Environment-friendly composite ink and preparation process thereof

Abstract

The invention provides environment-friendly composite ink and a preparation process thereof, and belongs to the technical field of ink preparation. The preparation process comprises the following steps: modifying the waterborne polyurethane; preparing a modified kaolin functional filler; and preparing the composite ink. Polyurethane is modified through glycerol monolaurate, and the flexibility, glossiness, adhesive force and corrosion resistance of the ink can be improved through long-chain alkyl and hydroxyl of the glycerol monolaurate; the casein is modified by nutgall tannin, so that the mechanical strength, the adhesive force, the water resistance and the dryness of the ink are enhanced; the modified casein modified kaolin improves the dispersibility of the filler, improves the wear resistance and adhesive ability of the ink, accelerates drying and prevents the pigment from sinking to the bottom.

Description

Technical Field

[0001] The present invention relates to the technical field of ink preparation, and in particular to an environmentally friendly composite ink and a preparation process thereof. Background Art

[0002] Printing inks, as core consumables in the modern printing industry, are attracting increasing attention for their performance and environmental impact. Traditional solvent-based inks release large amounts of volatile organic compounds (VOCs), such as toluene, xylene, ketones, and esters, during production and use. These VOCs not only pose a serious threat to operator health (such as respiratory irritation and neurological damage), but are also important precursors to photochemical smog and PM2.5 fine particulate matter, significantly polluting the atmospheric environment.

[0003] The rapid development of the printing industry and the growing popularity of environmental protection concepts have led to higher demands on the performance and environmental friendliness of inks. Water-based inks, which use water as their primary dispersion medium or solvent and significantly reduce VOCs, are currently the leading environmentally friendly ink trend. However, printing performance and drying speed are bottlenecks. The high latent heat of evaporation of water results in a drying speed far lower than that of solvent-based inks, impacting printing efficiency and energy consumption. Furthermore, they exhibit poor adhesion to non-absorbent substrates such as plastic films and metals. Furthermore, the water resistance and abrasion resistance of some water-based inks fail to meet the requirements of high-end packaging.

[0004] Therefore, an environmentally friendly composite ink and a preparation process thereof are proposed to solve the above problems. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide an environmentally friendly composite ink and a preparation process thereof.

[0006] A process for preparing an environmentally friendly composite ink comprises the following steps:

[0007] S1: Modification of waterborne polyurethane

[0008] The modified waterborne polyurethane emulsion is prepared by reacting isophorone diisocyanate, polytetramethylene glycol, dimethylol propionic acid, trimethylol propane and glyceryl monolaurate, wherein the weight ratio of isophorone diisocyanate, polytetramethylene glycol, dimethylol propionic acid, trimethylol propane and glyceryl monolaurate is 23-25:38-42:2.95-3.05:2.56-3.12:2.35-2.53;

[0009] S2: Preparation of modified kaolin functional filler

[0010] The pH of the casein aqueous solution is first adjusted to 11.0-11.2, and then gallic tannin and glycerol are added for modification to obtain gallic tannin-modified casein. Then, kaolin is pretreated with a silane coupling agent KH-550, and then the pretreated kaolin is modified with the gallic tannin-modified casein.

[0011] S3: Preparation of composite ink

[0012] First, 40-50 parts by weight of modified waterborne polyurethane emulsion, 20-30 parts by weight of deionized water, 10-12 parts by weight of pigment, and 0.1-0.3 parts by weight of defoamer are mixed, and then 8-10 parts by weight of modified kaolin functional filler and 1-2 parts by weight of wetting dispersant are added to prepare a composite ink.

[0013] Furthermore, step S1 of modifying the waterborne polyurethane specifically includes the following steps:

[0014] S1.1: 23-25 ​​parts by weight of isophorone diisocyanate, 38-42 parts by weight of polytetramethylene glycol, 2.95-3.05 parts by weight of dimethylolpropionic acid, 2.56-3.12 parts by weight of trimethylolpropane, and 2.35-2.53 parts by weight of glyceryl monolaurate are mixed and added to a three-necked flask equipped with a condenser reflux apparatus, a nitrogen protection device, and an electric stirrer;

[0015] S1.2: Add 8-10 parts by weight of N,N-dimethylacetamide to a three-necked flask, then stir and react at 60-62°C for 30-40 minutes, then heat to 80-82°C, add 0.5-0.8 parts by weight of dibutyltin dilaurate, stir and react at 360-380r / min until the -NCO group content reaches the theoretical value, then cool to 40-42°C, and add 10-15 parts by weight of acetone to reduce the viscosity, then add 2.12-2.38 parts by weight of triethylamine, stir and disperse at 500-600r / min for 15-20 minutes, then add deionized water at 800-1200rpm and stir for 10-12 minutes, then perform vacuum low-pressure distillation to obtain a modified aqueous polyurethane emulsion with a solid content of 40-42%.

