Water hydroxyl number

The mixture is kept for 3 hours at 105°C after the oxide addition is complete. By this time, the pressure should become constant. The mixture is then cooled to 50°C and discharged into a nitrogen-filled botde. The catalyst is removed by absorbent (magnesium siUcate) treatment followed by filtration or solvent extraction with hexane. In the laboratory, solvent extraction is convenient and effective, since polyethers with a molecular weight above about 700 are insoluble in water. Equal volumes of polyether, water, and hexane are combined and shaken in a separatory funnel. The top layer (polyether and hexane) is stripped free of hexane and residual water. The hydroxyl number, water, unsaturation value, and residual catalyst are determined by standard titration methods. 

Ion exchange/gravimetry Bromide/bromate titration Ethylene oxide acetaldehyde 1,4-dioxane hydroxyl number water content... 

Polyethers prepared from propylene oxide are soluble in most organic solvents. The products with the highest hydroxyl number (lowest molecular weight) are soluble in water, not in nonpolar solvents such as hexane. The solubihty of 3000 molecular weight triols is high enough in solvents such as toluene, hexane, and methylene chloride that the triols can be purified by a solvent extraction process. 

There are no generally accepted specifications manufacturers set their own specifications for hydroxyl number range, melt viscosity, water content, etc. Typical properties of Du Pont Terathane PTMEG are Hsted in Table 2, and selected thermal properties are given in Table 3 (260). For all grades, water content is <0.015 wt % ash, <0.001 wt % iron, <1 ppm peroxide, <5 ppm as H2O2 and flash point TOC is >163°C. 

Step 2 A mixture of 118 parts of the product of Step 1, having hydroxyl number of 260, 2 parts of solid NaH, and 100 parts of toluene was heated to 125° to 150°C In an autoclave. Ethylene oxide was added slowly over a period of 2 /2 hours until 261 parts of ethylene oxide were absorbed. This corresponds to 11 mols of ethylene oxide per mol of phenol in the product of Step 1. The toluene was then removed by steam distillation and the water by vacuum distillation at 10°C. The product was obtained as a viscous paste having a corrected hydroxyl number of 97. It was readily soluble in water and had marked detergent properties. 

Thus, a polyester sample (1-3 g, exactly weighed) is dissolved in 25 mL of a titrated solution of acetic anhydride in dry pyridine (10% mass). The solution is heated to reflux for 1 h. After cooling, 50 mL pyridine and 10 mL water are added. The excess acetic acid present in the resulting solution is titrated by aqueous potassium hydroxide (0.5 mol/L) using a potentiometric titrator. The determination must be carried out in duplicate and a blank titration must be performed under the same conditions. The mass of polyester and the concentration of reactants should be adjusted to ensure that at least a fourfold excess of acetic anhydride is used. The final result (OH content) is expressed in mmol OH/g polyester or as the hydroxyl number, defined as the number of milligrams of KOH required to neutralize the acetic acid consumed per gram of polyester. [Hydroxyl number = (number of mmol OH/g polyester) x 56.106.]... 

A reaction vessel was charged with behenyl alcohol (0.652 kg), 1,10-decanediol (101 kg), and zinc oxide (6 g) and then heated to 230°C. The reaction began at about 170°C and was monitored by the amount of water generated and hydroxyl number of sample aliquots. When the reaction was completed, the product was used without purification. 

Isocyanate index (index number) = I (X)(actual amount of isocyanate used)/ (equivalent amount of isocyanate required). An excess of isocyanate groups is used in some applications like flexible foam. The analytical values required for isocyanate formulas are the isocyanate value, hydroxyl number, residual acid value (acid number), and water content. The last two parameters reflect the following reactions ... 

Sorbitol Polyol-Modified Isocyanurate Foam (71). This foam was prepared according to the following procedure. Potassium 2-ethylhex-anoate containing 4% water was used as the catalyst (soluble in polyether polyols). 94 g of sorbitol-based polyether polyol having a hydroxyl number of 490, 8.5 g of the potassium 2-ethylhexanoate, 120 g of tris(chloroethyl) phosphate, 5 g of silicone surfactant, and 90 g of... 

This behaviour is a consequence of the extremely high hydroxyl number of water (OH = 6233.3 mg KOH/g). At higher levels of water, there is a tendency for the hydroxyl number of monomers to increase - it is practically impossible to obtain polyethers with low hydroxyl numbers such as 25-36 mg KOH/g. For higher MW polyethers, the ratio of monomers starter is high and the cumulative quantity of water introduced into the reaction with monomers is high. 

Molecular weight, daltons Hydroxyl number, mg KOH/g Acidity, mg KOH/g Water, % Viscosity at 25 °C, mPa-s Unsaturation, mequiv/g (functionality)... 

The evolution of the polyesterification reaction is monitored by measuring the quantity of water distilled and by the determination of acid number, hydroxyl number and viscosity. 

A very interesting Mannich polyol, of low functionality (f = 3.5 OH groups/mol) and low hydroxyl number (OH = 325 mg KOH/g), derived from nonyl phenol was developed successfully for all water blown rigid PU foams [19]. 

Hydrogenated castor oil is a solid with a melting point of 82-86 °C, having similar hydroxyl number to castor oil, of around 160-162 mg KOH/g. Hydrogenated castor oil is used in coatings and gives adhesion, flexibility, water repellency and chemical resistance [36]. 

Thus, by reaction of epoxidised soybean oil with a mixture of methanol - water in the presence of an acidic catalyst, polyols are obtained, with an hydroxyl number in the range 200-210 mg KOH/g and a viscosity between 10,000-16,000 mPa-s at 25 °C [59, 61]. 

To a 1-liter stainless steel autoclave are added 230 gm (0.8 mole) of stearyl alcohol and 0.9 gm of sodium methoxide powder. The reactor is purged with nitrogen. Then 408 gm (7.0 mole) of propylene oxide is added over a 16-hr period while the temperature is kept at 130°-135°C. After the reaction is complete the mixture is cooled and the volatiles are eliminated by heating on a water bath for 15-20 min. Then dilute sulfuric acid is added to neutralize the catalyst and the product is washed with 1 liter of water at 60°C, followed by two washings with 500 ml of water at 60°C. The product is dried imder reduced pressure to give 548 gm (99%) of a light-yellow product having a hydroxyl number of 94. 

To a 1-liter, three-necked, round-botton flask equipped with a mechanical stirrer, reflux condenser, thermometer, and addition funnel is added 57 gm (0.75 mole) of propylene glycol and 7.5 gm (0.19 mole) of sodium hydroxide. The flask is purged with nitrogen to remove air and heated to 120°C with stirring to dissolve the sodium hydroxide. Then propylene oxide is added (40-45 mole). The reaction mixture is cooled under nitrogen, neutralized with dilute sulfuric acid, filtered, and dried under redueed pressure to give a water-insoluble product with MW 1620 as determined by hydroxyl number or acetylation analytical procedures. 

---