Warm Global Customers
With China Plastic Machinery
With China Plastic Machinery
Chlorosulfonated polyethylene (CSM) was first industrialized by Dupont in the United States in 1952. Chlorosulfonated polyethylene is made from low-density polyethylene or high-density polyethylene through chlorination and chlorosulfonation reactions. It is a white or yellow elastomer that can dissolve in aromatic hydrocarbons and chlorinated hydrocarbons but not in fats and alcohols. It can only swell but not dissolve in ketones and ethers. It has excellent ozone resistance, atmospheric aging resistance, chemical corrosion resistance, etc., and good physical and mechanical properties, aging resistance, heat resistance and low temperature resistance, oil resistance, flame resistance, wear resistance, and electrical insulation resistance. It has a wide range of uses. Currently, only a few countries in the world, such as the United States, Japan, Russia and China, have built equipment. The global total annual production capacity is about 75,000 tons, which is close to the production capacity.
Chlorosulfonated polyethylene is a special chlorine-containing elastomer material with a highly saturated chemical structure made from polyethylene as the main raw material through chlorination and chlorosulfonation reactions. It is a special rubber variety with high performance quality. Its appearance is white or milky elastic material with thermoplasticity. Because of the chlorosulfonyl active group in the molecular structure, it shows high activity, and is especially resistant to chemical corrosion, ozone oxidation, oil erosion, flame retardant and other properties. It also has weather resistance, heat resistance, ion radiation resistance, low temperature resistance, abrasion resistance, electrical insulation and excellent mechanical properties. CSM was developed for military engineering purposes in the early days. However, its large permanent deformation also limits its scope of use.
It is a saturated elastomer with polyethylene as the main chain, with an average molecular weight of 30,000 to 120,000. Among them, CSM2910 is 30,000, CSM4010 is 40,000, CSM3304 is 120,000, and CSM2305 is 100,000. Chlorosulfonated polyethylene is a white or milky white flake or granular solid with a relative density of 1.07 to 1.28. Mooney viscosity 30~90. Brittle temperature -56~-40¡æ. The chemical structure of CSM is completely saturated, and it has excellent ozone resistance, weather resistance, heat resistance, flame retardancy, water resistance, chemical resistance, oil resistance, wear resistance, etc. The solubility parameter of CSM is ¦Ä=8.9, which dissolves aromatic hydrocarbons and halogenated hydrocarbons, and only swells but does not dissolve in ketones, esters, and ethers; it is insoluble in aliphatic hydrocarbons and alcohols.
It has the common properties of raw rubber and its own unique properties, such as excellent ozone resistance, atmospheric aging resistance, chemical corrosion resistance, etc., good physical and mechanical properties, aging resistance, heat resistance and low temperature resistance, oil resistance, flame resistance, wear resistance, and electrical insulation resistance.
There are two methods for producing chlorosulfonated polyethylene, namely solvent method and gas-solid method.
Traditional solvent method: It is a liquid phase manufacturing process that uses chlorine, sulfur dioxide, etc. as chlorosulfonylating agents. Its main disadvantage is the low utilization rate of sulfur dioxide (20-30%), and the chlorine content of the product is only 25-45%. The sulfur content is 0.8-1.7%, and the fatal disadvantage is that carbon tetrachloride is required as a solvent. In addition, the post-processing procedures of this liquid phase process are relatively cumbersome (removal of acidic gases, CSM condensation and separation operations, etc.).
Gas phase method: The synthesis process was reported as early as the 1980s, but the earliest industrial device was not put into use until 2009. This process was independently developed by a Chinese company, and the product was successfully trial-produced in the same year. In May 2010, the gas-solid method of chlorosulfonated polyethylene production process passed the scientific and technological achievement appraisal organized by the China Petroleum and Chemical Industry Federation. The biggest breakthrough of the gas-solid production process is that it does not use organic solvents at all, and the materials are directly contacted by the reaction gas, which shortens the process flow and makes the process green and environmentally friendly.
CSM has been widely used in the fields of wires and cables, waterproof coiled materials, and the automotive industry, and has become a commonly used special rubber. Anti-corrosion coatings prepared with CSM as the basic material have a wide range of uses.
CSM is widely used in the automotive industry abroad, and its application in this area in China is almost blank at present. With the acceleration of the localization process of spare parts in China's automotive industry, the potential consumption of CSM in the automotive industry is huge. It is estimated that the potential demand for CSM in the automotive industry in 2005 should be at least 3,000 tons.
CSM is used in industry to manufacture products such as pipes, conveyor belts, and seals with special properties. For example, the laminated tube made with CSM as the inner layer has low permeability to fluorocarbon refrigerants and is suitable for refrigerant delivery pipes. When manufacturing CSM-fluororubber laminated tubes, if peroxide is added, the peel strength of the laminated product can be greatly improved. The laminated product is suitable for manufacturing pipes and containers for transporting and storing fuel oil.
CSM can be blended and modified with other rubbers. CSM can be blended with fluororubber to improve the processing performance of the blended rubber. CSM can be blended with ethylene-propylene rubber to improve the physical and mechanical properties and thermophysical characteristics of the vulcanized rubber. Adding CSM and isoprene rubber to EVA polymer can produce slip resistance, wear resistance, and oil resistance. CSM can be mixed with PVC and PU in an extruder and then vulcanized to produce vulcanized rubber with improved oil resistance and ozone resistance.
Some people think that the statement that "MgO, ZnO is the CSM vulcanization system" is unreasonable. Most of the information on the coordination and vulcanization of CSM and chlorinated polymers comes from Japan, such as the chlorinated polyethylene and chlorosulfonated polyethylene section in the first volume of the Rubber Industry Handbook. Some academic literature contains some information about this type, but it is still plagiarized (it cannot be said to be a reference, because I have not given myself experiments and thinking).
