Antiwear additives

Sulfuiized and sulfurchlorinated unsaturated compounds and meicaptans are used as lubricant additives (antiwear, friction modification, load-carrying, extreme pressure and temperature, corrosion inhibition, and antioxidants), refinery catalyst regeneration compounds, steel processing (annealing) aids, and vulcanization catalysts (see Lubrication and lubricants). 

Though ashless dispersants made by Mannich condensation reaction, functionalized ethylene-propylene dispersants, and succinate ester dispersants can be used in ATF formulations, succin-imide dispersants are more commonly nsed. The dispersants used in ATFs have similar chanistries as those described in engine oil applications, except in most cases the molecular weights of the polyisobutyl hydrocarbon chain of the dispersants used in ATFs are lower. Furthermore, the dispersant molecules are reacted with boric acid and caped with additional antiwear chemistries. 

Lubricants, Fuels, and Petroleum. The adipate and azelate diesters of through alcohols, as weU as those of tridecyl alcohol, are used as synthetic lubricants, hydrauHc fluids, and brake fluids. Phosphate esters are utilized as industrial and aviation functional fluids and to a smaH extent as additives in other lubricants. A number of alcohols, particularly the Cg materials, are employed to produce zinc dialkyldithiophosphates as lubricant antiwear additives. A smaH amount is used to make viscosity index improvers for lubricating oils. 2-Ethylhexyl nitrate [24247-96-7] serves as a cetane improver for diesel fuels and hexanol is used as an additive to fuel oil or other fuels (57). Various enhanced oil recovery processes utilize formulations containing hexanol or heptanol to displace oil from underground reservoirs (58) the alcohols and derivatives are also used as defoamers in oil production. 

The fluid is formulated from a premium mineral od-base stock that is blended with the required additive to provide antiwear, mst and corrosion resistance, oxidation stabdity, and resistance to bacteria or fungus. The formulated base stock is then emulsified with ca 40% water by volume to the desired viscosity. Unlike od-in-water emulsions the viscosity of this type of fluid is dependent on both the water content, the viscosity of the od, and the type of emulsifier utilized. If the water content of the invert emulsion decreases as a result of evaporation, the viscosity decreases likewise, an increase in water content causes an increase in the apparent viscosity of the invert emulsion at water contents near 50% by volume the fluid may become a viscous gel. A hydrauHc system using a water-in-od emulsion should be kept above the freezing point of water if the water phase does not contain an antifreeze. Even if freezing does not occur at low temperatures, the emulsion may thicken, or break apart with subsequent dysfunction of the hydrauHc system. 

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. 

Antiwear Compounds. Additives are used in many lubricating oils to reduce friction, wear, and scuffing and scoring under boundary lubrication conditions, ie, when fuU lubricating films cannot be maintained. Two general classes of materials are used to prevent metallic contact. 

Siace surface reactions iavolved with antiwear and EP additives depend not only on the type of mbbiag materials but also oa operatiag temperature, surface speed, and corrosion questions, selection should be carefully iategrated with the oil type, machine design, and operatiag coaditioas. 

The principal valeraldehyde derivatives, -amyl and 2-methylbutyl alcohols, are used predominandy to make ziac diamyldithiophosphate lube oil additives (see Amyl alcohols Lubrication and lubricants), which are employed primarily in automotive antiwear appHcations. Similady, the / -valerate and 2-methylbutyrate esters of pentaerythritol and trimethylolpropane are used ia aeromotive synlube formulations and as refrigerant lubricants. 

Table 8 summarizes domestic consumption by use for amyl alcohols. About 55% of the total 1-pentanol and 2-methyl-1-butanol production is used for zinc diamyldithiophosphate lubrication oil additives (150) as important corrosion inhibitors and antiwear additives. Amyl xanthate salts are useful as frothers in the flotation of metal ores because of their low water solubiUty and miscibility with phenoHcs and natural oils. Potassium amyl xanthate, a collector in flotation of copper, lead, and zinc ores, is no longer produced in the United States, but imports from Germany and Yugoslavia were 910 —1100 t in 1989 (150). 

Applications. The capabiHties of a gc/k/ms in separating and identifying components in complex mixtures is very high for a broad spectmm of analytical problems. One area where k information particularly complements ms data is in the differentiation of isomeric compounds. An example is in the analysis of tricresyl phosphates (TCPs) used as additives in a variety of products because of thek lubricating and antiwear characteristics (see Lubrication and lubricants). One important use of TCPs is in hydrauHc fluid where they tenaciously coat metal surfaces thereby reducing friction and wear. Tricresyl phosphate [1330-78-5] (7.2 21 exists in a variety of isomeric forms and the commercial product is a complex mixture of these isomers. 

In the lightening of petroleum hydrocarbon oil, esters of mercaptocarboxyhc acids can modify radical behavior during the distillation step (58). Thioesters of dialkanol and trialkanolamine have been found to be effective multihinctional antiwear additives for lubricants and fuels (59). Alkanolamine salts of dithiodipropionic acid [1119-62-6] are available as water-soluble extreme pressure additives in lubricants (60). 

Hydraulic Fluids and Lubricants. The use of borate esters in hydrauHc fluids (qv) and lubricants (see Lubrication and lubricants) has been described in numerous patents (40,43,44). A variety of borate esters have been described that can be used as multiflinctional lubricant additives having antiwear and antifriction properties (45). 

