Hyperbranched polyurethane acrylate UV light-cured resin and preparation process thereof

Abstract

The invention discloses hyperbranched polyurethane acrylate UV light-cured resin and a preparation process thereof, and belongs to the technical field of hyperbranched UV light-cured resin. The preparation process disclosed by the invention adopts step-by-step prepolymerization and comprises the following steps: firstly, constructing a linear polymer main chain skeleton by using low-polarity dihydric alcohol, and continuously reacting an obtained primary polyurethane prepolymer with a polyol monomer consisting of trimethylolpropane, trimethylolpropane monoallyl ether, dimethylolpropionic acid and pentaerythritol to obtain a secondary polyurethane prepolymer; and finally, carrying out end capping by adopting pentaerythritol triacrylate. The prepared hyperbranched polyurethane acrylate UV light-cured resin is high in curing speed, low in viscosity, high in hardness and good in flexibility, and can be applied to various fields such as UV plastic coatings, precise ink-jet printing and wood coatings.

Description

Technical Field

[0001] The invention belongs to the technical field of hyperbranched UV light-curing resins, and particularly relates to a hyperbranched polyurethane acrylate UV light-curing resin and a preparation process thereof. Background Art

[0002] Hyperbranched UV-curable resins, a new type of low-viscosity, multifunctional UV resin that has rapidly developed in recent years, have become a key material for addressing the shortcomings of traditional UV resins due to the unique properties brought about by their three-dimensional dendritic structure. Compared with conventional linear resins, hyperbranched resins offer significant advantages such as low viscosity, high solubility, and high reactivity. Their molecular structure lies somewhere between dendritic macromolecules and linear polymers, retaining the highly branched three-dimensional tree structure while avoiding the chain entanglements of linear molecules. These properties enable them to significantly reduce the amount of solvents and reactive diluents used, while significantly reducing defects such as poor coating adhesion caused by volume shrinkage during UV monomer curing.

[0003] Hyperbranched polyurethane acrylate (HBPUA), due to its unique spherical molecular structure, can significantly improve the resin's rheological properties (low viscosity, high solids content), cure rate, and shrinkage resistance of the cured film. It is widely used in light-curing coatings, inks, adhesives, and 3D printing. Currently, linear polyurethane prepolymers are primarily prepared through polymerization of polyol monomers and isocyanates, which are then end-capped with acrylate monomers such as hydroxyethyl methacrylate (HEMA) to produce the resin product. However, existing products generally suffer from issues with balancing cure speed, hardness, and flexibility, and the synthesis process is also prone to gelling. Summary of the Invention

[0004] In response to the problems raised in the background technology, the purpose of the present invention is to provide a hyperbranched polyurethane acrylate UV light-curing resin and a preparation process thereof. The hyperbranched polyurethane acrylate UV light-curing resin prepared by the present invention has the advantages of fast curing, low viscosity, high hardness and good flexibility.

[0005] The present invention specifically adopts the following technical solutions: The present invention provides a method for preparing a hyperbranched polyurethane acrylate UV light-curing resin, comprising the following steps: S1. Mixing isocyanate and catalyst, raising the temperature to 40-80° C., and then adding diol to react to obtain an isocyanate-terminated primary polyurethane prepolymer; S2. Mix the obtained isocyanate-terminated primary polyurethane prepolymer with a polyol monomer, add a catalyst and stir evenly, and heat to 60-80° C. to react to obtain an isocyanate-terminated secondary polyurethane prepolymer; Wherein, the polyol monomer consists of trimethylolpropane monoallyl ether, dimethylolpropionic acid, trimethylolpropane and pentaerythritol; S3. Add pentaerythritol triacrylate to the obtained isocyanate-terminated secondary polyurethane prepolymer, raise the temperature to 70-90° C. for reaction, and obtain a hyperbranched polyurethane acrylate UV light-curing resin.

[0006] Furthermore, the isocyanate described in S1 is one of isophorone diisocyanate, hexamethylene diisocyanate, and diphenylmethane diisocyanate.

[0007] Furthermore, the diol described in S1 includes one or more of polypropylene glycol, polybutylene glycol, polybutylene caproate, and polycarbonate diol.