[0016] Furthermore, step S2 of preparing the modified kaolin functional filler specifically includes the following steps:

[0017] S2.1: Adding sodium hydroxide solution to a 6-8 wt% casein aqueous solution to adjust the pH to 11.0-11.2, stirring at 200-300 rpm for 20-30 minutes, then adding 0.5-0.8 parts by weight of gallic tannin, stirring for 20-30 minutes, then adding 3-5 parts by weight of glycerol, continuing to stir for 10-12 minutes, and then stirring at 80-82° C. for 40-50 minutes to obtain a gallic tannin-modified casein emulsion;

[0018] S2.2: Add 0.06-0.08 parts by weight of silane coupling agent KH-550 to 10-12 parts by weight of anhydrous ethanol, then add 1-2 parts by weight of acetic acid, stir and mix at 400-500 rpm for 40-50 min, then add 1-2 parts by weight of kaolin pre-dispersion liquid, stir and react for 30-40 min, and then ultrasonicate for 20-30 min to obtain a suspension;

[0019] S2.3: heating the suspension to 80-82° C. and stirring at 500-600 rpm for 4-5 hours, then centrifuging the suspension. Washing the precipitate obtained by centrifugation repeatedly with water and anhydrous ethanol until neutral, and then drying the precipitate at 80-82° C. for 40-48 hours to obtain pretreated kaolin.

[0020] S2.4: Add 1-2 parts by weight of pretreated kaolin to 10-12 parts by weight of deionized water, then heat to 80-82°C and stir for 2-3 hours. Then add 20-23 parts by weight of gallic tannin modified casein emulsion and continue stirring for 2-3 hours. Then cool to room temperature and filter to obtain modified kaolin functional filler.

[0021] Furthermore, step S3 of preparing the composite ink specifically includes the following steps:

[0022] S3.1: Add 40-50 parts by weight of a modified aqueous polyurethane emulsion, 20-30 parts by weight of deionized water, 10-12 parts by weight of a pigment, and 0.1-0.3 parts by weight of a defoamer to a stirred tank and stir at a stirring rate of 800-1000 rpm for 20-30 minutes to obtain a mixed emulsion;

[0023] S3.2: Add 8-10 parts by weight of modified kaolin functional filler and 1-2 parts by weight of wetting and dispersing agent to the mixed emulsion, and stir at a stirring rate of 600-800 r / min for 20-30 minutes to obtain a composite ink.

[0024] Furthermore, the kaolin pre-dispersion liquid in step S2.2 is specifically obtained by mixing kaolin and anhydrous ethanol in a mass ratio of 1-2:30 and uniformly dispersing them.

[0025] Furthermore, in step S3.1, the pigment is one or more of permanent yellow, permanent red and phthalocyanine blue.

[0026] Furthermore, the defoaming agent in step S3.1 is one or more of TEGOFoamex K3, TEGOFoamex 810, and TEGOFoamex 825.

[0027] Furthermore, in step S3.2, the wetting and dispersing agent is one or more of BYK-180, BYK-190 and Silok-7117.

[0028] An environmentally friendly composite ink is prepared by any one of the processes for preparing an environmentally friendly composite ink.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects:

[0030] 1. The present invention modifies polyurethane by monolaurin. The long-chain alkyl group of monolaurin is embedded in the polyurethane molecular chain as a flexible chain segment, which can reduce the interaction force between the molecular chains and make the ink have good flexibility and bending resistance after film formation. The hydroxyl group in its glyceride structure can participate in the chain extension reaction of the polyurethane to form a more regular molecular network, promote the ink to form a smooth and uniform film layer during the drying process, and improve the gloss and texture of the printed matter. In addition, the hydrophobicity of the long-chain alkyl group can form a better interface interaction with hydrophobic substrates such as plastics and metals, reduce the repulsion of the ink on the surface of the substrate, and improve the adhesion strength. The long-chain alkyl group of monolaurin can form a hydrophobic layer on the surface of the film layer, which can reduce the penetration of water, solvents or chemical media into the film layer, enhance the water resistance, scrub resistance and corrosion resistance of the ink, and is suitable for long-term use in outdoor or packaging fields.

