A kind of methylated amino resin and its synthesis method

Abstract

The present invention discloses a methylated amino resin and its synthesis method, belonging to the technical field of amino resin preparation, and comprising the following steps: adding methanol to the hydroxymethylated intermediate product, adjusting the pH to 3 - 4.2 with acid, controlling the temperature at 60 - 65 °C, carrying out a heat preservation reaction for 3 - 4 h, then adjusting the pH to 8.8 - 9 with alkali, raising the temperature to 110 - 115 °C for distilling off water, cooling to 45 - 50 °C and adding auxiliary components, then raising the temperature to 85 °C for a constant temperature reaction for 3 - 4 h, after cooling to room temperature, standing for 4 - 6 h and then filtering, heating the filtrate under normal pressure for distillation for 1 - 2 h, then starting the vacuum system, with a vacuum degree of -0.085 MPa, carrying out heat preservation treatment at 70 °C for 3.5 - 4 h, pumping the product into the finished product kettle, adding isobutanol, and stirring evenly to obtain the methylated amino resin. Compared with the existing methylated amino resin, the content of free formaldehyde is lower, and the paint film formed after crosslinking has good toughness and good water resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of amino resins, and particularly relates to a methylated amino resin and a synthesis method thereof. Background Art

[0002] Amino resins refer to resins obtained by an addition reaction of a compound containing an -NH2 functional group with an aldehyde to obtain a compound containing a -CH2OH functional group, and then etherifying with an alcohol and simultaneously carrying out a polycondensation reaction. Due to the special chemical structure with multiple functional groups in amino resins, they are often used as crosslinking agents for various matrix resins such as alkyd resins and epoxy resins, thereby improving the properties of coatings such as gloss, hardness, and corrosion resistance.

[0003] According to different etherifying agents, amino resins are divided into methylated amino resins, butylated amino resins, and mixed etherified amino resins. Among them, compared with butylated amino resins, methylated amino resins have the characteristics of high solid content, excellent miscibility, good film-forming properties, reduced emissions, good water solubility, and less resin loss during baking, and are more economical and environmentally friendly. However, the current content of methylated amino resins is relatively high. For example, in a preparation method of a partially methylated amino resin disclosed in Chinese Patent CN104829797B, melamine and paraformaldehyde are subjected to hydroxylation reaction, and then methanol is added to form a methylated amino resin. The preparation method of this patent has a high conversion rate and safe reaction generation, but the content of free formaldehyde in the obtained methylated amino resin can only be controlled below 1.5%, which is still a relatively high content. And methylated amino resins, as crosslinking agents in coatings, are widely used in furniture wood paints and wall decorations. During the curing process, the free formaldehyde in the resin volatilizes, which is harmful to the environment and human health. Therefore, it is necessary to provide a methylated amino resin with a lower content of free formaldehyde and a synthesis method. Summary of the Invention

[0004] The purpose of the present invention is to provide a methylated amino resin and a synthesis method thereof to solve the problems in the background art.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A synthesis method of a methylated amino resin includes the following steps:

[0007] First step: Add a formaldehyde solution, a catalyst, and melamine to a reaction kettle, heat up to 60 - 65°C while stirring, then add an alkali to adjust the pH to 8.8 - 9, keep the temperature for reaction for 1 - 3 h, and then heat up to 70°C for reaction for 2 h to obtain a hydroxymethylated intermediate product;

[0008] Step 2: Add methanol to the hydroxymethylated intermediate, adjust the pH to 3 - 4.2 with acid, control the temperature at 60 - 65 °C, hold the temperature for 3 - 4 h for reaction. Then adjust the pH to 8.8 - 9 with base, raise the temperature to 110 - 115 °C for dehydration by distillation. Cool down to 45 - 50 °C and add the auxiliary component. Then raise the temperature to 85 °C for constant temperature reaction for 3 - 4 h. After cooling to room temperature, let it stand for 4 - 6 h and then filter. Heat the filtrate for atmospheric distillation for 1 - 2 h. Then turn on the vacuum system, with a vacuum degree of -0.085 MPa, hold the temperature at 70 °C for heat treatment for 3.5 - 4 h. Transfer the product to the finished product kettle, add isobutanol, and stir evenly to obtain the methylated amino resin.

