Compressor oil having a high viscosity index

Abstract

The present invention relates to the use of polyalkyl(meth)acrylates in compressor oils. The present invention relates in particular to a method of increasing the energy efficiency of a compressor by operating the compressor with a compressor oil comprising a viscosity index improver based on polyalkyl(meth)acrylates.

Description

Technical Field

[0001] This invention relates to the use of poly(meth)acrylate alkyl esters in compressor oils. More particularly, this invention relates to a method for improving the energy efficiency of a compressor by operating the compressor using a compressor oil containing a viscosity index improver based on poly(meth)acrylate alkyl esters. Background Technology

[0002] Conventional compressors belong to the group of rotary or reciprocating machines. They compress various gases, such as air, carbon dioxide, or other refrigerants. Small refrigeration compressors are used in household refrigerators, while larger compressors are used for cooling warehouses.

[0003] The call for sustainable development and mitigating the effects of global warming makes low energy consumption and high efficiency essential for existing compressor technologies. The energy-saving potential is enormous, given the widespread availability and ubiquitous use of household refrigerators. The same applies to compressed air used in pneumatic systems across virtually all industries, including commercial and industrial sectors.

[0004] The most common refrigeration cycle is accomplished by circulating, evaporating, and condensing the refrigerant in a closed system. Evaporation occurs at low temperatures and low pressures, while condensation occurs at high temperatures and high pressures. This makes it possible to transfer heat from low-temperature regions to high-temperature regions.

[0005] The important internal components of a refrigerator are refrigerant, compressor, condenser, expansion valve or capillary tube, evaporator, cooling compartment or freezer compartment.

[0006] The refrigerant flows through all the internal components of the refrigerator. It performs the cooling action in the evaporator. In the evaporator (cooling compartment or freezer compartment), it absorbs heat from the substance being cooled and releases it into the atmosphere via the condenser. The refrigerant continuously circulates through all the internal components of the refrigerator. The compressor draws the refrigerant from the evaporator and discharges it at high pressure and temperature. The compressor is driven by an electric motor and is the main power-consuming device in the refrigerator. The refrigerant from the compressor enters the condenser, where it is cooled by the atmosphere, thus losing the heat it absorbed in the evaporator and compressor. The refrigerant leaving the condenser enters the expansion tank. As the refrigerant passes through the capillary tube, its pressure and temperature drop abruptly. At very low pressure and temperature, the refrigerant enters the evaporator or freezer compartment. The evaporator is a heat exchanger. In the evaporator, the refrigerant absorbs heat from the substance being cooled, evaporates, and is then drawn into the compressor. This cycle repeats continuously.

[0007] In the refrigeration cycle, the compressor is the most sensitive component and must be properly lubricated to achieve a long service life. Lubricants used in refrigeration compressors reduce friction, prevent wear, and act as a seal between the high-pressure and low-pressure sides.

[0008] Refrigerators have a structure in which a mixture of refrigerant and compressor oil circulates within a closed system. This necessitates high compatibility between the compressor oil and the refrigerant. In addition, other challenges for compressor oil include good sealing performance and protection against wear and corrosion of the compressor unit.

[0009] Household refrigerators use isobutane (R600a) as a refrigerant, which is considered a novel and proven technology. However, research on efficiency improvements has primarily focused on the refrigerant and the compressor itself, as it is the main energy-consuming component in the refrigeration cycle. The compressor is lubricated, and therefore, the lubricant is one of the decisive factors affecting overall efficiency within the compressor. Besides the compatibility of the chemical composition of the lubricant and refrigerant, the resulting compressor performance is also important.

[0010] In the field of lubricants and lubrication technology, compressor oils are particularly important. The long lifespan expected of refrigerant compressors is closely related to the high-quality requirements of lubricants.

[0011] In addition to its favorable miscibility with the corresponding refrigerant, good cold flow performance, high anti-aging properties, and high chemical and thermal stability also play an important role.

[0012] Interactions with other substances (especially refrigerants) in the refrigeration cycle place very specific demands on lubricants at some extreme temperature differences and require them to have a wide temperature operating window.

[0013] In the field of refrigeration systems, the demand for energy efficiency is high. One starting point for improving energy efficiency is to use refrigeration oils with low viscosity (i.e., low viscosity grades). The common standard for compressor oils using isobutane as a refrigerant is ISO viscosity grade (ISO VG) 7, sometimes ISO VG 5. However, further reductions in viscosity are desired.

[0014] The challenge associated with dilute base fluids is ensuring the compatibility of the oil with the refrigerant, namely the refrigerant's solubility in the oil, sealing performance, and protection against wear and corrosion.