[0031] 2. The gallic tannins in the present invention are rich in polyphenolic hydroxyl groups of pyrogallol / catechol structure, and have extremely strong adhesion and coordination ability. After the gallic acid tannins are modified with casein through the high hydroxyl density of the gallic acid tannins, the gallic acid tannins react with the casein through chemical bonds such as hydrogen bonds, hydrophobic bonds, and ionic bonds, thereby enhancing the interaction between the casein molecular chains. The modification improves the flexibility and polarity of the casein molecular chains, which can significantly enhance the mechanical strength of the ink after film formation and the adhesion to the substrate, reducing the problem of shedding or scratching during the printing process. In addition, casein itself has poor water resistance and is easily dissolved or swelled by water. After the gallic acid tannins are modified, the cross-linked network can reduce the hydrophilicity of the molecular chain. At the same time, the hydrophobic aromatic ring structure of the gallic acid tannins can also reduce the penetration of water molecules. The phenolic hydroxyl groups of the gallic acid tannins can promote the hydrogen bonding between casein molecules, accelerate the drying and curing of the ink on the substrate surface, and at the same time, the uniform cross-linked network can make the film formation smoother and improve the gloss of the ink.

[0032] 3. The present invention adopts casein-modified kaolin modified with gallic tannin, which can enhance the interfacial interaction between kaolin and water-based polyurethane matrix through physical entanglement and chemical bonding. In addition, the gallic tannin-modified casein on the surface of the modified kaolin can form a hydration layer in water, which prevents the agglomeration of kaolin particles through the steric hindrance effect, thereby improving the dispersibility and bonding strength of the filler in the ink, and can improve the wear resistance of the ink and the adhesion ability of the water-based ink on offset paper and coated paper. On the other hand, the lamellar structure of the added modified kaolin can absorb moisture in the ink to achieve the effect of rapid drying. In addition, the lamellar structure of the modified kaolin and the gallic tannin-modified casein on the surface can "support" the pigment particles to avoid sinking to the bottom during long-term storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, further serve to explain the principles of the invention and to enable one skilled in the art to make and use the invention.

[0034] Figure 1 This is a process flow chart for preparing an environmentally friendly composite ink used in an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The following describes in detail the preparation process of an environmentally friendly composite ink provided by the present invention, with reference to the accompanying drawings and specific examples. It is also noted that, for the sake of completeness, the following examples are best and preferred embodiments, and those skilled in the art may employ alternative methods for implementing known techniques. Furthermore, the accompanying drawings are intended only to provide a more detailed description of the embodiments and are not intended to limit the present invention.

[0036] Example 1

[0037] An environmentally friendly composite ink and its preparation process, such as Figure 1 As shown, the following steps are included:

[0038] S1: Modification of waterborne polyurethane

[0039] S1.1: 23 parts by weight of isophorone diisocyanate, 38 parts by weight of polytetramethylene glycol, 2.95 parts by weight of dimethylolpropionic acid, 2.56 parts by weight of trimethylolpropane, and 2.35 parts by weight of glyceryl monolaurate were mixed and added to a three-necked flask equipped with a condenser reflux apparatus, a nitrogen blanket, and an electric stirrer;

[0040] S1.2: 8 parts by weight of N,N-dimethylacetamide were added to a three-necked flask, followed by stirring and reacting at 60°C for 30 minutes. The mixture was then heated to 80°C, 0.5 parts by weight of dibutyltin dilaurate was added, and the mixture was stirred and reacted at 360 rpm until the -NCO group content reached the theoretical value. The mixture was then cooled to 40°C, 10 parts by weight of acetone was added to reduce the viscosity, and 2.12 parts by weight of triethylamine was added. The mixture was stirred and dispersed at 500 rpm for 15 minutes. Deionized water was then added and stirred at 800 rpm for 10 minutes. The mixture was then subjected to vacuum low-pressure distillation to obtain a modified waterborne polyurethane emulsion with a solid content of 40%;

[0041] S2: Preparation of modified kaolin functional filler

[0042] S2.1: A sodium hydroxide solution was added to a 6 wt % casein aqueous solution to adjust the pH to 11.0, and the mixture was stirred at 200 rpm for 20 minutes. Then, 0.5 parts by weight of gallic tannin was added, and the mixture was stirred for 20 minutes. Then, 3 parts by weight of glycerol was added, and the mixture was stirred for 10 minutes. The mixture was then stirred at 80° C. for 40 minutes to obtain a gallic tannin-modified casein emulsion.

