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

[Technical field]

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

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

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

[0004] For example, Patent Document 1 discloses a method for recovering pulp fibers from a used absorbent article containing pulp fibers and a superabsorbent polymer. The method is characterized by including a step of treating a used absorbent article 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, to inactivate the superabsorbent polymer. The document also discloses that the used absorbent article is placed in a washing machine containing the aqueous solution, and the article is decomposed by utilizing centrifugal force. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication "JP Patent Publication No. 2018-24964" Summary of the Invention [Problem to be solved by the invention]

[0006] The conventional technology described above involves breaking down absorbent articles into their constituent components (materials) and reusing the recovered pulp fibers as resources. However, in the conventional technology described above, adhesive remains in the constituent components obtained by breaking down the absorbent article, and there is a possibility that the constituent components may adhere to each other again. Furthermore, if adhesive remains 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 technology 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 is capable of sufficiently removing adhesive from a material, and a method for removing adhesive using the adhesive remover. [Means for solving the problem]

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

[0009] Contains oil and 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 value of greater than 5 and being liquid at room temperature. Effect of the Invention

[0010] According to one aspect of the present invention, it is possible to provide an adhesive remover capable of sufficiently removing an adhesive from a material, and a method for removing an adhesive using the adhesive remover. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments of the present invention will be described in detail. However, the present invention is not limited to this, and various modifications are possible within the described range, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments are also included in the technical scope of the present invention. In addition, unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more, B or less". In addition, 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 contains one or more selected from the group consisting of vegetable oil, ester oil, aliphatic carboxylic acid, and mineral oil, the iodine value of the vegetable oil is 70 to 160, the ester oil has three or less ester groups in one molecule, and the surfactant contains an anionic surfactant and / or a nonionic surfactant having an HLB value of more than 5 and being liquid at room temperature. Such an adhesive remover has the advantage that it can sufficiently remove adhesive from materials. According to the above configuration, articles bonded with an adhesive can be separated into each material without any adhesive remaining. Therefore, it has the advantage that articles bonded with an adhesive can be suitably recycled. Such an effect also contributes to the achievement of, for example, Goal 12 "Responsible Consumption and Production" of the Sustainable Development Goals (SDGs) advocated by the United Nations.

[0013] In addition, the above-mentioned configuration has the advantage that the adhesive can be sufficiently removed from the material, so that the article can 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 become sticky again after the adhesive is removed. In other words, the above-mentioned configuration has the advantage that articles bonded with an adhesive can be efficiently recycled.

[0014] In addition, when the article made by bonding materials with an adhesive is a disposable diaper, the adhesive remover can penetrate into the inside of the disposable diaper even when the disposable diaper is rolled up, and the adhesive can be removed. In other words, the adhesive remover has the advantage that the article can be disassembled by removing the adhesive without opening the rolled up disposable diaper after use. In addition, the pulp and SAP (super absorbent polymer) can be separated and recovered from the disposable diaper, and also the nonwoven fabric, film, rubber thread, etc. can be separated and recovered.

[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 that it easily penetrates into the adhesive and can sufficiently 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, and has an advantage that the adhesive can be dissolved and removed from the article.

[0017] In addition, the oil is preferably liquid at room temperature. This 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 selected from the group consisting of vegetable oil, ester oil, aliphatic carboxylic acid, and mineral oil. The oil more preferably comprises vegetable oil or ester oil, and even 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 adhesive from materials. The oil may be a mixture of at least two or more selected from the group consisting of vegetable oil, ester oil, aliphatic carboxylic acid, and mineral oil.

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

[0020] (1-1-1. Vegetable oil) The adhesive remover preferably contains vegetable oil, which has the advantage that the adhesive can be more thoroughly removed from the material.

[0021] The adhesive remover preferably does not contain animal oil, since animal oil is often in solid form and tends to be difficult to mix with a surfactant at room temperature.

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

[0023] The adhesive remover may contain multiple types of vegetable oil. Here, the "iodine value of vegetable oil" refers to the iodine value of one 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 of multiple types of vegetable oils contained in the adhesive remover when the adhesive remover contains multiple types of vegetable oils. That is, when the adhesive remover contains multiple types of vegetable oils, the iodine value of the mixed vegetable oil made of the 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 fats and oils. 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 oils, the "iodine value of the vegetable oil" is determined by a measurement method conforming to 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 and 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 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 oil, olive oil, and rapeseed oil, and even more preferably soybean oil and / or rice oil. This configuration has the advantage that the adhesive can 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 viewpoints 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 that the adhesive can 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 that the adhesive can be more sufficiently removed from the material.

