A process for the preparation of a biuret polyisocyanate composition

Abstract

The application provides a biuret polyisocyanate composition and a preparation method thereof. The preparation method comprises the following steps: adding a catalyst into isocyanate to obtain a premix solution of isocyanate; after the premix solution is heated, a biuret reagent is added to react, and a reaction solution is obtained; and diisocyanate monomers in the reaction solution are removed to obtain a target product. In the application, the gas escape rate Vg in the reaction process is controlled, so that the dissolution rate Ws of gaseous biuret reagent is 0.5-20V / V%. The turbidity of the target product obtained by the application is less than 0.5NTU, and the turbidity increases by-10%-5% after the target product is stored at room temperature for 15 months.

Description

Technical Field

[0001] This invention belongs to the field of isocyanates, specifically relating to a biuret polyisocyanate composition and its preparation method. Background Technology

[0002] Polyurethane coatings contain a special structure of urethane bonds, which gives them excellent chemical resistance, good impact and abrasion resistance, flexible curing conditions, strong adhesion, and good high and low temperature resistance. As a result, they can be widely used in many fields such as automobiles, ships, engineering machinery, rail transportation, furniture and construction, and aerospace.

[0003] Aliphatic or alicyclic polyisocyanates are one of the main raw materials for polyurethane coatings, used in combination with acrylic resins, polyester resins, alkyd resins, etc. During the film-forming process, the NCO groups in the polyisocyanate react and combine with the hydroxyl groups in the resin to form a polyurethane structure, giving the coating film polyurethane properties. Among them, biuret polyisocyanates, due to the presence of unique hydrogen bonds, give their coatings good adhesion and flexibility, making significant contributions in fields such as bridges, ships, and construction machinery.

[0004] There are many methods for preparing aliphatic or alicyclic biuret polyisocyanates, which generally involve reacting diisocyanate or polyisocyanate monomers with biureting agents (water, amines, alcohols, etc.). The reported preparation methods can be categorized by the biureting agent, mainly into aqueous and amine methods. Patent US3201372 uses water as the biureting agent; patent US4837359A records the use of diamines with a molecular weight less than 300 as the biureting agent.

[0005] In the current industrial production of biuret polyisocyanates, both of the above methods have some obvious problems: 1) When using the water method, the reaction of diisocyanate or polyisocyanate with water during the reaction process will generate a large amount of CO2, which will carry the reaction liquid to the tail gas system. The reaction liquid continues to react to form polyurea products, clogging the condenser and gas phase pipeline. If the condensate flows back to the reactor, it will cause the product to appear white and have high turbidity, and will also cause reactor contamination and shorten the operating cycle. 2) When using the amine method, higher reaction temperatures and high-intensity reaction mixers are required. After the mixing efficiency decreases, reactor contamination and high product turbidity will occur.

[0006] US4028392A discloses the reaction of water with isocyanates in the presence of hydrophilic organic solvents (such as trialkyl phosphates and ethylene glycol methyl ether acetate). EP0259233A2 discloses the addition of methyl and / or ethyl phosphates and alkoxyalkyl carboxylic acids as solubilizers during the reaction of water with isocyanates. A common drawback of these two patents is that the solvents or solvent mixtures used in the process can result in a cloudy final product, and complex distillation processes are required to remove the solvents, leading to reduced separation efficiency.

[0007] CN101072805B discloses a method for preparing colorless polyisocyanates containing biuret groups and which are stable in storage from di- or polyisocyanates using water and / or water vapor as biuretizing agents. This method solves the problem of water dispersion by using water vapor. However, although the loss of HDI is reduced to some extent by using cold HDI to wash the tail gas, the polyurea generated by the reaction of HDI with the moisture in the tail gas will still cause blockage of the tail gas pipeline and contamination of the reaction vessel. At the same time, it will also make the obtained product more turbid.

[0008] CN107057012B discloses a method for preparing biuret polyisocyanate, in which water vapor is dispersed near the insertion tube by an ultrasonic generator of a specific size during a specific stage of the reaction, resulting in a product with low turbidity. However, the ultrasonic generator can become adhered to by polyurea substances, affecting the ultrasonic effect and requiring regular cleaning.

