Aqueous polyurethane printing ink and process for its preparation

Abstract

The present application relates to the technical field of printing ink, and discloses a kind of water-based polyurethane printing ink and its preparation process, the present application simultaneously uses polytetrahydrofuran ether diol (PTMEG) and polycaprolactone diol (PCL) as soft segment raw material, PTMEG provides excellent flexibility and hydrolysis resistance, PCL provides high strength and wear resistance, synergistic effect makes the water-based polyurethane prepared simultaneously has excellent mechanical properties, water resistance and folding resistance, especially suitable for the harsh requirements of shoe material printing;Ether bond in PTMEG molecular chain endows material with good low-temperature performance and flexibility, ensuring that the ink layer does not crack when the shoe material is repeatedly bent;Ester group structure in PCL molecular chain endows material with high crystallinity and cohesive energy, significantly improves the wear resistance and adhesion of ink, meets the requirements of shoe material on durability.

Description

Technical Field

[0001] This invention relates to the field of printing ink technology for shoe materials, specifically to a water-based polyurethane printing ink and its preparation process. Background Technology

[0002] Footwear printing inks are widely used for printing logos, patterns, and labels on athletic shoes, casual shoes, children's shoes, and other footwear products. Traditional solvent-based inks release large amounts of volatile organic compounds (VOCs) during the printing process, which not only pollutes the environment and harms the health of production workers, but also allows solvent residues to penetrate into the shoe materials, affecting wearing comfort and safety.

[0003] Water-based inks use water as the main solvent, reducing VOC emissions by 90% to 95% compared to solvent-based inks, making them a key focus of the footwear printing industry for environmentally friendly inks. Waterborne polyurethane (WPU), as the core binder resin for water-based inks, exhibits broad application prospects in the footwear printing field due to its low VOC emissions, excellent adhesion, good mechanical properties, and tunable molecular structure.

[0004] However, existing waterborne polyurethane ink binders still face the following technical bottlenecks: The limited performance of raw materials makes it difficult to meet the complex requirements of footwear materials: Footwear printing substrates are diverse (PU leather, TPU, EVA, rubber, etc.), placing different demands on ink adhesion, flexibility, abrasion resistance, and folding resistance. Existing waterborne polyurethanes mostly employ a single soft segment structure, making it difficult to simultaneously achieve a balance between high strength and high elasticity.

[0005] A significant conflict exists between flexural strength and printability: Footwear materials must withstand repeated bending during use, requiring inks with excellent flexural strength and crack resistance. However, the preparation of waterborne polyurethane inks necessitates the introduction of hydrophilic groups to achieve water dispersion, which inevitably reduces their water resistance and flexural strength. In high-humidity and high-temperature environments (such as in the hot-pressing process of footwear materials), existing waterborne polyurethane inks are prone to problems such as film peeling, whitening, and decreased adhesion, severely limiting their application in high-end footwear printing.

[0006] The modification methods are limited and lack synergistic effects: Existing technologies mostly use a single modifier (such as only organosilicon or only side-chain modification) to modify waterborne polyurethane, resulting in limited modification effects. Organosilicon modification can improve water resistance but may reduce adhesion; side-chain modification can improve anti-blocking properties but may affect emulsion stability. There is a lack of multi-component, multi-level synergistic modification strategies.

[0007] In summary, developing a water-based polyurethane shoe material printing ink that combines excellent adhesion, folding resistance, abrasion resistance, mechanical properties, and environmental friendliness is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] The purpose of this application is to provide a water-based polyurethane printing ink and its preparation process. The present invention aims to solve the following technical problems existing in the prior art: (1) the performance of the binder of water-based polyurethane ink is single and it is difficult to meet the diversified needs of shoe materials; (2) the existing water-based polyurethane ink is difficult to meet the requirements in terms of adhesion, water resistance, folding resistance, mechanical properties and printability at the same time; (3) the binder with a single structure has poor compatibility with different substrates.

