EP0430528A1

EP0430528A1 - Lube oil additive package containing viscosity index improver

Info

Publication number: EP0430528A1
Application number: EP90312577A
Authority: EP
Inventors: Kenneth Oliver Henderson
Original assignee: Afton Chemical Corp
Current assignee: Afton Chemical Corp
Priority date: 1989-11-29
Filing date: 1990-11-19
Publication date: 1991-06-05
Also published as: CA2029842A1; AU6683390A; JPH03212496A

Abstract

A storage stable, non-gelling liquid crankcase lubricant additive concentrate includes an ashless dispersant, a viscosity index improver and diluent oil.

Description

The present invention relates to concentrates for formulating lubricating compositions and, more particularly, relates to concentrates which include a viscosity index improver.
Lubricant additive concentrates, such as those which are blended with mineral or synthetic base oils to form motor oils, normally contain various additives including dispersants, detergents, corrosion and oxidation inhibitors, and wear reducing agents along with some process oil. Viscosity index improvers are also added to the motor oils to reduce viscosity changes which would normally accompany temperature changes, i.e., the oil resists thickening at low temperatures and resists thinning out at high temperatures. Certain viscosity index improvers also function as dispersants, for example, those described in U.S. Patent 4,519,929.
In practice, viscosity index improvers, including those which also function as dispersants, cause irreversible gelling of the concentrate when added thereto. For this reason, viscosity index improvers are generally packaged separately and added to the base oil separately from the lubricant additive concentrates.
It has now been discovered that viscosity index improvers can be included with other lubricant additives in a lubricant additive concentrate without causing gelling. In particular, viscosity index improvers can be added to a concentrate which includes an ashless dispersant, diluent oil and, optionally, other additives, in amounts to effect a ratio of diluent oil to active ingredients of at least about 0.6: 1, preferably to effect a ratio ranging from 0.7: 1 to 3.3: 1. Accordingly, this invention provides a storage stable crankcase lubricant additive concentrate which comprises an ashless dispersant and diluent oil along with an effective amount of a viscosity index improver.
The present invention resides in the discovery that within a certain ratio of diluent oil to active additive ingredients, viscosity index improvers can be included in a concentrate containing diluent oil, ashless dispersant and, optionally, other additives such as detergents, antioxidants, antiwear compositions, anticorrosion compositions and the like. The resulting concentrate is a storage stable liquid that does not gel or show significant amounts of precipitation on standing. It is added to mineral or synthetic base oils to provide an effective crankcase lubricating composition.
The term viscosity index improver as used herein denotes elastomeric polymer compositions which impart improved fluidity characteristics to the oil so that the tendency of the oil to change viscosity in response to a change in temperature is reduced. Viscosity index improvers, or viscosity modifiers, impart high and low temperature operability to the lubricating oil and permit it to remain relatively viscous at elevated temperatures and relatively fluid at low temperatures. Viscosity modifiers are generally high molecular weight hydrocarbon polymers and polyesters. The viscosity modifiers may also be derivatized to include other properties or functions, such as the addition of dispersancy properties. These oil soluble viscosity modifying polymers will generally have number average molecular weights of from 10³ to 10⁷, preferably 10⁴ to 10⁶, e.g., 20,000 to 250,000, as determined by gel permeation chromatography or osmometry.
Examples of hydrocarbon polymers suitable for preparing viscosity index improvers include homopolymers and copolymers of two or more monomers of C₂ to C₃₀, e.g. C₂ to C₈ olefins, including both alpha olefins and internal olefins, which may be straight or branched, aliphatic, aromatic, alkyl-aromatic, or cycloaliphatic. Frequently they will be of ethylene with C₃ to C₃₀ olefins. Particularly preferred are the copolymers of ethylene and propylene. Other polymers can be used such as polyisobutylenes, homopolymers and copolymers of C₆ and higher alpha olefins, atactic polypropylene, hydrogenated polymers and copolymers and terpolymers of styrene, e.g., with isoprene and/or butadiene and hydrogenated derivatives thereof. The polymer may be degraded in molecular weight, for example by mastication, extrusion, oxidation or thermal degradation, or it may be oxidized and as such contain oxygen. Also included are derivatized polymers such as post-grafted interpolymers of ethylenepropylene with an active monomer such as maleic anhydride which may be further reacted with an alcohol, or an amine, e.g., an alkylene polyamine or an alkylene hydroxy amine, e.g. see U.S. Pat. No.s 4,089,794; 4,160,739; 4,137,185. Other derivatized polymers useful in the compositions of the present invention include copolymers of ethylene and propylene reacted or grafted with nitrogen compounds, e.g., see U.S. Pat. Nos. 4,068,056; 4,068,058; 4,146,489 and 4,149,984.
