Method of cleaning heat transfer sheet and method of producing recycled raw material

Abstract

To provide a method of cleaning a heat transfer sheet, the method achieving both excellent washability and excellent low foamability.SOLUTION: A method of cleaning a heat transfer sheet includes: a preparation step of preparing crushed pieces of the heat transfer sheet; and a cleaning step of cleaning a plurality of the crushed pieces using a neutral aqueous cleaning solution. The thickness of the heat transfer sheet is 3.5 μm or more and 12 μm or less, and the aqueous cleaning solution contains: a cleaning agent that includes at least a nonionic surfactant; and water. The cleaning step includes a first cleaning process in which the a plurality of crushed pieces are cleaned using first aqueous cleaning solution that is the above-mentioned aqueous cleaning solution, and a second cleaning process in which, after the first cleaning process, the a plurality of crushed pieces are cleaned using second aqueous cleaning solution that is the above-mentioned aqueous cleaning solution.SELECTED DRAWING: Figure 1

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 resource recycling. For example, Patent Document 1 discloses a method for separating and recovering a laminated film having at least a plastic film layer and a layer selected from a plastic film layer, a vapor-deposited film layer, and a metal foil layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7239070 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 limited. In the cleaning process, a cleaning solution is typically added to the crushed pieces of the thermal transfer sheet to bleach the coloring material contained in the crushed pieces and remove dirt from the crushed pieces. Because the crushed pieces of the thermal transfer sheet are thin and have little stiffness, they tend to clump together. Therefore, it is difficult to achieve good cleanability compared to cleaning targets such as thick resin sheets.

[0005] The present inventors have discovered that adding a surfactant to a cleaning solution can suppress the aggregation of fragments. However, adding a surfactant to a cleaning solution makes the cleaning solution more likely to foam during the cleaning process. When foam is generated in the cleaning solution, it is more likely to overflow from a tank, and overflow reduces work efficiency. Therefore, good low-foaming properties (low foaming) are required during the cleaning process. However, attempts to achieve good low-foaming properties may not result in good cleaning performance.

[0006] The present disclosure has been made in view 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 good low foaming properties. [Means for solving the problem]

[0007] 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 using a neutral aqueous cleaning liquid, wherein the thickness of the thermal transfer sheet is 3.5 μm or more and 12 μm or less, the aqueous cleaning liquid contains a cleaning agent including at least a nonionic surfactant and water, and the cleaning step comprises a first cleaning step of cleaning the crushed pieces using a first aqueous cleaning liquid that is the aqueous cleaning liquid, and a second cleaning step of cleaning the crushed pieces using a second aqueous cleaning liquid that is the aqueous cleaning liquid after the first cleaning step.

[0008] 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-described method for cleaning a thermal transfer sheet. [Effects of the Invention]

[0009] The present disclosure has the effect of providing a method for cleaning a thermal transfer sheet that achieves both good cleaning properties and good low foaming properties. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a flow diagram illustrating a method for cleaning a thermal transfer sheet according to the present disclosure. [Figure 2] 1 is a schematic cross-sectional view illustrating a thermal transfer sheet according to the present disclosure. [Figure 3] FIG. 2 is a schematic plan view illustrating a fragment according to the present disclosure. [Figure 4] 1 is a schematic cross-sectional view illustrating a thermal transfer sheet according to the present disclosure. [Figure 5] 1 is a schematic cross-sectional view illustrating a thermal transfer sheet according to the present disclosure. [Figure 6] 1 is a schematic cross-sectional view illustrating a thermal transfer sheet according to the present disclosure. [Figure 7] FIG. 2 is a schematic plan view illustrating a fragment according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Below, embodiments will be described 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. Furthermore, to clarify the description, the drawings may show the width, thickness, and shape of each part schematically compared to the actual form, but this is merely an example and should not be interpreted as limiting.

[0012] In this specification, when describing a mode in which another component is placed on a certain component, the term "above" or "below" is used, unless otherwise specified, to include both a case in which another component is placed directly above or below the certain component so as to be in contact with the component, and a case in which another component is placed above or below the certain component with another component interposed therebetween. Also, in this specification, when describing a mode in which another component is placed on the surface of a certain component, the term "on the surface" or "on the surface side" is used, unless otherwise specified, to include both a case in which another component is placed directly above or below the certain component so as to be in contact with the component, and a case in which another component is placed above or below the certain component with another component interposed therebetween.

[0013] 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.

[0014] A. How to clean the thermal transfer sheet Fig. 1 is a flow diagram illustrating a method for cleaning a thermal transfer sheet according to the present disclosure. As shown in Fig. 1, in the method for cleaning a thermal transfer sheet according to the present disclosure, first, crushed pieces of the thermal transfer sheet are prepared (preparation step). Next, the crushed pieces are washed using a neutral aqueous cleaning solution (cleaning step). The cleaning step further includes a first cleaning step in which the crushed pieces are washed using a first aqueous cleaning solution, and a second cleaning step in which the crushed pieces are washed using a second aqueous cleaning solution.

[0015] 2A and 2B are schematic cross-sectional views illustrating a thermal transfer sheet according to the present disclosure, specifically illustrating a thermal transfer sheet before being crushed. As shown in FIG. 2A, the 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. T The thermal transfer sheet 10 is arranged along the line . The thickness of the thermal transfer sheet 10 is defined as T. In the present disclosure, the thickness T is typically 3.5 μm or more and 12 μm or less. As shown in FIG. 2(b), the thermal transfer sheet 10 may have a release layer 3 between the substrate layer 1 and the color material layer 2. As shown in FIG. 2(c), the thermal transfer sheet 10 may have a primer layer 4 between the substrate layer 1 and the color material layer 2. As shown in FIG. 2(d), the thermal transfer sheet 10 may have a substrate layer 1 and a protective layer 5.

[0016] FIG. 3 is a schematic plan view illustrating fragments according to the present disclosure. As shown in FIG. 3, fragments 11 of a thermal transfer sheet are prepared in the present disclosure. Next, a cleaning process is performed in which the fragments 11 are cleaned using a neutral aqueous cleaning solution. The cleaning process further includes (i) a first cleaning process in which the fragments are cleaned using a first aqueous cleaning solution containing water and a cleaning agent containing at least a nonionic surfactant, and (ii) a second cleaning process in which the fragments are cleaned using a second aqueous cleaning solution containing water and a cleaning agent containing at least a nonionic surfactant after the first cleaning process.

[0017] According to the present disclosure, by performing a first cleaning treatment using a first aqueous cleaning solution and a second cleaning treatment using a second aqueous cleaning solution, it is possible to achieve both good cleaning properties and good low-foaming properties. Conventionally, used thermal transfer sheets, or unused but unnecessary thermal transfer sheets, have been discarded as industrial waste without being recycled. When reusing thermal transfer sheets as resources, a cleaning treatment process for cleaning the thermal transfer sheets is required so that recycling destinations are not limited.

