Additives crystal modifiers

Uses Lubricant for thread finishes wax additive crystal modifier thickener emulsifier, opacifier in cosmetics emulsifier, solubilizer, dispersant for foods and pharmaceuticals Regulatory FDA 21CFR 172.854 Manuf./Distrib. ASiE Connock http //WWW. connock. co. uk Trade Name Synonyms Calgene PGS-1010 t[Lambent Tech, http //www.petroferm.com], Caplube 8448 f[ABITEC http //www.abiteccorp.com]-, Caprol 10G10S t[ABITEC http //www.abiteccorp.com], Caprol JB t[ABITEC http //www.abiteccorp.com], DREWMULSE 10-10-S t[Stepan http //www.Stepan, com]... 

Uses Lubricant for thread finishes wax additive crystal modifier thickener emulsifier, opacifier in cosmetics emulsifier, solubilizer, dispersant for foods and pharmaceuticals... 

The impurity interacts with the band structure of the host crystal, modifying it, and often introducing new levels. An analysis of the band structure provides information about the electronic states of the system. Charge densities, and spin densities in the case of spin-polarized calculations, provide additional insight into the electronic structure of the defect, bonding mechansims, the degree of localization, etc. Spin densities also provide a direct link with quantities measured in EPR or pSR, which probe the interaction between electronic wavefunctions and nuclear spins. First-principles spin-density-functional calculations have recently been shown to yield reliable values for isotropic and anisotropic hyperfine parameters for hydrogen or muonium in Si (Van de Walle, 1990) results will be discussed in Section IV.2. 

Operability additives must often be used at high treat rates, 1,000 ppm or higher, to obtain a reduction in LTFT temperature greater than 10°F (5.6°C). Some wax crystal modifiers provide LTFT performance. However, as with operability additives, the performance should always be evaluated before use. 

The addition of a wax crystal modifier to diesel fuel is a common and well-accepted alternative to kerosene dilution. Wax crystal modifiers are typically polymeric compounds which have the ability to co-crystallize with wax to alter the size, shape, and structure of the wax crystal lattice. 

The most common type of wax crystal modifier used to reduce the pour point and filtration temperature of distillate fuel is based on ethylene vinylacetate (EVA) copolymer chemistry. These compounds are quite common throughout the fuel additive industry. The differences, however, are found in the variation in the molecular weight and the acetate ratio of the copolymer. 

It is known that wax can begin the process of organization into a crystal structure above the actual, observable cloud point temperature. Because of this fact, the wax crystal modifier should be added at a temperature at least 20°F (11.1°C) above the cloud point of the fuel. Addition at this higher temperature helps to ensure that the modifier is completely solubilized in the fuel prior to the formation of the wax crystals. 

When wax crystal modifiers are added to cold fuel, even to fuel well above its cloud point, modifiers may not dissolve properly. The polymeric nature of wax crystal modifiers makes them quite viscous at low temperatures. Additive suppliers will often provide modifiers in a highly dilute form (i.e., 10% or 20% solution), so they will remain fluid at low temperatures. 

However, if a typical, nondiluted wax crystal modifier is added to fuel which is at a cold temperature of+10°F to +20°F (-12.2°C to -6.7°C), it may not dissolve completely in this fuel. The result will be additive accumulation as a viscous layer at the bottom of a fuel or storage tank. Ultimately, the additive will be trapped by a filter as it flows from the tank. 

A second, and even worse possibility, would be the addition of cold additive to cold fuel. In this case, the additive would not dissolve at all and would set as a gelled mass at the bottom of the fuel tank. When the gelled wax crystal modifier does move from the tank, it may plug a cold fuel line or filter. If allowed to reach a pump, the gelled additive could cause sticking of pistons or other pump parts. 

Occasionally, wax crystal modifiers will not provide the performance anticipated. Either the response to additive treatment was much less than expected or no response was obtained. When this occurs, it is quite possible that the fuel was previously treated with a wax crystal modifier. Under these circumstances, the expected performance of secondary treatment with wax crystal modifier is minimal. 

Some chemical additives such as corrosion inhibitors, wax crystal modifiers, detergents, and demulsifiers provide performance which is difficult to duplicate through refining without adversely affecting some other fuel property. Other additives such as metal chelators, fuel sweeteners, biocides, lubricity improvers, foam control agents and combustion enhancers can also be used to solve fuel performance problems. 

In addition to refining techniques, compounds identified as wax crystal modifiers are available for use in contending with the effects of wax in fuels. Wax crystal modifiers, also called pour point depressants or cold flow improvers, are typically polymeric compounds which have the ability to crystallize with fuel wax as it forms. By co-crystallizing with wax, the modifiers typically effect a change in the size, shape, and conformation of wax crystals. Other wax crystal modifiers function by dispersing or inhibiting the nucleation or growth of wax crystals within a fuel or oil. 

