Preparation method of thermal sublimation transfer printing paper coating composition containing polysaccharide-based material

Abstract

The present invention relates to the field of heat transfer printing technology, and discloses a method for preparing a heat sublimation transfer printing paper coating composition containing a polysaccharide-based material, comprising the following steps: (1) acid-hydrolyzing starch with an alcohol acid solution to obtain acid-hydrolyzed starch; (2) mixing the acid-hydrolyzed starch with an oxidizing agent, performing an oxidation reaction, and then performing an alkalization treatment to obtain an alkalized starch; (3) mixing the alkalized starch with an etherifying agent, performing an etherification reaction, and obtaining a polysaccharide-based material; and (4) mixing the polysaccharide-based material with an auxiliary agent to obtain a heat sublimation transfer printing paper coating composition. The heat sublimation transfer printing paper coating composition obtained by the preparation method of the present invention can meet the requirements of heat sublimation transfer printing and achieve an ideal effect without adding low-viscosity and high-substitution CMC, thereby effectively reducing the cost of the heat sublimation transfer printing paper coating.

Description

Technical Field

[0001] The invention relates to the technical field of heat transfer printing, in particular to a method for preparing a heat sublimation transfer printing paper coating composition containing a polysaccharide-based material. Background Art

[0002] Thermal transfer printing technology has been widely adopted due to its advantages, including a short process flow, fine patterns, high flexibility, and low wastewater discharge. Four main methods of thermal transfer printing exist: sublimation, swimming transfer, melting, and ink layer peeling. Sublimation is the most commonly used method in industrial production. In thermal sublimation transfer printing, a dye ink is first printed onto thermal transfer paper to form a pattern. The ink-containing side of the thermal transfer paper is then bonded to the fabric, where the ink sublimates under high temperature and pressure, transferring the pattern to the fabric.

[0003] By applying a coating on the printing base paper, the printing effect can be improved. In thermal sublimation transfer printing, the quality of the coating on the thermal transfer paper is directly related to the transfer effect. Therefore, the requirements for the thermal transfer paper coating are very high. It is required that it has a certain ink absorption capacity while also being able to effectively prevent the ink from entering the deep layer of the coating, so that the ink only stays on the surface of the coating to achieve a high ink transfer rate. At the same time, it is also required that the ink in the coating can be quickly transferred to the fabric during the thermal sublimation process.

[0004] Traditional low-viscosity, high-substitution carboxymethyl cellulose (CMC) is relatively expensive due to limitations in raw materials, labor, and process. The cost of the formulated thermal transfer paper coating is difficult to reduce after it is applied to the machine, resulting in a high unit cost of the coating applied to the printing base paper. Therefore, many coated paper processing companies are currently in urgent need of optimizing the coating formulation process to reduce costs and enhance the competitiveness of their own products. Compared to CMC, starch-based materials have a higher cost-performance ratio and hold great application prospects in thermal transfer paper coatings. However, existing starch-based materials, when used alone, are difficult to meet the requirements of thermal sublimation transfer printing and still need to be compounded with low-viscosity, high-substitution CMC.

[0005] For example, patent CN201711254668.9 discloses a method for producing modified starch for thermal transfer printing paper, in which starch is modified under specific conditions by an alkaline catalyst, a modifier (one or more selected from a mixture of bishydroxymethyl urea, aliphatic dihalides and epoxy halides, borates, phosphorus oxychloride, citric acid, a dibasic acid anhydride and acetic acid or propionic acid) and a synergist (one or more selected from polyquaternary ammonium salts, sodium silicate, fatty alcohol polyether sulfate, dodecyl sulfonate, OP-10, dodecyl sulfate, NP-10, emulsified oil, AEO-9, polyester, PVA, polyethylene oxide, PAM). Although the obtained modified starch has strong resistance to acid and alkali and high temperature stability, it does not have suitable film-forming properties and adhesive consistency, and cannot be coated and sized alone. Therefore, it still needs to be compounded with low-viscosity and high-substitution CMC to achieve the ideal effect in thermal sublimation transfer printing, resulting in a still high coating cost. Summary of the Invention

[0006] To address the technical problem of existing starch-based materials requiring the addition of low-viscosity, high-substitution CMC in thermal sublimation transfer printing paper coatings, resulting in high coating costs, the present invention provides a method for preparing a thermal sublimation transfer printing paper coating composition containing a polysaccharide-based material. The thermal sublimation transfer printing paper coating composition obtained by this preparation method meets the requirements of thermal sublimation transfer printing and achieves ideal results without the need for the addition of low-viscosity, high-substitution CMC, thereby effectively reducing the cost of thermal sublimation transfer printing paper coatings.

[0007] The specific technical solutions of the present invention are:

[0008] A method for preparing a thermal sublimation transfer printing paper coating composition containing a polysaccharide-based material comprises the following steps:

[0009] (1) acid-hydrolyzing starch with an alcohol acid solution to obtain acid-hydrolyzed starch;

[0010] (2) mixing the acid-hydrolyzed starch with an oxidant to carry out an oxidation reaction, and then performing an alkalization treatment to obtain an alkalized starch;

[0011] (3) mixing the alkalized starch with an etherifying agent to carry out an etherification reaction to obtain a polysaccharide-based material;

[0012] (4) Mixing the polysaccharide-based material with an auxiliary agent to obtain a thermal sublimation transfer printing paper coating composition.

[0013] In step (1), the degree of polymerization of starch can be reduced by acid hydrolysis, so that when the polysaccharide-based material finally obtained is used for the thermal sublimation transfer printing paper coating, the coating viscosity can be reduced and the concentration of the polysaccharide-based material can be increased, thereby further ensuring that there is sufficient coating thickness after sizing, bringing about moderate hydrophobicity and air permeability, and ensuring that the ink is easily transferred from the coating to the fabric after thermal sublimation treatment.

