Self-adsorbing foam laminate

Abstract

An object of the present invention is to provide a self-adsorptive foam laminate sheet having excellent degassing properties after heating and pressurization. The self-adsorptive foam laminate sheet of the present invention comprises a synthetic paper substrate and a self-adsorptive foam sheet. Furthermore, the self-adsorptive foam sheet is formed using a self-adsorptive foam sheet composition comprising a polymer, a crosslinking agent, and a wax agent.

Description

Technical Field

[0001] The invention relates to a self-adsorbing foamed laminate sheet. Background Art

[0002] In recent years, as adhesive sheets for use on smooth adherends such as window glass, self-adsorbing sheet-like components made of a foam material having a plurality of fine pores, namely self-adsorbing foam sheets (hereinafter sometimes referred to as "foam sheets"), have been used. The bonding method of the self-adsorbing foam sheet is not paste bonding, but rather it is adsorbed on the adherend by utilizing the fine pores. Therefore, compared with adhesive sheets that are bonded by paste bonding in the past, the self-adsorbing foam sheet is easy to re-paste and can be preferably used for applications such as wallpaper, posters, and stickers. Moreover, when used for these applications, the self-adsorbing foam sheet is used in the form of a self-adsorbing foam laminated sheet (hereinafter sometimes referred to as "laminated sheet") laminated with a substrate (synthetic paper substrate) composed of synthetic paper. By applying decoration such as printing on the surface of the synthetic paper substrate side of the self-adsorbing foam laminated sheet, it can be advantageously used for the above-mentioned applications.

[0003] Furthermore, various studies have been conducted in order to improve the performance of self-adsorptive foam laminate sheets.

[0004] For example, Patent Document 1 discloses improvements in a composition for preparing a foam sheet constituting a laminated sheet (hereinafter referred to as a "self-adsorptive foam sheet composition," sometimes abbreviated as a "foam sheet composition"). Furthermore, according to Patent Document 1, a laminated sheet comprising a foam sheet formed from a foam sheet composition containing a polymer having predetermined properties and a crosslinking agent can suppress resin residue on adherend glass even after weathering.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: International Publication No. 2018 / 151274. Summary of the Invention

[0008] Problems to be solved by the invention

[0009] Here, for the laminated sheet, when the surface of one side of the foam sheet is adsorbed onto the adherend, it is required to have the property of easily removing the trapped air remaining between the sheet and the adherend (i.e., excellent degassing properties). In particular, the laminated sheet is sometimes exposed to high temperature and pressurized environments during transportation, and therefore it is required that the laminated sheet maintains excellent degassing properties even after heating and pressurization (i.e., excellent degassing properties after heating and pressurization). However, according to the research of the present inventors, the above-mentioned existing laminated sheets still have room for improvement in terms of degassing properties after heating and pressurization.

[0010] Therefore, an object of the present invention is to provide a self-adsorptive foam laminate sheet having excellent degassing properties after heating and pressurization.

[0011] Solutions for solving problems

[0012] The present inventors conducted intensive research to address the above-mentioned issues. They discovered that forming a foam sheet using a composition for a foam sheet comprising a polymer, a crosslinking agent, and a wax agent on a synthetic paper substrate enables the laminated sheet to exhibit excellent degassing properties even after heating and pressurization, leading to the completion of the present invention.

[0013] That is, the present invention aims to advantageously solve the above-mentioned problems. The self-adsorptive foam laminate sheet of the present invention is characterized in that it is a self-adsorptive foam laminate sheet comprising a synthetic paper substrate and a self-adsorptive foam sheet, wherein the self-adsorptive foam sheet is formed using a self-adsorptive foam sheet composition comprising a polymer, a crosslinking agent, and a wax agent. Forming a foam sheet using a foam sheet composition comprising a polymer, a crosslinking agent, and a wax agent on a synthetic paper substrate in this manner enables the laminate sheet to exhibit excellent degassing properties even after heating and pressurization.

[0014] In the present invention, "synthetic paper" refers to a synthetic paper obtained by forming a resin composition containing a thermoplastic resin and a filler into a film.

[0015] In the self-adsorptive foam laminated sheet of the present invention, the polymer preferably comprises 60% to 99% by mass of (meth)acrylate monomer units. Forming the foam sheet using a composition for a foam sheet containing a polymer comprising (meth)acrylate monomer units in the aforementioned ratio allows for a laminated sheet that maintains good self-adhesion (adhesion to an adherend) while suppressing resin residue on the adherend.

[0016] In the present invention, a polymer “containing a monomer unit” means “a polymer obtained using the monomer contains a repeating unit derived from the monomer.” In the present invention, “(meth)acrylate” means acrylate and / or methacrylate.

[0017] Furthermore, in the self-adsorptive foam laminated sheet of the present invention, the polymer preferably contains 0.1% to 10% by mass of unsaturated carboxylic acid monomer units. Forming the foam sheet using a composition for a foam sheet containing a polymer containing unsaturated carboxylic acid monomer units in the aforementioned ratio can impart sufficient strength to the foam sheet. Furthermore, a laminated sheet can be obtained that maintains good self-adhesive strength while suppressing resin residue on adherends.

[0018] Furthermore, in the self-adsorptive foam laminate sheet of the present invention, the polymer preferably does not have N-methylol groups. If a foam sheet is formed using a foam sheet composition containing a polymer that does not have N-methylol groups, the generation of formaldehyde can be sufficiently suppressed during foaming and curing of the foam sheet composition.

[0019] In the self-adsorptive foam laminate sheet of the present invention, the wax agent preferably comprises a fatty acid ester having a fatty acid moiety with a carbon number of 16 or more and 34 or less. If a fatty acid ester having a fatty acid moiety (a structure derived from a fatty acid in the fatty acid ester) with a carbon number within the above range is used as the wax agent, the degassing properties of the laminate sheet after heating and pressurization can be further improved.

[0020] Furthermore, in the self-adsorptive foam laminate sheet of the present invention, the fatty acid ester preferably has an alcohol moiety having a carbon number of 30 or more and 34 or less. If a fatty acid having an alcohol moiety (a structure derived from an alcohol in the fatty acid ester) having a carbon number within the above range is used as the wax agent, the degassing properties of the laminate sheet after heating and pressurization can be further improved.

[0021] Furthermore, in the self-adsorptive foam laminate sheet of the present invention, the amount of the fatty acid ester blended is preferably 0.5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the polymer. Using a foam sheet composition having a wax blended amount within this range per 100 parts by mass of the polymer further improves the degassing properties of the laminate sheet after heating and pressurization.

[0022] Effects of the Invention

[0023] The present invention can provide a self-adsorptive foam laminate sheet having excellent degassing properties after heating and pressurization. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart illustrating an example of a method for producing the self-adsorptive foam laminate sheet of the present invention.

[0025] Figure 2 This is an explanatory diagram showing a schematic configuration of an evaluation apparatus used to evaluate the degassing properties of a self-adsorptive foam laminate sheet in Examples and Comparative Examples. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present invention will be described in detail.

[0027] The self-adsorptive foam laminate sheet of the present invention comprises a foam layer comprising a self-adsorptive foam sheet obtained using a composition for a self-adsorptive foam sheet, and a synthetic paper substrate serving as a support layer for the foam layer. The foam sheet may be formed directly on the synthetic paper substrate or through an arbitrary layer.

[0028] (Self-adsorbing foam sheet)

[0029] The foam sheet forming the foam layer in the laminate sheet of the present invention can be formed by crosslinking and foaming a predetermined self-adsorptive foam sheet composition.

[0030] <Composition for self-adsorptive foam sheet>

[0031] The composition for a foam sheet contains a polymer, a crosslinking agent, and a wax agent, and optionally contains a solvent and other additives.

[0032] Furthermore, by forming a foam sheet on a synthetic paper substrate using the foam sheet composition, it is possible to obtain the laminated sheet of the present invention having excellent degassing properties after heating and pressing.

