Self-cleaning super-durable single-component outer wall waterproof coating

Abstract

The application discloses a kind of self-cleaning super-durable single-component outer wall waterproof coating, belong to high polymer material field.The modified castor oil-based waterborne polyurethane is prepared by adding isocyanate monomer to carry out polymerization after castor oil and polyethylene glycol are mixed, then modified by monohydroxy silicone oil, the waterproof coating is prepared by mixing and stirring with defoaming agent, dispersing agent, thickening agent and light stabilizer in the modified castor oil-based waterborne polyurethane.The monohydroxy silicone oil is used in the modified castor oil-based waterborne polyurethane to modify polyurethane solution, so that the surface of prepared waterproof coating is rich in Si-O-Si bond, has high contact angle with water, strong hydrophobicity, has self-cleaning ability, castor oil has certain biodegradability, and no organic solvent is used in preparation process, with environmental protection, the waterproof coating has good mechanical property and good yellowing resistance.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, and in particular to a self-cleaning, ultra-weather-resistant, single-component exterior wall waterproof coating. Background Technology

[0002] Polyurethane waterproof coatings are polymeric waterproof coatings made primarily of polyurethane resin. They are prepared by the condensation polymerization of isocyanate groups (-N=C=O) in isocyanate monomers and hydroxyl groups (-OH) in glycol monomers. This type of environmentally friendly waterproof coating cures upon contact with air, forming a strong waterproof film. Single-component polyurethane waterproof coatings are made primarily of isocyanate with the addition of other additives. Single-component polyurethane coatings exhibit good physical properties and strong adhesion. Castor oil is a triglyceride of fatty acids. Castor oil-based polyurethane coatings are a new type of polymer material that has emerged in my country in recent years. These coatings are characterized by a high solids content. The long-chain nonpolar fatty acids in the castor oil component give the coating film good hydrolysis resistance and flexibility. The synthesis of this type of coating involves reacting castor oil with polyisocyanates to produce a prepolymer, which is then used to formulate a single-component or two-component coating. Polyurethane waterproof coatings made from castor oil have high tensile strength, high elasticity and elongation at break, good durability and temperature adaptability, excellent waterproof effect and long service life, and are therefore widely used.

[0003] CN105504206A discloses a method for synthesizing castor oil-based blocked waterborne polyurethane. The method involves reacting castor oil, polyethylene glycol, and a hydrophilic chain extender with diisocyanate in a hydrophilic solvent to obtain an NCO-terminated polyurethane prepolymer. This prepolymer is then capped with a blocking agent to obtain a blocked polyurethane prepolymer. Finally, after neutralization with a neutralizing agent, the prepolymer is dispersed in deionized water to obtain the castor oil-based blocked waterborne polyurethane. Castor oil, an important renewable resource, is used in this invention, and the blocked waterborne polyurethane synthesized from it exhibits a high degree of self-crosslinking.

[0004] CN112210061A discloses a method for preparing an organosilicon-modified castor oil-based waterborne polyurethane membrane. The main raw material formula is as follows: castor oil, hydroxypropyl polysiloxane, isocyanate, catalyst, hydrophilic chain extender, organic solvent, neutralizing agent, salting agent, small molecule chain extender, end-capping agent, and deionized water, to obtain a high-viscosity, high-temperature resistant, and superhydrophobic polyurethane membrane.

[0005] CN113912811A discloses a silicone / castor oil dual-modified waterborne polyurethane resin, its preparation method, and its application. The raw materials for preparing the silicone / castor oil dual-modified waterborne polyurethane resin include a combination of specific proportions of polymeric polyol, castor oil, polyether-modified silicone, diisocyanate, catalyst, and chain extender. By selecting polyether-modified silicone to improve the compatibility between silicone and polyurethane, and combining it with castor oil to dual-modify the waterborne polyurethane resin, it can gradually reduce dependence on petroleum-based raw materials by using castor oil as a direct raw material, thereby improving the renewability of polyurethane resin. At the same time, it combines the performance advantages of both castor oil and silicone, resulting in a waterborne polyurethane resin with excellent mechanical properties, wear resistance, heat resistance, and hydrolysis resistance. Moreover, the polyurethane resin film has a soft and smooth feel after formation, making it very suitable for the synthetic leather industry.

