Film blowing production process

Abstract

The invention discloses a film blowing production process which comprises the following steps that: (1) a film bubble thickness detector continuously detects the original thickness of each point in the peripheral direction of a film bubble; (2) each original salient point thickness control mechanism starts to carry out film bubble thickness-reducing operation; (3) in all normal point thickness control mechanisms, one part of normal point thickness control mechanisms are selected to carry out film bubble thickness-increasing operation; (4) an absolute value d of a difference value of c and b is calculated, wherein d is equal to the absolute value of c-b; (5) d is compared with e, and a step (6) is started; and (6), a complete-cycle thickness control mechanism reduces a complete-cycle thickness of the film bubble according to the detected results of the film bubble thickness detector, and the complete-cycle film bubble average thickness is reduced to be a. After a film bubble produced by the film blowing production process is rolled, accumulative errors of the thickness of each point are uniformly distributed in the axial direction of a coiled material, so that a bursting phenomenon is avoided; and moreover, a conventional mechanical rotary traction process and conventional equipment can be omitted.

Description

technical field [0001] The invention belongs to the technical field of plastic film production technology, and in particular relates to a blown film production technology. Background technique [0002] The plastic film can be produced by blown film equipment using a blown film process. The blown film equipment is provided with an extrusion die, the extrusion die is provided with a circular extrusion port, and a circular cooling air ring is provided above the extrusion die. During production, the high-temperature molten resin material is extruded from the extrusion die, and then cooled by the cooling air ring to form a circular bubble. The circular bubble is flattened by a herringbone plate and becomes a double-layer film. Afterwards, it can be rolled up; the middle of the conventional cooling air ring is provided with an air guide interlayer 3, and the shape of the air guide interlayer 3 on the horizontal projection is circular, and the cooling air flows from the air inlet o...

AI Technical Summary

Problems solved by technology

[0012] However, although the above-mentioned rotary traction device has solved the rib bursting phenomenon well, it has paid a very high price: the mechanical structure of the rotary traction device is complicated, the equipment volume is large, and when the film runs through the rotary traction mechanism, the surface of the film will be in contact with each other. The surface of the movable guide roller will slide and twist relative to each other, and the surface of the film will have sliding friction with the surface of the movable guide roller, and the film will be easily injured by accident

[0013] At the same time, although the local thickness control mechanism of the film bubble can control the thickness of the local point of the film bubble, it still cannot be simply and directly used to replace the rotating traction device. Larger, it can reach about 8-11% of the film thickness at most, and it is impossible to reduce the thickness of the film to 8-11% by simply adjusting the temperature, because if the temperature is raised blindly, it is attempted to use the temperature increase to reduce the thickness of the film to 8-11%. The -11% mechanical error factor is completely thinned and eliminated, and the temperature rise required is too large, which will cause the bubble to not condense at this point, and even under the action of compressed air in the bubble, the bubble will rupture at this point and make the The air pressure in the bubble is lost, which leads to a serious problem of bubble collapse; 2. As mentioned above, even if the overthickness of the bump caused by mechanical reasons is within the control capability of the local thickness control mechanism, it is still due to the local thickness of the bubble. The control accuracy of the thickness control mechanism is very low, so no matter how it is controlled, it is difficult to accurately eliminate the bumps and avoid the bursting phenomenon by relying solely on the local thickness control mechanism of the bubble

Images