A coating, a preparation method thereof and its application

Abstract

The invention discloses a coating, a preparation method and an application thereof. The coating comprises, by weight, the following effective ingredients: 25-50 parts of polyurethane; 10-25 parts of aliphatic dibasic acid; 10-30 parts of hyperbranched polyester; and 20-40 parts of microcapsules. The microcapsules comprise a membrane, an inner liquid encapsulated within the membrane, and a hollow portion. The hollow portion accounts for 20-40% of the total volume of the membrane. The coating preparation method comprises the following steps: dispersing the inner liquid, then adding a membrane stock liquid, stirring or ultrasonically homogenizing, performing a polymerization reaction, and simultaneously introducing gas to obtain the microcapsules. The coating comprises portions with different refractive indices, so that the surface of the material has a matte texture, thereby improving the reflectivity of the material.

Description

Technical Field

[0001] The invention relates to a coating, a preparation method and application thereof, and belongs to the technical field of functional reagents. Background Art

[0002] Different material surfaces have different visual properties. For example, metal has a smooth surface and does not absorb light easily. Most of the light will be reflected back. Therefore, the reflectivity of metal is very high, resulting in high reflectivity and luster. The metal surface can also greatly enhance the intensity of reflected light. The metal surface with complete reflective properties reflects much more light than a flat object. Therefore, the reflective effect of the metal surface is more obvious and more dazzling. In some applications, the reflection on the surface of an object is too large, which can easily cause visual glare and affect the object, such as forming strong glare, which greatly reduces the sensory comfort of the object. The common way to change the surface properties in the prior art is to add a coating to the surface of the material. The coating changes the visual perception of the material and improves its durability and protection. There is still a lot of room for improvement in coating agents in this regard. Summary of the Invention

[0003] In order to overcome the deficiencies of the prior art, the first object of the present invention is to provide a coating having portions with different refractive indices, so that the surface of the material has a matte texture and the light reflection of the material is improved.

[0004] The second object of the present invention is to provide a method for preparing the above-mentioned coating to form a coating containing a specific microcapsule structure.

[0005] The third object of the present invention is to provide an application of the above-mentioned coating, which is a thermal curing method for the coating. The progressive thermal curing method can form spaces with different refractive indices inside the coating, reduce the reflection of the material surface, and have both good transparency and good diffuse reflection effect.

[0006] The first object of the present invention can be achieved by adopting the following technical solution: a coating comprising the following active ingredients in parts by weight:

[0007]

[0008] The microcapsule comprises a membrane body, an inner liquid coated in the membrane body and a hollow part; the hollow part accounts for 20-40% of the total volume of the membrane body.

[0009] Furthermore, the polyurethane is sulfonate polyurethane.

[0010] Furthermore, the hyperbranched polyester is a hyperbranched polyester modified with fatty acid.

[0011] Furthermore, the particle size of the microcapsule is 10-40 nm.

[0012] Furthermore, the film is prepared from at least one of tetraethoxysilane, tetramethoxysilane and polydialkylsiloxane.

[0013] Furthermore, the inner liquid is at least one of polyacrylate, methyl methacrylate and ethyl methacrylate.

[0014] Furthermore, the coating material further comprises acrylic resin.

[0015] Furthermore, the acrylic resin is a hydroxy acrylic resin.

[0016] The second object of the present invention can be achieved by adopting the following technical solution: a method for preparing a coating, the coating comprising microcapsules; the microcapsules comprising a membrane, an inner liquid coated within the membrane, and a hollow portion; the hollow portion accounting for 20-40% of the total volume of the membrane; the preparation method comprising the steps of: dispersing the inner liquid, then adding the membrane stock solution, stirring or ultrasonically homogenizing, performing a polymerization reaction, and simultaneously introducing gas to obtain the microcapsules;

[0017] Alternatively, the inner liquid is added to a dispersant for dispersion to obtain a dispersion; the polymerized membrane is added to the dispersion to allow the dispersion to be absorbed into the membrane, and then the dispersant in the membrane is removed to form a hollow portion to obtain a microcapsule.

