Composition for self-adsorbing foamed sheets and self-adsorbing foamed laminated sheets

Abstract

The purpose of the present invention is to provide a self-adhesive foam sheet composition that can be used to obtain a self-adhesive foam layered sheet that shows less reduction in self-adhesive force over time. The self-adhesive foam sheet composition according to the present invention is characterized by containing a polymer, an oxazoline-based crosslinking agent, and a wax agent.

Description

[Technical Field]

[0001] This invention relates to a composition for self-adsorbing foamed sheets and a self-adsorbing foamed laminated sheet. [Background technology]

[0002] In recent years, self-adhesive foam sheets (hereinafter sometimes abbreviated as "foam sheets"), which are sheet-like components made of foam material having numerous fine pores and possessing self-adhesion properties, have been used as adhesive sheets for application to smooth substrates such as window glass. The adhesive method of self-adhesive foam sheets is not adhesive bonding, but rather adhesion to the substrate using fine pores. Therefore, self-adhesive foam sheets are easier to reposition than conventional adhesive sheets that use adhesive bonding, and are suitable for applications such as wallpaper, posters, and stickers. When used in these applications, self-adhesive foam sheets are usually used in the form of self-adhesive foam laminated sheets (hereinafter sometimes abbreviated as "laminated sheets"), which are laminated with a base material. By applying decorations such as printing to the surface of the base material side of this self-adhesive foam laminated sheet, it can be used advantageously for the aforementioned applications.

[0003] Furthermore, in order to improve the performance of self-adsorbing foam laminated sheets, improvements have been made to the compositions used in the preparation of the foam sheets that constitute the laminated sheets (hereinafter referred to as "compositions for self-adsorbing foam sheets," and sometimes abbreviated as "compositions for foam sheets").

[0004] For example, Patent Document 1 proposes a foam sheet composition comprising a polymer having predetermined properties and a crosslinking agent. Furthermore, a laminated sheet comprising a foam sheet formed from the foam sheet composition of Patent Document 1 can suppress the residue of resin on the adherend, such as glass, even after weathering. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2018 / 151274 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In this context, the laminated sheet is required to have the property of easily removing air pockets remaining between the sheet and the adherend when the foamed sheet side is adhered to the adherend (i.e., excellent air release properties). In particular, since the laminated sheet may be exposed to high temperature and pressurized environments during transportation, it is required to maintain excellent air release properties even after heating and pressurizing (i.e., excellent air release properties after heating and pressurizing).

[0007] The inventors' research revealed that by forming a foamed sheet using a foamed sheet composition containing a polymer, a crosslinking agent, and a wax agent, the laminated sheet comprising the foamed sheet can exhibit excellent air release properties even after heating and pressurizing.

[0008] However, further investigation by the present inventors revealed that the laminated sheet comprising the foamed sheet formed using the above-mentioned foamed sheet composition had room for improvement in terms of reducing the decrease in self-adhesion (adhesion to the adherend) over time.

[0009] Therefore, the present invention aims to provide a self-adhesive foam laminated sheet that exhibits less reduction in self-adhesion over time, and a composition for a self-adhesive foam laminated sheet that can be used to obtain said self-adhesive foam laminated sheet. [Means for solving the problem]

[0010] The inventors diligently conducted research with the aim of solving the above problems. As a result, the inventors discovered that by forming a foamed sheet using a composition for foamed sheets containing a polymer, an oxazoline-based crosslinking agent, and a wax agent, the decrease in the self-adhesion strength of a laminated sheet comprising the foamed sheet over time can be reduced, and thus the present invention was completed.

[0011] In other words, the present invention aims to advantageously solve the above problems, and the self-adsorbing foam sheet composition of the present invention is characterized by comprising a polymer, an oxazoline-based crosslinking agent, and a wax agent. In this way, by forming a foam sheet using a foam sheet composition comprising a polymer, an oxazoline-based crosslinking agent, and a wax agent, the decrease in self-adhesion strength of the laminated sheet comprising the foam sheet over time can be reduced.

[0012] In the present invention, it is preferable that the polymer in the self-adsorbing foam sheet composition contains 60% to 99% by mass of (meth)acrylate monomer units. By using a foam sheet composition containing a polymer with (meth)acrylate monomer units in the above proportion, a laminated sheet can be obtained that maintains good self-adhesion while suppressing resin residue on the adherend. In this invention, "a polymer containing monomer units" means "a polymer obtained using those monomers contains repeating units derived from the monomers." Also, in this invention, "(meth)acrylate" means acrylate and / or methacrylate.

[0013] Furthermore, in the self-adsorbing foam sheet composition of the present invention, it is preferable that the amount of the oxazoline-based crosslinking agent is 0.5 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the polymer. By using a foam sheet composition in which the amount of the oxazoline-based crosslinking agent per 100 parts by mass of the polymer is within the above range, it is possible to maintain good self-adhesion of the laminated sheet while further reducing the decrease in self-adhesion over time.

[0014] In the self-adsorbing foam sheet composition of the present invention, it is preferable that the waxing agent includes a fatty acid ester having a fatty acid portion with 16 to 34 carbon atoms. By using a fatty acid ester as the waxing agent that has a fatty acid portion (a structure derived from the fatty acid in the fatty acid ester) with a carbon number within the above range, the air release properties of the laminated sheet after heating and pressurizing can be improved.

[0015] Furthermore, in the self-adsorbing foam sheet composition of the present invention, it is preferable that the amount of the wax agent is 0.5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the polymer. By using a foam sheet composition in which the amount of the wax agent per 100 parts by mass of polymer is within the above range, the air release properties after heating and pressurizing of the laminated sheet can be improved.

[0016] Furthermore, the present invention aims to advantageously solve the above problems, and the self-adsorbing foam laminated sheet of the present invention is a self-adsorbing foam laminated sheet comprising a substrate and a self-adsorbing foam sheet formed using any of the above-described self-adsorbing foam sheet compositions, characterized in that the substrate is a paper substrate other than a synthetic paper substrate, a plastic substrate, a fiber substrate, a metal substrate, or a glass substrate. In this way, a laminated sheet comprising a foam sheet formed using the above-described foam sheet composition on a paper substrate other than a synthetic paper substrate, a plastic substrate, a fiber substrate, a metal substrate, or a glass substrate exhibits less decrease in self-adhesion over time. In this invention, "synthetic paper" means a film made from a resin composition containing a thermoplastic resin and a filler. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a self-adhesive foam laminated sheet that exhibits little decrease in self-adhesion over time, and a composition for a self-adhesive foam laminated sheet that can be used to obtain the self-adhesive foam laminated sheet. [Brief explanation of the drawing]

[0018] [Figure 1]This is a flowchart for explaining an example of a method for manufacturing a self - adsorbing foamed laminated sheet according to the present invention. [Figure 2] This is an explanatory diagram showing a schematic configuration of an evaluation apparatus used for evaluating the air - venting property of a self - adsorbing foamed laminated sheet in Examples and Comparative Examples.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described in detail. Here, the composition for a self - adsorbing foamed sheet of the present invention can be suitably used when obtaining a self - adsorbing foamed sheet which is a component of the self - adsorbing foamed laminated sheet of the present invention. Further, the self - adsorbing foamed laminated sheet of the present invention includes a self - adsorbing foamed sheet formed using the composition for a self - adsorbing foamed sheet of the present invention.

