A method for preparing environmentally friendly water-soluble engraving gravure ink

Abstract

The present invention relates to the technical field of ink, and discloses a method for preparing an environmentally friendly water-soluble engraving gravure ink, which is operated as follows: placing porous staple fibers in water, adding surfactants, stirring after heating to 40-60°C, and obtaining a suspension; adding pigments to the suspension in batches, standing and filtering after sufficient stirring, drying the filtrate, and obtaining porous staple fibers filled with pigments; selecting polyethylene glycol with a melting point of 35-60°C, heating and melting, adding porous staple fibers, slowly stirring and filtering, dispersing the porous staple fibers, cooling at room temperature, and slowly stirring and mixing with anhydrous ink connecting materials to obtain ink slurry; mixing water and an auxiliary agent uniformly to obtain an aqueous diluent; mixing the ink slurry and the aqueous diluent before spraying, and spraying after sufficient grinding. The present invention blocks nano pigments in porous staple fibers, and the pigments in the ink slurry will not diffuse out from the surface micropores of the porous staple fibers, and the porous staple fibers are stably dispersed, thereby avoiding the problem of pigment agglomeration and precipitation.

Description

Technical Field

[0001] The invention relates to the technical field of inks, and in particular to a method for preparing an environmentally friendly water-soluble engraving gravure ink. Background Art

[0002] Ink for gravure printing is a relatively advanced type of ink. It has very high requirements for ink solid content, fluidity, adhesion, color saturation and other indicators. In order to ensure that the ink has uniform and high chroma, the pigment content in the ink is usually increased as much as possible. However, a high content of inorganic particle state pigment is an important test for the stability of the ink. The pigment will inevitably agglomerate or even precipitate, resulting in uneven color and poor color fastness after printing. In severe cases, it may even fail to print normally.

[0003] One way to increase the solid content of pigments in inks is to use oil-based inks. Organic solvents added to oil-based inks can increase the ink's ability to carry pigments, but the environmental pollution of organic solvents limits the use of oil-based inks. Chinese patent CN107459867 A discloses an ultra-high solid content, low-viscosity aqueous polyurethane composite ink, which is an AB two-component aqueous polyurethane composite ink. The aqueous acrylic resin in component A and the aqueous polyurethane resin in component B are mixed to form an ink that evenly disperses nanoparticles. The ink in this patent has a high solid content, but similar to traditional aqueous inks, the pigment particles are also directly dispersed in the aqueous polyurethane binder, especially the nano-sized inorganic particle pigments used in this patent are more likely to agglomerate during the printing process, affecting the printing quality. Summary of the invention

[0004] Aiming at the problem that high-content pigments in existing water-based inks are prone to agglomeration and precipitation, the present invention provides a method for preparing an environmentally friendly water-soluble engraving gravure ink, comprising the following steps:

[0005] 1) Pretreatment of porous staple fibers

[0006] Place porous short fibers with depressions or holes on the surface into water, add surfactant, heat to 40-60°C and stir to obtain a suspension;

[0007] 2) Filling the paint

[0008] Add pigments to the suspension of step 1) in batches, stir thoroughly, let stand and filter, and dry the filtrate to obtain porous short fibers filled with pigments;

[0009] 3) Sealing pigment

[0010] Select polyethylene glycol with a melting point of 35-60°C, heat and melt it, add it to the porous staple fibers in step 2), slowly stir and filter to disperse the porous staple fibers, and cool at room temperature;

[0011] 4) Preparation of ink paste

[0012] The porous short fibers cooled in step 3) and the waterless ink connecting material are slowly mixed under stirring to prepare ink slurry;

[0013] 5) Preparation of aqueous diluent

[0014] Mix water and the auxiliary agent evenly to prepare an aqueous diluent;

[0015] 6) Spraying

[0016] Before spraying, mix the ink slurry with water-based diluent, grind it thoroughly and then spray it.

