US2435124A - Method of dispersing a foam-reducing silicon-containing compound - Google Patents

Description

Patented Jan. 27, 1948 I METHOD OF DISPERS ING A FOAM-REDUC- ING SILICON-CONTAINING COMPOUND Loren C. Bollinger, Martinez, Calif., asslgnor to Shell Development Company, San Francisco, Calii.'., a corporation of Delaware No Drawing. Application January 22, 1945, Serial No. 574,039

Claims. (Cl. 252-495) This invention relates to a method of providing organic compositions, for example,- lubricating oil, other hydrocarbons or other petroleum fractions, etc., with amounts of certain foam-reducing substances in a, practical, economical manner. It also pertains to certain organic substances containing concentrated amounts of the presently described foam-reducing agents, plus, if desired, other additives such as detergents, anti-oxidants, wear-reducing compounds, extreme pressure additives, anti-corrosive agents, etc., which compositions are adapted to be incorporated readily into such media as mineral lubricating oil and the like. Other ob-' jects and advantages of the present invention will be appreciated from the following description and claims.

The undesired foaming of organic compositions, particularly solutions and emulsions, under conditions of processing or use, presents a vexing problem in many fields. For example, foam preventive measures have been found necessary in the manufacture of glue, the preparation of paper, the purification of sewage, the distillation or other treatment of oils, tars and other organic products, etc. A

Thus the formation of foam or froth in lubricating oil systems frequently occurs in operations under conditions in which oil and air are agitated together. In particular, foaming takes place in reductionv and transmission gears andis an especially serious problem, for example, in aero-engines in which a "dry-sump lubrica-' tion system is employed. In such engines the.

lubricating oil is supplied by a feed pump to the:

engine. After use the oil drains to a sump and is withdrawn from the engine by a scavenge: pump and returned to the oil reservoir for re-- 1 delivery to the engine by the feed pump. The

scavenge pump generally has a capacity for han-' dling at least twice as much oil as it actually withdraws from the engine sump and hence it "sucks several volumes of air with each volume of oil. The resultant mixing of oil and air in the pump causes the oil to be returned to thereservoir largely in the form of a froth. If the froth does not break rapidly in the tank it may be taken up and supplied to the engine by the feed pump with the result that the engine receives more air than oil and the bearings are, in effect, starved of lubricant. This condition may cause vapor locking of the pressure pump and a serious drop of the oil pressure. Another 0b-:

jectionable result of frothing in engine. lubricants is that it can lead to loss of oil through the 55 vents of the oil reservoi since the tank maybe Detergents for lubricating oils normally employed in concentrations of about 0.25 to 5 w.% which may cause foaming comprise the oil-soluble salts of various bases with detergent forming acids. Such bases include metal as well as organic bases. Metal bases include those of the alkali metals as well as Cu, Mg. Ca, Sr, Ba, Zn, Cd, Al, Sn, Pb, Cr, Mn, Fe, Ni, G0, etc. Organic bases include various nitrogen bases as primary, secondary, tertiary and quaternary amines.

Examples of detergent forming acids are the various fatty acids of, say, 10 to 30 carbon atoms, wool fat acids, paramn wax acids (produced by oxidation of parafi'in wax), chlorinated fatty acids, aromatic carboxylic acids including aromatic fatty acids, aromatic hydroxy fatty acids, paraflin wax benzoic acids, various alkyl salicylic acids, phthalic acid mono esters, aromatic keto acds, aromatic ether acids, diphenols as di-(alkylphenol) sulfides and disulfides, methylene di-(alkylphenols) sulfonic acids such as'may be produced by treatment of alkyl aromatic hydrocarbons or high boiling petroleum oils with sulfuric acid; sulfuric acid mono esters; phosphoric acid mono and di esters, including the corresponding thio phosphoric acids, phosphonic and' arsonic acids, etc. An outstanding group of detergents are the metallic phenates or compounds wherein a phen olic hydrogen atom has been replaced by a me-; tallic ion. Such compounds may be mono or polynuclear, the nucleii may have one or'more alkyl (or other) side chains and/or two or more nucleii may be linked through one or more carbon, nitrogen, oxygen, phosphorus, aluminum, boron, arsenic, antimony or sulfur atoms. Among the metall c phenates, a particularly effective class of detergents are the metal salts, especially the alkaline-earth metal salts, of oil-sol-- uble phenol resins which contain free phenolic groups. These may be obtained by condensing an" alkylated aromatic hydroxy compound (phenol, naphthol, etc.) with a low molecular weight coupling agent (formaldehyde, acetaldehyde, etc.) to produce an oil-miscible resin having free phenolic groups which are'then reacted with a basic agent (lime, barium hydroxide, etc.) toform the metallic'salt. One type of such compounds is shown 1. in U. S. Patent 2,250,188.. These may be exemaasarac pliiled by the calcium salt of methylene'bis para iso-octyl phenol wherein n is a small integer such as 2, 3, 4 or a mixture of these. I

Non-metallic detergents which may cause foaming include compounds such as the phosphatides, e. g., lecithin; certain fatty oils as rape-.

ment of group VIB of the periodic table which element is preferably oxygen.