[0033] <<Polymer>>

[0034] The polymer used in the composition for a foam sheet forms a resin matrix in a foam sheet obtained by foaming and crosslinking the composition for a foam sheet.

[0035] Here, the polymer is not particularly limited and can include, for example, at least one monomer unit selected from the group consisting of a (meth)acrylate monomer unit, an unsaturated carboxylic acid monomer unit, a vinyl cyanide monomer unit, and an alkenyl aromatic monomer unit. Furthermore, the polymer can include monomer units other than the (meth)acrylate monomer unit, the unsaturated carboxylic acid monomer unit, the vinyl cyanide monomer unit, and the alkenyl aromatic monomer unit (hereinafter referred to as "other monomer units").

[0036] [(Meth)acrylate monomer unit]

[0037] The (meth)acrylate monomer unit is a repeating unit derived from a (meth)acrylate monomer. The inclusion of the (meth)acrylate monomer unit in the polymer imparts flexibility to the resulting foam sheet and allows the production of a laminated sheet having excellent self-adhesive properties.

[0038] The (meth)acrylate monomer is not particularly limited, and examples thereof include alkyl (meth)acrylate monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, n-heptyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and n-dodecyl (meth)acrylate; and alkoxyalkyl (meth)acrylate monomers such as 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, and ethoxymethyl (meth)acrylate.

[0039] In addition, the (meth)acrylate monomer may be used alone or in combination of two or more.

[0040] Furthermore, in the present invention, "(meth)acrylic acid" means acrylic acid and / or methacrylic acid.

[0041] Here, from the viewpoint of further improving the softness of the foam sheet and further ensuring good self-adhesiveness of the laminated sheet, the (meth)acrylate monomer is preferably an alkyl (meth)acrylate monomer, and more preferably an alkyl (meth)acrylate monomer having an alkyl group (bonded to a non-carbonyl oxygen atom) with 1 to 14 carbon atoms (hereinafter sometimes abbreviated as "C1-14 alkyl (meth)acrylate monomer").

[0042] Examples of C1-14 alkyl (meth)acrylate monomers include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, n-heptyl acrylate, n-hexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, n-octyl methacrylate, and n-dodecyl methacrylate. Among these, n-butyl acrylate, ethyl acrylate, and 2-ethylhexyl acrylate are preferred from the perspectives of self-adhesion and cost.

[0043] And, with the whole repeating units (whole monomeric units) comprised by polymer as 100 mass %, the ratio of (methyl) acrylate monomeric unit in polymer is preferably more than 60 mass %, more preferably more than 70 mass %, more preferably more than 80 mass %, particularly preferably more than 85 mass %, preferably below 99 mass %, more preferably below 95 mass %, more preferably below 92 mass %.If the ratio of (methyl) acrylate monomeric unit in polymer is more than 60 mass %, then the self-adhesive force of laminate can be fully guaranteed.On the other hand, if the ratio of (methyl) acrylate monomeric unit in polymer is below 99 mass %, then the self-adhesive force of laminate can not excessively improve.Therefore, the resin residue of laminate can be suppressed in adherend.

[0044] [Unsaturated carboxylic acid monomer unit]

[0045] The unsaturated carboxylic acid monomer unit is a repeating unit derived from an unsaturated carboxylic acid monomer.

[0046] Specific examples of unsaturated carboxylic acid monomers include α,β-ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; α,β-ethylenically unsaturated polycarboxylic acids such as itaconic acid, maleic acid, and fumaric acid; and α,β-ethylenically unsaturated polycarboxylic acid partial esters such as monomethyl itaconate, monobutyl maleate, and monopropyl fumarate. Furthermore, compounds having groups that can be derived into carboxylic acid groups by hydrolysis, such as maleic anhydride and itaconic anhydride, can also be used. Among these, from the perspective of reactivity with a cross-linking agent described later, stability of the polymer latex, and cost, itaconic acid, acrylic acid, and methacrylic acid are preferred, and acrylic acid is more preferred.

[0047] In addition, the unsaturated carboxylic acid monomer may be used alone or in combination of two or more.

[0048] Moreover, with the total repeating units (total monomeric units) comprised by polymer as 100 mass %, the ratio of the unsaturated carboxylic acid monomeric units in polymer is preferably more than 0.1 mass %, more preferably more than 0.5 mass %, further preferably more than 1 mass %, preferably below 10 mass %, more preferably below 5 mass %, further preferably below 2.5 mass %.By making the ratio of the unsaturated carboxylic acid monomeric units in polymer be more than 0.1 mass %, the cross-linking reaction utilizing cross-linking agent described later can be made to be carried out fully.As a result, sufficient intensity can be given to the foam sheet obtained, and the resin residue of laminated sheet is suppressed in adherend.On the other hand, by making the ratio of the unsaturated carboxylic acid monomeric units in polymer be below 10 mass %, the viscosity of the polymerization system during polymerization easily is maintained at suitable range, and in addition, the cross-linking of polymer also can not be carried out excessively, and the self-adhesive force of laminated sheet can not be impaired.

[0049] [Cyanide vinyl monomer unit]

[0050] The vinyl cyanide monomer unit is a repeating unit derived from a vinyl cyanide monomer. Specific examples of vinyl cyanide monomers include α,β-ethylenically unsaturated nitrile monomers. The α,β-ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an α,β-ethylenically unsaturated compound having a nitrile group, and examples thereof include acrylonitrile; α-halogenated acrylonitriles such as α-chloroacrylonitrile and α-bromoacrylonitrile; and α-alkyl acrylonitriles such as methacrylonitrile and α-ethylacrylonitrile. Among these, acrylonitrile is preferred from the viewpoint of increasing the cohesive force of the composition for the foam sheet and increasing the breaking strength of the foam sheet.

[0051] Furthermore, the vinyl cyanide monomer may be used alone or in combination of two or more.

[0052] And, be 100 mass % with the whole repeating units (whole monomeric units) comprised by polymer, the ratio of the cyanide vinyl monomeric unit in polymer is preferably more than 1 mass %, more preferably more than 3 mass %, further preferably more than 5 mass %, particularly preferably more than 8 mass %, preferably below 30 mass %, more preferably below 20 mass %, further preferably below 15 mass %.If the ratio of the cyanide vinyl monomeric unit in polymer is more than 1 mass %, then sufficient intensity can be given to the foam sheet obtained, and the resin residue of laminated sheet can be suppressed in adherend.On the other hand, if the ratio of the cyanide vinyl monomeric unit in polymer is below 30 mass %, then the flexibility of the foam sheet obtained can be guaranteed fully, the laminated sheet with good self-adhesive power can be obtained.

[0053] [Alkenyl aromatic monomer unit]

[0054] The alkenyl aromatic monomer unit is a repeating unit derived from an alkenyl aromatic monomer. Specific examples of alkenyl aromatic monomers include styrene, α-methylstyrene, α-chlorostyrene, vinyltoluene, and divinylbenzene. Among these, styrene is preferred from the perspective of polymerizability and cost.

[0055] Furthermore, the alkenyl aromatic monomer may be used alone or in combination of two or more.

[0056] And, with the whole repeating units (whole monomeric units) included in polymer as 100 mass %, the ratio of the alkenyl aromatic monomeric unit in polymer is preferably more than 0.5 mass %, more preferably more than 1 mass %, more preferably more than 1.5 mass %, particularly preferably more than 2 mass %, preferably below 20 mass %, more preferably below 10 mass %, more preferably below 5 mass %.If the ratio of the alkenyl aromatic monomeric unit in polymer is more than 0.5 mass %, then based on the hydrophobicity of alkenyl aromatic monomeric unit, it is possible to prevent water from immersing in foam sheet, it is possible to improve the water resistance of laminate.On the other hand, if the ratio of the alkenyl aromatic monomeric unit in polymer is below 20 mass %, it is possible to fully ensure the flexibility of the foam sheet obtained, obtain the laminate with good self-adhesive power.

