HK1188464B - Thickened grease composition - Google Patents

Abstract

A thickened grease composition is provided by process of heating a mineral oil and 12-hydroxystearic acid with lithium hydroxide and forming a simple lithium grease to which at least one component selected from the group comprising succinic acid, glutaric acid, adipic acid, 6-hydroxycaproic acid, dimethyl succinate, dimethyl glutarate, dimethyl adipate, methyl hydroxycaproate, cyclohexanediols, methyl 5-hydroxyvalerate, methyl valerate, gamma butyrolactone, and methyl levulinate or mixtures thereof.

Description

Thickened grease composition

Cross Reference to Related Applications

This application claims priority from U.S. provisional application serial No. 61/423,719 filed on 16/2010 and U.S. provisional application serial No. 61/446,079 filed on 24/2/2011.

Technical Field

The present disclosure relates to greases and thickened greases. More particularly, it relates to a thickened grease composition having performance characteristics intermediate between those of a simple lithium-based grease and those of a complex lithium-based grease.

Background

Simple lithium-based greases and lithium complex greases are well known in the art. They are the most common type of grease in use and have a wide range of industrial uses and good versatility of use. It is estimated that lithium-based greases account for about half of the total grease market.

Currently, a problem in the market for greases is the need for greases with better performance characteristics than simple lithium-based greases. A particularly sought attribute of grease performance is improvement in mechanical and thermal stability. Currently, this need for higher performance is met by lithium complex greases, see, for example, U.S. patent No. 4,410,435 to Naka et al.

Lithium complex greases possess many of the characteristics of simple lithium soap greases and also have a higher drop point, allowing the greases to be used at higher temperatures. The dropping point of lithium complex greases is higher than that of simple lithium soap greases due to the presence of a second thickener component, known as a complexing agent. Modern lithium complex greases typically use shorter chain length difunctional carboxylic acids such as azelaic acid or adipic acid. The lithium salts of these materials are typically present in significantly lower proportions than simple lithium soap thickeners. An alternative to the use of complexing agents is boric acid. The use of this substance also results in an elevated drop point.

Due to their improved performance characteristics, lithium complex greases can be significantly more expensive to prepare than simple lithium greases. Therefore, there is a need for lithium-based greases having properties intermediate between those of simple lithium-based greases and those of lithium complex greases.

Summary of The Invention

The present invention relates to thickened lithium-based greases having performance characteristics that are within the performance characteristics of simple lithium-based greases and lithium complex greases. The thickened greases described herein contain a mixture of acids and esters and provide improvements in drop point, mechanical stability, roll stability, and oil break-down relative to simple lithium-based greases. One embodiment of the present invention comprises:

a) a first component comprising a mineral oil or a synthetic oil;

b) lithium hydroxide; and

c) a second component selected from the group consisting of: succinic acid, glutaric acid, adipic acid, 6-hydroxycaproic acid, dimethyl succinate, dimethyl glutarate, dimethyl adipate, methyl hydroxycaproate, cyclohexanediols, methyl 5-hydroxypentanoate, methyl valerate, gamma butyrolactone and methyl levulinate or mixtures thereof.

In another embodiment, the second component comprises about 10 to about 60 weight percent methyl hydroxycaproate, about 20 to about 95% dimethyl adipate, about 1 to about 10 weight percent dimethyl glutarate, about 0.1 to about 5 weight percent dimethyl succinate, about 0.1 to about 7 weight percent cyclohexanediols, about 0.01 to about 7 weight percent methyl 5-hydroxypentanoate, about 0.01 to about 5 weight percent gamma butyrolactone, and about 0.01 to about 10 weight percent methyl levulinate.

In another embodiment, the first component additionally comprises 12-hydroxystearic acid.

In another embodiment, the 12-hydroxystearic acid is provided in an amount of from about 5 to about 99.5 wt.% of the grease composition.

In another embodiment, lithium hydroxide is added in an amount less than the stoichiometric amount of the second component.

In another embodiment, the second component has an acid number of about 0.07mg KOH/g, a water content of about 0.04 wt.%, and a hydroxyl number of about 257 KOH/g.

In another embodiment, the product mixture has a drop point temperature property of about 180 ℃ to about 250 ℃.

