Preparation process of a thermal transfer paper with an ultra-low elongation rate

Abstract

The present invention relates to the technical field of thermal transfer paper, and specifically discloses a preparation process of a thermal transfer paper with an ultra-low shrinkage rate. Bamboo pulp and bleached softwood kraft pulp are used as raw materials for the mixed pulp, and are mixed with modified silica-coated graphene, nanocellulose, sizing agent, and loosening agent to prepare a base material. An ink-absorbing material, a fixing agent, silica-coated graphene, and a leveling agent are mixed to obtain a mixed coating. The mixed coating is coated on the base material, and after calendering and leveling treatment, an ultra-low shrinkage rate thermal transfer paper is obtained. Among them, the silica-coated graphene has excellent mechanical properties, and together with nanocellulose, generates a binding force with the fiber structure in the mixed pulp, which can significantly improve the paper strength, make the paper have a certain stiffness and anti-curling performance, and the obtained thermal transfer paper has the characteristics of ultra-low shrinkage rate, high strength, and high ink acceptance capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal transfer paper, and specifically provides a preparation process for a thermal transfer paper with an ultra-low shrinkage rate. Background Art

[0002] The thermal transfer process is different from traditional printing techniques and belongs to a waterless dyeing technique, which can reduce sewage pollution caused by printing and dyeing. The thermal transfer process does not directly print on the substrate. Instead, the ink is first printed on the thermal transfer paper, and then the side with the pattern on the thermal transfer paper is attached to the object to be printed. Then, an electric iron or a heat press is used to appropriately heat and press on the back of the paper, and the pattern can be transferred to the substrate. This method is convenient and fast, and the pattern is delicate, clear, and three-dimensional, which is deeply loved by consumers. Among them, thermal transfer paper is the abbreviation of thermal transfer printing paper, also known as thermal transfer paper or heat transfer paper, which is one of the main consumables in the thermal transfer process. As the carrier of thermal transfer printing products, it plays a very important role in the transfer printing industry and is one of the key links determining the printing quality, and has a wide range of applications in industries such as textiles, electronics, and construction.

[0003] During the use of thermal transfer paper, it is required that the transfer paper has good conformability, is suitable for high-speed printing and curling, and has high thermal conductivity, so that during the thermal transfer process, the temperature can be appropriately reduced, the transfer speed can be increased, the cost can be effectively reduced, and the efficiency can be improved. Traditional thermal transfer paper becomes wet and swollen due to absorbing ink, causing the paper to swell and deform, arching up, resulting in a change in the lateral elongation of the paper, affecting the printing quality, and there will also be friction with the print head, causing the printed pattern to become dirty, and seriously damaging the print head. During the transfer process, due to the high temperature, the thermal transfer paper will also warp and curl, causing misregistration during transfer and resulting in transfer failure. The existing transfer paper has low strength, and it is difficult to return to a completely flat state after being curled and stored, which will also cause low thermal transfer efficiency and affect the thermal transfer effect at the same time.

[0004] Therefore, it is of great practical value and significance to develop a thermal transfer paper with an ultra-low shrinkage rate, high strength, and high ink acceptance. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a preparation process for a thermal transfer paper with an ultra-low shrinkage rate, which solves the problems of high shrinkage rate, low strength, and low ink acceptance of thermal transfer paper.

[0006] In order to achieve the above object, the present invention discloses a preparation process for a thermal transfer paper with an ultra-low shrinkage rate, including the following steps:

[0007] Step 1: Prepare the substrate, place bamboo pulp and bleached softwood kraft pulp in a beating machine to beat them respectively, and after beating, mix the two evenly to obtain a mixed pulp;

[0008] Transfer the mixed slurry to a batching tank, then add modified silica-coated graphene, nanocellulose, sizing agent and loosening agent. After mixing evenly, pump it into a headbox, form it through a Fourdrinier machine, dehydrate, press and dry it. Control the vacuum degree at 0.09 - 0.15 MPa, the drying temperature at 105 - 110 °C, and control the moisture content at 5 - 6% to obtain a substrate;

[0009] Step Two: Coating. Mix the ink-absorbing material, disperse dye fixing agent, silica-coated graphene and leveling agent evenly to obtain a mixed coating;

[0010] Coat the mixed coating on the substrate prepared in Step One by coating. After coating, dry it at 55 - 65 °C to obtain a coated substrate;

[0011] Step Three: Processing and coiling into finished products. After calendering and leveling the coated substrate with a controllable medium-high soft roll calender, wind it up, and use a high-speed paper machine to slit, rewind and package to obtain a thermal transfer paper with ultra-low elongation rate.

