US2930757A - Lubricating compositions containing salts of monocarboxylic acids and free alkalinity - Google Patents

Description

March 29, 1960 A. J. MORWAY ET AL 2,930,757

LUBRICATING COMPOSITIONS CONTAINING SALTS 0F MONOCARBOXYLIC ACIDS AND FREE ALKALINITY Filed Oct. 16, 1957 Eiv 1) l.

VISCOSITY AT IOOF. OF FINISHED LUBRICANTS S r M n e V .m

r J .IM W W o.mo Mm S d M' u mum AHH By 56 a M Attorney United States Patent Arnold J. Morway, Clark, N.J., and Henry F. Lipiuski and Hugh T. Shearer, Jr., Pittsburgh, Pa., assiguors to Esso Research and Engineering Company, a corporation of Delaware Application October 16, 1957, Serial No. 690,561

9 Claims. (Cl. 25240.7)

This invention relates to new and useful lubricant thick-- ener concentrates, to lubricating compositions containing the thickener concentrates and to their methods of preparation. More particularly, the invention pertains to improvements in the manufacture of lubricating oil dispersed mixtures of metal salts of low molecular weight monocarboxylic acids and moderate molecular weight monocarboxylic acids and to finished lubricants containing them.

It is known to prepare anhydrous lubricating oil thickener concentrates comprising lubricating oil dispersions of mixtures of metal salts of low molecular weight monocarboxylic acids having from 1 to 3 carbon atoms per molecule and metal salts of moderate molecular weight monocarboxylic acids having from about 7 to 10 carbon atoms per molecule. The known process comprises coneutralizing low molecular weight and moderate molecular weight monocarboxylic acids with a metal base in a lubricating oil menstruum at temperatures in the'range of about 250 to 350 F. to form a lubricating oil thickener concentrate. The lubricating oil thickener concentrate is then dispersed at temperatures in the range of about 80 to 350 F. in additional lubricating oil to form finished lubricants having outstanding extreme pressure properties, detergency properties, and other desirable lubricant characteristics. In this known process no attempt'is made to control the free alkalinity of the lubricating oil thickener concentrates other than to approach stoichiometric proportions. It has now been found that products prepared without controlling the free alkalinity of the thickener concentrates results in products of varying and uncertain viscosity. It is desirable that the finished lubricants have as low a viscosity at 100 F. as possible for ease of pumping and dispensing though mechanical dispensers. However, a lowering in viscosity must not take place by decreasing the mixed salt content of the finished lubricants since the mixed salts impart the detergency and wear reducing properties.

The present invention is based on the surprising discovery that an increase in the free alkalinity of thickener concentrates of the above type to between 1% and 1.8 wt. percent, expressed as sodium hydroxide, and based on the weight of the thickener concentrate, materially lowers the viscosity of the finished lubricants to provide ease of handling and dispensing without necessitating any lowering of the mixed salt content. Moreover, the neutralization potentials of the finished lubricants are increased without aflecting their stability or anti-wear properties. This is an important factor where residual fuels of high sulfur content are employed inan engine in conjunction with the lubricants because the free alkalinity of the lubricants helps to neutralize sulfuric acid formed therein under combustion conditions.

Accordingly, a feature of the present invention is that lubricating oil thickener concentrates comprising a high alkalinity lubricating oil dispersion of a mixture of metal salts of low molecular weight monocarboxylic acids and metal salts of 'moderate molecular weight monocarboxylic "ice 2 acids can be prepared. which are useful for preparing finished lubricants of controlled viscosity. t

Another feature of the present invention is that finished lubricants can be prepared by dispersing the above thickener concentrates in additional lubricating oil.

The high alkalinity lubricating oil thickener concentrates of the present invention can vbe prepared by coneutralizing low molecular weight and moderate molecular weight monocarboxylic acids in a lubricating oil medium at elevated temperatures with a quantity of metal base sufiicient to produce thickeners having a free 'alka-, linity in the range of about 1 to 1.8 wt. percent, based on the weight of the thickener. However, it is not necessary to co-neutralize the acids in a lubricating oil medium. A portion or all of the metal salt of either or both of the acids can be preformed under substantially dehydration conditions. Thereafter the salts and any required free monocarboxylic acids and metal base are mixed with the lubricating oil and the resulting mixture heated to a temperature in the range of 250 to 350 F.

The figure is a plot of the free alkalinity of thickener concentrates prepared in accordance with the invention against the viscosity of finished lubricants prepared from the thickener concentrates in accordance withcthe invention.

The low molecular weight acids used to form components of the salt mixtures are saturated and unsaturated monocarboxylic acids having from 1 to 3 carbon atoms, such as formic, acetic, propionic, acrylic, and lactic acids. Acetic acid is especially preferred. Mixedlow molecular weight carboxylic acids wherein the acids contain from about 1 to 3 carbon atoms and have an average saponification value of above about 540 can also be employed.

