Method for washing heat transfer sheet and method for manufacturing recycled raw material

Abstract

To provide a method for washing a heat transfer sheet which satisfies both good washability and environmental load reduction.SOLUTION: A washing method includes: a preparation step of preparing crushed pieces of a thermal transfer sheet; and a washing treatment step of subjecting the crushed pieces to washing treatment. A thickness of the thermal transfer sheet is 3.5-12 μm. The washing treatment step uses an aqueous washing liquid including surfactant and having a pH of 5.5-9.0.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a method for cleaning a thermal transfer sheet and a method for producing recycled raw materials. [Background technology]

[0002] One approach to environmental issues is the reuse of resources. For example, Patent Document 1 discloses a method for separating and recovering a laminate, which includes a step of immersing a laminate having at least a plastic substrate layer and a printed layer in a release liquid, releasing the printed layer to a predetermined size, and recovering the plastic substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7284903 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, when a used thermal transfer sheet is reused as a resource, a cleaning process is required to clean the thermal transfer sheet so that recycling destinations are not restricted. In the cleaning process, a cleaning liquid is usually added to the crushed pieces of the thermal transfer sheet to decolorize the coloring material contained in the crushed pieces and to remove dirt from the crushed pieces. The crushed pieces of the thermal transfer sheet are thin and have little stiffness, so they tend to aggregate together. Therefore, the cleaning ability is reduced compared to the cleaning target such as waste paper. On the other hand, if an alkaline cleaning liquid, an acidic cleaning liquid, or a solvent-based cleaning liquid is used, post-processing is required, which leads to a burden on the environment.

[0005] The present disclosure has been made in consideration of the above-mentioned circumstances, and has as its main object to provide a method for cleaning a thermal transfer sheet that achieves both good cleaning properties and reduced environmental impact. [Means for solving the problem]

[0006] The present disclosure provides a method for cleaning a thermal transfer sheet, the method comprising a preparation step of preparing crushed pieces of the thermal transfer sheet and a cleaning step of cleaning the crushed pieces, the thermal transfer sheet having a thickness of 3.5 μm or more and 12 μm or less, and wherein an aqueous cleaning solution containing a surfactant and having a pH of 5.5 or more and 9.0 or less is used in the cleaning step.

[0007] The present disclosure provides a method for producing recycled raw materials, which includes a cleaning step of cleaning a thermal transfer sheet using the above-mentioned method for cleaning a thermal transfer sheet.

[0008] The present disclosure has an effect of providing a method for cleaning a thermal transfer sheet that achieves both good cleaning properties and reduced environmental impact. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view illustrating a thermal transfer sheet according to the present disclosure. [Diagram 2] FIG. 2 is a schematic plan view illustrating a fragment according to the present disclosure. [Diagram 3] 1 is a schematic cross-sectional view illustrating a thermal transfer sheet according to the present disclosure. [Figure 4] 1 is a schematic cross-sectional view illustrating a thermal transfer sheet according to the present disclosure. [Diagram 5] 1 is a schematic cross-sectional view illustrating a thermal transfer sheet according to the present disclosure. [Figure 6] FIG. 2 is a schematic plan view illustrating a fragment according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The following describes the embodiments with reference to the drawings. However, the present disclosure can be implemented in many different forms and is not limited to the description of the embodiments exemplified below. In addition, in order to clarify the description, the drawings may show the width, thickness, and shape of each part in a schematic manner compared to the actual form, but this is merely an example and should not be interpreted as being limiting.

[0011] In this specification, when describing a mode in which another component is disposed on a certain component, the term "above" or "below" includes both a case in which another component is disposed directly above or below a certain component so as to be in contact with the component, and a case in which another component is disposed above or below a certain component via another component, unless otherwise specified. In addition, in this specification, when describing a mode in which another component is disposed on the surface of a certain component, the term "on the surface" or "on the surface side" includes both a case in which another component is disposed directly above or below a certain component so as to be in contact with the component, and a case in which another component is disposed above or below a certain component via another component, unless otherwise specified.

[0012] The method for cleaning a thermal transfer sheet and the method for producing recycled raw materials according to the present disclosure will be described in detail below.

[0013] A. How to clean the thermal transfer sheet FIG. 1 is a schematic cross-sectional view illustrating a thermal transfer sheet according to the present disclosure, specifically, a thermal transfer sheet before being crushed. As shown in FIG. 1(a), a thermal transfer sheet 10 has, for example, a base layer 1 and a color material layer 2. The base layer 1 and the color material layer 2 are arranged in a thickness direction D. T1(c), the thermal transfer sheet 10 may have a primer layer 4 between the substrate layer 1 and the color material layer 2. Also, as shown in FIG. 1(d), the thermal transfer sheet 10 may have a substrate layer 1 and a protective layer 5. Also, as shown in FIG. 1(b), the thermal transfer sheet 10 may have a release layer 3 between the substrate layer 1 and the color material layer 2. Also, as shown in FIG. 1(d), the thermal transfer sheet 10 may have a substrate layer 1 and a protective layer 5.