[0018] Furthermore, the inner liquid is added into a dispersant for dispersion to obtain a dispersion; the membrane stock solution is added into the dispersion for polymerization reaction, and then the dispersant in the membrane is removed to form a hollow part to obtain a microcapsule.

[0019] The third object of the present invention can be achieved by adopting the following technical scheme: a coating is applied, after which the coating is subjected to a primary heat curing at a temperature of 55-80°C for a time of 2-8 minutes; and then a secondary heat curing is carried out at a temperature of 90-150°C for a time of 30-60 minutes; the coating comprises the following active ingredients in parts by weight: 25-50 parts of polyurethane; 10-25 parts of aliphatic dibasic acid; 10-30 parts of hyperbranched polyester; and 20-40 parts of microcapsules; the microcapsules comprise a membrane body, an inner liquid encapsulated in the membrane body, and a hollow portion; and the hollow portion occupies 20-40% of the total volume of the membrane body.

[0020] Furthermore, after the coating is applied, a primary heat curing is performed at a temperature of 55-80°C for 2-8 minutes; a secondary heat curing is performed at a temperature of 90-150°C for 30-60 minutes; and a tertiary heat curing is performed at a temperature of 150-180°C for 1-10 minutes.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The coating of the present invention makes the surface of the material have a matte texture, improves the reflection of the material, and even if there are scratches, it is not easy to see;

[0023] 2. The coating of the present invention can be used on a variety of materials such as glass, wood, metal, etc.

[0024] 3. The coating of the present invention has good flatness, smooth surface, good transparency, and the microcapsules are evenly distributed inside the formed coating film;

[0025] 4. The method for preparing the coating of the present invention provides a method for forming a coating containing a specific microcapsule structure;

[0026] 5. The coating of the present invention forms a film by gradual thermal curing, so that spaces with different refractive indices are formed inside the coating, reducing the reflection on the surface of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The material of Example 1 before surface coating;

[0028] Figure 2 After coating the surface of the material in Example 1;

[0029] Figure 3 The material of Example 2 before surface coating;

[0030] Figure 4 The surface of the material in Example 2 is coated. DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0032] A coating comprising the following active ingredients in parts by weight:

[0033]

[0034] Sulfonate polyurethane can maintain good stability in a wide pH environment, has high bonding strength, and is water-resistant and heat-resistant.

[0035] Aliphatic dibasic acids are used to control the Tg of the coating.

[0036] Hyperbranched polyester helps to disperse the microcapsules and stabilizes the uniform distribution of the microcapsules in the coating, while making the coating easier to thermoset into a film; hyperbranched polyester has a highly branched structure and a large number of terminal functional groups that are well connected with the sulfonate polyurethane and the film body. The hyperbranched polyester and the sulfonate polyurethane form a binding structure and fix the microcapsules therein; when the coating is applied, the microcapsules are inside the coating and do not float on the surface, which does not affect the smoothness of the surface after the coating is cured and formed, and the coating surface has good smoothness.

[0037] The microcapsules consist of a membrane, an inner liquid encapsulating the membrane, and a hollow core. The hollow core accounts for 20-40% of the total membrane volume. The microcapsules have a particle size of 10-40 nm. During thermal curing of the coating, the gas in the hollow core expands, while the sulfonate polyurethane undergoes initial curing and the membrane expands, increasing the density of the microcapsule's exterior. The resulting film has refractive indices of approximately 1 for the hollow core and 1.4 for the inner liquid. The refractive indices of the sulfonate polyurethane and hyperbranched polyester are both approximately 1.5-1.7. Different refractive index regions are formed inside and outside the microcapsule, absorbing and reflecting light of different wavelengths. This increases the coating's diffuse reflectance and significantly reduces surface reflections. Furthermore, the microcapsules help improve the coating's light transmittance.

