Polyisocyanate composition and preparation method thereof

Abstract

The invention discloses a phosphorus-containing polyisocyanate composition and a preparation method thereof.The phosphorus-containing polyisocyanate composition is prepared by reacting aliphatic or alicyclic diisocyanate under the action of a trimerization catalyst, and in the composition, the total phosphorus content is 1-50 ppm; wherein the ratio of the content of the phosphorus element in the water-phase extracting solution of the polyisocyanate composition to the total content of the phosphorus element in the polyisocyanate composition is 0.05-0.5. The composition can inhibit turbidity even under moisture conditions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of isocyanate, and particularly relates to a method for preparing a polyisocyanate composition with excellent flocculation stability in a solvent from a fatty diisocyanate. BACKGROUND

[0002] Polyurethane resin coatings are known as coatings with excellent wear resistance, chemical resistance, and stain resistance, and in particular, polyurethane resin coatings using non-yellowing polyisocyanates derived from hexamethylene diisocyanate and isophorone diisocyanate have further excellent weather resistance, and thus have been widely used for various purposes for a long time. Isocyanate curing agents are usually diluted with an organic solvent when used, and the dilution ratio is generally less than 40%. Moisture in the solvent and moisture in the air introduced during repeated opening and closing are the main causes of the formation of flocculation during storage.

[0003] Flocculation refers to the formation of solids in a visible form. It ranges from only a small amount of turbidity and fine sediment formed by vortexing around the longitudinal axis of the storage container, to suspended flocculation and severe sedimentation.

[0004] Some of the prior art solves the problem of isocyanate flocculation by adding additional water scavengers, such as the addition of tetraphosphoric acid ester in CN110621712A, the addition of trialkyltin chloride in EP2038746(A1), the addition of bis-trimethylsilylacetamide or hexamethyldisilazane in US2008257214(A1), and the disclosure of imino alcohols and oxazolidines as water scavengers with different advantages in US5 328 635. However, these compounds must be added in stoichiometric amounts, and the decomposition products formed consume NCO groups, affecting downstream applications.

[0005] Another part is to modify various components in the polyisocyanate composition, and control the proportions of specific components such as uretonimine, urethane, uretdione, uretonimine, and imino oxadiazinedione in the polyisocyanate composition, such as controlling the proportions of uretdione, uretonimine, and imino oxadiazinedione in CN106604944A, and controlling the proportions between urea groups, uretonimine, and urethane in CN107189039 A. However, these polyisocyanate compositions all have a large number of modified components and complex processes, and the increase in modified components will adversely affect the physical properties of the composition, such as hardness establishment, chemical resistance, and other application properties, affecting downstream applications. SUMMARY

[0006] The present application aims to provide a polyisocyanate composition with excellent flocculation stability. The inventors of the present application have found that a polyisocyanate composition which can inhibit turbidity even under a humid condition can be obtained by introducing an acidic phosphorus compound into the polyisocyanate composition and controlling the ratio of the phosphorus content in the water phase extract of the polyisocyanate composition to the total phosphorus content in the polyisocyanate composition, thereby completing the present application.

[0007] To achieve the above-mentioned object, the technical solution adopted by the present application is as follows:

[0008] A polyisocyanate composition with excellent flocculation stability has the following characteristics:

[0009] (1) It is prepared by trimerization of one or more diisocyanate monomers selected from aliphatic or alicyclic diisocyanates, wherein the ratio of the phosphorus content in the water phase extract of the polyisocyanate composition to the total phosphorus content in the polyisocyanate composition is (0.05-0.5):1; preferably (0.1-0.4):1.

[0010] (2) The polyisocyanate composition contains one or more combinations of uretdione groups, allophanate groups, carbamate groups, iminooxadiazinedione groups, biuret groups and uretonimine groups.

[0011] (3) The total phosphorus content in the composition is 1-50 ppm based on the total mass of the polyisocyanate composition. If the composition contains a solvent, the mass of the polyisocyanate composition does not include the solvent.

