RU2292341C1 - Method for preparing melamine adduct with acid - Google Patents

Abstract

FIELD: chemistry of polymers, chemical technology.

SUBSTANCE: invention relates to the improved method for synthesis of melamine adducts with acids of the order: cyanuric, phosphoric, boric acid in the presence of liquid medium that are modifying agents of polymers. Method involves homogenization of melamine and acid powders in a mixer at temperature from 20°C to 80°C and then prepared mixture is subjected for effect by deformation shift at temperature from 20°C to 150°C at the shift rate value 5-400 s^-1 and the total deformation shift value from 1.5 x 10³ to 2.0 x 10⁵%. The ratio of melamine to acid is from 2:1 to 1:2 preferably. Effect by the deformation shift is carried out in mechanical reactor of auger type. Invention provides simplifying process in synthesis of end substances, significant decreasing consumptions and avoiding pollution of environment.

EFFECT: improved method of synthesis.

2 cl, 10 ex

Description

The invention relates to synthetic organic chemistry, and in particular to methods for producing derivatives of melamine in the form of its adducts with various acids, which can be used in the chemical industry for the production of active fillers or polymer modifiers in order to improve the operational properties of the latter, such as heat resistance, fire resistance, etc. .

A number of methods are known for preparing melamine derivatives by reacting starting materials in an aqueous medium. For example, there is a known method for producing melamine cyanurate (an adduct of melamine with cyanuric acid), comprising mixing and grinding melamine [M] with cyanuric acid [CC] with a ratio of components from 1: 9 to 9: 1 (wt.) In an aqueous medium ( from 20 to 2000% by weight to the weight of the whole mixture) in a cylindrical two-blade mixer at 0-250 ° C for 5 minutes to 5 hours [Japanese patent, JP 54055587, publ. 05/05/1979; European patent, EP 1438353, publ. July 21, 2004]. The disadvantages of this method are the difficulties in the allocation of the target product associated with the need for filtering, especially in the case of using a small amount of water. An increase in the amount of water facilitates the filtering process, but this leads to an increase in the volume of the reaction system and production facilities, as well as water consumption. Overcoming difficulties in filtering is achieved according to another method, including the interaction of finely ground starting components to a particle diameter of ≤100 μm, with a ratio of M to CK = 1: 1 (mol), followed by heating, evacuating the mixture (water content 50-500% weight .) [Japanese Patent JP 55147266, publ. November 17, 1980]. The selection of the target product is carried out by distillation of water by vacuum, followed by drying. The disadvantages of the method is the multi-stage process, requiring large energy costs associated with the need for fine grinding of the starting products and evacuation. Drying the product, in addition to energy consumption (supply of hot air), is accompanied by large losses of the target product, which is carried away by the air flow into the atmosphere, which leads to environmental poisoning or requires the installation of bulky and expensive structures.

A known method of producing melamine pyrophosphate (adduct of melamine with pyrophosphoric acid), comprising the steps of:

a) the interaction of a solution of an alkali metal salt (Na, K) of phosphoric acid with an acid-type ion-exchange resin at 0 ° C;

b) the resulting condensation product (pyrophosphoric acid) is added to suspension M at 0 ° C to obtain the target adduct [US Pat. No. 6,268,494, publ. July 31, 2001]. The process of interaction of the components proceeds by first passing a 2.5% (wt.) Aqueous solution (deionized water) of tetrasodium pyrophosphate through a column with an ion exchange resin, and then the resulting pyrophosphoric acid (PC) is reacted with M. The target product is isolated by filtration, washing with deionized water and drying at 100 ° C. The yield of melamine pyrophosphate is 94 ± 1%.

The disadvantage of this method is the multi-stage process, the need to use bulky equipment and deionized water.

A known method of producing borate of melamine (adduct of melamine with boric acid) [US patent, US 5854155, publ. December 29, 1998]. The interaction of the starting components is carried out in the presence of CaCO ₃ in the mixer for 6 hours at 90 ° C and in an atmosphere of a stream of 90% humidity with continuous temperature control of the system. The ratio of the starting components: boric acid (CD) to M is approximately 2: 1 (in moles).

The disadvantages of this method are the complexity and multi-stage process. The yield of the target product is not specified.