[0014] Fig. 2 is a schematic plan view illustrating the crushed pieces in the present disclosure. As shown in Fig. 2, in the present disclosure, crushed pieces 11 of a thermal transfer sheet are prepared (preparation step). Next, the crushed pieces 11 are washed (washing step). One of the features of the present disclosure is that an aqueous washing liquid containing a surfactant and having a pH of 5.5 to 9.0 is used in the washing step.

[0015] According to the present disclosure, by using an aqueous cleaning solution containing a surfactant and having a pH of 5.5 to 9.0, it is possible to achieve both good cleaning properties and reduced environmental impact. Conventionally, used thermal transfer sheets, or unused but unnecessary thermal transfer sheets, have been discarded as industrial waste without being recycled. When reusing the thermal transfer sheet as a resource, a cleaning process for cleaning the thermal transfer sheet is required so that recycling destinations are not limited.

[0016] In the cleaning process, a cleaning liquid is usually added to the crushed pieces of the thermal transfer sheet to bleach the coloring material contained in the crushed pieces and to remove dirt from the crushed pieces. The crushed pieces of the thermal transfer sheet are thin and have little stiffness. Therefore, as shown in FIG. 2, multiple crushed pieces 11 aggregate with each other. The cleaning liquid does not easily penetrate into the area where multiple crushed pieces 11 aggregate, so the cleaning ability decreases. On the other hand, if an alkaline cleaning liquid, an acidic cleaning liquid, or a solvent-based cleaning liquid is used, post-processing is required, which is an environmental burden.

[0017] In contrast, in the cleaning process in the present disclosure, an aqueous cleaning solution containing a surfactant and having a pH of 5.5 to 9.0 is used. By using a surfactant, it is possible to suppress the fragments from flocculating. As a result, the deterioration of cleaning properties is suppressed. In addition, by using an aqueous cleaning solution having a pH of 5.5 to 9.0, post-treatment neutralization is unnecessary or easy, for example, compared to the case where an alkaline cleaning solution or an acidic cleaning agent is used. Therefore, it is possible to reduce the environmental load. In addition, by using an aqueous cleaning solution using water as a solvent, post-treatment is unnecessary or easy, for example, compared to the case where a solvent-based cleaning solution is used. Therefore, it is possible to reduce the environmental load. In this way, in the present disclosure, it is possible to achieve both good cleaning properties and reduced environmental load.

[0018] 1. Preparation process The preparation step in the present disclosure is a step of preparing crushed pieces of a thermal transfer sheet. The crushed pieces are obtained by crushing the thermal transfer sheet. The crushed pieces may be prepared by crushing the thermal transfer sheet by oneself, or may be prepared by collecting the crushed pieces obtained by another person crushing the thermal transfer sheet. In addition, as described below, the preparation step and the cleaning treatment step may be performed. That is, the crushed pieces may be cleaned while the thermal transfer sheet is being crushed.

[0019] (1) Thermal transfer sheet As shown in FIG. 1(a), the thickness of the thermal transfer sheet 10 is T. The thickness T is usually 3.5 μm or more and 12 μm or less, and may be 4 μm or more and 11 μm or less, or 6 μm or more and 10 μm or less. When the thermal transfer sheet is in the above range, the fragments tend to aggregate together. In contrast, in the present disclosure, the aggregation of the fragments can be suppressed by using an aqueous cleaning solution containing a surfactant. In addition, if the thermal transfer sheet is too thick or too thin, the thermal transferability may decrease.

[0020] As shown in Fig. 1(a), the thermal transfer sheet 10 may have a base material layer 1 and a color material layer 2. As shown in Fig. 1(d), the thermal transfer sheet 10 may have a base material layer 1 and a protective layer 5. Each layer constituting the thermal transfer sheet will be described below.

[0021] (i) Base material layer The substrate layer is preferably a resin film. The resin used for the resin film is not particularly limited, but examples thereof include polyester, polyamide, polyolefin, vinyl resin, vinyl acetal resin, (meth)acrylic resin, imide resin, cellulose resin, styrene resin, polycarbonate, and ionomer.

[0022] Examples of the polyester include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), 1,4-polycyclohexylene dimethylene terephthalate, and terephthalic acid-cyclohexane dimethanol-ethylene glycol copolymer. Examples of the polyamide include nylon 6 and nylon 6,6. Examples of the polyolefin include polyethylene (PE), polypropylene (PP), and polymethylpentene. Examples of the vinyl resin include polyvinyl chloride, polyvinyl alcohol (PVA), polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, and polyvinylpyrrolidone (PVP).

