NO841283L - LUBRICANT FOR USE IN CONNECTION WITH ALCOHOL FUELS - Google Patents

Description

The present invention relates to an additive formulation for use with common self-propagating lubricants ■ to provide a lubricant suitable for internal combustion engines that burn alcohol fuels such as methanol or ethanol.

Commonly used self-moving lubricants are not effective in alcohol combustion machines, which is shown by severe machine wear and increasing lubricant consumption. One reason for this is the large difference in chemical reactivity for the combustion products from. gasoline and alcohol self-propelled fuel systems. In an alcohol fuel system, several lubricant degradation reactions occur that are not found in the gasoline fuel system. These chemical reactions cause

increased corrosion of alcohol fuels. E.g. methanol is easily oxidized by the formation of formaldehyde and formic acid. This reaction is shown in reaction scheme 1.

Most vehicles using methanol fuel suffer from severe upper cylinder corrosion and wear due to formic acid formed during methanol combustion. Formic acid reacts with common self-propagating lubricants' organic amine additives, which act as antioxidants, corrosion inhibitors; and anti-wear agents. The amine additives neutralize the formic acid. however, common additives seem out

capable of properly neutralizing the amount of ant-

acid formed during methanol combustion. These reactions are indicated in reaction schemes 2 and 3.

Formaldehyde. is highly reactive with phenolic and glycolic additives. Formaldehyde reacts with the phenols used as antioxidants and with the polymer-containing hydroxyl groups used as ashless dispersants. These reactions take place under acidic conditions and are increased as the organic amine additives are removed by reaction with formic acid. These formaldehyde reactions, which are indicated in reaction scheme (4), contribute significantly to oil breakdown in a. methanol fuel system.

There is a need for a lubricant additive that minimizes the oxidation of methanol to formaldehyde and formic acid and minimizes strong formaldehyde and formic acid reactions in order to extend the lifetime of the lubricant additives, as these otherwise quickly disappear when reacted with formaldehyde and formic acid.

Similarly, there is a need for a lubricant additive that minimizes the oxidation of ethanol to acetaldehyde

and acetic acid and minimizes strong reactions with these components.

Another significant problem in an alcohol fuel system is

that zinc dialkyldithiophosphate, an essential multifunctional additive in most common lubricants, is easily transesterified and thereby loses many of its anti-wear properties. The transesterification reaction involves the exchange of an alcohol alkyl group, so

such as methanol or ethanol, with an existing ester, such as zinc dialkyldithiophosphate, to form a new ester. A transesterification reaction is shown in reaction scheme 5.

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The transesterification reaction is acid-catalysed and therefore occurs after the amine base additives in the lubricant have disappeared by reaction of formaldehydes and acids formed during the combustion process. Transesterification is not a primary mechanism for oil degradation in hydrocarbon fuel systems, but is a primary mechanism for oil degradation in methanol and other alcohol fuel systems. When e.g. methanol and ethanol are mixed with petrol, the degree of the transesterification reaction is proportional to the amount of alcohol in the mixture.

Another reason for increased corrosion in an alcohol combustion machine is the increased solubility of carbon dioxide in the alcohol. E.g. Carbon dioxide is much more soluble in methanol than in water. Both water and methanol are normally present in the colder parts of the crankshaft housing as the combustion product. Water reacts with the fuel combustion products

such as SO3, NO2 and CO2, forming the corresponding acids, sulfuric acid, nitric acid and carbonic acid as shown in reaction equations 6, 7 and 8.

These acids which react with metals in the machine are one of the main reasons. to corrosion in an internal combustion engine. The lubricants normally used in a hydrocarbon fuel system effectively neutralize these acids with basic additives such as organic amines and alkali metal compounds. However, the amount of carbon dioxide is significant in I

higher in a methanol or other alcohol fuel system than in a petrol fuel system due to the increased solubility of C02 in alcohols. The same can apply to nitric acid formed from the N0.2 combustion product. Absorption of carbon dioxide turns out to be an important reason for the unexpectedly high corrosion of alcoholic fuels.

