A direct-jet acid dye digital printing ink and its application

Abstract

The present invention relates to a direct-jet acid dye digital printing ink and its application. In parts by weight, the ink includes 10 to 35 parts of acid dye, 1 to 3 parts of dispersant, 10 to 30 parts of polyol moisturizing solvent, 0.05 to 1.2 parts of pH buffer solution, 10 to 50 parts of thermosensitive gel material, 1 to 2 parts of wetting agent, 0.2 to 1 part of preservative, 0.2 to 1 part of surfactant and 6 to 60 parts of deionized water; the ink is in a solution state with a viscosity of 1 to 20 centipoise seconds under the condition that the temperature is lower than the gel temperature, and in a gel state under the condition that the temperature is higher than the gel temperature, and the ink gel temperature is 30 to 60 degrees. The present invention adds safe and environmentally friendly thermosensitive gel material to the ink. During digital printing processing, by reasonably controlling the fabric temperature, the ink droplets undergo gelation transformation after being inked on the fabric, and the ink penetration is suppressed without any pretreatment, thereby shortening the process flow and improving the quality of digital printing products.

Description

Technical Field

[0001] The present invention relates to the technical field of digital printing, and in particular to an acid dye digital printing ink and application thereof. Technical Background

[0002] The traditional dye printing process requires high-temperature steaming after printing, which consumes a lot of water, electricity, coal, steam and labor. In addition, after washing, mixed sewage containing a large amount of slurry, dyes and other compounds will be produced, and the cost of sewage treatment is high. At present, the slurry used by domestic enterprises has poor biodegradability and may contain toxic and harmful substances. The wastewater discharge of the printing and dyeing industry accounts for 70% of the entire industry. How to effectively treat the printing and dyeing wastewater and realize resource utilization is facing great challenges. At the same time, there are about 2,000 varieties of dyes that can be produced in my country, and more than 800 varieties of dyes are produced all year round. Acid dyes are one of the important categories. my country is a major producer and seller of acid dyes. In 2018, my country's acid dye production was 44,800 tons, imports were 14,100 tons, exports were 11,500 tons, and consumption was 47,400 tons. However, the printing and dyeing industry is also facing challenges such as ecological safety issues brought about by increasing health and safety consumption, overcapacity problems brought about by changes in international market demand, and contradictions between resources and environmental carrying capacity formed after the rapid expansion of industry production capacity.

[0003] Digital textile printing technology is a new printing technology that uses a dedicated inkjet printer to print design drawings on textiles. Compared with traditional printing technology, the printing process is greatly simplified and the working speed is greatly improved. In addition, it has the advantages of low consumption, low pollution and personalized customization, and is one of the important development directions in the field of textile printing. In recent years, digital inkjet printing technology has received widespread attention and rapid development in China's printing and dyeing industry. From 2014 to 2019, the proportion of digital inkjet printing increased from 1.8% to 11.2%, of which the proportion of digital direct printing products in the total printing volume increased from 0.5% to 2.1%; the proportion of digital transfer products in the total printing volume increased from 1.3% to 9.1%. In 2020, under the influence of the epidemic and the pull of the market, digital inkjet printing quickly adapted to market changes, met new consumer needs, and further expanded its market application (see literature: In-depth analysis of the development status and trends of global digital inkjet printing for textiles [J]. Screen Printing Industry, 2021(06):50-56). In order to avoid the problem of penetration and meet the conditions required for the combination of dye and fiber, digital printing must pre-treat the fabric so that the surface of the fabric is evenly covered with a layer of paste, thereby improving the penetration phenomenon and improving the printing quality.

[0004] The prior art discloses a cationic emulsion prepared by semi-continuous seed emulsion polymerization method using styrene (St) and acrylic acid J ester (BA) as main monomers, acrylic acid (AA) as functional monomer, nonylphenol polyoxyethylene ether (OP-10) and methacryloyloxyethyl trimethyl ammonium chloride (DMC) as emulsifiers. When the emulsion is used as a pretreatment liquid for coating inkjet printing, it can prevent penetration and print-through to a certain extent. However, the emulsion film still has problems such as low hardness and high brittleness (see the literature: Preparation and performance study of pretreatment emulsion for coating inkjet printing [J]. Journal of Beijing Institute of Fashion Technology (Natural Science Edition), 2021, 41(02): 13-18); The prior art reports that the ionicity and viscosity of polyacrylamide polymer treatment agents are important factors affecting the color effect of inkjet printing. Therefore, 35% ionic anionic polyacrylamide is used to treat the fabric, but it has a certain effect on color fastness and whiteness, and it still belongs to the process of pre-treatment of the fabric (see literature: Effect of polymer surface treatment on inkjet printing of silk fabrics [J]. Knitting Industry, 2021(05): 50-54).

