Method for separating adhesive and base material

Abstract

Provided is a method for easily separating an adhesive and a base material from a mixture containing the adhesive and the base material.　According to an embodiment of the present invention, a method for separating an adhesive and a base material involves: separating an adhesive and a base material from a mixture (A) containing the adhesive, the base material, and a first organic solvent; and performing at least one kind of operation selected from the group consisting of (i), (ii), and (iii). (i) Operation for stirring the mixture (A) in a saturated aqueous solution of the first organic solvent. (ii) Operation for stirring the mixture (A) in a liquid mixture in which at least one kind selected from the group consisting of a second organic solvent and a third organic solvent, in an amount exceeding a saturation amount is mixed with water. (iii) Operation for recovering an immersed mixture (B) obtained after the mixture (A) is immersed in the third organic solvent, and stirring the mixture (B) in water.

Description

How to separate adhesive and base material

[0001] The present invention relates to a method for separating a pressure-sensitive adhesive from a substrate.

[0002] Pressure-sensitive adhesive tapes are used in large quantities for attaching labels and the like to articles and packaging materials, for packing packaging materials, for use in the manufacturing processes of electronic and optical components, for masking purposes, etc. In particular, in recent years, the use of pressure-sensitive adhesive tapes in the manufacturing processes of electronic and optical components has been increasing, resulting in the generation of large amounts of waste pressure-sensitive adhesive tape at manufacturing sites and the like.

[0003] Waste adhesive tapes are usually disposed of by being incinerated or by being taken to a waste disposal site, but such disposal methods are not desirable from the viewpoints of reducing the environmental load and recycling resources.

[0004] Therefore, it is necessary to reduce the above-mentioned disposal of adhesive tape waste as much as possible and reuse resources. Recycling of adhesive tape materials is considered as a means to reduce the amount of waste disposal of adhesive tape. If recycling technology for adhesive tape materials can be established, it will lead to a reduction in CO2 emissions associated with fossil resource mining, and is expected to have a significant effect on solving the problem of climate change.

[0005] Typical materials for adhesive tapes include an adhesive and a substrate. Typically, adhesive tapes are obtained by dissolving a polymer (sometimes referred to as a base polymer) and additives such as a crosslinking agent in a solvent to form an adhesive composition, applying the adhesive composition to a substrate, and optionally heating and drying the composition to promote a crosslinking reaction, thereby forming an adhesive on the substrate (see, for example, Patent Document 1).

[0006] Japanese Patent Application Laid-Open No. 2021-175796

[0007] An object of the present invention is to provide a method for easily separating a pressure-sensitive adhesive and a substrate from a mixture containing the pressure-sensitive adhesive and the substrate.

[0008] [1] A method for separating a PSA and a substrate according to an embodiment of the present invention is a method for separating a PSA and a substrate from a mixture (A) containing the PSA, a substrate, and a first organic solvent, the method comprising: (i) stirring the mixture (A) in a saturated aqueous solution of the first organic solvent; (ii) stirring the mixture (A) in a mixed solution with water containing at least one organic solvent selected from the group consisting of a second organic solvent and a third organic solvent in an amount exceeding saturation; and (iii) immersing the mixture (A) in the third organic solvent, recovering the immersed mixture (B), and stirring the mixture (B) in water. [2] In the separation method described in [1] above, the first organic solvent may be an organic solvent having an HSP value of 10 to 45. [3] In the separation method according to [1] or [2] above, the second organic solvent may be an organic solvent having an HSP value of 10 to 45 and a solubility in water of more than 10 g / L and not more than 500 g / L at 20°C. [4] In the separation method according to any of [1] to [3] above, the third organic solvent may be an organic solvent having an HSP value of 10 to 45 and a solubility in water of not more than 10 g / L at 20°C. [5] In the separation method according to any of [1] to [4] above, the mixture may be allowed to stand after the stirring. [6] In the separation method according to any of [1] to [5] above, the pressure-sensitive adhesive may be a pressure-sensitive adhesive contained in a pressure-sensitive adhesive tape. [7] In the separation method according to any of [1] to [6] above, the substrate may be a substrate contained in a pressure-sensitive adhesive tape.

[0009] According to the present invention, it is possible to provide a method for easily separating a pressure-sensitive adhesive and a substrate from a mixture containing the pressure-sensitive adhesive and the substrate.

[0010] When the expression "weight" appears in this specification, it may be read as "mass," which is commonly used as an SI unit indicating weight.

[0011] In this specification, the term "specific gravity" refers to the commonly used specific gravity, which is the specific gravity when the specific gravity of water is taken as 1.

[0012] The method for separating a pressure-sensitive adhesive and a substrate according to an embodiment of the present invention is a method for separating the pressure-sensitive adhesive and the substrate from a mixture (A) containing the pressure-sensitive adhesive, the substrate, and a first organic solvent.

[0013] As the adhesive, any appropriate adhesive may be used as long as it does not impair the effects of the present invention. The adhesive may be of one type or two or more types. A typical example of such an adhesive is an acrylic adhesive.

[0014] As the acrylic pressure-sensitive adhesive, any appropriate acrylic pressure-sensitive adhesive may be employed as long as it does not impair the effects of the present invention. Representative examples of such acrylic pressure-sensitive adhesives include waste acrylic pressure-sensitive adhesives (sometimes referred to as "waste acrylic pressure-sensitive adhesives"). Examples of waste acrylic pressure-sensitive adhesives include acrylic pressure-sensitive adhesives contained in acrylic pressure-sensitive adhesive tapes collected after use, mixtures containing acrylic pressure-sensitive adhesives obtained by subjecting acrylic pressure-sensitive adhesive tapes collected after use to any appropriate treatment, acrylic pressure-sensitive adhesives that remain on adherends when the acrylic pressure-sensitive adhesive tape is peeled from the adherend to which the acrylic pressure-sensitive adhesive tape has been attached, and acrylic pressure-sensitive adhesives attached to acrylic pressure-sensitive adhesive manufacturing equipment.

[0015] As the substrate, any appropriate substrate can be adopted as long as the effects of the present invention are not impaired. The substrate may be one type only or two or more types. A representative example of such a substrate is a substrate contained in a pressure-sensitive adhesive tape.

[0016] Any appropriate substrate can be used as the substrate as long as it does not impair the effects of the present invention. Representative examples of such substrates include substrates that are waste (sometimes referred to as "waste substrates"). Examples of waste substrates include substrates contained in adhesive tapes collected after use, and mixtures containing substrates obtained by subjecting adhesive tapes collected after use to any appropriate treatment.

[0017] Any appropriate material can be used as the substrate material as long as it does not impair the effects of the present invention. A typical example of such a substrate material is a resin material.

[0018] Examples of resin materials that can be used as the substrate include acrylic resins such as polyimide (PI), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and polymethyl methacrylate (PMMA), polycarbonate, triacetyl cellulose (TAC), polysulfone, polyarylate, polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA), polyamide (nylon), wholly aromatic polyamide (aramid), polyvinyl chloride (PVC), polyvinyl acetate, polyphenylene sulfide (PPS), fluorine-based resins, and cyclic olefin polymers.

[0019] The adhesive tape may be used in the manufacture of electronic and optical components. During such manufacturing, the adhesive may remain on the adherend. In the method for separating the adhesive and the substrate according to an embodiment of the present invention, such an adherend may also be treated as the substrate. Any suitable adherend may be treated as the substrate as long as it is used as an adherend in the above-described manufacturing process. Examples of such an adherend include silicon wafers, ceramic semiconductors, and glass.

[0020] Any appropriate organic solvent can be used as the first organic solvent as long as it does not impair the effects of the present invention. The first organic solvent may be one type or two or more types. Typical examples of such first organic solvents include organic solvents having an HSP value of 10 to 45, and this HSP value is preferably 15 to 40, more preferably 15 to 35, even more preferably 15 to 30, and particularly preferably 15 to 25.

[0021] Examples of organic solvents having an HSP value of 10 to 45 include alcohols having an HSP value of 10 to 45, hydrocarbons having an HSP value of 10 to 45, ketones having an HSP value of 10 to 45, esters having an HSP value of 10 to 45, ethers having an HSP value of 10 to 45, amines having an HSP value of 10 to 45, nitriles having an HSP value of 10 to 45, carboxylic acids having an HSP value of 10 to 45, terpenes having an HSP value of 10 to 45, nitro compounds having an HSP value of 10 to 45, and halogen compounds having an HSP value of 10 to 45.

[0022] Examples of alcohols having an HSP value of 10 to 45 include methanol (HSP value = 29.4), ethanol (HSP value = 26.5), 1-propanol (HSP value = 24.6), 2-propanol (IPA) (HSP value = 23.6), 1-butanol (HSP value = 23.2), 1-pentanol (HSP value = 21.7), 1-hexanol (HSP value = 21.2), benzyl alcohol (HSP value = 23.8), diethylene glycol (HSP value = 27.9), dipropylene glycol (HSP value = 26.4), and benzyl alcohol (HSP value = 23.8).

[0023] Examples of hydrocarbons with an HSP value of 10 to 45 include benzene (HSP value = 18.5), toluene (HSP value = 18.2), styrene (HSP value = 19.1), hexane (HSP value = 14.9), cyclohexane (HSP value = 16.8), heptane (HSP value = 15.3), and methylcyclohexane (HSP value = 16.0).

[0024] Examples of ketones having an HSP value of 10 to 45 include acetone (HSP value = 19.9) and methyl ethyl ketone (HSP value = 19.1).

[0025] An example of an ester having an HSP value of 10 to 45 is ethyl acetate (HSP value = 18.2).

