WO2024075371A1

WO2024075371A1 - Method for separating/recovering base

Info

Publication number: WO2024075371A1
Application number: PCT/JP2023/027358
Authority: WO
Inventors: 寛之古野; 辰矢渡部
Original assignee: ａｒｔｉｅｎｃｅ株式会社; トーヨーケム株式会社; 東洋インキ株式会社; 東洋モートン株式会社
Priority date: 2022-10-03
Filing date: 2023-07-26
Publication date: 2024-04-11
Also published as: JP2024053186A; JP7224577B1

Abstract

The present invention addresses the problem of providing a method for efficiently separating/recovering a base from a layered body obtained by layering a support body, an adhesive layer, and the base in this order. The problem can be solved by providing a method for separating/recovering a base from a layered body obtained by layering a support body, an adhesive layer, and the base in this order. The method is characterized in that: the support body is an air permeable film or a nonwoven fabric having a Gurley permeability of 10 to 1000 sec/100 mL; the method includes a step for immersing the layered body in a separation liquid to separate the base from the adhesive layer; the pH of the separation liquid at 25°C is 13.3 or higher; and the dynamic surface tension of the separation liquid at 1000 msec when measured at 25°C is 60 mN/m or less.

Description

Method for separating and recovering substrate

The present invention relates to a method for separating and recovering a substrate from a laminate formed by bonding a substrate to an adhesive sheet having an adhesive layer and a support.

In recent years, the amount of general waste or industrial waste, including packages made of plastic film, plastic bottles, and other plastic products, has been steadily increasing, and waste disposal has become a major environmental issue. Examples of the plastic products include food packaging packages using plastic films. Such food packaging packages may be laminated with a sheet containing an adhesive layer. Such multi-layered food packaging packages contain multiple different materials, so there is a problem that they cannot be recycled as they are.
Regarding material recycling of such multi-layered packaging materials, for example, Patent Document 1 discloses an adhesive sheet using a water-disintegrable or alkali-disintegrable base paper as a support and having an adhesive area on at least one side of the base paper, while Patent Document 2 discloses an alkali-peelable film label that is attached to a product or its container.

JP 2010-043226 A JP 2003-241669 A

However, in Patent Document 1, the amount of residue when the base paper is subjected to a disintegration test is less than 50 mg, and preferably fully disintegrable, but when attempting to filter the disintegrated pulp from the plastic film pieces as the base material, there is a problem that the filtration pressure causes the pulp dispersion to aggregate the film pieces together, clogging the filter. Although this problem can be solved by introducing a filtration device with a filter washing function, the initial investment cost is high, and the pulp component must ultimately be discarded, resulting in low recycling efficiency.
In addition, when price tag stickers are used for plastic packaging materials such as food trays and packs, sufficient adhesive strength must be maintained even in the presence of frost or condensation that occurs during chilled storage or when changing the storage environment from frozen to refrigerated, and water-resistant adhesive strength is required. However, in the case of film labels such as those described in Patent Document 2, the alkaline processing solution can only act on the exposed adhesive portion at the edge during alkaline peeling, so it is necessary to increase the alkaline peelability of the adhesive. This creates the need to increase the hydrophilicity of the adhesive, which creates the problem of making it difficult to achieve both water-resistant adhesive strength and the like.
Therefore, an object of the present invention is to provide a method for efficiently separating and recovering a substrate from a laminate formed by bonding a substrate to an adhesive sheet that has both alkali peelability and water-resistant adhesion.

The present inventors have conducted extensive research to solve the above problems and have completed the present invention.
That is, the present invention relates to the following [1] to [3].

[1] A method for separating and recovering a substrate from a laminate in which a support, a pressure-sensitive adhesive layer, and a substrate are laminated in this order, comprising the steps of:
the support is a nonwoven fabric or a breathable film having a Gurley air permeability of 10 to 1000 seconds/100 mL;
a step of immersing the laminate in a release liquid to release the base material from the pressure-sensitive adhesive layer,
The pH of the desorption liquid at 25° C. is 13.3 or more,
and the dynamic surface tension of the eluent measured at 25° C. for 1000 ms is 60 mN/m or less.

[2] The pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer containing an acrylic copolymer,
The method for separating and recovering a substrate according to [1], wherein the acrylic copolymer is a copolymer of a monomer mixture containing a (meth)acrylate having a carboxyl group, and the acid value of the acrylic copolymer is 0.1 to 100 mgKOH/g.

[3] The method for separating and recovering a substrate according to [1] or [2], wherein the coating amount of the pressure-sensitive adhesive layer is 10 to 30 g/ ^m2 .

The present invention provides a method for efficiently separating and recovering a substrate from a laminate formed by bonding a substrate to an adhesive sheet that has both alkali peelability and water-resistant adhesion.

The present invention will be described in detail below. Needless to say, other embodiments are also included in the scope of the present invention as long as they are consistent with the gist of the present invention. In addition, in this specification, a numerical range specified using "~" includes the numerical values written before and after "~" as the lower and upper limit values.
Before describing the present invention in detail, the following terms are defined: (Meth)acrylic acid includes acrylic acid and methacrylic acid; (Meth)acrylate includes acrylate and methacrylate; and Monomer is a monomer having an ethylenically unsaturated double bond.
Unless otherwise noted, the various components appearing in this specification may be used independently as a single type, or as a mixture of two or more types.

The present invention is a method for separating and recovering a substrate from a laminate, which includes a step of immersing a laminate obtained by bonding a substrate to an adhesive sheet having an adhesive layer and a support in a release liquid having a pH of 13.3 or more at 25°C and a dynamic surface tension of 60 mN/m or less at 25°C and 1000 msec to release the substrate. The support is a nonwoven fabric or breathable film having a Gurley air permeability of 10 to 1000 sec/100 mL.

<Laminate>
The laminate used in the present invention is a laminate in the order of a support, a pressure-sensitive adhesive layer, and a substrate. The method for producing the laminate is not particularly limited, and it can be produced by a conventionally known method. For example, it can be produced by laminating a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer and a support to a substrate.

<Adhesive sheet>
The adhesive sheet can be formed by coating the adhesive composition described below on a support and drying it. Alternatively, the adhesive sheet can be formed by coating the adhesive composition described below on a release liner, drying it to form an adhesive layer, and then laminating the support. The support is a nonwoven fabric or breathable film having a Gurley air permeability of 10 to 1000 seconds/100 mL. By using a support having a Gurley air permeability of 1000 seconds/100 mL or less, it is possible to improve the permeability of the release liquid into the support in the laminate, increase the contact area between the adhesive layer and the release liquid, and improve the release efficiency. In order to further improve the release efficiency, it is preferable that the Gurley air permeability is 100 seconds/100 mL or less.
Furthermore, by making the Gurley air permeability of the support 10 seconds/100 mL or more, the water-resistant adhesive strength of the adhesive sheet is maintained, making it possible to prevent peeling due to immersion in water when frost or condensation occurs.
The water-resistant adhesive strength can be evaluated, for example, by the method described in the Examples. The water-resistant adhesive strength measured by this method must be 300 gf/25 mm or more, preferably 350 gf/25 mm or more, and most preferably 450 gf/25 mm or more.

Gurley air permeability is measured using the method described in JIS P8117:2009. It is also possible to convert ISO air permeability or Oken air permeability to Gurley air permeability using the method described in JIS P8117:2009.

(Support)
The material of the support of the present invention is not particularly limited. For example, olefins such as polyethylene or polypropylene, polyesters such as polyethylene terephthalate, and petroleum-based materials such as polyamides can be used, as well as regenerated fibers such as rayon and cupra, and natural fibers such as cotton. However, petroleum-based materials are preferred because regenerated fibers, natural fibers, and pulp (base paper) are finely dispersed in the release agent of the present invention and may cause problems in filtration. When a nonwoven fabric is used as the support, the processing method can be a spunlace method, a spunbond method, a thermal bond method, an air-through method, a needle punch method, or the like. When a breathable film is used as the support, a stretching method or the like can be used.

