KR100449883B1 - A method for manufacturing methylated melamine-formaldehyde resins - Google Patents

Abstract

The present invention relates to a method for producing methylated melamine, which is used in a neutral atmosphere by using 0.0001 to 0.1 moles of one or more metal salt catalysts selected from the group consisting of zinc acetate, sodium acetate, potassium acetate, lead acetate, magnesium acetate and sodium methoxide. The methylolation step of reacting the melamine and formaldehyde by proceeding the reaction, the step of removing the unreacted material and water in the reactants after the reaction proceeds using a thin film distillation apparatus, and the salts and ions remaining in the reactants using magnesium silicate It characterized in that it comprises a step of removing, and by using the methylolation reaction under the middle component atmosphere can not only significantly reduce the amount of acid used in the methoxylation step, as a result of the salt remaining in the reactants after the reaction and Methylation due to drastically reduced ionic content Grameen has high production efficiency of the benefits of a high-purity product.

Description

A method of manufacturing methylated melamine {A METHOD FOR MANUFACTURING METHYLATED MELAMINE-FORMALDEHYDE RESINS}

The present invention relates to a method for producing methylated melamine, and more particularly, to reduce the amount of salt produced in the reaction product by carrying out a methylolation reaction in a neutral atmosphere, and to remove the resulting salt and residual ions by using an adsorbent, further unreacted By removing formaldehyde and methanol through a thin film evaporator (TFE), the present invention relates to a method for producing an improved methylated melamine that can increase production efficiency and increase the purity of the final product.

In general, methylated melamine is widely used as a crosslinking agent for paints, coatings, adhesives and tires due to its excellent crosslinking ability, mechanical and chemical properties and heat resistance. The methylated melamine is a transparent liquid, but may have a pale white turbidity depending on the degree of methylolation and methoxylation, or may be mixed with white carbon and used in powder form depending on the intended use.

The crosslinking reaction of methylated melamine proceeds with the release of methanol as a transesterification reaction with alcohols. Therefore, it emits highly volatile low-boiling methanol, so that when used in thermosetting paint, crosslinking reaction occurs at low temperature, drying speed is high, and solubility in paint solvent is also excellent.

However, since formaldehyde is used as a reactant of melamine in the reaction of obtaining methylated melamine, there is a problem that unreacted formaldehyde remaining in the product is released when the crosslinking reaction proceeds after the reaction is completed. Is going intensively.

Conventional patents related to the synthesis of methylated melamine are known, but US Patent No. 3,487,048 has a ratio of melamine and formaldehyde of 1: 3 to 6 to react with an acid catalyst and neutralize it with alkali again to form unreacted formaldehyde. A method of obtaining a product having a content of less than 16% by weight is provided.

In U.S. Pat.Nos. 4,183,832 and 4,183,832, melamine and form are formed under alkaline atmosphere of pH 8.5 to 9.5 to synthesize methoxy methyl melamine with low content of unreacted formaldehyde used as binder in glass fiber mats. By reacting aldehyde to synthesize methylol melamine, it is then subjected to methoxylation reaction using methanol under acidic atmosphere, neutralized with triethanolamine, and unreacted formaldehyde is removed by reacting with urea. There is provided a method of obtaining methylated melamine having a content of the reaction formaldehyde of less than 6% by weight. However, when synthesized in this way, the amount of salts and ions increases in the final product and impurities such as urea-formaldehyde condensate are generated.

U.S. Patent No. 3,488,350 provides a method of proceeding a methoxylation reaction using a cation exchange resin. This synthesis method completely separates the methylolation reaction and the methoxylation reaction, making it difficult to continuously produce the product and dehydrating, washing, There is a problem that must be recovered.

In US Pat. No. 3,322,762, high-purity products were synthesized by adding methanol twice in the methylolation and methoxylation processes. In the methylolation process, formaldehyde is used as paraformaldehyde. In this case, methanol used in the methoxylation process is pre-injected to facilitate stirring of the reactants. However, methanol is known as a substance that interferes with the methylolation reaction. Therefore, if the reaction is carried out by adding only a minimum amount to facilitate stirring without adding the entire amount of methanol, high-purity methoxy methyl melamine having high content of hexamethoxymethylmelamine (HMMM) Can be synthesized. However, even in this case, since a basic catalyst is used in the methylolation process, a large amount of salts and ions are generated.

U.S. Patent No. 4,433,143 provides that the reaction ratio of melamine and formaldehyde is 1: 3 to 5 and is reacted under an alkaline atmosphere of pH 8-9.