[0026] Examples of ethers having an HSP value of 10 to 45 include tetrahydrofuran (HSP value=19.5) and cyclopentyl methyl ether (HSP value=17.8).

[0027] An example of an amine having an HSP value of 10 to 45 is aniline (HSP value = 23.7).

[0028] An example of a nitrile having an HSP value of 10 to 45 is acetonitrile (HSP value = 24.4).

[0029] An example of a carboxylic acid having an HSP value of 10 to 45 is acetic acid (HSP value = 21.4).

[0030] Terpenes having an HSP value of 10 to 45 include, for example, d-limonene (HSP value = 17.8).

[0031] An example of a nitro compound having an HSP value of 10 to 45 is nitrobenzene (HSP value = 22.8).

[0032] Examples of halogen compounds having an HSP value of 10 to 45 include chloroform (HSP value=18.9) and carbon tetrachloride (HSP value=17.8).

[0033] The HSP value is the "Hansen solubility parameter value", and is calculated by multiplying the Hildebrand solubility parameter value by the dispersion term (δ D ), polar term (δ P ), and the hydrogen bond term (δ H ) and the parameter value takes into account the polarity of the substance. The dispersion term (term related to van der Waals forces), polar term (term related to dipole moments), and hydrogen bond term (term related to hydrogen bonds) can be expressed in three-dimensional coordinates.

[0034] The Hansen solubility parameter value of a mixture of two or more liquids can be calculated from the volume fractions of the dispersion term, polar term, and hydrogen bond term of each solvent, as shown in the following formula (1). D1 and δ D2 is the dispersion term of each liquid component, δ P1 and δ P2 is the polarity term of each liquid component, δ H1 and δ H2 is the hydrogen bond term of each liquid component, and φ1 and φ2 are the volume fractions of each liquid component. m = {(δ D1 φ1+δD2 φ2) 2 + (δ P1 φ1+δ P2 φ2) 2 + (δ H1 φ1+δ H2 φ2) 2} 1 / 2 ...(1)

[0035] The Hansen Solubility Parameter values ​​for each solvent are included in "HSPiP Version 5." For solvents not included, the values ​​estimated by "HSPiP Version 5" are used.

[0036] In the method for separating a pressure-sensitive adhesive and a substrate according to an embodiment of the present invention, the mixture (A) containing a pressure-sensitive adhesive, a substrate, and a first organic solvent may have any appropriate composition and content ratio as long as it contains the pressure-sensitive adhesive and substrate to be separated, and also the first organic solvent, as long as the effects of the present invention are not impaired.

[0037] One embodiment of the mixture (A) is a mixture obtained by impregnating a pressure-sensitive adhesive tape containing a pressure-sensitive adhesive and a substrate with a pressure-sensitive adhesive treatment liquid containing a first organic solvent. Here, "impregnating with a pressure-sensitive adhesive treatment liquid" refers to impregnating the pressure-sensitive adhesive contained in the pressure-sensitive adhesive tape with the pressure-sensitive adhesive treatment liquid, for example, by immersing at least a portion of the pressure-sensitive adhesive in the pressure-sensitive adhesive treatment liquid. This is because the pressure-sensitive adhesive treatment liquid penetrates into the pressure-sensitive adhesive when at least a portion of the pressure-sensitive adhesive is immersed in the pressure-sensitive adhesive treatment liquid. Therefore, the entire pressure-sensitive adhesive tape may be immersed in the pressure-sensitive adhesive treatment liquid, or at least a portion of the pressure-sensitive adhesive tape and at least a portion of the pressure-sensitive adhesive may be immersed in the pressure-sensitive adhesive treatment liquid.

[0038] The pressure-sensitive adhesive treatment liquid containing the first organic solvent may have any appropriate composition and content ratio as long as it contains the first organic solvent, as long as the effects of the present invention are not impaired.

[0039] One embodiment of the pressure-sensitive adhesive treatment liquid containing the first organic solvent contains the first organic solvent, water, and an alkaline compound.

[0040] The total content of the first organic solvent, water, and alkaline compound in the PSA treatment liquid containing the first organic solvent is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, even more preferably 90% by weight to 100% by weight, particularly preferably 95% by weight to 100% by weight, and most preferably 98% by weight to 100% by weight, in terms of being able to further exhibit the effects of the present invention.

[0041] In the PSA treatment liquid containing the first organic solvent, the content of water when the total of the first organic solvent and water is taken as 100% by volume is preferably 15% by volume to 99.9% by volume, more preferably 25% by volume to 99.9% by volume, even more preferably 55% by volume to 99.9% by volume, particularly preferably 65% ​​by volume to 99.9% by volume, and most preferably 85% by volume to 99.9% by volume, in order to further exhibit the effects of the present invention.

[0042] In the PSA treatment liquid containing the first organic solvent, when the total of the first organic solvent and water is taken as 100% by volume, the content of the first organic solvent is preferably 0.1% by volume to 85% by volume, more preferably 0.1% by volume to 75% by volume, even more preferably 0.1% by volume to 45% by volume, particularly preferably 0.1% by volume to 35% by volume, and most preferably 0.1% by volume to 15% by volume, in order to further exhibit the effects of the present invention.

[0043] The concentration of the alkaline compound in the PSA treatment liquid containing the first organic solvent is preferably 0.001% by weight to 50% by weight, more preferably 1% by weight to 30% by weight, even more preferably 1% by weight to 15% by weight, particularly preferably 1% by weight to 10% by weight, and most preferably 1% by weight to 5% by weight, in terms of being able to further exhibit the effects of the present invention.

[0044] When the mixture (A) is a mixture obtained by impregnating a pressure-sensitive adhesive tape containing a pressure-sensitive adhesive and a substrate with a pressure-sensitive adhesive treatment solution containing a first organic solvent, the impregnation is preferably performed by at least one method selected from the group consisting of stirring and ultrasonic irradiation, whereby the first organic solvent is dispersed in water, and the pressure-sensitive adhesive can be selectively and efficiently impregnated with the first organic solvent in the pressure-sensitive adhesive treatment solution, thereby improving the separation efficiency of the pressure-sensitive adhesive.

[0045] As a stirring method, any appropriate stirring method can be adopted depending on the type of adhesive, etc., as long as the effects of the present invention are not impaired. As for the stirring time, any appropriate stirring time can be adopted depending on the type of adhesive, etc., as long as the effects of the present invention are not impaired.

[0046] As the method of ultrasonic irradiation, any appropriate ultrasonic irradiation method can be adopted depending on the type of adhesive, etc., as long as the effects of the present invention are not impaired. As for the time of ultrasonic irradiation, any appropriate ultrasonic irradiation time can be adopted depending on the type of adhesive, etc., as long as the effects of the present invention are not impaired.

[0047] When the mixture (A) is a mixture obtained by impregnating a pressure-sensitive adhesive tape containing a pressure-sensitive adhesive and a substrate with a pressure-sensitive adhesive treatment liquid containing a first organic solvent, any appropriate temperature can be adopted for the temperature during the impregnation as long as the effects of the present invention are not impaired. Such a temperature is preferably 10°C or higher, more preferably 15°C or higher, even more preferably 20°C or higher, even more preferably 25°C or higher, even more preferably 30°C or higher, and particularly preferably 35°C or higher, from the viewpoint of being able to further exhibit the effects of the present invention, and the upper limit is preferably 120°C or lower, more preferably 100°C or lower, and even more preferably 80°C or lower.

[0048] When mixture (A) is a mixture obtained by impregnating a pressure-sensitive adhesive tape containing a pressure-sensitive adhesive and a substrate with a pressure-sensitive adhesive treatment liquid containing a first organic solvent, the amount of the pressure-sensitive adhesive treatment liquid containing the first organic solvent used per 100 parts by weight of the pressure-sensitive adhesive tape is preferably 100 to 6,000 parts by weight, more preferably 200 to 3,000 parts by weight, even more preferably 200 to 1,000 parts by weight, particularly preferably 200 to 800 parts by weight, and most preferably 200 to 400 parts by weight.

[0049] In one typical embodiment of the mixture (A), the PSA is impregnated with a first organic solvent (hereinafter referred to as a "first organic solvent-impregnated PSA"). Accordingly, one typical embodiment of the mixture (A) is a first organic solvent-impregnated PSA that includes a PSA, a substrate, and a first organic solvent, and the PSA is impregnated with at least a portion of the first organic solvent. The amount of the first organic solvent impregnated in the first organic solvent-impregnated PSA can vary depending on factors such as the type and amount of the PSA, the type and amount of the first organic solvent, the composition of the PSA treatment liquid, and the conditions for impregnation with the PSA treatment liquid.

[0050] A method for separating a PSA and a substrate according to an embodiment of the present invention is a method for separating a PSA and a substrate from a mixture (A) containing the PSA, the substrate, and a first organic solvent, and includes at least one operation selected from the group consisting of the following (i), (ii), and (iii): (i) an operation of stirring the mixture (A) in a saturated aqueous solution of the first organic solvent; (ii) an operation of stirring the mixture (A) in a mixed solution with water containing at least one organic solvent selected from the group consisting of a second organic solvent and a third organic solvent in an amount exceeding saturation; and (iii) an operation of immersing the mixture (A) in the third organic solvent, recovering the immersed mixture (B), and stirring the mixture (B) in water.

[0051] In each of the above steps (i) to (iii), the mixture may be allowed to stand after stirring.