They may be represented by the formulae Silicone Meta silicate Ortho silicate The several R's represent the sam or different saturated predominantly non-aromatic organic radicals (i. e., the alkylor cycloalkyl radical may have an aromatic or other substituent but it is attached to the X or $1 atom by an aliphatic; carbon atom), X represents an oxygen, sulfur,

selenium or tellurium atom and n is an integer I "associated compound as used herein and in the.

amyls. etc.are most effective in controlling the foamin ofwater-in-oil emulsions or of single phase organic liquids such as mineral oil, other hydrocarbons, or other organic liquids (e. g., alkyl succinic acids). The foremost example of this class is polymerized dimethyl silicone.

When oil-ln-water emulsions are present at some times and not at others, mixtures of these high and low molecular weight silicon oxides or esters are. employed.

Silicones may be prepared by hydrolyzing an alkyl silicon halide, such as the chloride, bromide, or iodide and (partially or completely) dehydrating the resulting hydroxy compound. The preparation of polymeric dimethyl silicone is shown in 63 JACS 798 (1941). Mixtures of such silicon halides containing different alkyl radicals and/or different halogen radicals may likewise be hydrolyzed to yield (in the case of silicon halides containing diflerent alkyl radicals) mixed silicones; that is, compounds of the formula wherein R1 and R: are alkyl radicals which do not contain the same number of carbon atoms or radicals which may or may not contain the same number of carbon atoms but are distinguished by their different substituents such as esterifled sulfonic, alkow, nitro, halogen, etc., groups. Likewise, diflerent monomers may be copolymerized. .ation or polymerization of the silicon compounds may be promoted by heating the monomer or low molecular weight polymer in the presence of oxygen and an acidic agent such as H01, H2804, HaPOc, HF, BFa, Bra, etc. For example. the degree of polymerization and foaminhibiting property of polymeric dimethyl silicone was very considerably increased by refluxing it with a few drops of concentrated hydrochloric acid at l20l38 C. for about 16 hours. ortho silicate may be polymerized by simply distilling in the presence of water.

The meta silicates may be prepared by reacting the desired alcohol, mercaptan, selenol or tellurol (or mixture thereof) with silicon tetrachloride and water in the proportions wherein x stands for 'o, s, se, Te, etc. The reaction may be effectedfrom room temperature up to about 350 C. unless a lower boiling alcohol "is used in the reaction in which case a temperployed by refluxing the reaction mixture.

ature below the boiling point of the alcohol is maintained. Higher temperatures may be em- The reaction may be effected either without a diluent appended claims is intended to cover both the highly polymerized and the more loosely associated complexes.

Those silicon compounds of the above types which contain a minimum total of about 24 saturated carbon atoms in the monomeric unit are most efiective in controlling the foaming of oilin-water emulsions such as soluble cutting oils. They may be exemplified by dicetyl silicone.

Those compounds having a total of about 10 or less carbon atoms-in the monomerthat is, when R stands for an aliphatic radical such as methyl, ethyl, nor iso-propyl. the various bu y l or with an inert solvent for the reactants such as water, dioxane, etc. Reaction time is on the order of a few hours to a day.

The desired ortho silicates may be obtained by ester exchange reaction with tetra ethyl ortho silicate [(C2HsOhSl], a commercial product. Tetra methyl ortho silicate may likewise be used; such compounds can be obtained by reaction of sich with anhydrous alcohol. In the present ester xchange reaction, the ortho silicate is heated with an alcohol (or corresponding mercaptan, selenium or tellurium compound) possessing the alkyl radical or radicals which it is desired to incorporate in the silicate. the boiling point of ethyl alcohol (which is driven 03 from the ortho silicate) up to about 200" 0.,

and preferably between about l00-150 C., is em- A temperature fromployed. The reaction is promoted by anhydrous acidic or basic catalysts such as benzene sulfonic acid, paratoluene-sulfonic acid, sodium ethoxide, etc. If desired, suflicient toluene or other solvent may be added so as to form an azeotrope with the ethyl alcohol produced. Reaction time is 2 to 3 hours or more depending on the eiliciency of the ethyl alcohol removed.

Amounts of these silicon compounds, particularly of dimethyl silicone, which produce appreciable foam reduction may be as little as one part per million by weight. Normally, concentrations of the low molecular weight silicon compounds from about 0.0001%' to 0.01 weight and seldom above 0.1% are employed. Larger amounts of the higher molecular weight silicon oxides or esters such as dicetyl silicone, in the range of 0.05% to 0.5 weight may be used, particularly in emulsions such as soluble cutting oils comprising both very viscous base oils (for instance, on the order of 100 to 150 S. U. S. at 210 F.) and also a considerable quantity of emulsifying agent (say on the order of to 35% weight) both of which tend to increase foaming.

While these quantities can be dispersed in the organic medium by mechanical agitation in the laboratory, such a procedure frequently is not feasible when applied to viscous oils on a commercial scale; also, the limit of solubility of these silicon compounds in lubricating oil does not greatly exceed the quantities used for foam reduction so that it is not practical to try to make up concentrates of the foam inhibitor in the viscous lubricating oil and then try to blend the concentrate into the bulk oil.

