A weather-resistant polyurethane paint and a method for preparing the same

Abstract

The application relates to the technical field of paint, in particular to a preparation method of polyurethane paint with good weather resistance, which comprises the following raw materials in parts by weight: main resin 40-60 parts, first powder 5-15 parts, second powder 3-10 parts, solvent 10-20 parts and additive 1-3 parts. In the preparation method, the first powder is subjected to carbonization and silane treatment, active groups formed on the surface of the first powder can be chemically crosslinked with the main resin, a "molecular bridge" is formed to tightly connect inorganic particles and organic resin, a firm interface bonding layer is formed, a lot of "small hooks" are added between the polyurethane paint and the steel plate, the polyurethane paint and the steel plate are tightly connected, the bonding force between the polyurethane paint and the base material is enhanced, the polyurethane paint can be firmly attached in different temperature environments, and the weather resistance of the paint is improved.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a polyurethane paint with good weather resistance and its preparation method. Background Technology

[0002] Polyurethane paint is a coating with polyurethane resin as the main film-forming substance. It is usually made by mixing isocyanate components and polyol components in a certain proportion, cross-linking and curing. Its paint film is tough and wear-resistant, chemically resistant, has strong adhesion and full gloss, and has excellent weather resistance and mechanical properties. It can be adapted to different substrates by adjusting the formula.

[0003] When existing polyurethane coatings are bonded to the substrate, the lack of effective chemical bonding between inorganic particles and organic resins leads to insufficient interfacial adhesion. Under environmental influences such as temperature changes, the coating film is prone to peeling and detachment, which seriously affects its weather resistance.

[0004] Based on this, the present invention provides a polyurethane paint with good weather resistance and its preparation method. Summary of the Invention

[0005] The purpose of this invention is to provide a polyurethane paint with good weather resistance and its preparation method, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a polyurethane paint with good weather resistance, comprising the following raw materials in parts by weight: 40-60 parts of main resin, 5-15 parts of first powder, 3-10 parts of second powder, 10-20 parts of solvent, and 1-3 parts of additives.

[0007] Preferably, the method for preparing the weather-resistant polyurethane paint includes the following steps:

[0008] S1: Add the first powder, the second powder, the additive and the solvent into the disperser, set the speed to 2000-3000 r / min, and stir continuously for 30-50 min to obtain a mixed slurry;

[0009] S2: Add the main resin to the reactor, then add ethyl acetate (30-60% of the main resin by mass), set the temperature to 60-70℃, the rotation speed to 200-300 r / min, and stir continuously for 1 hour.

[0010] S3: Add the mixed slurry to the reaction vessel of S2, set the rotation speed to 800-900 r / min, and continue stirring for 2-3 hours to obtain the paint;

[0011] S4: Transfer the paint to a curing tank, set the temperature to 40-50℃, let it stand for 24 hours, then pass it through a filter with a pore size of 10-15μm and take the filtrate, which is a polyurethane paint with good weather resistance.

[0012] Preferably, the method for preparing the first powder includes the following steps:

[0013] Step 1: Select plant waste as raw material, crush it to 0.5-1.5mm to obtain crushed material;

[0014] Step 2: Place the crushed material into a carbonization furnace and heat it to 500-800℃ at a heating rate of 10℃ / min under nitrogen protection. After holding the temperature for 2-4 hours, remove the material and allow it to cool naturally at room temperature to obtain carbonized material.

[0015] Step 3: Add the carbonized material to the ball mill, set the speed to 400-500 r / min, grind for 4-5 hours, and then sieve to obtain the primary first powder with a particle size of 50-200 nm;

[0016] Step 4: Add the primary first powder to the mixer, then add 2-3% of the mass of the primary first powder with silane coupling agent KH-550, set the speed to 200-300 r / min, the temperature to 60-70℃, and continue stirring for 1-2 hours. Then transfer it to a drying oven and dry it at 80-90℃ for 2-3 hours, and then grind it to obtain the first powder.

[0017] Preferably, the second powder preparation method includes the following steps:

[0018] Step 1: Pass industrial flue gas into a spray tower and spray it with a 10% sodium hydroxide solution to obtain a mixture. Then filter the mixture and collect the precipitate.

