An aqueous polyurethane printing ink and its preparation process

Abstract

The present invention relates to the technical field of inks, and specifically to an aqueous polyurethane printing ink and a preparation process thereof. In the present invention, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, dimethylethoxyvinylsilane, and 1,1,3,3-tetramethyldisiloxane are reacted to obtain a vinyl epoxy organosilicon co-crosslinking agent; after isophorone diisocyanate reacts with polyethylene glycol 2000, it is respectively blocked with glycidol and 2-hydroxyethyl methacrylate and mixed to obtain a mixed polyurethane material; the vinyl epoxy organosilicon co-crosslinking agent is added to the mixed polyurethane material to obtain an aqueous polyurethane binder; the aqueous polyurethane binder, ethanol, isopropanol, a dispersant, a wetting agent, a leveling agent, an antifoaming agent, carbon black powder, a photoinitiator, and an epoxy curing agent are mixed to obtain an aqueous polyurethane printing ink with heat and humidity resistance and high adhesion performance.

Description

Technical Field

[0001] The invention relates to the technical field of inks, in particular to a water-based polyurethane printing ink and a preparation process thereof. Background Art

[0002] Compared with solvent-based inks, water-based inks have the advantage of being green and environmentally friendly, which can greatly reduce safety issues in food packaging and reduce the harm caused by harmful substances to the human body. Therefore, they are more widely used in the plastic food packaging industry. The most commonly used water-based ink is water-based polyurethane ink. The printing performance of water-based polyurethane ink is mainly determined by the water-based polyurethane binder. Therefore, it is particularly important to improve the heat resistance, water resistance and adhesion performance of the water-based polyurethane binder.

[0003] At present, water-based polyurethane has problems such as poor hydrophobicity and easy swelling in water. In addition, since the substrates are mostly polymer materials, the low polarity surface leads to low printing adhesion of the ink, which makes it easy for the pattern to become blurred after printing and fade when exposed to water or heat, resulting in poor printing effect. The key to improving the printing adaptability of water-based polyurethane ink is to improve the water resistance, heat resistance and adhesion performance of the polyurethane adhesive material. Therefore, it is very necessary to develop a water-based polyurethane printing ink based on the above properties. Summary of the invention

[0004] The object of the present invention is to provide a water-based polyurethane printing ink and a preparation process thereof to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a water-based polyurethane printing ink and a preparation process thereof, comprising the following steps:

[0006] Step 1:

[0007] Ethanol and deionized water are mixed in a weight ratio of 10:1 to obtain an ethanol aqueous solution; 3-[(2,3)-epoxypropyloxy]propylmethyldimethoxysilane and dimethylethoxyvinylsilane are added to the ethanol aqueous solution, stirred for 10-15 minutes, and then heated to 70-80°C, and a catalyst dibutyltin dilaurate is added to the mixture while maintaining the temperature, and the mixture is reacted for 3-4 hours. After vacuum rotary evaporation, the product is mixed with 1,1,3,3-tetramethyldisiloxane, and a Custer catalyst is added. The mixture is reacted for 48-52 hours while maintaining the temperature at 60-70°C under a nitrogen environment to obtain a vinyl epoxy silicone co-crosslinking agent;

[0008] Step 2:

[0009] S1: Vacuum dehydrate polyethylene glycol 2000 at 110 - 120 °C for 2 - 3 h. Mix isophorone diisocyanate with polyethylene glycol 2000, heat up to 70 - 80 °C, use dibutyltin dilaurate as a catalyst, keep the temperature for reaction for 2 - 3 h, cool down to 50 - 60 °C, add dimethylolpropionic acid, heat up to 70 - 80 °C and continue the reaction for 1 - 2 h. Adjust the viscosity by adding acetone during the reaction process to obtain a polyurethane prepolymer;

