Variable viscosity index lubricating greases

Abstract

A method of tuning a viscosity or temperature behavior is described. The method includes steps of determining a target grease property selected from providing a base oil and a phase change material, combining the base oil and phase change material to form a tunable grease, and testing the tunable grease to ensure the tunable grease satisfies the target grease property. A tunable grease including a base oil and a phase change material is also provided.

Description

Atty Docket No: 47075-04443TITLE VARIABLE VISCOSITY INDEX LUBRICATING GREASESCROSS REFERENCE TO RELATED APPLICATION

[0001] This Application claims priority to U.S. Provisional Patent Application Serial No.63 / 777,042, titled “Variable Viscosity Index Lubricating Greases,” fded on March 25, 2025, which is expressly incorporated by reference herein in its entirety.FIELD OF INVENTION

[0002] The present disclosure generally relates to a lubricating grease easily modified to specific desired functions or properties and a method of making the same.BACKGROUND

[0003] Grease compositions serve an important role as lubricants in various industrial and automotive applications. There are a wide variety of products and chemistries for lubricating greases, each having its own advantages and drawbacks.SUMMARY

[0004] In one aspect, a method of tuning a viscosity or temperature behavior of a grease is described. The method includes steps including determining a target grease property, providing a base oil and a phase change material, combining the base oil and the phase change material to form a tunable grease, and testing the tunable grease to ensure the tunable grease satisfies the target grease property. In one aspect, the viscosity as a function of temperature is tuned based on intended use of grease. In one aspect, the target grease property is tunable based on an amount of the phase change material present in the tunable grease.

[0005] In another aspect, a tunable grease comprising a base oil and a phase change material is provided.Atty Docket No: 47075-04443BRIEF DESCRIPTION OF THE DRAWINGS

[0006] In the accompanying figures, chemical formulas, chemical structures, and experimental data are given that, together with the detailed description provided below, describe example embodiments.

[0007] FIGS. 1A-1C graphically represent the impact of PCM concentration on cone penetration.

[0008] FIGS. 2A-2C graphically represent the impact of PCM concentration on dropping point.

[0009] FIGS. 3A-3E graphically represent the impact of PCM concentration on base oil viscosity as a function of temperature.

[0010] FIGS. 4A-4E graphically represent the impact of PCM concentration on grease storage modulus as a function of temperature.DETAILED DESCRIPTION

[0011] The present disclosure utilizes a secondary structural phase in greases to provide unique properties based on the material chosen. The present disclosure uses natural and / or synthetic waxes that change the viscosity profde of the base oil in the grease as a function of temperature. In the present disclosure, this can be tuned to give an increase in viscosity with temperature, a decrease in viscosity as a function of temperature, or hold viscosity constant with temperature. This brings the advantage of a highly tunable viscosity delivery system for lubricating greases in diverse environments. This will bring improvements in energy efficiency, load carrying capacity, wear protection, and temperature profile of grease lubricated applications.Atty Docket No: 47075-04443

[0012] The present disclosure utilizes a secondary solid component, incorporated into the native grease structure that provides unique properties. The secondary component is a solid wax / synthetic hydrocarbon base solid that has limited room temperature solubility in the grease base oil and has a specific melting point or range that is chosen to give a specific behavior. The secondary solid component can be incorporated into the grease in different ways depending on the desired properties, either through mechanical mixing at a low temperature, or through melting and recrystallization at a temperature below the melting point of the wax.

[0013] The present disclosure as described here has the advantages of delivering a grease that has a tunable viscosity delivery system that is designed to provide bester performance requirements of a specific application. Further advantages of the greases of the present disclosure include maintaining constant viscosity over a broad temperature range, producing viscosity increase with increasing temperature, providing significant viscosity reduction with increasing temperature. Further the greases of the present disclosure reduce the amount of traditional grease structural components necessary to provide a desired grease. For example, the greases of the present disclosure may contain reduced amounts of lithium.