[0014] Etherification introduces new groups into starch to replace hydroxyl groups. This process easily increases the degree of polymerization of starch and the viscosity of the slurry, affecting its performance in thermal sublimation transfer printing paper coatings. To this end, the present invention performs oxidation (step (2)) before etherification, which can stabilize the starch and enable it to maintain a low degree of polymerization during subsequent etherification. As a result, the prepared polysaccharide-based material has a low slurry viscosity. When used in thermal sublimation transfer printing paper coatings, it is helpful to accelerate the transfer of ink from the coating to the fabric, thereby achieving better printing effects.

[0015] In step (2), the starch is fully mixed with an alkali to obtain alkalization, which promotes starch expansion, allowing the alkali molecules to effectively penetrate into the starch granules, and undergo hydrogen proton substitution reaction with the hydroxyl groups on the starch structure to form the structural unit of starch sodium, which can form the active center point of the starch sodium etherification reaction, which is conducive to the subsequent etherification reaction. In addition, the present invention adopts the order of oxidation first and then alkalization, which has the following effects: through oxidation treatment, the molecular polymerization degree can be further reduced on the basis of acidification and degradation treatment, and moderate oxidation helps to maintain the white color of starch during the subsequent high alkalinity and high temperature reaction process, so that the finally obtained polysaccharide-based material has a higher whiteness and the paste has a stable color and transparency.

[0016] Under the combined effect of the above factors, the polysaccharide-based material prepared by the present invention can completely replace low-viscosity, high-substitution, and high-priced CMC when used in thermal sublimation transfer printing paper coatings. It does not need to be compounded with low-viscosity, high-substitution CMC to meet the requirements of thermal sublimation transfer printing and achieve ideal effects - it has good film-forming properties and adhesive consistency, can quickly transfer ink from thermal transfer paper to fabrics, shortens the drying time of thermal transfer paper ink, and has a high ink transfer rate, thereby achieving ideal printing effects and color performance, and better presenting the transferred color pattern.

[0017] Preferably, in step (2), before the oxidation reaction, a stabilizer is mixed with the acid-hydrolyzed starch and the oxidant, wherein the stabilizer is one or more of L-cysteine, sodium bisulfite, sorbic acid, sodium sulfite and ascorbic acid; and the mass ratio of the starch in step (1) to the stabilizer in step (2) is 100:0.1 to 0.3.

[0018] By adding the above-mentioned stabilizers in appropriate amounts, the starch can maintain a more stable color and alkali resistance. The reason is speculated to be that the starch raw materials often contain a small amount of protein. The above-mentioned stabilizers can react with the disulfide bonds in these proteins, breaking the disulfide bonds in the protein molecules and converting them into sulfhydryl bonds, thereby moderately modifying the protein in the starch and reducing the possibility of color change under alkaline conditions.

[0019] Preferably, in step (1), the alkyd solution is a mixture of ethanol and oxalic acid, the acid hydrolysis temperature is 20-50° C., and the mass ratio of starch, ethanol and oxalic acid is 100:5.0-12.0:0.15-0.30.

[0020] If hydrogen chloride is used to acid-hydrolyze starch, although its degree of polymerization can be effectively reduced, the resulting acid-hydrolyzed starch contains a large amount of water-soluble matter, which is not conducive to obtaining a stable and uniform water-soluble starch modified product after subsequent alkalization and etherification treatments. However, the present invention uses an alcoholic acid solution, which can better protect the starch while reducing the starch degree of polymerization (DP) value, so that the obtained alcohol-hydrolyzed starch contains a large amount of stable water-insoluble matter, which is conducive to obtaining a stable and uniform water-soluble starch modified product after subsequent alkalization and etherification treatments, thereby providing a guarantee for improving the performance of starch in thermal sublimation transfer printing paper coatings in later applications.

[0021] Preferably, in step (1), during the acid hydrolysis process, the obtained acid-hydrolyzed starch is sampled and tested, and the acid hydrolysis is stopped when the degradation standard is reached; the sampling and testing method and the degradation standard are as follows: the acid-hydrolyzed starch sample is mixed with water to form an 11.5-12.5wt% slurry, and a 19-21wt% sodium hydroxide solution with a mass 1.8-1.9 times that of the acid-hydrolyzed starch sample is added under stirring. After the addition, stirring is continued for 15-18s, and then the solution is poured into a Tu-4 viscosity cup to test the alkali flow rate value. The alkali flow rate value in the range of 40-50s meets the degradation standard.

[0022] For the polysaccharide-based materials used in thermal sublimation transfer printing paper coatings, the present invention team has noted that in the process of acid hydrolysis of starch, precise control of the degree of degradation is particularly important. When the degree of degradation is too high, the polysaccharide-based material finally obtained will not be able to reach a suitable slurry concentration, the slurry is light and thin, and the viscosity is too low, resulting in poor adhesion performance. During the application process, the ink will not be able to stay on the surface of the coating and will easily penetrate deep into the coating, thereby increasing the penetration of the ink in the later stage, affecting the ink transfer rate, and the printed color pattern effect is not good, and the late transfer pattern is not clear enough. When the degree of degradation is insufficient, the slurry viscosity of the polysaccharide-based material is too high and it is impossible to prepare a coating slurry with a higher concentration. When used, it is easy to cause the thermal sublimation transfer printing paper coating to form a viscous state, with poor scraping performance, and the coating cannot reach a given thickness to form a given water resistance. In the later stage, it will also cause increased ink penetration, and the ink transfer rate is affected. The uniformity and flatness of the formed coating are poor, and the speed at which the ink is transferred from the coating to the fabric is slow, and the color performance of the printing is poor. On this basis, the present invention adopts a new degradation degree detection and control method, which can accurately control the degradation degree of acid-hydrolyzed starch; by adopting the degradation degree detection method and corresponding degradation degree control standard in the present invention, it can better provide the necessary guarantees and conditions for obtaining this new printing material with the required quality index range and state and certain expansion performance after moderate etherification in the later stage.

