Preparation method of extinction curing agent

Abstract

The invention relates to a preparation method of a matting curing agent. According to the method, the sec-butyl acetate aqueous solution and the anhydride are creatively adopted for hydrolysis, then the hydrolysis product and the 2-phenylimidazoline form a complex, the process yield is high and can reach 99% or above, the product purity is high and can reach 99.9%, and the problem that the price of pyromellitic acid serving as a raw material of an existing extinction curing agent B68 is high is solved; after the reaction is completed, azeotrope of sec-butyl acetate and water in reaction liquid is evaporated from the top of the reactor, condensed by the heat exchanger and then fed into the solvent recovery tank to be recycled, no waste water is basically generated in the production process, and the problem that a large amount of waste water is generated in the existing production process of the extinction curing agent B68 is solved.

Description

Technical Field

[0001] The invention belongs to the field of chemical industry, and particularly relates to a method for preparing a matting curing agent. Background Art

[0002] Powder coatings, as a new type of solvent-free solid coating, offer advantages such as being solvent-free, pollution-free, recyclable, and environmentally friendly. They are widely used in automotive, home appliance, and indoor and outdoor corrosion protection applications. Currently, the most commonly used matting curing agent in E-12 epoxy resin powder coating systems is B68, a complex salt of pyromellitic acid and 2-phenylimidazoline. This complex salt utilizes the difference in the reaction rate between the two groups and the epoxy reaction to create a rough surface on the epoxy resin, resulting in diffuse reflection of light and achieving matting.

[0003] Patent CN109824500A discloses a method for synthesizing 2-phenylimidazoline adducts, specifically disclosing an adduct reaction between 2-phenylimidazoline and pyromellitic anhydride. After the reaction mass is discharged into a cooling tower, crystallization is carried out by cooling, and a centrifuge is introduced for solid-liquid separation. The yield of this reaction is not reported. This application directly reacts pyromellitic anhydride with 2-phenylimidazoline. This patented reaction involves the presence of solvents such as ketones and benzene, which are highly toxic. The production route is long, the solvent is not recycled, and the used solvent contains raw materials or products, which constitutes hazardous waste and has high disposal costs.

[0004] Patent CN104744989A mentions the use of a mixture of tartaric acid, citric acid, 1,2-diaminocyclohexanetetraacetic acid, and ethylenediamine, diethylenetriamine, and o-phenylenediamine, containing amino and carboxyl functional groups, to create an epoxy resin matting agent. Ethanol was used as the solvent. The yield of this reaction was not reported.

[0005] Patent CN105968050A mentions an epoxy resin matting curing agent, which adopts the addition reaction of ethylene glycol trimellitate and imidazoline amine, and uses alcohol or water as a solvent in the preparation process, with a yield of 98%.

[0006] Most of the above-mentioned production processes for matting curing agent B68 use water as a solvent, generating large amounts of wastewater during production. While some existing technologies use organic solvents, these methods provide limited information on yield and solvent purity. This significant wastewater generation during the production of B68 matting curing agent leads to a significant increase in production costs. Furthermore, the high price of the raw material, pyromellitic acid, necessitates improvements to the current production process for matting curing agent B68 to reduce costs and minimize waste emissions. Summary of the Invention

[0007] The first technical problem to be solved by the present invention is the high price of pyromellitic acid, the raw material of the existing matting curing agent B68. The second technical problem to be solved by the present invention is the problem that a large amount of wastewater is generated in the production process of the existing matting curing agent B68, resulting in a sharp increase in production costs. Therefore, the present invention provides a method for preparing a matting curing agent.

[0008] The present invention is achieved through the following technical solutions:

[0009] The present invention provides a method for preparing a matting curing agent, comprising the following steps:

[0010] 1) adding anhydride and aqueous ester solution into a reactor;

[0011] 2) preheating the reactor to hydrolyze the anhydride into acid, and then adding 2-phenylimidazoline and ester, preferably dropwise or in batches, to the reactor;

[0012] 3) heating the reactor to carry out heat preservation reaction;

[0013] 4) After the reaction is completed, the reaction solution is allowed to stand to allow the product in the reaction solution to precipitate as a solid, and the solid product in the reaction solution is dried (e.g., oven-dried) to obtain the matte curing agent.

[0014] Wherein, the esters are esters that can azeotrope with water.