[0043] S2.2: 0.06 parts by weight of silane coupling agent KH-550 was added to 10 parts by weight of anhydrous ethanol, followed by 1 part by weight of acetic acid. The mixture was stirred and mixed at 400 rpm for 40 minutes. Then, 1 part by weight of kaolin pre-dispersion was added, the mixture was stirred for 30 minutes, and then ultrasonicated for 20 minutes to obtain a suspension.

[0044] S2.3: The suspension was heated to 80°C and stirred at 500 rpm for 4 hours, followed by centrifugation. The precipitate obtained by centrifugation was repeatedly washed with water and anhydrous ethanol until neutral, and then dried at 80°C for 40 hours to obtain pretreated kaolin.

[0045] S2.4: 1 part by weight of pretreated kaolin was added to 10 parts by weight of deionized water, and the mixture was heated to 80°C and stirred for 2 hours. Then, 20 parts by weight of gallic tannin-modified casein emulsion was added and the mixture was stirred for another 2 hours. The mixture was then cooled to room temperature and filtered to obtain a modified kaolin functional filler.

[0046] The kaolin pre-dispersion liquid is specifically obtained by mixing kaolin and anhydrous ethanol in a mass ratio of 1:30 and uniformly dispersing them;

[0047] S3: Preparation of composite ink

[0048] S3.1: Add 40 parts by weight of the modified aqueous polyurethane emulsion, 20 parts by weight of deionized water, 10 parts by weight of phthalocyanine blue, and 0.1 parts by weight of TEGO Foamex K3 to a stirred tank and stir at a stirring rate of 800 rpm for 20 minutes to obtain a mixed emulsion;

[0049] S3.2: Add 8 parts by weight of modified kaolin functional filler and 1 part by weight of BYK-180 to the mixed emulsion, and stir at a stirring rate of 600 r / min for 20 minutes to obtain a composite ink.

[0050] Example 2

[0051] A preparation process of an environmentally friendly composite ink, such as Figure 1 As shown, the following steps are included:

[0052] S1: Modification of waterborne polyurethane

[0053] S1.1: 25 parts by weight of isophorone diisocyanate, 42 parts by weight of polytetramethylene glycol, 3.05 parts by weight of dimethylolpropionic acid, 3.12 parts by weight of trimethylolpropane, and 2.53 parts by weight of glyceryl monolaurate were mixed and added to a three-necked flask equipped with a condenser reflux apparatus, a nitrogen blanket, and an electric stirrer;

[0054] S1.2: 10 parts by weight of N,N-dimethylacetamide were added to a three-necked flask, followed by stirring and reacting at 60°C for 30 minutes. The mixture was then heated to 80°C, 0.8 parts by weight of dibutyltin dilaurate was added, and the mixture was stirred and reacted at 360 rpm until the -NCO group content reached the theoretical value. The mixture was then cooled to 40°C, 15 parts by weight of acetone was added to reduce the viscosity, and 2.38 parts by weight of triethylamine was added. The mixture was stirred and dispersed at 500 rpm for 15 minutes. Deionized water was then added and stirred at 800 rpm for 10 minutes. The mixture was then subjected to vacuum low-pressure distillation to obtain a modified waterborne polyurethane emulsion with a solid content of 42%.

[0055] S2: Preparation of modified kaolin functional filler

[0056] S2.1: A sodium hydroxide solution was added to an 8 wt % casein aqueous solution to adjust the pH to 11.2, and the mixture was stirred at 200 rpm for 20 minutes. 0.8 parts by weight of gallic tannin was then added, and the mixture was stirred for 20 minutes. 5 parts by weight of glycerol was then added, and the mixture was stirred for 10 minutes. The mixture was then stirred at 80° C. for 40 minutes to obtain a gallic tannin-modified casein emulsion.

[0057] S2.2: 0.08 parts by weight of silane coupling agent KH-550 was added to 12 parts by weight of anhydrous ethanol, followed by 2 parts by weight of acetic acid. The mixture was stirred and mixed at 400 rpm for 40 minutes. Then, 2 parts by weight of kaolin pre-dispersion was added, the mixture was stirred for 30 minutes, and then ultrasonicated for 20 minutes to obtain a suspension.

[0058] S2.3: The suspension was heated to 80°C and stirred at 500 rpm for 4 hours, followed by centrifugation. The precipitate obtained by centrifugation was repeatedly washed with water and anhydrous ethanol until neutral, and then dried at 80°C for 40 hours to obtain pretreated kaolin.