[0012] Preferably, in Step One, the bamboo pulp concentration is 6.5 - 8%, the beating degree after beating is 36 - 38 °SR, the bleached kraft softwood pulp concentration is 5.5 - 7%, and the beating degree after beating is 28 - 31 °SR; the mass ratio of the beaten bamboo pulp and bleached kraft softwood pulp in the mixed slurry is 100:65 - 115.

[0013] Further, in Step One, the bleached kraft softwood pulp is pine pulp.

[0014] Preferably, in Step One, the mass ratio of the mixed slurry, modified silica-coated graphene, nanocellulose, sizing agent and loosening agent is 100:8 - 13:1 - 3:1.2 - 2:0.2 - 0.3.

[0015] Preferably, the sizing agent in Step One includes one of cationic polymers, rosin sizing agents and alkyl ketene dimers; the loosening agent in Step One includes sodium silicate.

[0016] Further, the cationic polymer in Step One is cationic starch.

[0017] Preferably, the bamboo pulp in Step One is obtained by kraft pulping of dry bamboo chips.

[0018] Preferably, the preparation method of the modified silica-coated graphene in Step One includes the following steps:

[0019] (1) Ultrasonically disperse graphene oxide into a mixed acid, which is obtained by mixing sulfuric acid and nitric acid with a volume ratio of 4:1, for acidification treatment. The mass ratio of graphene oxide to the mixed acid is 100:285 - 340. The temperature of the acidification treatment is 90 - 95 °C, and the time is 3 - 4 h. After the treatment is completed, filter, wash with deionized water, and dry to obtain acidified graphene. Then disperse the acidified graphene into a mixed solution of ethanol, ammonia water, and deionized water. After mixing evenly, add tetraethyl orthosilicate and react at 25 - 35 °C for 3 - 5 h. After the reaction is completed, wash with deionized water, centrifuge at a rate of 6000 r / min, and vacuum dry at 60 °C for 8 h to obtain silica-coated graphene;

[0020] (2) Ultrasonically disperse the silica-coated graphene into N,N-dimethylformamide, then add sodium hydroxide and hexadecene succinic anhydride. After mixing evenly, add 4-dimethylaminopyridine and react at 60 - 70 °C for 4 - 5 h. The mass ratio of N,N-dimethylformamide, silica-coated graphene, sodium hydroxide, hexadecene succinic anhydride, and 4-dimethylaminopyridine is 1500 - 1800:100:2 - 4:65 - 85:5 - 9. After the reaction is completed, filter, wash with deionized water, and dry at 80 °C for 12 h to obtain modified silica-coated graphene.

[0021] Preferably, in step (1), the concentration of sulfuric acid used in the preparation process of the modified silica-coated graphene is 12 mol / L, and the concentration of nitric acid is 10 mol / L.

[0022] Preferably, the mass ratio of the ink-absorbing material, disperse dye fixing agent, silica-coated graphene, and leveling agent in step two is 65 - 85:3 - 5:5 - 8:0.2 - 0.4.

[0023] Furthermore, the silica-coated graphene is the same as the silica-coated graphene in step one.

[0024] Preferably, the leveling agent in step two is a silicone-based leveling agent.

[0025] Preferably, the coating amount during the coating process in step two is 2.5 - 3.5 g / m 2 .

[0026] Preferably, the ink-absorbing material in step two includes one of sodium carboxymethyl cellulose, sodium carboxymethyl starch, and sodium alginate.

[0027] Preferably, the fixing agent in step two includes one of dodecyl trimethyl ammonium chloride, cetyl trimethyl ammonium chloride, and octadecyl trimethyl ammonium chloride.

[0028] Preferably, during the calendering and leveling process in Step 3, the roll pressure is 120 - 140 kN / m 2 , and the temperature on the roll surface is 125 - 150 °C.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The silica-coated graphene prepared in the present invention has a rich pore structure, which can improve the ink-holding ability of the transfer paper. After modification, it can be evenly dispersed in the substrate. At the same time, the silica-coated graphene has excellent mechanical properties. Acting together with nanocellulose, it can combine with the fiber structure in the mixed slurry to generate a binding force, significantly improving the paper strength, making the paper have a certain stiffness and anti-curling performance. After being curled and stored for a period of time, it can also quickly return to a flat state. It can also reduce the shrinkage rate of the paper during the thermal transfer process. The long-chain carbon-based hydrophobic structure on the hexadecene succinic anhydride introduced on the surface of the silica-coated graphene has excellent hydrophobic properties. After forming a film, it has a low surface energy and shows strong hydrophobic effects, effectively preventing the paper from swelling and deforming due to water absorption, accelerating the drying speed of the ink, increasing the ink release rate at the same time, and improving the ink-carrying capacity of the paper. At the same time, the flexibility is improved, increasing the ability of the paper to resist repeated folding. The folding endurance of the sized paper is improved. The added sizing agent can endow the paper with water absorption ability and has a good internal sizing effect. Based on the paper surface coating, the water absorption is controlled within a suitable range. The loosening agent, which is also an adhesive and dry strength agent, binds and expands during the paper drying process, increasing the bulk and dry strength of the paper.