The nonwoven fabric can be compounded with a sealing agent to adjust its air permeability. There are no particular limitations on the compounding method, and examples include coating methods using a roll coater, blade coater, gravure coater, air knife coater, bar coater, and spray, and impregnation methods such as size press and dipping. Coating is preferred from the standpoint of releasability.

When the nonwoven fabric and the sealant are combined, from the viewpoint of releasability, the acid value of the sealant is preferably 20 mg KOH/g or more, and more preferably 25 mg KOH/g or more.

Nonwoven fabrics can be calendered to adjust their air permeability. Calendering can be used on-machine or off-machine as appropriate, and the shape of the pressure device, pressure nip residue, heating, etc. are adjusted as appropriate in accordance with normal calendering processing devices.

[Release liner]
As the release liner (sometimes called a separator), any conventionally known one can be used without any particular limitation. For example, a release liner obtained by treating at least one surface of a suitable substrate (for example, glassine paper, craft paper, clay-coated paper, paper laminated with a resin film such as polyethylene, or paper coated with a resin such as polyvinyl alcohol or an acrylic copolymer) with a release agent such as a fluororesin or silicone resin can be preferably used.

[Coating method]
The coating method can be a known method, and the adhesive sheet of the present invention can be obtained by applying the adhesive composition onto a support or a release liner using various known coating devices such as a comma coater, a reverse coater, a slot die coater, a lip coater, a gravure chamber coater, a curtain coater, etc., and drying the composition. In addition, after applying the adhesive composition onto the release liner or the like, it is preferable to dry the composition at 80°C to 120°C. By setting the drying temperature to 80°C or higher, an adhesive sheet can be obtained in an appropriate time, and by setting the drying temperature to 120°C or lower, thermal deterioration of the support or release liner can be prevented.

From the viewpoint of achieving both water-resistant adhesion and releasability, the coating amount of the adhesive layer is preferably 10 to 30 g/ ^m2 . A coating amount of 10 g/m2 or ^more makes it easier to ensure water-resistant adhesion, while a coating amount of 30 g/ ^m2 or less makes it easier to ensure releasability.

Furthermore, the pressure-sensitive adhesive sheet of the present invention preferably has an adhesive strength of 3 N or more in a 180° peel test, in order to be used for food packaging that does not require re-peeling.
The 180° peel test method is as follows: A sheet containing a pressure-sensitive adhesive layer and a support is prepared with a width of 25 mm and a length of 100 mm, and the release sheet is peeled off from the pressure-sensitive adhesive sheet in an atmosphere of 23° C. and 50% relative humidity, so that the exposed pressure-sensitive adhesive layer is attached to a substrate and pressure-bonded once with a 2 kg roll. After leaving it for 24 hours, the sheet is peeled off in the 180° direction at a speed of 300 mm/min using a tensile tester.

(Adhesive Layer)
The pressure-sensitive adhesive layer in the present invention plays a role in separating the substrate by dissolution with a release liquid, peeling, etc. The pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition, and examples of the resin contained in the pressure-sensitive adhesive composition include acrylic copolymers, urethane copolymers, polyester copolymers, polyamide copolymers, etc., and it is preferable to contain an acrylic copolymer.

((Acrylic copolymer))
The acrylic copolymer is a copolymer obtained by polymerizing a mixture of (meth)acrylate monomers. Examples of (meth)acrylate monomers include (meth)acrylates having a carboxyl group, (meth)acrylates having an alkyl group, (meth)acrylates having an ethylene glycol chain or a propylene glycol chain, and (meth)acrylates having a hydroxyl group. In terms of releasability, it is preferable to include a (meth)acrylate having a carboxyl group.

The acid value of the acrylic copolymer is preferably 0.1 to 100 mgKOH/g. By having an acid value of the acrylic copolymer of 0.1 to 100 mgKOH/g, it becomes easier to achieve both water-resistant adhesion and releasability.

[(Meth)acrylate having a carboxyl group]
Examples of (meth)acrylates having a carboxyl group include (meth)acrylic acid, β-carboxyethyl acrylate, ω-carboxypolycaprolactone monoacrylate, 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl hexahydrophthalic acid, etc. From the standpoint of adhesive performance and cost, it is preferable to use (meth)acrylic acid.

[(Meth)acrylate having an alkyl group]
Examples of the (meth)acrylate having an alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, and dodecyl (meth)acrylate.

[(Meth)acrylate having an ethylene glycol chain or a propylene glycol chain]
Examples of the (meth)acrylate having an ethylene glycol chain or a propylene glycol chain include methoxy(meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, and ethoxypolypropylene glycol (meth)acrylate.

[(Meth)acrylate having a hydroxyl group]
Examples of the (meth)acrylate having a hydroxyl group include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate; and glycol mono(meth)acrylates such as polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, and 1,4-cyclohexanedimethanol mono(meth)acrylate.

[Other monomers]
Monomers other than those mentioned above can also be used as long as they are copolymerizable with the (meth)acrylate monomer. Examples of other monomers include self-crosslinking monomers such as acetoacetoxyethyl (meth)acrylate, 3-(trimethoxysilyl)propyl (meth)acrylate, 3-(triethoxysilyl)propyl (meth)acrylate, 3-(methyldimethoxysilyl)propyl (meth)acrylate, 3-(methyldiethoxysilyl)propyl (meth)acrylate, vinyltrimethoxysilane, and vinyltriethoxysilane, epoxy group-containing monomers such as glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl methacrylate, and 1,2-epoxy-4-vinylcyclohexane, and amino group-containing monomers such as aminomethyl (meth)acrylate, dimethylaminomethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and dimethylaminopropyl (meth)acrylate. amide group-containing monomers such as diacetone (meth)acrylamide, (meth)acrylamide, and the like; imide group-containing monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide; and other vinyl monomers such as vinyl acetate, styrene, methylstyrene, vinyl toluene, and acrylonitrile.

((Production of Acrylic Copolymer))
The acrylic copolymer is a copolymer obtained by polymerizing a mixture of (meth)acrylate monomers. The polymerization method may be a typical polymerization method such as solution polymerization or emulsion polymerization.

[Production by emulsion polymerization]
The acrylic copolymer can be obtained, for example, by emulsion polymerization.
First, the monomers are mixed to obtain a homogeneous mixed solution, which may be used for polymerization as is, or may be added with water and a surfactant in part or in whole, stirred, and then used for polymerization after being made into an emulsion.

After preparing these mixed solutions or emulsions, polymerization is carried out in the presence of a polymerization initiator. The method for this may be to charge the entire mixed solution or emulsion into a reaction vessel and initiate polymerization, or to charge a portion of the mixed solution or emulsion into a reaction vessel and initiate polymerization, and then add it in several portions, or to charge a portion of the mixed solution or emulsion into a reaction vessel and initiate polymerization, and then add the remainder dropwise continuously, or to charge water and, if necessary, a portion or all of the surfactant into the reaction vessel in advance, and then add the entire amount dropwise continuously. When polymerizing using a mixed solution, it is preferable to charge the entire amount of the surfactant and a portion or all of the water into the reaction vessel in advance.

As a method of adding the polymerization initiator, the entire amount may be charged in the reaction vessel in advance, the entire amount may be added after the temperature is raised, a portion may be charged in the reaction vessel and then divided into several portions after the polymerization is started, a portion may be charged in the reaction vessel and then the remainder may be added continuously dropwise after the polymerization is started, or the entire amount may be added continuously. When the polymerization initiator is added in portions or continuously, it may be added in portions or continuously into the reaction vessel alone, or may be added in portions or continuously in a state where it is mixed with a mixed solution or emulsion. After the polymerization initiator is added by these methods, the polymerization initiator may be added once or twice or more times in order to increase the reaction rate. In this manner, the acrylic copolymer of the present invention can be obtained.

The surfactant used in the emulsion polymerization is preferably selected from anionic surfactants and nonionic surfactants. In addition, the surfactant may be a reactive surfactant having a radically polymerizable functional group, or a non-reactive surfactant having no radically polymerizable functional group, and both can be used in combination.

