Digital painting heat transfer printing body paper and preparation process thereof

Abstract

The invention relates to the technical field of papermaking, and particularly provides a preparation process of digital inkjet printing heat transfer printing body paper, the digital inkjet printing heat transfer printing body paper sequentially comprises an ink absorption coating, a body paper layer and a stable layer from top to bottom, the preparation process comprises the following steps: S100, adding a papermaking additive into beaten bleached chemical pulp, and stirring to obtain a slurry; making paper on a net, and drying to obtain a raw paper layer; s200, after at least part of the upper surface of the body paper layer is coated with ink absorption coating paint, first drying treatment is carried out, and the body paper layer with an ink absorption coating is obtained; and S300, after at least part of the lower surface of the body paper layer is coated with the stable layer coating, second drying treatment is carried out, and the digital inkjet heat transfer printing body paper is obtained. According to the digital inkjet heat transfer printing body paper, the upper coating and the lower coating are symmetrically designed, so that the paper is not prone to deformation under damp and hot stress, color fixation can be rapidly achieved, ink is prevented from permeating into the deep position of a paper base, warping and shrinkage can be reduced at the high temperature, and it is guaranteed that patterns are accurately transferred and do not deform.

Description

Technical Field

[0001] The present invention relates to the technical field of papermaking, and in particular to a digital inkjet thermal transfer base paper and a preparation process thereof. Background Art

[0002] Digital inkjet thermal transfer paper is specially coated to withstand the application of digital inkjet inks (primarily sublimation inks) while providing excellent thermal transfer properties. During the transfer process, the ink sublimates into a vaporous state and penetrates the substrate, permanently attaching the image.

[0003] At present, digital inkjet thermal transfer base paper is usually prepared by directly coating the surface of the base paper layer with a functional coating to give the base paper layer the ability to control ink diffusion, increase ink absorption and drying speed; however, with the development of printing technology, the current digital inkjet thermal transfer base paper is still poor in terms of ink absorption performance and coating stability, making it difficult to adapt to the current printing process, resulting in low quality of printed products.

[0004] Therefore, there is an urgent need to provide a digital inkjet thermal transfer base paper and a preparation process thereof to meet the needs of the current market. Summary of the Invention

[0005] The present invention aims to solve at least one of the above problems.

[0006] The present invention provides a preparation process of digital inkjet thermal transfer base paper. The digital inkjet thermal transfer base paper comprises, from top to bottom, an ink-absorbing coating, a base paper layer, and a stabilizing layer. The preparation process comprises the following steps: S100, adding papermaking additives to the bleached chemical pulp after beating, making paper on a screen, and drying it to obtain a base paper layer; S200, coating at least a portion of the upper surface of the base paper layer with an ink-absorbing coating, and then performing a first drying process to obtain a base paper layer having an ink-absorbing coating; S300, coating at least a portion of the lower surface of the base paper layer with a stabilizing layer coating, and then performing a second drying process to obtain a digital inkjet thermal transfer base paper; The beating degree of bleached chemical pulp is 38-45°SR; the weight of the base paper layer is 30-35g / m 2 .

[0007] In the above technical features, the bleached chemical pulp includes bleached coniferous pulp, bleached broadleaf pulp, bleached bamboo pulp and bleached waste paper pulp; and / or the papermaking auxiliaries include wet strength agents, fillers, sizing agents, retention and drainage aids and defoaming agents.

[0008] In any of the above technical features, the mass ratio of bleached coniferous pulp, bleached broadleaf pulp, bleached bamboo pulp and bleached waste paper pulp is 1: (1.8-2): (0.5-0.6): (0.2-0.3).

[0009] In any of the above technical features, in step S200, the preparation process of the ink-absorbing coating material includes the following steps: S201, adding polyvinyl alcohol to hot water, stirring until the polyvinyl alcohol is completely dissolved, continuing the stirring, and adding silica sol during the stirring process, adjusting the pH, to obtain a first mixed solution; S202, adding a dispersant, a defoaming agent and a thickener to the first mixed liquid in sequence to obtain an ink-absorbing coating.

[0010] In any of the above technical features, the pH is adjusted to 6.5-8.0; and / or the viscosity of the ink-absorbing coating is 100-300 mPa·s.

