Acrylic modified TPU (thermoplastic polyurethane) resin, preparation method thereof and application of acrylic modified TPU resin in low-temperature curing ink

Abstract

The invention belongs to the technical field of polyurethane elastomers and application thereof, and particularly relates to acrylic modified TPU (thermoplastic polyurethane) resin, a preparation method thereof and application of the acrylic modified TPU resin in low-temperature curing ink. The acrylic modified TPU resin is prepared from the following raw materials: polyol, hydroxyl and carboxyl acrylic resin, diisocyanate, a chain extender and a catalyst. The acrylic modified TPU resin is used for preparing the low-temperature curing ink, and the method mainly comprises the following steps: dissolving the acrylic modified TPU resin in a solvent, sequentially adding aliphatic blocked polyisocyanate, an oxazoline polymer and the like, stirring and curing to obtain the low-temperature curing ink; the aliphatic blocked polyisocyanate is an HDI (Hexamethylene Diisocyanate) tripolymer. According to the TPU resin chemically modified by the acrylic resin and the preparation method of the TPU resin, the compatibility of the TPU resin and the acrylic resin is remarkably improved, and the TPU resin has low-temperature curing performance, adhesive force, flexibility and tolerance and is suitable for the field of high-performance low-temperature curing ink.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane elastomers and their application technology, specifically relating to acrylic modified TPU resins, their preparation methods, and their application in low-temperature curing inks. Background Technology

[0002] With the rapid development of digital printing and flexible substrate packaging industries, the market demand for high-performance, environmentally friendly printing inks is becoming increasingly urgent. Traditional ink systems face severe challenges, especially on textiles (such as polyester and elastic fibers), PVC synthetic leather, TPU films, and various heat-sensitive plastic substrates. These substrates generally cannot withstand high-temperature, long-term baking and curing processes; otherwise, they are prone to material deformation, aging, yellowing, or loss of elasticity.

[0003] Currently, inks suitable for flexible and heat-sensitive substrates mostly rely on single resin systems or simple physical blends. For example, while single vinyl chloride (PVC) resin inks offer good flexibility, they generally suffer from insufficient adhesion and easy migration of plasticizers. Thermoplastic polyurethane (TPU) resin inks exhibit excellent abrasion resistance and elasticity, but are expensive and their adhesion to certain polar or non-polar substrates is difficult to guarantee. While acrylic or styrene resins have good adhesion and fast drying, their coatings are often brittle and have poor folding resistance, making it difficult to meet the bending requirements of flexible substrates. Although physical blending of different resins can compensate for their respective shortcomings to some extent, the compatibility issues between different resin molecular chains often lead to uneven microstructure in the coating, affecting its mechanical properties, appearance, and durability. More notably, in order to achieve sufficient crosslinking density and performance, the aforementioned traditional systems typically rely on high curing temperatures (usually above 120°C) or long curing times (70°C / 15-25 min), which fundamentally contradicts the processing requirements of heat-sensitive substrates and constitutes a long-standing technical bottleneck in this field.

[0004] To address the aforementioned issues, some improvements have been attempted in existing technologies. For example, patent CN121227111A discloses a bio-based elastomer thermal transfer ink and its low-temperature microwave curing method. This method relies on the formation of hydrogen bonds between the carboxyl groups at the ends of the prepolymer and the fabric fibers, as well as the covalent bonds between the silane and the fabric. This mechanism is effective for polar textiles such as cotton and polyester, but for non-polar or weakly polar plastic substrates such as PVC, TPU, and PE, the hydrogen bonding effect is weak, making it difficult to form a firm adhesion and limiting its application range. Furthermore, the physical blending followed by curing method can easily lead to uneven distribution of crosslinking points and poor network integrity, which may affect the final chemical resistance, solvent resistance, heat resistance, and creep resistance of the coating, especially under complex stress or harsh environments.

[0005] Patent CN109679406A discloses a low-temperature curing screen printing ink, which also uses a physical blending system to achieve low-temperature curing. It also uses an extremely complex physical compounding to meet multiple performance requirements. However, this approach also brings insurmountable defects such as high compatibility risk, system instability, complex process, and inherent performance bottlenecks. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the defects of thermoplastic polyurethane (TPU) resin in the prior art when used in inks, such as high curing temperature, insufficient adhesion to low surface energy substrates, and poor chemical resistance and weather resistance. The present invention provides a TPU resin chemically modified with acrylic resin and its preparation method, which significantly improves the compatibility between TPU resin and acrylic resin, and endows it with excellent low-temperature curing performance, adhesion, flexibility and toughness, making it particularly suitable for the field of high-performance low-temperature curing inks.

