Waterborne polyurethane color fixing agent, novel pyrography ink and preparation method of novel pyrography ink

Abstract

The invention relates to the field of digital ink-jet printing, and discloses a waterborne polyurethane color fixing agent, novel pyrography ink and a preparation method thereof, the pyrography ink comprises 20%-40% of a pigment dispersion, 10%-30% of waterborne polyurethane resin, 5%-10% of the waterborne polyurethane color fixing agent, 0.2%-2% of a surfactant, 10%-30% of a water-soluble organic solvent, 0.1%-0.5% of a bactericide and the balance of water; according to the pyrography ink, the color fastness of pyrography patterns is effectively improved, and meanwhile, the printing fluency and the standby stability of the ink are kept; meanwhile, the invention provides a waterborne polyurethane color fixing agent and a preparation method of the novel pyrography ink.

Description

Technical Field

[0001] The invention relates to the field of digital inkjet printing, and in particular to a water-based polyurethane color fixing agent and a novel heat transfer ink and a preparation method thereof. Background Art

[0002] In the digital inkjet printing industry, white ink heat transfer is a new printing process that prints patterns on various materials through a special thermal transfer process. It has the advantages of bright colors, no substrate selection, simple process, and green environmental protection. It is widely used in clothing, luggage, furniture and other fields. As an important material for digital printing, heat transfer ink has been extensively studied.

[0003] Among the existing heat transfer ink technologies, patent application number 202011449544.8 discloses a heat transfer water-based white ink suitable for Epson nozzles and a preparation method thereof, wherein the heat transfer water-based white ink includes a pigment dispersion, a resin, a curing agent, an acid-base regulator, a wetting agent, a surfactant, a bactericide and water, and has smooth printing on all Epson nozzles, good standby performance, high fastness, not easy to regain moisture, good covering, no ink flow on any film, and no mutual smudge with color inks; application number 202111383586.0 discloses a digital heat transfer ink, which particularly uses a reasonable ink system of water-based polycarbonate polyurethane, dispersed acrylic resin and water-based blocked isocyanate, which has excellent wetting and leveling properties, and strong storage stability at high temperature and room temperature, and a low sedimentation rate. None of the above patents involve the technical difficulties of poor color fastness that still exist in heat transfer inks.

[0004] In order to improve the color fastness, the common practice in existing patents is to design a color-fixing ink-carrying layer on the surface of the thermal transfer paper / film. For example, the color-fixing ink-carrying layer designed in the patent with application number CN202411270795.8 includes components such as sodium carboxymethyl cellulose, polyurethane emulsion, vinyl acrylate-ethylene copolymer, cationic polyacrylamide, wax emulsion, etc., which can directly fix the pigment or dye molecules in the ink to improve the color fastness of the transfer pattern. However, there are few patent reports on improving color fastness from the perspective of ink formulation. The main reason is that anionic inks are incompatible with cationic color fixers, and adding color fixers to the ink is likely to destroy the stability of the ink itself. Patent No. 202410994502.4 discloses a high-performance heat transfer white ink, which can significantly improve the adhesion and water resistance of the heat transfer white ink by adding an aziridine curing agent to the ink, while increasing the drying speed of the ink and shortening the production cycle. However, adding aziridine curing agent to the water-based formula will slowly hydrolyze in 3-5 days. The viscosity of the system tends to increase within two weeks and may form a gel, which will lead to poor standby stability, poor fluidity, and eventually clogging of the nozzle.

[0005] To solve the above problems, the applicant has conducted research and improvement on the existing technology, and provided an aqueous polyurethane color fixative, a new type of heat transfer ink with color fixing function and its preparation method. The first objective is to propose a new method to improve color fastness; the second objective is to maintain the printing fluidity and standby stability of the ink while improving color fastness. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide an aqueous polyurethane color fixative, a new type of heat transfer ink with color fixing function and its preparation method. The heat transfer ink effectively improves the color fastness of the heat transfer pattern while maintaining the printing fluidity and standby stability of the ink.