[0052] In the method for separating a PSA and a substrate according to an embodiment of the present invention, after each of the above steps (i) to (iii), the separated PSA (which may be an organic solvent-impregnated PSA in which the PSA is impregnated with an organic solvent) and the substrate may be separated and recovered, and may be dried or washed, as necessary. In addition, water and the organic solvent may be separated and recovered, as necessary.

[0053] Each of the operations (i) to (iii) will be described below.

[0054] <<Operation (i)>> In operation (i), a mixture (A) containing a PSA, a substrate, and a first organic solvent is stirred in a saturated aqueous solution of the first organic solvent. That is, in operation (i), the mixture (A) is stirred in a saturated aqueous solution of the same first organic solvent as the first organic solvent contained therein. Note that in the "saturated aqueous solution of the first organic solvent," water and the first organic solvent are typically in a compatible state.

[0055] In the step (i), the content of the mixture (A) in the saturated aqueous solution of the first organic solvent is preferably 0.1% by weight to 80% by weight, more preferably 0.1% by weight to 50% by weight, even more preferably 0.1% by weight to 20% by weight, and particularly preferably 0.1% by weight to 5% by weight, in terms of being able to further exhibit the effects of the present invention.

[0056] In step (i), when a mixture (A) containing a pressure-sensitive adhesive, a substrate, and a first organic solvent is stirred in a saturated aqueous solution of the first organic solvent, the first organic solvent impregnated in the pressure-sensitive adhesive, i.e., the first organic solvent, can be apparently retained in the pressure-sensitive adhesive in the saturated aqueous solution of the first organic solvent under stirring (the same state occurs even if the first organic solvent is replaced with the first organic solvent contained in the saturated aqueous solution of the first organic solvent). In this way, if the first organic solvent impregnated in the first organic solvent-impregnated pressure-sensitive adhesive can be retained, re-adhesion between the pressure-sensitive adhesive and the substrate can be effectively suppressed. If the first organic solvent impregnated in the first organic solvent-impregnated pressure-sensitive adhesive is dissolved, the pressure-sensitive adhesive may aggregate and solidify during mixing with water, which may cause re-adhesion to the substrate.

[0057] In step (i), in order to facilitate separation of the first organic solvent-impregnated PSA from the substrate, the specific gravity of the PSA before being impregnated with the first organic solvent is preferably 0.5 to 2.5, more preferably 0.5 to 2.0, even more preferably 0.5 to 1.8, and particularly preferably 0.5 to 1.5.

[0058] <<Embodiment (i-1)>> As a representative embodiment (i-1) of the procedure (i), an embodiment in which 1-butanol (HSP value = 23.2, specific gravity = 0.81) is used as the first organic solvent will be described below. Note that the procedure (i) is not limited to the case in which 1-butanol is used as the first organic solvent.

[0059] In embodiment (i-1), the mixture (A) contains a PSA, a substrate, and 1-butanol, and is typically a PSA impregnated with at least a portion of the 1-butanol (hereinafter referred to as a "1-butanol-impregnated PSA").

[0060] In embodiment (i-1), the 1-butanol impregnated in the 1-butanol-impregnated PSA can be apparently retained in the PSA in a saturated aqueous solution of 1-butanol under stirring (the same state occurs even if the 1-butanol is replaced with 1-butanol contained in the saturated aqueous solution of 1-butanol). In this way, if the 1-butanol impregnated in the 1-butanol-impregnated PSA can be retained, re-adhesion between the PSA and the substrate can be effectively suppressed. If the 1-butanol impregnated in the 1-butanol-impregnated PSA elutes, the PSA may aggregate and solidify in the aqueous solution, potentially causing re-adhesion to the substrate.

[0061] Therefore, in embodiment (i-1), when mixture (A) is stirred in a saturated aqueous solution of 1-butanol (typically, water / 1-butanol = 92 / 8 (weight ratio)), the 1-butanol-impregnated PSA may be present in the saturated aqueous solution of 1-butanol. If the specific gravity of the 1-butanol-impregnated PSA is smaller than that of the saturated aqueous solution of 1-butanol, the 1-butanol-impregnated PSA will float in the saturated aqueous solution of 1-butanol.

[0062] In order to allow the 1-butanol-impregnated PSA to easily float in a saturated aqueous solution of 1-butanol, the specific gravity of the PSA before being impregnated with 1-butanol is preferably 0.5 to 2.0, more preferably 0.5 to 1.5, even more preferably 0.5 to 1.3, and particularly preferably 0.5 to 1.1.

[0063] On the other hand, in embodiment (i-1), when mixture (A) contains, as a substrate, a substrate having a specific gravity greater than that of a saturated aqueous solution of 1-butanol (for example, a polyethylene terephthalate (PET) substrate), the substrate will sink in the saturated aqueous solution of 1-butanol.

[0064] Thus, in operation (i), the PSA and the substrate in the mixture (A) are separated due to the difference in specific gravity in the saturated aqueous solution of the first organic solvent. The PSA and the substrate separated in the saturated aqueous solution of the first organic solvent are separated and recovered by any appropriate method (for example, recovery of the supernatant using the overflow caused by adding an excess amount of the saturated aqueous solution of the first organic solvent).

[0065] In operation (i), particularly when the specific gravity of the first organic solvent-impregnated adhesive is smaller than the specific gravity of a saturated aqueous solution of the first organic solvent and the specific gravity of the substrate is larger than the specific gravity of a saturated aqueous solution of the first organic solvent, the first organic solvent-impregnated adhesive floats up and the substrate sinks, enabling efficient separation.

[0066] <<Operation (ii)>> In operation (ii), a mixture (A) containing a pressure-sensitive adhesive, a substrate, and a first organic solvent is stirred in a mixed solution with water containing at least one organic solvent selected from the group consisting of a second organic solvent and a third organic solvent in an amount exceeding saturation. Note that "a mixed solution with water containing at least one organic solvent selected from the group consisting of a second organic solvent and a third organic solvent in an amount exceeding saturation" refers to a mixed solution of at least one organic solvent selected from the group consisting of a second organic solvent and a third organic solvent and water, in which the amount of at least one organic solvent selected from the group consisting of the second organic solvent and the third organic solvent exceeds the saturation amount relative to water. Furthermore, in the "mixed solution with water containing at least one organic solvent selected from the group consisting of a second organic solvent and a third organic solvent in an amount exceeding saturation," water and at least one organic solvent selected from the group consisting of the second organic solvent and the third organic solvent are in a phase-separated state.

[0067] In the step (ii), the content of the mixture (A) in the mixed solution containing at least one selected from the group consisting of the second organic solvent and the third organic solvent in an amount exceeding the saturation amount with water is preferably 0.1% by weight to 80% by weight, more preferably 0.1% by weight to 50% by weight, even more preferably 0.1% by weight to 20% by weight, and particularly preferably 0.1% by weight to 5% by weight, in order to further exhibit the effects of the present invention.

[0068] Any appropriate organic solvent can be used as the second organic solvent as long as it does not impair the effects of the present invention. The second organic solvent may be a single type or two or more types. Typical examples of such second organic solvents include organic solvents having an HSP value of 10 to 45 and a water solubility of more than 10 g / L and not more than 500 g / L at 20°C. The HSP value is preferably 15 to 40, more preferably 15 to 35, even more preferably 15 to 30, and particularly preferably 15 to 25. The water solubility at 20°C is preferably 15 g / L to 400 g / L, more preferably 20 g / L to 300 g / L, particularly preferably 25 g / L to 200 g / L, and most preferably 30 g / L to 100 g / L.

[0069] The second organic solvent is typically a slightly water-soluble organic solvent that is slightly soluble in water, as described above.

[0070] Examples of the second organic solvent include 1-butanol (HSP value = 23.2, solubility in water = 77 g / L (20°C), specific gravity = 0.81), benzyl alcohol (HSP value = 23.8, solubility in water = 35 g / L (25°C), specific gravity = 1.04), and ethyl acetate (HSP value = 18.2, solubility in water = 83 g / L (20°C), specific gravity = 0.90).

[0071] Any appropriate organic solvent can be used as the third organic solvent as long as it does not impair the effects of the present invention. The third organic solvent may be one type only, or two or more types. Representative examples of such third organic solvents include organic solvents having an HSP value of 10 to 45 and a solubility in water of 10 g / L or less at 20°C. The HSP value is preferably 15 to 40, more preferably 15 to 35, even more preferably 15 to 30, and particularly preferably 15 to 25. The solubility in water at 20°C is preferably 0 g / L to 9 g / L.

[0072] The third organic solvent is typically a water-insoluble organic solvent that is hardly soluble in water, as described above.

[0073] Examples of the third organic solvent include toluene (HSP value = 18.2, solubility in water = 526 mg / L (25°C), specific gravity = 0.87), nitrobenzene (HSP value = 22.8, solubility in water = 1.8 g / L (25°C), specific gravity = 1.21), chloroform (HSP value = 18.9, solubility in water = 8 g / L (20°C), specific gravity = 1.48), and carbon tetrachloride (HSP value = 17.8, solubility in water = 800 mg / L (20°C), specific gravity = 1.63).

[0074] When the second organic solvent is the same as the first organic solvent, if a mixture (A) containing a PSA, a substrate, and the first organic solvent is stirred in a mixture containing water containing the second organic solvent at a level exceeding saturation, the first organic solvent impregnated in the PSA, i.e., the first organic solvent, can be apparently retained in the PSA in the mixture with water containing the second organic solvent (=first organic solvent) at a level exceeding saturation under stirring (the same state occurs even if the second organic solvent (=first organic solvent) is replaced). In this way, if the first organic solvent impregnated in the first organic solvent-impregnated PSA can be retained, reattachment between the PSA and the substrate can be effectively suppressed. If the first organic solvent impregnated in the first organic solvent-impregnated PSA is dissolved, the PSA may aggregate and solidify during mixing with water, potentially causing reattachment to the substrate.

