Plastic packaging recycling method

The so-called green packaging should generally have the following aspects: First, the implementation of packaging reduction (Reduce), packaging to meet the protection, beautification, convenience and other functions, the minimum amount, should not be over-packaging. Second, the packaging should be easy to recycle, reuse, and reuse. The purpose of recycling is achieved through measures such as the use of recycled recycling or incineration of thermal energy (on the premise of not producing toxic substances). Third, plastic packaging waste can be degraded (Degradable), which ultimately does not form permanent waste, and thus achieve the purpose of improving the soil. Reduce, Reuse, Recycle, and Degradable are the 3R1D principles recognized by the world today for the development of green packaging.

To promote the specific requirements of green packaging: First, try to recycle, recycle, and reuse recycled plastics; second, develop and use biodegradable plastics as soon as possible.

Recycling recycling

For plastic packaging, such as thin-film food packaging bags, shopping bags, garbage bags, beverage bottles, fast food boxes, etc. due to the short life cycle (one-time use), the amount of discarded is more worthy of attention. Among them, the most widely used polyester films and polyester bottles. Discarded polyester films and polyester bottles can be recycled, reused, and reused in two ways.

1. The physical method is to crush the clean PET waste film or the waste PET bottle and then granulate it into a regeneration slice through the extrusion granulation equipment and directly use the new material. Physical methods Re-granulated PET chips have no change in chemical structure but only a slight reduction in molecular weight and do not affect use. The twin-screw extruder and the compression-densified extrusion granulator are the equipment used for recycling granulation. The characteristics of these two recycling granulation equipments are that they do not need to be dried before processing and they are directly fed with clean crushed materials. Extruder melt plasticized, through the exhaust vacuum exhaust, the melt through the porous die can create a regular shape, uniform size PET particles, and the viscosity is reduced, can be recycled. Similarly, scraps of corners such as BOPP, CPP, and PK films can also be reused after regranulation using the above method. This saves resources and protects the environment.

2. Chemical methods Still using polyester as an example, alcoholysis can be used. Because polyester is based on FFA and EG as the main raw material, the polymer obtained by esterification and polycondensation reaction. Because the polycondensation reaction is a reversible reaction, under certain conditions, the PET corner waste can use the alcoholysis method to recover the purified PET comminuted material, and use methanol or triethylene glycol to depolymerize the PET into monomers or parts under the action of a basic catalyst. Depolymerizes into oligomers and then re-polymerizes the monomers or oligomers into PET resin for reuse in packaging materials or in the manufacture of polyester staple fibers.

PET corner scraps can also be added during the alcoholysis process by adding a certain amount of ethylene glycol and glycerol to ethanol at 2100C to carry out polycondensation and then adding some ethyl acetate, xylene and other substances. High-performance polyester enameled wire paint.

In the alcoholysis method, an appropriate alcohol, such as 2-ethyl-1-hexanol, can be used for alcoholysis PET waste and adding tetrabutyl phthalate to obtain dioctyl phthalate which is used as PVC. Plasticizers and precision mechanical lubricants.

Development of degradable plastics

Plastics have excellent overall properties, including high chemical stability, resistance to acid and alkali corrosion, and mildew resistance. Even if buried deep underground, it may not be able to rot for hundreds of years. Over time, over time, waste plastics cannot be eliminated due to their durability and become a serious hazard. Degradable plastics is an effective way to solve "white pollution" and is an important development direction of packaging plastics.

The durability of plastics stems from its chemical structure. Synthetic plastics are mostly composed of repeating long-chain or heterocyclic hydrocarbon molecules. These molecular chains are strongly bound and it is difficult to degrade and completely destroy it under natural conditions. . Therefore, research and development of degradable plastics have become an irresistible mission for chemists.

Degradable plastic refers to a kind of plastic whose chemical structure changes, long-chain macromolecules are destroyed, and the molecular weight degrades to low-molecules in a certain time and under a specific environment. The biodegradable plastic packaging material not only has the functions and characteristics of traditional plastics, but also can be decomposed and reduced in the natural environment through the action of ultraviolet light in sunlight or microorganisms in soil and water after the service life is completed, and finally be non-toxic. The form reentered the ecological environment.

There are currently three types of degradable plastics, which are biodegradable plastics, photodegradable plastics and light/biodegradable plastics.