[0007] To achieve the first objective, the present invention provides the following technical solutions:

[0008] An aqueous polyurethane color fixative, comprising the following steps:

[0009] S1: Weigh oligomeric polyol into a four-necked flask, slowly heat up under mechanical stirring, evacuate and maintain the vacuum degree below -0.09 MPa, remove water for 2 h and then slowly cool down;

[0010] S2: Weigh isocyanate and catalyst and add them into the four-necked flask, mechanically stir and introduce dry nitrogen, add acetone during the reaction to reduce viscosity, and slowly cool down when the -NCO percentage content reaches 10% - 15%;

[0011] S3: When slowly cooling down to 70 °C, add anionic hydrophilic chain extender and crosslinking agent dissolved in acetone in advance. When the -NCO percentage content reaches 2% - 5%, slowly cool down. When cooling down to 60 °C, add a capping agent, completely seal the remaining -NCO groups and then cool down to obtain an anionic aqueous polyurethane;

[0012] S4: Cool the anionic aqueous polyurethane obtained in step S3 to 30 °C, add deionized water according to the solid content of 30%, and use an electric stirrer to stir and disperse at high speed for 30 min; rotary evaporate the acetone solvent to obtain an anionic aqueous polyurethane color fixative with an internal crosslinked structure.

[0013] Preferably, in step S1, slowly heat up to 115 °C and slowly cool down to 80 °C; the oligomeric polyol is one or more of polypropylene glycol - 1000, trimethylol polyethylene glycol monomethyl ether, and polytetrahydrofuran ether diol - 1000.

[0014] Preferably, the isocyanate is one or more of isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, and dicyclohexylmethane diisocyanate.

[0015] Preferably, the catalyst is dibutyltin dilaurate.

[0016] Preferably, the anionic hydrophilic chain extender is one or more of N,N-dimethylolpropionic acid, dimethylolbutyric acid, 1,2-propanediol-3-sulfonate, and 1,4-butanediol-2-sulfonate.

[0017] Preferably, the crosslinking agent is trimethylolpropane and the capping agent is sodium bisulfite.

[0018] To achieve the second object, the present invention provides the following technical solution:

[0019] A novel heat transfer ink, by weight percentage, comprises: 20% - 40% of pigment dispersion, 10% - 30% of aqueous polyurethane resin, 5% - 10% of the above-mentioned aqueous polyurethane fixing agent, 0.2% - 2% of surfactant, 10% - 30% of water-soluble organic solvent, 0.1% - 0.5% of bactericide, and the balance is water.

[0020] Preferably, the pigment dispersion is titanium white color paste; the aqueous polyurethane resin is W-6061, W-6110; the surfactant is one or more of non-silicon surfactants and silicone surfactants.

[0021] Preferably, the water-soluble organic solvent is one or more of ethylene glycol, propylene glycol, glycerol, diethylene glycol, triethylene glycol, and triethylene glycol monobutyl ether; the bactericide is BIT-20.

[0022] To achieve the third object, the present invention provides the following technical solution:

[0023] A preparation method of a novel heat transfer ink, comprising the following steps: sequentially adding pigment dispersion, aqueous polyurethane resin, aqueous polyurethane fixing agent, surfactant, water-soluble organic solvent, and bactericide into deionized water, stirring and mixing evenly with water, and then filtering with a 0.45μm filter membrane to obtain heat transfer ink.

[0024] In the preparation process of the aqueous polyurethane fixing agent, each end of the isocyanate contains an isocyanate group (-NCO). Under the catalytic conditions of a certain temperature and the catalyst dibutyltin dilaurate, it reacts with the added oligomeric polyol and anionic hydrophilic chain extender successively to form a linear polymer with a repeating urethane bond structure. Then, a crosslinking agent is added to continue chain extension, developing the linear structure into a three-dimensional network structure while increasing the molecular weight. The remaining isocyanate is blocked with a capping agent to obtain an anionic aqueous polyurethane fixing agent.

