Bio-based polyurethane coating and preparation method thereof

Abstract

The invention discloses a bio-based polyurethane coating, and belongs to the technical field of polyurethane coatings. The coating comprises the following components in parts by weight: 90-100 parts of modified vegetable oil polyol, 30-50 parts of isocyanate, 0.5-3 parts of a catalyst, 10-20 parts of a water-resistant agent, 3-7 parts of a cross-linking agent, 2-5 parts of a chain extender and 3-7 parts of a reinforcing agent, the modified vegetable oil polyhydric alcohol is obtained by mixing vegetable oil polyhydric alcohol and an amido solution and then carrying out ultrasonic dispersion; the reinforcing agent is obtained by compounding tocopherol and hydrotalcite; the water-resistant agent is obtained by compounding span-80 and gamma-aminopropyl triethoxy silane. The invention further discloses a preparation method of the water-resistant agent. The polyurethane coating prepared by the invention solves the problem of poor water resistance of polyurethane prepared by vegetable oil polyol at present, and other specific components are added to synergistically improve the mechanical properties and stability of the coating.

Description

Technical Field

[0001] The present application relates to a bio-based polyurethane coating and a preparation method thereof, belonging to the technical field of polyurethane coatings. Background Art

[0002] The preparation of polyurethanes primarily involves the polymerization of polyols and isocyanates. Currently, the polyols and isocyanates used in polyurethane systems are primarily derived from petroleum resources. With the depletion of petroleum resources and the intensification of environmental concerns, the use of green, renewable biomass resources to prepare polyols or isocyanates, and subsequently synthesize bio-based polyurethanes, has become a key development direction for my country's strategic emerging materials and biomass industries.

[0003] Bio-based polyurethane raw materials are less toxic, more abundant in sources, and more environmentally friendly.

[0004] Patent CN 119592200 A discloses a bio-based polyurethane coating and its preparation method. The raw material used in the coating is vegetable oil polyol instead of traditional petroleum-based polyol. This helps to solve problems such as oil resource shortages and environmental pollution. However, it may have the following problems: 1) The fatty acid chain structure of vegetable oil polyols may lead to insufficient water resistance in the coating film after formation, thereby reducing the stability of the film. 2) The addition of a large amount of solvent can reduce the viscosity of the vegetable oil, promote thorough mixing with the isocyanate, and improve the surface smoothness of the coating, but it may also lead to increased VOC emissions and slower coating drying speed. Summary of the Invention

[0005] To address the aforementioned issues, a bio-based polyurethane coating and its preparation method are provided. This bio-based polyurethane coating addresses the poor water resistance of polyurethanes currently prepared using vegetable oil polyols. It also maintains excellent compatibility between the vegetable oil polyol and isocyanate without adding a significant amount of organic solvent to the prepolymer mixture. Furthermore, the addition of other specific components synergistically enhances the coating's mechanical properties, water resistance, and stability.

[0006] The specific implementation plan of this application is as follows: The present application provides a bio-based polyurethane coating, comprising the following components in parts by weight: 90-100 parts of modified vegetable oil polyol, 30-50 parts of isocyanate, 0.5-3 parts of catalyst, 10-20 parts of water-resistant agent, 3-7 parts of cross-linking agent, 2-5 parts of chain extender, and 3-7 parts of reinforcing agent; The modified vegetable oil polyol is obtained by mixing vegetable oil polyol with an amide solution; the enhancer is obtained by compounding tocopherol and hydrotalcite; The water-resistant agent is obtained by compounding Span-80 and gamma-aminopropyltriethoxysilane.

[0007] Optionally, the water-resistant agent is prepared by the following method: Span-80 is added to anhydrous ethanol and stirred at 30-40° C. to obtain a dissolving solution; γ-aminopropyltriethoxysilane accounting for 10-20% of the mass of the dissolving solution is added and stirred for 1-2 hours, and the ethanol is removed by vacuum distillation to obtain a solution.

[0008] Optionally, the amide-containing compound in the amide-based solution includes polyacrylamide and N,N-dimethylformamide.

[0009] Optionally, the enhancer is obtained by mixing tocopherol and hydrotalcite in a mass ratio of (5-8):2.

[0010] Optionally, the hydroxyl value of the vegetable oil polyol is greater than 150 mg KOH / g.

