Isocyanate-containing crystalline thixotropic agent, and synthesis method and application thereof

Abstract

The application discloses a synthesis method of a crystalline thixotropic agent containing isocyanate, which comprises the following steps: S1, mixing isocyanate and linear monohydric alcohol to prepare a mixture; S2, stirring the mixture to prepare a reactant; S3, cooling the reactant to prepare the crystalline thixotropic agent containing isocyanate; wherein in the step S1, the ratio of the molar amount of NCO in the isocyanate to the molar amount of hydroxyl in the linear monohydric alcohol is 1: (0.215-0.95). In addition, the application also provides the thixotropic agent prepared by the above method, and the prepared thixotropic agent can be applied in paints and adhesives. The isocyanate and the linear monohydric alcohol are mixed according to a specific ratio to generate the crystalline thixotropic agent containing isocyanate, and the generated crystalline thixotropic agent containing isocyanate can be well compatible with a polyurethane system, so that the prepared paint or adhesive has good thixotropic performance.

Description

Technical Field

[0001] This application relates to the field of coatings and adhesives, and in particular to an isocyanate-containing crystalline thixotropic agent, its synthesis method, and its application. Background Technology

[0002] Polyurethane possesses good stability, chemical resistance, resilience, and mechanical properties, making it a suitable matrix material for coatings and adhesives. During facade construction and crack repair, coatings and adhesives are prone to flowing due to gravity, leading to uneven film application and incomplete crack filling. Therefore, thixotropic agents need to be added to coatings and adhesives to prevent the material from flowing under gravity, even when unaffected by construction.

[0003] Currently, the most commonly used thixotropic agents in coatings and adhesives include fumed silica, polyamide wax, and hydrogenated castor oil.

[0004] Fumed silica has a high specific surface area and strong interfacial tension, making it highly susceptible to adsorbing moisture. Even when fumed silica undergoes high-temperature dehydration during the preparation of coatings and adhesives, moisture inevitably remains due to its porous structure and uneven heating. Polyurethane contains highly reactive isocyanates, which cause the residual moisture in the fumed silica to cross-link with the isocyanates during storage, leading to gelation and rendering the product unusable.

[0005] Because polyamide wax is a highly polar material, it needs to be activated by adding a certain amount of alcohol solvents. However, the active hydrogen of alcohols readily reacts with isocyanate ions. Furthermore, due to the similarity between the amide bonds in polyamide wax and the polyester bonds in polyurethane, polyamide wax is easily dissolved in polyurethane systems, resulting in poor thixotropic properties of the product.

[0006] Hydrogenated castor oil contains active hydroxyl groups, which react with isocyanates in polyurethane, resulting in poor or even no thixotropic effect in the product.

[0007] Therefore, there is an urgent need for a thixotropic agent that can be used in polyurethane systems to give the resulting coatings or adhesives better thixotropic properties. Summary of the Invention

[0008] In order to solve at least one of the above-mentioned technical problems, and to develop a thixotropic agent applicable to polyurethane systems so that the prepared coatings or adhesives have better thixotropic properties, this application provides an isocyanate-containing crystalline thixotropic agent, its synthesis method and application.

[0009] On the one hand, this application provides a method for synthesizing an isocyanate-containing crystalline thixotropic agent, comprising the following steps: S1. Mix isocyanate and straight-chain monohydric alcohol to obtain a mixture, and stir to obtain the reactant; S2. Cool the reactants obtained in step S1 to obtain the isocyanate-containing crystalline thixotropic agent. In step S1, the molar ratio of NCO in the isocyanate to the molar ratio of hydroxyl groups in the straight-chain monohydric alcohol is 1:(0.215~0.95).

[0010] By adopting the above technical solution, isocyanate and linear monohydric alcohol are mixed in a specific ratio to generate a crystalline thixotropic agent containing isocyanate. The generated crystalline thixotropic agent containing isocyanate is well compatible with polyurethane systems, thereby giving the prepared coatings or adhesives good thixotropic properties. Moreover, the synthesis method of the thixotropic agent provided in this application has mild reaction conditions, fewer reaction steps, and is safe, reliable, and has good process stability, making it suitable for industrial production. In addition, the crystalline thixotropic agent containing isocyanate prepared in this application is also well applicable to epoxy resin systems and polyaspartic acid ester resin systems, giving the obtained coatings or adhesives good thixotropic properties.

