Impact-absorbing material

Abstract

To provide an impact-absorbing material with excellent shock absorbency and wearability.SOLUTION: There is provided an impact-absorbing material containing a polymer that satisfies both (1) and (2) below. (1) The storage modulus G' obtained from dynamic solid viscoelastic testing at a circumferential velocity of 2.7 m / s ranges from 6 to 60 MPa. (2) The ratio of the storage modulus G' at a circumferential velocity of 2.7 m / s to the storage modulus G' at a circumferential velocity of 0.1 m / s, obtained through dynamic solid viscoelastic testing, is 4.0 or greater.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an impact absorbing material. [Background technology]

[0002] Impact absorbing materials are used in a wide range of fields, such as clothing equipped with impact absorbing components used in nursing care, protective sports equipment to protect the human body from impact, and transportation equipment such as pallets to protect transported items from impact.

[0003] A variety of materials have traditionally been used as impact absorbing materials, including various foams and thermoplastic elastomers. However, in recent years, in particular with the miniaturization of electrical and electronic materials, there has been an increase in the use of non-foamed impact absorbing films and foams with high loss tangent (tanδ) peaks measured by dynamic viscoelasticity measurement, providing excellent impact absorption, in order to improve impact absorption in a space-saving manner.

[0004] Generally, shock-absorbing materials are softened to increase contact time and ensure impact attenuation, but this requires a large amount of deformation. Conversely, if the material is hard, the load increases with a small amount of deformation, and the impact propagates to the object being protected. Therefore, it is known that introducing a foam structure into a hard material causes it to yield before the load increases significantly, efficiently absorbing impact energy. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-3004 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-124848 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-168775 [Patent Document 4] Japanese Patent Application Publication No. 2019-182981 Summary of the Invention [Problem to be solved by the invention]

[0006] However, because the material is inherently hard, this results in a loss of flexibility and issues with wearability. This makes it difficult to apply the material to protective equipment, electronic devices, and automotive components. On the other hand, attempts to improve flexibility tend to result in a loss of shock absorption and an increase in the thickness of the required material, again resulting in issues with wearability. An object of the present invention is to provide a shock absorbing material that is excellent in shock absorption properties and wearability. [Means for solving the problem]

[0007] The present invention includes the following aspects: [Section 1] An impact absorbing material comprising a polymer that satisfies the following (1) and (2): (1) The storage modulus G' at a peripheral speed of 2.7 m / s obtained by a dynamic solid viscoelasticity test is 6 to 60 MPa; (2) The ratio of the storage modulus G' at a peripheral velocity of 2.7 m / s to the storage modulus G' at a peripheral velocity of 0.1 m / s obtained by a dynamic solid viscoelasticity test is 4.0 or more. [Section 2] Item 1. The impact absorbing material according to item 1, wherein the polymer is a polymer having a foam structure. [Section 3] Item 3. The impact absorbing material according to item 2, wherein the ratio of G' at a peripheral speed of 2.7 m / s to G' at a peripheral speed of 0.1 m / s obtained by a dynamic solid viscoelasticity test of the polymer matrix having the foam structure is 2.5 or more. [Section 4] Item 4. The impact absorbing material according to item 2 or 3, wherein the loss tangent (tanδ) at a peripheral speed of 2.7 m / s obtained by a dynamic solid viscoelasticity test of the polymer matrix having the foam structure is 0.5 or more. [Section 5] Item 5. The impact absorbing material according to any one of items 2 to 4, wherein the polymer having an expanded structure has an expansion ratio of 1.2 to 3.5. [Section 6] Item 6. The impact absorbing material according to any one of items 1 to 5, which has a flat plate shape and a thickness of 0.3 to 500 mm. [Section 7] Item 7. The impact absorbing material according to any one of items 1 to 6, wherein the polymer is an elastomer. [Section 8] Item 8. The impact absorbing material according to any one of items 1 to 7, wherein the polymer is a polyolefin-based thermoplastic elastomer, a polyurethane-based thermoplastic elastomer, a thermosetting polyurethane resin, a polyamide-based thermoplastic elastomer, a polyester-based thermoplastic elastomer, a polyvinyl chloride-based thermoplastic elastomer, an acrylic-based thermoplastic elastomer, or a polystyrene-based thermoplastic elastomer. [Section 9] Item 7. The impact absorbing material according to any one of items 1 to 6, wherein the polymer is an epoxy resin. [Section 10] Item 7. The impact absorbing material according to any one of items 2 to 6, wherein the polymer having a foamed structure is a foam obtained by foaming a composition containing an epoxy resin, a curing agent, and a foaming agent. [Section 11] Item 9. The impact absorbing material according to any one of items 2 to 8, wherein the polymer having an expanded structure is a foam obtained by foaming a composition containing a polystyrene-based thermoplastic elastomer and a foaming agent. [Section 12] Item 12. The shock-absorbing material according to any one of items 1 to 11, for use in protectors, flooring materials, automobile cushions, automobile bumpers, shock-absorbing sheets for electronic components, buffer materials, sporting goods, transport equipment, drone components, and shock-absorbing sheets for drone landing ports. [Section 13] Item 12. The impact absorbing material according to item 11, wherein the curing agent is an amine-based curing agent. [Section 14] Item 14. The impact absorbing material according to item 11 or 13, wherein the foaming agent comprises a thermally expandable capsule or ammonium bicarbonate. [Section 15] A foam obtained by foaming a composition containing an epoxy resin, a curing agent, and a foaming agent, the content of the curing agent in the composition is 80 to 120 mass% relative to the content of the epoxy resin in the composition; Item 15. The impact absorbing material according to item 11, 13, or 14, wherein the content of the foaming agent in the composition is 0.1 to 20% by mass based on the total mass of the composition. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an impact absorbing material that is excellent in impact absorption properties and wearability. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Terminology> In this specification, numerical ranges indicated using "to" indicate ranges that include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. Furthermore, when the composition contains multiple substances corresponding to each component, the amount of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified.

[0010] As used herein, the term "polymer" does not necessarily refer to a polymeric compound itself, but may refer to various forms depending on the context. For example, and without limitation, "polymer" may refer to a polymeric composition obtained by polymerizing a monomer in a system containing an additive such as a polymerization initiator or a catalyst, depending on the context. Furthermore, for example, "polymer" may refer to a polymeric material containing such a polymeric composition. Furthermore, for example, "polymer" may refer to a crosslinked polymeric composition or material obtained by crosslinking a polymeric compound using a crosslinking agent or the like.

[0011] As used herein, the term "a polymer matrix having a foamed structure" refers to a non-foamed form of the polymer. For example, when the term "epoxy resin foam matrix" is used, the term refers to a polymer produced by the same process as the foam, which is produced from a composition containing an epoxy resin, a curing agent, and a blowing agent, except that the composition does not contain a blowing agent.

[0012] In this specification, "shock absorption" refers to the property of absorbing shocks caused by falls, collisions, drops, etc., thereby reducing the shock received by the object to be protected. Specifically, "excellent shock absorption" refers to excellent shock attenuation evaluated by measuring the peak load described in the examples, and excellent shock diffusion evaluated by measuring the shock diffusion rate.

[0013] In this specification, "wearability" refers to the ease of movement or the degree of ease of movement of the subject wearing the impact absorbing material of the present invention. Specifically, "excellent wearability" means that the flexibility evaluated by measuring the bending rigidity at the required thickness at 0.1 m / s as described in the examples is excellent, and the thickness evaluated by measuring the maximum sinkage is small. In this specification, "flexibility" refers to the softness or the degree of ease of bending of the subject.

[0014] <Shock absorbing material> The impact absorbing material of the present invention will be described below.

