CN112708088B - Melamine resin and preparation method and application thereof - Google Patents
Melamine resin and preparation method and application thereof Download PDFInfo
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- CN112708088B CN112708088B CN202110026204.2A CN202110026204A CN112708088B CN 112708088 B CN112708088 B CN 112708088B CN 202110026204 A CN202110026204 A CN 202110026204A CN 112708088 B CN112708088 B CN 112708088B
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- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G12/00—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
- C08G12/02—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes
- C08G12/40—Chemically modified polycondensates
- C08G12/42—Chemically modified polycondensates by etherifying
- C08G12/424—Chemically modified polycondensates by etherifying of polycondensates based on heterocyclic compounds
- C08G12/425—Chemically modified polycondensates by etherifying of polycondensates based on heterocyclic compounds based on triazines
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Abstract
The invention relates to the technical field of amino resin preparation, and particularly relates to melamine resin and a preparation method and application thereof. The preparation method of the melamine resin comprises the following steps: (1) mixing and stirring melamine, formaldehyde and water, then heating, and adjusting the pH value to obtain a hydroxymethyl monomer solution; (2) adding the hydroxymethyl monomer solution into a sulfonic acid compound solution, and continuously stirring to obtain a prepolymer solution; (3) and adding the epoxy compound into the prepolymer solution, and continuously stirring to obtain the melamine resin. The preparation method has the advantages that through measures of reducing the using amount of formaldehyde in the raw materials, reducing the generation of methylene ether bonds and the like, the content of the formaldehyde is greatly reduced, simultaneously, the water solubility and the storage stability of the product are improved, and the problems of high cost, reduced application performance and the like are solved.
Description
Technical Field
The invention relates to the technical field of amino resin preparation, and particularly relates to melamine resin and a preparation method and application thereof.
Background
Retanning plays an important role in leather making, can change the tissue dispersion state of collagen fibers of skins, improve the quality of finished leather, improve the surface charge of the collagen fibers and provide conditions for permeation and absorption of subsequent materials. In the prior art, amino resin represented by melamine resin is widely used in the retanning process, but the traditional melamine resin often has the problem that the content of free formaldehyde exceeds the standard, so that the further application of the melamine resin is greatly limited.
The free formaldehyde in the melamine resin mainly comes from two aspects, firstly, unreacted formaldehyde remains in the system after the reaction is finished, because the amino-containing compound and the formaldehyde carry out reversible reaction, excessive formaldehyde is often needed to promote the forward progress of the reaction in the resin synthesis process, and therefore, a part of formaldehyde remains in the system; and secondly, the new free formaldehyde generated in the using process of the amino resin is generated because the stability of hydroxymethyl bonds, methylene ether bonds and the like generated in the synthesis process of the amino resin is low, and the formaldehyde can be generated by continuous hydrolysis in the using process.
The preparation of low-formaldehyde melamine resin is always the focus of research in recent years, and the existing production process usually adopts measures of changing the synthesis process, adding a formaldehyde scavenger, using substituted aldehydes and the like to reduce the formaldehyde content in the finished product. Although the above method has a certain effect, there are problems such as an increase in product cost and a decrease in application performance.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
The first purpose of the invention is to provide a preparation method of melamine resin, which greatly reduces the content of formaldehyde, improves the water solubility and storage stability of the product, and solves the problems of high cost, reduced application performance and the like by measures of reducing the dosage of formaldehyde in raw materials, reducing the generation of methylene ether bonds and the like.
The second purpose of the invention is to provide the melamine resin, which is prepared by the preparation method. The melamine resin has good water solubility, low free formaldehyde content and excellent liquid stability.
In order to achieve the above purpose of the present invention, the following technical solutions are adopted:
a preparation method of melamine resin comprises the following steps:
(1) mixing and stirring melamine, formaldehyde and water, then heating, and adjusting the pH value to obtain a hydroxymethyl monomer solution;
(2) adding the hydroxymethyl monomer solution into a sulfonic acid compound solution, and continuously stirring to obtain a prepolymer solution;
(3) and adding the epoxy compound into the prepolymer solution, and continuously stirring to obtain the melamine resin.
The melamine resin prepared by the prior art often has the problem of excessive content of free formaldehyde. In order to reduce the content of formaldehyde, people usually adopt measures such as changing the synthesis process, adding a formaldehyde scavenger, using alternative aldehydes and the like to reduce the content of formaldehyde in the finished product. Although the above method has a certain effect, there are problems such as an increase in product cost and a decrease in application performance.