The preferred hydrocarbon polymers are ethylene copolymers containing from 15 to 90 wt. % ethylene copolymerized with 10 to 85 wt. % of at least one C₃ to C₂₈ alpha-olefin. Most preferably, the hydrocarbon copolymers are 30 to 80 wt. % ethylene copolymerized with 20 to 70 wt. % of a C₃ to C₁₈ alpha-olefin. Particularly preferred hydrocarbon polymers are those of ethylene and the C₃ to C₈ alpha-olefins. Of the particularly preferred hydrocarbon polymers, those of ethylene and propylene are most preferred. While not essential, such copolymers preferably have a degree of cystallinity of less than 25 Wt. %, as determined by X-ray and differential scanning calorimetry.
Other alpha-olefins suitable for use in place of propylene to form the above copolymers, or to be used in combination with ethylene and propylene to form a terpolymer, tetrapolymer, and so forth, include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and the like; also useful are branched chain alpha-olefins, such as 4-methyl-1-pentene, 4-methyl-1-hexene, 5-methylheptene-1, and the like, and mixtures thereof.
Terpolymer, tetrapolymers, and the like, of ethylene, the C₃₋₂₈ alpha-olefin, and a non-conjugated diolefin or mixtures of such diolefins may also be used. The amount of the non-conjugated diolefin generally ranges from 0.5 to 20 mole percent, preferably from 1 to 7 mole percent, most preferably 1.5 to 5.5 mole percent based on the total amount of ethylene and alpha-olefin present.
The polyester viscosity index (V.I.) improvers are generally polymers of esters of ethylenically unsaturated C₃ to C₈ mono- and/or dicarboxylic acids such as methacrylic and acrylic acids, maleic acid, maleic anhydride, fumaric acid, and the like. Examples of unsaturated esters that may be used in this embodiment of the present invention include aliphatic saturated mono alcohols of at least 1 carbon atom up to about 25 carbon atoms and preferably of from 12 to 20 carbon atoms, such as decyl acrylate, lauryl acrylate, stearyl acrylate, eicosanyl acrylate, docosanyl acrylate, decyl methacrylate, diamyl fumarate, lauryl methacrylate, cetyl methacrylate, stearyl methacrylate, and the like and mixtures thereof. Other esters include the vinyl alcohol esters of C₂ to C₂₂ fatty or mono carboxylic acids, preferably the saturated fatty or mono carboxylic acids, such as vinyl acetate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, and the like and mixtures thereof. Copolymers of vinyl alcohol esters with unsaturated acid esters such as the copolymer of vinyl acetate with dialkyl fumarates, can also be used.
The esters may be copolymerized with still other unsaturated monomers such as olefins e.g. 0.2 to 5 moles of C₂-C₂₀ aliphatic or aromatic olefin per mole of unsaturated ester, or per mole of unsaturated acid or anhydride followed by esterification, e.g., copolymers of styrene with maleic anhydride esterified with alcohols and amines. See U.S. Pat. No. 3,702,300. In such copolymerized esters, 0.2 to 5 moles of C₂-C₂₀ aliphatic or aromatic olefin per mole of unsaturated ester is used. Instead of the unsaturated ester, the corresponding unsaturated acid or anhydride may be first treated with the olefin and the resulting copolymer esterified with alcohols or reacted with amines.
The term dispersant viscosity index improver as used herein denotes polymer compositions which not only enhance the viscosity characteristics of the oil but also contain functional groups to impart improved dispersancy to crankcase lubricants used in spark ignition and compression ignition engines so as to assist in dispersing the sludge formed in the lubricant oil during operation of the engines. Thus, the above described hydrocarbon polymers or polyesters may be grafted with, or copolymerized with, polymerizable unsaturated nitrogen-containing monomers to impart dispersant characteristics to the V.I. improvers. Examples of suitable unsaturated nitrogen-containing monomers include those containing 4 to 20 carbon atoms such as amine substituted olefins, e.g., p-(beta-diethyl-aminoethyl)styrene; basic nitrogen-containing heterocycles carrying a polymerizable ethylenically unsaturated substituent, e.g. the vinyl pyridines and the vinyl alkyl pyridines such as 2-vinyl-pyridine, 4-vinyl-pyridine, 3-vinyl-pyridine, 3-methyl-5-vinyl-pyridine, 4-methyl-2-vinyl-pyridine, 4-ethyl-2-vinyl-pyridine and 2-butyl-1-vinyl-pyridine and the like. N-vinyl lactams are also suitable as functionalizing groups to produce dispersant viscosity index improvers, e.g. N-vinyl pyrrolidones or N-vinyl piperidones.
