HIGH VISCOSITY POLYACRYLATE BASE FLUIDS

Abstract

The present invention relates to low molecular weight polyalkyl acrylate polymers, a process for their preparation, and their use as high-viscosity base fluids. The present invention further relates to lubricating compositions comprising such low molecular weight polyalkyl acrylate polymers and to the use of such compositions as automatic transmission fluids, manual transmission fluids, continuously variable transmission fluids, gear oil formulations, industrial gear oil formulations, axle fluid formulations, dual-clutch transmission fluids, dedicated hybrid transmission fluids, or as hydraulic oils.

Description

HIGH VISCOSITY POLYACRYLATE BASE FLUIDS IVIA / a / ZUZZ / UU 11OO The present invention relates to low molecular weight polyalkyl acrylate polymers, a process for their preparation, and their use as high-viscosity base fluids. It also relates to lubricating compositions comprising such low molecular weight polyalkyl acrylate polymers and to the use of such compositions as automatic transmission fluids, manual transmission fluids, continuously variable transmission fluids, gear oil formulations, industrial gear oil formulations, axle fluid formulations, dual-clutch transmission fluids, dedicated hybrid transmission fluids, or as hydraulic oils. High-viscosity base fluids are commonly used to increase the viscosity index (VI) and thicken lubricant formulations with demanding shear stability requirements. A typical application is in gear oils, which have very stringent requirements due to high mechanical stress and a wide operating temperature range. High viscosity base fluids are known to have a kinematic viscosity at 100 °C (KV100) of 30 to 1000 cSt. Industrial gearboxes are expected to operate under high temperatures and heavy loads, and in environments often contaminated with dirt, process residues, and water. Without proper protection, the gears will wear out prematurely. This means certain parts will need to be replaced more frequently, the oil will need to be changed more often, and worst of all, equipment downtime is expected. Today's gear-driven equipment is designed to operate in a wide range of applications and often has to withstand harsh environments. Gearboxes are typically becoming smaller and are manufactured from lighter, more sophisticated materials, yet they must be more durable than ever. As a result, greater demands are placed on gear oil lubricants, and more attention must be paid to the use of high-performance base fluids and additives. Typical products in this market are high-viscosity polyalphaolefins (PAOs) and metallocene-catalyzed PAOs (mPAOs), which are usually sold in viscosity ranges from 40 to 300 cSt at 100 °C (Choudary et al. Lubr. Sci. 2012, 2344). High-viscosity PAO-based formulations are known to have the best low-temperature performance, but their weakness is low polarity. Due to the nonpolar nature of PAO base oils, dispersion inhibitor (DI) packs and aging products dissolve poorly in the oil, leading to various problems. Higher polarity is provided by alpha-olefin copolymers with maleates (US 5,435,928), alpha-olefin oligomers with alkyl acrylates (US 3,968,148), or alpha-olefin copolymers with alkyl methacrylates (US 5,691,284). Alternatively, PAOs with ester-functionalized monomers (EP2970532) or polyvinyl ethers (US 2013 / 0165360) can be applied. A major advantage of using high-viscosity polar base fluids is that low-viscosity polar fluids, such as esters, should not be used as compatibilizers for the DI pack. Low-viscosity polar fluids are known to cause problems with linings and seals, which is less of an issue with high-viscosity fluids. Another class of high-viscosity base fluids are polyalkyl (meth)acrylates (PAMA) (US 2013 / 229016). PAMAs are well known for their use as viscosity index (VI) improvers in lubricants and can be adjusted to achieve the highest performance level. US patent 2013 / 229016 is directed to lubricants for transmission systems and wind power plants, comprising at least 30% by weight of polyalkyl methacrylate. The working examples described all consist of methacrylates containing alkyl side chains with a minimum of 10 carbon atoms. Pure alkyl acrylates are not disclosed. Alkyl acrylates are not used in viscosity index (VI) improver applications. Although literature exists (Rashad et al. J. of Petr. Sci. and Engineering 2012, 173-177; Evin et al. J. of Sol. Chem 1994, 325-338) and patents (WO 96 / 17517), it is generally known that the performance of polyacrylates as VI improvers is inferior to that of polymethacrylates. Specifically, patent WO 96 / 17517 mentions the unexpected discovery that poly(alkyl acrylate) esters typically fail to adequately reduce the effect of temperature on viscosity when used in hydraulic fluids. Branched alcohols are commonly used in the preparation of PAMA VI enhancers. Among others, long-chain monobranched Guerbet alcohols are known to be one of the classes of alcohols that provide a favorable branching pattern for use as VI enhancers (US 2004 / 0077509). Branching inhibits the crystallization of alcohols; and when incorporated into a polymer, it will prevent the polymer chains from crystallizing. Short-chain alcohols with branching patterns, such as ethylhexanol and propylheptanol, are accessible via a reaction sequence involving hydroformylation and aldol condensation, starting from propene or butene, respectively. These alcohols are commercially attractive because they are produced on a large industrial scale for a variety of applications. The use of polymers comprising ethylhexyl methacrylate (EP 0 937 769) and / or propylheptyl methacrylate (US 2012 / 245068) as PAMA VI enhancers is described in the literature. It has now been surprisingly discovered that high viscosity base fluids prepared from low molecular weight polyalkyl acrylates behave remarkably differently than low molecular weight polyalkyl methacrylates. Polyalkyl acrylates comprising at least 95% by weight of acrylates exhibit excellent oil solubility, even at lower temperatures, compared to the corresponding polyalkyl methacrylates, although polyalkyl acrylates have a lower carbon-to-oxygen ratio. Therefore, a first object of the present invention relates to polyalkyl acrylates, comprising: (a) 95 to 100% by weight of branched C8-ium alkyl acrylates; and (b) 0 to 5% by weight of C1-20 alkyl (meth)acrylates, characterized in that the weight average molecular weight is in the range of 7,000 to 25,000 g / mol and the residual monomer content is 0.1% or less. The content of each component (a) and (b) is based on the total composition of polyalkyl acrylate. In a particular embodiment, the proportions of components (a) and (b) add up to 100% by weight. The molar ratio of carbon to oxygen in polyalkyl acrylates is preferably in the range of 4.5:1 to 7.5:1, more preferably in the range of 5:1 to 7:1, and even more preferably in the range of 5.5:1 to 6.5:1. The weight average molecular weight Mw of the polyalkyl acrylate polymers according to the present invention is preferably in the range of 10,000 to 20,000 g / mol. Preferably, the polyalkyl acrylate polymers according to the present invention have a polydispersity index (PDI) Mw / Mn in the range of 1.5 to 3.5, more preferably in the range of 1.5 to 3. Mwy Mnse are determined by size exclusion chromatography (SEO) using commercially available polymethyl methacrylate standards. The determination is affected by gel permeation chromatography with THF as the eluent. The term acrylate refers to esters of acrylic acid; the term (meth)acrylate refers to both esters of acrylic acid and esters of methacrylic acid. Branched Cs-ium alkyl acrylates for use according to the invention are esters of acrylic acid and branched alcohols having 8 to 10 carbon atoms. The term Cs-ium alkyl