The invention provides a preparation method of melamine resin, which solves the problems of cost increase, application performance reduction and the like while greatly reducing the content of formaldehyde by measures of reducing the dosage of formaldehyde in raw materials, reducing the generation of methylene ether bond and the like.
Firstly, the method innovatively uses excessive melamine to react with formaldehyde, so that the conversion rate of the formaldehyde in reactants can be greatly improved, and the content of unreacted residual formaldehyde is reduced.
Then, the invention changes the traditional method of crosslinking by hydroxymethyl condensation polymerization, and adds sulfonic acid compound during condensation polymerization, and introduces amino and sulfonic acid group into the system, thereby further consuming residual formaldehyde on one hand, and reducing the generation of methylene ether bond by blocking hydroxymethyl through amino on the other hand. Meanwhile, the water solubility of the system can be improved by introducing sulfonic acid groups.
Finally, in order to make up the problems of small molecular weight of the product, poor filling effect of the retanning agent and the like caused by the reduction of the degree of the polycondensation reaction between the hydroxymethyl groups, the invention introduces an epoxy compound in the final stage of the reaction, increases the molecular weight of the product and improves the filling effect through the reaction of an epoxy group and active groups such as the hydroxymethyl group, the amino group and the like. In addition, the addition of the epoxy compound can further consume unreacted hydroxymethyl in the system, thereby achieving the aim of improving the storage stability of the product.
Preferably, the mass ratio of the melamine to the formaldehyde to the sulfonic acid compound to the epoxy compound is 5-15: 2-8: 8-40: 1-6.
More preferably, the mass ratio of the melamine, the formaldehyde, the water, the sulfonic acid compound and the epoxy compound is 5-15: 2-8: 20-60: 8-40: 1-6.
The melamine resin with better performance and less formaldehyde content can be prepared by adopting the raw materials in the proportioning range.
Preferably, in step (1), the formaldehyde comprises: one of a formaldehyde solution and paraformaldehyde.
Preferably, in the step (1), the temperature is raised to 60-80 ℃.
Preferably, in step (1), the pH is adjusted to 8.0-9.0.
Preferably, in the step (1), the stirring time is 40-120 min.
With the above-mentioned range of parameters, a more satisfactory methylol monomer solution can be obtained.
Preferably, in the step (2), the sulfonic acid compound includes: one of sulfanilic acid and sodium sulfanilate.
Preferably, in the step (2), before the hydroxymethyl monomer solution is added to the sulfonic acid compound solution, a step of adjusting the pH of the sulfonic acid compound solution is further included.
More preferably, the pH of the sulfonic acid compound solution is adjusted to 5.0 to 6.0.
Preferably, the hydroxymethyl monomer is added dropwise.
Preferably, in the step (2), the stirring time is 30-60 min.
With the parameters in the above range, prepolymer solutions more satisfactory can be prepared.
Preferably, in the step (3), the epoxy compound includes: glycidyl ether, glycidyl amine, glycidyl ester and epoxidized vegetable oil.
More preferably, the glycidyl ether is glycerol triglycidyl ether.
More preferably, the glycidylamine is 4- (2, 3-glycidoxy) -N, N-bis (2, 3-epoxypropyl) aniline.
More preferably, the glycidyl ester is 4, 5-epoxy tetrahydrophthalic acid diglycidyl ester.
More preferably, the epoxidized vegetable oil is epoxidized soybean oil.
The melamine resin with more excellent performance can be prepared by selecting the raw materials.
Preferably, in the step (3), the stirring time is 120-240 min.
The melamine resin which meets the requirements can be prepared by adopting the parameters.
The preparation method of the melamine resin provided by the invention is simple to operate, mild in condition and low in raw material cost, and is beneficial to further popularization and application of products.
The melamine resin is prepared by the preparation method.
The melamine resin has good water solubility, low free formaldehyde content and excellent liquid stability.
The melamine resin is applied to leather industry, textile industry, optical materials, resin materials, plastics and packaging materials.
Preferably, the melamine resin is used in the leather industry as a retanning agent.
The amino resin represented by the melamine resin is widely used in the retanning process, and the melamine resin provided by the invention has good water solubility, low free formaldehyde content and excellent liquid stability, and is beneficial to further application and popularization of the melamine resin in the retanning process.
