A novel self-cleaning coating and its preparation method

Abstract

The present invention provides a novel self-cleaning coating comprising the following raw materials in parts by weight: 80-100 parts of acrylic emulsion, 5-10 parts of titanium dioxide composite material, 20-45 parts of filler, 30-45 parts of water, and 5-15 parts of an additive. The titanium dioxide composite material is a nano-scale titanium dioxide material doped with manganese and magnesium ions. The coating produced from the novel self-cleaning coating has excellent stain resistance and strong self-cleaning ability.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and in particular to a novel self-cleaning coating and a preparation method thereof. Background Art

[0002] With the rapid development of the modern construction industry and the advancement of technology, people's requirements for coatings have also risen. Exterior building coatings are exposed to the atmosphere, experiencing changes in the natural environment such as wind, sun, rain, dust, and smog. Furthermore, with increasingly serious environmental pollution, the amount of dust and suspended pollutants in the atmosphere is high, which can easily stain the coating and, over time, can easily cause the coating to lose its original decorative effect.

[0003] Therefore, it is necessary to seek a coating that can produce a coating with excellent anti-fouling performance and strong self-cleaning ability. Summary of the Invention

[0004] The purpose of the present invention is to provide a novel self-cleaning coating and a preparation method thereof, so that the prepared coating has excellent anti-fouling performance and strong self-cleaning ability.

[0005] According to one aspect of the present invention, a new self-cleaning coating is provided, comprising the following raw materials in parts by weight: 80 to 100 parts of acrylic emulsion, 5 to 10 parts of titanium dioxide composite material, 20 to 45 parts of filler, 30 to 45 parts of water, and 5 to 15 parts of additives; the titanium dioxide composite material is a nano-scale titanium dioxide material, and the titanium dioxide composite material is doped with manganese ions and magnesium ions.

[0006] The present invention introduces nano-scale titanium dioxide material into the coating, and utilizes the super-hydrophilic effect presented by the titanium dioxide composite material under the action of light, which can reduce the contact angle of the coating prepared by the novel self-cleaning coating, so that water droplets form a water film on the surface of the coating. Under the action of gravity, the water film removes the pollutants on the surface of the coating, achieving a self-cleaning effect. On the other hand, compared with undoped nano-scale titanium dioxide, the titanium dioxide composite material doped with manganese ions and magnesium ions provided by the present invention has better photocatalytic ability, can widen the light response range, and improve quantum efficiency. When the titanium dioxide composite material in the coating is exposed to light, it will promote the separation of electrons and holes, and the positively charged holes will oxidize the organic molecules on the surface of the coating, while the negatively charged electrons can combine with oxygen in the external environment to form superoxide radicals, and the superoxide radicals will attack the organic molecules on the surface of the coating. Thus, by adding the titanium dioxide composite material to the coating, the organic matter on the surface of the coating is converted into carbon dioxide and water, and the water can separate the dirt on the surface of the coating from the coating, further achieving the effect of self-cleaning of the coating.

[0007] Preferably, the titanium dioxide composite material is doped with divalent manganese ions and divalent magnesium ions.

[0008] Ti 4+ The ionic radius of Mn is 60.5 pm. 2+ The ionic radius of Mn is 67pm, and the ionic radius of the two is similar, so 2+ Can enter the titanium dioxide lattice and 4+ Replacement is carried out, thereby greatly reducing the excitation energy required for the transition between electrons and holes. 2+ The ionic radius of Mg is 72 pm, which is much larger than that of titanium ion. 2+ Substitution of Ti 4+ The possibility is small, so Mg 2+ They are evenly dispersed on the surface of titanium dioxide, not only inhibiting the growth of titanium dioxide crystals and making the resulting titanium dioxide composite material have a uniform particle size distribution; they also promote the detachment of oxygen atoms from the titanium dioxide crystals, accelerating the generation of holes in the titanium dioxide composite material, thereby improving the self-cleaning performance of the coating. Therefore, doping titanium dioxide with divalent manganese ions and divalent magnesium ions can make the titanium dioxide composite material have excellent photocatalytic activity, and thus the coating prepared by applying the new self-cleaning coating has excellent self-cleaning performance.