[0015] The impact absorbing material of the present invention comprises the following (1) and (2): (1) The storage modulus G' at a peripheral speed of 2.7 m / s obtained by dynamic solid viscoelasticity testing is 6 to 60 MPa; (2) The ratio of the storage modulus G' at a peripheral velocity of 2.7 m / s to the storage modulus G' at a peripheral velocity of 0.1 m / s, as determined by a dynamic solid viscoelasticity test, is 4.0 or more; The polymers include those which satisfy the following:

[0016] In this specification and claims, the values ​​of "storage modulus G'" and "tan δ" at a peripheral speed of 0.1 m / s or 2.7 m / s are parameters obtained by performing a dynamic solid viscoelasticity test on a polymer under conditions in which a circular plate is rotated at the above peripheral speeds.

[0017] In the present invention, the storage modulus G' may be directly obtained by performing a dynamic viscoelasticity test under the above peripheral speed conditions. Alternatively, in the present invention, the frequency dependence of dynamic viscoelasticity may be measured under multiple temperature conditions, a master curve at a specific temperature may be created based on the temperature-time conversion rule, and the storage modulus G' at the above peripheral speed may be indirectly calculated. A specific method for indirectly calculating the storage modulus G' is described in the Examples section.

[0018] The impact absorbing material of the present invention contains a polymer having a storage modulus G' value of 6 to 60 MPa at 2.7 m / s, as determined by a dynamic solid viscoelasticity test. If this value is 6 to 60 MPa, the impact absorbing material can achieve both favorable impact properties and flexibility. While this value is not particularly limited as long as it is within the above range, it is preferably 8 MPa or more from the viewpoint of impact attenuation, and may be, for example, 10 MPa or more, 15 MPa or more, or 18 MPa or more. Alternatively, this value may be 60 MPa or less, for example, 35 MPa or less, 28 MPa or less, or 25 MPa or less.

[0019] Furthermore, the polymer has a storage modulus G' (G' 0.1 ) at a peripheral speed of 2.7 m / s. 2.7 ) ratio is 4.0 or more (i.e., G' 2.7 / G' 0.1 ≧4.0). The ratio is not particularly limited as long as it is within the above range, but from the viewpoint of achieving both impact properties and flexibility, it is preferably 4.5 or more, and more preferably 5.0 or more. The ratio is also not particularly limited as long as it is within the above range, but it may be 15 or less, 10 or less, or 7 or less.

[0020] The impact absorbing material of the present invention can absorb impacts favorably by having the storage modulus G' as described above.

[0021] In a preferred embodiment, the impact absorbing material of the present invention comprises a polymer having a foamed structure. By including a polymer having a foamed structure, the impact absorbing material of the present invention can absorb impacts more efficiently.

[0022] The foam structure of the polymer having the foam structure may be either a closed-cell structure or an open-cell structure.

[0023] The expansion ratio of the polymer having the above-mentioned foamed structure is not particularly limited, but is preferably, for example, 1.2 to 3.5 from the viewpoint of impact properties, and from the viewpoint of achieving both impact properties and moldability, is more preferably 1.3 to 3.0, and even more preferably 1.4 to 1.9, and may be, for example, 1.5 to 1.7. In this specification, the expansion ratio is determined by dividing the volume of the same mass of polymer after expansion by the volume before expansion. The expansion ratio in the present invention may be measured as described in the examples.

[0024] In another embodiment, the expansion ratio of the polymer having the foamed structure may be 1.2 to 3.0, 1.3 to 2.0, or 1.4 to 2.0.

[0025] Furthermore, the impact absorbing material of the present invention can solve the problems of the present invention even if the foaming ratio is 1.2 to 1.9 and the storage modulus G' is 3.5 or more.

[0026] The average bubble size of the polymer having a foamed structure is not particularly limited, but is, for example, 3 μm to 1000 μm, and more preferably 5 μm to 400 μm. In this specification, the term "bubble size" refers to the diameter of a bubble in a polymer having a foamed structure when the bubble is viewed as a circle having the same area as the bubble. The average bubble size in the present invention is measured by image analysis of a cross-sectional observation image. For example, a cross-section of the polymer is exposed by any method, such as cutting or freeze fracture, and an image of the exposed cross-section is obtained using an optical microscope or electron microscope. The bubble size is then measured using image analysis software such as ImageJ. 50 to 500 bubbles are counted, and the average value is evaluated.

[0027] As a method for obtaining the polymer having the foam structure, various methods commonly used in foam molding, such as physical foaming or chemical foaming, may be used. In this specification, the physical foaming method refers to a method in which a gas component such as nitrogen or carbon dioxide is dissolved and dispersed in a polymer composition before curing under high pressure, and a cellular structure is formed by heating, reducing the pressure, mechanical mixing, or the like. In this specification, the chemical foaming method refers to a method in which a cellular structure is formed by gas generated by thermal decomposition of a chemical foaming agent (including foaming by thermally expandable capsules) added to the polymer composition before curing (or by expansion of the thermally expandable capsules by heating). From the viewpoints of obtaining a uniform foam structure and achieving both impact absorption and wearability, the chemical foaming method is preferred.

[0028] An example of a method for obtaining a polymer having the foamed structure by a physical foaming method is a method for forming a foamed structure by mechanically foaming an emulsion containing a polymer composition before curing a resin material. Examples of foaming devices include high-speed shear devices, vibration devices, and pressurized gas ejection devices. Among these foaming devices, high-speed shear devices are preferred from the viewpoint of reducing the bubble size and producing a large volume. This method for obtaining a polymer having a foamed structure can be applied to the formation of any polymer composition.

[0029] The bubbles generated by mechanical stirring are gases trapped in the emulsion. Any suitable gas can be used as long as it is inert to the emulsion and does not impair the effects of the present invention. Examples of such gases include air, nitrogen, and carbon dioxide.

[0030] An example of a method for obtaining a polymer having the foamed structure by chemical foaming is to add a chemical foaming agent to a polymer composition before curing or molding, and form a cellular structure using the gas generated by thermal decomposition of the chemical foaming agent (or by expansion of thermally expandable capsules due to heating). The chemical foaming agent can be thermally decomposed, for example, during the curing or molding process of the polymer composition. The type of such curing or molding process is not particularly limited, and the cellular structure can be formed by the chemical foaming agent in any known method for curing or molding.

[0031] The chemical blowing agent may be organic or inorganic. The chemical blowing agent may be aromatic or aliphatic. Examples of organic blowing agents include hydrazine-based blowing agents such as 4,4'-oxybis(benzenesulfonylhydrazide), diphenylsulfone-3,3'-disulfonylhydrazide allylbis(sulfonylhydrazide), and paratoluenesulfonylhydrazide; azo-based blowing agents such as azodicarbonamide (ADCA), azobisformamide, and azobisisobutyronitrile; fluorinated alkane-based blowing agents such as trichloromonofluoromethane; semicarbazide-based blowing agents such as p-toluenesulfonylsemicarbazide; triazole-based blowing agents such as 5-morpholyl-1,2,3,4-thiatriazole; and N-nitroso-based blowing agents such as N,N-dinitrosoterephthalamide. Examples of inorganic blowing agents include ammonium carbonate, ammonium bicarbonate, ammonium nitrite, ammonium borohydride, and azides. The chemical blowing agent may also be used in combination with a blowing aid (eg, urea).

[0032] These foaming agents may be used alone or in combination. The chemical foaming agent may be used in the form of a masterbatch in which the chemical foaming agent is incorporated into a base polymer. Examples of the base polymer include low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, polystyrene, acrylonitrile-styrene copolymer, and acrylonitrile-butadiene-styrene copolymer.

