JP2003012654A - Method for methylation of melamine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for methylation of melamine. SOLUTION: In this method for melamine methylation, melamine is reacted with methylamine in the presence of an acidic catalyst by heating under pressure and at least one or more amino groups of the melamine are substituted with methylamino groups.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to melamine (2,
4,6-triamino-1,3,5-triazine) and methylamine (monomethylamine) are heated in the presence of an acidic catalyst to react under pressure, and at least 1 of the melamine
The present invention relates to a method for methylating melamine, which comprises substituting one or more amino groups with methylamino groups.

Concretely, by reacting melamine and methylamine in an autoclave in the presence of an acidic catalyst, 2,4-diamino-6-methylamino-1,3,5-triazine (mono compound) as a target substance is reacted. ), 2-amino-
Methylmelamines of 4,6-bis (methylamino) -1,3,5-triazine (bis form) and 2,4,6-tris (methylamino) -1,3,5-triazine (tris form) To get

Methylmelamines are pesticides, drugs, dyes,
It is a useful compound group that is widely used as various flame-retardant materials as various fine chemical intermediates such as paints and various resin materials, especially as aminoplast former components.

[0004]

2. Description of the Related Art A synthetic method by the reaction of cyanuric chloride and alkylamine has been reported as a production of alkyl melamines [J. Amer. Chem. Soc], Vol. 73. , 2984
Page, 1951; JP-A-3-215564 (corresponding patent: US Pat. No. 5,124,379); and US Pat. No. 4,886,882]. This synthetic method requires the use of expensive cyanuric chloride, multiple reactions for the synthesis of mono- and bis-forms of alkyl melamines, and post-treatment with hydrochloric acid.

There is also a synthetic method shown in US Pat. No. 2,228,161 (corresponding patent: British Patent No. 496,690). This synthetic method is a method of reacting melamine with alkylamine hydrochloride. This reaction is a solid reaction, the handling amount becomes very large by using hydrochloric acid, corrosion occurs due to the use of hydrochloric acid salt at high temperature, and measures for equipment and product quality are required, and It is necessary to treat hydrochloric acid as a post-treatment. Here, as a method for synthesizing methylmelamine, a method in which melamine and methylamine hydrochloride are reacted in a solid phase at 200 ° C. is disclosed. In this synthetic method, the yield of trimethylmelamines is 2-amino-4,6-bis (methylamino) -1,
3,5-triazine (bis form) is 50 to 55%,
It is reported that a small amount of 2,4,6-tris (methylamino) -1,3,5-triazine (tris form) was obtained.

The method of reducing from methylol melamine has a low yield and requires handling of a by-product polymer.

[0007]

The present invention provides a method for methylating melamine.

More specifically, methyl melamines can be obtained in a simple process from inexpensive raw materials of melamine and methyl amine, and the obtained mono- and bis-forms of methyl melamines can be obtained.
And a method in which the composition ratio of the tris-substituted product can be controlled.

[0009]

In a first embodiment of the present invention, melamine and methylamine are heated in the presence of an acidic catalyst and reacted under pressure to remove at least one amino group of the melamine. A method for methylating melamine, which is characterized by substituting a methylamino group.

In the second embodiment, the reaction temperature is 160-
First at 250 ° C. and a reaction pressure of 5 MPa or more
It is the melamine methylation method described in the embodiment.

The third embodiment is the melamine methylation method described in the first embodiment or the second embodiment, which further uses a solvent.

The fourth embodiment is the method for methylating melamine described in the third embodiment using trialkylamines as a solvent.

In the fifth embodiment, the reaction is carried out while removing the generated ammonia to increase the production ratio of the tris-form and bis-form of the methylamino group, the second, third, or It is the melamine methylation method described in the fourth embodiment.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Each of the above-described embodiments will be specifically described below.

After charging melamine, an acidic catalyst and a solvent into an autoclave, a cylinder of methylamine is connected and the autoclave is cooled with a dry ice-acetone refrigerant. Then, methylamine is blown into the autoclave in a gaseous state from a cylinder of methylamine while weighing with a balance. After blowing a predetermined amount, the charging is completed.