[0009] As a further scheme of the present invention, the mass ratio of the formaldehyde solution, melamine, methanol and the auxiliary component is 4.6 - 5.3:1:2.6 - 4.1:1.5 - 3. The mass fraction of the formaldehyde solution is 44 - 50%, the addition amount of the catalyst is 3.5 - 5.5% of the mass of melamine, and the dosage of isobutanol is 2.5 - 3.0% of the mass of melamine.

[0010] As a further scheme of the present invention, the auxiliary component is prepared through the following steps:

[0011] Step 1: Add castor oil, glacial acetic acid and phosphoric acid into a flask, dropwise add hydrogen peroxide, control the dropping rate at 2 - 3 drops / second. After the dropping is completed, raise the temperature to 50 °C and stir for reaction for 4 h. After the reaction is completed, wash the reaction product with distilled water until neutral, and perform vacuum distillation to obtain epoxidized castor oil.

[0012] Step 2: Add the epoxidized castor oil into absolute ethanol, dropwise add the absolute ethanol solution of tetraethylenepentamine at 60 °C. After the dropping is completed, hold the temperature for reaction for 4 - 6 h. After the reaction is completed, distill out the absolute ethanol under reduced pressure to obtain the auxiliary component.

[0013] As a further scheme of the present invention, in Step 1, the mass ratio of castor oil, glacial acetic acid, phosphoric acid and hydrogen peroxide is 100:15:1:80, and the mass fraction of hydrogen peroxide is 30%.

[0014] As a further scheme of the present invention, in Step 2, the mass ratio of the epoxidized castor oil and tetraethylenepentamine is 100:25 - 27, and the ethanol solution of tetraethylenepentamine is composed of tetraethylenepentamine and absolute ethanol according to the dosage ratio of 1 g:5 - 8 mL.

[0015] The present invention uses an oxidation system composed of glacial acetic acid, phosphoric acid and hydrogen peroxide to oxidize the unsaturated double bonds in the structure of castor oil into epoxy groups to obtain epoxidized castor oil. Then, the epoxy groups on the molecular chain of epoxidized castor oil react with the amino groups in tetraethylenepentamine to undergo ring-opening reaction, introducing a multi-amino structure and forming new hydroxyl groups. Combining with the hydroxyl groups in castor oil itself, a modified castor oil rich in hydroxyl and amino groups, that is, the auxiliary component, is obtained.

[0016] As a further solution of the present invention, the catalyst is phthalic anhydride or phthalic anhydride.

[0017] As a further solution of the present invention, the base is one or more of sodium hydroxide, potassium bicarbonate, and sodium bicarbonate.

[0018] As a further solution of the present invention, the acid is one or more of formic acid, oxalic acid, hydroiodic acid, iodic acid, nitrous acid, sulfurous acid, and hypochlorous acid.

[0019] As a further solution of the present invention, a methylated amino resin is prepared by the above synthesis method.

[0020] Advantages of the present invention:

[0021] 1. The present invention uses paraformaldehyde and melamine as the main raw materials, methanol as the etherifying agent, and auxiliary components as additives. With a specific raw material ratio, through the method of chemical synthesis and modification, the obtained methylated amino resin has a lower free formaldehyde content compared with the existing methylated amino resin, and the paint film formed after cross-linking has good toughness and water resistance.

[0022] 2. The present invention uses castor oil as the substrate, and through epoxidation reaction and ring-opening reaction, an auxiliary component is obtained. This auxiliary component contains rich hydroxyl groups, amino groups, and flexible alkyl long chains. The presence of numerous hydroxyl and amino groups can undergo a condensation reaction with the free formaldehyde in the synthetic resin system, reducing the formaldehyde content, and introducing flexible alkyl long chains to improve the toughness and water resistance of the paint film after cross-linking. Specific embodiments

[0023] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0024] Example 1

[0025] This example provides an auxiliary component, which is prepared through the following steps:

[0026] Step 1: Add 100 g of castor oil, 15 g of glacial acetic acid, and 80 g of phosphoric acid into a flask, dropwise add hydrogen peroxide, control the dropping rate at 2 drops / second. After the dropping is completed, raise the temperature to 50 °C and stir for 4 h. After the reaction is completed, wash the reaction product with distilled water until neutral, and perform vacuum distillation to obtain epoxy castor oil. The mass fraction of hydrogen peroxide is 30%.