[0033] Furthermore, as a method for obtaining the polymer having the foam structure, there is a method in which thermally expandable capsules are added to a polymer composition before curing, and the thermally expandable capsules are expanded during a heating step to form a cellular structure. In this specification, the term "thermally expandable capsule" refers to a composition having a shell and a thermally expandable encapsulated component, which, when heated, softens the shell and simultaneously vaporizes the encapsulated component, thermally expands, and can form hollow particles.

[0034] The type of the shell is not particularly limited, but it can be formed from, for example, a nitrile polymer.

[0035] The type of the encapsulated component is not particularly limited, but examples include substances that have the property of vaporizing or expanding when heated, such as at least one selected from the group consisting of hydrocarbons such as isoalkanes and normal alkanes. Examples of isoalkanes include isobutane, isopentane, 2-methylpentane, 2-methylhexane, and 2,2,4-trimethylpentane, and examples of normal alkanes include n-butane, n-propane, n-hexane, n-heptane, and n-octane. These hydrocarbons may be used alone or in combination.

[0036] When obtaining a polymer having the above-described foamed structure by a chemical foaming method, multiple chemical foaming agents may be used in combination. For example, 4,4'-oxybis(benzenesulfonylhydrazide) and azodicarbonamide may be used in combination. Alternatively, a chemical foaming agent may be used in combination with a thermally expandable capsule.

[0037] In this specification, the foaming agent may be the compound itself as exemplified above, or may be a composition containing the compound as exemplified above.

[0038] When the polymer having the foamed structure is obtained by a chemical foaming method, the foaming agent preferably contains ammonium bicarbonate or a thermally expandable capsule.

[0039] In a preferred embodiment, the polymer having the foamed structure has a storage modulus G' (G' b0.1 ) at a peripheral speed of 2.7 m / s. b2.7 ) ratio is 2.5 or more (i.e., G' b2.7 / G' b0.1 ≧2.5). b2.7 / G' b0.1 If the G' ratio is 2.5 or more, the impact absorbing material containing the polymer having the foam structure can achieve both flexibility under low-speed deformation and impact attenuation under high-speed deformation, which is preferable. The G' ratio of the base material may be, for example, 3.0 or more, 5.0 or more, or 7.0 or more. The G' ratio of the base material may be, for example, 15.0 or less, or 10.0 or less.

[0040] In a preferred embodiment, the polymer having a foamed structure has a loss tangent (tanδ) at a peripheral speed of 2.7 m / s, as determined by a dynamic viscoelasticity test of the base material, of 0.5 or more. A tanδ of 0.5 or more is preferred because an impact absorbing material containing the polymer having a foamed structure has improved impact attenuation. The tanδ may be, for example, 1.0 or more or 1.3 or more. The tanδ may also be, for example, 4.0 or less, 2.0 or less, or 1.6 or less.

[0041] In a preferred embodiment, the polymers of the present invention are elastomers.

[0042] The elastomer may be either a thermoplastic elastomer or a thermosetting elastomer.

[0043] In one embodiment, the polymer is a thermoplastic elastomer. The type of thermoplastic elastomer is not particularly limited, but examples thereof include polyolefin-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polystyrene-based thermoplastic elastomers, polyvinyl chloride-based thermoplastic elastomers, and acrylic-based thermoplastic elastomers.

[0044] In another embodiment, the polymer is a thermosetting elastomer. The type of thermosetting elastomer is not particularly limited, but examples thereof include polyurethane-based thermosetting elastomers, natural rubber, isoprene rubber, butadiene rubber, ethylene propylene rubber, nitrile rubber, styrene butadiene rubber, butyl rubber, and carboxyl-terminated butadiene nitrile rubber.

[0045] In a preferred embodiment, the polymer is a polyolefin-based thermoplastic elastomer, a polyurethane-based thermoplastic elastomer, a thermosetting polyurethane resin, a polyamide-based thermoplastic elastomer, a polyester-based thermoplastic elastomer, a polyvinyl chloride-based thermoplastic elastomer, an acrylic-based thermoplastic elastomer, or a polystyrene-based thermoplastic elastomer. Impact absorbing materials containing these elastomers may have better properties (such as impact absorption and flexibility).

[0046] In another preferred embodiment, the polymer is a polystyrene-based thermoplastic elastomer. If the polymer is a polystyrene-based thermoplastic elastomer, an impact absorbing material having a better balance between impact absorption and flexibility can be obtained.

[0047] The polystyrene-based thermoplastic elastomer is not particularly limited, and various known polystyrene-based thermoplastic elastomers may be used, such as styrene homopolymer, styrene-butadiene-styrene block copolymer (SBS), styrene-butadiene-butylene-styrene block copolymer (SBBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-styrene-ethylene-butylene-styrene block copolymer (SSEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), styrene-isoprene-styrene block copolymer (SIPS), styrene-isobutylene-styrene block copolymer (SIBS), methyl methacrylate-butadiene-styrene copolymer, etc. The above polystyrene-based thermoplastic elastomers may be used alone or in combination of two or more.

[0048] In a more preferred embodiment, the polymer is a copolymer of styrene and butadiene, particularly a styrene-styrene-ethylene-butylene-styrene block copolymer (SSEBS).

[0049] In another preferred embodiment, the polymer is an epoxy resin. When the polymer is an epoxy resin, an impact absorbing material having a better balance between impact absorption and flexibility can be obtained.

[0050] The epoxy resin is not particularly limited, and various known epoxy resins may be used, such as bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, bisphenol AF epoxy resins, dicyclopentadiene epoxy resins, trisphenol epoxy resins, naphthol novolac epoxy resins, phenol novolac epoxy resins, alicyclic epoxy resins having an ester skeleton, tert-butyl-catechol epoxy resins, naphthalene epoxy resins, naphthol epoxy resins, anthracene epoxy resins, glycidylamine epoxy resins, glycidyl ester epoxy resins, cresol novolac epoxy resins, biphenyl epoxy resins, linear aliphatic epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, heterocyclic epoxy resins, spiro ring-containing epoxy resins, cyclohexanedimethanol epoxy resins, naphthylene ether epoxy resins, trimethylol epoxy resins, and tetraphenylethane epoxy resins. The above epoxy resins may be used alone or in combination.

[0051] In a more preferred embodiment, the polymer contained in the impact absorbing material of the present invention is a bisphenol A type epoxy resin.

[0052] In a preferred embodiment, the polymer having a foam structure of the present invention includes a thermoplastic polymer, a thermosetting polymer, and the like.

[0053] Examples of thermoplastic polymers include crystalline resins such as polyolefin resins, polyamide resins, polyester resins, polyacetal resins, polylactic acid, and polyphenylene sulfide, amorphous resins such as polycarbonate resins, styrene resins, acrylic resins, urethane resins, halogen-containing resins, petroleum resins, coumarone resins, polyvinyl alcohol, polyvinyl acetate, and polyphenylene oxide, and thermoplastic elastomers. Examples of types of thermoplastic elastomers include those described above. More preferred are thermoplastic polymers that are excellent in moldability, productivity, recyclability, etc. in addition to impact absorption properties, and specifically, polyolefin resins, polyamide resins, styrene resins, and thermoplastic elastomers are more preferred.

[0054] Examples of thermosetting polymers include phenolic resins, urea resins, melamine resins, epoxy resins, unsaturated polyester resins, and thermosetting elastomers (e.g., synthetic rubbers), with epoxy resins being preferred. Examples of types of thermosetting elastomers and epoxy resins include those described above.

