Resin for heat transfer printing ink and preparation method thereof

Abstract

The invention discloses resin for heat transfer printing ink. The resin comprises dihydric alcohol, tribasic acid, a catalyst and a solvent. According to the invention, by researching the composition of dihydric alcohol and selecting a composition of ethylene glycol, 1, 4-cyclohexanedimethanol and terephthalyl alcohol, the molecular chain length of polyester can be effectively increased, and the molecular weight is increased, so that the stability and the surface energy of the resin are improved, and the adsorption capacity of the ink resin on a film (such as PET) with low surface energy is effectively realized; and the dragging tensile strength among polyester type ink molecules in the heat transfer printing process is reduced, so that the pattern contour is clearer, and the edge is free of sawteeth. Meanwhile, an ink heat transfer printing pattern prepared from the resin has the characteristics of small thickness and high dyne value.

Description

Technical Field

[0001] The invention belongs to the field of resin materials, and in particular relates to a resin for thermal transfer ink and a preparation method thereof. Background Art

[0002] Thermal transfer ink refers to the ink that prints patterns and texts on special paper / film, and then transfers the printed patterns and texts to other materials by contact heating. Its ingredients generally include base resin, coloring material, wetting agent, dispersant, etc. According to the base resin classification, there are mainly polyester ink and acrylic ink. As we all know, the surface energy of acrylic resin is low. The ink prepared by acrylic resin has poor adhesion to smooth film materials and low surface energy substrates (such as PET film). It is easy to fall off and separate after application, and fails the hundred grid test. The brittleness of polyester resin is worse than that of acrylic acid, and it has strong flexibility. After thermal transfer, the ink will separate from PET to the material. The molecules in polyester ink will be stretched, which often causes the ink outside the transfer pattern to be involved on the film substrate, resulting in unclear pattern contours and large jagged edges, affecting the quality of the product.

[0003] Chinese patent CN112250854A discloses a UV ink oligomer resin for thermal transfer film and its preparation method and application. By studying polycarbonate-based oligomers and acrylic monomers containing double bonds, a UV curing ink with suitable viscosity is prepared to achieve the effect of UV curing energy saving. Chinese patent CN111592643A discloses a polyester resin for thermal transfer powder coating and its preparation method. The transfer material is high-precision paper. The study uses polyols and polyacids to condense to obtain a product surface with bright image colors, and the transfer effect can be comparable to printing, and the thermal transfer product is durable.

[0004] Different from this, the present invention mainly aims at the problems of weak brittleness of existing polyester resins and unclear contours of the transfer patterns and large edge jaggedness when used on PET films, and develops and synthesizes a branched polyester resin with strong brittleness, moderate molecular weight and good adsorption capacity. The ink resin of the present invention can be widely used in thermal transfer inks, especially in various film materials with smooth surfaces and substrates with low surface energy. Summary of the invention

[0005] In view of the above shortcomings of the prior art, the present invention provides a resin for thermal transfer ink and a preparation method thereof.

[0006] A first object of the present invention is to provide a resin for thermal transfer ink.

[0007] The components of the thermal transfer ink resin of the present invention include diol, tribasic acid, catalyst and solvent.

[0008] The diol composition is a mixture of multiple diols. Further, the diol is a composition of ethylene glycol, 1,4-cyclohexanedimethanol, and terephthalene glycol. Specifically, the diol is 20 to 50 parts of ethylene glycol, 50 to 90 parts of 1,4-cyclohexanedimethanol, and 50 to 80 parts of terephthalene glycol. In some embodiments, the ratio of ethylene glycol, 1,4-cyclohexanedimethanol, and terephthalene glycol is 31:73:70. The inventors have found through research that the selection of specific polyol molecules can effectively increase the molecular chain length of polyester and increase the molecular weight, thereby improving the stability and surface energy of the resin, effectively realizing the adsorption capacity of the ink resin on films with low surface energy (such as PET), and reducing the tensile strength of the polyester ink molecules during the thermal transfer process, so that the pattern contour is clearer and the edge has no jagged effect.

[0009] The tribasic acid is selected from 150 to 220 parts of trimellitic anhydride. Further, 180 to 200 parts of trimellitic anhydride.