[0010] S2: Take the polyurethane prepolymer, mix it with hydroxyethyl methacrylate at a molar ratio of isocyanate group to hydroxyl group of 1:1, add inhibitor p - methoxyphenol and catalyst dibutyltin dilaurate, heat up to 70 - 80 °C and react for 2 - 3 h to obtain double - bond - terminated polyurethane; Take the polyurethane prepolymer, mix it with glycidyl at a molar ratio of isocyanate group to hydroxyl group of 1:1, add catalyst dibutyltin dilaurate, heat up to 60 - 70 °C and react for 2 - 3 h to obtain epoxy - group - terminated polyurethane; Mix the double - bond - terminated polyurethane and epoxy - group - terminated polyurethane at a mass ratio of 1:1, use triethylamine as a neutralizer, neutralize at 45 - 55 °C, add distilled water and stir to emulsify, then remove acetone by vacuum distillation to obtain a mixed polyurethane material; Mix 92 - 95% of the mixed polyurethane material and 5 - 8% of vinyl epoxy organosilicon cross - linking aid to obtain an aqueous polyurethane binder;

[0011] Step 3:

[0012] Grind carbon black and sieve it to obtain carbon black powder with a mesh size of 300 - 500; By weight, mix the aqueous polyurethane binder, ethanol, isopropanol, dispersant, wetting agent, leveling agent, defoamer, carbon black powder, photo - initiator, and epoxy curing agent, and stir to obtain an aqueous polyurethane printing ink.

[0013] Furthermore, in step 1, the molar ratio of 3 - [(2,3) - epoxypropoxy] propylmethyldimethoxysilane, dimethylethoxyvinylsilane, and 1,1,3,3 - tetramethyldisiloxane is 2:4:1.

[0014] Furthermore, in S1, the dosage of each component, by weight, is 110 - 120 parts of isophorone diisocyanate, 180 - 200 parts of polyethylene glycol 2000, 15 - 18 parts of dimethylolpropionic acid, and 18 - 22 parts of acetone.

[0015] Furthermore, in S2, the double - bond - terminated polyurethane and epoxy - group - terminated polyurethane are mixed at a mass ratio of 1:1.

[0016] Furthermore, in S2, the solid content of the mixed polyurethane material is 30 - 40%.

[0017] Further, in S2, in the aqueous polyurethane binder, the content of each component is, by weight percentage, 90-95% of the mixed polyurethane material and 5-10% of the vinyl epoxy organosilicon crosslinking aid.

[0018] Further, in step 3, in the aqueous polyurethane printing ink, the content of each component is, by weight parts, 100 parts of the aqueous polyurethane binder, 20-30 parts of ethanol, 5-10 parts of isopropanol, 1.2-1.6 parts of the dispersant, 1-1.5 parts of the wetting agent, 1.4-1.8 parts of the leveling agent, 0.8-1.2 parts of the defoaming agent, 8-13 parts of carbon black powder, 1-1.5 parts of the photoinitiator, and 7-10 parts of the epoxy curing agent.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention provides a preparation method of an aqueous polyurethane printing ink, which mixes an aqueous polyurethane binder, ethanol, isopropanol, a dispersant, a wetting agent, a leveling agent, a defoaming agent, carbon black powder, a photoinitiator, and an epoxy curing agent, and stirs to obtain the aqueous polyurethane printing ink.

[0020] In order to improve the printing performance of the aqueous polyurethane ink, the present invention modifies the aqueous polyurethane binder. First, a polyurethane prepolymer terminated with an isocyanate group is obtained by reacting isophorone diisocyanate and polyethylene glycol 2000. After the polyurethane prepolymer is terminated with 2-hydroxyethyl methacrylate and glycidyl, respectively, the two different polyurethanes are mixed to obtain a mixed polyurethane material; due to the different curing conditions of the two polyurethanes, after the mixed polyurethane material is cured, the two form an interpenetrating three-dimensional network physically, greatly improving the crosslinking density between the chain segments, thereby improving the adhesion performance of the coating on the substrate surface.