[0055] The impact absorbing material of the present invention may also contain multiple types of polymers such as those exemplified above. For example, the impact absorbing material of the present invention may contain a blend of a thermosetting elastomer and an epoxy resin, or a blend of a thermoplastic elastomer and an epoxy resin.

[0056] The impact absorbing material of the present invention can be produced from a composition (hereinafter also referred to as a precursor composition) containing the above polymer and various additives, etc. In addition to the foaming agent exemplified above, such a precursor composition may also contain a curing agent, a crosslinking agent, a plasticizer, a filler, etc.

[0057] The content of the foaming agent in the entire precursor composition is not particularly limited, and may be, for example, 0.1% by mass or more, 1% by mass or more, 3% by mass or more, 5% by mass or more, or 10% by mass or more, preferably 1% by mass or more. The content of the foaming agent in the entire precursor composition may be 20% by mass or less, 10% by mass or less, 5% by mass or less, or 3% by mass or less, preferably 5% by mass or less.

[0058] The precursor composition preferably contains a curing agent. Various curing agents may be used as the curing agent depending on the type of polymer contained in the impact absorbing material. In particular, when the polymer contained in the impact absorbing material is an epoxy resin, the precursor composition preferably contains a curing agent.The cured product may be a known product, for example, aliphatic amines such as diethylaminopropylamine, hexamethylenediamine, methylpentamethylenediamine, trimethylhexamethylenediamine, guanidine, and oleylamine; menthenediamine, isophoronediamine, norbornanediamine, piperidine, N,N'-dimethylpiperazine, N-aminoethylpiperazine, 1,2-diaminocyclohexane, bis(4-amino-3-methylcyclohexyl)methane, and bis(4-aminocyclohexyl)methan. Alicyclic amines such as cyclohexane, polycyclohexylpolyamine, and 1,8-diazabicyclo[5,4,0]undecene-7 (DBU); 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5,5]undecane (ATU), morpholine, N-methylmorpholine, polyoxypropylenediamine, polyoxypropylenetriamine, polyoxypropylenepolyamine, polyoxyethylenediamine, trimethylolpropanepoly(oxypropylene)triamine, and 3-butoxypropylamine hydroxyl group-containing amines such as diethanolamine and triethanolamine; acid anhydrides such as methylhexahydrophthalic anhydride, hydrogenated methylnadic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and dodecylsuccinic anhydride; phenolic resins such as novolac phenolic resin and resol phenolic resin; urea resins such as methylol group-containing urea resin; melamine resins such as methylol group-containing melamine resin; polyamide amines such as polyamides obtained by reacting dimer acid with polyamines such as diethylenetriamine and triethylenetetramine, and polyamides using polycarboxylic acids other than dimer acid; imidazoles such as 2-ethyl-4-methylimidazole; dicyandiamide; epoxy-modified amines obtained by reacting the above-mentioned amines with an epoxy compound, and modified amines such as Mannich-modified amines, Michael addition-modified amines, and ketimines obtained by reacting the above-mentioned amines with formalin or phenols. These curing agents may be used alone or in combination of two or more.

[0059] The amount of the curing agent is not particularly limited and may be, for example, an amount sufficient to consume 80% to 100% of the epoxy groups present in the epoxy resin composition. The amount of curing agent may be an insufficient amount, such that less than 80% (e.g., 50%) of the epoxy groups are consumed, or an excessive amount exceeding the amount sufficient to consume 100%. An insufficient or excessive amount of curing agent can reduce the crosslink density of the epoxy resin. The crosslink density of the epoxy resin can significantly affect the mechanical properties of the impact absorbing material of the present invention, so by appropriately adjusting the amount of curing agent, an impact absorbing material with the desired mechanical properties can be obtained.

[0060] The precursor composition may contain a crosslinking agent. Various crosslinking agents may be used depending on the type of polymer contained in the impact absorbing material. In particular, when the polymer contained in the impact absorbing material is a thermosetting elastomer, the precursor composition preferably contains a crosslinking agent. The crosslinking agent becomes activated by heating and can crosslink the thermosetting elastomer. The crosslinking agent may be a known agent, such as sulfur, sulfur compounds, oximes, nitroso compounds, quinone compounds, polyamines, peroxides (particularly organic peroxides), etc. The crosslinking agent may be used in combination with a crosslinking aid (e.g., zinc oxide).

[0061] The crosslinking agent may contain an organic peroxide. Examples of the organic peroxide include ketone peroxide, peroxyketal, hydroperoxide, dialkyl peroxide, acyl peroxide, peroxyester, and peroxydicarbonate. Specific examples include tert-butyl hydroperoxide, p-menthane hydroperoxide, dicumyl peroxide, tert-butyl peroxide, 1,3-bis(tert-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, benzoyl peroxide, and tert-butyl peroxybenzoate.

[0062] The amount of the crosslinking agent in the precursor composition is not particularly limited and may be 0.01% by mass or more, 0.1% by mass or more, 0.3% by mass or more, 0.5% by mass or more, 1% by mass or more, 3% by mass or more, 5% by mass or more, 8% by mass or more, or 10% by mass or more, preferably 0.1% by mass or more. The amount of the crosslinking agent in the precursor composition may be 25% by mass or less, 20% by mass or less, 10% by mass or less, 5% by mass or less, 2.5% by mass or less, or 1% by mass or less, preferably 5% by mass or less.

[0063] The precursor composition may contain a plasticizer. The addition of a plasticizer makes it possible to adjust the wearability and impact absorption properties of the impact absorbing material of the present invention. The plasticizer may be one that can swell or dissolve the polymer contained in the impact absorbing material of the present invention. Examples of plasticizers include phthalate esters such as di(2-ethylhexyl) phthalate, butyl benzyl phthalate, dinonyl phthalate, diisononyl phthalate, diisodecyl phthalate, diundecyl phthalate, diheptyl phthalate, and butyl phthalyl butyl glycolate; aliphatic dibasic acid esters such as dioctyl adipate, didecyl adipate, and dioctyl sebacate; polyglycol benzoate esters such as polyoxyethylene glycol dibenzoate and polyoxypropylene glycol dibenzoate; phosphate esters such as tributyl phosphate and tricresyl phosphate; and hydrocarbons such as alkyl-substituted diphenyls, alkyl-substituted terphenyls, partially hydrogenated alkyl terphenyls, paraffinic process oils, naphthenic process oils, aromatic process oils, and pine oil.

[0064] The amount of the plasticizer in the precursor composition is not particularly limited and may be 3% by mass or more, 5% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, or 50% by mass or more, preferably 20% by mass or more. The amount of the plasticizer in the precursor composition may be 60% by mass or less, 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, or 10% by mass or less, preferably 50% by mass or less.

[0065] The precursor composition may contain a filler. Addition of a filler can adjust the wearability and impact absorption properties of the impact absorbing material of the present invention. Examples of fillers include heavy calcium carbonate, surface-untreated calcium carbonate, surface-treated calcium carbonate (e.g., fatty acid-treated calcium carbonate), fume silica, hydrophobic silica, precipitated silica, carbon black, talc, mica, clay, glass beads, balloons such as microballoons, shirasu balloons, glass balloons, silica balloons, plastic balloons, and organic powder-coated plastic balloons; plastic particles; inorganic fibers such as glass fibers and metal fibers; organic fibers such as polyethylene fibers and polypropylene fibers; aluminum borate, silicon carbide, silicon nitride, potassium titanate, graphite; needle-shaped crystalline fillers such as acicular calcium carbonate, magnesium borate, titanium diboride, chrysotile, and wollastonite; aluminum flakes, aluminum powder, and iron powder. These fillers may be used alone or in combination.