Among surfactants, reactive surfactants are anionic surfactants that have one or more unsaturated double bonds capable of radical polymerization in the molecule. Examples include sulfosuccinate surfactants and alkylphenol ether surfactants.

Examples of non-reactive anionic surfactants include polyoxyethylene polycyclic phenyl ether sulfates, higher fatty acid salts such as sodium stearate, alkylaryl sulfonates such as sodium dodecylbenzenesulfonate, alkyl sulfates such as sodium lauryl sulfate, polyoxyethylene alkyl ether sulfates such as sodium polyoxyethylene lauryl ether sulfate, and polyoxyethylene alkyl aryl ether sulfates such as sodium polyoxyethylene nonylphenyl ether sulfate.

Examples of non-reactive nonionic surfactants include polyoxyethylene alkyl phenyl ethers such as polyoxyethylene nonyl phenyl ether and polyoxyethylene octyl phenyl ether; polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether and polyoxyethylene oleyl ether; polyoxypolycyclic phenyl ethers such as polyoxyethylene distyrenated phenyl ether; polyoxyethylene sorbitan fatty acid esters, etc. Surfactants can be used alone or in combination of two or more types.

Among the above surfactants, it is preferable to use reactive or non-reactive anionic surfactants because they provide good polymerization stability. It is preferable to use 0.5 to 3 parts by mass of the surfactant per 100 parts by mass of the monomer mixture.

A polymerization initiator is used for emulsion polymerization. The polymerization initiator may be either water-soluble or oil-soluble, but when using an oil-soluble initiator, it is necessary to dissolve it in a water-miscible solvent beforehand. It is preferable to use a water-soluble polymerization initiator, which does not require such a procedure.

Examples of water-soluble polymerization initiators include potassium persulfate, sodium persulfate, ammonium persulfate, ammonium (amine) salt of 4,4'-azobis-4-cyanovaleric acid, 2,2'-azobis(2-methylamidoxime) dihydrochloride, 2,2'-azobis(2-methylbutanamidoxime) dihydrochloride tetrahydrate, 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]-propionamide}, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], etc. Among these, potassium persulfate and sodium persulfate are preferred.

The water-soluble polymerization initiator is preferably used in an amount of 0.01 to 1.0 parts by mass, more preferably 0.02 to 0.5 parts by mass, per 100 parts by mass of the monomer mixture. The amount of 0.01 to 1.0 part by mass can further improve the polymerization reactivity.

Furthermore, the water-soluble polymerization initiator may be a redox-based polymerization initiator (a combination of an oxidizing agent and a reducing agent). Examples of the oxidizing agent include ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide, and p-methane hydroperoxide. Examples of the reducing agent include sodium sulfite, acidic sodium sulfite, Rongalite, and ascorbic acid.

For redox polymerization initiators, it is preferable to use 0.01 to 1.0 parts by mass of the oxidizing agent and reducing agent, and more preferably 0.02 to 0.5 parts by mass, per 100 parts by mass of the monomer mixture. By using 0.01 to 1.0 parts by mass, polymerization reactivity can be improved.

When carrying out emulsion polymerization, a buffering agent can be used to adjust the pH as necessary. There are no particular limitations on the buffering agent, so long as it has a pH buffering effect on the reaction solution of the emulsion polymerization. Examples of buffering agents include sodium bicarbonate, potassium bicarbonate, monosodium phosphate, monopotassium phosphate, disodium phosphate, trisodium phosphate, sodium acetate, ammonium acetate, sodium formate, ammonium formate, and trisodium citrate.

It is preferable to use less than 5 parts by weight of the buffer per 100 parts by weight of the monomer mixture, and more preferably less than 3 parts by weight.

In emulsion polymerization, a chain transfer agent can be used as necessary to adjust the molecular weight. As the chain transfer agent, for example, a compound having a thiol group or a hydroxyl group is generally known. Examples of the compound having a thiol group include mercaptans such as lauryl mercaptan, 2-mercaptoethyl alcohol, dodecyl mercaptan, and mercaptosuccinic acid, alkyl mercaptopropionates such as n-butyl mercaptopropionate and octyl mercaptopropionate, and alkoxyalkyl mercaptopropionates such as methoxybutyl mercaptopropionate. In addition, alcohols such as methyl alcohol, n-propyl alcohol, isopropyl alcohol (IPA), t-butyl alcohol, and benzyl alcohol can be used alone or in combination of two or more types.
The amount of the chain transfer agent is preferably 0.01 to 7.5 parts by mass, and more preferably 0.03 to 3.0 parts by mass, based on 100 parts by mass of the monomer mixture.

Furthermore, known additives such as neutralizing agents, leveling agents, preservatives, defoamers, thickeners, and pigment dispersants can be added as optional components.

The amount of neutralizing agent to be added is preferably 0.1 to 5 parts by mass per 100 parts by mass of the acrylic copolymer in order to adjust the pH of the acrylic copolymer. By adding 0.1 to 5 parts by mass, the pH of the acrylic copolymer can be adjusted, and the storage stability of the acrylic copolymer is improved.

The amount of leveling agent to be added is preferably 0.1 to 1 part by mass per 100 parts by mass of the acrylic copolymer. Adding 0.1 parts by mass or more improves the leveling properties during coating and can suppress repelling and shrinkage. Adding 1 part by mass or less can suppress a decrease in adhesive strength and removability when the adhesive layer is formed.

The preservative is preferably added in an amount of 0.1 to 1 part by mass per 100 parts by mass of the acrylic copolymer. Adding 0.1 parts by mass or more can prevent spoilage and bacterial growth in the water-based adhesive. Adding 1 part by mass or less can prevent a decrease in adhesive strength and removability when the adhesive layer is formed.

The amount of antifoaming agent to be added is preferably 0.1 to 1 part by mass per 100 parts by mass of the acrylic copolymer. Adding 0.1 parts by mass or more can suppress foaming during application of the water-based adhesive and can also suppress repelling caused by foaming. Adding 1 part by mass or less can suppress a decrease in adhesive strength and removability when the adhesive layer is formed.

The amount of thickener to be added is preferably 0.1 to 5 parts by mass per 100 parts by mass of the acrylic copolymer. Adding 0.1 parts by mass or more can thicken the water-based adhesive, suppressing shrinkage and repelling during application. Adding 5 parts by mass or less can suppress a decrease in adhesive strength and removability when the adhesive layer is formed.

Pigment dispersions are used when the adhesive layer requires hiding properties and color development. The amount of pigment dispersion to be mixed is preferably 0.1 to 5 parts by mass per 100 parts by mass of acrylic copolymer. By mixing 0.1 parts by mass or more, the hiding properties and color development of the adhesive layer can be improved. By mixing 5 parts by mass or less, the decrease in adhesive strength and removability when the adhesive layer is formed can be suppressed.

[Production by solution polymerization]
The acrylic copolymer can also be obtained by adding a polymerization initiator to a monomer mixture and carrying out solution polymerization. The solvent used in the solution polymerization is preferably, for example, methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, xylene, hexane, acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, n-propanol, isopropanol, etc., and more preferably ethyl acetate.

In solution polymerization, it is preferable to add about 0.001 to 1 part by mass of a polymerization initiator to 100 parts by mass of the monomer mixture to carry out polymerization. Polymerization can usually be carried out for 6 to 20 hours at a temperature of about 50°C to 90°C under a nitrogen gas flow. In addition, during polymerization, the molecular weight of the copolymer can be appropriately adjusted using a chain transfer agent.

Examples of chain transfer agents used in solution polymerization include n-dodecyl mercaptan, mercaptoisobutyl alcohol, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol, glycidyl mercaptan, α-methylstyrene dimer, carbon tetrachloride, chloroform, and hydroquinone. The chain transfer agent can be used in an amount of about 0.01 to 1 part by mass per 100 parts by mass of the monomer mixture.

The polymerization initiators used in solution polymerization are generally azo compounds and organic peroxides.
Examples of azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'-azobis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-hydroxymethylpropionitrile), and 2,2'-azobis(2-(2-imidazolin-2-yl)propane).