[0025] On the one hand, sodium bisulfite is used as a capping agent for the anionic aqueous polyurethane fixing agent to temporarily block the isocyanate groups, ensuring that there are sufficient isocyanate bonds during application to form chemical crosslinks with the hydroxyl and carboxyl groups on the fabric surface and crosslink into a film on the fabric surface. On the other hand, this product has a certain solubility in the hot stamping white ink, has good stability in the white ink, can crosslink into a macromolecular network structure by itself, can form a macromolecular compound with the organic pigments on the upper layer of the white ink, plays a "bridging" role between the fiber and the organic pigments, and coats the organic pigments on the fiber surface to prevent the organic pigments from falling off, thereby improving various color fastnesses of the dyed fabric while maintaining the soft hand feeling of the fabric.

[0026] Due to the adoption of the above technical solutions, the present invention has remarkable technical effects:

[0027] 1. The hot stamping ink prepared with the aqueous polyurethane fixing agent of the present invention can effectively improve the rubbing fastness and washing fastness of the printed pattern.

[0028] 2. The stability of the hot stamping ink of the present invention is improved, and the anionic aqueous polyurethane fixing agent and the ink system have good compatibility, maintaining good printing fluidity. Specific embodiments

[0029] Example 1

[0030] (1) Synthesis of anionic aqueous polyurethane fixing agent: Weigh 49 parts of polypropylene glycol - 1000 into a four-necked flask, slowly heat up to 115°C under mechanical stirring, evacuate and maintain the vacuum degree below -0.09 MPa, remove water for 2 h and then slowly cool down. Cool down to 80°C, weigh 40 parts of isophorone diisocyanate and 0.1 part of dibutyltin dilaurate, stir mechanically, and introduce dry nitrogen. Acetone is added during the reaction to reduce the viscosity. When the -NCO percentage content reaches 11.7%, cool down. Slowly cool down to 70°C, add 5 parts of the small molecule chain extender dimethylolbutyric acid and 3.9 parts of the crosslinking agent trimethylolpropane. When the -NCO percentage content reaches 2.1%, cool down. Cool down to 60°C and add 2 parts of the capping agent sodium bisulfite. After completely blocking the remaining -NCO groups, cool down to obtain the anionic aqueous polyurethane fixing agent. Cool the polymer obtained by the above method to 30°C, add deionized water according to the solid content of 30%, and disperse with a high-speed electric stirrer for 30 min. Rotate and evaporate the acetone solvent to obtain a thermally reactive anionic aqueous polyurethane emulsion.

[0031] (2) Preparation of hot stamping white ink: 30% titanium white color paste, 15% aqueous polyurethane resin W-6110, 10% synthesized anionic aqueous polyurethane fixing agent, 2% surfactant, 25% water-soluble organic solvent, 0.2% bactericide, and the rest is water.

[0032] The preparation method is as follows: Add the above components into deionized water in sequence. After stirring and mixing evenly, filter with a 0.45 μm filter membrane to obtain the white ink for heat transfer printing.

[0033] Example 2:

[0034] (1) Synthesis of anionic aqueous polyurethane fixing agent: Weigh 49 parts of polypropylene glycol - 1000 into a four-necked flask. Under mechanical stirring, slowly heat up to 115 °C, evacuate the air and maintain the vacuum degree below -0.09 MPa. After removing water for 2 h, slowly cool down. When the temperature drops to 80 °C, weigh 40 parts of isophorone diisocyanate and 0.1 part of dibutyltin dilaurate, stir mechanically, and introduce dry nitrogen. Acetone is added during the reaction to reduce the viscosity. When the -NCO percentage content reaches 12.4%, cool down. Slowly cool down to 70 °C, add 5 parts of the small molecule chain extender N, N-dimethylolpropionic acid and 3.9 parts of the crosslinking agent trimethylolpropane. When the -NCO percentage content reaches 2.9%, cool down. When the temperature drops to 60 °C, add 2 parts of the end-capping agent sodium bisulfite. After completely blocking the remaining -NCO groups, cool down to obtain the anionic aqueous polyurethane fixing agent. Cool the polymer obtained by the above method to 30 °C, add deionized water according to the solid content of 30%, and stir and disperse at high speed with an electric stirrer for 30 min. Rotavaporize the acetone solvent to obtain a thermally reactive anionic aqueous polyurethane emulsion.

