Aqueous polyurethane microspheres, and methods and applications thereof

Abstract

The application discloses a kind of water-based polyurethane microspheres and its preparation method and application, preparation method includes: in the reaction kettle is added 100g solid content 5~15% water-based polyurethane emulsion, under the condition of mechanical stirring, 2~15mL / min droping speed is added 2~15mL concentration 0.1~0.6mol / L calcium chloride solution to reaction system, until water-based polyurethane changes from emulsion state to suspension state, obtain water-based polyurethane microspheres suspension;The water-based polyurethane microspheres suspension prepared above is carried out spray drying to obtain powdery, water-based polyurethane microspheres with matting property;The water-based polyurethane microspheres of the application are prepared by coordination coacervation method, there is no harmful substance such as any organic solvent added in the whole preparation process, can meet the requirement of green environmental protection, the water-based polyurethane microspheres prepared have good light scattering characteristics due to the concave-convex gully structure on surface, have excellent matting effect when applied to leather surface matting coating.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology, and relates to matte polyurethane coatings, specifically to an aqueous polyurethane microsphere, its preparation method, and its application. Background Technology

[0002] In recent years, with the development of aesthetic preferences and safety considerations, the demand for matte polyurethane coatings in automotive interiors and home decoration has been increasing. Existing water-based matte surface treatment processes for leather typically use inorganic matting powders or organic polymer microsphere matting powders as the matting component. Inorganic matting powders have poor compatibility with the coating, leading to problems such as whitening upon stretching and folding, and easy peeling. Furthermore, due to their numerous pores, the refractive index of the matting component differs significantly from that of the coating itself, resulting in low color purity in the coating.

[0003] Chinese patent CN113845642 discloses the preparation and application of polyurea matting microspheres with light scattering properties. Compared with inorganic matting powder, organic microspheres with polyurea components can significantly improve their compatibility with waterborne polyurethane. The particle size and surface roughness of polyurea microspheres can be controlled by adjusting the amount of hydrophilic monomer, solvent ratio, monomer amount, SiO2 amount and addition method, which can meet different matting requirements. However, the preparation process of this method is complicated, requires high-end equipment, and is costly. In addition, the use of organic solvents to adjust the viscosity of the system during the preparation process generates certain pollution. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a waterborne polyurethane microsphere, its preparation method, and its application. This microsphere provides excellent matting effect when used as a matting coating on leather surfaces, and its adjustable particle size can meet different matting requirements. The preparation process is simple, green, and environmentally friendly.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A method for preparing waterborne polyurethane microspheres includes the following steps:

[0007] Step 1: Add 100g of aqueous polyurethane emulsion with a solid content of 5-15% to the reaction vessel. Under mechanical stirring, add 2-15mL of calcium chloride solution with a concentration of 0.1-0.6mol / L to the reaction system at a dropping rate of 2-15mL / min until the aqueous polyurethane changes from an emulsion state to a suspension state, thus obtaining an aqueous polyurethane microsphere suspension.

[0008] Step 2: Spray-dry the aqueous polyurethane microsphere suspension prepared in Step 1 to obtain powdered aqueous polyurethane microspheres with matting properties.

[0009] Preferably, the mechanical stirring speed in step one is 200 to 1000 rpm.

[0010] Preferably, the drying temperature of the spray drying in step one is 180°C, the peristaltic pump speed is 35 rpm, and the fan is set to 45.0 Hz.

[0011] This invention also protects an aqueous polyurethane microsphere prepared by the method described above, with an average particle size ranging from 8 to 15 μm.

[0012] Furthermore, the surface of the waterborne polyurethane microspheres prepared by this invention has an uneven groove structure.

[0013] The present invention also protects the application of the above-described aqueous polyurethane microspheres in a matte coating on leather surfaces.