[0009] In current industrial production processes, filters are used to filter biuret reaction intermediates or products to ensure that the turbidity of the final product meets customer requirements. Therefore, the filters need to be cleaned regularly, which undoubtedly increases production costs and brings significant safety risks. Summary of the Invention

[0010] One of the objectives of this invention is to provide a method for preparing a low-turbidity biuret polyisocyanate composition, wherein the composition obtained by this method has low turbidity and the turbidity does not change significantly during storage.

[0011] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0012] A method for preparing a biuret polyisocyanate composition, the method comprising the following steps:

[0013] S1: Adding a catalyst to isocyanate yields a premix of isocyanate;

[0014] S2: After heating the premixed solution, add the biuretizing reagent to react and obtain the reaction solution;

[0015] S3: Remove the diisocyanate monomer from the reaction solution to obtain the target product;

[0016] In S2, the gas escape rate Vg during the reaction is controlled so that the solubility rate Ws of the gaseous biuretizing reagent is 0.5-20V / V%.

[0017] Among them, the turbidity of the target product obtained by S3 is less than 0.5 NTU, and the turbidity increases by -10% to 5% after 15 months of storage at room temperature.

[0018] The inventors made a surprising discovery during their research: by reducing the gas escape rate Vg during the reaction, they could increase the solubility of water vapor, promote the reaction between water vapor and diisocyanate, make the reaction more complete, reduce the production of insoluble substances, and thus reduce the turbidity of the final product.

[0019] In one embodiment of the present invention, the diisocyanate monomer S1 is a diisocyanate containing 4-20 carbon atoms in addition to the NCO group on the carbon chain, preferably one or more of 1,4-cyclohexane diisocyanate, methylcyclohexyl diisocyanate, cyclohexanedimethylene diisocyanate, naphthalene diisocyanate, isophorone diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate, more preferably one or more of isophorone diisocyanate, 1,4-cyclohexane diisocyanate, pentamethylene diisocyanate, and hexamethylene diisocyanate, and most preferably hexamethylene diisocyanate.

[0020] In one embodiment of the present invention, the catalyst in S1 is a protic acid, preferably one or more of monoalkyl phosphate, dialkyl phosphate, monoaryl phosphate, diaryl phosphate, monocarboxylic acid, or dicarboxylic acid; preferably, the amount of catalyst added is 500-5000 ppm of the mass of the diisocyanate monomer, more preferably 1000-3000 ppm.

[0021] In one embodiment of the present invention, the premixing time in S1 is 10-30 min.

[0022] In one embodiment of the present invention, the biuretizing agent in S2 is water vapor; preferably, the molar ratio of the biuretizing agent to the diisocyanate monomer is 1:(4-15), more preferably 1:(5-10). The above-mentioned biuretizing agent is a commonly used reagent in the art, and other biuretizing agents can also be used in the present invention.

[0023] In one embodiment of the present invention, the reaction temperature in S2 is 100-240°C, preferably 110-180°C.

[0024] In one embodiment of the invention, the gas escape rate Vg in S2 is 1-15V / V%, preferably 1-5V / V%.

[0025] In one embodiment of the present invention, the reaction time in S2 is 0.5-5h.

[0026] In one embodiment of the present invention, S3 removes the diisocyanate monomer from the reaction solution via an evaporator, preferably via a two-stage thin-film evaporator. This monomer removal process is a commonly used method in this field; other monomer removal processes can also be used in this invention.

[0027] Another object of the present invention is to provide a biuret polyisocyanate composition.

[0028] A biuret polyisocyanate composition, the composition being prepared by the above-described preparation method, wherein the turbidity of the composition is less than 0.5 NTU, and the turbidity increases by -10 to 5% after 15 months of storage at room temperature.

[0029] Another object of the present invention is to provide the use of a biuret polyisocyanate composition.