[0023] Preferably, in step (2), the oxidant is one or more of hydrogen peroxide, percarbonate and peracetic acid, the temperature of the oxidation reaction is 30-50° C., and the time is 30-60 min; the mass ratio of the starch in step (1) to the oxidant in step (2) is 100:0.3-0.6.

[0024] The temperature of the oxidation reaction depends on the selected oxidant. It is necessary to consider whether it can react in time at a certain temperature to achieve the desired oxidation effect (for the present invention, the oxidation effect that needs to be achieved is to make the starch reach a predetermined state at the beginning of etherification and avoid the increase of the degree of polymerization of starch during the etherification process), and the residual amount of the oxidant should be as small as possible, while also taking into account the color of the starch. When the above-mentioned oxidant is selected, the oxidation reaction can be carried out at a suitable temperature, and with a suitable oxidation temperature range, it can be avoided that the oxidation reaction temperature is too high, which leads to a darkening of the starch color, the yellowing of the obtained polysaccharide-based material, and low viscosity, while also avoiding that the oxidation reaction temperature is too low, which leads to poor oxidation effect, and the degree of polymerization of starch after etherification is too high, which makes it difficult to meet the requirements of thermal sublimation transfer printing. Under the above-mentioned oxidant and oxidation temperature selection, by controlling the amount of oxidant and the oxidation time within a specific range, it is possible to achieve the ideal oxidation effect while avoiding the residual oxidant causing the viscosity stability of the coating configured later to decrease during use and storage, resulting in unstable coating slurry amount, and paper disease problems due to inconsistent glue intake of the coating.

[0025] Preferably, in step (2), the alkali used in the alkalization treatment is caustic soda, the temperature of the alkalization treatment is 30-50° C., and the time is 50-60 min; the mass ratio of the starch in step (1) to the alkali in step (2) is 100:5.0-7.5.

[0026] If the alkalization temperature is too high, the color of the polysaccharide-based material will turn yellow, and the starch will easily gelatinize, resulting in low subsequent etherification efficiency; when the alkalization temperature is too low or the time is too short, the degree of starch alkalization is insufficient, which will also result in low subsequent etherification efficiency.

[0027] Preferably, in step (3), the etherifying agent is monochloroacetic acid and / or its sodium salt, the temperature of the etherification reaction is 60-75° C., and the time is 1-3 hours; and the mass ratio of the starch in step (1) to the etherifying agent in step (3) is 100:12-18.

[0028] Preferably, in step (4), the auxiliary agent includes modified starch; the preparation method of the modified starch includes the following steps: after mixing starch with an alkaline catalyst solution, adding a modifier aqueous solution for modification, then adding a synergist aqueous solution, adjusting the pH to 5.0-10.0, and then separating the product; the modifier is one or more of bis(hydroxymethyl)urea, aliphatic dihalide and epoxy halide, borate, phosphorus oxychloride, citric acid, a mixture of dibasic acid anhydride and acetic acid or propionic acid, and the synergist is one or more of polyquaternary ammonium salt, sodium silicate, fatty alcohol polyether sulfate, dodecyl sulfonate, OP-10, dodecyl sulfate, NP-10, emulsified oil, AEO-9, polyester, PVA, polyethylene oxide, and PAM.

[0029] The modified starch obtained by the above-mentioned preparation method has the characteristics of extremely strong resistance to acid and alkali and high temperature stability. The polysaccharide-based material prepared by the present invention is compounded with the modified starch, and the two cooperate with each other to form a specific entangled network structure, which can play a synergistic role. Specifically, the polysaccharide-based material prepared by the present invention is a water-soluble substance with strong hydrophilicity. It can form a stable glue of appropriate concentration after being dissolved in water at room temperature, while the modified starch obtained by the above-mentioned preparation method is a non-water-soluble substance. It does not show viscosity (or has extremely low viscosity) under room temperature configuration. It always exists as a mixed high-molecular organic material in a suspended state, forming a coating composition with a stable molecular structure that can withstand strong acid and alkali properties. When the above-mentioned polysaccharide-based material and the modified starch are applied to the coating of coated paper together, they can be interdependent, and the molecular chains of the two starches are interspersed with each other. While meeting the sizing requirements and being simpler and more convenient to use, they provide the best composite performance for the stable existence of the later printing ink and achieving high-standard ink pattern transfer.

[0030] Furthermore, the modified starch may be the modified starch described in patent CN201711254668.9, and the preparation steps are as follows:

[0031] (I) Slurry preparation: adding starch raw material to an alkaline catalyst solution and mixing and stirring to form a starch slurry; the mass percentage of the alkaline catalyst solution is 0.1 to 5%; the mass concentration of starch in the starch slurry is 35% to 42%;

[0032] (II) Modification reaction: adding a modifier aqueous solution to a starch slurry, and then reacting at 15-55° C. for 5-24 hours to obtain a modified starch slurry; the modifier is selected from one or more of bis(hydroxymethyl)urea, aliphatic dihalides and epoxy halides, borates, phosphorus oxychloride, citric acid, and a mixture of a dibasic acid anhydride and acetic acid or propionic acid; the amount of the modifier used is 0.5-3% by weight of the starch raw material, and the mass concentration of the modifier aqueous solution is 2-8%;

[0033] (III) Synergistic reaction: adding an aqueous solution of a synergist to the modified starch slurry, and then adjusting the pH to 5.0-10.0 to obtain a crude slurry; the synergist is selected from one or more of polyquaternium salts, sodium silicate, fatty alcohol polyether sulfate, dodecyl sulfonate, OP-10, dodecyl sulfate, NP-10, emulsified oil, AEO-9, polyester, PVA, polyethylene oxide, and PAM; the amount of the synergist used is 0.2-2% by weight of the starch raw material, and the mass concentration of the aqueous solution of the synergist is 5-25%;

[0034] (IV) Finally, the crude slurry is filtered, washed, dehydrated, dried, sieved, weighed, and packaged to obtain modified starch.

