Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic -co- compound
Reexamination Certificate
2000-03-31
2002-10-08
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
C508S485000, C252S079000, C560S199000, C044S398000
Reexamination Certificate
active
06462001
ABSTRACT:
The present invention relates to esters containing more than one ester linkage, hereinafter known as “complex” esters, to formulations comprising one or more of these complex esters and to various uses of the complex esters and the formulations. More specifically, the present invention relates to complex esters and their use as an additive and/or a base fluid and/or thickener in various types of formulations suitable for use in lubrication applications, for example gear oils, hydraulic fluids, compressor oils, greases and four-stroke oils. The present invention also relates to formulations comprising one or more of these complex esters.
Complex esters are known in the art. For instance, DE-A-2620645 discloses a process for lubricating a two stroke engine by using a two stroke lubricating oil of which the base oil consists of at least one hydrocarbon oil and a complex ester. The complex ester results from esterification of trimethylolpropane with at least one saturated, linear or slightly branched C
4
-C
36
saturated, aliphatic dicarboxylic acid and a mixture of at least one linear or slightly branched C
2
-C
14
monocarboxylic acid and at least one saturated, linear or slightly branched aliphatic C
15
-C
30
monocarboxylic acid. Maximum kinematic viscosity at 98,9 C (Vk,
98.9
) of the complex ester suitably is only 25 cSt, which corresponds to a typical viscosity of a two-stroke oil.
In FR-A-2,187,894, a process for lubricating two stroke engines or rotary engines is disclosed, wherein use is made of a lubricating oil of which the base oil is a complex ester having a kinematic viscosity of more than 6 cSt at 98,9 C. In this reference complex esters are defined as esters formed by condensation of a polycarboxylic acid with a mono- and polyalcohol or as esters' formed by condensation of a polyol with a poly- and monocarboxylic acid. Several examples of complex esters are given: adipate/trimethylolpropane/heptanol having a Vk,
98.9
of 19,2 cSt, adipate/trimethylolpropane/dodecanoic acid having a Vk,
98.9
of 13,7 cSt and azelaic acid/pentaerythritollheptanoic acid/dodecanoic acid having a Vk,98.9 of 15,4 cSt. Again, these low viscosities are typical for two-stroke engine oils.
DE-A-2130850 discloses a lubricant composition containing or consisting of at least one low viscosity and one high viscosity component, where the high viscosity component is a complex ester having a kinematic viscosity at 99 C of more than 50 cSt and a flat viscosity-temperature behaviour. The complex esters are obtained by esterification of unbranched dicarboxylic acids having at least 10 carbon atoms with tri- or tetrafunctional alcohols and stopping with monoalcohols of which at least 25% is linear and low molecular. Trimethylolpropane and pentaerythritol are listed as suitable alcohols, whilst n-butanol and n-hexanol are mentioned as suitable low molecular monoalcohol chain stopping agent.
It has been found that complex esters having improved properties can be obtained by selecting certain compounds for use in the production of the complex ester so as to reduce or remove the number of free alcohol and/or carboxylic acid groups in the ester and so terminate the esterification process. Such compounds are hereinafter referred to as “chain stopping agents”. We have found that monoalcohols having relatively long carbon chains, i.e. of 14 carbon atoms or more, or monocarboxylic acids having at least 7 carbon atoms provide surprising improvements in properties of the complex esters.
In WO-A-97108277 two categories of ester base stocks for smokeless two stroke engine lubricants are disclosed. The first category are ester base stocks comprising a first ester having a viscosity at 100 C of 2 cSt or less and a second ester having a viscosity such that when the fust and second ester are mixed, the resulting mixture has a viscosity at 100 C of 3.0 to 20.0 cSt and a smoke index of at least 75. The second ester may be a stopped, i.e. chain terminated, or unstopped, i.e. still having some functionality, complex ester. The second category of ester base stocks is formed by one or more esters selected from the group consisting of (a) linear oligoesters having a molecular weight of 3000 Daltons or less, (b) complex, non-hindered polyesters wherein the polyol is a molecule having one or more beta hydrogen atoms, (c) complex, non-hindered polyesters wherein the polyol component is a non-hindered polyol having at least 3 OH groups and (d) esters wherein the polyol component is a hindered polyol and the carboxylic acid is a mono- or polycarboxylic acid or a mixture thereof. Several complex esters of the various categories are described, but most of them have a relatively low kinematic viscosity. The stopped complex ester having the highest kinematic viscosity at 100 C (44,5 cSt) is an ester of trimethylolpropane, dimer acid and oleic acid (C18:1 monoacid) as the chain stopping agent.
However, it has been found that the use of dimer acid, i.e. mainly dimerised fatty acids also comprising some trimerised fatty acids, as the sole polycarboxylic acid component has some disadvantages in terms of interaction with certain additive packages comprising sulphur- and/or phosphorus-containing components. Therefore, it would be advantageous to provide a complex ester not comprising dimer acid as the sole polycarboxylic acid component. Furthermore, it would be advantageous if such stopped complex esters could be provided having high kinematic viscosities at 100 C, i.e. 30 cSt or higher.
The present invention aims to provide a complex ester having a relatively high viscosity, which can be used as a functional fluid itself or in various formulations as a functional fluid, for example a lubricating formulation. Furthermore, and depending on the application, the complex ester should provide high oxidation stability and excellent lubricity, whilst, desirably, possessing good biodegradability characteristics. It will be appreciated that the latter is highly desired in view of the increasing environmental awareness and corresponding demand for environmentally friendly products.
Accordingly, the first aspect of the invention relates to a complex ester obtainable by an esterification reaction between at least one polyfunctional alcohol and at least one polyfunctional carboxylic acid and a chain stopping agent, wherein
(a) the polyfunctional alcohol is a hindered or non-hindered, aliphatic polyol,
(b) the polyfunctional carboxylic acid comprises an aliphatic dicarboxylic acid containing from 9 to 18 carbon atoms, dimerised and/or trimerised fatty acids or mixtures thereof, with the proviso that dimerised and trimerised fatty acids do not constitute more than 80% by weight, preferably not more than 50% by weight, of the total amount of polyfunctional carboxylic acid used,
(c) the chain stopping agent comprises either an aliphatic monocarboxylic acid selected from the group consisting of straight chain saturated acids containing from 7 to 22, preferably from 7 to 14, carbon atoms, branched saturated acids containing from 7 to 24 carbon atoms, straight or branched unsaturated acids containing from 16 to 24 carbon atoms and mixtures thereof or at least one aliphatic, straight or branched, saturated or unsaturated, monofuntional alcohol containing at least 14 carbon atoms, and preferably not having more than 24 carbon atoms, and
(d) the complex ester has a kinematic viscosity at 100 C (Vk,
100
) of from 30 to 1000 cSt, preferably from 30 to 200 cSt.
Preferably the complex ester according to the first aspect of the invention is obtained by an esterification reaction between at least one polyfunctional alcohol and at least one polyfunctional carboxylic acid and a chain stopping agent
The polyfunctional alcohol preferably is a hindered polyol, more preferably a neopentyl polyol. Examples of suitable neopentyl polyols are neopentyl glycol, dipentaerythritol, trimethylolpropane and pentaerythritol, the latter two being particularly preferred.
The polyfunctional carboxylic acid preferably comprises at least one aliphatic dicarboxylic acid having from 9
Kenbeek Dirk
Van der Waal Gijsbert
Verboom Cornelis
McAvoy Ellen M.
Pillsbury & Winthrop LLP
Unichema Chemie BV
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