[0020] (Composition for a self - adsorbing foamed sheet) The composition for a foamed sheet of the present invention contains a polymer, an oxazoline - based cross - linking agent, and a wax agent, and optionally further contains a solvent and other additives. And, by forming a foamed sheet using the composition for a foamed sheet of the present invention on a paper substrate other than a synthetic paper substrate, a plastic substrate, a fiber substrate, a metal substrate, or a glass substrate, a laminated sheet with less reduction in self - adhesion over time can be obtained. And a laminated sheet including a foamed sheet formed using the composition for a foamed sheet of the present invention can exhibit good self - adhesion both initially (i.e., immediately after production) and over time because the reduction in self - adhesion over time is small. In addition, a laminated sheet including a foamed sheet formed using the composition for a foamed sheet of the present invention also has excellent air - venting property after heating and pressurization.

[0021] (Polymer) The polymer used in the composition for a foamed sheet of the present invention forms a resin matrix in the foamed sheet obtained by foaming and cross - linking the composition for a foamed sheet.

[0022] Here, the polymer is not particularly limited, but may include, for example, at least one monomer unit selected from the group consisting of (meth)acrylate monomer units, unsaturated carboxylic acid monomer units, vinyl cyanide monomer units, and alkenyl aromatic monomer units. The polymer may also contain monomer units other than (meth)acrylate monomer units, unsaturated carboxylic acid monomer units, vinyl cyanide monomer units, and alkenyl aromatic monomer units (hereinafter referred to as "other monomer units").

[0023] <<(meth)acrylate monomer units>> (Meth)acrylate monomer units are repeating units derived from (meth)acrylate monomers. The inclusion of (meth)acrylate monomer units in the polymer imparts flexibility to the resulting foamed sheet, making it possible to obtain a laminated sheet with good self-adhesion.

[0024] The (meth)acrylate monomer is not particularly limited, but examples 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. Furthermore, the (meth)acrylate monomer may be used alone or in combination of two or more types. In addition, in this invention, "(meth)acrylic" means acrylic and / or methacrylic.

[0025] Here, as the (meth)acrylate monomer, an alkyl (meth)acrylate monomer is preferred from the viewpoint of further enhancing the flexibility of the foamed sheet and ensuring even better self-adhesion of the laminated sheet, and an alkyl (meth)acrylate monomer with 1 to 14 carbon atoms in the alkyl group (bonded to the non-carbonyl oxygen atom) is more preferred (hereinafter sometimes abbreviated as "C1-14 (meth)acrylate alkyl monomer").

[0026] Examples of C1-14 (meth)acrylate alkyl ester 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 viewpoint of self-adhesion and cost.

[0027] Furthermore, the proportion of (meth)acrylate monomer units in the polymer is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 85% by mass or more, preferably 99% by mass or less, more preferably 95% by mass or less, even more preferably 92% by mass or less, and particularly preferably 89% by mass or less. If the proportion of (meth)acrylate monomer units in the polymer is 60% by mass or more, sufficient self-adhesion strength of the laminated sheet can be ensured. On the other hand, if the proportion of (meth)acrylate monomer units in the polymer is 99% by mass or less, the self-adhesion strength of the laminated sheet will not become excessively high. Therefore, resin residue of the laminated sheet on the adherend can be suppressed.

[0028] <<Unsaturated carboxylic acid monomer units>> The unsaturated carboxylic acid monomer unit is a repeating unit derived from an unsaturated carboxylic acid monomer. Specific examples of unsaturated carboxylic acid monomers include, for example, 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 itaconic acid, monobutyl maleate, and monopropyl fumarate. In addition, compounds having groups that can be converted to carboxylic acid groups by hydrolysis, such as maleic anhydride and itaconic anhydride, can also be used in the same way. Among these, itaconic acid, acrylic acid, and methacrylic acid are preferred, with acrylic acid being more preferred, from the viewpoint of reactivity with the crosslinking agent described later, the stability of the polymer latex, and cost. Furthermore, unsaturated carboxylic acid monomers may be used individually or in combination of two or more.

[0029] Furthermore, the proportion of unsaturated carboxylic acid monomer units in the polymer is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 2.5% by mass or less, based on 100% by mass of all repeating units (total monomer units) contained in the polymer. By having a proportion of unsaturated carboxylic acid monomer units in the polymer of 0.1% by mass or more, the crosslinking reaction by the crosslinking agent described later can be carried out sufficiently. As a result, it is possible to impart sufficient strength to the resulting foamed sheet while suppressing resin residue on the adherend of the laminated sheet. On the other hand, by having a proportion of unsaturated carboxylic acid monomer units in the polymer of 10% by mass or less, it becomes easier to maintain the viscosity of the polymerization system within an appropriate range during polymerization, and the crosslinking of the polymer does not proceed excessively, which impairs the self-adhesion strength of the laminated sheet.

[0030] <<Vinyl cyanide monomer unit>> The vinyl cyanide monomer unit is a repeating unit derived from the 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, but examples include acrylonitrile; α-halogenoacrylonitriles such as α-chloroacrylonitrile and α-bromoacrylonitrile; and α-alkylacrylonitriles such as methacrylonitrile and α-ethylacrylonitrile. Among these, acrylonitrile is preferred from the viewpoint of improving the cohesive force of the foam sheet composition and increasing the fracture strength of the foam sheet. Furthermore, vinyl cyanide monomers may be used individually or in combination of two or more types.

