Medium boilers

For the purpose of polymer/additive analysis it is useful to rank solvents according to their boiling point ranges into low boilers (b.p. <100°C), medium boilers (b.p. 100-150°C) and high boilers (b.p. >150°C). Based on their evaporation numbers, solvents can be subdivided into four groups high volatility (< 10), moderate volatility (10-35), low volatility (35-50) and very low volatility (>50). 

Table 3.16 gives the criteria for entrainer selection [7]. Medium-boiler entrainer is valid for both minimum and maximum azeotropes, but this condition is difficult... 

High boiler Yes (extractive distillation) Medium-boiler min azeo with B... 

Medium boiler New minimum azeotrope with A, the low-boiling component. New maximum azeotrope with B, the high-boiling component. 

Many organics, particularly sugars, completely carbonize at medium boiler pressures. This carbonization produces organic acids as the sugars are reductively decomposed. In high-pressure boiler systems using coordinated phosphate/pH programs, these acids can drive the pH down to 3 or 4. 

Already, it has been shown that by oxidizing three cuts, naphtha, kerosene, and wax distillate, nitrocellulose solvents distilling through the whole range of low boilers," medium boilers," liigh boilers, plasticizers md softeners" may be prepared. These solvents are largely mixtures of is ter s, alcohols, and ethers with ketones and aldehydes removed. 

A first choice, valid for both minimum and maximum azeotropes, would be a medium-boiler entrainer. Such condition is difficult to fulfil in practice because in the most cases the species forming azeotropes have close boiling points. However, such entrainers can be found (see Example 9.1). 

Low boiler Medium-boiler maximum azeotrope with A No... 

Medium boiler New minimum azeotrope with A, the low boiling component. 

Although finely ground limestone costs less than hydrated lime per ton of sulfur removed, the latter has generally been favoured by operators of small to medium boilers, because of its greater reactivity and because it produces about 40 % less residue than limestone. 

A paint formulation therefore always contains several solvents low boilers, medium boilers, and a small proportion of high boilers. The vapor pressure of the individual solvents in the mixture is described by Raoult s law ... 

Composition of Paint-Solvent Mixtures. The composition of a paint-solvent mixture is governed by the application conditions, drying temperature, and drying time of the paint. The solvent mixture in a paint that undergoes physical drying at room temperature contains ca. 45% low boilers, ca. 45% medium boilers, and ca. 10% high boilers. 

Methyl butyl ketone [591-78-6] (MBK, 2-hexanone) is slightly soluble in water, miscible with organic solvents. Being a medium boiler it dissolves cellulose nitrate, vinyl polymers and copolymers, and natural and synthetic resins. It increases the dilutability with non-solvents and diluents. As a paint solvent, methyl butyl ketone is important only in hot-spraying and coil-coating paints. It has a very low MAK value and is recommended as a solvent because it is photochemically inactive and does not, therefore, contribute to the formation of photosmog. ... 

This is a simpler classification by relative speed of evaporation which is usually expressed relative to either butyl acetate or diethyl ether. There is no rigid distinction but fast solvents or low boilers typically evaporate more than twice as fast as butyl acetate slow solvents or high boilers typically evaporate less than half as fast as butyl acetate. Medium boilers fit between these two limits. 

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