[0008] Furthermore, the diol is composed of polypropylene glycol, polybutylene caproate, and polycarbonate diol in a molar ratio of (2-3.6):1:(0.4-1).

[0009] Furthermore, the diol in S1 is slowly added to the isocyanate through a constant pressure dropping funnel, with the feeding amount being a molar ratio of isocyanate group to hydroxyl group of 2:1; after the diol is added, the reaction is maintained at a constant temperature of 60°C for 2-3 hours.

[0010] Furthermore, the catalysts in S1 and S2 are both organic bismuth catalysts, preferably DY-20; the amount of catalyst added in S1 is 0.04%-0.1% of the mass of the isocyanate, and the amount of catalyst added in S2 is 0.01%-0.05% of the mass of the primary polyurethane prepolymer.

[0011] Furthermore, the polyol monomer in S2 is composed of trimethylolpropane monoallyl ether, dimethylolpropionic acid, trimethylolpropane and pentaerythritol in a molar ratio of (1.4-2):1:(1.8-3):(0.05-0.15).

[0012] Furthermore, the addition ratio of the isocyanate-terminated primary polyurethane prepolymer and the polyol monomer in S2 is n(NCO):n(OH)=2:1, and the method of mixing the polyol monomer and the isocyanate-terminated primary polyurethane prepolymer is: first, trimethylolpropane monoallyl ether and dimethylolpropionic acid are slowly added to the primary polyurethane prepolymer while applying high-energy ultrasound, and the addition / ultrasound time is controlled to be 20-30 min, and then trimethylolpropane and pentaerythritol are added; the reaction time after adding the catalyst is 2-4 h.

[0013] Furthermore, the molar ratio of the isocyanate-terminated secondary polyurethane prepolymer to pentaerythritol triacrylate in S3 is 1:(3.1-3.3), and the reaction is terminated when the isocyanate group content of the system is 0.

[0014] The preparation process of the present invention utilizes a step-by-step prepolymerization process, first constructing a linear polymer backbone with a low-polarity diol. To enhance the basic flexibility, weather resistance, and water resistance of the resulting UV-curable resin, the present invention utilizes polypropylene glycol, polybutylene caproate, and polycarbonate diols and optimizes their ratios. This effectively enhances hydrophilicity and adhesion, balances hardness and toughness, and lays the foundation for the ultimate production of a high-performance resin. The introduction of branching nodes and reaction sites is key to forming a hyperbranched structure. Therefore, the present invention utilizes trimethylolpropane monoallyl ether, dimethylolpropionic acid, and pentaerythritol in combination with trimethylolpropane as the polyol monomer combination. Trimethylolpropane (TMP) exhibits excellent branching properties, reactivity, and controllable viscosity, along with good compatibility, making it suitable as the main branching node. Trimethylolpropane monoallyl ether and dimethylolpropionic acid, due to the electronic effects of adjacent substituents and steric hindrance, provide primary hydroxyl groups with varying reactivity. This difference in activity not only effectively avoids the crosslinking gel defects caused by traditional polyol monomers, but also further balances flexibility and water resistance. Pentaerythritol (PENTA) can serve as a core branching point, significantly improving hardness and crosslink density. High-energy ultrasound promotes the dispersion and reaction of TMPM and DMP, inhibiting microphase separation and improving uniformity, thereby further improving chemical and water resistance, increasing cure speed and adhesion, and reducing brittleness. Finally, the present invention uses pentaerythritol triacrylate as an end-capping agent to impart UV curability, completing the preparation of the resin. The present process utilizes step-by-step prepolymerization, which facilitates control of the reaction extent and molecular structure while fully utilizing the synergistic effects of the aforementioned monomers to compensate for performance deficiencies introduced by the different monomers, effectively reducing side reactions and improving product quality.

[0015] The present invention also provides a hyperbranched polyurethane acrylate UV light-curing resin obtained by the preparation method.