[0019] Step 2: Mix the precipitate with 5% hydrochloric acid at a solid-liquid ratio of 1:(5-7), then add it to the reaction vessel, set the speed to 150-200 r / min, and stir continuously for 30-50 min. Then transfer it to a centrifuge, set the speed to 3000-4000 r / min, and continue to separate for 30-50 min to obtain the solid separated product.

[0020] Step 3: Transfer the solid separated material to a drying oven and dry it at 100-120℃ for 3-4 hours to obtain the primary functional powder;

[0021] Step 4: Transfer the primary functional powder to a calcining furnace and heat it to 500-600℃ at a heating rate of 10-15℃ / min. Calcinate for 2-3 hours, then cool it at room temperature to obtain the second powder.

[0022] Preferably, the main resin is composed of isocyanate and polyol, with the mass ratio of isocyanate to polyol being 1:1.

[0023] Preferably, the main resin preparation method includes the following steps: adding isocyanate and polyol to a reaction vessel, and stirring continuously for 1-3 hours at 200-300 r / min and 60-70℃ to obtain the main resin.

[0024] Preferably, the solvent may be selected from at least one of butyl acetate and propylene glycol methyl ether acetate, and the additive is prepared by mixing a leveling agent, a dispersant and an ultraviolet absorber in a mass ratio of 1:1:1.

[0025] Preferably, the leveling agent may be selected from at least one of isophorone and diacetone alcohol, the dispersant may be selected from at least one of polyacrylamide and methylpentanol, and the ultraviolet absorber may be selected from at least one of UV-531 and UV-327.

[0026] Preferably, the plant waste can be any one of coffee grounds, rice husks, and straw.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1. In this preparation method, the first powder is treated with carbonization and silane. The active groups formed on its surface can chemically crosslink with the main resin to form a "molecular bridge" that tightly connects the inorganic particles with the organic resin, forming a strong interfacial bonding layer. It is like adding many "small hooks" between the polyurethane paint and the steel plate, so that they are tightly connected. This can enhance the bonding force between the polyurethane paint and the substrate, so that the polyurethane paint can adhere firmly under different temperature environments and improve the weather resistance of the paint.

[0029] 2. In this preparation method, the second powder is treated with industrial flue gas and calcined to form a component with a dense crystalline structure. These rigid particles are uniformly distributed in the paint film, forming a "skeleton support" to maintain the spatial structure of the paint film. When the humid and hot environment causes the resin matrix to absorb water and swell, the rigid structure of the second powder can effectively resist deformation, maintain the stability of the paint film hardness, resist the influence of the humid and hot environment, and allow the polyurethane paint to maintain good performance in humid and high-temperature places.

[0030] 3. In this preparation method, the first powder and the second powder have a synergistic effect. The porous structure of the first powder increases the pigment dispersion area and reduces the light absorption concentration points. The crystal structure of the second powder has the effect of scattering and reflecting ultraviolet rays, which improves the ability of polyurethane paint to resist ultraviolet rays and maintains the stability and weather resistance of polyurethane paint. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1: This example provides a method for preparing a polyurethane paint with good weather resistance, comprising the following raw materials in parts by weight: 40 parts of main resin, 5 parts of first powder, 3 parts of second powder, 10 parts of solvent, and 1 part of additive.

[0033] The preparation method of polyurethane paint with good weather resistance includes the following steps:

[0034] S1: Add the first powder, the second powder, the additive and the solvent into the disperser, set the speed to 2000 r / min, and stir continuously for 30 min to obtain a mixed slurry;

[0035] S2: Add the main resin to the reactor, then add ethyl acetate (30% of the main resin by mass), set the temperature to 60℃, the speed to 200r / min, and stir continuously for 1h.

[0036] S3: Add the mixed slurry to the reaction vessel of S2, set the rotation speed to 800 r / min, and continue stirring for 2 hours to obtain the paint;

[0037] S4: Transfer the paint to a curing tank, set the temperature to 40℃, let it stand for 24 hours, then pass it through a 10μm filter and take the filtrate, which is a polyurethane paint with good weather resistance.

[0038] The preparation method of the first powder includes the following steps:

[0039] Step 1: Select plant waste as raw material, crush it to 0.5mm, and obtain crushed material;

[0040] Step 2: Place the crushed material into a carbonization furnace, heat it to 500°C at a heating rate of 10°C / min under nitrogen protection, maintain the temperature for 2 hours, then remove it and allow it to cool naturally at room temperature to obtain carbonized material.

