JP4835816B2 - Methylation of melamine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, melamine (2,4,6-triamino-1,3,5-triazine) and methylamine (monomethylamine) are heated in the presence of an acidic catalyst and reacted under pressure. The present invention relates to a method for methylating melamine, wherein one or more amino groups are substituted with methylamino groups.
[0002]
Specifically, 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), -Amino-4,6-bis (methylamino) -1,3,5-triazine (bis) and 2,4,6-tris (methylamino) -1,3,5-triazine (tris) Methyl melamines are obtained.
[0003]
Methylmelamines are a group of useful compounds widely used as flame retardant materials as various fine chemical intermediates such as agricultural chemicals, medicines, dyes, paints, as various resin materials, particularly as aminoplast former components. is there.
[0004]
[Prior art]
As a method for producing alkylmelamines, a synthesis method by reaction of cyanuric chloride with alkylamine has been reported (J. Amer. Chem. Soc, 73, 2984, 1951). Year; JP-A-3-215564 (corresponding patent: US Pat. No. 5,124,379); and US Pat. No. 4,886,882). In this synthesis method, it is necessary to use expensive cyanuric chloride, to carry out a plurality of reactions for synthesizing mono- and bis-forms of alkylmelamines, and to treat hydrochloric acid in post-treatment.
[0005]
There is also a synthesis method shown in US Pat. No. 2,228,161 (corresponding patent: British Patent No. 496,690). This synthesis method is a method in which melamine and alkylamine hydrochloride are reacted. This reaction is a solid reaction, the handling amount becomes very large by using hydrochloric acid, the use of hydrochloride at a high temperature causes corrosion and requires measures for equipment and product quality, and It is necessary to treat hydrochloric acid in the post-treatment. Here, a method of reacting melamine and methylamine hydrochloride at 200 ° C. in a solid phase is disclosed as a synthesis method of methylmelamine. In this synthesis method, the yield of trimethylmelamines is 50 to 55% of 2-amino-4,6-bis (methylamino) -1,3,5-triazine (bis), and 2,4,6 -It has been reported that a small amount of tris (methylamino) -1,3,5-triazine (tris form) was obtained.
[0006]
The method of reducing from methylolmelamine has a low yield and requires handling of a polymer as a by-product.
[0007]
[Problems to be solved by the invention]
The present invention provides a method for methylating melamine.
[0008]
Specifically, a method is provided in which methyl melamines can be obtained in a simpler process than inexpensive raw materials such as melamine and methylamine, and the composition ratio of mono-, bis-, and tris-substitutions of the obtained methyl melamines can be controlled. To do.
[0009]
[Means for Solving the Problems]
In the first embodiment of the present invention, melamine and methylamine are reacted in the presence of an acidic catalyst at a reaction temperature of 160 to 250 ° C. and a reaction pressure of 5 MPa or more under heat and pressure. A method for methylating melamine, wherein at least one amino group is substituted with a methylamino group.
[0011]
The second embodiment is the melamine methylation method according to the first embodiment using a solvent.
[0012]
The third embodiment is the melamine methylation method according to the second embodiment using trialkylamine as a solvent.
[0013]
The fourth embodiment is a melamine according to the first embodiment, the second embodiment , or the third embodiment in which the reaction is performed while removing the generated ammonia to increase the generation ratio of the tris body and the bis body of the methylamino group. This is a methylation method.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Each of the above embodiments will be specifically described below.
[0015]
Melamine, an acidic catalyst, and a solvent are charged into an autoclave, a methylamine cylinder is connected, and the autoclave is cooled with a dry ice-acetone refrigerant. Then, methylamine is blown into the autoclave in a gaseous form while being measured with a balance from a methylamine cylinder. After injecting a predetermined amount, the preparation is completed.
[0016]
Thereafter, the autoclave is heated to react at a reaction temperature of 190 ° C.
[0017]
A reaction temperature of 140 to 300 ° C. is used, but if the temperature is high, side reactions occur and the yield deteriorates, and the reaction pressure also increases. Preferably it is 160-250 degreeC, More preferably, it is 160-200 degreeC. The reaction is an equilibrium reaction in which methylamine and ammonia are substituted, and reaches an equilibrium at 190 ° C. in about 2 hours. When ammonia is removed from the system, the equilibrium is tilted and the reaction rate increases rapidly.
[0018]
The substitution product composition of the reaction product can be relatively controlled, and a yield of about 40 to 80% can be obtained as a tris body.
[0019]
In the absence of solvent, the reaction pressure is 6 to 8 MPa at a reaction temperature of 170 ° C. and 11 to 12 MPa at a reaction temperature of 190 ° C. For example, when 50 parts by weight is used with respect to 100 parts by weight of melamine using triethylamine as a solvent, the pressure is 4 to 6 MPa. Use of solvents is easier in terms of equipment and safety.