[0057] [Other monomer units]

[0058] Other monomer units are repeating units derived from other monomers copolymerizable with the above-mentioned monomers.

[0059] Here, examples of other monomers include conjugated diene monomers, α,β-ethylenically unsaturated polycarboxylic acid complete ester monomers, carboxylic acid unsaturated alcohol ester monomers, olefin monomers, and monomers having other functional groups. These monomers may be used alone or in combination of two or more. Specific examples of such other monomers are not particularly limited, and for example, monomers described in International Publication No. 2018 / 151274 may be used.

[0060] Furthermore, from the viewpoint of sufficiently suppressing the generation of formaldehyde when the composition for a foam sheet is foamed and cured, the polymer preferably does not have an N-methylol group. More specifically, the polymer preferably does not contain a monomer unit having an N-methylol group.

[0061] Here, examples of the monomer having an N-methylol group include N-methylol acrylamide and N-methylol methacrylamide.

[0062] [Polymer properties]

[0063] -Glass transition temperature-

[0064] The glass transition temperature of the polymer is preferably -10°C or lower, more preferably -13°C or lower, even more preferably -17°C or lower, even more preferably -20°C or lower, and particularly preferably -26°C or lower. If the polymer has a glass transition temperature of -10°C or lower, the self-adhesive strength of the laminate sheet can be sufficiently ensured, and the laminate sheet and adherend can be well adhered to prevent moisture from penetrating between the adherend and the laminate sheet. Consequently, the water resistance of the laminate sheet can be improved.

[0065] The lower limit of the glass transition temperature of the polymer is not particularly limited, but is preferably -40°C or higher from the viewpoint of sufficiently suppressing the resin of the laminate sheet from remaining on the adherend.

[0066] The glass transition temperature of a polymer can be measured by the method described in Examples of this specification.

[0067] -Gel fraction-

[0068] The gel fraction of the polymer is preferably 95% by mass or less, more preferably 93% by mass or less, and even more preferably 91% by mass or less. A gel fraction of 95% by mass or less allows for the production of foam sheets and laminated sheets having suitable self-adhesive strength and excellent smoothness. The lower limit of the gel fraction of the polymer is not particularly limited, and can be, for example, 50% by mass or more, or 70% by mass or more.

[0069] The gel fraction of the polymer can be measured using the method described in Examples of this specification.

[0070] [Polymer Preparation Method]

[0071] The polymerization method used to obtain the polymer is not particularly limited and may be any method such as solution polymerization, emulsion polymerization, suspension polymerization, or bulk polymerization, or methods other than these. The type and amount of the polymerization initiator, emulsifier, dispersant, etc. used in the polymerization are also not particularly limited. During the polymerization, the method of adding the monomer, polymerization initiator, emulsifier, dispersant, etc. is also not particularly limited. Furthermore, the polymerization temperature, pressure, and stirring conditions are also not particularly limited.

[0072] The polymer can also be used in a solid state. However, when used in a latex state containing the polymer (polymer latex), such as a latex obtained by emulsion polymerization or a latex obtained by post-emulsification of the polymer, it is easy to handle when mixing with a cross-linking agent, a wax agent, etc., and it is also easy to foam the resulting foam sheet composition.

[0073] Here, when the polymer is used in the form of a polymer latex to prepare a composition for a foam sheet as described above, from the viewpoint of maintaining the density of the resulting foam sheet, the solid content concentration of the polymer latex is preferably 40% by mass or more, more preferably 45% by mass or more, further preferably 50% by mass or more, particularly preferably 52% by mass or more, and preferably 70% by mass or less, more preferably 58% by mass or less.

[0074] <<Crosslinking Agent>>

[0075] The crosslinking agent contained in the composition for the foam sheet is not particularly limited as long as it is a crosslinking agent that can form a crosslinked structure with the above-mentioned polymer (especially the unsaturated carboxylic acid monomer unit of the above-mentioned polymer). Examples of such crosslinking agents include carbodiimide crosslinking agents; epoxy crosslinking agents; Examples of crosslinking agents include oxazoline-based crosslinking agents; polyfunctional isocyanate-based crosslinking agents such as toluene diisocyanate, trimethylolpropane toluene diisocyanate, and diphenylmethane triisocyanate; metal salt-based crosslinking agents; metal chelate-based crosslinking agents; and peroxide-based crosslinking agents. Of these, epoxy-based crosslinking agents are preferred, and compounds having two or more epoxy groups per molecule are more preferred. Preferred epoxy-based crosslinking agents include fatty acid polyglycidyl ethers, glycerol polyglycidyl ether, and ethylene glycol diglycidyl ether.

[0076] Here, the epoxy crosslinking agent may be synthesized using a known method, or a commercial product may be used. Examples of commercially available epoxy crosslinking agents include "RIKA BOND (registered trademark)" manufactured by Nippon Paint Resins Co., Ltd.

[0077] Epoxy cross-linking agent reacts with the functional group etc. (such as the carboxylic acid group from the unsaturated carboxylic acid monomer unit) in the above-mentioned polymer by its epoxy group, thus forming a cross-linked structure in the molecule or intermolecular of the polymer.If epoxy cross-linking agent is used, it is possible to form a foam sheet with appropriate self-adhesive force, excellent strength.Therefore, if the foam sheet composition comprising epoxy cross-linking agent is used as a cross-linking agent, it is possible to suppress the resin residue of the laminated sheet in the adherend.

[0078] In the present invention, it is preferred not to use a cross-linking agent that generates formaldehyde, such as melamine-formaldehyde resin, urea-formaldehyde resin, or phenol-formaldehyde resin.

[0079] Here, relative to 100 parts by mass of the above-mentioned polymer, the amount of the cross-linking agent in the composition for the foam sheet is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, further preferably 3 parts by mass or more, particularly preferably 5.5 parts by mass or more, preferably 20 parts by mass or less, more preferably 10 parts by mass or less. By the amount of the cross-linking agent being within the above-mentioned range, a foam sheet that maintains strength and elasticity appropriately can be obtained. Therefore, when the pressure applied to the foam sheet is released, the foaming cells in the flattened foam sheet can return to their original shape. Moreover, the self-adhesive force of the laminate can be ensured, and the resin residue of the laminate can be fully suppressed in the adherend.

[0080] <<Wax>>

[0081] As the wax agent that foam sheet of the present invention is used for the wax agent that comprises composition, as long as it is the wax agent that comprises fatty acid ester (particularly the ester of higher fatty acid and higher alcohol), then is not particularly limited.And, take the wax agent as 100 mass % as the whole, the content of the fatty acid ester in the wax agent is preferably greater than 50 mass % and is below 100 mass % (i.e. being principal component), more preferably more than 70 mass % and below 100 mass %, further preferably more than 80 mass % and below 100 mass %, particularly preferably more than 90 mass % and below 100 mass %.In addition, wax agent can comprise a kind of fatty acid ester, also can comprise the fatty acid ester of two or more.

[0082] In the foam sheet formed using the foam sheet composition, the wax agent functions as a light release agent. Furthermore, it is presumed that foaming and curing the foam sheet composition, which contains the wax agent in a polymer, improves the interconnected pore structure and elasticity of the foam sheet, thereby enabling excellent degassing properties of a laminated sheet comprising the foam sheet after heating and pressurization.

[0083] Examples of the wax agent include natural wax, synthetic wax, and mixtures thereof, and natural wax is preferably used.

[0084] Here, as a specific example of a natural wax, as long as it contains fatty acid esters from nature, it is not particularly limited, and examples include natural waxes from plants such as rice bran wax, sugarcane wax, carnauba wax, candelilla wax, jojoba oil, Japan wax, moringa seed oil (moringa oil); natural waxes from animals such as beeswax, sperm whale oil, and lanolin; natural waxes from minerals such as montan wax, ozokerite, and ceresin. Among these, moringa seed oil is preferred from the viewpoint of further improving the degassing property after heating and pressurizing the laminated sheet. These natural waxes can be purified from natural materials using known methods, or commercially available products can be used. Commercially available products of natural waxes include, for example, "refined moringa oil" manufactured by Nitto Bussan Co., Ltd.

