JPH05310716A - Production of melamine cyanurate - Google Patents

Abstract

PURPOSE:To provide a process for producing melamine cyanurate having excellent powder characteristics, capable of deceasing the viscosity of aqueous dispersion slurry in production and giving a flame-retardant synthetic resin while suppressing the lowering of the mechanical properties of the resin by compounding the melamine cyanurate to a resin. CONSTITUTION:The objective melamine cyanurate can be produced by reacting 100 pts.wt. of melamine and cyanuric acid in total with 200-1,100 pts.wt. of water and 0.1-10 pts.wt. of a mixture of a polyvinyl alcohol and/or a cellulose ether under mixing at room temperature or under heating and spray-drying the reaction product.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing melamine cyanurate. More specifically, it relates to a method for industrially inexpensively producing melamine cyanurate, which is suitable as a flame retardant for synthetic resins, lubricants, etc., from melamine and cyanuric acid.

[0002]

BACKGROUND OF THE INVENTION Melamine cyanurate is widely used as a flame retardant or lubricant for synthetic resins such as polyamide, polyester and epoxy resins. (Japanese Patent Publication 58-2
No. 5379, Japanese Patent Publication No. 62-54157). A method for producing melamine cyanurate is a method in which a white precipitate of melamine cyanurate is deposited by a neutralization reaction by mixing an aqueous solution of melamine and an aqueous solution of cyanuric acid, and the precipitate is obtained by filtration, drying, and pulverization (special Kosho 45
-5595) or a method of reacting a solid dispersion aqueous solution of melamine and cyanuric acid to obtain melamine cyanurate in the aqueous solution (JP-A-54-55588).

Further, as a measure for sufficiently dispersing melamine cyanurate in a synthetic resin to maintain good flame retardancy and sufficient mechanical properties of the resin, an organic diamine is added to melamine and cyanuric acid to polymerize polyamide. When added at the same time, a method of finely dispersing melamine cyanurate to obtain a melamine cyanurate / polyamide composition having good dispersibility (JP-A-56-127620) has been proposed. It gets complicated.

There is also a proposal to blend a polyamide resin with an organic phosphite ester in addition to melamine cyanurate to maintain flame retardancy and improve tensile elongation and impact resistance (JP-A-58). No. 183747). Furthermore, as a method for suppressing the deterioration of the mechanical properties of the resin when melamine cyanurate is blended with the resin during the production of melamine cyanurate, JP-A-3-122143 discloses that the organic compound is used in a water-soluble organic solvent. Although a method of obtaining a melamine cyanurate that is surface-treated with the polymer by performing a reaction of melamine and cyanuric acid in the coexistence of a solvent-soluble polymer and water, using a large amount of an organic solvent, There is a problem that an increase in manufacturing cost cannot be avoided.

A method for producing melamine cyanurate, which is inexpensive and has good dispersibility in a synthetic resin and which suppresses deterioration of mechanical properties of the synthetic resin, has not yet been proposed.

[0006]

When industrially producing melamine cyanurate from an aqueous solution or dispersion of melamine and cyanuric acid, the product melamine cyanurate is a product that removes water from an aqueous dispersion slurry of melamine cyanurate. Then need to be dried. Increasing the slurry concentration of melamine cyanurate can significantly reduce the cost of removing water by reducing the water content in the slurry, and is extremely important for industrially inexpensively producing melamine cyanurate. , The viscosity of the melamine cyanurate slurry is significantly increased, and stirring and transportation of the slurry are limited.

If the dried particles of melamine cyanurate are too small, the fluidity of the powder is poor, and adhesion in the apparatus and blockage during transportation of the powder occur. In addition, the product collection in the cyclone does not go well and the product goes to the dust collector, resulting in a significant decrease in production efficiency. When melamine cyanurate is blended with a synthetic resin, it is necessary to exhibit sufficient flame retardant properties, but there is a problem in that the mechanical properties of the synthetic resin deteriorate.

The object of the present invention is to reduce the viscosity of the water-dispersed slurry of melamine cyanurate during the production of melamine cyanurate, and the powder properties of the resulting melamine cyanurate are also good, and the melamine cyanurate prepared by compounding the powder is synthesized. It is an object of the present invention to provide a method for producing melamine cyanurate capable of suppressing deterioration of mechanical properties of a resin to a low level.

[0009]

Means for Solving the Problems That is, according to the present invention, in producing melamine cyanurate from melamine and cyanuric acid, polyvinyl alcohol and / or cellulose ethers are dispersed in water together with melamine and cyanuric acid at room temperature. Alternatively, the present invention relates to a method for producing melamine cyanurate, which comprises reacting melamine with cyanuric acid under heating and then spray-drying the obtained aqueous dispersion slurry of melamine cyanurate.

