US2877182A - Organosilicon lubricants - Google Patents

Description

United States Patent ORGANOSILICON LUBRICANTS 5 John J. May, Midland, Mich., asslgnor to Dow Corning iCorporation, Midland, Mich., a corporation of Michgan No Drawing. Application September 8, 1952 Serial No. 308,531

8 Claims. (Cl. 252-496) Y This invention relates to organosilicon lubricants. The lubricants of this invention comprise mixtures of fluid organosiloxanes having the'general formula R;.si0, T

where n has an average value of from 2.0 to 2.9 and R may be methyl, monocyclic aryl, halogenated aryl hydrocarbon, or mixtures thereof and from 0.25 percent by weight to 5 percent by weight, based on the siloxane, of a halogenated fatty acid having one to 12 carbon atoms.

Siloxane lubricants are well known for their ability to withstand extreme temperature conditions, e. g. temperatures at which petroleum oil lubricants can not be 9 used. However, at ordinary temperatures, these known siloxane lubricants compare very unfavorably to the petroleum lubricants in general lubrication properties.

At the present time no known siloxane lubricant can be satisfactorily substituted for petroleum lubricants for use at ordinary temperatures," particularly where high pressure conditions exist and when bearing surfaces are both steel.

Although siloxane lubricants have been much improved for high pressure use (e. g. boundary lubrication) such as those described and claimed in the copending application of Chester C. Currie, Serial No. 270,771, now U. S. Patent No. 2,642,395, assigned to the same assignee as this invention, they still leave much to be desired when compared with organic lubricants at ordinary temperatures. It is the object of this invention to prepare siloxane lubricants which not only have the heretofore known utility at high and low temperatures, but which also compare favorably with petroleum oil at ordinary temperatures.

The objects of this invention are obtained merely by admixing halogenated fatty acids having 1 to 12 carbon atoms with the siloxane fluid. The halogenated fatty acids may be employed in amounts ranging from 0.25 to 5 percent by weight based on the siloxane. No advantage is gained in employing amounts larger than 5 percent. 5 The advantages of this invention are only partially obtained by employing amounts smaller than 0.25 percent. Any halogenated fatty acid having from 1 to 12 carbon atoms is operative in this invention. The preferred acids are the alpha and/or beta halogenated fatty acids having 1 to 6 carbons in which the halogen is bromine or chlorine. No advantage is ordinarily gained by employing acids halogenated beyond the tri-, or tetra-halo stage. Specific examples of operative acids are dichloroacetic acid, alphabromocaproic acid, trichloroacetic acid, alpha-chloropropionic acid, alpha-bromopropionic acid, alpha-bromobutyric acid, beta-chloropropionic acid, alpha, beta-dichlorobutyric acid, alpha-chlorovaleric acid, gammabromovaleric acid, bromoor chloro-capric acids, the chloroand bromo-lauric acids and iodo-acetic acid.

The above acid additives may be simply admixed with the siloxane fluid, employing ordinary mixing equipment.

Mixing may occasionally be facilitated by moderate warmmg. p

The siloxane fluids which are employed in this invention are those having the general formula I where n has an average value of from 2.0 to 2.9 and where R is methyl, aryl hydrocarbon, or halogenated aryl hydrocarbon radicals, or any mixture of such radicals. It is preferred, however, that at least 37 percent of the total number of R radicals in the siloxane fluid be methyl. In this invention R may be, for example, methyl, phenyl, tolyl, iodotolyl, dichlorophenyl, heptachloroxenyl, dichloroxenyl, bromophenyl and dibromoxenyl. 1

Preferred are theftriorganosilyl endblocked dimethylsiloxane fluids and methylphenylsiloxane fluids. These fluids are well known in the art and commercially available. Al'so' preferred are'the halogenated aryl 'siloxane fluid copolymers described and claimedfin' U; S. Patent No. 2,599,984. Methods of preparing the s'iloxane fluids employed in this invention are well known in the art.

The siloxa'ne lubricants of this invention may be readily compounded into greases by admixing with various known thickening agents, as for example, metallic salts of higher fatty acids such as lithium stearate, graphite, clay, carbon black, silica gels, fumed silica, etc. Methods of preparing siloxane greases are well known in the art. Preferably the acids of this invention are milled into the grease.

Other additives well known in the lubrication field such as anti-oxidizing agents may be added to the mixtures. of this invention.

The mixtures of compositions of this invention were tested on a Falex lubricant testing machine. This machine is commercially used in the lubrication" industry and from it may be obtained measurements which accurately indicate the ability of the lubricant to prevent wear between moving metal parts under pressure; The operation and nature of the Falex machine is described'by Victor A. Ryan in Lubrication Engineering, September 1946, pp. 102-104. f

'The *test substantially involves rotating a shaft between two'V-blocks as pressure is applied to the bearing surface. The resulting wear of shaft'and the V-block when operated under agiven load for a given period of time is measured by means of a ratchet wheel. The wear is expressed in teeth wear, one tooth wear being equal to .0000556 inch of wear'in depth. a

The lubricants of this invention were tested at room temperature in the following manner. I i r The Falex machine employing steel'V-blocks and steel shafts was started and a load of 50 pounds gauge was applied in a machine run offive minutes. At the end of this period load loss was noted and tooth wear ismeasured. The load was readjusted to 50 lbs. (to-compensate for load loss, if any) and a machine run for a second five minutes is made after which the above observations were again noted. Next a pound load was applied over two five minute intervals in the samemanner observing load loss and tooth wear in each interval as before, and finally a 200 pound load is applied over two five minute intervals in identical manner. I

In Table 1 of Example 1 the total load loss (L) and total tooth wear (T) of the six successive intervals mentioned in the preceding paragraph are totaled. Since both load loss and tooth wear are essential for proper evalua'tion of a lubricant, a factor consisting of their product divided by 100 has been included in the .table to-make comparison more clear. In the examples all mixtures weretested 'over the sixintervals mentioned above unless otherwise indicated.