acrylates encompasses individual acrylic esters with an alcohol of a certain carbon chain length, as well as mixtures of acrylic esters with alcohols of different carbon chain lengths. Suitable branched C8w alkyl acrylates include, for example, 2-ethylhexyl acrylate, 3-isopropylheptyl acrylate, and / so-decyl acrylate. The C1-20 alkyl (meth)acrylates for use according to the invention are esters of (meth)acrylic acid and linear or branched-chain alcohols having from 1 to 20 carbon atoms and are different from the branched C8-10 alkyl acrylates as described above. The term C1-20 alkyl methacrylates encompasses individual (meth)acrylic esters with an alcohol of a certain chain length, as well as mixtures of (meth)acrylic esters with alcohols of different chain lengths. Suitable C1-20 alkyl (meth)acrylates include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, so-propyl (meth)acrylate, n-butyl (meth)acrylate, so-butyl (meth)acrylate, terebutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (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, and so on. 5-methyltridecyl, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate and eicosyl (meth)acrylate. Another first object of the present invention is directed to polyalkyl acrylates, which consist of 100% by weight of branched Cs-w alkyl acrylates. Another first object of the present invention is directed to polyalkyl acrylates, wherein the Cs-io alkyl acrylate is selected from the group consisting of ethylhexyl acrylate and propylheptyl acrylate. Another first object of the present invention is directed to polyalkyl acrylates, wherein the Cs-io alkyl acrylate is ethylhexyl acrylate. Another first object of the present invention relates to polyethylenehexyl acrylate, which has a weight average molecular weight in the range of 10,000 to 20,000 g / mol and is characterized by a residual monomer content of 0.1% or less. A second object of the present invention is directed to the use of polyalkyl acrylates, as described above in this document, as base oils in lubricant formulations, especially in formulations of oils for industrial gears. The use is primarily directed towards the preparation of ISO 220 formulations or ISO 320 formulations, in which the KV4o of the lubricant formulation is 220 mm2 / s ± 10% or 320 mm2 / s ± 10%, respectively. The ISO 220 formulation prepared in this way is characterized by a VI of 125 or higher, preferably in the range of 130 to 150. The ISO 320 formulation prepared in this way is characterized by a VI of 140 or higher, preferably in the range of 150 to 180. A second object of the present invention is directed to a method for lubricating an industrial gear, comprising the steps of: (i) use at least one polyalkyl acrylate as described above as a base oil; (i) optionally combining the polyalkyl acrylate with another base oil selected from the group consisting of Group II API oils, Group III API oils, Group IV API oils and mixtures thereof; and (iii) applying the formulation prepared according to (i) to an industrial gear. A third object of the present invention is directed to a base oil composition, comprising: (A) 70 to 95% by weight of at least one polyalkyl acrylate, comprising: (a) 95 to 100% by weight of branched Ce-w alkyl acrylates; and (b) 0 to 5% by weight of C1-20 alkyl (meth)acrylates, characterized in that the weight average molecular weight is in the range of 7,000 to 25,000 g / mol and the residual monomer content is 0.1% or less; and (B) 5 to 30% by weight of a base oil selected from the group consisting of Group II API oils, Group III API oils, Group IV API oils and mixtures thereof. The content of each component (a) and (b) is based on the total weight of the base oil composition. In one particular embodiment, the proportions of components (A) and (B) add up to 100% by weight. The content of each component (a) and (b) is based on the total composition of polyalkyl acrylate. In a particular embodiment, the proportions of components (a) and (b) add up to 100% by weight. Another third object of the present invention relates to a base oil composition, wherein the polyalkyl acrylates (A) consist of 100% by weight of branched Cs-w alkyl acrylates. Another third object of the present invention relates to a base oil composition, wherein the alkyl acrylate Cs w is selected from the group consisting of ethylhexyl acrylate and propylheptyl acrylate. Another third object of the present invention relates to a base oil composition, wherein the alkyl acrylate Cs w is ethylhexyl acrylate. A third object of the present invention relates to a base oil composition comprising: (A) 70 to 95% by weight of polyethylenehexyl acrylate, having a weight average molecular weight in the range of 10,000 to 20,000 g / mol and characterized by a residual monomer content of 0.1% or less; and (B) 5 to 30% by weight of a base oil selected from the group consisting of Group II API oils, Group III API oils, Group IV API oils and mixtures thereof. A fourth object of the present invention is directed to the use of a base oil composition as described above for the preparation of an industrial gear oil. Another fourth object of the present invention relates to a process for preparing an industrial gear oil composition, the process comprising: combining 70 to 95% by weight of at least one polyalkyl acrylate, comprising: (a) 95 to 100% by weight of branched Cs-w alkyl acrylates; and (b) 0 to 5% by weight of C1-20 alkyl (meth)acrylates, characterized in that the weight average molecular weight is in the range of 7,000 to 25,000 g / mol and the residual monomer content is 0.1% or less, with up to 30% by weight of a base oil selected from the group consisting of Group II API oils, Group III API oils, Group IV API oils and mixtures thereof. Another fourth object of the present invention is directed to a method for lubricating an industrial gear, comprising the steps of: (i) prepare a base oil composition as described above; and (ii) apply the base oil composition prepared according to (i) to an industrial gear. A fifth object of the present invention is directed to a lubricating composition, comprising: (A) 20 to 60% by weight of at least one polyalkyl acrylate, comprising: (a) 95 to 100% by weight of branched Ce w alkyl acrylates; and (b) 0 to 5% by weight of C1-20 alkyl (meth)acrylates, characterized in that the weight average molecular weight is in the range of 7,000 to 25,000 g / mol and the residual monomer content is 0.1% or less; (B) 40 to 80% by weight of a base oil selected from the group consisting of Group II API oils, Group III API oils, Group IV API oils and mixtures thereof; and (C) 0 to 5% by weight of one or more additives. The content of each component (A), (B), and (C) is based on the total weight of the lubricant composition. In one particular embodiment, the proportions of components (A), (B), and (C) add up to 100% by weight. The content of each component (a) and (b) is based on the total composition of polyalkyl acrylate. In a particular embodiment, the proportions of components (a) and (b) add up to 100% by weight. In nonpolar formulations based on Group II, III, and IV base oils and polyolefin thickeners, it is common practice to add a Group V base oil, such as esters or alkylated naphthalenes, to dissolve the additives. Due to the solvency provided by the highly polar polyacrylates of the present invention, no additional compatibilizer is added to the formulations described herein. MA / a / ¿u¿¿ / uu / 100 invention. The base oil to be used in the lubricating composition comprises an oil of lubricating viscosity. Such oils include natural and synthetic oils, oils derived from hydrocracking, hydrogenation and hydrofinishing, unrefined, refined, re-refined oils or mixtures thereof. Base oil can also be defined as specified by the American Petroleum Institute (API) (see