The present invention will be described in more detail below. Melamine used as a raw material of the present invention is a compound which is industrially obtained by reacting urea under high pressure and is known as a raw material of a melamine resin. Further, the cyanuric acid used as the raw material of the present invention is industrially obtained by a condensation reaction of urea, and usually two tautomers of enol type and keto type are considered, but the cyanuric acid referred to in the present invention is enol type. Includes molds and / or keto molds.

As the polyvinyl alcohol (hereinafter referred to as PVA) used as an additive in the present invention, a commercially available ordinary water-soluble PVA can be used. The saponification degree of PVA is related to the solubility in water, and if it is too high, the solubility in water decreases, which is a practical obstacle. Therefore, the saponification degree of PVA is preferably 99 or less. As the cellulose ethers used as an additive in the present invention, commercially available water-soluble methyl cellulose partially hydrolyzed, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose and the like can be used.

The method for producing melamine cyanurate according to the present invention comprises PVA and / or cellulose ethers,
Melamine and cyanuric acid are dispersed in water and reacted at room temperature or while heating to obtain a slurry of melamine cyanurate in water. At this time, PVA and / or cellulose ethers used as additives are
A method in which melamine and cyanuric acid are previously dissolved in water and then dispersed in water in which the additive is dissolved is preferable.
It is not preferable to add the above PVA and / or cellulose ethers to the aqueous dispersion slurry after the reaction of melamine and cyanuric acid.

The mixing ratio of melamine and cyanuric acid is usually in the range of 1: 0.7 to 1: 1.4 by molar ratio, and the amount of water is 100 parts by weight of the total amount of melamine and cyanuric acid. , 200-1100 parts by weight, preferably 300-
It is 1000 parts by weight. Even if it exceeds 1100 parts by weight, there is no problem in production, but the production amount of melamine cyanurate is reduced, which is not economical. If it is less than 200 parts by weight,
The viscosity of the water-dispersed slurry increases, the power of the stirrer in the reactor and the power of the pump for transporting the slurry increase, and manufacturing becomes difficult.

The amount of the PVA and / or cellulose ethers added is 0.1 to 10 parts by weight, preferably 0.2 to 2 parts by weight, based on 100 parts by weight of the total amount of melamine and cyanuric acid. .. If it is less than 0.1 part by weight, the addition effect is not obtained, and if it exceeds 10 parts by weight, melamine cyanurate adheres to the inner wall of the drier when spray-drying the obtained aqueous dispersion of melamine cyanurate described below. As a result, the drying efficiency is reduced and the melamine cyanurate is insufficiently dried.

The reaction is usually carried out under normal pressure and the temperature is from room temperature to 1
The reaction temperature is 50 to 95 ° C., preferably 80 to 90 ° C., in view of reaction rate and production control.
℃. The reaction time varies depending on the reaction temperature and the like, but is usually in the range of 1 to 2 hours. The water-dispersed slurry of melamine cyanurate thus obtained is spray-dried to obtain the product melamine cyanurate. For spray drying, an ordinary spray dryer can be used, and the drying temperature is usually 100 to 400 ° C.

Dried melamine cyanurate is PVA
And / or spherical melamine cyanurate particles surface-treated with cellulose ethers. The average particle size can be normally 30 to 120 μm, and
Generation of fine powder of 10 μm or less is extremely small. An aqueous dispersion slurry of melamine cyanurate obtained by the method of the present invention,
In the method of separating by filtration and drying, since the drying speed is slow, the obtained melamine cyanurate becomes a tough solid, and a pulverizing and classifying step is required as a post step, resulting in high cost. In addition, in the step of separating by filtration, the added PVA and / or cellulose ethers flow out to the filtrate side in a large amount, and the concentration of PVA and / or cellulose ethers in the surface-treated melamine cyanurate is uniform. There is no quality problem.

In the method for producing melamine cyanurate using PVA and / or cellulose ether of the present invention, the viscosity increase of the water-dispersed slurry of melamine and cyanuric acid is suppressed, and compared with the case where PVA and / or cellulose ether are not used. Then, since the viscosity of the resulting water-dispersed slurry of melamine cyanurate is significantly reduced, the solid content concentration of melamine cyanurate in the water dispersion can be increased, and the cost for evaporating water can be reduced, Melamine cyanurate can be produced at low cost. Further, since the PVA and / or cellulose ethers of the present invention act as a binder for melamine cyanurate, the generation of fine powder of 10 μm or less during spray drying is extremely small.

