Resin foam and foam member

Abstract

To provide a resin foam that is excellent in terms of flexibility and low dustiness.SOLUTION: [1] A resin foam according to an embodiment of the present invention has a cell structure and satisfies formula (1). Formula (1): Interlayer strength (N / 20 mm)>apparent density (g / cm3)×40+3. [2] The resin foam described in [1] may have an apparent density of at most 0.4 g / cm3. [3] The resin foam described in [1] or [2] may have an interlayer strength of at least 3 N / 20 mm.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a resin foam and a foamed member.

Background Art

[0002] For protecting the screen of electronic devices, substrates, electronic components, etc., foams are frequently used as cushioning materials. In such foams, it is required to be excellent in flexibility so as to preferably exhibit cushioning properties. However, when trying to enhance flexibility, a problem arises in that dust generation becomes easy. That is, in the prior art, a foam in which flexibility and low dust generation are highly compatible has not been realized.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a resin foam excellent in flexibility and low dust generation.

Means for Solving the Problems

[0005] [1] The resin foam according to an embodiment of the present invention has a cell structure and satisfies the following formula (1). Interlayer strength (N / 20 mm)> Apparent density (g / cm 3 ) × 40 + 3 ··· (1) [2] The resin foam according to [1] above may have an apparent density of 0.4 g / cm 3 or less. [3] The resin foam described in [1] or [2] above may have an interlayer strength of 3 N / 20 mm or more. [4] The resin foam described in any one of [1] to [3] above may have an average cell diameter of 50 μm or more. [5] The resin foam described in any one of [1] to [4] above may have a 50% compression load of 40 N / cm 2 or less. [6] In the resin foam described in any one of [1] to [5] above, the thickness recovery rate after maintaining a load of 1000 g / cm 2 on the resin foam for 120 seconds may be 80% or more. [7] The resin foam described in any one of [1] to [6] above may have a coefficient of variation of the cell diameter of 0.6 or less. [8] The resin foam described in any one of [1] to [7] above may contain recycled resin, and the recycled resin ratio in the resin foam may be 0.2 or more and may satisfy the following formula (2). Apparent density (g / cm 3 ) < 0.046 × recycled resin ratio + 0.0121 ··· (2) [9] The resin foam described in [8] above may contain polyolefin as the recycled resin.

[10] The resin foam described in [9] above may have a melt flow rate (MFR) of less than 10 g / 10 min at a temperature of 230°C for the polyolefin as the recycled resin.

[11] The resin foam described in [9] or

[10] above may have a melt tension of 10 cN or more for the polyolefin as the recycled resin.

[12] The resin foam described in any one of [9] to

[11] above may have a die swell ratio at the melting point of the polyolefin as the recycled resin + 20°C of 1.5 or less.

[13] The resin foam described in any one of [9] to

[12] above may have the polyolefin being polyethylene or polypropylene.

[14] The resin foam described in any one of [9] to

[13] above may be a mixture of a polyolefin other than a polyolefin-based elastomer and a polyolefin-based elastomer.

[15] The resin foam described in any one of [1] to

[14] above may have a die swell ratio at the melting point of the resin composition forming the resin foam + 20 °C of 1.5 or less.

[16] The resin foam described in any one of [1] to

[15] above may have a heat-melted layer on one or both sides.

[17] 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, and the resin foam layer may be the resin foam described in any one of [1] to

[16] above.

Effect of the Invention

[0006] According to the present invention, a resin foam excellent in flexibility and low dust generation property can be provided.

Brief Description of the Drawings

[0007]

Figure 1

Mode for Carrying Out the Invention

[0008] A. Resin foam The resin foam according to an embodiment of the present invention satisfies the following formula (1). Interlayer strength (N / 20 mm) > Apparent density (g / cm 3 ) × 40 + 3 ··· (1)

[0009] In this specification, the interlayer strength is the interlayer strength at 23 °C, which is the maximum load when the resin foam is pulled in the thickness direction and the resin foam breaks (peels off). The measurement method of the interlayer strength will be described later.

[0010] In an embodiment of the present invention, the resin foam has a cell structure. Examples of the cell structure include a closed-cell structure, an open-cell structure, and a semi-continuous semi-closed cell structure (a cell structure in which a closed-cell structure and an open-cell structure coexist). Preferably, the cell structure of the resin foam is a semi-continuous semi-closed cell structure. Typically, the resin foam is obtained by foaming a resin composition containing a recycled resin. The resin composition is a composition containing at least the resin constituting the resin foam.

[0011] In an embodiment of the present invention, by satisfying the formula (1), it may be possible to provide a resin foam that has excellent flexibility and exhibits sufficient interlayer strength. The resin foam having excellent interlayer strength has low dust generation properties and is suitable as a cushioning material that requires cleanliness and is used for protecting the screens of electronic devices, protecting substrates, protecting electronic components, etc. Further, a resin foam having excellent punching processability can be obtained. More specifically, according to the above embodiment, even when punched, the shape change such as the thickness change is small, and even when the thickness is temporarily reduced by punching, it shows a favorable behavior of recovering in a short time, and a resin foam having excellent punchability can be obtained. According to an embodiment of the present invention, the above effects can be obtained even for a thin layer.

[0012] {Interlayer strength (N / 20 mm)} - {apparent density (g / cm 3 ) × 40 + 3}, the calculated value is preferably 5 or less, more preferably 4 or less, and even more preferably 2.6 or less.

[0013] The interlayer strength of the resin foam is preferably 3 N / 20 mm or more, more preferably 4 N / 20 mm or more, still more preferably 5 N / 20 mm or more, and particularly preferably 6 N / 20 mm or more. If it is within such a range, a resin foam with suppressed dust generation can be obtained. The higher the interlayer strength of the resin foam, the more preferable it is, but the upper limit thereof 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.

[0014] 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 preferably 0.4 g / cm 3 or less, more preferably 0.2 g / cm 3 or less, still more preferably 0.1 g / cm 3 or less, still more preferably 0.08 g / cm 3 or less, still more preferably 0.05 g / cm 3 or less, and particularly preferably 0.04 g / cm 3 or less. If the apparent density is within the above range, a resin foam excellent in punching processability and excellent in flexibility and stress dispersibility can be obtained. Note that the foamability can be judged by the apparent density. The method for measuring the apparent density will be described later.

[0015] In one embodiment, the resin foam can be obtained, for example, by adding recycled resin. In one embodiment, in the resin foam, the ratio of recycled resin is 0.2 or more, more preferably 0.4 or more, still more preferably 0.5 or more, particularly preferably 0.6 or more, and most preferably 0.7 or more. By adding recycled resin at such a ratio, the above effects become remarkable. Also, a resin foam excellent in the effect of suppressing carbon dioxide emissions can be provided. The upper limit of the ratio of recycled resin in the resin foam can be 0.9, 0.85 or 0.75. Within such a range, a resin foam excellent in foamability and punching processability can be obtained.

[0016] In the present specification, "recycled resin" means a resin that is reused through foam molding. In one embodiment, the "recycled resin" can be a resin that has received a temperature history of (melting point + 10°C) or higher. The "recycled resin" may be a resin that has received a temperature history of (melting point + 5°C) or higher. By using a resin that has received a predetermined temperature history, a resin foam excellent in flexibility and with suppressed dust generation can be obtained. Also, the "recycled resin ratio" is the weight ratio of the recycled resin to the resin foam.

[0017] In one embodiment, the resin foam satisfies the following formula (2). Apparent density (g / cm 3 ) < 0.046 × recycled resin ratio + 0.0121 ···(2) If formula (2) is satisfied, a resin foam with suppressed carbon dioxide emissions and excellent punching processability can be provided.

[0018] In one embodiment, the value calculated by [{0.046 × recycled resin ratio} + 0.0121] can preferably be 0.025 or more, 0.030 or more, or 0.040 or more. Also, it can be 0.070 or less, 0.060 or less, or 0.050 or less.

[0019] In one embodiment, the value calculated by [{0.046 × recycled resin ratio} + 0.0121 - apparent density (g / cm 3 )] can be 0.015 or less, 0.01 or less, 0.008 or less, 0.005 or less, or 0.003 or less. Also, the value calculated by {0.046 × recycled resin ratio} + 0.0121 - apparent density (g / cm 3 ) can be 0.0001 or more, 0.0005 or more, 0.0008 or more, or 0.001 or more. If it is within the above range, it is possible to provide a resin foam that suppresses carbon dioxide emissions and has excellent punching processability.

[0020] The thickness recovery rate (instantaneous recovery rate) after maintaining a load of 1000 g / cm 2 on the resin foam for 120 seconds is preferably 80% or more, more preferably 82% or more, still more preferably 84% or more, still more preferably 86% or more, and particularly preferably 90% or more. If it is within such a range, it is possible to provide a resin foam that has excellent punching processability. The higher the instantaneous recovery rate, the more preferable it is, but the upper limit is, for example, 99% (preferably 100%). The method for measuring the instantaneous recovery rate will be described later.

[0021] The apparent density of the resin foam is preferably 0.01 g / cm 3 or more, and more preferably 0.02 g / cm 3 or more. Also, the apparent density of the resin foam is preferably 0.4 g / cm 3 or less, more preferably 0.2 g / cm 3 or less, more preferably 0.1 g / cm 3 or less, still more preferably 0.08 g / cm 3 or less, still more preferably 0.05 g / cm 3 or less, and particularly preferably 0.04 g / cm 3 or less. If the apparent density is within the above range, it is possible to obtain a resin foam that has excellent punching processability and excellent flexibility and stress dispersibility. Note that the foamability can be judged by the apparent density. The method for measuring the apparent density will be described later.

[0022] The cell ratio of the resin foam is preferably 97% or less, more preferably 96% or less. The cell ratio of the 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.