[0017] In step 1) of the present invention, the length of the porous staple fiber is 0.2-2 mm, the fiber diameter is 0.2-1.5 μm, and the material is PA66, para-aramid, PET or PAN. A strong alkali heating corrosion method is used to etch depressions on the fiber surface; the surfactant is selected from one of KH550, KH560 or sodium lauryl sulfate. On the one hand, the surfactant can combine with the amino, hydroxyl and other functional groups that appear after the fiber is corroded, so that the porous staple fiber is evenly dispersed in the water. On the other hand, the surfactant reduces the interfacial energy between the pigment and the surface of the porous staple fiber, so that the pigment can more easily enter the interior of the porous staple fiber.

[0018] In step 2) of the present invention, the selected pigment particle size is 10-200 nm, and is one of carbon black, pigment red 48:2, pigment red 149, pigment yellow 150, pigment yellow 180, pigment blue 27 or pigment blue 60. The width of the depression on the surface of the porous staple fiber is between 100 nm and 1 μm, and the nano-sized pigment can be easily filled in the depression on the surface of the porous staple fiber.

[0019] In step 3) of the present invention, the polyethylene glycol with a melting point of 35-60° C. is specifically selected from a combination of one or more of PEG1000, PEG1500, PEG2000 or PEG4000. PEG has a low melting point and is highly soluble in water, and is suitable for temporarily blocking the pigment in the porous staple fiber.

[0020] In the ink slurry obtained in step 4) of the present invention, the weight of the porous short fibers accounts for 30% to 50%, the weight of the waterless ink binder accounts for 50% to 70%, and the waterless ink binder is aqueous polyurethane. In a waterless environment, polyethylene glycol will not dissolve in the polyurethane slurry, the porous short fibers are evenly dispersed in the polyurethane slurry, and the pigment blocked inside the porous short fibers will not be released into the polyurethane slurry.

[0021] In step 5) of the present invention, according to the raw material ratio, the auxiliary agent can be selected from one, two or three of a stabilizer, a volatilizer or a film-forming agent. Specifically, the stabilizer is sodium dodecyl sulfate or sodium lauryl sulfate, the volatilizer is one of methanol, ethanol or dimethyl sulfoxide, and the film-forming agent is dodecyl alcohol ester.

[0022] In step 6) of the present invention, the amount ratio of the ink slurry and the aqueous diluent must ensure that the solid content of the ink after mixing is 75% to 90%.

[0023] The beneficial effects of the present invention are as follows:

[0024] 1. The present invention first seals the nano-pigment in the surface depressions of the porous staple fibers, and then mixes the porous staple fibers with a waterless ink binder to prepare ink slurry. The pigment will not diffuse out from the porous staple fibers in the ink slurry, and the porous staple fibers can be stably and evenly dispersed in the waterless ink binder, thereby avoiding the problem of inorganic particle pigment agglomeration and precipitation during the storage of the ink; before use, after the aqueous diluent and the ink slurry are mixed, the polyethylene glycol on the surface of the porous staple fibers will quickly dissolve in water, releasing the pigment into the system, and the ink is used for printing within a short time after the pigment is released, and even before the ink is dried after printing, the pigment particles are released, thereby minimizing the time and probability of pigment agglomeration, and the pigment in the ink is evenly dispersed and the color printed at a high solid content has better chroma and depth;

[0025] 2. The present invention adds porous staple fibers to the ink, which can increase the strength of the ink. Compared with the existing ink with added fibers, the pigment loaded in the porous staple fibers of the present invention cannot be completely released. The pigment remaining in the porous staple fibers makes the porous staple fibers colorful, avoiding the color difference caused by the colorless fibers in the existing ink with added fibers. After the ink dries, the pigment is fixed in the porous staple fibers, further improving the color fastness of the ink. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the SEM image of the porous aramid staple fiber film obtained in Example 1.