[0011] In any of the above technical features, in step S300, the preparation process of the stabilization layer coating includes the following steps: S301, adding the filler into distilled water for pre-dispersion treatment to obtain a filler dispersion; S302, adding a film-forming agent and a friction modifier to the filler dispersion in sequence, stirring evenly, and adjusting the pH to obtain a stable layer coating; The filler includes at least one of talc, light calcium carbonate, kaolin and bentonite, or a combination thereof; and the film-forming agent includes at least one of gelatinized starch, VAE emulsion or acrylic copolymer, or a combination thereof.

[0012] In any of the above technical features, the particle size of the filler is 0.5-2 μm; and / or the pH is adjusted to 6.0-8.0; and / or the viscosity of the stabilization layer coating is 80-150 mPa·s.

[0013] In any of the above technical features, the temperature of the first drying treatment is 50-110°C; and / or the temperature of the second drying treatment is 60-90°C.

[0014] In any of the above technical features, the thickness of the ink-absorbing coating is 2-3 μm; and / or the thickness of the base paper layer is 25-30 μm; and / or the thickness of the stabilizing layer is 1-2 μm.

[0015] The present invention also provides a digital inkjet thermal transfer base paper, which is prepared using a preparation process according to any one of the above technical features. Therefore, the beneficial effects of any of the above technical solutions are included and will not be elaborated here.

[0016] After adopting the technical solution of the present invention, the technical effects that can be achieved are as follows: 1. The symmetrical design of the upper and lower coatings on the digital inkjet thermal transfer base paper of this invention makes the paper less susceptible to deformation under moist heat stress. This not only allows for rapid color fixation and prevents ink from penetrating deep into the paper base, ensuring sharp edges and saturated colors, but also reduces warping and shrinkage at high temperatures, ensuring accurate and distortion-free pattern transfer. 2. The base paper layer provides overall mechanical strength, maintains paper flatness, and withstands the thermal stress of high-speed printing and transfer. It is made of bleached chemical pulp with a dense fiber network and high strength. The ink-absorbing coating is applied to the upper surface of the base paper layer, which can quickly absorb inkjet dyes and inks, fix pigment particles, prevent ink diffusion, and improve image clarity. The stabilizing layer is applied to the lower surface of the base paper layer to prevent paper warping and curling during transfer, balance the upper and lower surface tension of the paper, and improve paper feed performance and thermal stability. 3. In the preparation process, after the base paper layer is prepared, the ink-absorbing coating and the stabilizing layer coating are coated separately to avoid warping caused by wetting of the front and back surfaces at the same time. DETAILED DESCRIPTION

[0017] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below in conjunction with specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other.

[0018] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below.

[0020] In related technologies, digital inkjet thermal transfer base paper is a specially coated paper that can withstand the application of digital inkjet inks (primarily sublimation inks) while also exhibiting excellent thermal transfer properties. Currently, digital inkjet thermal transfer base paper is typically prepared by applying a functional coating directly to the surface of the base paper layer. This coating imparts the ability to control ink diffusion, increase ink absorption, and increase drying speed. However, with the advancement of printing technology, current digital inkjet thermal transfer base paper still exhibits poor ink absorption and coating stability, making it difficult to adapt to current printing processes, resulting in low-quality printed products.

[0021] In view of this, the present invention provides a digital inkjet thermal transfer base paper and a preparation process thereof. By coating an ink-absorbing layer on the upper surface of the base paper layer and further providing a stabilizing layer on the lower surface of the base paper layer, the stability, printing adaptability and other capabilities of the digital inkjet thermal transfer base paper are improved, and the base paper layer still has high performance at a lower grammage, meeting the requirements of green environmental protection.

[0022] Specifically, this embodiment provides a preparation process for digital inkjet thermal transfer base paper. The digital inkjet thermal transfer base paper comprises, from top to bottom, an ink-absorbing coating, a base paper layer, and a stabilizing layer. The preparation process includes the following steps: S100, adding papermaking additives to the bleached chemical pulp after beating, making paper on a screen, and drying it to obtain a base paper layer; S200, coating at least a portion of the upper surface of the base paper layer with an ink-absorbing coating, and then performing a first drying process to obtain a base paper layer having an ink-absorbing coating; S300: After coating at least a portion of the lower surface of the base paper layer with a stabilizing layer coating, a second drying process is performed to obtain a digital inkjet thermal transfer base paper.