[0023] The cell number density of the 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 2 or more. Within such a range, a resin foam having preferable flexibility and excellent punching processability can be obtained. Also, the higher the cell number density, the easier it is to store energy when compressed, and a resin foam having excellent compression recovery force can be obtained. The upper limit of the cell number density of the resin foam is preferably 400 cells / mm 2 or less, more preferably 350 cells / mm 2 or less, still more preferably 300 cells / mm 2 or less, still more preferably 250 cells / mm 2 or less, particularly preferably 200 cells / mm 2 or less. The cell number density of the resin foam is the number density in the cell cross-section observed in a randomly selected cross-section of the resin foam, and can be determined by image analysis of the resin foam cross-section.

[0024] The average cell diameter of the resin foam is preferably 300 μm or less, more preferably 270 μm or less, still more preferably 250 μm or less, still more preferably 220 μm or less, still more preferably 200 μm or less, and particularly preferably 180 μm or less. If it is within such a range, a resin foam excellent in impact absorbency can be obtained. In one embodiment, the average cell diameter of the resin foam is 180 μm or less. Further, the average cell diameter of the resin foam is preferably 20 μm or more, more preferably 50 μm or more, still more preferably 80 μm or more, still more preferably 100 μm or more, still more preferably 110 μm or more, and particularly preferably 120 μm or more. If the average cell diameter is within the above range, a resin foam having high interlayer strength, excellent flexibility and stress dispersibility, and preferably exhibiting impact absorbency can be obtained. Further, a resin foam excellent in compression recovery, punching processability, and resistance to repeated impacts can be obtained. In one embodiment, the average cell diameter of the resin foam is 120 μm or more. If it is within such a range, a resin foam having particularly excellent interlayer strength can be obtained. The method for measuring the average cell diameter will be described later.

[0025] The maximum cell diameter of the resin foam is preferably 400 μm or less, more preferably 350 μm or less, still more preferably 300 μm or less, particularly preferably 250 μm or less, and most preferably 220 μm or less. Further, the maximum cell diameter of the resin foam is preferably 40 μm or more, more preferably 80 μm or more, still more preferably 120 μm or more, and particularly preferably 160 μm or more. If it is within such a range, a resin foam particularly excellent in impact absorbency can be obtained. In one embodiment, the maximum cell diameter of the resin foam is 250 μm or less.

[0026] The coefficient of variation of the cell diameter of the resin foam is preferably 0.6 or less, more preferably 0.55 or less, still more preferably 0.5 or less, still more preferably 0.4 or less, and particularly preferably 0.35 or less. Within such a range, deformation due to impact becomes uniform, local stress loading is prevented, the stress dispersibility is excellent, and a resin foam with particularly excellent shock absorbency can be obtained. The coefficient of variation is preferably as small as possible, and its 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.

[0027] When the cell structure of the resin foam is a semi - continuous and semi - independent cell structure, the proportion of the independent cell structure therein is preferably 40% or less, more preferably 30% or less. In this specification, the proportion of the independent cell structure of the resin foam is obtained, for example, by submerging the measurement object in water in an environment of temperature 23°C and humidity 50%, measuring the subsequent mass, and then measuring the mass again after sufficiently drying in an oven at 80°C. Also, for continuous cells, since water can be retained, the mass fraction is measured and obtained as continuous cells.

[0028] The aspect ratio of the cells of the resin foam is preferably 4 or less, more preferably 3 or less, still more preferably 2 or less, still more preferably 1.5 or less, and particularly preferably 1.3 or less. Within such a range, a resin foam with excellent shock absorbency can be provided. The aspect ratio of the cells of the resin foam is, for example, 1 or more, preferably greater than 1.1. The method for measuring the aspect ratio of the cells of the resin foam will be described later.

[0029] The thickness of the cell wall of the resin foam is preferably 0.1 μm or more, more preferably 0.3 μm or more, still more preferably 0.5 μm or more, particularly preferably 0.7 μm or more, and most preferably 1 μm or more. Also, the thickness of the cell wall of the resin foam is preferably 10 μm or less, more preferably 8 μm or less, still more preferably 5 μm or less, particularly preferably 4 μm or less, and most preferably 3 μm or less. If it is within such a range, a resin foam having appropriate strength can be obtained. Such a resin foam is excellent in punching processability, and prevents tearing, dust generation, and remaining pieces during punching. Further, if the thickness of the cell wall is within the above range, a resin foam having more excellent flexibility and stress dispersibility can be obtained. The thickness of the cell wall 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.

[0030] The 50% compression load of the resin foam is preferably 40 N / cm 2 or less, more preferably 20 N / cm 2 or less, still more preferably 10 N / cm 2 or less, still more preferably 5 N / cm 2 or less, particularly preferably 4 N / cm 2 or less, and most preferably 3 N / cm 2 or less. If it is within such a range, a resin foam having preferable flexibility and excellent punching processability 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 the resin foam is the stress (N) when compressed until the compression rate reaches 50%, converted per unit area (1 cm 2 ).

[0031] The 25% compression load of the resin foam is preferably 25 N / cm 2 or less, more preferably 15 N / cm 2 or less, still more preferably 10 N / cm 2 or less, still more preferably 6 N / cm2 is as follows, more preferably 5 N / cm 2 is as follows, particularly preferably 3 N / cm 2 is as follows, most preferably 2 N / cm 2 is as follows. Within such a range, a resin foam having preferable flexibility and shock absorbency 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 the resin foam is the stress (N) when compressed until the compression rate reaches 25% converted per unit area (1 cm 2 ).

[0032] The thickness of the above resin foam is preferably 8000 μm or less, more preferably 5000 μm or less, still more preferably 4000 μm or less, and particularly preferably 2000 μm or less. Also, the thickness of the resin foam is preferably 100 μm or more, more preferably 200 μm or more, still more preferably 300 μm or more, and particularly preferably 400 μm or more. Within such a range, it is advantageous in that a fine and uniform cell structure can be formed and excellent shock absorbency can be exhibited.

[0033] The shock absorbency of the above resin foam is preferably 40% or more, more preferably 55% or more, still more preferably 60% or more, still more preferably 70% or more, particularly preferably 75% or more, and most preferably 80% or more. Also, the shock absorbency of the resin foam is, for example, 97% or less, preferably 99% or less. The shock absorbency is measured as follows. · On the impact force sensor, a resin foam, double-sided tape (product number: No. 5603W, manufactured by Nitto Denko), and a PET film (product number: Diafoil MRF75, manufactured by Mitsubishi Rayon) are arranged in this order to form a test piece. A 66 g iron ball is dropped onto the test piece from a height of 50 cm above the PET film, and the impact force F1 is measured. · Also, the iron ball is dropped directly onto the impact force sensor as described above, and the blank impact force F0 is measured. · From F1 and F0, the shock absorbency (%) is calculated by the formula (F0 - F1) / F0 × 100.

[0034] The stress retention of the resin foam is preferably 60% or more, more preferably 63% or more. Also, the stress retention of the resin foam is preferably 100% or less, more preferably 95% or less. Within such a range, a resin foam excellent in stress dispersibility and capable of exhibiting excellent shock absorbency even in a thin film can be obtained. In this specification, the above stress retention means the ratio (tensile strength after holding for 120 seconds / tensile strength immediately after stretching × 100) between the tensile strength immediately after stretching and the tensile strength after holding for 120 seconds after stretching a resin foam (width 10 mm × length 100 mm) at a speed of 300 m / min in the length direction by 20%.

[0035] In one embodiment, the resin foam as described above can be formed by using, as the resin constituting the resin foam, a resin having a die swell ratio of 1.4 or less at the melting point (the melting point of the resin constituting the resin foam) + 20°C. By using a resin having a die swell ratio within the above range, shrinkage during resin foam formation can be prevented, a resin foam with a thick thickness can be formed, and the resin foam can contain bubbles with a small bubble size. The die swell ratio at the melting point of the resin constituting the resin foam + 20°C is preferably 1.2 or less, more preferably 1.1 or less. The lower limit value 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 discharged resin when the molten resin is discharged from the die by the diameter of the die. The die swell ratio is calculated by extruding a resin in a molten state at the 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 and measuring the diameter of the obtained string-shaped molded product, according to the formula of the diameter of the molded product (mm) / die diameter (mm). Also, the melting point of the resin is measured by the peak top temperature of the endothermic peak obtained by differential scanning calorimetry (DSC) measurement. The differential scanning calorimetry (DSC) measurement is performed using a differential scanning calorimeter (for example, product name "Q-2000", TA Instruments) under the conditions of a sample weight of 3 mg and a heating rate of 10°C / min. When there are two or more peaks, the peak top temperature on the high temperature side is taken as the melting point.

[0036] In one embodiment, the resin foam as described above can be formed by using a resin having a shear viscosity at the melting point (the melting point of the resin constituting the resin foam) + 20°C of 3000 Pa·s or less. If a resin having a shear viscosity within the above range is used, when forming the resin foam, the gas used for forming the cell structure can be preferably dispersed, and as a result, a resin foam with a small cell size can be obtained. The shear viscosity of the resin constituting the resin foam at the melting point + 20°C is preferably 2500 Pa·s or less, more preferably 2100 Pa·s or less, still 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, the shear viscosity can be measured by extruding a resin in a molten state at the melting point + 20°C through a die with a length of 10 mm and a diameter of 1 mmφ at a shear rate of 20 mm / s.

[0037] The above resin foam may have a heat-melt layer on one or both of its surfaces. The resin foam having a heat-melt layer can be obtained, for example, by rolling the resin foam (or a precursor of the resin foam (foamed structure)) using a pair of heating rolls heated to a temperature equal to or higher than the melting temperature of the resin composition constituting the resin foam.

[0038] The above resin foam can be formed by any suitable method as long as the effects of the present invention are not impaired. Such methods typically include a method of foaming a resin composition containing a resin material (polymer).

