Resin foam and foam member

Abstract

Provided is a resin foam that exhibits superior flexibility, die-punching properties, and breakdown resistance.　A resin foam according to an embodiment of the present application has a cellular structure, wherein the relationship [-1.5 × the toughness (unit: MPa) + 6 < the interlaminar strength (unit N / 20 mm) < -1.5 × the toughness (unit: MPa) + 35] is satisfied, and the thickness recovery factor after subjecting the resin foam to a load of 1000 g / cm2 for 120 seconds is 80% or greater.

Description

Resin foam and foam member 【0001】 The present invention relates to a resin foam and a foam member. 【0002】 For the protection of the screen of electronic devices, the protection of substrates, the protection of electronic components, etc., foams are frequently used as cushioning materials. In such foams, it is required to be excellent in flexibility so that cushioning properties can be preferably exhibited. In recent years, in accordance with the trend of thinning of electronic devices, it has been required to narrow the clearance of the portion where the cushioning material is disposed. Furthermore, with the miniaturization, multifunctionalization, etc. of electronic devices, the electronic components used also tend to be miniaturized, and there are cases where smaller cushioning materials (foams) are required. 【0003】 Also, usually, when obtaining a foam of a desired shape, punching processing of a foam stock is performed. In punching processing, a high pressure is applied to the foam using a mold to obtain a foam having a desired shape. In conventional foams, the thickness reduced by punching processing may not be sufficiently restored after the processing, and as a result, a thickness change may occur. Such a phenomenon particularly becomes a problem in manufacturing a foam applied to a location with a narrow clearance. 【0004】 Further, the cushioning material (foam) may be used in a narrow width along with the above miniaturization. Even during narrow-width processing, it is punched and processed into a predetermined shape, and then picked up using a carrier tape, and the carrier tape is peeled off when assembling it to a predetermined member. At this time, problems may occur from the viewpoint of assembly property, such as the handling of the foam becoming difficult or the foam being broken. It is difficult to provide a foam having excellent punching processability and excellent assembly property. 【0005】 Japanese Patent Application Laid-Open No. 2017-186504, Japanese Patent Application Laid-Open No. 2015-034299, Japanese Patent Application Laid-Open No. 2006-312308 【0006】 An object of the present invention is to provide a resin foam excellent in flexibility, punching processability, and fracture resistance. 【0007】1. The resin foam according to the embodiment of the present invention is a resin foam having a cellular structure that satisfies the formula [-1.5 × toughness (unit: MPa) + 6 < interlaminar strength (unit: N / 20 mm) < -1.5 × toughness (unit: MPa) + 35], and the resin foam is filled with 1000 g / cm³ ２ 1. The thickness recovery rate after maintaining the applied load for 120 seconds is 80% or more. 2. The resin foam described in item 1 above may have a toughness of 0.7 MPa or more. 3. The resin foam described in item 1 or 2 above may have an interlayer strength of 3 N / 20 mm or more. 4. The resin foam described in any of items 1 to 3 above has an apparent density of 0.4 g / cm³. ３ The following may also apply: 5. The resin foam described in any of items 1 to 4 above has a 50% compression load of 40 N / cm ２The following may also apply: 6. The resin foam described in any of items 1 to 5 above may have an average bubble diameter of 1000 μm or less. 7. The resin foam described in any of items 1 to 6 above may have a coefficient of variation of the bubble diameter of 0.6 or less. 8. The resin foam described in any of items 1 to 7 above may contain a polyolefin resin. 9. The resin foam described in item 8 above contains a polyolefin as the polyolefin resin, and the polyolefin may be polyethylene or polypropylene. 10. The resin foam described in item 8 or 9 above may contain a mixture of a polyolefin other than a polyolefin elastomer and a polyolefin elastomer as the polyolefin resin. 11. The resin foam described in any of items 1 to 10 above may contain recycled resin. 12. The resin foam described in item 11 above may contain a polyolefin as the recycled resin. 13. The resin foam described in item 12 above may have a melt flow rate (MFR) of polyolefin as the recycled resin at a temperature of 230°C of less than 10 g / 10 min. 14. 12. The resin foam described in 12 or 13 above may have a melt tension of 10 cN or more for the polyolefin as the recycled resin. 15. The resin foam described in any of 1 to 14 above may contain a plant-derived polyolefin resin. 16. The resin foam described in 15 above may contain a plant-derived polyolefin as the plant-derived polyolefin resin, and the melt flow rate (MFR) of the plant-derived polyolefin at a temperature of 230°C may be less than 20 g / 10 min. 17. The resin foam described in 16 above may have a melt tension of 10 cN or more for the plant-derived polyolefin. 18. The resin foam described in any of 1 to 17 above may have a heat-melting layer on one or both sides. 19. The foamed member according to an embodiment of the present invention has a resin foam layer and an adhesive layer disposed on at least one side of the resin foam layer, wherein the resin foam layer is the resin foam described in any of 1 to 18 above. 【0008】According to the present invention, it is possible to provide a resin foam that is excellent in flexibility, die-cutting processability, and fracture resistance (for example, fracture resistance when assembled into a predetermined part). 【0009】 This is a schematic cross-sectional view of a foamed member according to one embodiment of the present invention. 【0010】 A. Resin Foam The resin foam according to the embodiment of the present invention satisfies the formula [-1.5 × toughness (unit: MPa) + 6 < interlaminar strength (unit: N / 20 mm) < -1.5 × toughness (unit: MPa) + 35]. Furthermore, the above resin foam can be subjected to 1000 g / cm³ ２ The thickness recovery rate (hereinafter also referred to as the instantaneous recovery rate) after maintaining the applied load for 120 seconds is 80% or more. 【0011】 In this specification, toughness corresponds to the area under the elongation-strength-strength-breaking curve (the so-called SS curve) obtained in a tensile strength test at a measurement temperature of 23°C, from the origin to the point of failure. Details of the measurement method will be described later. 【0012】 In this specification, interlaminar strength refers to the interlaminar strength at 23°C, which is the maximum load at which the resin foam breaks (delaminates) when pulled in the thickness direction. The method for measuring interlaminar strength will be described later. 【0013】 In embodiments of the present invention, the resin foam has a cellular structure. Examples of cellular structures include closed-cell structures, open-cell structures, and semi-open-cell structures (a cellular structure in which closed-cell and open-cell structures are mixed). In one embodiment, the resin foam is obtained by foaming a resin composition containing recycled resin and / or plant-derived resin. The resin composition is a composition containing at least the resin that constitutes the resin foam. 【0014】In embodiments of the present invention, by configuring the resin foam to satisfy the formula [-1.5 × toughness (unit: MPa) + 6 < interlaminar strength (unit: N / 20 mm) < -1.5 × toughness (unit: MPa) + 35] and to have an instantaneous recovery rate of 80% or more, it is possible to provide a resin foam that has excellent flexibility while also being excellent in die-cutting processability and fracture resistance. More specifically, according to the above embodiments, even when die-cut, the shape changes such as thickness changes are small, and even if the thickness is temporarily reduced by die-cutting, it recovers in a short time, exhibiting desirable behavior, and a resin foam with excellent die-cutting processability can be obtained. According to embodiments of the present invention, the above effects can be obtained even if the resin foam is thin or has a narrow shape. Furthermore, a resin foam with excellent fracture resistance is advantageous in terms of ease of assembly. For example, when the resin foam is attached to a carrier tape and then peeled off, the resin foam may tear and remain on the carrier tape; when the resin foam is applied to electronic equipment, etc., the resin foam may tear and break; and other such problems can be prevented. A resin foam satisfying the above characteristics can be obtained, for example, by using multiple types of resins with different MFRs as the resins constituting the resin foam, and by adjusting the blending ratio of these resins. 【0015】 The above resin foam more preferably satisfies the formula [-1.5 × toughness (unit: MPa) + 7 < interlaminar strength (unit: N / 20 mm) < -1.5 × toughness (unit: MPa) + 33], and even more preferably satisfies the formula [-1.5 × toughness (unit: MPa) + 8 < interlaminar strength (unit: N / 20 mm) < -1.5 × toughness (unit: MPa) + 30]. By configuring it in this way, the above effect becomes remarkable. 【0016】The interlayer strength of the above resin foam is preferably 3 N / 20 mm or more, more preferably 3.2 N / 20 mm or more, more preferably 3.5 N / 20 mm or more, even more preferably 3.7 N / 20 mm or more, even more preferably 4 N / 20 mm or more, even more preferably 4.2 N / 20 mm or more, even more preferably 4.5 N / 20 mm or more, even more preferably 4.7 N / 20 mm or more, and particularly preferably 5 N / 20 mm or more. Within this range, a resin foam with particularly excellent fracture resistance and assembly properties can be obtained. The interlayer strength of the resin foam is preferably as high as possible as long as the effects of the present invention are obtained, but its upper limit is, for example, 500 N / 20 mm. The upper limit of the interlayer strength of the resin foam may be 100 N / 20 mm, 50 N / 20 mm, 25 N / 20 mm, 15 N / 20 mm, or 10 N / 20 mm. Within this range, a resin foam with excellent shock absorption can be obtained. 【0017】 The toughness of the above resin foam is preferably 0.7 MPa or higher, more preferably 1 MPa or higher, even more preferably 1.5 MPa or higher, and particularly preferably 2 MPa or higher. Within this range, a resin foam with particularly excellent fracture resistance and assembly properties can be obtained. Furthermore, the toughness of the above resin foam is preferably 20 MPa or lower, more preferably 15 MPa or lower, and even more preferably 10 MPa or lower. Within this range, a resin foam with excellent shock absorption can be obtained. 【0018】 1000 g / cm³ of the above resin foam ２ The thickness recovery rate (hereinafter also referred to as the instantaneous recovery rate) after maintaining the applied load for 120 seconds is preferably 85% or more, more preferably 88% or more, even more preferably 90% or more, even more preferably 93% or more, and particularly preferably 95% or more. Within this range, the above effect becomes significant. In particular, a resin foam with excellent die-cutting processability can be obtained. A higher instantaneous recovery rate is preferable, but its upper limit is, for example, 99% (preferably 100%). The method for measuring the instantaneous recovery rate will be described later. 【0019】The apparent density of the resin foam is preferably 0.01 g / cm ３ or more, more preferably 0.02 g / cm ３ or more. Also, the apparent density of the resin foam is, for example, 0.4 g / cm ３ or less, 0.2 g / cm ３ or less, 0.18 g / cm ３ or less, 0.15 g / cm ３ or less, 0.13 g / cm ３ or less, 0.1 g / cm ３ or less, 0.08 g / cm ３ or less, 0.05 g / cm ３ or less or 0.04 g / cm ３ or less. If the apparent density is within the above range, a resin foam excellent in punching processability and having excellent flexibility and stress dispersibility can be obtained. Note that the foaming property can be judged by the apparent density. The method for measuring the apparent density will be described later. 【0020】 The cell ratio of the above resin foam is preferably 97% or less, more preferably 96% or less. The cell ratio (cell rate) of the above resin foam is preferably 30% or more, more preferably 50% or more, and still more preferably 60% or more. Within such a range, a resin foam having appropriate flexibility can be obtained. 【0021】 The cell number density of the above resin foam is preferably 30 cells / mm ２ or more, more preferably 50 cells / mm ２ or more, still more preferably 70 cells / mm ２ or more, still more preferably 80 cells / mm ２ or more, still more preferably 90 cells / mm ２ or more, still more preferably 100 cells / mm ２ or more, particularly preferably 110 cells / mm ２ or more, and most preferably 120 cells / mm ２That concludes the explanation. Within this range, it is possible to obtain a resin foam that is preferably flexible and has excellent die-cutting properties. Furthermore, the higher the number density of air bubbles, the easier it is to store energy when compressed, and a resin foam with excellent compression recovery properties can be obtained. The upper limit of the number density of air bubbles in the resin foam is preferably 400 bubbles / mm². ２ A more preferable result is 350 pieces / mm ２ And more preferably 300 pieces / mm ２ And more preferably 250 pieces / mm ２ And, particularly preferably, 200 pieces / mm ２ The number density of bubbles in a resin foam is the number density of bubbles observed in a randomly selected cross-section of the resin foam, and can be determined by image analysis of the cross-section of the resin foam. 【0022】 The average cell diameter of the resin foam described above is, for example, 1000 μm or less, 500 μm or less, 300 μm or less, 200 μm or less, 150 μm or less, 100 μm or less, 90 μm or less, 80 μm or less, 70 μm or less, 65 μm or less, or 60 μm or less. Within this range, a resin foam with excellent shock absorption can be obtained. Furthermore, the average cell diameter of the resin foam described above is preferably 20 μm or more, more preferably 25 μm or more, and even more preferably 30 μm or more. If the average cell diameter is within the above range, a resin foam can be obtained that has high interlayer strength, excellent flexibility and stress distribution, and desirable shock absorption. Furthermore, a resin foam can be obtained that has excellent compression recovery, excellent punching processability, and excellent resistance to repeated impacts. The method for measuring the average cell diameter will be described later. 