[0016] Compared with the prior art, the present invention has the following beneficial effects: To address the shortcomings of existing hyperbranched polyurethane acrylate products, the present invention employs a step-by-step prepolymerization process. Low-polarity diols are first used to construct a linear polymer backbone. The resulting primary polyurethane prepolymer is then reacted with a polyol monomer consisting of trimethylolpropane, trimethylolpropane monoallyl ether, dimethylolpropionic acid, and pentaerythritol to produce a secondary polyurethane prepolymer. Finally, pentaerythritol triacrylate is used to cap the end caps. The hyperbranched polyurethane acrylate UV-curable resin prepared by the present invention exhibits strong adhesion, fast curing speed, low viscosity, high hardness, and good flexibility. It can be used in a variety of applications, including UV plastic coatings, precision inkjet printing, and wood coatings. DETAILED DESCRIPTION

[0017] To make the objects, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be described clearly and completely below in conjunction with the examples. Where specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or the conditions recommended by the manufacturer. Where the manufacturer of the reagents or instruments is not specified, all are commercially available conventional products.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art in the art. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0019] Example 1 A method for preparing a hyperbranched polyurethane acrylate UV light-curing resin comprises: 1. Weigh polypropylene glycol (PPG2000), polybutylene glycol caproate (PBA1000), and polycarbonate diol (CD220) in a molar ratio of 2.8:1:0.8 as diols for later use. Add isophorone diisocyanate to a reactor and heat to 40°C. Add 0.08% by weight of an organobismuth catalyst, DY-20, and stir to mix thoroughly. Then, slowly drip the diol into the reactor via a constant pressure dropping funnel (the molar ratio of isocyanate group to hydroxyl group is 2:1). Maintain the temperature at 60°C using circulating water and react at this temperature for 3 hours to obtain an isocyanate-terminated primary polyurethane prepolymer.

[0020] 2. Weigh trimethylolpropane monoallyl ether, dimethylolpropionic acid, trimethylolpropane, and pentaerythritol in a molar ratio of 1.8:1:2.6:0.1 as polyol monomers for later use. Add the polyol monomers to the reaction system from step 1 (the ratio of the primary polyurethane prepolymer to the polyol monomer is n(NCO):n(OH) = 2:1): Slowly add trimethylolpropane monoallyl ether and dimethylolpropionic acid while applying high-energy ultrasound (40 kHz, 180 W). Control the addition / ultrasound time to 25 minutes. After the addition is complete, continue adding trimethylolpropane and pentaerythritol and mix. Add 0.03% of the mass of the primary polyurethane prepolymer as an organobismuth catalyst DY-20, stir and mix thoroughly. Maintain the temperature at 68°C using circulating water and react at this temperature for 3 hours to obtain an isocyanate-terminated secondary polyurethane prepolymer.

[0021] 3. Add 3.2 times the molar amount of dehydrated pentaerythritol triacrylate of the secondary polyurethane prepolymer to the system after the reaction in step 2, raise the temperature to 80°C and react at a constant temperature until the isocyanate group content of the system is 0, thereby obtaining a hyperbranched polyurethane acrylate UV light-curing resin.

[0022] Example 2 A method for preparing a hyperbranched polyurethane acrylate UV light-curing resin comprises: 1. Weigh polypropylene glycol (PPG2000), polybutylene glycol caproate (PBA1000), and polycarbonate diol (CD220) in a molar ratio of 2:1:1 as diols for later use. Add isophorone diisocyanate to a reactor and heat to 40°C. Add 0.08% by weight of an organobismuth catalyst, DY-20, and stir to mix thoroughly. Then, slowly drip the diol into the reactor via a constant pressure dropping funnel (the amount is based on a 2:1 molar ratio of isocyanate groups to hydroxyl groups). Maintain the temperature at 60°C using circulating water and react at this temperature for 3 hours to obtain an isocyanate-terminated primary polyurethane prepolymer.

[0023] 2. Weigh trimethylolpropane monoallyl ether, dimethylolpropionic acid, trimethylolpropane, and pentaerythritol in a molar ratio of 2:1:2:0.05 as polyol monomers for later use. Add the polyol monomers to the reaction system from step 1 (the ratio of the primary polyurethane prepolymer to the polyol monomer is n(NCO):n(OH) = 2:1): Slowly add trimethylolpropane monoallyl ether and dimethylolpropionic acid while applying high-energy ultrasound (40 kHz, 180 W). Control the addition / ultrasound time to 25 minutes. After the addition is complete, continue adding trimethylolpropane and pentaerythritol and mix. Add 0.03% of the mass of the primary polyurethane prepolymer as an organobismuth catalyst DY-20, stir and mix thoroughly. Maintain the temperature at 68°C using circulating water and react at this temperature for 3 hours to obtain an isocyanate-terminated secondary polyurethane prepolymer.