[0007] The acrylic-modified TPU resin of the present invention comprises the following raw materials: polyol, hydroxyl and carboxyl acrylic resin, diisocyanate, chain extender, and catalyst. The polyol is a polyether polyol or a polyester polyol, the hydroxyl and carboxyl acrylic resin is hydroxyethyl methacrylate resin and methacrylate resin, and the diisocyanate is isophorone diisocyanate or 1,6-hexamethylene diisocyanate.

[0008] The preferred acrylic-modified TPU resin comprises the following raw materials by weight: 35-42 parts polyol, 26-35 parts hydroxyl and carboxyl acrylic resin, 17-22 parts diisocyanate, 8-12 parts chain extender, and 0.08-0.15 parts catalyst. This formulation range is crucial for achieving an ideal balance of performance. The polyol ratio determines the resin's flexibility and low-temperature flexibility; the hydroxyl / carboxyl acrylic resin ratio directly affects the resin's polarity, adhesion, and subsequent crosslinking density; diisocyanate and chain extender together constitute the hard segments, and their dosage controls the material's hardness, modulus, and cohesive strength. This formulation ensures that the molar ratio of -NCO to total -OH (from polyol, acrylic resin, and chain extender) is within an appropriate range, allowing the reaction to proceed fully and the molecular weight to increase to the ideal level, while avoiding side reactions or storage instability due to excessive -NCO.

[0009] In the preferred acrylic-modified TPU resin raw materials, the polyether polyol is polytetrahydrofuran ether diol (PTMG) with a molecular weight of 1000-2000 g / mol; the polyester polyol is polycaprolactone with a molecular weight of 1000-2000 g / mol. PTMG imparts excellent low-temperature toughness, hydrolysis resistance, and microbial resistance to the modified resin, making it suitable for applications requiring high flexibility. Polycaprolactone provides good mechanical strength, abrasion resistance, and adhesion to various materials. Controlling the molecular weight within the 1000-2000 g / mol range is to balance the resin's processing flowability (lower molecular weight, lower viscosity) with the final physical and mechanical properties of the film (appropriately higher molecular weight results in better mechanical properties).

[0010] In the preferred acrylic-modified TPU resin raw materials, the mass ratio of hydroxyethyl methacrylate resin to methacrylic acid resin is 1.5:1 to 2.5:1. Hydroxyethyl methacrylate provides hydroxyl groups that react with isocyanates, incorporating acrylic segments into the polyurethane backbone; methacrylic acid provides carboxyl groups, which can not only react with isocyanates but also crosslink with oxazoline groups and blocked isocyanates in subsequent ink applications. This chemical modification forms a compatibilized interpenetrating network or graft structure, giving the resin both the elasticity and abrasion resistance of TPU and the adhesion, gloss, and weather resistance of acrylic resins.

[0011] In preferred acrylic-modified TPU resin raw materials, the chain extender is 1,2-ethylene glycol, 1,4-butanediol, or 1,6-hexanediol. Small-molecule diol chain extenders react with diisocyanates to form rigid urethane segments (hard segments), the length (number of carbon atoms) of which affects the regularity and crystallinity of the hard segments. 1,4-Butanediol is the most commonly used chain extender, capable of forming regular hard segment microregions, imparting good strength and elasticity to the material. 1,2-ethylene glycol forms harder segments with stronger polarity, which can improve the modulus and adhesion of the material. 1,6-hexanediol provides longer flexible intervals, allowing the material to maintain strength while being more flexible. Selection based on final performance requirements allows for precise control of the microphase separation degree and physical properties of the modified resin.