Compared with the prior art, the invention has the beneficial effects that:
(1) the preparation method of the melamine resin provided by the invention innovatively uses excessive melamine to react with formaldehyde, greatly reduces the formaldehyde consumption in the raw materials, can effectively improve the conversion efficiency of the formaldehyde, and reduces the content of free formaldehyde in the product.
(2) According to the preparation method of the melamine resin, the sulfonic acid compound is introduced to participate in the polycondensation reaction of the hydroxymethyl group, so that the generation of methylene ether bonds can be effectively reduced, and further, the free formaldehyde generated in the use process of the melamine resin is reduced. Meanwhile, the water solubility of the system is improved by introducing sulfonic acid groups.
(3) According to the preparation method of the melamine resin, the epoxy compound is introduced, and the molecular weight of the product is improved and the filling effect is improved through the reaction of the epoxy group and active groups such as hydroxymethyl and amino. Meanwhile, the addition of the epoxy compound further consumes unreacted hydroxymethyl in the system, so that the storage stability of the product can be improved.
(4) The preparation method of the melamine resin provided by the invention is simple to operate, mild in condition and low in raw material cost, and is beneficial to further popularization and application of products.
(5) The melamine resin prepared by the preparation method provided by the invention has good water solubility, low free formaldehyde content and excellent liquid stability.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 shows an IR spectrum of a melamine resin provided in example 1 of the present invention.
Detailed Description
The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and the detailed description, but those skilled in the art will understand that the following described embodiments are some, not all, of the embodiments of the present invention, and are only used for illustrating the present invention, and should not be construed as limiting the scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
Example 1
The preparation method of the melamine resin provided in this embodiment includes the following steps:
(1) weighing 50g of melamine and 20g of paraformaldehyde, placing the melamine and the paraformaldehyde into a three-neck flask, adding 100g of water, uniformly stirring, heating to 60 ℃, continuously stirring for 40min, and continuously adjusting the pH value of the system to 8 to obtain a hydroxymethyl monomer solution;
(2) weighing 81g of sulfanilic acid, dissolving in 120g of water, adjusting the pH value to 6 to obtain a sulfonic acid compound solution, dropwise adding the hydroxymethyl monomer solution into the sulfonic acid compound solution, and continuously stirring for 60min to obtain a prepolymer solution;
(3) and weighing 15g of glycerol triglycidyl ether, adding the glycerol triglycidyl ether into the prepolymer solution, and continuously stirring for 120min to obtain the melamine resin.
Example 2
The preparation method of the melamine resin provided in this embodiment includes the following steps:
(1) weighing 80g of melamine and 55g of formaldehyde solution, placing the melamine and the formaldehyde solution in a three-neck flask, adding 100g of water, uniformly stirring, heating to 65 ℃, continuously stirring for 60min, and continuously adjusting the pH value of the system to 8.3 during the stirring to obtain a hydroxymethyl monomer solution;
(2) weighing 220g of sodium sulfanilate, dissolving in 230g of water, adjusting the pH value to 5.7 to obtain a sulfonic acid compound solution, dropwise adding the hydroxymethyl monomer solution into the sulfonic acid compound solution, and continuously stirring for 45min to obtain a prepolymer solution;
(3) and (3) weighing 14g of 4- (2, 3-epoxypropoxy) -N, N-di (2, 3-epoxypropyl) aniline, adding the weighed materials into the prepolymer solution, and continuously stirring for 160min to obtain the melamine resin.
Example 3
The preparation method of the melamine resin provided in this embodiment includes the following steps:
(1) weighing 120g of melamine and 100g of paraformaldehyde, putting the melamine and the paraformaldehyde into a three-neck flask, adding 100g of water, uniformly stirring, heating to 76 ℃, continuously stirring for 100min, and continuously adjusting the pH value of the system to 8.8 during the stirring to obtain a hydroxymethyl monomer solution;
(2) weighing 400g of sodium sulfanilate, dissolving the sodium sulfanilate in 450g of water, adjusting the pH value of the water sulfanilate to 5.0 to obtain a sulfonic acid compound solution, dropwise adding the hydroxymethyl monomer solution into the sulfonic acid compound solution, and continuously stirring for 30min to obtain a prepolymer solution;
(3) and weighing 62g of epoxidized soybean oil, adding the weighed epoxidized soybean oil into the prepolymer solution, and continuously stirring for 180min to obtain the melamine resin.
