A UV-resistant polyurethane composite coating

Abstract

The present invention provides a UV-resistant polyurethane composite coating, belonging to the field of coatings. The UV-resistant polyurethane composite coating provided by the present invention comprises: component A and component B, wherein component A comprises: a water-based polyacrylate dispersion containing triazine groups and modified silica nanoparticles; and component B comprises: an isocyanate curing agent. The UV-resistant polyurethane composite coating of the present invention utilizes a resin containing triazine UV-absorbing groups. The vibration of these triazine groups causes UV absorption in the range of 280 to 380 nm. Furthermore, the coating has a lighter color, high temperature resistance, and good solubility. Consequently, the coating formed by the composite coating is transparent, weather-resistant, and has excellent UV absorption properties.

Description

Technical Field

[0001] The present invention relates to the field of coatings, and in particular to an anti-ultraviolet polyurethane composite coating. Background Art

[0002] Polyurethane coatings, with their excellent mechanical and chemical properties, are widely used in wood coatings, automotive refinish coatings, floor coatings, and electronic coatings. With the depletion of the global ozone layer and the greenhouse effect, ultraviolet radiation reaching the ground is becoming increasingly intense. Under the influence of strong UV radiation and oxygen, the polymer matrix of the coating undergoes photodegradation. This continuous loss of components causes the coating to shrink, reduce thickness, and become brittle and crack, leading to failure. Polyurethane coatings are inherently UV-resistant, so they require UV protection during use.

[0003] In the prior art, UV absorbers mainly include benzotriazoles and benzophenones. Benzotriazole compounds are not easily degraded and easily migrate into the environment during use, causing pollution. Benzophenone compounds have poor light stability and are easily oxidized and discolored.

[0004] Current research on polyurethane UV resistance typically involves the addition of inorganic nanoparticles or UV inhibitors. Patent CN1412261A discloses a nano-UV-resistant polyurethane coating that significantly improves its UV resistance by adding nano-titanium dioxide. Patent CN116377728A discloses a method for preparing a modified sericin UV-resistant coating, in which a UV absorber is added to a curing agent and coated on the outer layer of the fabric to enhance its UV resistance. Summary of the Invention

[0005] The present invention is made to solve the above problems and aims to provide an anti-ultraviolet polyurethane composite coating which is applicable to a variety of substrates, has good storage stability, good transparency, and very excellent anti-ultraviolet performance and can be used in plateau areas.

[0006] The present invention provides an anti-ultraviolet polyurethane composite coating having the following characteristics, comprising: component A and component B, wherein component A comprises: a waterborne polyacrylate dispersion containing triazine groups and modified silicon dioxide nanoparticles; component B comprises: an isocyanate curing agent.

[0007] The anti-ultraviolet polyurethane composite coating provided by the present invention may also have the following characteristics: wherein component A further includes a defoaming agent and / or a wetting agent.

[0008] The anti-ultraviolet polyurethane composite coating provided by the present invention may also have the following characteristics: wherein, the preparation method of the water-based polyacrylate dispersion containing triazine groups includes the following steps: forming a mixed monomer solution by mixing a mixed monomer solvent in a solvent, and dividing it into a mixed monomer solution A and a mixed monomer solution B, and reacting the mixed monomer solution A to obtain a reaction liquid A; adding the mixed monomer solution B dropwise to the reaction liquid, and continuing the reaction to obtain a reaction liquid B; removing the solvent from the reaction liquid B, and adding water and an emulsifier to obtain the mixed monomer, wherein the mixed monomer comprises at least: methyl methacrylate, 1,3,5-triacryloylhexahydro-1,3,5-triazine, hydroxyethyl acrylate, styrene, dimethylaminoethyl methacrylate, isobornyl acrylate, an initiator, and a chain transfer agent.

[0009] The anti-ultraviolet polyurethane composite coating provided by the present invention may also have the following characteristics: wherein the mass ratio of the mixed monomer solution A to the mixed monomer solution B is (1-2): (1-2).

