One-pot method for synthesizing butanol etherified benzoguanamine formaldehyde resin

Abstract

The invention discloses a method for synthesizing butanol etherified benzoguanamine formaldehyde resin by one-pot method. The method comprises the following steps: adding high-purity dicyandiamide, high-purity benzonitrile and butanol into a reaction container, using an inorganic base as a catalyst, and fully reacting to generate the benzoguanamine; cooling the benzoguanamine to 90 DEG C, adding paraformaldehyde, and using the inorganic base as a catalyst to perform a hydroxymethylation reaction; adding an organic acid to a system after the hydroxymethylation reaction to adjust the pH value, heating and refluxing to perform an etherification reaction and dehydration until the tolerance is 5.5-6.0; adding ammonia water to the system after the etherification reaction and dehydration, reacting at 90-95 DEG C for 0.5-1h, adding pure water, heating and refluxing for 1h, and standing to separate a water layer; heating and dehydrating, and then reducing the pressure to dealcoholize to obtain the butanol etherified benzoguanamine formaldehyde resin. The method has simple operating steps. Compared with the traditional discontinuous production method, the total wastewater volume can be reduced by more than 70%-80%, energy consumption can be saved by 20%-30%, water treatment costs can be reduced, and it is more environmentally friendly and reduces costs.

Description

Technical Field

[0001] The invention relates to the technical field of benzoguanamine resins, and in particular to a method for synthesizing butanol etherified benzoguanamine formaldehyde resin by a one-pot method. Background Art

[0002] Butylated benzoguanamine formaldehyde resin is a multifunctional polymer that can react with polymers with hydroxyl, carboxyl, amide and other groups. It can be used as a crosslinking agent for most coating matrix resins such as alkyd resins, acrylic resins, saturated polyester resins, epoxy resins, epoxy esters and other resins. After crosslinking, a tough three-dimensional network structure coating is obtained. The coating has the advantages of high gloss, excellent light and color retention, excellent heat resistance, high hardness, high fullness, excellent chemical corrosion resistance, etc. Therefore, it is widely used in automobiles, construction machinery, household appliances, coils, cans and other products.

[0003] The traditional method for synthesizing butanol-etherified benzoguanamine formaldehyde resin uses purified and dried benzoguanamine powder and formaldehyde aqueous solution as reactants to carry out hydroxymethylation and etherification reaction for preparation, and the synthesis of benzoguanamine and the synthesis of butanol-etherified benzoguanamine formaldehyde resin are divided into two independent processes for discontinuous synthesis. Most benzoguanamine uses dicyandiamide and benzonitrile as raw materials, uses inorganic base as catalyst, and heats and reacts under alkyl alcohol solvent. After dealcoholization, crude benzoguanamine is obtained, and then it is washed and purified for many times, dewatered, dried, and sieved to obtain a white crystalline powder product; wherein, the amount of water used in the washing step is usually 5-8 times the mass of the finished benzoguanamine, and the amount of wastewater is large. In the preparation process of butanol-etherified benzoguanamine formaldehyde resin, there are reaction wastewater produced by etherification reaction and wastewater generated by product washing and purification. This results in a large amount of wastewater generated in the entire preparation cycle of butanol-etherified benzoguanamine, high post-treatment costs, and is unfavorable to the environment. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a one-pot method for synthesizing butanol-etherified benzoguanamine formaldehyde resin. The method has simple operation steps and can reduce the total wastewater volume by more than 70%-80% compared with the traditional discontinuous production method, save energy consumption by 20%-30%, reduce water treatment costs, be more environmentally friendly, and reduce costs.

[0005] In order to achieve the above object, the present invention provides a one-pot method for synthesizing butanol-etherified benzoguanamine formaldehyde resin, which comprises the following steps:

[0006] (1) adding high-purity dicyandiamide, high-purity benzonitrile and butanol into a reaction container, using an inorganic base as a catalyst, and fully reacting to generate benzoguanamine;

[0007] (2) cooling the benzoguanamine in step (1) to 90° C., adding paraformaldehyde, and carrying out a hydroxymethylation reaction with an inorganic base as a catalyst;

[0008] (3) adding an organic acid to the system after the hydroxymethylation reaction to adjust the pH value to 5.0-6.0, and heating and refluxing to carry out etherification reaction and dehydration until the tolerance is 5.5-6.0;

[0009] (4) adding aqueous ammonia to the system after dehydration of the etherification reaction, reacting at 90-95° C. for 0.5-1 h, adding pure water, heating under reflux for 1 h, standing to separate the water layer, and removing the unreacted raw materials and reaction by-products remaining in the product; heating to dehydrate, and then reducing the pressure to dealcoholize to obtain a butanol-etherified benzoguanamine formaldehyde resin with a free formaldehyde content of less than 0.7%.