[0012] In the present application, the phosphorus content in the water phase extract of the polyisocyanate composition refers to the phosphorus content measured in the water phase after extraction of the composition with water, which is converted to the phosphorus content extracted from the polyisocyanate composition. The specific test method is as follows:

[0013] Take 10 g of polyisocyanate composition sample, 10 g of dichloromethane and 10 g of deionized water and mix them. After mixing, use a vertical shaker to shake for 5-10 min. After shaking, use a Luxiang instrument high-speed centrifuge at a speed of 10000 rpm for 5-10 min. Take the supernatant and use ICP to analyze the phosphorus content A in the water phase extract of the polyisocyanate composition sample.

[0014] The total phosphorus content (B) in the polyisocyanate composition was obtained using an electron energy dispersive spectroscopy (EDX) analyzer. The researchers discovered that when the phosphorus content in the polyisocyanate composition is 1-50 ppm, and the ratio of phosphorus content in the aqueous extract of the polyisocyanate composition to the total phosphorus content in the polyisocyanate composition (A / B) is 0.05-0.5, the prepared polyisocyanate composition exhibits excellent flocculation stability.

[0015] Furthermore, in the composition, the ratio of phosphorus content in the aqueous extract to total phosphorus content in the polyisocyanate composition is (0.05-0.5):1, preferably (0.1-0.4):1, more preferably 0.1-0.35:1, for example, it can be 0.05:1, 0.12:1, 0.21:1, 0.3:1, 0.35:1, 0.38:1, etc.

[0016] The rheological viscosity of the polyisocyanate composition described in this invention is preferably 400-4000 mPa·s at 25°C, and the rheological viscosity growth rate of the polyisocyanate composition after 15 months of storage at 30°C is ≤10%.

[0017] The method for preparing the polyisocyanate composition described in this invention includes the following steps:

[0018] S1: Using aliphatic or alicyclic diisocyanate as the starting material, a trimerizing catalyst is added at a certain temperature to catalyze the reaction. After the desired conversion rate is achieved, a phosphoric acid-containing compound is added to terminate the reaction, and a reaction solution is obtained.

[0019] S2: The reaction solution obtained in S1 is subjected to low-temperature freezing treatment, and the reaction solution is filtered after low-temperature treatment;

[0020] S3: Remove the unreacted aliphatic or alicyclic diisocyanate monomers to obtain a polyisocyanate composition.

[0021] In the above preparation method, the aliphatic or alicyclic diisocyanate is at least one of tetramethylene-1,4-diisocyanate, pentamethylene-1,5-diisocyanate, hexamethylene-1,6-diisocyanate, lysine diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate, preferably at least one of hexamethylene-1,6-diisocyanate and pentamethylene-1,5-diisocyanate.

[0022] The trimerizing catalyst is one or more of a quaternary ammonium salt and a quaternary ammonium base; wherein, the quaternary ammonium salt and / or quaternary ammonium base is preferably one or more of tetramethylammonium acetate, tetramethylammonium octanoate, 2-hydroxypropyltrimethylisooctanoate ammonium salt, and N,N,N-trimethylbenzylammonium hydroxide.

[0023] The amount of trimerizing catalyst used is 10-400 ppm of the mass of aliphatic diisocyanate;

[0024] Furthermore, technicians can determine the reaction temperature based on different catalysts, with the preferred reaction temperature being 40–100°C, and more preferably 50–80°C.

[0025] The conversion rate is typically 10-50%.

[0026] Preferably, the phosphoric acid compound added in step S1 is one or more of phosphoric acid, dimethyl phosphate, diethyl phosphate, dipropyl phosphate, dibutyl phosphate, dipentyl phosphate, dioctyl phosphate, monobutyl phosphate, and diisooctyl phosphate, with dibutyl phosphate, diisooctyl phosphate, and monobutyl phosphate being the most preferred. The addition amount is 30-300 ppm, based on the mass of diisocyanate.

[0027] Furthermore, to achieve the effects described in this invention, the terminated reaction solution needs to be subjected to low-temperature treatment. The low-temperature treatment temperature is -50 to 10°C, preferably -30 to 0°C; the treatment time is 10-120 min, preferably 30-90 min.