[0011] Optionally, the catalyst includes a zinc-based catalyst, a bismuth-based catalyst, and a zirconium-based catalyst; the zinc-based catalyst includes zinc 2-ethylhexanoate and zinc cyclohexane; the bismuth-based catalyst includes bismuth neodecanoate and bismuth 2-ethylhexanoate.

[0012] Optionally, the chain extender includes diaminopropionic acid and 1,3-propylene glycol; and the cross-linking agent is selected from at least one of trimethylolpropane, pentaerythritol, and 4,4'-diaminodicyclohexylmethane.

[0013] Optionally, the isocyanate is selected from aliphatic isocyanate, alicyclic isocyanate, and amino acid-derived isocyanate; and the vegetable oil polyol includes castor oil-based polyol and high-epoxidized soybean oil polyol.

[0014] Furthermore, the present application also provides a method for preparing the above-mentioned bio-based polyurethane coating, comprising: Step 1: reacting vegetable oil polyol, isocyanate and catalyst under nitrogen protection for 1-2 hours at a reaction temperature of 50-65°C; Step 2: Add chain extender and cross-linker, and stir at 1000-1500 rpm and 55-65°C for 1-2 hours; Step 3: gradually add the enhancer to the water-resistant agent at 200-600 rpm, stir at 25-45°C for 2-4 hours to obtain a mixture; then add the mixture after the stirring in step 2 is completed, stir at a low speed at 25-40°C for 30-60 minutes, and obtain the coating after standing.

[0015] Optionally, the enhancer is obtained by mixing tocopherol and hydrotalcite in a ball mill at a rotation speed of 200-400 rpm for 0.5-1 hour. The beneficial effects of the present application include but are not limited to: 1. The modified vegetable oil polyol provided in this application is obtained by mixing a vegetable oil polyol with an amide solution. Adding it to the present application can improve the water resistance and surface drying speed of the polyurethane coating. This may be because the introduction of the amide group, on the one hand, prevents the aggregation of the long-chain alkyl groups of the vegetable oil polyol through the steric hindrance effect, making the vegetable oil polyol more easily dispersed in the isocyanate and improving the compatibility of the vegetable oil polyol and the isocyanate; on the other hand, the amide group can also form weak hydrogen bonds with the isocyanate group, further promoting the mixing uniformity of the vegetable oil polyol and the isocyanate.

[0016] 2. The specific water-resistant agent added to this application can improve the water resistance of polyurethane coatings. Due to the good compatibility of the prepolymer, the isocyanate groups in the system are more evenly distributed. The amino groups of γ-aminopropyltriethoxysilane can preferentially react with free isocyanate groups, covalently integrating γ-aminopropyltriethoxysilane into the polymer network to form a dense structure and improve water resistance.

[0017] 3. This application also adds a specific enhancer. The hydrophobic chains in tocopherol and Span-80 can aggregate and entangle to form a hydrophobic layer on the outside. The hydrophilic end of Span-80 is wrapped inside by the enhancer and is not exposed to water. The formed hydrophobic layer has good compatibility with the polyurethane matrix, further improving the water resistance of the coating.

[0018] 4. The proportion of bio-based raw materials in the components of this application is large, which overcomes the poor environmental protection problem brought by traditional polyurethane coatings and is more environmentally friendly. DETAILED DESCRIPTION

[0019] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0020] Unless otherwise specified, the raw materials and catalysts in the examples of this application were purchased from commercial sources.

[0021] The present application provides a bio-based polyurethane coating, characterized by comprising the following components in parts by weight: 90-100 parts of modified vegetable oil polyol, 30-50 parts of isocyanate, 0.5-3 parts of catalyst, 10-20 parts of water-resistant agent, 3-7 parts of cross-linking agent, 2-5 parts of chain extender, 3-7 parts of reinforcing agent.

[0022] The modified vegetable oil polyol is obtained by mixing the vegetable oil polyol with an amide solution; the enhancer is obtained by compounding tocopherol and hydrotalcite in a mass ratio of (5-8):2; The water-resistant agent is obtained by compounding Span-80 and γ-aminopropyltriethoxysilane, and is specifically prepared by the following method: Span-80 is added to anhydrous ethanol and stirred at 30-40° C. to obtain a dissolving solution; γ-aminopropyltriethoxysilane accounting for 10-20% of the mass of the dissolving solution is added and stirred for 1-2 hours, and the ethanol is removed by vacuum distillation to obtain a solution.