[0010] According to the method for synthesizing butanol-etherified benzoguanamine formaldehyde resin by one-pot method of an embodiment of the present invention, the method adopts one-pot method for preparation: first, dicyandiamide, benzonitrile, butanol and inorganic base are used as catalysts for heating and synthesizing benzoguanamine; after the synthesis of benzoguanamine, formaldehyde is directly added to carry out methylol reaction without butanol removal and recovery, acid neutralization, water washing, drying and crushing process, and then acid is added to carry out etherification reaction and condensation reaction under weak acid conditions, and post-treatment is carried out by adding water reflux, standing and stratifying to remove the water layer for purification, and then heating and dehydrating to form butanol-etherified benzoguanamine formaldehyde resin. The method has simple operation steps, and the solvent and etherification alcohol for benzoguanamine synthesis are both n-butanol, which eliminates the alcohol recovery process and water washing and purification process in the preparation process of benzoguanamine, and the water washing and purification process is placed in the final product step. Compared with the traditional discontinuous production method, the total wastewater volume can be reduced by more than 70-80%, energy consumption can be saved by 20-30%, water treatment costs can be reduced, it is more environmentally friendly, and the final cost of the product is greatly reduced.

[0011] Optionally, the inorganic base is sodium hydroxide, potassium hydroxide, aluminum hydroxide or calcium hydroxide.

[0012] Optionally, in step (1), the reaction temperature is 115-125° C. and the reaction time is 3-6 hours.

[0013] Optionally, in step (1), the purity of the high-purity dicyandiamide and the high-purity benzonitrile is 99.7%.

[0014] Optionally, in step (2), the purity of paraformaldehyde is 92-98%.

[0015] Optionally, in step (2), the pH is controlled to be 7-9, and the hydroxymethylation reaction is carried out at 85-95° C. for 2-3 hours. The weak alkalinity of controlling the pH to be 7-9 is to prevent the unreacted benzonitrile and dicyandiamide in the reaction system from undergoing alkaline hydrolysis to generate benzamide, benzoic acid ester, and biuret, thereby reducing the waste of raw materials, improving the quality of the product, and reducing the types and contents of organic matter in the post-treatment wastewater.

[0016] Optionally, in step (3), the organic acid is benzoic acid, phthalic anhydride, benzenesulfonic acid or acetic acid.

[0017] Optionally, in step (3), the reaction time is 4-6 hours.

[0018] Optionally, in step (4), the concentration of ammonia water is 20-28%. Ammonia water can react with free formaldehyde in the reaction product to generate hexamethyltetramine crystal precipitate, which settles in the lower water layer after standing, and can be removed in layers to reduce the free formaldehyde content in the product.

[0019] Optionally, in step (4), the temperature is increased for dehydration, and when the temperature reaches 100° C., the pressure is reduced and dealcoholization is performed at a vacuum degree of 0.03-0.04 MPa.

[0020] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is described below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not exclude the existence of other method steps before and after the combination step or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to limit the scope of the present invention. The change or adjustment of the relative relationship thereof shall also be regarded as the scope of the present invention without substantially changing the technical content.

[0022] In order to better understand the above technical scheme, the exemplary embodiments of the present invention are described in more detail below. Although exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0023] The test materials used in the present invention are all common commercial products and can be purchased in the market.

[0024] The present invention is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0025] Example 1

[0026] The one-pot method for synthesizing butanol etherified benzoguanamine formaldehyde resin comprises the following steps:

[0027] (1) In a 2L glass four-necked flask, 430g of butanol and 150g of 99.7% pure benzonitrile were added, and 122g of 99.7% pure dicyandiamide and 1.5g of sodium hydroxide were slowly added under stirring. The temperature was raised to reflux at a temperature between 115 and 120°C. After reflux reaction for 5h, heating was stopped and the temperature was lowered to obtain benzoguanamine.

