JP2005046770A - Coating film peeling off method, recycling method for plastic molded product and peeling off liquid used for these methods - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating film peeling off method which enables the dissolution/elimination of the coating film existing on a material surface such as plastic by chemical treatment with extremely less environment load without impairing a physical property of the material such as plastic, and a recycling method for a plastic molded product. <P>SOLUTION: In the coating film peeling off method for peeling off the coating film by a peeling off liquid and the recycling method for recycling the peeled off plastic, the coating film contains a thermoplastic resin binder and the peeling off liquid is formed by adding a peeling off accelerator comprising other organic solvents except for lower alcohol, organic acid or surfactant to lower alcohol or a solvent mixture of lower alcohol-water. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a coating film peeling method for peeling a coating film coated on the surface of a plastic molded product used in home appliances and electronic equipment, and to recover and recycle plastic from a plastic molded product having a coating film on the surface. The present invention relates to a method for recycling plastic molded products and a stripping solution used in these methods.

  The concept of plastic recycling can be divided into material recycling, which is recycling of the substance itself, and thermal recycling, which is recovery as fuel or incineration heat energy (Non-Patent Document 1 below). In Europe and the United States, the concept of material recycling, that is, plastic recycling, is the mainstream, but in Japan, concepts including energy recovery are common.

The amount of waste plastic in Japan in 1997 was about 9.5 million tons (about half of the production of 15.21 million tons), of which material recycling was 1.13 million tons, only 12%, and energy recovery accounted for 30%. The remaining 58% is completely unused (Non-Patent Document 2 below).
According to the Containers and Packaging Recycling Law, all plastics for containers and packaging have been targeted for recycling since April 2000, and this is a measure to gradually increase the ratio of material recycling, but it is still not enough compared to Europe and America. Regarding home appliance recycling, since home appliances are composites of different materials, there are many barriers such as recovery technology or cost for each material.

  Plastic molded products are used in various fields such as automobiles, home appliances, and electronic devices, and their types and combinations with different materials are diverse. Like the Home Appliance Recycling Law, it is inevitable that laws and regulations that require recycling of plastic itself will be established in the future, and measures must be taken as soon as possible. One of the causes that hinders the recycling and reuse of plastic molded products is the remaining coating film for imparting design properties.

  In order to minimize the influence of such a coating film, it is known to use a thermoplastic resin for the vehicle in the coating composition, but the type of plastic that can be applied is limited, and it is applied to impart design properties. When the film contains aluminum powder, pearl pigment or the like, the physical properties of the plastic may be further deteriorated at the time of recycling, and there are also problems with repeated re-pelletization, so that it has not yet spread.

In addition, a re-dissolvable cross-linking type paint in which a carbonyl group-containing resin is cross-linked with polyhydrazide has been developed. This is because the cross-linking is cut with a solvent containing water and acid, and the coating film can be dissolved and removed. However, since the acid used is a strong acid such as sulfonic acid, there is a problem of environmental impact and the plastic material. There is no denying the adverse effect on the physical properties of
There are conductive paints that have recently been put on the market, with re-peelability added to the electromagnetic shielding function. However, because the stripping solvent is dimethylethanolamine, it is estimated that the cost is high and there is a considerable impact on the environment. .

On the other hand, Patent Document 1 discloses that an easily decomposable resin composition containing a polyvinyl acetal resin as an easily decomposable resin and a binder resin is used for a coating film of a plastic molded product. The coating film formed from this composition has the property that it can be decomposed and desorbed by acid hydrolysis or dissolved and desorbed by a solvent such as ethyl alcohol. However, since the acid decomposition of the resin uses strongly acidic H ₂ SO ₄ or HCl, the physical properties of the plastic may be adversely affected. Another problem is that the removal of the coating film is insufficient by dissolution and desorption with an ethyl alcohol solvent or the like.

  There is an urgent need to develop technology to solve the above-mentioned issues related to plastic molded products used in home appliances and electronic devices, and to collect plastics with high purity and implement material recycling (mechanical recycling or chemical recycling). is there.

Norihisa Kusagawa, Plastic Recycling Yearbook, 1997 edition, p. 223, 1997 Ohmae, “What to do with plastic recycling”, p57-63, 2000 JP 2002-173571 A

  The present invention relates to a coating film peeling method and a plastic molded product recycling method capable of dissolving and desorbing a coating film existing on a plastic surface by chemical treatment with very little environmental load without impairing physical properties of the plastic material. It is an issue to provide.

  In order to solve the above-mentioned problems, the present inventors have conducted extensive research. As a result, when a specific stripping solution is used for a plastic molded article formed with a coating film containing a thermoplastic resin binder, the physical properties of the plastic itself. The new fact that the coating film can be easily removed and removed without damaging the material, and therefore the material can be reused as it is without being crushed or crushed. The present invention has been completed.

