US3014867A

US3014867A - Lubricating grease wherein the thickener is the metal soap of mixed acids and process for forming same

Info

Publication number: US3014867A
Application number: US671141A
Authority: US
Inventors: Ernest T Fronczak
Original assignee: Pure Oil Co
Current assignee: Pure Oil Co
Priority date: 1957-07-11
Filing date: 1957-07-11
Publication date: 1961-12-26
Anticipated expiration: 1978-12-26

Description

Unite This invention relates to grease'compositions and to a method for their preparation. More particularly this invention relates to a gelatinous grease composition containing an improved metal-soap gelling agent in a solventrefined lubricating oil blended with a solvent extract from the manufacture of lubricating oil stocks.

Greases are conventionally considered as gel systems of fluid lubricants, such as mineral lubricating oils or equivalent synthetic lubricating oils, and gelling agents, such as metal soaps or equivalent inorganic non-soap gelling agents. The most common greases are soap-thickened greases which are normally prepared by saponification of fats in mineral oil, followed by dehydration and dilution with mineral oil to the desired consistency. In the manufacture of greases, the highest consideration is given to obtaining of satisfactory physical properties of melting point, consistency (as measured by the cone penetration test), shear stability (as measured by change in worked consistency), free acid or alkali content, and stability in storage and use. in the economics of greasemaking the yield of grease is extremely important. The yield of grease is ordinarily defined as the relative amount of grease made from a unit amount of gelling agent which will produce greases of the same consistency. Thus, if 10% of one soap is required to produce a No. 2 grease and 15% of another soap is required to produce a No. 2 grease, the former grease is produced in much higher yield. Since greases are made from lubricating oil stocks, it is desirable to make greases from the cheaper solventrefined lubricating oils. However, it has been found that grease compositions prepared from solvent-refined lubricating oil stocks require a muchhigher proportion of soap (and are thus produced in lower yield) than the more expensive distilled lubricating oils. Since the soap represents a relatively high proportion of the cost of a grease, it is very desirable that greases be prepared which use very small amounts'of soap and which may use the inexpensive solvent-refined lubricating-oils.

One of the objects of this invention is to provide a grease composition containing a metal-soap gelling agent.

Another object of this invention is to provide a very high yield grease using an improved metal-soap gelling agent.

A further object of this invention is to provide an improved grease in high yield utilizing a solvent-refined lubricating oil base.

A further object of this invention is to provide an improved grease in-which the lubricating oil base is com posed of a mixture of solvent-refined lubricating oils and a solvent-extract from lubricating oil fractions.

A feature of this invention is the provision of an improved grease utilizing as the gelling agent a metal soap of mixed acids which are obtained as the volatile fraction from the vaccum distillation at 200-270 C, and 4-20 mm. pressure of the by-product acids obtained in the preparation of sebacic acid from castor oil by treatment with alkali.

States Patent 3,014,867 Patented-Dec; 25, 1961 ice Another feature of this invention is the provision of an improved. grease which utilizes as the mineral lubricating oil base. a solvent-refined lubricating oil, alone or in mixture with the solvent-extract from lubricating oil fractions, gelled by an alkali metal soap of the volatile fraction of the by-product acids obtained in the preparation of sebacic acid from castor oil by treatment with alkali.

Other objects and features of this invention will become apparent from time to time throughout the specification and claims as hereinafter related.

This invention is based upon the discovery that greases may: be prepared in highyield from lubricatingoils and a gelling agent which consistsof-a metal soap of the mixed acids which are obtained as the volatile fraction from the vacuurndistillation at 200270 C. and 4-20 mm. pressure of the by-product acids obtained in the preparation of sebacic. acid from castor. oil by treatment with alkali. These metal soaps produce satisfactory greases with any lubricating oil base but have been foundunexpectedly to produce very high yields from lubricating oil bases which consist of'solvent-refined lubricating oils, alone, or in combination with solvent-extracts from lubricating oilfractions. V

In the manufacture of greases according to this invention, the gelling agents used consist of metal soaps of mixed acids which are by products from the manufacture of sebacic acid from castor oil. These mixed'acids are prepared according to a process described in Cheetham et al., US. Patent 2,267,269, the process for which will be described more fully hereinafter, and are referred to hereinafter throughout the specification and claims as mixed acids I. Sebacic acid ismade commercially by fusing castor oil with caustic alkali, or (as described in Patent 2,182,056) by heating the two in the presence of Water under highpressure. The initial reaction products are octanol-2, methyl-hexyl ketone, the sodium salt of s'ebaci-c acid, and the sodium'salts of various by-product acids formed by side reactions. The octane-L2 and methyl-hexyl ketone are removed by distillation. acids formed by side reactions are separated by dissolving the residue in water and acidifying the same with a mineral acid to cause a separation into a lower aqueous layer and an upper oily layer. The lower layer, which is an aqueous solution of sodium sebacate,is drawn ofi'and acidifiedto'precipitate the sebacic acid. The upper oily layer contains the by-product acids for-med by side reactions. The byproduct acidsare separated by distillation at low pressures. These acids are subjected to a temperature of about to 200 C. and 20 mm. pressure for removal of the more volatile acid materials. The mixture is then subjected to progressively increasing temperatures between 200 and 270 C. and'a pressure gradually reducedfrom' 20 mm. to about 4 mm. At temperatures between 200 and 270 C; and pressures of 4'20 mm. a