Example 4
The preparation method of the melamine resin provided in this embodiment includes the following steps:
(1) weighing 100g of melamine and 70g of paraformaldehyde, placing the melamine and the paraformaldehyde in a three-neck flask, adding 200g of water, uniformly stirring, heating to 71 ℃, continuously stirring for 75min, and continuously adjusting the pH value of the system to 8.5 to obtain a hydroxymethyl monomer solution;
(2) weighing 280g of sodium sulfanilate, dissolving the sodium sulfanilate in 250g of water, adjusting the pH value of the water sulfanilate to 5.5 to obtain a sulfonic acid compound solution, dropwise adding the hydroxymethyl monomer solution into the sulfonic acid compound solution, and continuously stirring for 40min to obtain a prepolymer solution;
(3) 31.5g of glycerol triglycidyl ether is weighed and added into the prepolymer solution, and the mixture is continuously stirred for 150min to obtain the melamine resin.
Example 5
The preparation method of the melamine resin provided in this embodiment includes the following steps:
(1) weighing 150g of melamine and 75g of formaldehyde solution, placing the melamine and the formaldehyde solution in a three-neck flask, adding 250g of water, uniformly stirring, heating to 80 ℃, continuously stirring for 120min, and continuously adjusting the pH value of the system to 9.0 during the stirring to obtain a hydroxymethyl monomer solution;
(2) weighing 280g of sulfanilic acid, dissolving in 350g of water, adjusting the pH value to 5.2 to obtain a sulfonic acid compound solution, dropwise adding the hydroxymethyl monomer solution into the sulfonic acid compound solution, and continuously stirring for 30min to obtain a prepolymer solution;
(3) and weighing 25g of 4, 5-epoxy tetrahydrophthalic acid diglycidyl ester, adding the weighed 4, 5-epoxy tetrahydrophthalic acid diglycidyl ester into the prepolymer solution, and continuously stirring for 240min to obtain the melamine resin.
Comparative example 1
The preparation method of the melamine resin provided by the comparative example comprises the following steps:
(1) weighing 50g of melamine and 100g of paraformaldehyde, placing the melamine and the paraformaldehyde in a three-neck flask, adding 200g of water, uniformly stirring, heating to 60 ℃, continuously stirring for 40min, and continuously adjusting the pH value of the system to 8 to obtain a hydroxymethyl monomer solution;
(2) weighing 60g of sulfanilic acid, dissolving in 200g of water, adjusting the pH value to 3.5 to obtain a sulfonic acid compound solution, dropwise adding the hydroxymethyl monomer solution into the sulfonic acid compound solution, and continuously stirring for 20min to obtain a prepolymer solution;
(3) and (3) weighing 5g of glycerol triglycidyl ether, adding the glycerol triglycidyl ether into the prepolymer solution, and continuously stirring for 300min to obtain the melamine resin.
Comparative example 2
The preparation method of the melamine resin provided by the comparative example comprises the following steps:
(1) weighing 50g of melamine and 100g of paraformaldehyde, placing the melamine and the paraformaldehyde in a three-neck flask, adding 200g of water, uniformly stirring, heating to 60 ℃, continuously stirring for 40min, and continuously adjusting the pH value of the system to 8 to obtain a hydroxymethyl monomer solution;
(2) adjusting the pH value of the hydroxymethyl monomer solution to 3.5, and continuously stirring for 20min to obtain a prepolymer solution;
(3) weighing 15g N, N, N ', N ' -tetracyclooxypropyl-4, 4' -diaminodiphenylmethane, adding into the prepolymer solution, and continuously stirring for 120min to obtain melamine resin.
Comparative example 3
The preparation method of the melamine resin provided by the comparative example comprises the following steps:
(1) weighing 50g of melamine and 20g of paraformaldehyde, placing the melamine and the paraformaldehyde into a three-neck flask, adding 100g of water, uniformly stirring, heating to 60 ℃, continuously stirring for 40min, and continuously adjusting the pH value of the system to 8 to obtain a hydroxymethyl monomer solution;
(2) 81g of sulfanilic acid is weighed and dissolved in 120g of water, the pH value of the water is adjusted to 6, a sulfonic acid compound solution is obtained, then the hydroxymethyl monomer solution is dropwise added into the sulfonic acid compound solution, and the stirring is continued for 60min, so that the melamine resin is obtained.
Test example 1
The melamine resin prepared in example 1 of the present invention was subjected to an infrared spectrum test, and the test results are shown in fig. 1. In FIG. 1, a represents an infrared spectrum of melamine, b represents an infrared spectrum of a prepolymer, and c represents an infrared spectrum of a melamine resin.
