Recycling methods

Abstract

To provide a method for recycling plastic molded products that allows for the rapid removal of the coating layer on the surface of the plastic molded product. [Solution] A recycling method comprising the following steps: A recycling method for a plastic molded product having at least one coating layer obtained by applying a colored paint (X), wherein the recycling method includes an immersion step of immersing the plastic molded product having the coating layer in a coating stripping solution, and the colored paint (X) contains an acid group-containing polyolefin resin (X1) and / or an acid group-containing acrylic resin (X2).

Description

Technical Field

[0001] The present invention relates to a recycling method comprising an immersion step of immersing at least one coating film layer obtained by applying a colored coating material (X) to a plastic molded article in a coating film stripping liquid to strip the coating film, wherein the colored coating material (X) contains an acid group-containing polyolefin resin and / or an acid group-containing acrylic resin.

Background Art

[0002] Various industrial products (for example, plastic molded articles) have an organic coating film layer formed by applying a primer, a topcoat coating material or the like attached thereto for the purpose of imparting aesthetic properties and durability. However, for the purpose of reducing environmental load, when reusing or recycling the material of the article to be coated, it is necessary to remove the strongly adhered coating film layer.

[0003] As a method for stripping the coating film layer on the surface of a plastic molded article, a method of impregnating with a low-boiling organic solvent or performing ultrasonic treatment has been conventionally carried out. When impregnated with a low-boiling organic solvent, there is a problem that the volatilization amount of organic substances increases in the treatment step of the organic solvent containing the stripped coating film, and even in the ultrasonic treatment method, there is a problem that part of the coating film remains on the plastic molded article.

[0004] As a method using a coating film stripping liquid, Patent Document 1 describes a coating film stripping liquid containing a pyrrolidone-based compound, a hydrocarbon compound having 15 to 20 carbon atoms, a hydrophilic solvent, and a hydrophobic solvent, and a stripping method using the stripping liquid. However, from the viewpoint of the durability and the like of the plastic molded article having the coating film layer, the adhesive force is strong, and even when the stripping liquid described in Patent Document 1 is used, there is a problem that it is difficult to completely remove the coating film in a short time. In addition, depending on the type of the coating film, there are cases where the coating film cannot be easily stripped.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2004-168788 [Overview of the project] [Problems that the invention aims to solve]

[0006] The present invention provides a method for recycling plastic molded products that can remove the coating layer on the surface of the plastic molded product in a short time. [Means for solving the problem]

[0007] As a result of diligent research to solve the above problems, the present inventors have found that the above problems can be solved by a recycling method that includes an immersion step of immersing a plastic molded product having at least one coating layer obtained by applying a specific colored paint (X) in a coating stripping solution, and have completed the present invention.

[0008] In other words, the present invention provides a recycling method for reusing the following plastic molded products. Section 1. A method for recycling a plastic molded product having at least one coating layer obtained by applying a colored paint (X), The recycling method includes an immersion step of immersing a plastic molded product having the coating layer in a coating stripping solution. A recycling method characterized in that the colored paint (X) contains an acid group-containing polyolefin resin (X1) and / or an acid group-containing acrylic resin (X2). Section 2. The recycling method according to item 1, characterized in that the coating stripping solution contains a basic compound (A), a water-soluble organic solvent (B), and water, and based on 100% by mass of the total amount of the coating stripping solution, the basic compound (A) is in the range of 0.1 to 10% by mass and the water-soluble organic solvent (B) is in the range of 0.1 to 30% by mass. Section 3. The recycling method according to item 2, characterized in that the basic compound (A) contains an amine compound (a-1). Section 4. The recycling method according to item 3, characterized in that the amine compound (a-1) contains an alkanolamine (a-2). Section 5. The recycling method according to item 2, characterized in that the water-soluble organic solvent (B) has a solubility in water of 5 g or more per 100 mL of water (20°C) and contains a hydroxyl group-containing water-soluble organic solvent (b-1). Section 6. The recycling method according to item 1 or 2, characterized in that the immersion step is performed by heating the temperature of the paint film stripping solution to within the range of 30°C to 80°C. Section 7. The recycling method according to item 1 or 2, characterized in that the plastic molded product contains polypropylene. Section 8. A recycling method comprising the immersion step described in item 1 or 2 above, a dissolution step for dissolving a plastic molded product, and a recycling step for reusing the dissolved plastic molded product. Section 9. A colored paint (X) for forming a coating layer for recycling plastic molded products having at least one coating layer, The aforementioned at least one coating layer is formed by applying a colored paint (X) to a plastic molded product. The recycling process includes an immersion step in which the plastic molded product is immersed in a coating removal solution. A colored paint characterized in that the colored paint (X) contains an acid group-containing polyolefin resin (X1) and / or an acid group-containing acrylic resin (X2). [Effects of the Invention]

[0009] The recycling method of the present invention can remove the coating layer from the object to be coated (plastic molded product) in a short time. Furthermore, if an aqueous coating stripper with a low organic solvent content is used, the environmental impact is low. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments for carrying out the present invention will be described in detail.

[0011] It should be noted that the present invention is not limited to the following embodiments, and should be understood to include various modifications implemented within the scope that does not alter the gist of the present invention. In the present invention, the term "object to be coated" refers to a target object having a coating film layer (plastic molded article) with a paint or the like applied to its surface.

[0012] The recycling method according to the first aspect of the present invention is a recycling method for a plastic molded article having at least one coating film layer obtained by applying a colored paint (X), wherein the recycling method includes an immersion step of immersing the plastic molded article having the coating film layer in a coating film stripping solution, and the colored paint (X) contains an acid group-containing polyolefin resin (X1) and / or an acid group-containing acrylic resin (X2). In the recycling method of the present invention, other steps (for example, a washing step, a pulverization step, etc.) may be included before and after the immersion step.

[0013] The recycling method of the present invention is preferably a recycling method comprising, after the immersion step, a melting step of thermally melting the separated and recovered plastic molded article, and a reuse step of reusing the melted plastic. It should be noted that in the immersion step, the situation where the peeling of the coating film layer is only partial and further peeling is performed in subsequent steps is also included in the present invention. In addition, recycling the plastic in a state where the entire coating film layer is not peeled off is also included in the present invention.

[0014] Plastic molded products The plastic material used in the plastic molded articles of the present invention is not particularly limited, and examples include general-purpose plastics widely used in automotive parts and home appliances, such as polypropylene, polystyrene, ABS resin (acrylonitrile butadiene styrene resin), polycarbonate, nylon 6, and nylon 66. These may also be composites or mixtures, and may be modified in various ways. In particular, those containing polypropylene and / or ABS resin (acrylonitrile butadiene styrene resin) are preferred, and those containing polypropylene are preferred. Furthermore, it is preferable that the plastic molded product be made of an insulating material.