After that, the autoclave is heated to a reaction temperature of 190 ° C. to cause the reaction.

A reaction temperature of 140 to 300 ° C. is used, but if the temperature is high, a side reaction will occur and the yield will be poor, and the reaction pressure will also be high. It is preferably 160 to 250 ° C.,
More preferably, it is 160 to 200 ° C. The reaction is an equilibrium reaction in which methylamine and ammonia are replaced,
Equilibrium is reached in about 2 hours at ℃. When ammonia is removed from the system, the equilibrium tilts and the reaction rate rises.

The composition of the substitution product of the reaction product can be relatively controlled and a yield of about 40 to 80% as a tris product can be obtained.

The reaction pressure is 6 to 8 MPa at a reaction temperature of 170 ° C. and 11 to 11 at a reaction temperature of 190 ° C. in the absence of solvent.
It is 12 MPa. For example, when 50 parts by weight of triethylamine is used as a solvent and 100 parts by weight of melamine is used, the pressure becomes 4 to 6 MPa. It is easier to use a solvent in terms of equipment and safety.

The amount of methylamine is 30 to 5000 parts by weight with respect to 100 parts by weight of melamine. The higher the amount, the more tris compounds can be produced, and the smaller the amount, the lower substituted compounds will be. Further, although methylamine also serves as a solvent for dissolving melamine, depending on the amount of trialkylamines, the reaction rate becomes slow when the amount is small.

Instead of methylamine, an alkylamine having 4 or less carbon atoms (monoalkylamine) can be similarly reacted. When the carbon number increases, the pressure decreases and the reaction operation becomes easier.

As the acidic catalyst, a salt of a strong acid and a weak base,
A salt of a strong acid and a strong base, an acid or the like is used.

As the salt of strong acid and weak base, ammonium chloride (337 ° C. sublimation), ammonium sulfate, ammonium phosphate and the like are used. Further, a quaternary ammonium salt can also be used as an acidic catalyst. Considering the separation of the acidic catalyst in the post-treatment, a quaternary ammonium salt compound having a long-chain alkyl group such as trioctylmethylammonium chloride (TOMAC) is preferable.

As the salt of strong acid and strong base, sodium chloride, potassium chloride, etc. are used.

As the acid, hydrofluoric acid, hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, sulfamic acid and the like are used. These acids become salts in the reaction system.

The acidic catalyst is determined from the viewpoint of corrosion of the autoclave and the viewpoint of reaction rate, but ammonium chloride is more preferable when trialkylamines are used as the solvent.

The amount of the acidic catalyst is 0.1 to 30 parts by weight with respect to 100 parts by weight of melamine, but 1 to 5 parts by weight is preferable in consideration of separation from the product.

The trialkylamines as a solvent are 1
Although the carbon number of one alkyl group can be up to 10, triethylamine is preferable from the economical viewpoint. The amount of the solvent is 10 to 2000 parts by weight, preferably 50 to 500 parts by weight, based on 100 parts by weight of melamine. When it is used in a large amount, the pressure during the reaction decreases, but the reaction rate becomes slow and the productivity deteriorates.

The removal of ammonia can be achieved by gradually opening the valve of the autoclave and slowly releasing it. However, rectification under pressure is more efficient.

For purification from the reaction mixture, the reaction mixture is dissolved by heating and gradually added to the solvent to isolate the desired product as a slurry. As the solvent, esters such as ethyl acetate, alcohols such as methanol and ethanol, cellosolves, ethers such as dioxane, ethyl ether and isopropyl ether, acetonitrile, DM
F, DMSO, NMP and the like are used alone or in a mixture.

Alternatively, these solvents may be sent to an autoclave and then cooled to collect and isolate the resulting slurry.

Purification and isolation are also easy by solid distillation. In this case, it is necessary to use a catalyst having a very high boiling point and good thermal stability as a catalyst.

