foam, potentially causing obstacles to equipment using the resin foam. The method for measuring the average bubble diameter will be described later.

[0045] The coefficient of variation of the bubble diameter (pore diameter) of the aforementioned resin foam is preferably 0.5 or less, more preferably 0.48 or less, even more preferably 0.45 or less, particularly preferably 0.43 or less, and most preferably less than 0.4. If it falls within this range, the deviation in bubble deformation is smaller when additional compressive force is applied through processes such as punching. With such a resin foam, for example, when punching is performed, processed products (cut products) with excellent thickness accuracy can be obtained. Furthermore, if the coefficient of variation of the bubble diameter is within the above range, the deformation caused by impact becomes uniform, localized stress loading can be prevented, and a resin foam with excellent stress dispersion and particularly excellent impact resistance can be obtained. The smaller the coefficient of variation, the more preferred; its lower limit is, for example, 0.2 (preferably 0.15, more preferably 0.1, and even more preferably 0.01). The method for measuring the coefficient of variation of the bubble diameter will be described later.

[0046] The bubble ratio (porosity) of the aforementioned resin foam is preferably 30% or more, more preferably 50% or more, and even more preferably 80% or more. Within this range, a resin foam with moderate softness can be obtained. Such a resin foam exhibits excellent die-cutting processability, preventing the occurrence of cutting residue during die-cutting. Furthermore, if the bubble ratio is within the aforementioned range, a resin foam with low repulsive stress during compression can be obtained. With such a resin foam, when it is applied to areas with narrow gaps and slightly compressed, the stress exerted on other components can be reduced. For example, when the resin foam is applied to a display component, the stress exerted on that component can be mitigated / dispersed; therefore, this is useful from the viewpoint of reducing color unevenness and protecting the component. The upper limit of this bubble ratio is, for example, 99% or less. The method for measuring the bubble ratio will be described later.

[0047] The thickness of the bubble wall (pore wall) of the aforementioned resin foam is preferably 0.1 μm to 10 μm, more preferably 0.3 μm to 8 μm, further preferably 0.5 μm to 5 μm, particularly preferably 0.7 μm to 4 μm, and most preferably 1 μm to 3 μm. Within this range, a resin foam with appropriate strength can be obtained. Such a resin foam exhibits excellent die-cutting processability, preventing the generation of cutting fragments, dust, and cutting residues during die-cutting. Furthermore, if the bubble wall thickness is within the aforementioned range, a resin foam with superior flexibility and stress dispersion can be obtained. If the bubble wall thickness is too thin, the resin foam is prone to deformation under load, potentially resulting in insufficient stress dispersion. If the bubble wall thickness is too thick, the resin foam is not easily deformed under load, potentially leading to poor height difference tracking when used in equipment gaps. The method for measuring the bubble wall thickness will be described later.

[0048] When the bubble structure of the aforementioned resin foam is a semi-continuous, semi-independent bubble structure, the proportion of independent bubble structures is preferably 40% or less, more preferably 30% or less. In this specification, the independent bubble rate of the resin foam can be determined, for example, as follows: the test object is submerged in water in an environment of 23°C and 50% humidity, and its mass is subsequently measured. Then, after thorough drying in an oven at 80°C, the mass is measured again. Alternatively, if the bubbles are continuous, moisture can be retained; therefore, their mass can be measured and determined as continuous bubbles.

[0049] The tensile modulus of the aforementioned resin foam at 25°C is preferably 0.5 MPa or more, more preferably 0.6 MPa or more, further preferably 1 MPa or more, and particularly preferably 1.5 MPa or more. Within this range, a resin foam with appropriate strength can be obtained. Such a resin foam exhibits excellent die-cutting processability, preventing the generation of fragments, dust, and cutting residues during die-cutting. The upper limit of the tensile modulus of the resin foam at 25°C is, for example, 10 MPa. The tensile modulus can be measured as follows: using a tensile testing machine (e.g., Tansui Co., Ltd. "RTG-1201"), the sample is fixed with a chuck spacing of 40 mm, and a tensile test is performed at a tensile speed of 500 mm / min. A curve based on tensile strain and tensile strength is obtained, and the tensile modulus is determined by the slope of the straight line obtained by connecting the origin of this curve with the tensile strength at 10% of the tensile strain.

[0050] The elongation at break of the aforementioned resin foam at 25°C is preferably 120% or less, more preferably 110% or less, further preferably 100% or less, and particularly preferably 90% or less. Within this range, a resin foam with excellent flexibility and stress dispersion can be obtained. It should be noted that if the elongation at break is low, the deformation of the pore walls of the resin foam is smaller when a load is applied. For example, in the case of added filler material, slippage easily occurs at the interface between the resin constituting the resin foam and the filler material, further mitigating the load. On the other hand, if the elongation at break is too high, the deformation of the pore walls of the resin foam becomes large, potentially making it difficult to mitigate the load. The elongation at break can be measured based on JIS K 6767.

[0051] The non-foamed bending stress of the aforementioned resin foam is preferably 5 MPa or more, more preferably greater than 5 MPa, more preferably 7 MPa or more, and even more preferably 10 MPa or more. Within this range, a large amount of energy is required to deform the bubble walls (pore walls) of the resin foam, resulting in a resin foam with excellent impact absorption properties. The upper limit of this non-foamed bending stress is preferably 20 MPa, more preferably 15 MPa. Within this range, a resin foam with superior softness and stress dispersion can be obtained. "Non-foamed bending stress" refers to the bending stress of the resin molded body a after it has been restored to a bubble-free, non-foamed state (block-like) by hot pressing. The density of the resin molded body a can be the same as the density of the resin molded body b before foaming, formed from the resin composition described later. It should be noted that the bending stress of the resin molded body a (the non-foamed bending stress of the resin foam) can be the same as that of the resin molded body b. The method for measuring the bending stress is described below. That is, a resin molded body a is cut into pieces 20mm wide and 150mm long as a sample. The sample is placed on a 3-point bending fixture with a fulcrum distance of 100mm. An indentation test is conducted at an indentation speed of 5mm / min in an environment of 23℃×50%RH (manufactured by Shimadzu Corporation, trade name "AG-Xplus"). The load (g) when the sample is indented by 5mm is taken as the non-foamed bending stress.

[0052] The impact absorption of the above-mentioned resin foam is preferably 20% or more, more preferably 27% or more, further preferably 30% or more, particularly preferably 35% or more, and most preferably 40% or more. The impact absorption can be measured as described below.

[0053] • A test specimen was formed by sequentially mounting a resin foam, a double-sided tape (model: No. 5603W, manufactured by Nitto Denko), and a PET film (model: DIAFOIL MRF75, manufactured by Mitsubishi Resin) onto an impact force sensor. A 66g iron ball was dropped from a height of 50cm above the PET film onto the test specimen, and the impact force F1 was measured.

[0054] • In addition, the iron ball is dropped directly onto the impact sensor as described above, and the blank impact force F0 is measured.

[0055] • The shock absorption rate (%) is calculated based on F1 and F0 using the formula (F0-F1) / F0×100.

