KR970011370B1 - Lubricating composition - Google Patents

Abstract

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Description

Lubricating composition

The present invention relates to a lubricating composition having modified low temperature and high temperature properties, a process for its preparation and its use, in particular its use as an open gear lubricant.

Often, lubricating compositions are used in applications requiring satisfactory performance at extreme high and low temperatures. Examples of such applications include rotating gears on mining shovels, huge open gears on ball mills, and the like. The main complaint of using this type of product is that these products are very fragile at cold temperatures and prone to "run-off" at warmer temperatures.

Various combinations of additives have been proposed to correct the problem. For example, US Pat. No. 3,705,853 discloses a grease composition comprising a lubricating oil, a thicker and an ethylene terpolymer having a melt index in the range of from 0.5 to 200. Viscosity index improvers may be present, but no mention is made of greases containing ethylene copolymers (see US Pat. No. 3,904,543).

However, ethylene copolymers have been incorporated into various lubricating compositions. For example, US Pat. No. 4,115,343 discloses that the storage stability and antifoaming tendency of organosiloxane polymers in mineral oils can be improved by adding ethylene-vinyl acetate copolymers (EVA) to the dispersion. As another example, US Pat. No. 3,250,714 discloses EVA as a VI improver for mineral lubricants. However, no mention is made of the melt index of the polymer. U.S. Patent No. 3,947,368 states that EVA having a melt index of 5 to 580 is used as the pour point depressant in waxy lubricants. However, no mention is made of the presence of thickeners.

Therefore, none of the above references teaches or discloses lubricating compositions having good low temperature slumpability and high temperature adhesion of the compositions described herein.

In the broadest aspect, the invention relates to a lubricating composition having improved low and high temperature properties. More particularly, a copolymer of ethylene with at least one compound selected from the group of (1) lubricants, (2) thickeners, (3) VI improvers and (4) vinyl acetate, alkyl acrylates, or alkyl methacrylates It was confirmed that the lubricating composition had both excellent high temperature adhesiveness and low temperature slumpability. The ethylene copolymer used in the present invention should have a melt index of at least about 40 g / 10 minutes and contain about 10 to about 40 weight percent of vinyl acetate, alkyl acrylate or alkyl methacrylate. Preferably the melt index should be about 40 to about 10,000, more preferably about 40 to about 5000, and most preferably about 40 to about 2500 g / 10 minutes.

In another aspect the present invention relates to a method of increasing the slumpability of a lubricating composition at a temperature of about −20 ° C. or less and increasing its adhesion at a temperature of about 20 ° C. or more.

Essential ingredients of the present invention are copolymers of ethylene with lubricating oils, thickeners, VI improvers and at least one compound selected from the group of vinyl acetates, alkyl acrylates or alkyl methacrylates.

A wide variety of lubricants can be used to prepare the compositions of the present invention. Thus, the lubricant base may be any of the mineral oils, synthetic hydrocarbon oils or synthetic ester oils commonly used. Generally, applications require oils having a viscosity in the range of about 10 to about 1,000 cSt at 40 ° C., but the lubricants have a viscosity in the range of about 5 to 10,000 cSt at 40 ° C. The mineral lubricant base stocks used to prepare the lubricating composition can be conventionally refined base stocks derived from paraffinic, naphthenic and mixed base crudes. Synthetic lubricants that may be used include esters of dibasic acids such as poly-2-ethylhexyl sebacate, C ₁₃ of tetraethylene glycol, esters of glycols such as diester of oxo acid or 1 mole of sebacic acid, tetraethylene Complex esters such as esters produced with 2 moles of glycol and 2 moles of 2-ethylhexanoic acid. Other synthetic oils that can be used include polyalphaolefins; Alkyl benzenes (eg, alkylate products obtained by alkylation of benzene with tetrapropylene or with copolymers of ethylene and propylene silicone oils (eg ethyl phenyl polysiloxane, methyl polysiloxane, etc.); Polyglycol oils (eg, oils obtained by condensation of butyl alcohol and propylene oxide); And carbonate esters (e.g., products obtained by reacting a C ₈ oxo alcohol with ethyl carbonate to form a half ester and then reacting it with tetraethylene glycol and the like). Other suitable synthetic oils are polyphenyl ethers (eg, ethers having about 3 to 7 ether bonds and about 4 to 8 phenyl groups) (see US Pat. No. 3,424,678 column 3). Usually, lubricants make up the majority of the lubricating composition. Typically, the amount of lubricant is in the range of about 50 to about 90 weight percent, preferably about 70 to about 85 weight percent of the lubricating composition.

