Polyurethane ink binder suitable for solvent-free compounding as well as preparation method and application of polyurethane ink binder

Abstract

The invention discloses a polyurethane ink binder suitable for solvent-free compounding as well as a preparation method and application thereof, and belongs to the technical field of polyurethane ink. The problems that in the prior art, intaglio printing polyurethane ink is uneven in solvent-free composite coating, low in composite strength, fuzzy in pattern and the like when applied to solvent-free composite coating are solved. The preparation raw materials of the polyurethane ink binder comprise preparation raw materials of alcohol ester soluble polyurethane resin, ethyl acetate, n-propyl acetate and isopropanol. The alcohol ester soluble polyurethane resin is prepared from the following raw materials: polyol with branching degree of 40-60%, diisocyanate, a branching chain extender, a catalyst, an amine chain extender, an end-capping reagent and a silane coupling agent. The polyurethane ink binder can be applied to solvent-free compounding polyurethane ink, especially flexible package intaglio printing solvent-free compounding polyurethane ink, the stability of the polyurethane ink is guaranteed, the environmental protection property is excellent, the compounding strength is high, the solvent-free colloid solubility resistance is good, the leveling property is good, and the comprehensive performance of the product is excellent.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane ink technology, specifically relating to a polyurethane ink binder suitable for solvent-free lamination, its preparation method and application, and particularly to the application of this polyurethane ink binder in polyurethane inks for gravure printing on flexible packaging. Background Technology

[0002] Dry lamination and solvent-free lamination are two mainstream lamination processes in the domestic flexible packaging gravure printing industry. However, dry lamination adhesives contain organic solvents, which generate a large amount of solvent evaporation during the printing process, resulting in VOC emissions that seriously exceed standards. With increasingly stringent environmental regulations, and given that solvent-free lamination adhesives can cure solely through their own reaction without the need for drying, and due to their viscous nature, allow for high-speed and high-efficiency printing, solvent-free lamination is gradually becoming the more mainstream lamination process.

[0003] Polyurethane inks are composite inks mainly composed of pigments, dispersants, vinyl chloride resins, polyurethane ink binders, n-propyl acetate, ethyl acetate, isopropanol, and other solvents. The printing substrates are primarily PET and BOPP film materials. The polyurethane ink binder mainly consists of polyurethane resin, ester solvents, and alcohol solvents. Polyurethane resins are produced through polymerization reactions of isocyanates, polyesters or polyether polyols, and small-molecule chain extenders. Besides urethane groups, the macromolecular chains often contain ether bonds, ester bonds, urea bonds, and other groups. These groups readily form hydrogen bonds, and due to their excellent adhesion, abrasion resistance, scratch resistance, and adjustable hardness, they are increasingly widely used.

[0004] However, due to the high viscosity of solvent-free composite adhesives and the significant difference in polarity between them and polyurethane inks, their coating effect is far inferior to that of dry composite adhesives. They cannot be well coated on the surface of polyurethane inks, and during the printing process, defects such as white spots and bubbles are prone to occur.

[0005] Furthermore, since solvent-free laminating adhesives cannot effectively penetrate polyurethane inks, the lamination strength of the composite product depends in part on the adhesion of the polyurethane ink to the substrate. Therefore, solvent-free lamination places higher demands on the polyurethane inks used for lamination.

[0006] In addition, solvent-free adhesives have a high polyester content, which can easily cause the solvent-free adhesive to dissolve the polyurethane ink during lamination, resulting in blurred patterns on the laminated product.

[0007] Therefore, it is necessary to develop a polyurethane ink binder that is stable, environmentally friendly, has high composite strength, good resistance to solvent-free adhesive dissolution, and excellent leveling properties, suitable for solvent-free lamination. Summary of the Invention

[0008] The first technical problem to be solved by the present invention is to provide a polyurethane ink binder suitable for solvent-free lamination, so as to solve the problems of uneven coating, low lamination strength, and blurry pattern when gravure printing polyurethane ink binders are applied to solvent-free lamination in the prior art.

[0009] The second technical problem to be solved by the present invention is to provide a method for preparing and applying the above-mentioned polyurethane ink binder suitable for solvent-free lamination.

[0010] To address the aforementioned technical problems, the present invention provides the following technical solutions.