In another embodiment, the grease composition described in any one of the preceding claims may be formed by:

a) heating a first component to a temperature in a range between about 85 ℃ and about 90 ℃ and maintaining a liquid phase temperature for the first component;

b) adding an aqueous slurry of lithium hydroxide and evaporating the aqueous contents to form a heated mixture;

c) mixing the second component with the heated mixture to form a neutralized mixture, wherein the second component comprises terminal hydroxyl groups that function to oligomerize the neutralized mixture;

d) heating the neutralized mixture to about 210 ℃ to recover the vaporized methanol and the grease composition; and

e) cooling and isolating the grease composition.

Detailed Description

The present invention relates to thickened lithium-based greases having performance characteristics that are within the performance characteristics of simple lithium-based greases and lithium complex greases. The thickened lithium-based grease comprises a thickening component selected from the group comprising: succinic acid, glutaric acid, adipic acid, 6-hydroxycaproic acid, dimethyl succinate, dimethyl glutarate, dimethyl adipate, methyl hydroxycaproate, cyclohexanediols, methyl 5-hydroxypentanoate, methyl valerate, gamma butyrolactone and methyl levulinate or mixtures thereof.

All patents, patent applications, test procedures, priority documents, articles, publications, manuals, and other documents cited herein are fully incorporated by reference to the extent such disclosure is not inconsistent with this invention and for all jurisdictions in which such incorporation is permitted.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure, the preferred methods and materials are now described.

The term "liquidus temperature" as used herein, unless otherwise indicated, refers to a temperature above which the heated first component behaves as a liquid.

The term "acid number" as used herein, unless otherwise indicated, refers to the amount of base, expressed in milligrams of potassium hydroxide (KOH), required to neutralize the acidic components in one gram of sample.

The term "hydroxyl number" as used herein, unless otherwise specified, refers to the number of milligrams of KOH equivalent to one gram of sample.

According to a particular embodiment of the present invention, the thickened lithium-based grease composition is formed by the step of first providing a mixture of a first component comprising a mineral or synthetic oil. Any mineral oil, synthetic hydrocarbon oil, or synthetic ester oil known in the art may be used. The first component may also contain 12-hydroxystearic acid. The first component may then be heated to a range of about 85 ℃ to about 90 ℃ while mixing and maintaining a temperature that melts the 12-hydroxystearic acid.

Next, the aqueous contents are evaporated and an aqueous slurry of lithium hydroxide is added to form a heated mixture. The heated mixture is maintained at a substantially constant temperature, thereby forming a simple lithium-based grease. In embodiments herein, the lithium hydroxide is added in a sub-stoichiometric amount relative to the second component. It has been found experimentally that the addition of a substoichiometric amount of lithium hydroxide serves to oligomerize the second component and thicken the subsequently formed mixture.

A second component capable of substantially neutralizing lithium hydroxide in the mixture is then added to the heated mixture to form a neutralized mixture. The second component may be selected from the group comprising: succinic acid, glutaric acid, adipic acid, 6-hydroxycaproic acid, dimethyl succinate, dimethyl glutarate, dimethyl adipate, methyl hydroxycaproate, cyclohexanediols, methyl 5-hydroxypentanoate, methyl valerate, gamma butyrolactone and methyl levulinate or mixtures thereof. The neutralized mixture is then heated to about 210 ℃ and maintained at that temperature to substantially release the water and methanol thus formed. Finally, the remaining mixture was cooled to isolate the grease composition.

In a particular embodiment, the second component comprises an ester composition comprising about 40% by weight methyl hydroxycaproate and about 27% by weight dimethyl adipate. In addition, the ester composition may comprise about 3 wt% dimethyl glutarate, about 0.5 wt% dimethyl succinate, about 4 wt% cyclohexanediols, about 4 wt% methyl 5-hydroxypentanoate, about 2 wt% methyl valerate, about 2 wt% valerolactone, and about 0.7 wt% methyl levulinate. In a particular embodiment of the invention, the ester composition may have an acid number of about 0.07mg KOH/g, a water content of about 0.04 wt.%, and a hydroxyl number of about 257mg KOH/g.