[0023] Preferably, the digital inkjet thermal transfer base paper of the present invention comprises three layers: an ink-absorbing coating, a base paper layer, and a stabilizing layer. The base paper layer provides overall mechanical strength, maintains the flatness of the paper, and withstands the temperature stress of high-speed printing and transfer. It is made of bleached chemical pulp with a dense fiber network and high strength. The grammage of the base paper layer is preferably 30-35 g / m 2 , which can reduce the cost and energy consumption of the thermal transfer process while maintaining sufficient tensile strength and dimensional stability; the ink-absorbing coating is coated on the upper surface of the base paper layer, which can quickly absorb inkjet dyes and inks, fix pigment particles, prevent ink diffusion, and improve image clarity; the stabilizing layer is coated on the lower surface of the base paper layer to prevent paper warping and curling during transfer, balance the upper and lower surface tensions of the paper, and improve paper feeding performance and thermal stability; the overall symmetrical design of the upper and lower coatings of the digital inkjet thermal transfer base paper makes the paper less likely to deform under wet and hot stress. It can quickly fix the color and prevent the ink from penetrating deep into the paper base, ensuring sharp edges and saturated colors of the pattern, and can reduce warping and shrinkage at high temperatures to ensure accurate pattern transfer without deformation.

[0024] Preferably, in the process of preparing digital inkjet thermal transfer base paper, the bleached chemical pulp is first beaten. The bleached chemical pulp uses a pulp with a beating degree of 38-45°SR. Beating can enhance the internal hydrogen bonds of the paper, improve the dry strength and wet strength, and control the thermal deformation of the paper during the transfer process. At this beating degree, the fibers can be refined, the bonding between the fibers can be improved, and a smooth and dense paper surface can be formed, which is conducive to the uniform spreading of the ink-absorbing coating. Increasing the fiber density can reduce the capillary structure and prevent excessive penetration of the ink into the bottom layer. If the beating degree is excessive, the paper will be too dense, affecting the ink absorption and peeling performance, and affecting drainage, and increasing the energy consumption of paper drying. Therefore, the beating degree needs to be strictly controlled during the preparation process. Bleached chemical pulp includes bleached coniferous pulp, bleached broadleaf pulp, bleached bamboo pulp and bleached waste paper pulp, and the mass ratio of bleached coniferous pulp, bleached broadleaf pulp, bleached bamboo pulp and bleached waste paper pulp is 1: (1.8-2): (0.5-0.6): (0.2-0.3). Bleached coniferous pulp provides the main mechanical strength skeleton and can still maintain good tensile and folding resistance under low grammage conditions. Bleached broadleaf pulp significantly improves the smoothness and surface uniformity of paper, reduces the amount of ink-absorbing layer coating and improves coating uniformity. Since inkjet thermal transfer base paper has extremely high requirements for surface micro-flatness, it is necessary to add more bleached broadleaf pulp. Bleached bamboo pulp increases the rigidity and The paper can maintain its volume and stiffness at low grammage. At the same time, the tubular structure of bamboo pulp fiber can improve air permeability and help the coating dry evenly. Bleached waste paper pulp can reduce costs by improving the wettability of the paper base to the coating liquid through its high water absorption. Selecting less bleached waste paper pulp can avoid excessive short fibers that reduce the overall strength and cleanliness. Papermaking additives are added after beating and added to the wet pulp to optimize the fiber surface properties and internal structure simultaneously. Papermaking additives include wet strength agents, fillers, sizing agents, retention and filtration aids and defoaming agents. Wet strength agents can improve wet strength and prevent cracking or stratification during coating / printing. The dosage is usually 0.5-1.0% of the dry pulp mass. Fillers can reduce The dosage is usually 10-20% of the dry pulp mass to improve the cost, improve the smoothness, and adjust the pore structure of the paper. The sizing agent can increase the water resistance of the paper surface and prevent capillary penetration and coating penetration. The dosage is usually 0.5-2.0% of the dry pulp mass. In order to improve the retention rate of fillers, fine fibers and additives, reduce white water loss, improve cost efficiency, prevent additive agglomeration or bubble generation, and ensure the uniformity of the paper, it is necessary to further add retention aids, drainage aids and defoamers. The dosage is determined according to actual conditions and is not specifically limited here. Finally, the paper is made into paper on the net and dried. The base paper layer obtained in this way can ensure the high strength, appropriate water absorption and flatness of the paper base, providing a stable base for the coating layer.