The moderate molecular weight acids used to form a component of the salt mixtures are those aliphatic monocarboxylic acids containing from about 7 to 12. carbon atoms. Especially preferred are the low molecular weight coconut acids, which are a mixture of acids having from 8 to 12ccarbon atoms, averaging about 10 carbon atoms per molecule. 7 Either saturated orunsaturated acids can be utilized, although the saturated acids are preferred. Straight chain or substantially straight chain acids are also preferred. The average saponification value of the moderate molecular weight carboxylic acids should be about 310 to 440, preferably about 320 to, 350. Some" of the moderate molecular weight monocarboxylic acids coming within the above description are the following:

5-methyl-2-hexanoic Heptanoic (enanthic) Octanoic (cap'rylic) 2-ethyl 'hexanoic C branched chain acids Nonanoic (pelargonic) Decanoic (capric) C branched chain acids Commercial mixtures of moderate molecular weight carboxylic acids having an average saponification value of from about 310 to 400 can also be employed, such as those made by the 0x0 process, described in US. Patents No. 2,632,921; 2,537,577; and 2,553,364.

The thickener concentrates are formed by reacting from about 10 to 25 wt. percent, preferably 12 to 20 wt. percent of low molecular weight monocarboxylic acidspfrom about 1 .to 6 wt. percent, preferably 2 to 5 wt. percent of moderate molecular weight monocarboxylic acids, and from about 5 to 20 wt. percent, preferably 8 .to 15 wt. percentof a rnetal base in about 50 to wt. percent, preferably 60 to 75 wt. percent lubricating oil. Alternatively, the acids and base can be reacted in 40 to 60 wt. percent lubricating oil and from 20 to 15 wt; percent lubricating oil added thereafter to form the thickener concentrates. These thickener concentrates accordingly are composed of about 50 to 75 wt. percent, preferably 60 to 75 wt. percent lubricating oil and from about 50 to 25 wt. percent, preferably 40 to 25 wt. percent, of a mixture of the low and moderate molecular weight acid salts.

The mol ratio of low molecular weight monocarboxylic acids to moderate molecular weightmonocarboxylic acids forming the mixture of acids is in the range of 2:1 to 40:1, preferably 5:1 to 15:1.

The temperature at which the thickener concentrates are formed is an important aspect of the present invention, since the temperature of formation determines the physical and chemical characteristics of the resulting thickener concentrates and the finished lubricants made therefrom. Temperatures in the range of 250 to 350 F., preferably 300 to 320 F. are employed.

The finished lubricants of the invention are prepared by dispersing the above thickener concentrates in lubricating oil at a temperature in the range of about 80 to 350 F. to give a finished lubricant having from about 1 to 15 wt. percent, preferably 3 to 12 wt. percent mixed low and moderate molecular weight monocarboxylic acid metal salts present therein.

The metal bases used to neutralize the monocarboxylic acids are the alkaline earth metal bases or the heavy metal bases of groups I, II, IV and VIII of the periodic system, such as copper, zinc, lead, cobalt, strontium, and magnesium. The alkaline earth metal bases are preferred, and the calcium bases are particularly preferred. Alkali metals are not useful since lubricants containing them have poor structural stability.

The metal bases used are preferably the metal hydroxides although oxides and carbonatw can also be used. Two or more metal bases can be used, although in most instances only one metal base is employed.

The choice of lubricating oil used to form the thickener concentrates and the finished lubricants depends on the particular use contemplated for the lubricant. A wide variety of mineral as well as synthetic lubricating oils can be used. In general, the lubricating oil should have a viscosity within the range of about 60 to 2500 S.S.U. at 100 F. and about 35 to 200 S.S.U. at 210 F., a pour point of about +20 to -75 F., and a flash point of about 350 to 650 F. Oils having a viscosity index of 100 or higher are usually desirable, though oils having a lower viscosity index can be employed. As previously mentioned, synthetic as well as mineral lubricating oils can be employed as part or all of the liquid phase of the grease and they include synthetic lubricating oils of the hydrocarbon, hydrocarbon polymer, ester, complex ester, formal, mercaptal, polyalkylene oxide, silicone and similar types. Synthetic oils such as the simple diesters can also be used, e.g. di-2-ethylhexyl sebacate, di-isooctyl azelate and the complex esters formed from glycols or alcohols or both with dicarboxylic acids or monocarboxylic acids or both.

The finished lubricants can also be prepared by dispersing a thickener concentrate in a lubricating oil of different viscosity than the lubricating oil used to form the concentrate.

The invention will be understood more fully from the following specific examples.