【0023】 The maximum cell diameter of the resin foam described above is, for example, 1000 μm or less, 600 μm or less, 400 μm or less, 350 μm or less, preferably 300 μm or less, 250 μm or less, or 200 μm or less. Furthermore, the maximum cell diameter of the resin foam described above is preferably 40 μm or more, more preferably 80 μm or more, and even more preferably 110 μm or more. Within this range, a resin foam with particularly excellent shock absorption properties can be obtained. 【0024】 The coefficient of variation of the cell diameter (bubble diameter) of the resin foam described above is preferably 0.6 or less, more preferably 0.55 or less, even more preferably 0.5 or less, even more preferably 0.4 or less, and even more preferably less than 0.35. Within this range, deformation due to impact becomes uniform, localized stress loading is prevented, a resin foam with excellent stress dispersion and particularly excellent shock absorption can be obtained. The smaller the coefficient of variation, the better, but the lower limit is, for example, 0.15 (preferably 0.1, more preferably 0.01). The method for measuring the coefficient of variation of the cell diameter will be described later. 【0025】 When the cell structure of the resin foam described above is a semi-continuous semi-closed cell structure, the proportion of closed cell structures is preferably 40% or less, and more preferably 30% or less. In this specification, the proportion of closed cell structures in the resin foam is determined, for example, by immersing the object to be measured in water under conditions of 23°C and 50% humidity, measuring the mass thereafter, then thoroughly drying it in an oven at 80°C, and measuring the mass again. Alternatively, since open cells can retain moisture, the proportion can be determined by measuring the mass of those cells as open cells. 【0026】 The aspect ratio of the bubbles in the resin foam is preferably 4 or less, more preferably 3 or less, even more preferably 2 or less, even more preferably 1.5 or less, and particularly preferably 1.3 or less. Within this range, a resin foam with excellent shock absorption can be provided. The aspect ratio of the bubbles in the resin foam is, for example, 1 or more, and preferably greater than 1.1. A method for measuring the aspect ratio of the bubbles in the resin foam will be described later. 【0027】The thickness of the cell walls of the above-mentioned resin foam is preferably 0.1 μm or more, more preferably 0.3 μm or more, even more preferably 0.5 μm or more, particularly preferably 0.7 μm or more, and most preferably 1 μm or more. Alternatively, the thickness of the cell walls of the above-mentioned resin foam is preferably 10 μm or less, more preferably 8 μm or less, even more preferably 5 μm or less, particularly preferably 4 μm or less, and most preferably 3 μm or less. Within this range, a resin foam with appropriate strength can be obtained. Such a resin foam has excellent die-cutting properties, preventing tearing, dust generation, and uncut pieces during die-cutting. Furthermore, if the thickness of the cell walls is within the above range, a resin foam with superior flexibility and stress distribution can be obtained. The thickness of the cell walls can be measured by capturing an enlarged image of the cell portion of the resin foam and performing image analysis using the analysis software of the measuring instrument. 【0028】 The 50% compression load of the above resin foam is preferably 40 N / cm². ２ The following is more preferable: 20 N / cm ２ The following, and more preferably 15 N / cm ２ The following, and more preferably 10 N / cm ２ The following is particularly preferred: 5 N / cm ２ The following applies. Within this range, a resin foam with desirable flexibility and excellent die-cutting properties can be obtained. The lower limit of the 50% compression load of the resin foam is, for example, 0.5 N / cm. ２ The 50% compression load of a resin foam is the stress (N) when compressed to a compressibility of 50% per unit area (1 cm²). ２ This is the price per unit. 【0029】 The 25% compression load of the above resin foam is preferably 25 N / cm. ２ The following is more preferable: 15 N / cm ２ The following, and more preferably 10 N / cm ２ The following is more preferably 6 N / cm ２ The following is more preferably 5 N / cm ２The following is particularly preferred: 3 N / cm ２ The following is most preferably 2 N / cm ２ The following applies. Within this range, a resin foam with desirable flexibility and shock absorption can be obtained. The lower limit of the 25% compression load of the resin foam is, for example, 0.5 N / cm. ２ The 25% compression load of a resin foam is the stress (N) when compressed to a compressibility of 25% per unit area (1 cm²). ２ This is the price per unit. 【0030】 The thickness of the resin foam is preferably 8000 μm or less, more preferably 5000 μm or less, even more preferably 4000 μm or less, and particularly preferably 2000 μm or less. Alternatively, the thickness of the resin foam is preferably 100 μm or more, more preferably 200 μm or more, even more preferably 300 μm or more, and particularly preferably 400 μm or more. Within this range, a fine and uniform cellular structure can be formed, which is advantageous in that it can exhibit excellent shock absorption properties. 【0031】 The impact absorption of the above resin foam is preferably 40% or more, more preferably 55% or more, even more preferably 60% or more, even more preferably 70% or more, particularly preferably 75% or more, and most preferably 80% or more. Also, the impact absorption of the resin foam is, for example, 97% or less, preferably 99% or less. The impact absorption is measured as follows: A test specimen is formed by arranging the resin foam, double-sided tape (product number: No. 5603W, manufactured by Nitto Denko) and SUS304 plate (thickness 5 mm) in this order on an impact force sensor. An impact force F1 is measured by dropping a 55 g steel ball onto the test specimen from a height of 30 cm above the SUS304 plate. In addition, the impact force F0 of the blank is measured by dropping the steel ball directly onto the impact force sensor as described above. The impact absorption (%) is calculated from F1 and F0 using the formula (F0 - F1) / F0 × 100. 【0032】The stress-holding force of the above resin foam is preferably 60% or more, and more preferably 63% or more. Furthermore, the stress-holding force of the above resin foam is preferably 100% or less, and more preferably 95% or less. Within this range, a resin foam can be obtained that exhibits excellent stress dispersion and excellent shock absorption even in a thin film. In this specification, the above stress-holding force is the ratio of the tensile strength immediately after stretching to the tensile strength after holding for 120 seconds after stretching, when a resin foam (width 10 mm x length 100 mm) is stretched by 20% in the longitudinal direction at a speed of 300 m / min (tensile strength after holding for 120 seconds / stress-holding force immediately after stretching × 100). 【0033】 In one embodiment, the resin foam described above can be formed by using a resin having a die swell ratio of 1.4 or less at its melting point (the melting point of the resin constituting the resin foam) + 20°C as the resin constituting the resin foam. By using a resin with a die swell ratio within the above range, shrinkage during resin foam formation is prevented, and a thick resin foam can be formed, which may contain small bubbles. The die swell ratio at the melting point + 20°C of the resin constituting the resin foam is preferably 1.2 or less, and more preferably 1.1 or less. The lower limit of the die swell ratio of the above resin is, for example, 1.05 (preferably 1.02, more preferably 1.01). In this specification, the die swell ratio means the value obtained by dividing the diameter of the extruded resin by the diameter of the die when the molten resin is extruded from the die. The die swell ratio is calculated by extruding a resin molten at its melting point + 20°C through a die with a length of 10 mm and a diameter of 1 mm at a shear rate of 20 mm / s, measuring the diameter of the resulting string-like molded product, and then using the formula: diameter of molded product (mm) / die diameter (mm). The melting point of the resin is measured by the peak top temperature of the endothermic peak obtained by differential scanning calorimetry (DSC). Differential scanning calorimetry (DSC) is performed using a differential scanning calorimeter (e.g., product name "Q-2000", TA Instruments) under the conditions of a sample weight of 3 mg and a heating rate of 10°C / min. If there are two or more peaks, the peak top temperature of the higher-temperature peak is taken as the melting point. 【0034】In one embodiment, the resin foam described above can be formed by using a resin whose shear viscosity at the melting point (the melting point of the resin constituting the resin foam) + 20°C is 3000 Pa·s or less. By using a resin with a shear viscosity within the above range, the gas used to form the bubble structure during resin foam formation can be preferably dispersed, and as a result, a resin foam with small bubble size can be obtained. The shear viscosity at the melting point + 20°C of the resin constituting the resin foam is preferably 2500 Pa·s or less, more preferably 2100 Pa·s or less, even more preferably 2000 Pa·s or less, and particularly preferably 1900 Pa·s or less. The lower limit of the shear viscosity of the above resin is, for example, 500 Pa·s (preferably 700 Pa·s, more preferably 1000 Pa·s). In this specification, shear viscosity can be measured by extruding a resin molten at its melting point + 20°C using a die with a length of 10 mm and a diameter of 1 mmφ at a shear rate of 20 mm / s. 【0035】 In one embodiment, the resin foam can be obtained, for example, by adding recycled resin. In one embodiment, the recycled resin ratio in the resin foam is 0.2 or more, more preferably 0.4 or more, even more preferably 0.5 or more, particularly preferably 0.6 or more, and most preferably 0.7 or more. By adding recycled resin in such a ratio, the above effect becomes significant. Furthermore, a resin foam with excellent carbon dioxide emission reduction effect can be provided. The upper limit of the recycled resin ratio in the resin foam may be 0.9, 0.85, or 0.75. Within this range, a resin foam with excellent foaming properties and excellent die-cutting properties can be obtained. 【0036】In this specification, "recycled resin" means a resin that is reused after foam molding. In one embodiment, the "recycled resin" may be a resin that has undergone a temperature history of (melting point + 10°C) or higher. The "recycled resin" may also be a resin that has undergone a temperature history of (melting point + 5°C) or higher. By using a resin that has undergone a predetermined temperature history, a resin foam with excellent flexibility and suppressed dust generation can be obtained. Furthermore, the "recycled resin ratio" is the weight ratio of recycled resin to the resin foam. 【0037】 In one embodiment, the resin foam satisfies the following formula: apparent density (g / cm³) ３ ) < 0.55 × recycled resin ratio + 0.07 If this formula is satisfied, it is possible to provide a resin foam with excellent die-cutting processability while suppressing carbon dioxide emissions. 【0038】 In one embodiment, the value calculated by [{0.55 × recycled resin ratio} + 0.07] is preferably 0.05 or higher, 0.08 or higher, 0.1 or higher, 0.2 or higher, or 0.3 or higher. Also, the value calculated by [{0.55 × recycled resin ratio} + 0.07] may be 0.55 or lower, 0.50 or lower, or 0.45 or lower. 【0039】 In one embodiment, [{0.55 × recycled resin ratio} + 0.007 - apparent density (g / cm³)] ３ The value calculated using the formula ) may be 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, or 0.4 or less. Also, {0.55 × recycled resin ratio} + 0.007 - apparent density (g / cm³) ３ The value calculated by ) may be 0.001 or greater, 0.01 or greater, 0.05 or greater, or 0.1 or greater. Within the above range, it is possible to provide a resin foam with excellent die-cutting processability while suppressing carbon dioxide emissions. 【0040】In one embodiment, the resin foam contains a plant-derived resin. Using a plant-derived resin makes it possible to achieve both a reduction in carbon dioxide emissions and shock absorption. More preferably, it contains a plant-derived polyolefin resin. Even more preferably, it contains a plant-derived polypropylene resin. Using a plant-derived polypropylene resin makes the above effects more pronounced, and furthermore, a resin foam with excellent heat resistance can be obtained. The plant-derived resin is, １４ Contains C (radiocarbon-14, half-life 5730 years). The biomass content of the above plant-derived resin is preferably 50% or more, more preferably 70% or more, even more preferably 80% or more, and particularly preferably 90% or more. １４ The concentration of C can be measured by accelerator mass spectrometry. 【0041】 In one embodiment, the content of plant-derived resin in the resin foam is preferably more than 50% by weight, more preferably 45% by weight or more, and even more preferably 40% by weight or more. Within this range, the above effect becomes significant. 【0042】 The above-mentioned resin foam may have a heat-melt layer on one or both sides. A resin foam having a heat-melt layer can be obtained, for example, by rolling the resin foam (or a precursor (foamed structure) of the resin foam) using a pair of heated rolls heated to a temperature above the melting temperature of the resin composition constituting the resin foam. 【0043】 The above-mentioned resin foam can be formed by any suitable method, provided that the effects of the present invention are not impaired. Typical such methods include foaming a resin composition containing a resin material (polymer). 【0044】 A-1. Resin Composition The resin foam of the present invention can typically be obtained by foaming a resin composition. The resin composition comprises any suitable resin material (polymer). In one embodiment, the resin material in the resin composition comprises recycled resin. In the resin material, recycled resin and non-recycled resin may be used in combination. The resin composition may also contain plant-derived resin. 