the April 2008 version of Appendix E-API: Oil Base Interchangeability Guidelines for Passenger Car Motor Oils and Diesel Engine Oils, section 1.3 Subheading 1.3. Base Stock Categories). The API currently defines five groups of base stock lubricants (API 1509, Appendix E: API Base Oil Interchangeability Guidelines for Passenger Car Motor Oils and Diesel Engine Oils, September 2011). Groups I, II, and III are mineral oils, classified by their saturate and sulfur content and viscosity indices; Group IV consists of polyalphaolefins; and Group V includes all other oils, such as ester oils. The following table illustrates these API classifications. Saturated Group Sulfur content Viscosity index (VI) I < 90% 0.03% 80-120 II at least 90% not more than 0.03% 80-120 III at least 90% not more than 0.03% at least 120 IV All polyalphaolefins (PAOs) V All others not included in Groups I, II, III or IV (e.g. ester oils) The kinematic viscosity at 100 °C (KVi00) of the appropriate nonpolar base oils used to prepare a lubricating composition according to the present invention is preferably in the range of 5 mm2 / s to 15 mm2 / s, more preferably in the range of 6 mm2 / s to 113 mm2 / s, and even more preferably in the range of 8 mm2 / s to 12 mm2 / s, as determined in accordance with ASTM D445. The particularly preferred lubricants of the present invention comprise at least one base oil selected from the group consisting of Group II API oils, Group III API oils, polyalphaolefins (PAOs), and mixtures thereof. Other base oils that can be used according to the present invention are the Fischer-Tropsch Group II-III base oils. Fischer-Tropsch-derived base oils are known in the art. The term Fischer-Tropsch-derived means that a base oil is, or is derived from, a synthesis product of a Fischer-Tropsch process. A Fischer-Tropsch-derived base oil may also be called a GTL (Gas-to-Liquids) base oil. Suitable Fischer-Tropsch-derived base oils that can be conveniently used as a base oil in the lubricating composition of the present invention are, for example, those disclosed in patent documents EP 0 776 959, EP 0 668 342, WO 97 / 21788, WO 00 / 15736, WO 00 / 14188, WO 00 / 14187, WO 00 / 14183, WO 00 / 14179, WO 00 / 08115, WO 99 / 41332, EP 1 029 029, WO 01 / 18156, WO 01 / 57166 and WO 2013 / 189951. Especially for industrial gear oil formulations, API Group II, III, IV base oils or mixtures thereof are used. The lubricating composition according to the invention may also contain, as component (C), other additives selected from the group consisting of pour point depressants, dispersants, antifoaming agents, detergents, demulsifiers, antioxidants, anti-wear additives, extreme pressure additives, friction modifiers, anti-corrosion additives, colorants and mixtures thereof. The preferred pour point depressants are selected, for example, from the group consisting of alkylated naphthalene and phenolic polymers, polyalkyl methacrylates, maleate copolymer esters, and fumarate copolymer esters, which can be conveniently used as effective pour point depressants. The lubricating oil composition may contain from 0.1 wt% to 0.5 wt% of a pour point depressant. Preferably, no more than 0.3 wt% of a pour point depressant is used. Suitable dispersants include poly(isobutylene) derivatives, for example, poly(isobutylene)succinimides (PIBSI), which include borated PIBSI; and ethylenepropylene oligomers having N / O functionalities. Suitable antifoaming agents include, for example, silicone oils, fluorosilicone oils, and fluoroalkyl ethers. Preferred detergents include compounds containing metals, for example, phenoxides; salicylates; thiophosphonates, especially thiopyrophosphonates, thiophosphonates, and phosphonates; sulfonates; and carbonates. These compounds may contain metals such as calcium, magnesium, and barium. These compounds can be MA / a / ¿u¿¿ / uu / loo preferably used in a neutral or overbased form. Preferred demulsifiers include alkylene oxide copolymers and (meth)acrylates that include polar functional groups. Suitable antioxidants include, for example, phenols, e.g., 2,6-di-tert-butylphenol (2,6-DTB), butylated hydroxytoluene (BHT), 2,6-di-fert-butyl-4-methylphenol, 4,4'-methylenebis(2,6-di-fert-butylphenol); aromatic amines, especially alkylated diphenylamines, N-phenyl-1-naphthylamine (PNA), polymeric 2,2,4-trimethyldihydroquinone (TMQ); sulfur- and phosphorus-containing compounds, e.g., metal dithiophosphates, e.g., zinc dithiophosphates (ZnDTP), OOS triesters = reaction products of dithiophosphoric acid with activated double bonds of definites, cyclopentadiene, norbornadiene, apinene, polybutene, acrylic esters, maleic esters (ashless on combustion); organic sulfur compounds, for example, dialkyl sulfides, diaryl sulfides, polysulfides, modified phyols, thiophene derivatives, xanthates, thioglycols, thioaldehydes, sulfur-containing carboxylic acids;Heterocyclic sulfur / nitrogen compounds, especially dialkyldimercaptothiadiazoles, 2-mercaptobenzimidazoles; zinc bis(dialkyldithiocarbamate) and methylene bis(dialkyldithiocarbamate); organophosphorus compounds, for example triaryl and trialkyl phosphites; organocopper compounds and overbasified calcium and magnesium-based phenoxides and salicylates. Preferred anti-wear and extreme pressure additives include phosphorus compounds, e.g., trialkyl phosphates, triaryl phosphates, e.g., tricresyl phosphate, amine-neutralized mono- and dialkyl phosphates, ethoxylated mono- and dialkyl phosphates, phosphites, phosphonates, phosphines; compounds having sulfur and phosphorus, for example, metallic dithiophosphates, for example, zinc di-C3-12-dialkyldithiophosphates (ZnDTP), ammonium dialkyldithiophosphates, antimony dialkyldithiophosphates, molybdenum dialkyldithiophosphates, lead dialkyldithiophosphates, OOS triesters = reaction products of dithiophosphoric acid with activated double bonds of olefins, cyclopentadiene, norbornadiene, α-pinene, polybutene, acrylic esters, maleic esters, triphenyl phosphorothionate (TPPT); compounds having sulfur and nitrogen, for example zinc bis(amyldithiocarbamate) or methylenebis(d-n-butyldithiocarbamate);sulfur compounds with elemental sulfur and sulfur hydrocarbons H2S (diisobutylene, terpene); sulfur glycerides and fatty acid esters; superbasified sulfonates; chlorine compounds or solids such as graphite or molybdenum disulfide.; The friction modifiers used may include mechanically active compounds, for example, molybdenum disulfide, graphite (including fluorinated graphite), ML / a / zuzz / uu zioo poly(trifluoroethylene), polyamide, polyimide; adsorption layer-forming compounds, for example long-chain carboxylic acids, fatty acid esters, ethers, alcohols, amines, amides, imides; tribochemical layer-forming compounds, for example saturated fatty acids, phosphoric and thiophosphoric acid esters, xanthogenates, sulfur-containing fatty acids; polymer-like layer-forming compounds, for example ethoxylated dicarboxylic partial esters, dialkyl phthalates, methacrylates, unsaturated fatty acids, sulfur-containing compounds or organometallic compounds, for example molybdenum compounds (molybdenum dithiophosphates and molybdenum dithiocarbamates MoDTC) and combinations thereof with ZnDTP, copper-containing organic compounds. Some of the compounds listed above can serve multiple functions. ZnDTP, for example, is primarily an anti-wear additive and an extreme pressure additive, but it also acts as an antioxidant and corrosion inhibitor (in this case: a metal passivator / deactivator). The additives detailed above are described in detail, among others, in T. Mang, W. Dresel (eds.): Lubricants and Lubrication, Wiley-VCH, Weinheim 2001; RM Mortier, ST Orszulik (eds.): Chemistry and Technology of Lubricants. Dispersants (including borate dispersants) are preferably used at a concentration of 0% to 2% by