[0085] The wax agents may be used alone or in combination of two or more.

[0086] In addition, the fatty acid portion of the fatty acid ester contained in the wax agent preferably has 16 or more carbon atoms, more preferably 18 or more carbon atoms, preferably 34 or less carbon atoms, and more preferably 30 or less carbon atoms. If the carbon number of the fatty acid portion of the fatty acid ester is within the above range, the degassing property of the laminate after heating and pressurization can be further improved. Moreover, as specific examples of fatty acids with a carbon number of 16 or more and 34 or less, saturated fatty acids such as stearic acid (carbon number 18), arachidic acid (carbon number 20), and behenic acid (carbon number 22) can be cited; unsaturated fatty acids such as oleic acid (carbon number 18), linoleic acid (carbon number 18), and linolenic acid (carbon number 18) can be cited.

[0087] These fatty acids may be used alone or in combination of two or more.

[0088] The alcohol portion of the fatty acid ester contained in the wax preferably has 30 or more carbon atoms, and preferably 34 or less carbon atoms. If the carbon number of the alcohol portion of the fatty acid ester is within the above range, the degassing properties of the laminated sheet after heating and pressurization can be further improved. Specific examples of alcohols having 30 or more and 34 or less carbon atoms include myricyl alcohol (30 carbon atoms), melissyl alcohol (31 carbon atoms), shellac alcohol (32 carbon atoms), melissyl alcohol (33 carbon atoms), and tetratriacontanol (34 carbon atoms).

[0089] These alcohols may be used alone or in combination of two or more.

[0090] Here, the amount of the wax agent in the composition for the foam sheet is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, further preferably 1.5 parts by mass or more, particularly preferably 3.6 parts by mass or more, preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and further preferably 5 parts by mass or less, relative to 100 parts by mass of the polymer. If the amount of the wax agent is 0.5 parts by mass or more, the degassing property of the laminate after heating and pressurization can be further improved. On the other hand, if the amount of the wax agent is 10 parts by mass or less, the laminate obtained can be given good self-adhesiveness, and the degassing property of the laminate after heating and pressurization can be further improved.

[0091] In addition, the amount of the fatty acid ester having a fatty acid moiety with a carbon number of 16 or more and 34 or less in the foam sheet composition is preferably 0.5 or more by mass, more preferably 1 or more by mass, further preferably 1.5 or more by mass, preferably 10 or less by mass, more preferably 7 or less by mass, and further preferably 5 or less by mass relative to 100 parts by mass of the polymer. If the amount of the fatty acid ester having a fatty acid moiety with a carbon number of 16 or more and 34 or less is 0.5 or more by mass relative to 100 parts by mass of the polymer, the degassing property of the laminate after heating and pressing can be further improved. On the other hand, if the amount of the fatty acid ester having a fatty acid moiety with a carbon number of 16 or more and 34 or less is 10 or less by mass relative to 100 parts by mass of the polymer, good self-adhesion can be imparted to the resulting laminate, and the degassing property of the laminate after heating and pressing can be further improved.

[0092] Solvents

[0093] The solvent that can be optionally contained in the composition for a foam sheet is not particularly limited, but water is preferred. When water is used as the solvent, the water contained in the composition for a foam sheet can be, for example, water derived from a polymer latex.

[0094] <<Other additives>>

[0095] In order to improve the processability in the manufacturing process of the foam sheet and the laminated sheet and to improve the performance of the foamed and laminated sheet obtained, the composition for the foamed sheet can arbitrarily contain various additives. As such additives, foaming agents such as higher fatty acid salts and surfactants, foaming aids, thickeners, fillers, preservatives, mildew inhibitors, gelling agents, flame retardants, anti-aging agents, antioxidants, pigments, dyes, tackifiers, conductive compounds, water-proofing agents, oil-proofing agents, etc. can be cited. In addition, as specific examples of the above-mentioned other additives, there is no particular limitation, and known additives can be used, such as the additives described in International Publication No. 2016 / 147679.

[0096] <Properties of Foam Sheet>

[0097] The self-adsorptive foam sheet forming the foam layer in the laminated sheet of the present invention can be formed by crosslinking and foaming the above-mentioned foam sheet composition.

[0098] Here, the density of the self-adsorptive foam sheet is not particularly limited, but is preferably 0.1 g / cm 3 Above and 1.0g / cm 3 Below, more preferably 0.3g / cm 3 Above and 0.8g / cm 3 Below, more preferably 0.5 g / cm 3 Above and 0.7g / cm 3 If the density of the foam sheet is 0.1g / cm 3 Above, the strength of the foam sheet can be ensured. If the density of the foam sheet is 1.0g / cm 3 The following can further improve the degassing property of the laminated sheet after heating and pressing, and can sufficiently suppress the resin from remaining on the adherend.

[0099] The density of the foamed sheet can be calculated using the method described in Examples of this specification.

[0100] In addition, the thickness of the foam sheet is preferably more than 0.03mm, more preferably more than 0.05mm, more preferably more than 0.1mm, preferably less than 3mm, more preferably less than 1mm, more preferably less than 0.5mm, particularly preferably less than 0.2mm. If the thickness of the foam sheet is more than 0.03mm, it is possible to fully ensure the mechanical strength of the foam sheet and the laminate. On the other hand, if the thickness of the foam sheet is less than 3mm, it is possible to further improve the degassing after the heating and pressurization of the laminate. In addition, it is possible to obtain an excellent laminate with repeated attachment (reprocessing performance).

[0101] (Synthetic paper base material)

[0102] As the substrate in the laminated sheet of the present invention, a synthetic paper substrate is used. The synthetic paper substrate is not particularly limited as long as it is a substrate formed of synthetic paper as described above, but is preferably a substrate obtained by film-forming a compound (resin composition) containing a thermoplastic resin and a filler, and optionally other additives. The compound can be formed into a film using a known molding method.

[0103] <Thermoplastic resin>

[0104] Examples of thermoplastic resins include polyethylene resins (low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, etc.), polypropylene resins, polymethyl-1-pentene, ethylene-cyclic olefin copolymers and other polyolefin resins; polyamide resins such as nylon 6, nylon 6,6, and nylon 6,10; polyester resins such as polyethylene terephthalate and its copolymers, polyethylene naphthalate, and aliphatic polyesters; polycarbonate, atactic polystyrene, syndiotactic polystyrene, and polyphenylene sulfide. These can be used alone or in combination of two or more. Among these, polyolefin resins and polyester resins are preferred, and polypropylene resins are more preferred. Examples of polypropylene resins include propylene homopolymers, copolymers of propylene as the main component with α-olefins such as ethylene, 1-butene, 1-hexene, 1-heptene, and 4-methyl-1-pentene, and the like. In addition, there is no particular limitation on stereoregularity, and thermoplastic resins exhibiting isotactic or syndiotactic stereoregularity or various degrees of stereoregularity can be used. Furthermore, the copolymer may be a binary copolymer, a ternary copolymer, or a tetrapolymer, and may be a random copolymer or a block copolymer.

[0105] <Padding>

[0106] As the filler, an inorganic filler, an organic filler, or a mixture thereof can be used.

[0107] The inorganic filler is not particularly limited as long as it is composed of an inorganic compound. Examples thereof include fillers composed of at least one of inorganic compounds such as calcium carbonate, calcined clay, silica, diatomaceous earth, talc, mica, synthetic mica, sericite, kaolin, titanium oxide, barium sulfate, and aluminum oxide. Inorganic fillers may be used alone or in combination of two or more. Of these, fillers composed of calcium carbonate and titanium oxide are preferred.

[0108] As the organic filler, a filler composed of a resin of a different type from the thermoplastic resin as the main component can be used.