EXAMPLE I A lubricating oil thickener concentrate was prepared by mixing 1777 lbs. of hydrated lime and 7600 lbs. of a mineral oil of a viscosity of 1200 S.S.U. at 100 F. in an 18,000 lbs. capacity steam-heated double action paddled grease kettle. The components were intimately mixed to form a slurry and to the slurry was charged a blend of 2455 lbs. of glacial acetic acid and 595 lbs. of coconut acids (a mixture of 26% caprylic acid, 57% capric acid and 17% lauric acid) over a period of about 1 hour. After 30 minutes mixing, the temperature had increased to a temperature in the range of 180 to 200 F. External heating was then initiated and the temperature raised to 320 F. during the course of 4 hours. Thereafter, heating was discontinued and the mixture cooled by the addition of 5000 lbs. of the above mineral oil and by the passage of cold water through the kettle jacket. The resultant thickener was cooled to 110 F. and passed from the kettle through a Charlotte Mill with a 0.003" opening to a storage tank. The free alkalinity of the thickener concentrate was 1.14 wt. percent, as shown in Table I.

EXAMPLES H AND III These thickener concentrates were prepared in accordance with the process of Example I using the formulations given in Table I. The free alkalinities of these thickeners are also given in Table I.

EXAMPLES IV THROUGH VI These thickener concentrates were prepared for comparison with the thickener concentrates of the invention in accordance with the process given in Example I except that smaller quantities of lime than those required to yield a thickener concentrate having a free alkalinity between 1 and 1.8 wt. percent were employed. The free alkalinity of these thickener concentrates likewise are given in Table I.

1 Examples I, II, and III, are the thickeners 01' the invention. 1 A blend of approximately 26% coprylic acid, 57% capric acid and 17% lauric acid.

Finished lubricants were prepared from the thickener concentrates of Table I as shown in the following examples.

EXAMPLE VII The thickener concentrate prepared in Example I was passed through a Charlotte Mill a second time to a tank equipped with a side entrance paddle. 5900 gallons (44,- 840 lbs.) of mineral oil of 1200 S.S.U. viscosity at F. was added and the mixture intimately mixed at F. The finished lubricant was then passed through a Cornell homogenizer for deaeration and then through a Purolator filter having 0.015 spacing. The lubricant was then inspected and packaged. The inspection data for the lubricant are given in Table II.

EXAMPLES VIII THROUGH XII These lubricants were prepared according to process of Example VII using the thickener concentrates of Examples II through VI respectively. Each finished lubricant was prepared by mixing all of the appropriate thickener concentrate with 44,840 lbs. of the mineral oil of Example VII. The inspection data for these lubricants are also given in Table II.

It can be seen from Tables I and II that increasing the free alkalinity of the thickener concentrates produces a fluid lubricant product having a desirable lower viscosity.

If a lubricant of lower sulfated ash content is desired, such as for example, not over 5.5 the ash content obtained with a lubricant such as lubricant VI can easily be reduced to 5.5% by the addition of 9% mineral oil having a viscosity of 1200 S.S.U. at 100 F. to obtain a lubricant having a viscosity of 1705 S.S.U. at 100 F.

Table 11 [Finished Lubricants Properties X XI XII VII VIII IX Viscosity S.S.U./100 F 2, 150 2, 011 1, 910 l, 893 1, 863 1,852 Four Ball Wear Scar (Spot diam. mm. 1,800

75 O.-1 hour) 0. 20 0.22 0.21 0. 19 0.22 0.20 Sulfated Ash, Percent- 6. 56 5. 62 5. 80 5. 87 5. 97 6.00 Centrifuge Test (4 Hrs. at

1,500 rpm.) l. 8 1. 8 1. 8 1. 1. 8 1. 8 Water by Distillation,

Percent 0. 1 0. 1 O. 1 0. l 0. 1 0. 1 Screen Test (100 mesh).-- No lumps, gel or unreacted lime specks Dispensing (Manzell).. Satisfactory on 14 day test 1 Examples VII, VIII and IX are the finished lubricants of the invention.

It is to be noted that the amount of hydrated lime which is included in the above formulations to obtain the high alkalinity thickener concentrates is not appreciably higher than the amount used to obtain low alkalinity thickener concentrates. For example, comparing the data for Examples I and VI given in Table I, it can be seen that an increase of less than 6% in the amount of added hydrated lime produces an increase in free alkalinity of over 240%.

The decrease in viscosity of the lubricants produced by increasing the free alkalinity of the corresponding thickener concentrates is shown in the figure. In the figure the free alkalinity of the thickener concentrates of Table I is plotted against the viscosity of the corresponding finished lubricants of Table II. It can be seen that an increase in free alkalinity of from 0.48 to 1.64 produces a marked and surprising decrease in the viscosity of the lubricant. e

The lubricants prepared in accordance with the inven-'- tion can contain various conventional additives such as oxidation inhibitors, metal deactivators, corrosion preventatives, extreme pressure agents, dyes, and'the like as understood by those skilledin the art.