[0009] Firstly, the water-based polyurethane shoe material printing ink provided in this application adopts the following technical solution: it is prepared from raw materials comprising the following components: (1) Soft segment component: a mixture of polytetrahydrofuran ether glycol (PTMEG) and polycaprolactone glycol (PCL), wherein the mass ratio of PTMEG to PCL is 1:2 to 2:1; (2) Hard segment components: including isophorone diisocyanate (IPDI); (3) Hydrophilic chain extender: dimethylolpropionic acid (DMPA) or dimethylolbutyric acid (DMBA); (4) Small molecule chain extender: 1,4-butanediol (BDO); (5) Crosslinking modifier: silane coupling agent KH550; (6) Neutralizing agent: Triethylamine (TEA); (7) Catalyst: Dibutyltin dilaurate or organic rhodium catalyst.

[0010] By employing the above technical solution, this invention creatively combines polytetrahydrofuran ether glycol (PTMEG) and polycaprolactone glycol (PCL) as a mixed soft segment. PTMEG contains ether bonds in its molecular chain, exhibiting excellent chain flexibility, which imparts good low-temperature performance and hydrolysis resistance to polyurethane, making it particularly suitable for footwear materials used in humid environments. PCL contains ester groups in its molecular chain, possessing high crystallinity and cohesive energy, significantly improving the mechanical strength and abrasion resistance of polyurethane, meeting the durability requirements of footwear materials. The synergistic effect of these two components in a specific ratio ensures sufficient cohesive force in the ink binder to achieve high adhesion, while maintaining chain flexibility to guarantee film formation and folding resistance. Simultaneously, the introduction of the silane coupling agent KH550, with its active amino groups participating in the reaction, introduces the siloxane structure into the polyurethane backbone. During film formation, hydrolysis and condensation form a Si-O-Si three-dimensional crosslinked network, significantly increasing the crosslinking density and hydrophobicity of the film, thereby synergistically improving the ink's water resistance, heat resistance, and mechanical properties.

[0011] Preferably, the PTMEG is polytetrahydrofuran ether diol with a number-average molecular weight of 1000-3000 and a hydroxyl value of 56-112 mgKOH / g.

[0012] By employing the above technical solution, the molecular weight and hydroxyl value of PTMEG are controlled within a specific range, ensuring its suitability as a macromolecular diol in terms of reactivity and soft segment length. PTMEG within this range can react effectively with monomers such as IPDI, avoiding excessive crosslinking points and brittle films due to excessively low molecular weight, or poor compatibility and incomplete reaction due to excessively high molecular weight. The suitable hydroxyl value ensures the regular construction of the polyurethane molecular chain, laying the foundation for obtaining stable emulsions and high-performance films.

[0013] Preferably, the PCL is polycaprolactone diol with a number-average molecular weight of 2000-4000 and a hydroxyl value of 28-56 mgKOH / g.

[0014] By employing the above technical solution and selecting PCL within a specific molecular weight range, the ester group structure in its molecular chain can endow the material with excellent mechanical strength and abrasion resistance. PCL within this molecular weight range can effectively balance the crystallinity and flexibility of the soft segments, synergistically constructing a polyurethane structure with suitable microphase separation with PTMEG, thereby obtaining a binder material that combines high strength, high elasticity, and excellent abrasion resistance, making it particularly suitable for footwear materials that meet both durability and comfort requirements.

[0015] Preferably, the molar ratio of isocyanate groups to hydroxyl groups in the soft segment component of the IPDI, n(NCO):n(OH), is 1.2~1.5:1.

[0016] By employing the above technical solution, the isocyanate index (R value) can be controlled within the range of 1.2 to 1.5, allowing for precise regulation of the ratio of hard segments (composed of IPDI, DMPA, etc.) to soft segments in the polyurethane molecular chain. A suitable R value ensures a moderate prepolymer molecular weight, good emulsification, and a moderate degree of microphase separation between hard and soft segments in the final adhesive film. This provides sufficient polar groups (such as urethane bonds) to ensure adhesion to the shoe material substrate, while avoiding excessive hard segments leading to an overly hard film and reduced folding resistance, or insufficient hard segments resulting in insufficient cohesion, thus achieving the optimal balance between adhesion, mechanical strength, and flexibility.

