Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Compound of indeterminate structure – prepared by reacting a...
Reexamination Certificate
1999-11-02
2001-07-03
Johnson, Jerry D. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Compound of indeterminate structure, prepared by reacting a...
C508S288000, C508S291000, C548S546000
Reexamination Certificate
active
06255258
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to dispersant additives for use in lubricating oil and fuel compositions.
BACKGROUND OF THE INVENTION
Multigrade lubricating oils must operate in the presence of high levels of sludge and soot resulting from oxidation during use. This accumulation of sludge and soot can seriously impair the efficiency of the oil and can result in damage to components of an engine.
To avoid these problems the multigrade lubricating oils may be formulated with dispersant additives. Various organo-metallic additives have been used previously as dispersants, but it has been recognised that the use of these dispersants may result in the deposit of metal oxides on spark plugs and so may affect engine ignition.
In addition to dispersant additives, a typical multigrade oil may also comprise viscosity index (VI) improvers. These additives are intended to produce a balance between the maximum low and high temperature viscosities. Examples of such additives are disclosed in EP-A-0331397. The additives are described as nitrogen or ester-containing adducts which are post-reacted with at least one polyanhydride. The polyanhydride couples two or more molecules of the adduct, resulting in larger polymers which are more shear-sensitive and which contribute to the high temperature viscosity to a greater extent than the low temperature viscosity when compared to additives which have not undergone post-reaction.
The additives disclosed in EP-A-0331397 are claimed to improve the viscosity characteristics in an oil, and are intended to provide a balance in the low and high temperature viscosities of the oil. The dispersancy characteristics of the additives are not investigated. What is also clear is that the additives are formed by post-reactions with relatively high levels of polyanhydride, and that this is necessary to produce highly cross-linked molecules.
Similar additives to those disclosed in EP-A-0331397 are disclosed in U.S. Pat. No. 4,747,964, where the additives are tested for their dispersancy characteristics. However, the amount of polyanhydride used to produce the additives is again relatively high, being on average 3.6% w/w.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided an oil-soluble dispersant obtainable by reacting the reaction product of a polyamine and a long-chain hydrocarbyl-substituted dicarboxylic acid, anhydride or ester thereof with a polyanhydride, characterised in that the dispersant restricts the viscosity increase in an oil to below 8 Pa.s in the Haake rheology test defined herein at 2% w/w active matter and a shear rate of 0.26 s
−1
Pa.s.
DESCRIPTION OF THE INVENTION
Dispersants of the present invention are obtainable by reacting the hydrocarbyl-polyamine product with a suitable amount of polyanhydride. The hydrocarbyl-substituted dicarboxylic acid materials are well known in the art, e.g. as described in EP-A-0331397. Preferably, the long-chain hydrocarbon group is a polymer of a C
2
to C
18
, e.g. C
2
to C
5
, monoolefin with a molecular weight of between 700 to 5000. Suitable olefins include ethylene, propylene, butylene, isobutylene, etc. Preferred polyolefins are polyisobutylene and atactic polypropylene. The molar ratio of dicarboxylic acid, ester or anhydride: polyolefin is typically from 1:1 to 2:1. Examples of long-chain hydrocarbyl-substituted dicarboxylic acids, anhydrides and esters, include substituted succinic acid and succinic anhydride.
The polyamine compounds useful in the invention are preferably of the formula (I):
H
2
N—(CHR′)
x
—CH
2
—[A—CH
2
—(CHR′)
x
]
y
—NH
2
(I)
where A is NH or O; each R′ is H or methyl; x is 1-6; and y is 1-10 when A is NH, or 1-200 when A is O.
Examples of suitable polyamines include tetraethylene pentamine and polypropylene amines.
The polyanhydrides that are used in the present invention are known in the prior art and include pyromellitic dianhydride (PMDA), cyclohexyl dianhydride and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride.
Typically, the long-chain hydrocarbyl-substituted dicarboxylic acid, anhydride or ester will be reacted with a suitable polyamine at a molar ratio of 1:1 to 2:1.
The hydrocarbyl-polyamine product will in general be reacted with less than 6% w/w, preferably less than 3% w/w, and more preferably less than 2% w/w, polyanhydride.
The important feature is that the level of polyanhydride is such that the resultant dispersant restricts the viscosity increase in an oil.
The measurement of the viscosity increase is carried out using the Haake rheology test. This test comprises adding a known concentration (e.g. 2% w/w) of the dispersant under test to a mixture of other compounds, to produce a fully formulated oil. Carbon black (a soot “mimic”) is then added to the oil and mixed at an elevated temperature for a set period of time. The viscometric characteristics of the oil are then measured and compared with a standard dispersant under the same conditions.
The base oil blend used in the Haake rheology test consists of the following components:
Component
Concentration % w/w
Detergents (overbased calcium and
3.5
magnesium alkyl salicylates)
Anti-wear additive
1.13
(zinc dithiophosphate (ZDTP))
Viscosity index improver
5.88
(hydrogenated polyisoprene)
Pour point depressent
0.34
(polymethyacrylate)
Mixture of base oils
89.15
The Haake rheology test apparatus comprises a Haake RV 20 rheometer with RC 20 rheocontroller and CV 100 measuring system with a ZA 30 cup and rotor.
The samples are prepared by weighing (100/active matter) g of the dispersant sample, made up to 5.75 g with HVI-60-AL base oil, and then 50 g total mass with the base oil blend.
The carbon black (grade XC72) is activated at 140° C. for at least 12 hours prior to use in the rheology test. An amount, 0.25 to 0.30 g, of the carbon black is measured, and fully formulated oil is added in an amount as calculated by the formula:
M
FFO
=M
c
×20
where M
FFO
is the mass of the fully formulated oil (g), and M
c
is the mass of carbon black (g). The mixture is completely homogenised with the oil. The viscosity characteristics are then measured over a range of shear rates for 30 minutes. Viscosities measured at a shear rate of 0.26 s
−1
are quoted in Tables 1, 2 and 3.
As discussed above, the dispersant of the present invention may be used in lubricating oils. Accordingly, the present invention provides a lubricating oil composition comprising a major amount (more than 50%w) of a lubricating base oil and a minor amount (less than 50%w), preferably from 0.1 to 20%w, especially from 0.5 to 10%w (active matter), of a dispersant according to the present invention, the percentages by weight being based on the total weight of the composition.
A lubricant formulation may be produced by addition of an additive package to the lubricating oil. A minor amount of viscosity modifier may be included if the final lubricant formulation is to be a multigrade version. The type and amount of additive package used in the formulation depends on the final application, which can include spark-ignition and compression-ignition internal combustion engines, including automobile and truck engines, marine and railroad diesel engines, gas engines, stationary power engines and turbines.
The lubricant formulation is blended to meet a series of performance specifications as classified in the US by a tripartite arrangement between the Society of Automotive Engineers (SAE), American Petroleum Institute (API) and American Society for Testing and Materials (ASTM). Also the American Automobile Manufacturers Association (AAMA) and Japan Automobile Manufacturers Association Inc. (JAMA), via an organisation called the International Lubricant Standardisation and Approval Committee (ILSAC), jointly develop minimum performance standards for gasoline-fuelled passenger car engine oils.
In Europe, engine oil classifications are set by the Association des Constructeurs Europeens de l'Automobile (ACEA) in consultation with the Technical Committ
Clark Michael T.
Warren Graham A.
Infineum USA L.P.
Johnson Jerry D.
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