[0006] CN106675375B discloses a UV coating containing silicone-modified polyurethane acrylate, its preparation method, and its application: 61-64 parts of silicone-modified polyurethane acrylate, 3-5 parts of castor oil-based UV-curable polyurethane acrylate, 5-7 parts of sec-butyl acetate, 7-9 parts of isopropanol, 1-2 parts of ethyl acetate, 0.5-1 parts of polyether-modified polysiloxane leveling agent, 2-4 parts of photoinitiator, 3-4 parts of matting agent, and 9-10 parts of n-butyl acetate. The coating, prepared by reacting the polyether-modified polysiloxane leveling agent with a mixed solution of castor oil-based UV-curable polyurethane acrylate and silicone-modified polyurethane acrylate, exhibits excellent leveling effect, fast curing speed, hydrolysis resistance, low-temperature resistance, electrical insulation, and good adhesion. It also emits almost no volatile organic compounds, making it a coating with excellent overall performance.

[0007] In summary, while films prepared by the polymerization reaction of castor oil and isocyanate possess high mechanical properties, they suffer from yellowing and shortened lifespan when used as waterproof coatings. Therefore, the poor weather resistance, yellowing resistance, and mechanical properties of waterproof coatings remain pressing technical issues that need to be addressed. Summary of the Invention

[0008] To address the above problems, this invention provides a self-cleaning, ultra-weather-resistant, single-component exterior wall waterproof coating. The waterproof coating has resistance to yellowing, hydrophobicity, and high mechanical properties, and is environmentally friendly as it requires no organic solvents.

[0009] This invention provides a self-cleaning, ultra-weather-resistant, single-component exterior wall waterproof coating. The waterproof coating is prepared by adding defoamers, dispersants, thickeners, and light stabilizers to a modified castor oil-based waterborne polyurethane to form a casting liquid, which is then dried after scraping. The waterproof coating has a tensile strength of 0.9-1.2 MPa, an elongation at break of 410-515%, and a tensile strength retention rate of 75-85%. The water contact angle is 100-120°, and the yellowing resistance ΔE = 1.5-1.9. The modified castor oil-based waterborne polyurethane is prepared by mixing castor oil and polyethylene glycol, adding isocyanate monomers for polymerization, and then modifying with monohydroxy silicone oil. The molecular weight of the modified castor oil-based waterborne polyurethane is 41,000-45,000. In the infrared spectrum of the modified castor oil-based waterborne polyurethane, at 3355 cm⁻¹... -1 ±0.01cm -1 The NH stretching vibration peak appears at 2923 cm⁻¹. -1 ±0.01cm -1 and 2855cm -1 ±0.01cm -1 A CH stretching vibration peak appears at 1744 cm⁻¹. -1 ±0.01cm -1 and 1700cm -1 ±0.01cm -1 A C=O stretching vibration peak appears at 1524 cm⁻¹. -1 ±0.01cm -1 and 1460cm -1 ±0.01cm -1 A C=C stretching vibration peak appears at this location.

[0010] This invention also provides a method for preparing the self-cleaning, ultra-weather-resistant single-component exterior wall waterproof coating, comprising the following steps:

[0011] Step 1: Mix castor oil, polyethylene glycol, and catalyst under stirring and reflux to obtain a mixed solution;

[0012] Step 2: Under stirring conditions, add isocyanate monomer to the mixed solution to carry out the reaction and obtain a polyurethane solution;

[0013] Step 3: Under stirring conditions, add monohydroxy silicone oil to the polyurethane solution to carry out the modification reaction, then add chain extender and polymerization inhibitor to carry out the polymerization inhibition reaction, and obtain organosilicon modified polymerization solution.

[0014] Step 4: Under high-speed stirring, deionized water is added to the organosilicon-modified polymerization solution to convert it, thereby obtaining modified castor oil-based waterborne polyurethane.

[0015] Step 5: Mix and stir the modified castor oil-based waterborne polyurethane, defoamer, dispersant, thickener and light stabilizer to obtain a casting liquid. Coat the casting liquid onto a polytetrafluoroethylene board, apply it evenly with a coating machine and then dry it to obtain the self-cleaning ultra-weather-resistant single-component exterior wall waterproof coating.

[0016] Furthermore, the molecular weight of the polyethylene glycol in step 1 is 400.

[0017] Further, in step 1, the molar ratio of castor oil to polyethylene glycol is (2:1)-(3:1).

