JPH07188193A - Production of melamine cyanurate - Google Patents

Abstract

PURPOSE:To provide a method for economically producing high-purity melamine cyanurate, simplified in comparison with a conventional method. CONSTITUTION:The characteristic of this method for producing melamine cyanurate from melamine and cyanuric acid comprises adding <20 pts.wt. water to 100 pts.wt. of a mixture of melamine having <=10mum average particle diameter and cyanuric acid, and then reacting melamine with cyanuric acid.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing melamine cyanurate, and more particularly to a method for producing melamine cyanurate in the presence of a small amount of water using melamine and cyanuric acid in the form of fine powder.

[0002]

2. Description of the Related Art Conventionally, halogen-based flame retardants have been widely used as one kind of flame retardants for plastics, but they generate toxic substances such as dioxins when burned, and have high smoke emission.
There are some problems such as corrosion of the mold during molding, and there is an increasing demand for halogen-free and non-halogen compounds. Under such circumstances, substances having a triazine ring, such as melamine and melamine cyanurate, are being investigated as flame retardants. Melamine is directly used in urethane resin and melamine cyanurate is used in polyamide resin by several% to 30%.
It is known that flame retardancy can be imparted by mixing to some extent.

Melamine cyanurate is usually produced by dissolving melamine and cyanuric acid separately in water.
It was prepared by a method in which these aqueous solutions were mixed and reacted, and a precipitate of the sparingly soluble melamine cyanurate produced was filtered and dried.

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 it by filtration, etc. (3) It takes a long time to dry because the melamine cyanurate particles after separation contain a considerable amount of water (4) Since melamine cyanurate has a lump form in which fine particles are agglomerated, there is a problem that energy required for pulverization is very large.

As an industrial method, not a reaction of the above aqueous solution but a method of mediating water, that is, a method of reacting one or both of melamine and cyanuric acid in an aqueous solvent in a solid state ( Kaisho 54-14
1792), the production efficiency is improved and the filtration time is shortened as compared with the above reaction with an aqueous solution, but the above-mentioned drawbacks of (3) and (4) are not improved.

Similarly, for solid melamine and solid cyanuric acid, 2 parts of water are added per 100 parts by weight of the total amount.
A method in which 0 to 2000 parts by weight is added and the reaction is carried out while stirring or kneading (JP-A-54-55587), a uniform powder mixture of melamine and cyanuric acid having an average particle size of 100 μm or less is prepared, and then this mixture is added to this mixture. , A method of reacting by adding 30 to 300% of water based on the mixture (JP-A-54-55588).

As a method which does not use water, there is disclosed a method for producing melamine cyanurate by mixing and heating urea and melamine as a solid (JP-A-54-125690). In this method, it is necessary to use an expensive anticorrosive material in the reactor, and the mixture of urea and melamine reacts in the cloudy melt while deammonifying with heating, so the melamine cyanurate obtained is handled in blocks. It is not easy and the yield is insufficient, and further purification is necessary to obtain a highly pure product.

Further, even when melamine and cyanuric acid are used as raw materials, melamine and cyanuric acid react with each other to produce melamine cyanurate by setting the reaction temperature to 250 to 500 ° C. without using a liquid medium ( Japanese Patent Application No. 4-329696). Since this method does not use water, it has the advantage of not requiring filtration and drying steps.
The reaction must be carried out at an elevated temperature compared to the method using water at 50-500 ° C.

[0009]

However, the product obtained by reacting the above-mentioned water with addition of water and stirring or kneading can be subjected to a drying step for removing water, or a filtration / drying step. It was necessary to go through a crushing step, and when the amount of water added was reduced, it was difficult to obtain a high-purity product. It is an object of the present invention to provide an industrially excellent method for producing melamine cyanurate, which has a simplified production process as compared with conventional techniques.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that the amount of water to be added can be significantly increased by finely pulverizing melamine and cyanuric acid, which are reaction raw materials. It was found that the reaction proceeds even if the amount is reduced and high-purity melamine cyanurate is obtained, and that this reaction can be carried out under a relatively low temperature condition, and the present invention has been completed. That is, the present invention is a method for producing melamine cyanurate from melamine and cyanuric acid, in which less than 20 parts by weight of water is added to 100 parts by weight of a mixture of melamine and cyanuric acid having an average particle diameter of 10 μm or less to cause a reaction. And a method for producing melamine cyanurate.