[0109] For example, when a polyolefin resin is used as the above-mentioned thermoplastic resin, examples of the organic filler include fillers composed of at least one of polyethylene terephthalate, polybutylene terephthalate, polycarbonate, nylon 6, nylon 6,6, homopolymers of cyclic olefins, and copolymers of cyclic olefins and ethylene.

[0110] In addition, when a polyester resin is used as the above-mentioned thermoplastic resin, examples of the organic filler include fillers composed of at least one of polystyrene, polypropylene, polycarbonate, nylon 6, nylon 6,6, polymethyl-1-pentene, homopolymers of cyclic olefins, and copolymers of cyclic olefins and ethylene.

[0111] The organic filler may be used alone or in combination of two or more. The melting point of the resin constituting the organic filler is preferably from 120° C. to 300° C. Furthermore, the glass transition temperature of the resin constituting the organic filler is preferably from 120° C. to 280° C.

[0112] Furthermore, the content of the aforementioned filler in the synthetic paper substrate is preferably from 8% to 65% by mass, and more preferably from 10% to 60% by mass. By maintaining the filler content within this range, a balance between whiteness and opacity of the synthetic paper substrate can be achieved.

[0113] <Other additives>

[0114] Examples of other additives include antioxidants, light stabilizers, dispersants, and lubricants.

[0115] Examples of the antioxidant include hindered phenol-based, phosphorus-based, and amine-based antioxidants. The content of the antioxidant in the synthetic paper base material is, for example, 0.001% by mass or more and 1% by mass or less.

[0116] Examples of the light stabilizer include hindered amine, benzotriazole, and benzophenone-based light stabilizers. The content of the light stabilizer in the synthetic paper base material is, for example, 0.001% by mass or more and 1% by mass or less.

[0117] Examples of dispersants (particularly dispersants for the aforementioned inorganic fillers) include silane coupling agents, higher fatty acids such as oleic acid and stearic acid, metal soaps, polyacrylic acid, polymethacrylic acid, or salts thereof. The content of the dispersant in the synthetic paper substrate is, for example, 0.01% by mass to 4% by mass.

[0118] <Properties of Synthetic Paper Base Material>

[0119] The synthetic paper substrate is preferably a porous synthetic paper substrate. Specifically, the overall porosity of the synthetic paper substrate is preferably 5% or higher and 50% or lower, more preferably 15% or higher and 45% or lower. An overall porosity of 5% or higher improves the opacity and flexibility of the synthetic paper substrate, while an overall porosity of 50% or lower facilitates maintaining the mechanical strength of the synthetic paper substrate, such as tensile modulus, within an appropriate range.

[0120] In the present invention, the "overall porosity" can be determined by cutting out a cross section of the synthetic paper substrate, observing it with an electron microscope, and measuring the area ratio (%) of the pores in the entire area (100%).

[0121] Furthermore, the synthetic paper substrate may have a single-layer structure or a multi-layer structure. In the case of a single-layer structure, the synthetic paper substrate (film) may be unstretched, uniaxially stretched, or biaxially stretched. In the case of a multi-layer structure, the synthetic paper substrate may have a double-layer structure or a structure with three or more layers. In the case of a double-layer structure, the structure may be unstretched / uniaxially stretched, unstretched / biaxially stretched, uniaxially stretched / uniaxially stretched, uniaxially stretched / biaxially stretched, or biaxially stretched / biaxially stretched. In the case of a structure with three or more layers, any combination of the above-mentioned single-layer and double-layer structures may be used.

[0122] Furthermore, the whiteness of the synthetic paper substrate is preferably 80% or higher, more preferably 85% or higher. By setting the whiteness to 80% or higher, the content printed on the synthetic paper substrate can be more easily recognized.

[0123] In the present invention, "whiteness" can be measured according to the method described in JIS-L1015.

[0124] The opacity of the synthetic paper substrate can be adjusted appropriately depending on the intended use. Specifically, the opacity of the synthetic paper substrate is preferably 40% to 100%, more preferably 70% to 100%, and even more preferably 80% to 100%. An opacity of 40% or greater provides sufficient coverage for printing paper.

[0125] In the present invention, "opacity" can be measured according to the method described in JIS-P8138.

[0126] Furthermore, the thickness of the synthetic paper substrate is preferably 20 μm or greater and 900 μm or less, more preferably 30 μm or greater and 800 μm or less. A synthetic paper substrate thickness of 20 μm or greater improves the mechanical strength of the overall laminated sheet, enabling the formation of large-area posters, etc. On the other hand, a synthetic paper substrate thickness of 900 μm or less prevents the overall rigidity of the laminated sheet from becoming excessively high, reduces its weight, and prevents it from falling off during application.

[0127] (Method for producing self-adsorptive foam laminate sheet)

[0128] Hereinafter, an example of a method for producing the laminated sheet of the present invention will be described.

[0129] Figure 1 A flowchart illustrating an example of a method S10 for manufacturing a laminated sheet (hereinafter sometimes referred to as “manufacturing method S10”) is shown. Figure 1 As shown, the manufacturing method S10 includes a composition preparation step S1, a foaming step S2, and a sheeting step S3 in this order. Each step will be described below.

[0130] <Composition Preparation Step S1>

[0131] The composition preparation step S1 is a step of preparing a composition for a self-adsorptive foam sheet.

[0132] Specifically, in the composition preparation step S1 , the polymer, the crosslinking agent, and the wax agent as essential components, and the solvent and other additives used as desired can be mixed by any method to prepare the composition for the foam sheet.

[0133] For example, when a polymer latex is used to prepare a composition for a foam sheet, a crosslinking agent, a wax agent, and optionally other additives may be added to the polymer latex and mixed using a known method.

[0134] When a solid polymer is used without a solvent to prepare a composition for a foam sheet, the solid polymer, crosslinking agent, wax agent, and other optional additives can be mixed by a known method (for example, using a known roller, Henschel mixer, kneader, etc.).

[0135] Here, the viscosity of the composition for foaming sheets containing a solvent (for example, in the form of an emulsion or dispersion) is preferably 1000 mPa·s or more and 10000 mPa·s or less, more preferably 2000 mPa·s or more and 10000 mPa·s or less, and further preferably 3500 mPa·s or more and 5500 mPa·s or less. If the viscosity of the composition for foaming sheets is 1000 mPa·s or more, when the foam formed by the composition for foaming sheets is applied to the substrate to form a foam sheet, it is possible to prevent liquid dripping and difficulty in controlling the thickness. On the other hand, if the viscosity of the composition for foaming sheets is 10000 mPa·s or less, when forming the foam sheet, the foaming ratio will not be difficult to control due to mechanical foaming.

[0136] The viscosity of the composition for a foam sheet can be measured by the method described in Examples of this specification.

[0137] <Foaming Step S2>

[0138] The foaming step S2 is a step of foaming the composition for a foam sheet to obtain a foam of the composition for a foam sheet.

[0139] Specifically, in the foaming step S2, the composition for the foam sheet prepared in the composition preparation step S1 is foamed to obtain an uncured (uncrosslinked) foam. If the composition for the foam sheet is in the form of an emulsion or dispersion, a foamed emulsion or a foamed dispersion can be obtained.

[0140] As a foaming method, mechanical foaming is generally used. The expansion ratio can be appropriately adjusted, usually 1.2 times or more and 5 times or less, preferably 1.5 times or more and 4 times or less. The method of mechanical foaming is not particularly limited, and can be carried out by mixing a certain amount of air into the emulsion or dispersion of the composition for the foaming sheet and stirring continuously or intermittently using an Oakes mixer, a whisk, etc. The foaming emulsion or foaming dispersion thus obtained becomes a paste.

[0141] By forming pores through mechanical foaming, and then undergoing the sheeting step S3 described below, a foam sheet with excellent degassing properties can be obtained. Furthermore, when the expansion ratio is 1.2 times or greater, a decrease in degassing properties can be prevented, and when the expansion ratio is 5 times or less, a decrease in the strength of the foam sheet can be prevented.

