Alkoxylation Foams

TDA-derived polyols are made by alkoxylation. Polypropylene oxide adducts of I DA (14) and TDA-initiated polyether polyols (13,15) are used in rigid polyurethane foams and continue to be included in new formulations (62) as well as older appHcations. 

This type of alkoxylation chemistry cannot be performed with conventional alkali metal hydroxide catalysts because the hydroxide will saponify the triglyceride ester groups under typical alkoxylation reaction conditions. Similar competitive hydrolysis occurs with alternative catalysts such as triflic acid or other Brpnsted acid/base catalysis. Efficient alkoxylation in the absence of significant side reactions requires a coordination catalyst such as the DMC catalyst zinc hexacyano-cobaltate. DMC catalysts have been under development for years [147-150], but have recently begun to gain more commercial implementation. The use of the DMC catalyst in combination with castor oil as an initiator has led to at least two lines of commercial products for the flexible foam market. Lupranol Balance 50 (BASF) and Multranol R-3524 and R-3525 (Bayer) are used for flexible slabstock foams and are produced by the direct alkoxylation of castor oil. 

Mention has already been made of the numerous effects attendant upon chemical substitutions on the polysaccharide linear chain. Natural branches impart a dispersion stability to amylopectin that is not afforded amylose. One only has to compare cellulose ethers, deesterified chitin, and the lysis product of protopectin with the underivatized parent compound to appreciate the impact of chemical substituents on functionality. The loosening of compact, parallel structures with alkyl, hydroxyalkyl, and alkoxyl groups facilitates hydration and transforms insoluble, refractory polysaccharides to soluble, reactive polysaccharides. Not only do these substituents obstruct the crystallization tendency, they almost always confer secondary functionalities like q enhancement and foam, suspension, and freeze-thaw stabilization. 

Bottle washing in dairies and Fatty alcohol alkoxylates Low foam wetting agents... 

When a low foaming cleaner is desired, inclusion of alkoxylated mono alkyl quaternary salts is useful. Such quaternaries, containing both ethoxyl and propoxyl moieties, are effective [75]. 

In order for such glycosides to be utilized for polyurethane formation, further chemical modification is required to reduce hydrogen-bonding interactions. Chain extension, often by alkoxylation at elevated temperature and under pressure, is used to obtain suitable liquid polyols. Otey (if), for example, has modified EGG in this manner in a bulk alkoxylation to yield polyols that could then be used to form polyurethane foams. 

U.S. 5968496 (1999) U.S. 5922671 (1999) Linares et al. (Procter Gamble) Tracy et al. (Rhodia) (a) Imidazolinium amphoteric surfactant (b) polyol alkoxy ester (a)/(b) = 15 1-1 1 Bis-alkyphenol alkoxylated Gemini surfactants Excellent cleaning performance and mildness improved foam stability Improved surfactant properties mild and environmentally benign... 

The polyols for rigid foams (referred to as rigid polyols) discussed before (Chapters 13 and 14), are based on the alkoxylation of different polyols or polyamines, commercialised in a relatively high purity form. Some important starters for rigid polyols are obtained by the synthesis of the starter in situ, before the alkoxylation reaction, by the condensation reaction of some aromatic compounds (phenols, melamine and so on) with aldehydes (mainly formaldehyde), followed by the reaction of the resulting condensate with alkylene oxides. Some important rigid polyols based on the condensates mentioned are ... 

The last traces of alkylene oxides are removed by vacuum distillation at 100-110 °C. After the phenolic group alkoxylation, that is the first group which is alkoxylated, the resulting structure becomes much more stable and it is possible to develop degassing at higher temperature, without the risk of viscosity increase. The resulting Mannich polyols are used in polyurethane foam fabrication without any other supplementary purification. The reactions involved in the alkoxylation of Mannich bases to Mannich polyols are presented in reaction 15.10 [9]. 

An excellent polyol for urethane isocyanuric foams is a diol based on bisphenol A, alkoxylated with 8-9 mols of EO or with 4 mols of PO and 4-5 mols of EO (structures 15.31 and 15.32). 

A third process of solid bisphenol A alkoxylation is to use a suspension of solid bisphenol A in final polyether polyol (40-60% bisphenol A and 60-40% liquid polyether diol). This suspension, in the presence of a tertiary amine as catalyst, is ethoxylated at 80-95 °C, with 8-9 mols of EO/mol of bisphenol A. At the end of the reaction, all the solid bisphenol A was totally transformed into liquid polyether diols [30]. The resulting polyether diols are used successfully for production of urethane-isocyanuric foams with very good physico-mechanical properties and intrinsic fire resistance. 

Very interesting polyols for rigid PU foams are obtained by the simultaneous alkoxylation with PO (or EO) of a mixture from bisphenol A and a costarter, such as bisphenol A... 

The hyperbranched polyglycerols were used successfully as copolyols for rigid PU foams and after the alkoxylation of polyglycerols with PO and EO. Higher molecular weight polyether polyols used for elastic PU were obtained [16]. 

It is very interesting that in the alkoxylation (with PO or EO) of a flexible or semiflexible PU foam, the PU crosslinked polymer is transformed into a liquid product. 

The alkoxylation process is easy to apply to PU foams having a low concentration of urethane and urea groups such as flexible and semiflexible foams, integral skin foams, PU elastomers and so on. Urea groups react in a similar way with urethane groups, with the formation of oxazolidones and amines by an intramolecular alcoholysis of urea groups (reaction 20.15). 

By the hydrolysis of a flexible foam based on toluene diisocyanate (TDI) one obtains toluene diamine (2,4 and 2,6 isomers), the polyether triol and, of course, carbon dioxide. The difficulty of the process is the separation of the amine. The amine may be used for TDI synthesis (after a previous purification), or be transformed into a valuable rigid polyol (aminic polyol) by alkoxylation with PO and EO. 

By reacting urea groups from rigid PU foam scraps with DEG, amines are formed. The amines are transformed into rigid polyols by alkoxylation of the resulting polyol mixture. The idealised reaction for glycolysis of a rigid PU foam is presented in reaction 20.17. 

Figure 20.2 Technological scheme for recovery of rigid PU foam wastes by glycolysis process (variant) 1 Mills for PU scrap 2 Storage of ground rigid PU foam 3 Screw for powdered materials 4 Glycolysis and alkoxylation reactor 5 Electrical induction heaters 6 Filter press 7 Storage tank for the recovered polyol 8 Gear or screw (or...

A schematic diagram of the chemical recovery of rigid PU foam wastes by glycolysis is presented in Figure 20.3. Similar technological flows would be used for aminolysis or aminolysis - alkoxylation processes. 

Flexible polyether polyols based on high functionality starters (chain initiators) (for example a hexafunctional polyether polyol of equivalent weight 1000-2000, based on alkoxylation of sorbitol instead of glycerol), produces flexible PU foams with higher load bearing properties, but with a decrease in tensile strength and elongation. These polyols were used in carpet underlay [18]. 

Polystab. [Harcros UK] Alkoxylates solvent, hydrotrope, solubilize for polyurethane foam mfg. 

Olin (alkoxylated linear alcohol nonionic surfactant, low foam)... 

Rexopal. [Hart Chem. Ltd.] Alkoxylated alcohols low foaming emulsifier, wetting agent scouring agent for textiles. 

Solwax. [Van Schuppen] Alkoxylated lanolin or cholesterol derivs. emulsifier, foam stabilizer, softener, conditioner, emollient... 

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