Hot melt powder for binder resin layer, and use thereof

Abstract

To provide a hot-melt powder which is used for forming a binder resin layer for adhering an ink to an object, has good adhesion and fastness between the ink and the object, and has good sublimation resistance.SOLUTION: The hot melt powder includes acrylic particles that include an acrylic resin. The acrylic resin has a weight average molecular weight of 50000 to 150,000 and a glass transition temperature of 15 to 25 °C. The hot-melt powder has a volume-average particle size of 80 to 250 μm and a packed bulk density of 0.60 to 0. 80g / cm3.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a hot melt powder used to form a binder resin layer for adhering ink to an object, and to uses thereof. [Background technology]

[0002] In recent years, a method of thermally transferring a design by DTF (Direct To Film) printing has been attracting attention as a method of printing a design onto textile products such as clothing.

[0003] DTF printing involves first forming an ink layer and a binder resin layer in that order on a release film, then thermally transferring the binder resin layer and ink layer onto the printing object, and then peeling off the release film, thereby forming an ink layer on the surface of the printing object, such as a textile product (see, for example, Patent Document 1). This method is environmentally friendly because it does not require the evaporation of large amounts of solvent or water during the printing process.

[0004] The binder resin layer functions as a binder that adheres the ink layer to the surface of the printing substrate. The resin layer is usually formed by supplying hot-melt powder onto the ink layer, allowing it to adhere, and then heating it to melt and solidify it. Such hot-melt powder is required to achieve adhesion and robustness between the ink and the printing substrate, and polyurethane resin is preferably used (see paragraph

[0132] of Patent Document 1).

[0005] On the other hand, although not related to the application of adhering ink to an object, Patent Documents 2 and 3 describe acrylic resin powder that can be used as a general hot melt adhesive.

[0006] Furthermore, Patent Document 4 describes blending a (meth)acrylic polymer into a composition that is mixed with a colorant to form an ink layer. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2022-147673 [Patent Document 2] International Publication No. 2019 / 188930 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-128736 [Patent Document 4] Japanese Patent Application Laid-Open No. 2018-150390 Summary of the Invention [Problem to be solved by the invention]

[0008] As mentioned above, polyurethane resin is used as the hot melt powder in DTF printing, which has the advantage of good adhesion and durability after thermal transfer.

[0009] However, when polyurethane resin is used, it has been found that pigments and dyes contained in the printed material, such as textiles, can migrate over time or after heat treatment into the binder resin layer and ink layer formed from the polyurethane resin, causing the color of the ink layer to bleed. This color transfer is particularly likely to occur when black or dark-colored textiles are used. Although it is desirable to suppress such color transfer, it has been difficult to suppress it with polyurethane resins. The property of being resistant to color transfer will be hereinafter referred to as sublimation resistance.

[0010] Patent Documents 2 and 3 describe acrylic resin powders that can be used as general hot melt adhesives, but there is no mention of using them as a binder resin layer that adheres ink to an object, and there is no consideration of adhesion, robustness, or sublimation resistance after thermal transfer. The acrylic resin powders disclosed in these documents cannot achieve these physical properties.

[0011] Patent Document 4 describes forming an ink layer by mixing a (meth)acrylic polymer with a colorant, but does not describe at all the formation of a binder resin layer that adheres the ink to the target object, nor does it disclose a hot-melt powder. Even if the (meth)acrylic polymer disclosed in this document is used, the above-mentioned physical properties cannot be achieved.

[0012] In view of the above-mentioned current situation, the present invention aims to provide a hot-melt powder used to form a binder resin layer for adhering ink to an object, which has good adhesion and fastness between the ink and the object, and also has good sublimation resistance, and uses thereof. [Means for solving the problem]

[0013] The present inventors have conducted extensive research to solve the above-mentioned problems, and have found that the above-mentioned problems can be solved by using an acrylic resin as a material constituting a hot melt powder, controlling the weight average molecular weight and glass transition temperature of the acrylic resin within specific ranges, and controlling the volume average particle size and bulk density of the powder within specific ranges, thereby arriving at the present invention. That is, the present invention provides a hot melt powder for a binder resin layer that adheres ink to an object, comprising: The hot melt powder contains acrylic particles containing an acrylic resin, The acrylic resin has a weight average molecular weight of 50,000 to 150,000 and a glass transition temperature of 15 to 25°C, The hot-melt powder has a volume average particle size of 80 to 250 μm, The hot melt powder has a bulk density of 0.60 to 0.80 g / cm 3 The present invention relates to a hot melt powder. The present invention also provides a thermal transfer sheet comprising a release film, an ink layer, and a binder resin layer laminated in this order, The present invention also relates to a thermal transfer sheet, wherein the binder resin layer is a layer formed by melting and solidifying the hot-melt powder. Furthermore, the present invention provides a method for producing ... Adhering the hot melt powder to the surface of the ink layer; and The present invention also relates to a method for producing a thermal transfer sheet, which includes a step of melting and solidifying the hot-melt powder on the ink layer to form a binder resin layer. The present invention further provides an article including an article body, a binder resin layer, and an ink layer laminated in this order, The present invention also relates to an article in which the binder resin layer is a layer formed by melting and solidifying the hot melt powder. The present invention further provides a method for producing an article including an article body, a binder resin layer, and an ink layer laminated in this order, the method comprising the steps of: A step of thermocompression bonding the thermal transfer sheet to an article body; and and a step of peeling off the release film to obtain the article. [Effects of the Invention]

[0014] According to the present invention, there is provided a hot-melt powder used to form a binder resin layer for adhering ink to an object, which has good adhesion and fastness between the ink and the object, and also good sublimation resistance, and uses thereof. The hot-melt powder according to the present invention also has good adhesion to the ink layer. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail. The hot melt powder according to this embodiment is used to form a binder resin layer. The binder resin layer is a layer interposed between the ink layer and the surface of the object to allow the ink to adhere to the object. The details of the use will be described later.

