JPH07149738A - Granular melamine cyanurate and its production - Google Patents

Abstract

PURPOSE:To provide a method for producing granular melamine cyanurate in which the production process is simplified as compared with that of a conventional method and the melamine cyanurate having readily handleable properties is obtained. CONSTITUTION:The characteristic of this method for producing granular melamine cyanurate is to heat powdery melamine and powdery cyanuric acid in the substantial absence of a liquid medium at 250-500 deg.C. The granular melamine cyanurate is obtained by granulating a mixture of both powders and then heating the resultant granule in the method.

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, more specifically, melamine cyanurate obtained by heating melamine and cyanuric acid without using a liquid medium, particularly granular melamine cyanurate, And a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, a halogen-based flame retardant has been used as a kind of flame retardant for plastics, but the harmful effect on human body of combustion products has become a problem, and there is a strong demand for halogen-free and non-halogenated products. In this situation,
Substances having a triazine ring such as melamine and melamine cyanurate have been studied as flame retardants, and flame retardancy is imparted by directly mixing melamine in urethane resin and melamine cyanurate in polyamide resin by several% to 30%. It is known that you can.

Melamine cyanurate is usually prepared by a method in which melamine and cyanuric acid are dissolved in water, respectively, an aqueous solution thereof is mixed and reacted, and a precipitate of the hardly soluble melamine cyanurate produced is filtered and dried. It 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, and (2) the reaction product is fine particles. Therefore, it is not easy to separate the melamine cyanurate particles by filtration or the like. (3) Since the melamine cyanurate particles after separation contain a considerable amount of water, it takes a long time to dry.

As an industrial method, a method of mediating water rather than the reaction of the above aqueous solution, that is, 20 to 2000 parts by weight of water is added to 100 parts by weight of the total amount of solid melamine and solid cyanuric acid. , A method of reacting while stirring or kneading (JP-A-54-5558).
7); A powder homogeneous mixture of melamine and cyanuric acid having an average particle size of 100 μm or less is prepared, and then the mixture is mixed with
A method is disclosed in which 30 to 300% of water is added based on the mixture and the reaction is carried out (JP-A-54-55588). In all of these, water is added to cause a reaction, and therefore a step of drying and pulverizing after the reaction is required.

As a method of using a raw material different from the above method, a method of producing a 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 because the mixture of urea and melamine reacts in the cloudy melt while causing deammonification with heating, the resulting melamine cyanurate is handled in blocks. However, the yield is insufficient, and further purification is necessary to obtain a highly pure 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 conventional techniques and a powdery or granular melamine having excellent properties. It is to provide cyanurate.

[0008]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that not only so-called solid-liquid reaction via a liquid medium but also reaction between solid and solid under specific conditions. The present invention has been completed and the present invention has been completed. That is, powder melamine and powder cyanuric acid are mixed, and preferably the mixture is made into a granular form,
A method for producing melamine cyanurate characterized by heating to 250 to 500 ° C. and a powdery or granular melamine cyanurate obtained by this method.

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

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

Cyanuric acid is an enol type or a keto type.
There are two tautomers, and chemically the enol type is called cyanuric acid and the keto type isocyanuric acid. The cyanuric acid used in the present invention does not mean only the enol type, but the enol type and keto type. 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 of cyanuric acid to 1 of melamine, in order to obtain high-purity melamine cyanurate. Has a molar ratio of 1: 0.9-
1.1.

In the present invention, the method for mixing the powdered melamine and the powdered cyanuric acid is not particularly limited, but it is preferable to make them as uniform as possible. The higher the homogeneity, the more chances of contact between melamine molecules and cyanuric acid molecules increase, and the apparent reaction rate increases, which reduces the disruption of the molar balance due to sublimation, resulting in higher yields and less contamination of unreacted substances. Purity is improved.

The powdered melamine and powdered cyanuric acid to be fed to the reactor may be premixed before being introduced into the reactor, or may be heated after being introduced into the reactor while being mixed. May be.

When mixed, the powdered melamine and the powdered cyanuric acid have a particle size of 80 μm or less and an average particle size of 2
It should be 0 μm or less. For this purpose, for example, the particle size is 80 μm or less in advance and the average particle size is 20 μm.
It is necessary to prepare a mixture of powder melamine and powder cyanuric acid in advance by using powder melamine and powder cyanuric acid prepared to m or less, or using a mixer such as a Henschel mixer or Nauta mixer. Accordingly, a grinder such as a jet mill having a particle diameter of 80 μm or less and an average particle diameter of 20 μm or less is used.