Examples of organic peroxides include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di(2-ethoxyethyl)peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxypivalate, (3,5,5-trimethylhexanoyl)peroxide, dipropionyl peroxide, and diacetyl peroxide.

[Curing agent]
The pressure-sensitive adhesive layer in the present invention may further contain a curing agent. Examples of the curing agent include titanium chelate compounds, aluminum chelate compounds, zirconium chelate compounds, zinc oxide, aziridine compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, and hydrazide compounds. The curing agents may be used alone or in combination of two or more.
The curing agent is preferably blended in an amount of 0.01 to 10 parts by mass, more preferably 0.03 to 8 parts by mass, based on 100 parts by mass of the acrylic copolymer. By blending 0.01 to 10 parts by mass, adhesion to the substrate and cohesive strength are further improved.

[Tackifier resin]
The pressure-sensitive adhesive layer in the present invention may further contain a tackifier resin. Examples of the tackifier resin include rosin-based tackifier resins, synthetic hydrocarbon-based tackifier resins, terpene-based tackifier resins, terpene phenol-based tackifier resins, and emulsions using these. By including these tackifier resins, the water-resistant adhesive strength can be further improved.

Preferred rosin-based tackifying resins are rosin esters obtained by esterifying unmodified rosin such as gum rosin, tall oil rosin, and wood rosin with alcohol, modified rosins such as disproportionated rosin obtained by modifying unmodified rosin, polymerized rosin, and hydrogenated rosin, modified rosin esters such as disproportionated rosin esters obtained by further esterifying these modified rosins with alcohol, polymerized rosin esters, and hydrogenated rosin esters, and rosin phenols obtained by adding phenol to unmodified rosin. Among these, rosin esters and modified rosin esters are preferred because they further improve adhesive strength and transparency. Note that in rosin esters and modified rosin esters, some of the hydroxyl groups of the alcohol used for esterification may remain unreacted. Examples of alcohols used for esterification include monofunctional alcohols such as methanol, bifunctional alcohols such as ethylene glycol, trifunctional alcohols such as glycerin, and tetrafunctional alcohols such as pentaerythritol, but considering compatibility with acrylic copolymers, trifunctional or lower alcohols are preferred.

Examples of synthetic hydrocarbon-based adhesive resins include coumarone-based resins, coumarone-indene-based resins, styrene-based resins, xylene-based resins, phenol-based resins, and petroleum-based resins.

The softening point of the tackifier resin is preferably 0 to 160°C, more preferably 0 to 120°C, and even more preferably 0 to 100°C. A softening point of 0 to 160°C makes it easy to achieve both adhesive properties and releasability. The softening point is the softening temperature measured according to the dry bulb method specified in JIS K5902.

The tackifier resin is preferably used in an amount of 10 to 50 parts by mass, more preferably 15 to 40 parts by mass, per 100 parts by mass of the acrylic copolymer. By using 10 to 50 parts by mass of the tackifier resin, it becomes easier to achieve both water-resistant adhesion and releasability.

<Substrate>
Examples of the substrate constituting the laminate include polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene, polyester resins such as polyethylene terephthalate, vinyl acetate resins, polyimide resins, fluorine resins, polyvinyl chloride resins, plastic films made of resin materials such as cellophane, polyethylene nonwoven fabrics, polyester nonwoven fabrics, and vinylon nonwoven fabrics. The substrate may be a single or multiple laminates. In addition, a printed layer for displaying a trade name or the like, for decoration or aesthetic purposes, or an overcoat layer for protecting the printed layer or for imparting design properties such as gloss may be provided on the substrate. From the viewpoint of releasability and recyclability after separation and recovery, it is preferable that the substrate does not include a printed layer or an overcoat layer.

In the present invention, "detachment" refers to the adhesive layer being dissolved or swelled by the release liquid and peeled off, causing the substrate to detach from the laminate, and includes both cases where the adhesive layer dissolves and the substrate detaches, and cases where the adhesive layer does not dissolve but peels off due to neutralization, swelling, etc., causing the substrate to detach.

Since the present invention aims to obtain the substrate after the detachment as a recycled substrate or a regenerated substrate, it is preferable to remove as much of the adhesive layer and the like from the substrate as possible. Specifically, it is preferable that at least 50% by mass or more of the adhesive layer is detached in the area or film thickness direction out of 100% by mass of the adhesive layer. More preferably, it is preferable that 60% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more is detached.
The substrate recovery process after immersion in the desorption liquid to desorb the substrate can be freely selected according to the materials of the support and substrate, such as specific gravity separation or size separation.

<Removal solution>
The release liquid has a dynamic surface tension of 60 mN/m or less at 1000 ms at 25° C., which improves the permeability into the pores of the support and increases the contact area with the adhesive layer. In addition, the release liquid has a pH of 13.3 or more at 25° C., which makes it possible to swell or dissolve the adhesive layer and promotes peeling from the substrate, thereby improving the separation efficiency between the support and the substrate.
The release liquid may have a dynamic surface tension of 60 mN/m or less at 1000 ms measured at 25° C. and a pH of 13.3 or more at 25° C. From the viewpoints of the environment and maintaining the properties of the recycled material using the recovered base material, an aqueous solution is preferred. These release liquids may be heated.

[Dynamic surface tension modifier]
In order to reduce the dynamic surface tension, any dynamic surface tension regulator may be used, preferably a surfactant.

The type of surfactant may be, for example, nonionic, anionic, cationic, or amphoteric, and a suitable type and amount may be selected and used according to the required properties. From the viewpoint of releasing property and foaming property, it is preferable to include at least one of a nonionic surfactant and an anionic surfactant.
Moreover, the surfactant preferably has a structure to which alkylene oxide (hereinafter, also referred to as AO) is added, because this improves the releasability and reattachment properties.

(Nonionic surfactant)
The nonionic surfactant is not particularly limited as long as it has a dynamic surface tension reducing ability, but is preferably an alkylene oxide adduct to which an alkylene oxide is added. More preferably, it is a compound obtained by adding an alkylene oxide to an alcohol having active hydrogen (alcohol-based nonionic surfactant), a compound obtained by adding an alkylene oxide to an amine (amine-based nonionic surfactant), or a compound obtained by adding an alkylene oxide to a fatty acid (fatty acid-based nonionic surfactant). The above addition may be either random addition or block addition. In addition, the number of carbon atoms of the alkylene oxide is preferably 2 to 4.

[Alcohol-based nonionic surfactant]
Examples of alcohol-based nonionic surfactants include alkylene oxide adducts of primary or secondary alcohols having a total of 8 to 24 carbon atoms, and alkylene oxide adducts of alkylphenols having a total of 8 to 12 carbon atoms. The primary or secondary alcohols having a total of 8 to 24 carbon atoms may be either saturated or unsaturated.
Examples of the primary or secondary alcohol having a total of 8 to 24 carbon atoms include lauryl alcohol, stearyl alcohol, oleyl alcohol, dodecyl alcohol, arachidyl alcohol, behenyl alcohol, lignoceryl alcohol, and myristyl alcohol.
Examples of the alkylene oxide to be added to the alcohol include ethylene oxide, propylene oxide, and butylene oxide, and it is preferable that ethylene oxide is essential. The number of moles of the alkylene oxide to be added is preferably 1 to 100 moles, more preferably 2 to 50 moles, per mole of the alcohol or alkylphenol. The above range is preferable because it has excellent elimination properties.

[Amine-based nonionic surfactant]
Examples of the amine-based nonionic surfactant include alkylene oxide adducts of saturated or unsaturated primary or secondary amines having a total carbon number of 8 to 36. Examples of the amine include 2-ethylhexylamine, di-2-ethylhexylamine, laurylamine, dilaurylamine, tetradecylamine, ditetradecylamine, hexadecylamine, dihexadecylamine, stearylamine, distearylamine, oleylamine, dioleylamine, etc. The type and number of moles of alkylene oxide added are the same as those described in the above section on [Alcohol-based nonionic surfactants].

