A kind of water-based environmentally friendly printing ink and preparation method thereof

Abstract

The invention discloses a kind of water-based environmentally friendly printing ink and preparation method thereof, relate to the technical field of ink;The present invention is compounded with components such as polyurethane emulsion, color paste, deionized water, dispersant, defoamer, leveling agent, and adjusts its dosage to obtain polyurethane ink with excellent adhesion performance and excellent water resistance;Meanwhile, the scheme optimizes the preparation of polyurethane emulsion, introduces fluorine-containing chain extender octafluoro 1,6 hexanediol, isobornyl acrylate chain extender containing isobornyl ring structure, and octafluoro 1,6 hexanediol, isobornyl acrylate chain extender, 1,4 butanediol are compounded as compound chain extender to participate in polyurethane polymerization, the cross-linking density of prepared polyurethane emulsion is improved, and the introduction of hydrophobic group also can greatly improve the water resistance of polyurethane emulsion.Prepared ink has very excellent performance, can be widely applied to the surface printing of substrates such as plastic film, and practicality is higher.

Description

Technical Field

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

[0002] As environmental protection becomes increasingly important, the requirements for food packaging, in particular, are becoming increasingly stringent. The environmental performance requirements for inks used as printing materials for food packaging are also gradually increasing. Consequently, in this context, the development of environmentally friendly water-based inks has received significant attention. The most commonly used water-based ink is water-based polyurethane ink. The performance of water-based polyurethane inks hinges on the properties of the water-based polyurethane binder. Therefore, improving the properties of the water-based polyurethane binder is crucial to enhancing the printability of water-based polyurethane inks on plastic films.

[0003] Therefore, based on this situation, the present application discloses a water-based environmentally friendly printing ink and a preparation method thereof to solve this technical problem. Summary of the Invention

[0004] The object of the present invention is to provide a water-based environmentally friendly printing ink and a preparation method thereof, so as 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 solution: a method for preparing a water-based environmentally friendly printing ink, comprising the following steps:

[0006] Step (1): drying the polyester diol at 120-125° C. to remove moisture, then mixing the polyester diol and diphenylmethane diisocyanate, stirring evenly at 80-90° C., adding 2,2-dihydroxymethylpropionic acid and a compound chain extender, and reacting at 80-85° C. for 2-3 hours to obtain a polyurethane prepolymer; then adding epoxy resin to the polyurethane prepolymer, keeping the temperature at 80-85° C. for 1-2 hours, adding trimethylolpropane and a branched end epoxy monomer, and continuing the reaction for 1-2 hours. After the reaction is completed, cooling to 40-50° C., neutralizing with triethylamine for 20-30 minutes, and emulsifying and dispersing with deionized water to obtain a polyurethane emulsion;

[0007] Step (2): mixing the polyurethane emulsion, color paste, deionized water, defoaming agent, dispersant and leveling agent, stirring evenly, and standing for 20 to 30 minutes to obtain the printing ink.

[0008] In a more optimized solution, in step (2), the specific amounts of each component used are: by mass, 30 to 40 parts of polyurethane emulsion, 6 to 8 parts of color paste, 10 to 15 parts of deionized water, 0.5 to 1 part of dispersant, 0.2 to 0.3 parts of defoaming agent, and 1 to 1.5 parts of leveling agent.

[0009] In a more optimized solution, in step (1), the amounts of each component used, in parts by mass, are: 40 to 45 parts of polyester diol, 15 to 20 parts of diphenylmethane diisocyanate, 3 to 3.5 parts of 2,2-dihydroxymethylpropionic acid, 8 to 10 parts of compound chain extender, 4 to 5 parts of epoxy resin, 2 to 3 parts of branched end epoxy monomer, 1 to 1.5 parts of trimethylolpropane, and 2 to 3 parts of triethylamine.

[0010] In a more optimized solution, in step (1), the compound chain extender is isobornyl acrylate chain extender, 1,4-butanediol and octafluoro-1,6-hexanediol, with a mass ratio of (4-5):1:(4-5); the solid content of the polyurethane emulsion is 30%.

