Grease composition based on mixed complex soap and method for preparing same

Abstract

To provide: a zinc-alkali or alkaline earth metal mixed complex grease composition that shows an excellent additive response property, good mechanical stability, low temperature property, pumping property, and corrosion resistance; and a process therefor.SOLUTION: There is provided a mixed complex soap-based grease composition, comprising: a lubricating base oil; a saponifiable material; a metal oxide; an alkali or alkaline metal hydroxide; and a complexing acid. There is also provided a single-step open kettle process for preparing the composition comprises the steps of: a) mixing a saponifiable substance with a base oil; b) adding an aqueous solution of a complexing acid, zinc oxide, and an oxide or hydroxide of an alkali or alkaline earth metal to a mixture obtained in the step a); c) heating and dehydrating a mixture obtained in the step b) with continuous stirring; d) adding the base oil to a solid mass obtained in the step c); e) cooling a mixture obtained in the step d) and adding a performance enhancing additive as required; and f) homogenizing a mixture obtained in the step e).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to mixed complex soap-based grease compositions. Specifically, the present invention relates to zinc-alkali / alkaline earth metal mixed complex grease compositions. More specifically, the present invention relates to zinc-Na / Li / Ca mixed complex soap-based grease compositions that have inherent oxidation stability, extreme pressure and antiwear properties, and water resistance. The present invention also discloses a single-step, open-kettle, energy-efficient process for preparing zinc-alkali / alkaline earth metal mixed complex soap-based grease compositions that provides a smooth-textured grease composition with a relatively low thickener content while maintaining a desired viscosity. [Background technology]

[0002] Zinc (Zn) complex greases with dropping points comparable to those of lithium greases and matching those of 180-300°C are disclosed in U.S. Patent No. 1,236,285, European Patent Application Publication No. 3,845,622, Indian Patent Application No. 202021,000,297, and Indonesian Patent Application No. P00 2020 10687. These prior art documents also disclose a process for producing zinc complex greases through the reaction of a complexing agent and a fatty acid with zinc oxide in a lubricating oil. U.S. Patent No. 1,236,285 discloses a pure zinc complex grease that requires a thickener content of approximately 34 wt% to produce an NLGI 2 grade grease, necessitating the use of large amounts of metal oxides during processing. The high thickener content makes zinc complex greases relatively dense and expensive, which can be an obstacle to application and production. In view of this, greases with lower thickener content and improved properties are desired to make these compositions more viable.

[0003] U.S. Pat. No. 2,457,582 discloses compositions containing sodium tallow soap with zinc stearate as a minor component. Dropping points range from 130 to 176°C, and no complexing agents are used. The sodium to zinc ratio varies from 5:1 to 1:1 in the compositions disclosed under this invention. U.S. Pat. No. 2,445,936 discloses the use of 1 to 3% zinc 12-hydroxystearate to improve the water resistance of sodium and lithium greases. British Patent No. 1,039,753 discloses a method for preparing lubricating gels by coating surface-area-modified zinc oxide particles with an organic carboxylic acid, resulting in improved greases with superior water resistance and high-temperature stability.

[0004] However, although the prior art discloses some mixed soap-based grease compositions, there are no grease compositions based on zinc-based mixed complex soaps. In the prior art documents reported above, the zinc complex grease compositions are made with 100% zinc complex soaps that can be used at high temperatures as disclosed, and these grease compositions have a relatively high content of thickeners, making them relatively dense and expensive.

[0005] Therefore, there is a need for economical grease compositions with compatible dropping points and high performance properties that can be used over a range of elevated temperatures, and methods for preparing such grease compositions. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 1,123,6285 [Patent Document 2] European Patent Application Publication No. 3845622 [Patent Document 3] U.S. Patent No. 2,457,582 [Patent Document 4] U.S. Patent No. 2,445,936 [Patent Document 5] British Patent No. 1039753 Summary of the Invention [Problem to be solved by the invention]

[0007] It is a primary object of the present invention to provide a grease composition based on a mixed complex soap.

[0008] It is another object of the present invention to provide a mixed complex soap based grease composition that has a dropping point of 180-300°C compared to lithium based and lithium complex grease compositions that have inherent oxidation stability, extreme pressure, antiwear, and water resistance.

[0009] It is another object of the present invention to provide a mixed complex soap based grease composition that has excellent additive response, good mechanical stability, low temperature properties, pumpability and anti-corrosion properties.

[0010] It is a further object of the present invention to provide a single-step, open-kettle, energy-efficient process that provides a mixed complex soap-based grease composition with a relatively low thickener content and a smooth texture while maintaining a desired consistency. [Means for solving the problem]

[0011] This Summary is provided in a simplified form to introduce a selection of concepts that are further described in the Detailed Description.