[0020]
The amount of methylamine is 30 to 5,000 parts by weight with respect to 100 parts by weight of melamine. Further, although depending on the amount of trialkylamine, methylamine also becomes a solvent for dissolving melamine, so if it is small, the reaction rate becomes slow.
[0021]
Instead of methylamine, an alkylamine having 4 or less carbon atoms (monoalkylamine) can react in the same manner. As the number of carbon atoms increases, the pressure decreases and the reaction operation becomes easier.
[0022]
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.
[0023]
As the salt of the strong acid and the weak base, ammonium chloride (sublimation at 337 ° C.), ammonium sulfate, ammonium phosphate and the like are used. Quaternary ammonium salts can also be used as acidic catalysts. 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.
[0024]
Sodium chloride, potassium chloride, etc. are used as a salt of a strong acid and a strong base.
[0025]
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.
[0026]
The acidic catalyst is determined from the viewpoint of corrosion of the autoclave and from the viewpoint of the reaction rate, but ammonium chloride is more preferable when a trialkylamine is used as the solvent.
[0027]
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 view of separation from the product.
[0028]
The trialkylamine as the solvent can use up to 10 carbon atoms of one alkyl group, but 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, with respect to 100 parts by weight of melamine. If it is used in a large amount, the pressure during the reaction will decrease, but the reaction rate will slow down and the productivity will deteriorate.
[0029]
The removal of ammonia can be achieved by gradually opening the valve of the autoclave and slowly releasing it, but it is more efficient to perform rectification under pressure.
[0030]
In the purification from the reaction mixture, the reaction mixture is dissolved by heating and gradually added to a solvent to isolate the target product as a slurry. As the solvent, esters such as ethyl acetate, alcohols such as methanol and ethanol, cellsolves, ethers such as dioxane, ethyl ether and isopropyl ether, acetonitrile, DMF, DMSO, and NMP are used alone or in a mixture. It is done.
[0031]
Moreover, after sending these solvents into an autoclave, the slurry obtained by cooling may be collected and isolated.
[0032]
Also, purification and isolation are easy even with solid distillation. In this case, it is necessary to use a catalyst having a very high boiling point and good thermal stability.
[0033]
【Example】
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated still in detail, this invention is not limited to these.
[0034]
In all the examples, as shown in the reference examples, the product was separately synthesized in advance as a standard product (for example, a method for synthesizing a melamine derivative was described in Journal of American Chemical Society (J. Amer. Chem. Soc), 73, 2984, 1951; JP-A-3-215564 (corresponding patent: US Pat. No. 5,124,379); and US Pat. No. 4,886,882. According to the same procedure. ], A calibration curve was prepared using the product isolated as a pure product and an internal standard substance, and the amount of each product in the reaction product was accurately determined by the internal standard determination method using high performance liquid chromatography.
[0035]
The analysis conditions of the high performance liquid chromatography used are as follows.
[0036]
〔Analysis conditions〕
Eluent: H ₂ 0 / CH ₃ OH = 750/250 (v / v),
Detection method: UV 220 nm,
Column: GL Science Inertsil Ph 150 mm × 4.6 mmφ,
Flow rate: 1.0 mL / min,
Analysis temperature: 50 ° C.
Internal standard: Parachloroaniline.
[0037]
[Analysis conditions: Standard retention time (min)]
1) Melamine; 3.44
2) 2,4-diamino-6-methylamino-1,3,5-triazine (mono): 4.06,
3) 2-amino-4,6-bis (methylamino) -1,3,5-triazine (bis): 5.75,
4) 2,4,6-tris (methylamino) -1,3,5-triazine (tris form): 10.10.
5) Parachloroaniline (internal standard): 20.58.
[0038]
The standard 1,3,5-triazine derivative was synthesized according to the following reference example.
[0039]
Reference Example 1 (Synthesis of 2,4-diamino-6-chloro-1,3,5-triazine)
After dissolving 184.5 g (1.0 mol) of cyanuric chloride in 800 mL of acetonitrile at room temperature, 303.7 g (5.0 mol) of 28% aqueous ammonia solution was added to a solution cooled to 0 ° C. while stirring vigorously. It was dripped in 2 hours so that 10 degrees C or less may be maintained. After completion of the dropwise addition, the cooling was stopped and the mixture was stirred at room temperature for 1 hour, and 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 filtrate was dried at 50 ° C. for 6 hours under vacuum to obtain 115 g (yield 79%) of the title compound.