[0005] The block copolymers used in thermosensitive gel materials are non-toxic and harmless to the human body and have been widely used in biomedicine. The prior art discloses a thermosensitive hydrogel of a block polymer of degradable polycaprolactone-co-lactide-polyethylene glycol-polycaprolactone-co-lactide (PCLA-PEG-PCLA) prepared by ring-opening polymerization. Studies have found that thermosensitive hydrogels that undergo sol-gel transition with increasing temperature are an important class of injectable biomedical materials. Such materials can load drugs or cells at room temperature or low temperature, and form gels in situ after being injected into the human body, becoming a reservoir for sustained drug release or a scaffold for cell growth. At present, common thermosensitive gelling polymers include polyethylene glycol (PEG) / polypeptide block copolymers, polyorganophosphazenes, and PEG / polyester block copolymers (see literature: Amphiphilic copolymer thermosensitive hydrogels [J]. Science Bulletin, 2021, 66(18): 2245-2260). However, there have been no reports on their application in digital printing inks to solve the problem of seepage. Summary of the invention

[0006] The present invention aims at the deficiencies of the existing inkjet printing technology and provides a direct-jet acid dye digital printing ink and its application which can simplify the processing technology, inhibit ink penetration and improve printing clarity.

[0007] To achieve the above-mentioned purpose of the invention, the technical solution of the present invention provides a direct-jet acid dye digital printing ink, which includes, by weight, 10 to 35 parts of acid dye, 1 to 3 parts of dispersant, 10 to 30 parts of polyol moisturizing solvent, 0.05 to 1.2 parts of pH buffer solution, 10 to 50 parts of thermosensitive gel material, 1 to 2 parts of wetting agent, 0.2 to 1 part of preservative, 0.2 to 1 part of surfactant and 6 to 60 parts of deionized water; the ink is in a solution state at a temperature below 30 degrees Celsius, with a viscosity of 1 to 20 centipoise seconds, and in a gel state at a temperature of 30 to 60 degrees Celsius.

[0008] The direct-jet acid dye digital printing ink of the present invention has a temperature-sensitive gel material, which uses polyethylene glycol as an initiator, one of caprolactone, lactide, glycolide, or their copolymers as raw materials, and stannous octoate as a catalyst, and a polymerization reaction to obtain a block copolymer; the polyethylene glycol is monohydroxy polyethylene glycol, dihydroxy polyethylene glycol or multi-arm polyethylene glycol, and the molecular weight of the polyethylene glycol is 500-5000; the mass percentage of polyethylene glycol in the block copolymer is 10-90%.

[0009] The acid dyes described in the present invention include one or more of CI Acid Red 1, CI Acid Blue 80, CI Acid Blue 350, CI Acid Blue 62, CI Acid Blue 26, CI Acid Blue 193, CI Acid Blue 9, CI Acid Blue 62, CI Acid Yellow 117, CI Acid Yellow 72, CI Acid Yellow 23, CI Acid Yellow 121, CI Medium Black 11, CI Acid Yellow 99, and CI Acid Black 60.

[0010] The dispersant is one of dispersant MF-85A and dispersant IW2-3 or any combination thereof.

[0011] The polyol moisturizing solvent is one or any combination of diethylene glycol, ethylene glycol, glycerol and sorbitol.

[0012] The preservative is 1,2-benzisothiazolin-3-one or potassium sorbate.

[0013] The surfactant is one of OP-10, TX-10 and nonylphenol polyoxyethylene ether or any combination thereof.

[0014] The pH buffer solution is a buffer solution with a pH of 7 to 7.5 prepared from one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium dihydrogen phosphate, sulfuric acid and hydrochloric acid.

[0015] The wetting agent is a Tween surfactant or a Span surfactant.

[0016] The application of the direct-jet acid dye digital printing ink as described above is as follows: the fabric is heated to 40 to 60 degrees Celsius, the ink temperature is controlled so that it is in a solution state, and a direct-jet digital printing process is used to obtain a printed fabric product.