[0015] Insufficient lubrication of the compressor can lead to increased power consumption, reduced overall efficiency, or thermal radiation resulting in higher temperatures, as well as a shortened lifespan for both the oil and the equipment. Oil suitability can be tested on a standardized test bench for small-capacity refrigerant compressors, ensuring comparable test parameters for measuring refrigerant mass flow rate, compressor power consumption, calorimeter heat input, and compressor casing temperature.

[0016] It is well known in the lubricant industry that additives can provide performance benefits (such as wear and corrosion protection, improved oxidation stability) or solve sealing problems.

[0017] Commonly used, especially poly(meth)acrylates, are well-known additives used in various applications such as engine oils, transmission oils, gear oils, hydraulic fluids, greases, and metalworking fluids.

[0018] The use of alkyl poly(meth)acrylates as viscosity index improvers in compressor oils has not been reported to date.

[0019] Existing technology

[0020] US 2009 / 0062167 relates to a refrigeration oil composition comprising a blend of low-viscosity and high-viscosity base oils. No viscosity index improvers based on poly(meth)acrylates according to the present invention are disclosed, and no energy savings are reported.

[0021] US 2019 / 0241827 relates to a refrigeration oil containing a specific mineral oil (A) and at least one polymer (B) that exhibits excellent lubricity. No viscosity index improvers based on poly(meth)acrylates according to the present invention are disclosed, and no energy savings are reported.

[0022] EP 2337832 discloses a method for reducing noise generation in a hydraulic system, the method comprising contacting a hydraulic fluid comprising a poly(meth)acrylate polymer with the hydraulic system. The hydraulic fluid contains a viscosity index improver and has a viscosity index (VI) of at least 130. The VI improver is described as a poly(meth)acrylate having a molecular weight in the range of 10,000 to 200,000 g / mol, and is obtained by polymerizing a mixture of olefinically unsaturated monomers, the mixture preferably containing 50 to 95% by weight of C9 to C6 methacrylate. 16 Alkyl esters and 1 to 30% by weight of C1 to C8 alkyl methacrylates.

[0023] The invention described in EP 2337832 aims to reduce noise, which is achieved by increasing the viscosity of the oil at higher temperatures. For this effect, high viscosity and high density are beneficial, and the high VI of the fluid is the cause of the increased viscosity at operating temperatures.

[0024] In this invention, a similar approach is used to improve the energy efficiency of a completely different system.

[0025] The difference between hydraulic systems and compressor (e.g., pneumatic) systems lies in the medium used to transmit power. Pneumatic devices use easily compressible gases, such as air or other gases. Hydraulic devices, on the other hand, utilize relatively incompressible liquid media (such as mineral oil, ethylene glycol, water, synthetic oils, or high-temperature fire-resistant fluids) to transmit power.

[0026] Because of this key difference, other aspects regarding these two power sources are also addressed. Pneumatic units used in industrial applications typically operate at pressures ranging from 80 to 100 psi, while hydraulic units operate at 1,000 to 7,500 psi, or even exceeding 10,000 psi for specialized applications.

[0027] Additionally, a tank is needed to store the oil, from which the hydraulic system can draw oil in case of insufficient oil. However, in a pneumatic system, air can simply be drawn from the atmosphere and then purified via a filter and dryer.

[0028] Because pneumatic devices use compressible gases, they require compressors. In contrast, hydraulic devices use liquids within a system that includes pumps, valves, and actuators.

[0029] The temperature range in a compressor can be much wider than that in a hydraulic system, and air compressor oil needs to withstand prolonged exposure to hot air.

[0030] Hydraulic oil performance additives traditionally contain metals and generate ash, while compressor oils are ash-free.

[0031] EP 1987118 discloses the use of fluids with a viscosity index of at least 130 in hydraulic systems (such as engines or electric motors). Such fluids comprise (meth)acrylate C1 to C6 esters, (meth)acrylate C7 to C6 esters, and (meth)acrylate C7 to C6 esters in a mixture of API Group II or III mineral oils and polyalphaolefins with a molecular weight less than 10,000 g / mol. 40 Ester and optionally other monomers that can copolymerize with (meth)acrylates.

[0032] The difference between hydraulic fluids and compressor fluids lies in the use of a single fluid in hydraulic systems for both lubrication and operation, while compressors utilize two separately defined fluids. A common aspect is their widespread use in numerous applications where efficiency improvements are required. Summary of the Invention

[0033] The object of this invention is to provide a compressor oil that results in increased energy efficiency. Energy savings allow for the use of smaller compressors, which in turn leads to cheaper design and operation, i.e., reduced energy consumption while maintaining similar performance.

