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Main points of production control of square-bottom bag
Aug 02, 2017

The square bottom bag generally has 5 sides, front and back, two sides, as well as bottom face. The unique structure of the square bottom bag determines the convenience of packing three-dimensional goods or square products. This bag not only takes into account the packaging meaning of the plastic bag, but also expands the new packing idea, so it is now widely used in the production of children's lives.

With the wide application of the square bag, it also extends a lot of products, such as elastic band side bottom bag, wearing rope side bottom bag, rust-proof side bag, planting flower box side bottom bag, blue square bag, printing side bag and so on. The square bottom bag is generally transparent, can also be made of various colors, such as red, blue, thickness in 2 silk to 15 silk, the most widely used thickness of 8 silk and 10 silk, and most of the new material production, with good transparency, tensile strength, non-toxic, tasteless, toughness and so on.

Square bag has been very popular in recent years, but the bag-shaped because the corner is difficult to shape, the bottom of the hot seal up to eight layers, the bag requirements are higher. and the hot sealing bag is the plastic soft packaging production process of the last process, if produced waste, will produce a lot of waste. Therefore, in the production process, we must do a good job of each link.

1. Heat sealing temperature
The thermal seal temperature range of heat sealing material is the key factor to influence and control the heat seal quality. The temperature resistance of printing base material is good, such as boPET, Bopa and so on, improve the heat sealing temperature can improve the production rate, printing substrate temperature resistance, such as the use of Bopp as far as possible low heat sealing temperature, and by increasing pressure, reduce production speed or choose Low-temperature Thermal sealing material to ensure the strength of heat seal. Hot sealing temperature is too high, easy to make hot sealing material melt extrusion, reduce the heat seal thickness, increase the thickness and uneven welding edge.

2. Heat sealing pressure
The heat sealing pressure is provided by the pressure spring on the bag-making machine. The heat sealing pressure is related to the performance, thickness and heat seal width of the composite film. The heat sealing material has higher activation energy, and the effect of temperature increasing on the viscosity decreases, so the heat sealing pressure is small, so the molten material in the hot sealing area should be prevented from being extruded and the heat sealing effect can be lowered. and PE, pp for non-polar materials, activation energy is very small, the need for high pressure, on the thermal seal strength, interfacial sealing advantage.

3. Heat Sealing speed
The heat sealing speed embodies the production efficiency of the bag making machine, which is also an important factor affecting the strength and appearance of the Heat seal. The faster the heat sealing speed, the higher the heat seal temperature, to ensure that the heat seal strength and heat seal state to achieve the best value; under the same heat sealing temperature and pressure, the slower the heat sealing speed, the heat sealing material fusion will be more full, firmer, but can not cause root-cutting phenomenon.

4. Cooling condition
The cooling water of the bag making machine is usually running water or 20°c. Water temperature is too high, cold sealing knife pressure is not enough, cooling water circulation is not smooth, not enough circulation will lead to poor cooling, heat seal strength decline.

5. Number of heat seals
Good thermal seal generally requires more than 2 times. The bottom of the flat bottom bag is formed at most eight layers, and it is easy to produce the heat seal strength in the middle of the bottom material, too many times the heat sealing is easy to produce the root-cutting phenomenon. General flat bottom bag transverse heat sealing device is 5 groups.

6. Heat Sealing knife Clearance
Hot Sealing knife clearance refers to the hot sealing knife contact to the floor, the predetermined heat seal pressure transfer to the hot sealing surface pressure distance. In the same film thickness, the same heat sealing speed, hot sealing knife gap, heat sealing time is relatively small, the product thermal seal strength will be reduced. The general heat sealing knife clearance is set in 1. $number 5mm, which is related to film thickness, transfer performance, bag speed, etc.

7. Tension control
Tension control device is used to keep the film flat, easy to fold, intermittent feeding evenly, reduce the bag hot sealing parts of contraction and warping. The tension of the bag making machine is generally 0.1~0.15MPa. Because the bag process is complicated, the distance of the film is longer, the tension control of the main membrane and the organ material and the bottom material is high.

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