JP3127936B2 - Method for producing melamine cyanurate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing melamine cyanurate. More particularly, the present invention relates to a method for industrially and inexpensively producing melamine cyanurate suitable for flame retardants and lubricants of synthetic resins from melamine and cyanuric acid.

[0002]

2. Description of the Related Art Melamine cyanurate is widely used as a flame retardant or lubricant for synthetic resins such as polyamides, polyesters and epoxy resins. (Special Publication 58-2
No. 5379, JP-B-62-54157). The melamine cyanurate can be produced by mixing a melamine aqueous solution and a cyanuric acid aqueous solution to form a white precipitate of melamine cyanurate by a neutralization reaction. The precipitate is obtained by filtration, drying, and pulverization. Kosho 45
No. 5595) or a method in which a solid dispersion aqueous solution of melamine and cyanuric acid is reacted to obtain melamine cyanurate in the aqueous solution (JP-A-54-55588).

In addition, as a measure for dispersing melamine cyanurate sufficiently in a synthetic resin and maintaining good flame retardancy and sufficient mechanical properties of the resin, an organic diamine is added to melamine and cyanuric acid to polymerize polyamide. At times, melamine cyanurate is finely dispersed, and a method of obtaining a melamine cyanurate / polyamide composition having good dispersibility (Japanese Patent Application Laid-Open No. 56-127620) has been proposed. It gets complicated.

[0004] There is also a proposal to blend an organic phosphite in addition to melamine cyanurate to a polyamide resin to maintain flame retardancy and to improve tensile elongation and impact resistance (Japanese Patent Application Laid-Open No. 58-1983). 183747). Further, as a method for suppressing a decrease in mechanical properties of a resin when melamine cyanurate is added to the resin during production of melamine cyanurate, JP-A-3-122143 discloses an organic solvent in a water-soluble organic solvent. A method in which melamine and cyanuric acid are reacted in the presence of a polymer and water soluble in a solvent to obtain melamine cyanurate surface-treated with the polymer has been proposed, but using a large amount of an organic solvent, There is a problem that an increase in manufacturing cost cannot be avoided.

[0005] A method for producing melamine cyanurate, which is inexpensive, has good dispersibility in a synthetic resin, and suppresses a decrease in mechanical properties of the synthetic resin, has not yet been proposed.

[0006]

In the industrial production of melamine cyanurate from an aqueous solution or dispersion of melamine and cyanuric acid, the product, melamine cyanurate, removes water from a melamine cyanurate aqueous dispersion slurry. And need to be dried. Increasing the slurry concentration of melamine cyanurate reduces the water content in the slurry and can significantly reduce the cost of removing water, which is extremely important when industrially producing melamine cyanurate at low cost. , The viscosity of the melamine cyanurate slurry greatly increases, and this limits the stirring and transport of the slurry.

On the other hand, if the particles of the dried melamine cyanurate are too small, the fluidity of the powder is poor, causing adhesion in the apparatus and clogging during transport of the powder. In addition, the product collection in the cyclone does not go well and goes to the dust collector, and the production efficiency is greatly reduced. When melamine cyanurate is blended with the synthetic resin, it is necessary to show sufficient flame retardancy, but there is a problem that the mechanical properties of the synthetic resin are deteriorated.

An object of the present invention is to reduce the viscosity of an aqueous dispersion slurry of melamine cyanurate at the time of production of melamine cyanurate, to obtain a powder having good powder characteristics, and to synthesize An object of the present invention is to provide a method for producing melamine cyanurate, which can suppress a decrease in mechanical properties of a resin.

[0009]

That is, in 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, Alternatively, the present invention relates to a method for producing melamine cyanurate, comprising reacting melamine and cyanuric acid under heating, and then spray-drying the obtained aqueous dispersion slurry of melamine cyanurate.

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

The polyvinyl alcohol (hereinafter abbreviated as PVA) used as an additive in the present invention may be a commercially available ordinary water-soluble PVA. The degree of saponification of PVA is related to the solubility in water. If the degree of saponification is too high, the solubility in water is reduced, which is a practical obstacle. Therefore, the degree of saponification of PVA is preferably 99 or less. In addition, as the cellulose ethers used as an additive in the present invention, commercially available water-soluble methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, etc. obtained by partially etherifying cellulose can be used.