[0012] The present invention provides i) base oil, ii) saponifiable substances; iii) zinc oxide or zinc hydroxide; iv) oxides or hydroxides of alkali or alkaline earth metals; v) a complexing acid; and vi) performance enhancing additives as required; The present invention provides a lubricating zinc-alkali / alkaline earth metal mixed complex grease composition comprising:

[0013] The present invention also provides a) mixing a saponifiable material with a base oil to form a mixture; b) adding to the mixture obtained in step a) an aqueous solution of a complexing acid, zinc oxide, and an oxide or hydroxide of an alkali or alkaline earth metal; c) heating and dehydrating the mixture obtained in step b) with continuous stirring to obtain a solid mass; d) adding a base oil to the solid mass obtained in step c) to form a mixture; e) cooling the mixture obtained in step d) and adding performance enhancing additives as needed; f) homogenizing the mixture obtained in step e) to obtain a mixed complex grease composition; The present invention provides an open kettle, single-step process for preparing a zinc-alkali / alkaline earth metal mixed complex grease composition, comprising:

[0014] Abbreviation ZDDP: Zinc dialkyldithiophosphate 12-HSA: 12-hydroxystearic acid PAO: Polyalphaolefin PAG: Polyalkyl glycol DETAILED DESCRIPTION OF THE INVENTION

[0015] The NLGI grade represents a measure of the relative hardness of a grease used for lubrication, as designated by the Standard Classification of Lubricating Greases. The present invention includes all NLGI viscosity grades that are harder and softer than NLGI 2 and 3 grades, which can be produced by varying the thickener content.

[0016] As used herein, wt% is based on the total weight of the grease composition.

[0017] The present invention discloses a zinc-alkali / alkaline earth metal mixed complex grease composition, preferably a Zn-Na mixed complex grease composition, and a single-step, open-kettle, energy-efficient process that provides a smooth-textured grease composition with a relatively low thickener content while maintaining a desired viscosity. The present invention also discloses a method for producing a water-resistant complex grease in which the hydrophilic nature of the sodium soap is compensated for by the hydrophobic zinc soap, while the poor thickening ability of the zinc soap is compensated for by the good thickening ability of the sodium soap.

[0018] The present invention provides i) base oil, ii) saponifiable substances; iii) zinc oxide or zinc hydroxide; iv) alkali or alkaline earth metal oxides or hydroxides; v) a complexing acid; and vi) performance enhancing additives as required; The present invention provides a zinc-alkali / alkaline earth metal mixed complex grease composition comprising:

[0019] The present invention provides a) mixing a saponifiable material with a base oil to form a mixture; b) adding to the mixture obtained in step a) an aqueous solution of a complexing acid, zinc oxide, and an oxide or hydroxide of an alkali or alkaline earth metal; c) heating and dehydrating the mixture obtained in step b) with continuous stirring to obtain a solid mass; d) adding a base oil to the solid mass obtained in step c) to form a mixture; e) cooling the mixture obtained in step d) and adding performance enhancing additives as needed; and f) homogenizing the mixture obtained in step e) to obtain a mixed complex grease composition; The present invention provides an open kettle, single-step process for preparing a zinc-alkali / alkaline earth metal mixed complex grease composition, comprising:

[0020] According to an embodiment of the present invention, the base oil has a viscosity in the range of ISO VG2 to 3200, or a mixture thereof.

[0021] According to an embodiment of the present invention, the base oil is selected from API Group I-III mineral base oils, API Group IV synthetic base oils, ester base oils, paraffinic base oils, naphthenic base oils, and recycled base oils; the synthetic base oil is selected from polyalphaolefins (PAOs), polyalkyl glycols (PAGs), polyol esters, diesters, and alkylated aromatics.

[0022] According to another embodiment of the present invention, the base oil is present in the range of 65.0 to 90.0 wt %.

[0023] According to another embodiment of the present invention, the saponifiable substance is present in the range of 8.0 to 18.0 wt %.

[0024] According to another embodiment of the present invention, the alkali and alkaline earth metal oxides and hydroxides are present in the range of 0.20-3.0 wt%.

[0025] According to an embodiment of the present invention, the complexing acid is present in the range of 1.0-5.0 wt %.

[0026] According to an embodiment of the present invention, the performance enhancing additive is present in the range of 0.01-3 wt%.

[0027] According to an embodiment of the present invention, the saponifiable substance is a fatty acid selected from 12-hydroxystearic acid, stearic acid, oleic acid or mixtures thereof.

[0028] According to an embodiment of the present invention, the alkali or alkaline earth metal oxide or hydroxide is selected from sodium hydroxide, calcium oxide, calcium hydroxide, hydrated lime, lithium hydroxide, or lithium hydroxide monohydrate.

[0029] According to an embodiment of the present invention, the complexing acid is a dicarboxylic acid having C3 to C10 selected from malonic acid (C3), succinic acid (C4), glutaric acid (C5), adipic acid (C6), pimelic acid (C7), suberic acid (C8), azelaic acid (C9), or sebacic acid (C10).

[0030] According to an embodiment of the present invention, the mixing in step a) is carried out at a temperature in the range of 25-80°C.

[0031] According to another embodiment of the present invention, the heating comprises: i) heating at a temperature in the range of 90-100°C for 1 hour; ii) heating at a temperature in the range of 130-140°C for an additional hour; and iii) heating at a temperature in the range of 167-175°C for an additional 0.5-1.0 hour; It is carried out in three consecutive processes in a series of specific steps, including the steps

[0032] According to another embodiment of the present invention, the performance enhancing additive is selected from rust and corrosion inhibitors, metal deactivators, metal passivators, antioxidants, pressure additives, polymers, tackifiers, dyes, chemical markers, fragrances, anti-wear additives, or combinations thereof.

[0033] According to another embodiment of the present invention, the performance enhancing additive is a multifunctional performance enhancing additive selected from zinc dialkyldithiophosphates (ZDDP).

