Method for preparing crystal II-type ammonium polyphosphate with distribution of high polymerization degree and narrow molecular weight, and device therefor

Abstract

The invention discloses a method for preparing crystal II-type ammonium polyphosphate with distribution of high polymerization degree and narrow molecular weight. The method comprises the following steps: putting phosphorus pentoxide and diammonium phosphate which have equal molar ratio into a malaxator which can accurately control a temperature and heated by conducting oil for mixing; under the protection of inert gas, heating the materials in the malaxator to between 100 and 250 DEG C through the circulatory conducting oil; stopping introducing the inert gas; performing ammonification on the materials and heating the materials under an atmosphere of ammonia gas till the materials are totally molten down; stopping introducing the ammonia gas; after homogenization, introducing the ammonia gas again and heating the materials; throwing a surface treating agent into the malaxator; after material throwing is completed, continuously introducing the ammonia gas, keeping warm and mixing the materials; after reaction is finished, transferring the materials to a closed vessel and reducing the temperature; simultaneously, continuously introducing the ammonia gas till the temperature of the materials is below 100 DEG C; and obtaining a finished product. The method can prepare the crystal II -type ammonium polyphosphate with the distribution of the high polymerization degree and the narrow molecular weight; and the product has the characteristics of uniform granularity shape, small water-solubility, good heat resistance, high polymerization degree, narrow distribution of molecular weight and high crystal II-type purity.

Description

technical field [0001] The invention belongs to the field of preparation methods of chemical raw materials, and discloses a preparation method of crystalline type II ammonium polyphosphate with high polymerization degree and narrow molecular weight distribution. Background technique [0002] Ammonium polyphosphate (APP) is a highly efficient and environmentally friendly flame retardant with high nitrogen and phosphorus content. It has a variety of crystal forms from I to V, among which type II ammonium polyphosphate has the best thermal stability and water resistance, so it is widely used in the flame retardant fields of high-grade refractory coatings, resins, rubber paper, wood, fibers, etc. , which has the characteristics of low toxicity, no dripping, low smoke, etc., and is a good substitute for halogen flame retardants. [0003] The high degree of polymerization ammonium polyphosphate produced in the prior art is all synthesized with phosphorus pentoxide and diammonium ...

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Problems solved by technology

[0003] The high degree of polymerization ammonium polyphosphate produced in the prior art is all synthesized with phosphorus pentoxide and diammonium hydrogen phosphate as raw materials, but because of process control and equipment design, the range of polymerization degree of the synthesized product is relatively wide, wherein Doped with a relatively large amount of low-molecular-weight ammonium polyphosphate; because no effective cooling measures were taken during the reaction process, the product was broken due to high temperature in the kneader, affecting the quality of the chain, and no measures were taken to control the intensity of the reaction; In addition, the mixing, kneading, and crushing functions of the kneader are not strong enough to realize the complete transformation of the state of the material in the kneader; at the same time, a large amount of excess ammonia will be generated during the synthesis process

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