[0023] Examples of the vinyl acetal resin include polyvinyl acetoacetal and polyvinyl butyral. Examples of the (meth)acrylic resin include poly(meth)acrylate. "(meth)acrylic" includes both "acrylic" and "methacrylic", and "(meth)acrylate" includes both "acrylate" and "methacrylate". Examples of the imide resin include polyimide and polyetherimide. Examples of the cellulose resin include cellophane, cellulose acetate, nitrocellulose, cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB). Examples of the styrene resin include polystyrene (PS).

[0024] The resin used in the resin film is preferably polyester, more preferably PET or PEN, and even more preferably PET. This is because it has excellent heat resistance and mechanical strength. The base layer may be a laminate of resin films. The resin film may be a stretched film or an unstretched film. From the viewpoint of mechanical strength, the resin film is preferably a stretched film stretched in a uniaxial or biaxial direction. The thickness of the base layer is not particularly limited as long as a thermal transfer sheet having a predetermined thickness is obtained, but may be, for example, 1 μm or more and 7 μm or less, or 3 μm or more and 6 μm or less.

[0025] (ii) Color material layer The color material layer is a layer containing at least a color material. Examples of the hue of the color material include magenta, yellow, cyan, and black.

[0026] The coloring material may be a pigment or a dye. Examples of the coloring material include carbon black, acetylene black, lamp black, black smoke, iron black, aniline black, silica, calcium carbonate, titanium oxide, cadmium red, cadmium pon red, chrome red, vermilion, red iron oxide, azo pigments, alizarin lake, quinacridone, cochineal lake perylene, yellow ocher, aureolin, cadmium yellow, cadmium orange, chrome yellow, zinc yellow, Naples yellow, nickel yellow, greenish yellow, ultramarine, rock ultramarine, cobalt, phthalocyanine, anthraquinone, indicoid, cinnabar green, cadmium green, chrome green, phthalocyanine, azomethine, perylene, and aluminum pigments.

[0027] The coloring material may be a sublimable dye, such as diarylmethane dyes, triarylmethane dyes, thiazole dyes, merocyanine dyes, pyrazolone dyes, methine dyes, indoaniline dyes, acetophenone azomethine dyes, pyrazoloazomethine dyes, xanthene dyes, oxazine dyes, thiazine dyes, azine dyes, acridine dyes, azo dyes, spiropyran dyes, indolinospiropyran dyes, fluoran dyes, naphthoquinone dyes, anthraquinone dyes, and quinophthalone dyes.

[0028] The content of the color material in the color material layer is not particularly limited, but may be, for example, 5% by mass or more and 75% by mass or less, or 10% by mass or more and 50% by mass or less.

[0029] The color material layer may be a melt transfer type color material layer in which a color material such as a pigment or a dye is dispersed in a binder having thermal melting properties, or a sublimation transfer type color material layer in which a sublimation dye is dissolved or dispersed in a binder. Examples of the binder include resins. Examples of the resins include polyester, polyurethane, polyamide, polyimide, polycarbonate, polyolefin, (meth)acrylic resin, vinyl resin, styrene resin, cellulose resin, phenoxy resin, epoxy resin, and ionomer.

[0030] The melt transfer type coloring material layer may contain wax as a binder. Examples of the wax include microcrystalline wax, carnauba wax, paraffin wax, Fischer-Tropsch wax, polyethylene wax, Japanese wax, beeswax, whale wax, Japanese ivy wax, wool wax, shellac wax, candelilla wax, petrolatum, polyester wax, partially modified wax, fatty acid ester, and fatty acid amide. The melt transfer type coloring material layer may contain both resin and wax as a binder.

[0031] The melt transfer type color material layer may contain a cured product (crosslinked structure) of the binder. Examples of curing agents for curing the binder include isocyanate and carbodiimide. The melt transfer type color material layer may contain at least one cured product (crosslinked structure) of an actinic radiation curable monomer and an actinic radiation curable oligomer as a binder. The actinic radiation curable monomer and the actinic radiation curable oligomer refer to monomers and oligomers that are polymerized (cured) by irradiation with actinic radiation. The term "actinic radiation" refers to radiation that chemically acts on the actinic radiation curable monomer and the actinic radiation curable oligomer to promote polymerization. Examples of actinic radiation include visible light, ultraviolet light, X-rays, electron beams, α rays, β rays, and γ rays.

[0032] Examples of the actinic radiation curable monomer include urethane acrylate, epoxy acrylate, polyester acrylate, polyether acrylate, polyethylene acrylate, silicone acrylate, and polyol acrylate. The number of functional groups in the actinic radiation curable monomer is not particularly limited, but may be, for example, 2 or more, and may be, for example, 3 or more. On the other hand, examples of the actinic radiation curable oligomer include polymers or copolymers of the actinic radiation curable monomers. The number of functional groups in the actinic radiation curable oligomer is not particularly limited, but may be, for example, 2 or more, and may be, for example, 3 or more.