[0056] The shape of the aforementioned resin foam can be any suitable shape depending on the purpose. A typical example of such a shape is a sheet.

[0057] The resin foam may have a hot-melt layer on one or both sides. For example, a resin foam with a hot-melt layer can be obtained by calendering the resin foam (or the precursor (foam structure) of the resin foam) using a pair of heated rollers heated to a temperature above the melting temperature of the resin composition constituting the resin foam.

[0058] Without impairing the effects of the present invention, the above-described resin foam can be formed by any suitable method. A representative example of such a method is a method of foaming a resin composition containing a resin material (polymer).

[0059] A-1. Resin Composition

[0060] The resin foam of the present invention is typically obtained by foaming a resin composition. The resin composition comprises any suitable resin material (polymer).

[0061] Examples of the aforementioned polymers include acrylic resins, silicone resins, carbamate resins, polyolefin resins, ester resins, and rubber resins. One of these polymers may be used alone, or two or more may be used in combination.

[0062] The polymer content relative to 100 parts by weight of the resin composition is preferably 30 to 95 parts by weight, more preferably 35 to 90 parts by weight, further preferably 40 to 80 parts by weight, and particularly preferably 40 to 60 parts by weight. Within this range, a resin foam with superior flexibility and stress dispersion can be obtained.

[0063] In one embodiment, a polyolefin resin is used as the polymer described above.

[0064] The proportion of polyolefin resin relative to 100 parts by weight of the above polymer is preferably 50 parts by weight to 100 parts by weight, more preferably 70 parts by weight to 100 parts by weight, further preferably 90 parts by weight to 100 parts by weight, particularly preferably 95 parts by weight to 100 parts by weight, and most preferably 100 parts by weight.

[0065] As a polyolefin resin, at least one selected from polyolefins and polyolefin elastomers is preferred, and more preferably, polyolefins and polyolefin elastomers are used in combination. Polyolefins and polyolefin elastomers may be used individually or in combination of two or more. It should be noted that in this specification, the term "polyolefin" does not include "polyolefin elastomers".

[0066] When polyolefins and polyolefin elastomers are used as a combination of polyolefin resins, the weight ratio of polyolefin to polyolefin elastomer (polyolefin / polyolefin elastomer) is preferably 1 / 99 to 99 / 1, more preferably 10 / 90 to 90 / 10, further preferably 20 / 80 to 80 / 20, and particularly preferably 30 / 70 to 70 / 30. In one embodiment, the weight ratio of polyolefin to polyolefin elastomer (polyolefin / polyolefin elastomer) is preferably 25 / 75 to 75 / 25, more preferably 35 / 65 to 65 / 35. Within this range, compression recovery is excellent, shape changes (especially thickness changes) before and after processing can be suppressed during die-cutting, and a resin foam with appropriate strength and excellent die-cutting processability can be obtained.

[0067] As the polyolefin, any suitable polyolefin can be used without impairing the effects of the present invention. Examples of such polyolefins include linear polyolefins and branched (branched) polyolefins. In one embodiment, a branched polyolefin is used as the polyolefin resin. In this embodiment, only branched polyolefins can be used as the polyolefin, or a combination of branched and linear polyolefins can be used. By using branched polyolefins, a resin foam with a small average bubble diameter and excellent impact resistance can be obtained. The content of branched polyolefins is preferably 30 to 100 parts by weight, more preferably 80 to 120 parts by weight, relative to 100 parts by weight of polyolefin.

[0068] Examples of the aforementioned polyolefins include polymers comprising structural units derived from α-olefins. Polyolefins may consist solely of structural units derived from α-olefins, or they may consist of structural units derived from α-olefins and structural units derived from monomers other than α-olefins. When the polyolefin is a copolymer, any suitable copolymerization method can be employed. Examples include random copolymers and block copolymers.

[0069] As an α-olefin capable of constituting a polyolefin, preferably an α-olefin with 2 to 8 carbon atoms (preferably 2 to 6, more preferably 2 to 4) (e.g., ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, etc.). There may be only one α-olefin or two or more α-olefins.

[0070] Monomers other than α-olefins that constitute polyolefins include, for example, vinyl acetate, acrylic acid, acrylates, methacrylic acid, methacrylates, and vinyl alcohol, which are olefinic unsaturated monomers. There may be only one monomer other than α-olefins, or there may be two or more monomers.

[0071] Examples of polyolefins include: low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene (propylene homopolymer), copolymers of ethylene and propylene, copolymers of ethylene and α-olefins other than ethylene, copolymers of propylene and α-olefins other than propylene, copolymers of ethylene, propylene and α-olefins other than ethylene and propylene, copolymers of propylene and olefin unsaturated monomers, etc.

[0072] In one embodiment, a polypropylene-based polymer having structural units derived from propylene is used as the polyolefin. Examples of polypropylene-based polymers include polypropylene (propylene homopolymer), copolymers of ethylene and propylene, copolymers of propylene and α-olefins other than propylene, etc., with polypropylene (propylene homopolymer) being preferred. A single polypropylene-based polymer may be used alone, or two or more may be used in combination.

[0073] From the perspective of further demonstrating the effects of the present invention, the melt flow rate (MFR) of the polyolefin at a temperature of 230°C is preferably 0.2 g / 10 min to 10 g / 10 min, more preferably 0.25 g / 10 min to 5 g / 10 min, further preferably 0.3 g / 10 min to 3 g / 10 min, and particularly preferably 0.35 g / 10 min to 1.5 g / 10 min. It should be noted that, in this specification, the above-mentioned melt flow rate (MFR) refers to the MFR measured based on ISO 1133 (JIS-K-7210) under conditions of 230°C and a load of 2.16 kgf.

[0074] In one embodiment, two or more different polyolefins with a melt flow rate (MFR) at 230°C within the aforementioned range are used in combination. In this case, a polyolefin with a melt flow rate (MFR) at 230°C preferably 0.2 g / 10 min or more and less than 0.7 g / 10 min (more preferably 0.2 g / 10 min to 0.65 g / 10 min) and a polyolefin with a melt flow rate (MFR) at 230°C preferably 0.7 g / 10 min to 10 g / 10 min (more preferably 0.7 g / 10 min to 5 g / 10 min, further preferably 0.7 g / 10 min to 3 g / 10 min, particularly preferably 0.7 g / 10 min to 1.5 g / 10 min, and most preferably 0.7 g / 10 min to 1.3 g / 10 min) can be used in combination. In this way, a resin foam with a small average bubble diameter and excellent impact resistance can be obtained.

[0075] When using two or more different polyolefins with a melt flow rate (MFR) at 230°C within the aforementioned range, for example, a polyolefin with a melt flow rate (MFR) at 230°C preferably 0.2 g / 10 min or more and less than 0.7 g / 10 min (more preferably 0.2 g / 10 min to 0.65 g / 10 min), and a polyolefin with a melt flow rate (MFR) at 230°C preferably 0.7 g / 10 min to 10 g / 10 min (more preferably...) The weight ratio of the polyolefin (0.7g / 10 min to 5g / 10 min, more preferably 0.7g / 10 min to 3g / 10 min, particularly preferably 0.7g / 10 min to 1.5g / 10 min, and most preferably 0.7g / 10 min to 1.3g / 10 min) is preferably 1 / 99 to 99 / 1, more preferably 10 / 90 to 90 / 10, further preferably 20 / 80 to 80 / 20, particularly preferably 30 / 70 to 70 / 30, and most preferably 40 / 60 to 60 / 40.