[0010] The catalyst is selected from 0.5 to 2.5 parts of triphenyl phosphine, specifically 1.0 to 2.0 parts of triphenyl phosphine.

[0011] The solvent is an organic solvent, specifically, the organic solvent of the present invention is selected from dimethylformamide, dimethylacetamide or a combination thereof. The solvent is selected in an amount of 250 to 450 parts in the solution of the diol.

[0012] The molecular weight of the branched resin of the present invention is between 10,000 and 30,000, and a suitable molecular weight of the resin is beneficial to improving the thermal stability of the resin and maintaining good resin performance during the thermal transfer process.

[0013] The thermal transfer ink resin of the present invention can be added with carbon powder, dispersant, wetting agent and other additives to prepare thermal transfer ink, and thermally transferred to a PET film at a temperature of 180°C to 220°C. The 100-grid test is passed, and the transferred pattern has small jagged edges and clear contours.

[0014] Specifically, a better solution of the present invention may be as follows: The weight parts of each component of the raw materials are:

[0015] The second object of the present invention is to provide a method for preparing a thermal transfer ink resin. The preparation process steps are: (1) Preparation of diols: Diol monomers ethylene glycol, 1,4-cyclohexanedimethanol and terephthalimethanol are dissolved in equal parts of dimethylacetamide, stirred evenly and then placed in a constant pressure dropping funnel.

[0016] (2) Preparation of tribasic acid: Add trimellitic anhydride monomer, triphenylphosphine catalyst and the rest dimethylformamide into a glass bottle, protect with nitrogen, and heat to 120 degrees.

[0017] (3) Gradually drip the diol solution prepared in the first step into the tribasic acid solution in the glass bottle in the second step. Finish dripping in 1 hour and continue the reaction for 2 hours. (4) Raise the temperature to 200°C, evacuate the mixture and continue the reaction for 4 hours to synthesize a branched polyester resin.

[0018] Beneficial effects of the present invention: The branched polyester resin synthesized by the present invention is prepared from trimellitic anhydride, ethylene glycol, terephthalic alcohol, and 1,4-cyclohexanedimethanol as monomers, and is polycondensed into a branched polyester resin by a two-step method. After adding carbon powder, a dispersant, a wetting agent and other additives, it is prepared into a thermal transfer ink, and is thermally transferred to a PET film at a temperature of 180° C. to 220° C. The 100-grid test is passed, and the transferred pattern has a small jagged edge and a clear outline of the transferred pattern. In addition, the thermal transfer pattern using the resin-prepared ink of the present invention has the characteristics of small thickness and high dyne value. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a photo of the thermal transfer of Example 1 onto a PET film. Figure 2 This is the edge appearance of the sample in Example 1 magnified 100 times Figure 3 This is the edge appearance of the sample in comparative example 1 magnified 100 times Figure 4 This is the edge appearance of the sample in comparative example 2 magnified 100 times DETAILED DESCRIPTION

[0020] The embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application. Example 1

[0021] Weigh the ingredients as follows: Ethylene glycol 31g 1,4-Cyclohexanedimethanol 73g 70g of terephthalate Triphenylphosphine 1.53g Trimellitic anhydride 192g Dimethylformamide 366g Preparation method: (1) Preparation of diols: Diol monomers ethylene glycol, 1,4-cyclohexanedimethanol and terephthalimethanol were dissolved in equal parts of dimethylformamide, stirred evenly and then placed in a constant pressure dropping funnel.

[0022] (2) Preparation of tribasic acid: Add trimellitic anhydride monomer, triphenylphosphine catalyst and the rest dimethylformamide into a glass bottle, protect with nitrogen, and heat to 120 degrees.

[0023] (3) Gradually drip the diol solution prepared in the first step into the tribasic acid solution in the glass bottle in the second step. Finish dripping in 1 hour and continue the reaction for 2 hours. (4) Raise the temperature to 200°C, evacuate the mixture and continue the reaction for 4 hours to synthesize a branched polyester resin.