[Fatty acid-based nonionic surfactant]
The fatty acid-based nonionic surfactant is not particularly limited in structure, and examples thereof include alkylene oxide adducts of higher fatty acids having a total of 10 to 24 carbon atoms, fats and oils consisting of esters of the above-mentioned saturated or unsaturated higher fatty acids having a total of 10 to 24 carbon atoms and glycerin, and further alkylene oxide adducts of mixtures of the above-mentioned fats and oils and polyhydric alcohols having a carbon number of 2 to 10. The above-mentioned higher fatty acids having a total of 10 to 24 carbon atoms may be either saturated or unsaturated.
Examples of the higher fatty acids having a total of 10 to 24 carbon atoms include saturated higher fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, and behenic acid, and unsaturated higher fatty acids such as palmitoleic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, erucic acid, and ricinoleic acid. Examples of the dihydric to decahydric polyhydric alcohols include ethylene glycol, propylene glycol, glycerin, polyglycerin, sorbitol, sorbitan, and sucrose. The type and molar number of the alkylene oxide added are the same as those described in the section on [Alcohol-based nonionic surfactants] above.

(Anionic Surfactant)
The anionic surfactant is preferably a non-soap type, and examples thereof include sulfonic acid type anionic surfactants, sulfate ester type anionic surfactants, carboxylate type anionic surfactants, and phosphate ester type anionic surfactants.
[Sulfonic acid-based anionic surfactant]
Examples of the sulfonic acid anionic surfactant include alkylsulfonic acid, alkylbenzenesulfonic acid, alkylnaphthalenesulfonic acid, alkyldiphenyletherdisulfonic acid, alkylmethyltaurine, sulfosuccinic acid diester, alkylene oxide adduct of sulfonic acid, and their salts.Specific examples include hexanesulfonic acid, octanesulfonic acid, decanesulfonic acid, dodecanesulfonic acid, toluenesulfonic acid, cumenesulfonic acid, octylbenzenesulfonic acid, dodecylbenzenesulfonic acid, dinitrobenzenesulfonic acid, and lauryldodecylphenyletherdisulfonic acid.

[Sulfate ester-based anionic surfactants]
Examples of the sulfate anionic surfactant include sulfate (alkyl ether sulfate), alkylene oxide adduct of sulfate, and salts thereof. Specific examples include lauryl sulfate, myristyl sulfate, and polyoxyethylene lauryl ether sulfate.

[Carboxylic acid type anionic surfactant]
Examples of the carboxylic acid-based anionic surfactant include alkyl carboxylic acids, alkyl benzene carboxylic acids, alkylene oxide adducts of carboxylic acids, and salts thereof.Specific examples of the carboxylic acid-based anionic surfactant include lauric acid, myristic acid, palmitic acid, stearic acid, polyoxyethylene lauryl ether acetic acid, and polyoxyethylene tridecyl ether acetic acid.

[Phosphate ester-based anionic surfactant]
Examples of the phosphate anionic surfactant include phosphate (alkyl ether phosphate), alkylene oxide adduct of phosphate, and salts thereof.Specific examples include octyl phosphate, lauryl phosphate, tridecyl phosphate, myristyl phosphate, cetyl phosphate, stearyl phosphate, polyoxyethylene octyl ether phosphate, polyoxyethylene lauryl ether phosphate, etc.

The anionic surfactant preferably has an alkyl group having 2 to 24 carbon atoms or an alkenyl group having 2 to 24 carbon atoms, and more preferably has an alkyl group having 8 to 18 carbon atoms. The alkyl group or alkenyl group may be linear or branched.

When the anionic surfactant is an alkylene oxide adduct, examples of the alkylene oxide include ethylene oxide, propylene oxide, and butylene oxide, with ethylene oxide being preferred. The number of moles of alkylene oxide added is preferably 1 to 12 moles, and more preferably 1 to 8 moles, per mole of alcohol or alkylphenol. The above range is preferred because it has excellent release properties.

Examples of the salt constituting the anionic surfactant include metal salts such as sodium, potassium, magnesium, calcium, etc. These salts may be used alone or in combination of two or more.
Among these, from the viewpoint of releasability and reattachment, preferred anionic surfactants are sulfonate type and phosphate type, and more preferred are alkyl sulfonate, polyoxyalkylene alkyl ether sulfonate, polyoxyalkylene alkyl ether phosphate, etc.

(Cationic Surfactant)
Examples of cationic surfactants include alkylamine salts and quaternary ammonium salts. Specific examples of usable surfactants include stearylamine acetate, trimethyl coconut ammonium chloride, trimethyl beef tallow ammonium chloride, dimethyldioleyl ammonium chloride, methyl oleyl diethanol chloride, tetramethyl ammonium chloride, lauryl pyridinium chloride, lauryl pyridinium bromide, lauryl pyridinium disulfate, cetyl pyridinium bromide, 4-alkyl mercaptopyridine, poly(vinylpyridine)-dodecyl bromide, and dodecylbenzyl triethyl ammonium chloride.

(Amphoteric surfactant)
Examples of amphoteric surfactants include lauryl dimethylaminoacetate betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, coconut oil fatty acid amidopropyl dimethylaminoacetate betaine, polyoctyl polyaminoethyl glycine, and imidazoline derivatives.

These dynamic surface tension modifiers may be used alone or in combination of two or more. The content of the surfactant in the release liquid is preferably in the range of 0.1 to 10 mass%, more preferably in the range of 0.25 to 5 mass%, and most preferably 0.5 to 1 mass%, based on the total mass of the release liquid. A content of 0.1 mass% or more is preferable because it provides excellent release properties, and a content of 10 mass% or less is preferable from the viewpoint of foaming.

[Basic Compounds]
The release solution used in the present invention has a pH of 13.3 or more at 25° C., and therefore must contain a basic compound.
The basic compound is not particularly limited, and for example, sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH) ₂ ), ammonia, barium hydroxide (Ba(OH) ₂ ), and sodium carbonate (Na ₂ CO ₃ ) are preferably used. At least one of sodium hydroxide and potassium hydroxide is more preferably used.

[Antifoaming agent]
In order to suppress foaming when the dynamic surface tension modifier is added, a defoaming agent may be added to the release liquid. Examples of the defoaming agent include silicone-based compounds and non-silicone-based compounds.

(Silicone-based compounds)
Examples of the silicone-based compound include emulsion type, self-emulsifying type, oil type, oil compound type, and solvent type.

Emulsion type is a silicone-based defoamer made by emulsifying a silicone oil compound with an activator to create an O/W type emulsion. Examples include "KM-89" and "KM-98" made by Shin-Etsu Chemical Co., Ltd., "FC2913" and "SILFOAM SE47" made by Asahi Kasei Wacker Silicone, "BYK-015" and "BYK-1640" made by BYK Japan, and "TEGO Foamex 1488" made by Evonik Japan.

Self-emulsifying types are silicone-based defoamers that are 100% active ingredients and become emulsion-like when diluted and mixed with water. Examples include "KS-540" and "X-50-1176" made by Shin-Etsu Chemical Co., Ltd., and "SILFOAM SD670" and "SILFOAM SD850" made by Asahi Kasei Wacker Silicone Co., Ltd.

Oil-type defoamers are 100% silicone oil defoamers that do not contain solvents or additives. Examples include "KM-89" and "KM-98" made by Shin-Etsu Chemical Co., Ltd., "AK350" and "AK12500" made by Wacker Asahi Kasei Silicone, and "BYK-1770" made by BYK Japan.

Oil compound type is a silicone-based defoamer that combines silica particles with silicone oil. Examples include "KM-89" and "KM-98" made by Shin-Etsu Chemical Co., Ltd., "SILFOAM SC370" and "PULPSIL22274VP" made by Wacker Asahi Kasei Silicone, and "BYK-017" and "BYK-018" made by BYK Japan.

Solvent-based defoamers are silicone-based defoamers in which silicone oil is dissolved in a solvent. Examples include "KM-89" and "KM-98" manufactured by Shin-Etsu Chemical Co., Ltd., and "BYK-019" and "BYK-025" manufactured by BYK Japan.

