Antioxidant Additives for Lubricants

The crankcase of a gasoline or diesel engine is in reality a hydrocarbon oxidation reactor oil is submitted to strong agitation in the presence of air at high temperature (120°C) furthermore, metals such as copper and iron, excellent catalysts for oxidation, are present in the surroundings. 

Oxidation first produces soluble oxygenated compounds of molecular weights between 500 and 3000 that increase the viscosity of oil then they polymerize, precipitate, and form deposits. Oxidation also causes formation of low molecular weight organic acids which are very corrosive to metals. 

The lubricant oxidation mechanism is free-radical in nature and the additives act on the kinetic oxidation chain by capturing the reactive species either by decomposition of the peroxides, or by deactivation of the metal. 

Organic sulfur compounds such as sulfurized spermaceti oil, terpene sulfides, and aromatic disulfides have been used. Encumbered phenols such as di-tertiary-butylphenols and amines of the phenyl-alphanaphthylamine type are effective stopping the kinetic oxidation chain by creating stable radicals. 

However, the most widely used materials are the zinc dialkyl-dithiophosphates that have an anti-wear effect in addition to their antioxidant power and, besides, offer an attractive cost/effectiveness ratio. 

---

Polymer-type antioxidants have been prepared by Eriedel-Crafts reaction of -cresol andp- and/or y -chloromethylstyrene in the presence of boron trifluoride-etherate (198). The oligomeric product resulting from the alkylation of phenyl-a-naphthylamine using C12—15 propylene oligomer in the presence of AlCl or activated white clays is used as an antioxidant additive for lubricating oils (199). 

USE Formerly in the prodn of rocket fuels antioxidant additive for lubricants softener of copolymers. 

Among the butylenes, isobutylene has become one of the important starting materials for the manufacture of polymers and chemicals. There are many patents that describe the use of isobutylene or its derivatives to produce insecticides, antioxidants, elastomers, additives for lubricating oils, adhesives, sealants, and caulking compounds. Table 9 shows the use pattern of butylenes in the United States. 

Use Antioxidant, additive for high-pressure lubricants and greases, plasticizer and softening agent, antioxidant for edible fats and oils (up to 0.02% oil content). 

Zinc dithiophosphates The dominating position of ZnDTPs as additives for lubricating oils is due to their multifunctional performance. Not only do they act as antioxidants, but they also improve the wear inhibition of the lubricant and protect metals against corrosion. ZnDTPs are mainly used to formulate anti-wear hydraulic fluids and engine oils. 

C ref. index 1.4858 Toxicology LD50 (oral, rat) 100 mg/kg, (skin, rabbit) 810 mg/kg poison by Ing. and IP routes eye irritant mutagen TSCA listed Precaution Combustible Hazardous Decomp. Prods. Heated to decomp., emits very toxic fumes of Cl" and POx Storage Moisture-sensitive Uses Stabilizer and antioxidant for vinyl plastics intermediate for insecticides, flameproofing agents additive for lubricants, specialty soivs. 

Fuels, Lubricants, and Transmission Fluids. Polyol esters of neopentanoic acid have been used as high vacuum pumping hquids that are stable in chemically aggressive environments (70). Esters such as 6- -ani1inophenoxy)hexy1 pivalate are used as antioxidants for synthetic ester lubricants (71). PivaUc anhydride [1538-75-6] has been claimed as an antiknock additive for gasoline (72). 

The zinc. salts of these acids are extensively used as additives to lubricating oils to improve their extreme-pressure properties. The compounds also act as antioxidants, corrosion inhibitors and detergents. Short-chain dialkyl dithiophosphates and their sodium and ammonium salts are used as flotation agents for zinc and lead sulfide ores. The methyl and ethyl derivatives (RO)2P(S)SH and (RO)2P(S)CI are of particular interest in the large-scale manufacture of pesticides such as parathion, malathion, dimethylparathion, etc. For example parathion. which first went into production as an insecticide in Germany in 1947. is made by the following reaction sequence ... 

Used industrially as a textile finishing agent, antioxidant, paint solvent, additive for adhesives, additive for extreme pressure lubricant chemical intermediate for organic phosphorus compounds. 

The plasticizer-range alcohols are largely used as feedstock for production of high molecular weight diesters of phthalic, adipic, azelaic, and sulftiric acids. All these are used primarily in plasticizers for polyvinyl chloride (PVC) and other plastics. The plastics industry also uses them as additives for heat stabilization, to control the viscosity of PVC plastisols, ultraviolet absorbers, flame retardants, and antioxidants. They are also found in synthetic, lubricants, agricultural chemicals, and defoamers. 