[0014] Definitions:

[0015] Grease” or “grease compositions” as used herein refer to a combination of materials consisting of a solid, structural phase(s) and liquid, lubricating phase(s) resulting in a semi-solid mixture with NLGI cone penetration between 85 - 475 dmm.

[0016] ‘Mixture” refers to a collection of molecules or chemical substances. Each component in a mixture can be independently varied. A mixture may contain, or consist essentially of, two or more substances intermingled with or without a constant percentage composition, wherein each component may or may not retain its essential original properties, and where molecular phaseAtty Docket No: 47075-04443 mixing may or may not occur. Tn mixtures, the components making up the mixture may or may not remain distinguishable from each other by virtue of their chemical structure.

[0017] The following abbreviations are defined. PCM refers to “phase change material”, HC refers to “heat cycle” including a heating phase and a cooling phase after the heating phase. PE refers to “Polyethylene” and HDPE refers to “high-density polyethylene”, e.g., the density of HDPE ranges from 0.93 to 0.97 g / cm3.

[0018] To the extent that the term “includes” or “including” is used in the specification or the claims, it is intended to be inclusive in a manner like the term “comprising” as that term is interpreted when employed as a transitional word in a claim. Similarly, the term “consisting essentially of’ should be interpreted to mean a composition or mixture that contains the recited components and trace amounts of impurities, or additional components to the explicitly recited components in an amount of 5 wt % or less or alternatively 1 wt % or less. The term “consisting essentially of’ should be interpreted to mean a composition or mixture that contains one or two added components in addition to the explicitly recited components. In this definition of “consisting essentially of’, the word “component” can mean a chemical compound, a mixture or substance not explicitly defined as a part of the composition or mixture. The term comprising should be interpreted as containing only what is explicitly defined part of the composition or mixture. As used in the specification and the claims, the singular forms “a,” “an,” and “the” include the plural. Furthermore, to the extent that the term “or” is employed (e.g., A or B), it is intended to mean “A or B or both.” The term “about” or “approximately” is used in conjunction with a number, it is intended to include within ± 1 %, or within ± 0.5 % of the number.Atty Docket No: 47075-04443

[0019] As described in the examples, the methods disclosed herein permit a fine tuning so as to provide a grease with optimal performance properties for a specific use.

[0020] The base oil of the tunable grease of the present disclosure is not particularly limited. A group I, II, III, IV, or V base oil may be selected. Preferably a group II base oil is selected.

[0021] Full grease system as described herein is a base oil plus a PCM and any other preferred additive to obtain a fully formulated and functional grease optimized for a preferred function. In some aspects, the full grease system as described herein is a base oil, PCM, a thickener, and optionally other additives. In some aspects, the full grease system as described herein is a base oil, PCM, lithium 12-hydroxystearate, and optionally other additives.

[0022] The PCM of the tunable grease of the present disclosure is not particularly limited. As shown in the examples, a blend of a polyethylene and a wax forms a PCM according to an aspect of the present disclosure. The type of polyethylene, or high-density polyethylene, or type of wax is not limited.

[0023] Methods of making the tunable grease of the present disclosure are described in the Examples. Importantly, no out of the ordinary procedures, other than standard mixing, are required to practice the present disclosure.Example 1: Base OilThe base oil used for the oil testing and used to synthesize the grease was a neat ISO 220, solvent neutral, group II paraffinic base oil. All oil viscosity testing samples are made by dispersing varied concentrations of PCM in the ISO 220 base oil at the noted weight percent. All grease testing was performed using an NLGI #2 ISO 220 Lithium grease to which was added the noted weight percents of PCMs.Atty Docket No: 47075-04443 Example 2: Formulation of exemplary PCM

[0024] A PCM can be defined broadly as a viscosity / structure modification agent as a function of temperature.

[0025] PCM A: 50 / 50 (by weight) blend of HDPE and carnauba wax with a melting point of 107- 113°C.