[0059] S2.4: Add 2 parts by weight of pretreated kaolin to 12 parts by weight of deionized water, heat to 80°C, and stir for 2 hours. Then, add 23 parts by weight of gallic tannin-modified casein emulsion, continue stirring for 2 hours, cool to room temperature, and filter to obtain a modified kaolin functional filler.

[0060] The kaolin pre-dispersion liquid is specifically obtained by mixing kaolin and anhydrous ethanol in a mass ratio of 2:30 and uniformly dispersing them;

[0061] S3: Preparation of composite ink

[0062] S3.1: Add 50 parts by weight of modified aqueous polyurethane emulsion, 30 parts by weight of deionized water, 12 parts by weight of Permanent Red, and 0.3 parts by weight of TEGO Foamex 810 to a stirred tank and stir at a stirring rate of 800 rpm for 20 minutes to obtain a mixed emulsion;

[0063] S3.2: Add 10 parts by weight of modified kaolin functional filler and 2 parts by weight of BYK-190 to the mixed emulsion, and stir at a stirring rate of 600 r / min for 20 minutes to obtain a composite ink.

[0064] Example 3

[0065] A preparation process of an environmentally friendly composite ink, such as Figure 1 As shown, the following steps are included:

[0066] S1: Modification of waterborne polyurethane

[0067] S1.1: 23 parts by weight of isophorone diisocyanate, 38 parts by weight of polytetramethylene glycol, 2.95 parts by weight of dimethylolpropionic acid, 2.56 parts by weight of trimethylolpropane, and 2.35 parts by weight of glyceryl monolaurate were mixed and added to a three-necked flask equipped with a condenser reflux apparatus, a nitrogen blanket, and an electric stirrer;

[0068] S1.2: 8 parts by weight of N,N-dimethylacetamide were added to a three-necked flask, followed by stirring and reacting at 62°C for 40 minutes. The mixture was then heated to 82°C, 0.5 parts by weight of dibutyltin dilaurate was added, and the mixture was stirred and reacted at 380 rpm until the -NCO group content reached the theoretical value. The mixture was then cooled to 42°C, 10 parts by weight of acetone was added to reduce the viscosity, and 2.12 parts by weight of triethylamine was added. The mixture was stirred and dispersed at 600 rpm for 20 minutes. Deionized water was then added and stirred at 1200 rpm for 12 minutes. The mixture was then subjected to vacuum low-pressure distillation to obtain a modified waterborne polyurethane emulsion with a solid content of 40%;

[0069] S2: Preparation of modified kaolin functional filler

[0070] S2.1: A sodium hydroxide solution was added to a 6 wt % casein aqueous solution to adjust the pH to 11.0, and the mixture was stirred at 300 rpm for 30 minutes. Then, 0.5 parts by weight of gallic tannin was added, and the mixture was stirred for 30 minutes. Then, 3 parts by weight of glycerol was added, and the mixture was stirred for a further 12 minutes. The mixture was then stirred at 82° C. for 50 minutes to obtain a gallic tannin-modified casein emulsion.

[0071] S2.2: 0.06 parts by weight of silane coupling agent KH-550 was added to 10 parts by weight of anhydrous ethanol, followed by 1 part by weight of acetic acid. The mixture was stirred and mixed at 500 rpm for 50 minutes. Then, 1 part by weight of kaolin pre-dispersion was added, and the mixture was stirred for 40 minutes. The mixture was then ultrasonicated for 30 minutes to obtain a suspension.

[0072] S2.3: The suspension was heated to 82°C and stirred at 600 rpm for 5 h, followed by centrifugation. The precipitate obtained by centrifugation was repeatedly washed with water and anhydrous ethanol until neutral, and then dried at 82°C for 48 h to obtain pretreated kaolin.

[0073] S2.4: 1 part by weight of pretreated kaolin was added to 10 parts by weight of deionized water, and the mixture was heated to 82°C and stirred for 3 hours. Then, 20 parts by weight of gallic tannin-modified casein emulsion was added and the mixture was stirred for another 3 hours. The mixture was then cooled to room temperature and filtered to obtain a modified kaolin functional filler.

