CS263995B1 - Zinc magnesium magnesium double cyclo-tetrafluorates and process for their preparation - Google Patents

Abstract

The solution concerns new compounds of the type of double cyclo-tetraphosphates of zinc-magnesium of the formula c-Zn2-xMgxP40i2, where 0 < x < 2. Crystallization is prepared in a dry atmosphere from a melt with a temperature above 800 degrees Celsius, containing zinc and magnesium cations in a mutual molar ratio Zn/Mg corresponding to the relationship (2—xj/x and further containing phosphate anions in an amount corresponding to the ratio P2Os(Zn + -·(- Mg) equal to 0.96 to 1.1 during its solidification.

Description

BACKGROUND OF THE INVENTION The present invention relates to novel zinc-magnesium double cyclo-tetraphosphate compounds.

Among the compounds of the type of condensed phosphates one cation divalent © metal and the molar ratio of phosphorus pentoxide (P2O5) to the corresponding metal, equal to one, are known generally, first cyclo-tetraphosphate (Formula C-Me2 ^N P40i2j and secondly higher linear phosphates (formula Me ₁ / 2 ^II H _{; i} P _n 0 _{: il} , - | ₁ ).

This is also the case for zinc condensed phosphates, where both dicalcyclotaphosphate (c-Zn2P40i2) and higher linear zinc phosphates (Ζη _{η / 2} Η ₂ Ρ _η θ3 _{η +} ι] exist, even in the case of magnesium compounds where they exist higher linear phosphates (Mg _{n / 2} H _{; i} P _n O _{3 t} , ₊ i] i product with cyclic tetraphosphate anions (c-Mg2P40i2j) Double cyclo-tetraphosphates containing magnesium cations besides other divalent metal cations are gaining importance. the existence of condensed phosphates with pairs of these cations, but only as higher linear phosphates, but these higher linear phosphates of divalent metals, whether single-cation or double-cationic, have some properties that are They are less suitable because they are amorphous, non-crystalline, p They are also relatively easily soluble and some even tend to become wet.

Their thermal stability is limited by recrystallization temperatures (500-800 ° C). Due to the existence of simple higher linear phosphates (single cation) and simple cyclo-tetraphosphates with the corresponding cation, and especially from the comparison of their properties, it is expected that double compounds of the cyclo-tetrafosphate type, where one of the cations is magnesium, will have properties entirely other. They can be expected to be far more appropriate than higher linear phosphates for all the contemplated uses of condensed phosphates to date - both as special inorganic pigments and for agrochemical purposes.

SUMMARY OF THE INVENTION The present invention is based on zinc-magnesium double cyclo-tetraphosphates as novel compounds of the formula c-Zn ₂ - _x MgxP ₄₀ O ₂ , ρρρ-ΪΓν'Τ .''- »- '» ----- where 0 <x <2,

The lower and upper limits for x result from the fact that values of zero to two cannot be used, since they would no longer be a double product, but a pure, simple disodium cyclophosphate c-Zn2P40i2, rssp. o simple magnesium di-cyclophosphate C-M32P4O12. Zinc-magnesium double cyclo-tetraphosphates are white (colorless) substances whose densities range from 2.85 to 3.5 grams / cm ³ according to Zn / Mg ratio. They have a crystal structure in a monoclinic system with a spatial group C '2 / c.

Its lattice parameters vary according to the Zn / Mg ratio:

1.1749 to 1.1778 nm for α,

0.8278 to 0 _; 8305 nm for b,

0.9905 to 0.9910 nm for c,

118.83 ° to 118.94 ° for the beta angle and the volume of the elemental cell ranges from 0.8433 to 0.8492 nm ³ . Zinc-magnesium double cyclo-tetraphosphates are chemically and thermally very stable substances. They are insoluble in water, organic solvents and dilute mineral acids, but slowly dissolve in lye solutions. It melts only at high temperatures according to the Zn / Mg ratio in the range of 800 to 1160 ° C, the latent melting point being in the range of 33 to 85 kJ / mol. In a completely dry atmosphere or in a vacuum, they melt congruent, in an atmosphere containing at least traces of water vapor they melt non-congruent.