[0017] Preferably, the raw materials for preparing the composite modified waterborne polyurethane include, by mass parts: PTMEG: 10-30 servings; PCL: 20-40 servings; IPDI: 30-50 copies; DMPA: 3-8 parts; BDO: 2-5 servings; KH550: 1-5 servings; TEA: 2-6 servings; Catalyst: 0.05~0.2 parts.

[0018] By employing the above technical solution and quantitatively limiting the dosage of each component, a complete and optimized reaction system is formed. This formulation ensures the synergistic effect of PTMEG and PCL is maximized: PTMEG provides excellent flexibility and hydrolysis resistance, while PCL provides high strength and abrasion resistance. An appropriate amount of DMPA provides sufficient water dispersibility while avoiding the damage to water resistance caused by excessive hydrophilic groups; the specific addition of KH550 introduces moderate crosslinking, improves water resistance and strength, while avoiding excessive crosslinking that leads to brittle film and decreased storage stability. The synergistic effect of this formulation system results in a stable binder emulsion and an excellent overall film performance, providing a guarantee for the subsequent preparation of high-quality shoe material inks.

[0019] Secondly, the present invention provides a preparation process for the above-mentioned waterborne polyurethane shoe material printing ink, comprising the following steps: Step 1: Preparation of composite modified waterborne polyurethane binder: (1) Prepolymerization reaction: PTMEG and PCL are added to the reactor and dehydrated under vacuum at 100~120℃ for 1~2 hours; the temperature is lowered to 50~60℃, IPDI and catalyst are added, and the temperature is raised to 80~90℃ for 2~4 hours. (2) Chain extension reaction: Cool down to 60~70℃, add DMPA and BDO, and keep the reaction at this temperature for 1~2 hours; (3) KH550 grafting modification: Cool down to 40~50℃, add KH550, and keep the reaction at this temperature for 1~2 hours; (4) Neutralization and emulsification: Cool to 30~40℃, add TEA and neutralize for 10~30 minutes; then add deionized water, emulsify and disperse at high speed for 20~40 minutes, remove solvent, and obtain composite modified waterborne polyurethane emulsion; Step 2, Ink Preparation: Mix the water-based polyurethane emulsion prepared in Step 1 with pigments and additives, grind and disperse until the fineness is ≤20μm, and adjust the viscosity to obtain water-based polyurethane shoe material printing ink.

[0020] By adopting the above technical solution, this process is scientifically designed and logically clear. It employs a step-by-step process of "prepolymerization-chain extension-modification-neutralization and emulsification," strictly controlling the reaction temperature and time at each stage to ensure the full reaction of the PTMEG / PCL composite soft segment with IPDI and the successful grafting of KH550. In particular, placing the KH550 modification step after chain extension and before neutralization and emulsification ensures that KH550 chemically bonds with isocyanate groups through amino groups while preventing premature hydrolysis and condensation, thus ensuring the effectiveness of the modification. The final high-speed emulsification process produces an emulsion with uniform particle size and stable storage. The entire process is mild, controllable, and easy for industrial production.

[0021] Preferably, the pigment in step two is one or more of carbon black, titanium blue, basic fuchsin, or datura yellow; the additives include dispersants, thickeners, defoamers, and leveling agents.

[0022] By employing the above technical solution, it has been verified that the waterborne polyurethane binder prepared in this invention possesses excellent wetting, dispersion, and coating capabilities for different types of pigments (inorganic and organic), demonstrating its broad pigment compatibility. The use of dispersants and other additives further optimizes the pigment dispersion state, preventing flocculation and sedimentation; thickeners adjust the ink rheology to meet printing requirements; defoamers eliminate air bubbles; and leveling agents improve the appearance of the ink layer. These additives, in synergy with the high-performance binder, ensure that the ink has good printability and stable printing results.

