A thermal sublimation transfer paper coating and its preparation method

Abstract

This invention relates to the field of transfer paper coating technology, specifically to a thermal sublimation transfer paper coating and its preparation method. The invention first coats a photothermal dual-curing polyurethane emulsion onto a substrate paper, curing it to form a hydrophobic layer. The photothermal dual-curing polyurethane emulsion is composed of an epoxy-terminated silicone polyurethane modified with hydroxyl-terminated polydimethylsiloxane and capped with propylene glycol diglycidyl ester, and a double-bond capped polyurethane obtained by chain extension with glycerol monoglycidyl ether and capping with hydroxyethyl acrylate. Next, an ink-absorbing coating containing mercapto-modified silica, acrylamide monomer, and sodium carboxymethyl cellulose is coated onto the hydrophobic layer, cross-linking to form an ink-absorbing layer. Finally, a polyvinyl alcohol solution is coated onto the ink-absorbing layer to form a surface layer. The thermal sublimation transfer paper coating designed by this invention exhibits strong adhesion and excellent transfer effect.

Description

Technical Field

[0001] This invention relates to the field of transfer paper coating technology, specifically to a thermal sublimation transfer paper coating and its preparation method. Background Technology

[0002] Sublimation transfer is a new process that uses an inkjet printer filled with sublimation transfer ink to print images such as portraits, landscapes, and text onto sublimation transfer inkjet paper in a mirror image manner. The paper is then heated to about 200°C by a heat transfer device, causing the heat transfer ink on the paper to sublimate and penetrate into the substrate, thus realistically transferring the color image from the paper onto materials such as textiles, ceramic cups, ceramic plates, ceramic slabs, and metals.

[0003] The coating of sublimation transfer paper, as the main functional material carrying sublimation ink, directly affects the transfer effect. Sublimation transfer paper coatings typically use sodium carboxymethyl cellulose, polyvinyl alcohol, etc., as adhesives, and porous inorganic materials such as silica, talc, and calcium carbonate as pigments. However, existing sublimation transfer papers suffer from weak adhesion and poor compatibility with their coatings. Furthermore, current sublimation transfer technologies have drawbacks such as low ink absorption and dye molecule penetration into the substrate paper, affecting dye transfer rates. Therefore, modification is necessary. Summary of the Invention

[0004] The purpose of this invention is to provide a thermal sublimation transfer paper coating and its preparation method to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a thermal sublimation transfer paper coating and its preparation method, wherein the thermal sublimation transfer paper coating includes a hydrophobic layer coated on a substrate paper, an ink-absorbing layer coated on the hydrophobic layer, and a surface layer coated on the ink-absorbing layer; on the substrate paper, the weight of the hydrophobic layer per square meter is 1~2.5g, the weight of the ink-absorbing layer per square meter is 5~8g, and the weight of the surface layer per square meter is 2~4g; the preparation method of the thermal sublimation transfer paper coating includes the following steps:

[0006] Step 1:

[0007] By weight, 100 parts of photothermal dual-curing polyurethane emulsion, 0.3-0.5 parts of photoinitiator, and 10-14 parts of triethylenetetramine are mixed, coated onto the substrate paper, and cured at 70-80°C to form a hydrophobic layer.

[0008] Step 2:

[0009] The ink-absorbing layer coating is applied onto the hydrophobic layer and cured under ultraviolet light to form the ink-absorbing layer;

[0010] Step 3:

[0011] Polyvinyl alcohol powder is dissolved in deionized water to obtain a polyvinyl alcohol solution; the polyvinyl alcohol solution is coated onto the ink-absorbing layer and dried to form a surface layer.

[0012] Further, in step 1, the preparation method of the photothermal dual-curing polyurethane emulsion is as follows: epoxy-terminated silicone polyurethane and double-bond-terminated polyurethane are mixed at a mass ratio of (8~10):1, triethylamine is added to neutralize the pH to 7~7.5, and water is added for emulsification to obtain a photothermal dual-curing polyurethane emulsion with a solid content of 30~40%.