[0012] In the preferred acrylic-modified TPU resin raw materials, the catalyst is one or more of dibutyltin dilaurate (DBTDL), stannous octoate, and bismuth neodecanoate. DBTDL and stannous octoate have extremely high catalytic activity for the reaction of -NCO and -OH, which can significantly reduce the reaction temperature and shorten the reaction time, ensuring that polymerization is completed within a short residence time in a twin-screw extruder. Bismuth neodecanoate is an environmentally friendly catalyst with high activity and good hydrolysis resistance. Selecting appropriate catalysts and their dosage is key to achieving controllable and efficient polymerization reactions, avoiding gelation or side reactions, and ensuring stable resin quality.

[0013] The preparation method of the acrylic-modified TPU resin of this invention includes the following steps: polyol, hydroxyl, and carboxyl acrylic resin are mixed evenly and placed in container A; diisocyanate is placed in container B; chain extender and catalyst are placed in container C; the materials in containers A, B, and C are extruded using a twin-screw extruder to obtain the acrylic-modified TPU resin. The materials in containers A, B, and C are first injected into a twin-screw extruder through a casting machine, where the reaction takes place. The screw speed of the twin-screw extruder is 180-230 rpm. The polar carboxyl and hydroxyl groups in the modified resin enhance the interaction between the resin and the substrate surface (such as hydrogen bonding), improving adhesion. Simultaneously, by precisely controlling the ratio of TPU soft segments (polyol) to hard segments (isocyanate, chain extender, and acrylic resin), the microstructure of the resin is adjusted, giving it both good toughness and elastic recovery after film formation. This imparts excellent flexibility and impact resistance to the ink coating, overcoming the shortcomings of traditional acrylic inks, such as high brittleness and easy cracking. Continuous and high-efficiency production is achieved by employing a three-component metered feed and twin-screw reactive extrusion method. The screw speed setting (180-230 rpm) is crucial: too low a speed results in uneven material mixing and insufficient reaction; too high a speed may lead to excessive shear heat, causing localized overheating, degradation, or over-reaction (gelling). This speed range ensures that the material reaches its optimal state during conveying, mixing, reaction, and devolatilization (if any), yielding modified resin granules with controllable molecular weight distribution and uniform properties.

[0014] In the preferred method for preparing acrylic-modified TPU resin, the operating temperature range in the twin-screw extrusion process is set to 180~210℃. Under heating conditions, the blocked isocyanate (such as HDI trimer) deblocks and releases active -NCO groups, which react with the hydroxyl groups on the TPU-acrylic-modified resin and the active groups on the oxazoline polymer. Simultaneously, the carboxyl groups on the resin undergo ring-opening addition reactions with the oxazoline groups to form an amide ester crosslinking structure. This multiple crosslinking reaction proceeds efficiently at low temperatures, constructing a dense network that enables the ink coating to achieve excellent hardness, adhesion, solvent resistance, and scratch resistance after low-temperature curing.

[0015] The application of the acrylic-modified TPU resin described in this invention in low-temperature curing inks: The main steps for preparing low-temperature curing inks using acrylic-modified TPU resin are as follows: dissolving the acrylic-modified TPU resin in a solvent, sequentially adding an aliphatic blocked polyisocyanate, an oxazoline polymer, a catalyst, a leveling agent, a defoamer, and a colorant, stirring and curing to obtain the low-temperature curing ink; the aliphatic blocked polyisocyanate is an HDI trimer. The carboxyl and hydroxyl groups reserved in the resin can undergo multiple crosslinking reactions with the two crosslinking agents (blocked isocyanate and oxazoline) in the formulation upon heating. The HDI trimer provides an aliphatic structure, ensuring excellent resistance to yellowing and weathering of the coating; its blocked form ensures the stability of the ink stored at room temperature. Oxazoline has high reactivity with carboxyl groups and is insensitive to water, further enhancing the crosslinking density and coating durability. The synergistic effect of both allows for the construction of a dense three-dimensional network at a low temperature of 70-80℃, achieving rapid curing of high-performance coatings.

[0016] In preferred applications, the solvent is a mixture of acetone, ethyl acetate, and isopropanol. The preferred mass ratio of acetone, ethyl acetate, and isopropanol is 1:1:2 or 2:1:2. Acetone is a true solvent with good solubility for both TPU and acrylic segments and a fast evaporation rate; ethyl acetate is also a true solvent with strong solubility and a moderate evaporation rate; isopropanol is a co-solvent or latent solvent that can adjust the polarity of the system, improve flowability, and has a relatively slow evaporation rate. Using a ratio such as 1:1:2 or 2:1:2 can create a reasonable evaporation gradient, avoiding surface defects (such as prickly heat or orange peel) caused by excessively rapid evaporation of a single solvent, or affecting production efficiency due to excessively slow evaporation, thereby obtaining a coating with good leveling properties and a smooth appearance.