[0039] A-1. Resin Composition The resin foam of the present invention can typically be obtained by foaming a resin composition. The resin composition contains any suitable resin material (polymer). In one embodiment, in the above resin composition, the resin material contains a recycled resin. In the resin material, a recycled resin and a non-recycled resin may be used in combination.

[0040] Examples of the polymer include acrylic resins, silicone resins, urethane resins, polyolefin resins, ester resins, rubber resins, etc. The above polymer may be used alone as a single type, or in combination of two or more types.

[0041] The content ratio of the polymer is preferably 30 to 95 parts by weight, more preferably 35 to 90 parts by weight, still more preferably 40 to 80 parts by weight, and particularly preferably 40 to 60 parts by weight with respect to 100 parts by weight of the resin composition. Within such a range, a resin foam excellent in flexibility and stress dispersibility can be obtained.

[0042] The content ratio of the recycled resin is preferably 30 to 90 parts by weight, more preferably 40 to 85 parts by weight, and still more preferably 50 to 80 parts by weight with respect to 100 parts by weight of the above polymer.

[0043] In one embodiment, a polyolefin resin is used as the above polymer. In one embodiment, a polyolefin resin is used as the above recycled resin. That is, a polyolefin resin as a non-recycled resin and a polyolefin resin as a recycled resin can be used in combination.

[0044] The content ratio of the polyolefin resin (the total content ratio of the polyolefin resin as a recycled resin and the polyolefin resin as a non-recycled resin) is preferably 50 to 100 parts by weight, more preferably 70 to 100 parts by weight, still more preferably 90 to 100 parts by weight, particularly preferably 95 to 100 parts by weight, and most preferably 100 parts by weight with respect to 100 parts by weight of the above polymer.

[0045] As the polyolefin resin, preferably, at least one selected from the group consisting of polyolefins and polyolefin-based elastomers is mentioned, more preferably, a polyolefin and a polyolefin-based elastomer are used in combination. Each of the polyolefin and the polyolefin-based elastomer may be used alone as only one kind, or may be used in combination of two or more kinds. In the present specification, when referred to as "polyolefin", "recycled polyolefin", or "non-recycled polyolefin", "polyolefin-based elastomer" is not included. In one embodiment, recycled polyolefin is used as the polyolefin. The recycled polyolefin can be used in combination with non-recycled polyolefin. That is, in one embodiment, as the polyolefin resin, recycled polyolefin and / or non-recycled polyolefin and a polyolefin-based elastomer are used in combination.

[0046] When a polyolefin and a polyolefin-based elastomer are used in combination as the polyolefin resin, the weight ratio of the polyolefin (for example, the total of recycled polyolefin and non-recycled polyolefin) to the polyolefin-based elastomer (polyolefin / polyolefin-based elastomer) is preferably 1 / 99 to 99 / 1, more preferably 10 / 90 to 90 / 10, still more preferably 20 / 80 to 80 / 20, and particularly preferably 30 / 70 to 70 / 30. In one embodiment, the weight ratio of the polyolefin to the polyolefin-based elastomer (polyolefin / polyolefin-based elastomer) is preferably 25 / 75 to 75 / 25, more preferably 35 / 65 to 65 / 35. Within such a range, a resin foam excellent in compression recovery property, with shape change (particularly, thickness change) before and after punching processing suppressed, having appropriate strength, and excellent in punching processability can be obtained.

[0047] As the polyolefin, any suitable polyolefin can be employed as long as the effects of the present invention are not impaired. Examples of such polyolefins include linear polyolefins and branched (having branched chains) polyolefins. In one embodiment, a branched polyolefin is used as the polyolefin resin. In this embodiment, only the branched polyolefin may be used as the polyolefin, or the branched polyolefin and the linear polyolefin may be used in combination. By using the branched polyolefin, a resin foam having a small average cell diameter and excellent impact resistance can be obtained. Further, as the non-renewable resin, when the above-mentioned branched polyolefin is used, a resin foam excellent in punching processability can be obtained even when used in combination with the renewable resin. The content ratio of the branched polyolefin is preferably 30 to 100 parts by weight, more preferably 50 to 80 parts by weight, based on 100 parts by weight of the polyolefin.

[0048] Examples of the above polyolefin include polymers containing structural units derived from α-olefins. The polyolefin may be composed only of structural units derived from α-olefins, or 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 as the copolymerization form. Examples thereof include random copolymers and block copolymers.

[0049] Examples of the α-olefin that can constitute the polyolefin include α-olefins having 2 to 8 carbon atoms (preferably 2 to 6 carbon atoms, more preferably 2 to 4 carbon atoms) (for example, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, etc.). The α-olefin may be only one kind or two or more kinds.

[0050] 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. The monomers other than α-olefins may be only one kind or two or more kinds.

[0051] Specific 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, copolymers of propylene and ethylenically unsaturated monomers, and the like.

[0052] In one embodiment, a polypropylene-based polymer having a structural unit derived from propylene is used as the polyolefin. Examples of the polypropylene-based polymer include, for example, polypropylene (propylene homopolymer), copolymers of ethylene and propylene, copolymers of propylene and α-olefins other than propylene, and the like, and polypropylene (propylene homopolymer) is preferred. The polypropylene-based polymer may be used alone as only one kind or in combination of two or more kinds.

[0053] The melt flow rate (MFR) of the polyolefin at a temperature of 230°C is preferably from 0.25 g / 10 min to 20 g / 10 min, more preferably from 0.3 g / 10 min to 6 g / 10 min, still more preferably from 0.35 g / 10 min to 5 g / 10 min, particularly preferably from 0.35 g / 10 min to 1 g / 10 min, and most preferably from 0.35 g / 10 min to 0.6 g / 10 min, in terms of more effectively expressing the effects of the present invention. In the present 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.

[0054] The melt flow rate (MFR) of the polyolefin as a recycled resin at a temperature of 230°C is preferably less than 20 g / 10 min, more preferably less than 10 g / 10 min, still more preferably less than 6 g / 10 min, and even more preferably less than 5 g / 10 min. Also, the melt flow rate (MFR) of the polyolefin as the above recycled resin at a temperature of 230°C is preferably 0.25 g / 10 min or more, more preferably 0.3 g / 10 min or more, and still more preferably 0.35 g / 10 min or more. Within such a range, the effects of the present invention become remarkable. It is advantageous in that a resin foam excellent in impact absorbency can be obtained.

[0055] In one embodiment, the die swell ratio of the polyolefin as the above recycled resin at the melting point + 20°C is 1.5 or less (preferably 1.25 or less). Within such a range, a resin foam containing small bubbles and having a low density can be obtained. Such a resin foam is excellent in impact absorbency. It is also advantageous in that the amount of carbon dioxide emissions is small. The lower limit value of the die swell ratio of the polyolefin as the above recycled resin is, for example, 1.05 (preferably 1.02, more preferably 1.01).

[0056] The melt tension of the polyolefin as the recycled resin is preferably 10 cN or more, more preferably 15 cN or more, and even more preferably 18 cN or more. Also, the melt tension of the polyolefin as the recycled resin is preferably 50 cN or less, more preferably 45 cN or less. Within such a range, a resin foam containing small bubbles with a small bubble size and having a low density can be obtained. Such a resin foam is excellent in impact absorbency. Also, it is advantageous in terms of low carbon dioxide emissions.

[0057] The weight average molecular weight of the polyolefin can preferably be 500,000 or more, 550,000 or more, or 600,000 or more. Also, the weight average molecular weight of the polyolefin can preferably be 1,200,000 or less, 1,100,000 or less, or 1,000,000 or less. Within such a range, the die swell ratio and shear viscosity of the resin can be preferably adjusted. Also, the molecular weight distribution (weight average molecular weight / number average molecular weight) of the polyolefin can preferably be 5.5 or more, 6 or more, or 7 or more. Also, the molecular weight distribution of the polyolefin can preferably be 12 or less, 11 or less, or 10 or less. Within such a range, the die swell ratio and shear viscosity of the resin can be preferably adjusted. The weight average molecular weight and number average molecular weight can be determined by gel permeation chromatography measurement (solvent: tetrahydrofuran, polystyrene conversion).

[0058] As the polyolefin, commercially available products may be used, for example, "E110G" (manufactured by Prime Polymer Co., Ltd.), "EA9" (manufactured by Japan Polypropylene Corporation), "EA9FT" (manufactured by Japan Polypropylene Corporation), "E-185G" (manufactured by Prime Polymer Co., Ltd.), "WB140HMS" (manufactured by Borealis), "WB135HMS" (manufactured by Borealis), and the like.

[0059] As the polyolefin-based elastomer, any appropriate polyolefin-based elastomer can be adopted as long as the effects of the present invention are not impaired. Examples of such polyolefin-based elastomers include, for example, ethylene-propylene copolymers, ethylene-propylene-diene copolymers, ethylene-vinyl acetate copolymers, polybutene, polyisobutylene, chlorinated polyethylene, elastomers in which a polyolefin component and a rubber component are physically dispersed, elastomers having a structure in which a polyolefin component and a rubber component are microphase-separated, and so-called non-crosslinked thermoplastic olefin-based elastomers (TPO) such as these; a multiphase polymer having a sea-island structure in which crosslinked rubber particles are finely dispersed as domains (island phases) in a resin component A (olefin-based resin component A) forming a matrix and a rubber component B forming a domain, obtained by dynamically heat-treating a mixture containing the resin component A and the rubber component B in the presence of a crosslinking agent, which is a dynamically crosslinked thermoplastic olefin-based elastomer (TPV); and the like.

