Rigid polyurethane foam is widely used as insulation material for refrigerators due to its availability, ease of use and good thermal insulation. The insulation in refrigerators accounts for about 10% of the total weight of refrigerators. At present, the amount of refrigerator scrap is amazing. The speed of the rigid polyurethane foam is mainly for 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 the recovery of waste rigid polyurethane foam: combustion recovery heat method, physical recovery method, chemical recovery method.
Combustion recovery heat method
Polyurethane can generate a lot of heat when it is burned, so it is often used as fuel for incineration with municipal solid waste.
However, if the polyurethane is incompletely burned during the incineration process, it will produce toxic gas. It will cause 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. Fast.
TCL Aobo (Tianjin) Environmental Protection Development Co., Ltd. uses the combustion recovery heat method to dispose of the refrigerator polyurethane insulation materials dismantled by the company. They have adopted the international advanced level of mechanization, automated production process equipment, and established RDF (Garbage Derived Fuel). In the production line, the polyurethane obtained by disassembling the refrigerator is made into RDF granules that meet environmental protection requirements, and then incinerated. The direct recycling and reuse of these materials and the harmless treatment of harmful substances are solved. Improper environmental impact.
Schematic diagram of refrigerator dismantling and recycling of TCL Aobo (Tianjin) Company
Physical recycling
The physical recovery method of polyurethane refers to the method of directly utilizing the physical form of waste materials without destroying the chemical structure of the polymer itself, without changing its basic composition. There are crushing addition method, bonding processing method, extrusion molding. And other methods.
Crushing addition
Polyurethane trim and old waste are first cut or pulverized before application, and sieved to obtain fine powder of the required particle size. Generally speaking, hard polyurethane foam is easier to pulverize, and its crushing technology is also mature as follows: Precision cutting technology, Flachmatritsen extrusion Wait.
The fine pieces or powders of the waste polyurethane are pulverized as fillers and mixed 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 recycling and dismantling center and sent it to the company's most advanced polyurethane insulation board production line (German import) 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, 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 are not significantly weakened. .
Polyurethane for used refrigerators can also be added as a filler to polyurethane raw materials for the production of RIM (reaction injection molding) products, making energy absorbing foam and sound insulation foam.
Waste refrigerator polyurethane materials are also often used as fillers in building materials. For example: Cement, sand, water and waste rigid polyurethane foam powder are mixed on the bottom layer of the roof to be used as a thermal insulation layer for the roof, which has excellent thermal insulation properties and quality. Light, 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 used in refrigerators and the like is a single polyurethane, and its recycling is relatively easy.
Polyphenyl polymethylene polyisocyanate is usually 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. , prefabricated into a loose mat, placed in a mold coated with a mold release agent, pressed under high pressure and heat into a foam particle board or workpiece.
Due to the excellent water resistance of rigid polyurethane waste particle board, it is often used to make furniture used on board. In addition, polyurethane particle board has good resilience and is widely used as a gymnasium, polyurethane suspension floor.
Chemical recovery
Since the polymerization of polyurethane is reversible, the polyurethane can be depolymerized under certain reaction conditions to produce monomers.
There are 6 kinds of methods for depolymerization of polyurethane. There are 6 kinds of chemical recovery technologies: alcoholysis, hydrolysis, alkali hydrolysis, ammoniation, pyrolysis, hydrocracking. The monomer products recovered by depolymerization can be directly used. New product production.
However, the current industrial technology of chemical recovery is still not mature, the separation and purification of degradation products is difficult, and it will produce uncontrollable by-products.
Guangzhou Jutian Chemical Technology Co., Ltd. has been committed to the recycling of waste polyurethane. Based on waste polyurethane as the basic raw material, the company has obtained the low-cost renewable multi-products with similar properties of ordinary polyester and polyether polyols. Alcohol and other polyurethane products, the realization of raw material - product - recycling - raw material closed-loop recycling solutions have been successful.