In recent years, driven by economic growth, there has been an increasing demand for high-quality packaging for various goods. Irregularly shaped and sharp-edged items, such as those containing bones or fish bones, often encounter damage during the vacuum packaging process due to the stretching of aluminum layers in conventional aluminum-coated composite films. This necessitates the development of aluminum films with excellent puncture resistance.
For heavy-duty composite packaging films, besides meeting standard physical properties such as composite strength and tensile strength, puncture resistance is a crucial indicator. In practical applications, poor puncture resistance in films can lead to issues like package ruptures, thereby affecting the efficiency of packaging production lines.
To address these challenges, it has innovated a new type of durable puncture-resistant aluminum-coated film.
1. Structure
The puncture-resistant BOPET film for aluminum coating comprises an upper layer, a core layer, and a lower layer. The core layer, accounting for 60%-80% by weight, consists of PET polyester slices and ENBA copolymer-modified PET polyester slices. The upper layer, representing 5%-10% by weight, contains PET polyester slices, ENBA copolymer-modified PET polyester slices, and PET polyester anti-adhesive material. The lower layer, constituting 30%-35% by weight, comprises PET polyester slices and PET polyester anti-adhesive material. The thickness of the upper layer accounts for 8.3%-10.0% of the total film thickness, while the lower layer’s thickness represents 8.3%-9.0% of the total thickness.
2. Raw Materials
The copolymer-modified PET polyester slices are composed of ENBA (Ethylene-N-butyl acrylate) at 10%-30% and PET slices at 70%-90%. ENBA copolymer-modified PET polyester slices are obtained by melt blending ENBA with PET slices.
3. Preparation Method
3.1 The raw materials for the core layer are crystallized, dried, and then heated to form a molten core layer. The raw materials for the upper and lower layers are separately heated to form molten upper and lower layers. These layers are then combined and extruded into a film using a three-layer structural die head.
3.2 The film is cooled to form a cast film at a temperature of 25-30°C.
3.3 The cast film is preheated and longitudinally stretched to obtain a thick film at a temperature of 55-115°C.
3.4 After preheating, the thick film is transversely stretched, shaped, and then cooled to obtain the puncture-resistant BOPET film for aluminum coating at a preheating temperature of 107-112°C and shaping temperature of 238-245°C.
3.5 In step 3.1, the extrusion temperature is maintained at 270-280°C.
3.6 In step 3.1, the moisture content of the molten core layer, upper layer, and lower layer is less than 50 ppm.
3.7 In step 3.1, crystallization is carried out at a temperature of 155-160°C for 50-70 minutes, followed by drying at a temperature of 160-165°C for 120-240 minutes.
3.8 In step 3.3, longitudinal stretching is performed at a temperature of 116-120°C with a stretching ratio of 4.5-4.7.
3.9 In step 3.4, transverse stretching is conducted at a temperature of 112-120°C with a stretching ratio of 4.3-4.5.
The puncture-resistant BOPET film for aluminum coating offers numerous advantages in performance, production cost, environmental friendliness, and energy consumption. It can improve aluminum coating efficiency by over 30% and reduce production costs by more than 20%, demonstrating promising prospects for widespread application in various industries.