[0011] In a first aspect, the present invention provides a polyurethane ink binder suitable for solvent-free lamination, the raw materials for which are prepared include: The raw materials for preparing alcohol-ester soluble polyurethane resin are 29wt%-31wt%; Ethyl acetate 20.5wt%-30.5wt%; Propyl acetate 10.2wt%-20.2wt%; Isopropanol 25wt%-35wt%; The raw materials for preparing the alcohol-ester soluble polyurethane resin include: 100 parts by weight of polyols with a branching degree of 40%-60%; 14.5-25.5 parts by weight of diisocyanate; 3.4-5.5 parts by weight of branched chain extender; Catalyst: 0.05-0.06 parts by weight; Amine chain extenders, 5.3-12.3 parts by weight; 0.5-1.2 parts by weight of silane coupling agent; End-capping agent: 1.8-6.4 parts by weight.

[0012] Preferably, the viscosity of the polyurethane ink binder is 300-600 mPa·s (25°C).

[0013] Preferably, the polyol includes one or more of siloxane-modified polyols, fluorinated polyols, castor oil-based polyols, and sugar-derived polyols, with an average molecular weight of 1500-3000. More preferably, the polyol is one or more of the following: polydimethylsiloxane diol (i.e., hydroxyl-terminated polydimethylsiloxane), hydroxyl-terminated dimethylmethyl vinyl (siloxane and polysiloxane), 1,1,1,2,2-pentafluoro-3-methylbutane-3-ol, perfluoropolyether diol (i.e., hydroxyl-terminated perfluoropolyether), polyglycerol ricinoleate, maltotriose, sorbitol, and cyclic sugar alcohols.

[0014] Preferably, the diisocyanate includes one or a mixture of isophorone diisocyanate, toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and hexamethylene diisocyanate.

[0015] Preferably, the branching chain extender includes one of pentaerythritol, glycerol, and trimethylolpropane.

[0016] Preferably, the amount of the branching chain extender is 3.5-4.6 parts by weight.

[0017] Preferably, the catalyst comprises one of triethylenediamine, diethylenecyclohexylamine, dibutyltin dilaurate, tetraisobutyl titanate, and triethylamine.

[0018] Preferably, the amine chain extender includes one or more of ethylenediamine, diethylenetriamine, 4,4'-methylenebis(3-chloro-2,6-diethylaniline), and isophorone diamine, or a mixture thereof.

[0019] Preferably, the silane coupling agent comprises one or a mixture of several of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0020] Preferably, the capping agent comprises one or a mixture of several of ethanolamine, tert-butylamine, benzylamine, and octadecylamine.

[0021] Secondly, the present invention also provides a method for preparing the above-mentioned polyurethane ink binder suitable for solvent-free lamination, comprising the following steps: (1) Take each raw material according to the proportion; (2) Mix the polyol and diisocyanate and react at 75-135℃ for more than 4 hours to obtain the first reaction material; (3) First, mix the first reactant, n-propyl acetate, branching chain extender and catalyst, and react at 85℃-100℃ for more than 2 hours to obtain the second reactant; then mix the second reactant, amine chain extender, end-capping agent, silane coupling agent, ethyl acetate and isopropanol, and react at 50-60℃ for more than 1 hour to obtain a polyurethane ink binder suitable for solvent-free composite.

[0022] Preferably, in step (2), the polyol is preheated to 80°C before being mixed with diisocyanate.

[0023] Preferably, in step (2), after the polyol and diisocyanate are mixed, they are first reacted at 85-90℃ for 2 hours, and then reacted at 110-120℃ for 4 hours.

[0024] Preferably, in step (3), a portion of the catalyst is first mixed with the polyol and diisocyanate in step (2) and reacted at 75-135°C for more than 4 hours to obtain the first reactant. The remaining catalyst is then mixed with the first reactant, n-propyl acetate, and branching chain extender.

[0025] Preferably, in step (3), after the first reactant is cooled to 80°C, it is first mixed with n-propyl acetate, and then mixed with branching chain extender and catalyst at 55-65°C.

[0026] Preferably, in step (3), the amine chain extender, end-capping agent, silane coupling agent, ethyl acetate and isopropanol are first mixed and cooled to 35°C, and then mixed with the second reactant cooled to 45-60°C. More preferably, the mixture is mixed with the second reactant cooled to 50°C.

[0027] Thirdly, the present invention also provides the application of the above-mentioned polyurethane ink binder suitable for solvent-free lamination in the preparation of polyurethane inks.

[0028] Fourthly, the present invention also provides a polyurethane ink containing the above-mentioned solvent-free composite polyurethane ink binder.