(Non-silicone compounds)
Examples of the non-silicone compounds include fatty acid ester compounds, urea resin compounds, paraffin compounds, polyoxyalkylene glycol compounds, acrylic ester copolymers, ester polymers, ether polymers, amide polymers, emulsion types of mineral oils, polysiloxane adducts, fluorine compounds, vinyl polymers, acetylene alcohol, acrylic copolymers, special vinyl polymers, ethylene glycol, and higher alcohols (such as octyl alcohol and cyclohexanol).

The defoaming agent may be used alone or in combination of two or more kinds. The content of the defoaming agent in the defoaming liquid is preferably in the range of 0.01 to 5 mass% based on the total mass of the defoaming liquid, and more preferably in the range of 0.03 to 3 mass%. If it is 0.01 mass% or more, it has excellent defoaming properties, and if it is 5 mass% or less, it is less likely to remain on the substrate surface after defoaming, and has excellent cleaning properties.

The defoaming agent is preferably at least one selected from the group consisting of emulsion-type silicone compounds, self-emulsifying silicone compounds, and non-silicone compounds, from the viewpoints that it has good alkali resistance and is unlikely to reduce detachment or reattachment properties when combined with a dynamic surface tension modifier.

<Separation and recovery method>
The separation and recovery method after the desorption step is not particularly limited. For example, when the support and the substrate are made of the same material, they may be recovered through a washing step or a drying step without being separated. When the support and the substrate are made of different materials, they may be recovered without being separated depending on the application of the recycled material, or when a single material is to be obtained, they may be separated by a known separation method combining specific gravity separation or near infrared detection and an air jet, and then recovered through a washing step or a drying step as necessary.

The release liquid penetrates the edge of the laminate and comes into contact with the adhesive layer, dissolving or swelling it, thereby separating the substrate from the adhesive layer. Therefore, in order to efficiently proceed with the release process, it is preferable that the laminate is cut or crushed so that the adhesive layer is exposed on the cross section when it is immersed in the release liquid. In such a case, the substrate can be released in a shorter time.

The temperature of the release liquid when the laminate is immersed is preferably in the range of 25 to 100°C, more preferably 40 to 90, and particularly preferably 50 to 80°C. The immersion time in the release liquid is preferably in the range of 1 minute to 24 hours, more preferably 3 minutes to 6 hours, and preferably 5 minutes to 4 hours. The amount of release liquid used is preferably in the range of 50 to 100,000 times, and more preferably 10 to 10,000 times, the mass of the laminate, and it is preferable to stir or circulate the release liquid to improve the release efficiency. The rotation speed is preferably 80 to 5,000 rpm, and more preferably 80 to 4,000 rpm.

After the substrate is detached from the laminate and recovered, the resulting substrate is washed with water and dried, and the support and substrate are separated as necessary to obtain a recycled substrate. The removal rate of the adhesive sheet having the adhesive layer and support on the surface of the substrate is preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more, based on the area of the adhesive sheet before detachment.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" means "parts by mass" and "%" means "% by mass".
The blend amounts in the table are in parts by mass, and amounts other than water and solvent are calculated as non-volatile contents. Note that blanks in the table indicate that no blend was made.

The acid value of the acrylic copolymer was measured by the following method.
<Measurement of Acid Value>
1 g of acrylic copolymer was precisely weighed and placed in a stoppered Erlenmeyer flask, and dissolved in 100 mL of water or a mixture of toluene/ethanol (volume ratio: toluene/ethanol = 2/1), and then titrated with 0.1 N alcoholic potassium hydroxide solution. The acid value (unit: mgKOH/g) was calculated by the following formula. The acid value was the value of the dried sample.
Acid value={(5.61×a×F)/S}/(non-volatile content/100)
S: Amount of sample collected (g)
a: Amount of 0.1N alcoholic potassium hydroxide solution consumed (mL)
F: Factor of 0.1N alcoholic potassium hydroxide solution

<Production of Pressure-Sensitive Adhesive Composition>
[Production Example 1-1] (Production of Pressure-Sensitive Adhesive Composition (A-1))
0.1 parts of tert-dodecyl mercaptan as a chain transfer agent was dissolved in 85 parts of n-butyl acrylate and 15 parts of methacrylic acid. Furthermore, 6.7 parts of Newcol 707SF (aqueous solution of polyoxyethylene polycyclic phenyl ether sulfate salt, active ingredient 30%, manufactured by Nippon Nyukazai Co., Ltd.) as an anionic surfactant and 5.6 parts of a 5% aqueous solution of ammonium persulfate as an initiator were dissolved in 35 parts of ion-exchanged water, and the mixture was added and stirred to obtain an emulsion. This was placed in a dropping funnel.
Into a four-neck flask equipped with a stirrer, a condenser, a thermometer, and the dropping funnel, 72.5 parts of deionized water was charged, the air inside the flask was replaced with nitrogen gas, the internal temperature was raised to 80° C. with stirring, and 2.4 parts of a 5% aqueous ammonium persulfate solution was added. After 5 minutes, the emulsion was added dropwise from the dropping funnel over a period of 3 hours.
While the internal temperature was kept at 80°C, the mixture was further stirred and aged at 80°C for 4 hours, and then cooled to obtain an acrylic copolymer aqueous dispersion. To this aqueous dispersion, 0.3 parts of Adekanate B-940 (manufactured by ADEKA Corporation) as a defoaming agent, 0.2 parts of PELLEX OT-P (manufactured by Kao Corporation) as a leveling agent, and 0.05 parts of Levanax FX-360 (manufactured by Shoei Chemical Co., Ltd.) as a preservative were added, and the pH was adjusted (measured with a Horiba pH meter D-52) and the viscosity was adjusted with an alkaline thickener and aqueous ammonia to obtain a pressure-sensitive adhesive composition (A-1) with a pH of 8.0 and a viscosity of 2,000 mPa (BL type viscometer #4-12 rpm).

[Production Example 1-2] (Production of Pressure-Sensitive Adhesive Composition (A-2))
A pressure-sensitive adhesive composition (A-2) was obtained in the same manner as in [Production Example 1-1], except that the types and amounts of the monomer, surfactant, and initiator were changed as shown in Table 1.

[Production Example 1-3] (Production of Pressure-Sensitive Adhesive Composition (A-3))
In a four-neck flask equipped with a stirrer, a cooling tube, a thermometer, and the dropping funnel, 94.9 parts of n-butyl acrylate, 0.1 parts of 2-hydroxyethyl acrylate, 5 parts of acrylic acid, 100 parts of ethyl acetate, and 0.015 parts of 2,2'-azobisisobutyronitrile were charged under a nitrogen atmosphere. The mixture was heated while stirring to confirm the start of the polymerization reaction, and reacted at reflux temperature for 2 hours. Next, 0.005 parts of 2,2'-azobisisobutyronitrile was added to the reaction solution, and the reaction was continued for 6 hours. Thereafter, the reaction vessel was cooled, and 130 parts of ethyl acetate was added to obtain an acrylic copolymer solution. Just before the preparation of the adhesive sheet of Production Example 3-3, 0.5 parts of aluminum chelate A (manufactured by Kawaken Fine Chemicals, aluminum trisacetylacetonate) was mixed as a curing agent, and ethyl acetate was further added as a solvent to adjust the non-volatile content to 30%, to obtain an adhesive composition (A-3).

[Production Examples 1-4, 5] (Production of Pressure-Sensitive Adhesive Compositions (A-4, 5))
Pressure-sensitive adhesive compositions (A-4 to A-5) were obtained in the same manner as in [Production Example 1-3], except that the types and amounts of monomer, initiator, and curing agent were changed as shown in Table 1. However, the curing agent was added just before the preparation of the pressure-sensitive adhesive sheets in Production Examples 3-4 to 3-5.