[0076] As polyolefins, commercially available products can be used, such as: "E110G" (manufactured by Priman Polymer Co., Ltd.), "EA9" (manufactured by Nippon Polypropylene Co., Ltd.), "EA9FT" (manufactured by Nippon Polypropylene Co., Ltd.), "E-185G" (manufactured by Priman Polymer Co., Ltd.), "WB140HMS" (manufactured by Borealis Co., Ltd.), "WB135HMS" (manufactured by Borealis Co., Ltd.), etc.

[0077] As a polyolefin elastomer, any suitable polyolefin elastomer can be used within the scope of not impairing the effects of the present invention. Examples of such polyolefin elastomers include: ethylene-propylene copolymers, ethylene-propylene-diene copolymers, ethylene-vinyl acetate copolymers, polybutene, polyisobutylene, chlorinated polyethylene, elastomers obtained by physically dispersing polyolefin components and rubber components, elastomers having a structure in which polyolefin components and rubber components have undergone microphase separation, and so-called non-crosslinked thermoplastic olefin elastomers (TPO); dynamically crosslinked thermoplastic olefin elastomers (TPV) obtained by dynamically heat-treating a mixture containing a matrix-forming resin component A (olefin resin component A) and a domain-forming rubber component B in the presence of a crosslinking agent; and so on. This dynamically crosslinked thermoplastic olefin elastomer is a polymer having a multiphase system with a sea-island structure in which crosslinked rubber particles are finely dispersed as domains (island phases) in the resin component A, which serves as the matrix (sea phase).

[0078] Polyolefin elastomers preferably contain a rubber component. Examples of such rubber components include those described in Japanese Patent Application Publication No. 08-302111, 2010-241934, 2008-024882, 2000-007858, 2006-052277, 2012-072306, 2012-057068, 2010-241897, 2009-067969, and Japanese Patent Application Publication No. 03 / 002654.

[0079] Examples of elastomers having a microphase separation structure between the polyolefin component and the olefin rubber component include elastomers formed from polypropylene resin (PP) and ethylene propylene rubber (EPM), and elastomers formed from polypropylene resin (PP) and ethylene-propylene-diene rubber (EPDM). The weight ratio of the polyolefin component to the olefin rubber component (polyolefin component / olefin rubber) is preferably 90 / 10 to 10 / 90, more preferably 80 / 20 to 20 / 80.

[0080] Dynamically crosslinked thermoplastic olefin elastomers (TPVs) generally have a higher elastic modulus and lower compression set compared to non-crosslinked thermoplastic olefin elastomers (TPOs). Consequently, they exhibit good resilience and, when formulated into resin foams, demonstrate excellent resilience.

[0081] Dynamically crosslinked thermoplastic olefin elastomers (TPVs) refer to polymers that, as described above, are obtained by dynamically heat-treating a mixture containing a matrix-forming resin component A (olefin resin component A) and a domain-forming rubber component B under the presence of a crosslinking agent. These polymers have an island-island structure in which crosslinked rubber particles are finely dispersed as domains (island phases) within the resin component A, which serves as the matrix (sea phase).

[0082] Examples of dynamically crosslinked thermoplastic olefin elastomers (TPVs) include those described in Japanese Patent Application Publication No. 2000-007858, Japanese Patent Application Publication No. 2006-052277, Japanese Patent Application Publication No. 2012-072306, Japanese Patent Application Publication No. 2012-057068, Japanese Patent Application Publication No. 2010-241897, Japanese Patent Application Publication No. 2009-067969, and Japanese Re-applied No. 03 / 002654.

[0083] As a dynamically crosslinked thermoplastic olefin elastomer (TPV), commercially available products can be used, such as: "Zeotherm" (manufactured by Zeon Corporation of Japan), "THERMORUN" (manufactured by Mitsubishi Chemical Corporation), "Sarlink3245D" (manufactured by Toyobo Co., Ltd.), etc.

[0084] The melt flow rate (MFR) of the polyolefin elastomer at a temperature of 230°C is preferably 2 g / 10 min to 15 g / 10 min, more preferably 3 g / 10 min to 10 g / 10 min, further preferably 3.5 g / 10 min to 9 g / 10 min, particularly preferably 4 g / 10 min to 8 g / 10 min, and most preferably 4.5 g / 10 min to 7.5 g / 10 min.

[0085] The melt tension (at 190°C and at break) of polyolefin elastomers is preferably less than 10 cN, more preferably 5 cN to 9.5 cN.

[0086] The JIS A hardness of polyolefin elastomers is preferably 30° to 95°, more preferably 35° to 90°, further preferably 40° to 88°, particularly preferably 45° to 85°, and most preferably 50° to 83°. It should be noted that the JIS A hardness is measured based on ISO 7619 (JIS K6253).

[0087] In one embodiment, the aforementioned resin foam (i.e., resin composition) may further comprise a filler material. By including the filler material, a resin foam capable of deforming the bubble walls (pore walls) requiring significant energy can be formed, resulting in excellent impact absorption. Furthermore, the inclusion of the filler material enables the formation of a fine and uniform bubble structure, which is also advantageous in terms of exhibiting excellent impact absorption. The filler material can be used alone or in combination of two or more types.

[0088] The filler material is preferably contained in proportions of 10 to 150 parts by weight, more preferably 30 to 130 parts by weight, and even more preferably 50 to 100 parts by weight, relative to 100 parts by weight of the polymer constituting the resin foam. If this range is met, the aforementioned effects become significant.

[0089] In one embodiment, the filler material is an inorganic material. Examples of materials constituting an inorganic filler material include: aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, aluminum borate whiskers, silicon nitride, boron nitride, crystalline silicon dioxide, amorphous silicon dioxide, metals (e.g., gold, silver, copper, aluminum, nickel), carbon, graphite, etc.

[0090] In one embodiment, the filler material is an organic compound. Examples of materials constituting an organic filler material include polymethyl methacrylate (PMMA), polyimide, polyamide-imide, polyetheretherketone, polyetherimide, polyesterimide, etc.

[0091] Flame retardants can be used as the filler material mentioned above. Examples of flame retardants include brominated flame retardants, chlorinated flame retardants, phosphorus flame retardants, and antimony flame retardants. From a safety point of view, halogen-free and antimony-free flame retardants are preferred.

[0092] Examples of halogen-free and antimony-free flame retardants include compounds containing aluminum, magnesium, calcium, nickel, cobalt, tin, zinc, copper, iron, titanium, boron, etc. Examples of such compounds (inorganic compounds) include hydrated metal compounds such as aluminum hydroxide, magnesium hydroxide, magnesium oxide / nickel oxide hydrates, and magnesium oxide / zinc oxide hydrates.