[0015] Coating layer The at least one coating layer obtained by applying the colored paint (X) of the present invention is preferably in direct contact with at least a portion of the plastic molded product, and may be a single layer or a multi-layer coating of two or more layers. Furthermore, the uppermost layer may be a coating layer (insulating layer) that does not contain conductive pigments, and the topmost layer may be a transparent clear coating. The coating layer is preferably at least one coating layer obtained by spray coating and heat-drying at least one type of colored paint (X) onto a plastic molded product, and more preferably the first coating layer that is in direct contact with at least a part of the plastic molded product. The dry film thickness of the first coating layer is usually 3 μm to 50 μm, and preferably 5 μm to 20 μm.

[0016] Furthermore, it is preferable that at least one colored coating layer is applied to the upper layer of the coating layer, and it is even more preferable that a clear coating layer is applied to the uppermost layer (topmost layer) of the colored coating layer. The main purpose of the colored coating layer is to color the plastic molded product, and the main purpose of the clear coating layer is to give gloss to the multi-layer coating. The colored coating layer and the clear coating layer are preferably obtained by spray coating the colored paint and the clear paint.

[0017] Colored paint (X) The colored paint (X) that can be used in the present invention may use an organic solvent or water as a solvent, but from an environmental point of view, it is preferable that it contains 50% by mass or more (preferably 70% by mass or more, more preferably 80% by mass or more) of water, based on 100% by mass of the solvent. When it contains 50% by mass or more of water, it is called an "aqueous colored paint". Furthermore, the colored paint (X) contains at least one acid group-containing polyolefin resin (X1) and / or acid group-containing acrylic resin (X2) as resin components.

[0018] It is believed that the presence of acidic resin components such as resin (X1) and / or resin (X2) in the colored paint (X) further accelerates the paint removal effect during the subsequent immersion process due to the components (especially basic compounds) contained in the paint removal solution.

[0019] Acid group-containing polyolefin resin (X1) The acid group-containing polyolefin resin is preferably an acid group-containing polyolefin modified with an unsaturated carboxylic acid or an acid anhydride. Furthermore, when used as a resin for aqueous colored paints, an aqueous dispersion of the polyolefin in an aqueous medium is preferred.

[0020] Unsaturated carboxylic acid or acid anhydride-modified acid group-containing polyolefins are obtained, for example, by (co)polymerizing at least one olefin selected from olefins having 2 to 10 carbon atoms, such as ethylene, propylene, butylene, and hexene, and then grafting the polyolefin with an unsaturated carboxylic acid such as (meth)acrylic acid, maleic acid, fumaric acid, or itaconic acid, or their acid anhydrides, according to known methods. Polyolefins modified with maleic acid or its acid anhydride are particularly preferred. The amount of grafting with the unsaturated carboxylic acid or its acid anhydride is not strictly limited and can be varied according to the desired physical properties of the formed coating film, but generally, based on the solid content mass of the polyolefin, a range of 1 to 20% by mass, preferably 1.5 to 15% by mass, and more preferably 2 to 10% by mass is appropriate.

[0021] The polyolefin used in the acid group-containing polyolefin resin (X1) can be produced by methods known for themselves. For example, it can be produced by continuously adding alkylaluminum and a metallocene catalyst while supplying an olefin such as propylene or ethylene and hydrogen to a reaction vessel.

[0022] Furthermore, the acid group-containing polyolefin resin (X1) may be further modified with acrylic as needed. Examples of polymerizable unsaturated monomers used for this acrylic modification include alkyl esters of (meth)acrylic acid such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate; acrylic monomers such as (meth)acrylic acid, glycidyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylamide, and (meth)acrylonitrile; and styrene, which can be used individually or in combination of two or more. In this specification, "(meth)acrylic" means "acrylic or methacrylic," and "(meth)acrylate" means "acrylate or methacrylate."

[0023] As for the above acrylic modification method, for example, one method involves first reacting a polymerizable unsaturated group, such as glycidyl (meth)acrylate, which is reactive with the carboxyl groups in the acid group-containing polyolefin resin (X1), and then copolymerizing at least one other monomer with the acid group-containing polyolefin resin into which the polymerizable unsaturated group has been introduced. When modifying the acrylic, the amount of polymerizable unsaturated monomer used should preferably be within the range of 30% by mass or less, particularly 0.1 to 20% by mass, and even more particularly 0.15 to 15% by mass, based on the solid content mass of the resulting acid group-containing polyolefin resin (X1), from the viewpoint of compatibility with other components and adhesion of the formed coating film.

[0024] Furthermore, the acid group-containing polyolefin resin (X1) may be modified with a compound having a polyoxyalkylene chain, if necessary. Examples of polyoxyalkylene chains in the compound having a polyoxyalkylene chain include polyoxyethylene chains, polyoxypropylene chains, and blocked chains of polyoxyethylene and polyoxypropylene. Compounds having polyoxyalkylene chains preferably have a number-average molecular weight in the range of 400 to 3,000, more preferably 500 to 2,000. If the number-average molecular weight is less than 400, the hydrophilic effect cannot be fully exercised, and it may adversely affect the coating performance (especially water resistance). On the other hand, if it is greater than 3,000, it solidifies at room temperature, its solubility deteriorates, and it becomes difficult to handle. Modification with the compound having the polyoxyalkylene chain described above can be carried out, for example, by reacting an acid group-containing polyolefin resin (X1) with a compound having a hydroxyl group at one end and a polyoxyalkylene chain, or, if the acid group-containing polyolefin resin (X1) has been acrylic-modified as described above, by reacting it with a compound having a polymerizable unsaturated group at one end and a polyoxyalkylene chain.

[0025] Furthermore, the acid group-containing polyolefin resin (X1) may be further chlorinated as needed. Chlorination of polyolefins can be carried out, for example, by blowing chlorine gas into an organic solvent solution or dispersion of the polyolefin or its modified product, and the reaction temperature can be in the range of 50 to 120°C. The chlorine content in the chlorinated polyolefin (solids) can be changed according to the desired physical properties of the chlorinated polyolefin, but from the viewpoint of adhesion of the formed coating film, it is generally desirable to set it to 35% by mass or less, particularly 10 to 30% by mass, and even more particularly 12 to 25% by mass, based on the mass of the chlorinated polyolefin.

[0026] The polyolefin used in the acid group-containing polyolefin resin (X1) is preferably one that contains propylene as a polymerization unit, and the mass fraction of propylene in the acid group-containing polyolefin resin (X1) is preferably in the range of 0.5 to 0.99, and particularly 0.7 to 0.95, from the viewpoint of compatibility with other components and adhesion of the formed coating film.

[0027] The acid group-containing polyolefin resin (X1) obtained as described above may have a melting point in the range of 120°C or less, preferably 50 to 100°C, more preferably 60 to 90°C, and a weight-average molecular weight (Mw) in the range of 30,000 to 180,000, preferably 50,000 to 150,000, and more preferably 70,000 to 120,000. If the melting point and weight-average molecular weight of the acid group-containing polyolefin resin (X1) deviate from these ranges, the objective of the present invention will not be achieved, and the compatibility with other components and the interlayer adhesion between the formed coating film and the polyolefin substrate and topcoat coating layer will decrease, which is undesirable. Furthermore, from the viewpoint of adhesion as described above, it is desirable that the acid group-containing polyolefin resin (X1) has a heat of fusion in the range of 1 to 50 mJ / mg, particularly 2 to 50 mJ / mg.