[0031] In the present invention, the ink-absorbing material is selected as sodium carboxymethyl cellulose, etc. It has excellent ink-absorbing performance and high film-forming property. The formed functional coating is not easily penetrated into the base paper layer. At a low coating amount, it can have good ink-carrying capacity, reducing problems such as penetration blooming, low transfer rate, and pattern roughness caused by ink penetration. The disperse dye fixing agent in the coating can quickly combine and react with the anionic disperse dyes in the dye to form a water-resistant complex, preventing ink penetration, making the ink unable to spread, and making the image have high fineness. At the same time, it has a good sedimentation effect on the silica-coated graphene, obtaining a uniform mixed coating and making the coating more flat. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flow chart for preparing a thermal transfer paper with ultra-low shrinkage rate in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0034] Example 1

[0035] A preparation process of a thermal transfer paper with ultra-low elongation includes the following steps:

[0036] (1) Prepare the substrate

[0037] 1) Place bamboo pulp and bleached kraft pine pulp in a beating machine to beat them separately. After beating, mix them evenly. The concentration of bamboo pulp is 6.5%, the beating degree after beating is 36°SR, the concentration of bleached kraft softwood pulp is 5.5%, the beating degree after beating is 28°SR, and the mass ratio of the beaten bamboo pulp to the bleached kraft softwood pulp is 100:65 to obtain a mixed pulp;

[0038] 2) Ultrasonically disperse graphene oxide into a mixed acid, which is obtained by mixing sulfuric acid and nitric acid with a volume ratio of 4:1. The concentration of sulfuric acid is 12 mol / L, and the concentration of nitric acid is 10 mol / L. Perform acidification treatment. The mass ratio of graphene oxide to the mixed acid is 100:285. The temperature of the acidification treatment is 90 °C, and the time of the acidification treatment is 4 h. After the treatment is completed, filter, wash with deionized water, and dry to obtain acidified graphene. Then disperse the acidified graphene into a mixed solution of ethanol, ammonia water, and deionized water. After mixing evenly, add tetraethyl orthosilicate and react at 25 °C for 5 h. After the reaction is completed, wash with deionized water, centrifuge, the centrifugation rate is 6000 r / min, and vacuum dry at 60 °C for 8 h to obtain silica-coated graphene;

[0039] Ultrasonically disperse the silica-coated graphene into N,N-dimethylformamide, then add sodium hydroxide and hexadecene succinic anhydride. After mixing evenly, add 4-dimethylaminopyridine and react at 60 °C for 5 h. The mass ratio of N,N-dimethylformamide, silica-coated graphene, sodium hydroxide, hexadecene succinic anhydride, and 4-dimethylaminopyridine is 1500:100:2:65:5. After the reaction is completed, filter, wash with deionized water, and dry at 80 °C for 12 h to obtain modified silica-coated graphene;

[0040] (3) Add the mixed slurry, modified silica-coated graphene, nanocellulose, sizing agent cationic starch, and loosening agent sodium silicate with a mass ratio of 100:8:1:1.2:0.2 to the batching tank. After mixing evenly, pump it into the headbox, form it through a fourdrinier paper machine, dehydrate, press and dry. Control the vacuum degree at 0.09 MPa, the drying temperature at 105 °C, and control the moisture content at 5% to obtain the substrate;

[0041] (2) Coating

[0042] Mix the ink-absorbing material sodium carboxymethylcellulose, the disperse dye fixing agent cetyltrimethylammonium chloride, silica-coated graphene, and the silicone leveling agent with a mass ratio of 65:3:5:0.2 evenly to obtain the mixed coating;

[0043] Coat the mixed coating on the substrate prepared in step (1) by means of coating, with a coating amount of 2.5 g / m 2 , after coating, dry at 55 °C to obtain the coated substrate;

[0044] (3) Process the coiled finished product

[0045] After calendering and leveling the coated substrate with a controllable medium-high soft calender, during the calendering and leveling process, the roll pressure is 120 kN / m 2 , the temperature on the roll surface is 125 °C, wind up, slit, rewind, and package with a high-speed paper machine to obtain the thermal transfer paper with ultra-low shrinkage rate.

