Flexible foam wastes

In [74], a method of reclaiming of PUR flexible foam waste by grinding of foam scraps and heating in the presence of mono- and diethanolamine at a temperature of 130-150°C is described. The reaction process was considerably faster when monoethanolamine was used at elevated temperature. After the completion of the process, the degradation product underwent separation into... 

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. 

As much as a quarter of a flexible foam block can be wasted in downstream processing into flnished products. Thanks to the efforts of process technologists and engineers, this scrap material can be recycled by at least 17 basic methods. However, only a few have found significant practical applications. Most other PU scrap ends up as uncollectable domestic waste with perhaps one key exception, materials from end-of-life vehicles. WESTERN EUROPE-GENERAL Accession no. 709465... 

A split phase glycolysis process for the recovery of polyols from PU foam waste is described. Applications of the polyols in the manufacture of flexible and rigid PU foams are examined, and the economics of the process are analysed. 2 refs. 

In the area of flexible foams the regrinding of foam wastes and their incorporation into new foams is the current way of recycling [2], Rebounding process linking of cut PU foams wastes by an adhesive, to obtain new PU foam materials into high quality carpet underlay is another process without the chemical destruction of the PU polymer [3, 4, 5]. 

Chemical recovery processes by PU polymer breakdown through hydrolysis, glycolysis and aminolysis processes are extremely important because by using chemical reactions, the PU wastes are chemically transformed into new products which can possibly be used in the fabrication process of new PU. PU wastes are important raw materials for new polyols destined to become rigid and flexible foams. 

Chemical Recovery of Flexible PU Foam Wastes by Hydrolysis [12-24, 27]... 

The reaction product is the polyether polyol and the diamine, with DEG as solvent. The extraction of polyol with hexadecane and its evaporation lead to a high quality polyether polyol which could replace up to 50% virgin polyether polyol [12, 16, 34]. The polyol resulting from the hydrolysis of flexible foams is practically identical to the initial polyol which was used to make the original material of the PU foam waste. Because in the hydrolysis process new types of polyols do not appear, this type of technology is not described. 

A two-stage method of waste polyurethane degradation is described in [79]. In the first stage, scission of the polyurethane chain takes place at a temperature of 120°C in the presence of dialkanolamine and metal hydroxide e.g., KOH). Under these conditions, the reaction products include polyols, aromatic amines, short-chain ureas, and urea derivatives. The second stage is based on the alcox-ylation of the hydroxyl groups and the primary and secondary amine groups, e.g., by the use of propylene oxide. In this way, polyols with a hydroxyl number of 156-271 mg KOH/g and viscosity within the range of 1950-57 000 mPa s can be obtained. The flexible foams prepared from recycled polyols revealed favorable mechanical properties. 

A detailed examination of the advantages and disadvantages of polymer recycling by considering several life cycle analysis case studies is given in [82]. Here, a short description of the relevant life cycle analysis of flexible polyurethane foam wastes is presented, with emphasis on the relation between the start and the end of the product s life, i.e., including process and product design. 

Polyurethane materials are extremely versatile in that it is possible to produce a large variety of structures which range in properties from linear and flexible to crosslinked and rigid. The crosslinked PURs are thermosets, which are insoluble and infusible and therefore cannot be reprocessed by extrusion without suffering extensive thermal degradation. At present, the main sources of recyclable waste are flexible PUR foams and automobile waste. Waste and scraps of these materials may consist of 15-25% by weight of total PUR foam production. 

Glycolysis of flexible PU foams is also possible. At a ratio of PU waste DEG of 1-1.5 1, two layers are formed (the superior layer being rich in polyether), but at a higher ratio of 2-4 1 a homogeneous polyol mixture results, with an hydroxyl number of 360-390 mg KOH/g, which was used successfully in rigid PU foam fabrication [35]. 

There is no single method for treating polymethane (PUR) waste, due to the different quantities, qualities, mixes, and cleanliness. It is estimated that some 125,000 t of RIM polyurethane is used worldwide, 85% in automotive parts, mainly in bumper fascias. Current technologies for physical recycling of PURs are mainly directed towards flexible and rigid foams, but systems have also been developed for recycling reinforced reaction injection molded (RRIM) PURs, on the... 

For low density, flexible high resilient and rigid PU foam post-consumer wastes, a modified solid state shear extrusion (SSSE) technique was applied for their pulverisation. The fine powder obtained can be nsed as a filler and/or reinforcing material for polymers and mineral products with improved mechanical properties [257]. 

The use of PMDI as a binder for foimdry cores, rubber waste products, and solid rocket fuel are also known. Isocyanate-terminated prepolymers, often prepared from TDI or MDI with polyether polyols are also used as binders for composite products that require elastomeric properties. Athletic surfaces are sometimes prepared from groimd rubber tire scrap bonded with isocyanate-based prepolymers. Similarly, flexible polyurethane foam scrap is bonded with isocyanate prepolymers to form rebonded foam usefiil as carpet imderlay. Solidification of incineration ashes with PMDI-based binder systems is another waste disposal application. In this manner hazardous waste materials imdergo chemical fixation and detoxification. 

Wastes of cellular, flexible and elastomeric PUR were treated with diethanolamine at 140-190°C to give polyols having diethanolamino groups for use in the manufacture of rigid PUR foams [21]. 

ABS is a copolymer in which a rubbery polybutadiene phase is dispersed in a rigid but brittle styrene-acrylonitrile (SAN) phase. The presence of rubber particles imparts flexibility and impact strength to the material even at low temperatures. Due to its excellent strength, ABS pipes are also available whose pipe walls are made of foamed core rather than being solid walls, which decreases weight without compromising physical properties. The major use of ABS pipes is in drain, waste, and vent (DWV) applications. 

Wu C-H, Chang C-Y, Cheng C-M and Huang H-C (2003) Glycolysis of waste flexible polyurethane foam, Polym Degrad Stabil 80 103-111. 

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