10 sins of PET bottles

- Oct 07, 2020-

10 "sins" of PET bottles

Who is the most outstanding champion in recycling field for a variety of synthetic resins? There is no doubt that it is polyester PET plastic bottle!

PET bottles are high value-added waste, the recovery method is relatively simple, the technology is mature, and a complete industrial chain has been formed several years ago. Compared with other varieties, the recovery rate of PET bottles is very high. Through the establishment of deposit system, the recovery rate of PET bottles is about 90%, the overall recovery rate of EU in 2017 is 58.2%, Japan is over 92%, and that of Chinese PET beverage bottles can reach over 94%.

In addition, the recycling and reuse of PET bottles has formed a complete business model in China. From the waste collectors, waste stations, recycling and packaging plants, recycling and recycling industries, textile factories and other upstream and downstream enterprises, they can continue to profit from it. (but this is the case before. Now, because of the decline of crude oil price and expansion of production capacity, the whole industrial chain has a tendency to collapse. Enterprises can not profit only by market regulation, and more incentive policies or measures are needed to promote the vitality of the whole industrial chain.)

But there are also some problems in the recycling of PET bottles. We are short of "10 crimes of PET bottles".

1. At present, 70% of the labels of domestic beverage bottles are PVC.  PVC shrinkage film is the most widely used heat shrinkable label film material, which has low cost, good transparency and moderate shrinkage rate, which is generally between 40% and 60%, which requires high heat source. However, because the density of PVC and pet for bottle is close, it is difficult to separate by simple flotation method in recycling.


PVC mixing will not only seriously affect the quality of bottle, but also produce toxic and harmful substances. In the production process, the monomolecular vinyl chloride is not fully polymerized, and the plasticizer also contains harmful substances. These two substances are easy to release when they meet high temperature and oil, and toxic substances will enter human body with food for cancer. Green earth, the Hong Kong environmental protection organization, also points out that PVC contains chlorine, which can release dioxins with high toxicity when burned at high temperature. Dioxins can cause cancer, damage the nervous system, and lead to reproductive system disorder or immune system disorder.

In 2010, Coca Cola has launched new environmental protection non PVC film labels in China, and it is clear that all special promotional label must adopt PVC free shrink film. Coca Cola is the first international beverage company to realize all product labels in China to replace PVC label with new environmental protection package.

PVC labels have been listed as non recyclable in the worldwide guidelines for plastic packaging design.


2. The paper label and the paddle free label of PET bottle will cause pet pollution. PET bottle is used to clean and remove glue, label and other pollutants attached to the package by hot alkaline water. The fiber in paper label is very small, so it is difficult to remove it through filtration during cleaning, and increase the pressure of water treatment. The wood fiber contained in pulp will carbonize during processing and reduce the product quality of regenerated pet. Although the label without pulp paper is alkali resistant, it will sink, and it can not be separated from pet, which will pollute the recycled PET products.



Glue for fixing trademark paper

The adhesive of label will cause trouble to the back end treatment. At present, there are two kinds of adhesives commonly used in the market, solvent type and water-soluble adhesive. Solvent type is used mostly because of its low cost. However, solvent adhesives are mostly organic reagents, which are not friendly to the environment and difficult to clean, so it is difficult to recover.



Oil bottles in pet plastics

The proportion of oil bottles in recycled plastic bottles is 5% - 10%, and the remaining oil after use is about 5%. In addition, there are PET bottles with different contents such as soy sauce pot, vinegar pot and conditioning products. This bottle can be recycled and reused, but the quality of production products is low. In the process of recycling and regeneration, the mixed recovery is easy to form cross pollution. In the process of crushing and cleaning, the cost of sewage treatment is high, difficult to treat and low in value. Whether it is physical or chemical, the recovery of oil bottle is faced with various difficulties, and the cost of recovery is high. If the extension of producer responsibility system is implemented, the oil pot industry chain should bear more environmental responsibility than beverage bottles.

Pet recovery of oil bottle is a very complicated discussion. Except for oil pot, cosmetics bottle, condiment and other contents, it will cause trouble to recycle and regenerate, which limits the recovery of PET plastic bottles.


PET bottle handle, aluminum port, rubber gasket, etc

The design of handle, aluminum port and rubber gasket on PET bottle increases the difficulty of recycling PET bottle to a certain extent. PET plastic bottle mainly includes bottle embryo, bottle cap and label. Single material PET bottle embryo, PP or PE bottle cap can be separated and recycled by sorting. The higher the purity, the higher the quality, the higher the quality. However, the mixed impurities of pet will affect the quality of recycled products.