[0016] (hot melt powder) The hot melt powder includes acrylic particles containing an acrylic resin. The hot-melt powder may be composed solely of the acrylic particles, or may contain, in addition to the acrylic particles, resin particles other than acrylic particles or inorganic particles. The proportion of the acrylic particles in the hot-melt powder is preferably, for example, 70% by weight or more and 100% by weight or less. The lower limit may be 80% by weight or more, 90% by weight or more, or 95% by weight or more.

[0017] The acrylic particles refer to resin particles formed from an acrylic resin. The material constituting the acrylic particles may be the acrylic resin alone, or may contain, in addition to the acrylic resin, a resin other than the acrylic resin, a low-molecular-weight organic compound, or an inorganic component. The proportion of the acrylic resin in the acrylic particles is preferably, for example, 70% by weight or more and 100% by weight or less. The lower limit may be 80% by weight or more, 90% by weight or more, or 95% by weight or more.

[0018] The acrylic particles may be resin particles containing only a resin layer of a single composition, or may be resin particles containing multiple resin layers of different compositions, and are particularly preferably resin particles containing only a resin layer of a single composition.

[0019] The acrylic resin refers to a thermoplastic resin containing a (meth)acrylic monomer as a constituent monomer. However, the acrylic resin may further contain a monomer other than the (meth)acrylic monomer as a constituent monomer. The term "(meth)acrylic" is used to refer collectively to acrylic and methacrylic.

[0020] The content of the (meth)acrylic monomer is preferably 50% by weight or more and 100% by weight or less of the total amount of monomers constituting the acrylic resin, and the lower limit may be 70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, or 99% by weight or more.

[0021] The (meth)acrylic monomer is not particularly limited, and examples thereof include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate; aromatic ring-containing (meth)acrylates such as phenoxyethyl (meth)acrylate and benzyl (meth)acrylate; hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate; glycidyl (meth)acrylates such as glycidyl (meth)acrylate and glycidyl alkyl (meth)acrylate; alkoxy(meth)alkyl acrylates; (meth)acrylonitrile, substituted (meth)acrylonitrile, (meth)acrylamide, and 2-(dimethylamino)ethyl (meth)acrylate. The (meth)acrylic monomer may be used alone or in combination of two or more kinds, preferably in combination of two or more kinds, since this makes it easier to control the glass transition temperature of the acrylic resin.

[0022] Among these, (meth)acrylic acid alkyl esters are preferred, and methacrylic acid alkyl esters are particularly preferred. In this case, the methacrylic acid alkyl esters may be used alone, or the methacrylic acid alkyl esters may be used in combination with the acrylic acid alkyl esters and / or the aromatic vinyl compounds described below.

[0023] In particular, since it is easy to control the glass transition temperature of the acrylic resin within a predetermined range described below, it is preferable to use a (meth)acrylic acid alkyl ester having at least an alkyl group with a carbon number of 4 to 12, and it is particularly preferable to use a methacrylic acid alkyl ester having at least an alkyl group with a carbon number of 4 to 12. The content of such alkyl ester is preferably 50% by weight or more, and more preferably 60% by weight or more, of the total amount of monomers constituting the acrylic resin.

[0024] The constituent monomer other than the (meth)acrylic monomer is not particularly limited as long as it is a vinyl compound copolymerizable with the (meth)acrylic monomer, such as an aromatic vinyl compound.

[0025] The aromatic vinyl compound is not particularly limited, and examples thereof include unsubstituted vinyl aromatic compounds such as styrene and 2-vinylnaphthalene; substituted vinyl aromatic compounds such as α-methylstyrene; ring-alkylated vinyl aromatic compounds such as 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,5-dimethylstyrene, and 2,4,6-trimethylstyrene; ring-alkoxylated vinyl aromatic compounds such as 4-methoxystyrene and 4-ethoxystyrene; ring-halogenated vinyl aromatic compounds such as 2-chlorostyrene and 3-chlorostyrene; ring-ester-substituted vinyl aromatic compounds such as 4-acetoxystyrene; and ring-hydroxylated vinyl aromatic compounds such as 4-hydroxystyrene. Among these, substituted or unsubstituted styrene is preferred, styrene and / or α-methylstyrene is more preferred, and styrene is particularly preferred. The aromatic vinyl compound may be used alone or in combination of two or more.

[0026] From the viewpoint of the physical properties of the hot melt powder and the binder resin layer, the acrylic resin is preferably a non-crosslinked acrylic resin having no crosslinked structure, i.e., it is preferable that the acrylic resin does not contain a polyfunctional monomer such as allyl methacrylate or divinylbenzene as a constituent monomer.

[0027] (glass transition temperature) The glass transition temperature (hereinafter also referred to as "Tg") of the acrylic resin is set to 25°C or lower to improve adhesion and robustness between the ink and the printing object, and is preferably 20°C or lower. If the Tg of the acrylic resin exceeds 25°C, it becomes difficult to achieve sufficient adhesion and robustness. From the viewpoint of ease of recovery after production of acrylic particles, it is desirable to set the lower limit of the Tg of the acrylic resin to 15°C or higher.

[0028] When the acrylic resin is a homopolymer formed from one type of monomer, the standard analytical value described in the Polymer Data Handbook compiled by the Society of Polymer Science, etc. can be used as the glass transition temperature of the acrylic resin. When the acrylic resin is a copolymer formed from n types of monomers, the Tg (°C) of the copolymer can be calculated from the following FOX formula using the standard analytical values ​​of Tg related to the homopolymers of each monomer. Formula: 1 / (273+Tg)=Σ(Wn / (273+Tgn)) In the formula, Wn represents the mass fraction of monomer n, and Tgn represents the standard analytical value of Tg (°C) of a homopolymer of monomer n, where the mass fraction is the ratio of the amount of monomer n charged to the total amount of all monomers charged.

