A bio-based polyurethane waterproof coating and a preparation method thereof

Abstract

The present application relates to the technical field of paint, in particular to a kind of bio-based polyurethane waterproof coating and preparation method thereof.The coating is prepared from organic fluorine silicon crosslinking castor oil, dibutyltin dilaurate, HDI trimer, polytetrahydrofuran ether diol, 1,4-butanediol, filler, plasticizer and ultraviolet absorber, wherein the organic fluorine silicon crosslinking castor oil is obtained by silanization modification of methyl ricinoleate, and then hydrolysis crosslinking fluorine-containing silane.The preparation method is simple, the material performance is excellent, suitable for building waterproof, weather-resistant coating and other fields, has wide application potential and market value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coatings, in particular to a bio-based polyurethane waterproof coating and a preparation method thereof. BACKGROUND

[0002] In recent years, with the increasingly stringent environmental regulations and the deepening of the concept of sustainable development, bio-based polyurethane coatings have attracted widespread attention due to their renewable and low VOC emission characteristics. Castor oil, as a typical bio-based polyol raw material, contains hydroxyl groups in its molecular structure, which can directly react with isocyanate to form a polyurethane network, and has formed a certain application basis in the field of coatings.

[0003] Castor oil, as an important natural bio-based material, has attracted widespread attention from researchers due to its excellent chemical reactivity and abundant chemical modification sites. Castor oil molecules contain various functional sites such as hydroxyl groups and double bonds, which can be functionalized by various chemical modification methods, thereby designing and preparing bio-based polymer materials with excellent performance. However, when castor oil is directly used to prepare polyurethane-based resins, the long non-polar segment in its molecular structure can easily lead to insufficient hydrophobicity of the coating, and the low hydroxyl functionality of natural castor oil (average about 2.7) and the significant influence of hydroxyl activity on steric hindrance can result in insufficient cross-linking network density formed by reaction with isocyanate. This structural defect directly manifests as low mechanical strength of the coating and often causes interfacial peeling. More notably, the high proportion of rigid cyclic structures in the molecular chain makes the glass transition temperature (Tg) of the material generally higher than -10℃, which can easily cause brittle fracture in low temperature environments (such as -25℃).

[0004] In recent years, the application of organosilicon and fluorine-containing compounds in high-performance coatings has gradually increased. Organosilicon materials can significantly improve the mechanical properties and durability of the coating due to their high chemical stability, low surface energy, and high cross-linking density. At the same time, the low surface energy and special hydrophobicity of fluorine-containing materials in their chemical structure can further improve the waterproof performance of the coating. However, traditional fluorine-silicon modified coatings are mainly based on petroleum-based raw materials, and their complex synthesis process and high production cost limit their large-scale promotion. Therefore, realizing fluorine-silicon organic cross-linking modification based on castor oil bio-based raw materials can not only significantly improve the material performance, but also meet the direction of green chemistry and sustainable development. SUMMARY

[0005] Therefore, the purpose of the present application is to provide a bio-based polyurethane waterproof coating and a preparation method thereof to solve the problems of poor waterproofness and high low-temperature brittleness of castor oil-based polyurethane coatings.

[0006] In order to achieve the above purpose, the application provides a bio-based polyurethane waterproof coating prepared from the following raw materials in parts by weight: 80-100 parts of organic fluorosilicone cross-linked castor oil, 0.03-0.05 parts of dibutyltin dilaurate, 46-58 parts of HDI trimer, 7-9 parts of polytetrahydrofuran ether glycol, 3-4 parts of 1,4-butanediol, 4-6 parts of filler, 1-3 parts of plasticizer and 0.1-1 parts of ultraviolet absorber.