The process for producing melamine cyanurate according to the present invention comprises the steps of: preparing PVA and / or cellulose ethers;
Melamine and cyanuric acid are dispersed in water and reacted while mixing at room temperature or under heating to obtain a melamine cyanurate aqueous dispersion slurry. At this time, PVA and / or cellulose ethers used as additives are
A method in which melamine and cyanuric acid are dissolved in water in advance and then dispersed in water in which the additive is dissolved is preferable.
It is not preferable to add the above-mentioned PVA and / or cellulose ether 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 in molar ratio, and the amount of water is based on 100 parts by weight of the total amount of melamine and cyanuric acid. , 200 to 1100 parts by weight, preferably 300 to
1000 parts by weight. If the amount exceeds 1100 parts by weight, there is no problem in production, but the production amount of melamine cyanurate is reduced and it is not economical. If less than 200 parts by weight,
The viscosity of the aqueous dispersion slurry increases, and the power of the agitator in the reactor and the power of the pump for transporting the slurry increase, which makes production difficult.

The amount of the PVA and / or cellulose ether 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 of melamine and cyanuric acid. . When the amount is less than 0.1 part by weight, there is no effect of addition, and when the amount exceeds 10 parts by weight, the melamine cyanurate adheres to the wall in the dryer when spray-drying the obtained aqueous dispersion slurry of melamine cyanurate described below. As a result, the drying efficiency decreases, and the drying of melamine cyanurate becomes insufficient.

The reaction is usually carried out under normal pressure, at a temperature between room temperature and 1 ° C.
The reaction is carried out at a temperature of not higher than 00 ° C, but from the viewpoint of the reaction rate and production control, the reaction temperature is 50 to 95 ° C, preferably 80 to 90 ° C.
° C. The reaction time varies depending on the reaction temperature and the like, but is usually in the range of 1 to 2 hours. The aqueous dispersion slurry of melamine cyanurate thus obtained is spray-dried to obtain a product melamine cyanurate. Spray drying can be carried out using a usual spray dryer, and the drying temperature is usually 100 to 400 ° C.

The dried melamine cyanurate is PVA
And / or spherical melamine cyanurate particles surface-treated with cellulose ethers. The particle size is usually 30 to 120 μm as an average particle size,
The generation of fine powder of 10 μm or less is extremely small. The aqueous dispersion slurry of melamine cyanurate obtained by the method of the present invention,
In the method of separating by filtration and drying, the drying rate is low, so that the obtained melamine cyanurate becomes a strong solid, and a pulverizing and classifying step is required as a subsequent step, which increases the cost. Further, in the step of separation by filtration, a large amount of the added PVA and / or cellulose ether flows out to the filtrate side, and the concentration of PVA and / or cellulose ether in the surface-treated melamine cyanurate is uniform. Quality problem.

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

It is believed that the surface-treated melamine cyanurate obtained according to the present invention easily disperses in the synthetic resin, and the added PVA and / or cellulose ethers increase the adhesion between the synthetic resin and the melamine cyanurate. ,
The decrease in mechanical properties of the synthetic resin is suppressed, and the added PVA and / or cellulose ethers do not lower the flame retardancy of the synthetic resin.

Usually, 1 to 50 parts by weight of the surface-treated melamine cyanurate of the present invention is mixed with a synthetic resin.
As the synthetic resin to be blended, as a thermoplastic resin, polyethylene, polypropylene, polystyrene, ABS,
Examples thereof include polyphenylene sulfide, polycarbonate, polybutylene terephthalate, and polyamide. Examples of the thermosetting resin include an epoxy resin, a phenol resin, a urethane resin, and an unsaturated polyester resin. The surface-treated melamine cyanurate of the present invention is dispersed in the above-mentioned synthetic resin to give a flame-retardant, lubricated molded article, paint, or the like, by usual melt mixing, solution mixing, or the like.

The surface-treated melamine cyanurate of the present invention does not change its particle size even when blended in water, an organic solvent, an oil or the like, and has a small cohesiveness, so that it has good dispersibility and good lubrication. It is also used as an agent.

[0021]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. The viscosity of PVA in the examples was 4
% Aqueous solution at 20 ° C., and the viscosity of methylcellulose indicates the value of 2% aqueous solution at 20 ° C. 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 dissolved in 4 g with a stirrer, thermometer and condenser.
The mixture was heated at 80 ° C. for 2 hours while stirring in a neck flask to obtain an aqueous dispersion slurry of melamine cyanurate.