[0009] Preferably, the titanium dioxide composite material is prepared by the following steps: S1. uniformly mixing a titanium source material, a manganese source material, a magnesium source material, a dispersing aid and a solvent to obtain a mixed solution, stirring the mixed solution to cause a sol-gel reaction, and allowing the mixed solution to stand to obtain a gel; S2. drying the gel and calcining it at 350-500°C for 2-3 hours to obtain a titanium dioxide composite material.

[0010] Using a sol-gel method, which operates under mild conditions and requires simple procedures, manganese and magnesium ions are uniformly incorporated into titanium dioxide at the molecular level. Furthermore, by calcining the titanium dioxide at 350-500°C, a titanium dioxide composite material with a stable structure and uniform particle size is formed. If the calcination temperature is too high, the resulting titanium dioxide composite material will have an uneven particle size distribution. When introduced into the new self-cleaning coating, the titanium dioxide composite material will tend to aggregate locally, affecting the coating's dispersibility. If the calcination temperature is too low, it will be difficult to achieve a fully grown crystal structure.

[0011] Preferably, calculated according to the molar ratio, in the mixed solution, the manganese element: the magnesium element: the titanium element = 0.1-0.2: 0.05-0.1:1.

[0012] When the doping amounts of manganese and magnesium satisfy the above relationship, the prepared titanium dioxide composite material can make the coating have better self-cleaning performance. 4+ With Mn 2+ The valence states of Mn are not consistent, so 2+The replaceable amount is limited. If too much manganese source material is input, the excess manganese ions will accumulate on the surface of the titanium dioxide composite material, which will easily hinder the separation of electron-hole pairs. If too little manganese source material is input, the doped manganese ions will be too little, the photocatalytic performance of the titanium dioxide composite material will not be significantly improved, and the self-cleaning performance of the coating will not be greatly improved. Similarly, if too much magnesium source material is input, magnesium ions will accumulate in large quantities on the surface of the titanium dioxide composite material, thereby hindering the separation of electron-hole pairs. If too little magnesium source material is input, the regulation of the particle size distribution of the titanium dioxide composite material will not be obvious enough.

[0013] Preferably, calculated by molar ratio, in the titanium dioxide composite material, the ratio of manganese element:magnesium element:titanium element=0.14:0.07:1.

[0014] Preferably, the pH value of the mixed solution is first adjusted to 1.5 to 2.5, and then the mixed solution is subjected to a sol-gel reaction.

[0015] When the pH value of the mixed solution is between 1.5 and 2.5, it is easier for the mixed solution to transform into a gel state, and it is conducive to the generation of a titanium dioxide composite material with uniform particle size distribution.

[0016] Preferably, the acrylic emulsion comprises the following raw materials in parts by weight: 20-30 parts of acrylic monomer, 5-10 parts of functional monomer, 10-20 parts of silicone monomer, 2-8 parts of emulsifier, and 80-100 parts of solvent, wherein the functional monomer is glycidyl methacrylate.

[0017] The inventors discovered that while the introduction of titanium dioxide composite materials into a novel self-cleaning coating imparts strong self-cleaning properties, it also tends to yellow after exposure to sunlight. To reduce the risk of yellowing, the inventors introduced glycidyl methacrylate into an acrylic emulsion. This promotes directional bonding between acrylic monomers and glycidyl methacrylate, stabilizes the acrylic emulsion structure, and enhances compatibility with the titanium dioxide composite material. Using this acrylic emulsion to prepare a novel self-cleaning coating reduces the yellowing risk of the coating and improves its yellowing resistance.

