Waste PET plastic beverage bottle recycling technology

China's current consumption of PET plastic beverage bottles is very high. The recycling of used PET beverage bottles can not only reduce environmental pollution but also turn waste into treasure. However, only a small part is used, and the rest are discarded at will, causing waste of resources and environmental pollution. Therefore, its recycling technology has broad prospects.

PET beverage bottle recycling methods are chemical recovery and physical recovery. The chemical recycling method is a method of depolymerizing PET waste bottles under certain reaction conditions to produce useful chemicals, such as the production of low-grade fuel gasoline. The physical recycling method is a re-granulation method by separating, crushing, washing, and drying waste PET bottles. The physical recycling method mainly includes the following two methods: First, the waste PET bottles are shredded into pieces, HDPE, aluminum, paper and adhesive are separated from the PET, and the PET pieces are washed, dried and pelletized; Non-PET caps, bottoms, and labels on waste PET bottles are mechanically separated, washed, broken, and pelletized.

The former process: artificially remove stones, wood and other plastic products, as well as colored PET bottles. Recycled PET must not contain PVC impurities because its presence is a key factor affecting PET color. When the amount of PVC mixed is small, it can be separated manually on the conveyor belt. That is, when the torsion is applied, the PVC and the PET bottle produce different physical phenomena in the force part, the PVC bottle shows opaque marks, and the PET bottle does not have the ability to separate. Some companies also use PVC and PET with different melting points to pass broken PET and PVC chips through a conveyor equipped with a heater to control a certain temperature, and the PVC is melted and adhered to the conveyor belt so that it can be separated from PET.

Iron separation using ferromagnetic separator.

Some of the PET bottles were broken only once, and some of them were first broken up and then broken down. They eventually became 1.0-1.5 cm in size. At the outlet of the crusher, a screen with a 1.0-1.5 cm aperture was installed to control the size of the chips.

Washing and impurity separation techniques are the key to obtaining high quality recycled PET. Drink bottles usually use plastic PE or finger labels. The paper labels can be used as adhesives and can be glued during the blowing process of the bottles. When the PET bottles are broken, some of the labels are broken into pieces, and some of them are still stuck on the PET chips. After the break, PET is usually combined with a blower and cyclone separator. It can remove about 98% of loose label fragments. It can also be separated by suction tower separator. Broken PET chips are added vertically from the top of the separation tower. Reverse flow is formed. Using the difference between the specific gravity of PET and the label, the label is withdrawn, and the PET comes out from the bottom of the separator. In order to ensure the separation efficiency of the label, more than two sets of separation devices can be used in production.

The purpose of washing is to remove the binder, the ash and the residue in the original bottle. Wash 80-100oC hot water to soften or dissolve EVA adhesives or other types of adhesives attached to the label and the base. To prevent the peeled adhesive from adhering to the PET chips, add additives such as alkali and emulsification to the water. Agents or other special chemicals, cleaning fluids are generally determined by the factory according to the source and adhesive properties of the waste bottle. Its composition and content can be filtered. The cleaning solution can be used to filter out impurities and re-heat it for recycling. The washing can be performed with special agitators. In order to ensure the effect of cleaning, the washing process can be performed in a tank.

Separation of the base is achieved by separating the HDPE density of the base from the density of the PET. Separation was carried out in a septic tank, HDPE chips spilled from the top of the tank, and sinking PET chips went out from the bottom of the tank. Others use hydrocyclone separation instead of flotation tanks, and their separation is better.

PET chips usually use centrifugal dehydrator to reduce the moisture content of the chips to 2%, and then dried by a belt or tube dryer to reduce the moisture content to 0.5%.

PET can not contain aluminum impurities, even if trace aluminum impurities will affect the transparency of recycled PET, so the content of aluminum in recycled PET should be less than 50×10-6. The simplest method to separate aluminum is to manually remove the aluminum cap and aluminum before crushing. Ring or the use of electrostatic separation to reduce the aluminum content to 100 × 10-6, this separation can be carried out on the conveyor belt; If the PET debris further purified by the metal detection and separation system, the aluminum content of less than 5 × 10-6.