The present invention is considered to be a reaction between a solid and a solid or a solid and a gas. Since the particle size of the solid raw material affects the reaction rate, the powder melamine and the powder cyanuric acid to be subjected to the reaction are used. Is a particle size of 80 μm or less and an average particle size of 20 μm or less, preferably a particle size of 6 as described above.
0 μm or less and an average particle size of 0.5 to 10 μm, more preferably 30 μm or less and an average particle size of 0.5.
Those finely pulverized to ˜5 μm are suitable.

The powdered melamine and the powdered cyanuric acid having such particle diameters are kept as a solid without using a liquid medium.
Introduced in a reactor, 250-500 ° C, preferably 250-500 ° C
When heated to 430 ° C., more preferably 300 to 380 ° C., melamine cyanurate can be easily obtained in a heating time of about 10 minutes to 4 hours. Heating temperature is 250 ℃
If it does not satisfy the above condition, the reaction proceeds but is extremely slow, the yield of melamine cyanurate is poor, and unreacted melamine and cyanuric acid remain and the purity decreases. Above 500 ° C, not only the raw materials melamine and cyanuric acid,
Melamine cyanurate as a reaction product sublimes to cause 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-mentioned reaction, powdered melamine and powdered cyanuric acid are mixed in advance and granulated, whereby the raw materials and products are smoothly fluidized, and the reaction also proceeds favorably.

Although the reason for this is not clear, the mixture is compacted by granulating the mixture of the powdered melamine and the powdered cyanuric acid, and the reaction of the melamine and the cyanuric acid in a single granular particle causes unreacted granular particles. It is considered that sublimation to the outside is suppressed. Microscopically, it is considered that the consolidation increases the chances of contact between the melamine molecule and the cyanuric acid molecule, and the apparent reaction rate increases, so that the molar balance is not disturbed by sublimation.

The particle size of the powder melamine and the powder cyanuric acid constituting the granular mixture of the powder melamine and the powder cyanuric acid in the present invention is 80 μm or less, and the average particle size is 20 μm or less, preferably the particle size is 60 μm or less. And an average particle diameter of 0.5 to 10 μm, more preferably a particle diameter of 3
The average particle size is 0 μm or less and the average particle size is 0.5 to 5 μm. A mixture of melamine and cyanuric acid satisfying this condition is compressed by using a commercially available granulator and crushed if necessary, and the apparent particle size is in a range that is easy to handle, preferably 0.1 to 10 mm. The granular mixture is prepared to a degree. For example, a mixture of powder melamine and powder cyanuric acid is compressed using a dry granulator, and then the granular mixture is prepared by crushing, or by a semi-dry granulator,
The granular mixture may be prepared by compressing a mixture of powder melamine and powder cyanuric acid, extruding through a die, cutting to a desired length, and drying.

The mixed granules of the raw material powder melamine and the powder cyanuric acid obtained as described above as a solid, without using a liquid medium, are heated at 250 to 500 ° C. for 10 minutes to 4 hours. The melamine cyanurate can be obtained continuously or batchwise by heating so that In addition, an inert gas such as N ₂ gas may be introduced into the reactor during heating to prevent air from flowing into the reactor.

When the method of the present invention is applied to industrial production,
Although it is not necessary to use a special pressure closed vessel as the reactor, at least a reaction vessel having a tightness so that the raw materials and products are not volatilized is used. For example, the lower part equipped with equipment capable of heating the vessel wall may be a vertical cylinder having a cone shape and equipped with rotary valves at the raw material supply port and the reactant outlet port. In this case, the heating part inside the cylinder is used as a reaction zone, and the reaction product is continuously or batchwise taken out from the lower part so as to have a predetermined residence time, and a raw material suitable for it is fed from the upper part.

When using such a reactor, the use of mixed granules is particularly preferred. Since the granulated product has a good fluidity, it does not form a bridge inside the reactor and can freely move and drop at a speed commensurate with extraction and supply, and can be smoothly operated and not clogged. In order to promote heat transfer, a baffle plate may be provided inside the reactor so that the mixed granules can be dropped and moved in a lateral direction. Thus, melamine cyanurate can be obtained in high yield under normal pressure without pressurizing in the reactor.

