Adhesive remover and adhesive removal method using said adhesive remover

Abstract

The present invention addresses the problem of providing: an adhesive remover capable of sufficiently removing an adhesive from a material; and an adhesive removal method using said adhesive remover. The aforementioned problem can be solved by an adhesive remover containing an oil and a surfactant, wherein: the oil contains one or more types of substances selected from the group consisting of a specific vegetable oil, a specific ester oil, an aliphatic carboxylic acid, and a mineral oil; and the surfactant contains an anionic surfactant and / or a nonionic surfactant that has an HLB of more than 5 and that is liquid at room temperature.

Description

Adhesive remover and adhesive removal method using said adhesive remover

[0001] The present invention relates to an adhesive remover and an adhesive removal method using the adhesive remover.

[0002] Adhesives have been widely used in the fields of furniture, construction, electrical and electronic equipment, automobiles, packaging materials, clothing, household goods, etc. By bonding materials using adhesives, various articles are produced, such as packaging materials such as food packaging and cardboard boxes, books, sanitary products such as diapers, and car mats.

[0003] In recent years, from the viewpoint of reducing the burden on the environment, techniques for recycling used items have been attracting attention.

[0004] For example, Patent Document 1 discloses a method for recovering pulp fibers from used absorbent articles containing pulp fibers and a superabsorbent polymer. The method includes a step of treating the used absorbent articles with an aqueous solution containing 0.05% by mass or more of at least one terpene selected from the group consisting of terpene hydrocarbons, terpene aldehydes, and terpene ketones, and containing an inactivating agent capable of inactivating the superabsorbent polymer, thereby inactivating the superabsorbent polymer. Furthermore, Patent Document 1 discloses a method of disintegrating the used absorbent articles by placing them in a washing machine containing the aqueous solution and using centrifugal force.

[0005] Japanese Patent Publication No. 2018-24964

[0006] The conventional techniques described above involve breaking down absorbent articles into their constituent components (materials) and reusing the recovered pulp fibers as resources. However, in the conventional techniques described above, adhesives remain in the constituent components obtained by breaking down absorbent articles, which can cause the constituent components to reattach to each other. Furthermore, if adhesives remain in the recovered pulp fibers, quality problems may arise when the recovered pulp fibers are reused as resources. From these perspectives, there is room for improvement in the conventional techniques described above.

[0007] One embodiment of the present invention has been made in consideration of the above-mentioned problems, and its object is to provide an adhesive remover that can sufficiently remove adhesive from a material, and a method for removing adhesive using the adhesive remover.

[0008] In order to solve the above problems, an adhesive remover according to one embodiment of the present invention includes the following components.

[0009] An adhesive remover comprising an oil and a surfactant, wherein the oil comprises one or more oils selected from the group consisting of vegetable oils, ester oils, aliphatic carboxylic acids, and mineral oils, the vegetable oil having an iodine value of 70 to 160, the ester oil having three or less ester groups in one molecule, and the surfactant comprising an anionic surfactant and / or a nonionic surfactant having an HLB of greater than 5 and being liquid at room temperature.

[0010] According to one aspect of the present invention, it is possible to provide an adhesive remover that can sufficiently remove adhesive from a material, and a method for removing adhesive using the adhesive remover.

[0011] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to these, and various modifications are possible within the scope of the description. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. Unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more, B or less." Furthermore, in this specification, room temperature means 18°C ​​to 26°C.

[0012] [1. Adhesive Remover] An adhesive remover according to one embodiment of the present invention (hereinafter, sometimes referred to as "the adhesive remover") contains an oil and a surfactant, the oil containing one or more selected from the group consisting of vegetable oil, ester oil, aliphatic carboxylic acid, and mineral oil, the vegetable oil having an iodine value of 70 to 160, the ester oil having three or less ester groups per molecule, and the surfactant containing an anionic surfactant and / or a nonionic surfactant having an HLB greater than 5 and being liquid at room temperature. This adhesive remover has the advantage of being able to thoroughly remove adhesive from materials. According to this configuration, adhesively bonded articles can be separated into individual materials without any adhesive residue remaining. Therefore, it has the advantage of enabling the efficient recycling of adhesively bonded articles. These effects contribute to achieving, for example, Goal 12 of the United Nations' Sustainable Development Goals (SDGs), "Responsible Consumption and Production."

[0013] Furthermore, this configuration has the advantage that the adhesive can be sufficiently removed from the material, allowing the article to be separated into its constituent materials without using centrifugal force, etc. Furthermore, since the adhesive does not remain on the material, there is also the advantage that the materials will not re-adhere to each other after the adhesive is removed. In other words, this configuration has the advantage that articles bonded with an adhesive can be efficiently recycled.

[0014] Furthermore, when the article is a disposable diaper, which is made by bonding materials with an adhesive, the adhesive remover can penetrate into the interior of the diaper and remove the adhesive, even when the diaper is rolled up. This has the advantage of allowing the adhesive to be removed without opening the rolled up disposable diaper after use, thereby disassembling the article. Furthermore, this method has the advantage of not only separating and recovering pulp and SAP (superabsorbent polymer) from the disposable diaper, but also separating and recovering nonwoven fabric, film, rubber thread, and other components.

[0015] The adhesive remover is preferably liquid at room temperature. The viscosity of the adhesive remover is not particularly limited, but is preferably 15 mPa·s to 2600 mPa·s, and more preferably 30 mPa·s to 1700 mPa·s. This configuration has the advantage of easily penetrating into adhesives and being able to thoroughly remove the adhesive from the material. The viscosity of the adhesive remover varies depending on the components contained and the mixing ratio of the components. The adhesive remover is preferably oil-based. In this specification, "the adhesive remover is oil-based" means "an adhesive remover in which the total amount of oil and surfactant is greater than the amount of other components."

[0016] (1-1. Oil) The adhesive remover of the present invention contains oil. This configuration has the advantage that it can dissolve the adhesive and remove it from the article.

[0017] Furthermore, the oil is preferably liquid at room temperature, which has the advantage that it can be easily mixed with the surfactant at room temperature.