[0040]
Reference Example 2 (Synthesis of 2,4-diamino-6-methylamino-1,3,5-triazine)
A mixed solution of 14.5 g (0.1 mol) of 2,4-diamino-6-chloro-1,3,5-triazine synthesized in Reference Example 1 and 31.1 g (0.4 mol) of methylamine 40% aqueous solution Was heated with stirring and finally reacted at reflux temperature for 6 hours. After cooling the reaction solution, the product was filtered off, washed with cold water, and the filtrate was dried under vacuum at 70 ° C. for 6 hours to obtain 9.1 g (yield 65%) of the title compound. .
[0041]
Melting point: 269 ° C.
[0042]
Reference Example 3 (Synthesis of 2,4,6-tris (methylamino) -1,3,5-triazine)
While stirring 18.5 g (0.1 mol) of cyanuric chloride in 150 mL of acetonitrile and stirring the solution cooled to 0 ° C., 15.5 g (0.2 mol) of a 40% aqueous solution of methylamine was added at a reaction temperature of 5 ° C. It was dripped in 1 hour so as not to exceed. While further stirring, a solution of potassium hydrogen carbonate (20.0 g, 0.2 mol) in 100 mL of water was added dropwise at the same temperature. Thereafter, the reaction temperature was gradually raised and stirring was continued at 45 ° C. for 8 hours. After confirming that the conversion to 2,4-bis (methylamino) -6-chloro-1,3,5-triazine was completed by high performance liquid chromatography, the product was cooled and filtered. 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, and 31.1 g of methylamine 40% aqueous solution ( 0.4 mol) was added, and the mixture was further reacted for 6 hours under reflux with heating. After cooling, the precipitated crystals were filtered, washed thoroughly with water, and dried to obtain 13.1 g (yield 78%) of the title compound.
[0043]
Melting point: 133 ° C.
[0044]
Reference example 4
In the same manner as in Reference Example 3, 2-amino-4,6-bis (methylamino) -1,3,5-triazine was synthesized.
[0045]
Melting point: 291 ° C.
[0046]
Example 1
After charging 5 g of melamine and 0.1 g of ammonium chloride as an acidic catalyst into a 100 mL glass 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, 10 g was blown into the autoclave while measuring in a gaseous state from a methylamine cylinder and weighing the cylinder with a balance.
[0047]
Next, heating was performed so that the internal temperature of the autoclave became 190 ° C.
[0048]
On the way, from about 170 ° C., heat was generated in the autoclave, and the temperature rose near 10 ° C.
[0049]
Thereafter, the temperature was raised to 190 ° C., the pressure became 10 MPa, and the reaction was carried out at a reaction temperature of 190 ° C. for 2 hours.
[0050]
After the reaction, the autoclave was cooled, the valve was opened, the gaseous matter in the autoclave was drawn out of the system, and the autoclave was opened.
[0051]
The content mixture was dissolved in water and quantitatively analyzed. As a result, the conversion of the raw material melamine was 94.1%, and as a product, 2,4-diamino-6-methylamino-1,3,5-triazine was 21. 4%, 2-amino-4,6-bis (methylamino) -1,3,5-triazine 30.4%, 2,4,6-tris (methylamino) -1,3,5-triazine In a yield of 41.3%.
[0052]
Example 2
After charging 31 g of melamine and 0.5 g of ammonium chloride as an acidic catalyst into a 200 mL stainless steel autoclave, a methylamine cylinder was connected, and the autoclave was cooled with a dry ice-acetone refrigerant. When effervescence disappeared from the dry ice-acetone refrigerant, 96 g was blown into the autoclave while measuring the gas in a gaseous form from a methylamine cylinder with a balance.
[0053]
Next, heating was performed so that the internal temperature of the autoclave became 190 ° C.
[0054]
On the way, from about 170 ° C., heat was generated in the autoclave, and the temperature rose near 10 ° C. At 170 ° C., the pressure was 6 MPa.
[0055]
Thereafter, the temperature was raised to 190 ° C., the pressure became 11.5 MPa, and the reaction was carried out at a reaction temperature of 190 ° C. for 1 hour. In this reaction, the valve of the autoclave was loosened, the gas was gradually withdrawn intermittently, the reaction pressure was 6 MPa, and the reaction was terminated. Each time the gas was removed, the temperature of the autoclave increased by several degrees Celsius.
[0056]
After the reaction, the autoclave was cooled, the valve was opened, the gaseous matter in the autoclave was drawn out of the system, and the autoclave was opened. The inside of the autoclave turned brown and was corroded.
[0057]
The content mixture was dissolved in water and quantitatively analyzed. As a result, the conversion rate of the raw material melamine was 99.8%, and 2,4-diamino-6-methylamino-1,3,5-triazine was 0 as the product. .9%, 2-amino-4,6-bis (methylamino) -1,3,5-triazine 16.1%, 2,4,6-tris (methylamino) -1,3,5-triazine In a yield of 81.0%.
