Acrylate side group-containing waterborne polyurethane and method for preparing the same

Abstract

This invention relates to a waterborne polyurethane containing acrylate side groups and its preparation method. The technical solution involves synthesizing a polyurethane prepolymer by reacting diisocyanate, a polymeric diol, and a carboxyl-containing hydrophilic chain extender under nitrogen protection and mechanical stirring at 60-100°C for 1-10 hours. Then, a compound containing epoxy and acrylate groups is added and reacted under mechanical stirring at 50-100°C for 2-10 hours. After neutralization with a neutralizing agent and emulsification with a dispersant, the waterborne polyurethane containing acrylate side groups is obtained. This invention features widely available raw materials, a simple process, mild reaction conditions suitable for industrial production. The waterborne polyurethane containing acrylate side groups prepared by this method has high solids content, good stability, and can be rapidly cured under ultraviolet light. Its film exhibits high light transmittance, excellent mechanical properties, and good water resistance, showing broad application prospects in optical adhesives, electronic device packaging, and high-performance coatings.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology. Specifically, it relates to a waterborne polyurethane containing acrylate side groups and its preparation method. Background Technology

[0002] Waterborne polyurethane (WPU) uses water as a dispersion medium and has advantages such as being non-toxic, non-flammable, and environmentally friendly. It is widely used in adhesives, coatings, and inks.

[0003] However, traditional waterborne polyurethanes suffer from insufficient mechanical strength and poor water resistance due to their linear molecular structure and lack of crosslinking, limiting their application in high-end fields. To improve these properties, monohydroxy acrylates such as hydroxyethyl acrylate and hydroxyethyl methacrylate are often used as end-capping agents to obtain acrylate-containing waterborne polyurethanes, which can then be cured into films through free radical reactions. However, this method only introduces two acrylate groups at the end of the waterborne polyurethane, resulting in a very low content. The low crosslinking density in the cured material has very limited impact on improving material performance. To increase the acrylate content, acrylate groups can be introduced into the side chains of the waterborne polyurethane. For example, Zhang's research group (Bai CY, Zhang XY, Dai JB, et al. A new UV curable waterborne polyurethane: Effect of CCcontent on the film properties. Progress in Organic Coatings, 2006, 55(3):291-295.) used a synthesized compound containing diacrylate (PEDA) as a chain extender and hydroxyethyl acrylate as a capping agent to simultaneously introduce photosensitive groups into the side chains and ends of polyurethane, and prepared a series of waterborne polyurethanes. They found that the hardness, solvent resistance, thermal stability and tensile strength of the film were improved after photocuring. Shao Wei et al. (Shao Wei. Synthesis, Dual Curing Behavior and Urea Modification Study of Waterborne Photocurable Polyurethane with Side Group Double Bond Structure. Jiangxi: Nanchang Aviation University, 2021.) synthesized prepolymers containing different acrylate side groups and isocyanate ends using HDI trimer, hydroxyethyl acrylate or pentaerythritol triacrylate as raw materials. Then, diol was added for chain extension, and after neutralization and water dispersion, waterborne photocurable polyurethane with side group double bond structure was obtained. The gel content of the cured film reached 85.76%, and the water absorption rate of the film reached 5.3%.

[0004] The inventions and studies above have all produced waterborne polyurethanes containing acrylate side groups. Due to the introduction of acrylate groups, the water resistance and mechanical properties of waterborne polyurethanes have been improved. However, the following problems still exist: (1) The reactants need to be pre-synthesized, the process is complicated, and it is not conducive to large-scale production; (2) The reaction process and the amount of double bond introduction cannot be effectively controlled; (3) The elongation at break of the cured film is low and the material is brittle. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the prior art and provides a waterborne polyurethane with widely available raw materials, simple synthesis process, mild reaction conditions, and easily controllable acrylate group content, as well as its preparation method. The waterborne polyurethane containing acrylate side groups prepared by this method has high solid content, good stability, and can be rapidly cured under ultraviolet light. Its film has high light transmittance, excellent mechanical properties, and good water resistance, and has broad application prospects in optical adhesives, electronic device packaging, and high-performance coatings.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A polyurethane prepolymer was synthesized by reacting diisocyanate, polymeric diol, and a carboxyl-containing hydrophilic chain extender under nitrogen protection and mechanical stirring at 60–100 °C for 1–10 h. Then, a compound containing epoxy and acrylate groups was added and reacted under mechanical stirring at 50–100 °C for 2–10 h. After neutralization with a neutralizing agent and emulsification with a dispersant, an aqueous polyurethane containing acrylate side groups was obtained.