[0029] The standard analytical values ​​of Tg (°C) of the homopolymers of each monomer are as follows: Methyl methacrylate: 105°C, n-butyl methacrylate: 20°C, n-butyl acrylate: -54°C, styrene: 100°C, 2-ethylhexyl acrylate: -70°C

[0030] (Weight average molecular weight) The weight-average molecular weight of the acrylic resin is set within the range of 50,000 to 150,000. The weight-average molecular weight is a polystyrene-equivalent molecular weight measured by gel permeation chromatography (GPC). If the weight-average molecular weight is less than 50,000, the adhesion or robustness between the ink and the printed object will be insufficient. On the other hand, if it is greater than 150,000, the resin will be difficult to melt during binder resin layer formation or thermal transfer, which may result in poor adhesion. The lower limit is preferably 80,000 or more. The upper limit is preferably 130,000 or less. The weight average molecular weight can be controlled by adjusting the amount of a chain transfer agent used during polymerization of the acrylic resin.

[0031] (Volume average particle size of hot melt powder) The volume average particle diameter of the hot melt powder according to this embodiment is set to 80 μm or more and 250 μm or less from the viewpoints of adhesion between the ink and the printing substrate, robustness, sublimation resistance, and adhesion to the ink layer. If the volume average particle diameter is smaller than 80 μm, the hot melt powder is prone to scattering, making it difficult to remove from areas other than the intended printing surface, reducing adhesion to the ink layer, and tending to result in insufficient adhesion, robustness, or sublimation resistance after printing. On the other hand, if the volume average particle diameter is greater than 250 μm, the thickness of the binder resin layer increases, resulting in poor texture on the printed surface and difficulty in melting the resin during binder resin layer formation or thermal transfer, tending to result in reduced adhesion or robustness. The lower limit is preferably 100 μm or more, more preferably 120 μm or more. The upper limit is preferably 220 μm or less, more preferably 200 μm or less.

[0032] The volume average particle size of the hot melt powder can be controlled by the type and amount of dispersion stabilizer, emulsifier, etc. used in producing the acrylic particles, the solid concentration during particle dispersion, the dispersion conditions, etc.

[0033] The volume average particle size of the hot melt powder can be measured using a commercially available measuring device based on the laser diffraction / scattering method.

[0034] (Hot melt powder bulk density) The hot melt powder according to this embodiment has a bulk density of 0.60 g / cm 3 More than 0.80g / cm 3 Set the bulk density to 0.60g / cm 3 If the density is less than 0.80 g / cm, the number of fine primary particles increases, which makes the hot melt powder more likely to scatter, reducing adhesion to the ink layer, and the number of voids between the powder particles increases, which makes it difficult to transfer heat when forming the binder resin layer, and the adhesion or fastness or sublimation resistance after printing tend to be insufficient. 3 It is difficult to manufacture acrylic particles with a density exceeding 0.65 g / cm. 3The upper limit is 0.75 g / cm. 3 It is preferable that:

[0035] The above range of the packed bulk density can be achieved by producing acrylic particles by suspension polymerization. On the other hand, when acrylic particles are produced by emulsion polymerization, the primary particles become extremely fine, so the packed bulk density value is usually 0.3 to 0.5 g / cm. 3 It will be about that amount.

[0036] The packed bulk density is also called tapped bulk density, and is a value determined from the volume and weight when a powder is packed into a container such as a cylinder and then tapped.

[0037] The hot melt powder according to this embodiment preferably contains inorganic particles in addition to the acrylic particles. This can prevent blocking during recovery of the acrylic particles. The inorganic particles are preferably made of a material with a large specific surface area, such as silica, titanium dioxide, zinc oxide, or aluminum oxide.

[0038] Among these, titanium dioxide particles are preferably used in consideration of compatibility with white ink, which is a suitable example of a retention layer-forming ink described below. Furthermore, hydrophilic titanium dioxide particles are desirable in consideration of mixability with acrylic particles. The hydrophilic titanium dioxide particles refer to titanium dioxide particles that have not been subjected to a surface treatment, whereas titanium dioxide particles that have been subjected to a surface treatment using a silane compound or the like exhibit hydrophobic properties.

[0039] The amount of such inorganic particles, particularly titanium dioxide particles, used can be appropriately set from the viewpoint of the blocking suppression effect and maintaining the flexibility of the binder resin layer, but is preferably 0.1 to 1 part by weight per 100 parts by weight of acrylic particles. The lower limit is preferably 0.2 parts by weight or more, and the upper limit is preferably 0.8 parts by weight or less.

[0040] (Method of manufacturing acrylic particles) Acrylic particles can be produced by, for example, emulsion polymerization, mini-emulsion polymerization, or suspension polymerization. However, suspension polymerization is preferred because it is easier to satisfy the above-mentioned range of the bulk density. Generally, suspension polymerization can produce large particles with a primary particle diameter of several μm to 1000 μm, and the bulk density is usually 0.60 to 0.80 g / cm. 3 In addition, the particles obtained by suspension polymerization do not require steps such as coagulation or granulation after polymerization and can be easily washed, which has the advantage that the dispersion stabilizer or emulsifier used can be easily removed.

[0041] Suspension polymerization can be carried out by charging the above-mentioned monomers, dispersion stabilizer, polymerization initiator, chain transfer agent, etc. all at once, in portions, or continuously as required, and maintaining a predetermined polymerization temperature with stirring.