[0046] Example 2

[0047] A preparation process of a thermal transfer paper with ultra-low shrinkage rate, comprising the following steps:

[0048] (1) Prepare the substrate

[0049] 1) Place bamboo pulp and bleached kraft pine pulp in a refiner and beat them separately. After beating, mix them evenly. The concentration of bamboo pulp is 7%, the beating degree after beating is 37 °SR, the concentration of bleached kraft softwood pulp is 6%, the beating degree after beating is 30 °SR, and the mass ratio of the beaten bamboo pulp to the bleached kraft softwood pulp is 100:95 to obtain the mixed slurry;

[0050] (2) Ultrasonically disperse graphene oxide into a mixed acid, which is obtained by mixing sulfuric acid and nitric acid with a volume ratio of 4:1, where the concentration of sulfuric acid is 12 mol / L and the concentration of nitric acid is 10 mol / L, and conduct acidification treatment. The mass ratio of graphene oxide to the mixed acid is 100:310. The temperature of the acidification treatment is 92 °C, and the time of the acidification treatment is 3.5 h. After the treatment is completed, filter, wash with deionized water, and dry to obtain acidified graphene. Then disperse the acidified graphene into a mixed solution of ethanol, ammonia water, and deionized water. After mixing evenly, add tetraethyl orthosilicate and react at 30 °C for 4 h. After the reaction is completed, wash with deionized water, centrifuge at a centrifugation rate of 6000 r / min, and vacuum dry at 60 °C for 8 h to obtain silica-coated graphene;

[0051] Ultrasonically disperse the silica-coated graphene into N,N-dimethylformamide, then add sodium hydroxide and hexadecene succinic anhydride. After mixing evenly, add 4-dimethylaminopyridine and react at 65 °C for 4.5 h. The mass ratio of N,N-dimethylformamide, silica-coated graphene, sodium hydroxide, hexadecene succinic anhydride, and 4-dimethylaminopyridine is 1650:100:3:75:7. After the reaction is completed, filter, wash with deionized water, and dry at 80 °C for 12 h to obtain modified silica-coated graphene;

[0052] (3) Add a mixed slurry, modified silica-coated graphene, nanocellulose, sizing agent cationic starch, and loosening agent sodium silicate with a mass ratio of 100:10:1.5:1.5:0.24 to a batching tank. After mixing evenly, pump it into a headbox, form it through a Fourdrinier machine, dehydrate, press and dry, control the vacuum degree to be 0.12 MPa, the drying temperature to be 108 °C, and control the moisture content to be 5.5% to obtain a substrate;

[0053] (2) Coating

[0054] Mix carboxymethyl cellulose sodium as an ink-absorbing material, cetyltrimethylammonium chloride as a disperse dye fixing agent, silica-coated graphene, and an organosilicon leveling agent with a mass ratio of 75:4:6:0.3 evenly to obtain a mixed coating;

[0055] Coat the mixed coating on the substrate prepared in step one by coating. The coating amount is 2.8 g / m 2 , and after the coating is completed, dry at 60 °C to obtain a coated substrate;

[0056] (3) Process and curl the finished product

[0057] After using a controllable medium-high soft roll calender to perform calendering and leveling treatment on the coated substrate, during the calendering and leveling process, the roll pressure is 130 kN / m 2, the temperature of the roller surface is 140 °C, then wind up, use a high-speed paper machine for slitting, rewinding and packaging to obtain a thermal transfer paper with ultra-low shrinkage rate.

[0058] Example 3

[0059] A preparation process of a thermal transfer paper with ultra-low shrinkage rate, comprising the following steps:

[0060] (1) Prepare the base material

[0061] 1) Place bamboo pulp and bleached kraft pine pulp in a beating machine for beating respectively, and after beating, mix them evenly. Among them, the concentration of bamboo pulp is 7%, the beating degree after beating is 37°SR, the concentration of bleached kraft softwood pulp is 6%, the beating degree after beating is 30°SR, and the mass ratio of the beaten bamboo pulp to the bleached kraft softwood pulp is 100:95 to obtain a mixed pulp;