[0017] The principle of the present invention is: the temperature-sensitive gel material contained in the ink controls the temperature of the fabric above the solution-gel transition temperature of the ink, and the temperature of the ink is controlled below the solution-gel transition temperature. When the ink droplets are deposited on the fabric, the temperature rises rapidly, and then a gelation transition occurs, which inhibits the ink penetration and improves the printing clarity.

[0018] In the technical solution of the present invention, the block copolymer used in the thermosensitive gel material is non-toxic and harmless to the human body, the dyes and auxiliaries used in the preparation process are relatively environmentally friendly, do not affect the whiteness of the fabric, and the printed products are non-irritating to human skin, have low allergenicity, and can be oriented to a wider market; compounding with acid dyes to prepare digital printing inkjet inks with anti-seepage properties will run the concept of clean production throughout the entire production process, starting from the source, and reducing the subsequent pollution load; secondly, the comprehensive utilization of resources should be promoted by improving the process and updating the equipment, and energy consumption and material consumption should be reduced as much as possible, thereby reducing the amount of pollution generated.

[0019] The direct-injection acid dye digital printing ink provided by the present invention controls water consumption and energy consumption from the source, and improves and optimizes the terminal printing and dyeing wastewater treatment measures. Compared with the traditional disperse dye printing process, the use of ink containing thermosensitive gel greatly reduces the investment in equipment and personnel, effectively reduces the production and labor costs of enterprises, and realizes energy conservation and emission reduction in the true sense because the two processes of sizing and washing are omitted.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. A special thermosensitive gel material is selected to increase the viscosity and compounded with ink to obtain a thermosensitive solution-gel conversion ink for pre-treatment-free printing, which can control water consumption from the source, optimize wastewater treatment, reduce chemical consumption, and reduce the burden on the environment. The product is non-toxic, harmless and degradable, which is in line with green ecological textile manufacturing.

[0022] 2. No need to pre-treat the fabric, no transfer paper is required, and post-processing is omitted, which greatly reduces the process flow.

[0023] 3. The acid dye digital printing ink provided by the present invention adopts a temperature-sensitive material to control the viscosity of the ink. When the ink droplets are deposited on the heated fabric, the temperature rises rapidly, and then a gelation transformation occurs, which inhibits the ink penetration, improves the printing clarity, and significantly improves the quality of the printed products. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A polymerization reaction route for preparing a thermosensitive gel material provided in an embodiment of the present invention;

[0025] Figure 2 A comparison diagram of the pattern effects of the direct-jet acid dye digital printing ink provided in Example 4 of the present invention and the comparative ink used for inkjet printing; wherein, Figure A is the comparative inkjet printing product, and Figure B is the inkjet printing product of Example 4. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0027] Example 1

[0028] Take 20 parts of acid dye, 0.5 parts of dispersant, 20 parts of polyol moisturizing solvent, 0.6 parts of pH buffer solution, 10 parts of thermosensitive gel material, 1.2 parts of wetting agent, 0.5 parts of preservative, 0.8 parts of surfactant and 46.4 parts of deionized water.

[0029] In this embodiment, according to the technical scheme disclosed in Chinese invention patent CN102146200 A "A thermosensitive hydrogel based on chemically cross-linked gel particles and its preparation method", a thermosensitive gel material is prepared, with polyethylene glycol as an initiator, one of caprolactone, lactide, glycolide, or their copolymers as raw materials, stannous octoate as a catalyst, and a polymerization reaction to obtain a block copolymer; the polyethylene glycol is monohydroxy polyethylene glycol, dihydroxy polyethylene glycol or multi-arm polyethylene glycol, and the molecular weight of the polyethylene glycol is 500 to 5000, preferably 1000 to 2000, and particularly preferably between 1000 and 1500; the raw materials caprolactone, lactide, and glycolide can be selected from one of them, or can be their copolymers, including binary copolymers or ternary copolymers. The ratio of the polymerized polyester segment to polyethylene glycol is between 0.5 and 5, the preferred polyester / polyethylene glycol ratio is between 1 and 3, and the particularly preferred ratio is between 1 and 2; the mass percentage of polyethylene glycol in the block copolymer is 10 to 90%.