[0018] In one embodiment of the present invention, the oil comprises one or more oils selected from the group consisting of vegetable oil, ester oil, aliphatic carboxylic acid, and mineral oil. The oil preferably comprises vegetable oil or ester oil, and more preferably consists of vegetable oil or ester oil. This configuration has the advantage of having high affinity with surfactants and being able to more thoroughly remove adhesives from materials. The oil may also be a mixture of at least two or more oils selected from the group consisting of vegetable oil, ester oil, aliphatic carboxylic acid, and mineral oil.

[0019] In this adhesive remover, the oil content is preferably more than 10% by weight and less than 70% by weight, more preferably 15% by weight to 65% by weight, even more preferably 18% by weight to 60% by weight, still more preferably 20% by weight to 55% by weight, even more preferably 20% by weight to 50% by weight, and particularly preferably 20% by weight to 45% by weight, based on 100% by weight of the total of the oil and surfactant. This configuration has the advantage of having a strong affinity with the surfactant and being able to more thoroughly remove adhesives from materials.

[0020] (1-1-1. Vegetable Oil) The adhesive remover preferably contains vegetable oil. This configuration has the advantage of being able to more thoroughly remove adhesive from materials.

[0021] The adhesive remover preferably does not contain animal oil, as many animal oils are solid and tend to be difficult to mix with surfactants at room temperature.

[0022] When the adhesive remover contains vegetable oil, the vegetable oil has an iodine value of 70 to 160, more preferably 80 to 150, even more preferably 90 to 140, and particularly preferably 100 to 130. This configuration provides good affinity between the oil and the surfactant, and therefore the adhesive remover has the advantage of being able to more thoroughly remove adhesive from materials. Vegetable oils with a low iodine value (for example, 140 or less) are highly safe and can be handled with simple equipment.

[0023] The adhesive remover may also contain multiple types of vegetable oil. Here, the "iodine value of vegetable oil" refers to the iodine value of a single type of vegetable oil when the adhesive remover contains one type of vegetable oil, and refers to the iodine value of a mixed vegetable oil made up of multiple types of vegetable oils contained in the adhesive remover when the adhesive remover contains multiple types of vegetable oils. In other words, when the adhesive remover contains multiple types of vegetable oils, the iodine value of the mixed vegetable oil made up of multiple types of vegetable oils is 70 to 160.

[0024] In this specification, the iodine value refers to the number of grams of iodine (I) that can be added to 100 g of oil or fat. In other words, the higher the iodine value, the higher the degree of unsaturation of the fatty acids in the sample (the greater the number of double bonds). When the adhesive remover contains multiple types of vegetable oil, the "iodine value of the vegetable oil" is determined by a measurement method in accordance with JIS K 0070-1992. The vegetable oil may be a mixture of at least two or more types selected from the group consisting of semi-drying oils, non-drying oils, and drying oils.

[0025] In this specification, oils with an iodine value of 140 or more are referred to as drying oils, oils with an iodine value of more than 100 but less than 140 are referred to as semi-drying oils, and oils with an iodine value of 100 or less are referred to as non-drying oils.

[0026] In one embodiment of the present invention, the vegetable oil is preferably one or more selected from the group consisting of soybean oil, rice bran oil, olive oil, avocado oil, rice bran oil, orange seed oil, carrot seed oil, canola oil, apricot kernel oil, peach kernel oil, almond oil, crambe abyssinica seed oil, sesame oil, rice germ oil, watermelon seed oil, grapefruit seed oil, tomato seed oil, passionflower seed oil, wheat germ oil, corn oil, linseed oil, rapeseed oil, coconut oil, palm kernel oil, and castor oil, more preferably one or more selected from the group consisting of soybean oil, rice bran oil, olive oil, and rapeseed oil, and even more preferably soybean oil and / or rice bran oil. This configuration has the advantage of allowing the adhesive to be more thoroughly removed from the material.

[0027] In one embodiment of the present invention, the flash point of the vegetable oil is not particularly limited, but from the viewpoint of safety and ease of handling, it is preferably 150°C or higher, and more preferably 200°C or higher.

[0028] (1-1-2. Ester Oil) The adhesive remover preferably contains ester oil.

[0029] In one embodiment of the present invention, the ester oil has 3 or less ester groups in one molecule, preferably 2 or less ester groups, and more preferably 2 ester groups in one molecule, which has the advantage of enabling the adhesive to be more thoroughly removed from the material.

[0030] The SP value of the ester oil is preferably 8.0 to 9.5, more preferably 8.3 to 9.4, even more preferably 8.5 to 9.3, and particularly preferably 8.7 to 9.2. This configuration has the advantage of enabling the adhesive to be more thoroughly removed from the material.

[0031] In this specification, the term "SP value (solubility parameter)" refers to the Hansen solubility parameter (HSP value) defined by the Hansen method. The SP value δ is calculated by dividing the dispersion term of a substance by δ. d , polar term is δ p , the hydrogen bond term is δ h Then, δ = (δ d 2 +δ p 2 +δ h 2 ) 1 / 2 is a quantity δ defined by the following equation, which is a value specific to a material.

[0032] In one embodiment of the present invention, the ester oil is not particularly limited, but examples thereof include DOS (bis(2-ethylhexyl) sebacate), DIDA (diisodecyl adipate), DINA (diisononyl adipate), DOA (bis(2-ethylhexyl) adipate), diisobutyl adipate, 2-hexyldecyl adipate, di-2-heptylundecyl adipate, isostearyl isostearate, trimethylolpropane triisostearate, cetyl 2-ethylhexanoate, neopentyl glycol di-2-ethylhexanoate, trimethylolpropane tri-2-ethylhexanoate, cetyl octanoate, oleyl oleate, octyl oleate, and the like. Examples of suitable ester oils include ethyldodecyl, decyl oleate, neopentyl glycol dicaprate, 2-ethylhexyl succinate, isocetyl stearate, butyl stearate, diisopropyl sebacate, cetyl lactate, tetradecyl lactate, isopropyl myristate, octyldodecyl myristate, cetyl myristate, myristyl myristate, octyl palmitate, 2-ethylhexyl palmitate, 2-hexyldecyl palmitate, 2-heptylundecyl palmitate, cholesteryl 12-hydroxystearate, phytosteryl oleate, diisostearyl malate, para-methoxycinnamate, and pentaerythrityl tetrarosinate. The ester oil is preferably DOS. This configuration has the advantage of enabling adhesives to be more thoroughly removed from materials.

