Thanks for replying.
Consider the following to establish a starting point...
1. Before the milk enters the packing unit, it has been processed completely including refrigeration.
2. Processed milk is stored in a container (perhaps a 20 liters steel container
3. Photo of the desired packet is attached below
4. The packet is made from a long sheet of plastic film.
5. The film is folded to make a tube.
6. The tube is then sealed from the center by applying heat and pressure for a short duration, perhaps by pressing with hot a hot metal whose temperature is controlled.
7. A pipe is inserted in this tube, that will dispense milk.
8. Before the milk is injected, the lower end of the tube is clamped by hot metal and thus sealed.
9. Milk is dispensed.
10. The tube with sealed bottom is then slided downwards and the upper end is also sealed and cut from the parent tube.
11. The following pictures of existing machines will explain better.