[0014] Compared with the prior art, the present invention has the following technical effects:

[0015] This invention employs a coordination aggregation method to prepare waterborne polyurethane microspheres. Calcium ions coordinate with the carboxyl groups of polyurethane molecular chain segments, causing the waterborne polyurethane to aggregate into spheres. The entire preparation process involves the absence of any organic solvents or other harmful substances, meeting the requirements of green environmental protection. The prepared waterborne polyurethane microspheres have excellent light scattering characteristics due to their uneven, grooved surface structure, resulting in a good matting effect. Furthermore, because the particle size of the microspheres exhibits a normal distribution, microspheres of different sizes can form a rough coating micro-surface. The synergistic effect of these two factors makes it an excellent matting coating for leather surfaces.

[0016] The waterborne polyurethane microspheres prepared by this invention have excellent compatibility with waterborne polyurethane matting agents, and the matting coating does not exhibit whitening or stretching phenomena under hot pressing at 120°C and 5kg force.

[0017] In the preparation process of this invention, the polar groups such as urethane groups and urea groups inherent in the waterborne polyurethane itself, as well as the hydration effect of metal ions, can endow the waterborne polyurethane microspheres with good hydrophilicity, which is conducive to the rapid dispersion of microspheres in waterborne polyurethane and improves their dispersion stability in waterborne polyurethane.

[0018] This invention controls the particle size and surface roughness of waterborne polyurethane microspheres by adjusting the particle size, solid content, concentration and dropping rate of the coagulant solution, and type of coagulant, thereby meeting different levels of matting requirements. Attached Figure Description

[0019] Figure 1 This is a scanning electron microscope image of the aqueous polyurethane microspheres prepared in Example 1 of the present invention;

[0020] Figure 2The particle size distribution diagram of the aqueous polyurethane microspheres prepared in Example 1 of the present invention is shown.

[0021] Figure 3 This is a scanning electron microscope image of a leather surface before surface matte coating treatment.

[0022] Figure 4 This is a scanning electron microscope image of a leather surface after surface matte coating treatment prepared in Example 1 of the present invention;

[0023] Figure 5 Image showing the matte finish of leather surface before surface matte coating treatment;

[0024] Figure 6 The image shows the matte finish effect of the leather surface after treatment with the surface matte coating prepared in Example 1 of this invention. Detailed Implementation

[0025] The specific content of the present invention will be further explained in detail below with reference to the embodiments.

[0026] The waterborne polyurethane used in the following embodiments is manufactured by Luoyang Shuohao Environmental Protection New Materials Co., Ltd., and the model number is 1140.

[0027] The leveling agent is BYK 346, manufactured by BYK Chemical.

[0028] The thickener is Vesmody U604, manufactured by Wanhua Chemical.

[0029] Example 1:

[0030] Step 1: Add 100g of waterborne polyurethane emulsion with a solid content of 10% to the reaction vessel. Under mechanical stirring speed of 400rpm, add 2.6mL of calcium chloride solution with a concentration of 0.5mol / L dropwise to the reaction system at a dropping rate of 10mL / min until the waterborne polyurethane changes from an emulsion state to a suspension state, thus obtaining a waterborne polyurethane microsphere suspension.

[0031] Step 2: The aqueous polyurethane microsphere suspension prepared in Step 1 is spray-dried to obtain powdered, matting aqueous polyurethane microspheres. The spray drying temperature is 180℃, the peristaltic pump speed is 35 rpm, and the fan is set to 45.0 Hz. The surface of the aqueous polyurethane microspheres has an uneven groove structure, which scatters incident light. The average particle size of the microspheres is 10.36 μm.

[0032] By weight, 100 parts of waterborne polyurethane with a solid content of 15%, 8 parts of matte waterborne polyurethane microsphere powder, and 2 parts of leveling agent were added to a mixing tank and mixed evenly to obtain a dispersed phase. Then, 1.5 parts of waterborne thickener were added and stirred to disperse the mixture evenly until the viscosity reached 2000 mPa·s. The resulting slurry was coated onto various leather surfaces using a surface treatment coating roller and dried in an oven at 120℃ for 5 minutes to obtain a matte coating. The gloss of the coating (60°) decreased from 10.43% to 1.29%. The matte coating did not exhibit whitening or bleaching after hot pressing at 120℃ and 5 kg force.

