The search for the origins of extrusion molding technology may go back as far as the processing of macaroni and other food products, bricks and ceramics. It may be possible to trace the long history of extrusion to the processing of macaroni and other foodstuffs, bricks and ceramics. The earliest known use of extrusion for polymer processing was in 1845. There is more agreement that: began in 1845, patent applicant R. Brooman's patent application on extrusion molding to gutta-percha as the coating layer of the wire.
Then the extruder is the plunger type, the operation from manual to mechanical to hydraulic, progress, but this period in either form, only reflect the ease of operation and manual labor intensity of the difference, and the nature of the production process: intermittent, is the extruder **** the same characteristics of that period.
By 1879, the British M. Gray obtained the first use of Archimedes screw extruder patents, the same year another British F. Shaw also developed a screw extruder, and two years later, he will develop their own screw extruder into a product for sale. 1880, the Americans J. Royle also developed a screw extruder. Several different types of extruders sprang up in the relatively close years.
The earliest mass producer and seller of screw extruders was the German machine manufacturer Paul Troester, who produced and sold more than 500 screw extruders in the 20 years from L892 to 1912. It was the same manufacturer who developed and produced the extruder for thermoplastics in 1935. Prior to this, the extruder screw L/D ratio was about 3-5, apparently. Extrusion of rubber is not a problem, but for thermoplastics is not possible to meet the requirements of plasticization. The company in addition to increasing the extruder screw L/D ratio, but also in the heating method, charging device and transmission also made many improvements; to 1939, they developed the plastic extruder to a new stage, perhaps called the "modern single-screw extruder stage". This stage is characterized by the extruder using direct electric heating, air cooling, automatic temperature control devices, lined barrel and screw surface nitriding treatment, screw length and diameter ratio of 10, infinitely variable transmission.
Since the emergence of the modern single-screw extruder so far in the decades, the types of polymers that can be processed, the structure of the product, the form of expanding, making including extrusion molding process, molding equipment, research and development of new products, new processes, such as means of comprehensive advancement. Extrusion molding technology as one of the polymer processing technology, is accompanied by the development of polymer processing industry technology and growth.
The 1950s, the development of petrochemical industry makes the polymer industry rapidly mature; 60s, plastics, rubber, chemical fiber production of the three major synthetic materials to scale; 70s, the world's synthetic polymers in the total volume of the material has exceeded the metal materials. Polymers can only become products with use value through molding processing. Molding process is an indispensable part of the production of polymer materials.
Extrusion molding as a polymer processing industry in an important technology, is in the polymer resin application engineering technology, extrusion production equipment development technology in two aspects of mutual promotion, and interdependence and development. All kinds of extruded products: the early years of hard PVC pipe, covered wire, polystyrene, polypropylene and ABS sheet and plate, polyethylene blown film and coated film, etc., nowadays, PVC profiles, crosslinked polyethylene, aluminum-plastic composite, PPR tubing, bi-directional oriented polypropylene film, multi-layer **** extruded composite film, with high barrier, breathability, self-adhesive, heat-shrinkage, self-canceling, and other special performance film, functional masterbatch and self-extrusion. Performance of the film, functional masterbatch and color masterbatch, foam products; the use of extrusion processing means to prepare modified polymer materials; *** mixing enhancement, toughening technology, radiation modification technology, nano-composite technology, as well as a number of other new modification technology; a variety of structural and functional extruder and production line; mixing screw, exhaust extruder, twin-screw, multi-screw extruder, reactive extruders, combined Extruder, to adapt to the physical and chemical characteristics of polymer materials and the establishment of the molding device, with a variety of products required for the special features, the ability to implement the molding steps of the extrusion line auxiliary equipment, in pursuit of easy operation, precise control, energy saving and efficient, clean production goals and continuous improvement of the new equipment.
At present, the extrusion molding technology of many products has developed into a specialized complete set of technology including production process and production line equipment. Products can achieve high quality, production can be good economic benefits. Although the extrusion molding of new processing methods and theories of the rapid development of the period has passed, and is now in a much higher level than in the past and in the development of the period tends to slow down, but in the use of these technologies can still continue to innovate, develop new products. Manufacture of new materials, the formation of new technologies. Compared with other polymer molding methods, extrusion molding has many outstanding advantages.
(1) continuous production can be produced according to the needs of any length of pipe, plate, bar, profile, film, cable and monofilament.
(2)High production efficiency Extruder's stand-alone output is high, such as a 65mm diameter extrusion unit, the production of PVC film, the annual output of up to 450t or more.
(3) wide range of applications This processing method is widely used in the processing of rubber, plastics, fibers, especially plastic products, almost the vast majority of thermoplastic plastics and some thermosetting plastics can be processed with this method. In addition to direct molding products. Also available extrusion method for mixing, plasticizing, granulation, coloring, billet molding, etc., such as extruders and calenders with the production of calendered film; with the press, the production of a variety of compression molding parts; with blow molding machine, the production of hollow products. In the rubber products production process, the extrusion method for the manufacture of tread, inner tube, hose, as well as a variety of complex cross-section shape products and hollow, solid, rubber-covered semi-finished products, but also for the continuous mixing of filtered rubber, raw rubber, plasticizing and pelletizing and other purposes. In the petrochemical plant, the production of resin, extruder extrusion can be used to remove the water in the resin, with the extruder to complete a variety of grades of resin in the additives, modifiers, mixing, and complete the resin granulation process.
(4) a machine multi-purpose an extruder, can process a variety of materials and a variety of products. As long as according to the material performance characteristics and the shape and size of the product to replace the different screw and head, you can produce different products.
(5) simple equipment, less investment Compared with injection molding, calendering, extrusion equipment is relatively simple, easier to manufacture, lower equipment costs, installation and commissioning is more convenient. Equipment covers a smaller area, the plant and supporting facilities required for relatively simple.
The above advantages determine the importance of extrusion molding in polymer processing. The production of plastic products that use exclusively or contain extrusion process in the process accounts for about half of the total thermoplastic products. Products molded in this way are used in agriculture, construction, petrochemical, machinery manufacturing, medical devices, automotive, electronics, aerospace and other industrial sectors.