  That is, the coating film peeling method of the present invention is a coating film peeling method in which a coating film is peeled with a peeling liquid, wherein the coating film contains a thermoplastic resin binder, and the peeling liquid is a lower alcohol or a lower alcohol. -A mixed solvent of water, wherein at least one peeling accelerator selected from organic solvents other than the lower alcohol, organic acid and surfactant is added.

  The coating film peeling method of the present invention can be applied to peeling and removing a coating film formed on the surface of a metal, a woody material, a plastic or the like, and particularly peeling and removing the coating film formed on the surface of a plastic molded product. It is suitable for.

  The method for recycling a plastic molded product according to the present invention is a method of reusing the plastic molded product after removing the coating film from the surface of the plastic molded product with a stripping solution. A plastic resin binder, wherein the stripping solution is a mixed solvent of lower alcohol or lower alcohol-water, and at least one stripping accelerator selected from other organic solvents excluding the lower alcohol, organic acids, and surfactants It is characterized by adding.

Preferably, in the recycling method of the present invention, after the plastic molded product having a coating film on the surface is pulverized, the coating film is peeled and removed with the stripping solution, and the pulverized product is reused.
Specifically, the recycling method of the present invention includes a step of obtaining a plastic molded product, a step of applying a coating film on the surface of the obtained plastic molded product, a step of pulverizing the plastic molded product that has become unnecessary, It includes a step of peeling and removing the coating film from the pulverized product of the molded product with the stripping solution, and a step of reusing the pulverized product of the molded product from which the coating film has been removed.

The recycling method for peeling the coating film after pulverization is preferably applied to a coating film having an undercoat layer and a topcoat layer as described below. That is, in this recycling method, since the coating film is peeled and removed after pulverization, the peeling solution penetrates well into the undercoat layer exposed on the end face of the pulverized product, so that the coating film is easily peeled off from the surface of the molded product. be able to.
On the other hand, in the case of a small plastic molded product, it may be reused by being put into a molding machine as it is after being peeled off without being pulverized. The method of the present invention can also be applied to the case where a plastic molded product is pulverized after being peeled off, and then put into a molding machine for reuse.

  The coating film containing the thermoplastic resin binder in the present invention can be formed on the surface of a plastic molded article alone, but an undercoat layer containing the thermoplastic resin binder and a topcoat layer provided on the surface. It may consist of: Moreover, it is preferable that the said coating film contains an acrylic resin as a thermoplastic resin binder, and also contains the polyvinyl acetal resin as an easily decomposable polymer.

  The present invention also provides a stripping solution suitably used in these methods, which comprises a lower alcohol or a mixed solvent of lower alcohol-water, an organic solvent other than the lower alcohol, an organic acid, and a surface activity. It is characterized by the addition of at least one peeling accelerator selected from agents.

  According to the method of the present invention, the coating film can be easily dissolved and desorbed without damaging the physical properties of materials such as plastics and without increasing the environmental load. There is an effect that materials such as plastic can be recovered and reused with high purity.

  The plastic material used for the plastic molded product in the present invention is not particularly limited. For example, polystyrene (PS), ABS resin, polycarbonate (PC), polycarbonate / ABS resin (PC / ABS polymer alloy), polycarbonate / ASA resin (PC / ASA polymer alloy), 6-nylon, 66-nylon, polypropylene (PP) and other general-purpose plastics widely used for home appliances and electronic device moldings.

  The coating film applied to the surface of the plastic molded article is, for example, a film in which a designable topcoat layer is formed on the surface after applying an undercoat layer that exhibits peelability under the peeling conditions exemplified in the present invention. is there. The top coat layer preferably has resistance to various environmental tests. Specifically, the undercoat layer contains a thermoplastic resin binder. Examples of the thermoplastic resin binder include thermoplastic acrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl alcohol, polyethylene resin, coumarone resin, and the like. Moreover, it is preferable that the coating film contains a polyvinyl acetal resin together with the thermoplastic resin binder. The polyvinyl acetal resin is an easily decomposable polymer and has an action of facilitating the decomposition or dissolution and peeling of the coating film.

