Introduction of polyurethane rigid foam machinery with excellent performance (2)

　　1 used as filler

　　Waste rigid polyurethane foam plastic powder is often used as a filler for polyurethane building materials, such as the roof insulation layer. Mix cement, sand, water and waste rigid polyurethane foam powder on the bottom layer of the roof. The material has excellent thermal insulation properties. Lightweight (almost 1/2 of the density of the cement layer without waste rigid polyurethane foam), and the material can be nailed. In addition, according to the US-China Chemical Company, waste polyurethane can be used as a filler to produce RIM (reaction injection molding) products, energy-absorbing foams and sound-proof foams. The literature reports that if the obtained waste polyurethane powder is added to the raw material for the production of the original part, and the same part is produced again, because the powder has the same structure as the raw material, the amount can reach 20%, and the mechanical properties of the final product are not obvious. weaken. In Japan, waste rigid polyurethane foam has been used as a lightweight aggregate for mortar.

　　2　Extrusion molding

　　Extrusion molding is to transform the molecular chain into a medium-length chain through thermodynamics, and transform the PU material into a soft plastic material. This material is suitable for plastic parts with high strength and high hardness, but low elongation at break. For soft microporous PU foam waste, it can be pulverized into powder, blended into thermoplastic polyurethane, pelletized in an extrusion molding machine, and injection molding is used to manufacture shoe soles and other products. The German Bayer company has done this. Research.

　　3 　Recycling of chemical methods

　　Since the polymerization reaction of polyurethane is reversible, controlling certain reaction conditions, the polymerization reaction can proceed in the reverse direction, and will be gradually depolymerized into the original reactant or other substances, and then through distillation and other equipment, a pure raw material monomer can be obtained. Alcohol, isocyanate, amine, etc. Using chemical methods to treat waste polyurethane materials, recycling polyols, etc. as raw materials to prepare polyurethane again, has many sets of devices put into trial operation, which is one of the main directions of current efforts to recycle waste polyurethane.

　　There are six types of chemical recovery technologies: alcoholysis, hydrolysis, alkaline hydrolysis, ammonolysis, pyrolysis, and hydrocracking. The decomposition products produced by various methods are different. The alcoholysis method generally generates a mixture of polyols; the hydrolysis method generates polyols and polyamines; the alkaline hydrolysis method generates amines, alcohols and corresponding alkali carbonates; the ammonolysis method generates polyols, amines, and ureas; the pyrolysis method generates a mixture of gaseous and liquid fractions; The main products of the hydrocracking process are oil and gas.

　　In the 1970s, it was discovered that using hot water vapor under a certain pressure can degrade PU soft foam into diamine and polyether polyol. Direct hydrolysis is the use of steam to hydrolyze polyurethane waste or a mixture of water and glycol as a mixed hydrolysis agent to recover diamine and polyol. The composition of the hydrolyzed product is complex and difficult to separate and alcoholize, so I will not repeat it here.