【0045】 Examples of the polymers mentioned above include acrylic resins, silicone resins, urethane resins, polyolefin resins, ester resins, and rubber resins. These polymers may be used individually or in combination of two or more types. 【0046】 The polymer content is preferably 30 to 95 parts by weight, more preferably 35 to 90 parts by weight, even more preferably 40 to 80 parts by weight, and particularly preferably 40 to 60 parts by weight, per 100 parts by weight of the resin composition. Within this range, a resin foam with superior flexibility and stress dispersion can be obtained. 【0047】 When the above resin foam contains a plant-derived resin, the proportion of the plant-derived resin is preferably 30 to 90 parts by weight, more preferably 40 to 85 parts by weight, and even more preferably 50 to 80 parts by weight, per 100 parts by weight of the above polymer. 【0048】 When the above-mentioned resin foam contains recycled resin, the content ratio of recycled resin is preferably 30 to 90 parts by weight, more preferably 40 to 85 parts by weight, and even more preferably 50 to 80 parts by weight, per 100 parts by weight of the above-mentioned polymer. 【0049】 In one embodiment, a polyolefin resin is used as the polymer. In one embodiment, a polyolefin resin is used as the recycled resin. In one embodiment, a non-recycled polyolefin resin and a recycled polyolefin resin can be used in combination. In one embodiment, a plant-derived polyolefin resin is used as the polyolefin resin, and more preferably a plant-derived polypropylene resin is used. 【0050】The content ratio of the polyolefin resin is preferably 50 to 100 parts by weight, more preferably 70 to 100 parts by weight, even more preferably 90 to 100 parts by weight, particularly preferably 95 to 100 parts by weight, and most preferably 100 parts by weight, relative to 100 parts by weight of the polymer. 【0051】 Preferably, the polyolefin resin is at least one selected from the group consisting of polyolefins and polyolefin elastomers, and more preferably, polyolefins and polyolefin elastomers are used in combination. Polyolefins and polyolefin elastomers may each be used individually or in combination of two or more. In this specification, when "polyolefin," "recycled polyolefin," and "non-recycled polyolefin" are used, "polyolefin elastomers" are not included. In one embodiment, recycled polyolefin is used as the polyolefin. This recycled polyolefin may be used in combination with non-recycled polyolefin. That is, in one embodiment, recycled polyolefin and / or non-recycled polyolefin and a polyolefin elastomer are used in combination as the polyolefin resin. 【0052】When polyolefin and polyolefin-based elastomer are used in combination as a polyolefin-based resin, the weight ratio of polyolefin (e.g., the sum of recycled polyolefin and non-recycled polyolefin) to polyolefin-based elastomer (polyolefin / polyolefin-based elastomer) is preferably 1 / 99 to 99 / 1, more preferably 10 / 90 to 90 / 10, even more preferably 20 / 80 to 80 / 20, and particularly preferably 30 / 70 to 70 / 30. In one embodiment, the weight ratio of polyolefin to polyolefin-based elastomer (polyolefin / polyolefin-based elastomer) is preferably 25 / 75 to 75 / 25, and more preferably 35 / 65 to 65 / 35. Within this range, a resin foam can be obtained that exhibits excellent compression recovery, suppresses shape changes (especially thickness changes) before and after die-cutting, has appropriate strength, and has excellent die-cutting processability. 【0053】 In one embodiment, a plant-derived polyolefin (preferably a polypropylene polymer) is used as the polyolefin, and a plant-derived polyolefin elastomer is used as the polyolefin elastomer. In this case, the weight ratio of the polyolefin (i.e., plant-derived polyolefin) is preferably 50% by weight or more, more preferably 53% by weight or more, and even more preferably 60% by weight or more, based on the total weight of the polyolefin and the polyolefin elastomer. 【0054】As the polyolefin, any suitable polyolefin can be used as long as it does not impair the effects of the present invention. Examples of such polyolefins include linear polyolefins and branched (having branched) polyolefins. In one embodiment, a branched polyolefin is used as the polyolefin resin. In this embodiment, only a branched polyolefin may be used as the polyolefin, or a branched polyolefin and a linear polyolefin may be used in combination. By using a branched polyolefin, a resin foam with a small average cell diameter and excellent impact resistance can be obtained. Furthermore, if the above-mentioned branched polyolefin is used as the non-recycled resin, a resin foam with excellent die-cutting processability can be obtained even when used in combination with a recycled resin. The content ratio of the branched polyolefin is preferably 30 to 100 parts by weight, more preferably 50 to 80 parts by weight, per 100 parts by weight of polyolefin. 【0055】 Examples of the polyolefins mentioned above include polymers containing structural units derived from α-olefins. The polyolefin may be composed solely of structural units derived from α-olefins, or it may be composed 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 form can be adopted. Examples include random copolymers and block copolymers. 【0056】 As α-olefins that can constitute polyolefins, for example, α-olefins having 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.) are preferred. There may be only one α-olefin or two or more α-olefins. 【0057】Examples of monomers other than α-olefins that constitute polyolefins include ethylenically unsaturated monomers such as vinyl acetate, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, and vinyl alcohol. There may be only one monomer other than α-olefin, or there may be two or more monomers. 【0058】 Examples of polyolefins include, for example, 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, and copolymers of propylene and ethylenically unsaturated monomers. 【0059】 In one embodiment, a polypropylene polymer having propylene-derived structural units is used as the polyolefin. Examples of polypropylene polymers include polypropylene (propylene homopolymer), copolymers of ethylene and propylene, and copolymers of propylene and α-olefins other than propylene, with polypropylene (propylene homopolymer) being preferred. The polypropylene polymer may be used alone or in combination of two or more types. 【0060】 The above-mentioned plant-derived polyolefin is preferably a plant-derived polypropylene polymer. The plant-derived polypropylene polymer may be a homopolymer of plant-derived propylene, or a copolymer of plant-derived propylene and other monomers. If it is a copolymer, the content of the structural units based on plant-derived propylene in the copolymer is preferably 50 parts by weight or more, and more preferably 70 parts by weight or more, per 100 parts by weight of the plant-derived polypropylene polymer. 【0061】The above-mentioned plant-derived polypropylene polymer may be polypropylene produced using biomass as a raw material. For example, it may be a polypropylene polymer produced using biopropylene obtained by dehydrating propanol produced by fermentation. Alternatively, it may be a polypropylene polymer produced using biopropylene generated during the synthesis reaction of bioethylene. Furthermore, it may be a polypropylene polymer produced using biopropylene synthesized from bioethanol. 【0062】 The melt flow rate (MFR) of the polyolefin at a temperature of 230°C is preferably 0.25 g / 10 min to 20 g / 10 min, more preferably 0.3 g / 10 min to 6 g / 10 min, even more preferably 0.35 g / 10 min to 5 g / 10 min, particularly preferably 0.35 g / 10 min to 1 g / 10 min, and most preferably 0.35 g / 10 min to 0.6 g / 10 min, in order to better express the effects of the present invention. In this specification, the above melt flow rate (MFR) refers to the MFR measured at a temperature of 230°C and a load of 2.16 kgf (21.2 N) based on ISO 1133 (JIS-K-7210). In one embodiment, the die swell ratio and shear viscosity of the resin are controlled by the melt flow rate of the polyolefin constituting the resin foam. 【0063】 The melt flow rate (MFR) of the polyolefin used as the recycled resin at 230°C is preferably less than 20 g / 10 min, more preferably less than 10 g / 10 min, even more preferably less than 6 g / 10 min, and even more preferably less than 5 g / 10 min. Furthermore, the melt flow rate (MFR) of the polyolefin used as the recycled resin at 230°C is preferably 0.25 g / 10 min or more, more preferably 0.3 g / 10 min or more, and even more preferably 0.35 g / 10 min or more. Within this range, the effects of the present invention become remarkable. It is particularly advantageous in that a resin foam with excellent shock absorption properties can be obtained. 【0064】The melt flow rate (MFR) of the above plant-derived polyolefin at 230°C is preferably less than 20 g / 10 min, more preferably less than 10 g / 10 min, even more preferably less than 6 g / 10 min, even more preferably less than 5 g / 10 min, particularly preferably less than 1 g / 10 min, and most preferably 0.6 g / 10 min or less. Furthermore, the melt flow rate (MFR) of the above plant-derived polyolefin at 230°C is preferably 0.25 g / 10 min or more, more preferably 0.3 g / 10 min or more, and even more preferably 0.35 g / 10 min or more. Within this range, the effects of the present invention become remarkable. It is particularly advantageous in that a resin foam with excellent shock absorption properties can be obtained. 【0065】 In one embodiment, the die swell ratio at the melting point + 20°C of the polyolefin used as the recycled resin is 1.5 or less (preferably 1.25 or less). Within this range, a resin foam containing small bubbles and having low density can be obtained. Such a resin foam has excellent shock absorption properties. It is also advantageous in that it produces less carbon dioxide. The lower limit of the die swell ratio of the polyolefin used as the recycled resin is, for example, 1.05 (preferably 1.02, more preferably 1.01). 【0066】 In one embodiment, the die swell ratio of the plant-derived polyolefin at the melting point + 20°C is 1.5 or less (preferably 1.25 or less). Within this range, a resin foam containing small bubbles and having low density can be obtained. Such a resin foam has excellent shock absorption properties. It is also advantageous in that it has low carbon dioxide emissions. The lower limit of the die swell ratio of the plant-derived polyolefin is, for example, 1.05 (preferably 1.02, more preferably 1.01). 【0067】The melt tension of the polyolefin used as the recycled resin is preferably 10 cN or more, more preferably 15 cN or more, and even more preferably 18 cN or more. Furthermore, the melt tension of the polyolefin used as the recycled resin is preferably 50 cN or less, and more preferably 45 cN or less. Within this range, a resin foam containing small bubbles and having low density can be obtained. Such a resin foam has excellent shock absorption properties. It is also advantageous in that it produces less carbon dioxide. 【0068】 The melt tension of the above-mentioned plant-derived polyolefin is preferably 10 cN or more, more preferably 15 cN or more, even more preferably 20 cN or more, and particularly preferably 25 cN or more. Furthermore, the melt tension of the plant-derived polyolefin is preferably 50 cN or less, and more preferably 45 cN or less. Within this range, a resin foam containing small bubbles and having low density can be obtained. Such a resin foam has excellent shock absorption properties. It is also advantageous in that it has low carbon dioxide emissions. 【0069】 The weight-average molecular weight of the polyolefin is preferably 300,000 or more, 400,000 or more, 500,000 or more, 550,000 or more, or 600,000 or more. Alternatively, the weight-average molecular weight of the polyolefin is preferably 1,200,000 or less, 1,100,000 or less, or 1,000,000 or less. Within this range, the die swell ratio and shear viscosity of the resin can be favorably adjusted. Furthermore, the molecular weight distribution (weight-average molecular weight / number-average molecular weight) of the polyolefin is preferably 5.5 or more, 6 or more, or 7 or more. Also, the molecular weight distribution of the polyolefin is preferably 12 or less, 11 or less, or 10 or less. Within this range, the die swell ratio and shear viscosity of the resin can be favorably adjusted. The weight-average molecular weight and number-average molecular weight can be determined by gel permeation chromatography (solvent: tetrahydrofuran, polystyrene equivalent). 【0070】As for the polyolefin, commercially available products may be used, such as "E110G" (manufactured by Prime Polymer Co., Ltd.), "EA9" (manufactured by Nippon Polypropylene Co., Ltd.), "EA9FT" (manufactured by Nippon Polypropylene Co., Ltd.), "E-185G" (manufactured by Prime Polymer Co., Ltd.), "WB140HMS" (manufactured by Borealis), and "WB135HMS" (manufactured by Borealis). 【0071】 As the polyolefin elastomer, any suitable polyolefin elastomer can be used as long as it does not impair the effects of the present invention. Examples of such polyolefin elastomers include so-called non-crosslinked thermoplastic olefin elastomers (TPOs), such as ethylene-propylene copolymers, ethylene-propylene-diene copolymers, ethylene-vinyl acetate copolymers, polybutene, polyisobutylene, chlorinated polyethylene, elastomers in which polyolefin components and rubber components are physically dispersed, and elastomers having a structure in which polyolefin components and rubber components are microphase separated; and dynamically crosslinked thermoplastic olefin elastomers (TPVs), which are multiphase polymers obtained by dynamically heat-treating a mixture containing a resin component A (olefin resin component A) that forms a matrix and a rubber component B that forms domains in the presence of a crosslinking agent, and having a sea-island structure in which crosslinked rubber particles are finely dispersed as domains (island phases) in the resin component A which is the matrix (sea phase). 【0072】 The polyolefin elastomer preferably contains a rubber component. Examples of such rubber components are those described in Japanese Patent Publication No. 08-302111, Japanese Patent Publication No. 2010-241934, Japanese Patent Publication No. 2008-024882, Japanese Patent Publication No. 2000-007858, Japanese Patent Publication No. 2006-052277, Japanese Patent Publication No. 2012-072306, Japanese Patent Publication No. 2012-057068, Japanese Patent Publication No. 2010-241897, Japanese Patent Publication No. 2009-067969, and Japanese Patent Publication No. 03 / 002654. 