[0015] During the heat-keeping reaction, 2-phenylimidazoline and the polyacid obtained by hydrolysis of the acid anhydride undergo electron cloud pairing. The reaction equation of the present invention is as follows:

[0016] C9H 10 N2+O3C2-R-C2O3+2H2O→[C9H 10 N2] + [H2O4C2-R-C2O4H2] -

[0017] Furthermore, in the method for preparing the matting curing agent, in step 1), the water content in the aqueous ester solution is 1 to 20 wt%, preferably 3 to 15 wt% or 5 to 10 wt%; and / or,

[0018] In step 1), the acid anhydride is selected from at least one of pyromellitic anhydride, phthalic anhydride, and maleic anhydride. These acid anhydrides have good chemical bond stability compared to other acid anhydrides, and the resulting product has good extinction properties. Pyromellitic anhydride is preferred; and / or,

[0019] In step 1), the ester is at least one of sec-butyl acetate and isopropyl acetate, more preferably sec-butyl acetate. Sec-butyl acetate has a low solubility in the product salt, which is beneficial to improving the reaction conversion rate; and / or,

[0020] In step 1), the molar ratio of the anhydride groups in the acid anhydride to the water in the aqueous ester solution is 1:(0.8-1.2), preferably 1:(0.9-1.1), preferably 1:(0.95-1.05), and more preferably 1:1.

[0021] Furthermore, in the preparation method of the above-mentioned matting curing agent, in step 2), the reactor is preheated to 30-60°C, preferably 35-55°C, preferably 38-52°C, preferably 40-50°C. The hydrolysis effect is best at this temperature range, preferably 50°C.

[0022] Furthermore, in step 2), the molar ratio of 2-phenylimidazoline to the acid anhydride is 1:(0.8-1.2), preferably 1:(0.9-1.1), preferably 1:(0.95-1.05), preferably 1:1. If the molar ratio of 2-phenylimidazoline is too low, a relatively rough surface cannot be formed on the surface of the epoxy resin, thereby reducing the diffuse reflection effect. If the molar ratio of 2-phenylimidazoline is too high, the cost will increase.

[0023] Furthermore, in step 2), the ester is the same as the ester used in step 1), preferably sec-butyl acetate and / or isopropyl acetate, more preferably sec-butyl acetate.

[0024] Furthermore, in step 2), 2-phenylimidazoline and esters can be added separately or as a mixture, preferably as a mixture (obtained by dissolving or dispersing 2-phenylimidazoline in pure esters), and the mass ratio of 2-phenylimidazoline to esters is 1:0.5-5, preferably 1:0.7-3 or further 1:0.8-2.

[0025] Furthermore, in step 2), the addition time is generally 30 to 120 minutes, preferably 40 to 90 minutes, for example 60 minutes. The addition time generally depends on the amount of each reaction raw material, and there is no particular limitation on the addition rate, for example 100-200 mL per hour.

[0026] Furthermore, in the preparation method of the matting curing agent, in step 3), the reaction temperature of the heat preservation reaction is 70-95°C, preferably 75-92°C, 80-90°C, or 82-88°C.

[0027] Furthermore, in step 3), the reaction time of the insulation reaction is 1 to 5 hours, preferably 2 to 3 hours.

[0028] Furthermore, in the above-mentioned method for preparing the matting curing agent, in step 4), the standing time is not particularly limited, as long as the product is fully precipitated.

[0029] Furthermore, in step 4), the temperature of the reduced pressure distillation is 80-90° C., the pressure is -0.06 to -0.04 MPa, and the time is 3-6 h.

[0030] Furthermore, in step 4), the drying temperature is 40-80° C., further 50-60° C., and the drying time is 30 to 120 minutes.

[0031] Furthermore, in the above-mentioned method for preparing the matting curing agent, step 4) further comprises the following steps: subjecting the reactor (1) to reduced pressure distillation, and the liquid solvent in the reaction liquid is evaporated from the top of the reactor, condensed in a heat exchanger, and then enters a solvent recovery tank for recycling.

[0032] Furthermore, in the above-mentioned method for preparing the matting curing agent, the reactor is a reactor with a condenser.

[0033] The heat exchanger may be a shell and tube heat exchanger.

[0034] The present invention has the following beneficial effects:

[0035] (1) The preparation method of the matting curing agent of the present invention creatively adopts the method of first hydrolyzing sec-butyl acetate aqueous solution with acid anhydride and then forming a complex with 2-phenylimidazoline. The process has a high yield of more than 99% and a high product purity of 99.9%, which solves the problem of the high price of pyromellitic acid, the raw material of the existing matting curing agent B68;

[0036] (2) The preparation method of the matting curing agent of the present invention adopts an aqueous solution of sec-butyl acetate as a solvent for the first time. After the reaction is completed, the azeotrope of sec-butyl acetate and water in the reaction liquid is evaporated from the top of the reactor, condensed in a heat exchanger, and then enters a solvent recovery tank for recycling. Basically, no wastewater is generated during the production process, which solves the problem of generating a large amount of wastewater in the existing production process of matting curing agent B68, which leads to a sharp increase in production costs.

