Thermoset soft foam and elastomer have certain thermal softening plasticity at 100-220 ℃, which can achieve mutual bonding without using adhesive. Combined with the subsequent molding steps, uniform recycled products can be obtained, which is hot pressing. Bayer (now Covestro) has developed a recycling process for waste elastomer products. The waste is crushed into particles for preheating, and then molded with a pressure of more than 35MPa in a press at 180-185 ℃. This process can make 100% use of waste materials without using additives such as adhesives. Recycled products can be applied to components such as automobile battery shells, protective covers and covers.
The polyurethane soft foam can obtain fine particles through low-temperature crushing or grinding process. The dispersion of such particles can be added to polyols, which can be used to manufacture polyurethane foam or other products, effectively reducing production costs. By using the method of filling, the waste elastomer is broken into powder, which can be mixed into raw materials to make new elastomer. Japanese manufacturers use waste hard foam as lightweight aggregate for mortar.
Alcoholysis, aminolysis, hydrolysis and pyrolysis are the most commonly used chemical recovery methods for polyurethane. The polyurethane foam is decomposed into polyurethane raw materials or other chemical raw materials to realize transformation and reuse. For example, the most common method of alcoholysis is the alcoholysis of polyurethane foam, elastomer, etc. at a temperature of about 200 ℃ under the joint reaction of small molecule diols (ethylene glycol, propylene glycol, diethylene glycol, etc.) and catalysts. After several hours of reaction, regenerated polyols can be obtained, and then mixed with fresh polyols for manufacturing polyurethane materials. Another example is the amine hydrolysis recovery process once launched by Dow, which uses alkyl alcohol amine and catalyst to decompose waste polyurethane into high concentration dispersion, and then carries out alkylation reaction. After the aromatic amine in the product is taken out, a polyol with good performance and light color can be obtained. It is reported that this kind of recycling method has been reported by many examples.
In addition to the above-mentioned physical and chemical treatment methods, there are landfill treatment and biodegradable polyurethane. In view of the fact that some foams cannot be recycled, landfill treatment is adopted. In order to make them decompose faster under natural conditions and reduce environmental pressure, people have begun to develop biodegradable polyurethane. For example, cellulose, lignin or polycaprolactone and other biodegradable compounds are introduced into polyurethane molecules to fundamentally alleviate the problem of their difficult degradation.
It can be seen that polyurethane waste can be recycled by appropriate recycling methods to reduce environmental pollution and production costs. It is believed that more advanced polyurethane recycling methods will appear in the near future to achieve sustainable development in a real sense.