The invention further provides that zinc-magnesium double cyclo-tetraphosphates are prepared in such a way that the melt at a temperature above 800 ° C, preferably above 1160 ° C, containing zinc and magnesium cations in a Zn / Mg molar ratio corresponding to (2-x) / x and further comprising phosphate anions in an amount corresponding to a molar ratio of P2Os / (Zn + H-Mg) of 0.96 to 1.1, preferably of 1 to 1.005, is allowed to solidify in a completely dry atmosphere by cooling; preferably at a rate of less than 5 ° C / min to form a microcrystalline product. The melt temperature must be selected above the melting point, respectively. solidification of products having a Zn / Mg ratio of 800 to 1160 ° C. The ratio of the zinc and magnesium cations in the melt is selected according to the requirement for their content in the product, and the amount of magnesium cations can range from values close to zero to values close to two. The content of phosphate anions in the melt must correspond to a molar ratio P2Os / (Zn-MMg) equal to one, or values differing only slightly from one, corresponding to the total formula of c-Zn ₂ - _x Mg _x P ₄₀ 0 ₂ , otherwise By-products of other types of condensed phosphates have been formed and the proportion of the main product would be significantly reduced. Crystallization of the product by solidification from the cooling melt should be conducted in a completely dry atmosphere (or under vacuum), as even the presence of trace amounts of water vapor would again lead to condensation of phosphates with other anions and not with cyclotetaphosphate anions. According to the invention, the products can optionally be further purified by hydrochloric, sulfuric, nitric or phosphoric acid curing, since the double cyclo-tetraphosphates resist this cure, while the other products formed The preferred concentration of acids for curing is 0.05 to 10% w / w, where by-product separation is sufficiently effective, while the risk of attacking the main product is negligible.

The advantages of the invention are that it indicates the existence of new compounds which have not been known so far. These compounds accumulate advantageous physicochemical and application properties having simple divalent metal cyclotetrophosphates. Special pigment properties are emphasized and long-term solubility is influenced, which in turn is important for their agrochemical use.

Example 1

The melt prepared by melting 100 g of higher linear zinc phosphates and 81.6 g of higher linear magnesium phosphates at 1200 ° C was cooled in a dry atmosphere at a rate of 5 “Chnin. 181.6 g of a microcrystalline product was obtained, containing 98.5 wt. % zinc magnesium magnesium double cyclophosphate of formula ZnMgPiOis. White microcrystals are in a monoclinic system, spatial group C 2 / c, whose lattice parameters are a = 1.1774 nm, b = 0.8391 nm, c = 0.9900 nm, beta = 118.94 ° and the elementary cell volume 0 , 8468 nm ³ . Their density is 3.1 g / cm ³ , the melting point is 970 ° C and the heat of fusion is 58 kj / mol.

Example 2

The melt formed by melting 150 g of higher linear phosphates of zinc and 40.8 g of higher linear magnesium phosphates at 190.8 ° C, was cooled in a vacuum at 20 ^'Q C / min. 1180 grams of a microcrystalline product was obtained which contained 96.6 wt. % zinc magnesium magnesium double cyclotetrophosphate of formula c-Zni, ₅ Mgo, _{5 |} —P ₄ 0i ₂ . White microcrystals are in a monoclinic system, spatial group C 2 / c, whose lattice parameters are a = 1.1772 nm, b = 0.8300 nm, c = 0.9908 nm, beta = 118.88 ° elementary cell volume 0, 8477 mm ³ . Their density is 3.35 g / cm ³ , the melting point is 890 ° C and the heat of fusion is 44 kj / mol.

Example 3

The melt prepared by melting 50 g of higher linear zinc phosphates and 122.4 g of higher linear magnesium phosphates at 1230 ° C was cooled in a dry atmosphere at a rate of 2 ° C / min. 172.4 g of a microcrystalline product were obtained, containing 99.0 wt. % zinc magnesium magnesium double cyclophosphate of formula c-Zno with MgI 5P4O12.

White microcrystals are in monoclinic system, spatial group C 2 / c, whose lattice parameters are a = 1,1763 nm, b = 0,8284 nm, c = 0,9909 nm, beta = 118,93 ° and the volume of elementary cell is 0.8451 nm ³ . Their density is 3.03 g / cm ³ , the melting point is 1030 ° C and the heat of fusion is 72 kj / mol.

Claims (2)

Subject Double zinc cyclotetrophosphates of the formula c-Zm-xMgxPoO10, where 0 <X <2. 2. A process according to claim 1, wherein the melt has a temperature above 800 [deg.] C., preferably above 1160 [deg.] C., containing zinc and magnesium cations in a molar ratio Zn / Mg corresponding to (2-xj / / xa) The phosphate anion of the invention in an amount corresponding to a molar ratio of P2O5 / (Zn + Mg) of 0.96 to 1.1, preferably equal to 1 to 1.005, is allowed to solidify in a completely dry atmosphere by cooling, preferably at a rate of less than 5 ° C. min to form double zinc-magnesium cyclotrophosphates of microcrystalline nature, which are optionally purified by curing with hydrochloric, sulfuric, nitric or phosphoric acid, preferably a concentration of 0.05 to 10% by weight.