US3095376A

US3095376A - Grease composition and process for its preparation

Info

Publication number: US3095376A
Application number: US852979A
Authority: US
Inventors: Harvey E Hook; Harold A Woods
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1959-11-16
Filing date: 1959-11-16
Publication date: 1963-06-25
Anticipated expiration: 1980-06-25
Also published as: NL257915A; DE1137160B; GB915403A

Description

. proved grease compositions.

United States Patent 3,tl95,376 GREASE COMPOSETEON AND PROCESS FOR ITS PREPARA'HON Harvey E. Hook, Danville, and Harold A. Woods,

Martinez, Calii., assignors to Shell Gil Company, a corporation of Deiaware No Drawing. Filed Nov. 16, 1959, Ser. No. 852,979 a 6 Ciaims. (ill. 252-28) This invention relates to improved lubricating grease compositions. More particularly, the invention relates to greases gelled with oleophilic clays and containing a combination of extreme pressure additives as well as a process for the preparation of said grease.

Plastic lubricating compositions suit-able for general use throughout the mechanical arts should possess good lubricating properties and, for heavy duty use, should also inherently possess extreme pressure characteristics when operated in either a dry or wet environment. The latter condition is particularly prevalent in such industrial uses as steel rolling mill applications and the like.

It has been possible in the past to formulate clay grease compositions having good resistance to leaching by water as well as having desirable mechanical characteristics. The ability to operate under extreme loading, however, has not been satisfactorily obtained by the use of most Well known extreme pressure agents such as are employed in oil and grease compositions. The addition of certain inorganic oil-insoluble materials to grease-s for this purpose has been suggested, but it has been found in practice that if they impart any load bearing capacity to the grease this is at a maximum only when the latter is employed in substantially anhydrous environments. Once water is incorporated in the grease, either purposely or accidently, the

. those originally added. This causes the formation of a film (plating out) of the oil-insoluble additive on machinery being lubricated with the composition. Agglomeration of the particles on the other hand causes clogging of screens, plugging of lines and valves of centralized dispensing systems, and the impartingof a grittiness to the composition which is a disadvantageous feature.

It is an object of the present invention to provide im- It is a particular object of the invention to provide a process for the preparation of such compositions. It is a further particular object to provide improved clay grease compositions having extreme pressure properties not only under anhydrous conditions but under wet operating conditions as well. Other objects will become apparent from the following detailed description of the invention. t

Now, in accordance with the present invention, greases gelled with oleophilic clays can be improved with respect to their extreme pressure properties even under wet conditions as Well as dry by the combination therein of an alkali metal borate and a phosphorus and sulfur reaction prod uct ofan olefinic hydrocarbon, especially a terpene, and a phosphorus sulfide. Still in accordance with this inventiona process is provided for the preparation of such compositions which comprises separately forming a substantially anhydrous oleophilic clay grease oomposition and a substantially anhydrous oil suspension of the alkali metal bora-te in particulate form and commingling the bor-ate-oil suspension and the grease compositiomthe phosphorus sulfide-olefin reaction product preferably being added after incorporation of the alkali metal borate. Still in accordance with a preferred aspect of the invention,

more substantial improvements in extreme pressure properties are encountered when the subject grease compositions contain additive amounts of one or more lead soaps (particularly a lead napthenate), with or without a chlorinated aryl disulfide and/or a chlorinated hydrocarbon, all as more particularly described hereinafter.

Examples of the alkali metal bor-ate which may be used in the compositions of this invention include particularly the sodium borates (both hydrated and anhydrous) and including sodium meta-borate and sodium tetraborates, of which the preferred species is borax. Potassium bo-r-ate may be utilized, such as potassium meta-borate and potassium tetraborate. The corresponding lithium or cesium salts may be employed in addition to or in place of the potassium or sodium salts. These are to be utilized in the form of finely divided particles, the more finely divided the better but no critically limited particle size has been established. The borates should be employed in amounts between about 2 and about 10% by weight, based on the total grease composition, preferably between about 2.5 and 4.5 by weight thereof.

In accordance with the preferred process for the preparation of such greases, finely divided borax is suspended in the water-insoluble lubricating oil prior to incorporation in the substantially anhydrous grease composition. This is a relatively simple operation, but care must be exercised to Wet as effectively as possible the surfaces of the finely divided borate with the lubricating oil. This can be accomplished by slowly adding the oil to the borax with vigorous stirring. It is preferred that the suspension contain 0.252.5 parts of the ho-rate for each part by weight of the lubricating oil in which it is suspended. While the suspending operation may be conducted at about room temperature it may be desirable to warm the oil to a temperature between room temperature and about F. for the purpose of lowering the viscosity of the oil, thereby facilitating mixing of the powdered borate and the oil if this is necessary.