[0034] It has now been surprisingly discovered that compressor oils formulated with the polymethyl methacrylate-based viscosity index improver as defined in claim 1 allow for a significantly reduced specific energy requirement for compressor operation compared to operation using compressor oils without such a polymethyl methacrylate-based viscosity index improver. Invention Details

[0036] One object of the present invention relates to a method for improving the energy efficiency of a compressor, the method comprising operating the compressor with compressor oil, the method being characterized in that the compressor oil comprises:

[0037] (i) 1% to 30% by weight of a viscosity index improver based on alkyl polymethacrylate, comprising:

[0038] (a) 0% to 25% by weight of methyl methacrylate;

[0039] (b) 75% to 100% by weight of linear or branched (meth)acrylic acid C 10-18 Alkyl esters; and

[0040] (c) 0% to 2% by weight of (meth)acrylic acid linear or branched C 5-9 Alkyl esters or (meth)acrylic acid straight-chain or branched C 20-24 Alkyl esters, of which

[0041] The weight-average distribution of the viscosity index improver based on poly(meth)acrylate

[0042] Subquant (M) w Within the range of 5,000 to 400,000 g / mol;

[0043] (ii) 70% to 99% by weight of base oils selected from API Groups II, III, IV and V and mixtures thereof, and

[0044] (iii) 0% to 2.5% by weight of a zinc-free performance package, which contains at least an anti-wear agent, an anti-corrosion agent, and an antioxidant.

[0045] The compressor oil has a viscosity index of at least 140, preferably at least 160, and more preferably at least 180.

[0046] In another purpose, the compressor oil comprises:

[0047] (i) 1% to 20% by weight, preferably 1% to 15% by weight, preferably 1% to 10% by weight of a viscosity index improver based on polyalkyl methacrylate as further outlined above;

[0048] (ii) 80% to 99% by weight, preferably 85% to 99% by weight, preferably 90% to 99% by weight, of base oils selected from API Groups II, III, IV and V and mixtures thereof; and

[0049] (iii) 0% to 2.5% by weight of zinc-free performance packages containing at least anti-wear agents, corrosion inhibitors and antioxidants.

[0050] In another purpose, the viscosity index improver based on alkyl polymethacrylate comprises:

[0051] (a) 0.2% to 25% by weight, preferably 4% to 16% by weight of methyl methacrylate;

[0052] (b) 75% to 99.8% by weight, preferably 84% to 96% by weight, of linear or branched methacrylic acid. 10-18 Alkyl esters; and

[0053] (c) 0% to 2% by weight of (meth)acrylic acid linear or branched C 5-9 Alkyl esters or (meth)acrylic acid straight-chain or branched C 20-24 Alkyl esters.

[0054] The content of each component (i), (ii), and (iii) is based on the total composition of the compressor oil. In one particular embodiment, the total proportion of components (i), (ii), and (iii) is 100% by weight.

[0055] The content of each component (a), (b), and (c) is based on the total composition of the viscosity index improver based on poly(meth)acrylate. The total proportion of components (a), (b), and (c) is 100% by weight.

[0056] The weight-average molecular weight M of the polyalkyl acrylate polymer according to the present invention wPreferably, the concentration is at least 5,000 g / mol or 8,000 g / mol or 10,000 g / mol or 30,000 g / mol, and more preferably at most 400,000 g / mol or 200,000 g / mol or 100,000 g / mol or 80,000 g / mol; for example, in the range of 5,000 g / mol to 400,000 g / mol, preferably in the range of 5,000 g / mol to 200,000 g / mol or 5,000 g / mol to 100,000 g / mol or 8,000 g / mol to 100,000 g / mol or 10,000 g / mol to 200,000 g / mol or 30,000 g / mol to 100,000 g / mol or 10,000 g / mol to 80,000 g / mol.

[0057] M w The determination was performed using size exclusion chromatography (SEC) with commercially available polymethyl methacrylate (PMMA) standards. The determination was conducted by gel permeation chromatography using THF as the eluent.

[0058] The term "(meth)acrylate" refers to both esters of acrylic acid and esters of methacrylic acid. According to the present invention, methacrylates are preferred.

[0059] (Meth)acrylic acid C used in this invention 5-9 Alkyl esters are esters formed from (meth)acrylic acid and straight-chain or branched alcohols having 5 to 9 carbon atoms. The term "(meth)acrylic acid C" is used to describe these esters. 5-9 "Alkyl esters" include single (meth)acrylates formed with alcohols of a specific length, and also include mixtures of methacrylates formed with alcohols of different lengths.