The lubricating composition also contains a thickening agent that is dispersed in the lubricating oil to form a base grease. However, the particular thickener used is not critical and can vary widely. For example, the thickener is based on aluminum, barium, calcium, lithium, sodium soap, or a complex thereof. Soap thickeners can be derived from a wide range of animal oils, vegetable oils and greases as well as fatty acids derived therefrom. Such materials are well known in the art and are described, for example, in C. J. Boner, Manufacture and Application of Lubricating Greases, Chapter 4, Robert E. Krieger Publishing Company, Inc., New York (1971). Carbon black, silica and clays can be used as well as dyes, polyureas and other organic agents. Thickeners based on pyrrolidone may also be used. Preferred thickeners are based on clays, pyrrolidones, aluminum soaps, barium soaps, calcium soaps, lithium soaps, sodium soaps or combinations of these soaps. Particularly preferred thickening agents are based on lithium soaps, calcium soaps, aluminum soaps, composites thereof or mixtures thereof. More preferred thickening agents are based on lithium soaps, calcium soaps, composites thereof or mixtures thereof. Most preferred are lithium or lithium composite thickeners incorporating hydroxy fatty acids having 12 to 24 (preferably 16 to 20) carbon atoms. Preferred hydroxy fatty acids are hydroxy stearic acid (such as 9-hydroxy or 10-hydroxy stearic acid), of which 12-hydroxy stearic acid is most preferred (see US Pat. No. 3,929,651, the contents of which are incorporated herein by reference). Cited for reference). The thickener amount in the lubricant composition typically ranges from about 1 to about 15 weight percent. In most cases there is about 1 to about 10 weight percent, preferably about 2 to about 5 weight percent thickener in the composition.

VI improvers are also present in the lubricating composition. Viscosity modifiers are long chain, generally high molecular weight polymers (including polyesters) that render the lubricating composition functional at high and low temperatures by making the lubricating composition remain relatively viscous at elevated temperatures and useful at low temperatures. Viscosity modifiers may also induce to include other properties or functions, such as doubling of dispersibility. The fat soluble viscosity controlling polymers useful in the present invention generally have a number average molecular weight of about 300 to about 10 ⁶ , preferably about 500 to about 10 ⁴ , and more preferably about 1,000 to about 2,000. The amount of VI improver present in the lubricating composition varies depending on the particular VI improver used, its molecular weight, and the like. Typically, however, about 5 to about 40 weight percent (preferably about 10 to about 30 weight percent) of the lubricating composition is a VI improver.

Suitable VI modifiers may be based on hydrocarbon polymers, polyesters or mixtures thereof. Silye a suitable hydrocarbon polymer VI improvers is, C ₂ to C ₃₀ monomers (e.g., aliphatic, aromatic, alkyl of straight or branched chain, including both alpha olefins and internal olefins - C ₂ to C ₈ with the like aromatic, alicyclic Olefins) or more homopolymers and copolymers. Often VI improvers are polymers of isobutylene or copolymers of ethylene, propylene, butene or isobutylene with C ₂ to C ₃₀ olefins.

Polymers of isobutylene or copolymers of butene and isobutylene are preferred, and polymers of isobutylene are particularly preferred. Other polymers that can be used include homopolymers and copolymers of C ₆ and higher alpha olefins; Attacker polypropylene; Hydrogenated polymers, copolymers and terpolymers (for example with isoprene and / or butadiene and hydrogenated derivatives thereof). The polymer may lower the molecular weight by oxygenation, extrusion, oxidation, degradation, and the like and may contain oxygen.