[0042] The dispersion stabilizer is not particularly limited, but examples thereof include the following: Anionic water-soluble polymers: polyacrylic acid, sodium polyacrylate, potassium polyacrylate, polymethacrylic acid, sodium polymethacrylate, potassium polymethacrylate, sodium methacrylate-methacrylic acid alkyl ester copolymer, etc. Nonionic water-soluble polymers: polyvinyl alcohol; modified celluloses such as methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and carboxymethyl cellulose; polyvinylpyrrolidone, polyacrylamide; polyalkylene oxides such as polyethylene oxide, polyoxyethylene-polyoxypropylene block copolymer, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene nonylphenyl ether, polyethylene glycol fatty acid ester, and polyoxyethylene laurylamine. Poorly water-soluble inorganic salts: tricalcium phosphate, calcium sulfate, barium sulfate, sodium pyrophosphate, magnesium pyrophosphate, calcium carbonate, magnesium carbonate, titanium oxide, silicon dioxide, hydroxyapatite, kaolin, etc. The dispersion stabilizer may be used alone or in combination of two or more kinds, and among these, it is preferable to use modified cellulose and / or a poorly water-soluble inorganic salt.

[0043] From the viewpoint of dispersion stability and cost, the total amount of dispersion stabilizer added is preferably 0.2 to 15 parts by weight, more preferably 0.5 to 10 parts by weight, per 100 parts by weight of the total amount of monomers.

[0044] An emulsifier can also be used in combination as an auxiliary for the dispersion stabilizer. The emulsifier is not particularly limited, and anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, etc. can be used. From the viewpoint of maintaining stability during polymerization, anionic surfactants and nonionic surfactants are preferred. These emulsifiers may be used alone or in combination.

[0045] Furthermore, for the purpose of preventing emulsification, neutral salts such as sodium chloride, sodium sulfate, sodium dodecyl sulfate, and sodium nitrite may be added.

[0046] The polymerization initiator is preferably an initiator soluble in the monomer used, and is not particularly limited, but examples thereof include azo or diazo polymerization initiators such as 2,2'-azobis(dimethyl isobutyrate) and 2,2'-azobisisobutyronitrile; and peroxide polymerization initiators such as benzoyl peroxide, methyl ethyl ketone peroxide, and lauryl peroxide. From the viewpoint of a balance between molecular weight adjustment and polymerization temperature control, lauryl peroxide is particularly preferred.

[0047] The amount of the polymerization initiator used is not particularly limited, but is preferably in the range of 0.02 to 2 parts by weight, more preferably 0.1 to 1 part by weight, per 100 parts by weight of the total amount of the monomers.

[0048] It is preferable to use a chain transfer agent to adjust the molecular weight of the acrylic resin. The chain transfer agent is not particularly limited, but examples thereof include mercaptans such as n-dodecyl mercaptan; thioglycolic acid esters such as octyl thioglycolate; and α-methylstyrene dimer. These may be used alone or in combination. Among these, n-dodecyl mercaptan is preferred because it has a large chain transfer constant and is relatively easy to suppress odor during melting.

[0049] The amount of the chain transfer agent used is preferably in the range of 0.1 to 2 parts by weight, more preferably 0.2 to 1 part by weight, and even more preferably 0.2 to 0.5 parts by weight, per 100 parts by weight of the total amount of monomers. By appropriately adjusting the amount within this range, it is possible to control the molecular weight of the polymer within the above-mentioned numerical range.

[0050] The temperature during polymerization is not particularly limited, but is, for example, 50 to 80° C., and preferably 60 to 80° C. After the polymerization progresses and the top of the exothermic peak can be confirmed, it is preferable to continue the polymerization at 80 to 90° C. for a certain period of time in order to increase the polymerization conversion rate.

[0051] After forming acrylic particles by suspension polymerization, solid-liquid separation is performed to recover the acrylic particles. When a cellulose-based dispersion stabilizer is used in the suspension polymerization, if the dispersion stabilizer remains, the viscosity of the system increases due to the cellulose-based compound, making solid-liquid separation difficult. Therefore, by adding a cellulose-degrading enzyme before solid-liquid separation to decompose the cellulose-derived structure, the viscosity of the system can be reduced, making solid-liquid separation easier.

[0052] The amount of cellulolytic enzyme to be added is not particularly limited and can be set as appropriate, but is preferably 0.001 to 0.1 parts by weight per 100 parts by weight of the cellulose-based dispersion stabilizer.

[0053] Inorganic dispersion stabilizers may also be decomposed before solid-liquid separation. To decompose an inorganic dispersion stabilizer, an organic acid or an inorganic acid may be added. Among these, hydrochloric acid is preferably used from the viewpoints of treatment during solid-liquid separation and volatility.

[0054] In order to suppress blocking of the acrylic particles, it is preferable to add the inorganic particles described above to the acrylic particles. The timing of adding the inorganic particles is not particularly limited, and the inorganic particles may be added before solid-liquid separation or after solid-liquid separation and before drying.

[0055] (About the use of hot melt powder) The hot-melt powder according to this embodiment is used to form a binder resin layer by heating, melting, and solidifying it. The binder resin layer is a layer interposed between the ink layer and the surface of the printing object to allow the ink to adhere to the printing object. The hot-melt powder according to this embodiment is not used to form an ink composition by mixing it with a colorant as described in Patent Document 4. According to a preferred embodiment, the binder resin layer can realize thermal transfer of the ink layer onto a printing object.

[0056] According to a preferred embodiment, the hot melt powder according to the embodiment can be used as a hot melt powder required in DTF (Direct To Film) printing.

[0057] DTF printing is a method in which a hot melt powder is used to produce a thermal transfer sheet in which an ink layer and a binder resin layer are laminated in that order on a release film, and then the thermal transfer sheet is used to thermally transfer the binder resin layer and ink layer onto the surface of the object to be printed.

[0058] An example of a specific procedure for DTF printing will be described below. First, a desired design is printed on a release film (also called a peeling film or a base film) using design ink, then ink for forming a retention layer is printed on top of the design, and hot melt powder is then supplied onto the ink for forming the retention layer and allowed to adhere.