[0025] Preferably, after the preparation of the base paper layer, further surface coating of the base paper layer with ink-absorbing coating paint and first drying treatment are required to improve the mechanical bite of the coating layer with the fibers by utilizing the unsealed pores of the paper base to form an ink-absorbing coating layer on the surface of the base paper layer. The preparation process of the ink-absorbing coating paint comprises the following steps: S201, polyvinyl alcohol is added to hot water, and stirring treatment is performed until the polyvinyl alcohol is completely dissolved. The stirring treatment is continued, and silica sol is added during the stirring treatment. The pH is adjusted to obtain a first mixed solution; S202, a dispersing agent, a defoaming agent and a thickening agent are sequentially added to the first mixed solution to obtain an ink-absorbing coating paint.

[0026] Preferably, polyvinyl alcohol (PVA) is first added to hot water and completely dissolved. This is because PVA, as a film-forming agent and adhesive, is the main skeleton material of the coating layer. It can only be completely dissolved at a high temperature to form a uniform molecular chain network. If the dissolution is not sufficient, it will lead to uneven film formation, strength reduction and ink-absorbing layer powdering. The temperature of the hot water is preferably 85-95°C. Silica sol is an inorganic nano-particle, which is mainly used to build a microporous structure, improve the ink-absorbing speed and prevent color bleeding. It must be added after PVA is completely dissolved to form a stable liquid phase system. In this way, the particles can be prevented from aggregating and settling under high temperature or high shear conditions. If silica sol is added first and then PVA is dissolved by heating, the silica sol particles will lose stability due to temperature changes and pH fluctuations, causing flocculation and uneven distribution. The stability of silica sol is closely related to the pH. Adjusting the pH to 6.5-8.0 can prevent colloid aggregation and also optimize the interaction between PVA and silica sol, so that the coating layer forms a tough and porous film structure. The dispersing agent can promote the uniform dispersion of particles such as silica sol in the PVA matrix, prevent agglomeration, and improve the micro-uniformity of the coating layer and the controllability of the ink-absorbing layer pore structure. It must be added after the system is stable to effectively adsorb on the particle surface. The defoaming agent can remove the air bubbles introduced by stirring during the preparation process to avoid pinholes and shrinkage holes on the surface of the coating layer, ensuring the smoothness of the coating surface. The dispersing agent is added after the defoaming agent to precisely eliminate the formed foam without affecting the dispersion effect. The thickening agent can adjust the viscosity of the paint. The viscosity of the ink-absorbing coating paint can be adjusted to 100-300 mPa·s by adding the thickening agent according to the actual situation.

[0027] Furthermore, after the ink-absorbing coating is applied to the upper surface of the base paper layer, a first drying treatment is required. The first drying treatment is a zoned drying treatment. The first zone is a pre-drying treatment with a temperature of 50-65°C. The purpose is to evaporate surface moisture and prevent skinning; the second zone is a main drying treatment with a temperature of 70-90°C. The purpose is to quickly take away the main moisture and condense into a film structure; the third zone is a setting drying treatment with a temperature of 90-110°C. The purpose is to promote cross-linking of the film-forming agent to form a film and enhance adhesion; according to actual needs, a fourth zone slow cooling treatment can be added after the setting drying treatment with a temperature of 40-50°C. The purpose is to balance the moisture of the paper and prevent shrinkage and curling.

[0028] Preferably, after the ink-absorbing coating is formed in the first drying process, a stabilizing layer coating is applied to the lower surface of the base paper layer, that is, the other surface of the base paper layer opposite to the ink-absorbing coating, and a second drying process is performed. The temperature is 60-90°C. At this temperature, the film-forming agent is prevented from forming a film too quickly, resulting in uneven migration of internal moisture and cracking of the coating. The starch-based film-forming agent is prevented from becoming brittle after gelatinization. The coating is ensured to be evenly dried and have stable surface friction properties to form a stabilizing layer. The ink-absorbing coating and the stabilizing layer coating are applied separately to avoid warping caused by simultaneous wetting of the front and back surfaces. The stabilizing layer provides final dimensional stability and heat resistance, ensuring a stable paper shape during the subsequent thermal transfer process. The preparation process of the stabilizing layer coating includes the following steps: S301, adding the filler into distilled water for pre-dispersion treatment to obtain a filler dispersion; S302, adding a film-forming agent and a friction modifier to the filler dispersion in sequence, stirring evenly, adjusting the pH, and obtaining a stable layer coating.

