Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M145/00—Lubricating compositions characterised by the additive being a macromolecular compound containing oxygen
  • C10M145/02—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • C10M145/10—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing monomers having an unsaturated radical bound to a carboxyl radical, e.g. acrylate
  • C10M145/12—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing monomers having an unsaturated radical bound to a carboxyl radical, e.g. acrylate monocarboxylic
  • C10M145/14—Acrylate; Methacrylate
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M105/00—Lubricating compositions characterised by the base-material being a non-macromolecular organic compound
  • C10M105/08—Lubricating compositions characterised by the base-material being a non-macromolecular organic compound containing oxygen
  • C10M105/32—Esters
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M145/00—Lubricating compositions characterised by the additive being a macromolecular compound containing oxygen
  • C10M145/02—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • C10M145/10—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing monomers having an unsaturated radical bound to a carboxyl radical, e.g. acrylate
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M145/00—Lubricating compositions characterised by the additive being a macromolecular compound containing oxygen
  • C10M145/02—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • C10M145/10—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing monomers having an unsaturated radical bound to a carboxyl radical, e.g. acrylate
  • C10M145/16—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing monomers having an unsaturated radical bound to a carboxyl radical, e.g. acrylate polycarboxylic
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M171/00—Lubricating compositions characterised by purely physical criteria, e.g. containing as base-material, thickener or additive, ingredients which are characterised exclusively by their numerically specified physical properties, i.e. containing ingredients which are physically well-defined but for which the chemical nature is either unspecified or only very vaguely indicated
  • C10M171/02—Specified values of viscosity or viscosity index
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
  • F15B21/06—Use of special fluids, e.g. liquid metal; Special adaptations of fluid-pressure systems, or control of elements therefor, to the use of such fluids
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2209/00—Organic macromolecular compounds containing oxygen as ingredients in lubricant compositions
  • C10M2209/02—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • C10M2209/08—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing monomers having an unsaturated radical bound to a carboxyl radical, e.g. acrylate type
  • C10M2209/084—Acrylate; Methacrylate
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2209/00—Organic macromolecular compounds containing oxygen as ingredients in lubricant compositions
  • C10M2209/02—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • C10M2209/08—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing monomers having an unsaturated radical bound to a carboxyl radical, e.g. acrylate type
  • C10M2209/086—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing monomers having an unsaturated radical bound to a carboxyl radical, e.g. acrylate type polycarboxylic, e.g. maleic acid
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2030/00—Specified physical or chemical properties which is improved by the additive characterising the lubricating composition, e.g. multifunctional additives
  • C10N2030/02—Pour-point; Viscosity index
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2030/00—Specified physical or chemical properties which is improved by the additive characterising the lubricating composition, e.g. multifunctional additives
  • C10N2030/54—Fuel economy
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2040/00—Specified use or application for which the lubricating composition is intended
  • C10N2040/08—Hydraulic fluids, e.g. brake-fluids

Definitions

• the present invention relates to the improvement of energy efficiency in hydraulic systems.
• Hydraulic systems are designed to transmit energy and apply large forces with a high degree of flexibility and control. It is desirable to build systems that efficiently convert input energy from an engine, electric motor, or other source into usable work. Hydraulic power can be used to create rotary or linear motion, or to store energy for future use in an actuator. Hy- draulic systems provide a significantly more accurate and adjustable means to transmit energy than electrical or mechanical systems. In general, hydraulic systems are reliable, efficient, and cost effective, leading to their wide use in the industrial world. The fluid power industry is constantly improving the cost effectiveness of hydraulic systems by employing new mechanical components and materials of construction.
• Hydraulic fluid is not a critical design element of most hydraulic systems, it is typically the last system element selected, as it is assumed that a standard monograde oil will offer sufficient performance.
• Standard "HM" monograde oil is typically selected as it is the lowest cost option and has a long history of dependable performance with no maintenance issues.
• Outdoor applications of fluid power that experience wide variations in temperature will make use of lower viscosity grade fluids in the winter and higher viscosity grade fluids in the summer.
• Some hydraulic fluids are formulated with PAMA additives as viscosity index improvers, in order to achieve good low temperature fluidity properties under cold start-up conditions ("HV" grade oils).
• HV cold start-up conditions
• the document WO 2005014762 discloses a functional fluid having an improved fire resistance.
• the fluid can be used in hydraulic systems.
• the document is silent with regard to the energy efficiency of the fluid.
• the improvement of energy efficiency is a common object in all fields of technology. Usually such objects are achieved by construction improvements of the unit providing mechanical energy of the hydraulic system, e.g. a combustion engine or an electric motor. However, there is still a need for further improvements with regard to that object.
• a further common object of the present invention is the improvement of the performance of a hydraulic system.