[0034] The disclosed grease compositions have been found to possess inherent oxidation stability, extreme pressure and antiwear properties, and water resistance properties, as well as excellent additive response, good mechanical stability, low temperature properties, pumpability, and corrosion resistance. Grease compositions with specifically tailored dropping points between 180°C and 300°C were prepared through the in-situ formation of mixed complex soaps by the reaction of zinc oxide and sodium hydroxide with hydroxy fatty acids and dicarboxylic acids in a single step.

[0035] The in-situ incorporation of sodium in the zinc complex soap complex resulted in a grease composition with superior properties such as a high dropping point, excellent water resistance, excellent shear stability, inherent extreme pressure properties, and inherent antiwear performance. The hydrophobicity of the zinc complex soap helped to compensate for the hydrophilicity of the sodium soap, resulting in a water-resistant grease composition.

[0036] In accordance with another embodiment of the present invention, Zn-Li and Zn-Ca mixed soap complex grease compositions formulated with reduced amounts of thickener have been found to have relatively low dropping points.

[0037] In accordance with the present invention, a Zn-Na mixed complex grease composition is prepared with a complexing acid that is a dicarboxylic acid having a chain length of C2 to C12, preferably C6 to C10, along with one or a mixture of monocarboxylic fatty acids having carbon atoms of C12 to C20, preferably C16 to C18. The monocarboxylic fatty acid preferably has a hydroxyl functionality, such as 12-hydroxystearic acid (12-HSA). The resulting Zn-Na mixed complex grease has been found to exhibit a high dropping point and good water resistance.

[0038] According to an embodiment of the present invention, the Zn-Na mixed complex grease comprises 70.0 to 90.0 wt% of a base oil; 5.0 to 20.0 wt% of a saponifiable substance; 0.20 to 5.0 wt% of zinc oxide, 0.20 to 3.0 wt% of sodium hydroxide, and 1.0 to 5.0 wt% of one or more complexing acids.

[0039] According to embodiments of the present invention, Zn-Na mixed complex greases with dropping points similar to simple lithium-based grease / lithium complex grease compositions are made in an open kettle using a process that includes a maximum temperature of 165-175°C, thereby saving the time and expense associated with the higher temperatures reported in prior art processing methods for simple lithium-based grease / lithium complex grease compositions.

[0040] In accordance with a preferred embodiment of the present invention, at least one saponifiable material, one complexing acid, zinc oxide, and sodium hydroxide are employed. Softer or harder grades of grease are made by varying the ratio of zinc oxide metal to sodium hydroxide and the ratio of saponifiable material to complexing acid. Tailored dropping points are achieved by varying the complexing acids and their ratios and the ratio of zinc oxide metal to sodium hydroxide.

[0041] According to the present invention, the poor thickening ability of the zinc complex soap is compensated for by the good thickening ability of the sodium soap, and the poor water resistance of the sodium soap is compensated for by the water repellency of the zinc complex soap, leading to water resistance. The Zn-Na mixed complex grease composition requires a lower thickener content to achieve the desired viscosity compared to pure zinc complex grease. According to the present invention, the complexing acid not only increases the dropping point but also enhances the thickening ability of the complex thickener and improves the structure of the grease.

[0042] According to the present invention, saponifiable materials refer to fatty acids, hydroxy-substituted fatty acids, their esters, and mixtures thereof. Among the saponifiable materials, 12-hydroxystearic acid and stearic acid are preferred, with 12-hydroxystearic acid being most preferred. In embodiments of the present invention, the total amount of saponifiable materials varies between 8 wt% and 18 wt%. Preferably, the total amount of saponifiable materials in NLGI Grade 2 greases is between 10 wt% and 16 wt%, and most preferably between 12 wt% and 14 wt%.

[0043] According to an embodiment of the present invention, the saponifiable material is reacted with 1.0-5.0 wt. % zinc oxide and 0.20-3.0 wt. % alkali or alkaline earth metal oxide or hydroxide, or mixtures thereof, to form a grease composition. Of the alkali and alkaline earth metal oxides and hydroxides, sodium hydroxide is preferred. All metal oxide / hydroxide fatty acids and complexing acids are commercially available LR grades.

[0044] According to one embodiment of the present invention, a Zn-Na mixed complex grease composition with a dropping point similar to that of a lithium complex grease composition is produced by incorporating one or two complexing acids, which are added before or simultaneously with the addition of the alkali / alkaline hydroxide. The total amount of complexing acids is 1.0 wt% to 5.0 wt%, preferably 2.0 wt% to 4.0 wt%, and most preferably 2.5 wt% to 3.5 wt%. Suitable dicarboxylic acids are C3 to C10 dicarboxylic acids selected from malonic acid (C3), succinic acid (C4), glutaric acid (C5), adipic acid (C6), pimelic acid (C7), suberic acid (C8), azelaic acid (C9), and sebacic acid (C10).

[0045] According to an embodiment of the present invention, water is used to dissolve the sodium hydroxide pellets, which helps increase the reaction rate, but using an excess of water greater than three times the sodium hydroxide can cause excessive foaming.