The map relating to FIG. 1 is explained as follows: 3468cm in the figure for melamine a-1And 3418cm-1In the corresponding melamine to-NH2The two peaks disappear after the reaction and are replaced by 3352cm in the infrared spectrum of the product-1A new wider characteristic absorption peak appears, which corresponds to the stretching vibration peak of-OH, and proves that the melamine reacts with the formaldehyde. At the same time, 2924cm-1The new peak appears is the characteristic absorption peak of methylene generated after the reaction of the formaldehyde and the melamine, and the reaction of the melamine and the formaldehyde is explained again.
After sodium sulfanilate is introduced to participate in the reaction, the prepolymer b is 3374cm-1And 3319cm-1There is no primary amino group (-NH)2) The fermi characteristic absorption peak proves that the amino group of the sodium sulfanilate successfully reacts with the hydroxymethyl group. While 1176cm in b-1And 1033cm-1The positions are respectively an asymmetric stretching vibration peak and a symmetric stretching vibration peak of an S ═ O bond in the sulfonic acid group, and the sulfonic acid group is introduced into the product.
1122cm in melamine resin c-1The peak at (A) corresponds to the characteristic absorption peak of the tertiary amine in the epoxy compound. After introduction of the epoxy compound, the melamine resin c was present at 915cm-1The characteristic absorption peak of the epoxy group does not appear, which shows that the epoxy group successfully reacts with active groups such as amino, hydroxymethyl and the like in the system. In addition, 1353cm in prepolymer b and melamine resin c-1The peak corresponds to the skeleton vibration of the benzene ring, which shows that the benzene ring exists in the structures of the prepolymer b and the melamine resin c.
Therefore, the melamine resin containing the structures of hydroxyl, sulfonic acid group, triazine ring, benzene ring and the like is successfully prepared in the embodiment 1 of the invention.
Test example 2
The melamine resins prepared in examples 1 to 5 and comparative examples 1 to 3 were used as retanning agents to retanned cow leather shoe upper leather, and indicators of formaldehyde content, softness and thickening rate of the leather after retanning were tested.
The test method is as follows: putting the uniformly-cut blue leather of the raw material of the cowhide upper leather into a rotary drum, sequentially softening, retanning, neutralizing and washing by a conventional process, then adding a formaldehyde-free melamine resin retanning agent accounting for 8% of the weight of the blue leather and 100% of water, rotating the blue leather for 1 hour at the temperature of 35 ℃ and the pH value of 5.0-5.5, and then completing the retanning process by a conventional greasing and fixing process. And finally, according to the standard GB/T19941-2005 'determination of formaldehyde content in leather and fur chemical experiments', the formaldehyde content in the leather after retanning is determined by using a high performance liquid chromatography.
The test results were as follows:
1. by adopting the melamine resin prepared in the example 1 as the retanning agent, the softness of the wet cowhide blue leather after being subjected to retanning filling is 8.18mm, the thickening rate is 11.24%, and the leather after being subjected to retanning has good body and bone and excellent comprehensive performance. The formaldehyde content in the leather after retanning is 49.52mg/kg, and the requirement of direct contact with the skin in GB 20400-2006 can be met.
2. By adopting the melamine resin prepared in the example 2 as the retanning agent, the softness of the wet cowhide blue leather after being subjected to retanning filling is 8.31mm, the thickening rate is 12.90%, and the absorptivity of the retanning agent reaches 92.73%. The formaldehyde content in the leather after retanning is 31.59mg/kg, and the requirement of direct contact with the skin in GB 20400-2006 can be met.
3. By adopting the melamine resin prepared in the embodiment 3 as the retanning agent, the softness of the wet cowhide blue leather after being subjected to retanning filling is 8.52mm, the thickening rate is 13.80%, and the leather after being subjected to retanning is soft and plump and has excellent comprehensive performance. The formaldehyde content in the leather after retanning is 62.20mg/kg, and the requirement of direct contact with the skin in GB 20400-2006 can be met.
4. By adopting the melamine resin prepared in the example 4 as the retanning agent, the softness of the wet cowhide blue leather after being subjected to retanning filling is 8.57mm, the thickening rate is 12.46%, and the leather after being subjected to retanning is soft and plump and has excellent comprehensive performance. The formaldehyde content in the leather after retanning is 35.28mg/kg, and the requirement of direct contact with the skin in GB 20400-2006 can be met.
