WO2023074764A1 - 発泡シート及びそれを用いた電子・電気機器 - Google Patents

発泡シート及びそれを用いた電子・電気機器 Download PDF

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Publication number
WO2023074764A1
WO2023074764A1 PCT/JP2022/040019 JP2022040019W WO2023074764A1 WO 2023074764 A1 WO2023074764 A1 WO 2023074764A1 JP 2022040019 W JP2022040019 W JP 2022040019W WO 2023074764 A1 WO2023074764 A1 WO 2023074764A1
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Prior art keywords
foam sheet
sheet
mass
foam
urethane resin
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
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PCT/JP2022/040019
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English (en)
French (fr)
Japanese (ja)
Inventor
茉由季 山田
拓也 永澤
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Inoac Corp
Inoac Technical Center Co Ltd
Original Assignee
Inoue MTP KK
Inoac Corp
Inoac Technical Center Co Ltd
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Application filed by Inoue MTP KK, Inoac Corp, Inoac Technical Center Co Ltd filed Critical Inoue MTP KK
Priority to CN202280072012.8A priority Critical patent/CN118119653A/zh
Priority to KR1020247017148A priority patent/KR20240099334A/ko
Priority to JP2023556611A priority patent/JPWO2023074764A1/ja
Publication of WO2023074764A1 publication Critical patent/WO2023074764A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/30—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by mixing gases into liquid compositions or plastisols, e.g. frothing with air
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/0014—Use of organic additives
    • C08J9/0028—Use of organic additives containing nitrogen
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/0061—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof characterized by the use of several polymeric components
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
    • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
    • C08J9/122—Hydrogen, oxygen, CO2, nitrogen or noble gases
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2201/00—Foams characterised by the foaming process
    • C08J2201/04—Foams characterised by the foaming process characterised by the elimination of a liquid or solid component, e.g. precipitation, leaching out, evaporation
    • C08J2201/05—Elimination by evaporation or heat degradation of a liquid phase
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2203/00—Foams characterized by the expanding agent
    • C08J2203/06—CO2, N2 or noble gases
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2205/00—Foams characterised by their properties
    • C08J2205/02—Foams characterised by their properties the finished foam itself being a gel or a gel being temporarily formed when processing the foamable composition
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2375/00—Characterised by the use of polyureas or polyurethanes; Derivatives of such polymers
    • C08J2375/04—Polyurethanes

Definitions

  • the present invention relates to a foam sheet and an electronic/electric device using it.
  • Patent Document 1 discloses a foamed sheet composed of a foam having an average cell diameter of 10 to 200 ⁇ m, having a compression set of 80% or less at 80° C., and a shock absorption rate of change of ⁇ 20% or less. It is disclosed that the foamed sheet exhibits excellent impact absorption and excellent heat resistance even when the thickness is very thin.
  • the foam sheet disclosed in Patent Document 1 can be evaluated for local impact by the impact load method using steel balls, but it can be applied to a wide area of the display panel. There is a possibility that the impact applied (surface impact) may not be effective, and there is a possibility that the protection of the parts inside the equipment may be insufficient.
  • an object of the present invention is to provide a new foam sheet and an electronic/electric device using the foam sheet, which have superior effects.
  • a foam sheet containing a urethane resin and/or an acrylic resin as a resin component The foam sheet has a thickness of 0.06 to 1.0 mm, The foam sheet has a density of 0.05 to 1.00 g/cm 3 , When the urethane resin is included, the foam sheet has a gel fraction of 60% by mass or more, and when the acrylic resin is included, the foamed sheet has a gel fraction of more than 80% by mass.
  • the content of the resin component may be 60% by mass or more.
  • the density of the foam sheet is 0.10 to 0.55 g/cm 3
  • the acrylic resin is included, the density of the foam sheet is 0.10 to 0.80 g/cm 3 .
  • the gel fraction of the foam sheet is 60 to 90% by mass
  • the acrylic resin is included, the gel fraction of the foam sheet is more than 80% by mass and 95% by mass or less. good.
  • the foam sheet may be formed by foaming and curing a urethane resin composition containing a urethane emulsion and/or an acrylic resin composition containing an acrylic emulsion.
  • the urethane resin composition and/or the acrylic resin composition may further contain a water-dispersible isocyanate.
  • the foam sheet may be heated in an environment of 70° C. or higher for 20 hours or longer after forming the foam sheet.
  • Aspect (2) of the present invention is An electronic/electric device comprising any one of the foam sheets described above.
  • FIG. 1 is a schematic diagram showing a point impact absorption tester used for evaluation of the present disclosure
  • FIG. 1 is a schematic diagram showing a surface impact absorption tester used for evaluation of the present disclosure
  • FIG. 3 is a schematic diagram showing a compression set tester used for evaluation of the present disclosure.
  • the foam sheet of the present disclosure contains urethane resin and/or acrylic resin, has a thickness of 0.06 to 1.0 mm, a density of 0.05 to 1.00 g/cm 3 , and contains urethane resin.
  • the gel fraction of the foam sheet is 60% by mass or more, and when the acrylic resin is contained, the gel fraction of the foam sheet is more than 80% by mass, but the foam sheet of the present disclosure is not limited to this.
  • the thickness of the foam sheet of the present disclosure is 0.06-1.0 mm, preferably 0.08-0.5 mm.
  • the foam sheet of the present disclosure may be a foam sheet having a predetermined thickness by molding (eg, casting method), or may be a foam sheet processed to a predetermined thickness by splitting or the like after molding.
  • the term “thickness of the foamed sheet” refers to the thickness of the "foam formed into a sheet", and the thickness of other layers including the pressure-sensitive adhesive layer, the base material and the release liner. Do not include thickness.
  • the foam sheet of the present disclosure may have an altered layer called a skin layer on its surface.
  • the cells contained in the foam sheet of the present disclosure are not particularly limited as long as they do not inhibit the effects of the present disclosure, and may include any of closed cells, open cells, and semi-open cells.