[0031] Furthermore, the proportion of vinyl cyanide monomer units in the polymer is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, particularly preferably 8% by mass or more, preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, based on 100% by mass of all repeating units (total monomer units) contained in the polymer. If the proportion of vinyl cyanide monomer units in the polymer is 1% by mass or more, it is possible to impart sufficient strength to the resulting foamed sheet while suppressing resin residue on the adherend of the laminated sheet. On the other hand, if the proportion of vinyl cyanide monomer units in the polymer is 30% by mass or less, it is possible to obtain a laminated sheet with good self-adhesion while ensuring sufficient flexibility in the resulting foamed sheet.

[0032] <<Alkenyl aromatic monomer units>> Alkenyl aromatic monomer units are repeating units derived from alkenyl aromatic monomers. Specific examples of alkenyl aromatic monomers include styrene, α-methylstyrene, α-chlorostyrene, vinyltoluene, and divinylbenzene. Among these, styrene is preferred from the viewpoint of polymerizability and cost. Furthermore, alkenyl aromatic monomers may be used individually or in combination of two or more.

[0033] Furthermore, the proportion of alkenyl aromatic monomer units in the polymer is preferably 0.5% by mass or more, more preferably 1% by mass or more, even more preferably 1.5% by mass or more, particularly preferably 2% by mass or more, preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on the total repeating units (total monomer units) contained in the polymer being 100% by mass. If the proportion of alkenyl aromatic monomer units in the polymer is 0.5% by mass or more, water penetration into the foamed sheet can be prevented based on the hydrophobicity of the alkenyl aromatic monomer units, thereby improving the water resistance of the laminated sheet. On the other hand, if the proportion of alkenyl aromatic monomer units in the polymer is 20% by mass or less, sufficient flexibility of the resulting foamed sheet can be ensured, and a laminated sheet with good self-adhesion can be obtained.

[0034] <<Other monomeric units>> Other monomeric units are repeating units derived from other monomers copolymerizable with the monomers mentioned above. Other monomers include, for example, conjugated diene monomers, α,β-ethylenically unsaturated polycarboxylic acid complete ester monomers, carboxylic acid unsaturated alcohol ester monomers, olefin monomers, and other monomers having functional groups. These monomers may be used individually or in combination of two or more. Specific examples of such other monomers are not particularly limited, and for example, those described in International Publication No. 2018 / 151274 can be used.

[0035] Furthermore, from the viewpoint of sufficiently suppressing the generation of formaldehyde when foaming and curing the foam sheet composition, it is preferable that the polymer does not have N-methylol groups. More specifically, it is preferable that the polymer does not contain monomer units having N-methylol groups. Examples of monomers having an N-methylol group include N-methylolacrylamide and N-methylolmethacrylamide.

[0036] <<Properties>> [Glass transition temperature] Here, 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 even more preferably -31°C or lower. If the glass transition temperature of the polymer is -10°C or lower, the self-adhesion strength of the laminated sheet can be sufficiently ensured, and the laminated sheet can adhere well to the adherend, preventing moisture from penetrating between the adherend and the layers of the laminated sheet. Therefore, the water resistance of the laminated sheet can be improved. Furthermore, while the lower limit of the glass transition temperature of the polymer is not particularly limited, it is preferably -40°C or higher from the viewpoint of sufficiently suppressing resin residue on the substrate of the laminated sheet. The glass transition temperature of the polymer can be measured using the method described in the examples of this specification.

[0037] [Gel fraction] Here, the gel fraction of the polymer is preferably 95% by mass or less, more preferably 93% by mass or less, and even more preferably 80% by mass or less. If the gel fraction is 95% by mass or less, foamed sheets and laminated sheets with appropriate self-adhesion and excellent smoothness can be produced. Furthermore, the lower limit of the gel fraction of the polymer is not particularly limited, but for example, it can be 50% by mass or more, or 70% by mass or more. The gel fraction of the polymer can be measured using the method described in the examples of this specification.

[0038] <<Method for preparing polymers>> The polymerization method used to obtain the polymer is not particularly limited and may include solution polymerization, emulsion polymerization, suspension polymerization, bulk polymerization, or any other method. There are no particular restrictions on the type or amount of polymerization initiators, emulsifiers, dispersants, etc., used in polymerization. There are also no particular restrictions on the method of adding monomers, polymerization initiators, emulsifiers, dispersants, etc., during polymerization. Furthermore, there are no restrictions on polymerization temperature, pressure, stirring conditions, etc. While polymers can be used in solid form, using them in the form of polymer-containing latex (polymer latex), such as latex obtained by emulsion polymerization or latex obtained by post-emulsification of the polymer, makes mixing with crosslinking agents and waxes easier and is also convenient for foaming the resulting foam sheet composition. Here, as described above, when the polymer is used in the form of polymer latex to prepare a foam sheet composition, the solid content concentration of the polymer latex is preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, particularly preferably 52% by mass or more, preferably 70% by mass or less, and more preferably 58% by mass or less, from the viewpoint of maintaining the density of the resulting foam sheet.

[0039] <Oxazoline-based crosslinking agent> The foamed sheet composition of the present invention contains an oxazoline-based crosslinking agent. The oxazoline groups of the oxazoline-based crosslinking agent react with functional groups in the polymer (for example, carboxylic acid groups derived from unsaturated carboxylic acid monomer units) to form crosslinked structures within or between the polymer molecules. By using the foamed sheet composition of the present invention, which contains an oxazoline-based crosslinking agent, it is possible to form a foamed sheet that has excellent self-adhesion and whose self-adhesion does not easily decrease over time. Therefore, the decrease in self-adhesion over time of a laminated sheet comprising the foamed sheet can be reduced.

[0040] The oxazoline crosslinking agent is not particularly limited as long as it has one or more oxazoline groups in one molecule and can form a crosslinked structure with the polymer described above. The oxazoline crosslinking agent is assumed to be a component different from the polymer described above.

[0041] Furthermore, from the viewpoint of further reducing the decrease in self-adhesion strength of the laminated sheet over time, it is preferable to use a polymer obtained by polymerizing a monomer containing an oxazoline group (oxazoline group-containing monomer), i.e., an oxazoline group-containing polymer, as the oxazoline crosslinking agent. The oxazoline group-containing polymer may be a copolymer of an oxazoline group-containing monomer and a monomer other than the oxazoline group-containing monomer.

[0042] Furthermore, the glass transition temperature of the oxazoline group-containing polymer may be, for example, 20°C or higher, 30°C or higher, 40°C or higher, 50°C or higher, or 200°C or lower, 150°C or lower, or 100°C or lower.

[0043] Here, the oxazoline crosslinking agent may be synthesized by known methods or a commercially available product may be used. Examples of commercially available oxazoline crosslinking agents include "Epocross WS-300," "Epocross WS-500," and "Epocross WS-700" manufactured by Nippon Shokubai Co., Ltd.

