JPH0881482A - Method for producing melamine pyrophosphate - Google Patents

Abstract

(57) [Summary] [Structure] Crystals obtained by mixing and reacting melamine, hydrochloric acid, and pyrophosphate as raw materials are isolated, and then the average particle size is measured by a pulverizer such as a jet mill or a ball mill. To 10 μm or less. [Effect] With a simple operation, crystalline melamine pyrophosphate having a maximum intensity peak in X-ray analysis of 3.25Å can be obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing melamine pyrophosphate. More specifically, it relates to a method for producing a specific crystalline form of melamine pyrophosphate by pulverizing to a specific particle size or less.

[0002]

BACKGROUND ART Melamine pyrophosphate is used in foam expansion type fireproof and heat resistant paints. Melamine pyrophosphate is particularly suitable for this application because it releases large amounts of nitrogen-containing gas when heated.

Therefore, the performance of the foam-expansion-type fireproof and heat-resistant coating material is, of course, intended to maintain its performance as a coating material for the purpose of use, but it greatly affects the amount of melamine pyrophosphate contained therein. To be done.

The conventionally supplied crystalline form of melamine pyrophosphate, when dispersed in its aqueous medium, eg water,
When the amount of melamine pyrophosphate is increased, it has a drawback that the viscosity of the dispersion rapidly increases. Therefore, there is a limit to the amount to be added to the coating composition. As a result, this foam expansion paint often fails to adequately protect the substrate coated with it.

In this conventional melamine pyrophosphate, melamine is dispersed in water and reacted with a mineral acid such as hydrochloric acid or sulfuric acid to produce melamic acid. A general method is to produce this salt by reacting it with sodium pyrophosphate and then adding an acid to precipitate melamine pyrophosphate. The maximum intensity peak in the X-ray diffraction chart of the resulting melamine pyrophosphate is 4 It was .94Å.

Therefore, a method for producing a specific crystal form of melamine pyrophosphate (maximum intensity peak in X-ray diffraction chart: 3.25Å) which can increase the amount of addition while maintaining viscosity is proposed in JP-B-49-25675. ing. In a preferred embodiment, a sufficient amount of mineral acid is present in the aqueous medium at the time of the addition of pyrophosphate to provide 2 moles of melamine and 1
A method of making under conditions which provide a total of at least 4 hydrogen ion equivalents per mole of pyrophosphate.

However, although the melamine pyrophosphate obtained by this method can be effectively used, it is not reproducible due to severe reaction conditions, and it is very difficult to produce an effective melamine pyrophosphate by this method. is there.

Therefore, the inventors of the present invention have made earnest studies on a method for producing melamine pyrophosphate having a crystal form with a maximum intensity peak of 3.25Å in an X-ray diffraction chart.

[0009]

As a result, melamine pyrophosphate produced by any of the above-mentioned methods (that is, the maximum intensity peak in the X-ray diffraction chart is 3.2).
It was found that a specific crystalline form of melamine pyrophosphate can be produced by a simple operation of separating melamine pyrophosphate (not 5Å), separating and drying it and then pulverizing it so that the average particle size becomes 10 μm or less. Invented.

That is, according to the present invention, melamine and hydrochloric acid and pyrophosphate necessary for converting the melamine into a water-soluble hydrochloride are used as raw materials, and the crystals obtained by mixing and reacting these are isolated and then pulverized. Is a method for producing melamine pyrophosphate obtained by pulverizing so that the average particle size is 10 μm or less.

The present invention will be described in detail. In the present invention, first, melamine and hydrochloric acid and pyrophosphate necessary for making it a water-soluble hydrochloride are used as raw materials, and these are mixed and reacted to produce melamine pyrophosphate.

Any method may be used for the mixed reaction. For example, as one of the preferred embodiments, 2 mol of melamine is dispersed in an aqueous medium, sufficient amount of hydrochloric acid is added thereto to generate melamic acid, and then 1 mol of pyrophosphate is gradually added. It is a method of producing melamine pyrophosphate crystals. As another method, 1 mol of pyrophosphate is dissolved in an aqueous medium, 2 mol of melamine is dispersed therein, and a sufficient amount of hydrochloric acid is added to generate melamine pyrophosphate crystals. Can be mentioned.

The reaction temperature is preferably 65 ° C. or higher, and 65 ° C.
If it is less than the above, an unknown substance may be precipitated, which is not preferable.

In the present invention it is possible to use all suitable pyrophosphates. The most suitable are alkali metal pyrophosphates including ammonium salts, sodium salts and potassium salts of pyrophosphates or hydrates thereof,
Examples include ammonium pyrophosphate, sodium pyrophosphate, sodium acid pyrophosphate, potassium pyrophosphate, and potassium acid pyrophosphate. Such water-soluble pyrophosphate is suitable.

The slurry containing the melamine pyrophosphate crystals is separated into melamine pyrophosphate crystals and the filtrate by a conventional method to obtain melamine pyrophosphate crystals. The obtained crystals are dried using a conventional dryer. About 90 hours at about 90 ° C. is suitable.

The melamine pyrophosphate crystal form at this stage may be a conventionally used crystal form, that is, the maximum intensity peak in the X-ray diffraction chart is 4.94Å.

Melamine pyrophosphate crystals were crushed using a crusher.
By pulverizing to an average particle size of 10 μm or less, X
The maximum intensity peak in the line diffraction chart changes to 3.25Å, and the desired melamine pyrophosphate crystal is obtained. Preferably, the particle size of 20 μm or less is 90% or more.