[0059] The release film is not particularly limited, but is preferably one having heat resistance and strength sufficient to withstand the thermal transfer conditions described below, and examples thereof include resin films and paper. Resin films are particularly preferred. The type of resin constituting the resin film is not particularly limited, but is preferably a polyester resin such as polyethylene terephthalate.

[0060] Of the surfaces of the release film, at least the surface on which the design ink or the ink for forming the retention layer is printed has releasability. To impart releasability, the film surface is preferably coated with a release agent. The type of release agent is not particularly limited, and examples include silicone-based, fluorine-containing silicone-based, and non-silicone-based release agents.

[0061] Furthermore, it is preferable that an ink-receiving layer be formed on at least the surface of the release film on which the design ink or the ink for forming the retention layer is printed, in order to ensure the clarity of the design, etc. Examples of materials constituting such an ink-receiving layer include porous substances such as crystalline silica, amorphous silica, and aluminum silicate.

[0062] The design ink is not particularly limited, but is preferably a water-based ink containing a pigment. The type of pigment is not particularly limited, and examples thereof include azo-, indanthrene-, or imidazolone-based yellow pigments; azo-, quinacridone-, cromophthalic-, or diketopyrrolopyrrole-based red pigments; phthalocyanine-based blue pigments; carbon black; phthalocyanine-based green pigments; indanthrene-based orange pigments; oxazoline-based purple pigments; and white pigments such as titanium oxide, aluminum silicate, and zinc oxide. The water-based ink may also contain an organic resin for fixing to improve fastness.

[0063] The ink for forming the retention layer is not particularly limited, but is preferably a water-based ink containing a pigment. The same inks as the specific examples of the design inks described above can be used. Ink that does not contain a colorant such as a pigment, for example, a colorless ink or a colorless transparent ink, can also be used. Among these, it is preferable to use a white concealing ink containing a white pigment such as titanium oxide.

[0064] The method for printing the design ink or the ink for forming the retaining layer onto the release film is not particularly limited, but can be carried out by inkjet printing.

[0065] The hot melt powder is preferably supplied to the surface of the ink layer when the ink for forming the retention layer is not completely dry and is in a wet state, so that the hot melt powder adheres to the wet surface of the ink layer for forming the retention layer.

[0066] The method for supplying the hot melt powder is not particularly limited, but the resin powder may be scattered from above by utilizing gravity, or may be supplied by utilizing air currents or static electricity. Alternatively, the hot melt powder may be supplied by passing a release film having an ink layer through a container storing the hot melt powder.

[0067] Next, it is desirable to remove unnecessary resin powder from the supplied resin powder from the release film having the ink layer. The method for doing so is not particularly limited, but examples include a method of applying vibration to the back surface of the release film by means of striking or rotating contact with a rotating brush to cause the unnecessary resin powder to fall off, a method of suctioning and removing the unnecessary resin powder, and a method of applying an air current to remove the unnecessary resin powder.

[0068] Next, with the hot-melt powder attached to the surface of the ink layer for forming a retention layer, a heat treatment is performed to melt the resin powder, and then the resin powder is solidified and integrated by cooling. This forms a binder resin layer on the surface of the ink for forming a retention layer. At the same time, the drying of the ink layer can be accelerated.

[0069] The conditions for the heat treatment when forming the binder resin layer are not particularly limited, but for example, the heating temperature may be about 100 to 160° C. and the heating time may be about 1 to 5 minutes. Cooling may be natural cooling or forced cooling using a cooling device.

[0070] As a result of the above, a thermal transfer sheet is formed in which a design ink layer, a retention layer-forming ink layer, and a binder resin layer are laminated in this order on the surface of the release film. Such a thermal transfer sheet also constitutes one aspect of the present invention. The design ink layer and the retention layer-forming ink layer are sometimes collectively referred to as ink layers. However, the formation of the design ink layer can be omitted.

[0071] The thermal transfer sheet described above can be produced using a commercially available DTF printer.

[0072] Next, the ink layer is thermally transferred onto the surface of the printing object using the obtained thermal transfer sheet. During thermal transfer, the thermal transfer sheet is placed on the surface of the printing object (also referred to as the transfer object). At this time, the thermal transfer sheet is placed so that the binder resin layer of the thermal transfer sheet is in contact with the surface of the printing object. In this state, the binder resin layer is thermocompression-bonded to the printing object by applying heat and pressure. After cooling, the release film is peeled off. Thereafter, heat pressing may be performed again to fix the ink layer to the surface of the printing object. As a result of the above, an article can be obtained in which a binder resin layer, a retention layer-forming ink layer, and a design ink layer are laminated in this order on the surface of the printing object.

[0073] The conditions for heating and pressing during thermal transfer are not particularly limited and may be set appropriately, but for example, the transfer can be carried out within the range of 100 to 200° C. using a heat press or iron.

[0074] The printing object is not particularly limited, but it is particularly suitable for textile products. The textile product may be fabric or clothing (e.g., sportswear, T-shirts, underwear, sweatshirts, socks). The fibers may be natural or chemical fibers.

[0075] The color of the textile product is not particularly limited, and it may be colored or uncolored. However, the hot melt powder according to this embodiment has good sublimation resistance and is effective in suppressing color transfer from textile products to the ink layer surface over time or due to heat (transfer of dyes or pigments contained in textile products to the ink layer), making it particularly useful for printing on colored textile products (especially dark or black textile products). When the hot melt powder according to this embodiment is used, changes in the appearance of the ink layer are unlikely to occur even when printing on colored textile products. Therefore, there is no need to limit the color of the textile product to be printed, and the range of textile products that can be printed on can be expanded.