[0031] In this specification, the 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 , hydrogen bond term δ h Then, δ = (δ d 2 +δ p 2 +δ h 2 ) 1 / 2 This is a quantity δ defined by the following equation, which is specific to the 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 the ester oil 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, paramethoxycinnamate, and pentaerythritol tetrarosinate. The ester oil is more preferably DOS. This configuration has the advantage of being able to more thoroughly remove the adhesive from the material.

[0033] (1-1-3. Aliphatic carboxylic acids) The adhesive remover preferably contains an aliphatic carboxylic acid. Examples of the aliphatic carboxylic acid include monocarboxylic acid, dicarboxylic acid, anhydride acid, and polycarboxylic acid. 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 more preferably alkenylsuccinic acid or its anhydride. In addition, the aliphatic carboxylic acid is more preferably an unsaturated aliphatic carboxylic acid. This configuration has the advantage that the adhesive can be more fully removed 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, still 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 that the adhesive can be more sufficiently 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, white mineral oils, etc. More specifically, for example, spindle oil, liquid paraffin, etc. can be suitably used. This configuration has the advantage that the adhesive can be more sufficiently removed 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 that the adhesive can 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. Surfactants) The adhesive remover includes 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 includes a surfactant, making it possible to sufficiently remove the adhesive remover from the material in the article. This makes it easier to handle the separated material.

[0041] In one embodiment of the present invention, the surfactant comprises an anionic surfactant and / or a nonionic surfactant having an HLB of greater than 5 and being liquid at room temperature. In one embodiment of the present invention, the surfactant preferably comprises an anionic surfactant or a nonionic surfactant having an HLB of greater than 5 and being liquid at room temperature, and more preferably consists of a nonionic surfactant having an HLB of greater than 5 and being 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 value of more than 5 in 100% by weight of the surfactant 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 that the adhesive can be more thoroughly removed from the material.

[0043] In one embodiment of the present invention, the nonionic surfactant having an HLB of more than 5 is preferably contained in a larger amount than the anionic surfactant. In a total of 100% by weight of the anionic surfactant and the nonionic surfactant having an HLB of more than 5, the content of the nonionic surfactant having an HLB of more 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. This configuration has the advantage that the adhesive can be more thoroughly removed from the material.

[0044] In this specification, HLB (Hydrophile-Lipophile Balance) refers to a value that indicates the balance between lipophilicity and hydrophilicity in a surfactant. The HLB value of a substance that does not have a hydrophilic group is HLB=0, and the HLB value of a substance that has only hydrophilic groups and does not have lipophilic groups is HLB=20, and the value is obtained by dividing the two equally.

[0045] The HLB of a nonionic surfactant having an HLB 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 the adhesive from the material.

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

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

[0051] Polyoxyethylene castor oil is a compound obtained by addition polymerization of ethylene oxide to 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 ester and polyoxyalkylene di fatty acid ester. For example, the polyoxyalkylene mono fatty acid ester includes polyethylene glycol mono fatty acid ester such as polyethylene glycol monooleate, polyethylene glycol monostearate, polyethylene glycol monolaurate, and propylene glycol mono fatty acid ester such as propylene glycol monostearate, propylene glycol monolaurate, and propylene glycol monooleate.

[0054] The nonionic surfactant having an HLB of more than 5 is not particularly limited, but for example, polyoxyalkylene alkyl ethers such as DKS NL30 and DKS NL 50 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and sorbitan fatty acid esters such as Tween (registered trademark) 80 and Emazol O-120V (both polyoxyethylene (20) sorbitan monooleate) can be suitably used. This configuration has the advantage of having good affinity for oil and being able to sufficiently remove the adhesive from the material.

[0055] In one embodiment of the present invention, the anionic surfactant preferably contains a sulfonate, which has the advantage that the adhesive can be sufficiently removed 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, a polyoxyalkylene alkyl ether sulfonate, a polyoxyalkylene alkyl ether phosphate, etc. The anionic surfactant is more preferably an alkyl sulfonate. This configuration has the advantage that the adhesive can be sufficiently removed from the material.