[0026] PCM B: micronized hydrogenated castor oil wax with a melting point of 85-88 °C

[0027] PCM C: 50 / 50 (by weight) blend of polyethylene (PE) and amide wax with a melting point of 124-135 °CExample 3: Impact of PCM concentration on ASTM D217 cone penetration.

[0028] FIGS. 1A-1C demonstrate the impact of the different PCMs on the ASTM D217 cone penetration. The cone penetration test evaluates the firmness of the grease structure. The lower the penetration value, the firmer the grease structure. Each material was tested before a heat cycle (HC), with the PCM simply dispersed in the grease, then tested again after the heat cycle. The heat cycle involved dispersing the PCM into the grease and placing a sample into an oven at 120 °C for one hour and then cooled. During this cycle, the PCM was pushed through its phase changed and allowed to recrystallize into the native grease structure on cooling. These data show that PCM A has little effect on the grease before the heat cycle but causes a moderate firming effect after the heat cycle, especially at high PCM concentrations. PCM B shows a moderate firming effect before the heat cycle and a significant firming effect after heat cycling, even at low temperatures. PCM C shows little effect on the grease before the heat cycle and significant increase in firmness after the heat cycle. These data demonstrate tunability and dynamic evolution of properties controlled by the PCM chemistry and concentration.Atty Docket No: 47075-04443

[0029] The dispersion can be formed with a variety of methods or combination of methods. For example, mechanical mixing using a mixing blade on an overhead mixer, mixing with a planetary, centrifugal mixer or any traditional method of mixing a grease is acceptable. Importantly, the key point is that no major processing is required beyond mechanical mixing. Example 4: Impact of PCM concentration on ASTM D2265 dropping point.

[0030] FIGS. 2A-2C show the impact of PCM type and concentration on the dropping point of greases using the ASTM D2265 test which measures the temperature at which oil significantly separates from the grease structure. The dropping point of each was measured before and after the same heat cycle applied to the testing in FIGS. 1A-1C. The base grease without PCMs showed a dropping point of about 190 °C. The data shown in FIGS. 2A-2C demonstrate that the PCMs have little effect on the dropping point with either minor increases or no effect across all samples. Example 5: Impact of PCM concentration on base oil viscosity as a function of temperature.

[0031] FIGS. 3A-3E demonstrate the impact of the PCM material type and concentration on the viscosity behaviors of the base oil used in the grease. Examination of FIG. 3 A shows the native base oil viscosity as a function of temperature without a PCM. This demonstrates that the heat cycle has no effect on the viscosity of the base oil alone. FIGS. 3B-3D show the impact of PCM on the oil viscosity during a heat / cool cycle spanning 40 °C to 100 °C (e.g., heating to 100 °C and subsequently cooling to 40 °C).

[0032] In FIG. 3B, at 1 wt %, all PCMs have negligible impact on the oil viscosity during the heating phase, however on cooling PCM B and PCM C have strong effect and increase the viscosity by about 15% and about 50% respectively.Atty Docket No: 47075-04443

[0033] In FIG. 3C, at 5 wt %, PCM A and C have little effect on viscosity during the heating phase while PCM B shows a stabilization effect and mitigates viscosity reduction during the heating phase. In the cooling phase, PCM A shows a negligible effect on viscosity, while PCM B shows an increase of about 16% and PCM C shows an increase of about 169%.

[0034] In FIG. 3D, at 10 wt %, PCM A and C have little effect on viscosity during the heating phase, while PCM B shows a strong viscosity stabilization effect, effectively showing no viscosity loss to ~80 °C. In the cooling phase, PCM A shows a viscosity increase effect of about 30%, PCM B shows an increase of about 28%, and PCM C shows a large increase of about 283%. Close examination of the figures shows that PCM B and C exhibit some dynamics to their rates of change on cooling.