Examples of the monomer composition for forming the acrylic resin include non-functional monomers such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, isobutyl methacrylate, tertiary butyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid. Octyl acid, isodecyl methacrylate, lauryl methacrylate, lauryl tolulidyl methacrylate, tridecyl methacrylate, cetyl methacrylate-stearyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, or monofunctional monomers such as methacrylic acid, methacrylic 2-hydroxyethyl acid, 2-hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, methacryl Tertiary butylaminoethyl, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, or polyfunctional monomers such as ethylene dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, dimethacrylic acid Decaethylene glycol, pentadecaethylene glycol dimethacrylate, pentacontact ethylene glycol dimethacrylate, 1,3-butylene dimethacrylate, allyl methacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, dimethacrylic acid Examples include diethylene glycol phthalate.
Among them, methyl methacrylate 50 to 95% by weight, butyl methacrylate 5 to 25% by weight, lauryl methacrylate 0 to 10% by weight or stearyl methacrylate 0 to 10% by weight, methacrylic acid 1 to 10% by weight, preferably An acrylic resin containing 65 to 85% by weight of methyl methacrylate, 10 to 15% by weight of butyl methacrylate, 2 to 6% by weight of lauryl methacrylate or 2 to 6% by weight of stearyl methacrylate and 2 to 8% by weight of methacrylic acid is desirable. The acrylic resin has a weight average molecular weight of 5,000 to 50,000, preferably 10,000 to 30,000.

On the other hand, the polyvinyl acetal resin is composed of a polyvinyl acetal unit, a polyvinyl alcohol unit, and a polyvinyl acetate unit, and has different characteristics depending on the type of raw material aldehyde, the degree of acetalization, the composition ratio, and the degree of polymerization. The polyvinyl acetal resin used in the present invention is preferably polyvinyl butyral, in the range of 1 to 13% by weight of polyvinyl acetate units, 10 to 25% by weight of polyvinyl alcohol units, and 70 to 85% by weight of polyvinyl butyral units, preferably polyvinyl acetate units. It is desirable to contain 1 to 6 wt%, polyvinyl alcohol units 16 to 22 wt%, and polyvinyl butyral units 75 to 83 wt%. The average degree of polymerization of the polyvinyl acetal resin is 200 to 2400, preferably 300 to 2000 in terms of number average.
The mixing ratio of the thermoplastic resin binder and the polyvinyl acetal resin is 0 to 100 parts by weight of the polyvinyl acetal resin, preferably 0 to 50 parts by weight with respect to 100 parts by weight of the acrylic resin in consideration of the adhesion of the coating film to the plastic. There should be.

  The undercoat layer may contain components other than the thermoplastic resin binder and the polyvinyl acetal resin. You may contain binder resin other than an acrylic resin, especially binder resin excellent in adhesiveness with respect to a plastic raw material. This binder can be added to the undercoat layer to the extent that it does not impair the peelability. The resin to be added may be any resin as long as it has good dispersibility or can be mixed with the acrylic resin and polyvinyl acetal resin mixed system. As such a binder resin, for example, nitrocellulose, ethyl cellulose, cellulose acetate, epoxy resin, phenol resin, etc. as solvent-drying resins, urethane resins, acrylic urethane resins, epoxy resins, polyester resins, epoxy polyesters as crosslinking reaction types Examples thereof include resins.

  In addition, when considering the post-treatment of stripping waste liquid and environmental impact, natural or synthetic resins with known biodegradability are also added to the undercoat layer composition to the extent that adhesion to plastic materials is not impaired. can do. Examples of these biodegradable resins include starch, starch derivatives, cellulose, cellulose derivatives, chitin, chitosan derivatives, polysaccharides such as pullulan, curdlan, alginic acid, hyaluronic acid, dextran, gluten, casein, collagen, gelatin, and fibroin. , Sericin, keratin, casein, polyglutamic acid, polylysine and other polypeptides, polyhydroxybutyric acid, polyhydroxybutyric acid derivatives, polyhydroxybutyric acid polyhydroxyvaleric acid copolymer, etc., microbial-produced polyester, polyethylene glycol, polyvinyl alcohol, etc. Aliphatic polymers such as polymers, polyglycolic acid, polylactic acid, polyε-caprolactone, polyethylene succinate, polytetramethylene succinate, copoly (ε-caprolactone / ε-caprolactam) Esters, lacquer, cashew resin, shellac, and natural resins such as rosin.

  Although the undercoat layer can be combined with a design with one coat specification, a designable topcoat is applied on the peelable undercoat layer when the characteristics such as environmental tests required for each product are not satisfied. There is a need. The design top coat may be any combination of resins as long as it has excellent adhesion to the peelable undercoat layer and is compatible with various environmental tests. Specific examples of such resins include acrylic resins, urethane resins, acrylic urethane resins, silicon acrylic resins, epoxy resins, polyester resins, epoxy polyester resins, and fluorine-modified urethane resins.

  The peelable undercoat layer as described above can be formed by applying to the surface of the plastic material by a usual application method such as spray coating, roll coater, brush coating, or dipping. In addition, a design top coat layer to be applied to satisfy various required characteristics can be applied in the same manner. The dry film-forming method may be any of natural drying, forced heating drying, and ultraviolet irradiation. A so-called 2-coat 2-bake method in which a peelable undercoat layer is applied and dried to form a film, and then a designable topcoat is applied to form a film. Any so-called two-coat one-bake method may be employed in which after the peelable undercoat layer is applied, a designable topcoat is subsequently applied, followed by film formation.

