Polyisocyanate curing agent

Abstract

The invention discloses a polyisocyanate curing agent which comprises modified xylylene diisocyanate, and the modified xylylene diisocyanate is prepared by adopting xylylene diisocyanate and an active hydroxyl component to react with each other. The curing agent provided by the invention improves the problem that the blending performance of xylylene diisocyanate polyisocyanate and HDI tripolymer becomes poor, and the coating has good transparency and high hardness.

Description

Technical Field

[0001] The present invention relates to the field of curing agents, and particularly to a polyisocyanate curing agent. Background Art

[0002] Based on the performance of traditional aromatic isocyanates, xylylene diisocyanate (XDI) has better color retention and yellowing resistance, and is widely used in fields such as automotive interiors and outer coatings of electronic devices. As a coating curing agent, xylylene diisocyanate usually reacts with alcohols to form prepolymers for use. The curing agent has a fast reaction rate and high production efficiency, and its products have good hardness and yellowing resistance. However, the supply of XDI on the market is scarce and the price is high, resulting in the need to use a cheaper curing agent together during downstream use, such as hexamethylene diisocyanate (HDI) trimer, to balance costs. However, there are differences in the structures of different isocyanates, and blending will inevitably cause performance defects in the product.

[0003] Patent CN105940030A discloses a preparation method of a curing agent based on xylylene diisocyanate, and its basic application indicators are good. However, when this curing agent is blended with HDI trimer, it will cause a decrease in the hardness and transparency of the coating, affecting the basic performance of the paint film.

[0004] How to prepare a polyisocyanate curing agent with high transparency and high hardness after blending with HDI trimer is of great significance. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a polyisocyanate curing agent, which improves problems such as poor blending performance of xylylene diisocyanate-based polyisocyanates and HDI trimer, and has good coating transparency and high hardness.

[0006] To achieve the purpose of the present invention, the present invention provides the following technical solutions:

[0007] A polyisocyanate curing agent, comprising modified xylylene diisocyanate, wherein the modified xylylene diisocyanate is prepared by reacting xylylene diisocyanate with an active hydroxyl component.

[0008] In the present invention, the active hydroxyl component-containing substance includes water and alcohols, and the alcohol is an alcohol with a molecular weight of 32 to 300, preferably one or more of methanol, ethanol, propanol, butanol, pentanol, hexanol, ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, glycerol, 2-ethyl-2-hydroxymethyl-1,3-propanediol. Preferably, the molar ratio r of water to xylylene diisocyanate is 0.6×10 -2 ≤r≤2.2×10 -2 ;

[0009] Preferably, in the preparation process of the modified xylylene diisocyanate, the ratio R of the molar number of isocyanate groups of xylylene diisocyanate to the molar number of hydroxyl groups of the alcohol satisfies 4.0 ≤ R ≤ 8.0.

[0010] Preferably, the preparation method of the modified xylylene diisocyanate is: reacting xylylene diisocyanate, alcohol and water to prepare the modified xylylene diisocyanate.

[0011] The water includes the water contained in the alcohol. Appropriate water content of the alcohol can be directly obtained during the preparation of the alcohol, or water can be added by an external addition method.

[0012] In the preparation method of the modified xylylene diisocyanate, the reaction temperature is 60 - 90 °C, preferably 65 - 90 °C; the reaction time is 2.5 - 8.0 h, preferably 2.5 - 7.5 h.

[0013] The reaction solution containing the modified xylylene diisocyanate obtained after the reaction is subjected to evaporation separation to obtain the modified xylylene diisocyanate. The reaction solution is evaporated by a thin-film evaporator to separate unreacted xylylene diisocyanate, and the heavy components are collected. The separation parameters are as follows: the separation temperature is 130 - 210 °C, preferably 135 - 195 °C; the separation pressure is 0.1 - 120 Pa, preferably 10 - 100 Pa. It should be noted that the purpose of thin-film evaporation is to reduce the content of xylylene diisocyanate to less than 0.5%, and the selected separation parameters (temperature, pressure) only need to meet this requirement.

[0014] Preferably, the curing agent further includes a solvent;

[0015] Preferably, the modified xylylene diisocyanate and the solvent are mixed to obtain the curing agent;

[0016] Preferably, the mixing temperature of the modified xylylene diisocyanate and the solvent is 30 - 90 °C, and the solid content of the curing agent is 40% - 95%, preferably 50% - 90%. The solvent is selected from one or more of toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, toluene cyclohexanone, cyclohexane, n-hexane, tetrahydrofuran, chlorobenzene, dichlorobenzene, dichloromethane, dichloroethane, 1,3-dioxane, methyl acetate, ethyl acetate, butyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, ethyl propionate, propyl propionate, propyl butyrate, and preferably ethyl acetate.