weight, antifoaming agents at a concentration of 10 to 2500 ppm, detergents at a concentration of 0.05% to 1% by weight, demulsifiers at a concentration of 0% to 0.1% by weight, antioxidants at a concentration of 0.5% to 1.5% by weight, anti-wear and extreme pressure additives each at a concentration of 0.1% to 1% by weight, friction modifiers at a concentration of 0.05% to 2% by weight, anti-corrosion additives at a concentration of 0.05% to 0.5% by weight, and colorants at a concentration of 0.01% to 1% by weight. The concentration is based, in each case, on the total weight of the lubricating oil composition. Preferably, the total concentration of one or more additives (C) in a lubricating oil composition is up to 5% by weight, more preferably from 0.1% to 4% by weight, more preferably from 0.5% to 3% by weight, based on the total weight of the lubricating oil composition. Another fifth object of the present invention relates to a lubricating composition comprising: (A) 20 to 60% by weight of polyethylenehexyl acrylate, which has a weight The patented IVIA / a / ¿U¿¿ / UU ZIOO works without the addition of a chain transfer agent and with a comparatively small amount of initiator, relative to the molecular weight obtained. A sixth object of the present invention relates to a process for preparing polyalkyl acrylates as described above, the process comprising the steps of: (i) loading a reaction vessel with a base oil; (i) heat the base oil from step (i) to a reaction temperature of 130 °C to 170 °C; (i¡¡) constantly feed a mixture of branched Ce-io alkyl acrylates and 0.1 to 1.2% of an initiator, based on the amount of branched Cs io alkyl acrylates, to the reaction vessel for a time of 120 to 240 minutes; (iv) optionally, stir the reaction mixture obtained in step (iii) for a further 50 to 90 minutes; and (vi) cool the reaction mixture obtained in step (iv) to room temperature and obtain the desired polyalkyl acrylate. The base oil to be used in step (i) can be selected from the group consisting of API Group II oils, API Group III oils, API Group IV oils and mixtures thereof. The concentration of alkyl acrylates in the reaction mixture is 70 to 95% by weight, preferably 80 to 90% by weight. This means that the reaction mixture obtained in step (iii) contains 5 to 30% by weight, preferably 10 to 20% by weight, of base oil and 70 to 95% by weight, preferably 80 to 90% by weight, of alkyl acrylates. Usable initiators include azo initiators widely known in the technical field, such as AIBN and 1,1-azobiscyclohexanecarbonitrile, and also peroxy compounds such as methyl ethyl ketone peroxide, acetylacetone peroxide, dilauryl peroxide, tere-butyl per-2-ethylhexanoate, ketone peroxide, tert-butyl peroctoate, methylisobutyl ketone peroxide, cyclohexanone peroxide, dibenzoyl peroxide, tere-butyl peroxybenzoate, tere-butyl peroxyisopropylcarbonate, 2,5-bis(2-ethylhexanoylperoxy)-2,5-dimethylhexane, tere-butyl peroxy-2-ethylhexanoate, tere-butyl peroxy-3,5,5-trimethylhexanoate, dicumyl peroxide, 1,1-bis(tert-butylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, cumyl hydroperoxide, tert-butyl hydroperoxide, bis(4-tert-butylcyclohexyl) peroxydicarbonatemixtures of two or more of the aforementioned compounds with each other and mixtures of the aforementioned compounds with unspecified compounds that can also form free radicals. The preferred initiators are dicumyl peroxide and tere-butyl peroxy-2-ethylhexanoate. The invention has been further illustrated by the following non-limiting examples. Experimental Section Abbreviations BV apparent viscosity BV40 apparent viscosity at 40 °C BV100 apparent viscosity at 100 °C C600R Chevron Group II base oil with a KVwo of 12 cSt DDM dodecyl mercaptan EHA ethylhexyl acrylate, commercially available from Aldrich HA hexyl acrylate Hitec® 307 Package DI commercially available from Afton IDA β-so-decyl acrylate, commercially available from Aldrich ITDA β-so-tridecyl acrylate, commercially available from Aldrich KV kinematic viscosity measured in accordance with ASTM D445 KV40 kinematic viscosity measured at 40 °C in accordance with ASTM D445 KV100 kinematic viscosity measured at 100 °C in accordance with ASTM D445 KV-10 kinematic viscosity measured at 10 °C in accordance with ASTM D445 LA acrylate of lauryl, dodecyl acrylate, commercially available from Aldrich Mn average molecular weight in number M« average molecular weight NB3080 Nexbase® 3080; Neste Group III base oil with a KVwo of 7.9 cSt PAO6 polyalphaolefin base oil with a KVwo of 6 cSt. ΡΑΟ8 polyalphaolefin base oil with a KVwo of 8 cSt PDI polydispersity index PHA propylheptyl acrylate, commercially available from Aldrich PP pour point VI viscosity index VPL1-180 VISCOPLEX® 1-180, a commercially available pour point depressant from Evonik VPL 14-520 VISCOPLEX® 14-520, commercially available antifoam from Evonik Yubase 6 Group III base oil from SK Lubricants with a KV100 of 6 cSt Testing procedures The polyalkyl acrylates according to the present invention and comparative examples were characterized with respect to their molecular weight, PDI and apparent viscosity at 40 °C and 100 °C (BV40 and BV100). Molecular weights were determined by size exclusion chromatography (SEC) using commercially available polymethyl methacrylate (PMMA) standards. The determination was performed by gel permeation chromatography (GPC) according to DIN 55672-1 with THF as the eluent (flow rate: 1 mL / min; injected volume: 100 pl). The lubricating oil compositions including the polyalkyl acrylates according to the present invention and comparative examples were characterized with respect to kinematic viscosity at -10 °C (KV-w), 40 °C (KV4o) and 100 °C (KVi00) in accordance with ASTM D445, their viscosity index (VI) in accordance with ASTM D2270, their Brookfield viscosity in accordance with ASTM D-2983 and their pour point in accordance with ASTM D5950. The lubricating compositions were formulated with an ISO viscosity grade of 220 or 320, within a range of ±10%. The International Organization for Standardization viscosity grade, ISO VG, is recommended for industrial applications. The reference temperature of 40 °C represents the operating temperature of the machinery. This ISO viscosity classification is therefore based on the kinematic viscosity at 40 °C (KV4o). ινΐΛ / a / zuzz / uu / 1 oo ISO Viscosity Grade Midpoint Viscosity at 40 °C [mm2 / s] Kinematic Viscosity Limits at 40 °C [mm2 / s] 220 220 198 242 320 320 288 352 Measurements of tapered roller bearings were performed to determine the shear loss (20 hours, 60 °C, 5 kN and 1450 rpm) according to CEC L-45-A-99 and the corresponding kinematic viscosities measured at 40 °C (KV4o) and 100 °C (KV100) in accordance with ASTM D-445 In relation to the evaluation of gear oil formulations, foam tests were performed in accordance with ASTM D892 and air release was determined in accordance with DIN ISO 9120. Synthesis 1: General synthesis of polyalkyl acrylates using a CTA feeding procedure A round-bottom flask equipped with a glass stirring rod, nitrogen inlet, reflux condenser, and thermometer was charged with 41.9 g of NB3080. 