The melamine used in the present invention does not need to be a special one, and may be one generally available on the market. For example, an industrial melamine manufactured by Mitsui Toatsu Chemical Co., Ltd. (melting point 354 ° C., sublimation start temperature 210) ℃, average particle size 20μ
m).

Further, cyanuric acid is not special and may be those which are generally available on the market. For example, Shikoku Kasei Co., Ltd. product name ICA-P (melting point 360 degreeC, sublimation start temperature 230 degreeC, average particle diameter 80micrometer) is mentioned. In addition, cyanuric acid has two tautomers, an enol type and a keto type.
The keto type is referred to as isocyanuric acid, but the cyanuric acid used in the present invention does not mean only the enol type, but means both the enol type and the keto type.

The melamine and cyanuric acid used in the present invention have an average particle size of 10 μm or less, preferably 5 μm, when the melamine and cyanuric acid are uniformly mixed.
m or less. The method for obtaining such a mixture is not particularly limited, but for example, powdered melamine and powdered cyanuric acid prepared in advance with a pulverizer such as a jet mill so that the average particle diameter is 10 μm or less. Is obtained by mixing with a mixer such as a Henschel mixer or a Nauta mixer, or after mixing powder melamine and powder cyanuric acid in advance, if necessary with a crusher such as a jet mill. It can be obtained by adjusting the average particle diameter to 10 μm or less. The average particle size of the mixture is 1
If it is larger than 0 μm, the reaction does not proceed sufficiently and unreacted substances remain, resulting in a decrease in purity.

The mixing ratio of melamine and cyanuric acid of the present invention is preferably 1: 1 because melamine cyanurate is produced by an equimolar reaction. However, when the obtained reaction product may be a mixture of melamine cyanurate and melamine or a mixture of melamine cyanurate and cyanuric acid, the molar ratio may not be 1: 1.

In the present invention, the amount of water added is less than 20 parts by weight, preferably 5 to 15 parts by weight, based on 100 parts by weight of the mixture of melamine and cyanuric acid. Addition of 20 parts by weight or more is not preferable because it requires a long time for filtering and drying the reaction product.

Water may be added to melamine or cyanuric acid before mixing melamine and cyanuric acid having an average particle size of 10 μm or less, or may have an average particle size of 10 μm.
You may add to the homogeneous mixture of the melamine and cyanuric acid prepared below m.

There are various methods for reacting melamine and cyanuric acid. After adding water, the reaction is carried out at a predetermined temperature while stirring and mixing, or by adding water and further mixing. After the water is dispersed in the mixture, the reaction may be carried out at a predetermined temperature without stirring and mixing.

The reaction temperature may be arbitrary, but it is 40 to 3 because the reaction at a relatively low temperature, which is a feature of the present invention, is possible.
It is 50 ° C., preferably 80 to 250 ° C. When the reaction temperature is lower than 40 ° C, the reaction proceeds but the reaction rate is extremely slow and the reaction time becomes long, which is not practical. When the temperature is 350 ° C. or higher, the temperature dependence of the reaction time becomes small, and when the reaction is carried out at a temperature higher than this, the energy efficiency becomes poor. The reaction time is affected by the reaction temperature and the stirring condition, but is usually about 10 minutes to 5 hours.

The feature of the present invention is that the reaction can be carried out at a relatively low temperature and the melamine cyanurate obtained as a reaction product can be directly obtained as a product. Moreover, after completion of the reaction, if necessary, heating can be carried out at a suitable temperature for a short period of time, and the drying can be carried out as it is without taking out from the reactor. Since the amount of water to be added is very small in this way, the filtration step in the conventional method can be omitted, and since the generated melamine cyanurate can be dried in a short time, less energy is required for drying. Complete. By this, the reaction,
The two steps of drying can be carried out in one device, and the construction of a further simplified process is also possible.

Surprisingly, although the reason is not clear, the obtained melamine cyanurate does not aggregate into a lump and maintains a powder state because of finely pulverizing the raw material and adding a small amount of water. Since the product crushing step can be omitted, a very simplified process can be constructed.

[0021]

EXAMPLES The present invention will be described in more detail below with reference to examples.