[0046] Commonly used oils, such as petroleum-based naphthenic and paraffinic oils (API Groups I-III), are well known in the art and can be used in accordance with the present invention. Synthetic base oils, such as polyalphaolefins (PAOs), polyalkylene glycols (PAGs), and alkylated aromatics, are used to prepare grease compositions. In some cases, base oils with lower solvency can adversely affect the thickening effect, resulting in a softer grease composition, as would be readily understood by one of ordinary skill in grease manufacturing. In some cases, oils such as diesters and polyol esters are added after saponification to avoid interactions with the alkali / alkali hydroxide.

[0047] According to an embodiment of the present invention, the total amount of base oil added is typically between 65.0 and 90.0 wt %, and most preferably 80.0-85.0 wt %, for an NLGI Grade 2 grease.

[0048] Compositions according to the present invention are preferably made by the method described herein, which comprises the steps of: (1) adding and mixing a first portion of base oil, a hydroxy fatty acid, and a complexing acid in a suitable open grease kettle at a temperature ranging from ambient to about 80°C, (2) adding zinc oxide and sodium hydroxide (preferably dissolved in water) while continuing mixing, (3) gradually heating the mass to 90-100°C over one hour while continuing mixing, (4) gradually increasing the temperature of the mass to 130-140°C and maintaining this temperature for about one hour, (5) gradually increasing the temperature to 165-175°C over one hour and dehydrating for 0.5-1.0 hour, (6) adding a second portion of base oil while continuing to mix and cool to below 90°C, (7) adding performance enhancing additives below 90°C as needed, and (8) grinding / homogenizing the final grease to obtain a Zn-Na grease.

[0049] According to the present invention, the particular steps of the process are not critical to obtaining the grease. The temperature at which the base oil, hydroxy fatty acid, and complexing acid are added is not critical, but it is desirable that they be added at temperatures below 80°C. Also, the order of addition of the base oil, hydroxy fatty acid, dicarboxylic acid, zinc oxide, and sodium hydroxide relative to one another is not critical. In processing the grease composition, a single-step open kettle process is preferably used, as is a more than two-step process in which the complexing acid, zinc oxide, or sodium hydroxide is added in the second stage.

[0050] After saponification, water is removed from the grease by gradually heating and maintaining a constant temperature. Generally, the heating temperature should be between 150 and 180°C, and most preferably between 165 and 175°C. Furthermore, heating to temperatures above 180°C provides no additional benefit and causes the product to become more brown. A vacuum is applied along with the heating to quickly remove the water. Water promotes dissolution of the sodium hydroxide and helps initiate the reaction. However, the grease process is possible without water, and therefore water is not critical to the process.

[0051] (Example) The examples are for illustrative purposes only and are not intended to limit the scope of the invention in any way.

[0052] The development of the zinc mixed soap complex thickened grease composition builds on our previous research on high-temperature zinc complex grease compositions. To compensate for the lack of thickening ability of zinc soaps, alkali and alkaline earth metal soaps, such as lithium, sodium, potassium, calcium, and magnesium, were prepared in situ by reacting fatty acids and dicarboxylic acids with their respective oxides / hydroxides. The general procedure for preparing a mixed zinc soap-based complex grease composition is as follows: In a suitable open grease kettle, add and mix the first portion of a paraffinic base oil (Group I, ISO VG150), fatty acids, and complexing acids at a temperature ranging from ambient to approximately 80°C. While continuing to mix, add zinc oxide, alkali / alkaline oxides / hydroxides, and water, and heat the mixture to 90-100°C over one hour. The mass is then further increased in temperature to 130-140°C and maintained for one hour. The temperature of the whole was then gradually increased to 165-175°C over 1 hour for dehydration under vacuum, followed by the addition of the second portion of base oil with continuous mixing. It was then cooled to 90°C with continuous stirring and subsequently milled to obtain the final product. If necessary, additives may be added prior to milling.

[0053] The grease of the prior art example was made by reacting 5 wt% zinc oxide with 25 wt% 12-HSA and 4 wt% sebacic acid. As shown in Table 1, the grease compositions of Examples 1-5 were made using the same equipment and manufacturing process as the prior art examples, except for the following modifications: the saponifiable material was reduced from 25 to 15 wt%, 0.5 wt% of a different alkali / alkaline oxide / hydroxide was used, and the stoichiometric amount of zinc oxide was reduced. The grease of Example 1 was processed in a suitable open grease kettle by adding and mixing 50% of a total paraffinic base oil (Group I, ISO VG150), fatty acid, and complexing acid at temperatures ranging from ambient to approximately 80°C. With continuous mixing, zinc oxide and sodium hydroxide (aqueous solutions in equal parts water) were added, and the mass was continuously and gradually heated to 90-100°C over the course of one hour. The mass temperature was then increased to 130-140°C and maintained for 1 hour. The mass temperature was then gradually increased to 165-175°C over 1 hour. The resulting mass was completely dehydrated under vacuum for 0.5 to 1.0 hour, and the second portion of base oil was added with continued mixing. The mass was cooled to 90°C with continuous stirring and subsequently milled to obtain the final product. The compositions and test results of the grease compositions of Examples 1-5, along with those of the prior art, are shown in Table 1.