[0011] Optionally, in step S1, the isocyanate is selected from HDI trimer and HDI biuret.

[0012] Optionally, in step S1, the straight-chain monohydric alcohol has the following general structural formula: CH3(CH2) n OH, where n is between 11 and 29, and n is an integer.

[0013] Optionally, in step S1, the mixture is heated to 120-130°C while being stirred, and maintained at this temperature for 1.5-2.5 hours to obtain the reactant.

[0014] Optionally, in step S2, the reactants are cooled to 25°C and maintained at this temperature for 6 hours to obtain the isocyanate-containing crystalline thixotropic agent.

[0015] Secondly, this application provides a thixotropic agent prepared using the above-described method for synthesizing isocyanate-containing crystalline thixotropic agents.

[0016] Thirdly, this application provides the application of the above-mentioned isocyanate-containing crystalline thixotropic agent in the fields of coatings and adhesives.

[0017] Optionally, the coating contains 2-12% by mass of isocyanate crystalline thixotropic agent.

[0018] In summary, the present invention has at least one of the following beneficial technical effects: 1. This application mixes isocyanate and linear monohydric alcohol in a specific ratio to generate a crystalline thixotropic agent containing isocyanate. The generated crystalline thixotropic agent containing isocyanate is well compatible with polyurethane systems, thereby enabling the prepared coatings or adhesives to have good thixotropic properties.

[0019] 2. The method for synthesizing isocyanate-containing crystalline thixotropic agents provided in this application has mild reaction conditions, fewer reaction steps, and is safe, reliable, and has good process stability, making it suitable for industrial production.

[0020] 3. The isocyanate-containing crystalline thixotropic agent prepared in this application is also well applicable to epoxy resin systems and polyaspartic acid ester resin systems. The isocyanate-containing crystalline thixotropic agent prepared in this application has a wide range of applications. Detailed Implementation

[0021] The present application will be further described in detail below with reference to the embodiments.

[0022] This application describes a method for synthesizing isocyanate-containing crystalline thixotropic agents, comprising the following steps: S1. Mix isocyanate and straight-chain monohydric alcohol to obtain a mixture; S2. Stir the mixture to obtain the reactant; S3. Cool the reactants to obtain the isocyanate-containing crystalline thixotropic agent; In step S1, the ratio of the molar amount of NCO in the isocyanate to the molar amount of hydroxyl groups in the straight-chain monohydric alcohol is 1:(0.215~0.95).

[0023] The isocyanate-containing crystalline thixotropic agent of this application can be used in the fields of coatings and adhesives.

[0024] Currently, commonly used thixotropic agents in coatings and adhesives include fumed silica, polyamide wax, and hydrogenated castor oil. When these three thixotropic agents are added to polyurethane systems to prepare coatings or adhesives, gelation easily occurs during preparation or storage due to the highly reactive isocyanate groups in polyurethane, resulting in poor thixotropic effects in the final coatings or adhesives. The isocyanate-containing crystalline thixotropic agent prepared in this application is well-compatible with polyurethane and is also suitable for epoxy resin systems and polyaspartic acid ester resin systems. Therefore, the isocyanate-containing crystalline thixotropic agent prepared in this application has a wide range of applications.

[0025] Isocyanates and straight-chain monohydric alcohols are mixed in a specific ratio to generate isocyanate-containing crystalline thixotropic agents. These agents are well-compatible with polyurethane systems, resulting in coatings or adhesives with good thixotropic properties. The synthesis method for the isocyanate-containing crystalline thixotropic agents provided in this application features mild reaction conditions, fewer reaction steps, and is safe, reliable, and exhibits good process stability, making it suitable for industrial production. Specific Implementation

[0026] Example 1 A method for synthesizing a crystalline thixotropic agent containing isocyanate, comprising the following steps: S1. Add HDI trimer and n-dodecanool into a four-necked flask to prepare a mixture; S2. Under stirring conditions at 200 rpm, the mixture is heated to 125°C and maintained at this temperature for 2 hours to obtain the reactant; S3. Cool the reactants to 25°C and maintain this temperature for 6 hours to obtain the isocyanate-containing crystalline thixotropic agent, which is a white crystalline agent. In step S1, the HDI trimer is Wanhua isocyanate HT-100, the molar amount of NCO in the HDI trimer is 1 mol, and the molar amount of the hydroxyl group in the n-dodecanool is 0.6 mol.

