CA1295319C - Lubricant oil composition with improved friction reducing properties - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A lubricating oil composition having improved friction reducing properties and the method of reducing friction in internal combustion engines by lubricating said engines with said lubricating oil which contains an effective friction reducing amount of an additive which is the reaction product of dimer carboxylic acid and a polyhydric alcohol having at least 2 hydroxyl groups in combination with an oil soluble alkanol or an oil soluble alkyl phosphate.

Description

l~g~3~9 DETAILED DESCRIPTION OF THE INVENTION

This invention is directed to a lubricating oil composition containing an oxygenated (hydroxy) ester of a dimer acid in combination with an oil soluble alkanol or alkyl phosphate to provide improved friction reducing properties and to a method of reduc-ing friction in an internal combustion engine by using a lubricating oil composition which contains said addi-tives.

In one aspect the present invention provides a lubricating oil composition having improved friction reducing properties comprising:

(a) a major amount of a lubricating base o i 1 ;

(b) from 0.1 to 2.0 parts by weight of the reaction product of a dimer carboxylic acid having a total of 24 to 90 carbon atoms with 9 to 42 carbon atoms between carboxylic acid groups and a polyhydric alcohol having at least 3 to 18 carbon atoms per 100 parts by weight of said lubricating oil composition, said r.eaction product being formed using from 1 to 3 moles of alcohol per mole of dimer acid; and (c) from 1 to 10 parts by weight of an oil soluble compound per part of the reaction product of (b) wherein,said oil soluble compound is selected from the group consisting of alkanols and alkyl phosphates.
~b - la ~ 1 2~ ~ 31~

In another aspect the invention provides a method of reducing friction in an internal combustion engine comprising lubricating said engine using a lubricating oil composition containing an effective friction reducing amount of an additive which is the reaction product of a dimer carboxylic acid having 24 to 90 carbon atoms and a polyhydric alcohol having at least 2 hydroxyl groups and 3 to 18 carbon atoms, in combination with an oil soluble compound selected from the group consisting of alkanols and alkyl phosphates.

The friction reducing additive which is used in this invention is an oil soluble oxygenated (hydroxy) ester of a dimer acid (HEDA hydroxy ester of dimer acid) in combination with an oil soluble alkanol or alkyl phosphate, wherein the oxygenated (hydroxy) ester is preferably characterized by the formula:

(cH2)scH3 C ~ . C

HG ~ (CH2)5CH3 \ / / H
C C

RO- -(CH2)7 CH=CH¦CH2)7-C-OR
where R is selected ~rom the group consisting of -CH2-CH2~CH2cH2]noH;

with n being equal to 1 to 5 (hereafter designated as H~DA);

-CH2-CH2-N(CH2cH20H)2 ,. ~

3~9 (hereinafter designated as LA214);

and OH
(hereinafter designated as LA200).

The use of an oxygenated (hydroxy) ester of the dimer acid as a friction-reducing agent for oils in a gasoline engine can be limited by poor solubility in the lubricating oil and adverse interactions with other lubricating oil components, wherein some of these interactions show up as sediment formation. The present invention teaches that the solubilization and stabilization of the dimer acid esters in the lubricat-ing oils is improved by the addition of an oil-soluble alkanol or alkyl phosphate.

The oxygenated (hydroxy) esters of the dimer acid are classified as reaction products of a dimer carboxylic acid and a polyhydric alcohol. Such a reac-tion product may be a partial, di- or polyester, with typical formulae represented as follows when using a trihydric alcohol:
(1) HO - R ~ OOCRn ~ COOH
~2) HO ~R - OOCR" - COO- - R' - OH
¦OH OH
L n wherein R" is the hydrocarbon radical of the dimer acid; each R and R' may be the same or different hydro-carbon radicals associated with a trihydric alcohol;
and n is an integer which typically is 1 to 5 or ~29~;319 higher. It will, of course, be appreciated that the ester reaction products can be obtained by reacting a dimer carboxylic acid or a mixture of such acids with a trihydric alcohol or other polyhydric alcohol or mixtures of such alcohols.