Lubricant analysis. indicate that corrosion inhibitors composed of sulphonates, naphthenates or other alkali metals too quickly disappear by reaction with carbonic acid and lead to the precipitation of insoluble carbonates of the alkali metals. The precipitation reaction is shown in reaction equations 9 and 10.

This precipitation reaction competes with the neutralization of carbonic acid by organic amines. Although neutralization is faster and more likely to occur, the reaction with alkali metal salts increases as the organic amines disappear. Thus, there is a need for a lubricant additive where the disappearance of the organic amine additives due to the neutralization of formic acid and acetic acid and carbonic acid occurs less quickly and thereby reduces the probability that alkali metal salts will disappear during precipitation reactions as shown in reaction schemes 9 and 10.

It is a general object of the present invention to provide a lubricant additive for use in an alcohol-burning internal combustion engine which provides protection against corrosion and machine wear effects caused by alcohol.

Another object of the present invention is to provide a lubricant additive with increased capacity to neutralize acids.

It is a further object of the present invention

to provide a lubricant additive comprising an anti-wear agent which is not degraded by methanol or ethanol.

The present invention provides a lubricant additive which can be added to conventional self-propellant lubricants and provide a lubricant suitable for use in a methanol or ethanol combustion engine comprising a major amount of polyalkylene glycol of an alkene having 2 to 3 carbons and minor amounts of an aromatic primary amine, an aromatic secondary amine and a phosphoric acid ester. Preferred amounts of compounds in lubricant additives according to the present invention are approx. 93-98.5% by weight polyalkylene glycol, approx. 0.5-2.0% by weight of an aromatic primary amine, approx. 0.5-2.0% by weight of an aromatic secondary amine and approx. 0.5-2.0% by weight of a phosphoric acid ester.

The lubricant additive in the present invention comprises.. a polyalkylene glycol of an alkene with 1 to 2 carbons such as polypropylene glycol, polyisopropylene glycol or polyethylene glycol, and an aromatic primary amine such as ortho-, meta-, or paraphenylenediamine ortho-, meta-, or para-toluidine, '.aniline, naphthylamine>benzylamine, toluenediamine . or naphthalenediamine and an aromatic secondary amine such as N-phenyl-2-naphthylamine, phenyl-α-naphthylamine, phenyl-P - , naphthylamine, tolylnaphthylamine, diphenylamine, ditolylamine, phenyl-tolylamine, 4<1>4 -diaminodiphenylamine or N-methylaniline and a phosphoric acid ester such as ortho-, meta-, or para-tri-cresyl phosphate, dibutylphenyl phosphate, tributyl phosphate,' tri-2-ethylhexyl phosphate, trioctyl phosphate, diphenyl ortho phosphonate, dicresyl ortho phosphonate, trilauryl ortho phosphonate, tristea- ryl ortho phosphonate.

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A preferred polyalkylene glycol is polypropylene glycol

and a preferred polypropylene glycol is polypropylene glycol 2000. A preferred aromatic primary amine is ortho phenylenediamine! a preferred aromatic secondary amine is N-phenyl-2-naphthylamine, and a preferred phosphoric acid ester is ortho tricrecyl phosphate.

Preferably, the lubricant additive according to the present invention contains approx. 93 to 98.5% by weight of a polyalkylene glycol of an alkene with 1 to 2 carbon atoms, approx. 0.5 to 2.0% by weight of an aromatic primary amine, approx. 0.5 to 2.0% by weight of an aromatic secondary amine and approx. 0.5 to 2.0% by weight of a phosphoric acid ester.

A preferred mixture according to the present invention contains approx. 93 to 98.5% by weight polypropylene glycol 2000, approx. 0.5 to 2.0 wt% orthophenylene diamine, approx. 0.5 to 2.0% by weight N-phenyl-2-naphthylamine and approx. 0.5 to 2.0% by weight ortho tricrecyl phosphate.