[0011] In a more optimized scheme, in step (1), the preparation steps of the branched end epoxy monomer are as follows: take the terminal hydroxyl branched polyether, heat it to 110-120°C for vacuum dehydration, cool it with nitrogen, add a catalyst and stir evenly, then heat it to 60-65°C, slowly add epichlorohydrin dropwise, keep it warm for 7-8 hours, remove the unreacted raw materials in vacuo, cool it to 45-50°C, dilute it with toluene, then add solid sodium hydroxide, keep it warm for 4-6 hours, collect the product by filtration, and purify it to obtain a branched end epoxy monomer.

[0012] In a more optimized solution, the molar amount of the hydroxyl group, epichlorohydrin and sodium hydroxide of the hydroxyl-terminated branched polyether is 1:

[0013] (0.5~0.6): (0.9~1); the catalyst is boron trifluoride-ethyl ether, and the amount used is 0.5~1wt% of the total mass of the system.

[0014] In a more optimized solution, in step (1), the preparation steps of the isobornyl acrylate chain extender are as follows: take ethylenediamine, add isobornyl acrylate dropwise in an ice-water bath at 15-20°C, slowly add dropwise for 2-3 hours, then raise the temperature to 30-35°C, and keep the temperature for reaction for 4-6 hours to obtain the isobornyl acrylate chain extender.

[0015] In a more optimized solution, the molar ratio of ethylenediamine to isobornyl acrylate is 1:(2-2.1).

[0016] A more optimized solution is a printing ink prepared according to any one of the above methods for preparing a water-based environmentally friendly printing ink.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The invention discloses a water-based environmentally friendly printing ink and a preparation method thereof. The method comprises compounding components such as polyurethane emulsion, color paste, deionized water, dispersant, defoaming agent, and leveling agent, and adjusting the dosage thereof to prepare a polyurethane ink having excellent adhesion and water resistance. At the same time, the method optimizes the preparation of the polyurethane emulsion, introduces a fluorine-containing chain extender octafluoro-1,6-hexanediol and an isobornyl acrylate chain extender containing an isobornyl ring structure, and compounding octafluoro-1,6-hexanediol, isobornyl acrylate chain extender, and 1,4-butanediol as compound chain extenders to participate in polyurethane polymerization. The crosslinking density of the prepared polyurethane emulsion is improved, and the introduction of hydrophobic groups also greatly improves the water resistance of the polyurethane emulsion.

[0019] On the basis of this scheme, the present application also utilizes the reaction of terminal hydroxyl branched polyether and epichlorohydrin, and utilizes the hydroxyl epoxidation reaction of the terminal hydroxyl branched polyether. At this time, the amount of each substance is controlled to "the molar amount of the hydroxyl group of the terminal hydroxyl branched polyether, epichlorohydrin, and sodium hydroxide is 1: (0.5~0.6): (0.9~1)", to generate a branched terminal epoxy monomer. This monomer not only contains the epoxy group formed by epoxidation, but also contains the unreacted hydroxyl group. Therefore, it is added to the polyurethane polymerization process. This substance is combined with epoxy resin for toughening, which can not only improve the cross-linking performance of the polyurethane emulsion, but also toughen the polyurethane, and the overall comprehensive performance of the product is also improved.

[0020] In addition, the scheme also utilizes the reaction of ethylenediamine and isobornyl acrylate to form an isobornyl acrylate chain extender through a Michael addition reaction. The amount of the isobornyl acrylate chain extender and the branched-end epoxy monomer is adjusted in the scheme to prepare a polyurethane emulsion with the best performance. The polyurethane emulsion is used as an ink binder. The prepared ink has excellent water resistance, gloss and other properties. When the ink is applied to the surface of a plastic film for printing, its adhesion performance is also very excellent.

[0021] The present invention discloses a water-based environmentally friendly printing ink and a preparation method thereof. The solution adjusts the dosage of each component of the printing ink and optimizes the preparation of the connecting material polyurethane emulsion. The prepared ink has very excellent performance and can be widely used for surface printing of substrates such as plastic films, and has high practicality. DETAILED DESCRIPTION

[0022] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0023] In this example, the polyester diol is poly(1,4-butylene adipate) diol with a molecular weight of 2000; the epoxy resin is E-51; the colorant is Lithol Red BK; the defoamer is HR-2000; the dispersant is DP-518; and the leveling agent is BYK-333. The hydroxyl-terminated branched polyether is PP50, and the ethoxylated pentaerythritol (each pentaerythritol molecule reacts with an average of five ethylene oxide molecules) has an average molecular weight of 355 and was provided by Perstorp AB, Sweden.

