Improvements in or relating to synthetic lubricant compositions

Abstract

Abstract A lubricant composition comprises essentially a mono-hydroxy 1,2-polyoxypropylene fluid which is the addition product of a monohydric alcohol with 1,2-propylene oxide together with a small amount of an addition agent selected from one of the classes of compounds enumerated below, said addition agent being adapted to reduce consumption, maintain a substantially uniform viscosity during use, retard or repress corrosive conditions and to eliminate objectionable odours in the said composition. The composition is particularly suitable for engine crank-case lubrication. The monohydric alcohol includes any aliphatic or aromatic monohydroxy compound including phenols and naphthols, though these are not alcohols in the strict sense of the term. The most desirable polyoxypropylene monohydroxy base fluids are those made under such conditions that the reaction product is a material of high molecular weight substantially free from ash forming compounds or dark coloured diluents. The preparation is carried out in a closed system by adding the moisture-free 1, 2-propylene oxide with or without a small amount of ethylene oxide to the monohydroxy alcohol in the presence of an alkaline catalyst such as sodium or potassium hydroxide or the alcoholate of the alcohol used at a temperature within the range 80-130 DEG C. After the reaction has proceeded to the desired extent the catalyst is neutralized with acid, e.g. sulphuric acid or carbon dioxide and water and a solvent for the reaction product added, the layers separated and the polyoxypropylene compounds separated from the solvent layer. Suitable alcohols which may be used are methanol, ethanol, isopropanol, n-butanol, 2-ethylbutanol, n-hexanol, 2-ethylhexanol, n-octanol, tetradecanol, heptadecanol, benzyl alcohol, methyl phenyl carbinol and the like, phenols and naphthols. The products retain adequate body at high temperatures and do not become unusually viscous at low temperatures. The more useful fluids show a viscosity of more than 70 Saybolt Universal Seconds at 100 DEG F. or upwards of 3 centistokes at 210 DEG F. (for some purposes a viscosity of at least 125 Saybolt Universal Seconds is desirable), and retain flowability on cooling to -20 DEG F. or below. They also possess the property of maintaining a high degree of engine cleanliness under high temperature operating conditions. Decomposition by heat generated at hot spots occurs without excessive carbonisation and fouling by tarry deposits, the decomposition products being compounds largely of a volatile nature. The additives which may be incorporated in the monohydroxy 1, 2-polyoxypropylene fluids for the purposes enumerated above possess anti-oxidant characteristics, but it does not follow that any oil anti-oxidant will be capable of retarding consumption of the new synthetic lubricants. The additives fall into four categories: (1) phenols, including mono-, di-, and trihydric phenols, and substitution products thereof in other than the hydroxyl hydrogen; (2) aromatic amines, with one or more NH2 groups attached directly to the aromatic nucleus, including primary, secondary and tertiary amines; (3) organic bi-valent sulphur-bearing compounds such as mercaptans, amine sulphides, thioamides and thioanilides; (4) aromatic nitro-compounds, such as m-dinitrobenzene, 1-5-dinitronaphthalene and the like. Particularly effective results have been obtained with o-diamino aromatic compounds, secondary aromatic amines and phenols. The preferred weight of the additive is usually from about 1.0 per cent to 4.0 per cent by weight of the monohydroxy 1,2-polyoxypropylene fluid; as an over-all range, 0.2 per cent to 8.0 per cent is considered suitable. Data from full-scale engine tests are given, showing in the first instance the improvement by incorporating additives as described with the synthetic base fluid, and secondly a comparison in lubricant characteristics of the new synthetic lubricant composition with very good, aviation grade commercial mineral oils.ALSO:Polyoxypropylene ethers are prepared by reacting 1 : 2-propylene oxide with a monohydric alcohol in the presence of an alkaline catalyst by the method of Specification 601,604, as open to inspection under Sect. 91. The term "monohydric alcohol" is used in the present Specification in a wider sense than in Specification 601,604, included within it being any aliphatic or aromatic monohydroxy compound including phenols and naphthols, although these are not alcohols in the strict sense. The moisture-free 1 : 2-propylene oxide (with or without a small amount of ethylene oxide) is added to the monohydroxy alcohol in a closed system in the presence of a catalyst such as sodium or potassium hydroxide or the alcoholate of the alcohol used at a temperature within the range 80-130 DEG C. After the reaction has proceeded to the desired extent, the catalyst is neutralized with sulphuric or other acid, a solvent for the reaction product added, the layers separated and the polyoxypropylene compounds separated from the solvent layer. Suitable alcohols which may be used are methanol, ethanol, isopropanol, n-butanol, 2-ethylbutanol, n-hexanol, 2-ethylhexanol, n-octanol, tetradecanol, heptadecanol, benzyl alcohol, methyl phenyl carbinol and phenols and naphthols. The examples given of preparation of these polyoxypropylene ethers are identical with those given in Specification 601,604, as open to inspection under Sect. 91 with the exception of example 6, which deals with but does not describe in any detail the preparation of addition products of 1 : 2-propylene oxide with benzyl alcohol, phenol and b -naphthol. The addition products so obtained are used together with additives as lubricants (see Group III).

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