Examples of the dispersant viscosity index improving (DVII) compositions include alkyl methacrylate based copolymers, e.g., methyl methacrylate based copolymers, such as those containing N-vinylpyrrolidone and functionalized high molecular weight olefin polymers, especially ethylene-propylene based copolymers, which are reacted, i.e., are grafted, with vinyl monomers such as maleic anhydride, 2-vinyl pyridine, acrylonitrile, N-vinylpyrrolidone or an N-allyl amide to form graft copolymers. Other examples of DVII compositions include copolymers of olefins and the above described vinyl monomers. Additional examples include high molecular weight olefin polymers (to produce functionalized polyolefin elastomers) and high molecular weight olefin polymers which are oxidized and then reacted with a functionalizing component such as an amine or an amine and formaldehyde combination to thereby form a Mannich condensation product. Several of such dispersant viscosity index improvers and their methods of preparation are described, for example, in U.S. 4,411,804 and 4,519,929.
Ashless dispersants suitable for use in lubricating oils are well known in the art. Examples of such dispersants include polyolefin-substituted succinimides and/or succinimides of polyethylene polyamines such as diethylene triamine and tetraethylenepentamine. Additional examples include polyolefin-substituted succinimides of amido-amines. The polyolefin succinic substituent is preferably a polyisobutene group having a number average molecular weight of from 800 to 5000. Such ashless dispersants are more fully described in U.S. Patents 3,172,892; 3,219,666; 4,234,435; and 4,857,217.
Another useful class of ashless dispersants are the polyolefin succinic esters of mono- and polyhydroxy alcohols containing from 1 to 40 carbon atoms. Such dispersants are described in U.S. Patent 3,381,022 and U.S. Patent 3,522,179. Mixed ester-amides of polyolefin substituted succinic acid made using alkanols, amines and/or aminoalkanols also represent a useful class of ashless dispersants.
The succinic amide, imide and/or ester type ashless dispersants may be post-treated, e.g., boronated by reaction with a boron compound such as boric acid or maleated by reaction with maleic anhydride. In addition, the succinic amide, imide, and/or ester may be hydroxyalkylated by reaction with an alkylene oxide such as ethylene oxide or propylene oxide.
Other useful ashless dispersants include the neutralized reaction products of phosphorus sulfides and polyalkenes as well as elastomeric copolymers functionalized with an N-allyl amide, e.g., EPDM functionalized with diallylformamide. See, for example, U.S. 4,519,929.
Still other useful ashless dispersants are Mannich condensation products of polyolefin-substituted phenols, formaldehyde and polyethylene polyamine. Preferably, the polyolefin phenol is a polyisobutylene-substituted phenol in which the polyisobutylene group has a molecular weight of from 800 to 5000. The preferred polyethylene polyamine is tetraethylene pentamine. Such Mannich ashless dispersants are more fully described in U.S. Patents
3,368,972; 3,413,347; 3,442,808; 3,448,047; 3,539,633;
3,591,598; 3,600,372; 3,634,515; 3,697,574; 3,703,536;
3,704,308; 3,725,480; 3,726,882; 3,736,357; 3,751,365;
3,756,953; 3,792,202; 3,798,165; 3,798,247 and 3,803,039.
Mixtures of any of the above useful ashless dispersants, such as a mixture of a Mannich ashless dispersant with a succinimide dispersant or a mixture of a succinimide and a succinic ester, are also suitable for use in the present invention. Such mixtures may also be post-treated such as by boronation or maleation.
The concentrates of this invention can contain optional additives. See, for example, U.S. Pat. No. 4,857,217. For example, detergent additives are one such optional additive. As used in the compositions of the present invention, such additives include alkali and alkaline earth metal petroleum sulfonates, alkali and alkaline earth metal alkyl or alkaryl sulfonates, alkyl phenates and metal carboxylates. Examples of these are calcium petroleum sulfonates, magnesium petroleum sulfonates, barium alkaryl sulfonates, calcium alkaryl sulfonates, magnesium alkaryl sulfonates and calcium, and magnesium alkylsulfonates. Both neutral and overbased sulfonates or phenates, which have base numbers up to about 600 to provide acid neutralizing properties, can be beneficially used and are commercially available. These detergent additives are generally used in an amount to provide 0.05-1.5 weight percent alkaline earth metal and more preferably 0.1-1.0 weight percent. The lubricating oil compositions of the present invention preferably contain a calcium petroleum sulfonate or an alkaryl (e.g. alkylbenzene) sulfonate as a detergent additive.
Additional optional additives for the compositions of the present invention include ashless antioxidants such as hindered alkyl phenols, alkyl diphenyl amines, and sulfur-bridged alkyl phenols; antiwear/corrosion inhibitors such as dialkyl selenides, metal dithiocarbamates, sulfurized terpenes and zinc dihydrocarbyldithiophosphates (ZDDP); friction reducers and EP additives such as N-alkylglycine-amides, chlorinated paraffins, sulfurized olefins, sulfurized fatty oils, sulfurized hydroxy substituted fatty amides, and co-sulfurized fatty acid amides and esters; antifoam agents such as acrylate copolymers and silicones; and surfactants such as ethoxylated alkyl phenols and poly(alkyleneoxides).
