Biuret polyisocyanate compositions and methods for making same

Abstract

The application discloses a biuret polyisocyanate and a preparation method thereof, wherein the polyisocyanate has the following characteristics: 1) containing five biuret and seven biuret structures; 2) the content of the five biuret structure in the polyisocyanate is 15-25 wt%, preferably 18-23 wt%; 3) the content of the seven biuret structure in the polyisocyanate is 8-17 wt%, preferably 9-14 wt%; 4) the mass fraction ratio of the five biuret to the seven biuret is 0.9-3.1, preferably 1.3-2.5. By controlling the content and mass percentage of the five biuret and seven biuret structures in the biuret polyisocyanate to a certain level, the viscosity stability of the product is excellent. The biuret polyisocyanate obtained by the method has a viscosity growth rate of less than 20% after being stored for 12 months at 25 DEG C.

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 are widely used in numerous fields such as automotive, shipbuilding, construction machinery, rail transportation, furniture, construction, and aerospace due to their excellent chemical resistance, good impact and abrasion resistance, flexible curing conditions, strong adhesion, and good high and low temperature resistance. Aliphatic or alicyclic biuret polyisocyanates, as one of the main raw materials for polyurethane coatings, are used in combination with alkyd resins, acrylic resins, polyester resins, and amino resins. During application, the isocyanate groups in the polyisocyanate react with the hydroxyl groups in the resin to obtain the polyurethane structure, playing a crucial role in the preparation and use of coatings.

[0003] There are many methods for preparing aliphatic or alicyclic biuret polyisocyanates, mainly involving the reaction of diisocyanates or polyisocyanate monomers with biuretizing agents (water, amines, alcohols, etc.). Reported methods are categorized by the biuretizing agent, primarily into aqueous and amine methods. The aqueous method involves reacting the polyisocyanate monomer with excess water or a water donor to form urea, which is then reacted with excess polyisocyanate to form biuret. Patent CN107057012A uses water vapor as the biuretizing agent to prepare biuret polyisocyanates, while patent CN102321231B uses a mixture of crystalline hydrates, acetone, and water as the biuretizing agent. The amine method directly reacts the polyisocyanate with an amine to form urea, which is then reacted with excess polyisocyanate to form biuret. Patent US4837359A records the use of diamines with a molecular weight less than 300 as biuretizing agents.

[0004] The alicyclic or aliphatic biuret polyisocyanates prepared by the above methods all contain hydrogen bonds in their molecular structure, resulting in high viscosity of the final product. During long-term storage, the viscosity gradually increases, especially when stored above room temperature, severely impacting downstream applications. Downstream coating customers using biuret polyisocyanates as curing agents often cannot use them immediately and frequently require storage for a period before use. While extensive research has been conducted on the storage stability of biuret polyisocyanates, it has primarily focused on monomer stability.

[0005] Patent EP1831280B1 discloses a method for preparing colorless polyisocyanates containing biuret groups and which are stable in storage using water and / or water vapor as biuretizing agents. The product exhibits good monomer stability during long-term storage. After 6 months of storage at room temperature, the free HDI monomer content remains essentially unchanged, and after 6 months of storage at 50°C, the free HDI increases by less than 0.2 wt%. However, this patent method does not mention viscosity stability.

[0006] Publication patent EP 0716080A1 records the reaction of finely dispersed water with aliphatic and / or cycloaliphatic diisocyanates using an OH-acidic compound as a catalyst to obtain a polyisocyanate containing biuret. After the product is stored at 50°C for 42 days, the free HDI monomer growth is <0.2wt%.

[0007] Patent CN105601565B discloses a method for preparing biuret-containing polyisocyanates using polyisocyanates and water in the presence of substituted 8-aminomethylquinoline compounds and hydrazine derivatives. The product initially has a color number below 20 Hazen, and under the synergistic effect of substituted 8-aminomethylquinoline compounds and hydrazine hydrocarbon derivatives, the free HDI content increases by less than 0.1 wt% after 6 months of storage. However, this method does not mention the viscosity stability of the biuret polyisocyanate composition during storage.

[0008] Existing technologies mention how to prepare polyisocyanate compositions with good monomer stability, but there is no discussion on the viscosity stability of biuret polyisocyanate compositions, nor is there any mention of the viscosity stability of biuret polyisocyanate compositions during use after long-term storage.

[0009] Biuret polyisocyanate compositions struggle to maintain viscosity stability during long-term storage, exhibiting a gradual increase in viscosity that hinders their downstream applications. Therefore, a biuret polyisocyanate composition with superior viscosity stability remains urgently needed. Summary of the Invention

[0010] The purpose of this invention is to provide a biuret polyisocyanate composition with excellent viscosity stability, wherein the viscosity increase rate is <20% after storage at 25°C for 12 months.