All of the above compounds are available for purchase. The lubricant part additive according to the present invention is made by mixing together all the above-mentioned compounds. The lubricant additive according to the present invention is used by adding approx. 1/2 liter of the lubricant additive for a 4.7 liter oil change. The lubricant additive according to the present invention will provide effective protection against corrosion of machine wear caused by methanol or ethanol at oil change intervals of more than 4000 miles and in some cases up to 6000 miles.

Polyalkylene glycol, preferably polypropylene glycol,

acts as a methanol or ethanol solubilizer, a no-ash dispersant and an alder hide remover. A solubilizer of this type is required to dissolve the large amounts of methanol and ethanol that are introduced into the lubricant I|before combustion. The pylyalkylene glycol is solubilized. ! in

methanol or ethanol to thereby prevent dry spots

on the upper cylinder and inner surface. Without glycol, methanol and ethanol are insoluble in hydrocarbon lubricants and dry spots may occur. In addition, a polyallylene glycol contains hydroxyl groups that react with the aldehydes formed by oxidation of methanol or ethanol. The reaction product of a polyalkylene glycol and formaldehyde or acetaldehyde is also a good solvent for methanol or ethanol and continues to act as a methanol or ethanol solubilizer.

The aromatic primary amine, preferably ortho-phenylenediamine, acts primarily as a base number additive to neutralize formic acids, acetic acid and carbonic acids formed by oxidation of methanol or ethanol, and by reaction of water and carbon dioxide respectively.

The aromatic secondary amine, preferably N-phenyl-2 naphthylamine, also serves to neutralize formic or acetic acid and carbonic acids, but its primary function

is like an antioxidant. It minimizes the oxidation of methanol or ethanol to their respective aldehydes and acids.

The presence of larger amounts (about 0.5 to 2.0% by weight) of organic amines in the present invention compared to the amount normally contained in common lubricant additives (about 0.25% by weight) minimizes the disappearance of alkali metal salts such as naphthenates and sulfonates. The alkali metals disappear when they react with carbonic acid to form insoluble carbonates that compete with the neutralization of carbonic acid. The neutralization reaction is faster and occurs more easily,

but the precipitation reaction becomes a problem when the organic amines have disappeared. With more organic amines

present, more carbonic acid is neutralized and there is less carbonic acid available to react with the alkali metals.j

The phosphoric acid ester, preferably ortho tricrecyl phosphate, acts as an anti-wear agent and when used with methanol or ethanol fuel it is better than

the usual anti-wear agent, zinc dialkyldithiophosphate. Zinc dialkyldithiophosphate is used almost universally,

in self-moving lubricants for petrol.combustion engines, but loses its anti-wear properties quickly in a methanol or ethanol combustion engine, because it is easily transesterified with alcohols.

A lubricant additive can be measured based on amounts of wear elements so. such as iron, lead and copper detected in an oil sample by spectrophotometric analysis after the machine has run a certain number of miles after a

oil change. These metals or wear elements

-- appear in the lubricant as a result of severe corrosion or failure of certain machine components

made of this metal as well as normal mechanical wear.

Table 1 sets out criteria for measuring lubricant wear element data. The primary secondary source in the machine for each wear element is indicated as well as the average amount of ppm for each wear element that would be found in oil at the "run-in" point and at the "post-run-in" point. Machine wear levels during the break-in period tend to be relatively high. After the machine is run-in, wear levels reach a plateau and remain stable for approx. 50,000 miles, depending on the individual vehicle and the level of maintenance. The break-in point for an average machine is generally in the 0 - 10,000 mile range. The measurement criteria found in table 1 will be used to measure the data specified in examples 1 to . 5..

In examples 1 and 3, data are also included regarding the percent volume of diluted fuel, percent volume of total solids, percent volume of water, viscosity and base number for the examined oil sample.

The average amount of oil dilution caused by "blow-by" is approx. 3% for both alcohol and petrol fuel. The degree of dilution is significantly greater in cold weather due to increased condensation. A stuck choke, faulty dilution, low operating temperatures and "blow-by" are factors that most often contribute to fuel dilution. Dilution beyond 3% reduces the oil's viscosity and causes increased machine wear.