[0142] <Flake Forming Step S3>

[0143] The sheeting step S3 is a step of producing a foam sheet by performing a cross-linking reaction on the foam after the foam is formed into a sheet shape.

[0144] In the sheeting step S3, the method for forming the foam produced in the foaming step S2 into a sheet is not particularly limited. A preferred method includes, for example, coating the foam onto a desired synthetic paper substrate and forming the sheet. By coating the foam onto the desired synthetic paper substrate and allowing the crosslinking reaction to proceed, a laminated sheet can be obtained in which the foam sheet is directly formed onto the synthetic paper substrate.

[0145] Alternatively, the foam can be applied to a release sheet (e.g., a releasable engineering paper) instead of the synthetic paper substrate. Applying the foam to the release sheet and then subjecting it to a cross-linking reaction can yield a laminated body in which the foam sheet is directly attached to the release sheet. Furthermore, by peeling the release sheet from the foam sheet in the laminated body, the foam sheet can be obtained independently (as a separate film).

[0146] As a method for coating a foam on a synthetic paper substrate or a release sheet (hereinafter sometimes collectively referred to as "substrate, etc."), commonly known coating devices such as a coater, a rod coater, a roller coater, a reverse roller coater, a screen coater, a blade coater, and a notched wheel coater can be used.

[0147] As a method for crosslinking a foam coated in a sheet shape on a synthetic paper substrate, etc., a method of heating and drying the foam is preferred. As a method for heating and drying, there is no particular limitation as long as it is a method that can dry and crosslink the foam coated on a synthetic paper substrate, etc., and a known drying oven (for example, a hot air circulation oven, a hot oil circulation hot air oven, a far-infrared heating oven) can be used. The drying temperature can be, for example, 60°C or more and 180°C or less. In addition, it is preferred not to dry at a constant temperature, but to perform multi-stage drying by drying from the inside at a low temperature in the early stage of drying and by fully drying at a higher temperature in the later stage of drying.

[0148] The properties of the foam sheet (density, thickness, hardness, etc.) can be adjusted by changing, for example, the mixing ratio of cells, the composition of the foam sheet composition, the solid content concentration, and the drying and crosslinking conditions.

[0149] The laminated sheet obtained through the above-mentioned steps S1 to S3 is not particularly limited. For example, after attaching a spacer film to the self-adhesive surface (i.e., the surface on the foam sheet side), it can be wound by a winder and cut by pressure cutting, longitudinal cutting, etc. to be processed into a size that is easy to use.

[0150] (Application of laminated sheets)

[0151] The laminated sheet of the present invention can be printed on its synthetic paper substrate surface using, for example, offset printing, seal printing, flexographic printing, screen printing, gravure printing, laser printing, thermal transfer printing, inkjet printing, or the like.

[0152] Laminated sheets printed on a synthetic paper substrate can be advantageously used for outdoor applications such as promotional cards, so-called POP cards (posters, stickers, display advertisements, etc.), gardening POPs (ground tags, etc.), road signs (funerals, model homes, etc.), and signs (no entry, forest road construction, etc.).

[0153] Example

[0154] Hereinafter, the present invention will be described in detail based on Examples, but the present invention is not limited to these Examples. In the following description, "%" and "parts" indicating amounts are based on mass unless otherwise specified.

[0155] In addition, unless otherwise stated, in a polymer produced by polymerizing multiple monomers, the proportion of monomer units formed by polymerizing a particular monomer in the polymer generally corresponds to the ratio (feed ratio) of the monomer to the total monomers used in the polymerization of the polymer. Furthermore, in the Examples and Comparative Examples, the glass transition temperature and gel fraction of the polymer, the viscosity of the foam sheet composition, the density of the foam sheet, and the degassing properties (initial and after heating and pressurization) and formaldehyde emission of the laminated sheet were evaluated according to the following methods.

[0156] <Glass transition temperature of polymer>,

[0157] The glass transition temperature (Tg) of the polymer used as the material for the self-adsorptive foam laminate sheet was measured using the following method. A polymer latex containing the polymer was applied to a 50 μm thick polyethylene terephthalate film using a 250 μm applicator and dried at room temperature for 24 hours to obtain a film formed on the polyethylene terephthalate film. The film formed on the polyethylene terephthalate film (excluding the polyethylene terephthalate film) was used as a sample, and the glass transition temperature (°C) was measured using a differential scanning calorimeter (DSC7000X, manufactured by Hitachi High-Technologies Corporation) in accordance with JIS K 7121, at a measurement temperature of -50°C to 160°C and a heating rate of 10°C / minute.

[0158] <Gel Fraction of Polymer>

[0159] The gel fraction of the polymer used for the laminate is determined by the following method. The polymer is applied to a 50 μm thick polyethylene terephthalate (PET) film using a 250 μm applicator and dried at room temperature for 24 hours to obtain a resin film. A predetermined amount (X) (approximately 500 mg) of the film is accurately weighed as a sample and immersed in 100 ml of ethyl acetate at room temperature for 3 days. The insoluble components are filtered out using a 200-mesh metal mesh and air-dried at room temperature for 15 hours. The sample is then dried at 100°C for 2 hours and cooled at room temperature, and the weight of the sample (Y) is measured. X and Y are substituted into the following formula to calculate the gel fraction.

[0160] Gel fraction (%) = (Y) / (X) × 100

[0161] <Viscosity of Foam Sheet Composition>

[0162] The viscosity of the composition for a foam sheet was measured at 23° C. using a Brookfield viscometer (“VISCOTESTER VT-06” manufactured by RION Co., Ltd.).

[0163] <Density of Foam Sheet>

[0164] After making the laminated sheet, prepare a test piece cut into a size of 20 cm × 20 cm. Accurately weigh the mass of the cut test piece: Vg. In addition, accurately weigh the mass of the substrate cut into 20 cm × 20 cm: Wg. Then, use a thickness gauge to measure the thickness of the prepared laminated sheet and substrate respectively, and subtract the thickness of the substrate from the thickness of the laminated sheet to obtain the thickness of the foamed sheet: T cm. At this time, the thickness value is calculated by the average value when measuring 6 points. By substituting the measured values ​​of V, W, and T into the following formula, the density of the foamed sheet is calculated.

[0165] Density (g / cm 3 )=(VW) / (T×20×20)

[0166] <Outgassing properties>

[0167] <<Evaluation Device>>

[0168] Evaluation of outgassing properties using Figure 2 The evaluation device 100 shown is performed. Figure 2 The evaluation device 100 shown is a device for evaluating the degassing property of a laminated sheet 50 formed by laminating a foam sheet 51 and a base material 52. The device comprises: a sample fixing plate 10 having a through hole 11; a gas pressure feeding mechanism 40 for feeding air as gas at a constant pressure from the other surface side (the other side) of the sample fixing plate 10 through the through hole 11; Figure 2 (upper side in the middle) to one surface side ( Figure 2 The lower side is in the middle) for pressure feeding.

[0169] Here, the gas pressure feeding mechanism 40 includes a syringe 20, the tip of which is connected to the through hole 11 of the sample fixing plate 10 on the other surface side of the sample fixing plate 10; and a weight 30. In addition, the syringe 20 includes a needle 21, the tip of which is directed vertically downward ( Figure 2 The outer cylinder 22 is cylindrical, and the front end ( Figure 2 and a piston 23 that passes through the outer tube 22 from the rear end side of the outer tube 22.

[0170] In addition, the weight 30 is installed at the rear end of the piston 23 ( Figure 2 On the flange (the upper side end).

[0171] In addition, in the gas compression mechanism 40 having the above-mentioned structure, the piston 23 is pressed into the outer tube 22 by the dead weight of the piston 23 and the weight 30, and the air in the outer tube 22 is compressed and sent to one surface side (foam sheet 51) of the sample fixing plate 10 through the needle 21 and the through hole 11 at a certain pressure.

