Resin foam and foamed member

Abstract

Provided is a resin foam body that has high stress distributing capabilities and excellent heat resistance. A resin foam body according to the present invention has a cellular structure, an apparent density of 0.05 g / cm3 to 0.50 g / cm3, a 50% compression load of 2.0 N / cm2 to 30 N / cm2, and satisfies the relationship in formula (1) between the apparent density D (g / cm3) and the residue R (%) at 650°C. (1): 1 ≤ {(100-R) / D} / 100 ≤ 10

Description

Technical Field

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

Background Art

[0002] Foams are used for the purpose of protecting members such as batteries and substrates of mobile devices. However, in recent years, with the increase in processing speed due to high-capacity data communication, combined use of applications, etc., each member tends to generate heat easily. Therefore, the above-mentioned foam is required to withstand long-term use at high temperatures.

[0003] As a method of forming a foam having excellent heat resistance, a method of forming a foam using a resin having a high melting point (for example, 150 ° C or higher) can be considered. However, when a chemical blowing agent (for example, a thermal decomposition type blowing agent) is added to impart foamability, foaming may occur at the molding temperature of the high melting point resin, and it is difficult to obtain a foam using the high melting point resin.

[0004] On the other hand, regarding the size of the clearance of the portion where the foam is used, in recent years, it has been required to cope with a smaller clearance. In addition, when the foam is applied to a mobile device, unexpected loads are likely to be applied to each member due to dropping of the device or external pressure load. Therefore, if such a load can be effectively stress-dispersed, the impact can be absorbed and the destruction of the electronic device due to an unexpected load can be prevented. For this reason, there is a demand for a foam that can cope with a smaller clearance and has a higher level of stress dispersibility.

[0005] As a method of obtaining a foam without using a chemical foaming agent, a method has been studied in which an inert gas is dissolved in a polymer under high pressure and then the pressure is rapidly decreased to form a foamed structure. For example, Patent Document 1 discloses a method in which a thermoplastic polymer is charged into a pressure vessel, a high-pressure gas is charged while heating to the softening point of the polymer, and then the pressure is decreased to form bubbles. However, although the foam of Patent Document 1 has a certain degree of flexibility, it does not have heat resistance. Further, Patent Document 1 does not disclose or suggest anything about the stress dispersibility (impact absorbency) of the foam.

[0006] Also, Patent Document 2 discloses a method of imparting heat resistance to a polyolefin-based foam by selecting a polyolefin resin and a thermoplastic elastomer having a specific melting point. However, Patent Document 2 does not disclose or suggest anything about the stress dispersibility (impact absorbency) of the foam.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] An object of the present invention is to provide a resin foam having high stress dispersibility and excellent heat resistance.

Means for Solving the Problems

[0009] The resin foam of the present invention is a resin foam having a cellular structure, having an apparent density of 0.05 g / cm 3 ~0.50 g / cm 3 and a 50% compression load of 2.0 N / cm 2 ~30 N / cm 2and the apparent density D (g / cm 3 ), and the residue R (%) at 650 °C satisfy the relationship of the following formula (1). 1 ≦ {(100 - R) / D} / 100 ≦ 10 ···(1). In one embodiment, the average bubble diameter of the above bubbles is 10 μm to 200 μm. In one embodiment, the coefficient of variation of the bubble diameter of the above bubbles is 0.5 or less. In one embodiment, the porosity in the above bubble structure is 30% or more. In one embodiment, the thickness of the bubble wall in the above bubble structure is 0.1 μm to 10 μm. In one embodiment, the tensile elastic modulus of the above resin foam at 23 °C is 0.6 MPa or more. In one embodiment, the stress retention of the above resin foam is 60% or more. In one embodiment, the above resin foam contains a filler. In one embodiment, the above filler is an inorganic substance. In one embodiment, the above filler is an organic substance. In one embodiment, the resin constituting the above resin foam is a polyolefin-based resin. In one embodiment, the above polyolefin-based resin is a mixture of polypropylene other than polyolefin-based elastomer and polyolefin-based elastomer. In one embodiment, the above resin foam has a heat-melt layer on one side or both sides. According to another aspect of the present invention, a foamed member is provided. This foamed member includes a resin foam layer composed of the above resin foam, and an adhesive layer disposed on at least one side of the resin foam layer.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a resin foam having high stress dispersibility and excellent heat resistance.

Brief Description of the Drawings

[0011]

Figure 1

Embodiments for Carrying Out the Invention

[0012] ≪≪1. Resin Foam≫≫ The resin foam of the present invention has a cell structure, and the apparent density is 0.05 g / cm 3 ~0.50 g / cm 3 and the 50% compression load is 2.0 N / cm 2 ~30 N / cm 2 and the apparent density D (g / cm 3 ) and the residue R (%) at 650 °C satisfy the relationship of the following formula (1). 1 ≦ {(100 - R) / D} / 100 ≦ 10 ···(1) In this specification, the residue R means the residue at 650 °C when the resin foam is heated from 25 °C to 680 °C at a heating rate of 20 °C / min in a nitrogen gas atmosphere. The residue R can be measured, for example, using the product name "TG / DTA6200" manufactured by SII NanoTechnology Inc.

[0013] Due to the above configuration, the resin foam of the present invention has high stress dispersibility and heat resistance. In addition, the resin foam of the present invention is also excellent in flexibility. Since the resin foam of the present invention has high stress dispersibility, it can exhibit excellent shock absorbency even in a place with a narrow clearance. In addition, the above resin foam excellent in heat resistance can be suitably used as a protective member in devices that tend to become hot, such as high-performance mobile devices.

