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Analysis of the production process of meltblown cloth
Exxon Corporation of the United States started the research on meltblown technology in the 1960s, and obtained the first technology patent. This process is still the mainstream production process widely used in the meltblown nonwovens industry. . The production process of melt-blown nonwoven fabrics is to use polymer chips with high melt index (referred to as MFI), after extrusion heating, melting into a high-temperature melt with good flow properties, and using high-temperature, high-speed hot air flow from the spray. The thin flow of melt sprayed from the silk plate is blown into very fine fibers, which are gathered into a fiber web on a receiving device (such as a web forming machine), and are bonded to each other into cloth by their own waste heat. It has a short process flow (it only takes more than ten minutes from feeding material to forming a product), simple equipment (such as general production lines do not require equipment for consolidating fiber webs), and thin fibers (fiber diameter reaches micron level or even sub-nanometer level), Product features such as diversification of performance. Melt blowing is an important process for manufacturing fine filter materials and materials with high barrier properties. It is also a method for manufacturing nanomaterials, and it is a technology that is still developing rapidly. The first English letter of the meltblown nonwoven process is“M”, so the meltblown cloth has also become“M”cloth, meltblown system is also referred to as“M”system, sometimes called“MB”system. Generally, most of the independent meltblown nonwoven production lines have only one spinning system, and two or more meltblown systems can be configured in the production line according to market requirements to form MM or MMM production lines. In the SMS production line, the MB system is an important system, which has a great impact on the application performance (air permeability, barrier capacity) of the product. In order to improve the production capacity and product quality of the production line, a production line will be equipped with multiple MB system. Meltblown nonwovens were first developed in the United States in the 1950s, and were developed in my country in the early 1960s. It is directly spun into cloth from polypropylene chips with high melt index, which is a high-tech product. At present, the annual output in the United States is about 150,000 tons, and the annual output in my country is 5,000 tons. The production process of melt-blown nonwovens is as follows: the polypropylene chips (FR400-1200) are melted by a screw extruder, sprayed into fibers through a spinneret hole, and heated at a high speed (13000m/min). Under the blowing of the airflow, it is strongly stretched to form extremely fine short fibers. These short fibers are adsorbed on the netting curtain. Since the fibers can still maintain a high temperature after condensing into a net, the fibers can interact with each other. The adhesion becomes a meltblown non-woven fabric, which is finally packaged into rolls. 1. Screw extruder; 2. Metering pump; 3. Melt blowing device; 4. Receiving net; 5. Winding device; 6. Feeding device. The equipment of the melt-blown nonwoven continuous production line is about 6m high, 5m wide and 20m long. The production equipment is as follows: (1) Screw extruder: the screw diameter is generally 100~120mm, and the length/diameter ratio is 30 , whose purpose is to melt the slices. (2) Metering pump: Its function is to accurately measure, control the output and the fineness of the fiber, and it is a gear pump that continuously transports the melt to the spinneret. (3) Melt filter: its function is to filter out the impurities in the melt, so as not to block the spinneret hole. (4) Conveying net curtain: The melt-blown fibers are evenly received and spread on the net, and transported forward. There is a suction fan below it to discharge the hot air from above. (5) Spinning box: It is the key equipment of the melt-blown process. There is a long spinneret plate, which is covered with a long row of spinneret holes. Generally, there are about 1500 orifices per m long. There are hot air nozzles on both sides of the spinneret, and hot air nozzles are installed at the bottom, which form an angle of 50b with the nozzle holes. After the fibers are ejected, they are immediately stretched with high-speed hot air to blow the fibers. superfine fiber. (6) Feeding system: It consists of 3 measuring hoppers, which are respectively used to measure white chips, masterbatch and additives. The 3 components enter the mixing mixer below to mix evenly, that is, put into production. (7) Hot air blower and heater: Provide the temperature and pressure of the hot air used in the spinning air stretching. It is heated by electricity and consumes a large amount of electricity. (8) The coiling machine adopts fully automatic coiling, and packs the melt-blown cloth into rolls. The fiber characteristics of meltblown nonwovens are ultra-fine, and the minimum fiber diameter can reach 0.5Lm, generally between 1 and 5Lm. The finer the fiber, the better the quality of the meltblown cloth, but the output is relatively reduced. Due to the ultra-fine fibers, its large specific surface area and strong adsorption capacity are the most prominent advantages of meltblown cloth.
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