[0076] The hot melt powder for the binder resin layer according to this embodiment has good adhesion and fastness between the ink and the printing object, as well as good sublimation resistance. In addition, it can also have good adhesion to the ink layer. The adhesion to the ink layer is evaluated after the ink for forming the retention layer described above is printed, the powder is supplied to the wet ink layer surface in a wet state, and unnecessary powder is removed, and then the adhesion is evaluated based on whether the powder is evenly and completely adhered to the wet ink layer surface and / or whether no powder remains in areas where the powder adhesion is not required. If the adhesion is uneven, the uniformity of the binder resin layer that is formed may decrease, and the quality may be unstable in terms of adhesion, robustness, etc. Furthermore, if powder remains in unnecessary areas, the powder may be transferred to the printing object during thermal transfer, which may hinder smooth peeling of the release film and may also impair the appearance after printing.

[0077] The following items list preferred aspects of the present disclosure, but the present invention is not limited to the following items. [Item 1] A hot melt powder for a binder resin layer that adheres ink to an object, The hot melt powder contains acrylic particles containing an acrylic resin, The acrylic resin has a weight average molecular weight of 50,000 to 150,000 and a glass transition temperature of 15 to 25°C, The hot-melt powder has a volume average particle size of 80 to 250 μm, The hot melt powder has a bulk density of 0.60 to 0.80 g / cm 3 That is, hot melt powder. [Item 2] the acrylic resin contains alkyl (meth)acrylate as a constituent monomer, Item 2. The hot melt powder according to item 1, wherein the alkyl (meth)acrylate comprises an alkyl (meth)acrylate ester having an alkyl group having 4 to 12 carbon atoms. [Item 3] the hot melt powder further comprises titanium dioxide particles; 3. The hot melt powder according to item 1 or 2, wherein the content of the titanium dioxide particles is 0.1 to 1 part by weight per 100 parts by weight of the acrylic particles. [Item 4] A thermal transfer sheet comprising a release film, an ink layer, and a binder resin layer laminated in this order, A thermal transfer sheet, wherein the binder resin layer is a layer formed by melting and solidifying the hot-melt powder according to any one of items 1 to 3. [Item 5] forming an ink layer on the surface of a release film; A step of adhering the hot-melt powder according to any one of items 1 to 3 to the surface of the ink layer; and a step of melting and solidifying the hot melt powder on the ink layer to form a binder resin layer. [Item 6] An article comprising an article body, a binder resin layer, and an ink layer laminated in this order, 4. An article, wherein the binder resin layer is a layer formed by melting and solidifying the hot-melt powder according to any one of items 1 to 3. [Item 7] 7. The article according to item 6, wherein the article body is a textile product. [Item 8] A method for producing an article including an article body, a binder resin layer, and an ink layer laminated in this order, comprising: A step of thermocompression bonding the thermal transfer sheet according to item 4 to an article body; and and peeling off the release film to obtain the article. [Example]

[0078] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0079] (Method for measuring volume average particle size) The volume average particle size of the powder was measured using a measuring device based on the laser diffraction / scattering method, MT3000II manufactured by Microtrac Corp. The measurement sample was prepared by dispersing the collected powder in soapy water.

[0080] (Method for measuring compacted bulk density) The bulk density was measured by adding powder to a 25 mL measuring cylinder and tapping it. The powder was gradually added while tapping, and when the powder volume stopped moving from 20 mL, the weight of the powder was measured and the weight / volume (= 20 cm 3 ) was calculated.

[0081] (Method for measuring weight-average molecular weight) The weight-average molecular weight was determined by dissolving a sample in tetrahydrofuran (THF), filtering the soluble fraction through a filter with a filter diameter of 0.2 μm, and then using a high-speed GPC system (HLC-8220, manufactured by Tosoh Corporation) (sample solution: 20 mg sample / 10 mL THF, columns: one TSKguardcolumn SuperHZ-H and two TSKgel SuperHZM-H, both manufactured by Tosoh Corporation, column temperature: 40°C, detector: differential refractometer, flow rate: 0.35 mL / min, injection volume: 10 μL, calibration curve: standard polystyrene).

[0082] Example 1 800g of deionized water, 0.55g of disodium hydrogen phosphate, 82.5g of 10% tribasic calcium phosphate solution, and 0.11g of sodium nitrite were charged into a 3L polymerization reactor. Separately, 330g of butyl methacrylate, 104.5g of butyl acrylate, and 115.5g of methyl methacrylate were mixed, and then 1.1g of normal dodecyl mercaptan and 3.3g of lauryl peroxide were dissolved in the mixture. After confirming dissolution, the monomer mixture was charged into the 3L polymerization reactor, allowed to stand for a while, and then stirred at 300 rpm for 10 minutes. After stirring, 110g of 2% hydroxypropyl methylcellulose was added and the temperature was raised to 70°C while flowing nitrogen to initiate polymerization. After confirming the exothermic peak due to polymerization, the temperature was raised to 85°C and held for 3 hours to complete the polymerization, yielding a suspension of acrylic resin particles.

[0083] After polymerization, the suspension was cooled to below 50°C, 0.01 g of cellulose-degrading enzyme was added, and the mixture was stirred for 30 minutes, resulting in the decomposition of the cellulose-derived structure of hydroxypropyl methylcellulose. Furthermore, 165 g of 10% hydrochloric acid was added to decompose tribasic calcium phosphate. The suspension after the treatment was subjected to solid-liquid separation and then washed with water to obtain a dehydrated cake. 2.8 g of hydrophilic titanium dioxide (AEROXIDE P25, manufactured by Nippon Aerosil Co., Ltd.) was mixed with this dehydrated cake and then dried to obtain a spherical acrylic resin particle powder. The volume average particle diameter of this powder was 203 μm, and the compacted bulk density was 0.72 g / cm. 3 The weight average molecular weight of the acrylic resin was 128,000 and the Tg was 14.8°C.