[0023] Preferably, the mass fractions of each component in step two are: 60-80 parts of waterborne polyurethane emulsion, 5-20 parts of pigment, 0.5-2 parts of dispersant, 0.1-0.5 parts of thickener, 0.1-0.5 parts of defoamer, and 10-30 parts of deionized water.

[0024] By adopting the above technical solution, an optimized ink base formulation is provided. This formulation ensures the binder's dominant role in film formation, imparting excellent adhesion and cohesion to the ink layer; the appropriate pigment content guarantees color saturation and hiding power while avoiding ink layer chalking and decreased gloss due to excessive pigment; the precise dosage of additives effectively improves the ink's preparation and performance without affecting the stability of the main system. This formulation provides a raw material ratio basis for obtaining clear, durable, and aesthetically pleasing printed materials on various shoe material substrates (such as PU leather, TPU, EVA, rubber, etc.).

[0025] In summary, this application includes at least one of the following beneficial technical effects of waterborne polyurethane printing ink and its preparation process: 1. This invention uses both polytetrahydrofuran ether glycol (PTMEG) and polycaprolactone glycol (PCL) as soft segment raw materials. PTMEG provides excellent flexibility and hydrolysis resistance, while PCL provides high strength and abrasion resistance. The synergistic effect of the two makes the prepared waterborne polyurethane have excellent mechanical properties, water resistance and folding resistance, which is particularly suitable for the demanding requirements of shoe material printing. 2. The ether bonds in the PTMEG molecular chain endow the material with good low-temperature performance and flexibility, ensuring that the ink layer does not crack when the shoe material is repeatedly bent; the ester group structure in the PCL molecular chain endows the material with high crystallinity and cohesive energy, significantly improving the abrasion resistance and adhesion of the ink, meeting the durability requirements of the shoe material. 3. Waterborne polyurethane is chemically modified using silane coupling agent KH550. The amino groups in KH550 react with the isocyanate groups to introduce a siloxane structure. During the film formation process, hydrolysis and condensation form a three-dimensional cross-linked network of Si-O-Si, which significantly improves the cross-linking density and compactness of the film, thereby enhancing its water resistance, heat resistance and mechanical properties. 4. The water-based polyurethane shoe material ink prepared by this invention has an adhesion grade of 0 (100%), no peeling or whitening in the folding test, a water resistance grade of 1, a tensile strength of over 25 MPa, an elongation at break of >600%, and excellent abrasion resistance, which can meet the printing requirements of high-end shoe materials. Detailed Implementation

[0026] The following provides a further detailed description of this application.

[0027] The main raw materials used in the embodiments of this invention are sourced from: Polytetrahydrofuran ether diol (PTMEG): Industrial grade, Mn=2000, hydroxyl value approximately 56 mgKOH / g, BASF (China) Co., Ltd. Polycaprolactone diol (PCL): Industrial grade, Mn=3000, hydroxyl value approximately 37mgKOH / g, Hunan Juren Chemical New Material Technology Co., Ltd. Isophorone diisocyanate (IPDI): Industrial grade, Xuzhou Yihuiyang New Material Co., Ltd.; Dimethylolpropionic acid (DMPA): analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.; 1,4-Butanediol (BDO): Analytical grade, Tianjin Fuchen Chemical Reagent Factory; Silane coupling agent KH550: analytical grade, Shanghai Maclean Biochemical Technology Co., Ltd.; Triethylamine (TEA): Analytical grade, Fuchen (Tianjin) Chemical Reagent Co., Ltd.; Dibutyltin dilaurate: analytical grade, Shanghai Maclean Biochemical Technology Co., Ltd.; Water-based carbon black paste: Industrial grade, Shandong Yousuo Chemical Technology Co., Ltd.; Water-based titanium cyanide blue paste, water-based alkaline magenta paste, water-based datura yellow paste: industrial grade, Hebei Xingtai Hengji New Material Technology Co., Ltd.; Dispersant D045, Thickener D002, Defoamer D65: Industrial grade, Dongguan Haoyouduo New Materials Co., Ltd.