[0024] The resin of Example 1 was used, and after adding additives such as 30% carbon powder, 1% dispersant, and 0.5% wetting agent, a thermal transfer ink was prepared and tested on a thermal transfer paper PET film at 180° C. to 220° C. Example 2

[0025] Weigh the ingredients as follows: Ethylene glycol 24.8g 1,4-Cyclohexanedimethanol 86.4g 70g of terephthalate Triphenylphosphine 1.87g Trimellitic anhydride 192g Dimethylformamide 372g Preparation method: (1) Preparation of diols: Diol monomers ethylene glycol, 1,4-cyclohexanedimethanol and terephthalimethanol are dissolved in equal parts of dimethylacetamide, stirred evenly and then placed in a constant pressure dropping funnel.

[0026] (2) Preparation of tribasic acid: Add trimellitic anhydride monomer, triphenylphosphine catalyst and the rest dimethylformamide into a glass bottle, protect with nitrogen, and heat to 120 degrees.

[0027] (3) Gradually drip the diol solution prepared in the first step into the tribasic acid solution in the glass bottle in the second step. Finish dripping in 1 hour and continue the reaction for 2 hours. (4) Raise the temperature to 200°C, evacuate the mixture and continue the reaction for 4 hours to synthesize a branched polyester resin.

[0028] The resin of Example 1 was used, and after adding additives such as 30% carbon powder, 1% dispersant, and 0.5% wetting agent, a thermal transfer ink was prepared and tested on a thermal transfer paper PET film at 180° C. to 220° C. Example 3

[0029] Weigh the ingredients as follows: Ethylene glycol 37.2g 1,4-Cyclohexanedimethanol 72g 55.2g of terephthalic acid Triphenylphosphine 1.78g Trimellitic anhydride 192g Dimethylformamide 356g Preparation method: (1) Preparation of diols: Diol monomers ethylene glycol, 1,4-cyclohexanedimethanol and terephthalimethanol are dissolved in equal parts of dimethylacetamide, stirred evenly and then placed in a constant pressure dropping funnel.

[0030] (2) Preparation of tribasic acid: Add trimellitic anhydride monomer, triphenylphosphine catalyst and the rest dimethylformamide into a glass bottle, protect with nitrogen, and heat to 120 degrees.

[0031] (3) Gradually drip the diol solution prepared in the first step into the tribasic acid solution in the glass bottle in the second step. Finish dripping in 1 hour and continue the reaction for 2 hours. (4) Raise the temperature to 200°C, evacuate the mixture and continue the reaction for 4 hours to synthesize a branched polyester resin.

[0032] The resin of Example 1 was used, and after adding additives such as 30% carbon powder, 1% dispersant, and 0.5% wetting agent, a thermal transfer ink was prepared and tested on a thermal transfer paper PET film at 180° C. to 220° C.

[0033] Comparative Example 1: Weigh the ingredients of the raw materials as follows: Ethylene glycol 93g Triphenylphosphine 1.42g Trimellitic anhydride 192g Dimethylformamide 285g Preparation method: (1) Preparation of diols: Dissolve the diol monomer ethylene glycol in an equal amount of dimethylacetamide, stir evenly and place in a constant pressure dropping funnel.

[0034] (2) Preparation of tribasic acid: Add trimellitic anhydride monomer, triphenylphosphine catalyst and the rest dimethylformamide into a glass bottle, protect with nitrogen, and heat to 120 degrees.

[0035] (3) Gradually drip the diol solution prepared in the first step into the tribasic acid solution in the glass bottle in the second step. Finish dripping in 1 hour and continue the reaction for 2 hours. (4) Raise the temperature to 200°C, evacuate the mixture and continue the reaction for 4 hours to synthesize a branched polyester resin.

[0036] The resin of Example 1 was used, and after adding additives such as 30% carbon powder, 1% dispersant, and 0.5% wetting agent, a thermal transfer ink was prepared and tested on a thermal transfer paper PET film at 180° C. to 220° C.

