OVERBASED METAL CARBOXYLATE CALCITE-CONTAINING GREASES

Abstract

Grease precursors of overbased alkaline earth metal carboxylates are prepared by reacting an alkaline earth metal base and a carboxylic acid in the presence of a hydrocarbon liquid, a polyol and an alcohol. The resulting grease precursor has amorphous calcium carbonate and a calcite content of greater than 10% by weight. At least one converting agent is added to the grease precursor containing elevated levels of calcite. This mixture is heated followed by the removal of water to form calcite-containing greases having a calcite content greater than 12.5% by weight.

Description

TECHNICAL FIELD

The invention relates to greases prepared from an alkaline earth metal salt of a fatty acid. More particularly, the invention relates to greases prepared from calcite-containing overbased metal carboxylates.

BACKGROUND OF THE INVENTION

Grease manufacturing includes a multi-step process and numerous additives to provide property enhancements which present an increasing challenge to the specialty, food-grade and bio-based grease formulators. The resulting grease performance is also strongly dependent upon the processing conditions such as temperature, pressure, residence times and saponification stoichiometry.

An important step in the production of a grease is the formation of the thickener microstructure. The process constitutes a reaction between a carboxylic acid, an alkali or alkaline earth metal, water and a base oil. The microstructure of the crystalline material, or the matrix, in the grease enables the uptake and release of the lubricious oil. The microstructure resulting from the initial soap reaction and process conditions determines the grease properties.

Thixotropic greases or grease-like overbased metal carboxylate or other overbased metal-containing compositions having corrosion-inhibiting properties, and having utility for a variety of uses such as, for instance, in automobile and truck body undercoatings, and for various other purposes, are known to the art. Such greases or grease-like compositions have gone into quite widespread use either as such, or admixed with other ingredients to produce compositions for use in a variety of environments, and, generally speaking, they are characterized by reasonably good extreme pressure and antiwear properties, high dropping points, reasonably good resistance to mechanical breakdown, salt spray and water-corrosion resistance, thermal stability at high temperatures, and other desirable properties.

Overbased metal carboxylates are generally produced by carbonating a mixture of hydrocarbons, carboxylic acid, metal oxide (calcium oxide for example) or metal hydroxide (calcium hydroxide for example) and promoters such as methanol and water. In carbonation, the calcium oxide or hydroxide reacts with the gaseous carbon dioxide to form calcium carbonate. The carboxylic acid is neutralized with an excess of CaO or Ca(OH)₂ to form the carboxylate. The prior art known processes for overbasing calcium carboxylates produce high alkaline materials having a TBN of 300 mg KOH/gm or higher. The TBN is the measurement of alkaline reserve, which is the number of milligrams of potassium hydroxide equivalent to the amount of acid required to neutralize the alkaline constituents present in one gram of sample. An additive having a total base number higher than can be obtained from a stoichiometrically prepared calcium carboxylate alone is commonly termed “overbased” or, alternatively, is termed “superbasic”.

The addition of converting agents to overbased Newtonian solutions of calcium sulfonates or other overbased metal-containing materials along with heating and/or vigorous mixing, results in the formation of the non-Newtonian colloidal disperse systems. These converting agents include, among many others, water; alcohols, for instance, methanol, isobutanol, n-pentanol and many others or mixtures thereof or mixtures of alcohols with water; alkylene glycols; mono-lower alkyl ethers of alkylene glycols such as monomethylether of ethylene glycol; and numerous others such as lower aliphatic carboxylic acids exemplified by acetic acid and propionic acid; ketones; aldehydes; amines; phosphorus acids; alkyl and aromatic amines; certain imidazolines; alkanolamines; and, carbon dioxide as such, or better in combination with water. The resulting non-Newtonian colloidal disperse systems may be in the form of gels or greases depending upon the particular conditions, proportions and ingredients which are utilized in the preparation thereof.

In overbased calcium-containing Newtonian solutions, the calcium carbonate which is formed during the preparation of the Newtonian solutions appears to be in an amorphous form whereas, when the Newtonian solutions are converted into the non-Newtonian colloidal disperse systems, the dissolved amorphous calcium carbonate salt or complex is transformed into solid crystalline metal-containing particles of calcium carbonate, usually in the form of calcite, which then grow to form particle sizes which may range in size from about 40 to 50 angstroms (Å) or larger, for instance, up to 1000 Å or even up to about 5000 Å. The calcium carbonate component of the overbased metal carboxylate forms the core of a metal carboxylate micellar structure.