[0024] Example 1: A method for preparing a water-based environmentally friendly printing ink, comprising the following steps:

[0025] Step (1): Based on parts by mass, polyester diol is dried at 120°C to remove moisture, polyester diol and diphenylmethane diisocyanate are mixed, stirred at 80°C, 2,2-dihydroxymethylpropionic acid and a compound chain extender are added, and the mixture is reacted at 80°C for 3 hours to obtain a polyurethane prepolymer; epoxy resin is then added to the polyurethane prepolymer, the mixture is kept at 80°C for 1 hour, trimethylolpropane and a branched epoxy monomer are added, and the mixture is reacted for 2 hours. After the reaction is completed, the mixture is cooled to 40°C, neutralized with triethylamine for 30 minutes, and emulsified and dispersed with deionized water to obtain a polyurethane emulsion with a solid content of 30%. The compound chain extender is an isobornyl acrylate chain extender, 1,4-butanediol, and octafluoro-1,6-hexanediol, with a mass ratio of 5:1:4.

[0026] The specific amounts of each component used, in parts by mass, are: 42 parts of polyester diol, 20 parts of diphenylmethane diisocyanate, 3.5 parts of 2,2-dihydroxymethylpropionic acid, 8 parts of compound chain extender, 4 parts of epoxy resin, 2 parts of branched end epoxy monomer, 1.5 parts of trimethylolpropane, and 2.8 parts of triethylamine.

[0027] Step (2): by weight, 35 parts of polyurethane emulsion, 6 parts of color paste, 15 parts of deionized water, 0.3 parts of defoaming agent, 0.5 parts of dispersant and 1.5 parts of leveling agent were mixed, stirred evenly, and allowed to stand for 20 minutes to obtain the printing ink.

[0028] The preparation steps of the branched epoxy monomer are as follows: taking a hydroxyl-terminated branched polyether, heating it to 120°C for vacuum dehydration, cooling it with nitrogen, adding a catalyst and stirring it evenly, then heating it to 60°C, slowly adding epichlorohydrin dropwise, keeping it warm for 8 hours, removing unreacted raw materials in vacuo, cooling it to 45°C, diluting it with toluene, then adding solid sodium hydroxide, keeping it warm for 6 hours, collecting the product by filtration, and purifying it to obtain the branched epoxy monomer. The molar ratio of hydroxyl group, epichlorohydrin, and sodium hydroxide in the hydroxyl-terminated branched polyether is 1:0.55:1; the catalyst is boron trifluoride-ethyl ether, and the amount used is 0.8wt% of the total mass of the system.

[0029] The preparation steps for isobornyl acrylate chain extender are as follows: ethylenediamine is slowly added dropwise to isobornyl acrylate in a 15°C ice-water bath over 3 hours, then the temperature is raised to 30°C and the reaction is maintained for 6 hours to obtain the isobornyl acrylate chain extender. The molar ratio of ethylenediamine to isobornyl acrylate is 1:2.1.

[0030] Example 2: A method for preparing a water-based environmentally friendly printing ink, comprising the following steps:

[0031] Step (1): Based on parts by mass, polyester diol is dried at 120°C to remove moisture, polyester diol and diphenylmethane diisocyanate are mixed, stirred at 85°C, 2,2-dihydroxymethylpropionic acid and a compound chain extender are added, and the mixture is reacted at 85°C for 2.5 hours to obtain a polyurethane prepolymer; epoxy resin is then added to the polyurethane prepolymer, the mixture is kept at 85°C for 1.5 hours, trimethylolpropane and a branched epoxy monomer are added, and the mixture is reacted for 1.5 hours. After the reaction is completed, the mixture is cooled to 45°C, neutralized with triethylamine for 25 minutes, and emulsified and dispersed with deionized water to obtain a polyurethane emulsion with a solid content of 30%. The compound chain extender is an isobornyl acrylate chain extender, 1,4-butanediol, and octafluoro-1,6-hexanediol in a mass ratio of 5:1:4.