[0021] The present invention also adds a vinyl epoxy organosilicon co-crosslinking agent. 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane and dimethylethoxyvinylsilane are reacted to obtain an intermediate, and then the intermediate is reacted with 1,1,3,3-tetramethyldisiloxane to obtain the vinyl epoxy organosilicon co-crosslinking agent. The vinyl epoxy organosilicon co-crosslinking agent contains multiple reactive functional groups, which can participate in the photocuring and thermal curing reactions of the mixed polyurethane material, and further crosslink the two polyurethanes by chemical bonding, so that the force between the chain segments is enhanced, and the cohesive strength is also enhanced. The peel strength between the cured coating and the substrate is increased. Conventional polyurethane coatings will absorb moisture in the surrounding environment in a humid and hot environment, resulting in wrinkles, swelling and bubbling, and the thicker the coating film, the larger the bubbles; when the coating is thinner, the moisture will penetrate into the coating to generate osmotic pressure and form bubbles; after the vinyl epoxy organosilicon co-crosslinking agent is crosslinked with polyurethane, silicon-oxygen bonds are introduced into the molecular chain segments, reducing the surface energy of the cured coating, so it exhibits good hydrophobic and antifouling properties, ensuring that the coating does not deform in a humid and hot environment.

[0022] In addition, it should be supplemented that, on the one hand, the vinyl epoxy organosilicon co-crosslinking agent has more reactive functional groups. When its dosage is too high, it will lead to too high crosslinking density, restricting the movement ability of the polyurethane chain segments, so that the cohesive strength of the chain segments exceeds the bonding strength between it and the adhered substrate, and then resulting in a decrease in interfacial adhesion; on the other hand, the vinyl epoxy organosilicon co-crosslinking agent has a high silicone content and poor compatibility with the mixed polyurethane material. If its dosage is too high, delamination is likely to occur after physical blending of the two, resulting in poor stability of the ink and affecting the printing effect. Through repeated experiments, it is found that, by weight percentage, mixing 90-95% of the mixed polyurethane material and 5-10% of the vinyl epoxy organosilicon co-crosslinking agent gives the best performance of the aqueous polyurethane binder. Detailed implementation mode

[0023] Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0024] The materials and their sources used in the present invention: The dispersant is from Guangdong Zhonglianbang Fine Chemical Co., Ltd., product number BD-40; the defoamer is from Guangzhou Dachuan Fine Chemical Co., Ltd., product number H448; the leveling agent is from Shanghai Banggao Chemical Co., Ltd., product number JS-3018; the wetting agent is from Guangzhou Yangsong Trading Co., Ltd., product number WT-500; the carbon black is from Anhui Heiyu Pigment New Material Co., Ltd., model PowCarbon ® 4311F.

[0025] Example 1: An aqueous polyurethane printing ink and its preparation process, comprising the following steps:

[0026] Step 1:

[0027] Mix ethanol and deionized water in a weight ratio of 10:1 to obtain an ethanol aqueous solution; add 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane and dimethylethoxyvinylsilane to the ethanol aqueous solution, stir for 10 min, then heat to 70 °C, keep warm and add the catalyst dibutyltin dilaurate, react for 3 h, after rotary evaporation under reduced pressure, mix the product with 1,1,3,3-tetramethyldisiloxane, add the Karstedt catalyst, and react at 60 °C for 48 h in a nitrogen environment to obtain a vinyl epoxy organosilicon co-crosslinking agent; among them, the molar ratio of 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, dimethylethoxyvinylsilane, and 1,1,3,3-tetramethyldisiloxane is 2:4:1;

[0028] Step 2:

[0029] S1: Perform vacuum dehydration treatment on polyethylene glycol 2000 at 110 °C for 2 h, mix 120 g of isophorone diisocyanate with 180 g of polyethylene glycol 2000, heat to 70 °C, use dibutyltin dilaurate as a catalyst, keep warm and react for 2 h, cool to 50 °C and add 17 g of dimethylolpropionic acid, heat to 70 °C and continue to react for 1 h, add 20 g of acetone to adjust the viscosity during the reaction to obtain a polyurethane prepolymer;

