A polyurethane microsphere emulsion and its preparation method

Abstract

The present application discloses a polyurethane microsphere emulsion and a preparation method thereof, belonging to the field of coatings. A polyurethane microsphere emulsion comprises the following raw materials for preparation by weight percentage: 15% - 40% of an aqueous polyurethane resin; 10% - 35% of an acrylate monomer containing multiple carbon-carbon double bonds; 1% - 2% of a photosensitizer; the balance being water; the aqueous polyurethane resin is prepared from the following raw materials by weight percentage: 50% - 65% of a diisocyanate; 20% - 40% of a diol; 5% - 10% of a hydrophilic chain extender; 4.5% - 12.5% of an acrylate monomer containing a hydroxyl group and multiple carbon-carbon double bonds; 0.1% - 0.5% of a catalyst. The present application has the advantages of synthesizing polyurethane microspheres and polyurethane microsphere emulsions with a narrow particle size distribution, good stability and good mechanical properties.

Description

Technical Field

[0001] The present application relates to the field of coatings, and in particular to a polyurethane microsphere emulsion and a preparation method thereof. Background Art

[0002] Polyurethane microspheres contain polar groups such as urethane, porosity, and microphase separation structures. Polyurethane microspheres have been widely used in fields such as coatings and inks, and have functions of improving hand feeling, hardening, and anti-sticking.

[0003] Common synthesis methods of polyurethane microspheres include suspension method, inverse suspension method, grinding method, and self-emulsification method, etc. The suspension method and the inverse suspension method belong to mechanical forced dispersion, which forcibly disperses the urethane component in an incompatible medium for polymerization reaction. After completion, filtration, washing, and drying are carried out to obtain polyurethane microspheres. Such synthesis methods are relatively simple and efficient, and the particle size can be easily controlled by the shear rate. However, limited by the shear rate, only microspheres with larger particle sizes can be prepared, and the particle size distribution is not easy to control. The grinding method is to crush and then grind the already polymerized polyurethane resin to make it into microspheres, which is relatively simple and efficient and does not require complex post-treatment, but the prepared microspheres are irregularly spherical, with larger particle sizes and wider distributions. The self-emulsification method can directly disperse in water to form microspheres by introducing hydrophilic groups into the polyurethane chain segment, solving the problems of wide particle size distribution and large particle size of the previous methods. However, due to the introduction of hydrophilic groups and some diols, the hydrophilicity of the polyurethane microspheres is increased, the cross-linking density and solvent resistance of the microspheres are reduced, and the mechanical properties such as wear resistance of the microspheres are weakened, limiting the application of polyurethane microspheres. Therefore, it is still difficult to synthesize polyurethane microspheres and polyurethane microsphere emulsions with narrow particle size distribution, good stability, and good mechanical properties. Summary of the Invention

[0004] In order to synthesize polyurethane microspheres and polyurethane microsphere emulsions with narrow particle size distribution, good stability, and good mechanical properties, the present application provides a polyurethane microsphere emulsion and a preparation method thereof.

[0005] In a first aspect, a polyurethane microsphere emulsion provided by the present application adopts the following technical solution:

[0006] A polyurethane microsphere emulsion, comprising the following preparation raw materials in weight percentages:

[0007] Waterborne polyurethane resin 15%-40%;

[0008] Acrylate monomer containing multiple carbon-carbon double bonds 10%-35%;

[0009] Photosensitizer 1%-2%;

[0010] The balance is water;

[0011] The aqueous polyurethane resin is prepared from the following raw materials in weight percentages:

[0012] Diisocyanate 50%-65%;

[0013] Diol 20%-40%;

[0014] Hydrophilic chain extender 5%-10%;

[0015] Acrylate monomer containing hydroxyl group and multiple carbon-carbon double bonds 4.5%-12.5%;

[0016] Catalyst 0.1%-0.5%;

[0017] The diisocyanate includes a diisocyanate containing an alkyl group with a carbon atom number ≥ 12, where the carbon atom number is the carbon atom number of R in the OCN-R-NCO structure;

[0018] The diol contains a structural unit of -C6H 12±2 -.

