Preparation method of low-viscosity microcapsule-wrapped APP (ammonium polyphosphate)

Abstract

The invention discloses a preparation method of low-viscosity microcapsule-wrapped APP. The method comprises the steps as follows: in a reaction kettle, a melamine formaldehyde resin pre-polymer and APP are dispersed in a solvent; a curing agent solution is dripped; after dripping, a backflow reaction is performed for 0.5-5 h; the temperature is decreased to 40-50 DEG C; an end-sealing agent is dripped; after dripping, a heat preservation reaction is performed for 0.5-3 h; the mixture is cooled to a room temperature; then the mixture is filtered, washed with a solved and pumped; a rake type drier is used; and the mixture is dried for 6-24 h under a pressure reduction condition, so that microcapsule-wrapped APP powder is obtained. Compared with un-wrapped APP, the microcapsule-wrapped polyphosphate powder has the characteristics of low viscosity and water solubility, excellent flowing property and compatibility, high-temperature soaking resistance, precipitation resistance, excellent electrical property and the like. The APP can be applied to high polymer materials such as polyolefin and the like and can also be applied to fabrics, epoxy and coatings.

Description

technical field [0001] The invention relates to a method for preparing low-viscosity microcapsule-wrapped ammonium polyphosphate. Background technique [0002] APP is an excellent flame retardant. It has high phosphorus content and nitrogen content, and there is a P-N synergistic effect between them, so it has high flame retardant performance, and because it can be compounded with many other flame retardants to improve its flame retardancy and performance Sex, little smoke, low toxicity (LD50>10g / kg), so some people call it "environmentally friendly flame retardant". [0003] However, due to the characteristics of its own chemical structure, it has the following inherent defects. [0004] (1) High hygroscopicity. There are oxygen bonds in its chemical structure, and the oxygen bonds are often arranged on the outer surface, making it easy to absorb water molecules. Due to its hygroscopicity, it is not conducive to long-term storage, and its electrochemical performance ...

AI Technical Summary

Problems solved by technology

Due to its hygroscopicity, it is not conducive to long-term storage, and also reduces its electrochemical performance, which limits its application in the electrical industry.

[0005] (2) Poor compatibility and dispersion with the substrate

As a result of mechanical dispersion, APP powder is easy to form agglomerates in the local part of the material, which not only reduces the material properties, but also because of the lack of affinity between them, the flame retardant is easy to migrate from the inside of the material to the surface, causing "white frost" on the surface. The flame retardant performance gradually decreases

[0006] (3) The flame retardant durability is not good

[0007] (4) The thermal stability of APP is poor

Compared with unwrapped APP, the water solubility of the wrapped APP is significantly reduced and the thermal stability is improved, but this method still has shortcomings. The cross-linking density of the capsule material is affected by the ratio of melamine / phenol to formaldehyde, the reaction temperature And the influence of the pH value of the solution is large and difficult to control, and the reproducibility of the product is not good

[0010] In addition to the shortcomings mentioned above, the above patents ignore the following point: many prepolymers in the market can wrap APP, and the water solubility can also be very low, but in practical applications, they face the following Problems: 1. When the amount of ammonium polyphosphate added is high, the viscosity of the solvent system is relatively high, which cannot be dispersed and cannot be processed and used; 2. The powder is thorny, has poor fluidity and is not compact; and this problem is caused The most important reason is that when wrapping, due to the continuous curing of the melamine formaldehyde resin prepolymer during the reaction process, even if the powder has formed a wrapping layer, there are still some active groups exposed to continue the crosslinking reaction , causing the coating layer to have many branched chains, the surface is uneven, and the gap between the powders is increased, and the powders are not dense, which in turn leads to the reason that the viscosity is relatively high in the actual application process.

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