[0035] (2) Preparation of white ink for heat transfer printing: 30% titanium white color paste, 15% aqueous polyurethane resin, 8% synthesized anionic aqueous polyurethane fixing agent, 2% surfactant, 25% water-soluble organic solvent, 0.2% bactericide, and the rest is water.

[0036] The preparation method is as follows: Add the above components into deionized water in sequence. After stirring and mixing evenly, filter with a 0.45 μm filter membrane to obtain the white ink for heat transfer printing.

[0037] Example 3:

[0038] (1) Synthesis of anionic aqueous polyurethane color fixative: Weigh 49 parts of polypropylene glycol - 1000 into a four - necked flask. Under mechanical stirring, slowly heat up to 115 °C, evacuate the air and maintain the vacuum degree below - 0.09 MPa. After dehydrating for 2 h, slowly cool down. When the temperature drops to 80 °C, weigh 40 parts of isophorone diisocyanate and 0.1 part of dibutyltin dilaurate, stir mechanically, and introduce dry nitrogen. During the reaction, add acetone to reduce the viscosity. When the - NCO percentage content reaches 11.4%, cool down. Slowly cool down to 70 °C, add 5 parts of small - molecule chain extender 1,2 - propanediol - 3 - sulfonate and 3.9 parts of cross - linker trimethylolpropane. When the - NCO percentage content reaches 2.4%, cool down. When the temperature drops to 60 °C, add 2 parts of capping agent sodium bisulfite. After completely sealing the remaining - NCO groups, cool down to obtain an anionic aqueous polyurethane color fixative. Cool the polymer prepared by the above method to 30 °C, add deionized water according to the solid content of 30%, and use an electric stirrer to stir and disperse at high speed for 30 min. Rotavapor to remove the acetone solvent to obtain a thermo - reactive anionic aqueous polyurethane emulsion.

[0039] (2) Preparation of heat - transfer white ink: 30% titanium white color paste, 15% aqueous polyurethane resin, 5% synthesized anionic aqueous polyurethane color fixative, 2% surfactant, 25% water - soluble organic solvent, 0.2% fungicide, and the rest is water.

[0040] The preparation method is as follows: Add the above components into deionized water in sequence. After stirring and mixing evenly, filter with a 0.45 - μm filter membrane to obtain heat - transfer white ink.

[0041] Comparative example: A comparative heat - transfer white ink, whose composition is basically the same as that of Example 1, except that the synthesized anionic aqueous polyurethane color fixative is not added, and the preparation method is the same as that of Example 1.

[0042] Perform the following performance tests on the white inks in the examples and comparative examples.

[0043] (1) Fluidity test: Load the prepared heat - transfer white ink into the printer, perform a good cleaning of the print head before printing to ensure that there is no broken needle or broken line during printing. Under the same conventional printing conditions, continuously print color blocks on the PET transfer film, with a printing length of 5 m. After printing, print a test strip and observe whether there are broken needles or broken lines.

[0044] (2) Stand - by test: After the fluidity test of the heat - transfer white ink is completed, clean the print head and standby for 3 h; then perform the same conventional printing task and observe whether there are broken needles or broken lines.

[0045] (3) Stability test: The hot stamping white ink was filled in a sealed aging test bottle and placed in a constant temperature water bath at 60 °C for 14 days; then the aged ink was filled into the printer for a fluidity test to check for needle breakage and line breakage.

[0046] (4) Color fastness test: The hot stamping film obtained by printing during standby testing was hot stamped on the surface of the item to be hot stamped using a hot stamping machine.

[0047] The hot stamping products were tested. The rubbing color fastness was determined with reference to GB / T3920 - 2008, and the color fastness to washing was determined with reference to GB / T5713 - 2013. The above test results are shown in Table 1.