The components of the present invention are combined in a diluent oil such as mineral oil, synthetic oil or mixtures thereof in proportions by weight which are effective in providing a liquid concentrate which is a storage stable liquid composition in that it does not form a gel, or significant amounts of precipitate, on standing for at least 30 days at 70°C. Useful diluent oils for forming the concentrates include neutral mineral oils which can be process oils, which are solvent refined oils, and hydro-treated (hydrogen treated) oils. Examples include process oil #5 and 80 neutral oil.
Normally, the diluent oil is added to the lubricant additive concentrates either during their preparation and/or after preparation for ease of handling purposes, and this oil, in addition to all other oil, is included in calculating the total amount of oil required in providing the stable compositions of the invention. Accordingly, the proportions of all of the active components given herein are on the basis of "active ingredient" i.e. not including added oil.
To provide a concentrate, the ratio of the amount of oil based on the total weight of concentrate to the amount of active ingredients is typically from 0.4: 1 to 0.56: 1 for conventional dispersant-inhibitor (DI) packages without a viscosity index improver.
To provide a concentrate of the present invention which includes a viscosity index improver, the ratios of total oil (the sum of all oil utilized in the concentrate) to total active or additive ingredients (active ingredients not including any oil) are at least about 0.6: 1, preferably at least about 0.7: 1, most preferably from 0.7: 1 to 3.3: 1.
The composition can also comprise one or more of the other additives described above in effective amounts. For example, to the compositions of the present invention can be added up to about 10 weight percent ashless antioxidants (preferably 0.05 to 5 weight percent), up to about 15 weight percent detergent (preferably 5 to 10 weight percent), up to about 10 weight percent antiwear/corrosion inhibitor (preferably 0.05 to 5 weight percent), up to about 10 weight percent friction reducer (preferably 0.05 to 5 weight percent), up to about 2 percent surfactant (preferably 0.1 to 1 percent) and up to about 1 weight percent antifoam (preferably 0.01 to 0.1 weight percent). It is well known in the art that the presence of some of these other additives as well as other factors can cause a change in the above concentration parameters, i.e., the amount of components useful in the compositions of the present invention for dispersant, dispersant viscosity index improver and oil which are necessary to provide a stable concentrate. The type and molecular weight of the viscosity index improver will also shift the parameters. It is well within the ability of one skilled in the art to modify the weight percentages of each of the additives and the diluent oil to achieve a stable concentrate containing a selected dispersant viscosity index improver according to the teachings of the present invention.
The concentrates of the present invention can be formed using conventional blending equipment and techniques. They are blended with base oils in amounts to provide the required additive levels in the finished crankcase lubricating oils, e.g. treat rates of from 10 to 20 percent. Suitable base oils, as known in the art, include both mineral and synthetic oils and blends thereof.
Mineral oils include those of suitable viscosity refined from crude oil from all sources including Gulf coast, mid-continent, Pennsylvania, California, Mideast, North Sea, Alaska, the Far East and the like. Various standard refinery operations are useful in processing the mineral oil.
Synthetic oils include both hydrocarbon synthetic oils and synthetic esters. Useful synthetic hydrocarbon oils include liquid polymers of alpha-olefins having the proper viscosity. Especially useful are the hydrogenated liquid oligomers of C₆-C₁₂ alpha-olefins such as alpha-decene trimer. Likewise, alkyl-benzenes of proper viscosity can be used as a synthetic oil, such as didodecylbenzene.
Useful synthetic esters include the esters of both monocarboxylic acids and polycarboxylic acids as well as monohydroxy alkanols and polyols. Typical examples are didodecyl adipate, trimethylol propane tripelargonate, pentaerythritol tetracaproate, di(2-ethylhexyl)adipate, dilauryl sebacate and the like. Complex esters prepared from mixtures of mono- and dicarboxylic acids and mono- and polyhydroxyl alkanols can also be used.
The invention is further illustrated by, but is not intended to be limited to, the following examples wherein parts and percentages are by weight unless otherwise indicated.