[0017] Preferably, the polyisocyanate curing agent further includes an HDI trimer;

[0018] Preferably, the mass ratio of the modified benzylidene diisocyanate to the HDI trimer is 1:10 to 10:1, preferably 1:5 to 8:1.

[0019] The HDI trimer described in the present invention has a viscosity of 1500 - 4000 cP at 25°C.

[0020] The HDI trimer described in the present invention can be selected from one or more of HT-100, HT-600, and N3300, preferably HT-100.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] When traditional XDI curing agents are blended with HDI trimers for use, it will lead to a decrease in the transparency and hardness of the coating. After the modified benzylidene diisocyanate described in the present invention is blended with the HDI trimer, the coating is still transparent and has high hardness. The realization of the blendability of the XDI curing agent not only ensures the high performance of the coating from the perspective of downstream customers, but also reduces the comprehensive cost and increases the possibility of more combinations of this curing agent, making it more potential for application.

[0023] In some preferred embodiments of the present invention, after the modified benzylidene diisocyanate and the HDI trimer are blended at a mass ratio of 1:9, the turbidity is 0.58 - 1.78 NTU. Detailed Embodiments

[0024] The following examples will deeply illustrate the method provided by the present invention. However, the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the claims of the present invention. The specific application of the present invention is not limited to the applications mentioned in the examples. Those skilled in the art can make extended modifications to the present invention through the concept of the present invention, and these simple changes are within the protection scope of the present invention.

[0025] The following test methods are adopted in the embodiments of the present invention:

[0026] (1) Test method for turbidity: Use a turbidimeter (model 2100N) from HACH company to test the turbidity value of the sample.

[0027] (2) Test method for the content of free unreacted isocyanate monomer: Adopt the national standard GB / T18446-2009 and test it through an Agilent GC-7890B gas chromatograph of Agilent.

[0028] (3) Test method for viscosity: The dynamic mechanical viscosity is measured using a BrookField DV-IPrime viscometer with an S21 rotor at 25°C.

[0029] (4) Hardness test of the product swing rod: Prepare the original coating solution and test the pendulum hardness of the paint film according to GB / T 1730-2007.

[0030] (5) Transparency of the product: Observe the transparency of the coating visually. If there is turbidity or a foggy feeling, it is considered "unqualified".

[0031] In the following examples, the raw material information used is as follows:

[0032] HT-100: Wanhua Chemical, purity > 99%;

[0033] N3300: Covestro, purity > 99%;

[0034] Xylylene diisocyanate (XDI): Wanhua Chemical, purity > 99%;

[0035] 2-Ethyl-2-(hydroxymethyl)-1,3-propanediol: Jiangxi Gaoxin, purity > 99%;

[0036] Polyol: ACR7502, Tongde Chemical Industry, purity > 99%;

[0037] Ethyl acetate: Ruisheng Chemical Industry, purity > 99%;

[0038] Butyl acetate: Aladdin Reagent, purity > 99%;

[0039] Glycerol: Macklin Reagent, purity > 99%;

[0040] 1,3-Butanediol: Aladdin Reagent, purity > 99%;

[0041] Isobutanol: Macklin Reagent, purity > 99%;

[0042] If there is no special instruction for other raw materials and reagents, they can all be obtained through commercial channels.

[0043] The reaction, separation, and dilution processes of the following examples and comparative examples are all carried out in an environment with sufficient dry nitrogen.

[0044]

Example 1

[0045] Weigh 2500 g of xylylene diisocyanate and add it to a round-bottom flask. Heat it to 80 °C. Then weigh 237.66 g of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol and 2.46 g of water. After stirring and mixing at 25 °C for 1 h, add it to the flask and keep reacting at 80 °C for 3 h to obtain an NCO-terminated prepolymer reaction solution. Separate the isocyanate monomer in the reaction solution through a thin-film evaporator. The separation conditions are as follows: separation temperature 170 °C, separation pressure 20 Pa. Then, collect the heavy components and mix and dilute them with ethyl acetate to a solid content of 75%. After stirring and mixing evenly, a polyisocyanate curing agent is obtained.

[0046]

Example 2

[0047] Weigh 2500 g of xylylene diisocyanate and add it to a round-bottom flask. Heat it to 85 °C. Then weigh 237.66 g of 2-ethyl-2-hydroxymethyl-1,3-propanediol and 1.48 g of water. After stirring and mixing at 25 °C for 1 h, add them to the flask and keep reacting at 85 °C for 4 h to obtain an NCO-terminated prepolymer reaction solution. Separate the isocyanate monomer in the reaction solution through a thin-film evaporator. The separation conditions are as follows: separation temperature 195 °C, separation pressure 95 Pa. Then, collect the heavy components and mix them with ethyl acetate and dilute to a solid content of 75%. After stirring and mixing evenly, a polyisocyanate curing agent is obtained.