[0032] The specific amounts of each component used, in parts by mass, are: 42 parts of polyester diol, 20 parts of diphenylmethane diisocyanate, 3.5 parts of 2,2-dihydroxymethylpropionic acid, 9 parts of compound chain extender, 4 parts of epoxy resin, 2 parts of branched end epoxy monomer, 1.5 parts of trimethylolpropane, and 2.8 parts of triethylamine.

[0033] Step (2): by weight, 35 parts of polyurethane emulsion, 6 parts of color paste, 15 parts of deionized water, 0.3 parts of defoaming agent, 0.5 parts of dispersant and 1.5 parts of leveling agent were mixed, stirred evenly, and allowed to stand for 25 minutes to obtain the printing ink.

[0034] The preparation steps of the branched epoxy monomer are as follows: taking a hydroxyl-terminated branched polyether, heating it to 120°C for vacuum dehydration, cooling it with nitrogen, adding a catalyst and stirring it evenly, then heating it to 65°C, slowly adding epichlorohydrin dropwise, keeping it warm for 7.5 hours, removing the unreacted raw materials in vacuo, cooling it to 45°C, diluting it with toluene, then adding solid sodium hydroxide, keeping it warm for 5 hours, collecting the product by filtration, and purifying it to obtain the branched epoxy monomer. The molar ratio of hydroxyl group, epichlorohydrin, and sodium hydroxide in the hydroxyl-terminated branched polyether is 1:0.55:1; the catalyst is boron trifluoride-ethyl ether, used in an amount of 0.8wt% of the total mass of the system.

[0035] The preparation steps for isobornyl acrylate chain extender are as follows: ethylenediamine is slowly added dropwise to isobornyl acrylate in a 20°C ice-water bath over 2.5 hours, then the temperature is raised to 35°C and the reaction is maintained for 5 hours to obtain the isobornyl acrylate chain extender. The molar ratio of ethylenediamine to isobornyl acrylate is 1:2.1.

[0036] Example 3: A method for preparing a water-based environmentally friendly printing ink, comprising the following steps:

[0037] Step (1): Based on parts by mass, polyester diol is dried at 120°C to remove moisture, polyester diol and diphenylmethane diisocyanate are mixed, stirred at 90°C, 2,2-dihydroxymethylpropionic acid and a compound chain extender are added, and the mixture is reacted at 85°C for 2 hours to obtain a polyurethane prepolymer; epoxy resin is then added to the polyurethane prepolymer, the mixture is kept warm at 85°C for 2 hours, trimethylolpropane and a branched epoxy monomer are added, and the mixture is reacted for 1 hour. After the reaction is completed, the mixture is cooled to 40°C, neutralized with triethylamine for 30 minutes, and emulsified and dispersed with deionized water to obtain a polyurethane emulsion with a solid content of 30%. The compound chain extender is an isobornyl acrylate chain extender, 1,4-butanediol, and octafluoro-1,6-hexanediol in a mass ratio of 5:1:4.

[0038] The specific amounts of each component used, in parts by mass, are: 42 parts of polyester diol, 20 parts of diphenylmethane diisocyanate, 3.5 parts of 2,2-dihydroxymethylpropionic acid, 10 parts of compound chain extender, 4 parts of epoxy resin, 3 parts of branched end epoxy monomer, 1.5 parts of trimethylolpropane, and 2.8 parts of triethylamine.

[0039] Step (2): by weight, 35 parts of polyurethane emulsion, 6 parts of color paste, 15 parts of deionized water, 0.3 parts of defoaming agent, 0.5 parts of dispersant and 1.5 parts of leveling agent were mixed, stirred evenly, and allowed to stand for 30 minutes to obtain the printing ink.