200.0 g of EHA, 6.0 g of DDM, 0.5 g of tert-butylper-2-ethylhexanoate, and 4.5 g of NB3080 were added over 2 hours at 110 °C under bubbling nitrogen. Subsequently, 0.4 g of tert-butylper-2-ethylhexanoate and 3.6 g of NB3080 were fed to the reaction mixture over 1 hour. Synthesis 2: General synthesis of polyalkyl acrylates using ATRP 1.88 g of pentamethyldiethylenetriamine, 0.78 g of CuBr, and 100.0 g of EHA were purged with nitrogen for 30 minutes and heated to 65 °C. After the addition of 2.12 g of ethylene bis(2-bromoisobutyrate), the reaction mixture was heated to 95 °C. After 4 hours, 1.10 g of DDM was added. The mixture was stirred for 2 hours, cooled to room temperature, and purified by pressure filtration. After filtration, a clear, slightly yellow, highly viscous liquid was obtained, which was applied without further purification. Synthesis 3: General synthesis of polyalkyl acrylates using the novel acrylate procedure 0.85 g (0.5 wt. based on the amount of EHA) of dicumyl peroxide dissolved in 170.0 g of EHA was fed to 26.77 g of NB3080 under nitrogen at 150 °C for 3 hours. Optionally, after this time, the temperature of the mixture was lowered to 110 °C and 0.17 g of tert-butylper-2-ethylhexanoate (0.1 wt. based on the amount of EHA) dissolved in 3.23 g of NB3080 was added. After stirring for another hour, the resulting clear polymer solution was cooled and used in subsequent experiments without further purification. Synthesis 4: General synthesis of polyalkyl methacrylates A round-bottom flask equipped with a glass stirring rod, nitrogen inlet, reflux condenser, and thermometer was charged with 284.4 g of EHMA and 8.9 g of DDM. 0.75 g of tert-butylper-2-ethylhexanoate and 15.0 g of EHMA were added over 3 hours at 110 °C under bubbling nitrogen. After holding the temperature for 1 hour, 0.6 g of tert-butylper-2-ethylhexanoate was added. After another hour, a final dose of 0.6 g of tert-butylper-2-ethylhexanoate was added, and the solution was stirred at 110 °C for 1 hour. The resulting clear, highly viscous liquid was used without further purification. oo Table 1. Initiators used in the different syntheses Initiator Name A tert-butylper-2-ethylhexanoate B dicumyl peroxide C dicetyl peroxydicarbonate D tert-butylperbenzoate E 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane All the starter cultures are commercially available. Diacetyl peroxydicarbonate is commercially available from AkzoNobel. The compositions of the reaction mixtures used to prepare the working and comparative examples are shown in Table 2 below. The amounts of monomer and base oil always add up to 100%. The amounts of initiator and DDM are given relative to the total amount of monomer. Table 2. Compositions of the reaction mixtures used to prepare the working examples and the comparative examples Iniciador Ejemplo # Monómero Aceite Base A [%] B [%] c [%] D [%] E [%] DDM [%] 1 EHA NB3080 0.25 - — — - 3.00 2 EHA NB3080 0.25 - — — - 1.90 3 EHA NB3080 0.50 — — — — 1.90 4 EHA NB3080 — — — — — — 5 EHA NB3080 1.00 — — — — — 6 EHA NB3080 — 1.25 — — — — 7 EHA NB3080 — — 2.64 — — — 8 EHA NB3080 — 0.90 — — — — 9 EHA NB3080 — 0.90 — — - - 10 EHA NB3080 — 0.90 — — - - 11 EHA NB3080 — 0.90 — — - - 12 EHA NB3080 — 0.90 — — — — 13 EHA NB3080 — 0.90 — — — — 14 EHA NB3080 — 0.50 — — — — 15 EHA NB3080 — 0.90 — — — — 16 EHA NB3080 — 0.90 — — - - 17 EHA NB3080 — 0.50 — — - - 18 EHA NB3080 — 0.30 — — - - 19 EHA NB3080 — 0.20 — — - - 20 EHA NB3080 — 0.05 — — - - 21 EHA NB3080 — 0.50 — — — — 22 HA NB3080 — 0.50 — — — — 23 IDA NB3080 — 0.50 — — - - 24 LA NB3080 — 0.50 — — - - 25 HA NB3080 — 0.50 — — - - 26 ITDA NB3080 — 0.50 — — - - 27 EHA C600R — 0.50 — — - - 28 EHA C600R — 0.50 — — — — 29 EHA C600R — 0.50 — — — — 30 EHA C600R — 0.10 — — — — 31 EHA C600R — 0.20 — — — — 32 EHA C600R — 0.30 — — - - 33 EHA C600R — 0.40 — — - - 34 EHA Repair 6 — 0.50 — — - -. Initiator Example # Monomer Base Oil A [%] B [%] c [%] D [%] E [%] DDM [%] 35 EHA PAO 8 -- 0.50 — -- — — 36 EHA PAO 8 -- 0.50 — -- — — 37 PHA PAO 8 -- 0.50 — -- — — 37 PHA PAO 8 -- 0.50 — -- — — PAO 8 -- 0.50 — -- — — PAO — 39 PHA PAO 8 - 0.20 — - — — 40 PHA PAO 8 - 0.10 — - — — 41 EHA PAO 8 — 0.50 — -- — — 42 EHA PAO 8 -- 0.90 — -- — — 43 EHA PAO 8 -- 1.30 — -- — — — 43 EHA PAO 8 -- 1.30 — -- — — 48 -- PAO — 0.50 — 45 — PAO. EHA PAO 8 - - — - 0.50 — 46 EHMA — 0.25 -- — -- — 2.95 Conclusions: Examples 1 to 4 were prepared according to known procedures. Although temperature control and cost-effectiveness were poor, the target polymers could be prepared. Examples 1 to 4 are covered by claim 1 of the present invention and show good performance as base oils in lubricating compositions (see the results presented later in Table 5). In addition, Examples 1 to 3 contain a substantial amount of sulfur, which is considered detrimental to compatibility with certain metals and rubber seals. Examples 1 to 3 also contain high levels of residual monomer (see Table 4 later). Example 4 is produced by ATRP, which is very challenging in commercial production since lubricants require a contaminant-free product. Removing chemicals from the highly viscous product process has proven to be time-consuming, even at a laboratory scale. To achieve temperature control, a monomer feeding procedure was used. Attempts to adjust the molecular weight of the polymers to the target range below 25,000 g / mol using sulfur-containing chain transfer agents did not produce satisfactory levels of residual monomer. Apart from this, the required amounts of chain transfer agent to be used in this procedure were quite significant, leading to high levels of unwanted sulfur in the product (Examples 1 to 3; 1.90 and 3.00% DDM are used, respectively). Despite their positive effects on oxidation and wear performance, sulfur components are known to cause problems with yellow metals and rubber seals (see LR Rudnick, Lubricant Additives: Chemistry and Applications, 3rd Edition, 2017, p. 197ff). Examples 5, 7, 20, 22, 30, 44 and 45 are comparative examples since the molecular weight M is outside the claimed range of 7,000 to 25,000 g / mol. Examples 6, 8-19, 21, 23, 27-29 and 31-43 are in accordance with the present invention. Examples 22, 24-26 and 46 are comparative examples since they are prepared from monomers that are not included in claim 1. Table 3 below provides details on the preparation procedure used to synthesize working examples and comparative examples. IVIA / a / ZUZZ / UU 11OO Table 3. Procedure Details Example # Procedure Feeding Time [h] Temperature [°C] Concentration [%] 1 Synthesis 1 2 110 80 2 Synthesis 1 5 110 60 3 Synthesis 1 5 110 60 4 Synthesis 2 — — 50 5*> Synthesis 3 4 110 60 6 Synthesis 3 4 160 60 7*) Synthesis 3 4 84 60 8 Synthesis 3 4 160 60 9 Synthesis 3 4 160 80 10 Synthesis 3 4 160 85 11 Synthesis 3 3 160 85 12 Synthesis 3 3 150 85 13 Synthesis 3 3 150 85 14 Synthesis 3 3 150 90 15 Synthesis 3 3 150 90 16 Synthesis 3 3 150 85 17 Synthesis 3 2 150 85 18 Synthesis 3 3 150 85 Example # Procedure Feeding Time [h] Temperature [°C] Concentration [%] 19 Synthesis 3 3 150 85 20*' Synthesis 3 3 150 85 21 Synthesis 3 3 150 85 22*> Synthesis 3 3 150 85 23 Synthesis 3 3 150 75 24*' Synthesis 3 3 150 70 25*' Synthesis 3 3 150 50 26*' Synthesis 3 3 150 75 27 Synthesis 3 3 150 85 28 Synthesis 3 3 150 80 29 Synthesis 3 3 150 90 30*' Synthesis 3 3 150 80 31 Synthesis 3 3 150 90 32 Synthesis 3 3 150 90 33 Synthesis 3 3 150 90 34 Synthesis 3 3 150 85 35 Synthesis 3 3 150 85 36 Synthesis 3 3 150 85 37 Synthesis 3 3 150 85 38 Synthesis 3 3 150 80 39 Synthesis 3 3 150 90 40 Synthesis 3 3 150 90 41 Synthesis 3 3 150 80 42 Synthesis 3 3 150 85 43 Synthesis 3 3 150 85 44*' Synthesis 3 3 140 85 45*' Synthesis 3 3 125 85 46*' Synthesis 4 3 110 100 *) comparative example The first attempts to prepare the target polyacrylates in a batch procedure similar to poly(EHMA) (Synthesis 4, Example 46) failed due to poor temperature control. Good results were obtained using the ATRP process (Synthesis 2, Example 4), but due to its poor economics, a new procedure had to be developed. A novel chain-transfer agent-free feeding procedure was developed that yielded polymers with very low residual monomer content (Synthesis 3). Low molecular weights are achievable with good conversion and narrow molecular weight distributions. The procedure performs well, especially at elevated temperatures, which are beneficial for achieving high temperatures and good conversions (see, for example, Examples 5, 6, 7, 41, 44, and 45). In addition to the temperature, which must be adjusted to the respective initiator