[0033] (1-1-3. Aliphatic Carboxylic Acid) The adhesive remover preferably contains an aliphatic carboxylic acid. Examples of aliphatic carboxylic acids include monocarboxylic acids, dicarboxylic acids, acid anhydrides, and polycarboxylic acids. In one embodiment of the present invention, the aliphatic carboxylic acid is more preferably an aliphatic carboxylic acid or carboxylic acid anhydride having two carboxy groups, more preferably succinic acid or its anhydride, and even more preferably alkenylsuccinic acid or its anhydride. Furthermore, the aliphatic carboxylic acid is more preferably an unsaturated aliphatic carboxylic acid. This configuration has the advantage of being able to more thoroughly remove the adhesive from the material. In one embodiment of the present invention, the aliphatic carboxylic acid is more preferably at least one selected from the group consisting of dodecenylsuccinic acid, hexadecenylsuccinic acid, octadecenylsuccinic acid, and their anhydrides.

[0034] In one embodiment of the present invention, the molecular weight of the aliphatic carboxylic acid is not particularly limited, but for example, the weight average molecular weight is preferably 200 to 1,200, and more preferably 250 to 1,000.

[0035] (1-1-4. Mineral Oil) The adhesive remover preferably contains mineral oil.

[0036] The SP value of the mineral oil is preferably 8.0 to 9.5, more preferably 8.0 to 9.3, even more preferably 8.0 to 9.0, still more preferably 8.0 to 8.5, and particularly preferably 8.0 to 8.3. This configuration has the advantage of enabling the adhesive to be more thoroughly removed from the material.

[0037] In one embodiment of the present invention, the mineral oil having an SP value of 8.0 to 9.5 is not particularly limited, but examples thereof include aromatic hydrocarbons, paraffinic hydrocarbons, naphthenic hydrocarbons, light mineral oils, and white mineral oils. More specifically, for example, spindle oil and liquid paraffin can be suitably used. This configuration has the advantage of being able to more thoroughly remove the adhesive from the material.

[0038] In one embodiment of the present invention, the room temperature viscosity of the ester oil and the mineral oil is not particularly limited, but is preferably 1 mPa·s to 200 mPa·s, and more preferably 5 mPa·s to 100 mPa·s. This configuration has the advantage of enabling the adhesive to be more thoroughly removed from the material.

[0039] In one embodiment of the present invention, the flash points of the ester oil, the aliphatic carboxylic acid, and the mineral oil are not particularly limited, but from the viewpoints of safety and ease of handling, they are preferably 150°C or higher, and more preferably 200°C or higher.

[0040] (1-2. Surfactant) The adhesive remover contains a surfactant. This configuration allows the adhesive remover to be easily removed from the separated material. In other words, while oil alone is sufficient for dissolving the adhesive, the adhesive remover contains a surfactant, which allows the adhesive remover to be sufficiently removed from the material in the article. This makes the separated material easier to handle.

[0041] In one embodiment of the present invention, the surfactant comprises an anionic surfactant and / or a nonionic surfactant that has an HLB of greater than 5 and is liquid at room temperature. In one embodiment of the present invention, the surfactant preferably comprises an anionic surfactant or a nonionic surfactant that has an HLB of greater than 5 and is liquid at room temperature, and more preferably consists of a nonionic surfactant that has an HLB of greater than 5 and is liquid at room temperature.

[0042] In one embodiment of the present invention, the total content of the anionic surfactant and the nonionic surfactant having an HLB greater than 5 in 100% by weight of the surfactants is preferably 70% by weight or more, more preferably 90% by weight or more, and even more preferably 100% by weight. This configuration has the advantage of enabling the adhesive to be more thoroughly removed from the material.

[0043] In one embodiment of the present invention, it is preferable that the amount of nonionic surfactants with an HLB greater than 5 is greater than the amount of anionic surfactants. The amount of nonionic surfactants with an HLB greater than 5 is preferably 60% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 100% by weight, out of a total of 100% by weight of anionic surfactants and nonionic surfactants with an HLB greater than 5. This configuration has the advantage of enabling the adhesive to be more thoroughly removed from the material.

[0044] In this specification, HLB (Hydrophile-Lipophile Balance) refers to a numerical value that represents the balance between lipophilicity and hydrophilicity in a surfactant. The HLB is defined as a value obtained by dividing equally between a substance having no hydrophilic groups, which has an HLB of 0, and a substance having only hydrophilic groups, which has no lipophilic groups, which has an HLB of 20.

[0045] The HLB of a nonionic surfactant having an HLB of greater than 5 is preferably greater than 5 and not greater than 15, more preferably from 7 to 13, and even more preferably from 9 to 11. This configuration has the advantage of having good affinity for oil and being able to sufficiently remove adhesives from materials.

[0046] In one embodiment of the present invention, the nonionic surfactant is liquid at room temperature. This configuration has good affinity with oil, and allows the oil and surfactant to be mixed without requiring energy such as heating.

[0047] The nonionic surfactant is not particularly limited, but preferred examples include polyoxyalkylene alkyl ethers; polyoxyalkylene alkenyl ethers; polyoxyalkylene alkylphenyl ethers; polyoxyethylene castor oil; sorbitan fatty acid esters and alkylene oxide adducts thereof; polyoxyalkylene fatty acid esters; and polyoxyethylene hydrogenated castor oil.

[0048] Examples of polyoxyalkylene alkyl ethers include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene polyoxypropylene lauryl ether, polyoxypropylene cetyl ether, polyoxypropylene isocetyl ether, polyoxypropylene stearyl ether, and polyoxyethylene behenyl ether.

[0049] Examples of polyoxyalkylene alkenyl ethers include polyoxyethylene oleyl ether and polyoxypropylene oleyl ether.

[0050] Examples of polyoxyalkylene alkylphenyl ethers include polyoxyethylene octylphenyl ether.

[0051] Polyoxyethylene castor oil is a compound obtained by addition polymerization of ethylene oxide with castor oil. The average number of moles of ethylene oxide added is not particularly limited, but is preferably 2 to 100, and more preferably 10 to 50. Examples of the polyoxyethylene castor oil include NIKKOL CO-3, NIKKOL CO-10, and NIKKOL CO-35 (Nikko Chemicals); EMALEX C-20, EMALEX C-30, EMALEX C-40, and EMALEX C-50 (Nippon Emulsion); and Kolliphor EL (BASF).

