Ink set for coating-free thermal transfer printing and ink jet method for coating-free thermal transfer printing

Abstract

The invention provides an ink set for coating-free thermal transfer printing and an ink jet method for coating-free thermal transfer printing. The ink set comprises colored ink and colorless ink. The colored ink comprises disperse dye color paste, an alkali swelling thickening agent and a first PH control agent, the alkali swelling thickening agent is selected from a cross-linked polymer emulsion thickening agent containing an acidic group, and the PH of the colored ink is 3.0-3.5; the colorless ink comprises a second PH control agent, and the PH of the colorless ink ranges from 8.0 to 9.0. The colored ink contains the alkali swelling thickening agent, when the colored ink makes contact with the colorless ink, the colorless ink is alkaline, under alkaline neutralization, particles of the alkali swelling thickening agent swell rapidly, the viscosity of the colored ink is increased rapidly, anti-rheological liquid is formed, good suspension property and stability are achieved, ink droplets are formed on the surface of the coating-free heat sublimation transfer paper, and the anti-rheological property of the coating-free heat sublimation transfer paper is improved. And the motion trail that ink longitudinally permeates into the paper and transversely permeates to the periphery is well controlled, so that the purpose of improving the transfer printing rate is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of uncoated thermal transfer, and in particular to an ink set for uncoated thermal transfer and an inkjet method for uncoated thermal transfer. Background Art

[0002] As the world's main producer of sublimation transfer paper, China is advancing with the times and innovating under the impetus of increasing environmental protection and textile printing quality requirements. The main cost of inkjet sublimation transfer paper is the base paper and coating. Reducing the weight of the heat transfer paper and the thickness of the coating has become the main means of reducing the cost of sublimation transfer paper. Starting from the 100g sublimation transfer paper on the market in 2005, it has roughly experienced 5 stages of 70g, 60g, 45g, 40g and 31g over the years. With the lightweight of inkjet sublimation transfer paper, the price continues to decline. The possibility of further reducing the weight is getting smaller and smaller due to technical bottlenecks. This is because coated transfer paper needs to be coated with heat transfer coating on the basis of base paper. Reducing the weight of the base paper will make production unstable, and the heat transfer coating will cause the paper surface to warp, thus affecting inkjet printing and heat transfer. The cost reduction effect brought by lightweight thermal transfer paper is obvious. For this reason, the solution to further reduce costs is to produce uncoated ultra-thin transfer paper, starting at 28 grams of paper and gradually reducing it to 18 grams. This type of transfer paper eliminates the coating process, which greatly improves the production qualification rate, makes the paper surface smoother, and has better flexibility, further reducing the production cost of paper.

[0003] In actual application, uncoated sublimation transfer paper weighing about 20 grams can complete the transfer process in only 25 seconds under the environmental conditions of 220℃, which is equivalent to the efficiency of ordinary sublimation transfer paper. At the same time, uncoated sublimation transfer paper shows significant advantages in price, which is low in price. This feature greatly reduces the production cost. In addition, uncoated sublimation transfer paper has become an ideal choice in the field of environmental protection due to its higher recycling value, which is fully in line with the pursuit of green and sustainable production methods. Uncoated transfer paper has become a new trend in sublimation printing production with its low unit price, low gram weight and high ink carrying capacity.

[0004] Ordinary sublimation ink needs to be printed on high-weight, coated transfer paper, but since uncoated sublimation transfer paper has no coating, when using existing ink to print on uncoated sublimation transfer paper, the ink easily seeps to the back of the paper, resulting in a low transfer rate. The existing ink has poor adaptability and matching with uncoated sublimation transfer paper, resulting in white spots, color difference, poor color saturation and other problems on textiles, seriously affecting the quality and product qualification rate. Summary of the invention

[0005] The first object of the present invention is to provide an uncoated thermal transfer ink set, which is used to adapt to uncoated thermal sublimation transfer paper and improve the transfer rate.

[0006] The second object of the present invention is to provide an inkjet method for uncoated thermal transfer, which utilizes the above-mentioned uncoated thermal transfer ink set for printing.

[0007] To achieve the first purpose of the present invention, the present invention provides an ink set for uncoated thermal transfer, the ink set comprising a colored ink and a colorless ink; the colored ink comprises a disperse dye paste, an alkali swelling thickener and a first pH control agent, wherein the alkali swelling thickener is selected from a cross-linked polymer emulsion thickener containing an acidic group, and the pH of the colored ink is between 3.0 and 3.5; the colorless ink comprises a second pH control agent, and the pH of the colorless ink is between 8.0 and 9.0.