Solid substances in the machine oil normally consist of soot, metal salts, road grime, sludge and oxidized oil caused by undesirable machine operating conditions such as poor

ignition, ineffective air filters and "blow-by". These solids can cause machine malfunction if they prevent the oil from reaching critical machine and bearing surfaces. A total solids content greater than 3% indicates a serious problem.

Water content greater than 0.1% is generally considered too high in the vehicle using gasoline fuel. Due to the hygroscopic properties of alcohols, vehicles using this oil often have water content exceeding 0.5%. Higher water content accelerates both organic sludge formation and corrosion reactions. Higher values can come from atmospheric water mixing with the alcohol, leakage from the cooling system, low operating temperatures or an ineffective pollution control valve system.

A normal viscosity self-propagating lubricant has the same numerical value as the Society of Automotive Engineers (SAE). grade of the oil used. High viscosity values generally indicate oil degradation caused, in general, by fuel dilution. The viscosity values are not directly proportional to machine wear, and a change of 10 units in each direction

ning may indicate significant lubricant degradation.

The base number is a measure of the oil detergent effect and

its ability to prevent corrosion. New self-propelled

oils normally have a base number of 4 to 5. For any oil, a reading of 1 or less is indicative. a dangerous disappearance of additive reserves. A base number. on

2 is generally considered to provide a sufficient margin of protection in a petrol combustion engine.

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Example I

An oil sample comprising a normal self-moving lubricant and 10% by weight of the lubricant additive according to the present invention containing approx. 97 to 98.5% by weight polypropylene glycol 20'00, approx. 0.5 to 1.0 wt% ortho-phenylenediamine, approx. 0.5 to 1.0 wt% N-phenyl-2-naphthylamine and approx. 0.5 to 1.0 wt% ortho-tricrecyl phosphate was taken from the crankcase in methanol combustion engine A which had been driven the equivalent of 12,459 miles with an oil change approx. 2,000 before this. The sample contained less than 0.5 volume-% diluted fuel, 1.5 volume-% total solids are,. less than 0.05% water by volume and had a total base number of 3.70.

The oil had an initial viscosity of SAE 30 and the viscosity remained unchanged during the test.

The base number of 3.70 was well above the required base number of 2 indicating that aromatic primary and secondary amines had not disappeared and were still available to neutralize formic acid and carbonic acid and prevent oxidation of methanol to formaldehyde and formic acid.

Volume percentage of diluted fuel and volume percentage of total solids were well below the average 3% value which indicated that there was no increase in

machine wear. Volume percentage of water wax is well below the 0.1% value which is considered to be too large and thus does not indicate any corrosion problems due to water content. The viscosity of the oil sample was normal.

Spectrochemical analyzes showed that the following amounts of the wear element of the oil sample: 36 ppm iron, 66 ppm lead, 107

ppm copper, 2 ppm chromium, 4 ppm aluminium, 2 ppm nickel and 12 ppm tin. The machine had been driven the equivalent of 12.4 59 miles, which is slightly over the break-in distance of approx. 10,000 miles. The test will thus measure both

using entry and post-entry criteria. However, it should be noted that the distance is closer to the run-in distance and thus the run-in criterion is a more accurate measure of the degree of machine wear.

In table 1, the content of iron, lead, tin, nickel and aluminum in the sample was less than the average content of these wear elements at the drive-in distance. The Cob content was within the average range at the drive-in distance. Chromium content was at the lower end of the average range at run-in distance.

At the drive-in distance, the lead, chrome, nickel and aluminum contents were within the average range. The iron content was at the lower end of the average range.

~The data for Example 1 illustrate'that the lubricant additive

follows the present invention and is effective in a methanol combustion engine at. or close to the drive-in distance.

Example 2.

An oil sample comprising the usual self-propagating lubricant and 10% by weight lubricant additive used in Example 1 was taken. the crankshaft housing of the methanol driven ma-. skin A which had been driven the equivalent of 14,034 miles

with an oil change approx. 3,575 miles before this. It had

a total base figure of 3.08. The base number of 3.08 was well above the required base number of 2 which indicated that the aromatic primary and secondary amines had not disappeared and were still present to neutralize the acids and prevent oxidation of methanol.