[0052] Examples of sorbitan fatty acid esters include sorbitan monooleate, sorbitan monostearate, sorbitan monoisostearate, sorbitan monopalmitate, sorbitan monolaurate, sorbitan trioleate, sorbitan tristearate, sorbitan sesquistearate, sorbitan sesquioleate, sorbitan sesquiisostearate, and sorbitan coconut oil fatty acid. Examples of alkylene oxide adducts of sorbitan fatty acid esters include polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan monoisostearate, polyoxyethylene sorbitan monococonut oil fatty acid, polyoxyethylene sorbitan tristearate, and polyoxyethylene sorbitan trioleate.

[0053] The polyoxyalkylene fatty acid ester includes, for example, both polyoxyalkylene mono-fatty acid esters and polyoxyalkylene di-fatty acid esters. Examples of the polyoxyalkylene mono-fatty acid ester include polyethylene glycol mono-fatty acid esters such as polyethylene glycol monooleate, polyethylene glycol monostearate, and polyethylene glycol monolaurate; and propylene glycol mono-fatty acid esters such as propylene glycol monostearate, propylene glycol monolaurate, and propylene glycol monooleate.

[0054] The nonionic surfactant having an HLB of greater than 5 is not particularly limited, but examples of suitable polyoxyalkylene alkyl ethers include DKS NL30 and DKS NL 50 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), and examples of sorbitan fatty acid esters include Tween (registered trademark) 80 and Emazol O-120V (both polyoxyethylene (20) sorbitan monooleate). This configuration has the advantage of having good affinity for oil and being able to sufficiently remove adhesives from materials.

[0055] In one embodiment of the present invention, the anionic surfactant preferably includes a sulfonate, which has the advantage of being able to sufficiently remove the adhesive from the material.

[0056] The anionic surfactant is not particularly limited, but is preferably a sulfonate type or a phosphate type, and more preferably an alkyl sulfonate, polyoxyalkylene alkyl ether sulfonate, polyoxyalkylene alkyl ether phosphate, etc. The anionic surfactant is more preferably an alkyl sulfonate. This configuration has the advantage of being able to sufficiently remove adhesive from the material.

[0057] (1-3. Other Components) The adhesive remover may contain other components. Examples of other components include, but are not limited to, water, petroleum resin, hydrogenated petroleum resin, plant-derived resin, hydrogenated plant-derived resin, antibacterial agent, disinfectant, deodorizer, antifungal agent, preservative, fragrance, pigment, dye, dispersant, pH indicator, water-releasing agent, and rust inhibitor.

[0058] When the adhesive remover contains water, the adhesive remover that has soaked into the material can be easily washed away in the cleaning step (described below) after the removal step. The amount of water added is preferably 10 wt % or less of the total amount of the adhesive remover. When removing the adhesive from a constituent material of an article that contains a superabsorbent polymer as a constituent material, separating the superabsorbent polymer, and reusing it as a superabsorbent polymer for use in sanitary materials such as diapers, the adhesive remover preferably contains or does not contain water.

[0059] The adhesive remover may also contain an organic solvent within a range that allows for acceptable adhesive removal performance. Examples of organic solvents include toluene, limonene, chloroform, hexane, ethyl acetate, benzene, alcohol, acetic acid, and acetone.

[0060] When the adhesive remover contains an organic solvent, the content of the organic solvent is preferably 0% to 20% by weight, more preferably 0% to 15% by weight, even more preferably 0% to 10% by weight, and particularly preferably 0% to 5% by weight, relative to the total amount of the adhesive remover. This configuration has the advantage of being able to remove adhesives. The adhesive remover is preferably oil-based, with the total amount of oil and surfactant being greater than the amount of other components. It is also preferably a non-emulsifying type that does not contain components that are poorly compatible with oil.

[0061] (1-4. Adhesives) The adhesives that can be removed by the adhesive remover are not particularly limited, but are preferably, for example, hot melt adhesives, solvent-based adhesives, and water-based adhesives, and are preferably adhesives excluding curing adhesives. When the adhesive remover is used, it has the advantage of being able to remove the base polymer and tackifier, which are difficult to remove from the adhesive. In addition, since the tackifier can also be removed, it has the advantage of not leaving any adhesive residue on the material.

[0062] The adhesive remover is more preferably a hot melt adhesive remover, and the adhesive remover exhibits an adhesive removing effect more suitably for hot melt adhesives.

[0063] The hot melt adhesive is not particularly limited, but examples include synthetic rubber (elastomer)-based hot melt adhesives, polyamide-based hot melt adhesives, polyester-based hot melt adhesives, acrylic-based hot melt adhesives, EVA (ethylene vinyl acetate copolymer)-based hot melt adhesives, and olefin-based hot melt adhesives. Among these, synthetic rubber-based hot melt adhesives using elastomers and acrylic-based hot melt adhesives using elastomers are more preferred. This configuration has the advantage of allowing the adhesive to be sufficiently removed from the material.

[0064] Examples of solvent-based adhesives include (meth)acrylate-based, silicone-based, polyvinyl acetate-based, polyethylene vinyl acetate-based, polyisoprene rubber-based, styrene-methacrylate copolymer-based, styrene-butadiene rubber-based, styrene-isoprene rubber-based, methacrylate-butadiene-styrene copolymer-based, and combinations thereof. Among these, (meth)acrylate-based, polyisoprene rubber-based, styrene-methacrylate copolymer-based, styrene-butadiene rubber-based, styrene-isoprene rubber-based, methacrylate-butadiene-styrene copolymer-based, and combinations thereof are preferred. This configuration has the advantage of allowing the adhesive to be sufficiently removed from the material.

[0065] (1-5. Uses) The adhesive remover is suitable for use in removing adhesive from various items such as food packaging, cardboard, books, sanitary products (paper diapers, sanitary products, pet sheets, urine absorption pads, breast pads, etc.), and car mats.

[0066] [2. Adhesive Removal Method] (2-1. Adhesive Removal Step) An adhesive removal method according to one embodiment of the present invention (hereinafter, may be referred to as "this removal method") includes an adhesive removal step of removing adhesive from a material to which the adhesive is attached, using the adhesive remover described in [1. Adhesive Remover].