[0024] 3. Add 3.2 times the molar amount of dehydrated pentaerythritol triacrylate of the secondary polyurethane prepolymer to the system after the reaction in step 2, raise the temperature to 80°C and react at a constant temperature until the isocyanate group content of the system is 0, thereby obtaining a hyperbranched polyurethane acrylate UV light-curing resin.

[0025] Example 3 A method for preparing a hyperbranched polyurethane acrylate UV light-curing resin comprises: 1. Weigh polypropylene glycol (PPG2000), polybutylene glycol caproate (PBA1000), and polycarbonate diol (CD220) in a molar ratio of 3.6:1:0.4 for standby use. Add isophorone diisocyanate to a reactor and heat to 40°C. Add 0.08% by weight of an organobismuth catalyst, DY-20, and stir to mix thoroughly. Then, slowly drip the diol into the reactor via a constant pressure dropping funnel (the molar ratio of isocyanate group to hydroxyl group is 2:1). Maintain the temperature at 60°C using circulating water and react at this temperature for 3 hours to obtain an isocyanate-terminated primary polyurethane prepolymer.

[0026] 2. Weigh trimethylolpropane monoallyl ether, dimethylolpropionic acid, trimethylolpropane, and pentaerythritol in a molar ratio of 1.4:1:3:0.15 as polyol monomers for later use. Add the polyol monomers to the reaction system from step 1 (the ratio of the primary polyurethane prepolymer to the polyol monomer is n(NCO):n(OH) = 2:1): Slowly add trimethylolpropane monoallyl ether and dimethylolpropionic acid while applying high-energy ultrasound (40 kHz, 180 W). Control the addition / ultrasound time to 25 minutes. After the addition is complete, continue adding trimethylolpropane and pentaerythritol and mix. Add 0.03% of the mass of the primary polyurethane prepolymer as an organobismuth catalyst DY-20, stir and mix thoroughly. Control the temperature at 68°C using circulating water and react at this temperature for 3 hours to obtain an isocyanate-terminated secondary polyurethane prepolymer.

[0027] 3. Add 3.2 times the molar amount of dehydrated pentaerythritol triacrylate of the secondary polyurethane prepolymer to the system after the reaction in step 2, raise the temperature to 80°C and react at a constant temperature until the isocyanate group content of the system is 0, thereby obtaining a hyperbranched polyurethane acrylate UV light-curing resin.

[0028] Comparative Example 1 The step parameters are the same as those in Example 1, except that trimethylolpropane monoallyl ether is not added in step 2, that is, dimethylolpropionic acid, trimethylolpropane and pentaerythritol are weighed as polyol monomers in a molar ratio of 1:2.6:0.1.

[0029] Comparative Example 2 The step parameters are as described in Example 1, except that the ratio of the polyol monomer components in step 2 is adjusted to: the molar ratio of trimethylolpropane monoallyl ether, dimethylolpropionic acid, trimethylolpropane and pentaerythritol is 1.5:1.5:1.5:0.3.

[0030] Comparative Example 3 The step parameters are as in Example 1, except that in step 2, the polyol monomer is simultaneously added to the primary polyurethane prepolymer for mixing, and high-energy ultrasonic assistance is not applied.

[0031] Comparative Example 4 Refer to the step parameters of Example 1, except that triethanolamine and glycerol are used instead of trimethylolpropane monoallyl ether and dimethylolpropionic acid, that is, triethanolamine, glycerol, trimethylolpropane and pentaerythritol are weighed as polyol monomers in a molar ratio of 1.8:1:2.6:0.1.

[0032] Test example The resin samples prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests, and the results are shown in Table 1 (1% by weight of photoinitiator 1173 was added to each of the products; hardness was tested in accordance with GB / T 6739-2022; viscosity was tested in accordance with GB / T 13217.4; adhesion was tested in accordance with GB / T 9286-2021; and elongation at break was tested in accordance with GB / T 1040.4-2006).

[0033] Table 1 Test results of resin sample properties

[0034] According to the test results in Table 1, it can be seen that the hyperbranched polyurethane acrylate UV light-curing resin prepared by the process of the present invention has the advantages of fast curing, low viscosity, high hardness and good flexibility.