The abbreviations in Table 1 are described below.
2EHA: 2-ethylhexyl acrylate BA: n-butyl acrylate MA: methyl acrylate MMA: methyl methacrylate HEA: 2-hydroxyethyl acrylate MAA: methacrylic acid AA: acrylic acid 707SF: Newcol 707SF (aqueous solution of polyoxyethylene polycyclic phenyl ether sulfate, active ingredient 30%), manufactured by Nippon Nyukazai Co., Ltd.
KH-10: Aqualon KH-10 ((Polyoxyethylene-1-(allyloxymethyl) alkyl ether sulfate ester ammonium salt), manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
APS: ammonium persulfate AIBN: 2,2'-azobisisobutyronitrile Aluminum chelate A: Aluminum chelate A (aluminum trisacetylacetonate), manufactured by Kawaken Fine Chemicals Co., Ltd.
TDI/TMP: Trimethylolpropane adduct of tolylene diisocyanate (non-volatile content 37.5%)

<Support>
[Production Example 2-1] (Production of Support (B-2))
A reaction vessel (reaction tank) equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser was charged with 237.8 parts of water and 0.86 parts of Perex OT-P (Kao Corporation dioctyl sulfosuccinate sodium, active ingredient 70%). Separately, 69.5 parts of methyl methacrylate, 18.0 parts of n-butyl acrylate, 12.5 parts of methacrylic acid, 3.0 parts of t-dodecyl mercaptan, 2.01 parts of Perex OT-P, and 65.8 parts of water were mixed and stirred in advance to prepare an emulsion of ethylenically unsaturated monomers (first-stage dropping tank) to be dropped into the first stage. The internal temperature of the reaction vessel was raised to 80°C and nitrogen substitution was sufficiently performed, and then 12.1 parts of a 5% aqueous solution of potassium persulfate was added as an initiator to start emulsion polymerization. While maintaining the internal temperature at 80°C, the emulsion of the ethylenically unsaturated monomer to be dropped into the first stage and 5.5 parts of a 5% aqueous solution of potassium persulfate were dropped over 2 hours. After the dropping was completed, the mixture was reacted for 2 hours, and 9.9 parts of 25% aqueous ammonia was added while maintaining the temperature at 80°C to neutralize. Subsequently, the second stage ethylenically unsaturated monomer solution (second stage dropping tank) prepared by previously mixing 50.0 parts of methyl acrylate and 102.0 parts of n-butyl acrylate and 24.2 parts of a 10% aqueous solution of ammonium persulfate were dropped over 2 hours. After the dropping was completed, the mixture was reacted for another 3 hours while maintaining the temperature at 80°C to obtain an aqueous dispersion of resin fine particles. The acid value of the obtained resin fine particles was 31.2 mgKOH/g. Water was further added to this to adjust the non-volatile content to 40%, and a nonwoven fabric sealing agent was obtained.
A polyethylene terephthalate nonwoven fabric MF-90 (support (B-1), Gurley air permeability 0.1 seconds) manufactured by Japan Vilene Co., Ltd. was subjected to a calendar treatment using a pressure nip device consisting of a metal roll and an elastic roll at a metal roll surface temperature of 195°C, a nip pressure of 100 kN/m, and a treatment speed of 10 m/min, and then the sealing agent was applied thereto using a gravure coater so that the coating amount after drying would be 3 g/ ^m2 , and the fabric was air-dried at 80°C for 120 seconds. The Gurley air permeability of the resulting sealing-treated polyethylene nonwoven fabric (support (B-2)) was 15 seconds/100 mL.

[Production Example 2-2] (Production of Support (B-3))
A solution consisting of a high-density polyethylene polymer (melt mass-flow rate (hereinafter referred to as "MFR") = 0.8) and HFC refrigerant R32 was discharged from a nozzle under high temperature and high pressure conditions into a low temperature and low pressure region to flush the solvent and deposit it in a wire mesh shape to form fibrillated reticular fibers, which were then treated on both sides with a felt calendar at 138°C with a contact time of 5 seconds to obtain a polyethylene nonwoven fabric. The Gurley air permeability of the obtained nonwoven fabric (support (B-3)) was 4 seconds/100 mL.
The MFR was measured in accordance with JIS K7210-1:2014 at a temperature of 230° C. and a load of 2.16 kgf (21.2 N).

[Production Example 2-3] (Production of Support (B-4))
The filler obtained in Production Example 2-1 was applied to the support B-3 obtained in Production Example 2-2 by a gravure coater so that the coating amount after drying would be 3 g/ ^m2 , and the resulting product was air-dried for 120 seconds at 80° C. The Gurley air permeability of the resulting filler-treated polyethylene nonwoven fabric (support (B-4)) was 11 seconds/100 mL.

[Production Example 2-4] (Production of Support (B-6))
The sealant obtained in Production Example 2-1 was applied to a polyethylene nonwoven fabric Tyvek 1-73B (support (B-5), Gurley air permeability 22 seconds/100 mL) manufactured by DuPont-Asahi Flash Span Products Co., Ltd., using a gravure coater so that the coating amount after drying would be 3 g/ ^m2 , and the coating was air-dried at 80°C for 120 seconds. The resulting sealed polyethylene nonwoven fabric (support (B-6)) had a Gurley air permeability of 45 seconds/100 mL.

[Production Example 2-5] (Production of Support (B-7))
The support (B-5) was subjected to a calendering treatment using a pressure nip device consisting of a metal roll and an elastic roll at a metal roll surface temperature of 130° C., a nip pressure of 100 kN/m, and a treatment speed of 10 m/min. The resulting nonwoven fabric (support (B-7)) had a Gurley air permeability of 150 sec/100 mL.

[Production Example 2-6] (Production of Support (B-8))
The support (B-5) was subjected to a calendering treatment using a pressure nip device consisting of a metal roll and an elastic roll, with the metal roll surface temperature at 140° C., the nip pressure at 100 kN/m, and the treatment speed at 5 m/min. The Gurley air permeability of the obtained nonwoven fabric (support (B-8)) was 500 sec/100 mL.

[Production Example 2-7] (Production of Support (B-10))
A polypropylene nonwoven fabric Syntex (support (B-9), Gurley air permeability 180 sec/100 mL) manufactured by Mitsui Chemicals, Inc. was calendered using a pressure nip device consisting of a metal roll and an elastic roll at a metal roll surface temperature of 130° C., a nip pressure of 100 kN/m, and a processing speed of 10 m/min. The resulting nonwoven fabric (support (B-10)) had a Gurley air permeability of 450 sec/100 mL.

[Production Example 2-8] (Production of Support (B-11))
The filler obtained in Production Example 2-1 was applied to the support (B-9) by a gravure coater so that the coating amount after drying was 3 g/ ^m2 , and the nonwoven fabric was air-dried at 80° C. for 120 seconds. The Gurley air permeability of the obtained nonwoven fabric (support (B-11)) was 720 sec/100 mL.

[Production Example 2-9] (Production of Support (B-12))
94.6 parts of FS2016 manufactured by Sumitomo Chemical Co., Ltd. and 5 parts of HMS-PP manufactured by SunAllomer Co., Ltd. were added and mixed with 0.2 parts of N,N'-dicyclohexyl-2,6-naphthalenedicarboxamide (NU-100 manufactured by New Japan Chemical Co., Ltd.) as a β crystal nucleating agent, and 0.2 parts of crosslinked PMMA particles (Eposter MA1002 manufactured by Nippon Shokubai Co., Ltd.) as a slipping agent, and fed to a twin-screw extruder and melt-mixed at 200 ° C., extruded into a gut shape, cooled through a 20 ° C. water bath, cut into 3 mm lengths with a tip cutter, and then dried for 2 hours at 100 ° C. Next, the mixture was fed to an extruder heated to 200 ° C. and melted, extruded into a sheet shape through a T-die nozzle, and then attached to a cast drum heated to a surface temperature of 120 ° C., and cooled and solidified by blowing hot air at 120 ° C. from the non-drum side to produce an unstretched film. The unstretched film was introduced into an oven heated and maintained at 100 ° C., preheated, stretched 6 times in the MD direction, and cooled with a roll at 40 ° C. Then, the film stretched in the MD direction was introduced into a tenter while holding both ends with clips, and stretched 9 times in the TD direction in an atmosphere heated to 125 ° C. (area ratio: longitudinal stretch ratio × transverse stretch ratio = 54 times). In order to complete the crystal orientation of the microporous polypropylene film and impart flatness and dimensional stability, the film was subjected to a 5% transverse relaxation heat treatment at 150 ° C. in the tenter, uniformly cooled slowly, and then cooled to room temperature to obtain a microporous polypropylene film (support (B-12)). The Gurley air permeability of the obtained support (B-12) was 80 seconds/100 mL.