[0040] The preparation steps of the branched epoxy monomer are as follows: taking a hydroxyl-terminated branched polyether, heating it to 120°C for vacuum dehydration, cooling it with nitrogen, adding a catalyst and stirring it evenly, then heating it to 65°C, slowly adding epichlorohydrin dropwise, keeping it warm for 7 hours, removing unreacted raw materials in vacuo, cooling it to 50°C, diluting it with toluene, then adding solid sodium hydroxide, keeping it warm for 4 hours, collecting the product by filtration, and purifying it to obtain the branched epoxy monomer. The molar ratio of hydroxyl group, epichlorohydrin, and sodium hydroxide in the hydroxyl-terminated branched polyether is 1:0.55:1; the catalyst is boron trifluoride-ethyl ether, and the amount used is 0.8wt% of the total mass of the system.

[0041] The preparation steps for isobornyl acrylate chain extender are as follows: ethylenediamine is slowly added dropwise to isobornyl acrylate in a 20°C ice-water bath for 2 hours, then the temperature is raised to 35°C and the reaction is maintained for 4 hours to obtain the isobornyl acrylate chain extender. The molar ratio of ethylenediamine to isobornyl acrylate is 1:2.1.

[0042] Comparative Example 1: Example 3 was used as the control group. In Comparative Example 1, the compounded chain extender was only 1,4-butanediol, and the other steps remained unchanged.

[0043] A method for preparing a water-based environmentally friendly printing ink comprises the following steps:

[0044] Step (1): Based on parts by mass, polyester diol is dried at 120°C to remove moisture, polyester diol and diphenylmethane diisocyanate are mixed, stirred at 90°C, 2,2-dihydroxymethylpropionic acid and a compound chain extender are added, and the mixture is reacted at 85°C for 2 hours to obtain a polyurethane prepolymer; epoxy resin is then added to the polyurethane prepolymer, the mixture is kept at 85°C for 2 hours, trimethylolpropane and a branched end epoxy monomer are added, and the mixture is reacted for 1 hour. After the reaction is completed, the mixture is cooled to 40°C, neutralized with triethylamine for 30 minutes, and emulsified and dispersed with deionized water to obtain a polyurethane emulsion with a solid content of 30%. The compound chain extender is 1,4-butanediol.

[0045] The specific amounts of each component used, in parts by mass, are: 42 parts of polyester diol, 20 parts of diphenylmethane diisocyanate, 3.5 parts of 2,2-dihydroxymethylpropionic acid, 10 parts of compound chain extender, 4 parts of epoxy resin, 3 parts of branched end epoxy monomer, 1.5 parts of trimethylolpropane, and 2.8 parts of triethylamine.

[0046] Step (2): by weight, 35 parts of polyurethane emulsion, 6 parts of color paste, 15 parts of deionized water, 0.3 parts of defoaming agent, 0.5 parts of dispersant and 1.5 parts of leveling agent were mixed, stirred evenly, and allowed to stand for 30 minutes to obtain the printing ink.

[0047] The preparation steps of the branched epoxy monomer are as follows: taking a hydroxyl-terminated branched polyether, heating it to 120°C for vacuum dehydration, cooling it with nitrogen, adding a catalyst and stirring it evenly, then heating it to 65°C, slowly adding epichlorohydrin dropwise, keeping it warm for 7 hours, removing unreacted raw materials in vacuo, cooling it to 50°C, diluting it with toluene, then adding solid sodium hydroxide, keeping it warm for 4 hours, collecting the product by filtration, and purifying it to obtain the branched epoxy monomer. The molar ratio of hydroxyl group, epichlorohydrin, and sodium hydroxide in the hydroxyl-terminated branched polyether is 1:0.55:1; the catalyst is boron trifluoride-ethyl ether, and the amount used is 0.8wt% of the total mass of the system.

[0048] Comparative Example 2: Example 3 was used as the control group. The compound chain extender in Comparative Example 1 was only 1,4-butanediol and isobornyl acrylate chain extender, and the other steps remained unchanged.