[0018] In the cleaning process, a cleaning solution is typically applied to the thermal transfer sheet fragments to bleach the coloring material contained in the fragments and to remove dirt from the fragments. The thermal transfer sheet fragments are thin and have little stiffness. Therefore, as shown in Figure 3, multiple fragments 11 tend to clump together. Because the cleaning solution does not easily penetrate into the areas where multiple fragments 11 clump together, it is difficult to achieve good cleanability compared to cleaning objects such as thick resin sheets.

[0019] The present inventors have discovered that adding a surfactant to a cleaning solution can suppress the aggregation of fragments. However, adding a surfactant to a cleaning solution makes the cleaning solution more likely to foam during the cleaning process. Foaming in the cleaning solution can, for example, cause the solution to overflow from a tank, which reduces work efficiency. Therefore, good low-foaming properties are required during the cleaning process. However, attempts to achieve good low-foaming properties may not always result in good cleaning performance. For example, reducing the amount of detergent can easily achieve good low-foaming properties, but good cleaning performance may not be achieved. Furthermore, adding an anti-foaming agent to a cleaning solution can easily achieve good low-foaming properties, but the anti-foaming agent may inhibit the effectiveness of the detergent, resulting in poor cleaning performance.

[0020] In contrast, in the present disclosure, by performing a first cleaning treatment using a first aqueous cleaning liquid and a second cleaning treatment using a second aqueous cleaning liquid, it is possible to achieve both good cleaning properties and good low-foaming properties. Specifically, the first aqueous cleaning liquid and the second aqueous cleaning liquid each contain a nonionic surfactant. Nonionic surfactants, for example, have better cleaning properties for thermal transfer sheets than cationic surfactants. On the other hand, cationic surfactants have the advantage of being able to exhibit the redeposition suppression function described below, but tend to be less likely to provide good cleaning properties and good low-foaming properties than nonionic surfactants. In other words, nonionic surfactants tend to be more likely to provide good cleaning properties and good low-foaming properties than cationic surfactants.

[0021] However, even when a nonionic surfactant is used, it may be difficult to achieve both good cleaning performance and good low-foaming properties in a single cleaning process. In the present disclosure, an aqueous cleaning solution containing a nonionic surfactant is used to perform multiple cleaning processes, so that the cleaning process conditions can be controlled more precisely. For example, the concentration C1 of the nonionic surfactant in the first aqueous cleaning solution and the concentration C2 of the nonionic surfactant in the second aqueous cleaning solution can be set to, for example, the concentration C1 of the nonionic surfactant in the aqueous cleaning solution when performing a single cleaning process. X The concentration C1 and the concentration C2 can be lower than the concentration C1 and the concentration C2. This allows for good low-foaming properties to be obtained. On the other hand, when the concentrations C1 and C2 are low, cleaning properties tend to decrease, but good cleaning properties can be obtained by increasing the number of cleaning treatments (by performing the first cleaning treatment and the second cleaning treatment). Therefore, it is possible to achieve both high levels of cleaning properties and low-foaming properties.

[0022] Furthermore, by using a neutral aqueous cleaning solution, post-treatment such as neutralization is either unnecessary or easy compared to when an alkaline or acidic cleaning solution is used, thereby reducing the environmental impact. Furthermore, by using an aqueous cleaning solution, post-treatment is either unnecessary or easy compared to when a solvent-based cleaning solution is used, thereby reducing the environmental impact.

[0023] 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 by collecting crushed pieces obtained by another person crushing the thermal transfer sheet. Furthermore, as described below, the preparation step and the first cleaning process may be performed simultaneously. That is, the crushed pieces may be washed while the thermal transfer sheet is being crushed.

[0024] (1) Thermal transfer sheet As shown in FIG. 2(a), the thickness of the thermal transfer sheet 10 is designated as T. The thickness T is typically 12 μm or less, and may be 11 μm or less, 10 μm or less, or 9.0 μm or less. On the other hand, the thickness T is typically 3.5 μm or more, and may be 4.0 μm or more, or 5.0 μm or more. If the thickness T is within the above range, the fragments are likely to aggregate together. Furthermore, if the thermal transfer sheet is too thick or too thin, the thermal transferability may be reduced.

[0025] As shown in Figure 2(a), the thermal transfer sheet 10 may have a base material layer 1 and a colorant layer 2. Alternatively, as shown in Figure 2(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.

[0026] (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.

[0027] Examples of the polyester include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), 1,4-polycyclohexylene dimethylene terephthalate, and terephthalic acid-cyclohexanedimethanol-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).

[0028] 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).

[0029] The resin used for 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 substrate 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 uniaxially or biaxially. The thickness of the substrate layer is not particularly limited as long as a thermal transfer sheet having a predetermined thickness is obtained, but may be, for example, 10 μm or less, 8.0 μm or less, 6.0 μm or less, less than 5.0 μm, or 4.5 μm or less. On the other hand, the thickness of the substrate layer is, for example, 2.5 μm or more, 3.0 μm or more, or 3.5 μm or more.

[0030] (ii) Color material layer The coloring material layer is a layer containing at least a coloring material, and examples of the coloring material include magenta, yellow, cyan, and black.

[0031] 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 phosphate red, chrome red, vermilion, red iron oxide, azo pigments, alizarin lake, quinacridone, cochineal lake perylene, yellow ochre, 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.

[0032] The colorant may be a sublimable dye, such as a diarylmethane dye, a triarylmethane dye, a thiazole dye, a merocyanine dye, a pyrazolone dye, a methine dye, an indoaniline dye, an acetophenone azomethine dye, a pyrazoloazomethine dye, a xanthene dye, an oxazine dye, a thiazine dye, an azine dye, an acridine dye, an azo dye, a spiropyran dye, an indolinospiropyran dye, a fluoran dye, a naphthoquinone dye, an anthraquinone dye, or a quinophthalone dye.

[0033] 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.

[0034] The colorant layer may be a melt-transfer type colorant layer in which a colorant such as a pigment or dye is dispersed in a heat-melting binder, or a sublimation transfer type colorant 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.

[0035] The melt-transfer colorant layer may contain a wax as a binder. Examples of the wax include microcrystalline wax, carnauba wax, paraffin wax, Fischer-Tropsch wax, polyethylene wax, Japan wax, beeswax, whale wax, libota wax, wool wax, shellac wax, candelilla wax, petrolactam, polyester wax, partially modified wax, fatty acid ester, and fatty acid amide. The melt-transfer colorant layer may contain both a resin and a wax as a binder.

[0036] The melt-transfer colorant 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 colorant layer may contain, as the binder, a cured product (crosslinked structure) of at least one of an actinic radiation-curable monomer and an actinic radiation-curable oligomer. The actinic radiation-curable monomer and actinic radiation-curable oligomer refer to monomers and oligomers that polymerize (cure) when irradiated with actinic radiation. "Actinic radiation" refers to radiation that chemically reacts with the actinic radiation-curable monomer and 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.

[0037] Examples of actinic radiation-curable monomers 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, or may be 3 or more. On the other hand, examples of actinic radiation-curable oligomers 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, or may be 3 or more.

[0038] The thickness of the colorant 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 colorant layer and the substrate 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.

