Water-based environment-friendly printing ink and preparation method thereof

Abstract

The invention discloses water-based environment-friendly printing ink and a preparation method thereof, and relates to the technical field of ink. The polyurethane emulsion, the color paste, the deionized water, the dispersing agent, the defoaming agent, the flatting agent and other components are compounded, and the use amount of the components is adjusted, so that the polyurethane ink with excellent adhesion performance and excellent water resistance is prepared; meanwhile, according to the scheme, preparation of the polyurethane emulsion is optimized, a fluorine-containing chain extender octafluoro-1, 6-hexanediol and an isobornyl acrylate chain extender containing an isobornyl ring structure are introduced, and the octafluoro-1, 6-hexanediol, the isobornyl acrylate chain extender and 1, 4-butanediol are compounded to serve as a compound chain extender to participate in polyurethane polymerization, so that the polyurethane emulsion is prepared. The crosslinking density of the prepared polyurethane emulsion is improved, and the water resistance of the polyurethane emulsion can be greatly improved due to introduction of hydrophobic groups. The prepared ink has very excellent performance, can be widely applied to surface printing of base materials such as plastic films and the like, and is relatively high in practicability.

Description

Technical Field

[0001] The 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 green environmental protection is increasingly valued by people, especially in food packaging, the requirements are more stringent. As a printing material for food packaging, inks are also subject to increasingly higher environmental performance requirements. Therefore, in this context, the development of environmentally friendly water-based inks has received great attention. The most commonly used water-based ink is water-based polyurethane ink, and the core of the performance of water-based polyurethane ink is the performance of the water-based polyurethane binder. Therefore, it is necessary to improve the performance of the water-based polyurethane binder to improve the printability of water-based polyurethane ink on plastic film.

[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 an environmentally friendly water-based printing ink and a preparation method 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 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, 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;

[0007] Step (2): Mix the polyurethane emulsion, color paste, deionized water, defoamer, dispersant and leveling agent, stir evenly, and let stand 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 specific 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 a composite 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.

[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, and the mass ratio is (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: 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 warm for 7-8h, remove the unreacted raw materials in vacuo, cool it to 45-50°C, dilute it with toluene, then add solid sodium hydroxide, keep warm for 4-6h, collect the product by suction, purify it, and 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 terminal hydroxyl 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 scheme, in step (1), the preparation steps of isobornyl acrylate chain extender are: take ethylenediamine, add isobornyl acrylate dropwise in a 15-20°C ice water bath, slowly add dropwise for 2-3 hours, then raise the temperature to 30-35°C, keep warm for reaction for 4-6 hours, and obtain 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 beneficial effects achieved by the present invention are:

[0018] The invention discloses a water-based environmentally friendly printing ink and a preparation method thereof. The scheme comprises compounding components such as polyurethane emulsion, color paste, deionized water, dispersant, defoamer, leveling agent and the like, and adjusting the dosage thereof to prepare polyurethane ink with excellent adhesion performance and excellent water resistance performance. Meanwhile, the scheme 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, so that the crosslinking density of the prepared polyurethane emulsion is improved, and the introduction of hydrophobic groups can also greatly improve 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 terminal hydroxyl branched polyether. At this time, the amount of each substance is controlled to be "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)", and a branched terminal epoxy monomer is generated. The monomer contains not only the epoxy group formed by epoxidation, but also contains the hydroxyl group that has not reacted completely. Therefore, it is added to the polyurethane polymerization process. The substance is combined with epoxy resin for toughening, which can not only improve the cross-linking performance of the polyurethane emulsion, but also can 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 isobornyl acrylate chain extender through Michael addition reaction. The dosage of isobornyl acrylate chain extender and 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 excellent.