[0023] The amide group-containing compound in the amide group solution includes polyacrylamide and N,N-dimethylformamide.

[0024] The hydroxyl value of the vegetable oil polyol is greater than 150 mg KOH / g.

[0025] The catalyst includes zinc-based catalyst, bismuth-based catalyst, and zirconium-based catalyst; the zinc-based catalyst includes zinc 2-ethylhexanoate and zinc naphthenate; the bismuth-based catalyst includes bismuth neodecanoate and bismuth 2-ethylhexanoate.

[0026] The chain extender includes diaminopropionic acid and 1,3-propylene glycol; the cross-linking agent is selected from at least one of trimethylolpropane, pentaerythritol, and 4,4'-diaminodicyclohexylmethane.

[0027] The isocyanate is selected from aliphatic isocyanate, alicyclic isocyanate, and amino acid-derived isocyanate; the vegetable oil polyol includes castor oil-based polyol and high-epoxidized soybean oil polyol.

[0028] Also provided is a method for preparing the above-mentioned bio-based polyurethane coating, comprising the following steps: Step 1: reacting vegetable oil polyol, isocyanate and catalyst under nitrogen protection for 1-2 hours at a reaction temperature of 50-65°C; Step 2: Add chain extender and cross-linker, and stir at 1000-1500 rpm and 55-65°C for 1-2 hours; Step 3: gradually add the enhancer to the water-resistant agent at 200-600 rpm, stir at 25-45°C for 2-4 hours to obtain a mixture; then add the mixture after the stirring in step 2 is completed, stir at a low speed at 25-40°C for 30-60 minutes, and obtain the coating after standing.

[0029] The enhancer is obtained by mixing tocopherol and hydrotalcite in a ball mill at a rotation speed of 200-400 rpm for 1-2 hours.

[0030] Example 1 Bio-based polyurethane coating #1 A bio-based polyurethane coating comprising the following components in parts by weight: 100 parts of modified castor oil polyol, 50 parts of hexamethylene diisocyanate, 0.5 parts of 2-ethylhexanoate zinc (catalyst), 20 parts of water-resistant agent, 3 parts of trimethylolpropane (cross-linking agent), 2 parts of diaminopropionic acid (chain extender), and 3 parts of reinforcing agent.

[0031] The hydroxyl value of vegetable oil polyol is 160 mg KOH / g.

[0032] The modified castor oil polyol was prepared by magnetically stirring polyacrylamide in anhydrous xylene (powder:solvent = 1:3, w / v) at 60° C. for 30 minutes until the polyacrylamide was completely dissolved to form an amide solution.

[0033] An amide solution accounting for 5% by mass of the castor oil polyol was added to the castor oil polyol, and the mixture was stirred at 400 rpm for 20 minutes. The mixture was then heated to 70°C and distilled under reduced pressure (vacuum degree <10 mmHg) to remove xylene to obtain a modified castor oil polyol.

[0034] The enhancer is obtained by mixing tocopherol and hydrotalcite in a mass ratio of 8:2; The water-resistant agent is obtained by compounding Span-80 and γ-aminopropyltriethoxysilane, and is specifically prepared by the following method: Span-80 was added to anhydrous ethanol and stirred at 30°C to obtain a solution; γ-aminopropyltriethoxysilane accounting for 10% of the mass of the solution was added and stirred for 2 hours, and the ethanol was removed by vacuum distillation to obtain a solution.

[0035] A method for preparing the above-mentioned bio-based polyurethane coating comprises the following steps: Step 1: reacting vegetable oil polyol, isocyanate and catalyst under nitrogen protection for 2 hours at a reaction temperature of 50°C; Step 2: Add chain extender and cross-linker, and stir at 1000 rpm and 65°C for 2 h; Step 3: gradually add the enhancer to the water-resistant agent at 200 rpm, stir at 30°C for 4 hours to obtain a mixture; then add the mixture after the stirring in step 2 is completed, stir at a low speed at 40°C for 60 minutes, and obtain the coating after standing.