【0073】Elastomers having a structure in which the polyolefin component and the olefin-based rubber component are microphase-separated include, specifically, elastomers composed of polypropylene resin (PP) and ethylene-propylene rubber (EPM), and elastomers composed of polypropylene resin (PP) and ethylene-propylene-diene rubber (EPDM). The weight ratio of the polyolefin component to the olefin-based rubber component (polyolefin component / olefin-based rubber) is preferably 90 / 10 to 10 / 90, and more preferably 80 / 20 to 20 / 80. 【0074】 Dynamically crosslinked thermoplastic olefin elastomers (TPVs) generally have a higher elastic modulus and lower compression set than non-crosslinked thermoplastic olefin elastomers (TPOs). This results in good recovery properties, and when used as a resin foam, it can exhibit excellent resilience. On the other hand, non-crosslinked thermoplastic olefin elastomers (TPOs) are more flexible than TPVs and can contribute to improved shock absorption. By using TPVs and TPOs in combination, it is possible to provide a resin foam that exhibits both flexibility and excellent die-cutting and fracture resistance (e.g., fracture resistance during assembly into a predetermined part). 【0075】 Dynamically crosslinked thermoplastic olefin elastomers (TPVs), as described above, are obtained by dynamically heat-treating a mixture containing a resin component A (olefin resin component A) that forms the matrix and a rubber component B that forms the domains, in the presence of a crosslinking agent. They are multiphase polymers having a sea-island structure in which crosslinked rubber particles are finely dispersed as domains (island phases) in the resin component A, which is the matrix (sea phase). 【0076】 Examples of dynamically crosslinked thermoplastic olefin elastomers (TPVs) include those described in Japanese Patent Publication No. 2000-007858, Japanese Patent Publication No. 2006-052277, Japanese Patent Publication No. 2012-072306, Japanese Patent Publication No. 2012-057068, Japanese Patent Publication No. 2010-241897, Japanese Patent Publication No. 2009-067969, and Re-Table 03 / 002654, etc. 【0077】As the dynamically crosslinked thermoplastic olefin elastomer (TPV), commercially available products may be used, such as "Zeotherm" (manufactured by Nippon Zeon Co., Ltd.), "Thermoran" (manufactured by Mitsubishi Chemical Corporation), and "Sarlink 3245D" (manufactured by Toyobo Co., Ltd.). 【0078】 The melt flow rate (MFR) of the polyolefin elastomer at a temperature of 230°C is preferably 1.5 g / 10 min to 25 g / 10 min, more preferably 2 g / 10 min to 20 g / 10 min, and even more preferably 2 g / 10 min to 15 g / 10 min. In one embodiment, the die swell ratio and shear viscosity of the resin are controlled by the melt flow rate of the polyolefin elastomer constituting the resin foam. 【0079】 In one embodiment, two or more polyolefin elastomers having different melt flow rates (MFRs) at 230°C within the above range are used in combination. In this case, a polyolefin elastomer (low MFR polyolefin elastomer) having a melt flow rate (MFR) at 230°C is preferably 1.5 g / 10 min or more and less than 8 g / 10 min (more preferably 2 g / 10 min to 7 g / 10 min), and a polyolefin elastomer (high MFR polyolefin elastomer) having a melt flow rate (MFR) at 230°C is preferably 8 g / 10 min to 25 g / 10 min (more preferably 9 g / 10 min to 20 g / 10 min, and even more preferably 10 g / 10 min to 20 g / 10 min) can be used in combination. In this way, the melt tension of the polyolefin elastomer is favorably adjusted, and as a result, a resin foam can be provided that exhibits both flexibility, die-cutting processability, and fracture resistance (for example, fracture resistance when assembled into a predetermined part). 【0080】The blending ratio of the above high-MFR polyolefin elastomer to the low-MFR polyolefin elastomer (high-MFR polyolefin elastomer / low-MFR polyolefin elastomer; weight ratio) is preferably 0.15 or more, more preferably 0.2 or more, even more preferably 0.22 or more, particularly preferably 0.24 or more, and most preferably 0.26 or more. Furthermore, the blending ratio of the above high-MFR polyolefin elastomer to the low-MFR polyolefin elastomer (high-MFR polyolefin elastomer / low-MFR polyolefin elastomer; weight ratio) is preferably 2 or less, more preferably 1.5 or less, even more preferably 1.2 or less, even more preferably 1 or less, even more preferably 0.8 or less, particularly preferably 0.6 or less, and most preferably 0.45 or less. By setting the high-MFR polyolefin elastomer / low-MFR polyolefin elastomer within the above range, the melt tension of the polyolefin elastomer can be favorably adjusted, resulting in a resin foam that exhibits both flexibility, die-cutting processability, and fracture resistance (e.g., fracture resistance when assembled into a predetermined part). Furthermore, by setting the high-MFR polyolefin elastomer / low-MFR polyolefin elastomer within the above range, a fine and uniform cellular structure can be formed, resulting in a resin foam with excellent impact resistance. 【0081】 In one embodiment, the low MFR polyolefin elastomer may be the non-crosslinked thermoplastic olefin elastomer (TPO). Alternatively, the high MFR polyolefin elastomer may be the dynamically crosslinked thermoplastic olefin elastomer (TPV). 【0082】Therefore, the blending ratio of TPV to TPO (TPV / TPO; weight ratio) is preferably 0.15 or more, more preferably 0.2 or more, even more preferably 0.22 or more, particularly preferably 0.24 or more, and most preferably 0.26 or more. Furthermore, the blending ratio of TPV to TPO (TPV / TPO; weight ratio) is preferably 2 or less, more preferably 1.5 or less, even more preferably 1.2 or less, even more preferably 1 or less, even more preferably 0.8 or less, particularly preferably 0.6 or less, and most preferably 0.45 or less. By setting the TPV / TPO within the above range, the melt tension of the polyolefin elastomer is preferably adjusted, and as a result, a resin foam can be provided that exhibits both flexibility, die-cutting processability, and fracture resistance (for example, fracture resistance when assembled into a predetermined part). Furthermore, by setting the TPV / TPO within the above range, a fine and uniform cellular structure can be formed, resulting in a resin foam with excellent impact resistance. 【0083】 The melt tension (at 190°C, at break) of the polyolefin elastomer is preferably less than 10 cN, and more preferably 5 cN to 9.5 cN. In one embodiment, the die swell ratio and shear viscosity of the resin are controlled by the melt tension of the polyolefin elastomer constituting the resin foam. 【0084】 The JIS A hardness of polyolefin elastomers is preferably 30° to 95°, more preferably 35° to 90°, even more preferably 40° to 88°, particularly preferably 45° to 85°, and most preferably 50° to 83°. Note that JIS A hardness is measured according to ISO 7619 (JIS K6253). 【0085】In one embodiment, the resin foam (i.e., the resin composition) may further contain a filler. By including a filler, it is possible to form a resin foam that requires a large amount of energy to deform the cell walls, and this resin foam exhibits excellent shock absorption. Furthermore, including a filler is advantageous because it allows for the formation of a fine and uniform cell structure, which also contributes to excellent shock absorption. The filler may be used alone or in combination of two or more types. 【0086】 The content ratio of the above-mentioned filler is preferably 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. Within this range, the above-mentioned effect becomes significant. 【0087】 In one embodiment, the filler is an inorganic material. Examples of materials that constitute the inorganic filler 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 silica, amorphous silica, metals (e.g., gold, silver, copper, aluminum, nickel), carbon, graphite, and the like. 【0088】 In one embodiment, the filler is an organic substance. Examples of materials that constitute the organic filler include polymethyl methacrylate (PMMA), polyimide, polyamideimide, polyetheretherketone, polyetherimide, and polyesterimide. 【0089】 A flame retardant may be used as the filler material. Examples of flame retardants include bromine-based flame retardants, chlorine-based flame retardants, phosphorus-based flame retardants, and antimony-based flame retardants. Preferably, from the viewpoint of safety, a non-halogen-non-antimony flame retardant is used. 【0090】Examples of non-halogen-non-antimony 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 hydrate, and magnesium oxide / zinc oxide hydrate. 【0091】 The above-mentioned filler may be subjected to any appropriate surface treatment. Examples of surface treatments include silane coupling treatment and stearic acid treatment. 【0092】 The bulk density of the above-mentioned filler is preferably 0.8 g / cm³. ３ The following, and more preferably 0.6 g / cm³ ３ The following, and more preferably 0.4 g / cm³ ３ The following, and particularly preferably 0.3 g / cm³ ３ The following applies. Within this range, the filler can be incorporated with good dispersibility, and the effect of adding the filler can be fully realized even with a low filler content. Resin foams with a low filler content are advantageous in that they are highly foamed, flexible, and have excellent stress distribution and appearance. The lower limit of the bulk density of the filler is, for example, 0.01 g / cm³. ３ The concentration is preferably 0.05 g / cm³. ３ More preferably, 0.1 g / cm³ ３ That is the case. 【0093】 The number-average particle diameter (primary particle diameter) of the filler 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 can be contained with good dispersibility and a uniform buoyancy 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 diameter of the filler is, for example, 0.1 μm. The number-average particle diameter of the filler can be measured using a particle size analyzer (Microtrac II, Microtrac-Bell Co., Ltd.) with a suspension prepared by mixing 1 g of filler with 100 g of water as a sample. 【0094】 The specific surface area of ​​the above-mentioned filler is preferably 2 m². ２ / g or more, more preferably 4m ２ It is 1 / g or more, and more preferably 6m ２ The value is 1 / g or more. Within this range, the filler can be incorporated with good dispersibility and a uniform cellular 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 is, for example, 20 m². ２ The value is / g. The specific surface area of ​​the filler can be measured by the BET method, that is, by adsorbing molecules with a known adsorption area onto the filler surface under low temperature conditions using liquid nitrogen, and measuring the amount of adsorption. 【0095】 The resin composition may contain any other suitable components, as long as they do not impair 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 blended as resin materials, softeners, aliphatic compounds, anti-aging agents, antioxidants, light stabilizers, weathering agents, UV absorbers, dispersants, plasticizers, carbon, antistatic agents, surfactants, crosslinking agents, thickeners, rust inhibitors, silicone compounds, tension modifiers, shrinkage inhibitors, flow modifiers, gelling agents, curing agents, reinforcing agents, foaming agents, foaming nucleators, colorants (pigments, dyes, etc.), pH adjusters, solvents (organic solvents), thermal polymerization initiators, photopolymerization initiators, lubricants, crystal nucleating agents, crystallization accelerators, vulcanizing agents, surface treatment agents, and dispersion aids. 【0096】A-2. Formation of Resin Foam The resin foam of the present invention is typically obtained by foaming a resin composition. As for the foaming method (method of forming bubbles), methods commonly used in foam molding, such as physical methods and chemical methods, can be employed. That is, the resin foam may typically be a foam formed by foaming using a physical method (physical foam) or a foam formed by foaming using a chemical method (chemical foam). The physical method generally involves dispersing gaseous components such as air or nitrogen in a polymer solution and forming bubbles by mechanical mixing (mechanical foam). The chemical method generally involves forming cells with gas produced by the thermal decomposition of a foaming agent added to a polymer base, and obtaining a foam. 【0097】 The resin composition to be subjected to foam molding can be prepared, for example, by mixing its constituent components using any suitable melt-kneading apparatus, such as an open-type mixing roll, a closed-type Banbury mixer, a single-screw extruder, a twin-screw extruder, a continuous kneader, or a pressure kneader. 【0098】 <Embodiment 1 for Forming Resin Foam> One embodiment 1 for forming resin foam is a method in which a resin foam is formed by mechanically foaming an emulsion resin composition (an emulsion containing a resin material (polymer), etc.) through a step (step A). ​​Examples of foaming devices include high-speed shear type devices, vibration type devices, and pressurized gas discharge type devices. Among these foaming devices, a high-speed shear type device is preferred from the viewpoint of miniaturizing the bubble diameter and producing large volumes. This embodiment 1 for forming resin foam is applicable to formation from any resin composition. 【0099】 A higher solid content concentration in the emulsion is preferable from the viewpoint of film-forming properties. The solid content concentration of 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. 【0100】The bubbles generated by mechanical stirring are formed when gas is incorporated into the emulsion. Any suitable gas can be used as the gas, as long as it is inert to the emulsion and does not impair the effects of the present invention. Examples of such gases include air, nitrogen, and carbon dioxide. 【0101】 The foamed emulsion resin composition (bubble-containing emulsion resin composition) foamed by the above method can be applied to a substrate and dried in a step (step B) to obtain the foamed resin of the present invention. Examples of substrates include peeled plastic films (such as peeled polyethylene terephthalate films) and plastic films (such as polyethylene terephthalate films). 