The research and application of brominated polystyrene abroad was earlier, and the synthesis process was relatively mature. In the 1980s, the American Ferro Company and Great Lake Company took the lead in realizing the industrial production of brominated polystyrene. Great Lake Company and Ferro Company respectively represent two different brominated polystyrene synthesis processes. Great Lake Company uses styrene as raw material, brominates it to obtain brominated styrene monomer, and then polymerizes the monomer to obtain polybrominated styrene (PBS). U.S. Patent 5369202 provides its polybrominated styrene The synthesis method of ethylene product PDBS-80. The synthesis route of Great Lake Company is bromination first and then polymerization. This avoids the halogenation reaction of the bromination agent on the main chain, thus improving the thermal stability of the polybrominated styrene produced. Excellent, as a flame retardant, when melted and mixed with the flame retardant substrate, corrosive hydrogen halide gas will basically not be released and will not cause damage to operators and operating equipment. Moreover, polybrominated styrene products have excellent color and high whiteness. As an additive, the lighter the color, the wider the application range. In addition, brominated styrene monomers can be first prepared and then polymerized with monomers with other functional groups to improve the compatibility of polymers with certain resins, improve fluidity, and prevent materials from cracking. Bubble. However, the disadvantages of this synthesis route are that the synthesis route is too long, the synthesis process is complex, and the requirements for production equipment are high, which leads to an increase in product costs and a long production cycle, which reduces its market competitiveness. Secondly, the reactivity of tribromostyrene monomer is very high, making the polymerization difficult to control. Therefore, dibromostyrene is generally used for polymerization, resulting in a low bromine content of about 60% in the polymerized product. To achieve the same flame retardant effect, more amounts need to be added, which will have a greater impact on the original properties of the flame retardant material and increase the flame retardant cost.
Ferro Company uses a brominating agent to directly brominate polystyrene. U.S. Patent 4352909 provides a synthesis method for the company’s brominated polystyrene brand Pyro-Chek68PB. Ferro Company The synthesis process is simple, the technical requirements are not high, the raw materials used are commercial products, and the production cost is low. Therefore, most domestic researchers and manufacturers use this method to prepare brominated polystyrene. The polystyrene used for bromination can be directly commercially available polystyrene, or recycled polystyrene foam can be used, which not only realizes the reuse of waste polystyrene, but also saves costs. This process can achieve a higher degree of bromination, and up to three bromine substitutions can occur on the benzene ring. The bromine content of the brominated polystyrene product produced can reach 70%, so it can achieve ideal flame retardancy with a smaller amount of addition. The effect not only saves costs, but also reduces the impact on the flame-retardant substrate. Although this synthesis method has many advantages, the main problem is that while the brominating agent undergoes electrophilic substitution on the benzene ring of polystyrene, it also undergoes a small amount of free radical substitution on the main chain. Taking Pyro-Chek68PB as an example, the main chain halogenation amount (calculated as HBr) can reach 5000~6000ppm. Halogenation on the main chain not only has a negative impact on the color of the product, but also greatly reduces the thermal stability of the product. Since the bond energy of the aliphatic carbon-halogen bond is relatively low, it will break when heated to about 200°C, causing the brominated polystyrene to decompose in the early or middle stages of the material's processing temperature, releasing hydrogen halide gas, giving the material its original properties. Damage to performance and corrosion to processing equipment. Moreover, during the processing of the material, even a small amount of main chain halogenation will cause severe discoloration of the material, which will greatly limit the application scope of brominated polystyrene. Because brominated polystyrene is an additive, its color will affect the color of the flame retardant material. The lighter the color of the flame retardant, the wider the color range of the products that can be produced; if the color of the flame retardant is dark, it will be difficult to obtain light-colored products. Therefore, flame retardant manufacturers hope that the color of the flame retardant should be as light as possible, so that more colorful products can be obtained.