[0093] Any suitable surface treatment can be applied to the above-mentioned filler material. Examples of such surface treatments include silane coupling treatment and stearic acid treatment.

[0094] The preferred bulk density of the above-mentioned filler material is 0.8 g / cm³. 3 The following, or more preferably, is 0.6 g / cm³ 3 The following, and more preferably, is 0.4 g / cm³. 3 The following, particularly preferred, is 0.3 g / cm³. 3 The following applies. If the range is such, the filler material can be contained with good dispersibility, and even with a reduction in the filler material content, the effect of the filler material can be fully utilized. Resin foams with low filler material content are advantageous in terms of high foaming density, softness, excellent stress dispersion, and good appearance. The lower limit of the filler material's bulk density is, for example, 0.01 g / cm³. 3 The preferred value is 0.05 g / cm³. 3 More preferably 0.1 g / cm 3 .

[0095] The number-average particle size (primary particle size) of the aforementioned filler material is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 1 μm or less. Within this range, the filler material can be contained with good dispersibility and a uniform bubble structure can be formed. As a result, a resin foam with excellent stress dispersion and appearance can be obtained. The lower limit of the number-average particle size of the filler material is, for example, 0.1 μm. The number-average particle size of the filler material can be measured using a particle size analyzer (Micrtrac II, MICROTRAC BEL Co., Ltd.) as a sample, prepared by mixing 1 g of filler in 100 g of water.

[0096] The specific surface area of ​​the above-mentioned filler material is preferably 2m². 2 / g or more, preferably 4m 2 / g or more, further preferably 6m 2 / g or higher. Within this range, the filler material can be contained with good dispersibility and a uniform bubble structure can be formed. As a result, a resin foam with excellent stress dispersion and appearance can be obtained. The upper limit of the specific surface area of ​​the filler material is, for example, 20 m². 2 / g. The specific surface area of ​​the filler material can be determined using the BET method, which involves adsorbing molecules with a known adsorption area onto the surface of the filler material at low temperatures using liquid nitrogen, and then determining the amount adsorbed.

[0097] Any suitable other components may be included in the resin composition without impairing the effects of the present invention. Such other components may be one or more. Examples of such other components include: rubber, resins other than polymers used as resin materials, softeners, aliphatic compounds, anti-aging agents, antioxidants, light stabilizers, weathering agents, ultraviolet absorbers, dispersants, plasticizers, carbon, antistatic agents, surfactants, crosslinking agents, thickeners, rust inhibitors, organosilicon compounds, tension modifiers, anti-shrinkage agents, flow modifiers, gelling agents, curing agents, reinforcing agents, foaming agents, foaming nucleating agents, colorants (pigments, dyes, etc.), pH adjusters, solvents (organic solvents), thermal polymerization initiators, photopolymerization initiators, lubricants, crystallization nucleating agents, crystallization accelerators, vulcanizing agents, surface treatment agents, dispersing aids, etc.

[0098] A-2. Formation of Resin Foam

[0099] The resin foam of the present invention is typically obtained by foaming a resin composition. As a foaming method (a method for forming bubbles), methods commonly used in foaming molding, such as physical methods and chemical methods, can be employed. That is, the resin foam can be a foam formed by physical methods (physical foam) or a foam formed by chemical methods (chemical foam). Physical methods generally involve dispersing gaseous components such as air and nitrogen in a polymer solution and forming bubbles through mechanical mixing (mechanical foam). Chemical methods generally involve obtaining a foam by forming pores using gases generated from the thermal decomposition of a foaming agent added to a polymer matrix.

[0100] The resin composition to be foamed can be prepared by mixing the constituent components using any suitable melt mixing device, such as an open mixing roller, a non-open Banbury mixer, a single-screw extruder, a twin-screw extruder, a continuous mixer, a pressure kneader, or any suitable mechanism.

[0101] <Effective Method 1 for Forming Resin Foam>

[0102] As one embodiment 1 for forming a resin foam, an example is the following method: A resin foam is formed by a process (step A) of mechanically foaming an emulsion resin composition (an emulsion containing resin materials (polymers), etc.). Examples of foaming devices include high-speed shearing devices, vibration devices, and pressurized gas ejection devices. Among these foaming devices, high-speed shearing devices are preferred from the viewpoint of miniaturizing bubble diameter and producing large volumes. This embodiment 1 for forming a resin foam is applicable regardless of the type of resin composition used.

[0103] From the viewpoint of film-forming properties, a high concentration of solid components in the emulsion is preferred. The concentration of solid components in the emulsion is preferably 30% by weight or more, more preferably 40% by weight or more, and even more preferably 50% by weight or more.

[0104] The bubbles generated during foaming by mechanical stirring are formed by the introduction of gas into the emulsion. Any suitable gas can be used as long as it is inactive with the emulsion and does not impair the effects of the present invention. Examples of such gases include air, nitrogen, and carbon dioxide.

[0105] By applying the foamed emulsion resin composition (containing the bubble emulsion resin composition) obtained by the above method onto a substrate and then drying it (step B), the resin foam of the present invention can be obtained. Examples of substrates include: a plastic film that has undergone a peeling treatment (such as a peeled polyethylene terephthalate film), a plastic film (such as a polyethylene terephthalate film), etc.

[0106] In step B, any suitable method may be used as the coating method and drying method without impairing the effects of the present invention. Step B preferably includes: a pre-drying step B1 in which the bubble-containing emulsion resin composition coated on the substrate is dried at a temperature of 50°C or higher and less than 125°C; and a formal drying step B2 in which the composition is further dried at a temperature of 125°C or higher and less than 200°C.

[0107] By incorporating a pre-drying process B1 and a formal drying process B2, the coalescence and bursting of bubbles caused by a rapid temperature rise can be prevented. This is particularly important for thin foam sheets, where a rapid temperature increase can cause bubbles to coalesce and burst; therefore, the pre-drying process B1 is crucial. The temperature in the pre-drying process B1 is preferably 50°C to 100°C. The time for the pre-drying process B1 is preferably 0.5 minutes to 30 minutes, more preferably 1 minute to 15 minutes. The temperature in the formal drying process B2 is preferably 130°C to 180°C, more preferably 130°C to 160°C. The time for the formal drying process B2 is preferably 0.5 minutes to 30 minutes, more preferably 1 minute to 15 minutes.

[0108] <Effective Method 2 for Forming Resin Foam>

[0109] As one embodiment of forming a resin foam, a method of forming a foam by foaming a resin composition using a foaming agent can be cited. As the foaming agent, a foaming agent commonly used in foam molding can be used. From the viewpoint of environmental protection and low pollution to the foamed body, a high-pressure inert gas is preferred.

[0110] As an inert gas, any suitable inert gas can be used as long as it is inactive to the resin composition and can impregnate it. Examples of such inert gases include carbon dioxide, nitrogen, and air. These gases can also be used in mixtures. Among these, carbon dioxide is preferred from the viewpoint of high impregnation volume and fast impregnation rate of the resin material (polymer).