【0102】 In step B, any suitable coating method and drying method can be adopted as long as they do not impair the effects of the present invention. Preferably, step B includes a pre-drying step B1 in which the bubble-containing emulsion resin composition applied to the substrate is dried at 50°C or higher and less than 125°C, and a main drying step B2 in which it is then dried at 125°C or higher and 200°C or lower. 【0103】 By providing a pre-drying step B1 and a main drying step B2, it is possible to prevent the coalescence and bursting of bubbles due to a rapid rise in temperature. In particular, with thin foam sheets, bubbles coalescence and bursting occur due to a rapid rise in temperature, so providing a pre-drying step B1 is highly significant. The temperature in the pre-drying step B1 is preferably 50°C to 100°C. The duration of the pre-drying step B1 is preferably 0.5 minutes to 30 minutes, and more preferably 1 minute to 15 minutes. The temperature in the main drying step B2 is preferably 130°C to 180°C or lower, and more preferably 130°C to 160°C. The duration of the main drying step B2 is preferably 0.5 minutes to 30 minutes, and more preferably 1 minute to 15 minutes. 【0104】<Embodiment 2 for forming a resin foam> One embodiment 2 for forming a resin foam is a method in which a resin composition is foamed with a foaming agent to form a foam. As the foaming agent, one that is normally used in foam molding can be used, and from the viewpoint of environmental protection and low contamination of the foamed material, it is preferable to use a high-pressure inert gas. 【0105】 Any suitable inert gas can be used as the inert gas, as long as it is inert to the resin composition and can impregnate it. Examples of such inert gases include carbon dioxide, nitrogen gas, and air. These gases may be used in mixtures. Of these, carbon dioxide is preferred from the viewpoint of impregnating the resin material (polymer) in large quantities and having a fast impregnation rate. 【0106】 The inert gas is preferably in a supercritical state. In other words, it is particularly preferable to use supercritical carbon dioxide. In a supercritical state, the solubility of the inert gas in the resin composition is increased, allowing for high concentrations of inert gas to be incorporated. Furthermore, because the concentration of the inert gas becomes high during a rapid pressure drop, more bubble nuclei are generated. The density of the bubbles formed by the growth of these nuclei is higher than in other states, even if the porosity is the same, thus allowing for the production of fine bubbles. The critical temperature of carbon dioxide is 31°C and the critical pressure is 7.4 MPa. 【0107】Methods for forming a foam by impregnating a resin composition with a high-pressure inert gas include, for example, a gas impregnation step in which an inert gas is impregnated under high pressure into a resin composition containing a resin material (polymer), a depressurization 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-molded unfoamed molded body may be impregnated with the inert gas, or a molten resin composition may be impregnated with an inert gas under pressure and then molded under depressurization. These steps may be carried out in either a batch or continuous manner. That is, the resin composition may be pre-molded into an appropriate shape such as a sheet to form an unfoamed resin molded body, and then this unfoamed resin molded body may be impregnated with a high-pressure gas and foamed by releasing the pressure in a batch manner, or the resin composition may be kneaded with a high-pressure gas under pressure, molded and foamed simultaneously by releasing the pressure in a continuous manner. 【0108】An example of manufacturing foam using a batch method is shown below. For example, a resin sheet for foam molding is 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 uniformly kneading a resin composition using a kneader equipped with blades such as rollers, cams, kneaders, or Banbarri types, and then pressing it to a predetermined thickness using a hot plate press or the like. The resulting unfoamed resin molded body is placed in a high-pressure vessel, and high-pressure inert gas (such as supercritical carbon dioxide) is injected to impregnate the unfoamed resin molded body with the inert gas. Once sufficient impregnation with inert gas has occurred, the pressure is released (usually to atmospheric pressure) to generate bubble nuclei in the resin. The bubble nuclei may be grown at room temperature, but in some cases they may be grown by heating. As for heating methods, known and conventional methods such as water baths, oil baths, hot rolls, hot air ovens, far-infrared radiation, near-infrared radiation, and microwaves can be used. After growing bubbles in this manner, the foam can be obtained by rapidly cooling it with cold water or the like to fix its shape. The unfoamed resin molded body used for foaming is not limited to a sheet; various shapes can be used depending on the application. Furthermore, the unfoamed resin molded body can be manufactured using other molding methods such as injection molding, in addition to extrusion molding and press molding. 【0109】An example of a continuous foam manufacturing method is shown below. For example, a kneading and impregnation step is performed in which a resin composition is kneaded using an extruder such as a single-screw extruder or twin-screw extruder while a high-pressure gas (especially an inert gas, and even carbon dioxide) is injected (introduced) to sufficiently impregnate the resin composition with the high-pressure gas. A molding and depressurization step is performed in which the pressure is released (usually to atmospheric pressure) by pushing the resin composition through a die provided at the tip of the extruder, and molding and foaming are performed simultaneously. In addition, when foam molding using a continuous method, a heating step may be provided as needed to grow bubbles by heating. After growing bubbles in this way, the shape may be fixed by rapidly cooling with cold water or the like as needed. Furthermore, the introduction of high-pressure gas may be performed continuously or discontinuously. Furthermore, in the kneading and impregnation step and the molding and depressurization step, for example, an extruder or injection molding machine may be used. As for the heating method when growing bubble nuclei, any appropriate method can be mentioned, such as a water bath, oil bath, hot roll, hot air oven, far-infrared radiation, near-infrared radiation, or microwave. Any suitable shape can be adopted for the foam. Examples of such shapes include sheet-like, prismatic, cylindrical, and irregularly shaped forms. 【0110】 The amount of gas mixed when foam molding 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, in order to obtain a highly foamed resin foam. 【0111】The pressure used when impregnating the resin composition with an inert gas can be appropriately selected considering operability and other 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). When using supercritical carbon dioxide, the pressure is preferably 7.4 MPa or higher from the viewpoint of maintaining the supercritical state of carbon dioxide. If the pressure is lower than 6 MPa, bubble growth during foaming is significant, and the bubble diameter may become too large, making it impossible to obtain a desirable average cell diameter (average bubble diameter). This is because at low pressure, the amount of gas impregnated is relatively small compared to high pressure, the bubble nucleation rate decreases, and the number of bubble nuclei formed decreases, so the amount of gas per bubble increases, and the bubble diameter becomes extremely large. In addition, in the pressure range below 6 MPa, even a slight change in impregnation pressure can greatly change the bubble diameter and bubble density, making it difficult to control the bubble diameter and bubble density. 【0112】 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. When considering operability, the temperature is preferably 10°C to 350°C. When impregnating an unfoamed molded body with an inert gas, the impregnation temperature in the batch method is preferably 10°C to 250°C, and more preferably 40°C to 230°C. When extruding a molten polymer impregnated with gas to perform foaming and molding simultaneously, the impregnation temperature in the continuous method is preferably 60°C to 350°C. When carbon dioxide is used as the inert gas, the impregnation temperature is preferably 32°C or higher, and more preferably 40°C or higher, in order to maintain a supercritical state. 【0113】 In the depressurization process, the depressurization rate is preferably 5 MPa / second to 300 MPa / second in order to obtain uniform fine bubbles. 【0114】 The heating temperature in the heating process is preferably 40°C to 250°C, and more preferably 60°C to 250°C. 【0115】In one embodiment, after obtaining a foamed structure through a predetermined process (for example, after obtaining a resin foam by the method of <Embodiment 1> or <Embodiment 2>), the foamed structure is thinned, and then roll-rolled to obtain a resin foam. By going through such a process, a resin foam with an appropriately adjusted aspect ratio can be obtained. Furthermore, a resin foam with a thin thickness (for example, 0.2 mm or less) can be obtained. The above-mentioned roll-rolling may also form the heat-melted layer. 【0116】 The foam structure can be thinned using any suitable slicer. The thickness of the foam structure after thinning is preferably 0.01 mm or more, more preferably 0.05 mm or more, even more preferably 0.1 mm or more, and particularly preferably 0.15 mm or more. The upper limit of the thickness of the foam structure after thinning is preferably 3 mm or less, more preferably 2 mm or less, even more preferably 1.5 mm or less, even more preferably 1 mm or less, even more preferably 0.8 mm or less, and particularly preferably 0.5 mm or less. Within this range, the number of air bubbles in the resin foam is particularly well-adjusted, making it less prone to crushing during punching, and thus a resin foam with particularly excellent punching processability can be obtained. 【0117】 Preferably, the rolls used in the roll rolling process are heated rolls. The temperature of the rolls is preferably 150°C to 250°C, and more preferably 160°C to 230°C. 【0118】 The rolling ratio of the foam structure (thickness after rolling / thickness before rolling × 100) is preferably 80% or less, more preferably 10% to 80%, even more preferably 20% to 75%, and particularly preferably 30% to 75%. Within this range, a resin foam with an appropriately adjusted aspect ratio can be obtained. 【0119】 B. Foam Member Figure 1 is a schematic cross-sectional view of a foam member according to one embodiment. The foam member 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 made of the resin foam described above. 【0120】 The thickness of the adhesive layer is preferably 5 μm or more, more preferably 6 μm or more, even more preferably 7 μm or more, and particularly preferably 8 μm or more. Furthermore, the thickness of the adhesive layer is preferably 300 μm or less, more preferably 200 μm or less, even more preferably 100 μm or less, and most preferably 50 μm or less. By having the thickness of the adhesive layer within the above range, the foamed member of the present invention can exhibit excellent shock absorption. 【0121】 The adhesive layer can be a layer made of any suitable adhesive. Examples of adhesives that make up the adhesive layer include rubber-based adhesives (synthetic rubber-based adhesives, natural rubber-based adhesives, etc.), urethane-based adhesives, acrylic urethane-based adhesives, acrylic-based adhesives, silicone-based adhesives, polyester-based adhesives, polyamide-based adhesives, epoxy-based adhesives, vinyl alkyl ether-based adhesives, fluorine-based adhesives, and rubber-based adhesives. Preferably, the adhesive that makes up the adhesive layer is at least one selected from acrylic-based adhesives, silicone-based adhesives, and rubber-based adhesives. There may be only one such adhesive or two or more. The adhesive layer may be one layer or two or more layers. 【0122】 Adhesives can be classified by their adhesive form into, for example, emulsion-type adhesives, solvent-type adhesives, UV-crosslinked adhesives, electron beam-crosslinked adhesives, and hot-melt adhesives. There may be only one type of such adhesive, or two or more types. 【0123】 The water vapor permeability of the adhesive layer is preferably 50 g / m ２ - 24 hours)) or less, more preferably 30 (g / (m³) ２ - 24 hours)) or less, and more preferably 20 (g / (m ２ - 24 hours)) or less, and particularly preferably 10 (g / (m ２- 24 hours) or less. If the water vapor permeability of the adhesive layer is within the above range, the foamed sheet can stabilize its shock absorption without being affected by moisture. Note that water vapor permeability can be measured, for example, by a method in accordance with JIS Z 0208, under test conditions of 40°C and 92% relative humidity. 【0124】 The adhesive constituting the adhesive layer may contain any other suitable components as long as they do not impair the effects of the present invention. Examples of other components include other polymer components, softeners, antioxidants, curing agents, plasticizers, fillers, antioxidants, thermal polymerization initiators, photopolymerization initiators, ultraviolet absorbers, light stabilizers, colorants (such as pigments and dyes), solvents (organic solvents), surfactants (e.g., ionic surfactants, silicone-based surfactants, fluorinated surfactants, etc.), and crosslinking agents (e.g., polyisocyanate-based crosslinking agents, silicone-based crosslinking agents, epoxy-based crosslinking agents, alkyl etherified melamine-based crosslinking agents, etc.). Note that thermal polymerization initiators and photopolymerization initiators may be included in the materials for forming the polymer components. 【0125】 The foamed material described above can be manufactured by any suitable method. Examples of such methods include laminating a resin foam layer and an adhesive layer, or laminating an adhesive layer forming material and a resin foam layer, and then forming the adhesive layer by a curing reaction or the like. 