Adhesive

Abstract

The present invention achieves a sticky and adhesive agent excellent in a peeling property and a dispersion property of a water-absorbing material at the time of thermal melting. The sticky and adhesive agent contains a sticky and adhesive agent of a hot-melting type, a water-absorbing material, and a surfactant. The water-absorbing material contains a cellulose-based compound.

Description

[Technical Field]

[0001] This invention relates to adhesives. [Background technology]

[0002] In recent years, due to the growing global awareness of the SDGs, attention to recycling and reuse has increased. Against this backdrop, there is a growing demand for labels that can be easily peeled off the substrate during recycling. One way to achieve such labels is to use adhesives that become easier to peel off when exposed to water. For example, Patent Document 1 discloses a release-type adhesive composition containing 100 parts by weight of an adhesive base resin and 1 to 200 parts by weight of a water-absorbing crosslinked polymer, in which the adhesive strength decreases after water absorption. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2002 / 055626 [Overview of the project] [Problems that the invention aims to solve]

[0004] Adhesive compositions like the one described in Patent Document 1 are heated during manufacturing and coating onto substrates. However, the water-absorbing crosslinked polymer aggregates in the molten adhesive composition, leaving room for improvement in dispersibility.

[0005] One aspect of the present invention aims to provide a viscous adhesive that exhibits excellent release properties and dispersibility of water-absorbing substances during heating and melting. [Means for solving the problem]

[0006] The present invention includes the following embodiments. <1> It contains a hot-melt adhesive, a water-absorbing substance, and a surfactant. The above-mentioned water-absorbing substance-containing adhesive contains a cellulose-based compound. <2> The surfactant-containing adhesive according to <1> contains a nonionic surfactant. <3> The surfactant-containing adhesive according to <2> has an HLB of 18 or less. <4> The content of the above-mentioned water-absorbing substance is 0.5 to 45% by weight based on 100% by weight of the above-mentioned adhesive, and is the adhesive according to any one of <1> to <3>. <5> The content of the above-mentioned surfactant is 0.5 to 10% by weight based on 100% by weight of the above-mentioned adhesive, and is the adhesive according to any one of <1> to <4>. <6> The content of the cellulose-based compound in the above-mentioned water-absorbing substance is 70 to 100% by weight based on 100% by weight of the above-mentioned water-absorbing substance, and is the adhesive according to any one of <1> to <5>. <7>3] The above-mentioned cellulose-based compound D , , is 30 μm or less, D 95 is 100 μm or less, and is the adhesive according to any one of <1> to <6>. <8> An article in which a first adherend and a second adherend are adhered via an adhesive layer, where the above-mentioned adhesive layer contains the adhesive according to any one of to <7>.

Advantages of the Invention

[0007] According to one aspect of the present invention, an adhesive excellent in peelability and dispersibility of a water-absorbing substance during heat melting can be provided.

Modes for Carrying Out the Invention

[0008] Embodiments of the present invention will be described in detail below. However, the present invention is not limited to the embodiments specifically described. Those skilled in the art can make various modifications to the scope described herein. For example, embodiments obtained by appropriately combining the technical means disclosed in different embodiments are included within the technical scope of the present invention.

[0009] Unless otherwise specified herein, the numerical range "A to B" means "greater than or equal to A and less than or equal to B". In this specification, the term "adhesive" includes both adhesives and smudges. In one embodiment, the adhesive is an adhesive. In one embodiment, the adhesive is a smudge.

[0010] [1. Adhesives] An adhesive according to one embodiment of the present invention comprises a hot-melt adhesive, a water-absorbing substance, and a surfactant. The water-absorbing substance comprises a cellulosic compound. This composition improves the dispersibility of the water-absorbing substance during heating and melting, and reduces problems caused by the aggregation of the water-absorbing substance. Therefore, an adhesive with excellent coating properties and good coating properties can be provided. Examples of problems caused by the aggregation of water-absorbing substances include filter clogging and poor performance of the resulting coating (variation in film thickness, localization of water-absorbing substances, etc.).

[0011] According to the present inventors' findings, the adhesive using a water-absorbing crosslinked polymer disclosed in Patent Document 1 had the drawback of poor dispersibility of the water-absorbing substance when heated and melted. Such adhesives were difficult to use industrially because the dispersion of the water-absorbing substance was uneven when heated and melted (e.g., reduced coating properties). The adhesive according to one embodiment of the present invention solves the above problem by incorporating a cellulosic compound as the water-absorbing substance.

[0012] Adhesives with excellent release properties can contribute to achieving the Sustainable Development Goals (SDGs) advocated by the United Nations. For example, items attached with adhesives that have excellent release properties can be easily peeled off during recycling, thus contributing to achieving Goal 12, "Ensure sustainable consumption and production patterns." The adhesive according to one embodiment of the present invention may also be an easily peelable adhesive. Because easily peelable adhesives have excellent release properties, they can contribute to achieving the above-mentioned SDGs.

[0013] [1.1. Hot Melt Adhesives] A hot-melt adhesive is an adhesive that can be applied to a substrate by heating and melting it. Hot-melt adhesives typically contain a base polymer and a tackifying resin. They may also optionally contain plasticizers and / or waxes. An adhesive may contain only one type of hot-melt adhesive, or two or more types.

