Shanghai wax powder with you to understand the commonly used production methods of polyethylene wax

Shanghai wax powder with you to understand the common production methods of polyethylene wax:

At present, there are three main production methods of polyethylene wax: First, polyethylene wax synthesized by oligomerization of ethylene monomer, such as polyethylene wax synthesized by free radical oligomerization; The second is polyethylene wax prepared by the degradation of high polymer; The third is the by-product in the synthesis process of polyethylene, such as the polyethylene wax obtained by separating the by-product in the synthesis of polyethylene by high-pressure method.

1, ethylene polymerization method

There are three main ways to produce polyethylene wax by ethylene polymerization. One is polymerization with free radical catalyst under high temperature and high pressure. The second is polymerization under low pressure with Ziegler catalyst. The third is metallocene catalyst polymerization.

2, polyethylene cracking method

The molecular weight distribution of polyethylene wax produced by polymerization method is narrow, and the relative molecular weight size can be artificially controlled, but it must be carried out on a large device and the capital investment is large. Domestic manufacturers generally use the thermal cracking method of high molecular weight polyethylene production, the raw material used in this method can be polyethylene resin, it can also be polyethylene waste plastic, the former product grade is high, the latter product grade is low. High molecular weight polyethylene can be pyrolyzed to low molecular weight polyethylene wax under the condition of isolation of air, and the properties of the polyethylene wax prepared in this way (such as crystallinity, density, hardness and melting point) are affected by the cracking raw materials. Cracking processing methods are divided into cracking kettle method and extrusion method. Pyrolysis kettle method is a batch processing method, which is suitable for manufacturers with low production capacity and small production capacity; Extrusion method is continuous production, which is suitable for enterprises with large production capacity and high capacity.

Polyethylene wax can be prepared by using recovered polyethylene lysate. This technology raw material source is very rich and cheap, the process is relatively simple, low operating costs.

3, polyethylene by-product purification

In the reaction of ethylene polymerization to produce polyethylene, polyethylene wax products can be recovered from the mixture of low molecular weight components and solvents obtained by the by-product. After the solvent and initiator are removed from the by-product of the polyethylene plant, the molecular weight distribution of the product is still wide, which limits its application field and requires further purification by solvent separation. This by-product polyethylene wax product usually contains molecules with a relative molecular weight of about 1000, so it is lower than polyethylene wax products produced by ethylene polymerization in physical properties such as mechanical strength and heat resistance.

4. Modification of polyethylene wax

Polyethylene wax is a non-polar molecule, if the polar groups can be connected to the molecule, it will greatly expand the application field. These functionalized polyethylene waxes can be produced by copolymerization of ethylene and oxygen-containing monomer, and can also be oxidized, grafted and other chemical methods to introduce carboxyl groups, and then further modified by esterification, amidation, saponification and other chemical reactions. These functionalized polyethylene waxes can meet the requirements of different applications.