[0041] Step 3: Add the carbonized material to the ball mill, set the speed to 400 r / min, grind for 4 hours, and then sieve to obtain the primary first powder with a particle size of 50 nm;

[0042] Step 4: Add the primary first powder to the mixer, then add 2% by weight of the primary first powder silane coupling agent KH-550, set the speed to 200 r / min, the temperature to 60℃, and continue stirring for 1 hour. Then transfer it to the drying oven and dry it at 80℃ for 2 hours, and then grind it to obtain the first powder.

[0043] The second powder preparation method includes the following steps:

[0044] Step 1: Pass industrial flue gas into a spray tower and spray it with a 10% sodium hydroxide solution to obtain a mixture. Then filter the mixture and collect the precipitate.

[0045] Step 2: Mix the precipitate with 5% dilute hydrochloric acid at a solid-liquid ratio of 1:5, then add it to the reaction vessel, set the speed to 150 r / min, and stir continuously for 30 min. Then transfer it to a centrifuge, set the speed to 3000 r / min, and continue to separate for 30 min to obtain the solid separated product.

[0046] Step 3: Transfer the solid separation to a drying oven and dry at 100℃ for 3 hours to obtain primary functional powder;

[0047] Step 4: Transfer the primary functional powder to a calcining furnace, heat it to 500℃ at a heating rate of 10℃ / min, calcine for 2 hours, and then cool it at room temperature to obtain the second powder.

[0048] The main resin is composed of isocyanate and polyol, with a mass ratio of isocyanate to polyol of 1:1.

[0049] The main resin preparation method includes the following steps: adding isocyanate and polyol to a reaction vessel and stirring continuously for 1 hour at 200 r / min and 60°C to obtain the main resin.

[0050] The solvent is butyl acetate, and the additives are a mixture of leveling agent, dispersant and ultraviolet absorber in a mass ratio of 1:1:1.

[0051] The leveling agent is isophorone, the dispersant is polyacrylamide, and the ultraviolet absorber is UV-531.

[0052] Coffee grounds were chosen as the plant waste.

[0053] Example 2, a method for preparing a polyurethane paint with good weather resistance, comprising the following raw materials in parts by weight: 60 parts of main resin, 15 parts of first powder, 10 parts of second powder, 20 parts of solvent, and 3 parts of additive.

[0054] The preparation method of polyurethane paint with good weather resistance includes the following steps:

[0055] S1: Add the first powder, the second powder, the additive and the solvent into the disperser, set the speed to 3000 r / min, and stir continuously for 50 min to obtain a mixed slurry;

[0056] S2: Add the main resin to the reactor, then add ethyl acetate (60% of the main resin by mass), set the temperature to 70℃, the speed to 300r / min, and stir continuously for 1h.

[0057] S3: Add the mixed slurry to the reaction vessel of S2, set the speed to 900 r / min, and continue stirring for 3 hours to obtain the paint;

[0058] S4: Transfer the paint to a curing tank, set the temperature to 50℃, let it stand for 24 hours, then pass it through a 15μm filter and take the filtrate, which is a polyurethane paint with good weather resistance.

[0059] The preparation method of the first powder includes the following steps:

[0060] Step 1: Select plant waste as raw material, crush it to 1.5mm, and obtain crushed material;

[0061] Step 2: Place the crushed material into a carbonization furnace and heat it to 800°C at a rate of 10°C / min under nitrogen protection. After holding the temperature for 4 hours, remove the material and allow it to cool naturally at room temperature to obtain the carbonized material.

[0062] Step 3: Add the carbonized material to the ball mill, set the speed to 500 r / min, grind for 5 hours, and then sieve to obtain the primary first powder with a particle size of 200 nm;

[0063] Step 4: Add the primary first powder to the mixer, then add 3% by weight of the primary first powder silane coupling agent KH-550, set the speed to 300 r / min, the temperature to 70℃, and continue stirring for 2 hours. Then transfer it to the drying oven and dry it at 90℃ for 3 hours, and then grind it to obtain the first powder.

[0064] The second powder preparation method includes the following steps:

[0065] Step 1: Pass industrial flue gas into a spray tower and spray it with a 10% sodium hydroxide solution to obtain a mixture. Then filter the mixture and collect the precipitate.

[0066] Step 2: Mix the precipitate with 5% dilute hydrochloric acid at a solid-liquid ratio of 1:7, then add it to the reaction vessel, set the speed to 200 r / min, and stir continuously for 50 min. Then transfer it to a centrifuge, set the speed to 4000 r / min, and continue to separate for 50 min to obtain the solid separated product.

