Most of the film bags are made by heat sealing method, and they are also made by bonding method. According to their geometry, they can be basically divided into three categories: pillow bag, three-side sealed bag, four-side sealed bag. Whether standing upright without support can be divided into two categories: upright bags and non-upright bags.
Pillow bag
Pillow-shaped bags, also called back-sealing bags, have back, upper and lower seams, so that they have the shape of a pillow. Many small food bags are usually packed in pillow-shaped bags. The back seam of the pillow-shaped bag forms a fin. a package in which the inner layers of the film are sealed together and the seams protrude from the back of the packaged bag. The other form of the seal overlaps the seal, one of the inner layer and the other side The outer layer is bonded to form a flat seal. Since the fin seal is relatively strong, and the inner layer of the packaging material is heat-sealed, it is widely used. For example: the most common composite film bag, the inner layer is PE, the outer layer is a composite substrate. The overlapping seal is relatively not strong enough, and the inner and outer layers of the bag are required to be heat-sealing materials, so it is not used much, but it can save a little from the material. For example: non-composite pure PE The bag can be packaged in this way. The top and bottom seals are bonded to the inner layer of the bag.
Trilateral pocket
The three-side sealing pocket, that is, the bag has two side seams and a top seam. The bottom edge of the bag is formed by a horizontally folded film, and all the seals are formed by bonding the inner material of the film. There can be hem or not. When there are hem, they can stand upright on the shelf. One of the deformations of the three-side pocket is to use the original method of folding the bottom edge, which is achieved by bonding. Become a four-side pocket.
Four side pocket
Four-side sealing pockets, usually made of the top of two materials, sealed on both sides and bottom. It is possible to use two different plastic resin materials compared to the previously mentioned bags, if they can be bonded to each other. , made of front edge bonded four-side sealing pocket. Four-side sealing pocket can be made into various shapes, such as heart shape or oval shape.
Upright bag
An upright bag, that is, when it is full, can support the weight upright on the shelf. The upright bag has a hem, and when it is loaded, the hem will open, so that the bag has a relatively flat bottom to stand up. They are widely used to package liquid products such as kitchen cleaners, and because they can replace hard-pack materials such as cans and bottles, the market and usage are increasing. The stand-up pouch is designed with a horizontal bottom flap. It can be made of two pieces of flexible packaging material. In another product, only one film is used, the film is folded into an M shape to form the bottom edge; it can also be designed without the bottom fold, and the side folds or folds to form an overlap. The bottom of the flat sheet. This bag is not as secure as the bag with the hem at the bottom, and is mostly used for dry goods rather than liquid products. In both cases, a certain product weight folds the edges of the package, making The bag can stand on its own.
Large volume bag and high strength bag
It is usually used to package bulk products and has a load capacity of up to 5000kg. This bag has high tensile strength and can be used for liquid products (such as the container liquid film described in the previous section) and solid products. The material of the bag can be HDPE, PVC and polyester, but the most used materials are woven from PP flat yarn. Woven bags and bags for liquid products, usually containing PE film as the inner layer. When better barrier properties are required Aluminum foil or PVDC copolymer can be used. For waterproofing, the bag can be coated with PVC or rubber material. According to the material and application characteristics, the sealing of the bag can be heat sealed or stitched. Usually the large volume bag is filled from the top. Discharge from the bottom, it can also be equipped with nozzles or other shunting devices, or open the bag with a simple and rough cutting method. For bags stacked in the open air, add UV stabilizer to the resin ingredients to prevent premature aging of the bag and reduce the strength. .