[0027] Example 2 A method for synthesizing a crystalline thixotropic agent containing isocyanate, comprising the following steps: S1. Add HDI trimer and n-tetradecanoic acid to a four-necked flask to prepare a mixture; S2. Under stirring conditions at 200 rpm, the mixture is heated to 125°C and maintained at this temperature for 2 hours to obtain the reactant; S3. Cool the reactants to 25°C and maintain this temperature for 6 hours to obtain the isocyanate-containing crystalline thixotropic agent, which is a white crystalline agent. In step S1, the HDI trimer is Wanhua isocyanate HT-100, the molar amount of NCO in the HDI trimer is 1 mol, and the molar amount of the hydroxyl group in the n-tetradecanoic acid is 0.5 mol.

[0028] Example 3 A method for synthesizing a crystalline thixotropic agent containing isocyanate, comprising the following steps: S1. Add HDI trimer and n-hexadecyl alcohol to a four-necked flask to prepare a mixture; S2. Under stirring conditions at 200 rpm, the mixture is heated to 125°C and maintained at this temperature for 2 hours to obtain the reactant; S3. Cool the reactants to 25°C and maintain this temperature for 6 hours to obtain the isocyanate-containing crystalline thixotropic agent, which is a white crystalline agent. In step S1, the HDI trimer is Wanhua isocyanate HT-100, the molar amount of NCO in the HDI trimer is 1 mol, and the molar amount of the hydroxyl group in the n-hexadecyl alcohol is 0.43 mol.

[0029] Example 4 A method for synthesizing a crystalline thixotropic agent containing isocyanate, comprising the following steps: S1. Add HDI trimer and n-octadecyl alcohol to a four-necked flask to prepare a mixture; S2. Under stirring conditions at 200 rpm, the mixture is heated to 125°C and maintained at this temperature for 2 hours to obtain the reactant; S3. Cool the reactants to 25°C and maintain this temperature for 6 hours to obtain the isocyanate-containing crystalline thixotropic agent, which is a white crystalline agent. In step S1, the HDI trimer is Wanhua isocyanate HT-100, the molar amount of NCO in the HDI trimer is 1 mol, and the molar amount of the hydroxyl group in the n-octadecanool is 0.37 mol.

[0030] Example 5 A method for synthesizing a crystalline thixotropic agent containing isocyanate, comprising the following steps: S1. Add HDI trimer and n-eicosanol into a four-necked flask to prepare a mixture; S2. Under stirring conditions at 200 rpm, the mixture is heated to 125°C and maintained at this temperature for 2 hours to obtain the reactant; S3. Cool the reactants to 25°C and maintain this temperature for 6 hours to obtain the isocyanate-containing crystalline thixotropic agent, which is a white crystalline agent. In step S1, the HDI trimer is Wanhua isocyanate HT-100, the molar amount of NCO in the HDI trimer is 1 mol, and the molar amount of the hydroxyl group in the n-eicosanol is 0.33 mol.

[0031] Example 6 A method for synthesizing a crystalline thixotropic agent containing isocyanate, comprising the following steps: S1. Add HDI trimer and n-dodecanoic acid alcohol into a four-necked flask to prepare a mixture; S2. Under stirring conditions at 200 rpm, the mixture is heated to 125°C and maintained at this temperature for 2 hours to obtain the reactant; S3. Cool the reactants to 25°C and maintain this temperature for 6 hours to obtain the isocyanate-containing crystalline thixotropic agent, which is a white crystalline agent. In step S1, the HDI trimer is Wanhua isocyanate HT-100, the molar amount of NCO in the HDI trimer is 1 mol, and the molar amount of the hydroxyl group in the n-dodecanoic acid is 0.3 mol.

