Preparation method of biuret polyisocyanate composition

Abstract

The invention 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 premixed solution of isocyanate; heating the premixed liquid, adding a biuret reagent, and reacting to obtain a reaction liquid; and removing the diisocyanate monomer in the reaction liquid to obtain a target product. According to the method, the gas escape rate Vg in the reaction process is controlled, so that the dissolution rate Ws of the gaseous biuret reagent is 0.5-20V / V%. The turbidity of the obtained target product is less than 0.5 NTU, and the turbidity is increased by-10%-5% after the target product is stored at room temperature for 15 months.

Description

Technical Field

[0001] The invention belongs to the field of isocyanates, and in particular relates to a biuret polyisocyanate composition and a preparation method thereof. Background Art

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

[0003] Aliphatic or alicyclic polyisocyanates are one of the main raw materials for polyurethane coatings and are used in combination with acrylic resins, polyester resins, alkyd resins, etc. During the film-forming process of the coating, the NCO group in the polyisocyanate reacts and combines with the hydroxyl group in the resin to obtain a polyurethane structure, giving the coating film polyurethane characteristics. Among them, biuret polyisocyanates have good adhesion and flexibility due to the presence of special hydrogen bonds, and have made outstanding contributions in the fields of bridges, ships, engineering machinery, etc.

[0004] There are many methods for preparing aliphatic or alicyclic biuret polyisocyanates, which are generally obtained by reacting diisocyanate or polyisocyanate monomers with biuret reagents (water, amines, alcohols, etc.). The preparation methods recorded in the reported literature are classified according to the biuret reagent, mainly water method and amine method. Publication US3201372 uses water as the biuret reagent; Publication US4837359A records the reaction of diamines with a molecular weight of less than 300 as the biuret reagent.

[0005] In the current industrial production process of biuret polyisocyanate, both methods mentioned above have some obvious problems: 1) When using the water method, the reaction of diisocyanate or polyisocyanate with water will produce 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, blocking the condenser and gas phase pipeline. If the condensate flows back to the reactor, the product will turn white in appearance and have high turbidity. At the same time, it will cause pollution of the reactor and shorten the operation cycle. 2) When using the amine method, a higher reaction temperature and a high-strength reaction mixer are required. After the mixing efficiency decreases, it will cause pollution of the reactor and high turbidity of the product.

[0006] US4028392A discloses the reaction of water and isocyanate in the presence of a hydrophilic organic solvent (such as trialkyl phosphate and ethylene glycol methyl ether acetate). EP0259233A2 discloses the addition of methyl and / or ethyl phosphate and alkoxyalkyl carboxylate as solubilizers when water and isocyanate react. A common disadvantage of these two patents is that the solvent or solvent mixture used in the process makes the final product turbid, and a complex distillation process must be provided to remove the solvent and cause a decrease in separation efficiency.

[0007] CN101072805B discloses a method for preparing a colorless polyisocyanate containing biuret groups and being stable in storage from di- or polyisocyanates using water and / or water vapor as a biuretizing agent. The scheme adopts a water vapor method to solve the problem of water dispersion. However, since cold HDI is used to wash the tail gas, although the loss of HDI is reduced to a certain extent, the polyurea generated by the reaction of HDI with water in the tail gas will still cause blockage of the tail gas pipeline and pollution of the reactor, and will also cause the obtained product to be relatively turbid.

[0008] CN107057012B discloses a method for preparing biuret polyisocyanate, in which water vapor is dispersed near the insertion tube through an ultrasonic pipeline generator of a specific size at a specific stage of the reaction, so that a product with low turbidity can be obtained. However, the ultrasonic pipeline generator will be attached with polyurea substances, which will affect the ultrasonic effect and needs to be cleaned regularly.

[0009] In the current industrial production process, filters are used to filter the intermediates or products of the biuret reaction 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 greater safety risks. Summary of the invention

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

[0011] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

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

[0013] S1: adding a catalyst to isocyanate to obtain a premixed solution of isocyanate;

[0014] S2: After the premixed solution is heated, a biuret reagent is added to react to obtain a reaction solution;

[0015] S3: removing diisocyanate monomers from the reaction solution to obtain the target product;

[0016] Wherein, the gas evolution rate Vg during the reaction is controlled in S2 so that the dissolution rate Ws of the gaseous biuretizing agent is 0.5-20V / V%;

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

[0018] The inventors surprisingly found in their research that by reducing the gas evolution rate Vg during the reaction, the solubility rate of water vapor can be increased, promoting the reaction of water vapor and diisocyanate, making the reaction more complete, reducing the generation of insoluble matter, and thus reducing the turbidity of the final product.

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

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

[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), preferably 1:(5-10). The above-mentioned biuretizing agent is a commonly used agent 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 present invention, the gas evolution rate Vg in S2 is 1-15 V / V%, preferably 1-5 V / V%.

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

[0026] In one embodiment of the present invention, S3 removes the diisocyanate monomers in the reaction solution by an evaporator, preferably by a secondary thin film evaporator. The diisocyanate removal process is a commonly used method in the art, and other diisocyanate removal processes can also be used in the present invention.

