US3478107A - Branched chain butyl formaldehyde mercaptals - Google Patents

Description

United States Patent BRANCHED CHAIN BUTYL FORMALDEHYDE MERCAPTALS Billy Dale Vineyard, St. Louis, Mo., assignor to Monsanto Company, St. Louis, Mo., a corporation of Delaware No Drawing. Filed Feb. 6, 1967, Ser. No. 614,038 Int. Cl. C07c 149/10; Cm 1/38 U.S. Cl. 260-609 2 Claims ABSTRACT OF THE DISCLOSURE Branched-chain alkyl formaldehyde mercaptals which are useful as antiwear additives in lubricating oils.

This invention relates to certain new formaldehyde mercaptals and their use as antiwear additives in lubricating oil compositions.

As a result of the trend towards lower ash-containing lubricating oil compositions primarily through the use of non-metallic detergents, the ability of such compositions to control the wear of vital engine parts, for example, the valve train assembly, has become more difiicult. As a result, the use of metal-containing antiwear and/or extreme pressure (E.P.) additives has been increased in order to overcome the shortcomings of the non-metallic detergents. Obviously, such a solution of the wear problem is not consistent with the desire for a completely non-metallic formulation.

Accordingly, it is an object of this invention to provide certain non-metallic antiwear and/or E.P. additives which for convenience are hereinafter merely referred to as antiwear additives. It is a further object of this invention to provide non-metallic antiwear agents which can be substituted for present metallic antiwear additives, for example, zinc phosphorodithioates, to provide nonmetallic, ashless or low-ash lubricating oil compositions.

The formaldehyde mercaptals of the present invention are those represent by the structure where R and R are each independently branched-chain alkyl radicals having from 3 to 4 carbon atoms. The mercaptals of this invention can be prepared by reacting formaldehyde with a suitable mercaptan by procedures known to the art. The following examples will illustrate typical preparations of the mercaptals of this invention. Parts are parts by weight.

Example 1 Into a suitable reaction mixture there was charged 180 parts (2.0 moles) of tert.-butyl mercaptan and 30 parts (1.0 mole) of paraformaldehyde. Hydrogen chloride gas was bubbled through this mixture for 3 hours while maintaining the reaction mass at a temperature 'of -30 C. After completion of the hydrogen chloride addition, two layers formed, the lower of which, the aqueous layer, was removed. The organic layer was then extracted with hexane, washed with water and dried, after which the hexane was stripped and the remaining product frac tionated to give 170 parts of di-tert.-butyl formaldehyde mercaptal and had an index of refraction, n of 1.4903.

Example 2 The procedure of Example 1 was repeated using 125 parts (1.4 moles) of sec.-butyl mercaptan and 22.5 parts (0.75 mole) of paraformaldehyde. The desired pro-duct, di-sec.-butyl formaldehyde mercaptal, was obtained with 72% yield. The product had an index of refraction n of 1.4925.

3,478,107 Patented Nov. 11, 1969 Example 3 The procedure of Example 1 was repeated employing 152 parts (2.0 moles) of isopropyl mercaptan and 30 parts (1.0 mole) of paraformaldehyde. The desired product, diisopropyl formaldehyde mercaptal, was obtained with 82.5% yield.

The following example illustrates the preparation of a mixture of the mercaptals of this invention utilizing a mixed alkyl mercaptan.

Example 4 A mixture of 36 parts (0.4 mole) of tert.butyl mercaptan and 36 parts (0.4 mole) of sec-butyl mercaptan is saturated with about 0.2-0.4 part of hydrogen chloride. A formalin solution (0.4 mole of formaldehyde) is slowly added over approximately one hour. The reaction is quite exothermic and a temperature of 25-30 C. is maintained by cooling as well as controlling the rate of formalin addition. During the formalin addition, approximately 3-4 parts of HCl gas is added, then the reaction mixture is stirred for 6 hours at 25-30", while HCl gassing is continued at the rate of 1.5-2 parts/hour. The total HCl usage is approximately 13 parts. At the end of the hold period, HCl gassing and stirring is stopped and the lower aqueous layer is: allowed to separate. After drawing off the water layer, the organic layer is washed once with 20 parts of water, once with 20 parts of 2.5% lye solution and twice with 210 parts of water. The crude product is finally stripped at and 30 mm. Hg for one hour to provide 73.9 parts of a statistical mixture of disec.-butyl formaldehyde mercaptal, di-tert.- butyl formaldehyde mercaptal and see-butyl, tert.butyl formaldehyde mercaptal.

