Uretonimine aqueous coating curing agent, preparation method and application thereof

Abstract

The application discloses a preparation process of uretonimine curing agent which can be used as a water-based paint curing agent. The process comprises the following steps: 1) preparing uretonimine; and 2) quaternary ammonium saltizing the tertiary amine bond on the uretonimine to obtain a curing agent which can be dispersed in water. The quaternary ammonium saltization is directly performed on the uretonimine of the isocyanate itself, and no tertiary amine needs to be additionally introduced, so that the overall NCO content is effectively improved, the overall viscosity is reduced, and the economic value is higher.

Description

Technical Field

[0001] This invention relates to the field of waterborne coating curing agents, and more specifically to a method for preparing a urea-formaldehyde waterborne coating curing agent. Background Technology

[0002] Existing patented technologies for water-based HDI curing agents are all based on the modification of HDI trimers, such as patents CN201811138066.1, CN202010010505.1, and CN201910483215.6. These are all based on various types of trimer modifications. Because HDI trimers themselves have high viscosity and relatively low NCO content compared to HDI monomers, they determine the characteristics of high viscosity and low NCO in the final product.

[0003] Therefore, conventional water-based curing agents have high viscosity, poor water dispersibility, and low NCO content, resulting in many inconveniences and economic problems in construction.

[0004] Compared to conventional waterborne curing agents, this solution generates urethane from hydroxyl groups to urea, and further quaternizes the tertiary amine to obtain water solubility, resulting in superior water dispersibility. In addition, this solution has lower viscosity, higher NCO content, better performance and economic value, and is more suitable for waterborne systems. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a preparation process for a urea-formaldehyde waterborne coating curing agent, which can be used as a waterborne coating curing agent.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a urea-formaldehyde waterborne coating curing agent includes the following steps:

[0008] 1) Add polyisocyanate to the reactor to carry out the first step of the reaction. Add a certain amount of catalyst A and slowly add a hydroxyl-containing compound while stirring. After the addition is completed, continue stirring until NCO reaches the theoretical value. Then carry out the second step of the reaction. Continue stirring and add catalyst B, maintain the temperature, and react until NCO reaches the theoretical value.

[0009] 2) After the temperature drops to room temperature, add a quaternary ammonium salting agent to obtain a curing agent that has both NCO groups and is water-soluble, that is, a curing agent that has curing effect and can be dispersed in water.

[0010] Further, in step 1), the polyisocyanate is selected from at least one of isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), isophenyl dimethyl isocyanate (XDI), 1,3-di(isocyanate methyl)cyclohexane (H6XDI), toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and isocyanate polymers (HDI trimer, polymeric MDI), preferably hexamethylene diisocyanate.

[0011] Further, in step 1), catalyst A is selected from organometallic catalysts, preferably one or more of dibutyltin dilaurate, potassium isooctanoate (a potassium carboxylate), zinc carboxylate, and bismuth carboxylate, more preferably dibutyltin dilaurate, and its amount is 0-500 ppm of the total mass of isocyanate and hydroxyl-containing compounds; catalyst B is selected from organometallic catalysts, bismuth carboxylate, zinc carboxylate, organozirconium, preferably bismuth isooctanoate, and its amount is 24-609 ppm of the total mass of isocyanate and hydroxyl-containing compounds;

[0012] Further, the hydroxyl-containing compound in step 1) is selected from monofunctional alcohols, difunctional alcohols, and polyfunctional alcohols, preferably one or more of methanol, ethanol, ethylene glycol, propylene glycol, pentaerythritol, hydroxyethyl acrylate, and hydroxyethyl methacrylate, as well as other hydroxyl-containing compounds, more preferably methanol.

