Tea is one of the most distinctive famous and high-quality products in my country. Its outer packaging is decorated with books, paintings and prints, which increases the added value of this famous special product. The polyethylene film used for inner packaging is also required to have special properties, mainly: no peculiar smell, opaque, and astringent resistance.

The salivating film produced by ordinary film and LDPE has high transparency, and the surface of the film is unobstructed and astringent, which is not suitable for the requirements of tea inner packaging, and the film itself has a greasy odor, which is easily absorbed by the tea, resulting in the change of taste and deterioration of the tea. In view of the particularity of the film used for the inner packaging of tea, through scientific screening of various spleen resins and appropriate adjustments to the salivation process, the 1C7A grade was finally selected

The salivation film produced by resin can meet the quality requirements of tea inner packaging.

Resin selection

In order to meet the requirements of product performance and processing technology, ordinary film-grade resins add some additives such as lubricants, slip agents, and stabilizers to synthetic resins. Most of these additives are lipid low-molecular substances. After the resin is processed into a film , the additives will gradually migrate and precipitate to the surface of the film, causing a greasy odor that is easily absorbed by the tea leaves on the surface of the film, resulting in the taste and deterioration of the tea leaves. same

Similarly, because the resin contains additives, the film has good transparency and smooth surface after film formation, and is not suitable for the special requirements of tea packaging film. The 1C7A resin does not contain additives. After being processed into a film, its surface has no greasy odor, and the film has poor transparency.

2. Main equipment and technical parameters

(1) Extruder, the screw diameter is 90cm, the L/D is 30/1, and the maximum speed is 120r/min.

(2) T-shaped head with a width of 1200mm and a discharge gap of 0.04mm to 1mm.

(3) The cast film cooling roll has a diameter of 600mm and a length of 1400mm.

(4) The range of B-ray thickness measuring device is 0-80um.

(5) Corona treatment device with a power of 13kW.

(6) Double-station coiling device, the maximum coiling diameter is 500m

3. Process conditions and control parameters

(1) The screw speed is 50r/min

(2) The host current is 60A

(3) Extrusion back pressure is 0.12MPa

(4) The filter screen is 100 mesh and 3 layers

(5) The cooling roll temperature is 19°C

(6) The effect of corona treatment is that the surface wetting tension is ≥4×10-2N/m

(7) Die lip opening size is 0.05mm

(8) Film specification: width is 900mm, thickness is (40±1)um