Suitable VI improvers also include polyester VI improvers (which are generally polymers of esters of ethylenically unsaturated C ₃ to C ₈ mono- and dicarboxylic acids such as methacrylic acid, acrylic acid, maleic acid, maleic acid accompany, fumaric acid, etc.). Is). Examples of unsaturated esters that can be used include at least one carbon atom and preferred, such as decyl acrylate, lauryl acrylate, stearyl acrylate, decyl methacrylate, diamyl fumarate, cetyl methacrylate and the like and mixtures thereof. Preferably there are esters of aliphatic saturated mono alcohols having 12 to 20 carbon atoms. Other esters include vinyl alcohol esters of C ₂ to C ₂₂ fatty acids or monocarboxylic acids such as vinyl acetate, vinyl laurate, vinyl stearate and the like and mixtures thereof. The C ₂ to C ₂₂ fatty acid or monocarboxylic acid is preferably saturated. Copolymers of vinyl alcohol esters with unsaturated acid esters, such as copolymers of vinyl acetate and dialkyl fumarate, may also be used.

The lubricating composition also contains a copolymer of ethylene with at least one compound selected from the group of vinyl acetate, alkyl acrylates or alkyl methacrylates. Vinyl acetate is the preferred ethylene copolymer. The copolymer should have a melt index of at least about 40 g / 10 minutes and have a copolymer content of about 10 to 40 weight percent, preferably about 10 to about 30 weight percent. The melt index should preferably range from about 40 to about 10,000, more preferably from about 40 to about 5000, and most preferably from about 40 to about 2,500 g / 10 minutes. The amount of copolymer added should range from about 1 to about 20 weight percent (preferably from about 1 to about 10 weight percent) based on the total weight of the composition.

The specific VI improvers and polymers used are readily available from various chemical suppliers on the market. Therefore, their production methods are well known to those skilled in the art.

The lubricating composition also contains small amounts of auxiliary additives (including, but not limited to, corrosion inhibitors, extreme pressure wear agents, pour point depressants, tackiness agents, antioxidants, dyes, etc., incorporated for special purposes). can do. The total amount of the additives typically ranges from about 2 to about 5 weight percent based on the total amount of the lubricating composition. In addition, solid lubricants such as molybdenum disulfide and graphite may be present in the composition and are typically from about 1 to about 5 weight percent (preferably from about 1.5 to about 3 weight percent) for molybdenum disulfide and from about 3 to about 15 weight percent (preferably about 6 to about 12 weight percent).

One or more solvents (typically about 10 to about 40 weight percent) may be added as a diluent to the lubricating composition to improve the dispensing properties of the lubricating composition. Suitable solvents include pure hydrocarbon solvents, mixed hydrocarbon solvents, chlorinated hydrocarbon solvents or mixtures thereof, which typically have an atmospheric boiling point of about 30 ° C to about 300 ° C.

Suitable pure hydrocarbon solvents include toluene, orthoxylene, meta-xylene, mesitylene, ethylbenzene, butylbenzene, hexane, heptane, octane, isooctane and the like or mixtures thereof. Typically these solvents have a solidification point (or melting point) of about −25 ° C. or less (preferably −40 ° C. or less).

Suitable mixed hydrocarbon solvents include kerosene, Varsol, naphtha and the like or mixtures thereof. Typically these solvents have a flow point of about −25 ° C. or less, preferably about −40 ° C. or less.

Suitable hydrocarbon chloride solvents include n-propylchloride, isopropyl chloride, n-butylchloride, iso-butylchloride, secondary-butylchloride, pentyl chloride, hexyl chloride, dichloromethane, trichloromethane, 1,1-dichloroethane , 1,2-dichloroethane, trichloroethylene, chlorobenzene and the like and mixtures thereof, with 1,1,1-trichloroethane being particularly preferred.