[0027] Step 2: Add 100 g of epoxy castor oil into 1000 mL of absolute ethanol. At 60°C, dropwise add an absolute ethanol solution containing 25 g of tetraethylenepentamine. After the addition is complete, keep the temperature for reaction for 4 h. After the reaction is over, distill off the absolute ethanol under reduced pressure to obtain the auxiliary component. The ethanol solution of tetraethylenepentamine is composed of tetraethylenepentamine and absolute ethanol according to the dosage ratio of 1 g:5 mL.

[0028] Example 2

[0029] This example provides an auxiliary component, which is prepared through the following steps:

[0030] Step 1: Add 100 g of castor oil, 15 g of glacial acetic acid and 80 g of phosphoric acid into a flask. Dropwise add hydrogen peroxide, control the dropping rate at 3 drops per second. After the addition is complete, raise the temperature to 50°C and stir for reaction for 4 h. After the reaction is over, wash the reaction product with distilled water until neutral, and then distill under reduced pressure to obtain epoxy castor oil. The mass fraction of hydrogen peroxide is 30%;

[0031] Step 2: Add 100 g of epoxy castor oil into 1000 mL of absolute ethanol. At 60°C, dropwise add an absolute ethanol solution containing 27 g of tetraethylenepentamine. After the addition is complete, keep the temperature for reaction for 6 h. After the reaction is over, distill off the absolute ethanol under reduced pressure to obtain the auxiliary component. The ethanol solution of tetraethylenepentamine is composed of tetraethylenepentamine and absolute ethanol according to the dosage ratio of 1 g:8 mL.

[0032] Example 3

[0033] A synthesis method of a methylated amino resin, comprising the following steps:

[0034] The first step: Add 46 g of formaldehyde solution, a catalyst and 10 g of melamine into a reaction kettle. While stirring, raise the temperature to 60°C, then add alkali to adjust the pH to 8.8. After keeping the temperature for reaction for 1 h, raise the temperature to 70°C and react for 2 h to obtain a hydroxymethylated intermediate product. The mass fraction of the formaldehyde solution is 44%, and the addition amount of the catalyst is 3.5% of the mass of melamine;

[0035] The second step: Add 26 g of methanol to the hydroxymethylated intermediate product, add acid to adjust the pH to 3, control the temperature at 60°C, keep the temperature for reaction for 3 h. Then add alkali to adjust the pH to 8.8, raise the temperature to 110°C to distill off water, cool down to 45°C and add 15 g of the auxiliary component of Example 1. Then raise the temperature to 85°C and keep the temperature for reaction for 3 h. After cooling to room temperature, let it stand for 4 h and then filter. Heat the filtrate and distill it under normal pressure for 1 h. Then turn on the vacuum system, with a vacuum degree of -0.085 MPa, keep the temperature at 70°C for heat treatment for 3.5 h. Transfer the product to a finished product kettle, add isobutanol, and the dosage of isobutanol is 2.5% of the mass of melamine. After stirring evenly, obtain the methylated amino resin.

[0036] Among them, the catalyst is phthalic anhydride, the base is sodium hydroxide, and the acid is formic acid.

[0037] Example 4

[0038] A method for synthesizing a methylated amino resin, comprising the following steps:

[0039] First step: Add 50 g of formaldehyde solution, a catalyst, and 10 g of melamine to a reaction kettle, heat up to 63 °C while stirring, then add a base to adjust the pH to 9, keep the temperature for reaction for 2 h, then heat up to 70 °C and react for 2 h to obtain a hydroxymethylated intermediate product. The mass fraction of the formaldehyde solution is 48%, and the addition amount of the catalyst is 4.5% of the mass of melamine.

[0040] Second step: Add 30 g of methanol to the hydroxymethylated intermediate product, add an acid to adjust the pH to 4, control the temperature at 63 °C, keep the temperature for reaction for 3.5 h, then add a base to adjust the pH to 9, heat up to 112 °C for dehydration by distillation, cool down to 48 °C, add 23 g of the auxiliary component of Example 2, then heat up to 85 °C and keep the temperature for reaction for 3.5 h. After cooling to room temperature, let it stand for 5 h and then filter. The filtrate is heated under normal pressure for distillation for 1.5 h, then the vacuum system is turned on, the vacuum degree is -0.085 MPa, and it is kept at 70 °C for heat treatment for 3.8 h. The product is pumped into a finished product kettle, and isobutanol is added. The dosage of isobutanol is 2.8% of the mass of melamine. After stirring evenly, a methylated amino resin is obtained.