• the performance of a hydraulic system is improved by using a combustion engine or an electric motor having more power.
• such approach is usually connected with higher energy consumption.
• a fluid having a VI of at least 130 provides an unexpected improvement of the energy efficiency of a hydraulic system. Furthermore, the system performance of a hydraulic system can be improved in an unforeseeable manner.
• the hydraulic fluid of the present invention shows an improved low temperature performance and broader temperature operating window.
• the hydraulic fluid of the present invention can be sold on a cost favorable basis with fast investment pay-back time.
• the hydraulic fluid of the present invention exhibits good resistance to oxidation and is chemically very stable, compared to a standard HM fluid.
• the viscosity of the hydraulic fluid of the present invention can be adjusted over a broad range. Furthermore, the hydraulic fluids of the present invention are appropriate for high pressure applications. The hydraulic fluids of the present invention show a minimal change in viscosity due to good shear stability.
• the hydraulic fluid used according to the present invention has a viscosity index of at least 130, preferably at least 150, more preferably at least 180 and most preferably at least 200. According to a preferred embodiment of the present invention, the viscosity index is in the range of 150 to 400, more preferably 200 to 300. The viscosity index can be determined ac- cording to ASTM D 2270.
• the use according to the present invention provides an improvement of the energy efficiency of a hydraulic system.
• the expression energy efficiency means a better effectiveness of the energy provided to the hydraulic system in order to achieve a defined result.
• the energy consumption of the system may be lowered at least 5%, more preferably at least 10 % and more preferably at least 20%, based upon the energy consumption of a system using a monograde hydraulic fluid having a VI of about 100 and providing the same work or result of the system.
• the type of energy usually depends on the unit providing mechanical energy to the hydraulic system. Additionally, the energy consumption based upon a defined period of time can be improved.
• system performance of the hydraulic system can be improved.
• the expression system performance means the work productivity being done by the hydraulic system within a defined period of time.
• the system performance can be improved at least 5%, more preferably at least 10 % and more preferably at least 20%.
• the type of work depends on the hydraulic system. In preferred systems, the work cycles per hour are improved.
• the improvement of energy consumption and system performance can be observed at all typical engine or electrical motor operating speeds. Preferentially, the improvement of energy consumption and system performance can be determined at the about 90% of the maximum performance of the unit providing mechanical energy to the hydraulic system, e.g. 90% throttle, if a combustion engine is used.
• engine speed can be reduced to decrease load and stress while delivering the same amount of hydraulic power.
• Fluids having a viscosity index of at least 130 are well known in the art. Usually, these fluids are used, e.g. in combustion engines and gears as a lubricant oil.
• the viscosity of the hydraulic fluid of the present invention can be adapted with in wide range.
• ISO VG 15, 22, 32, 46, 68, 100, 150 fluid grades can be achieved, e.g.
• the kinematic viscosity 40 0 C according to ASTM D 445 of is the range of 15 mm 2 /s to 150 mm 2 /s, preferably 28 mm 2 /s to 110 mm 2 /s.
• preferred hydraulic fluids are NFPA (National Fluid Power Association) multigrade fluids, e.g. double, triple, quadra and/or penta grade fluids as defined by NFPA T2.13.13 -2002.
• Preferred fluids comprise at least a mineral oil and/or a synthetic oil.
• Mineral oils are substantially known and commercially available. They are in general obtained from petroleum or crude oil by distillation and/or refining and optionally additional purification and processing methods, especially the higher-boiling fractions of crude oil or petroleum fall under the concept of mineral oil. In general, the boiling point of the mineral oil is higher than 200 0 C, preferably higher than 300 0 C, at 5000 Pa. Preparation by low temperature distillation of shale oil, coking of hard coal, distillation of lignite under exclusion of air as well as hydrogenation of hard coal or lignite is likewise possible.
• mineral oils are also produced from raw materials of plant origin (for example jojoba, rape- seed (canola), sunflower, and soybean oil) or animal origin (for example tallow or neat foot oil). Accordingly, mineral oils exhibit different amounts of aromatic, cyclic, branched and linear hydrocarbons, in each case according to origin.
• paraffin-base, naphthenic and aromatic fractions in crude oil or mineral oil, where the term paraffin-base fraction stands for longer-chain or highly branched isoalkanes and naphthenic fraction stands for cycloalkanes.
• mineral oils in each case according to origin and processing, exhibit different fractions of n-alkanes, isoalkanes with a low degree of branching, so called monomethyl-branched paraffins, and compounds with heteroatoms, especially O, N and/or S, to which polar properties are attributed. How- ever, attribution is difficult, since individual alkane molecules can have both long-chain branched and cycloalkane residues and aromatic components.
• classification can be done in accordance with DIN 51 378.
• Polar components can also be determined in accordance with ASTM D 2007.