[0028] Here, the melting point and heat of fusion are obtained by using a differential scanning heat capacity analyzer "DSC-5200" (manufactured by Seiko Electronics Industries, Ltd., product name) to heat 20 mg of acid group-containing polyolefin resin from -100°C to 150°C at a heating rate of 10°C / min and measuring the amount of heat. The melting point of the acid group-containing polyolefin resin (X1) can be adjusted by changing the composition of the polyolefin, particularly the amount of α-olefin monomer. If it is difficult to determine the heat of fusion, the sample may be heated to 120°C, cooled at 10°C / min, left to stand for two days or more, and the amount of heat may be measured using the method described above.

[0029] Furthermore, the weight-average molecular weights of acid-containing polyolefin resins (X1) and acid-containing acrylic resins (X2) were calculated by converting the weight-average molecular weights measured by gel permulation chromatography to the weight-average molecular weight of polystyrene. These values ​​were measured using "HLC / GPC150C" (Water, Inc., trade name, 60cm x 1) at a column temperature of 135°C, with o-dichlorobenzene as the solvent and a flow rate of 1.0 ml / min. The injection sample was prepared by dissolving 5 mg of polyolefin in 3.4 ml of o-dichlorobenzene at 140°C for 1 to 3 hours. As for the column used for gel permulation chromatography, "GMHHR-H(S)HT" (Tosoh Corporation, trade name) can be mentioned.

[0030] In the present invention, when an acid group-containing polyolefin resin (X1) is used in an aqueous colored paint, the aqueous dispersion can be obtained by dispersing the acid group-containing polyolefin resin (X1) in an aqueous medium. In this case, if necessary, some or all of the carboxyl groups in the acid group-containing polyolefin resin (X1) can be neutralized with an amine compound and / or dispersed in aqueous solution using an emulsifier. Furthermore, if the acid group-containing polyolefin resin (X1) has polyoxyalkylene chains, it is possible to disperse the acid group-containing polyolefin resin (X1) in an aqueous medium without using the amine compound or emulsifier, or using only small amounts thereof. Examples of the amine compounds mentioned above include tertiary amines such as triethylamine, tributylamine, dimethylethanolamine, and triethanolamine; secondary amines such as diethylamine, dibutylamine, diethanolamine, and morpholine; and primary amines such as propylamine and ethanolamine. When using the above-mentioned amine compound, the amount used is preferably in the range of 0.1 to 2.0 molar equivalents (preferably 0.2 to 1.0 molar equivalents) relative to the carboxyl groups in the acid group-containing polyolefin resin (X1).

[0031] Examples of the emulsifiers mentioned above include nonionic emulsifiers such as polyoxyethylene monooleyl ether, polyoxyethylene monostearyl ether, polyoxyethylene monolauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene phenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, sorbitan monolaurate, sorbitan monostearate, sorbitan monostearate, sorbitan trioleate, and polyoxyethylene sorbitan monolaurate; anionic emulsifiers such as sodium salts and ammonium salts of alkyl sulfonic acid, alkylbenzene sulfonic acid, and alkyl phosphoric acid; and polyoxyalkylene group-containing anionic emulsifiers having an anionic group and a polyoxyalkylene group such as a polyoxyethylene group or a polyoxypropylene group in one molecule, and reactive anionic emulsifiers having the anionic group and a polymerizable unsaturated group in one molecule. These can be used individually or in combination of two or more.

[0032] The amount of the emulsifier used should generally be 30 parts by mass or less, and particularly within the range of 0.5 to 25 parts by mass, per 100 parts by mass of the solid content of the acid group-containing polyolefin resin (X1).

[0033] Acid group-containing acrylic resin (X2) The acid group-containing acrylic resin (X2) in the present invention is not particularly limited as long as it is an acrylic resin having an acidic functional group, and any acrylic resin that is known in itself can be used. However, it is particularly preferable that the acidic functional group is at least one acidic functional group selected from a sulfonic acid group, a phosphoric acid group, and a carboxyl group. Furthermore, it is preferable that the acid group-containing acrylic resin (X2) acts as a pigment dispersion resin when dispersing a pigment containing conductive carbon, as described later.

[0034] Such acid group-containing acrylic resins (X2) can usually be obtained by copolymerizing an acid-functional group-containing polymerizable unsaturated monomer with other ethylenically unsaturated monomers. The resulting acid group-containing acrylic resin (X2) is preferably composed of acid-functional group-containing polymerizable unsaturated monomer units in a range of generally 1 to 40% by mass, and particularly 2 to 30% by mass.

[0035] Examples of polymerizable unsaturated monomers containing acidic functional groups include (meth)acrylamide-alkanesulfonic acids such as 2-acrylamide-2-methylpropanesulfonic acid; polymerizable unsaturated monomers containing sulfonic acid groups such as sulfoalkyl (meth)acrylates such as 2-sulfoethyl (meth)acrylate; polymerizable unsaturated monomers containing phosphate groups such as 2-methacryloyloxyethyl acid phosphate, 2-alloyloxyethyl acid phosphate, polymerizable unsaturated monomers obtained by adding glycidyl methacrylate to monoalkyl (e.g., butyl, decyl, lauryl, stearyl, etc.) phosphoric acid, polymerizable unsaturated monomers obtained by adding glycidyl methacrylate to benzyl phosphoric acid; and polymerizable unsaturated monomers containing carboxyl groups such as (meth)acrylic acid. These monomers can be used individually or in combination of two or more.

[0036] Examples of polymerizable unsaturated monomers containing ionic functional groups other than acid groups include tertiary amino group-containing polymerizable unsaturated monomers such as N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-di-t-butylaminoethyl (meth)acrylate, and N,N-dimethylaminobutyl (meth)acrylate; 2-(methacryloyloxy)ethyltrimethylammonium chloride, 2-(methacryloyloxy)ethyltrimethylammonium bromide, and 2-(methacryloyloxy)ethyltrimethylammonium Examples include (meth)acryloyloxyalkyltrialkylammonium salts such as monoium dimethyl phosphate; (meth)acryloylaminoalkyltrialkylammonium salts such as methacryloylaminopropyltrimethylammonium chloride and methacryloylaminopropyltrimethylammonium bromide; tetraalkyl (meth)acrylates such as tetrabutylammonium (meth)acrylate; and trialkylbenzylammonium (meth)acrylates such as trimethylbenzylammonium (meth)acrylate, which contain quaternary ammonium bases and are polymerizable unsaturated monomers.