  The thicknesses of the undercoat layer and the topcoat layer are not particularly limited, but the undercoat layer has a thickness of 2 to 15 μm, and the topcoat layer has a thickness of about 10 to 30 μm for easy peeling. Is appropriate. However, considering the adhesion between the undercoat layer and the plastic and the adhesion between the undercoat layer and the topcoat layer, the undercoat layer preferably has a thickness of 5 to 10 μm.

  The plastic molded article thus coated is sent to the recycling process after being used. In the recycling step, the plastic molded product is crushed and then dissolved and desorbed by the stripping solution of the present invention described later. In other words, because the peeling surface of the coating film is exposed directly in the treatment tank by crushing the plastic molded product in advance, the undercoat layer peels off the plastic surface due to erosion from the peelable undercoat layer. Therefore, the designable top coat layer can be dissolved and desorbed at normal temperature and pressure. After the peeling process, the plastic can be cleaned and subjected to material recycling through a filtration and drying process.

  The stripping solution of the present invention is obtained by adding at least one of an organic solvent other than the lower alcohol, an organic acid, and a surfactant as a stripping accelerator to a mixed solvent of lower alcohol or lower alcohol-water.

  Examples of the lower alcohol include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, n-amyl alcohol, sec-amyl alcohol, 3-pentanol, 2-methyl-1-butanol, isoamyl alcohol, tert-amyl alcohol, sec-isoamyl alcohol, neopentyl alcohol, 1-hexanol, 2-methyl-1-pentanol, 4-methyl-2-pentanol, 2-ethyl Examples include lower aliphatic alcohols having 1 to 6 carbon atoms such as -1-butanol, and it is particularly preferable to use ethanol which has little influence on plastic materials.

  When the lower alcohol is used by mixing with water, the lower alcohol is 80% by weight or more, preferably 85% by weight or more, more preferably 90% by weight or more based on the total amount of the mixed solvent of the lower alcohol-water. Is good.

  Moreover, as another organic solvent used as a peeling accelerator, various solvents including a polar solvent can be used. For example, 1-heptanol, 2-heptanol, 3-heptanol, 1-octanol, 2-octanol, 2 -Ethyl-1-hexanol, 1-nonanol, 3,5,5-trimethyl-1-hexanol, 1-decanol, 1-undecanol, 1-dodecanol, allyl alcohol, propargyl alcohol, benzyl alcohol, cyclohexanol, 1-methyl Cyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 4-methylcyclohexanol, α-terpineol, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2- Butanediol, 1,3-butanediol, 1,4-butanediol 2,3-butanediol, 1,5-pentanediol, 2-butene-1,4-diol, 2-methyl-2,4-pentanediol, 2-ethyl-1,3-hexanediol, glycerin, 2 -Alcohols other than the above lower alcohols such as ethyl-2- (hydroxymethyl) -1,3-propanediol and 1,2,6-hexanetriol; ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol mono Glycol derivatives such as ethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether (PGM), dimethyl sulfoxide (DMSO), propylene glycol monomethyl ether acetate (PGMAC), N-methyl-2-pyrrolidone (NM2P) Etc. Can.

  Examples of organic acids used as the release accelerator include acetic acid, acrylic acid, malonic acid, succinic acid, maleic acid, fumaric acid, benzoic acid, 2-naphthoic acid, phthalic acid, isophthalic acid, terephthalic acid, nicotinic acid, Isonicotinic acid, 2-furoic acid, formic acid, propionic acid, propiolic acid, butyric acid, isobutyric acid, methacrylic acid, palmitic acid, stearic acid, oleic acid, oxalic acid, glutaric acid, adipic acid, cinnamic acid, glycolic acid, Examples include lactic acid, glyceric acid, malic acid, tartaric acid, citric acid, glyoxylic acid, pyruvic acid, acetoacetic acid, benzylic acid, anthranilic acid, ethylenediaminetetraacetic acid, carbamic acid, oxamic acid, performic acid, peracetic acid, perbenzoic acid, etc. It is done. Of these, polybasic acids such as malonic acid, succinic acid, maleic acid, fumaric acid, malic acid, tartaric acid, and citric acid have little environmental impact and are excellent in the effect of removing the coating film, so that they can be suitably used. .