[0038] The membrane is composed of tetraethoxysilane (TEOS), tetramethoxysilane (TMOS) or polydialkylsiloxane (PDMS); and the internal liquid is at least one of polyacrylate, methyl methacrylate and ethyl methacrylate.

[0039] After curing, the film is slightly harder than polyurethane and hyperbranched polyester, and acts as a support inside the formed coating to maintain the coating's adherence to the material surface, making it less likely to deform or fall off.

[0040] Hydroxyl acrylic resin is used to dilute sulfonate polyurethane. Sulfonate polyurethane has a high viscosity. Dilution before thermosetting helps to improve the uniformity of the components in the coating, especially the uniformity of microcapsules, and enhance the overall flexibility of the coating.

[0041] The coating preparation method is as follows:

[0042] Preparation steps of microcapsules: Microcapsules are prepared by one of the following methods:

[0043] 1) Dispersing the inner liquid, then adding the membrane stock solution, stirring or ultrasonically homogenizing, and then carrying out polymerization reaction while introducing gas to obtain microcapsules;

[0044] 2) adding the inner liquid to a dispersant for dispersion to obtain a dispersion; adding the polymerized membrane to the dispersion, ultrasonically or by high-speed stirring to allow the dispersion to be absorbed into the membrane; then removing the dispersant from the membrane and replacing it with gas to form a hollow portion, thereby obtaining a microcapsule;

[0045] 3) Adding the inner liquid to a dispersant for dispersion to obtain a dispersion; adding the membrane stock solution to the dispersion for polymerization; then removing the dispersant from the membrane and replacing it with gas to form a hollow portion to obtain a microcapsule. The gas is air or carbon dioxide.

[0046] The dispersant used is a reagent with a solubility rate of ≤10% v / v in the internal liquid. In a specific embodiment, the dispersant can be water. The dispersant in the membrane can be removed by reduced pressure drying (pressure below 300 Pa, 20-40° C., 30 min-1 h), centrifugation (centrifugation in a 1500 rpm centrifuge for 2-3 min), ultrafiltration, or evaporation. All of these methods can effectively remove the dispersant and form a hollow portion that accounts for 20-40% of the total volume of the microcapsule.

[0047] Mixing steps: sulfonate polyurethane, aliphatic dibasic acid and hydroxy acrylic resin are mixed, then microcapsules are added and mixed, and finally fatty acid-modified hyperbranched polyester is added and mixed evenly to obtain a coating.

[0048] Sulfonate polyurethane and aliphatic dibasic acid are diluted with hydroxy acrylic resin, microcapsules are mixed, and finally fatty acid-modified hyperbranched polyester is added to connect the sulfonate polyurethane and microcapsule membrane.

[0049] The above-mentioned coating is applied to the surface of the material to reduce the strong reflection of the surface, make the surface look softer and improve the tolerance of the material; the coating is covered on the surface of the material by thermosetting, and the thermosetting process is: after the coating is applied to the surface of the material, it is subjected to a primary thermosetting process at a temperature of 55-80°C and a time of 2-8 minutes; then a secondary thermosetting process is carried out at a temperature of 90-150°C and a time of 30-60 minutes; and a tertiary thermosetting process is carried out at a temperature of 150-180°C and a time of 1-10 minutes.

[0050] The thermal curing process utilizes a three-step heating process. During the first thermal curing step, the internal liquid and sulfonate polyurethane begin to solidify. The gas within the hollow microcapsules expands due to the heat, stretching the film and forming air pockets within the coating. Scanning electron microscopy reveals an expansion of 10-25% by volume. The flexibility of the tetraethoxysilane, tetramethoxysilane, and polydialkylsiloxane films allows for a 10-25% volume expansion of the hollow microcapsules, while still effectively encapsulating the internal liquid and hollow microcapsules, maintaining structural integrity within the resulting film. The initial curing of the sulfonate polyurethane forms a framework for the coating, making it less susceptible to deformation and conforming to the surface. The second curing step primarily involves the initial curing of the sulfonate polyurethane and hyperbranched polyester, while the third curing step involves the curing of the hyperbranched polyester. This gradual thermal curing process prevents the coating's viscosity from increasing too rapidly, which could trigger side reactions. More importantly, it creates spaces within the coating with varying refractive indices, reducing surface reflection, resulting in both excellent transparency and diffuse reflection.