[0067] The material to which the adhesive is applied is not particularly limited, but examples thereof include plastic, plastic film, pulp, highly absorbent polymer, paper, nonwoven fabric, rubber thread, cardboard, felt, and urethane foam.

[0068] The method for removing adhesive from a material to which adhesive is attached using the adhesive remover is not particularly limited, but examples include immersing the material in the adhesive remover. Here, the material to be immersed in the adhesive remover may be a single material or multiple and / or different types of materials, as long as the material has adhesive attached thereto. Each material may be bonded by the adhesive, or at least a portion of the material may be unbonded. The material to be immersed in the adhesive remover may be an article whose constituent components (materials) are bonded by the adhesive. Heating may be performed during the process of removing the adhesive from the material. From the viewpoints of reducing energy consumption and miniaturizing equipment, the method of immersing the material in the adhesive remover is more preferred. From the viewpoint of adhesive removal efficiency, the method of immersing and stirring is preferred.

[0069] (2-2. Cleaning Step) The present removal method preferably further includes a step of cleaning the material from which the adhesive has been removed with water, in other words, a step of cleaning with a water-based cleaning liquid. Here, the water-based cleaning liquid refers to a cleaning liquid consisting of water or containing water. This allows the adhesive remover that has soaked into the material to be washed away, making the material easier to handle.

[0070] The temperature of the aqueous cleaning liquid is not limited, but is preferably 40°C to 80°C from the viewpoint of shortening the cleaning time. The temperature of the aqueous cleaning liquid is more preferably 45°C to 80°C, more preferably 50°C to 80°C, even more preferably 55°C to 80°C, and particularly preferably 60°C to 80°C. This configuration has the advantage of being able to sufficiently remove adhesive from the material. In particular, setting the temperature of the aqueous cleaning liquid to 40°C to 80°C makes it easier to wash away oil components.

[0071] The aqueous cleaning solution is not particularly limited, and may contain substances other than water as long as it can remove the adhesive remover from the material and clean the material to the extent that it can be reused. Since the aqueous cleaning solution preferably contains water as its primary component, the weight of water relative to the total weight of water and substances other than water (total weight of the aqueous cleaning solution) is preferably at least 60% by weight, and more preferably 90% by weight or more. Examples of water include tap water, soft water, hard water, carbonated water, alkaline ionized water, pure water, and mixtures thereof. Examples of substances other than water include alcohol, acetone, etc. If the article contains a superabsorbent polymer and the superabsorbent polymer is not to be reused as a superabsorbent polymer, the aqueous cleaning solution may further contain a water-repellent agent as a substance other than water. The concentration of the water-repellent agent in the aqueous cleaning solution can be determined depending on the amount of superabsorbent polymer contained in the article whose constituent material will be cleaned by immersion in the aqueous cleaning solution, but is preferably 0.1% by weight to 10% by weight. Examples of water-repellent agents include calcium chloride, magnesium sulfate, citric acid, and acetic acid. By including a water-repellent in the aqueous cleaning solution, it is possible to prevent the water-absorbent polymer from absorbing water when the adhesive is removed from the material and then the remover is removed from the material by washing with the aqueous cleaning solution, thereby facilitating handling. When a superabsorbent polymer is used for an application other than water absorption (for example, fuel, etc.), the inclusion of a water-repellent in the superabsorbent polymer does not cause any problems and handling is also facilitated, so it is preferable to include a water-repellent in the aqueous cleaning solution.

[0072] (2-3. Separation Step) When a superabsorbent polymer is contained in a material in an article bonded with an adhesive, the present removal method preferably further includes a separation step of separating the material from which the adhesive has been removed into the superabsorbent polymer and a material other than the superabsorbent polymer, after the adhesive removal step of removing the adhesive from the material to which the adhesive has adhered using an adhesive remover. By providing this separation step without performing a water washing step after the adhesive removal step, the superabsorbent polymer can be regenerated after separation without the superabsorbent polymer becoming difficult to handle due to water absorption in the water washing step or being altered by a water-releasing agent, making it easier to reuse the superabsorbent polymer.

[0073] The method for separating the material from which the adhesive has been removed in the adhesive removal step into the superabsorbent polymer and materials other than the superabsorbent polymer is not particularly limited, but examples include filter separation, centrifugation, and the like. In the case of filter separation, the mesh size of the filter may be appropriately determined according to the size of the material contained in the article removed from the adhesive remover. For example, a filter with a mesh size of 0.01 mm to 5 mm is used. The superabsorbent polymer passes through the filter together with the adhesive remover, while materials other than the superabsorbent polymer do not pass through the filter, allowing the superabsorbent polymer to be separated from materials other than the superabsorbent polymer.

[0074] This removal method preferably further includes a step of washing the separated superabsorbent polymer with an organic solvent and / or a step of washing materials other than the superabsorbent polymer with an aqueous cleaning solution. Superabsorbent polymers are generally made of cross-linked polyacrylic acid and its salts, which have the property of absorbing water and swelling. Because superabsorbent polymers become difficult to handle when they absorb water, a water-repellent agent such as calcium chloride is used when washing with an aqueous cleaning solution. However, the use of a water-repellent agent changes the structure of the superabsorbent polymer, making it unable to absorb water (deteriorating), making it difficult to reuse it as a superabsorbent polymer. To prevent this problem, it is preferable to wash the superabsorbent polymer with an organic solvent. Materials other than the superabsorbent polymer (e.g., nonwoven fabrics, pulp, and films) are preferably washed with an aqueous cleaning solution as described above to reduce environmental impact. The aqueous cleaning solution used to wash materials other than the superabsorbent polymer can be the same as the aqueous cleaning solution described in the process of washing materials from which the adhesive has been removed. In addition, if the superabsorbent polymer is not to be reused or if it is not a problem if the superabsorbent polymer contains water, the material from which the adhesive has been removed may be cleaned with the aforementioned aqueous cleaning solution without separating the superabsorbent polymer from materials other than the superabsorbent polymer. In one embodiment, this removal method includes an adhesive removal step of removing the adhesive from the material to which the adhesive has been attached of an adhesive-bonded article; a separation step of separating the material from which the adhesive has been removed into the superabsorbent polymer and materials other than the superabsorbent polymer; and a cleaning step of washing the superabsorbent polymer separated in the separation step with an organic solvent. If the article is immersed in an organic solvent to remove the adhesive, a larger amount of organic solvent is used than in this removal method. Furthermore, in such cases, the organic solvent cannot be easily removed when reusing materials other than the superabsorbent polymer, such as nonwoven fabric, pulp, or film, which requires a lot of effort.