Examples 1-9

These examples illustrate storage stable concentrates having a selected viscosity index improver included therewith according to the teachings of the present invention. The liquid crankcase concentrate formulations identified in Table 1 are prepared by blending all additive ingredients in an amount of diluent oil followed by blending therein an oil solution of a viscosity index improver. The concentrates thus prepared are held at 70°C to determine storage stability (days at 70°C without gel formation). For the purpose of determining gelation for these examples, visual determinations are made. If the concentrate contains a thick, sometimes tacky mass (usually on the top of the fluid) or contains a web-like structure dispersed throughout the fluid (usually appearing as a stringy mass when poured), such concentrates are identified as "gelled".

Example 10

A formulation was prepared according to the procedure of Example 1-9 which included 2.07 wt. percent of a commercial pyrrolidone containing acrylate type dispersant viscosity index improver (DVI improver or DVII) (Acryloid 956 DVII Rohm & Haas) 68.53 wt. percent total oil and 12.03 wt. percent alkenyl (Mn about 1300) succinimide ashless dispersant (ratio of total oil to total active ingredient is 2.2). No gel formed after 57 days at 70°C. A formulation which contained 1.73 wt. % of the Acryloid 956 DVII, 15.09 wt. % succinimide dispersant and 62.98 wt. % diluent oil (ratio of total oil to total active ingredient is 1.7) was also stable for 57 days.