  The surfactant used as the peeling accelerator may be anionic, cationic, nonionic or amphoteric. Examples of anionic surfactants include carboxylates, sulfonates, sulfate esters, and phosphate esters, and examples of cationic surfactants include aliphatic amine salts, aliphatic quaternary ammonium salts, and benzalkonium chloride salts. Benzethonium chloride, pyridinium salt, imidazolinium salt is an ether type, ester ether type, ester type, nitrogen-containing type as a nonionic surfactant, carboxybetaine type, aminocarboxylate as an amphoteric surfactant, Examples include imidazolinium betaine, lecithin, alkylamine oxide and the like. Among them, nonionic surfactant polyoxyethylene (23) lauryl ether, polyoxyethylene (8) octylphenyl ether, polyoxyethylene (9) octylphenyl ether, polyoxyethylene (10) octylphenyl ether, polyoxyethylene (20) Sorbitan monolaurate, polyoxyethylene (20) sorbitan monopalmitate, polyoxyethylene (20) sorbitan monostearate, polyoxyethylene (20) sorbitan monooleate, polyoxyethylene (20) sorbitan trioleate Is effective.

  By adding these peeling accelerators to a mixed solvent of lower alcohol or lower alcohol-water, dissolution peeling of the coating film can be promoted. The addition amount of these peeling accelerators is not particularly limited, and can be appropriately determined as long as the load on the environment is not increased and the peeling performance of the peeling liquid is not impaired. Specifically, the addition amount of the peeling accelerator varies depending on the type of the peeling accelerator to be used, but generally 0.1 to 100% by weight with respect to the total amount of the lower alcohol or the mixed solvent of lower alcohol-water, Preferably it is 0.5-50 weight%, More preferably, it is 0.5-10 weight%. More specifically, it may be 0 to 30% by weight of an organic solvent other than the lower alcohol, 0 to 50% by weight of an organic acid, and 0 to 20% of a surfactant (however, an organic solvent other than the lower alcohol, an organic acid) And the surfactant must not be 0 at the same time).

  Furthermore, in the present invention, it is preferable to add at least one selected from a polycation compound and a polyhydric alcohol as a peeling acceleration aid to the peeling liquid in addition to the above peeling accelerator. The addition amount of the peeling acceleration aid is desirably in the range of 0 to 10% by weight with respect to the total amount of the peeling solution.

  As the polycation compound, for example, chitosan, chitosan derivatives, polyallylamine, polyethyleneimine, polyvinylamine, polyornithine, polylysine and the like, which are polycation polymers having an amino group in the molecule, can be used. In addition, poly (allylbiguanide-co-allylamine), poly (allyl-N-carbamoylguanidino-co-allylamine), which are derivatives of polyallylamine, and the like are also useful as the polycation compound in the present invention. These have a specific effect on agglomeration flocking of dissolved and desorbed coating film components, and have the advantage that the waste liquid can be filtered and removed quickly and easily.

  As the polyhydric alcohol, for example, glycerin, ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol and the like can be used. These polyhydric alcohols also act as thickeners.

Next, a coating film peeling method and a recycling method using the same will be described. As described above, only a peelable coating containing at least a thermoplastic resin binder, or a plastic molded product in which a designable topcoat layer is applied on the surface of a peelable undercoat layer containing at least a thermoplastic resin binder is a product. First, after crushing, the coating film is peeled off using the above-described stripping solution.
The stripping method can be either batch type or continuous type. The crushed plastic is immersed in a treatment tank containing the stripping solution, or the stripping solution is showered on the crushed plastic.

The treatment time required to dissolve and peel the coating film from the plastic surface by dipping or showering varies depending on the composition of the stripping solution, the thickness and composition of the coating film, and is usually 0.5 to 180 minutes, preferably 2 ~ 15 minutes. The stripping treatment can be performed at room temperature, but may be performed while heating the stripping solution.
What is necessary is just to filter the peeling coating film contained in peeling liquid, circulating the peeling liquid in a processing tank, or the showered peeling liquid with a circulation pump. If necessary, the coating film can be efficiently peeled off by applying ultrasonic treatment to the crushed plastic molded article, or by applying physical pressure and physical abrasion as needed.
Moreover, you may perform peeling of a coating film before the grinding | pulverization of a plastic molded product. In particular, when a plastic molded product is recycled and used as it is, the coating film can be peeled off without being pulverized, dried and then coated again.

  The plastic molded product recycling method of the present invention was performed by washing the plastic material from which the coating film was peeled off from the surface by the above-described coating film peeling method, filtering and drying, and verifying the physical properties of the plastic material after peeling the coating film. Then, it is recycled by carrying out re-pelletization. Moreover, you may add a virgin material to a reproduction | regeneration pellet as needed.

  As described above, the method according to the present invention is applied to plastic coatings that have hindered the recyclability of plastic products in the past, thereby further improving the response to the Home Appliance Recycling Law.

  In the above embodiment, the peeling method and the recycling method of the coating film coated on the plastic molded product have been described. However, the peeling method of the present invention is not limited to this, and contains the above-described thermoplastic resin binder. Metal undercoat, antirust paint, ship bottom paint, woodwork paint, anti-sticking paint, can coating, plastic primer, packaging film ink, screen for forming a peelable undercoat layer or peelable coating agent It can be applied to a peeling process for printing inks, adhesives, pressure-sensitive adhesives, spray pastes, films, binders, and the like.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not limited only to a following example.