[0008] As can be seen from the above scheme, the colored ink contains an alkali swelling thickener, which has the property of rapid swelling and thickening when encountering alkali. The alkali swelling thickener contains an acidic group, and the colored ink is acidic as a whole. In an acidic system, it has excellent liquid fluidity and good compatibility, ensuring the smoothness of printing. When the colored ink contacts the colorless ink, the colorless ink is alkaline. Under alkaline neutralization, the particles of the alkali swelling thickener expand rapidly, and the viscosity of the colored ink increases rapidly, forming an anti-rheological liquid with good suspension and stability. Ink droplets are formed on the surface of the uncoated thermal sublimation transfer paper, which well controls the movement trajectory of the ink penetrating longitudinally into the paper and laterally around, thereby achieving the purpose of improving the transfer rate.

[0009] A further solution is that the alkali swelling thickener is selected from methyl benzoate polymers, and the alkali swelling thickener is added to the colored ink in an amount of 0.6% to 1% by mass.

[0010] As can be seen from the above scheme, methyl benzoate polymer has an excellent thickening effect. Adding this amount of alkali swelling thickener can ensure good jetting stability and ink control of colored ink. Avoid adding too much alkali swelling thickener, which will cause the colored ink to have too high viscosity on paper after alkaline neutralization with colorless ink, forming a three-dimensional concave-convex feeling, and unevenly diffuse on the dye fabric during transfer, affecting the clarity of the pattern; also avoid adding too little alkali swelling thickener, which will cause the colored ink to be unable to form a stable anti-rheological liquid after alkaline neutralization with colorless ink, and the ink will penetrate vertically into the paper and horizontally around, and no clear image can be obtained.

[0011] A further solution is that the first pH control agent is selected from organic acids, and the amount of the first pH control agent added to the colored ink is 0.3% to 0.5% by mass.

[0012] It can be seen from the above scheme that the alkali swelling thickener contains an acidic group, has a very low viscosity in an acidic system within the pH range, has good fluidity and good compatibility, and ensures the stability of the colored ink.

[0013] A further solution is that the second pH control agent is selected from organic amines and their derivatives, and the amount of the second pH control agent added to the colorless ink is 0.5% to 2% by mass.

[0014] In a further embodiment, the second pH control agent is selected from 95% AMP and / or 99% triethanolamine.

[0015] It can be seen from the above scheme that organic amines and their derivatives have the performance of stably, efficiently and rapidly neutralizing acidic groups.

[0016] In a further embodiment, the colored ink further comprises a first polyol, and the first polyol is selected from diols having a molecular weight in the range of 55 to 100.

[0017] In a further embodiment, the first polyol is selected from one or more of ethylene glycol, 1,2-propylene glycol, and 1,4-butanediol.

[0018] It can be seen from the above scheme that the first polyol under the above conditions can provide good moisture retention for the ink, while not generating a large amount of oil smoke and being easy to dry.

[0019] A further solution is that the colorless ink further includes a second polyol and an ethylene glycol polymer, the second polyol is selected from diols with a molecular weight in the range of 55 to 100, and the ethylene glycol polymer is selected from polyethylene glycol with a molecular weight of 2000 to 6000.

[0020] In a further embodiment, the second polyol is selected from one or more of ethylene glycol, 1,2-propylene glycol, and 1,4-butanediol.

[0021] It can be seen from the above scheme that the ethylene glycol polymer with a molecular weight of 2000-6000 added to the ink has good flow properties, ensuring the smoothness of the colorless ink. At the same time, it can form a filling layer on the surface of the uncoated paper, providing relatively flat conditions for the printing of colored inks, and reducing the excessive penetration of colorless ink into the uncoated paper, providing uniform and rapid reaction conditions for the alkaline neutralization when further printing colored inks.

[0022] In a further embodiment, the colored ink further comprises a first surfactant, and the colorless ink further comprises a second surfactant, and both the first surfactant and the second surfactant are selected from acetylene glycol surfactants.

[0023] It can be seen from the above scheme that the acetylene glycol surfactant can further reduce the longitudinal penetration of ink into the interior of the uncoated thermal sublimation transfer paper.

[0024] A further solution is that the dye in the disperse dye paste is selected from low-temperature dyes or medium-temperature dyes.