[0013] Further, the preparation method of epoxy-terminated silicone polyurethane is as follows: Hydroxyl-terminated polydimethylsiloxane and polyethylene glycol 1000 are vacuum dehydrated at 100-120℃ for 1-2 hours; the hydroxyl-terminated polydimethylsiloxane and polyethylene glycol 1000 are mixed at a weight ratio of 1:(6-10) to obtain a mixed diol; 2-2.2 parts by weight of isophorone diisocyanate are added to 3-3.5 parts of the mixed diol under nitrogen protection, and the reaction is carried out at 70-80℃ for 2-3 hours using dibutyltin dilaurate as a catalyst to obtain a silicone prepolymer; the temperature is lowered to 40-50℃, and 0.27-0.36 parts of 1,4-butanediol are added for chain extension reaction for 0.5-1 hour; 1.2-1.3 parts of propylene glycol diglycidyl ester are added for end-capping reaction for 1-2 hours to obtain epoxy-terminated silicone polyurethane.

[0014] Furthermore, the preparation method of double-bond-terminated polyurethane includes the following steps:

[0015] S1: Weigh glycerol and epichlorohydrin, use concentrated sulfuric acid as a catalyst (the amount of concentrated sulfuric acid is 0.5~0.6% of the total weight of the reactants), heat in a water bath to 50~60℃ and react for 3~4h. After cooling, add sodium hydroxide solution with a mass concentration of 30~40% and react at 30~40℃ for 3~4h. Filter to remove insoluble matter, remove water by vacuum distillation to obtain glycerol monoglycidyl ether.

[0016] S2: Polyethylene glycol 1000 is vacuum dehydrated at 100~120℃ for 1~2h. By weight, 11~15 parts of isophorone diisocyanate, 10 parts of polyethylene glycol 1000, and 2~3 parts of glycerol monoglycidyl ether are mixed under nitrogen atmosphere. Dibutyltin dilaurate is used as a catalyst and the mixture is reacted at 70~80℃ for 1~3h. The temperature is then lowered to 50~60℃, and 3~4.5 parts of 2-hydroxyethyl acrylate are added and reacted for 4~5h to obtain double-bond-terminated polyurethane.

[0017] Furthermore, in S1, the molar ratio of glycerol, epichlorohydrin, and sodium hydroxide is 1:1:1.

[0018] Furthermore, the preparation method of the ink-absorbing layer coating is as follows: by weight, 30-50 parts of sodium carboxymethyl cellulose and 50-70 parts of acrylamide monomer are dissolved in 200 parts of deionized water, 0.3-0.5 parts of N,N-methylenebisacrylamide, 1-1.2 parts of glutaraldehyde, and 0.5-0.7 parts of photoinitiator are added, and 4-5 parts of mercapto-modified silica are added while stirring to obtain the ink-absorbing layer coating.

[0019] Further, the preparation method of mercapto-modified silica is as follows: by weight, take 5 parts of anhydrous ethanol, 1 part of deionized water, 0.03~0.06 parts of ammonia water, and 0.02~0.05 parts of 3-mercaptopropyltrimethoxysilane and mix them. Stir at 50~60℃ for 1~2h to obtain a mixed solution. Add 2~3 parts of nano-silica to 100 parts of the mixed solution, disperse ultrasonically for 1~2h, filter, wash with anhydrous ethanol and deionized water, and dry to obtain mercapto-modified silica.

[0020] Furthermore, in step 2, during UV curing, the exposure energy is 800~1000 mJ / cm². 2 The curing time is 60~90s.

[0021] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0022] This invention provides a method for preparing a thermal sublimation transfer paper coating, wherein the coating is composed of a hydrophobic layer, an ink-absorbing layer, and a surface layer. The hydrophobic layer is formed by coating a photothermal dual-curing polyurethane emulsion onto a substrate paper and then curing it. In preparing the photothermal dual-curing polyurethane emulsion, this invention first introduces hydroxyl-terminated polydimethylsiloxane into a polyurethane prepolymer, and then uses propylene glycol diglycidyl ester for end-capping to obtain an epoxy-terminated silicone polyurethane with good hydrophobic properties. Next, glycerol monoglycidyl ether is synthesized using glycerol, epichlorohydrin, and sodium hydroxide as raw materials. This glycerol monoglycidyl ether is then introduced into the polyurethane prepolymer as a chain extender, and hydroxyethyl acrylate is used for end-capping to obtain a double-bond-terminated polyurethane. Finally, the epoxy-terminated silicone polyurethane and the double-bond-terminated polyurethane are mixed to obtain the photothermal dual-curing polyurethane emulsion. A photothermal dual-curing polyurethane emulsion is coated onto a substrate paper. Under the action of a curing agent, the epoxy groups in the two different polyurethanes cross-link to form a dense hydrophobic layer. The presence of the hydrophobic layer effectively prevents dye molecules from entering the substrate paper and avoids dye from seeping into the substrate paper.