[0037] Other ethylenically unsaturated monomers are polymerizable unsaturated monomers other than those listed above, which can be appropriately selected and used from those already known, depending on the desired properties of the acid group-containing acrylic resin (X2). Examples of such other ethylenically unsaturated monomers include C1-C24 linear or cyclic alkyl(meth)acrylates such as methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, tert-butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, n-octyl(meth)acrylate, lauryl(meth)acrylate, stearyl(meth)acrylate, cyclohexyl(meth)acrylate, isobornyl(meth)acrylate, and tridecyl(meth)acrylate. Examples include acrylate monomers; hydroxyl group-containing polymerizable unsaturated monomers such as 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate; acrylamide and methacrylamide; oxetane ring-containing (meth)acrylates such as 3-ethyl-3-(meth)acryloyloxymethyl oxetane, 3-methyl-3-(meth)acryloyloxymethyl oxetane, and 3-butyl-3-(meth)acryloyloxymethyl oxetane; aromatic vinyl compounds such as styrene, α-methylstyrene, and vinyltoluene; and (meth)acrylonitrile and vinyl acetate. These polymerizable unsaturated monomers can be used individually or in combination of two or more.

[0038] From the viewpoint of water dispersibility and other factors, it is desirable that the acid group-containing acrylic resin (X2) further contains polyoxyalkylene chains. The introduction of the polyoxyalkylene chains can be carried out, for example, by copolymerizing a polymerizable unsaturated monomer having polyoxyalkylene chains with the ionic functional group-containing polymerizable unsaturated monomer and other ethylenically unsaturated monomers during the production of the acid group-containing acrylic resin (X2).

[0039] Examples of polymerizable unsaturated monomers having the polyoxyalkylene chain mentioned above include tetraethylene glycol (meth)acrylate, methoxytetraethylene glycol (meth)acrylate, ethoxytetraethylene glycol (meth)acrylate, n-butoxytetraethylene glycol (meth)acrylate, tetrapropylene glycol (meth)acrylate, methoxytetrapyroprene glycol (meth)acrylate, ethoxytetrapropylene glycol (meth)acrylate, n-butoxytetrapropylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and ethoxypolyethylene glycol (meth)acrylate. Among these, polyethylene glycol (meth)acrylate and polypropylene glycol (meth)acrylate are particularly preferred. These can be used individually or in combination of two or more.

[0040] Furthermore, the acid group-containing acrylic resin (X2) preferably contains a hydroxyl group-containing polymerizable unsaturated monomer, from the viewpoint of crosslinking with the crosslinking agent in the colored paint (X) or the crosslinking agent that migrates from the upper coating film.

[0041] The production of the acid group-containing acrylic resin (X2) (copolymerization of the monomer) can be carried out by known methods, such as solution polymerization in an organic solvent or emulsion polymerization in water, but solution polymerization is preferred.

[0042] The acid group-containing acrylic resin (X2) preferably has a weight-average molecular weight in the range of approximately 3,000 to 300,000, more preferably 5,000 to 150,000, and more preferably 8,000 to 50,000. The acid group-containing acrylic resin (X2) can be neutralized with a neutralizing agent as needed to make it water-soluble or water-dispersible.

[0043] The colored paint (X) of the present invention preferably contains either an acid group-containing polyolefin resin (X1) or an acid group-containing acrylic resin (X2), and more preferably contains both an acid group-containing polyolefin resin (X1) and an acid group-containing acrylic resin (X2). Furthermore, when both resin (X1) and resin (X2) are included, from the viewpoint of adhesion and water resistance of the formed coating film, it is desirable that the amounts of acid group-containing polyolefin resin (X1) and acid group-containing acrylic resin (X2) blended are generally within the range of 20 to 90% by mass, particularly 30 to 70% by mass, and even more particularly 30 to 60% by mass for the acid group-containing polyolefin resin (X1), and generally within the range of 0.5 to 50% by mass, preferably 1 to 30% by mass, and even more particularly 5 to 30% by mass for the acid group-containing acrylic resin (X2), based on the total resin solids mass in the composition.

[0044] pigment The colored paint (X) of the present invention preferably contains a pigment.

[0045] From the viewpoint of imparting conductivity to the coating film, the aforementioned pigment is preferably one that contains conductive carbon. Pigments other than conductive carbon include pigments that are commonly used in the paint industry and are known in themselves, such as coloring pigments, extender pigments, and conductive pigments. If the coating film of the colored paint (X) is conductive, electrostatic coating can be used as the coating method for applying paint to that coating film.

[0046] Examples of the conductive carbon mentioned above include conductive carbon black, carbon nanotubes, carbon nanofibers, and carbon microcoils. The conductive carbon is selected based on its brightness and conductivity, and is suitable for use in 600m applications. 2 / g or more, especially 800m 2 / g or more, especially 1000m 2 It is desirable that the specific surface area be greater than or equal to / g.

[0047] Examples of the above-mentioned coloring pigments include titanium dioxide, red iron oxide, aluminum paste, azo pigments, and phthalocyanine pigments. Examples of extender pigments include talc, silica, calcium carbonate, barium sulfate, and zinc oxide. These can be used individually or in combination of two or more. Furthermore, the conductive pigments mentioned above are not particularly limited as long as they can impart conductivity to the formed coating film, and may be in particulate, flake, or fibrous (including whisker) form. Examples include metal powders such as silver, nickel, copper, graphite, and aluminum. Other examples include pigments coated with antimony-doped tin oxide, phosphorus-doped tin oxide, needle-shaped titanium oxide surface-coated with tin oxide / antimony, antimony oxide, zinc antimonate, indium tin oxide, and tin oxide on the surface of carbon or graphite whiskers; pigments coated with at least one conductive metal oxide selected from the group consisting of tin oxide, antimony-doped tin oxide, tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), phosphorus-doped tin oxide, and nickel oxide on the surface of flake-shaped mica; and conductive pigments containing tin oxide and phosphorus on the surface of titanium dioxide particles. These can be used individually or in combination of two or more types.

[0048] In particular, when a paint that forms a highly bright coating film is desired as the composition of the present invention, it is desirable that the pigment contains a white pigment, and among them titanium dioxide in particular. From the viewpoint of design and chemical resistance, it is preferable to use a pigment with an average particle size in the range of approximately 0.05 to approximately 2 μm, and especially 0.1 to 1 μm.

[0049] The amount of pigment used is generally preferably in the range of 0.5 to 200 parts by mass, more preferably 1 to 150 parts by mass, and even more preferably 5 to 150 parts by mass, per 100 parts by mass of total resin solids in the composition, from the viewpoint of adhesion and water resistance of the formed coating film. The amount of conductive carbon used is preferably determined from the viewpoint of brightness and conductivity of the formed coating film, and is usually preferably in the range of 0.5 to 30 parts by mass, more preferably 1 to 20 parts by mass, and even more preferably 3 to 20 parts by mass, per 100 parts by mass of total resin solids in the composition. Furthermore, when the above white pigment is used, its content is preferably selected so that the L value of the formed coating film is 35 or more, and is usually suitable in the range of 50 to 150 parts by mass, preferably 70 to 130 parts by mass, and even more preferably 70 to 120 parts by mass, per 100 parts by mass of total resin solids in the composition.

[0050] Other ingredients The colored paint (X) of the present invention can be prepared, for example, by mixing the acid group-containing polyolefin resin (X1), acid group-containing acrylic resin (X2), and a pigment that can be optionally contained, according to a conventional method, and diluting it with a solvent (e.g., deionized water) as appropriate.