[0039] (iii) Protective layer The protective layer (OP layer) is a transparent layer containing a resin. The resin used for 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 colorant such as a fluorescent whitening agent, or may not contain a colorant. 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 to 2.0 μm. The thermal transfer sheet may have both one or more colorant layers and a protective layer on one side of the base layer. Examples of the one or more colorant layers include a red colorant layer (Mg layer), a yellow colorant layer (Ye layer), a blue colorant layer (Cy layer), and a black colorant layer (Bk layer).

[0040] (iv) Other layers As shown in FIG. 2(b), the thermal transfer sheet 10 may have a release layer 3 between the substrate layer 1 and the colorant layer 2. The provision of the release layer 3 can improve transferability. The release layer is preferably made of a material that is easily cleaned with an aqueous 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 curing agents that cure the binder include isocyanate and carbodiimide. The release layer may contain a cured product (crosslinked structure) of at least one 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.

[0041] 4 is a schematic cross-sectional view illustrating a thermal transfer sheet according to the present disclosure, specifically showing a melt transfer type thermal transfer sheet. The peel layer 3 shown in FIG. 4 is usually transferred to the transferee side as 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, it is possible to suppress the occurrence of sticking caused by a thermal head. T In the above, an adhesive layer 7 may be provided on the side opposite to the base layer 1 with respect to the colorant layer 2. By providing the adhesive layer 7, it is possible to improve adhesion to the transfer target. Known structures can be adopted for the release layer 3, back layer 6, and adhesive layer 7.

[0042] As shown in FIG. 2(c), the thermal transfer sheet 10 may have a primer layer 4 between the substrate layer 1 and the colorant layer 2. By providing the primer layer 4, the adhesion between the substrate layer 1 and the colorant layer 2 can be improved. The primer layer is preferably made of a material that is easy to wash off with a cleaning solution, and preferably contains a resin. Examples of such resins include polyester, vinyl resin, (meth)acrylic resin, styrene resin, polyamide, polyether, urethane resin, and cellulose resin.

[0043] FIG. 5 is a schematic cross-sectional view illustrating a thermal transfer sheet according to the present disclosure, specifically showing a sublimation transfer type thermal transfer sheet. The primer layer 4 shown in FIG. 5 improves the adhesion between the substrate layer 1 and the colorant 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, it is possible to suppress the occurrence of sticking caused by a thermal head. Furthermore, the thermal transfer sheet 10 has a thickness D 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. Known configurations can be adopted for the primer layer 4, the back layer 6, and the second primer layer 8.

[0044] FIG. 6 is a schematic cross-sectional view illustrating a thermal transfer sheet according to the present disclosure, specifically showing a thermal transfer sheet having a protective layer (OP layer). The primer layer 4 shown in FIG. 6 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 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, it is possible to suppress the occurrence of sticking caused by a thermal head. Furthermore, the thermal transfer sheet 10 has a thickness D TIn the thermal transfer sheet of 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 can be adopted for the primer layer 4, the back layer 6, and the second primer layer 8. Note that the thermal transfer sheet of the present disclosure may further have known layers not shown in FIGS. 4 to 6.

[0045] (2) Shattered fragments The crushed pieces in the present disclosure are obtained by crushing a 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 colorant layer. The crushed pieces may have a release layer or a primer layer between the substrate layer and the colorant layer. The crushed pieces may also have at least a substrate layer and a protective layer. Furthermore, the crushed pieces may have each of the layers described above in "(1) Thermal Transfer Sheet." The thickness of the crushed pieces is also usually the same as the thickness of the thermal transfer sheet before crushing. The thickness of the thermal transfer sheet is as described above.

[0046] The planar shape of the fragments is not particularly limited. The planar shape of the fragments refers to the outer edge shape of the fragments when observed from the thickness direction. Here, the fragments are classified into fragments X and fragments Y according to their planar shape. Fragments X have a planar shape that is quadrangular or a shape that can be approximated to a quadrangle. On the other hand, fragments Y are fragments that do not fall under the category of fragments X.

[0047] As shown in Figure 7(a), the shape of the fragments 11 in plan view may be rectangular (quadrilateral). On the other hand, as shown in Figures 7(b) and (d), the fragments 11 may have a cutout 12 in part. Even in such a case, if the cutout 12 is small, the shape of the fragments 11 in plan view will be a shape that can approximate a quadrangle. The "shape that can approximate a quadrangle" is defined as follows: As shown in Figures 7(c) and (e), imagine a virtual quadrangle 13 (rectangle or square) that is inscribed in the fragments 11. Let the area of ​​the virtual quadrangle 13 be S.A The area of ​​the fragment 11 is S B Let's say S A S against B The ratio (S B / S A ) is 0.8 or more, it corresponds to a "shape that can be approximated as a rectangle."

[0048] As shown in Figures 7(a) and 7(c), the length of the short side of the crushed fragment X is L1, and the length of the long side of the crushed fragment X is L2. The aspect ratio (L2 / L1) is not particularly limited, but may be, for example, 1.5 to 10.0, 2.0 to 9.0, or 2.0 to 5.0. Although not specifically shown, the planar shape of the crushed fragment X may be a square (rectangle). A square includes a rectangle with an aspect ratio (L2 / L1) of 1.0 to less than 1.5. L1 may be, for example, 1 mm to 5 cm, or 3 mm to 3.5 cm. On the other hand, L2 may be, for example, 1 mm to 10 cm, or 3 mm to 9 cm. Furthermore, as shown in Figure 7(c), when the planar shape of the crushed fragment X is a shape that can be approximated to a rectangle, L1 and L2 are set based on a virtual rectangle 13.

[0049] On the other hand, as shown in Figure 7(f), the fragments 11 may have a complex shape. In this case, too, as shown in Figure 7(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." If multiple imaginary rectangles 13 can be assumed, S B / S A The largest one is adopted. The planar shape of the fragment 11 shown in Figure 7(f) is neither a "rectangle" nor a "shape that can be approximated to a rectangle," so it does not fall under fragment X, but rather fragment Y. The proportion of fragment X to the total of fragment X and fragment Y, based on the number, may be, for example, 10% or more and 90% or less, or 20% or more and 80% or less.

[0050] 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 crushed pieces described above.

[0051] 2. Cleaning process The cleaning process in the present disclosure is a process of cleaning a plurality of crushed fragments using a neutral aqueous cleaning solution. The aqueous cleaning solution contains a cleaning agent including at least a nonionic surfactant and water. The cleaning process further includes a first cleaning process in which the plurality of crushed fragments are cleaned using a first aqueous cleaning solution, and a second cleaning process in which the plurality of crushed fragments are cleaned using a second aqueous cleaning solution after the first cleaning process.

[0052] (1) First cleaning process In the first cleaning process, the crushed pieces are cleaned using a first aqueous cleaning solution. The first aqueous cleaning solution is neutral and contains water and a cleaning agent containing at least a nonionic surfactant.

