ZhangJiaGang Antron Machinery,Co.,Ltd

PET application status

PET application status

Since PET in 1941, first by the British J. Tt. Whinfield and J. T. Dickon has been successfully developed and has been used as a fiber raw material for nearly 70 years.

PET has excellent comprehensive properties and maintains excellent physical properties over a wide temperature range. It has high impact strength, good friction and rigidity, high hardness, low hygroscopicity, small dimensional stability, excellent electrical properties, and most organic solvents. It is also highly stable with inorganic acids and resistant to creep, fatigue, and friction and abrasion. Therefore, it has become the most productive variety among synthetic fibers.

PET is not only used as a raw material for processing fiber and related products of polyester fiber enterprises, but also used in bottles, films, etc., and is widely used in the fields of packaging, electronics, medical and health, construction, automobile, etc., where packaging is the largest polyester. The non-fiber application market is also the fastest growing area for PET. The total PET production in the world is growing rapidly. In 2005, the total world PET production reached 40,910 kt, and it is expected to reach 52,520 kt by the end of this year. According to Euromonitor's research data, the global PET bottle producer's total output is growing at a rate of 7% per year (in 2008, the figure was 288 billion). In recent years, China's PET production capacity and output have also increased significantly, reaching 12530kt as of 2005. With the maturity of PET application technology, Asia will become a key demand area for PET. It is estimated that by 2010, Asian demand will account for 29% of the world's total demand.

 The discarded PET material itself has no toxic effect, but its degradation cycle is long in the natural environment. Due to the large amount of use, the discarded PET also causes huge environmental pollution and waste of resources, especially after PET is combined with other materials, such as starch coating. The layer, which causes the PET to naturally degrade in the environment, produces higher BOD and COD values. Recycling waste PET can not only reduce environmental pollution, but also turn waste into treasure.

At present, China's polyester recycling has not formed a broad sense of saving social energy and environmental awareness, recycling technology is relatively backward, the development of recycling and reprocessing products market lags, making domestic polyester materials only for various reasons, the recovery rate is only 6%~~10%, of which 40%~~60% are used for fiber production. Unrecovered waste polyester has caused considerable waste of resources and pollution, and recycled products have not been maximized by social and economic benefits. The recycling of polyester is not only conducive to the sustainable development of the environment and industry, but also a profitable industry.

 Waste PET recycling process

At present, the recycling technology of discarded PET is mainly divided into physical recycling technology and chemical recycling technology.

Physical recycling techniques include:

(1) Direct recovery, cleaning and reuse.

(2) Waste PET is collected, classified, cleaned and pulverized and divided into two cases: one is waste PET pulverized and granulated as a product, and partially added to other plastic products to reduce the cost of the plastic; Second, the waste PET is pulverized and granulated, and then re-inflated and stretched to form a new package. The physical recycling technology is relatively simple, but it will lead to a decline in the mechanical properties of the material, and it is not suitable to produce high-grade products.

The TDD technology, the viscosity-increasing technology in the recycling process, is the most successful example in the near future. The technology pulverizes, dries, coagulates and preheats the original processed materials. The cutting and compacting device combines the past two processes into a simple process, so that the quality of the product is not affected by fluctuations in moisture and moisture, and differences in the ratio of raw material density. This technology can reduce the loss of processed polymers and improve the quality of recycled materials.

Chemical recycling technologies include:

(1) Direct fiber production technology

Waste PET is processed by processing, sorting, purifying, drying, and chemical degradation without adding necessary additives, and granulating to meet the quality standards of spinning raw materials. Short fibers are formed by melt spinning and then processed into textiles or non-textiles. Such as geotextiles, needle-punched carpets and automotive interior materials.

(2) Conversion technology to convert polyester resin raw materials

The PET is converted into a polyester intermediate raw material by direct degradation or directly converted into a monomer, and then used for the production of polyester, mainly an alcoholysis technique and a hydrolysis method. Alcohol hydrolysis mainly includes fatty alcohol degradation method, aromatic alcohol degradation method, monohydric alcohol degradation method, glycol degradation method and supercritical degradation method; hydrolysis can be mainly divided into acidic hydrolysis, neutral hydrolysis and alkaline hydrolysis. Acidic hydrolysis generally uses concentrated sulfuric acid, concentrated nitric acid or concentrated phosphoric acid as a catalyst. The reaction time is short, but the recovery process produces a large amount of inorganic salts and wastewater. The use of high-concentration acid will corrode the equipment; alkaline hydrolysis will also have a large amount of waste acid and alkali. Discharge; the use of neutral hydrolysis can directly degrade PET into monomers for the synthesis of polyester, and does not produce acid-base waste, is an environmental process.

The alcoholysis recovery of waste PET materials has an important role in protecting the environment and conserving resources. The products obtained by degradation can be used as raw materials for industrial production, and have broad market prospects, but still have many shortcomings. The chemical recovery process is complicated by the physical recovery process, and the industrialization investment cost is high.

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