Halogen-free flame retardant red phosphorus vacuum dryer

Red phosphorus is a new type of halogen-free flame retardant that has attracted great attention in recent years. It is non-toxic, odorless, low-smoke and highly efficient. When a small amount of red phosphorus is added to polymers, it can achieve a significant flame retardant effect. The main mechanism of its flame retardancy is that red phosphorus is first heated and decomposes Pn→P4→P2. During the decomposition process, red phosphorus can seize oxygen from the polymer or the air, and red phosphorus turns into oxygen-containing phosphoric acid. These oxygen-containing phosphoric acids have extremely strong hygroscopicity, causing the surface of burning polymers to carbonize. The carbonized layer can reduce the oxidation heat on the polymer surface and at the same time prevent the release of volatile components in the polymer. In addition, the pyrolysis free radicals PO· of red phosphorus can capture a large number of H· and HO· free radicals in the combustion flame, cutting off the oxidation chain of the flame. Therefore, red phosphorus is an efficient flame retardant. However, the ignition point of red phosphorus is 240℃, which is relatively low. It is flammable and its dust is prone to explosion, causing problems in the use, storage and transportation of red phosphorus. Moreover, red phosphorus is prone to moisture absorption and oxidation into acid, releasing phosphine PH3, which is toxic. Red phosphorus is an inorganic compound and is difficult to dissolve in polymers. These are all the shortcomings of red phosphorus as a flame retardant. The solution to the above problems is to modify the surface of red phosphorus, and the effective method is microencapsulation of red phosphorus.

The high efficiency and cost-effectiveness of microcapsule-coated red phosphorus flame retardants have obvious advantages among numerous flame retardants both at home and abroad. However, it also has its own drawbacks. This is because red phosphorus itself is a flammable substance with a high content and small particle size. During the batching and stirring stages in the production process, it is prone to generating a large amount of dust. After long-term use, the production workshop and equipment are covered with a layer of red dust everywhere. A slight mistake may cause a fire. It poses a great threat to people's lives and property safety. In recent years, there have been many safety accidents caused by microcapsule-coated red phosphorus flame retardant dust igniting fires, resulting in injuries and the destruction of factories.

At present, the drying of microcapsule-coated red phosphorus flame retardants mainly uses ovens or drying rooms, and the materials are statically heated and dried in the material trays. The baking time should be more than 10 hours, and the middle part of the tray is very difficult to dry thoroughly. The loading and discharging time is long, the efficiency is low, and there is a lot of dust. It is neither safe nor environmentally friendly.

The working principle of the vacuum dryer for microencapsulated red phosphorus halogen-free flame retardant

Batch operation of halogen-free flame retardant vacuum dryer: After the wet microencapsulated red phosphorus dehydrated by the centrifuge enters the dryer, it is dried by jacket and stirring heating. High vacuum design has obvious advantages for products that are sensitive to drying temperature. It also features good heat conduction, rapid drying, and low energy consumption. This machine adopts an inflatable sealed half ball valve, which ensures thorough and convenient unloading. It features excellent vacuum and pressure-resistant sealing performance, a design without dead corners and easy cleaning, stable performance and a long service life, guaranteeing the continuous processing of products without any loss.

The internal heating helical ribbon single cone dryer is a highly efficient, multi-functional, fully enclosed vertical vacuum drying equipment integrating vacuum distillation, crushing, powder mixing and drying. Its drying efficiency is 3 to 5 times that of the double-cone rotary vacuum dryer and vacuum oven of the same specification. Based on long-term industry production experience, Wuxi Shuangrui has significantly enhanced the working efficiency of its improved single-cone vacuum dryer. It can not only be used for drying heat-sensitive materials but also for the mixing, reaction and drying of powders and powders, as well as powders and liquids.

Improved Design of Safety Production Process for Vacuum Dryer of Microencapsulated Red Phosphorus Halogen-free Flame retardant

(1) The multi-layer design integrates the online operation of the centrifuge. The single-cone dryer can be conveniently connected to the discharge port of the bag-flipping centrifuge to achieve solid-liquid separation from microencapsulated red phosphorus production to the drying and mixing of the final product.

(2) Turn on the heating device of the vacuum dryer, heat it up, evacuate the air, and dry for several hours to obtain the finished microcapsules coated with red phosphorus flame retardant.

(3) The single-cone vacuum dryer is equipped with spray nozzles inside the cavity. After the material is stirred, the mixing movement direction is a compound movement of axial, radial and circumferential movements, which has an excellent mixing effect. Through the spray system, liquid phosphate ester can be continuously atomized onto the surface of the material, and the microcapsules can be coated with red phosphorus flame retardant to remove dust. The entire process is safe, environmentally friendly and highly efficient. Achieve the goal of neither dust flying nor gathering.

(4) The vacuum single-cone dryer is equipped with a cooling device, which enables the microcapsules coated with red phosphorus flame retardant to cool down rapidly after drying, thereby enhancing production efficiency.

(5) The bottom spherical stop vacuum discharge valve enables the vacuum single-cone dryer to achieve automatic discharge, realizing a closed process during the drying and mixing process, which complies with the relevant regulations on the safe production of microencapsulated red phosphorus.

(6) The discharge of the single-cone dryer is directly connected to the crusher or the fully enclosed powder conveying equipment, which can better ensure that the entire process is completed in a fully enclosed environment.