[0054] [Table 1]

[0055] Example 1, a zinc complex grease mixed with a small amount of sodium soap, produced an NLGI Grade 2 grease with the highest dropping point of all the alkali / alkaline oxide / hydroxide greases used. Thus, the zinc soap's low thickening ability is compensated for by the sodium soap, which also leads to a more effective complex, as evidenced by the higher dropping point. Similarly, Example 2, a zinc complex grease mixed with a small amount of lithium soap treated with 0.50 wt% lithium hydroxide monohydrate, produced an NLGI Grade 1 grease with a dropping point of 225°C, demonstrating that lithium soap also provides some improvement in thickening ability or yield. Example 3, a zinc complex grease made with a small amount of calcium soap, also produced an NLGI Grade 1-2 viscosity, but with a dropping point of around 190°C. Example 4, made with a small amount of magnesium soap, was found to have a poorer structure, a softer grease, and a lower dropping point of around 125°C. Example 5, made with a small amount of potassium soap, was found to have a poorer grease structure, a softer grease, and a low dropping point below 180°C.

[0056] Furthermore, Examples 7 through 10 were processed using the same equipment and manufacturing process as described in Example 1, except that lithium hydroxide monohydrate and hydrated lime were used at different levels of processing to obtain Zn-Li and Zn-Ca mixed complex grease compositions with trace amounts of lithium and calcium soaps, respectively. As shown in Table 2, Example 6, which has a low thickener content and a composition similar to our prior art pure zinc complex grease, resulted in a softer grease with an NLGI 0 dropping point greater than 260°C, while Example 7, which was processed with 0.25 wt% lithium hydroxide monohydrate, resulted in a grease composition with a worked penetration of 331 and a dropping point of 228°C, indicating a Zn-Li complex grease with a viscosity superior to that of the pure zinc complex grease but a slightly lower dropping point. In Example 8, 1.00 wt% lithium hydroxide monohydrate, the zinc complex grease was blended with lithium soap to give it a softer viscosity, resulting in a softer grease with a dropping point around 180°C.

[0057] [Table 2]

[0058] As in Example 3, a zinc complex grease mixed with a small amount of calcium soap treated with 0.50 wt% slaked lime produced an NLGI Grade 2 grease with a dropping point of around 180°C. As shown in Table 2, Example 9 gave a softer grease with a dropping point of 181°C, and Example 10 produced an NLGI Grade 3 grease composition with a dropping point of around 180°C. Therefore, it was found that increasing the calcium soap content in the Zn-Ca mixed complex grease only increased the thickening, and the dropping point remained around 180°C.

[0059] As noted in Table 1, the Zn-Na mixed combination yielded the best results compared to other mixed zinc-alkali / alkaline metal soap combinations. Furthermore, the zinc to sodium ratio was optimized to optimize the thickener content to obtain greases with desired viscosity and properties. As shown in Table 3, Examples 11 to 15 were processed using the same ingredients, equipment, and manufacturing process as Example 1, except that the sodium hydroxide content was increased and the zinc oxide content was stoichiometrically decreased. The compositions and test data for the grease compositions of Examples 11 to 15 are provided in Table 3.

[0060] [Table 3]

[0061] As shown in Table 3, Examples 11-15 demonstrate that increasing the sodium soap content results in better viscosity of the grease composition. As shown in Table 3, no adverse effect on the dropping point was observed by increasing the sodium soap content. The introduction of sodium soap resulted in a change in water-resistance behavior. However, the water-resistance behavior was found to be within the normal range, as the hydrophilic characteristics of the soda soap were complemented by the water-repellent characteristics of the zinc soap. In the grease of Example 14, where the sodium content was higher than the zinc content, i.e., 0.82:1.00, the water-washing characteristics were still maintained but relatively increased. As shown in Table 3, the water-resistant properties of the Zn-Na mixed complex grease composition were well maintained when the zinc content was higher relative to the sodium content. In Example 15, further increases in the sodium soap content resulted in better grease viscosity. Increasing the sodium soap content relative to the zinc soap had an adverse effect on the water-washing properties. The water-resistant properties of the Zn-Na mixed complex grease composition were well maintained when the zinc content was higher relative to the sodium content. Furthermore, the predominant role of sodium soaps in water solubility is evident, and increasing sodium over zinc affects water resistance properties.

[0062] To study the effect of complexing acid content on grease performance, Examples 16 to 21 were processed using the same equipment and manufacturing process as in Example 1, except that the sebacic acid content was varied from 0.00 to 5.00 wt% using 13 wt% 12-HSA and 1.00 wt% sodium hydroxide, along with the required amount of zinc oxide. As shown in Table 4, Example 16, made with 0.00 wt% sebacic acid, produced a softer grade with a dropping point below 180°C, indicating the need for complexing acid for thickening and dropping point enhancement. As shown in Table 4, a gradual increase in viscosity and dropping point was observed with increasing complexing acid content. Consequently, complexing acid not only increases the dropping point but also helps to increase the thickening effect of the Zn-Na mixed complex thickener system. In Example 19, a grease made with 3.00 wt. % complexing acid, with a total thickener content of around 19 wt. %, and a dropping point above 270° C. is a more preferred composition.

[0063] [Table 4]

[0064] To demonstrate the effect of different complexing acids other than sebacic acid (C10), the grease compositions of Examples 22 to 28 were processed using the same equipment and manufacturing process as mentioned in Example 1. Various complexing acids ranging from C3 to C10 dicarboxylic acids, such as malonic acid (C3), succinic acid (C4), glutaric acid (C5), adipic acid (C6), pimelic acid (C7), suberic acid (C8), azelaic acid (C9), and sebacic acid (C10), were used at 3.00 wt% to prepare Zn-Na mixed complex greases. As shown in Table 5, all dicarboxylic acids yielded Zn-Na mixed complex grease compositions with dropping points ranging from 180 to 280°C and NLGI grades of 2 to 3. Among the different complexing acids, the grease compositions made with pimelic acid, suberic acid, azelaic acid, and sebacic acid were found to have dropping points above 260°C and particle-free structures, as shown in Table 5. The use of sebacic acid is shown in Example 19 of Table 4. Therefore, among different dicarboxylic acids, C8 to C10 dicarboxylic acids were found to be the most suitable for the Zn-Na mixed complex grease composition.

