Ethanol solvency

Typical cosolvents include methanol [67-56-17, ethanol [64-17-5] isopropyl alcohol [67-65-OJ, or toluene. The selection of cosolvents depends on the requirement of the formula and their interaction with other ingredients. Methanol is a common cosolvent in methylene chloride formulas since it has good solvency and is needed to swell ceUulose-type thickening agents. A typical methylene chloride formula used to strip wood is as follows (7). 

Smyth HDC, Mejia-Millan EA, Hickey AJ. The effect of ethanol on solvency vapor pressure, and emitted droplet size of solution metered dose inhalers containing HFA 134a. Respir Drug Delivery VIII 2002 2 735-738. 

In the switch from CFC to the more polar HFA propellants, one of the major problems has been inadequate solubility of the surfactants (used to stabilize the micronized drag particles) in the HFA. Solubility can be adjusted within the CFC propellant, e.g. CFC 12 is a far better solvent than CFC 11. However, for HFAs, blends do not exist and so solvency can only be addressed by using a cosolvent such as ethanol. It must be remembered that changing the solvency of the propellant will almost certainly affect the all-important vapor pressure and thus the MM AD, the particle velocity and the deposition site. Alternative stabilizers have been investigated and include PVP, fluorinated surfactants and Poloxamers. In addition to solubility effects, difficulties associated with the use of HFAs also include incompatibility with elastomer components in the metering valves. 

Considerable research was carried out in the 1980s using ethanol and isopropanol as oil extraction solvents. Ethanol is unusual because its oil solvating capacity is temperature and moisture-dependent. Oil solubility is relatively low at room temperature and moisture contents above the water alcohol azeotrope. Thus, the moisture content of the flakes must be in equilibrium with the alcohol (e.g., 2% for 95% ethanol and 7% for 91% isopropanol) (Wan Wakelyn, 1997), otherwise the solvency changes. Differences in oil solubility afford inexpensive means of oil separation from the solvent by merely cooling the miscella to separate an oil-rich phase without evaporating the bulk solvent. 

Figure 5.2 presents a similar plot for a poly(methyl methacrylate) latex sterically stabilized in n-heptane by poly(12-hydroxystearic acid). In this instance, however, the reduction in the solvency of the dispersion medium for the stabilizing moieties was achieved by adding a miscible nonsolvent (specifically ethanol) to the dispersion medium (Napper, 1968a). Flocculation was again accompanied by an abrupt increase in turbidity when a certain volume fraction of ethanol was added to the ra-heptane. In this instance, it was possible to observe the slow flocculation of the latex particles (i.e. flocculation apparently in the presence of a small repulsive potential energy barrier at a rate slower than that predicted by Smoluchowski, 1917). It is, however, usually diflicult to detect such slow flocculation because of the sharpness of the transition from stability to flocculation for stericaUy stabilized dispersions. 

The influence exerted by particle size on the CFV of poIy(methyl methacrylate) latices stabilized by low molecular weight (1750) poly(12-hydroxystearic acid) in n-heptane has already been presented in Section S.3.5 (see especially Table 5.6). Ethanol and n-propanol were used as nonsolvents (Napper, 1968b). As the particle size increased, the CFV was found to decrease. It was deduced therefrom that the latex particles became progressively easier to coagulate as the particle size increased because incipient instability was manifest under progressively better solvency conditions than those of 0-solvents. This assuredly implicates the van der Waals attraction between the core particles in the coagulation process since the London attraction also increases with increasing particle size. 

Most nonhydrocarbon solvents, whether inorganic or organic, are pure substances. They include water, ethanol, and glycol ether. Most hydrocarbon solvents are mixtures including the complex mixtures of hydrocarbons present in petroleum distillates or the carefully engineered solvent blends used in automotive paints. These blends and mixtures are chosen to produce the desired solvency, evaporation rates, flash point, and other factors applicable to any process. A significant number of organic solvents are flammable. 