Table 1 below shows the concentration ranges in weight percent for ester compositions within the scope of the present invention. Higher or lower concentrations of particular components (e.g., dimethyl adipate, methyl hydroxycaproate, etc.) can be obtained by selective product separation. In one embodiment, for each concentration range a-E indicated in table 1, components other than methyl hydroxycaproate and dimethyl adipate may optionally be present. For example, one embodiment of the ester composition comprises about 10 to 60 weight percent methyl hydroxycaproate and about 20 to 80 weight percent dimethyl adipate. In another example, an embodiment of the ester composition includes about 15 to 50 weight percent methyl hydroxycaproate and about 30 to 70 weight percent dimethyl adipate. In any of the embodiments disclosed herein or shown in table 1, the composition may comprise less than about 20 wt.% of the oligomeric ester. For example, the composition may comprise about 0.001 to 20 wt.%, about 0.001 to 14 wt.%, or about 0.001 to 10 wt.% of the oligomeric ester. It should be understood that: it is within the scope of the present invention to select concentrations from any one of the columns of table 1 in combination with concentrations from any other column of table 1, provided that the sum of the concentrations is less than or equal to 100 wt.%. Any composition may comprise less than about 5 wt.% methyl valerate (e.g., about 0.01 to about 5 wt.%, about 0.01 to 3 wt.%, 0.01 to 1.5 wt.%, about 0.01 to 0.1 wt.%) and/or less than about 10 wt.% valerolactone (e.g., about 0.01 to 10 wt.%, about 0.01 to 7 wt.%, 0.01 to 4 wt.%, 0.01 to 2 wt.%).

TABLE 1

Suitable ester mixtures include those under the trade nameThose sold and commercially available from INVISTA Specialty Intermediates. These mixtures contain predominantly dimethyl adipate and other oxygen-containing species built around the 6-carbon backbone. Useful ester mixtures may contain a variety of other esters, hydroxyl groups-a compound and an oxygen containing component. In one embodiment, the ester mixture isA mixture of esters of brandy, comprising: dimethyl adipate (30-95 wt%); dimethyl glutarate (0-10% by weight); dimethyl succinate (0-2 wt%); a hydroxy compound (0-50% by weight); having a hydroxyl number of typically 100-200mg KOH/g; and an acid number (mg KOH/g) of typically 1.5, up to 5; and typically 0.1, max 0.5 water (wt%). In addition, other known complexing agents, such as the methyl ester of dodecanedioic acid, can be used.

Commercially available ester mixtures (e.g. ester mixtures)Brand esters) provides at least a convenient and repeatable fit of the lithium-based grease. The acid mixture thus formed may be further reacted with other metal ions in their hydroxide form, such as calcium or aluminum. Furthermore, the ester compound is suitable for both batch and continuous processes. Because the methyl ester form of these acids is liquid at low temperatures, it is particularly well suited for use in continuous processes.

It is believed, but not by way of limitation, that the synergy between the components of the acid mixture aids in the formation of the complex, thereby enhancing the handling of the grease so that the variation between batches is substantially more uniform. The treatment of these grease compositions is suitable for both batch and continuous treatment techniques known to the skilled person.

Further in accordance with particular embodiments disclosed herein, the soap thickener (12-hydroxystearic acid) is provided to the grease in an amount of about 5 to 15 wt.%. Further, the ratio between the range of 12-hydroxystearic acid and acid mixture can vary from a blend substantially free of 12-hydroxystearic acid to a blend containing about 99.5% by weight of 12-hydroxystearic acid.

Another advantage of the ester mixture is that it provides both thickening and partial coordination capabilities. In the case of the "dropping point" temperature performance, an adjustable range between the dropping point temperature performance of simple lithium-based greases (typically 180 ℃) and the dropping point temperature performance of complex lithium-based greases (typically > 250 ℃) can be obtained.

Examples

The following examples demonstrate the invention and its ability to be used in applications. The invention is capable of other and different embodiments and its several details are capable of modifications in various obvious respects, all without departing from the scope and spirit of the present invention. Accordingly, the embodiments should be considered as illustrative in nature and not restrictive.

For grease dropping points over a wide temperature range, the dropping point can be tested using ASTM D2265-06 standard test method. ASTM D217A/B/D can be used; the penetration of the Grease (lubricating Grease) was tested for mechanical stability. Roller stability may be tested using ASTM D1831-00(2006) and oil loss may be tested using the oil separation lubricating storage in ASTM D1742-06.