[0023] The ink-absorbing coating is applied onto the hydrophobic layer. During the curing process, the mercapto-modified silica, acrylamide monomer, and sodium carboxymethyl cellulose undergo cross-linking. Because the hydrophobic layer contains unsaturated carbon-carbon double bonds, it bonds chemically with the ink-absorbing layer, improving not only adhesion but also the compatibility between the coatings. The interpenetrating network resin formed after curing expands upon absorbing water, thus increasing ink absorption. Furthermore, the porous structure of silica provides pores for the network resin, further enhancing ink absorption, shortening transfer time, and improving transfer efficiency.

[0024] A polyvinyl alcohol solution is coated onto the ink-absorbing layer to form a surface layer. At room temperature, polyvinyl alcohol has a strong water permeability, while at high temperature, the hydrogen bonding between polyvinyl alcohol molecules decreases, thus providing larger gaps. This facilitates the rapid and complete sublimation of dye molecules from the coating material, improving the transfer effect.

[0025] The thermal sublimation transfer paper coating designed in this invention not only has strong adhesion to the substrate paper, but also high adhesion and compatibility between coatings, resulting in good transfer effect. It reduces ink penetration, burrs, and image ghosting problems, effectively improving image accuracy. Detailed Implementation

[0026] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Materials and sources used in this invention: The base paper is transfer printing paper with a paper density of 94 g / m³. 3 The following materials were used: 1. Suzhou Zhihuibao Digital Technology Co., Ltd.; 2. Polyvinyl alcohol powder from Anhui Wanwei Group Co., Ltd., model 04-88(L); 3. Hydroxyl-terminated polydimethylsiloxane from Jiangsu Kexing New Materials Co., Ltd., model F-1.5; 4. Photoinitiator 184 from Shanghai Aladdin Biochemical Technology Co., Ltd.; 5. Nano silica from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., model XFI03; 6. Sodium carboxymethyl cellulose (molecular mass 4000, degree of substitution 1.2) from Jiangsu Parker Co., Ltd.

[0028] Example 1: A thermal sublimation transfer paper coating and its preparation method, comprising the following steps:

[0029] Step 1:

[0030] 100g of photothermal dual-curing polyurethane emulsion, 0.5g of photoinitiator, and 14g of triethylenetetramine were mixed, coated onto a substrate paper, and cured at 70℃ to form a 2.5g / m² emulsion. 2 Hydrophobic layer; wherein, the preparation method of photothermal dual-curing polyurethane emulsion includes the following steps:

[0031] S11: Hydroxyl-terminated polydimethylsiloxane and polyethylene glycol 1000 were vacuum dehydrated at 120℃ for 1 h. The hydroxyl-terminated polydimethylsiloxane and polyethylene glycol 1000 were mixed at a weight ratio of 1:9 to obtain a mixed diol. Under nitrogen protection, 2.2 kg of isophorone diisocyanate was added to 3.5 kg of the mixed diol, and the reaction was carried out at 70℃ for 2 h with dibutyltin dilaurate as a catalyst to obtain a silicon-containing prepolymer. The temperature was lowered to 40℃, and 0.36 kg of 1,4-butanediol was added for chain extension reaction for 0.5 h. 1.3 kg of propylene glycol diglycidyl ester was added for end-capping reaction for 1 h to obtain epoxy-terminated silicone-containing polyurethane.

[0032] S12: Weigh glycerol and epichlorohydrin, use concentrated sulfuric acid as a catalyst (the amount of concentrated sulfuric acid is 0.5% of the total weight of the reactants), heat to 50°C in a water bath and react for 3 hours. After cooling, add 40% sodium hydroxide solution and react at 30°C for 3 hours. Filter to remove insoluble matter, and remove water by vacuum distillation to obtain glycerol monoglycidyl ether; wherein the molar ratio of glycerol, epichlorohydrin and sodium hydroxide is 1:1:1.

[0033] S13: Polyethylene glycol 1000 was vacuum dehydrated at 120℃ for 1 hour. By weight, 13 kg of isophorone diisocyanate, 10 kg of polyethylene glycol 1000, and 2.5 kg of glycerol monoglycidyl ether were mixed under nitrogen atmosphere. Dibutyltin dilaurate was used as a catalyst and the mixture was reacted at 70℃ for 1 hour. The temperature was then lowered to 50℃, and 4.2 kg of 2-hydroxyethyl acrylate was added and reacted for 4 hours to obtain double-bond-terminated polyurethane.