The alcohol used in preparing the friction reducing reaction product additive of this invention is a polyhydric alcohol having at least 2 hydroxyl groups and from 3 to 18 carbon atoms. Generally, such com-pounds will be aliphatic and may contain branched or unbranched hydrocarbon groups, as well as other func-tional groups, such as nitrogen, sulfur and phosphorus.
Such polyhydric alcohols will contain at least 2 hydro-xyl groups and may contain more, generally from 3 to 6 hydroxyl groups, with the upper amount limited by the degree of solubility and effectiveness of the reaction product in the lubricating oil composition. Prefer-ably, such polyhydric alcohol will contain 2 to 4 hydroxyl groups and 3 to 12 carbon atoms. More pre-ferably, such polyhydric alcohol will be saturated, contain 3 hydroxyl groups and 3 to 8 carbon atoms.
Compounds of this type include diethylene glycol, glycerol ~i.e., l, 2, 3 propane ~riol), 1, 2, 6-trihydroxyhexane and 2, 2', 2" nitrilotriethanol.

~ he carboxylic acid used in preparing the oxygenated (hydroxy) esters of the dimer acid riction reducing reaction product of this invention will be a dimer of an aliphatic saturated or unsaturated car-boxylic acid, said dimer acid having a total of 24 to 90 carbon atoms, and from 9 to 42 carbon between the carboxylic acid groups. Preferably, the dimer acid will have a total of 24 to 60 carbon atoms and 12 to 42 carbon atoms between the carboxylic acid groups, and 2~

more preferably a total of 24 to 44 carbon atoms and 16 to 22 carbon atoms between the carboxylic acid groups.

The molar quantities of the dimer acid and polyhydric alcohol reactants may be adjusted so as to secure either a complete ester or partial ester and generally from 1 to 3 or more moles of polyhydric alcohol will be used per mole of dimer acid and pre-ferably from 2 to 3 moles of alcohol per mole of acid.

While any of the dimer acids and polyhydric alcohols described above may be used in preparing the friction reducing additive of this invention, the most preferred esters, as set forth above, are those wherein the carboxyl groups are separated from the closest carboxyl group by from 2 to 12 carbon atoms. Parti-cularly useful ester additives are obtained when the acid used is a dimer of a fatty acid, preferably those fatty acids containing 12 to 22 carbon atoms. Such dimers are, of course, clearly taught in U. S. Patent No. 3,180,832, which was granted on April 27, 1965, and U. S. Patent No. 3,429,817, which was granted on February 25, 1969, and as here indlcated the hydro-carbon portion of the dimer carboxylic acid thus obtained may contain a 6 member ring. The formation of the dimer frorn linolelc acid, oleic acid and mixtures of these acids is illustrated by the following reac-tions: A
/ \
A. CH3(cH2)4cH=cHcH2cH~cH(cH2)7 9, 12 Linoleic Acid 2 molecules CH3(CH2)sCH=CHCH=CH(CH2)7COOH 9-11 acid t 9, 11 Linoleic Acid Diels-Alder HOOC(CH2)7CH=CH '7 \ tCH2)5CH3 HOOC(CH2)7 ~ CH2 )5CH3 lZg~3~g Linoleic Acid Dimer (dilinoleic acid) 2 molecules B. CH3(CH2)7cH=cH(cH2)7cOoH ~ Ci~ 7 Diels Alder Oleic Acid CH3(CH2)7CH=C (CH2)7COOH
CH3(CH2)7CH2CH(CH2) 7COOH
Oleic Acid Dimer (Dioleic Acid) Diels Alder C. 9,11 Linoleic Acid + Oleic Acid CH3(CH2)6CHCH=CH(CH2)7COOH
CH3(c~2)4cHcH=cHcH=cH(cH2)7cooH
Mixed Dimer It will, of course, be appreciated that while the reac-tions illustrated produce the dimers, commercial appli-cation of the reactions will generally also lead to trimer formation and, in some cases, the product thus obtained will contain minor amounts of unreacted monomer or monomers. As a result, commercially avail-able dimer acids may contain as much as 25~ trimer and the use of such mixtures is within the scope of the present invention. It is also noted that prepared dimer acids may be saturated or unsaturated. While in some instances the unsaturated dimer acids are preferred, it is also contemplated that if desired dimer acids formed having one or more saturated bonds may have such unsaturation removed, e.g., by hydrogena-tion.

The ester friction reducing additive of this invention will generally be used at a concentratoin level of from 0.1 to 2.0 parts by weight per 100 parts of lubricating oil composition, more preferably from 0.1 to 1.0, and most preferably from 0.2 to 1.0 parts.