[0028] (2) The glass four-necked flask in step (1) was cooled to 90° C., 142 g of 93% pure paraformaldehyde was added, and a 30% aqueous sodium hydroxide solution was added to adjust the pH to 7.5-8.0, and a hydroxymethylation reaction was carried out at 90-92° C. for 3 hours.

[0029] (3) After the reaction in step (2), phthalic anhydride is added to adjust the pH value to 5.0-5.5, and the temperature is raised to reflux at a temperature between 115-120° C. to carry out etherification reaction and dehydration. The reaction time is 4-6 hours. Sampling is started to test the tolerance at the 4th hour, and sampling is then taken every 1 hour until the tolerance reaches 5.5-6.0, then heating is stopped and the temperature is lowered.

[0030] (4) Post-treatment: Add 15g of 25% aqueous ammonia, react at 90-95°C for 1h, add 400g of pure water, heat and reflux for 1h, let stand to remove the lower layer of water, and remove the water-soluble raw materials and by-products in the product. Heat and dehydrate, when the temperature reaches 100°C, decompress and dealcoholize under a vacuum degree of 0.03-0.04Mpa to remove the residual formaldehyde in the product, and remove 70g of butanol (the butanol can be recycled) to obtain the product butanol etherified benzoguanamine formaldehyde resin.

[0031] The reaction yield of this example is 83.2%. The product resin is measured as follows: solid content is 68.16%, viscosity is 110s (25° C.), and free formaldehyde content is 0.55%.

[0032] Example 2

[0033] The one-pot method for synthesizing butanol etherified benzoguanamine formaldehyde resin comprises the following steps:

[0034] (1) In a 2L glass four-necked flask, 405g of butanol and 150g of 99.7% pure benzonitrile were added, and 122g of 99.7% pure dicyandiamide and 1.5g of sodium hydroxide were slowly added under stirring. The temperature was raised to reflux at a temperature between 115 and 120°C. After reflux reaction for 6h, heating was stopped and the temperature was lowered to obtain benzoguanamine.

[0035] (2) The glass four-necked flask in step (1) was cooled to 90° C., 118.5 g of 93% pure paraformaldehyde was added, and a 30% aqueous sodium hydroxide solution was added to adjust the pH to 7.5-8.0, and a hydroxymethylation reaction was carried out at 88-90° C. for 2.5 hours.

[0036] (3) After the reaction in step (2), phthalic anhydride is added to adjust the pH value to 5.0-5.5, and the temperature is raised to reflux at a temperature between 115-120° C. to carry out etherification reaction and dehydration. The reaction time is 4-6 hours. Sampling is started to test the tolerance at the 4th hour, and sampling is then taken every 1 hour until the tolerance reaches 5.5-6.0, then heating is stopped and the temperature is lowered.

[0037] (4) Post-treatment: Add 15g of 25% aqueous ammonia, react at 90-95°C for 1h, add 400g of pure water, heat and reflux for 1h, let stand to remove the lower layer of water, and remove the water-soluble raw materials and by-products in the product. Heat and dehydrate, when the temperature reaches 100°C, decompress and dealcoholize under a vacuum degree of 0.03-0.04Mpa to remove the residual formaldehyde in the product, and remove 70g of butanol (the butanol can be recycled) to obtain the product butanol etherified benzoguanamine formaldehyde resin.

[0038] The reaction yield of this example is 83.8%, and the product resin is measured as follows: solid content is 67.8%, viscosity is 90s (25° C.), and free formaldehyde content is 0.4%.

[0039] Example 3

[0040] The one-pot method for synthesizing butanol etherified benzoguanamine formaldehyde resin comprises the following steps:

[0041] (1) In a 2L glass four-necked flask, 460g of butanol and 150g of 99.7% pure benzonitrile were added, and 122g of 99.7% pure dicyandiamide and 1.5g of sodium hydroxide were slowly added under stirring. The temperature was raised to reflux at a temperature between 115 and 120°C. After reflux reaction for 6h, heating was stopped and the temperature was lowered to obtain benzoguanamine.

[0042] (2) The glass four-necked flask in step (1) was cooled to 90° C., 156 g of 93% pure paraformaldehyde was added, and a 30% aqueous sodium hydroxide solution was added to adjust the pH to 8.5-9.0, and a hydroxymethylation reaction was carried out at 90-92° C. for 2.5 hours.