[0034] S14: Mix epoxy-terminated silicone polyurethane and double-bond-terminated polyurethane at a mass ratio of 8:1, add triethylamine to neutralize the pH to 7, and emulsify with water to obtain a photothermal dual-curing polyurethane emulsion with a solid content of 40%.

[0035] Step 2:

[0036] The ink-absorbing coating was applied onto the hydrophobic layer and then cured under ultraviolet light at an exposure energy of 1000 mJ / cm². 2 The curing time is 60 seconds, and the dried product forms an 8g / m³. 2 The ink-absorbing layer; wherein, the preparation method of the ink-absorbing layer coating includes the following steps:

[0037] S21: Mix 5 kg of anhydrous ethanol, 1 kg of deionized water, 60 g of ammonia, and 50 g of 3-mercaptopropyltrimethoxysilane, and stir at 50 °C for 1 h to obtain a mixed solution; add 3 g of nano-silica to 100 g of the mixed solution, ultrasonically disperse for 1 h, filter, rinse with anhydrous ethanol and deionized water, and dry to obtain mercapto-modified silica;

[0038] S22: Dissolve 300g sodium carboxymethyl cellulose and 500g acrylamide monomer in 2kg deionized water, add 4g N,N-methylenebisacrylamide, 10g glutaraldehyde and 5g photoinitiator, stir and add 40g mercapto-modified silica to obtain ink-absorbing coating.

[0039] Step 3:

[0040] Polyvinyl alcohol powder was dissolved in deionized water to obtain a 20% (w / w) polyvinyl alcohol solution; the polyvinyl alcohol solution was coated onto an ink-absorbing layer and dried to form a 4 g / m² ink layer. 2 Surface layer.

[0041] Example 2: A thermal sublimation transfer paper coating and its preparation method, comprising the following steps:

[0042] Step 1:

[0043] 100g of photothermal dual-curing polyurethane emulsion, 0.5g of photoinitiator, and 14g of triethylenetetramine were mixed, coated onto a substrate paper, and cured at 75℃ to form a 2.5g / m² emulsion. 2 Hydrophobic layer; wherein, the preparation method of photothermal dual-curing polyurethane emulsion includes the following steps:

[0044] S11: Hydroxyl-terminated polydimethylsiloxane and polyethylene glycol 1000 were vacuum dehydrated at 120℃ for 1 h. The hydroxyl-terminated polydimethylsiloxane and polyethylene glycol 1000 were mixed at a weight ratio of 1:9 to obtain a mixed diol. Under nitrogen protection, 2.2 kg of isophorone diisocyanate was added to 3.5 kg of the mixed diol, and the reaction was carried out at 75℃ for 2.5 h with dibutyltin dilaurate as a catalyst to obtain a silicon-containing prepolymer. The temperature was lowered to 45℃, and 0.36 kg of 1,4-butanediol was added for chain extension reaction for 0.5 h. 1.3 kg of propylene glycol diglycidyl ester was added for end-capping reaction for 1.5 h to obtain epoxy-terminated silicone polyurethane.

[0045] S12: Weigh glycerol and epichlorohydrin, use concentrated sulfuric acid as a catalyst (the amount of concentrated sulfuric acid is 0.5% of the total weight of the reactants), heat to 55℃ in a water bath and react for 3.5h. After cooling, add 40% sodium hydroxide solution and react at 35℃ for 3.5h. Filter to remove insoluble matter, and remove water by vacuum distillation to obtain glycerol monoglycidyl ether; wherein the molar ratio of glycerol, epichlorohydrin and sodium hydroxide is 1:1:1.

[0046] S13: Polyethylene glycol 1000 was vacuum dehydrated at 120℃ for 1 hour. By weight, 13 kg of isophorone diisocyanate, 10 kg of polyethylene glycol 1000, and 2.5 kg of glycerol monoglycidyl ether were mixed under nitrogen atmosphere. Dibutyltin dilaurate was used as a catalyst, and the mixture was reacted at 75℃ for 2 hours. The temperature was then lowered to 55℃, and 4.2 kg of 2-hydroxyethyl acrylate was added and reacted for 4.5 hours to obtain double-bond-terminated polyurethane.

[0047] S14: Mix epoxy-terminated silicone polyurethane and double-bond-terminated polyurethane at a mass ratio of 8:1, add triethylamine to neutralize the pH to 7, and emulsify with water to obtain a photothermal dual-curing polyurethane emulsion with a solid content of 40%.