`` ~2~;3:~9 The oil soluble alkanols which are added to the lubricating base oil and the oxygenated (hydroxy) ester of the dimer acid are:

R
wherein R = 2-16 carbon atoms and is straight chained or branched and R is H or a straight or branched hydrocarbon chain containing 1 to 5 carbon atoms.

The oil-soluble alkanol will generally be used at a concentration of from 1 to 10 parts by weight per part of the ester friction reducing additive, more preferably 1 to 5, and most preferably about 2 to about 4.

The lubricating base oil will generally comprise a major amount of the lubricating composition, i.e., at least 50% by weight thereof, and will include liquid hydrocarbons, such as the mineral lubricating oils and the synthetic lubricating oils, and mixtures thereof. The synthetic oils which can be used include diester oils, such as di(2-ethylhexyl) sebacate, azelate and adipate; complex ester oils, such as those formed from dicarboxylic acids, glycols and either monobasic acids or monohydric alcoholsi silicone oils;
sulfide esters; organic carbonates; and other synthetic oils known in the art.

Other additives, known in the art, may be added to the oil composition of the present invention to form a finished oil. Such additives include disper-sants, antiwear agents, antioxidants, corrosion inhi-bitors, detergents, pour point depressants, extreme pressure additives, viscosity index improvers, etc.
These additives are typically disclosed, for example, - ~2~319 in Lubricant Additives by C. V. Smalheer and R. Kennedy Smith, 1967, pages 1-11, and in U. S. Patent ~o. 4,105,571.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following Examples are further illustra-tive of this invention and are not to be construed as limitations thereof.

Example 1 Oils A and B are fully formulated SF quality SAE lOW-30 passenger car engine oils. Each oil is formulated with standard additives used in the industry to meet the requirements of current gasoline engines.
Oils A and B contain the same viscosity index improvers, dispersants, detergents, antioxidants, pour depressants and antifoamant additives. Oil A contains a zinc dialkyl dithiophosphate antiwear additive made with primary alcohols, while oil B contains a zinc dialkyl dithiophosphate antiwear additive made with secondary alcohols. This is the only difference between oils A and B.

Oil A and oil B, each formulated with 0.5 weight percent HEDA solubilized with CgOH at a 3/1 alcohol/HEDA weight ratio were tested for relative friction using a ball on cylinder test, described in the Journal of_the American Society of Lubricating Engineers, entitled ASLE Transactions, Volume 4, pages 1-11, 1961. In essence, the apparatus consists basi-cally of a fixed metal ball loaded against a rotating cylinder. The weight on the ball and the rotation of the cylinder can be varied during any given test or from test to test. Also, the time of any given test can ` ~z~3~g be varied. Generally, however, steel on steel is used at a constant load, constant rpm, and a fixed time and in each of the tests of these examples a 4 Kg load, 0.26 rpm and 70 minutes was used.

Ball-on-Cylinder (BOC) Test Test Conditions Load on Ball, kg = 4 Cylinder Speed, rpm = .26 Oil Sump Temp., C = 104 Test Duration, Minutes = 70 BOC Coefficient of Friction (COF) at 70 Minutes (0 = Best) After 3 Hours Oil Fresh Oil LST*
_ Reference 0.260 0.280 Oil A
+ HEDA/OXOCgOH = 1/3) 0.050 0.065 Reference 0.250 --Oil B
+ HEDA/OXOCgOH = 1/3) 0.055 0.070 Reference 0.220 --Oil A 0-090 ~~
Oil B 0.125 0.105 *See U. S. Patent No. 4,479,883, column 6, lines 5S-60.

As summarized above, oil A and oil B, each with 0.5 weight percent HEDA and 1.5 weight percent CgOH, gave lower BOC friction than the base case oils without HEDA/Cg alcohol (oil A or oil B). As indicated in U. S. Patent No. 4,479,883, the BOC data on the 31g oxidized oil from the 3 hour Lube Stability Test (LST) is a better predictor of fuel economy differences during ield service than fresh oil data.