[0057] (1-3. Other ingredients) The adhesive remover may contain other components, which are not particularly limited, but include, for example, water, petroleum resin, hydrogenated petroleum resin, plant-derived resin, hydrogenated plant-derived resin, antibacterial agent, bactericide, 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) following the removal step. The amount of water added is preferably 10% by weight or less based on 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, it is preferable that the adhesive remover does not contain water.

[0059] The adhesive remover may contain an organic solvent within a range that allows for acceptable adhesive removal performance. Examples of the organic solvent 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% by weight to 20% by weight, more preferably 0% by weight to 15% by weight, even more preferably 0% by weight to 10% by weight, and particularly preferably 0% by weight to 5% by weight, based on 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-emulsified type that does not contain components that are poorly compatible with oil.

[0061] (1-4. Adhesive) The adhesive that can be removed by the adhesive remover is not particularly limited, but for example, hot melt adhesives, solvent-based adhesives, and water-based adhesives are preferred, and curing adhesives are preferred. When the adhesive remover is used, it has the advantage that it can also remove the base polymer and tackifier that are difficult to remove from the adhesive. In addition, since the tackifier can also be removed, it has the advantage that no adhesive remains on the material.

[0062] The adhesive remover is more preferably a hot melt adhesive remover, and is more effective at removing adhesives from hot melt adhesives.

[0063] The hot melt adhesive is not particularly limited, but examples thereof 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 that the adhesive can 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 that the adhesive can be sufficiently removed from the material.

[0065] (1-5.Applications) This adhesive remover is suitable for use in removing adhesives from a variety of items, including food packaging, cardboard, books, sanitary products (paper diapers, sanitary products, pet sheets, urine pads, breast pads, etc.), and car mats.

[0066] 2. How to remove adhesive (2-1. Adhesive removal process) An adhesive removal method according to one embodiment of the present invention (hereinafter, sometimes referred to as "this removal method") includes an adhesive removal step in which the adhesive is removed from a material to which the adhesive is adhered 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 plastics, plastic films, pulp, highly water-absorbent polymers, paper, nonwoven fabrics, rubber threads, cardboard, felt, and urethane foam.

[0068] The method of removing an adhesive from a material to which an adhesive is attached using the adhesive remover is not particularly limited, and examples thereof include a method of 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 multiple types of materials as long as the material has an adhesive attached thereto, and each material may be in a state of being bonded by an adhesive, or at least a part of the material may not be bonded. The material to be immersed in the adhesive remover may be an article in which components (materials) are bonded by an adhesive. Heating may be performed during the process of removing the adhesive from the material. From the viewpoint of reducing energy usage and miniaturizing equipment, the method of immersing the material in the adhesive remover is more preferable. From the viewpoint of adhesive removal efficiency, the method of immersing and stirring is preferable.

[0069] (2-2. Cleaning process) It is preferable that the present removal method further includes a step of washing the material from which the adhesive has been removed with water, in other words, a step of washing with a water-based cleaning liquid. Note that the water-based cleaning liquid here means a cleaning liquid consisting of water or containing water. This makes it possible to wash away the adhesive remover that has soaked into the material, making it easier to handle the material.

[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 that the adhesive can be sufficiently removed from the material. In particular, when the temperature of the aqueous cleaning liquid is set to 40°C to 80°C, oil components can be easily washed away.

[0071] The aqueous cleaning liquid is not particularly limited, and may contain substances other than water as long as it can remove the adhesive remover from the material and can clean the material to such an extent that it can be reused. Since the aqueous cleaning liquid is preferably mainly composed of water, the weight of water relative to the total weight of water and substances other than water (total weight of the aqueous cleaning liquid) is preferably at least 60% by weight or more, 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. When an article contains a highly water-absorbent polymer and the highly water-absorbent polymer is not reused as a highly water-absorbent polymer, the aqueous cleaning liquid may further contain a water-repellent agent, etc., as a substance other than water. The concentration of the water-repellent agent in the aqueous cleaning liquid may be determined according to the amount of the highly water-absorbent polymer contained in the article whose constituent material is to be cleaned by immersing it in the aqueous cleaning liquid, 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-releasing agent in the aqueous cleaning solution, the water-absorbent polymer can be prevented 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, making handling easier. When the superabsorbent polymer is used for purposes other than water absorption (e.g., fuel, etc.), there is no problem even if the superabsorbent polymer contains a water-releasing agent, and handling is also easier, so it is preferable to include a water-releasing agent in the aqueous cleaning solution.