[0075] The organic solvent used to wash the superabsorbent polymer separated in the separation process is not particularly limited in type, purity, etc., as long as it can wash away the adhesive remover that has soaked into the material and clean the superabsorbent polymer to the extent that it can be reused. Examples of the organic solvent include polar solvents, nonpolar solvents, and mixtures thereof. Polar solvents include alcohols such as methanol, ethanol, and glycerin; ketones such as acetone and methyl ethyl ketone; ethers such as diethyl ether and tetrahydrofuran; esters such as ethyl acetate and butyl acetate; and dimethyl sulfoxide. Nonpolar solvents include aliphatic compounds such as hexane, cyclohexane, and limonene; and aromatic hydrocarbons such as toluene and xylene. From the viewpoint of adhesive remover solubility, the organic solvent preferably has a molecular weight of 200 or less. Polar solvents are more preferably methanol or ethanol. Nonpolar solvents are more preferably pentane, hexane, or cyclohexane.

[0076] When washing a superabsorbent polymer with an organic solvent, one type of organic solvent or multiple organic solvents may be used, and there is no limit to the number of washings. For example, a single organic solvent may be used, or a mixed solvent of multiple organic solvents may be used, or washing with a polar solvent followed by washing with a nonpolar solvent, or washing with a nonpolar solvent followed by washing with a polar solvent may be used. When a mixed solvent of a polar solvent and a nonpolar solvent is used, the ratio of the polar solvent to the nonpolar solvent may be 1:9 to 9:1 by volume. When washing a superabsorbent polymer with an organic solvent, washing with a mixture of polar and nonpolar solvents or using them in stages is preferred. The step of washing with an organic solvent is usually carried out at room temperature, but may be heated as appropriate.

[0077] The method for washing the material from which the adhesive has been removed in the adhesive removal step, and the superabsorbent polymer or material other than the superabsorbent polymer separated in the separation step is not particularly limited, but examples include a method in which the object to be washed is stirred in an aqueous cleaning solution or an organic solvent using a washing machine, stirring blades, agitator, etc. The number of times washing is also not particularly limited, and may be one or more times.

[0078] <Summary> One embodiment of the present invention includes the following configuration.

[0079] [1] An adhesive remover comprising an oil and a surfactant, wherein the oil comprises one or more selected from the group consisting of vegetable oil, ester oil, aliphatic carboxylic acid, and mineral oil, the vegetable oil having an iodine value of 70 to 160, the ester oil having three or less ester groups in one molecule, and the surfactant comprising an anionic surfactant and / or a nonionic surfactant having an HLB of greater than 5 and being liquid at room temperature.

[0080] [2] The adhesive remover according to [1], wherein the content of the oil is more than 10% by weight and less than 70% by weight, relative to 100% by weight of the total of the oil and the surfactant.

[0081] [3] The adhesive remover according to either [1] or [2], wherein the HLB of the nonionic surfactant is 15 or less.

[0082] [4] The adhesive remover according to any one of [1] to [3], wherein the SP values ​​of the ester oil and the mineral oil are both 8.0 or more and 9.5 or less.

[0083] [5] The adhesive remover according to any one of [1] to [4], which is a hot melt adhesive remover.

[0084] [6] An adhesive removal method including an adhesive removal step of removing an adhesive from a material to which the adhesive is attached using the adhesive remover according to any one of [1] to [5].

[0085] [7] The adhesive removal method described in [6], further comprising a cleaning step of using water to clean the material from which the adhesive has been removed by the adhesive removal step.

[0086] [8] The adhesive removal method described in [6], wherein the material contains a superabsorbent polymer, and the method includes a separation step of separating the material from which the adhesive has been removed into the superabsorbent polymer and a material other than the superabsorbent polymer.

[0087] [9] The adhesive removal method according to [8], further comprising a washing step of washing the highly absorbent polymer separated in the separation step with an organic solvent.

[0088]

[10] The adhesive removal method according to [8] or [9], further comprising a washing step of washing with water the materials other than the highly water-absorbent polymer separated in the separation step.

[0089] Examples will be described below, but the present invention is not limited to the following examples.

[0090] [Materials] The following materials were used in the following examples and comparative examples.

[0091] <Oil> (Vegetable oils) ・Soybean oil (iodine value 131): manufactured by Kaneda Co., Ltd. ・Rice bran oil (iodine value 104): manufactured by Boso Oil & Fats Co., Ltd. ・Rapeseed oil (iodine value 110): manufactured by Yonezawa Oil Mills Co., Ltd. ・Olive oil (iodine value 85): manufactured by J-Oil Mills Co., Ltd. ・Linseed oil (iodine value 187): manufactured by Nippon Flour Mills Co., Ltd. (Ester oil) ・DOS (bis(2-ethylhexyl) sebacate: 2 ester groups per molecule, SP value 9.1): manufactured by New Japan Chemical Co., Ltd. ・ATBC (acetyl tributyl citrate: 4 ester groups per molecule, SP value 9.8): manufactured by Taoka Chemical Co., Ltd. (Aliphatic carboxylic acids) ・Alkenylsuccinic anhydride (maleic acid-modified α-olefin) (SP value 10.1): manufactured by Seiko PMC Co., Ltd., AS-1532 (Mineral oil)・Moresco White "P-200" (liquid paraffin: SP value 8.1): manufactured by MORESCO Corporation ・Cosmo Neutral 150 (aromatic mineral oil: SP value 8.7): manufactured by Cosmo Oil Lubricants Co., Ltd. <Other> ・d-Limonene <Surfactant> (nonionic surfactant) ・DKS NL 15 (HLB = 5, liquid): manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・DKS NL 30 (HLB = 8, liquid): manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・DKS NL 50 (HLB = 10, liquid): manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・DKS NL Dash 410 (HLB = 12, liquid): manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ・DKS NL 110 (HLB = 14, semi-solid): manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Emazol O-120V (HLB=15, liquid): manufactured by Kao Corporation DKS NL 180 (HLB=16, semi-solid): manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. DKS NL 450F (HLB=18, solid): manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. (anionic surfactant) Sulfol 430A (surfactant (sodium sulfonate) 65%, spin oil 30%, water 5%, liquid): manufactured by MORESCO Corporation <Solvent> Water <Releasant> Citric acid [Method of preparing evaluation samples] A hot melt adhesive (rubber-based, manufactured by MORESCO Corporation) was applied to a first substrate (spunbond nonwoven fabric) at a coating temperature of 150°C using a ZIP coater (manufactured by Suntool Corporation). The application amount was 5 g / m ２The coating width was 15 mm. Next, a second substrate (polyethylene film) was laminated on the surface of the first substrate coated with the hot melt adhesive, and the laminate was prepared by pressing at 23°C. The time from when the hot melt adhesive was applied to the first substrate to when the second substrate was pressed and the laminate was prepared was 0.5 seconds. A sample of the obtained laminate was cut into a 50 x 50 mm piece so that the 15 mm wide adhesive-coated portion was located in the center, parallel to one side, and used as an evaluation sample.