[0019] By adopting the above technical solution, the aqueous polyurethane resin is first synthesized, and then polyurethane microspheres are prepared by using the good dispersibility of the aqueous polyurethane resin in water, so that the dispersibility of the polyurethane microspheres is better, the particle size distribution is narrow, and finally a polyurethane microsphere emulsion that does not form a film is obtained.

[0020] The raw materials for preparing the aqueous polyurethane resin contain an acrylate monomer containing a hydroxyl group and multiple carbon-carbon double bonds, so that the acrylate monomer is doped after the synthesis of the aqueous polyurethane resin. Therefore, during the preparation of the polyurethane microsphere emulsion, the acrylate monomer containing multiple carbon-carbon double bonds and the acrylate monomer containing a hydroxyl group and multiple carbon-carbon double bonds are fully polymerized, which strengthens the polyurethane microspheres, improves the crosslinking density, and improves the mechanical properties such as the wear resistance of the polyurethane microspheres.

[0021] By using the above specific diisocyanate and diol in combination, the prepared aqueous polyurethane has a good emulsifying effect, can replace the conventional emulsifier to emulsify the acrylate monomer, so that no additional emulsifier needs to be added, the soap-free condition is achieved, and it has excellent long-term stability and thermal storage stability after polymerization, effectively avoiding stratification and demulsification.

[0022] Optionally, the structural unit of -C6H 12±2 - includes the structural unit of -C6H 10 -, the structural unit of -C6H 12 -, and the structural unit of -C6H 14 -.

[0023] -C6H 12±2 - is the structural unit between two hydroxyl groups in the diol.

[0024] Optionally, the average molecular weight of the diol is 500 to 1000.

[0025] By adopting the above technical solution, the average molecular weight of the diol falls within the above range, which helps to exert the cooperative effect of the diol and the diisocyanate, plays the role of replacing the conventional emulsifier to emulsify the acrylate monomer, realizes the improvement of the stability of the polyurethane microsphere emulsion, and makes the prepared microspheres have excellent light extinction effect, which is suitable for specific application scenarios of topcoats.

[0026] Optionally, the diol comprises one or more of polycarbonate diol, vegetable oil-based diol and polycaprolactone diol.

[0027] By adopting the above technical solution, using the above type of diol that satisfies the -C6H 12±2 - structural unit, the dispersion of the polyurethane microspheres is better and the particle size distribution is narrower.

[0028] Optionally, the polycarbonate diol is selected from one or more of PH-50, PH-100, UP-50 and UP-100 of Ube, Japan, or one or more of T5650E, T5650J and T5651 of Asahi Kasei, Japan.

[0029] Optionally, the vegetable oil-based diol is selected from one or two of castor oil-modified diol and cashew shell oil bio-based diol.

[0030] Optionally, the polycaprolactone diol is selected from PCL 305 of Daicel, Japan.

[0031] Optionally, the diisocyanate of an alkyl group with carbon atoms ≥ 12 accounts for ≥ 10% in the total mass of the diisocyanate.

[0032] By adopting the above technical solution, the required dosage of the specific diisocyanate is small. It can not only add other types of diisocyanates to save costs, but also combine other types of diisocyanates to obtain better performance and meet the stability requirements of the emulsion.

[0033] Optionally, the diisocyanate comprises one or two of 4,4'-dicyclohexylmethane diisocyanate and dimer fatty acid diisocyanate.

[0034] The dimer fatty acid diisocyanate contains 36 carbon atoms.

[0035] By adopting the above technical solution, the above type of diisocyanate can meet the requirement of an alkyl group with carbon atoms ≥ 12 and realize stable and soap-free functions with a specific diol.

[0036] Optionally, the acrylate monomer containing multiple carbon-carbon double bonds is an acrylate monomer containing at least four carbon-carbon double bonds.

[0037] By adopting the above technical solution, the acrylate monomer containing at least four carbon-carbon double bonds plays a role in promoting crosslinking, increasing the crosslinking density of the polyurethane microspheres. At the same time, a crosslinked protective layer is formed by the acrylate to improve the high-temperature resistance and solvent resistance.