[0072] (2-3. Separation process) When the material in the article bonded with an adhesive contains a superabsorbent polymer, the 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 is attached using an adhesive remover. By providing the separation step without performing a step of washing with water 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 washing step using water 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 the material 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, and the material other than the superabsorbent polymer does not pass through the filter, so that the superabsorbent polymer and the material other than the superabsorbent polymer can be separated.

[0074] It is more preferable that the present removal method 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. Generally, crosslinked polyacrylic acid and its salts are used as superabsorbent polymers, and they have the property of absorbing water and swelling. When the superabsorbent polymer absorbs water, it becomes difficult to handle, so when washing with an aqueous cleaning solution, a water-releasing agent such as calcium chloride is used. However, when a water-releasing agent is used, the structure of the superabsorbent polymer changes and it becomes unable to absorb water (it is altered), so that it becomes 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 fabric, pulp, film) are preferably washed with an aqueous cleaning solution as described above in order to reduce the environmental load. The aqueous cleaning solution for washing materials other than the superabsorbent polymer can be the same as the aqueous cleaning solution described in the step of washing the material from which the adhesive has been removed. In addition, when the superabsorbent polymer is not reused or when there is no problem even if the superabsorbent polymer contains water, the material from which the adhesive has been removed may be washed with the above-mentioned aqueous cleaning solution without separating the material into the superabsorbent polymer and the material other than the superabsorbent polymer. In one embodiment, the present removal method includes an adhesive removal step of removing the adhesive from the material to which the adhesive of the article adheres, a separation step of separating the material from which the adhesive has been removed into the superabsorbent polymer and the material other than the superabsorbent polymer, and a washing step of washing the superabsorbent polymer separated in the separation step with an organic solvent. When the article is immersed in an organic solvent to remove the adhesive, the amount of organic solvent used is greater than that of the present removal method. In addition, in such a case, when reusing materials other than the superabsorbent polymer, such as nonwoven fabric, pulp, and film, the organic solvent cannot be easily removed, which requires a lot of work.

[0075] The organic solvent for washing the superabsorbent polymer separated in the separation step is not particularly limited in type, purity, etc., as long as it can wash away the adhesive remover soaked into the material and can wash the superabsorbent polymer to an extent that it can be reused. Examples of the organic solvent include polar solvents, nonpolar solvents, and mixtures thereof. Examples of 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. Examples of nonpolar solvents include aliphatic compounds such as hexane, cyclohexane, and limonene; and aromatic hydrocarbons such as toluene and xylene. From the viewpoint of the solubility of the adhesive remover, it is preferable that the organic solvent has a molecular weight of 200 or less. It is more preferable that the polar solvent is methanol or ethanol. It is more preferable that the nonpolar solvent is pentane, hexane, or cyclohexane.

[0076] The method of washing the superabsorbent polymer with an organic solvent may use one kind of organic solvent or multiple organic solvents, 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 and then washing with a nonpolar solvent, or washing with a nonpolar solvent and then washing with a polar solvent. When using a mixed solvent of a polar solvent and a nonpolar solvent, the ratio of the polar solvent to the nonpolar solvent may be 1:9 to 9:1 on a volume basis. As a method of washing the superabsorbent polymer with an organic solvent, it is preferable to wash the polymer by mixing a polar solvent and a nonpolar solvent or by using them stepwise. The step of washing with an organic solvent is usually carried out at room temperature, but may be heated appropriately.

[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 may include a method in which the object to be washed is stirred in an aqueous washing liquid or an organic solvent using a washing machine, stirring blades, agitator, etc. The number of washings is also not particularly limited, and may be one or more times.

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

[0079] [1] Contains oil and surfactants, 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 value of greater than 5 and being liquid at room temperature.

[0080] [2] The content of the oil is: The adhesive remover according to [1], wherein the content 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 one of [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 removing 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 cleaning the material from which the adhesive has been removed by the adhesive removal step with water.