[0035] Preferably, in step (4), the auxiliary agent further comprises a solid acid and a dispersant, and the mass ratio of the polysaccharide-based material, modified starch, solid acid and dispersant is 65:30-35:2-4:0.5-1.

[0036] By adding solid acid, the pH value can be stabilized, so that the coating has better shear resistance during use, can maintain better viscosity stability after being put into the machine, and the molecular structure of the glue is more stable, so that the coating sizing rate on the printing base paper is consistent, and the thickness of the film formed on the paper is uniform, thereby avoiding the uneven coating thickness on the thermal transfer paper before and after coating, which leads to poor printing effect.

[0037] Preferably, the dispersant is NP-10 and sodium tripolyphosphate in a mass ratio of 1:2.5 to 3.5.

[0038] The combination of the two nonionic and anionic surfactants with different dispersivities can moderately reduce the surface adhesion of the later paste and provide appropriate tension, improve wettability and control foam generation, while also effectively improving the anti-rheological properties of the coating.

[0039] Preferably, the solid acid is one or more of zirconium oxide, potassium citrate, aluminum oxide, fumaric acid and aluminum silicate.

[0040] Compared with the prior art, the present invention has the following advantages:

[0041] (1) The present invention adopts the method of acidolysis → oxidation → alkalization → etherification of alkyd solution to modify starch. When the obtained polysaccharide-based material is used in thermal sublimation transfer printing coating, it does not need to be compounded with low-viscosity, high-substitution, and high-priced CMC. It can meet the requirements of thermal sublimation transfer printing and achieve ideal effects, thereby effectively reducing the cost of thermal sublimation transfer printing paper coating.

[0042] (2) The present invention can achieve a better transfer printing effect by 1○ precisely controlling the degradation degree during the acid hydrolysis process + 2○ selecting a specific oxidant during oxidation and controlling the oxidation temperature, time and amount of the oxidant + 3○ controlling the alkalization temperature and time. The obtained polysaccharide-based material can effectively prevent the ink from entering deep into the coating when used in thermal sublimation transfer printing, and can easily transfer the ink from the coating to the fabric, thereby improving the ink transfer rate and preventing the polysaccharide-based material from yellowing. DETAILED DESCRIPTION

[0043] The present invention will be further described below with reference to the embodiments.

[0044] Overall embodiment

[0045] A method for preparing a thermal sublimation transfer printing paper coating composition containing a polysaccharide-based material comprises the following steps:

[0046] (1) acid-hydrolyzing starch with an alcohol acid solution to obtain acid-hydrolyzed starch;

[0047] (2) mixing the acid-hydrolyzed starch with an oxidant to carry out an oxidation reaction, and then performing an alkalization treatment to obtain an alkalized starch;

[0048] (3) mixing the alkalized starch with an etherifying agent to carry out an etherification reaction to obtain a polysaccharide-based material;

[0049] (4) Mixing the polysaccharide-based material with an auxiliary agent to obtain a thermal sublimation transfer printing paper coating composition.

[0050] As a specific embodiment, in step (1), the alkyd solution is a mixture of ethanol and oxalic acid, the acid hydrolysis temperature is 20-50°C, and the mass ratio of starch, ethanol and oxalic acid is 100:5.0-12.0:0.15-0.30.

[0051] As a specific embodiment, in step (1), during the acid hydrolysis process, the obtained acid-hydrolyzed starch is sampled and tested, and the acid hydrolysis is stopped when the degradation standard is reached; the sampling and testing method and the degradation standard are as follows: the acid-hydrolyzed starch sample is mixed with water to form an 11.5-12.5wt% slurry, and a 19-21wt% sodium hydroxide solution with a mass 1.8-1.9 times that of the acid-hydrolyzed starch sample is added under stirring. After the addition, stirring is continued for 15-18s, and then the alkali flow rate value is poured into a Tu-4 viscosity cup to test the alkali flow rate value. The alkali flow rate value in the range of 40-50s meets the degradation standard.

[0052] As a specific embodiment, in step (2), the oxidant is one or more of hydrogen peroxide, percarbonate and peracetic acid, the temperature of the oxidation reaction is 30-50° C., and the time is 30-60 min; the mass ratio of the starch in step (1) to the oxidant in step (2) is 100:0.3-0.6.

[0053] As a specific embodiment, in step (2), before the oxidation reaction, a stabilizer is mixed with the acid-hydrolyzed starch and the oxidant, and the stabilizer is one or more of L-cysteine, sodium bisulfite, sorbic acid, sodium sulfite and ascorbic acid; the mass ratio of the starch in step (1) to the stabilizer in step (2) is 100:0.1 to 0.3.

[0054] As a specific embodiment, in step (2), the alkali used in the alkalization treatment is caustic soda, the temperature of the alkalization treatment is 30-50°C, and the time is 50-60 minutes; the mass ratio of the starch in step (1) to the alkali in step (2) is 100:5.0-7.5.

[0055] As a specific embodiment, in step (3), the etherifying agent is monochloroacetic acid and / or its sodium salt, the temperature of the etherification reaction is 60-75° C., and the time is 1-3 hours; the mass ratio of the starch in step (1) to the etherifying agent in step (3) is 100:12-18.