[0074] The kaolin pre-dispersion liquid is specifically obtained by mixing kaolin and anhydrous ethanol in a mass ratio of 1:30 and uniformly dispersing them;

[0075] S3: Preparation of composite ink

[0076] S3.1: Add 40 parts by weight of modified aqueous polyurethane emulsion, 20 parts by weight of deionized water, 10 parts by weight of Permanent Yellow, and 0.1 parts by weight of TEGO Foamex 825 to a stirred tank and stir at a stirring rate of 1000 rpm for 30 minutes to obtain a mixed emulsion;

[0077] S3.2: Add 8 parts by weight of modified kaolin functional filler and 1 part by weight of Silok-7117 to the mixed emulsion, and stir at a stirring rate of 800 r / min for 30 minutes to obtain a composite ink.

[0078] Comparative Example 1

[0079] Compared with Example 1, the difference of Comparative Example 1 is that, in Comparative Example 1, glyceryl monolaurate in step S1 is removed, and the other steps remain unchanged to prepare the composite ink, which is recorded as Comparative Example 1.

[0080] Comparative Example 2

[0081] Compared with Example 1, the difference of Comparative Example 2 is that step S2 is removed in Comparative Example 2, and the modified kaolin functional filler in step S3.2 is replaced by kaolin. The other steps remain unchanged to prepare the composite ink, which is recorded as Comparative Example 2.

[0082] Comparative Example 3

[0083] Compared with Example 1, the difference of Comparative Example 3 is that step S2.1 is removed in Comparative Example 3, and the gallic tannin-modified casein emulsion in step S2.4 is replaced by casein emulsion, and the other steps remain unchanged to prepare the composite ink, which is recorded as Comparative Example 3.

[0084] Comparative Example 4

[0085] Compared with Example 1, Comparative Example 4 is different in that the modified kaolin functional filler in step S2 and step S3.2 is removed from Comparative Example 4, and the composite ink is prepared with the remaining steps unchanged, which is recorded as Comparative Example 4.

[0086] Adhesion test:

[0087] Adhesion tests were performed on Examples 1-3 and Comparative Examples 1-4. The test results are shown in Table 1.

[0088] Table 1. Adhesion test results of Examples 1-3 and Comparative Examples 1-4

[0089]

[0090] It can be seen from the data in Table 1 that the composite ink prepared by the present invention can be adapted to various substrates and significantly improves the adhesion to the substrate; it can be seen from the data in Comparative Example 1 that the adhesion fastness of the ink to the substrate can be significantly improved by modifying the polyurethane with monolaurin; and it can be seen from the data in Comparative Examples 2-4 that the adhesion of the ink can be improved by adding casein-modified kaolin modified with gallic tannin as a functional filler to the ink.

[0091] Water resistance test:

[0092] The water resistance of Examples 1-3 and Comparative Example 1 was measured. The measurement results are shown in Table 2.

[0093] Water resistance: Prints prepared using the composite inks of Examples 1-3 and Comparative Example 1 were half immersed in 50°C water for 24 hours. The printed parts were then removed and allowed to air dry at room temperature. The water resistance of the immersed and unimmersed sections was then observed and compared. The results were then graded from 0 to 5, with grades 0-5 indicating decreasing water resistance.

[0094] Level 0: There is no visible difference between the immersed part and the non-immersed part, and the water is basically not stained;

[0095] Level 1: The soaked part is slightly discolored, the pattern details are slightly blurred, but still clearly recognizable, and the water is very slightly stained;

[0096] Level 2: The color of the soaked part becomes significantly lighter, the edge of the pattern begins to become blurred and diffused, and the degree of dyeing deepens;

[0097] Level 3: The pattern on the soaked part is severely blurred, the color is lost over a large area, and the water stain is deep;

[0098] Level 4: The pattern on the soaked part almost disappears, the color is basically off, and the water stain is strong;

[0099] Level 5: The soaked part completely loses its original pattern and color, and the water is dyed into a strong ink color.

[0100] Table 2. Water resistance test results of Examples 1-3 and Comparative Example 1

[0101] Water resistance Example 1 Level 1 Example 2 Level 1 Example 3 Level 1 Comparative Example 1 Level 3

[0102] From the data in Table 2, it can be seen that the water resistance of ink can be enhanced by modifying polyurethane with monolaurin.

[0103] Friction resistance test:

[0104] The friction resistance of Examples 1-3 and Comparative Examples 1, 2, and 4 was measured. The measurement results are shown in Table 3.

[0105] Friction resistance: The printed products prepared using the composite inks of Examples 1-3 and Comparative Examples 1, 2, and 4 were tested for abrasion resistance. They were rubbed back and forth 100 times with an eraser at a force of 5N. The printed products were divided into six different levels from 0 to 5 according to the degree of wear. Levels 0 to 5 indicate that the friction resistance gradually decreases. The wiping results were observed.