[0030] Use of a biuret polyisocyanate composition, wherein the composition is prepared by the above-described preparation method or is the above-described composition, wherein the composition is used as a low-turbidity biuret polyisocyanate, preferably for use in two-component polyurethane coatings, and preferably for use in coatings for large ships, high-speed railways, and cross-sea bridges.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] By controlling the water vapor solubility rate (Ws) during the reaction process to 0.5-20V / V%, the final product has a turbidity of less than 0.5 NTU, and the turbidity increases by -10% to 5% after 15 months of storage at room temperature. Detailed Implementation

[0033] To better understand the technical solution of the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments. Those skilled in the art will understand that, under the guidance of this specification, some modifications or adjustments can be made to the present invention. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

[0034] Information on the main raw materials used in this invention:

[0035] Hexamethylene diisocyanate, Wannate HDI, Wanhua Chemical, 99%

[0036] Isophorone diisocyanate, Wannate IPDI, Wanhua Chemical, 99%

[0037] Diisooctyl phosphate, Aladdin reagent, 98.5%

[0038] Dibutyl phosphate, Aladdin reagent, 98.5%

[0039] Propionic acid, Aladdin reagent, 98.5%

[0040] The formula for calculating the gas escape rate Vg is as follows:

[0041] Vg = V / (ms / Ts)*18 / 22.4

[0042] Where V: gas escape rate during the reaction (unit, L / min); ms: mass of water vapor (unit, g); Ts: time for water vapor to be introduced into the reaction (unit, min).

[0043] The formula for calculating the solubility of water vapor, Ws, is as follows:

[0044] Ws = V f / V0

[0045] Among them, V f V0: Volume of the reaction liquid before the introduction of steam (unit: ml); V0: Volume of the reaction liquid before the introduction of steam (unit: ml).

[0046] The test methods used for the samples obtained in the test examples of this invention are as follows:

[0047] Turbidity determination: The 2100N Hach turbidimeter was used for testing at 25℃. The analytical results were retained to two decimal places.

[0048] Viscosity determination: The Brookfield RC / S rheometer was used for testing at 25°C.

[0049] Color number determination: The color number of biuret polyisocyanate was tested using a BYK LCS IV colorimeter and the Hazen color standard was used.

[0050] Unless otherwise specified, the reaction system is kept under the protection of a dry inert gas (nitrogen) throughout the entire reaction process.

[0051]

Example 1

[0052] 1) Add 1680g hexamethylene diisocyanate and 3.36g diisooctyl phosphate to a pressure-resistant flask, start stirring to premix for 20 minutes;

[0053] 2) After premixing, the circulating oil bath was turned on to raise the temperature to 160℃. Then, 36g of water vapor was added at a uniform rate, controlling the gas escape rate to 1.2% during the reaction. The reaction time was 180min, yielding the reaction solution. The calculated solubility of water vapor during the reaction was 19.2%.

[0054] 3) The biuret reaction solution obtained above is passed through a two-stage scraped film evaporator to remove monomers, thereby obtaining the biuret polyisocyanate. The first-stage separation temperature is 135℃, and the absolute separation pressure is 80 Pa; the second-stage separation temperature is 145℃, and the absolute separation pressure is 10 Pa.

[0055] The prepared polyisocyanate product was tested and found to have a viscosity of 7850 cP at 25°C, a color number of 10 Hazen, and a turbidity of 0.18 NTU. After 15 months of storage at room temperature, the turbidity was 0.17 NTU.

[0056]

Example 2

[0057] 1) Add 1680g hexamethylene diisocyanate and 5.04g dibutyl phosphate to a pressure-resistant flask, start stirring to premix for 30 minutes;

[0058] 2) After premixing, the circulating oil bath was turned on to raise the temperature. When the temperature reached 120℃, 18g of water vapor was added at a uniform rate. The gas escape rate during the reaction was controlled at 3.2%, and the reaction time was 130min to obtain the reaction solution. The calculation showed that the solubility rate of water vapor during the reaction was 13.3%.

[0059] 3) The biuret reaction solution obtained above is passed through a two-stage scraped film evaporator to remove monomers, thereby obtaining the biuret polyisocyanate. The first-stage separation temperature is 130℃, and the absolute separation pressure is 70 Pa; the second-stage separation temperature is 145℃, and the absolute separation pressure is 20 Pa.

[0060] The prepared polyisocyanate product was tested and found to have a viscosity of 7115 cP at 25°C, a color number of 8 Hazen, and a turbidity of 0.26 NTU. After 15 months of storage at room temperature, the turbidity was 0.27 NTU.

[0061]

Example 3

[0062] 1) Add 1680g hexamethylene diisocyanate and 1.68g propionic acid to a pressure-resistant flask, start stirring to premix for 30 minutes;

[0063] 2) After premixing, the circulating oil bath was turned on to raise the temperature to 200℃. 24g of water vapor was then added at a uniform rate, controlling the gas escape rate at 5.6% during the reaction. The reaction time was 90 minutes, yielding the reaction solution. The calculated solubility of water vapor during the reaction was 8.7%.