[0018] Further, in step 1, the molar ratio of the catalyst to the polyethylene glycol is (0.002:500) - (0.03:500).

[0019] Furthermore, the catalyst in step 1 is dibutyltin dilaurate.

[0020] Furthermore, the stirring speed in step 1 is 500-800 r / min.

[0021] Further, in step 1, the heating and reflux to a temperature of 50-80°C is carried out for 30-50 minutes. Further, in step 2, the stirring speed is 500-800 r / min.

[0022] Further, in step 2, the molar ratio of the isocyanate monomer to the castor oil in the mixed solution is (3.9:1)-(4.8:1).

[0023] Furthermore, the isocyanate monomer in step 2 is isophorone diisocyanate (IPDI).

[0024] Furthermore, the reaction temperature in step 2 is 50-80℃, and the reaction time is 30-60 min.

[0025] Furthermore, the isocyanate content in the polyurethane solution in step 2 is 70-80%.

[0026] Furthermore, in step 2, both castor oil and polyethylene glycol in the mixed solution contain a large number of hydroxyl groups. The hydroxyl groups undergo a condensation reaction with the isocyanate group in the isocyanate monomer to form a polymer chain structure.

[0027] Furthermore, the stirring speed in step 3 is 500-800 r / min.

[0028] Further, in step 3, the molar ratio of the monohydroxy silicone oil to the castor oil in the polyurethane solution is (2:1)-(3:1).

[0029] Further, the monohydroxy silicone oil in step 3 is α-[3-[1,3,3,3-tetramethyl-1-(trimethylsilyl-oxo)disiloxane]-propyl-ω-hydroxypolyoxyethylene].

[0030] Furthermore, the temperature of the modification reaction in step 3 is 50-80℃, and the reaction time is 20-30 min.

[0031] Further, the molar ratio of the chain extender in step 3 to the polyethylene glycol in step 1 is (1:5) to (1:7).

[0032] Further, in step 3, the molar ratio of the polymerization inhibitor to the chain extender is (1.8:1.4)-(1.8:1).

[0033] Furthermore, the polymerization inhibitor in step 3 is hydroquinone.

[0034] Further, the chain extender in step 3 is one or more of 2,2-dimethylolpropionic acid (DMPA) or 2,2-dimethylolbutyric acid (DMBA).

[0035] Furthermore, in step 3, the temperature of the polymerization inhibition reaction is 50-80℃, and the reaction time is 20-40 min.

[0036] Furthermore, the isocyanate content in the organosilicon-modified polymerization solution in step 3 is 0.

[0037] Furthermore, the high-speed stirring speed in step 4 is 1500-2000 r / min.

[0038] Further, in step 4, the mass ratio of the deionized water to the organosilicon-modified polymerization solution is (1:1) to (3:1).

[0039] Furthermore, the conversion process in step 4 is as follows: the oily organosilicon modified polymer solution is mixed with deionized water under high-speed stirring to form an oil-in-water modified castor oil-based waterborne polyurethane.

[0040] Further, in step 5, the mass ratio of the modified castor oil-based waterborne polyurethane, defoamer, dispersant, thickener, and light stabilizer is (1000:4:3:0.1:5) - (1000:4:3:0.1:3).

[0041] Furthermore, the defoamer in step 5 is polydimethylsiloxane.

[0042] Furthermore, the dispersant in step 5 is ammonium polyacrylate.

[0043] Furthermore, the thickener in step 5 is a nonionic polyurethane associative thickener.

[0044] Furthermore, the light stabilizer in step 5 is a benzophenone-based ultraviolet absorber.

[0045] Furthermore, in step 5, the mixing speed is 1200-1500 r / min, and the mixing time is 10-30 min.

[0046] Furthermore, in step 5, the film thickness of the film scraping machine is 1.5-2mm.

[0047] Furthermore, in step 5, the drying temperature is 23-25℃, the drying humidity is 50%, and the drying time is 7 days.