[0033] Example 2:

[0034] Step 1: Add 100g of waterborne polyurethane emulsion with a solid content of 10% to the reaction vessel. Under mechanical stirring speed of 400rpm, add 13mL of calcium chloride solution with a concentration of 0.1mol / L dropwise to the reaction system at a dropping rate of 8mL / min until the waterborne polyurethane changes from an emulsion state to a suspension state, thus obtaining a waterborne polyurethane microsphere suspension.

[0035] Step 2: The aqueous polyurethane microsphere suspension prepared in Step 1 is spray-dried to obtain powdered, matting aqueous polyurethane microspheres. The spray drying temperature is 180℃, the peristaltic pump speed is 35 rpm, and the fan is set to 45.0 Hz. The surface of the aqueous polyurethane microspheres has an uneven groove structure, which scatters incident light. The average particle size of the microspheres is 11.57 μm.

[0036] By weight, 100 parts of waterborne polyurethane with a solid content of 15%, 8 parts of matte waterborne polyurethane microsphere powder, and 2 parts of leveling agent were added to a mixing tank and mixed evenly to obtain a dispersed phase. Then, 1.5 parts of waterborne thickener were added and stirred to disperse the mixture evenly until the viscosity reached 2000 mPa·s. The resulting slurry was coated onto various leather surfaces using a surface treatment coating roller and dried in an oven at 120℃ for 5 minutes to obtain a matte coating. The gloss of the coating (60°) decreased from the original 10.43% to 1.36%. The matte coating did not exhibit whitening or bleeding after hot pressing at 120℃ and 5 kg force.

[0037] Example 3:

[0038] Step 1: Add 100g of waterborne polyurethane emulsion with a solid content of 10% to the reaction vessel. Under mechanical stirring speed of 400rpm, add 10.4mL of calcium chloride solution with a concentration of 0.4mol / L dropwise to the reaction system at a dropping rate of 8mL / min until the waterborne polyurethane changes from an emulsion state to a suspension state, thus obtaining a waterborne polyurethane microsphere suspension.

[0039] Step 2: The aqueous polyurethane microsphere suspension prepared in Step 1 is spray-dried to obtain powdered, matting aqueous polyurethane microspheres. The spray drying temperature is 180℃, the peristaltic pump speed is 35 rpm, and the fan is set to 45.0 Hz. The surface of the aqueous polyurethane microspheres has an uneven groove structure, which scatters incident light. The average particle size of the microspheres is 12.21 μm.

[0040] According to the mass ratio, add 100 parts of waterborne polyurethane with a solid content of 15%, 8 parts of matte waterborne polyurethane microsphere powder, and 2 parts of leveling agent to a mixing tank, and mix evenly to obtain a dispersed phase. Then add 2 parts of waterborne thickener, stir to disperse the mixture evenly, and bring the viscosity to 3000 mPa·s. Apply the obtained slurry to the surface of various leathers using a surface treatment coating roller, and dry it in an oven at 120℃ for 5 minutes to obtain a surface matte coating. The gloss of the coating (60°) decreased from the original 10.43% to 1.54%. The matte coating did not show whitening or whitening after hot pressing at 120℃ and 5kg force.

[0041] Example 4:

[0042] Step 1: Add 100g of waterborne polyurethane emulsion with a solid content of 5% to the reaction vessel. Under mechanical stirring speed of 200rpm, add 2mL of calcium chloride solution with a concentration of 0.1mol / L dropwise to the reaction system at a dropping rate of 15mL / min until the waterborne polyurethane changes from an emulsion state to a suspension state, thus obtaining a waterborne polyurethane microsphere suspension.