[0014] The apparent density of the resin foam of the present invention is preferably 0.06 g / cm 3 ~0.45 g / cm 3 more preferably 0.07 g / cm 3 ~0.40 g / cm 3 even more preferably 0.08 g / cm 3 ~0.35 g / cm 3It is like this. Within such a range, a resin foam excellent in stress dispersibility can be obtained. The method for measuring the apparent density will be described later.

[0015] The 50% compression weight of the resin foam of the present invention is preferably 2.5 N / cm 2 ~25 N / cm 2 and more preferably 3.0 N / cm 2 ~20 N / cm 2 and even more preferably 3.5 N / cm 2 ~15 N / cm 2 It is like this. Within such a range, a resin foam excellent in stress dispersibility can be obtained. The method for measuring the apparent density will be described later.

[0016] As described above, the apparent density D (g / cm 3 ) and the residue R (%) at 650 °C satisfy the relationship of the following formula (1). 1 ≤ {(100 - R) / D} / 100 ≤ 10 ···(1) Preferably, the apparent density D (g / cm 3 ) and the residue R (%) at 650 °C satisfy the relationship of the following formula (2). More preferably, the apparent density D (g / cm 3 ) and the residue R (%) at 650 °C satisfy the relationship of the following formula (3). Even more preferably, the apparent density D (g / cm 3 ) and the residue R (%) at 650 °C satisfy the relationship of the following formula (4). If the apparent density D and the residue R are in such a relationship, a resin foam in which high stress dispersibility and heat resistance are highly compatible can be obtained. 2 ≤ {(100 - R) / D} / 100 ≤ 9.5 ···(2) 3 ≤ {(100 - R) / D} / 100 ≤ 8.5 ···(3) 3.5 ≤ {(100 - R) / D} / 100 ≤ 8 ···(4)

[0017] The residue R of the resin foam of the present invention at 650 °C is preferably 10% by weight or more, more preferably 15% by weight or more, still more preferably 20% by weight or more, particularly preferably 25% by weight, and most preferably 35% by weight or more. If it is in such a range, a resin foam having particularly excellent heat resistance can be obtained. The upper limit of the residue R is, for example, 80% by weight, and in one embodiment, it is 60% by weight. In one embodiment, the residue R may be an inorganic component (for example, an inorganic filler) contained in the resin foam.

[0018] The resin foam of the present invention has a cell structure (bubble structure). Examples of such a cell structure (bubble structure) include a closed-cell structure, an open-cell structure, and a semi-continuous semi-closed-cell structure (a bubble structure in which a closed-cell structure and an open-cell structure coexist). The cell structure of the resin foam of the present invention is preferably an open-cell structure or a semi-continuous semi-closed-cell structure, and more preferably a semi-continuous semi-closed-cell structure. When the cell structure of the resin foam of the present invention is a semi-continuous semi-closed-cell structure, the proportion of the closed-cell structure therein is preferably 40% or less, and more preferably 30% or less.

[0019] The closed-cell ratio of the resin foam of the present invention is determined, for example, by immersing the measurement object in water in an environment of a temperature of 23 °C and a humidity of 50%, measuring the subsequent mass, and then measuring the mass again after sufficiently drying it in an oven at 80 °C. In addition, since an open-cell structure can retain moisture, the mass fraction thereof is measured and determined as an open-cell structure.

[0020] The average cell diameter (average bubble diameter) of the above-mentioned bubbles is preferably 10 μm to 200 μm, more preferably 15 μm to 180 μm, still more preferably 20 μm to 150 μm, particularly preferably 23 μm to 120 μm, and particularly preferably 25 μm to 100 μm. If it is in such a range, a resin foam having more excellent flexibility and stress dispersibility can be obtained. In addition, a resin foam having excellent compression recovery and excellent resistance to repeated impacts can be obtained. The method for measuring the average cell diameter will be described later.

[0021] The coefficient of variation of the bubble diameter (cell diameter) of the above-mentioned bubbles is preferably 0.5 or less, more preferably 0.48 or less, still more preferably 0.45 or less, particularly preferably 0.43 or less, and most preferably less than 0.4. If it is within such a range, deformation due to impact becomes uniform, local stress loading is prevented, the stress dispersion property is excellent, and a resin foam having particularly excellent impact resistance can be obtained. The smaller the coefficient of variation, the more preferable, but the lower limit thereof is, for example, 0.2 (preferably 0.15, more preferably 0.1, still more preferably 0.01). The method for measuring the coefficient of variation of the bubble diameter will be described later.

[0022] The cell ratio of the above-mentioned cell structure is preferably 30% or more, more preferably 50% or more, still more preferably 80% or more. If it is within such a range, a resin foam having a small rebound stress during compression can be obtained. Such a resin foam can reduce the stress applied to other members when the resin foam is slightly compressed and applied to a location with a narrow clearance. For example, when the resin foam is applied to a display member, the stress applied to the display member can be relaxed and dispersed, which is useful from the viewpoints of reducing color unevenness and protecting the member. The upper limit of the cell ratio is, for example, 99% or less. The method for measuring the cell ratio will be described later.

[0023] The thickness of the cell wall in the above-mentioned cell structure is preferably 0.1 μm to 10 μm, more preferably 0.3 μm to 8 μm, still more preferably 0.5 μm to 5 μm, particularly preferably 0.7 μm to 4 μm, and most preferably 1 μm to 3 μm. If it is within such a range, a resin foam having more excellent flexibility and stress dispersion property can be obtained. If the thickness of the cell wall is too thin, the resin foam may easily deform under a load, and there is a possibility that a sufficient stress dispersion effect cannot be obtained. If the thickness of the cell wall is too thick, the resin foam becomes difficult to deform under a load, and there is a possibility that the step following property deteriorates when used in the gap of a device. 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.

