Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic -co- compound
Reexamination Certificate
1994-11-17
2001-01-16
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic -co- compound
C508S466000
Reexamination Certificate
active
06174843
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to wax dispersant and pour point improver additives for hydrocarbon lubricating oils derived from petroleum.
Two problems encountered with hydrocarbon lubricating oils are visible wax particles and the need for pour point improvement. Wax particles in lubricating oil can cause blockage of filters and delivery lines on equipment and engines, thus interfering with the flow of oil to moving parts. Wax particles in lubricating oils also cause the oil to look hazy. This is especially a problem in those oils such as automotive oils, turbine oils and the like which are desirably bright and clear in appearance at room temperature. These oils typically include fractions taken from paraffinic or naphthenic crude oils or crude oil blends from the Pennsylvania, Mid-Continent, Gulf Coast and West Coast regions.
Wax haze is generally not a problem in light oils such as household lubricants and naphthenic-type lubricating oils of less than about 200 SSU viscosity at 100° F. Visible wax haze is primarily a problem in medium viscosity range oils such as naphthenic lube oils between 200 and 850 SSU viscosity at 100° F. Wax haze or particles are considered to be present in more viscous oils; but discernment is difficult because these oils are dark and opaque.
The presence of wax haze is typically detected by simple observation with the human eye and at room temperatures—i.e., about 60° to 80° F. (15° to 26° C.). Instruments which measure light transmission may be employed to help determine the clarity of an oil. However, simple visual observation is normally relied upon.
The pour point of a lubricating oil can greatly affect the type of environments in which it can be used. Additionally, lowering the pour point of lubricating oils aids in pipeline transport and pumpability. The pour point of various viscosities of lubricating oils without additives ranges from +9° C. for high viscosity oils to −18° C. for low viscosity oils. Pour point depressants can typically lower pour points as much as 30° C.
Using additives to reduce the pour point of various oils is well-known in the industry. Long chain fatty alkanol esters of copolymers of styrene and maleic anhydride and copolymers of alpha-olefins and maleic anhydride esterified with alcohols have been used as pour point depressants for fuels and lubricants. Other compounds which have been used as additives and dispersants are styrene-maleic anhydride copolymers reacted with aliphatic alcohols and tertiary amino alcohols, and ethylene vinyl acetate copolymers.
One important feature of an additive is that it be effective in small quantities. Another important feature is that the additive not produce unwanted by-products with its use in lubricating oil. An additive should also ideally perform more than one function so that fewer different additives have to be blended into the lubricating oil. Effectiveness in all viscosities and being liquid for ease of use are also desirable attributes in an additive. At the current time there is no additive available which acts both as a wax dispersant and a pour point improver much less one which meets the above criteria.
SUMMARY OF THE INVENTION
The current invention provides a composition which both lowers pour point and acts as a wax dispersant in lubricating oils, thus reducing the haziness that oils exhibit at room temperature. The composition is comprised of an esterified styrene-maleic anhydride copolymer and an esterified alpha-olefin maleic anhydride copolymer. The synergistic effect of the two copolymers together provides a more effective pour point improver than would be supplied by either copolymer alone. This means that less of the composition is necessary to gain the desired results. Additionally, both copolymers are esterified with alcohols and do not add any other elements to the lubricating oil which will result in undesired by-products. The composition is liquid at most temperatures in which it would be used, and it can be used in lubricating oils of all viscosities. The current invention also provides for a method of adding the described compositions to lubricating oil to disperse wax particles and lower the pour point of the oil.
DETAILED DESCRIPTION OF THE INVENTION
This invention provides for a novel composition which can be added to a lubricating oil to disperse wax particles and lower the pour point. The composition is a mixture or blend of an esterified styrene-maleic anhydride copolymer and an esterified alpha-olefin maleic anhydride copolymer.
The preferred esterified styrene-maleic anhydride copolymer has the structure
with each R being an independently selected alkyl group and X being the number of repeating units ranging from about 60 to about 400. It is preferred that the alkyl group be a straight chain alkyl group of from 16 to 30 carbon atoms. It is more preferred that the esterified styrene-maleic anhydride be the reaction product of a styrene-maleic anhydride copolymer with one or more alcohols having from 18 to 26 carbon atoms. In the most preferred composition the alcohols are a mixture of C
20+
alcohols and C
22
alcohol. The alcohols are preferably combined in about a three to one ratio with the C
20+
alcohols dominating. The esterified styrene-maleic anhydride acts as the wax dispersant and also acts as a pour point depressant. The preferred molecular weight of the styrene-maleic anhydride copolymer before esterification is 12,000 to 80,000 and the most preferred molecular weight is 24,000 to 60,000.
The preferred structure of the alpha-olefin maleic anhydride copolymer is
with each R
1
being an independently selected alkyl group, “n” is a whole number from 3-33 and X being the number of repeating units ranging from about 20 to about 220. The preferred alkyl groups are straight chain alkyl groups of 2 to 20 carbon atoms. More preferably the esterified alpha-olefin maleic anhydride is a reaction product of an alpha-olefin maleic anhydride copolymer and a mixture of alcohols having from about 4 to 18 carbon atoms. In the most preferred composition the alcohols have about 9 to 18 carbon atoms.
The preferred alpha-olefin maleic anhydride copolymer before esterification has a molecular weight over 12,000 and the preferred molecular weight is about 18,000 to about 40,000. In the preferred composition, the esterified alpha-olefin maleic anhydride before esterification is the reaction product of maleic anhydride and an alpha-olefin having about 6 to 36 carbon atoms with the most preferred alpha-olefins being linear alpha-olefins having 10 to 18 carbon atoms.
The esterified styrene-maleic anhydride copolymer and the esterified alpha-olefin maleic anhydride copolymer may be utilized in any ratio depending upon the amount of wax dispersion and pour point depression needed in the lubricating oil but should contain at least 10% of either component. The preferred ratio is from about three to one to about one to three. The most preferred ratio of esterified styrene-maleic anhydride copolymer to esterified alpha-olefin maleic anhydride copolymer is two to one.
Alpha-olefin maleic anhydride copolymers and styrene-maleic anhydride copolymers and methods of their preparation are well-known in the art. See, for example, U.S. Pat. Nos. 3,560,455 and 4,391,721 which are incorporated by reference. The styrene-maleic anhydride copolymer is generally prepared as follows. Equal molar proportions of maleic anhydride and styrene are co-polymerized. These beginning components are well-known in the art and are commercially available. The polymerization reaction is initiated by a suitable catalyst, preferably a free radical initiator and more preferably a peroxide catalyst such as benzoyl peroxide, tertiarybutyl hydroperoxide or di-t-butyl peroxide. The most preferred catalyst is t-butyl perbenzoate.
Appropriate diluents which can be used in the reaction include various heavy aromatic solvents. The duration and temperature of the reaction depend upon the desired molecular weight of the styrene-maleic anhydride copolymer. For
Peyton Kim B.
Wang Sophia L.
Breininger Thomas M.
Martin Michael B.
McAvoy Ellen M.
Nalco Chemical Company
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