In the case of an overbased alkaline earth metal carboxylate of a higher carboxylic acid such as oleic acid, the conversion agents such as water and acetic or propionic acid, when added to the Newtonian solution of amorphous calcium carbonate and calcium carboxylate, gives only partial conversion of the amorphous calcium carbonate to vaterite, a spherical form of calcium carbonate, and none of the desirable calcite is formed. This is in contrast to the overbased calcium sulfonates, which when treated with the conversion agents, form calcite or calcite and vaterite micelles from the amorphous overbased calcium sulfonates.

Notwithstanding the state of the art as described herein, there is a need for further improvements in preparing greases that are prepared from grease precursors of calcite-containing overbased alkaline earth metal carboxylates that have a balance of properties for low temperature mobility, extreme pressure, anti-wear, water washout and dropping point temperature.

SUMMARY OF THE INVENTION

In general, one aspect of the invention is to provide a grease precursor that includes a hydrocarbon liquid, a polyol, an alcohol, wherein the alcohol has at least 8 carbon atoms, an overbased alkaline earth metal salt of a fatty acid an overbased alkaline earth metal salt of a fatty acid comprising calcite, wherein the calcite is present in an amount of greater than 10% by weight of the grease precursor.

Another aspect of the invention is to provide a method for preparing a grease precursor. The method includes the steps of:

(a) preparing a mixture comprising a carboxylic acid, wherein the carboxylic acid is a fatty acid, a base oil, a polyol and an alcohol, wherein the alcohol has at least 8 carbons;

(b) neutralizing the carboxylic acid with an initial amount of alkaline earth metal base to form an alkaline earth metal carboxylate mixture;

(c) heating the alkaline earth metal carboxylate mixture;

(d) adding an additional amount of an alkaline earth metal salt to the alkaline earth metal carboxylate mixture;

(e) carbonating the mixture to neutrality to form amorphous alkaline earth metal carbonate in the alkaline earth metal carboxylate mixture, wherein water generated in situ during carbonation promotes a conversion of the amorphous alkaline earth metal carbonate to calcite;

(f) repeating steps (d) and (e) at least one more time; and

(g) removing water from the alkaline earth metal carboxylate mixture to obtain a grease precursor having a an amount of calcite greater than 10% by weight.

A further aspect of the invention is to provide a method for preparing a grease. The method includes the steps of:

(a) preparing a mixture comprising a carboxylic acid, wherein the carboxylic acid is a fatty acid, a base oil, at least one polyol and at least one alcohol, wherein the alcohol has at least 8 carbons;

(b) neutralizing the carboxylic acid with an initial amount of alkaline earth metal base to form an alkaline earth metal carboxylate mixture;

(c) heating the alkaline earth metal carboxylate mixture;

(d) adding an additional amount of an alkaline earth metal salt to the alkaline earth metal carboxylate mixture;

(e) carbonating the mixture to neutrality to form amorphous alkaline earth metal carbonate in the alkaline earth metal carboxylate mixture, wherein water generated in situ during carbonation promotes a conversion of the amorphous alkaline earth metal carbonate to calcite;

(f) repeating steps (d) and (e) at least one more time;

(g) removing water from the alkaline earth metal carboxylate mixture to obtain a grease precursor having an amount of calcite greater than 10% by weight;

(h) adding and mixing at least one conversion agent to the grease precursor to form a converted mixture, wherein the conversion agent is selected from the group consisting of a hydrocarbon oil, water and a C₁-C₅ carboxylic acid;

(i) heating the converted mixture of (h); and

(j) removing water from the converted mixture to obtain a grease having an amount of calcite greater than 12.5% by weight.

Yet another aspect of the invention is to provide a method for preparing a grease. The method includes the steps of:

(a) preparing a mixture comprising a carboxylic acid, wherein the carboxylic acid is a fatty acid, a base oil, at least one polyol and at least one alcohol, wherein the alcohol has at least 8 carbon atoms;

(b) neutralizing the carboxylic acid with an initial amount of alkaline earth metal base to form an alkaline earth metal carboxylate mixture;

(c) heating the alkaline earth metal carboxylate mixture;

(d) adding an additional amount of an alkaline earth metal salt to the alkaline earth metal carboxylate mixture;

(e) carbonating the mixture to neutrality to form amorphous alkaline earth metal carbonate in the alkaline earth metal carboxylate mixture, wherein water generated in situ during carbonation promotes a conversion of the amorphous alkaline earth metal carbonate to calcite;

(f) repeating steps (d) and (e) at least one more time;

(g) removing an amount of water from the alkaline earth metal carboxylate mixture to obtain a grease precursor having an amount of calcite greater than 25% by weight;

(h) adding and mixing the grease precursor to at least an amount of an overbased calcium carboxylate to form a grease precursor-overbased calcium carboxylate mixture, wherein the overbased calcium carboxylate contains amorphous calcium carbonate and is substantially free of calcite;

(i) adding and mixing at least one conversion agent to the grease precursor-overbased calcium carboxylate mixture to form a converted mixture, wherein the conversion agent is selected from the group consisting of a hydrocarbon oil, water and a C₁-C₅ carboxylic acid;

(j) heating the converted mixture of (i); and

(k) removing water from the converted mixture to obtain a grease having an amount of calcite greater than 8.0% by weight.