[0010] The anti-ultraviolet polyurethane composite coating provided by the present invention may also have the following characteristics: wherein, in the mixed monomer solution A or the mixed monomer solution B, the mass ratio of methyl methacrylate, 1,3,5-triacryloylhexahydro-1,3,5-triazine, hydroxyethyl acrylate, styrene, dimethylaminoethyl methacrylate, and isobornyl acrylate is 30:(5-15):30:(5-15):10:10.

[0011] The anti-ultraviolet polyurethane composite coating provided by the present invention may also have the following characteristics: wherein, in the mixed monomer, the content of 1,3,5-triacryloylhexahydro-1,3,5-triazine is 5wt%-15wt%.

[0012] The anti-ultraviolet polyurethane composite coating provided by the present invention may also have the following characteristics: wherein the solvent is selected from any one or more of toluene, xylene, propylene glycol butyl ether, and acetone.

[0013] The anti-ultraviolet polyurethane composite coating provided by the present invention may also have the following characteristics: wherein the initiator is selected from any one or more of azobisisobutyronitrile, azobisisoheptanenitrile, and benzoyl peroxide.

[0014] The anti-ultraviolet polyurethane composite coating provided by the present invention may also have the following characteristics: wherein the emulsifier is selected from one of polyvinyl alcohol, quaternary ammonium salt, and alkyl sulfate; and the chain transfer agent is any one of dodecyl mercaptan, mercaptoethanol, and α-methylstyrene linear dimer.

[0015] The anti-ultraviolet polyurethane composite coating provided by the present invention may also have the following characteristics: wherein, the preparation method of modified silica nanoparticles comprises the following steps: in the presence of an acid catalyst, using trimethoxy (3,3,3-trifluoropropyl) silane to modify nano-silica, after the reaction is completed, centrifugation, purification, and drying to obtain.

[0016] The anti-ultraviolet polyurethane composite coating provided by the present invention may also have the following characteristics: wherein, in the preparation method of modified silica nanoparticles, the modification step is carried out in a solvent, preferably, the solvent is one of toluene, tetrahydrofuran, and xylene.

[0017] The anti-ultraviolet polyurethane composite coating provided by the present invention may also have the following characteristics: wherein the acid catalyst is selected from any one of trifluoroacetic acid, hydrochloric acid, and sulfuric acid.

[0018] The anti-ultraviolet polyurethane composite coating provided by the present invention may also have the following characteristics: wherein, the preparation method of modified silica nanoparticles includes the following steps: dispersing nano-silica in a solvent, adding trimethoxy (3,3,3-trifluoropropyl) silane and an acid catalyst, carrying out a modification reaction, centrifuging, purifying, and drying to obtain the product.

[0019] The UV-resistant polyurethane composite coating provided by the present invention may also have the following characteristics: wherein the molar ratio of the hydroxyl group of the aqueous polyacrylate dispersion containing triazine groups in component A to the NCO group in the isocyanate curing in component B is (1.3-1.5):1.

[0020] The anti-ultraviolet polyurethane composite coating provided by the present invention may also have the following characteristics: wherein the content of the modified silicon dioxide nanoparticles in the coating formed by the anti-ultraviolet polyurethane composite coating is 1 wt%-6 wt%.

[0021] Functions and effects of the invention

[0022] According to the UV-resistant polyurethane composite coating involved in the present invention, since the resin used has triazine UV-absorbing groups, the vibration of these triazine groups will cause UV absorption of 280 to 380 nm. In addition, it has the characteristics of lighter color, high temperature resistance and good solubility, so that the coating formed by the composite coating is transparent, weather-resistant and has excellent UV absorption performance.

