JP2024017140A - How to remove layers from the substrate - Google Patents

Abstract

The present invention provides a method for easily and reliably removing a layer from a substrate to which the layer is attached. [Solution] A method for removing a layer from a substrate, the substrate to which a layer containing a compound (A) having a structure represented by general formula (1): CO-O-Si is removed with a treatment solution (B ), wherein the treatment liquid (B) is an alkaline aqueous solution with a pH of 8.5 or more or a mixed solution of an alkaline aqueous solution with a pH of 8.5 or more and an organic solvent. be. [Selection diagram] None

Description

The present invention relates to a method for removing a layer from a substrate to which the layer has been deposited.

In recent years, as environmental awareness has increased, research and development regarding the recycling of paper and plastic products (for example, containers and films) has been actively promoted. The main uses of paper and plastic products include documents, catalogs, packaging, and containers, and their surfaces are generally processed in various ways, such as adding decorative layers and various functional layers using various printing methods. has been done. In the recycling process, it is required to remove the layer adhering to the substrate. The process of removing layers from the substrate is a process that greatly affects the quality of recycled materials, and if the removal of layers is insufficient, the quality of recycled materials will deteriorate. At the same time, reducing costs related to recycling is also an important element for promoting recycling, and implementing the removal process easily and reliably is an important issue to be solved in promoting recycling business.

JP-A-2005-344054 (Patent Document 1) describes an active energy ray-curable overcoat varnish for deinking. Although good deinking properties have been shown, adhesion and water resistance have not been evaluated. Hydrophilic monomers such as hydroxyl groups, carboxyl groups, carboxylic acid amides, sulfone groups, epoxide groups, and ether groups are essential components, and films formed from these hydrophilic monomer compositions generally have poor water resistance. Further, there are problems such as poor adhesion to highly hydrophobic substrates. In particular, it is difficult to adhere to olefin base materials such as polyethylene and polypropylene.

JP-A-63-57675 (Patent Document 2) exemplifies an antifouling paint using an acrylic polymer resin having a molecular structure represented by the following general formula (1).
CO-O-Si (1)
This is a technology in which the material becomes hydrophilic by being hydrolyzed in seawater, and then dissolves in the seawater over several years. The above-mentioned removal step in recycling is a technique for quickly removing the adhered layer from the base material, and the design concept is fundamentally different from the technique described in Patent Document 2.

Japanese Patent Application Publication No. 2005-344054 Japanese Unexamined Patent Publication No. 63-57675

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for easily and reliably removing a layer from a substrate to which the layer is attached.

As a result of intensive studies to achieve the above object, the present inventor found that if the layer contains a compound having a specific molecular structure, an alkaline aqueous solution with a pH of 8.5 or more or an alkaline aqueous solution with a pH of 8.5 or more and an organic solvent can be used. The present inventors have discovered that it can be easily and reliably removed from a substrate by immersing it in a mixed solution of the following, and have completed the present invention.

Therefore, the method of the present invention is a method for removing a layer from a substrate, and the substrate to which a layer containing a compound (A) having a structure represented by the following general formula (1) is attached is treated with a treatment liquid (B). The method is characterized in that the treatment liquid (B) is an alkaline aqueous solution with a pH of 8.5 or more or a mixed solution of an alkaline aqueous solution with a pH of 8.5 or more and an organic solvent. .
CO-O-Si (1)

In a preferred embodiment of the method of the present invention, the layer containing the compound (A) is a layer cured by irradiation with active energy rays.

In another preferred embodiment of the method of the present invention, the substrate is immersed in the treatment liquid (B) for 5 minutes to 48 hours.

In another preferred embodiment of the method of the present invention, the temperature of the treatment liquid (B) when the substrate is immersed in the treatment liquid (B) is 25 to 80°C.

In another preferred embodiment of the method of the present invention, stirring, bubbling, or ultrasonic irradiation is performed when the substrate is immersed in the treatment liquid (B).

In another preferred example of the method of the present invention, the structure represented by the general formula (1) of the compound (A) is derived from a polymerizable compound represented by the following general formula (2).
CH ₂ =C(R1)-CO-O-Si(R2)(R3)(R4) (2)
(In the formula, R1 is H or a methyl group, and R2, R3, and R4 are each independently a saturated hydrocarbon group, an unsaturated hydrocarbon group, or an aromatic group.)

