JP3142702B2 - Granular melamine cyanurate and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to melamine cyanurate and a method for producing the same, and more particularly to melamine cyanurate obtained by heating melamine and cyanuric acid without using a liquid medium, in particular, granular melamine cyanurate, And a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, halogen-based flame retardants have been used as one type of flame retardant for plastics. However, there is a problem of harmfulness of combustion products to the human body, and there is an increasing demand for low halogenated halogen-free products. In such a situation,
Substances having a triazine ring, such as melamine and melamine cyanurate, have been studied as flame retardants. Flame retardancy is imparted by directly mixing melamine in a urethane resin and melamine cyanurate in a polyamide resin in a range of several percent to 30%. It is known that it can.

[0003] Melamine cyanurate is usually prepared by dissolving melamine and cyanuric acid in water, mixing and reacting the aqueous solutions, and filtering off and drying the resulting precipitate of hardly soluble melamine cyanurate. Was.

However, when this method is carried out on an industrial scale, (1) the solubility of melamine and cyanuric acid in water is low and a concentrated aqueous solution cannot be prepared, so that the production efficiency is low. (3) The melamine cyanurate particles after separation contain a considerable amount of water and require a long time for drying.

As an industrial method, water is mediated instead of the above-mentioned aqueous solution reaction, that is, 20 to 2,000 parts by weight of water is added per 100 parts by weight of solid melamine and solid cyanuric acid to solid melamine and solid cyanuric acid. Reaction with stirring or kneading (Japanese Patent Application Laid-Open No. 54-5558).
7); preparing a powder homogeneous mixture of melamine and cyanuric acid having an average particle size of 100 μ or less, and then adding
A method of reacting by adding 30 to 300% of water based on the mixture (JP-A-54-55588) is disclosed. All of these require a step of drying and pulverizing after the reaction in order to react by adding water.

As a method using a raw material different from the above method, a method of producing melamine cyanurate by mixing and heating urea and melamine in a solid state (JP-A-54-12569).
0) is disclosed. This method requires the use of expensive corrosion-resistant materials in the reactor, and the mixture of urea and melamine reacts in the cloudy melt while deammonating with heating, so the resulting melamine cyanurate is handled in block form. However, the purification is not easy and the yield is insufficient. Further purification is required to obtain a high-purity product.

[0007]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a method for producing melamine cyanurate, which has a simplified production process and is industrially superior to the prior art, and a powdery or granular melamine having excellent properties. To provide cyanurate.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, it has been found that a reaction between a solid and a solid under specific conditions is not a so-called solid-liquid reaction via a liquid medium. It has been found that the present invention proceeds, and the present invention has been completed. That is, powder melamine and powder cyanuric acid are mixed, preferably the mixture is granulated,
A method for producing melamine cyanurate, which is heated to 250 to 500 ° C, and a powdery or granular melamine cyanurate obtained by this method.

The melamine powder used in the present invention is commercially available. For example, industrial melamine (melting point: 354 ° C., sublimation starting temperature: 210 ° C., average particle diameter: 20 μm) manufactured by Mitsui Toatsu Chemicals, Inc. may be mentioned.

[0010] Powdered cyanuric acid is also generally commercially available. For example, Shikoku Kasei Co., Ltd., product name ICA-P
(Melting point 360 ° C, sublimation start temperature 230 ° C, average particle size 8
0 μm).

Cyanuric acid has two types, enol type and keto type.
There are two tautomers.Chemically, the enol form is referred to as cyanuric acid, and the keto form is referred to as isocyanuric acid.The cyanuric acid used in the present invention does not mean only the enol form, but the enol form and keto form. It includes both.

In the production method of the present invention, the molar ratio of the powdered melamine to the powdered cyanuric acid used is 0.5 to 2.0 cyanuric acid to 1 melamine. Is from 1: 0.9 to
1.1.

In the present invention, there is no particular limitation on the method of mixing the powdered melamine and the powdered cyanuric acid, but it is preferable to make the mixing as uniform as possible. The higher the homogeneity, the greater the chance of contact between the melamine molecules and the cyanuric acid molecules, the higher the apparent reaction rate, the less the sublimation of the mole balance due to sublimation, the higher the yield, and the lower the mixing of unreacted substances. Purity is improved.