[0024] The elongation at break of the resin foam of the present invention at 23°C is preferably 120% or less, more preferably 110% or less, still more preferably 105% or less, even more preferably 100% or less, particularly preferably 95% or less, and most preferably 90% or less. If it is within such a range, a resin foam excellent in stress dispersibility and excellent in impact absorbability even in a thin form can be obtained. When the elongation at break in the tensile test is small, when a load is applied to the resin foam, the deformation of the cell wall of the resin foam becomes small. For example, when a filler is added, slippage easily occurs at the interface between the resin constituting the resin foam and the filler, and the load can be more effectively relaxed. The lower limit of the above elongation at break is preferably 1% or more, more preferably 5% or more, still more preferably 10% or more, particularly preferably 15% or more, and most preferably 20% or more. On the other hand, if the elongation at break in the tensile test is too large, the deformation of the cell wall of the resin foam becomes large, and there is a possibility that it becomes difficult to relax the load. The elongation at break can be measured in accordance with JIS K 6767.

[0025] The dimensional change rate when the above resin foam is placed in an environment of 120°C for 500 hours is preferably 1% or less, more preferably 0.8% or less. The smaller the dimensional change rate, the more preferable it is, but the lower limit is realistically 0.1% (preferably 0.05%). The measuring method of the above dimensional change rate will be described later.

[0026] The tensile elastic modulus of the above resin foam at 23°C is preferably 0.6 MPa or more, more preferably 0.7 MPa to 5 MPa, still more preferably 1 MPa to 4 MPa. If it is within such a range, a resin foam excellent in stress dispersibility and capable of exhibiting excellent impact absorbability even in a thin film can be obtained. The measuring method of the above tensile elastic modulus will be described later.

[0027] The stress retention of the above resin foam is preferably 60% or more, more preferably 63% to 100%, and still more preferably 63% to 95%. Within such a range, a resin foam with excellent stress dispersion and capable of exhibiting excellent shock absorption even in a thin film can be obtained. In this specification, the above stress retention refers to the ratio (tensile strength after holding for 120 seconds / tensile strength immediately after stretching × 100) of the tensile strength immediately after stretching and the tensile strength after holding for 120 seconds when the resin foam (width 10 mm × length 100 mm) is stretched by 20% at a speed of 300 m / min in the length direction.

[0028] As the shape of the resin foam of the present invention, any appropriate shape can be adopted according to the purpose. Such shapes typically include a sheet shape, and in this case, the resin foam of the present invention can be treated as a resin foam layer.

[0029] When the shape of the resin foam of the present invention is sheet-like (i.e., in the case of a resin foam layer), its thickness is preferably 30 μm to 5000 μm, more preferably 35 μm to 4000 μm, still more preferably 40 μm to 3000 μm, and particularly preferably 45 μm to 2500 μm. The resin foam of the present invention can exhibit excellent shock absorption even if it is thin. Such a resin foam can be suitably used as a protective material applied to a minute clearance.

[0030] The resin foam of the present invention may have a heat-melt layer on one or both of its sides. 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) 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.

[0031] The resin foam of the present invention can be formed by any appropriate 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).

[0032] ≪1-1. Resin Composition≫ The resin foam of the present invention contains any suitable resin. The resin foam can typically be obtained by foaming a composition containing a resin (resin composition).

[0033] As the resin constituting the resin foam (that is, the resin contained in the resin composition), any suitable resin can be used as long as the effects of the present invention are not impaired. Examples of such resins include acrylic resins, silicone resins, urethane resins, polyolefin resins, ester resins, rubber resins, and the like. The resin may be only one kind or two or more kinds.

[0034] The content ratio of the resin 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, based on 100 parts by weight of the resin foam.

[0035] In one embodiment, the resin foam contains a polyolefin resin. The polyolefin resin may be only one kind or two or more kinds.

[0036] The content ratio of the polyolefin 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, and particularly preferably 95 to 100 parts by weight, based on 100 parts by weight of the resin foam.

[0037] The polyolefin resin preferably includes at least one selected from the group consisting of polyolefins and polyolefin-based elastomers, and more preferably, a form in which a polyolefin and a polyolefin-based elastomer are used in combination. The polyolefin may be only one kind or two or more kinds. The polyolefin-based elastomer may be only one kind or two or more kinds. In this specification, when referring to "polyolefin", "polyolefin-based elastomer" is not included.

[0038] When using polyolefin and polyolefin-based elastomer in combination as the polyolefin-based resin, the content ratio of polyolefin and 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 terms of weight ratio.

[0039] As the polyolefin, any suitable polyolefin can be adopted 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.

[0040] Examples of such polyolefins include polymers composed of α-olefins, that is, polymers having at least structural units derived from α-olefins in one molecule. Such polyolefins may be polymers composed only of α-olefins or polymers composed of α-olefins and monomer components other than α-olefins.

[0041] The polyolefin may be a homopolymer or a copolymer containing two or more monomers. When the polyolefin is a copolymer, any suitable copolymerization form can be adopted. Examples of such copolymerization forms include random copolymers and block copolymers.

[0042] Examples of the α-olefins that can constitute the polyolefin preferably include α-olefins having 2 to 8 carbon atoms (such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, etc.). The α-olefins that can constitute the polyolefin may be only one kind or two or more kinds.

[0043] Examples of monomer components other than α-olefins that can constitute polyolefins include ethylenically unsaturated monomers such as vinyl acetate, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, and vinyl alcohol. The monomer component other than α-olefins that can constitute polyolefins may be only one kind or two or more kinds.

[0044] 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.

[0045] As polyolefins, in terms of being able to more effectively exhibit the effects of the present invention, preferably, polymers (polypropylene-based polymers) composed of propylene as an essential monomer component, that is, polymers having structural units derived from at least propylene. Examples of such polypropylene-based polymers include, for example, polypropylene (propylene homopolymer), copolymers of ethylene and propylene, copolymers of propylene and α-olefins other than propylene, and the like, and preferably polypropylene (propylene homopolymer). The polypropylene-based polymers may be only one kind or two or more kinds.