[0029] The principle of this invention is as follows: Polyurethane inks have a significantly different polarity compared to solvent-free composite adhesives, resulting in poor coating adhesion to the ink layer surface. This invention introduces a silane coupling agent into the polyurethane ink binder, achieving excellent wetting effects and thus improving the uneven coating of polyurethane inks. This effectively solves problems such as white spots and bubbles during printing. Furthermore, the NH4+ in the silane coupling agent... 2- When combined with an NCO group, SIO - The full bonding with the substrate can greatly increase the adhesion of polyurethane ink to the substrate, thereby improving the overall strength of the solvent-free composite.

[0030] Solvent-free laminating adhesives often contain a high polyester content, which can lead to the solvent-free adhesive dissolving the polyurethane ink during lamination, resulting in blurred images on the laminated sample. This invention utilizes highly branched polyols to increase the branching and cross-linking degree of the polyurethane ink binder, thereby preventing ink dissolution. Simultaneously, the porous structure generated by the highly branched cross-linking also facilitates the penetration of the solvent-free laminating adhesive, improving the overall lamination strength of the solvent-free composite.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: The polyurethane ink binder of the present invention is suitable for solvent-free lamination and can be applied to polyurethane inks for solvent-free lamination, especially polyurethane inks for solvent-free lamination of flexible packaging gravure printing. It ensures excellent stability and environmental friendliness of the polyurethane ink, high lamination strength, good resistance to solvent-free adhesive dissolution, good leveling performance, and excellent overall product performance.

[0032] The present invention provides a method for preparing a solvent-free polyurethane ink binder. First, a highly branched polyol is reacted with a diisocyanate. Then, an alcohol-ester soluble polyurethane resin is used as the matrix component, and ethyl acetate, n-propyl acetate, and isopropanol are used as solvent components. Afterward, amine chain extenders, branched chain extenders, end-capping agents, and silane coupling agents are added for modification, thereby obtaining a high-performance polyurethane ink binder. Detailed Implementation

[0033] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments.

[0034] The polyurethane ink binder of the present invention, suitable for solvent-free lamination, comprises 29wt%-31wt% of raw materials for preparing alcohol-ester soluble polyurethane resin, 20.5wt%-30.5wt% of ethyl acetate, 10.2wt%-20.2wt% of n-propyl acetate, and 25wt%-35wt% of isopropanol; the raw materials for preparing alcohol-ester soluble polyurethane resin include 100 parts by weight of polyol, 14.5-25.5 parts by weight of diisocyanate, 3.5-4.6 parts by weight of branching chain extender, 0.05-0.06 parts by weight of catalyst, 5.3-12.3 parts by weight of amine chain extender, 1.8-6.4 parts by weight of end-capping agent, and 0.5-1.2 parts by weight of silane coupling agent.

[0035] The viscosity of the polyurethane ink binder for solvent-free lamination of the present invention is 300-600 mPa·s (25°C). In some embodiments, 300 Pa·s, 350 mPa·s, 400 Pa·s, 450 mPa·s, 500 Pa·s, 550 mPa·s, and 600 Pa·s are used. Preferably, 467-483 mPa·s is used, and more preferably, 469-473 mPa·s is used.

[0036] In the raw materials of the solvent-free polyurethane ink binder of the present invention, the amount of the alcohol-ester soluble polyurethane resin preparation raw material is 29-31 wt%. For example, in some embodiments, 29 wt%, 29.5 wt%, 30 wt%, 30.5 wt%, and 31 wt% are used. Preferably, it is 30 wt%-30.8 wt%, more preferably 30.3 wt%-30.5 wt%.

[0037] In the raw materials for preparing the alcohol-ester soluble polyurethane resin of the present invention, the polyol is a highly branched polyol with a branching degree of 40%-60%, such as 40%, 45%, 50%, 55%, 60% in some embodiments, preferably 42-53%, and more preferably 46-53%. The polyol includes one or more of siloxane-modified polyols, fluorinated polyols, castor oil-based polyols, and sugar-derived polyols; preferably polydimethylsiloxane diol (i.e., hydroxyl-terminated polydimethylsiloxane), hydroxyl-terminated dimethylmethyl vinyl (siloxane and polysiloxane), 1,1,1,2,2-pentafluoro-3-methylbutane-3-ol, perfluoropolyether diol (i.e., hydroxyl-terminated perfluoropolyether), polyglycerol castor oil ester, maltotriol, sorbitol, and cyclic sugar alcohols. The average molecular weight of the polyol is between 1500 and 3000, such as in some embodiments 1500, 1800, 2000, 2200, 2500, 2800, 3000, preferably 1500-2500.