[0032] Example 7 A method for synthesizing a crystalline thixotropic agent containing isocyanate, comprising the following steps: S1. Add HDI trimer and n-hexadecanoic acid to a four-necked flask to prepare a mixture; S2. Under stirring conditions at 200 rpm, the mixture is heated to 125°C and maintained at this temperature for 2 hours to obtain the reactant; S3. Cool the reactants to 25°C and maintain this temperature for 6 hours to obtain the isocyanate-containing crystalline thixotropic agent, which is a white crystalline agent. In step S1, the HDI trimer is Wanhua isocyanate HT-100, the molar amount of NCO in the HDI trimer is 1 mol, and the molar amount of the hydroxyl group in the n-hexadecyl alcohol is 0.25 mol.

[0033] Example 8 A method for synthesizing a crystalline thixotropic agent containing isocyanate, comprising the following steps: S1. Add HDI trimer, dibutyltin dilaurate and n-triacontanol into a four-necked flask to prepare a mixture; S2. Under stirring conditions at 200 rpm, the mixture is heated to 125°C and maintained at this temperature for 2 hours to obtain the reactant; S3. Cool the reactants to 25°C and maintain this temperature for 6 hours to obtain the isocyanate-containing crystalline thixotropic agent, which is a white crystalline agent. In step S1, the HDI trimer is Wanhua isocyanate HT-100, the molar amount of NCO in the HDI trimer is 1 mol, the mass fraction of tin in the dibutyltin dilaurate is 0.02%, and the molar amount of hydroxyl groups in the n-trianecanol is 0.215 mol.

[0034] Example 9 A method for synthesizing a crystalline thixotropic agent containing isocyanate, comprising the following steps: S1. Add HDI biuret, dibutyltin dilaurate and n-octadecyl alcohol to a four-necked flask to prepare a mixture; S2. Under stirring conditions at 200 rpm, the mixture is heated to 125°C and maintained at this temperature for 2 hours to obtain the reactant; S3. Cool the reactants to 25°C and maintain this temperature for 6 hours to obtain the isocyanate-containing crystalline thixotropic agent, which is a white crystalline agent. In step S1, the HDI biuret is Asahi Kasei's HDI biuret with model number 24A-100, the molar amount of NCO in the HDI biuret is 1 mol, the mass fraction of tin in the dibutyltin dilaurate is 0.02%, and the molar amount of hydroxyl groups in the n-octadecanool is 0.37 mol.

[0035] Example 10 A method for synthesizing a crystalline thixotropic agent containing isocyanate, comprising the following steps: S1. HDI trimer, dibutyltin dilaurate and n-octadecyl alcohol are added into a four-necked flask to prepare a mixture; S2. Under stirring conditions at 200 rpm, the mixture is heated to 125°C and maintained at this temperature for 2 hours to obtain the reactant; S3. Cool the reactants to 25°C and maintain this temperature for 6 hours to obtain the isocyanate-containing crystalline thixotropic agent, which is a white crystalline agent. In step S1, the HDI trimer is Wanhua isocyanate HT-100, the molar amount of NCO in the HDI trimer is 1 mol, the mass fraction of tin in the dibutyltin dilaurate is 0.02%, and the molar amount of hydroxyl groups in the n-octadecanool is 0.95 mol.

[0036] Example 11 A method for synthesizing a crystalline thixotropic agent containing isocyanate, comprising the following steps: S1. Add HDI trimer, dibutyltin dilaurate and n-triacontanol into a four-necked flask to prepare a mixture; S2. Under stirring conditions at 200 rpm, the mixture is heated to 125°C and maintained at this temperature for 2 hours to obtain the reactant; S3. Cool the reactants to 25°C and maintain this temperature for 6 hours to obtain the isocyanate-containing crystalline thixotropic agent, which is a white crystalline agent. In step S1, the HDI trimer is an isocyanate of Asahi Kasei with the model number TPA-100, the molar amount of NCO in the HDI trimer is 1 mol, the mass fraction of tin in the dibutyltin dilaurate is 0.02%, and the molar amount of hydroxyl groups in the n-trianecanol is 0.95 mol.