[0037] (3) The preparation method of the matting curing agent of the present invention adopts an aqueous solution of sec-butyl acetate as a solvent, which solves the problem of the disposal of aqueous sec-butyl acetate solutions of different proportions in the production process and gives full play to the role of the sec-butyl acetate solvent. Since the sec-butyl acetate aqueous solution currently needs to be distilled twice to obtain the sec-butyl acetate solvent, the process also reduces the step of re-purifying the sec-butyl acetate. After the reaction, the purity of the sec-butyl acetate in the aqueous solution of sec-butyl acetate is improved, and the purity of the sec-butyl acetate after the reaction can generally be increased to 98%. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0039] Figure 1 1-4 is a process flow chart of the preparation method of the matting curing agent;

[0040] Among them: 1-reactor, 2-solvent recovery tank, 3-heat exchanger. DETAILED DESCRIPTION

[0041] The technical solutions of the present invention will be described clearly and completely below with reference to the accompanying drawings. In the embodiments described below, the technical features of each embodiment can be combined arbitrarily.

[0042] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "top", "bottom", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0043] Figure 1 The process flow diagram of the preparation method of the matting curing agent of Examples 1-3 is shown, which includes: a reactor 1, a solvent recovery tank 2 and a heat exchanger 3. The top inlet of the reactor 1 is connected to the raw material feed pipeline, the top outlet of the reactor 1 is connected to the inlet of the heat exchanger 3 (the cooling medium in the heat exchanger can be water) via a pipeline, the bottom outlet of the reactor 1 is connected to the product discharge pipeline, the outlet of the heat exchanger 3 is connected to the inlet of the solvent recovery tank 2 via a pipeline, and the outlet of the solvent recovery tank 2 is returned to the reactor 1 via a pipeline.

[0044] In the following examples and comparative examples of the present invention, pyromellitic anhydride was purchased from Jiangsu Nantong Zhonghe Company with a chemical purity of 99.9%;

[0045] Phthalic anhydride was purchased from Shandong Jinhe Chemical Company with a purity of more than 99%;

[0046] Maleic anhydride was purchased from Baozhen Chemical Company with a purity of more than 99%;

[0047] 2-Phenylimidazoline was purchased from Yunke Chemical Company with a purity of more than 99.9%.

[0048] Example 1

[0049] The preparation method of the matt curing agent of this embodiment comprises the following steps: 1) adding pyromellitic anhydride (1 mol) and 720 g of 5% water-containing sec-butyl acetate solution into a reactor 1 with a condenser; 2) preheating the reactor 1 to 50° C., and subsequently dripping a mixed solution of 2-phenylimidazoline (1 mol) and sec-butyl acetate (200 g) into the reactor 1; 3) after all the dripping is completed, heating the reactor 1 to 80° C. and keeping the temperature under normal pressure for reaction for 3 h; 4) after the reaction is completed, standing the reaction solution to allow the product to precipitate as a solid, and then subjecting the reactor 1 to vacuum distillation at a temperature of 80° C. and a pressure of −0.04 MPa for 5 h. The azeotrope of sec-butyl acetate and water in the reaction solution is evaporated from the top of the reactor 1, condensed in a heat exchanger 3, and then enters a solvent recovery tank 2 for recycling and reuse. The solid product in the reaction solution is dried, and its structure is confirmed by liquid chromatography. 363.6 g of the product is collected, with a yield of 99.9% and a purity of 99.9%.

[0050] Example 2

[0051] The preparation method of the matte curing agent of this embodiment comprises the following steps: 1) adding phthalic anhydride (1 mol) and 180 g of 10% water-containing sec-butyl acetate solution into a reactor 1 equipped with a condenser; 2) preheating the reactor 1 to 50° C., and then dropwise adding a mixed solution of 2-phenylimidazoline (1 mol) and sec-butyl acetate (200 g) into the reactor 1; 3) after all the dropwise additions are completed, heating the reactor 1 to 85° C. at normal pressure and keeping the temperature for reaction for 2.5 hours; 4) after the reaction is completed, standing the mixture for 1 minute. The product in the reaction solution was precipitated as a solid, and then the reactor 1 was subjected to reduced pressure distillation at a temperature of 85° C., a pressure of −0.05 MPa, and a time of 4 h. The azeotrope of sec-butyl acetate and water in the reaction solution was distilled from the top of the reactor 1, condensed in the heat exchanger 3, and then entered the solvent recovery tank 2 for recycling. The solid product in the reaction solution was dried, and its structure was confirmed by liquid chromatography. 292.7 g of the product was collected, with a yield of 99.6% and a purity of 99.9%.