[0023] Furthermore, nano-silica modified with fluorine segments is also used in combination, so that more nanoparticles can be distributed on the surface by utilizing its surface mobility. Silica nanoparticles have a strong scattering ability for ultraviolet light below 390nm, which can further protect the internal coating, thus greatly improving the coating's anti-ultraviolet ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is an infrared image of the polyacrylate dispersion in Example 1 of the present invention;

[0025] Figure 2 is an infrared image of the modified silica particles in Example 1 of the present invention;

[0026] Figure 3 1 is the transmission curve of the polyurethane coatings of Examples 1, 2, and 3 of the present invention and the polyurethane coatings of Comparative Examples 1, 2, and 3 within a wavelength range of 250 nm to 800 nm;

[0027] Figure 4 3 are pictures of the polyurethane coatings of Examples 1, 2, and 3 of the present invention and the polyurethane coating of Comparative Example 1 after artificial accelerated aging tests on wood. DETAILED DESCRIPTION

[0028] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is described in detail below with reference to embodiments and drawings.

[0029] In the following examples and test cases, silica particles, brand Si-6, were purchased from Shanghai Excilon Co., Ltd. Polyvinyl alcohol emulsifier HT-15, defoamer SE-15, wetting agent G-61, and isocyanate curing agent LP-811 were all purchased from Kinlitai Co., Ltd.

[0030] The remaining reagents and equipment were commercially available unless otherwise specified.

[0031] <Example 1>

[0032] This embodiment provides a method for preparing an ultraviolet-resistant polyurethane composite coating, comprising the following steps:

[0033] Step 1: Prepare mixed monomer solution A and mixed monomer solution B. Both mixed monomer solutions are prepared by mixing 7.5 g of methyl methacrylate (MMA), 1.25 g of 1,3,5-triacryloylhexahydro-1,3,5-triazine (TRT), 7.5 g of hydroxyethyl acrylate (HPA), 3.75 g of styrene (St), 2.5 g of dimethylaminoethyl methacrylate (DMAEMA), 2.5 g of isobornyl acrylate (IBOA), 0.025 g of azobisisobutyronitrile, and 0.025 g of α-methylstyrene linear dimer.

[0034] Step 2: Add 50 ml of acetone to a four-necked flask equipped with a thermometer, condenser, and stirrer, then add mixed monomer solution A. The mixture reacts at 75°C and 800 rpm for two hours. Then, slowly add mixed monomer solution B dropwise to the four-necked flask over half an hour using a peristaltic pump, maintaining a constant stirring speed of 75°C and 800 rpm. After the addition is complete, incubate for one hour, then add 10 mg of azobisisobutyronitrile and continue incubating for another 30 minutes. The reaction mixture is then subjected to a rotary evaporator to remove the solvent, and 50 ml of water and 5 g of polyvinyl alcohol are added to the mixture and emulsified in a blender to obtain a water-based polyacrylate dispersion.

[0035] Step 3: Disperse 10g of nano-silica in 50mL of toluene and ultrasonically disperse to form a silica dispersion. Dissolve 30g of trimethoxy (3,3,3-trifluoropropyl) silane (TFTX) in 50mL of anhydrous tetrahydrofuran and add it to the silica dispersion. Stir at room temperature for 1 hour, add 10ml of 10M trifluoroacetic acid in toluene and continue stirring. After 3 hours, add 8ml of 13M trifluoroacetic acid in toluene and stir at room temperature for another 24 hours. After the reaction is completed, centrifuge the particles at 11000rpm, ultrasonically disperse them in 40ml of toluene again and centrifuge them again to remove unreacted coupling agent molecules, take the solid, and dry the solid at 120°C under vacuum for 2h to obtain nanocomposite particles.

[0036] Step 4: 20 g of waterborne polyacrylate dispersion, 0.31 g of nano-silica composite particles, 2 g of SE-15, and 2 g of G-61 were added to a high-speed disperser and stirred for half an hour. After standing to eliminate bubbles, the resulting dispersion was mixed with 13.5 g of waterborne polyurethane curing agent LP-811 (according to an NCO / OH molar ratio of 1.3:1) to obtain an anti-UV polyurethane composite coating.