• the fraction of n-alkanes in the preferred mineral oils is less than 3 wt%, and the fraction of O, N and/or S-containing compounds is less than 6 wt%.
• the fraction of aromatic compounds and monomethyl-branched paraffins is in general in each case in the range of 0-40 wt%.
• mineral oil comprises mainly naphthenic and paraffin-base alkanes, which in general have more than 13, preferably more than 18 and especially preferably more than 20 carbon atoms.
• the fraction of these compounds is in general at least 60 wt%, preferably at least 80 wt%, without any limitation intended by this.
• a preferred mineral oil contains 0.5-30 wt% aromatic components, 15-40 wt% naphthenic components, 35-80 wt% paraffin-base components, up to 3 wt% n-alkanes and 0.05-5 wt% polar components, in each case with respect to the total weight of the mineral oil.
• the hydraulic fluid is based on mineral oil from API Group I, II, or III.
• a mineral oil containing at least 90 % by weight saturates and at most about 0.03 % sulfur measured by elemental analysis is used.
• API Group II oils are preferred.
• Synthetic oils are, among other substances, organic esters like carboxylic esters and phosphate esters; organic ethers like silicone oils and polyalkylene glycol; and synthetic hydrocarbons, especially polyolefins. They are for the most part somewhat more expensive than the mineral oils, but they have advantages with regard to performance. For an explanation reference is made to the 5 API classes of base oil types (API: American Petroleum Institute).
• Synthetic hydrocarbons especially polyolefins are well known in the art.
• polyal- phaolefins are preferred. These compounds are obtainable by polymerization of al- kenes, especially alkenes having 3 to 12 carbon atoms, like propene, hexene-1, octene-1, and dodecene-1.
• Preferred PAOs have a number average molecular weight in the range of 200 to 10000 g/mol, more preferably 500 to 5000 g/mol.
• the hydraulic fluid may comprise an oxygen containing compound selected from the group of carboxylic acid esters, poly- ether polyols and/or organophosphorus compounds.
• the oxygen containing compound is a carboxylic ester containing at least two ester groups, a diester of carboxylic acids containing 4 to 12 carbon atoms and/or a ester of a polyol.
• an oxygen containing compound as a basestock, the fire resistance of the hydraulic fluid can be improved.
• Phosphorus ester fluids can be used as a component of the hydraulic fluid such as alkyl aryl phosphate ester; trialkyl phosphates such as tributyl phosphate or tri-2-ethylhexyl phosphate; triaryl phosphates such as mixed isopropylphenyl phosphates, mixed t-butylphenyl phosphates, trixylenyl phosphate, or tricresylphosphate.
• Additional classes of organophosphorus compounds are phosphonates and phosphinates, which may contain alkyl and/or aryl substituents.
• Dialkyl phosphonates such as di-2-elhylhexylphosphonate; alkyl phosphinates such as di-2-elhylhexylphosphinate are useful.
• alkyl group herein linear or branched chain alkyls comprising 1 to 10 carbon atoms are preferred.
• aryl group herein aryls comprising 6 to 10 carbon atoms that maybe substituted by alkyls are preferred.
• the hydraulic fluids may contain 0 to 60 % by weight, preferably 5 to 50% by weight organophosphorus compounds.
• carboxylic acid esters reaction products of alcohols such as polyhydric alcohol, monohydric alcohol and the like, and fatty acids such as mono carboxylic acid, poly carboxylic acid and the like can be used.
• Such carboxylic acid esters can of course be a partial ester.
• Carboxylic acid esters may have one carboxylic ester group having the formula R-COO-R, wherein R is independently a group comprising 1 to 40 carbon atoms.
• Preferred ester compounds comprise at least two ester groups. These compounds may be based on poly carboxylic acids having at least two acidic groups and/or polyols having at least two hydroxyl groups.
• the poly carboxylic acid residue usually has 2 to 40, preferably 4 to 24, especially 4 to 12 carbon atoms.
• Useful polycarboxylic acids esters are, e.g., esters of adipic, azelaic, sebacic, phthalate and/or dodecanoic acids.
• the alcohol component of the polycarboxylic acid com- pound preferably comprises 1 to 20, especially 2 to 10 carbon atoms.
• oxoalcohols can be used such as diethylene glycol, triethylene glycol, tetraethylene glycol up to decamethylene glycol.
• esters of polycarboxylic acids with alcohols comprising one hydroxyl group are described in Ullmanns Encyclopadie der Technischen Chemie, third edition, vol. 15, page 287 -292, Urban & Schwarzenber (1964)).
• Useful polyols to obtain ester compounds comprising at least two ester groups contain usually 2 to 40, preferably 4 to 22 carbon atoms.