[0046] The melt flow rate (MFR) of the polyolefin at a temperature of 230°C is preferably from 0.2 g / 10 min to 10 g / 10 min, more preferably from 0.25 g / 10 min to 5 g / 10 min, still more preferably from 0.3 g / 10 min to 3 g / 10 min, and particularly preferably from 0.35 g / 10 min to 1.5 g / 10 min, in terms of more effectively expressing the effects of the present invention. The melt flow rate (MFR) of the polyolefin at a temperature of 230°C refers to the MFR measured at a temperature of 230°C and a load of 2.16 kgf based on ISO 1133 (JIS-K-7210).

[0047] As the polyolefin, in terms of more effectively expressing the effects of the present invention, it is preferable to use in combination two or more polyolefins having different melt flow rates (MFRs) within the above range at a temperature of 230°C. In this case, it is a combination of a polyolefin having a melt flow rate (MFR) at a temperature of 230°C preferably of 0.2 g / 10 min or more and less than 0.7 g / 10 min (more preferably from 0.2 g / 10 min to 0.65 g / 10 min) and a polyolefin having a melt flow rate (MFR) at a temperature of 230°C preferably of 0.7 g / 10 min to 10 g / 10 min (more preferably from 0.7 g / 10 min to 5 g / 10 min, still more preferably from 0.7 g / 10 min to 3 g / 10 min, particularly preferably from 0.7 g / 10 min to 1.5 g / 10 min, and most preferably from 0.7 g / 10 min to 1.3 g / 10 min).

[0048] As polyolefins, when two or more polyolefins having different melt flow rates (MFR) at a temperature of 230°C are used in combination, for example, the melt flow rate (MFR) at the above temperature of 230°C is preferably 0.2 g / 10 min or more and less than 0.7 g / 10 min (more preferably 0.2 g / 10 min to 0.65 g / 10 min), and the melt flow rate (MFR) at a temperature of 230°C is preferably 0.7 g / 10 min to 10 g / 10 min (more preferably 0.7 g / 10 min to 5 g / 10 min, still more preferably 0.7 g / 10 min to 3 g / 10 min, particularly preferably 0.7 g / 10 min to 1.5 g / 10 min, and most preferably 0.7 g / 10 min to 1.3 g / 10 min). The content ratio of these polyolefins is, in terms of weight ratio, preferably 1 / 99 to 99 / 1, more preferably 10 / 90 to 90 / 10, still more preferably 20 / 80 to 80 / 20, particularly preferably 30 / 70 to 70 / 30, and most preferably 40 / 60 to 60 / 40, in terms of being able to more effectively exhibit the effects of the present invention.

[0049] 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), etc. can be mentioned.

[0050] 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 domains, obtained by dynamically heat-treating a mixture containing a resin component A and a rubber component B in the presence of a crosslinking agent, which is a dynamically crosslinked thermoplastic olefin-based elastomer (TPV); and the like.

[0051] 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.

[0052] 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. From the viewpoint of compatibility, the weight ratio of the polyolefin component to the olefin-based rubber component is preferably 90 / 10 to 10 / 90, more preferably 80 / 20 to 20 / 80, as polyolefin component / olefin-based rubber.

[0053] The dynamically crosslinked thermoplastic olefin elastomer (TPV) generally has a higher elastic modulus and a smaller compression set than the non-crosslinked thermoplastic olefin elastomer (TPO). As a result, it has good recoverability and can exhibit excellent recoverability when used as a foam.

[0054] As described above, the dynamically crosslinked thermoplastic olefin elastomer (TPV) is obtained by dynamically heat-treating a mixture containing a resin component A (olefin resin component A) that forms a matrix and a rubber component B that forms domains in the presence of a crosslinking agent, and 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 that is the matrix (sea phase).

[0055] 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-Pub. No. 03 / 002654, and the like.

[0056] As the dynamically crosslinked thermoplastic olefin elastomer (TPV), commercially available products may be used, and examples include "Zeotherm" (manufactured by Nippon Zeon Co., Ltd.), "Thermolan" (manufactured by Mitsubishi Chemical Corporation), "Surlyn 3245D" (manufactured by Toyobo Co., Ltd.), and the like.

[0057] The melt flow rate (MFR) of the polyolefin-based elastomer at a temperature of 230°C is preferably 2 g / 10 min to 15 g / 10 min, more preferably 3 g / 10 min to 10 g / 10 min, still more preferably 3.5 g / 10 min to 9 g / 10 min, particularly preferably 4 g / 10 min to 8 g / 10 min, and most preferably 4.5 g / 10 min to 7.5 g / 10 min. The melt flow rate (MFR) of the polyolefin-based elastomer at a temperature of 230°C refers to the MFR measured at a temperature of 230°C and a load of 2.16 kgf based on ISO 1133 (JIS-K-7210).

[0058] The melt tension (at 190°C, at break) of the polyolefin-based elastomer is preferably less than 10 cN, more preferably 5 cN to 9.5 cN.

[0059] The JIS A hardness of the polyolefin-based elastomer is preferably 30° to 95°, more preferably 35° to 90°, still more preferably 40° to 88°, particularly preferably 45° to 85°, and most preferably 50° to 83°. The JIS A hardness refers to the hardness measured based on ISO 7619 (JIS K6253).

[0060] In one embodiment, the resin foam (i.e., the resin composition) may further contain a filler. By containing 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 absorbency. Also, by containing the filler, a fine and uniform cell structure can be formed, which is also advantageous in that excellent shock absorbency can be exhibited. The filler may be used alone or in combination of two or more.