In CR and CIIR, because they contain highly active allyl chloride, metal oxides can be used for crosslinking. Chlorinated polymers such as CSM and CM do not have such active chlorine as a vulcanization active point, so they cannot be vulcanized so easily. Fortunately, in CSM, sulfonation is carried out, and a highly active "sulfonyl chloride" group appears, which can be vulcanized much more easily than CM. The commonly used TRA in the CSM formula is the most effective vulcanizer for CSM (not a vulcanization accelerator). When there is no oxide such as magnesium oxide, CSM can also be vulcanized. After adding magnesium oxide, it only plays the role of an acid absorber and can improve the performance.
But there is one strange thing. After adding zinc oxide (ZnO), the vulcanization efficiency is affected. This shows that zinc oxide can not only accelerate the dehydrochlorination (HCl), but also cause the instability of the rubber. In polymers without highly active chlorine, ZnO can only accelerate the dehydrochlorination rate when heated. (Introduction to the information: It is not ZnO itself that causes the dehydrochlorination, but ZnCl2 generated by the reaction of Zn and Cl. The mechanism of this place can be found in the chapter of organic chemistry
The difference between CSM rubber and other rubbers is that even without adding reinforcing fillers, its vulcanized rubber has a high static vulcanization strength. This is because the vulcanization structure of CSM has unique characteristics. The side groups generated during the vulcanization process associate with the polarity of the cross-linking bonds to form particles. These particles not only play the role of vulcanization network, but also have the function of physical crosslinking points.
However, fillers can still improve the process performance of rubber, improve the heat resistance and wear resistance of vulcanized rubber, and reduce costs. Commonly used reinforcing fillers include carbon black, calcium carbonate, kaolin, diatomaceous earth, white carbon black, talcum powder, etc. The extent of the role of fillers depends on their particle size. The finer the particles, the better the performance of the resulting vulcanized rubber. Among inorganic fillers, white carbon black can guarantee the highest heat resistance. Diatomaceous earth can improve the tear strength of vulcanized rubber and increase its rigidity and hardness.
To improve the weather resistance of vulcanized rubber, kaolin should be used, and it has the following characteristics: good dielectric properties, and it does not decrease after absorbing moisture, and it has excellent dynamic properties. In light-colored products, barium sulfate and zinc barium white can be effectively filled, and titanium dioxide can improve the color brightness and weather resistance of vulcanized rubber.
CSM vulcanized rubber containing fillers has high chemical stability. Thermal cracking carbon black, barite, etc. can make vulcanized rubber obtain the best hydrochloric acid resistance. For sulfuric acid resistance, the fillers that can achieve the best effect are thermal cracking carbon black, kaolin, barite, diatomaceous earth, etc. For nitric acid resistance, it is thermal cracking carbon black.
Plasticizers are used in chlorosulfonated polyethylene rubber to improve the process properties of the rubber, the low-temperature properties of the vulcanized rubber, and to improve its elasticity and reduce hardness. The most commonly used petroleum oils, ointments and ester plasticizers in CSM rubber. The amount can be slightly more than in other rubbers. In vulcanized rubber that is in contact with chemicals, the amount of plasticizer should be reduced to a minimum.
For rubber to be used at low temperatures, it is best to use ester plasticizers. Such as DOP, DOA, DOS, etc. Chlorinated paraffin is used as a flame retardant in other rubbers. In CSM, in addition to flame retardancy, it can also improve tensile strength and improve the retention rate of elongation after heat aging, and the low-temperature performance is also good. Chlorination of about 40% is good, and chlorides above 50% have improved flame retardancy but poor low-temperature performance.
The role of the stabilizer is to prevent the degradation of chlorosulfonated polyethylene rubber during production, storage and use. Commonly used are stearates, organotin, magnesium oxide, etc. Magnesium oxide is a good and common stabilizer that can effectively absorb by-products such as hydrogen chloride. The relationship between magnesium oxide activity and vulcanizate performance is shown in Table 2-1.
Table 2-1 Effect of magnesium oxide activity on CSM physical properties
Except for high-temperature exposure, CSM rubber vulcanizates usually do not require the addition of antioxidants. When the temperature exceeds 120 degrees, the antioxidant NBC is the most effective stabilizer and also acts as an activation promoter, but it also damages the processing safety performance.
In order to improve the sticking of CSM rubber on the roll on the training mill and calender and improve the extrusion performance, waxes with good compatibility with CSM, such as microcrystalline wax, can be used. In addition, petroleum and paraffin waxes can also be used, but their sprayability limits their usage. It is effective to use polyethylene glycol below 77 degrees and polyethylene wax above 77 degrees as processing aids. When used in combination with nitrile rubber, styrene-butadiene rubber, and cis-1,1,2-dimethylformamide, it can not only reduce costs and improve adhesion, but also improve processing performance, especially for cis-1,1,2-dimethylformamide. Adding 3-5 parts by mass can improve processing performance.
In order to improve the self-adhesion of the rubber, low molecular weight coumarone-indole resin is generally used. Adding about 10 parts by mass of petroleum resin can also effectively improve the self-adhesion of the rubber.
Due to the good color stability of chlorosulfonated polyethylene, products of various colors with quite good performance can be produced. Because many organic colorants will react with polymers during the CSM vulcanization process, the colorants suitable for CSM are mostly inorganic compounds. The colorant not only has a coloring effect on the vulcanized rubber, but also protects the CSM from the effects of ultraviolet light.
If you are interested in our company and machine, feel free to contact our sales engineer. We will contact you as soon as possible.