[0030] S2: Take the polyurethane prepolymer, mix it with hydroxyethyl methacrylate according to the molar ratio of isocyanate group to hydroxyl group of 1:1, add the inhibitor p-hydroxyanisole and the catalyst dibutyltin dilaurate, heat to 70 °C and react for 2 h to obtain a double-bond terminated polyurethane; take the polyurethane prepolymer, mix it with glycidol according to the molar ratio of isocyanate group to hydroxyl group of 1:1, add the catalyst dibutyltin dilaurate, heat to 60 °C and react for 2 h to obtain an epoxy group-terminated polyurethane; mix the double-bond terminated polyurethane and the epoxy group-terminated polyurethane in a mass ratio of 1:1, use triethylamine as a neutralizing agent, neutralize at 45 °C, add distilled water and stir to emulsify, then remove acetone by vacuum distillation to obtain a mixed polyurethane material with a solid content of 30%; by weight percentage, mix 95% of the mixed polyurethane material and 5% of the vinyl epoxy organosilicon co-crosslinking agent to obtain an aqueous polyurethane binder;

[0031] Step 3:

[0032] The carbon black was ground and sieved to obtain carbon black powder with a mesh size of 500; 100 g of aqueous polyurethane binder, 26 g of ethanol, 8 g of isopropanol, 1.4 g of dispersant, 1.3 g of wetting agent, 1.6 g of leveling agent, 1.1 g of defoamer, 12 g of carbon black powder, 1 g of photoinitiator 1173, and 8 g of isophorone diamine were mixed and stirred to obtain aqueous polyurethane printing ink.

[0033] Example 2: An aqueous polyurethane printing ink and its preparation process, comprising the following steps:

[0034] Step 1:

[0035] Ethanol and deionized water were mixed at a weight ratio of 10:1 to obtain an ethanol aqueous solution; 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane and dimethylethoxyvinylsilane were added to the ethanol aqueous solution, stirred for 13 min and then heated to 75 °C, and the catalyst dibutyltin dilaurate was added under insulation. The reaction was carried out for 3.5 h, and after rotary evaporation under reduced pressure, the product was mixed with 1,1,3,3-tetramethyldisiloxane, and the Kaster catalyst was added. The reaction was carried out at 65 °C for 50 h under a nitrogen atmosphere to obtain a vinyl epoxy organosilicon co-crosslinking agent; among them, the molar ratio of 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, dimethylethoxyvinylsilane, and 1,1,3,3-tetramethyldisiloxane was 2:4:1;

[0036] Step 2:

[0037] S1: Polyethylene glycol 2000 was subjected to vacuum dehydration treatment at 115 °C for 2.5 h. 120 g of isophorone diisocyanate was mixed with 180 g of polyethylene glycol 2000, heated to 75 °C, and reacted for 2.5 h with dibutyltin dilaurate as a catalyst. After cooling to 55 °C, 17 g of dimethylolpropionic acid was added, and the temperature was raised to 75 °C and the reaction was continued for 1.5 h. 20 g of acetone was added during the reaction to adjust the viscosity to obtain a polyurethane prepolymer;

[0038] S2: Take the polyurethane prepolymer, mix it with hydroxyethyl methacrylate at a molar ratio of isocyanate group to hydroxyl group of 1:1, add the inhibitor p-hydroxyanisole and the catalyst dibutyltin dilaurate, and heat to 75 °C for reaction for 2.5 h to obtain a double bond-terminated polyurethane; take the polyurethane prepolymer, mix it with glycidol at a molar ratio of isocyanate group to hydroxyl group of 1:1, add the catalyst dibutyltin dilaurate, and heat to 65 °C for reaction for 2.5 h to obtain an epoxy group-terminated polyurethane; the double bond-terminated polyurethane and the epoxy group-terminated polyurethane were mixed at a mass ratio of 1:1, neutralized at 50 °C with triethylamine as a neutralizing agent, stirred and emulsified with distilled water, and then acetone was removed by distillation under reduced pressure to obtain a mixed polyurethane material with a solid content of 30%; by weight percentage, 93% of the mixed polyurethane material and 7% of the vinyl epoxy organosilicon co-crosslinking agent were mixed to obtain an aqueous polyurethane binder;

[0039] Step 3:

[0040] Grind the carbon black and screen it to obtain carbon black powder with a mesh size of 500; mix 100 g of waterborne polyurethane binder, 26 g of ethanol, 8 g of isopropanol, 1.4 g of dispersant, 1.3 g of wetting agent, 1.6 g of leveling agent, 1.1 g of defoamer, 12 g of carbon black powder, 1 g of photoinitiator 1173, and 8 g of isophorone diamine, and stir to obtain waterborne polyurethane printing ink.