[0060] The polyolefin-based elastomer preferably contains a rubber component. Examples of such rubber components include those described in JP-A-08-302111, JP-A-2010-241934, JP-A-2008-024882, JP-A-2000-007858, JP-A-2006-052277, JP-A-2012-072306, JP-A-2012-057068, JP-A-2010-241897, JP-A-2009-067969, Re-Pub. 03 / 002654, and the like.

[0061] Specific examples of elastomers having a structure in which a polyolefin component and an olefin-based rubber component are microphase-separated include elastomers composed of a polypropylene resin (PP) and an ethylene-propylene rubber (EPM), elastomers composed of a polypropylene resin (PP) and an ethylene-propylene-diene rubber (EPDM), and the like. 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, more preferably 80 / 20 to 20 / 80.

[0062] Dynamically crosslinked thermoplastic olefin elastomers (TPV) generally have a higher elastic modulus and lower compression set than non-crosslinked thermoplastic olefin elastomers (TPO). As a result, they have good recoverability and can exhibit excellent recoverability when used as resin foams.

[0063] As described above, a dynamically crosslinked thermoplastic olefin elastomer (TPV) is obtained by dynamically heat-treating a mixture containing a resin component A (olefin resin component A) forming a matrix and a rubber component B forming domains in the presence of a crosslinking agent, and is a multiphase polymer having a sea-island structure in which crosslinked rubber particles are finely dispersed as domains (island phase) in the resin component A which is the matrix (sea phase).

[0064] Examples of the dynamically crosslinked thermoplastic olefin elastomer (TPV) include those described in JP-A-2000-007858, JP-A-2006-052277, JP-A-2012-072306, JP-A-2012-057068, JP-A-2010-241897, JP-A-2009-067969, Re-Publ. 03 / 002654, and the like.

[0065] As the dynamically crosslinked thermoplastic olefin elastomer (TPV), commercially available products may be used, and examples thereof include "Zeotherm" (manufactured by Nippon Zeon Co., Ltd.), "Thermolan" (manufactured by Mitsubishi Chemical Corporation), "Surlyn 3245D" (manufactured by Toyobo Co., Ltd.), and the like.

[0066] The melt flow rate (MFR) of the polyolefin-based elastomer at 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-based elastomer constituting the resin foam.

[0067] In one embodiment, two or more polyolefin elastomers having different melt flow rates (MFR) at a temperature of 230°C are used in combination. In this case, the polyolefin elastomer having a melt flow rate (MFR) at a temperature of 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 5 g / 10 min) (low MFR polyolefin elastomer), and the melt flow rate (MFR) at a temperature of 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) (high MFR polyolefin elastomer) can be used in combination. By doing so, the melt tension of the polyolefin elastomer is preferably adjusted, and as a result, the effects of the present invention become remarkable.

[0068] The blending ratio of the low MFR polyolefin elastomer to the high MFR polyolefin elastomer (low MFR polyolefin elastomer / high MFR polyolefin elastomer; weight ratio) is preferably 1.5 to 5, more preferably 1.8 to 3.5, and particularly preferably 2 to 3. Within such a range, the melt tension of the polyolefin elastomer is preferably adjusted, and as a result, the effects of the present invention become remarkable.

[0069] The melt tension (at 190°C, at break) of the polyolefin elastomer is preferably less than 10 cN, 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.

[0070] The JIS A hardness of the polyolefin elastomer 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°. The JIS A hardness is measured based on ISO7619 (JIS K6253).

[0071] In one embodiment, the resin foam (i.e., the resin composition) may further contain a filler. By including the filler, a resin foam that requires a large amount of energy to deform the cell walls can be formed, and the resin foam exhibits excellent shock absorption. Also, by including the filler, it is advantageous in that a fine and uniform cell structure can be formed and excellent shock absorption can be exhibited. The filler may be used alone as only one type, or may be used in combination of two or more types.

[0072] The content ratio of the filler is preferably 10 parts by weight to 150 parts by weight, more preferably 30 parts by weight to 130 parts by weight, and still more preferably 50 parts by weight to 100 parts by weight with respect to 100 parts by weight of the polymer constituting the resin foam. If it is within such a range, the above effects become remarkable.

[0073] In one embodiment, the filler is an inorganic substance. Examples of the material constituting the filler that is an inorganic substance include aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, aluminum borate whisker, silicon nitride, boron nitride, crystalline silica, amorphous silica, metals (e.g., gold, silver, copper, aluminum, nickel), carbon, graphite, and the like.

[0074] In one embodiment, the filler is an organic substance. Examples of the material constituting the filler that is an organic substance include polymethyl methacrylate (PMMA), polyimide, polyamideimide, polyetheretherketone, polyetherimide, polyesterimide, and the like.

[0075] As the above-mentioned filler, a flame retardant may be used. Examples of the flame retardant include bromine-based flame retardants, chlorine-based flame retardants, phosphorus-based flame retardants, antimony-based flame retardants, etc. Preferably, from the viewpoint of safety, a non-halogen-non-antimony-based flame retardant is used.

[0076] Examples of the non-halogen-non-antimony-based flame retardant 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, hydrate of magnesium oxide-nickel oxide, hydrate of magnesium oxide-zinc oxide, etc.

[0077] The above-mentioned filler may be subjected to any appropriate surface treatment. Examples of the surface treatment include silane coupling treatment, stearic acid treatment, etc.

[0078] The bulk density of the above-mentioned filler is preferably 3 0.8 g / cm or less, more preferably 3 0.6 g / cm or less, still more preferably 3 0.4 g / cm or less, and particularly preferably 3 0.3 g / cm or less. Within such a range, the filler can be contained with good dispersibility, and the filler addition effect can be sufficiently exerted while reducing the content of the filler. A resin foam with a low filler content is advantageous in terms of high foaming, flexibility, and excellent stress dispersibility and appearance. The lower limit value of the bulk density of the filler is, for example, 3 0.01 g / cm, preferably 3 0.05 g / cm, more preferably 3 0.1 g / cm.

[0079] The number average particle diameter (primary particle diameter) of the above filler is preferably 5 μm or less, more preferably 3 μm or less, and still more preferably 1 μm or less. If it is within such a range, the filler can be contained with good dispersibility, and a uniform cell structure can be formed. As a result, a resin foam excellent in stress dispersibility and appearance can be obtained. The lower limit value 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 distribution meter (MicrtracII, Microtrac Bell Co., Ltd.) with a suspension prepared by mixing 1 g of the filler with 100 g of water as a sample.

[0080] The specific surface area of the above filler is preferably 2 m 2 / g or more, more preferably 4 m 2 / g or more, and still more preferably 6 m 2 / g or more. If it is within such a range, the filler can be contained with good dispersibility, and a uniform cell structure can be formed. As a result, a resin foam excellent in stress dispersibility and appearance can be obtained. The upper limit value of the specific surface area of the filler is, for example, 20 m 2 / g. The specific surface area of the filler can be measured by the BET method, that is, a molecule with a known adsorption occupation area is adsorbed on the filler surface at a low temperature using liquid nitrogen, and measured from the adsorption amount.

[0081] The resin composition may contain any appropriate other components as long as the effects of the present invention are not impaired. Such other components may be only one kind or two or more kinds. Examples of such other components include rubber, resins other than polymers compounded as resin materials, softeners, aliphatic compounds, anti-aging agents, antioxidants, light stabilizers, weathering agents, ultraviolet absorbers, dispersants, plasticizers, carbon, antistatic agents, surfactants, crosslinking agents, thickeners, rust preventives, silicone-based compounds, tension modifiers, shrinkage preventives, fluidity modifiers, gelling agents, curing agents, reinforcing agents, foaming agents, foam nucleating agents, colorants (pigments, dyes, etc.), pH adjusters, solvents (organic solvents), thermal polymerization initiators, photoinitiators, lubricants, crystal nucleating agents, crystallization accelerators, vulcanizing agents, surface treatment agents, dispersion aids, and the like.

[0082] A-2. Formation of Resin Foam The resin foam of the present invention is typically obtained by foaming a resin composition. As the foaming method (method for forming bubbles), methods usually used in foam molding, such as physical methods and chemical methods, can be adopted. That is, the resin foam may typically be a foam (physical foam) formed by foaming by a physical method, or a foam (chemical foam) formed by foaming by a chemical method. The physical method generally disperses gas components such as air and nitrogen in a polymer solution and forms bubbles by mechanical mixing (mechanical foam). The chemical method is generally a method of forming cells by gas generated by thermal decomposition of a foaming agent added to a polymer base and obtaining a foam.

[0083] The resin composition to be subjected to foam molding may be prepared, for example, by mixing the constituent components using any suitable means with any suitable melt-kneading apparatus, such as an open-type mixing roll, a non-open-type Banbury mixer, a single-screw extruder, a twin-screw extruder, a continuous kneader, a pressure kneader, etc.

[0084] <Embodiment 1 of Forming Resin Foam> As one embodiment 1 of forming a resin foam, for example, there is a form in which a resin foam is formed through a step (step A) of mechanically foaming and foaming an emulsion resin composition (an emulsion containing a resin material (polymer), etc.). Examples of the foaming device include a high-speed shear type device, a vibration type device, a pressurized gas discharge type device, etc. Among these foaming devices, from the viewpoints of miniaturization of bubble diameter and large-capacity production, a high-speed shear type device is preferable. This one embodiment 1 of forming a resin foam is applicable to the formation from any resin composition.

[0085] The solid content concentration of the emulsion is preferably high from the viewpoint of film-forming property. The solid content concentration of the emulsion is preferably 30% by weight or more, more preferably 40% by weight or more, and still more preferably 50% by weight or more.

[0086] When foamed by mechanical agitation, the bubbles are formed by gas being incorporated into the emulsion. As the gas, any suitable gas can be employed 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, carbon dioxide, and the like.