[0048] Table 1

[0049]

[0050]

[0051] It can be analyzed from Table 1 that the hot stamping ink prepared by adding the self - synthesized anionic aqueous polyurethane color fixing agent can effectively improve the rubbing fastness and washing fastness of the printed pattern; moreover, the aqueous polyurethane color fixing agent and the ink system have good compatibility and maintain good printing fluidity.

[0052] The above - mentioned are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A waterborne polyurethane color fixing agent, characterized in that, It includes the following steps: S1: Weigh oligomeric polyol into a four-necked flask, slowly heat it up under mechanical stirring, evacuate the air and keep the vacuum degree below -0.09 MPa, remove water for 2 h and then slowly cool it down; S2: Weigh isocyanate and catalyst and add them into the four-necked flask, stir mechanically and introduce dry nitrogen. Add acetone during the reaction to reduce the viscosity. When the -NCO percentage content reaches 10%-15%, slowly cool it down; S3: When slowly cooling down to 70 °C, add anionic hydrophilic chain extender and crosslinking agent previously dissolved in acetone. When the -NCO percentage content reaches 2%-5%, slowly cool it down. Cool it down to 60 °C and add a capping agent. After completely blocking the remaining -NCO groups, cool it down to obtain an anionic waterborne polyurethane; S4: Cool the anionic waterborne polyurethane obtained in step S3 to 30 °C, add deionized water according to the solid content of 30%, and stir and disperse it at a high speed with an electric stirrer for 30 min; Rotavaporize the acetone solvent to obtain an anionic waterborne polyurethane fixing agent with an internal crosslinked structure.

2. The aqueous polyurethane color fixing agent according to claim 1, characterized in that, In step S1, slowly heat up to 115 °C and slowly cool down to 80 °C; The oligomeric polyol is one or more of polypropylene glycol-1000, trimethylol polyethylene glycol monomethyl ether, and polytetrahydrofuran ether glycol-1000.

3. The waterborne polyurethane color fixing agent according to claim 1, characterized in that, The isocyanate is one or more of isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, and dicyclohexylmethane diisocyanate.

4. The waterborne polyurethane color fixing agent according to claim 1, characterized in that, The catalyst is dibutyltin dilaurate.

5. The waterborne polyurethane color fixing agent according to claim 1, characterized in that, The anionic hydrophilic chain extender is one or more of N,N-dimethylolpropionic acid, dimethylolbutyric acid, 1,2-propanediol-3-sulfonate, and 1,4-butanediol-2-sulfonate.

6. The aqueous polyurethane color fixing agent according to claim 1, wherein The crosslinking agent is trimethylolpropane, and the capping agent is sodium bisulfite.

7. A novel heat transfer ink, characterized in that, By weight percentage, it includes: 20%-40% of pigment dispersion, 10%-30% of waterborne polyurethane resin, 5%-10% of the waterborne polyurethane fixing agent according to any one of claims 1-6, 0.2%-2% of surfactant, 10%-30% of water-soluble organic solvent, 0.1%-0.5% of bactericide, and the rest is water.

8. A novel heat transfer ink according to claim 7, characterized in that, The pigment dispersion is titanium white color paste; The waterborne polyurethane resin is W-6061 and W-6110 of Mitsui Chemicals, Japan; The surfactant is one or more of non-silicon surfactants and silicone surfactants.

9. The preparation method of a novel heat transfer ink according to claim 7, characterized in that, The water-soluble organic solvent is one or more of ethylene glycol, propylene glycol, glycerol, diethylene glycol, triethylene glycol, and triethylene glycol monobutyl ether; The bactericide is BIT-20.

10. A preparation method of a novel heat transfer ink according to any one of claims 7-9, characterized in that, It includes the following steps: Add pigment dispersion, waterborne polyurethane resin, waterborne polyurethane fixing agent, surfactant, water-soluble organic solvent, and bactericide into deionized water in sequence. After adding water and stirring to mix evenly, filter it with a 0.45 μm filter membrane to obtain heat transfer ink.

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