[0048] Step 2:

[0049] The ink-absorbing coating was applied onto the hydrophobic layer and then cured under ultraviolet light at an exposure energy of 900 mJ / cm². 2 The curing time is 75 seconds, and the dried product forms an 8g / m³. 2 The ink-absorbing layer; wherein, the preparation method of the ink-absorbing layer coating includes the following steps:

[0050] S21: Mix 5 kg of anhydrous ethanol, 1 kg of deionized water, 60 g of ammonia, and 50 g of 3-mercaptopropyltrimethoxysilane, and stir at 55 °C for 1.5 h to obtain a mixed solution; add 3 g of nano-silica to 100 g of the mixed solution, ultrasonically disperse for 1.5 h, filter, wash with anhydrous ethanol and deionized water, and dry to obtain mercapto-modified silica;

[0051] S22: Dissolve 300g sodium carboxymethyl cellulose and 500g acrylamide monomer in 2kg deionized water, add 4g N,N-methylenebisacrylamide, 10g glutaraldehyde and 5g photoinitiator, stir and add 45g mercapto-modified silica to obtain ink-absorbing coating.

[0052] Step 3: Dissolve polyvinyl alcohol powder in deionized water to obtain a 20% (w / w) polyvinyl alcohol solution; coat the polyvinyl alcohol solution onto the ink-absorbing layer and dry to form a 4 g / m² solution. 2 Surface layer.

[0053] Example 3: A thermal sublimation transfer paper coating and its preparation method, comprising the following steps:

[0054] Step 1:

[0055] 100g of photothermal dual-curing polyurethane emulsion, 0.5g of photoinitiator, and 14g of triethylenetetramine were mixed, coated onto a substrate paper, and cured at 80℃ to form a 2.5g / m² emulsion. 2 Hydrophobic layer; wherein, the preparation method of photothermal dual-curing polyurethane emulsion includes the following steps:

[0056] S11:

[0057] Hydroxyl-terminated polydimethylsiloxane and polyethylene glycol 1000 were vacuum dehydrated at 120℃ for 1 hour. The hydroxyl-terminated polydimethylsiloxane and polyethylene glycol 1000 were then mixed at a weight ratio of 1:9 to obtain a mixed diol. Under nitrogen protection, 2.2 kg of isophorone diisocyanate was added to 3.5 kg of the mixed diol, and the reaction was carried out at 80℃ for 3 hours using dibutyltin dilaurate as a catalyst to obtain a silicon-containing prepolymer. The temperature was lowered to 50℃, and 0.36 kg of 1,4-butanediol was added for chain extension reaction for 1 hour. 1.3 kg of propylene glycol diglycidyl ester was added for end-capping reaction for 2 hours to obtain an epoxy-terminated silicone-containing polyurethane.

[0058] S12: Weigh glycerol and epichlorohydrin, use concentrated sulfuric acid as a catalyst (the amount of concentrated sulfuric acid is 0.5% of the total weight of the reactants), heat to 60°C in a water bath and react for 4 hours. After cooling, add 40% sodium hydroxide solution and react at 40°C for 4 hours. Filter to remove insoluble matter, and remove water by vacuum distillation to obtain glycerol monoglycidyl ether; wherein the molar ratio of glycerol, epichlorohydrin and sodium hydroxide is 1:1:1.

[0059] S13: Polyethylene glycol 1000 was vacuum dehydrated at 120℃ for 1 hour. By weight, 13 kg of isophorone diisocyanate, 10 kg of polyethylene glycol 1000, and 2.5 kg of glycerol monoglycidyl ether were mixed under nitrogen atmosphere. Dibutyltin dilaurate was used as a catalyst, and the mixture was reacted at 80℃ for 3 hours. The temperature was then lowered to 60℃, and 4.2 kg of 2-hydroxyethyl acrylate was added and reacted for 5 hours to obtain double-bond-terminated polyurethane.

[0060] S14: Mix epoxy-terminated silicone polyurethane and double-bond-terminated polyurethane at a mass ratio of 8:1, add triethylamine to neutralize the pH to 7, and emulsify with water to obtain a photothermal dual-curing polyurethane emulsion with a solid content of 40%.