Spectrochemical analysis showed that the following amounts of wear elements were present in the oil sample: 52 ppm iron, 64 ppm lead, 102 ppm copper, 1 ppm chromium, 5 ppm aluminum

nium, 1 ppm nickel and 10 ppm tin. When the machine was run

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corresponding to 14,034 miles, the criteria shown in table 1 were used for the post-run-in assessment.

In table 1, the iron, lead, chrome, aluminium, nickel and tin content in the sample was well within the average range at the post-run-in distance.

The data in examples 1 and 2 including the base numbers indicate that the lubricant additive according to the present invention will be effective at 4,000 mile oil change intervals, and should be effective at longer oil change intervals up to 6,000 miles. The low wear element levels in examples 1 and 2 also indicate that machine A was in good condition.

- Example 3.

An oil sample comprising a conventional self-propellant ■ lubricant and 10% by weight of the lubricant additive used

in example 1 was taken from the crankshaft housing in methanol-powered machine B which had been driven the equivalent of 31,724 miles

with an oil change approx. 2,000 miles before this. The oil sample contained less than 0.5 volume-% diluted fuel,

about. 5.0 volume-% total solids, less than 0.05 volume-% water and had a total base number of 2.38. The oil had an initial viscosity of SAE 30 which remained unchanged during the test.

Base numbers were greater than the required base number of 2 indicating that significant amounts of primary and secondary aromatic amines were available to neutralize acids and prevent oxidation of methanol.

Volume percent of diluted fuel and volume percent of total solids were far below the average of 3%

value and thus did not indicate any increase in machine wear. Volume percent water was also far below. The 0.1% yerdi is considered too high, and thus indicates .

nor on any serious corrosion problems on

due to the presence of water. The amount of solids was greater than the average value of 3%, which indicates that more than the average amount of solids is present. The viscosity of the oil sample was normal.

The spectrochemical data show that the following wear elements were present in these amounts: 47 ppm iron, 44 ppm lead, 83 ppm copper, 17 ppm chromium, 4 ppm aluminium, 2 ppm nickel and 14 ppm tin. The wear element content of iron, lead, aluminum and nickel was within the average range in table 1 for post-run-in distance. Thus, example 3 also illustrates that the lubricant additive according to the present invention is effective in a methanol combustion engine at "after break-in" distance.

. Example 4.

An oil sample comprising a conventional self-propagating1 lubricant and 10% by weight lubricant additive used in Example

1 was taken from the crankshaft housing of methanol-powered machine B which had been driven the equivalent of 33,307 miles with an oil shift approx. 3,583 miles before this. The oil sample had a total base number of 2.46. The base number is greater than the required base number of 2 and therefore indicates that there are significant amounts of primary and secondary aromatic amines available to neutralize acids and prevent oxidation and methanol. Spectrochemical data show that the following wear elements are present in these amounts: 85 pp, iron, 63 ppm lead, 7 6 ppm copper, 16 ppm chromium, 3 ppm aluminum, 1 ppm nickel and 11 ppm tin. The wear element contents of iron, lead, aluminum and nickel were within the average range shown in table 1 for the run-in distance. The copper content was . 1 ppm higher than the average amount, but not much less than 100 ppm

which is considered too high. Thus exem- illustrates;

pel 4 that the lubricant additive according to the present op-

f.filling is effective in a methanol combustion engine at break-in distance, and that it would be effective at 4000 mile oil change intervals.

Example 5.

An oil sample comprising a common self-propellant lubricant and 10% by weight lubricant additive used in Example

1 was taken from the crankshaft housing of the methanol fueled machine

B which had been driven the equivalent of 34,815 miles with an oil change approx. 5,091 miles prior to this. The oil sample had a total base number of 1-68. Although the base number is slightly less than base number 2, it still indicates that there are sufficient amounts of primary and 'secondary' aromatic amines to neutralize acids and prevent oxidation of methanol.

