Polyesters from ethylene oxide

The most important compounds are polyetherols, polyesterols, and graft polyols (Figure 1). Polyetherols are the most common polyols and most commercial products are made chiefly from ethylene oxide and propylene oxide. Polyesterols are widely used in elastomeric polyurethanes. Typical compounds are aliphatic polyesters, such as poly(ethyl-ene adipate), made so that there are only hydroxyl end groups, with no residual acid groups. Graft polyols (also called polymer polyols) consist of a matrix of a conventional polyol, which also contains rubbery (such as styrene/acrylonitrile copolymer) particles chemically bound to polyol molecules. These grafted particles reinforce the final polyurethane, giving improved physical properties. 

HOCHj CHjOH. Colourless, odourless, rather viscous hygroscopic liquid having a sweet taste, b.p. 197 C. Manufactured from ethylene chlorohydrin and NaHC03 solution, or by the hydration of ethylene oxide with dilute sulphuric acid or water under pressure at 195°C. Used in anti-freezes and coolants for engines (50 %) and in manufacture of polyester fibres (e.g. Terylene) and in the manufacture of various esters used as plasticizers. U.S. production 1979 1 900 000 tonnes. 

The polyols used are of three types polyether, polyester, and polybutadiene. The polyether diols range from 400 to about 10,000 g/mol. The most common polyethers are based on ethylene oxide, propylene oxide, and tetrahydrofuran or their copolymers. The ether link provides low temperature flexibility and low viscosity. Ethylene oxide is the most hydrophilic and thus can increase the rate of ingress of water and consequently the cure rate. However, it will crystallize slowly above about 600 g/mol. Propylene oxide is hydrophobic due to hindered access to the ether link, but still provides high permeability to small molecules like water. Tetrahydrofuran is between these two in hydrophobicity, but somewhat more expensive. Propylene oxide based diols are the most common. 

II. B polyethylene glycol, ethylene oxide, polystyrene, diisocyanates (urethanes), polyvinylchloride, chloroprene, THF, diglycolide, dilac-tide, <5-valerolactone, substituted e-caprolactones, 4-vinyl anisole, styrene, methyl methacrylate, and vinyl acetate. In addition to these species, many copolymers have been prepared from oligomers of PCL. In particular, a variety of polyester-urethanes have been synthesized from hydroxy-terminated PCL, some of which have achieved commercial status (9). Graft copolymers with acrylic acid, acrylonitrile, and styrene have been prepared using PCL as the backbone polymer (60). 

The most direct route towards functionalized aliphatic polyesters is based on the functionalization of polyester chains. This approach is a very appealing because a wide range of functionalized aliphatic polyesters could then be made available from a single precursor. This approach was implemented by Vert and coworkers using a two-step process. Eirst, PCL was metallated by lithium diisopropylamide with formation of a poly(enolate). Second, the poly(enolate) was reacted with an electrophile such as naphthoyl chloride [101], benzylchloroformate [101] acetophenone [101], benzaldehyde [101], carbon dioxide [102] tritiated water [103], ot-bromoacetoxy-co-methoxy-poly(ethylene oxide) [104], or iodine [105] (Fig. 26). The implementation of this strategy is, however, difficult because of a severe competition between chain metallation and chain degradation. Moreover, the content of functionalization is quite low (<30%), even under optimized conditions. 

Suitable starting compounds are polyesters from poly(ethylene oxide) and adipic acid, also poly(propylene oxide) or poly(oxytetramethylene) with molecular weights around 2,000, whose hydroxy end groups can be reacted with very... 

Figure 4.1 Analysis of a polyester sample for ethylene oxide (EO) showing Freon 12 used as a diluent in the sterilization process. (From Reference 186.)...

Polyurethane is also used as a foam, mostly in sheet form as an underlay or middle layer for example in fruit bins. The following starting materials for polyurethane foam can be used polyester with hydroxyl end groups made from adipic acid, diethylene glycol, trimethylol propane as well as polyether based on ethylene oxide and/or propylene oxide with free hydroxyl groups in combination with 2,4-toluene diisocyanate and 2,6-toluene diisocyanate. Stabilizers, dispersants and amines (as catalysts in amounts up to 1.2 %) can be used. 

Ethylene oxide, the simplest epoxide, is an intermediate in the manufacture of both ethylene glycol, used for automobile antifreeze, and polyester polymers. More than 4 million tons of ethylene oxide is produced each year in the United Slates by air oxidation of ethylene over a silver oxide catalyst at 300 "C. This process is not useful for other ejroxides, however, and is of little value in the laboratory. Note that the name cfhyletie oxide is not a systematic one because Ihe -cue ending implies the presence of a double bond in the molecule. The name is frequently used, however, because ethylene oxide is derived from ethylene by addition of an oxygen atom. Other simple epoxides are named similarly. The systematic name for ethylene oxide is 1,2-epoxyethanc. 

Kissel T, Li YX, Unger E. ABA-triblock copolymers from biodegradable polyester A-blocks and hydrophilic poly (ethylene oxide) B-blocks as a candidate for in situ forming hydrogel delivery systems for proteins. Adv. Drug Deliv. Rev. 2002 54 99-134. 

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