[0041] Among them, the catalyst is phthalic anhydride, the base is potassium bicarbonate, and the acid is oxalic acid.

[0042] Example 5

[0043] A method for synthesizing a methylated amino resin, comprising the following steps:

[0044] First step: Add 53 g of formaldehyde solution, a catalyst, and 10 g of melamine to a reaction kettle, heat up to 65 °C while stirring, then add a base to adjust the pH to 9, keep the temperature for reaction for 3 h, then heat up to 70 °C and react for 2 h to obtain a hydroxymethylated intermediate product. The mass fraction of the formaldehyde solution is 50%, and the addition amount of the catalyst is 5.5% of the mass of melamine.

[0045] Step 2: Add 41 g of methanol to the hydroxymethylated intermediate, adjust the pH to 4.2 with acid, control the temperature at 65 °C, keep the temperature for 4 h, then adjust the pH to 9 with base, raise the temperature to 115 °C for dehydration by distillation, cool down to 50 °C, add 30 g of the auxiliary component of Example 2, then raise the temperature to 85 °C for constant temperature reaction for 4 h. After cooling to room temperature, let it stand for 6 h and then filter. Heat the filtrate for normal pressure distillation for 2 h, then turn on the vacuum system, with a vacuum degree of -0.085 MPa, keep the temperature at 70 °C for heat treatment for 4 h. Transfer the product to the finished product kettle, add isobutanol, and the amount of isobutanol used is 3.0% of the mass of melamine. After stirring evenly, a methylated amino resin is obtained.

[0046] Among them, the catalyst is phthalic anhydride, the base is sodium hydroxide, and the acid is sulfurous acid.

[0047] Comparative Example 1

[0048] This comparative example provides a methylated amino resin. Compared with Example 3, the auxiliary component is not added, and the other raw materials and preparation process are the same as those in Example 3.

[0049] Perform performance tests on the methylated amino resins obtained by the synthesis methods of Example 3, Example 4, Example 5 and Comparative Example 1. The test contents are as follows:

[0050] I. Determine the product indexes of the methylated amino resins obtained in the examples and comparative examples

[0051] 1) Determination of free formaldehyde content: Determine the free formaldehyde content in the resin according to the method for determining the free formaldehyde content in resin finishing agents (GB / T 5544 - 85). The test results are shown in Table 1;

[0052] 2) Determination of solid content: The test method for solid content is determined according to GB / T 1725 - 1979. The test results are shown in Table 1;

[0053] 3) Viscosity determination: Use a digital display viscometer NDJ - 8S to test the apparent viscosity of the methylated amino resin. The viscosity value is tested under the condition of 25 ± 0.5 °C, and the unit is mPa·s. The test results are shown in Table 1;

[0054] II. Using the methylated amino resins obtained from the examples and comparative examples as crosslinking agents respectively, mix 60 g of alkyd resin and 40 g of crosslinking agent evenly, add 60 g of toluene for dilution, add 3.7 g of p-toluenesulfonic acid as the acid curing agent, 0.1 g of BYK071 as the defoaming agent, and 0.1 g of BYK358 as the leveling agent, stir evenly to obtain paint samples. Use sandpaper to polish several iron sheets, remove the surface stains, then wash and dry them for standby. Immerse the iron sheets in each group of paints respectively and make the paint evenly cover the surface of the iron sheets, and let it stand at room temperature for 30 min; Gently touch the surface of the paint film with your finger. If you feel a bit sticky but not sticky to the finger and no paint sticks to the finger, then the paint film is surface dry. Then put the iron sheets into a constant temperature blast drying oven at 130 °C and dry for 30 min. Test the adhesion, impact resistance, flexibility, and corrosion resistance of the paint films on the iron sheets respectively;

[0055] Test the adhesion of the paint film according to GB / T 1720-79(89), and evaluate the adhesion according to the integrity of the paint film within the circular rolling line scratch range. The adhesion is divided into grades 1-7, where grade 1 is the best, indicating that the paint film is intact, and grade 7 is the worst. The test results are shown in Table 2;

[0056] Conduct flexibility detection according to the provisions of GB / T1731-1993, and the test results are shown in Table 2;

[0057] Conduct water resistance detection according to the provisions of GB / T1733-93, and the test results are shown in Table 2;

[0058] Table 1

[0059] Project Example 3 Example 4 Example 5 Comparative Example 1 Free formaldehyde content / % 0.13 0.11 0.08 0.62 Solid content / % 82.4 83.1 85.6 80.6 Viscosity / mPa·s 2680 2715 2787 2633

[0060] As can be seen from Table 1, the properties of the methylated amino resins obtained in Example 3, Example 4, and Example 5 not only meet the usage indicators, but also have extremely low formaldehyde content compared to Comparative Example 1, which is environmentally friendly and healthy.