[0033] The thickness of the color material layer is not particularly limited as long as a thermal transfer sheet having a predetermined thickness is obtained, but may be, for example, 0.3 μm or more and 7 μm or less, or 1 μm or more and 6 μm or less. The color material layer and the base layer may be arranged so as to be in direct contact with each other, or may be arranged via another layer. Examples of the other layer include a release layer and a primer layer.

[0034] (iii) Protective layer The protective layer (OP layer) is a transparent layer containing a resin. The resin used in the protective layer is not particularly limited, but examples thereof include polyester, polystyrene, polyurethane, (meth)acrylic resin, (meth)acrylic urethane resin, and vinyl chloride-vinyl acetate copolymer. The resin may be, for example, a silicone-modified resin. The protective layer may contain a coloring material such as a fluorescent whitening agent, or may not contain a coloring material. The thickness of the protective layer is not particularly limited as long as a thermal transfer sheet having a predetermined thickness is obtained, but is, for example, 0.1 μm or more and 2.0 μm or less. The thermal transfer sheet may have both one or more types of coloring material layers and a protective layer on one side of the base layer. Examples of the one or more types of coloring material layers include a red coloring material layer (Mg layer), a yellow coloring material layer (Ye layer), a blue coloring material layer (Cy layer), and a black coloring material layer (Bk layer).

[0035] (iv) Other layers As shown in FIG. 1(b), the thermal transfer sheet 10 may have a release layer 3 between the substrate layer 1 and the colorant layer 2. By providing the release layer 3, the transferability can be improved. The release layer is preferably made of a material that is easily washed with a cleaning solution, and preferably contains a resin. Examples of the resin include (meth)acrylic resin, vinyl resin, styrene resin, cellulose resin, polyester, polyurethane, polyamide, polyimide, and polycarbonate. The release layer may contain a cured product (crosslinked structure) of a binder. Examples of the curing agent that cures the binder include isocyanate and carbodiimide. The release layer may contain at least one cured product (crosslinked structure) of an actinic radiation curable monomer and an actinic radiation curable oligomer as a binder. The release layer may also contain additives such as a lubricant, an ultraviolet absorber, a light stabilizer, and an antioxidant.

[0036] FIG. 3 is a schematic cross-sectional view illustrating a thermal transfer sheet according to the present disclosure, specifically, a melt-transfer type thermal transfer sheet. The release layer 3 shown in FIG. 3 is usually transferred to the transferee side as a part of the transfer layer α during thermal transfer. The thermal transfer sheet 10 is oriented in the thickness direction D T In the thermal transfer sheet 10, a back layer 6 may be provided on the opposite side of the color material layer 2 with respect to the base layer 1. By providing the back layer 6, the occurrence of sticking caused by a thermal head can be suppressed. T In the present invention, an adhesive layer 7 may be provided on the opposite side of the color material layer 2 from the base layer 1. By providing the adhesive layer 7, it is possible to improve the adhesion to the transfer target. The release layer 3, the back layer 6 and the adhesive layer 7 may have a known configuration.

[0037] As shown in FIG. 1(c), the thermal transfer sheet 10 may have a primer layer 4 between the substrate layer 1 and the color material layer 2. By providing the primer layer 4, the adhesion between the substrate layer 1 and the color material layer 2 can be improved. The primer layer is preferably made of a material that is easily washed with a cleaning solution, and preferably contains a resin. Examples of the resin include polyester, vinyl resin, (meth)acrylic resin, styrene resin, polyamide, polyether, urethane resin, and cellulose resin.

[0038] FIG. 4 is a schematic cross-sectional view illustrating a thermal transfer sheet according to the present disclosure, specifically, a sublimation transfer type thermal transfer sheet. The primer layer 4 shown in FIG. 4 improves the adhesion between the substrate layer 1 and the color material layer 2. The thermal transfer sheet 10 is formed in the thickness direction D T In the thermal transfer sheet 10, a back layer 6 may be provided on the opposite side of the color material layer 2 with respect to the base layer 1. By providing the back layer 6, the occurrence of sticking caused by a thermal head can be suppressed. T In the above, a second primer layer 8 may be provided between the base layer 1 and the back layer 6. By providing the second primer layer 8, the adhesion between the base layer 1 and the back layer 6 is improved. For the primer layer 4, the back layer 6, and the second primer layer 8, a known configuration may be adopted.

[0039] FIG. 5 is a schematic cross-sectional view illustrating a thermal transfer sheet according to the present disclosure, specifically, a thermal transfer sheet having a protective layer (OP layer). The primer layer 4 shown in FIG. 5 improves the adhesion between the protective layer 5 and the adhesive layer 7. The adhesive layer 7 according to the present disclosure may be a heat seal layer. The thermal transfer sheet 10 has a thickness direction D T In the thermal transfer sheet 10, a back layer 6 may be provided on the opposite side of the color material layer 2 with respect to the base layer 1. By providing the back layer 6, the occurrence of sticking caused by a thermal head can be suppressed. TIn the thermal transfer sheet according to the present disclosure, a second primer layer 8 may be provided between the base layer 1 and the back layer 6. By providing the second primer layer 8, the adhesion between the base layer 1 and the back layer 6 is improved. Known configurations may be adopted for the primer layer 4, the back layer 6, and the second primer layer 8. Note that the thermal transfer sheet according to the present disclosure may further have a known layer not shown in Figs. 3 to 5.