[0027] Figure 2 This is the ESEM image of the ink prepared in Example 1. DETAILED DESCRIPTION

[0028] In order to better explain the present invention, further description will be given in conjunction with the following specific embodiments, but the present invention is not limited to the specific embodiments. Example 1

[0029] A method for preparing an environmentally friendly water-soluble engraving gravure black ink comprises the following steps:

[0030] 1. First, add para-aramid staple fibers with a length of 1 mm and a fiber diameter of 0.8 μm to a potassium hydroxide solution with a concentration of 15 wt%, then add dimethyl sulfoxide, heat to 60 ° C and stir for 1 day, dilute the liquid and vacuum filter, and after repeated washing, a porous aramid staple fiber film is obtained, the porous aramid staple fiber film is added to water, KH560 is added, heated to 60 ° C and stirred to obtain a suspension;

[0031] 2. Add carbon black with a particle size of 50 nm to the suspension in portions, stir for 6 hours, let it stand and filter, and dry the filtrate to obtain porous aramid staple fibers loaded with carbon black;

[0032] 3. Mix PEG1000 and PEG1500 in a weight ratio of 1:1 and heat to 55°C. After completely melting, add the aramid staple fiber in step 2 and stir slowly for 30 minutes to fully soak the aramid staple fiber. After heat preservation and filtration, disperse the aramid staple fiber as much as possible and cool at room temperature.

[0033] Fourth, in a solvent-free environment, the molar ratio of isocyanate group to hydroxyl group is controlled to be (1.02-1.1):1, MDI and polyester polyol are mixed and heated to 65°C, and reacted under the catalysis of an organic tin catalyst to obtain a water-based polyurethane with a number average molecular weight of 20,000, wherein the polyester polyol is obtained by polymerization of malonic acid and propylene glycol, and the aramid staple fiber cooled in step 3 is slowly mixed with the obtained water-based polyurethane under stirring to obtain an ink slurry, in which the weight proportion of the aramid staple fiber in the ink slurry is 50%;

[0034] 5. Add 3% sodium dodecyl sulfate, 5% ethanol and 2% dodecyl alcohol ester to deionized water, and stir evenly to prepare an aqueous diluent;

[0035] 6. Mix the ink paste of step 4 and the aqueous diluent of step 5 to prepare an environmentally friendly water-soluble engraving gravure black ink, the solid content of the ink is 85%, and complete printing as soon as possible after mixing.

[0036] Figure 1 This is a SEM image of the porous aramid staple fiber film obtained in step 1 of Example 1. It can be seen from the image that the surface of the porous aramid staple fiber has relatively uniform depressions, and the width of the depressions is about 100 nm. Figure 2 This is the ESEM image of the porous aramid staple fibers in the ink obtained in step six of Example 1. It can be seen from the figure that the aramid staple fibers are evenly dispersed in the ink, and the released carbon black is also evenly dispersed in the ink without agglomeration. There is still a large amount of carbon black in the aramid staple fibers, making the aramid staple fibers black. Example 2

[0037] A method for preparing an environmentally friendly water-soluble engraving gravure red ink comprises the following steps:

[0038] 1. Add PA66 staple fibers with a length of 2 mm and a fiber diameter of 1 μm to a 10 wt% potassium hydroxide solution, then add dimethyl sulfoxide, heat to 60°C and stir for 1 day, dilute the liquid and vacuum filter, wash repeatedly to obtain a porous PA66 staple fiber film, add the porous PA66 staple fiber film to water, add KH550, heat to 65°C and stir to obtain a suspension;

[0039] 2. Add Pigment Red 149 with a particle size of 100 nm to the suspension in portions, stir for 6 hours, filter it, and dry the filtrate to obtain porous PA66 staple fibers filled with Pigment Red 149;

[0040] 3. Heat PEG1500 to 50°C, add the PA66 staple fiber in step 2 after it is completely melted, stir slowly for 30 minutes to fully soak the PA66 staple fiber, disperse the PA66 staple fiber as much as possible after heat preservation and filtration, and cool at room temperature;