[0008] in:

[0009] The molar ratio of the diisocyanate to the polymeric diol is (2~5):1;

[0010] The molar ratio of the carboxyl-containing hydrophilic chain extender to the polymeric diol is (1~4):1;

[0011] The molar ratio of the compound containing epoxy and acrylate groups to the polymer diol is (0.5~3.5):1;

[0012] The molar ratio of the neutralizing agent to the polymeric diol is (0.1~3.5):1;

[0013] The molar ratio of the dispersant to the polymeric diol is (50~300):1.

[0014] The polymeric diol is one of polytetramethylene ether diol, polycaprolactone diol, and polycarbonate diol.

[0015] The diisocyanate is one of diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

[0016] The hydrophilic chain extender is one of dimethylolpropionic acid and dimethylolbutyric acid.

[0017] The compound containing epoxy and acrylate groups is one of glycidyl acrylate, glycidyl methacrylate, and 2-methyl-2,3-epoxypropyl methacrylate.

[0018] The neutralizing agent is one of triethylamine, sodium hydroxide, and triethanolamine.

[0019] The dispersant is water.

[0020] By adopting the above technical solution, the present invention has the following positive effects compared with the prior art:

[0021] A polyurethane prepolymer is synthesized by reacting diisocyanate, polymeric diol, and a carboxyl-containing hydrophilic chain extender under nitrogen protection with mechanical stirring at 60–100 °C for 1–10 h. Then, compounds containing epoxy and acrylate groups are added and reacted with mechanical stirring at 50–100 °C for 2–10 h. After neutralization with a neutralizing agent and emulsification with a dispersant, an aqueous polyurethane containing acrylate side groups is obtained. This preparation process is simple, the reaction conditions are mild, the cost is low, and it is easy to industrialize.

[0022] The raw materials used in this invention are widely available; by adjusting the raw material feeding ratio, waterborne polyurethanes with different acrylate side group contents can be prepared in order to control the crosslinking density after curing, and the resulting polymer cured film has high light transmittance, excellent mechanical properties and good water resistance.

[0023] The structure of the aqueous polyurethane containing acrylate side groups prepared in this invention was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy analysis. Its solid content can reach 50%, and it has good stability.

[0024] Therefore, this invention has the advantages of wide availability of raw materials, simple synthesis process, mild reaction conditions, easy control of product structure and easy industrial production. The prepared waterborne polyurethane containing acrylate side groups has high solid content and good stability, and can be cured quickly under ultraviolet light. Its film has high light transmittance, excellent mechanical properties and good water resistance, and has broad application prospects in optical adhesives, electronic device packaging and high-performance coatings. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments, but this is not intended to limit the scope of protection thereof.

[0026] Example 1

[0027] A waterborne polyurethane containing acrylate side groups and its preparation method. The preparation steps are as follows:

[0028] A polyurethane prepolymer was synthesized by reacting diisocyanate, polymeric diol, and a carboxyl-containing hydrophilic chain extender under nitrogen protection and mechanical stirring at 60–75 °C for 7–10 h. Then, compounds containing epoxy and acrylate groups were added and reacted under mechanical stirring at 80–100 °C for 2–3 h. After neutralization with a neutralizing agent and emulsification with a dispersant, an aqueous polyurethane containing acrylate side groups was obtained. Wherein:

[0029] The molar ratio of the diisocyanate to the polymeric diol is (4~5):1;

[0030] The molar ratio of the carboxyl-containing hydrophilic chain extender to the polymeric diol is (3~4):1;

[0031] The molar ratio of the compound containing epoxy and acrylate groups to the polymer diol is (2.5~3.5):1;

[0032] The molar ratio of the neutralizing agent to the polymeric diol is (0.1~3.5):1;

[0033] The molar ratio of the dispersant to the polymeric diol is (50~100):1.