[0018] Preferably, the acrylic emulsion is prepared by the following steps: uniformly mixing an organosilicon monomer with an acrylate monomer, a functional monomer, an initiator, water, and an emulsifier, and reacting the resulting mixture at 70-90° C. for 3-5 hours to obtain the acrylic emulsion.

[0019] By adjusting the reaction temperature and reaction time, the occurrence of side reactions can be reduced, which is beneficial for controlling the morphology of the final product.

[0020] Preferably, the acrylic monomer consists of butyl acrylate and methyl methacrylate in a molar ratio of 2:1.

[0021] The acrylic monomers used in this invention do not contain structures prone to yellowing, such as phenyl and phenolic compounds. Furthermore, a 2:1 molar ratio of butyl acrylate to methyl methacrylate facilitates further cross-linking between the acrylic monomers and the functional monomers, forming a stable three-dimensional network structure, thereby improving the coating's yellowing resistance and substrate adhesion.

[0022] Preferably, the additives include 0.5-2 parts of cellulose, 0.1-1 parts of bactericide, 0.05-0.3 parts of defoamer, 1-5 parts of ethylene glycol, 3-7 parts of film-forming aid, and 0.1-1 parts of thickener.

[0023] According to another aspect of the present invention, a method for preparing the above-mentioned novel self-cleaning coating is provided, comprising the following steps: uniformly mixing water, part of the additives and the acrylic emulsion to obtain a coating intermediate, and then uniformly mixing the coating intermediate with the remaining raw materials to obtain the novel self-cleaning coating.

[0024] The novel self-cleaning coating provided in this solution has simple preparation process steps, convenient operation, mild conditions and good economic benefits. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0026] Example 1

[0027] This embodiment provides a new self-cleaning coating, and the specific preparation method is as follows:

[0028] (1) Preparation of titanium dioxide composite materials

[0029] The titanium dioxide composite material is a nano-scale titanium dioxide material, and the titanium dioxide composite material is doped with Mn 2+ and Mg 2+ .

[0030] The titanium dioxide composite material is prepared according to the following steps:

[0031] S1. A titanium source material, a dispersing aid, and a solvent are uniformly mixed to obtain a dispersion, and a manganese source material and a magnesium source material are sequentially added dropwise to the dispersion to obtain a mixed solution. In this mixed solution, the molar ratio of manganese, magnesium, and titanium is 0.14:0.07:1. A nitric acid solution is added dropwise to the mixed solution to adjust the pH of the mixed solution to 2. The mixed solution is vigorously stirred for 30 minutes to allow the mixed solution to undergo a sol-gel reaction, and allowed to stand to obtain a gel.

[0032] S2. The gel was dried at 90°C for 8 hours and calcined at 450°C for 2.5 hours to obtain a titanium dioxide composite material.

[0033] In this embodiment, butyl titanate is selected as the titanium source material, a MnSO4 solution with a concentration of 1 mol / L is selected as the manganese source material, a MgSO4 solution with a concentration of 1 mol / L is selected as the magnesium source material, anhydrous ethanol is selected as the solvent, and a dispersing aid can be appropriately selected according to actual conditions.

[0034] (2) Preparation of acrylic emulsion

[0035] The acrylic emulsion is prepared from raw materials including: 27 parts of acrylic monomer, 7 parts of functional monomer, 16 parts of silicone monomer, 5 parts of emulsifier, and 90 parts of solvent. The acrylic monomer is composed of butyl acrylate and methyl methacrylate in a molar ratio of 2:1, and the functional monomer is glycidyl methacrylate.

[0036] The acrylic emulsion is prepared according to the following steps: organic silicon monomer, acrylic ester monomer, functional monomer, initiator, water and emulsifier are uniformly mixed, and the resulting mixture is reacted at 80° C. for 4 hours to obtain the acrylic emulsion.

[0037] (3) Preparation of new self-cleaning coatings

[0038] The raw materials for preparing the new self-cleaning coating include: 90 parts of acrylic emulsion, 8 parts of titanium dioxide composite material, 32 parts of filler, 35 parts of water, 1 part of cellulose, 0.6 parts of fungicide, 0.2 parts of defoamer, 3 parts of ethylene glycol, 5 parts of film-forming aid, and 0.5 parts of thickener.