[0038] In the raw materials for preparing the alcohol-ester soluble polyurethane resin of the present invention, the diisocyanate includes one or more mixtures selected from isophorone diisocyanate, toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and hexamethylene diisocyanate. The amount of diisocyanate used is 14.5-25.5 parts by weight. For example, in some embodiments, 14.5, 15.5, 16.5, 17.5, 18.5, 19.5, 20.5, 21.5, 22.5, 23.5, 24.5, and 25.5 parts by weight are used. Preferably, it is 15.5-20 parts by weight.

[0039] In the raw materials for preparing the alcohol-ester soluble polyurethane resin of the present invention, the branching chain extender includes one of pentaerythritol, glycerol, and trimethylolpropane. The amount of branching chain extender used is 3.4-5.5 parts by weight. For example, in some embodiments, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, and 5.5 are used. Preferably, 3.5-4.6 parts by weight is used. More preferably, 3.8-4.2 parts by weight is used.

[0040] In the preparation raw materials of the alcohol-ester soluble polyurethane resin of the present invention, the catalyst includes one of triethylenediamine, diethylenecyclohexylamine, dibutyltin dilaurate, tetraisobutyl titanate, and triethylamine.

[0041] In the raw materials for preparing the alcohol-ester soluble polyurethane resin of the present invention, the amine chain extender includes one or more of ethylenediamine, diethylenetriamine, 4,4'-methylenebis(3-chloro-2,6-diethylaniline), and isophorone diamine, or a mixture thereof. The amount of the amine chain extender is 5.3-12.3 parts by weight. For example, in some embodiments, 5.3, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, and 12.3 are used. Preferably, it is 6.3-10.2 parts by weight, and more preferably, it is 6.5-8.8 parts by weight.

[0042] In the raw materials for preparing the alcohol-ester soluble polyurethane resin of the present invention, the capping agent includes one or a mixture of several of monoethanolamine, tert-butylamine, benzylamine, and octadecylamine. The amount of capping agent used is 1.8-6.4 parts by weight. For example, in some embodiments, 1.8, 2.0, 2.5, 3.0, 3.5, 4, 4.5, 5, 5.5, 6, and 6.4 are used. Preferably, it is 3.4-5.8 parts by weight, more preferably 3.5-4.8 parts by weight.

[0043] In the raw materials for preparing the alcohol-ester soluble polyurethane resin of the present invention, the silane coupling agent includes one or a mixture of several selected from γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane. The amount of silane coupling agent used is 0.5-1.2 parts by weight. For example, in some embodiments, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, and 1.2 parts by weight are used. Preferably, 0.6-1.0 parts by weight is used, more preferably 0.8-0.9 parts by weight.

[0044] In the raw materials of the solvent-free polyurethane ink binder of the present invention, the amount of ethyl acetate is 20.5wt%-30.5wt%. For example, in some embodiments, 20.5wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, and 30.5wt% are used. Preferably, it is 25.3wt%-25.8wt%, more preferably 25.6wt%-25.7wt%.

[0045] In the raw materials of the solvent-free polyurethane ink binder of the present invention, the amount of n-propyl acetate is 10.2wt%-20.2wt%. For example, in some embodiments, 10.2wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, and 20.2wt% are used. Preferably, it is 13.4wt%-15.5wt%, more preferably 15.1wt%-15.3wt%.

[0046] In the raw materials of the solvent-free polyurethane ink binder of the present invention, the amount of isopropanol is 25wt%-35wt%. For example, in some embodiments, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, and 35wt% are used. Preferably, it is 28.3wt%-30.8wt%, more preferably 28.5wt%-29.1wt%.

[0047] The present invention provides a method for preparing a solvent-free polyurethane ink binder, comprising the following steps: (1) Take each raw material according to the proportion; (2) Mix the polyol and diisocyanate and react at 75-135℃ for more than 4 hours to obtain the first reaction material; (3) First, mix the first reactant, n-propyl acetate, branching chain extender and catalyst, and react at 85-100℃ for more than 2 hours to obtain the second reactant; then mix the second reactant, amine chain extender, end-capping agent, silane coupling agent, ethyl acetate and isopropanol, and react at 50-60℃ for more than 1 hour to obtain a polyurethane ink binder suitable for solvent-free composite.