[0007] Further, the organic fluorosilicone cross-linked castor oil is prepared by the following method: castor oil methyl ester, 3-mercapto propyl triethoxysilane and 2-hydroxy-2-methyl-1-phenylpropanone are added into tetrahydrofuran, stirred at room temperature for 5-7 hours, irradiated with ultraviolet light during the stirring process, the solvent is removed by rotary evaporation, deionized water, anhydrous ethanol and tridecafluorooctyl triethoxysilane are added, the pH is adjusted to 8.0-8.5 with ammonia water, stirred for 2.5-3.5 hours, and the solvent is removed by rotary evaporation to obtain the organic fluorosilicone cross-linked castor oil.

[0008] Preferably, the weight ratio of the castor oil methyl ester, 3-mercapto propyl triethoxysilane, 2-hydroxy-2-methyl-1-phenylpropanone, tetrahydrofuran, deionized water, anhydrous ethanol and tridecafluorooctyl triethoxysilane is 40-60:30.5-45.8:0.7-1:80-120:180-220:40-60:3.4-4.5.

[0009] Preferably, the castor oil methyl ester is obtained by methanol hydrolysis of castor oil.

[0010] Preferably, the preparation steps of the castor oil methyl ester are as follows: anhydrous methanol and potassium hydroxide are added into castor oil, heated to 43-48℃, stirred for 5-7 hours, then the reaction product is neutralized with sulfuric acid, the upper oil phase is washed with deionized water until neutral, and then the water is removed by rotary evaporation to obtain the castor oil methyl ester.

[0011] Preferably, the weight ratio of the anhydrous methanol, potassium hydroxide and castor oil is 8-12:0.4-0.6:40-60.

[0012] Preferably, the wavelength of the ultraviolet light irradiation is 365 nm, and the intensity is 6 mW / cm.

[0013] Preferably, the NCO content of the HDI trimer is 20-23 g / 100 g.

[0014] Preferably, the weight average molecular weight of the polytetrahydrofuran ether glycol is 800-1500.

[0015] Preferably, the filler is nano-silicon dioxide with an average particle size of 10-50 nm.

[0016] Preferably, the plasticizer is epoxy soybean oil.

[0017] Preferably, the ultraviolet absorber is UV-531.

[0018] Further, the application also provides a preparation method of the bio-based polyurethane waterproof coating, comprising the following steps: under the protection of nitrogen, the organofluorosilicon cross-linked castor oil is heated to 78-85 DEG C, and then dibutyltin dilaurate and HDI trimer are added, and stirring reaction is carried out for 2-3 h, and then the temperature is reduced to 60-68 DEG C, and then polytetrahydrofuran ether diol is added, and stirring reaction is continued for 30-50 min, and then 1, 4-butanediol is added, and stirring reaction is continued for 25-35 min, and then fillers, plasticizers and ultraviolet absorbers are added, and dispersion is carried out at 1800-2200 rpm for 20-30 min, and finally, under the vacuum degree of-0.093-7 MPa, the bio-based polyurethane waterproof coating is obtained by maintaining for 30-50 min.

[0019] The beneficial effects of the application are as follows:

[0020] The application significantly improves the comprehensive performance of the coating by preparing a coating material with an organofluorosilicon cross-linking structure through silanization modification of methyl ricinoleate. The organofluorosilicon cross-linking system combines the low surface energy characteristics of fluorocarbon chains and the high cross-linking stability of silicon-oxygen networks, so that the coating has excellent mechanical strength, water resistance and low-temperature flexibility. The introduction of fluorocarbon segments forms a hydrophobic layer on the surface of the coating, effectively reducing the free energy and permeability of water molecules on the surface of the coating, thereby improving the waterproof performance of the material. At the same time, the interpenetration of the silicon-oxygen network structure and the coating matrix gives the material higher strength and durability.

[0021] The application introduces methyl ricinoleate, which exhibits excellent controllability in molecular reactivity and network formation. The linear structure reduces the steric hindrance between molecules, promotes efficient grafting of silane components and forms a more uniform cross-linking structure. The synergistic effect of flexible ester segments and cross-linking networks improves the low-temperature bending performance of the coating by dispersing stress, effectively avoiding crack propagation. In addition, the thiol silane provides high chemical activity, further improving the regularity and functionalization degree of the molecular chain, so that the material achieves a perfect balance between surface performance and internal toughness. The coating prepared by the application has excellent comprehensive performance, wide application potential and market value. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the application clearer, the application is further described in detail below with reference to specific examples.