[0017] In preferred applications, the oxazoline polymer is Nippon Shokubai EPOCROS WS-700 or EPOCROS K-2020E. EPOCROS WS-700 and K-2020E are commercially available polyoxazoline functional polymers specifically designed for crosslinking with carboxyl groups. They exhibit high reactivity with the carboxyl groups in the resin of this invention, resulting in good crosslinking efficiency and significantly improving the solvent resistance, chemical resistance, heat resistance, and adhesion of the coating. These specific models are optimized in terms of molecular weight, functionality, and compatibility with other components to ensure stable presence and effective function in the ink system.

[0018] In preferred applications, the catalyst is one or more of dibutyltin dilaurate (DBTDL), stannous octoate, and bismuth neodecanoate. The primary function of this catalyst is to promote the deblocking reaction of the blocked isocyanate during heating, and the reaction of the resulting active -NCO with the resin hydroxyl groups and ambient moisture (minor). Similar to the resin synthesis stage, selecting a suitable catalyst can effectively lower the curing temperature, accelerate the curing reaction process, and ensure sufficient cross-linking is completed at the set low temperature (60-80℃) and within a short time, thereby optimizing production efficiency and guaranteeing coating performance.

[0019] In preferred applications, the leveling agent is BYK-361. BYK-361 is a polyether-modified polydimethylsiloxane leveling agent that can effectively reduce the surface tension of inks, improve substrate wettability, promote leveling of the paint film before curing, eliminate possible brush marks, orange peel and other surface defects, and obtain a smooth and flat coating appearance.

[0020] In preferred applications, the defoamer is BYK-066. BYK-066 is a defoaming polymer solution containing hydrophobic particles. During stirring and application, it effectively inhibits foam generation and quickly breaks down existing bubbles, preventing defects such as pinholes and fisheyes in the ink coating and ensuring the density and integrity of the coating film.

[0021] In preferred applications, the pigment is titanium dioxide. Titanium dioxide is the highest-performing white pigment.

[0022] In preferred applications, the curing temperature is 70-80°C. The stirring speed during curing is 300-500 rpm. The curing time is 2-4 hours. A temperature of 70-80°C promotes the full dissolution and uniform dispersion of all components (especially the resin) in the solvent, and also preliminarily activates the crosslinking agent (slight unsealing or pre-reaction), improving the storage stability of the ink and the consistency of its curing performance after application. A speed of 300-500 rpm provides sufficient shear force to ensure uniform dispersion of pigments and additives without introducing excessive air bubbles. A curing time of 2-4 hours ensures that the system reaches a physical and preliminary chemical equilibrium.

[0023] In preferred applications, the ink is stirred and matured before being filtered through a 400-600 mesh screen. Using a 400-600 mesh (approximately 38-23μm) screen effectively ensures the cleanliness and fineness of the ink, preventing clogging of nozzles or screens during spraying or printing, and ensuring smooth application and a smooth coating surface.

[0024] The application of the acrylic-modified TPU resin of the present invention in low-temperature curing inks is based on a total weight ratio of 100 parts acrylic-modified TPU resin and 50 parts other raw materials. The total weight ratio of the catalyst in the preparation of the acrylic-modified TPU resin and the catalyst in the ink raw materials is 0.2-0.4 parts. The other raw materials preferably include 10-15 parts aliphatic blocked polyisocyanate, 5-10 parts oxazoline polymer, 0.1-0.3 parts leveling agent, 0.1-0.3 parts defoamer, 1-3 parts colorant, and 25.7-32.8 parts mixed solvent.

[0025] This invention involves prepolymerizing polyols, hydroxyl and carboxyl acrylic resins, and diisocyanates to end-cap, grafting acrylic segments onto the TPU backbone, and simultaneously introducing carboxyl groups from methacrylic acid into the side chains. The result is a bifunctional acrylic-modified TPU resin with side chains rich in both carboxyl (-COOH) and hydroxyl (-OH) groups. This resin combines the excellent elastomer properties of TPU with the strong adhesion and high reactivity of acrylic resins. A multi-layered, high-performance crosslinking network is constructed using an aliphatic blocked isocyanate and oxazoline compound system, achieving low-temperature curing performance.