  • the term "semi-open cell” refers to a structure having small pores in cells, unlike closed cells, and having a structure in which adjacent cells have smaller pores than open cells. refers to a structure with an air permeability of 2 to 80 ml/(cm2/s) according to the Frazier type method of JIS L1096 A method. Since the closed cells contain gas in the cells, they have a strong elastic characteristic to the foam sheet, and the foam sheet containing more closed cells becomes more elastic. Therefore, the compression set of the foam sheet tends to be low. On the contrary, open cells allow the gas in the cells to move freely, so that the elastic properties of the foam sheet are relatively weak. Therefore, the compressive residual strain of the foam sheet tends to be high. Semi-open cells exhibit an intermediate effect between closed cells and open cells.
  • the density of the foam sheet is 0.05 to 1.00 g/cm 3
  • the lower limit is 0.05 g/cm 3 or more and 0.10 g/cm 3 .
  • the upper limit is 1.00 g/cm 3 or less, 0.55 g/cm 3 or less, 0.50 g/cm 3 or less, 0.30 g/cm 3 or less .
  • it can be 0.20 g/cm 3 or less.
  • the density of the foam sheet is 0.05 to 1.00 g/cm 3
  • the lower limit is 0.05 g/cm 3 or more, 0.10 g/cm 3 or more, 0.15 g/cm 3 or more. cm 3 or more . cm 3 or less.
  • the density of the foamed sheet is within such a range, the foamed sheet can have superior point impact absorption rate and surface impact absorption rate and lower compressive residual strain even if it is thin.
  • the density of the foamed sheet is the apparent density, which is measured according to JIS K7222:2005 "Foamed plastics and rubbers - Determination of apparent density”.
  • the foam sheet When the density of the foam sheet is low, the foam sheet contains a large number of cells, so the elastic properties of the cells have a stronger effect. Conversely, when the density of the foam sheet is high, the viscoelastic properties of the resin have a relatively strong effect. By adjusting the elastic properties of these cells and the viscoelastic properties of the resin, it is possible to adjust the point impact absorption rate, surface impact absorption rate, and compressive residual strain of the foamed sheet.
  • the gel fraction of the foam sheet is 60% by mass or more, preferably 60 to 90% by mass, more preferably 60 to 80% by mass.
  • the gel fraction of the foam sheet is more than 80% by mass, preferably more than 80% by mass and 95% by mass or less, more preferably more than 80% by mass. It is 90% by mass or less.
  • the gel fraction is within such a range, it is possible to obtain a foamed sheet which is excellent in point impact absorption and surface impact absorption and has a lower compressive residual strain even though it is thin.
  • the gel fraction is measured according to the following procedure.
  • a predetermined amount of pyridine eg, 20 mL
  • acrylic resin> 50 mg of the foam sheet is immersed in a predetermined amount of pyridine (eg, 20 mL), heated to 100° C., and heated for 24 hours.
  • the residue of the foamed sheet remaining undissolved is taken out, dried and weighed.
  • the gel fraction is calculated by dividing the resulting mass by 50 mg.
  • the gel fraction is determined by the number of cross-linking points contained in the resin component described later, for example, the number of hydroxyl groups in the resin component (for example, hydroxyl groups in urethane resin) and the number of amino groups having hydrogen, the amount of cross-linking agent added, and the amount of heat. It can be adjusted by adjusting reaction conditions such as temperature. When specifically adjusting the number of hydroxyl groups in the resin component, for example, the hydroxyl value of the urethane resin in the resin component and the amount of the isocyanate compound added as the cross-linking agent are adjusted to obtain the desired gel fraction. good.
  • a foam sheet according to the present disclosure can be formed on a substrate. By doing so, it becomes possible to impart strength to the foam sheet.
  • the method of forming the foamed sheet on the substrate is not particularly limited, and examples thereof include a method of coating the foam-forming composition directly on the substrate, a method of providing a pressure-sensitive adhesive layer, and laminating.
  • a laminate in which a substrate, an adhesive layer, and a release liner are arranged in this order is formed in advance, and a foam sheet is placed on the surface of the substrate opposite to the side on which the adhesive layer is present. It may be integrally molded.
  • a release agent layer may be provided on the surface of the base material on which the foam sheet is formed. By doing so, the substrate can be used as a release liner.
  • a release agent layer may be provided on the surface of the substrate opposite to the foam sheet forming side.
  • the foam sheet according to the present disclosure can be provided with an adhesive layer on one side or both sides of its surface. By providing the adhesive layer, it becomes easy to fix the electronic/electric parts using the foam sheet.
  • the foam sheet provided with an adhesive layer on one side or both surfaces can further have a release liner on the surface of the adhesive layer.
  • a release liner By providing a release liner, it is possible to prevent damage to the adhesive layer during transportation or before use.
  • the foam sheet according to the present disclosure includes the foam sheet according to the present disclosure
  • foams other than the foam sheet of the present disclosure base materials, adhesive layers, and other known Layers may be stacked in any desired number and in any desired order.
  • the present A foam sheet having a plurality of disclosed foam sheets may be used.
  • the foam sheet of the present disclosure contains urethane resin and/or acrylic resin.
  • the foamed sheet of the present disclosure is obtained by foaming and curing a urethane resin composition containing a urethane resin and/or an acrylic resin composition containing an acrylic resin.
  • the urethane resin composition is not particularly limited as long as it can produce the foamed sheet of the present disclosure, but can contain, for example, a resin component containing a urethane resin, a foaming agent, a dispersion medium, a crosslinking agent, and other additives.
  • the acrylic resin composition is not particularly limited as long as it can produce the foamed sheet of the present disclosure. can be done.
  • the resin component according to the present disclosure includes urethane resin and/or acrylic resin.
  • the urethane resin may include any of polyurethane-based resins such as polyether-based and polyester-based resins.
  • a urethane resin and/or an acrylic resin it is possible to impart material strength to the foam sheet, and the resulting foam sheet has the advantage of being excellent in flexibility and having a low compression set.
  • the foam sheet can be particularly preferably used when the adherend is a sticky glass or the like.
  • the urethane resin it is preferable to use a urethane emulsion because the density and cell diameter can be easily adjusted by the gas mixing method.
  • the number of cross-linking points (such as hydroxyl groups and amino groups having hydrogen) contained in the urethane resin. More specifically, by adjusting the number of hydroxyl groups (hydroxyl value) contained in the urethane resin and the amount of the cross-linking agent added (adjusting the isocyanate index, which will be described later), a foamed sheet with a desired gel fraction can be obtained. Obtainable.