[0064] 3) The biuret reaction solution obtained above is passed through a two-stage scraped film evaporator to remove monomers, thereby obtaining the biuret polyisocyanate. The first-stage separation temperature is 155℃, and the absolute separation pressure is 85 Pa; the second-stage separation temperature is 160℃, and the absolute separation pressure is 20 Pa.

[0065] The prepared polyisocyanate product was tested and found to have a viscosity of 8120 cP at 25°C, a color number of 11 Hazen, and a turbidity of 0.38 NTU. After 15 months of storage at room temperature, the turbidity was 0.36 NTU.

[0066]

Example 4

[0067] 1) Add 2223g IPDI and 3.36g diisooctyl phosphate to a pressure-resistant flask, start stirring to premix for 30 minutes;

[0068] 2) After premixing, the circulating oil bath was turned on to raise the temperature to 140℃. 12g of water vapor was then added at a uniform rate, controlling the gas escape rate to be 9.3% during the reaction. The reaction time was 110 minutes, yielding the reaction solution. The calculated solubility of water vapor during the reaction was 4.5%.

[0069] 3) The biuret reaction solution obtained above is passed through a two-stage scraped film evaporator to remove monomers, thereby obtaining the biuret polyisocyanate. The first-stage separation temperature is 133℃, and the absolute separation pressure is 78 Pa; the second-stage separation temperature is 142℃, and the absolute separation pressure is 16 Pa.

[0070] The prepared polyisocyanate product was tested and found to have a viscosity of 7635 cP at 25°C, a color number of 15 Hazen, and a turbidity of 0.33 NTU. After 15 months of storage at room temperature, the turbidity was 0.30 NTU.

[0071]

Example 5

[0072] 1) Add 2223g IPDI and 2.22g dibutyl phosphate to a pressure-resistant flask, turn on the stirrer to premix for 30 minutes;

[0073] 2) After premixing, the circulating oil bath was turned on to raise the temperature to 220℃. 45g of water vapor was then added at a uniform rate, controlling the gas escape rate to 14.1% during the reaction. The reaction time was 80 minutes, yielding the reaction solution. The calculated solubility of water vapor during the reaction was 2.1%.

[0074] 3) The biuret reaction solution obtained above is passed through a two-stage scraped film evaporator to remove monomers, thereby obtaining the biuret polyisocyanate. The first-stage separation temperature is 147°C, and the absolute separation pressure is 85 Pa; the second-stage separation temperature is 152°C, and the absolute separation pressure is 20 Pa.

[0075] The prepared polyisocyanate product was tested and found to have a viscosity of 9105 cP at 25°C, a color number of 10 Hazen, and a turbidity of 0.42 NTU. After 15 months of storage at room temperature, the turbidity was 0.40 NTU.

[0076] Comparative Example 1

[0077] Compared with Example 1, the only difference is that the gas escape rate is controlled at 31V / V% during the reaction.

[0078] Calculations show that the solubility of water vapor during the reaction process is 0.2%.

[0079] The biuret reaction solution obtained above was passed through a two-stage scraped film evaporator to remove monomers, yielding the biuret polyisocyanate. The first-stage separation temperature was 135°C, and the absolute separation pressure was 80 Pa; the second-stage separation temperature was 145°C, and the absolute separation pressure was 10 Pa.

[0080] The prepared polyisocyanate product was tested and found to have a viscosity of 8460 cP at 25°C, a color number of 16 Hazen, and a turbidity of 0.82 NTU. After 15 months of storage at room temperature, the turbidity was 0.93 NTU.

[0081] Comparative Example 2

[0082] Compared to Example 2, the only difference was that the gas escape rate was controlled at 89V / V% during the reaction. The calculated solubility of water vapor during the reaction was 0.3%.

[0083] The biuret reaction solution obtained above was passed through a two-stage scraped film evaporator to remove monomers, yielding the biuret polyisocyanate. The first-stage separation temperature was 130°C, and the absolute separation pressure was 70 Pa; the second-stage separation temperature was 145°C, and the absolute separation pressure was 20 Pa.