[0061] The content ratio of the above-mentioned filler is preferably 10 to 150 parts by weight, more preferably 30 to 130 parts by weight, and still more preferably 50 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 will be remarkable.

[0062] In one embodiment, the above-mentioned filler is an inorganic substance. Examples of the material constituting the inorganic filler include aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, aluminum borate whisker, silicon nitride, boron nitride, crystalline silica, amorphous silica, metals (such as gold, silver, copper, aluminum, nickel), carbon, graphite, etc.

[0063] In one embodiment, the above-mentioned filler is an organic substance. Examples of the material constituting the organic filler include polymethyl methacrylate (PMMA), polyimide, polyamideimide, polyetheretherketone, polyetherimide, polyesterimide, etc.

[0064] A flame retardant may be used as the above-mentioned filler. 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.

[0065] 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.

[0066] The above filler may be subjected to any appropriate surface treatment. Examples of the surface treatment include silane coupling treatment, stearic acid treatment, and the like.

[0067] The bulk density of the above filler is preferably 0.8 g / cm 3 or less, more preferably 0.6 g / cm 3 or less, still more preferably 0.4 g / cm 3 or less, and particularly preferably 0.3 g / cm 3 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, 0.01 g / cm 3 and preferably 0.05 g / cm 3 and more preferably 0.1 g / cm 3 and is as follows.

[0068] 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. 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 analyzer (MicrtracII, Microtrac Bell Corporation) with a suspension prepared by mixing 1 g of the filler with 100 g of water as a sample.

[0069] The specific surface area of the above filler is preferably 2 m 2 / g or more, more preferably 4 m 2 / g or more, still more preferably 6 m 2is / g or more. 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, by adsorbing a molecule with a known adsorption occupation area on the filler surface at a low temperature using liquid nitrogen and measuring from the amount of adsorption.

[0070] The resin composition may contain any other appropriate 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 the polymers blended 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, cell 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.

[0071] ≪1-2. 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 cells), methods usually used in foam molding, such as physical methods and chemical methods, can be adopted. That is, the resin foam of the present invention 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 a gas component such as air or nitrogen in a polymer solution and forms cells by mechanical mixing (mechanical foam). The chemical method is generally a method of forming cells with the gas generated by the thermal decomposition of a foaming agent added to a polymer base to obtain a foam.

[0072] The above resin composition can be prepared, for example, by mixing the constituent components using any suitable means, 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., in any suitable melting and kneading apparatus.

[0073] <Embodiment 1 for forming the resin foam of the present invention> As one embodiment 1 for forming the resin foam of the present invention, for example, there is a form in which a resin foam is formed through a step (step A) of mechanically foaming an emulsion resin composition (an emulsion containing a resin material, etc.) to cause foaming. 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 the cell diameter and large-capacity production, a high-speed shear type device is preferable. This one embodiment 1 for forming the resin foam of the present invention is applicable to the formation from any resin composition.

[0074] 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.

[0075] The cells formed by mechanical stirring are those in which gas is 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 a gas include air, nitrogen, carbon dioxide, etc.

[0076] The resin foam of the present invention can be obtained by passing through a step (step B) of coating the emulsion resin composition foamed by the above method (the bubble-containing emulsion resin composition) on a substrate and drying it. Examples of the substrate include a peeled plastic film (a peeled polyethylene terephthalate film, etc.), a plastic film (a polyethylene terephthalate film, etc.).

[0077] In Process B, as the coating method and the drying method, any appropriate method can be adopted as long as the effects of the present invention are not impaired. Process B preferably includes a preliminary drying step B1 of drying the bubble-containing emulsion resin composition applied 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.

[0078] By providing the preliminary drying step B1 and the main drying step B2, it is possible to prevent the coalescence of bubbles and the rupture of bubbles due to a rapid temperature rise. In particular, in a foamed sheet with a small thickness, bubbles coalesce and rupture 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.

[0079] <Embodiment 2 for forming the resin foam of the present invention> As one embodiment 2 for forming the resin foam of the present invention, there is a form in which the 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 contamination to the foamable material, it is preferable to use a high-pressure inert gas.

[0080] 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, etc. 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.

[0081] The inert gas is preferably in a supercritical state. That is, it is particularly preferable to use carbon dioxide in a supercritical state. In the supercritical state, the solubility of the inert gas in the resin composition increases more, 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 is larger than in other states even when the porosity is the same. Thus, fine bubbles can be obtained. The critical temperature of carbon dioxide is 31°C, and the critical pressure is 7.4 MPa.

[0082] 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 the resin composition with an inert gas under high pressure, a pressure reduction step of reducing the pressure after this step to foam the resin, and a heating step of growing the bubbles by heating if necessary. In this case, the pre-formed unfoamed molded body may be impregnated with the inert gas, or the molten resin composition may be impregnated with the inert gas under pressure and then molded during pressure reduction. These steps may be carried out in either a batch system or a continuous system. That is, after the resin composition is pre-molded into an appropriate shape such as a sheet to form an unfoamed resin molded body, this unfoamed resin molded body may be impregnated with a high-pressure gas and foamed by releasing the pressure, which is a batch system, or the resin composition may be kneaded with a high-pressure gas under pressure, the pressure may be released simultaneously with molding, and molding and foaming may be carried out simultaneously, which is a continuous system.

[0083] An example of manufacturing a foam by a batch method is shown below. For example, a resin sheet for foam molding is produced by extruding a resin composition using an extruder such as a single-screw extruder or a twin-screw extruder. Alternatively, 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 an unfoamed resin molded body is produced by pressing it to a predetermined thickness using a hot plate press or the like. The unfoamed resin molded body thus obtained 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 and 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 to be foamed 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 to be foamed can be produced by other molding methods such as injection molding in addition to extrusion molding and press molding.