[0013] Further, in step 1), the molar ratio of NCO to the hydroxyl group of the hydroxyl-containing compound in the polyisocyanate is 4-20:1;

[0014] Furthermore, in step 1), the temperature of the first stage of the reaction is 20-100℃, and the reaction time is determined based on whether NCO reaches the theoretical value (the theoretically calculated NCO content when all -OH is reacted). The temperature of the second stage is 60-150℃, and the reaction time is determined based on whether NCO reaches the theoretical value (the theoretically calculated NCO content when all carbamate is reacted).

[0015] Further, the quaternizing agent in step 2) is selected from halogenated hydrocarbons, epoxides, or sulfonic acids and sulfonates, preferably iodomethane, chloromethylbenzene, chloroethane, dimethyl sulfate, ethylene oxide, and at least one of sulfonic acids and sulfonates such as p-benzenesulfonic acid, methyl p-benzenesulfonate, and butanesulfonate lactone, preferably methanesulfonic acid.

[0016] Furthermore, in step 2), the amount of quaternizing agent used is 0.1-1 times the molar amount of hydroxyl groups (-OH molar amount) in the hydroxyl-containing compound in step 1);

[0017] Furthermore, in step 2), the quaternization reaction temperature is 0-150℃ and the reaction time is 1-3h.

[0018] On the other hand, the present invention also provides a urea-formaldehyde waterborne coating curing agent prepared by the above method.

[0019] Finally, the present invention also provides the application of the curing agent, which can be used in combination with conventional oil-based curing agents to make the entire curing agent system water-dispersible, and can be used in the field of water-based coating curing agents such as water-based industrial paints and water-based wood coatings.

[0020] The present invention has the following beneficial effects: As a quaternary ammonium salt compound, it has very good hydrophilicity. Compared with the conventional method of achieving hydrophilicity through quaternization, this method directly performs quaternization on the urea carbamate of the isocyanate itself, without the need to introduce additional tertiary amines, thereby effectively increasing the overall NCO content and reducing the overall viscosity, improving water dispersibility, and having greater economic value. Attached Figure Description

[0021] Figure 1 The infrared spectrum of the curing agent in Example 5 is shown.

[0022] Figure 2 This is a comparison of the dispersion of Example 1 and Comparative Example 3 in water. Detailed Implementation

[0023] 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.

[0024] (1) The raw materials used in the following examples are from the following sources:

[0025] Hexamethylene diisocyanate (HDI), sourced from Wanhua Chemical Group Co., Ltd.

[0026] Isophorone diisocyanate (IPDI), sourced from Wanhua Chemical Group Co., Ltd.

[0027] Methanol, purchased from Tianjin Damao Chemical Reagent Factory

[0028] Hydroxyethyl acrylate was purchased from Beijing Innocare Technology Co., Ltd.; p-hydroxyanisole (MEHQ) was purchased from Beijing Innocare Technology Co., Ltd.

[0029] Dibutyltin dilaurate (T12) was purchased from Beijing Innocare Technology Co., Ltd.

[0030] Bismuth carboxylate (8210), purchased from Beijing Innocare Technology Co., Ltd.;

[0031] Methylsulfonic acid, purchased from Beijing Innocare Technology Co., Ltd.;

[0032] Iodimethane, purchased from Beijing Innocare Technology Co., Ltd.;

[0033] (2) Test method:

[0034] Viscosity test: Viscosity was tested at 25°C using a viscometer;

[0035] NCO content test: The test was conducted using a potentiometric titrator;

[0036] Water dispersibility test: Observe the dispersibility and test the stability, where: good: can be evenly dispersed by hand stirring; poor: can be dispersed by high-speed mechanical stirring; bad: cannot be dispersed.

[0037] Example 1

[0038] Prepared according to the following method:

[0039] 300g of hexamethylene diisocyanate (HDI) was added to a 1L four-necked flask. The oil bath temperature was controlled at 60℃. 0.02g of dibutyltin dilaurate was added, and 28.5g of methanol was added dropwise using a peristaltic pump. After the theoretical NCO reached 34.28%, 0.1g of bismuth carboxylate (8210) catalyst was added. After reacting at 80℃ for about 20h, the NCO reached 22.88%. The reaction was stopped to obtain urea carbamate. The mixture was cooled to room temperature, and 85.5g of methanesulfonic acid was added. The mixture was reacted at room temperature for 3h to obtain a curing agent with NCO groups that can be dispersed in water.