What is claimed is: l

1. A lubricant thickener concentrate which comprises about 50 to 75 wt. percent of a lubricating oil having a viscosity in the range of 60 to 2500 S.S.U. at 100- F., and about 25 to 50 wt. percent of a mixture of alkaline earth metal salts of low molecular weight monocarboxylic acids having from 1 to 3 carbon atoms per molecule and alkaline earth metal salts of moderate molecular weight monocarboxylic acids having from 7 to 12 carbon atoms per molecule, the mol ratio of said low to said moderate molecular weight acids being in the range of 2:1 to 40:1, said thickener concentrate having a free alkalinity inthe range of 1 to 1.8 Wt. percent.

2. The lubricant thickener concentrate of claim 1 wherein the mol ratio of low 'to moderate molecule weight acids is in the range of 5:1 to 15:1.

3. The lubricant thickener concentrate of claim 1 wherein said concentrate is prepared at a temperature in the boxylic acids having from 8 to1 2 carbon atoms per adding suflicient alkaline earth metal base to the mixture I to obtain a thickener concentrate having a free alkalinity in therrange of 1 to 1.8 wt. percent.

6. The method of preparing a lubricant thickener concentrate having a free alkalinity in the range of 1 to 1.8

wt. percent comprising dispersing 10 to Wt. percent low molecular weight monocarboxylic acids having from 1 to 3 carbon atoms per molecule, 1 to 6 wt. percent moderate molecular weight monocarboxylic acids having from 7 to 12 carbon atoms per molecule, and suflicient alkaline earth metal base to obtain a thickener concentrate having a free alkalinity in the rangeoof 1 to 1.8%, in

50 to 75 wt. percent lubricating oil having a viscosity in the range'of 60 to 2500 S.S.U. at 100 F., and heating said dispersion to a temperature in the range of 250 to 350 F. to produce said concentrate. v J 7. The method of preparing a lubricant thickener concentrate having a free alkalinity-in the range of 1 to 1.8

Wt. percent comprising forming a mixture of 12 .to 20 wt. percent low molecular weight monocarboxylic acids having from 1 to 3 carbon atoms per molecule, 2 to 5 wt. percent moderate molecular weight monocarboxylic acids" having from 7 to 12 carbon atoms per molecule, suflicient alkaline earth metal base to obtaina thickener concentrate having a free alkalinity in the range of 1- to 1.8%, in 60 7 H575 wt. percent lubricating oil' having a viscosity in the range of 60 to 2500 S.S.U at 100 F. and heating said mixture to a temperature in the range of 250 to 350 F.

to produce said concentrate.

8. The method of preparing a'lubricant thickener .concentrate according to claim 7 wherein the low molecular weight monocarboxylic acids are acteic acid, the moderate molecular weight monocarboxylic acids are a mixture of monocarboxylic acids having from 8 to 12 carbon atoms per molecule, and the metal base is an alkaline earth metal base.

9. The method of claim 8 wherein the alkaline earth metal base is calcium hydroxide.

I V I References Cited in the file of this patent UNITED STATES PATENTS 2,070,014 Lincoln'et al. Feb. 9, 1931 2,265,791 Zimmer et al. Dec. 9, 1941 2,503,969 Rudel et al. Apr. 11, 1950 2,755,256 Dilworth et a1 July 17, 1956 2,758,973 Morway etal. Aug. 14, 1956 2,839,470 Warren et al. June 17, 1958 FOREIGN PATENTS 778,651 Great Britain July 10, 1951

Claims (1)

1. A LUBRICANT THICKENER CONCENTRATE WHICH COMPRISES ABOUT 50 TO 75 WT. PERCENT OF A LUBRICATING OIL HAVING A VISCOSITY IN THE RANGE OF 60 TO 2500 S.S.U. AT 100*F., AND ABOUT 25 TO 50 WT. PERCENT OF A MIXTURE OF ALKALINE EARTH METAL SALTS OF LOW MOLECULAR WEIGHT MONOCARBOXYLIC ACIDS HAVING FROM 1 TO 3 CARBON ATOMS PER MOLECULE AND ALKALINE EARTH METAL SALTS OF MODERATE MOLECULAR WEIGHT MONOCARBOXYLIC ACIDS HAVING FROM 7 TO 12 CARBON ATOMS PER MOLECULE, THE MOL RATIO TO SAID LOW TO SAID MODERATE MOLECULAR WEIGHT ACIDS BEING IN THE RANGE OF 2:1 TO 40:1, SAID THICKENER CONCENTRATE HAVING A FREE ALKALINITY IN THE RANGE OF 1 TO 1.8 WT. PERCENT.

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