[0066] The amount of the filler in the precursor composition is not particularly limited and may be 5% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, or 60% by mass or more, preferably 10% by mass or more. The amount of the filler in the precursor composition may be 80% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, 40% by mass or less, or 30% by mass or less, preferably 60% by mass or less.

[0067] In a preferred embodiment, the polymer is a foam obtained by foaming a composition containing an epoxy resin, a curing agent, and a blowing agent (hereinafter referred to as an epoxy resin composition). In this case, the epoxy resin is preferably an intermediate of the epoxy resin exemplified above. Any of the curing agents and blowing agents listed above may be used. Two or more types of epoxy resin intermediates, curing agents, and blowing agents may be used in combination. The type of the epoxy resin intermediate is preferably a bisphenol A-type epoxy resin intermediate. From the viewpoint of improving impact absorption and flexibility, the type of the curing agent is preferably an amine-based curing agent, more preferably amines having an ether bond, and even more preferably polyoxypropylene polyamine. The type of the blowing agent is preferably a thermally expandable capsule.

[0068] In a more preferred embodiment, the polymer is a foam obtained by foaming a composition containing a bisphenol A type epoxy resin, an amine-based curing agent, and a thermally expandable capsule.

[0069] The content of the epoxy resin (intermediate) in the entire epoxy resin composition is not particularly limited, and may be, for example, 10% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, or 60% by mass or more, and preferably 40% by mass or more. The content of the epoxy resin (intermediate) in the entire epoxy resin composition may be 90% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, or 40% by mass or less, and preferably 70% by mass or less.

[0070] The content of the curing agent in the entire epoxy resin composition is not particularly limited, but may be, for example, 10% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, or 60% by mass or more, and preferably 40% by mass or more. The content of the curing agent in the entire epoxy resin composition may be 90% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, or 40% by mass or less, and preferably 70% by mass or less.

[0071] The content of the blowing agent in the entire epoxy resin composition is not particularly limited, and may be, for example, 0.1% by mass or more, 1% by mass or more, 3% by mass or more, 5% by mass or more, or 10% by mass or more, and preferably 1% by mass or more. The content of the blowing agent in the entire epoxy resin composition may be 20% by mass or less, 10% by mass or less, 5% by mass or less, or 3% by mass or less, and preferably 5% by mass or less.

[0072] In another preferred embodiment, the polymer is a foam obtained by foaming a composition containing a polystyrene-based thermoplastic elastomer and a blowing agent (hereinafter referred to as a polystyrene-based thermoplastic elastomer composition). Any of the foaming agents listed above may be used. Two or more types of polystyrene-based thermoplastic elastomers and blowing agents may be used in combination. The polystyrene-based thermoplastic elastomer is preferably a copolymer of styrene and butylene, and a styrene-styrene-ethylene-butylene-styrene block copolymer (SSEBS) is particularly preferred. The type of blowing agent is preferably a chemical blowing agent, and more preferably an inorganic blowing agent. From the viewpoint of improving kneadability and foamability, the blowing agent is more preferably used in the form of a masterbatch.

[0073] The content of the polystyrene-based thermoplastic elastomer in the entire polystyrene-based thermoplastic elastomer composition is not particularly limited, but may be, for example, 30% by mass or more, 50% by mass or more, 70% by mass or more, 90% by mass or more, or 95% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more.

[0074] The content of the blowing agent in the entire polystyrene-based thermoplastic elastomer composition is not particularly limited, and may be, for example, 0.1% by mass or more, 1% by mass or more, 3% by mass or more, 5% by mass or more, or 10% by mass or more, preferably 1% by mass or more. The content of the blowing agent in the entire polystyrene-based thermoplastic elastomer composition may be 20% by mass or less, 10% by mass or less, 5% by mass or less, or 3% by mass or less, preferably 5% by mass or less.

[0075] From the viewpoint of improving kneadability and moldability, the polystyrene-based thermoplastic elastomer composition may contain a plasticizer. Any of the plasticizers listed above may be used, but process oil is preferred, and paraffin-based process oil is more preferred. Two or more types of plasticizers may also be used in combination.

[0076] The content of the plasticizer in the entire polystyrene-based thermoplastic elastomer composition is not particularly limited, and may be, for example, 0.1% by mass or more, 1% by mass or more, 3% by mass or more, 5% by mass or more, or 10% by mass or more, preferably 1% by mass or more. The content of the plasticizer in the entire polystyrene-based thermoplastic elastomer composition may be 20% by mass or less, 10% by mass or less, 5% by mass or less, or 3% by mass or less, preferably 5% by mass or less.

[0077] The impact absorbing material of the present invention can be used in a wide range of fields, such as in impact absorbing clothing used in nursing care, as sports protectors to protect the human body from impact, or as an application to transport equipment such as pallets to protect transported items from impact. For example, when attaching the impact absorbing material to clothing, it may be attached to the inside of the clothing so as to come into direct contact with the human body, or it may be attached so that another piece of fabric or the like is interposed between the impact absorbing material and the human body.

[0078] The shape of the impact absorbing material of the present invention is not particularly limited, and may be, for example, a flat plate (or sheet) having a thickness of 0.3 to 500 mm. When used in clothing, an impact absorbing material of this shape can be attached by, for example, sewing it directly to the back of the clothing. Depending on the body part to be protected, the flat impact absorbing material can be cut appropriately and multiple pieces can be combined and attached. The thickness can be adjusted appropriately within the above range, taking into consideration the balance between the desired energy absorbency and flexibility depending on the body part to be protected and the intended use. For example, when the impact absorbing material of the present invention is used as a component requiring hardness and impact absorption, such as an automobile bumper, it is effective to increase the thickness. On the other hand, when the impact absorbing material is used as a component requiring flexibility when worn, such as a nursing care cloth, it is effective to decrease the thickness. From the viewpoint of improving wearability, a smaller thickness is preferred.

[0079] The impact-absorbing material of the present invention can provide good impact absorption and flexibility by being used in a variety of products, such as protectors, flooring materials, automobile cushions, automobile bumpers, impact-absorbing sheets for electronic components, buffer materials, sporting goods, transport equipment such as pallets, drone components, and impact-absorbing sheets for drone landing ports.

[0080] <Method of manufacturing impact absorbing material> The impact absorbing material of the present invention is produced by curing the precursor composition. Here, "curing" in this specification means that the resin (or its intermediate) or elastomer (or its intermediate) in the precursor composition is polymerized or crosslinked by light irradiation or heat, resulting in a decrease in fluidity.

[0081] The precursor composition may be cured by either light irradiation or heating, but is preferably cured by heating, because when the polymer contained in the impact absorbing material has a foamed structure, the foamed structure can be efficiently formed by the generated bubbles, whether by physical foaming or chemical foaming.

[0082] The impact absorbing material of the present invention is produced by plasticizing a thermoplastic resin composition by heating and molding it into a predetermined shape. The thermoplastic resin composition is a composition containing a thermoplastic resin such as those exemplified above, and may contain a plasticizer, a foaming agent, etc. such as those exemplified above. The impact absorbing material of the present invention can be obtained by mixing the thermoplastic resin composition by dry blending or the like, and then molding it by, for example, extrusion molding, press molding, injection molding, blow molding, etc. From the viewpoint of obtaining an impact absorbing material having the desired impact absorption properties and flexibility, extrusion molding is particularly preferred as a molding method.

[0083] Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims. [Example]

[0084] Examples of the present invention will be specifically described below, but unless otherwise specified in the specification, the examples do not limit the present invention.

[0085] In the present invention, the physical properties were measured as follows.

