Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic sulfur compound – wherein the sulfur is single bonded...
Reexamination Certificate
2002-12-13
2004-11-23
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic sulfur compound, wherein the sulfur is single bonded...
C508S409000, C508S466000, C508S468000, C508S472000, C508S585000, C508S591000, C208S018000, C208S019000
Reexamination Certificate
active
06821933
ABSTRACT:
The present invention relates to an additive composition composed of flow improvers, poly-&agr;-olefins and organic acids and also to their use for improving the cold flow and storage properties of crude oils.
Depending on their origin or the way in which they were processed, crude oils, residue oils, oil distillates, for example diesel fuel, mineral oils, lubricants, hydraulic fluids, etc., comprise greater or lesser proportions of n-paraffins and asphaltenes which present particular problems because they crystallize out and agglomerate when the temperature is reduced and may thus lead to deterioration in the flow properties of these oils. This deterioration in the flow properties of the oils is referred to as solidification of the oil. The pour point is the standard term for the temperature at which an oil, for example mineral oil, diesel fuel or hydraulic fluid, is still just able to flow as it is cooled. However, the pour point is not identical to the yield point. The yield point is a nonspecific term not covered by standards for the temperature at which a solid begins to flow under given measuring conditions. The deterioration in the flow properties may result in these oils blocking vessels, pipes, valves or pumps, for example in the course of transport, storage and/or processing, in particular in the case of paraffinic oils which are difficult to inhibit. Furthermore, paraffin precipitations require elevated pressures on re-start of pipelines (yield point).
Particular difficulties occur in practice when the wax appearance temperature (WAT) and in particular the intrinsic pour point of these oils is above ambient temperature, in particular at 20° C. or higher. In view of the decreasing world oil reserves and increasing exploitation of deposits which deliver crude oils having high intrinsic pour points, the conveyance and transport of such problematic oils are becoming ever more important.
There is a range of measures of thermal or mechanical nature for restoring or maintaining the flowability, for example scraping the crystallized paraffin from the pipe interior by regular pigging, heating entire pipelines or flushing procedures using solvents. A more elegant method is undoubtedly to combat the causes of the phenomenon by adding flow improvers which are also known as pour point depressants or paraffin inhibitors. In general, it is advantageous to depress the pour point to values below the respective ambient temperature, in particular to values of about 10° C. and below.
The way in which these flow improvers are effective is generally explained by their inhibition of the crystallization of paraffins and asphaltenes and by their cocrystallization with the paraffins or paraffin-asphaltene adducts which leads to the formation of smaller paraffin crystals which are no longer able to aggregate or form a network which impairs the flowability. The consequence is a reduction of the pour point and the maintenance of the flowability of the oil at low temperature. The effectiveness of the flow improvers depends both on their chemical construction (composition) and on their concentration.
U.S. Pat. No. 3,567,597 describes mineral oil distillates comprising crude oils, shale oils and residue oils which comprise, as pour point depressants, a copolymer which is a copolymer of ethylene and a vinyl ester of a saturated aliphatic C
1
to C
30
-monocarboxylic acid and has an average molecular weight of from 4000 to 60,000 and comprises from 40 to 95% by weight of ethylene.
DE-A-20 57 168 discloses a process for reducing the frictional flux in oleaginous liquids flowing through pipelines and a shear-resistant additive effective in low concentrations with which the frictional losses in oleaginous liquids can be reduced. To this end, a small amount of at least one high molecular weight polymer which is derived from at least one &agr;-olefin having from 6 to 20 carbon atoms (polyolefin) is added to the liquids.
EP-A-0 176 641 discloses that the properties of poly-&agr;-olefins as flow accelerants for liquid hydrocarbons can be improved by carrying out the polymerization of the &agr;-olefins by the Ziegler process in the presence of a dialkylaluminum halide and a trialkylaluminum compound.
GB-A-2 305 437 discloses pour point depressants for crude oils. These comprise a reaction product from an alkylphenol having on average more than 30 carbon atoms in the alkyl radical with an aldehyde having from 1 to 12 carbon atoms. These pour point depressants are suitable for treating crude oils which have a pour point of over 4° C.
EP-A-0 311 452 discloses additives for improving the cold flow behavior of fuels and lubricants. The additives comprise an alkylphenol-aldehyde resin which has a molecular weight of at least 3000 and from 6 to 50 carbon atoms in the alkyl radical and exhibits a specific distribution of the carbon chain lengths of the alkyl radicals.
U.S. Pat. No. 3,735,770 discloses a process for improving the flowability of crude oils under cold conditions. This process comprises the addition of copolymers of ethylene with unsaturated carboxylic esters, or of alkylphenols to the oil.
EP-A-0 857 776 discloses mixtures of ethylene copolymers and alkylphenol-formaldehyde resins, with or without paraffin dispersants (polar nitrogen compounds), for improving the cold properties of mineral oils. However, in paraffin-rich crude oils comprising long-chain paraffins, these mixtures do not show sufficient effectiveness.
A disadvantage of the known flow improvers for crude and residue oils is their insufficient effectiveness in many cases and the resulting high use concentrations, in particular in oils having a high proportion of long-chain n-paraffins having more than 30 carbon atoms. Furthermore, the known flow improvers support the sedimentation of the precipitated paraffin crystals of relatively high specific gravity by reducing the viscosity of the additivized oil. Although high molecular weight poly-&agr;-olefins are able to improve the flow behavior of oils, they do not improve their cold behavior. A further disadvantage is the high intrinsic pour points of the flow improvers which require heating and/or very high dilution for the metering.
Additives are therefore sought which have improved properties as pour point depressants, i.e. still have sufficient effectiveness even at low dosage and, in comparison to prior art pour point depressants, have a lower intrinsic pour point at equally high concentration and are effective in a variety of oils, in particular in paraffinic oils. The additive shall reduce the cloud point, the viscosity and the yield point of the oil under cold conditions, and delay or prevent the sedimentation of the precipitated paraffin crystals.
It has now been found that, surprisingly, the required properties of the additive can be achieved by a ternary mixture of active ingredients.
The invention therefore provides additives for improving the flowability of mineral oils comprising
A) from 1 to 40% by weight of at least one copolymer which is oil-soluble and is a cold-flow improver for mineral oils selected from
A1) copolymers of from 80 to 96.5 mol % of ethylene and from 3.5 to 20 mol % of vinyl esters of carboxylic acids having from 1 to 20 carbon atoms and/or (meth)acrylic esters of alcohols having from 1 to 8 carbon atoms, and
A2) homo- or copolymers of esters which bear C
10
-C
30
-alkyl radicals and are esters of ethylenically unsaturated carboxylic acids comprising up to 20 mol % of further olefinically unsaturated compounds,
B) from 20 to 80% by weight of at least one poly-&agr;-olefin having a molecular weight of from 250 to 5000 which is derived from monoolefins having from 3 to 5 carbon atoms, and
C) from 5 to 70% by weight of at least one organic acid selected from
C1) alkylphenol-aldehyde resins of the formula 1
where R
1
and R
2
are each independently H or alkyl radicals having from 1 to 30 carbon atoms, but where both radicals may not at the same time be H, n is an integer from 3 to 50 and R
3
is H or an alkyl radical having from 1 to 4 carbon atoms, and
C2) ali
Feustel Michael
Krull Matthias
Oschmann Hans-Jörg
Clariant International Ltd.
McAvoy Ellen M.
Silverman Richard P.
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