Another aspect of the invention is to provide a method for preparing a grease precursor. The method includes the steps of:

(a) preparing a mixture comprising a carboxylic acid, wherein the carboxylic acid is a fatty acid; a base oil; a polyol; and an alcohol, wherein the alcohol has at least 8 carbon atoms;

(b) neutralizing the carboxylic acid with an initial amount of alkaline earth metal base to form an alkaline earth metal carboxylate mixture;

(c) heating the alkaline earth metal carboxylate mixture;

(d) adding an additional amount of an alkaline earth metal base to the alkaline earth metal carboxylate mixture;

(e) carbonating the mixture to neutrality to form amorphous alkaline earth metal carbonate in the alkaline earth metal carboxylate mixture, wherein water generated in situ during carbonation promotes a conversion of the amorphous alkaline earth metal carbonate to calcite;

(f) repeating steps (d) and (e) at least one more time; and

(g) removing water from the alkaline earth metal carboxylate mixture to obtain a grease precursor having a an amount of calcite greater than 25% by weight.

DETAILED DESCRIPTION OF THE INVENTION

Overbased alkaline earth metal carboxylates are utilized in the formation of grease precursors having elevated levels of calcite. These calcite-containing grease precursors, when combined with a conversion agent, are subsequently converted into greases having improved properties for low temperature mobility, extreme pressure, anti-wear, water washout and dropping point temperature.

The alkaline earth metal of the carboxylate of the grease precursor is selected from the group consisting of calcium, barium, magnesium and strontium. These metals are derived from metal oxides and hydroxides, and in some instances, metal sulfides and hydrosulfides. For example, the grease precursor can include an overbased calcium carboxylate.

The carboxylic acid portion of the grease precursor, which includes fatty acids, including C₈-C₃₀ saturated, unsaturated carboxylic acids of 8 to 30 carbon atoms, either alone or in combination with each other, or reactive equivalents of carboxylic acids. Examples of useful carboxylic acids and fatty acids include but are not limited to caprylic acid, capric acid, lauric acid, myristic acid, myristoleic acid, 2-ethylhexanoic acid, decanoic acid, dodecanoic acid, pentadecanoic acid, palmitic acid, palmitoleic acid, stearic acid, 12-hydroxystearic acid, oleic acid, ricinoleic acid, linoleic acid, linoleic acid, arachidic acid, gadoleic acid, behenic acid, erucic acid, and mixtures of any of these acids.

The grease precursor also includes an alcohol that promotes the formation of the overbased alkaline earth metal carboxylate. The alcohol includes aliphatic alcohols that contain at least 8 carbon atoms. In one example, an aliphatic alcohol having 8 to 14 carbon atoms or more can be used. Examples of such aliphatic alcohols include isodecanol, dodecanol, octanol, tridecanol, tetradecanol or mixtures thereof. For example, one aliphatic alcohol is Epal 14-18. It has been found that when a higher aliphatic alcohol is employed in making the overbased product, phenol may be excluded from the reaction as a promoter.

The overbased metal carboxylates of the grease precursors are prepared containing at least 15% by weight or more of the alkaline earth metal as calcium. In the preparation of higher metal-containing overbased products, for example, containing at least 15% by weight metal, it has been found suitable to use a polyol. The polyol can be a glycol or a glycol ether. The glycol or glycol ether may be selected from the group consisting of diethylene glycol monobutyl ether (butyl Carbitol®), triethylene glycol, dipropylene glycol, diethylene glycol monomethyl ether, ethylene glycol monobutyl ether, and mixtures thereof.

A base oil is also employed for preparing and containing the overbased materials in the grease precursor. The base oil can be a hydrocarbon liquid that generally includes any hydrocarbon diluent. Most generally, the liquid hydrocarbon is selected from the group of hydrocarbon oils, mineral spirits, non-aromatic hydrocarbons and polyalphaolefins (PAOs).