[0061] Step 2: Apply the ink-absorbing coating onto the hydrophobic layer and cure it under ultraviolet light at an exposure energy of 1000 mJ / cm². 2 The curing time is 90 seconds, and the dried product forms an 8g / m³. 2 The ink-absorbing layer; wherein, the preparation method of the ink-absorbing layer coating includes the following steps:

[0062] S21: Mix 5 kg of anhydrous ethanol, 1 kg of deionized water, 60 g of ammonia, and 50 g of 3-mercaptopropyltrimethoxysilane, and stir at 60 °C for 2 h to obtain a mixed solution; add 3 g of nano-silica to 100 g of the mixed solution, ultrasonically disperse for 2 h, filter, rinse with anhydrous ethanol and deionized water, and dry to obtain mercapto-modified silica;

[0063] S22: Dissolve 300g sodium carboxymethyl cellulose and 500g acrylamide monomer in 2kg deionized water, add 4g N,N-methylenebisacrylamide, 10g glutaraldehyde and 5g photoinitiator, stir and add 50g mercapto-modified silica to obtain ink-absorbing coating.

[0064] Step 3: Dissolve polyvinyl alcohol powder in deionized water to obtain a 20% (w / w) polyvinyl alcohol solution; coat the polyvinyl alcohol solution onto the ink-absorbing layer and dry to form a 4 g / m² solution. 2 Surface layer.

[0065] Comparative Example 1: Coating prepared using conventional techniques.

[0066] Mix 40g of nano-silica, 300g of sodium carboxymethyl cellulose, 400g of polyvinyl alcohol, and 2kg of deionized water, coat the mixture onto the surface of a substrate paper, and dry to form a 14.5g / m² mixture. 2 coating.

[0067] Comparative Example 2: No hydrophobic layer was set, and the other parameters were the same as in Example 2.

[0068] Step 1:

[0069] The ink-absorbing coating was applied to the substrate paper and then cured under ultraviolet light at an exposure energy of 900 mJ / cm². 2 The curing time is 75 seconds, and the dried product forms an 8g / m³. 2 The ink-absorbing layer; wherein, the preparation method of the ink-absorbing layer coating includes the following steps:

[0070] S1: Mix 5 kg of anhydrous ethanol, 1 kg of deionized water, 60 g of ammonia, and 50 g of 3-mercaptopropyltrimethoxysilane, and stir at 55 °C for 1.5 h to obtain a mixed solution; add 3 g of nano-silica to 100 g of the mixed solution, ultrasonically disperse for 1.5 h, filter, rinse with anhydrous ethanol and deionized water, and dry to obtain mercapto-modified silica;

[0071] S2: Dissolve 300g sodium carboxymethyl cellulose and 500g acrylamide monomer in 2kg deionized water, add 4g N,N-methylenebisacrylamide, 10g glutaraldehyde and 5g photoinitiator, stir and add 45g mercapto-modified silica to obtain ink-absorbing coating.

[0072] Step 2: Dissolve polyvinyl alcohol powder in deionized water to obtain a 20% (w / w) polyvinyl alcohol solution; coat the polyvinyl alcohol solution onto the ink-absorbing layer and dry to form a 4 g / m² solution. 2 Surface layer.

[0073] Comparative Example 3: An epoxy-terminated silicone polyurethane emulsion was used instead of the photothermal dual-curing polyurethane emulsion, and the remaining parameters were the same as in Example 3.

[0074] Step 1:

[0075] 100g of epoxy-terminated silicone-containing polyurethane emulsion, 0.5g of photoinitiator, and 14g of triethylenetetramine were mixed and coated onto a substrate paper, then cured at 80℃ to form a 2.5g / m² emulsion. 2 A hydrophobic layer; wherein, the preparation method of the epoxy-terminated silicone polyurethane emulsion includes the following steps:

[0076] S11: Hydroxyl-terminated polydimethylsiloxane and polyethylene glycol 1000 were vacuum dehydrated at 120℃ for 1 hour. The hydroxyl-terminated polydimethylsiloxane and polyethylene glycol 1000 were mixed at a weight ratio of 1:9 to obtain a mixed diol. Under nitrogen protection, 2.2 kg of isophorone diisocyanate was added to 3.5 kg of the mixed diol, and the reaction was carried out at 80℃ for 3 hours with dibutyltin dilaurate as a catalyst to obtain a silicon-containing prepolymer. The temperature was lowered to 50℃, and 0.36 kg of 1,4-butanediol was added for chain extension reaction for 1 hour. 1.3 kg of propylene glycol diglycidyl ester was added for end-capping reaction for 2 hours to obtain epoxy-terminated silicone-containing polyurethane.