[0048] In step (2) of the present invention, it is preferred that the polyol is preheated to 80°C before being mixed with the diisocyanate.

[0049] In step (2) of the present invention, it is preferred that the polyol and diisocyanate are mixed and reacted at 85-90℃ for 2 hours, and then reacted at 110-120℃ for 4 hours.

[0050] In step (3) of the present invention, after the first reactant is cooled to 80°C, it is first mixed with n-propyl acetate, and then mixed with branching chain extender and catalyst at 55-65°C.

[0051] In step (3) of the present invention, a portion of the catalyst can be mixed with the polyol and diisocyanate in step (2) and reacted at 75-135°C for more than 4 hours to obtain the first reaction material. The remaining catalyst is then mixed with the first reaction material, n-propyl acetate, and branching chain extender.

[0052] In step (3) of the present invention, it is preferable to first mix the amine chain extender, end capping agent, silane coupling agent, ethyl acetate and isopropanol, cool to 35°C, and then mix with the second reactant cooled to 45-60°C, more preferably mix with the second reactant cooled to 50°C.

[0053] In steps (1)-(3) of the present invention, it is preferable to mix until uniform each time and to use a uniform heating rate.

[0054] The polyurethane ink binder of the present invention, suitable for solvent-free lamination, can be used in the preparation of polyurethane inks.

[0055] The present invention also provides polyurethane inks containing solvent-free composite polyurethane ink binders.

[0056] It should be noted that there are no special limitations on the above application methods and polyurethane ink formulations, and existing technologies can be referenced. As long as the solvent-free polyurethane ink binder of this invention is used, the polyurethane ink can be guaranteed to have excellent stability and environmental friendliness, high composite strength, good resistance to solvent-free adhesive dissolution, excellent leveling performance, and superior overall product performance.

[0057] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments.

[0058] In the following examples and comparative examples, various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, all materials, reagents, apparatus, instruments, equipment, etc., used in the following examples and comparative examples are commercially available. Room temperature in the examples and comparative examples is defined as 10–30°C.

[0059] Example 1 A polyurethane ink binder suitable for solvent-free lamination is prepared from 30 wt% of alcohol-ester soluble polyurethane resin (134.25 g), 25.8 wt% ethyl acetate, 13.4 wt% n-propyl acetate, and 30.8 wt% isopropanol. The alcohol-ester soluble polyurethane resin is prepared from 100 g of polydimethylsiloxane diol (42% branching, Zhejiang Kaister New Material Co., Ltd., CAS No. 31692-79-2) with an average molecular weight of 2000, 20 g of isophorone diisocyanate, 3.8 g of trimethylolpropane, 0.05 g of dibutyltin dilaurate, 6.3 g of isophorone diamine, 0.6 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and 3.5 g of octadecylamine. The viscosity of the polyurethane ink binder is measured to be 473 mPa·s (25°C).

[0060] A method for preparing polyurethane ink binders suitable for solvent-free composite inks includes: (1) Take each component according to the proportion; (2) Add polydimethylsiloxane diol to the reactor and heat it to 80°C. Continue to add isophorone diisocyanate to the reactor, stir and mix well, and then heat it to 120°C for 4 hours to obtain the first reaction material. (3) Turn off the heating and turn on the reflux water. After cooling the first reaction material to 80°C, mix it with n-propyl acetate. Turn on the heating device and control the temperature at 55°C. Add trimethylolpropane and dibutyltin dilaurate. Stir quickly (300r / min) until uniform, then gradually raise the temperature to 100°C and continue the reaction for 2 hours to obtain the second reaction material, which is ready for use. In another reaction vessel, isophorone diamine, γ-(2,3-epoxypropoxy)propyltrimethoxysilane and octadecylamine are added sequentially, and ethyl acetate and isopropanol are added for dilution. After mixing evenly, the second reactant is added at a uniform rate over 0.5 h, stirred and heated to 50-60 °C. After reacting for 1 h, the material is discharged to obtain the solvent-free polyurethane ink binder for composite inks.