[0035] In FIG. 3E, at 20 wt %, PCM A has little effect on viscosity during the heating phase. PCM C exhibits a stabilization effect with little difference between the 40 °C and 100 °C values. PCM B exhibits a highly dynamic viscosity behavior with a dramatically increase in viscosity by about 150% at ~ 80 °C, and the viscosity decreases to less than the original value at 100 °C. In the cooling phase, PCM A demonstrates a strong viscosity increase of about 283%. PCM B shows a more modest increase of about 74%, and PCM C also shows a strong increase of about 397%.

[0036] These data show that inclusion of different chemistries and concentrations of PCMs can have dramatic and tunable effects on the base oil viscosity. This dynamic behavior could be utilized to deliver specific viscosity / temperature behaviors ideal to certain situations and conditions.Example 6: Impact of PCM concentration on grease storage modulus as a function of temperature.Atty Docket No: 47075-04443

[0037] FIGS. 4A-4E demonstrate the impact of the PCM material type and concentration on the storage modulus of the grease. This modulus is representative of the solid like character of the grease with a higher value indicating a firmer grease. Examination of FIG 4A shows the native grease modulus as a function of temperature. This data shows that the modulus of the grease without PCM softens slightly with temperature but recovers to near the original value after the heat cycle, showing the cycle has a minimal effect on the property.

[0038] In FIG. 4B, at 1 wt %, all PCMs have a minor increase in the modulus of the grease before the heat cycle and a large impact on the modulus after the cooling phase, with an increase of 25% for PCM A, a 58% increase for PCM B, and a 97% increase for PCM C. Additionally, the modulus increase during temperature reduction is non-linear and shows areas of increase or decrease to various extents.

[0039] In FIG. 4C, at 5 wt %, dynamic changes in modulus occur across all PCMs. PCM A shows a relatively linear increase in modulus during the cooling phase with an ultimate increase in modulus of 400%. PCM B shows a modulus plateauing effect from 25 °C to 80 °C followed by minor softening. On cooling there is a dramatic increase in modulus around 80 °C, showing a final increase of 922%. PCM C shows little modulus change during the heating phase, and on cooling, there is a sharp increase of modulus to a maximum around 80 °C of -800% followed by a decrease to a modulus increase of 100% at 25 °C.

[0040] In FIG. 4D, at 10 wt %, the same behavior trends occur but are amplified in magnitude. PCM A exhibits a linear increase in modulus on cooling with an ultimate increase of 1400%. PCM B demonstrates the same dramatic increase in modulus at around 80 °C during cooling showing a final increase of 4000%. PCM C shows the same dynamic modulus spike at around 80 °C followed by a decrease with a final modulus increase of 430%.Atty Docket No: 47075-04443

[0041] In FIG. 4E, at 20 wt %, similar behaviors occur but are further amplified in magnitude. PCM A shows little modulus impact during heating, but a significant increase in modulus around 60 °C on cooling to a final increase of 7800%. PCM B exhibits unique behavior with a starting modulus increase of 1900% above the original value at 25 °C, a relative plateau until around 70 °C, followed by softening towards the original value. On cooling, it exhibits a sharp increase in modulus at around 70 °C with a final increase of 6700%. PCM C shows little effect on modulus before the heat cycle and a minor increase in modulus during the heating phase. During cooling the material shows a sharp increase in modulus at around 90 °C to a maximum of 4600% increase, followed by a decrease to a final increase of 350%.

[0042] Based on examples discussed above, a method of tuning a viscosity or temperature behavior of a grease includes steps including determining a target grease property as a function of temperature, providing a base oil and a phase change material, combining the base oil and phase change material to form a tunable grease, and testing the tunable grease to ensure the tunable grease satisfies the target grease property. The target grease property is tunable based on an amount of the phase change material present in the tunable grease.