[0035] The embodiments described above merely represent several preferred embodiments of the present invention. While the descriptions are relatively specific and detailed, they are not intended to limit the present invention. It should be noted that those skilled in the art will readily appreciate that the present invention is susceptible to various variations and modifications. Any modifications, equivalent substitutions, or improvements within the scope of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A method for preparing a hyperbranched polyurethane acrylate UV light-curing resin, characterized in that: The following steps are included: S1. Mixing isocyanate and catalyst, raising the temperature to 40-80° C., and then adding diol to react to obtain an isocyanate-terminated primary polyurethane prepolymer; S2. Mix the obtained isocyanate-terminated primary polyurethane prepolymer with a polyol monomer, add a catalyst and stir evenly, raise the temperature to 60-80° C. for reaction, and obtain an isocyanate-terminated secondary polyurethane prepolymer; Wherein, the polyol monomer consists of trimethylolpropane monoallyl ether, dimethylolpropionic acid, trimethylolpropane and pentaerythritol; S3. Add pentaerythritol triacrylate to the obtained isocyanate-terminated secondary polyurethane prepolymer, raise the temperature to 70-90° C. for reaction, and obtain a hyperbranched polyurethane acrylate UV light-curing resin.

2. The method for preparing a hyperbranched polyurethane acrylate UV light-curing resin according to claim 1, wherein The isocyanate described in S1 is one of isophorone diisocyanate, hexamethylene diisocyanate, and diphenylmethane diisocyanate.

3. The method for preparing a hyperbranched polyurethane acrylate UV light-curing resin according to claim 1, wherein The diol described in S1 includes one or more of polypropylene glycol, polybutylene glycol, polybutylene caproate, and polycarbonate diol.

4. The method for preparing a hyperbranched polyurethane acrylate UV light-curing resin according to claim 3, wherein: The diol is composed of polypropylene glycol, polybutylene caproate and polycarbonate diol in a molar ratio of (2-3.6):1:(0.4-1).

5. The method for preparing a hyperbranched polyurethane acrylate UV light-curing resin according to claim 1, wherein The diol in S1 was slowly added to the isocyanate through a constant pressure dropping funnel, with the molar ratio of isocyanate group to hydroxyl group being 2:

1. After the diol was added, the reaction was maintained at a constant temperature of 60°C for 2-3 hours.

6. The method for preparing a hyperbranched polyurethane acrylate UV light-curing resin according to claim 1, wherein The catalysts described in S1 and S2 are both organic bismuth catalysts. The amount of catalyst added in S1 is 0.04%-0.1% of the mass of the isocyanate, and the amount of catalyst added in S2 is 0.01%-0.05% of the mass of the primary polyurethane prepolymer.

7. The method for preparing a hyperbranched polyurethane acrylate UV light-curing resin according to claim 1, wherein: The polyol monomer S2 is composed of trimethylolpropane monoallyl ether, dimethylolpropionic acid, trimethylolpropane and pentaerythritol in a molar ratio of (1.4-2):1:(1.8-3):(0.05-0.15).

8. The method for preparing a hyperbranched polyurethane acrylate UV light-curing resin according to claim 1, wherein: The addition ratio of the isocyanate-terminated primary polyurethane prepolymer and the polyol monomer in S2 is n(NCO):n(OH)=2:

1. The method for mixing the polyol monomer and the isocyanate-terminated primary polyurethane prepolymer is as follows: first, trimethylolpropane monoallyl ether and dimethylolpropionic acid are slowly added to the primary polyurethane prepolymer while applying high-energy ultrasound, and the addition / ultrasound time is controlled to be 20-30 minutes, and then trimethylolpropane and pentaerythritol are added; the reaction time after adding the catalyst is 2-4 hours.

9. The method for preparing a hyperbranched polyurethane acrylate UV light-curing resin according to claim 1, wherein The molar ratio of the isocyanate-terminated secondary polyurethane prepolymer to pentaerythritol triacrylate in S3 is 1:(3.1-3.3), and the reaction is terminated when the isocyanate group content of the system reaches 0.

10. The hyperbranched polyurethane acrylate UV light-curing resin obtained by the preparation method according to any one of claims 1 to 9.

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