The process for preparing the overbased calcium carboxylates for use as grease precursors includes the reaction of an alkaline earth metal base and a carboxylic acid to form an alkaline earth metal carboxylate mixture, with an equivalent ratio of metal base to the carboxylic acid greater than 1:1 in the presence of a liquid hydrocarbon, an aliphatic alcohol, and a glycol ether. In one example, the carboxylic acid is a fatty acid, the fatty acid being oleic acid, the liquid hydrocarbon is a 4 CST PAO, the aliphatic alcohol is Epal 14-18, and the glycol ether is propylene glycol. The mixture is acidified, through a process of carbonation, to produce amorphous alkaline earth metal carbonate, for example calcium carbonate. The step of carbonation involves treating the mixtures described above with an acidic gas in the absence of free oxygen until the titratable basicity is determined using phenolphthalein. Generally, the titratable basicity is reduced to a base number below about 10. The mixing and carbonation steps require no unusual operating conditions other than the exclusion of free oxygen.

By the term “acidic gas” as used in this specification and in the claims is meant a gas which upon reaction with water will produce an acid. Thus, such gases as sulfur dioxide, sulfur trioxide, carbon dioxide, carbon disulfide, hydrogen sulfide, etc., are exemplary of the acidic gases which are useful in the preparation of the overbased metal carboxylates disclosed. When carbon dioxide is used the alkaline earth carbonate is formed. When the sulfur gases are used, the sulfate, sulfide and sulfite salts are formed.

During carbonation the mixture may be heated to a temperature which is sufficient to drive off some of the water contained in the mixture or the water generated during the reaction of the base and the carboxylic acid can be retained during the overbasing reactions. The treatment of the mixture with the carbon dioxide preferably is conducted at elevated temperatures, and the range of temperatures used for this step may be any temperature above ambient temperature in the range from about 75° C. (about 165° F.) to about 200° C. (about 390° F.). Higher temperatures may be used such as 250° C. (about 480° F.), but there is no apparent advantage in the use of such higher temperatures. Ordinarily, a temperature of about 80° C. (about 175° F.) to 150° C. (about 300° F.) is satisfactory.

During carbonation, a non-slurried, dry alkaline earth metal base, liquid hydrocarbon and an aliphatic alcohol are added in relative amounts at a controlled rate of base addition. Water is removed from the reaction product to produce a grease precursor containing amorphous calcium carbonate and elevated levels of calcite that is substantially free of vaterite and aragonite. Generally, the process be conducted in the absence of free oxygen and, for this purpose, an atmosphere of nitrogen is used.

EXAMPLES

Formation of Overbased Calcium Oleate as Grease Precursor

Example 1

In a 3-liter reactor was placed 507.2 g. of oleic acid, 972.6 g. of 4 CST PAO, 270.0 g. of Epal 14-18 and 109.1 g. of propylene glycol. The mixture was heated with stirring to about 38° C. (100° F.) to melt the Epal 14-18, followed by the addition of 50 g. of water and an initial amount of lime (70.8 g.), as the alkaline earth metal base, was added to neutralize the oleic acid. The heating was continued to about 93° C. (200° F.) and the first portion of 207.5 g of lime (Microcal HF) was added. The mixture was carbonated at about 93° C. (200° F.) with carbon dioxide at a rate of 2 SCFH until the lime was consumed and neutralized, as indicated by a colorless spot on a phenolphthalein-saturated filter paper. The carbonation took approximately 1 hour and 35 minutes. The carbon dioxide addition was stopped, and a second 207.5 g. portion of lime was added. The carbon dioxide addition at about 93° C. (200° F.) was resumed at 3 SCFH for about another 1 hour and 30 minutes, when the phenolphthalein paper test showed the lime was consumed and neutralized. A third and a fourth 207.5 g. portions of lime were added and the carbonation to neutrality was repeated for about 1 hour. When the reaction was neutral after the fourth lime portion was carbonated, the carbon dioxide was stopped and the water produced from the reaction of the lime and the oleic acid was removed under vacuum and heating to about 149° C. (300° F.). The product was analyzed to contain the following physical parameters which include no detectable vaterite or aragonite by X-ray diffraction analysis:

% Ca by weight: 15.95

% Calcite by weight: 10.28

TBN: 409.4

The grease precursor containing amorphous calcium carbonate and elevated levels of calcite can then be converted into a grease. Converting agents useful in this invention include, among many others, water; alcohols, for instance, methanol, isopropyl alcohol isobutanol, n-pentanol and many others or mixtures thereof or mixtures of alcohols with water; alkylene glycols; mono-lower alkyl ethers of alkylene glycols such as monomethylether of ethylene glycol (methyl Cellosolve); and numerous others such as lower aliphatic carboxylic acids exemplified by acetic acid and propionic acid; ketones; aldehydes; amines; phosphorus acids; alkyl and aromatic amines; alkanolamines; and, also, carbon dioxide as such, or better in combination with water.