表１に示すように、アクリル樹脂ＡＡの溶解において、エタノール−水混合溶媒に上記剥離促進剤をそれぞれ添加することにより、エタノール−水混合溶媒のみで溶解するのに比べて溶け残りが少なかった。 25 wt% of acrylic resin for undercoat containing 80 wt% of methyl methacrylate and 10 wt% of butyl methacrylate as monomers (weight average molecular weight 25,000, glass transition point 80 ° C .; hereinafter referred to as acrylic resin AA) in ethyl acetate % And dispensed into polypropylene caps with a diameter of 28 mm. After being dried at 80 ° C. for 24 hours, it was allowed to cool to room temperature and peeled off from the cap (the dry weight per acrylic resin film was 100 to 120 mg).
As shown in Table 1, 1% by weight of each of the following peeling accelerators was added to an ethanol-water mixed solvent in which the mixing ratio of ethanol and water was changed to prepare a test solution. Next, the above-mentioned films were immersed one by one in 4 g of each test solution, the change in the shape of the film after 24 hours was observed at room temperature, and the following criteria were evaluated.
(Peeling accelerator)
Dimethyl sulfoxide (DMSO)
Propylene glycol monomethyl ether acetate (PGMAC)
Propylene glycol monomethyl ether (PGM)
N-methyl-2-pyrrolidone (NM2P)
Fumaric acid citric acid monohydrate DL-malic acid
TritonX-100 (polyoxyethylene (10) octylphenyl ether, manufactured by Wako Pure Chemical Industries, Ltd.)
Tween80 (polyoxyethylene (20) sorbitan monooleate, manufactured by Wako Pure Chemical Industries, Ltd.)
(Evaluation criteria)
◎: Complete dissolution ○: Partial dissolution remaining △: Partial dissolution ×: No change Table 1 shows the results.

As shown in Table 1, in the dissolution of the acrylic resin AA, by adding each of the above-described peeling accelerators to the ethanol-water mixed solvent, there was less undissolved residue compared to the case of dissolving with only the ethanol-water mixed solvent.

The coating film peeling effect of various peeling accelerators was examined with actual coating films. First, stripping solution No. having each component composition (% by weight) shown in Table 2. 1-17 were prepared.

表３に示すように、剥離液に含有される有機酸としてはフマル酸の効果が優れており、また、キトサンの添加により、剥離促進剤とキトサンとの相乗効果と共に剥離した塗膜の凝集フロック化が観察された。 In each test tube (diameter 12 mm × length 75 mm), 4 g of the test stripping solution shown in Table 2 was put. On the other hand, ABS resin test piece with acrylic resin AA (above) applied to the undercoat and acrylic resin lacquer enamel applied to the topcoat [dimensions: 50 × 7 × 0.3 mm, ABS resin used: product made by UMG ABS The name “EX 18A”] was prepared. One piece of this test piece was immersed in each stripping solution, observed over time at room temperature, and evaluated according to the following criteria.
◎: Completely peeled ○: Somewhat remains, but can be physically removed Δ: Most remains on the ABS resin, but can be physically removed ×: No change Table 3 shows the results.

As shown in Table 3, the effect of fumaric acid is excellent as the organic acid contained in the stripping solution, and the flocs of the coating film stripped together with the synergistic effect of the stripping accelerator and chitosan by adding chitosan. Observed.

アンダーコートは、ポリビニルブチラール単独ではプラスチック素材（ABS、PC/ABS、HIPS）に付着しないが、アクリル樹脂を混合することで付着性は確保出来た。 [Test Example 1]
(Undercoat layer adhesion test)
Each plastic case shown in Table 4 (PC / ABS polymer alloy, ABS is as described above, and HIPS is high-impact polystyrene) prepared by degreasing and washing with isopropyl alcohol was prepared. Next, a paint having a composition (weight ratio) shown in Table 4 was spray applied to the surface of each plastic casing to form an undercoat layer.
Details of the undercoat paint are as follows.
(1) Butyral resin (polyvinyl butyral): trade name Denka Butyral 3000-1 manufactured by Denki Kagaku Kogyo Co., Ltd.
(2) Acrylic resin A: Trade name LR-510 manufactured by Mitsubishi Rayon Co., Ltd.
(3) Acrylic resin AA: The above acrylic resin (4) Solvent for dissolution: n-butanol / n-butyl acetate / cyclohexanone / butyl cellosolve = 15/40/15/30 (weight ratio))
Each resin is diluted to 50% with a solvent for dissolution to obtain a viscous liquid paint, which is spray-coated on the surface of each plastic casing and dried at 60 ° C. for 30 minutes to give a film thickness of about 2 to 10 μm. A membrane was obtained.
Subsequently, the adhesion of the coating film was examined by a cross cut test (JIS K 5600-5-6). The evaluation was confirmed by the number of sheets peeled off by the adhesive tape, and 100 (the number of adhered eyes) / 100 (the number of grids) that did not peel the tape was regarded as acceptable. The results are shown in Table 4.