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

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

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

[0030] A use of a biuret polyisocyanate composition, wherein the composition is prepared by the above-mentioned preparation method, or is the above-mentioned composition, and the composition is used as a low-turbidity biuret polyisocyanate, preferably for a two-component polyurethane coating, preferably for a large ship coating, a high-speed railway coating, and a cross-sea bridge coating.

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

[0032] By controlling the water vapor dissolution rate Ws during the reaction to 0.5-20V / V%, the turbidity of the final product is less than 0.5NTU, and the turbidity increases by -10% to 5% after storage at room temperature for 15 months. DETAILED DESCRIPTION

[0033] In order to better understand the technical solution of the present invention, the content of the present invention is further described below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments. It can be understood by those skilled in the art that some modifications or adjustments can be made to the present invention under the guidance of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

[0034] In the present invention, the main raw material information used is:

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

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

[0037] Dioctyl phosphate, Aladdin reagent, 98.5%

[0038] Dibutyl phosphate, Aladdin reagent, 98.5%

[0039] Propionic acid, Aladdin reagent, 98.5%

[0040] The calculation formula of gas escape rate Vg is as follows:

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

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

[0043] The calculation formula of water vapor dissolution rate Ws is as follows:

[0044] Ws=V f / V0

[0045] Among them, V f : The volume of the reaction solution when the water vapor is introduced (unit, ML); V0: The volume of the reaction solution before the water vapor is introduced (unit, ML).

[0046] The test method used for the samples obtained in the test example of the present invention is as follows:

[0047] Turbidity determination: 2100N Hach turbidity meter was used for testing, the test condition was 25℃, and the analysis results were retained to the second decimal place.

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

[0049] Color number determination: The color number of biuret polyisocyanate was tested using BYK LCS IV colorimeter and Hazen color scale test.

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

[0051] [Example 1]

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

[0053] 2) After the premixing is completed, the circulating oil bath is turned on to raise the temperature. When the temperature rises to 160°C, 36g of water vapor is added at a uniform rate. The gas emission rate during the reaction is controlled to be 1.2%. The reaction time is 180min to obtain a reaction liquid. According to calculations, the solubility rate of water vapor during the reaction is 19.2%;

[0054] 3) The biuret reaction liquid obtained above is passed through a two-stage scraper-type scraping film system thin film evaporator to remove monomers to obtain the biuret polyisocyanate, wherein the first stage separation temperature is 135° C. and the separation absolute pressure is 80 Pa; the second stage separation temperature is 145° C. and the separation absolute pressure is 10 Pa.

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

[0056] [Example 2]

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

[0058] 2) After the premixing is completed, the circulating oil bath is turned on to raise the temperature. When the temperature rises to 120°C, 18g of water vapor is added at a uniform rate. The gas emission rate during the reaction is controlled to be 3.2%. The reaction time is 130min to obtain a reaction liquid. According to calculations, the solubility rate of water vapor during the reaction is 13.3%;

[0059] 3) The biuret reaction liquid obtained above is passed through a two-stage scraper-type scraping film system thin film evaporator to remove monomers to obtain the biuret polyisocyanate, wherein the first stage separation temperature is 130°C and the separation absolute pressure is 70Pa; the second stage separation temperature is 145°C and the separation absolute pressure is 20Pa.

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

[0061] [Example 3]

[0062] 1) Add 1680 g of hexamethylene diisocyanate and 1.68 g of propionic acid into a pressure flask, start stirring to premix, and stir for 30 min;

[0063] 2) After the premixing is completed, the circulating oil bath is turned on to raise the temperature. When the temperature rises to 200°C, 24g of water vapor is added at a uniform rate. The gas emission rate during the reaction is controlled to be 5.6%. The reaction time is 90 minutes to obtain a reaction liquid. According to calculations, the solubility rate of water vapor during the reaction is 8.7%;

[0064] 3) The biuret reaction liquid obtained above is passed through a two-stage scraper-type scraping film system thin film evaporator to remove monomers to obtain the biuret polyisocyanate. The first stage separation temperature is 155°C and the separation absolute pressure is 85Pa; the second stage separation temperature is 160°C and the separation absolute pressure is 20Pa.

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

[0066] [Example 4]

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

[0068] 2) After the premixing is completed, the circulating oil bath is turned on to raise the temperature. When the temperature rises to 140°C, 12g of water vapor is added at a uniform rate. The gas emission rate during the reaction is controlled to be 9.3%, and the reaction time is 110min to obtain a reaction liquid. According to calculations, the solubility rate of water vapor during the reaction is 4.5%;

[0069] 3) The biuret reaction liquid obtained above is passed through a two-stage scraper-type scraping film system thin film evaporator to remove monomers to obtain the biuret polyisocyanate. The first stage separation temperature is 133° C. and the separation absolute pressure is 78 Pa; the second stage separation temperature is 142° C. and the separation absolute pressure is 16 Pa.