Formation of Grease from Overbased Calcium Oleate Grease Precursor

Example 2

With a grease precursor containing amorphous calcium carbonate and elevated levels of calcite made using Star 4 Group III oil as the base oil, wherein the grease precursor measured 16.45% Ca by weight, TBN 403, 13% calcite by weight, 600 g. of the precursor was placed in a reactor followed by the addition of 400 g. of 350 SUS oil, 50 g. of water, and 40 g. of glacial acetic acid. The mixture was heated at about 104° C. (220° F.) for approximately 2 hours and 20 minutes under reflux conditions in a nitrogen atmosphere. Next, water was removed under vacuum. The resulting grease was analyzed and found to contain 17.9% calcite by weight and 6.7% vaterite by weight.

The grease was then tested and yielded the following results:

Cone Penetration                 305
Load Wear Index (ASTM D 2596-97) 57.48
Last Non-Seizure Load            32 Kg
Weld Load (ASTM D 2596-97)       500 Kg
Four Ball Wear (ASTM 2266-01)    0.50 mm
Water Washout (ASTM D 1264-00)   0.3%

Example 3

Example 2 was repeated, except that 30.0 g. of lime was added to the reaction mixture. The mixture was heated at about 104° C. (220° F.) for approximately 2 hours and 20 minutes under reflux conditions in a nitrogen atmosphere. Next, water was removed under vacuum. The resulting grease had a cone penetration of 213. The grease was further let down 50% with an additional amount of 350 SUS oil resulting in a cone penetration of 265. The let down grease was analyzed and found to contain 16.3% calcite by weight and 5.0% vaterite by weight.

Example 4

The PAO-containing grease precursor of Example 1 was gelled by the same process as described in Example 2. In a reactor 600 g. of the precursor containing amorphous calcium carbonate and elevated levels of calcite, 400 g. of 8 CST PAO, 30 g. lime, 50 g. of water, and 48 g. of glacial acetic acid were mixed. The mixture was heated at about 104° C. (220° F.) for approximately 2 hours and 20 minutes under reflux conditions in a nitrogen atmosphere. Next, water was removed under vacuum. The resulting grease was analyzed and found to contain 13.3% calcite and 7.5% vaterite and had a cone penetration of 232. This grease was further let down to a #2 grease with 8 CST PAO (to 53% precursor). This let down grease was analyzed and found to contain 26.6% calcite by weight and had a cone penetration of 235. The let down grease was then tested and yielded the following results:

Load Wear Index (ASTM D 2596-97) 69.5
Last Non-Seizure Load            63 Kg
Weld Load (ASTM D 2596-97)       500 Kg
Four Ball Wear (ASTM 2266-01)    0.49 mm
Water Washout (ASTM D 1264-00)   2.5%

The grease precursor containing amorphous calcium carbonate and elevated levels of calcite can also be added to a substantially calcite-free overbased calcium carboxylate material and gelled to form a calcite-containing grease. In particular, the grease precursor containing amorphous calcium carbonate and elevated levels of calcite can also be added to a clear, isotropic substantially calcite-free overbased calcium carboxylate material and gelled to form a calcite-containing grease having elevated performance in terms of load wear index, last non-seizure load and weld load.

Generally, the conversion of a clear, isotropic overbased calcium carboxylate material to a gel or grease is substantially devoid of calcite. Treatment of the clear, isotropic substantially calcite-free overbased calcium carboxylate material, that contains micelles of amorphous calcium carbonate, with a variety of conversion agents, such as acetic and propionic acid, either alone or in combination thereof, yields a vaterite-containing gel or grease. The amorphous calcium carbonate present in the clear liquid is partially converted to vaterite, a spherical form of crystalline calcium carbonate, and not calcite, a plate-like form of crystalline calcium carbonate.

Further Examples

Formation of Overbased Calcium Oleate as Grease Precursor

Example 5

In a 4-liter reaction flask, equipped with an overhead stirrer, heating mantle, gas inlet tube (subsurface) and condenser with a Dean-Stark trap, was placed 507.22 g. of oleic acid, 108.02 g. of propylene glycol, 270 g. of dodecyl alcohol, 972.0 g. of white mineral oil (Drakesol™ 60) and 50.2 g. of water. The mixture was heated with stirring to 37.8° C. (100° F.) and 70.84 g. of calcium hydroxide, as the alkaline earth metal base, was added. The mixture was heated further to 200° F. and an additional 209.0 g. of calcium hydroxide was added.