[0061] Example 2 A polyurethane ink binder suitable for solvent-free lamination is prepared from 30.5 wt% (131.85 g) of alcohol-ester soluble polyurethane resin, 25.3 wt% ethyl acetate, 15.1 wt% n-propyl acetate, and 29.1 wt% isopropanol. The alcohol-ester soluble polyurethane resin is prepared from 100 g of polydimethylsiloxane diol with an average molecular weight of 1500 (branching degree 42%, Zhejiang Kaister New Material Co., Ltd., CAS No. 31692-79-2), 15.5 g isophorone diisocyanate, 5.5 g pentaerythritol, 0.05 g dibutyltin dilaurate, 6.5 g ethylenediamine, 0.9 g γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and 3.4 g octadecylamine. The viscosity of the polyurethane ink binder is measured to be 483 mPa·s (25℃).

[0062] The above-mentioned method for preparing polyurethane ink binders for solvent-free composite inks includes: (1) Take each component according to the proportion; (2) Add polydimethylsiloxane diol to the reactor and heat it to 80°C. Continue to add isophorone diisocyanate to the reactor, stir and mix well, and then heat it to 120°C for 4 hours to obtain the first reaction material. (3) Turn off the heating and turn on the reflux water. After cooling the first reaction material to 80°C, mix it with n-propyl acetate. Turn on the heating device and control the temperature at 55°C. Add pentaerythritol and dibutyltin dilaurate. Stir quickly (300 r / min) until uniform, then gradually raise the temperature to 100°C and continue the reaction for 2 hours to obtain the second reaction material, which is ready for use. In another reaction vessel, ethylenediamine, γ-(2,3-epoxypropoxy)propyltrimethoxysilane and octadecylamine are added sequentially, and ethyl acetate and isopropanol are added for dilution. After mixing evenly, the second reactant is added at a uniform rate over 0.5 hours, stirred and heated to 50-60°C. After reacting for 1 hour, the product is discharged to obtain the solvent-free polyurethane ink binder for composite inks.

[0063] Example 3 A polyurethane ink binder suitable for solvent-free lamination is prepared from 30.3 wt% of alcohol-ester-soluble polyurethane resin (141.25 g), 25.7 wt% ethyl acetate, 15.5 wt% n-propyl acetate, and 28.5 wt% isopropanol. The alcohol-ester-soluble polyurethane resin is prepared from 100 g of 1,1,1,2,2-pentafluoro-3-methylbutane-3-ol (branching degree 53%, Santa Cruz Biotechnology, CAS No. 374-46-9) with an average molecular weight of 2500, 20 g of hexamethylene diisocyanate, 4.2 g of glycerol, 0.05 g of dibutyltin dilaurate, 10.2 g of diethylenetriamine, 1.0 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and 5.8 g of octadecylamine. The viscosity of the polyurethane ink binder is measured to be 467 mPa·s (25°C).

[0064] A method for preparing polyurethane ink binders suitable for solvent-free composite inks includes: (1) Take each component according to the proportion; (2) 1,1,1,2,2-pentafluoro-3-methylbutane-3-ol was added to the reaction vessel and heated to 80°C. Hexamethylene diisocyanate was then added to the reaction vessel and stirred until well mixed. The mixture was then heated to 120°C and reacted for 4 hours to obtain the first reaction material. (3) Turn off the heating and turn on the reflux water. After cooling the first reaction material to 80°C, mix it with n-propyl acetate. Turn on the heating device and control the temperature at 55°C. Add glycerol and dibutyltin dilaurate. Stir quickly (300r / min) until uniform, then gradually raise the temperature to 100°C and continue the reaction for 2 hours to obtain the second reaction material, which is ready for use. Diethylenetriamine, γ-(2,3-epoxypropoxy)propyltrimethoxysilane and octadecylamine were added sequentially to another reactor, and ethyl acetate and isopropanol were added for dilution. After mixing evenly, the second reactant was added at a uniform rate over 0.5 h, stirred and heated to 50-60 °C. After reacting for 1 h, the product was discharged to obtain the solvent-free polyurethane ink binder for composite inks.

[0065] Example 4 A polyurethane ink binder suitable for solvent-free lamination is prepared from 30.8 wt% (137.85 g) of alcohol-ester soluble polyurethane resin, 25.6 wt% ethyl acetate, 15.3 wt% n-propyl acetate, and 28.3 wt% isopropanol. The alcohol-ester soluble polyurethane resin is prepared from 100 g of sorbitol (46% branching degree) with an average molecular weight of 2000, 20 g of hexamethylene diisocyanate, 3.4 g of trimethylolpropane, 0.05 g of dibutyltin dilaurate, 8.8 g of isophorone diamine, 0.8 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and 4.8 g of octadecylamine. The viscosity of the polyurethane ink binder is measured to be 469 mPa·s (25°C).