[0053] (i) Detergents The first aqueous cleaning solution contains a cleaning agent containing at least a nonionic surfactant. In this disclosure, a cleaning agent refers to a component that contributes to improved cleaning performance and is soluble or compatible with water. The use of a surfactant suppresses aggregation of the fragments, improving cleaning performance. Examples of surfactants other than nonionic surfactants include cationic surfactants, anionic surfactants, and amphoteric surfactants. Other examples of cleaning agents include antifoaming agents. By appropriately adjusting the amount of antifoaming agent, it is possible to prevent the contact area between the fragments and the aqueous cleaning solution from being reduced by bubbles, thereby improving cleaning performance. Other examples of cleaning agents include amphipathic glycol-based solvents and glycol ether-based solvents. These solvents have both a portion with high affinity for water (hydrophilic groups) and a portion with low affinity for water (hydrophobic groups), allowing them to wet and penetrate not only hydrophilic materials but also hydrophobic materials, improving cleaning performance.

[0054] Examples of nonionic surfactants include ether-based surfactants such as polyoxyalkylene alkyl ethers, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyalkylene lauryl ethers; epoxy-based surfactants such as ethylene oxide propylene oxide block copolymers; ester-based surfactants such as 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, and sucrose fatty acid esters; amine-based surfactants such as polyoxyethylene alkylamines; amide-based surfactants such as polyoxyethylene fatty acid amides, fatty acid alkylolamides, and alkylalkanolamides; and glycol-based surfactants such as acetylene glycol, oxyethylene adducts of acetylene glycol, and polyethylene glycol polypropylene glycol block copolymers.

[0055] Examples of cationic surfactants include ammonium salt surfactants such as didecyl dimethyl ammonium salt, distearyl dimethyl ammonium salt, dioctyl dimethyl ammonium salt, distearyl dihydroxyethyl ammonium salt, di-beef tallow alkyl dimethyl ammonium salt, di(stearoyloxyethyl) dimethyl ammonium salt, di(oleoyloxyethyl) dimethyl ammonium salt, di(stearoyloxyisopropyl) dimethyl ammonium salt, di(oleoyloxyisopropyl) dimethyl ammonium salt, and di(oleoyloxybutyl) dimethyl ammonium salt. The ammonium salt surfactant is preferably an ammonium halide surfactant such as an ammonium chloride surfactant or an ammonium bromide surfactant. Other examples of cationic surfactants include methosulfate surfactants such as didecyl dimethyl ammonium methosulfate, di(palmitoyloxyethyl) dimethyl ammonium methosulfate, di(stearoyloxyethyl) methyl hydroxyethyl ammonium methosulfate, and tri(stearoyloxyethyl) methyl methosulfate.

[0056] Examples of anionic surfactants include sulfonate-based surfactants such as alkylbenzenesulfonates, alkylphenylsulfonates, alkylnaphthalenesulfonates, sulfonates of higher fatty acid esters, and sulfonates of higher alcohol ethers; sulfate ester salt-based surfactants such as sulfate ester salts of higher fatty acid esters and sulfate ester salts of higher alcohol ethers; fatty acid salt-based surfactants such as higher fatty acid salts; sulfosuccinate-based surfactants such as higher alkyl sulfosuccinates; carboxylate-based surfactants such as polyoxyethylene alkyl ether carboxylates; sulfate-based surfactants such as polyoxyethylene alkyl ether sulfates; and phosphate-based surfactants such as alkyl phosphates and polyoxyethylene alkyl ether phosphates.

[0057] Examples of amphoteric surfactants include betaine surfactants and amine oxide surfactants. Examples of betaine surfactants include imidazoline betaines, alkyldimethylaminoacetic acid betaines, fatty acid amidopropyl betaines, and sulfobetaines. Examples of amine oxide surfactants include alkyldimethylamine oxides.

[0058] In the first aqueous cleaning liquid, the ratio of the nonionic surfactant to all surfactants is not particularly limited, but may be, for example, 30% by mass or more, 50% by mass or more, 70% by mass or more, 90% by mass or more, or even 100% by mass. In addition to the nonionic surfactant, the first aqueous cleaning liquid may further contain at least one of a cationic surfactant, an anionic surfactant, and an amphoteric surfactant. When the first aqueous cleaning liquid contains a cationic surfactant, it is preferable that the first aqueous cleaning liquid further contains an antifoaming agent. Because cationic surfactants tend to increase the foaming property of the aqueous cleaning liquid, it is preferable to reduce the foaming property with an antifoaming agent.

[0059] On the other hand, the first aqueous cleaning liquid may not contain a cationic surfactant, may not contain an anionic surfactant, or may not contain an amphoteric surfactant. In the present disclosure, "the first aqueous cleaning liquid does not contain A" means both a case where the first aqueous cleaning liquid does not contain A (e.g., a cationic surfactant) at all, and a case where the first aqueous cleaning liquid contains a trace amount of A (e.g., a cationic surfactant) but the concentration is so low that A does not exhibit its function. The same applies to "the second aqueous cleaning liquid does not contain A" described below.

[0060] The first aqueous cleaning liquid may or may not contain a defoaming agent as a cleaning agent. Examples of the defoaming agent include silicone-based defoaming agents, mineral oil-based defoaming agents, oil-based defoaming agents, fatty acid-based defoaming agents, fatty acid ester-based defoaming agents, alcohol-based defoaming agents, amide-based defoaming agents, phosphate ester-based defoaming agents, and metal soap-based defoaming agents.

[0061] Silicone-based antifoaming agents may be emulsion-type, self-emulsifying, oil-type, oil compound-type, or solvent-type. Examples of emulsion-type silicone-based antifoaming agents include Kao's "Antifoam E-20," Shin-Etsu Chemical's "KM-89" and "KM-98," Asahi Kasei Wacker Silicone's "FC2913" and "SILFOAM SE47," and BYK-Chemie Japan's "BYK-015" and "BYK-1640." Examples of self-emulsifying silicone-based antifoaming agents include Shin-Etsu Chemical's "KS-540" and "X-50-1176," and Asahi Kasei Wacker Silicone's "SILFOAM SD670" and "SILFOAM SD850."

[0062] Examples of oil-type silicone defoamers include "KM-89" and "KM-98" manufactured by Shin-Etsu Chemical Co., Ltd., "AK350" and "AK12500" manufactured by Asahi Kasei Wacker Silicone, and "BYK-1770" manufactured by BYK Japan. Examples of oil-compound silicone defoamers include "KM-89" and "KM-98" manufactured by Shin-Etsu Chemical Co., Ltd., "SILFOAM SC370" and "PULPSIL22274VP" manufactured by Asahi Kasei Wacker Silicone, and "BYK-017" and "BYK-018" manufactured by BYK Japan. Examples of solvent-type silicone defoamers include "KM-89" and "KM-98" manufactured by Shin-Etsu Chemical Co., Ltd., and "BYK-019" and "BYK-025" manufactured by BYK Japan.

[0063] The first aqueous cleaning liquid may contain at least one of an amphipathic glycol solvent and a glycol ether solvent as a cleaning agent. Alternatively, the first aqueous cleaning liquid may not contain at least one of an amphipathic glycol solvent and a glycol ether solvent as a cleaning agent. Examples of amphipathic glycol solvents or glycol ether solvents include propylene glycol, ethylene glycol, diethylene glycol, propylene glycol monomethyl ether, and dipropylene glycol monomethyl ether.