• Examples are neopentyl glycol, diethylene glycol, dipropylene glycol, 2,2-dimethyl-3-hydroxypropyl-2',2'-dimethyl-3'-hydroxy propionate, glycerol, trimethylolethane, trimethanol propane, trimethylolnonane, ditrimethylol- propane, pentaerythritol, sorbitol, mannitol and dipentaerythritol.
• the carboxylic acid component of the polyester may contain 1 to 40, preferably 2 to 24 carbon atoms.
• linear or branched saturated fatty acids such as formic acid, acetic acid, propionic acid, oc- tanoic acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, unde- canoic acid, lauric acid, tridecanoic acid, myrisric acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, arachic acid, behenic acid, isomyiristic acid, isopalmitic acid, isostearic acid, 2,2-dimethylbutanoic acid, 2,2-dimethylpentanoic acid, 2,2-dimethyloctanoic acid, 2-ethyl-2.3,3-trimethylbutanoic acid, 2,2,3,4- tetramethylpentanoic acid, 2,5,5-trimethyl-2-t-butylhexanoic acid, 2,3,3
• Especially useful compounds comprising at least two ester groups are, e.g., neopentyl glycol tallate, neopentyl glycol dioleate, propylene glycol tallate, propylene glycol dioleate, di- ethylene glycol tallate, and diethylene glycol dioleate.
• ethers are useful as a component of the hydraulic fluid.
• polyether polyols are used as a component of the hydraulic fluid of the present invention. These compounds are well known. Examples are polyalkylene glycols like, e.g., polyethylene glycols, polypropylene glycols and polybutylene glycols.
• the polyalkylene glycols can be based on mixtures of alkylene oxides. These compounds preferably comprise 1 to 40 alkylene oxide units, more preferably 5 to 30 alkylene oxide units.
• Polybutylene glycols are preferred com- pounds for anhydrous fluids.
• the polyether polyols may comprise further groups, like e.g., alkylene or arylene groups comprising 1 to 40, especially 2 to 22 carbon atoms.
• the hydraulic fluid is based on a synthetic basestock comprising polyalphaolefin (PAO), carboxylic esters (diester, or polyol es- ter), a vegetable ester, phosphate ester (trialkyl, triaryl, or alkyl aryl phosphates), and/or polyalkylene glycol (PAG).
• Preferred synthetic basestocks are API Group IV and/or Group V oils.
• the hydraulic fluid is obtainable by mixing at least two components.
• At least one of the components shall be a base oil with a kinematic viscosity at 40 0 C according to ASTM D 445 of 35 mm 2 /s or less.
• the hydraulic fluid comprises at least 60 % by weight of at least one component having a kinematic viscosity at 40 0 C according to ASTM D 445 of 35 mm 2 /s or less.
• at least one of the components may have a viscosity index of 120 or less.
• the hydraulic fluid may comprise at least 60 % by weight of at least one component having a viscosity index of 120 or less.
• a polymeric viscosity index improver can be used as a component of the hydraulic fluid.
• Viscosity index improvers are well known and, e.g. disclosed in Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition on CD-ROM, 1997.
• Preferred polymers useful as VI improvers comprise units derived from alkyl esters having at least one ethylenically unsaturated group. These polymers are well known in the art. Preferred polymers are obtainable by polymerizing, in particular, (meth)acrylates, maleates and fumarates. The term (meth)acrylates includes methacrylates and acrylates as well as mix- tures of the two. These monomers are well known in the art.
• the alkyl residue can be linear, cyclic or branched.
• Mixtures to obtain preferred polymers comprising units derived from alkyl esters contain 0 to 100 wt%, preferably 0,5 to 90 wt%, especially 1 to 80 wt%, more preferably 1 to 30 wt%, more preferably 2 to 20 wt% based on the total weight of the monomer mixture of one or more ethylenically unsaturated ester compounds of formula (I)
• R is hydrogen or methyl
• R 1 means a linear or branched alkyl residue with 1-6, especially 1 to 5 and preferably 1 to 3 carbon atoms
• R 2 and R 3 are independently hydrogen or a group of the formula -COOR, where R means hydrogen or an alkyl group with 1-6 carbon atoms.
• component (a) are, among others, (meth)acrylates, fumarates and maleates, which derived from saturated alcohols such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate and hexyl (meth)acrylate; cycloalkyl (meth)acrylates, like cyclopentyl (meth)acrylate.
• saturated alcohols such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate and hexyl (me
• the monomer compositions to obtain the polymers comprising units derived from alkyl esters contain 0 - 100 wt%, preferably 10-99 wt%, especially 20-95 wt% and more preferably 30 to 85 wt% based on the total weight of the monomer mixture of one or more ethylenically unsaturated ester compounds of formula (II)
• R is hydrogen or methyl
• R 4 means a linear or branched alkyl residue with 7-40, especially 10 to 30 and preferably 12 to 24 carbon atoms
• R 5 and R 6 are independently hydrogen or a group of the formula -COOR", where R" means hydrogen or an alkyl group with 7 to 40, especially 10 to 30 and preferably 12 to 24 carbon atoms.