[0051] Example 1:

[0052] A coating comprising the following active ingredients in parts by weight as shown in Table 1:

[0053] Table 1: Ingredients by weight in Example 1

[0054] Element parts by weight Sulfonate polyurethane 30 servings Aliphatic dibasic acid 15 servings Fatty acid modified hyperbranched polyester 25 servings microcapsules 35 servings Hydroxylated acrylic resin 10 servings

[0055] The preparation of the coating includes the following steps:

[0056] The microcapsule preparation steps include: using polyacrylate as the inner liquid, dispersing it in water, then adding polydialkylsiloxane, stirring or ultrasonically homogenizing it, and then performing a polymerization reaction while simultaneously introducing air to obtain the microcapsules. The microcapsules consist of a membrane, an inner liquid encapsulating the membrane, and a hollow portion. The hollow portion accounts for an average percentage of 33% of the total volume of the membrane. The average particle size of the microcapsules is 25 nm.

[0057] Mixing steps: sulfonate polyurethane, aliphatic dibasic acid and hydroxy acrylic resin are mixed, then microcapsules are added and mixed, and finally fatty acid-modified hyperbranched polyester is added and mixed evenly to obtain a coating.

[0058] The paint was applied to the surface of the wood material and subjected to a primary heat curing at 65°C for 6 minutes; a secondary heat curing at 95°C for 34 minutes; and a tertiary heat curing at 160°C for 2 minutes. The film thickness was 10 μm, the microcapsule membrane boundary was visible, and the average particle size was 30 nm. Figure 1 and Figure 2 These are pictures of the material surface before and after coating.

[0059] Example 2:

[0060] A coating comprising the following active ingredients in parts by weight as shown in Table 2:

[0061] Table 2: Ingredients by weight of Example 2

[0062] Element parts by weight Sulfonate polyurethane 30 servings Aliphatic dibasic acid 15 servings Fatty acid modified hyperbranched polyester 25 servings microcapsules 35 servings Hydroxylated acrylic resin 10 servings

[0063] The preparation of the coating includes the following steps:

[0064] The microcapsule preparation steps include: dispersing methyl methacrylate as an inner liquid in water, then adding polydialkylsiloxane, stirring or ultrasonically homogenizing, and then performing a polymerization reaction while simultaneously introducing air to obtain microcapsules. The microcapsules comprise a membrane, an inner liquid encapsulating the membrane, and a hollow portion. The hollow portion accounts for an average percentage of 35% of the total volume of the membrane. The average particle size of the microcapsules is 32 nm.

[0065] Mixing steps: sulfonate polyurethane, aliphatic dibasic acid and hydroxy acrylic resin are mixed, then microcapsules are added and mixed, and finally fatty acid-modified hyperbranched polyester is added and mixed evenly to obtain a coating.

[0066] The coating was applied to the surface of the aluminum alloy material and subjected to a primary thermal curing at a temperature of 75°C for 6 minutes; a secondary thermal curing was then carried out at a temperature of 110°C for 42 minutes; and a tertiary thermal curing was carried out at a temperature of 172°C for 5 minutes. The film thickness was 12 μm, the microcapsule membrane boundary was visible, and the average particle size was 38.5 nm. Figure 3 and Figure 4 These are pictures of the material surface before and after coating.