[0052] Example 3

[0053] The preparation method of the matte curing agent of this embodiment comprises the following steps: 1) adding maleic anhydride (1 mol) and 120 g of 15% water-containing sec-butyl acetate solution to a reactor 1 equipped with a condenser; 2) preheating the reactor 1 to 50° C., and then dropwise adding a mixed solution of 2-phenylimidazoline (1 mol) and sec-butyl acetate (200 g) to the reactor 1; 3) after all the dropwise additions are completed, heating the reactor 1 to 90° C. at normal pressure and keeping the temperature for 2 h; 4) after the reaction is completed, standing the reactor 1 for 1 h. The product in the reaction solution precipitated as a solid, and then the reactor 1 was subjected to reduced pressure distillation at a temperature of 90° C., a pressure of −0.06 MPa, and a time of 3 h. The azeotrope of sec-butyl acetate and water in the reaction solution was evaporated from the top of the reactor 1, condensed in the heat exchanger 3, and then entered the solvent recovery tank 2 for recycling. The solid product in the reaction solution was dried, and its structure was confirmed by liquid chromatography. 242.3 g of the product was collected, with a yield of 99.4% and a purity of 99.9%.

[0054] Example 4

[0055] The preparation method of the matt curing agent of this embodiment comprises the following steps: 1) adding pyromellitic anhydride (1 mol) and 720 g of 5% water isopropyl acetate solution into a reactor 1 with a condenser; 2) preheating the reactor 1 to 50° C., and then dripping a mixed solution of 2-phenylimidazoline (1 mol) and isopropyl acetate (200 g) into the reactor 1; 3) after all the dripping is completed, heating the reactor 1 to 80° C. under normal pressure and keeping the temperature for reaction for 3 h; 4) after the reaction is completed, standing the reaction solution to allow the product in the reaction solution to precipitate as a solid, and then subjecting the reactor 1 to reduced pressure distillation at a temperature of 80° C. and a pressure of −0.04 MPa for 5 h. The azeotrope of sec-butyl acetate and water in the reaction solution is evaporated from the top of the reactor 1, condensed by a heat exchanger 3, and then enters a solvent recovery tank 2 for recycling and reuse. The solid product in the reaction solution is dried, and its structure is confirmed by liquid chromatography. 363.2 g of the product is collected, with a yield of 99.8% and a purity of 99.1%.

[0056] The products prepared in Examples 1-4 were subjected to a board test. The materials and steps required for the board test are consistent with those in patent CN109824500A. The ingredients were purchased from Huangshan Debang Powder Material Co., Ltd. and tested with a gloss meter. The results showed that the gloss of the products prepared in Examples 1-4 was 2-4 degrees, achieving a low-light effect. According to the GB1731 standard test, the impact resistance of the products prepared in Examples 1-4 was 50kg.cm (i.e., all passed the test). This shows that the matte curing agent prepared in the present invention has excellent matte curing performance and can meet the needs of industrial production.

[0057] Comparative Example 1

[0058] The reaction was basically the same as in Example 1, except that ethanol was used instead of sec-butyl acetate. Since the weight ratio of ethanol to water during azeotropy was 95.6% ethanol and 4.4% water, compared to a ratio of water close to 20% for sec-butyl acetate, and the solubility of salt in ethanol was low, the reaction conversion rate was significantly lower than that in Example 1.

[0059] Comparative Example 2

[0060] The reaction was basically the same as in Example 1, except that water was used instead of sec-butyl acetate. However, the amount of water was not easy to control. If the amount of water was too little, the system could not be dispersed. If the amount of water was too much, a large amount of wastewater would be generated due to the formation of a complex that was insoluble in water. At the same time, the reaction conversion rate was significantly reduced.