[0064] The concentration of the cleaning agent in the first aqueous cleaning solution is not particularly limited, but may be, for example, 0.1% by mass or more, or may be 0.2% by mass or more, or may be 0.3% by mass or more. If the cleaning agent concentration is too low, good cleaning properties may not be obtained. On the other hand, the cleaning agent concentration in the first aqueous cleaning solution may be, for example, 15% by mass or less, or may be 10% by mass or less, or may be 5% by mass or less. If the cleaning agent concentration is too high, it may be difficult to maintain good low-foaming properties.

[0065] When the first aqueous cleaning liquid contains a surfactant and an antifoaming agent, the mass of the antifoaming agent relative to the mass of the surfactant is not particularly limited, but may be, for example, 0.05 to 1.5 times, 0.08 to 1.0 times, or 0.1 to 0.5 times.

[0066] The concentration of the surfactant in the first aqueous cleaning liquid is not particularly limited, but may be, for example, 0.1% to 1.0% by mass, 0.15% to 0.5% by mass, or 0.15% to 0.3% by mass. In particular, the concentration of the nonionic surfactant in the first aqueous cleaning liquid may be, for example, 0.1% to 1.0% by mass, 0.15% to 0.5% by mass, or 0.15% to 0.3% by mass.

[0067] The concentration of the antifoaming agent in the first aqueous cleaning liquid is not particularly limited, but may be, for example, 0% by mass or more and 0.15% by mass or less, 0.005% by mass or more and 0.1% by mass or less, or 0.01% by mass or more and 0.05% by mass or less.

[0068] (ii) First aqueous cleaning solution The first aqueous cleaning solution contains a solvent whose main component is water. The 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, or 70% by mass or more, or even 90% by mass or more.

[0069] The first aqueous cleaning liquid is neutral. "Neutral" means that the pH of the first aqueous cleaning liquid is 5.5 or more and 9.0 or less at 25°C. If the pH of the first aqueous cleaning liquid is within the above range, neutralization treatment is unnecessary or the burden of the neutralization treatment is reduced. Furthermore, the surface tension of the first 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.

[0070] (iii) Cleaning method In the first cleaning process, a plurality of crushed fragments are cleaned using a first aqueous cleaning solution. In the first cleaning process, a large number of crushed fragments are cleaned. Because each crushed fragment is thin and has little stiffness, the crushed fragments tend to aggregate together. In contrast, in the present disclosure, the use of a first aqueous cleaning solution containing a nonionic surfactant can prevent the crushed fragments from aggregating together.

[0071] The mass of water contained in the first aqueous cleaning solution relative to the total mass of the crushed fragments is, for example, 160 times or more, or may be 180 times or more, or may be 200 times or more. If the mass of water (water volume) is too small, the first aqueous cleaning solution containing the cleaning agent cannot penetrate into the interior of the aggregated crushed fragments, and good cleaning performance may not be achieved. On the other hand, the mass of water contained in the first aqueous cleaning solution relative to the total mass of the crushed fragments is, for example, 600 times or less, or may be 550 times or less, or may be 500 times or less. If the mass of water (water volume) is too large, a large amount of the first aqueous cleaning solution is required, which may reduce the efficiency of the cleaning process.

[0072] The mass of the cleaning agent contained in the first aqueous cleaning solution relative to the total mass of the crushed pieces is, for example, 1 to 85 times, or alternatively 1.2 to 40 times, or 1.5 to 15 times. If the mass of the cleaning agent (amount of cleaning agent) is too small, good cleaning performance may not be obtained. On the other hand, if the mass of the cleaning agent (amount of cleaning agent) is too large, it may be difficult to maintain good low-foaming properties during the cleaning process.

[0073] The method for cleaning the crushed pieces using the first aqueous cleaning solution is not particularly limited, but examples include a method of immersing the crushed pieces in the first aqueous cleaning solution. The temperature of the first aqueous cleaning solution during immersion is not particularly limited, but may be, for example, 25°C or higher and 100°C or lower, or 30°C or higher and 80°C or lower. The immersion time is, for example, 1 minute or longer and 24 hours or shorter.

[0074] It is preferable to agitate the first aqueous cleaning solution in which the crushed fragments are immersed. Agitation improves the cleaning effect. When agitating the first aqueous cleaning solution in which the crushed fragments are immersed, media such as beads may be used, or no media may be used. In the former case, the media dispersed in the first aqueous cleaning solution come into contact with the crushed fragments, improving cleaning performance, but at the same time, making foam more likely to be generated. In the latter case, cleaning performance is lower than in the former case, but foam generation can be suppressed.

[0075] The above-described preparation step and the first cleaning treatment may be carried out simultaneously. For example, the preparation step and the first cleaning treatment can be carried out simultaneously by using a wet crusher to crush the thermal transfer sheet while cleaning the crushed pieces.

[0076] The washing process may include a separation process after the first washing process, in which the washed fragments are separated from the first aqueous washing solution containing the washed fragments. Examples of the separation method include a method using a filter or a method using a centrifuge.

[0077] The washing process may include a water washing process (rinsing process) in which the washed crushed pieces are washed with water after the first washing process. By performing the water washing process, the first aqueous cleaning solution remaining on the crushed pieces can be removed. The water washing process may be performed simultaneously with the separation process or after the separation process. Furthermore, the separation process may be performed again after the water washing process. Furthermore, the water used in the water washing process may be heated. That is, the washed crushed pieces may be washed with warm water. The temperature of the warm water is, for example, 35°C or higher and 60°C or lower.

[0078] (2) Second cleaning process In the second cleaning treatment, the crushed pieces are cleaned using a second aqueous cleaning solution, which is neutral and contains water and a cleaning agent containing at least a nonionic surfactant.

[0079] (i) Detergents The second aqueous cleaning liquid contains a cleaning agent containing at least a nonionic surfactant. The cleaning agent is the same as the cleaning agent in the first aqueous cleaning liquid described above. The nonionic surfactant contained in the second aqueous cleaning liquid and the nonionic surfactant contained in the first aqueous cleaning liquid may be the same compound or different compounds. In the latter case, the nonionic surfactant contained in the first aqueous cleaning liquid may have higher cleaning properties than the nonionic surfactant contained in the second aqueous cleaning liquid. For example, in the examples described below, nonionic surfactant N1 has higher cleaning properties than nonionic surfactant N2. Note that cleaning properties and low foaming properties often have a trade-off relationship, and high cleaning properties tend to result in low low foaming properties (high foaming properties). In particular, it is preferable to focus mainly on cleaning of crushed fragments in the first cleaning process.

[0080] In the second aqueous cleaning liquid, the ratio of the nonionic surfactant to all surfactants is not particularly limited, but may be, for example, 20% by mass or more, 30% by mass or more, 50% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 100% by mass. The second aqueous cleaning liquid may further contain at least one of a cationic surfactant, an anionic surfactant, and an amphoteric surfactant in addition to the nonionic surfactant.

[0081] The second aqueous cleaning liquid preferably contains a cationic surfactant in addition to the nonionic surfactant. The addition of the cationic surfactant can prevent the colorant layer or protective layer detached from the crushed fragments from reattaching to the base layer of the crushed fragments (performing a reattachment prevention function), thereby improving cleaning performance. The ratio of the cationic surfactant to the total of the nonionic surfactant and the cationic surfactant is, for example, 1 mass% or more and 80 mass% or less.