[0172] Furthermore, in the evaluation apparatus 100 having the above-described structure, for example, after the laminate 50 is attached to the surface of one side (opposite to the needle 21 side) of the sample fixing plate 10 to which the needle 21 is fixed, so as to cover the through-hole 11 (step (A)), the piston 23 equipped with the weight 30 is inserted to a position L from the front end of the outer cylinder 22, the outer cylinder 22 is connected to the needle 21, and the time required for the piston 23 to advance a distance L due to the weight of the piston 23 and the weight 30 is measured (step (B)). This allows the degassing properties of the laminate 50 to be evaluated. Specifically, when the air within the outer cylinder 22 is forced out of the through-hole 11 at a constant pressure due to the weight of the piston 23 and the weight 30, if the distance L and the amount of air forced out of the outer cylinder 22 are constant, the lower the degassing properties of the laminate 50, the longer the time required for the laminate 50 to advance the distance L, and the higher the degassing properties of the laminate 50, the shorter the time required for the laminate 50 to advance the distance L. Therefore, the degassing properties of the laminated sheet 50 can be quantitatively evaluated based on the time required for the piston 23 to advance a distance L. Furthermore, since the evaluation can be performed under conditions where the amount and pressure of the compressed air are constant, the degassing properties can be evaluated with high repeatability. Furthermore, since the evaluation can be performed with the laminated sheet 50 attached to the sample fixing plate 10, the degassing properties of the laminated sheet 50 attached to the adherend can be accurately evaluated.

[0173] In addition, a transparent polycarbonate plate (50 mm × 50 mm) with a thickness of 1 mm was used as the sample fixing plate 10, a glass syringe with a capacity of 2 mL and a metal syringe needle with a diameter of 2 mm was used as the syringe 20, and a weight with a weight of 30 g attached to the piston 23 with double-sided tape was used as the weight 30.

[0174] <<Evaluation of Outgassing Properties (Initial)>>

[0175] After the laminated sheet was produced, it was cut into a size of 40 mm×40 mm, and this was used as a sample to be evaluated.

[0176] Then, the surface of the foam sheet side of the prepared sample is attached to the surface of one side (the side opposite to the needle 21 side) of the sample fixing plate 10 fixed with a needle 21 in a manner that covers the through-hole 11 and does not enter air (process (A)), the piston 23 equipped with a weight 30 is inserted into the position where the scale of the outer cylinder 22 is 2mL, and the outer cylinder 22 is connected to the needle 21. Then, the hand is removed from the weight 30 and the piston 23, and the time required until the piston 23 and the weight 30 fall completely due to their own weight (that is, until 2mL of air is forced to flow) is measured (process (B)). This measurement operation is repeated 3 times, the average value of the measured time is calculated, and the following benchmark evaluation is performed. The smaller the average value, the more excellent the degassing (initial) of the laminated sheet.

[0177] A: The average measurement time is less than 10 seconds

[0178] B: The average value of the measured time is greater than 10 seconds and less than 20 seconds

[0179] C: The average value of the measured time is greater than 20 seconds and less than 30 seconds

[0180] D: The average value of the measured time is greater than 30 seconds

[0181] <<Evaluation of Degassing Properties (After Heating and Pressurizing)>>

[0182] The laminated sheet was cut into a size of 80 mm × 120 mm and subjected to a 110 g / cm 2 The laminate was then subjected to pressure at 23°C and 50% RH for 24 hours. The pressure was then released and the laminate was allowed to stand for 24 hours. The laminate was then cut into 40 mm x 40 mm pieces, which served as evaluation samples. Other than this, the laminate was measured and evaluated using the same procedures as in "Evaluation of Degassing Properties (Initial)." The smaller the average value, the better the degassing properties (after heating and pressurization) of the laminate.

[0183] <Formaldehyde emission>

[0184] A self-adsorptive foam sheet was prepared. A spacer film was attached to the surface of the foam layer (adsorptive layer). The sheet was then cut into 200 mm x 200 mm pieces to prepare test pieces. The test piece was placed in a 5 L Tedlar sampling bag and sealed. 2 L of air was then sealed in a thermostat set at 23°C and 50% RH for 6 hours. The formaldehyde concentration in the bag was then measured using a detector tube (Gas Technology Co., Ltd., No. 91L). Formaldehyde concentrations below 0.1 ppm were designated "A," while those exceeding 0.1 ppm were designated "B."

[0185] (Example 1)

[0186] <Preparation of Polymer>

[0187] A monomer mixture consisting of 64 parts of ethyl acrylate, 12 parts of 2-ethylhexyl acrylate, 12 parts of n-butyl acrylate, 9 parts of acrylonitrile, 2 parts of styrene, and 1 part of acrylic acid, and 0.4 parts of sodium polyoxyethylene alkyl ether sulfate (manufactured by Kao Corporation: LATEMUL E-118B) were mixed with 27.0 parts of deionized water and stirred to obtain a monomer emulsion.

[0188] Separately from the above, a glass reaction vessel equipped with a reflux cooler, dropping funnel, thermometer, nitrogen inlet, and stirrer was prepared. 43.0 parts of deionized water and 0.2 parts of sodium polyoxyethylene alkyl ether sulfate were placed in this glass reaction vessel and heated to 80°C while stirring. Then, while maintaining the temperature at 80°C, 0.3 parts of ammonium persulfate dissolved in 5.7 parts of deionized water was added, followed by the slowly added monomer emulsion obtained above over 4 hours. After the addition was completed, stirring was continued for a further 4 hours, and then the reaction was cooled to terminate, yielding a reaction mixture. The polymerization conversion at this point was nearly 100% (98% or more). The resulting reaction mixture was adjusted to pH 5.0 with 5% aqueous ammonia, and 2.5 parts of polyoxyethylene lauryl ether (EMULGEN 120 manufactured by Kao Corporation) was added, followed by concentration to yield a polymer latex having a solids concentration of 55%. The glass transition temperature and gel fraction of the polymer contained in the resulting polymer latex were then measured. The results are shown in Table 1.

[0189] <Preparation of Foam Sheet Composition>

[0190] 100 parts of the above-mentioned polymer latex (i.e., 55 parts of the polymer contained in the polymer latex), 3 parts (5.5 parts per 100 parts of the polymer) of an epoxy crosslinking agent (RIKA BOND EX-8, fatty acid polyglycidyl ether, manufactured by Nippon Paint Resins Co., Ltd.), 2 parts (3.6 parts per 100 parts of the polymer) of a wax agent (a fatty acid ester containing a fatty acid moiety having 16 to 34 carbon atoms), and 4 parts of a foam stabilizer (ammonium stearate, manufactured by San Nopco Co., Ltd., NOPCO DC-100A) were added to a mixing container in this order. Finally, a thickener (sodium polyacrylate, manufactured by Toagosei Co., Ltd., ARON A-20L) was added to adjust the viscosity to 4250 mPa·s to obtain a composition for a foam sheet.

[0191] <Preparation of synthetic paper substrate>

[0192] 74% of a propylene homopolymer (Novatec PP: MA4, manufactured by Japan Polychem), 10% of a high-density polyethylene (Novatec HD: HJ360, manufactured by Japan Polychem), and 16% of calcium carbonate (Softon 1800, manufactured by Bihoku Powder Industry Co., Ltd.) were melt-kneaded at 250°C. The mixture was then fed through a die set at 250°C and extruded into a sheet. The sheet was then cooled with a chill roll to obtain an unstretched sheet. The resulting unstretched sheet was heated to 135°C and stretched in the longitudinal direction at a ratio of 4 to form the substrate layer (b).

[0193] Next, 52% of a propylene homopolymer (Novatec PP: EA8, manufactured by Japan Polychem), 3% of a high-density polyethylene (Novatec HD: HJ360, manufactured by Japan Polychem), and 45% of calcium carbonate (Softon 1800, manufactured by Beihoku Powder Industry Co., Ltd.) were melt-kneaded at 250°C using different extruders. The mixture was then fed to a die set at 250°C and extruded into sheets as the surface layer (a) and back layer (c), which were laminated on both sides of the above-mentioned substrate layer (b). The sheets were then cooled to 60°C to obtain a three-layer laminated film (a / b / c).