[0037] The content of nano silicon dioxide composite particles in the coating formed by adopting the anti-ultraviolet polyurethane composite coating is 1%.

[0038] <Example 2>

[0039] This embodiment provides a method for preparing an ultraviolet-resistant polyurethane composite coating, comprising the following steps:

[0040] Step 1: Prepare mixed monomer solution A and mixed monomer solution B. Both mixed monomer solutions are prepared by mixing 7.5 g of methyl methacrylate (MMA), 2.25 g of 1,3,5-triacryloylhexahydro-1,3,5-triazine (TRT), 7.5 g of hydroxyethyl acrylate (HPA), 2.75 g of styrene (St), 2.5 g of dimethylaminoethyl methacrylate (DMAEMA), 2.5 g of isobornyl acrylate (IBOA), 0.025 g of azobisisobutyronitrile, and 0.025 g of α-methylstyrene linear dimer.

[0041] Step 2: Add 50 ml of acetone to a four-necked flask equipped with a thermometer, condenser, and stirrer, then add mixed monomer solution A. The mixture reacts at 75°C and 800 rpm for two hours. Then, slowly add mixed monomer solution B dropwise to the four-necked flask over half an hour using a peristaltic pump, maintaining a constant stirring speed of 75°C and 800 rpm. After the addition is complete, incubate for one hour, then add 10 mg of azobisisobutyronitrile and continue incubating for another 30 minutes. The reaction solution is then subjected to a rotary evaporator to remove the solvent, and 50 ml of water and 5 g of polyvinyl alcohol are added to the mixture and emulsified in a blender to obtain a water-based polyacrylate dispersion.

[0042] Step 3: Disperse 10g of nano-silica in 50mL of toluene and ultrasonically disperse to form a silica dispersion. Dissolve 30g of trimethoxy (3,3,3-trifluoropropyl) silane (TFTX) in 50mL of anhydrous tetrahydrofuran and add it to the silica dispersion. Stir at room temperature for 1 hour, add 10ml of 10M trifluoroacetic acid in toluene and continue stirring. After 3 hours, add 8ml of 13M trifluoroacetic acid in toluene and stir at room temperature for another 24 hours. After the reaction is completed, centrifuge the particles at 11000rpm, ultrasonically disperse them in 40ml of toluene again and centrifuge them again to remove unreacted coupling agent molecules. Take the solid and dry it at 120°C under vacuum for 2h to obtain nanocomposite particles.

[0043] Step 4: 20 g of waterborne polyacrylate dispersion, 0.39 g of nano-silica composite particles, 2 g of SE-15, and 2 g of G-61 were added to a high-speed disperser and stirred for half an hour. After standing to eliminate bubbles, the resulting dispersion was mixed with 13.5 g of waterborne polyurethane curing agent LP-811 (according to an NCO / OH molar ratio of 1.3:1) to obtain an anti-UV polyurethane composite coating.

[0044] The content of nano silicon dioxide composite particles in the coating formed by adopting the anti-ultraviolet polyurethane composite coating is 3%.

[0045] <Example 3>

[0046] This embodiment provides a method for preparing an ultraviolet-resistant polyurethane composite coating, comprising the following steps:

[0047] Step 1: Prepare mixed monomer solution A and mixed monomer solution B. Both mixed monomer solutions are prepared by mixing 7.5 g of methyl methacrylate (MMA), 3.25 g of 1,3,5-triacryloylhexahydro-1,3,5-triazine (TRT), 7.5 g of hydroxyethyl acrylate (HPA), 1.75 g of styrene (St), 2.5 g of dimethylaminoethyl methacrylate (DMAEMA), 2.5 g of isobornyl acrylate (IBOA), 0.025 g of azobisisobutyronitrile, and 0.025 g of α-methylstyrene linear dimer.