[0038] In addition, generally speaking, when the acrylate monomer containing at least four unsaturated double bonds crosslinks and polymerizes in the polyurethane emulsion, it is easy to form precipitation or even slag. However, in this application, with the cooperation of specific diisocyanates and diols, it is possible to achieve the stability of the acrylate monomer containing at least four unsaturated double bonds during emulsion polymerization, promote the formation of polyurethane microspheres, and the obtained polyurethane microspheres can be stably dispersed in water.

[0039] Optionally, the acrylate monomer containing multiple carbon-carbon double bonds is selected from one or more of pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, bis-trimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate.

[0040] Optionally, the acrylate monomer containing hydroxyl and multiple carbon-carbon double bonds is selected from one or more of pentaerythritol triacrylate, pentaerythritol three-four acrylate, pentaerythritol dimethacrylate, and pentaerythritol diacrylate monostearate.

[0041] By adopting the above technical solution, the above types of unsaturated acrylate monomers all contain hydroxyl groups, which can react and combine with diisocyanates during the synthesis of the aqueous polyurethane resin, thereby improving the doping stability of the unsaturated acrylate monomer in the aqueous polyurethane resin and further enhancing the abrasion resistance of the polyurethane microsphere emulsion.

[0042] Generally speaking, pentaerythritol three-four acrylate contains pentaerythritol triacrylate and pentaerythritol tetraacrylate, and the mass ratio of pentaerythritol triacrylate to pentaerythritol tetraacrylate is 1:1.

[0043] Optionally, the hydrophilic chain extender is selected from one or two of dihydroxy acids and dihydroxyamines.

[0044] Optionally, the catalyst is a tin catalyst.

[0045] In the second aspect, a preparation method of a polyurethane microsphere emulsion provided by this application adopts the following technical solution:

[0046] A preparation method of a polyurethane microsphere emulsion includes the following steps:

[0047] Preparation of aqueous polyurethane resin: Diisocyanate, diol, hydrophilic chain extender, acrylate monomer containing hydroxyl group and multiple carbon-carbon double bonds, and catalyst are mixed and heated at 75-95 °C for reaction. After the reaction, aqueous polyurethane resin is obtained;

[0048] Preparation of aqueous polyurethane microsphere emulsion precursor: The aqueous polyurethane resin, acrylate monomer containing multiple carbon-carbon double bonds, photosensitizer and water are stirred and mixed to obtain an aqueous polyurethane microsphere emulsion precursor;

[0049] Preparation of polyurethane microsphere emulsion: The aqueous polyurethane microsphere emulsion precursor is polymerized by photoinitiation to obtain a polyurethane microsphere emulsion.

[0050] By adopting the above technical solution, aqueous polyurethane resin is first synthesized and then polyurethane microsphere emulsion is prepared, which improves the dispersion of polyurethane microspheres. Moreover, through the cooperation of specific diisocyanate and diol, the dispersion of acrylate monomer containing hydroxyl group and multiple carbon-carbon double bonds is improved, so that the raw materials for preparing aqueous polyurethane resin can complete the reaction at one time, saving processes and improving production efficiency.

[0051] Optionally, in the step of preparing the aqueous polyurethane microsphere emulsion precursor, a pH regulator is also added.

[0052] By adopting the above technical solution, the pH regulator can adjust the pH of the reaction system, thereby obtaining a more stable dispersion system.

[0053] Optionally, the pH regulator is triethylamine.

[0054] In summary, the present application has the following beneficial effects:

[0055] 1. By combining aqueous polyurethane with acrylate to form a polyurethane microsphere precursor, and then realizing crosslinking, the dispersion of polyurethane microspheres is better, the particle size distribution is narrow, the acrylate monomer containing multiple carbon-carbon double bonds and the acrylate monomer containing hydroxyl group and multiple carbon-carbon double bonds are fully polymerized, which has a reinforcing effect on polyurethane microspheres, improves the crosslinking density, and improves the mechanical properties such as wear resistance of polyurethane microspheres.

[0056] 2. By using a specific diisocyanate in combination with a diol, the prepared aqueous polyurethane has a good emulsifying effect, can replace conventional emulsifiers to emulsify acrylate monomers, so that no additional emulsifier needs to be added, achieving a soap-free condition, and has excellent long-term stability and thermal storage stability after polymerization, effectively avoiding stratification and demulsification. Detailed Embodiments

[0057] The following further details the present application.