[0077] S12: Triethylamine is added to epoxy-terminated silicone polyurethane to neutralize the pH to 7, and water is added for emulsification to obtain an epoxy-terminated silicone polyurethane emulsion with a solid content of 40%.

[0078] Step 2: Apply the ink-absorbing coating onto the hydrophobic layer and cure it under ultraviolet light at an exposure energy of 1000 mJ / cm². 2 The curing time is 90 seconds, and the dried product forms an 8g / m³. 2 The ink-absorbing layer; wherein, the preparation method of the ink-absorbing layer coating includes the following steps:

[0079] S21: Mix 5 kg of anhydrous ethanol, 1 kg of deionized water, 60 g of ammonia, and 50 g of 3-mercaptopropyltrimethoxysilane, and stir at 60 °C for 2 h to obtain a mixed solution; add 3 g of nano-silica to 100 g of the mixed solution, ultrasonically disperse for 2 h, filter, rinse with anhydrous ethanol and deionized water, and dry to obtain mercapto-modified silica;

[0080] S22: Dissolve 300g sodium carboxymethyl cellulose and 500g acrylamide monomer in 2kg deionized water, add 4g N,N-methylenebisacrylamide, 10g glutaraldehyde and 5g photoinitiator, stir and add 50g mercapto-modified silica to obtain ink-absorbing coating.

[0081] Step 3: Dissolve polyvinyl alcohol powder in deionized water to obtain a 20% (w / w) polyvinyl alcohol solution; coat the polyvinyl alcohol solution onto the ink-absorbing layer and dry to form a 4 g / m² solution. 2 Surface layer.

[0082] Experiment: Performance tests were conducted on the thermal sublimation transfer papers prepared in Examples 1-3 and Comparative Examples 1-3.

[0083] Coating adhesion: Refer to GB / T9286-1998 Cross-cut test for varnishes and paints.

[0084] Transfer rate: The transfer rate test method is as follows: using a four-color desktop inkjet printer, four-color (100% C, 100% M, 100% Y, 100% K) color block patterns are printed on digital sublimation transfer paper. After drying, the color blocks are transferred to white 100% polyester fabric using a flatbed transfer machine. The transfer temperature is set to 200℃ and the time is 30s. Referring to the requirements for reflection density measurement in the standard GB / T 18722-2002 "Application of Reflection Density Measurement and Colorimetric Measurement in Printing Process Control", the density of the four-color blocks on the fabric after transfer is measured using an X-Rite 528 color density meter, which is the transfer color density; the density of the four-color blocks remaining on the paper after transfer is measured, which is the residual color density. The transfer rate of the four color block patterns is measured on the transfer paper separately and the average value is taken.

[0085] Transfer rate = Transfer color density / (Transfer color density + Residual color density) × 100%.

[0086] Transfer effect: Observe the accuracy of the transferred image and whether there is any ghosting problem.

[0087] The experimental results are shown in Table 1.

[0088] Table 1. Performance Tests of Sublimation Transfer Paper

[0089]

[0090] Conclusions: Data from Examples 1-3 show that the thermal sublimation transfer paper coating prepared by this invention exhibits excellent performance. Data from Example 1 and Comparative Example 1 show that, compared to conventional coatings, the coating of this invention has superior adhesion, achieving a transfer rate of over 90% during thermal transfer, with high pattern accuracy and no ghosting issues. Data from Example 2 and Comparative Example 2 show that the hydrophobic layer in this invention not only improves the adhesion between the substrate paper and the ink-absorbing layer but also prevents dye molecules from binding to the substrate paper, thus improving the thermal sublimation effect of dye molecules and transfer efficiency. Data from Example 3 and Comparative Example 3 show that the presence of double-bond-terminated polyurethane in the photothermal dual-curing polyurethane emulsion strengthens the bond between the formed hydrophobic layer and the ink-absorbing layer, improving the adhesion and compatibility between coatings and resulting in better transfer performance.