5. By adopting the melamine resin prepared in the example 5 as the retanning agent, the softness of the wet cowhide blue leather after being subjected to retanning filling is 8.42mm, the thickening rate is 11.57%, and the leather after being subjected to retanning is soft and plump and has excellent comprehensive performance. The formaldehyde content in the leather after retanning is 54.93mg/kg, and the requirement of direct contact with the skin in GB 20400-2006 can be met.
6. By adopting the melamine resin prepared in the comparative example 1 as the retanning agent, the softness of the wet cowhide blue leather after being subjected to retanning filling is 8.06mm, the thickening rate is 12.82%, and the formaldehyde content in the leather after being subjected to retanning is 187mg/kg, so that the requirement of the formaldehyde content in direct contact with the skin in GB 20400-.
7. By adopting the melamine resin prepared in the comparative example 2 as the retanning agent, the softness of the wet cowhide blue leather after being subjected to retanning filling is 8.13mm, the thickening rate is 7.19%, and the formaldehyde content in the leather after being subjected to retanning is 219mg/kg, which cannot meet the requirement of the GB 20400-2006 on the formaldehyde content directly contacting the skin.
8. By adopting the melamine resin prepared in the comparative example 3 as the retanning agent, the softness of the wet cowhide blue leather after being subjected to retanning filling is 8.26mm, the thickening rate is 8.82%, and the formaldehyde content in the leather after being subjected to retanning is 194mg/kg, which cannot meet the requirement of the GB 20400-2006 on the formaldehyde content directly contacting the skin.
While particular embodiments of the present invention have been illustrated and described, it will be appreciated that the above embodiments are merely illustrative of the technical solution of the present invention and are not restrictive; those of ordinary skill in the art will understand that: modifications may be made to the above-described embodiments, or equivalents may be substituted for some or all of the features thereof without departing from the spirit and scope of the present invention; the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention; it is therefore intended to cover in the appended claims all such alternatives and modifications that are within the scope of the invention.
Claims (13)
1. The preparation method of the melamine resin is characterized by comprising the following steps:
(1) mixing and stirring melamine, formaldehyde and water, then heating, and adjusting the pH value to obtain a hydroxymethyl monomer solution;
(2) adding the hydroxymethyl monomer solution into a sulfonic acid compound solution, and continuously stirring to obtain a prepolymer solution;
(3) adding epoxy compound into the prepolymer solution, and continuously stirring to obtain melamine resin;
the mass ratio of the melamine to the formaldehyde to the sulfonic acid compound to the epoxy compound is 5-15: 2-8: 8-40: 1 to 6;
in the step (2), the sulfonic acid compound includes: one of sulfanilic acid and sodium sulfanilate;
in the step (3), the epoxy compound includes: one of glycidyl ether, glycidyl amine, glycidyl ester and epoxidized vegetable oil;
the glycidyl ether is glycerol triglycidyl ether;
the glycidylamine is 4- (2, 3-epoxypropoxy) -N, N-di (2, 3-epoxypropyl) aniline;
the glycidyl ester is 4, 5-epoxy tetrahydrophthalic acid diglycidyl ester;
the epoxidized vegetable oil is epoxidized soybean oil.
2. The method according to claim 1, wherein in the step (1), the formaldehyde comprises: one of a formaldehyde solution and paraformaldehyde.
3. The production method according to claim 1, wherein in the step (1), the temperature is raised to 60 to 80 ℃.
4. The method according to claim 1, wherein in the step (1), the pH is adjusted to 8.0 to 9.0.
5. The method according to claim 1, wherein in the step (1), the stirring time is 40 to 120 min.
6. The method according to claim 1, wherein the step (2) further comprises a step of adjusting the pH of the sulfonic acid compound solution before adding the methylol monomer solution to the sulfonic acid compound solution.
7. The production method according to claim 6, wherein the pH of the sulfonic acid compound solution is adjusted to 5.0 to 6.0.
8. The method according to claim 6, wherein the methylol monomer is added dropwise.
9. The method according to claim 1, wherein in the step (2), the stirring time is 30 to 60 min.
10. The method as claimed in claim 1, wherein the stirring time in step (3) is 120-240 min.
11. A melamine resin, characterized in that it is obtained by the process according to any one of claims 1 to 10.
12. Use of the melamine resin according to claim 11 in leather industry, textile industry, optical materials, resinous materials, plastics, encapsulating materials.
13. Use according to claim 12, characterized in that the melamine resin is used in the leather industry as a retanning agent.
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