[0060] Suitable (meth)acrylic acid C 5-9 Alkyl esters include, for example, amyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and nonyl (meth)acrylate.

[0061] (Meth)acrylic acid C used in this invention 10-18 Alkyl esters are esters formed from (meth)acrylic acid and straight-chain or branched alcohols having 10 to 18 carbon atoms. The term "(meth)acrylic acid C..." 10-18 "Alkyl esters" include single (meth)acrylates formed with alcohols of a specific length, and also include mixtures of (meth)acrylates formed with alcohols of different lengths.

[0062] Suitable (meth)acrylic acid C 10-18Alkyl esters include, for example, 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, hexadecyl (meth)acrylate, heptadecanyl (meth)acrylate, and octadecyl (meth)acrylate.

[0063] (Meth)acrylic acid C used in this invention 20-24 Alkyl esters are esters formed from (meth)acrylic acid and a straight-chain alcohol having 20 to 24 carbon atoms. The term "(meth)acrylic acid C..." 20-24 "Alkyl esters" include single (meth)acrylates formed with alcohols of a specific length, and also include mixtures of (meth)acrylates formed with alcohols of different lengths.

[0064] Suitable (meth)acrylic acid straight-chain C 20-24 Alkyl esters include, for example, eicosyl (meth)acrylate and docosyl (meth)acrylate.

[0065] The dispersant monomers used in this invention are selected from hydroxyethyl methacrylate, N,N-dimethylaminoethyl methacrylate (DMAEMA), N-(3-(dimethylamino)propyl)methacrylamide (DMAPMAm), and N-vinylpyrrolidone (NVP).

[0066] To synthesize the viscosity index improver (i) based on poly(meth)acrylate alkyl esters, the monomer mixture described above can be polymerized by any known method. Classical free radical polymerization can be performed using conventional free radical initiators. These initiators are well known in the art. Examples of such free radical initiators are azo initiators, such as 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2-methylbutyronitrile), and 1,1-azobiscyclohexanenitrile; peroxides, such as methyl ethyl ketone peroxide, acetylacetone peroxide, dilauroyl peroxide, tert-butyl per-2-ethylhexanoate, ketone peroxide, methyl isobutyl ketone peroxide, cyclohexanone peroxide, and benzoyl peroxide. Acyl, tert-butyl perbenzoate, tert-butyl peroxyisopropyl carbonate, 2,5-bis(2-ethylhexanoyl-peroxy)-2,5-dimethylhexane, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, dicumyl peroxide, 1,1-bis(tert-butylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, cumene hydroperoxide, and tert-butyl hydroperoxide.

[0067] Poly(meth)acrylates with lower molecular weights can be obtained by using chain transfer agents. This technique is well-known and widely practiced in the polymer industry and is described in Odian's Principles of Polymerization, 1991.

[0068] Additionally, novel polymerization techniques, such as ATRP (atom transfer radical polymerization) and / or RAFT (reversible addition schisis chain transfer), can be applied to obtain useful polymers derived from alkyl esters. These methods are well known. ATRP reaction methods are described, for example, by J.S. Wang et al., J. Am. Chem. Soc., Vol. 117, pp. 5614-5615 (1995), and by Matyjaszewski, Macromolecules, Vol. 28, pp. 7901-7910 (1995). Furthermore, variations of the above-mentioned ATRP are disclosed in patent applications WO 96 / 30421, WO 97 / 47661, WO 97 / 18247, WO 98 / 40415, and WO 99 / 10387, which are explicitly referenced for the purposes of disclosure. The RAFT method is widely described, for example, in WO 98 / 01478, which is explicitly referenced for the purposes of disclosure.

[0069] The polymerization can be carried out under normal pressure, reduced pressure, or increased pressure. The polymerization temperature is in the range of -20 to 200°C, preferably 60 to 120°C, but is not intended to be limited thereto. The polymerization can be carried out with or without a solvent. The term solvent should be interpreted broadly herein. According to a preferred embodiment, the polymer can be obtained by polymerization in API Group I, II, or III mineral oils or in API Group IV synthetic oils.

[0070] The base oils used in the compressor oil contain oils of lubricating viscosity. Such oils include natural and synthetic oils, oils derived from hydrocracking, hydrotreating and hydrofining, unrefined, refined, refined oils, or mixtures thereof.

[0071] The base oil may also be defined as specified by the American Petroleum Institute (API) (see the April 2008 edition of "Appenix E - API Base Oil Interchangeability Guidelines for Passenger Car Motor Oils and Diesel Engine Oils", Section 1.3, subheading 1.3, "Base Stock Categories").

