1. Stretch film production process
As mentioned earlier, the current production of stretch film is mainly based on casting method. As we all know, the performance of a film depends on its thickness. For a film or a film bag, its performance actually depends on its thinnest point (the weakest point of performance). The casting method is beneficial to increase the thickness of the film. Therefore, in the case of meeting the same strength requirements, using the casting method to produce stretched film can reduce the thickness of the film, reduce unit consumption, save raw materials, and reduce production costs compared with the production of stretched film by blow molding; In the case of a certain amount of people added, the stretch film produced by casting method and the stretch film produced by blow molding method have greater surface viscosity, so in the case of the same surface viscosity requirements, the stretch film produced by casting method Stretch film, compared with the production of stretch film by blow molding method, can reduce the amount of tackifier, thereby reducing the formulation cost of the film; in addition, the stretch film produced by casting method is more transparent than the stretch film produced by blow molding method. Sex is better. Due to the above reasons, in the production of stretch film, the casting method and the blow molding method have shown obvious advantages in the competition, and become the mainstream method of producing stretch film today. Nanjing Sumino Seiko Stretch Film Equipment


1. Process conditions (temperature distribution)
After determining the molding process route (equipment type) and formula of polyethylene stretch film, reasonable temperature parameter setting is an indispensable element to obtain high-quality polyethylene stretch film. Examples of reference temperatures when casting polyethylene stretch films are as follows.

(1) Extruder and die head
The feeding section is 190°C, the filter is 280°C, the connecting pipe is 280°C, and the die head is 270°C.

(2) Quench roll I is 16°C; II is 19°C.

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2. The main factors affecting the surface viscosity of the film

(1) The effect of the amount of tackifier added on the self-adhesiveness of the film
In order to obtain good and stable viscosity, the polyethylene winding film containing tackifier PIB needs to be stored for 24~72 hours after production, so that the tackifier can fully separate out to the surface of the film. The self-adhesiveness (shear peel strength) measured after the stretch film was produced for 72 hours when containing different amounts of tackifier masterbatch. The self-adhesiveness of the film has a positive correlation with the amount of tackifier masterbatch: the increase in the amount of tackifier masterbatch increases the surface viscosity of the film, but when the amount of tackifier masterbatch is too much, the precipitation of the tackifier It will gather into blocks on the surface of the film, causing uneven self-adhesiveness on the surface of the film, and even making it difficult to open the film roll. Therefore, in the cast winding film, the amount of polyisobutylene is 2%~2.5%, and the content of polyisobutylene masterbatch Dosage generally does not exceed 4%.



(2) The influence of the thickness of the film on the self-adhesiveness of the film

When the proportion of tackifier added to polyethylene is the same, the thicker the film is, the more tackifier may precipitate on the surface of the film, so the viscosity of the film surface is greater.



(3) Influence of the surface temperature of the quench roll on the self-adhesiveness of the film

The influence of the surface temperature of the cast cooling roll on the self-adhesiveness of the film shows an inverse correlation: the lower the surface temperature of the chill roll, the higher the surface viscosity of the produced cast winding film. However, the surface temperature of the quench roll is too low. During casting, the water vapor in the air will condense on the surface of the chill roll to form water. The existence of condensed water will not only reduce the self-adhesiveness of the winding film, but also affect the production. The smooth progress, so the temperature of the cast quenching roll is generally controlled in the range of 20~25°C. www.susumino.comNanjing Susumo Seiko Stretch Film Equipment



3. Abnormal situations in production and countermeasures
(1) Film shrinkage is serious

①The temperature of the casting chill roll is low, so the temperature of the chill roll needs to be increased appropriately;

② The electrostatic lock effect is not good, and the static electricity needs to be adjusted;
③The vacuum of the double-cavity negative pressure bellows installed at the casting film roller is too small or the pressure roller is not pressed well, and the vacuum degree and pressure roller need to be adjusted.

(2) crystal point
① The material is dirty, pay attention to the cleanliness of the material;

②Extrusion temperature is too low, poor plasticization, the temperature should be raised appropriately;

③The extrusion temperature is too high, and the material stays in the barrel for too long, resulting in gelation of the material, and the temperature should be appropriately lowered;

④The shear force is too small and the plasticization is poor during extrusion, so the back pressure needs to be increased appropriately.

(3) Insufficient membrane viscosity
① The thickness of the viscous layer is not enough, and the proportion of the viscous layer needs to be increased;

② The amount of tackifier added to the viscous layer is not enough, and the proportion of tackifier needs to be increased;

③ Check whether the polyethylene resin contains a lot of additives such as slip agent. If there is a lot of slip agent, other grades of polyethylene should be used;

④The surface temperature of the chilled roller of the casting machine is too high, so the temperature of the chilled roller needs to be lowered appropriately.



Nanjing Sumino Precision Machinery Co., Ltd. has a professional cast film production line. The company's main cast film production lines include: TPU hot melt adhesive film production line, CPP/CPE cast film production line, EVA solar energy packaging film production line, PE hygienic and breathable Film production line, PVDF cast film production line, PP three-dimensional film production line, medical blood purification film production line, multi-layer co-extruded barrier film production line, LLDPE stretch film production line, etc.