[0028] After the reaction is complete, the unreacted diisocyanate monomers are removed by means of molecular evaporation, distillation, etc. The concentration of unreacted diisocyanate monomers remaining in the obtained polyisocyanate composition can be less than 1% by mass, preferably less than 0.5% by mass, and more preferably less than 0.3% by mass.

[0029] In one specific implementation method, the aqueous extract of the polyisocyanate composition can be obtained as follows: 10g of the polyisocyanate composition sample, 10g of dichloromethane, and 10g of deionized water are mixed. After mixing, the mixture is shaken for 10 minutes using a Hengao HVS-10M vertical shaker. After shaking, it is centrifuged at 10,000 rpm for 10 minutes using a Lu Xiangyi high-speed centrifuge. The supernatant is collected, and the phosphorus content (A) in the aqueous extract of the polyisocyanate composition is analyzed by ICP.

[0030] The polyisocyanate composition further includes one or more of the following structures obtained by trimerization: urethane structure of formula (2), urea carbamate structure of formula (3), urea diketone structure of formula (4), iminooxadiazine diketone structure of formula (5), biuret group structure of formula (6), and urea ketone imine structure of formula (7).

[0031]

[0032]

[0033] Among them, the urea dione structure shown in formula (4) is formed by the thermal reaction of two isocyanate groups, and the iminooxadiazine dione structure shown in formula (5) is formed by a side reaction during the trimerization of diisocyanate.

[0034] The polyisocyanate composition of the present invention can be used as a curing agent in two-component automotive refinish paints, wood coatings, and industrial anti-corrosion applications, and is particularly suitable for applications where solvent dilution is used in high temperature and high humidity environments.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The present invention identifies and controls the key factors affecting the flocculation stability of the composition, and the resulting polyisocyanate composition does not exhibit flocculation stability problems after being diluted and stored for more than 300 days.

[0037] (2) The preparation process of the polyisocyanate composition provided by the present invention is simple and can be applied to various auxiliary agent systems and various isocyanate raw material systems, that is, it has broad spectrum and is easy to industrialize. Detailed Implementation

[0038] 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.

[0039] <Determination of Phosphorus Content in Aqueous Extract>

[0040] Take 10g of the polyisocyanate composition sample, 10g of dichloromethane, and 10g of deionized water and mix them. After mixing, shake the mixture using a Hengao HVS-10M vertical shaker for 10 minutes. After shaking, centrifuge the mixture at 10,000 rpm for 10 minutes using a Lu Xiangyi high-speed centrifuge. Take the supernatant and analyze the phosphorus content (X) in the aqueous extract of the polyisocyanate composition sample using ICP.

[0041] <Determination of Total Phosphorus Content> The total phosphorus content of the products in the examples and comparative examples was determined using an electron energy dispersive spectroscopy (EDX) analyzer to analyze the phosphorus content Y in the polyisocyanate composition samples.

[0042] <Product Viscosity Determination> The viscosity of the products in the examples and comparative examples was measured using a Brookfield RC / S rheometer, rotor model CC-40, in a constant temperature water bath, with the temperature controlled at 25±0.1℃. Shear rate 25S -1 -250S -1 .

[0043] <Determination of Product Color> The color of the products in the examples and comparative examples was measured using a BYK-Gardner GmbH / USA colorimeter.

[0044] <Determination of HDI monomer mass concentration>

[0045] Place a 20 mL sample vial on a digital balance, accurately weigh 1 g of the sample, and add it. Next, accurately weigh 0.04 g of nitrobenzene (internal standard solution) and add it to the sample vial. Finally, add 9 mL of ethyl acetate to the sample vial and cap it. Stir thoroughly to prepare the test sample. Perform colorimetric analysis on the test sample under the following conditions to quantify the amount of HDI monomer.

[0046] Device: Shimadzu Corporation, "GC-8A"

[0047] Pillar: Made by Shin-Ho Chemical Co., Ltd., "Silicone OV-17"

[0048] Column oven temperature: 120℃

[0049] Injection / detector temperature: 160℃.

[0050] <NCO content (%)>

[0051] The NCO content (%) is determined by neutralizing the isocyanate groups in the sample with an excess of 2 mol / L amine, followed by back titration with 1 mol / L hydrochloric acid.