[0067] Step 3: Transfer the solid separation to a drying oven and dry at 120℃ for 4 hours to obtain primary functional powder;

[0068] Step 4: Transfer the primary functional powder to a calcining furnace, heat it to 600℃ at a heating rate of 15℃ / min, calcine for 3 hours, and then cool it at room temperature to obtain the second powder.

[0069] The main resin is composed of isocyanate and polyol, with a mass ratio of isocyanate to polyol of 1:1.

[0070] The main resin preparation method includes the following steps: adding isocyanate and polyol to a reaction vessel and stirring continuously for 3 hours at 300 r / min and 70°C to obtain the main resin.

[0071] The solvent can be propylene glycol methyl ether acetate, and the additive is a mixture of leveling agent, dispersant and ultraviolet absorber in a mass ratio of 1:1:1.

[0072] Among them, diacetone alcohol is selected as the leveling agent, methyl pentanol is selected as the dispersant, and UV-327 is selected as the ultraviolet absorber.

[0073] Among them, straw is selected as the plant waste.

[0074] Example 3: A method for preparing a polyurethane paint with good weather resistance, comprising the following raw materials in parts by weight: 50 parts of main resin, 10 parts of first powder, 7 parts of second powder, 15 parts of solvent, and 2 parts of additive.

[0075] The preparation method of polyurethane paint with good weather resistance includes the following steps:

[0076] S1: Add the first powder, the second powder, the additive and the solvent into the disperser, set the speed to 2500 r / min, and stir continuously for 40 min to obtain a mixed slurry;

[0077] S2: Add the main resin to the reactor, then add ethyl acetate (45% of the main resin by mass), set the temperature to 65℃, the speed to 250r / min, and stir continuously for 1h.

[0078] S3: Add the mixed slurry to the reaction vessel of S2, set the rotation speed to 850 r / min, and continue stirring for 2.5 h to obtain the paint;

[0079] S4: Transfer the paint to a curing tank, set the temperature to 45℃, let it stand for 24 hours, then pass it through a 12μm filter and take the filtrate, which is a polyurethane paint with good weather resistance.

[0080] The preparation method of the first powder includes the following steps:

[0081] Step 1: Select plant waste as raw material, crush it to 1mm to obtain crushed material;

[0082] Step 2: Place the crushed material into a carbonization furnace and heat it to 650°C at a rate of 10°C / min under nitrogen protection. After holding the temperature for 3 hours, remove the material and allow it to cool naturally at room temperature to obtain the carbonized material.

[0083] Step 3: Add the carbonized material to the ball mill, set the speed to 450 r / min, grind for 4.5 h, and then sieve to obtain the primary first powder with a particle size of 100 nm;

[0084] Step 4: Add the primary first powder to the mixer, then add 2.5% of the primary first powder by mass of silane coupling agent KH-550, set the speed to 250 r / min, the temperature to 65℃, and continue stirring for 1.5 h. Then transfer it to the drying oven and dry it at 85℃ for 2.5 h, and then grind it to obtain the first powder.

[0085] The second powder preparation method includes the following steps:

[0086] Step 1: Pass industrial flue gas into a spray tower and spray it with a 10% sodium hydroxide solution to obtain a mixture. Then filter the mixture and collect the precipitate.

[0087] Step 2: Mix the precipitate with 5% dilute hydrochloric acid at a solid-liquid ratio of 1:6, then add it to the reaction vessel, set the speed to 180 r / min, and stir continuously for 40 min. Then transfer it to a centrifuge, set the speed to 3500 r / min, and continue to separate for 40 min to obtain the solid separated product.

[0088] Step 3: Transfer the solid separation to a drying oven and dry at 110℃ for 3.5 hours to obtain primary functional powder;

[0089] Step 4: Transfer the primary functional powder to a calcining furnace, heat it to 550°C at a heating rate of 12°C / min, calcine for 2.5 hours, and then cool it at room temperature to obtain the second powder.

[0090] The main resin is composed of isocyanate and polyol, with a mass ratio of isocyanate to polyol of 1:1.

[0091] The main resin preparation method includes the following steps: adding isocyanate and polyol to a reaction vessel and stirring continuously for 2 hours at 250 r / min and 65°C to obtain the main resin.