Additives affect the recovery of PET plastic bottles

Some enterprises add additives such as colorants and other additives to pet, and food contact grade materials. There are clear regulations on the types and quantities of additives. Whether the bottles with various additives produced now meet the standards of food contact grade materials needs to be clarified.



Colored PET plastic bottle

Although recyclers can use automatic sorting machine to screen colored bottles from colorless logistics lines, colored PET plastic bottles can only be mixed together to make black particles, which reduces the value of recycled products. The market acceptance is low and the price is cheap, and the application range of production products is narrow.

PET bottle body has color, label package, recycling value is low, difficult

1. Light blue bottles are now widely used in the market for high-end recycling, and the requirements for the color of bottle pieces are higher and higher. Some customers who do high-end recycled PET materials report that the sorted transparent PET bottles often contain some light blue bottles. This light blue bottle is very light in color, and is often recognized as transparent by the naked eye and equipment. It is also a big difficulty to separate these light blue bottles from transparent PET bottles.

2. In most automatic sorting systems, due to different polymers reflecting different light, when infrared light irradiates the packaging materials, the conventional carbon black pigment used to make black plastics will absorb all or most of NIR light. The electromagnetic radiation of carbon black to visible light and infrared point band confuses the traditional optical sensing sorter, and the NIR sorting sensor can not even "see" black Color packaging, not to mention separating polymers.

However, taolang's AutoSort sorting equipment is a flexible, energy-saving and easy to maintain photoelectric sorting system, which is suitable for a wide range of mixed waste separation. As objects speed up on the conveyor belt, flying beam? Technology uses the point scanning principle to detect materials and colors over the same point and time range. The online calibration function ensures the accuracy and stability of separation. This is a sensor based PET bottle sorting technology, as a leading form of photoelectric separation technology, can realize the sorting of black plastic.



PE bottle cap

At present, most of the bottle cap materials on the market are PE and PP. Because the specific gravity of PE and water is similar, it is difficult to separate it clearly in water, which reduces the purity and the value of recycling.


Blending modification of pet with other resins

It is difficult to separate the composites of pet and other resins. PET  Limited by its own performance, it is usually not used to make packaging covers, handles, accessories, labels and other components, but it is blended with other resins to meet the required performance. The mixed materials and additives are difficult to be removed in the sorting stage. When recycling, it is necessary to evaluate its impact on the application of recycled PET products, increase the recycling process, and even can not be recycled Raw, can only be treated as waste.

1. PLA or PVC bottle

In addition, due to the lack of bio plastic labeling methods, people can not sort PLA and other plastics. Although the current PLA does not constitute serious pollution, a large number of PLA plastic bottles are difficult to separate, which hinders the recycling of PET bottles. PVC material can not be separated, affecting the recovery, increasing the difficulty of recycling.

2. PETG material

Pet matrix resin mainly considers the physical and chemical compatibility between materials and pet. Incompatible materials will have a negative impact on the processing and properties of pet. For example, PETG materials have lower melting point and glass transition temperature than ordinary PET materials, and will soften and become sticky when pet is processed and dried, which will harden the PET particles and affect the feeding of pet processing.


The viscosity of PET bottle fluctuates widely

The viscosity of PET bottles for different purposes fluctuates widely. The viscosity of carbonated beverage bottle grade slice (BG85) is about 0.87dl/g, that of hot filling beverage bottle grade slice (bg801) is about 0.78dl/g, that of mineral water bottle grade slice (bg80) is about 0.80dl/g, and that of edible oil bottle grade slice (bg802) is about 0.83dl/g. The fluctuation range of viscosity of PET beverage bottles on the market should be reduced as far as possible, so as to control the quality of recycled materials.


Ink on bottle

Direct printing ink will lose color and change color of pet during recycling and cleaning, which will pollute recycled PET products.  Reduce the value of products, not conducive to recycling. However, some direct printing inks will not cause similar problems. There is no clear understanding of inks in the industry, and tests are needed to determine the impact.


Some special designs on the bottle body

Some special anti tampering functions of PET bottle body are usually integrated with the bottle body design. If these anti tamper sleeves or safety covers cannot be removed from the bottle body or removed by sorting equipment, it will have adverse effects on the recovery. If these parts are to be used, the material of floating water should be selected to facilitate the separation and sorting of pet in the float sink tank, so as to ensure that they can be completely removed from the bottle body without residue.

In addition, PVC or PLA bottles, which look like pet bottles, are difficult to recycle in the system.