Analysis of the production process of melt blown cloth

The American Exxon Company started the research of melt blown technology in the 1960s and obtained the technology patent for the first time. This process is still the mainstream production process widely used in the meltblown nonwovens industry. It is characterized by the use of a single row of spinneret holes and hot air drafting. The drafting hot air blows out at a certain angle from both sides of the spinneret. . The production process of meltblown nonwoven fabrics is to use polymer chips with high melt index (referred to as MFI), which are extruded and heated and melted into a high-temperature melt with good flow properties. The thin stream of melt sprayed from the wire 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 the waste heat of its own is used to bond each other into a production process. It has a short process flow (it only takes more than ten minutes from feeding to forming a product), simple equipment (such as a general production line does not require equipment for consolidating fiber webs), and fine fibers (fiber diameters reach the micron level or even sub-nanometer level), Product features such as diversified performance. Melt blown method is currently 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 nonwovens process is 'MGenerally, most independent meltblown nonwoven production lines have only one spinning system, and two or more meltblown systems can also be configured in the production line according to market requirements to form a MM or MMM production line. In the SMS production line, the MB system is an important system, which has a great impact on the application performance (breathability, barrier capacity) of the product. In order to improve the production capacity of the production line and the quality of the product, a production line will be equipped with multiple MB system. Meltblown nonwovens were first developed in the United States in the 1950s, and my country also developed them in the early 1960s. It is directly spun into cloth from polypropylene chips with high melt index. It 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: the polypropylene chips (FR400-1200) are melted through a screw extruder, and they are ejected into fibrous form through the spinneret holes, and heated at 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. Because the fibers are condensed into a net, they can still maintain a higher temperature, so that the fibers can interact with each other. The adhesion becomes a melt-blown 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 continuous production line of meltblown nonwovens is about 6m high, about 5m wide, and about 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. , Its purpose is to melt the slices. (2) Metering pump: Its function is to accurately measure, control the output and the fineness of the fiber. It is a gear pump that continuously delivers the melt to the spinneret. (3) Melt filter: Its function is to filter out impurities in the melt to avoid clogging the spinneret holes. (4) Conveying net curtain: The melt blown fiber is evenly received and spread on the net, and transported forward. There is a suction fan under it to discharge the hot air coming down from the top. (5) Spinning box: It is the key equipment of the melt-blown process. There is a strip-shaped spinneret, which is covered with a long row of spinneret holes. Generally, there are about 1500 nozzle holes per m length. The two sides of the spinneret are equipped with hot air nozzles, and there are hot air nozzles underneath, which form an angle of 50b with the nozzle holes. After the fibers are ejected, the high-speed hot air is used to stretch the air flow immediately to blow the fibers and become superfine fiber. (6) Feeding system: It is composed of 3 measuring hoppers, which are used to measure white slices, masterbatch, and additives. The 3 components enter the mixing mixer below to mix evenly, and then they are put into production. (7) Hot air blower and heater: provide the temperature and pressure of the hot air used in the spinning air drawing, use electricity for heating, and consume a lot of power. (8) The coiling machine adopts automatic coiling, and the melt blown cloth is packaged in rolls. Meltblown nonwovens are characterized by ultra-fine fibers, and their fiber diameter can reach 0.5Lm at the smallest, generally between 1~5Lm. The finer the fiber, the better the quality of the meltblown cloth, but the output is relatively reduced. Because the fiber is superfine, its specific surface area is large, and the adsorption capacity is strong, which is the most prominent advantage of melt blown cloth.