[0040] (2) Debris The crushed pieces in the present disclosure are obtained by crushing the thermal transfer sheet. Therefore, the layer structure of the crushed pieces is usually the same as the layer structure of the thermal transfer sheet before crushing. For example, the crushed pieces may have at least a substrate layer and a coloring material layer. The crushed pieces may have a release layer or a primer layer between the substrate layer and the coloring material layer. The crushed pieces may also have at least a substrate layer and a protective layer. Furthermore, the crushed pieces may have each layer described in "(1) Thermal Transfer Sheet" above. The thickness of the crushed pieces is usually the same as the thickness of the thermal transfer sheet before crushing. The thickness of the thermal transfer sheet is as described above.

[0041] The planar shape of the crushed pieces is not particularly limited. The planar shape of the crushed pieces refers to the outer edge shape of the crushed pieces when the crushed pieces are observed from the thickness direction. Here, the crushed pieces are classified into crushed pieces X and crushed pieces Y according to the planar shape. The crushed pieces X have a planar shape that is a rectangle or a shape that can be approximated to a rectangle. On the other hand, the crushed pieces Y are crushed pieces that do not fall under the category of crushed pieces X.

[0042] As shown in FIG. 6(a), the shape of the fragment 11 in plan view may be a rectangle (quadrangle). On the other hand, as shown in FIG. 6(b) and (d), the fragment 11 may have a cutout 12 in part. Even in such a case, if the cutout 12 is small, the shape of the fragment 11 in plan view will be a shape that can approximate a quadrangle. A "shape that can approximate a quadrangle" is defined as follows. As shown in FIG. 6(c) and (e), imagine a virtual quadrangle 13 (rectangle or square) that is inscribed in the fragment 11. Let the area of ​​the virtual quadrangle 13 be S.A The area of ​​the fragment 11 is S B Let us assume that S A S for B The ratio (S B / S A ) is 0.8 or more, the shape is considered to be "approximately rectangular."

[0043] As shown in Fig. 6(a) and (c), the length of the short side of the fragment X is L 1 Let the length of the long side of the fragment X be L 2 The aspect ratio (L 2 / L 1 ) is not particularly limited, but may be, for example, 1.5 or more and 10.0 or less, 2.0 or more and 9.0 or less, or 2.0 or more and 5.0 or less. Although not particularly shown, the planar shape of the crushed pieces X may be a square (rectangle). The square has an aspect ratio (L 2 / L 1 ) is 1.0 or more and less than 1.5. 1 For example, L may be 1 mm or more and 5 cm or less, and may be 3 mm or more and 3.5 cm or less. 2 For example, L may be 1 mm or more and 10 cm or less, and may be 3 mm or more and 9 cm or less. Also, as shown in FIG. 6(c), when the planar shape of the crushed piece X is a shape that can be approximated to a rectangle, L 1 and L 2 is set based on the imaginary rectangle 13.

[0044] On the other hand, as shown in FIG. 6(f), the fragments 11 may have a complex shape. In this case, too, as shown in FIG. 6(g), a virtual quadrangle 13 (rectangle or square) is assumed to be inscribed in the fragments 11. B / S A If the ratio is less than 0.8, it does not fall under the category of "a shape that can be approximated as a rectangle." In addition, if multiple imaginary rectangles13 can be assumed, S B / S AThe largest one is adopted. The planar shape of the fragment 11 shown in FIG. 6(f) is neither a "rectangle" nor a "shape that can be approximated to a rectangle", so it does not correspond to the fragment X, but to the fragment Y. The proportion of the fragment X to the total of the fragment X and the fragment Y may be, for example, 10% or more and 90% or less, or 20% or more and 80% or less, based on the number of pieces.

[0045] The crushed pieces are obtained by crushing the thermal transfer sheet. Examples of crushing devices for crushing the thermal transfer sheet include jaw crushers, impact crushers, cutter mills, stamp mills, ring mills, roller mills, jet mills, and hammer mills. The crushing conditions for the thermal transfer sheet are not particularly limited, and are appropriately adjusted so as to obtain the above-mentioned crushed pieces.

[0046] 2. Cleaning process The washing step in the present disclosure is a step of washing the crushed pieces. In the washing step, an aqueous washing liquid containing a surfactant and having a pH of 5.5 to 9.0 is used.

[0047] (1) Water-based cleaning solution The aqueous cleaning liquid contains a surfactant. Examples of the surfactant include a nonionic surfactant, an anionic surfactant, a cationic surfactant, and an amphoteric surfactant. The aqueous cleaning liquid may contain only one type of surfactant, or may contain two or more types of surfactants.