The lubricating compositions of the present invention usually first disperse or mix the thickener in the lubricant for about 1 to about 8 hours or more (preferably about 1 to about 4 hours) and then at elevated temperatures (e.g., depending on the specific thickener used). From about 60 ° C. to about 260 ° C. until the mixture is enriched. The VI improver, ethylene copolymer and other additives are then added while cooling the mixture to ambient temperature (typically about 25 ° C.). Although the VI improver and the ethylene copolymer can be added together or separately in any order, it is preferred to add as described below to obtain a lubricating composition having the desired low temperature and high temperature properties.

As the mixture cools, it is preferred to add ethylene copolymers (eg EVA) at temperatures of about 120 ° C to about 180 ° C. The ethylene copolymer can be added at a temperature outside the above range, but the copolymer tends to coalesce at lower temperatures and does not disperse properly in the mixture. At higher temperatures the copolymer is thermally unstable. Preferably, the VI improver is added at a temperature of about 80 ° C to about 190 ° C. It is also possible to add additional lubricants within the latter temperature range in order to obtain the desired grease consistency and oil viscosity properties. Other additives (above mentioned additives and solid lubricants) are usually added at a temperature of about 50 ° C to about 100 ° C. Finally, solvent is added to the mixture at ambient temperature to about 50 ° C. (preferably between about 25 ° C. and about 40 ° C.) to provide the required dispensing capacity. Low temperature is preferred in case of solvent addition to avoid excessive evaporation. Usually, the composition is blended or mixed during the addition of the components.

The components of the lubricating composition can be mixed, blended or ground in a number of ways that can be readily selected by those skilled in the art. Suitable means include external mixers, roll mills, internal mixers, Benbury mixers, screw-extruders, augers, colloid mills, homogenizers and the like.

The lubricating composition of the present invention can be suitably used in essentially any application that requires good lubrication at both high and low temperatures. Examples of such applications include open gears, rollers, bearings, wire ropes, cables and the like. However, the composition is particularly well suited for use as an open gear lubricant.

In another aspect, the present invention relates to a method of increasing slumpability at a temperature of about −20 ° C. or lower and adhesion at a temperature of about 20 ° C. or higher of the lubricating composition, wherein the composition comprises (a) a lubricant (b) a thickener, and (c) a VI enhancer, the process comprising copolymers of ethylene with at least one compound selected from the group of vinyl acetate, alkyl acrylates or alkyl methacrylates, which is at least about 40 g / 10 Vinyl acetate, alkyl acrylates for the composition with a melt index of minutes (preferably about 40 to about 10,000, more preferably about 40 to about 5,000, and most preferably about 40 to 2,500 g / 10 minutes) Or about 10 to about 40 weight percent, preferably about 10 to about 30 weight percent, alkyl methacrylate content).

The invention will be better understood by reference to the following examples which are not intended to suggest the scope of the claims appended hereto.

Example 1-Preparation of Base Grease Composition

The base grease composition is prepared in a Hobart mixing apparatus. Open mixing vessels are equipped with thermal radiation and thermal insulation. 300 g of 12-hydroxy stearic acid and 915 g of 100SUS (@ 100 ° F.) hydrogenated naphthenic distillate (commercially available as Exxon Oil 1502) were added and the mixture was heated to 70 ° C. with constant stirring. The mixture is neutralized by slowly adding 45 g of LiOH.H ₀ O in 150 g of water at 70 ° C. over 1 hour at which time the temperature is maintained between 70 ° and 110 ° C. After the alkali addition is complete, the temperature is raised to 150 ° C. and maintained at this temperature until dehydration is complete. Alkali content was determined by acid titration to 0.2% by mass (expressed as NaOH equivalent), indicating that neutralization was complete. The temperature of the mixture is then raised to 190 ° C. to 200 ° C. and held at this temperature for about 30 minutes. Following this “cook-out” the mixture was cooled to about 120 ° C. by slowly adding 500 g of Pennsylvania Resin (2600 SUS @ 210 ° F.) and 500 g of polybutene (800 cSt at 100 ° C.), followed by pen resin. 345 g (Penn Resin) and 86 g polybutene are added to obtain the desired oil viscosity (about 1000 cSt at 40 ° C.). Next, to obtain a smoother grease consistency while maintaining the desired ratio of mineral oil to VI improver, add 500 additional 500 g aliquots (195 g of 1502 oil, 180 g of pen resin and 125 g of polybutene). Containing). The oil addition is carried out slowly to avoid the formation of a separate oil phase. The composition is then passed through a charlotte colloid mill once. The milled product has a 298 millimeter / 10 cone cone penetration as measured by ASTM D217.