In another preferred example of the method of the present invention, the structure represented by the general formula (1) of the compound (A) is derived from a polymerizable compound represented by the following general formula (3).
CH ₂ =C(R1)-CO-O-Si(R5) ₃ (3)
(In the formula, R1 is H or a methyl group, and R5 is an isopropyl group or a butyl group.)

In another preferred embodiment of the method of the invention, the layer containing the compound (A) is not removed from the substrate even when immersed in a neutral to acidic aqueous solution.

According to the present invention, it is possible to provide a method for easily and reliably removing a layer from a substrate to which the layer is attached.

The present invention will be explained in detail below. The present invention relates to a method for removing a layer from a substrate, comprising the step of immersing the substrate to which the layer is attached in a treatment liquid. This method of removing a layer from a substrate is also referred to herein as the "method of the invention."

The substrate treated by the method of the invention has a layer attached thereto, which layer has the following general formula (1):
CO-O-Si (1)
It includes a compound (A) having the structure shown below. Here, the "CO" part in general formula (1) is a carbonyl group, and can also be expressed as "C(=O)", and general formula (1) can be replaced by C(=O)-O-Si. It is also possible to express it as The oxygen atom of the "--O--Si" moiety in general formula (1) is bonded to the carbon atom of the carbonyl group "CO".
Since the CO-O-Si structure can be easily decomposed by a hydrolysis reaction using an alkaline aqueous solution, a film with the CO-O-Si structure can be easily and reliably removed from the substrate. can be done. For example, when a hydrolysis reaction is carried out using an aqueous sodium hydroxide solution, the structure represented by general formula (1) decomposes into CO--O ^-- Na ⁺ and Si--OH. Furthermore, since the structure represented by the general formula (1) does not undergo a hydrolysis reaction in a neutral or acidic aqueous solution, it does not reduce water resistance or resistance to acidic aqueous solutions. Further, by using the compound (A) having the structure represented by the general formula (1), the layer on the base material can be removed with an alkaline aqueous solution without making the layer hydrophilic. As a result, the layer containing the compound (A) having the molecular structure represented by the general formula (1) also has the effect of adhesion to various base materials such as PET and polyolefin and water resistance.

Compound (A) has a structure shown in general formula (1) in the molecule: CO-O-Si (1)
Although there are no particular limitations other than having the following, a polymer is preferable since it constitutes a layer formed on a base material. Further, the compound (A) is usually a polymer obtained by polymerizing a polymerizable compound, and is different from a polymerizable compound.

The structure represented by the general formula (1) of compound (A) is preferably derived from the polymerizable compound represented by the following general formula (2), and is preferably derived from the polymerizable compound represented by the following general formula (3). More preferably.
CH ₂ =C(R1)-CO-O-Si(R2)(R3)(R4) (2)
In formula (2), R1 is H or a methyl group, and R2, R3, and R4 are each independently a saturated hydrocarbon group, an unsaturated hydrocarbon group, or an aromatic group. The saturated hydrocarbon group and the unsaturated hydrocarbon group are preferably hydrocarbon groups having 4 or less carbon atoms.
CH ₂ =C(R1)-CO-O-Si(R5) ₃ (3)
In formula (3), R1 is H or a methyl group, and R5 is an isopropyl group or a butyl group.

For example, by obtaining compound (A) by polymerizing a raw material containing a polymerizable compound represented by general formula (2), the structure represented by general formula (1) of compound (A) can be changed to the structure represented by general formula (2). The compound (A) is derived from the polymerizable compound represented by the general formula (1) by obtaining the compound (A) by polymerizing raw materials containing the polymerizable compound represented by the general formula (3). The structure is derived from a polymerizable compound represented by general formula (3).

Examples of the polymerizable compound that can be used in the synthesis of compound (A) include polymers, oligomers, monomers, etc., but polymerizable monomers are particularly preferred from the viewpoint of a high degree of freedom in blending design. Furthermore, as the polymerizable compound, at least a polymerizable compound having a structure represented by general formula (1) is used, but a polymerizable compound not having a structure represented by general formula (1) may be used in combination. is also possible. By using a polymerizable compound that does not have the structure represented by general formula (1), it is possible to develop solvent resistance.