[0043] (3) After the reaction in step (2), phthalic anhydride is added to adjust the pH value to 5.0-5.5, and the temperature is raised to reflux at a temperature between 115-120° C. to carry out etherification reaction and dehydration. The reaction time is 4-6 hours. Sampling is started to test the tolerance at the 4th hour, and sampling is then taken every 1 hour until the tolerance reaches 5.5-6.0, then heating is stopped and the temperature is lowered.

[0044] (4) Post-treatment: Add 25g of 25% aqueous ammonia, react at 90-95°C for 1h, add 450g of pure water, heat under reflux for 1h, let stand to remove the lower layer of water, and remove the water-soluble raw materials and by-products in the product. Heat and dehydrate, and when the temperature reaches 100°C, decompress and dealcoholize under a vacuum degree of 0.03-0.04Mpa to remove the residual formaldehyde in the product, and remove 75g of butanol (the butanol can be recycled) to obtain the product butanol etherified benzoguanamine formaldehyde resin.

[0045] The reaction yield of this example is 82.9%, and the product resin is measured as follows: solid content is 68.6%, viscosity is 125s (25° C.), and free formaldehyde content is 0.65%.

[0046] Test example

[0047] The performance and application performance of the products of Examples 1-3 and Comparative Example (butylated benzoguanamine formaldehyde resin CYMEL659 produced by Allchem ​​Resins) were measured:

[0048] 1. Solid content test: According to GB1725, use an aluminum foil disc with a diameter of 70-75mm, weigh 1-1.1g of the sample to be tested, bake it at 180℃ for 15min, weigh it, and calculate the solid content.

[0049] 2. Viscosity test: According to GB / T1723, use T-4 viscosity test cup to measure the outflow time of the coating material at a temperature of 25°C.

[0050] 3. Free formaldehyde test: According to GB / T 32684-2016, weigh a certain amount of butylated benzoguanamine formaldehyde resin, add hydroxylamine hydrochloride to convert formaldehyde into oxime, and titrate the hydrochloric acid generated in the reaction with sodium hydroxide standard solution to calculate the mass fraction of free formaldehyde.

[0051] 4. Pencil hardness test: According to GB / T6739, use a Chinese pencil to measure the maximum pencil hardness that does not break the coating.

[0052] 5. Gloss test: According to GB / T 9754, use a gloss meter to measure the gloss of the coating at a 60° angle.

[0053] 6. Impact resistance test: According to GB / T 1732, use a 1Kg hammer of the impact tester to drop the coating to be tested from a height of 50cm to observe whether there are cracks in the coating after the impact.

[0054] 7. Scratch resistance test: According to GB / T 9279, use a scratch resistance tester to measure the minimum load value that can penetrate the coating, which is the scratch resistance value of the coating.

[0055] 8. Machining performance test: After the sample is made by the mold punch, it is steamed at high temperature together with the coating sample according to the steaming performance test method to observe the degree of damage of the arc position.

[0056] 9. Adhesion test: According to GB / T 1720, use a grid knife to make 6 cross grids with an interval of 1mm on the coating, then tear the grid with tape and visually observe the peeling of the coating.

[0057] 10. Retort resistance test: According to GB / T 1733, after the coating is prepared, it is steamed in a high-pressure vertical sterilizer at 127°C for 65 minutes in water phase and steam phase to observe whether the coating has abnormalities such as water vapor penetration and whitening.

[0058] The performance of the product is shown in Table 1:

[0059] Table 1 Product performance comparison

[0060]

[0061]

[0062] The products of Examples 1-3 and the products of the comparative example were applied to the three-piece can exterior coating (butylated benzoguanamine formaldehyde resin accounted for about 20% in the formula) of Fujian Herun Packaging Coating Co., Ltd. for performance comparison, as shown in Table 2 below:

[0063] Table 2 Test results of embodiments and comparative examples applied to overcoat paint

[0064]

[0065] It can be seen from Table 1 and Table 2 that the butanol-etherified benzoguanamine formaldehyde resin prepared according to the embodiment of the present invention has product performance that reaches the level of similar products of Allnex Resins Co., Ltd.