[0014] (Base polymer) Examples of base polymers include styrene-based block copolymers, acrylic polymers, olefin polymers, polyester polymers, polyamide polymers, or combinations thereof. Among these, styrene-based block copolymers, acrylic polymers, olefin polymers, or combinations thereof are preferred because they have excellent processability and are readily available. The hot-melt adhesive may contain only one type of base polymer or two or more types.

[0015] Examples of styrene-based block copolymers include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene-styrene block copolymer (SEBS), and styrene-ethylene-propylene-styrene block copolymer (SEPS). Examples of acrylic-based polymers include acrylic block copolymers (such as methyl methacrylate-n-butyl acrylate-methyl methacrylate block copolymer and methyl methacrylate-2-ethylhexyl acrylate-methyl methacrylate block copolymer). Examples of olefin-based polymers include homopolymers and copolymers of olefin monomers (ethylene, propylene, butene, etc.). More specific examples of olefin-based polymers include poly-α-olefin, amorphous poly-α-olefin (APAO), ethylene / α-olefin copolymer, propylene / α-olefin copolymer, ethylene-vinyl acetate copolymer, and ethylene-ethyl acrylate copolymer.

[0016] The lower limit of the base polymer content in a hot-melt adhesive may be 25% by weight or more, 30% by weight or more, 35% by weight or more, or 39% by weight or more, based on 100% by weight of the hot-melt adhesive. The upper limit of the base polymer content in a hot-melt adhesive may be 85% by weight or less, 80% by weight or less, 75% by weight or less, 70% by weight or less, or 65% by weight or less, based on 100% by weight of the hot-melt adhesive. If the base polymer content is within the above ranges, the adhesive properties of the adhesive will be improved.

[0017] (Adhesive-granting resin) Examples of tackifying resins include rosin-based resins, terpene-based resins, petroleum-based resins, and styrene-based resins. Hot-melt adhesives may contain only one type of tackifying resin or two or more types.

[0018] Examples of rosin-based resins include natural rosin (gum rosin, tall rosin, wood rosin, etc.), disproportionate rosin, polymerized rosin, glycerol esters of these rosins, and pentaerythritol esters of these rosins. Hydrogenated rosin-based resins (such as hydrides of the rosin-based resins mentioned above) are also used.

[0019] Examples of terpene resins include terpene resins, hydrocarbon-modified terpene resins, aromatic-modified terpene resins, and phenol-modified terpene resins. Hydrogenated terpene resins (such as hydrides of the above-mentioned terpene resins) are also used.

[0020] Examples of petroleum-based resins include aliphatic petroleum resins, alicyclic petroleum resins, and aromatic petroleum resins. Hydrogenated petroleum-based resins (such as hydrides of the aforementioned petroleum resins) are also used.

[0021] Examples of styrene-based resins include polymers composed of styrene monomers and copolymers of styrene monomers. Examples of styrene monomers include styrene, methylstyrene, vinyltoluene, methoxystyrene, tertiary butylstyrene, and chlorostyrene. More specific examples of styrene-based resins include styrene homopolymers and α-methylstyrene homopolymers. Hydrogenated styrene-based resins (such as hydrides of the styrene-based resins mentioned above) are also used.

[0022] The lower limit of the tackifying resin content in a hot-melt adhesive may be greater than 0% by weight, 5% or more by weight, 10% or more by weight, 15% or more by weight, or 20% or more by weight, based on 100% by weight of the hot-melt adhesive. The upper limit of the tackifying resin content in a hot-melt adhesive may be 70% or less by weight, 65% or less by weight, 60% or less by weight, 55% or less by weight, or 50% or less by weight, based on 100% by weight of the hot-melt adhesive. If the tackifying resin content is within the above ranges, the adhesive properties of the adhesive will be improved.

[0023] (Plasticizer) Examples of plasticizers include oils. Examples of oils include mineral oils, synthetic oils, vegetable oils, and fatty acid esters. Hot-melt adhesives may contain only one type of plasticizer, two or more types, or none at all.

[0024] Specific examples of mineral oils include process oils (paraffinic process oils, naphthenic process oils, aromatic process oils, etc.) and liquid paraffin. Examples of paraffins contained in paraffinic process oils include n-paraffins, isoparaffins, and derivatives of their saturated hydrocarbons. Examples of naphthenes contained in naphthenic process oils include cycloparaffinic hydrocarbons such as cyclopentane and cyclohexane, and their derivatives. Paraffinic process oils are process oils that contain a relatively large amount of paraffin, and naphthenic process oils are process oils that contain a relatively large amount of naphthenes. In addition to these, these process oils may further contain paraffin and / or naphthenes and / or aromatic compounds.

[0025] These mineral oils can be commercially available if they can be used to obtain the desired hot-melt adhesive. Examples of commercially available paraffinic process oils include PS-32, Diana Fresia S32, and Diana Process Oil PW-90 (all manufactured by Idemitsu Kosan Co., Ltd.). Examples of commercially available naphthenic process oils include Diana Fresia N90 (manufactured by Idemitsu Kosan Co., Ltd.), NYFLEX223A (manufactured by Japan Chemtec Co., Ltd.), and SNH68 (manufactured by Sankyo Yuka Kogyo Co., Ltd.).

[0026] Specific examples of synthetic oils include ether oil, ester oil, phosphate ester, chlorinated paraffin, ethylene-α-olefin oligomer, polybutene, low molecular weight polybutadiene, polyisoprene, and hydrogenated versions thereof, all of which are liquid at 25°C.