The substantially anhydrous. grease composition with which the oil suspension of the alkali metal borate is cornmingled may be well known in the art wherein the principal gelling agent present is an olephilic clay, preferably an oleophilic montmorillinitic clay, such as b-entonite or hectorite. The oleophilic character of the clay grease gelling agent is imparted thereto by reacting with or adsorbing on the clay surface a cationic oleophilic surface aotive agent, particularly relatively highmolecular weight amines, amino amides, or quaternary ammonium compounds, all of which are known in the art.

The clays which are useful as startingmaterials for making the modified oleophilic clay in accordance with these known principles are those exhibiting substantially base exchange properties, and particularly those exhibiting com arativel high base exchan e ro erties and conas those referred to in US. Patent 2,531,427, issued to E. A. Hauser. Suitable cationic materials for adsorption on clays are described in numerous patents including U.S. 2,831,809 and 2,875,152. The clays are normally converted to a satisfactory oleophilic form by the use of 0.25-

1.5 parts by weight of the cationic material for each part by weight of the degangued clay.

The oil ingredient in the greases provided by this invention may be any of the oils of lubricating grade customarily used in compounding greases. The oil may be a refined, unrefined or semi-refined, parafiinic, naphthenic or asphaltic base mineral oil having a viscosity of from about 50 to about 4000 SUS at 100 F. Synthetic lubricants may be employed in place of, or in addition to the mineral oils. The various classes of synthetic lubricants are Well known in the art and do not require detailed description here. Typical classes of such lubricants include phosphates, such as tris(2-ethylhexyl)phosphate, dicarboxylates, such as bis(2-ethylhexyl)sebacate and corresponding silicates and borates.

The incorporation of an alkali metal borate in the described class of oleophilic clay greases imparts a surprising amount of load carrying ability and, even more unexpected, oxidation resistance, to the compositions when they are operated in the virtual absence of water. However, it has been found that when water is present, such as may occur, for example, in wheel bearings under wet driving conditions or in steel mill rolling lubricants, the lubricating characteristics of the grease are maintained but the extreme pressure properties are seriously degraded. Hence, the prime objective of this invention is to overcome this disadvantageous reduction in extreme pressure properties by borate-containing greases in the presence of water. It has been discovered that this feature is overcome by the presence in the grease, together with the borate, of a phosphorusand sulfur-containing reaction product formed between an olefin hydrocarbon of at least 8 carbon atoms, and particularly a cyclic olefin such as a terpene, and a phosphorus sulfide.

The agent cooperating with the borax for the preservation of extreme pressure properties under wet operating conditions is preferably prepared by reaction at temperatures between about 100 and about 160 of a phosphorus sulfide and a bicyclic terpene or a material predominantly comprised of a bicyclic terpene. All of the phosphorus sulfides, such as P 8 P 8 P P 8 P 8 etc. are contemplated as reactants in the preparation of these reaction products but P 8 is particularly preferred. As used herein, the designation bicyclic terpene refers to those terpenes which are characterized by the presence of one double bond in the molecule and built up of a two-rings system. Illustrative of such compounds are pinene, camphene and fenchene. Typical oils containing such materials are turpentine oil, the major constituent of which is pinene. i

Although a complete understanding of the chemical composition of the reaction products of phosphorus sulfides and bicyclic terpenes has not been achieved at this time, a partial understanding of their composition may be obtained by noting the characteristics involved in the reaction. For example, the reaction is exothermic and the viscosity increases appreciably during reaction. Little, if any hydrogen sulfide is evolved. Therefore, the reaction product contains phosphorus and sulfur in substantially the same amounts and ratios as in the particular phosphorus sulfide reacted with the terpene. It would, therefore, appear that the reaction is one of addition, that is, addition of phosphorus sulfide at a site of unsaturation present in the terpene.

(The proportions of reagents used in the preparation of these reaction products may be varied in order to obtain reaction products having different degrees of oil-solubility, tailored to meet the solubility characteristics of the oil or grease employed. In this regard, it is preferred that about one mole of phosphorus sulfide be reacted with four moles of a bicyclic terpene in order to obtain a reaction product relatively soluble in ordinary petroleum oils. Suitable ratios for most purposes contemplated are 1 mole of phosphorus sulfide for 3-5 moles of bicyclic I terpene.