[0058] Example 1

[0059] Preparation of aqueous polyurethane resin:

[0060] Weigh 50 g of diisocyanate, 40 g of diol, 5 g of hydrophilic chain extender, 4.5 g of acrylate monomer containing hydroxyl group and multiple carbon-carbon double bonds, and 0.5 g of catalyst. Among them, the diisocyanate is specifically composed of 4,4'-dicyclohexylmethane diisocyanate and hexamethylene diisocyanate, and the proportion of 4,4'-dicyclohexylmethane diisocyanate in the total mass of the diisocyanate is 50%; the diol is specifically polycarbonate diol, PH-50 from Ube Industries, Japan, with an average molecular weight of 500; the hydrophilic chain extender is specifically dimethylolbutanoic acid; the acrylate monomer containing hydroxyl group and multiple carbon-carbon double bonds is specifically pentaerythritol triacrylate; the catalyst is specifically dibutyltin dilaurate.

[0061] Add the diisocyanate, diol, hydrophilic chain extender, acrylate monomer containing hydroxyl group and multiple carbon-carbon double bonds, and catalyst into the reaction kettle at one time, heat up to 95 °C, react for 8 h, discharge and package for standby to obtain the aqueous polyurethane resin.

[0062] Preparation of precursor of aqueous polyurethane microsphere emulsion:

[0063] Weigh 15 g of the aqueous polyurethane resin prepared in the previous step, 20 g of acrylate monomer containing multiple carbon-carbon double bonds, 2 g of pH regulator, 2 g of photosensitizer, and 61 g of water. Among them, the acrylate monomer containing multiple carbon-carbon double bonds is specifically bis(trimethylolpropane) tetraacrylate; the pH regulator is specifically triethylamine; the photosensitizer is specifically photosensitizer 184.

[0064] Stir and mix the aqueous polyurethane resin, acrylate monomer containing multiple carbon-carbon double bonds, photosensitizer and water, and shear at a rate of 2000 rpm for 30 min to obtain the precursor of aqueous polyurethane microsphere emulsion.

[0065] Preparation of polyurethane microsphere emulsion:

[0066] Put the precursor of aqueous polyurethane microsphere emulsion obtained in the previous step into a glass tube, irradiate it under an 800 mJ ultraviolet lamp for 5 min, and take it out to obtain the polyurethane microsphere emulsion.

[0067] Example 2

[0068] Weigh 65 g of diisocyanate, 23 g of diol, 5.9 g of hydrophilic chain extender, 6 g of acrylate monomer containing hydroxyl group and multiple carbon-carbon double bonds, and 0.1 g of catalyst. Among them, the diisocyanate is specifically composed of 4,4'-dicyclohexylmethane diisocyanate and hexamethylene diisocyanate, and the proportion of 4,4'-dicyclohexylmethane diisocyanate in the total mass of the diisocyanate is 10%; the diol is specifically polycarbonate diol, PH-100 from Ube, Japan, with an average molecular weight of 1000; the hydrophilic chain extender is specifically dimethylolpropionic acid; the acrylate monomer containing hydroxyl group and multiple carbon-carbon double bonds is specifically pentaerythritol triacrylate and tetraacrylate; the catalyst is specifically dibutyltin dilaurate.

[0069] Add the diisocyanate, diol, hydrophilic chain extender, acrylate monomer containing hydroxyl group and multiple carbon-carbon double bonds, and catalyst into the reaction kettle at one time, heat up to 75 °C, react for 8 h, discharge and package for standby to obtain the aqueous polyurethane resin.

[0070] Prepare the precursor of the aqueous polyurethane microsphere emulsion:

[0071] Weigh 20 g of the aqueous polyurethane resin prepared in the previous step, 30 g of acrylate monomer containing multiple carbon-carbon double bonds, 3 g of pH regulator, 1 g of photosensitizer, and 41 g of water. Among them, the acrylate monomer containing multiple carbon-carbon double bonds is specifically pentaerythritol tetraacrylate; the pH regulator is specifically triethylamine; the photosensitizer is specifically photosensitizer 184.