The surface-treated melamine cyanurate obtained according to the present invention is easily dispersed in a synthetic resin, and it is considered that the added PVA and / or cellulose ethers enhance the adhesion between the synthetic resin and melamine cyanurate. ,
The deterioration of mechanical properties of the synthetic resin is suppressed, and the added PVA and / or cellulose ether does not decrease the flame retardancy of the synthetic resin.

Usually, the surface-treated melamine cyanurate of the present invention is incorporated in a synthetic resin in an amount of 1 to 50 parts by weight.
The synthetic resin to be blended includes thermoplastic resins such as polyethylene, polypropylene, polystyrene, ABS,
Examples thereof include polyphenylene sulfide, polycarbonate, polybutylene terephthalate, and polyamide, and examples of the thermosetting resin include epoxy resin, phenol resin, urethane resin, unsaturated polyester resin, and the like. The surface-treated melamine cyanurate of the present invention is dispersed in the above synthetic resin by a usual melt mixing, solution mixing or the like to obtain a molded product, a paint or the like having flame retardancy and lubricity.

The surface-treated melamine cyanurate of the present invention does not change in particle size even when blended with water, an organic solvent, fats and oils, etc., and has a small cohesive property, and therefore has good dispersibility and good lubrication. It is also used as an agent.

[0021]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. The viscosity of PVA in the examples is 4
% Aqueous solution shows the value at 20 ° C., and the viscosity of methylcellulose shows the value at 20 ° C. of the 2% aqueous solution. Example 1 0.5 g of commercially available PVA (viscosity 32 cps, saponification degree 88) was dissolved in 600 g of water, and then 100 g of melamine and 102.4 g of cyanuric acid were mixed with a stirrer, a thermometer and a cooling pipe.
The mixture was placed in a necked flask and heated at 80 ° C. for 2 hours with stirring to obtain an aqueous dispersion slurry of melamine cyanurate.

Subsequently, the resulting water-dispersed slurry of melamine cyanurate was dried at 250 ° C. with a spray dryer manufactured by Ajisawa Niro Atomizer to obtain surface-treated particles of melamine cyanurate. Example 2 0.5 g of commercially available PVA (viscosity 27 cps, saponification degree 97)
Was used in the same manner as in Example 1 to obtain surface-treated particles of melamine cyanurate. Example 3 Using 5 g of commercially available PVA (viscosity 32 cps, saponification degree 88), the surface-treated particles of melamine cyanurate were obtained in the same manner as in Example 1. Example 4 The amount of water blended in Example 1 was changed to 465 g, and melamine cyanurate particles surface-treated in the same manner as in Example 1 were obtained. Example 5 Instead of the PVA of Example 1, a commercially available methyl cellulose (viscosity 1500 cps, methoxyl group substitution degree 1.8) was used.
The same procedure as in Example 1 was carried out except that 0.5 g was used to obtain surface-treated particles of melamine cyanurate. Comparative Example 1 In Example 1, particles of melamine cyanurate were obtained without adding PVA. Comparative Example 2 Using 40 g of commercially available PVA (viscosity 27 cps, saponification degree 97), an aqueous dispersion slurry of melamine cyanurate was obtained in the same manner as in Example 1.

Subsequently, the resulting water-dispersed slurry of melamine cyanurate was dried at 250 ° C. with a spray dryer manufactured by Ajisawa Niro Atomizer, but the melamine cyanurate particles adhered to the inside of the spray dryer and could not be manufactured. .. Comparative Example 3 In Example 1, 0.2 g of commercially available sodium polyacrylate (molecular weight 240,000) was added in place of PVA, but the solid content in the slurry settled and agglomerated, and a good slurry was not obtained, resulting in spray drying. I could not do it.

Table 1 shows the measurement results of the viscosity of the water-dispersed melamine cyanurate slurry at the time of production and the amount of fine powder of the obtained melamine cyanurate in Examples and Comparative Examples.
Further, the melamine cyanurate particles obtained in Examples and Comparative Examples were added in an amount of 10 parts by weight with respect to 100 parts by weight of 6-nylon resin (Amilan CM-1007) manufactured by Toray Industries, Inc. The mixture was kneaded at ℃ and cooled in an aqueous solution to obtain a compound. Then, after vacuum drying at 40 ° C. for 24 hours, injection molding was performed, flame retardancy was made, and a mechanical property test was performed. The results are also shown in Table 1. The measurement and determination methods were as follows. (A) Slurry Viscosity The viscosity of a water-dispersed slurry of melamine cyanurate at 23 ° C. was measured with a rotational viscometer. 8000 cps
At the above viscosity, industrial production was judged to be difficult due to the increase in stirring power when reacting melamine cyanurate and the limit of power of the slurry transport pump. The unit is cps. (B) Amount of fine powder The particle size of melamine cyanurate was measured by the centrifugal sedimentation method, and the weight% of 10 μm or less, which is a problem in cyclone collection, is shown. When it was 10% or more, it was determined that it was difficult to collect with an industrial device. (C) Flame-retardant According to the vertical flame-retardant evaluation method of UL-94. (D) Mechanical properties Izod according to ASTM D-256 at 23 ° C
The elongation at break of the impact test and the tensile test according to ASTM D-638 was measured. The unit is kg-c
Displayed in m / cm,%.