[0030] See attached Figure 1 , which is the polymerization reaction route for preparing the thermosensitive gel material provided in this embodiment; in the figure, n, x, and y are the number of polymer structural units, wherein the preferred range of n is 33 to 34, i.e. the molecular weight of the PEG used is 1500; the preferred range of x+y is 10 to 13, i.e. the molecular weight of the synthesized PCLA is 1610 to 2080; the number average molecular weight of the block polymer is in the range of 6200 to 8500. The specific steps are as follows:

[0031] (1) Connecting a block copolymer of polyethylene glycol and polyester to a cross-linkable group to form a macromonomer;

[0032] (2) In a selective solvent, the macromolecular monomers self-assemble into micelles or aggregates thereof, and stannous octoate is added as a catalyst to initiate the ring-opening polymerization of caprolactone and lactide to form chemically cross-linked nanoparticles;

[0033] (3) dispersing the chemically cross-linked nanoparticles in an aqueous medium;

[0034] (4) Raise the temperature to achieve overall physical gelation and form block copolymers.

[0035] In this embodiment, the acid dye is one or more of CI Acid Red 1, CI Acid Blue 80, CI Acid Blue 350, CI Acid Blue 62, CI Acid Blue 26, CI Acid Blue 193, CI Acid Blue 9, CI Acid Blue 62, CI Acid Yellow 117, CI Acid Yellow 72, CI Acid Yellow 23, CI Acid Yellow 121, CI Medium Black 11, CI Acid Yellow 99, and CI Acid Black 60;

[0036] The dispersant is prepared by mixing the following raw materials by weight: 5 parts of dispersant MF-85A and 2 parts of dispersant IW;

[0037] The polyol moisturizer is prepared by mixing the following raw materials by weight: 3 parts of diethylene glycol, 2.5 parts of ethylene glycol, 1.5 parts of glycerol and 0.5 parts of sorbitol;

[0038] The pH regulator is one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium dihydrogen phosphate, sulfuric acid, and hydrochloric acid, which are configured into a buffer solution with a pH of 7 to 7.5;

[0039] The wetting agent is a Tween surfactant or a Span surfactant;

[0040] The preservative is 1,2-benzisothiazolin-3-one or potassium sorbate;

[0041] The surfactant is one or more of OP-10, TX-10 and nonylphenol polyoxyethylene ether.

[0042] The above materials were placed in a container and stirred at a speed of 700 rpm for a total of 75 minutes. The stirred materials were filtered, first using a 0.8um filter membrane, then using a 0.45um filter membrane, and finally the filtrate was filtered using a 0.22um filter membrane to obtain a finished ink, which was recorded as a 2% sample.

[0043] The ink prepared by the above method is used for digital printing. The nylon fabric is heated to 75 degrees Celsius, and the ink is heated to below 30 degrees Celsius to be in a solution state. The ink is printed using a Plante digital printing machine to obtain a digitally printed nylon fabric product.

[0044] Example 2

[0045] The thermosensitive gel material was prepared according to the method provided in Example 1. Other raw materials were the same as those in Example 1.

[0046] Take 20 parts of acid dye, 0.5 parts of dispersant composition, 20 parts of polyol moisturizing solvent, 0.6 parts of pH buffer solution, 20 parts of thermosensitive gel material, 1.2 parts of wetting agent, 0.5 parts of preservative, 0.8 parts of surfactant and 36.4 parts of deionized water; put deionized water, acid dye, thermosensitive gel material, etc. into a container in order and stir, stir at a high speed of 700 rpm for 75 minutes, filter the stirred material, first filter with a 0.8um filter membrane, then filter with a 0.45um filter membrane, and finally filter the filtrate with a 0.22um filter membrane to obtain a finished ink, recorded as a 4% sample.

[0047] The nylon fabric is heated to 63 degrees Celsius and the ink is heated to 30 degrees Celsius and printed using the Plante digital printing machine.

[0048] Example 3

[0049] The thermosensitive gel material was prepared according to the method provided in Example 1. Other raw materials were the same as those in Example 1.

[0050] Take 20 parts of acid dye, 0.5 parts of dispersant composition, 20 parts of polyol moisturizing solvent, 0.6 parts of pH buffer solution, 30 parts of thermosensitive gel material, 1.2 parts of wetting agent, 0.5 parts of preservative, 0.8 parts of surfactant and 26.4 parts of deionized water; put deionized water, acid dye, thermosensitive gel material, etc. into a container in order and stir, stir at a high speed of 700 rpm for 75 minutes, filter the stirred material, first filter with a 0.8um filter membrane, then filter with a 0.45um filter membrane, and finally filter the filtrate with a 0.22um filter membrane to obtain a finished ink, recorded as a 6% sample.

[0051] The nylon fabric is heated to 60 degrees Celsius, the ink is heated to below 30 degrees Celsius, and printed using the Plante digital printing machine.