[0075] On the other hand, when the second organic solvent is different from the first organic solvent, when a mixture (A) containing a PSA, a substrate, and the first organic solvent is stirred in a mixture containing water containing the second organic solvent at a level exceeding saturation, the first organic solvent impregnated in the PSA, i.e., the first organic solvent impregnated in the first organic solvent-impregnated PSA, may be replaced by the second organic solvent in the mixture containing water at a level exceeding saturation under stirring. In this way, when the first organic solvent impregnated in the first organic solvent-impregnated PSA is replaced by the second organic solvent, the PSA still retains the organic solvent, effectively suppressing re-adhesion between the PSA and the substrate. If the first organic solvent impregnated in the first organic solvent-impregnated PSA is not dissolved and replaced by the second organic solvent, the PSA may aggregate and solidify during the mixture containing water, potentially causing re-adhesion to the substrate.

[0076] Similarly, when the third organic solvent is the same as the first organic solvent, when a mixture (A) containing a PSA, a substrate, and the first organic solvent is stirred in a mixture containing water containing the third organic solvent at a level exceeding saturation, the first organic solvent impregnated in the PSA, i.e., the first organic solvent, can be apparently retained in the PSA in the mixture with water containing the third organic solvent (=first organic solvent) at a level exceeding saturation under stirring (the same state occurs even if the third organic solvent (=first organic solvent) is replaced). In this way, if the first organic solvent impregnated in the first organic solvent-impregnated PSA can be retained, reattachment between the PSA and the substrate can be effectively suppressed. If the first organic solvent impregnated in the first organic solvent-impregnated PSA is dissolved, the PSA may aggregate and solidify during the mixture containing water, potentially causing reattachment to the substrate.

[0077] On the other hand, if the third organic solvent is different from the first organic solvent, when a mixture (A) containing a PSA, a substrate, and the first organic solvent is stirred in a mixture with water containing the third organic solvent at a level exceeding saturation, the first organic solvent impregnated in the PSA, i.e., the first organic solvent, may be replaced by the third organic solvent in the mixture with water containing the third organic solvent at a level exceeding saturation under stirring. In this way, when the first organic solvent impregnated in the first organic solvent-impregnated PSA is replaced by the third organic solvent, the PSA still retains the organic solvent, effectively suppressing reattachment between the PSA and the substrate. If the first organic solvent impregnated in the first organic solvent-impregnated PSA is not dissolved and replaced by the third organic solvent, the PSA may aggregate and solidify during mixing with water, potentially causing reattachment to the substrate.

[0078] <<Embodiment (ii-1)>> As a representative embodiment (ii-1) of operation (ii), an embodiment employing 1-butanol (HSP value = 23.2, solubility in water = 77 g / L (20°C), specific gravity = 0.81) as the second organic solvent will be described below. In addition, in this embodiment (ii-1), a mixture containing a PSA, a substrate, and 1-butanol will be described as a representative example of mixture (A).

[0079] Note that the procedure (ii) is not limited to the case where 1-butanol is used as the second organic solvent, and the procedure (ii) is not limited to the case where the mixture (A) contains a pressure-sensitive adhesive, a substrate, and 1-butanol.

[0080] In embodiment (ii-1), the mixture (A) contains a pressure-sensitive adhesive, a substrate, and 1-butanol, and typically the pressure-sensitive adhesive is a 1-butanol-impregnated pressure-sensitive adhesive.

[0081] In embodiment (ii-1), the 1-butanol impregnated in the 1-butanol-impregnated PSA can be apparently retained in the PSA when the PSA is stirred in a mixed solution with water containing 1-butanol in excess of the saturation amount (the same state occurs even if the 1-butanol in the mixed solution is replaced). Thus, if the 1-butanol impregnated in the 1-butanol-impregnated PSA can be retained, re-adhesion between the PSA and the substrate can be effectively suppressed. If the 1-butanol impregnated in the 1-butanol-impregnated PSA elutes, the PSA may aggregate and solidify in the aqueous solution, potentially causing re-adhesion to the substrate.

[0082] Therefore, in embodiment (ii-1), when mixture (A) is stirred in a mixed solution with water containing 1-butanol in excess of the saturation amount (for example, water / 1-butanol = 90 / 10 (weight ratio)), a 1-butanol-impregnated PSA may be present in the mixed solution with water containing 1-butanol in excess of the saturation amount. When a mixed solution with water containing 1-butanol in excess of the saturation amount is allowed to stand, it may form two layers, with an upper layer being 1-butanol and a lower layer being a saturated aqueous solution of 1-butanol. The specific gravity of the 1-butanol-impregnated PSA is almost always greater than the specific gravity of 1-butanol. In such cases, if the supernatant of 1-butanol is a very thin film, as in the Examples described below, the 1-butanol-impregnated PSA will appear to float. On the other hand, there are also cases where the specific gravity of the 1-butanol-impregnated PSA is smaller than the specific gravity of 1-butanol. In such cases, the 1-butanol-impregnated PSA will float in a mixed solution with water containing 1-butanol in excess of the saturation amount.

[0083] In embodiment (ii-1), in order to allow the 1-butanol-impregnated PSA to easily float in a mixed solution with water containing 1-butanol in an amount exceeding saturation, the PSA has a specific gravity of preferably 0.5 to 2.0, more preferably 0.5 to 1.5, even more preferably 0.5 to 1.3, and particularly preferably 0.5 to 1.1.

[0084] On the other hand, in embodiment (ii-1), when mixture (A) contains, as a substrate, a substrate having a larger specific gravity than a saturated aqueous solution of 1-butanol (for example, a polyethylene terephthalate (PET) substrate), the substrate will settle in a mixed liquid with water containing 1-butanol in an amount exceeding the saturation amount.

[0085] Thus, in embodiment (ii-1), the PSA and the substrate in mixture (A) are separated due to the difference in specific gravity in a mixed solution with water containing 1-butanol in excess of the saturation amount. The PSA and the substrate separated in the mixed solution with water containing 1-butanol in excess of the saturation amount are separated and recovered by any appropriate method (for example, recovery of the supernatant using the overflow caused by the excessive addition of a mixed solution with water containing 1-butanol in excess of the saturation amount).

[0086] In operation (ii-1), particularly when the specific gravity of the first organic solvent-impregnated pressure-sensitive adhesive is greater than that of the first organic solvent, the layer of the first organic solvent that exceeds the saturated amount is made thin, or when the specific gravity of the first organic solvent-impregnated pressure-sensitive adhesive is less than that of the first organic solvent and the specific gravity of the substrate is greater than that of a saturated aqueous solution of the first organic solvent, the first organic solvent-impregnated pressure-sensitive adhesive floats to the top and the substrate sinks, enabling efficient separation.

[0087] <<Embodiment (ii-2)>> As another representative embodiment (ii-2) of operation (ii), an embodiment in which benzyl alcohol (HSP value = 23.8, solubility in water = 35 g / L (25°C), specific gravity = 1.04) is used as the second organic solvent will be described below. Furthermore, in this embodiment (ii-2), a mixture containing a PSA, a substrate, and 1-butanol will be used as a representative example of mixture (A) for the description.

[0088] Note that the procedure (ii) is not limited to the case where benzyl alcohol is used as the second organic solvent, and the procedure (ii) is not limited to the case where the mixture (A) contains a pressure-sensitive adhesive, a substrate, and 1-butanol.

[0089] In embodiment (ii-2), the mixture (A) contains a pressure-sensitive adhesive, a substrate, and 1-butanol, and typically the pressure-sensitive adhesive is a 1-butanol-impregnated pressure-sensitive adhesive.

[0090] In embodiment (ii-2), the 1-butanol impregnated in the 1-butanol-impregnated PSA may be replaced by benzyl alcohol in a mixed solution containing benzyl alcohol in excess of the saturation amount under stirring with water (hereinafter, the PSA after replacement is referred to as the "benzyl alcohol-impregnated PSA"). When the 1-butanol impregnated in the 1-butanol-impregnated PSA is replaced with benzyl alcohol in this way, the PSA still retains the organic solvent, effectively preventing re-adhesion between the PSA and the substrate. If the 1-butanol impregnated in the 1-butanol-impregnated PSA is not dissolved and replaced by benzyl alcohol, the PSA may aggregate and solidify in the mixture containing water, potentially causing re-adhesion to the substrate.

[0091] Therefore, in embodiment (ii-2), when mixture (A) is stirred in a mixed solution with water containing benzyl alcohol in excess of the saturation level (for example, water / benzyl alcohol = 50 / 50 (weight ratio)), the benzyl alcohol-impregnated PSA may be present in the mixed solution with water containing benzyl alcohol in excess of the saturation level. When the mixed solution with water containing benzyl alcohol in excess of the saturation level is allowed to stand, it may form two layers: an upper layer is a saturated aqueous solution of benzyl alcohol and a lower layer is benzyl alcohol. Therefore, embodiment (ii-2) can be separated into the following two modes. <Separation Mode 1> When the specific gravity of the benzyl alcohol-impregnated PSA is smaller than that of the saturated aqueous solution of benzyl alcohol and the specific gravity of the substrate is larger than that of benzyl alcohol, the benzyl alcohol-impregnated PSA floats to the top and the substrate sinks. <Separation Form 2> When the specific gravity of the benzyl alcohol-impregnated adhesive is greater than that of benzyl alcohol and the specific gravity of the substrate is less than that of a saturated aqueous solution of benzyl alcohol, the benzyl alcohol-impregnated adhesive settles and the substrate floats up.