[0029] Preferably, since the filler surface has different degrees of hydrophobicity or agglomeration tendency, if the film-forming agent system is directly added, lumps will be formed, resulting in local uneven coating. Therefore, the filler needs to be pre-dispersed to make it evenly dispersed in water, establish a stable aqueous phase system in advance, reduce the risk of agglomeration when subsequent components are added, and create conditions for the effective coating of subsequent film-forming agents and particles; the filler is preferably at least one of talcum powder, light calcium carbonate, kaolin and bentonite or a combination thereof, and the particle size is preferably 0.5-2μm. These fillers can provide mechanical strength, dimensional stability and folding resistance of the back coating; increase the weight and stiffness of the coating and inhibit paper curling; then add the film-forming agent to form a continuous phase of the coating, firmly bind the filler particles, and provide toughness and folding resistance. The film-forming agent is added after the filler is evenly dispersed to avoid premature increase in the viscosity of the film-forming agent, which affects the dispersion effect of the filler. The film-forming agent is preferably at least one of gelatinized starch, VAE emulsion or acrylic copolymer, or a combination thereof. Gelatinized starch is low in price and has good film-forming properties, but has poor water resistance. It can be compounded with other film-forming agents to improve performance. VAE emulsion has good toughness and high bonding strength, and is suitable for improving the folding and wear resistance of the coating. Acrylic copolymer has excellent water resistance and weather resistance, and can improve the long-term stability of the back coating. Finally, a friction modifier is added. The friction modifier must be added after the film-forming agent is evenly distributed to ensure that the modifier is evenly distributed on the surface and internal structure of the coating. It can improve the friction coefficient when the back contacts the equipment conveyor belt and roller to prevent slipping or sticking. After stirring evenly, the pH is adjusted to 6.0-8.0. At this time, the film-forming agent has the best stability, and no gelation or stratification will occur. A stable layer coating with good performance can be obtained, and the viscosity of the stable layer coating is 80-150 mPa·s.

[0030] Preferably, the ink-absorbing coating is to quickly absorb moisture and dyes / pigments in the inkjet ink, keep the pattern edge clear, prevent diffusion or bleeding, and provide sufficient coloring depth and saturation. If it is less than 2μm, the ink absorption capacity is insufficient, ink accumulation, slow drying, and edge feathering occur. If it is greater than 3μm, the ink penetrates too much in the vertical direction, the surface color density decreases, the pattern becomes weak, and the coating is prone to cracking. Therefore, the thickness of the ink-absorbing coating is preferably 2-3μm; the base paper layer provides overall mechanical strength and stiffness, supports the double-sided coating, withstands certain thermal stress and tension during thermal transfer, and ensures that the paper does not deform during drying and curling. If the thickness is less than 25μm, the mechanical strength is insufficient and it is easy to break and curl. A thickness greater than 30μm will lead to a decrease in flexibility, a decrease in transfer efficiency, and an increase in drying energy consumption. Therefore, the thickness of the base paper layer is preferably 25-30μm; the stabilizing layer is used to adjust the back friction coefficient, inhibit paper curling caused by uneven evaporation of water, and increase the flatness and dimensional stability of the paper. The thickness is preferably 1-2μm.

[0031] Example 1 The embodiment provides a digital inkjet thermal transfer base paper, which comprises, from top to bottom, an ink absorption coating layer, a base paper layer and a stabilizing layer, wherein the thickness of the ink absorption coating layer is 2 microns, the thickness of the base paper layer is 25 microns, and the thickness of the stabilizing layer is 1 micron; and the preparation process comprises the following steps: S100, after adding papermaking additives to bleached chemical pulp after beating, the paper is formed on a wire and dried to obtain a base paper layer; S200, after coating at least part of the upper surface of the base paper layer with ink absorption coating, first drying treatment is performed, the first drying treatment is zoned drying treatment, the first temperature is 50 DEG C, the second temperature is 70-90 DEG C, and the third zone temperature is 90 DEG C, to obtain a base paper layer with an ink absorption coating; S300, after coating at least part of the lower surface of the base paper layer with a stabilizing layer coating, second drying treatment is performed at 60 DEG C to obtain a digital inkjet thermal transfer base paper; The beating degree of the bleached chemical pulp is 38 SR; the grammage of the base paper layer is 30 g / m 2 The bleached chemical pulp comprises bleached coniferous wood pulp, bleached broad-leaved wood pulp, bleached bamboo pulp and bleached waste paper pulp, and the mass ratio is 1:1.8:0.5:0.2; the papermaking additives comprise wet strength agent, filler, sizing agent, retention and drainage aid and defoaming agent.

