US2389227A - Pneumatic tool lubricant - Google Patents

Description

Patented Nov. 20, 1945 PNEUMATIC TOOL LUBRICANT Donald L. Wright, Westfleld, N. J., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application September 15, 1943, Serial No. 502,461

7 Claims.

This invention relates to a new and improved lubricant for pneumatic tools, such as percussion type drills and similar high speed compressed air machines and steam machines. More particularly, this invention relates to a lubricating composition comprising mainly a viscous hydrocarbon oil blended with minor proportions of a nondrying thickened fatty oil and of a high molecular weight linear organic oxygen-containing polymer for providing eflicient lubrication to surfaces of fast moving machine parts and to their guides, such as rapidly reciprocating pistons and their cylinder walls, the lubricant on such surfaces bein exposed during the machine operation to erosive action by forceful streams of gases and condensate which accompany the use of gases like compressed air or steam.

Pneumatic tools present peculiar problems in lubrication. In general, they are rugged portable machines subjected to rough handling. Although they need constant and eflicient lubrication at all times, they cannot be equipped very easily with automatic lubricant feeding systems which are delicate or which have large supply reservoirs.

Added difllculties in lubricating these machines arise from the rapid jarring movements of, and high gas velocities against lubricated parts, since these mechanical actions tend to separate the lubricant from the metal surfaces. Variations of temperatures occur in difierent parts of these machines. Gas expansion causes intense cooling in the surrounding parts and condensation of water vapor present in the usual gaseous or pneumatic fluids, compressed air and steam, while impacts and friction cause relatively intense heating in other parts. Moisture condensed from a pneumatic fluid in the machine tends to wash away a film of lubricant non-resistant to this action, and temperature variations afiect the fluidity of lubricants which have viscosities sensitive to these variations. When used outdoors and in mines, these machines are subject to environmental temperatures which intensify these temperature variations, Lubricants are undesirable if they flow too freely over the heated parts of the tool, also, if they have sufflciently high viscosity in contact with the heated parts but congeal in contact with cooler parts or in the lubricator.

Materials have been compounded in the past to make lubricants having advantageous properties in one respect or another, but lubricants with the desired combinations of qualities, particularly those of adhesiveness and moisture resistance have not been available. In my prior Patent 2,228,429, I have disclosed and claimed a pneumatic tool lubricant which satisfies the above requirements, but the present invention is a still further improvement over said prior element.

An object of the present invention is to prochurned to a foamy mass, 6, ability to resist moisture and adhere to metallic surfaces even when emulsified, and 7, other qualities determined by speciflc requirements of the service.

In accordance with the objects of this invention, an improved lubrication of pneumatic tools is obtained by a composition which is able to give a lubricating film protection on working parts under rapid mechanical action regardless of moisture deposition.

Broadly, this invention involves the blending of a viscose hydrocarbon oil, such as a petroleum lubricating oil fraction, with a non-drying viscous oxidized or thickened fatty oil and with a small amount of an oxygen-containing high molecular weight polymer which normally is substantially solid. By a proper selection and proportioning of these ingredients, a blend can be obtained having suitable viscosity and pour point characteristics to assure proper flowing and penetration and which protectively stays on rubbing surfaces under severe operating conditions.

Preferably, the principal ingredientsof blends found to have wide adaptability for use in many kinds of air driven percussion type tools including outdoor equipment during all seasons of the year are a mineral lubricating oil having a viscosity in the range of about to 925 Saybolt seconds at 100 degrees F. and a pour point below about +10 F., a non-drying thickened fatty oil, and a semi-solid to solid adhesive high molecular weight polymer. As the mineral oil ingredient, a lubricating oil fraction from a naphthenic crude, such as from a Colombian or Coastal crude, answers the purpose well, although, if desired, one may use lube oils derived from other types of crude, such as asphaltic, paramnic, mixed base, etc., provided they are selected or treated, as by dewaxing, etc., to have a suitable low pour point. Blown rape seed oil is particularly suitable as the non-drying thickened fatty oil.

Such additives include polymers of vinyl ethers having the general formula B: H O=(!l-1i in which R1 is an unsubstituted or substituted aliphatic, aromatic, or hydroaromatic radical, and R215 a hydrogen atom or a substituted or unsubstituted aliphatic radical, e. g., vinyl oleyl ether. vinyl isobutenyl ether, vinyl meta-cresyl ether, vinyl cyclohexyl ether, vinyl octadecyl ether, vinyl chloroethyl ether, vinyl amino propyl ether, a-ethylvinyl isohexyl ether, a-chloromethyl vinyl lauryl ether, etc.; polymers of vinyl esters having me general formula (CH2=CR2OOC) n-Rl, in which R1 and R2 are as above and n is an integer having a value of 1 or more, e. g., vinyl stearate, vinyl ester of acids obtained by oxidation of paraflln wax, vinyl chloropropionate, vinyl aminopalmitate, vinyl adipate, vinyl citrate, etc. polymers of acrylic acid esters having the general formula, R'OOCC (X) =CH2, in which R is an unstituted or substituted aliphatic, aromatic, or h'ydroaromatic group, preferably containing at least carbon atoms, and X is a H or a halogen atom, or a CH: group or a CzHs group, e. g., lauryl acrylate, cetyl acrylate, octadecyl acrylate, amylphenyl methacrylate, lsoheptyl cyclohexyl chloroacrylate, chlorodecyl methacrylate, etc., especially such polyacrylic esters having a molecular weight of 1,000 to 10,000, although polymers having higher molecular weights such as 20,000 or even 50,000, or more may be used.

