US2270888A - Nondrying water-washable lapping and grinding composition - Google Patents

Description

Patented Jan. 27, 1942 NONDRYING WATER-WASHABLE LAPPING AND GRINDING COMPOSITION Dean K. Murray and John M. Olson, St. Paul,

Minn., assignors to Minnesota Mining & Manufacturing Company, St. Paul, Minn., a corporation of Delaware No Drawing. Application August 3, 1940,

Serial No. 351,260

8 Claims.

This invention relates to abrasive compositions for grinding and lapping articles such as gears and valves, particularly gears.

After gears are cut, the teeth are frequently further finished by grinding or lapping.

tive art and wherever silent transmission and precision are desirable Usually two or more gears that are to engage each other when assembled in a machine are 10 ground or lapped by turning them together with their teeth enmeshed as they will be in the machine, at the same time applying an abrasive to the teeth at the point where they enmesh.

The abrasive should cover evenly all the sur- 15 face of each tooth during the time that it engages another tooth.

To apply the abrasive, the art has tried dispersing finely ground abrasive particles in a variety of liquid, plastic or viscid vehicles and then 20 turning enmeshed gears'with one or more of then gears partially immersed in a bath of such dispersion. a

It is important that the abrading power of such a dispersion of abrasive should be uniform 2 for a substantial period of time, i. e., for the penod required to finish one set of gears or, in" automatic grinding, for a much longer period preferably limited only by the life of the powdered 3 or finely dividedabrasive itself.

The water-base dispersions heretofore known cannot accomplish this because the heat that is developed by grinding under the necessary pres- I sure, especially when the gears are large, dries f Fresh moisture may of 35 out the dispersion. course be derived from the bath or mixture in which the gears are turning but the dry abrasive left from the dried out portion will then be added so that the abrading force that the gears receive gradually increases during, grinding and the .required uniformityis thus lost.

On the other-hand, ordinary oil-base dispersions heretofore known, though they do-notdry out, are unsatisfactory because they remain on the gears after grinding and require expensive treatment such, as baths in naphtha or the like to remove all traces of abrasive followed by soap spray or other baths to remove the naphtha, followed by still a third bath in oil to cover the freshly ground surfaces with a protective oil I This 5 practice is particularly followed in the automocoating. Additionally, in the absence of hendling machinery, the naphtha baths injure the operator's hands and present a cumbersome, time-consuming task. I

The importance of a final oil coating may be readily seen from the fact that many metal articles, for example ordinary| steel gears, when freshly ground, are especially susceptible to rust and when the washing after grinding is by water or soap and water, where a water-soluble .base grinding compound is employed, gears have been known to rust within a very few minutes as they emerge from the baths and pass along the carrier, unless the freshly ground surfaces are protected by a coating of oil. I

Therefore, in view of these and of other factors, an object of our invention is to provide an abrasive composition:

Which will flow at grinding temperatures so as to spread abrasive particles evenly over all the contacting parts of two surfaces that are being ground or lapped together;

Which will not melt or decompose at grinding temperatures, but which will maintain a con- 5 sistency suflicient to hold the abrasive against the surfaces to be abraded;

Which will possess adequate lubricating power, i. e., sufficient body" or viscosity to keep the moving surfaces apart under the maximum pres- 0 sure, and which will retain such lubricating power at grinding temperatures throughout approximately the life of the abrasive particles;

In which the oils will not oxidize sufficiently to cause 'gumming";

Which will hold the abrasive particles in suspension throughout the life of the abrasive particles;

Whose abrading power will be uniform throughout the life of the abrasive particles;

Which will not dry out at grinding temperatures;

Which may be washed from the article to the desired xtent after grinding simply by a spray of hot water or a hot water soap solution;

Whose components are such and are so arranged inrelation to each other in the dispersion that one washing by a spray of hot water or a hot water-soap solution will completely carry away all traces of abrasive particles while lubricate and to leaving a thin protective film of abrasive-free oil on the article after grinding; and

Which is adapted to lapping in general, i. e.,

.to render grinding compositions emulsiflable by the addition of the well+known emulsifier, soap, in various forms. For example, there have been suggestions of the use of certain petrolatum and oil bases with an admixture of mineral oil sulfonates, but such sulfonates contain electrolytes which inhibit the functions of the sulfonates that are necessary to the attainment of the de-,

sired objectives, and, furthermore, the nature of the oil and/or petrolatum bases of such compositions are materially differentfrom those which we have found desirable to employ.