  • the hydroxyl value of the urethane resin is not particularly limited as long as the effects of the present disclosure are not inhibited. For example, it can be 3 mgKOH/g or more, preferably 5 mgKOH/g or more.
  • the upper limit of the hydroxyl value of the urethane resin is not particularly limited, it is preferably, for example, 500 mgKOH/g or less, 250 mgKOH/g or less, or 100 mgKOH/g or less.
  • the hydroxyl value of the urethane resin is within such a range, the addition of a cross-linking agent makes it possible to easily adjust the gel fraction to a desired range.
  • the hydroxyl value of the urethane resin is measured according to the acid value measurement method described in JIS K0070: 1992 "Testing methods for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponifiable matter of chemical products". is the value
  • Examples of methods for preparing a urethane emulsion include the following methods (I) to (III).
  • An active hydrogen-containing compound, a compound having a hydrophilic group, and a urethane prepolymer containing a terminal isocyanate group having a hydrophilic group obtained by reacting a polyisocyanate is mixed with an aqueous solution containing a neutralizing agent.
  • a method of adding a neutralizing agent in advance to a prepolymer, mixing with water to disperse it in water, and then reacting it with a polyamine to obtain a urethane emulsion is a method of adding a neutralizing agent in advance to a prepolymer, mixing with water to disperse it in water, and then reacting it with a polyamine to obtain a urethane emulsion.
  • a urethane prepolymer containing a terminal isocyanate group having a hydrophilic group obtained by reacting an active hydrogen-containing compound, a compound having a hydrophilic group, and a polyisocyanate is mixed with an aqueous solution containing a neutralizer and a polyamine.
  • an aqueous solution containing polyamine is added and mixed to obtain a urethane emulsion.
  • Polyisocyanates used in the preparation of the urethane resin include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, and 2,4′.
  • a polyisocyanate having a valence of 3 or more may be used in combination within a range that does not impair the effects of the present disclosure. These can be selected in consideration of the viscoelastic properties of the resin (including urethane resin) contained in the foam sheet. By this selection, it is possible to adjust the point impact absorption rate, surface impact absorption rate, and compression set property of the foamed sheet.
  • Examples of compounds having hydrophilic groups include polyester polyols, polyether polyols, polycarbonate polyols, polyacetal polyols, polyacrylate polyols, polyesteramide polyols, polythioether polyols, and polybutadiene-based polyolefin polyols. These high molecular weight compounds may be used in combination of two or more.
  • a known polyester polyol may be used as the polyester polyol. These can be selected in consideration of the viscoelastic properties of the resin contained in the foam sheet. By this selection, it is possible to adjust the point impact absorption rate, surface impact absorption rate, and compression set property of the foamed sheet.
  • an emulsifier may be used as long as the effects of the present disclosure are not impaired.
  • emulsifiers include nonionic emulsifiers such as polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene styrenated phenyl ether, and polyoxyethylene sorbitol tetraoleate; fatty acid salts such as sodium oleate; Anionic emulsifiers such as sulfates, alkylbenzenesulfonates, alkylsulfosuccinates, naphthalenesulfonates, alkanesulfonate sodium salts, alkyldiphenylethersulfonate sodium salts; polyoxyethylene alkyl sulfates, polyoxyethylene alkylphenyl sulfates Examples include nonionic anionic emulsifiers such as
  • the resin component according to the present disclosure is not limited as long as it does not impede the effects of the present disclosure, other than the urethane resin.
  • (meth)acrylic resin polystyrene resin
  • polyethylene polypropylene
  • polyethylene-polypropylene copolymer etc.
  • Polyolefin resin vinyl acetate copolymer (EVA) resin; polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polytrimethylene terephthalate (PTT ) and other polyester resins; resol type and novolac type phenolic resins; epoxy resins; silicone resins; polyvinyl chloride resins; urea resins; polyimide resins; A copolymer obtained by copolymerizing the constituent monomers of can be used. Furthermore, emulsions of these resins and copolymers obtained by copolymerizing the constituent monomers of these resins can be used. These can be used singly or in combination.
  • water is an essential component of the dispersion medium for the resin component when the urethane-based emulsion is included, but a mixture of water and a water-soluble solvent may also be used.
  • the water-soluble solvent includes, for example, alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl carbitol, ethyl cellosolve, and butyl cellosolve, polar solvents such as N-methylpyrrolidone, and the like. You may use the mixture etc. of
  • Viscosity can be measured, for example, with a Brookfield viscometer (25° C.).
  • the viscosity of the resin component can be, for example, 100 to 15,000 mPa ⁇ s, preferably 2000 to 15,000 mPa ⁇ s. When the viscosity is within such a range, the bubble holding power during molding becomes sufficient, and finer cells can be molded. In this way, the viscosity of the resin component can be used to adjust the cell diameter and shape of the foamed sheet. affected. When the viscosity is within such a range, the point impact absorption rate, surface impact absorption rate, and compression set property of the foamed sheet can be made more excellent.
  • Foaming agent anionic surfactant
  • the anionic surfactant functions as a foaming agent for the urethane resin composition.
  • anionic surfactants include sodium laurate, sodium myristate, sodium stearate, ammonium stearate, sodium oleate, potassium oleate soap, potassium castor oil soap, potassium coconut oil soap, sodium lauroyl sarcosinate, sodium myristoyl sarcosinate, sodium oleyl sarcosinate, sodium cocoyl sarcosinate, sodium coconut oil alcohol sulfate, sodium polyoxyethylene lauryl ether sulfate, sodium alkylsulfosuccinate, sodium laurylsulfoacetate, sodium alkylbenzenesulfonate, sodium ⁇ -olefinsulfonate, etc.
  • sodium alkyl sulfosuccinate is particularly preferred. These can be used singly or in combination.
  • the foamed sheet of the present disclosure has fine and uniform cells by using an amphoteric surfactant in addition to an anionic surfactant. That is, by adding an amphoteric surfactant, the cell diameter and cell density of the foamed sheet can be adjusted, and the point impact absorption rate, surface impact absorption rate, and compression set property of the foamed sheet are not affected. be. In addition, when an amphoteric surfactant is used, the density and distribution of cells in the foamed sheet are likely to be uniform, so it is possible to obtain a foamed sheet having uniform surface impact resistance in the plane of the sheet.