To obtain the best results, it is preferable to use a jet mill, a ball mill or the like as the crusher.
Examples of jet mills include Jet-O-Miser and Micromis
er, Blow-Knox, Trost Jet Mill, pneumatic jet mill, single track jet mill, etc. are used. The best results are obtained when the ball mill is pulverized for 3 hours or more.

The melamine pyrophosphate of the present invention can be easily distinguished by X-ray analysis. In the X-ray diffraction chart of melamine pyrophosphate obtained by the present invention, 1
Lines or diffraction peaks are shown with a mutual plane spacing of 0.64Å. Furthermore, in the X-ray diffraction chart of the melamine pyrophosphate of the present invention, there are other peaks at lower relative intensities. In the X-ray diffraction chart of the crystal provided by the present invention, the maximum intensity is at the peak of 3.25Å.

The melamine pyrophosphate obtained according to the present invention can give a slurry having a low viscosity. 100g of water
The amounts that can be added to the above were compared using a B-type viscometer. As a result, the crystalline form of melamine pyrophosphate having a maximum intensity peak of 4.94Å was 140 Pois when 100 g was added. On the other hand, 180 g of the crystalline melamine pyrophosphate of the present invention could be added. As described above, the crystalline form of melamine pyrophosphate of the present invention can be used more advantageously because the amount of addition can be increased while maintaining the viscosity.

[0021]

EXAMPLES The present invention will be specifically described below with reference to examples, but the scope of the present invention is not limited thereto. In the following, all parts and% are parts by weight and% by weight.

Example 1 To 2090 g of water at 90 ° C. in a 3 l reactor with stirrer,
Add 130.6 g of melamine with stirring and add 216
g of 35% hydrochloric acid is added. Keep at 90 ° C, 137.4
g sodium pyrophosphate is added at a rate of 20 g / min. After the addition is completed, the temperature is kept at 90 ° C. and aged for 15 minutes.

The slurry thus obtained was separated by a conventional method and dried to obtain 205.7 g of melamine pyrophosphate crystals. In the X-ray analysis of the melamine pyrophosphate obtained here,
The peak at 10.64Å was not seen, and the maximum intensity was shown at 4.94Å.

The melamine pyrophosphate crystals were pulverized with a single track jet mill (manufactured by Seishin Enterprise Co., Ltd.) to obtain finely pulverized melamine pyrophosphate having an average particle size of 4.6 μm.

Comparative Example 1 The crusher of Example 1 was changed to a free mill (made by Nara Machinery Co., Ltd.)
Pulverized melamine pyrophosphate having an average particle size of 83 μm was obtained.

X-ray analysis of the melamine pyrophosphate obtained in Example 1 and Comparative Example 1 gave the results shown in Table 1.

[0027]

[Table 1]

When 100 parts of melamine pyrophosphate of Comparative Example 1 was mixed with 100 parts of water, a highly viscous paste was produced. When 100 parts of melamine pyrophosphate of Example 1 was mixed, an aqueous slurry was obtained. Was given.

Example 2 The crusher of Example 1 was replaced with a ball mill and crushed for 3 hours,
Melamine pyrophosphate having an average particle size of 5.6 μm and 5.6 μm was obtained. X-ray analysis of the obtained melamine pyrophosphate showed 10.
A peak was shown at 64Å and a maximum intensity was shown at 3.25Å.

Comparative Example 2 When the grinding time was set to 2 hours in Example 2, the obtained melamine pyrophosphate had an average particle size of 100 μm, and in this X-ray analysis, a peak at 10.64Å was not observed, 4.94
Maximum strength was indicated by Å.

Example 3 2090 g of water at 90 ° C. was charged into a 3 l reactor equipped with a stirrer, to which 137.4 g of sodium pyrophosphate was added and dissolved. To this, 130.6 g of melamine was added, followed by 216 g of 35% hydrochloric acid to generate melamine pyrophosphate crystals.

The slurry thus obtained was separated by a conventional method and dried to obtain 205.7 g of melamine pyrophosphate crystals. In the X-ray analysis of the melamine pyrophosphate obtained here,
The peak at 10.64Å was not seen, and the maximum intensity was shown at 4.94Å.

The melamine pyrophosphate crystals were ground with a single track jet mill (manufactured by Seishin Enterprise Co., Ltd.) to obtain finely ground melamine pyrophosphate having an average particle size of 4.6 μm. X-ray analysis of the obtained melamine pyrophosphate showed a peak at 10.64Å and a maximum intensity at 3.25Å.

[0034]

INDUSTRIAL APPLICABILITY According to the present invention, the melamine pyrophosphate produced by any method can be used in the production of a specific crystalline form of melamine pyrophosphate, which was achieved by the prior art only under specific reaction conditions. However, it could be achieved by a simple method of crushing with a jet mill and / or a ball mill to an average particle size of 10 μm or less.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ken Nishimura 7-1, 1-1 Hikoshimasako-cho, Shimonoseki City, Yamaguchi Prefecture Mitsui Toatsu Chemical Co., Ltd.

Claims (3)

[Claims] 1. A method for producing a crystalline product of melamine pyrophosphate, the maximum intensity peak of which is 3.25Å in an X-ray diffraction chart, wherein melamine, hydrochloric acid and pyrophosphate are used as raw materials, and a mixed reaction is carried out. After isolating the obtained crystals, the average particle size was 1 with a crusher.
A method for producing a specific crystalline form of melamine pyrophosphate, which comprises pulverizing to a particle size of 0 μm or less. 2. The method for producing melamine pyrophosphate according to claim 1, wherein the pulverizer is a jet mill and / or a ball mill. 3. The method for producing melamine pyrophosphate according to claim 1, wherein the pyrophosphate is sodium pyrophosphate.