[0026] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention modifies TPU with acrylic resin by grafting acrylic segments onto the TPU backbone to obtain a bifunctional acrylic-modified TPU resin with side chains rich in both carboxyl and hydroxyl groups. This solves the compatibility problem of multiphase materials, avoids phase separation, and provides abundant reaction sites for the entire system, laying the foundation for subsequent performance improvement. At the same time, low-temperature crosslinking ensures that the collision reaction efficiency of -NCO and -OH is improved through the synergistic effect of the "dual crosslinking channel" and the "composite catalyst", significantly reducing the curing temperature to 60-80℃. This achieves energy saving and consumption reduction, and broadens the application range of inks on heat-sensitive substrates. Meanwhile, low-temperature crosslinking ensures the excellent durability of the coating.

[0027] (2) The acrylic-modified TPU resin prepared by the present invention is particularly suitable for formulating low-temperature curing inks. This ink system achieves rapid curing and crosslinking at a low temperature of 60-80℃ by pre-introducing reactive carboxyl and hydroxyl groups into the resin and working synergistically with the oxazoline polymer and blocked isocyanate crosslinking agent in the formulation.

[0028] (3) The low-temperature curing ink formulation provided by the present invention has a simple process, good storage stability, and exhibits excellent adhesion and flexibility to a variety of plastic and metal substrates. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments.

[0030] Example 1 (1) The preparation method of the acrylic modified TPU resin of the present invention includes the following steps: 40 parts of polycaprolactone 2000, 20 parts of hydroxyethyl methacrylate resin and 10 parts of methacrylate resin are mixed evenly and placed in container A. 21.8 parts of 1,6-hexamethylene diisocyanate are placed in container B. 8 parts of 1,4-butanediol and 0.1 parts of DBTDL are placed in container C. The materials in containers A, B and C are injected into a twin-screw extruder through a casting machine. The extrusion reaction is carried out in the twin-screw extruder at a speed of 230 rpm and a working temperature of 210°C to obtain acrylic modified TPU-1.

[0031] (2) The method for preparing the low-temperature curing ink of the present invention includes the following steps: dissolving the above acrylic modified TPU-1 in 32.8 parts of solvent (acetone: ethyl acetate: isopropanol = 1:1:2 mass ratio), and sequentially adding 10 parts of HDI trimer, 5 parts of EPOCROS WS-700, 0.05 parts of DBTDL, 0.05 parts of bismuth neodecanoate, 0.1 parts of BYK-361, 0.1 parts of BYK-066, and 2 parts of titanium dioxide. Under 80°C, the mixture is stirred at 300 rpm for 4 hours until the system is uniform and stable. The finished ink is obtained by filtering through a 600-mesh filter.

[0032] Example 2 (1) The preparation method of the acrylic modified TPU resin of the present invention includes the following steps: 35 parts of PTMG2000, 22 parts of hydroxyethyl methacrylate resin and 13 parts of methacrylate resin are mixed evenly and placed in container A. 17.7 parts of 1,6-hexamethylene diisocyanate are placed in container B. 12 parts of 1,2-ethylene glycol and 0.1 parts of stannous octoate are placed in container C. The materials in containers A, B and C are injected into a twin-screw extruder through a casting machine. The extrusion reaction is carried out in the twin-screw extruder at a speed of 220 rpm and a working temperature of 200°C to obtain acrylic modified TPU-2.

[0033] (2) The method for preparing the low-temperature curing ink of the present invention includes the following steps: dissolving the above acrylic modified TPU-2 in 26.7 parts of solvent (acetone: ethyl acetate: isopropanol = 2:1:2 mass ratio), and sequentially adding 15 parts of HDI trimer, 8 parts of EPOCROS K-2020E, 0.1 parts of stannous octoate, 0.1 parts of bismuth neodecanoate, 0.15 parts of BYK-361, 0.15 parts of BYK-066, and 1 part of titanium dioxide. Under 70°C, the mixture is stirred at 400 rpm for 3 hours until the system is uniform and stable. After filtration through a 500-mesh filter, the finished ink is obtained.