[0049] A method for preparing a water-based environmentally friendly printing ink comprises the following steps:

[0050] Step (1): Based on parts by mass, polyester diol is dried at 120°C to remove moisture, polyester diol and diphenylmethane diisocyanate are mixed, stirred at 90°C, 2,2-dihydroxymethylpropionic acid and a compound chain extender are added, and the mixture is reacted at 85°C for 2 hours to obtain a polyurethane prepolymer; epoxy resin is then added to the polyurethane prepolymer, the mixture is kept warm at 85°C for 2 hours, trimethylolpropane and a branched epoxy monomer are added, and the reaction is continued for 1 hour. After the reaction is completed, the mixture is cooled to 40°C, neutralized with triethylamine for 30 minutes, and emulsified and dispersed with deionized water to obtain a polyurethane emulsion with a solid content of 30%. The compound chain extender is an isobornyl acrylate chain extender and 1,4-butanediol in a mass ratio of 4:1.

[0051] The specific amounts of each component used, in parts by mass, are: 42 parts of polyester diol, 20 parts of diphenylmethane diisocyanate, 3.5 parts of 2,2-dihydroxymethylpropionic acid, 10 parts of compound chain extender, 4 parts of epoxy resin, 3 parts of branched end epoxy monomer, 1.5 parts of trimethylolpropane, and 2.8 parts of triethylamine.

[0052] Step (2): by weight, 35 parts of polyurethane emulsion, 6 parts of color paste, 15 parts of deionized water, 0.3 parts of defoaming agent, 0.5 parts of dispersant and 1.5 parts of leveling agent were mixed, stirred evenly, and allowed to stand for 30 minutes to obtain the printing ink.

[0053] The preparation steps of the branched epoxy monomer are as follows: taking a hydroxyl-terminated branched polyether, heating it to 120°C for vacuum dehydration, cooling it with nitrogen, adding a catalyst and stirring it evenly, then heating it to 65°C, slowly adding epichlorohydrin dropwise, keeping it warm for 7 hours, removing unreacted raw materials in vacuo, cooling it to 50°C, diluting it with toluene, then adding solid sodium hydroxide, keeping it warm for 4 hours, collecting the product by filtration, and purifying it to obtain the branched epoxy monomer. The molar ratio of hydroxyl group, epichlorohydrin, and sodium hydroxide in the hydroxyl-terminated branched polyether is 1:0.55:1; the catalyst is boron trifluoride-ethyl ether, and the amount used is 0.8wt% of the total mass of the system.

[0054] The preparation steps for isobornyl acrylate chain extender are as follows: ethylenediamine is slowly added dropwise to isobornyl acrylate in a 20°C ice-water bath for 2 hours, then the temperature is raised to 35°C and the reaction is maintained for 4 hours to obtain the isobornyl acrylate chain extender. The molar ratio of ethylenediamine to isobornyl acrylate is 1:2.1.

[0055] Comparative Example 3: Example 3 was used as a control group. No branched end epoxy monomer was added in Comparative Example 3, and the remaining steps remained unchanged.

[0056] A method for preparing a water-based environmentally friendly printing ink comprises the following steps:

[0057] Step (1): Based on parts by mass, polyester diol is dried at 120°C to remove moisture, polyester diol and diphenylmethane diisocyanate are mixed, stirred at 90°C, 2,2-dihydroxymethylpropionic acid and a compound chain extender are added, and the mixture is reacted at 85°C for 2 hours to obtain a polyurethane prepolymer; epoxy resin is then added to the polyurethane prepolymer, the mixture is kept at 85°C for 2 hours, trimethylolpropane is added, and the reaction is continued for 1 hour. After the reaction is completed, the mixture is cooled to 40°C, neutralized with triethylamine for 30 minutes, and emulsified and dispersed with deionized water to obtain a polyurethane emulsion with a solid content of 30%. The compound chain extender is an isobornyl acrylate chain extender, 1,4-butanediol, and octafluoro-1,6-hexanediol, with a mass ratio of 5:1:4.

[0058] The specific amount of each component used is as follows, in parts by mass: 42 parts of polyester diol, 20 parts of diphenylmethane diisocyanate, 3.5 parts of 2,2-dihydroxymethylpropionic acid, 10 parts of compound chain extender, 4 parts of epoxy resin, 1.5 parts of trimethylolpropane, and 2.8 parts of triethylamine.