[0048] The beneficial effects of this invention are:

[0049] 1. This invention prepares a polyurethane solution by mixing castor oil and polyethylene glycol, reacting it with isocyanate monomers, and then modifying it with monohydroxy silicone oil to obtain the modified castor oil-based waterborne polyurethane. The polyethylene glycol contains ether chains, which are hydrophilic and facilitate polyurethane emulsification during polymerization. Castor oil has a certain degree of biodegradability. Furthermore, this invention does not use organic solvents in the synthesis of the modified castor oil-based waterborne polyurethane, resulting in low odor and environmental friendliness. The siloxane bonds in the monohydroxy silicone oil act as weather-resistant components, improving the weather resistance of the modified castor oil-based waterborne polyurethane. Its low surface energy also enriches the surface of the prepared self-cleaning, ultra-weather-resistant single-component exterior wall waterproof coating with Si-O-Si bonds, resulting in a high contact angle with water, strong hydrophobicity, and self-cleaning ability. Therefore, the prepared self-cleaning, ultra-weather-resistant single-component exterior wall waterproof coating has high mechanical properties and resistance to yellowing. Moreover, the synthesis process of the self-cleaning, ultra-weather-resistant single-component exterior wall waterproof coating in this invention is simple, easy to operate, and readily scalable for industrial production. Attached Figure Description

[0050] Figure 1 The image shows the infrared spectrum of the modified castor oil-based waterborne polyurethane described in Example 1. Detailed Implementation

[0051] The invention will be described in detail below with reference to the embodiments:

[0052] This invention provides a modified castor oil-based waterborne polyurethane, its preparation method, and a waterproof coating. The preparation process is simple, but it has high mechanical properties and strong weather resistance, which greatly expands its application in industrial production.

[0053] Example 1

[0054] This embodiment provides a self-cleaning, ultra-weather-resistant, single-component exterior wall waterproof coating. The waterproof coating is prepared by adding defoamer, dispersant, thickener, and light stabilizer to a modified caster oil-based waterborne polyurethane to form a casting liquid, which is then dried after scraping. The waterproof coating has a tensile strength of 1.15 MPa, an elongation at break of 421.17%, and a tensile strength retention rate of 80%. The water contact angle of the waterproof coating is 119°, and the yellowing resistance ΔE = 1.89. The modified caster oil-based waterborne polyurethane is prepared by mixing caster oil and polyethylene glycol, adding isocyanate monomers for polymerization, and then modifying with monohydroxy silicone oil. The molecular weight of the modified caster oil-based waterborne polyurethane is 42,500.

[0055] This embodiment also provides a method for preparing the self-cleaning, ultra-weather-resistant, single-component exterior wall waterproof coating, comprising the following steps:

[0056] Step 1: 0.1 mol castor oil, 0.05 mol polyethylene glycol and 0.002 g dibutyltin dilaurate are heated to 75°C and refluxed under stirring at 800 r / min for 30 min to obtain a mixed solution;

[0057] Step 2: Under stirring at 800 r / min, add 0.48 mol of isophorone diisocyanate to the mixed solution and react at 75°C for 60 min to obtain a polyurethane solution. At this time, the isocyanate (-NCO) content in the polyurethane solution is 70%.

[0058] Step 3: Under stirring at 800 r / min, add 0.28 mol of α-[3-[1,3,3,3-tetramethyl-1-(trimethylsilyl-oxo)disiloxane]-propyl-ω-hydroxypolyoxyethylene] to the polyurethane solution. After modification reaction at 75°C for 30 min, add 0.014 mol of 2,2-dimethylolpropionic acid and 0.02 g of hydroquinone. After polymerization inhibition reaction at 75°C for 30 min, obtain the organosilicon modified polymerization solution. At this time, the isocyanate (-NCO) content in the organosilicon modified polymerization solution is 0.

[0059] Step 4: Under high-speed stirring at 1500 r / min, 600 g of deionized water is added to the organosilicon-modified polymerization solution to obtain an oil-in-water modified castor oil-based waterborne polyurethane.

[0060] Step 5: Mix 1000g of the modified castor oil-based waterborne polyurethane, 4g of defoamer, 3g of dispersant, 0.1g of thickener and 5g of light stabilizer at 1200r / min for 20min to obtain a casting liquid. Coat the casting liquid onto a polytetrafluoroethylene board and apply it evenly using a 1.5mm coating machine. Then dry it at 23℃ and 50% humidity for 7 days to obtain the self-cleaning, ultra-weather-resistant, single-component exterior wall waterproof coating.