Carbon dioxide gas was bubbled into the mixture through the subsurface gas addition tube at a rate of 1.4 SLPH (standard liters per hour) for approximately 48 minutes, at which point the lime had been consumed, as indicated by a colorless spot when the mixture was spotted on phenolphthalein-saturated filter paper. The carbon dioxide addition was continued for an additional 5 minutes. A second 209.0 g. portion of lime was added, and the carbon dioxide addition continued at 1.4 SLPH for approximately 47 minutes, until the lime had been consumed and the reaction mixture was near neutral. The carbon dioxide addition was continued an additional 5 minutes. The lime addition and carbon dioxide addition for 52 minutes was repeated twice more. A total of 836.0 g of lime was added and subjected to carbonation.

At the end of the last addition period of carbon dioxide, the gas was changed to nitrogen at 5 SCFH (standard cubic feet per minute) and the temperature of the reaction mixture was gradually raised to 300° F. over a one hour period. The nitrogen flow and heating at about 149° C. (300° F.) was continued until no additional water accumulated in the Dean-Stark trap. A total of 260.67 g. of distillate was collected. The product, a thick slurry, contained no detectable vaterite or aragonite by X-ray diffraction analysis.

The product was analyzed to contain the following physical parameters:

% Ca by weight: 16.38

% Calcite by weight: 36.7%

Formation of Grease from Overbased Calcium Carboxylate Grease Precursor

Example 6

In a 5-gallon Patterson Grease Kettle (Patterson Industries (Canada) Limited), were placed 3 kg. of a clear, isotropic non-calcite-containing overbased 10% calcium carboxylate material, 3 kg. of an overbased calcium carboxylate precursor containing 17.93% calcium by weight and 25.7% calcite by weight, 4 kg. of Drakesol™ 600 white oil and 300 g. of lime. After the addition of a mixture of 480 g. of glacial acetic acid and 520 g. of water with agitation, access to the kettle was closed. The kettle was then heated to about 103° C. (218° F.) over a 1-hour period in the closed vessel. Next, water was removed through a condenser. A total of 400 ml of water was collected. A total of 1750 g. of let-down oil (Drakesol™ 600) was added to the mixture, followed by and the batch cooled to 168° F. over a 1.5 hour period. The grease was homogenized and cooled to room temperature. The finished grease had a cone penetration of 289, and contained 10.97% vaterite by weight and 8.1% calcite by weight. The grease was then tested and yielded the following results:

Load Wear Index (ASTM D 2596-97) 50.7
Last Non-Seizure Load            80 Kg
Weld Load (ASTM D 2596-97)       400 Kg
Four Ball Wear (ASTM 2266-01)    0.42 mm

Formation of Grease from Overbased Calcium Carboxylate Without Grease Precursor

Example 7

In a 5-gallon Patterson Grease Kettle were placed 7 kg. kg of a clear, isotropic non-calcite-containing overbased 10% calcium carboxylate material, 3 kg. of Drakesol 600, 380 g. of water, and 228 g. of glacial acetic acid. The mixture was heated with agitation over a 45 minute period to a temperature of about 106° C. (223° F.), at which time 195 ml of water was removed by distillation over a time period of about 20 minutes. The grease was homogenized and allowed to cool to room temperature. The finished grease had a cone penetration of 274.5, and a vaterite content of 10.97% by weight. The grease was then tested and yielded the following results:

Load Wear Index (ASTM D 2596-97) 42.1
Last Non-Seizure Load            63 Kg
Weld Load (ASTM D 2596-97)       315 Kg
Four Ball Wear (ASTM 2266-01)    0.40 mm

The grease precursor containing amorphous calcium carbonate and elevated levels of calcite offers processing benefits in addition to performance when compared to the conventional grease-making process where saponification may be necessary. This is due to the “pre-saponified” nature and fast gellation properties of the overbased grease precursor. Relative to the conventional grease-making process, the preparation of a grease from an overbased calcium oleate grease precursor results in an improvement in energy costs given that the average gellation temperature is about 104° C. (220° F.). The grease further containing amorphous calcium carbonate and elevated levels of calcite reduces the cycle time by eliminating the need for the introduction of other grease additives in order to achieve equal or better performance.