[0025] A further solution is that, measured by mass percentage, the colored ink includes 20% to 40% of disperse dye paste, 10% to 20% of a first polyol, 0.6% to 1.0% of an alkali swelling thickener, 0.3% to 0.5% of a first PH controller, 0.5% to 2.0% of a first surfactant, 0.05% to 0.5% of a first bactericide and the remainder is deionized water; measured by mass percentage, the colorless ink includes 15% to 25% of a second polyol, 2% to 4% of an ethylene glycol polymer, 0.5% to 2% of a second PH controller, 0.5% to 2.0% of a second surfactant, 0.05% to 0.5% of a first bactericide and the remainder is deionized water.

[0026] It can be seen from the above scheme that the colored ink and colorless ink of the above composition can ensure that the colored ink expands under the alkaline neutralization of the colorless ink, thereby reducing the ink's longitudinal penetration into the paper and transverse penetration around it, thereby improving the transfer rate.

[0027] A further solution is that the ink set is applied to the field of digital inkjet thermal transfer printing technology, including but not limited to the field of textile digital printing.

[0028] To achieve the second purpose of the present invention, the present invention provides an inkjet method for uncoated thermal transfer, which uses an uncoated thermal transfer ink set as described in any of the above items for printing, and the inkjet method includes the following steps: S1: printing colorless ink: printing colorless ink onto the surface of uncoated thermal transfer paper so that the colorless ink completely covers the uncoated thermal transfer paper; S2: printing colored ink: continuing to print colored ink according to a preset pattern on the uncoated thermal transfer paper covered with colorless ink.

[0029] It can be seen from the above scheme that in the application of inkjet printing, colored ink and colorless ink can be completed in the same machine and the same instruction. The colorless ink can be distributed on the nozzles at the left and right ends of the scanning printer nozzle arrangement, and can also be distributed on the first row of nozzles of the single pass printer. It is not sprayed on demand, but sprayed as a base for the entire page to serve as a base for the colored ink. After the colored ink is printed, the viscosity will increase rapidly under the alkaline neutralization of the colorless ink to form an anti-rheological liquid with good suspension and stability. It stays on the surface of the uncoated paper and will not penetrate vertically into the inside of the paper, nor will it penetrate horizontally around. After transfer, a clear pattern and a high dye transfer rate are obtained. DETAILED DESCRIPTION

[0030] The ink set for uncoated thermal transfer provided by the present invention comprises colored ink and colorless ink.

[0031] Calculated by mass percentage, the colored ink includes 20% to 40% of disperse dye paste, 10% to 20% of a first polyol, 0.6% to 1.0% of an alkali swelling thickener, 0.3% to 0.5% of a first pH controller, 0.5% to 2.0% of a first surfactant, 0.05% to 0.5% of a first bactericide and the balance deionized water.

[0032] Calculated by mass percentage, the colorless ink includes 15% to 25% of a second polyol, 2% to 4% of an ethylene glycol polymer, 0.5% to 2% of a second pH control agent, 0.5% to 2.0% of a second surfactant, 0.05% to 0.5% of a first bactericide and the remainder deionized water.

[0033] In the colored ink, the dye in the disperse dye paste is selected from low-temperature disperse dyes or medium-temperature disperse dyes. The first polyol is selected from diols with a molecular weight in the range of 55 to 100, specifically, the first polyol is selected from one or more of ethylene glycol, 1,2-propylene glycol, and 1,4-butanediol. The alkali swelling thickener is selected from a cross-linked polymer emulsion thickener containing an acidic group, preferably, the alkali swelling thickener is selected from a methyl benzoate polymer, specifically, it can be selected from one of DOW ACULYN 22 and DOW ACULYN 28. The first PH control agent is selected from an organic acid, preferably, the first PH control agent is citric acid. The first surfactant is selected from an acetylene glycol surfactant, specifically, it can be Surfynol 465, a surfactant produced by Evonik of Germany. The first bactericide can be BIT (1,2-benzisothiazol-3-one).

[0034] In the colorless ink, the second polyol is selected from diols with a molecular weight in the range of 55 to 100, specifically, the second polyol is selected from one or more of ethylene glycol, 1,2-propylene glycol, and 1,4-butanediol. The ethylene glycol polymer is selected from polyethylene glycol with a molecular weight of 2000 to 6000, preferably, the ethylene glycol polymer is selected from one of polyethylene glycol 2000, polyethylene glycol 4000, and polyethylene glycol 6000. The second pH control agent is selected from organic amines and their derivatives, preferably, the second pH control agent is selected from 95% AMP and / or 99% triethanolamine, 95% AMP is Dow's AMP-95 additive, the chemical name of 95% AMP is 2-amino-2-methyl-1-propanol, the structural formula is (CH3)2C(NH2)CH2OH, wherein the active ingredient content is 95%, and 99% triethanolamine is triethanolamine with a purity of 99%. The second surfactant is selected from acetylene glycol surfactants, specifically, Surfynol 465, a surfactant produced by Evonik of Germany. The second fungicide may be BIT (1,2-benzisothiazol-3-one).