[0084] Examples of manufacturing a foam in a continuous manner are 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 (particularly 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 or the like provided at the tip of the extruder, and foam molding is performed by a molding depressurization step that simultaneously performs molding and foaming. Further, when performing 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. Further, the introduction of the high-pressure gas may be performed continuously or discontinuously. Furthermore, in the kneading impregnation step and the molding depressurization step, for example, an extruder or an injection molding machine can be used. In addition, 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 a shaped shape.

[0085] When foam molding a resin composition, the mixing amount of the gas is, in terms of obtaining a highly foamed foam, for example, preferably 2 parts by weight to 10 parts by weight, more preferably 2.5 parts by weight to 8 parts by weight, and even more preferably 3 parts by weight to 6 parts by weight with respect to 100 parts by weight of the resin composition.

[0086] When impregnating the resin composition with an inert gas, 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 addition, when using supercritical carbon dioxide, 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, 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. As a result, the gas amount per bubble increases conversely, and the bubble diameter becomes extremely large. Further, 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.

[0087] 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 the non-foamed molded body with an inert gas, the impregnation temperature in the batch method is preferably 10°C to 250°C, more preferably 40°C to 230°C. In addition, when impregnating a molten polymer with a gas and simultaneously performing foaming and molding by extrusion, the impregnation temperature in the continuous method is preferably 60°C to 350°C. When 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.

[0088] 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.

[0089] The heating temperature in the heating step is preferably 40°C to 250°C, more preferably 60°C to 250°C.

[0090] ≪≪2. Foamed member≫≫ The foamed member of the present invention includes a resin foam layer composed of the above resin foam, and an adhesive layer disposed on at least one side of the resin foam layer.

[0091] The thickness of the resin foam layer of the foamed member of the present invention is preferably 30 μm to 5000 μm, more preferably 35 μm to 4000 μm, still more preferably 40 μm to 3000 μm, and particularly preferably 45 μm to 2500 μm. When the thickness of the resin foam layer is within the above range, the resin foam layer can easily follow even a minute clearance. Further, when the thickness of the resin foam layer is within the above range, air bubbles can be uniformly contained, and excellent shock absorbency can be exhibited.

[0092] The thickness of the adhesive layer is preferably 5 μm to 300 μm, more preferably 6 μm to 200 μm, still more preferably 7 μm to 100 μm, and particularly preferably 8 μm to 50 μm. When the thickness of the adhesive layer is within the above range, the foamed member of the present invention can exhibit excellent shock absorbency.

[0093] As the adhesive layer, a layer made of any appropriate 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.

[0094] As adhesives, when classified by the form of adhesion, for example, emulsion adhesives, solvent adhesives, ultraviolet crosslinking (UV crosslinking) adhesives, electron beam crosslinking (EB crosslinking) adhesives, hot melt adhesives (hot melt type adhesives), etc. can be mentioned. Such adhesives may be only one type or two or more types.

[0095] The water vapor transmission rate of the adhesive layer is preferably 50 (g / (m 2 ·24 h)) or less, more preferably 30 (g / (m 2 ·24 h)) or less, still more preferably 20 (g / (m 2 ·24 h)) or less, and particularly preferably 10 (g / (m 2 ·24 h)) or less. If the water vapor transmission rate of the adhesive layer is within the above range, the foamed sheet of the present invention can stabilize the shock absorption property without being affected by moisture.

[0096] The adhesive constituting the adhesive layer may contain any appropriate other components as long as the effects of the present invention are not impaired.

[0097] 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 (for example, ionic surfactants, silicone-based surfactants, fluorine-based surfactants, etc.), crosslinking agents (for example, 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.

[0098] The foamed member of the present invention can be manufactured by any appropriate method. Examples of the method for manufacturing the foamed member of the present invention include a method of laminating a resin foamed 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 foamed layer.

Examples

[0099] Hereinafter, the present invention will be specifically described by way of examples. However, 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. In addition, when "parts" are described, it means "parts by weight" unless otherwise specified, and when "%" is described, it means "% by weight" unless otherwise specified.

[0100] <Measurement method of apparent density> The density (apparent density) of the resin foam was calculated as follows. The resin foam structures 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. Then, it was calculated by the following formula. Apparent density (g / cm 3 ) = Weight of test piece / Volume of test piece

[0101] <Measurement method of 50% compression load> The measurement was carried out according to the method for measuring the compression hardness of foams described in JIS K 6767. Specifically, the resin foam structures 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 10 mm / min until the compression rate reached 50% was converted per unit area (1 cm 2 ) and taken as the 50% compression load (N / cm 2 ).

[0102] <Measurement method of average cell diameter (average cell size) and coefficient of variation of cell diameter (cell size)> Using a digital microscope (trade name "VHX-500", manufactured by Keyence Corporation) as a measuring instrument, an enlarged image of the cell part of the resin foam structure obtained in the examples and comparative examples was captured, and the average cell diameter (average cell size) (μm) was obtained by image analysis using the analysis software of the measuring instrument. The number of cells in the captured enlarged image was about 400. In addition, the standard deviation was calculated from all the data of the cell diameter, and the coefficient of variation was calculated using the following formula. Coefficient of variation = Standard deviation / Average cell diameter (average cell size)

[0103] <Measurement Method of Bubble Ratio (Cell Ratio)> Measurements were carried out under the environment of a temperature of 23°C and a humidity of 50%. The resin foam structures obtained in the examples and comparative examples were punched out with a punching blade type of 100 mm × 100 mm, and the dimensions of the punched samples were measured. Also, the thickness was measured with a 1 / 100 dial gauge having a diameter (φ) of the measurement terminal of 20 mm. From these values, the volumes of the resin foam structures obtained in the examples and comparative examples were calculated. Next, the weights of the resin foam structures obtained in the examples and comparative examples were measured with an upper pan balance having a minimum scale of 0.01 g or more. From these values, the bubble ratio (cell ratio) of the resin foam structures obtained in the examples and comparative examples was calculated.