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

[0012] A biuret polyisocyanate composition comprising pentauret and heptauret structures; wherein the content of the pentauret structure in the composition is 15-25 wt%, preferably 18-23 wt%; the content of the heptauret structure in the composition is 8-17 wt%, preferably 9-14 wt%; and the mass fraction ratio of pentauret to heptauret is 0.9-3.1, preferably 1.3-2.5.

[0013] The viscosity increase rate of the biuret polyisocyanate composition is <20% after storage at 25°C for 12 months.

[0014] In addition to the pentaurea and heptaurea structures mentioned above, as is known to those skilled in the art, the polyisocyanates containing biuret structures also include high-biuret, triuret, and ureidone structures generated by the reaction of diisocyanates with biuretizing agents such as water.

[0015]

[0016] Further, the content of the high urea is 20-40 wt%, preferably 25-38 wt%, the content of the diureta is 2-4 wt%, preferably 2.5-3.5 wt%, and the content of the triureta is 30-40 wt%, preferably 35-38 wt%.

[0017] In another aspect, the present invention also provides a method for preparing the aforementioned biuret polyisocyanate composition, the method comprising the following steps:

[0018] S1: The biuretizing agent is added at a constant rate to the preheated aliphatic or alicyclic diisocyanate monomer. Catalyst 1 is used to make the two react. The molar ratio n(diisocyanate):n(biuretizing agent) = (3.5-15):1, preferably (5-10):1, is controlled to obtain reaction solution A.

[0019] S2: Add catalyst 2 to reaction solution A, stop adding biuretizing reagent and increase temperature to continue reaction to obtain final reaction solution;

[0020] S3: The alicyclic or aliphatic diisocyanate monomers in the reaction solution are removed by secondary thin-film evaporation to obtain the final product.

[0021] In this invention, the diisocyanate mentioned in S1 is one or more diisocyanates containing 4-20 carbon atoms in addition to the NCO group on the carbon chain, preferably isophorone diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexyl diisocyanate, norbornene diisocyanate, trimethyl-1,6-hexamethylene diisocyanate, tetramethyl-m-phenylenediamine diisocyanate, lysine diisocyanate, cyclohexane One or more of the following diisocyanates: dimethylene diisocyanate, phenyl diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, and terephthalene diisocyanate; more preferably, one or more of the following diisocyanates: pentamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and 1,4-cyclohexane diisocyanate; even more preferably, pentamethylene diisocyanate and / or hexamethylene diisocyanate; and most preferably, hexamethylene diisocyanate.

[0022] In this invention, the biuretizing agent in S1 is one or more of water vapor, crystalline hydrate, and liquid water, preferably water vapor.

[0023] In this invention, catalyst 1 in S1 is one or more of monoalkyl phosphate, dialkyl phosphate, monoaryl phosphate, and diaryl phosphate; the total amount of catalyst 1 is 500-5000 ppm of the mass of diisocyanate monomer, preferably 1000-3000 ppm.

[0024] In this invention, the catalyst 2 in S2 is one or more of triethylamine, triethylenediamine, and N-methylmorpholine; the total amount of catalyst 2 is 500-5000 ppm of the mass of the diisocyanate monomer, preferably 1000-3000 ppm.

[0025] In this invention, the reaction temperature of S1 is controlled at 80-220℃, preferably 100-200℃; the reaction temperature of S2 is controlled at 100-240℃, preferably 120-220℃.

[0026] In this invention, the reaction time of S1 is controlled to be 1-4 hours, preferably 1.5-3 hours; the reaction time of S2 is controlled to be 0.5-2 hours, preferably 1-1.5 hours.

[0027] In this invention, the separation conditions for the two-stage thin-film evaporation in S3 are as follows: the separation temperature of the first-stage thin-film evaporator is controlled at 95-220℃ and the absolute separation pressure is controlled at 1-500Pa; the separation temperature of the second-stage thin-film evaporator is controlled at 120-240℃ and the absolute separation pressure is controlled at 1-400Pa.

[0028] In this invention, the thin-film evaporator is a roller-type scraped film system thin-film evaporator or a scraper-type scraped film system thin-film evaporator.