[0041] Fourth, in a solvent-free environment, the molar ratio of isocyanate group to hydroxyl group is controlled to be (1.02-1.05):1, TDI and polyester polyol are mixed and heated to 70°C, and reacted under the catalysis of an organic tin catalyst to obtain a water-based polyurethane with a number average molecular weight of 15,000, wherein the polyester polyol is obtained by polymerization of oxalic acid and propylene glycol, and the PA66 staple fiber cooled in step 3 is slowly mixed with the obtained water-based polyurethane under stirring to obtain an ink slurry, in which the weight proportion of PA66 staple fiber in the ink slurry is 45%;

[0042] 5. Add 4% sodium lauryl sulfate, 6% dimethyl sulfoxide and 3% dodecyl alcohol ester to deionized water, and stir evenly to prepare an aqueous diluent;

[0043] 6. Mix the ink paste of step 4 and the aqueous diluent of step 5 to prepare an environmentally friendly water-soluble engraved gravure red ink, the solid content of the ink is 78%, and complete printing as soon as possible after mixing. Example 3

[0044] A method for preparing an environmentally friendly water-soluble engraving gravure yellow ink comprises the following steps:

[0045] 1. First, add PET staple fibers with a length of 0.5 mm and a fiber diameter of 200 nm to a potassium hydroxide solution with a concentration of 15 wt%, then add dimethyl sulfoxide, heat to 70°C and stir for 1 day, dilute the liquid and vacuum filter, wash repeatedly to obtain a porous PET staple fiber film, add the porous PET staple fiber film to water, add sodium lauryl sulfate, heat to 65°C and stir to obtain a suspension;

[0046] 2. Add Pigment Yellow 150 with a particle size of 30 nm to the suspension in portions, stir for 6 hours, let stand and filter, and dry the filtrate to obtain porous PET staple fibers filled with Pigment Yellow 150;

[0047] 3. Heat PEG2000 to 55°C, add the PET staple fibers from step 2 after it is completely melted, stir slowly for 30 minutes to fully soak the PET staple fibers, disperse the PET staple fibers as much as possible after heat preservation and filtration, and cool at room temperature;

[0048] Fourth, in a solvent-free environment, the molar ratio of isocyanate group to hydroxyl group is controlled to be (1.02-1.05):1, MDI and polyester polyol are mixed and heated to 70°C, and reacted under the catalysis of an organic tin catalyst to obtain a water-based polyurethane with a number average molecular weight of 30,000, wherein the polyester polyol is obtained by polymerization of maleic acid and butanediol, and the PET staple fibers cooled in step 3 are slowly mixed with the obtained water-based polyurethane under stirring to obtain an ink slurry, wherein the weight proportion of the PET staple fibers in the ink slurry is 50%;

[0049] 5. Add 4% sodium lauryl sulfate, 6% dimethyl sulfoxide and 3% dodecyl alcohol ester to deionized water, and stir evenly to prepare an aqueous diluent;

[0050] 6. Mix the ink paste of step 4 and the aqueous diluent of step 5 to prepare an environmentally friendly water-soluble engraving gravure yellow ink, the solid content of the ink is 75%, and complete printing as soon as possible after mixing.

[0051] Comparative Example 1

[0052] A method for preparing aramid-waterborne polyurethane carbon black ink comprises the following steps: placing the waterborne polyurethane, para-aramid staple fibers, and carbon black in Example 1 into a mixed solution of water, sodium dodecyl sulfate, ethanol, and dodecyl alcohol ester, stirring them fully, and then grinding them to obtain the ink. The weight fractions of the components are: 40% waterborne polyurethane, 15% para-aramid staple fibers, 25% carbon black, 2% sodium dodecyl sulfate, 2% ethanol, 1% dodecyl alcohol ester, and the balance is water.