In addition, in US Pat. No. 5,821,323, the reaction ratio of melamine and formaldehyde is 1: 2.6 to 4.6, and the reaction is carried out in an alkaline atmosphere at pH 8, where the content of unreacted formaldehyde is less than 0.5% by weight, and the content of N-substituted methylol is 6.0. Provided is a method for producing a methylated melamine crosslinking agent that is less than% by weight.

However, in order to neutralize all of the above reactions by proceeding in an alkaline atmosphere, a large amount of acid must be injected in the methoxylation reaction, and as a result, there is a problem that the amount of salts and ions generated increases. It is required.

The present invention has been made to solve the conventional problems as described above, by proceeding the methylolation reaction in a neutral atmosphere, the methoxylation reaction can proceed with a small amount of acid, and as a result reduce the amount of salts and ions produced by these An object of the present invention is to provide a method for producing methylated melamine having improved removal efficiency.

Still another object of the present invention is to remove unreacted materials by using a thin film distillation apparatus to prevent crosslinking of the product and to enable a rapid continuous process, and to improve treatment efficiency by removing salts and ions using magnesium silicate. do.

The present invention provides a methylolation step of reacting melamine and formaldehyde in a neutral atmosphere using a metal salt catalyst;

Using an acid catalyst in the product to carry out the methoxylation reaction in an acidic atmosphere;

Neutralizing the reactant with an alkali after the methoxylation reaction is completed;

Removing unreacted methanol and formaldehyde in the neutralized reactant and water generated during the reaction;

It is to provide a method for producing methylated melamine comprising the step of adsorbing the salt and ions remaining in the reactants by the above step.

Hereinafter, the present invention will be described in more detail.

The methylolation reaction is a condensation reaction between melamine and formaldehyde, which can be used to synthesize methylol melamine, which occurs as a nucleophilic bond between the amine in the melamine molecule and the carbon atom in the formaldehyde molecule. The reaction rate is increased. Therefore, general synthesis reaction of methylol melamine proceeds in alkaline atmosphere of pH 9-11 using a basic catalyst as a nucleophilic catalyst. Subsequently, the methoxylation reaction proceeds under an acidic atmosphere of pH 3 or less by introducing a large amount of acidic catalyst by transesterification reaction between methylol melamine and methanol.

Therefore, after the reaction is completed, a large amount of salts and ions are present in the reactants.

However, the present invention is characterized in that the pH of the reaction system in which the methylolation reaction proceeds is neutral, and the methylolation reaction of the present invention is a nucleophilic catalyst such as zinc acetate, potassium acetate, sodium acetate (sodium acetate), lead acetate (lead acetate), magnesium acetate (magnesium acetate), sodium methoxide (sodium methoxide) is used in a mixture of one or two or more selected from the group proceeds in a neutral atmosphere.

The molar ratio of melamine, paraformaldehyde and methanol used in the methylolation reaction is 1: 3 to 30:10 to 70, preferably 1:10 to 20:30 to 50. In addition, in the nucleophilic neutral catalyst used in the methylolation reaction, the pH is adjusted to 6.5 to 7.5 by adding 0.0001 to 0.1 mol to 1 mol of melamine, and the methylolation reaction is performed at 50 to 80 ° C.

After the methylolation reaction is completed, the pH of the reaction mixture is adjusted to 3.0 to 5.0, preferably 3.0 to 4.0 by injecting at least one acid catalyst selected from the group consisting of formic acid, acetic acid, hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid. The methoxylation reaction proceeds for a time.

Upon completion of the methoxylation reaction, the reaction system is neutralized with one or more bases selected from potassium hydroxide, sodium hydroxide and amines.

Residues such as unreacted formaldehyde, methanol, and water generated during the reaction are present in the neutralized reactant, and thus, removal thereof is required to obtain a high purity final product. It is characterized by removing impurities using. Such a thin film distillation apparatus can prevent crosslinking during the removal of impurities as compared to the conventional vacuum removal process, and thus, there is an advantage in that the stability of the product can be achieved.

The operating conditions of the thin film distillation apparatus used in the present invention is preferably a temperature of 80 to 150 ° C, a pressure of 100 torr or less, a rotational speed of 200 to 300 rpm, a flow rate of 0.01 to 2.0 liters / hour.

The reactants from which the unreacted substances have been removed are turbid liquids in which salts precipitate and have white particles. After the addition of magnesium silicate 0.1 to 10% by weight to the purified reaction to remove the salt and the remaining ions and stirred for 1 to 5 hours at 80 to 150 ℃ and filtered to obtain a final product from which the salt and ions are removed Will be.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples, and the scope of the claims is not exceeded by those skilled in the art to which the present invention pertains. It can be variously modified within.