[0033]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

In all of the examples, as shown in the reference examples, the product was separately synthesized beforehand as a standard product (for example, the method for synthesizing a melamine derivative was described in Journal of American Chemical Society (J. Amer.Chem.So
c), 73, 2984, 1951; JP-A-3-21
5564 (corresponding patent: US Pat. No. 5,124,3
79); and US Pat. No. 4,886,882. ], A calibration curve was prepared from the isolated pure product and the internal standard substance, and the amount of each product in the reaction product was accurately determined by the internal standard determination method by high performance liquid chromatography.

The analytical conditions of the high performance liquid chromatography used are as follows.

[Analysis conditions] Eluent: H ₂ 0 / CH ₃ OH = 750/250 (v /
v), detection method: UV 220 nm, column: GL Science Inertsil Ph 1
50 mm × 4.6 mmφ, flow rate: 1.0 mL / min, analysis temperature: 50 ° C., internal standard substance: parachloroaniline.

[Analysis conditions: standard retention time (m
in)] 1) Melamine; 3.44, 2) 2,4-diamino-6-methylamino-1,3,5
-Triazine (mono body): 4.06, 3) 2-amino-4,6-bis (methylamino) -1,
3,5-triazine (bis form): 5.75, 4) 2,4,6-tris (methylamino) -1,3,5
-Triazine (tris form): 10.10, 5) parachloroaniline (internal standard): 20.58.

The standard 1,3,5-triazine derivative was synthesized according to the following Reference Example.

Reference Example 1 (Synthesis of 2,4-diamino-6-chloro-1,3,5-triazine) Cyanuric chloride (184.5 g, 1.0 mol) was dissolved in acetonitrile (800 mL) at room temperature and then at 0 ° C. A solution of 28% ammonia in water 30
3.7 g (5.0 mol) was added dropwise over 2 hours so that the reaction temperature was kept below 10 ° C. After completion of the dropping, cooling was stopped, the mixture was stirred at room temperature for 1 hour, then gradually heated to 45 ° C. and further reacted for 4 hours. After cooling, the product was filtered off and washed with a large amount of water. The filtered product was dried under vacuum at 50 ° C. for 6 hours to obtain 115 g (yield 79%) of the title compound.

Reference Example 2 (Synthesis of 2,4-diamino-6-methylamino-1,3,5-triazine) 2,4-Diamino-6-chloro-synthesized in Reference Example 1
A mixed solution of 14.5 g (0.1 mol) of 1,3,5-triazine and 31.1 g (0.4 mol) of a 40% aqueous solution of methylamine was heated with stirring to finally reach a reflux temperature. And reacted for 6 hours. After cooling the reaction solution, the product was filtered off, washed with cold water, and the filtered product was dried under vacuum at 70 ° C. for 6 hours to give 9.1 g of the title compound (yield: 65
%)Obtained.

Melting point: 269 ° C.

Reference Example 3 (Synthesis of 2,4,6-tris (methylamino) -1,3,5-triazine) 18.5 g (0.1 mol) of cyanuric chloride was dissolved in 150 mL of acetonitrile, and the mixture was heated to 0 ° C. While stirring the cooled solution, 15.5 g (0.2%) of a 40% aqueous solution of methylamine was added.
Mol) was added dropwise over 1 hour so that the reaction temperature did not exceed 5 ° C. While continuing stirring, potassium hydrogen carbonate 20.
A solution of 0 g (0.2 mol) in 100 mL of water was added dropwise at the same temperature. Then, the reaction temperature was gradually raised and stirring was continued at 45 ° C. for 8 hours. 2,4-by high performance liquid chromatography
After confirming that the conversion to bis (methylamino) -6-chloro-1,3,5-triazine was completed, it was cooled and the product was filtered off. After thoroughly washing the filter cake with water, the 2,4-bis (methylamino) -6-chloro-1,
3,5-Triazine was suspended in 100 mL of water, 31.1 g (0.4 mol) of a 40% aqueous solution of methylamine was added, and the mixture was further reacted under heating under reflux for 6 hours. After cooling, the precipitated crystals were filtered, washed thoroughly with water, and dried to give the title compound (13.1 g, yield 78%).

Melting point: 133 ° C.

Reference Example 4 In the same manner as in Reference Example 3, 2-amino-4,6-bis (methylamino) -1,3,5-triazine was synthesized.