【0126】 The present invention will be specifically described below with reference to examples, but the present invention is not limited in any way to these examples. The test and evaluation methods in the examples are as follows. When "parts" is written, it means "parts by weight" unless otherwise specified, and when "%" is written, it means "percent by weight" unless otherwise specified. 【0127】 <Evaluation Method> (1) Apparent Density The density (apparent density) of the resin foam was calculated as follows. The resin foam obtained in the examples and comparative examples was punched out to a size of 20 mm x 20 mm to make test pieces, and the dimensions of the test pieces were measured with calipers. Next, the weight of the test pieces was measured with an electronic balance. Then, it was calculated using the following formula: Apparent density (g / cm³) ３ ) = Weight of test specimen / Volume of test specimen 【0128】 (2) 50% Compression Load The compression hardness of the resin foam was measured in accordance with the method for measuring compression hardness of resin foam described in JIS K 6767. Specifically, the resin foam obtained in the examples and comparative examples was cut into 30 mm x 30 mm size test pieces, and the stress (N) when compressed at a compression speed of 10 mm / min until the compression ratio reached 50% was measured per unit area (1 cm²). ２ Converted to a unit per unit, 50% compressive load (N / cm ２ ) 【0129】 (3) 25% Compression Load The compression hardness of the resin foam was measured in accordance with the method for measuring the compression hardness of resin foam described in JIS K 6767. Specifically, the resin foam obtained in the examples and comparative examples was cut into 30 mm x 30 mm size test pieces, and the stress (N) when compressed at a compression speed of 10 mm / min until the compression ratio reached 25% was measured per unit area (1 cm²). ２ Converted to a unit per unit, 25% compressive load (N / cm ２ ) 【0130】 (4) Coefficient of variation of average bubble diameter (average cell diameter), maximum bubble diameter (maximum cell diameter), and bubble diameter (cell diameter) The resin foam was cut using a razor blade in the TD (direction perpendicular to the flow direction) and perpendicular to the main surface of the resin foam (thickness direction). A digital microscope (product name "VHX-500", manufactured by Keyence Corporation) was used as a measuring instrument to capture images of the cut surface of the resin foam, and the number-average bubble diameter (average cell diameter) and maximum bubble diameter (maximum cell diameter) were determined by image analysis using the analysis software of the same measuring instrument. The number of bubbles in the captured magnified image was approximately 400. In addition, the standard deviation was calculated from all the cell diameter data, and the coefficient of variation was calculated using the following formula: Coefficient of variation = Standard deviation / Average bubble diameter (average cell diameter) 【0131】(5) The recycled resin contained in the melt tension resin foam was extruded into a molten strand at an extrusion speed of 8.8 mm / min using a twin capillary rheometer "RH7-2" (manufactured by Rosand Precision Co., Ltd.) at a temperature 20°C higher than the melting point of the recycled resin and with an orifice diameter of 1 mmφ. The strand was then taken up at a take-up speed of 0.5 m / min. The take-up speed was increased by 0.1 m / min increments, and the melt tension at which the strand of resin broke was defined as the "melt tension". 【0132】 (6) Interlayer strength resin foam (width: 20 mm x length: 120 mm) was stored for 24 hours or more in an atmosphere of temperature: 23 ± 2°C and humidity: 50 ± 5 RH% (pretreatment conditions conform to JIS Z 0237), then fixed to a SUS plate using double-sided adhesive tape (product name "No. 5000NS", manufactured by Nitto Denko Corporation) measuring 20 mm in width and 120 mm in length, and pressed onto the opposite side with double-sided adhesive tape (product name "No. 5000NS", manufactured by Nitto Denko Corporation) using a 2 kg roller for one back-and-forth motion. After being left for 30 minutes, it was prepared as a sample for measurement. The above sample was peeled at a peel angle of 90° at a speed of 300 mm / min using a tensile testing machine, and the strength at which the resin foam broke was measured. 【0133】 (7) Toughness Under an ambient temperature of 23°C, the tensile strength (tensile strength MPa) and tensile elongation (elongation (%)) of the resin foam were measured based on the tensile strength and tensile elongation sections of JIS K 6767. The area under the curve from the origin to the point of failure, obtained by plotting the tensile elongation on the X axis and the tensile strength on the Y axis, was numerically calculated and the resulting value was defined as toughness (MPa). 【0134】(8) A die-cuttable resin foam was punched using a mold (two cutting blades (product name "NCA07", thickness 0.7 mm, cutting edge angle 43°, manufactured by Nakayama Co., Ltd.)) to create 10 mm x 10 mm size pieces in the MD direction (flow direction) and TD direction (direction perpendicular to the flow direction). The cross section with the greater thickness change between the MD and TD directions was observed with a microscope (product name "VHX-2000", manufactured by Keyence Corporation), and the thickness of the edges and center was measured from the image. Using the measured thickness, the thickness recovery rate after processing was measured using the following formula. A larger thickness recovery rate indicates less shape change due to punching and superior die-cutting performance. Thickness recovery rate after processing (%) = 100 × (1 - (thickness of center - thickness of edges) / thickness of center) 【0135】 (9) Thickness recovery rate (instantaneous recovery rate) 1000 g / cm² of resin foam ２ The resin foam was subjected to a load and maintained for 120 seconds. The compression was then released, and the thickness of the foam was measured 0.5 seconds after the release (thickness 0.5 seconds after the compression was released). The thickness recovery rate (instantaneous recovery rate) was calculated from the thickness 0.5 seconds after the compression was released and the thickness of the resin foam before the load was applied (initial thickness) using the following formula: Thickness recovery rate (%) = {(thickness 0.5 seconds after the compression was released) / (initial thickness)} × 100 【0136】 (10) A flattened sheet of resin foam (70 mm x 220 mm in size) after punching was placed on a polypropylene plate, and two processing blades (product name "NCA07", thickness 0.7 mm, cutting edge angle 43°, manufactured by Nakayama Co., Ltd.) fixed with a 1.8 mm spacer in between were pressed into the foam to punch it out (cut it). The cutting width was set to 2.5 mm. Two hours after punching, the foam was observed visually and with a digital microscope, and samples with little crushing at the punched area (almost no difference in thickness between the punched area (edge) and other parts of the foam) were evaluated as having excellent assembly quality as "○", and samples with large crushing at the punched area (edge) (the upper edge of the punched area of ​​the foam was rounded, and there was a large difference in thickness between the punched area and other parts of the foam) were evaluated as "×". 【0137】 (11) A sheet-like piece of resin foam (70 mm x 220 mm in size) was placed on a polypropylene plate and two cutting blades (product name "NCA07", thickness 0.7 mm, cutting edge angle 43°, manufactured by Nakayama Co., Ltd.), fixed with a 1.8 mm spacer in between, were pressed in to punch out (cut) the foam. The cutting width was set to 2.5 mm. Two hours after punching out, with one end of the test piece fixed in the longitudinal direction, the test piece was assembled to the housing while tension was applied in the longitudinal direction using a load of 5 N. At this time, samples that were not cut were evaluated as having excellent assembly quality as "○", and samples that were cut were evaluated as "×". 【0138】 (12) A test specimen was formed by arranging a resin foam (sample size 70 mm square), double-sided tape (product number: No. 5603W, manufactured by Nitto Denko) and a SUS304 plate (thickness 5 mm) in that order on an impact force sensor. The impact force F1 was measured by dropping a 55 g steel ball onto the test specimen from a height of 30 cm above the SUS304 plate. The impact force F0 of the blank was also measured by dropping the steel ball directly onto the impact force sensor as described above. The impact absorption (%) was calculated from F1 and F0 using the formula (F0 - F1) / F0 × 100. 【0139】 [Example 1] Polypropylene (linear PP, MFR: 0.4 g / 10 min (230°C, load 21.2 N), density: 0.9 g / cm³) ３ ) 25 parts by weight, polypropylene (MFR: 1.3 g / 10 min (230°C, load 21.2 N), density: 0.9 g / cm³ ３30 parts by weight of ) 45 parts by weight of polyolefin elastomer (non-crosslinked thermoplastic olefin elastomer (TPO), melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 59°) 12 parts by weight of polyolefin elastomer (dynamically crosslinked thermoplastic olefin elastomer (TPV), melt flow rate (MFR): 15 g / 10 min, JIS A hardness: 82°) 8 parts by weight of magnesium hydroxide (product name "KISUMA 5P", manufactured by Kyowa Chemical Industry Co., Ltd.) 10 parts by weight of carbon (product name "Asahi #35", manufactured by Asahi Carbon Co., Ltd.) and 1 part by weight of stearic acid monoglyceride were kneaded at a temperature of 200°C in a twin-screw kneader manufactured by Japan Steel Works, Ltd. (JSW), then extruded into strands, water-cooled and molded into pellets. These pellets were fed into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) under an atmosphere of foaming temperature of 172°C. The carbon dioxide gas was injected at a ratio of 4.3 parts by weight per 100 parts by weight of resin. After the carbon dioxide gas was sufficiently saturated, the material was cooled to a temperature suitable for foaming, and then extruded from the die to obtain a sheet-like resin foam A. Furthermore, it was thinned using a slicer to obtain a resin foam with a thickness of 1.0 mm. The obtained resin foam was subjected to the above evaluation. The results are shown in Table 1. 【0140】 [Example 2] A sheet-like resin foam A was obtained in the same manner as in Example 1. Furthermore, it was thinned using a slicer to obtain a resin foam with a thickness of 0.3 mm. The obtained resin foam was then passed through the gap between the rolls of a pair of rolls heated to 210°C to obtain a resin foam with a thickness of 0.1 mm. In this way, a resin foam consisting of a surface layer / foam layer / surface layer was obtained. The obtained resin foam was subjected to the evaluation described above. The results are shown in Table 1. 【0141】 [Example 3] Polypropylene (linear PP, MFR: 0.4 g / 10 min (230°C, load 21.2 N), density: 0.9 g / cm³) ３ ) 20 parts by weight, polypropylene (MFR: 1.3 g / 10 min (230°C, load 21.2 N), density: 0.9 g / cm³ ３35 parts by weight of ) 45 parts by weight of polyolefin elastomer (non-crosslinked thermoplastic olefin elastomer (TPO), melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 59°) 12 parts by weight of polyolefin elastomer (dynamically crosslinked thermoplastic olefin elastomer (TPV), melt flow rate (MFR): 15 g / 10 min, JIS A hardness: 82°) 8 parts by weight of magnesium hydroxide (product name "KISUMA 5P", manufactured by Kyowa Chemical Industry Co., Ltd.) 10 parts by weight of carbon (product name "Asahi #35", manufactured by Asahi Carbon Co., Ltd.) and 1 part by weight of stearic acid monoglyceride were kneaded at a temperature of 200°C in a twin-screw kneader manufactured by Japan Steel Works, Ltd. (JSW), then extruded into strands, water-cooled and molded into pellets. These pellets were fed into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) under an atmosphere of foaming temperature of 172°C. The carbon dioxide gas was injected at a ratio of 4.3 parts by weight per 100 parts by weight of resin. After the carbon dioxide gas was sufficiently saturated, the material was cooled to a temperature suitable for foaming, and then extruded from the die to obtain a sheet-like resin foam. Furthermore, the foam was thinned using a slicer to obtain a resin foam with a thickness of 1.0 mm. The obtained resin foam was subjected to the evaluation described above. The results are shown in Table 1. 【0142】 [Example 4] Polypropylene (MFR: 1.3 g / 10 min (230°C, load 21.2 N), density: 0.9 g / cm³) ３) 35 parts by weight, polypropylene (linear PP, MFR: 0.5 g / 10 min (230°C, load 21.2 N)) 20 parts by weight, polyolefin elastomer (non-crosslinked thermoplastic olefin elastomer (TPO), melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 59°) 45 parts by weight, polyolefin elastomer (dynamically crosslinked thermoplastic olefin elastomer (TPV), melt flow rate (MFR): 15 g / 10 min, JIS A hardness: 82°) 12 parts by weight, magnesium hydroxide (product name "KISUMA") Eight parts by weight of "5P" (manufactured by Kyowa Chemical Industry Co., Ltd.), ten parts by weight of carbon (product name "Asahi #35" manufactured by Asahi Carbon Co., Ltd.), and one part by weight of stearic acid monoglyceride were kneaded at a temperature of 200°C in a twin-screw kneader manufactured by Japan Steel Works, Ltd., then extruded into strands, water-cooled, and formed into pellets. These pellets were fed into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) in an atmosphere with a foaming temperature of 172°C. The carbon dioxide gas was injected at a ratio of 4.3 parts by weight per 100 parts by weight of resin. After the carbon dioxide gas was sufficiently saturated, it was cooled to a temperature suitable for foaming, and then extruded from the die to obtain a sheet-like resin foam. Furthermore, it was thinned using a slicer to obtain a resin foam with a thickness of 1.0 mm. The obtained resin foam was subjected to the above evaluation. The results are shown in Table 1. 【0143】 [Example 5] A resin foam was obtained in the same manner as in Example 4, except that the amount of polyolefin elastomer (non-crosslinked thermoplastic olefin elastomer (TPO), melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 59°) was 40 parts by weight, and the amount of polyolefin elastomer (dynamically crosslinked thermoplastic olefin elastomer (TPV), melt flow rate (MFR): 15 g / 10 min, JIS A hardness: 82°) was 17 parts by weight. The obtained resin foam was subjected to the above evaluation. The results are shown in Table 1. 