Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic compound containing boron
Reexamination Certificate
1998-12-11
2003-09-23
Medley, Margaret (Department: 1714)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic compound containing boron
C508S291000, C508S485000, C508S486000, C252S077000, C252S078100
Reexamination Certificate
active
06624123
ABSTRACT:
SCOPE OF THE INVENTION
The present invention relates to lubricating fluids having improved filterability characteristics, and to effective additives for improving the filterability characteristics of lubricating fluids such as hydraulic oils. The present invention relates more particularly to lubricating fluids and additives containing an effective quantity of an agent improving filterability which contains at least one polar group consisting in a succinic acid derivative and at least one polyolefinic chain and having a molecular weight (Mn) of about 500 to about 2500.
TECHNOLOGICAL BACKGROUND
Most lubricating oils currently in use, such as hydraulic fluids and similar fluids, contain additives which are designed to confer optimum performances as regards the prevention of wear, protection against rust, demulsibility, thermal stability, stability towards hydrolysis and oxidation stability, air release capacity, and foam prevention. Moreover, hydraulic oils have to exhibit extremely good filterability properties which are measured and evaluated using a certain number of detailed filterability tests such as the AFNOR NFE 48690, 48691 and 48693, CETOP RP 124H, DENISON and PALL tests.
Unfortunately, the formulation scope required to satisfy the principal performance criteria often militates against good filterability because, in general, the use of additives is harmful for filterability. For example, the use of viscosity index (VI) improvers and pour point depressors (PPD) has made it more difficult to formulate oils having a high viscosity index and/or better properties at low temperatures.
The filterability of hydraulic oils is currently an important technical point because it is an important imperative for current and future formulations. Indeed, most hydraulic systems use decontamination filters. The contaminants may be metal particles, dust, lacquers, polymers resulting from oxidation and thermal stability factors. In fact, limiting pollution by hydraulic oils has becoming a deciding factor for obtaining good performances under operating conditions, also including improved wear prevention by reducing abrasive particles. Consequently, the trend is to reduce the porosity of the filters (in line) even further to a value of about 3 micrometers in certain cases.
Consequently, filterability tests in a dry and in a damp medium have been developed for evaluating, and offering means of improving, the filterability performances of hydraulic oils. However, in view of the very fine porosity of the filters used in these bench tests and also because of the presence of water in some of these operating procedures, the performances of hydraulic oils are sometimes lower than the acceptable criteria.
As the presence of water has an adverse effect on the filterability performance of hydraulic oils, most of the bench-scale filterability tests used at present include a period of storage of the oil artificially contaminated with water. The presence of water poses a problem because water undergoes adsorption on the calcium carbonates and calcium hydroxides forming part of the calcium salt detergents which are often present in hydraulic additives. Moreover, water interacts with the ZDDP liberating ZnO. These interactions lead to fine deposits which tend to block the filters.
Various technologies have been used in the past in an attempt to solve these problems. The most commonly used means known to date include the use of metal carboxylates in the manner described in the document GB 2 293 389, reducing the concentrations of ZDDP from about 8 mM/kg of oil to a value equal to or less than about 4 mM/kg of oil, or formulating additives with particular viscosity index improvers which are less harmful for filterability.
SUMMARY OF THE INVENTION
The inventors have discovered that it is possible to improve the filterability properties of lubricating oils by using agents improving filterability containing at least one polar group and at least one polyolefinic chain having a particular length. More interestingly, if the compounds described below are used, the filterability performances are improved but this improvement obtained is not generally harmful for the principal performance criteria and may even have positive effects in certain cases.
The present invention relates in a general manner to a lubricating fluid, particularly a hydraulic oil, comprising:
1) a predominant amount of an oil having a viscosity suitable for lubrication, and
2) from 0.03% to 0.06% of an agent improving filterability, corresponding to the following formula:
R—Z
wherein Z represents
i) an ester of succinic acid comprising the reaction product of a succinic anhydride and an aliphatic polyhydric alcohol; or
ii) a succinimide comprising the reaction product of a succinic anhydride and a polyamine, the said reaction product being treated with an after-treatment agent; and
R represents a polyolefin having a molecular weight (Mn) of 500 to 2500 and an Mw/Mn ratio of 1 to 5.
Examples of after-treatment agents are cyclic carbonates, boric acid and boric acid derivatives.
The present invention also relates to an additive for a lubricating fluid composition. The additive comprises an effective quantity of an agent improving filterability corresponding to the above-mentioned description. The present invention also relates to the use of such compounds for increasing the filterability of oil compositions, particularly hydraulic oils.
Although the additives and compounds of the present invention are particularly useful for increasing the filterability of hydraulic oils, they may also be used for improving the filterability of other types of oil. The present invention is now described in more detail below.
DETAILED DESCRIPTION OF THE INVENTION
The inventors have discovered that two particular categories of compound are useful for improving the filterability properties of lubricating oils. These compounds all prove to have in common a structural characteristic which comprises at least one of the polar groups corresponding to the above-mentioned definition and at least one polyolefinic chain having a particular length.
In order better to demonstrate the structural relationship between the polar group and the polyolefinic chain of the agents improving filterability of the present invention, specific examples of the two preferred groups of compounds and of the reaction substances used to prepare said compounds are set out below.
Reaction Substance Consisting in a Succinic Anhydride
The process for the preparation of succinic anhydrides with alkenyl or alkyl substituents comprising the reaction of a polyolefin and a maleic anhydride has been described in practice.
In the case of the categories of compounds described in the present invention, the alkenyl or alkyl group R has an Mn value of about 500 to about 2500 and an Mw/Mn ratio of about 1 to about 5.
The preferred Mn intervals depend on the chemical nature of the agent improving filterability. Polyolefinic polymers suitable for the reaction with maleic anhydride include polymers containing a predominant quantity of C
2
to C
5
monoolefins, for example, ethylene, propylene, butylene, isobutylene and pentene.
A highly suitable polyolefinic polymer is polyisobutene.
The succinic anhydride preferred as a reaction substance is PIBSA, that is, polyisobutenyl succinic anhydride.
If the agent improving filterability contains a succinimide comprising the reaction product of a succinic anhydride with a polyamine, the alkenyl or alkyl substituent of the succinic anhydride serving as the reaction substance consists preferably of polymerised isobutene having an Mn value of about 1200 to about 2500. More advantageously, the alkenyl or alkyl substituent of the succinic anhydride serving as the reaction substance consists in a polymerised isobutene having an Mn value of about 2100 to about 2400.
The polyisobutenes having an Mn value of about 2200 are highly suitable.
If the agent improving filterability contains an ester of succinic acid comprising the reaction product of a succinic anhydride and an aliphati
Batelier Dominique
Cazin Jacques
Clement Olivier Pascal Marie
Sausse Christophe Le
Chevron Chemical S.A.
Lee S. G. K.
Medley Margaret
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