[0062] 2) Ultrasonically disperse graphene oxide into a mixed acid, which is obtained by mixing sulfuric acid and nitric acid with a volume ratio of 4:1. Among them, the concentration of sulfuric acid is 12 mol / L and the concentration of nitric acid is 10 mol / L for acidification treatment. The mass ratio of graphene oxide to the mixed acid is 100:310, the temperature of the acidification treatment is 92 °C, and the time of the acidification treatment is 3.5 h. After the treatment is completed, filter, wash with deionized water, and dry to obtain acidified graphene. Then disperse the acidified graphene into a mixed solution of ethanol, ammonia water and deionized water, mix evenly, add tetraethyl orthosilicate, react at 30 °C for 4 h. After the reaction is completed, wash with deionized water and centrifuge at a centrifugation rate of 6000 r / min, and vacuum dry at 60 °C for 8 h to obtain silica-coated graphene;

[0063] Disperse the silica-coated graphene ultrasonically into N,N-dimethylformamide, then add sodium hydroxide and hexadecene succinic anhydride, mix evenly, add 4-dimethylaminopyridine, and react at 65 °C for 4.5 h. The mass ratio of N,N-dimethylformamide, silica-coated graphene, sodium hydroxide, hexadecene succinic anhydride and 4-dimethylaminopyridine is 1650:100:3:75:7. After the reaction is completed, filter, wash with deionized water, and dry at 80 °C for 12 h to obtain modified silica-coated graphene;

[0064] 3) Add the mixed pulp, modified silica-coated graphene, nanocellulose, sizing agent cationic starch and loosening agent sodium silicate with a mass ratio of 100:12:2.5:1.8:0.28 to the batching tank, mix evenly, pump it into the headbox, form it through a fourdrinier paper machine, dehydrate, press and dry, control the vacuum degree to be 0.12 MPa, the drying temperature to be 108 °C, and control the moisture content to be 5.5% to obtain the base material;

[0065] (2) Coating

[0066] Mix sodium carboxymethyl cellulose as an ink-absorbing material, cetyltrimethylammonium chloride as a disperse dye fixing agent, graphene coated with silica, and an organosilicon leveling agent with a mass ratio of 75:4:6:0.3 evenly to obtain a mixed coating;

[0067] Coat the mixed coating on the substrate prepared in step (1) by means of coating, with a coating amount of 3.2 g / m 2 , and after the coating is completed, dry it at 60 °C to obtain the coated substrate;

[0068] (3) Process the coiled finished product

[0069] After performing calendering and leveling treatment on the coated substrate using a controllable medium-high soft calender, during the calendering and leveling process, the roll pressure is 130 kN / m 2 , the temperature on the roll surface is 140 °C, wind it up, and use a high-speed paper machine to slit, rewind, and package to obtain a thermal transfer paper with an ultra-low shrinkage rate.

[0070] Example 4

[0071] A preparation process for a thermal transfer paper with an ultra-low shrinkage rate, comprising the following steps:

[0072] (1) Prepare the substrate

[0073] 1) Place bamboo pulp and bleached kraft pine pulp in a refiner and beat them separately. After beating, mix them evenly. Among them, the concentration of bamboo pulp is 8%, the beating degree after beating is 38 °SR, the concentration of bleached kraft softwood pulp is 7%, the beating degree after beating is 31 °SR, and the mass ratio of the beaten bamboo pulp to the bleached kraft softwood pulp is 100:115 to obtain a mixed pulp;

[0074] 2) Ultrasonically disperse graphene oxide into a mixed acid, which is obtained by mixing sulfuric acid and nitric acid with a volume ratio of 4:1, where the concentration of sulfuric acid is 12 mol / L and the concentration of nitric acid is 10 mol / L, and perform acidification treatment. Among them, the mass ratio of graphene oxide to the mixed acid is 100:340, the temperature of the acidification treatment is 95 °C, the time of the acidification treatment is 3 h. After the treatment is completed, filter, wash with deionized water, and dry to obtain acidified graphene. Then disperse the acidified graphene into a mixed solution of ethanol, ammonia water, and deionized water, mix evenly, add tetraethyl orthosilicate, and react at 35 °C for 3 h. After the reaction is completed, wash with deionized water, centrifuge, with a centrifugation rate of 6000 r / min, and vacuum dry at 60 °C for 8 h to obtain graphene coated with silica;

[0075] The silica-coated graphene is ultrasonically dispersed in N,N-dimethylformamide, then sodium hydroxide and hexadecene succinic anhydride are added. After mixing evenly, 4-dimethylaminopyridine is added, and the reaction is carried out at 70 °C for 4 h. The mass ratio of N,N-dimethylformamide, silica-coated graphene, sodium hydroxide, hexadecene succinic anhydride and 4-dimethylaminopyridine is 1800:100:4:85:9. After the reaction is completed, filtration is carried out, washed with deionized water, and dried at 80 °C for 12 h to obtain modified silica-coated graphene;