[0036] The enhancer is obtained by mixing tocopherol and hydrotalcite in a ball mill at a rotation speed of 400 rpm for 2 hours.

[0037] Example 2 Bio-based polyurethane coating #2 The difference from Example 1 is that the component ratio is different: 90 parts of modified castor oil polyol, 30 parts of hexamethylene diisocyanate, 3 parts of zinc 2-ethylhexanoate (catalyst), 10 parts of water-resistant agent, 4 parts of trimethylolpropane (cross-linking agent), 5 parts of diaminopropionic acid (chain extender), and 3 parts of reinforcing agent.

[0038] Example 3 Bio-based polyurethane coating #3 The difference from Example 1 is that the component ratio is different: 95 parts of modified castor oil polyol, 30 parts of hexamethylene diisocyanate, 1 part of zinc 2-ethylhexanoate (catalyst), 15 parts of water-resistant agent, 7 parts of trimethylolpropane (cross-linking agent), 3 parts of diaminopropionic acid (chain extender), and 5 parts of reinforcing agent.

[0039] Example 4 Bio-based polyurethane coating #4 The difference from Example 1 is that the enhancer is obtained by mixing tocopherol and hydrotalcite in a mass ratio of 5:2.

[0040] Example 5 Bio-based polyurethane coating #5 The difference from Example 1 is that the vegetable oil polyol is soybean oil polyol.

[0041] Example 6 Bio-based polyurethane coating #6 The difference from Example 1 is that the isocyanate used is isophorone diisocyanate.

[0042] Example 7 Bio-based polyurethane coating #7 The difference from Example 1 is that the hydroxyl value of the vegetable oil polyol is 120 mg KOH / g.

[0043] Comparative Example 1 Polyurethane Coating Comparison #1 The difference from Example 1 is that the modified castor oil polyol is different.

[0044] The modified castor oil polyol is obtained by mixing castor oil polyol with a PAA (polyacrylic acid) aqueous solution accounting for 7% by mass of the castor oil polyol and stirring at high speed.

[0045] Comparative Example 2 Polyurethane Coating Comparison #2 The difference from Example 1 is that unmodified castor oil polyol is used.

[0046] Comparative Example 3 Polyurethane Coating Comparison #3 The difference from Example 1 is that Span-80 is replaced by alkylphenol polyoxyethylene ether.

[0047] Comparative Example 4 Polyurethane Coating Comparison #4 The difference from Example 1 is that Span-80 is not added.

[0048] Comparative Example 5 Polyurethane Coating Comparison #5 The difference from Example 1 is that no tocopherol is added to the enhancer.

[0049] Comparative Example 6 Polyurethane Coating Comparison #6 The difference from Example 1 is that tocopherol is replaced with di(2,2,6,6-tetramethylpiperidinyl) diamate.

[0050] Test Example 1 The polyurethane coatings prepared in the above examples and comparative examples were subjected to performance tests, with the testing standard referring to GB / T19250-2013 "Polyurethane Waterproof Coatings". The results are shown in Table 1 below.

[0051] Table 1 Performance test results

[0052] The data in the table above demonstrate that the polyurethane coatings prepared in the examples of this application exhibit excellent water resistance and mechanical properties, a short open-dry time, and excellent environmental friendliness. They meet national standards and offer significantly improved performance compared to existing technologies. Furthermore, testing conducted in accordance with GB / T 19250-2013 shows that the polyurethane coatings in the examples can achieve a bond strength of 3.5 MPa under standard conditions and over 3.0 MPa on a damp surface.

[0053] Compared to Comparative Examples 1-2, the introduction of amide groups in these examples prevented the aggregation of the long-chain alkyl groups of the vegetable oil polyols through steric hindrance, making the vegetable oil polyols more easily dispersed in the isocyanate and improving the compatibility between the vegetable oil polyols and the isocyanate. The introduced amide groups also formed weak hydrogen bonds with the isocyanate groups, further promoting the mixing uniformity of the vegetable oil polyols and the isocyanate. However, in Comparative Example 1, the polarity of the carboxyl groups in the polyacrylic acid was too strong, which did not match the polarity of the aliphatic isocyanate. This resulted in an inability to improve the compatibility between the vegetable oil polyols and the isocyanate, resulting in poor performance of the resulting coating.