[0040] Example 2

[0041] Prepared according to the following method:

[0042] 300g of isophorone diisocyanate (IPDI) was added to a 1L four-necked flask. The oil bath temperature was controlled at 60℃. 0.02g of dibutyltin dilaurate was added, and 21.5g of methanol was added dropwise using a peristaltic pump. After the theoretical NCO content reached 26.49%, 0.1g of bismuth carboxylate (8210) catalyst was added. After reacting at 80℃ for about 20 hours, the NCO content reached 17.71%. The reaction was stopped to obtain urea carbamate. The mixture was cooled to room temperature, and 64.5g of methanesulfonic acid was added. The mixture was reacted at room temperature for 3 hours to obtain a curing agent with NCO groups that can be dispersed in water.

[0043] Examples 3-7

[0044] The differences between the preparation methods of the water-based curing agents in Examples 3-7 and those in Example 1 are shown in Table 1:

[0045] Table 1 Examples 3-7

[0046] Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 First step reaction temperature 20℃ 100℃ 60℃ 60℃ 60℃ 60℃ 60℃ 60℃ 60℃ Types and amounts of polyisocyanates added HDI HDI HDI HDI HDI HDI HDI HDI HDI 300 300 300 300 300 300 300 300 300 First step catalyst addition amount 0.164 0 0.02 0.02 0.02 0.02 0.02 0.02 0.02 Types and amounts of hydroxyl compounds added methanol Pentanol HEA methanol methanol methanol methanol methanol methanol 28.5 78.5 103.5 11.42 5.72 28.5 28.5 28.5 28.5 Second step reaction temperature 80℃ 80℃ 80℃ 80℃ 80℃ 60℃ 150℃ 80℃ 80℃ Second step: Catalyst addition amount 0.1 0.1 0.1 0.1 0.1 0.2 0.008 0.1 0.1 Types and amounts of quaternary ammonium salt reagents Methylsulfonic acid Methylsulfonic acid Methylsulfonic acid Methylsulfonic acid Methylsulfonic acid Methylsulfonic acid Methylsulfonic acid Iodomethane Methyl p-benzenesulfonate 85.5 64.5 85.5 34.2 17.1 85.5 85.5 12.7 83 Third step reaction temperature 0℃ room temperature room temperature room temperature room temperature room temperature room temperature room temperature 150℃

[0047] Comparative Example 1

[0048] 300g of hexamethylene diisocyanate (HDI) was added to a 1L four-necked flask. The oil bath temperature was controlled at 60℃. 0.02g of dibutyltin dilaurate was added, and 57g of methanol was added dropwise using a peristaltic pump. After the NCO content reached 21.06%, 0.1g of bismuth carboxylate (8210) catalyst was added. After reacting at 80℃ for about 20 hours, the NCO content reached 10.58%. The reaction was stopped to obtain urea carbamate. The mixture was cooled to room temperature, and 84g of methanesulfonic acid was added. The mixture was reacted at room temperature for 3 hours to obtain a curing agent with NCO groups that can be dispersed in water.

[0049] Comparative Example 2

[0050] 300g of hexamethylene diisocyanate (HDI) was added to a 1L four-necked flask. The oil bath temperature was controlled at 60℃. 0.02g of dibutyltin dilaurate was added, and 28g of methanol was added dropwise using a peristaltic pump. The reaction was stopped when the NCO content reached 34.28%, and urethane was obtained. The mixture was cooled to room temperature, and 84g of methanesulfonic acid was added. The mixture was reacted at room temperature for 3 hours to obtain a curing agent with NCO groups that can be dispersed in water.