[0032] Embodiment 2 The embodiment provides a digital inkjet thermal transfer base paper, which comprises, from top to bottom, an ink absorption coating layer, a base paper layer and a stabilizing layer, wherein the thickness of the ink absorption coating layer is 2 microns, the thickness of the base paper layer is 25 microns, and the thickness of the stabilizing layer is 1 micron; and the preparation process comprises the following steps: S100, after adding papermaking additives to bleached chemical pulp after beating, the paper is formed on a wire and dried to obtain a base paper layer; S200, after coating at least part of the upper surface of the base paper layer with ink absorption coating, first drying treatment is performed, the first drying treatment is zoned drying treatment, the first temperature is 50 DEG C, the second temperature is 70 DEG C, and the third zone temperature is 90 DEG C, to obtain a base paper layer with an ink absorption coating; S300, after coating at least part of the lower surface of the base paper layer with a stabilizing layer coating, second drying treatment is performed at 60 DEG C to obtain a digital inkjet thermal transfer base paper; The beating degree of the bleached chemical pulp is 45 SR; the grammage of the base paper layer is 35 g / m 2 The bleached chemical pulp comprises bleached coniferous wood pulp, bleached broad-leaved wood pulp, bleached bamboo pulp and bleached waste paper pulp, and the mass ratio is 1:2:0.6:0.3; the papermaking additives comprise wet strength agent, filler, sizing agent, retention and drainage aid and defoaming agent; the viscosity of the ink absorption coating is 100 mPa·s, the viscosity of the stabilizing layer coating is 80 mPa·s, and the preparation process of the ink absorption coating comprises the following steps: S201, polyvinyl alcohol is added to 85℃ hot water, stirring treatment until polyvinyl alcohol is completely dissolved, continue stirring treatment, and add silica sol in the process of stirring treatment, adjust pH to 6.5, to obtain a first mixed solution; S202, dispersant, defoaming agent and thickening agent are sequentially added to the first mixed solution to obtain an ink absorption coating; The preparation process of the stable layer coating includes the following steps: S301, light calcium carbonate with a particle size of 0.5μm is added to distilled water for pre-dispersion treatment to obtain a filler dispersion liquid; S302, starch and friction modifier are sequentially added to the filler dispersion liquid, stirring is uniform, and pH is adjusted to 6.0 to obtain a stable layer coating.

[0033] Example 3 The present embodiment provides a digital inkjet thermal transfer base paper, which comprises, from top to bottom, an ink absorption coating, a base paper layer and a stable layer, the thickness of the ink absorption coating is 2μm, the thickness of the base paper layer is 30μm, and the thickness of the stable layer is 2μm, and the preparation process includes the following steps: S100, after adding papermaking additives to the bleached chemical pulp after beating, the pulp is formed into paper on a wire and dried to obtain a base paper layer; S200, after coating at least part of the upper surface of the base paper layer with the ink absorption coating, first drying treatment is performed, the first drying treatment is a zoned drying treatment, the first temperature is 65℃, the second temperature is 80℃, the third zone temperature is 100℃, and the fourth zone temperature is 50℃, to obtain a base paper layer with an ink absorption coating; S300, after coating at least part of the lower surface of the base paper layer with the stable layer coating, second drying treatment is performed at 80℃ to obtain a digital inkjet thermal transfer base paper; Wherein, the beating degree of the bleached chemical pulp is 42°SR; the grammage of the base paper layer is 33g / m 2 , the bleached chemical pulp includes bleached coniferous pulp, bleached broadleaf pulp, bleached bamboo pulp and bleached waste paper pulp, the mass ratio is 1:1.9:0.6:0.3, the papermaking additives include wet strength agent, filler, sizing agent, retention and drainage aid and defoaming agent; the viscosity of the ink absorption coating is 300mPa·s, the viscosity of the stable layer coating is 150mPa·s, and the preparation process of the ink absorption coating includes the following steps: S201, polyvinyl alcohol is added to 85℃ hot water, stirring treatment until polyvinyl alcohol is completely dissolved, continue stirring treatment, and add silica sol in the process of stirring treatment, adjust pH to 8.0, to obtain a first mixed solution; S202, dispersant, defoaming agent and thickening agent are sequentially added to the first mixed solution to obtain an ink absorption coating; The preparation process of the stabilization layer coating includes the following steps: S301, adding talc powder with a particle size of 2 μm into distilled water for pre-dispersion treatment to obtain a filler dispersion; S302, sequentially adding VAE emulsion and friction modifier to the filler dispersion, stirring evenly, adjusting the pH to 8.0, and obtaining a stabilizing layer coating.