[0023] In the specific embodiment of the application, the castor oil is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., and the item number is C110663.

[0024] Example 1

[0025] (1) 8 g of anhydrous methanol and 0.4 g of potassium hydroxide were added to 40 g of castor oil, warmed to 43°C, stirred for 5 h, and then the reaction product was neutralized with sulfuric acid, the upper oil phase was washed with deionized water until neutral, and then water was removed by rotary evaporation to obtain methyl ricinoleate;

[0026] (2) 40 g of methyl ricinoleate, 30.5 g of 3-mercaptopropyl triethoxysilane, and 0.7 g of 2-hydroxy-2-methyl-1-phenylpropanone were added to 80 g of tetrahydrofuran, stirred at room temperature for 5 h, and irradiated with ultraviolet light at a wavelength of 365 nm and an intensity of 6 mW / cm during stirring, and then the solvent was removed by rotary evaporation, 180 g of deionized water, 40 g of anhydrous ethanol, and 3.4 g of tridecafluorooctyl triethoxysilane were added, the pH was adjusted to 8.0 with ammonia water, stirred for 2.5 h, and then the solvent was removed by rotary evaporation to obtain an organic fluorosilicon cross-linked castor oil;

[0027] (3) 80 g of the organic fluorosilicon cross-linked castor oil was warmed to 78°C under nitrogen protection, 0.03 g of dibutyltin dilaurate and 46 g of HDI trimer (NCO content 21.5 g / 100 g) were added, stirred for 2 h, cooled to 60°C, 7 g of polytetrahydrofuran ether glycol (weight average molecular weight 1000) was added, and stirring was continued for 30 min, 3 g of 1,4-butanediol was added, and stirring was continued for 25 min, 4 g of nano-silicon dioxide (average particle size 20 nm), 1 g of epoxy soybean oil, and 0.1 g of ultraviolet absorber UV-531 were added, and dispersed at 1800 rpm for 20 min, and finally maintained at a vacuum degree of -0.093 MPa for 30 min to obtain a bio-based polyurethane waterproof coating.

[0028] Example 2:

[0029] (1) 10 g of anhydrous methanol and 0.5 g of potassium hydroxide were added to 50 g of castor oil, warmed to 45°C, stirred for 6 h, and then the reaction product was neutralized with sulfuric acid, the upper oil phase was washed with deionized water until neutral, and then water was removed by rotary evaporation to obtain methyl ricinoleate;

[0030] (2) 50 g of methyl ricinoleate, 38.2 g of 3-mercaptopropyl triethoxysilane, and 0.8 g of 2-hydroxy-2-methyl-1-phenylpropanone were added to 100 g of tetrahydrofuran, stirred at room temperature for 6 h, and irradiated with ultraviolet light at a wavelength of 365 nm and an intensity of 6 mW / cm during stirring, and then the solvent was removed by rotary evaporation, 200 g of deionized water, 50 g of anhydrous ethanol, and 3.8 g of tridecafluorooctyl triethoxysilane were added, the pH was adjusted to 8.2 with ammonia water, stirred for 3 h, and then the solvent was removed by rotary evaporation to obtain an organic fluorosilicon cross-linked castor oil;

[0031] (3) Under the protection of nitrogen, 90 g of organic fluorine-silicon cross-linked castor oil was heated to 80 °C, 0.04 g of dibutyltin dilaurate and 52 g of HDI trimer (NCO content 21.5 g / 100 g) were added, and stirred for 2.5 h, cooled to 65 °C, 8 g of polytetrahydrofuran ether glycol (weight average molecular weight 1000) was added, and the stirring reaction was continued for 40 min, 3.5 g of 1,4-butanediol was added, and the stirring reaction was continued for 30 min, 5 g of nano-silicon dioxide (average particle size 20 nm), 2 g of epoxy soybean oil and 0.5 g of ultraviolet absorber UV-531 were added, and dispersed at 2000 rpm for 25 min, and finally maintained at a vacuum degree of -0.095 MPa for 40 min to obtain a bio-based polyurethane waterproof coating.