• (meth)acrylates, fumarates and maleates that derive from saturated alcohols such as 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, 2-tert-butylheptyl (meth)acrylate, octyl (meth)acrylate, 3-isopropylheptyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, 5-methylundecyl (meth)acrylate, dodecyl (meth)acrylate, 2-methyldodecyl (meth)acrylate, tridecyl (meth)acrylate, 5-methyltridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, 2-methylhexadecyl (meth)acrylate, heptadecyl
• the ester compounds with a long-chain alcohol residue, especially component (b), can be obtained, for example, by reacting (meth)acrylates, fumarates, maleates and/or the corresponding acids with long chain fatty alcohols, where in general a mixture of esters such as (meth)acrylates with different long chain alcohol residues results.
• These fatty alcohols include, among others, Oxo Alcohol® 7911 and Oxo Alcohol ® 7900, Oxo Alcohol® 1100 (Monsanto); Alphanol® 79 (ICI); Nafol® 1620, Alfol® 610 and Alfol® 810 (Sasol); Epal® 610 and Epal® 810 (Ethyl Corporation); Linevol® 79, Linevol® 911 and Dobanol® 25L (Shell AG); Lial 125 (Sasol); Dehydad® and Dehydad® and Lorol® (Cognis).
• the (meth)acrylates are particularly preferred over the maleates and furmarates, i.e., R 2 , R 3 , R 5 , R 6 of formulas (I) and (II) represent hydrogen in particularly preferred embodiments.
• mixtures of ethylenically unsaturated ester compounds of formula (II) preference is given to using mixtures of ethylenically unsaturated ester compounds of formula (II), and the mixtures have at least one (meth)acrylate having from 7 to 15 carbon atoms in the alcohol radical and at least one (meth) acrylate having from 16 to 30 carbon atoms in the alcohol radical.
• the fraction of the (meth)acrylates having from 7 to 15 carbon atoms in the alcohol radical is preferably in the range from 20 to 95% by weight, based on the weight of the monomer composition for the preparation of polymers.
• the fraction of the (meth)acrylates having from 16 to 30 carbon atoms in the alcohol radical is preferably in the range from 0.5 to 60% by weight based on the weight of the monomer composition for the preparation of the polymers comprising units derived from alkyl esters.
• the weight ratio of the (meth)acrylate having from 7 to 15 carbon atoms in the alcohol radical and the (meth) acrylate having from 16 to 30 carbon at- oms in the alcohol radical is preferably in the range of 10: 1 to 1:10, more preferably in the range of 5:1 to 1,5:1.
• Component (c) comprises in particular ethylenically unsaturated monomers that can co- polymerize with the ethylenically unsaturated ester compounds of formula (I) and/or (II).
• the comonomers include, among others, hydroxyalkyl (meth)acrylates like 3-hydroxypropyl (meth)acrylate, 3,4-dihydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2- hydroxypropyl (meth)acrylate, 2,5-dimethyl-l,6-hexanediol (meth)acrylate, 1,10-decanediol (meth)acrylate;
• aminoalkyl (meth)acrylates and aminoalkyl (meth)acrylamides like N-(3- dimethylaminopropyl)methacrylamide, 3-diethylaminopentyl (meth)acrylate, 3- dibutylaminohexadecyl (meth)acrylate;
• nitriles of (meth)acrylic acid and other nitrogen-containing (meth)acrylates like N- (methacryloyloxyethyl)diisobutylketimine, N-(methacryloyloxyethyl)dihexadecylketimine, (meth)acryloylamidoacetonitrile, 2-methacryloyloxyethylmethylcyanamide, cyanomethyl (meth)acrylate;
• aryl (meth)acrylates like benzyl (meth)acrylate or phenyl (meth)acrylate, where the acryl residue in each case can be unsubstituted or substituted up to four times;
• carbonyl-containing (meth)acrylates like 2-carboxyethyl (meth)acrylate, carboxymethyl (meth)acrylate, oxazolidinylethyl (meth)acrylate,
• (meth)acrylates of halogenated alcohols like 2,3-dibromopropyl (meth)acrylate, A- bromophenyl (meth)acrylate, l,3-dichloro-2-propyl (meth)acrylate, 2-bromoethyl (meth)acrylate, 2-iodoethyl (meth)acrylate, chloromethyl (meth)acrylate;
• oxiranyl (meth)acrylate like 2, 3-epoxybutyl (meth)acrylate, 3,4-epoxybutyl (meth)acrylate, 10,11 epoxyundecyl (meth)acrylate, 2,3-epoxycyclohexyl (meth)acrylate, oxiranyl (meth)acrylates such as 10,11-epoxyhexadecyl (meth)acrylate, glycidyl (meth)acrylate;