The granular melamine cyanurate of the present invention is
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 a product as it is because the purity can be made sufficiently high without particular purification by appropriately selecting the reaction conditions. Usually 98
~ 99.9%, bulk specific gravity is 0.3 ~ 1.4g / ml
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 raw material powder melamine and the powder cyanuric acid. That is, the bulk specific gravity of the granular melamine cyanurate can be increased by increasing the compression ratio of the mixed granule. The apparent particle size of the granular melamine cyanurate is preferably about 0.1 to 10 mm, but since it can be obtained while substantially maintaining the shape of the raw material granular mixture, the apparent particle size at the stage of the raw material granular mixture is It may be controlled to a desired size.

The granular melamine cyanurate can be used as a product as it is, but it can be commercialized by adjusting the particle size by a general crushing 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. In such a case, the granules obtained by the method of the present invention using a jet mill or the like. Finely pulverized melamine cyanurate may be used.

The granular melamine cyanurate of the present invention comprises
Larger bulk specific gravity than powder melamine cyanurate,
Since there is little scattering and adhesion to equipment, there is little loss during manufacturing and packaging, and handling is easy. Further, since it is more compact than powder, it is possible to reduce the cost for transportation, storage and the like.

[0027]

The present invention will be described in more detail with reference to the following examples.

Example 1 In a Henschel mixer with a volume of 10 liters, 2.0 kg of industrial melamine (melting point 354 ° C., sublimation start temperature 210 ° C., average particle size 20 μm) manufactured by Mitsui Toatsu Chemicals, Inc. and cyanuric acid manufactured by Shikoku Kasei Co., Ltd. , Trade name ICA-P (melting point 360 ° C.,
Sublimation start temperature 230 ° C, average particle size 80 μm) 2.0k
g and charged for 10 minutes at room temperature. Then, using a jet mill, the total amount of the mixture was 33.4 kg / at room temperature.
Continuous feeding at h resulted in 3.91 kg of finely ground mixture. The average particle size of this finely pulverized mixture was 3.94 μm (measured by a laser beam diffractometry volumetric standard). 78.25 g of this finely pulverized mixture was placed in an evaporation dish, the surface was 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. Yield is 95.8%, purity is 99.2%, average particle size is 4.8.
It was 3 μm. The differential thermal analysis chart of the obtained melamine cyanurate is shown in FIG. The differential thermal analysis charts of the raw materials melamine and cyanuric acid are shown in FIGS.
It was shown to.

Example 2 As a result of carrying out the same procedure as in Example 1 except that the mixture as it was after mixing was used in a Henschel mixer without using a jet mill, the yield was 80.7% and the purity was 93. It was 0.8%. It is considered that the yield is lower than that in Example 1 because the particle diameter of the raw material is large.

Comparative Example 1 Industrial melamine manufactured by Mitsui Toatsu Chemicals, Inc. (average particle size 100 μm
m) 2.0 kg and cyanuric acid manufactured by Shikoku Kasei, trade name I
The same procedure as in Example 1 was carried out except that 2.0 kg of CA-P (average particle size: 80 μm) was not used and the milling was not carried out by the jet mill. The yield was 14.2% and the purity was 3%.
It was 8.7%.

Example 3 Using 78.58 g of the finely ground mixture obtained in Example 1, 30
77. Same as Example 1, except heating at 0 ° C. for 4 hours.
45 g of melamine cyanurate was obtained. Yield 98.6
%, The purity was 99.1%, and the average particle size was 6.21 μm.

Example 4 Industrial melamine manufactured by Mitsui Toatsu Chemicals, Inc. (average particle size 20 μm)
m) 6.3 g and cyanuric acid manufactured by Shikoku Kasei Co., Ltd., which was finely pulverized in advance using a jet mill, trade name ICA-P
6.5 g of (average particle diameter 3.1 μm) and 50 g were put into a stainless steel 50 ml autoclave capable of heating up to 500 ° C.,
The temperature was gradually raised to 350 ° C. with stirring. Then, the mixture was heated and held 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 9 g of granular urea (melting point 132 ° C., average particle size 1 mm), melamine 4.5, manufactured by Mitsui Toatsu Chemicals, in place of cyanuric acid.
As a result of the same procedure as in Example 4 except that the temperature was 300 g and the temperature was 300 ° C., a block-like melamine cyanurate having a yield of 93% and a purity of 87.2% was obtained.