The mixed formaldehyde mercaptals of this invention, that is, those in which R and R are different alkyl groups, can be prepared in pure form, that is, not in a mixture such as Example 4, by reacting a suitable mercaptan with formaldehyde and HCl to provide a chloromethyl alkyl sulfide which in turn is reacted with a sodium mercaptide of a suitable structure in order to provide the desired compound. A typical procedure of such formaldehyde mercaptals is illustrated by Example 5 below.

Example 5 A mixture of 18 parts (0.2 mole) of tert.-butyl mercaptan, 6 parts (0.2 mole) of formaldehyde (as paraformaldehyde) and 30 ml. of ethanol is charged to the flask and cooled to 0 C. Gaseous HCl is passed slowly into the stirred solution maintained at 0", until 7.3 parts (0.2 mole) of the acid have been added. The aqueous layer is removed and the tert.-buty1 chloromethyl sulfide recovered by fractionation distillation under reduced pressure.

To a prepared solution of 4.6 parts (0.2 g. atm s.) of sodium and 40 ml. of ethanol, sec.butyl mercaptan (18 parts, 0.2 mole) and 27.7 parts (0.2 mole) of tert.-butyl chloromethyl sulfide are added. Heat is evolved during the addition of the chloromethyl sulfide. The resulting mixture is stirred for an additional 3 hours; after filtration the solvent is stripped under vacuum. The residual product is subjected to vacuum distillation to provide tert.-butyl, sec.-butyl formaldehyde mercaptal.

Examples of other formaldehyde mercaptals of this invention include isopropyl-sec.-butyl formaldehyde mercaptal, diisobutyl formaldehyde mercaptal, isobutyl, tert.- butyl formaldehyde mercaptal and isobutyl, sec.-butyl formaldehyde mercaptal.

Lubricating oils which can be used as base oils to which the formaldehyde mercaptals of this invention are added include those having a naphthenic, paraflinic or other hy drocarbon base as well as lubricating oils derived from coal products and also synthetic oils such as the alkylene polymers, alkenylene oxide polymers, dicarboxylic acid esters, alkylated benzene silicate esters, silicon polymers, polyphenyl ethers, polyphenyl thioethers and the like. The concentration of the mercaptals of this invention in lubricating oils generally used to improve the antiwear properties of the base oil can range from as low as about 0.01% to about 10% by weight.

Two tests were utilized to demonstrate the ER or antiwear properties of the mercaptals of this invention. These tests were the Four-Ball Wear Test and the GMMS (Oldsmobile) Sequence I Test. Utilizing these tests, the following results were noted.

TABLE I Four-ball wear test Mercaptal, Example: Scar diameter, mm.

4 0.40 Base oil 2.13

All tests at 45 kg. loading for 10 minutes at a speed of 1300 r.p.m. Additive concentration was 0.5% by weight.

NOTE-All tests were run at an additive concentration of 0.25% by weight.

Of the formaldehyde mercaptals of this invention, disee-butyl formaldehyde mercaptal and see-butyl, tert.- butyl formaldehyde mercatpal are outstanding. For example, it has been found that the sec.-butyl, tert.-butyl formaldehyde mercaptal mixture of Example 4 shows essentially no increase in average wear in the Sequence I Test to a concentration as low as 0.04% by weight.

From the above, it is clear that the addition to lubricating oils of the formaldehyde mercaptals of this invention brings with it a substantial improvement in the ER or antiwear qualities of said oils. Nevertheless, the greater proportion of the commercial lubricating oils sold today is subject to a large number of uses and it is, therefore, generally necessary to employ more than one type of additive in a finished lubricant formulation. Thus, the mercaptals of this invention can be used in combination with other types of additives such as metal-containing and/or non-metallic dispersants, corrosion inhibitors, oxide inhibitors, other antiwear agents, viscosity index improvers, pour point depressants, anti-foaming agents and the like.

The embodiments of this invention in which an exclusive property or privilege is claimed are defined as follows:

1. A compound of the structure where R and R are each see-butyl.

2. A compound of the structure RSCH SR where R is sec.-butyl and R is tert.-buty1.

References Cited UNITED STATES PATENTS 2,571,114 10/1951 Crouch 260-609 OTHER REFERENCES Brown et al.: J. Amer. Chem. Soc. vol. 87 (1965), pp. 4559-69.

Levi: Chem. Abstracts, vol. 27, pp. 268-269 (1933).

CHARLES B. PARKER, Primary Examiner D. R. PHILLIPS, Assistant Examiner US. Cl. X.R. 25 2--45