[0072] The API currently defines five groups of lubricant base materials (API 1509, Annex E—API Base Oil Interchangeability Guide for Bus and Diesel Engine Oils, September 2011). Groups I, II, and III are mineral oils, classified by the amount of saturates and sulfur they contain and by their viscosity index; Group IV is polyalphaolefins; and Group V is all other substances, including, for example, ester oils. The following table illustrates these API classifications exemplarily.

[0073]

[0074] The kinematic viscosity (KV) at 100°C of a suitable non-polar base oil for preparing the compressor oil according to the present invention 100 Preferably, the 1mm measurement is based on ASTM D445. 2 / s to 20mm 2 Within the range of / s, more preferably within 2mm 2 / s to 10mm 2 Within the range of / s.

[0075] The particularly preferred compressor oil of the present invention comprises at least one base oil selected from API Group II oils, API Group III oils, polyalphaolefins (PAOs) and mixtures thereof.

[0076] Another base oil available according to the invention is a Fischer-Tropsch-derived base oil from Groups II-III.

[0077] Fischer-Tropsch derived base oils are known in the art. The term "Fischer-Tropsch derived" means that the base oil is or is derived from a synthetic product of the Fischer-Tropsch process. Fischer-Tropsch derived base oils may also be referred to as GTL (Gastrointestinal Utilization) base oils. Suitable Fischer-Tropsch derived base oils that can be conveniently used as base oils in the compressor oils of the present invention are, for example, those disclosed in the following 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 029029, WO 01 / 18156, WO 01 / 57166 and WO 2013 / 189951.

[0078] The compressor oil used according to the present invention may further contain one or more additional additives selected from pour point depressants, dispersants, defoamers, detergents, demulsifiers, antioxidants, anti-wear additives, extreme pressure additives, friction modifiers, corrosion inhibitors, metal deactivators and metal passivators and mixtures thereof, preferably anti-wear additives, corrosion inhibitors and antioxidants.

[0079] The compressor oil used according to the invention preferably contains up to 2.5% by weight, more preferably from 0.5% to 1.5% by weight, a performance package containing at least anti-wear agents, anti-corrosion agents, and antioxidants.

[0080] The performance package is preferably zinc-free, and more preferably completely ash-free.

[0081] Preferred pour point depressants, such as those selected from alkylated naphthalene and phenolic polymers, alkyl polymethacrylates, maleate copolymers, and fumarate copolymers, can be conveniently used as effective pour point depressants. The compressor oil may contain 0.1% to 0.5% by weight of the pour point depressant. Preferably, no more than 0.3% by weight of the pour point depressant is used.

[0082] Suitable dispersants include poly(isobutylene) derivatives, such as poly(isobutylene)succinimide (PIBSI), including borated PIBSI; and ethylene-propylene oligomers having N / O functional groups. The compressor oil may contain from 0.05% to 5% by weight of at least one dispersant based on the total weight of the compressor oil.

[0083] Suitable defoamers include, for example, silicone oils, fluorosilicone oils, and fluoroalkyl ethers. The compressor oil may contain at least one defoamer at a weight percentage of 0.01% to 0.02% based on the total weight of the compressor oil.

[0084] The detergents include metal-containing compounds such as phenolates; salicylates; thiophosphonates, especially thiopyrophosphonates, thiophosphonates, and phosphonates; sulfonates, and carbonates. These compounds may, in particular, contain calcium, magnesium, and barium as metals. These compounds are preferably used in neutral or highly alkaline forms.

[0085] Preferred demulsifiers include epoxy alkyl copolymers and (meth)acrylates containing polar functional groups.

[0086] Suitable antioxidants include, for example, phenols such as 2,6-di-tert-butylphenol (2,6-DTB), 2,6-di-tert-butyl-4-ethylphenol, butylated hydroxytoluene (BHT), 2,6-di-tert-butyl-4-methylphenol, and 4,4'-methylenebis(2,6-di-tert-butylphenol); aromatic amines, especially alkylated diphenylamine, N-phenyl-1-naphthylamine (PNA), N,N'-diphenyl-p-phenylenediamine, and polymerized 2,2,4-trimethyldihydroquinone (TMQ); "OOS trimer" = reaction products formed by dithiophosphate with activated double bonds from: alkenes, cyclopentadiene, norbornene, α-pinene, polybutene, acrylates, and maleates (ashless when burned); organophosphorus compounds such as triaryl phosphites and trialkyl esters; organocopper compounds and highly basic calcium and magnesium phenolates and salicylates. The compressor oil may contain at least one antioxidant, ranging from 0.05% to 5% by weight based on the total weight of the compressor oil.