Furthermore, polymerizable compounds can be classified into monofunctional polymerizable compounds and polyfunctional polymerizable compounds depending on the number of polymerizable functional groups. Examples of monofunctional polymerizable compounds include monofunctional polymerizable monomers having one functional group that exhibits reactivity when irradiated with active energy rays (for example, monofunctional polymerizable monomers that have one polymerizable unsaturated group) and irradiated with active energy rays. Examples include monofunctional polymerizable oligomers having one functional group that sometimes exhibits reactivity (for example, monofunctional polymerizable oligomers having one polymerizable unsaturated group). Examples of polyfunctional polymerizable compounds include polyfunctional polymerizable monomers that have two or more functional groups that exhibit reactivity when irradiated with active energy rays (e.g., polyfunctional polymerizable monomers that have two or more polymerizable unsaturated groups), and activated Examples include polyfunctional polymerizable oligomers having two or more functional groups that exhibit reactivity upon energy ray irradiation (for example, polyfunctional polymerizable oligomers having two or more polymerizable unsaturated groups).

Examples of functional groups that exhibit reactivity upon irradiation with active energy rays include polymerizable functional groups such as carbon-carbon double bonds constituting acryloyl groups, methacryloyl groups, vinyl groups, or allyl groups, epoxy groups, and oxetane rings. It will be done.

The polymerizable oligomer is preferably an acrylate oligomer. Further, the number of functional groups in the polymerizable oligomer is preferably 2 or more, more preferably 4 or more. The molecular weight of the polymerizable oligomer is preferably 1,000 to 20,000. Here, the molecular weight of the polymerizable oligomer is the weight average molecular weight in terms of polystyrene.

The polymerizable compound having the structure represented by general formula (1) is preferably a monofunctional polymerizable compound, more preferably a monofunctional polymerizable monomer, and a preferred specific example is triisopropylsilyl (meth ) acrylate, trialkylsilyl (meth)acrylate such as tributylsilyl (meth)acrylate. The polymerizable compounds having the structure represented by the general formula (1) may be used alone or in combination of two or more.

As used herein, the term (meth)acrylate means methacrylate or acrylate. In addition, when a prefix indicating plurality is attached to (meth)acrylate, such as di(meth)acrylate, tri(meth)acrylate, etc., each (meth)acrylate part may be the same or different. Good too.

In the synthesis of compound (A), when a polymerizable compound having a structure represented by general formula (1) and a polymerizable compound not having a structure represented by general formula (1) are used together, in general formula (1), The proportion of the polymerizable compound not having the structure represented by general formula (1) to the total of the polymerizable compound having the structure shown and the polymerizable compound not having the structure represented by general formula (1) is , preferably 50 to 95% by mass. The polymerizable compounds not having the structure represented by the general formula (1) may be used alone or in combination of two or more.

Furthermore, in the synthesis of compound (A), it is preferable to use a highly hydrophilic polymerizable compound from the viewpoint of efficiently removing the layer from the base material. A highly hydrophilic polymerizable compound can easily incorporate water into the layer, and therefore can promote the hydrolysis reaction of the structure represented by general formula (1). Examples of the highly hydrophilic polymerizable compound include, in particular, a polymerizable compound having an amide structure, a polymerizable compound having a polyalkylene oxide structure, a polymerizable compound having a hydroxyl group, a polymerizable compound having a carboxyl group (or a salt thereof), Examples include polymerizable compounds having a sulfonic acid group (or a salt thereof) and polymerizable compounds having an amino group (or a quaternary salt thereof). Furthermore, the most suitable highly hydrophilic polymerizable compound is acryloylmorpholine. On the other hand, using a large amount of highly hydrophilic polymerizable compounds may cause deterioration of water resistance. Furthermore, if a large amount of a highly hydrophilic polymerizable compound is used, it may become a factor in deteriorating the adhesion to a low polar base material such as polypropylene (PP). Therefore, the amount of the highly hydrophilic polymerizable compound is preferably 10 to 40% by mass based on the total amount of polymerizable compounds used in the synthesis of compound (A).