Other contaminants that can originate from plastic containers are the additives necessary to turn the raw polymer into adequate containers. While PE may be used without any additive, the other plastics are virtually useless alone but are converted into highly serviceable products by combining them with other substances or materials. The additives most commonly found in plastics used for pharmaceutical products are antioxidants, heat stabilizers, lubricants, plasticizers, fillers, and colorants. These additives can be in liquid, solid, or fine particle forms and are used in amounts varying from less than 1% to more than 50% of the plastic mass. The additives necessary for each of the selected types of polymers are described in Table 23. 

Alternatively, the container may contain an opacifying agent, e.g., titanium dioxide. The use of multilayered bags was demonstrated to inhibit photochemical decomposition of vitamin E in TPN fat emulsions (Allwood and Martin, 2000). PVC films discolor on irradiative exposure due to photochemical degradation of the polymer (Hollande and Laurent, 1997). Plastic containers for parenteral use may contain several additives, e.g., antioxidants, stabilizers, plasticizers, lubricants, impact modifiers, and coloring matter when justified and authorized. In an appendix, the European Pharmacopoeia presents a list of plastic additives that may be used (European Pharmacopoeia, 2002). The additives should not be extracted by the contents in such quantities as to alter efficacy or stability of the product or to present any risk of toxicity (European Pharmacopoeia, 2002). However, organic additives extracted in concentrations below the detection limits of the analytical methods authorized by the European Pharmacopoeia may be sufficient to initiate photosensitized reactions in the formulation. 

One more important requirement for lubricating oils, which can be improved by adding additives, is the ability to keep their properties for a long time. One of the most important additives used to improve this ability of oils is antioxidants. 

The monograph states that the nature and amount of additive used will depend on the type of polymer, the process used to convert it into a container and the intended purpose of the container. Approved additives include antioxidants, stabilisers, plasticisers, lubricants, colour and impact modifiers. Anti-static and mould release agents can be used only for containers for oral and external preparations. Specific permitted additives are given in the specification for the material within the pharmacopoeial monograph. 

Additives in lubricants that extend the temperature range of their utility are antioxidants and control the acidity that would build up during use are important ingredients in most motor oils. Review three additives that are utilized [57-59] and explain the reasons for their beneficial properties. 

Poly(thioether)s should not be confused with poly(sulfide)s, in that the term poly refers directly to the sulfide linkage, i.e., —Sn—, but at the same time to a polymer. These types of polymers are used in a completely different field of application, e.g., additives for elastomers, antioxidants for lubricating oils, intermediates for the production of organic chemicals, insecticides, germicides, and as an additive to diesel fuels to improve the octane number and ignition qualities of these fuels. These polymeric types are not dealt with in this chapter. 

Chem. Descrip. Triisodecyl phosphite CAS 25448-25-3 EiNECS/ELiNCS 246-998-3 Uses Heat stabilizer for polyolefins, PU, PVC, PET, coatings, lubricants improves color in rigid and plasticized PVC chelating agent with metal carboxylates as polymer additives, esp. for chlorinated polymers such as PVC and chlorinated PE antioxidant and EP agent for lubricants Properties APHA 50 max. clear liq. sp.gr. 0.884-0.904 (25/15.5 C) dens. 7.4 Ib/gal vise. 15 cps acid no. 0.05 max. flash pt. (COC) 420 F ref. index 1.4530-1.4610 6.2% P Toxicology Skin irritant... 

Uses Antioxidant for lubricants, rubber, waxes monomer stabilizer insecticide mfg. of dyes polymerization inhibitor for acrylic ester monomers chain transfer agent in rubber prod. polymerization control agent in food-pkg. adhesives food and feed additive treatment of food-producing animals mfg. of chlorpromazine and related antipsychotic drugs anthelmintic drug antioxidant in dry rosin size in mfg. of paper/paper-board in contact with aq./fatty foods in food-contact rubber articles for repeated use... 

Toxicology LD50 (oral, rat) 6300 mg/kg TSCA listed Uses Antioxidant/stabilizer for polyolefins, polyamides, PU, PVC, PS, rubbers, cellulosics, food-grade polymers, food-pkg. adhesives antioxidant in lubricants for incidental food-contact use metal deactivator Regulatay FDA 21CFR 175.105,178.2010,178.3570 Manuf./Distrib. Ciba Spec. Chems./Addit. 

---