[0076] (3) A mixed slurry with a mass ratio of 100:13:3:2:0.3, modified silica-coated graphene, nanocellulose, sizing agent cationic starch and loosening agent sodium silicate are added to the batching tank. After mixing evenly, it is pumped into the headbox, formed by a fourdrinier paper machine, dehydrated, pressed and dried. The vacuum degree is controlled at 0.15 MPa, the drying temperature is 110 °C, and the water content is controlled at 6% to obtain the substrate;

[0077] (2) Coating

[0078] Carboxymethyl cellulose sodium as the ink-absorbing material, cetyltrimethylammonium chloride as the disperse dye fixing agent, silica-coated graphene and silicone leveling agent with a mass ratio of 85:5:8:0.4 are mixed evenly to obtain a mixed coating;

[0079] The mixed coating is coated on the substrate prepared in step one by coating, and the coating amount is 3.5 g / m 2 , after the coating is completed, it is dried at 65 °C to obtain the coated substrate;

[0080] (3) Processing and curling into finished products

[0081] After the coated substrate is calendered and leveled using a controllable medium-high soft calender, during the calendering and leveling process, the roll pressure is 140 kN / m 2 , the temperature on the roll surface is 150 °C, wound up, slit, rewound and packaged using a high-speed paper machine to obtain a thermal transfer paper with ultra-low elongation.

[0082] Comparative Example 1

[0083] A preparation process of a thermal transfer paper with ultra-low elongation, comprising the following steps:

[0084] (1) Preparing the substrate

[0085] 1) Place bamboo pulp and bleached kraft pine pulp in a refiner for beating respectively. After beating, mix them evenly. Among them, the concentration of bamboo pulp is 7%, the beating degree after beating is 37°SR, the concentration of bleached kraft softwood pulp is 6%, the beating degree after beating is 30°SR, and the mass ratio of the beaten bamboo pulp to the bleached kraft softwood pulp is 100:95 to obtain a mixed pulp;

[0086] 2) Add the mixed pulp, graphene oxide, nanocellulose, sizing agent cationic starch, and loosening agent sodium silicate with a mass ratio of 100:12:2.5:1.8:0.28 to a batching tank, mix evenly, then pump it into a headbox, form it through a fourdrinier paper machine, dehydrate, press and dry. Control the vacuum degree at 0.12 MPa, the drying temperature at 108 °C, and control the moisture content at 5.5% to obtain a base material;

[0087] (2) Coating

[0088] Mix the ink-absorbing material sodium carboxymethylcellulose, disperse dye fixing agent cetyltrimethylammonium chloride, silica-coated graphene, and silicone leveling agent with a mass ratio of 75:4:6:0.3 evenly to obtain a mixed coating;

[0089] Coat the mixed coating on the base material prepared in step one by coating method, and the coating amount is 3.2 g / m 2 , after coating, dry at 60 °C to obtain the coated base material;

[0090] (3) Processing and curling into finished products

[0091] After calendering and leveling the coated base material with a controllable medium-high soft roll calender, during the calendering and leveling process, the roll pressure is 130 kN / m 2 , the temperature on the roll surface is 140 °C, wind up, and use a high-speed paper machine to slit, rewind, and package to obtain a thermal transfer paper with ultra-low shrinkage rate.

[0092] Comparative Example 2

[0093] A preparation process of a thermal transfer paper with ultra-low shrinkage rate, comprising the following steps:

[0094] (1) Prepare the base material

[0095] 1) Place bamboo pulp and bleached kraft pine pulp in a refiner for beating respectively. After beating, mix them evenly. Among them, the concentration of bamboo pulp is 7%, the beating degree after beating is 37°SR, the concentration of bleached kraft softwood pulp is 6%, the beating degree after beating is 30°SR, and the mass ratio of the beaten bamboo pulp to the bleached kraft softwood pulp is 100:95 to obtain a mixed pulp;