However, in all of the prior attempts known to us, one adjustment of ingredients or of process steps'made to correct a defect would cause a.

new defect to appear in the end product, whereupon new adjustments or changes would have to be made, but these, in turn, would cause still different defects, etc. For example, a grease or oil base heavy enough to keep its body at grinding temperatures might fstick and resist emulsification so much as o make it impossible to wash the composition off after grinding, but an increase or change of the emulsifying agent might, in turn, lower the lubricating power below requirements, and then if an oil or lubricant were added, this would in turn thin the composition below the required viscosity or perhaps destroy the uniformity of the dispersionof abrasive particles, etc.

Until the present invention no composition that approached any substantial satisfaction of all the above many, varied and exacting requirements was known to us nor, to our knowledge, to the art.

It has'been our discovery, however, that all the above named exacting requirements may be more nearly met by a single inexpensive composition if made in conformity to principles that we have discovered and that are illustrated by the materials and the manner of mixing them described herein.

Broadly speaking, a preferred form of our composition comprises a dispersion or suspension of abrasive particles in an intimate admixture of a grease and an emulsifiable oil. By -grease is meant an oil or oil-bearing mixture that is viscid, i. e., that will not flow, at ordinary roomtemperatures;

Functions of the grease, among others, are to give body or viscosity to our grinding composition. A function of the emulsifiable oil, among others, is to promote substantial emulsiiication or removal of the entirecomposition, except for a thin film of .oil or grease particles in actual contact with the metal, when it iswashed with the hot water or soap and water spray after grinding. i

More particularly the grease is preferably of the type formed by the addition of soap to mineral -oil,'and one which will not decompose or separate at the elevated temperatures developed in grinding. nor yet be of too heavy viscosity.

Such a'grease may be that made by the addition to petroleum oil of a soap such as a calcium soap the present invention is commercially available of a hydrogenated fatty compound after the manner described in Hilliker Patent No. 1,989,197. A form thereof satisfactory for the purposes of at the present time under the trade name Superla, being a product of the Standard Oil Company of Indiana. It will not decompose nor flow at temperatures ranging up to between 170 and -220 F., and if some breakdown of its structure does take'place above such 'a temperature, the separation is slow and it yields soft instead of hard soap so that there is a minimum of loss of lubricating power. It is substantially completely non-emulsifiable in water before being used in the present composition.

The emuls'ifiable oil is preferably one containing no alcohol, formed by the addition to mineral .or petroleum lubricating oil of a small quantity of purified mineral oil sulfonates, from which the electrolytes such as alkali sulfate have been removed, and of a smaller quantity of soda rosin soap. Such emulsifiable oil may, for example, be

' produced in the manner described in'Adams et al.

' proven its ability to last for the full life of-the Patent No. 2,039,377, or in any other suitable manner. It is substantially completely emulsiflable in or with water. The mineral oil sulfonates may be preferentially oil soluble or preferentially water soluble. They are sometimes referred to as mahogany soap, but a purified mahogany soap is desired.

Alkali sulfates, like all electrolytes, tend to inhibit the formation of emulsions, so that their presencein the sulfonates inhibits the functioning of such sulfonates as emulsifiers. Similarly,

alcohol inhibits the formation of emulsion. Hence the sulfonates should be free 'or substantially free of these materials.

The grease and the emulsifiable oil may be mixed in a suitable mixer, for example, a socalled pony mixer. After they are thoroughly mixed but while the mixer is still running, the

abrasive particles are added. They are preferably sprinkled into the liquid; at a rate slow enough so that all the particles are caught and suspended in the whirling liquid before they reach the bottom of the mixer.

Preferably no heat is applied but'heat is generated by the mixing. When allowed to stand the composition sets up as a gel in about 24 Therefore it should be poured into its hours. shipping containers as soon as the mixing is completed. Under the heat of grinding, when in use, it loses its gel form somewhat and acquires the proper consistency.

It requires no aging but is. ready for immediate use.

There being no material in this composition thatis volatile at grinding temperatures, no even at far higher temperatures, the composition does not dry out. In actual commercial use it has abrasive, i. e., until the particles are worn down and must be discarded, without loss of moisture or substantial change of viscosity. The wateremulsifiable oil may have a boiling point of approximately400 F., though oils of bther boiling points may be used, but they are preferably well abovethe highest possible grinding temperature that may be encountered.