[0067] Example 3:

[0068] A coating comprising the following active ingredients in parts by weight as shown in Table 3:

[0069] Table 3: Ingredients by weight of Example 3

[0070] Element parts by weight Sulfonate polyurethane 45 servings Aliphatic dibasic acid 20 servings Fatty acid modified hyperbranched polyester 15 servings microcapsules 25 servings Hydroxylated acrylic resin 8 servings

[0071] The preparation of the coating includes the following steps:

[0072] The microcapsule preparation steps include: dispersing methyl methacrylate as an inner liquid in water to obtain a dispersion; adding a polymerized polydialkylsiloxane film to the dispersion, and ultrasonically or by high-speed stirring to allow the dispersion to be absorbed into the film; then, drying under reduced pressure (pressure below 300 Pa, 30° C., 1 hour) to remove the dispersant from the film and replace it with air to form a hollow portion, thereby obtaining the microcapsule; the hollow portion accounts for an average percentage of 25% of the total volume of the film; and the average particle size of the microcapsules is 18 nm.

[0073] Mixing steps: sulfonate polyurethane, aliphatic dibasic acid and hydroxy acrylic resin are mixed, then microcapsules are added and mixed, and finally fatty acid-modified hyperbranched polyester is added and mixed evenly to obtain a coating.

[0074] The coating was applied to the surface of the metal material and subjected to a primary thermal curing at 65°C for 3 minutes; a secondary thermal curing at 140°C for 35 minutes; and a tertiary thermal curing at 166°C for 8 minutes. The film thickness was 16 μm, the microcapsule membrane boundary was visible, and the average particle size was 20 nm.

[0075] Example 4:

[0076] A coating comprising the following active ingredients in parts by weight as shown in Table 4:

[0077] Table 4: Ingredients by weight of Example 4

[0078] Element parts by weight Sulfonate polyurethane 36 servings Aliphatic dibasic acid 21 servings Fatty acid modified hyperbranched polyester 26 servings microcapsules 33 servings Hydroxylated acrylic resin 14 servings

[0079] The preparation of the coating includes the following steps:

[0080] The microcapsule preparation steps include: using polyacrylate as an internal liquid and dispersing it in water to obtain a dispersion; adding tetraethoxysilane to the dispersion to carry out a polymerization reaction; then centrifuging (1500 rpm for 2.5 minutes) to remove the dispersant from the membrane and replace it with air, forming a hollow portion to obtain the microcapsule; the hollow portion accounts for an average of 28% of the total volume of the membrane; and the average particle size of the microcapsules is 33 nm.

[0081] Mixing steps: sulfonate polyurethane, aliphatic dibasic acid and hydroxy acrylic resin are mixed, then microcapsules are added and mixed, and finally fatty acid-modified hyperbranched polyester is added and mixed evenly to obtain a coating.

[0082] The coating was applied to the surface of the metal material and subjected to a primary thermal curing at 70°C for 7 minutes; a secondary thermal curing was then carried out at 100°C for 55 minutes; and a tertiary thermal curing was carried out at 160°C for 9 minutes. The film thickness was 20 μm, the microcapsule membrane boundary was visible, and the average particle size was 40 nm.

[0083] Comparative Example:

[0084] No microcapsules were added to the coating, and the remaining parameters and characteristics were the same as those in Example 2.

[0085] Detection:

[0086] Light transmittance: The coatings obtained in Examples 1-4 were applied to both sides of borosilicate glass, and the light transmittance was tested after curing;

[0087] Hardness: tested according to GB / T6739-2006 standard;

[0088] Wear resistance: tested according to GB / T 23988-2009 standard;

[0089] Adhesion: tested according to GB / T 9286-1998 standard;

[0090] Impact resistance: tested according to GB / T 1732-1993 standard;

[0091] Flexibility: Tested according to GB / T 1731-1993 standard.