[0056] As a specific embodiment, in step (4), the auxiliary agent includes modified starch; the preparation method of the modified starch includes the following steps: after mixing starch with an alkaline catalyst solution, adding a modifier aqueous solution for modification, and then adding a synergist aqueous solution, adjusting the pH to 5.0-10.0, and then separating the product; the modifier is one or more of bis(hydroxymethyl)urea, aliphatic dihalide and epoxy halide, borate, phosphorus oxychloride, citric acid, a mixture of dibasic acid anhydride and acetic acid or propionic acid, and the synergist is one or more of polyquaternary ammonium salt, sodium silicate, fatty alcohol polyether sulfate, dodecyl sulfonate, OP-10, dodecyl sulfate, NP-10, emulsified oil, AEO-9, polyester, PVA, polyethylene oxide, and PAM.

[0057] In the above specific implementation, optionally:

[0058] The dispersant is NP-10 and sodium tripolyphosphate in a mass ratio of 1:2.5 to 3.5;

[0059] The solid acid is one or more of zirconium oxide, potassium citrate, aluminum oxide, fumaric acid and aluminum silicate;

[0060] The preparation steps of the modified starch are as follows:

[0061] (I) Slurry preparation: adding starch raw material to an alkaline catalyst solution and mixing and stirring to form a starch slurry; the mass percentage of the alkaline catalyst solution is 0.1 to 5%; the mass concentration of starch in the starch slurry is 35% to 42%;

[0062] (II) Modification reaction: adding a modifier aqueous solution to a starch slurry, and then reacting at 15-55° C. for 5-24 hours to obtain a modified starch slurry; the modifier is selected from one or more of bis(hydroxymethyl)urea, aliphatic dihalides and epoxy halides, borates, phosphorus oxychloride, citric acid, and a mixture of a dibasic acid anhydride and acetic acid or propionic acid; the amount of the modifier used is 0.5-3% by weight of the starch raw material, and the mass concentration of the modifier aqueous solution is 2-8%;

[0063] (III) Synergistic reaction: adding an aqueous solution of a synergist to the modified starch slurry, and then adjusting the pH to 5.0-10.0 to obtain a crude slurry; the synergist is selected from one or more of polyquaternium salts, sodium silicate, fatty alcohol polyether sulfate, dodecyl sulfonate, OP-10, dodecyl sulfate, NP-10, emulsified oil, AEO-9, polyester, PVA, polyethylene oxide, and PAM; the amount of the synergist used is 0.2-2% by weight of the starch raw material, and the mass concentration of the aqueous solution of the synergist is 5-25%;

[0064] (IV) Finally, the crude slurry is filtered, washed, dehydrated, dried, sieved, weighed, and packaged to obtain modified starch.

[0065] Example 1

[0066] A polysaccharide-based material is prepared by the following steps, and is made into a thermal sublimation transfer printing paper coating composition:

[0067] (1) Pour 1000 g of starch into a 5 L kneader, start stirring, spray a mixed solution of 100 g of ethanol and 2.7 g of oxalic acid, and then transfer it to a reactor. Keep it warm at 40 ° C under closed stirring conditions. Take samples at regular intervals to detect the degree of degradation. The method is as follows: take 22 g of the absolutely dry product and add 160 g of water to prepare a starch slurry. Stir and add 20 g of 20 wt% sodium hydroxide solution. Stir for 15 seconds, then pour it into a Tu-4 viscosity cup and test the alkali flow rate value. When the measured alkali flow rate value drops to 45 seconds, end this reaction.

[0068] (2) Add 4 g of hydrogen peroxide and 2 g of sodium sulfite to the product obtained in step (1), and stir the mixture at 40° C. for 50 min.

[0069] (3) Add 60 g of caustic soda to the product obtained in step (2), and stir the reaction at 40° C. for 55 min.

[0070] (4) Add 152 g of monochloroacetic acid to the product of step (3), stir for 20 min, heat to 68° C., and keep warm for 2 h. After desolventizing, unloading, air drying, crushing, and sieving, a polysaccharide-based material is obtained.

[0071] (5) A polysaccharide-based material, a solid acid, a composite dispersant, and a modified starch (prepared according to Example 1 in patent CN201711254668.9) in a mass ratio of 65:3.5:0.5:31 were fed into a mixer and mixed to obtain a thermal sublimation transfer printing paper coating.

[0072] Example 2

[0073] A polysaccharide-based material is prepared by the following steps, and is made into a thermal sublimation transfer printing paper coating composition:

[0074] (1) Pour 1000 g of starch into a 5 L kneader, start stirring, spray a mixed solution of 50 g of ethanol and 1.5 g of oxalic acid, and then transfer it to a reactor. Under closed stirring conditions at a temperature of 30°C, carry out heat preservation reaction. Samples are taken at regular intervals to detect the degree of degradation. The method is as follows: take 22 g of absolute dry product and add 160 g of water to prepare a starch slurry, stir and add 20 g of 20 wt% sodium hydroxide solution, stir for 15 seconds, and then pour it into a Tu-4 viscosity cup to test the alkali flow rate value. When the measured alkali flow rate value drops to 50 seconds, the reaction is terminated.

[0075] (2) Add 3 g of hydrogen peroxide and 1 g of sodium sulfite to the product obtained in step (1), and stir the mixture at 30° C. for 30 min.

[0076] (3) Add 50 g of caustic soda to the product obtained in step (2), and stir the reaction at 30° C. for 50 min.

[0077] (4) Add 150 g of monochloroacetic acid to the product of step (3), stir for 15 minutes, heat to 60° C., and keep warm for 1 hour. After desolventizing, unloading, air drying, crushing, and sieving, a polysaccharide-based material is obtained.