[0051] The colored paint (X) of the present invention may further contain, if necessary, a urethane resin or a polyester resin as a vehicle component. Furthermore, the colored paint (X) of the present invention may optionally contain a crosslinking agent. Typically, an amino resin and / or (blocked) polyisocyanate can be used as the crosslinking agent, which can react with the hydroxyl groups contained in the acid group-containing acrylic resin (X2), etc. Therefore, when a crosslinking agent is used, it is preferable that the acid group-containing acrylic resin (X2) has hydroxyl groups. Among these, (blocked) polyisocyanate is preferred when a crosslinking agent is included.

[0052] Examples of the above-mentioned amino resins include melamine resin, urea resin, and benzoguanamine resin, with melamine resin being particularly preferred. Among the melamine resins, alkyl etherified melamine resins etherified with alkyl groups such as methyl, ethyl, n-butyl, isobutyl, hexyl, and 2-ethylhexyl are especially preferred, and they may be of either hydrophobic or hydrophilic type. These melamine resins may further contain methylol groups, imino groups, etc. The amino resins typically have a number average molecular weight in the range of 500 to 5,000, and particularly 800 to 3,000.

[0053] The above-mentioned (blocked) polyisoanates are polyisocyanate compounds having two or more free isocyanate groups in one molecule, or those in which the isocyanate groups are blocked with a blocking agent.

[0054] The colored coating (X) of the present invention may optionally contain a terpene resin from the viewpoint of coating compatibility. Examples of the terpene resin include terpenes, terpene-phenols, and hydrogenated aromatic terpene resins. The terpene resin preferably has a melting point in the range of 30 to 120°C. Furthermore, the terpene resin is usually used in an amount of 30% by mass or less, preferably in the range of 5 to 20% by mass, based on the total resin solids content in the composition.

[0055] The colored paint (X) of the present invention may further contain, as necessary, paint additives such as a curing catalyst, a rheology control agent, an antifoaming agent, and an organic solvent.

[0056] Soaking process The immersion step of the present invention is a step of immersing a plastic molded product having at least one coating layer obtained by applying the colored paint (X) in a coating stripping solution.

[0057] In the aforementioned immersion step, for example, heating the temperature of the paint stripping solution to within the range of 30 to 100°C, preferably 30 to 80°C, and particularly preferably 30 to 60°C, improves its penetration and peelability. The immersion time is preferably 1 minute to 4 hours, and more preferably 10 minutes to 2 hours. After immersion in the paint stripping solution, the plastic molded product can be removed from the solution and washed as appropriate with various solvents (for example, water-soluble solvents such as acetone or ethanol). Furthermore, a drying step can be added after the immersion step, with a drying time of 10 minutes to 2 hours being preferable, and a drying temperature of typically 30°C to 100°C, preferably 30°C to 80°C.

[0058] As described above, by immersing the product in a paint stripping solution for a certain period of time, the paint layer can be easily peeled off and separated from the plastic molded product. The immersion step may be performed only once or multiple times. If the immersion step is performed multiple times, the paint stripping solution used may be the same or different.

[0059] Furthermore, plastic molded products having a coating layer may be crushed as needed. The crushing step can be performed before or after the immersion step. If the crushing step is performed before the immersion step, the surface area of ​​the organic coating layer can be increased, allowing for more effective removal.

[0060] The crushing machine is not particularly limited, but examples include hammer crushers, roll crushers, air-jet crushers, mascolloiders, ball mills, power mills, pin mills, shear friction crushers, cutter crushers, impact crushers, homogenizers, ultrasonic crushers, etc., and one type can be used alone or two or more types can be used.

[0061] Paint stripper The coating stripping solution preferably contains a basic compound (A), a water-soluble organic solvent (B), and water (C). More preferably, the basic compound (A) is in the range of 0.1 to 10% by mass and the water-soluble organic solvent (B) is in the range of 0.1 to 30% by mass, based on 100% by mass of the total amount of the coating stripping solution.

[0062] Basic compound (A) The aforementioned basic compound (A) is an ingredient that improves peelability, but many of them have a strong odor, which can worsen the working environment during compounding and the peeling process. Furthermore, they are generally expensive, which can increase costs. Therefore, it is necessary to keep the content to the minimum required level.

[0063] The basic compound (A) is typically present in an amount of 0.1 to 10% by mass, preferably 0.3 to 7% by mass, more preferably 0.5 to 4% by mass, even more preferably 0.6 to 3% by mass, and particularly preferably 0.8 to 2% by mass, based on 100% by mass of the total amount of the coating stripping solution. Furthermore, it is believed that the basic compound (A) improves peelability by reacting with the acid group-containing resin contained in the coating layer.

[0064] Examples of the basic compound (A) include amine compounds (described later); carbonates such as sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate; metal hydroxides such as sodium hydroxide, potassium hydroxide, and calcium hydroxide; and metal alkoxides. These can be used individually or in combination of two or more. In particular, it is preferable that the mixture contains an amine compound (a-1).

[0065] Examples of the amine compound (a-1) include ammonia, primary amines, secondary amines, tertiary amines, and the like.

[0066] Primary amines include, for example, ethylamine, n-propylamine, sec-propylamine, n-butylamine, sec-butylamine, i-butylamine, tert-butylamine, pentylamine, hexylamine, heptylamine, octylamine, decylamine, laurylamine, mystyrylamine, 1,2-dimethylhexylamine, 3-pentylamine, 2-ethylhexylamine, allylamine, aminoethanol, 1-aminopropanol, 2-amino-2-methyl-1-propanol, 2-aminopropanol, aminobutanol, aminopentanol, aminohexanol, 3-ethoxypropylamine, 3-propoxypropylamine, 3-isopropoxypropylamine, 3-butoxypropylamine, 3-isobutoxypropylamine, 3-(2-ethylhexyloxy)propylamine, aminocyclopentane, aminocyclohexane, aminonorbornene, aminomethylcyclohexane, aminobenzene, benzylamine, phenethylamine, α-phenylethylamine Primary monoamines such as mine, naphthylamine, furfurylamine; ethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,2-diaminobutane, 1,3-diaminobutane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, dimethylaminopropylamine, diethylaminopropylamine, bis-(3-aminopropyl) ether, 1,2-bis-(3-aminopropoxy)ethane, 1 ,3-bis-(3-aminopropoxy)-2,2'-dimethylpropane, aminoethylethanolamine, 1,2-bisaminocyclohexane, 1,3-bisaminocyclohexane, 1,4-bisaminocyclohexane, 1,3-bisaminomethylcyclohexane, 1,4-bisaminomethylcyclohexane, 1,3-bisaminoethylcyclohexane, 1,4-bisaminoethylcyclohexane, 1,3-bisaminopropylcyclohexane, 1,4-bisaminopropylcyclohexane, hydrogenated 4,4'-Diaminodiphenylmethane, 2-Aminopiperidine, 4-Aminopiperidine, 2-Aminomethylpiperidine, 4-Aminomethylpiperidine, 2-Aminoethylpiperidine, 4-Aminoethylpiperidine, N-Aminoethylpiperidine, N-Aminopropylpiperidine, N-Aminoethylmorpholine, N-Aminopropylmorpholine, Isophoronediamine, Menthanediamine, 1,4-Bisaminopropylpiperazine, o-Phenylenediamine, m-Phenylenediamine, p-Phenylenediamine, 2,4-Tolylenediamine, 2,6-Tolylenediamine, 2,4-Toluenediamine, m-Aminobenzylamine, 4-Chloro-o-Phenylenediamine, Tetrachloro-p-Xylylenediamine, 4-Methoxy-6-methyl-m-Phenylenediamine, m-Xylylenediamine, p-Xylylenediamine, 1,5-Naphthalenediamine, 2,6-Naphthalenediamine, Benzidine, 4,4'-Bis( o-Toluidine), dianisidine, 4,4'-diaminodiphenylmethane, 2,2-(4,4'-diaminodiphenyl)propane, 4,4'-diaminodiphenyl ether, 4,4'-thiodianiline, 4,4'-diaminodiphenylsulfone, 4,4'-diaminoditolylsulfone, methylenebis(o-chloroaniline), 3,9-bis(3-aminopropyl)2,4,8,10-tetraoxaspiro[5,5]undecane, diethylenetriamine, Examples include primary polyamines such as iminobispropylamine, methyliminobispropylamine, bis(hexamethylene)triamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, N-aminoethylpiperazine, N-aminopropylpiperazine, 1,4-bis(aminoethylpiperazine), 1,4-bis(aminopropylpiperazine), 2,6-diaminopyridine, and bis(3,4-diaminophenyl)sulfone.

