What are the common hot melt adhesive film forming methods?
Coating method Coating methods are commonly used to produce release films. Coating methods can be divided into: smooth roll coating, textured coating, blade coating, spray coating and curtain coating. According to different products, different coating characteristics are adopted and different coating methods are used. The key characteristics of release films produced by coating methods include coating uniformity, high residual adhesion, flatness and high cleanliness. Blow molding The resin is melted and plasticized by the extruder, and drawn vertically upward from the annular head. After being inflated, it is introduced into the traction roller from the herringbone plate, and then the finished product is obtained through the guide roller and the coiling device. The blow molding method causes the vertical and horizontal molecules of the product to be stretched to different degrees due to an inflation process. The temperature resistance and heat sealing performance of the product will be greatly affected Casting method The resin is melted and plasticized by the extruder, and extruded from the die head through the slit die, so that the molten material is close to the cooling roller, and then the finished product is obtained by peeling, stretching, slitting and rolling. The production efficiency of the casting method is very high, and the product quality is stable. There is less waste in the production process, and it is easier to realize online recycling of edges and wastes, and the utilization rate of materials is high Blow Molding vs Casting The annular die and the multi-layered die core used in the blow molding method have very high requirements on the machining accuracy and assembly accuracy and are particularly difficult to control. If there is a small error in the machining and matching accuracy, it cannot be compensated by adjustment, so the thickness of the product is The tolerance is basically about ±10% The casting method adopts a flat die head, and there is a special retention groove in the die head, which can ensure the uniformity of the material flow, and the uniformity of the die lip gap can be automatically controlled by the automatic adjustment device of the die head, and the control accuracy is very high. Thick films can also be controlled below ±3% Blow molding can produce some hot melt adhesive film products, but the flatness and uniformity of the film are not as good as that of casting film, especially as a hot melt adhesive. Large shrinkage can easily lead to poor bonding The molecular arrangement of the film-making film by the casting method is orderly, and the cooling speed of the product is fast, which is beneficial to improve the transparency, gloss and thickness uniformity of the product, and the product texture is soft and tough; the impact resistance, heat resistance and low temperature adaptability are better than blow molding Calendering The resin is melted and plasticized by an extruder, extruded from the die head through a slit die, rolled and cooled by a three-roll calender, and then passed through a cooling conveying roller and a coiling device to obtain the finished product The calendering method is superior to the blow molding method in various product performance indicators, thickness uniformity, and product thermal shrinkage; calendering also has great advantages in product thickness range and raw material adaptability. However, in terms of investment, the calendering process is more than ten times higher than the blow molding process. Compared with the casting method, the production line of the same scale, because the casting method adopts a vertical operation, its operation is more complicated and difficult, and the casting method cannot produce products with a thickness of more than 1.5mm. 