[0096] (2) Ultrasonically disperse graphene oxide into a mixed acid, which is obtained by mixing sulfuric acid and nitric acid with a volume ratio of 4:1. The concentration of sulfuric acid is 12 mol / L, and the concentration of nitric acid is 10 mol / L. Acidification treatment is carried out, where the mass ratio of graphene oxide to the mixed acid is 100:310. The temperature of the acidification treatment is 92 °C, and the time of the acidification treatment is 3.5 h. After the treatment is completed, filter, wash with deionized water, and dry to obtain acidified graphene. Then disperse the acidified graphene into a mixed solution of ethanol, ammonia water, and deionized water. After mixing evenly, add tetraethyl orthosilicate and react at 30 °C for 4 h. After the reaction is completed, wash with deionized water, centrifuge at a centrifugation rate of 6000 r / min, and vacuum dry at 60 °C for 8 h to obtain silica-coated graphene;

[0097] Ultrasonically disperse the silica-coated graphene into N,N-dimethylformamide, then add sodium hydroxide and hexadecene succinic anhydride. After mixing evenly, add 4-dimethylaminopyridine and react at 65 °C for 4.5 h. The mass ratio of N,N-dimethylformamide, silica-coated graphene, sodium hydroxide, hexadecene succinic anhydride, and 4-dimethylaminopyridine is 1650:100:3:75:7. After the reaction is completed, filter, wash with deionized water, and dry at 80 °C for 12 h to obtain modified silica-coated graphene;

[0098] (3) Add a mixed slurry, modified silica-coated graphene, nanocellulose, sizing agent cationic starch, and loosening agent sodium silicate with a mass ratio of 100:12:2.5:1.8:0.28 to a batching tank. After mixing evenly, pump it into a headbox, form it through a fourdrinier machine, dehydrate, press and dry. Control the vacuum degree to be 0.12 MPa, the drying temperature to be 108 °C, and control the water content to be 5.5% to obtain a substrate;

[0099] (2) Process the coiled finished product

[0100] After performing calendering and leveling treatment on the substrate using a controllable medium-high soft roll calender, during the calendering and leveling process, the roll pressure is 130 kN / m 2 , the temperature on the roll surface is 140 °C, wind up, cut, rewind, and package using a high-speed paper machine to obtain a thermal transfer paper with ultra-low elongation.

[0101] In the examples and comparative examples of the present invention, the graphene oxide used is multi-layer graphene oxide purchased from Suzhou Hengqiu Technology Co., Ltd. (purity > 95 wt%, thickness 3.4 - 8 nm, sheet diameter 10 - 50 μm); cationic starch is purchased from Guangdong Hongxin Biotechnology Co., Ltd., product number 88688; nano-cellulose is purchased from Funa New Materials Technology (Shanghai) Co., Ltd., product number 9112; sodium carboxymethyl cellulose is purchased from Hebei Yanxing Chemical Industry Co., Ltd.; sodium silicate is purchased from Huangshan Shexian Zhongjia Chemical Industry Co., Ltd.; other reagents are all commercially available.

[0102] The ultra-low stretch rate thermal transfer papers prepared in Examples 1 - 4 and Comparative Examples 1 - 2 were used as samples for performance testing. Samples with similar grammage were selected. The standard reference GB / T 451.2 - 2002 Determination of Basis Weight of Paper and Board was selected. After the samples were selected, the corresponding tests were as follows:

[0103] 1) Stretch rate test: The test was carried out in accordance with the test standard of GB / T 459 - 2002 Test Methods for Stretchability of Paper and Board.

[0104] 2) Tensile strength test: The test was carried out in accordance with the test standard of GB / T 12914 - 2018 Determination of Tensile Strength of Paper and Board - Constant Rate of Elongation Method (20 mm / min).

[0105] 3) Water absorbency test: The test was carried out in accordance with the test standard of GB / T 1540 - 2002 Determination of Water Absorbency of Paper and Board (Köbe method).

[0106] The test results are shown in Table 1:

[0107] Table 1

[0108]

[0109] From the test results in Table 1, it can be seen that Examples 1 - 4 have a lower stretch rate, higher tensile strength, effectively improve the warping problem, better water absorbency, stronger ink loading capacity, will not penetrate, and have a clearer pattern during transfer compared with Comparative Examples 1 - 2.

[0110] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. All equivalent changes and improvements made within the scope of the application of the present invention shall still fall within the scope covered by the patent of the present invention.