  • the amphoteric surfactant which is electrically neutral, enters between the molecules of the anionic surfactant, thereby making the bubbles more stable and reducing the size of the bubbles. Therefore, by using an anionic surfactant and an amphoteric surfactant together, the cell diameter and density of the foamed sheet can be further adjusted, and the point impact absorption rate and surface impact absorption rate of the foamed sheet , the compression set property can be adjusted.
  • amphoteric surfactant that can be used in the present disclosure is not particularly limited, and amphoteric surfactants such as amino acid type, betaine type, and amine oxide type can be used. These can be used singly or in combination. It is preferable to use a betaine-type amphoteric surfactant because the effect of the amphoteric surfactant described above is higher.
  • amino acid-type amphoteric surfactants include N-alkyl or alkenyl amino acids or salts thereof.
  • An N-alkyl or alkenyl amino acid has an alkyl group or alkenyl group bonded to a nitrogen atom, and one or two "-R-COOH" (wherein R represents a divalent hydrocarbon group, preferably It is an alkylene group, and preferably has 1 to 2 carbon atoms.) is bonded.
  • R represents a divalent hydrocarbon group, preferably It is an alkylene group, and preferably has 1 to 2 carbon atoms.
  • amphoteric surfactant both mono-isomer and di-isomer can be used.
  • the alkyl group and alkenyl group may be linear or branched.
  • amino acid-type amphoteric surfactants include sodium lauryldiaminoethylglycinate, sodium trimethylglycinate, sodium cocoyl taurate, sodium cocoyl methyl taurate, sodium lauroyl glutamate, potassium lauroyl glutamate, lauroylmethyl- ⁇ -alanine, and the like. be done.
  • betaine-type amphoteric surfactants examples include alkylbetaine, imidazolinium betaine, carbobetaine, amidocarbobetaine, amidobetaine, alkylamidobetaine, sulfobetaine, amidosulfobetaine, and phosphobetaine.
  • betaine-type amphoteric surfactants include lauryl betaine, stearyl betaine, lauryldimethylamino betaine, myristyldimethylamino betaine, stearyldimethylamino betaine, lauramidopropyldimethylamino betaine, and isostearamide.
  • Ethyldimethylaminoacetate betaine isostearamidopropyldimethylaminoacetate betaine, isostearamidoethyldiethylaminoacetate betaine, isostearamidopropyl diethylaminoacetate betaine, isostearamideethyldimethylaminohydroxysulfobetaine, isostearamidopropyldimethylaminohydroxysulfobetaine , isostearamidoethyldiethylaminohydroxysulfobetaine, isostearamidopropyldiethylaminohydroxysulfobetaine, N-lauryl-N,N-dimethylammonium-N-propylsulfobetaine, N-lauryl-N,N-dimethylammonium-N-( 2-hydroxypropyl)sulfobetaine, N-lauryl-N,N-dimethyl-N-(2-hydroxy-1-sulf
  • Amine oxide type amphoteric surfactants include, for example, lauryldimethylamine-N-oxide and oleyldimethylamine-N-oxide.
  • amphoteric surfactants can be used alone or in combination. Among these, it is preferable to use a betaine-type amphoteric surfactant in the method for producing a foamed sheet of the present disclosure.
  • Cross-linking agent (curing agent)
  • a cross-linking agent curing agent
  • the viscoelastic properties of the foamed sheet can be adjusted, and the point impact absorption rate, surface impact absorption rate, and compression residual strain of the foamed sheet can be adjusted.
  • cross-linking agent may be added in a necessary amount depending on the application.
  • Cross-linking methods using a cross-linking agent include, for example, physical cross-linking, ionic cross-linking, and chemical cross-linking, and the cross-linking method can be selected according to the type of water-dispersible resin.
  • the cross-linking agent known cross-linking agents can be used, and epoxy-based cross-linking agents, melamine-based cross-linking agents, isocyanate-based cross-linking agents, carbodiimide-based cross-linking agents, oxazoline-based cross-linking agents and the like can be used depending on the functionality contained in the resin formulation system used.
  • Isocyanate-based and epoxy-based cross-linking agents are preferable because they can prevent material destruction of the adherend and foam sheet by increasing material strength. Two or more of these cross-linking agents may be used in combination.
  • the isocyanate-based cross-linking agent used in the preparation of the urethane resin it is preferable to use a water-dispersible polyfunctional isocyanate.
  • the water-dispersible polyfunctional isocyanate include a compound in which a polyfunctional isocyanate is microencapsulated to impart water dispersibility, and a compound in which an isocyanate group is protected with a hydrophilic component.
  • a commercially available product may be used as the water-dispersed polyfunctional isocyanate, for example, polyisocyanate manufactured by Asahi Kasei Corporation (Duranate WB40-100, WB40-80D, WT20-100, WT30-100, WT70-100, WR80-70P , WE50-100) and the like.
  • the water-dispersible polyfunctional isocyanate may be used alone or in combination of two or more.
  • the urethane resin composition according to the present disclosure can contain, as other additives, known additives (for example, nonionic surfactants, etc.) that are added to foams.
  • known additives for example, nonionic surfactants, etc.
  • the surfactant for dispersing the water-dispersible resin is a surfactant for dispersing the water-dispersible resin, and unlike an anionic surfactant, it may not have an effect as a foaming agent.
  • Such a surfactant may be appropriately selected according to the selected water-dispersible resin.
  • an acrylic emulsion As the acrylic resin, it is preferable to use an acrylic emulsion because the density and cell diameter can be easily adjusted by the gas mixing method.
  • a method for producing an acrylic emulsion aqueous dispersion of acrylic resin
  • a polymerization initiator and, if necessary, an emulsifier and a dispersion stabilizer for example, a (meth)acrylic ester-based monomer is subjected to essential polymerization.
  • a (meth)acrylic ester-based monomer is subjected to essential polymerization.
  • a (meth)acrylic ester-based monomer is subjected to essential polymerization.
  • Two or more acrylic emulsions may be used in combination.
  • (meth)acrylic acid in this specification includes methacrylic acid and acrylic acid.
  • methyl (meth)acrylate includes methyl methacrylate and methyl acrylate.
