What are the common hot melt adhesive film molding methods?

Coating method

The coating method is often used to produce release film. The coating methods can be divided into: smooth roll coating, anilox coating, scraper coating, spray coating and curtain coating. Different coating methods are adopted according to different products and coating characteristics. The key characteristics of release film produced by coating method include coating uniformity, high residual adhesion, flatness and high cleanliness.

Blow molding

The resin is melted and plasticized by the extruder, and is vertically led out from the annular head. After being blown, it is led into the traction roller by the herringbone plate, and then the finished product is obtained through the guide roller and coiling device. Blow molding has a blowing process, which causes the vertical and horizontal molecules of the product to be stretched to varying degrees. The temperature resistance and heat sealing performance of the product will be greatly affected.

Streamer method

The resin is melted and plasticized by the extruder, and extruded from the die head through the slit die mouth to make the molten material cling to the cooling roller, and then the finished product is obtained by peeling, stretching, slitting and coiling.

The production efficiency of tape casting is very high, and the product quality is stable. There is less waste in the production process, and it is easy to realize online recycling of edge and waste materials, and the utilization rate of materials is high.

Blow molding VS tape casting

The annular die head and multi-layer superimposed die core used in the blow molding method have very high requirements on the processing accuracy and assembly accuracy and are particularly difficult to control. If there is a small error in the processing and fitting accuracy, it cannot be compensated by adjustment, so the thickness tolerance of the product is basically about ± 10%.

The tape casting method adopts a flat die head, which is equipped with a special retention groove to ensure the uniformity of material flow. The uniformity of die lip clearance can be automatically controlled through the automatic adjustment device of the die head, with very high control accuracy. The thicker film 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 tape casting. Especially as hot melt adhesive, during the heating process of hot melt bonding, the heat shrinkage of blow molding film is large, which is easy to lead to poor bonding.

The film molecules of tape casting method are arranged orderly, and the cooling speed of the product is fast, which is conducive to improving the transparency, glossiness 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 those of blow molding.

Calendering method

The resin is melted and plasticized by an extruder, extruded from the die head through a slit die, calendered and cooled by a three roller calender, and then cooled by 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 performance indexes, thickness uniformity and product thermal shrinkage; Calendering also has great advantages in product thickness range and raw material adaptability.

But in terms of investment, the calendering process is more than ten times higher than the blow molding process.

Compared with the tape casting method, the production line of the same scale is more complex and difficult to operate due to the vertical operation of the tape casting method, and the tape casting method cannot produce products with a thickness of more than 1.5mm.

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