Dichloromethane [75-09-2] (methylene chloride) is a colorless, highly volatile, neutral liquid with a characteristic odor. It is insoluble in water but miscible with organic solvents. It has a very good solvency for many organic substances, such as fats, oils, waxes, and resins. Bitumen, rubber, chlorinated rubber, polystyrene, postchlorinated poly(vinyl chloride), vinyl chloride copolymers, polyacrylates, and cellulose esters are also soluble. The solubility spectrum can be expanded by adding other solvents. A mixture of methanol or ethanol and dichloromethane is a good solvent for cellulose ethers and acetyl cellulose. Cellulose nitrate is, however, insoluble. 

Methylbenzyl alcohol [98-85-1] (1-phenyl-ethanol, 1-phenylethyl alcohol, phenyl-methylcarbinol) is an almost colorless, neutral liquid that has limited miscibility with water and a weak, bitter, almond-like odor. It has a high solvency for alcohol-soluble cellulose nitrate, cellulose acetate, and cellulose acetobutyrate for many natural and synthetic resins and for fats and oils. In contrast to benzyl alcohol, it is miscible with white spirit. 

Ethyl acetate [79-20-9] is a colorless, neutral liquid that is partially miscible with water and has a pleasant, fruity odor. It has a good solvency for cellulose nitrate, cellulose ethers, chlorinated rubber, poly(vinyl acetate), vinyl chloride copolymers, polyacrylates, polystyrene, fats, oils, and many natural and synthetic resins (alkyd resins, saturated polyesters, ketone resins). Cellulose acetate is, however, dissolved only in the presence of small amounts of ethanol. Poly(vinyl chloride) is insoluble. 

Butyl diglycol [112-34-5] [2-(2-butoxyethoxy)ethanol, diethylene glycol monobutyl ether] is a clear, colorless, neutral liquid with a pleasantly mild odor. It is miscible with water and organic solvents, including aliphatic compounds. Butyl diglycol has a high solvency for cellulose nitrate, cellulose ethers, chlorinated rubber, poly(vinyl acetate), polyacrylates, and some oils, as well as for many synthetic resins, natural resins, and dyes. Polystyrene, poly(vinyl chloride), fats, and most oils are not dissolved. 

Using mixed solvents (e.g. ethyl acetate, ethanol and retarder such as ethoxypropanol) enables the printer to adjust solvency or evaporation rates by altering the relative proportions this is often necessitated by changes in ink composition, substrate or ambient air conditions. Where single solvents are used, printers are restricted by resin types and therefore the properties that can be achieved. In addition, adjustment to press conditions (e.g. web speed or air flow) is the only method available to control the evaporation rate and can be very time consuming leading to increased press downtime. 

Acetone, isopropanol and ethanol are used in the manufacture of nitrocellulose explosives. Again solvency properties are important. The alcohols are also used as damping materials for nitrocellulose resins, making them safe to handle and transport. 

Amyl acetate is used as an active solvent in nitrocellulose, cellulose esters, and cellulose ethers lacquers. Addition of ethanol to the amyl acetate enhances its solvency for these resins. The 2-ethyl hexyl acetate dissolves nitrocellulose and many other natural and synthetic resins. This slow evaporating solvent is useful in brushing and dipping lacquer applications. Cyclohexyl acetate is a useful solvent for nitrocellulose and cellulose ethers in spray and brushing lacquer applications. 

Table 14.4 lists the names and compositions of the fluorinated hydrocarbon solvent blends that were used in the past for cleaning applications. New replacement fluorinated solvents that have zero ozone depletion potential are also listed in Table 14.4. The physical properties of all the fluorinated solvents and blends are listed in Table 14.5. 1,1,2-Trichlorotrifluoroethane (CFC 113) has poor solvency for the soils normally encountered in cleaning operations. The patented Freon formulations from DuPont utilize CFC blends containing acetone, methanol, ethanol, isopropanol, and methylene chloride (Table 14.4)...

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