[0037] Comparative Example 1 A method for synthesizing a thixotropic agent includes the following steps: S1. Add HDI trimer and n-dodecanool into a four-necked flask to prepare a mixture; S2. Under stirring conditions at 200 rpm, the mixture is heated to 125°C and maintained at this temperature for 2 hours to obtain the reactant; S3. Cool the reactants to 25°C and maintain this temperature for 6 hours to obtain a thixotropic agent, which is a colorless and transparent liquid. In step S1, the HDI trimer is Wanhua isocyanate HT-100, the molar amount of NCO in the HDI trimer is 1 mol, and the molar amount of the hydroxyl group in the n-dodecanool is 0.4 mol.

[0038] Comparative Example 2 A method for synthesizing a thixotropic agent includes the following steps: S1. Add HDI trimer and n-octadecyl alcohol to a four-necked flask to prepare a mixture; S2. Under stirring conditions at 200 rpm, the mixture is heated to 125°C and maintained at this temperature for 2 hours to obtain the reactant; S3. Cool the reactants to 25°C and maintain this temperature for 6 hours to obtain the thixotropic agent, which is a white crystalline substance. In step S1, the HDI trimer is Wanhua isocyanate HT-100, the molar amount of NCO in the HDI trimer is 1 mol, and the molar amount of the hydroxyl group in the n-octadecanool is 0.25 mol.

[0039] Comparative Example 3 A method for synthesizing a thixotropic agent includes the following steps: S1. Add HDI trimer, dibutyltin dilaurate and n-triacontanol into a four-necked flask to prepare a mixture; S2. Under stirring conditions at 200 rpm, the mixture is heated to 125°C and maintained at this temperature for 2 hours to obtain the reactant; S3. Cool the reactants to 25°C and maintain this temperature for 6 hours to obtain the thixotropic agent, which is a white crystalline substance. In step S1, the HDI trimer is Wanhua isocyanate HT-100, the molar amount of NCO in the HDI trimer is 1 mol, the mass fraction of tin in the dibutyltin dilaurate is 0.02%, and the molar amount of hydroxyl groups in the n-trianecanol is 0.15 mol.

[0040] Comparative Example 4 A method for synthesizing a thixotropic agent includes the following steps: S1. Add HDI trimer and n-decanool to a four-necked flask to prepare a mixture; S2. Under stirring conditions at 200 rpm, the mixture is heated to 125°C and maintained at this temperature for 2 hours to obtain the reactant; S3. Cool the reactants to 25°C and maintain this temperature for 6 hours to obtain the thixotropic agent, which is a white crystalline substance. In step S1, the HDI trimer is Wanhua isocyanate HT-100, the molar amount of NCO in the HDI trimer is 1 mol, and the molar amount of the hydroxyl group in the n-decanol is 0.6666 mol.

[0041] Comparative Example 5 A method for synthesizing a thixotropic agent includes the following steps: S1. Add HDI trimer, dibutyltin dilaurate and 2-octyldodecanool to a four-necked flask to prepare a mixture; S2. Under stirring conditions at 200 rpm, the mixture is heated to 125°C and maintained at this temperature for 2 hours to obtain the reactant; S3. Cool the reactants to 25°C and maintain this temperature for 6 hours to obtain the thixotropic agent, which is a colorless and transparent liquid. In step S1, the HDI trimer is Wanhua isocyanate HT-100, the molar amount of NCO in the HDI trimer is 1 mol, the mass fraction of tin in the dibutyltin dilaurate is 0.02%, and the molar amount of hydroxyl groups in the 2-octyldodecanool is 0.7 mol.

[0042] Comparative Example 6 A method for synthesizing a thixotropic agent includes the following steps: S1. Add HDI trimer, dibutyltin dilaurate and n-triacontanol into a four-necked flask to prepare a mixture; S2. Under stirring conditions at 200 rpm, the mixture is heated to 125°C and maintained at this temperature for 2 hours to obtain the reactant; S3. Cool the reactants to 25°C and maintain this temperature for 6 hours to obtain the thixotropic agent, which is a white crystalline substance. In step S1, the HDI trimer is Wanhua isocyanate HT-100, the molar amount of NCO in the HDI trimer is 1 mol, the mass fraction of tin in the dibutyltin dilaurate is 0.02%, and the molar amount of hydroxyl groups in the n-trianecanol is 1 mol.