[0027] Specific examples of vegetable oils include olive oil, rice germ oil, corn oil, camellia oil, tsubaki oil, castor oil, jojoba seed oil, eucalyptus leaf oil, and their derivatives (including hydrogenated oils).

[0028] Specific examples of fatty acid esters include isopropyl myristate, octyldodecyl myristate, glyceryl triisooctanoate, diisopropyl adipate, diethyl sebacate, dibutyl sebacate, dioctyl sebacate, dodecyl sebacate, cetyl ethylhexanoate, cetyl palmitate, ethylhexyl palmitate, isopropyl palmitate, tributyl acetylcitrate, medium-chain triglyceride, ethylene glycol salicylate, and glycol distearate.

[0029] The lower limit of the plasticizer content in a hot-melt adhesive may be 0% or more by weight, 5% or more by weight, 7% or more by weight, or 10% or more by weight, based on 100% by weight of the hot-melt adhesive. The upper limit of the plasticizer content in a hot-melt adhesive may be 30% or less by weight, 25% or less by weight, 20% or less by weight, 15% or less by weight, or 10% or less by weight, based on 100% by weight of the hot-melt adhesive. For example, by incorporating wax or the like instead of a plasticizer, a hot-melt adhesive composition without plasticizers may be obtained. If the plasticizer content is within the above ranges, the adhesive properties of the adhesive will be improved.

[0030] (wax) Examples of waxes include animal-based waxes, plant-based waxes, polyolefin-based waxes, mineral-based waxes, and synthetic waxes. Hot-melt adhesives may contain only one type of wax, two or more types, or none at all.

[0031] Examples of animal-based waxes include shellac wax and beeswax. Examples of plant-based waxes include carnauba wax, rice wax, and sapwood wax. Examples of polyolefin waxes include polyethylene wax, polypropylene wax, and ethylene-vinyl acetate copolymer waxes. Examples of mineral waxes include paraffin wax and microcrystalline wax. An example of synthetic wax is Fischer-Tropsch wax. Aliphatic hydrocarbon waxes are preferred as waxes. Among the waxes mentioned above, polyolefin waxes, paraffin wax, microcrystalline wax, and Fischer-Tropsch wax are examples of aliphatic hydrocarbon waxes.

[0032] The lower limit of the wax content in a hot-melt adhesive may be 0% by weight or more, 0.1% by weight or more, 0.3% by weight or more, or 0.5% by weight or more, based on 100% by weight of the hot-melt adhesive. The upper limit of the wax content in a hot-melt adhesive may be 20% by weight or less, 15% by weight or less, 10% by weight or less, or 5% by weight or less, based on 100% by weight of the hot-melt adhesive. If the wax content is within the above ranges, it is easier to impart the desired function to the adhesive. Hot-melt adhesives do not need to contain wax.

[0033] (Content of hot melt adhesive) The lower limit of the hot-melt adhesive content in the adhesive is preferably 50% by weight or more, more preferably 55% by weight or more, even more preferably 60% by weight or more, and particularly preferably 65% ​​by weight or more, based on 100% by weight of the adhesive. The upper limit of the hot-melt adhesive content in the adhesive is preferably 99% by weight or less, and more preferably 98% by weight or less, based on 100% by weight of the adhesive. If the hot-melt adhesive content is within the above range, it is easy to obtain an adhesive with sufficient adhesive properties.

[0034] [1.2. Water-absorbing substances] The adhesive contains a water-absorbing substance. The water-absorbing substance contains a cellulosic compound. Adhesives with such a composition have improved dispersibility of the water-absorbing substance when heated and melted. The adhesive may contain only one type of water-absorbing substance or two or more types. The water-absorbing substance may contain only one type of cellulosic compound or two or more types.

[0035] Examples of cellulosic compounds include cellulose and cellulose derivatives, but cellulose derivatives are preferred. Examples of cellulose derivatives include carboxyalkylcellulose and hydroxyalkylcellulose (the number of carbon atoms in the alkyl group is, for example, 1 to 4). More specific examples of cellulose derivatives include carboxymethylcellulose, hydroxypropylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, and hydroxypropylmethylcellulose. Cellulose derivatives may also be in the form of salts. Examples of salts include sodium salts, potassium salts, calcium salts, and ammonium salts. More specific examples of cellulose derivatives in the form of salts include carboxymethylcellulose sodium, carboxymethylcellulose calcium, carboxymethylcellulose potassium, and carboxymethylcellulose ammonium.

[0036] Among these, sodium carboxymethylcellulose, hydroxypropylcellulose, and hydroxyethylcellulose, and hydroxypropylmethylcellulose are preferred from the viewpoint of the dispersibility of the water-absorbing substance when heated and melted. Furthermore, sodium carboxymethylcellulose is more preferred from the viewpoint of water absorption. In one embodiment, the cellulose compound is preferably an uncrosslinked cellulose compound.

[0037] When the cellulose-based compound is an ether-type cellulose derivative (such as sodium carboxymethyl cellulose), the lower limit of the degree of etherification of the hydroxyl group can be 0.1 or more or 0.5 or more. Also, the upper limit of the degree of etherification can be 1.6 or less or 1.0 or less. The degree of etherification of the cellulose derivative is the average number of etherified hydroxyl groups per glucose unit and takes a value of 0 to 3. The degree of etherification of the cellulose derivative can be appropriately selected by those skilled in the art in consideration of the balance with other components contained in the adhesive.