Example 2 Table I lists the surfactants and alcohols tested as solubiiizers for dimer acid esters. The designation CO for the solubilizer refers to a series of ethoxylated nonyl phenols produced by GAF Corp.
under the trademark name IgepalR. The prefix OXO
refers to oil soluble alcohols manufactured by the OXO
process. The designation DM refers to the Igepal DMR
series of ethoxylated dinonyl phenols manufactured by the GAF Corp. SpansR are products of ICI Americas, Inc.; TetronicsR are products of BASF Wyandott Corp.;
TritonsR are products of Rohm and Haas, Inc.; AerosolR
are products of American Cyanamid; and EmphosR desig-nates a series of alkyl phosphates manufactured by Witco Chemical Corp. Of all the materials tested, only the alkanols and alkyl phosphates formed clear solutions, with HEDA in oil A at the ratios of solu-bilizer/ester indicated in the second column of Table I.

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Example 3 A series of alkanols, including C6, C8 and C13, were used as solubilization agents with HEDA in lubricating oils A and a. Shown in Table II is the appearance of the oils using 0.5 weight percent HEDA
solubilized by the alkanols. As illustrated, solubili-zation of HEDA in oil B requires more alkanol than required by oil A to obtain a bright and clear oil. To test the stability of these systems, oil A, containing 0.5 weight percent of HEDA, solubilized with 3 parts of CgOH per part of HEDA was stored two months at 22C
with no apparent change. In addition, this oil was temperature cycled for one-half hour at 100C, one and one-half hours at -14C, one-half hour at -40C and one hour at 100C with no apparent change in clarity. Also indicated is the criticality of the chain length in the alkanol. C13OH is less effective in solubilizing HEDA
in both oil A and oil B relative to CgOH and C6OH.

TABLE II

Solubilization of 0.5 Wt.%
HEDA bY Oxo-Alcohols Appearance( Alcohol Ester Oil Oil Alcohol a. P. oC Ratio A B

(1) l-Bright and Clear; 2-Clear

Claims (10)

1. A lubricating oil composition having improved friction reducing properties comprising:

(a) a major amount of a lubricating base oil;

(b) from 0.1 to 2.0 parts by weight of the reaction product of a dimer carboxylic acid having a total of 24 to 90 carbon atoms with 9 to 42 carbon atoms between carboxylic acid groups and a polyhydric alcohol having at least 3 to 18 carbon atoms per 100 parts by weight of said lubricating oil composition, said reaction product being formed using from 1 to 3 moles of alcohol per mole of dimer acid; and (c) from 1 to 10 parts by weight of an oil soluble compound per part of the reaction product of (b) wherein said oil soluble compound is selected from the group consisting of alkanols and alkyl phosphates.

2. The composition of claim 1 wherein said dimer carboxylic acid has 24 to 60 carbon atoms and said polyhydric alcohol has 3 to 12 carbon atoms.

3. The composition of claim 2 wherein said polyhydric alcohol has 2 or more hydroxyl groups.

4. The composition of claim 2 wherein from 0.1 to 1.0 parts by weight of said reaction product is used.

5. The composition of claim 4 wherein said alcohol is selected from the group consisting of di-ethylene glycol, glycerol, 1, 2, 6 trihydroxyhexane and 2, 2', 2" nitrilotriethanol.

6. The composition of claim 4 wherein said carboxylic acid is a fatty acid which contains 12 to 22 carbon atoms.

7. The composition of claim 6 wherein from 0.1 to 1.0 parts by weight of said reaction product is used and said alcohol is selected from the group con-sisting of diethylene glycol, glycerol, 1, 2, 6 trihydroxy-exane and 2, 2', 2" nitrilotriethanol.

8. The composition of claim 1 wherein said alkanol is characterized by the formula:

where R = 2-16 carbon atoms and can be linear or branched and R is H or a straight or branched hydro-carbon chain containing 1 to 5 carbon atoms.

9. The composition of claim 1 wherein said alkyl phosphate is characterized by the formula:

where R1 is an alkyl or alkyl aryl group of 6-18 carbons on the alkyl chain and R2 is the same as R1 or H.

10. A method of reducing friction in an internal combustion engine comprising lubricating said engine using a lubricating oil composition containing an effective friction reducing amount of an additive which is the reaction product of a dimer carboxylic acid having 24 to 90 carbon atoms and a polyhydric alcohol having at least 2 hydroxyl groups and 3 to 18 carbon atoms, in combination with an oil soluble com-pound selected from the group consisting of alkanols and alkyl phosphates.