[0082] The concentration of the cationic surfactant in the second aqueous cleaning liquid may be higher than the concentration of the cationic surfactant in the first aqueous cleaning liquid (including a concentration of 0% by mass). For example, the first cleaning process may focus primarily on cleaning the crushed debris, and the second cleaning process may focus on cleaning the crushed debris while preventing re-adhesion, thereby achieving both high levels of cleaning performance and low foaming. The concentration of the cationic surfactant in the first aqueous cleaning liquid (including a concentration of 0% by mass) may be, for example, 0.9 times or less, 0.6 times or less, 0.3 times or less, or 0.1 times or less, of the concentration of the cationic surfactant in the second aqueous cleaning liquid.

[0083] When the second aqueous cleaning liquid contains a cationic surfactant, it is preferable that the second aqueous cleaning liquid further contains an antifoaming agent. Because cationic surfactants tend to increase the foaming property of aqueous cleaning liquids, it is preferable to reduce the foaming property by using an antifoaming agent. Furthermore, when the concentration of the cationic surfactant in the second aqueous cleaning liquid is higher than the concentration of the cationic surfactant in the first aqueous cleaning liquid (including a concentration of 0% by mass), it is preferable that the concentration of the antifoaming agent in the second aqueous cleaning liquid is higher than the concentration of the antifoaming agent in the first aqueous cleaning liquid (including a concentration of 0% by mass). On the other hand, the second aqueous cleaning liquid may not contain a cationic surfactant, an anionic surfactant, or an amphoteric surfactant.

[0084] The second aqueous cleaning liquid may or may not contain a defoaming agent as a cleaning agent, which is the same as the defoaming agent in the first aqueous cleaning liquid described above.

[0085] The concentration of the cleaning agent in the second aqueous cleaning liquid is not particularly limited, but may be, for example, 0.1% by mass or more, or may be 0.2% by mass or more, or may be 0.3% by mass or more. If the concentration of the cleaning agent is too low, good cleaning performance may not be obtained. On the other hand, the concentration of the cleaning agent in the second aqueous cleaning liquid may be, for example, 15% by mass or less, or may be 10% by mass or less, or may be 5% by mass or less. If the concentration of the cleaning agent is too high, it may be difficult to maintain good low-foaming properties. Furthermore, the concentration of the cleaning agent in the second aqueous cleaning liquid may be higher, the same as, or lower than the concentration of the cleaning agent in the first aqueous cleaning liquid. The term "same as" above means that the ratio of the concentration (mass%) of the cleaning agent in the first aqueous cleaning liquid to the concentration (mass%) of the cleaning agent in the second aqueous cleaning liquid is 0.9 to 1.1 times.

[0086] When the second aqueous cleaning liquid contains a surfactant and an antifoaming agent, the ratio of the mass of the antifoaming agent to the mass of the surfactant is not particularly limited, but may be, for example, 0.05 to 1.5 times, 0.08 to 1.0 times, or 0.1 to 0.5 times.

[0087] The surfactant concentration in the second aqueous cleaning liquid is not particularly limited, but may be, for example, 0.1% by mass or more and 1.0% by mass or less, or 0.15% by mass or more and 0.5% by mass or less, or 0.15% by mass or more and 0.3% by mass or less. In particular, the nonionic surfactant concentration in the second aqueous cleaning liquid may be, for example, 0.1% by mass or more and 1.0% by mass or less, or 0.15% by mass or more and 0.5% by mass or less, or 0.15% by mass or more and 0.3% by mass or less. Furthermore, the surfactant concentration in the second aqueous cleaning liquid may be higher, the same as, or lower than the surfactant concentration in the first aqueous cleaning liquid. The term "same as" as used herein means that the ratio of the surfactant concentration (mass%) in the first aqueous cleaning liquid to the surfactant concentration (mass%) in the second aqueous cleaning liquid is 0.9 to 1.1 times.

[0088] The concentration of the antifoaming agent in the second aqueous cleaning liquid is not particularly limited, but may be, for example, 0% by mass or more and 0.15% by mass or less, or 0.005% by mass or more and 0.1% by mass or less, or 0.01% by mass or more and 0.05% by mass or less. The concentration of the antifoaming agent in the second aqueous cleaning liquid may be higher, the same as, or lower than the concentration of the antifoaming agent in the first aqueous cleaning liquid. The term "same as" above means that the ratio of the concentration (% by mass) of the antifoaming agent in the first aqueous cleaning liquid to the concentration (% by mass) of the antifoaming agent in the second aqueous cleaning liquid is 0.9 to 1.1 times.

[0089] (ii) Second aqueous cleaning solution The second aqueous cleaning liquid contains a solvent whose main component is water. The 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, or 70% by mass or more, or even 90% by mass or more.

[0090] The second aqueous cleaning liquid is neutral. The second aqueous cleaning liquid being neutral means that the pH of the second aqueous cleaning liquid is 5.5 or more and 9.0 or less at 25°C. If the pH of the second aqueous cleaning liquid is within the above range, neutralization treatment is not required or the burden of the neutralization treatment is reduced. Furthermore, the surface tension of the second 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.

[0091] (iii) Cleaning method In the second cleaning process, a plurality of crushed pieces are cleaned using a second aqueous cleaning solution. In the second cleaning process, a large number of crushed pieces are cleaned. Details of the second cleaning process are basically the same as those described above for the first cleaning process, except that the second aqueous cleaning solution is used instead of the first aqueous cleaning solution.

[0092] The washing process may include a separation process after the second washing process, in which the washed fragments are separated from the second aqueous washing solution containing the washed fragments. Examples of the separation method include a method using a filter or a method using a centrifuge.

[0093] The washing process may include a water washing process (rinsing process) in which the washed crushed pieces are washed with water after the second washing process. By performing the water washing process, the second aqueous cleaning solution remaining on the crushed pieces can be removed. The water washing process may be performed simultaneously with the separation process or after the separation process. Furthermore, the separation process may be performed again after the water washing process. Furthermore, the water used in the water washing process may be heated. That is, the washed crushed pieces may be washed with warm water. The temperature of the warm water is, for example, 35°C or higher and 60°C or lower.

[0094] The washing process may include a drying process for drying the washed crushed pieces after the second washing process. The drying process may be performed after the separation process. The drying conditions are not particularly limited, and are preferably adjusted appropriately so as to obtain the desired recycled material.

[0095] 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 above in "A. Method for cleaning the thermal transfer sheet."

[0096] According to the present disclosure, by washing a thermal transfer sheet using the above-mentioned washing method, it is possible to obtain recycled raw materials while achieving both good washability and good low-foaming properties. The washing process is the same as that described above in "A. Method for washing a thermal transfer sheet," so a description thereof will be omitted here.

[0097] The method for producing recycled materials may optionally include a pelletizing step of pelletizing the washed crushed pieces, thereby obtaining recycled materials in the form of pellets.