[0034] Example 3 (1) The preparation method of the acrylic modified TPU resin of the present invention includes the following steps: 42 parts of PTMG2000, 18 parts of hydroxyethyl methacrylate resin and 8 parts of methacrylate resin are mixed evenly and placed in container A. 21.7 parts of isophorone diisocyanate are placed in container B. 10 parts of 1,6-hexanediol and 0.1 parts of stannous octoate are placed in container C. The materials in containers A, B and C are injected into a twin-screw extruder through a casting machine. The extrusion reaction is carried out in the twin-screw extruder at a speed of 210 rpm and a working temperature of 180°C to obtain acrylic modified TPU-3.

[0035] (2) The method for preparing the low-temperature curing ink of the present invention includes the following steps: dissolving the above acrylic modified TPU-3 in 25.8 parts of solvent (acetone: ethyl acetate: isopropanol = 2:1:2 mass ratio), and sequentially adding 12 parts of HDI trimer, 10 parts of EPOCROS WS-700, 0.1 parts of stannous octoate, 0.1 parts of bismuth neodecanoate, 0.1 parts of BYK-361, 0.1 parts of BYK-066, and 2 parts of titanium dioxide. Under 80°C, the mixture is stirred at 500 rpm for 2 hours until the system is uniform and stable. The mixture is then filtered through a 400-mesh filter to obtain the finished ink.

[0036] Comparative Example 1 (1) Preparation of acrylic modified TPU-4: 60 parts of polycaprolactone 2000 and 10 parts of methacrylic resin were mixed evenly and placed in container A. 21.8 parts of 1,6-hexamethylene diisocyanate were placed in container B. 8 parts of 1,4-butanediol and 0.1 parts of DBTDL were placed in container C. The materials in containers A, B and C were injected into a twin-screw extruder through a casting machine. The reaction was carried out in the twin-screw extruder at a speed of 230 rpm and a working temperature of 210 ℃ to obtain acrylic modified TPU-4.

[0037] (2) Preparation of finished ink: The acrylic modified TPU-4 resin prepared above was dissolved in 32.8 parts of solvent (acetone: ethyl acetate: isopropanol = 1:1:2 mass ratio), and 10 parts of HDI trimer, 5 parts of EPOCROS WS-700, 0.05 parts of DBTDL, 0.05 parts of bismuth neodecanoate, 0.1 parts of BYK-361, 0.1 parts of BYK-066, and 2 parts of titanium dioxide were added in sequence. The mixture was stirred at 300 rpm for 4 hours at 80°C until the system was uniform and stable. The finished ink was obtained by filtering through a 600-mesh filter.

[0038] Comparative Example 2 (1) Preparation of acrylic modified TPU-5: 50 parts of polycaprolactone 2000 and 20 parts of hydroxyethyl methacrylate resin were mixed evenly and placed in container A. 21.8 parts of 1,6-hexamethylene diisocyanate were placed in container B. 8 parts of 1,4-butanediol and 0.1 parts of DBTDL were placed in container C. The materials in containers A, B and C were injected into a twin-screw extruder through a casting machine. The reaction was carried out in the twin-screw extruder at a speed of 230 rpm and a working temperature of 210℃ to obtain acrylic modified TPU-5.

[0039] (2) Preparation of finished ink: The acrylic modified TPU-5 resin prepared above was dissolved in 32.8 parts of solvent (acetone: ethyl acetate: isopropanol = 1:1:2 mass ratio), and 10 parts of HDI trimer, 5 parts of EPOCROS WS-700, 0.05 parts of DBTDL, 0.05 parts of bismuth neodecanoate, 0.1 parts of BYK-361, 0.1 parts of BYK-066, and 2 parts of titanium dioxide were added in sequence. The mixture was stirred at 300 rpm for 4 hours at 80°C until the system was uniform and stable. The finished ink was obtained by filtering through a 600-mesh filter.

[0040] Comparative Example 3 (1) Preparation of acrylic modified TPU-6: 70 parts of polycaprolactone 2000 were mixed evenly and placed in container A. 21.8 parts of 1,6-hexamethylene diisocyanate were placed in container B. 8 parts of 1,4-butanediol and 0.1 parts of DBTDL were placed in container C. The materials in containers A, B and C were injected into a twin-screw extruder through a casting machine. The reaction was carried out in the twin-screw extruder at a speed of 230 rpm and a working temperature of 210 ℃ to obtain acrylic modified TPU-6.