Extruded PET extrusion granulation and raw PET extrusion granulation are different from other materials except for the other aspects. Extrusion granulation can use single-screw or twin-screw extruders, but in the design must take into account the traditional extruder's feed pressure is too large, change to the feed part of the larger size of the screw, if the twin-screw extruder Better results.

The latter process: The recycling method is to separate the non-PET components in the PET bottle, and then crush and recover. It is the first artificial separation of stones, wood and other plastic products and colored beverage bottles. The separation of PVC bottles can be done manually or by PVC separation equipment. The separation of metal iron can be performed using a magnet separator. After the beverage bottle passes through the conveyor, it enters the cleaning machine. The bottle enters the processing production line vertically. The bottle cap and pull ring are removed through the ring remover and the decapper, and the bottle cap is removed after being weighed to ensure that the bottle weight exceeds the standard. Separate it from the production line.

Then inject 100ml boiling water into each waste PET bottle, dissolve the remaining beverage in the bottle, hold the bottle clamped, wash the bottle with high-pressure water, soften the adhesive with hot water, and then the base falls off by itself, plastic or paper label Get out. After washing, the bottom of the bottle is cut off and the water in the bottle is released. The crushing is just like the equipment in the first process, and the PET bottle is dried in a continuous dryer until the moisture content is less than 0.05%. Extrusion granulation is the same as bottom.


Both of the above recycling technologies are used in factories. The process has its own characteristics. The first recovery method is relatively easy to form large-scale production, but the separation technology is more complicated, there are more separation equipments and the investment is larger. The second method has higher product purity, less equipment, and less investment, but is only applicable to intact beverage bottles without breakage, and the compressed or damaged beverage bottles need to be separated and recycled by other methods. In fact, waste plastic bottles are considered to be transportable after they have been squashed and packed. Secondly, the cut bottle base recovery is basically performed according to the first method, so the second recovery method has a large limitation.

Domestic use recycled PET to make colored pesticide bottles instead of glass bottles to reduce product damage. Overseas use recycled PET for PET packaging. Australia uses recycled PET as an intermediate layer material for three-layer bottles, and recycled PET is widely used for the production of 3-17 dtex staple fibers for non-woven fabrics. The United States also uses recycled PET to produce 6.6-9.9 dtex hollow fiber as a filler material for cotton wool. Recycled PET can also be used for clothing fibers. For example, the Dyersburg fabric factory in the US uses 100% recycled polyester PET chips for the production of suede fabrics, the Wellman Fiber Company develops outdoor fabrics, and the recycled PET fiber blends with other fibers. The blending rate can reach 89%. The company also cooperates with other companies to produce polyester staple fibers for use as raw materials from waste PET beverages. The US Patagonia company used recycled PET fiber blended with other fibers to produce sportswear with a blending rate of 80%.

Teijin Corporation of Japan has also recently developed a recycling method for DMT (dimethylphthalate terephthalate) and EG (ethylene glycol) from used PET bottles. The waste PET bottles were first crushed and cleaned, and then dissolved in EG. In the process, PET was depolymerized at the boiling point temperature of EG and 0.1 Mpa to produce hydroxyethyl bis-terephthalate (BHET). After filtration, the filter residue and additives were removed to react BHET with methanol, and DMT and EG were produced by transesterification reaction at the boiling temperature of methanol and 0.1 Mpa pressure. After distillation, DMT and EG are separated, and DMT is refined through a recrystallization process; EG is purified by distillation and methanol can be recycled. The purity of the recovered DMT and EG reaches 99.99%, and the production cost is comparable to that of the general DMT and EG methods. DMT can be converted to pure TPA (terephthalic acid) for the manufacture of bottle grade PET resins. The circulating device can generate about 10% of the company's raw materials for resin production.

PET single screw plastic extruder

Model screw diameter, mm length to diameter ratio L/D screw speed, r/min motor power kw output, kg/h

SJP-14014025

SJP-15015025