[0052] Generally, commercially available solvents have low water content. Therefore, this test involves adding additional water to the solvent to accelerate flocculation of the diluted sample. In this application example, the flocculation stability of a polyisocyanate composition was tested using n-butyl acetate with a water content of 600 ppm. The water content was measured by Karl-Fischer titration.

[0053] Flocculation Measurement: To measure flocculation, a 30% (w / w) polyisocyanate composition solution was prepared using butyl acetate with a water content of 600 ppm as described above. 60 g of the 30% (w / w) polyisocyanate composition was placed in a 100 ml screw-cap container, purged with nitrogen, and stored tightly sealed at 23°C (ambient humidity 50%). The sample vial was illuminated with a strong flashlight to observe the number of days (d) at which flocculation occurred in the polyisocyanate solution.

[0054] Flocculation score:

[0055] 0: The last day before flocculation was measured, or no flocculation occurred during the entire test;

[0056] 1a: The first day when very slight turbidity or fine sediment was measured and was only visible to the naked eye;

[0057] 1b: The last day on which only very slight turbidity or fine sediment was measured and was only visible to the naked eye;

[0058] 2: The first day when clearly identifiable sediment or flocculent material was measured;

[0059] 3: Initial gelation;

[0060] X: No further measurements were taken.

[0061] <Chemical Raw Material Information>

[0062] HDI: Hexamethylene diisocyanate, Wanhua Chemical Group Co., Ltd.

[0063] PDI: Pentamethylene diisocyanate, Mitsui Chemicals Co., Ltd.

[0064] 2-Hydroxypropyltrimethylisooctanoate ammonium salt, Evonik

[0065] N,N,N-Trimethylbenzylammonium hydroxide, Aladdin reagent

[0066] Phosphoric acid, Aladdin reagent

[0067] diisooctyl phosphate, Aladdin reagent

[0068] Dibutyl phosphate, Aladdin reagent

[0069] The following examples are intended to illustrate the present invention, but the present invention is not limited to these examples.

[0070]

Example 1

[0071] 1000g of HDI was heated to 60°C, and 1g (0.77mmol) of a 20% (w / w) hexanol solution of 2-hydroxypropyltrimethylisooctanoate ammonium salt (purchased from Evonik) was added. When the NCO group content in the reaction solution reached 29.3%, the conversion rate was approximately 40%. The reaction was terminated by adding 0.19g (0.90mmol) of di-n-butyl phosphate. The resulting reaction solution was frozen at -20°C for 60 min and then filtered using a 0.45µm filter to obtain the treated reaction solution. Next, the solution was purified twice using a thin-film evaporator at 160°C and 0.2 Torr to obtain a polyisocyanate composition H1 with an HDI monomer concentration of 0.12%.

[0072] The prepared polyisocyanate composition had a color of 16 Hazen, a viscosity of 2280 mPa·s (25℃), a phosphorus concentration of 15 ppm, a phosphorus concentration of 3.8 ppm in the aqueous extract of the composition, and a P value of 0.25.

[0073]

Example 2

[0074] 1000g of HDI was heated to 60°C, and 2g (3.0mmol) of a 20% (w / w) tetramethylammonium acetate (purchased from Evonik) solution in n-hexanol was added. When the NCO group content in the reaction solution reached 29.3%, the conversion rate was approximately 40%. The reaction was terminated by adding 0.11g (1.1mmol) of phosphoric acid. The resulting reaction solution was frozen at -30°C for 60 min and then filtered using a 0.45µm filter to obtain the treated reaction solution. Next, the solution was purified twice using a thin-film evaporator at 160°C and 0.2 Torr to obtain a polyisocyanate composition H2 with an HDI monomer concentration of 0.12%.

[0075] The prepared polyisocyanate composition had a color of 14 Hazen, a viscosity of 2350 mPa·s (25℃), a phosphorus concentration of 42 ppm, a phosphorus concentration of 6.2 ppm in the aqueous extract of the composition, and a P value of 0.15.