[0038] The shape of the cellulose-based compound can be particulate. The lower limit of the average particle diameter (D 50 ) of the cellulose-based compound may be 1 μm or more, preferably 10 μm or more. The upper limit of the average particle diameter (D 50 ) of the cellulose-based compound may be 300 μm or less or 150 μm or less, preferably 60 μm or less or 30 μm or less. If the average particle diameter (D 50 ) is above the lower limit, the cellulose-based compound is less likely to aggregate in the adhesive. If the average particle diameter (D 50 ) is below the upper limit, it is easy to achieve good coating properties and the adhesive layer can be made thinner. The average particle diameter (D 50 ) referred to here is the value at which the cumulative volume based on the total volume in the particle size distribution measured by the laser diffraction / scattering method is 50%. The value (D 95 ) at which the cumulative volume based on the total volume in the particle size distribution of the cellulose-based compound is 95% is larger than D 50 . The upper limit of D 95 may be 500 μm or less, preferably 200 μm or less or 150 μm or less, more preferably 100 μm or less. The lower limit of D 95 is not particularly limited, but for example, it is 3 μm or more. If D 95 is within this range, it is easy to achieve good coating properties and the adhesive layer can be made thinner. D 50 and D 95 are measured by the method described in the examples. When it is difficult to measure by the laser diffraction / scattering method, the particle diameter of the primary particles appearing in the scanning or transmission electron microscope image can be measured and the average value can be calculated.

[0039] In the case of water-soluble cellulosic compounds such as sodium carboxymethylcellulose, the lower limit of the viscosity of the aqueous solution of the cellulosic compound may be 5 mPa·s or more, more preferably 50 mPa·s or more. The upper limit of the viscosity of the aqueous solution of the cellulosic compound may be 120,000 mPa·s or less, more preferably 50,000 mPa·s or less. Here, the viscosity is measured as a 1-5% by weight aqueous solution at 25°C. The viscosity of the cellulosic compound may be appropriately selected by those skilled in the art, taking into account the balance with other components contained in the adhesive.

[0040] The lower limit of the water-absorbing substance content in adhesives is preferably 0.5% by weight or more, more preferably 1% by weight or more, even more preferably 5% by weight or more, and particularly preferably 10% by weight or more, based on 100% by weight of the adhesive. The upper limit of the water-absorbing substance content in adhesives is preferably 45% by weight or less, more preferably 40% by weight or less, and even more preferably 30% by weight or less, based on 100% by weight of the adhesive. If the water-absorbing substance content is 45% by weight or less, it is easier to produce an adhesive that exhibits the desired adhesive properties. If the water-absorbing substance content is 0.5% by weight or more, it is easier to produce an adhesive that exhibits the desired release properties.

[0041] The lower limit of the content of cellulosic compounds in the water-absorbing material is preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more, based on 100% by weight of the water-absorbing material. The upper limit of the content of cellulosic compounds in the water-absorbing material can be 100% by weight or less, 97% by weight or less, or 95% by weight or less, based on 100% by weight of the water-absorbing material. In one embodiment, the water-absorbing material consists only of cellulosic compounds. If the content of cellulosic compounds in the water-absorbing material is within the above range, the dispersibility of the water-absorbing material during heating and melting is improved.

[0042] Examples of water-absorbing substances other than cellulose compounds include cross-linked synthetic polymers, polysaccharides other than cellulose compounds, and protein-based polymers. In one embodiment, the adhesive contains almost no cross-linked synthetic polymers as water-absorbing substances. The proportion of cross-linked synthetic polymers to the total weight of the water-absorbing substances may be 5% by weight or less, 3% by weight or less, 1% by weight or less, 0.1% by weight or less, or 0.01% by weight or less. The water-absorbing substances do not need to contain cross-linked synthetic polymers.

[0043] Crosslinked synthetic polymers are water-absorbing substances obtained by crosslinking a water-absorbing resin with a crosslinking agent. Examples of water-absorbing resins to be crosslinked include unsaturated carboxylic acids and their neutralized products. Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, β-hydroxyacrylic acid, and β-acrylohydroxypropionic acid. More specific examples of crosslinked synthetic polymers include crosslinked products of hydrolyzed starch-acrylonitrile graft polymers, crosslinked products of neutralized starch-acrylic acid graft polymers, crosslinked products of saponified vinyl acetate-acrylic acid ester copolymers, crosslinked products of hydrolyzed acrylonitrile copolymers, crosslinked products of hydrolyzed acrylamide copolymers, crosslinked products of partially neutralized polyacrylic acid, carboxyl group-containing crosslinked polyvinyl alcohol modified products, crosslinked isobutylene-maleic anhydride copolymers, polyethylene oxide crosslinked products, and crosslinked urethane modified products. In this specification, crosslinked cellulose derivatives are not included in crosslinked synthetic polymers.

[0044] Examples of polysaccharides other than cellulose compounds include guar gum, locust bean gum, xanthan gum, karaya gum, pectin, alginic acid, chitin, and chitosan. Examples of protein-based polymers include gelatin and collagen.

[0045] [1.3. Surfactants] The adhesive contains a surfactant. Including a surfactant makes it easier to obtain an adhesive that exhibits good release properties. The surfactant may also be a component of a hot-melt adhesive. The adhesive may contain only one type of surfactant, or two or more types.