[0111] The inert gas is preferably in a supercritical state. Specifically, supercritical carbon dioxide is particularly preferred. In the supercritical state, the solubility of the inert gas in the resin composition is further increased, allowing for high concentrations of the inert gas to be incorporated. Furthermore, the high concentration of the inert gas results from a rapid decrease in pressure, leading to the formation of more bubble nuclei. Even with the same porosity, the density of bubbles formed from these nuclei is greater compared to other states, thus yielding fine bubbles. It should be noted that the critical temperature of carbon dioxide is 31°C and the critical pressure is 7.4 MPa.

[0112] As a method for forming a foamed body by impregnating a resin composition with a high-pressure inert gas, examples include methods that involve the following steps: a gas impregnation step in which an inert gas is impregnated into a resin composition containing a resin material (polymer) under high pressure; a decompression step in which the pressure is reduced after the gas impregnation step to foam the resin material (polymer); and a heating step in which bubbles are grown by heating as needed. In this case, a pre-formed unfoamed molded body can be impregnated with an inert gas, or the inert gas can be impregnated into a molten resin composition under pressure and then molding is performed under decompression. These steps can be performed in either an intermittent or continuous manner. That is, it can be an intermittent method in which the resin composition is pre-formed into a suitable shape such as a sheet to form an unfoamed resin molded body, and then a high-pressure gas is impregnated into the unfoamed resin molded body and the pressure is released to foam it; or it can be a continuous method in which the resin composition is mixed with a high-pressure gas under pressure, molded, and then the pressure is released to simultaneously perform molding and foaming.

[0113] The following illustrates an example of manufacturing foamed materials in an intermittent manner. For instance, resin sheets for foam molding are produced by extruding a resin composition using an extruder such as a single-screw extruder or a twin-screw extruder. Alternatively, an unfoamed resin molded body is produced by pre-mixing the resin composition uniformly using a bladed mixer such as a roller, cam, kneader, or Banbury type, and then pressing it to a given thickness using hot plate pressure. This unfoamed resin molded body is then placed in a high-pressure vessel, and a high-pressure inert gas (such as supercritical carbon dioxide) is injected to impregnate the unfoamed resin molded body. When the inert gas has been sufficiently impregnated, the pressure is released (usually to atmospheric pressure), generating bubble nuclei in the resin. The bubble nuclei can grow directly at room temperature, but depending on the circumstances, they can also be grown by heating. As heating methods, known and conventional methods such as water baths, oil baths, hot rollers, hot air ovens, far-infrared radiation, near-infrared radiation, and microwaves can be used. After the bubbles are grown in this way, they are rapidly cooled and their shape is fixed by cold water, thus obtaining a foamed body. It should be noted that the unfoamed resin molded body supplied for foaming is not limited to sheet form; various shapes of unfoamed resin molded bodies can be used depending on the application. Furthermore, in addition to extrusion molding and pressure molding, unfoamed resin molded bodies for foaming can also be manufactured by other molding methods such as injection molding.

[0114] The following illustrates an example of continuous foam manufacturing. For instance, foam molding is performed through a mixing and impregnation process followed by a molding decompression process. In the mixing and impregnation process, a resin composition is mixed using an extruder such as a single-screw or twin-screw extruder, while high-pressure gas (particularly an inert gas, such as carbon dioxide) is injected (introduced) to fully impregnate the resin composition. In the molding decompression process, the resin composition is extruded through a die or similar device located at the front end of the extruder, thereby releasing pressure (typically to atmospheric pressure), simultaneously performing molding and foaming. Furthermore, when performing continuous foam molding, a heating process can be included as needed to grow the bubbles. After the bubbles have grown, their shape can be fixed by rapid cooling with cold water or the like. The introduction of high-pressure gas can be continuous or discontinuous. Additionally, extruders and injection molding machines can be used in the mixing and impregnation process and the molding decompression process. It should be noted that any suitable heating method can be used to promote bubble growth, such as a water bath, oil bath, hot roller, hot air oven, far-infrared radiation, near-infrared radiation, or microwave. As for the shape of the foam, any suitable shape can be used. Examples of such shapes include sheet-like, prismatic, cylindrical, and irregular shapes.

[0115] From the viewpoint of obtaining a highly foamed resin foam, the amount of gas mixed during the foaming molding of the resin composition is preferably 2% to 10% by weight, more preferably 2.5% to 8% by weight, and even more preferably 3% to 6% by weight relative to the total amount of the resin composition.

[0116] The pressure at which the inert gas impregnates the resin composition can be selected with consideration for operability and other suitable factors. Such a pressure is preferably 6 MPa or higher (e.g., 6 MPa to 100 MPa), and more preferably 8 MPa or higher (e.g., 8 MPa to 50 MPa). It should be noted that, from the viewpoint of maintaining the supercritical state of carbon dioxide, the pressure is preferably 7.4 MPa or higher when using supercritical carbon dioxide. At pressures below 6 MPa, bubble growth during foaming is significant, and the bubble diameter becomes excessively large, sometimes making it impossible to obtain the preferred average pore diameter (average bubble diameter). This is because, at low pressures, the amount of gas impregnated is relatively less compared to high pressures, the bubble nucleus formation rate decreases, and the number of bubble nuclei formed decreases, thus increasing the average amount of gas per bubble and resulting in a very large bubble diameter. Furthermore, in the pressure range below 6 MPa, even slight changes in impregnation pressure can lead to significant changes in bubble diameter and bubble density, making it difficult to control bubble diameter and bubble density.

[0117] The temperature during the gas impregnation process varies depending on the type of inert gas used and the components in the resin composition, and can be selected within a wide range. Taking into account operability, a temperature of 10°C to 350°C is preferred. When impregnating an unfoamed molded article with an inert gas, the impregnation temperature is preferably 10°C to 250°C, more preferably 40°C to 230°C, in the case of intermittent operation. Furthermore, when extruding the gas-impregnated molten polymer and simultaneously foaming and molding, the impregnation temperature is preferably 60°C to 350°C, in the case of continuous operation. It should be noted that when using carbon dioxide as an inert gas, in order to maintain a supercritical state, the impregnation temperature is preferably 32°C or higher, more preferably 40°C or higher.

[0118] In the decompression process, the decompression rate is preferably 5 MPa / s to 300 MPa / s in order to obtain uniform microbubbles.

[0119] The heating temperature in the heating process is preferably 40℃~250℃, more preferably 60℃~250℃.

[0120] In one embodiment, after obtaining a foamed structure through a given process (for example, after obtaining a resin foam by the method of <Embodiment 1> or <Embodiment 2>), the foamed structure is thinned into a film, and then rolled to obtain a resin foam. By performing this process, a resin foam with an appropriately adjusted aspect ratio can be obtained. Furthermore, a thin resin foam (for example, less than 0.2 mm) can be obtained. Sometimes, the aforementioned hot-melt layer is also formed during the rolling process.

[0121] The film formation of the foamed structure can be performed using any suitable slicing machine. The thickness of the film-formed foamed structure is preferably 0.18 mm to 1 mm, more preferably 0.2 mm to 0.8 mm, and even more preferably 0.3 mm to 0.7 mm.