The amount of the structure (COOSi) represented by general formula (1) contained in the layer containing compound (A) is preferably 0.4 to 1.8 mol/kg. Here, the atomic weights are H=1.01, C=12.01, O=16.00, and Si=28.09.

The layer containing compound (A) can contain a colorant. There are no particular limitations on the colorant, and colorants commonly used in paints, inks, etc. can be used as appropriate, and they may be dyes or pigments. The amount of colorant contained in the layer is, for example, from 0.1 to 25% by weight. The coloring agents may be used alone or in combination of two or more.

The layer containing the compound (A) contains, as other components, a natural resin, an antioxidant, an ultraviolet absorber, an infrared absorber, a plasticizer, a rust preventive, a solvent, a non-reactive polymer, a filler, an antifoaming agent, Conductivity imparting agent, conductive particles, stress relaxation agent, penetrating agent, light guiding agent, refractive index adjusting agent, metal oxide particles, bright material, magnetic material, phosphor, antibacterial agent, antiviral agent, algae preventive agent, Additives such as fungicides can be contained as necessary.

Layers containing compound (A) are applied to substrates for various purposes. There are various functional layers that are applied to the base material, such as a decorative layer that is used to add letters, pictures, patterns, etc. to the base material, and a protective layer that is used to protect the base material. Examples include a base layer, a gloss-imparting layer, a refractive index adjusting layer, an unevenness-imparting layer, etc. for the purpose of imparting adhesion, fixability, etc. to the layer or substrate. Moreover, not only one type of layer containing the compound (A) but also multiple types of layers may be provided on the base material.

The substrate treated by the method of the present invention is not particularly limited. The shape of the base material includes, for example, a film shape, a sheet shape, a plate shape, and the like. Examples of the base material include epoxy resin, ABS resin, polycarbonate (PC) resin, polyvinyl chloride (PVC) resin, polystyrene (PS) resin, polymethyl methacrylate (PMMA) resin, polyethylene terephthalate (PET) resin, Plastics such as polyethylene (PE) resin and polypropylene (PP) resin, metals such as iron, stainless steel, and aluminum, paper, synthetic paper, wood, cement, concrete, plaster, calcium silicate, calcium carbonate, glass, ceramics, etc. These composite materials can be mentioned. Specific examples of the base material include PET film, PP film, PE film, PVC sheet, tarpaulin, plastic cardboard, acrylic board, polystyrene (PS) board, PP molding material, composite material of PP and calcium carbonate, etc. .

In the present invention, when a plurality of layers are provided to the base material, it is not necessary that all the layers contain the compound (A), and there may be a layer that does not contain the compound (A). good. However, from the viewpoint of completely removing the layer from the base material, particularly from the viewpoint of recycling the base material, it is desirable that the layer directly attached to the base material is a layer containing the compound (A). For example, a layer that is attached to the base material via a layer containing compound (A) may be a layer that does not contain compound (A).

The base material to which the layer containing the compound (A) is attached can be manufactured by forming the layer containing the compound (A) on the base material. The method for forming the layer containing compound (A) is not particularly limited, and includes printing methods using inkjet ink, printing methods such as gravure, letterpress, silk screen, planography, and offset, electrophotographic printing methods using toner, roll coaters, and curtains. Coating methods include flow coater and spray. Other methods include transfer and film attachment. When forming a layer containing multiple types of compounds (A), it is also possible to employ different formation methods.

In one embodiment of the method of the present invention, the layer containing compound (A) is formed by gravure printing, letterpress printing, silk screen printing, lithography, or offset printing.

In another embodiment of the method of the invention, the layer comprising compound (A) is formed by inkjet ink printing.

In another embodiment of the method of the invention, the layer comprising compound (A) is formed by electrophotographic printing.

In another embodiment of the method of the invention, the layer containing compound (A) is formed by painting.

The raw material for forming the layer containing compound (A) may be in the form of ink, toner, paint, etc., and is appropriately selected depending on the method for forming the layer containing compound (A). Further, the compound (A) may be present in the raw material, or the compound (A) may be synthesized by polymerization of a polymerizable compound or the like when forming a layer containing the compound (A). For example, when the raw material for forming a layer containing compound (A) is an active energy ray-curable composition, compound (A) can be synthesized by polymerizing the polymerizable compound by irradiation with active energy rays. .