[0032] Example 3:

[0033] (1) 12 g of anhydrous methanol and 0.6 g of potassium hydroxide were added to 60 g of castor oil, heated to 48 °C, stirred for 7 h, and then the reaction product was neutralized with sulfuric acid, the upper oil phase was washed with deionized water until neutral, and then the water was removed by rotary evaporation to obtain methyl ricinoleate;

[0034] (2) 60 g of methyl ricinoleate, 45.8 g of 3-mercaptopropyl triethoxysilane and 1 g of 2-hydroxy-2-methyl-1-phenylpropanone were added to 120 g of tetrahydrofuran, stirred at room temperature for 7 h, and irradiated with ultraviolet light at a wavelength of 365 nm and an intensity of 6 mW / cm during stirring, and then the solvent was removed by rotary evaporation, 220 g of deionized water, 60 g of anhydrous ethanol and 4.5 g of tridecafluorooctyl triethoxysilane were added, the pH was adjusted to 8.5 with ammonia water, stirred for 3.5 h, and then the solvent was removed by rotary evaporation to obtain organic fluorine-silicon cross-linked castor oil;

[0035] (3) Under the protection of nitrogen, 100 g of organic fluorine-silicon cross-linked castor oil was heated to 85 °C, 0.05 g of dibutyltin dilaurate and 58 g of HDI trimer (NCO content 21.5 g / 100 g) were added, and stirred for 3 h, cooled to 68 °C, 9 g of polytetrahydrofuran ether glycol (weight average molecular weight 1000) was added, and the stirring reaction was continued for 50 min, 4 g of 1,4-butanediol was added, and the stirring reaction was continued for 35 min, 6 g of nano-silicon dioxide (average particle size 20 nm), 3 g of epoxy soybean oil and 1 g of ultraviolet absorber UV-531 were added, and dispersed at 2200 rpm for 20-30 min, and finally maintained at a vacuum degree of -0.097 MPa for 50 min to obtain a bio-based polyurethane waterproof coating.

[0036] Comparative Example 1:

[0037] The difference between Comparative Example 1 and Example 2 is that the methyl ricinoleate in step (2) is replaced by castor oil;

[0038] Comparative Example 2:

[0039] The difference between Comparative Example 2 and Example 2 is that the organofluorosilicone crosslinking castor oil in step (3) is replaced by castor oil;

[0040] Comparative Example 3:

[0041] The difference between Comparative Example 3 and Example 2 is that the 3-mercaptopropyl triethoxysilane in step (2) is replaced by methyl triethoxysilane;

[0042] Comparative Example 4:

[0043] The difference between Comparative Example 4 and Example 2 is that no tridecafluorooctyl triethoxysilane is added in step (2);

[0044] Performance test:

[0045] Coating preparation: the coating prepared by the examples and comparative examples is applied on the concrete substrate by using the draw coating method, the wet film thickness is controlled to be 1.2±0.1 mm, and then it is pre-cured in a 40℃ oven for 2h, and then it is transferred into a constant temperature room for curing for 5 days, to obtain a coating.

[0046] Adhesion test: according to GB / T 5210-2006, the coating sample is fixed on the clamps of a tensile testing machine, a 20mm diameter aluminum ingot bonding head is used, and the maximum tensile force value is recorded and converted into megapascal (MPa) at a rate of 1mm / min, and the average value of three samples is taken, and the results are shown in Table 1.