[0035] The above materials can all be purchased on the market.

[0036] The colored ink can be obtained by the following steps: by mass percentage, 20% to 40% of disperse dye paste, 10% to 20% of the first polyol, 0.6% to 1.0% of the alkali swelling thickener, 0.3% to 0.5% of the first pH control agent, 0.5% to 2.0% of the first surfactant, 0.05% to 0.5% of the first bactericide and the balance of deionized water are mixed and stirred evenly, and finally filtered through a 0.5 μm pore size filter membrane or filter element.

[0037] The colorless ink can be obtained by the following steps: by mass percentage, 15% to 25% of the second polyol, 2% to 4% of the ethylene glycol polymer, 0.5% to 2% of the second pH control agent, 0.5% to 2.0% of the second surfactant, 0.05% to 0.5% of the first bactericide and the remainder of deionized water are mixed and stirred evenly, and finally filtered through a 0.5 μm pore size filter membrane or filter element.

[0038] The inkjet method for coating thermal transfer of the present invention can be used to print using the ink set for non-coating thermal transfer of the present invention. Specifically, the inkjet method comprises the following steps:

[0039] S1: Printing colorless ink: Printing colorless ink onto the surface of uncoated thermal transfer paper so that the colorless ink covers the uncoated thermal transfer paper;

[0040] S2: Printing colored ink: Continue to print colored ink according to the preset pattern on the uncoated thermal transfer paper covered with colorless ink.

[0041] The technical solution of the present invention is further illustrated below through specific embodiments to provide a better understanding of the present invention.

[0042] 1. Configure colored ink

[0043] The colored inks in the ink set are configured according to the mass percentage composition shown in Table 1 below.

[0044] Table 1

[0045]

[0046]

[0047] 2. Configure colorless ink

[0048] The colorless ink in the ink set was configured according to the mass percentage composition shown in Table 2 below.

[0049] Table 2

[0050]

[0051]

[0052] It should be noted that the Disperse Red 60 in the above table is a disperse dye raw powder purchased from Jiangsu Yabang Dyestuff Co., Ltd.; polyethylene glycol 6000 is a conventional ethylene glycol polymer for ink purchased from Hai'an Petrochemical Plant in Jiangsu Province, China; Surfynol 465 is an acetylene glycol surfactant for inkjet ink purchased from EVONIK in Germany.

[0053] The colored ink in Table 1 and the colorless ink in Table 2 were mixed according to mass percentage, stirred evenly, and filtered to prepare.

[0054] 3. Performance Test

[0055] The specific process of printing test on fabric is:

[0056] The colored ink and the colorless ink are used to print 100% pure color blocks on the printer of the EPSON I3200 nozzle. First, the colorless ink is printed on the 23g uncoated paper as a base, so that the colorless ink completely covers the 23g uncoated paper. Then, the colored ink is printed on the 23g uncoated paper that has been printed with the colorless ink. After the printed uncoated paper is dried, a transfer process is performed at 220°C for 25 seconds to transfer the ink on the uncoated paper to the polyester cloth to obtain a semi-finished fabric with a printed pattern.

[0057] Test Item 1: Transfer Rate Test

[0058] On the semi-finished fabric, the same color block is tested, the color density of 9 points is tested, and the average value is calculated. If the result is greater than or equal to 1.6, it is judged as A; if the result is greater than 1.3 and less than 1.6, it is judged as B; if the result is less than 1.3, it is judged as C. The test results are shown in Table 3.

[0059] Test Item 2: Clarity Test

[0060] On the semi-finished fabric tested, the edge of the same color point is very clear and has no bleeding, which is judged as A; there is slight bleeding, which is judged as B; the bleeding is obvious or serious, which is judged as C. The test results are shown in Table 3.

[0061] Test Item 3: Uniformity Test

[0062] On the semi-finished fabric, the same color block is tested, the color density of 9 points is tested, and the maximum value minus the minimum value. If the result is less than or equal to 0.5, it is judged as A. If the result is greater than 0.5 and less than 1.0, it is judged as B. If the result is greater than 1.0, it is judged as C. The test results are shown in Table 3.