Undercoat does not adhere to plastic materials (ABS, PC / ABS, HIPS) with polyvinyl butyral alone, but adhesion can be secured by mixing acrylic resin.

表５から、意匠性トップコート層では、アンダーコート層がアクリル樹脂Ａまたはアクリル樹脂ＡＡを含有していれば付着性は確保出来、ブチラール樹脂／アクリル樹脂ＡＡの混合系ではブチラール樹脂の濃度が５０％以下であれば付着性は確保出来ることがわかる。
また、アンダーコートがブチラール樹脂／アクリル樹脂ＡＡ＝１／２（重量比）であり、トップコート層が上記（1）〜（4）のいずれかから形成された塗膜は、いずれも組成が水／エタノール／フマル酸＝１２／８５／３（重量％）からなる剥離液により完全に剥離することができた。 [Test Example 2]
(Topcoat layer adhesion test)
In the same manner as in Test Example 1, the paint shown in Table 5 was sprayed onto the surface of the undercoat layer coated on the ABS to form a topcoat layer.
The top coat layer paint used is as follows.
(1) Acrylic resin lacquer enamel: trade name Polynal No. 500 manufactured by Ohashi Chemical Industry Co., Ltd.
(2) Amine-epoxy curable acrylic resin paint (trade name Polynal No. 800 (S) manufactured by Ohashi Chemical Industry Co., Ltd.)
(3) Acrylic urethane resin paint 1 (trade name Polynar No. 800 (N) manufactured by Ohashi Chemical Industry Co., Ltd.)
(4) Acrylic urethane resin paint 2 (trade name Polynar No. 800 (HN) manufactured by Ohashi Chemical Industry Co., Ltd.)
These paints were applied on the undercoat layer and dried to obtain a topcoat layer having a thickness of 10 to 20 μm. The drying conditions were 60 ° C. for 30 minutes with the paint (1) and 30 minutes at 80 ° C. with the paints (2) to (4).
After forming the undercoat layer in this manner, the adhesion of the coating film on the ABS was examined by a cross cut test (JIS K 5600-5-6) in the same manner as in Test Example 1. The results are shown in Table 5.

From Table 5, the adhesiveness can be secured if the undercoat layer contains acrylic resin A or acrylic resin AA in the design top coat layer, and the concentration of butyral resin is 50 in the mixed system of butyral resin / acrylic resin AA. It can be seen that the adhesiveness can be ensured if it is not more than%.
The undercoat is butyral resin / acrylic resin AA = 1/2 (weight ratio), and the coating film in which the topcoat layer is formed from any one of the above (1) to (4) has a water composition. It was possible to completely peel off with a stripping solution comprising / ethanol / fumaric acid = 12/85/3 (wt%).

表６から明らかなように、剥離性アンダーコートは膜厚５〜１０μmで、意匠性トップコートは膜厚２０μm以上で付着性が確保できた。また、作業工程では、２コート１ベーク、２コート２ベークとも付着性が確保できた。 [Test Example 3]
(Coating adhesion test)
A peelable undercoat layer and a design topcoat layer were formed in the same manner as in Test Example 2, and a coating film having the composition and thickness shown in Table 6 was obtained. The coating film was formed by either 2-coat 1-bake or 2-coat 2-bake.
Then, in the same manner as in Test Example 1, the adhesion of the coating film was examined by a cross cut test (JIS K 5600-5-6). The results are shown in Table 6.

As is apparent from Table 6, the peelable undercoat had a film thickness of 5 to 10 μm, and the design topcoat had a film thickness of 20 μm or more, and adhesion could be secured. Also, in the work process, adhesion could be ensured for both 2 coat 1 bake and 2 coat 2 bake.

各プラスチック片を上記剥離液に浸漬し、剥離開始から３０分おきに手動で撹拌し、浸漬から３時間後にプラスチック片を回収した。回収後、プラスチックの表面を研磨紙（三共理化学（株）製のケンマロン#320）で研磨後、エタノールで洗浄し乾燥した。このようにして塗膜剥離した各プラスチック片の物性を評価した。また、比較のため、無塗装プラスチック片についても同様にして物性を評価した。結果を表８〜１２にそれぞれ示す。 A stripping solution prepared with a composition of water / ethanol / fumaric acid / Tween 80 / chitosan / glycerin = 10/83/3/1 / 0.1 / 2.9 (% by weight) is put into a 60 L stainless steel bath, and the stripping solution temperature is set. Was adjusted to 25-30 ° C.
On the other hand, the following three types were used as test plastics.
-ABS piece: Trade name “EX 18A” manufactured by UMG ABS, dimensions 127 × 70 × 3 mm
PC / ABS (polymer alloy) piece: “C6600” manufactured by GE Plastics, dimensions 150 × 150 × 2 mm
PS piece: “H9152” manufactured by A & M Styrene Co., Ltd., dimensions 150 × 150 × 2 mm
On the surface of these plastic pieces, an undercoat layer made of acrylic resin AA (supra) and a topcoat layer made of the same acrylic urethane resin paint 1 enamel as used in Test Example 2 were formed in this order. Table 7 shows the film thicknesses of the undercoat layer and the topcoat layer.