[0043] Step 2: The aqueous polyurethane microsphere suspension prepared in Step 1 is spray-dried to obtain powdered, matting aqueous polyurethane microspheres. The spray drying temperature is 180℃, the peristaltic pump speed is 35 rpm, and the fan is set to 45.0 Hz. The surface of the aqueous polyurethane microspheres has an uneven groove structure, which scatters incident light. The average particle size of the microspheres is 8 μm.

[0044] By weight, add 100 parts of waterborne polyurethane with a solid content of 5%, 5 parts of matte waterborne polyurethane microsphere powder, and 1 part of leveling agent to a mixing tank, and mix evenly to obtain a dispersed phase. Then add 1 part of waterborne thickener, stir to disperse the mixture evenly, and bring the viscosity to 1500 mPa·s. Apply the obtained slurry to the surface of various leathers using a surface treatment coating roller, and dry it in an oven at 120°C for 2 minutes to obtain a matte surface coating.

[0045] Example 5:

[0046] Step 1: Add 100g of aqueous polyurethane emulsion with a solid content of 15% to the reaction vessel. Under mechanical stirring speed of 1000rpm, add 15mL of calcium chloride solution with a concentration of 0.6mol / L dropwise to the reaction system at a dropping rate of 2mL / min until the aqueous polyurethane changes from an emulsion state to a suspension state, thus obtaining an aqueous polyurethane microsphere suspension.

[0047] Step 2: The aqueous polyurethane microsphere suspension prepared in Step 1 is spray-dried to obtain powdered, matting aqueous polyurethane microspheres. The spray drying temperature is 180℃, the peristaltic pump speed is 35 rpm, and the fan is set to 45.0 Hz. The surface of the aqueous polyurethane microspheres has an uneven groove structure, which scatters incident light. The average particle size of the microspheres is 15 μm.

[0048] By weight, add 100 parts of waterborne polyurethane with a solid content of 10%, 10 parts of matte waterborne polyurethane microsphere powder, and 1.5 parts of leveling agent to a mixing tank, and mix thoroughly to obtain a dispersed phase. Then add 0.2 parts of waterborne thickener, stir to disperse the mixture evenly, and bring the viscosity to 1000 mPa·s. Apply the resulting slurry to the surface of various leathers using a surface treatment coating roller, and dry it in an oven at 120°C for 2 minutes to obtain a matte surface coating.

[0049] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A method for preparing waterborne polyurethane microspheres, characterized in that, Includes the following steps: Step 1: Add 100g of aqueous polyurethane emulsion with a solid content of 5-15% to the reaction vessel. Under mechanical stirring, add 2-15mL of calcium chloride solution with a concentration of 0.1-0.6mol / L to the reaction system at a dropping rate of 2-15mL / min until the aqueous polyurethane changes from an emulsion state to a suspension state, thus obtaining an aqueous polyurethane microsphere suspension. Step 2: Spray-dry the aqueous polyurethane microsphere suspension prepared in Step 1 to obtain powdered aqueous polyurethane microspheres with matting properties.

2. The method for preparing aqueous polyurethane microspheres as described in claim 1, characterized in that, The mechanical stirring speed described in step one is 200–1000 rpm.

3. The method for preparing aqueous polyurethane microspheres as described in claim 1, characterized in that, The spray drying temperature described in step one is 180℃, the peristaltic pump speed is 35rpm, and the fan is set to 45.0Hz.

4. An aqueous polyurethane microsphere prepared by the method according to any one of claims 1 to 3, characterized in that, The average particle size ranges from 8 to 15 μm.

5. The aqueous polyurethane microspheres as described in claim 4, characterized in that, The surface has an uneven, grooved structure.

6. The application of an aqueous polyurethane microsphere as described in claim 5 in a matte coating on leather surfaces.

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