[0046] Examples of surfactants include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. From the viewpoint of compatibility, nonionic surfactants are preferred. Adhesives containing nonionic surfactants tend to exhibit good compatibility when heated and melted. In addition, such adhesives are less prone to bleed-out when stored at room temperature.

[0047] Examples of nonionic surfactants include ether type, ester ether type, ester type, and alkanolamide type. Examples of ester type nonionic surfactants include polyoxyethylene alkyl ethers (polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene myristyl ether, polyoxyethylene octyldodecyl ether, polyoxyethylene hydrogenated castor oil, etc.). Examples of ester ether type nonionic surfactants include fatty acid polyoxyethylene sorbitan (polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan triisostearate, tetraoleate polyoxyethylene sorbitan, etc.) and fatty acid polyethylene glycol (polyethylene glycol monolaurate, polyoxyethylene glycol monostearate, polyethylene glycol distearate). Examples of ester-type nonionic surfactants include sucrose fatty acid esters (sucrose stearate, sucrose palmitate, sucrose myristicate, sucrose oleate, and sucrose laurate). Among these, polyoxyethylene alkyl ethers are preferred due to their excellent peelability and adhesive properties. Among polyoxyethylene alkyl ethers, polyoxyethylene lauryl ether is preferred.

[0048] The lower limit of the HLB of nonionic surfactants is preferably 4 or higher, and more preferably 5 or higher. The upper limit of the HLB of surfactants is preferably 18 or lower, more preferably 17 or lower, and even more preferably 15 or lower. The HLB of surfactants is calculated by the Griffin method. If the HLB of surfactants is within the above range, they tend to exhibit good compatibility when heated and melted. When the adhesive contains two or more types of surfactants, the proportion of surfactants with an HLB of 18 or lower is preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more, relative to the total weight of surfactants.

[0049] The lower limit of the surfactant content in adhesives is preferably 0.5% by weight or more, more preferably 0.7% by weight or more, and even more preferably 1% by weight or more, based on 100% by weight of the adhesive. The upper limit of the surfactant content in adhesives is preferably 13% by weight or less, more preferably 10% by weight or less, even more preferably 7% by weight or less, and particularly preferably 5% by weight or less, based on 100% by weight of the adhesive. Adhesives with a surfactant content of 13% by weight or less tend to exhibit good adhesiveness and compatibility. Adhesives with a surfactant content of 0.5% by weight or more tend to exhibit good release properties.

[0050] The lower limit of the content of nonionic surfactant in the surfactant is preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more, based on 100% by weight of the surfactant. The upper limit of the content of nonionic surfactant in the surfactant can be 100% by weight or less, 97% by weight or less, or 95% by weight or less, based on 100% by weight of the surfactant. In one embodiment, the surfactant consists only of nonionic surfactant. If the content of nonionic surfactant in the surfactant is within the above range, it tends to exhibit good compatibility when heated and melted.

[0051] [1.4. Other Ingredients] The adhesive may further contain components other than those mentioned above. Examples of other components include water-soluble fillers, coupling agents, organic solvents, thixotropic agents, viscosity modifiers, colorants, weathering agents, discoloration inhibitors, curing agents, antioxidants, heat stabilizers, light stabilizers, UV absorbers, inorganic particles, carbon fibers, conductive particles, fillers, antistatic agents, flame retardants, antibacterial agents, and fragrances. Surfactants may also be components contained in hot-melt adhesives. The adhesive may contain only one type of other component, or two or more types. The adhesive may contain only one type of component belonging to the same category (e.g., water-soluble fillers), or two or more types.

[0052] Examples of antioxidants include phenolic antioxidants, organosulfur antioxidants, and phosphorus antioxidants. Examples of phenolic antioxidants include Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 2,6-Di-tert-butyl-4-ethylphenol. Examples of organosulfur antioxidants include dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, and distearyl-3,3'-thiodipropionate. An example of a phosphorus antioxidant is Tris(2,4-di-tert-butylphenyl)phosphite. These antioxidants may be used individually or in combination of two or more types.

[0053] The lower limit of the content of other components in the adhesive may be 0% by weight or more, 1% by weight or more, or 3% by weight or more, based on 100% by weight of the adhesive. The upper limit of the content of other components in the adhesive may be 10% by weight or less, 7% by weight or less, or 5% by weight or less, based on 100% by weight of the adhesive. If the content of other components is within the above ranges, it is easier to impart the desired function to the adhesive. The adhesive does not need to contain other components.

[0054] The lower limit of the viscosity of adhesives at 180°C is usually 100 mPa·s or higher, preferably 1,000 mPa·s or higher, and more preferably 3,000 mPa·s or higher, from the viewpoint of coating properties. The upper limit of the viscosity of adhesives at 180°C is usually 100,000 mPa·s or lower, preferably 50,000 mPa·s or lower, and more preferably 30,000 mPa·s or lower, from the viewpoint of coating properties. The viscosity at 180°C is measured in accordance with JIS K 6862.

[0055] The lower limit of the softening point of adhesives is usually 70°C or higher, preferably 80°C or higher, and more preferably 90°C or higher, from the viewpoint of coatability and heat resistance (adhesive residue). The upper limit of the softening point of adhesives is usually 150°C or lower, preferably 140°C or lower, and more preferably 130°C or lower, from the viewpoint of coatability and heat resistance (adhesive residue). The softening point is measured in accordance with JIS K 6863.