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

[0071] [Example 5]

[0072] 1) Add 2223 g IPDI and 2.22 g dibutyl phosphate into a pressure flask, start stirring to premix, and stir for 30 min;

[0073] 2) After the premixing is completed, the circulating oil bath is turned on to raise the temperature. When the temperature rises to 220°C, 45g of water vapor is added at a uniform rate. The gas emission rate during the reaction is controlled to be 14.1%. The reaction time is 80 minutes to obtain a reaction liquid. According to calculations, the solubility rate of water vapor during the reaction is 2.1%;

[0074] 3) The biuret reaction liquid obtained above is passed through a two-stage scraper-type scraping film system thin film evaporator to remove monomers to obtain the biuret polyisocyanate. The first stage separation temperature is 147°C and the separation absolute pressure is 85Pa; the second stage separation temperature is 152°C and the separation absolute pressure is 20Pa.

[0075] After testing, the viscosity of the prepared polyisocyanate product at 25° C. was 9105 cP, the color number was 10 Hazen, and the turbidity was 0.42 NTU. After being stored at room temperature for 15 months, the turbidity was 0.40 NTU.

[0076] [Comparative Example 1]

[0077] Compared with Example 1, the only difference is that the gas evolution rate during the reaction is controlled to be 31V / V% to carry out the reaction.

[0078] It was calculated that the dissolution rate of water vapor during the reaction was 0.2%;

[0079] The obtained biuret reaction liquid is passed through a two-stage scraper-type scraping film system thin film evaporator to remove monomers to obtain the biuret polyisocyanate, wherein the first stage separation temperature is 135°C and the separation absolute pressure is 80Pa; the second stage separation temperature is 145°C and the separation absolute pressure is 10Pa.

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

[0081] [Comparative Example 2]

[0082] Compared with Example 2, the only difference is that the gas emission rate during the reaction is controlled to be 89V / V% for the reaction. According to calculation, the dissolution rate of water vapor during the reaction is 0.3%;

[0083] The obtained biuret reaction liquid is passed through a two-stage scraper-type scraping film system thin film evaporator to remove monomers to obtain the biuret polyisocyanate, wherein the first stage separation temperature is 130°C and the separation absolute pressure is 70Pa; the second stage separation temperature is 145°C and the separation absolute pressure is 20Pa.

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

[0085] It is easy to understand that the above embodiments are only examples for clear explanation and do not mean that the present invention is limited thereto. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the present invention.

Claims

1. A method for preparing a biuret polyisocyanate composition, characterized in that: The preparation method comprises the following steps: S1: adding a catalyst to isocyanate to obtain a premixed solution of isocyanate; S2: After the premixed solution is heated, a biuret reagent is added to react to obtain a reaction solution; S3: removing diisocyanate monomers from the reaction solution to obtain the target product; Wherein, the gas evolution rate Vg during the reaction is controlled in S2 so that the dissolution rate Ws of the gaseous biuretizing agent is 0.5-20V / V%; Among them, the turbidity of the target product obtained by S3 is less than 0.5NTU, and the turbidity increases by -10% to 5% after storage at room temperature for 15 months.

2. The preparation method according to claim 1, characterized in that: S1 The diisocyanate monomer is a diisocyanate having 4 to 20 carbon atoms in addition to the NCO group on the carbon chain, preferably one or more of 1,4-cyclohexane diisocyanate, methylcyclohexyl diisocyanate, cyclohexane dimethylene diisocyanate, naphthalene diisocyanate, isophorone diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate, more preferably the diisocyanate is one or more of isophorone diisocyanate, 1,4-cyclohexane diisocyanate, pentamethylene diisocyanate, and hexamethylene diisocyanate, most preferably hexamethylene diisocyanate; and / or, the catalyst in S1 is a protonic acid, preferably one or more of monoalkyl phosphate, dialkyl phosphate, monoaryl phosphate, diaryl phosphate, monocarboxylic acid or dicarboxylic acid; Preferably, the catalyst is added in an amount of 500-5000 ppm, preferably 1000-3000 ppm, based on the mass of the diisocyanate monomer; And / or, the premixing time in S1 is 10-30 min.

3. The preparation method according to claim 1, characterized in that: S2 The biuretizing agent is water vapor; Preferably, the molar ratio of the biuretizing agent to the diisocyanate monomer is 1:(4-15), preferably 1:(5-10); and / or, the reaction temperature in S2 is 100-240° C., preferably 110-180° C.; and / or, the gas evolution rate Vg in S2 is 1-15 V / V%, preferably 1-5 V / V%; And / or, the reaction time in S2 is 0.5-5h.

4. The preparation method according to claim 1, characterized in that: S3 removes the diisocyanate monomers in the reaction liquid by an evaporator, preferably by a secondary thin film evaporator.

5. A biuret polyisocyanate composition, which is prepared by the preparation method according to any one of claims 1 to 4, characterized in that: The turbidity of the composition is less than 0.5 NTU, and the turbidity increases by -10 to 5% after being stored at room temperature for 15 months.

6. Use of a biuret polyisocyanate composition, wherein the composition is prepared by the preparation method described in any one of claims 1 to 4, or is the composition described in claim 5, and the composition is used as a low-turbidity biuret polyisocyanate, preferably for two-component polyurethane coatings, and more preferably for large ship coatings, high-speed railway coatings, and cross-sea bridge coatings.