[0029] Through in-depth research, the inventors surprisingly discovered that by controlling the content and mass percentage of pentaurene and heptaurene structures in biuret polyisocyanates to a certain level, the product exhibits excellent viscosity stability. The biuret polyisocyanate composition obtained using the method of this invention shows a viscosity increase of <20% after storage at 25°C for 12 months. Detailed Implementation

[0030] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0031] Main raw material information:

[0032] Hexamethylene diisocyanate, Wannate HDI, Wanhua Chemical, 99%

[0033] Isophorone diisocyanate, Wannate IPDI, Wanhua Chemical, 99%

[0034] dibutyl phosphate, Sigma-Aldrich, 99%

[0035] Diisooctyl phosphate, Sigma-Aldrich, 98%

[0036] Diphenyl phosphate, Aladdin reagent, 98%

[0037] Triethylamine, Sigma-Aldrich, 99%

[0038] Triethylenediamine, Sigma-Aldrich, 99.5%

[0039] In the embodiments of the present invention, the mass percentage of each component in biuret polyisocyanate was obtained by gel chromatography (MZ-Gel SDplus10E3A 5μm column, 35℃, tetrahydrofuran mobile phase, flow rate: 1.0mL / min, analysis time: 40min). The mass percentages of urea diketone, triuret, pentauret, heptauret, and high urea were calculated using "Uret-W", "Tri-W", "Penta-W", "Hepta-W", and "High-W", respectively. Uret-W is the peak area percentage of the second-order eluting peak in gel chromatography, Tri-W is the peak area percentage of the third-order eluting peak in gel chromatography, Penta-W is the peak area percentage of the fourth-order eluting peak in gel chromatography, Hepta-W is the peak area percentage of the fifth-order eluting peak in gel chromatography, and High-W is the sum of the peak area percentages of the peaks after the fifth-order eluting peak in gel chromatography.

[0040] Viscosity determination: The Brookfield RC / S rheometer was used for testing at 25°C.

[0041] Color number determination: The color number of biuret polyisocyanate was tested using a BYK LCS IV colorimeter and the Hazen color standard was used.

[0042] Gas chromatography (DB-1701 30m×0.25mm×0.25μm column, acetonitrile mobile phase, 4μL feed rate, 20:1 split ratio, 240-280℃ test temperature) was used to quantify catalyst 1 in the reaction solution as a monitoring method to determine the reaction endpoint.

[0043] Unless otherwise specified, the reaction system is kept under the protection of a dry inert gas (nitrogen) from before the reaction until the addition of the catalyst and throughout the entire reaction process.

[0044]

Example 1

[0045] 1) Add 1 kg of hexamethylene diisocyanate to the reactor via a peristaltic pump, heat up and start stirring. When the temperature reaches 130°C, add 1.0 g of diisooctyl phosphate via a peristaltic pump and add 38 g of water via a steam generator. Control the reaction time to 120 min.

[0046] 2) Raise the temperature of the reaction system to 150℃, stop adding water, add 1.0g of triethylamine and continue the reaction, controlling the reaction time to 60min, to obtain biuret reaction solution;

[0047] 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 150℃, and the absolute separation pressure is 100 Pa; the second-stage separation temperature is 120℃, and the absolute separation pressure is 50 Pa.

[0048] The prepared polyisocyanate product, after testing, had a viscosity of 7739 cP at 25°C and a color number of 12 Hazen. The contents of urea diketone, triuret, and high-urethane were 2.8 wt%, 36.5 wt%, and 25.3 wt%, respectively. The pentauret content (Penta-W) was 20 wt%, and the heptauret content (Hepta-W) was 15.4 wt%, with a Penta-W / Hepta-W ratio of 1.29. After storage at 25°C for 12 months, the viscosity of the product was 8816 cP, representing a viscosity increase of 13.9%.

[0049]

Examples 2-8

[0050] Polyisocyanates were prepared according to the method in Example 1 and under different operating conditions as shown in Table 1. The viscosity, color number, pentaurea and heptaurea content and mass percentage of the prepared polyisocyanates are shown in Table 1. The viscosity increase is shown in Table 2.

[0051] Comparative Example 1

[0052] Preparation of biuret polyisocyanates:

[0053] 1) Add 1 kg of hexamethylene diisocyanate to the reactor via a peristaltic pump, heat up and start stirring. When the temperature reaches 130°C, add 0.5 g of diisooctyl phosphate via a peristaltic pump and add 30 g of water via a steam generator. Control the reaction time to 120 min.

[0054] 2) Raise the temperature of the reaction system to 220℃, stop adding water, and control the reaction time to 240 min to obtain the biuret reaction solution;

[0055] 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 150℃, and the absolute separation pressure is 100 Pa; the second-stage separation temperature is 120℃, and the absolute separation pressure is 50 Pa.

[0056] The prepared polyisocyanate product, after testing, had a viscosity of 8246 cP at 25°C and a color number of 17 Hazen. The contents of urea diketone, triuret, and high-urethane were 3.1 wt%, 37.2 wt%, and 31 wt%, respectively. The pentauret content (Penta-W) was 13 wt%, and the heptauret content (Hepta-W) was 15.7 wt%, with a Penta-W / Hepta-W ratio of 0.83. After storage at 25°C for 12 months, the viscosity of the product was 13108 cP, representing a viscosity increase of 58.9%.

[0057] Comparative Example 2

[0058] The reaction was carried out according to Example 3, except that catalyst 2 was not added in S2, resulting in the final reaction solution. After separating and removing the free HDI monomer, the product indicators and storage stability were monitored and tested. The test results are shown in Tables 1 and 2.