[0098] 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 within the technical scope of the present disclosure. [Example]

[0099] [Example 1] The thermal transfer sheet used was a thermal transfer sheet X (sublimation transfer type thermal transfer sheet, DS621, manufactured by Dai Nippon Printing Co., Ltd.). The thickness of the thermal transfer sheet X was 6.0 μm, and the thickness of the base layer constituting the thermal transfer sheet X was 4.5 μm. Next, the thermal transfer sheet was shredded using a ribbon shredder (device name: GRASYS BiT) to obtain shredded pieces. The cutting method was twisted micro-cutting, and the maximum shredding speed was 12 m / min.

[0100] A first aqueous cleaning solution was then prepared containing surfactant N1 (an ether-based nonionic surfactant, Emulgen 106, manufactured by Kao Corporation) as a cleaning agent and antifoaming agent (a silicone-based antifoaming agent, Antifoam E-20, manufactured by Kao Corporation) and water as a solvent. The surfactant N1 and antifoaming agent were mixed in a mass ratio of surfactant N1:antifoaming agent = 87.5:12.5. The cleaning agent concentration in the first aqueous cleaning solution was 0.3 mass%, and the mass of water was 50 g.

[0101] The resulting first aqueous cleaning solution was then added to a container, and the container was heated in a hot water bath until the temperature of the first aqueous cleaning solution reached 50°C to 55°C. Next, the crushed pieces were placed in a 100 mL beaker, and the heated first aqueous cleaning solution was added. The mixture was stirred at room temperature at 300 rpm for 10 minutes (first cleaning treatment). The amount of crushed pieces added was 0.1 g. After stirring, the washed crushed pieces were collected using a sieve with 2 mm openings.

[0102] A second aqueous cleaning solution was then prepared containing surfactant N2 (an ether-based nonionic surfactant, Dash 403, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and surfactant C1 (an ammonium halide-based cationic surfactant, CTAB, manufactured by Kanto Chemical Co., Inc.) as cleaning agents, and water as a solvent. The surfactant N2 and surfactant C1 were mixed in a mass ratio of surfactant N2:surfactant C1 = 99:1. The concentration of the cleaning agent in the second aqueous cleaning solution was 0.3 mass%, and the mass of water was 50 g.

[0103] The resulting second aqueous cleaning solution was then added to a container, and the container was heated in a hot water bath until the temperature of the second aqueous cleaning solution reached 50°C to 55°C. Next, the crushed pieces were placed in a 100 mL beaker, and the heated second aqueous cleaning solution was added. The mixture was stirred at room temperature at 300 rpm for 10 minutes (second cleaning treatment). After stirring, the washed crushed pieces were collected using a sieve with 2 mm openings. Next, the collected crushed pieces were placed in 50 g of hot water at 50°C to 55°C and stirred at room temperature at 300 rpm for 5 minutes (rinsing process). Next, after stirring, the washed crushed pieces were collected using a sieve with 2 mm openings, drained, and dried.

[0104] [Examples 2 and 3] The crushed pieces of the thermal transfer sheet were washed in the same manner as in Example 1, except that the blending ratio of surfactant N2 and surfactant C1 in the second aqueous cleaning liquid was changed as shown in Table 1.

[0105] [Examples 4 to 10] The crushed pieces of the thermal transfer sheet were cleaned in the same manner as in Example 1, except that the type of thermal transfer sheet was changed as shown in Table 1, the formulation of surfactant N2 and surfactant C1 in the second aqueous cleaning liquid was changed as shown in Table 1, and an antifoaming agent (a silicone-based antifoaming agent, Antifoam E-20, manufactured by Kao Corporation) was added to the second aqueous cleaning liquid in the formulation shown in Table 1. In Table 1, thermal transfer sheet Y is a melt-transfer type thermal transfer sheet (V300, manufactured by Dai Nippon Printing Co., Ltd.). The thickness of thermal transfer sheet Y was 6.0 μm, and the thickness of the base layer constituting thermal transfer sheet Y was 4.5 μm. Also in Table 1, thermal transfer sheet Z is a melt-transfer type thermal transfer sheet (TR3075, manufactured by Dai Nippon Printing Co., Ltd.). The thickness of thermal transfer sheet Z was 12 μm, and the thickness of the base layer constituting thermal transfer sheet Z was 4.5 μm.

[0106] [Examples 11 to 16] The crushed pieces of the thermal transfer sheet were cleaned in the same manner as in Example 1, except that the type and composition of the surfactant in the first aqueous cleaning liquid, the composition of the antifoaming agent in the first aqueous cleaning liquid, the type and composition of the surfactant in the second aqueous cleaning liquid, and the composition of the antifoaming agent in the second aqueous cleaning liquid were changed as shown in Table 1.

[0107] [Comparative Examples 1 to 4] The crushed pieces of the thermal transfer sheet were washed in the same manner as in Example 1, except that the type and composition of the surfactant in the first aqueous cleaning solution and the composition of the antifoaming agent in the first aqueous cleaning solution were changed as shown in Table 1 and the second cleaning treatment was not performed.

[0108] [evaluation] (cleanability) Ten pieces of the crushed pieces obtained in the examples and comparative examples after the second cleaning treatment were stacked, and the visual transmission density was measured using a black-and-white transmission densitometer (X-Rite 341C). A visual transmission density of less than 0.2 was evaluated as A+, a visual transmission density of 0.2 or more but less than 0.3 was evaluated as A, a visual transmission density of 0.3 or more but less than 0.5 was evaluated as B, a visual transmission density of 0.5 or more but less than 0.6 was evaluated as C, and a visual transmission density of 0.6 or more was evaluated as D. The results are shown in Table 1.

[0109] (low foaming) In the examples and comparative examples, the first aqueous cleaning solution and the second aqueous cleaning solution before cleaning were added to a 100 mL measuring cylinder (JIS R 3505:1994 compliant) with an inner diameter of 28 mm. After leaving the cylinder to stand for a while, it was vigorously shaken up and down 100 times (approximately 30 seconds). After shaking, the measuring cylinder was left to stand, and the foam height was visually read. A foam height of less than 5 mm was evaluated as A+, a foam height of 5 mm or more but less than 10 mm was evaluated as A, a foam height of 10 mm or more but less than 30 mm was evaluated as B, a foam height of 30 mm or more but less than 40 mm was evaluated as C, and a foam height of 40 mm or more was evaluated as D. The results are shown in Table 1.

[0110] [Table 1]

[0111] As shown in Table 1, it was confirmed that in Examples 1 to 16, good cleaning performance and good low-foaming properties were obtained by performing the first cleaning treatment and the second cleaning treatment. On the other hand, in Comparative Example 1, good low-foaming properties were not obtained because the first aqueous cleaning solution did not contain an antifoaming agent and the concentration of the cleaning agent (nonionic surfactant) in the first aqueous cleaning solution was high. Also, in Comparative Examples 2 and 3, good low-foaming properties were obtained because the first aqueous cleaning solution contained an antifoaming agent, but good cleaning performance was not obtained because the amount of antifoaming agent added was too high. Also, in Comparative Example 4, good cleaning performance was obtained but good low-foaming properties were not obtained because a cationic surfactant was used as the cleaning agent in the first aqueous cleaning solution.

