Chemical recovery of flexible polyurethane foam wastes

Abstract

The development of a chemical process for the recovery of polyols from flexible polyurethane foam wastes with enough quality to be reutilized in foaming has been a major challenge for scientists during recent years. In that way the objective of chemical recycling of PU wastes is the recovery of its major constituent, the polyol, in an environmental friendly way that is performed with the lowest cost and without hazardous residues production. The glycolysis of PU wastes in the presence of a large excess of glycolitic agent allows one to obtain a polyol rich upper phase and a bottom phase containing mainly glycol and isocyanate derivatives. Different metal octoates derived from cycloaliphatic carboxylic acids can be used as the catalyst with suitable catalytic activity. The optimization of process conditions has demonstrated that there is a narrow window of process conditions (relation between phases, temperature, catalyst, etc) in which the split phase glycolysis can be carried out. The recovered polyols have to be subjected to purification by aqueous liquid-liquid extraction before refoaming in a conventional formulation mixed with fresh ones in a large range of proportions. The excess of glycolyzing agent in the bottom phase has to be returned to the cycle by vacuum distillation. The vacuum residue containing the isocyanate derivatives can be applied as an initiator in the synthesis of rigid polyols, allowing the complete use of the glycolyzates from PU recycling.

Simple process for separation and recycling of nylon 6 and polyurethane components from waste nylon 6/polyurethane debris

“…Clearly, the dissolving efficiency of PU in all tests is randomly distributed on both sides of the averaged value line (mid-value ¼ 42%). The result shows that the solubility of PU in DMF changes very little with the changing of dissolution time and temperature, which is somewhat different to that of the previous reported optimum operation condition of 70 C and 4 h. 14 So, it is necessary to investigate the effect of shorter dissolution time on the solubility of the PU component in DMF. Surprisingly, the result implies that, at 100 C, the solubility of PU remains stable even when the dissolution time decreases to less than 20 min, as shown in Figure 1(b).…”

“…In the past decades, many researchers devoted themselves to the recovery of waste PU [13][14][15] or PA6 fabrics. 16,17 Recently, a method was introduced to selectively separate and recycle PU components by heat treatment; 18 however, washing pyrolyzed PU with ethanol fails to fully recover the PU waste and brings environmental pollution.…”

Methods of Responsibly Managing End-of-Life Foams and Plastics Containing Flame Retardants: Part II

“…Reactions with 1,2-propanediol produced polyols and amines (Feng et al, 2004). Other results using ground rigid PUR foams reacting with diols >200°C showed efficient production of recycled polyols comparable to virgin polyols (Molero et al, 2010;Aguado et al, 2011).…”

Chemical Recycling of Flexible Polyurethane Foams to Recover High Quality Polyols

“…Existing methods of chemical recycling of PUF waste suffer from incomplete degradation of urethane groups and lack of selectivity for degradation of urethane bonds alone, as urea bonds in PUF hard segments also degrade, resulting in differently functionalized polyols containing various side products 23 . For this reason, RPs are used only as partial replacements of VPs in formulations for the production of new exible PUFs 23,35 . The aim of our work was to develop a cost-and energy-e cient recycling process for exible PUFs distinguished by a high DD urethane in order to produce RPs that are close equivalent to VPs in terms of functionality, molar mass, and purity since only in this way RPs are suitable for re-polymerization into exible PUFs of the same quality and performance as those produced from VPs.…”

“…Currently, split-phase glycolysis is considered to be the most e cient PUF recycling method 23,35 . Since both glycolysis and thermal degradation of urethane groups are reversible reactions, a large excess of glycol reagent per urethane group is required to shift the equilibrium toward the desired product formation.…”