As for the powdered melamine and the powdered cyanuric acid to be supplied to the reactor, those which have been mixed in advance before being introduced into the reactor may be used, or the heating reaction may be carried out with mixing after being introduced into the reactor. You may.

The powder melamine and the powder of cyanuric acid when mixed have a particle diameter of 80 μm or less and an average particle diameter of 2 μm.
The thickness is set to 0 μm or less. For this purpose, for example, a particle diameter of 80 μm or less and an average particle diameter of 20 μm
m or less, using a powdered melamine and powdered cyanuric acid, or using a mixer such as a Henschel mixer or a Nauta mixer, to prepare a mixture of powdered melamine and powdered cyanuric acid in advance. Accordingly, a powder having a particle diameter of 80 μm or less and an average particle diameter of 20 μm or less is used by a pulverizer such as a jet mill.

The present invention is considered to be a reaction between a solid and a solid or between a solid and a gas. Since the particle size of the solid raw material affects the reaction rate, powder melamine and powder cyanuric acid used for the reaction are used. Has a particle diameter of 80 μm or less and an average particle diameter of 20 μm or less as described above,
0 μm or less, and an average particle diameter of 0.5 to 10 μm, more preferably a particle diameter of 30 μm or less, and an average particle diameter of 0.5
Those finely pulverized to ５5 μm are preferred.

The powdered melamine and the powdered cyanuric acid having such particle diameters are kept in a solid state without using a liquid medium.
250-500 ° C. introduced into the reactor, preferably 250-500 ° C.
When heated to 430 ° C, more preferably 300 to 380 ° C, melamine cyanurate can be easily obtained with a heating time of about 10 minutes to 4 hours. Heating temperature is 250 ℃
If less than the above, the reaction proceeds but is very slow, the yield of melamine cyanurate is poor, and unreacted melamine and cyanuric acid remain to lower the purity. At 500 ° C or higher, not only melamine and cyanuric acid as raw materials,
The reaction product, melamine cyanurate, sublimes and causes a complicated reaction, resulting in a decrease in purity and yield due to an increase in impurities. If necessary, an inert gas such as N ₂ gas may be introduced into the reactor to prevent air from being mixed.

In the above reaction, the powdered melamine and the powdered cyanuric acid are preliminarily mixed and granulated, whereby the raw materials and the products can be fluidly handled and the reaction preferably proceeds.

The reason for this is not clear, but the mixture is compacted by granulation of the mixture of powdered melamine and powdered cyanuric acid, and the unreacted granular particles are formed by the reaction of melamine and cyanuric acid in a single granular particle. It is considered that sublimation to the outside is suppressed. From a microscopic viewpoint, it is considered that the consolidation increases the chance of contact between the melamine molecule and the cyanuric acid molecule and increases the apparent reaction rate, so that the sublimation does not disturb the molar balance.

In the present invention, the particle diameter of powder melamine and powder cyanuric acid constituting the granular mixture of powder melamine and powder cyanuric acid is not more than 80 μm, and the average particle diameter is not more than 20 μm, preferably not more than 60 μm. And an average particle diameter of 0.5 to 10 μm, more preferably a particle diameter of 3
0 μm or less, and the average particle size is 0.5 to 5 μm. A mixture of melamine and cyanuric acid that satisfies this condition is compressed using a commercially available granulator, and is crushed if necessary, so that the apparent particle size is in a range where the apparent particle size is easy to handle, preferably 0.1 to 10 mm. A granular mixture is prepared to the extent required. For example, a mixture of powdered melamine and powdered cyanuric acid is compressed using a dry granulator, and then the granulated mixture is prepared by crushing, or by a semi-dry granulator,
The granulated mixture may be prepared by compressing a mixture of powdered melamine and powdered cyanuric acid, extruding from a die, cutting to a desired length, and drying.

The raw granulated mixture of powdered melamine and powdered cyanuric acid obtained as described above is heated in a solid state at 250 to 500 ° C. for 10 minutes to 4 hours without using a liquid medium. By heating such that melamine cyanurate can be obtained continuously or batchwise. In addition, an inert gas such as N ₂ gas may be introduced into the reactor as needed at the time of heating to prevent air from flowing into the reactor.