Example 5 An industrial melamine manufactured by Mitsui Toatsu Chemical Co., Ltd. (melting point 354 ° C., sublimation start temperature 210 ° C., average particle diameter 20 μ) was added to a Nauta mixer (manufactured by Hosokawa Micron Co., Ltd.) having a volume of 100 liters.
m) 20.0 kg and 20.0 kg of cyanuric acid manufactured by Shikoku Kasei Co., Ltd., trade name ICA-P (melting point 360 ° C., sublimation start temperature 230 ° C., average particle size 80 μm) were charged and mixed at room temperature for 1 hour. Then, this mixture was pulverized by a jet mill to have an average particle diameter of 3.24 μm, and then made into granules having an average particle diameter of 1 mm by a dry granulator Pharmapactor L2000 / 50P type (manufactured by Hosokawa Micron).

This was stored in a raw material hopper 1 at the upper portion of the reactor 3 shown in FIG. 2 having a vertical cylinder shape with a diameter of 2 inches and a length of 1 meter equipped with an internal thermometer, from which a rotary valve 2 was used. Was continuously supplied to the reactor at a rate of 1 liter per hour, and approximately the same amount was continuously withdrawn from the reactor from the lower portion using a 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 part was set to 1 hour.

The operation was continued for about 1 day continuously, but there was no trouble such as clogging in the middle, the yield was 98.9%, and the purity was 98.
Granular melamine cyanurate with 5% and an average particle diameter of 1 mm was obtained. After the operation was completed, the inside of the reactor was observed, but no powder adhesion or deposition was observed. Further, the obtained granular product was pulverized with a jet mill to obtain a powdery product having an average particle diameter of 4.83 μm. As a result of differential thermal analysis of melamine cyanurate obtained by crushing,
There was a single peak as shown in FIG. 1, and the sublimation initiation temperature was 290 ° C.

Comparative Example 3 The same procedure as in Example 5 was carried out except that the granulation was omitted and the mixed powder was supplied to the reactor as it was, so that the lower part of the reactor could not be discharged smoothly after 6 hours. It became blocked and it became impossible to continue operation. The reason is that the powder formed a bridge inside the reactor.

Example 6 5 kg of the mixed granule obtained in Example 5 was charged into the reactor shown in FIG. 2 and heated at 350 ° C. for 2 hours. After the reaction was completed, the product was extracted and 4.95 kg of granular product (yield 9
9.0%, purity 98.7%) was obtained, and further pulverized by 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 to have a peak similar to that of the chart shown in FIG.

Example 7 Same as Example 5 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, a single peak was shown as in FIG. 1, and the sublimation initiation temperature was 295 ° C.

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

Comparative Example 4 Example 4 was repeated except that the reaction temperature was 200 ° C. and the residence time was 4 hours. At this time, melamine cyanurate was scarcely 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 carried out continuously in the same manner as in. The operation was continued for about a day, but there was no trouble such as clogging during the operation, and the operation was smooth. The yield was 98.5% and the purity was 98.3%.

[0043]

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

[Brief description of drawings]

FIG. 1 is a differential thermal analysis chart 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 raw material melamine.

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

[Explanation of symbols]

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

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuri Izumi 1-6 Takasago, Takaishi-shi, Osaka Mitsui Toatsu Chemical Co., Ltd.

Claims (12)

[Claims] 1. A method for producing melamine cyanurate, which comprises 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 powder melamine and the powder cyanuric acid are heated while being mixed. 3. The method according to claim 1, wherein a mixture of powdered melamine and powdered cyanuric acid is prepared and then the mixture is heated. 4. The method according to claim 1, wherein a mixture of powder melamine and powder cyanuric acid is made into granules, and the granules are then heated. 5. The powder melamine and the powder cyanuric acid each have an average particle diameter of 20 μm or less.
The manufacturing method described. 6. The method according to claim 4, wherein the particle size of the granule is 0.1 to 10 mm. 7. A vertical reactor having a cone-shaped lower part is used, and granules of a mixture of powdered melamine and powdered cyanuric acid are fed from the upper part of the reactor and heated, and then the lower part of the reactor. The product is withdrawn more continuously or batchwise.
The manufacturing method 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 granular melamine cyanurate obtained by granulating a mixture of powder melamine and powder cyanuric acid and then heating at 250 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.
/ Ml, The granular melamine cyanurate according to claim 9. 11. The granular melamine cyanurate of claim 9, wherein the granules of the mixture of powdered melamine and powdered cyanuric acid are obtained by compressing the mixture. 12. A powdery melamine cyanurate prepared by grinding a mixture of powdered melamine and powdered cyanuric acid into granules, heating the granules to 250 to 500 ° C., and grinding the resulting granular melamine cyanurate.