distillate is obtained which constitutes about 40% of the by-product acids: This distillate consists of a mixture of fatty acids, both saturated and unsaturtaed, of very un" certain composition, which is referred to in the specifica tion and claims as mixed acids 1. Mixed'acids I consist of a very complex mixture of fatty acids containing from 11 to 18 carbon atoms per molecule, including both satu rated and unsaturated acids. Among the unsaturated acids there are some with cis configurations and some with trains configurations. The exact analysis of the composition has-never been completely Worked out and thecomposit'ion has never been reproduced by a synthetic mixture of fatty acids because of its complexity and The because of the somewhat unique combination of titre, acid value and iodine value. Mixed acids I contain about C1143 acids, about 25% (1 acids and about 60% C1648 acids. These mixed acids have the following properties:

Titre 35-38 Iodine value 36-42 Fatty acid (calculated as percent oleic acid) 112-115 Acid val 220-256 Saponification value 221-227 NPA color 1 /2 The mixed acids I are as previously defined. The metallic hydroxide may be any alkali metal hydroxide, such as NaOI-I, LiOH, or KOI-I, or alkaline earth metal hydroxide, such as Ca(OI-l) Mg(OH) or Ba(OH) but is preferably sodium hydroxide. In this composition any suitable bright stock extract or neutral oil may be used, dependent only upon the economic factors in making the grease and the type of grease desired. A satisfactory grease may also be prepared using solvent-refined oils without any solvent-extract, or using distilled lubricating oils. The coupling agent may be any conventional grease coupling agent, such as glycerol, ethylene glycol or other liquid glycols, or liquid polyethylene tglycols.

In preparing a grease from the above ingredients, the acids, coupling agent, bright stock extract, and about of the solvent-refined neutral oil are charged to a greasemaking kettle and heated to 120-130 F., with agitation. When the mixture has reached a temperature of 120- 130 F. the metal hydroxide is added as a 35-40% solution in water. The batch is gradually heated to a temperature of 210-220 F. to complete the neutralization of the acids and to evaporate part of the water. The temperature of the batch is then increased to 320-340 F. for a time sufficient to complete the dehydration of the grease composition. After the evaporation of water from the grease mixture is completed, the grease is cut to any desired soap concentration by adding the remainder of the solvent-refined neutral oil. The diluted grease mixture is then cooled to 180-190 F. and homogenized in a colloid mill or other suitable shearing device to produce a smooth, fine-textured grease.

The utility and superior properties of greases produced according to this invention are illustrated by the following examples, which, however, should not be considered as limiting the grease compositions to those specifically described.

Example 1 A grease was prepared according to this invention from the following ingredients in the proportions indicated:

The bright stock extract used is a highly aromatic oil of high viscosity. It is obtained as the phenol extract from the production of solvent-refined high V.I. bright stock and has the following physical and chemical properties:

Physical:

s lfi 'ty 60 F 0 9% pee c gravr gpjusnds/gallgn 8.100

viscosi 100 F 27,000 150 F 2,447 210 F see NPA color 5 dilute Flash, F 530 Pour, F. 65 Percent volatile 3 hrs. 325 F 0.06 Chemical:

Percent aromatics Percent asphaltenes Aniline point, "F Rostler analysis:

Percent nitrogen bases 4 Percent group 1 ucldififins 23. Percent group 2 acidifllns 58 Percent saturated hydrocarbons The neutral oil used was a 200 SUS at F., solventrefincd neutral oil having the following properties:

API gravity 29.5 Flash 400 F. min. Fire 465 F. mln. Viscosity, sns at 100 F 200 Pour 0 F. Color NPA 3 max. Carbon r i 0.05% max Sulfur 0.45% max Ash 0.01% max Neutralization number 0.1 max Viscosity in x 90 min Carbowax 1500 is a polyethylene glycol produced by Carbide and Carbon Chemicals Company consisting of a mixture of polyethylene glycols of the general formula HOCZHAOC HQHOH, and having an average molecular weight between 500 and 600.