【0144】 [Example 6] Polypropylene (MFR: 1.3 g / 10 min (230°C, load 21.2 N), density: 0.9 g / cm³) ３) 35 parts by weight, polypropylene (linear PP, MFR: 0.5 g / 10 min (230°C, load 21.2 N)) 20 parts by weight, polyolefin elastomer (non-crosslinked thermoplastic olefin elastomer (TPO), melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 59°) 29 parts by weight, polyolefin elastomer (dynamically crosslinked thermoplastic olefin elastomer (TPV), melt flow rate (MFR): 15 g / 10 min, JIS A hardness: 82°) 29 parts by weight, magnesium hydroxide (product name "KISUMA") Eight parts by weight of "5P" (manufactured by Kyowa Chemical Industry Co., Ltd.), ten parts by weight of carbon (product name "Asahi #35" manufactured by Asahi Carbon Co., Ltd.), and one part by weight of stearic acid monoglyceride were kneaded at a temperature of 200°C in a twin-screw kneader manufactured by Japan Steel Works, Ltd., then extruded into strands, water-cooled, and formed into pellets. These pellets were fed into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) in an atmosphere with a foaming temperature of 178°C. The carbon dioxide gas was injected at a ratio of 3.1 parts by weight per 100 parts by weight of resin. After the carbon dioxide gas was sufficiently saturated, it was cooled to a temperature suitable for foaming, and then extruded from the die to obtain a sheet-like resin foam. Furthermore, it was thinned using a slicer to obtain a resin foam with a thickness of 1.0 mm. The obtained resin foam was subjected to the above evaluation. The results are shown in Table 1. 【0145】 [Example 7] Polypropylene (MFR: 1.3 g / 10 min (230°C, load 21.2 N), density: 0.9 g / cm³) ３) 30 parts by weight, polypropylene (linear PP, MFR: 0.5 g / 10 min (230°C, load 21.2 N)) 25 parts by weight, polyolefin elastomer (non-crosslinked thermoplastic olefin elastomer (TPO), melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 59°) 45 parts by weight, polyolefin elastomer (dynamically crosslinked thermoplastic olefin elastomer (TPV), melt flow rate (MFR): 15 g / 10 min, JIS A hardness: 82°) 12 parts by weight, magnesium hydroxide (product name "KISUMA") Eight parts by weight of "5P" (manufactured by Kyowa Chemical Industry Co., Ltd.), ten parts by weight of carbon (product name "Asahi #35" manufactured by Asahi Carbon Co., Ltd.), and one part by weight of stearic acid monoglyceride were kneaded at a temperature of 200°C in a twin-screw kneader manufactured by Japan Steel Works, Ltd., then extruded into strands, water-cooled, and formed into pellets. These pellets were fed into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) in an atmosphere with a foaming temperature of 180°C. The carbon dioxide gas was injected at a ratio of 2.8 parts by weight per 100 parts by weight of resin. After the carbon dioxide gas was sufficiently saturated, it was cooled to a temperature suitable for foaming, and then extruded from the die to obtain a sheet-like resin foam. Furthermore, it was thinned using a slicer to obtain a resin foam with a thickness of 1.0 mm. The obtained resin foam was subjected to the above evaluation. The results are shown in Table 1. 【0146】 [Example 8] Polypropylene (MFR: 1.3 g / 10 min (230°C, load 21.2 N), density: 0.9 g / cm³) ３ ) 30 parts by weight, polypropylene (recycled resin, linear PP, MFR: 0.47 g / 10 min (230°C, load 21.2 N), density: 0.9 g / cm³ ３25 parts by weight of ) 45 parts by weight of polyolefin elastomer (non-crosslinked thermoplastic olefin elastomer (TPO), melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 59°), 12 parts by weight of polyolefin elastomer (dynamically crosslinked thermoplastic olefin elastomer (TPV), melt flow rate (MFR): 15 g / 10 min, JIS A hardness: 82°), 8 parts by weight of magnesium hydroxide (product name "KISUMA 5P", manufactured by Kyowa Chemical Industry Co., Ltd.), 10 parts by weight of carbon (product name "Asahi #35", manufactured by Asahi Carbon Co., Ltd.), and 1 part by weight of stearic acid monoglyceride were kneaded at a temperature of 200°C in a twin-screw kneader manufactured by Japan Steel Works, Ltd. (JSW), then extruded into strands, water-cooled and molded into pellets. These pellets were fed into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) under an atmosphere of foaming temperature of 172°C. The carbon dioxide gas was injected at a ratio of 4.3 parts by weight per 100 parts by weight of resin. After the carbon dioxide gas was sufficiently saturated, the material was cooled to a temperature suitable for foaming, and then extruded from the die to obtain a sheet-like resin foam. Furthermore, the foam was thinned using a slicer to obtain a resin foam with a thickness of 1.0 mm. The obtained resin foam was subjected to the evaluation described above. The results are shown in Table 1. 【0147】 [Example 9] Polypropylene (recycled resin, linear PP, MFR: 0.47 g / 10 min (230°C, load 21.2 N), density: 0.9 g / cm³) ３55 parts by weight of ) 45 parts by weight of polyolefin elastomer (non-crosslinked thermoplastic olefin elastomer (TPO), melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 59°), 12 parts by weight of polyolefin elastomer (dynamically crosslinked thermoplastic olefin elastomer (TPV), melt flow rate (MFR): 15 g / 10 min, JIS A hardness: 82°), 8 parts by weight of magnesium hydroxide (product name "KISUMA 5P", manufactured by Kyowa Chemical Industry Co., Ltd.), 10 parts by weight of carbon (product name "Asahi #35", manufactured by Asahi Carbon Co., Ltd.), and 1 part by weight of stearic acid monoglyceride were kneaded at a temperature of 200°C in a twin-screw kneader manufactured by Japan Steel Works, Ltd. (JSW), then extruded into strands, water-cooled, and molded into pellets. These pellets were fed into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) under an atmosphere of foaming temperature of 175°C. The carbon dioxide gas was injected at a ratio of 3.9 parts by weight per 100 parts by weight of resin. After the carbon dioxide gas was sufficiently saturated, the material was cooled to a temperature suitable for foaming, and then extruded from the die to obtain a sheet-like resin foam. Furthermore, the foam was thinned using a slicer to obtain a resin foam with a thickness of 1.0 mm. The obtained resin foam was subjected to the evaluation described above. The results are shown in Table 1. 【0148】 [Example 10] A sheet-like resin foam was obtained in the same manner as in Example 9. Furthermore, it was thinned using a slicer to obtain a resin foam with a thickness of 0.3 mm. The obtained resin foam was then passed through the gap between the rolls of a pair of rolls heated to 210°C to obtain a resin foam with a thickness of 0.1 mm. In this way, a resin foam consisting of a surface layer / foam layer / surface layer was obtained. The obtained resin foam was subjected to the evaluation described above. The results are shown in Table 1. 【0149】 [Example 11] Polypropylene (recycled resin, linear PP, MFR: 0.47 g / 10 min (230°C, load 21.2 N), density: 0.9 g / cm³) ３75 parts by weight of ) , 22 parts by weight of polyolefin elastomer (non-crosslinked thermoplastic olefin elastomer (TPO), melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 59°), 6 parts by weight of polyolefin elastomer (dynamically crosslinked thermoplastic olefin elastomer (TPV), melt flow rate (MFR): 15 g / 10 min, JIS A hardness: 82°), 8 parts by weight of magnesium hydroxide (product name "KISUMA 5P", manufactured by Kyowa Chemical Industry Co., Ltd.), 10 parts by weight of carbon (product name "Asahi #35", manufactured by Asahi Carbon Co., Ltd.), and 1 part by weight of stearic acid monoglyceride were kneaded at a temperature of 200°C in a twin-screw kneader manufactured by Japan Steel Works, Ltd. (JSW), then extruded into strands, water-cooled, and molded into pellets. These pellets were fed into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) under an atmosphere of foaming temperature of 178°C. The carbon dioxide gas was injected at a ratio of 2.9 parts by weight per 100 parts by weight of resin. After the carbon dioxide gas was sufficiently saturated, the material was cooled to a temperature suitable for foaming, and then extruded from the die to obtain a sheet-like resin foam. Furthermore, the foam was thinned using a slicer to obtain a resin foam with a thickness of 1.0 mm. The obtained resin foam was subjected to the evaluation described above. The results are shown in Table 1. 【0150】 [Example 12] Polypropylene (bio-naphtha derived resin, linear PP, manufactured by SABIC, trade name "61EK61PS", MFR: 0.3 g / 10 min (230°C, load 21.2 N), density: 0.88 g / cm³) ３55 parts by weight of ) 29 parts by weight of polyolefin elastomer (non-crosslinked thermoplastic olefin elastomer (TPO), melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 59°) 29 parts by weight of polyolefin elastomer (dynamically crosslinked thermoplastic olefin elastomer (TPV), melt flow rate (MFR): 15 g / 10 min, JIS A hardness: 82°) 8 parts by weight of magnesium hydroxide (product name "KISUMA 5P", manufactured by Kyowa Chemical Industry Co., Ltd.) 10 parts by weight of carbon (product name "Asahi #35", manufactured by Asahi Carbon Co., Ltd.) and 1 part by weight of stearic acid monoglyceride were kneaded at a temperature of 200°C in a twin-screw kneader manufactured by Japan Steel Works, Ltd. (JSW), then extruded into strands, water-cooled and molded into pellets. These pellets were fed into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) under an atmosphere of foaming temperature of 172°C. The carbon dioxide gas was injected at a ratio of 4.3 parts by weight per 100 parts by weight of resin. After the carbon dioxide gas was sufficiently saturated, the material was cooled to a temperature suitable for foaming, and then extruded from the die to obtain a sheet-like resin foam. Furthermore, the foam was thinned using a slicer to obtain a resin foam with a thickness of 1.0 mm. The obtained resin foam was subjected to the evaluation described above. The results are shown in Table 1. 【0151】 [Comparative Example 1] Polypropylene (linear PP, MFR: 0.4 g / 10 min (230°C, load 21.2 N), density: 0.9 g / cm³) ３ ) 45 parts by weight, polypropylene (MFR: 1.3 g / 10 min (230°C, load 21.2 N), density: 0.9 g / cm³ ３20 parts by weight of resin, 35 parts by weight of polyolefin elastomer (non-crosslinked thermoplastic olefin elastomer (TPO), melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 59°), 8 parts by weight of magnesium hydroxide (product name "KISUMA 5P", manufactured by Kyowa Chemical Industry Co., Ltd.), 10 parts by weight of carbon (product name "Asahi #35", manufactured by Asahi Carbon Co., Ltd.), and 1 part by weight of monoglyceride stearate were mixed at a temperature of 200°C in a twin-screw kneader manufactured by Japan Steel Works, Ltd., then extruded into strands, water-cooled and formed into pellets. These pellets were fed into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) in an atmosphere with a foaming temperature of 175°C. The carbon dioxide gas was injected at a ratio of 4.5 parts by weight per 100 parts by weight of resin. After sufficiently saturating with carbon dioxide gas, the material was cooled to a temperature suitable for foaming, and then extruded from the die to obtain a sheet-like resin foam. Furthermore, it was thinned using a slicer to obtain a resin foam with a thickness of 1.0 mm. The obtained resin foam was subjected to the evaluation described above. The results are shown in Table 1. 【0152】 [Comparative Example 2] Polypropylene (linear PP, propylene homopolymer, MFR: 0.4 g / 10 min (230°C, load 21.2 N), density: 0.90 g / cm³) ３40 parts by weight of ethylene (0% by weight, propylene (100% by weight)), 39 parts by weight of polyolefin elastomer (dynamically crosslinked thermoplastic olefin elastomer (TPV), melt flow rate (MFR): 15 g / 10 min, JIS A hardness: 79°), 5 parts by weight of magnesium hydroxide (product name "KISUMA 5P", manufactured by Kyowa Chemical Industry Co., Ltd.), 10 parts by weight of carbon (product name "Asahi #35", manufactured by Asahi Carbon Co., Ltd.), and 1 part by weight of stearic acid monoglyceride were kneaded at a temperature of 200°C in a twin-screw kneader manufactured by Japan Steel Works, Ltd., then extruded into strands, water-cooled and formed into pellets. These pellets were fed into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) in an atmosphere with a foaming temperature of 171°C. Carbon dioxide gas was injected at a ratio of 4.1 parts by weight per 100 parts by weight of resin. After the carbon dioxide gas was sufficiently saturated, the resin was cooled to a temperature suitable for foaming, and then extruded from the die to obtain a sheet-like resin foam. Furthermore, the foam was thinned using a slicer to obtain a resin foam with a thickness of 1.0 mm. The obtained resin foam was subjected to the evaluation described above. The results are shown in Table 1. 【0153】 [Comparative Example 3] A sheet-like resin foam was obtained in the same manner as in Comparative Example 2. Furthermore, it was thinned using a slicer to obtain a resin foam with a thickness of 0.3 mm. The obtained resin foam was then passed through the gap between the rolls (the space between the rolls) of a pair of rolls heated to 210°C to obtain a resin foam with a thickness of 0.1 mm. In this way, a resin foam consisting of a surface layer / foam layer / surface layer was obtained. 【0154】 [Comparative Example 4] A sheet-like resin foam was obtained in the same manner as in Comparative Example 1. Furthermore, it was thinned using a slicer to obtain a resin foam with a thickness of 1.1 mm. Then, the obtained resin foam was passed through the gap between the rolls (the space between the rolls) of a pair of rolls heated to 210°C to obtain a resin foam with a thickness of 0.1 mm. In this way, a resin foam consisting of a surface layer / foam layer / surface layer was obtained. 【0155】[Comparative Example 5] A sheet-like resin foam was obtained in the same manner as in Comparative Example 1. Furthermore, it was thinned using a slicer to obtain a resin foam with a thickness of 0.9 mm. The obtained resin foam was then passed through the gap between the rolls (the space between the rolls) of a pair of rolls heated to 210°C to obtain a resin foam with a thickness of 0.1 mm. In this way, a resin foam consisting of a surface layer / foam layer / surface layer was obtained. 【0156】 【0157】 【0158】 The resin foam of the present invention can be suitably used, for example, as a cushioning material for electronic devices. 【0159】 100 Foamed material 10 Resin foam layer (resin foam) 20 Adhesive layer