[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 materials other than the highly water-absorbent polymer separated in the separation step. EXAMPLES

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

[0090] 〔material〕 In the following examples and comparative examples, the following materials were used:

[0091] ≪Oil≫ (vegetable oil) Soybean oil (iodine value 131): Kaneda Co., Ltd. Rice oil (iodine value 104): manufactured by Boso Oils and Fat Co., Ltd. Rapeseed oil (iodine value 110): Yonezawa Oil Mills Olive oil (iodine value 85): J-Oil Mills Linseed oil (iodine value 187): made by Nippon Flour Mills (Ester oil) DOS (bis(2-ethylhexyl) sebacate: 2 ester groups per molecule, SP value 9.1): New Japan Chemical Co., Ltd. ATBC (acetyl tributyl citrate: 4 ester groups per molecule, SP value 9.8): Taoka Chemical Co., Ltd. (Aliphatic carboxylic acids) Alkenylsuccinic anhydride (maleic acid modified α-olefin) (SP value 10.1): Seiko PMC, AS-1532 (Mineral oil) MORESCO White "P-200" (liquid paraffin: SP value 8.1): manufactured by MORESCO Cosmo Neutral 150 (aromatic mineral oil: SP value 8.7): Cosmo Oil Lubricants <Other> d-Limonene <Surfactants> (Nonionic surfactant) DKS NL 15 (HLB=5, liquid): Daiichi Kogyo Seiyaku Co., Ltd. DKS NL 30 (HLB=8, liquid): 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): Daiichi Kogyo Seiyaku Co., Ltd. DKS NL 450F (HLB=18, solid): Daiichi Kogyo Seiyaku Co., Ltd. (Anionic surfactants) Sulfol 430A (surfactant (sodium sulfonate) 65%, spin oil 30%, water 5%, liquid): MORESCO <Solvent> ·water <Water-releasing agent> Citric acid [Method of preparing evaluation samples] A hot melt adhesive (rubber-based, MORESCO) was applied to the first substrate (spunbond nonwoven fabric) using a ZIP coater (Suntool Co., Ltd.) at a coating temperature of 150°C. The coating amount was 5 g / m 2The width of application was 15 mm. Next, a second substrate (polyethylene film) was laminated on the surface of the first substrate on which the hot melt adhesive was applied, and pressure-bonded at 23°C to prepare a laminate. The time from when the hot melt adhesive was applied to the first substrate to when the second substrate was pressure-bonded and a laminate was prepared was 0.5 seconds. A sample of the obtained laminate was cut into 50 x 50 mm 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 Remover (Examples 1 to 19, Comparative Examples 1 to 8)] The oil and surfactant were weighed out in a predetermined amount into a glass container so as to obtain the ratio (parts by weight) shown in Tables 1 to 3. The mixture was stirred for 1 minute in a room temperature environment until no phase separation occurred, to obtain an adhesive remover. In addition, in Examples 5 and 11, in which Sulfol 430A was used as the surfactant, the surfactant (sodium sulfonate), oil, and water were contained in the Sulfol 430A used. Therefore, in Examples 5 and 11, the surfactant (sodium sulfonate) was blended so that the content of the surfactant relative to 100% by weight of the adhesive remover was 50% by weight.

[0093] [Removal of adhesive 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 hot water was added to the glass bottle and thoroughly stirred 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] (Adhesive remover mixture) ◎ (Excellent): The liquid is transparent when mixed. 〇 (Good): The liquid is uniform in the mixed state. △ (bad): The mixture separated after standing for 3 hours. × (Not acceptable): The mixture separates or becomes solid. (Peeling state of the evaluation sample after immersion in adhesive remover) ◯ (Good): Evaluation sample peeled off × (Fail): The evaluation sample does not peel off. (Surface condition of evaluation sample after cleaning) ◎ (Excellent): No slime 〇(Good): A small amount of slime × (Not acceptable): Slimy or residual hot melt adhesive present In this specification, the term "sliminess" refers to sliminess 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). [Table 1] [Table 2]