[0072] Stir and mix the aqueous polyurethane resin, acrylate monomer containing multiple carbon-carbon double bonds, photosensitizer and water, and shear at a rate of 2000 rpm for 30 min to obtain the precursor of the aqueous polyurethane microsphere emulsion.

[0073] Prepare the polyurethane microsphere emulsion:

[0074] Put the precursor of the aqueous polyurethane microsphere emulsion obtained in the previous step into a glass tube, irradiate it under an 800 mJ ultraviolet lamp for 5 min, and take it out to obtain the polyurethane microsphere emulsion.

[0075] Example 3

[0076] Prepare the aqueous polyurethane resin:

[0077] Weigh 57 g of diisocyanate, 20 g of diol, 10 g of hydrophilic chain extender, 12.5 g of acrylate monomer containing hydroxyl group and multiple carbon-carbon double bonds, and 0.5 g of catalyst. Among them, the diisocyanate is specifically 4,4'-dicyclohexylmethane diisocyanate; the diol is specifically polycarbonate diol, PH-50 from Ube, Japan, with an average molecular weight of 500; the hydrophilic chain extender is specifically dimethylolbutanoic acid; the acrylate monomer containing hydroxyl group and multiple carbon-carbon double bonds is specifically pentaerythritol triacrylate; the catalyst is specifically dibutyltin dilaurate.

[0078] Add the diisocyanate, diol, hydrophilic chain extender, acrylate monomer containing hydroxyl group and multiple carbon-carbon double bonds, and catalyst into the reaction kettle at one time, heat up to 85 °C, react for 8 h, discharge and package for standby to obtain the aqueous polyurethane resin.

[0079] Prepare the precursor of the aqueous polyurethane microsphere emulsion:

[0080] Weigh 35 g of the aqueous polyurethane resin prepared in the previous step, 10 g of acrylate monomer containing multiple carbon-carbon double bonds, 3.5 g of pH regulator, 1.5 g of photosensitizer, and 50 g of water. Among them, the acrylate monomer containing multiple carbon-carbon double bonds is specifically bis(trimethylolpropane) tetraacrylate; the pH regulator is specifically triethylamine; the photosensitizer is specifically photosensitizer 184.

[0081] Stir and mix the aqueous polyurethane resin, acrylate monomer containing multiple carbon-carbon double bonds, photosensitizer and water, and shear at a rate of 2000 rpm for 30 min to obtain the precursor of the aqueous polyurethane microsphere emulsion.

[0082] Prepare the polyurethane microsphere emulsion:

[0083] Put the precursor of the aqueous polyurethane microsphere emulsion obtained in the previous step into a glass tube, irradiate it under an 800 mJ ultraviolet lamp for 5 min, and take it out to obtain the polyurethane microsphere emulsion.

[0084] Example 4

[0085] The difference between this example and Example 1 is that in the step of preparing the aqueous polyurethane resin, 4,4'-dicyclohexylmethane diisocyanate is replaced with an equal amount of dimer fatty acid diisocyanate, that is, the diisocyanate is specifically composed of dimer fatty acid diisocyanate and hexamethylene diisocyanate, and the proportion of dimer fatty acid diisocyanate in the total mass of the diisocyanate is 50%.

[0086] Example 5

[0087] The difference between this example and Example 1 lies in that in the step of preparing the aqueous polyurethane resin, the polycarbonate diol is replaced by castor oil-modified diol with a hydroxyl value of 140, an equivalent weight of 400, and a grade of C-140, that is, the diol is specifically castor oil-modified diol.

[0088] Comparative Example 1

[0089] The difference between this comparative example and Example 1 lies in that in the step of preparing the aqueous polyurethane resin, the polycarbonate diol is replaced by polybutylene glycol with an average molecular weight of 500, that is, the diol is specifically polybutylene glycol.

[0090] Comparative Example 2

[0091] The difference between this comparative example and Example 1 lies in that in the step of preparing the aqueous polyurethane resin, 4,4'-dicyclohexylmethane diisocyanate is replaced with an equal amount of hexamethylene diisocyanate, that is, the diisocyanate is specifically composed of hexamethylene diisocyanate.

[0092] Comparative Example 3

[0093] The difference between this comparative example and Example 1 lies in that in the step of preparing the aqueous polyurethane resin, trimethylolpropane triacrylate is replaced with an equal amount of 2-hydroxyethyl acrylate.