[0056] [2. Methods and Uses of Adhesives and Seals] [2.1. Manufacturing method] Adhesives can be manufactured according to conventional methods. For example, adhesives can be manufactured by the following process. 1. Heat and knead the tackifying resin and plasticizer until they are completely melted. 2. Add the base polymer to the resulting molten material. Heat and knead until the base polymer is completely melted. 3. Add the water-absorbing substance and surfactant to the molten material obtained in step 2 and disperse them uniformly. This will yield the desired adhesive.

[0057] In one embodiment, the method for producing adhesive may include a step of producing a hot-melt adhesive. For example, the hot-melt adhesive produced by the following steps may be cooled, reheated, and then an absorbent substance and a surfactant may be added to produce the adhesive. The surfactant and additives may be added when producing the hot-melt adhesive. 1. Heat and knead the tackifying resin and plasticizer until they are completely melted. 2. Add more base polymer and allow to melt completely.

[0058] [2.2.Application] An article according to one aspect of the present invention is bonded between a first adherend and a second adherend via an adhesive layer. This adhesive layer contains an adhesive according to one embodiment of the present invention. In one embodiment, the adhesive layer consists solely of the adhesive. In other embodiments, the adhesive layer contains other components (such as thermochromic agents, fillers, antioxidants, heat stabilizers, light stabilizers, UV absorbers, surfactants, colorants, antistatic agents, flame retardants, antibacterial agents, fragrances, etc.).

[0059] In one embodiment, the adhesive is an easily peelable adhesive that can be easily removed from the adherend when immersed in water. Therefore, when an article is immersed in water, the first adherend and the second adherend can be easily separated. Examples of articles include substrates to which labels are attached (glass substrates, plastic substrates, metal substrates, paper substrates, etc.). The adhesive is particularly suitable for use as an easily peelable adhesive for labels. [Examples]

[0060] [Measurement method] (Preparation of each sample) A sample was obtained by applying the adhesive according to the example or comparative example to high-quality paper by heat pressing. The coating thickness of the adhesive was 320 μm.

[0061] (Attachment to glass plate) The sample was molded to the dimensions described later. Then, the sample was attached to a glass plate using the following procedure. The ambient temperature during attachment was 23°C. ● Samples coated with adhesive containing hot melt 1 and hot melt 2. 1. A load of 2 kgf was applied to the glass plate using a roller. ● Samples coated with adhesive containing hot melt 3 and hot melt 4. 1. The surface of the sample was heated for 10 seconds using a 90°C hot plate. 2. The material was attached to the glass plate using a roller with a load of 2 kgf applied.

[0062] (adhesive) The adhesive properties were evaluated using the following procedure. 1. A sample measuring 20mm in width and 25mm in length was attached to a glass plate. 2. The peel strength was measured when the adhesive was peeled off in a 180-degree direction 20 minutes after application. The peeling speed was 300 mm / min. The adhesive properties were evaluated based on the measured peel strength values. The specific evaluation criteria are as follows. A:2.0N / 10mm or more B: 1.0N / 10mm or more, less than 2.0N / 10mm C: Less than 1.0 N / mm (Peelability) The peelability was evaluated using the following procedure. 1. A sample measuring 5mm in width and 5mm in length was attached to a glass plate. 2. Thirty minutes after application, the glass plate was immersed in 23°C water. The time it took for the sample to peel off the glass plate was measured to evaluate its peelability. The specific evaluation criteria are as follows: A: Less than 30 minutes B: 30 minutes or more but less than 120 minutes C: 120 minutes or more (Compatibility and dispersibility) The compatibility and dispersibility were evaluated using the following procedure. 1. 50g of the sample was placed in a mayonnaise bottle (volume: 140mL) and left to stand in a constant temperature bath at 160°C. 2. Phase separation of the adhesive and aggregation of water-absorbing substances over time were visually observed. The time required for phase separation of the adhesive was measured, and its compatibility and dispersibility were evaluated. The specific evaluation criteria are as follows: ● Evaluation of compatibility A: The adhesive did not undergo phase separation even after 5 hours. B: Phase separation occurred in the adhesive within 2-5 hours. C: Phase separation occurred in less than 2 hours. ● Evaluation of variance A: The water-absorbing substance did not coagulate even after 5 hours. B: The water-absorbing substance aggregated within 2-5 hours. C: The water-absorbing substance aggregated in less than 2 hours.

[0063] (Particle size) The volume-based particle size distribution of a water-absorbing substance was measured using a LA-960V2 manufactured by Horiba, Ltd. The refractive index was set to 1.5. In the particle size distribution, D is defined as the value at which the cumulative volume, counted from the smallest particle size, reaches 50%. 50 In the particle size distribution, D is defined as the value at which the cumulative volume reaches 95% when counting from the smallest particle size. 95 That's what I decided.