[0054] In Comparative Examples 3-4, the compatibility between the alkylphenol polyoxyethylene ether and the polyurethane molecular chain may be very general, and the uneven dispersion will reduce the overall density of the coating film, resulting in relatively poor performance of the product such as water resistance.

[0055] Compared with Comparative Examples 5-6, the water resistance and other properties of the examples of the present application are significantly improved; this may be because tocopherol has relatively strong hydrophobicity, and the hydrophobic chains in tocopherol and Span-80 can aggregate and entangle to form a hydrophobic layer located on the outside, and the hydrophilic end of Span-80 is wrapped by the reinforcing agent and is not exposed to water; the compatibility between the hydrophobic layer and the polyurethane matrix is ​​good, which can further improve the water resistance of the coating.

[0056] In addition, the temperature and time ranges of each process in the preparation method of the present application are parameters with relatively good performance effects explored during multiple experiments of the present application.

[0057] The foregoing is merely an embodiment of the present application, and the scope of protection of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc. made within the technical ideas and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A bio-based polyurethane coating, characterized in that: The invention comprises the following components in parts by weight: 90-100 parts of modified vegetable oil polyol, 30-50 parts of isocyanate, 0.5-3 parts of catalyst, 10-20 parts of water-resistant agent, 3-7 parts of cross-linking agent, 2-5 parts of chain extender, and 3-7 parts of reinforcing agent; The modified vegetable oil polyol is obtained by mixing vegetable oil polyol with an amide solution; the enhancer is obtained by compounding tocopherol and hydrotalcite; The water-resistant agent is obtained by compounding Span-80 and gamma-aminopropyltriethoxysilane.

2. The bio-based polyurethane coating according to claim 1, characterized in that The water-resistant agent is prepared by the following method: Span-80 is added to anhydrous ethanol and stirred at 30-40° C. to obtain a dissolving solution; γ-aminopropyltriethoxysilane accounting for 10-20% of the mass of the dissolving solution is added and stirred for 1-2 hours, and the ethanol is removed by vacuum distillation to obtain a solution.

3. The bio-based polyurethane coating according to claim 1, characterized in that The amide group-containing compound in the amide group solution includes polyacrylamide and N,N-dimethylformamide.

4. The bio-based polyurethane coating according to claim 1, characterized in that The enhancer is obtained by compounding tocopherol and hydrotalcite in a mass ratio of (5-8):

2.

5. The bio-based polyurethane coating according to claim 1, characterized in that The hydroxyl value of the vegetable oil polyol is greater than 150 mg KOH / g.

6. The bio-based polyurethane coating according to claim 1, characterized in that The catalyst includes zinc catalyst, bismuth catalyst and zirconium catalyst; zinc catalyst includes zinc 2-ethylhexanoate and zinc naphthenate; the bismuth catalyst includes bismuth neodecanoate and bismuth 2-ethylhexanoate.

7. The bio-based polyurethane coating according to claim 1, characterized in that The chain extender includes diaminopropionic acid and 1,3-propylene glycol; the cross-linking agent is selected from at least one of trimethylolpropane, pentaerythritol, and 4,4'-diaminodicyclohexylmethane.

8. The bio-based polyurethane coating according to claim 1, characterized in that The isocyanate is selected from aliphatic isocyanate, alicyclic isocyanate, and amino acid-derived isocyanate; the vegetable oil polyol includes castor oil-based polyol and high-epoxidized soybean oil polyol.

9. A method for preparing a bio-based polyurethane coating as claimed in claim 1, characterized in that: The steps include: Step 1: reacting vegetable oil polyol, isocyanate and catalyst under nitrogen protection for 1-2 hours at a reaction temperature of 50-65°C; Step 2: Add chain extender and cross-linker, and stir at 1000-1500 rpm and 55-65°C for 1-2 hours; Step 3: gradually add the enhancer to the water-resistant agent at 200-600 rpm, stir at 25-45°C for 2-4 hours to obtain a mixture; then add the mixture after the stirring in step 2 is completed, stir at a low speed at 25-40°C for 30-60 minutes, and obtain the coating after standing.

10. The preparation method according to claim 9, characterized in that The enhancer is obtained by mixing tocopherol and hydrotalcite in a ball mill at a rotation speed of 200-400 rpm for 1-2 hours.

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