[0094] Comparative Example 4

[0095] The difference between this comparative example and Example 1 lies in that in the step of preparing the aqueous polyurethane resin, trimethylolpropane triacrylate is replaced with an equal amount of ethyl acrylate.

[0096] Comparative Example 5

[0097] The difference between this comparative example and Example 1 lies in that in the step of preparing the aqueous polyurethane microsphere emulsion precursor, ditrimethylolpropane tetraacrylate is replaced with an equal amount of ethyl acrylate.

[0098] Comparative Example 6

[0099] The difference between this comparative example and Example 1 lies in that in the step of preparing the aqueous polyurethane resin, the acrylate monomer containing hydroxyl and multiple carbon-carbon double bonds is not added; instead, in the step of preparing the aqueous polyurethane microsphere emulsion precursor, 4.5 g of the acrylate monomer containing hydroxyl and multiple carbon-carbon double bonds is added, and the acrylate monomer containing hydroxyl and multiple carbon-carbon double bonds is specifically trimethylolpropane triacrylate.

[0100] Performance Testing

[0101] Microsphere particle size distribution test: The particle size distribution of the polyurethane microsphere emulsion was tested using an emulsion particle size analyzer to obtain the dispersibility, and the results are shown in Table 1.

[0102] Storage stability test: The polyurethane microsphere emulsion was stored in a sealed manner at a storage temperature of 60 ± 1 °C. After 7 days of storage, it was observed whether the polyurethane microsphere emulsion showed stratification or demulsification. The results are shown in Table 1.

[0103] Heat resistance stability test: The polyurethane microsphere emulsion was dried at 120 °C, and it was observed whether the microspheres adhered to each other.

[0104] Solvent resistance test: The polyurethane microsphere emulsion was dried at 120 °C to obtain dried microspheres. The microspheres were separately dispersed in toluene, acetone, and ethyl acetate to obtain dispersed emulsions. It was observed whether the microspheres showed dissolution and swelling. Then, the dispersed emulsions were dried at 120 °C, and the state after drying was observed.

[0105] Application detection

[0106] Take a commercially available polyurethane emulsion used for industrial paints. The polyurethane microsphere emulsions prepared in each example and comparative example were added to the polyurethane emulsion to obtain a new polyurethane emulsion. The mass ratio of the polyurethane microsphere emulsion in the polyurethane emulsion was 10%. Then, the new polyurethane emulsion was coated on a PC board and dried at 60 °C for 15 min to obtain a paint film. The film-forming thickness was 15 μm. The following properties were tested, and the properties of the original polyurethane emulsion, that is, the polyurethane emulsion without adding the polyurethane microsphere emulsion, were compared.

[0107] Matting test: The glossiness of the paint film was measured using a glossiness meter with an incident angle of 60°. The results are shown in Table 2. The glossiness of the paint film made from the original polyurethane emulsion was 90%. The smaller the glossiness of the paint film made from the new polyurethane emulsion, the better the matting effect.

[0108] Abrasion resistance test: The abrasion resistance of the paint film was tested using an RCA paper tape abrasion tester with a load of 175 g. The number of times the paper tape rubbed when the paint film showed wear was recorded. The results are shown in Table 2. The number of friction times of the paint film made from the original polyurethane emulsion was 3 times. The more the number of friction times of the paint film made from the new polyurethane emulsion, the better the abrasion resistance.

[0109] Table 1

[0110]

[0111]

[0112] Table 2

[0113] Glossiness Number of friction times Example 1 20％ 10 Example 2 24％ 9 Example 3 25％ 10 Example 4 24％ 11 Example 5 22％ 10 Comparative Example 1 68％ 3 Comparative Example 2 34％ 5 Comparative Example 3 25％ 5 Comparative Example 4 38％ 4 Comparative Example 5 22％ 5 Comparative Example 6 32％ 5

[0114] As can be seen from Table 1, the polyurethane microsphere emulsions prepared in Examples 1-5 have the advantages of good stability, high temperature resistance and solvent resistance, and the dispersity δ of the particle size distribution is <0.1, showing monodispersity. By comparing with Comparative Examples 1-6, it can be known that the above advantages are inseparable from the combination of a diisocyanate containing a specific number of carbon atoms and a diol with a specific structural unit, so that an emulsifier can be replaced to obtain a soap-free emulsion with stable dispersion. In addition, two acrylate monomers containing multiple carbon-carbon double bonds are successively combined with the polyurethane, and the crosslinking of the two acrylate monomers increases the crosslinking density of the polyurethane microspheres, improving the structural stability of the polyurethane microspheres, thereby balancing the stability of the microsphere emulsion and the high temperature and solvent resistance of the microspheres.