[0059] Step (2): by weight, 35 parts of polyurethane emulsion, 6 parts of color paste, 15 parts of deionized water, 0.3 parts of defoaming agent, 0.5 parts of dispersant and 1.5 parts of leveling agent were mixed, stirred evenly, and allowed to stand for 30 minutes to obtain the printing ink.

[0060] The preparation steps of the isobornyl acrylate chain extender are as follows: ethylenediamine is slowly added dropwise to isobornyl acrylate in a 20°C ice-water bath for 2 hours, then the temperature is raised to 35°C and the reaction is maintained at this temperature for 4 hours to obtain the isobornyl acrylate chain extender. The molar ratio of ethylenediamine to isobornyl acrylate is 1:2.1.

[0061] Comparative Example 4: Example 3 was used as the control group. In Comparative Example 4, no branched-end epoxy monomer was added, and the compounded chain extender was only 1,4-butanediol, and the other steps remained unchanged.

[0062] A method for preparing a water-based environmentally friendly printing ink comprises the following steps:

[0063] Step (1): Based on parts by mass, polyester diol is dried at 120°C to remove moisture, polyester diol and diphenylmethane diisocyanate are mixed, stirred at 90°C, 2,2-dihydroxymethylpropionic acid and a compound chain extender are added, and the mixture is reacted at 85°C for 2 hours to obtain a polyurethane prepolymer; epoxy resin is then added to the polyurethane prepolymer, the mixture is kept at 85°C for 2 hours, trimethylolpropane is added, and the reaction is continued for 1 hour. After the reaction is completed, the mixture is cooled to 40°C, neutralized with triethylamine for 30 minutes, and emulsified and dispersed with deionized water to obtain a polyurethane emulsion with a solid content of 30%. The compound chain extender is 1,4-butanediol.

[0064] The specific amount of each component used is as follows, in parts by mass: 42 parts of polyester diol, 20 parts of diphenylmethane diisocyanate, 3.5 parts of 2,2-dihydroxymethylpropionic acid, 10 parts of compound chain extender, 4 parts of epoxy resin, 1.5 parts of trimethylolpropane, and 2.8 parts of triethylamine.

[0065] Step (2): by weight, 35 parts of polyurethane emulsion, 6 parts of color paste, 15 parts of deionized water, 0.3 parts of defoaming agent, 0.5 parts of dispersant and 1.5 parts of leveling agent were mixed, stirred evenly, and allowed to stand for 30 minutes to obtain the printing ink.

[0066] Detection experiment:

[0067] 1. Prepare a polyurethane emulsion according to the method disclosed in Examples 1 to 3 and Comparative Examples 1 to 3, pour it into a mold groove, place it horizontally so that its surface is flat and uniform without bubbles, and dry it to obtain a polyurethane coating film; test the water absorption rate of the polyurethane coating film, wherein when testing the water absorption rate, cut the coating film into 2 cm × 2 cm squares with a thickness of 2 cm, soak the coating film in distilled water, take it out after soaking for 24 hours, wipe off the water, and calculate the water absorption rate.

[0068] 2. The printing inks prepared in Examples 1-3 and Comparative Examples 1-3 were tested for adhesion. The substrate was an OPP film. After printing the ink, the film was laid flat. 3M tape was applied over the ink layer. After the tape was firmly adhered, it was quickly peeled off at a 90° angle. The area of ​​the ink layer covered by the tape (X) and the remaining area (Y) after the tape was peeled off were recorded. Adhesion strength was calculated as Y / X × 100%.

[0069] 3. Cut the dried ink sample into strips 10 cm long and 1.5 cm wide. Soak half of the strip in distilled water. After soaking for 24 hours, compare the ink color change of the soaked part and the unsoaked part, as well as the water staining, and rate them.

[0070] Level 1: The water does not stain at all and the ink layer does not change color at all; Level 2: The water stains slightly and the ink layer changes color or fades slightly; Level 3: The water stains obviously and the ink layer changes color or fades obviously; Level 4: The water stains seriously and the ink layer changes color or fades seriously.