• phosphorus-, boron- and/or silicon-containing (meth)acrylates like 2- (dimethylphosphato)propyl (meth)acrylate, 2-(ethylphosphito)propyl (meth)acrylate, 2- dimethylphosphinomethyl (meth)acrylate, dimethylphosphonoethyl (meth)acrylate, diethyl- methacryloyl phosphonate, dipropylmethacryloyl phosphate, 2-(dibutylphosphono)ethyl (meth)acrylate, 2,3-butylenemethacryloylethyl borate, methyldiethoxymethacryloylethoxysil- iane, diethylphosphatoethyl (meth)acrylate;
• sulfur-containing (meth)acrylates like ethylsulfinylethyl (meth)acrylate, 4-thiocyanatobutyl (meth)acrylate, ethylsulfonylethyl (meth)acrylate, thiocyanatomethyl (meth)acrylate, methyl- sulfinylmethyl (meth)acrylate, bis(methacryloyloxyethyl) sulfide; heterocyclic (meth)acrylates like 2-(l-imidazolyl)ethyl (meth)acrylate, 2-(4- morpholinyl)ethyl (meth)acrylate and l-(2-methacryloyloxyethyl)-2-pyrrolidone;
• vinyl halides such as, for example, vinyl chloride, vinyl fluoride, vinylidene chloride and vi- nylidene fluoride;
• heterocyclic vinyl compounds like 2-vinylpyridine, 3-vinylpyridine, 2-methyl-5- vinylpyridine, 3-ethyl-4-vinylpyridine, 2,3-dimethyl-5-vinylpyridine, vinylpyrimidine, vi- nylpiperidine, 9-vinylcarbazole, 3-vinylcarbazole, 4-vinylcarbazole, 1-vinylimidazole, 2- methyl-1-vinylimidazole, N-vinylpyrrolidone, 2-vinylpyrrolidone, N-vinylpyrrolidine, 3- vinylpyrrolidine, N-vinylcaprolactam, N- vinylbutyro lactam, vinyloxolane, vinylfuran, vinyl- thiophene, vinylthiolane, vinylthiazoles and hydrogenated vinylthiazoles, vinyloxazoles and hydrogenated vinyloxazoles;
• maleic acid derivatives such as maleic anhydride, methylmaleic anhydride, maleinimide, me- thylmaleinimide;
• fumaric acid and fumaric acid derivatives such as, for example, mono- and diesters of fu- marie acid.
• Monomers that have dispersing functionality can also be used as comonomers. These monomers are well known in the art and contain usually hetero atoms such as oxygen and/or nitrogen.
• hetero atoms such as oxygen and/or nitrogen.
• hydroxyalkyl (meth)acrylates, ami- noalkyl (meth)acrylates and aminoalkyl (meth)acrylamides, (meth)acrylates of ether alcohols, heterocyclic (meth)acrylates and heterocyclic vinyl compounds are considered as dispersing comononers.
• Especially preferred mixtures contain methyl methacrylate, lauryl methacrylate and/or stearyl methacrylate.
• the components can be used individually or as mixtures.
• the hydraulic fluid of the present invention preferably comprises polyalkylmethacrylate polymers.
• polyalkylmethacrylate polymers obtainable by polymerizing compositions comprising alkyl- methacrylate monomers are well known in the art.
• these polyalkylmethacrylate polymers comprise at least 40 % by weight, especially at least 50 % by weight, more preferably at least 60 % by weight and most preferably at least 80 % by weight methacrylate repeating units.
• these polyalkylmethacrylate polymers comprise C 9 -C24 methacry- late repeating units and Ci-Cs methacrylate repeating units.
• the molecular weight of the polymers derived from alkyl esters is not critical. Usually the polymers derived from alkyl esters have a molecular weight in the range of 300 to 1,000,000 g/mol, preferably in the range of range of 10000 to 200,000 g/mol and more preferably in the range of 25000 to 100,000 g/mol, without any limitation intended by this. These values refer to the weight average molecular weight of the polymers.
• the alkyl(meth)acrylate polymers exhibit a polydis- persity, given by the ratio of the weight average molecular weight to the number average molecular weight Mw/Mn, in the range of 1 to 15, preferably 1.1 to 10, especially prefera- bly 1.2 to 5.
• the polydispersity may be determined by gel permeation chromatography (GPC).
• the monomer mixtures described above can be polymerized by any known method.
• Con- ventional radical initiators can be used to perform a classic radical polymerization. These initiators are well known in the art. Examples for these radical initiators are azo initiators like 2,2'-azodiisobutyronitrile (AIBN), 2,2'-azobis(2-methylbutyronitrile) and 1,1 azo- biscyclohexane carbonitrile; peroxide compounds, e.g. methyl ethyl ketone peroxide, acetyl acetone peroxide, dilauryl peroxide, tert.
