Polyol oxidation

Oxidations by dioxygenases cw-hydroxylation of aromatic double bonds. Oxidations catalyzed by oxidases regio- and stereoselective oxidations of polyols oxidations of carbohydrates oxidations of hydroxy steroids oxidations of alkyl phenols to form chiral /7-hydroxybenzylic alcohols hydroxylation of phenols oxidation of amino acids to keto acids. 

Isocyanate prepolymers were prepared in glass reaction vessels in a laboratory fume hood. The reaction vessel was equipped with a stirrer, temperature controller and nitrogen inlet. The reaction was carried out under a dry-nitrogen atmosphere to minimise exposnre to atmospheric moisture and polyol oxidation. 

A number of commercial phosphoms-containing polyols have been made by the reaction of propylene oxide and phosphoric or polyphosphoric acid. Some have seen commercial use but tend to have hydrolytic stabiHty limitations and are relatively low in phosphoms content. BASF s Pluracol 684 is a high functionahty polyol containing 4.5% P, sold for Class 11 rigid foam use. 

Nonreactive additive flame retardants dominate the flexible urethane foam field. However, auto seating appHcations exist, particularly in Europe, for a reactive polyol for flexible foams, Hoechst-Celanese ExoHt 413, a polyol mixture containing 13% P and 19.5% Cl. The patent beHeved to describe it (114) shows a reaction of ethylene oxide and a prereacted product of tris(2-chloroethyl) phosphate and polyphosphoric acid. An advantage of the reactive flame retardant is avoidance of windshield fogging, which can be caused by vapors from the more volatile additive flame retardants. 

Other Fire-Resistant Hydraulic Fluids. Phosphate and more recently polyol esters are marketed as fire-resistant compounds. They are formulated with additives to control wear, oxidation, corrosion, and misting. Seal compatibdity and solvency characteristics of these fluids may be quite different from those of mineral ods. 

HydroxyethyUiydrazine (11) is a plant growth regulator. It is also used to make a coccidiostat, furazoHdone, and has been proposed, as has (14), as a stabilizer in the polymerization of acrylonitrile (72,73). With excess epoxide, polysubstitution occurs and polyol chains can form to give poly(hydroxyaLkyl) hydrazines which have been patented for the preparation of cellular polyurethanes (74) and as corrosion inhibitors for hydrauHc fluids (qv) (75). DialkyUiydrazines, R2NNH2, and alkylene oxides form the very reactive amineimines (15) which react further with esters to yield aminimides (16) ... 

Oxo aldehyde products range from C to C, ie, detergent range, and are employed principally as intermediates to alcohols, acids, polyols, and esters formed by the appropriate reduction, oxidation, or condensation chemistry. The 0x0 reaction has been the subject of various reviews (4). 

Unsaturation value can be determined by the reaction of the akyl or propenyl end group with mercuric acetate ia a methanolic solution to give acetoxymercuric methoxy compounds and acetic acid (ASTM D4671-87). The amount of acetic acid released ia this equimolar reaction is determined by titration with standard alcohoHc potassium hydroxide. Sodium bromide is normally added to convert the iasoluble mercuric oxide (a titration iaterference) to mercuric bromide. The value is usually expressed as meg KOH/g polyol which can be converted to OH No. units usiag multiplication by 56.1 or to percentage of vinyl usiag multiplication by 2.7. 

The tendency of aliphatic ethers toward oxidation requires the use of antioxidants such as hindered phenoHcs (eg, BHT), secondary aromatic amines, and phosphites. This is especially tme in polyether polyols used in making polyurethanes (PUR) because they may become discolored and the increase in acid number affects PUR production. The antioxidants also reduce oxidation during PUR production where the temperature could reach 230°C. A number of new antioxidant products and combinations have become available (115,120,124—139) (see Antioxidants). 

Solubility. PPO polyols with a molecular weight below 700 are water soluble. The triol is slightly more water soluble than the diol. The solubihty in water decreases with increasing temperature. This inverse solubiUty causes a cloud point which is important in characteri2ing copolymers of propylene oxide and ethylene oxide. 

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. 

Propylene oxide [75-56-9] (methyloxirane, 1,2-epoxypropane) is a significant organic chemical used primarily as a reaction intermediate for production of polyether polyols, propylene glycol, alkanolamines (qv), glycol ethers, and many other useful products (see Glycols). Propylene oxide was first prepared in 1861 by Oser and first polymerized by Levene and Walti in 1927 (1). Propylene oxide is manufactured by two basic processes the traditional chlorohydrin process (see Chlorohydrins) and the hydroperoxide process, where either / fZ-butanol (see Butyl alcohols) or styrene (qv) is a co-product. Research continues in an effort to develop a direct oxidation process to be used commercially. 

Polymerization to Polyether Polyols. The addition polymerization of propylene oxide to form polyether polyols is very important commercially. Polyols are made by addition of epoxides to initiators, ie, compounds that contain an active hydrogen, such as alcohols or amines. The polymerization occurs with either anionic (base) or cationic (acidic) catalysis. The base catalysis is preferred commercially (25,27). 

Some of the simplest polyols are produced from reaction of propylene oxide and propylene glycol and glycerol initiators. Polyether diols and polyether triols are produced, respectively (27) (see Glycols). 

Propylene oxide can be copolymerized with other epoxides, such as ethylene oxide (qv) (25,29,30) or tetrahydrofiiran (31,32) to produce copolymer polyols. Copolymerization with anhydrides (33) or CO2 (34) results in polyesters and polycarbonates (qv), respectively. 

Ammonia, and Amines. Isopropanolamine is the product of propylene oxide and ammonia ia the presence of water (see Alkanolamines). Propylene oxide reacts with isopropanolamine or other primary or secondary amines to produce A/- and A/,A/-disubstituted isopropanolamines. Propylene oxide further reacts with the hydroxyl group of the alkanolamines to form polyether polyol derivatives of tertiary amines (50), or of secondary amines ia the presence of a strong base catalyst (51). 

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