[0087] Preferred anti-wear and extreme pressure additives include phosphorus compounds, such as trialkyl phosphates, triaryl phosphates, such as tricresyl phosphate, amine-neutralized mono- and dialkyl phosphates, ethoxylated mono- and dialkyl phosphates, phosphites, phosphonates, or phosphine. The compressor oil may contain from 0.05% to 3% by weight of at least one anti-wear and extreme pressure additive based on the total weight of the compressor oil.

[0088] Examples of metal passivators include triazoles, thiadiazoles, and salicylate compounds, such as N,N'-disalicylate-1,2-diaminopropane.

[0089] Rust inhibitors are widely used. Common chemicals include carboxylates, such as succinate half-esters, sulfonates, alkylamines, and phosphates, such as amine-neutralized phosphate esters.

[0090] The friction modifiers used may include mechanically active compounds such as molybdenum disulfide, graphite (including fluorinated graphite), poly(trifluoroethylene), polyamide, and polyimide; compounds that form an adsorption layer such as long-chain carboxylic acids, fatty acid esters, ethers, alcohols, amines, amides, and imides; compounds that form a layer through tribochemical reactions such as saturated fatty acids, phosphoric acid and thiophosphate esters, xanthogenates, and sulfurized fatty acids; and compounds that form a polymeric layer such as ethoxylated dicarboxylic acid metaesters, dialkyl phthalates, methacrylates, unsaturated fatty acids, and sulfurized olefins.

[0091] All components that are part of the formulation need to exhibit acceptable compatibility with the refrigerant over a wide operating temperature range.

[0092] The additives detailed above are described in particular in T. Mang, W. Dresel (eds.): "Lubricants and Lubrication", Wiley-VCH, Weinheim 2001; and R.Mortier, S.T. Orszulik (eds.): "Chemistry and Technology of Lubricants".

[0093] The total concentration of one or more additives in the compressor oil is up to 5% by weight, preferably from 0.1% to 4% by weight, and more preferably from 0.5% to 3% by weight, based on the total weight of the compressor oil.

[0094] Another object of the present invention relates to a method for improving the energy efficiency of a compressor as further outlined above, wherein the compressor is selected from household or home refrigeration units, air compressors and CO2 compressors.

[0095] Another object of the present invention relates to a method for improving the energy efficiency of a compressor as further outlined above, wherein the compressor is part of a household or home refrigeration unit, the base oil (ii) is selected from API Group IV or V oils and mixtures thereof, and the compressor oil has a kinematic viscosity at 40°C in the range of 2.88 to 7.48 cSt.

[0096] This range includes ISO viscosity grades 3 to 7.

[0097] The refrigerant used in homes or household refrigeration units can be isobutane or propane, with isobutane being preferred.

[0098] Another object of the present invention relates to a method for improving the energy efficiency of a household or domestic refrigeration unit using isobutane or propane, preferably isobutane, as a refrigerant, the method comprising operating the refrigeration unit with compressor oil, wherein the compressor oil comprises:

[0099] (i) 1% to 10% by weight of a viscosity index improver based on alkyl polymethacrylate, comprising:

[0100] (a) 0.2% to 25% by weight, preferably 4% to 16% by weight, of methyl methacrylate; and

[0101] (b) 75% to 99.8% by weight, preferably 84% to 96% by weight of (meth)acrylic acid C 10-18 Alkyl esters; of which

[0102] The weight-average molecular weight (M) of the viscosity index improver based on poly(meth)acrylate is...w The concentration is between 5,000 and 200,000 g / mol, preferably between 10,000 and 200,000 g / mol.

[0103] Within the range of g / mol;

[0104] (ii) 90% to 99% by weight of API Group IV or V base oils and their mixtures, and

[0105] (iii) 0% to 2.5% by weight of a zinc-free performance package, which contains at least an anti-wear agent, an anti-corrosion agent, and an antioxidant.

[0106] The compressor oil described herein has a kinematic viscosity at 40°C in the range of 2.88 to 7.48 cSt and a viscosity index of at least 140, preferably at least 160, more preferably at least 180.

[0107] In another preferred embodiment, the base oil (ii) is selected from cycloalkane oils of API Group V and mixtures thereof, characterized by C N The value is at least 40%.

[0108] The content of each component (i), (ii), and (iii) is based on the total composition of the compressor oil. In one particular embodiment, the total proportion of components (i), (ii), and (iii) is 100% by weight.