Closest to the claimed invention is a method for producing melamine cyanurate (adduct M with CK), comprising heating a dry powder mixture of M and CK at 250-500 ° C in the absence of any liquid medium, while the particle sizes of both M and CK each individually do not exceed 20 microns [US patent, US 5493023, publ. 02.20.1996]. The ratio of M to CC is from 1: 0.5 to 1: 2.0 (in moles), best from 1: 0.9 to 1: 1.1. The process is preferably carried out in an inert gas environment, such as, for example, N ₂ . Pre-mix the components at room temperature. Essentially, this method is carried out during the interaction of components in the melt (the melting temperature M is 250 ° C, and the temperature of the beginning of sublimation is 210 ° C, the melting temperature of the CC is 360 ° C, and the temperature of the beginning of sublimation is 230 ° C)). In this regard, the process is accompanied by a loss of reagents due to sublimation. In addition, expensive equipment (autoclave) is required, the process is accompanied by large energy costs associated with the need to maintain high temperature for a long period of time (up to several hours).

The objective of the invention is to provide a method that allows to obtain adducts M with various acids in a single technological mode. In addition, the method could be carried out without large water and energy costs with obtaining the target products with a large yield and would be environmentally friendly, would not require the stage of separation or capture of the final product.

The problem is solved in that a universal method has been created for the production of various adducts M with acids: cyanuric or pyrophosphoric, or boric in the absence of a liquid medium. The method consists in the fact that powdered M and acid are pre-homogenized in a mixer at a temperature of from 20 ° to 80 ° C, then the resulting homogeneous mixture is subjected to shear deformation at a temperature of from 20 to 150 ° C at a shear rate of 5-400 s ^-1 and the total shear strain from 1.5 · 10 ³ to 2.0 · 10 ⁵ %. The ratio of M to acid (molar) is preferably from 2: 1 to 1: 2. If cyanuric acid is used as the acid, adduct M with any of the tautomeric forms of the acid or a mixture thereof is obtained. In the case of pyrophosphoric or boric acid, adduct M with the corresponding acid is obtained. All adducts are obtained in powder form. The duration of the impact of shear deformation is mainly from 3 to 30 minutes. The effect of shear deformation can be carried out on a screw-type mechanochemical reactor.

The solution of this problem became possible due to the fact that the process of interaction of the starting reagents is carried out, unlike the known methods, not in solution, and not in the melt, but by the interaction of the starting products in a solid powder state under the action of shear strain.

The magnitude of the shear strain was determined by a known method [AS, SU 1423657, publ. in 1988], based on the following parameters:

γ — shear strain;

ω is the rotation speed of the mixer screws (100 rpm or 628 rad / min);

Q - apparatus productivity (0.14 kg / min);

L is the length of the shear zone (6 × 10 ^-2 m).

R _i - the inner radius of the mixer body (27.5 · 10 ^-3 m);

ρ is the polymer density, kg / m ³ (930 kg / m ³ );

S is the cross-sectional area of the working area (0.4 · 10 ^-3 m ² );

R ₀ is the average radius of the cross section of the grinding element (26.0 · 10 ³ m).

The content of the obtained adducts was determined by the intensity of the corresponding characteristic bands in the IR spectra of the reaction products.

The structures of the obtained adducts were proved by the coincidence of the DTA curves and the temperatures of the onset of sublimation for the adduct M with CC and melamine cyanurate, respectively, by the presence of crystalline reflections on the X-ray scattering curves of the adduct M with PC at angles of 20: 8.25 °, 18.0 °, and 27.5 °, characteristic of melamine pyrophosphate, as well as the presence in the IR spectra of the obtained adducts of bands characteristic of melamine cyanurate, melamine pyrophosphate and melamine borate, respectively.

The invention can be illustrated by the following examples.

Example 1. 252 g of powdered M is mixed with 258 g of powdered CK (molar ratio 1: 1) in a rotary paddle mixer at 40 ° C. Next, the resulting mixture is subjected to shear strain in a screw-type mechanochemical reactor at 80 ° C, an average shear rate of 60 s ⁻¹ to a total shear strain of 5.0 × 10 ⁴ % for 10 minutes. The yield of adduct M with a CC of 95 wt.%, Adduct purity of 97%. The content of adduct M with CK was determined by the intensity of the characteristic band of 1090 cm ^-1 in the IR spectrum of the reaction product. The temperature determined at the start of sublimation of the obtained adduct by DTA is 295 ° C, which is typical for melamine cyanurate.