[0048]

Example 3

[0049] Weigh 2500 g of xylylene diisocyanate and add it to a round-bottom flask. Heat it to 80 °C. Then weigh 163.12 g of glycerol and 2.01 g of water. After stirring and mixing at 25 °C for 1 h, add them to the flask and keep reacting at 80 °C for 4 h to obtain an NCO-terminated prepolymer reaction solution. Separate the isocyanate monomer in the reaction solution through a thin-film evaporator. The separation conditions are as follows: separation temperature 165 °C, separation pressure 25 Pa. Then, collect the heavy components and mix them with ethyl acetate and dilute to a solid content of 75%. After stirring and mixing evenly, a polyisocyanate curing agent is obtained.

[0050]

Example 4

[0051] Weigh 2500 g of xylylene diisocyanate and add it to a round-bottom flask. Heat it to 60 °C. Then weigh 116.50 g of 2-ethyl-2-hydroxymethyl-1,3-propanediol, 123.94 g of glycerol and 2.87 g of water. After stirring and mixing at 25 °C for 1 h, add them to the flask and keep reacting at 60 °C for 8 h to obtain an NCO-terminated prepolymer reaction solution. Separate the isocyanate monomer in the reaction solution through a thin-film evaporator. The separation conditions are as follows: separation temperature 135 °C, separation pressure 10 Pa. Then, collect the heavy components and mix them with ethyl acetate and dilute to a solid content of 75%. After stirring and mixing evenly, a polyisocyanate curing agent is obtained.

[0052]

Example 5

[0053] Weigh 2500 g of xylylene diisocyanate and add it to a round-bottom flask. Heat it to 65 °C. Then weigh 239.45 g of 1,3-butanediol and 3.25 g of water. After stirring and mixing at 25 °C for 1 h, add them to the flask and keep reacting at 65 °C for 5 h to obtain a terminal NCO prepolymer reaction solution. Separate the isocyanate monomer in the reaction solution through a thin-film evaporator. The separation conditions are as follows: separation temperature 180 °C, separation pressure 30 Pa. Then, collect the heavy components and mix them with ethyl acetate and dilute to a solid content of 75%. After stirring and mixing evenly, a polyisocyanate curing agent is obtained.

[0054]

Example 6

[0055] Weigh 2500 g of xylylene diisocyanate and add it to a round-bottom flask. Heat it to 90 °C. Then weigh 85.45 g of glycerol, 75.02 g of isobutanol and 4.14 g of water. After stirring and mixing at 25 °C for 1 h, add them to the flask and keep reacting at 90 °C for 2.5 h to obtain a terminal NCO prepolymer reaction solution. Separate the isocyanate monomer in the reaction solution through a thin-film evaporator. The separation conditions are as follows: separation temperature 175 °C, separation pressure 50 Pa. Then, collect the heavy components and mix them with ethyl acetate and dilute to a solid content of 75%. After stirring and mixing evenly, a polyisocyanate curing agent is obtained.

[0056]

Example 7

[0057] Weigh 2500 g of xylylene diisocyanate and add it to a round-bottom flask. Heat it to 90 °C. Then weigh 108.03 g of 2-ethyl-2-hydroxymethyl-1,3-propanediol, 67.14 g of isobutanol and 5.26 g of water. After stirring and mixing at 25 °C for 1 h, add them to the flask and keep reacting at 90 °C for 7.5 h to obtain a terminal NCO prepolymer reaction solution. Separate the isocyanate monomer in the reaction solution through a thin-film evaporator. The separation conditions are as follows: separation temperature 165 °C, separation pressure 45 Pa. Then, collect the heavy components and mix them with ethyl acetate and dilute to a solid content of 75%. After stirring and mixing evenly, a polyisocyanate curing agent is obtained.

[0058]

Comparative Example 1

[0059] Weigh 2500 g of xylylene diisocyanate and add it to a round-bottom flask. Heat it to 80 °C. Then weigh 237.66 g of 2-ethyl-2-hydroxymethyl-1,3-propanediol and 1.10 g of water. After stirring and mixing at 25 °C for 1 h, add them to the flask and keep reacting at 80 °C for 3 h to obtain a terminal NCO prepolymer reaction solution. Separate the isocyanate monomer in the reaction solution through a thin-film evaporator. The separation conditions are as follows: separation temperature 170 °C, separation pressure 20 Pa. Then, collect the heavy components and mix them with ethyl acetate and dilute to a solid content of 75%. After stirring and mixing evenly, a polyisocyanate curing agent is obtained.