[0061] like Figure 1 The image shows the infrared spectrum of the modified castor oil-based waterborne polyurethane described in Example 1, where the horizontal axis (Wavenumber) represents the wavenumber. As can be seen from the figure, the modified castor oil-based waterborne polyurethane exhibits a wavenumber at 3355 cm⁻¹. -1 ±0.01cm -1 The NH stretching vibration peak appears at 2923 cm⁻¹. -1 ±0.01cm -1 and 2855cm -1 ±0.01cm -1 A CH stretching vibration peak appears at 1744 cm⁻¹. -1 ±0.01cm -1 and 1700cm -1 ±0.01cm -1 A C=O stretching vibration peak appears at 1524 cm⁻¹. -1 ±0.01cm -1 and 1460cm -1 ±0.01cm -1 A C=C stretching vibration peak appears at this location.

[0062] Example 2

[0063] This embodiment provides a self-cleaning, ultra-weather-resistant, single-component exterior wall waterproof coating. The waterproof coating is prepared by adding defoamer, dispersant, thickener, and light stabilizer to a modified caster oil-based waterborne polyurethane to form a casting liquid, which is then dried after scraping. The waterproof coating has a tensile strength of 0.98 MPa, an elongation at break of 511.43%, and a tensile strength retention rate of 85%. The water contact angle of the waterproof coating is 105°, and the yellowing resistance ΔE = 1.68. The modified caster oil-based waterborne polyurethane is prepared by mixing caster oil and polyethylene glycol, adding isocyanate monomers for polymerization, and then modifying with monohydroxy silicone oil. The molecular weight of the modified caster oil-based waterborne polyurethane is 41,000.

[0064] This embodiment also provides a method for preparing the self-cleaning, ultra-weather-resistant, single-component exterior wall waterproof coating, comprising the following steps:

[0065] Step 1: 0.1 mol castor oil, 0.05 mol polyethylene glycol and 0.002 g dibutyltin dilaurate are heated to 50 °C and refluxed under stirring at 500 r / min for 50 min to obtain a mixed solution;

[0066] Step 2: Under stirring at 500 r / min, add 0.45 mol of isophorone diisocyanate to the mixed solution and react at 50°C for 30 min to obtain a polyurethane solution. At this time, the isocyanate (-NCO) content in the polyurethane solution is 76%.

[0067] Step 3: Under stirring at 500 r / min, add 0.22 mol of α-[3-[1,3,3,3-tetramethyl-1-(trimethylsilyl-oxo)disiloxane]-propyl-ω-hydroxypolyoxyethylene] to the polyurethane solution. After modification reaction at 50°C for 20 min, add 0.01 mol of 2,2-dimethylolpropionic acid and 0.02 g of hydroquinone. After polymerization inhibition reaction at 50°C for 40 min, obtain the organosilicon modified polymerization solution. At this time, the isocyanate (-NCO) content in the organosilicon modified polymerization solution is 0.

[0068] Step 4: Under high-speed stirring at 2000 r / min, 600 g of deionized water is added to the organosilicon-modified polymerization solution to obtain an oil-in-water modified castor oil-based waterborne polyurethane.

[0069] Step 5: Mix 1000g of the modified castor oil-based waterborne polyurethane, 4g of defoamer, 3g of dispersant, 0.1g of thickener, and 3g of light stabilizer at 1500r / min for 20min to obtain a casting liquid. Coat the casting liquid onto a polytetrafluoroethylene board and apply it evenly using a 1.5mm coating machine. Then dry it at 25℃ and 50% humidity for 7 days to obtain the self-cleaning, ultra-weather-resistant, single-component exterior waterproof coating.

[0070] Example 3

[0071] This embodiment provides a self-cleaning, ultra-weather-resistant, single-component exterior wall waterproof coating. The waterproof coating is prepared by adding defoamer, dispersant, thickener, and light stabilizer to a modified caster oil-based waterborne polyurethane to form a casting liquid, which is then dried after scraping. The waterproof coating has a tensile strength of 1.19 MPa, an elongation at break of 431.23%, and a tensile strength retention rate of 78%. The water contact angle of the waterproof coating is 116°, and the yellowing resistance ΔE = 1.65. The modified caster oil-based waterborne polyurethane is prepared by mixing caster oil and polyethylene glycol, adding isocyanate monomers for polymerization, and then modifying with monohydroxy silicone oil. The molecular weight of the modified caster oil-based waterborne polyurethane is 43,000.