Example 1

1. Put 1 mol of melamine, 20 mol of paraformaldehyde, 60 mol of methanol, and 0.01 mol of zinc acetate in a 4-necked reactor equipped with a thermometer, agitator, and reflux, and raise the temperature to 70 ° C for 1 hour until it becomes completely transparent at pH 6.8. Reacted.

2. The reactor gradually changed from a transparent phase to a pale white cloudy phase, and formic acid was added thereto to adjust the pH to 3.5, followed by reaction at 70 ° C. for 15 hours.

3. The solution was neutralized with 50% sodium hydroxide (NaOH) solution to pH 7.2.

4. The solution was passed through a thin film distillation apparatus under conditions of a temperature of 120 ° C., a pressure of 50 Torr, a rotational speed of 300 rpm, and a flow rate of 1.0 liter / hour.

5. To remove salts and ions of the reactants separated by the thin film distillation apparatus, 2% by weight of magnesium silicate was purified and reacted at 110 ° C. for 2 hours, followed by filtration to obtain a colorless transparent liquid product.

6. As a result of analysis, the final product was 23.4% of hexamethoxymethylmelamine (HMMM), unreacted formaldehyde 1.4%, water 2.7%, and the unreacted product recovered from the thin film distillation unit was formaldehyde 14%, methanol 80%, Water was 6%.

Example 2-4

Experiment with the same reactor and reaction conditions as in Example 1 (pH, reaction temperature, reaction time, catalyst) and the reaction process by changing only the molar ratio of the reactants, the results are shown in Table 1.

Reactant ratio (melamine / paraformaldehyde / methanol) HMMM Content% Example 2 1/20/45 21.3 Example 3 1/15/60 18.1 Example 4 1/15/45 18.3

Example 5

1. Into the same device as Example 1, 1 mol of melamine, 20 mol of paraformaldehyde, 60 mol of methanol was added, 0.01 mol of sodium methoxide was added thereto, and the temperature was raised to 70 ° C. for 1 hour until a complete transparent phase was obtained at pH 7.2. .

2. When the reactor became a very light white cloudy phase in the transparent phase, formic acid was added to adjust the pH to 4.0 and reacted at 70 ° C. for 15 hours.

3. The solution, completely transparent, was neutralized with 50% sodium hydroxide solution to pH 7.5.

4. The solution was passed through a thin film distillation apparatus at a temperature of 120 ° C., a pressure of 50 Torr or less, a rotation speed of 200 rpm, and a flow rate of 1.0 liter / hour.

5. To remove salts and ions of the reactants separated by the thin film distillation apparatus, 1% by weight of magnesium silicate was added thereto, and the mixture was reacted at 100 ° C for 1 hour, followed by filtration to obtain a colorless transparent liquid product.

6. As a result, the final products were HMMM 24.3%, formaldehyde 1.2%, water 2.4%, and the unreacted products recovered from the thin film distillation apparatus were 11% formaldehyde, 82% methanol, and 7% water.

Example 6-7

Experiment with the same reactor and reaction conditions as in Example 5 (pH, reaction temperature, reaction time, catalyst) and the reaction process by changing only the molar ratio of the reactants, the results are shown in Table 2.

Reactant ratio (melamine / paraformaldehyde / methanol) HMMM Content% Example 6 1/20/45 20.2 Example 7 1/15/45 18.9

Example 8

1. Put 1 mol of melamine, 15 mol of paraformaldehyde, 15 mol of methanol, and 0.01 mol of sodium methoxylate in a four-necked reactor equipped with a thermometer, agitator, and reflux device, and raise the temperature to 70 ℃ until it becomes completely transparent at pH 6.7. The reaction was time.

2. The reactor gradually changed from a transparent phase to a pale white cloudy phase, and 15 mol of methanol was added thereto, and the pH was adjusted to 3.0 with formic acid, followed by reaction at 70 ° C. for 15 hours.

3. The solution was neutralized with 50% sodium hydroxide (NaOH) solution to pH 7.1.

4. The solution was passed through a thin film distillation apparatus under conditions of a temperature of 120 ° C., a pressure of 50 Torr, a rotational speed of 300 rpm, and a flow rate of 1.0 liter / hour.

5. To remove salts and ions of the reactants separated by the thin film distillation apparatus, 1% by weight of magnesium silicate was added thereto and reacted at 110 ° C. for 2 hours, followed by vacuum filtration to obtain a colorless transparent liquid product.