[0048] Step 2: Add 50 ml of acetone to a four-necked flask equipped with a thermometer, condenser, and stirrer, then add mixed monomer solution A. The mixture reacts at 75°C and 800 rpm for two hours. Then, slowly add mixed monomer solution B dropwise to the four-necked flask over half an hour using a peristaltic pump, maintaining a constant stirring speed of 75°C and 800 rpm. After the addition is complete, incubate for one hour, then add 10 mg of azobisisobutyronitrile and continue incubating for another 30 minutes. The reaction mixture is then subjected to a rotary evaporator to remove the solvent, and 50 ml of water and 5 g of polyvinyl alcohol are added to the mixture and emulsified in a blender to obtain a water-based polyacrylate dispersion.

[0049] Step 3: Disperse 10g of nano-silica in 50mL of toluene and ultrasonically disperse to form a silica dispersion. Dissolve 30g of trimethoxy (3,3,3-trifluoropropyl) silane (TFTX) in 50mL of anhydrous tetrahydrofuran and add it to the silica dispersion. Stir at room temperature for 1 hour, add 10ml of 10M trifluoroacetic acid in toluene and continue stirring. After 3 hours, add 8ml of 13M trifluoroacetic acid in toluene and stir at room temperature for another 24 hours. After the reaction is completed, centrifuge the particles at 11000rpm, ultrasonically disperse them in 40ml of toluene again and centrifuge them again to remove unreacted coupling agent molecules, take the solid, and dry the solid at 120°C under vacuum for 2h to obtain nanocomposite particles.

[0050] Step 4: 20 g of waterborne polyacrylate dispersion, 0.55 g of nano-silica composite particles, 2 g of SE-15, and 2 g of G-61 were added to a high-speed disperser and stirred for half an hour. After standing to eliminate bubbles, the resulting dispersion was mixed with 13.5 g of waterborne polyurethane curing agent LP-811 (according to an NCO / OH molar ratio of 1.3:1) to obtain an anti-UV polyurethane composite coating.

[0051] The content of nano silicon dioxide composite particles in the coating formed by adopting the anti-ultraviolet polyurethane composite coating is 5%.

[0052] Comparative Example 1

[0053] This comparative example provides a method for preparing a polyurethane coating, comprising the following steps:

[0054] Step 1: Prepare mixed monomer solution A and mixed monomer solution B. Both mixed monomer solutions are prepared by mixing 7.5 g of methyl methacrylate (MMA), 7.5 g of hydroxyethyl acrylate (HPA), 5 g of styrene (St), 2.5 g of dimethylaminoethyl methacrylate (DMAEMA), 2.5 g of isobornyl acrylate (IBOA), 0.025 g of azobisisobutyronitrile, and 0.025 g of α-methylstyrene linear dimer.

[0055] Step 2: Add 50 ml of acetone to a four-necked flask equipped with a thermometer, condenser, and stirrer, then add mixed monomer solution A. The mixture reacts at 75°C and 800 rpm for two hours. Then, slowly add mixed monomer solution B dropwise to the four-necked flask over half an hour using a peristaltic pump, maintaining a constant stirring speed of 75°C and 800 rpm. After the addition is complete, incubate for one hour, then add 10 mg of azobisisobutyronitrile and continue incubating for another 30 minutes. The reaction mixture is then subjected to a rotary evaporator to remove the solvent, and 50 ml of water and 5 g of polyvinyl alcohol are added to the mixture and emulsified in a blender to obtain a water-based polyacrylate dispersion.

[0056] Step 3: Add 20 g of waterborne polyacrylate dispersion, 2 g of SE-15, and 2 g of G-61 into a high-speed disperser and stir for half an hour. After standing to eliminate bubbles, the resulting dispersion and 13.5 g of waterborne polyurethane curing agent LP-811 (according to an NCO / OH molar ratio of 1.3:1) are mixed to obtain an anti-UV polyurethane composite coating.

