Liquid nitrogen cryogenic treatment equipment is used to prepare powder at low temperature
2020-04-26 11:48:00
Liquid nitrogen cryogenic treatment equipment is an ideal equipment for preparing rubber powder by low temperature pulverization. The boiling point of liquid nitrogen is －196 ℃, and it is easy to obtain the ideal low temperature effect. At the same time, liquid nitrogen is a by-product of the gas-making industry and needs to be utilized. In addition, liquid nitrogen is colorless, odorless, non-toxic, and has no environmental pollution, so it is an ideal refrigerant for freezing and crushing rubber and many materials. There are two methods of liquid nitrogen pulverization. One is to freeze and pulverize the waste tire after being divided and cut into pieces; The utilization form of liquid nitrogen is also divided into pre-cooling treatment pulverization and non-pre-cooling treatment pulverization.
1. Application of low temperature crushing process for preparing rubber powder
With the advent of low-temperature technology, freeze crushing is gradually recognized and developed. In 1927, a company in the United States proposed dry ice as a refrigerant to crush rubber, paste, and sticky materials. The method is to mix the powdered material with dry ice, and put it into a ball mill or grinder to crush it.
In general, the application of rubber powder can be divided into two major areas: one is direct molding or combined with new rubber to make products, which belongs to the scope of the rubber industry; the second is the application in the broad field of non-rubber industry. Now more and more manufacturers around the world use rubber powder instead of virgin materials, which is not only beneficial to environmental protection, but more importantly because the use of rubber powder can effectively reduce costs, improve performance, and obtain effects not obtained by other materials. It can be widely used as rubber, filler and composite materials for tires, hoses, tapes, rubber shoes, rubber industrial products (recycled rubber), wires, cables and building materials. Rubber powder can also be used with plastics, such as polyethylene, polyvinyl chloride, polypropylene, polyurethane, etc., to improve performance and reduce costs.
The use of rubber powder to modify asphalt for road laying is also widely used. Roads laid with rubber powder modified asphalt are used in many developed countries such as Canada, the United States, Belgium, France, and the Netherlands. Some provinces and cities in China have entered Jiangxi, Hubei, Guangzhou, Beijing and other places, and have laid experimental sections in succession. Practice has proved that roads paved with rubber powder modified asphalt can reduce pavement cracking and softening, the road surface is not easy to freeze and slip, improve driving safety, and can also increase the life of the road surface, at least increase the service life of ordinary asphalt road Doubled.
Second, the principle of low temperature crushing
Low temperature crushing is to use some materials to crush under the cold and brittle characteristics under low temperature conditions, which can obtain finer particles. Crushing materials under low temperature conditions can maintain the quality and value of the materials. In foreign countries, low-temperature crushing has been industrialized, using the cooling capacity of liquid nitrogen or natural gas to crush waste tires to obtain fine frozen rubber powder. Use the refrigerant to quickly freeze the material to be crushed below the cold and brittle temperature, and then send the frozen material to the crushing device for crushing. Low temperature crushing can crush materials that are difficult to crush at normal temperature, such as rubber and thermoplastics. Crush heat-sensitive materials to prevent deterioration during crushing. The crushed products are well formed, with large pile ratio and good fluidity. As the temperature decreases, the tensile strength, hardness, and compressive strength of materials such as rubber and plastics will increase, while their impact toughness and elongation will decrease. brittleness".
The crystalline state of rubber occurs mostly at low temperatures or in a stretched state. Under normal circumstances, rubber is in an amorphous state. When the rubber is frozen below the glass transition temperature by the cooling medium, the rubber molecular chain will be in a frozen state, the rubber loses its elasticity and becomes as brittle as ordinary glass. Crushing rubber below the glass transition temperature is as convenient as crushing glass and stones at room temperature, and the rubber can be crushed very finely. In order to prevent the rubber powders obtained by freezing and crushing from returning to normal temperature and causing mutual adhesion, a certain amount of release agent should be added to the crushed rubber powders, or the powder particles should be surface coated.
3. Development and current status of low temperature crushing process for preparing rubber powder
In recent years, a major breakthrough in waste rubber recycling technology in developed countries in the world economy is the manufacture of rubber powder of different fineness to replace recycled rubber, which is widely used in transportation, construction, rubber products and sports venues. Since the 1980s, the United States, Germany, the Netherlands, Sweden, Japan, Australia, Canada and other countries have successively established a batch of waste rubber powder companies, whose production capacity has greatly exceeded that of reclaimed rubber. For example, in the United States, recycled rubber accounted for 41% in 1990, while rubber powder production accounted for 59%. Currently, recycled rubber production has been eliminated. In the late 1970s, Japan's rubber powder production accounted for 37%, and in the 1980s, it exceeded 65%. It is a country that retains a large proportion of recycled rubber production (35%). From 1982, Russia gradually used all the waste rubber for rubber powder production. By the early 1990s, its rubber powder output had exceeded 350,000 tons. The main reason is that the production process of rubber powder is simplified. Compared with the production of recycled rubber, it saves a lot of equipment, factory buildings, power and manpower, does not use chemical raw materials such as softeners and activators, and does not exist pollution of waste water, exhaust gas and dust. There are obvious improvements, and the performance of rubber powder after vulcanization is better than that of reclaimed rubber, which has created favorable conditions for the rubber product industry to reduce product costs and increase benefits. At present, in terms of the application of rubber powder at home and abroad, new application fields are constantly being developed. The application value of rubber powder has been changed from rubber substitute materials, liquid nitrogen cryogenic treatment equipment to industrial fillers and toughened modified materials for the building materials and plastics industries. Tend to be vast.
Nuoruida (Tianjin) science and Technology Co., Ltd. is committed to research, development, and sales of liquid nitrogen cryogenic equipment. Using European technology, we provide a variety of equipment. The main equipment is liquid nitrogen equipment, cryogenic furnace, cryogenic processing equipment, low temperature assembly equipment, cryogenic assembly equipment, and so on.