[0058]
Example 3
After charging 31 g of melamine, 10 g of triethylamine as a solvent, and 0.5 g of ammonium chloride as an acidic catalyst into a 200 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 while measuring the gas in a gaseous form from a methylamine cylinder with a balance.
[0059]
Next, heating was performed so that the internal temperature of the autoclave became 190 ° C.
[0060]
On the way, from about 170 ° C., heat was generated in the autoclave, and the temperature rose near 10 ° C. At 170 ° C., the pressure was 6 MPa.
[0061]
Thereafter, the temperature was raised to 190 ° C., the pressure became 9 MPa, and the reaction was carried out at a reaction temperature of 190 ° C. for 1 hour.
[0062]
After the reaction, the autoclave was cooled, the valve was opened, the gaseous matter in the autoclave was drawn out of the system, and the autoclave was opened. No corrosion in the autoclave was observed.
[0063]
The content mixture was dissolved in water and quantitatively analyzed. As a result, the conversion of the raw material melamine was 96.1%, and as the product, 2,4-diamino-6-methylamino-1,3,5-triazine was 16%. 0.5%, 2-amino-4,6-bis (methylamino) -1,3,5-triazine is 38.2%, 2,4,6-tris (methylamino) -1,3,5-triazine Were each obtained in a yield of 41.0%.
[0064]
Example 4
4 g of triethylamine was added as a solvent, 0.2 g of sodium chloride was employed as an acidic catalyst, and the other reaction conditions were the same as in Example 1.
[0065]
The content mixture was dissolved in water and quantitatively analyzed. As a result, the conversion rate of the raw material melamine was 89.3%, and as the product, 2,4-diamino-6-methylamino-1,3,5-triazine was 30. 0.9%, 35.8% 2-amino-4,6-bis (methylamino) -1,3,5-triazine, 2,4,6-tris (methylamino) -1,3,5-triazine In a yield of 21.7%.
[0066]
Example 4
Using 0.2 g of ammonium sulfate and 0.2 g of potassium chloride as the acidic catalyst, the reaction was carried out in the same manner as in Example 1, and the other reaction conditions were carried out in the same manner as in Example 1.
[0067]
The content mixture was dissolved in water and quantitatively analyzed. As a result, the conversion rate of the raw material melamine was 98.8%, and as a product, 2,4-diamino-6-methylamino-1,3,5-triazine was 17%. 0.0%, 2-amino-4,6-bis (methylamino) -1,3,5-triazine is 49.3%, 2,4,6-tris (methylamino) -1,3,5-triazine In a yield of 32.0%.
[0068]
【The invention's effect】
According to the present invention, a method for synthesizing methylmelamines with inexpensive raw materials of methylamine and melamine could be provided.
[0069]
And the substitution composition ratio of methylmelamines can be controlled by removing the amount of methylamine and the generated ammonia. In particular, the yield of 2,4,6-tris (methylamino) -1,3,5-triazine trimethylmelamine (tris form) could exceed 80%.
[0070]
Furthermore, since this reaction can only be performed at high pressure and requires high temperature, the material of the reactor becomes a problem. However, as a method of avoiding corrosion of the reaction vessel and high pressure during the reaction, trialkylamine is used as a solvent. Found to use. As a result, the corrosion of the autoclave was eliminated, and the pressure also depended on the amount of solvent used, but at a reaction temperature of 190 ° C., the pressure became 7 MPa or less, and the apparatus could be structured at a low pressure.
[0071]
Here, methyl melamines are useful compounds that give flexibility to the melamine resin, and are excellent in that they are highly water-soluble and can be arbitrarily mixed with melamine and polymerized with formalin.
[0072]
As an example, to give flexibility to a melamine resin, the flexibility test was conducted by preparing an impregnated paper impregnated with a resin solution obtained by adding a tris resin to a melamine resin, and processing the impregnated paper into a laminated cured sheet. [Evaluation Example 2 of JP-A-9-143238 (corresponding patent: WO97 / 11102)] is clarified.
[0073]
The melamine resin produced from melamine is very hard and can be used even if it is a mixture of mono-, bis-, and tris-forms of methylmelamine as long as it is intended to impart flexibility as an improvement in brittleness. be able to.

Claims (4)

Melamine and methylamine are reacted in the presence of an acidic catalyst at a reaction temperature of 160 to 250 ° C. and a reaction pressure of 5 MPa or more under heating and pressure, and at least one amino group of the melamine is converted to methyl. A method for methylating melamine, characterized by substituting an amino group. Further methylation method melamine according to claim 1 using a solvent. The method for methylating melamine according to claim 2 , wherein a trialkylamine is used as a solvent. The method for methylating melamine according to claim 1, 2 or 3, wherein the reaction is carried out while removing generated ammonia to increase the production ratio of tris and bis forms of methylamino groups.