[0063] Table 3

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072] As can be seen from Table 3 above, the ink set of the present invention utilizes the alkali swelling thickener contained in the colored ink, which has the performance of rapid expansion and thickening when encountering alkali. The alkali swelling thickener contains an acidic group, and the colored ink is acidic as a whole. In an acidic system, it has excellent liquid fluidity and good compatibility, ensuring the process of printing. When the colored ink contacts the colorless ink, the colorless ink is alkaline. Under alkaline neutralization, the particles of the alkali swelling thickener expand rapidly, and the viscosity of the colored ink increases rapidly, forming an anti-rheological liquid with good suspension and stability. Ink droplets are formed on the surface of the uncoated thermal sublimation transfer paper, which well controls the movement trajectory of the ink penetrating longitudinally into the paper and laterally to the surroundings, and the obtained fabric has high transfer ink, high clarity, and high uniformity.

[0073] The specific embodiments described in the present invention are only used to describe the specific implementation process of the ink set for uncoated thermal transfer paper in detail, rather than limiting the implementation process. Any modification and improvement of this method, and the replacement and use of similar or similar substances within the scope or category of the patent, shall fall within the scope of protection of the present invention.

Claims

1. An ink set for uncoated thermal transfer, characterized in that: The ink set includes colored ink and colorless ink; The colored ink comprises disperse dye paste, an alkali swelling thickener and a first pH control agent, wherein the alkali swelling thickener is selected from a cross-linked polymer emulsion thickener containing an acidic group, and the pH of the colored ink is between 3.0 and 3.5; The colorless ink includes a second pH control agent, and the pH of the colorless ink is between 8.0 and 9.

0.

2. The uncoated thermal transfer ink set according to claim 1, characterized in that: The alkali swelling thickener is selected from methyl benzoate polymers. The alkali swelling thickener is added to the colored ink in an amount of 0.6% to 1% by mass.

3. The uncoated thermal transfer ink set according to claim 1, characterized in that: The first pH control agent is selected from organic acids, and the amount of the first pH control agent added to the colored ink is 0.3% to 0.5% by mass.

4. The uncoated thermal transfer ink set according to claim 1, characterized in that: The second PH control agent is selected from organic amines and their derivatives. The amount of the second PH control agent added to the colorless ink is 0.5% to 2% by mass.

5. The uncoated thermal transfer ink set according to any one of claims 1 to 4, characterized in that: The colored ink further includes a first polyol, which is selected from diols having a molecular weight in the range of 55-100.

6. The uncoated thermal transfer ink set according to any one of claims 1 to 4, characterized in that: The colorless ink further comprises a second polyol and an ethylene glycol polymer, wherein the second polyol is selected from diols with a molecular weight in the range of 55 to 100, and the ethylene glycol polymer is selected from polyethylene glycol with a molecular weight in the range of 2000 to 6000.

7. The uncoated thermal transfer ink set according to any one of claims 1 to 4, characterized in that: The colored ink further includes a first surfactant, and the colorless ink further includes a second surfactant, and both the first surfactant and the second surfactant are selected from acetylene glycol surfactants.

8. The uncoated thermal transfer ink set according to any one of claims 1 to 4, characterized in that: The dye in the disperse dye paste is selected from low-temperature dyes or medium-temperature dyes.

9. The uncoated thermal transfer ink set according to any one of claims 1 to 4, characterized in that: The colored ink comprises, by mass percentage, 20% to 40% of disperse dye paste, 10% to 20% of a first polyol, 0.6% to 1.0% of an alkali swelling thickener, 0.3% to 0.5% of a first pH control agent, 0.5% to 2.0% of a first surfactant, 0.05% to 0.5% of a first bactericide, and the balance of deionized water; In terms of mass percentage, the colorless ink includes 15% to 25% of a second polyol, 2% to 4% of an ethylene glycol polymer, 0.5% to 2% of a second pH controller, 0.5% to 2.0% of a second surfactant, 0.05% to 0.5% of a first bactericide and the remainder of deionized water.

10. An inkjet method for coating-free thermal transfer, characterized in that: The inkjet method uses an uncoated thermal transfer ink set as claimed in any one of claims 1 to 9 for printing, and the inkjet method comprises the following steps: S1: Printing colorless ink: Printing the colorless ink onto the surface of the uncoated thermal transfer paper so that the colorless ink completely covers the uncoated thermal transfer paper; S2: Printing colored ink: Continue to print colored ink according to a preset pattern on the uncoated thermal transfer paper covered with the colorless ink.

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