[0044] The amount of oxazoline-based crosslinking agent in the foam sheet composition is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 3 parts by mass or more, even more preferably 6 parts by mass or more, even more preferably 10 parts by mass or more, preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, per 100 parts by mass of the polymer. If the amount of oxazoline-based crosslinking agent is 0.5 parts by mass or more per 100 parts by mass of polymer, the decrease in the self-adhesion strength of the laminated sheet comprising the formed foam sheet over time can be further reduced. On the other hand, if the amount of oxazoline-based crosslinking agent is 30 parts by mass or less per 100 parts by mass of polymer, excessive crosslinking of the polymer can be suppressed, and sufficient self-adhesion strength of the laminated sheet comprising the formed foam sheet can be ensured.

[0045] <Waxing agent> The waxing agent included in the foamed sheet composition of the present invention is not particularly limited as long as it contains a fatty acid ester (especially an ester of a higher fatty acid and a higher alcohol). The fatty acid ester content in the waxing agent is preferably more than 50% by mass and 100% by mass or less (i.e., the main component), more preferably 70% by mass or more and 100% by mass or less, even more preferably 80% by mass or more and 100% by mass or less, and particularly preferably 90% by mass or more and 100% by mass or less, based on 100% by mass of the entire waxing agent. The waxing agent may contain one type of fatty acid ester, or it may contain two or more types of fatty acid esters.

[0046] Here, the wax agent functions as a light release agent in the foamed sheet formed using the foamed sheet composition. It is presumed that by foaming and curing the foamed sheet composition, which contains the wax agent to the polymer described above, the recovery properties are improved due to the light release even when the insides of the interconnected cells of the foamed sheet are pressed together, and thus the air release properties of the laminated sheet equipped with the foamed sheet after heating and pressurizing can be improved.

[0047] Examples of waxing agents include natural waxes, synthetic waxes, and mixtures thereof, but it is preferable to use natural waxes. Here, specific examples of natural waxes are not particularly limited as long as they contain naturally derived fatty acid esters, but include, for example, plant-derived natural waxes such as rice bran wax, sugarcane wax, carnauba wax, candelilla wax, jojoba oil, wood wax, and moringa seed oil; animal-derived natural waxes such as beeswax, sperm whale oil, and sheep's wool fat; and mineral-derived natural waxes such as montan wax, ozokerite, and cerasine. Among these, moringa seed oil is preferred from the viewpoint of further improving the air release properties after heating and pressurizing the laminated sheet. These natural waxes may be refined from natural materials using known methods, or commercially available products may be used. An example of a commercially available natural wax is "Refined Moringa Oil" manufactured by Nitto Bussan Shoji Co., Ltd. The waxing agent may be used individually or in combination of two or more types.

[0048] Furthermore, 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 fewer carbon atoms, and more preferably 30 or fewer carbon atoms. If the number of carbon atoms in the fatty acid portion of the fatty acid ester is within the above range, the air release properties after heating and pressurizing the laminated sheet can be further improved.Specific examples of fatty acids with 16 to 34 carbon atoms include, for example, saturated fatty acids such as stearic acid (18 carbon atoms), arachidic acid (20 carbon atoms), and behenic acid (22 carbon atoms); and unsaturated fatty acids such as oleic acid (18 carbon atoms), linoleic acid (18 carbon atoms), and linolenic acid (18 carbon atoms). These fatty acids may be used individually or in combination of two or more.

[0049] Furthermore, the alcohol portion of the fatty acid ester contained in the wax agent preferably has 30 or more carbon atoms, and preferably 34 or fewer carbon atoms. If the number of carbon atoms in the alcohol portion of the fatty acid ester is within the above range, the air release properties after heating and pressurizing the laminated sheet can be further improved.Specific examples of alcohols with 30 to 34 carbon atoms include, for example, myricyl alcohol (30 carbon atoms), melicyl alcohol (31 carbon atoms), lacceryl alcohol (32 carbon atoms), cellomericyl alcohol (33 carbon atoms), and tetratriacontanol (34 carbon atoms). These alcohols may be used individually or in combination of two or more.

[0050] Here, the amount of wax in the foam sheet composition is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 1.5 parts by mass or more, even more preferably 3.6 parts by mass or more, preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the polymer. If the amount of wax is 0.5 parts by mass or more per 100 parts by mass of the polymer, the air release properties after heating and pressurizing the laminated sheet can be further improved. On the other hand, if the amount of wax is 10 parts by mass or less per 100 parts by mass of the polymer, good self-adhesion properties can be imparted to the resulting laminated sheet, and the air release properties after heating and pressurizing the laminated sheet can be further improved. Furthermore, the amount of fatty acid ester having a fatty acid portion with 16 to 34 carbon atoms in the foamed sheet composition is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 1.5 parts by mass or more, preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the polymer. If the amount of fatty acid ester having a fatty acid portion with 16 to 34 carbon atoms is 0.5 parts by mass or more per 100 parts by mass of the polymer, the air release properties after heating and pressurizing the laminated sheet can be further improved. On the other hand, if the amount of fatty acid ester having a fatty acid portion with 16 to 34 carbon atoms is 10 parts by mass or less per 100 parts by mass of the polymer, good self-adhesion properties can be imparted to the resulting laminated sheet, and the air release properties after heating and pressurizing the laminated sheet can be further improved.

[0051] <Solvent> The solvent that the foam sheet composition of the present invention may optionally contain is not particularly limited, but water is preferred. Here, when water is used as the solvent, the water contained in the foam sheet composition can be, for example, water derived from polymer latex.

[0052] <Other additives> The foam sheet composition of the present invention may optionally contain various additives to improve processability in the manufacturing process of foam sheets and laminated sheets, and to improve the performance of the resulting foam sheets and laminated sheets. Examples of such additives include foam stabilizers such as higher fatty acid salts and surfactants, foaming aids, thickeners, fillers, preservatives, antifungal agents, gelling agents, flame retardants, anti-aging agents, antioxidants, pigments, dyes, tackifiers, conductive compounds, water-resistant agents, and oil-resistant agents. Specific examples of the other additives mentioned above are not limited to known additives, such as those described in International Publication No. 2016 / 147679.

[0053] (Self-adhesive foam laminated sheet) The laminated sheet of the present invention comprises a foamed layer made of a foamed sheet obtained using the foamed sheet composition of the present invention described above, and a substrate as a support layer that supports the foamed layer. The foamed sheet may be formed directly on the substrate, or it may be formed on the substrate via any layer.