• AIBN 2,2'-azodiisobutyronitrile
• 2-methylbutyronitrile 2,2'-azobis(2-methylbutyronitrile)
• 1,1 azo- biscyclohexane carbonitrile 1,1 azo- biscyclohexane carbonitrile
• peroxide compounds e.g. methyl ethyl
• Chain transfer agents Low molecular weight poly(meth)acrylates can be obtained by using chain transfer agents. This technology is ubiquitously known and practiced in the polymer industry and is described in Odian, Principles of Polymerization, 1991.
• chain transfer agents are sulfur containing compounds such as thiols, e.g. n- and t - dodecanethiol, 2- mercaptoethanol, and mercapto carboxylic acid esters, e.g. methyl-3-mercaptopropionate.
• Preferred chain transfer agents contain up to 20, especially up to 15 and more preferably up to 12 carbon atoms.
• chain transfer agents may contain at least 1, especially at least 2 oxygen atoms.
• the low molecular weight poly(meth)acrylates can be obtained by using transition metal complexes, such as low spin cobalt complexes.
• transition metal complexes such as low spin cobalt complexes.
• novel polymerization techniques such as ATRP (Atom Transfer Radical Polymerization) and or RAFT (Reversible Addition Fragmentation Chain Transfer) can be applied to obtain useful polymers derived from alkyl esters. These methods are well known.
• ATRP Atom Transfer Radical Polymerization
• RAFT Reversible Addition Fragmentation Chain Transfer
• the polymerization can be carried out at normal pressure, reduced pressure or elevated pressure.
• the polymerization temperature is also not critical. However, in general it lies in the range of -20-200 0 C, preferably 0-130 0 C and especially preferably 60-120 0 C, without any limitation intended by this.
• the polymerization can be carried out with or without solvents.
• solvent is to be broadly understood here.
• the polymer is obtainable by a polymerization in API Group II or Group III mineral oil. These solvents are disclosed above.
• PAO polyalphaolefin
• the PAO has a number average molecular weight in the range of 200 to 10000, more preferably 500 to 5000. This solvent is disclosed above.
• the hydraulic fluid may comprise 0.5 to 50 % by weight, especially 1 to 30 % by weight, and preferably 5 to 20% by weight, based on the total weight of the fluid, of one or more polymers derived from alkyl esters.
• the hydraulic fluid comprises at least 10 % by weight of one or more polymers derived from alkyl esters.
• the fluid may comprise at least two polymers having a different monomer composition.
• at least one of the polymers is a polyolefin.
• the polyolefin is useful as a viscosity index improver.
• polyolefins include in particular polyolefin copolymers (OCP) and hydrogenated sty- rene/diene copolymers (HSD).
• OCP polyolefin copolymers
• HSD hydrogenated sty- rene/diene copolymers
• the polyolefin copolymers (OCP) to be used according to the invention are known per se. They are primarily polymers synthesized from ethylene, propylene, isoprene, butylene and/or further olefins having 5 to 20 carbon atoms. Systems which have been grafted with small amounts of oxygen- or nitrogen-containing monomers (e.g. from 0.05 to 5% by weight of maleic anhydride) may also be used.
• the copolymers which contain diene components are generally hydrogenated in order to reduce the oxida- tion sensitivity and the crosslinking tendency of the viscosity index improvers.
• the molecular weight Mw is in general from 10 000 to 300 000, preferably between 50 000 and 150 000.
• Such olefin copolymers are described, for example, in the German Laid-Open Applications DE-A 16 44 941, DE-A 17 69 834, DE-A 19 39 037, DE-A 19 63 039, and DE-A 20 59 981.
• Ethylene/propylene copolymers are particularly useful and terpolymers having the known ternary components, such as ethylidene-norbornene (cf. Macromolecular Reviews, Vol. 10 (1975)) are also possible, but their tendency to crosslink must also be taken into account in the aging process.
• the distribution may be substantially random, but sequential polymers comprising ethylene blocks can also advantageously be used.
• the ratio of the monomers ethylene/propylene is variable within certain limits, which can be set to about 75% for ethylene and about 80% for propylene as an upper limit. Owing to its reduced tendency to dissolve in oil, polypropylene is less suitable than ethylene/propylene copolymers. In addi- tion to polymers having a predominantly atactic propylene incorporation, those having a more pronounced isotactic or syndiotactic propylene incorporation may also be used.
• Such products are commercially available, for example under the trade names Dutral® CO 034, Dutral® CO 038, Dutral® CO 043, Dutral® CO 058, Buna® EPG 2050 or Buna® EPG 5050.