[0028] The testing methods used in the embodiments of this invention are as follows: Infrared spectroscopy test: Fourier transform infrared spectrometer (IRSpirit type, Shimadzu) was used for testing, with a scanning range of 4000-400cm^-1. Particle size testing: The particle size was measured using a nano-laser particle size analyzer (ZS90, Malvern), with the emulsion diluted to a solid content of 0.3%. Tensile property test: The test was conducted using an electronic universal testing machine (XWW-20A type, Shanghai Jiezhun), with a tensile rate of 100 mm / min; Contact angle test: Tested using a contact angle measuring instrument (SDC-100, Shengding Precision); Water absorption test: The film was soaked for 24 hours, and the water absorption rate was calculated; Adhesion test: Refer to GB / T9286-2021 and use the cross-cut adhesion test. Folding endurance test: Fold the printed material 180° repeatedly 100 times on a folding endurance tester and observe the changes in the ink layer; Abrasion resistance test: Refer to GB / T1768-2006 and use the Taber abrasion tester for testing; Water resistance test: Refer to GB / T13217.5-2008, soak for 24 hours and observe; Gloss test: The gloss at 60° was tested using a multi-angle gloss meter (JFL-B206085, Tianjin Jinfulun). Fineness test: The fineness test was conducted using a scraper fineness gauge (QXD0-100 type, Tianjin Yonglida). Initial dryness test: Refer to GB / T13217.5-2008 for testing. Example

[0029] (1) Preparation of composite modified waterborne polyurethane binder Add 20g PTMEG and 30g PCL to a three-necked flask and dehydrate under vacuum at 0.08MPa and 110℃ for 1.5 hours. Cool to 50℃, install a spiral condenser and electric stirrer, add 35g IPDI and 0.1g dibutyltin dilaurate, and heat to 85℃ to react for 3 hours.

[0030] Cool to 65°C, add 5g DMPA and 3g BDO, and keep the reaction at this temperature for 1.5 hours.

[0031] Cool to 45℃, add 3g KH550, and keep the reaction at this temperature for 1 hour.

[0032] The mixture was cooled to 35°C, and 4.5g of TEA was added to neutralize it for 20 minutes. The reactants were then transferred to an emulsification tank, and 150g of deionized water was added at 800 rpm. The mixture was emulsified at high speed for 30 minutes, and the solvent was removed under reduced pressure to obtain a composite modified waterborne polyurethane emulsion with a solid content of approximately 32%, denoted as WPU-1.

[0033] (2) Formulation of water-based polyurethane shoe material printing ink Take 80g of WPU-1 emulsion, add 10g of water-based carbon black paste, 1.5g of dispersant D045, 0.3g of thickener D002, 0.3g of defoamer D65 and 8g of deionized water, grind and disperse in an agate mortar until the fineness is ≤20μm, adjust the viscosity, and obtain water-based polyurethane shoe material screen printing ink, denoted as Ink-1. Example

[0034] The process is basically the same as in Example 1, except that the mass ratio of PTMEG to PCL is adjusted to 1:1 (PTMEG 25g, PCL 25g), the amount of KH550 added is 4g, the prepared waterborne polyurethane emulsion is designated as WPU-2, and the ink is designated as Ink-2. Example

[0035] The process is basically the same as in Example 1, except that the mass ratio of PTMEG to PCL is adjusted to 1.5:1 (PTMEG 30g, PCL 20g), the amount of KH550 added is 5g, and the prepared waterborne polyurethane emulsion is designated as WPU-3 and the ink as Ink-3. Example

[0036] The process is basically the same as in Example 1, except that the ratio of n(NCO):n(OH) is adjusted to 1.3:1 (IPDI dosage is 40g). The prepared waterborne polyurethane emulsion is designated as WPU-4, and the ink is designated as Ink-4. Example