  • polymerizable monomers examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, (meth) ) hexyl acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, octadecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, nonyl (meth) acrylate, ( (Meth)acrylic acids such as dodecyl methacrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, phenyl (meth)acrylate, and benzyl (meth)acrylate Ester-based monomers; acrylic acid, methyl (meth)acrylate, propyl (
  • the acrylic emulsion may be a commercially available one, as long as resin fine particles are dispersed in water as a continuous phase, and may contain a dispersant such as a surfactant as necessary.
  • the solid content concentration of the acrylic emulsion is preferably 30% by weight or more, more preferably 40% by weight or more, and still more preferably 50% by weight or more.
  • the components of the resin fine particles include acrylic resins, acrylic styrene resins, acrylic silicone resins, etc. Among these, acrylic silicone resins are particularly preferable.
  • Commercially available resin emulsions include Microgel E-1002, E-5002 (styrene-acrylic resin emulsion, manufactured by Nippon Paint Co., Ltd.), Boncoat 4001 (acrylic resin emulsion, manufactured by Dainippon Ink and Chemicals, Inc.), and Boncoat.
  • a known emulsifier or the like may be used.
  • Viscosity Viscosity (mPa ⁇ s) Viscosity is measured with a Brookfield viscometer (25° C.).
  • the viscosity of the acrylic emulsion is preferably 1,000 to 20,000 mPa ⁇ s. It is more preferably 8,000 to 15,000 mPa ⁇ s. This is because when the viscosity is 5,000 or more, the foam holding power during molding becomes sufficient, finer cells can be molded, and the adhesive strength tends to be higher. Conversely, if the viscosity is 20,000 or less, the shearing force applied to the raw material during molding can be reduced, so that distorted cells can be prevented from being molded, and sufficient adhesive strength can be obtained.
  • the dispersion medium of the acrylic emulsion composition contains water as an essential component, but may be a mixture of water and a water-soluble solvent.
  • the water-soluble solvent includes, for example, alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl carbitol, ethyl cellosolve, and butyl cellosolve, polar solvents such as N-methylpyrrolidone, and the like. You may use the mixture etc. of
  • Foaming agent anionic surfactant
  • Anionic surfactants function as foaming agents in acrylic emulsion compositions.
  • anionic surfactants include sodium laurate, sodium myristate, sodium stearate, ammonium stearate, sodium oleate, potassium oleate soap, potassium castor oil soap, potassium coconut oil soap, sodium lauroyl sarcosinate, sodium myristoyl sarcosinate, sodium oleyl sarcosinate, sodium cocoyl sarcosinate, sodium coconut oil alcohol sulfate, sodium polyoxyethylene lauryl ether sulfate, sodium alkylsulfosuccinate, sodium laurylsulfoacetate, sodium alkylbenzenesulfonate, sodium ⁇ -olefinsulfonate, etc.
  • sodium alkyl sulfosuccinate is particularly preferred.
  • the anionic surfactant used in the present embodiment preferably has an HLB of 10 or more, more preferably 20 or more, in order to facilitate dispersion in the acrylic emulsion composition. , 30 or more.
  • the foam according to the present embodiment has fine and uniform cells by using an amphoteric surfactant in addition to an anionic surfactant.
  • the presence of the electrically neutral surfactant between the molecules of the anionic surfactant can further stabilize the bubbles and reduce the size of the bubbles. Therefore, the delamination strength can be improved. Therefore, it is preferable to use both an anionic surfactant and an amphoteric surfactant.
  • amphoteric surfactant that can be used in the present disclosure is not particularly limited, and amphoteric surfactants such as amino acid type, betaine type, and amine oxide type can be used. Betaine-type amphoteric surfactants are preferred because the above effects are higher. Further, C10-12 are preferred from the viewpoint of easiness of entering between the molecules of the anionic surfactant.
  • amino acid-type amphoteric surfactants include N-alkyl or alkenyl amino acids or salts thereof.
  • An N-alkyl or alkenyl amino acid has an alkyl group or alkenyl group bonded to a nitrogen atom, and one or two "-R-COOH" (wherein R represents a divalent hydrocarbon group, preferably It is an alkylene group, and preferably has 1 to 2 carbon atoms.) is bonded.
  • R represents a divalent hydrocarbon group, preferably It is an alkylene group, and preferably has 1 to 2 carbon atoms.
  • amphoteric surfactant both mono-isomer and di-isomer can be used.
  • the alkyl group and alkenyl group may be linear or branched.
  • amino acid-type amphoteric surfactants include sodium lauryldiaminoethylglycinate, sodium trimethylglycinate, sodium cocoyl taurate, sodium cocoyl methyl taurate, sodium lauroyl glutamate, potassium lauroyl glutamate, lauroylmethyl- ⁇ -alanine, and the like. be done.
  • betaine-type amphoteric surfactants include alkylbetaine, imidazolinium betaine, carbobetaine, amidocarbobetaine, amidobetaine, alkylamidobetaine, sulfobetaine, amidosulfobetaine, and phosphobetaine.
  • betaine-type amphoteric surfactants include lauryl betaine, stearyl betaine, lauryldimethylamino betaine, stearyldimethylamino betaine, lauramidopropyldimethylamino betaine, isostearamideethyldimethylamino betaine, Isostearamidopropyl dimethylamino betaine, Isostearamide ethyl diethylamino acetate betaine, Isostearamide propyl diethylamino acetate betaine, Isostearamide ethyl dimethylamino hydroxysulfobetaine, Isostearamide propyl dimethylamino hydroxysulfobetaine, Isostearamide ethyl diethylamino acetate Hydroxysulfobetaine, isostearamidopropyldiethylaminohydroxysulfobetaine, N-lauryl-N,N-di
  • Amine oxide type amphoteric surfactants include, for example, lauryldimethylamine-N-oxide and oleyldimethylamine-N-oxide.
  • amphoteric surfactants described above it is preferable to use betaine-type amphoteric surfactants in the method for producing a foam according to the present disclosure. is particularly preferred.
  • alkyl betaine that can be used in the present disclosure include stearyl betaine, lauryl betaine, and the like
  • imidazolinium betaine include 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, and the like.