[0109] The content of each component (a) and (b) is based on the total composition of the viscosity index improver based on poly(meth)acrylate. The total proportion of components (a) and (b) is 100% by weight.

[0110] Another object of the present invention relates to a method for improving the energy efficiency of a home or household refrigeration unit as further outlined above, wherein the compressor oil has a pour point of -60°C or lower.

[0111] Another object of the present invention relates to a method for improving the energy efficiency of a compressor as further outlined above, wherein the compressor is an air compressor, the base oil (ii) is selected from API Groups II, III and IV or mixtures thereof, and the compressor oil has a kinematic viscosity at 40°C in the range of 28.8 to 74.8 cSt.

[0112] This range includes ISO viscosity grades 32 to 68.

[0113] Another object of the present invention relates to a method for improving the energy efficiency of an air compressor, the method comprising operating the air compressor with compressor oil, wherein the compressor oil comprises:

[0114] (i) 1% to 20% by weight of a viscosity index improver based on polyalkyl methacrylate, comprising:

[0115] (a) 0.2% to 25% by weight of methyl methacrylate;

[0116] (b) 75% to 99.8% by weight of (meth)acrylic acid C 10-18 Alkyl esters;

[0117] and

[0118] (c) 0% to 2% by weight of (meth)acrylic acid linear or branched C 5-9 Alkyl esters or (meth)acrylic acid straight-chain or branched C 20-24 Alkyl esters, of which

[0119] The weight-average molecular weight (M) of the viscosity index improver based on poly(meth)acrylate is... w The concentration is in the range of 5,000 to 400,000 g / mol, preferably in the range of 5,000 to 200,000 g / mol, and more preferably in the range of 10,000 to 80,000 g / mol.

[0120] Within the range;

[0121] (ii) 80% to 99% by weight of API Group II, III or IV base oils or mixtures thereof, and

[0122] (iii) 0% to 2.5% by weight of a zinc-free performance package, which contains at least an anti-wear agent, an anti-corrosion agent, and an antioxidant.

[0123] The compressor oil described herein has a kinematic viscosity at 40°C in the range of 28.8 to 74.8 cSt and a viscosity index of at least 140, preferably at least 160, more preferably at least 180.

[0124] The content of each component (i), (ii), and (iii) is based on the total composition of the compressor oil. In one particular embodiment, the total proportion of components (i), (ii), and (iii) is 100% by weight.

[0125] The content of each component (a), (b), and (c) is based on the total composition of the viscosity index improver based on poly(meth)acrylate. The total proportion of components (a), (b), and (c) is 100% by weight.

[0126] Another object of the present invention relates to a method for improving the energy efficiency of an air compressor as further outlined above, wherein the VI improver based on polyalkyl methacrylate further comprises (c) up to 5% by weight of a dispersant monomer selected from hydroxyethyl methacrylate, N,N-dimethylaminoethyl methacrylate (DMAEMA), N-(3-(dimethylamino)propyl)methacrylamide (DMAPMAm), and N-vinylpyrrolidone (NVP).

[0127] Typical compressed air systems operate at pressures of at least 5 bar, or even higher pressures when greater force is required. Some blow molding applications even operate at 40 bar.

[0128] The compressor oil of this invention has a stronger effect on compressor performance under high pressure.

[0129] Preferably, the air compressor operates at a pressure of at least 5 bar, more preferably at least 7 bar, and even more preferably at least 9 bar.

[0130] Another object of the present invention relates to a method for improving the energy efficiency of a compressor as further outlined above, wherein the compressor is a carbon dioxide compressor, the base oil (ii) is selected from API III, IV or V oils and mixtures thereof, and the compressor oil has a kinematic viscosity at 40°C in the range of 41.4 to 110 cSt.

[0131] This range includes ISO viscosity grades 46 to 100.

[0132] Another object of the present invention relates to a method for improving the energy efficiency of a carbon dioxide compressor, the method comprising operating the carbon dioxide compressor with compressor oil, wherein the compressor oil comprises:

[0133] (i) 1% to 20% by weight of a viscosity index improver based on polyalkyl methacrylate, comprising:

[0134] (a) 0.2% to 25% by weight, preferably 4% to 16% by weight, of methyl methacrylate; and

[0135] (b) 75% to 99.8% by weight, preferably 84% to 96% by weight of (meth)acrylic acid C 10-18 Alkyl esters; of which

[0136] The weight-average molecular weight (M) of the viscosity index improver based on poly(meth)acrylate is... w The concentration is in the range of 5,000 to 100,000 g / mol, preferably in the range of 30,000 to 100,000 g / mol;

[0137] (ii) 80% to 95% by weight of polyolester base oil or a mixture of different polyester base oils; and

[0138] (iii) 0% to 2.5% by weight of a zinc-free performance package, which contains at least an anti-wear agent, an anti-corrosion agent, and an antioxidant.