[0104] <Measurement Method of Residue of Resin Foam at 650°C> 5 mg of the resin foam structures obtained in the examples and comparative examples were placed in a platinum container, and the temperature was raised under a nitrogen gas atmosphere at a rate of 20°C / min in the measurement range from 25°C to 680°C, and the residue at 650°C was measured using TG / DTA6200 (manufactured by SII NanoTechnology Inc.).

[0105] <Measurement Method of Tensile Elastic Modulus of Resin Foam> Based on the tensile elongation section of JIS K 6767, the tensile elongation (%) and tensile strength of the foam were measured, and in a graph with the tensile elongation on the X-axis and the tensile strength on the Y-axis, the ratio of the change in the tensile strength in the region of 0% to 10% of the tensile elongation was calculated as the tensile elastic modulus.

[0106] <Measurement Method of Stress Retention of Resin Foam> The resin foam (width 10 mm × length 100 mm) was stretched by 20% in the length direction at a speed of 300 m / min, and the ratio (tensile strength after holding for 120 seconds / stress retention immediately after stretching × 100) between the tensile strength immediately after stretching and the tensile strength after holding for 120 seconds was obtained, and this ratio was defined as the stress retention of the resin foam.

[0107] <Measurement Method of Stress Dispersion Degree (Property)> Figure 1 is a schematic cross-sectional view of the stress relaxation tester 1000 used for the measurement of stress dispersion degree. As shown in Fig. 1, a polycarbonate plate (200 mm × 300 mm × thickness 1 mm) 200 was placed on an iron support 100, and a stress measurement film 300 (trade name "Press Scale" (two-sheet, for low pressure (4LW), manufactured by Fuji Film Co., Ltd., a sheet having a surface where the pressurized part changes color, 50 mm × 50 mm × thickness 0.16 mm) was placed thereon. Next, a resin foam structure (150 mm × 200 mm × thickness 0.5 mm) 400 obtained in the examples and comparative examples to be measured was placed on the stress measurement film 300, and a double-sided adhesive tape (No. 5603, manufactured by Nitto Denko Corporation, thickness 0.03 mm) 500 was pasted thereon, a spacer 600 with a thickness of 0.3 mm was arranged, and an ABS plate (200 mm × 300 mm × thickness 3 mm) 700 was placed on the top. From above, an iron ball (φ25 mm) 800 was placed at the center, and a load of 100 N was applied for 1 min. Thereafter, the color change of the stress measurement film 300 was observed, and those in which the color did not spread from the center of the stress measurement film 300 and was in a dot shape were designated as C, those in which the color spread from the center of the stress measurement film 300 up to 25 mm were designated as B, and those in which the color spread greatly from the center of the stress measurement film 300 to the 50 mm end were designated as A.

[0108] <Method for measuring dimensional change rate> The dimensional change rate of the resin foam was measured by Method B in JIS K 6767:1999K "Foamed Plastics - Polyethylene - Test Methods". The test piece size was 150 mm × 150 mm. Three straight lines parallel to each other in the longitudinal and transverse directions were marked at 50 mm intervals at the center of the test piece. Next, the test piece was put into a hot air circulation dryer at 120 °C and left for 500 hours. Thereafter, the test piece was taken out, left at room temperature for 1 hour, and then the length of the marked line was measured. The dimensional change rate was determined by the formula |(L1 - L0)| / L0 × 100 from the average length L0 (mm) of the marked line before heating and the average length L1 (mm) of the marked line after heating.

[0109] 〔Example 1〕 Polypropylene [Melt Flow Rate (MFR) (230°C): 0.40 g / 10 min]: 50 parts by weight, Polypropylene [Melt Flow Rate (MFR) (230°C): 2.40 g / 10 min]: 25 parts by weight, Polyolefin-based elastomer [Melt Flow Rate (MFR): 6 g / 10 min, JIS A hardness: 79°]: 25 parts by weight, Magnesium hydroxide: 100 parts by weight (trade name "KISUMA 5P" manufactured by Kyowa Chemical Industry Co., Ltd.), 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), and then extruded into strands, and after water cooling, formed into pellets. 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 (12 after injection) MPa in an atmosphere of 220°C. The carbon dioxide gas was injected at a ratio of 3.5 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 a die to obtain a sheet-shaped resin foam A with a thickness of 1.8 mm. In this foam, the apparent density was 0.085 g / cm 3 , the 650°C residue was 36%, the tensile modulus was 1.6 MPa, and the stress retention rate was 70%. The evaluation results for resin foam A, including these results, are shown in Table 1.

[0110] 〔Example 2〕 In the same manner as in Example 1, resin foam A was obtained. The resin foam A was passed through the gap between a pair of rolls where one roll was heated to 200°C (the gap between the rolls) to obtain a resin foam B with a thickness of 0.15 mm. The gap between the rolls (clearance) was set so that a resin foam B with a thickness of 0.15 mm could be obtained. In this foam, the apparent density was 0.18 g / cm 3 , the 650°C residue was 36%, the tensile modulus was 2.1 MPa, and the stress retention rate was 66%. The evaluation results for resin foam B, including these results, are shown in Table 1.