When the method of the present invention is applied to industrial production,
It is not necessary to use a special pressurized closed vessel for the reactor, but a closed closed reaction vessel at least in which the raw materials and products are not volatilized is used. For example, the lower part provided with the equipment capable of heating the vessel wall may have a vertical cylindrical shape having a cone shape, and may be provided with a rotary valve at a supply port of a raw material and an outlet of a reactant. In this case, the heating section inside the cylinder is used as a reaction zone, the reaction product is continuously or batchwise extracted from the lower portion so as to have a predetermined residence time, and the corresponding raw material is fed from the upper portion.

When such a reactor is used, the use of a mixed granulated product is particularly preferred. Since the granulated product has good fluidity, it can be freely moved and dropped at a speed commensurate with extraction and supply without forming a bridge inside the reactor and can be smoothly operated to prevent clogging. In order to promote heat transfer, a baffle plate may be provided inside the reactor so that the mixed granulated material is promoted to move laterally as it falls. As described above, melamine cyanurate can be obtained in high yield at normal pressure without pressurization in the reactor.

The granular melamine cyanurate of the present invention comprises:
It is obtained by heating the above-mentioned granular mixture of powdered melamine and powdered cyanuric acid at 250 to 500 ° C, particularly preferably 300 to 380 ° C, for 10 minutes to 4 hours without using a liquid medium. The granular melamine cyanurate obtained by this production method can be used as it is as a product because the purity can be sufficiently increased without any particular purification by appropriately selecting the reaction conditions. Usually 98 purity
９９99.9%, and the bulk specific gravity is 0.3-1.4 g / ml.
It is. The bulk specific gravity of the granular melamine cyanurate can be adjusted by changing the compressibility at the stage of granulating the mixture of the powdered melamine and the powdered cyanuric acid as raw materials. That is, the bulk specific gravity of the granular melamine cyanurate can be increased by increasing the compression ratio of the mixed granulated product. The apparent particle size of the granular melamine cyanurate is preferably about 0.1 to 10 mm. It may be controlled to a desired size.

The granular melamine cyanurate can be used as a product as it is, but can be commercialized by adjusting the particle diameter by a general pulverizing means such as a jet mill or a ball mill according to the application. . For example, when used as a flame retardant such as polyamide, it is preferable to disperse melamine cyanurate in the polymer as uniformly as possible, and in such a case, the granules obtained by the method of the present invention using a jet mill or the like. Melamine cyanurate finely pulverized may be used.

The granular melamine cyanurate of the present invention comprises:
Bulk specific gravity is larger than powder melamine cyanurate,
Since there is little scattering, adhesion to equipment, etc., there is little loss during production and packaging, and handling is easy. Further, since it is more compact than powder, costs for transportation, storage and the like can be reduced.

[0027]

EXAMPLES The present invention will be described more specifically with reference to the following examples.

Example 1 In a Henschel mixer having a volume of 10 liters, 2.0 kg of industrial melamine (melting point: 354 ° C., sublimation start temperature: 210 ° C., average particle diameter: 20 μm) manufactured by Mitsui Toatsu Chemicals Co., Ltd. and cyanuric acid manufactured by Shikoku Chemicals Co., Ltd. , Trade name ICA-P (melting point 360 ° C,
Sublimation start temperature 230 ° C, average particle size 80μm) 2.0k
g and mixed at room temperature for 10 minutes. Then, using a jet mill, the total amount of the mixture was 33.4 kg /
h to give 3.91 kg of a finely ground mixture. The average particle size of this finely pulverized mixture was 3.94 μm (measured by a laser beam diffraction method based on volume). 78.25 g of this finely pulverized mixture was placed in an evaporating dish, covered with aluminum foil, placed in an electric furnace and heated at 350 ° C. for 1 hour to obtain 74.99 g of melamine cyanurate. The yield is 95.8%, the purity is 99.2%, and the average particle size is 4.8.
It was 3 μm. FIG. 1 shows a differential thermal analysis chart of the obtained melamine cyanurate. The differential thermal analysis charts of the raw material melamine and cyanuric acid are shown in FIGS.
It was shown to.

Example 2 A reaction was carried out in the same manner as in Example 1 except that the mixture was mixed with a Henschel mixer without using a jet mill, and the reaction was carried out. As a result, the yield was 80.7% and the purity was 93. 0.8%. It is considered that the reason why the yield was lower than that in Example 1 is that the particle size of the raw material was large.