[0076]

Example 3

[0077] 1000g of PDI was heated to 65°C, and 0.6g (0.72mmol) of a 20% trimethylbenzylammonium hydroxide n-butanol solution was added. When the NCO group content in the reaction solution reached 30.3%, 0.18g (0.86mmol) of di-n-butyl phosphate was added to terminate the reaction. The resulting reaction solution was frozen at -20°C for 10 min and then filtered through a 0.45µm filter to obtain the treated reaction solution. Next, the solution was purified twice using a thin-film evaporator at 160°C and 0.2 Torr to obtain a polyisocyanate composition H3 with a PDI monomer concentration of 0.14%.

[0078] The prepared polyisocyanate composition had a color of 13 Hazen, a viscosity of 2354 mPa·s (25℃), a phosphorus concentration of 30 ppm, a phosphorus concentration of 12 ppm in the aqueous extract of the composition, and a P value of 0.40.

[0079]

Example 4

[0080] 1000g of IPDI was preheated to 70℃, and 0.6g (0.72mmol) of a 20% trimethylbenzylammonium hydroxide n-butanol solution was added. When the NCO group content in the reaction solution reached 29.1%, 0.18g (0.86mmol) of di-n-butyl phosphate was added to terminate the reaction. The resulting reaction solution was frozen in a 0℃ refrigerator for 60min, and then filtered through a 0.45µm filter to obtain the treated reaction solution. Next, it was purified twice using a thin-film evaporator at 150℃ and 0.2 Torr, and dissolved in 30% n-butyl acetate (i.e., the dissolved solution contained 30% butyl acetate and 70% curing agent) to obtain a polyisocyanate composition H4 with an IPDI monomer mass concentration of 0.15%.

[0081] The prepared polyisocyanate composition had a color of 21 Hazen and a viscosity of 1354 mPa·s (25℃) after dilution with 30% butyl acetate. Based on the mass of the isocyanate curing agent, the phosphorus concentration in the polyisocyanate composition was 36 ppm, the phosphorus concentration in the aqueous extract of the composition was 16 ppm, and the P value was 0.45.

[0082] Comparative Example 1

[0083] Compared with Example 1, the difference is that the reaction terminator is added without any treatment and separation is carried out directly.

[0084] 1000g of HDI was heated to 60°C, and 1g (0.77mmol) of a 20% (w / w) hexanol solution of 2-hydroxypropyltrimethylisooctanoate ammonium salt (purchased from Evonik) was added. When the NCO group content in the reaction solution reached 29.3%, the reaction conversion was approximately 40%. The reaction was terminated by adding 0.19g (0.90mmol) of di-n-butyl phosphate. Then, the mixture was purified twice using a thin-film evaporator at 160°C and 0.2 Torr to obtain a polyisocyanate composition D1 with an HDI monomer concentration of 0.12%.

[0085] The prepared polyisocyanate composition had a color of 16 Hazen, a viscosity of 2280 mPa·s (25℃), a phosphorus concentration of 45 ppm, a phosphorus concentration of 27 ppm in the aqueous extract of the composition, and a P value of 0.60.

[0086] Comparative Example 2

[0087] The difference compared to Example 3 is the addition of an excessive amount of phosphorus-containing terminator.

[0088] 1000g of PDI was heated to 65°C, and 0.6g (0.72mmol) of a 20% trimethylbenzylammonium hydroxide n-butanol solution was added. When the NCO group content in the reaction solution reached 30.3%, 0.36g (1.71mmol) of di-n-butyl phosphate was added to terminate the reaction. The resulting reaction solution was frozen at -20°C for 10 min and then filtered through a 0.45µm filter to obtain the treated reaction solution. Next, the solution was purified twice using a thin-film evaporator at 160°C and 0.2 Torr to obtain a polyisocyanate composition D2 with a PDI monomer concentration of 0.14%.

[0089] The prepared polyisocyanate composition had a color of 14 Hazen, a viscosity of 2354 mPa·s (25℃), a phosphorus concentration of 85 ppm, a phosphorus concentration of 41 ppm in the aqueous extract of the composition, and a P value of 0.48.

[0090]

Application Example

[0091] Flocculation experiment: The measurement method described above was used, and the experimental results are shown in Table 1.