[0047] Water resistance test: according to GB / T 1733-1993, the coating sample is soaked in deionized water at (23±2)℃, the liquid level is 10mm higher than the sample, and after soaking for 168h, it is taken out and dried, and the retention rate of the coating is evaluated by using the grid method (1mm×1mm grid), and the results are shown in Table 1.

[0048] Moisture permeability test: according to GB / T 17146-2015, the demolded coating is placed in a test box, the temperature of the test box is controlled to be (38±0.6)℃, and the relative humidity is controlled to be (90±2)%, and the 24h moisture permeability is weighed and converted into g / (m 2 ·h), and the results are shown in Table 1.

[0049] Low temperature bending property: according to GB / T 17146-2015, the demolded coating sample is placed in a low temperature box at -25℃ for 2h, and then it is immediately bent on a bending instrument at 180°, and whether cracks are generated on the surface of the coating is observed.

[0050] Table 1 Performance test results

[0051]

[0052] Data analysis:

[0053] From the data of examples 1-3 in Table 1, it can be seen that the coatings prepared by the present application exhibit excellent comprehensive performance in adhesion, water resistance, moisture permeability and low-temperature bending performance, which is mainly due to the organic fluorosilicon crosslinking system formed by the silanization modification of methyl ricinoleate, and the low surface energy characteristics of the fluorocarbon chain segment help to reduce the surface free energy of the coating. In the process of polyurethane chain extension, the flexible segment of polytetrahydrofuran ether diol and the rigid structure of HDI trimer form microphase separation, which may enhance the mechanical strength through the hard segment crystalline region, and the soft segment maintains the elastic deformation ability.

[0054] From the data of examples 2 and comparative example 1 in Table 1, it can be seen that example 2 exhibits more outstanding performance than comparative example 1, which may be due to the introduction of methyl ricinoleate, which enhances the reactivity of the coating and the controllability of the molecular structure. Compared with castor oil, methyl ricinoleate has a linear structure with smaller steric hindrance, which helps to graft 3-mercaptopropyl triethoxysilane, and is more conducive to crosslinking after silane hydrolysis, thereby forming a uniform crosslinking network, which improves the mechanical properties of the coating while reducing the permeation of water molecules. In addition, the moderate flexibility of the ester group and the structural stability of the siloxane network synergistically allow the material to disperse stress through the microzone slip of molecular chain segments during low-temperature deformation, avoiding crack propagation caused by stress concentration.

[0055] From the data of examples 2 and comparative example 2 in Table 1, it can be seen that compared with castor oil, organic fluorosilicon crosslinked castor oil can significantly improve the water resistance and low-temperature bending property of the coating, which is mainly due to the formation of a hydrophobic layer on the coating surface by the fluoralkyl chain, effectively reducing the adsorption energy of water molecules. The interpenetrating structure of the siloxane crosslinking network and the polyurethane matrix may produce a synergistic enhancement effect, in which the rigid siloxane network bears mechanical stress, and the elastic polyurethane matrix absorbs deformation energy. This composite structure may improve the flexibility of the material at low temperature by limiting the thermal motion of molecular chain segments.

[0056] From the data of examples 2 and comparative example 3 in Table 1, it can be seen that after replacing 3-mercaptopropyl triethoxysilane with methyl triethoxysilane, the adhesion, water resistance and low-temperature bending property of the coating are all decreased, which is mainly due to the high reactivity of mercapto groups, which may promote the click chemistry reaction between silane reagents and methyl ricinoleate, forming a more regular graft structure. This directional grafting may optimize the arrangement and orientation of molecular chains, allowing the fluorocarbon chain segment to be more orderly enriched on the surface of the coating.

[0057] As can be seen from the data of Example 2 and Comparative Example 4 in Table 1, the tridecafluorooctyltriethoxysilane not only significantly affects the water resistance of the coating, but also affects the low-temperature bending property, which is probably due to the steric hindrance effect of the fluorinated group regulating the spatial distribution of the crosslinking reaction, adjusting the crosslinking density, so that the coating has both surface hydrophobicity and internal toughness.

