Mixtures of aluminum phosphite with sparingly soluble aluminum salts and foreign ions, process for the production thereof and the use thereof

A process for preparing a mixture of aluminum phosphite with sparingly soluble aluminum salts and nitrogen-free extraneous ions, where the mixture of aluminum phosphite comprises:

• 80 to 99.898% by weight of an aluminum phosphite of the formula (I)
• Al2(HPO3)3xH2O (I)
• where x is 0 to 4;
• 0.1% to 10% by weight of the sparingly soluble aluminum salts;
• and
• 0.002 to 10% by weight of the nitrogen-free extraneous ions,
• the process comprising crystallizing in a ratio of 2.5 to 3.5 mol of a non-salt phosphorus source with 2 mol of a sparingly soluble aluminum salt in the presence of an auxiliary acid at 50 to 180° C. in a solvent and at a solids concentration of 2 to 60%.

A flame-retardant thermoplastic or thermoset polymer molding composition or polymer molding, film, filament or fiber comprising

• 0.1 to 45% by weight of a mixture of aluminum phosphite with sparingly soluble aluminum salts and nitrogen-free extraneous ions;
• 55 to 99.9% by weight of thermoplastic or thermoset polymer or mixtures thereof;
• 0 to 55% by weight of additives;
• and
• 0 to 55% by weight of filler or reinforcing materials,
• where the sum of the components is 100% by weight, and
• wherein the mixture of aluminum phosphite with sparingly soluble aluminum salts and nitrogen-free extraneous ions comprises:
• 80 to 99.898% by weight of an aluminum phosphite of the formula (I)
• Al2(HPO3)3xH2O (I)
• where x is 0 to 4;
• 0.1 to 10% by weight of the sparingly soluble aluminum salts;
• and
• 0.002 to 10% by weight of the nitrogen-free extraneous ions.

A flame-retardant thermoplastic or thermoset polymer molding composition or polymer molding, film, filament or fiber comprising

• 0.1 to 45% by weight of a flame retardant mixture comprising 0.1 to 50% by weight of a mixture of aluminum phosphite with sparingly soluble aluminum salts and nitrogen-free extraneous ions;
• 50 to 99.9% by weight of a flame retardant, 55 to 99.9% by weight of a thermoplastic or thermoset polymer or mixtures thereof;
• 0 to 55% by weight of additives;
• and
• 0 to 55% by weight of filler or reinforcing materials,
• where the sum of the components is 100% by weight, and
• wherein the mixture of aluminum phosphite with sparingly soluble aluminum salts and nitrogen-free extraneous ions comprises:
• 80 to 99.898% by weight of an aluminum phosphite of the formula (I)
• Al2(HPO3)3xH2O (I)
• where x is 0 to 4;
• 0.1 to 10% by weight of the sparingly soluble aluminum salts;
• and
• 0.002 to 10% by weight of the nitrogen-free extraneous ions.