Another type of high molecular weight oxygencontaining substance which can b used for the purpose of this invention is the class of condensation products or polyesters of substituted fatty acids having the general formula in which R is a H atom or an unsubstituted or substituted aliphatic, aromatic, or hydroaromatic group, a: and it may equal 0 or any integer provided that m+ll equals at least 5, and where n is 0 or an integer and m is a whole number and Z is a flmctional group which has one replaceable hydrogen atom, Z being capable of esterifying a carboxyl group. Some of these polyesters are described in U. 8. Patent 2,147,647, and are typified by the polyester having a molecular weight of about 14,000 obtained by po yesterification of 12- hydroxy stearic acid in the presence of a small amount of adipic acid.

These various polymers range from viscous, tacky oils to tough, elastic, almost colorless, and substantially solid mass. Chemically, these oxygen-containing polymers are characterized as highly saturated in that they have an iodine number below 20, preferably below 10, and frequently below 1 or 2.

About 0.1 to 1.0% of this material is readily dissolved in the blend of hydrocarbon oil and nondrying thickened fatty oil and when th'us dissolved forms a homogeneous mixture having a stable cohesiveness to be perceived in the formation of long strings or threads when the mixture is pulled apart. This cohesiveness is stable to light, air, heat and moisture.

Usually the percentage of thickened fatty oil should be in the range of about 1-15%, generally about 5-10% will be found most useful. The lubricating oil base stock will, except for possible minor amounts of addition agents such as antioxidants, dyes, pour depressors, etc., comprise the Viscosity of mineral oil (sec. Saybolt at F.) ercen 100 200 300 800 Mineral oi (naphthenic base) 94. 7 92.5 94.7 89.0 Polymerized lauryl methacrylate 0.3 0.5 0. 3 1.0 Blown rape seed oil 5. 0 7. 0 5.0 10.0

1 Average molecular weight about 10,000.

Each of these blends has a very satisfactory low pour point and a high viscosity index, which is the measurement of variation in viscosity with temperature changes of the oil according to the procedure described in the article by Dean and Davis, Chemical and Metallurgical Engineering,

vol. 36, 1929, page 618. These various blends are particularly suitable for lubrication of pneumatic rock drills, Examples 2 and 3 being intended primarily for use in temperate climates while Example l is especially adapted for use in colder climates and Example 4 in hotter climates.

'Although particular compositions with specific ingredients and proportions have been described, the invention is not limited thereto, The invention can also be carried out with other fatty oils of vegetable or animal origin having qualities similar to those of blown rape seed oil. Nondrying thickened fatty oils having high viscosities may be prepared from rape seed oil, cotton seed oil, maize oil, seal oil, and sperm oil by airblowing, or by other known methods of thickening, such as catalytic or electrical polymerization which reduce the iodine numbers of such oils to below 75. To prepare the ordinary connnercial non-drying thickened fatty oils by air blowing, air is blown into a natural fatty oil with stirring for a period of about 15 to 30 hours at a temperature of about F. until the desired speciiiic gravity or viscosity of the thickened oil is reached. Rape seed oil, for example, would be treated in this manner until its specific gravity is raised from about 0.914 to between about 0.968 and 0.990 as determined at 60 F.

The proportioning of the thickened fatty oil to themineral oil depends largely upon the viscosities of these ingredients and the desired viscosity for the blend, particularly when a pour depressant is used for ultimately reducing the pour point of the blend. The mineral oil need not be so restricted as to its source if the pour point of its blend with the fatty oil is not required to be of the order obtained in the specific examples. Lubricating oils with, flash points above the flash point of a gas oil from all types of crude oils may be used. Synthetic lubricating oils with low pour points may be used. Al though the mineral lubricating oils are preferably'selected from naphthenic base crudes, some dewaxed parafflnic base oils may also be used. As another alternative modification of the high molecular weight oxygen-containing linear type polymer, one may use copolymers, such as described in Patent 2.l25,885, made by copolymerizing acrylic acid esters of two diilerent monohydric aliphatic alcohols, for instance ethyl alpha methacrylate and lauryl alpha methacrylate, or the ethyl and mono octadecyl alpha methacrylates.