As to the washability of this composition, commercial usage has shown that it will wash off readily from the article after grinding by use of a spray of hot water orf'a hot water-soap solution (about F), however leaving a desired thin protective film of abrasive-free oil on the freshly ground metal, but leaving the ground gears or the like free of abrasive particles. The strength of the soap spray may readily be adiusted to leave the proper or desired amount of oil film behind, a strengthening of the soap solution resulting in a decrease in the amount of oil film that remains. Another factorwhich determines what strength of soap solution is re-- quired for washing is the proportion of the ingredients of the composition, since the internal physical structure of the mixture apparently determines, in part, the degree of emulsification that occurs during the wash.

No bath of naphtha is required after grinding and hence no final bath or coating of protective oil need be applied. The one bath of water or soap spray replaces the three baths which were required after using the oilor grease-base compositions heretofore known.

It is hard to say with certitude why combinations made in accordance with the present invention produce a grinding composition that is water-washable in this manner. The particles are uniformly dispersed throughout the suspension, and yet the spray of water, or soap and water, removes the particles as well as the nonemulsiflable grease but, which is important, leaves behind a small quantity of abrasive-free oil as a film on the metal.

Ordinarily it might seem that if all the abrasive particles were washed away, all the oil would be carried away with them. However, particles of the oleaginous ingredients, the same being of a viscous or mobile nature, are capable of flowing together or agglomerating and exerting forces of have to precede the formation of an oil-ln-water emulsion. The film would thus beheld to the abraded surface by strong surface tension or almost molecular forces. V

Whatever the reasons may be, the manner in which the abrasive particles are held in the suspension is such that the resulting combination of interfacial tensions and/or other complex forces permits the abrasive particles to be removed by the spray and separated from at least a portion of the original mineral or'petroleum oil, from which either the grease or the emulsifiable oil was made. Perhaps the novel step of combining a. soap-containing grease with a soapcontaining oil, in the first of which the soap is a water-insoluble polyvalent metal soap and in the second of which the soap is. a mineral oil sulfonate with or without a soda rosin soap, in each of which the soap is thoroughly disseminated in the oil (or grease) before the two are mixed together and before the abrasive is added, contributes something to the particular manner of. suspension and the physical relation of the ingredients in our grinding composition.

A soap-oil grease such as is used in the described composition can be developed so as to possess a higher melting point than can be developed in 100% petroleum hydrocarbon greases such as are derived from the residues of distillation of petroleum This is of great importance in the grinding-in of heavy gears where high grinding temperatures are developed. Too thin a composition fails to hold the abrasve particles in suspension or to keep them properly distributed especially if coarse particles are being used, or fails to maintain the required lubrication. However, not all greases having a high softening point are suitable because some are too sticky due to their ingredients and others lack the particular structure necessary to produce a composition that will react to the grinding and the washing in accordance with the particular com.- bination of objectives of the present invention.

The emulsifiable oil washes off readily and this is an important factor in the carrying away of the abrasive particles, whatever their relation to the other ingredients of the suspension may be. The greater the quantity of emulsifiable oil, the more easily the residue will wash off after grinding, but the quantity of such oil can not be increased to the point where it begins to thin the grease enough to disturb the uniform suspension of the abrasive or to weaken its lubricating power. Nor can the quantity of emulsifiable oil be permitted to reach a point where it will destroy the capacity of the composition to release the'abrasive particles while retaining a clear oil film on the abraded article upon washing.

The abrasive may be silicon carbide, aluminous oxide, flint, garnet or other abrasives known to the art, or a combination of any two or more abrasives, depending upon the type of work to be done.

If the abrasive is coarse, its weight in proportion to the entire formula should preferably be increased over the weight that would be used of a finer abrasive.

.The compositions made according to this invention in addition to possessing the highly desirable quality of being at once non-drying and water-washable, are also found to be freefrom any tendency to stick or gum up during use; nor do they lack the full cutting power that is commensurate with the type of abrasive particles used, as has been the case with various other emulsifiable' or semi-emulsifiable compositions heretofore suggested.