  • Cross-linking agent A cross-linking agent (curing agent) according to the present disclosure may include an isocyanurate compound or an isocyanate-based cross-linking agent.
  • An isocyanurate compound is a compound having an isocyanurate ring.
  • the isocyanurate compound is not particularly limited as long as it does not inhibit the effects of the present disclosure.
  • isocyanurate compounds include aliphatic diisocyanate isocyanurate compounds, aliphatic isocyanate silane isocyanurate compounds, (meth)acrylic compounds having an isocyanurate ring, thiol compounds having an isocyanurate ring, and isocyanurate rings. and glycidyl compounds having
  • isocyanurate compounds of aliphatic diisocyanates include isocyanurate compounds of aliphatic diisocyanates such as hexamethylene diisocyanate (HDI), pentamethylene diisocyanate, trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, and norbornane diisocyanate (NBDI).
  • HDI hexamethylene diisocyanate
  • TMHDI trimethylhexamethylene diisocyanate
  • lysine diisocyanate lysine diisocyanate
  • norbornane diisocyanate NBDI
  • isocyanurate compounds of aliphatic isocyanate silanes include isocyanurate compounds of aliphatic isocyanate silanes such as isocyanatopropyltriethoxysilane and isocyanatopropyltrimethoxysilane.
  • (Meth)acrylic compounds having an isocyanurate ring include ethoxylated isocyanuric acid triacrylate, ⁇ -caprolactone-modified tris(2-acryloxyethyl) isocyanurate; hexamethylene diisocyanate (HDI), pentamethylene diisocyanate, and trimethylhexamethylene diisocyanate.
  • compounds obtained by reacting aliphatic diisocyanates such as (TMHDI), lysine diisocyanate, and norbornane diisocyanate (NBDI) with hydroxyl group-containing acrylamide monomers such as hydroxyethyl acrylamide and hydroxyl group-containing acrylates such as 4-hydroxybutyl acrylate; mentioned.
  • Thiol compounds having an isocyanurate ring include tris(ethyl-3-mercaptopropionate) isocyanurate, 1,3,5-tris(3-mercaptobutyryloxyethyl)-1,3,5-triazine-2 , 4,6(1H,3H,5H)-trione and the like.
  • Examples of glycidyl compounds having an isocyanurate ring include 1,3,5-tris(2,3-epoxypropyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione and the like. mentioned.
  • isocyanurate compounds aliphatic or alicyclic diisocyanate isocyanurate compounds are preferred, and aliphatic ones are more preferred.
  • the reaction mixture after mechanical stirring can be discharged at an appropriate time, and by using a trimer, the mechanical properties of the foam sheet can be suitably It is possible to obtain a foamed sheet having excellent point impact absorption performance.
  • a water-dispersible polyfunctional isocyanate as the isocyanate-based cross-linking agent used in the preparation of the acrylic resin.
  • the water-dispersible polyfunctional isocyanate include a compound in which a polyfunctional isocyanate is microencapsulated to impart water dispersibility, and a compound in which an isocyanate group is protected with a hydrophilic component.
  • a commercially available product may be used as the water-dispersed polyfunctional isocyanate, for example, polyisocyanate manufactured by Asahi Kasei Corporation (Duranate WB40-100, WB40-80D, WT20-100, WT30-100, WT70-100, WR80-70P , WE50-100) and the like.
  • the water-dispersible polyfunctional isocyanate may be used alone or in combination of two or more.
  • surfactant for dispersing water-dispersible resin is a surfactant for dispersing the water-dispersible resin (unlike an anionic surfactant, foaming may not have an effect as an agent). Such a surfactant may be appropriately selected according to the selected water-dispersible resin.
  • the blending amount of the water-dispersible resin (solid content) in the liquid medium is preferably 30 to 80 parts by weight with respect to 100 parts by weight of the liquid medium. By setting it as such a range, the effect that a stable foam can be shape
  • the preferred compounding ratio of the foam according to the present disclosure will be described below. Unless otherwise specified, the blending amounts and blending ratios in the following description are based on the solid content.
  • the amount of the anionic surfactant to be blended is 1.0 to 10 parts based on the total amount of the acrylic emulsion in the acrylic emulsion composition (the total of the solid content and non-solid content is 100 parts by weight). Parts by weight are preferred, and 3 to 10 parts by weight are more preferred. By setting it as such a range, the effect that it is easy to carry out suitable foaming and can shape
  • the amount of the amphoteric surfactant is 0.5 to 10 parts by weight based on the total amount of the acrylic emulsion in the acrylic emulsion composition (the total of the solid content and non-solid content is 100 parts by weight). parts are preferred, and 1 to 5 parts by weight are more preferred. By setting it as such a range, the effect that it is easy to carry out suitable foaming and can shape
  • the weight ratio of the cross-linking agent to the acrylic emulsion (solid content) in the acrylic emulsion composition is 0.01 to 0.01. 12. It is preferably between 0.025 and 0.05. By setting it as such a range, it is possible to mold a foam having a small compressive residual strain.
  • the component constituting the "solid content" of the urethane-based emulsion in this specification is the component excluding the dispersion medium from the entire urethane-based emulsion.
  • the content (solid content) of the urethane-based emulsion is not particularly limited, but for example, when the total weight of the foam sheet is 100% by weight, the urethane resin should be blended so that it is 70% by weight or more.
  • the amount of the anionic surfactant blended in the urethane resin composition is preferably 1.0 to 10 parts by mass, based on the total amount of the resin components (the total solid content is 100 parts by mass), and 3 to 10 parts by mass. 10 parts by mass is more preferable. By setting it as such a range, the effect that it is easy to carry out suitable foaming and can shape
  • the amount of the amphoteric surfactant is preferably 0.5 to 10 parts by mass based on the total amount of the resin components in the urethane resin composition (the total of the solid content and non-solid content is 100 parts by mass). , more preferably 1 to 5 parts by mass.
  • the amount of the cross-linking agent is 0.5 to 10 parts by mass based on the total amount of the resin component in the urethane resin composition (the total of the solid content and non-solid content is 100 parts by mass). Preferably, 1 to 5 parts by mass is more preferable. With such a range, a foamed sheet having a desired gel fraction can be easily obtained by reaction with the cross-linking points of the resin component.