[0043] The physical appearance and melting point of the thixotropic agents prepared in Examples 1-11 and Comparative Examples 1-6 are shown in Table 1 below.

[0044] Table 1 Example 1 White crystals 64～75 Example 2 White crystals 68～77 Example 3 White crystals 71～81 Example 4 White crystals 73～85 Example 5 White crystals 75～87 Example 6 White crystals 76～90 Example 7 White crystals 79～92 Example 8 White crystals 83～96 Example 9 White crystals 64～75 Example 10 White crystals 115 Example 11 White crystals 122 Comparative Example 1 Colorless and transparent liquid — Comparative Example 2 White crystals 50～55 Comparative Example 3 White crystals 80～85 Comparative Example 4 White crystals 50～60 Comparative Example 5 Colorless and transparent liquid — Comparative Example 6 White crystals 120～132 Note: “—” in the table indicates that there is no fixed melting point.

[0045] The thixotropic agents obtained in Examples 1-11 and Comparative Examples 1-6 were added to polyurethane resin, epoxy resin, and polyaspartic acid ester resin, respectively. After heating to dissolve, the solutions were cooled to 25°C to obtain the corresponding finished products. The results of the finished product states are shown in Table 2 below. The polyurethane resin is Wanhua's HT100, the epoxy resin is Nan Ya's E51, and the polyaspartic acid ester resin is our company's F420. Heating to dissolve means heating to the melting point in Table 1, for example, heating to 75°C in Example 1 and to 77°C in Example 2. The HT100 finished product refers to the finished product obtained by adding the thixotropic agent to the polyurethane resin, heating to dissolve, and then cooling to 25°C. Similarly, the E51 and F420 finished products can be obtained, which will not be described in detail here.

[0046] Table 2 As can be seen from the test results in Tables 1 and 2, the thixotropic agent prepared by reacting HDI trimer or HDI biuret with a straight-chain monohydric alcohol in a specific ratio has good thixotropic properties. The prepared thixotropic agent is suitable for polyurethane systems, as well as epoxy resin systems and polyaspartic acid ester resin systems, and has wide applicability.

[0047] In Examples 1-11, HDI trimer or HDI biuret reacts with a straight-chain monohydric alcohol to obtain an active thixotropic agent containing isocyanate groups. The molar amount of hydroxyl groups required for the preparation of the active thixotropic agent is different for straight-chain monohydric alcohols with different molecular weights. The molar amount of hydroxyl groups required for the preparation of the active thixotropic agent is more for straight-chain monohydric alcohols with smaller molecular weights.

[0048] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for synthesizing a crystalline thixotropic agent containing isocyanate, characterized in that, Includes the following steps: S1. Mix isocyanate and straight-chain monohydric alcohol to obtain a mixture, and stir to obtain the reactant; S2. Cool the reactants obtained in step S1 to obtain the isocyanate-containing crystalline thixotropic agent. In step S1, the molar ratio of NCO in the isocyanate to the molar ratio of hydroxyl groups in the straight-chain monohydric alcohol is 1:(0.215~0.95). In step S1, the isocyanate is selected from HDI trimer and HDI biuret; In step S1, the straight-chain monohydric alcohol has the following general structural formula: CH3(CH2) n OH, where n is 20~29 and n is an integer.

2. The method for synthesizing the isocyanate-containing crystalline thixotropic agent according to claim 1, characterized in that, In step S1, the mixture is heated to 120-130°C while being stirred, and maintained at this temperature for 1.5-2.5 hours to obtain the reactant.

3. The method for synthesizing the isocyanate-containing crystalline thixotropic agent according to claim 1, characterized in that, In step S2, the reactants are cooled to 25°C and maintained at this temperature for 6 hours to obtain the isocyanate-containing crystalline thixotropic agent.

4. An isocyanate-containing crystalline thixotropic agent prepared by the synthesis method of the isocyanate-containing crystalline thixotropic agent according to claim 1.

5. The use of the isocyanate-containing crystalline thixotropic agent according to claim 4 in coatings or adhesives.

6. The application of the isocyanate-containing crystalline thixotropic agent according to claim 5 in coatings, characterized in that, The coating contains 2-12% by mass of isocyanate crystalline thixotropic agent.

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