Lubrication Additive. Cerium fluoride, CeF, can be used as an additive to lubricant formulations to improve extreme pressure and antiwear behavior (43). The white soHd has a crystal stmcture that can be pictured as [CeF] layers separated by [F] atom sheets, a layer stmcture analogous to that of M0S2, a material that CeF resembles in properties. 

Chlorinated paraffins with the general molecular formula x 2x-y+2) have been manufactured on a commercial basis for over 50 years. The early products were based on paraffin wax feedstocks and were used as fine retardants and plasticizers in surface coatings and textile treatments and as extreme pressure—antiwear additives in lubricants. The development of chlorinated paraffins into new and emerging technologies was constrained principally because of the limitations of grades based on paraffin wax and the lack of suitable alternative feedstocks to meet the demands of the new potential markets. 

Ethers, esters, amides and imidazolidines containing an epithio group are said to be effective in enhancing the antiwear and extreme pressure peiformance of lubricants. Other uses of thiiranes are as follows fuel gas odorant (2-methylthiirane), improvement of antistatic and wetting properties of fibers and films [poly(ethyleneglycol) ethers of 2-hydroxymethyl thiirane], inhibition of alkene metathesis (2-methylthiirane), stabilizers for poly(thiirane) (halogen adducts of thiiranes), enhancement of respiration of tobacco leaves (thiirane), tobacco additives to reduce nicotine and to reduce phenol levels in smoke [2-(methoxymethyl)thiirane], stabilizers for trichloroethylene and 1,1,1-trichloroethane (2-methylthiirane, 2-hydroxymethylthiirane) and stabilizers for organic compounds (0,0-dialkyldithiophosphate esters of 2-mercaptomethylthiirane). The product of the reaction of aniline with thiirane is reported to be useful in the flotation of zinc sulfide. 

For use in lubrication oils Ca salts of isostearyl ether carboxylic acids are described as multifunctional additives to achieve a good water tolerance of the oil and good antiwear characteristics [182]. 

Moreover, stable liquid systems made up of nanoparticles coated with a surfactant monolayer and dispersed in an apolar medium could be employed to catalyze reactions involving both apolar substrates (solubilized in the bulk solvent) and polar and amphiphilic substrates (preferentially encapsulated within the reversed micelles or located at the surfactant palisade layer) or could be used as antiwear additives for lubricants. For example, monodisperse nickel boride catalysts were prepared in water/CTAB/hexanol microemulsions and used directly as the catalysts of styrene hydrogenation [215]. 

Adhesion promoters Antifogging agents Antistatic agents Antiwear additives Coupbng agents... 

SFE has been used extensively in the analysis of solid polymers. Supercritical fluid extraction of liquid samples is undertaken less widely because dissolution or entrainment of the matrix can occur. As illustrated elsewhere SFE has also been applied for the analysis of liquid poly(alkylene glycol) (PAG) lubricants and sorbitan ester formulations [370]. The analysis of PAG additives (antioxidants, biocides and anticorrosion, antiwear and antifoaming agents) is hindered by the presence of the low molecular weight PAG matrix (liquid) and therefore a method for the selective separation of additives from PAG is required. The PAG... 

In the area of process monitoring TLC has been used for the study of the thermal decomposition of zinc di-isopropyl dithiophosphate (antiwear additive in lubricating oils) [458]. TLC analysis has been reported as a quality control tool for analysis of dispersing agents (alkylsalicylates, thioalkylphenolates), AOs (dithiophosphates, dialkyldithiophosphates) and their intermediates in lubricating oil (UV detection,... 

GC-MS and GC-AED techniques were used for the direct analysis of used tyre vacuum pyrolysis oil [255]. Antioxidants and antiwear additives (0.25-5 wt% DODPA, a-NPA, TCPs, TPP, IPPs) in lubricating synthetic oils, essentially esters of branched-chain alcohols such as pentaerythritol, neopentylglycol and trimethylolpropane, were determined by means of GC-SIM-MS using diphenylamine (DPA) as an internal standard [256] similarly, TCPs, TPP, IPPs, DPs and I2P were quantitatively analysed by GC-FPD using triethylphosphate (TEP) as an internal standard. RSD values of 3-6% were reported for GC-SIM-MS, and 7-9 % for GC-FPD. 

Zinc dialkyldithiophosphates (ZDDPs), which act as antiwear additives in lubricating oils and were postulated to exist in various molecular forms (monomer, dimer or neutral form, and basic form), were studied by multi-edge (Zn K-, P K- and S K-) XAS for structural assessment [311]. Grazing incidence absorption spectroscopy measurements have provided evidence for breakdown of the ZDDP molecule following its adsorption on to a steel substrate surface [312]. XANES and CEMS were used to study the interaction of per-fluoropolyalkyl ether (PFPAE) additives with Fe-based alloys [313],... 

In addition, organophosphate esters also are used as antiwear additives in hydraulic fluids and other lubricants of the organophosphate esters discussed in this profile, Durad 110, 125, 220B, and 300 are categorized by their manufacturers as antiwear additives and not as hydraulic fluids (FMC 1991c, 1991 d, 1992a, 1992b Marino and Placek 1994). 

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