Application of PET bottles in daily product packaging

Application of PET bottles in daily product packaging

1 background

PET bottles have excellent display effects on the contents. It is widely used as a substitute for glass bottles and PVC bottles. One of the drivers of its success was the transition from using refillable bottles to single-use bottles, which reduced safety hazards caused by improper handling or cleaning.

2 Characteristics of PET packaging

PET stands for polyethylene terephthalate. PET film has the characteristics of transparency, oil resistance, fragrance retention, hygienic reliability, and wide operating temperature range (can be used for high-temperature cooking and freezing packaging). However, PET film has poor thermal sealing properties and must be used in combination with other films (heat sealing layers), coupled with rigidity Strong and easy to wrinkle, the application of PET film in packaging is subject to certain limitations.

PET hollow containers (especially stretch blow molded bottles) can give full play to the excellent properties of PET, have a good display effect on the contents, and have a low cost. Therefore, PET bottles are basically used as packaging containers using the stretch blow molding process. Among them, the most commonly used are small bottles with a capacity of 10mL to 2L, and there are also large bottles with a capacity of 30L.

PET bottles have excellent properties such as high strength, light weight, good transparency, wear resistance, scratch resistance, dimensional stability, good air tightness, odorless, tasteless, non-toxic and acid and alkali resistant. Therefore, PET bottles are widely used in the packaging of carbonated drinks, mineral water and other beverage products.

3 Problems and causes of PET bottles

3.1 Labels for round bottles

Cylindrical bottle labels are rarely labeled. The main reason is that the structural characteristics make the label display surface small, and the labeling surface has a large curvature, which is prone to label warping. Therefore, sleeve labels are often used for this type of bottle shape, which can maximize the display surface of the product and avoid defects that are prone to labeling.

3.2 Coordination of bottleneck and lid

The bottle material is PET and the lid material is PP. Both materials are relatively rigid. In this way, there will be a loosening phenomenon when the ribs are matched, so improvements need to be considered when designing the rib structure. At the same time, due to the strong rigidity of the two materials, users need to use greater force to screw the cap.

3.3 Forming of bottles

It is relatively easy to form round bottles, but after filling, flat bottles are prone to appear due to factors such as the temperature of the filled product or changes in external temperature and air pressure. Flat bottles are more difficult to form, mainly due to the addition of a handle function. In order to increase the display surface, the inflation ratio is high, and there are problems such as deformation of the labeling surface.

4 Solutions and improvement measures

4.1 Use of shrink labels

In order to solve the above problems, after careful observation and in-depth analysis, the following improvement measures should be taken for the use of shrink labels:

1) The bottle-shaped design must have fixed positions above and below the label position;

2) There should be a blank area of about 2 mm on the upper and lower edges of the label to facilitate the label edges to be shrunk and tightened neatly;

3) Use a test label with grid lines to conduct a shrinkage test to determine the deformation position and degree for reference in label decoration design to achieve an acceptable deformation range;

4) The size of the label in the shrinkage direction should be designed to be as small as possible while ensuring operation;

5) The shrinking equipment requires high temperature control accuracy, uniform temperature in the shrinking working area, and basically consistent feeding quantity and interval to ensure the quality of label shrinkage.

4.2 Coordination of bottle neck and lid

1) Due to the strong rigidity of the bottle and cap materials, the thread fit is prone to loosening. Tests have shown that when the rigidity difference between the two materials is large, the capping torque decreases less after a certain period of time; conversely, when the rigidity difference between the two materials is small, the capping torque decreases more after a certain period of time. In order to improve this problem, the inclination of the thread needs to be adjusted to make it as flat as possible while ensuring smooth rotation.

2) The solution to the problem of high capping force is to use capping equipment or tools. This not only ensures the quality of capping, reduces the labor intensity of operators, but also improves labor efficiency.

4.3 Deformation of round bottles

The main reason for the deformation is that the density of the contents changes due to the influence of temperature, resulting in a smaller bottle volume and an increase in external pressure, resulting in a flat bottle phenomenon. To this end, the main improvement measures taken are:

1) Adjust the product filling temperature to basically reach the ambient temperature, which can reduce the range of temperature changes and thereby reduce the probability of flat bottles;

2) Improve the pressure resistance of the round bottle. The method is: A) Optimize the bottle blowing process, improve the uniformity of the bottle wall, and improve the pressure resistance of the bottle; B) Increase the weight of the bottle to improve the pressure resistance of the bottle; C) Add reinforcing ribs to the bottle to improve the pressure resistance of the bottle. The pressure resistance of the body; D) The use of hot filling bottle forming process, which significantly reduces the deformation phenomenon; E) The above methods are combined.

3) Change the bottle structure to improve the visual impact of bottle deformation.

4) Design a system that can freely adjust the internal and external pressure balance of the bottle. The structural design should be breathable and liquid-proof. When a pressure difference occurs, it can be freely adjusted to achieve internal and external balance, thereby fundamentally solving the resulting bottle deformation problem. The main methods are: A) Breathable gasket; B) Breathable device; C) Breathable structure, forming mold solution.

4.4 Forming of flat bottles

1) PET bottles cannot be molded with handles, which is a major drawback of PET bottles. However, the need to have handles is now fulfilled by adding/combining prefabs. We also achieve this in practical applications.

2) Increasing the inflation ratio in order to increase the display surface of flat bottles is a difficult challenge for the PET bottle molding process. To this end, there must be strict standards for the production process, process management, and quality control, which are also related to the production of billet tubes. These are also serious challenges to the technical strength and management level of the manufacturer.

3) The biggest problem when forming flat bottles is the depression of the labeling surface. To this end, the main solutions taken are: stabilizing the process conditions and parameters to make the bottle wall thickness as uniform as possible; increasing the cooling molding time to improve the stability of the molding; adjusting and modifying the mold to increase the curvature of the labeling surface; Properly sandblast the easily deformed parts to improve cooling molding and stress changes.

4) Due to the pressure deformation of flat bottles during labeling, the labels will have serious wrinkles, blistering and other problems. Conventional labeling machines cannot achieve normal labeling and it is difficult to produce qualified products. Therefore, a series of improvements have been made to the labeling machine: A) Air blowing and pressurized labeling. The labeling machine adds an inflatable and pressurized system, which rushes compressed air into the bottle before labeling, so that it can withstand a certain pressure without deformation, ensuring the smooth operation of the labeling machine; B) Improve the labeling scraper. Ordinary labeling scrapers are not strong enough and elastic enough to apply the label firmly and smoothly, resulting in bubbles and edge warping. We use a scraper form that combines rubber and stainless steel to achieve a combination of rigidity and softness, thereby smoothing and sticking the label firmly and improving the quality and effect of labeling.

5 Conclusion

PET bottles are widely used in different industries around the world due to their excellent performance and affordable price. With the continuous development and improvement of PET bottle application technology, such as the application of multi-layer composites, blended materials and additives, its scope of use will become more and more extensive. It is believed that with the improvement of packaging technology, the application of PET packaging containers will develop rapidly in the near future, especially the wide application in daily chemical products, which will play a good role in improving the display effect of product contents and increasing the added value of products. effect.