[0087] By passing through the step of coating and drying (step B) the emulsion resin composition foamed by the above method (the emulsion resin composition containing bubbles) on a substrate, the resin foam of the present invention can be obtained. Examples of the substrate include a peeled plastic film (such as a peeled polyethylene terephthalate film), a plastic film (such as a polyethylene terephthalate film), and the like.

[0088] In step B, as the coating method and the drying method, any suitable method can be adopted as long as it does not impair the effects of the present invention. Step B preferably includes a preliminary drying step B1 of drying the emulsion resin composition containing bubbles coated on the substrate at 50°C or higher and lower than 125°C, and then a main drying step B2 of further drying at 125°C or higher and 200°C or lower.

[0089] By providing the preliminary drying step B1 and the main drying step B2, coalescence of bubbles and bursting of bubbles due to a rapid temperature rise can be prevented. In particular, in a foamed sheet with a small thickness, bubbles coalesce and burst due to a rapid temperature rise, so the significance of providing the preliminary drying step B1 is great. The temperature in the preliminary drying step B1 is preferably 50°C to 100°C. The time of the preliminary 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 time of the main drying step B2 is preferably 0.5 minutes to 30 minutes, and more preferably 1 minute to 15 minutes.

[0090] <Embodiment 2 for forming a resin foam> As one embodiment 2 of forming a resin foam, there is a form in which a resin composition is foamed with a foaming agent to form a foam. As the foaming agent, those usually used in foam molding can be used, and from the viewpoints of environmental protection and low pollution to the foamable material, it is preferable to use a high-pressure inert gas.

[0091] As the inert gas, any appropriate inert gas can be adopted as long as it is inert to the resin composition and can be impregnated. Examples of such inert gases include carbon dioxide, nitrogen gas, air, and the like. These gases may be used in combination. Among these, carbon dioxide is preferable from the viewpoints of a large impregnation amount into the resin material (polymer) and a high impregnation rate.

[0092] The inert gas is preferably in a supercritical state. That is, it is particularly preferable to use supercritical carbon dioxide. In the supercritical state, the solubility of the inert gas in the resin composition further increases, high-concentration mixing of the inert gas is possible, and the inert gas becomes highly concentrated during a rapid pressure drop. Therefore, the generation of gas nuclei increases, and the density of the bubbles formed by the growth of the gas nuclei becomes larger than that in other states even when the porosity is the same, so that fine bubbles can be obtained. The critical temperature of carbon dioxide is 31°C, and the critical pressure is 7.4 MPa.

[0093] As a method for forming a foam by impregnating a resin composition with a high-pressure inert gas, for example, there are a gas impregnation step of impregnating an inert gas into a resin composition containing a resin material (polymer) under high pressure, a depressurization step of reducing the pressure after this step to foam the resin material (polymer), and a heating step of growing the bubbles by heating if necessary. In this case, an unfoamed molded body pre-molded may be impregnated with an inert gas, or a molten resin composition may be impregnated with an inert gas under a pressurized state and then molded during depressurization. These steps may be carried out in either a batch system or a continuous system. That is, a batch system may be used in which the resin composition is pre-molded into an appropriate shape such as a sheet to form an unfoamed resin molded body, and then this unfoamed resin molded body is impregnated with a high-pressure gas and foamed by releasing the pressure, or a continuous system may be used in which the resin composition is kneaded with a high-pressure gas under pressure, the pressure is released simultaneously with molding, and molding and foaming are carried out simultaneously.

[0094] An example of manufacturing a foam by a batch method is shown below. For example, a resin composition is extruded using an extruder such as a single-screw extruder or a twin-screw extruder to produce a resin sheet for foam molding. Alternatively, the resin composition is uniformly kneaded using a kneader provided with blades such as a roller, a cam, a kneader, or a Banbury type, and then press-worked to a predetermined thickness using a hot plate press or the like to produce an unfoamed resin molded body. The thus obtained unfoamed resin molded body is placed in a high-pressure vessel, and a high-pressure inert gas (such as carbon dioxide in a supercritical state) is injected to impregnate the unfoamed resin molded body with the inert gas. When the inert gas is sufficiently impregnated, the pressure is released (usually to atmospheric pressure) to generate bubble nuclei in the resin. The bubble nuclei may be grown at room temperature as they are, or may be grown by heating in some cases. As the heating method, known or conventional methods such as a water bath, an oil bath, a hot roll, a hot air oven, far-infrared rays, near-infrared rays, and microwaves can be adopted. After growing the bubbles in this way, the foam can be obtained by rapidly cooling with cold water or the like and fixing the shape. Note that the unfoamed resin molded body used for foaming is not limited to a sheet-like material, and various shapes can be used according to the application. In addition, the unfoamed resin molded body used for foaming can also be produced by other molding methods such as injection molding in addition to extrusion molding and press molding.

[0095] An example of manufacturing a foam in a continuous manner is shown below. For example, while kneading a resin composition using an extruder such as a single-screw extruder or a twin-screw extruder, a high-pressure gas (especially an inert gas, and more particularly carbon dioxide) is injected (introduced), and the resin composition is impregnated with a sufficiently high-pressure gas in a kneading impregnation step. The pressure is released (usually to atmospheric pressure) by extruding the resin composition through a die provided at the tip of the extruder, etc., and foam molding is performed by a molding depressurization step that simultaneously performs molding and foaming. Also, during foam molding in a continuous manner, a heating step of growing bubbles by heating may be provided as necessary. After growing the bubbles in this way, they may be rapidly cooled with cold water or the like as necessary to fix the shape. Also, the introduction of the high-pressure gas may be performed continuously or discontinuously. Further, in the kneading impregnation step and the molding depressurization step, for example, an extruder or an injection molding machine can be used. Note that as a method of heating when growing gas nuclei, any appropriate method such as a water bath, an oil bath, a heat roll, a hot air oven, far-infrared rays, near-infrared rays, or microwaves can be mentioned. As the shape of the foam, any appropriate shape can be adopted. Examples of such shapes include a sheet shape, a prismatic shape, a cylindrical shape, and an irregular shape.

[0096] When foam molding a resin composition, the mixing amount of the gas is, in terms of being able to obtain a highly foamed resin foam, for example, preferably 2% by weight to 10% by weight, more preferably 2.5% by weight to 8% by weight, and even more preferably 3% by weight to 6% by weight with respect to the total amount of the resin composition.

[0097] When impregnating an inert gas into a resin composition, the pressure can be appropriately selected in consideration of operability and the like. Such a pressure is, for example, preferably 6 MPa or more (for example, 6 MPa to 100 MPa), more preferably 8 MPa or more (for example, 8 MPa to 50 MPa). In the case of using carbon dioxide in a supercritical state, the pressure is preferably 7.4 MPa or more from the viewpoint of maintaining the supercritical state of carbon dioxide. When the pressure is lower than 6 MPa, the bubble growth during foaming is significant, and the bubble diameter becomes too large, and it may not be possible to obtain a preferable average cell diameter (average bubble diameter). This is because when the pressure is low, the impregnation amount of the gas is relatively less than that at high pressure, the bubble nucleation rate decreases, and the number of formed bubble nuclei decreases, so the amount of gas per bubble increases conversely and the bubble diameter becomes extremely large. Also, in the pressure region lower than 6 MPa, since the bubble diameter and bubble density change greatly only by slightly changing the impregnation pressure, it is likely to be difficult to control the bubble diameter and bubble density.

[0098] The temperature in the gas impregnation step varies depending on the type of the inert gas used, the components in the resin composition, etc., and can be selected within a wide range. When considering operability and the like, it is preferably 10°C to 350°C. When impregnating an inert gas into an unfoamed molded body, the impregnation temperature in the batch type is preferably 10°C to 250°C, more preferably 40°C to 230°C. Also, when extruding a gas-impregnated molten polymer to perform foaming and molding simultaneously, the impregnation temperature in the continuous type is preferably 60°C to 350°C. In the case of using carbon dioxide as the inert gas, in order to maintain the supercritical state, the temperature during impregnation is preferably 32°C or more, more preferably 40°C or more.

[0099] In the pressure reduction step, the pressure reduction rate is preferably 5 MPa / second to 300 MPa / second in order to obtain uniform fine bubbles.

[0100] The heating temperature in the heating step is preferably 40°C to 250°C, more preferably 60°C to 250°C.

[0101] 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. Also, a resin foam with a small thickness (for example, 0.2 mm or less) can be obtained. The above-mentioned heat-melted layer may be formed by the above roll rolling.

[0102] The thinning of the foamed structure can be carried out using any suitable slicer. The thickness of the foamed structure after thinning is preferably 0.01 mm or more, more preferably 0.05 mm or more, still more preferably 0.1 mm or more, and particularly preferably 0.15 mm or more. Also, the upper limit of the thickness of the foamed structure after thinning is preferably 3 mm or less, more preferably 2 mm or less, still more preferably 1.5 mm or less, still more preferably 1 mm or less, still more preferably 0.8 mm or less, and particularly preferably 0.5 mm or less. If it is within such a range, the number of bubbles in the resin foam is particularly preferably adjusted, and it is difficult for collapse to occur due to punching, so that a resin foam with particularly excellent punching processability can be obtained.

[0103] Preferably, the roll used for the above roll rolling is a heating roll. The temperature of the roll is preferably 150°C to 250°C, and more preferably 160°C to 230°C.

[0104] The rolling rate of the foamed structure (thickness after rolling / thickness before rolling × 100) is preferably 80% or less, more preferably 10% to 80%, still more preferably 20% to 75%, and particularly preferably 30% to 75%. If it is within such a range, a resin foam with an appropriately adjusted aspect ratio can be obtained.

[0105] B. Foam member FIG. 1 is a schematic cross-sectional view of a foamed member according to one embodiment. The foamed 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 composed of the resin foam.