[0086] [Dynamic solid viscoelasticity test] Using a melt viscoelasticity analyzer, ARES-G2 (Waters), frequency dependence measurements were performed on disk-shaped specimens with a diameter of 8 mm and thicknesses of 2 to 11 mm under a nitrogen atmosphere at frequencies of 30 to 1 Hz, shear strains of 0.05 to 2%, and temperatures ranging from 80 to 100°C. The storage modulus G', loss tangent tanδ, and (G' at a peripheral speed of 2.7 m / s) / (G' at a peripheral speed of 0.1 m / s) (hereinafter referred to as the G' ratio) were calculated from the measured values ​​obtained using a master curve at a reference temperature of 25°C based on the temperature-time conversion rule. These measurements were performed on both the polymer foam and the polymer foam matrix.

[0087] [Expansion ratio] The expansion ratio was calculated from (density of the polymer having an expanded structure) / (density of the base material of the polymer having an expanded structure). The density was calculated from (mass of the test piece) / (apparent volume of the test piece) for a test piece of a predetermined shape.

[0088] [Bending stiffness @2.7m / s] Bending stiffness (MPa mm 4 ) is the tensile modulus of elasticity E1 (MPa) of the test specimen and the second moment of area I (mm 4 ) and the second moment of area I of the test piece is calculated using the following formula (1). I=W×Z1 3 / 12 (1) where W is the width (mm) of the test piece, and Z1 is the thickness (mm) of the test piece. In the present invention, the width W of the test piece is 40 mm. The tensile modulus E1 was calculated from the storage modulus G' of 2.7 m / s obtained by the dynamic solid viscoelasticity test, so that E1 ≈ 3G'.

[0089] Peak Load Using an impact testing machine AM10T (manufactured by Imatek), a high-speed compression test was performed using a 40mm square, 5-7mm thick test piece in which a 20mm diameter SUS impactor with a mass of 10.67kg was dropped from a height of 30cm onto the center of the test piece.The peak load measurement results were evaluated for impact attenuation according to the following criteria. ◎: Peak load is 12.00kN or less ○: Peak load is over 12.00kN and 15.00kN or less ×: Peak load exceeds 15.00 kN

[0090] [Impact Diffusion Rate] In the high-speed compression test, pressure-sensitive paper (Pre-sheet MS PS, Fujifilm) was placed between the test specimen and the test specimen stage to visualize the load transmitted through the test specimen. The obtained pressure-sensitive paper was analyzed by image analysis, and the impact diffusion rate was calculated using the following formula. (Impact diffusion rate) = (Impact surface area (cm 2 )) / (Collider area (cm 2 )) The impact surface area was measured using image analysis software to measure the area of ​​the colored part of the pressure-sensitive paper. In the present invention, the impactor area is the area of ​​a circular impact surface with a diameter of 2 cm. The impact diffusion rate measurement results were evaluated for impact diffusion properties according to the following criteria. ◎: Impact diffusion rate is 1.15 or more ○: Impact diffusion rate is over 1.10 and less than 1.15 ×: Impact diffusion rate is 1.10 or less

[0091] (Maximum sinking amount) In the high-speed compression test, the maximum displacement of the impactor obtained was taken as the maximum sinking amount. The required thickness was evaluated based on the measurement results of the maximum sinking amount according to the following criteria. 〇: Maximum sinking amount is 6.00mm or less ×: Maximum sinking amount exceeds 6.00 mm

[0092] (Bending stiffness at required thickness @0.1m / s) The bending stiffness at 0.1 m / s was calculated using the above maximum sinking amount as the required thickness. 4 ) is the tensile modulus of elasticity E2 (MPa) of the test specimen and the second moment of area I (mm 4 ) and the second moment of area I of the test piece is calculated using the following equation (2). I=W×Z2 3 / 12 (2) where W is the width (mm) of the test piece, and Z2 is the maximum sinking amount (mm). In the present invention, the width W of the test piece is 40 mm. The tensile modulus E2 was calculated from the storage modulus G' at 0.1 m / s obtained by a dynamic solid viscoelasticity test, so that E2 ≈ 3G'. The bending rigidity measurement results for the required thickness were evaluated according to the following criteria. 〇: Maximum sinking amount is 8000MPa·mm 4 below ×: Maximum sinking amount is 8000MPa·mm 4 super

[0093] (Evaluation of polymer matrix with foam structure) The polymers having a foamed structure used in Examples 1 to 7 and Comparative Examples 1 to 5 were measured for their physical properties as a base material. The method for producing the base material was the same as the method for producing each foam described in the following Examples, except that no foaming agent was added to the resin precursor liquid. The storage modulus G' and G' ratio (G' 2.7 / G' 0.1 ) and loss tangent tanδ are shown in Table 1 below. Note that evaluation of base material C has not been carried out.

[0094] [Table 1]

[0095] The production examples and evaluation results of each foam are shown below.

[0096] (Production of cured epoxy resin foam) Example 1 35.1 g of bisphenol A-type epoxy resin intermediate (Sika Biresin® TD150(A) manufactured by Sika Japan Co., Ltd.) and 35.1 g of polyoxypropylene polyamine (TRANSLUX D150 HARDENER(B) manufactured by Sika Japan Co., Ltd.) were weighed into a PE kneading container and kneaded in a planetary vacuum mixer to obtain a resin precursor liquid. Next, 63.0 g of the resulting resin precursor liquid and 6.33 g of thermally expandable capsules (031DU40 manufactured by Nippon Phillite Co., Ltd.) were kneaded in the same manner as above and then poured into a SUS mold. The mold was then heated in an oven set to 90°C for 4 hours to cure.

[0097] Example 2 35.8 g of bisphenol A-type epoxy resin intermediate (Sika Biresin® TD150(A) manufactured by Sika Japan Co., Ltd.) and 35.8 g of polyoxypropylene polyamine (TRANSLUX D150 HARDENER(B) manufactured by Sika Japan Co., Ltd.) were weighed into a PE kneading container and kneaded in a planetary vacuum mixer to obtain a resin precursor liquid. Next, 63.0 g of the resulting resin precursor liquid and 3.15 g of thermally expandable capsules (031 DU 40 manufactured by Nippon Phillite Co., Ltd.) were kneaded in the same manner as above and then poured into a stainless steel mold. The mold was then heated in an oven set to 90°C for 4 hours to cure.

[0098] Example 3 30.0 g of bisphenol A-type epoxy resin intermediate (Sika Biresin® TD150(A) manufactured by Sika Japan Co., Ltd.) and 30.1 g of polyoxypropylene polyamine (TRANSLUX D150 HARDENER(B) manufactured by Sika Japan Co., Ltd.) were weighed into a PE kneading container and kneaded in a planetary vacuum mixer to obtain a resin precursor liquid. Next, the resulting resin precursor liquid and 0.96 g of thermally expandable capsules (Expancel 920 DE 80d30 manufactured by Nippon Phillite Co., Ltd.) were kneaded in the same manner as above and then injected into a stainless steel mold. The mold was then heated in an oven set to 90°C for 3 hours to cure.

[0099] Example 4 30.0 g of bisphenol A-type epoxy resin intermediate (Sika Biresin® TD150(A) manufactured by Sika Japan Co., Ltd.) and 30.0 g of polyoxypropylene polyamine (TRANSLUX D150 HARDENER(B) manufactured by Sika Japan Co., Ltd.) were weighed into a PE kneading container and kneaded in a planetary vacuum mixer to obtain a resin precursor liquid. Next, the resulting resin precursor liquid and 0.96 g of thermally expandable capsules (Expancel 920 DE 80 d30 manufactured by Nippon Phillite Co., Ltd.) were kneaded in the same manner as above and then injected into a stainless steel mold. The mold was then heated in an oven set to 90°C for 3 hours to cure.