[0067] Examples of secondary amines include secondary monoamines such as diethylamine, dipropylamine, di-n-butylamine, di-sec-butylamine, diisobutylamine, di-n-pentylamine, di-3-pentylamine, dihexylamine, dioctylamine, di(2-ethylhexyl)amine, methylhexylamine, diallylamine, pyrrolidine, piperidine, 2,4-lupetidine, 2,6-lupetidine, 3,5-lupetidine, diphenylamine, N-methylaniline, N-ethylaniline, dibenzylamine, methylbenzylamine, dinaphthylamine, pyrrole, indoline, indole, and morpholine; N,N'-dimethylethylenediamine, N,N'-dimethyl-1,2-diaminopropane, N,N'-dimethyl-1,3-diaminopropane, N,N'-dimethyl-1,2-diaminobutane, N,N'-dimethyl-1,3-diaminobutane, N,N' -Dimethyl-1,4-diaminobutane, N,N'-dimethyl-1,5-diaminopentane, N,N'-dimethyl-1,6-diaminohexane, N,N'-dimethyl-1,7-diaminoheptane, N,N'-diethylethylenediamine, N,N'-diethyl-1,2-diaminopropane, N,N'-diethyl-1,3-diaminopropane, N,N'-diethyl-1,2-diaminobutane, N,N'-diethyl-1,3-diaminobutane Examples include secondary polyamines such as N,N'-diethyl-1,4-diaminobutane, N,N'-diethyl-1,6-diaminohexane, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 2,6-dimethylpiperazine, homopiperazine, 1,1-di-(4-piperidyl)methane, 1,2-di-(4-piperidyl)ethane, 1,3-di-(4-piperidyl)propane, and 1,4-di-(4-piperidyl)butane.

[0068] Examples of tertiary amines include trimethylamine, triethylamine, tri-n-propylamine, tri-iso-propylamine, tri-1,2-dimethylpropylamine, tri-3-methoxypropylamine, tri-n-butylamine, tri-iso-butylamine, tri-sec-butylamine, tri-pentylamine, tri-3-pentylamine, tri-n-hexylamine, tri-n-octylamine, tri-2-ethylhexylamine, tri-dodecylamine, tri-laurylamine, dicyclohexylethylamine, cyclohexyldiethylamine, tricyclohexylamine, N,N-dimethylhexylamine, N-methyldihexylamine, N,N-dimethylcyclohexylamine, N-methyldicyclohexylamine, N,N-diethylethanolamine, N,N-dimethylethanolamine, N-ethyldiethanolamine, triethanolamine, tribenzylamine, N,N-dimethylbenzylamine, diethylbenzylamine Tertiary monoamines such as dilamines, triphenylamine, N,N-dimethylamino-p-cresol, N,N-dimethylaminomethylphenol, 2-(N,N-dimethylaminomethyl)phenol, N,N-dimethylaniline, N,N-diethylaniline, pyridine, quinoline, N-methylmorpholine, N-methylpiperidine, 2-(2-dimethylaminoethoxy)-4-methyl-1,3,2-dioxabornane, 2-,3-,4-picoline, etc.; tetramethylethylenediamine Examples include pyrazine, N,N'-dimethylpiperazine, N,N'-bis((2-hydroxy)propyl)piperazine, hexamethylenetetramine, N,N,N',N'-tetramethyl-1,3-butanamine, 2-dimethylamino-2-hydroxypropane, diethylaminoethanol, N,N,N-tris(3-dimethylaminopropyl)amine, 2,4,6-tris(N,N-dimethylaminomethyl)phenol, and tertiary polyamines such as heptamethylisobiguanide.

[0069] These can be used individually or in combination of two or more. Furthermore, it is preferable that they do not contain aromatic amines.

[0070] While all of the aforementioned amine compounds (a-1) can be suitably used, water-soluble amine compounds are preferred from the viewpoint of solubility in water, which is the main solvent, and alkanolamines (a-2) are preferred. Here, an alkanolamine is an amine compound having an alcohol group.

[0071] Since it is preferable that no amine compound remains after drying the coated material following peeling, the molecular weight of the amine compound (a-1) is preferably less than 1,000, more preferably 500 or less, even more preferably 300 or less, particularly preferably 200 or less, and even more preferably 100 or less. For the same reason, the upper limit of the boiling point of the amine compound is preferably 400°C or less, more preferably 300°C or less, and even more preferably 200°C or less. The lower limit is preferably 50°C or higher, more preferably 80°C or higher, and even more preferably 100°C or higher.

[0072] Furthermore, the amine value of the amine compound (a-1) is usually 5 mg KOH / g or more, preferably 50 mg KOH / g or more, more preferably 100 mg KOH / g or more, and is usually within the range of 1,000 mg KOH / g or less.

[0073] Water-soluble organic solvent (B) The aforementioned water-soluble organic solvent (B) is a component that does not contain basic functional groups other than the basic compound (A), and is a component that increases penetration into the coating layer. However, if it has a strong odor, the working environment may deteriorate during compounding or stripping processes. Also, since it is more expensive than water, it may increase costs. Therefore, it is necessary to keep the content to the minimum necessary.

[0074] The content of the water-soluble organic solvent (B) is typically 0.1 to 30% by mass, preferably 1 to 30% by mass, more preferably 2 to 25% by mass, even more preferably 4 to 18% by mass, and particularly preferably 5 to 15% by mass, based on 100% by mass of the total amount of the coating stripping solution. Here, "water solubility" in this invention means that the solubility in water at 20°C is 5 g or more per 100 mL of water (at 20°C).