[0106] The thickness of the adhesive layer is preferably 5 μm or more, more preferably 6 μm or more, still more preferably 7 μm or more, and particularly preferably 8 μm or more. Also, the thickness of the adhesive layer is preferably 300 μm or less, more preferably 200 μm or less, still more preferably 100 μm or less, and most preferably 50 μm or less. When the thickness of the adhesive layer is within the above range, the foamed member of the present invention can exhibit excellent shock absorbency.

[0107] As the adhesive layer, a layer made of any suitable adhesive can be employed. Examples of the adhesive constituting the adhesive layer include rubber-based adhesives (such as synthetic rubber-based adhesives and natural rubber-based adhesives), 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. The adhesive constituting the adhesive layer is preferably at least one selected from acrylic-based adhesives, silicone-based adhesives, and rubber-based adhesives. Such an adhesive may be only one kind or two or more kinds. The adhesive layer may be one layer or two or more layers.

[0108] When classified by the adhesion form, examples of the adhesive include emulsion-type adhesives, solvent-type adhesives, ultraviolet crosslinking-type (UV crosslinking-type) adhesives, electron beam crosslinking-type (EB crosslinking-type) adhesives, and hot melt-type adhesives (hot melt adhesives). Such an adhesive may be only one kind or two or more kinds.

[0109] The water vapor transmission rate of the adhesive layer is preferably 50 (g / (m 2 ·24 hours)) or less, more preferably 30 (g / (m 2·24 hours) or less, more preferably 20 (g / (m 2 ·24 hours) or less, particularly preferably 10 (g / (m 2 ·24 hours) or less. If the water vapor transmission rate of the adhesive layer is within the above range, the foamed sheet can stabilize its shock absorbency without being affected by moisture. The water vapor transmission rate can be measured, for example, according to the method specified in JIS Z 0208 under the test conditions of 40°C and a relative humidity of 92%.

[0110] The adhesive constituting the adhesive layer may contain any other appropriate components as long as the effects of the present invention are not impaired. Examples of other components include other polymer components, softeners, anti-aging agents, curing agents, plasticizers, fillers, antioxidants, thermal polymerization initiators, photopolymerization initiators, ultraviolet absorbers, light stabilizers, colorants (such as pigments and dyes), solvents (organic solvents), surfactants (e.g., ionic surfactants, silicone-based surfactants, fluorine-based surfactants, etc.), 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 the thermal polymerization initiator and the photopolymerization initiator may be included in the material for forming the polymer component.

[0111] The above foamed member can be manufactured by any appropriate method. Examples of methods for manufacturing the foamed member include a method of laminating a resin foam layer and an adhesive layer, and a method of forming the adhesive layer by a curing reaction or the like after laminating the forming material of the adhesive layer and the resin foam layer.

Examples

[0112] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples in any way. The test and evaluation methods in the examples and the like are as follows. Note that when "parts" are described, it means "parts by weight" unless otherwise specified, and when "%" is described, it means "% by weight" unless otherwise specified.

[0113] <Evaluation Method> (1) Apparent density The density (apparent density) of the resin foam was calculated as follows. The resin foams obtained in the examples and comparative examples were punched out into test pieces with a size of 20 mm × 20 mm, and the dimensions of the test pieces were measured with a vernier caliper. Next, the weight of the test piece was measured with an electronic balance. And it was calculated by the following formula. Apparent density (g / cm 3 ) = Weight of test piece / Volume of test piece

[0114] (2) 50% Compression load It was measured according to the method for measuring the compression hardness of resin foams described in JIS K 6767. Specifically, the resin foams obtained in the examples and comparative examples were cut out into test pieces with a size of 30 mm × 30 mm, and the stress (N) when compressed at a compression rate of 50% until the compression rate reached 50% at a compression speed of 10 mm / min was converted per unit area (1 cm 2 ) and taken as the 50% compression load (N / cm 2 ).

[0115] (3) 25% Compression load It was measured according to the method for measuring the compression hardness of resin foams described in JIS K 6767. Specifically, the resin foams obtained in the examples and comparative examples were cut out into test pieces with a size of 30 mm × 30 mm, and the stress (N) when compressed at a compression rate of 25% until the compression rate reached 25% at a compression speed of 10 mm / min was converted per unit area (1 cm 2 ) and taken as the 25% compression load (N / cm 2 ).

[0116] (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 in a direction perpendicular to the main surface (thickness direction) of the resin foam using a razor blade. Using a digital microscope (product name "VHX-500", manufactured by Keyence Corporation) as a measuring instrument, an image of the cut surface of the resin foam was captured, and by performing image analysis using the analysis software of the measuring instrument, the number average bubble diameter (average cell diameter) and the maximum bubble diameter (maximum cell diameter) were determined. The number of bubbles in the captured enlarged image was about 400. Also, 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)

[0117] (5) Bubble diameter aspect ratio Using a digital microscope (product name "VHX-2000, manufactured by Keyence Corporation) as a measuring instrument, the aspect ratio of the bubbles in the resin foams obtained in the examples and comparative examples was measured by the following method. The resin foam was cut in a direction perpendicular to the main surface (thickness direction) of the resin foam using a razor blade, and the cut surface was observed at a magnification of 100 times within a predetermined area (3 mm 2 ) using a microscope (for example, "VHX-2000" manufactured by Keyence), and the length in the thickness direction and the length in the direction perpendicular to the thickness direction of one bubble were measured. The same measurement was performed for all the bubbles present within the predetermined area. The aspect ratio of the bubble was calculated as the length in the direction perpendicular to the thickness direction ÷ the length in the thickness direction, and the same calculation was performed for all the bubbles and averaged to obtain the "aspect ratio of the bubbles in the resin foam".

[0118] (6) Melt tension The recycled resin contained in the resin foam was extruded in a molten strand shape at a temperature 20 °C higher than the melting point of the recycled resin and an orifice diameter of 1 mmφ using a twin-capillary rheometer "RH7-2 type" (manufactured by Rosand Precision) at an extrusion speed of 8.8 mm / min, and the strand was pulled at a take-up speed of 0.5 m / min. The take-up speed was increased by 0.1 m / min each time, and the melt tension when the strand-shaped resin broke was defined as the "melt tension".

[0119] (7) Die swell ratio Using an extensional viscometer (trade name: "RH-7", manufactured by Malvern) as the measuring instrument, a sample (size: 5 mm square) was placed into a cylinder at a temperature 20 °C higher than the melting point of the resin constituting the resin foam, and melted over 7 minutes. Then, the melt was extruded through a die with a length of 10 mm and a diameter of 1 mm φ at a shear rate of 20 mm / s, and the diameter of the resulting string-shaped molded product was measured using a digital caliper (trade name: "CD67-s PM", manufactured by Mitutoyo Corporation), and the die swell ratio was calculated from the following formula. Die swell ratio = diameter of molded product (mm) / die diameter (mm) As the above samples, recycled resin contained in the resin foam and resin composition for forming the resin foam were used, and the die swell ratio was measured for these samples.

[0120] (8) CO derived from raw materials 2 Generation amount [kg / m 2 When manufacturing petroleum-derived resin (non-recycled resin), the CO 2 generation amount is 1.8 kg / kg-resin, and when manufacturing recycled resin, the CO 2 generation amount is 0 kg / kg-resin. When the weight of petroleum-derived resin (non-recycled resin) contained in 1 m 2 of the foam is wp and the weight of recycled resin is wb, the CO 2 generation amount derived from the raw materials of the foam can be calculated as 1.8 × wp + 0 × wb.

[0121] (9) Punching processability ​The resin foam was punched using a mold (two cutting blades (product name "NCA07", thickness 0.7 mm, blade angle 43°, manufactured by Nakayama Corporation)) to a size of 10 mm x 10 mm in the MD direction (flow direction) and TD direction (direction perpendicular to the flow direction), respectively, and the cross section in the MD direction and the TD direction with the larger thickness change was observed with a microscope (product name "VHX-2000", manufactured by Keyence Corporation), and the thickness of the end and center were measured from the image. The measured thickness was used to calculate the thickness recovery rate after processing using the following formula. The larger the thickness recovery rate, the smaller the shape change due to punching and the better the punching processability. Thickness recovery rate after processing (%) = 100 x (1 - (center thickness - edge thickness) / center thickness)

[0122] (10) Thickness recovery rate (instantaneous recovery rate) Resin foam, 1000g / cm 2 The load was applied and maintained for 120 seconds, the compression was released, and the thickness of the resin foam 0.5 seconds after the release (thickness 0.5 seconds after the compressed state was released) was measured. The thickness recovery rate (instantaneous recovery rate) was calculated from the "thickness 0.5 seconds after the compressed state was released" and the thickness of the resin foam before the load was applied (initial thickness) according to the following formula. Thickness recovery rate (%) = {(thickness 0.5 seconds after releasing the compression state) / (initial thickness)} x 100

[0123] (11) Damage to the carrier tape after processing A resin foam (width: 10 mm × length: 120 mm) was stored for 24 hours or more under an atmosphere of temperature: 23±2°C and humidity: 50±5RH% (pretreatment conditions conforming to JIS Z 0237), and then fixed to a SUS plate using a double-sided adhesive tape (product name "No. 5603", manufactured by Nitto Denko Corporation) with a width of 10 mm × length of 120 mm, and pressed with a 2 kg roller once back and forth so that the opposite side of the resin foam was in contact with the adhesive layer surface of a weak adhesive carrier tape (product name "3165S", manufactured by Kern Instruments), and left for 24 hours to prepare a measurement sample. The above carrier tape was quickly peeled off by hand, and the peeled state was visually confirmed to evaluate whether or not the foam adhered to the surface of the carrier tape. In Table 1, when there was no adhesion of the foam to the surface of the carrier tape, it was described as "○", when fragments of the foam were observed, it was "△", and when interfacial failure of the foam was observed, it was "×".