[0092] The results are shown in Table 5:

[0093] Table 5 Test results of Examples 1-4 and Comparative Examples

[0094] project Example 1 Example 2 Example 3 Example 4 Comparative Example Light transmittance (%) 98.3 98.1 97.4 97.6 93.3 hardness 8H 8H 7H 7H 5H Wear resistance (L / μm) 1410 1382 1310 1350 1050 Adhesion (grade) 0 0 0 0 1 impact resistant qualified qualified qualified qualified qualified flexibility qualified qualified qualified qualified qualified Diffuse reflectivity (%) 98 97.6 96.4 97.7 83.2

[0095] Those skilled in the art can make various other corresponding changes and modifications based on the technical solutions and concepts described above, and all of these changes and modifications should fall within the scope of protection of the claims of the present invention.

Claims

1. A coating, characterized in that: Contains the following active ingredients in parts by weight: Polyurethane 25-50 parts; 10-25 parts of aliphatic dibasic acid; 10-30 parts of hyperbranched polyester; 20-40 parts of microcapsules; The microcapsule comprises a membrane body, an inner liquid coated in the membrane body, and a hollow portion; the hollow portion occupies 25-28% of the total volume of the membrane body; the polyurethane is a sulfonate polyurethane; The film is prepared from at least one of tetraethoxysilane, tetramethoxysilane and polydialkylsiloxane; The inner liquid is at least one of polyacrylate, methyl methacrylate and ethyl methacrylate; The coating is cured by the following method: after the coating is applied, a primary heat curing is performed at a temperature of 55-80° C. for 2-8 minutes; and a secondary heat curing is performed at a temperature of 90-150° C. for 30-60 minutes.

2. The coating according to claim 1, wherein The hyperbranched polyester is a hyperbranched polyester modified with fatty acid.

3. The coating according to claim 1, wherein The particle size of the microcapsule is 10-40 nm.

4. The coating according to claim 1, wherein The coating also includes an acrylic resin.

5. A method for preparing a coating, characterized in that: The coating comprises the following active ingredients in parts by weight: 25-50 parts of polyurethane; 10-25 parts of aliphatic dibasic acid; 10-30 parts of hyperbranched polyester; and 20-40 parts of microcapsules. The microcapsule comprises a membrane, an inner liquid coated within the membrane, and a hollow portion; the hollow portion occupies 25-28% of the total volume of the membrane; the polyurethane is a sulfonate polyurethane; the membrane is prepared from at least one of tetraethoxysilane, tetramethoxysilane, and polydialkylsiloxane; and the inner liquid is at least one of polyacrylate, methyl methacrylate, and ethyl methacrylate; The preparation method includes the following steps: dispersing the inner liquid, then adding the membrane stock solution, stirring or ultrasonically homogenizing, performing a polymerization reaction, and simultaneously introducing gas to obtain microcapsules; Alternatively, the inner liquid is added to a dispersant for dispersion to obtain a dispersion; the polymerized membrane is added to the dispersion to allow the dispersion to be absorbed into the membrane, and then the dispersant in the membrane is removed to form a hollow portion to obtain a microcapsule.

6. The method for preparing the coating according to claim 5, wherein: The inner liquid is added into a dispersant for dispersion to obtain a dispersion liquid; the membrane original liquid is added into the dispersion liquid for polymerization reaction, and then the dispersant in the membrane body is removed to form a hollow part to obtain a microcapsule.

7. An application of a coating, characterized in that, After the coating is applied, a primary heat curing is performed at a temperature of 55-80°C for 2-8 minutes; and a secondary heat curing is performed at a temperature of 90-150°C for 30-60 minutes. The coating comprises, by weight, the following active ingredients: 25-50 parts of polyurethane; 10-25 parts of aliphatic dibasic acid; 10-30 parts of hyperbranched polyester; and 20-40 parts of microcapsules. The microcapsules comprise a membrane, an inner liquid encapsulated within the membrane, and a hollow portion. The hollow portion accounts for 25-28% of the total volume of the membrane. The polyurethane is sulfonate polyurethane; the membrane is prepared from at least one of tetraethoxysilane, tetramethoxysilane and polydialkylsiloxane; and the inner liquid is at least one of polyacrylate, methyl methacrylate and ethyl methacrylate.

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