Polyurethanes glycolysis

A variety of processes for polyurethane degradation by reaction with different glycols has been described in the literature during the last 30 years.76-83 Polyurethane glycolysis is usually carried out with an excess of glycols at temperatures around 200 °C and in many cases working at atmospheric pressure. After several hours of reaction, the polyurethane is completely liquefied and depolymerized, and catalysts are not necessary. 

Polyurethane chemolysis can be performed by processes similar to those applied to PET. Thus, polyurethane glycolysis yields a mixture of polyols, which can be reused in the formulation of new polyurethanes. Likewise, polyurethane hydrolysis leads to the formation of polyols, diamines and carbon dioxide. The diamine can be subsequently transformed into the corresponding isocyanate by reaction with phosgene, whereas the polymer-... 

Glycolysis is the most promising approach for the chemical recycling of polyurethanes.1 The chemistry of PUR depolymerization is complicated by the presence of other chemical groups in the polymer, such as ureas, allophanates, and biurets. 

The glycolysis of rigid polyurethane foams produces polyol products which can be reintroduced into the production cycle of PUR insulation materials to form materials with properties practically equivalent to dtose of materials produced using virgin polyols. Aromatic amines produced as by-products in die glycolysis process are toxic and therefore undesired side products. The most frequently observed side product is diphenylmedianediamine (DMDA), which is formed... 

Example 5. Glycolysis to Yield Polyols Used to Synthesize Polyurethanes.63 A... 

Example 4. Glycolysis of Polyurethanes with Propylene Oxide after Pretreatment with a Mixture of Diethanolamine and Potassium Hydroxide.57 Polyurethane scrap was treated with a mixture of diethanolamine and potassium hydroxide at a temperature between about 80 and 140° C with stirring to form an intermediate product. The weight ratio of the scrap PUR polymer to the mixture of diethanolamine and potassium hydroxide was from about 15 1 to 30 1. The intermediate product was reacted with propylene oxide at a temperature of from about 100 to 120°C in a closed reaction vessel to form a polyol. The propylene oxide was added at a rate to maintain a pressure of from about 2 to 5 atm (29-73 psi). The progress of the reaction was followed by following the change of pressure with time. When the pressure remained constant, the reaction of the intermediate product with propylene oxide was considered to be complete. The crude polyol obtained was treated with 10 mol % excess of dodecylbenzene sulfonic acid to remove the potassium hydroxide. 

Example 5. Glycolysis of Polyurethanes with Propylene Oxide after Pretreatment with Ethanolamine.55 A rigid polyurethane foam (ca. 100 g) was dissolved in 30 g ethanolamine by heating. Excess ethanolamine was stripped, leaving a clear solution. Infrared and GPC analysis indicated that the clear solution obtained contained some residual polyurethane, aromatic polyurea, aliphatic polyols, aromatic amines, and N,N -bis(f -hydroxyethyljurea. Next the mixture was dissolved in 45 g propylene oxide and heated at 120°C in an autoclave for 2 h. The pressure increased to 40 psi and then fell to 30 psi at the end of the 2-h heating period. The product was a brown oil with a hydroxyl number of485. 

Propylene glycol, glycolysis of polyurethanes with, 572 Propylene oxide (PO), glycolysis of polyurethanes with, 572-573 Propylene oxide (PO) polyols, 211, 223 Proton exchange membrane fuel cells (PEMFCs), 272-273 Proton NMR integrations, 386. See also H NMR spectroscopy Protonic acids, reactions catalyzed by, 67-68... 

Journal of Applied Polymer Science 11, No. 12, 19th Sept. 2000, p.2646-56 DESAMINATED GLYCOLYSIS OF WATER-BLOWN RIGID POLYURETHANE FOAMS... 

The recycling of contaminated polyurethane waste is described with reference to a glycolysis process developed by Bayer and Daimler-Benz in which the wastes from three-layer composite instrument panels are treated. The reuse of contaminated PU is achieved by dispersely integrating the impurities in the secondary polyol during the glycolytic dissociation. The impurities are modified in such a way that they act as a filler in the secondary polyol. 3 refs. 

ICI Polyurethanes and du Vergier are evaluating a PU recycling method. The three-year project aims to use a pilot plant to demonstrate the practicality of the split-phase glycolysis process that ICI has developed. Work will initially focus on flexible foams based on MDI and specially made at Id s Rozenberg plant. In the second phase, the unit will use post-industrial waste. Assuming the trials are successful, a full-scale unit to handle at least 5000 t/y of scrap foam will be built. 

Glycolysis of PETP leads to oligomers that are polycondensed with eaprolaetone. The obtained diols are extended with hexamethylene diisoeyanate. In eertain conditions the polyurethanes are totally miseible with PVC, leading to acceptable meehanieal eharaeteristies for the blend. A relation between the strueture of the polyurethane and miscibility with PVC is described. The mechanical characteristics of the blend depends on the polyurethane chemical structure. 34 refs. 

Recycling. The methods proposed for the recycling of polyurethanes include pyrolysis, hydrolysis, and glycolysis. Regrind from polyurethane RIM elastomers is used as filler in some RIM as well as compression molding applications. The RIM chips are also used in combination with rubber chips in the construction of athletic fields, tennis courts, and pavement of working roads of golf courses. 

Three methods of recycling of polyurethane foam have been proposed hydrolysis, pyrolysis and glycolysis. 

Plastics with a carbonyl group can be converted to monomers by hydrolysis or glycolysis. Condensation polymers such as polyesters and nylons can be depolymerized to form monomers. For Polyurethanes (PURs), what is obtained is not the initial monomer, but a reaction product of the monomer diamine, which can be converted to diisocyanate. For PURs. hydrolysis is attractive as they can be easily broken down to polyols and diamines. The only issue is to separate them later. Steam-assisted hydrolysis has been shown to yield 60 to 80 percent recovery of polyols from PUR foam products. A twin screw extruder can be used as a reactor for hydrolysis. Glycolysis of PURS, yields mixture of polyols that can be reused directly. 

Polyurethane-immobilized LOD is being used for whole blood lactate determination in the Glukometer as well as in the ECA 20 (ESAT 6660). Dilution of the samples with the buffer described in Section 5.2.3.1 provides both complete inhibition of glycolysis and immediate hemolysis. As is shown by the correlation equations the method is quite reliable ... 

In addition to the possible reuse of BHET in the preparation of fresh PET polymer, two other processes have been proposed starting from the PET glycolysis products preparation of unsaturated polyesters20-27 and synthesis of polyester polyols.28-32 The latter can be used in the formulation of polyurethanes and polyisocyanurate foams26-30 (see Figure 2.1). 

A wide range of chemical agents, catalysts and conditions for the glycolysis of unsaturated polyester resins, used in the manufacture of buttons, have been described in a recent patent.34 In addition to different metal acetates, the following compounds have been proposed to be catalytically active in PET glycolysis sodium methylate, sodium ethylate, sodium hydroxide, methane-sulfonic acid, magnesium oxide, barium oxide and calcium oxide. Different applications of the depolymerization products were described, e.g., preparation of fresh unsaturated polyesters by reaction with maleic acid, maleic acid/ phthalic anhydride or maleic anhydride/terephthalic acid or the synthesis of polyurethane resins by reaction with a diisocyanate. 

The most important chemolysis methods so far developed to reverse the polyurethane polymerization reaction shown in Scheme 2.2 are glycolysis and hydrolysis. These processes are reviewed next, together with other less widely investigated treatments. 

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