The olefin-phosphorus sulfide reaction product is preferably employed in amounts between about 0.5% and about 5% by weight based on the total grease composition. The additive is preferably incorporated in the greases subsequent to addition of borax. Conveniently, however, it is added to the composition subsequent to dehydration and prior to milling of the composition for the purpose of creating a suitable grease structure.

The addition of these reaction products has been found to have the surprising effect of maintaining the extreme pressure properties of the borax even when water is present. The low cost of borax makes it a desirable additive to employ in large scale use, such as in steel mill rolling greases. Now, with the ability to maintain the extreme pressure properties of the borax grease even in the presence of water by incorporation of the phosphorus sulfideterpene reaction product, a highly satisfactory low cost industrial lubricant is provided. The means by which this maintenance of extreme pressure properties in the presence of water is attained has not been elucidated at this time. However, it has been determined that many other proprietary products useful in themselves as extreme pressure agents have failed to provide borax-containing oleophilic clay greases with the desired maintenance of extreme pressure properties in the presence of water.

The combination of alkali metal borate with the phosphorusand sulfur-containing reaction products with a bicyclic terpene cures the water sensitivity of borax when contained in grease but does not provide the grease composition with maximum extreme pressure properties. These are substantially improved by the further incorporation of a lead naphthenate to the extent of 0.25-2% based on the total weight of the grease. The improvement in extreme pressure properties without damage to the grease structure is a surprising feature of the invention in view of the mild extreme pressure properties which lead naphthenate exhibits in the absence of other materials. Moreover, when utilized alone in amounts in excess of 1%, lead naphthenate hardened the unworked penetration of a grease so that an unduly wide spread occurred between unworked and worked penetrations. Lead naphthenates are materials well known in the art and may be prepared by reaction of lead compounds with naphthenic acids such as those obtained from certain American crudes, especially those obtained from California. These acids are obtained as mixtures and have average molecular weights of about 250 or higher. In producing lead naphthenate the requisite amount of a lead oxide, such as litharge, is added to the acid and the temperature is raised to eifect reaction. The proportion of lead is in the order of 25-35% and it is preferred to make the lead naphthenate from the oxide instead of utilizing other lead salts although these, such as carbonates, may be employed, if desired.

Still further improvements in the extreme pressure properties of the described class of greases is effected by the addition of a chlorinated diaryl disulfide. This may contain about 10% chlorine, although both larger and smaller percentages may be used. Bis(parach1orobenzyl) disulfide is the preferred species but other corresponding compounds may be utilized such as bis(paraphenyl)disulfide, bis(metachloroparatolyl)disulfide and the corresponding chlorinated xylene disulfides, as well as mixed disulfides such as paria-chloro benzyl and para-chloro phenyl disulfide. These materials are preferably employed in amounts between about 0.25 and 2.5% by weight of the total grease composition.

Chlorinated waxes, higher molecular weight hydrocarbons, such as paratfins, may be employed in place of or in addition to the chlorinated diaryl disulfide. The chlorinated waxes are preferably chlorinated parafiin Wax containing from 20 to 50% chlorine, preferably from 30 to 45% by Weight. Corresponding chlorinated rubber may be used.

The following examples illustrate the advantages gained by the use of the process and product of this invention.

Example 1 Formula. percent w. Sample A Sample B Hectorite clay 4. 90 5.03 Amide of 'lctraethylenepentamine and tall oil acids 3. 69 3.79 Phosphoric Acid 0. 40 0. 41 Sodium Nitrite 0. 46 0. 47 Ihenyl-alpha-na-phthylamine 0. 46 0. 47 Borax (Impalpable Powder) r. 3. 3.00 Pass-turpentine Reaction Product. 2.00 Lead Naphthenate 0.50 Lubricating Oil 84. 59 86.83

13.1. Timken Test, lbs:

0 K load, dry 50 20 OK load, wet 35 10 or less a Added to the grease as a 50/50 concentrate of borax and oil after dehydration.

b Saturated with water.

Example II vBy adding the borax as an oil-borax mixture a subrnicron size dispersion Was obtained, no plating out Was experienced during homogenizing or in bearing tests, and the grease was excellent in all respects, as long as the borax comprised at least 65% by weight of particles having less than 50 micron diameters. If the proportion of larger particles is greater than about 35%, it is p neferred that the oil suspension of the borate be added to the grease at an elevated temperature and the resulting mixture stirred for 1560 minutes at 200-300 F. in order to obtain maximum dispersion.