[0092] Preparation of Adhesive Removers (Examples 1 to 19, Comparative Examples 1 to 8) Predetermined amounts of oil and surfactant were weighed into glass containers to achieve the ratios (parts by weight) shown in Tables 1 to 3. The mixture was stirred at room temperature for 1 minute until no phase separation occurred, yielding adhesive removers. Furthermore, in Examples 5 and 11, in which Sulfol 430A was used as the surfactant, the Sulfol 430A used contained surfactant (sodium sulfonate), oil, and water. Therefore, in Examples 5 and 11, the surfactant (sodium sulfonate) was blended to a content of 50% by weight relative to 100% by weight of the adhesive remover.

[0093] [Adhesive removal using adhesive remover (Examples 1 to 19, Comparative Examples 1 to 8)] The evaluation sample was placed in 10 g of adhesive remover and immersed for 1 hour. The evaluation sample separated in the adhesive remover. The immersed evaluation sample was removed from the remover and placed in another glass bottle. 100 g of 60°C warm water was added to the glass bottle and stirred well for 10 seconds. The above process was repeated two more times for cleaning. The washed evaluation sample was removed and dried, and its condition was confirmed. Whether the adhesive and adhesive remover were sufficiently removed from the material was evaluated according to the following evaluation criteria.

[0094] (Mixed state of adhesive remover) ◎ (Excellent): Liquid is transparent when mixed ○ (Good): Liquid is uniform when mixed △ (Bad): Mixture separates after being left to stand for 3 hours × (Fail): Mixture separates or becomes solid (Peeling state of evaluation sample after immersion in adhesive remover) ○ (Good): Evaluation sample peels off × (Fail): Evaluation sample does not peel off (Surface condition of evaluation sample after washing) ◎ (Excellent): No slime ○ (Good): Slight slime present × (Fail): Slime present or hot melt adhesive remains In this specification, "slime" refers to slime caused by oil contained in the adhesive remover.

[0095] [Viscosity] The viscosity was measured in accordance with JIS K 6862. The viscosity of the oil and adhesive remover at 23°C was measured using a Brookfield B-type viscometer RVDV2T (rotor with spindle No. 21).

[0096] (Discussion) Table 1 shows the results of evaluating adhesive removers prepared by mixing various surfactants with soybean oil (iodine value 131). Examples 1 to 5, which used an anionic surfactant or a nonionic surfactant with an HLB greater than 5 and liquid at room temperature, were able to sufficiently remove the adhesive from the sample and also remove the adhesive remover from the substrate by washing. On the other hand, in Comparative Example 1, which used a nonionic surfactant with an HLB of 5 or less, some of the oil and adhesive from the adhesive remover remained on the substrate after washing. In addition, in Comparative Example 2, which used a semi-solid nonionic surfactant, some of the adhesive remained on the substrate after washing. Comparative Examples 3 and 4, which used a semi-solid or solid nonionic surfactant, were unsuitable because the surfactant did not dissolve in the oil and separated.

[0097] Table 2 shows the results of evaluating adhesive removers containing various surfactants mixed with various oils other than soybean oil. Examples 6 to 9, which used vegetable oils with iodine values ​​of 70 to 160, were able to sufficiently remove adhesive from the samples, and the adhesive remover was also able to be removed from the substrate after cleaning. Similar results were also obtained for Examples 10 to 15, which used ester oils with two or fewer ester groups per molecule, aliphatic carboxylic acids, and mineral oils. However, Comparative Example 5, which used ATBC with three or more ester groups per molecule, was unable to sufficiently remove the adhesive, and adhesive remained on the substrate after cleaning. Comparative Example 6, which used linseed oil alone with an iodine value of over 160, was pyrophoric and difficult to handle, making it unsuitable for the present invention.

[0098] The results of Examples 16 to 19 and Comparative Example 7 in Table 3 demonstrate that the inclusion of a surfactant in the adhesive remover enabled sufficient adhesive removal from the samples, allowing the adhesive remover to be washed away from the substrate after cleaning. This allows the recovered articles to be easily reused as resources. Meanwhile, Comparative Example 8 shows the results of an attempt to use the removal method of the present invention with a conventional terpene (d-limonene) aqueous solution. The conventional technology utilizes the centrifugal force of a washing machine to decompose articles with adhesive attached. When the removal method of the present invention was attempted using the conventional terpene aqueous solution, the limonene separated from the water, and the sample did not peel off simply by immersing it in the terpene aqueous solution. Furthermore, the adhesive remained on the substrate even after cleaning the sample, demonstrating that the conventional terpene aqueous solution is unable to remove adhesive from substrates.

[0099] [Removal of Adhesive (Disposable Diaper) Using Adhesive Remover] (Adhesive Removal) A commercially available disposable diaper for children, which had been secured with hook tape and rolled up, was placed in an adhesive remover prepared by mixing 50 parts by weight of soybean oil and 50 parts by weight of Emazol O-120V, and immersed for 1 hour. The disposable diaper was released from its position in the adhesive remover, and the surface layer was separated.