In preparing this grease the mixed acids I, bright stock extract, Carbowax 1500, and about 20% of the solventrefined neutral oil were charged to the grease-making kettle and heated to about -130 F., with agitation. When the temperature of the mixture reached 120-l30 the sodium hydroxide was added as a concentrated solution (about 35-40% concentration). The temperature of the batch was increased first to a temperature of about 2l0-220 F. to complete neutralization of the acids and evaporate part of the water, and then to about 320-340 F. to complete evaporation of the water from the grease mixture. After the grease mixture was completely dehydrated, the remainder of the natural oil was added to cut the soap concentration to a predetermined desired level. The diluted grease mixture was then cooled to 180-190 F. and homogenized in a colloid mill (a Marco Kom-Bi-Nator) to produce a smooth, finetextured grease. The grease produced from these components, utilizing this method of compounding, was a No. 0 grease having an unworked penetration of 352 and a worked penetration of 351. The consistency of this grease is very unusual and excellent for the soap concentrations employed. The narrow spread between worked and unworked penetrations is particularly noteworthy since it is indicative of the excellent shear or consistency stability of the grease.

Example 2 Example 3 Another grease was prepared from the following ingredients, in the proportion indicated:

Component: Concentration (wt. percent) Mixed acids I 8.92 Sodium hydroxide (as concentrated aqueous solution) 1.62

Bright stock extract (as defined in Example 1) 8.84 200 vis. solvent-extracted neutral oil (as defined in Example 1) 79.68 Glycerol 0.89

This grease was prepared by the identical procedure used amass? in Examples 1 and 2, with the glycerol being added at the same point in the processing in place of the Carbo wax 1500. A No. 2 grease was obtained which had an unworked penetration of 273 and a worked penetration of 290. As in the case of Examples 1 and 2, the grease obtained is in unexpectedly high yield and has a narrow range of worked and unworked penetration, indicative of high shear or consistency stability.

Example 4 In still another experiment a grease was prepared using conventional soap stock or fat to illustrate the problems encountered in preparing greases from solvent-refined oils with conventional grease-making soaps. This grease was prepared from the following components in the proportions indicated:

Component: Concentration (wt. percent) Beef tallow 6.42 Hydrogenated fish oil 6.42 Sodium hydroxide (in 35% aqueous solution) 2.07 200 vis. solvent-refined neutral oil (as defined in Example 1) 16.98

350 vis. solvent-refined neutral oil 1 68.11

This oil was a solvent-refined neutral oil produced by phenol extraction of lubricating oil stocks and having the following properties API gravity 30.5 Flash 460 F. min. Fire 510 F. min. Viscosity, SUS at 100 F 350 our 0 F. max. Color NPA 2 Carbon 0.03% max. Ash 0.01% max. Sulfur 0.30% max. Viscosity index 100 min.

This grease was prepared using standard, open-kettle procedure for preparation of soda greases, with the glycerol coupling agent being produced in situ by the saponification of the fats. The grease which was prepared in this manner is typical of greases prepared from solvent- When a grease is prepared in accordance with Example 4 using a mineral oil base consisting of a mixture of bright stock extract and 200 vis. solvent-refined neutral oil, in the proportions indicated in Example 2, a grease is obtained which has an unworked consistency corresponding to a No. 0 grease but which degenerates upon working into a fluid product.

Example 6 When a grease is prepared using the procedures described in Examples 1 to 3 with a mineral oil base consisting of 200 vis. solvent-refined neutral oil and 350 vis. solventrefined neutral oil in the proportions indicated in Example 4, but using the sodium soap of mixed acids 1, and glycerol as a coupling agent, a stable, No. 3 grease is obtained.

It has been found that satisfactory greases can be made with any mineral oil base using alkali metal or alkaline earth metal soaps of mixed acids 1, together with a glycerol, ethylene glycol, or polyethylene glycol coupling agent. it has also been found that While the sodium soaps of mixed acids i produce excellent greases with ordinary mineral oil bases, these soaps are of unexpected utility in preparing greases from the cheaper and more 6 difficultly gelled solvent-refined'oils' or mixtures of solvent-refined oils with solvent extracts.

While there have been described several preferred embodiments of this invention, including several specific examples of the best mode of carrying out this invention, it should be understood that within the scope of the appended claims this invention may be practiced otherwise than as specifically described.

What is claimed is:

.1. A lubricating grease consisting essentially of a major proportion of a mineral oil selected from the group consisting of solvent-refined lubricating oils and mix tures of solvent-refined lubricating oils with aromatic solvent extracts obtained in the solvent refining of lubrieating oils, and a minor proportion of a soap selected 'rom the groupconsisting of alkali metal soaps and alkaline earth metal soaps of mixed acids 1, mixed acids I being obtained as the volatile fraction from the vacuum distillation at 200-270 C. and 4-20 mm. pressure of the by-product acids obtained in the preparation of sebacic acid from castor oil by treatment with alkali, said soap being present in amount sufficient to produce a gellike grease structure.