[0111] 〔 Comparative Example 2 〕 Polypropylene [Melt Flow Rate (MFR) (230 °C): 0.40 g / 10 min]: 19 parts by weight, Polypropylene [Melt Flow Rate (MFR) (230 °C): 1.1 g / 10 min]: 19 parts by weight, Polyolefin-based elastomer [Melt Flow Rate (MFR): 6 g / 10 min, JIS A hardness: 79°]: 67 parts by weight, Magnesium hydroxide: 80 parts by weight (trade name "KISUMA 5P" manufactured by Kyowa Chemical Industry Co., Ltd.), 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 after water cooling, formed into pellets. These pellets were fed into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 (12 after injection) MPa in an atmosphere of 220 °C. The carbon dioxide gas was injected at a ratio of 3 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 a die to obtain a sheet-shaped resin foam C with a thickness of 1.8 mm. In this foam, the apparent density was 0.07 g / cm 3 , the 650 °C residue was 34%, the tensile modulus was 0.6 MPa, and the stress retention rate was 75%. The evaluation results for the resin foam C, including these results, are shown in Table 1.

[0112] 〔Example 4〕 Polypropylene [Melt Flow Rate (MFR) (230 °C): 0.40 g / 10 min]: 32.5 parts by weight, Polypropylene [Melt Flow Rate (MFR) (230 °C): 1.1 g / 10 min]: 32.5 parts by weight, Polyolefin-based elastomer [Melt Flow Rate (MFR): 6 g / 10 min, JIS A hardness: 79°]: 35 parts by weight, Magnesium hydroxide: 120 parts by weight (trade name "KISUMA 5P" manufactured by Kyowa Chemical Industry Co., Ltd.), 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 (12 after injection) MPa in an atmosphere of 220 °C. The carbon dioxide gas was injected at a ratio of 3.5 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 a die to obtain a sheet-shaped resin foam D with a thickness of 2.0 mm. In this foam, the apparent density was 0.07 g / cm 3 , the 650 °C residue was 45%, the tensile modulus was 0.71 MPa, and the stress retention rate was 63%. The evaluation results for the resin foam D, including these results, are shown in Table 1.

[0113] 〔Example 5〕 An apparent density of 0.3 g / cm 3 was obtained, the 650 °C residue was 10%, the tensile modulus was 2.4 MPa, and the stress retention rate was 65%. A resin foam E mainly composed of polyethylene was prepared. The evaluation results for the resin foam E are shown in Table 1.

[0114] 〔Comparative Example 1〕 Polypropylene [Melt Flow Rate (MFR) (230 °C): 0.40 g / 10 min]: 22.5 parts by weight, Polypropylene [Melt Flow Rate (MFR) (230 °C): 1.1 g / 10 min]: 22.5 parts by weight, Polyolefin-based elastomer [Melt Flow Rate (MFR): 6 g / 10 min, JIS A hardness: 79°]: 55 parts by weight, Magnesium hydroxide: 10 parts by weight (trade name "KISUMA 5P" manufactured by Kyowa Chemical Industry Co., Ltd.), 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 after water cooling, formed into pellets. 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 (12 after injection) MPa in an atmosphere of 220 °C. The carbon dioxide gas was injected at a ratio of 5.5 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 a die to obtain a sheet-like resin foam structure with a thickness of 1.8 mm. The above resin foam was passed through the gap between a pair of rolls where one roll was heated to 200 °C (the gap between the rolls) to obtain a resin foam F with a thickness of 0.15 mm. The gap between the rolls was set so that a resin foam F with a thickness of 0.15 mm could be obtained. In this foam, the apparent density was 0.07 g / cm 3 , the 650 °C residue was 14%, the tensile modulus was 0.55 MPa, and the stress retention rate was 56%. The evaluation results for the resin foam F, including these results, are shown in Table 1.

[0115]

Table 1

[0116] From the results of the dimensional change rate at 120 °C, it can be seen that the resin composition of the present invention is excellent in heat resistance. In addition to being excellent in heat resistance, the resin composition of the present invention is also excellent in stress dispersibility.

Industrial Applicability

[0117] The resin foam of the present invention can be suitably used, for example, as a cushioning material for electronic devices.

Description of Reference Numerals

[0118] Stress relaxation tester 1000 Iron support 100 Polycarbonate plate 200 Stress measurement film 300 Resin foam structure 400 Double-sided adhesive tape 500 Spacer 600 ABS plate 700 Iron ball 800

Claims

1. A resin foam having a bubble structure, wherein the resin constituting the resin foam is a polyolefin resin, the polyolefin resin is a mixture of polypropylene other than polyolefin elastomer and polyolefin elastomer, The apparent density is 0.05 g / cm ３ to 0.50 g / cm ３ and the 50% compression load is 6 N / cm2 to 15 N / cm2, Apparent density D (g / cm ３ ), and the residue R (%) at 650 °C satisfy the relationship of the following formula (1), and and the tensile elastic modulus at 23 °C is 0.6 MPa or more, resin foam. 1 ≤ { (100 - R) / D} / 100 ≤ 10... (1)

2. The resin foam according to Claim 1, wherein the average bubble diameter of the bubbles is 10 μm to 200 μm.

3. The resin foam according to Claim 1 or 2, wherein the coefficient of variation of the bubble diameter of the bubbles is 0.5 or less.

4. The resin foam according to any one of Claims 1 to 3, wherein the bubble ratio in the bubble structure is 30% or more.

5. The resin foam according to any one of Claims 1 to 4, wherein the thickness of the bubble wall in the bubble structure is 0.1 μm to 10 μm.

6. The resin foam according to any one of Claims 1 to 5, wherein the stress retention is 60% or more.

7. The resin foam according to any one of Claims 1 to 6, comprising a filler.

8. The resin foam according to Claim 7, wherein the filler is an inorganic substance.

9. The resin foam according to Claim 7, wherein the filler is an organic substance.

10. The resin foam according to any one of Claims 1 to 9, having a heat-melt layer on one side or both sides.

11. A foamed member comprising a resin foam layer composed of the resin foam according to any one of Claims 1 to 10, and an adhesive layer disposed on at least one side of the resin foam layer. foamed member.

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