[0057] Comparative Example 2

[0058] This comparative example provides a method for preparing an anti-ultraviolet polyurethane composite coating, comprising the following steps:

[0059] Step 1: Prepare mixed monomer solution A and mixed monomer solution B. Both mixed monomer solutions are prepared by mixing 7.5 g of methyl methacrylate (MMA), 7.5 g of hydroxyethyl acrylate (HPA), 5 g of styrene (St), 2.5 g of dimethylaminoethyl methacrylate (DMAEMA), 2.5 g of isobornyl acrylate (IBOA), 0.025 g of azobisisobutyronitrile, and 0.025 g of α-methylstyrene linear dimer.

[0060] Step 2: Add 50 ml of acetone to a four-necked flask equipped with a thermometer, condenser, and stirrer, then add mixed monomer solution A. The mixture reacts at 75°C and 800 rpm for two hours. Then, slowly add mixed monomer solution B dropwise to the four-necked flask over half an hour using a peristaltic pump, maintaining a constant stirring speed of 75°C and 800 rpm. After the addition is complete, incubate for one hour, then add 10 mg of azobisisobutyronitrile and continue incubating for another 30 minutes. The reaction mixture is then subjected to a rotary evaporator to remove the solvent, and 50 ml of water and 5 g of polyvinyl alcohol are added to the mixture and emulsified in a blender to obtain a water-based polyacrylate dispersion.

[0061] Step 3: Disperse 10g of nano-silica in 50mL of toluene and ultrasonically disperse to form a silica dispersion. Dissolve 30g of trimethoxy (3,3,3-trifluoropropyl) silane (TFTX) in 50mL of anhydrous tetrahydrofuran and add it to the silica dispersion. Stir at room temperature for 1 hour, add 10ml of 10M trifluoroacetic acid in toluene and continue stirring. After 3 hours, add 8ml of 13M trifluoroacetic acid in toluene and stir at room temperature for another 24 hours. After the reaction is completed, centrifuge the particles at 11000rpm, ultrasonically disperse them in 40ml of toluene again and centrifuge them again to remove unreacted coupling agent molecules, take the solid, and dry the solid at 120°C under vacuum for 2h to obtain nanocomposite particles.

[0062] Step 4: 20 g of waterborne polyacrylate dispersion, 0.31 g of nano-silica composite particles, 2 g of SE-15, and 2 g of G-61 were added to a high-speed disperser and stirred for half an hour. After standing to eliminate bubbles, the resulting dispersion was mixed with 13.5 g of waterborne polyurethane curing agent LP-811 (according to an NCO / OH molar ratio of 1.3:1) to obtain an anti-UV polyurethane composite coating.

[0063] The content of nano silicon dioxide composite particles in the coating formed by adopting the anti-ultraviolet polyurethane composite coating is 0.8%.

[0064] Comparative Example 3

[0065] This embodiment provides a method for preparing an ultraviolet-resistant polyurethane composite coating, comprising the following steps:

[0066] Step 1: Prepare mixed monomer solution A and mixed monomer solution B. Both mixed monomer solutions are prepared by mixing 7.5 g of methyl methacrylate (MMA), 1.75 g of 1,3,5-triacryloylhexahydro-1,3,5-triazine (TRT), 7.5 g of hydroxyethyl acrylate (HPA), 3.25 g of styrene (St), 2.5 g of dimethylaminoethyl methacrylate (DMAEMA), 2.5 g of isobornyl acrylate (IBOA), 0.025 g of azobisisobutyronitrile, and 0.025 g of α-methylstyrene linear dimer.

[0067] Step 2: Add 50 ml of acetone to a four-necked flask equipped with a thermometer, condenser, and stirrer, then add mixed monomer solution A. The mixture reacts at 75°C and 800 rpm for two hours. Then, slowly add mixed monomer solution B dropwise to the four-necked flask over half an hour using a peristaltic pump, maintaining a constant stirring speed of 75°C and 800 rpm. After the addition is complete, incubate for one hour, then add 10 mg of azobisisobutyronitrile and continue incubating for another 30 minutes. The reaction mixture is then subjected to a rotary evaporator to remove the solvent, and 50 ml of water and 5 g of polyvinyl alcohol are added to the mixture and emulsified in a blender to obtain a water-based polyacrylate dispersion.