Spectrochemical data show that the following wear elements were present in these amounts: 77 ppm iron, 160 ppm lead, 67 ppm copper, 10 ppm chromium, 0 ppm aluminum,

1 ppm nickel and 0 ppm tin. The wear element content

of iron, copper and nickel were within the average range for post-run-in distance as shown in table 1. Less than average amounts of aluminum and tin were found in the sample. Thus, example 5 illustrates that the lubricant additive according to the present invention is effective in a methanol-powered machine at post-run-in distance at 5,000 mile oil change intervals.

Machine B of Examples 3, 4 and 5 was in poor condition at the start of the trial as evidenced by the high chromium levels 2,000 miles after the oil change. The wear-eleme.nt content levels and base numbers in examples 3, 4 and 5 did not change significantly during the trial period,

which indicated that the lubricant additive according to the present invention is also effective in machines in poor condition.

Example 6.

Oil samples were taken from a methanol-powered self-propelled machine before running the machine and 20 hours after continuous running of the machine in three test trials. In that

in the first trial, the oil in the machine did not contain any lubricant additive. In the second and third trials, the oil in the machine contained 10% by weight of lubricant additive according to the present invention. The following wear element data were obtained by spectrochemical analysis.

When trial 1 was compared to the trial trials

2 and 3, the wear element content indicated that without a lubricant additive according to the present invention, a methanol combustion engine gets a significant increase

of machine wear. The increase is particularly evident from the iron content. In test trial 1, after 20 hours of continuous driving, 125 ppm of iron were present, while in test trials 2 and 3, after 20 hours of continuous driving, only 14 and 21 ppm of iron were present, respectively.

In test run 1, the amount of all wear elements generally increased after 20 hours of machine operation, while in test run 2 the content of lead, chromium, aluminum and nickel remained the same, while the copper content decreased and the tin content increased by only 2 ppm. In test run 3, the lead, aluminium, nickel and tin content remained the same, while the copper content decreased and the chromium content increased by 1 ppm. Thus, one can conclude that a methanol combustion engine that uses a lubricant additive according to the present invention will have less machine wear than one without a lubricant additive according to the present invention.

Claims (9)

1. Lubricant additive for use with alcohol fuel is characterized in that it comprises a major part of a polyalkylene glycol of an alkene with 2 to 3 carbon atoms and smaller amounts of an aromatic primary amine, an aromatic secondary amine and a phosphoric acid ester. 2. Lubricant additive for use with alcohol fuel, characterized in that it includes approx. 93.0 to 98.5% by weight of a polypropylene glycol, approx. 0.5 to 2.0% by weight of an aromatic primary amine, approx. 0.5 to 2.0% by weight of an aromatic secondary amine, approx. 0.5 to 2.0% by weight of a phosphoric acid ester. 3. Lubricant additive according to claim 1. characterized in that the polyalkylene glycol of an alkene with 2 to 3 carbon atoms is polypropylene glycol 2000. 4. Lubricant additive according to claim 2, characterized in that the polypropylene glycol is polypropylene glycol 2000. 5. The lubricant additive according to claim 1 or 2, characterized in that the aromatic primary amine is ortho-phenylenediamine. 6. Lubricant additive according to claim 1 or 2, characterized in that the secondary amine is N-phenyl-2-naphthylamine. 7. Lubricant additive according to claim 1 or 2, characterized in that the phosphoric acid ester is ortho-tricrecyl phosphate. 8. Lubricant additive according to claim 2, characterized in that the polypropylene glycol content is approx. 97.0 to 98.5% by weight, the aromatic primary amine in- . the team is approx. 0.5 to 1.0% by weight, the aromatic sec the amine content is approx. 0.5 to 1.0% by weight and the phosphoric acid ester content is approx. 0.5 to 1.0% by weight. 9. Lubricant additive for use with alcohol fuels, characterized in that it comprises approx. 97-98.5% by weight polypropylene glycol 2000, approx. 0.5 to 1.0 wt% ortho-phenylenediamine, approx. 0.5 to 1.0% by weight N-phenyl-2-naphthylamine and approx. 0.5 to 1.0% by weight Ortho-tricrecyl phosphate.