Waterproof coiled material, film-coated metal plate, preparation method and roof

Abstract

The invention provides a waterproof coiled material, a preparation method, a film-coated metal plate and a roof. The waterproof coiled material comprises a main body layer and a waterproof layer, wherein the main body layer comprises polyvinyl chloride; the self-cleaning layer comprises waterborne polyurethane, a raw material for forming the waterborne polyurethane comprises hydrophilic chain extension waterborne polyurethane, and the hydrophilic chain extension waterborne polyurethane is obtained by performing chain extension modification through a hydrophilic chain extender.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical materials, in particular to a waterproofing membrane, a coated metal sheet, a preparation method and a roof. BACKGROUND

[0002] PVC waterproofing membranes are widely used in industrial and commercial roofing waterproofing systems due to their soft texture and excellent welding performance. Since the service life of a roof is generally 20 years and it is exposed to the open air, the surface layer of the waterproof roof is prone to dirt, affecting the overall appearance of the building. When the roof has been in use for some time, the dirt adhered to the high molecular layer of the roof surface is not easily removed by natural methods such as rain washing, resulting in a dirty and worn appearance of the light-colored roof after a period of use. Especially when the roof is also paved with photovoltaic modules, this kind of dirt phenomenon not only affects the appearance of the roof, but also affects the reflection of the roof, resulting in a decrease in reflectivity and a decrease in light collection of the double-sided photovoltaic module.

[0003] Therefore, the current waterproofing membrane, coated metal sheet, preparation method and roof still need to be improved. SUMMARY

[0004] The present application aims to provide a waterproofing membrane, a coated metal sheet, a preparation method and a roof to solve or alleviate one or more technical problems in the related art.

[0005] As a first aspect of the embodiments of the present application, the present application provides a waterproofing membrane. The waterproofing membrane comprises: a main body layer comprising polyvinyl chloride; and a self-cleaning layer comprising a waterborne polyurethane, wherein the raw materials for forming the waterborne polyurethane comprise a hydrophilic chain-extended waterborne polyurethane obtained by chain extension modification with a hydrophilic chain extender.

[0006] According to an embodiment of the present application, the hydrophilic chain-extended waterborne polyurethane is a hydrophilic chain-extended waterborne polyurethane emulsion.

[0007] According to an embodiment of the present application, the hydrophilic chain-extended waterborne polyurethane emulsion comprises isocyanate, polyether polyol and a hydrophilic chain extender.

[0008] According to one embodiment of the present application, the isocyanate is selected from at least one of toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate; the polyether polyol includes at least one of a polyether diol and a fluorine-containing polyol; the hydrophilic chain extender includes an anionic or cationic chain extender; wherein the anionic chain extender includes at least one of dimethylol propionate, dimethylol butyrate; the cationic chain extender includes at least one of methyldiethanolamine, ethylenediamine sulfonate sodium, N,N-(2-hydroxyethyl)-2-aminosulfonic acid sodium, 1,4-butanediol-2-sulfonic acid sodium, and a diamine or diol compound containing sulfonic acid group or sulfonic acid sodium group.

[0009] According to one embodiment of the present application, the ratio of the isocyanate, the polyether polyol and the hydrophilic chain extender in the hydrophilic chain-extended waterborne polyurethane emulsion is (30-150):(30-180):(30-100).

[0010] According to one embodiment of the present application, the waterborne polyurethane coating includes the hydrophilic chain-extended waterborne polyurethane emulsion, a cellulose ether and an additive, the additive including at least one of a pH adjuster, a bactericidal preservative and a defoaming agent; wherein the pH adjuster includes at least one of an acidic adjuster and an alkaline adjuster; the bactericidal preservative includes at least one of an inorganic bactericidal preservative and an organic bactericidal preservative; the defoaming agent includes at least one of a silicone-based, a mineral oil-based and a polyether-based defoaming agent.

[0011] According to one embodiment of the present application, the waterborne polyurethane coating includes:

[0012]

[0013] According to one embodiment of the present application, the additive further includes a dispersant; the dispersant includes at least one of an inorganic dispersant and an organic dispersant.

[0014] According to one embodiment of the present application, the waterborne polyurethane coating further includes a solvent to adjust the viscosity and solid content of the coating; wherein the solvent includes an aqueous solution.