[0124] (12) Interfacial strength After storing a resin foam (width: 20 mm × length: 120 mm) in an atmosphere at a temperature of 23 ± 2°C and a humidity of 50 ± 5 RH% for 24 hours or more (the pretreatment conditions conform to JIS Z 0237), it was fixed to a SUS plate using a double-sided adhesive tape (product name "No. 5000NS", manufactured by Nitto Denko Corporation) with a width of 20 mm × length of 120 mm, and a double-sided adhesive tape (product name "No. 5000NS", manufactured by Nitto Denko Corporation) was pressure-bonded to the opposite surface under the conditions of a 2 kg roller and one reciprocation, and left for 30 minutes to obtain a measurement sample. Using the above sample, it was peeled off at a peeling angle of 90° at a speed of 300 mm / min using a tensile testing machine, and the strength at the time when the resin foam was broken was measured.

[0125] (13) Impact absorbency On an impact force sensor, a resin foam, a double-sided tape (product number: No. 5603W, manufactured by Nitto Denko Corporation), and a PET film (product number: Diafoil MRF75, manufactured by Mitsubishi Plastics) were arranged in this order to form a test piece. An iron ball of 66 g was dropped onto the test piece from a height of 50 cm above the PET film, and the impact force F1 was measured. Also, the iron ball was dropped directly onto the impact force sensor as described above, and the blank impact force F0 was measured. From F1 and F0, the impact absorbency (%) was calculated by the formula (F0 - F1) / F0 × 100.

[0126] [Example 1] [Preparation of Composition for Polyolefin-Based Resin Foam (Virgin Pellets)] Polypropylene (propylene homopolymer, MFR: 0.4 g / 10 min (230°C, load 21.2 N), density: 0.90 g / cm 3, ethylene content: 0 wt%, propylene content: 100 wt%, weight-average molecular weight: 645,000, molecular weight distribution: 8.43) 50 parts by weight, polyolefin-based elastomer (melt tension at 230 °C: 16 cN) 50 parts by weight, magnesium hydroxide (trade name "KISUMA 5P", manufactured by Kyowa Chemical Industry Co., Ltd.) 10 parts by weight, carbon (trade name "Asahi #35", manufactured by Asahi Carbon Co., Ltd.) 10 parts by weight, and monoglyceride stearate 1 part by weight were kneaded in a twin-screw kneader manufactured by Japan Steel Works, Ltd. at a cylinder temperature of 200 °C to obtain a composition for a polyolefin-based resin foam. This composition was extruded into strands, and after water cooling, it was formed into cylindrical pellets with a cross-sectional radius of 2 mm and a height of 4 mm to obtain virgin pellet A. [Preparation of Polyolefin-Based Resin Foam] Virgin pellet A was charged into a single-screw extruder manufactured by JSW, and carbon dioxide was injected at a pressure of 13 (12 after injection) MPa in an atmosphere of 220 °C. Carbon dioxide was injected at 5 wt% of the polymer component of the composition for polyolefin-based resin foam. After sufficient saturation with carbon dioxide, it was extruded from the die to obtain a polyolefin-based resin foam. [Preparation of Recycled Resin Pellets] The waste foam (the skin layer part of the foam and the unnecessary part after punching) recovered in the above polyolefin-based resin foam manufacturing process was made into recycled pellets using a crusher-integrated short-screw extruder manufactured by Hagiwara Industry Co., Ltd. Specifically, the waste foam was charged into the hopper of a crusher equipped with a single-screw shredder using a nip-type feed roll with a speed adjustment mechanism, and was pressed against the single-screw shredder by a slider installed in the hopper and shredded. The shredded waste foam was fed into the extruder by a feed flight installed on the shredder extension, melted at a cylinder temperature of 180 °C and a screw rotation speed of 130 rpm. The melted waste foam was removed of foreign matter by a screen mesh (#60) provided at the extruder outlet, and then fed into a hot-cut pelletizer through the nozzle holes of a circular die, and formed into cylindrical pellets with a cross-sectional radius of 2 mm and a height of 4 mm to obtain recycled resin pellet B. [Preparation of Resin Foam Containing Recycled Resin] Polypropylene (propylene homopolymer, MFR: 0.4 g / 10 min (230 °C, load 21.2 N), density: 0.90 g / cm 3 , ethylene content: 0 wt%, propylene content: 100 wt%, weight average molecular weight: 645000, molecular weight distribution: 8.43) 31 parts by weight, recycled resin pellet B (MFR: 4.0 g / 10 min (230 °C, load 21.2 N) 55 parts by weight, polyolefin-based elastomer (melt flow rate (MFR): 15 g / 10 min, JIS A hardness: 79°) 10 parts by weight, polyolefin-based elastomer (melt flow rate (MFR): 2.2 g / 10 min, JIS A hardness: 69°) 4 parts by weight, magnesium hydroxide (trade name "KISUMA 5P" manufactured by Kyowa Chemical Industry Co., Ltd.) 5 parts by weight, carbon (trade name "Asahi #35" manufactured by Asahi Carbon Co., Ltd.) 10 parts by weight, and monoglyceride stearate 1 part by weight were kneaded at a temperature of 200 °C using a twin-screw kneader manufactured by Japan Steel Works, Ltd. (JSW), then extruded into strands, and formed into pellets after water cooling. These pellets were charged 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 176 °C. The carbon dioxide gas was injected at a ratio of 5.2 parts by weight per 100 parts by weight of the resin. After sufficiently saturating the carbon dioxide gas, it was cooled to a temperature suitable for foaming and then extruded from the die to obtain a sheet-shaped resin foam. Furthermore, it was thinned using a slicer to obtain a resin foam A with a thickness of 1.0 mm. The obtained resin foam A was subjected to the above evaluation. The results are shown in Table 1.

[0127] 〔Example 2〕 Polypropylene (propylene homopolymer, MFR: 0.4 g / 10 min (230 °C, load 21.2 N), density: 0.90 g / cm 3, ethylene content: 0 wt%, propylene content: 100 wt%, weight average molecular weight: 645000, molecular weight distribution: 8.43) 26 parts by weight, recycled resin pellet B (MFR: 4.0 g / 10 min (230 °C, load 21.2 N)) 55 parts by weight, polyolefin elastomer (melt flow rate (MFR): 15 g / 10 min, JIS A hardness: 79°) 17 parts by weight, polyolefin elastomer (melt flow rate (MFR): 2.2 g / 10 min, JIS A hardness: 69°) 7.3 parts by weight, magnesium hydroxide (trade name "KISUMA 5P", manufactured by Kyowa Chemical Industry Co., Ltd.) 5 parts by weight, carbon (trade name "Asahi #35", manufactured by Asahi Carbon Co., Ltd.) 10 parts by weight, and monoglyceride stearate 1 part by weight were kneaded at a temperature of 200 °C using a twin-screw kneader manufactured by Japan Steel Works, Ltd. (JSW), then extruded into strands, and formed into pellets after water cooling. These pellets were put 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 174 °C. The carbon dioxide gas was injected at a ratio of 4.8 parts by weight per 100 parts by weight of the resin. After sufficiently saturating the carbon dioxide gas, it was cooled to a temperature suitable for foaming and then extruded from the die to obtain a sheet-shaped resin foam. Furthermore, it was thinned using a slicer to obtain a resin foam B with a thickness of 1.0 mm. The obtained resin foam B was subjected to the above evaluation. The results are shown in Table 1.

[0128] 〔Example 3〕 Polypropylene (propylene homopolymer, MFR: 0.4 g / 10 min (230 °C, load 21.2 N), density: 0.90 g / cm 3, ethylene content: 0 wt%, propylene content: 100 wt%, weight average molecular weight: 645000, molecular weight distribution: 8.43) 18 parts by weight, recycled resin pellet B (MFR: 4.0 g / 10 min (230 °C, load 21.2 N)) 55 parts by weight, polyolefin elastomer (melt flow rate (MFR): 15 g / 10 min, JIS A hardness: 79°) 22.5 parts by weight, polyolefin elastomer (melt flow rate (MFR): 2.2 g / 10 min, JIS A hardness: 69°) 9.6 parts by weight, magnesium hydroxide (trade name "KISUMA 5P", manufactured by Kyowa Chemical Industry Co., Ltd.) 5 parts by weight, carbon (trade name "Asahi #35", manufactured by Asahi Carbon Co., Ltd.) 5 parts by weight, and monoglyceride stearate 1 part by weight were kneaded at a temperature of 200 °C using a twin-screw kneader manufactured by Japan Steel Works, Ltd. (JSW), then extruded into strands, and formed into pellets after water cooling. These pellets were put 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 173 °C. The carbon dioxide gas was injected at a ratio of 4.8 parts by weight per 100 parts by weight of the resin. After sufficiently saturating the carbon dioxide gas, it was cooled to a temperature suitable for foaming and then extruded from the die to obtain a sheet-shaped resin foam. Furthermore, it was thinned using a slicer to obtain a resin foam C with a thickness of 1.0 mm. The obtained resin foam C was subjected to the above evaluation. The results are shown in Table 1.