[0039] The novel self-cleaning coating is prepared by the following steps: water, cellulose, fungicide, ethylene glycol and acrylic emulsion are uniformly mixed to obtain a coating intermediate, and the coating intermediate is then uniformly mixed with the remaining raw materials to obtain the novel self-cleaning coating.

[0040] Example 2

[0041] This example uses the preparation method described in Example 1 to prepare a novel self-cleaning coating. This example differs from Example 1 in that, in step S2 of preparing the titanium dioxide composite material, the calcination temperature and time are adjusted. In this example, calcination is performed at 350°C for 3 hours. The remaining raw material ratios and preparation method remain identical to those in Example 1.

[0042] Example 3

[0043] This example uses the preparation method described in Example 1 to prepare a novel self-cleaning coating. This example differs from Example 1 in that, in step S2 of preparing the titanium dioxide composite material, the calcination temperature and time are adjusted. In this example, calcination is performed at 500°C for 2 hours. The remaining raw material ratios and preparation method remain identical to those in Example 1.

[0044] Example 4

[0045] This example uses the preparation method provided in Example 1 to prepare a novel self-cleaning coating. This example differs from Example 1 in that, during the preparation of the titanium dioxide composite material, the amounts of the titanium source, manganese source, and magnesium source were adjusted so that the molar ratio of manganese, magnesium, and titanium in the mixed solution was 0.05:0.03:1. The remaining raw material ratios and preparation method remained strictly consistent with those in Example 1.

[0046] Example 5

[0047] This example uses the preparation method provided in Example 1 to prepare a novel self-cleaning coating. This example differs from Example 1 in that, during the preparation of the titanium dioxide composite material, the amounts of the titanium source, manganese source, and magnesium source were adjusted so that the molar ratio of manganese, magnesium, and titanium in the mixed solution was 0.1:0.05:1. The remaining raw material ratios and preparation method remained strictly consistent with those in Example 1.

[0048] Example 6

[0049] This example uses the preparation method provided in Example 1 to prepare a novel self-cleaning coating. This example differs from Example 1 in that, during the preparation of the titanium dioxide composite material, the amounts of the titanium source, manganese source, and magnesium source were adjusted so that the molar ratio of manganese, magnesium, and titanium in the mixed solution was 0.2:0.1:1. The remaining raw material ratios and preparation method remained strictly consistent with those in Example 1.

[0050] Example 7

[0051] This example uses the preparation method provided in Example 1 to prepare a novel self-cleaning coating. This example differs from Example 1 in that, during the preparation of the titanium dioxide composite material, the amounts of the titanium source, manganese source, and magnesium source were adjusted so that the molar ratio of manganese, magnesium, and titanium in the mixed solution was 0.25:0.15:1. The remaining raw material ratios and preparation method remained strictly consistent with those in Example 1.

[0052] Example 8

[0053] This example uses the preparation method provided in Example 1 to prepare a novel self-cleaning coating. The difference between this example and Example 1 is that during the preparation of the titanium dioxide composite material, the pH value of the mixed solution is set to 1.5. The remaining raw material ratios and preparation method are strictly consistent with those in Example 1.

[0054] Example 9

[0055] This example uses the preparation method provided in Example 1 to prepare a novel self-cleaning coating. This example differs from Example 1 in that the pH of the mixed solution is set to 2.5 during the preparation of the titanium dioxide composite material. The remaining raw material ratios and preparation method remain strictly consistent with those in Example 1.

[0056] Example 10

[0057] This example uses the preparation method provided in Example 1 to prepare a novel self-cleaning coating. This example differs from Example 1 in that the acrylic emulsion preparation step is omitted. In addition, a commercially available pure acrylic emulsion of equal mass is used in place of the acrylic emulsion used in Example 1. This commercially available pure acrylic emulsion is manufactured by BASF and is designated A754. The remaining raw material ratios and preparation method remain identical to those in Example 1.