[0072] This embodiment also provides a method for preparing the self-cleaning, ultra-weather-resistant, single-component exterior wall waterproof coating, comprising the following steps:

[0073] Step 1: 0.15 mol castor oil, 0.05 mol polyethylene glycol and 0.0013 g dibutyltin dilaurate are heated to 75 °C and refluxed under stirring at 800 r / min for 30 min to obtain a mixed solution.

[0074] Step 2: Under stirring at 800 r / min, add 0.48 mol of isophorone diisocyanate to the mixed solution and react at 75°C for 60 min to obtain a polyurethane solution. At this time, the isocyanate (-NCO) content in the polyurethane solution is 70%.

[0075] Step 3: Under stirring at 800 r / min, add 0.28 mol of α-[3-[1,3,3,3-tetramethyl-1-(trimethylsilyl-oxo)disiloxane]-propyl-ω-hydroxypolyoxyethylene] to the polyurethane solution. After modification reaction at 75°C for 30 min, add 0.01 mol of 2,2-dimethylolpropionic acid and 0.02 g of hydroquinone. After polymerization inhibition reaction at 75°C for 30 min, obtain the organosilicon modified polymerization solution. At this time, the isocyanate (-NCO) content in the organosilicon modified polymerization solution is 0.

[0076] Step 4: Under high-speed stirring at 1500 r / min, 600 g of deionized water is added to the organosilicon-modified polymerization solution to obtain an oil-in-water modified castor oil-based waterborne polyurethane.

[0077] Step 5: Mix 1000g of the modified castor oil-based waterborne polyurethane, 4g of defoamer, 3g of dispersant, 0.1g of thickener and 5g of light stabilizer at 1200r / min for 20min to obtain a casting liquid. Coat the casting liquid onto a polytetrafluoroethylene board and apply it evenly using a 1.5mm coating machine. Then dry it at 23℃ and 50% humidity for 7 days to obtain the self-cleaning, ultra-weather-resistant, single-component exterior wall waterproof coating.

[0078] Example 4

[0079] This embodiment provides a self-cleaning, ultra-weather-resistant, single-component exterior wall waterproof coating. The waterproof coating is prepared by adding defoamer, dispersant, thickener, and light stabilizer to modified cast polyurethane to form a casting liquid, which is then dried after scraping. The waterproof coating has a tensile strength of 1.09 MPa, an elongation at break of 410.98%, and a tensile strength retention rate of 81%. The water contact angle of the waterproof coating is 110°, and the yellowing resistance ΔE = 1.54. The modified castor oil-based waterborne polyurethane is prepared by mixing castor oil and polyethylene glycol, adding isocyanate monomers for polymerization, and then modifying with monohydroxy silicone oil. The molecular weight of the modified castor oil-based waterborne polyurethane is 42,000.

[0080] This embodiment also provides a method for preparing the self-cleaning, ultra-weather-resistant, single-component exterior wall waterproof coating, comprising the following steps:

[0081] Step 1: 0.1 mol castor oil, 0.05 mol polyethylene glycol and 0.002 g dibutyltin dilaurate are heated to 50 °C and refluxed under stirring at 500 r / min for 50 min to obtain a mixed solution;

[0082] Step 2: Under stirring at 500 r / min, add 0.45 mol of isophorone diisocyanate to the mixed solution and react at 50°C for 30 min to obtain a polyurethane solution. At this time, the isocyanate (-NCO) content in the polyurethane solution is 75%.

[0083] Step 3: Under stirring at 500 r / min, add 0.22 mol of α-[3-[1,3,3,3-tetramethyl-1-(trimethylsilyl-oxo)disiloxane]-propyl-ω-hydroxypolyoxyethylene] to the polyurethane solution. After modification reaction at 50°C for 20 min, add 0.01 mol of 2,2-dimethylolbutyric acid and 0.02 g of hydroquinone. After polymerization inhibition reaction at 50°C for 40 min, obtain the organosilicon modified polymerization solution. At this time, the isocyanate (-NCO) content in the organosilicon modified polymerization solution is 0.

[0084] Step 4: Under high-speed stirring at 2000 r / min, 600 g of deionized water is added to the organosilicon-modified polymerization solution to obtain an oil-in-water modified castor oil-based waterborne polyurethane.