[0041] Example 3: A waterborne polyurethane printing ink and its preparation process, including the following steps:

[0042] Step 1:

[0043] Mix ethanol and deionized water according to a weight ratio of 10:1 to obtain an ethanol aqueous solution; add 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane and dimethylethoxyvinylsilane to the ethanol aqueous solution, stir for 15 min, then heat up to 80 °C, keep warm and add the catalyst dibutyltin dilaurate, react for 4 h, after rotary evaporation under reduced pressure, mix the product with 1,1,3,3-tetramethyldisiloxane, add the Kaster catalyst, and react at 70 °C for 52 h under a nitrogen atmosphere to obtain a vinyl epoxy organosilicon co-crosslinking agent; among them, the molar ratio of 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, dimethylethoxyvinylsilane, and 1,1,3,3-tetramethyldisiloxane is 2:4:1;

[0044] Step 2:

[0045] S1: Perform vacuum dehydration treatment on polyethylene glycol 2000 at 120 °C for 3 h, mix 120 g of isophorone diisocyanate with 180 g of polyethylene glycol 2000, heat up to 80 °C, use dibutyltin dilaurate as a catalyst, keep warm and react for 3 h, cool down to 60 °C, add 17 g of dimethylolpropionic acid, heat up to 80 °C and continue to react for 2 h, and add 20 g of acetone to adjust the viscosity during the reaction to obtain a polyurethane prepolymer;

[0046] S2: Take the polyurethane prepolymer, mix it with 2-hydroxyethyl methacrylate at a molar ratio of isocyanate group to hydroxyl group of 1:1, add the inhibitor p-methoxyphenol and the catalyst dibutyltin dilaurate, heat up to 80 °C and react for 3 h to obtain the double bond-terminated polyurethane; take the polyurethane prepolymer, mix it with glycidyl at a molar ratio of isocyanate group to hydroxyl group of 1:1, add the catalyst dibutyltin dilaurate, heat up to 70 °C and react for 3 h to obtain the epoxy group-terminated polyurethane; mix the double bond-terminated polyurethane and the epoxy group-terminated polyurethane at a mass ratio of 1:1, use triethylamine as the neutralizer, neutralize at 55 °C, add distilled water and stir to emulsify, then remove acetone by vacuum distillation to obtain a mixed polyurethane material with a solid content of 30%; by weight percentage, mix 90% of the mixed polyurethane material and 10% of the vinyl epoxy organosilicon co-crosslinking agent to obtain the waterborne polyurethane binder.

[0047] Step 3:

[0048] Grind the carbon black and sieve it to obtain carbon black powder with a mesh size of 500; mix 100 g of the waterborne polyurethane binder, 26 g of ethanol, 8 g of isopropanol, 1.4 g of dispersant, 1.3 g of wetting agent, 1.6 g of leveling agent, 1.1 g of defoamer, 12 g of carbon black powder, 1 g of photoinitiator 1173, and 8 g of isophorone diamine, and stir to obtain the waterborne polyurethane printing ink.

[0049] Comparative Example 1: Prepare the polyurethane binder using conventional technology.

[0050] Step 1:

[0051] Perform vacuum dehydration treatment on polyethylene glycol 2000 at 110 °C for 2 h, mix 120 g of isophorone diisocyanate and 180 g of polyethylene glycol 2000, heat up to 70 °C, use dibutyltin dilaurate as the catalyst, keep the temperature for reaction for 2 h, cool down to 50 °C, add 17 g of dimethylolpropionic acid, heat up to 70 °C and continue to react for 1 h, add 20 g of acetone during the reaction to adjust the viscosity to obtain the polyurethane prepolymer; use triethylamine as the neutralizer, neutralize at 45 °C, add distilled water and stir to emulsify, add 4.6 g of ethylenediamine and react for 30 min, remove acetone by vacuum distillation to obtain a waterborne polyurethane binder with a solid content of 30%.