[0122] Preferably, the roller used for the above-mentioned roll calendering is a heated roller. The temperature of the roller is preferably 150°C to 250°C, more preferably 160°C to 230°C.

[0123] The calendering rate (thickness after calendering / thickness before calendering × 100) of the foamed structure is preferably 80% or less, more preferably 10% to 80%, further preferably 20% to 75%, and particularly preferably 30% to 75%. If it is within this range, a resin foam with an aspect ratio appropriately adjusted can be obtained.

[0124] B. Foamed components

[0125] Figure 1This is a cross-sectional schematic diagram of a foamed component according to one embodiment. The foamed component 100 has a resin foam layer 10 and an adhesive layer 20 disposed on at least one side of the resin foam layer 10. The resin foam layer 10 is composed of the aforementioned resin foam.

[0126] The thickness of the adhesive layer is preferably 5 μm to 300 μm, more preferably 6 μm to 200 μm, even more preferably 7 μm to 100 μm, and particularly preferably 8 μm to 50 μm. By keeping the thickness of the adhesive layer within the above range, the foamed component of the present invention can exhibit excellent impact absorption.

[0127] As the adhesive layer, a layer formed of any suitable adhesive can be used. Examples of adhesives constituting the adhesive layer include: rubber-based adhesives (synthetic rubber-based adhesives, natural rubber-based adhesives, etc.), urethane-based adhesives, acrylic urethane-based adhesives, acrylic adhesives, silicone-based adhesives, polyester-based adhesives, polyamide-based adhesives, epoxy-based adhesives, vinyl alkyl ether-based adhesives, fluorinated adhesives, and rubber-based adhesives. Preferably, the adhesive constituting the adhesive layer is selected from at least one of acrylic adhesives, silicone adhesives, and rubber-based adhesives. There may be only one type of adhesive or two or more types. The adhesive layer may be one layer or two or more layers.

[0128] As adhesives, if classified by bonding method, examples include: emulsion adhesives, solvent-based adhesives, UV crosslinking adhesives, electron beam crosslinking adhesives, and hot melt adhesives. Such adhesives can be of one type or two or more.

[0129] The water vapor permeability of the adhesive layer is preferably 50 g / m³. 2 • Less than 24 hours, more preferably 30 g / (m 2 • Less than 24 hours, more preferably 20 g / (m 2 • Less than 24 hours, preferably 10 g / (m 2 • 24 hours or less. If the water vapor permeability of the adhesive layer is within the above range, the foam sheet can stabilize the shock absorption without being affected by moisture. It should be noted that the water vapor permeability can be determined, for example, by the method based on JIS Z 0208, under test conditions of 40°C and 92% relative humidity.

[0130] Other suitable components may also be included in the adhesive constituting the adhesive layer without impairing the effects of the present invention. Examples of such other components include: other polymer components, softeners, anti-aging agents, curing agents, plasticizers, fillers, antioxidants, thermal polymerization initiators, photopolymerization initiators, ultraviolet absorbers, light stabilizers, colorants (pigments, dyes, etc.), solvents (organic solvents), surfactants (e.g., ionic surfactants, silicone surfactants, fluorinated surfactants, etc.), crosslinking agents (e.g., polyisocyanate crosslinking agents, silicone crosslinking agents, epoxy crosslinking agents, alkyl etherified melamine crosslinking agents, etc.). It should be noted that thermal polymerization initiators and photopolymerization initiators may be included in the materials used to form the polymer components.

[0131] The aforementioned foamed components can be manufactured by any suitable method. Examples of methods for manufacturing foamed components include: a method of manufacturing by laminating a resin foam layer with an adhesive layer; and a method of manufacturing by forming an adhesive layer by laminating an adhesive layer forming material with a resin foam layer and then forming an adhesive layer through a curing reaction, etc.

[0132] Example

[0133] The present invention will now be described in detail with reference to embodiments, but the present invention is not limited to these embodiments in any way. It should be noted that the testing and evaluation methods in the embodiments, etc., are as described below. It should be noted that when "parts" are used, unless otherwise specified, they refer to "parts by weight," and when "%" are used, unless otherwise specified, they refer to "% by weight."

[0134] <Evaluation Methods>

[0135] (1) Apparent density

[0136] The density (apparent density) of the resin foam was calculated as described below. The resin foam obtained in the examples / comparative examples was punched into 20mm × 20mm pieces as test pieces. The dimensions of the test pieces were measured with calipers, and the weight of the test pieces was measured using an electronic balance and calculated using the following formula.

[0137] Apparent density (g / cm³) 3 = Weight of test piece / Volume of test piece

[0138] (2) 25% compressive load

[0139] The compressive hardness of the resin foam was determined according to the method described in JIS K 6767. Specifically, the resin foam obtained in the examples / comparative examples was cut into 30mm × 30mm pieces as test pieces, and compressed at a compression rate of 10mm / min until the compression ratio reached 25%. The stress (N) at this point was converted into the stress per unit area (cm²). 2 The value of ) is taken as 25% of the compressive load (N / cm). 2 ).

[0140] (3) Aspect ratio of the bubble

[0141] As a measuring instrument, the aspect ratio of the air bubbles in the resin foam obtained in the Examples / Comparative Examples was measured using a digital microscope (trade name "VHX-2000", manufactured by Keyence Co., Ltd.) by the following method.

[0142] • Cut the resin foam using a die-cutting mold, and observe the cut section at 100x magnification using a microscope (e.g., Keyence "VHX-2000") to examine a given area (3 mm²). 2 The range is used to measure the length of a bubble in the thickness direction and the length in the lateral direction.

[0143] • Perform the same measurement on all bubbles present in a given area.

[0144] • The aspect ratio of the bubble is calculated by dividing the length in the horizontal direction by the length in the thickness direction. The same calculation is performed on all bubbles, and the average value is taken as the "aspect ratio of the bubbles in the resin foam".

[0145] (4) The coefficient of variation of average bubble diameter (average pore diameter) and bubble diameter (pore diameter)

[0146] Using a digital microscope (trade name "VHX-2000", manufactured by Keyence Co., Ltd.) as the measuring instrument, magnified images of the bubble portions of the resin foam obtained in the Examples / Comparative Examples were imported. The number-average bubble diameter (average pore diameter) (μm) was determined by image analysis using the same measuring instrument's analysis software. The imported magnified images contained approximately 400 bubbles. Furthermore, the standard deviation was calculated based on all pore diameter data, and the coefficient of variation was calculated using the following formula.

[0147] Variation coefficient = Standard deviation / Average bubble diameter (average pore diameter)

[0148] (5) Bubble rate (porosity)

[0149] The measurements were conducted in an environment with a temperature of 23°C and a humidity of 50%. The resin foam obtained in the Examples / Comparative Examples was punched using a 100mm × 100mm die, and the dimensions of the punched samples were measured. Additionally, the thickness was measured using a 1 / 100 micrometer with a measuring terminal diameter (φ) of 20mm. The volume of the resin foam obtained in the Examples / Comparative Examples was calculated based on these values. Next, the weight of the resin foam obtained in the Examples / Comparative Examples was measured using a balance with a minimum graduation of 0.01g or higher. The bubble rate (porosity) of the resin foam obtained in the Examples / Comparative Examples was calculated based on these values.