We claim as our invention:

1. A grease composition comprising a major proportion of a lubricating oil, a grease-forming proportion of a colloidally dispersed clay, said clay being Waterproofed with a cationic hydrophobic surface active agent, 210% by weight of an alkali metal borate, at least 65% by weight of said borate being particles having diameters of less than 50 microns, O.252% by weight of a lead naphthenate and 0.55% by Weight of a phosphorusand sulfur-containing reaction product obtained b reaction of a bicyclic terpene and a phosphorus sulfide.

2. A grease composition comprising a major proportion of a mineral lubricating oil, a grease-forming proportion of a colloidally dispersed clay, said clay being Waterproofed with a cationic hydrophobic surface active agent, 210% by weight of borax, 0.252% by weight of a lead naphth-enate and 0.5-5% by Weight of a phosphorusand sulfur-containing reaction product obtained by reaction of a bicyclic terpene and a phosphorus sultide, at least 65 by weight of borax having particle size diameters of less than 50 microns.

3. The process for the preparation of a grease containing borax which comprises mim'ng horax and oil together,

whereby a 'borax-oil suspension is formed and dispersing the suspension in a substantially anhydrous oleophilic clay grease composition by mixing followed by milling, said composition containing 0.252% by Weight of a lead naphthenate and 0.55% by Weight of a phosphorusand sulfur-containing reaction product of a bicyclic terpene and a phosphorus sulfide, at least by weight of borax having particle size diameters of less than 50 microns.

4. The process for the preparation of a grease containing an alkali metal borate which comprises forming a suspension of 0.252.5 parts by Weight of particulate borate in 1 part of a lubricating oil, at least 65% by weight of said borate being particles having diameters of less than 50 microns and thereafter adding the suspension to a substantially anhydrous oleophilic clay grease composition, said grease composition containing 0.25-2% by weight of a lead napthenate and (LS-5% by weight of a phosphorus and sulfur-containing reaction product of a bicyclic terpene and a phosphorus sulfide.

5. In a process for the formation of a grease composition having improved extreme pressure properties in the presence of water, the steps comprising forming a substantially anhydrous composition of grease-forming components, said composition comprising a major proportion of a mineral lubricating oil, a grease-forming proportion of an organophilic montmorillonite clay 0.252% by weight of a lead napthenate and 0.55% by weight of a phosphorusand sulfur-containing reaction product of a bicyclic terpene and a phosphorus sulfide; separately forming a substantially anhydrous lubricating oil suspension of 025-25 parts particulate alkali metal borate per part by Weight of oil, :at least 65 by Weight of said borate being particles having diameters of less than 50 microns; and commingling the composition and suspension.

6. In a process for the formation of a grease composition having improved extreme pressure properties in the presence of Water, the steps comprising forming a substantially anhydrous composition of grease-forming components, said composition comprising a major proportion of a lubricating oil, 0.'25-2% by Weight of a lead naphthenate, a grease-forming proportion of an organophilic montmorillonite clay and 0.5-5% by Weight of a phosphorusand sulfur-containing reaction product of a bicyclic terpene and a phosphorus sulfide; separately forming a substantially anhydrous lubricating oil suspension of 0.25-2.5 parts particulate alkali metal borate per part by weight of oil, at least 65 by weight of said borate being particles having diameters of less than 50 microns; and :commingling the composition and suspension.

References Cited in the file of this patent UNITED STATES PATENTS 2,654,712 Cyphers et a1. Oct. 6, 1953 2,932,615 Jordan et a1. Apr. 12, 1960 FOREIGN PATENTS 789,421 Great Britain Jan. 22, 1958

Claims

1. A GREASE COMPOSITION COMPRISING A MAJOR PROPORTION OF LUBRICATING OIL, A GREASE-FORMING PROPORTION OF A COLLODIALLY DISPERSED CLAY, SAID CLAY BEING WATERPROOFED WITH A CATIONIC HYDROPHOBIC SURFACE ACTIVE AGENT, 2-10% BY WEIGHT OF AN ALKALI METAL BORATE, AT LEAST 65% BY WEIGHT OF SAID BORATE BEING PARTICLES HAVING DIAMETERS OF LESS THAN 50 MICRONS, 0.25-2% BY WEIGHT OF A LEAD NAPHTHENATE AND 0.5-5% BY WEIGHT OF A PHOSPHORUS- AND SULFUR-CONTAINING REACTION PRODUCT OBTAINED BY REACTION OF A BICYCLIC TERPENE AND A PHOSPHORUS SULFIDE.