[0015] According to one embodiment of the present application, the waterborne polyurethane coating further includes at least one of a functional filler, nano-titanium dioxide and nano-silicon dioxide, the functional filler including at least one of mica flake and titanium dioxide.

[0016] In another aspect of the present application, a method for preparing the waterproofing membrane as described above is provided. The method includes:

[0017] providing a body layer;

[0018] A waterborne polyurethane coating is applied on one side of the main layer to form a self-cleaning layer.

[0019] According to one embodiment of the present application, the method comprises: mixing isocyanate and polyether polyol and subjecting to emulsion polymerization to prepare a polyurethane prepolymer, and then adding a hydrophilic chain extender to prepare a hydrophilic chain-extended waterborne polyurethane emulsion; mixing the hydrophilic chain-extended waterborne polyurethane emulsion with additives, continuously dispersing at a speed of 400-500 r / min for 5-15 min, and then adding a cellulose ether and continuously dispersing at a speed of 500-650 r / min for 10-15 min to prepare the waterborne polyurethane coating; and applying the waterborne polyurethane coating on the surface of the main layer, and then drying and curing by hot air, and cooling, and then aging at room temperature for one week to obtain the waterborne polyurethane coating. The drying and curing by hot air is performed at a drying tunnel temperature of 60-100 ℃, a length of 30-50 m, and a speed of 10-30 m / min.

[0020] In another aspect of the present application, the present application provides a coated metal sheet. The coated metal sheet comprises: a polymer waterproof layer formed by the waterproofing membrane as described above; an adhesive layer on the side of the polymer waterproof layer having polyvinyl chloride; and a metal layer on the side of the adhesive layer away from the polymer waterproof layer.

[0021] In another aspect of the present application, the present application provides a roof. The roof comprises the coated metal sheet as described above.

[0022] The waterproofing membrane provided by the present application has a coating layer of waterborne polyurethane on the exposed surface. The coating layer can improve the self-cleaning ability of the exposed surface of the polyvinyl chloride main layer, and obtain an exposed surface with relatively lower surface energy by improving the compactness of the exposed surface. Thus, the adhesion of dust and oil stains is reduced, and the difficulty of removing impurities such as oil stains from the surface of the waterproofing membrane is reduced. Therefore, the waterproofing membrane can rely on natural conditions such as rainwater washing to achieve effective cleaning and reduce the degree of dirt on the exposed surface of the waterproofing membrane caused by use.

[0023] The above summary is intended to illustrate the present application and is not intended to be limiting thereof in any way. Further aspects, embodiments and features of the present application will be readily apparent from the detailed description which follows. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 A structural schematic diagram of a waterproofing membrane according to one embodiment of the present application is shown;

[0025] Figure 2 A structural schematic diagram of a coated metal sheet according to one embodiment of the present application is shown.

[0026] Explanation of reference signs: 10 - main body layer, 20 - self-cleaning layer, 100 - metal layer, 200 - high-molecular waterproof layer, 300 - adhesive layer. DETAILED DESCRIPTION

[0027] In the following, only certain exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present application, and different embodiments can be combined arbitrarily without conflict. Therefore, the following description is considered to be essentially exemplary rather than limiting.

[0028] In a first aspect of the present application, a waterproofing membrane is provided. Referring to Figure 1 The waterproofing membrane comprises a main body layer 10 and a self-cleaning layer 20. The main body layer 10 comprises polyvinyl chloride, and the self-cleaning layer 20 comprises waterborne polyurethane. The raw material for forming the waterborne polyurethane comprises a hydrophilic chain-extended waterborne polyurethane, which is obtained by chain extension modification with a hydrophilic chain extender. The waterproofing membrane can improve the self-cleaning ability of the exposed surface of the membrane, thereby reducing the adhesion of dust and oil stains, and reducing the difficulty of removing impurities such as oil stains from the surface of the waterproofing membrane. The adhesion between the self-cleaning layer and the main body layer is good, and the interface performance matching degree is high, and the self-cleaning layer can be set by a relatively simple coating process. Therefore, the waterproofing membrane can rely on natural conditions such as rainwater washing to achieve effective cleaning, reduce the degree of dirt on the exposed surface of the waterproofing membrane caused by use, and has a long service life.