[0092] The solvent is butyl acetate, and the additives are a mixture of leveling agent, dispersant and ultraviolet absorber in a mass ratio of 1:1:1.

[0093] The leveling agent is isophorone, the dispersant is methylpentanol, and the ultraviolet absorber is UV-327.

[0094] Among them, rice husks are selected as the plant waste.

[0095] Comparative Example 1: The difference between this comparative example and Examples 1-3 is that no first powder is added during the preparation of the weather-resistant polyurethane paint in this comparative example.

[0096] Comparative Example 2 differs from Examples 1-3 in that no second powder is added during the preparation of the weather-resistant polyurethane paint in this comparative example.

[0097] Comparative Example 3 differs from Examples 1-3 in that: in the preparation of the weather-resistant polyurethane paint in this comparative example, traditional calcium carbonate filler is used to replace the first and second powders.

[0098] After preparing polyurethane paint according to the preparation methods of Examples 1-3 and Comparative Examples 1-3, the paint was coated on a standard steel plate to form a paint sample, and its performance was tested.

[0099] UV aging test: Place the paint sample in a UV aging chamber and irradiate it with a wavelength of 280-400nm and an intensity of 50W / ㎡ for 7-10 days. After the test, observe the degree of color change of the paint sample and record the results in the table below. The results are divided into 1-10, with 1 being the best and 10 being the worst.

[0100] Humid heat aging test: Place the paint sample in an environment of 50℃ and 95% humidity for 72 hours, then scratch the surface of the paint sample with a pencil. The hardness of the paint sample is judged by the hardness of the pencil that can leave a scratch and the pencil hardness is recorded in the table below.

[0101] Hot and cold cycle adhesion test: The paint sample was cycled 10 times at -20℃ to 60℃, with each cycle lasting 2 hours. After that, the adhesion between the paint sample and the steel plate was tested by cross-cutting method, and the results were recorded in the table below.

[0102]

[0103] By comparing the data in the table, it can be seen that Comparative Example 1 achieved an adhesion level of 4 after thermal cycling, while Examples 1-3 remained stable at level 1. This is because the first powder was treated with carbonization and silane, and the active groups formed on its surface could chemically cross-link with the main resin, acting like a "molecular bridge" to tightly connect the inorganic particles with the organic resin, forming a strong interfacial adhesive layer. It's like adding many "small hooks" between the paint sample and the steel plate, making them tightly connected, which can enhance the bonding force between the paint sample and the substrate, allowing the paint to adhere firmly under different temperature environments and improving the weather resistance of the paint. However, without the first powder, the connection between the paint sample and the steel plate becomes very fragile, and the force generated by thermal changes can easily separate them.

[0104] By comparing the data in the table, it can be seen that after experiencing a humid and hot environment, the hardness of Comparative Example 2 is 3B, while that of Examples 1-3 remains at 4H. This is because the second powder, through industrial flue gas treatment and calcination, forms a component with a dense crystalline structure. These rigid particles are evenly distributed in the paint film, acting as a "skeleton support" to maintain the spatial structure of the paint film. When the humid and hot environment causes the resin matrix to absorb water and swell, the rigid structure of the second powder can effectively resist deformation, maintain the stability of the paint film hardness, and resist the effects of the humid and hot environment, allowing the paint to maintain good performance even in humid and high-temperature environments. However, without the second component, the resin matrix lacks support, and after absorbing water, the molecular chain spacing increases, the flexibility decreases, and the hardness decreases significantly, causing the paint sample to easily soften and deform in a humid and hot environment.

[0105] The data in the comparison table show that Comparative Example 3 had a color difference of 8 after UV irradiation, while Examples 1-3 maintained a difference of 1-1.5. This is because traditional calcium carbonate fillers have smooth surfaces and lack photoprotection, making it impossible to effectively disperse or absorb UV energy. As a result, the light energy directly acts on the resin molecular chains, triggering an oxidation and breakage reaction. The first powder and the second powder have a synergistic effect. The porous structure of the first powder increases the pigment dispersion area and reduces the light absorption concentration points. The crystal structure of the second powder has a scattering and reflecting effect on UV light. At the same time, the surface energy after silane treatment forms a "capture-dissipation" system with the UV absorber, converting light energy into harmless heat energy, improving the paint sample's ability to resist UV light, maintaining the color stability of the paint, and enhancing the paint's weather resistance.