[0106] Level 0: No visible changes on the printed surface;

[0107] Level 1: Under close observation, very fine scratches appear on the printed surface;

[0108] Level 2: Shallow scratches can be clearly seen on the printed surface;

[0109] Level 3: Scratches are more obvious and the color fades to a certain extent;

[0110] Level 4: The printed surface has dense and obvious scratches, and the color has faded significantly;

[0111] Level 5: After wiping, the ink on the printed surface is almost completely peeled off and the color is basically gone.

[0112] Table 3. Friction resistance test results of Examples 1-3 and Comparative Examples 1, 2, and 4

[0113] Friction resistance Example 1 Level 1 Example 2 Level 1 Example 3 Level 1 Comparative Example 1 Level 3 Comparative Example 2 Level 3 Comparative Example 4 Level 4

[0114] From the data in Table 3, it can be seen that the use of monolaurin-modified polyurethane in the present invention can improve the friction resistance of the ink. From the data in Comparative Examples 2 and 4, it can be seen that the use of gallic tannin-modified casein-modified kaolin can improve the wear resistance of the ink.

[0115] Gloss test:

[0116] The glossiness of Examples 1-3 and Comparative Example 3 was measured. The measurement results are shown in Table 4.

[0117] The printed products prepared with the composite inks of Examples 1-3 and Comparative Example 3 were placed in an oven at 80° C. for 4 h, and then the glossiness was measured at an angle of 60°.

[0118] Table 4. Glossiness measurement results of Examples 1-3 and Comparative Example 3

[0119] Glossiness (%) Example 1 94.3 Example 2 94.5 Example 3 94.2 Comparative Example 3 83.4

[0120] From the data in Table 4, it can be seen that the glossiness of ink can be improved after casein is modified with gallic tannin.

[0121] (VOCs) content, printing effect and fixing speed test:

[0122] The volatile organic compound (VOCs) content, printing effect and fixing speed of Examples 1-3 were measured. The measurement results are shown in Table 5.

[0123] The VOC content of the ink is determined according to the standard GB38507-2020 "Limits of Volatile Organic Compounds (VOCs) in Inks".

[0124] Printing quality test: The ink was printed on a PET film using a high-speed rotary printing press at a speed of 200m / min. The print quality was evaluated based on the degree of clarity and legibility. A represents clear and smooth lines, B represents relatively clear lines with slightly thicker lines, and C represents fuzzy and blurry lines.

[0125] Fixation speed test: At a temperature of 25°C and a humidity of 60-70%, after the printing adaptometer has developed the color, the fixing speed is measured using a fixing speed measuring machine.

[0126] Table 5. Performance measurement results of Examples 1-3

[0127]

[0128] It can be seen from the data in Table 5 that the ink prepared by the present invention has a low volatile organic compound (VOCs) content and is environmentally friendly, and has a good printing effect while achieving a faster fixing speed.

[0129] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A process for preparing an environmentally friendly composite ink, characterized in that: The steps include: S1: Modification of waterborne polyurethane The modified waterborne polyurethane emulsion is prepared by reacting isophorone diisocyanate, polytetramethylene glycol, dimethylol propionic acid, trimethylol propane and glyceryl monolaurate, wherein the weight ratio of isophorone diisocyanate, polytetramethylene glycol, dimethylol propionic acid, trimethylol propane and glyceryl monolaurate is 23-25:38-42:2.95-3.05:2.56-3.12:2.35-2.53; S2: Preparation of modified kaolin functional filler The pH of the casein aqueous solution is first adjusted to 11.0-11.2, and then gallic tannin and glycerol are added for modification to obtain gallic tannin-modified casein. Then, kaolin is pretreated with a silane coupling agent KH-550, and then the pretreated kaolin is modified with the gallic tannin-modified casein. S3: Preparation of composite ink First, 40-50 parts by weight of modified waterborne polyurethane emulsion, 20-30 parts by weight of deionized water, 10-12 parts by weight of pigment, and 0.1-0.3 parts by weight of defoamer are mixed, and then 8-10 parts by weight of modified kaolin functional filler and 1-2 parts by weight of wetting dispersant are added to prepare a composite ink.