It has been found however that the present silicon oxides and esters are freely miscible at ordinary temperature in amounts up to 50% or more by volume with predominantly hydrocarbon compositions such as petroleum fractions which have a viscosity oi. less than about 50 S. U. S. at 100 F. Such petroleum fractions are variously known (as their viscosity varies) as spray oils, gas oils, kerosene, mineral seal oil, and the like,

while in some cases, even more volatile liquids maybe used.

Concentrates of the silicon foam-inhibitors in these solvents may readily be incorporated in measured amounts into lubricating oils and other viscous media with a minimum of agitation such as that provided by air-blowing or passing some other gas through the oil. It will be seen that the small amount of hydrocarbon vehicle thus dispersed with the silicon compound will generally not be enough to appreciably affect the physical properties such as viscosity, flash or fire point etc., of the medium in which they are incorporated. When a very volatile solvent such as petroleum ether is employed, it may be substantially completely removed from the lubricating oil by the air blowing which is used to distribute the concentrate through the bulk 011. At the same time, the dilution of the silicon compound with this vehicle allows a more exact determination of the quantity of silicon compound which it is desired to disperse in the medium. In other words, it provides the means for a verneir-like calibration of the amount of silicon compound incorporated.

As illustrative of a preferred concentrate, a

solution of 4% v. of dimethyl silicone polymers in a mineral seal oil, i. e., an aliphatic spray oil having a viscosity of about 40 to-50 S. U. S. at 100 F., may be conveniently used to introduce said agents into lubricating oils.

of the silicon compounds with the hydrocarbon vehicle.

Such concentrates of lubricating oil additives (suitable for dispersion in about 10 volumes of lubricating oil) may contain about 0.001 to 0.005% w. of the present foam reducing silicon V oxides or'esters, about 2.5 to 5.0% w. of an oilsoluble detergent and about 1.0 to 3.0% weight of an oil-soluble antioxidant.

Thus a hydrocarbon solvent, for example mineral seal oil which is an aliphatic spray oil having a viscosity of about 40 to 50' S. U. S. at F., may contain about 0.0025% dimethyl silicone polymers, about 2.5 to 5.0% weight of oil-soluble detergenhand about 1.0 to 3.0% weight of an anti-oxidant. Incorporation of 1 cc. of this concentrate in 10 cc. of lubricating oil produced the desired quantities in the compounded lubricating oil.

I claim as my invention:

1. A method of dispersing a, foam-reducing silicon-containing compound in a hydrocarbon lubricating oil which comprises dissolving a compound having a formula selected from the group consisting of R\ R0 /Si=0) and R an R0 wherein each R is a saturated non-aromatic organic radical, and n and m are positive integers of at least 2, in an aliphatic low-boiling hydrocarbon having a Saybolt Universal viscosity of less than 50 seconds at 100 F., adding said hydrocarbon containing said foam-reducing compound into a, hydrocarbon lubricating oil and passing a gas through said oil thereby dispersing the foam-reducing compound in the oil and substantially removing the relatively low-boiling hydrocarbon vehicle from the lubricating oil.

3. A method of dispersing afoam-reducing silicon-containing compound in a hydrocarbon lubricating oil which comprises dissolving a compound having a formula selected from the group consisting of wherein each R is a saturated non-aromatic organic radical, and n and m are positive integer of at least 2, in an aliphatic hydrocarbon having a Saybolt Universal viscosity of less than about 50 seconds at 100 F., and then incorporating said hydrocarbon containing said foam-reducing comv pound into a hydrocarbon lubricating oil.

4. A method of dispersing polymeric dimethyl silicone in a hydrocarbon lubricating oil which comprises dissolving the polymeric dimethyl silicone in an aliphatic hydrocarbon having a Saybolt Universal viscosity of less than about 50 seconds at 100 F. and then incorporating said hydrocarbon containing said silicon compound into a lubricating oil by agitation caused by passing gas through said oil.

5. A method of dispersing polymeric dimethyl silicone in a lubricating oil which comprises dissolving the polymeric dimethyi silicone in an alphatic hydrocarbon having a Saybolt Universal viscosity of less than about 50 seconds at 100 F. and then incorporating said hydrocarbon containing said silicon compound into a hydrocarbon lubricating oil.

LOREN C. BOILING-ER. 25

Rmusnarwas strap The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,416,504 Trautman Feb. 25, 1947 2,406,971 Sowa, Sept. 3, 1946 2,386,259 Norton Oct. 9, 1945 2,384,384 McGregor et al Sept. 4, 1945 2,375,007 Larsen et al May 1, 1945 2,371,763 Lazar et al Mar. 20, 1945 2,242,400 Loane May 20, 1941 2,129,281 Lincoln Sept. 6, 1938 OTHER REFERENCES I Chemical and Metallurgical Engineering, Aug. 1944, "Heat Stability Features New Group of 20 Synthetic Resins, page 109. "New Products and Materials, pages 135 and 136.