[0029] According to one embodiment of the present application, the hydrophilic chain-extended waterborne polyurethane is a hydrophilic chain-extended waterborne polyurethane emulsion. The hydrophilic chain-extended waterborne polyurethane emulsion includes isocyanate, polyether polyol, and hydrophilic chain extender. Specifically, the hydrophilic chain-extended waterborne polyurethane emulsion is prepared by emulsion polymerization of isocyanate and polyether polyol to obtain a polyurethane prepolymer, and then adding a hydrophilic chain extender to modify the prepolymer. The mixing ratio of isocyanate, polyether polyol, and hydrophilic chain extender in the hydrophilic chain-extended waterborne polyurethane emulsion is not particularly limited, and is preferably (30-150):(30-180):(30-100). In addition, the types of isocyanate, polyether polyol, and hydrophilic chain extender are not particularly limited, for example, in one specific example, the isocyanate can include but is not limited to toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, or a combination thereof, and preferably isophorone diisocyanate. The polyether polyol can include but is not limited to polyether diol, fluorine-containing polyol, or a combination thereof, and preferably includes polyether diol. The hydrophilic chain extender includes anionic chain extender, cationic chain extender, or a combination thereof, and the anionic chain extender includes but is not limited to at least one of dimethylol propanoic acid and its salt, dimethylol butanoic acid and its salt, and the cationic chain extender includes but is not limited to at least one of methyldiethanolamine, ethylenediamine sulfonic acid sodium, N,N-(2-hydroxyethyl)-2-aminosulfonic acid sodium, 1,4-butanediol-2-sulfonic acid sodium, and a diamine or diol compound containing sulfonic acid group or sulfonic acid sodium group, and the hydrophilic chain extender preferably includes dimethylol propanoic acid. The emulsion of this type has excellent mechanical properties and water resistance after curing, as well as good adhesion, flexibility, and weather resistance, thus improving the interfacial adhesion between the self-cleaning layer and the main layer, and ensuring reliable peel strength between the self-cleaning layer and the main layer. In addition, the addition of the emulsion of this type can maintain the flexibility of the self-cleaning layer, so that the flexibility of the roll material does not decrease significantly, and the softness of the roll material is maintained.

[0030] According to one embodiment of the present application, the specific formation of the self-cleaning layer is not particularly limited, for example, it can be formed by a waterborne polyurethane coating, and the waterborne polyurethane coating can contain the aforementioned hydrophilic chain-extended waterborne polyurethane emulsion. The waterborne emulsion system has better environmental performance, and the waterborne emulsion system and the main layer proposed in the present application have good compatibility, and the self-cleaning layer can be conveniently formed by providing a coating.

[0031] In one embodiment, the hydrophilic chain-extended waterborne polyurethane emulsion, the cellulose ether, and the additive can be mixed in any ratio. In one embodiment, the additive can include, but is not limited to, a pH adjuster, a bactericide, a defoamer, or a combination thereof. In one embodiment, the additive can further include a dispersant. In one embodiment, the additive can further include one or more of an oxygen scavenger, an antioxidant, a thixotropic agent, an ultraviolet light absorber, a light stabilizer, and a leveling agent.

[0032] In one embodiment, the pH adjuster can include, but is not limited to, an acid adjuster, a base adjuster, or a combination thereof. In one embodiment, the acid adjuster can include at least one of an inorganic acid and an organic acid, such as, but not limited to, hydrochloric acid, sulfuric acid, nitric acid, acetic acid, citric acid, lactic acid, and the like. In one embodiment, the base adjuster can include at least one of an organic base and an inorganic base, such as, but not limited to, a monoalkanolamine, an alkali metal salt, such as, but not limited to, isobutanolamine, aqueous ammonia, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, and the like. In one embodiment, the bactericide can include, but is not limited to, an inorganic bactericide, an organic bactericide, or a combination thereof, and can be potassium carbonate. In one embodiment, the inorganic bactericide can include at least one of sulfurous acid, a sulfite, a peroxide, hypochlorous acid, a hypochlorite, and chloramine. In one embodiment, the organic bactericide can include at least one of an organic sulfur, an organic bromine, and a nitrogen-containing heterocyclic compound. In one embodiment, the defoamer can include, but is not limited to, a silicone-based defoamer, a mineral oil-based defoamer, and a polyether-based defoamer, such as, but not limited to, at least one of dimethicone, polyoxypropylene, glycerol, ether ethylene oxide, a fat, a wax, an aliphatic amide, and the like, and can be NXZ. In one embodiment, the dispersant can include, but is not limited to, an inorganic dispersant and an organic dispersant. In one embodiment, the inorganic dispersant can include at least one of a silicate, such as, but not limited to, water glass, and an alkali metal phosphate, such as, but not limited to, sodium tripolyphosphate, sodium hexametaphosphate, and sodium pyrophosphate. In one embodiment, the organic dispersant can include at least one of triethylhexylphosphoric acid, sodium dodecyl sulfate, methylcellosolve, a cellulose derivative, polyacrylamide, guar gum, and a fatty acid polyethylene glycol ester. In one embodiment, the additive can further include one or more of an oxygen scavenger, an antioxidant, a thixotropic agent, an ultraviolet light absorber, a light stabilizer, and a leveling agent.