[0021] The 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 a connecting material polyurethane emulsion. The prepared ink has very excellent performance, can be widely used in surface printing of substrates such as plastic films, and has high practicality. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In this embodiment, the polyester diol is polyadipate-1,4-butylene glycol ester diol, with a molecular weight of 2000; the epoxy resin is E-51; the color paste is Lithol Red BK; the defoamer is HR-2000; the dispersant is DP-518; and the leveling agent is BYK-333. The terminal hydroxyl branched polyether is PP50, and the ethoxylated pentaerythritol (on average, each pentaerythritol molecule reacts with 5 ethylene oxide molecules) has an average molecular weight of 355, provided by Swedish Perstorp AB.

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

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

[0026] The specific amount of each component used, in parts by mass, is: 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 are mixed, stirred evenly, and allowed to stand for 20 minutes to obtain the printing ink.

[0028] The preparation steps of the branched end epoxy monomer are as follows: take the terminal hydroxyl branched polyether, heat to 120°C for vacuum dehydration, cool with nitrogen, add a catalyst and stir evenly, then heat to 60°C, slowly drop epichlorohydrin, keep warm for 8 hours, remove the unreacted raw materials in vacuum, cool to 45°C, dilute with toluene, then add solid sodium hydroxide, keep warm for 6 hours, collect the product by suction filtration, purify, and obtain the branched end epoxy monomer. The molar ratio of hydroxyl, epichlorohydrin, and sodium hydroxide of the terminal hydroxyl 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 of isobornyl acrylate chain extender are as follows: take ethylenediamine, add isobornyl acrylate dropwise in a 15°C ice water bath, slowly add dropwise for 3 hours, then heat to 30°C, keep warm for 6 hours to obtain isobornyl acrylate chain extender. The molar ratio of ethylenediamine to isobornyl acrylate is 1:2.1.

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

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

[0032] The specific amount of each component used, in parts by mass, is: 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 are mixed, stirred evenly, and allowed to stand for 25 minutes to obtain the printing ink.

[0034] The preparation steps of the branched end epoxy monomer are as follows: take the terminal hydroxyl branched polyether, heat to 120°C for vacuum dehydration, cool with nitrogen, add a catalyst and stir evenly, then heat to 65°C, slowly drop epichlorohydrin, keep warm for 7.5 hours, remove the unreacted raw materials in vacuum, cool to 45°C, dilute with toluene, then add solid sodium hydroxide, keep warm for 5 hours, collect the product by suction filtration, purify, and obtain the branched end epoxy monomer. The molar ratio of hydroxyl, epichlorohydrin, and sodium hydroxide of the terminal hydroxyl 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.

[0035] The preparation steps of isobornyl acrylate chain extender are as follows: take ethylenediamine, add isobornyl acrylate dropwise in a 20°C ice water bath, slowly add dropwise for 2.5 hours, then heat to 35°C, keep warm for 5 hours to obtain isobornyl acrylate chain extender. The molar ratio of ethylenediamine to isobornyl acrylate is 1:2.1.

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

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

[0038] The specific amount of each component used, in parts by mass, is: 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 are mixed, stirred evenly, and allowed to stand for 30 minutes to obtain the printing ink.

[0040] The preparation steps of the branched end epoxy monomer are as follows: take the terminal hydroxyl branched polyether, heat to 120°C for vacuum dehydration, cool with nitrogen, add a catalyst and stir evenly, then heat to 65°C, slowly add epichlorohydrin, keep warm for 7 hours, remove the unreacted raw materials in vacuum, cool to 50°C, dilute with toluene, then add solid sodium hydroxide, keep warm for 4 hours, collect the product by suction filtration, purify, and obtain the branched end epoxy monomer. The molar ratio of hydroxyl, epichlorohydrin and sodium hydroxide of the terminal hydroxyl 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 of isobornyl acrylate chain extender are as follows: take ethylenediamine, add isobornyl acrylate dropwise in a 20°C ice water bath, slowly add dropwise for 2 hours, then heat to 35°C, keep warm and react for 4 hours to obtain isobornyl acrylate chain extender. The molar ratio of ethylenediamine to isobornyl acrylate is 1:2.1.