Claims

1. A preparation process of a thermal transfer paper with an ultra-low elongation rate, characterized in that: It includes the following steps: Step 1: Place bamboo pulp and bleached softwood kraft pulp in a refiner for beating respectively. After beating, mix the two evenly to obtain a mixed pulp; Transfer the mixed pulp to a batching tank, then add modified silica-coated graphene, nanocellulose, sizing agent and loosening agent. After mixing evenly, pump it into a headbox, form it through a fourdrinier machine, dehydrate, press and dry. Control the vacuum degree to be 0.09 - 0.15 MPa, the drying temperature to be 105 - 110 °C, and control the water content to be 5 - 6% to obtain a substrate; The preparation method of the modified silica-coated graphene in Step 1 includes the following steps: Ultrasonically disperse graphene oxide into a mixed acid, which is obtained by mixing sulfuric acid and nitric acid with a volume ratio of 4:1, and carry out acidification treatment. The mass ratio of graphene oxide to the mixed acid is 100:285 - 340, the temperature of acidification treatment is 90 - 95 °C, and the time of acidification treatment is 3 - 4 h. After the treatment is completed, filter, wash with deionized water, and dry to obtain acidified graphene. Then disperse the acidified graphene into a mixed solution of ethanol, ammonia water and deionized water. After mixing evenly, add tetraethyl orthosilicate and react at 25 - 35 °C for 3 - 5 h. After the reaction is completed, wash with deionized water, centrifuge, with a centrifuge speed of 6000 r / min, and vacuum dry at 60 °C for 8 h to obtain silica-coated graphene; Ultrasonically disperse silica-coated graphene into N,N-dimethylformamide, then add sodium hydroxide and hexadecene succinic anhydride. After mixing evenly, add 4-dimethylaminopyridine and react at 60 - 70 °C for 4 - 5 h. The mass ratio of N,N-dimethylformamide, silica-coated graphene, sodium hydroxide, hexadecene succinic anhydride and 4-dimethylaminopyridine is 1500 - 1800:100:2 - 4:65 - 85:5 - 9. After the reaction is completed, filter, wash with deionized water, and dry at 80 °C for 12 h to obtain modified silica-coated graphene; Step 2: Mix the ink-absorbing material, fixing agent, silica-coated graphene and leveling agent evenly to obtain a mixed coating; Coat the mixed coating on the substrate prepared in Step 1 by coating. After the coating is completed, dry at 55 - 65 °C to obtain a coated substrate; The preparation method of the silica-coated graphene in Step 2 is the same as that of the silica-coated graphene in Step 1; Step 3: Use a controllable medium-high soft roll calender to calender and flatten the coated substrate, then wind it up, and use a high-speed paper machine to slit, rewind and package to obtain a thermal transfer paper with ultra-low elongation.

2. The preparation process of a thermal transfer paper with an ultra-low elongation rate according to claim 1, characterized in that: In Step 1, the concentration of bamboo pulp is 6.5 - 8%, the beating degree after beating is 36 - 38 °SR, the concentration of bleached softwood kraft pulp is 5.5 - 7%, and the beating degree after beating is 28 - 31 °SR; the mass ratio of bamboo pulp and bleached softwood kraft pulp after beating in the mixed pulp is 100:65 - 115.

3. The preparation process of a thermal transfer paper with an ultra-low elongation rate according to claim 1, characterized in that: In the first step, the mass ratio of the mixed slurry, modified silica-coated graphene, nanocellulose, sizing agent and loosening agent is 100:8-13:1-3:1.2-2:0.2-0.

3.

4. The preparation process of a thermal transfer paper with an ultra-low elongation rate according to claim 1, characterized in that: In the first step, the sizing agent includes one of cationic polymers, rosin sizing agents and alkyl ketene dimers; in the first step, the loosening agent includes sodium silicate.

5. The preparation process of a thermal transfer paper with an ultra-low elongation rate according to claim 1, characterized in that: In the second step, the mass ratio of the ink-absorbing material, fixing agent, silica-coated graphene and leveling agent is 65-85:3-5:5-8:0.2-0.

4.

6. The preparation process of a thermal transfer paper with an ultra-low elongation rate according to claim 1, characterized in that: The coating amount during the coating process in the second step is 2.5 - 3.5 g / m 2 .

7. The preparation process of a thermal transfer paper with an ultra-low elongation rate according to claim 1, characterized in that: In the second step, the ink-absorbing material includes one of sodium carboxymethyl cellulose, sodium carboxymethyl starch and sodium alginate.

8. The preparation process of a thermal transfer paper with an ultra-low elongation rate according to claim 1, characterized in that: In the second step, the fixing agent includes one of dodecyl trimethyl ammonium chloride, cetyl trimethyl ammonium chloride and octadecyl trimethyl ammonium chloride.

9. The preparation process of a thermal transfer paper with an ultra-low elongation rate according to claim 1, characterized in that: During the calendering and leveling process in Step 3, the roll pressure is 120 - 140 kN / m 2 , and the temperature on the roll surface is 125 - 150 °C.

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