[0092] Thus, in embodiment (ii-2), the PSA and the substrate in mixture (A) are separated due to the difference in specific gravity in a mixed solution with water containing benzyl alcohol in excess of the saturation amount. The PSA and the substrate separated in the mixed solution with water containing benzyl alcohol in excess of the saturation amount are separated and recovered by any appropriate method (for example, recovery of the supernatant using the overflow caused by the addition of an excess of a mixed solution with water containing benzyl alcohol in excess of the saturation amount).

[0093] As described above, in embodiment (ii-2), particularly, (1) when the specific gravity of the second organic solvent-impregnated pressure-sensitive adhesive is smaller than that of a saturated aqueous solution of the second organic solvent and the specific gravity of the substrate is larger than that of the second organic solvent, the second organic solvent-impregnated pressure-sensitive adhesive floats up and the substrate sinks, or (2) when the specific gravity of the second organic solvent-impregnated pressure-sensitive adhesive is larger than that of the second organic solvent and the specific gravity of the substrate is smaller than that of a saturated aqueous solution of the second organic solvent, the second organic solvent-impregnated pressure-sensitive adhesive sinks and the substrate floats up, enabling efficient separation.

[0094] In embodiment (ii-2), in order to allow the second organic solvent-impregnated PSA to easily float in a mixed liquid with water containing the second organic solvent in an amount exceeding saturation, the PSA has a specific gravity of preferably 0.5 to 1.0, more preferably 0.5 to 0.9, even more preferably 0.5 to 0.8, and particularly preferably 0.5 to 0.7.

[0095] In embodiment (ii-2), in order to allow the second organic solvent-impregnated PSA to easily precipitate in a mixed liquid with water containing the second organic solvent in an amount exceeding saturation, the PSA has a specific gravity of preferably 1.0 to 2.5, more preferably 1.1 to 2.5, even more preferably 1.2 to 2.5, and particularly preferably 1.3 to 2.5.

[0096] <<Embodiment (ii-3)>> As yet another representative embodiment (ii-3) of operation (ii), an embodiment in which chloroform (HSP value = 18.9, solubility in water = 8 g / L (20°C), specific gravity = 1.48) is used as the third organic solvent will be described below. Furthermore, in this embodiment (ii-3), a representative example of mixture (A) will be described as containing a pressure-sensitive adhesive, a substrate, and 1-butanol.

[0097] Note that the procedure (ii) is not limited to the case where chloroform is used as the third organic solvent, and the procedure (ii) is not limited to the case where the mixture (A) contains a pressure-sensitive adhesive, a substrate, and 1-butanol.

[0098] In embodiment (ii-3), the mixture (A) contains a pressure-sensitive adhesive, a substrate, and 1-butanol, and typically the pressure-sensitive adhesive is a 1-butanol-impregnated pressure-sensitive adhesive.

[0099] In embodiment (ii-3), the 1-butanol impregnated in the 1-butanol-impregnated PSA may be replaced with chloroform in a mixed solution containing water and chloroform exceeding the saturation level under stirring (hereinafter, the PSA after the replacement is referred to as a "chloroform-impregnated PSA"). In this way, when the 1-butanol impregnated in the 1-butanol-impregnated PSA is replaced with chloroform, the PSA still retains the organic solvent, which can effectively prevent re-adhesion between the PSA and the substrate. If the 1-butanol impregnated in the 1-butanol-impregnated PSA is not dissolved and replaced with chloroform, the PSA may aggregate and solidify in the mixture containing water, potentially causing re-adhesion to the substrate.

[0100] Therefore, in embodiment (ii-3), when mixture (A) is stirred in a mixed solution with water containing chloroform in excess of saturation (for example, water / chloroform = 50 / 50 (weight ratio)), the chloroform-impregnated PSA may be present in the mixed solution with water containing chloroform in excess of saturation. When the mixed solution with water containing chloroform in excess of saturation is allowed to stand, it may become two layers, with an upper layer being a saturated aqueous solution of chloroform and a lower layer being chloroform. Therefore, embodiment (ii-3) may have the following two separation modes. <Separation Mode 1> When the specific gravity of the chloroform-impregnated PSA is greater than that of chloroform and the specific gravity of the substrate is less than that of a saturated aqueous solution of chloroform, the chloroform-impregnated PSA will settle and the substrate will float. <Separation Form 2> When the specific gravity of the chloroform-impregnated adhesive is smaller than that of a saturated aqueous solution of chloroform and the specific gravity of the substrate is larger than that of chloroform, the chloroform-impregnated adhesive floats to the surface and the substrate sinks.

[0101] In embodiment (ii-3), when the mixture is left to stand after stirring, it may float near the interface between the upper layer (a saturated aqueous solution of chloroform) and the lower layer (chloroform). In this case, the mixture can be separated by stirring the mixture without leaving it to stand.

[0102] Thus, in embodiment (ii-3), the PSA and the substrate in mixture (A) are separated due to the difference in specific gravity in a mixed solution with water containing chloroform in excess of the saturation amount. The PSA and the substrate separated in the mixed solution with water containing chloroform in excess of the saturation amount are separated and recovered by any appropriate method (for example, recovery of the supernatant using the overflow caused by the addition of an excess of a mixed solution with water containing chloroform in excess of the saturation amount).

[0103] As described above, in embodiment (ii-3), particularly, (1) when the specific gravity of the third organic solvent-impregnated pressure-sensitive adhesive is greater than that of the third organic solvent and the specific gravity of the substrate is less than that of a saturated aqueous solution of the third organic solvent, the third organic solvent-impregnated pressure-sensitive adhesive sinks and the substrate floats, or (2) when the specific gravity of the third organic solvent-impregnated pressure-sensitive adhesive is less than that of a saturated aqueous solution of the third organic solvent and the specific gravity of the substrate is greater than that of the third organic solvent, the third organic solvent-impregnated pressure-sensitive adhesive floats and the substrate sinks, thereby enabling efficient separation.

[0104] In embodiment (ii-3), in order to allow the third organic solvent-impregnated PSA to easily float in a mixed liquid with water containing the third organic solvent in an amount exceeding saturation, the PSA has a specific gravity of preferably 0.5 to 0.8, more preferably 0.5 to 0.7, and even more preferably 0.5 to 0.6.

[0105] In embodiment (ii-3), in order to allow the third organic solvent-impregnated PSA to easily precipitate in a mixed liquid with water containing the third organic solvent in an amount exceeding saturation, the PSA has a specific gravity of preferably 0.8 to 2.5, more preferably 1.0 to 2.5, even more preferably 1.2 to 2.5, and particularly preferably 1.5 to 2.5.

[0106] <<Operation (iii)>> In operation (iii), a mixture (A) containing a pressure-sensitive adhesive, a substrate, and a first organic solvent is immersed in a third organic solvent, and then the immersed mixture (B) is recovered, and the mixture (B) is stirred in water.

[0107] In step (iii), the first organic solvent and the third organic solvent are typically different.

[0108] In step (iii), the mixture (A) is immersed in a third organic solvent, whereby the first organic solvent impregnated in the PSA contained in the mixture (A), i.e., the first organic solvent, is replaced with the third organic solvent. Thus, the mixture (B) is a third organic solvent-impregnated PSA, which contains a PSA, a substrate, and a third organic solvent, and the PSA is impregnated with at least a portion of the third organic solvent. When the mixture (B) is stirred in water, the separation form can vary as follows, depending on the specific gravities of the third organic solvent-impregnated PSA and the substrate contained in the mixture (B):

[0109] In one separation mode, when the specific gravity of the third organic solvent-impregnated adhesive is smaller than that of water and the specific gravity of the substrate is larger than that of water, when the mixture (B) is stirred in water, the third organic solvent-impregnated adhesive floats to the surface in the water and the substrate sinks in the water.

[0110] In another form of separation, when the specific gravity of the third organic solvent-impregnated adhesive is greater than that of water and the specific gravity of the substrate is less than that of water, when the mixture (B) is stirred in water, the third organic solvent-impregnated adhesive settles in the water and the substrate floats to the top in the water.

[0111] In the step (iii), the proportion of the third organic solvent used relative to 100 parts by weight of the mixture (A) is preferably 50 parts by weight to 1,000 parts by weight, more preferably 100 parts by weight to 1,000 parts by weight, even more preferably 150 parts by weight to 1,000 parts by weight, and particularly preferably 200 parts by weight to 1,000 parts by weight, in terms of being able to further exhibit the effects of the present invention.

[0112] In the step (iii), the proportion of water used relative to 100 parts by weight of the mixture (B) is preferably 50 parts by weight to 1,000 parts by weight, more preferably 100 parts by weight to 1,000 parts by weight, even more preferably 150 parts by weight to 1,000 parts by weight, and particularly preferably 200 parts by weight to 1,000 parts by weight, in terms of being able to further exhibit the effects of the present invention.

[0113] <<Embodiment (iii-1)>> As a representative embodiment (iii-1) of operation (iii), an embodiment employing toluene (HSP value = 18.2, specific gravity = 0.87) as the third organic solvent will be described below. Furthermore, in this embodiment (iii-1), a representative example of mixture (A) will be described as containing a pressure-sensitive adhesive, a substrate, and 1-butanol.

[0114] Note that the procedure (iii) is not limited to the case where toluene is used as the third organic solvent, and the procedure (iii) is not limited to the case where the mixture (A) contains a pressure-sensitive adhesive, a substrate, and 1-butanol.