[0092] Table 1. Results of Flocculation / Sedimentation Experiment

[0093] flocculation H1 H2 H3 H4 D1 D2 0(d) 400 400 345 298 99 131 1a(d) X X 400 367 131 164 1b(d) X X X 400 165 211 2(d) X X X X 242 289

[0094] Comparing the experimental results in the table above, the diluted polyisocyanate compositions in Comparative Examples 1 and 2 showed poorer flocculation stability than other samples, with flocculation occurring after 99 and 131 days of storage, respectively. This indicates that the flocculation stability of the diluted polyisocyanate compositions in Examples 1-4 was significantly improved compared to the compositions in the comparative examples. In particular, when the ratio of phosphorus content in the aqueous extract of the polyisocyanate composition to the total phosphorus content in the polyisocyanate composition was 0.15-0.25:1 (see Examples 1-2), the flocculation stability remained normal after 400 days of storage at room temperature, demonstrating excellent flocculation stability.

[0095] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A polyisocyanate composition, characterized in that, The polyisocyanate composition is prepared by trimerization of one or more diisocyanate monomers selected from aliphatic or alicyclic diisocyanates, wherein the ratio of phosphorus content in the aqueous extract of the composition to total phosphorus content in the polyisocyanate composition is (0.05-0.5):1; preferably (0.1-0.4):

1.

2. The polyisocyanate composition according to claim 1, characterized in that, The polyisocyanate composition contains one or more combinations of ureidone group, ureocarbamate group, carbamate group, iminooxadiazine dione group, biuret group and ureone imine.

3. The composition according to claim 1 or 2, characterized in that, Based on the total mass of the polyisocyanate composition, the total phosphorus content in the composition is 1-50 ppm.

4. The polyisocyanate composition according to any one of claims 1-3, characterized in that, The aliphatic or alicyclic diisocyanate is at least one of tetramethylene-1,4-diisocyanate, pentamethylene-1,5-diisocyanate, hexamethylene-1,6-diisocyanate, lysine diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate.

5. The method for preparing the polyisocyanate composition according to any one of claims 1-4, characterized in that, The method includes the following steps: S1: Using aliphatic or alicyclic diisocyanate as the starting material, a trimerizing catalyst is added at a certain temperature to catalyze the reaction. After the desired conversion rate is achieved, a phosphoric acid-containing compound is added to terminate the reaction, and a reaction solution is obtained. S2: The reaction solution obtained in S1 is subjected to low-temperature freezing treatment, and the reaction solution is filtered after low-temperature treatment; S3: Remove the unreacted aliphatic or alicyclic diisocyanate monomers to obtain a polyisocyanate composition.

6. The preparation method according to claim 5, characterized in that, The trimer catalyst is one or more of quaternary ammonium salts and quaternary ammonium bases; preferably, it is one or more of tetramethylammonium acetate, tetramethylammonium octanoate, 2-hydroxypropyltrimethylisooctanoate ammonium salt, and N,N,N-trimethylbenzylammonium hydroxide. Preferably, the amount of trimerizing catalyst used is 10-400 ppm of the mass of diisocyanate.

7. The preparation method according to claim 5, characterized in that, The reaction temperature of S1 is 40–100℃, preferably 50–80℃; the conversion rate is 10–50%.

8. The preparation method according to claim 5, characterized in that, The phosphoric acid compound S1 is one or more of phosphoric acid, dimethyl phosphate, diethyl phosphate, dipropyl phosphate, dibutyl phosphate, dipentyl phosphate, dioctyl phosphate, monobutyl phosphate, and diisooctyl phosphate, preferably dibutyl phosphate, diisooctyl phosphate, and monobutyl phosphate. Preferably, the amount added is 30-300 ppm by mass of diisocyanate.

9. The preparation method according to claim 5, characterized in that, The S2 reaction solution is subjected to a low-temperature treatment at -50 to 10°C, preferably -30 to 0°C; the treatment time is 10 to 120 min, preferably 30 to 90 min.

10. The preparation method according to claim 5, characterized in that, The concentration of unreacted diisocyanate monomer remaining in the polyisocyanate composition obtained by S3 is less than 1% by mass, preferably less than 0.5% by mass, and more preferably less than 0.3% by mass.

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