In the method of the present invention, the layer containing compound (A) is preferably a layer cured by irradiation with active energy rays. It is often difficult to remove a layer cured by active energy rays from a substrate, so the use of compound (A) is particularly effective. The raw material for forming the active energy ray-cured layer, that is, the active energy ray-curable composition will be described below.

As used herein, the active energy ray-curable composition refers to a composition that can be cured by irradiation with active energy rays such as ultraviolet rays, visible light, and electron beams. Compounds that sometimes cause polymerization reactions through reactive functional groups (e.g., carbon-carbon double bonds constituting acryloyl, methacryloyl, vinyl, or allyl groups, polymerizable groups such as epoxy groups, oxetane rings, etc.) A composition containing.

The active energy ray-curable composition contains a polymerizable compound having a structure represented by the general formula (1) described above, and optionally a polymerizable compound not having a structure represented by the general formula (1) described above. Compounds, colorants, and other components may be included as appropriate.

The active energy ray-curable composition can contain a photopolymerization initiator. The photopolymerization initiator has the effect of starting the polymerization of the above-mentioned polymerizable compound when irradiated with active energy rays. The amount of the photopolymerization initiator is preferably 1 to 25% by weight, more preferably 3 to 20% by weight, particularly preferably 3 to 15% by weight based on the solid content of the composition. In order to properly initiate the photopolymerization reaction, the content of the photopolymerization initiator is preferably 1% by mass or more, and if it is 25% by mass or less, precipitation is unlikely to occur even at low temperatures. Furthermore, in order to accelerate the initiation reaction of the photopolymerization initiator, it is also possible to use an auxiliary agent such as a photosensitizer.

In this specification, the solid content refers to components excluding volatile components such as solvents, and is a component that will ultimately form a film. Generally commercially available polymerizable compounds such as polymerizable monomers and polymerizable oligomers are considered to have 100% solid content unless it is disclosed that they have been diluted with an organic solvent. Moreover, "solid content" is sometimes referred to as "nonvolatile content".

Examples of photopolymerization initiators include benzophenone compounds, acetophenone compounds, thioxanthone compounds, and phosphine oxide compounds, but from the viewpoint of curability, the wavelength of the active energy rays to be irradiated and the absorption of the photopolymerization initiator are important. It is preferable that the wavelengths overlap as much as possible. That is, it is preferable that the absorption wavelength of the photopolymerization initiator overlaps with the range of 350 nm or more and 400 nm or less. Further, the photopolymerization initiator preferably includes an acylphosphine oxide initiator from the viewpoint of LED curing and coloring during curing. The photopolymerization initiators may be used alone or in combination of two or more.

The active energy ray-curable composition may further contain a surface conditioner from the viewpoint of improving wettability to the base material. As used herein, the surface conditioning agent refers to a substance that has a hydrophilic site and a hydrophobic site in its molecular structure, and can adjust the surface tension of the composition by adding it.

In the active energy ray-curable composition, other components such as a solvent and a non-reactive polymer may be used as necessary.

In order to suppress decomposition of the structure represented by general formula (1), it is preferable that the active energy ray-curable composition is not placed in a strong alkaline atmosphere. It can be evaluated by a method such as stirring and mixing the active energy ray-curable composition and ion-exchanged water at a mass ratio of 1/1, and then measuring the pH of the aqueous phase. Although there is a balance with other components such as water, the pH of the aqueous phase is preferably 12 or less, more preferably 10 or less, and particularly preferably 8 or less.

On the other hand, in order to suppress the polymerization reaction that occurs after producing the active energy ray-curable composition until it becomes a film formed by irradiation with active energy rays, it is preferable that the acidic component contained be small. The acid value of the active energy ray-curable composition can be evaluated by a method such as measuring according to JIS K-0070-1992, and is preferably 30 or less, more preferably 5 or less, and particularly preferably 1 or less. In addition, when the active energy ray-curable composition contains an organic solvent, the acid value is calculated using the following calculation formula (4).
Measured value x 100/(100-organic solvent content of composition (mass%)) (4)

The active energy ray-curable composition is preferably an inkjet ink, and in this case, an inkjet printing method is selected as the method for applying it to the substrate.