[0052] Step 2:

[0053] Grind the carbon black and sieve it to obtain carbon black powder with a mesh size of 500; mix 100 g of the waterborne polyurethane binder, 26 g of ethanol, 8 g of isopropanol, 1.4 g of dispersant, 1.3 g of wetting agent, 1.6 g of leveling agent, 1.1 g of defoamer, 12 g of carbon black powder, 1 g of photoinitiator 1173, and 8 g of isophorone diamine, and stir to obtain the waterborne polyurethane printing ink.

[0054] Comparative Example 2: Without adding vinyl epoxy silicone crosslinking aid, and the remaining parameters are the same as those in Example 2.

[0055] Step 1:

[0056] S1: Polyethylene glycol 2000 was vacuum dehydrated at 115 °C for 2.5 h. 120 g of isophorone diisocyanate and 180 g of polyethylene glycol 2000 were mixed, and the temperature was raised to 75 °C. Dibutyltin dilaurate was used as a catalyst, and the reaction was carried out at a constant temperature for 2.5 h. Then the temperature was lowered to 55 °C, 17 g of dimethylolpropionic acid was added, and the temperature was raised to 75 °C and the reaction continued for 1.5 h. 20 g of acetone was added during the reaction to adjust the viscosity, and a polyurethane prepolymer was obtained.

[0057] S2: Take the polyurethane prepolymer, mix it with hydroxyethyl methacrylate according to the molar ratio of isocyanate group to hydroxyl group of 1:1, add the inhibitor p-hydroxyanisole and the catalyst dibutyltin dilaurate, and raise the temperature to 75 °C for reaction for 2.5 h to obtain a double-bond terminated polyurethane; take the polyurethane prepolymer, mix it with glycidyl according to the molar ratio of isocyanate group to hydroxyl group of 1:1, add the catalyst dibutyltin dilaurate, and raise the temperature to 65 °C for reaction for 2.5 h to obtain an epoxy-group terminated polyurethane; mix the double-bond terminated polyurethane and the epoxy-group terminated polyurethane according to the mass ratio of 1:1, use triethylamine as a neutralizer, neutralize at 50 °C, add distilled water and stir to emulsify, and then remove acetone by vacuum distillation to obtain an aqueous polyurethane binder with a solid content of 30%.

[0058] Step 3:

[0059] The carbon black was ground and sieved to obtain carbon black powder with a mesh size of 500; 100 g of the aqueous polyurethane binder, 26 g of ethanol, 8 g of isopropanol, 1.4 g of dispersant, 1.3 g of wetting agent, 1.6 g of leveling agent, 1.1 g of defoamer, 12 g of carbon black powder, 1 g of photoinitiator 1173, and 8 g of isophorone diamine were mixed and stirred to obtain an aqueous polyurethane printing ink.

[0060] Comparative Example 3: Increase the dosage of vinyl epoxy silicone crosslinking aid, and the remaining parameters are the same as those in Example 3.

[0061] Step 1:

[0062] Mix ethanol and deionized water at a weight ratio of 10:1 to obtain an ethanol aqueous solution; add 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane and dimethylethoxyvinylsilane to the ethanol aqueous solution, stir for 15 min, then heat up to 80 °C, keep warm and add the catalyst dibutyltin dilaurate, react for 4 h, after rotary evaporation under reduced pressure, mix the product with 1,1,3,3-tetramethyldisiloxane, add the Karstedt catalyst, and react at 70 °C for 52 h under a nitrogen environment to obtain a vinyl epoxy organosilicon co-crosslinking agent; wherein, the molar ratio of 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, dimethylethoxyvinylsilane, and 1,1,3,3-tetramethyldisiloxane is 2:4:1;

[0063] Step 2:

[0064] S1: Carry out vacuum dehydration treatment on polyethylene glycol 2000 at 120 °C for 3 h, mix 120 g of isophorone diisocyanate with 180 g of polyethylene glycol 2000, heat up to 80 °C, use dibutyltin dilaurate as a catalyst, keep warm and react for 3 h, cool down to 60 °C and add 17 g of dimethylolpropionic acid, heat up to 80 °C and continue to react for 2 h, add 20 g of acetone during the reaction to adjust the viscosity to obtain a polyurethane prepolymer;