[0034] Example 4 This embodiment provides a digital inkjet thermal transfer base paper, which comprises, from top to bottom, an ink-absorbing coating, a base paper layer, and a stabilizing layer. The thickness of the ink-absorbing coating is 3 μm, the thickness of the base paper layer is 28 μm, and the thickness of the stabilizing layer is 2 μm. The preparation process includes the following steps: S100, adding papermaking additives to the bleached chemical pulp after beating, making paper on a screen, and drying it to obtain a base paper layer; S200, after coating at least a portion of the upper surface of the base paper layer with an ink-absorbing coating, performing a first drying process, wherein the first drying process is a zoned drying process with a first temperature of 60° C., a second temperature of 90° C., a third zone temperature of 110° C., and a fourth zone temperature of 40° C., to obtain a base paper layer having an ink-absorbing coating; S300, coating at least a portion of the lower surface of the base paper layer with a stabilizing layer coating, and then performing a second drying process at 90° C. to obtain a digital inkjet thermal transfer base paper; The beating degree of bleached chemical pulp is 40°SR; the weight of the base paper layer is 32g / m 2 The bleached chemical pulp includes bleached softwood pulp, bleached hardwood pulp, bleached bamboo pulp, and bleached waste paper pulp in a mass ratio of 1:1.9:0.6:0.3. The papermaking additives include a wet strength agent, a filler, a sizing agent, a retention and drainage aid, and a defoaming agent. The viscosity of the ink-absorbing coating is 200 mPa·s, and the viscosity of the stabilizing layer coating is 100 mPa·s. The preparation process of the ink-absorbing coating includes the following steps: S201, adding polyvinyl alcohol to 95° C. hot water, stirring until the polyvinyl alcohol is completely dissolved, continuing the stirring, and adding silica sol during the stirring process, adjusting the pH to 7.0, to obtain a first mixed solution; S202, adding a dispersant, a defoaming agent, and a thickener to the first mixed liquid in sequence to obtain an ink-absorbing coating; The preparation process of the stabilization layer coating includes the following steps: S301, adding kaolin and bentonite with a particle size of 1.5 μm into distilled water for pre-dispersion treatment to obtain a filler dispersion; S302, adding acrylic copolymer and friction modifier to the filler dispersion in sequence, stirring evenly, adjusting the pH to 7.0, and obtaining a stabilizing layer coating.

[0035] Performance Testing Taking commercially available digital inkjet thermal transfer base paper as a comparative example, the following tests were conducted on the digital inkjet thermal transfer base paper of Examples 1-4 and the comparative example: Thermal transfer rate test: Using a fixed amount of ink and the same pattern, the digital inkjet thermal transfer base paper was allowed to equilibrate for 2 hours at a temperature of 23±1°C and a humidity of 50±5%. The heat press temperature was 200°C, the pressure was 0.25MPa, and the printing time was 30 seconds. After printing and before transfer, the color density of five fixed locations on the base paper was measured. Each color was measured separately. After transfer, the color density of the corresponding location on the substrate was measured. The remaining color density on the base paper was also measured again. The color density value of each point was recorded and the thermal transfer rate was calculated. At least five points were selected for each group, and the average value was taken. Longitudinal tensile strength test: Use a paper tensile testing machine to stretch the paper at a speed of 20 mm / min until the sample breaks, and then calculate the longitudinal tensile strength; Ink absorption time test: Cut a 30mm×30mm sample and drop a drop of ink vertically onto the sample surface using a micro syringe. Record the time when the edge of the drop stops expanding and the surface gloss disappears or stops flowing. Surface roughness test: Use a stylus roughness tester to test the surface roughness; The test results are shown in Table 1: Table 1 As can be seen from Table 1, all properties of Examples 1-4 are better than those of the comparative example, indicating that the digital inkjet thermal transfer base paper and the preparation method thereof of the present invention can bring better performance. The surface of the digital inkjet thermal transfer base paper of the present invention is smoother, which is conducive to printing resolution and ink dot restoration. The color saturation and efficiency after transfer are significantly improved, the inkjet compatibility is improved, and the longitudinal tensile strength is high, indicating that the digital inkjet thermal transfer base paper of the present invention can ensure high strength even at a lower grammage.