When selecting the inkjet printing method, the active energy ray-curable composition is prepared by filtering the mixture obtained by mixing various components using a filter with a pore size of about 1/10 or less of the nozzle diameter of the inkjet print head. can be prepared.

When an inkjet printing method is selected, the viscosity of the active energy ray-curable composition at 40° C. is preferably 5 to 25 mPa·s, more preferably 5 to 20 mPa·s. If the viscosity of the composition at 40° C. is within the range specified above, good ejection stability can be obtained. Ink viscosity can be measured using a cone-plate viscometer.

When an inkjet printing method is selected, the surface tension of the active energy ray-curable composition at 25° C. is preferably 20 to 35 mN/m, more preferably 23 to 33 mN/m. If the surface tension of the composition at 25° C. is within the range specified above, good ejection stability can be obtained. Surface tension can be measured by a platinum plate method or the like.

Various inkjet printers can be used for inkjet printing. Examples of the inkjet printer include an inkjet printer that ejects an ink composition using a charge control method or a piezo method. Furthermore, large-sized inkjet printers, specifically inkjet printers intended for printing on articles produced on industrial lines, can also be suitably used. Further, as a method, a multi-pass method (scan method) or a single-pass method can be used.

After the active energy ray-curable composition is applied to a substrate by printing or the like, a cured film is formed by irradiation with active energy rays. As a light source for active energy rays, a high-pressure mercury lamp, a metal halide lamp, an LED lamp, etc. can be used. The active energy ray preferably has a dominant wavelength of 350 to 400 nm. The cumulative amount of active energy rays is preferably in the range of 100 to 2000 mJ/cm ² .

Regarding the base material to which the layer containing the compound (A) is attached, it is preferable that the layer containing the compound (A) is not removed from the base material even if it is immersed in a neutral or acidic aqueous solution. Here, the acidic aqueous solution is a 5% by mass acetic acid aqueous solution or 0.1M hydrochloric acid.

Regarding the base material to which the layer containing the compound (A) is attached, the layer containing the compound (A) is classified as 0, 1 or 2 in the cross-cut method adhesion test based on JIS K-5600-5-6:1999. Preferably, test results are available. However, in the cross-cut method adhesion test, the substrate surface to which the layer containing compound (A) is attached is polyethylene terephthalate or polypropylene.

Specific examples of the substrate to which the layer containing the compound (A) is attached include articles such as plastic films, labels, paper, and plastic molded products.

In the method of the present invention, the treatment liquid is an alkaline aqueous solution with a pH of 8.5 or more or a mixed solution of an alkaline aqueous solution with a pH of 8.5 or more and an organic solvent. In this specification, this treatment liquid is also referred to as "treatment liquid (B)." By immersing the base material to which the layer containing compound (A) is attached in the treatment liquid (B), the layer containing compound (A) can be easily removed from the base material.

In the method of the present invention, dipping may be performed by immersing at least the layer containing the compound (A) in the treatment liquid (B), but the entire substrate to which the layer containing the compound (A) is attached is immersed in the treatment liquid (B). It is preferable to submerge it inside.

In the method of the present invention, removal means removal of the layer containing the compound (A) attached to the base material. For example, when the base material is coated with only a decorative layer such as letters, pictures, patterns, etc. removes (e.g., separates) the decorative layer from the base material, and if it has another functional layer in addition to the decorative layer, removes (e.g., separates) the decorative layer and another functional layer from the base material. . Furthermore, if the base material is a recycled material, it is desirable to remove all components that would lead to a decline in the quality of the recycled material. Here, the quality of recycled materials mainly refers to color changes due to coloring and physical properties that the materials had before recycling.

Although a treatment liquid consisting only of an organic solvent is conceivable, a treatment liquid using an organic solvent is undesirable because it has problems such as deterioration of the working environment due to volatilization of VOCs and problems with handling as a hazardous substance. Furthermore, when the base material is a recycled material, there are problems such as the penetration of organic solvents into the recycled material and the tendency for additives such as plasticizers to be leached from the recycled material, which is not preferable in terms of quality. Therefore, in the present invention, the processing liquid consisting only of an organic solvent is excluded from the processing liquid (B). The content of the organic solvent in the treatment liquid (B) is preferably 50% by mass or less, more preferably 10% or less, and even more preferably is not included.