[0059] Comparative Example 3

[0060] The reaction was carried out according to Example 7, except that catalyst 2 was not added in S2, resulting in the final reaction solution. After separating and removing the free HDI monomer, the product indicators and storage stability were monitored and tested. The test results are shown in Tables 1 and 2.

[0061] Table 1

[0062]

[0063]

[0064] Table 2. Viscosity stability test

[0065]

[0066]

Claims

1. A biuret polyisocyanate composition, said composition comprising pentauret and heptauret structures; wherein the content of the pentauret structure in the composition is 15-25 wt%; the content of the heptauret structure in the composition is 8-17 wt%; and the mass fraction ratio of pentauret to heptauret is 0.9-3.

1.

2. The biuret polyisocyanate composition according to claim 1, characterized in that, The composition contains pentaurene and heptaurene structures; the content of the pentaurene structure in the composition is 18-23 wt%; the content of the heptaurene structure in the composition is 9-14 wt%; and the mass fraction ratio of pentaurene to heptaurene is 1.3-2.

5.

3. The method for preparing the biuret polyisocyanate composition according to claim 1 or 2, characterized in that, The method includes the following steps: S1: Add the biuretizing agent to the preheated aliphatic or alicyclic diisocyanate monomer at a uniform rate, using catalyst 1 to allow the two to react, and control the molar ratio n (diisocyanate):n (biuretizing agent) = (3.5-15):1; S2: Add catalyst 2 to reaction solution A, stop adding biuretizing reagent and increase temperature to continue reaction to obtain final reaction solution; S3: The alicyclic or aliphatic diisocyanate monomers in the reaction solution are removed by secondary thin-film evaporation to obtain the final product.

4. The preparation method according to claim 3, characterized in that, S1 molar ratio n (diisocyanate):n (biuretizing agent) = (5-10):

1.

5. The preparation method according to claim 3, characterized in that, The diisocyanate mentioned in S1 is one or more diisocyanates that contain 4-20 carbon atoms in addition to the NCO group on the carbon chain.

6. The preparation method according to claim 5, characterized in that, The diisocyanate mentioned in S1 is one or more of the following: isophorone diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexyl diisocyanate, norbornene diisocyanate, trimethyl-1,6-hexamethylene diisocyanate, lysine diisocyanate, and cyclohexane dimethylene diisocyanate.

7. The preparation method according to any one of claims 3-6, characterized in that, The biuretizing agent described in S1 is one or more of water vapor, crystalline hydrate, and liquid water.

8. The preparation method according to any one of claims 3-6, characterized in that, The catalyst 1 described in S1 is one or more of monoalkyl phosphate, dialkyl phosphate, monoaryl phosphate, and diaryl phosphate; the total amount of catalyst 1 is 500-5000 ppm of the mass of the diisocyanate monomer.

9. The preparation method according to claim 8, characterized in that, The total amount of catalyst 1 used in S1 is 1000-3000 ppm of the mass of the diisocyanate monomer.

10. The preparation method according to any one of claims 3-6, characterized in that, The catalyst 2 mentioned in S2 is one or more of triethylamine, triethylenediamine, and N-methylmorpholine; the total amount of catalyst 2 is 500-5000 ppm of the mass of the diisocyanate monomer.

11. The preparation method according to claim 10, characterized in that, The total amount of catalyst 2 used in S2 is 1000-3000 ppm of the mass of the diisocyanate monomer.

12. The preparation method according to any one of claims 3-6, characterized in that, The reaction temperature of S1 is controlled at 80-220℃; the reaction temperature of S2 is controlled at 100-240℃.

13. The preparation method according to claim 12, characterized in that, The reaction temperature of S1 is controlled at 100-200℃; the reaction temperature of S2 is controlled at 120-220℃.

14. The preparation method according to any one of claims 3-6, characterized in that, The reaction time of S1 is controlled within 1-4 hours; the reaction time of S2 is controlled within 0.5-2 hours.

15. The preparation method according to claim 14, characterized in that, The reaction time of S1 is controlled within 1.5-3 hours; the reaction time of S2 is controlled within 1-1.5 hours.

16. The preparation method according to any one of claims 3-6, characterized in that, The secondary thin-film evaporation conditions in S3 are as follows: the separation temperature of the first-stage thin-film evaporator is controlled at 95-220℃ and the absolute separation pressure is controlled at 1-500Pa; the separation temperature of the second-stage thin-film evaporator is controlled at 120-240℃ and the absolute separation pressure is controlled at 1-400Pa.

17. The preparation method according to claim 16, characterized in that, The thin-film evaporator is either a roller-type scraped film system thin-film evaporator or a scraper-type scraped film system thin-film evaporator.

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