The overbasing chemistry provides for grease formulations that can be registered as food grade, biodegradable and biobased. The overbased precursor contains calcium oleate, promoters made from materials that include propylene glycol and lauryl alcohol, all of which are listed under the NSF registry for incidental food contact. The base oils used in the precursor formulations can be either synthetic or non-synthetic. The gelled material can be adjusted to the NLGI grade grease by using a suitable oil to yield a H1 food grade grease. A vegetable derived formulation can be adjusted to meet an NLGI #2 grease by using natural soybean oil, for example, rendering the resulting grease biodegradable. The grease can be categorized as biobased and biodegradable when the grease is made from vegetable-derived oleic acid and a let down oil consisting of a vegetable-derived oil such as canola or palm oil.

Based upon the foregoing disclosure, it should now be apparent that the grease precursor containing elevated levels of calcite as described herein will carry out the objects set forth hereinabove. It is, therefore, to be understood that any variations evident fall within the scope of the claimed invention and thus, the selection of specific component elements can be determined without departing from the spirit of the invention herein disclosed and described.

Claims

1. A grease precursor comprising:

a hydrocarbon liquid;

a polyol;

an alcohol, wherein the alcohol has at least 8 carbon atoms; and

an overbased alkaline earth metal salt of a fatty acid comprising amorphous calcium carbonate and calcite, wherein the calcite is present in an amount of greater than 10% by weight of the grease precursor.

2. The precursor of claim 1 being substantially free of vaterite and aragonite.

3. The precursor of claim 1 having a TBN of greater than 400.

4. The precursor of claim 1, wherein the fatty acid is a C12-C22 fatty acid.

5. The precursor of claim 4, wherein the fatty acid is oleic acid.

6. The process of claim 1, wherein an alkaline earth metal of the overbased alkaline earth metal salt is selected from the group consisting of calcium, barium, magnesium and strontium.

7. The precursor of claim 1, wherein the overbased alkaline earth metal salt is calcium oleate.

8. The precursor of claim 1, wherein the alcohol is an aliphatic alcohol of at least 14 carbon atoms.

9. The precursor of claim 1, wherein the polyol is a glycol or a glycol ether selected from the group consisting of diethylene glycol monobutyl ether, triethylene glycol, dipropylene glycol, diethylene glycol monomethyl ether, ethylene glycol monobutyl ether, and mixtures thereof.

10. A method for preparing a grease precursor, the method comprising the steps of:

(a) preparing a mixture comprising a carboxylic acid, wherein the carboxylic acid is a fatty acid; a base oil; a polyol; and an alcohol, wherein the alcohol has at least 8 carbon atoms;

(b) neutralizing the carboxylic acid with an initial amount of alkaline earth metal base to form an alkaline earth metal carboxylate mixture;

(c) heating the alkaline earth metal carboxylate mixture;

(d) adding an additional amount of an alkaline earth metal base to the alkaline earth metal carboxylate mixture;

(e) carbonating the mixture to neutrality to form amorphous alkaline earth metal carbonate in the alkaline earth metal carboxylate mixture, wherein water generated in situ during carbonation promotes a conversion of the amorphous alkaline earth metal carbonate to calcite;

(f) repeating steps (d) and (e) at least one more time; and

(g) removing water from the alkaline earth metal carboxylate mixture to obtain a grease precursor having a an amount of calcite greater than 10% by weight.

11. The method of claim 10, wherein the precursor is substantially free of vaterite and aragonite.

12. The method of claim 10 having a TBN of greater than 400.

13. The method of claim 10, wherein the fatty acid is a C12-C22 fatty acid.

14. The method of claim 13, wherein the fatty acid is oleic acid.

15. The method of claim 10, wherein the alkaline earth metal is selected from the group consisting of calcium, barium, magnesium and strontium.

16. The method of claim 10, wherein the alkaline earth metal carboxylate mixture includes calcium oleate and calcium carbonate.

17. The method of claim 10, wherein the alcohol is an aliphatic alcohol of at least 14 carbon atoms.

18. The method of claim 10, wherein the polyol is a glycol or a glycol ether selected from the group consisting of diethylene glycol monobutyl ether, triethylene glycol, dipropylene glycol, diethylene glycol monomethyl ether, ethylene glycol monobutyl ether, and mixtures thereof.

19. A method of preparing a grease, the method comprising the steps of:

preparing the grease precursor of claim 10;

adding and mixing at least one conversion agent to the grease precursor to form a converted mixture, wherein the conversion agent is selected from the group consisting of a hydrocarbon oil, water and a C1-C5 carboxylic acid;

heating the converted mixture; and

removing water from the converted mixture to obtain a grease having an amount of calcite greater than 12.5% by weight.