[0115] In embodiment (iii-1), the mixture (A) contains a pressure-sensitive adhesive, a substrate, and 1-butanol, and typically the pressure-sensitive adhesive is a 1-butanol-impregnated pressure-sensitive adhesive.

[0116] In embodiment (iii-1), by immersing mixture (A) in toluene, the 1-butanol impregnated in the 1-butanol-impregnated PSA contained in mixture (A) can be replaced with toluene. Next, the immersed mixture (B) is removed. Mixture (B) contains a PSA, a substrate, and toluene, and the PSA is a toluene-impregnated PSA. When this mixture (B) is stirred in water, the following two separation modes are possible. <Separation Mode 1> When the specific gravity of the toluene-impregnated PSA is smaller than that of water and the specific gravity of the substrate is larger than that of water, the toluene-impregnated PSA floats in the water, and the substrate sinks in the water. <Separation Mode 2> When the specific gravity of the toluene-impregnated PSA is larger than that of water and the specific gravity of the substrate is smaller than that of water, the toluene-impregnated PSA sinks in the water, and the substrate floats in the water.

[0117] As described above, in embodiment (iii-1), particularly, (1) when the specific gravity of the third organic solvent-impregnated pressure-sensitive adhesive is smaller than that of water and the specific gravity of the substrate is larger than that of water, the third organic solvent-impregnated pressure-sensitive adhesive floats up and the substrate sinks, or (2) when the specific gravity of the third organic solvent-impregnated pressure-sensitive adhesive is larger than that of water and the specific gravity of the substrate is smaller than that of water, the third organic solvent-impregnated pressure-sensitive adhesive sinks and the substrate floats up, thereby enabling efficient separation.

[0118] In embodiment (iii-1), in order to allow the third organic solvent-impregnated PSA to easily float in water, the PSA has a specific gravity of preferably 0.5 to 1.2, more preferably 0.5 to 1.1, even more preferably 0.5 to 1.0, and particularly preferably 0.5 to 0.9.

[0119] In embodiment (iii-1), in order to allow the third organic solvent-impregnated PSA to easily settle in water, the PSA has a specific gravity of preferably 1.1 to 2.5, more preferably 1.5 to 2.5, even more preferably 1.8 to 2.5, and particularly preferably 2.0 to 2.5.

[0120] <<Embodiment (iii-2)>> As another representative embodiment (iii-2) of operation (iii), an embodiment employing chloroform (HSP value = 18.9, specific gravity = 1.48) as the third organic solvent will be described below. Furthermore, in this embodiment (iii-2), a representative example of mixture (A) will be described as containing a pressure-sensitive adhesive, a substrate, and 1-butanol.

[0121] Note that the procedure (iii) is not limited to the case where chloroform is used as the third organic solvent, and the procedure (iii) is not limited to the case where the mixture (A) contains a pressure-sensitive adhesive, a substrate, and 1-butanol.

[0122] In embodiment (iii-2), the mixture (A) contains a pressure-sensitive adhesive, a substrate, and 1-butanol, and typically the pressure-sensitive adhesive is a 1-butanol-impregnated pressure-sensitive adhesive.

[0123] In embodiment (iii-2), by immersing mixture (A) in chloroform, the 1-butanol impregnated in the 1-butanol-impregnated PSA contained in mixture (A) can be replaced with chloroform. Next, the immersed mixture (B) is removed. Mixture (B) contains a PSA, a substrate, and chloroform, and the PSA is a chloroform-impregnated PSA. When this mixture (B) is stirred in water, the following two separation modes are possible. <Separation Mode 1> When the specific gravity of the chloroform-impregnated PSA is smaller than that of water and the specific gravity of the substrate is larger than that of water, the chloroform-impregnated PSA floats in the water, and the substrate sinks in the water. <Separation Mode 2> When the specific gravity of the chloroform-impregnated PSA is larger than that of water and the specific gravity of the substrate is smaller than that of water, the chloroform-impregnated PSA sinks in the water, and the substrate floats in the water.

[0124] As described above, in embodiment (iii-2), particularly, (1) when the specific gravity of the third organic solvent-impregnated pressure-sensitive adhesive is smaller than that of water and the specific gravity of the substrate is larger than that of water, the third organic solvent-impregnated pressure-sensitive adhesive floats up and the substrate sinks, or (2) when the specific gravity of the third organic solvent-impregnated pressure-sensitive adhesive is larger than that of water and the specific gravity of the substrate is smaller than that of water, the third organic solvent-impregnated pressure-sensitive adhesive sinks and the substrate floats up, enabling efficient separation.

[0125] In embodiment (iii-2), in order to allow the third organic solvent-impregnated pressure-sensitive adhesive to easily float in water, the specific gravity of the pressure-sensitive adhesive is preferably 0.5 to 0.8, more preferably 0.5 to 0.7, and even more preferably 0.5 to 0.6.

[0126] In embodiment (iii-2), in order to allow the third organic solvent-impregnated PSA to easily settle in water, the PSA has a specific gravity of preferably 0.8 to 2.5, more preferably 1.0 to 2.5, even more preferably 1.2 to 2.5, and particularly preferably 1.5 to 2.5.

[0127] In embodiment (iii-2), chloroform (specific gravity = 1.48), which has a high specific gravity, is used as the third organic solvent, so the specific gravity of the chloroform-impregnated PSA can preferably be greater than that of water. Therefore, in this case, in embodiment (iii-2), it is preferable to select a substrate having a specific gravity smaller than that of water as the substrate. A typical example of a substrate having a specific gravity smaller than that of water is an olefin-based substrate.

[0128] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The test and evaluation methods used in the examples are as follows.

[0129] The adhesive tapes, substrates and solvents used in the examples and comparative examples were as follows.

[0130] [Production Example 1] An acrylic adhesive tape (manufactured by Nitto Denko Corporation, product name "No. 3195MS," after foaming) was cut into a size of 20 mm x 20 mm to prepare an adhesive tape sample. Potassium hydroxide was added to a mixed solution of 1-butanol / water = 10 / 90 (weight ratio) to a concentration of 3 wt% to prepare an adhesive treatment solution. 3.2 kg of the adhesive tape sample and 12.8 kg of the adhesive treatment solution heated to 70°C were placed in a 20 L pail and stirred for 30 minutes using a drum shaker (manufactured by Misugi Co., Ltd., product name "Mazemazeman"), followed by solid-liquid separation using a filter, and a solid mixture (A1) was recovered. The resulting mixture (A1) was a mixture in which the acrylic adhesive derived from "No. 3195MS" and the PET substrate were entangled, and the adhesive was impregnated with 1-butanol.

[0131] [Production Example 2] The same procedure as in Production Example 1 was carried out, except that the acrylic adhesive tape (manufactured by Nitto Denko Corporation, product name "No. 3195MS", after foaming) was replaced with an acrylic adhesive tape (manufactured by Nitto Denko Corporation, product name "RP207"), and a solid mixture (A2) was recovered. The obtained mixture (A2) was a mixture in which the acrylic adhesive derived from "RP207" and the PET substrate were entangled, and the adhesive was impregnated with 1-butanol.

[0132] [Production Example 3] An acrylic adhesive portion was physically cut and separated from an acrylic adhesive tape (manufactured by Nitto Denko Corporation, product name "No. 3195MS," after foaming) to prepare an acrylic adhesive sample. Separately, an olefin substrate (manufactured by Toray Industries, Inc., product name "Torayfan") was cut into 20 mm x 20 mm pieces to prepare an olefin substrate sample. A 3 wt% potassium hydroxide solution was added to a 1-butanol / water mixed solution (10 / 90 by weight). A 1-L flask was charged with 30 g of the acrylic adhesive sample, 90 g of the olefin substrate sample, and 600 g of the adhesive treatment solution. The mixture was stirred for 30 minutes while immersed in a water bath heated to 70°C. Solid-liquid separation was performed using a filter, and a solid mixture (A3) was recovered. The resulting mixture (A3) was a mixture in which the acrylic adhesive derived from "No. 3195MS" and the olefin-based substrate were entangled, and the adhesive was impregnated with 1-butanol.

[0133] [Production Example 4] The same procedure as in Production Example 3 was carried out, except that instead of physically cutting and separating an acrylic pressure-sensitive adhesive portion from an acrylic pressure-sensitive adhesive tape (manufactured by Nitto Denko Corporation, product name "No. 3195MS", after foaming) to prepare an acrylic pressure-sensitive adhesive sample, an acrylic pressure-sensitive adhesive portion was physically cutting and separating from an acrylic pressure-sensitive adhesive tape (manufactured by Nitto Denko Corporation, product name "RP207") to prepare an acrylic pressure-sensitive adhesive sample, and a solid mixture (A4) was recovered. The obtained mixture (A4) was a mixture in which the acrylic pressure-sensitive adhesive derived from "RP207" and the olefin-based substrate were entangled, and the pressure-sensitive adhesive was impregnated with 1-butanol.

[0134] Example 1: Saturated aqueous solution of mixture (A1) and 1-butanol Mixture (A1) was added to a saturated aqueous solution of 1-butanol, a water / 1-butanol mixture (weight ratio: 92 / 8), so that the content of mixture (A1) was 5% by weight, and the mixture was stirred at 25°C for 1 minute and then allowed to stand. The state of separation during stirring and after allowing to stand was observed. The results are shown in Table 2.

[0135] Example 2: Saturated aqueous solution of mixture (A2) and 1-butanol Mixture (A2) was added to a saturated aqueous solution of 1-butanol, a water / 1-butanol mixture (weight ratio: 92 / 8), so that the content of mixture (A2) was 5% by weight, and the mixture was stirred at 25°C for 1 minute and then allowed to stand. The state of separation during stirring and after standing was observed. The results are shown in Table 2.