[0061] Table 2

[0062]

[0063]

[0064] As can be seen from Table 2, compared with Comparative Example 1, the methylated amino resins obtained in Example 3, Example 4, and Example 5 not only have high adhesion, but also have good flexibility and outstanding oil resistance, and have high practical value.

[0065] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0066] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for synthesizing a methylated amino resin, characterized in that, It includes the following steps: First step: Add formaldehyde solution, catalyst and melamine into the reactor, heat up to 60 - 65 °C while stirring, then add alkali to adjust the pH to 8.8 - 9, keep the temperature for reaction for 1 - 3 h and then heat up to 70 °C for reaction for 2 h to obtain the hydroxymethylated intermediate product; Second step: Add methanol into the hydroxymethylated intermediate product, add acid to adjust the pH to 3 - 4.2, control the temperature at 60 - 65 °C, keep the temperature for reaction for 3 - 4 h, then add alkali to adjust the pH to 8.8 - 9, heat up to 110 - 115 °C for dehydration by distillation, cool down to 45 - 50 °C and add the auxiliary component, then heat up to 85 °C for constant temperature reaction for 3 - 4 h, after cooling to room temperature, stand for 4 - 6 h and then filter, heat the filtrate for atmospheric distillation for 1 - 2 h, then start the vacuum system, keep the vacuum degree at -0.085 MPa and keep the temperature at 70 °C for heat treatment for 3.5 - 4 h, pump the product into the finished product kettle, add isobutanol, stir evenly to obtain the methyl etherified amino resin; The auxiliary component is prepared through the following steps: Step 1: Add castor oil, glacial acetic acid and phosphoric acid into the flask, dropwise add hydrogen peroxide solution, control the dropping rate at 2 - 3 drops / second, after the dropping is completed, heat up to 50 °C and stir for reaction for 4 h, after the reaction is completed, wash the reaction product with distilled water until neutral, and perform vacuum distillation to obtain epoxy castor oil; Step 2: Add epoxy castor oil into absolute ethanol, dropwise add the ethanol solution of tetraethylenepentamine at 60 °C, after the dropping is completed, keep the temperature for reaction for 4 - 6 h, after the reaction is completed, distill out absolute ethanol under reduced pressure to obtain the auxiliary component.

2. The synthesis method of a methylated amino resin according to claim 1, characterized in that, The mass ratio of the formaldehyde solution, melamine, methanol and the auxiliary component is 4.6 - 5.3:1:2.6 - 4.1:1.5 - 3, and the mass fraction of the formaldehyde solution is 44 - 50%.

3. The synthesis method of a methylated amino resin according to claim 1, characterized in that, The addition amount of the catalyst is 3.5 - 5.5% of the mass of melamine.

4. The synthesis method of a methylated amino resin according to claim 1, characterized in that, The dosage of isobutanol is 2.5 - 3.0% of the mass of melamine.

5. The synthesis method of a methylated amino resin according to claim 1, characterized in that, In step 1, the mass ratio of castor oil, glacial acetic acid, phosphoric acid and hydrogen peroxide solution is 100:15:1:80, and the mass fraction of hydrogen peroxide solution is 30%.

6. The synthesis method of a methylated amino resin according to claim 1, characterized in that, In step 2, the mass ratio of epoxy castor oil and tetraethylenepentamine is 100:25 - 27, and the ethanol solution of tetraethylenepentamine is composed of tetraethylenepentamine and absolute ethanol according to the dosage ratio of 1 g:5 - 8 mL.

7. The synthesis method of a methylated amino resin according to claim 1, characterized in that, The catalyst is phthalic anhydride.

8. An etherified amino resin, characterized in that, It is prepared by the synthesis method described in any one of claims 1 - 7.

Images