[0058] Example 11

[0059] This example uses the preparation method provided in Example 1 to prepare a novel self-cleaning coating. This example differs from Example 1 in that, during the preparation of the acrylic emulsion, the molar ratio of butyl acrylate to methyl methacrylate in the acrylic monomers is set to 1:1. The remaining raw material ratios and preparation method remain identical to those in Example 1.

[0060] Example 12

[0061] This embodiment refers to the preparation method provided in Example 1 to prepare a new self-cleaning coating. The difference between this embodiment and Example 1 is that in the process of preparing the titanium dioxide composite material, the type of manganese source material is adjusted so that the titanium dioxide composite material is doped with Mn 4+ and Mg 2+The rest of the raw material ratios and preparation methods were strictly consistent with those in Example 1.

[0062] Comparative Example 1

[0063] This comparative example used the preparation method described in Example 1 to prepare a coating. This comparative example differs from Example 1 in that the addition of a magnesium source material was omitted during the preparation of the titanium dioxide composite material, resulting in a titanium dioxide composite material free of magnesium. The remaining raw material ratios and preparation method remained identical to those in Example 1.

[0064] Comparative Example 2

[0065] This comparative example used the preparation method described in Example 1 to prepare a coating. This comparative example differs from Example 1 in that the addition of a manganese source was omitted during the preparation of the titanium dioxide composite material, resulting in a titanium dioxide composite material free of manganese. The remaining raw material ratios and preparation method remained identical to those in Example 1.

[0066] Comparative Example 3

[0067] This comparative example prepared a coating using the same method as described in Example 1. This comparative example differs from Example 1 in that the preparation of the titanium dioxide composite material was omitted, and an equal mass of commercially available nano-anatase titanium dioxide was used in place of the titanium dioxide composite material used in Example 1 during the preparation of the novel self-cleaning coating. The remaining raw material ratios and preparation methods remained strictly consistent with those in Example 1.

[0068] Test Case

[0069] Test objects: the novel self-cleaning coatings provided in Examples 1 to 12 and Comparative Examples 1 to 3.

[0070] Test items:

[0071] (1) Storage stability: Refer to GB / T 6753.3-1986 Test method for storage stability of coatings. When obvious settling of lumps (corresponding to settling grade 8) is detected, record the time when the coating of the test object appears to have lumps during storage.

[0072] (2) Self-cleaning performance: Referring to the test method in GB / T 31815-2015 Self-cleaning coatings for exterior building surfaces, a 90-day outdoor rain stain test was conducted to test the self-cleaning performance of the coatings prepared from the test objects.

[0073] (3) Yellowing resistance: According to the test method in GB / T 23987-2009 Paint and varnish coatings - Artificial weathering exposure to fluorescent ultraviolet light and water, the coatings prepared from the test objects were placed at (60±3)℃ and irradiance of 0.68W / m2 , dry phase (no condensation) fluorescent UV aging machine, keep continuous light for 168 hours, take out after the end of irradiation, compare with the coating without light, record and measure the color change (△E) detection.

[0074] Test results: as shown in Table 1.

[0075] Table 1. Performance test results of each test object

[0076]

[0077]

[0078] Result analysis:

[0079] By comparing the coatings corresponding to the new self-cleaning coatings prepared in Examples 1 to 12 with the coatings prepared in Comparative Examples 1 to 3, it can be found that the coatings corresponding to Examples 1 to 12 have higher self-cleaning performance. This shows that the titanium dioxide composite material doped with manganese ions and magnesium ions has better photocatalytic ability, which can remove pollutants on the surface of the coating and achieve a self-cleaning effect of the coating.