Example 11

A formulation according to Example 10 was prepared except that the DVI improver was replaced by 2.07 wt. percent of an oxidized, functionalized (Schiff's base) olefin polymer type dispersant viscosity index (DVI) improver (Amoco 6906 DVII) and the total oil was adjusted to 68.53 wt. percent. The concentrate was stable after 57 days at 70°C.

Example 12

A formulation according to Example 10 was prepared except that the DVI improver was replaced by 2.07 wt. percent of a succinimide grafted olefin polymer type DVI improver (Paratone 856 DVII, Exxon Corporation) and the total oil was adjusted to 68.53 wt. percent. The concentrate was stable after 57 days at 70°C.

Example 13

A formulation according to Example 10 was prepared except that the DVI improver was replaced by 2.07 wt. percent of a Mannich reaction product type DVI improver (Amoco 6565, Amoco Corporation) and the total oil was adjusted to 68.53 wt. percent. The concentrate was stable after 57 days at 70°C.

Examples 14-21

Table 2 contains examples which illustrate additional additive concentrates of the present invention wherein a viscosity index improver (VII) is added to a concentrate and held at 70°C for at least about 30 days without causing a gel to form in the concentrate. These concentrates were prepared according to the procedures utilized in Examples 1-13 except that the ratio of total oil (the sum of all oil utilized in the concentrate) to total additives (active ingredients not including any oil) was varied. In the table, the letters a-i represent dispersants and VI improvers according to the following scheme:

a. Alkenyl (Mn about 1300) succinimide ashless dispersant
b. Alkenyl (Mn about 900) succinimide ashless dispersant
c. Alkenyl (Mn about 2100) succinimide ashless dispersant
d. EPDM (Ortholeum 2052), 40,000 Mn, grafted with about 5% N,N-diallyl formamide
e. Mixture of (d) and (f)
f. Olefin copolymer type VII which is a non-dispersant type (Ortholeum 2052)
g. Amoco 6565 identified, in Ex. 13
h. Acryloid 702 DVII, from Rohm & Haas, which is an acrylate type non-dispersant VI improver
i. Olefin copolymer type VII (Paratone 715, from Exxon corp.)

Examples 22-25

Summarized in Table 3, these examples illustrate the effect of varying the ratio of total oil to total active ingredients to achieve a concentrate which does not gel. The letters a, d and g represent dispersants and VI improvers according to the scheme set forth for Table 2, the concentrates being prepared as in Example 1.

Claims

A lubricant additive concentrate comprising a diluent oil, an ashless dispersant and a viscosity index improver, said concentrate having a ratio of total oil to total active ingredients which provides a storage stable liquid.
A concentrate according to claim 1 wherein the ashless dispersant comprises a polyolefin substituted succinimide.
A concentrate according to claim 1 or 2 wherein the ashless dispersant comprises a polyisobutenyl substituted succinimide with the polyisobutenyl group having a number average molecular weight of from 800 to 5,000.
A concentrate according to any one of claims 1 to 3 wherein said viscosity index improver is an olefinic hydrocarbon polymer or a polyester.
A concentrate according to any one of claims 1 to 3 wherein the viscosity index improver comprises an alkyl methacrylate based polymer or a succinimide grafted polyolefin.
A concentrate according to any one of claims 1 to 3 wherein said viscosity index improver is a dispersant viscosity index improver comprising an olefinic hydrocarbon polymer functionalized with N-vinylpyrrolidone, 2-vinyl pyridine, acrylonitrile, and/or an N-allyl amide.
A concentrate according to any one of claims 1 to 3 wherein the viscosity index improver is a dispersant viscosity index improver and comprises a functionalized polyolefin elastomer.
A concentrate according to any one of the preceding claims wherein said ratio is at least 0.6: 1
A concentrate according to claim 8 wherein said ratio is between 0.7: 1 and 3.3: 1.
A method of preparing a storage stable liquid lubricant additive concentrate as claimed in any one of the preceding claims for crankcase lubricants said method comprising blending the dispersant and the additional lubricant additives into a diluent oil and blending therewith an oil solution of the viscosity index improver.