[0041] (2) Preparation of finished ink: The acrylic modified TPU-6 resin prepared above was dissolved in 32.8 parts of solvent (acetone: ethyl acetate: isopropanol = 1:1:2 mass ratio), and 10 parts of HDI trimer, 5 parts of EPOCROS WS-700, 0.05 parts of DBTDL, 0.05 parts of bismuth neodecanoate, 0.1 parts of BYK-361, 0.1 parts of BYK-066, and 2 parts of titanium dioxide were added in sequence. The mixture was stirred at 300 rpm for 4 hours at 80°C until the system was uniform and stable. The finished ink was obtained by filtering through a 600-mesh filter.

[0042] Comparative Example 4 (1) Preparation of acrylic modified TPU-7: 35 parts of PTMG2000, 22 parts of hydroxyethyl methacrylate resin and 13 parts of methacrylate resin were mixed evenly and placed in container A. 17.7 parts of 1,6-hexamethylene diisocyanate were placed in container B. 12 parts of 1,2-ethylene glycol and 0.1 parts of stannous octoate were placed in container C. The materials in containers A, B and C were injected into a twin-screw extruder through a casting machine. The extrusion reaction was carried out in the twin-screw extruder at a speed of 220 rpm and a working temperature of 200℃ to obtain acrylic modified TPU-7.

[0043] (2) Preparation of finished ink: Dissolve the above acrylic modified TPU-7 in 40.7 parts of solvent (acetone: ethyl acetate: isopropanol = 2:1:2 mass ratio), and add 8 parts of EPOCROS K-2020E, 0.1 parts of stannous octoate, 0.1 parts of bismuth neodecanoate, 0.15 parts of BYK-361, 0.15 parts of BYK-066 and 1 part of titanium dioxide in sequence. Stir at 400 rpm for 3 hours at 80℃ until the system is uniform and stable. Filter through a 500 mesh filter to obtain the finished ink.

[0044] Comparative Example 5 (1) Preparation of acrylic modified TPU-8: 35 parts of PTMG2000, 22 parts of hydroxyethyl methacrylate resin and 13 parts of methacrylate resin were mixed evenly and placed in container A. 17.7 parts of 1,6-hexamethylene diisocyanate were placed in container B. 12 parts of 1,2-ethylene glycol and 0.1 parts of stannous octoate were placed in container C. The materials in containers A, B and C were injected into a twin-screw extruder through a casting machine. The extrusion reaction was carried out in the twin-screw extruder at a speed of 220 rpm and a working temperature of 200 ℃ to obtain acrylic modified TPU-8.

[0045] (2) Preparation of finished ink: Dissolve the above acrylic modified TPU-8 in 33.7 parts of solvent (acetone: ethyl acetate: isopropanol = 2:1:2 mass ratio), and add 15 parts of HDI trimer, 0.1 parts of stannous octoate, 0.1 parts of bismuth neodecanoate, 0.15 parts of BYK-361, 0.15 parts of BYK-066, and 1 part of titanium dioxide in sequence. Stir at 400 rpm for 3 hours at 80℃ until the system is uniform and stable. Filter through a 500-mesh filter to obtain the finished ink.

[0046] The acrylic-modified TPUs obtained in Examples 1-3 and Comparative Examples 1-5 were subjected to performance tests according to the following standards.

[0047] (1) Mechanical properties (tensile strength, elongation at break): The test was conducted according to GB / T528-2009. Two types of dumbbell-shaped specimens were cut into them. The obtained particle injection molded specimens were then cut into dumbbell-shaped specimens that met the standard for data testing. The results are shown in Table 1.

[0048] (2) Hardness (A) test: Hardness test was performed according to ASTM-D2240. The results are shown in Table 1.

[0049] The finished inks obtained in Examples 1-3 and Comparative Examples 1-5 were subjected to performance tests according to the following standards.

[0050] (3) Curing performance: The test is conducted according to GB / T 13217.7-2009. Under the condition of 70℃ / 3min, the curing performance is excellent if no fingerprints are left when rubbed and there is no stickiness. If the color does not fade after 5 wipings with a cotton cloth soaked in alcohol, the curing performance is good if slight fading occurs, and the curing performance is poor if severe fading occurs.