[0037] The process is basically the same as in Example 1, except that the ratio of n(NCO):n(OH) is adjusted to 1.4:1 (IPDI dosage is 45g). The prepared waterborne polyurethane emulsion is designated as WPU-5, and the ink is designated as Ink-5. Example

[0038] The process is basically the same as in Example 3, except that the organic rhodium catalyst MC-710 is used instead of dibutyltin dilaurate. The prepared waterborne polyurethane emulsion is designated as WPU-6, and the ink is designated as Ink-6. Example

[0039] The process is basically the same as in Example 3, except that water-based titanium cyanide blue paste is used instead of carbon black paste to prepare blue water-based polyurethane shoe material ink, denoted as Ink-7. Example

[0040] The process is basically the same as in Example 3, except that a water-based alkaline magenta paste is used instead of carbon black paste to prepare a magenta water-based polyurethane shoe material ink, denoted as Ink-8. Example

[0041] The process is basically the same as in Example 3, except that water-based datura yellow paste is used instead of carbon black paste to prepare a yellow water-based polyurethane shoe material ink, denoted as Ink-9.

[0042] Comparative Example 1 (Single PTMEG soft segment) The process is basically the same as in Example 1, except that only PTMEG (50g) is used for the soft segment, and PCL is not used. The prepared aqueous polyurethane emulsion is designated as D-WPU-1.

[0043] Comparative Example 2 (Single PCL Soft Segment) The process is basically the same as in Example 1, except that only PCL (50g) is used for the soft segment, and PTMEG is not used. The prepared aqueous polyurethane emulsion is designated as D-WPU-2.

[0044] Comparative Example 3 (without KH550) The process is basically the same as in Example 1, except that KH550 is not added for modification. The prepared waterborne polyurethane emulsion is designated as D-WPU-3.

[0045] Comparative Example 4 (Ordinary Polyester Polyol) The process is basically the same as in Example 1, except that ordinary polyester polyol (PBA, Mn=2000) is used instead of PTMEG and PCL. The resulting waterborne polyurethane emulsion is designated as D-WPU-4.

[0046] Performance Testing and Results Analysis The performance of the aqueous polyurethane emulsions and inks prepared in Examples 1-9 and Comparative Examples 1-4 was tested, and the results are shown in Tables 1-3.

[0047] Table 1. Performance test results of waterborne polyurethane emulsion sample Appearance Average particle size / nm Solid content / % Storage stability / month WPU-1 Milky white with a bluish tint 58.2 32.1 >6 WPU-2 Milky white with a bluish tint 60.5 31.9 >6 WPU-3 Milky white with a bluish tint 63.8 32.4 >6 WPU-4 milky 79.5 32.0 >6 WPU-5 milky 91.2 32.2 >6 WPU-6 Milky white with a bluish tint 62.1 32.1 >6 D-WPU-1 translucent 45.8 32.6 5 D-WPU-2 milky 82.6 31.8 4 D-WPU-3 Milky white with a bluish tint 59.8 32.3 5 D-WPU-4 milky 68.5 32.0 4 As shown in Table 1, the aqueous polyurethane emulsions prepared in the embodiments of the present invention have moderate particle size (58~91nm), solid content of about 32%, and storage stability of more than 6 months. Comparative Example 1 (single PTMEG) emulsion has small particle size but insufficient strength; Comparative Example 2 (single PCL) emulsion has larger particle size and poorer stability; Comparative Example 3 (unmodified) has slightly poorer stability.

