Aromatic polyester polyols

Polyester Polyols. Initially polyester polyols were the preferred raw materials for polyurethanes, but in the 1990s the less expensive polyether polyols dominate the polyurethane market. Inexpensive aromatic polyester polyols have been introduced for rigid foam appHcations. These are obtained from residues of terephthaHc acid production or by transesterification of dimethyl terephthalate (DMT) or poly(ethylene terephthalate) (PET) scrap with glycols. 

Groupe TBI is investing about FFr3m to build a 15,0001/ y aromatic polyester polyols plant on a greenfield site at Issoire, near Lyons. The novel, patented process uses postconsumer waste bottles made from PETP as feedstock. PU and modified PIR foams made using the APPs have excellent fire performance and good dimensional stability. GROUPE TBI... 

Over 4 billion PETP bottles will be available for colleetion across Europe in 1999. PUR Products has introduced technology into the UK which involves glycolysis of postconsumer PETP into materials for the manufacture of rigid urethane foams for building insulation. This application offers a substantial new market for aromatic polyester polyols derived from glycolised PETP recyclate. PUR(PRODUCTS)LTD. 

Mannich polyols, aromatic polyester polyols, novolak-based polyols) lead, by the reaction with crude MDI, to very rigid polyurethane structures [2] (see Chapter 15). 

The most important oligo-polyols for rigid polyurethanes are polyether polyols and aromatic polyester polyols [1-4, 6]. The aromatic polyether polyols, based on condensates of aromatic compounds with aldehydes, become very important polyols, especially after the introduction of new blowing agents (see Chapter 21). 

Of course the thermal stability and char yield depend on the polyol structure too and the aromatic polyols are superior to aliphatic polyols from this point of view. This is the reason for the extremely rapid growth of aromatic polyester polyols, of low functionality, low viscosity and low cost. 

The aromatic polyester polyols were developed based on the following cheap and accessible raw materials ... 

Aromatic Polyester Polyols from Bottom Residues Resulting in DMT Fabrication [4, 6,10,11]... 

The bottom residues from DMT fabrication are benzyl and methyl esters of dicarboxylic and tricarboxylic acids with biphenyl or triphenyl structures together with DMT [4, 6. By the transesterification reactions of these complex ester residues with diethyleneglycol (DEG), aromatic polyester polyols with a functionality in the range 22-23 OH groups/mol are obtained. 

Generally, these residues from DMT fabrication are difficult to transport and are used on-site to be transformed into aromatic polyester polyols by transglycolysis [4]. Excellent rigid polyester polyols are obtained from pure DMT (reaction 16.1). 

Aromatic Polyester Polyols from Polyethylene Terephthalate Wastes (Bottles, Films, Fibres) [12-24]... 

PET wastes, proved to be an excellent raw material for low cost aromatic polyester polyols. By transesterification with DEG and (or) propylene glycol or dipropyleneglycol (DPG), liquid, low viscosity and low functionality aromatic polyester polyols were obtained. Due to the low cost, DEG is the preferred glycol for transesterification (reaction 16.3) [4, 6-8, 12]. 

The characteristics of some aromatic polyester polyols derived from the glycolysis of PET wastes are presented next ... 

Polyester polyols with equivalent weight of 167, functionality of 2 OH groups/mol, hydroxyl number of 310-350 mg KOH/g and viscosity of 1,300-3,000 mPa-s at 25 °C, are used in thermal insulation of appliances. The initial ratio between DEG and PET used in synthesis, followed by the utilisation of one of the previously mentioned procedures avoids solidification (section 16.2, a-e), and means that a large range of aromatic polyester polyols, having various hydroxyl numbers, functionalities and aromaticity can be obtained. 

Aromatic Polyester Polyols Based on Phthalic Anhydride (PA) [25,26]... 

PA is commercialised in large quantities (especially for use in plasticisers, such as dioctylphthalate and unsaturated polyesters), in high purity form. The aromatic polyester polyols based on PA, due to the purity of the raw materials, are colourless liquids and the process of fabrication, is very reproducible (good consistency). The polyester polyols based on PA and DEG are synthesised in two steps ... 

All the aromatic polyester polyols have a high aromaticity, of around 20%. 

Due to the low cost, the excellent physico-mechanical properties of the resulting urethane - isocyanuric foams, thermal and fire resistance and low level of smoke generation, the most important applications of aromatic polyester polyols are for rigid PU/PIR foams in the boardstock market (continuous rigid foam lamination) and for building insulation. 

The rigid PU/PIR foams [1,4-32] enjoyed an enormous success in recent years, making the aromatic polyester polyols dominate the USA polyol for rigid foam business, bypassing the polyether polyol business [4, 6. In Europe, the penetration of PU/PIR rigid foams based on aromatic polyesters has been limited, but the tendency is for a slow growth of aromatic polyester production. 

By using similar chemistry, aromatic polyester polyol structures are obtained by alkoxylation of the phthalic anhydride reaction product with glycerol (reaction 16.10). By the propoxylation of the reaction product of pyromellitic anhydride with DEG, tetrafunctional, highly viscous aromatic polyester polyols (16.11) are obtained. 

The most important structures of rigid polyester polyols presented in this chapter (Chapter 4.4) are the low functionality aromatic polyester polyols with terephthalic or phthalic structures, used for PU/PIR rigid foams. 

Uses PU intermediate for adhesives, coatings, and cast elastomers Features Mixed aliphatic/aromatic polyester polyol with all primary hydroxyl functionality the aromatic acid lends hardness and heat resist. Properties Gardner 4 solid m.w. 3200 dens. 10.2 Ib/gal vise. 8500 cps (60 C) acid no. 1.0 hyd. no. 35 Lexorez 3130-120 [Inolex]... 

Synonyms Polyester polyol, aromatic Polyester polyol, crosslinked Polyester polyol, linear Polyester polyol, slightly branched Polyol, flexible Properties Vise. liqs. to waxy solids... 

Polyurethane-modified polyisocyanurate (PIR) foams have a reputation for being the most flame resistant of the PU related foams used for insulation. They are increasingly being made from an aromatic polyester polyol (APP) and the isocyanate is most often MDI. Unlike pol5mrethanes, however, the amount of MDI is comparatively high. Isoeyanate indices of 250 or higher are used... 

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