Comparative Example 1 Industrial melamine manufactured by Mitsui Toatsu Chemicals Co., Ltd. (average particle size 100 μm)
m) 2.0 kg of cyanuric acid manufactured by Shikoku Chemicals, trade name I
Using 2.0 kg of CA-P (average particle size: 80 μm) and omitting pulverization by a jet mill, the same procedure as in Example 1 was carried out. The yield was 14.2% and the purity was 3%.
It was 8.7%.

Example 3 Using 78.58 g of the pulverized mixture obtained in Example 1, 30
Except that heating was carried out at 0 ° C. for 4 hours, the same procedure as in Example 1 was carried out.
45 g of melamine cyanurate were obtained. Yield 98.6
%, Purity 99.1%, and average particle diameter was 6.21 μm.

Example 4 Industrial melamine manufactured by Mitsui Toatsu Chemicals Co., Ltd. (average particle size 20 μm)
m) 6.3 g of cyanuric acid manufactured by Shikoku Kasei Co., Ltd., which was previously pulverized using a jet mill, trade name: ICA-P
(Average particle size: 3.1 μm) into a 50 ml stainless steel autoclave that can be heated to 500 ° C.
The temperature was gradually raised to 350 ° C. while stirring. Next, the mixture was heated and maintained at 350 ° C. for 1 hour with stirring to obtain 12.2 g of melamine cyanurate. The yield was 98.3%, the purity was 99.6%, and the average particle size was 18.4 μm.

Comparative Example 2 In place of cyanuric acid, 9 g of granular urea (melting point: 132 ° C., average particle diameter: 1 mm) manufactured by Mitsui Toatsu Chemicals, Inc. and melamine: 4.5
g, and a temperature of 300 ° C., except that a melamine cyanurate having a yield of 93% and a purity of 87.2% was obtained in the same manner as in Example 4.

Example 5 A 100-liter Nauter mixer (manufactured by Hosokawa Micron Corporation) was placed in an industrial melamine manufactured by Mitsui Toatsu Chemicals Co., Ltd. (melting point: 354 ° C., sublimation starting temperature: 210 ° C., average particle size: 20 μm).
m) 20.0 kg, 20.0 kg of cyanuric acid manufactured by Shikoku Chemicals Co., Ltd., trade name ICA-P (melting point: 360 ° C., sublimation start temperature: 230 ° C., average particle diameter: 80 μm) were charged and mixed at room temperature for 1 hour. Then, the mixture was pulverized with a jet mill to an average particle diameter of 3.24 μm, and then granulated with an average particle diameter of 1 mm using a dry granulator Pharmapactor Model L2000 / 50P (manufactured by Hosokawa Micron Corporation).

This is stored in a raw material hopper 1 at the upper part of a reactor 3 shown in FIG. 2 having a diameter of 2 inches and a length of 1 meter and provided with an internal thermometer. Then, the mixture was continuously supplied to the reactor at a rate of 1 liter per hour, and approximately the same amount was continuously extracted from the reactor from the lower portion using the rotary valve 5. At that time, the internal reaction temperature was controlled by the heater 4 to be 350 ° C., and the retention time in the constant temperature section was set to 1 hour.

The operation was carried out for about one day continuously, but there was no trouble such as clogging on the way, the yield was 98.9%, and the purity was 98.0%.
5%, a granular melamine cyanurate having an average particle diameter of 1 mm was obtained. After the operation was completed, the inside of the reactor was observed, but no adhesion or deposition of powder was observed. Further, the obtained granular product was pulverized using a jet mill to obtain a powdery product having an average particle size of 4.83 μm. As a result of differential thermal analysis of melamine cyanurate obtained by grinding,
As shown in FIG. 1, there was a single peak, and the sublimation start temperature was 290 ° C.

Comparative Example 3 The procedure of Example 5 was repeated, except that the granulation was omitted and the mixed powder was supplied to the reactor as it was. It was blocked and operation could not be continued. The reason is that the powder formed a bridge inside the reactor.

Example 6 5 kg of the mixed granulated product obtained in Example 5 was charged into a reactor shown in FIG. 2 and heated at 350 ° C. for 2 hours. After the completion of the reaction, the granulated product was withdrawn (4.95 kg, yield 9).
9.0%, purity: 98.7%), and further crushed with a jet mill in the same manner as in Example 5 to obtain a powder. When the powder was subjected to differential thermal analysis, it was found that the powder had the same peak as the chart shown in FIG.