[0048] Table 2. Performance test results of waterborne polyurethane films sample Tensile strength / MPa Elongation at break / % 24h water absorption rate / % Contact angle / ° Adhesion rating resistance to boiling WPU-1 24.5 612 15.8 92 Level 0 No peeling, no whitening WPU-2 26.8 588 13.5 96 Level 0 No peeling, no whitening WPU-3 29.2 565 11.2 101 Level 0 No peeling, no whitening WPU-4 31.5 532 9.5 105 Level 0 No peeling, slight whitening WPU-5 34.8 486 7.8 109 Level 1 No peeling, slight whitening WPU-6 28.5 578 11.8 99 Level 0 No peeling, no whitening D-WPU-1 18.5 685 12.5 95 Level 1 Small amount of peeling, whitening D-WPU-2 32.5 412 22.5 78 Level 1 Small amount of peeling, whitening D-WPU-3 19.5 525 25.5 73 Level 2 Noticeable peeling and whitening D-WPU-4 22.5 485 20.5 80 Level 1 Small amount of peeling, whitening As shown in Table 2, the waterborne polyurethane films prepared in the embodiments of the present invention exhibit excellent comprehensive performance. Compared with the comparative examples, the products of the embodiments have higher tensile strength (24.5~34.8MPa), moderate elongation at break (486~612%), lower water absorption (7.8~15.8%), larger contact angle (92~109°), adhesion grade 0 for most (only WPU-5 is grade 1), excellent abrasion resistance (8.9~18.5mg), and better folding resistance. Among them, Example 3 (PTMEG:PCL=1.5:1, KH550 addition 5%) has the best comprehensive performance.

[0049] Table 3. Performance Test Results of Waterborne Polyurethane Footwear Ink sample Pigment type Fineness / μm Initial drying time / mm / 30s Adhesion rating Water resistance rating 60° gloss / GU Printing effect Ink-1 carbon black 15 45 Level 0 Level 1 78 good Ink-2 carbon black 15 42 Level 0 Level 1 80 good Ink-3 carbon black 15 40 Level 0 Level 1 85 Excellent Ink-4 carbon black 20 36 Level 0 Level 1 82 good Ink-5 carbon black 20 32 Level 1 Level 1 78 good Ink-6 carbon black 15 41 Level 0 Level 1 83 Excellent Ink-7 Titanium Blue 15 38 Level 0 Level 1 84 Excellent Ink-8 Basic fuchsin 15 39 Level 0 Level 1 81 Excellent Ink-9 Dadanhuang 15 38 Level 0 Level 1 80 Excellent D-Ink-1 carbon black 15 48 Level 1 Level 2 72 generally D-Ink-2 carbon black 20 32 Level 1 Level 2 75 generally D-Ink-3 carbon black 20 30 Level 2 Level 2 62 Poor D-Ink-4 carbon black 20 35 Level 0 Level 2 70 generally As shown in Table 3, the waterborne polyurethane shoe material inks prepared in the embodiments of the present invention exhibit excellent printability. The fineness is 15-20 μm, meeting the requirements for screen printing; the initial drying time is 32-45 mm / 30 s, indicating a moderate drying speed; the adhesion is mostly grade 0 (only Ink-5 is grade 1), far superior to the comparative examples; the water resistance is all grade 1 (best), while the comparative examples are mostly grade 2; the 60° gloss is 78-85 GU, indicating good to excellent printing results. In particular, Examples 3 (Ink-3) and Examples 6-9 all exhibit excellent comprehensive performance under different pigment systems, indicating that the binder of the present invention has good pigment compatibility.

[0050] The water-based polyurethane shoe material printing ink prepared by this invention has excellent comprehensive performance and environmental protection characteristics, and can be widely used in the following fields: (1) Printing on sports shoes: Excellent folding resistance and abrasion resistance, suitable for printing logos and patterns on shoe uppers, tongues, insoles and other parts; (2) Printing on casual shoes: Good flexibility and adhesion, suitable for printing on various PU leather, TPU and EVA shoe materials; (3) Children's shoe printing: No VOCs emissions, safe and environmentally friendly, suitable for children's footwear products with strict hygiene requirements; (4) Functional shoe material printing: Excellent water resistance and heat resistance, suitable for shoe material parts that require thermoforming or high temperature treatment; (5) Color printing: It is compatible with a variety of pigments and can prepare inks of different colors to meet the diverse printing needs of shoe materials.

[0051] The preparation process of this invention is simple, the raw materials are readily available, and the cost is controllable, which has good prospects for industrial production and economic benefits.