[0048] Examples of nonionic surfactants include polyoxyalkylene alkyl ethers, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyglycerin fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene fatty acid amides, fatty acid alkylol amides, alkyl alkanol amides, acetylene glycol, oxyethylene adducts of acetylene glycol, and polyethylene glycol polypropylene glycol block copolymers.

[0049] Examples of anionic surfactants include alkylbenzenesulfonates, alkylphenylsulfonates, alkylnaphthalenesulfonates, higher fatty acid salts, sulfates of higher fatty acid esters, sulfonates of higher fatty acid esters, sulfates and sulfonates of higher alcohol ethers, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, and polyoxyethylene alkyl ether phosphates.Specific examples of anionic surfactants include dodecylbenzenesulfonates, isopropylnaphthalenesulfonates, monobutylphenylphenol monosulfonates, monobutylbiphenylsulfonates, and dibutylphenylphenol disulfonates.

[0050] Examples of cationic surfactants include didecyl dimethyl ammonium chloride, didecyl dimethyl ammonium methosulfate, distearyl dimethyl ammonium chloride, dioctyl dimethyl ammonium chloride, distearyl dihydroxyethyl ammonium chloride, di-tallow alkyl dimethyl ammonium chloride, di(stearoyloxyethyl)dimethyl ammonium chloride, di(oleoyloxyethyl)dimethyl ammonium chloride, di(palmitoyloxyethyl)dimethyl ammonium methosulfate, di(stearoyloxyisopropyl)dimethyl ammonium chloride, di(oleoyloxyisopropyl)dimethyl ammonium chloride, di(oleoyloxybutyl)dimethyl ammonium chloride, di(stearoyloxyethyl)methyl hydroxyethyl ammonium methosulfate, and tri(stearoyloxyethyl)methyl methosulfate.

[0051] Examples of amphoteric surfactants include betaine surfactants and amine oxide surfactants. Examples of betaine surfactants include imidazoline betaines, alkyl dimethyl amino acetic acid betaines, fatty acid amidopropyl betaines, and sulfobetaines. Examples of amine oxide surfactants include alkyl dimethyl amine oxides.

[0052] The concentration of the surfactant in the aqueous cleaning liquid is not particularly limited, but is, for example, 0.001% by mass or more and 10% by mass or less, optionally 0.005% by mass or more and 7% by mass or less, optionally 0.03% by mass or more and 5% by mass or less, or optionally 0.05% by mass or more and 3% by mass or less.

[0053] The aqueous cleaning liquid contains a solvent mainly composed of water in addition to the above-mentioned surfactant. The above-mentioned solvent may contain only water, or may further contain a water-soluble organic solvent. The proportion of water in the total solvent is, for example, 50% by mass or more, 70% by mass or more, or 90% by mass or more. The aqueous cleaning liquid may contain an antifoaming agent such as a silicone compound or a non-silicone compound in addition to the above-mentioned surfactant and solvent.

[0054] The pH of the aqueous cleaning liquid is usually 5.5 or more and 9.0 or less at 25°C. If the pH of the aqueous cleaning liquid is too high or too low, neutralization treatment is required when disposing of the liquid. On the other hand, if the pH of the aqueous cleaning liquid is within the above range, neutralization treatment is not required or the burden of neutralization treatment is reduced. In addition, the surface tension of the aqueous cleaning liquid is not particularly limited, but is preferably 25 mN / m or more and 50 mN / m or less. This is because the colorant layer fused to the base layer by heating during thermal transfer can be effectively decolorized.

[0055] (2) Cleaning method The cleaning process in the present disclosure is a process of cleaning a plurality of crushed pieces. In the cleaning process, a large number of crushed pieces are cleaned. Since each crushed piece is thin and has little stiffness, a large number of crushed pieces 11 tend to aggregate together. In contrast, in the present disclosure, an aqueous cleaning solution containing a surfactant is used to prevent the crushed pieces from aggregating together.

[0056] The method of cleaning the crushed pieces using the above-mentioned aqueous cleaning liquid is not particularly limited, but for example, a method of immersing the crushed pieces in the aqueous cleaning liquid can be mentioned. The temperature of the aqueous cleaning liquid during immersion is not particularly limited, but for example, it may be 25°C or more and 100°C or less, or 30°C or more and 80°C or less. The immersion time is, for example, 1 minute or more and 24 hours or less. It is also preferable to stir the aqueous cleaning liquid in which the crushed pieces are immersed. By stirring, the cleaning effect is improved. In addition, the above-mentioned preparation step and the cleaning treatment step may be performed simultaneously. For example, the preparation step and the cleaning treatment step can be performed simultaneously by using a wet crusher to crush the thermal transfer sheet while washing the crushed pieces.

[0057] The washing survival rate of the crushed pieces before and after the washing treatment step is preferably 10% or less. The method for measuring the washing survival rate will be described in detail in the examples below.