[0066] According to the method for synthesizing butanol-etherified benzoguanamine formaldehyde resin by one-pot method according to the embodiment of the present invention, the one-pot method is adopted for preparation: using dicyandiamide, benzonitrile, butanol solvent, inorganic base as catalyst to heat and synthesize benzoguanamine, after the synthesis of benzoguanamine, it does not go through butanol removal and recovery, acid neutralization, water washing, drying and crushing process, directly adding formaldehyde to carry out methylol reaction, then adding acid to carry out etherification reaction and condensation reaction under weak acidic conditions, post-treatment adding water reflux, standing and stratifying to remove water layer for purification, and then heating and dehydrating to prepare butanol-etherified benzoguanamine formaldehyde resin. The process operation steps are simple, the solvent and etherification alcohol for benzoguanamine synthesis are both n-butanol, which saves the alcohol recovery process and water washing and purification process in the preparation process of benzoguanamine, but the water washing and purification process is placed in the final product step. Compared with the traditional discontinuous production method, the total wastewater volume can be reduced by more than 70-80%, energy consumption can be saved by 20-30%, water treatment costs can be reduced, it is more environmentally friendly, and the final cost of the product is greatly reduced. In addition, the method uses 93% pure polyformaldehyde to replace the 37% formaldehyde aqueous solution used in the traditional production method, which reduces the water content in the reaction system, and adopts appropriate reaction material ratio, reaction temperature, reaction time, pH value and other process conditions to control, so that the hydroxymethylation reaction is more complete, thereby promoting the balance of etherification reaction and polycondensation reaction. The molecular weight distribution of the obtained product resin is uniform and the distribution width is narrow. 50% of the hydroxymethyl groups are etherified by n-butanol, and a certain number of active groups such as -NH and -CH2OH are retained in the molecular structure, which ensures excellent miscibility with the matrix resin, and effectively cross-links during the film-forming process, giving the coating film excellent hardness, scratch resistance, gloss, adhesion, high temperature cooking resistance and other characteristics. Furthermore, the method adopts a chemical treatment method of adding ammonia water and free formaldehyde in the reaction product to generate hexamethylenetetramine crystal precipitation, and removes free formaldehyde in the product resin by a material method of water washing, stratification and reduced pressure distillation. The treatment efficiency is high and the residual free formaldehyde can be controlled to less than 0.7%.

[0067] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms should not be understood as necessarily being directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0068] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A one-pot method for synthesizing butanol-etherified benzoguanamine formaldehyde resin, characterized in that: The following steps are involved: (1) adding high-purity dicyandiamide, high-purity benzonitrile and butanol into a reaction container, using an inorganic base as a catalyst, and fully reacting to generate benzoguanamine; (2) cooling the benzoguanamine in step (1) to 90° C., adding paraformaldehyde, and carrying out a hydroxymethylation reaction with an inorganic base as a catalyst; (3) adding an organic acid to the system after the hydroxymethylation reaction to adjust the pH value to 5.0-6.0, and heating and refluxing to carry out etherification reaction and dehydration until the tolerance is 5.5-6.0; (4) adding aqueous ammonia to the system after dehydration of the etherification reaction, reacting at 90-95° C. for 0.5-1 h, adding pure water, heating under reflux for 1 h, standing to separate the water layer, and removing the unreacted raw materials and reaction by-products remaining in the product; heating to dehydrate, and then reducing the pressure to dealcoholize to obtain a butanol-etherified benzoguanamine formaldehyde resin with a free formaldehyde content of less than 0.7%.

2. The method according to claim 1, characterized in that The inorganic base is sodium hydroxide, potassium hydroxide, aluminum hydroxide or calcium hydroxide.

3. The method according to claim 1, characterized in that In step (1), the reaction temperature is 115-125° C. and the reaction time is 3-6 hours.

4. The method according to claim 1, characterized in that In step (1), the purity of high-purity dicyandiamide and high-purity benzonitrile is 99.7%.

5. The method according to claim 1, characterized in that In step (2), the purity of paraformaldehyde is 92-98%.

6. The method according to claim 1, characterized in that In step (2), the pH is controlled to be 7-9, and the hydroxymethylation reaction is carried out at 85-95° C. for 2-3 hours.

7. The method according to claim 1, characterized in that In step (3), the organic acid is benzoic acid, phthalic anhydride, benzenesulfonic acid or acetic acid.

8. The method according to claim 1, characterized in that In step (3), the reaction time is 4-6 hours.

9. The method according to claim 1, characterized in that, in step (4), the concentration of aqueous ammonia is 20-28%.

10. The method according to claim 1, characterized in that, in step (4), the temperature is raised for dehydration, and when the temperature reaches 100°C, the decompression and de-alcoholization are carried out under a vacuum degree of 0.03-0.04 MPa.

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