[0150] (6) Thickness of bubble wall (pore wall)

[0151] Using a digital microscope (trade name "VHX-2000", manufactured by Keyence Co., Ltd.) as the measuring instrument, magnified images of the bubble portions of the resin foam obtained in the Examples / Comparative Examples were imported. The thickness (μm) of the bubble walls (pore walls) was determined by image analysis using the same measuring instrument's analysis software. The imported magnified images contained approximately 400 bubbles.

[0152] (7) Tensile modulus

[0153] The tensile modulus was determined using a tensile testing machine (RTG-1201, manufactured by Tansui Co., Ltd.). The sample (size: 10mm × 80mm) was fixed with a chuck spacing of 40mm, and a tensile test was conducted at a tensile speed of 500mm / min. A curve based on tensile strain and tensile strength was obtained. The tensile modulus was determined by the slope of the straight line connecting the origin of this curve to the tensile strength at 10% tensile strain.

[0154] (8) Punching processability

[0155] The resin foam was die-cut using a die (two cutting blades, trade name "NCA07", 0.5mm thickness, 45° tip angle, manufactured by NAKAYAMA Co., Ltd.). The cross-section was observed using a microscope (trade name "VHX-2000", manufactured by Keyence Co., Ltd.), and the thickness at the ends and center was measured based on the images. The thickness recovery rate after processing was determined using the measured thickness and the following formula. The higher the thickness recovery rate, the smaller the shape change caused by die-cutting, and the better the die-cutting processability.

[0156] Thickness recovery rate after processing = 100 × (1 - (thickness at the center - thickness at the end) / thickness at the center)

[0157] (9) Shock absorption

[0158] A test specimen was formed by sequentially mounting a resin foam, a double-sided tape (product number: No. 5603W, manufactured by Nitto Denko), and a PET film (product number: DIAFOIL MRF75, manufactured by Mitsubishi Resin) onto an impact force sensor. A 66g iron ball was dropped from a height of 50cm above the PET film onto the test specimen, and the impact force F1 was measured.

[0159] In addition, the iron ball was dropped directly onto the impact sensor as described above, and the blank impact force F0 was measured.

[0160] The shock absorption rate (%) was calculated based on F1 and F0 using the formula (F0-F1) / F0×100.

[0161] (10) Elastic strain energy

[0162] Based on the tensile elongation of JIS K 6767, the tensile elongation (%) and tensile strength (kPa) of the resin foam were measured. The area of ​​the region with tensile elongation of 0 to 10% was calculated from the area enclosed by the tensile SS curve obtained with tensile elongation as the x-axis and tensile strength as the y-axis, and was taken as the elastic strain energy.

[0163] (11) Non-foamed bending stress

[0164] Using a vacuum compression molding machine (IVM-70: Iwaki Kogyo Co., Ltd.), the resin foam was pressurized for 5 minutes at a temperature of (melting point +70°C) and a pressure of 15 MPa, thereby obtaining a non-foamed resin molded body a.

[0165] A sample was cut from a resin molded body a, with a width of 20 mm and a length of 150 mm. The sample was placed on a 3-point bending fixture with a fulcrum distance of 100 mm and an indentation test was conducted at an indentation speed of 5 mm / min in an environment of 23°C and 50% RH. The load (g) when the sample was indented by 5 mm was taken as the non-foamed bending stress.

[0166] (12) Thickness recovery rate

[0167] For resin foam, when applying 1000g / cm³ to the resin foam... 2 The resin foam was kept under load for 120 seconds, then the compression was released, and the thickness of the resin foam was measured 0.5 seconds after the compression was released (thickness 0.5 seconds after the compression was released). The thickness recovery rate was calculated using the following formula based on the thickness 0.5 seconds after the compression was released and the thickness of the resin foam before the load was applied (initial thickness).

[0168] Thickness recovery rate (%) = {(thickness 0.5 seconds after decompression) / (initial thickness)} × 100

[0169] [Example 1]

[0170] Using a twin-screw extruder manufactured by Japan Steel Works (JSW), 65 parts by weight of polypropylene (melt flow rate (MFR) (230°C): 0.40 g / 10 min), 35 parts by weight of polyolefin elastomer (melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79°), 120 parts by weight of magnesium hydroxide (trade name "KISUMA 5P", manufactured by Kyowa Chemical Industry), 10 parts by weight of carbon (trade name "Asahi #35", manufactured by Asahi Carbon Co., Ltd.), and 1 part by weight of glyceryl monostearate were mixed at 200°C, extruded as a filament, and water-cooled to form granules. These granules were then fed into a single-screw extruder manufactured by JSW, and carbon dioxide gas was injected at 13 MPa (12 MPa after injection) in an atmosphere at 220°C. Carbon dioxide gas was injected at a ratio of 3 parts by weight to 100 parts by weight of resin. After fully saturating the carbon dioxide gas, the material is cooled to a suitable temperature for foaming and then extruded from a die to obtain a sheet-like foamed structure a. Further, the foamed structure a is thinned using a slicing machine to obtain a foamed structure a1 with a thickness of 0.5 mm.

[0171] Furthermore, the aforementioned foamed structure a1 was passed through the gap between a pair of rollers heated to 230°C to obtain a resin foam A1 with a thickness of 0.15 mm. It should be noted that the gap between the rollers was set in a manner that yields a resin foam A1 with a thickness of 0.15 mm.

[0172] The obtained resin foam A1 was used for the above evaluations (1) to (8). The results are shown in Table 1.

[0173] [Example 2]

[0174] Foamed structure a was obtained in the same manner as in Example 1. Furthermore, foamed structure a was thinned using a slicing machine to obtain foamed structure a2 with a thickness of 0.35 mm.

[0175] Furthermore, the aforementioned foamed structure a2 was passed through the gap between a pair of rollers heated to 230°C to obtain a resin foam A2 with a thickness of 0.15 mm. It should be noted that the gap between the rollers was set in a manner that yields a resin foam A2 with a thickness of 0.15 mm.

[0176] The obtained resin foam A2 was used for the above evaluations (1) to (8). The results are shown in Table 1.

[0177] [Example 3]

[0178] Foamed structure a was obtained in the same manner as in Example 1. Furthermore, the foamed structure a was thinned using a slicing machine to obtain a foamed structure a3 with a thickness of 0.30 mm.

[0179] Furthermore, the aforementioned foamed structure a3 was passed through the gap between a pair of rollers heated to 200°C to obtain a resin foam A3 with a thickness of 0.15 mm. It should be noted that the gap between the rollers was set in a manner that yields a resin foam A3 with a thickness of 0.15 mm.

[0180] The obtained resin foam A3 was used for the above evaluations (1) to (8). The results are shown in Table 1.

[0181] [Example 4]

[0182] Foamed structure a was obtained in the same manner as in Example 1. Furthermore, the foamed structure a was thinned using a slicing machine to obtain a foamed structure a4 with a thickness of 0.20 mm.