[0052] The embodiments described herein are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Identical components are indicated by the same reference numerals. Therefore, all equivalent changes made to the structure, shape, and principle of this application should be included within the scope of protection of this application.

Claims

1. A water-based polyurethane printing ink, characterized in that: The binder is a composite modified waterborne polyurethane, prepared from raw materials comprising the following components: Soft segment component: a mixture of polytetrahydrofuran ether glycol (PTMEG) and polycaprolactone glycol (PCL); Hard segment components: include isophorone diisocyanate (IPDI); Hydrophilic chain extenders: dimethylolpropionic acid (DMPA) or dimethylolbutyric acid (DMBA); Small molecule chain extender: 1,4-Butanediol (BDO); Crosslinking modifier: silane coupling agent KH550; Neutralizing agent: Triethylamine (TEA); Catalyst: Dibutyltin dilaurate or organorhodium catalyst.

2. The water-based polyurethane printing ink according to claim 1, characterized in that: The mass ratio of PTMEG to PCL is 1:2 to 2:

1.

3. The water-based polyurethane printing ink according to claim 1, characterized in that: The PTMEG is polytetrahydrofuran ether diol, with a number-average molecular weight of 1000-3000 and a hydroxyl value of 56-112 mgKOH / g.

4. The water-based polyurethane printing ink according to claim 1, characterized in that: The PCL is polycaprolactone diol, with a number-average molecular weight of 2000-4000 and a hydroxyl value of 28-56 mgKOH / g.

5. The water-based polyurethane printing ink according to claim 1, characterized in that: The molar ratio of isocyanate groups to hydroxyl groups in the soft segment component of the IPDI, n(NCO):n(OH), is 1.2~1.5:

1.

6. The water-based polyurethane printing ink according to claim 1, characterized in that: The amounts of each component, by mass, are as follows: PTMEG: 10-30 servings; PCL: 20-40 servings; IPDI: 30-50 copies; DMPA: 3-8 parts; BDO: 2-5 servings; KH550: 1-5 servings; TEA: 2-6 servings; Catalyst: 0.05~0.2 parts.

7. A preparation process for the waterborne polyurethane printing ink as described in any one of claims 1-6, characterized in that: Includes the following steps: Step 1: Preparation of composite modified waterborne polyurethane binder: (1) Prepolymerization reaction: PTMEG and PCL are added to the reactor and dehydrated under vacuum at 100~120℃ for 1~2 hours; the temperature is lowered to 50~60℃, IPDI and catalyst are added, and the temperature is raised to 80~90℃ for 2~4 hours. (2) Chain extension reaction: Cool down to 60~70℃, add DMPA and BDO, and keep the reaction at this temperature for 1~2 hours; (3) KH550 grafting modification: Cool down to 40~50℃, add KH550, and keep the reaction at this temperature for 1~2 hours; (4) Neutralization and emulsification: Cool to 30~40℃, add TEA and neutralize for 10~30 minutes; then add deionized water, emulsify and disperse at high speed for 20~40 minutes, remove solvent, and obtain composite modified waterborne polyurethane emulsion; Step 2: Ink preparation: Mix the water-based polyurethane emulsion prepared in Step 1 with pigments and additives, grind and disperse until the fineness is ≤20μm, and adjust the viscosity to obtain water-based polyurethane shoe material printing ink.

8. The preparation process of a water-based polyurethane printing ink according to claim 7, characterized in that: The pigment mentioned in step two is one or more of carbon black, titanium cyan blue, basic fuchsin, or datura yellow; the additives include dispersants, thickeners, defoamers, and leveling agents.

9. The preparation process of a water-based polyurethane printing ink according to claim 7, characterized in that: The mass fractions of each component in step two are as follows: 60-80 parts of waterborne polyurethane emulsion, 5-20 parts of pigment, 0.5-2 parts of dispersant, 0.1-0.5 parts of thickener, 0.1-0.5 parts of defoamer, and 10-30 parts of deionized water.