[0052] Example 4

[0053] The thermosensitive gel material was prepared according to the method provided in Example 1. Other raw materials were the same as those in Example 1.

[0054] Take 20 parts of acid dye, 0.5 parts of dispersant composition, 20 parts of polyol moisturizing solvent, 0.6 parts of pH buffer solution, 40 parts of thermosensitive gel material, 1.2 parts of wetting agent, 0.5 parts of preservative, 0.8 parts of surfactant and 16.4 parts of deionized water; put deionized water, acid dye, thermosensitive gel material, etc. into a container in order and stir, stir at a high speed of 700 rpm for 75 minutes, filter the stirred material, first filter with a 0.8um filter membrane, then filter with a 0.45um filter membrane, and finally filter the filtrate with a 0.22um filter membrane to obtain a finished ink, recorded as 8% sample.

[0055] The nylon fabric is heated to 55 degrees Celsius, the ink is heated to below 30 degrees Celsius, and printed using the Plante digital printing machine.

[0056] A comparative example was prepared, in which the ink composition was the above-mentioned formula provided in this embodiment without the thermosensitive gel. The ink provided in the comparative example was applied to inkjet printing.

[0057] See attached Figure 2 , which is a comparison diagram of the pattern effects of the direct-injection acid dye digital printing ink provided in this embodiment and the comparative ink used for inkjet printing; wherein, Figure A is the finished product of the comparative inkjet printing, and Figure B is the finished product of the inkjet printing of Example 4. Figure 2 It can be seen that after the edge of the printed product in Figure A is enlarged, the ink seeps into the fabric severely, and the printed lines are blurred. After the edge of the printed product in Figure B is enlarged, the ink seepage into the fabric is significantly weakened, and the printed lines are clear.

[0058] Example 5

[0059] The thermosensitive gel material was prepared according to the method provided in Example 1. Other raw materials were the same as those in Example 1.

[0060] Take 20 parts of acid dye, 0.5 parts of dispersant composition, 20 parts of polyol moisturizing solvent, 0.6 parts of pH buffer solution, 50 parts of thermosensitive gel material, 1.2 parts of wetting agent, 0.5 parts of preservative, 0.8 parts of surfactant and 6.4 parts of deionized water; put deionized water, acid dye, thermosensitive gel material, etc. into a container in order and stir, stir at a high speed of 700 rpm for 75 minutes, filter the stirred material, first filter with a 0.8um filter membrane, then filter with a 0.45um filter membrane, and finally filter the filtrate with a 0.22um filter membrane to obtain a finished ink, recorded as a 10% sample.

[0061] The samples prepared in the above embodiments of the present invention were tested and characterized, and the results are shown in Table 1. From the results in Table 1, it can be seen that the surface tension of the thermosensitive dyes with a polymer mass fraction of 2%, 4%, 6%, 8% and 10% will drop sharply within a short period of time after the surface aging begins. When the surface aging time reaches a certain point, the surface tension of the thermosensitive dye remains almost unchanged as the surface aging time increases. When the surface tension of the thermosensitive dye is stable, the order of surface tension is: thermosensitive dye with a triblock mass fraction of 10%> thermosensitive dye with a triblock mass fraction of 8%> thermosensitive dye with a triblock mass fraction of 6%> thermosensitive dye with a triblock mass fraction of 4%> thermosensitive dye with a triblock mass fraction of 2%.

[0062] The modulus changes of the samples of Examples 1 to 5 with temperature were tested. Analysis showed that at 50°C, the modulus of the samples increased sharply, indicating that at this time, the energy stored due to elastic (reversible) deformation and the energy lost due to viscous deformation (irreversible) were both large, and the viscosity of the samples was large; and the storage modulus line was always above the loss line but the difference between the two was not large, indicating that the material was semi-solid and had good gel properties.

[0063] The digital printing inkjet ink provided in the present invention can be applied to micro-piezoelectric and thermal foaming printers; it has stable quality and can be stored for a long time, and complies with the light industry standard QB / T2730-2005 of the People's Republic of China. The evaluation results of the products prepared in Examples 1 to 5 of the present invention are shown in Table 1.