Subsequently, the obtained aqueous dispersion slurry of melamine cyanurate was dried at 250 ° C. with a spray dryer manufactured by Ajisawa Nilo Atomizer Co. to obtain melamine cyanurate particles whose surface was treated. Example 2 0.5 g of commercially available PVA (viscosity 27 cps, saponification degree 97)
Was used to obtain melamine cyanurate particles surface-treated in the same manner as in Example 1. Example 3 Particles of melamine cyanurate surface-treated in the same manner as in Example 1 were obtained using 5 g of commercially available PVA (viscosity 32 cps, saponification degree 88). Example 4 Particles of melamine cyanurate surface-treated in the same manner as in Example 1 were obtained by changing the amount of water in Example 1 to 465 g. Example 5 Instead of PVA of Example 1, commercially available methylcellulose (viscosity 1500 cps, degree of methoxyl group substitution 1.8)
0.5 g of melamine cyanurate particles treated in the same manner as in Example 1 except for using 0.5 g were obtained. Comparative Example 1 In Example 1, particles of melamine cyanurate were obtained without adding PVA. Comparative Example 2 An aqueous dispersion slurry of melamine cyanurate was obtained in the same manner as in Example 1 using 40 g of commercially available PVA (viscosity 27 cps, saponification degree 97).

Subsequently, the obtained aqueous dispersion slurry of melamine cyanurate was dried at 250 ° C. with a spray drier manufactured by Ajisawa Nilo Atomizer Co., Ltd., but the melamine cyanurate particles adhered to the spray drier and could not be produced. . Comparative Example 3 In Example 1, 0.2 g of a commercially available sodium polyacrylate (molecular weight: 240,000) was added instead of PVA, but the solid content in the slurry was settled and agglomerated, resulting in a poor slurry and spray drying. I could not do it.

Table 1 shows the measurement results of the viscosity of the melamine cyanurate in the aqueous dispersion slurry and the amount of the fine powder of the obtained melamine cyanurate at the time of production in Examples and Comparative Examples.
In addition, the melamine cyanurate particles obtained in Examples and Comparative Examples were used in a 6-nylon resin ( trade name, manufactured by Toray Industries, Inc.).
Amilan CM-1007) 100 parts by weight and 10 parts by weight
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 shown in Table 1.
The measurement and the judgment method were performed by the following methods. (A) Slurry Viscosity The viscosity of the aqueous dispersion slurry of melamine cyanurate at 23 ° C. was measured by a rotational viscometer. 8000 cps
With the above viscosity, industrial production was judged to be difficult due to an increase in stirring power when reacting melamine cyanurate and the limitation of the power of the slurry transport pump. The unit is expressed in cps. (B) Amount of fine powder The particle size of melamine cyanurate is measured by a centrifugal sedimentation method. When it was 10% or more, it was determined that collection was difficult 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 at 23 ° C. according to ASTM D-256
The elongation at break of the impact test and the tensile test according to ASTM D-638 were measured. The unit is kg-c
It is expressed in m / cm and%.

[0025]

[Table 1]

From Examples and Comparative Example 1, it can be seen that the viscosity of the slurry is significantly increased without adding PVA and / or cellulose ethers, which makes production difficult.
In addition, the amount of fine powder is large, and the collection efficiency in the cyclone decreases. Also, the mechanical properties of nylon have been reduced. Comparative Example 2 and Examples show that there is a limit to the amount of PVA and / or cellulose ether added, and that if too large, melamine cyanurate is insufficiently dried and adheres to the inside of the device. From Comparative Example 3, it can be seen that even if PVA and / or cellulose ethers are not used, a reduction in slurry viscosity can be achieved, but it is not suitable for spray drying.

The flame retardancy of both Examples and Comparative Examples when added to nylon was V-0, and the addition of PVA and / or cellulose ethers did not reduce the flame retardancy of nylon. As described above, the addition of the PVA and / or cellulose ethers of the present invention lowers 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 with little fine powder and little reduction in mechanical properties of the synthetic resin.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-122143 (JP, A) JP-A-54-55588 (JP, A) JP-A-56-32470 (JP, A) (58) Field (Int. Cl. ⁷ , DB name) C07D 251/54 CA (STN) REGISTRY (STN)

Claims (3)

(57) [Claims] 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, and the melamine and cyanuric acid are dispersed at room temperature or under heating. And then spray-drying the obtained aqueous dispersion slurry of melamine cyanurate, thereby producing 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, wherein the amount of the polyvinyl alcohol and / or the cellulose ether is 0.1 to 10 parts by weight based on 100 parts by weight of the total amount of melamine and cyanuric acid. A method for producing melamine cyanurate.