[0075] Any of the water-soluble organic solvents (B) can be suitably used, but specifically, one or more selected from the group consisting of, for example, ethylene glycol, ethylene glycol monoalkyl ethers (e.g., methyl ether, ethyl ether, butyl ether, etc.), diethylene glycol, diethylene glycol monoalkyl ethers (e.g., methyl ether, ethyl ether, butyl ether, etc.), glyme solvents (e.g., ethylene glycol dimethyl ether, etc.), diglyme solvents (e.g., diethylene glycol dimethyl ether, etc.), alcohol solvents (e.g., methanol, ethanol, propanol, n-butanol, s-butanol, t-butanol, isobutanol, etc.), propylene glycol, propylene glycol monoalkyl ethers (e.g., methyl ether, ethyl ether, butyl ether, etc.), dipropylene glycol, dipropylene glycol monoalkyl ethers (e.g., methyl ether, ethyl ether, butyl ether, etc.), etc., can be used. These can be used individually or in combination of two or more. Furthermore, it is preferable that the product does not contain aromatic alcohols, which have poor solubility in water, or pyrrolidone-based solvents, which have an impact on the environment.

[0076] While any of the aforementioned water-soluble organic solvents (B) can be suitably used, from the viewpoint of solubility in water (C), which is the main solvent, a hydroxyl group-containing water-soluble organic solvent (b-1) is preferred, and a hydroxyl group-containing water-soluble organic solvent (b-2) containing an ether group is even more preferred. Furthermore, from the viewpoint of odor suppression and drying properties, the boiling point of the water-soluble organic solvent (B) is preferably 400°C or lower as an upper limit, more preferably 300°C or lower, and even more preferably 200°C or lower. The lower limit is preferably 50°C or higher, more preferably 80°C or higher, and even more preferably 100°C or higher.

[0077] Other components of paint stripper The coating stripping solution that can be used in the present invention may contain other components as needed, in addition to the above components, such as other solvents, resins, neutralizing agents, defoaming agents, preservatives, pigments, surfactants, and the like.

[0078] Second aspect (colored paint) A second aspect of the present invention is a colored paint (X) for forming a coating layer for recycling plastic molded articles having at least one coating layer, wherein the at least one coating layer is formed by painting the colored paint (X) onto the plastic molded article. The recycling process includes an immersion step in which the plastic molded product is immersed in a coating removal solution. The colored paint (X) is a colored paint containing an acid group-containing polyolefin resin (X1) and / or an acid group-containing acrylic resin (X2). Furthermore, the colored paint (X) of the second embodiment of the present invention is identical to the colored paint (X) of the first embodiment. Furthermore, the recycling method in the second aspect of the present invention is the same as the recycling method in the first aspect, and includes an immersion step of immersing a plastic molded product having a coating layer in a coating stripping solution (the same as the coating stripping solution in the first aspect). Furthermore, it is preferable that the coating layer formed by applying the colored paint (X) is the first coating layer that is in direct contact with at least a part of the plastic molded product.

[0079] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these specific embodiments. [Examples]

[0080] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto. In each example, "parts" refers to parts by mass, and "%" refers to mass percent.

[0081] Production of acid group-containing acrylic resin (1) In a standard acrylic resin reaction vessel equipped with a stirrer, thermometer, and reflux condenser, 35 parts of ethylene glycol monobutyl ether were charged and heated and stirred, maintaining a temperature of 110°C. To this, a mixture consisting of 10 parts styrene, 40 parts methyl methacrylate, 25 parts n-butyl methacrylate, 10 parts 2-hydroxyethyl methacrylate, 5 parts methacrylic acid, 10 parts "NF Bysomer PEM6E" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name, polyethylene glycol monomethacrylate, molecular weight approximately 350), 4 parts azobisisobutyronitrile, and 20 parts isobutyl alcohol was added dropwise over 3 hours. After the dropwise addition was complete, the mixture was aged at 110°C for 30 minutes, and then an additional catalyst mixture consisting of 15 parts ethylene glycol monobutyl ether and 0.5 parts azobisisobutyronitrile was added dropwise over 1 hour. After aging at 110°C for 1 hour, the mixture was cooled to obtain an acid-containing acrylic resin (1) solution with a solid content of 55%. The acid group-containing acrylic resin (1) had an acid value of 33 mgKOH / g, a hydroxyl value of 43 mgKOH / g, and a weight-average molecular weight of approximately 20,000.

[0082] Production of acid group-free acrylic resin (2) In a standard acrylic resin reaction vessel equipped with a stirrer, thermometer, and reflux condenser, 35 parts of ethylene glycol monobutyl ether were charged and heated and stirred, maintaining a temperature of 110°C. To this, a mixture consisting of 10 parts styrene, 40 parts methyl methacrylate, 20 parts n-butyl methacrylate, 10 parts 2-hydroxyethyl methacrylate, 20 parts "NF Bysomer PEM6E" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name, polyethylene glycol monomethacrylate, molecular weight approximately 350), 4 parts azobisisobutyronitrile, and 20 parts isobutyl alcohol was added dropwise over 3 hours. After the dropwise addition was complete, the mixture was aged at 110°C for 30 minutes, and then an additional catalyst mixture consisting of 15 parts ethylene glycol monobutyl ether and 0.5 parts azobisisobutyronitrile was added dropwise over 1 hour. After aging at 110°C for 1 hour, the mixture was cooled to obtain an acid-free acrylic resin (2) solution with a solid content of 55%. The acid-free acrylic resin (2) had an acid value of 0 mgKOH / g, a hydroxyl value of 43 mgKOH / g, and a weight-average molecular weight of approximately 20,000.

[0083] Preparation of colored paint (1) 55 parts by solids weight of aqueous polypropylene / ethylene copolymer [an ethylene-propylene copolymer (ethylene content 5%) obtained using a metallocene catalyst, modified with 8% by weight of maleic acid, with a melting point of 80°C and Mw of approximately 100,000, neutralized by equivalent amount with dimethylethanolamine, and further dispersed in water using 10 parts of emulsifier per 100 parts of polypropylene / ethylene copolymer], 30 parts by solids weight of "UX5210" (manufactured by Sanyo Chemical Industries, Ltd., product name, urethane dispersion), 15 parts by solids weight of the above acid group-containing acrylic resin (1) solution, 120 parts by solids weight of "JR-806" (manufactured by Teika Co., Ltd., product name, titanium white), and conductive carbon (specific surface area approximately 1200 m²) 2 Four parts of carbon black pigment ( / g) were mixed according to a conventional method and diluted with deionized water to obtain a conductive colored coating (1) with a solid content of 40%.