In using mineral oils having relatively higher pour points, a small amount of synthetic pour point depressants may be added, particularly those containing long alkyl group branches. These alkyl groups should have preferably 10 to 30 carbon atoms in straight chains, andmay be Joined to other long alkyl groups or a cyclic group, preferably to a polycyclic group, e. g., a naphthyl or a naphthol group. The method of synthesizing these products is wellknown in the art and described in U. S. Patent No. 1,815,022, granted to G. H. B. Davis, July 14, 1931. In general, this method involves the reaction of chloroparafilns withone another or with aromatics, such as naphthalene, in the presence of a Friedel- Crafts type of catalyst, These pour point depressants in a concentration of only about 0.5 to 3% lower the pour points of compositions described in the preceding examples by more than 5 F,

The description of the aforementioned'compositions as being particularly intended for use in percussion air drills, in which specific requirements may exist for low pour points, adhesive ness, and constancy of viscosity under widely varying temperature conditions, is not intended to limit the invention to such a specific use for tnese compositions. Blends prepared in accordance with this invention are useful for other purposes, such as Jackv hammers, stopers, drifters,

. wagon drills, chippers, tempers, riveters, pavement breakers. and similar mechanisms having high speed reciprocating pistons activated by compressed air or steam. The present invention has several distinct advantages over compositions prepared heretofore; one important advantage is that the high molecular weight linear type oxygen-containing polymers, particularly the polymerized acrylic acid esters, have a tendency to emulsify to a greater extent than do the simple high molecular weight Ease oi. emulsiflcation permits better adherence oi the lubricant to the working surfaces 01 pneumatic tools where emulsion-producing moisture is generally present. therefore a reduced consumption of the lubricant is eflected, Another advantage of such oxygen-containing polymers is their relatively high resistance to molecular weight breakdown, and consequent decrease of adhesivity and viscosity during use.

Lubricant compositions of this invention may be applied through any of. the systems of lubrication usuall employed with pneumatic tools. Hand oiling is still common, but special line lubricators for injecting small quantities into the air stream at a point about ten feet from the tool are increasing. Line lubrlcators assure lubrication without attention over long periods. The compositions 01 this invention are stable and homogeneous, being even superior in these respects to the lubricants of my prior patent.

Other ingredients may be added in minor amounts. as might be desired for further improving the lubricant, but such agents as sludge dispersers, oxidation inhibitors, corrosion inhibitors and oiliness agents are in general unnecessary.

I do not desire to be limited to any given speclflc illustration of the invention because there may be relatively wide variation in the kinds and hydrocarbon polymers such as polyisobutylene.

proportions of the materials used without departing from the broader scope of the invention. I desire to be limited only by the following claims in which it is my intention to claim all novelty as broadly as the prior art permits.

I claim:

1. A lubricant having a viscosity in the range of about 150 to 1000 seconds Saybolt at 100 F. adapted for use in compressed air and steam motivated machines having high speed reciprocating pistons, which comprises a major proportion of a hydrocarbon lubricating oil and about 1 to 15% of a non-drying thickened fatty oil and about 0.1 to 1.0%.01 a linear oxygen-containing polymer which normally"'ls"plastic to solid, has

an iodine number below 20 and a molecular weight of at least 1,000, said polymer being a polymer or an oxygen-containing organic compound having the group J=(/.liz. 2. A lubricant according'to claim 1 in which the polymer is composed or only carbon, hydrogen and oxygen, and has a molecular weight oi'atleast 5,000.

3. A lubricant adapted for use in pneumatic tools which comprises about 85 to 95% of a pctroleum lubricating oil having a viscosity in the range of about 100 to 950 Baybolt seconds at 100" F. and a maximum pour point of +l0 F., about 0.1 to 0.5% of a normally semi-solid to solid acrylic acid ester polymer having a molecular weight oi at least 5,000 and a small amount of a nonrying thickened fatty oil.

4. A pneumatic tool lubricant having a stable cohesiveness, good emulsification tendencies, a maximum pour point below +10 F., a viscosity in the range of about 150 to 1000 Saybolt seconds at 100 l-"., and comprising in major proportion a petroleum lubricating oil having a viscosity in the range or about 100 to 950 Saybolt seconds at teristics, having a viscosity of about 400 to 600 1 seconds'saybolt at 100 F., a maximum pour point of about -10" R, and comprising in major proportion a hydrocarbon lubricating oil having a viscosity 0! about 200 to 400 seconds Saybolt at 100 F., 1 to 15% of blown rape seed oil, and 0.1%

to 1.0% of acrylic acid ester polymer having a molecular weight of about 5,000 to 50,000.

6. A compressed-air driven rock drill lubricant having a viscosityin the range of about 490 to 515 saybolt seconds at 100 F., a maximum pour point of-about. -25 F. and comprising about 92.7% of a naphthenic base lubricating oil having a viscosity in the range of about 300 to 315' Saybolt seconds at 100 F., about 7.0% or blown rape seed oil, and about 0.2 to 0.5% of lauryl' alpha methacrylate polymer having a molecular of a non-drying thickened iatty oll'ana about 0.1

to 1.0% of. a normally semi-solid to solid acrylic acid ester polymer.

- mm n warorrr.