• the hydrogenated styrene/diene copolymers are likewise known, these polymers being described, for example, in DE 21 56 122. They are in general hydrogenated iso- prene/styrene or butadiene/styrene copolymers.
• the ratio of diene to styrene is preferably in the range from 2:1 to 1:2, particularly preferably about 55:45.
• the molecular weight Mw is in general from 10000 to 300 000, preferably between 50000 and 150000.
• the proportion of double bonds after the hydro- genation is not more than 15%, particularly preferably not more than 5%, based on the number of double bonds before the hydrogenation.
• Hydrogenated styrene/diene copolymers can be commercially obtained under the trade name SHELLVIS® 50, 150, 200, 250 or 260.
• At least one of the polymers of the mixture comprises units derived from monomers selected from acrylate monomers, methacrylate monomers, fumarate monomers and/or maleate monomers. These polymers are described above.
• the weight ratio of the polyolefin and the polymer comprises units derived from monomers selected from acrylate monomers, methacrylate monomers, fumarate monomers and/or maleate monomers may be in the range of 1:10 to 10:1, especially 1:5 to 5:1.
• the hydraulic fluid may comprise usual additives. These additive include e.g. antioxidants, antiwear agents, corrosion inhibitors and/or defoamers, often purchased as a commercial additive package.
• the hydraulic fluid has a viscosity according to ASTM D 445 at 40°C in the range of 10 to 120 mm 2 /s, more preferably 22 to 100 mm 2 /s.
• the hydraulic system includes the following components:
• a unit creating mechanical energy e.g. a combustion engine or an electrical motor.
• a fluid flow or force-generating unit that converts mechanical energy into hydraulic energy, such as a pump.
• Piping for transmitting fluid under pressure 4.
• a unit that converts the hydraulic energy of the fluid into mechanical work such as an actuator or fluid motor.
• motors There are two types of motors, cylindrical and rotary.
• a control circuit with valves that regulate flow, pressure, direction of movement, and applied forces.
• a fluid reservoir that allows for separation of water, foam, entrained air, or debris be- fore the clean fluid is returned to the system through a filter.
• a liquid with low compressibility capable of operating without degradation under the conditions of the application (temperature, pressure, radiation).
• the system may be operated at high pressures.
• the improvement of the present invention can be achieved at pressures in the range of 50 to 500 bar, preferably 100 to 350 bar.
• the fluid is used in military hydraulic systems, in hydraulic launch assist systems, in industrial, marine, mining and/or mobile equipment hydraulic systems.
• the present invention provides a hydraulic system comprising a hydraulic fluid having a VI of at least 130, a unit for creating mechanical power, a unit that converts me- chanical power into hydraulic energy, and a unit that converts hydraulic energy into mechanical work.
• engine speed can be reduced to decrease load and stress while delivering the same amount of hydraulic power.
• the mechanical power output of the engine or electrical motor can be operated at less than 98% of its full power capacity to deliver the same amount of hydraulic power as the hydraulic system utilizing an HM grade fluid with a viscosity index less than 120.
• a field test was conducted comparing fuel consumption rates in a 2001 Caterpillar model 318CL hydraulic excavator. Hydraulic flow is generated by a dual piston pump feeding 2 rotary motors to drive the tracks, 1 rotary motor to power the swivel, and 3 linear actuators to power the boom, swivel and bucket.
• a standardized work protocol was developed which involved moving a pile of loose earth 100 feet. The excavator takes a full scoop of earth, the cab rotates 180 degrees, and travels at full speed in a straight line to dump the bucket. After dumping the load, the cab rotates back 180 degrees and returns in the same track back to the starting point. This completes one work cycle. Diesel fuel consumption was measured for a work day that progressed according to the following schedule:
• the monograde oil was then exchanged for "HV" multigrade oil following a triple flush procedure.
• the multigrade oil was an NFPA grade L32-100, which is an appropriate replacement for this monograde oil according to NFPA recommended practice T2.13.13-2002.
• the same work protocol was then followed at both full throttle and 90% throttle, measuring the total number of work cycles and total fuel consumption.
• the example 1 was performed at full throttle and example 2 was performed at 90% throttle. The results are shown in Table 1.
• the NFPA quadra grade fluid used in this test was formulated from a blend of Group I and Group II mineral oil, plus the Dynavis® additive system (from Degussa — RohMax Oil Addi- tives).
• the Dynavis* 1 additive system consists of a shear stable polyalkylmethacrylate viscosity index improver (VISCOPLEX® 8-219) manufactured and diluted in Group II mineral oil,
• the formulation contained Group II PAMA additive at 16 weight percent, and a zinc based antiwear package at 0.8 weight percent, which enables the fluid to meet the major global performance standards. This extremely high treat rate of PAMA is unusual and not found in any commercial hydraulic fluid.

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