[0100] Example 5 25.0 g of bisphenol A-type epoxy resin intermediate (Sika Biresin® TD150(A) manufactured by Sika Japan Co., Ltd.) and 26.3 g of polyoxypropylene polyamine (TRANSLUX D150 HARDENER(B) manufactured by Sika Japan Co., Ltd.) were weighed into a PE kneading container and kneaded in a planetary vacuum mixer to obtain a resin precursor liquid. Next, the resulting resin precursor liquid and 1.08 g of thermally expandable capsules (031 DU 40 manufactured by Nippon Phillite Co., Ltd.) were kneaded in the same manner as above and then poured into a SUS mold. The mold was then heated in an oven set to 90°C for 3 hours to cure.

[0101] Example 6 41.21 g of bisphenol A epoxy resin intermediate (Sika Biresin® TD150(A) manufactured by Sika Japan Co., Ltd.), 5.69 g of trimethylolpropane poly(oxypropylene) triamine (JEFFAMINET-403 manufactured by Huntsman Japan Co., Ltd.), and 11.12 g of 3-butoxypropylamine (JEFFADDMW-781 manufactured by Huntsman Japan Co., Ltd.) were weighed into a PE kneading container and kneaded in a planetary vacuum mixer to obtain a resin precursor solution. Next, the resulting resin precursor solution and 1.02 g of thermally expandable capsules (Expancel 920 DE 80 d30 manufactured by Nippon Phillite Co., Ltd.) were kneaded in the same manner as above and then poured into a stainless steel mold. The mold was then heated in an oven set to 90°C for 3 hours to cure.

[0102] Example 7 20.02 g of bisphenol A-type epoxy resin intermediate (Sika Biresin (registered trademark) TD150 (A) manufactured by Sika Japan Co., Ltd.) and 20.01 g of polyoxypropylene polyamine (TRANSLUX D150 HARDENER (B) manufactured by Sika Japan Co., Ltd.) were weighed into a PE kneading container and kneaded in a planetary vacuum mixer to obtain a resin precursor liquid. Next, the obtained resin precursor liquid and 0.46 g of ammonium bicarbonate (manufactured by Fujifilm Wako Co., Ltd.) were kneaded in the same manner as above and then poured into a SUS mold. The mold was then heated in an oven set to 90°C for 3 hours to cure.

[0103] Example 8 A styrene-based thermoplastic elastomer (manufactured by Asahi Kasei Corporation, SOE (registered trademark) S1605) was dry-blended with 2% by mass of a foaming agent masterbatch (manufactured by Sankyo Kasei Co., Ltd., Cellmic MB 3064P), and the mixture was molded into a foam sheet using a single-screw extruder (manufactured by Ono Seisakusho Co., Ltd.).

[0104] Example 9 A styrene-based thermoplastic elastomer (SOE (registered trademark) S1605, manufactured by Asahi Kasei Corporation) and 4% by mass of a plasticizer (Diana Process Oil PW-90, manufactured by Idemitsu Kosan Co., Ltd.) were kneaded using a co-rotating twin-screw extruder (Omega 30H, manufactured by STEER Corporation) and molded into pellets. The process oil was injected using a plunger pump (manufactured by Takumina Corporation). 3% by mass of a masterbatch (Cellmike MB 3064P, manufactured by Sankyo Kasei Co., Ltd.) was added to the molded pellets and dry-blended, and a foam sheet was molded using a single-screw extruder (manufactured by Ono Seisakusho Co., Ltd.).

[0105] Comparative Example 1 23.1 g of bisphenol A-type epoxy resin intermediate (Sika Biresin® TD150(A) manufactured by Sika Japan Co., Ltd.) and 23.0 g of polyoxypropylene polyamine (TRANSLUX D150 HARDENER(B) manufactured by Sika Japan Co., Ltd.) were weighed into a PE kneading container and kneaded using a planetary vacuum mixer to obtain a resin precursor liquid. Next, the resulting resin precursor liquid and 1.47 g of thermally expandable capsules (Expancel 920 DE 80 d30 manufactured by Nippon Phillite Co., Ltd.) were kneaded in the same manner as above and then poured into a stainless steel mold. The mold was then left to stand horizontally at 23°C for 48 hours. The mixture was then heated and cured in an oven set at 90°C for 3 hours.

[0106] Comparative Example 2 32.1 g of bisphenol A-type epoxy resin intermediate (Sika Biresin® TD150(A) manufactured by Sika Japan Co., Ltd.) and 32.1 g of polyoxypropylene polyamine (TRANSLUX D150 HARDENER(B) manufactured by Sika Japan Co., Ltd.) were weighed into a PE kneading container and kneaded in a planetary vacuum mixer to obtain a resin precursor liquid. Next, 19.0 g of the resulting resin precursor liquid and 0.97 g of thermally expandable capsules (031 DU 40 manufactured by Nippon Phillite Co., Ltd.) were kneaded in the same manner as above and then poured into a SUS mold. The mold was then heated in an oven set to 95°C for 4 hours to cure.

[0107] Comparative Example 3 25.0 g of bisphenol A-type epoxy resin intermediate (Sika Biresin (registered trademark) TD150 (A) manufactured by Sika Japan Co., Ltd.) and 25.0 g of polyoxypropylene polyamine (TRANSLUX D150 HARDENER (B) manufactured by Sika Japan Co., Ltd.) were weighed into a PE kneading container and kneaded in a planetary vacuum mixer to obtain a resin precursor liquid. Next, the obtained resin precursor liquid and 2.0 g of ammonium bicarbonate (manufactured by Fujifilm Wako Co., Ltd.) were kneaded in the same manner as above, and then poured into a SUS mold. The mold was then heated in an oven set to 90°C for 2 hours to cure.

[0108] In Examples 1 to 7 and Comparative Examples 1 to 3, the "polymer base material having a foamed structure" corresponds to base material A in Table 1.

[0109] Comparative Example 4 A shock absorbing pad from Kaneka Hip Protector (manufactured by Kaneka Corporation) was used. In this shock absorbing pad, the "polymer base material having a foam structure" corresponds to base material B in Table 1.

[0110] Comparative Example 5 A shock absorbing pad from Gunze Hip Protector (Gunze Ltd.) was used. In this shock absorbing pad, the "polymer base material having a foam structure" corresponds to another base material not listed in Table 1.

[0111] Comparative Example 6 33.7 g of styrene-based thermoplastic elastomer (SOE® S1605, manufactured by Asahi Kasei Corporation) and 1.85 g (5% by mass) of plasticizer (Diana Process Oil PW-90, manufactured by Idemitsu Kosan Co., Ltd.) were weighed and added to the mixer of a Labo Plastomill (Labo Plastomill 10C100, manufactured by Toyo Seiki Seisaku-sho Co., Ltd.). After preheating to 130°C for 1 minute, the mixture was mixed at 130°C, 300 rpm, and for 3 minutes. Then, 1.48 g (4% by mass) of blowing agent masterbatch (EE207, manufactured by Eiwa Chemical Industry Co., Ltd.) was added and mixed at 130°C, 300 rpm, and for 12 minutes, yielding a white mass. 12.2 g of the resulting block was placed in a frame of stainless steel spacers for pressing (100 mm in outer length, 100 mm in outer width, 60 mm in inner length, 60 mm in inner width, 7 mm thick) and compression molded using a compression molding machine (Kando Metal Industries Co., Ltd.) at a temperature of 210°C and a pressure of 50 MPa for 15 minutes, after which the heating switch was turned off and the material was allowed to cool overnight under pressure. The molded product was removed from the stainless steel plate set with the stainless steel spacers still sandwiched in place, and a white foamed thermoplastic elastomer plate was obtained.