A 3000 g aliquot of the product having a 298 millimeter / 10 permeability is returned to the mixing vessel and six additional 500 g aliquots of the 1502 / pen resin / polybutene blend are added. Since the mixing vessel is so small that it is difficult to obtain a base grease with an appropriate consistency, about 1000 g of product is removed from the mixing vessel and another 500 g aliquot of blend is added to the remaining product. The resulting base grease has a consistency of 367 millimeters / 10 as measured by ASTM D217 and has the following composition.

Lithium hydroxide · H ₂ O0.25% by weight

12-hydroxystearic acid1.69 wt%

100SUS @ 100 ℉ Hydrotreated Naphthenic Distillate38.22% by weight

PA resin (2600 SUS @ 210 ℉) 35.31 wt%

Polybutene (800 cSt @ 100 ° C) 24.53 wt%

The lubricating composition used in Examples 2 and 3 (below) is prepared from the base grease as follows. About 400 g of base grease is mixed at 125 ° C. with each of the requisite amounts of the following commercially available polymers. The 60 stroke working penetration of each of these mixtures was then measured by ASTM D217.

TABLE 1

The mixture is then cooled and mixed with trichloroethane to give a final solvent concentration of 25% by weight of the test composition.

Example 2 Influence of Various Polymers on Low Temperature Slump Properties

The slump (ie flow) tendency of each polymer modified composition prepared in Example 1 is determined from the cone yield value. To measure cone yield, a round container of 90 mm in diameter and 60 mm in depth is filled with a sample of each of the above compositions and the surface is smoothed with a spatula if necessary. Each sample was chilled for 4 hours at −40 ° C. so that the penetration furnace was measured with a standard grease penetrometer and a description is provided in ASTM D217. For this measurement a special right-angle cone with a base of 62 millimeters was used. The total weight of the cone and handle was 66.7 g. Permeability measurements were made at −40 ° C. after 10 seconds instead of 5 seconds used in the normal test using standard cones. The measurement is made within 1 minute of removing the sample from the cooling box to avoid excessive warming of the sample. Conical yield yields the penetration at −40 ° C. using the following formula.

Past experience indicates that less than about 80 cone yield values are characteristic of lubricants with good slumpability.

The cone yield of each sample was measured and the results are summarized in Table 2.

TABLE 2

(1) 60 stroke working penetration before adding solvent.

(2) Penetration degree at -40 ° C for the final product.

(3) Average of two samples giving yields of 34 and 43.

(4) Samples could not be prepared because the polymer could not be dispersed in the base grease.

The data in Table 2 shows that samples containing polymer A-F have good slumpability at -40 ° C and 2% by weight concentration. However, samples containing polymer E at a concentration of 6% by weight had poor slumpability and samples containing polymer F could not be prepared.

Example 3 Influence of Various Polymers on High Temperature Adhesion

The adhesiveness of the samples prepared in Example 1 was measured by spreading 10 g of each sample on separate aluminum plates. The plates were then suspended vertically at 65 ° C. for 24 hours in a circulation oven. Subsequently, the weight change of each plate was calculated on the basis of excluding the solvent, and the degree of surface covering was visually measured. The results of this test are shown in Table 3.

TABLE 3

(1) Values from Table 2.

(2) Weight loss is based on products without trichloroethane.