[0066] The above-mentioned method for preparing polyurethane ink binders suitable for solvent-free lamination includes: (1) Take each component according to the proportion; (2) Sorbitol was added to the reaction vessel and heated to 80°C. Hexamethylene diisocyanate was added to the reaction vessel and stirred until well mixed. The mixture was then heated to 120°C and reacted for 4 hours to obtain the first reaction material. (3) Turn off the heating and turn on the reflux water. After cooling the first reaction material to 80°C, mix it with n-propyl acetate. Turn on the heating device and control the temperature at 55°C. Add trimethylolpropane and dibutyltin dilaurate. Stir quickly (300r / min) until uniform, then gradually raise the temperature to 100°C and continue the reaction for 2 hours to obtain the second reaction material, which is ready for use. In another reaction vessel, isophorone diamine, γ-(2,3-epoxypropoxy)propyltrimethoxysilane and octadecylamine are added sequentially, and ethyl acetate and isopropanol are added for dilution. After mixing evenly, the second reactant is added at a uniform rate over 0.5 hours, stirred and heated to 50-60°C. After reacting for 1 hour, the material is discharged to obtain the solvent-free polyurethane ink binder for composite inks.

[0067] Comparative Example 1 The existing polyurethane ink binder is prepared from 30wt% alcohol ester-soluble polyurethane resin (150.4g), 35wt% ethyl acetate (175.5g), 25wt% isopropanol (125g), and 10wt% n-propyl ester (50g). The alcohol ester-soluble polyurethane resin is prepared from 100g of poly(1,4-butanediol adipate) polyol with an average molecular weight of 1500, 35.4g of toluene diisocyanate, and 15g of isophorone diamine. The viscosity of the polyurethane ink binder is tested to be 500 mPa·s (25℃).

[0068] The above-mentioned existing methods for preparing polyurethane ink binders include: (1) Take each component according to the proportion; (2) Add poly(1,4-butanediol adipate) to the reactor and heat to 60°C. Continue to add toluene diisocyanate to the reactor, stir and mix well, then heat to 85°C and react for 4 hours. Turn off the heating and turn on the reflux water, then cool to 50-60°C to obtain the reaction material. (3) In another reactor, add isophorone diamine, ethyl acetate and isopropanol in sequence. After stirring and mixing evenly at 35°C, add it to the reaction material at a uniform rate within 0.5h. Stir and heat to 50-60°C. After reacting for 1h, discharge the material to obtain the existing polyurethane ink binder.

[0069] The polyurethane resin binders prepared in Examples 1-4 and Comparative Example 1 were dispersed evenly in a sand mill according to the formulations shown in Table 1 below to produce gravure inks.

[0070] Table 1. Formulation of Gravure Inks

[0071] The gravure inks prepared according to Table 1 in Examples 1-4 and Comparative Example 1 were subjected to application performance tests. The methods and results of the performance tests are shown in Table 2.

[0072] Table 2. Methods and results of performance testing for gravure inks

[0073] The adhesion strength of the ink was tested using a physical destructive method. A uniform grid was drawn on the coating surface with a special tool, and after covering it with pressure-sensitive adhesive, it was quickly peeled off. The percentage of the coating area that detached was observed. The smaller the detached area, the higher the adhesion level. As shown in Table 2, the percentage of the non-detached area in Examples 1-4 was over 80%, indicating a significant improvement in the adhesion strength of the ink. After printing the ink onto the film substrate, a solvent-free adhesive was evenly applied to the ink layer using a coater, and then another substrate to be laminated was applied. The distribution of the adhesive was observed. As shown in Table 2, the solvent-free adhesive in Examples 1-4 could be completely leveled, while white spots appeared in Comparative Example 1. This indicates that the ink surface was well wetted, thereby improving the leveling properties of the adhesive. The ink of this invention has a high degree of cross-linking and can withstand the ink-dissolving disadvantage caused by a higher proportion of polyester adhesive. As shown in Table 2, Examples 1-4 showed no ink-dissolving phenomenon after lamination with solvent-free adhesive, which greatly surpassed the ink-dissolving resistance of existing polyurethane inks and met the requirements for solvent-free lamination of polyurethane inks. In summary, the polyurethane ink binder of the present invention is more suitable for the performance requirements of solvent-free composite polyurethane inks, and has superior overall performance.