[0065] [Table 5]

[0066] Various common mono-, di-, and tribasic organic acids, such as acetic acid (monobasic), phthalic acid (dibasic), terephthalic acid (dibasic), oxalic acid (dibasic), salicylic acid (monobasic), benzoic acid (monobasic), boric acid (tribasic), lactic acid (monobasic), citric acid (tribasic), and malic acid (dibasic), were used in place of sebacic acid at the same treatment level of 3.00 wt % and processed similarly to Example 1, and the resulting overall grease composition was found to have a dropping point below 200°C, indicating low complexation.

[0067] According to one embodiment of the present invention, various commonly available saponifiable substances, including 12-hydroxystearic acid, stearic acid, hydrogenated castor oil, and mutton tallow, were used to prepare a Zn-Na mixed complex grease composition, using the same equipment and manufacturing process as described in Example 1. The best results were obtained with 12-HSA and stearic acid. Hydrogenated castor oil and mutton tallow yielded softer grades with lower dropping points than 12HSA. This may be due to the weak basicity of zinc oxide, which is unable to hydrolyze triglyceride esters to obtain free saponifiable acids and form soaps. Hydrogenated castor oil or mutton tallow can be used in proportion to sodium hydroxide in the first step of ester hydrolysis and subsequent saponification. In the second step, 12-HSA, the complexing acid, can be reacted with zinc oxide to prepare the grease. 12-HSA and stearic acid were found to be more suitable for preparing a Zn-Na mixed complex grease composition, while 12-HSA is more preferred.

[0068] Although the examples provided herein correspond to NLGI Grades 2 or 3, it should be understood that the scope of the present invention further includes all NLGI viscosity grades harder and softer than NLGI Grades 2 and 3. Those skilled in the art will understand upon reading this application, including the examples contained herein, that modifications and variations to the compositions and methodologies for making similar compositions may be within the scope of the present invention.

[0069] To demonstrate the closed reactor process, a batch of grease was made using the same raw materials and ingredients as in Example 19 according to the following process: In a closed reactor, 50% of the total base oil was charged to the reactor, followed by the same amount of 12-hydroxystearic acid, dicarboxylic acid, zinc oxide, and sodium hydroxide in water. The reactor was sealed, and the mass temperature was gradually increased to 110-115°C and maintained at this temperature for 1 hour with continuous stirring. The mass temperature was then increased to 130-140°C and maintained for 1 hour. The material was then heated to 170-175°C for an additional hour. The reactor was then carefully depressurized to avoid soap leakage. After this, the mixture was maintained at 170-175°C with continuous stirring for 30 minutes under vacuum to completely dehydrate it. A cutback was made using the remaining base oil. The heat was turned off, and cold oil was circulated to facilitate cooling. When the mass cooled to 90-95°C, the grease was milled in a homogenizer to obtain a smooth, homogeneous product. All test data for the closed-kettle batch grease was found to be similar to that of the open-kettle grease batch (Example 19), indicating that the developed composition can be used in both open-kettle and closed-reactor processes. However, the open-kettle process is preferred because it eliminates the need for reactor pressurization and provides shorter dewatering times.

[0070] The detailed description and claims of the present invention are shown in Table 6. In Examples 29 and 30, grease compositions were processed using the same equipment, manufacturing process, and similar compositions as Example 19, except that the base oil and performance-enhancing additive additions were adjusted to produce the differences. The viscosity of the base oil was adjusted to VG150 using a blend of two Group I paraffinic base oils with viscosities of 400 cSt and 95 cSt at 40°C. According to the present invention, NLGI 2 and 3 grade Zn-Na mixed complex greases can be formed with a combination of 12-hydroxystearic acid (13.00 wt%), sebacic acid (3.00 wt%), zinc oxide (2.00 wt%), and sodium hydroxide (1.00 wt%). The resulting greases were found to have dropping points above 260°C, which is in the range of other soap complex grease compositions. Mechanical stability was found to be excellent, at +30 units after 100,000 double strokes. Example 19 is a grease based on a Zn-Na mixed complex without any performance-enhancing additives. Examples 29 and 30 demonstrate that grease compositions made according to the present invention are useful for extreme pressure industrial applications. As shown in Table 6, superior additive response was observed, providing better extreme pressure and antiwear properties compared to Example 19. In Example 29, a multifunctional grease additive package, such as LZ5235 and Hitec 552, significantly increased the weld load from 180 kg to over 400 kg with IP239. As shown in Example 30, the synergistic effect of zinc-based additives increased the extreme pressure and antiwear properties of the grease composition. Zinc dialkyldithiophosphate (ZDDP) showed excellent synergistic effects, increasing the weld load from 180 kg to over 500 kg, as shown in Table 6. The ZDDP additives used were from various sources, such as Elco 105, LZ677, and LZ1395, which provided similar results. Furthermore, in Examples 29 and 30, apart from the excellent results in extreme pressure and anti-wear properties, other grease properties such as oxidation stability and corrosion resistance were also found to be excellent, demonstrating the synergistic effect of the Zn-Na mixed complex grease with the zinc-containing additive.