[0078] (5) The polysaccharide-based material, solid acid, composite dispersant and modified starch (prepared according to Example 2 in patent CN201711254668.9) with a mass ratio of 65:3.5:0.5:31 were fed into a mixer and mixed to obtain a thermal sublimation transfer printing paper coating.

[0079] Example 3

[0080] A polysaccharide-based material is prepared by the following steps, and is made into a thermal sublimation transfer printing paper coating composition:

[0081] (1) Pour 1000 g of starch into a 5 L kneader, start stirring, spray a mixed solution of 120 g of ethanol and 3 g of oxalic acid, and then transfer it to a reactor. Keep it warm under a closed stirring condition at a temperature of 50 ° C. Samples are taken at regular intervals to detect the degree of degradation. The method is as follows: take 22 g of the absolutely dry product and add 160 g of water to prepare a starch slurry, stir and add 20 g of 20 wt% sodium hydroxide solution, stir for 15 seconds, and then pour it into a Tu-4 viscosity cup to test the alkali flow rate value. When the measured alkali flow rate value drops to 40 seconds, the reaction is terminated.

[0082] (2) Add 6 g of hydrogen peroxide and 3 g of sodium sulfite to the product obtained in step (1), and stir the mixture at 50° C. for 60 min.

[0083] (3) Add 75 g of caustic soda to the product obtained in step (2), and stir the reaction at 50° C. for 60 min.

[0084] (4) Add 155 g of monochloroacetic acid to the product of step (3), stir for 30 min, heat to 75° C., and keep warm for 3 h. After desolventizing, unloading, air drying, crushing, and sieving, a polysaccharide-based material is obtained.

[0085] (5) A polysaccharide-based material, a solid acid, a composite dispersant, and a modified starch (prepared according to Example 1 in patent CN201711254668.9) in a mass ratio of 65:3.5:0.5:31 were fed into a mixer and mixed to obtain a thermal sublimation transfer printing paper coating.

[0086] Example 4

[0087] The only difference between this embodiment and embodiment 1 is that in step (5), the modified starch is replaced with a polysaccharide-based material of equal mass.

[0088] Example 5

[0089] The only difference between this embodiment and embodiment 1 is that in step (2), sodium sulfite is not added.

[0090] Comparative Example 1

[0091] The only difference between this comparative example and Example 1 is that in step (5), the polysaccharide-based material is replaced with an equal mass of modified starch.

[0092] Comparative Example 2

[0093] The only difference between this comparative example and Example 1 is that in step (1), the alcohol-acid solution acid hydrolysis method is replaced with the hydrogen chloride alcohol acid hydrolysis method. Step (1) of this comparative example is as follows: a mixed solution consisting of 100 g of ethanol and 2 g of HCl is added to 1000 g of starch, and the mixture is kept warm at 40°C under closed stirring conditions. The degradation degree of the product is detected using the same method as in Example 1, and the reaction time is based on the time when the alkali flow rate value measured for the product drops to 45 seconds.

[0094] Comparative Example 3

[0095] The only difference between this comparative example and Example 1 is that the order of step (3) and step (2) is interchanged, that is, the alkalization treatment is performed first and then the oxidation reaction is performed. The specific process of this comparative example is as follows:

[0096] (1) Same as Example 1.

[0097] (2) Add 75 g of caustic soda to the product obtained in step (1), and then add 3 g of sodium sulfite, and stir the reaction at a temperature of 50° C. for 60 min.

[0098] (3) Add 6 g of hydrogen peroxide to the product obtained in step (2), and stir the reaction at 50° C. for 60 min.

[0099] (4) Same as Example 1.

[0100] (5) Same as Example 1.

[0101] Comparative Example 4

[0102] The only difference between this comparative example and Example 1 is that in step (1), the reaction is stopped when the alkali flow rate value measured by sampling is 65s.

[0103] Comparative Example 5

[0104] The only difference between this comparative example and Example 1 is that in step (1), the reaction is stopped when the alkali flow rate value measured by sampling is 32s.

[0105] Comparative Example 6

[0106] The only difference between this comparative example and Example 1 is that in step (2), potassium persulfate is used as the oxidant and the oxidation reaction temperature is changed to 60°C.

[0107] Comparative Example 7

[0108] The only difference between this comparative example and Example 1 is that in step (2), the oxidation reaction temperature is changed to 25°C.

[0109] Comparative Example 8

[0110] The only difference between this comparative example and Example 1 is that in step (3), the alkalization temperature is changed to 60°C.

[0111] Comparative Example 9

[0112] The only difference between this comparative example and Example 1 is that in step (3), the alkalization temperature is changed to 25°C.

[0113] Test Example 1: Quality indicators of polysaccharide-based materials

[0114] The polysaccharide-based materials synthesized in Examples 1 to 5 and Comparative Examples 2 to 9 were taken and their quality indicators were tested. The results are shown in Table 1.

[0115] Table 1 Quality indicators of polysaccharide-based materials

[0116]

[0117]

[0118] Test Example 2: Quality indicators of thermal sublimation transfer printing paper coating composition

[0119] The thermal sublimation transfer printing paper coating compositions prepared in Examples 1 to 5 and Comparative Examples 1 to 9 were added with water to prepare 16 wt % thermal sublimation transfer printing coatings, and their quality indicators were tested. The results are shown in Table 2.

[0120] Table 2 Quality indexes of thermal sublimation transfer printing paper coating composition

[0121]

[0122] In Table 2, the evaluation method for viscosity stability is as follows:

[0123] After adding water to prepare a 16wt% thermal sublimation transfer printing coating, after preliminary testing at room temperature 25°C, it was placed on a stirrer at 50-100rpm / min for continuous stirring, and the viscosity value data of the samples were tested for 1h, 2h, and 3h respectively. The viscosity stability was then indicated by the calculation ratio of 100%-(1h-3h) / 1h*100%.