system, the molecular weight can be controlled by various measures. Surprisingly small is the influence of the amount of initiator. Very small amounts of initiator result in an increase in molecular weight, but variations of around 0.5% by weight in the initiator content result in negligible changes in molecular weight (Examples 16-20, 29, 31, 32, 33, 42, and 43). Feeding times also have a minor influence within a reasonable window of 2 to 4 hours (see Examples 10, 11, 17, and 21). The molecular weight can also be influenced by the amount of base oil in the residue at the start of the reaction (see Examples 8-10, 22, 25 and 27-29). The characteristics of the polyalkyl acrylates prepared in the course of the present invention are described in Table 4 below. Table 4. Characteristics of the polyalkyl acrylates prepared according to the present invention Example # Mw [g / mol] Mn [g / mol] PDI ReMo [%] BV40 [mm2 / s] BV100 [mm2 / s] VI 1*> 13,000 7,060 1.84 0.24 1141 104.4 185 2*) 16,500 8,440 1.95 0.54 499 54.4 175 3*> 15,600 8,010 1.95 0.49 480 52.4 173 4*) 14,400 8,460 1.70 0.01 323 38.3 165 5*> 34,400 11,300 3.04 0.05 1076 108.1 197 6 7,590 4,730 1.60 0.04 294 31.9 149 7*> 52,200 15,700 3.32 0.18 1472 148.6 214 8 7,130 4,650 1.53 0.03 287 30.8 147 9 10,500 5,560 1.89 0.01 983 85.4 170 10 12,600 5,960 2.11 0.01 1577 126.3 180 11 11,600 5,750 2.02 0.02 1329 108.6 175 12 16,700 7,060 2.37 0.01 2191 172.1 194 13 13,900 6,430 2.16 <0.01 1798 144.5 187 14 18,600 7,400 2.51 <0.01 3457 252.7 208 15 18,700 7,270 2.57 0.09 3348 244.9 206 Example # Mw [g / mol] Mn [g / mol] PDI ReMo [%] BV40 [mm2 / s] BV100 [mm2 / s] VI 16 15.100 6.720 2.25 0.01 1936 153.7 189 17 15.200 7.030 2.16 <0.01 2078 162.0 190 18 16,100 7,240 2.22 0.01 2155 170.0 194 19 17,200 7,500 2.29 0.03 2311 183.0 198 20*> 30,900 10,300 3.00 0.03 4360 339.2 231 21 15,200 7,190 2.11 0.06 2131 168.6 194 22*) 53,600 11,800 4.54 0.10 3446 318.3 247 23 15,400 7,490 2.06 -- 975 82.9 166 24*> 15,600 8,530 1.83 -- 314 43.0 192 25*> 14,800 7,570 1.96 -- 61 9.6 138 26*> 14,700 7,270 2.02 -- 1320 95.9 157 27 16,300 7,470 2.18 0.02 2723 203.8 198 28 13,700 6,930 1.98 0.06 1872 138.2 176 29 18,800 7,670 2.45 0.05 4441 305.1 212 30*> 25,100 9,830 2.55 -- 6444 434.1 231 31 23,300 9,320 2.50 -- — -- - 32 20,600 8,640 2.38 -- — . -- - 33 20,800 8,900 2.34 -- — -- - 34 16,100 7,270 2.21 0.02 2165 172.0 195 35 18,600 8,380 2.22 <0.01 2771 216.1 206 36. 17,300 8,060 2.15 0.04 2537 200.4 203 37 14,100 7,270 1.94 <0.01 1671 145.8 197 38 11,500 6,560 1.75 0.09 0.02 1016 90.6 175 39 15,400 7,770 1.98 0.05 2556 201.0 203 40 17,800 8,800 2.02 -- — -- - 41 14,900 7,600 1.96 0.04 1645 138.0 190 42 20,200 8,530 2.37 -- — 229.0 - 43 20,200 8,190 2.47 -- 2704 221.8 213 44 30,900 10,200 3.03 <0.01 4587 345.7 229 45*> 96,700 16,400 5.90 <0.01 13648 993.3 290. It can be seen that all polymers prepared by Synthesis 3 have residual monomer contents of 0.1% or even well below. All working examples that conform to the present invention have apparent viscosities (BV40) well above 320 mm² / s, i.e., they can be easily formulated with an ISO viscosity grade of 320. It is more visible that polymers having a weight average molecular weight of approximately 7,000 g / mol show borderline apparent viscosities at 40 °C (see Examples 6 and 8), i.e., they can only be formulated with an ISO viscosity grade of 220 or lower. Different acrylate monomers were used to generate homopolymers for evaluation as high-viscosity base fluids. Hexyl acrylate has proven completely unsuitable, as the apparent viscosity of the synthesized polymers was too low to be useful (Example 25). Even with a massive increase in molecular weight, the high treatment rate and the expected lack of shear stability were so poor that no further investigations were carried out (Example 22). Lubricant Compositions To test the performance of acrylate polymers prepared according to the present invention, lubricating compositions were prepared using the acrylate polymers as a base fluid and mixing them with other base oils to achieve ISO viscosity grades of 220 and 320. The results for typical formulation parameters such as KV100, VI, PP and Brookfield viscosity are presented in the following Tables 5 to 9. While acrylates and methacrylates are often considered interchangeable in the field of viscosity modifiers, the results presented in the present invention clearly show a difference when used as high-viscosity base materials. Whereas the EHMA homopolymer (Example 46) exhibited very poor miscibility with Nexbase 3080 (an API Group III oil) and phase separation was observed, no such problems were found for the EHA homopolymers in any of the solvents and concentrations used. Poly(lauryl acrylate, LA) (Example 24) showed poor performance in terms of treatment rate and low-temperature properties in a fully formulated ISO 320 formulation. Both poly(isodecyl acrylate) (Example 23) and poly(isotridecyl acrylate) (Example 26) showed insufficient low-temperature performance compared to poly(EHA). Improved low-temperature performance was observed for the MA / a / ¿u¿¿ / uu / loo poly(propylheptyl acrylate) (Examples 37-40) at the cost of a slightly higher treatment rate compared to poly(EHA). Due to the high conversion of the monomers and the absence of other volatile components in the process, such as chain transfer agents, the flash points of acrylate polymers are very high. Data are provided for Example 27, and the measured flash point (COC ASTM D92 procedure) was the same as that specified for the Chevron 600R thinning oil used in the process (Example 27). For the use of Example 30, precipitation was observed in an ISO 220 formulation in API Group III base oil. Since this was not observed for other samples with a lower molecular weight, it can be concluded that in all other experiments perfect compatibility with the oil was observed, even in base oils of extremely low solvency, which is limited to molecular weights below 25,000 g / mol for EHA homopolymers. Table 5. Formulation data of compositions A formulated in accordance with ISO 320 (KV40= 320 ±10%) Composition A-1 A-2 A-3 A-4 A-5 A-6 A-7 A-8 A-9 Example 1 [%] 65.70 — — — — — — -- — Example 2 [%] - 80.90 — - - — -- - — Example 3 [%] - — 81.80 - - — -- - — Example 4 [%] - — — 46.9 -- — -- - — Example 9 [%] -- — — - 69.00 — -- -- — Example 10 [%] -- — — - -- 63.00 -- -- — Example 12 [%] - — — - - — 58.00 - — Example 13 [%] - - — - - — -- 60.20 — Example 21 [%] 58.00 Viscoplex 1180 [%] 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 Hitec 307 [%] 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 NB3080 [%] 30.95 15.75 14.85 49.75 27.65 33.65 38.65 36.45 38.65 Total Mixture [%] 100.0 100.0 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Polymer Content [%] 52.6 48.5 49.1 46.9 55.2 53.55 49.3 51.8 49.3 KV40 [mm2 / s] 326.1 322.9 319.4 317.8 321.2 322.2 322.0 320.9 317.1 Composition A-1 A-2 A-3 A-4 A-5 A-6 A-7 A-8 A-9 KV100 [mm2 / s] 37.45 37.71 37.03 36.73 35.27 35.71 36.65 36.07 36.21 VI 164 167 165 164 156 157 162 159 162 KV.10 [mm2 / s] 14,020 14,270 14,618 14,828 14,913 14,661 14,713 Brookfield (Air) [mPas] 184,000 510,000 244,000 140,000 152,000 216,000 160,000 188,000 498,000 240,000 140,000 152,000 200,000 152,000 PP [°C] -33 -36 -30 -39 -33 -36 -33 KRL at 20 hours KV40 [mm2 / s] 320.5 314.7 317.5 KV100 [mm2 / s] 36.78 36.74 35.93 Shear loss at 100 °C [%] 1.8 2.6 0.8 Reference oil value RL 209 [%] 9.9 9.9 10.2 IVIA / a / ZUZZ / UU / lOO Table 6. Formulation data of compositions A formulated in accordance with ISO 320 (KV40= 320 ± 10%) Composition A-10 A-11 A-12 A-13 A-14 A-15 A-16 A-17 Example 23 [%] 67.50 - — - — — — — Example 24 [%] — 96.65 — - — — — — Example 26 [%] — - 62.00 - — — — — Example 35 [%] — -- — 54.70 — — — — Example 36 [%] — - — - 56.00 — — — Example 37 [%] — - — - — 62.40 — — Example 41 [%] — - — - — — 61.20 — Example 46 [%] 30.55 Viscoplex 1-180 [%] 0.70 0.70 0.70 - — — — 0.70 Hitec 307 [%] 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 NB3080 [%] 29.15 - 34.65 - — — — 66.10 PAO 8 — - — 42.65 41.35 34.95 36.15 — Total Mixture [%] 100.0 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Polymer Content [%] 50.63 67.66 46.50 46.50 47.60 53.04 48.96 30.55 KV40 [mm2 / s] 314.5 315.5 313.6 325.3 325.1 328.1 323.2 309.8 Composition A-10 A-11 A-12 A-13 A-14 A-15 A-16 A-17 KV100 [mm2 / s] 35.20 42.94 33.06 38.02 37.86 38.13 37.09 31.54 VI 158 193 147 167 166 166 163 141 KV.10 [mm2 / s] 15,695 solid 16,180 solid Brookfield (Air) [mPas] 220,000 solid 200,000 108,000 94,000 82,000 110,000 solid 216,000 solid 212,000 112,000 96,000 81,000 106,000 Solid PP [°C] -39 -6 -36 -36 -39 -45 -36 ??? KRL at 20 hours KV40 [mm2 / s] 315.3 317.0 324.5 311.0 KVwo [mm2 / s] 36.86 36.79 37.69 35.76 Shear loss at 100 °C [%] 3.1 2.8 1.2 3.6 Reference oil value RL 209 [%] 9.7 9.7 9.7 8.3 Table 7. Formulation data of compositions A formulated in accordance with ISO 320 (KV40= 320 ± 10%) Composition A-18 A-19 A-20 A-21 A-22 A-23 A-24 A-25 A-26 A-27 Example 34 [%] 57.80 61.00 62.70 — -- — — — — — Example 27 [%] — — — 42.0 -- — — — — Example 35 [%] — — — — 54.70 — — — — Example 36 [%] — — — — -- 56.00 — — — Example 37 [%] — — — — -- — 62.40 — — Example 39 [%] — — — — -- — — 57.60 — Example 40 [%] — — — — -- — — — 54.70 — Example 41 [%] 61.20 Viscoplex 1180 [%] 0.70 0.70 — 0.80 -- — — — — Hitec 307 [%] 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 Chevron 600R [%] — — — 54.50 -- — — — — — NB3080 [%] 38.85 - — — -- — - - - - Yubase 6 [%] — 35.65 — — -- — - - - - Composition A18 A-19 A-20 A-21 A-22 A-23 A-24 A-25 A-26 A-27 PAO 6 [%] — — 34.65 — -- — — -- — — PAO 8 [%] — — — — 42.65 41.35 34.95 39.75 42.65 36.15 Total Mixture [%] 100.0 100.0 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Polymer Content [%] 49.13 51.85 53.30 35.70 46.50 47.60 53.04 51.84 49.23 48.96 Viscoplex 14520 top treatment [ppm] 2000 2000 2000 KVW [mm2 / s] 324.7 324.6 322.7 319.2 325.3 325.1 328.1 323.7 317.0 323.2 KV100 [mm2 / s] 37.37 37.89 38.31 32.37 38.02 37.86 38.13 38.06 38.05 37.09 VI 164 167 169 142 167 166 166 168 170 163 Brookfield (Air) [mPas] 128,000 95,000 143,970 108,000 94,000 82,000 80,000 74,000 110,000 130,000 96,000 112,000 96,000 81,000 80,000 72,000 106,000 PP [°C] -36 -36 -39 -33 -36 -39 -45 -48 -45 -36 KRL at 20 hours KV40 [mm2 / s] 310.8 309.6 313.3 309.3 315.3 317.0 324.5 311.0 KV100 [mm2 / s] 35.69 36.13 37.21 31.69 36.86 36.79 37.69 35.76 Shear loss at 100 °C [%] 4.5 4.6 2.9 2.1 3.1 2.8 1.2 3.6 Reference oil value RL 209 [%] 10.1 10.1 10.1 9.7 9.7 9.7 8.3 Water content Karl Fischer [%] 0.02 0.02 0.02 Flash point [°C] 238 232 234. For ISO 320 formulations, the data disclosed in Tables 5 to 6 show that for EHA and PHA polymers, the required polymer content is 40 to 60% by weight. The polymers according to the present invention exhibit good solubility in used base oils (i.e., Group III and IV oils, as well as their mixtures) at all temperatures up to the pour point (PP) of the formulation. The polymers of the present invention also show good low temperature behavior (see KV.10 and BF-26 values) and pour points, which is remarkable for polymers that have such high polarities. The formulations comprising the polymers of the present invention have a high VI of approximately 160. This means that the KVwo of the formulations is higher than the KVwo of a regular ISO 460 mineral oil-based formulation. This allows for a combination of high equipment protection and good low-temperature flow properties. Formulation A17 yields the surprising result that the EHMA polymer differs from EHA polymers; the EHMA polymer is incompatible with base oils at low temperatures, even though the treatment rate is substantially lower. Such a difference between acrylates and methacrylates has not been previously reported, as oil-soluble VI improvers are not pushed as hard to the limits of solubility. The combination of high treatment rates and a fairly thick, nonpolar base oil with low solvency is a special case not covered by the prior art to date. When comparing different acrylate homopolymers, poly-LA (A-11) is clearly unsuitable because the formulation solidifies at temperatures above 10 °C. While poly-IDA performs slightly worse in terms of VI and low-temperature properties compared to EHA and PHA polymers, the gap is wider for poly-LTDA. Furthermore, poly-LTDA has lower polarity, making it less promising than the other options. Table 8. Foam test Composition A-18 A-19 A-20 sequence I Foam after Blowing Period at 24 °C [mL] 0 0 0 sequence I Foam after 10 min at 24 °C [mL] 0 0 0 Composition A-18 A-19 A-20 Sequence I Collapse time at 24 °C [s] 0 0 0 Sequence II Foam after Blowout Period at 94 °C [mL] 210 40 50 Sequence II Foam after 10 min at 94 °C [mL] 0 0 0 Sequence II Collapse time at 94 °C [s] 334 129 134 Sequence III Foam after Blowout Period at 24 °C [mL] 0 0 0 Sequence III Foam after 10 min at 24 °C [mL] 0 0 0 Sequence III Collapse time at 24 °C [s] 0 0 0 Due to the high polarity of some of the polymer blocks, an impact on performance tests involving interfaces was expected. No significant effects were observed in air release and foam tests. Fluid filtration presented no problems, confirming the visual observation that the polymer and additives were completely dissolved in the oil phase. Table 9. Formulation data of compositions B formulated in accordance with ISO 220 (KV40= 220 ± 10%) Composition B-1 B-2 B-3 B-4 B-5 B-6 Example 28 [%] 35.00 — -- — — — Example 29 [%] - 28.00 - — — — Example 30 [%] — — 25.00 — — — Example 32 [%] — — -- 27.10 — — Example 33 [%] — — -- — 27.10 — Example 31 [%] — — -- — — — Hitec 307 [%] 2.65 2.65 2.65 2.65 2.65 2.65 Chevron 600R [%] 62.35 69.35 72.35 70.25 70.25 — Total Mixture [%] 100.0 100.0 100.00 100.00 100.00 100.00 Polymer content [%] 28.00 25.20 20.00 24.39 24.39 — KV40 [mm2 / s] 218.7 217.9 219.8 220.9 219.8 — KV100 [mm2 / s] 23.51 23.67 24.14 24.00 23.93 — VI 133 134 137 135 136 — Composition B-1 B-2 B-3 B-4 B-5 B-6 KRL at 20 hours KV40 [mm2 / s] 216.5 209.2 KV100 [mm2 / s] 23.23 22.80 Shear loss at 100 °C [%] 1.2 3.7 Shear loss of RL 209 at 100 °C [%] 10.1 10.1 For ISO 220 formulations, the data disclosed in Table 9 show that the minimum required polymer content is approximately 20% by weight. The polymers according to the present invention exhibit good solubility in used base oils (i.e., Group III and IV oils, as well as their blends) at all temperatures up to the pour point of the formulation. The resulting formulations have a high VI of approximately 130. Unlike the formulations described above, the ISO 220 formulations in Table 9 focus more on optimizing formulation costs than on performance. For this reason, the treatment rate of the acrylate polymers was minimized by choosing the lowest viscosity grade and a Group II base fluid. The Group II base fluid not only offers an economic advantage due to the simpler refining process, but it also has a higher viscosity than the Group III and IV base fluids used in the previous examples, allowing the polymer treatment rate to be reduced to below 30% by weight while maintaining excellent shear stability. At such low treatment rates, the positive influence on the VI is less pronounced, but still quite substantial. Not visible in the provided data, but evident during formulation and research, is that the function of the polymers of the invention as compatibilizers between additives and nonpolar base oils is not affected at all at the reduced treatment rates. Considering that a 10 wt% addition of a low-viscosity polar base material with strong dissolving power is not uncommon in industrial gear oils based on nonpolar base materials, this is an excellent result for the polyacrylates.