[0061] Comparative Example 3

[0062] The preparation method of the matt curing agent of this embodiment comprises the following steps: 1) adding pyromellitic anhydride (1 mol) and 720 g of ethyl acetate solution containing 5% water to a reactor 1 with a condenser; 2) preheating the reactor 1 to 50° C., and then dripping a mixed solution of 2-phenylimidazoline (1 mol) and ethyl acetate (200 g) into the reactor 1; 3) after all the dripping is completed, heating the reactor 1 to 70° C. and keeping the temperature under normal pressure for reaction for 3 h; 4) after the reaction is completed, standing the reaction solution to allow the product to precipitate as a solid, and then subjecting the reactor 1 to vacuum distillation at a temperature of 80° C. and a pressure of −0.04 MPa for 5 h. The azeotrope of sec-butyl acetate and water in the reaction solution is evaporated from the top of the reactor 1, condensed by a heat exchanger 3, and then enters a solvent recovery tank 2 for recycling and reuse. The solid product in the reaction solution is dried, and its structure is confirmed by liquid chromatography. 361.7 g of the product is collected, with a yield of 99.4% and a purity of 95.1%.

[0063] Compared with sec-butyl ester solvents, ethyl acetate has a lower boiling point and its azeotropic temperature with water is only 70 degrees, which cannot reach a good reaction temperature. There are still many raw materials in the reaction product that have not reacted completely, and the effect is poor.

[0064] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a matting curing agent, characterized in that: The following steps are involved: 1) adding anhydride and aqueous ester solution into a reactor; 2) preheating the reactor to hydrolyze the anhydride into acid, and then adding 2-phenylimidazoline and esters into the reactor; 3) heating the reactor to carry out heat preservation reaction; 4) After the reaction is completed, the reaction solution is allowed to stand to allow the product in the reaction solution to precipitate as a solid, and the solid product in the reaction solution is dried to obtain the matte curing agent. Wherein, the esters are esters that can azeotrope with water.

2. The method for preparing a matting curing agent according to claim 1, wherein: In step 1), the water content in the aqueous ester solution is 1-20 wt%, preferably 3-15 wt% or 5-10 wt%; and / or, In step 1), the acid anhydride is selected from at least one of pyromellitic anhydride, phthalic anhydride, and maleic anhydride, preferably pyromellitic anhydride; and / or, In step 1), the ester is sec-butyl acetate and / or isopropyl acetate, preferably sec-butyl acetate; and / or, In step 1), the molar ratio of the anhydride groups in the acid anhydride to the water in the aqueous ester solution is 1:(0.8-1.2), preferably 1:(0.9-1.1), preferably 1:(0.95-1.05), and more preferably 1:

1.

3. The method for preparing a matting curing agent according to claim 1 or 2, wherein: In step 2), the reactor (1) is preheated to 30-60°C, preferably 40-50°C, more preferably 50°C; and / or, In step 2), the molar ratio of 2-phenylimidazoline to the acid anhydride is 1:(0.8-1.2), preferably 1:(0.9-1.1), preferably 1:(0.95-1.05), more preferably 1:1; and / or, In step 2), the ester is an ester that can azeotrope with water, preferably at least one of sec-butyl acetate and isopropyl acetate, more preferably sec-butyl acetate; and / or, In step 2), in the mixed solution of 2-phenylimidazoline and ester, the mass ratio of 2-phenylimidazoline to ester is 1:0.5-5, preferably 1:0.7-3 or further 1:0.8-2; and / or, In step 2), the dropwise addition time is 30 to 120 min, preferably 40 to 90 min, for example 60 min.

4. The method for preparing a matting curing agent according to any one of claims 1 to 3, characterized in that: In step 3), the reaction temperature of the insulation reaction is 70 to 95° C., preferably 80 to 90° C.; and / or, In step 3), the reaction time of the insulation reaction is 1 to 5 hours, preferably 2 to 3 hours.

5. The method for preparing a matting curing agent according to any one of claims 1 to 4, characterized in that: Step 4) also includes the following steps: the reactor is subjected to reduced pressure distillation, and the liquid solvent in the reaction liquid is evaporated from the top of the reactor and condensed in a heat exchanger and then enters a solvent recovery tank for recycling.

6. The method for preparing a matting curing agent according to claim 5, wherein: In step 4), the temperature of the reduced pressure distillation is 80-90° C., the pressure is -0.06 to -0.04 MPa, and the time is 3-6 h.

7. The method for preparing a matting curing agent according to any one of claims 1 to 6, characterized in that: The reactor is a reactor with a condenser.

8. The method for preparing a matting curing agent according to any one of claims 1 to 7, characterized in that: In step 2), 2-phenylimidazoline and esters are added dropwise or in batches to the reactor.

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