[0183] Furthermore, the aforementioned foamed structure a4 was passed through the gap between a pair of rollers heated to 200°C to obtain a resin foam A4 with a thickness of 0.15 mm. It should be noted that the gap between the rollers was set in a manner that yields a resin foam A4 with a thickness of 0.15 mm.

[0184] The obtained resin foam A4 was used for the above evaluations (1) to (8). The results are shown in Table 1.

[0185] [Example 5]

[0186] Using a twin-screw mixer manufactured by Japan Steel Works (JSW), 55 parts by weight of polypropylene (melt flow rate (MFR) (230°C): 0.40 g / 10 min), 20 parts by weight of polypropylene (melt flow rate (MFR) (230°C): 2.1 g / 10 min), 25 parts by weight of polyolefin elastomer (melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79°), 120 parts by weight of magnesium hydroxide (trade name "KISUMA 5P", manufactured by Kyowa Chemical Industry), 10 parts by weight of carbon (trade name "Asahi #35", manufactured by Asahi Carbon Co., Ltd.), and 1 part by weight of glyceryl monostearate were mixed at 200°C, extruded in filament, and water-cooled to form granules. The granules were fed into a single-screw extruder manufactured by Nippon Steel Corporation, and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) in an atmosphere of 220°C. Carbon dioxide gas was injected at a ratio of 2.8 parts by weight relative to 100 parts by weight of resin. After fully saturating with carbon dioxide gas, the mixture was cooled to a suitable temperature for foaming and extruded from a die to obtain a sheet-like foamed structure b. Furthermore, the foamed structure b was thinned using a slicing machine to obtain a foamed structure b1 with a thickness of 0.3 mm.

[0187] Furthermore, the aforementioned foamed structure b1 was passed through the gap between a pair of rollers heated to 200°C to obtain a resin foam B with a thickness of 0.15 mm. It should be noted that the gap between the rollers was set in a manner that yielded a resin foam B with a thickness of 0.15 mm.

[0188] [Example 6]

[0189] Using a twin-screw mixer manufactured by Japan Steel Works (JSW), 55 parts by weight of polypropylene (melt flow rate (MFR) (230°C): 0.40 g / 10 min), 10 parts by weight of polypropylene (melt flow rate (MFR) (230°C): 2.1 g / 10 min), 10 parts by weight of polypropylene (melt flow rate (MFR) (230°C): 2.4 g / 10 min), 25 parts by weight of polyolefin elastomer (melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79°), 120 parts by weight of magnesium hydroxide (trade name "KISUMA 5P", manufactured by Kyowa Chemical Industry), 10 parts by weight of carbon (trade name "Asahi #35", manufactured by Asahi Carbon Co., Ltd.), and 1 part by weight of glyceryl monostearate were mixed at 200°C, extruded in filament, and water-cooled to form granules. The granules were fed into a single-screw extruder manufactured by Nippon Steel Corporation, and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) in an atmosphere of 220°C. Carbon dioxide gas was injected at a ratio of 2.6 parts by weight relative to 100 parts by weight of resin. After fully saturating with carbon dioxide gas, the mixture was cooled to a suitable temperature for foaming and extruded from a die to obtain a sheet-like foamed structure b. Furthermore, the foamed structure b was thinned using a slicing machine to obtain a foamed structure b1 with a thickness of 0.3 mm.

[0190] Furthermore, the aforementioned foamed structure b1 was passed through the gap between a pair of rollers heated to 200°C to obtain a resin foam B with a thickness of 0.15 mm. It should be noted that the gap between the rollers was set in a manner that yielded a resin foam B with a thickness of 0.15 mm.

[0191] [Comparative Example 1]

[0192] Foamed structure a was obtained in the same manner as in Example 1. Furthermore, the foamed structure a was thinned using a slicing machine to obtain a resin foam C with a thickness of 0.15 mm.

[0193] The obtained resin foam C was used for the above evaluations (1) to (8). The results are shown in Table 1.

[0194] [Comparative Example 2]

[0195] A resin foam with polyurethane as the main component was prepared (apparent density: 0.7 g / cm³). 3 (25% compressive load 100 kPa, bubble length-to-diameter ratio: 1.8). The resulting resin foam was supplied to (1) to (8) above. The results are shown in Table 1.

[0196] [Table 1]

[0197] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 <![CDATA[Apparent density [g / cm 3 > 0.24 0.20 0.16 0.14 0.15 0.18 0.07 0.70 25% compressive load [kPa] 50 30 25 22 24 30 18 100 Bubble aspect ratio [-] 2.8 2.0 1.8 1.6 1.8 1.8 1.2 1.8 Average bubble diameter [μm] 75 75 75 75 70 80 75 80 Bubble rate [%) 75 80 84 86 85 82 93 30 Bubble diameter variation coefficient [-] 0.3 0.3 0.3 0.3 0.27 0.32 0.3 0.5 Pore ​​wall thickness [μm] 2.0 2.0 2.0 2.0 1.9 2.1 2.0 3.2 Thickness recovery rate [%) 90.0 87.0 87.0 85.0 85.0 85.0 70.0 60.0 Bending stress [MPa] in non-foamed state 10.2 10.2 10.2 10.2 10.4 11.5 10.2 4.0 Tensile modulus [MPa] 2.5 2.4 2.2 1.7 2.1 2.5 1.0 2.5 Thickness recovery rate after processing [%) 93 93 87 87 86 85 53 60 Shock absorption [%) 45 40 40 35 40 40 15 10 Slice thickness [mm] 0.5 0.35 0.3 0.2 0.3 0.3 0.15 - Heat treatment thickness [mm] 0.15 0.15 0.15 0.15 0.15 0.15 - -

[0198] Industrial applicability

[0199] The resin foam of the present invention can be suitably used, for example, as a cushioning material for electronic devices.

Claims

1. A resin foam having a bubble structure, The apparent density of this resin foam is 0.15 g / cm³. 3 ~0.30g / cm 3 With a 25% compressive load of 0.1 kPa to 80 kPa, and a tensile modulus of over 2.1 MPa at 25°C, The independent bubble rate of this resin foam is below 40%, and the thickness recovery rate is above 72%. The resin foam has air bubbles with an aspect ratio of 1.5 or higher.

2. The resin foam according to claim 1, wherein the average bubble diameter is 10μm~200μm.

3. The resin foam according to claim 1 or 2, wherein the bubble rate is 30% or more.

4. The resin foam according to claim 1 or 2, wherein the coefficient of variation of the bubble diameter is less than 0.

5.

5. The resin foam according to claim 1 or 2, wherein the thickness of the bubble wall is 0.1 μm to 10 μm.

6. The resin foam according to claim 1 or 2, comprising a polyolefin resin.

7. The resin foam according to claim 6, wherein, The polyolefin resin is a mixture of polyolefin elastomer and polyolefins other than polyolefin elastomer.

8. The resin foam according to claim 1 or 2, wherein it has a hot-melt layer on one or both sides.

9. A foamed component having a resin foam layer and an adhesive layer disposed on at least one side of the resin foam layer. The resin foam layer is the resin foam body according to any one of claims 1 to 8.

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