[0085] Step 5: Mix 1000g of the modified castor oil-based waterborne polyurethane, 4g of defoamer, 3g of dispersant, 0.1g of thickener, and 3g of light stabilizer at 1500r / min for 20min to obtain a casting liquid. Coat the casting liquid onto a polytetrafluoroethylene board and apply it evenly using a 1.5mm coating machine. Then dry it at 25℃ and 50% humidity for 7 days to obtain the self-cleaning, ultra-weather-resistant, single-component exterior waterproof coating.

[0086] Comparative Example 1

[0087] This comparative example provides a waterproof coating, which is prepared by adding defoamer, dispersant, thickener and light stabilizer to waterborne polyurethane to form a casting liquid, and then drying it after coating; the waterproof coating has a tensile strength of 0.77 MPa, an elongation at break of 600%, a tensile strength retention rate of 80%, a water contact angle of 30°, and a yellowing resistance ΔE=2.05; the waterborne polyurethane is obtained by mixing castor oil and polyethylene glycol and then adding isocyanate monomer for polymerization; the molecular weight of the waterborne polyurethane is 40,000.

[0088] This comparative example also provides a method for preparing the waterproof coating, comprising the following steps:

[0089] Step 1: 0.1 mol castor oil, 0.05 mol polyethylene glycol and 0.002 g dibutyltin dilaurate are heated to 50 °C and refluxed under stirring at 500 r / min for 50 min to obtain a mixed solution;

[0090] Step 2: Under stirring at 500 r / min, add 0.45 mol of isophorone diisocyanate to the mixed solution and react at 50°C for 30 min to obtain a prepolymer solution;

[0091] Step 4: Under high-speed stirring at 2000 r / min, add 600 g of deionized water to the prepolymer solution to obtain an oil-in-water waterborne polyurethane.

[0092] Step 5: Mix 1000g of the waterborne polyurethane, 4g of defoamer, 3g of dispersant, 0.1g of thickener and 3g of light stabilizer at 1500r / min for 20min to obtain a casting solution. Coat the casting solution onto a polytetrafluoroethylene plate and coat it evenly with a 1.5mm coating machine. Then dry it at 25℃ and 50% humidity for 7 days to obtain the waterproof coating.

[0093] In Examples 1-4 and Comparative Example 1, the defoamer is polydimethylsiloxane, the dispersant is ammonium polyacrylate (CX003), the thickener is a nonionic polyurethane associative thickener (RM12W), and the light stabilizer is a benzophenone-based ultraviolet absorber (BP10); the molecular weight of the polyethylene glycol is 400.

[0094] The content of isocyanate (-NCO) in the polyurethane solution and the content of isocyanate (-NCO) in the organosilicon modified polymerization solution in Examples 1-4 were both detected by the acetone-di-n-butylamine method.

[0095] In Examples 1-4 and Comparative Example 1, the tensile strength retention rate test method is the plastic xenon lamp light source exposure test method, which conforms to GB / T 9344-1988; the yellowing resistance ΔE test conforms to GB / T 23987-2009, and the test time is 168h.

[0096] Table 1 shows the properties of polyurethane in Examples 1-4 and Comparative Example 1.

[0097]

[0098] As shown in Table 1, the modified castor oil-based waterborne polyurethane described in this invention has a large molecular weight because of the reaction between castor oil and isophorone diisocyanate.

[0099] Table 2 shows the performance of the waterproof coatings in Examples 1-4 and Comparative Example 1.

[0100]

[0101] As shown in Table 2, the waterproof coating of the present invention has a large water contact angle, better self-cleaning properties during use, better resistance to yellowing, and can be used for a long time under ultraviolet light. At the same time, the waterproof coating of the present invention has higher tensile strength.

[0102] As can be seen from the above, the modified castor oil-based waterborne polyurethane described in this application has a high molecular weight, and the waterproof coating prepared therefrom has good weather resistance, good performance, strong self-cleaning properties, a wide range of applications, low cost, and a very high market prospect.

[0103] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A self-cleaning, ultra-weather-resistant, single-component exterior wall waterproof coating, characterized in that, The waterproof coating is prepared by adding defoamer, dispersant, thickener and light stabilizer to modified castor oil-based waterborne polyurethane to form a casting liquid, which is then dried after coating. The waterproof coating has a tensile strength of 0.9-1.2 MPa, an elongation at break of 410-515%, a tensile strength retention rate of 75-85%, a water contact angle of 100-120°, and a yellowing resistance ΔE of 1.5-1.