[0136] Example 3: Mixture of Mixture (A1) and Water / 1-butanol = 90 / 10 (weight ratio) Mixture (A1) was added to a water / 1-butanol = 90 / 10 (weight ratio) mixture, which was a mixture of water and 1-butanol containing more than a saturated amount of 1-butanol, so that the content ratio was 5 wt %, and the mixture was stirred at 25°C for 1 minute, and then allowed to stand. The state of separation during stirring and when allowed to stand was observed. The results are shown in Table 2.

[0137] Example 4: Mixture of Mixture (A2) and Water / 1-butanol = 90 / 10 (weight ratio) Mixture (A2) was added to a water / 1-butanol = 90 / 10 (weight ratio) mixture, which was a mixture of water and 1-butanol containing more than a saturated amount of 1-butanol, so that the content ratio was 5 wt %, and the mixture was stirred at 25°C for 1 minute, and then allowed to stand. The separation status during stirring and when allowed to stand was observed. The results are shown in Table 2.

[0138] Example 5: Mixture of Mixture (A1) and Water / Toluene = 90 / 10 (weight ratio) Mixture (A1) was added to a water / toluene = 90 / 10 (weight ratio) mixture, which was a mixture of water and toluene containing more than a saturated amount of toluene, so that the content ratio was 5 wt%, and the mixture was stirred at 25 ° C. for 1 minute, and then allowed to stand. The separation status during stirring and when allowed to stand was observed. The results are shown in Table 2.

[0139] Example 6: Mixture of Mixture (A2) and Water / Toluene = 90 / 10 (weight ratio) Mixture (A2) was added to a water / toluene = 90 / 10 (weight ratio) mixture, which was a mixture of water and toluene containing more than a saturated amount of toluene, so that the content ratio was 5 wt%, and the mixture was stirred at 25 ° C. for 1 minute, and then allowed to stand. The separation status during stirring and when allowed to stand was observed. The results are shown in Table 2.

[0140] Example 7: Mixture of Mixture (A1) and Water / Ethyl Acetate = 90 / 10 (weight ratio) Mixture (A1) was added to a water / ethyl acetate = 90 / 10 (weight ratio) mixture, which was a mixture of water and ethyl acetate containing more than the saturated amount of ethyl acetate, so that the content of Mixture (A1) was 5 wt %, and the mixture was stirred at 25 ° C. for 1 minute, and then allowed to stand. The separation status during stirring and when allowed to stand was observed. The results are shown in Table 2.

[0141] Example 8: Mixture of Mixture (A2) and Water / Ethyl Acetate = 90 / 10 (weight ratio) Mixture (A2) was added to a water / ethyl acetate = 90 / 10 (weight ratio) mixture, which was a mixture of water and ethyl acetate containing more than the saturated amount of ethyl acetate, so that the content of Mixture (A2) was 5 wt %, and the mixture was stirred at 25°C for 1 minute and then allowed to stand. The separation status during stirring and when allowed to stand was observed. The results are shown in Table 2.

[0142] Example 9: Mixture of Mixture (A2) and Water / Benzyl Alcohol = 50 / 50 (weight ratio) Mixture (A2) was added to a 50 / 50 (weight ratio) water / benzyl alcohol mixture, which was a mixture of water and benzyl alcohol containing more than a saturated amount of benzyl alcohol, so that the content of Mixture (A2) was 5 wt %, and the mixture was stirred at 25°C for 1 minute and then allowed to stand. The separation status during stirring and after standing was observed. The results are shown in Table 3.

[0143] Example 10: Mixture of Mixture (A3) and Water / Benzyl Alcohol = 50 / 50 (weight ratio) Mixture (A3) was added to a 50 / 50 (weight ratio) water / benzyl alcohol mixture, which was a mixture of water and benzyl alcohol containing more than a saturated amount of benzyl alcohol, so that the content of Mixture (A3) was 5 wt %, and the mixture was stirred at 25°C for 1 minute and then allowed to stand. The separation status during stirring and after standing was observed. The results are shown in Table 3.

[0144] Example 11: Mixture of Mixture (A1) and Water / Chloroform = 50 / 50 (weight ratio) Mixture (A1) was added to a water / chloroform = 50 / 50 (weight ratio) mixture, which was a mixture of water and chloroform containing more than a saturated amount of chloroform, so that the content ratio was 5 wt %, and the mixture was stirred at 25 ° C. for 1 minute, and then allowed to stand. The separation status during stirring and when allowed to stand was observed. The results are shown in Table 3.

[0145] Example 12: Mixture of Mixture (A2) and Water / Chloroform = 50 / 50 (weight ratio) Mixture (A2) was added to a water / chloroform = 50 / 50 (weight ratio) mixture, which was a mixture of water and chloroform containing more than a saturated amount of chloroform, so that the content ratio was 5 wt %, and the mixture was stirred at 25 ° C. for 1 minute, and then allowed to stand. The separation status during stirring and when allowed to stand was observed. The results are shown in Table 3.

[0146] Example 13: Mixture of Mixture (A3) and Water / Chloroform = 50 / 50 (weight ratio) Mixture (A3) was added to a water / chloroform = 50 / 50 (weight ratio) mixture, which was a mixture of water and chloroform containing more than a saturated amount of chloroform, so that the content ratio was 5 wt %, and the mixture was stirred at 25 ° C. for 1 minute, and then allowed to stand. The separation status during stirring and when allowed to stand was observed. The results are shown in Table 3.

[0147] Example 14: Mixture of Mixture (A4) and Water / Chloroform = 50 / 50 (weight ratio) Mixture (A4) was added to a water / chloroform = 50 / 50 (weight ratio) mixture, which was a mixture of water and chloroform containing more than a saturated amount of chloroform, so that the content ratio was 5 wt %, and the mixture was stirred at 25 ° C. for 1 minute, and then allowed to stand. The separation status during stirring and when allowed to stand was observed. The results are shown in Table 3.

[0148] Example 15: Mixture of Mixture (A1) and Water / Carbon Tetrachloride = 50 / 50 (weight ratio) Mixture (A1) was added to a water / carbon tetrachloride = 50 / 50 (weight ratio) mixture, which was a mixture of water and carbon tetrachloride containing more than a saturated amount of carbon tetrachloride, so that the content of Mixture (A1) was 5 wt %, and the mixture was stirred at 25°C for 1 minute and then allowed to stand. The separation status during stirring and after standing was observed. The results are shown in Table 4.

[0149] Example 16: Mixture of Mixture (A2) and Water / Carbon Tetrachloride = 50 / 50 (weight ratio) Mixture (A2) was added to a water / carbon tetrachloride = 50 / 50 (weight ratio) mixture, which was a mixture of water and carbon tetrachloride containing more than a saturated amount of carbon tetrachloride, so that the content of Mixture (A2) was 5 wt %, and the mixture was stirred at 25°C for 1 minute and then allowed to stand. The state of separation during stirring and when allowed to stand was observed. The results are shown in Table 4.

[0150] Example 17: Mixture of Mixture (A3) and Water / Carbon Tetrachloride = 50 / 50 (weight ratio) Mixture (A3) was added to a water / carbon tetrachloride = 50 / 50 (weight ratio) mixture, which was a mixture of water and carbon tetrachloride containing more than a saturated amount of carbon tetrachloride, so that the content ratio was 5 wt %, and the mixture was stirred at 25°C for 1 minute, and then allowed to stand. The separation status during stirring and when allowed to stand was observed. The results are shown in Table 4.

[0151] Example 18: Mixture of Mixture (A4) and Water / Carbon Tetrachloride = 50 / 50 (weight ratio) Mixture (A4) was added to a water / carbon tetrachloride = 50 / 50 (weight ratio) mixture, which was a mixture of water and carbon tetrachloride containing more than a saturated amount of carbon tetrachloride, so that the content ratio was 5 wt %, and the mixture was stirred at 25°C for 1 minute, and then allowed to stand. The separation status during stirring and when allowed to stand was observed. The results are shown in Table 4.

[0152] [Comparative Example 1] Mixture (A1) was added to water so that the content was 5 wt %, and the mixture was stirred at 25°C for 1 minute, and then allowed to stand. The separation state during stirring and after being allowed to stand was checked. In both cases, the pressure-sensitive adhesive and the substrate settled in an entangled state. The results are shown in Table 4.

[0153] [Comparative Example 2] Mixture (A2) was added to water so that the content was 5 wt %, and the mixture was stirred at 25°C for 1 minute, and then allowed to stand. The separation status during stirring and after allowing to stand was checked. In both cases, the pressure-sensitive adhesive and the substrate settled in an entangled state. The results are shown in Table 4.

[0154]

[0155]

[0156]

[0157] According to Examples 1 and 2, it can be seen that operation (i) (an operation of stirring the mixture (A1) or (A2) containing the adhesive, the substrate, and the first organic solvent) allows the adhesive to float up and the substrate to sink, utilizing the difference in specific gravity, thereby separating the adhesive and the substrate.

[0158] Examples 3 to 8 show that operation (ii) (an operation of stirring mixture (A1) or (A2) containing a pressure-sensitive adhesive, a substrate, and a first organic solvent in a mixed solution with water containing at least one organic solvent selected from the group consisting of a second organic solvent and a third organic solvent in an amount exceeding saturation) allows the pressure-sensitive adhesive to float and the substrate to sink, utilizing the difference in specific gravity, thereby enabling the pressure-sensitive adhesive and the substrate to be separated.