[0071] [Table 6-1] [Table 6-2]

[0072] The present invention has the following advantages over the prior art: The present invention discloses zinc-based soap complex grease compositions mixed with alkali / alkaline earth metal salts, preferably small amounts of sodium salts such as complex soaps, which have a combination of excellent properties such as high dropping point, inherent oxidation stability, extreme pressure, antiwear, and water resistance, with a relatively low thickener content. The grease composition containing the Zn-Na complex soap of the present invention as a main component has a specially adjusted dropping point of 180 to 300°C. The Zn-Na complex soap based grease compositions of the present invention are prepared in a time-saving and energy-saving process in an open kettle through the in situ formation of zinc-sodium mixed metal complex soaps based on the reaction of fatty acids and complexing acids with the corresponding metal oxides and hydroxides in a single step. • In the present invention, the poor thickening ability of zinc soap is complemented by the superior thickening ability of sodium soap, while the hydrophilicity of sodium soap is complemented by the hydrophobic, water-repellent zinc soap, resulting in a water-resistant complex grease.

[0073] (Addendum) (Appendix 1) i) base oil, ii) saponifiable substances; iii) zinc oxide or zinc hydroxide; iv) oxides or hydroxides of alkali or alkaline earth metals; v) a complexing acid; and vi) performance enhancing additives as required; 1. A zinc-alkali / alkaline earth metal mixed complex grease composition comprising:

[0074] (Appendix 2) The base oil has a viscosity in the range of ISO VG2 to 3200 or a mixture thereof, The base oil is selected from API Group I-III mineral base oils, API Group IV synthetic base oils, ester base oils, paraffinic base oils, naphthenic base oils and re-refined base oils; The synthetic base oil is selected from polyalphaolefins (PAOs), polyalkyl glycols (PAGs), polyol esters, diesters, and alkylated aromatics. Attachment 1: The grease composition of claim 1.

[0075] (Appendix 3) The base oil is present in a range of 65.0 to 90.0 wt %, The saponifiable substance is present in an amount of 8.0 to 18.0 wt %, The alkali or alkaline earth metal oxide or hydroxide is present in the range of 0.20 to 3.0 wt %, the complexing acid is present in the range of 1.0 to 5.0 wt %, and The performance enhancing additive is present in the range of 0.01 to 3 wt %. Attachment 1: The grease composition of claim 1.

[0076] (Appendix 4) the saponifiable substance is a fatty acid selected from 12-hydroxystearic acid, stearic acid, oleic acid, or a mixture thereof; the alkali or alkaline earth metal oxide or hydroxide is selected from sodium hydroxide, calcium oxide, calcium hydroxide, slaked lime, lithium hydroxide or lithium hydroxide monohydrate; the complexing acid is a C3 to C10 dicarboxylic acid selected from malonic acid (C3), succinic acid (C4), glutaric acid (C5), adipic acid (C6), pimelic acid (C7), suberic acid (C8), azelaic acid (C9), or sebacic acid (C10); the performance enhancing additive is selected from a rust inhibitor, a corrosion inhibitor, a metal deactivator, a metal passivator, an antioxidant, a pressure additive, a polymer, a tackifier, a dye, a chemical marker, a fragrance, an anti-wear additive, or a combination thereof; Attachment 1: The grease composition of claim 1.

[0077] (Appendix 5) a) mixing a saponifiable material with a base oil to form a mixture; b) adding to the mixture obtained in step a) an aqueous solution of a complexing acid, zinc oxide, and an oxide or hydroxide of an alkali or alkaline earth metal; c) heating and dehydrating the mixture obtained in step b) with continuous stirring to obtain a solid mass; d) adding a base oil to the solid mass obtained in step c) to form a mixture; e) cooling the mixture obtained in step d) and adding performance enhancing additives as needed; and f) homogenizing the mixture obtained in step e) to obtain a mixed complex grease composition; 1. An open kettle, single step process for preparing a zinc-alkali / alkaline earth metal mixed complex grease composition comprising:

[0078] (Appendix 6) The mixing in step a) is carried out at a temperature ranging from 25 to 80°C. The process described in Appendix 5.

[0079] (Appendix 7) The heating in step c) i) heating at a temperature in the range of 90-100°C for 1 hour; ii) heating at a temperature in the range of 130-140°C for an additional hour; and iii) heating at a temperature in the range of 167-175°C for an additional 0.5-1.0 hour; A series of specific steps is carried out in three consecutive steps, including The process described in Appendix 5.

[0080] (Appendix 8) The base oil has a viscosity in the range of ISO VG2 to 3200 or a mixture thereof, The base oil is selected from API Group I-III mineral base oils, API Group IV synthetic base oils, ester base oils, paraffinic base oils, naphthenic base oils and re-refined base oils; The synthetic base oil is selected from polyalphaolefins (PAOs), polyalkyl glycols (PAGs), polyol esters, diesters, and alkylated aromatics. The process described in Appendix 5.