[0071]

[0072] Conclusion: The present invention discloses a water-based environmentally friendly printing ink and a preparation method thereof. The scheme adjusts the dosage of each component of the printing ink and optimizes the preparation of the binder polyurethane emulsion. The prepared ink has very excellent performance and can be widely used for surface printing of substrates such as plastic films, and has high practicality.

[0073] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A method for preparing a water-based environmentally friendly printing ink, characterized in that: The following steps are involved: Step (1): drying the polyester diol at 120-125°C to remove moisture, then mixing the polyester diol and diphenylmethane diisocyanate, stirring evenly at 80-90°C, adding 2,2-dihydroxymethylpropionic acid and a compound chain extender, reacting at 80-85°C for 2-3 hours to obtain a polyurethane prepolymer; then adding epoxy resin to the polyurethane prepolymer, keeping the temperature at 80-85°C for 1-2 hours, adding trimethylolpropane and a branched end epoxy monomer, continuing the reaction for 1-2 hours, cooling to 40-50°C after the reaction is completed, neutralizing with triethylamine for 20-30 minutes, and emulsifying and dispersing with deionized water to obtain a polyurethane emulsion; Step (2): mixing the polyurethane emulsion, color paste, deionized water, defoaming agent, dispersant and leveling agent, stirring evenly, and letting it stand for 20 to 30 minutes to obtain the printing ink; In step (1), the preparation steps of the branched end epoxy monomer are as follows: take the terminal hydroxyl branched polyether, heat it to 110-120°C for vacuum dehydration, cool it with nitrogen, add a catalyst and stir evenly, then heat it to 60-65°C, slowly add epichlorohydrin dropwise, keep it warm for 7-8 hours, remove the unreacted raw materials in vacuo, cool it to 45-50°C, dilute it with toluene, then add solid sodium hydroxide, keep it warm for 4-6 hours, collect the product by filtration, and purify it to obtain a branched end epoxy monomer; The molar ratio of the hydroxyl group of the hydroxyl-terminated branched polyether, epichlorohydrin, and sodium hydroxide is 1: (0.5-0.6): (0.9-1); In step (1), the compound chain extender is isobornyl acrylate chain extender, 1,4-butanediol and octafluoro-1,6-hexanediol, with a mass ratio of (4-5):1:(4-5); the solid content of the polyurethane emulsion is 30%.

2. The method for preparing a water-based environmentally friendly printing ink according to claim 1, characterized in that: In step (2), the specific amount of each component is: in parts by mass, 30 to 40 parts of polyurethane emulsion, 6 to 8 parts of color paste, 10 to 15 parts of deionized water, 0.5 to 1 part of dispersant, 0.2 to 0.3 parts of defoaming agent, and 1 to 1.5 parts of leveling agent.

3. The method for preparing a water-based environmentally friendly printing ink according to claim 1, characterized in that: In step (1), the specific amounts of the components used are, in parts by mass, 40 to 45 parts of polyester diol, 15 to 20 parts of diphenylmethane diisocyanate, 3 to 3.5 parts of 2,2-dihydroxymethylpropionic acid, 8 to 10 parts of a compound chain extender, 4 to 5 parts of an epoxy resin, 2 to 3 parts of a branched-end epoxy monomer, 1 to 1.5 parts of trimethylolpropane, and 2 to 3 parts of triethylamine.

4. The method for preparing a water-based environmentally friendly printing ink according to claim 1, characterized in that: The catalyst is boron trifluoride-ethyl ether, and the amount used is 0.5-1 wt% of the total mass of the system.

5. The method for preparing a water-based environmentally friendly printing ink according to claim 1, characterized in that: In step (1), the preparation steps of isobornyl acrylate chain extender are as follows: take ethylenediamine, add isobornyl acrylate dropwise in an ice water bath at 15-20°C, slowly add dropwise for 2-3 hours, then heat to 30-35°C, keep warm and react for 4-6 hours to obtain isobornyl acrylate chain extender.

6. The method for preparing a water-based environmentally friendly printing ink according to claim 5, characterized in that: The molar ratio of ethylenediamine to isobornyl acrylate is 1:(2-2.1).

7. Printing ink prepared according to the method for preparing a water-based environmentally friendly printing ink according to any one of claims 1 to 6.

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