[0124] Test Example 3: Application Performance of Thermal Sublimation Transfer Printing Paper Coating Composition

[0125] The thermal sublimation transfer printing paper coating compositions prepared in Examples 1 to 5 and Comparative Examples 1 to 9 were added with water to prepare a thermal sublimation transfer printing coating having a concentration of 16 wt %. The application performance was evaluated as follows:

[0126] First, a high-speed disperser was turned on in a mixing drum at a speed of 1000 r / min, and a measured thermal sublimation transfer printing paper coating composition was added. Water was added to prepare a thermal sublimation transfer printing coating with a concentration of 16wt%. After stirring for 30 minutes, the coating was filtered through a 250-mesh sieve and ready for use. The following steps were followed to conduct an application experiment and evaluate the application performance: the coating was tested for solid content and viscosity, then metered and coated onto thermal transfer printing paper. After drying and moisture balance, the paper was then printed with ink and subjected to a transfer printing test at 180°C for 30 seconds on a thermal transfer machine. After testing and analysis, a comprehensive evaluation of the drying speed and transfer effect was completed.

[0127] After the above application evaluation test, the application data shown in Table 3 below were obtained.

[0128] Table 3 Application performance of thermal sublimation transfer printing paper coating composition

[0129] project Tu-4 flow rate Coating amount Drying speed Transfer effect rating Comprehensive evaluation unit s g min / / index 40～50 / ＜2.0 ＞0.75 / Example 1 43 3.28 ＜2.0 0.86 good Example 2 49 3.14 ＜2.0 0.88 good Example 3 44 3.36 ＜2.0 0.83 good Example 4 41 3.27 ＜2.0 0.75 meet the standards Example 5 42 3.19 ＜2.0 0.85 good Comparative Example 1 13 3.02 3.5 0.59 Not up to standard Comparative Example 2 18 3.13 3.9 0.53 Not up to standard Comparative Example 3 13 3.21 3.7 0.57 Not up to standard Comparative Example 4 124 3.26 5.0 0.43 Not up to standard Comparative Example 5 19 3.22 3.9 0.63 Not up to standard Comparative Example 6 15 3.28 4.2 0.65 Not up to standard Comparative Example 7 16 3.10 3.7 0.56 Not up to standard Comparative Example 8 21 3.05 3.5 0.59 Not up to standard Comparative Example 9 30 3.25 4.0 0.64 Not up to standard

[0130] According to the test results obtained in test cases 1 to 3, it can be seen that:

[0131] (1) In Example 1, modified starch and polysaccharide-based materials were compounded, while in Example 4 and Comparative Example 1, only polysaccharide-based materials and modified starch were used, respectively. From the test results, compared with Example 1, the coating composition of Comparative Example 1 with a viscosity of 16 wt% was too low, the flow rate was too fast, the drying speed was too slow during use, and the transfer effect was poor. In Example 4, all the modified starch was replaced with polysaccharide-based materials. Since the modified starch was replaced, the subsequent transfer printing coating lacked the necessary organic acid- and alkali-resistant insoluble substances as the coating hydrophobicity and ink diversion gap channels, which would significantly affect the ink transfer effect of the subsequent coating layer, and the pattern clarity was relatively poor.

[0132] (2) Compared with Example 1, the stabilizer sodium sulfite was not added in Example 5. From the test results, the whiteness of the polysaccharide-based material prepared in Example 5 was significantly lower than that in Example 1. This may be because the starch raw material contains a small amount of protein. Sodium sulfite can react with the disulfide bonds in these proteins, breaking the disulfide bonds in the protein molecules and converting them into sulfide-hydrogen bonds, thereby moderately modifying the protein in the starch and reducing the possibility of color change under alkaline conditions.

[0133] (3) Example 1 adopts the alcohol acid hydrolysis method, while Comparative Example 2 adopts the hydrogen chloride alcohol acid hydrolysis method. From the test results, compared with Example 1, the polysaccharide-based material 5wt% prepared in Comparative Example 2 has a lower viscosity, the coating composition 16wt% has a lower viscosity, and the flow rate is faster. When used, the drying speed is too slow, and the transfer effect is not good. This may be because the hydrogen chloride alcohol acid hydrolysis product of starch contains more water-soluble substances, which is not conducive to obtaining a stable and uniform water-soluble starch modified product after subsequent alkalization and etherification treatment. The alcohol acid solution can better protect the starch, and there are more stable non-water-soluble substances in the acid hydrolysis product, which is conducive to obtaining a stable and uniform water-soluble starch modified product through subsequent alkalization and etherification treatment.

[0134] (4) In Example 1, the order of alkalization followed by oxidation was adopted, while in Comparative Example 3, the order of the two was reversed. From the test results, compared with Example 1, the polysaccharide-based material prepared in Comparative Example 3 had lower whiteness and 5wt% viscosity, and the coating composition had a lower viscosity at 16wt%, a faster flow rate, and a slow drying speed during use, resulting in poor transfer effect. This may be because moderate oxidation helps to keep the starch white in the subsequent high alkalinity and high temperature reaction process, and when the order is reversed, the starch is effectively catalyzed and decomposed by the added alkali after the oxidant enters the starch due to the addition of alkali in the alkalization, resulting in a decrease in viscosity. At the same time, it also increases the starch gelatinization expansion product, resulting in a significant impact on the color of the product.