Melting point: 291 ° C.

Example 1 Melamine 5 g, ammonium chloride 0.1 as an acidic catalyst
After charging g into a 100 mL glass autoclave,
A methylamine cylinder was connected and the autoclave was cooled with dry ice-acetone refrigerant. When foam disappears from the dry ice-acetone refrigerant, from the methylamine cylinder in a gaseous state, while weighing the cylinder with a balance, 10 g
Was blown into the autoclave.

Next, the internal temperature of the autoclave is 190 ° C.
It heated so that it might become the temperature of.

On the way, from about 170 ° C., heat was generated in the autoclave and the temperature rose near 10 ° C.

Then, the temperature is raised to 190 ° C. and the pressure is adjusted to 10
The pressure became MPa, and the reaction was performed at a reaction temperature of 190 ° C. for 2 hours.

After the reaction, the autoclave was cooled, the valve was opened, the gaseous substance in the autoclave was discharged to the outside of the system, and the autoclave was opened.

The content mixture was dissolved in water and quantitatively analyzed, and as a result, the conversion rate of melamine as a raw material was 94.1%, and the product, 2,4-diamino-6-methylamino-1,
2,5-triazine 21.4%, 2-amino-4,6
-Bis (methylamino) -1,3,5-triazine is 3
0.4%, 2,4,6-tris (methylamino) -1,
3,5-triazine was obtained in a yield of 41.3%.

Example 2 31 g of melamine and ammonium chloride as an acid catalyst of 0.
After charging 5 g in a 200 mL stainless steel autoclave, a methylamine cylinder was connected and the autoclave was cooled with a dry ice-acetone refrigerant. When the dry ice-acetone refrigerant stopped foaming, 96 g was blown into the autoclave in a gaseous state from a methylamine cylinder while measuring the cylinder with a balance.

Next, the internal temperature of the autoclave is 190 ° C.
It heated so that it might become the temperature of.

On the way, from about 170 ° C., heat was generated in the autoclave and the temperature rose to about 10 ° C. 170
At 0 ° C., the pressure was 6 MPa.

Then, the temperature is raised to 190 ° C. and the pressure is set to 1
The pressure became 1.5 MPa, and the reaction was performed at a reaction temperature of 190 ° C. for 1 hour. In this reaction, the valve of the autoclave was loosened to intermittently gradually withdraw the gas and the reaction pressure was set to 6 MPa to complete the reaction. Each time the gas was vented, the temperature of the autoclave rose by a few degrees.

After the reaction, the autoclave was cooled, the valve was opened, the gaseous substance in the autoclave was discharged to the outside of the system, and the autoclave was opened. The inside of the autoclave turned brown and corrosion was observed.

As a result of dissolving the content mixture in water and quantitatively analyzing it, the conversion of the raw material melamine was 99.8%, and the product, 2,4-diamino-6-methylamino-1,
0.9% 3,5-triazine, 2-amino-4,6-
Bis (methylamino) -1,3,5-triazine is 1
6.1%, 2,4,6-tris (methylamino) -1,
3,5-triazine was obtained in a yield of 81.0%.

Example 3 31 g of melamine and 10 g of triethylamine as a solvent
And 200 g of 0.5 g of ammonium chloride as an acidic catalyst
After charging into a mL stainless steel autoclave, a methylamine cylinder was connected and the autoclave was cooled with a dry ice-acetone refrigerant. When foaming disappeared from the dry ice-acetone refrigerant, 63 g was blown into the autoclave in a gaseous state from a methylamine cylinder while measuring the cylinder with a balance.

Next, the internal temperature of the autoclave is 190 ° C.
It heated so that it might become the temperature of.

On the way, from about 170 ° C., heat was generated in the autoclave and the temperature rose near 10 ° C. 170
At 0 ° C., the pressure was 6 MPa.

Then, the temperature is raised to 190 ° C. and the pressure is 9M.
It became Pa, and the reaction was performed at a reaction temperature of 190 ° C. for 1 hour.