[0065] S2: Take the polyurethane prepolymer, mix it with hydroxyethyl methacrylate according to the molar ratio of isocyanate group to hydroxyl group of 1:1, add the inhibitor p-hydroxyanisole and the catalyst dibutyltin dilaurate, heat up to 80 °C and react for 3 h to obtain a double bond-terminated polyurethane; take the polyurethane prepolymer, mix it with glycidol according to the molar ratio of isocyanate group to hydroxyl group of 1:1, add the catalyst dibutyltin dilaurate, heat up to 70 °C and react for 3 h to obtain an epoxy group-terminated polyurethane; mix the double bond-terminated polyurethane and the epoxy group-terminated polyurethane at a mass ratio of 1:1, use triethylamine as a neutralizing agent, neutralize at 55 °C, add distilled water and stir to emulsify, then remove acetone by reduced pressure distillation to obtain a mixed polyurethane material with a solid content of 30%; by weight percentage, mix 85% of the mixed polyurethane material and 15% of the vinyl epoxy organosilicon co-crosslinking agent to obtain an aqueous polyurethane binder;

[0066] Step 3:

[0067] Grind carbon black and sieve to obtain carbon black powder with a mesh size of 500; mix 100 g of aqueous polyurethane binder, 26 g of ethanol, 8 g of isopropanol, 1.4 g of dispersant, 1.3 g of wetting agent, 1.6 g of leveling agent, 1.1 g of defoaming agent, 12 g of carbon black powder, 1 g of photoinitiator 1173, and 8 g of isophorone diamine, and stir to obtain an aqueous polyurethane printing ink.

[0068] Experiment: Prepare aqueous polyurethane printing ink according to the methods in Examples 1 to 3 and Comparative Examples 1 to 3 and coat it on the surface of a PET board (Foshan Shouke Plastic Technology Co., Ltd., product number 033). Naturally dry it at room temperature for 24 h, then dry it in an oven at 50 °C for 24 h. Irradiate it with ultraviolet light of 30 mW / cm 2

[0069] for 30 - 40 min, and thermally cure it at 120 °C for 2 h to form a glue film with a thickness of 50 μm. Use the sessile drop method of a dynamic contact angle measuring instrument to measure the hydrophilic-hydrophobic degree of the dried glue film. Refer to GB / T 2791-1995 and use a peel strength tester to test the T-peel strength. Place it in a test chamber with a set temperature of 70 ± 1 °C and a humidity of 95 ± 3% for 3 d to test the damp heat resistance performance, and observe the apparent morphology of the surface glue film. The experimental results are shown in the following table.

[0070]

[0071] Conclusion: The data of Examples 1 to 3 show that the aqueous polyurethane ink prepared by the present invention has good performance. The data of Example 1 and Comparative Example 1 show that compared with conventional aqueous polyurethane inks, the product in Example 1 has stronger surface hydrophobicity, greater adhesion strength to the substrate, and damp heat resistance. The data of Example 2 and Comparative Example 2 show that adding vinyl epoxy silicone co-crosslinking agent is beneficial to improving the adhesion performance between the ink and the substrate, and at the same time can improve the hydrophobic and damp heat resistance performance. The data of Example 3 and Comparative Example 3 show that excessive amount of vinyl epoxy silicone co-crosslinking agent will lead to a decrease in the adhesion effect between the ink and the substrate.