[0074] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A polyurethane ink vehicle, characterized in that, Preparation raw materials include: alcohol ester soluble polyurethane resin preparation raw materials 29wt%-31wt%; ethyl acetate 20.5wt%-30.5wt%; n-propyl acetate 10.2wt%-20.2wt%; isopropyl alcohol 25wt%-35wt%; The preparation raw materials of the alcohol ester soluble polyurethane resin include: 100 parts by weight of polyol with a branching degree of 40%-60%; 14.5-25.5 parts by weight of diisocyanate; 3.4-5.5 parts by weight of branched chain extender; 0.05-0.06 parts by weight of catalyst; 5.3-12.3 parts by weight of amine chain extender; 0.5-1.2 parts by weight of silane coupling agent; 1.8-6.4 parts by weight of end-capping agent.

2. The polyurethane ink vehicle according to claim 1, wherein, The polyurethane ink binder has one or more of the following characteristics, and the viscosity of the polyurethane ink binder at 25℃ is 300-600mPa·s; The polyol includes one or more of siloxane modified polyol, fluorine modified polyol, castor oil based polyol, and sugar derived polyol, and the average molecular weight of the polyol is 1500-3000; The diisocyanate includes a mixture of one or more of isophorone diisocyanate, toluene diisocyanate, 4,4'-diphenyl methane diisocyanate, and hexamethylene diisocyanate; The branched chain extender includes one of pentaerythritol, glycerol, and trimethylolpropane; The catalyst includes one of triethylenediamine, diethylenediamine, dibutyltin dilaurate, tetraisobutyl titanate, and triethylamine; The amine chain extender includes a mixture of one or more of ethylenediamine, diethylenetriamine, 4,4'-methylenebis(3-chloro-2,6-diethyl aniline), and isophorone diamine; The silane coupling agent includes a mixture of one or more of γ-(2,3-epoxypropoxy) propyl trimethoxysilane, γ-aminopropyl triethoxysilane, γ-glycidyl ether propyl trimethoxysilane, and γ-methacryloyloxypropyl trimethoxysilane; The end-capping agent includes a mixture of one or more of ethanolamine, tert-butylamine, benzylamine, and octadecylamine.

3. The polyurethane ink vehicle according to claim 2, wherein, The polyol includes one or more of polydimethylsiloxane diol, hydroxyl-terminated dimethyl methyl vinyl (siloxane and polysiloxane), 1,1,1,2,2-pentafluoro-3-methyl butane-3-ol, perfluoro polyether diol, polyglycerol ricinoleate, maltotriitol, sorbitol, and cyclitol.

4. The process for the preparation of polyurethane ink vehicles according to any one of claims 1 to 3, characterized in that, The method includes the following steps: (1) Take each raw material according to the ratio; (2) Mix the polyol and diisocyanate, and react at 75-135℃ for more than 4h to obtain a first reaction material; (3) Mix the first reaction material, n-propyl acetate, branched chain extender, and catalyst, and react at 85-100℃ for more than 2h to obtain a second reaction material; then mix the second reaction material, amine chain extender, end-capping agent, silane coupling agent, ethyl acetate, and isopropyl alcohol, and react at 50-60℃ for more than 1h to obtain a polyurethane ink binder suitable for solvent-free compounding.

5. The method for preparing polyurethane ink binder according to claim 4, characterized in that, In step (2), after mixing the polyol and diisocyanate, first react at 85-90℃ for 2h, and then react at 110-120℃ for 4h.

6. The method for preparing polyurethane ink binder according to claim 4, characterized in that, In step (2), the polyol is first preheated to 80℃, and then mixed with the diisocyanate.

7. The method for preparing polyurethane ink binder according to claim 4, characterized in that, In step (3), part of the catalyst is first mixed with the polyol and diisocyanate in step (2) to obtain a first reaction material, and the remaining catalyst is mixed with the first reaction material, n-propyl acetate and the branching chain extender.

8. The method for preparing polyurethane ink binder according to claim 4, characterized in that, In step (3), the first reaction material is first mixed with n-propyl acetate after being cooled to 80℃, and then mixed with the branching chain extender and catalyst at 55-65℃. The amine chain extender, end-capping agent, silane coupling agent, ethyl acetate and isopropyl alcohol are first mixed, and then cooled to 35℃, and then mixed with the second reaction material cooled to 45-60℃.

9. Use of the polyurethane ink binder according to any one of claims 1-3 in the preparation of a polyurethane ink.

10. A polyurethane ink comprising the polyurethane ink binder according to any one of claims 1-3.

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