[0058] It should be understood by those of ordinary skill in the art that the above discussion of any of the embodiments is merely exemplary and is not intended to suggest that the scope of the application is limited to these examples; the above embodiments or technical features among different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the application as described above, which are not provided in details for the sake of brevity.

Claims

1. A bio-based polyurethane waterproofing coating, characterized in that, Prepared from the following raw materials by weight parts: 80-100 organic fluorosilicone cross-linked castor oil, 0.03-0.05 dibutyltin dilaurate, 46-58 HDI trimer, 7-9 polytetrahydrofuran ether glycol, 3-4 1,4-butanediol, 4-6 filler, 1-3 plasticizer and 0.1-1 UV absorber; The preparation method of the organic fluorosilicone cross-linked castor oil is as follows: castor oil methyl ester, 3-mercapto propyl triethoxysilane and 2-hydroxy-2-methyl-1-phenylpropanone are added into tetrahydrofuran, stirred at room temperature for 5-7h, irradiated with ultraviolet light during stirring, and the solvent is removed by rotary evaporation, then deionized water, anhydrous ethanol and tridecafluorooctyl triethoxysilane are added, the pH is adjusted to 8.0-8.5 with ammonia water, stirred for 2.5-3.5h, and the solvent is removed by rotary evaporation to obtain the organic fluorosilicone cross-linked castor oil; The weight ratio of the castor oil methyl ester, 3-mercapto propyl triethoxysilane, 2-hydroxy-2-methyl-1-phenylpropanone, tetrahydrofuran, deionized water, anhydrous ethanol and tridecafluorooctyl triethoxysilane is 40-60:30.5-45.8:0.7-1:80-120:180-220:40-60:3.4-4.

5.

2. The bio-based polyurethane waterproofing coating according to claim 1, characterized in that, The preparation steps of the castor oil methyl ester are as follows: anhydrous methanol and potassium hydroxide are added into castor oil, heated to 43-48℃, stirred for 5-7h, then the reaction product is neutralized with sulfuric acid, the upper oil phase is washed with deionized water until neutral, and then the water is removed by rotary evaporation to obtain the castor oil methyl ester.

3. The bio-based polyurethane waterproofing coating according to claim 2, characterized in that, The weight ratio of the anhydrous methanol, potassium hydroxide and castor oil is 8-12:0.4-0.6:40-60.

4. The bio-based polyurethane waterproofing coating of claim 1, wherein, The wavelength of the ultraviolet light irradiation is 365nm, and the intensity is 6mW / cm.

5. The bio-based polyurethane waterproofing coating of claim 1, wherein, The NCO content of the HDI trimer is 20-23g / 100g.

6. The bio-based polyurethane waterproofing coating of claim 1, wherein, The weight average molecular weight of the polytetrahydrofuran ether glycol is 800-1500.

7. The bio-based polyurethane waterproofing coating of claim 1, wherein, The filler is nano silicon dioxide with an average particle size of 10-50nm.

8. The bio-based polyurethane waterproofing coating of claim 1, wherein, The plasticizer is epoxy soybean oil, and the UV absorber is UV-531.

9. A method for the preparation of a bio-based polyurethane water-proof coating according to any one of claims 1-8, characterized in that, The steps include: Under nitrogen protection, the organic fluorosilicone cross-linked castor oil is heated to 78-85℃, dibutyltin dilaurate and HDI trimer are added, stirred for 2-3h, cooled to 60-68℃, polytetrahydrofuran ether glycol is added, and the stirring reaction is continued for 30-50min, then 1,4-butanediol is added, and the stirring reaction is continued for 25-35min, then the filler, plasticizer and UV absorber are added, dispersed at 1800-2200rpm for 20-30min, and finally maintained at a vacuum degree of -0.093-7MPa for 30-50min to obtain the bio-based polyurethane waterproof coating.

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