Each plastic piece was immersed in the above stripping solution, manually stirred every 30 minutes from the start of peeling, and the plastic piece was collected 3 hours after the immersion. After recovery, the plastic surface was polished with abrasive paper (Kenmaron # 320 manufactured by Sankyo Rikagaku Co., Ltd.), washed with ethanol, and dried. Thus, the physical property of each plastic piece which peeled the coating film was evaluated. For comparison, the physical properties of uncoated plastic pieces were evaluated in the same manner. The results are shown in Tables 8 to 12, respectively.

表８に示すように、ＡＢＳ樹脂に関しては、無塗装のバージン材と塗膜剥離後のＡＢＳ片の物性にはほとんど差が認められなかった。

As shown in Table 8, with respect to the ABS resin, there was almost no difference between the physical properties of the unpainted virgin material and the ABS piece after peeling the coating film.

表９、１０に示すように、PC/ABSの塗膜剥離後のサンプルを破砕し、物性テストを実施した結果、無塗装のバージン材との明らかな差は認められなかった。ただし面衝撃性においては、延性破壊率が低下し、若干脆化が認められたが、リサイクルプラスチックとしての許容範囲である。

As shown in Tables 9 and 10, the sample after peeling the PC / ABS coating film was crushed and subjected to a physical property test. As a result, no clear difference from the unpainted virgin material was observed. However, in terms of surface impact, the ductile fracture rate decreased and some embrittlement was observed, but this is an acceptable range for recycled plastics.

表１１，１２に示すように、ＰＳ素材上の塗膜を剥離させた破砕フレークは、無塗装のバージン材に比べて面衝撃強度において若干の低下が認められたが、アクリル系の塗膜が混入した場合に比べその低下度合いは小さく、実用可能なレベルであった。

As shown in Tables 11 and 12, the crushed flakes from which the paint film on the PS material was peeled showed a slight decrease in surface impact strength compared to the unpainted virgin material. Compared to the case of mixing, the degree of decrease was small and practical.

Claims (10)

  A coating film peeling method for peeling a coating film with a peeling liquid, wherein the coating film contains a thermoplastic resin binder, and the peeling liquid contains a lower alcohol or a mixed solvent of lower alcohol-water with the lower alcohol. A coating film peeling method characterized by adding at least one peeling accelerator selected from other organic solvents, organic acids and surfactants. After removing the coating film from the surface of the plastic molded product with a peeling solution, the plastic molded product is recycled by reusing the plastic molded product,
The coating film contains a thermoplastic resin binder, and the stripping solution is at least one selected from a mixed solvent of lower alcohol or lower alcohol-water, other organic solvents excluding the lower alcohol, organic acids, and surfactants. A method for recycling a plastic molded product, characterized by adding a seed peeling accelerator.   The method for recycling a plastic molded article according to claim 2, wherein after the plastic molded product having a coating film on the surface is pulverized, the coating film is peeled and removed with the stripper, and the pulverized product is reused.   The step of obtaining a plastic molded product, the step of applying a coating film on the surface of the obtained plastic molded product, the step of pulverizing the plastic molded product that is no longer needed, and the release liquid from the pulverized product The method for recycling a plastic molded product according to claim 2 or 3, comprising a step of peeling and removing the coating film and a step of reusing the pulverized product of the molded product from which the coating film has been removed.   The recycling method according to any one of claims 2 to 4, wherein the coating film contains a polyvinyl acetal resin together with the thermoplastic resin binder.   The recycling method according to any one of claims 2 to 5, wherein the coating film comprises an undercoat layer containing the thermoplastic resin binder and a topcoat layer provided on the surface thereof.   A stripping solution used in the method according to any one of claims 1 to 7, wherein the organic solvent other than the lower alcohol, an organic acid, and a surfactant are mixed with a mixed solvent of lower alcohol or lower alcohol-water. A stripping solution comprising at least one stripping accelerator selected from the group consisting of:   The stripping solution according to claim 7, wherein the lower alcohol is ethanol.   The stripping solution according to claim 7, wherein the organic acid is a polybasic acid. The stripping solution according to claim 7, further comprising at least one selected from a polycation compound and a polyhydric alcohol as a stripping acceleration aid.