[0081] (Appendix 9) the saponifiable substance is a fatty acid selected from 12-hydroxystearic acid, stearic acid, oleic acid, or a mixture thereof; the complexing acid is a C3 to C10 dicarboxylic acid selected from malonic acid (C3), succinic acid (C4), glutaric acid (C5), adipic acid (C6), pimelic acid (C7), suberic acid (C8), azelaic acid (C9), or sebacic acid (C10); the alkali or alkaline earth metal oxide or hydroxide is selected from sodium hydroxide, calcium oxide, calcium hydroxide, slaked lime, lithium hydroxide or lithium hydroxide monohydrate; the performance enhancing additive is selected from a rust inhibitor, a corrosion inhibitor, a metal deactivator, a metal passivator, an antioxidant, a pressure additive, a polymer, a tackifier, a dye, a chemical marker, a flavoring agent, an anti-wear additive, or a combination thereof; The process described in Appendix 5.

[0082] (Appendix 10) The base oil is present in a range of 65.0 to 90.0 wt %, The saponifiable substance is present in an amount of 8.0 to 18.0 wt %, The alkali or alkaline earth metal oxide or hydroxide is present in the range of 0.20 to 3.0 wt %, the complexing acid is present in the range of 1.0 to 5.0 wt %, and The performance enhancing additive is present in the range of 0.01 to 3 wt %. The process described in Appendix 5.

Claims

1. i) a base oil; ii) a fatty acid selected from the group consisting of 12-hydroxystearic acid, stearic acid, oleic acid, and mixtures thereof; iii) zinc oxide or zinc hydroxide; iv) 0.20 to 3.0 wt % sodium hydroxide; v) a C3 to C10 dicarboxylic acid selected from the group consisting of malonic acid (C3), succinic acid (C4), glutaric acid (C5), adipic acid (C6), pimelic acid (C7), suberic acid (C8), azelaic acid (C9) and sebacic acid (C10), and vi) performance enhancing additives; It consists of the base oil is present in the range of 65.0 to 90.0 wt %; The fatty acid described in ii) is present in the range of 8.0 to 18.0 wt %, the zinc oxide is present in the range of 0.20 to 5.0 wt %; The dicarboxylic acid described in v) above is present in the range of 1.0 to 5.0 wt %; and the performance enhancing additive is present in the range of 0.01 to 3 wt %; Zinc-sodium mixed complex grease composition.

2. the base oil has a viscosity in the range of ISO VG2 to 3200 or a mixture thereof; the base oil is selected from the group consisting of API Group I-III mineral base oils, API Group IV synthetic base oils, ester base oils, paraffinic base oils, naphthenic base oils and rerefined base oils; The synthetic base oil is selected from the group consisting of polyalphaolefins (PAOs), polyalkyl glycols (PAGs), polyol esters, diesters, and alkylated aromatic compounds. The grease composition according to claim 1.

3. the performance enhancing additive is selected from the group consisting of rust inhibitors, corrosion inhibitors, metal deactivators, metal passivators, antioxidants, pressure additives, polymers, tackifiers, dyes, chemical markers, fragrances, anti-wear additives, and combinations thereof; The grease composition according to claim 1.

4. a) mixing a fatty acid with a base oil to form a mixture; b) adding to the mixture obtained in step a) an aqueous solution of dicarboxylic acid, zinc oxide present in the range of 0.20 to 5.0 wt %, and sodium hydroxide present in the range of 0.20 to 3.0 wt %; c) heating and dehydrating the mixture obtained in step b) with continuous stirring to obtain a solid mass; d) adding said base oil to the solid mass obtained in step c) to form a mixture; e) cooling the mixture obtained in step d) and adding performance enhancing additives; and f) homogenizing the mixture obtained in step e) to obtain a mixed complex grease composition; It consists of the fatty acid is selected from the group consisting of 12-hydroxystearic acid, stearic acid, oleic acid, and mixtures thereof; the dicarboxylic acid is selected from the group consisting of malonic acid (C3), succinic acid (C4), glutaric acid (C5), adipic acid (C6), pimelic acid (C7), suberic acid (C8), azelaic acid (C9) and sebacic acid (C10); An open kettle, single-step process for preparing a zinc-sodium mixed complex grease composition.

5. The mixing of step a) is carried out at a temperature ranging from 25 to 80°C.

5. The process of claim 4.

6. The heating in step c) is i) heating at a temperature in the range of 90-100°C for 1 hour; ii) heating at a temperature in the range of 130-140°C for an additional hour; and iii) heating at a temperature in the range of 167-175°C for an additional 0.5-1.0 hour; A series of specific steps is carried out in three consecutive steps, consisting of:

5. The process of claim 4.

7. the base oil has a viscosity in the range of ISO VG2 to 3200 or a mixture thereof; the base oil is selected from the group consisting of API Group I-III mineral base oils, API Group IV synthetic base oils, ester base oils, paraffinic base oils, naphthenic base oils and rerefined base oils; The synthetic base oil is selected from the group consisting of polyalphaolefins (PAOs), polyalkyl glycols (PAGs), polyol esters, diesters, and alkylated aromatic compounds.

5. The process of claim 4.

8. the performance enhancing additive is selected from the group consisting of rust inhibitors, corrosion inhibitors, metal deactivators, metal passivators, antioxidants, pressure additives, polymers, tackifiers, dyes, chemical markers, flavoring agents, anti-wear additives, and combinations thereof; 5. The process of claim 4.

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