9. The modified castor oil-based waterborne polyurethane is prepared by mixing castor oil and polyethylene glycol, adding isocyanate monomers for polymerization, and then modifying with monohydroxy silicone oil. The modified castor oil-based waterborne polyurethane has a molecular weight of 41,000-45,000; in the infrared spectrum of the modified castor oil-based waterborne polyurethane, at 3355 cm⁻¹... -1 ±0.01cm -1 The NH stretching vibration peak appears at 2923 cm⁻¹. -1 ±0.01cm -1 and 2855cm -1 ±0.01cm -1 The CH stretching vibration peak appears at 1744 cm⁻¹. -1 ±0.01cm -1 and 1700cm -1 ±0.01cm -1 A C=O stretching vibration peak appears at 1524 cm⁻¹. -1 ±0.01cm -1 and 1460cm -1 ±0.01cm -1 A C=C stretching vibration peak appears at this location; The molecular weight of the polyethylene glycol is 400; The molar ratio of castor oil to polyethylene glycol is (2:1)-(3:1); The molar ratio of the isocyanate monomer to the castor oil in the mixed solution is (3.9:1)-(4.8:1). The monohydroxy silicone oil is α-[3-[1,3,3,3-tetramethyl-1-(trimethylsilyl-oxo)disiloxane]-propyl-ω-hydroxypolyoxyethylene]; The preparation method of the self-cleaning, ultra-weather-resistant, single-component exterior wall waterproof coating includes the following steps: Step 1: Mix castor oil, polyethylene glycol, and catalyst under stirring and reflux to obtain a mixed solution; Step 2: Under stirring conditions, add isocyanate monomer to the mixed solution to carry out the reaction and obtain a polyurethane solution; Step 3: Under stirring conditions, add monohydroxy silicone oil to the polyurethane solution to carry out the modification reaction, then add chain extender and polymerization inhibitor to carry out the polymerization inhibition reaction, and obtain organosilicon modified polymerization solution. Step 4: Under high-speed stirring conditions, deionized water is added to the organosilicon-modified polymerization solution to convert it, thereby obtaining modified castor oil-based waterborne polyurethane. Step 5: Mix and stir the modified castor oil-based waterborne polyurethane, defoamer, dispersant, thickener and light stabilizer to obtain a casting liquid. Coat the casting liquid onto a polytetrafluoroethylene board, apply it evenly with a coating machine and then dry it to obtain the self-cleaning ultra-weather-resistant single-component exterior wall waterproof coating.

2. A method for preparing the self-cleaning, ultra-weather-resistant, single-component exterior wall waterproof coating as described in claim 1, characterized in that, Includes the following steps: Step 1: Mix castor oil, polyethylene glycol, and catalyst under stirring and reflux to obtain a mixed solution; Step 2: Under stirring conditions, add isocyanate monomer to the mixed solution to carry out the reaction and obtain a polyurethane solution; Step 3: Under stirring conditions, add monohydroxy silicone oil to the polyurethane solution to carry out the modification reaction, then add chain extender and polymerization inhibitor to carry out the polymerization inhibition reaction, and obtain organosilicon modified polymerization solution. Step 4: Under high-speed stirring conditions, deionized water is added to the organosilicon-modified polymerization solution to convert it, thereby obtaining modified castor oil-based waterborne polyurethane. Step 5: Mix and stir the modified castor oil-based waterborne polyurethane, defoamer, dispersant, thickener and light stabilizer to obtain a casting liquid. Coat the casting liquid onto a polytetrafluoroethylene board, apply it evenly with a coating machine and then dry it to obtain the self-cleaning ultra-weather-resistant single-component exterior wall waterproof coating.

3. The preparation method according to claim 2, characterized in that, The isocyanate monomer in step 2 is isophorone diisocyanate.

4. The preparation method according to claim 2, characterized in that, The isocyanate content in the polyurethane solution in step 2 is 70-80%.

5. The preparation method according to claim 2, characterized in that, The isocyanate content in the organosilicon-modified polymerization solution in step 3 is 0.

6. The preparation method according to claim 2, characterized in that, The conversion process in step 4 is as follows: the oily organosilicon modified polymer solution is mixed with deionized water under high-speed stirring to form an oil-in-water modified castor oil-based waterborne polyurethane.

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