[0084] Example 2 550 g of deionized water, 110 g of 10% tribasic calcium phosphate solution, and 55 g of 1% sodium dodecylbenzenesulfonate solution were charged into a 3-L polymerization reactor. Separately, 330 g of butyl methacrylate, 88 g of butyl acrylate, and 132 g of methyl methacrylate were mixed, and then 1.1 g of normal dodecyl mercaptan and 3.3 g of lauryl peroxide were dissolved in the mixture. After confirming dissolution, the monomer mixture was charged into the 3-L polymerization reactor, allowed to stand for a while, and then stirred at 300 rpm for 10 minutes. After stirring, the temperature was raised to 70 °C while flowing nitrogen to initiate polymerization. After confirming the exothermic peak due to polymerization, the temperature was raised to 85 °C and held for 3 hours to complete the polymerization, yielding a suspension of acrylic resin particles.

[0085] After polymerization, the suspension was cooled to below 50°C, and 165 g of 10% hydrochloric acid was added to decompose the tricalcium phosphate. The suspension after the treatment was subjected to solid-liquid separation and then washed with water to obtain a dehydrated cake. 2.8 g of hydrophilic titanium dioxide (AEROXIDE P25, manufactured by Nippon Aerosil Co., Ltd.) was mixed with this dehydrated cake and then dried to obtain a spherical acrylic resin particle powder. The volume average particle diameter of this powder was 124 μm, and the compacted bulk density was 0.69 g / cm. 3 The weight average molecular weight of the acrylic resin was 129,000 and the Tg was 19.7°C.

[0086] Examples 3 to 9 A powder of spherical acrylic resin particles was obtained in the same manner as in Examples 1 or 2, except that the types and amounts of materials used were changed according to the description in Table 1. The volume average particle size, packed bulk density, weight average molecular weight and Tg of the acrylic resin of the powder are shown in Table 1.

[0087] (Comparative Example 1) 800g of deionized water, 0.55g of disodium hydrogen phosphate, 66g of 10% tribasic calcium phosphate solution, and 0.11g of sodium nitrite were charged into a 3L polymerization reactor. Separately, 330g of butyl methacrylate, 88g of butyl acrylate, and 132g of methyl methacrylate were mixed, and then 1.1g of normal dodecyl mercaptan and 3.3g of lauryl peroxide were dissolved in the mixture. After confirming dissolution, the monomer mixture was charged into the 3L polymerization reactor, allowed to stand for a while, and then stirred at 250 rpm for 10 minutes. After stirring, 55g of 2% hydroxypropyl methylcellulose was added and the temperature was raised to 70°C while flowing nitrogen to initiate polymerization. After confirming the exothermic peak due to polymerization, the temperature was raised to 85°C and held for 3 hours to complete the polymerization, yielding a suspension of acrylic resin particles.

[0088] After polymerization, the suspension was cooled to below 50°C, 0.01 g of cellulose-degrading enzyme was added, and the mixture was stirred for 30 minutes, resulting in the decomposition of the cellulose-derived structure of hydroxypropyl methylcellulose. Furthermore, 165 g of 10% hydrochloric acid was added to decompose tribasic calcium phosphate. The suspension after the treatment was subjected to solid-liquid separation and then washed with water to obtain a dehydrated cake. 2.8 g of hydrophilic titanium dioxide (AEROXIDE P25, manufactured by Nippon Aerosil Co., Ltd.) was mixed with this dehydrated cake and then dried to obtain a spherical acrylic resin particle powder. The volume average particle diameter of this powder was 285 μm and the compacted bulk density was 0.76 g / cm. 3 The weight average molecular weight of the acrylic resin was 125,000 and the polymer Tg was 19.7°C.

[0089] (Comparative Example 2) 600g of deionized water, 275g of 10% tribasic calcium phosphate solution, and 110g of 1% sodium dodecylbenzenesulfonate solution were charged into a 3L polymerization reactor. Separately, 330g of butyl methacrylate, 88g of butyl acrylate, and 132g of methyl methacrylate were mixed, and then 1.1g of normal dodecyl mercaptan and 3.3g of lauryl peroxide were dissolved in the mixture. After confirming dissolution, the monomer mixture was charged into the 3L polymerization reactor, allowed to stand for a while, and then stirred at 4000 rpm with a homomixer for 10 minutes. After stirring, the mixture was heated to 70°C while flowing nitrogen to initiate polymerization. After confirming the exothermic peak due to polymerization, the mixture was heated to 85°C and held for 3 hours to complete the polymerization, yielding a suspension of acrylic resin particles.

[0090] After polymerization, the suspension was cooled to below 50°C, and 410 g of 10% hydrochloric acid was added to decompose the tricalcium phosphate. The suspension after the treatment was subjected to solid-liquid separation and then washed with water to obtain a dehydrated cake. 8.4 g of hydrophilic titanium dioxide (AEROXIDE P25, manufactured by Nippon Aerosil Co., Ltd.) was mixed with this dehydrated cake and then dried to obtain a spherical acrylic resin particle powder. The volume average particle diameter of this powder was 54 μm, and the compacted bulk density was 0.61 g / cm. 3 The weight average molecular weight was 123,000 and the polymer Tg was 19.7°C.

[0091] (Comparative Examples 3 to 6) A powder of spherical acrylic resin particles was obtained in the same manner as in Comparative Example 1, except that the types and amounts of materials used were changed according to the description in Table 1. The volume average particle size, packed bulk density, weight average molecular weight and Tg of the acrylic resin of the powder are shown in Table 1.

[0092] (Evaluation method) The acrylic resin particle powders obtained in each Example or Comparative Example, or polyurethane powder (volume average particle diameter 180 μm, irregular shape, polymer Tg: −48° C.) in Comparative Example 7 were used to carry out the following evaluations.

