Lubricants pour point

White, waxy nearly odorless solids used as defoamers and feedstock for emulsifiers, lubricants, pour point depressants, and synthetic waxes and binders. 

For combined cycle turbines Single lubrication system Low pour point Extreme pressure and anti-wear properties Hydrolysis stability Water separation... 

Although lubricant base stocks have been subjected to dewaxing processes, they still contain large amounts of paraffins that result in a high pour point for the oil. In the paragraph on the cold behavior of diesel fuels, additives were mentioned that modify the paraffin crystalline system and oppose the precipitation of solids. 

The problem is similar to the case of lubricating oils polyalkylnaphthalenes or alkyl polymethacrylates called pour point depressants have been commercialized to lower the pour point. 

Examples of pour point depressants for lubricating oils. 

Long-chain esters of pentaerythritol have been used as pour-point depressants for lubricant products, ranging from fuel oils or diesel fuels to the high performance lubricating oils requited for demanding outiets such as aviation, power turbines, and automobiles. These materials requite superior temperature, viscosity, and aging resistance, and must be compatible with the wide variety of metallic surfaces commonly used in the outiets (79—81). 

Alkylated aromatics have excellent low temperature fluidity and low pour points. The viscosity indexes are lower than most mineral oils. These materials are less volatile than comparably viscous mineral oils, and more stable to high temperatures, hydrolysis, and nuclear radiation. Oxidation stabihty depends strongly on the stmcture of the alkyl groups (10). However it is difficult to incorporate inhibitors and the lubrication properties of specific stmctures maybe poor. The alkylated aromatics also are compatible with mineral oils and systems designed for mineral oils (see Benzene Toulene Xylenes and ethylbenzene). ... 

Practically all lubricating oils contain at least one additive some oils contain several. The amount of additive that is used varies from < 0.01 to 30% or more. Additives can have detrimental side effects, especially if the dosage is excessive or if interactions with other additives occur. Some additives are multifimctional, eg, certain VI improvers also function as pour-point depressants or dispersants. The additives most commonly used in hydrautic fluids include pour-point depressants, viscosity index improvers, defoamers, oxidation inhibitors, mst and corrosion inhibitors, and antiwear compounds. 

Low temperature filtration (qv) is a common final refining step to remove paraffin wax in order to lower the pour point of the oil (14). As an alternative to traditional filtration aided by a propane or methyl ethyl ketone solvent, catalytic hydrodewaxing cracks the wax molecules which are then removed as lower boiling products. Finished lubricating oils are then made by blending these refined stocks to the desired viscosity, followed by introducing additives needed to provide the required performance. Table 3 Usts properties of typical commercial petroleum oils. Methods for measuring these properties are available from the ASTM (10). 

Poly(alkylene glycol)s have a number of characteristics that make them desirable as lubricants. Compared to petroleum lubricants, they have lower pour points, a higher viscosity index, and a wider range of solubilities including water, compatibility with elastomers, less tendency to form tar and sludge, and lower vapor pressure (35). 

One hquid in this class intended for aircraft engine use is described in military specification MIL-L-87100 for operation from +15 to 300°C. Limitations of this class of synthetics are pour points of +5°C and higher, relatively poor lubricity, and high cost of 265/L ( 1000 + /gal) (44). Polyphenyl ether greases are available with good radiation resistance for appHcations in the temperature range of +5 to 288°C. 

Branched-chain acids have a wide variety of industrial uses as paint driers (7), vinyl stabilizers (8), and cosmetic products (9). Cobalt and manganese salts of 2-ethyIhexanoic acid and neodecanoic acid are used as driers for paint, varnishes, and enamels litbium, magnesium, calcium, and aluminum salts of 2-ethyIhexanoic acid are used in the formation of greases and lubricants (see Driers and metallic soaps). Derivatives of isostearic acid have been used as pour point depressants in two-cycle engine oils, as textile lubricants, and in cosmetic formulations. Further industrial appHcations can be found (10). 