  • a urethane emulsion is used as the resin component and an isocyanate cross-linking agent is used as the cross-linking agent
  • the gel fraction of the foam sheet can be adjusted by adjusting the isocyanate index of the urethane resin composition.
  • the isocyanate index is not particularly limited as long as the effects of the present disclosure are not inhibited. ⁇ 200, more preferably 20-150.
  • the isocyanate index is a value obtained by multiplying the ratio of the number of moles of all active hydrogen contained in the urethane resin composition to the number of moles of isocyanate groups in the isocyanate-based cross-linking agent by 100 (number of moles of isocyanate/activity number of moles of hydrogen x 100).
  • the isocyanate index of the urethane resin composition is within this range, it is possible to obtain a foamed sheet with a predetermined gel fraction. That is, it is possible to obtain a foamed sheet excellent in point impact absorption rate, surface impact absorption rate and compressive residual strain property.
  • the method for manufacturing a foam sheet according to the present disclosure includes a raw material preparation step and a foaming/curing step.
  • a foaming/curing step for example, a urethane resin composition containing at least an emulsion and a foaming agent is foamed using, for example, a mechanical froth method to form a foam-forming composition, and the foam-forming composition is foamed.
  • the urethane resin composition may further contain a cross-linking agent, and in the above step, the foam-forming composition may be cured by applying energy to cross-link the resin constituting the emulsion via the cross-linking agent. good.
  • Raw Material Preparing Step the raw materials described above are mixed to prepare a urethane resin composition and/or an acrylic resin composition, which is a raw material mixture of a foam sheet.
  • the mixing method at this time is not particularly limited, but for example, the components may be mixed while being stirred in a container such as a mixing tank for mixing the respective components.
  • Foaming/Curing Step In the foaming/curing step, a predetermined foaming gas is added to the urethane resin composition and/or the acrylic resin composition obtained in the raw material preparation step, and these are sufficiently mixed to form a urethane resin composition.
  • the product and/or the acrylic resin composition is made to have a large number of air bubbles (composition for forming a foam).
  • This foaming/curing step is usually carried out by sufficiently mixing the raw material mixture of the liquid foam sheet obtained in the raw material preparation step and the foaming gas using a mixing device such as a mixing head.
  • Foaming gas The foaming gas mixed with the urethane resin composition and/or the acrylic resin composition in the stirring and foaming process forms the cells in the foam sheet.
  • the amount determines the expansion ratio and density of the resulting foamed sheet. That is, it contributes to the point impact absorption rate, surface impact absorption rate, and compressive residual strain of the foam sheet.
  • the desired density of the foam sheet and the volume of the raw material of the foam sheet (for example, the internal volume of the mold into which the raw material of the foam sheet is injected) are used to determine the required density of the foam sheet. It is sufficient to calculate the mass of the raw material and determine the amount of the foaming gas so as to obtain the desired volume based on this mass.
  • Air is mainly used as the type of foaming gas, but inert gases such as nitrogen, carbon dioxide, helium, and argon can also be used.
  • the mechanical froth method is a method in which the urethane resin composition is stirred with a stirring blade or the like to mix air in the air into the urethane resin composition to foam.
  • any stirrer generally used in the mechanical froth method can be used without particular limitation, and for example, a homogenizer, a dissolver, a mechanical froth foamer and the like can be used.
  • this mechanical floss method by adjusting the mixing ratio of the urethane resin composition and/or the acrylic resin composition and air, it is possible to obtain a foamed sheet having a density suitable for various uses.
  • Other foaming methods can be used in combination, but when a foaming method using a chemical foaming agent is used in combination, the density can be increased by increasing the proportion of closed cells.
  • By adjusting the density it is possible to adjust the point impact absorption rate, surface impact absorption rate, and compressive residual strain of the foamed sheet.
  • the mixing time of the urethane resin composition and air is not particularly limited, but it is usually 1 to 10 minutes, preferably 2 to 6 minutes.
  • the mixing temperature is not particularly limited, it is usually room temperature.
  • the stirring speed in the above mixing is preferably 200 rpm or more (more preferably 500 rpm or more) in order to make the air bubbles fine, and is preferably 2000 rpm or less in order to smoothly discharge the foam-forming composition from the foaming machine. (800 rpm or less is more preferable).
  • foam sheet The foam-forming composition foamed as described above can be formed into a foam sheet having a desired thickness by known means such as casting using a doctor knife or doctor roll.
  • the foamed sheet of the present disclosure can be self-crosslinked, but the foamed sheet may be cured by applying energy to crosslink the resin constituting the emulsion via a crosslinking agent.
  • the step of applying energy is not particularly limited, but includes, for example, a heating step (thermal cross-linking).
  • the dispersion medium in the molded foam-forming composition is evaporated.
  • the drying method in this case is not particularly limited, but for example, hot air drying may be used.
  • the drying temperature and drying time are not particularly limited, either. It is possible to adjust the gel fraction of the foam sheet by adjusting the heating temperature and heating time.
  • the dispersion medium evaporates from the foam-forming composition, and the path through which this vapor escapes communicates from the inside to the outside of the foam sheet, resulting in open or semi-open cells.
  • the foaming gas mixed in the stirring/foaming step remains as it is, it becomes closed cells in the obtained foamed sheet, and the mixed foaming gas is released when the steam escapes in this step.
  • open cells or semi-open cells in the obtained foam sheet that is, in the present disclosure, the structure is such that some of the cells in the foam sheet are open cells and the remaining cells are closed cells.
  • the point impact absorption rate, surface impact absorption rate, and compressive residual strain of the foamed sheet can also be adjusted by such a cell structure.
  • the cross-linking (curing) reaction of the raw material proceeds and completes in the heating process.
  • the raw materials are cross-linked by the above-described cross-linking agent to form a cured foam sheet.
  • the heating means at this time is not particularly limited as long as it can sufficiently heat the raw material and crosslink (harden) the raw material.
  • a tunnel heating furnace or the like can be used.
  • the heating temperature and heating time may be any temperature and time at which the raw material can be crosslinked (cured). Just do it.
  • a step of further heating after forming the foamed sheet can be included.
  • a known method can be used as the heating method, and for example, a constant temperature bath or the like can be used in which a predetermined temperature is kept constant.