2. A grease according to claim 1 in which said soap is present in the mineral oil in a concentration correspending to the amount of soap produced by neutralization of 3-20% by weight of the composition of mixed acids 1 with 0.75-5.0% by weight of the composition of a hydroxide of a metal of the group consisting of alkali metals and alkaline earth metals.

3. A grease according to claim 1 in which said mineral oil is a solvent-refined lubricating oil.

4. A grease according to claim 2 which includes a coupling agent for said soap and said mineral oil.

5. A grease according to claim 2 in which said mineral oil is a solvent-refined lubricating oil, said metal hydroxide is sodium hydroxide, and the composition includes a coupling agent of the class consisting of glycerol, ethylene glycol, and liquid polyethylene glycols.

6. A grease according to claim 2 prepared from the following starting materials:

Percent Mixed acids I 3-20 Metal hydroxide 0.75-5.0 Aromatic oil consisting of the solvent extract from production high V.I. bright stock 6-12 200 vis. solvent-refined neutral oil -85 Coupling agent of the class consisting of glycerol, glycol, and liquid poly-ethylene glycol 0.3-6.0

7. A grease according to claim 2 prepared from the following starting materials:

Mixed acids I 4.17 Sodium hydroxide 0.88 Aromatic oils obtained as the solvent extract in production of high V1. bright stock 10.01 200 vis. solvent-refined neutral oil 83.90 Mixture of polyethylene glycols having average molecular weight of 500-600 1.04

8. A grease according to claim 2 prepared from the following starting materials:

Mixed acids I 8.92 Sodium hydroxide 1.62 Aromatic oils produced as a solvent extract from the production of high V.I. bright stock 8.84 200 vis. solvent-refined neutral oil 79.68 Glycerol 0.89

9. A method of producing a grease as defined in claim 4 in which a mixture of mixed acids I, coupling agent, and part of the oil is charged to a grease-making kettle and heated to l20-130 F. with agitation, the

etal hydroxide is added in concentrated aqueous solution to the heated mixture, the resulting m xture is heated to 210-220 F. until mixed acids I are neutralized, the

mixture is heated to 320340 F. to evaporate all Water therefrom, the remainder of the oil is added to cut the grease to the desired soap concentration, and the diluted grease is cooled to 180190 F. and homogenized.

10. A method of producing a grease as defined in claim 6 in which a mixture of mixed acids I, coupling agent, bright stock extract, and part of the solvent-refined neutral oil is charged to a grease-making kettle and heated to 120130 F. with agitation, the metal hydroxide is added in concentrated aqueous solution to the heated mixture, the resulting mixture is heated to 210- 220 F. until mixed acids I are neutralized, the mixture is heated 320340 F. to evaporate all water therefrom, the remainder of the solvent-refined neutral oil is added to produce the desired soap concentration in the grease, and the diluted grease is cooled to 180-190 F. and homogenized.

References Cited in the file of this patent The Manufacture and Application of Lubricating Greases, Boner, Reinhold Pub. Corp., New York, 1954, pages 138, 139, 443 and 952.

Claims

1. A LUBRICATING GREASE CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF A MINERAL OIL SELECTED FROM THE GROUP CONSISTING OF SOLVENT-REFINED LUBRICATING OILS AND MIXTURES OF SOLVENT-REFINED LUBRICATING OILS WITH AROMATIC SOLVENT EXTRACTS OBTAINED IN THE SOLVENT REFINING OF LUBRICATING OILS, AND A MINOR PROPORTION OF A SOAP SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL SOAPS AND ALKALINE EARTH METAL SOAPS OF MIXED ACIDS I, MIXED ACIDS I BEING OBTAINED AS THE VOLATILE FRACTION FROM THE VACUUM DISTILLATION AT 200*-270*C. AND 4-20 MM. PRESSURE OF THE BY-PRODUCT ACIDS OBTAINED IN THE PREPARATION OF SEBACIC ACID FROM CASTOR OIL BY TREATMENT WITH ALKALI, SAID SOAP BEING PRESENT IN AMOUNT SUFFICIENT TO PRODUCE A GELLIKE GREASE STRUCTURE.

2. A GREASE ACCORDING TO CLAIM 1 IN WHICH SAID SOAP IS PRESENT IN THE MINERAL OIL IN A CONCENTRATION CORRESPONDING TO THE AMOUNT OF SOAP PRODUCED BY NEUTRALIZATION OF 3-20% BY WEIGHT OF THE COMPOSITION OF MIXED ACIDS I WITH 0.75-5.0% BY WEIGHT OF COMPOSITION OF A HYDROXIDE OF A METAL OF THE GROUP CONSISTING OF ALKALI METALS AND ALKALINE EARTH METALS.