Calendering

After plasticizing the thermoplastic, it is stretched under pressure into a film or sheet forming process by a roll gap of the calender. In the rubber processing process, the film can be calendered into a certain thickness and width of the film. After plasticizing the thermoplastic, it is stretched under pressure into the film or sheet by the calender roll gap. In the rubber processing process, the rubber can be calendered into a film of a certain thickness and width, or the pattern is pressed on the film for molding the next product. The calendering method is also used to hang the fabric and the steel cord, and to bond the film to the film, the film and the hanging fabric. Therefore, it is one of the main processes of rubber processing. In plastic processing, the calendering method is mainly used for processing polyvinyl chloride film, sheet, and artificial leather, floor leather, waterproofing membrane and the like.
Calenders are often classified by the number and arrangement of rolls. The number of rollers has two rolls, three rolls, and four rolls. The three-roll calender is mainly used to produce sheets (see color map). The four-roller can produce thinner products and can also perform double-sided adhesive application, which is currently widely used. There are many ways to arrange the rollers (Fig. 1), and they are used more in the inverted L-shape and the Z-shape, and the gaps of the rollers can be adjusted. The specification of the calender is expressed by the outer diameter of the drum and the length of the working portion of the drum. The rollers can be heated by steam or superheated water. Usually the calender must also be combined with other auxiliary equipment into a production line (Fig. 2) for production. The auxiliary machine includes a feeding device (such as a twin roll machine or an extruder), a metal detector, a take-off roller, a cooling device, a thickness gauge, a winding device, a cutting device, and the like. If it is required to be combined with the fabric (such as glue), there are also a drying device, a preheating roller, a laminating device, and the like.
Product calendering process 1 film and sheet: The blank sent to the calender is first tested by a metal detector to prevent the inclusions from damaging the surface of the roller, and then pressed into a certain thickness by the calender roll, and then supported by the take-up roll. After leaving the calender and then cooling and coiling, the product is obtained. An embossing process is performed between the separation roller and the cooling roller as necessary. Factors affecting the quality of the rolled product are roll temperature, roll speed, roll speed ratio, nip stock and roll pitch.

2 composite with fabric: there are two methods of glue and rub. The use of calender roll pressure to attach the film to the fabric is called a topping. For example, a curtain roll is commonly used for a double-roller with a four-roll calender (Fig. 3). When the glue is applied, the two rollers rotate at the same speed (v2 and v3), and the pressure is applied to the fabric by the pressure of the roller. If the above method contains more glue between the two rolls, and the pressure is used to press the glue between the gaps of the fabric structure, it is called pressure glue, which is an improvement of the above method. In actual production, the textile is often coated on one side and pressure-applied on the other side. The rubbing glue (Fig. 4) is used to rub the rubber into the seams and crepe lines of the fabric by using different speeds of the calender rolls. In the three-roll calender, the rubber is rubbed, and the middle roller has a higher rotation speed than the upper and lower rollers.

The gluing method has less damage to the fabric and a faster production speed, but the adhesion of the rubber layer and the fabric is slightly lower, and it is mostly used for fabrics with thin latitude and longitude density of thin fabrics and cords. The glue is suitable for canvas compact fabrics. Polyvinyl chloride artificial leather can also be produced in a similar manner.
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