[0112] Furthermore, when Examples 1 to 3 are compared with Example 11, it is confirmed that the use of a cationic surfactant in addition to a nonionic surfactant improves the cleaning properties. This is presumably because the use of a cationic surfactant can prevent the colorant layer or protective layer detached from the crushed fragments from reattaching to the base layer of the crushed fragments.

[0113] Furthermore, when Examples 1 to 3 are compared, cleaning properties were particularly excellent in Examples 2 and 3. Thus, when the second aqueous cleaning liquid contains a nonionic surfactant and a cationic surfactant as cleaning agents but does not contain an antifoaming agent as cleaning agents, it is preferable that the proportion of the cationic surfactant relative to the total of the nonionic surfactant and the cationic surfactant is 5 mass % or more and 10 mass % or less.

[0114] Furthermore, when Examples 4 to 10, 15, and 16 are compared, cleaning properties are particularly excellent in Examples 4, 5, 8 to 10, and 16. Thus, when the second aqueous cleaning liquid contains a nonionic surfactant and a cationic surfactant as cleaning agents and also contains an antifoaming agent as cleaning agents, the proportion of the cationic surfactant relative to the total of the nonionic surfactant and the cationic surfactant is preferably 20 mass% or more and 60 mass% or less.

[0115] Furthermore, when Example 12 was compared with Example 13, the cleaning performance and low-foaming properties were comparable. Furthermore, when Example 12 was compared with Example 5, it was confirmed that the cleaning performance was improved by using a cationic surfactant in the second aqueous cleaning solution, rather than the first aqueous cleaning solution. Furthermore, when Examples 12 and 13 were compared with Example 14, it was confirmed that by appropriately adjusting the amount of antifoaming agent, the low-foaming properties were improved without reducing the cleaning performance. Furthermore, when Example 15 was compared with Example 16, it was confirmed that a large amount of antifoaming agent tended to reduce the cleaning performance.

[0116] Thus, the present disclosure provides, for example, the following inventions.

[0117] [1] A method for cleaning a thermal transfer sheet, comprising: 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 with a neutral water-based cleaning solution, The thickness of the thermal transfer sheet is 3.5 μm or more and 12 μm or less, The aqueous cleaning liquid contains a cleaning agent containing at least a nonionic surfactant and water, The cleaning treatment step is a first cleaning treatment for cleaning the plurality of crushed pieces using a first aqueous cleaning solution that is the aqueous cleaning solution; a second cleaning process in which the plurality of crushed pieces are cleaned using a second aqueous cleaning solution, which is the aqueous cleaning solution, after the first cleaning process; A method for cleaning a thermal transfer sheet, comprising:

[0118] [2] The method for cleaning a thermal transfer sheet according to [1], wherein the concentration of the nonionic surfactant in the first aqueous cleaning liquid and the concentration of the nonionic surfactant in the second aqueous cleaning liquid are each 1.0 mass % or less.

[0119] [3] The method for cleaning a thermal transfer sheet according to [1] or [2], wherein the second aqueous cleaning liquid contains a cationic surfactant as the cleaning agent.

[0120] [4] The method for cleaning a thermal transfer sheet according to [3], wherein in the second aqueous cleaning liquid, the proportion of the cationic surfactant relative to the total of the nonionic surfactant and the cationic surfactant is 1% by mass or more and 80% by mass or less.

[0121] [5] the second aqueous cleaning liquid contains an antifoaming agent as the cleaning agent, The method for cleaning a thermal transfer sheet according to [3], wherein the proportion of the cationic surfactant relative to the total of the nonionic surfactant and the cationic surfactant is 20% by mass or more and 60% by mass or less.

[0122] [6] the second aqueous cleaning liquid does not contain an antifoaming agent as the cleaning agent, The method for cleaning a thermal transfer sheet according to [3], wherein the proportion of the cationic surfactant relative to the total of the nonionic surfactant and the cationic surfactant is 5% by mass or more and 10% by mass or less.

[0123] [7] The method for cleaning a thermal transfer sheet according to any one of [1] to [6], wherein the first aqueous cleaning liquid contains the nonionic surfactant as a main surfactant component.

[0124] [8] The method for cleaning a thermal transfer sheet according to any one of [1] to [7], wherein the first aqueous cleaning liquid contains an antifoaming agent as the cleaning agent.

[0125] [9] The method for cleaning a thermal transfer sheet according to any one of [1] to [7], wherein the first aqueous cleaning liquid does not contain an antifoaming agent as the cleaning agent.

[0126]

[10] The method for cleaning a thermal transfer sheet according to any one of [1] to [9], wherein the thermal transfer sheet has a base layer and at least one of a colorant layer and a protective layer.

[0127]

[11] 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

[10] . [Explanation of symbols]

[0128] 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 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 with a neutral water-based cleaning solution, The thickness of the thermal transfer sheet is 3.5 μm or more and 12 μm or less, The aqueous cleaning liquid contains a cleaning agent containing at least a nonionic surfactant and water, The cleaning treatment step includes: a first cleaning treatment for cleaning the plurality of crushed pieces using a first aqueous cleaning solution that is the aqueous cleaning solution; a second cleaning process in which the plurality of crushed pieces are cleaned using a second aqueous cleaning solution, which is the aqueous cleaning solution, after the first cleaning process; A method for cleaning a thermal transfer sheet, comprising:

2. 2. The method for cleaning a thermal transfer sheet according to claim 1, wherein the concentration of the nonionic surfactant in the first aqueous cleaning liquid and the concentration of the nonionic surfactant in the second aqueous cleaning liquid are each 1.0 mass % or less.

3. The method for cleaning a thermal transfer sheet according to claim 1 , wherein the second aqueous cleaning liquid contains a cationic surfactant as the cleaning agent.

4. 4. The method for cleaning a thermal transfer sheet according to claim 3, wherein in the second aqueous cleaning liquid, the proportion of the cationic surfactant relative to the total of the nonionic surfactant and the cationic surfactant is 1% by mass or more and 80% by mass or less.

5. the second aqueous cleaning liquid contains an antifoaming agent as the cleaning agent, The method for cleaning a thermal transfer sheet according to claim 3 , wherein the proportion of the cationic surfactant relative to the total of the nonionic surfactant and the cationic surfactant is 20% by mass or more and 60% by mass or less.

6. the second aqueous cleaning liquid does not contain an antifoaming agent as the cleaning agent, The method for cleaning a thermal transfer sheet according to claim 3 , wherein the proportion of the cationic surfactant relative to the total of the nonionic surfactant and the cationic surfactant is 5% by mass or more and 10% by mass or less.

7. The method for cleaning a thermal transfer sheet according to claim 1 , wherein the first aqueous cleaning liquid contains the nonionic surfactant as a main surfactant component.

8. The method for cleaning a thermal transfer sheet according to claim 1 , wherein the first aqueous cleaning liquid contains an antifoaming agent as the cleaning agent.

9. The method for cleaning a thermal transfer sheet according to claim 1 , wherein the first aqueous cleaning liquid does not contain an antifoaming agent as the cleaning agent.

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

11. 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 claims 1 to 10.

Images