Example 7 The procedure of Example 5 was repeated except that the reaction temperature was 400 ° C. and the residence time was 30 minutes. Yield 95.7%, purity 99.3%
Met. As a result of differential thermal analysis of the obtained product, it showed a single peak as in FIG. 1 and the sublimation start temperature was 295 ° C.

Example 8 The procedure of Example 5 was repeated except that the reaction temperature was 300 ° C. and the residence time was 2 hours. At this time, the yield was 99.2% and the purity was 98.2%. As a result of differential thermal analysis of the obtained product, it showed a single peak as in FIG. 1 and the sublimation start temperature was 288 ° C.

Comparative Example 4 The procedure of Example 5 was repeated except that the reaction temperature was 200 ° C. and the residence time was 4 hours. At this time, almost no melamine cyanurate was obtained, and a granular mixture of melamine and cyanuric acid as raw materials was discharged from the lower part of the reactor.

Example 9 Example 5 was repeated except that a heating kneader type reactor was used.
The reaction was continuously performed in the same manner as described above. The operation was continued for approximately one day, but the operation was smooth without any trouble such as clogging. The yield was 98.5% and the purity was 98.3%.

[0043]

According to the present invention, melamine cyanurate can be produced in a simplified process as compared with the conventional method, and a granular melamine cyanurate which is easy to handle can be provided.

[Brief description of the drawings]

FIG. 1 is a chart of differential thermal analysis of melamine cyanurate obtained in Example 1 of the present invention.

FIG. 2 is a schematic sectional view of a reactor in Example 5 of the present invention.

FIG. 3 is a chart of a differential thermal analysis of a raw material melamine.

FIG. 4 is a chart of a differential thermal analysis of a raw material cyanuric acid.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw material hopper 2 Supply rotary valve 3 Vertical reactor 4 Heater 5 Extraction rotary valve

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuri Izumi 1-6-6 Takasago, Takaishi-shi, Osaka Mitsui East Pressure Chemical Co., Ltd. (56) References JP-A-54-55588 (JP, A) JP-A Sho 54-55587 (JP, A) JP-A-55-147266 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07D 251/54 CA (STN) REGISTRY (STN)

Claims (12)

(57) [Claims] 1. A method for producing melamine cyanurate, comprising heating powdered melamine and powdered cyanuric acid at 250 to 500 ° C. in the substantial absence of a liquid medium. 2. The method according to claim 1, wherein the heating is carried out while mixing the powdered melamine and the powdered cyanuric acid. 3. The method according to claim 1, wherein a mixture of the powdered melamine and the powdered cyanuric acid is prepared, and then the mixture is heated. 4. The method according to claim 1, wherein a mixture of the powdered melamine and the powdered cyanuric acid is granulated, and the granules are heated. 5. The powder melamine and the powder of cyanuric acid each having an average particle diameter of 20 μm or less.
The manufacturing method as described. 6. The method according to claim 4, wherein the particle size of the granules is 0.1 to 10 mm. 7. Using a vertical reactor having a cone-shaped lower portion, supplying granules of a mixture of powdered melamine and powdered cyanuric acid from the upper portion of the reactor, heating the mixture, and then heating the lower portion of the reactor. The product is withdrawn more continuously or batchwise.
The manufacturing method as described. 8. The method according to claim 4, wherein the granules of the mixture of the powdered melamine and the powdered cyanuric acid are obtained by compressing the mixture. 9. A mixture of powdered melamine and powdered cyanuric acid is granulated and then added to the mixture without the use of a liquid medium.
Granular melamine cyanurate obtained by heating to 0 to 500 ° C. 10. The obtained granular melamine cyanurate has a particle size of 0.1 to 10 mm and a bulk specific gravity of 0.3 to 1.4 g.
The granular melamine cyanurate according to claim 9, wherein the amount of the melamine cyanurate is 10 g / ml. 11. The granular melamine cyanurate according to claim 9, wherein the granules of a mixture of the powdered melamine and the powdered cyanuric acid are obtained by compressing the mixture. 12. A mixture of powdered melamine and powdered cyanuric acid is formed into granules, and the granules are then formed using a liquid medium.
A method for producing powdery melamine cyanurate , wherein the powdery melamine cyanurate obtained is heated to 250 to 500 ° C. and the obtained granular melamine cyanurate is pulverized.