[0106] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0107] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a polyurethane paint with good weather resistance, characterized in that, It includes the following raw materials in parts by weight: 40-60 parts of main resin, 5-15 parts of first powder, 3-10 parts of second powder, 10-20 parts of solvent, and 1-3 parts of additives; The method for preparing the weather-resistant polyurethane paint includes the following steps: S1: Add the first powder, the second powder, the additive and the solvent into the disperser, set the speed to 2000-3000 r / min, and stir continuously for 30-50 min to obtain a mixed slurry; S2: Add the main resin to the reactor, then add ethyl acetate (30-60% of the main resin by mass), set the temperature to 60-70℃, the rotation speed to 200-300 r / min, and stir continuously for 1 hour. S3: Add the mixed slurry to the reaction vessel of S2, set the rotation speed to 800-900 r / min, and continue stirring for 2-3 hours to obtain the paint; S4: Transfer the paint to a curing tank, set the temperature to 40-50℃, let it stand for 24 hours, then pass it through a filter with a pore size of 10-15μm and take the filtrate, which is a polyurethane paint with good weather resistance. The preparation method of the first powder includes the following steps: Step 1: Select plant waste as raw material, crush it to 0.5-1.5mm to obtain crushed material; Step 2: Place the crushed material into a carbonization furnace and heat it to 500-800℃ at a heating rate of 10℃ / min under nitrogen protection. After holding the temperature for 2-4 hours, remove the material and allow it to cool naturally at room temperature to obtain carbonized material. Step 3: Add the carbonized material to the ball mill, set the speed to 400-500 r / min, grind for 4-5 hours, and then sieve to obtain the primary first powder with a particle size of 50-200 nm; Step 4: Add the primary first powder to the mixer, then add 2-3% of the mass of the primary first powder with silane coupling agent KH-550, set the speed to 200-300 r / min, the temperature to 60-70℃, and continue stirring for 1-2 hours. Then transfer it to the drying oven and dry it at 80-90℃ for 2-3 hours, and then grind it to obtain the first powder. The second powder preparation method includes the following steps: Step 1: Pass industrial flue gas into a spray tower and spray it with a 10% sodium hydroxide solution to obtain a mixture. Then filter the mixture and collect the precipitate. Step 2: Mix the precipitate with 5% hydrochloric acid at a solid-liquid ratio of 1:(5-7), then add it to the reaction vessel, set the speed to 150-200 r / min, and stir continuously for 30-50 min. Then transfer it to a centrifuge, set the speed to 3000-4000 r / min, and continue to separate for 30-50 min to obtain the solid separated product. Step 3: Transfer the solid separated material to a drying oven and dry it at 100-120℃ for 3-4 hours to obtain the primary functional powder; Step 4: Transfer the primary functional powder to a calcining furnace and heat it to 500-600℃ at a heating rate of 10-15℃ / min. Calcinate for 2-3 hours, then cool it at room temperature to obtain the second powder.

2. The method for preparing a weather-resistant polyurethane paint according to claim 1, characterized in that, The main resin is composed of isocyanate and polyol, with a mass ratio of isocyanate to polyol of 1:

1.

3. The method for preparing a weather-resistant polyurethane paint according to claim 1, characterized in that, The method for preparing the main resin includes the following steps: adding isocyanate and polyol to a reaction vessel and stirring continuously for 1-3 hours at 200-300 r / min and 60-70℃ to obtain the main resin.

4. The method for preparing a weather-resistant polyurethane paint according to claim 1, characterized in that, The solvent may be selected from at least one of butyl acetate and propylene glycol methyl ether acetate, and the additive is prepared by mixing leveling agent, dispersant and ultraviolet absorber in a mass ratio of 1:1:

1.

5. The method for preparing a weather-resistant polyurethane paint according to claim 4, characterized in that, The leveling agent may be selected from at least one of isophorone and diacetone alcohol, the dispersant may be selected from at least one of polyacrylamide and methylpentanol, and the ultraviolet absorber may be selected from at least one of UV-531 and UV-327.

6. The method for preparing a weather-resistant polyurethane paint according to claim 1, characterized in that, The plant waste can be any one of coffee grounds, rice husks, and straw.

7. A polyurethane paint with good weather resistance, characterized in that, It is prepared by the method for preparing a weather-resistant polyurethane paint as described in any one of claims 1 to 6.

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