Recently, a novel coronavirus pneumonia confirmed case in Qingdao has aroused widespread concern in the whole society. A gratifying news is that in less than five days from the discovery of three asymptomatic infected persons on October 11 to 18:00 on the 14th, nearly 9 million copies of new coronavirus nucleic acid have been sampled in Qingdao. So far, 5410386 copies of the results have been obtained. In addition to the 12 confirmed cases, no new positive samples have been found. It is understood that Qingdao Libao will complete the detection of 11 million people in the city by 16.
In the past half a year, China has explored a set of effective prevention and control mechanism for epidemic normalization.
It can be said that a big tool to prevent the spread of the virus atmosphere is the mask. Mask has become a daily necessity. It can not only filter bacteria and viruses in the air, but also block the transmission of viruses and bacteria from the wearer.
Melt blown cloth plays an important role in the structure of mask, and the main raw material is polypropylene. So where does polypropylene come from?
Polypropylene production process
The process methods of polypropylene are classified into the following categories: solvent method, solution method, liquid phase bulk method and gas phase bulk method.
Solvent polymerization method: propylene monomer is dissolved in an inert liquid phase solvent and polymerized in solvent under the action of catalyst. The polymer is suspended in the solvent in the state of solid particle transportation.
Solution polymerization: using high boiling point straight chain hydrocarbon as solvent, operating at a temperature higher than the melting point of polypropylene, all the polymers obtained are dissolved in the solvent and distributed uniformly.
Liquid phase bulk polymerization: without solvent in the system, propylene monomer is polymerized in liquid phase in a kettle reactor.
Gas phase bulk polymerization: no solvent was introduced into the system, and propylene monomer was polymerized in gas phase in the reactor.
Catalyst in polymerization process
Ziegler Natta catalyst is widely used in industry. Since its appearance in the late 1950s, it has experienced from the first generation to the fourth generation through the joint research of various countries. Its catalytic performance has been continuously improved, which has promoted the rapid development of polypropylene industry.
The generalized Ziegler Natta catalyst refers to the mixture of group I to III metal alkyl compounds and group IV to VIII transition metal salts. In order to make the catalyst play a role and shape in the polymerization process, the support and the third component will be used.
Metal alkyl compounds play the role of alkylation in the polymerization process to produce active substances, also can clear the system impurities and adjust the reaction rate of each group. The most commonly used are alkyl aluminum compounds, such as diisobutyl aluminum chloride, triisobutyl aluminum and trioctyl aluminum.
The transition metal salts are mainly titanium, vanadium, chromium, cobalt and nickel. The most commonly used is titanium tetrachloride.
The commonly used carrier is magnesium chloride. The third commonly used components are: ethyl anisate, 2-ethylhexyl alcohol and ethyl benzoate.
Source: official account of the Mo Bay