The data in Table 3 show that samples containing 2500 MI EVA (polymers A and B) perform well at concentrations of 2 and 6 wt% with weight loss ranging from 48 to 69%. But most importantly, the remaining composition at the end of the test formed an evenly distributed adhesive coating on the plate without revealing a surface. Samples containing Polymer D (39 MI EVA) also performed well at concentrations of 2% by weight. The samples containing SBS 416 (Polymer E) and LLDPE (Polymer F) both performed poorly, showing some large exposed areas visible to the naked eye at the end of the test. Thus, only lubricating compositions containing polymers A, B and D provided good adhesion at 65 ° C.

The data in Tables 2 and 3 show that samples with good adhesion at high temperatures and good slump at low temperatures contain polymers A, B and D, ie at least about 40 g / min (most preferably about 40 to about 2500 g / 10 minutes) and a ethylene-vinyl acetate copolymer containing about 10 to 40% by weight of vinyl acetate (preferably about 10 to about 30% by weight).

Claims (15)

A copolymer of ethylene with (a) a lubricant, (b) thickener, (c) VI improver and (d) at least one compound selected from the group of (d) vinyl acetate, alkyl acrylate or alkyl methacrylate, wherein The copolymer has a melt index of at least about 40 g / 10 minutes and a vinyl acetate, alkylacrylate or alkyl methacrylate content of about 10 to about 40 weight percent). The composition of claim 1, wherein the copolymer has a melt index in the range of about 40 to about 10,000 g / 10 minutes. The composition of claim 2 wherein the copolymer has a melt index in the range of about 40 to about 2500 g / 10 minutes. The composition of claim 1 wherein the thickener is based on clay, pyrrolidone, aluminum soap, barium soap, calcium soap, lithium soap, sodium soap or a combination of these soaps. (a) at least about 50 to about 90 weight percent of lubricating oil, (b) about 1 to about 15 weight percent thickener based on aluminum soap, barium soap, calcium soap, lithium soap, sodium soap or a combination thereof, ( c) about 5 to about 40 weight percent of a VI improver that is a polymer of isobutylene or a copolymer of ethylene, propylene, butene or isobutylene with C ₃ to C ₃₀ olefins and (d) vinyl acetate, alkyl acrylate or alkyl meta A copolymer of ethylene with at least one compound selected from the crowd of acrylates, wherein the copolymer has a melt index of at least about 40 g / 10 minutes and about 10 to about 40 weight percent vinyl acetate, alkyl acrylate or alkyl methacrylate And from about 1 to about 20 weight percent. 6. The composition of claim 5, wherein the copolymer of (d) has a melt index in the range of about 40 to about 10,000 g / 10 minutes. The composition of claim 6, wherein the copolymer of (d) has a melt index in the range of about 40 to about 2500 g / 10 minutes. 6. The composition of claim 5, wherein the thickener is based on aluminum soap, calcium soap, lithium soap, composites thereof or mixtures thereof. The composition of claim 8, wherein the thickener is based on calcium soap, lithium soap, composites thereof, or mixtures thereof. 10. The composition of claim 9, wherein the thickener is a lithium soap or lithium composite soap based on hydroxy fatty acids having 12 to 24 carbon atoms. The composition of claim 10, wherein the hydroxy fatty acid comprises hydroxy stearic acid. The composition of claim 11, wherein the hydroxy stearic acid comprises 12-hydroxy stearic acid. 6. The composition of claim 5, wherein the copolymer of (d) comprises ethylene-vinyl acetate. The composition of claim 13, wherein the vinyl acetate content is about 10 to about 30 weight percent. in a lubricating composition comprising (a) at least about 50 to about 90 weight percent of lubricating oil, (b) about 1 to about 15 weight percent of a thickener, and (c) about 5 to about 40 weight percent of a VI improver. Copolymer of ethylene with one or more compounds selected from the group of acrylates or alkyl methacrylates, wherein the copolymer has a melt index of at least about 40 g / 10 minutes and about 10 to about 40 weight percent vinyl acetate, alkyl acrylate Or an alkyl methacrylate content) to increase the slumpability of the lubricating composition at a temperature of about -20 ° C. or less and to the lubricating composition at a temperature of about + 20 ° C. or more, including adding about 1 to about 20 weight percent. How to increase the adhesion of.