[0096] [Table 3] (Consideration) Table 1 shows the results of evaluating adhesive removers in which various surfactants were mixed with soybean oil (iodine value 131). In Examples 1 to 5, which used an anionic surfactant or a nonionic surfactant with an HLB value of more than 5 and which is liquid at room temperature, the adhesive could be sufficiently removed from the sample, and the adhesive remover could be removed from the substrate by washing. On the other hand, in Comparative Example 1, which used a nonionic surfactant with an HLB value of 5 or less, some of the oil and adhesive from the adhesive remover remained on the substrate after washing. In Comparative Example 2, which used a semi-solid nonionic surfactant, the adhesive also 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 in which various surfactants were mixed with various oils other than soybean oil. In Examples 6 to 9, which used vegetable oils with an iodine value of 70 to 160, the adhesive could be sufficiently removed from the samples, and the adhesive remover could be removed from the substrate after cleaning. In addition, in Examples 10 to 15, which used ester oils having two or less ester groups in one molecule, aliphatic carboxylic acids, and mineral oils, the results were similar. However, in Comparative Example 5, which used ATBC having three or more ester groups in one molecule, the adhesive could not be sufficiently removed, and the adhesive remained on the substrate after cleaning. Comparative Example 6, which used linseed oil alone with an iodine value of more than 160, is pyrophoric and difficult to handle, and is therefore unsuitable for the present invention.

[0098] From the results of Examples 16 to 19 and Comparative Example 7 in Table 3, it was found that the adhesive remover containing a surfactant could sufficiently remove the adhesive from the sample, and the adhesive remover could be washed off from the substrate after cleaning. This allows the collected articles to be easily reused as resources. On the other hand, Comparative Example 8 shows the results of an attempt to use the removal method of the present invention using a conventional terpene (d-limonene) aqueous solution. In the conventional technology, the centrifugal force of a washing machine is used to decompose articles to which adhesive is 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. In addition, the adhesive remained on the substrate even after the sample was cleaned, which shows that the conventional terpene aqueous solution cannot remove the adhesive from the substrate.

[0099] [Removing adhesive using an adhesive remover (disposable diapers)] (Adhesive removal) A commercially available disposable diaper for children, which was fixed 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 soaked for 1 hour. The diaper came loose in the adhesive remover, and the surface layer was separated.

[0100] (Washing with water) After lightly wringing the paper diaper out of the adhesive remover, the paper diaper was placed in a laundry net and put into a washing machine. 20 g of calcium chloride (water-releasing agent) was added to the washing tub, and 10 L of warm water at 60°C was added, and the paper diaper was stirred in the washing machine for 15 minutes. After the stirring, water was added, rinsing was performed twice, and the paper diaper was dehydrated for 5 minutes. The paper diaper was removed from the laundry net and evaluated. The paper diaper was separated into each substrate (material), and no adhesive or remover remained on each substrate (material), and there was no slime. This result was better than the result (Comparative Example 8) performed by the method described in Patent Document 1. It should be noted that the adhesive could be removed without stirring while the paper diaper was immersed in the adhesive remover, but it was possible to remove the adhesive in a short time by stirring during immersion. Since the highly absorbent polymer is altered by the water-releasing agent, it is difficult to reuse the highly absorbent polymer as a water-absorbing material, but since no adhesive or the like remains on the substrate, this is a treatment method suitable for reusing the substrate.

[0101] (Separation and washing of superabsorbent polymers and other materials) After soaking a baby's disposable diaper in the adhesive remover for 1 hour using the method described in (Adhesive Removal), the adhesive remover in which the disposable diaper was soaked was passed through a filter to separate it into the superabsorbent polymer (filtrate side) and materials other than the superabsorbent polymer (filter cake side). When the separated materials other than the superabsorbent polymer were washed with water in the same manner as described above, neither the adhesive nor the adhesive remover remained in each material, and there was no slime.

[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 remaining adhesive or adhesive remover was found.

[0103] When water was poured onto the superabsorbent polymer after it had been washed with an organic solvent, the 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] In addition, a paper diaper was immersed in the adhesive remover used in Examples 1 to 19 to remove the adhesive, and then the superabsorbent polymer was separated from the non-superabsorbent polymer. It was confirmed that the same good effect 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 60°C warm water (10 L). After agitation, water was added and the materials were rinsed twice and then dehydrated for 5 minutes. No adhesive or adhesive remover remained on any of the materials, and there was no slime or stickiness. [Industrial Applicability]

[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.

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