[0054] <Self-adsorbing foam sheet> The self-adsorbing foamed sheet that forms the foamed layer in the laminated sheet of the present invention is formed by crosslinking and foaming the foamed sheet composition of the present invention. Here, the density of the self-adsorbing foam sheet is not particularly limited, but is 0.1 g / cm³. 3 Preferably, it is 0.3 g / cm³ or more. 3 It is more preferable that the amount be greater than or equal to 0.5 g / cm³. 3 It is even more preferable that the amount be greater than or equal to 1.0 g / cm³. 3 Preferably, it is 0.8 g / cm³. 3 It is more preferable that the following is the case: 0.7 g / cm³ 3 It is even more preferable that the density of the foam sheet is 0.1 g / cm³. 3 If the above is true, the strength of the foam sheet is ensured, 1.0 g / cm² 3 The following conditions can further improve the air release properties after heating and pressurizing the laminated sheet while sufficiently suppressing resin residue on the adherend. The density of the foamed sheet can be calculated using the method described in the examples of this specification. Furthermore, the thickness of the foam sheet is preferably 0.03 mm or more, more preferably 0.05 mm or more, even more preferably 0.1 mm or more, preferably 3 mm or less, more preferably 1 mm or less, even more preferably 0.5 mm or less, and particularly preferably 0.2 mm or less. If the thickness of the foam sheet is 0.03 mm or more, sufficient mechanical strength of the foam sheet and laminated sheet can be ensured. On the other hand, if the thickness of the foam sheet is 3 mm or less, the air release properties after heating and pressurizing of the laminated sheet can be further improved. In addition, a laminated sheet with excellent reworkability can be obtained.

[0055] <Base material> As the substrate in the laminated sheet of the present invention, a paper substrate other than a synthetic paper substrate, a plastic substrate, a fiber substrate, a metal substrate, or a glass substrate can be used. The thickness of the substrate is not particularly limited, but for example, it can be between 10 μm and 200 μm.

[0056] <<Paper base material>> The paper substrate is not particularly limited as long as it is not a synthetic paper substrate. Examples include high-quality paper, art paper, coated paper, kraft paper, and these paper substrates laminated with a thermoplastic resin such as polyethylene.

[0057] <<Plastic base material>> Examples of plastic substrates include polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polystyrene resins; polyvinyl chloride resins; acrylic resins; polycarbonate resins; polyamide resins; fluororesins such as polytetrafluoroethylene; and sheet-like substrates made of mixtures or laminates of these resins.

[0058] <<Fiber material>> Examples of fiber substrates include natural fibers such as cotton and silk; polyamide synthetic fibers; polyester synthetic fibers; polypropylene synthetic fibers; polyvinyl chloride synthetic fibers; polyvinyl alcohol synthetic fibers; semi-synthetic fibers such as acetate; recycled artificial fibers such as rayon; and sheet-like substrates made of mixtures or laminates of these fibers.

[0059] <<Metal base material>> The metal substrate is not particularly limited, but examples include sheet-like substrates made of metals such as iron, copper, aluminum, gold, platinum, and silver, as well as alloys or laminates thereof.

[0060] <<Glass substrate>> The glass substrate is not particularly limited, but examples include sheet-like substrates made of soda-lime glass, borosilicate glass, alkali-free glass, quartz glass, and the like.

[0061] <Method for manufacturing self-adhesive foam laminated sheets> The following describes an example of a method for manufacturing the laminated sheet of the present invention.

[0062] Figure 1 shows a flowchart illustrating an example of a method S10 for manufacturing a laminated sheet (hereinafter sometimes abbreviated as "manufacturing method S10"). As shown in Figure 1, manufacturing method S10 includes a composition preparation step S1, a foaming step S2, and a sheet formation step S3 in that order. Each step will be described below.

[0063] <<Composition preparation process S1>> Composition preparation step S1 is a step of preparing a composition for a self-adsorbing foam sheet.

[0064] Specifically, in the composition preparation step S1, a composition for foamed sheets can be prepared by mixing, in any manner, a polymer, an oxazoline-based crosslinking agent, and a wax agent, which are essential components, along with a solvent and other additives used as desired.

[0065] For example, when using polymer latex in the preparation of a foam sheet composition, this polymer latex can be mixed with an oxazoline-based crosslinking agent, a waxing agent, and other optional additives in a known manner. Furthermore, if a solid polymer is used instead of a solvent in the preparation of the foam sheet composition, the solid polymer, an oxazoline-based crosslinking agent, a waxing agent, and any other additives used may be mixed by a known method (for example, using a known roll, Henschel mixer, kneader, etc.).

[0066] Here, the viscosity of the foam sheet composition containing the solvent (for example, in the form of an emulsion or dispersion) is preferably 1,000 mPa·s or more, more preferably 2,000 mPa·s or more, even more preferably 3,500 mPa·s or more, preferably 10,000 mPa·s or less, more preferably 10,000 mPa·s or less, and even more preferably 5,500 mPa·s or less. If the viscosity of the foam sheet composition is 1,000 mPa·s or more, it is possible to prevent liquid dripping and difficulty in controlling the thickness when forming a foam sheet by coating the foam formed from the foam sheet composition onto a substrate. On the other hand, if the viscosity of the foam sheet composition is 10,000 mPa·s or less, it is not difficult to control the foaming ratio by mechanical foaming when forming a foam sheet. The viscosity of the foam sheet composition can be measured by the method described in the examples of this specification.

[0067] <<Foaming process S2>> The foaming step S2 is a step in which the foaming composition for foamed sheets is foamed to obtain a foamed product of the foamed sheet composition.

[0068] Specifically, in the foaming step S2, the foamed sheet composition prepared in the composition preparation step S1 is foamed to obtain a foam in an unsolidified (uncrosslinked) state. If the foamed sheet composition is in the form of an emulsion or dispersion, a foamed emulsion or foamed dispersion is obtained.

[0069] For foaming, mechanical foaming is usually employed. The foaming ratio can be adjusted as appropriate, but it is usually 1.2 times or more, preferably 1.5 times or more, and usually 5 times or less, preferably 4 times or less. The method of mechanical foaming is not particularly limited, but it can be carried out by mixing a certain amount of air into the emulsion or dispersion of the foam sheet composition and stirring it continuously or in batches using an oak mixer, whisk, etc. The foamed emulsion or foamed dispersion thus obtained becomes creamy. By forming pores through the mechanical foaming process described above, a foamed sheet with excellent air-releasing properties can be obtained through the subsequent sheeting process S3 described later. Note that if the foaming ratio is 1.2 times or higher, a decrease in air-releasing properties can be prevented, and if it is 5 times or lower, a decrease in the strength of the foamed sheet can be prevented.