Claims

1. A resin foam having a cellular structure that satisfies the formula [-1.5 × toughness (unit: MPa) + 6 < interlaminar strength (unit: N / 20 mm) < -1.5 × toughness (unit: MPa) + 35], and the resin foam contains 1000 g / cm³ ２ A resin foam in which the thickness recovery rate is 80% or more after being maintained for 120 seconds under the applied load.

2. The resin foam according to claim 1, wherein the toughness is 0.7 MPa or more.

3. The resin foam according to claim 1, wherein the interlayer strength is 3 N / 20 mm or more.

4. The apparent density is 0.4 g / cm³. ３ The resin foam according to claim 1, which is as follows:

5. The 50% compression load is 40 N / cm. ２ The resin foam according to claim 1, which is as follows:

6. The resin foam according to claim 1, wherein the average bubble diameter is 1000 μm or less.

7. The resin foam according to claim 1, wherein the coefficient of variation of the bubble diameter is 0.6 or less.

8. The resin foam according to claim 1, comprising a polyolefin resin.

9. The resin foam according to claim 8, wherein the polyolefin resin comprises a polyolefin, and the polyolefin is polyethylene or polypropylene.

10. The resin foam according to claim 8, wherein the polyolefin resin is a mixture of a polyolefin other than a polyolefin elastomer and a polyolefin elastomer.

11. The resin foam according to claim 1, comprising recycled resin.

12. The resin foam according to claim 11, wherein the recycled resin comprises polyolefin.

13. The resin foam according to claim 11, wherein the melt flow rate (MFR) of the polyolefin as the recycled resin at a temperature of 230°C is less than 10 g / 10 min.

14. The resin foam according to claim 11, wherein the melt tension of the polyolefin as the recycled resin is 10 cN or more.

15. The resin foam according to claim 1, comprising a plant-derived polyolefin resin.

16. The resin foam according to claim 15, wherein the plant-derived polyolefin resin comprises a plant-derived polyolefin, and the melt flow rate (MFR) of the plant-derived polyolefin at a temperature of 230°C is less than 20 g / 10 min.

17. The resin foam according to claim 15, wherein the melt tension of the plant-derived polyolefin is 10 cN or more.

18. The resin foam according to claim 1, having a heat-melting layer on one or both sides.

19. A foamed member having a resin foam layer and an adhesive layer disposed on at least one side of the resin foam layer, wherein the resin foam layer is the resin foam described in any one of claims 1 to 18.

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