Example 1 In a Henschel mixer having a volume of 10 liters, 1.95 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. , Trade name ICA-P (melting point 360
C., sublimation start temperature 230.degree. C., average particle size 80 .mu.m) 2.
00 kg was charged and mixed at room temperature for 10 minutes. Then, using a jet mill, the entire amount of the mixture was ground at room temperature,
3.88 kg of finely ground mixture was obtained. The average particle size of this finely pulverized mixture was 2.63 μm (measured by a laser beam diffraction method based on volume).

30 g of this finely pulverized mixture was placed in a magnetic crucible, 4.5 g of water was further added, and the mixture was thoroughly mixed with a spoon for 10 minutes at room temperature. Then, the crucible was covered with a lid and placed in an electric furnace. Heated at ° C for 2 hours. As a result, 29.5
g of melamine cyanurate was obtained. At this time, the yield was 98.3%, the purity was 98.8%, and the average particle size was 6.5.
It was 9 μm. As a result of thermogravimetric analysis chart of the obtained melamine cyanurate, the sublimation initiation temperature was 290 ° C. This chart is shown in (FIG. 1). 10 in this figure
No weight loss was observed at around 0 ° C., and water was completely evaporated during the reaction, which shows that the filtration and drying steps are unnecessary.

Comparative Example 1 30 g of the finely pulverized mixture obtained in Example 1 was placed in a glass beaker having a capacity of 500 ml containing 100 g of water and reacted at 95 ° C. for 1 hour while stirring. After that, water was separated by vacuum filtration and dried at 120 ° C.
It took 8 hours to completely dry. The melamine cyanurate obtained at this time was in a lump form, and this was pulverized with a ball mill to 14.7 μm. The result of thermogravimetric analysis of the obtained melamine cyanurate showed a single peak as in (FIG. 1).

Comparative Example 2 Industrial melamine manufactured by Mitsui Toatsu Chemicals, Inc. (average particle size 20 μm
m) and Shikoku Kasei's cyanuric acid, trade name ICA-P
Example 1 was repeated except that (average particle size 80 μm) was used as it was without fine pulverization. A thermogravimetric analysis chart of the product obtained at this time is shown in (FIG. 2). From this figure,
It can be seen that a large amount of melamine and cyanuric acid, which are the raw materials, remain unreacted. The thermogravimetric analysis charts of melamine and cyanuric acid are shown in (FIG. 3) and (FIG. 4), respectively.

Comparative Example 3 The same procedure as in Example 1 was carried out except that 30 g of the finely ground mixture obtained in Example 1 was placed in a magnetic crucible and no water was added, but melamine cyanurate was scarcely obtained, and thermogravimetric analysis was performed. The chart showed that it was a mixture of melamine and cyanuric acid.

Example 2 Industrial melamine (average particle size 3.10 μm) 1.95 k manufactured by Mitsui Toatsu Kagaku Co., which was finely pulverized in advance using a jet mill.
g, and finely ground cyanuric acid manufactured by Shikoku Kasei Co., Ltd., trade name ICA-P (average particle size 2.88 μm) 2.00 k
and g were placed in a heating type Henschel mixer having a volume of 10 liters, 0.6 kg of water was further added, and the temperature was raised to 200 ° C. while mixing. Furthermore, while mixing, 200 ℃
When reacted for 2 hours, 3.93 kg of melamine cyanurate was obtained. At this time, the yield was 99.0% and the purity was 99.2%. The thermogravimetric analysis chart was the same as (Fig. 1) and showed a single peak.

[0028]

Industrial Applicability According to the present invention, it is possible to provide a simplified and economical method for producing melamine cyanurate with high purity as compared with the conventional method, which is industrially advantageous.

[Brief description of drawings]

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

FIG. 2 is a thermogravimetric analysis chart of the product obtained in Comparative Example 2 of the present invention.

FIG. 3 is a thermogravimetric analysis chart of raw material melamine.

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

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

Claims (2)

[Claims] 1. A method for producing melamine cyanurate from melamine and cyanuric acid, wherein the average particle size is 10 μm.
A method for producing melamine cyanurate, which comprises adding less than 20 parts by weight of water to 100 parts by weight of a mixture of melamine and cyanuric acid of m or less and reacting. 2. A mixture 100 of melamine and cyanuric acid.
The method according to claim 1, wherein the amount of water added is 5 to 15 parts by weight with respect to parts by weight.