Distillate fuel filtration temperatures can be reduced by 10°F to 18°F (about 5°C to 10°C) by most wax crystal modifiers. Greater response is possible, but additive treating rate can be quite high. Also, fuels with low initial filtration temperatures often respond more effectively to wax crystal modifier treatment than high-filtration-temperature fuels. 

Fuels treated with a cloud point improver (CPI) may require additional CPI treatment whenever a wax crystal modifier is used to reduce the pour point of the fuel. Often, the cloud point of a CPI-treated fuel will increase whenever a pour point improver is used. To compensate for this phenomenon, additional CPI must be added to recover the lost performance. 

If testing indicates that the oil has reversion tendencies, the addition of higher treating rates of a wax crystal modifier can sometimes overcome the reversion problem. 

Sometimes, reversion tendencies cannot be overcome by the addition of higher treat rates of a wax crystal modifier. Under these circumstances, only dilution by low-viscosity products or the constant addition of heat will keep the oil fluid at temperatures below its base pour point. 

Additive A chemical substance added to a product to impart or improve certain properties. Typical fuel additives include antioxidants, cetane improvers, corrosion inhibitors, demulsifiers, detergents, dyes, metal deactivators, octane improvers, and wax crystal modifiers. 

Addadi and coworkers (1985) have shown that chirality can be induced by the use of selective additives which modify crystal morphology. Thus, when (R, S)-threonine is crystallized in the presence of impurities, enantiomeric excess greater than 95% is readily obtained. The strategy also affords a means of determining the absolute configuration of the additive molecule. 

Proceeding from the aforesaid, it is possible to admit, that modified hexsaazocyclanes PETP - fibres possess the greater degree crystalline state. It once again confirms the conclusion made earlier, that entered molecules hexsaazocyclanes become the additional centers of crystallization, thus, increasing a degree crystallization modified PETP - fibers. 

Dry or solvent free crystallization is also possible but these methods often require the addition of crystal modifiers that become incorporated into the product (108). Losses during crystallization can be very high as the crystals entrain large amounts of fatty acid. However, these losses may be reduced by physically pressing the crystals to remove the entrained solution (109). Linoleic acid-rich products of dry crystallization would be preferred starting materials for CLA production over those of solvent crystallized products but the losses incurred in dry crystallization may prohibit this method of manufacture. Crystal modifiers may be selected so that they do not adversely affect the quality or acceptance of the final product. 

More conventional chemical treatments (sometimes referred to as inhibition) use one or more of four groups of additives that includes threshold agents, crystal modifiers, dispersants and surfactants. 

As described in Chapter 8 robust crystal stmctures can be produced under certain conditions, but that crystal structure and growth may be affected by the presence of impurities. The effect is utilised in scale control by the use of additives. Unlike threshold treatment the use of crystal modifiers does not prevent... 

These authors demonstrate the effectiveness of a threshold agent (aceto diphosphonic acid) and a crystal modifying additive (polymaleic acid) Fig. 14.4 shows the plot of fouling resistance with time and it will be evident that the asymptotic fouling resistance has been reached in each example. The fouling resistance in the presence of both these additives is significantly less than that obtained with no inhibitor present. 

It is of interest to gauge performance of additives against the Ryznar Index for the water. Fig. 14.7 shows the effect of the threshold additive acetodiphosphonic acid and the crystal modifier polymaleic acid at different Ryznar indices. As would be expected from the definition of the Ryznar Index, the scaling is increased as the index is reduced when there is no additive present. In the presence of the threshold agent the rate of scaling is also reduced but below a Ryznar Index of about 4.5, the threshold effect is exceeded and the scaling rate rapidly rises. 

Crystal modifiers may be added to liquids subject to freezing fouling, e.g. crude oils to reduce the problem of wax deposition. The principal difficulty here is generally the cost of the treatment as large quantities of additive are required to be effective. 

In Chapter 14 the use of additives to combat potential fouling was discussed. In the use of chemical treatment for cooling water there has to be an emphasis on effective and rapid dispersion since the concentration of the additives employed must be low, i.e. a few mg/l where possible, to minimise cost and to reduce potential pollution problems. In general the additive formulation will be based on the need to limit corrosion (i.e. the use of corrosion inhibitors), scale formation (i.e. the use of crystal modifiers, dispersants or threshold chemicals or a combination) and biofouling (i.e. the use of biocides and dispersants). In many installations additives are injected on the suction side of the main pump so that turbulence within the pump will provide rapid mixing. In very large cooling systems multiple injection nozzles will be required to enhance distribution. 

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