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

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

[0044] Step (1): In parts by mass, the polyester diol is dried at 120°C to remove moisture, the polyester diol and diphenylmethane diisocyanate are mixed, stirred evenly at 90°C, 2,2-dihydroxymethyl propionic acid and a compound chain extender are added, and the reaction is carried out at 85°C for 2 hours to obtain a polyurethane prepolymer; epoxy resin is added to the polyurethane prepolymer, and the reaction is carried out at 85°C for 2 hours, trimethylolpropane and branched end epoxy monomer are added, and the reaction is continued for 1 hour. After the reaction is completed, the temperature is lowered to 40°C, and triethylamine is used for neutralization for 30 minutes, and deionized water is used for emulsification and dispersion to obtain a polyurethane emulsion with a solid content of 30%. The compound chain extender is 1,4-butanediol.

[0045] The specific amount of each component used, in parts by mass, is: 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 are mixed, stirred evenly, and allowed to stand for 30 minutes to obtain the printing ink.

[0047] The preparation steps of the branched end epoxy monomer are as follows: take the terminal hydroxyl branched polyether, heat to 120°C for vacuum dehydration, cool with nitrogen, add a catalyst and stir evenly, then heat to 65°C, slowly add epichlorohydrin, keep warm for 7 hours, remove the unreacted raw materials in vacuum, cool to 50°C, dilute with toluene, then add solid sodium hydroxide, keep warm for 4 hours, collect the product by suction filtration, purify, and obtain the branched end epoxy monomer. The molar ratio of hydroxyl, epichlorohydrin and sodium hydroxide of the terminal hydroxyl 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 is used as the control group. The compound chain extender in Comparative Example 1 is only 1,4-butanediol and isobornyl acrylate chain extender, and the other steps remain unchanged.

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

[0050] Step (1): In parts by mass, the polyester diol is dried at 120°C to remove moisture, the polyester diol and diphenylmethane diisocyanate are mixed, stirred evenly at 90°C, 2,2-dihydroxymethyl propionic acid and a compound chain extender are added, and the reaction is carried out at 85°C for 2 hours to obtain a polyurethane prepolymer; epoxy resin is then added to the polyurethane prepolymer, and the reaction is carried out at 85°C for 2 hours, trimethylolpropane and branched end epoxy monomer are added, and the reaction is continued for 1 hour. After the reaction is completed, the temperature is lowered to 40°C, and triethylamine is used for neutralization for 30 minutes, and deionized water is used for emulsification and dispersion to obtain a polyurethane emulsion with a solid content of 30%. The compound chain extender is an acrylate isobornyl ester chain extender and 1,4-butanediol, and the mass ratio is 4:1.

[0051] The specific amount of each component used, in parts by mass, is: 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 are mixed, stirred evenly, and allowed to stand for 30 minutes to obtain the printing ink.

[0053] The preparation steps of the branched end epoxy monomer are as follows: take the terminal hydroxyl branched polyether, heat to 120°C for vacuum dehydration, cool with nitrogen, add a catalyst and stir evenly, then heat to 65°C, slowly add epichlorohydrin, keep warm for 7 hours, remove the unreacted raw materials in vacuum, cool to 50°C, dilute with toluene, then add solid sodium hydroxide, keep warm for 4 hours, collect the product by suction filtration, purify, and obtain the branched end epoxy monomer. The molar ratio of hydroxyl, epichlorohydrin and sodium hydroxide of the terminal hydroxyl 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 of isobornyl acrylate chain extender are as follows: take ethylenediamine, add isobornyl acrylate dropwise in a 20°C ice water bath, slowly add dropwise for 2 hours, then heat to 35°C, keep warm and react for 4 hours to obtain 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 the control group. No branched end epoxy monomer was added in Comparative Example 3, and the other steps remained unchanged.

