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The principle and method of improving the thermal stability of chlorinated paraffin
Add time:2021-03-09 Number of views: 2255

1. The principle of improving thermal stability

The thermal degradation mechanism of chlorinated paraffins: Firstly, it is due to the presence of unstable chlorine atoms in the molecular structure (generally considered to be the terminal chlorine atoms of the carbon chain). This part of the chlorine atoms is easy to dehydrochloride to produce ethylenic bonds. Once the ethylenic bonds are generated, the catalysis of the removed hydrogen chloride accelerates the process of continuing dehydrochlorination, thus producing a conjugated double-bonded polyene structure, which is easy to polymerize to form glue The substance is soluble in the material. In addition, double bonds are easily attacked by oxygen to form tertiary carbon alcohols, which also form ethylenic bonds in acidic media. Polyene laminates and oxidized carbonyl compounds are the reasons for the color of the product. To maintain the stability of the product, it is necessary to eliminate or prevent these adverse reactions.

2. Methods to improve the thermal stability of chlorinated paraffins

(1) Refining raw material paraffin wax. Because the crude wax for chlorinated paraffins, in addition to straight-chain alkanes, there are organic compounds such as branched-chain alkanes, cycloalkanes, aromatic hydrocarbons and basic nitrogen. The content of these unbranched alkanes above 0.5% will affect the thermal stability of chlorinated paraffins. Because in the nucleophilic reaction of chlorinated alkanes, the branched alkane chloride produced by the thermal chlorination process often eliminates one molecule of hydrogen chloride to obtain alkenes; in the thermal chlorination process, aromatics can generate side-chain chlorinated aromatics and have longer Conjugated chlorinated aromatic hydrocarbons. These compounds are easily pyrolyzed and condensed to produce alkenes; basic nitrogen organic compounds such as pyridine, quinoline, etc., are catalysts for the dehydrochlorination of chlorinated alkanes, and chlorinated alkanes are dehydrochlorinated to produce alkenes. Therefore, the active carbon adsorption refining method is generally used to refine the raw wax, with low investment and simple process, which can reduce organic compounds such as aromatics, cycloalkanes and basic nitrogen in the raw materials.

(2) Improvement of chlorination reaction. Because relatively low temperature chlorination has better thermal stability than high temperature chlorination, the production process conditions are improved. For example, thermal chlorination can also choose to add catalysts and chlorination processes that can fully circulate the reaction liquid; photochlorination can be selected The light source with strong light efficiency is the initiator, and the process of fully dispersing chlorine gas in the reaction liquid, such as the chlorination kettle with stirring device. Thereby lowering the reaction temperature, increasing the chlorination reaction speed, reducing the free chlorine and hydrogen chloride in the chlorinated paraffin to a relatively low value, while preventing the end of the chlorinated paraffin from entering unstable chlorine atoms, thereby reducing the dehydrochlorination of the chlorinated paraffin The reaction slows down the thermal degradation process of chlorinated paraffin, thereby improving the thermal stability of chlorinated paraffin.

(3) The choice of heat stabilizer. The choice of thermal stabilizer must have the following properties: quickly combine with the generated hydrogen chloride to prevent the medium from being acidic; quickly react with the oxidizing active substance to prevent its further reaction; react with the polyene structure to form a stable substance to prevent further dehydrochlorination; stabilizer It should not affect the color of chlorinated paraffin products, the toxicity of acid value products, etc.

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