[0034] In this embodiment:

[0035] The polymeric diol is polycaprolactone diol.

[0036] The diisocyanate mentioned is diphenylmethane diisocyanate.

[0037] The carboxyl-containing hydrophilic chain extender is dimethylolpropionic acid.

[0038] The compound containing epoxy and acrylate groups is glycidyl acrylate.

[0039] The neutralizing agent is triethylamine.

[0040] The dispersant is water.

[0041] Example 2

[0042] A waterborne polyurethane containing acrylate side groups and its preparation method. The preparation steps are as follows:

[0043] A polyurethane prepolymer was synthesized by reacting diisocyanate, polymeric diol, and a carboxyl-containing hydrophilic chain extender under nitrogen protection and mechanical stirring at 75–85°C for 5–7 h. Then, compounds containing epoxy and acrylate groups were added and reacted under mechanical stirring at 70–80°C for 3–5 h. After neutralization with a neutralizing agent and emulsification with a dispersant, an aqueous polyurethane containing acrylate side groups was obtained. Wherein:

[0044] The molar ratio of the diisocyanate to the polymeric diol is (3~4):1;

[0045] The molar ratio of the carboxyl-containing hydrophilic chain extender to the polymeric diol is (2~3):1;

[0046] The molar ratio of the compound containing epoxy and acrylate groups to the polymer diol is (1.5~2.5):1;

[0047] The molar ratio of the neutralizing agent to the polymeric diol is (1.5~2.5):1;

[0048] The molar ratio of the dispersant to the polymeric diol is (100~200):1.

[0049] In this embodiment:

[0050] The polymer diol is polytetramethylene ether diol.

[0051] The diisocyanate mentioned is hexamethylene diisocyanate.

[0052] The carboxyl-containing hydrophilic chain extender is dihydroxymethylbutyric acid.

[0053] The compound containing epoxy and acrylate groups is glycidyl methacrylate.

[0054] The neutralizing agent is triethanolamine.

[0055] The dispersant is water.

[0056] Example 3

[0057] A waterborne polyurethane containing acrylate side groups and its preparation method. The preparation steps are as follows:

[0058] A polyurethane prepolymer was synthesized by reacting diisocyanate, polymeric diol, and a carboxyl-containing hydrophilic chain extender under nitrogen protection and mechanical stirring at 85-90°C for 3-5 h. Then, compounds containing epoxy and acrylate groups were added and reacted under mechanical stirring at 60-70°C for 5-7 h. After neutralization with a neutralizing agent and emulsification with a dispersant, an aqueous polyurethane containing acrylate side groups was obtained. Wherein:

[0059] The molar ratio of the diisocyanate to the polymeric diol is (2.5~3):1;

[0060] The molar ratio of the carboxyl-containing hydrophilic chain extender to the polymeric diol is (1.5~2):1;

[0061] The molar ratio of the compound containing epoxy and acrylate groups to the polymeric diol is (1~1.5):1;

[0062] The molar ratio of the neutralizing agent to the polymeric diol is (1~1.5):1;

[0063] The molar ratio of the dispersant to the polymeric diol is (200~250):1.

[0064] In this embodiment:

[0065] The polymer diol is polycarbonate diol.

[0066] The diisocyanate mentioned isophorone diisocyanate.

[0067] The carboxyl-containing hydrophilic chain extender is dihydroxymethylbutyric acid.

[0068] The compound containing epoxy and acrylate groups is 2-methyl-2,3-epoxypropyl methacrylate.

[0069] The neutralizing agent is sodium hydroxide.

[0070] The dispersant is water.