[0053] Table 1 shows the performance test results of the inks obtained in Examples 1 to 3 and Comparative Example 1. From the data in Table 1, it can be seen that due to the addition of staple fibers and the lack of pigment agglomeration, the inks obtained in Examples 1 to 3 have high indicators and balanced performance. The components of the ink in Comparative Example 1 are simply mixed, so both the para-aramid staple fibers and the carbon black will agglomerate and precipitate, resulting in a certain gap in the performance of the ink compared with the inks obtained in Examples 1 to 3.

[0054] Table 1. Performance test results of inks obtained in Examples 1 to 3 and Comparative Example 1

[0055]

[0056] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an environmentally friendly water-soluble engraving gravure ink, characterized in that: The following steps are involved: 1) Pretreatment of porous staple fibers Place porous short fibers with depressions or holes on the surface into water, add surfactant, heat to 40-60°C and stir to obtain a suspension; 2) Filling the paint Add pigments to the suspension of step 1) in batches, stir thoroughly, let stand and filter, and dry the filtrate to obtain porous short fibers filled with pigments; 3) Sealing pigment Select polyethylene glycol with a melting point of 35-60°C, heat and melt it, add it to the porous staple fibers in step 2), slowly stir and filter to disperse the porous staple fibers, and cool at room temperature; 4) Preparation of ink paste The porous short fibers cooled in step 3) and the waterless ink connecting material are slowly mixed under stirring to prepare ink slurry; 5) Preparation of aqueous diluent Mix water and the auxiliary agent evenly to prepare an aqueous diluent; 6) Spraying Before spraying, mix the ink slurry with water-based diluent, grind it thoroughly and then spray it.

2. The method for preparing the environmentally friendly water-soluble engraving gravure ink according to claim 1, characterized in that: In step 1), the length of the porous staple fibers is 0.2-2 mm, and the fiber diameter is 0.2-1.5 μm.

3. The method for preparing the environmentally friendly water-soluble engraving gravure ink according to claim 2, characterized in that: The porous staple fibers are selected from one of PA66 fibers, para-aramid fibers, PET fibers or PAN fibers.

4. The method for preparing the environmentally friendly water-soluble engraving gravure ink according to claim 1, characterized in that: In step 1), the surfactant is one of KH550, KH560 or sodium lauryl sulfate.

5. The method for preparing the environmentally friendly water-soluble engraving gravure ink according to claim 1, characterized in that: In step 2), the particle size of the pigment is 10-200 nm, and the pigment is selected from one of carbon black, pigment red 48:2, pigment red 149, pigment yellow 150, pigment yellow 180, pigment blue 27 or pigment blue 60.

6. The method for preparing the environmentally friendly water-soluble engraving gravure ink according to claim 1, characterized in that: In step 3), the polyethylene glycol is selected from a combination of one or more of PEG1000, PEG1500, PEG2000 or PEG4000.

7. The method for preparing the environmentally friendly water-soluble engraving gravure ink according to claim 1, characterized in that: In step 4), the weight fractions of the porous staple fibers and the waterless ink binder are: 30% to 50% of the porous staple fibers and 50% to 70% of the waterless ink binder.

8. The method for preparing the environmentally friendly water-soluble engraving gravure ink according to claim 7, characterized in that: The waterless ink connecting material is water-based polyurethane.

9. The method for preparing the environmentally friendly water-soluble engraving gravure ink according to claim 1, characterized in that: In step 5), the auxiliary agent is one, two or three of a stabilizer, a volatilizer or a film-forming agent, the stabilizer is sodium dodecyl sulfate or sodium lauryl sulfate, the volatilizer is one of methanol, ethanol or dimethyl sulfoxide, and the film-forming agent is dodecyl alcohol ester.

10. The method for preparing the environmentally friendly water-soluble engraving gravure ink according to claim 1, characterized in that: In step 6), after the ink slurry and the aqueous diluent are mixed, the solid content of the mixed liquid is 75% to 90%.

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