[0159] According to Examples 9 and 10, by performing operation (ii) (an operation of stirring the mixture (A2) or (A3) containing a pressure-sensitive adhesive, a substrate, and a first organic solvent in a mixed solution with water containing at least one organic solvent selected from the group consisting of a second organic solvent and a third organic solvent in an amount exceeding saturation), it is possible to utilize the difference in specific gravity to separate the pressure-sensitive adhesive from the substrate, with the pressure-sensitive adhesive floating up in Example 9 and the substrate settling down in Example 10, and the pressure-sensitive adhesive settling down in Example 10.

[0160] According to Examples 11 to 18, it was found that operation (ii) (an operation of stirring any of mixtures (A1) to (A4) containing a pressure-sensitive adhesive, a substrate, and a first organic solvent in a mixed solution with water containing at least one organic solvent selected from the group consisting of a second organic solvent and a third organic solvent in an amount exceeding saturation) allowed the pressure-sensitive adhesive to settle and the substrate to float in an agitated state, thereby enabling separation of the pressure-sensitive adhesive and the substrate. Note that in a stationary state, at least one of the pressure-sensitive adhesive and the substrate floated near the interface, making separation difficult, but in a stirred state, separation was possible as described above.

[0161] In both Comparative Examples 1 and 2, the PSA and the substrate settled in an entangled state and could not be separated. This is presumably because the first organic solvent impregnated in the first organic solvent-impregnated PSA contained in mixture (A1) or mixture (A2) was eluted, causing the PSA to aggregate and solidify, resulting in re-adhesion to the substrate.

[0162] [Example 19]: Toluene substitution of mixture (A1) 100 g of mixture (A1) and 500 g of toluene were placed in a 1 L beaker and allowed to stand for at least 1 minute to allow the toluene to soak in the mixture, after which the mixture (B19) was collected. Subsequently, mixture (B19) was added to water to a content of 5 wt %, stirred at 25°C for 1 minute, and then allowed to stand. The separation status during stirring and after standing was monitored. The results are shown in Table 5.

[0163] [Example 20]: Toluene substitution of mixture (A2) 100 g of mixture (A2) and 500 g of toluene were placed in a 1 L beaker and allowed to stand for at least 1 minute to allow the toluene to soak in the mixture, after which the mixture (B20) was collected. Subsequently, mixture (B20) was added to water to a content of 5 wt %, stirred at 25°C for 1 minute, and then allowed to stand. The separation status during stirring and after standing was monitored. The results are shown in Table 5.

[0164] [Example 21]: Substitution of Mixture (A2) with Benzyl Alcohol 100 g of Mixture (A2) and 500 g of benzyl alcohol were placed in a 1 L beaker and allowed to stand for at least 1 minute to allow the benzyl alcohol to soak in the mixture, after which the soaked mixture (B21) was recovered. Subsequently, Mixture (B21) was added to water to a content of 5 wt %, stirred at 25°C for 1 minute, and then allowed to stand. The separation status during stirring and after standing was monitored. The results are shown in Table 5.

[0165] [Example 22]: Substitution of Mixture (A3) with Benzyl Alcohol 100 g of Mixture (A3) and 500 g of benzyl alcohol were placed in a 1 L beaker and allowed to stand for at least 1 minute to allow the benzyl alcohol to soak in the mixture, after which the soaked mixture (B22) was collected. Subsequently, Mixture (B22) was added to water to a content of 5 wt %, stirred at 25°C for 1 minute, and then allowed to stand. The separation status during stirring and after standing was monitored. The results are shown in Table 5.

[0166] Example 23: Nitrobenzene Substitution of Mixture (A3) 100 g of mixture (A3) and 500 g of nitrobenzene were placed in a 1 L beaker and allowed to stand for at least 1 minute to allow the nitrobenzene to soak. The soaked mixture (B23) was then recovered. Subsequently, water was added to the mixture (B23) to a concentration of 5 wt %, and the mixture was stirred at 25°C for 1 minute and then allowed to stand. The separation status during stirring and after standing was monitored. The results are shown in Table 5.

[0167] Example 24: Nitrobenzene Substitution of Mixture (A4) 100 g of mixture (A4) and 500 g of nitrobenzene were placed in a 1 L beaker and allowed to stand for at least 1 minute to allow the nitrobenzene to soak. The soaked mixture (B24) was then recovered. Subsequently, mixture (B24) was added to water to a concentration of 5 wt %, stirred at 25°C for 1 minute, and then allowed to stand. The separation status during stirring and after standing was monitored. The results are shown in Table 5.

[0168] [Example 25]: Chloroform substitution of mixture (A3) 100 g of mixture (A3) and 500 g of chloroform were placed in a 1 L beaker and allowed to stand for at least 1 minute to allow the chloroform to soak in the mixture, after which the mixture (B25) was collected. Subsequently, mixture (B25) was added to water to a content of 5 wt %, stirred at 25°C for 1 minute, and then allowed to stand. The separation status during stirring and after standing was monitored. The results are shown in Table 6.

[0169] [Example 26]: Chloroform substitution of mixture (A4) 100 g of mixture (A4) and 500 g of chloroform were placed in a 1 L beaker and allowed to stand for at least 1 minute to allow the chloroform to soak in the mixture, after which the mixture (B26) was recovered. Subsequently, mixture (B26) was added to water to a content of 5 wt %, stirred at 25°C for 1 minute, and then allowed to stand. The separation status during stirring and after standing was monitored. The results are shown in Table 6.

[0170] [Example 27]: Substitution of Mixture (A3) with Carbon Tetrachloride 100 g of Mixture (A3) and 500 g of carbon tetrachloride were placed in a 1 L beaker and allowed to stand for at least 1 minute to allow the carbon tetrachloride to soak in the mixture. The soaked mixture (B27) was then recovered. Subsequently, Mixture (B27) was added to water to a concentration of 5 wt %, stirred at 25°C for 1 minute, and then allowed to stand. The separation status during stirring and after standing was monitored. The results are shown in Table 6.

[0171] [Example 28]: Substitution of Mixture (A4) with Carbon Tetrachloride 100 g of Mixture (A4) and 500 g of carbon tetrachloride were placed in a 1 L beaker and allowed to stand for at least 1 minute to allow the carbon tetrachloride to soak in the mixture. The soaked mixture (B28) was then recovered. Subsequently, Mixture (B28) was added to water to a concentration of 5 wt %, stirred at 25°C for 1 minute, and then allowed to stand. The separation status during stirring and after standing was monitored. The results are shown in Table 6.

[0172]

[0173]

[0174] According to Examples 19 and 20, by performing operation (iii) (immersing mixture (A1) or (A2) in a third organic solvent, recovering the immersed mixture (B19) or (B20), and stirring mixture (B19) or (B20) in water) from mixture (A1) or (A2) containing an adhesive, a substrate, and a first organic solvent, it is possible to utilize the difference in specific gravity to cause the adhesive to float and the substrate to sink during stirring, thereby separating the adhesive and the substrate.

[0175] According to Examples 21 and 22, by performing operation (iii) (immersing mixture (A2) or (A3) in a third organic solvent, recovering the immersed mixture (B21) or (B22), and stirring mixture (B21) or (B22) in water) from mixture (A2) or (A3) containing an adhesive, a substrate, and a first organic solvent, it is possible to utilize the difference in specific gravity and, under stirring conditions, in Example 21, the adhesive floats up and the substrate sinks, while in Example 22, the adhesive sinks and the substrate floats up, thereby separating the adhesive and the substrate.

[0176] Examples 23 to 28 show that operation (iii) (immersing mixture (A3) or (A4) in a third organic solvent, recovering any of mixtures (B23) to (B28) after the immersion, and stirring any of mixtures (B23) to (B28) in water) from mixture (A3) or (A4) containing a pressure-sensitive adhesive, a substrate, and a first organic solvent allows the pressure-sensitive adhesive and the substrate to be separated by utilizing the difference in specific gravity during stirring, with the pressure-sensitive adhesive settling and the substrate floating up.

[0177] The method for separating adhesive and substrate according to the embodiment of the present invention can be effectively used to recycle the large amount of waste adhesive tape generated at manufacturing sites of electronic components and optical components, for example.

Claims

1. A method for separating an adhesive and a substrate from a mixture (A) containing an adhesive, a substrate, and a first organic solvent, comprising carrying out at least one operation selected from the group consisting of the following (i), (ii), and (iii): (i) stirring the mixture (A) in a saturated aqueous solution of a first organic solvent, (ii) stirring the mixture (A) in a mixed liquid with water containing at least one organic solvent selected from the group consisting of a second organic solvent and a third organic solvent in an amount exceeding saturation, and (iii) immersing the mixture (A) in a third organic solvent, recovering the mixture (B) after the immersion, and stirring the mixture (B) in water.

2. The method according to claim 1, wherein the first organic solvent is an organic solvent having an HSP value of 10 to 45.

3. The separation method according to claim 1, wherein the second organic solvent is an organic solvent having an HSP value of 10 to 45 and a solubility in water of more than 10 g / L and not more than 500 g / L at 20°C.

4. The method according to claim 1, wherein the third organic solvent is an organic solvent having an HSP value of 10 to 45 and a solubility in water of 10 g / L or less at 20°C.

5. The method of claim 1, wherein the mixture is allowed to stand after the stirring.

6. The sorting method according to claim 1, wherein the adhesive is an adhesive contained in an adhesive tape.

7. The sorting method according to claim 1, wherein the substrate is a substrate contained in an adhesive tape.

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