[0033] According to one embodiment of the present application, the waterborne polyurethane coating includes the following components:

[0034]

[0035] According to the embodiments of the present application, the self-cleaning ability of the self-cleaning layer can be improved by further adding functional fillers, nano-titanium dioxide, nano-silicon dioxide or a combination thereof in the raw materials for forming the waterborne polyurethane coating. For example, fillers with good light reflecting performance can be added to improve the brightness of the self-cleaning layer as a whole and the surface performance of the self-cleaning layer, so that the self-cleaning layer with stronger light reflecting ability and smoother surface can be obtained. Specifically, the functional fillers include at least one of mica flakes and titanium dioxide. In some examples, the amount of the functional fillers added can be controlled according to other components of the waterborne polyurethane coating to ensure that the coating components can have good uniformity, so as to prevent the uniformity of the coating from being reduced due to excessive addition of fillers. In a specific example, when the functional fillers are included in the raw materials, the additives preferably include dispersants to allow the functional fillers to be sufficiently dispersed in the mixture.

[0036] According to an embodiment of the present application, the waterborne polyurethane coating can further include a solvent for adjusting the viscosity and solid content of the coating to avoid that the prepared coating is too viscous to be unfavorable for coating operation. The type of the solvent used is not particularly limited, but in order to avoid introducing extra components, water solution is preferably used as the solvent.

[0037] In another aspect of the present application, a method for preparing the waterproofing membrane described above is provided. The method includes the steps of providing a main body layer and forming a self-cleaning layer. Specifically, the method can coat the waterborne polyurethane coating on one side of the main body layer to form the self-cleaning layer.

[0038] According to an embodiment of the present application, the method includes: mixing isocyanate and polyether polyol and allowing them to undergo emulsion polymerization to prepare a polyurethane prepolymer, and then adding a hydrophilic chain extender to modify the chain extension to prepare a hydrophilic chain-extended waterborne polyurethane emulsion; mixing the hydrophilic chain-extended waterborne polyurethane with additives, and then adding a cellulose ether to mix thoroughly to prepare the waterborne polyurethane coating; coating the waterborne polyurethane coating on the surface of the main body layer, and then drying and curing by hot air with a drying tunnel temperature of 60-100°C, a length of 30-50 m and a speed of 10-30 m / min, and cooling and maturing at room temperature for one week.

[0039] In one embodiment, the step of mixing the hydrophilic chain-extended waterborne polyurethane, the additives and the cellulose ether can be performed using a dispersing device so that the materials can be mixed evenly. Specifically, the hydrophilic chain-extended waterborne polyurethane emulsion can be added into the dispersing device, then the additives are added, and the dispersing is continued for 5-15 min at a rotation speed of 400-500 r / min, and then the cellulose ether is added and the dispersing is continued for 10-15 min at a rotation speed of 500-650 r / min, to obtain the waterborne polyurethane coating. The type of the dispersing device used is not particularly limited as long as it has a certain volume and can realize the dispersing function, for example, including but not limited to a dispersing cylinder.

[0040] In one embodiment, the way of applying the waterborne polyurethane coating to the surface of the substrate layer is not particularly limited, for example, at least one of the following methods can be used, including but not limited to die coating, rod coating, roll coating, gravure coating. However, in one embodiment, in order to coat more evenly, the waterborne polyurethane coating is preferably applied to the surface of the substrate layer using an anilox roller. The specification of the anilox roller used is preferably 50-200 mesh.