Cosmetics. Castor od and its derivatives are utilized in cosmetic and personal care products. The low pour point and high viscosity produce lubricity and wetting properties desired in Hpsticks. Basic Hpstick contains 20—44 wt % castor od, which also acts as an ideal dispersant for pigments (116). One Hpstick formula contains 38 wt % castor od and 9.5% glycerol monoricinoleate (117). 

A number of higher n-alkyl methacrylate polymers have found commercial usage. The poly-(n-butyl-), poly-(n-octyl-) and poly-(n-nonyl methacrylate)s have found use as leathering finishes whilst polyflauryl methacrylate) has become useful as a pour-point depressant and improver of viscosity temperature characteristics of lubricating oils. 

This technology has been utilized by BP Chemicals for the production of lubricating oils with well defined characteristics (for example, pour point and viscosity index). It is used in conjunction with a mixture of olefins (i.e., different isomers and different chain length olefins) to produce lubricating oils of higher viscosity than obtainable by conventional catalysis [33]. Unichema Chemie BV have applied these principals to more complex monomers, using them with unsaturated fatty acids to create a mixture of products [34]. 

The pour point of the lubricant should be at least 10°C lower than the expected minimum ambient starting temperature. If the ambient starting temperature approaches the pour point, sump heaters may be required to ease starting and ensure adequate lubrication. Viscosity ranges are provided to allow for variations such as surface finish, temperature rise, loading and speed. 

Because the paraffin and mixed-base crudes yield lubricating oil fractions of high quality, means had to be devised in the early days of the petroleum industry to separate the wax from the oil. The removal of wax from petroleum fractions is one of the most important phases in the production of lubricating oils and fuel oils of low pour point, and has received the attention of many investigators. 

The process is applicable to the full range of lubricating oil stocks, including distillate and residual fractions (18), and unrefined stocks as well as those which have received selective solvent treatment. In production of oils of 0° F. pour point, the difference between the temperature of filtration and the pour point is usually 30° to 40° F. 

Before 1925, there were a few compounded oils made for special purposes, such as lubrication of marine engines and steam cylinders, but additives were not used in automotive crankcase oils. In the 1930 s, chemical compounds made by condensation of chlorinated paraffin wax with naphthalene were found to lower the pour points of oils. Pour depressants (9) apparently are adsorbed on small wax crystals which separate from oils when they are chilled. The protective adsorbed layer of additive prevents the normal interlacing of larger wax crystals which forms a gel. In 1934 polymerized unsaturated hydrocarbons first came into large scale commercial use to lower the temperature coefficient of viscosity of oils. Other compounds for increasing the viscosity index of oils have since become common. 

More recent developments in this country have included synthesis of relatively stable oils of low volatility, low pour point, and high viscosity index by esterification of octyl alcohols, such as 2-ethylhexanol, with dibasic acids such as adipic acid and sebacic acid (3). Octyl alcohols may be synthesized from petroleum hydrocarbons via the oxo process. Although of relatively high cost, these synthetic oils find general application in making greases for lubrication of antifriction bearings and instruments in aircraft. 

The unusual properties of silicones make them useful for some special applications as lubricants (20). They are relatively resistant to deterioration by heat or oxidation, and have the desirable properties of high viscosity index, low pour point, and low volatility. They may promote wear in steel-to-steel bearing surfaces under conditions of sliding friction, and are not generally useful for such applications. Silicones are satisfactory lubricants in antifriction bearings and in some bearing combinations other than steel sliding on steel. 

These processes have made available a variety of microcrystalline waxes of low oil content and valuable properties (44) Neutral and bright stock lubricating oils with pour points of —30° to 0° F. have also become available commonly as result of this notable advance in technology. 

POUR POINT DEPRESSANT. An additive for lubricating and automotive oils that lowers the pour point (or increases the flow point) by 11.0°C. The agents now generally used are polymerized higher esters of acrylic add derivatives. They are most effective with low-viscosity oils. See also Petroleum. 

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