[0043] The phase change material is present in an amount of about 0.5 wt % - about 40 wt %, about 0.5 wt % - about 35 wt %, about 0.5 wt % - about 30 wt %, about 0.5 wt % - about 25 wt %, about 1 wt % - about 20 wt %, about 1 wt % - about 15 wt %, about 1 wt % - about 10 wt %, about 1 wt % - about 5 wt %, about 1 wt %, about 5 wt %, about 10 wt %, about 15 wt %, about 20 wt %, about 25 wt %, about 30 wt %, about 35 wt %, or about 40 wt % of the tunable grease.

[0044] These data show that inclusion of different chemistries and concentrations of PCMs can have dramatic and tunable effects on the modulus of the grease as a function of temperature.Atty Docket No: 47075-04443 This dynamic behavior could be utilized to deliver specific structure / temperature behaviors ideal to certain situations and conditions.

[0045] As stated above, while the present application has been illustrated by the description of embodiments, and while the embodiments have been described in considerable detail, it is not the intention to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art, having the benefit of this application. Therefore, the application, in its broader aspects, is not limited to the specific details and illustrative examples shown. Departures may be made from such details and examples without departing from the spirit or scope of the general inventive concept.

Claims

Atty Docket No: 47075-04443CLAIMS1. A method of tuning a viscosity or temperature behavior of a grease, the method comprising:determining a target grease property as a function of temperature;providing a base oil and a phase change material;combining the base oil and phase change material to form a tunable grease, wherein the target grease property is tunable based on an amount of the phase change material present in the tunable grease; andtesting the tunable grease to ensure the tunable grease satisfies the target grease property.

2. The method of claim 1, wherein the phase change material is present in an amount between about 0.5 wt % and about 40 wt % of the tunable grease.

3. The method of claim 1 , wherein the phase change material is present in an amount between about 1 wt % and about 20 wt % of the tunable grease.

4. The method of claim 1, wherein the phase change material is wax or polyethylene.

5. The method of claim 1, wherein the target grease property comprises a viscosity variation profile as a function of temperature.

6. The method of claim 1, wherein the target prese property comprises a storage modulus variation profile as a function of temperature.Atty Docket No: 47075-04443 7. The method of claim 1, wherein the combining the base oil and the phase change material comprises mixing the base oil with a blend of high-density polyethylene (HDPE), wax, polyethylene (PE), or a combination thereof.

8. The method of claim 1, wherein the blend comprises the HDPE and the wax with a melting point between 107 °C and 113 °C.

9. The method of claim 7, wherein the blend comprises the wax with a melting point between 85 °C and 88 °C.

10. The method of claim 7, wherein the blend comprises the PE and the wax with a melting point between 124 °C and 135 °C.

11. The method of claim 1, wherein the base oil is selected from Group I, II, III, IV, and V base oil.

12. A tunable grease comprising:a base oil, anda phase change material, wherein a viscosity or temperature behavior of the tunable grease is dependent on an amount of the phase change material present in the tunable grease.

13. The tunable grease of claim 12, wherein the base oil is selected from Group I, II, III, IV, and V base oil.Atty Docket No: 47075-0444314. The tunable grease of claim 12, wherein the phase change material is present in an amount between about 1 wt % and about 20 wt % of the tunable grease.

15. The tunable grease of claim 12, wherein the phase change material is present in an amount between about 1 wt % and about 10 wt % of the tunable grease.

16. The tunable grease of claim 12, wherein the phase change material is present in an amount between about 1 wt % and about 5 wt % of the tunable grease.

17. The tunable grease of claim 12, wherein the phase change material is a blend of high-density polyethylene (HDPE), wax, polyethylene (PE), or a combination thereof.

18. The tunable grease of claim 17, wherein the the blend comprises the HDPE and the wax with a melting point between 107 °C and 113 °C.

19. The tunable grease of claim 17, wherein the blend comprises the wax with a melting point between 85 °C and 88 °C.

20. The tunable grease of claim 17, wherein the blend comprises the PE and the wax with a melting point between 124 °C and 135 °C.

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