Example 1

In one example of the preparation of a lithium grease composition according to the invention, a stirred batch grease kettle was equipped with an overhead condenser and charged with 10kg of ISO32 hydrocracked mineral oil and 0.6kg of 12-hydroxystearic acid. The mixture was then heated to 90 ℃ and heated slurry containing lithium hydroxide monohydrate was added to just neutralize the mixture. Once most of the water had evaporated, 0.6kg was addedEsters (ester mixtures with compositions as shown in range "C" in table 1).The ester comprised 21% methyl 6-hydroxycaproate, 55% dimethyl adipate, 5% dimethyl glutarate, 1% dimethyl succinate and 1% methyl levulinate. After this step, if necessary, more lithium hydroxide monohydrate is slowly added to neutralize the mixture.

The resulting mixture was held at this temperature until most of the water and methanol were removed, and then gradually heated to 210 ℃ and held at this temperature for 15 minutes. During the final heating stage, residual methanol and water are distilled overhead and condensed.

The product lithium complex grease was cooled to 80 ℃ over 1 hour and ground before discharging into a suitable container.

Examples 2 to 6

The procedure of example 1 can be repeated with different ester mixtures as shown below in table 2. In various embodiments, the resulting grease compositions may be tested using the methods listed above. Using these formulations and preparation methods described above, a drop point range of about 180 ℃ to about 250 ℃ for the resulting grease composition can be obtained.

TABLE 2

It should be noted that ratios, concentrations, amounts, and other numerical data may be expressed herein in a range format. It is to be understood that such range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a concentration range of "about 0.1% to about 5%" should be interpreted as: not only are concentrations of about 0.1% to about 5% by weight specifically mentioned included, but individual concentrations (e.g., 1%, 2%, 3%, and 4%) and subranges (e.g., 0.5%, 1.1%, 2.2%, 3.3%, and 4.4%) within the indicated ranges are also included. The term "about" can include ± 1%, ± 2%, ± 3%, ± 4%, ± 5%, ± 8% or ± 10% of the modified value or values. Further, the phrase "about 'x' to 'y'" includes "about 'x' to about 'y'".

While illustrative embodiments of the invention have been described in detail, it is to be understood that the invention is capable of other and different embodiments and that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is not intended that the scope of the claims herein be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the present invention, including all features which would be treated as equivalents thereof by those skilled in the art to which the invention pertains.

Claims (6)

1. A grease composition formed by the steps of:

a) heating a first component comprising a mineral or synthetic oil to a temperature in the range between 85 ℃ and 90 ℃ and maintaining a liquid phase temperature for the first component;

b) adding an aqueous slurry of lithium hydroxide and evaporating the aqueous contents to form a heated mixture;

c) mixing a second component with the heated mixture to form a neutralized mixture, the second component comprising an ester composition comprising 10 to 60 weight percent methyl hydroxycaproate, 20 to 80 weight percent dimethyl adipate, 1 to 15 weight percent dimethyl glutarate, 0.1 to 5 weight percent dimethyl succinate, 0.1 to 7 weight percent cyclohexanediols, 0.1 to 7 weight percent methyl 5-hydroxyvalerate, 0.01 to 5 weight percent gamma butyrolactone, and 0.01 to 10 weight percent methyl levulinate, wherein the second component comprises terminal hydroxyl groups that function to oligomerize the neutralized mixture;

d) heating the neutralized mixture to about 210 ℃ to recover the vaporized methanol and the grease composition; and

e) cooling and isolating the grease composition.

2. Grease composition according to claim 1, wherein the first component additionally comprises 12-hydroxystearic acid.

3. Grease composition according to claim 2, wherein the 12-hydroxystearic acid is provided in an amount of 5 to 15 wt.% of the grease composition.

4. Grease composition according to claim 1, wherein lithium hydroxide is added in a lower stoichiometric amount than the second component.

5. The grease composition of claim 1, wherein the second component has an acid number of about 0.07mg KOH/g, a water content of about 0.04 wt.%, and a hydroxyl number of about 257mg KOH/g.

6. Grease composition according to claim 1, wherein the product mixture has a dropping point temperature performance of 180 ℃ to 250 ℃.