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

[0057] Step (1): In parts by mass, the polyester diol is dried at 120°C to remove moisture, and then the polyester diol and diphenylmethane diisocyanate are mixed, stirred evenly at 90°C, 2,2-dihydroxymethyl propionic acid and a compound chain extender are added, and the reaction is carried out at 85°C for 2 hours to obtain a polyurethane prepolymer; then epoxy resin is added to the polyurethane prepolymer, and the reaction is carried out at 85°C for 2 hours, trimethylolpropane is added, and the reaction is continued for 1 hour. After the reaction is completed, the temperature is lowered to 40°C, and triethylamine is used for neutralization for 30 minutes, and deionized water is used for emulsification and dispersion to obtain a polyurethane emulsion with a solid content of 30%. The compound chain extender is an acrylate isobornyl ester chain extender, 1,4-butanediol and octafluoro-1,6-hexanediol, and the mass ratio is 5:1:4.

[0058] The specific amount of each component used, in parts by mass, is: 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 are 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: take ethylenediamine, add isobornyl acrylate dropwise in a 20°C ice water bath, slowly add dropwise for 2 hours, then heat to 35°C, keep warm and react 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 an environmentally friendly water-based printing ink comprises the following steps:

[0063] Step (1): In parts by mass, the polyester diol is dried at 120°C to remove moisture, the polyester diol and diphenylmethane diisocyanate are mixed, stirred evenly at 90°C, 2,2-dihydroxymethyl propionic acid and a compound chain extender are added, and the reaction is carried out at 85°C for 2 hours to obtain a polyurethane prepolymer; epoxy resin is added to the polyurethane prepolymer, and the reaction is carried out at 85°C for 2 hours, trimethylolpropane is added, and the reaction is continued for 1 hour. After the reaction is completed, the temperature is lowered to 40°C, and triethylamine is used for neutralization for 30 minutes, and deionized water is used for emulsification and dispersion 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, in parts by mass, is: 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 are 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 to make its surface flat and uniform without bubbles, and dry it to obtain a polyurethane coating film; test the water absorption 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. Take the printing inks prepared in Examples 1 to 3 and Comparative Examples 1 to 3 and test their adhesion properties. The substrate is an OPP film. After printing the ink, the film is laid flat and a 3M tape is covered on the ink layer. After it is firmly adhered, it is quickly peeled off from 90°. The tape coverage area X of the ink layer and the remaining area Y after peeling are recorded, and the adhesion strength is calculated as Y / X×100%.

[0069] 3. Cut the dried ink sample into strips with a length of 10 cm and a width of 1.5 cm. 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 make a rating.

[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 connecting material polyurethane emulsion. The prepared ink has very excellent performance and can be widely used in 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 present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

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): Mix the polyurethane emulsion, color paste, deionized water, defoamer, dispersant and leveling agent, stir evenly, and let stand for 20 to 30 minutes to obtain the printing ink.

2. The method for preparing a water-based environmentally friendly printing ink according to claim 1, characterized in that: In step (2), the specific amounts of the components 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.

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, 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 composite 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 3, characterized in that: In step (1), the compound chain extender is isobornyl acrylate chain extender, 1,4-butanediol and octafluoro-1,6-hexanediol, and the mass ratio is (4-5):1:(4-5); the solid content of the polyurethane emulsion is 30%.

5. The method for preparing a water-based environmentally friendly printing ink according to claim 1, characterized in that: In step (1), the preparation step of the branched end epoxy monomer is 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 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 warm for 4-6 hours, collect the product by suction filtration, purify it, and obtain the branched end epoxy monomer.

6. The method for preparing a water-based environmentally friendly printing ink according to claim 5, characterized in that: The molar ratio of the hydroxyl group, epichlorohydrin and sodium hydroxide of the terminal hydroxyl branched polyether is 1: (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.

7. The method for preparing a water-based environmentally friendly printing ink according to claim 4, characterized in that: In step (1), the preparation steps of isobornyl acrylate chain extender are: 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 for reaction for 4-6 hours, and obtain isobornyl acrylate chain extender.

8. The method for preparing a water-based environmentally friendly printing ink according to claim 7, characterized in that: The molar ratio of ethylenediamine to isobornyl acrylate is 1:(2-2.1).

9. Printing ink prepared according to the method for preparing a water-based environmentally friendly printing ink according to claim 1.

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