[0041] The present application provides a coated metal sheet. Referring to Figure 2 The coated metal sheet has a polymer waterproof layer 200, an adhesive layer 300 and a metal layer 100. The polymer waterproof layer is formed by the waterproofing membrane described above, the adhesive layer is located on the side of the polymer waterproof layer having polyvinyl chloride, and the metal layer is located on the side of the adhesive layer away from the polymer waterproof layer. The coated metal sheet has all the features and advantages of the waterproofing membrane described above, which will not be repeated here.

[0042] In another aspect of the present application, the present application provides a roof. The roof comprises the coated metal sheet described above. The roof has all the features and advantages of the coated metal sheet described above, which will not be repeated here.

[0043] The methods used in the following examples are conventional methods unless otherwise specified, and the reagents used are commercially available reagents unless otherwise specified.

[0044] Example 1

[0045] The raw materials of the waterborne polyurethane coating are as follows (all the following raw materials are by weight):

[0046]

[0047] Among them, the hydrophilic chain-extended water-based polyurethane emulsion is prepared by mixing isophorone diisocyanate and polyether diol and performing emulsion polymerization to obtain a polyurethane prepolymer, and then adding a dimethylol propionate chain extender to perform chain extension modification to obtain the hydrophilic chain-extended water-based polyurethane emulsion, wherein the mixing ratio of isophorone diisocyanate, polyether diol and dimethylol propionate is 100:90:15.

[0048] The pH regulator in the waterborne polyurethane coating is isobutanolamine, the bactericidal preservative is kason, and the defoaming agent is NXZ.

[0049] The hydrophilic chain-extended aqueous polyurethane emulsion was mixed with a pH regulator, a bactericidal preservative, and a defoaming agent according to the above mixing ratio, and dispersed continuously for 10 minutes at a speed of 450 r / min. Then, cellulose ether was added and dispersed continuously for 13 minutes at a speed of 600 r / min to prepare the aqueous polyurethane coating.

[0050] A PVC glass fiber reinforced layer (0.8 mm thick) was selected as the main layer, and the above-mentioned water-based polyurethane coating was coated on the surface of the main layer. After hot air drying and curing, it was cooled and matured at room temperature for one week. The hot air drying oven temperature was 80°C, the length was 45 m, and the speed was 10 m / min.

[0051] A 0.6mm thick galvanized metal sheet was selected, and 50g of galvanized metal was applied on both sides as the metal layer to form a coated metal sheet.

[0052] Example 2

[0053] The remaining parameters are the same as those in Example 1, except that isophorone diisocyanate is replaced by toluene diisocyanate, and the chain extender is replaced by methyldiethanolamine.

[0054] Example 3

[0055] The remaining parameters are the same as those in Example 1, except that: 50 parts of hydrophilic chain-extended aqueous polyurethane emulsion.

[0056] Example 4

[0057] The remaining parameters are the same as those in Example 1, except that 3 parts of nano-titanium dioxide are added to the first component of the self-cleaning layer.

[0058] Comparative Example 1

[0059] The remaining parameters are the same as those in Example 1, except that the PVC glass fiber reinforcement layer is not coated with water-based polyurethane coating.

[0060] Comparative Example 2

[0061] The remaining parameters are the same as those in Example 1, except that a commercially available two-component polyurethane coating is coated on the surface of the PVC glass fiber reinforcement layer.

[0062] The coated metal sheets obtained in the above examples and comparative examples were tested for stain resistance by immersion A method according to GB / T 9780-2013, and for adhesion by grid method according to GBT9286-2021, and the results are shown in the following table:

[0063] Table 1

[0064] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Stain resistance 10％ 12％ 10％ 10％ 41％ 35％ Stain resistance rating 1 2 1 1 4 4 Adhesion 0 0 0 0 - 0

[0065] From the above Table 1, it can be seen that Examples 1-4 all have good stain resistance, and the comparative examples all have poor stain resistance, with lower stain resistance grade and higher pollution degree (4 grade). Examples 1-4 all have good adhesion (0 grade is that the cutting edge is completely smooth, and there is no falling off in the grid).

[0066] In addition, the terms "first", "second", etc. are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implying the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0067] The above application provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the present application, the components and settings of specific examples are described in the above. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeatedly refer to numbers and / or letters in different examples, and such repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed.