[0064] [Each ingredient] The following materials were used as components of the adhesive:

[0065] (Ingredients of hot-melt adhesive) • Base polymer 1: SIS5403P (styrene-isoprene-styrene block copolymer, JSR Corporation) • Base polymer 2A: LA3320 (acrylic polymer, Kuraray Co., Ltd.) • Base polymer 2B: LA2114 (liquid acrylic polymer, Kuraray Co., Ltd.) • Base polymer 3: VESTOPLAST 704 (amorphous poly-α-olefin, Evonik Corporation) • Base polymer 4: UltraCene 722 (ethylene-vinyl acetate copolymer, Tosoh Corporation) • Wax 1: Petrocene 353 (Polyethylene wax, Tosoh Corporation) • Wax 2: Sarawax SX105 (Fischer-Tropsch Wax, Shell) ·Tackifying resin 1: SYLVARES SA-100 (α-methylstyrene, Kraton Corporation) • Tackifying resin 2: Alcon M-100 (hydrogenated petroleum resin, Arakawa Chemical Industries, Ltd.) • Tackifying resin 3: Alcon P-115 (hydrogenated petroleum resin, Arakawa Chemical Industries, Ltd.) • Tackifying resin 4: iMarb P-100 (hydrogenated petroleum resin, Idemitsu Kosan Co., Ltd.) • Plasticizer 1: DOS (Di(2-ethylhexyl) sebacate, Toyokuni Oil Co., Ltd.) • Plasticizer 2: SP-52M (Liquid paraffin, Cosmo Oil Lubricants Co., Ltd.) • Antioxidant 1: ADEKA Stab AO-60G (phenolic antioxidant, ADEKA Corporation) • Antioxidant 2: Irgafos 168 (phosphorus-based antioxidant, BASF SE) (water absorbing substance) • Absorbent substance 1: Sunrose F10LC (sodium carboxymethylcellulose, viscosity in 1% aqueous solution: 90-130 mPa·s, degree of etherification: 0.55-0.65, D 50 :45μm, D 95 :133μm, Nippon Paper Industries Co., Ltd.) • Absorbent material 2: Sunrose F10MC (sodium carboxymethylcellulose, viscosity in 1% aqueous solution: 50-150 mPa·s, degree of etherification: 0.65-0.75, D 50 :42μm, D 95 :174μm, Nippon Paper Industries Co., Ltd.) • Absorbent material 3: Sunrose F120MC (sodium carboxymethylcellulose, viscosity in 1% aqueous solution: 800-1200 mPa·s, degree of etherification: 0.65-0.75, D 50 : 52 μm, D 95 :174μm, Nippon Paper Industries Co., Ltd.) • Absorbent material 4: Sunrose F350HC (sodium carboxymethylcellulose, viscosity in 1% aqueous solution: 2000-4000 mPa·s, degree of etherification: 0.8-1.0, D 50 : 59 μm, D 95 :200μm, Nippon Paper Industries Co., Ltd.) • Water-absorbing substance 5: L-HPC LH-31 (hydroxypropylcellulose, insoluble in water, degree of etherification: 0.33, D 50 :19μm, D 95 :133μm, Shin-Etsu Chemical Co., Ltd.) • Absorbent material 6: Daicel SP-200 (hydroxyethylcellulose, viscosity in 5% aqueous solution: 80-170 mPa·s, degree of etherification: 1.0-1.3%, Daicel Mirise Co., Ltd.) • Absorbent material 7: Metholose NE-4VF (hydroxypropyl methylcellulose, degree of etherification by methoxy group: 0.57~0.72, degree of etherification by hydroxypropoxy group: 0.12~0.36, D 50 :13μm, D 95 :34μm, Shin-Etsu Chemical Co., Ltd.) • Absorbent material 8: Absorbent material (carboxymethylcellulose sodium, crushed product of Sunrose F10LC (Nippon Paper Industries Co., Ltd.), D) prepared by size adjustment according to the method described in the manufacturing example. 50 :14μm, D 95 :62μm) • Absorbent material 9: Junron PW-120 (cross-linked polyacrylic acid, D 50 :14μm, D 95 :77μm, Toagosei Co., Ltd.) • Absorbent material 10: AQUPEC SW-703ER (cross-linked acrylic acid-alkyl methacrylate copolymer, Sumitomo Seika Co., Ltd.) (Surfactants) • Surfactant 1: DKS NL-30 (Polyoxyethylene lauryl ether, HLB: 8.1, Daiichi Kogyo Seiyaku Co., Ltd.) • Surfactant 2: DKS NL-15 (Polyoxyethylene lauryl ether, HLB: 5.0, Daiichi Kogyo Seiyaku Co., Ltd.) • Surfactant 3: DKS NL-100 (Polyoxyethylene lauryl ether, HLB: 13.8, Daiichi Kogyo Seiyaku Co., Ltd.) • Surfactant 4: DKS NL-180 (Polyoxyethylene lauryl ether, HLB: 16.1, Daiichi Kogyo Seiyaku Co., Ltd.) [Manufacturing example] (Adjusting the size of the water-absorbing material) Using a single-track jet mill FS-4 (Seishin Corporation), Sunrose F10LC (carboxymethylcellulose sodium, Nippon Paper Industries Co., Ltd.) was pulverized to obtain water-absorbing material 8.

[0066] (Preparation of hot-melt adhesive) Hot-melt adhesives 1-4 were prepared by mixing each material according to the composition (unit: parts by weight) shown in Table 1 below. The specific procedure is as follows. 1. Tackifying resin, plasticizer, wax, and antioxidant were added to a kneader. These were heated and kneaded at 150-190°C until completely melted. 2. The base polymer was added to the resulting molten material. By heating and kneading at 150-190°C, the base polymer was uniformly dispersed in the molten material. In this way, hot-melt adhesives 1-4 were obtained.