[0025]

[Table 1]

From Example and Comparative Example 1, it is understood that the slurry viscosity is significantly increased and the production is difficult unless PVA and / or cellulose ethers are added.
In addition, the amount of fine powder is large and the collection efficiency in the cyclone becomes small. In addition, the mechanical properties of nylon are also reduced. From Comparative Example 2 and Examples, it can be seen that the amount of PVA and / or cellulose ether added is limited, and if the amount is too large, the melamine cyanurate is insufficiently dried and adheres to the inside of the apparatus. It can be seen from Comparative Example 3 that the slurry viscosity can be reduced without using PVA and / or cellulose ethers, but it is not suitable for spray drying.

The flame retardancy when added to nylon in both Examples and Comparative Examples was V-0, and addition of PVA and / or cellulose ethers did not reduce the flame retardancy of nylon. From the above, the addition of the PVA and / or cellulose ethers of the present invention reduces the slurry viscosity in the production of melamine cyanurate,
It can be seen that the obtained surface-treated melamine cyanurate is an excellent method for producing melamine cyanurate, which has a small amount of fine powder and a synthetic resin with little deterioration in mechanical properties.

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[Procedure amendment]

[Submission date] July 30, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction content]

Table 1 shows the measurement results of the viscosity of the water-dispersed melamine cyanurate slurry at the time of production and the amount of fine powder of the obtained melamine cyanurate in Examples and Comparative Examples.
In addition, the particles of melamine cyanurate obtained in Examples and Comparative Examples were mixed with Toray 6-nylon resin ( trade name).
Amilan CM-1007) 10 parts to 100 parts by weight
Parts by weight were added, and the mixture was kneaded at 250 ° C. with a twin-screw extruder and cooled in an aqueous solution to obtain a compound. After performing continued for 24 hours by vacuum drying at 40 ° C., the flame retardant properties make injection molding,
A mechanical property test was performed. The results are also shown in Table 1.
The measurement and determination methods were as follows. (A) Slurry Viscosity The viscosity of a water-dispersed slurry of melamine cyanurate at 23 ° C. was measured with a rotational viscometer. 8000 cps
At the above viscosity, industrial production was judged to be difficult due to the increase in stirring power when reacting melamine cyanurate and the limit of power of the slurry transport pump. The unit is cps. (B) Amount of fine powder The particle size of melamine cyanurate was measured by the centrifugal sedimentation method, and the weight% of 10 μm or less, which is a problem in cyclone collection, is shown. When it was 10% or more, it was determined that it was difficult to collect with an industrial device. (C) conforming to the vertical-type flame retardant evaluation method of the flame retardant of UL-94. (D) Mechanical properties Izod according to ASTM D-256 at 23 ° C
The elongation at break of the impact test and the tensile test according to ASTM D-638 was measured. The unit is kg-c
Displayed in m / cm,%.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction content]

[0025]

[Table 1]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masayoshi Shirakawa 1 722, Tsuboi-cho, Funabashi-shi, Chiba Nissan Chemical Co., Ltd. Central Research Laboratory

Claims (3)

[Claims] 1. When producing melamine cyanurate from melamine and cyanuric acid, polyvinyl alcohol and / or cellulose ethers are dispersed in water together with melamine and cyanuric acid, and melamine and cyanuric acid are mixed at room temperature or under heating. And then spray-drying the obtained water-dispersed slurry of melamine cyanurate to produce a melamine cyanurate. 2. The method for producing melamine cyanurate according to claim 1, wherein the amount of water is 200 to 1100 parts by weight based on 100 parts by weight of the total amount of melamine and cyanuric acid. 3. The method according to claim 1 or 2, wherein the amount of polyvinyl alcohol and / or cellulose ether is 0.1 to 10 parts by weight with respect to 100 parts by weight of the total amount of melamine and cyanuric acid. Method for producing melamine cyanurate.