[0093] (Coating onto polyester resin film) A 25% titanium oxide white pigment dispersion was applied to one side of a polyester resin film (100 μm thick) coated with a silicone wax-containing release agent using a No. 26 bar coater and dried at 70°C for 1 minute to form a white ink layer. The acrylic resin particle powder or polyurethane powder obtained in each Example or Comparative Example was sprinkled on the surface of the white ink layer so that the powder adhered to the entire white ink layer. The film was then tapped to remove excess powder. The film was then heated at 125°C for 3 minutes and 30 seconds to melt and solidify the powder, forming a binder resin layer.

[0094] (Transfer process onto textile fabric) The film with the white ink layer and binder resin layer formed was placed on the surface of a black textile fabric with the binder resin layer facing the textile fabric, pressed at 150°C for 15 seconds, and cooled. After cooling, the polyester resin film was peeled off and pressed again at 150°C for 15 seconds, leaving the white ink printed on the textile fabric. The following evaluations were carried out using this textile fabric.

[0095] (Evaluation of Adhesion) After applying the adhesive cloth tape to the printed surface of the textile fabric, the surface of the adhesive tape was rubbed with the cap of a pen 50 times to firmly adhere the adhesive tape to the textile fabric, and then the adhesive tape was quickly peeled off by pulling it vertically. After peeling, it was checked whether the printed surface was adhering to the adhesive surface of the adhesive tape, and the adhesion to the textile fabric was evaluated. The evaluation criteria were as follows: Good: The printed surface does not adhere to the adhesive surface at all. ×: The printed surface is attached to the adhesive surface.

[0096] (Evaluation of washing resistance) Based on the household washing machine method (JIS L 1930), a textile fabric printed with white ink was washed 10 times in a washing machine using the C4M method, and the printed surface of the textile fabric was checked for peeling. The evaluation criteria were as follows: ⊚: No peeling is observed on the printed surface. ◯: Minute peeling is observed, but it is not noticeable macroscopically. △: Some peeling is observed. ×: Peeling is observed over the entire surface.

[0097] (Evaluation of sublimation resistance) Fabrics printed with white ink were heated at 60°C for 48 hours to check whether the black pigment contained in the fabric rose to the printed surface. If the printed surface changed from white to a dark color or black, it was judged to have poor sublimation resistance. ◎: No change in white color was observed compared to before heating. ◯: There is a slight change in the white color, but it is not a problem. △: A change to a darker color can be recognized. ×: Discolored to black.

[0098] (Evaluation of adhesion to ink layer) After the powder was sprinkled on the white ink layer on the polyester resin film and the excess powder was removed, the presence or absence of powder on the film surface in areas where the ink layer was not formed was confirmed by touch. Furthermore, for the fiber fabric printed with the white ink, the presence or absence of a binder resin layer on the surface of the fiber fabric other than the printed surface was also confirmed by touch. ◯: No powder remains and no binder resin layer is present. ×: Powder remains and / or the binder resin layer remains. The results of each evaluation are shown in Table 1.

[0099] [Table 1]

[0100] It can be seen from Table 1 that the acrylic resin particle powder of each example has good adhesion to the ink layer, adhesion and fastness (washing resistance) after thermal transfer, and sublimation resistance.

[0101] On the other hand, in Comparative Example 1, the volume average particle diameter of the acrylic resin particle powder was larger than the specified range, and the adhesion and robustness after thermal transfer were insufficient, and in Comparative Example 2, the volume average particle diameter was smaller than the specified range, and both evaluation items were insufficient. Furthermore, in Comparative Example 3, the weight-average molecular weight of the acrylic resin was smaller than the specified range, and in Comparative Example 4, the weight-average molecular weight was larger than the specified range. In both cases, the adhesion and robustness after thermal transfer, as well as the sublimation resistance, were insufficient. In Comparative Example 5, the glass transition temperature of the acrylic resin was lower than the specified range, causing blocking during drying and making it impossible to recover the acrylic resin particle powder.In Comparative Example 6, the glass transition temperature was higher than the specified range, resulting in insufficient adhesion and robustness after thermal transfer. Furthermore, it is clear that the sublimation resistance is insufficient in Comparative Example 7, which used polyurethane powder.

Claims

1. A hot melt powder for a binder resin layer that adheres ink to an object, The hot melt powder contains acrylic particles containing an acrylic resin, The acrylic resin has a weight average molecular weight of 50,000 to 150,000 and a glass transition temperature of 15 to 25°C, The hot-melt powder has a volume average particle size of 80 to 250 μm, The hot melt powder has a bulk density of 0.60 to 0.80 g / cm ３ That is, hot melt powder.

2. the acrylic resin contains alkyl (meth)acrylate as a constituent monomer, The hot melt powder according to claim 1 , wherein the alkyl (meth)acrylate comprises an alkyl (meth)acrylate ester having an alkyl group having 4 to 12 carbon atoms.

3. the hot melt powder further comprises titanium dioxide particles; 2. The hot melt powder according to claim 1, wherein the content of the titanium dioxide particles is 0.1 to 1 part by weight per 100 parts by weight of the acrylic particles.

4. A thermal transfer sheet comprising a release film, an ink layer, and a binder resin layer laminated in this order, A thermal transfer sheet, wherein the binder resin layer is a layer formed by melting and solidifying the hot melt powder according to any one of claims 1 to 3.

5. forming an ink layer on the surface of a release film; A step of adhering the hot melt powder according to any one of claims 1 to 3 to the surface of the ink layer; and a step of melting and solidifying the hot melt powder on the ink layer to form a binder resin layer.

6. An article comprising an article body, a binder resin layer, and an ink layer laminated in this order, An article, wherein the binder resin layer is a layer formed by melting and solidifying the hot melt powder according to any one of claims 1 to 3.

7. The article according to claim 6 , wherein the article body is a textile product.

8. A method for producing an article including an article body, a binder resin layer, and an ink layer laminated in this order, comprising: a step of thermocompression bonding the thermal transfer sheet according to claim 4 to an article body; and and peeling off the release film to obtain the article.

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