[0068] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any skilled person in the art can easily think of various changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A waterproofing membrane characterized in that, Comprise: a main layer, the main layer comprising polyvinyl chloride; a self-cleaning layer, the self-cleaning layer comprising water-based polyurethane, wherein the raw material for forming the water-based polyurethane comprises a hydrophilic chain-extended water-based polyurethane, the hydrophilic chain-extended water-based polyurethane being obtained by chain extension modification with a hydrophilic chain extender.

2. The waterproofing membrane of claim 1, wherein, The hydrophilic chain-extended water-based polyurethane is a hydrophilic chain-extended water-based polyurethane emulsion.

3. The waterproofing membrane of claim 1, wherein, The hydrophilic chain-extended water-based polyurethane emulsion comprises isocyanate, polyether polyol, and hydrophilic chain extender.

4. The waterproofing membrane of claim 3, wherein, At least one of the following conditions is met: The isocyanate is selected from at least one of toluene diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate; The polyether polyol comprises at least one of polyether diol and fluorine-containing polyol; The hydrophilic chain extender comprises anionic or cationic chain extender; The anionic chain extender comprises at least one of dimethylol propanoate and dimethylol butanoate; The cationic chain extender comprises at least one of methyldiethanolamine, sodium ethylenediamine sulfonate, N,N-(2-hydroxyethyl)-2-sodium aminosulfonate, 1,4-butanediol-2-sodium sulfonate, and a diamine or diol compound containing sulfonic acid group or sodium sulfonate group.

5. The waterproofing membrane of claim 3, wherein The ratio of isocyanate, polyether polyol, and hydrophilic chain extender in the hydrophilic chain-extended water-based polyurethane emulsion is (30-150):(30-180):(30-100).

6. The waterproofing membrane of claim 3, wherein The water-based polyurethane coating comprises the hydrophilic chain-extended water-based polyurethane emulsion, cellulose ether, and additives, The additives comprise at least one of pH adjuster, bactericidal preservative, and defoaming agent; The pH adjuster comprises at least one of acidic adjuster and basic adjuster; The bactericidal preservative comprises at least one of inorganic bactericidal preservative and organic bactericidal preservative; The defoaming agent comprises at least one of silicone-based, mineral oil-based, and polyether-based defoaming agent.

7. The waterproofing membrane of claim 6, wherein, The water-based polyurethane coating comprises:

8. The waterproofing membrane of claim 6, wherein, The additives further comprise dispersant, the dispersant comprising at least one of inorganic dispersant and organic dispersant.

9. The waterproofing membrane of claim 6, wherein, The water-based polyurethane coating further comprises solvent to adjust the viscosity and solid content of the coating; The solvent comprises aqueous solution.

10. The waterproofing membrane of claim 6, wherein The water-based polyurethane coating further comprises at least one of functional filler, nano titanium dioxide, and nano silicon dioxide, the functional filler comprising at least one of mica flake and titanium dioxide.

11. A method of preparing a waterproofing membrane according to any one of claims 1 to 10, characterised in that, Comprise: providing a main layer; coating water-based polyurethane coating on one side of the main layer to form a self-cleaning layer.

12. The method of claim 11, wherein, The method comprises: mixing isocyanate and polyether polyol and performing emulsion polymerization to obtain polyurethane prepolymer, and then adding hydrophilic chain extender to perform chain extension modification to obtain hydrophilic chain-extended water-based polyurethane emulsion; mixing the hydrophilic chain-extended water-based polyurethane emulsion and additives, continuously dispersing at a speed of 400-500 r / min for 5-15 min, then adding cellulose ether and continuously dispersing at a speed of 500-650 r / min for 10-15 min to obtain the water-based polyurethane coating; The water-based polyurethane coating is applied to the surface of the main body layer, and after hot air drying and curing, it is cooled and matured at room temperature for one week to obtain the product.

13. A coated metal sheet, characterized by Comprise: a polymer waterproof layer formed by the waterproofing membrane according to any one of claims 1-10; an adhesive layer on the side of the polymer waterproof layer with polyvinyl chloride; a metal layer on the side of the adhesive layer away from the polymer waterproof layer.

14. A roof characterized in that The coated metal sheet according to claim 13.

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