[0194] The resulting three-layer laminated film was then heated again to 180°C and stretched in the transverse direction using a tenter at a ratio of 9. It was then annealed at 160°C, cooled to 60°C, and the edges were cut to obtain a synthetic paper substrate consisting of a multilayer stretched resin film.

[0195] <Preparation of Laminated Sheet>

[0196] The composition for a foam sheet obtained as described above was stirred with a whisk to foam it so that the expansion ratio became 1.6 times, and the stirring speed was further reduced and stirring was continued for 5 minutes.

[0197] The foamed composition for the foam sheet (foam) was applied to the synthetic paper substrate using a 0.3 mm applicator. The foam was placed in a drying oven and held at 80°C for 1.33 minutes, 120°C for 1.33 minutes, and 140°C for 1.33 minutes for drying and crosslinking, thereby obtaining a laminated sheet having the foam sheet on the synthetic paper substrate. The thickness of the dried foam sheet was 0.133 mm. Various evaluations were performed using the resulting laminated sheet. The results are shown in Table 1.

[0198] (Example 2)

[0199] A composition for a foam sheet and a laminated sheet were prepared or produced in the same manner as in Example 1 except that the polymer prepared as described below was used. Evaluation was then performed in the same manner as in Example 1. The results are shown in Table 1.

[0200] <Preparation of Polymer>

[0201] A monomer mixture consisting of 56 parts of ethyl acrylate, 15 parts of 2-ethylhexyl acrylate, 18 parts of n-butyl acrylate, 8 parts of acrylonitrile, 2 parts of styrene, and 1 part of acrylic acid, and 0.4 parts of sodium polyoxyethylene alkyl ether sulfate (LaTEMUL E-118B manufactured by Kao Corporation) were mixed with 27.0 parts of deionized water and stirred to obtain a monomer emulsion. A polymer latex was obtained in the same manner as in Example 1 except for this.

[0202] (Comparative Example 1)

[0203] <Preparation of Polymer>

[0204] A monomer mixture consisting of 46.9 parts of ethyl acrylate, 45.8 parts of n-butyl acrylate, 5.9 parts of acrylonitrile, and 1.4 parts of N-methylolacrylamide was mixed with 0.4 parts of sodium polyoxyethylene alkyl ether sulfate (LaTEMUL E-118B manufactured by Kao Corporation) in 27.0 parts of deionized water and stirred to obtain a monomer emulsion. Otherwise, the same procedures as in Example 1 were followed to obtain a polymer latex. Evaluation was then performed in the same manner as in Example 1. The results are shown in Table 1.

[0205] <Preparation of Foam Sheet Composition>

[0206] The polymer latex obtained as described above was used, and the amount of crosslinking agent added was changed from 3 parts to 3.6 parts (i.e., 6.5 parts of crosslinking agent per 100 parts of polymer). In addition, no wax agent was added. Other than this, the same procedure as in Example 1 was followed to prepare a composition for a foam sheet.

[0207] <Production of Laminated Sheet>

[0208] A laminated sheet was produced in the same manner as in Example 1 except that the expansion ratio was set to 2 times instead of 1.6 times and the foam sheet composition obtained above was used. The evaluation was then performed in the same manner as in Example 1. The results are shown in Table 1.

[0209] (Comparative Example 2)

[0210] <Preparation of Polymer>

[0211] A monomer mixture consisting of 70 parts of n-butyl acrylate, 14 parts of methyl methacrylate, 14 parts of styrene, and 2 parts of itaconic acid was mixed with 0.4 parts of sodium polyoxyethylene alkyl ether sulfate (LaTEMUL E-118B manufactured by Kao Corporation) in 27.0 parts of deionized water and stirred to obtain a monomer emulsion. Otherwise, the same procedures as in Example 1 were followed to obtain a polymer latex. Evaluation was then performed in the same manner as in Example 1. The results are shown in Table 1.

[0212] <Preparation of Foam Sheet Composition>

[0213] The polymer latex obtained as described above was used, and the amount of crosslinking agent added was changed from 3 parts to 3.6 parts (i.e., 6.5 parts of crosslinking agent per 100 parts of polymer). In addition, no wax agent was added. Other than this, the same procedure as in Example 1 was followed to prepare a composition for a foam sheet.

[0214] <Production of Laminated Sheet>

[0215] A laminated sheet was produced in the same manner as in Example 1 except that the foam sheet composition obtained above was used. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

[0216] In addition, in Table 1 shown below,

[0217] "EA" represents ethyl acrylate units,

[0218] "MMA" means methyl methacrylate units,

[0219] "2EHA" represents 2-ethylhexyl acrylate units,

[0220] "BA" represents n-butyl acrylate units,

[0221] "AA" represents acrylic acid units,

[0222] "IA" represents itaconic acid unit,

[0223] "AN" represents acrylonitrile unit,

[0224] "ST" represents styrene units,

[0225] "NMA" represents N-methylol acrylamide units,

[0226] "Tg" means glass transition temperature.

[0227] [Table 1]

[0228]

[0229] As apparent from Table 1, in Examples 1 and 2 using the foam sheet composition containing a polymer, a crosslinking agent, and a wax agent, a laminated sheet having excellent degassing properties after heating and pressing can be formed.

[0230] On the other hand, it was found that in Comparative Examples 1 and 2 using a composition for a foam sheet containing no wax agent, it was not possible to form a laminated sheet having excellent degassing properties after heating and pressing.

[0231] Industrial applicability

[0232] According to the present invention, a self-adsorptive foam laminate sheet having excellent degassing properties after heating and pressurization can be provided.

[0233] Description of Reference Numerals

[0234] S1: Composition production process

[0235] S2: Foaming process

[0236] S3: Flake process

[0237] S10: Method for manufacturing laminated sheets

[0238] 10: Sample fixing plate

[0239] 11: Through hole

[0240] 20: Syringe

[0241] 21: Needle

[0242] 22: Outer cylinder

[0243] 23: Pistons

[0244] 30: Weights

[0245] 40: Gas pressure delivery mechanism

[0246] 50: Laminated sheets

[0247] 51: Foam sheet

[0248] 52: Base material

[0249] 100: Evaluation device

Claims

1. A self-adsorbing foam laminate sheet comprising a synthetic paper substrate and a self-adsorbing foam sheet, The synthetic paper substrate is composed of a multi-layer resin stretched film. The self-adsorptive foam sheet is formed using a composition for a self-adsorptive foam sheet comprising a polymer, a cross-linking agent, and a wax agent. The gel fraction of the polymer is 50% by mass or more and 95% by mass or less, The ratio of the alkenyl aromatic monomer unit in the polymer is 0.5% by mass or more and 20% by mass or less, based on 100% by mass of all repeating units contained in the polymer.

2. The self-adsorptive foam laminate sheet according to claim 1, wherein The polymer contains 60% by mass or more and 99% by mass or less of a (meth)acrylate monomer unit.

3. The self-adsorptive foam laminate sheet according to claim 1 or 2, wherein The polymer contains 0.1% by mass or more and 10% by mass or less of an unsaturated carboxylic acid monomer unit.

4. The self-adsorptive foam laminate sheet according to claim 1 or 2, wherein The polymer has no N-hydroxymethyl groups.

5. The self-adsorptive foam laminate sheet according to claim 1 or 2, wherein The wax agent includes a fatty acid ester having a fatty acid moiety having 16 to 34 carbon atoms.

6. The self-adsorptive foam laminate sheet according to claim 5, wherein The fatty acid ester has an alcohol portion having 30 or more and 34 or less carbon atoms.

7. The self-adsorptive foam laminate sheet according to claim 5, wherein The amount of the fatty acid ester in the composition for a self-adsorptive foam sheet is 0.5 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of the polymer.

Images