The type of organic solvent can be used without any particular restriction as long as it can maintain a uniform mixed solution state without separating from the alkaline aqueous solution under the conditions of use. Examples of organic solvents include alcohols, glycol ethers, and amides.

The pH (hydrogen ion concentration) of the alkaline aqueous solution is pH 8.5 or higher, preferably pH 9 or higher, and more preferably pH 11 or higher in terms of ease of removal of the layer containing compound (A). Note that, in the case of a mixed solution with an organic solvent, the pH value is the value of the aqueous solution before mixing.

The alkaline aqueous solution is preferably a sodium hydroxide aqueous solution.

In the method of the present invention, the temperature of the treatment liquid (B) can be adjusted when the substrate to which the layer containing the compound (A) is attached is immersed in the treatment liquid (B). ) is, for example, 25 to 80°C, preferably 40°C or higher, more preferably 60°C or higher in terms of ease of removal of the layer containing compound (A). When the treatment liquid (B) is a mixed solution of an alkaline aqueous solution and an organic solvent, the temperature can be set in consideration of the boiling point of the organic solvent to be mixed.

In the method of the present invention, the time for immersing the substrate to which the layer containing compound (A) is attached in the treatment liquid (B) is preferably from 5 minutes to 48 hours, and more preferably from 5 minutes to 2 hours. More preferred.

In the method of the present invention, stirring, bubbling, or ultrasonic irradiation is preferably performed when the substrate to which the layer containing the compound (A) is attached is immersed in the treatment liquid (B). By not allowing the substrate to which the layer containing compound (A) is attached to stand still in the treatment liquid (B), the layer containing compound (A) can be removed more easily than when it is left standing. Therefore, it is preferable. Inert gas such as air or nitrogen can be used for bubbling.

The method of the present invention can be used for recycling substrates. That is, another aspect of the present invention is a method for recycling a base material, in which a base material to which a layer containing a compound (A) having a structure represented by the above general formula (1) is attached is treated with a treatment liquid ( This method includes a step of immersing the base material in B) and a step of recovering the base material from which the layer containing the compound (A) has been removed from the treatment liquid (B). The recovered base material can be reused. Further, before the above-mentioned dipping step, a step of crushing the base material to which the layer containing the compound (A) is attached may be provided.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to the Examples below.

○Production method of test plate After coating the liquid with the composition for layer 1-1, layer 1-2, layer 1-3, layer 1-4 or layer 1-5 listed in Table 1 on the base material, 385 nm LED It was irradiated with a light amount of 2,000 mw/cm ² and 1,000 mJ/cm ² using a curing method. In this way, a base material (test plate) to which the layer was attached was produced. For layer 1-1, layer 1-2, layer 1-3 and layer 1-4, bar coater #3 was used when applying the liquid to the substrate, and for layer 1-5, the liquid was applied to the substrate. Bar coater #4 was used during coating.
Layer 1-1, layer 1-3, layer 1-4, and layer 1-5 are layers containing a polymer composed of TIPX, ACMO, THFA, and 1700B as a compound (A). Layer 1-2 is a layer containing a polymer composed of ACMO, THFA and 1700B, and does not contain compound (A).
If necessary, apply a liquid having the composition for layer 2-1 listed in Table 1 to layer 1-1 of the test plate using a commercially available UV curable inkjet ink printer under 8-pass conditions at a resolution of 720 x 600 dpi. , and was cured by light irradiation using the above LED. In this way, a test plate having a two-layer laminated structure was produced.
Layer 2-1 is a layer containing a polymer composed of ACMO, THFA, and 1700B, and does not contain compound (A).
Tables 2 to 5 show the amounts of the structure (COOSi) represented by general formula (1) contained in layer 1-1, layer 1-2, layer 1-3, layer 1-4 and layer 1-5.