[0084] Preparation of colored paint (2) 55 parts by solids weight of aqueous polypropylene / ethylene copolymer [ethylene-propylene copolymer obtained using a metallocene catalyst (ethylene content 5%). Further dispersed in water using 15 parts emulsifier per 100 parts of polypropylene / ethylene copolymer], 30 parts by solids weight of UX5210 (manufactured by Sanyo Chemical Industries, Ltd., product name, urethane dispersion), 15 parts by solids weight of the above acid group-free acrylic resin (2) solution, 120 parts by solids weight of JR-806 (manufactured by Teika Co., Ltd., product name, titanium white), and conductive carbon (specific surface area approximately 1200 m²) 2 Four parts of carbon black pigment ( / g) were mixed according to a conventional method and diluted with deionized water to obtain a conductive colored coating (2) with a solid content of 40%. Furthermore, the above-mentioned colored paint (2) does not contain an acid group-containing resin.

[0085] Preparation of test coated object [test piece (1)] Degreased polypropylene was spray-coated with the colored paint (1) prepared as described above to a dry film thickness of approximately 10 μm, preheated at 80°C for 3 minutes, then electrostatically coated with "WBC#713T" (manufactured by Kansai Paint Co., Ltd., product name, water-based colored base coat paint) as a colored base coat paint to a dry film thickness of approximately 15 μm, preheated at 80°C for 3 minutes, and then electrostatically coated with "Soflex #520 Clear" (manufactured by Kansai Paint Co., Ltd., product name, acrylic urethane solvent-based clear paint) as a clear coat paint to a dry film thickness of approximately 30 μm, and heated and dried at 120°C for 30 minutes to obtain a test coated object. The test coated object was cut into approximately 10 cm squares and further exposed outdoors for 2 months to obtain test pieces (1).

[0086] Preparation of test coated specimens [test piece (2)] Degreased polypropylene was spray-coated with the colored paint (2) prepared as described above to a dry film thickness of approximately 10 μm, preheated at 80°C for 3 minutes, then electrostatically coated with "WBC#713T" (manufactured by Kansai Paint Co., Ltd., product name, water-based colored base coat paint) as a colored base coat paint to a dry film thickness of approximately 15 μm, preheated at 80°C for 3 minutes, and then electrostatically coated with "Soflex #520 Clear" (manufactured by Kansai Paint Co., Ltd., product name, acrylic urethane solvent-based clear paint) as a clear coat paint to a dry film thickness of approximately 30 μm, and heated and dried at 120°C for 30 minutes to obtain a test coated object. The test coated object was cut into approximately 10 cm squares and further exposed outdoors for 2 months to obtain test pieces (2).

[0087] Examples 1-18 and Comparative Examples 1-2 The raw materials listed in Table 1 below were mixed and thoroughly stirred to prepare paint stripping solutions Z1 to Z18. Next, the aforementioned test pieces (1) or (2) were immersed in the paint stripping solutions at the liquid temperature and immersion time shown in Table 1, and then the test pieces were removed from the paint stripping solutions. Subsequently, the plastic molded product having a coating layer can be recycled after the coating is removed.

[0088] [Table 1]

[0089] (Abbreviations in Table 1) • DMEA: N,N-dimethylethanolamine (molecular weight 89, boiling point 134°C, solubility in water: infinite (20°C)) • TEOA: Triethanolamine (molecular weight 149, boiling point 208°C, solubility in water: infinite (20°C)) • AMP: 2-amino-2-methyl-1-propanol (molecular weight 89, boiling point 165°C, solubility in water: infinite (20°C)) • TEA: Triethylamine (molecular weight 101, boiling point 89.3°C, solubility in water: 17.0 g / 100 ml) Solvent 1: Ethylene glycol monobutyl ether (boiling point 171°C, solubility in water: infinite (20°C)) • Solvent 2: Ethylene glycol mono-t-butyl ether (boiling point 152°C, solubility in water: infinite (20°C)) Solvent 3: n-butanol (boiling point 117.7°C, solubility in water: 7.7g / 100ml (20°C)). • Solvent 4: s-butanol (boiling point 100°C, solubility in water: infinite (20°C)) Solvent 5: t-butanol (boiling point 82.4°C, solubility in water: infinite (20°C)). Solvent 6: Isobutanol (boiling point 108°C, solubility in water: 8.7g / 100ml (20°C)) Solvent 7: Propylene glycol monopropyl ether (boiling point 149°C, solubility in water: infinite (20°C)) Solvent 8: Benzyl alcohol (boiling point 205°C, solubility in water: 3.5g / 100ml (20°C)).

[0090] (Evaluation test) In the above-described examples and comparative examples, after removing the test specimen from the paint stripping solution, the paint stripping solution adhering to the surface was wiped off. Then, masking tape was applied and the tape was peeled off in one swift motion. The surface was observed and the peelability was evaluated according to the following criteria, and the evaluation results are shown in Table 1. A grade of "S," "A," "B," or "C" is considered a passing grade, while "D" is considered a failing grade.

[0091] (Evaluation of peelability) S: The coating film has been completely removed from the substrate (object to be coated). A: The coating has almost completely peeled off the substrate, with only a small amount remaining at the edges of the test piece. B: The area of ​​the surface where the coating has peeled off from the substrate is 50% or more. C: The area of ​​the surface where the coating has peeled off from the substrate is 10% or more but less than 50%. D: The area of ​​the surface where the coating has peeled off from the substrate is less than 10%.

Claims

1. A method for recycling a plastic molded product having at least one coating layer obtained by applying a colored paint (X), The recycling method includes an immersion step of immersing a plastic molded product having the coating layer in a coating stripping solution. A recycling method characterized in that the colored paint (X) contains an acid group-containing polyolefin resin (X1) and / or an acid group-containing acrylic resin (X2).

2. The recycling method according to claim 1, characterized in that the coating stripping solution contains a basic compound (A), a water-soluble organic solvent (B), and water, and based on 100% by mass of the total amount of the coating stripping solution, the basic compound (A) is in the range of 0.1 to 10% by mass and the water-soluble organic solvent (B) is in the range of 0.1 to 30% by mass.

3. The recycling method according to claim 2, characterized in that the basic compound (A) contains an amine compound (a-1).

4. The recycling method according to claim 3, characterized in that the amine compound (a-1) contains an alkanolamine (a-2).

5. The recycling method according to claim 2, characterized in that the water-soluble organic solvent (B) has a solubility in water of 5 g or more per 100 mL of water (20°C) and contains a hydroxyl group-containing water-soluble organic solvent (b-1).

6. The recycling method according to claim 1 or 2, characterized in that the immersion step is performed by heating the temperature of the paint film stripping solution to within the range of 30°C to 80°C.

7. The recycling method according to claim 1 or 2, characterized in that the aforementioned plastic molded product contains polypropylene.

8. A recycling method comprising: an immersion step according to claim 1 or 2; a dissolution step for dissolving a plastic molded product; and a recycling step for reusing the dissolved plastic molded product.

9. A colored paint (X) for forming a coating layer for recycling plastic molded products having at least one coating layer, The aforementioned at least one coating layer is formed by applying a colored paint (X) to a plastic molded product. The recycling process includes an immersion step in which the plastic molded product is immersed in a coating removal solution. A colored paint characterized in that the colored paint (X) contains an acid group-containing polyolefin resin (X1) and / or an acid group-containing acrylic resin (X2).

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