[0068] Step 3: Add 20 g of waterborne polyacrylate dispersion, 2 g of SE-15, and 2 g of G-61 into a high-speed disperser and stir for half an hour. After standing to eliminate bubbles, the resulting dispersion and 13.5 g of waterborne polyurethane curing agent LP-811 (according to an NCO / OH molar ratio of 1.3:1) are mixed to obtain an anti-UV polyurethane composite coating.

[0069] <Test Example 1>

[0070] Substrate adhesion

[0071] The polyurethane coatings provided in Examples 1-3 were coated on wood, steel, cloth and ABS plastic plates using a 70 μm wire rod, and the adhesion was measured using the cross-hatch method.

[0072] The test results are shown in Table 1.

[0073] Table 1 Substrate Adhesion Test Table

[0074]

[0075] <Test Example 2>

[0076] Physical property testing

[0077] The aqueous polyacrylate dispersion and modified silica nanoparticles prepared in Example 1 were subjected to infrared analysis, and the data are shown in the attached Figure 1 With attached Figure 2 .exist Figure 1 Medium, 3409cm -1 The hydroxyl peak is at 2900-3001cm -1 The stretching vibration of the unsaturated C-H bond is 1739 cm -1 The ester peak in acrylic acid is 1455 cm -1 The C=N peak in the triazine group is 1370 cm -1 , 890cm -1 is the stretching vibration of the benzene ring, 1230cm -1It is the bending vibration peak of CH. 780cm -1 and 1044cm -1 It is the ether bond peak in isobornyl ester. From the infrared image, it can be seen that the resin was successfully prepared.

[0078] exist Figure 2 In the modified silica infrared image, it can be seen that 1368 cm -1 The CH bending vibration has 1230cm -1 The stretching vibration of the CF bond at shows that this modification method is successful.

[0079] <Test Example 3>

[0080] UV resistance test

[0081] The polyurethane coatings provided in Examples 1-3 and Comparative Examples 1-3 were respectively tested for ultraviolet performance. The specific method was as follows: the polyurethane coatings provided in Examples 1-3 and Comparative Examples 1-3 were respectively coated on optical glass (90% visible light transmittance) using a 100 μm wire rod, and ultraviolet spectrum testing was performed using UV-4100, with a test wavelength of 250 nm to 800 nm.

[0082] See attached for test results Figure 3 .

[0083] From the attached Figure 3 As can be seen, the transmittance of all examples and the comparative example in the visible light band above 500nm is not much different, all exceeding 81%, indicating that the coatings are transparent. With increasing content of triazine groups and modified nano-silica particles, especially Example 3, the transmittance in the ultraviolet region of 250nm-392nm reaches 0, which can be considered to cover the daily solar ultraviolet radiation (primarily 280nm-400nm).

[0084] <Test Example 4>

[0085] Coating yellowing value test

[0086] The polyurethane coatings in Examples 1, 2, 3 and Comparative Example 1 were applied to wood using a 75 μm wire rod and subjected to a 300-h weathering test in an artificial accelerated aging chamber. The specific parameters were as follows: chamber temperature 60°C; 4 h of UV exposure and 4 h of spraying (reciprocating cycle); test wavelength and intensity: QUVB (280-320 nm), 0.81 W / m 2 . See attached for photos after UV aging Figure 4 The yellowing value is tested according to the national standard GB11186, 3-89 color difference calculation. The specific yellowing values ​​are shown in Table 2, and the data are the average value of three tests.