  • the heating temperature and heating time are not particularly limited as long as the properties of the foamed sheet can be made to be predetermined, but for example, the heating temperature can be 50 to 150° C., and the heating time can be 1 to 48 hours. can do. These can be freely set depending on the presence and type of the resin component and the cross-linking agent. , 70 to 100° C.) for 20 hours or longer, and more preferably 80° C. or higher (for example, 80 to 100° C.) for 20 hours or longer.
  • foam sheet It can be used as a shock absorbing sheet for protecting parts and the like. In particular, it is useful for protecting flexible OLEDs; liquid crystal panels, organic EL panels, touch panels, etc. of wearable devices, which are thin and have large areas.
  • the foam sheet of the present disclosure can be used by being attached in advance to the electronic/electric component to be protected. By doing so, workability is improved when assembling the electronic/electrical parts.
  • Crosslinking agent 3 water-dispersed isocyanate: WT21-100, manufactured by Asahi Kasei Corporation, HDI isocyanate, solid content 100%
  • NCO 14.1 wt%
  • Crosslinking agent 4 water-dispersed isocyanate: WT31-100, manufactured by Asahi Kasei Corporation, HDI isocyanate, solid content 100%
  • NCO 17.5 wt%
  • Crosslinking agent 5 water-dispersed isocyanate): Asahi Kasei Corporation, WE50-100, HDI isocyanate, solid content 100%
  • NCO 11.4 wt%
  • Crosslinking agent 6 water-dispersed isocyanate: Asahi Kasei Corporation, WL72-100, HDI isocyanate, solid content 100%
  • NCO 21.3 wt%
  • Each raw material described in each example and comparative example was blended to make a urethane resin composition or acrylic resin composition of each example and comparative example.
  • Air or an inert gas such as nitrogen gas is added to the obtained urethane resin composition or acrylic resin composition of each example and each comparative example, and foaming is performed by a mechanical froth method (at a foaming condition of 100 to 1000 rpm), Each foamed sheet was obtained by casting on a PET release liner using a doctor knife and molding to a predetermined thickness, followed by heat treatment (in an oven or a drying oven). Each obtained foamed sheet was subjected to secondary heating under the conditions (secondary curing) shown in Table 1 to obtain foamed sheets of each example and each comparative example. The density of the foamed sheet in each example and each comparative example was adjusted by changing the injection amount of air or an inert gas such as nitrogen gas, the rotation speed of the mixer, and the drying conditions.
  • the thickness of the foam sheet was measured with a thickness gauge.
  • Each foamed sheet (thickness is shown in Table 1) was molded into a 5 cm long x 5 cm wide square and used as a test piece.
  • the test piece is placed on the sample stage of the compression set tester shown in FIG. Arranged so as to surround the perimeter of the piece. The spacers were spaced apart so that they would not come into contact with the specimen even during the compression test. Place a stainless steel compression plate that compresses and deforms the test piece so as to cover the entire test piece and spacer. and tightened the positioning nut.
  • Each foam sheet in this state was heated to 70° C. and heated for 22 hours. After that, after removing the compression plate, the sample was allowed to stand for 30 minutes in an environment of 22°C.
  • Compression residual strain (%) (thickness before compression - thickness after compression release) / thickness before compression x 100 (formula 1)
  • evaluation of compression residual strain was performed according to the following criteria. B (Good): Compressive residual strain is less than 10%
  • the point impact absorption rate was calculated by the following formula 2 for the measurement results under each measurement condition after conducting a point impact absorption test using a drop-type impact absorption tester (Fig. 1).
  • a drop-type impact absorption tester Fig. 1
  • the foamed sheet of each example and comparative example was processed to a size of ⁇ 50 mm and placed on a sample stage, and an impactor (steel ball) weighing 32 g was placed at 10 cm, 20 cm, and 30 cm in an environment at a temperature of 23 ° C. , was dropped from a height of
  • the point impact absorption rate was calculated based on Equation (2).
  • Point impact absorption rate (%) ⁇ (f a0 ⁇ f a1 )/f a0 ⁇ 100 (Formula 2)
  • f a0 is the impact load when the impact absorption test is performed without placing the sample on the sample table
  • f a1 is the impact load when the impact absorption test is performed with the sample placed on the sample table.
  • impact load was measured by a sensor installed on the sample stage.
  • the point impact absorption rate was evaluated according to the following criteria. B (Good): Point impact absorption rate is over 10%
  • C Normal
  • Point impact absorption rate is 5% or more and 10% or less
  • F Point impact absorption rate is less than 5%
  • the plane impact absorption rate was calculated by the following formula 3 after conducting a plane impact absorption test using a drop type impact absorption tester (Fig. 2). The measurement was carried out by setting a sample processed to a size of ⁇ 50 mm on a sample stage, and further by providing a 5 mm-thick acrylic plate at a position where the impactor of the sample comes into contact. The measurement conditions were an air temperature of 23° C., an impactor (steel ball) weighing 32 g, and the impactor being dropped from heights of 10 cm, 20 cm, and 30 cm. The surface impact absorption rate was calculated based on Equation (3).
  • Variation in compression residual strain in long sheet A urethane resin composition having raw materials and compounding ratios shown in Table 2 was agitated and foamed by a mechanical floss method, and then applied to a PET substrate. The obtained foam layer was molded to a thickness of 0.10 mm using a comma coater. After drying the molded foam layer in a drying oven (drying oven temperature: 50 to 180°C, drying time: 0.5 to 5 minutes), UV ink is applied to the foam layer to prevent blocking, followed by UV irradiation. did The foam layer was wound up on a roll sample to produce a long sheet (roll shape) having a length of 110 m.
  • the resulting long sheets were secondarily heated under the conditions (secondary curing) shown in Table 2 to obtain long sheets of each example and each comparative example.
  • the innermost edge of the roll-shaped long sheet is set to 0 m (0 m from the winding core), and at positions of 0 m, 35 m, 70 m, and 105 m from the winding core, each 5 cm long x 5 cm wide square test piece. was cut out, and the compression residual strain was measured as described above.
  • a standard deviation ⁇ was calculated as an index of variation from the obtained compressive residual strain. Evaluation was made according to the following criteria based on the calculated standard deviation ⁇ . B (good): standard deviation ⁇ is 1.0 or less

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