[Production Example 2-10] (Production of Support (B-13))
The filler obtained in Production Example 2-1 was applied to the support (B-7) by a gravure coater so that the coating amount after drying would be 3 g/ ^m2 , and the nonwoven fabric was air-dried for 120 seconds at 80° C. The Gurley air permeability of the obtained nonwoven fabric (support (B-13)) was 1300 sec/100 mL.

The Gurley air permeability of each support is summarized in Table 2.

<Production of Pressure-Sensitive Adhesive Sheet>
[Production Example 3-1] (Production of Pressure-Sensitive Adhesive Sheet (C-1))
The adhesive composition (A-1) was applied onto a release sheet using a comma coater, dried in a drying oven at 100°C for 120 seconds, and then laminated to a support (B-5) to obtain an adhesive sheet (C-1). The applied amount of the adhesive was 26.2 g/ ^m2 .

[Production Examples 3-2 to 21] (Production of Pressure-Sensitive Adhesive Sheets (C-2 to 21))
Pressure-sensitive adhesive sheets (C-2 to 21) were obtained in the same manner as in [Production Example 3-1], except that the compositions and blending amounts were changed as shown in Table 3. However, the contents of the supports (B-1), (B-5), (B-9), (B-14) and (B-15) were as follows.
Support (B-1): Polyethylene terephthalate nonwoven fabric MF-90 manufactured by Japan Vilene Co., Ltd. (support (B-1), Gurley air permeability 0.1 sec/100 mL)
Support (B-5): Tyvek 1-73B polyethylene nonwoven fabric manufactured by Asahi DuPont Flash Spun Products Co., Ltd. (support (B-5), Gurley air permeability 22 seconds/100 mL) Support (B-9): Syntex polypropylene nonwoven fabric manufactured by Mitsui Chemicals, Inc. (support (B-9), Gurley air permeability 180 seconds/100 mL)
Support (B-14): Commercially available glassine paper (Gurley air permeability 15 seconds/100 mL)
Support (B-15): Commercially available polyethylene film (thickness 25 μm, Gurley air permeability 1300 sec/100 mL or more)

<Production of eluent>
[Production Example 4-1] (Production of elution solution (D-1))
0.25 parts of Emulgen A-60 manufactured by Kao Corporation as a surfactant, 2 parts of sodium hydroxide, and 97.75 parts of water were mixed and stirred with a disperser to obtain a elution liquid (D-1).

[Production Examples 4-2 to 4-18] (Production of Elution Solutions (D-2 to 4-18))
Elimination solutions (D-2 to 18) were obtained in the same manner as in [Production Example 4-1], except that the compositions and amounts were changed as shown in Tables 4-1 and 4-2 (hereinafter, Table 4).

In Table 4, Lipocard 16-29 is manufactured by Lion Specialty Chemicals Co., Ltd., and the other surfactants are manufactured by Kao Corporation.

[Example 1]
The laminate was prepared and the releasability was evaluated by the following method. The waterproof adhesive strength of the laminate was also measured.
[Production of Laminate]
Each pressure-sensitive adhesive sheet (C-1) produced in Production Example 3-1 was cut into a size of 25 mm x 100 mm in an atmosphere of 23°C and relative humidity of 50%, and the release sheet was peeled off to expose the pressure-sensitive adhesive layer, which was attached to a substrate (polyethylene film, 30 mm x 120 mm, thickness 50 µm), and pressure-bonded once back and forth with a 2 kg roll to obtain a laminate.

[Water-resistant adhesive strength]
After peeling off the edge of the adhesive sheet of 25 mm x 20 mm from the laminate, the adhesive layer was attached to the laminate by folding about 10 mm inward. The sample was immersed in ion-exchanged water for 20 minutes, and then removed from the ion-exchanged water. After the water on the surface was wiped off, the substrate side was reinforced with a SUS plate and the adhesive strength was measured in accordance with JIS Z 0237:2009. The obtained value was regarded as the water-resistant adhesive strength.
It was determined that if the water-resistant adhesive strength is 300 gf/25 mm or more, peeling due to immersion in water when frost or condensation occurs can be prevented.

(Evaluation of releasability)
400 g of the release solution (D-4) and 12 g of a sample cut into a size of 1 cm × 1 cm of the laminate were placed in a 1000 mL stainless steel beaker, and the mixture was stirred under conditions of 80 ° C. and 2000 rpm. The substrate after release floating near the treatment liquid surface was scooped up, washed with water, and dried to separate and recover the substrate.

In the separation and recovery test, 10 substrates were recovered 15 minutes, 30 minutes, and 1 hour after the start of stirring, and then washed with water and dried. The presence or absence of absorption peaks of the adhesive was confirmed using FT-IR for a total of 30 locations on the front and back of the substrate, and evaluated according to the following criteria.
A (very good): In the substrate recovered 15 minutes after the start of stirring, the number of points at which absorption peaks of the pressure-sensitive adhesive layer were confirmed was less than 5.
B (Excellent): In the substrate recovered 30 minutes after the start of stirring, the number of points at which absorption peaks of the pressure-sensitive adhesive layer were confirmed for the first time was less than 5.
C (practical): In the substrate recovered 1 hour after the start of stirring, the number of points at which absorption peaks of the pressure-sensitive adhesive layer were confirmed for the first time was less than 5.
D (not practical): In the substrate recovered 1 hour after the start of stirring, absorption peaks of the adhesive layer were confirmed in 6 or more locations.

[Examples 2 to 34, Comparative Examples 1 to 8]
A separation and recovery test was carried out and a release property evaluation was performed in the same manner as in Example 1, except that the substrate and pressure-sensitive adhesive sheet of the laminate, and the release liquid were changed to those shown in Table 5. However, in Comparative Example 3, the distinction between the support and the substrate was judged by the thickness.
In Comparative Example 2, no absorption peaks of the adhesive layer were confirmed in the 10 substrates collected 15 minutes after the start of stirring, but the glassine paper support was dispersed in the release solution, and it took time to wash with water, so it was determined to be impractical. In Comparative Examples 7 and 8, the adhesive strength was at a level that it peeled off before the start of the measurement, so the release property test could not be carried out.

The substrates in Table 5 are described below.
PET: polyethylene terephthalate film, thickness 200 μm
PE: polyethylene film, thickness 50 μm
PP: Polypropylene film, thickness 50 μm

The above evaluation results show that the laminate separation and recovery method of the present invention makes it possible to efficiently separate and recover the substrate from a laminate in which a water-resistant adhesive sheet and a substrate are bonded together.

This application claims priority based on Japanese Patent Application No. 2022-159279, filed on October 3, 2022, the entire disclosure of which is incorporated herein by reference.

Claims

A method for separating and recovering a substrate from a laminate in which a support, a pressure-sensitive adhesive layer, and a substrate are laminated in this order, comprising the steps of:
the support is a nonwoven fabric or a breathable film having a Gurley air permeability of 10 to 1000 seconds/100 mL;
a step of immersing the laminate in a release liquid to release the base material from the pressure-sensitive adhesive layer,
A method for separating and recovering a substrate, wherein the pH of the release liquid at 25°C is 13.3 or more, and the dynamic surface tension of the release liquid at 1000 msec measured at 25°C is 60 mN/m or less.
The method for separating and recovering a substrate according to claim 1, wherein the adhesive layer is an adhesive layer containing an acrylic copolymer, the acrylic copolymer being a copolymer of a monomer mixture containing a (meth)acrylate having a carboxyl group, and the acid value of the acrylic copolymer is 0.1 to 100 mgKOH/g.
The method for separating and recovering a substrate according to claim 1 or 2, characterized in that the coating amount of the pressure-sensitive adhesive layer is 10 to 30 g/ m2 .