[0037] Comparative Example 2: Weigh the ingredients of the raw materials as follows: 1,4-Cyclohexanedimethanol 108g 103.5 g of terephthalic acid Triphenylphosphine 2.02g Trimellitic anhydride 192g Dimethylformamide 403.5g Preparation method: (1) Preparation of diols: Dissolve diol 1,4-cyclohexanedimethanol and p-phenylenedimethanol in equal parts of dimethylformamide, stir evenly, and then place in a constant pressure dropping funnel.

[0038] (2) Preparation of tribasic acid: Add trimellitic anhydride monomer, triphenylphosphine catalyst and the rest dimethylformamide into a glass bottle, protect with nitrogen, and heat to 120 degrees.

[0039] (3) Gradually drip the diol solution prepared in the first step into the tribasic acid solution in the glass bottle in the second step. Finish dripping in 1 hour and continue the reaction for 2 hours. (4) Raise the temperature to 200°C, evacuate the mixture and continue the reaction for 4 hours to synthesize a branched polyester resin.

[0040] The resin of Example 1 was used, and after adding additives such as 30% carbon powder, 1% dispersant, and 0.5% wetting agent, a thermal transfer ink was prepared and tested on a thermal transfer paper PET film at 180° C. to 220° C.

[0041] Experimental Results Example 1, Comparative Example 1 and Comparative Example 2 were prepared into thermal transfer inks, and the transfer patterns were subjected to a hundred-grid test, appearance profile test, thickness test and dyne value test on a thermal transfer paper PET film at 180° C. to 220° C.

[0042] 1. Testing equipment and testing standards are as follows:

[0043] 2. Test results

[0044] The results show that: (1) Compared with Comparative Example 1, the ink prepared by the resin of the present invention has a clear appearance after thermal transfer. Increasing the type of diol can effectively solve the problem of unclear pattern outline and large edge jaggedness caused by using polyester resin.

[0045] (2) Compared with Comparative Example 2, the ink prepared by the resin of the present invention passed the 100-grid test after thermal transfer. Increasing the type of diol can effectively improve the adhesion of the ink on the film material with a smooth surface and pass the 100-grid test.

Claims

1. A resin for thermal transfer ink, comprising diol, tribasic acid, catalyst, and solvent, characterized in that: The composition comprises the following components in parts by weight: 20~50 parts of ethylene glycol 1,4-cyclohexanedimethanol 50~90 parts 50~80 parts of terephthalic acid 0.5 to 2.5 parts of triphenylphosphine 150~220 parts of trimellitic anhydride 250~450 parts of solvent.

2. The resin of thermal transfer ink according to claim 1, characterized in that: The catalyst is selected from 1.0 to 2.0 parts of triphenylphosphine.

3. The resin of thermal transfer ink according to claim 1, characterized in that: The molecular weight of the resin ranges from 10,000 to 30,000.

4. The resin of thermal transfer ink according to claim 1, characterized in that: The ratio of ethylene glycol, 1,4-cyclohexanedimethanol and 1,4-dimethylol is 31:73:

70.

5. The resin of thermal transfer ink according to claim 2, characterized in that: The tribasic acid is selected from 180 to 200 parts of trimellitic anhydride.

6. The resin of thermal transfer ink according to claim 1, characterized in that: The solvent is dimethylformamide, dimethylacetamide or a combination thereof.

7. A method for preparing a thermal transfer ink resin according to claim 1, 2, 3, 4, 5 or 6, characterized in that: The following steps are involved: (1) Preparation of diols: Dissolve diol monomers ethylene glycol, 1,4-cyclohexanedimethanol and terephthalimethanol in equal parts of solvent, stir evenly and place in a constant pressure dropping funnel: (2) Preparation of tribasic acid: Add trimellitic anhydride monomer, triphenylphosphine catalyst, and remaining solvent into a glass bottle, protect with nitrogen, and heat to 120 degrees: (3) Gradually drip the diol solution prepared in the first step into the tribasic acid solution in the glass bottle in the second step. Finish dripping in 1 hour and continue the reaction for 2 hours. (4) Raise the temperature to 200°C, evacuate the mixture and continue the reaction for 4 hours to synthesize a branched polyester resin.

8. Use of the resin of the thermal transfer ink according to claim 1, 2, 3, 4, 5 or 6 in preparing a thermal transfer ink for PET film.

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