Disposal and reuse of waste polystyrene plastics

1 Introduction

With the rapid development of the plastics industry, various plastic products are increasingly used in fields such as industry, agriculture, health care, and people's daily life. At present, the total output of plastics in the world has exceeded 100 million tons, and used plastics have become used. Rubbish, a serious environmental pollution, has become a public hazard. For example, Styrofoam is a kind of shock-proof material for all kinds of household appliances, precision instruments and other vulnerable items, resulting in a large amount of waste plastics each year. Styrofoam used in fast food supplies was disposed of in various places in the human environment and formed the well-known “white pollution”. The plastic film used in agriculture is dispersed in the soil and is not easily degraded, which seriously affects the quality of the soil and does not utilize the growth of crops.

2 Disposal and Utilization of Waste Plastics

After years of research, countries have made some progress in the development of waste plastics processing and utilization technologies. The following are some of the commonly used methods described below.

2.1 Incineration Technology

Incineration of waste plastics is a simple method of disposal, but secondary pollution can occur if it is not handled properly. Japan has developed a waste incinerator (continuous fluidized-bed incinerator) and it has begun operations, processing 5 tons of waste plastics daily.

2.2 Chemical regeneration technology

2.2.1 Manufacturing Various Fuel Oil Products

The technology developed by Fujifilm Recycling Company of Japan uses zeolite as a catalyst to catalytically crack waste polyolefin in a special reactor to obtain high-quality fuel oil, gasoline, kerosene, and diesel. And it has built a production unit with an annual processing capacity of 5000 tons. The technology developed by the Japan Institute of Physical Chemistry, through the addition of special composite catalysts and reaction promoters, enables the catalytic cracking reaction to be rapidly completed at a relatively low temperature to produce various fuel oils. A chemical plant in Beijing uses pyrolysis of waste plastics to produce gasoline and diesel. The annual treatment capacity is 3,000 tons, and 350 kg of gasoline and diesel can be produced per ton of waste plastic.

2.2.2 Manufacturing Chemical Raw Materials

After the waste polystyrene foam was purified, it was dissolved in ethyl acetate solvent, and the solution was filtered to remove impurities. Finally, the resulting solution was spray-dried. After drying, a powdered polystyrene resin is obtained while recycling the solvent for recycling. There are technical reports that styrene monomers can be prepared from waste polystyrene foam. The waste polystyrene was pulverized and air-dried to remove impurities to obtain small-particle raw materials. The liquid defoamer was used for defoaming and degassing the contents to reduce the volume of the particles, and then to enter the cracking furnace to perform the cracking reaction at 300°C or more. The pyrolysis product is a yellow-brown liquid and the main components are styrene monomer, polystyrene, toluene and ethylbenzene. Styrene monomer can be separated by distillation.

2.3 Reuse of Waste Plastics

Because thermoplastics have the characteristics of repetitive molding processes, all thermoplastic waste plastics can be recycled to prepare sandals, shoe soles, and buckets. The typical process flow is:

Sorting→Cleaning→Crushing→Kneading→Plasticizing and Granulating→Mold Processing

2.4 Manufacturing Engineering Plastics

Chengdu Silicone Research Center has developed a new technology for recycling waste polystyrene foam. This technology puts the waste polystyrene foam into the high-boiling gelling solvent, and then adds the toughening modified resin, pigment and various additives to mix. Finally, the desolventization process was used to make engineering plastics. Can be widely used in the production of electronic equipment, electrical components and enclosures, this method has been completed in Chengdu and Fuzhou industrial production facilities. It has been reported that a variety of modified resins such as waste polystyrene foam and phenolic resin are blended in the presence of a heat stabilizer, and the resulting product can replace the expensive ABS engineering plastic to manufacture the outer shell of industrial products.

2.5 The use of adhesives

2.5.1 PS self-adhesive

The waste polystyrene plastic is pulverized and dissolved in an organic solvent, and the plasticizer is added and mixed uniformly. Sizing on plastic film made of adhesive tape.

2.5.2 PS modified adhesive

The waste polystyrene plastic dissolved in a solvent into a homogeneous solution, and then added activator oxidized ketone, the initiator oxidized butyl benzoate, heated to 90 ~ 120 °C, adding modified monomers (acrylonitrile, allyl alcohol ), reaction in the reactor for 2h, so that polystyrene to connect new functional groups, thereby changing the nature, and then add fillers such as calcium silicate, will be a good water resistance, adhesive strength of the white viscous adhesive. Its water resistance is 10 times that of white latex, and its shear strength is more than 3 times that of white latex.

2.6 Utilization of Coatings

The waste polystyrene plastic, rosin, glycerin, zinc oxide dissolved in a solvent, obtained polystyrene modified resin, adding a variety of fillers are pigments, can be made into a variety of PS quick-drying paint by grinding and filtering, the product is dry Fast, stable performance, good chemical resistance, widely used for anti-corrosion of various facilities.

2.7 Utilization of Building Materials

2.7.1 waterproof caulking ointment

The waste polyvinyl chloride film, polyurethane resin, dioctyl phthalate, coal tar, and organic diluents are uniformly mixed, heated and polymerized, condensed into colloidal substances, and then light calcium carbonate and silica fume flour are added and mixed. After the paste is ready to paste paste. The product can be used for the waterproofing of waterproofing projects such as roofing, underground engineering, etc. It can also be used as building caulking material. Its excellent performance, in line with construction requirements.

2.7.2 Manufacturing of Building Materials

American AFCO Company took the lead in the development and production of plastic "wood." The method is to pulverize various waste plastics into a molten state, and then extrusion molding, to produce various shapes of plastic "wood", its products can use saws, nails, drills and other processing methods, excellent corrosion resistance. Wuhan University of Technology developed and developed a new technology that converts almost completely used polystyrene foam into new foam products. This technology activates waste polystyrene foam and molds it into various boards. According to reports, the waste polystyrene plastic is crushed into particles of 5 mm or less, and used as a filler and a mixture of cement to make a lightweight building block. In addition, a layer of polystyrene pellets is added between the two layers of the composite board to make a heat insulation material.

3 Conclusion

The disposal and use of waste plastics is extremely beneficial to environmental protection and resource utilization. Many countries have developed technologically feasible production processes. The only problem that needs to be addressed is reducing costs. The collection, classification, separation and screening costs of waste plastics in production account for a considerable proportion, and separation technologies should be actively developed. At the same time, corresponding laws and regulations should be formulated to promote the discarding of waste plastics and provide favorable conditions for reducing production costs. Related Science and Technology Work The people are also studying some new methods. Such as the United States innovative plastic products company will be mixed waste plastics without direct processing into industrial plastic products. In short, the disposal and utilization of waste plastics must be technically feasible and economically reasonable in order to create good social and economic benefits.