Rigid polyurethane foam is widely used as the insulation material of refrigerators because of its availability, ease of use and good thermal insulation. The insulation material in refrigerators accounts for about 10% of the total weight of refrigerators. At present, the amount of refrigerator scrap is increasing at an alarming rate, but the handling and disposal methods of rigid polyurethane foam are mainly stacking, landfilling and incineration, resulting in land waste and air pollution, so the need for resource recycling is particularly urgent. .
In general, there are three main methods for recovering waste rigid polyurethane foam: combustion recovery heat method, physical recovery method, and chemical recovery method.
Combustion recovery heat method
Polyurethane can generate a large amount of heat when it is burned, so it is often used as a fuel for incineration with municipal solid waste.
However, if the polyurethane is incompletely burned during the incineration process, it will produce toxic gases. create pollution. If the corresponding technology is used to improve the combustion efficiency and the tail gas treatment is done well, the advantages of this treatment method are also very significant, and the treatment is quicker.
TCL Aobo (Tianjin) Environmental Protection Development Co., Ltd. uses the combustion recovery heat method to treat the refrigerator polyurethane insulation material disassembled by the company. They adopted the internationally advanced mechanized and automated production process equipment, established the RDF (garbage-derived fuel) production line, and made the polyurethane obtained by disassembling the refrigerator into RDF granules that meet environmental protection requirements, and then incinerated it. The direct recycling and reuse of these materials, the harmful treatment of harmful substances, to solve the environmental impact of improper home appliance disassembly.
Schematic diagram of refrigerator dismantling and recycling of TCL Aobo (Tianjin) Company
Physical recycling
The physical recovery method of polyurethane refers to a method directly used after changing the physical form of the waste material without destroying the chemical structure of the polymer itself without changing its basic composition. There are methods such as pulverization addition, bonding processing, and extrusion molding.
Crushing addition
Polyurethane trim and old waste are first cut or pulverized and sieved to obtain a fine powder of the desired particle size before application. Generally speaking, rigid polyurethane foam is easier to pulverize, and its pulverization technology is also relatively mature, such as precision cutting technology, Flachmatritsen extrusion.
The fine pieces or powders after the pulverization of the waste polyurethane are often mixed as a filler into raw materials or other materials for recycling.
Anhui Xingang Furnace Co., Ltd. crushed a large amount of rigid polyurethane recovered from its own waste household appliance recycling and dismantling center and sent it to the company's most advanced polyurethane insulation board production line (Germany imported) to recycle it and achieved good results.
It is reported in the literature that if the obtained waste polyurethane powder is added to the raw material for producing the original part, the same part is produced again, and since the powder has the same structure as the raw material, the amount can be up to 20%. The mechanical properties of the final product were not significantly impaired.
Polyurethanes for used refrigerators can also be added as fillers to polyurethane raw materials for the production of RIM (Reactive Injection Molding) products, making energy absorbing foams and sound insulating foams.
Waste refrigerator polyurethane materials are also often used as fillers in building materials. For example, the cement, sand, water and waste rigid polyurethane foam powder are mixed on the bottom layer of the roof to be used as the thermal insulation layer of the roof. The heat insulation performance is excellent and the quality is light, which is deeply loved by the construction industry.
Japan also has lightweight aggregate products that use waste rigid polyurethane foam as a mortar.
Adhesive compression molding
The rigid polyurethane foam waste material for refrigerators and the like is a single polyurethane, and its recycling is relatively easy.
Polyphenyl polymethylene polyisocyanate is commonly used as an adhesive. The adhesive is evenly dispersed between the waste foam chips, the amount of the adhesive is about 5%~10% of the mass of the waste material, and after being uniformly mixed, the loose mat is pre-formed and placed in the mold coated with the release agent. Medium, foamed particle board or workpiece under high pressure and heat.
Since the rigid polyurethane waste particle board is excellent in water resistance, it is commonly used to make furniture for use on ships. In addition, polyurethane particle board has good resilience and is widely used as a stadium floor and polyurethane suspension floor.
Chemical recovery
Since the polymerization of polyurethane is reversible, it is possible to depolymerize the polyurethane under certain reaction conditions to produce a monomer.
There are six methods for depolymerizing polyurethane. There are six kinds of chemical recovery technologies: alcoholysis, hydrolysis, alkalilysis, ammoniation, pyrolysis, and hydrocracking. The monomer product recovered by the depolymerization method can be directly used in new product production.
However, the current industrial technology of chemical recovery is still immature, and the separation and purification of degradation products are difficult, and uncontrollable by-products are produced.
Guangzhou Jutian Chemical Technology Co., Ltd. has been committed to the recycling of waste polyurethane, using waste polyurethane as the basic raw material, using the technical solutions of independent intellectual property rights to obtain low-cost renewable multi-components with similar properties to ordinary polyester and polyether polyols. Alcohol and other polyurethane products have achieved success in the closed-loop recycling of raw material-product-recycling-feedstocks.
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