[0087] Table 2 Color difference and yellowing value of wood-based polyurethane coatings

[0088] Example 1 Example 2 Example 3 Comparative Example 1 Yellowing value Δb 2.8 1.8 1.7 20.1 Color difference ΔE 3.1 1.9 1.85 22.5

[0089] Depend on Figure 4 As shown in Table 2, with the increase of the content of triazine groups and modified nano-silica particles, the weather resistance of the coating is greatly improved.

[0090] Functions and Effects of the Embodiments

[0091] According to the anti-UV polyurethane composite coating involved in the above embodiment, since the resin used has triazine ultraviolet absorption groups, the vibration of these triazine groups will cause ultraviolet absorption of 280 to 380 nm, and it also has the characteristics of lighter color, high temperature resistance and good solubility, so that the coating formed by the composite coating is transparent, weather-resistant and has excellent ultraviolet absorption performance.

[0092] Furthermore, nano-silica modified with fluorine segments is also used in combination, so that more nanoparticles can be distributed on the surface by utilizing its surface mobility. Silica nanoparticles have a strong scattering ability for ultraviolet light below 390nm, which can further protect the internal coating, thus greatly improving the coating's anti-ultraviolet ability.

[0093] The above embodiments are preferred examples of the present invention and are not intended to limit the scope of protection of the present invention.

Claims

1. An anti-ultraviolet polyurethane composite coating, characterized in that: include: Component A and Component B, Wherein, component A comprises: an aqueous polyacrylate dispersion containing triazine groups and modified silica nanoparticles; Component B includes: isocyanate curing agent, The preparation method of the aqueous polyacrylate dispersion containing triazine groups comprises the following steps: The mixed monomers are dissolved in a solvent to form a mixed monomer solution, which is then divided into a mixed monomer solution A and a mixed monomer solution B. allowing the mixed monomer solution A to react to obtain a reaction solution A; Adding the mixed monomer solution B dropwise to the reaction solution A and continuing the reaction to obtain reaction solution B; Remove the solvent from the reaction solution B, add water and an emulsifier, and obtain: The mixed monomers at least include: methyl methacrylate, 1,3,5-triacryloylhexahydro-1,3,5-triazine, hydroxyethyl acrylate, styrene, dimethylaminoethyl methacrylate, isobornyl acrylate, initiator, chain transfer agent, The preparation method of the modified silicon dioxide nanoparticles comprises the following steps: In the presence of an acid catalyst, trimethoxy (3,3,3-trifluoropropyl) silane is used to modify nano-silica. After the reaction is completed, the nano-silica is centrifuged, purified, and dried to obtain the product.

2. The UV-resistant polyurethane composite coating according to claim 1, characterized in that: in, Component A also includes a defoamer and / or a wetting agent.

3. The UV-resistant polyurethane composite coating according to claim 1, characterized in that: in, In the mixed monomer, the content of 1,3,5-triacryloylhexahydro-1,3,5-triazine is 5 wt % to 15 wt %.

4. The UV-resistant polyurethane composite coating according to claim 1, characterized in that: in, The solvent is selected from any one or more of toluene, xylene, propylene glycol butyl ether, and acetone.

5. The UV-resistant polyurethane composite coating according to claim 1, characterized in that: in, The initiator is selected from any one or more of azobisisobutyronitrile, azobisisoheptanenitrile and benzoyl peroxide.

6. The UV-resistant polyurethane composite coating according to claim 1, characterized in that: in, The emulsifier is selected from one of polyvinyl alcohol, quaternary ammonium salt, and alkyl sulfate; the chain transfer agent is any one of dodecyl mercaptan, mercaptoethanol, and α-methylstyrene linear dimer.

7. The UV-resistant polyurethane composite coating according to claim 1, characterized in that: in, The acid catalyst is selected from any one of trifluoroacetic acid, hydrochloric acid and sulfuric acid.

8. The UV-resistant polyurethane composite coating according to claim 1, characterized in that: in, The molar ratio of the hydroxyl group of the aqueous polyacrylate dispersion containing triazine groups in the component A to the NCO group of the isocyanate curing in the component B is (1.3-1.5):1.

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