〇Material details/TIPX: Triisopropylsilyl acrylate (Organic Synthetic Chemical Industry Co., Ltd.)
・ACMO: Acryloylmorpholine (KJ Chemicals Co., Ltd.)
・THFA: Tetrahydrofurfuryl acrylate (Kyoeisha Chemical Co., Ltd.)
・1700B: Purple light UV-1700B (Mitsubishi Chemical Corporation)
・TPO: SB-PI718 (SHUANG-BANG INDUSTRIAL CORP.)
・DETX: SB-PI799 (SHUANG-BANG INDUSTRIAL CORP.)
・pig. Bk7: Carbon black (pigment black No.7)
- Polycarbonate: Obtained from TP Giken Co., Ltd.
・LIMEX IJ Sheet S: TBM Co., Ltd. ・Reco Board: Acta Co., Ltd. Ultra Yupo FEBG 150: Yupo Corporation Co., Ltd.

〇 Method for removing the layer from the base material Using a cylindrical container with a diameter of 5 cm, add 50 mL of the treatment liquid and a 1.5 cm x 1.5 cm test plate, and remove the layer from the base material by leaving it still, stirring, and using ultrasonic waves. I tried to remove the layer.
Tables 2 to 5 show the layer structure of the test plate, the type of treatment liquid, the pH of the treatment liquid, the temperature of the treatment liquid during immersion, and the standing, stirring, and ultrasonic conditions.
Regarding the type of treatment liquid, NaOHaq means an aqueous sodium hydroxide solution, EtOH means ethanol, AcOHaq means an acetic acid aqueous solution, and HClaq means an aqueous solution of hydrogen chloride. When the treatment liquid is a mixed solution, its mass ratio is shown in the table. For example, NaOHaq/EtOH=80/20 indicates that the treatment liquid is a mixed solution of 80% by mass of an aqueous sodium hydroxide solution and 20% by mass of ethanol.
Stirring was performed using a magnetic stirrer at 400 RPM.
The cylindrical container in which the test plate was immersed in the treatment liquid was placed in a water bath at the same temperature as the treatment liquid, and the ultrasonic treatment was performed at 28 kHz.

〇Evaluation method - Removal of layer Visual evaluation was performed and judgment was made based on the following criteria. The evaluation results are shown in "Coating film removability" in Tables 2 to 5.
In addition, the time until even a portion of the base material was exposed was measured. The measurement times are shown in Tables 2 to 5, "Time required to expose base material or immersion time". However, in Comparative Examples 1 to 4, the base material was not exposed, so the immersion time of the test plate in the treatment liquid is shown.
〇The coating layer is completely removed within 168 hours, and the entire surface of the base material is exposed. ×No base material is exposed after 168 hours.

Claims (8)

A method for removing a layer from a substrate, comprising the step of immersing a substrate to which a layer containing a compound (A) having a structure represented by the following general formula (1) is attached in a treatment liquid (B), A method characterized in that the treatment liquid (B) is an alkaline aqueous solution with a pH of 8.5 or more or a mixed solution of an alkaline aqueous solution with a pH of 8.5 or more and an organic solvent.
CO-O-Si (1) 2. The method according to claim 1, wherein the layer containing the compound (A) is a layer cured by irradiation with active energy rays. The method according to claim 1 or 2, wherein the substrate is immersed in the treatment liquid (B) for a period of 5 minutes to 48 hours. The method according to claim 1 or 2, characterized in that the temperature of the treatment liquid (B) when the substrate is immersed in the treatment liquid (B) is 25 to 80°C. 3. The method according to claim 1, wherein stirring, bubbling, or ultrasonic irradiation is performed when the substrate is immersed in the treatment liquid (B). The method according to claim 1 or 2, wherein the structure represented by the general formula (1) of the compound (A) is derived from a polymerizable compound represented by the following general formula (2).
CH ₂ =C(R1)-CO-O-Si(R2)(R3)(R4) (2)
(In the formula, R1 is H or a methyl group, and R2, R3, and R4 are each independently a saturated hydrocarbon group, an unsaturated hydrocarbon group, or an aromatic group.) 7. The method according to claim 6, wherein the structure represented by the general formula (1) of the compound (A) is derived from a polymerizable compound represented by the following general formula (3).
CH ₂ =C(R1)-CO-O-Si(R5) ₃ (3)
(In the formula, R1 is H or a methyl group, and R5 is an isopropyl group or a butyl group.) 3. The method according to claim 1, wherein the layer containing the compound (A) is not removed from the substrate even when immersed in a neutral or acidic aqueous solution.