[0115] As can be seen from Table 2, when the polyurethane microsphere emulsions prepared in Examples 1-5 are applied to industrial paints, they can improve the wear resistance of the industrial paint film and achieve a matting effect, which can meet the requirements of matte films. By comparing with the applications of the polyurethane microsphere emulsions in Comparative Examples 1-6, it can be known that the crosslinking of two acrylate monomers containing multiple carbon-carbon double bonds increases the crosslinking density of the polyurethane microspheres, enhancing the hardness and wear resistance of the polyurethane microspheres, thereby improving the wear resistance of industrial paints; and the combination of a diisocyanate containing a specific number of carbon atoms and a diol with a specific structural unit stabilizes the polyurethane microsphere emulsion, so that the stability of the polyurethane microspheres in industrial paints is also guaranteed, giving full play to their contribution to the wear resistance of the film.

[0116] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications without creative contributions to this specific embodiment as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A polyurethane microsphere emulsion, characterized in that: The preparation raw materials include the following weight percentages: Waterborne polyurethane resin: 15% - 35%; Acrylate monomer containing multiple carbon-carbon double bonds: 10% - 30%; Photosensitizer: 1% - 2%; The balance is water; The waterborne polyurethane resin is prepared from the following raw materials in weight percentages: Diisocyanate: 50% - 65%; Diol: 20% - 40%; Hydrophilic chain extender: 5% - 10%; Acrylate monomer containing hydroxyl group and multiple carbon-carbon double bonds: 4.5% - 12.5%; Catalyst: 0.1% - 0.5%; The diisocyanate includes one or two of 4,4'-dicyclohexylmethane diisocyanate and dimer fatty acid diisocyanate; The acrylate monomer containing multiple carbon-carbon double bonds is selected from one or more of pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, bis-trimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate; The acrylate monomer containing hydroxyl group and multiple carbon-carbon double bonds is selected from one or more of pentaerythritol triacrylate, pentaerythritol three-four acrylate, pentaerythritol dimethacrylate, and pentaerythritol diacrylate monostearate; The pentaerythritol three-four acrylate includes pentaerythritol triacrylate and pentaerythritol tetraacrylate, and the mass ratio of pentaerythritol triacrylate to pentaerythritol tetraacrylate is 1:1; The average molecular weight of the diol is 500 - 1000; The diol includes one or more of polycarbonate diol, vegetable oil-based diol, and polycaprolactone diol; 2. The polyurethane microsphere emulsion according to claim 1, wherein: The hydrophilic chain extender is selected from one or two of dihydroxy acid and dihydroxy amine; 3. A method for preparing a polyurethane microsphere emulsion according to any one of claims 1-2, characterized in that: It includes the following steps: Prepare waterborne polyurethane resin: Mix and heat the diisocyanate, diol, hydrophilic chain extender, acrylate monomer containing hydroxyl group and multiple carbon-carbon double bonds, and catalyst at 75 - 95°C for reaction, and obtain waterborne polyurethane resin after the reaction ends; Prepare the precursor of waterborne polyurethane microsphere emulsion: Stir and mix the waterborne polyurethane resin, acrylate monomer containing multiple carbon-carbon double bonds, photosensitizer, and water to obtain the precursor of waterborne polyurethane microsphere emulsion; Prepare polyurethane microsphere emulsion: The precursor of waterborne polyurethane microsphere emulsion is polymerized by light irradiation to obtain polyurethane microsphere emulsion.

4. The preparation method of a polyurethane microsphere emulsion according to claim 3, characterized in that: In the step of preparing the precursor of waterborne polyurethane microsphere emulsion, a pH regulator is also added.

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