Claims

1. Use of polyalkyl acrylates, comprising: (a) 95 to 100% by weight of branched Cs-io alkyl acrylates; and (b) 0 to 5% by weight of C1-20 alkyl (meth)acrylates, characterized in that the weight average molecular weight is in the range of 7,000 to 25,000 g / mol and the residual monomer content is 0.1% or less, as base oils in lubricant formulations, especially in industrial gear oil formulations.

2. The use according to claim 1, characterized in that the polyalkyl acrylates consist of 100% by weight of branched Ce-w alkyl acrylates.

3. The use according to claim 1 or 2, characterized in that the Ce-w alkyl acrylate is selected from the group consisting of 2-ethylhexyl acrylate and 2-propylheptyl acrylate.

4. Base oil composition, comprising: (A) 70 to 95% by weight of at least one polyalkyl acrylate, comprising: (a) 95 to 100% by weight of branched Ce-io alkyl acrylates; and (b) 0 to 5% by weight of C1-20 alkyl (meth)acrylates, characterized in that the weight average molecular weight is in the range of 7,000 to 25,000 g / mol and the residual monomer content is 0.1% or less; and (B) 5 to 30% by weight of a base oil selected from the group consisting of Group II API oils, Group III API oils, Group IV API oils and mixtures thereof, based on the total weight of the base oil composition.

5. Base oil composition according to claim 4, characterized in that the polyalkyl acrylate (A) consists of 100% by weight of branched Ce-io alkyl acrylates.

6. Base oil composition according to claim 4 or 5, characterized in that the Ce-w alkyl acrylate is selected from the group consisting of 2-ethylhexyl acrylate and 2-propylheptyl acrylate.

7. Base oil composition according to claim 4 or 5, characterized in that the Cs-io alkyl acrylate is ethylhexyl acrylate.

8. Use of a base oil composition in accordance with any MA / a / ¿u¿¿ / uu / 100 of the preceding claims as an industrial gear oil.

9. Polyalkyl acrylates, comprising: (a) 95 to 100% by weight of branched Cs-io alkyl acrylates; and (b) 0 to 5% by weight of C1-20 alkyl (meth)acrylates, characterized in that the weight average molecular weight is in the range of 7,000 to 25,000 g / mol and the residual monomer content is 0.1% by weight or less.

10. Polyalkyl acrylates according to claim 9, consisting of 100% by weight of branched Cs-io alkyl acrylates.

11. Polyalkyl acrylates according to claim 9 or 10, characterized in that the Ce-w alkyl acrylate is selected from the group consisting of 2-ethylhexyl acrylate and 2-propylheptyl acrylate.

12. Polyalkyl acrylates according to claim 9 or 10, characterized in that the Ce-io alkyl acrylate is ethylhexyl acrylate.

13. Lubricating composition, comprising: (A) 20 to 60% by weight of at least one polyalkyl acrylate, comprising: (a) 95 to 100% by weight of branched Ce-w alkyl acrylates; and (b) 0 to 5% by weight of C1.20 alkyl (meth)acrylates, based on the total weight of the polyalkyl acrylate, characterized in that the weight average molecular weight is in the range of 7,000 to 25,000 g / mol and the residual monomer content is 0.1% by weight or less; (B) 40 to 80% by weight of a base oil selected from the group consisting of Group II API oils, Group III API oils, Group IV API oils and mixtures thereof; and (C) 0 to 5% by weight of one or more additives, based on the total weight of the lubricant composition.

14. Lubricating composition according to claim 8, characterized in that one or more additional additives (C) are selected from the group consisting of pour point depressants, dispersants, antifoaming agents, detergents, demulsifiers, antioxidants, anti-wear additives, extreme pressure additives, friction modifiers, anti-corrosion additives, colorants and mixtures thereof.

15. A process for preparing polyalkyl acrylates, comprising: (a) 95 to 100 wt% of branched Cs-w alkyl acrylates; and (b) 0 to 5 wt% of C1-20 alkyl (meth)acrylates, IVIA / a / ZUZZ / UU 11OO, characterized in that the weight average molecular weight is in the range of 7,000 to 25,000 g / mol and the residual monomer content is 0.1 wt% or less, the process comprising the steps of: (i) loading a reaction vessel with a base oil; (ii) heating the base oil of step (i) to a reaction temperature of 130 °C to 170 °C; (iii) continuously feeding a mixture of branched Cs-w alkyl acrylates and 0.1 to 1.2% of an initiator, based on the amount of branched Ce-w alkyl acrylates, to the reaction vessel for a time of 120 to 240 minutes; 10 (iv) optionally, stir the reaction mixture obtained in step (iii) for a further 50 to 90 minutes; and (vi) cool the reaction mixture obtained in step (iv) to room temperature and obtain the desired polyalkyl acrylate.