[0051] (4) Adhesion test: The test was conducted according to GB / T 9286-2021. A 1mm × 1mm grid was drawn on the surface of the cured ink film using a cross-cutting tool (drawing to the substrate). Special adhesive tape was applied and then quickly peeled off at 500mm / min. The extent of ink film peeling off the edges of the grid was observed, and the test results were graded according to Table 1 of GB / T 9286-2021. The results are shown in Table 2.

[0052] Table 1. Results of Mechanical Performance Tests

[0053] Table 2. Results of Ink Product Performance Tests

[0054] As can be seen from the test data in Tables 1 and 2, this invention achieves the synthesis of acrylic-modified TPU. The mechanical properties are improved through the introduction of hydroxyl and carboxyl acrylic resins. In Example 1, compared to the comparative example, the adhesion of the TPU ink using only one type of acrylic-modified TPU is significantly reduced. This is because the grafting of acrylic resin onto the TPU chain makes the compatibility more stable and less prone to phase separation. In Example 2, compared to the comparative example, the low-temperature curing performance cannot be achieved without a curing agent. This indicates that the blocking curing agent reacts with the highly reactive functional groups introduced onto the molecular chain, and the specific catalyst lowers the activation energy required for the resin crosslinking reaction, thereby effectively reducing the curing temperature and increasing the curing time.

Claims

1. An acrylic-modified TPU resin, characterized in that, The raw materials include: polyol, hydroxyl and carboxyl acrylic resin, diisocyanate, chain extender, and catalyst. The polyol is a polyether polyol or a polyester polyol, the hydroxyl and carboxyl acrylic resin is hydroxyethyl methacrylate resin and methacrylic resin, and the diisocyanate is isophorone diisocyanate or 1,6-hexamethylene diisocyanate.

2. The acrylic-modified TPU resin according to claim 1, characterized in that: The raw materials include the following components by weight: 35-42 parts polyol, 26-35 parts hydroxyl and carboxyl acrylic resin, 17-22 parts diisocyanate, 8-12 parts chain extender, and 0.08-0.15 parts catalyst.

3. The acrylic-modified TPU resin according to claim 1 or 2, characterized in that: The polyether polyol is polytetrahydrofuran ether diol with a molecular weight of 1000-2000 g / mol; the polyester polyol is polycaprolactone with a molecular weight of 1000-2000 g / mol.

4. The acrylic-modified TPU resin according to claim 1 or 2, characterized in that: The mass ratio of hydroxyethyl methacrylate resin to methacrylic acid resin is 1.5:1 to 2.5:

1.

5. A method for preparing the acrylic-modified TPU resin according to claim 1, characterized in that, The process includes the following steps: mixing polyol, hydroxyl and carboxyl acrylic resins evenly and placing them in container A; placing diisocyanate in container B; placing chain extender and catalyst in container C; and extruding the materials from containers A, B and C using a twin-screw extruder to obtain acrylic modified TPU resin.

6. The method for preparing acrylic-modified TPU resin according to claim 5, characterized in that: The operating temperature range in the twin-screw extrusion process is set to 180~210℃.

7. The application of the acrylic-modified TPU resin according to claim 1 in low-temperature curing ink, characterized in that, The application involves using acrylic-modified TPU resin to prepare low-temperature curing ink. The main steps are as follows: dissolving acrylic-modified TPU resin in a solvent, sequentially adding aliphatic blocked polyisocyanate, oxazoline polymer, catalyst, leveling agent, defoamer, and colorant, stirring and curing to obtain low-temperature curing ink; the aliphatic blocked polyisocyanate is an HDI trimer.

8. The application of the acrylic-modified TPU resin according to claim 7 in low-temperature curing inks, characterized in that: The solvent is a mixture of acetone, ethyl acetate, and isopropanol.

9. The application of the acrylic-modified TPU resin according to claim 8 in low-temperature curing inks, characterized in that: The oxazoline polymer is EPOCROS WS-700 or EPOCROS K-2020E.

10. The application of the acrylic-modified TPU resin according to any one of claims 7 to 9 in low-temperature curing inks, characterized in that: The curing temperature is 70~80℃.

Images