[0112] Comparative Example 7 A styrene-based thermoplastic elastomer (Hybrar 7125, manufactured by Kuraray Co., Ltd.) and a styrene-based thermoplastic elastomer (Hybrar 7127, manufactured by Kuraray Co., Ltd.) were mixed in a mass ratio of 25:75 using a co-rotating twin-screw extruder (Omega 30H, manufactured by STEER) and pelletized. 35.5 g of the resulting pellets and 1.48 g (4 mass% of the total) of a blowing agent masterbatch (EE207, manufactured by Eiwa Chemical Industry Co., Ltd.) were added to the mixer of a Labo Plastomill (Labo Plastomill 10C100, manufactured by Toyo Seiki Seisakusho Co., Ltd.) and mixed at 140 °C, 300 rpm, and for 7 minutes to obtain a white mass. 15.1 g of the resulting block was placed in a frame of stainless steel spacers for pressing (100 mm in outer length, 100 mm in outer width, 60 mm in inner length, 60 mm in inner width, 7 mm thick) and compression-molded for 15 minutes at 210°C and 50 MPa pressure using a compression molding machine (Kando Metal Industries Co., Ltd.). After that, the heating switch was turned off and the block was allowed to cool overnight under pressure. The molded product was removed from the stainless steel plate set with the stainless steel spacers still sandwiched in place, and a white foamed thermoplastic elastomer plate was obtained.

[0113] Comparative Example 8 35.5 g of styrene-based thermoplastic elastomer (Hybrar 7125F, manufactured by Kuraray Co., Ltd.) and 1.48 g (4% by mass) of blowing agent masterbatch (EE207, manufactured by Eiwa Chemical Industry Co., Ltd.) were added to the mixer of a Labo Plastomill (Labo Plastomill 10C100, manufactured by Toyo Seiki Seisakusho Co., Ltd.) and mixed at 130 °C, 300 rpm, and 7 min to obtain a white mass. 17.4 g of the resulting mass was placed in a stainless steel spacer frame (100 mm x 100 mm, 60 mm x 60 mm, 7 mm thick) and compression molded at 210 °C and 50 MPa for 15 min using a compression molding machine (Shindo Metal Industries Co., Ltd.). The heating was then turned off and the mixture was allowed to cool under pressure overnight. The molded product was removed from the stainless steel plate set with the stainless steel spacer still in place to obtain a white foamed thermoplastic elastomer plate.

[0114] Comparative Example 9 35.5 g of styrene-based thermoplastic elastomer (Hybrar 7125F, manufactured by Kuraray Co., Ltd.) and 1.48 g (4% by mass) of blowing agent masterbatch (EE207, manufactured by Eiwa Chemical Industry Co., Ltd.) were added to the mixer of a Labo Plastomill (Labo Plastomill 10C100, manufactured by Toyo Seiki Seisakusho Co., Ltd.) and mixed at 130 °C, 300 rpm, and for 7 minutes to obtain a white mass. 12.0 g of the resulting mass was placed in a 100 mm x 100 mm x 60 mm stainless steel spacer frame. Compression molding was performed for 15 minutes using a compression molding machine (Shindo Metal Industries Co., Ltd.) at 210 °C and 50 MPa pressure. The heating was then turned off and the mixture was allowed to cool overnight under pressure. The molded product was removed from the stainless steel plate set, still sandwiched between the press spacers, to obtain a white foamed thermoplastic elastomer plate.

[0115] The above examples and comparative examples were each evaluated for the above evaluation items (impact attenuation, impact diffusion, thinness, and flexibility). The results are shown in Table 2. In Table 2, the examples were evaluated as anything other than x in all items, with favorable examples receiving one or more ⊚ evaluations and more favorable examples receiving two ⊚ evaluations. [Table 2]

[0116] The results of Examples 1 to 9 and Comparative Examples 1, 2, 4, and 6 to 9 show that when the ratio of the storage modulus G' at a peripheral speed of 2.7 m / s to the storage modulus G' at a peripheral speed of 0.1 m / s is 4.0 or more, the shock attenuation and shock diffusion properties are excellent, the thickness is small, and the flexibility is also excellent. From the results of Examples 1 to 9 and Comparative Examples 3, 5, 8 and 9, it can be seen that when the storage modulus G' at a peripheral speed of 2.7 m / s is 6 to 60 MPa, the impact attenuation and impact diffusion properties are excellent, the thickness is small and the flexibility is also excellent. From the above, it can be seen from the results of Examples 1 to 9 and Comparative Examples 1 to 9 that the impact absorbing material of the present invention is excellent in impact absorption properties and wearability.

[0117] Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims. [Industrial Applicability]

[0118] The impact-absorbing material of the present invention can be suitably used in a wide variety of applications, and is useful as, for example, protectors, flooring materials, automobile cushions, automobile bumpers, impact-absorbing sheets for electronic components, buffer materials, sporting goods, transport equipment such as pallets, drone components, impact-absorbing sheets for drone landing ports, etc.

Claims

1. An impact absorbing material comprising a polymer that satisfies the following (1) and (2): (1) The storage modulus G' at a peripheral speed of 2.7 m / s obtained by a dynamic solid viscoelasticity test is 6 to 60 MPa; (2) The ratio of the storage modulus G' at a peripheral speed of 2.7 m / s to the storage modulus G' at a peripheral speed of 0.1 m / s, as determined by a dynamic solid viscoelasticity test, is 4.0 or more.

2. The impact absorbing material according to claim 1 , wherein the polymer is a polymer having a foam structure.

3. 3. The impact absorbing material according to claim 2, wherein the ratio of G' at a peripheral speed of 2.7 m / s to G' at a peripheral speed of 0.1 m / s obtained by a dynamic solid viscoelasticity test of the polymer matrix having the foam structure is 2.5 or more.

4. 3. The impact absorbing material according to claim 2, wherein the loss tangent (tan δ) at a peripheral speed of 2.7 m / s obtained by a dynamic solid viscoelasticity test of the polymer matrix having the foamed structure is 0.5 or more.

5. 3. The impact absorbing material according to claim 2, wherein the polymer having the foamed structure has an expansion ratio of 1.2 to 3.

5.

6. 2. The impact absorbing material according to claim 1, which has a flat plate shape and a thickness of 0.3 to 500 mm.

7. The impact absorbing material of claim 1 , wherein the polymer is an elastomer.

8. 2. The impact absorbing material according to claim 1, wherein the polymer is a polyolefin-based thermoplastic elastomer, a polyurethane-based thermoplastic elastomer, a thermosetting polyurethane resin, a polyamide-based thermoplastic elastomer, a polyester-based thermoplastic elastomer, a polyvinyl chloride-based thermoplastic elastomer, an acrylic-based thermoplastic elastomer, or a polystyrene-based thermoplastic elastomer.

9. The impact absorbing material according to claim 1 , wherein the polymer is an epoxy resin.

10. 3. The impact absorbing material according to claim 2, wherein the polymer having a foamed structure is a foam obtained by foaming a composition containing an epoxy resin, a curing agent, and a foaming agent.

11. 3. The impact absorbing material according to claim 2, wherein the polymer having an expanded structure is a foam obtained by foaming a composition containing a polystyrene-based thermoplastic elastomer and a foaming agent.

12. The impact absorbing material according to claim 1 for use in protectors, flooring materials, automobile cushions, automobile bumpers, impact absorbing sheets for electronic components, buffer materials, sporting goods, transport equipment, drone components, and impact absorbing sheets for drone landing ports.

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