Polyethers for polyurethanes

Desmophen Polyesters and polyethers for polyurethanes Farbenfabriken Bayer AG... 

This concept of molecular tailoring to introduce units giving the required mechanical and physical properties has led to the provision of a variety of linear and branched polyesters and polyethers for polyurethane production. These intermediates may have molecular weights of the order of 500-3000, be crystalline or amorphous, contain atoms or groups which contribute to molecular flexibility or stiffness, and be linear or branched according to the requirements for use in elastomers, flexible or rigid foams, coatings, etc. 

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. 

About 60% of the propylene oxide made is polymerized to polypropylene glycol and other polyethers for use in polyurethane foams and adhesives. Propylene glycol is also widely used in polyester resins based on maleic anhydride. 

Wheels and tires are one of the major uses of cast polyurethane elastomers. We commonly see these on fork lift trucks and shopping carts, where their excellent abrasion resistance, resistance to oil, and good elasticity are valued. In industrial settings we find polyurethane covers on rollers used for paper, steel, and textile conveyor systems. In such applications, their excellent cut and abrasion resistance help prolong their useful life. If used in hot and humid conditions, polyether-based polyurethanes are preferred. 

The use of naturally derived complex carbon compounds as raw materials for polyurethane polymers is not new to the industry. Since the advent of polyether polyols, polyurethane polymers have utilized natural sources of renewable carbon. 

Alkoxylation with, for example, propylene oxide (PO). Preferred amine is triethanolamine, or ammonia and other alkanolamines used amine can also be quaternized Best example is triethanol with 14.9 PO units Contains vinyl ester acetal functionalities besides some unreacted vinyl alcohol monomer units. Preferred aldehyde is butyraldehyde Backbone, for example, polyalkylene glycol, polyalkyl-eneimine, polyether, or polyurethane, and active functional side groups made from grafting VP or VCap to backbone using radical initiators TBA (tributylammonium groups)... 

The reactive oligomer can be any low-molar-mass polymer containing at least a couple of double bonds. It can be based on a polyester, polyether, or polyurethane backbone. One mole of a, oo-OH-terminated polyester or polyether is prereacted with two moles of acrylic acid to obtain an a, oo-diacrylate oligomer. For polyurethanes, 1 mole of a, m-diisocyanate oligomer is prereacted with 2 moles of hydroxyethylacrylate (Sec. 2.2.3c). 

In practice, up to 90% of polyurethanes are used in compression, a few percent in torsion, and very little in tension. There is considerable data on the tensile stress against tensile strain (elongation) for polyurethanes. Most polyurethane specification sheets provide this data. Figure 7.3 and Figure 7.4 show typical stress-strain curves for both polyester and polyether polyurethanes. 

For polyether-based polyurethane at 70 to 80°C, the properties are only 50% of the original, whereas at 110°C the value drops to about 20%. This gives a normal safe working temperature of 80°C. Figure 7.10 illustrates the aging effect on different cure systems. This working range can be increased by the use of isocyanates such as PPDI in the polyurethane (Chin et al., 1992). 

This method relies on the fact that the isotopes of certain atoms have electrons that will flip under certain conditions. This change in state can be detected, and how they are connected can be shown. The H and 13C isotopes are able to produce resonance spectra for polyurethane raw materials and cured samples. ASTM method D4273 details a method to determine the primary hydroxyl content of polyether polyols. 

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. 

Impact A process for making long-chain polyol polyethers as precursors for polyurethanes. Developed by Arco, acquired by Bayer in 2000. A further development was CAOS. 

Oligomeric carbodiimides are efficient stabilizers for polyester, polyester based polyurethanes, polyether based polyurethanes and polyether based poly(urethane ureas). Oligomeric carbodiimides are commercially available under the trade name Stabaxol from Rhein Chemie, a subsidiary of Bayer. 

Pyrolysis could be considered as an nnsnitable way of recycling for polyurethanes because the liquid product is extremely viscous and can solidify over time [41]. The main reason of the severe instability of polynrethane pyrolysate is the reactivity of the diisocyanate component, the regained polynrethane-forming reactant. The other component of thermoplastic polyurethanes is either a polyether or a polyester which could lead to stable pyrolysis liquid if the reactive diisocyanate is eliminated from it. 

The ingredients for polyurethane flexible foam are Freon 11, polyether polyol-triol, polyurethane and TDI. Polyurethane fire-resistant rigid foam is produced from Freon 11, polyether polyol-hexol, polyether polyol-phosphorus, polyisocyanates and polyurethane. MDI foam has advantages over TDI foam, particularly in that it is easier and safer to handle, and for this reason is widely used as a thermal insulation. Flexible foams account for over 60% of the consumption of polyurethanes31,32. 

Polyurethanes were prepared by both prepolymer and oneshot methods. Our poljraiers were molded at about 190° C Into 0.3 mm sheets. A commercial supplier provided 0 25 mm sheets of polyester based and polyether based polyurethanes. These were used as received, except for cutting. 

There is an alternative method of making functional derivatives for polymerization. Durene can be condensed with formaldehyde in the presence of hydrochloric acid and zinc chloride to give the bis-chloromethyl durene(75). This can be converted into a number of derivatives from which polymers can be made, e.g. durene-1,4-dicarboxylic acid for polyamides(76), the diacetic acid for polyesters(77,78) or for polyamides(79), the diisocyanatomethyl derivative for polyureas and polyurethanes(80,81), the dimethanol derivative for polyurethanes(82) and for epoxies(83), while the bis chloromethyl derivative has also been proposed for making polyethers (with bisphenol A)(84). In each case, the attraction from the durene derivative has been the introduction of higher melting points and inproved softening properties. None of these polymers have been commercialized, possibly in part because of the difficulty of obtaining durene at suitable-prices. 

High resolution solid-state NMR spectroscopy is also a very powerful method for characterizing the solid structure and the local motion of different solid polymers. We recently characterized the crystalline-noncrystalline structure for different crystalline and liquid crystalline polymers, such as polyolefins [7-12], polyesters [13-15], polyether [16], polyurethanes [17, 18] and polysaccharides, including cellulose [19-29], amylose [30, 31] and dextran [32]. On the basis of these analytical methods, we also investigated the intra- and intermolecular hydrogen bonds of PVA in both crystalline and noncrystalline regions as well as in the frozen solution state. In this chapter. 

Various types of polymers are used to formulate propellants and explosives. The nature of polymers is identified by their chemical bond structure. Two types of copolymers are used to formulate modern propellants and explosives (1) polyurethane copolymer and (2) polybutadiene copolymer. The chemical bond structures of polyether and polyester are used for polyurethane copolymers. Since the molecular concentration of oxygen is relatively high for polyurethane binder, this class of binder is used to achieve high combustion efficiency with low oxidizer concentration of crystalline materials. On the other hand, the heat of formation of polybutadiene copolymer is high and the molecular concentration of oxygen is low when compared with polyurethane copolymer. This class of binder is used to achieve a high combustion temperature when mixed with crystalline oxidizer particles. 

Figure 1.2 World consumption of polyether and polyester polyols for polyurethanes...

An oligo-polyol for polyurethanes, may have two, three, four, five, six, seven or a maximum of eight hydroxyl groups/mol. Polyols with a higher number of hydroxyl groups/mol are rarely used (for example dendritic polyols). Oligo-polyols with only one hydroxyl groups/mol are present in all the polyether polyols based on propylene oxide (see Chapters 4.1.1-4.1.4). 

ASTM D4273, Standard Test Methods for Polyurethane Raw Materials Determination of Primary Hydroxyl Content in Polyether Polyols, 1999. 

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