[0064] Table 1

[0065] Test items Conductivity (20℃μS / cm) Surface tension (20℃Mn / m ) Viscosity (20℃mPa.s) pH Intermittent printing effect cold resistance stability standard 1000～10000 30～65 1.5～4.0 5.0～10.0 Intermittent printing for 7 days, the effect is the same as the standard -20℃ room temperature, good reducibility, no deterioration or taste, can print normally (40±1)℃, sealed for 120h, no deterioration Example 1 7500 37.5 2.5 6.5 qualified qualified qualified Example 2 7551 38.1 3.0 6.4 qualified qualified qualified Example 3 7480 38.4 3.3 6.7 qualified qualified qualified Example 4 6500 38.7 4.2 7.1 qualified qualified qualified Example 5 8023 38.9 4.4 6.9 qualified qualified qualified Comparative Example 7340 37.2 2.3 6.5 qualified qualified qualified

[0066] In summary, referring to the experimental data of comparative examples 1 to 5 and the comparative examples, it can be known that by adding a thermosensitive gel material, a dispersant composition, a polyol moisturizing solvent composition, a pH adjuster, a wetting agent, etc. to the ink, the prepared acidic ink has an efficient printing effect without pre-treatment, and has the characteristics of easy coloring and firm coloring, antibacterial and non-discoloration; a combination of multiple surfactants is adopted, and surfactants with low contact angles and dynamic surface tension are selected to give the ink better leveling and wettability; when placed for a long time at room temperature, the pH value does not drop significantly, so the ink will not become more acidic due to long storage time, thereby corroding the nozzle; and, during long-term storage, it is not easy to hydrolyze to produce some difficult-to-dissolve substances, which makes the ink difficult to filter and clogs the nozzle, thereby increasing the stability of the ink.

Claims

1. An application of direct-jet acid dye digital printing ink, characterized in that: The direct-jet acid dye digital printing ink comprises, by weight, 10 to 35 parts of acid dye, 1 to 3 parts of dispersant, 10 to 30 parts of polyol moisturizing solvent, 0.05 to 1.2 parts of pH buffer solution, 10 to 50 parts of thermosensitive gel material, 1 to 2 parts of wetting agent, 0.2 to 1 part of preservative, 0.2 to 1 part of surfactant and 6 to 60 parts of deionized water; the ink is in a solution state at a temperature below 30 degrees Celsius, with a viscosity of 1 to 20 centipoise seconds, and in a gel state at a temperature of 30 to 60 degrees Celsius; the thermosensitive gel material is polyethylene glycol. The initiator is one of caprolactone, lactide, glycolide, or their copolymers as raw materials, stannous octoate is used as a catalyst, and the polymerization reaction obtains a block copolymer; the polyethylene glycol is monohydroxy polyethylene glycol, dihydroxy polyethylene glycol or multi-arm polyethylene glycol, and the molecular weight of the polyethylene glycol is 500-5000; the mass percentage of polyethylene glycol in the block copolymer is 10-90%; the dispersant is one of dispersant MF-85A and dispersant IW2-3 or any combination thereof; the polyol moisturizing solvent is one of diethylene glycol, ethylene glycol, glycerol, and sorbitol or any combination thereof; The application method is: heating the fabric to 40-60 degrees Celsius, controlling the temperature of the ink so that it is in a solution state, and adopting a direct-injection digital printing process to obtain a printed fabric product.

2. The use of a direct-injection acid dye digital printing ink according to claim 1, characterized in that: The acid dyes include one or more of CI Acid Red 1, CI Acid Blue 80, CI Acid Blue 350, CI Acid Blue 62, CI Acid Blue 26, CI Acid Blue 193, CI Acid Blue 9, CI Acid Blue 62, CI Acid Yellow 117, CI Acid Yellow 72, CI Acid Yellow 23, CI Acid Yellow 121, CI Medium Black 11, CI Acid Yellow 99, and CI Acid Black 60.

3. The use of a direct-injection acid dye digital printing ink according to claim 1, characterized in that: The preservative is 1,2-benzisothiazolin-3-one or potassium sorbate.

4. The use of a direct-injection acid dye digital printing ink according to claim 1, characterized in that: The surfactant is one of OP-10, TX-10 and nonylphenol polyoxyethylene ether or any combination thereof.

5. The use of a direct-injection acid dye digital printing ink according to claim 1, characterized in that: The pH buffer solution is a buffer solution with a pH of 7 to 7.5 prepared from one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium dihydrogen phosphate, sulfuric acid and hydrochloric acid.

6. The use of a direct-injection acid dye digital printing ink according to claim 1, characterized in that: The wetting agent is a Tween surfactant or a Span surfactant.

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