Polyols capping

Polyol-Glycerol-based poly(oxypropylene) poly(oxyethylene) polyol capped with (ximary hydroxyl groups, 6000 mol.wt. Isocyanate - modified TDl... 

In this chapter, the dramatic effect that monol content or polyol functionality has on processability and properties of polyurethane cast elastomers is discussed. This effect is shown for elastomers prepared by both the prepolymer and one-shot processes. Further improvements in elastomer processability and formulating latitude can be achieved by incorporating oxyethylene moieties into the polyol backbone. For one-shot elastomer processes, ultra-low monol PPG polyols capped with ethylene oxide have been commercialised. 

Phosphites. Tertiary phosphites are also commonly used and are particularly effective ia most mixed metal stabilizers at a use level of 0.25—1.0 phr. They can take part ia a number of different reactions duting PVC processing they can react with HCl, displace activated chlorine atoms on the polymer, provide antioxidant functionaHty, and coordinate with the metals to alter the Lewis acidity of the chloride salts. Typical examples of phosphites are triphenyl phosphite [101 -02-0], diphenyl decyl phosphite [3287-06-7], tridecyl phosphite [2929-86-4], and polyphosphites made by reaction of PCl with polyols and capping alcohols. The phosphites are often included in commercial stabilizer packages. 

Polyurethane foams are formed by reaction with glycerol with poly(propylene oxide), sometimes capped with poly(ethylene oxide) groups with a reaction product of trimethylolpropane and propylene oxide or with other appropriate polyols. A typical reaction sequence is shown below, in which HO—R—OH represents the diol. If a triol is used, a cross-linked product is obtained. 

Other polyamine derivatives are used to break the oil/water emulsions produced at times by petroleum wells. Materials such as polyether polyols prepared by reaction of EDA with propylene and ethylene oxides (309) the products derived from various ethyleneamines reacting with isocyanate-capped polyols and quaternized with dimethyl sulfate (310) and mixtures of PEHA with oxyalkylated alkylphenol—formaldehyde resins (311) have been used. 

The PPG polyols are also available with ethylene oxide capping, which pro-... 

Filter/dry OH-functionality of polyol depends on structure of R Difficult to "cap all 2° OH groups with EO Side reactions (esp. proton abstraction) limit functionality of Urethane-grade polyol product and create unwanted functional groups... 

The ATO Chemie process involves the formation of an adipic acid-capped hard segment block of poly(ll-aminoundecanoic) of molecular weight 800-1500, joined with a soft segment of polyol in a polyesterification process. 

Hsu, C., Zhao, M. and Bergstrom, L., Aromatic polyol end-capped unsaturated polyetherester resins and resin compositions containing the same... 

A number of issues related to this reaction should be discussed. First, a polymer is rarely isolated in this form. In the early 1950s a technology was developed that has since come to be known as the one-shot process. While the technique certainly produces a capped polyol, it immediately reacts further to achieve its ultimate form (Figure 2.6, bottom). You will notice that the capped polyol still has isocyanate functionalities as end groups. Regardless of the process, these end groups must continue to react (by the addition of water and/or a catalyst) to complete the process. While this reaction produces one of the most commonly constructed polyurethanes, it is rarely isolated as an end product. 

Sample Preparation Weigh about 0.5 g of sample and reflux with 20 mL of ethanolic 1 N potassium hydroxide solution for 2 h. Reduce the volume of ethanol by evaporation at 45° to 50° in a stream of nitrogen. Add 10 mL of water, and acidify with concentrated hydrochloric acid. Extract the fatty acids from the aqueous phase with successive 20-mL volumes of hexane. Wash the hexane extracts with 20 mL of water, and combine the wash with the aqueous phase. Adjust the aqueous polyol solution to pH 7.0 with aqueous potassium hydroxide solution with the aid of a pH meter. Evaporate to 2 to 3 mL under reduced pressure, and extract three times with 30 mL of boiling ethanol. Filter off any residue, and evaporate the ethanol under reduced pressure to yield a viscous liquid mixture of polyols. Transfer and dissolve 0.1 g of the mixture into a 10-mL capped vial containing 0.5 mL of warm pyridine previously dried over potassium hydroxide. Add 0.2 mL of hexamethyldisilazane, shake, add 2 mL of trimethylchloro-silate, and shake again. Place the vial on a warm plate at about 80° for 3 to 5 min. Check that white fumes are present, indicating an excess of reagent. 

Figure 11.36 By extending the polyol reaction for a ven time period, various polyhedral shapes capped with 100 and 111 faces can be obtained in high yield, a) A schematic of the nucleation and growth process, in which silver continuously deposits onto the 100 faces to eventually result in a completely 111 -bound octahedron, b to f) SEM images of cubes, truncated cubes, cuboctahedra, truncated octahedra, and octahedra, respectively (scale bar 100 nm). Reproduced with permission from reference [91]. (2006) Wiley-VCH Verlag GmbH Co. KGaA.

Normally a 70/30 to 50/50 blend of a 4500-6500 EO-capped polyether triol with a polymer polyol is used, together with an 80 20 blend of TDI (80/20 isomer ratio) and polymeric MDI. Recently, higher-solids-content graft polyols, e.g., 30-50% solid polyols, have become available in the market. 

Sample Identification. Given the number of samples and compositions, a general code was created as explained in Table II. In this table, the polyol type is identified by molecular weight and ethylene oxide content. Thus 40/15 refers to a polyol with M = 4000 and 15% (w/w) of ethylene oxide end capping agent. The last two labels in Table 2 indicate mold temperature and catalyst content. 

FLEXIBLE BACKBONE 1. Polyether polyols made with propylene oxide and "capped" with ethylene oxide. 

Graft polyols made from grafting polyacrylonitrile onto the basic polyether (also ethylene oxide -"capped"). 

A High Molecular Weight, Ethylene Oxide Capped Polyether Polyol with a Hydroxyl Number of 34. 

Figure 7. Infrared spectra of isocyanate formation of model Type C (R = CHS) (Spectrum A, azide and Spectrum B, isocyanate) and of capped lignin-derived polyol.

Capped polyols, prepared by reacting polyols in non-polar solvents (benzene or ethyl acetate) with excess diisocyanate (HDI), reacted with cellulose fibers at ambient temperature. Simple immersion of preformed fiber mats (blotting paper) followed by air-drying resulted in drastic increases in sheet strength properties. This is indicated in Table X. 

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