After the reaction, the autoclave was cooled, the valve was opened, the gaseous substance in the autoclave was discharged to the outside of the system, and the autoclave was opened. No corrosion was found inside the autoclave.

The content mixture was dissolved in water and quantitatively analyzed. As a result, the conversion rate of melamine as a raw material was 96.1%, and the product, 2,4-diamino-6-methylamino-1,
3,5-triazine 16.5%, 2-amino-4,6
-Bis (methylamino) -1,3,5-triazine is 3
8.2%, 2,4,6-tris (methylamino) -1,
3,5-triazine was obtained in a yield of 41.0%.

Example 4 4 g of triethylamine was added as a solvent, 0.2 g of sodium chloride was adopted as an acidic catalyst, and other reaction conditions were the same as in Example 1.

As a result of dissolving the content mixture in water and quantitatively analyzing it, the conversion of the raw material melamine was 89.3%, and the product, 2,4-diamino-6-methylamino-1,
3,5-triazine 30.9%, 2-amino-4,6
-Bis (methylamino) -1,3,5-triazine is 3
5.8%, 2,4,6-tris (methylamino) -1,
3,5-triazine was obtained in a yield of 21.7%.

Example 4 Ammonium sulfate (0.2 g) and potassium chloride (0.2 g) were used as acidic catalysts and reacted in the same manner as in Example 1,
The other reaction conditions were the same as in Example 1.

The content mixture was dissolved in water and quantitatively analyzed. As a result, the conversion rate of melamine as a raw material was 98.8%, and the product, 2,4-diamino-6-methylamino-1,
3,5-triazine 17.0%, 2-amino-4,6
-Bis (methylamino) -1,3,5-triazine is 4
9.3%, 2,4,6-tris (methylamino) -1,
3,5-triazine was obtained in a yield of 32.0%.

[0068]

Industrial Applicability According to the present invention, it is possible to provide a method for synthesizing methyl melamines with inexpensive raw materials of methylamine and melamine.

The composition ratio of the substitution product of methylmelamines can be controlled by controlling the amount of methylamine and the generated ammonia. Especially 2, 4, 6
The yield of -tris (methylamino) -1,3,5-triazinetrimethylmelamine (tris form) could exceed 80%.

Furthermore, since this reaction can be carried out only at high pressure and requires high temperature, the material of the reactor becomes a problem, but as a method for avoiding corrosion and high pressure of the reaction vessel at the time of reaction, trialkylamine It has been found to use the class as a solvent. As a result, the autoclave was not corroded, and the pressure was 7 MPa or less at the reaction temperature of 190 ° C., although the pressure also depended on the amount of the solvent used, and the low-pressure structure of the apparatus became possible.

Here, the methyl melamines are useful compounds which give flexibility to the melamine resin, and are also excellent in that they are highly water-soluble and can be arbitrarily mixed with melamine and polymerized with formalin.

As an example, imparting flexibility to a melamine resin was evaluated by preparing an impregnated paper in which a resin solution obtained by adding a tris-type resin to a melamine resin was prepared, and processing the impregnated paper into a laminated cured sheet. Flexibility test [JP-A-9-1432]
No. 38 publication (corresponding patent: WO97 / 11102) evaluation example 2].

The melamine resin produced from melamine is very hard and even if it is a mixture of mono-, bis-, and tris-methyl melamines for the purpose of imparting flexibility to improve brittleness. You can fulfill your purpose.

Claims (5)

[Claims] 1. A melamine characterized in that melamine and methylamine are heated in the presence of an acidic catalyst and reacted under pressure to replace at least one amino group of the melamine with a methylamino group. Methylation method. 2. The melamine methylation method according to claim 1, wherein the reaction temperature is 160 to 250 ° C., and the reaction pressure is 5 MPa or more. 3. The method for methylating melamine according to claim 1, which further uses a solvent. 4. The method for methylating melamine according to claim 3, wherein trialkylamines are used as the solvent. 5. The method for methylating melamine according to claim 1, 2, 3 or 4, wherein the reaction is performed while removing the generated ammonia to increase the production ratio of the tris-form and bis-form of the methylamino group.