[0058] B. Manufacturing methods for recycled materials The method for producing recycled materials according to the present disclosure includes a cleaning step for cleaning the thermal transfer sheet. In the cleaning step, the thermal transfer sheet is cleaned using the cleaning method described in "A. Method for cleaning the thermal transfer sheet" above.

[0059] According to the present disclosure, by cleaning the thermal transfer sheet using the above-mentioned cleaning method, it is possible to obtain recycled raw materials while achieving both good cleaning properties and reduced environmental impact. The cleaning process is the same as that described in "A. Method for cleaning thermal transfer sheet" above, so the description here is omitted.

[0060] The method for producing recycled raw materials may include a separation step of separating the washed crushed pieces from the suspension containing the washed crushed pieces after the washing step. Examples of the separation method include a method using a filter and a method using a centrifuge.

[0061] The method for producing recycled raw materials may include a water washing step of washing the washed crushed pieces with water after the washing step. By carrying out the water washing step, the aqueous cleaning solution remaining in the crushed pieces can be removed. The water washing step may be carried out simultaneously with the separation step or after the separation step.

[0062] The method for producing recycled materials may include a drying step for drying the washed crushed pieces after the washing step. The drying conditions are not particularly limited, and are preferably adjusted appropriately so as to obtain the desired recycled materials. The drying step may be performed after the separation step or after the water washing step. In addition, the washed crushed pieces may be pelletized to produce pelletized recycled materials, if necessary.

[0063] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present disclosure and exhibits similar effects is included in the technical scope of the present disclosure. EXAMPLES

[0064] [Example 1] As the thermal transfer sheet, a melting type thermal transfer sheet A (V300, manufactured by Dai Nippon Printing Co., Ltd.) was used. Next, the thermal transfer sheet was shredded using a ribbon shredder (device name: GRASYS BiT) to obtain shredded pieces. The cutting method was twisted microcut, and the shredding speed was set to a maximum of 12 m / min. Next, an aqueous cleaning solution (pH 8.2) containing a nonionic surfactant A (DKS Dash403, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) at a concentration of 0.3% by mass was prepared as a cleaning solution. Next, 0.5 g of the obtained shredded pieces was placed in a container, and 50 ml of the aqueous cleaning solution was added and stirred for 0.5 hours. In this way, the shredded pieces of the thermal transfer sheet were washed.

[0065] [Example 2] The crushed pieces of the thermal transfer sheet were washed in the same manner as in Example 1, except that melt-type thermal transfer sheet B (TR3075, manufactured by Dai Nippon Printing Co., Ltd.) was used as the thermal transfer sheet.

[0066] [Example 3] The crushed pieces of the thermal transfer sheet were washed in the same manner as in Example 1, except that dye-sublimation thermal transfer sheet A (DS621; Mg panel, manufactured by Dai Nippon Printing Co., Ltd.) was used as the thermal transfer sheet.

[0067] [Example 4] The crushed pieces of the thermal transfer sheet were washed in the same manner as in Example 1, except that dye-sublimation thermal transfer sheet B (DS621; OP panel, manufactured by Dai Nippon Printing Co., Ltd.) was used as the thermal transfer sheet.

[0068] [Examples 5 and 6] The crushed pieces of the thermal transfer sheet were washed in the same manner as in Examples 1 and 3, except that an aqueous cleaning solution (pH 7.3) containing a nonionic surfactant B (Emulgen 106, Kao Corporation) at a concentration of 0.3 mass% was used as the cleaning solution.

[0069] [Examples 7 and 8] The crushed pieces of the thermal transfer sheet were washed in the same manner as in Examples 1 and 3, except that an aqueous cleaning solution (pH 8.5) containing an anionic surfactant (Hitenol NF-08, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) at a concentration of 0.3 mass% was used as the cleaning solution. [Comparative Example 1] The crushed pieces of the thermal transfer sheet were washed in the same manner as in Example 4, except that methyl ethyl ketone (MEK), a solvent-based washing liquid, was used as the washing liquid.

[0070] [evaluation] (Measurement of cleaning residual rate) The cleaning survival rate (colorant survival rate) of the fragments before and after cleaning was calculated. Specifically, the fragments before and after cleaning were scanned with a scanner (CanoScan9000F) at a resolution of 600 dpi, color mode: grayscale, and no color correction, and the captured image was binarized using image analysis software (ImageJ), and the number of dots from 0 to 150 was counted. The cleaning survival rate was calculated using the following formula. Cleaning remaining rate (%) = (number of dots after cleaning) / (number of dots before cleaning) x 100

[0071] The cleaning survival rate was evaluated according to the following criteria. The results are shown in Tables 1 and 2. A: Washing residual rate is 10% or less B: The residual rate after cleaning is greater than 10%

[0072] [Table 1]

[0073] [Table 2]

[0074] As shown in Tables 1 and 2, it was confirmed that Examples 1 to 8 had a low cleaning residual rate and good cleaning properties. This is presumably because the use of an aqueous cleaning solution containing a surfactant could suppress the aggregation of the crushed pieces. In addition, since an aqueous cleaning solution was used in Examples 1 to 8, it was possible to reduce the environmental load. On the other hand, since a solvent-based cleaning solution was used in Comparative Example 1, post-treatment of the solvent-based cleaning solution was required, and it was not possible to reduce the environmental load. Furthermore, Comparative Example 1 had a higher cleaning residual rate than Examples 1 to 8. This is presumably because the use of a solvent-based cleaning solution could not suppress the aggregation of the crushed pieces.