[0060]

Comparative Example 2

[0061] Weigh 2500 g of xylylene diisocyanate and add it to a round-bottom flask. Heat it to 80 °C. Then weigh 237.66 g of 2-ethyl-2-hydroxymethyl-1,3-propanediol and 7.41 g of water. After stirring and mixing at 25 °C for 1 h, add them into the flask and keep reacting at 80 °C for 3 h to obtain a terminal NCO prepolymer reaction solution. Separate the isocyanate monomer in the reaction solution through a thin-film evaporator. The separation conditions are as follows: separation temperature 170 °C, separation pressure 20 Pa. Then, collect the heavy components and mix them with ethyl acetate and dilute to a solid content of 75%. After stirring and mixing evenly, a polyisocyanate curing agent is obtained.

[0062] Mix the modified xylylene diisocyanate obtained in the examples and comparative examples with HDI trimer at a mass ratio of 1:9, and test the turbidity of the mixture. The results are shown in Table 1.

[0063] Coating stock solution preparation method: Mix the prepared modified xylylene diisocyanate with HDI trimer at a mass ratio of 3:7 to obtain a polyisocyanate composition. Mix the acrylic polyol (ACR7502, Tongde Chemical Industry) with the polyisocyanate composition, and the equivalent ratio of the isocyanate group in the polyisocyanate composition to the hydroxyl group in the acrylic polyol (NCO / OH) is 1.02. Then adjust it to a coating with a solid content of 50% using a mixed solvent (composition: ethyl acetate / butyl acetate = 1 / 1 / (mass ratio)).

[0064] Test the pendulum hardness and transparency of the coating film. The test results are shown in Table 1.

[0065] Table 1 Basic indexes and performance test results of examples and comparative examples

[0066]

Claims

1. A polyisocyanate curing agent, characterized in that, It includes modified xylylene diisocyanate, and the modified xylylene diisocyanate is prepared by reacting xylylene diisocyanate with an active hydroxyl component.

2. The curing agent according to claim 1, characterized in that, The active hydroxyl component includes water and an alcohol, and the alcohol is an alcohol with a molecular weight of 32 to 300, preferably one or more of methanol, ethanol, propanol, butanol, pentanol, hexanol, ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, glycerol, 2-ethyl-2-hydroxymethyl-1,3-propanediol; Preferably, the molar ratio r of water to xylylene diisocyanate is 0.6×10 -2 ≤ r ≤ 2.2×10 -2 .

3. The curing agent according to claim 1 or 2, characterized in that, In the preparation of the modified xylylene diisocyanate, the ratio R of the number of moles of isocyanate groups in xylylene diisocyanate to the number of moles of hydroxyl groups in the alcohol satisfies 4.0 ≤ R ≤ 8.

0.

4. The curing agent according to any one of claims 1 to 3, characterized in that, The preparation method of the modified xylylene diisocyanate is: reacting xylylene diisocyanate, an alcohol and water to prepare the modified xylylene diisocyanate.

5. The curing agent according to any one of claims 1-4, characterized in that, In the preparation method of the modified xylylene diisocyanate, the reaction temperature is 60 - 90 °C, preferably 65 - 90 °C; the reaction time is 2.5 - 8.0 h, preferably 2.5 - 7.5 h.

6. The curing agent according to any one of claims 1-5, characterized in that, The reaction solution containing the modified xylylene diisocyanate obtained after the reaction is separated by evaporation to obtain the modified xylylene diisocyanate; Preferably, the reaction solution is separated by evaporation using a thin-film evaporator; Preferably, the separation parameters are as follows: the separation temperature is 130 - 210 °C, preferably 135 - 195 °C; the separation pressure is 0.1 - 120 Pa, preferably 10 - 100 Pa.

7. The curing agent according to any one of claims 1-6, characterized in that, The curing agent further includes a solvent; Preferably, the modified xylylene diisocyanate and the solvent are mixed to obtain the curing agent; Preferably, the mixing temperature of the modified xylylene diisocyanate and the solvent is 30 - 90 °C, and the solid content of the curing agent is 40% - 95%, preferably 50% - 90%; Preferably, the solvent is selected from one or more of toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, toluene cyclohexanone, cyclohexane, n-hexane, tetrahydrofuran, chlorobenzene, dichlorobenzene, dichloromethane, dichloroethane, 1,3-dioxane, methyl acetate, ethyl acetate, butyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, ethyl propionate, propyl propionate, butyl propionate, preferably ethyl acetate.

8. The curing agent according to any one of claims 1-7, characterized in that, The polyisocyanate curing agent further includes an HDI trimer; Preferably, the mass ratio of the modified xylylene diisocyanate to the HDI trimer is 1:10 - 10:1, preferably 1:5 - 8:1; Preferably, the viscosity of the HDI trimer at 25 °C is 1500 - 4000 cP; Preferably, the HDI trimer is selected from one or more of HT-100, HT-600, N3300, preferably HT-100.

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