6. As a result of analysis, the final product was 16.1% of hexamethoxymethylmelamine (HMMM), unreacted formaldehyde 1.4%, water 1.8%, and the unreacted material recovered from the thin film distillation unit was formaldehyde 18%, methanol 68%, Water was 14%.

Examples 9-13

The same reactor and reaction conditions as in Example 6 (reaction temperature, reaction time, catalyst) and the reaction process were carried out by changing only the molar ratio of the reactants and the pH of the methoxylation process.

Reactant ratio (melamine / formaldehyde / methanol ¹ + methanol ² HMMM Content% Example 9 1/10/15 + 15 11.1 Example 10 1/10/8 + 32 23.5 Example 11 1/12/10 + 35 28.5 Example 12 1/15/15 + 30 26.6 Example 13 1/20/30 + 30 30.4

Comparative Example 1

1.Into a four-necked reactor equipped with a thermometer, agitator and reflux, add 1 mol of melamine, 20 mol of paraformaldehyde, 60 mol of methanol, and 50% sodium hydroxide solution at 0.4% by weight to obtain a completely transparent phase at pH 8.2. The reaction was carried out for 1 hour.

2. The reactor gradually changed from a transparent phase to a pale white cloudy phase, and formic acid was added 1.4 wt% to adjust the pH to 3.5 and reacted at 70 ° C. for 15 hours. (The amount of formic acid used in Example 1 was 0.2% by weight)

3. The solution was neutralized with 50% sodium hydroxide (NaOH) solution to pH 7.2.

4. The solution was passed through a thin film distillation apparatus under conditions of a temperature of 120 ° C., a pressure of 50 Torr, a rotational speed of 300 rpm, and a flow rate of 1.0 liter / hour.

5. To remove salts and ions of the reactants separated by the thin film distillation apparatus, 2% by weight of magnesium silicate was added and reacted at 110 ° C. for 2 hours, followed by vacuum filtration to obtain a colorless transparent liquid product.

6. As a result of analysis, the final product was hexamethoxymethylmelamine (HMMM) 14.0%, unreacted formaldehyde 2.1%, water 3.0%, and the unreacted material recovered from the thin film distillation unit was 18% formaldehyde, 79% methanol, Water was 3%.

According to the present invention, the methylolation reaction of melamine and formaldehyde, which has been performed under an alkaline atmosphere of pH 8.0 or above, is performed at pH 6.5 to 7.5, thereby reducing the amount of acid required in the successive methoxylation reaction to significantly produce salts and ions. The efficiency of the manufacturing process is reduced by removing unreacted substances with a thin film distillation apparatus and removing the generated salts and ions through magnesium silicate.

Claims (5)

A methylolation step of synthesizing methylol melamine by reacting melamine and formaldehyde in the presence of a nucleophilic catalyst; A methoxylation step of advancing the reaction by injecting an acid catalyst into the reactant after the methylolation step is completed; A neutralization step of neutralizing the reactant having undergone the methoxylation step; In the method for obtaining a methylated melamine consisting of a residue removal step of removing the residue other than the methylated melamine after the neutralization step, As the nucleophilic catalyst, at least one metal salt catalyst selected from the group consisting of zinc acetate, sodium acetate, potassium acetate, lead acetate, magnesium acetate, and sodium methoxylated is used to conduct a methylolation reaction in a neutral atmosphere of pH 6.5 to 7.5. Method for producing methylated melamine, characterized in that. The method of claim 1, wherein the metal salt catalyst is a method for producing methylated melamine, characterized in that 0.01 to 0.05 mole is used per 1 mole of melamine. 0.01 to 0.05 mol of at least one metal salt catalyst selected from the group consisting of 10-20 mol of formaldehyde, 30-60 mol of methanol, zinc acetate, sodium acetate, potassium acetate, lead acetate, magnesium acetate, sodium methoxide relative to 1 mol of melamine Mixing to proceed with methylolation under a neutral atmosphere of pH 6.5 to 7.5; Advancing the methoxylation reaction under an atmosphere of pH 3 to 5 using at least one acidic methoxylation catalyst selected from the group consisting of formic acid, acetic acid, hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid; Neutralizing the reactant obtained from the methoxylation reaction with sodium hydroxide; Separating the neutralized reactants through a thin film distillation apparatus at a temperature of 100 to 150 ° C., a pressure of 100 torr or less, a rotational speed of 200 to 300 rpm, and a flow rate of 0.1 to 1.0 liter / hour; A method for producing methylated melamine, comprising the step of adding 0.1 to 10% by weight of magnesium silicate to the separated reactants to remove salts and ions remaining in the reactants. delete delete