2. The process for preparing an environmentally friendly composite ink according to claim 1, characterized in that: Step S1: Modification of waterborne polyurethane, specifically comprising the following steps: S1.1: 23-25 ​​parts by weight of isophorone diisocyanate, 38-42 parts by weight of polytetramethylene glycol, 2.95-3.05 parts by weight of dimethylolpropionic acid, 2.56-3.12 parts by weight of trimethylolpropane, and 2.35-2.53 parts by weight of glyceryl monolaurate are mixed and added to a three-necked flask equipped with a condenser reflux apparatus, a nitrogen protection device, and an electric stirrer; S1.2: Add 8-10 parts by weight of N,N-dimethylacetamide to a three-necked flask, then stir and react at 60-62°C for 30-40 minutes, then heat to 80-82°C, add 0.5-0.8 parts by weight of dibutyltin dilaurate, stir and react at 360-380r / min until the -NCO group content reaches the theoretical value, then cool to 40-42°C, and add 10-15 parts by weight of acetone to reduce the viscosity, then add 2.12-2.38 parts by weight of triethylamine, stir and disperse at 500-600r / min for 15-20 minutes, then add deionized water at 800-1200rpm and stir for 10-12 minutes, then perform vacuum low-pressure distillation to obtain a modified aqueous polyurethane emulsion with a solid content of 40-42%.

3. The process for preparing an environmentally friendly composite ink according to claim 2, characterized in that: Step S2: Preparation of modified kaolin functional filler, specifically comprising the following steps: S2.1: Adding sodium hydroxide solution to a 6-8 wt% casein aqueous solution to adjust the pH to 11.0-11.2, stirring at 200-300 rpm for 20-30 minutes, then adding 0.5-0.8 parts by weight of gallic tannin, stirring for 20-30 minutes, then adding 3-5 parts by weight of glycerol, continuing to stir for 10-12 minutes, and then stirring at 80-82° C. for 40-50 minutes to obtain a gallic tannin-modified casein emulsion; S2.2: Add 0.06-0.08 parts by weight of silane coupling agent KH-550 to 10-12 parts by weight of anhydrous ethanol, then add 1-2 parts by weight of acetic acid, stir and mix at 400-500 rpm for 40-50 min, then add 1-2 parts by weight of kaolin pre-dispersion liquid, stir and react for 30-40 min, and then ultrasonicate for 20-30 min to obtain a suspension; S2.3: heating the suspension to 80-82° C. and stirring at 500-600 rpm for 4-5 hours, then centrifuging the suspension. Washing the precipitate obtained by centrifugation repeatedly with water and anhydrous ethanol until neutral, and then drying the precipitate at 80-82° C. for 40-48 hours to obtain pretreated kaolin. S2.4: Add 1-2 parts by weight of pretreated kaolin to 10-12 parts by weight of deionized water, then heat to 80-82°C and stir for 2-3 hours. Then add 20-23 parts by weight of gallic tannin modified casein emulsion and continue stirring for 2-3 hours. Then cool to room temperature and filter to obtain modified kaolin functional filler.

4. The process for preparing an environmentally friendly composite ink according to claim 3, characterized in that: step The preparation of S3 composite ink specifically includes the following steps: S3.1: Add 40-50 parts by weight of a modified aqueous polyurethane emulsion, 20-30 parts by weight of deionized water, 10-12 parts by weight of a pigment, and 0.1-0.3 parts by weight of a defoamer to a stirred tank and stir at a stirring rate of 800-1000 rpm for 20-30 minutes to obtain a mixed emulsion; S3.2: Add 8-10 parts by weight of modified kaolin functional filler and 1-2 parts by weight of wetting and dispersing agent to the mixed emulsion, and stir at a stirring rate of 600-800 r / min for 20-30 minutes to obtain a composite ink.

5. The process for preparing an environmentally friendly composite ink according to claim 3, characterized in that: In step S2.2, the kaolin pre-dispersion liquid is specifically obtained by mixing kaolin and anhydrous ethanol in a mass ratio of 1-2:30 and uniformly dispersing them.

6. The process for preparing an environmentally friendly composite ink according to claim 4, characterized in that: In step S3.1, the pigment is one or more of permanent yellow, permanent red and phthalocyanine blue.

7. The process for preparing an environmentally friendly composite ink according to claim 4, characterized in that: The defoaming agent in step S3.1 is one or more of TEGOFoamex K3, TEGOFoamex 810, and TEGOFoamex 825.

8. The process for preparing an environmentally friendly composite ink according to claim 4, characterized in that: In step S3.2, the wetting and dispersing agent is one or more of BYK-180, BYK-190 and Silok-7117.

9. An environmentally friendly composite ink, characterized in that: The environmentally friendly composite ink is prepared by the preparation process of any one of claims 1 to 8.

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