Example 2. Performed similarly to example 1, however, in contrast to it, the temperature in the mixer is 20 ° C, and in the mechanochemical reactor 120 ° C. Yield 98 wt.%, Adduct purity 99%.

Example 3. Performed similarly to example 1, however, in contrast to it, the temperature in the mixer is 80 ° C, and in the mechanochemical reactor 150 ° C. Yield 94 wt.%, Adduct purity 95%.

Example 4. Performed similarly to example 2, but in contrast to it, the average shear rate is 5 s ^-1 , the total shear strain is 1.5 × 10 ³ %, and the exposure time is 30 minutes. Yield 60%, adduct purity 65%.

Example 5. Performed similarly to example 2, but in contrast to it, the average shear rate is 400 s ^-1 , the total shear strain is 2.0 × 10 ⁵ %, and the exposure duration is 3 minutes. Yield 98%, adduct purity 98.5%.

Example 6. 252 g of powdered M is mixed with 178 g of powdered PC (molar ratio 2: 1) in a rotary paddle mixer at 20 ° C. Next, the resulting mixture is subjected to shear strain in a screw-type mechanochemical reactor at 20 ° C, an average shear rate of 5 s ^-1 to a total shear strain of 1.5 × 10 ³ % for 30 minutes. The yield of adduct M with PC 75 wt.%, The purity of the adduct 80%. The content of adduct M with PC was determined by the intensity of the characteristic bands 1690 cm ^-1 and 1720 cm ^-1 in the IR spectrum of the reaction product.

Example 7. Performed similarly to example 6, however, in contrast to it, the average shear rate is 400 s ^-1 , the total shear strain is 2.0 × 10 ⁵ %, and the exposure duration is 3 minutes. Yield 96%, adduct purity 97%.

Example 8. 252 g of powdered M is mixed with 124 g of powdered BK (molar ratio 1: 2) in a batch mixer paddle at 20 ° C. Next, the resulting mixture is subjected to shear deformations in a screw-type mechanochemical reactor at 20 ° C, an average shear rate of 5 s ^-1 to a total shear strain of 1.5 × 10 ³ % for 30 minutes. The yield of adduct M with BC 60 wt.%, Adduct purity 65%. The content of adduct M with CD was determined by the intensity of the characteristic band 3395 cm ^-1 in the IR spectrum of the reaction product.

Example 9. Performed similarly to example 8, however, in contrast to it, the average shear rate is 400 s ^-1 , the total shear strain is 2.0 × 10 ⁵ %, and the exposure duration is 3 minutes. Yield 97%, adduct purity 98%.

Example 10. Performed similarly to example 9, however, in contrast to it, the temperature in the mixer is 80 ° C and in the mechanochemical reactor 150 ° C. Yield 92%, adduct purity 95%.

As can be seen from the above examples, the claimed method allows to obtain adducts of melamine with various acids in a single technological mode. In addition, the method is carried out without large water and energy costs with obtaining the target products with a large yield and is environmentally friendly, does not require the stage of separation or capture of the final product.

Claims (7)

1. A method of obtaining a melamine adduct with an acid selected from the series: cyanuric, pyrophosphoric, boric in the absence of a liquid medium, which consists in the fact that the powdered melamine and acid are pre-homogenized in a mixer at a temperature of from 20 to 80 ° C, then the resulting homogeneous mixture is subjected the effect of shear deformation at a temperature of from 20 to 150 ° C at a shear rate of 5-400 s ^-1 and a total shear strain of from 1.5 · 10 ³ to 2.0 · 10 ⁵ %. 2. The method according to claim 1, characterized in that the molar ratio of melamine to acid is 2: 1 ÷ 1: 2. 3. The method according to claim 2, characterized in that cyanuric acid is used as the acid to produce a melamine adduct from any of the tautomeric forms of the acid or mixtures thereof. 4. The method according to claim 2, characterized in that pyrophosphoric acid is used as the acid to produce a melamine adduct with pyrophosphoric acid. 5. The method according to claim 2, characterized in that boric acid is used as the acid to produce an adduct of melamine with boric acid. 6. The method according to any one of claims 1 to 5, characterized in that the duration of the impact of shear deformation is mainly from 3 to 30 minutes 7. The method according to any one of claims 1 to 5, characterized in that the action of shear strain is carried out on a screw-type mechanochemical reactor.