[0129] 〔Example 4〕 Polypropylene (propylene homopolymer, MFR: 0.4 g / 10 min (230 °C, load 21.2 N), density: 0.90 g / cm 3, ethylene content: 0 wt%, propylene content: 100 wt%, weight average molecular weight: 645,000, molecular weight distribution: 8.43) 31 parts by weight, recycled resin pellet B (MFR: 4.0 g / 10 min (230 °C, load 21.2 N)) 61 parts by weight, polyolefin-based elastomer (melt flow rate (MFR): 15 g / 10 min, JIS A hardness: 79°) 7 parts by weight, polyolefin-based elastomer (melt flow rate (MFR): 2.2 g / 10 min, JIS A hardness: 69°) 3 parts by weight, magnesium hydroxide (trade name "KISUMA 5P" manufactured by Kyowa Chemical Industry Co., Ltd.) 5 parts by weight, carbon (trade name "Asahi #35" manufactured by Asahi Carbon Co., Ltd.) 10 parts by weight, and monoglyceride stearate 1 part by weight were kneaded at a temperature of 200 °C using a twin-screw kneader manufactured by Japan Steel Works, Ltd. (JSW), then extruded into strands, and formed into pellets after water cooling. These pellets were charged 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 4.7 parts by weight per 100 parts by weight of the resin. After sufficiently saturating the carbon dioxide gas, it was cooled to a temperature suitable for foaming and then extruded from the die to obtain a sheet-shaped resin foam. Furthermore, it was thinned using a slicer to obtain a resin foam C with a thickness of 1.0 mm. The obtained resin foam C was subjected to the above evaluation. The results are shown in Table 1.

[0130] 〔Example 5〕 When producing the resin foam containing recycled resin, except that the foaming temperature was 167 °C and the injection amount of carbon dioxide gas was 3.5 parts by weight per 100 parts by weight of the resin, a resin foam was obtained in the same manner as in Example 4. Furthermore, it was thinned using a slicer to obtain a resin foam D with a thickness of 1.0 mm. The obtained resin foam D was subjected to the above evaluation. The results are shown in Table 1.

[0131] 〔Example 6〕 When producing a resin foam containing recycled resin, the foaming temperature was set to 170 °C, and the injection amount of carbon dioxide gas was set to 4.5 parts by weight with respect to 100 parts by weight of the resin. A resin foam was obtained in the same manner as in Example 4, except for the above. Furthermore, it was thinned using a slicer to obtain a resin foam E with a thickness of 1.0 mm. The obtained resin foam E was subjected to the above evaluation. The results are shown in Table 1.

[0132] [Example 7] Polypropylene (propylene homopolymer, MFR: 0.4 g / 10 min (230 °C, load 21.2 N), density: 0.90 g / cm 3 , ethylene content: 0 wt%, propylene content: 100 wt%, weight average molecular weight: 645000, molecular weight distribution: 8.43) 24 parts by weight, recycled resin pellet B (MFR: 4.0 g / 10 min (230 °C, load 21.2 N) 73 parts by weight, polyolefin-based elastomer (melt flow rate (MFR): 15 g / 10 min, JIS A hardness: 79°) 6 parts by weight, polyolefin-based elastomer (melt flow rate (MFR): 2.2 g / 10 min, JIS A hardness: 69°) 2 parts by weight, magnesium hydroxide (trade name "KISUMA 5P" manufactured by Kyowa Chemical Industry Co., Ltd.) 5 parts by weight, carbon (trade name "Asahi #35" manufactured by Asahi Carbon Co., Ltd.) 10 parts by weight, and monoglyceride stearate 1 part by weight were kneaded at a temperature of 200 °C using a twin-screw kneader manufactured by Japan Steel Works, Ltd. (JSW), then extruded into strands, and formed into pellets after water cooling. These pellets were put 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. The carbon dioxide gas was injected at a ratio of 4 parts by weight with respect to 100 parts by weight of the resin. After sufficiently saturating the carbon dioxide gas, it was cooled to a temperature suitable for foaming and then extruded from the die to obtain a sheet-shaped resin foam. Furthermore, it was thinned using a slicer to obtain a resin foam F with a thickness of 1.0 mm. The obtained resin foam F was subjected to the above evaluation. The results are shown in Table 1.

[0133] [Example 8] When producing the resin foam containing recycled resin, the foaming temperature was set at 170 °C, and the injection amount of carbon dioxide gas was set at a ratio of 3.9 parts by weight with respect to 100 parts by weight of the resin. Otherwise, in the same manner as in Example 7, a resin foam was obtained. Furthermore, it was thinned using a slicer to obtain a resin foam G with a thickness of 1.0 mm.

[0134] [Comparative Example 1] [Production of Composition for Polyolefin-based Resin Foam (Virgin Pellets)] 45 parts by weight of polypropylene (melt tension at 230 °C is 25 cN), 45 parts by weight of polyolefin-based elastomer (melt tension at 230 °C is 16 cN), 10 parts by weight of polyethylene, 1 part by weight of monoglyceryl stearate, 10 parts by weight of magnesium hydroxide, and 10 parts by weight of carbon were kneaded at a cylinder temperature of 200 °C using a twin-screw kneader manufactured by Japan Steel Works, Ltd. to obtain a composition for polyolefin-based resin foam. This composition was extruded into strands and formed into cylindrical pellets with a cross-sectional radius of 2 mm and a height of 4 mm after water cooling to obtain virgin pellets C. [Production of Polyolefin-based Resin Foam] Virgin pellets C were put into a single-screw extruder manufactured by JSW, and carbon dioxide was injected at a pressure of 13 (12 after injection) MPa in an atmosphere of 220 °C. Carbon dioxide was injected at 5% by weight of the polymer component of the composition for polyolefin-based resin foam. After sufficiently saturating with carbon dioxide, it was extruded from the die to obtain a polyolefin-based resin foam. [Production of Recycled Resin Pellets] From the waste foam recovered in the above polyolefin-based resin foam manufacturing process, recycled resin pellets D were produced by the method described in Example 1. [Production of Resin Foam Containing Recycled Resin] To 90 parts by weight of virgin pellet C, 23 parts by weight of recycled resin pellet D was blended, and the mixture was charged into a short-axis extruder manufactured by Japan Steel Works, Ltd. Carbon dioxide was injected at a pressure of 13 (12 after injection) MPa in an atmosphere of 220°C. Carbon dioxide was injected at 5% by weight of the polymer component of the resin pellets. After sufficient saturation of the gas, it was extruded from the die to obtain a recycled resin-containing polyolefin-based resin foam. Furthermore, it was made into a thin film using a slicer to obtain a resin foam H with a thickness of 1.0 mm.

[0135] [Comparative Example 2] Polypropylene (propylene homopolymer, MFR: 0.4 g / 10 min (230°C, load 21.2 N), density: 0.90 g / cm 3 , ethylene content: 0% by weight, propylene content: 100% by weight, weight average molecular weight: 645000, molecular weight distribution: 8.43) 50 parts by weight, polyolefin-based elastomer (melt tension at 230°C is 16 cN) 50 parts by weight, magnesium hydroxide (trade name "KISUMA 5P" manufactured by Kyowa Chemical Industry Co., Ltd.) 10 parts by weight, carbon (trade name "Asahi #35" manufactured by Asahi Carbon Co., Ltd.) 10 parts by weight, and monoglyceride stearate 1 part by weight were kneaded at a temperature of 174°C using a twin-screw kneader manufactured by Japan Steel Works, Ltd. (JSW), and then extruded into strands and formed into pellets after water cooling. These pellets were charged 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 of 220°C. Carbon dioxide gas was injected at a ratio of 5.2 parts by weight per 100 parts by weight of the resin. After sufficient saturation of the carbon dioxide gas, 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 made into a thin film using a slicer to obtain a resin foam I with a thickness of 1.0 mm. The obtained resin foam was subjected to the above evaluation. The results are shown in Table 1.

[0136] [Comparative Example 3] A resin foam was obtained in the same manner as in Example 7, except that the foaming temperature was 169°C and the injection amount of carbon dioxide gas was 3.5 parts by weight per 100 parts by weight of the resin during the production of the resin foam. Furthermore, it was thinned using a slicer to obtain a resin foam J with a thickness of 1.0 mm.

[0137]

Table 1

Industrial Applicability

[0138] The resin foam of the present invention can be suitably used, for example, as a cushioning material for electronic devices.

Explanation of Reference Numerals

[0139] 100 Foaming member 10 Resin foam layer (resin foam) 20 Adhesive layer

Claims

1. It has a cellular structure, Satisfying the following formula (1): Interlaminar strength (N / 20 mm) > apparent density (g / cm ３ ) × 40 + 3 ... (1) Resin foam.

2. Apparent density: 0.4 g / cm ３ The resin foam according to claim 1 , wherein:

3. The resin foam according to claim 1, having an interlaminar strength of 3 N / 20 mm or more.

4. The resin foam according to claim 1 , having an average cell diameter of 50 μm or more.

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

6. The resin foam has a weight per unit area of ​​1000 g / cm ２ The resin foam according to claim 1, having a thickness recovery rate of 80% or more after maintaining a load of 1.0 mm for 120 seconds.

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

8. The resin foam contains recycled resin, and the recycled resin ratio in the resin foam is 0.2 or more; Satisfying the following formula (2): Apparent density (g / cm ３ ) < 0.046 × recycled resin ratio + 0.0121 ... (2) The resin foam according to claim 1 .

9. The resin foam according to claim 8 , wherein the recycled resin contains a polyolefin.

10. The resin foam according to claim 9, wherein the polyolefin as the recycled resin has a melt flow rate (MFR) at a temperature of 230°C of less than 10 g / 10 min.

11. The resin foam according to claim 9, wherein the polyolefin as the recycled resin has a melt tension of 10 cN or more.

12. The resin foam according to claim 9, wherein the polyolefin as the recycled resin has a die swell ratio of 1.5 or less at a melting point +20°C of the recycled resin.

13. The resin foam according to claim 9 , wherein the polyolefin is polyethylene or polypropylene.

14. The resin foam according to claim 9 , wherein the polyolefin is a mixture of a polyolefin other than a polyolefin-based elastomer and a polyolefin-based elastomer.

15. The resin foam according to claim 1 , wherein the resin composition forming the resin foam has a die swelling ratio of 1.5 or less at a melting point +20° C. of the resin composition.

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

17. A pressure-sensitive adhesive layer is provided on at least one side of the resin foam layer. The resin foam layer is the resin foam according to any one of claims 1 to 16. Foam material.

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