Polyurethane recycling technology gradually attracts attention

According to the European Association of Isocyanate Production (ISOPA), the recycling of polyurethanes has become increasingly important, especially in the European region, where the disposal of waste has become less and less, and waste disposal costs have also risen wildly. . As the government has increased the “closed-loop” production requirements for the production cycle of polyurethane products, many innovative recycling technologies have emerged in the past two decades, and many of these technologies have now been commercialized.
What kind of special recycling process is suitable for a particular product depends on the material itself. At the same time, it must also consider a series of economic and environmental issues. For example, if PUR ingredients are burned together with a large amount of other fertilizers, the desired effect cannot be achieved. However, if the pure PUR is only burned, the waste can be regenerated by melting into a new PUR material.
Impact of Standard Regulations
The European Union is currently implementing very stringent new standards for the regeneration of packaging, automotive parts, electrical and electronic materials, and energy recovery. These new standards undoubtedly have a great impact on general plastics, especially polyurethane. In addition, in the near future, many countries in the European center will stop using landfills to dispose of their rubbish.
Although in North America, the regulations on recycling are relatively less stringent, more and more manufacturers and people using plastics are voluntarily and automatically developing renewable projects. Their goal is to reduce the government's mandatory directives. Several business groups, such as the American Polyurethane Industry Association (API) and the European Union's Isocyanate Production Committee (ISOPA), have actively launched the PUR recycling technology and recycling concept.
Materials and Method
Typical recyclable PUR materials come from fast-moving consumer products such as everyday items, cars, mattresses, carpet underlays and backings, and upholstered sofas. Fragmentation in industrial processes is also another major source of PUR recycled materials.
According to the Polyurethane Recycling and Recycling Committee (PURRC), PUR accounts for about 5% of all waste plastics. At the same time, the range of products that can be recycled is also relatively wide. Especially PUR carpet liners are highly recyclable. In 2002, 98% of U.S. manufacturers using PUR materials to produce carpet liners used PUR foam chips. Of the debris used, about 6% came from fast-moving products.
PUR carpet backing and cushioning (Source: Bayer MaterialScience)
Although traffic is also a major application area of ​​PUR, there is still relatively little research on the recovery of PUR materials for transportation. Because the cost of separating PUR from auto parts or components is relatively high. However, car manufacturers around the world have begun designing PUR seat cushions that are easy to recycle and regenerate. Reaction injection molding can produce recycled parts into automotive parts, such as bumper shells and protective panels. This method has been applied in many fields such as automotive and non-automotive fields.
The methods used in the regeneration process of PUR products are all energy regeneration, such as: sintering, and then use the heat generated in the sintering process to generate electricity. Another good strategy is to use a mechanical recycling process, such as grinding the PUR, reusing the PUR material, and filling it in the preformed PUR product. The third method is the chemical recovery method, which breaks the PUR molecular chain and returns it to the monomer state, and then re-polymerizes these monomers into a new PUR product.
Energy regeneration
When PUR is used as a waste product, such as solid waste in cities or major components in a variety of fast-moving consumer goods produced from various flammable materials, then sintering to obtain heat energy is the most commonly used. One of the recycling methods. As a fuel, PUR can provide the same amount of energy as coal provides. After sintering, the volume of PUR will be reduced by 1% of the initial volume, thus reducing the floor space occupied by the waste after sintering.
Polyurethane Heat Content (Source: European Isocyanate Production Association ISOPA)
Mechanical recycling
The PUR waste is ground into a powder, and then these powders are reused and recycled by various mechanical recycling methods. The waste products in this recycling method mainly come from the factory's scraps and scraps and fast-moving goods. It has been seen that ground PUR powders can be used as fillers in PUR foams or elastomers. When used as a filler, milled powders are usually first added to the polyol process. For molded PUR products, such as car seat backs, the PUR powder content can reach 20% without affecting any appearance or performance conditions.
Grinding process (source: ISOPA)
Mechanical recycling of PUR into powder is a process that uses a variety of grinding equipment and cutting. As a filler, the size of PUR particles must be less than 200 microns, and preferably less than 100 microns.
PUR foam fragments can be reconnected by the action of heat, pressure, and adhesives. Reconnecting usually produces a lot of noise. Similar to the re-bonding process is pressure bonding, PUR particles can be coated and cured with the cross-linking agent under heat and pressure conditions. The same height of the product is mainly controlled by the pressure at the time of cross-linking. These products include car floors and tire covers.
The connection between bubbles (source: ISOPA)
RIM and reinforced RIM parts can also be made into a variety of small particles that can form solid parts for the automotive industry under high pressure and heat conditions. These hot-pressed solid parts contain up to 100% of RIM recyclate.
Recycling refrigerator panel (Source: Bayer Material Science)
Chemical recovery
Destruction of PUR molecular chains to form small molecules, also known as chemical analysis, is one of the most important methods in PUR recovery. The properties of PUR products made from recycled monomers are generally similar to those of products made from pure PUR monomers. According to PURRC, chemical analysis methods can extract 90% of polyhydroxy compounds from semi-rigid foams. The amount of this recovered monomer used for production can account for 30% of the formulation. PURRC said that rigid foam can also receive the same effect.
There are several important processes in chemical recycling:
Hydrolysis, PUR waste can be hydrolyzed under heat and pressure to produce polyester polyols and diamines that can be separated, purified, and reused.
Degradation of bio-alcohol, under this condition, PUR foam is reacted at high temperature (above 200°C) and catalyst in glycol. High molecular weight polyurethane chains and many other branches all form low molecular weight polyols and other liquid products in this process. After purification, polyols can be used to produce a variety of different products such as rigid foams, flexible foams, and shoe soles. Genduo's degradation of bio-alcoholic hydrolysis has been applied in many European countries.
Ammonolysis, the recycling of PUR foam under heat and pressure and ammonia conditions. However, this recycling method is still in the research stage.

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