[0070] <<Sheet Formation Process S3>> The sheet formation process S3 is a process in which a foamed sheet is produced by forming the foam into a sheet and then performing a cross-linking reaction on the foam.

[0071] In the sheet formation step S3, the method for forming the foam produced in the foaming step S2 into a sheet is not particularly limited. A preferred method is, for example, to coat the foam onto a desired substrate and form it into a sheet. In this way, by coating the foam onto a desired substrate and allowing the crosslinking reaction to proceed, a laminated sheet can be obtained in which the foamed sheet is directly provided on the substrate.

[0072] Furthermore, the foam coating can be applied to a release sheet (such as process paper with release properties) instead of the above-mentioned substrate. By coating the foam onto the release sheet and allowing the crosslinking reaction to proceed, a laminate can be obtained in which the foam sheet is directly attached to the release sheet. Then, by peeling the release sheet from the foam sheet of this laminate, the foam sheet can be obtained independently (as an independent film).

[0073] As a method for coating a foam onto a substrate or release sheet (hereinafter, these may be collectively referred to as "substrate, etc."), commonly known coating equipment such as applicators, bar coaters, roll coaters, reverse roll coaters, screen coaters, doctor knife coaters, and comma knife coaters can be used.

[0074] A preferred method for crosslinking a foam coated in a sheet-like manner on a substrate is to heat-dry the foam. The heat-drying method is not particularly limited as long as it can dry and crosslink the foam coated on the substrate, and known drying ovens (for example, hot air circulating ovens, hot oil circulating hot air chambers, far-infrared heater chambers) can be used. The drying temperature can be, for example, 60°C to 180°C. Furthermore, it is preferable to perform multi-stage drying, where the foam is dried from the inside at a low temperature in the initial stages, and then thoroughly dried at a higher temperature in the later stages, rather than drying at a constant temperature.

[0075] Furthermore, the properties of the foamed sheet (density, thickness, hardness, etc.) can be adjusted, for example, by changing the ratio of air bubbles, the composition of the foamed sheet composition, the solid content concentration, and the drying and crosslinking conditions.

[0076] The laminated sheet obtained through the above-described steps S1 to S3 is not particularly limited, but for example, after a separator film is attached to the self-adhesive side (i.e., the side with the foamed sheet), it can be wound up by a winding machine and cut into a usable size by press cutting, slitting, etc.

[0077] <Applications of laminated sheets> The laminated sheet of the present invention can be printed on its substrate surface using methods such as offset printing, label printing, flexographic printing, screen printing, gravure printing, laser printers, thermal transfer printers, and inkjet printers. Laminated sheets with printing applied to the base material surface can be advantageously used for outdoor applications such as sales promotion cards, so-called POP cards (posters, stickers, displays, etc.), gardening POP (insert labels, etc.), road signs (funeral signs, housing exhibitions, etc.), and signboards (no entry, forest road work signs, etc.). [Examples]

[0078] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" used to express quantities refer to mass unless otherwise specified. Furthermore, in polymers produced by polymerizing multiple types of monomers, the proportion of a monomer unit formed by polymerizing a certain monomer in the polymer is, unless otherwise specified, usually equal to the ratio of that particular monomer to the total monomers used in the polymerization of the polymer (the starting ratio). 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 air release properties (initial and after heating and pressurizing) and self-adhesion strength (initial and over time) of the laminated sheet were evaluated by the following methods.