Biodegradable plastic is a plastic that can be decomposed by microorganisms and enzymes in the soil in a wet environment, ie, it can be as spoiled as organic plants, and is finally decomposed into carbon dioxide and water.

Photodegradable plastics add oxygen-containing functional groups such as hydroxyl groups during resin synthesis, or add photosensitizers or excessive metal complexes during processing of plastics, relying on the absorption of ultraviolet rays in sunlight to destroy macromolecular chains, making plastics brittle and collapse. solution.

It can be seen that biodegradable plastics are the most promising in biodegradable plastics. At present, the world's biodegradable plastics are mainly made of aliphatic polyester or aliphatic polyester mixed starch. Aliphatic polyesters mainly include polycaprolactone (PCL), polybutylene (PBS) and its copolymers, polylactic acid (PLA) produced from renewable resources, and polyhydroxybutyric acid produced by microorganisms ( PHB) etc. After biodegradable plastics are decomposed into water and carbon dioxide, they will not be harmful to the environment. At the same time, it can also be used to make compost and return to nature as a fertilizer or soil conditioner.

Related

Development of Degradable Plastics at Home and Abroad

Germany's BASF has built an Ecofiex production facility for biodegradable plastics in Germany, with an annual production capacity of 6,000 tons, which is scheduled to be put into production in early 2006. BASF has built an 8,000 tonne/year Ecoflex unit in Ludwigshafen, Germany. After the new plant is put into operation, the total annual production capacity of BASF's biodegradable plastic Ecofiex will reach 14,000 tons. Ecofiex is usually used in combination with recycled materials such as starch, fiber, and polylactic acid. In addition, the company also introduced the branded ECOHEXD aliphatic diol and aromatic dicarboxylic acid polymerized fully degradable polyester, which can be used to produce packaging films.

Eastar-Bio, a new copolymer resin developed by Eastman Chemical Co., USA, is a copolymer made from adipic acid, terephthalic acid and butylene glycol, and can be applied to films and coating materials. This material can be contacted directly with food to meet sanitary requirements and is non-toxic after degradation. It dissolves into the environment after 12 weeks of degradation.

Of particular interest is the use of polylactic acid to make biodegradable plastics. The polylactic acid plant built by Cargill Road Polymers in the United States was put into production by the end of 2001 with an annual output of 140,000 tons. Japan's Mitsubishi Plastics, Zhongfang Synthetic Fibers, Uniqarka, and Kurarei have signed contracts with the US company to expand the application of polylactic acid in Japan. Mitsubishi Plastics Co., Ltd. is building an annual production capacity of 3,500 tons of degradable thin film manufacturing equipment, and will expand to 10,000 tons per year, and strive to become Japan's largest manufacturer of degradable plastics.

In China, biodegradable plastics have also been developed. It is understood that Harbin Weilida has signed a contract with German Wood Company to introduce PLA production technology and a polylactic acid production plant with a capacity of 10,000 tons. It is based on corn as a raw material, after the conversion of dextrose - fermentation - lactic acid - pre-polyester - a high-temperature catalytic cross-fat forming - distillation - polymerization - polylactic acid.

Polylactic acid can be used for disposable packaging (medical supplies, foods), agricultural films, garbage bags, etc. According to news, a few days ago, the Institute of Physical and Chemical Technology of the Chinese Academy of Sciences and the Yangzhou Hanjiang Jiaguan Polymer Material Factory held a signing ceremony for the cooperation of the PBS project, marking the world’s advanced level of green and new materials – after the fully degradable plastic project is put into production, China It will become the third country to achieve PBS industrialization after Japan and the United States.

PBS is also a fully degradable plastic that can be used to process foaming materials, household appliances, industrial packaging materials, etc. The material is buried in the soil for about 3 months, which means it can achieve 100% degradation and will not cause environmental pollution. The application of the product into production will solve the problem of white pollution caused by non-recyclable plastic products. The PBS project has been included in the National Eleventh Five-Year Plan and has been included in the national guidelines for medium and long-term science and technology planning. After the project is put into production, it can achieve an annual output of PBS 13,000 tons, and it is expected to reach production in the first quarter of 2006. It is estimated that the demand for degradable plastics in the country is about 1 million tons, and the development prospect of the degradable plastics market is very broad.

Author/Feng Shuming