Background and overview[1]
Ammonium polyphosphate, referred to as APP, is a nitrogen-containing phosphate and is a white powder. Ammonium polyphosphate can be divided into three types according to its degree of polymerization: oligopolymer, medium polyphosphate, and high polymer. The greater the degree of polymerization, the smaller the water solubility. According to its structure, it can be divided into crystalline and amorphous forms. Crystalline ammonium polyphosphate is a water-insoluble and long-chain polyphosphate. There are five variants from I to V. Among them, high-polymerization crystalline type II ammonium polyphosphate has significant advantages in the field of polymer materials due to its good water insolubility, high decomposition temperature, and good compatibility with polymer materials. Compared with halogen-containing flame retardants, crystalline type II ammonium polyphosphate has the characteristics of low toxicity, low smoke, and inorganic. It is a new type of high-efficiency inorganic flame retardant.
Preparation[1-3]
Report 1,
A method for preparing crystalline type II ammonium polyphosphate directly from type I ammonium polyphosphate as raw material is as follows:
The raw materials are: 5kg of type I ammonium polyphosphate with an average degree of polymerization of 30, and 50g of condensation agent; the condensation agent is composed of ammonium dihydrogen phosphate and urea, with ammonium dihydrogen phosphate 32.86 (0.286 mol) and urea 17.14g ( 0.286 mol), the particle size of type I ammonium polyphosphate and urea is >150 μm, and the particle size of ammonium dihydrogen phosphate is <150 μm.
The process steps are as follows:
(1) Add type I ammonium polyphosphate and urea to the first crushing and screening machine 1 and crush them to ≤150 μm (passing a 100 mesh sieve), then add the crushed type I ammonium polyphosphate, urea and ammonium dihydrogen phosphate Mix evenly in mixing tank 2 and then put it into material storage tank 3;
(2) Add the mixture of Type I ammonium polyphosphate, urea and ammonium dihydrogen phosphate in the storage tank 3 to the microwave tube furnace reactor 4 and start the stirring mechanism and microwave heating mechanism of the reactor to stir The speed is set to 20 rpm. Heat the mixture of type I ammonium polyphosphate, urea and ammonium dihydrogen phosphate to 100°C under stirring at a heating rate of 2.5°C/min. When it reaches 100°C, pass it into the microwave tube furnace reactor. Gas ammonia, the amount of gas ammonia introduced is limited to maintaining the ammonia partial pressure in the microwave tube furnace reactor at 0.085Mpa during the reaction process;
(3) Continue to microwave the mixture of type I ammonium polyphosphate, urea and ammonium dihydrogen phosphate to 170°C with stirring at a heating rate of 3.0°C/min and keep it at 170°C for 2.5 hours with stirring. , after the holding time expires, continue to microwave the mixture of type I ammonium polyphosphate, urea and ammonium dihydrogen phosphate to 280°C with stirring at a heating rate of 3.0°C/min and keep it at 280°C for 2.5 hours with stirring. , and then lower the temperature to cool the reaction product. When the temperature of the reaction product drops to 100°C, turn off the ammonia gas and continue cooling to room temperature to obtain crystalline type II ammonium polyphosphate;
(4) Use the second crushing and screening machine 5 to crush the obtained type II ammonium polyphosphate to the required particle size, and then use the packaging machine 6 to package the emulsifier.
The crystalline type II ammonium polyphosphate prepared by this method was analyzed with an X-ray diffractometer. The purity was higher than 99%. The nuclear magnetic resonance method was used to analyze the average polymerization degree of 1127. The thermogravimetric method was used to analyze and measure the thermal decomposition temperature. Greater than 281℃.
Report 2,
A method for preparing ammonium polyphosphate with cross-linking reactive groups, the steps are as follows:
(1) Silica sol-coated ammonium polyphosphate: Add 100g of ammonium polyphosphate and ml of ethanol into the reaction vessel, mix, stir and disperse. Then, add 25g of silica sol dropwise into the reaction system. At 20°C, After mixing and stirring for 8 hours, filter and wash with ethanol solvent.
(2) Silane coupling agent treatment of ammonium polyphosphate: Add 100g of ammonium polyphosphate and ml of ethanol coated with silica sol in step (1) into the reaction vessel, mix, stir and disperse, then add 5g dropwise Silane coupling agent KH-550 is used to graft-modify the surface of ammonium polyphosphate, and at the same time, 2.37g of ammonia water dispersed in 20 ml of ethanol is added dropwise to hydrolyze the silane coupling agent. After reacting at 80°C for 2 hours, the mixture is filtered and washed. , dried to obtain the coated ammonium polyphosphate.
Report 3,
A method for preparing melamine resin-coated ammonium polyphosphate with excellent water resistance is achieved through the following steps:
Step 1. Pretreatment of ammonium polyphosphate: According to the mass ratio of anhydrous methanol and sodium dodecyl benzene sulfonate activator of 25:1, mix anhydrous methanol and dodecyl benzene sulfonic acid Mix the sodium activator evenly to obtain a pre-treatment solution. Add the pre-treatment solution into a reaction kettle with heating and stirring function; add ammonium polyphosphate into the pre-treatment solution and stir for 20 minutes at a reaction temperature of 35 to 55°C. , to obtain a pre-treatment solid-liquid mixture of ammonium polyphosphate, in which the amount of ammonium polyphosphate added is 50% of the mass of the pre-treatment solution;
Step 2. Preparation of coating treatment solution: a. Mix melamine, formaldehyde solution and water according to the mass ratio of industrial grade melamine, 37% (mass) formaldehyde solution and water in order of 1:2:45. Obtain a mixed solution, adjust the pH value of the mixed solution to 8.5~9.0, and then continue the stirring reaction at a temperature of 80°C for 60 minutes to obtain a melamine resin solution; b. Cool the melamine resin solution obtained in step a to 40~ After reaching 65°C, add a conditioner to it, keep it warm and stir for 30 minutes to react to obtain a coating treatment solution; where the added amount of the conditioner is 0.5% of the mass of melamine in the melamine resin solution, and the mass ratio of the conditioners is 1: Made of 2:2 urea, polyvinyl alcohol and resorcinol;
Step 3: According to the mass ratio of the pretreated ammonium polyphosphate solid-liquid mixture obtained in step 1 and the coating treatment liquid obtained in step 2 to 1:2.5, mix the pretreated ammonium polyphosphate solidMix the liquid mixture and the coating treatment liquid evenly to obtain a mixed liquid, and then add 10% initiator by mass of the coating treatment liquid to the mixed liquid (the initiator is a mixture of 90% (mass fraction) phosphoric acid and ethanol in a mass ratio of 1:1) , to obtain a coating system, adjust the pH value of the coating system to 5.0~5.5, and then react at a temperature of 70°C for 120 minutes to obtain a reaction system, and then filter the reaction system to obtain wet materials, and then put the wet materials at 110°C After drying at a temperature of for 60 minutes, melamine resin-coated ammonium polyphosphate is obtained, and the preparation method of melamine resin-coated ammonium polyphosphate is completed.