[0075] Thus, in the present disclosure, for example, the following inventions are provided:

[0076] [1] A method for cleaning a thermal transfer sheet, comprising the steps of: The method for cleaning the thermal transfer sheet includes a preparation step of preparing crushed pieces of the thermal transfer sheet, and a cleaning step of cleaning the crushed pieces, The thickness of the thermal transfer sheet is 3.5 μm or more and 12 μm or less, The method for cleaning a thermal transfer sheet, wherein the cleaning treatment step uses an aqueous cleaning liquid containing a surfactant and having a pH of 5.5 to 9.0.

[0077] [2] The thermal transfer sheet has at least a base layer and a color material layer, The method for cleaning a thermal transfer sheet according to [1], wherein the crushed pieces are decolorized in the cleaning treatment step.

[0078] [3] The method for cleaning a thermal transfer sheet according to [2], wherein the thermal transfer sheet has a release layer between the base layer and the color material layer.

[0079] [4] The method for cleaning a thermal transfer sheet according to [2], wherein the thermal transfer sheet has a primer layer between the base layer and the color material layer.

[0080] [5] The method for cleaning a thermal transfer sheet according to any one of [1] to [4], wherein the thermal transfer sheet has at least a base layer and a protective layer.

[0081] [6] The method for cleaning a thermal transfer sheet according to any one of [1] to [5], wherein the aqueous cleaning liquid contains at least one of a nonionic surfactant, an anionic surfactant, a cationic surfactant, and an amphoteric surfactant as the surfactant.

[0082] [7] The method for cleaning a thermal transfer sheet according to any one of [1] to [6], wherein the plurality of crushed pieces include crushed pieces X having a rectangular shape or a shape that can be approximated to a rectangular shape in a plan view.

[0083] [8] The method for cleaning a thermal transfer sheet according to any one of [1] to [7], wherein the rate of the crushed pieces remaining after cleaning is 10% or less before and after the cleaning treatment step.

[0084] [9] A method for producing recycled raw materials, comprising a cleaning step of cleaning a thermal transfer sheet using the method for cleaning a thermal transfer sheet according to any one of [1] to [8]. [Explanation of symbols]

[0085] 1...Base material layer 2...color material layer 3…Release layer 4…Primer layer 5…Protective layer 6…Back layer 7...Adhesive layer 8...Second primer layer 10...Thermal transfer sheet 11...Debris

Claims

1. A method for cleaning a thermal transfer sheet, comprising the steps of: The method for cleaning the thermal transfer sheet includes a preparation step of preparing crushed pieces of the thermal transfer sheet, and a cleaning step of cleaning the crushed pieces, The thickness of the thermal transfer sheet is 3.5 μm or more and 12 μm or less, The method for cleaning a thermal transfer sheet, wherein the cleaning treatment step uses an aqueous cleaning liquid containing a surfactant and having a pH of 5.5 or more and 9.0 or less.

2. The thermal transfer sheet has at least a base layer and a color material layer, The method for cleaning a thermal transfer sheet according to claim 1 , wherein the crushed pieces are decolorized in the cleaning treatment step.

3. The method for cleaning a thermal transfer sheet according to claim 2 , wherein the thermal transfer sheet has a release layer between the base layer and the color material layer.

4. The method for cleaning a thermal transfer sheet according to claim 2 , wherein the thermal transfer sheet has a primer layer between the base layer and the color material layer.

5. The method for cleaning a thermal transfer sheet according to claim 1 , wherein the thermal transfer sheet has at least a base layer and a protective layer.

6. The method for cleaning a thermal transfer sheet according to claim 1 , wherein the aqueous cleaning liquid contains, as the surfactant, at least one of a nonionic surfactant, an anionic surfactant, a cationic surfactant, and an amphoteric surfactant.

7. The method for cleaning a thermal transfer sheet according to claim 1 , wherein the plurality of crushed pieces include crushed pieces X each having a shape that is rectangular or approximates a rectangle in a plan view.

8. 2. The method for cleaning a thermal transfer sheet according to claim 1, wherein a rate of the fragments remaining after cleaning is 10% or less before and after the cleaning treatment step.

9. A method for producing recycled raw materials, comprising a cleaning step of cleaning a thermal transfer sheet by using the method for cleaning a thermal transfer sheet according to any one of claims 1 to 8.

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