[0091] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a thermal sublimation transfer paper coating, characterized in that: Includes the following steps: Step 1: 100 parts of light-heat dual-curing polyurethane emulsion, 0.3-0.5 parts of photoinitiator, 10-14 parts of triethylenetetramine are mixed by weight parts, coated on the base paper, and cured at 70-80°C to form 1-2.5 g / m 2 hydrophobic layer; Step 2: Apply the ink-receptive layer coating to the hydrophobic layer and UV cure, dry to form 5-8 g / m 2 ink-receptive layer; Step 3: Dissolve the polyvinyl alcohol powder in deionized water to obtain a polyvinyl alcohol solution; coat the polyvinyl alcohol solution onto the ink absorption layer and dry to form a 2-4 g / m 2 surface layer; The preparation method of photothermal dual-curing polyurethane emulsion is as follows: epoxy-terminated silicone polyurethane and double-bond-terminated polyurethane are mixed at a mass ratio of (8~10):1, triethylamine is added to neutralize the pH to 7~7.5, and water is added for emulsification to obtain a photothermal dual-curing polyurethane emulsion with a solid content of 30~40%. The preparation method of epoxy-terminated silicone polyurethane is as follows: Hydroxyl-terminated polydimethylsiloxane and polyethylene glycol 1000 are vacuum dehydrated at 100-120℃ for 1-2 hours; the hydroxyl-terminated polydimethylsiloxane and polyethylene glycol 1000 are mixed at a weight ratio of 1:(6-10) to obtain a mixed diol; 2-2.2 parts by weight of isophorone diisocyanate are added to 3-3.5 parts of the mixed diol under nitrogen protection, and the mixture is reacted at 70-80℃ for 2-3 hours using dibutyltin dilaurate as a catalyst to obtain a silicone prepolymer; the temperature is lowered to 40-50℃, and 0.27-0.36 parts of 1,4-butanediol are added for chain extension reaction for 0.5-1 hours; 1.2-1.3 parts of propylene glycol diglycidyl ester are added for end-capping reaction for 1-2 hours to obtain epoxy-terminated silicone polyurethane. A method for preparing double-bond-terminated polyurethane includes the following steps: S1: Weigh glycerol and epichlorohydrin, use concentrated sulfuric acid as catalyst, heat to 50-60℃ in a water bath and react for 3-4 hours. After cooling, add 30-40% sodium hydroxide solution and react at 30-40℃ for 3-4 hours. Filter to remove insoluble matter and remove water by vacuum distillation to obtain glycerol monoglycidyl ether. S2: Polyethylene glycol 1000 is vacuum dehydrated at 100~120℃ for 1~2h. By weight, 11~15 parts of isophorone diisocyanate, 10 parts of polyethylene glycol 1000, and 2~3 parts of glycerol monoglycidyl ether are mixed under nitrogen atmosphere. Dibutyltin dilaurate is used as a catalyst and the mixture is reacted at 70~80℃ for 1~3h. The temperature is then lowered to 50~60℃, and 3~4.5 parts of 2-hydroxyethyl acrylate are added and reacted for 4~5h to obtain double-bond-terminated polyurethane.

2. The method for preparing a thermal sublimation transfer paper coating according to claim 1, characterized in that: In S1, the molar ratio of glycerol, epichlorohydrin, and sodium hydroxide is 1:1:

1.

3. The method for preparing a thermal sublimation transfer paper coating according to claim 1, characterized in that: The preparation method of the ink-absorbing layer coating is as follows: by weight, 30-50 parts of sodium carboxymethyl cellulose and 50-70 parts of acrylamide monomer are dissolved in 200 parts of deionized water, 0.3-0.5 parts of N,N-methylenebisacrylamide, 1-1.2 parts of glutaraldehyde, and 0.5-0.7 parts of photoinitiator are added, and 4-5 parts of mercapto-modified silica are added while stirring to obtain the ink-absorbing layer coating.

4. The method for preparing a thermal sublimation transfer paper coating according to claim 3, characterized in that: The preparation method of mercapto-modified silica is as follows: Take 5 parts by weight of anhydrous ethanol, 1 part of deionized water, 0.03-0.06 parts of ammonia water, and 0.02-0.05 parts of 3-mercaptopropyltrimethoxysilane and mix them. Stir at 50-60℃ for 1-2 hours to obtain a mixed solution. Add 2-3 parts of nano-silica to 100 parts of the mixed solution, disperse by ultrasonication for 1-2 hours, filter, wash with anhydrous ethanol and deionized water, and dry to obtain mercapto-modified silica.

5. The method for preparing a thermal sublimation transfer paper coating according to claim 1, characterized in that: In step 2, during UV curing, the exposure energy is 800~1000 mJ / cm². 2 The curing time is 60~90s.

6. The method for preparing a thermal sublimation transfer paper coating according to claim 1, characterized in that: The mass concentration of the polyvinyl alcohol solution is 15%~20%.

7. The thermal sublimation transfer paper coating prepared by the preparation method according to any one of claims 1 to 6.

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