[0100] (Washing with Water) After lightly wringing the disposable diapers removed from the adhesive remover, the disposable diapers were placed in a laundry net and placed in a washing machine. 20 g of calcium chloride (water-releasing agent) and 10 L of 60°C hot water were added to the washing machine tub and agitated for 15 minutes. After agitation, water was added, rinsing was performed twice, and the diapers were dehydrated for 5 minutes. The disposable diapers were removed from the laundry net and evaluated. The disposable diapers were separated into their respective substrates (materials), and no adhesive or remover remained on each substrate (material), nor was there any slime. This result was better than the result obtained by the method described in Patent Document 1 (Comparative Example 8). While adhesive removal was possible without agitation while the disposable diapers were immersed in the adhesive remover, agitation during immersion enabled removal in a shorter time. Because the water-releasing agent alters the superabsorbent polymer, it is difficult to reuse the superabsorbent polymer as a water-absorbing material. However, because no adhesive or other residue remains on the substrate, this treatment method is suitable for reusing the substrate.

[0101] (Separation into superabsorbent polymer and other materials and washing) After soaking disposable baby diapers in an adhesive remover for 1 hour using the method described in (Adhesive removal), the adhesive remover in which the disposable diapers had been soaked was passed through a filter to separate the superabsorbent polymer (filtrate side) and materials other than the superabsorbent polymer (filter residue side). When the separated materials other than the superabsorbent polymer were washed with water as described above, no adhesive or adhesive remover remained in either material, and no slime was found.

[0102] The separated superabsorbent polymer was immersed in room temperature methanol for 1 minute and stirred. The superabsorbent polymer was removed from the methanol and immersed in room temperature n-hexane for 1 minute and stirred. The superabsorbent polymer removed from the n-hexane was not slimy or sticky, and no residual adhesive or adhesive remover was found.

[0103] When water was poured onto the superabsorbent polymer after washing with an organic solvent, the superabsorbent polymer absorbed the water and swelled, indicating that the superabsorbent polymer from which the adhesive had been removed using this washing method could be reused as a water-absorbing material without being altered.

[0104] Furthermore, disposable diapers were immersed in the adhesive remover used in Examples 1 to 19 to remove the adhesive, and then the superabsorbent polymer was separated from other substances. It was confirmed that similarly favorable effects could be obtained by washing the separated superabsorbent polymer with an organic solvent.

[0105] Similarly, the materials other than the separated superabsorbent polymer were agitated for 15 minutes in a washing machine in hot water (10 L) at 60° C. After agitation, the materials were rinsed twice with water and then dehydrated for 5 minutes, after which no adhesive or adhesive remover remained on any of the materials, and there was no slime or stickiness.

[0106] The present invention can be used to remove adhesives.

Claims

1. An adhesive remover for removing an adhesive attached to an article containing a highly water-absorbent polymer, The adhesive remover comprises an oil and a surfactant, The oil comprises at least one selected from the group consisting of vegetable oils, ester oils, aliphatic carboxylic acids, and mineral oils; The vegetable oil has an iodine value of 70 to 160; The ester oil has three or less ester groups in one molecule, The adhesive remover, wherein the surfactant comprises an anionic surfactant and / or a nonionic surfactant having an HLB of more than 5 and being liquid at room temperature.

2. An adhesive remover for removing adhesive adhering to a highly absorbent polymer or nonwoven fabric, comprising: The adhesive remover comprises an oil and a surfactant, The oil comprises at least one selected from the group consisting of vegetable oils, ester oils, aliphatic carboxylic acids, and mineral oils; The vegetable oil has an iodine value of 70 to 160; The ester oil has three or less ester groups in one molecule, The adhesive remover, wherein the surfactant comprises an anionic surfactant and / or a nonionic surfactant having an HLB of more than 5 and being liquid at room temperature.

3. The content of the oil is: The adhesive remover according to claim 1 or 2, which is more than 10% by weight and less than 70% by weight, relative to 100% by weight of the total of the oil and the surfactant.

4. The adhesive remover according to claim 1 or 2, wherein the HLB of the nonionic surfactant is 15 or less.

5. The adhesive remover according to claim 1 or 2, wherein the SP value of the ester oil and the SP value of the mineral oil are both 8.0 or more and 9.5 or less.

6. The adhesive remover according to claim 1 or 2, which is a hot melt adhesive remover.

7. An adhesive remover as described in claim 1 or 2, wherein the oil has a flash point of 150°C or higher.

8. The adhesive remover of claim 1 or 2, which does not contain water.

9. an adhesive removing step of immersing an article having a material bonded with an adhesive in an adhesive remover containing an oil and a surfactant, and removing the adhesive from the material to which the adhesive is attached; The material includes a highly absorbent polymer; The oil comprises at least one selected from the group consisting of vegetable oils, ester oils, aliphatic carboxylic acids, and mineral oils; The vegetable oil has an iodine value of 70 to 160; The ester oil has three or less ester groups in one molecule, The adhesive removal method, wherein the surfactant comprises an anionic surfactant and / or a nonionic surfactant having an HLB of greater than 5 and which is liquid at room temperature.

10. The method includes an adhesive removal step of removing adhesive from a material to which adhesive has been attached using an adhesive remover containing an oil and a surfactant, the material is a superabsorbent polymer or a nonwoven fabric; The oil comprises at least one selected from the group consisting of vegetable oils, ester oils, aliphatic carboxylic acids, and mineral oils; The vegetable oil has an iodine value of 70 to 160; The ester oil has three or less ester groups in one molecule, The adhesive removal method, wherein the surfactant comprises an anionic surfactant and / or a nonionic surfactant having an HLB of greater than 5 and which is liquid at room temperature.

11. The adhesive removal method according to claim 9 or 10, further comprising a cleaning step of cleaning, with water, the material from which the adhesive has been removed in the adhesive removing step.

12. The adhesive removal method according to claim 9 or 10, further comprising a separation step of separating the material from which the adhesive has been removed into the highly water-absorbent polymer and a material other than the highly water-absorbent polymer.

13. The adhesive removal method according to claim 12, further comprising a washing step of washing the highly water-absorbent polymer separated in the separating step with an organic solvent.

14. The adhesive removal method according to claim 12, further comprising a washing step of washing, with water, materials other than the highly water-absorbent polymer separated in the separating step.