[0051] Comparative Example 3

[0052] 300g of hexamethylene diisocyanate (HDI) was added to a 1L four-necked flask. The oil bath temperature was controlled at 60℃. 0.02g of dibutyltin dilaurate was added, and 28g of methanol was added dropwise using a peristaltic pump. After the theoretical NCO reached 34.28%, 0.1g of bismuth carboxylate (8210) catalyst was added. After reacting at 80℃ for about 20h, the NCO reached 22.89%. The reaction was stopped to obtain urethane ester. The mixture was then cooled to room temperature to obtain the relevant product.

[0053] Table 2 shows the comparison of the properties of the waterborne curing agents prepared in Examples 1-11 and Comparative Examples 1-3 with those of commercially available waterborne curing agents after being mixed with HT-500 at a mass ratio of 5:95: Table 2: NCO, viscosity, water dispersibility.

[0054] Table 2. Performance Test Results

[0055] NCO% Viscosity (mPa·s, 25℃) Water dispersibility Example 1 23.33 430 good Example 2 23.16 510 good Example 3 23.33 440 good Example 4 23.23 460 good Example 5 23.19 490 good Example 6 24.16 410 Poor Example 7 24.51 400 Poor Example 8 23.33 420 good Example 9 23.33 450 good Example 10 23.52 430 good Example 11 23.33 440 Poor Comparative Example 1 22.85 780 Difference Comparative Example 2 23.78 solid Difference Comparative Example 3 23.56 420 Difference Aquolin® 161 18.7 2500 good Aquolin®268 20.5 6000 good

[0056] 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 method for preparing a urea-formaldehyde waterborne coating curing agent, comprising the following steps: 1) Add polyisocyanate to the reactor to carry out the first step of the reaction. Add a certain amount of catalyst A and slowly add a hydroxyl-containing compound while stirring. After the addition is completed, continue stirring until NCO reaches the theoretical value. Then carry out the second step of the reaction. Continue stirring and add catalyst B, maintain the temperature, and react until NCO reaches the theoretical value. 2) After the temperature drops to room temperature, add a quaternizing agent to obtain a curing agent that has both NCO groups and is water-soluble, i.e., a curing agent that has curing properties and can be dispersed in water; In step 1), the polyisocyanate is selected from at least one of isophorone diisocyanate and hexamethylene diisocyanate; in step 1), the hydroxyl-containing compound is selected from one or more of methanol, hydroxyethyl acrylate, and hydroxyethyl methacrylate; in step 2), the quaternizing agent is selected from at least one of iodomethane, methyl p-benzenesulfonate, and methanesulfonic acid; the amount of the quaternizing agent in step 2) is 0.1-1 times the molar amount of the hydroxyl-containing compound in step 1); and the molar ratio of NCO in the polyisocyanate and the hydroxyl group of the hydroxyl-containing compound in step 1) is 4-20:

1.

2. The preparation method according to claim 1, characterized in that, In step 1), catalyst A is selected from organometallic catalysts, and its dosage is 0-500 ppm of the total mass of isocyanate and hydroxyl-containing compounds; catalyst B is selected from organometallic catalysts, bismuth carboxylate, zinc carboxylate, organozirconium, and its dosage is 24-609 ppm of the total mass of isocyanate and hydroxyl-containing compounds.

3. The preparation method according to claim 2, characterized in that, In step 1), catalyst A is selected from one or more of dibutyltin dilaurate, potassium isooctanoate (a potassium carboxylate), zinc carboxylate, and bismuth carboxylate; catalyst B is selected from bismuth isooctanoate.

4. The preparation method according to any one of claims 1-3, characterized in that, The temperature of the first stage of the reaction in step 1) is 20-100℃, and the temperature of the second stage is 60-150℃.

5. The preparation method according to any one of claims 1-3, characterized in that, The quaternization reaction in step 2) is carried out at a temperature of 0-150℃ and for a time of 1-3 hours.

6. A urea-formaldehyde waterborne coating curing agent prepared by the preparation method according to any one of claims 1-5.

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