[0071] Example 4

[0072] A waterborne polyurethane containing acrylate side groups and its preparation method. The preparation steps are as follows:

[0073] A polyurethane prepolymer was synthesized by reacting diisocyanate, polymeric diol, and a carboxyl-containing hydrophilic chain extender under nitrogen protection with mechanical stirring at 90–100 °C for 1–3 h. Then, compounds containing epoxy and acrylate groups were added and reacted with mechanical stirring at 50–60 °C for 7–10 h. After neutralization with a neutralizing agent and emulsification with a dispersant, an aqueous polyurethane containing acrylate side groups was obtained. Wherein:

[0074] The molar ratio of the diisocyanate to the polymeric diol is (2~2.5):1;

[0075] The molar ratio of the carboxyl-containing hydrophilic chain extender to the polymeric diol is (1~1.5):1;

[0076] The molar ratio of the compound containing epoxy and acrylate groups to the polymer diol is (0.5~1):1;

[0077] The molar ratio of the neutralizing agent to the polymeric diol is (0.1~1):1;

[0078] The molar ratio of the dispersant to the polymeric diol is (250~300):1.

[0079] In this embodiment:

[0080] The polymeric diol is polycaprolactone diol.

[0081] The diisocyanate mentioned is toluene diisocyanate.

[0082] The carboxyl-containing hydrophilic chain extender is dihydroxymethylbutyric acid.

[0083] The compound containing epoxy and acrylate groups is glycidyl acrylate.

[0084] The neutralizing agent is triethanolamine.

[0085] The dispersant is water.

Claims

1. A waterborne polyurethane containing acrylate side groups and its preparation method, characterized in that... The preparation method is as follows: A polyurethane prepolymer was synthesized by reacting diisocyanate, polymeric diol, and a carboxyl-containing hydrophilic chain extender under nitrogen protection with mechanical stirring at 60–100 °C for 1–10 h. Then, compounds containing epoxy and acrylate groups were added and reacted with mechanical stirring at 50–100 °C for 2–10 h. After neutralization with a neutralizing agent and emulsification with a dispersant, an aqueous polyurethane containing acrylate side groups was obtained. Wherein: The molar ratio of the diisocyanate to the polymeric diol is (2~5):1; The molar ratio of the carboxyl-containing hydrophilic chain extender to the polymeric diol is (1~4):1; The molar ratio of the compound containing epoxy and acrylate groups to the polymer diol is (0.5~3.5):1; The molar ratio of the neutralizing agent to the polymeric diol is (0.1~3.5):1; The molar ratio of the dispersant to the polymeric diol is (50~300):

1.

2. The aqueous polyurethane containing acrylate side groups according to claim 1 and its preparation method, characterized in that... The polymeric diol is one of polytetramethylene ether diol, polycaprolactone diol, and polycarbonate diol.

3. The aqueous polyurethane containing acrylate side groups according to claim 1 and its preparation method, characterized in that... The diisocyanate is one of diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

4. The aqueous polyurethane containing acrylate side groups according to claim 1 and its preparation method, characterized in that... The carboxyl-containing hydrophilic chain extender is one of dimethylolpropionic acid and dimethylolbutyric acid.

5. The aqueous polyurethane containing acrylate side groups according to claim 1 and its preparation method, characterized in that... The compound containing epoxy and acrylate groups is one of glycidyl acrylate, glycidyl methacrylate, and 2-methyl-2,3-epoxypropyl methacrylate.

6. The aqueous polyurethane containing acrylate side groups according to claim 1 and its preparation method, characterized in that... The neutralizing agent is one of triethylamine, sodium hydroxide, and triethanolamine.

7. The aqueous polyurethane containing acrylate side groups according to claim 1 and its preparation method, characterized in that... The dispersant is water.

8. A waterborne polyurethane containing acrylate side groups, characterized in that... The waterborne polyurethane containing acrylate side groups is the waterborne polyurethane containing acrylate side groups prepared by any one of claims 1 to 7 and the preparation method thereof.