[0067] [Table 1] (Preparation of adhesive) The materials were mixed together according to the compositions shown in Tables 2-4 below (unit: parts by weight) to prepare the adhesive. The specific procedure is as follows. 1. Hot melt adhesive was added to the mixer. These were heated and mixed at 150-190°C until completely melted. 2. A water-absorbing substance and a surfactant were added to the resulting molten material to obtain a viscous adhesive.

[0068] [Table 2] [Examples 1-8, Comparative Examples 1-2] See Table 2 below. In Examples 1 to 4, hot-melt adhesives containing different types of base polymers were formulated. All of the resulting adhesives exhibited excellent adhesion, release properties, compatibility, and dispersibility.

[0069] In Examples 5-8, the amounts of hot-melt adhesive, water-absorbing substance, and surfactant were varied. All of the resulting adhesives exhibited excellent adhesion, release properties, compatibility, and dispersibility. In Comparative Examples 1-2, adhesives were prepared without the addition of water-absorbing substance or surfactant. The resulting adhesives exhibited poor release properties. From the viewpoint of adhesion and release properties, the more preferable amounts of water-absorbing substance and surfactant are as follows (all values ​​are based on 100% by weight of the adhesive). • Lower limit of the amount of absorbent material: Between 1% and 25% by weight (for example, 5% or more by weight or 10% or more by weight) • Upper limit of water-absorbing substance content: Between 25% and 40% by weight (e.g., 30% or less by weight) • Lower limit of surfactant content: Between 0.5% and 1% by weight (e.g., 0.7% or more by weight) • Maximum amount of surfactant: Between 1% and 10% by weight (for example, 7% or less by weight or 5% or less by weight)

[0070] [Table 3] [Examples 9-15, Comparative Examples 3-6] See Table 3 below (for reference, the results for Example 1 are also included in Table 3). In Examples 9-15 and Comparative Examples 3-6, the type of water-absorbing substance was varied. In Examples 9-15, a cellulose-based compound was used as the water-absorbing substance. The resulting adhesives all exhibited excellent adhesion, release properties, compatibility, and dispersibility. In Comparative Examples 3-6, a water-absorbing substance other than a cellulose-based compound was used. The resulting adhesives all exhibited poor dispersibility of the water-absorbing substance. From these results, it can be seen that if the water-absorbing substance is a cellulose-based compound, an adhesive with excellent dispersibility of the water-absorbing substance, stable quality, and suitability for industrial applications can be obtained. Conversely, if the water-absorbing substance is not a cellulose-based compound, an adhesive with poor dispersibility of the water-absorbing substance and unsuitability for industrial applications can be obtained.

[0071] The adhesives in Examples 14 and 15 are D 50 and D 95A water-absorbing substance with low density was used. As a result, the adhesive layer could be made thinner compared to other examples. Furthermore, when the adhesives of Examples 14 and 15 were applied using a coating apparatus with a filter, the coating could be performed without clogging the filter, indicating that an adhesive with excellent coatability was obtained.

[0072] [Table 4] [Examples 16-18] See Table 4 below (for reference, the results for Example 1 are also included in Table 4). In Examples 16-18, the HLB of the surfactant was varied. All of the resulting adhesives exhibited excellent adhesion, release properties, compatibility, and dispersibility. From the viewpoint of compatibility, a more preferable upper limit for the HLB of the surfactant is between 13.8 and 16.1 (for example, 15.0 or less, preferably 13.8 or less). [Industrial applicability]

[0073] This invention can be used for adhesives and smudges, etc.

Claims

1. An easily removable adhesive for use with at least one of a glass substrate, a plastic substrate, a metal substrate, or a paper substrate as the adherend, It contains a hot-melt adhesive, a water-absorbing substance, and a surfactant. The above water-absorbing substance contains a cellulose-based compound. The content of the above water-absorbing substance is 0.5 to 45% by weight, assuming the weight of the above easily peelable adhesive is 100% by weight. The content of cellulosic compounds in the above-mentioned water-absorbing material is 70 to 100% by weight, assuming the weight of the above-mentioned water-absorbing material is 100% by weight. An easily peelable adhesive, wherein the amount of the surfactant is 0.7 to 10% by weight, based on the weight of the easily peelable adhesive being 100% by weight.

2. An easily peelable adhesive comprising a hot melt adhesive, a water-absorbing substance, and a surfactant, The above water-absorbing substance contains a cellulose-based compound. The content of the above water-absorbing substance is 0.5 to 45% by weight, assuming the weight of the above easily peelable adhesive is 100% by weight. The content of cellulosic compounds in the above-mentioned water-absorbing material is 70 to 100% by weight, assuming the weight of the above-mentioned water-absorbing material is 100% by weight. The amount of the above surfactant is 0.7 to 10% by weight, assuming the weight of the above easily removable adhesive is 100% by weight. An easily removable adhesive for labeling.

3. The easily peelable adhesive according to claim 1 or 2, wherein the surfactant includes a nonionic surfactant.

4. The easily peelable adhesive according to claim 3, wherein the HLB of the above-mentioned surfactant is 8.1 to 13.

8.

5. The above cellulose-based compounds are, D50 is 1 to 30 μm, D95 is 100 μm or less. The easily peelable adhesive according to claim 1 or 2.

6. An easily peelable adhesive according to claim 1, for use as a label.

7. An article in which a first adherend and a second adherend are bonded together via an adhesive layer, An article wherein the adhesive layer contains the easily peelable adhesive described in claim 1 or 2.

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