[0080] The test performance of the coatings prepared in Examples 1-3 shows that the photocatalytic performance of the titanium dioxide composite material increases with increasing calcination temperature, and the self-cleaning performance of the coating also increases with increasing temperature. The test performance of Examples 1 and 4-7 shows that during the preparation of the titanium dioxide composite material, the storage stability and self-cleaning performance of the resulting coatings increase with increasing proportions of manganese and magnesium in the mixed solution. Comparing the test performance of Examples 1 and 8-9 shows that a pH value of 1.5-2.5 facilitates the transition of the mixed solution to a gel state and facilitates the production of a titanium dioxide composite material with a uniform particle size distribution. Comparing the color differences of the coatings prepared in Examples 1 and 10-11 shows that the use of acrylic emulsions in the coatings of Examples 1 and 11 effectively reduces the risk of yellowing of the coatings, and the coating prepared in Example 1 exhibits better adhesion to the substrate than the coating prepared in Example 11. Comparing the test performance of the coatings prepared in Example 1 with that in Example 12, it can be found that compared with the coatings doped with Mn 4+ and Mg 2+ Titanium dioxide composite material doped with Mn 2+ and Mg 2+ The titanium dioxide composite material has better photocatalytic performance, and the corresponding coating also has better self-cleaning performance.

[0081] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A new self-cleaning coating, characterized in that: The invention comprises the following raw materials in parts by weight: 80-100 parts of acrylic emulsion, 5-10 parts of titanium dioxide composite material, 20-45 parts of filler, 30-45 parts of water, and 5-15 parts of additive; the titanium dioxide composite material is a nano-scale titanium dioxide material, and the titanium dioxide composite material is doped with divalent manganese ions and divalent magnesium ions; The titanium dioxide composite material is prepared by the following steps: S1. The titanium source material, the manganese source material, the magnesium source material, the dispersing aid and the solvent are uniformly mixed to obtain a mixed solution, and the mixed solution is stirred to undergo a sol-gel reaction and allowed to stand to obtain a gel; S2. drying the gel and calcining it at 350-500° C. for 2-3 hours to obtain the titanium dioxide composite material.

2. The novel self-cleaning coating according to claim 1, characterized in that: According to the molar ratio, in the mixed solution, the manganese element: the magnesium element: the titanium element=0.1~0.2:0.05~0.1:

1.

3. The novel self-cleaning coating according to claim 1, characterized in that: The pH value of the mixed solution is first adjusted to 1.5-2.5, and then the mixed solution is subjected to a sol-gel reaction.

4. The novel self-cleaning coating according to claim 1, characterized in that: The acrylic emulsion comprises the following raw materials in parts by weight: 20-30 parts of acrylic monomer, 5-10 parts of functional monomer, 10-20 parts of silicone monomer, 2-8 parts of emulsifier, and 80-100 parts of solvent, wherein the functional monomer is glycidyl methacrylate.

5. The novel self-cleaning coating according to claim 4, characterized in that: The acrylic emulsion is prepared by the following steps: uniformly mixing the organosilicon monomer, the acrylic ester monomer, the functional monomer, the initiator, the water, and the emulsifier, and reacting the resulting mixture at 70-90° C. for 3-5 hours to obtain the acrylic emulsion.

6. The novel self-cleaning coating according to claim 4, characterized in that: The acrylic monomer consists of butyl acrylate and methyl methacrylate in a molar ratio of 2:

1.

7. The novel self-cleaning coating according to claim 1, characterized in that: The auxiliary agent includes 0.5-2 parts of cellulose, 0.1-1 parts of bactericide, 0.05-0.3 parts of defoamer, 1-5 parts of ethylene glycol, 3-7 parts of film-forming auxiliary agent and 0.1-1 parts of thickener.

8. A method for preparing the novel self-cleaning coating according to any one of claims 1 to 7, characterized in that: The following steps are involved: The water, part of the auxiliary agent and the acrylic emulsion are mixed evenly to obtain a coating intermediate, and the coating intermediate is then mixed evenly with the remaining raw materials to obtain the novel self-cleaning coating.

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