[0084] The prepared polyisocyanate product was tested and found to have a viscosity of 7996 cP at 25°C, a color number of 22 Hazen, and a turbidity of 0.78 NTU. After 15 months of storage at room temperature, the turbidity was 0.85 NTU.

[0085] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a biuret polyisocyanate composition, characterized in that, The preparation method includes the following steps: S1: Adding a catalyst to isocyanate yields a premix of isocyanate; S2: After heating the premixed solution, add the biuretizing reagent to react and obtain the reaction solution; S3: Remove the diisocyanate monomer from the reaction solution to obtain the target product; Wherein, the biuretizing agent described in S2 is water vapor; In S2, the gas escape rate Vg during the reaction is controlled so that the solubility Ws of the gaseous biuretizing reagent is 0.5-20V / V%. The formula for calculating the gas escape rate Vg is as follows: Vg = V / (ms / Ts) * 18 / 22.4 Where V: gas escape rate during the reaction, in L / min; ms: mass of water vapor, in g; Ts: time for water vapor to be introduced during the reaction, in min; The formula for calculating the solubility Ws is as follows: Ws=V f / V0 Among them, V f V0: Volume of the reaction liquid when water vapor has been completely introduced, in ml; V0: Volume of the reaction liquid before water vapor is introduced, in ml. Among them, the turbidity of the target product obtained by S3 is less than 0.5 NTU, and the turbidity increases by -10% to 5% after 15 months of storage at room temperature.

2. The preparation method according to claim 1, characterized in that, The diisocyanate monomer described in S1 is a diisocyanate containing 4-20 carbon atoms in addition to the NCO group on the carbon chain; And / or, the catalyst described in S1 is a protic acid; And / or, the premixing time in S1 is 10-30 min.

3. The preparation method according to claim 2, characterized in that, The diisocyanate monomer S1 is one or more of 1,4-cyclohexane diisocyanate, methylcyclohexyl diisocyanate, cyclohexane dimethylene diisocyanate, naphthalene diisocyanate, isophorone diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate. And / or, the catalyst described in S1 is one or more of monoalkyl phosphate, dialkyl phosphate, monoaryl phosphate, diaryl phosphate, monocarboxylic acid, or dicarboxylic acid; The catalyst described in S1 is added in an amount of 500-5000 ppm of the mass of the diisocyanate monomer.

4. The preparation method according to claim 3, characterized in that, S1 The diisocyanate monomer is one or more of isophorone diisocyanate, 1,4-cyclohexane diisocyanate, pentamethylene diisocyanate, and hexamethylene diisocyanate; The catalyst mentioned in S1 is added in an amount of 1000-3000 ppm of the mass of the diisocyanate monomer.

5. The preparation method according to claim 4, characterized in that, The diisocyanate monomer in S1 is hexamethylene diisocyanate.

6. The preparation method according to claim 1, characterized in that, The reaction temperature in S2 is 100-240℃; And / or, the gas escape rate Vg in S2 is 1-15V / V%; And / or, the reaction time in S2 is 0.5-5h.

7. The preparation method according to claim 6, characterized in that, The molar ratio of the biuretizing agent to the diisocyanate monomer described in S2 is 1:(4-15). And / or, the reaction temperature in S2 is 110-180℃; And / or, the gas escape rate Vg in S2 is 1-5V / V.

8. The preparation method according to claim 7, characterized in that, The molar ratio of the biuretizing agent to the diisocyanate monomer in S2 is 1:(5-10).

9. The preparation method according to claim 1, characterized in that, S3 removes the diisocyanate monomer from the reaction solution using an evaporator.

10. The preparation method according to claim 9, characterized in that, S3 removes the diisocyanate monomer from the reaction solution through a two-stage thin-film evaporator.

11. A biuret polyisocyanate composition, said composition being prepared by the method according to any one of claims 1-10, characterized in that, The composition has a turbidity of less than 0.5 NTU, and its turbidity increases by -10 to 5% after 15 months of storage at room temperature.

12. Use of a biuret polyisocyanate composition, said composition being prepared by any one of claims 1-10, or being the composition of claim 11, said composition being used as a low-turbidity biuret polyisocyanate.

13. The use according to claim 12, wherein the composition is used in a two-component polyurethane coating.

14. The use according to claim 13, wherein the composition, when used as a two-component polyurethane coating, is used for coatings of large ships, high-speed railways, or cross-sea bridges.