[0079] <Glass transition temperature of polymers> The glass transition temperature (Tg) of the polymer used as a material for a self-adsorbing foamed laminated sheet was measured by the following method. Polymer latex containing the polymer was coated onto 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 this 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 calorimetry analyzer (DSC7000X, Hitachi High-Tech Science Corporation) in accordance with JIS K 7121, under conditions of a measurement temperature of -50°C to 160°C and a heating rate of 10°C / min. <Gel fraction of polymer> The gel fraction of the polymer used for the laminated sheet was measured by the following method. The polymer was applied onto a polyethylene terephthalate (PET) film with a thickness of 50 μm using an applicator with a thickness of 250 μm, and dried at room temperature for 24 hours to obtain a resin film. Using this film as a sample, a predetermined amount (X) (about 500 mg) was precisely weighed, immersed in 100 ml of ethyl acetate at room temperature for 3 days, the insoluble matter was filtered through a 200-mesh wire mesh, air-dried at room temperature for 15 hours, then dried at 100 °C for 2 hours, cooled at room temperature, and the weight (Y) of the sample was measured. The gel fraction was calculated by substituting X and Y into the following formula. Gel fraction (%) = (Y) / (X) × 100 <Viscosity of the composition for the foamed sheet> Using a B-type viscometer (manufactured by Lion Corporation, "VISCOTESTER VT-06"), the viscosity of the composition for the foamed sheet was measured at 23 °C. <Density of the foamed sheet> After preparing the laminated sheet, a test piece cut out to a size of 20 cm × 20 cm was prepared. The mass of the cut-out test piece: X g was precisely weighed, and the mass of the base material cut out to 20 cm × 20 cm: Y g was precisely weighed. Then, the thicknesses of the prepared laminated sheet and the base material were measured using a thickness gauge, and by subtracting the thickness of the base material from the thickness of the laminated sheet, the thickness of the foamed sheet: T cm was obtained. At this time, the thickness value was calculated from the average value when measured at 6 points. The density of the foamed sheet was calculated by substituting the measured values of X, Y, and T into the following formula. Density (g / cm 3 ) = (X - Y) / (T × 20 × 20) <Air permeability> <<Evaluation apparatus>> The evaluation of air permeability was carried out using the evaluation apparatus 100 shown in Figure 2. The evaluation apparatus 100 shown in Figure 2 is an apparatus for evaluating the air permeability of the laminated sheet 50 formed by laminating the foamed sheet 51 and the base material 52, and includes a sample fixing plate 10 having a through hole 11 and a gas pumping mechanism 40 for pumping air as a gas through the through hole 11 from the other surface side (the upper side in Figure 2) to the one surface side (the lower side in Figure 2) of the sample fixing plate 10 at a constant pressure. Here, the gas pressurization mechanism 40 includes a syringe 20 whose tip is connected to a through-hole 11 of the sample fixing plate 10 on the other surface side of the sample fixing plate 10, and a weight 30. The syringe 20 is connected to the sample fixing plate 10 with its tip pointing vertically downward (downward in Figure 2) and includes a needle 21 inserted and fixed into the through-hole 11 of the sample fixing plate 10, a cylindrical outer cylinder 22 whose tip (lower end in Figure 2) is connected to the through-hole 11 via the needle 21, and a piston 23 inserted into the outer cylinder 22 from the rear end side of the outer cylinder 22. The weight 30 is mounted on a flange located at the rear end (upper end in Figure 2) of the piston 23. Furthermore, in the gas pumping mechanism 40 having the above-described configuration, the piston 23 is pushed into the outer cylinder 22 by the weight of the piston 23 and the weight 30, and the air inside the outer cylinder 22 is pumped at a constant pressure to one surface side (foam sheet 51) of the sample fixing plate 10 via the needle 21 and the through hole 11. In the evaluation device 100 having the above-described configuration, for example, after attaching the laminated sheet 50 to one surface (the side opposite to the needle 21) of the sample fixing plate 10 to which the needle 21 is fixed, so as to cover the through hole 11 (step (A)), the outer cylinder 22, into which a piston 23 with a weight 30 attached is inserted to a position where the distance from the tip is L, is connected to the needle 21, and the time required for the piston 23 to advance the distance L due to the weight of the piston 23 and weight 30 is measured (step (B)), thereby the air venting ability of the laminated sheet 50 can be evaluated. That is, the air inside the outer cylinder 22 is pushed out from the through hole 11 at a constant pressure due to the weight of the piston 23 and weight 30. If the distance L is kept constant and the amount of air pushed out from inside the outer cylinder 22 is kept constant, the time it takes for the laminated sheet 50 to advance the distance L will be longer for laminated sheets 50 with low air venting ability, and the time it takes for the laminated sheet 50 to advance the distance L will be shorter for laminated sheets 50 with high air venting ability. Therefore, the air-releasing properties of the laminated sheet 50 can be quantitatively evaluated by the time required for the piston 23 to travel a distance L. Furthermore, since the evaluation can be performed under constant conditions for the amount and pressure of the compressed air, the air-releasing properties can be evaluated with high repeatability. In addition, since the evaluation can be performed with the laminated sheet 50 attached to the sample fixing plate 10, the air-releasing properties of the laminated sheet 50 when attached to the adherend can be accurately evaluated. For the sample fixing plate 10, a 1 mm thick transparent polycarbonate plate (50 mm x 50 mm) was used; for the syringe 20, a 2 mL capacity glass syringe with a 2 mm diameter metal syringe needle was used; and for the weight 30, a 30 g weight attached to the piston 23 with double-sided tape was used. <<Evaluation of air release properties (initial)>> After fabricating the laminated sheets, they were cut to a size of 40 mm x 40 mm and used as the samples for evaluation. Then, the foam sheet side of the prepared sample was attached to one side (opposite the needle 21 side) of the sample fixing plate 10 to which the needle 21 was fixed, so as to cover the through hole 11 and prevent air from entering (step (A)). After that, the outer cylinder 22, into which the piston 23 with the weight 30 attached was inserted to the position where the scale was 2 mL, was connected to the needle 21. After that, the weight 30 and piston 23 were released, and the time required for the piston 23 and weight 30 to fall completely under their own weight (i.e., until 2 mL of air was pressurized) was measured (step (B)). This measurement operation was repeated three times, and the average value of the measured time was calculated and evaluated according to the following criteria. The smaller this average value, the better the air release properties (initial) of the laminated sheet. A: The average measured time is 10 seconds or less. B: The average measured time is between 10 and 20 seconds. C: The average measured time is between 20 and 30 seconds. D: The average measured time exceeds 30 seconds. <<Evaluation of air release properties (after heating and pressurizing)>> After cutting the laminated sheet to a size of 80mm x 120mm, it was subjected to a temperature of 60℃ and 80%RH, with a density of 110g / cm². 2 The laminated sheet was subjected to pressure and left for 24 hours. After that, the pressure was released and it was left to stand for 24 hours under conditions of 23°C and 50% RH. The laminated sheet was then cut into 40mm x 40mm pieces, which were used as the samples for evaluation. Otherwise, the same procedure as for "Evaluation of Air Release (Initial)" was used for measurement and evaluation. A smaller average value indicates that the laminated sheet has superior air release properties (after heating and pressurizing). <Self-adhesion> <<Evaluation of initial self-attachment ability>> After preparing the laminated sheet, it was cut into 25mm x 125mm strips to form test specimens. These were bonded to a PET film, air was removed with a squeegee, and then pressed once back and forth with a 2kgf roller. After pressing, the excess PET film protruding from the laminated sheet was removed with scissors, and the sample was left to stand for more than 15 hours at 23°C and 50%RH to obtain a sample in which the laminated sheet and PET film were bonded together. The edges of the laminated sheet and PET film of this sample were clamped with the chucks of an autograph and peeled at a speed of 300mm / min. The peeling force (N / cm) at this time was defined as the initial self-adhesion force of the laminated sheet to the adherend. <<Evaluation of self-adhesion over time>> After preparing the laminated sheet, it was left to stand for 40 days at 23°C and 50% RH. The sheet was then cut into 25mm x 125mm strips to prepare test pieces. The peel force (N / cm) was measured in the same manner as the initial self-adhesion strength evaluation, except that it was bonded to the PET film that would serve as the substrate. The peel force at that time was defined as the self-adhesion strength of the laminated sheet to the substrate over time. A smaller difference between the initial self-adhesion strength and the self-adhesion strength over time indicates a smaller decrease in self-adhesion strength over time.