A preferred formula for a gear grinding composition made in accordance with the principles of the present invention is as follows:

Percentage by weight Grease 44 to 50 Emulsifiable oil 22 to 25 Abrasive 34 to 25 The above formula may be varied appreciably,

but it is ordinarily preferred that the water emulsifiable oil be present to the extent, approximately, of 45% to 55% of the grease.

Under some circumstances a composition of lower viscosity is required. This may be secured by using less grease or more emulsiflable oil or by adding a mineral oil such as spindle oil or by a combination of these three steps. One reason for using a mineral oil along with an increase of emulsifiable oil to produce a thinner mixture is that a mineral oil such as spindle oil is a somewhat better lubricant than the emulsifiable oil. Generally, thinner compositions are required for gear lapping'by automatic machinery than for lapping by a hand-fed machine although the composition of Formula I has been frequently employed successfully in commercial use in automatic gear lapping machines. The use of high prising abrasive suspended in a complex comprising a polyvalent metal soapbearing grease or low viscosity compositions depends on a va- 4 riety of circumstances such as the type of work,

the speed of the grinding machine, the type of the machine,'the manner of applying the composition, etc.

A preferred formula for a composition of lower I viscosity is as follows:

sulfates and other electrolytes.

- Percentage by weight Grease .1. 16 Mineral oil 16 Emulsiflabie nil 33 Abrasive ..'35

A preferred formula for a composition of still lower viscosity is as follows:

III

Percentage by weight Grease 8 Mineral oi1 Emulsifiable oil 35' Abrasive 32 Although our invention is especially illustrated herein by compositions particularly suitable for gear lapping or grinding, it is to'be understood that our invention-is not so limited and comprehends similar compositions and other uses within the scope of this application as embraced by the appendedclaims. v

We claim: 1. A grinding and lapping composition of gel-like nature comprising first, a substantially water-insoluble oleaginous complex composed of a heavy oleaginous hydrocarbon substance and polyvalent metal soap and second a hydrocarbon oil modified to be emulsifiable in water alone in I 5. The composition of claim 2 further charac terized in that the said ingredients are present in the following weight percentage ranges:

Grease 44 to 50 Emulsifiable' oil 22 to 25 Abrasive 34 to 25 6. The composition of claim 4 further characterized in that it contains mineral oil in intimate admixture with the said grease and the said emulsifiable oil, said mineral oil being a good lubricant and being substantially non-emulsifiabie relative to the said emulsifiable oil.

7. The composition of claim 4 further charac- ,terized in that it contains mineraloil in intimate admixture with the said grease and the said emulsifiable oil, said mineral oil beinga good lubricant and. being substantially non-emulsi flable relative to said emulsifiable oil, and the said ingredients, including the abrasive grits,

being present in the following weight percentage ranges:

Grease 16 to 8 Mineral oil 16 to 25 Emulsifiable oil 33 to 35 Abrasive 35 to 32 intimate admixture, and, third, finely divided abrasive particles disseminated in said admixture, said modified hydrocarbon oil being present to the extent of to of the said water-.

insoluble oleaginous complex.

2. A grinding and lapping composition cornprising abrasive suspended in a complexcomprising a water-emulsifiable modified mineral oil and a grease made from mineral oil and poly-.

valent metal soap, said grease having a melting point of from F. to 220 F.

3. A grinding and lapping composition com- 8. A gear or valve grinding composition comprising abrasive particles disseminated in an intimate admixture of a grease and an emulsiilable oil, said grease comprising a hydrocarbon oil and a divalent'metal soap of a hydrogenated fatty acid and said emulsifiable oil being substantially free of alcohol and comprising a hydrocarbon oil containing refined preferentially oil soluble mineral oil sulfonates in solution.

DEAN K. MURRAY. JOHN M. oLsoN.

. CERTIFICATE OF CORRECTION.

Patent No. 2,270,888. Janna- .27, 191m.

4 I DEAN K. MURRAY, ET AL.

c It is hereby certified that error appears in the printed specification of the ebove numbered patent requiring correction as follows: Page 2, first column, lineg for' "quantities" read --qualit1es--;.a'nd second column,l 1ne 58,1for "no"- read nerand that the said Letters Patent shquld be read with this correction therein that the same may conform to the record or the casein the Patent Office. I 1

Signedend sealed his Zhthday of narch,, A. n. 19h2.

I r v 5eni-y Van'Arsda1e, V 11) r I Acting Comissioner of Patents