[0135] (5) Compared with Example 1, the degree of acid hydrolysis of Comparative Example 4 is lower, and the degree of acid hydrolysis of Comparative Example 5 is higher. From the test results, compared with Example 1, the viscosity of the polysaccharide-based material 5wt% prepared in Comparative Example 4 is higher, and the viscosity of the coating composition 16wt% is higher, and the flow rate is slower, while the opposite is true for Comparative Example 5. In addition, the coating compositions of Comparative Examples 4 and 5 both dry slowly during use and have poor transfer effects.

[0136] (6) In Example 1, hydrogen peroxide was used as the oxidant, and the acid-hydrolyzed starch was oxidized well at 40°C to achieve the desired oxidation effect; in Comparative Example 6, potassium persulfate was used as the oxidant, requiring a higher oxidation temperature (60°C); and in Comparative Example 7, the oxidation temperature was set at 25°C. From the test results, compared with Example 1, the polysaccharide-based material prepared in Comparative Example 6 had lower whiteness and 5wt% viscosity, and the coating composition had a lower viscosity at 16wt% and a faster flow rate. In contrast, the coating compositions of Comparative Example 7 dried too slowly during use, resulting in poor transfer effects.

[0137] (7) In Example 1, Comparative Example 8, and Comparative Example 9, the alkalization temperature was set to 40°C, 60°C, and 25°C, respectively. The test results show that compared with Example 1, the polysaccharide-based material prepared in Comparative Example 8 has a lower whiteness. The 5wt% viscosity of the polysaccharide-based materials in Comparative Examples 8 and 9 is relatively low. The 16wt% viscosity of the coating composition is relatively low, the flow rate is relatively fast, and the drying speed is too slow during use, resulting in poor transfer effect. This may be because when the alkalization temperature is too high, the starch is prone to gelatinization, resulting in low subsequent etherification efficiency. When the alkalization temperature is too low, the starch alkalization degree is insufficient, which also results in low subsequent etherification efficiency.

[0138] Unless otherwise specified, the raw materials and equipment used in the present invention are commonly used in the art; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0139] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a thermal sublimation transfer printing paper coating composition containing a polysaccharide-based material, characterized in that: The following steps are involved: (1) The starch was acid-hydrolyzed with an alcohol acid solution. During the acid-hydrolyzed starch, a sample was taken. The acid-hydrolyzed starch sample was mixed with water to form an 11.5-12.5 wt% slurry. A 19-21 wt% NaOH solution with a mass 1.8-1.9 times that of the acid-hydrolyzed starch sample was added under stirring. After the addition, stirring was continued for 15-18 seconds. The alkali flow rate value was then poured into a Tu-4 viscosity cup to test the alkali flow rate value. When the alkali flow rate value was within the range of 40-50 seconds, it met the degradation standard and the acid hydrolysis was stopped. (2) mixing the acid-hydrolyzed starch with an oxidant, subjecting the mixture to an oxidation reaction at 30-50°C for 30-60 minutes, and then subjecting the mixture to an alkalization treatment to obtain alkalized starch; the oxidant is at least one of hydrogen peroxide, percarbonate, and peracetic acid, and the mass ratio of the oxidant to the starch is 0.3-0.6:100; (3) Mixing the alkalized starch with the etherifying agent, and subjecting the mixture to an etherification reaction at 30-50°C for 50-60 minutes to obtain a polysaccharide-based material; (4) Mixing the polysaccharide-based material with the auxiliary agent to obtain a thermal sublimation transfer printing paper coating composition.

2. The preparation method according to claim 1, wherein In step (2), before the oxidation reaction, a stabilizer is mixed with the acid-hydrolyzed starch and the oxidant, wherein the stabilizer is one or more of L-cysteine, sodium bisulfite, sorbic acid, sodium sulfite and ascorbic acid.

3. The preparation method according to claim 2, wherein The mass ratio of the starch in step (1) to the stabilizer in step (2) is 100:0.1-0.

3.

4. The preparation method according to claim 1, wherein In step (1), the alkyd solution is a mixture of ethanol and oxalic acid, the acid hydrolysis temperature is 20-50° C., and the mass ratio of starch, ethanol and oxalic acid is 100:5.0-12.0:0.15-0.

30.

5. The preparation method according to claim 1, wherein In step (2), the alkali used in the alkalization treatment is caustic soda; the mass ratio of the starch in step (1) to the alkali in step (2) is 100:5.0~7.

5.

6. The preparation method according to claim 1, wherein In step (3), the etherifying agent is monochloroacetic acid and / or its sodium salt, the temperature of the etherification reaction is 60-75° C., and the time is 1-3 hours.

7. The preparation method according to claim 6, wherein The mass ratio of the starch in step (1) to the etherifying agent in step (3) is 100:12-18.

8. The preparation method according to claim 1, wherein In step (4), the auxiliary agent includes modified starch; the preparation method of the modified starch includes the following steps: after mixing starch with an alkaline catalyst solution, adding a modifier aqueous solution for modification, and then adding a synergist aqueous solution, adjusting the pH to 5.0-10.0, and then separating the product; the modifier is one or more of bis(hydroxymethyl)urea, aliphatic dihalide and epoxy halide, borate, phosphorus oxychloride, citric acid, a mixture of dibasic acid anhydride and acetic acid or propionic acid, and the synergist is one or more of polyquaternary ammonium salt, sodium silicate, fatty alcohol polyether sulfate, dodecyl sulfonate, OP-10, dodecyl sulfate, NP-10, emulsified oil, AEO-9, polyester, PVA, polyethylene oxide, and PAM.

9. The preparation method according to claim 8, wherein In step (4), the auxiliary agent further comprises a solid acid and a dispersant, and the mass ratio of the polysaccharide-based material, the modified starch, the solid acid and the dispersant is 65:30~35:2~4:0.5~1.

10. The preparation method according to claim 9, characterized in that The dispersant is NP-10 and sodium tripolyphosphate in a mass ratio of 1:2.5-3.5.

Images