[0072] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent substitution on some of the technical features. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A process for preparing a water-based polyurethane printing ink, characterized in that: The method comprises the following steps: grinding carbon black and sieving to obtain carbon black powder; mixing water-based polyurethane connecting material, ethanol, isopropanol, dispersant, wetting agent, leveling agent, defoaming agent, carbon black powder, photoinitiator and epoxy curing agent, and stirring to obtain water-based polyurethane printing ink; The waterborne polyurethane binder is made by the following process: S1: performing vacuum dehydration treatment on polyethylene glycol 2000 at 110-120°C for 2-3h, mixing isophorone diisocyanate and polyethylene glycol 2000, raising the temperature to 70-80°C, using dibutyltin dilaurate as a catalyst, keeping the temperature for reaction for 2-3h, lowering the temperature to 50-60°C, adding dimethylolpropionic acid, raising the temperature to 70-80°C, and continuing the reaction for 1-2h. During the reaction, adding acetone to adjust the viscosity, and obtaining a polyurethane prepolymer; S2: Take a polyurethane prepolymer, mix it with hydroxyethyl methacrylate in a molar ratio of isocyanate group to hydroxyl group of 1:1, add inhibitor p-hydroxyanisole and catalyst dibutyltin dilaurate, heat it to 70~80℃ and react for 2~3h to obtain a double-bond terminated polyurethane; take a polyurethane prepolymer, mix it with glycidol in a molar ratio of isocyanate group to hydroxyl group of 1:1, add catalyst dibutyltin dilaurate, heat it to 60~70℃ and react for 2~3h to obtain an epoxy-terminated polyurethane; mix the double-bond terminated polyurethane and the epoxy-terminated polyurethane in a mass ratio of 1:1, use triethylamine as a neutralizer, neutralize at 45~55℃, add distilled water, stir and emulsify, and then remove acetone by reduced pressure distillation to obtain a mixed polyurethane material; mix the mixed polyurethane material and vinyl epoxy silicone co-crosslinking agent to obtain a waterborne polyurethane connecting material; In S2, the content of each component in the waterborne polyurethane binder is, by weight percentage, 90-95% of mixed polyurethane material and 5-10% of vinyl epoxy silicone co-crosslinking agent; Vinyl epoxy silicone co-crosslinking agent is prepared by the following process: Ethanol and deionized water are mixed in a weight ratio of 10:1 to obtain an ethanol aqueous solution; 3-[(2,3)-epoxypropyloxy]propylmethyldimethoxysilane and dimethylethoxyvinylsilane are added to the ethanol aqueous solution, stirred for 10-15 minutes, and then heated to 70-80°C, and a catalyst dibutyltin dilaurate is added while maintaining the temperature, and the reaction is carried out for 3-4 hours. After reduced pressure rotary evaporation, the product is mixed with 1,1,3,3-tetramethyldisiloxane, and a Custer catalyst is added. Under a nitrogen environment, the temperature is maintained at 60-70°C and the reaction is carried out for 48-52 hours to obtain a vinyl epoxy silicone co-crosslinking agent.

2. The process for preparing a water-based polyurethane printing ink according to claim 1, characterized in that: The particle size of carbon black powder is 300~500 mesh.

3. The process for preparing a water-based polyurethane printing ink according to claim 1, characterized in that: The content of each component in the water-based polyurethane printing ink, by weight, is 100 parts of water-based polyurethane binder, 20-30 parts of ethanol, 5-10 parts of isopropanol, 1.2-1.6 parts of dispersant, 1-1.5 parts of wetting agent, 1.4-1.8 parts of leveling agent, 0.8-1.2 parts of defoaming agent, 8-13 parts of carbon black powder, 1-1.5 parts of photoinitiator, and 7-10 parts of epoxy curing agent.

4. The process for preparing a water-based polyurethane printing ink according to claim 1, characterized in that: In S1, the amounts of the components, by weight, are 110-120 parts of isophorone diisocyanate, 180-200 parts of polyethylene glycol 2000, 15-18 parts of dimethylol propionic acid, and 18-22 parts of acetone.

5. The process for preparing a water-based polyurethane printing ink according to claim 1, characterized in that: In S2, double bond terminated polyurethane and epoxy terminated polyurethane are mixed in a mass ratio of 1:

1.

6. The process for preparing a water-based polyurethane printing ink according to claim 1, characterized in that: In S2, the solid content of the mixed polyurethane material is 30-40%.

7. The process for preparing a water-based polyurethane printing ink according to claim 1, characterized in that: The molar ratio of 3-[(2,3)-epoxypropyloxy]propylmethyldimethoxysilane, dimethylethoxyvinylsilane, and 1,1,3,3-tetramethyldisiloxane is 2:4:1.

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