The followingexar'nple's illtis ever, the scope of this invention is limited only as set forth in the claims.

EXAMPLE 1 mixtures, of Table. 1 were prepared employing a commercial triinethylsiloxy end-blocked dimethylsiloxane polymer having a viscosity of 350 Cs. at 25 C. The additives as listed in column 1, of the table were directly mixed into the siloxane by means of laboratory stirrers. The amount of additive added is tabulated as per cent by weight based on the siloxane.

. intuit, V Additive 2% Dichloroacetic acid. I

2% alpha-Bromocaproic acid. 6% Trichloroacetic acid.

. 5% Dlchloroacet ic acid.

2% alpha-Chloropropionic acid. 2% alpha-Bromopropionlcacid. 2% alpha-Bromobutyric acid. 1% beta-Chloropropionic acid.

l-8, inclusive, were tested on the Falex machine in accordance with the test above described with the results as shown in Table 1.

EXAMPLE 2 The efiect of the additives of this invention upon a fluid siloxane composed of mol percent C H CH SiO units, 75 mol percent .(CH SiO, units and percent (CH SiO units is shown in Table 2 below. Mixture A consists of the siloxane without additive, andmixture B consists of thetsiloxane to which has been added 2 percent by weight (based on the siloxane) of alphabromobutyric acid. Themixtures A and B were tested in the manner of Example 1.

Table 2 Mixture 1'. T E

a 100 314 2,198 B V 47 45 21 Table3 shows the. effect of the addition of alphahromobutyric acid to a siloxane fluid composed of .45 mol percent phenylmethylsiloxane units, 45 mol percent dijm'ethylsiloxane units. (CH SiO, and 10 mol percent trimethylsiloxane units (CH5) SiO g,.when testedin accordance with Example 1. Mixture A is without additive;

trate this invention. How- 7 mixture B has 2% by weight (based on the siloxane) alpha-bromobutyric acid.

Table 3 Mixture L '1 100 A 700 604 4, 228 B lfil 119 191 EXAMPLE 3 Two grams alpha-bromobutyric acid were added to 100 grams of a fluid siloxane having a composition of 75 mol percent dimethylsiloxane units, 14 mol percent trimethylsiloxane units, .5 mOlperc'ent phenylmethylsiloxane units, and 6 mol percent of dichlorophenylsiloxane units. Mixing was readily accomplished by a laboratory stirrer. The total load loss and tooth wear of the. siloxane with and without theadditive was determined on the Falex machine after two 5:minute intervals at 50 pounds, two 5-minute intervals at 100 pounds, and two 5-minute intervals at 200 pounds, and found to be as follows:

A fluid siloxane polymer composed of mol percent phenylmethylsiloxane units and 10 mol percent'trimethylsiloxane units was tested with and without an, additive in the Falex machine over two fiveminute intervals at 50 pound loads and two five-minute intervals at pound loads with the following result:

A fluid lubricant having excellent lubrication properties at ordinary temperatures is obtained when 2% by weight (based on the siloxane) diiodoacetic acid is admixed with the siloxane of Example 3.

That which is claimed is:

1. As a composition of matter a mixture consisting essentially of (a) a fluid organopolysiloxane having the general unit formula where n has an average value of 2.0 to 2.9 and Ris a hydrocarbon radical selected from the 'group consisting of methyl, monocyclic aryl, and halogenated aryl hydrocarbon radicals and in said siloxane at least 37 percent of the total number of R radicals being methyl radicals and (b) 0.25 to 5 percent by weight based on the siloxane of a halogenated fatty acid of 1 to 12 carbon atoms.

2. The composition of claim 1 wherein R is methyl.

3.. A grease consisting essentially of the composition of claim 1 and a minor amount of a thickening agent.

7 4. As a composition of matter, a mixture consisting essentially of (a) a fluid organopolysiloxane having the average general unit formula 5 where n has an average value of 2.0 to 2.9 and R is a hydrocarbon radical selected from the group consisting of methyl, monocyclic aryl,-and halogenated aryl hydrocarbon radicals and in said siloxane at least 37 percent of the total number of R radicals being methyl radicals and (b) 0.25 to 5 percent by weight of a halogenated fatty acid of 1 to 6 carbon atoms.

5. The composition of claim 4 wherein R is methyl. 6. As a composition of matter a mixture consisting essentially of (a) a fluid organopolysiloxane having the general unit formula R,.SiO T where n has an average value of 2.0 to 2.9 and R is a hydrocarbon radical selected from the group consisting of methyl, monocyclic aryl, and halogenated aryl hydrocarbon radicals and in said siloxane at least 37 percent of the total number of R radicals being methyl radicals and (b) 0.25 to 5 percent byweight of a halogenated fatty acid of 1 to 6 carbon atoms and in said acid the halogen being selected from the group consisting of chlorine and bromine.

7. The composition of claim 6 wherein R is methyl. 8. A grease consisting essentially of the composition of claim 6 and a minor amount of thickening agent.

References Cited in the file of this patent UNITED STATES PATENTS 2,262,773 Lincoln et a1. Nov. 18, 1941 2,471,850 Wilcock May 31, 1949 FOREIGN PATENTS 453,114 Great Britain Aug. 31, 1936 20 September 1949.

Claims (1)

1. AS A COMPOSITION OF MATTER A MIXTURE CONSISTING ESSENTIALLY OF (A) A FLUID ORGANOPOLYSILIXANE HAVING THE GENERAL UNIT FORMULA