20. A method for preparing a grease, the method comprising the steps of:

(a) preparing a mixture comprising a carboxylic acid, wherein the carboxylic acid is a fatty acid, a base oil, at least one polyol and at least one alcohol, wherein the alcohol has at least 8 carbon atoms;

(b) neutralizing the carboxylic acid with an initial amount of alkaline earth metal base to form an alkaline earth metal carboxylate mixture;

(c) heating the alkaline earth metal carboxylate mixture;

(d) adding an additional amount of an alkaline earth metal salt to the alkaline earth metal carboxylate mixture;

(e) carbonating the mixture to neutrality to form amorphous alkaline earth metal carbonate in the alkaline earth metal carboxylate mixture, wherein water generated in situ during carbonation promotes a conversion of the amorphous alkaline earth metal carbonate to calcite;

(f) repeating steps (c) and (d) at least one more time;

(g) removing water from the alkaline earth metal carboxylate mixture to obtain a grease precursor having an amount of calcite greater than 10% by weight;

(h) adding and mixing at least one conversion agent to the grease precursor to form a converted mixture, wherein the conversion agent is selected from the group consisting of a hydrocarbon oil, water and a C1-C5 carboxylic acid;

(i) heating the converted mixture of (h); and

(j) removing water from the converted mixture to obtain a grease having an amount of calcite greater than 12.5% by weight.

21. The grease precursor prepared in accordance with the process of claim 10.

22. The grease prepared in accordance with the process of claim 20.

23. A method for preparing a grease, the method comprising the steps of:

(a) preparing a mixture comprising a carboxylic acid, wherein the carboxylic acid is a fatty acid, a base oil, at least one polyol and at least one alcohol, wherein the alcohol has at least 8 carbon atoms;

(b) neutralizing the carboxylic acid with an initial amount of alkaline earth metal base to form an alkaline earth metal carboxylate mixture;

(c) heating the alkaline earth metal carboxylate mixture;

(d) adding an additional amount of an alkaline earth metal salt to the alkaline earth metal carboxylate mixture;

(e) carbonating the mixture to neutrality to form amorphous alkaline earth metal carbonate in the alkaline earth metal carboxylate mixture, wherein water generated in situ during carbonation promotes a conversion of the amorphous alkaline earth metal carbonate to calcite;

(f) repeating steps (d) and (e) at least one more time;

(g) removing an amount of water from the alkaline earth metal carboxylate mixture to obtain a grease precursor having an amount of calcite greater than 25% by weight;

(h) adding and mixing the grease precursor to at least an amount of an overbased calcium carboxylate to form a grease precursor-overbased calcium carboxylate mixture, wherein the overbased calcium carboxylate contains amorphous calcium carbonate and is substantially free of calcite;

(i) adding and mixing at least one conversion agent to the grease precursor-overbased calcium carboxylate mixture to form a converted mixture, wherein the conversion agent is selected from the group consisting of a hydrocarbon oil, water and a C1-C5 carboxylic acid;

(j) heating the converted mixture of (i); and

(k) removing water from the converted mixture to obtain a grease having an amount of calcite greater than 8.0% by weight.

24. A method for preparing a grease precursor, the method comprising the steps of:

(a) preparing a mixture comprising a carboxylic acid, wherein the carboxylic acid is a fatty acid; a base oil; a polyol; and an alcohol, wherein the alcohol has at least 8 carbon atoms;

(b) neutralizing the carboxylic acid with an initial amount of alkaline earth metal base to form an alkaline earth metal carboxylate mixture;

(c) heating the alkaline earth metal carboxylate mixture;

(d) adding an additional amount of an alkaline earth metal base to the alkaline earth metal carboxylate mixture;

(e) carbonating the mixture to neutrality to form amorphous alkaline earth metal carbonate in the alkaline earth metal carboxylate mixture, wherein water generated in situ during carbonation promotes a conversion of the amorphous alkaline earth metal carbonate to calcite;

(f) repeating steps (d) and (e) at least one more time; and

(g) removing water from the alkaline earth metal carboxylate mixture to obtain a grease precursor having a an amount of calcite greater than 25% by weight.

25. A method of preparing a grease, the method comprising the steps of:

preparing the grease precursor of claim 24;

adding and mixing the grease precursor to at least an amount of an overbased calcium carboxylate to form a grease precursor-overbased calcium carboxylate mixture, wherein the overbased calcium carboxylate contains amorphous calcium carbonate and is substantially free of calcite;

adding and mixing at least one conversion agent to the grease precursor to form a converted mixture, wherein the conversion agent is selected from the group consisting of a hydrocarbon oil, water and a C1-C5 carboxylic acid;

heating the converted mixture; and

removing water from the converted mixture to obtain a grease having an amount of calcite greater than 8.0% by weight.