Butyl rubber is a ****polymer of isobutylene and isoprene, which was put into industrial production in 1943.
The biggest advantage of butyl rubber:
Good air tightness. It is also resistant to heat, ozone, aging, chemicals, and has shock-absorbing, electrically insulating properties.
Disadvantages:
Slow vulcanization, poor processing performance.
Main Uses:
Making inner tubes of various tires, innerliners of tubeless tires, various sealing gaskets, lining of containers for corrosive liquids, pipelines and conveyor belts in chemical industry, and waterproofing materials in agriculture.
In 2005, China's butyl rubber consumption of nearly 150,000 tons, less than 30,000 tons of domestic butyl rubber, 80% rely on imports, from 1999 to 2004, the average annual growth rate of imports reached 26.9%. As a result, the international oil market prices continue to rise, butyl rubber prices also continue to climb. In recent years the price of butyl rubber from 15,000 yuan / T or so, the rise presented in the 32,000 yuan / T or more. The price of butyl rubber products, although the price has risen, but the overall calculation of the price increase of not more than 30%, far from catching up with the price of butyl rubber doubled the rise. So a lot of enterprises using butyl rubber to turn their attention to the best alternative to butyl rubber - butyl recycled rubber.
Butyl reclaimed rubber in addition to similar properties of the original polymer, but also has some special advantages of cooperation, such as improved dimensional stability, lower heat rise, reduce scorching. Air tightness with the same original butyl rubber, better than other synthetic rubber to retain the original raw rubber of various properties, so butyl recycled rubber operating well, is the manufacture of tire inner tube best choice of material. Butyl rubber contains a small amount of isoprene, so its degree of unsaturation is low, its vulcanized rubber aging resistance is very good, which indicates that it is very resistant to oxidation, the test also proved that the waste of vulcanized butyl rubber regeneration, the role of oxygen plays a small role, so the regeneration of desulfurization is more difficult than the natural rubber.
At present, there are six or seven kinds of domestic butyl recycled rubber production process, mainly cooking method, frying method, extrusion method, microwave method, radiation method, high-temperature continuous catalytic method, chemical and mechanical method, etc., but no matter what kind of method, the purpose is to use the most economical, the most scientific method of waste butyl rubber by the mesh structure into a linear structure.
With the rapid development of China's tire industry, butyl rubber consumption is rising rapidly, especially the rapid development of radial tires, coupled with the introduction of the national "butylation of medical corks" standard, the state put forward the butylation of the tire inner tube, the domestic and foreign markets, the strong demand for butyl rubber, to promote the development of the butyl recycled rubber. However, due to the shortage of raw materials for the production of domestic butyl recycled rubber, waste butyl inner tube from the previous year's more than 2,000 yuan / T, rose to the current 6,100 yuan / T or so, the waste capsule from 800 yuan / T or so rose to the current 3,800 yuan / T or so, medical corks from 1,000 yuan / T or so rose to the current 2,000 yuan / T or so. Although the price of butyl recycled rubber has risen, but it can not catch up with the price increase of waste butyl rubber. So many butyl recycled rubber manufacturers from high profit into micro-profit or unprofitable. Analyze the reason is mainly backward production process methods, the production of butyl recycled rubber physical properties of the index is too low, can only be sold at a low price, but the manufacturer is unprofitable, and a large amount of valuable resources are wasted.
The traditional method of desulfurization is currently more prevalent in the country, most manufacturers choose the dynamic tank desulfurization, or fire frying tank desulfurization, the shortcomings of the above two methods are: dynamic desulfurization, just to provide high temperature and high pressure desulfurization conditions, desulfurization of the long time, but also need to join the expensive softening aids, the key is that you can not be friction on the desulfurization of raw materials for extrusion. So it will cause the surface of the raw material to be charred and carbonized, while the interior of the raw material can not be desulfurized, resulting in the product surface there is no depolymerization of the particles present, which affects the quality of the product. Fiery frying cans due to the inability to accurately control the temperature, carbonization and coking phenomenon is more serious than dynamic desulfurization, so the physical properties of the product index is also not ideal. The biggest problem of the above two desulfurization methods is the generation of a large amount of waste steam secondary pollution. Advantages of kneading method of desulfurization
One, do not use expensive additives, if necessary, in order to obtain a relatively low Mooney viscosity only need to add part of the softener (mechanical oil).
Second, less investment in equipment, a daily output of 7 to 8 tons of butyl recycled rubber desulfurization of special kneading machine, a one-time investment of only 170,000 yuan. Only need to match a 1.63 air compressor.
Three, accurate temperature control, in order to obtain the best Menni viscosity, just adjust the temperature of the kneading machine. The Menni viscosity ML (1 + 4) 100 ℃ can be arbitrarily adjusted between 40 ~ 60.
Four, tensile strength and other physical indicators of small loss. Random sampling of the waste tires used before processing, measured the average value. After processing of recycled rubber tensile strength value, than the average value before processing only decreased by 0.3 ~ 0.5MPa. This is other ways of desulfurization can not be compared. Pinch refining method of desulfurization temperature control butyl recycled rubber raw materials from a wide range of sources, varying, in terms of butyl waste inner tube, the highest tensile strength can reach more than 10MPa, the lowest only 6.3MPa, so the specific gravity is different.
After a long period of observation and testing, the critical temperature of high strength and light specific gravity is low. On the contrary, the critical temperature is high, butyl rubber content determines the critical temperature of desulfurization. After each batch of raw materials into the factory must be on the raw material of the tensile strength or specific gravity of random sampling, and then according to the actual data to calculate the desulfurization temperature (i.e. critical temperature). Butyl raw materials, such as butyl capsules, have a relatively high desulfurization temperature because they are not sulfur vulcanization systems, but resin vulcanization systems or tin chloride vulcanization systems. Temperature on the impact of Menni viscosity butyl recycled rubber quality is good or bad, the first physical index is Menni viscosity, and then the tensile strength and elongation.
At present, because the domestic production of large size butyl inner tube enterprises use butyl recycled rubber Mooney viscosity requirements is ML (1 + 4) 100 ℃ 55 ± 5, and the production of bicycles, motorcycles, and other small inner tube enterprises require Mooney viscosity is ML (1 + 4) 100 ℃ 45 ± 5, and some special enterprises and even require the Mooney viscosity of ML (1 + 4) 100 ℃ 40 below. Menni viscosity high tensile strength is also high, but the process is not good, Menni viscosity low tensile strength is also low, but the process is good.
So in the kneading method of desulfurization, in order to ensure that the strength indicators, reduce the Mooney viscosity, can be added to softeners (mechanical oil) to adjust the Mooney viscosity. Critical temperature and thermal oxidation control butyl rubber is synthetic rubber, so in the kneading method of desulfurization to control the critical temperature is very critical, when the raw materials in the kneading machine after friction, extrusion temperature rise to the critical temperature, has completed the swelling, activation, mechanical depolymerization and other processes, and then is the process of thermal oxidation, if you can't cool down in a timely manner to abort the thermal oxidation process of the rubber material will be coked and carbonized, so the control of critical temperature and the timely suspension of the thermal oxidation process is critical. Therefore, it is important to control the critical temperature and abort the thermal oxidation process in time.
Must be promptly put into the opening machine for cooling. Pollution control methods of kneading method of desulfurization butyl recycled rubber production process is only at the critical temperature, produce a small amount of atomized fumes. Installation of air collection cover above the kneading machine, with a fan sent to the water curtain condensation smoke removal device, completely harmless emissions. The condensate can be recycled, and the floating materials contained in the water can be fished out to make softener or fuel.