[0080] (Example 1) <Preparation of polymers> A monomer mixture consisting of 56 parts ethyl acrylate, 15 parts 2-ethylhexyl acrylate, 18 parts n-butyl acrylate, 8 parts acrylonitrile, 2 parts styrene, and 1 part acrylic acid, along with 0.4 parts sodium polyoxyethylene alkyl sulfate (manufactured by Kao Corporation: Latemul E-118B), was mixed and stirred to obtain a monomer emulsion. Next, separately from the above, a glass reaction vessel equipped with a reflux condenser, dropping funnel, thermometer, nitrogen inlet, and stirrer was prepared. 43.0 parts of deionized water and 0.2 parts of polyoxyethylene alkyl sulfate sodium were added to this glass reaction vessel, and the temperature was raised to 80°C while stirring. While maintaining the temperature at 80°C, 0.3 parts of ammonium persulfate dissolved in 5.7 parts of deionized water were added, followed by the monomer emulsion obtained above, which was gradually added over 4 hours. After the addition was complete, stirring was continued for another 4 hours, and then the reaction was terminated by cooling to obtain the reaction mixture. The polymerization conversion rate at this time was approximately 100% (98% or more). The obtained reaction mixture was adjusted to pH 5.0 with 5% aqueous ammonia, 2.5 parts of polyoxyethylene lauryl ether (Kao Corporation: Emulgen 120) were added, and the mixture was concentrated to obtain a polymer latex with a solid content of 55%. The glass transition temperature and gel fraction of the polymer contained in the obtained polymer latex were then measured. The results are shown in Table 1. <Preparation of Composition for Foamed Sheets> In a mixing container, 100 parts of the above polymer latex (i.e., 55 parts of the polymer contained in the polymer latex), 6 parts of an oxazoline-based crosslinking agent (Nippon Shokubai Co., Ltd., Epocross WS-700, oxazoline group-containing polymer, glass transition temperature: 50°C), 2 parts of a waxing agent (containing a fatty acid ester having a fatty acid portion with 16 to 34 carbon atoms), and 4 parts of a foam stabilizer [ammonium stearate (Sunopco, Inc., Nopco DC-100A)] were added in this order. Finally, a thickening agent [sodium polyacrylate (Toagosei Co., Ltd., Aron A-20L)] was added to adjust the viscosity to 4250 mPa·s, thereby obtaining a composition for foamed sheets. <Fabrication of laminated sheets> The foam sheet composition obtained as described above was stirred with a whisk until the foaming ratio was 1.6 times, and then the stirring speed was reduced and stirring was continued for 5 minutes. A foamed foam sheet composition (foam) was coated onto a substrate (a 50 μm thick sheet made of polyethylene terephthalate) using a 0.3 mm applicator. This was placed in a drying oven and dried and crosslinked at 80°C for 1.33 minutes, 120°C for 1.33 minutes, and 140°C for 1.33 minutes to obtain a laminated sheet with the foamed sheet on the substrate. The thickness of the foamed sheet after drying was 0.140 mm. Various evaluations were performed using the obtained laminated sheet. The results are shown in Table 1.

[0081] (Comparative Example 1) In the preparation of the foam sheet composition, 3 parts of an epoxy crosslinking agent (Licabond EX-8, fatty acid polyglycidyl ether, manufactured by Japan Coating Resin Co., Ltd.) were added instead of 6 parts of an oxazoline crosslinking agent (Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd.) during the preparation of the foam sheet composition. Except for this change, the polymer was prepared, the foam sheet composition was prepared, and a laminated sheet was fabricated in the same manner as in Example 1. The thickness of the foam sheet after drying was 0.140 mm. Various evaluations were performed using the obtained laminated sheet. The results are shown in Table 1.

[0082] (Reference example 1) In the preparation of the polymer, the monomer composition in the monomer mixture used was changed from 56 parts ethyl acrylate, 15 parts 2-ethylhexyl acrylate, 18 parts n-butyl acrylate, 8 parts acrylonitrile, 2 parts styrene, and 1 part acrylic acid to 14 parts methyl methacrylate, 70 parts n-butyl acrylate, 2 parts itaconic acid, and 14 parts styrene. In addition, when preparing the foam sheet composition, 3 parts epoxy crosslinking agent (Ricabond EX-8, fatty acid polyglycidyl ether, manufactured by Japan Coating Resin Co., Ltd.) was added instead of 6 parts oxazoline crosslinking agent (Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd.), and 2 parts wax agent (containing a fatty acid ester having a fatty acid portion with 16 to 34 carbon atoms) was omitted. Except for these changes, the polymer, foam sheet composition, and laminated sheet were prepared in the same manner as in Example 1. The thickness of the foam sheet after drying was 0.140 mm. The air release properties were evaluated using the obtained laminated sheet. The results are shown in Table 1.

[0083] In addition, in Table 1 shown below, "EA" represents the ethyl acrylate unit. "MMA" indicates a methyl methacrylate unit. "2EHA" indicates the 2-ethylhexyl acrylate unit. "BA" indicates the n-butyl acrylate unit. "AA" indicates the unit of acrylic acid. "IA" indicates the itaconic acid unit. "AN" indicates the acrylonitrile unit. "ST" indicates the styrene unit. "Tg" indicates the glass transition temperature.

[0084] [Table 1]

[0085] Table 1 shows that in Example 1, which used a foam sheet composition containing a polymer, an oxazoline-based crosslinking agent, and a waxing agent, a laminated sheet was formed with less decrease in self-adhesion over time compared to Comparative Example 1, which used a foam sheet composition containing a crosslinking agent other than an oxazoline-based crosslinking agent. [Industrial applicability]

[0086] According to the present invention, it is possible to provide a self-adhesive foam laminated sheet that exhibits little decrease in self-adhesion over time, and a composition for a self-adhesive foam laminated sheet that can be used to obtain the self-adhesive foam laminated sheet. [Explanation of symbols]

[0087] S1 Composition preparation process S2 Foaming process S3 Sheet Forming Process S10 Method for manufacturing laminated sheets 10 Sample fixing plate 11 Through hole 20 syringes 21 needles 22 Outer cylinder 23 pistons 30 weights 40. Gas pressure feeding mechanism 50 Laminated Sheets 51 Foam Sheet 52 Base material 100 Evaluation device

Claims

1. The product comprises a polymer, an oxazoline-based crosslinking agent, and a waxing agent. The proportion of alkenyl aromatic monomer units in the polymer is 0.5% by mass or more and 20% by mass or less. The aforementioned waxing agent is a composition for a self-adsorbing foam sheet, comprising a fatty acid ester having a fatty acid portion with 16 to 34 carbon atoms.

2. The composition for a self-adsorbing foamed sheet according to claim 1, wherein the polymer contains 60% by mass or more and 99% by mass or less of (meth)acrylate monomer units.

3. The composition for a self-adsorbing foamed sheet according to claim 1 or 2, wherein the amount of the oxazoline-based crosslinking agent is 0.5 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the polymer.

4. The composition for a self-adsorbing foamed sheet according to any one of claims 1 to 3, wherein the amount of the waxing agent is 0.5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the polymer.

5. A self-adsorbent foam laminated sheet comprising a base material and a self-adsorbent foam sheet formed using the self-adsorbent foam sheet composition described in any one of claims 1 to 4, A self-adsorbing foamed laminated sheet in which the substrate is a paper substrate other than a synthetic paper substrate, a plastic substrate, a fiber substrate, a metal substrate, or a glass substrate.

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