[0036] Throughout this specification, terms such as "one embodiment," "some embodiments," and "specific embodiments" mean that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0037] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A process for preparing digital inkjet thermal transfer base paper, characterized in that: The digital inkjet thermal transfer base paper comprises, from top to bottom, an ink-absorbing coating, a base paper layer, and a stabilizing layer. The preparation process comprises the following steps: S100, adding papermaking additives to the bleached chemical pulp after beating, making paper on a screen, and drying it to obtain a base paper layer; S200, coating at least a portion of the upper surface of the base paper layer with an ink-absorbing coating, and then performing a first drying process to obtain a base paper layer having an ink-absorbing coating; S300, coating at least a portion of the lower surface of the base paper layer with a stabilizing layer coating, and then performing a second drying process to obtain the digital inkjet thermal transfer base paper; Wherein, the beating degree of the bleached chemical pulp is 38-45°SR; The base paper layer has a grammage of 30-35 g / m 2 .

2. The preparation process according to claim 1, characterized in that The bleached chemical pulp includes bleached softwood pulp, bleached hardwood pulp, bleached bamboo pulp and bleached waste paper pulp; and / or The papermaking auxiliary agents include wet strength agents, fillers, sizing agents, retention and drainage aids and defoaming agents.

3. The preparation process according to claim 2, characterized in that The mass ratio of the bleached coniferous pulp, the bleached hardwood pulp, the bleached bamboo pulp and the bleached waste paper pulp is 1:(1.8-2):(0.5-0.6):(0.2-0.3).

4. The preparation process according to claim 1, characterized in that In step S200, the preparation process of the ink-absorbing coating material includes the following steps: S201, adding polyvinyl alcohol to hot water, stirring until the polyvinyl alcohol is completely dissolved, continuing the stirring process, and adding silica sol during the stirring process, adjusting the pH, to obtain a first mixed solution; S202: adding a dispersant, a defoaming agent, and a thickener to the first mixed liquid in sequence to obtain the ink-absorbing coating.

5. The preparation process according to claim 4, characterized in that: The pH is adjusted to 6.5-8.0; and / or The viscosity of the ink-absorbing coating is 100-300 mPa·s.

6. The preparation process according to claim 1, characterized in that In step S300, the preparation process of the stabilization layer coating includes the following steps: S301, adding the filler into distilled water for pre-dispersion treatment to obtain a filler dispersion; S302, adding a film-forming agent and a friction modifier to the filler dispersion in sequence, stirring evenly, and adjusting the pH to obtain the stabilizing layer coating; Wherein, the filler comprises at least one of talc, light calcium carbonate, kaolin and bentonite or a combination thereof; The film-forming agent includes at least one of gelatinized starch, VAE emulsion or acrylic copolymer or a combination thereof.

7. The preparation process according to claim 6, characterized in that: The particle size of the filler is 0.5-2 μm; and / or The pH is adjusted to 6.0-8.0; and / or The viscosity of the stabilizing layer coating is 80-150 mPa·s.

8. The preparation process according to claim 1, characterized in that The temperature of the first drying treatment is 50-110°C; and / or The temperature of the second drying treatment is 60-90°C.

9. The production process according to claim 1, characterized in that: The thickness of the ink-absorbing coating is 2-3 μm; and / or The base paper layer has a thickness of 25-30 μm; and / or The thickness of the stabilizing layer is 1-2 μm.

10. A digital inkjet thermal transfer base paper, characterized in that: The digital inkjet thermal transfer base paper is prepared using the preparation process described in any one of claims 1 to 9.

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