[0139] The compressor oil described herein has a kinematic viscosity at 40°C in the range of 41.4 to 110 cSt and a viscosity index of at least 140, preferably at least 160, more preferably at least 180.

[0140] The content of each component (i), (ii), and (iii) is based on the total composition of the compressor oil. In one particular embodiment, the total proportion of components (i), (ii), and (iii) is 100% by weight.

[0141] The content of each component (a) and (b) is based on the total composition of the viscosity index improver based on poly(meth)acrylate. The total proportion of components (a) and (b) is 100% by weight.

[0142] The compressor oil commonly used in carbon dioxide compressors is usually based on polyol esters, which have a viscosity of 68 cSt at 40°C.

[0143] Commercially available Fuchs based on polyol esters C-oil can be used at KV values ​​of 55, 80, and 178cSt. 40 The viscosity index is always well below 150.

[0144] Another object of the present invention relates to a method for improving the energy efficiency of a carbon dioxide compressor, the method comprising operating the carbon dioxide compressor with compressor oil, wherein the compressor oil comprises:

[0145] (i) 1% to 30% by weight of a viscosity index improver based on alkyl polymethacrylate, comprising:

[0146] (a) 0.2% to 25% by weight, preferably 4% to 16% by weight, of methyl methacrylate; and

[0147] (b) 75% to 99.8% by weight, preferably 84% to 96% by weight of (meth)acrylic acid C 10-18 Alkyl esters; of which

[0148] The weight-average molecular weight (M) of the viscosity index improver based on poly(meth)acrylate is... w The concentration is in the range of 5,000 to 100,000 g / mol, preferably from 10,000 g / mol to 80,000 g / mol;

[0149] (ii) 80% to 99% by weight of polyalphaolefin base oil or a mixture of different polyalphaolefin base oils; and

[0150] (iii) 0% to 2.5% by weight of a zinc-free performance package, which contains at least an anti-wear agent, an anti-corrosion agent, and an antioxidant.

[0151] The compressor oil described herein has a kinematic viscosity at 40°C in the range of 41.4 to 110 cSt and a viscosity index of at least 140, preferably at least 160, more preferably at least 180.

[0152] The content of each component (i), (ii), and (iii) is based on the total composition of the compressor oil. In one particular embodiment, the total proportion of components (i), (ii), and (iii) is 100% by weight.

[0153] The content of each component (a) and (b) is based on the total composition of the viscosity index improver based on poly(meth)acrylate. The total proportion of components (a) and (b) is 100% by weight.

[0154] Another object of the present invention relates to a method for improving the energy efficiency of a carbon dioxide compressor, the method comprising operating the carbon dioxide compressor with compressor oil, wherein the compressor oil comprises:

[0155] (i) 1% to 30% by weight of a viscosity index improver based on alkyl polymethacrylate, comprising:

[0156] (a) 0% to 25% by weight of methyl methacrylate;

[0157] (b) 60% to 99.8% by weight of (meth)acrylic acid C 10-18 Alkyl esters;

[0158] and

[0159] (c) 0% to 40% C 8-12 α-olefins, in which

[0160] The weight-average distribution of the viscosity index improver based on poly(meth)acrylate

[0161] Subquant (M) w Within the range of 5,000 to 100,000 g / mol;

[0162] (ii) 70% to 99% by weight of polyalphaolefin base oil or a mixture of different polyalphaolefin base oils; and

[0163] (iii) 0% to 2.5% by weight of a zinc-free performance package, which contains at least an anti-wear agent, an anti-corrosion agent, and an antioxidant.

[0164] The compressor oil described herein has a kinematic viscosity at 40°C in the range of 41.4 to 110 cSt and a viscosity index of at least 140, preferably at least 150, more preferably at least 160.

[0165] The content of each component (i), (ii), and (iii) is based on the total composition of the compressor oil. In one particular embodiment, the total proportion of components (i), (ii), and (iii) is 100% by weight.

[0166] The content of each component (a), (b), and (c) is based on the total composition of the viscosity index improver based on poly(meth)acrylate. The total proportion of components (a), (b), and (c) is 100% by weight.

[0167] Compressor oils commonly used in air compressors are typically based on API Group I, II, or III oils, which have a viscosity of 46 cSt at 40°C and a viscosity index below 140. These oils are available from all major oil and compressor original equipment manufacturers (OEMs), such as Kaeser Sigma Fluid MOL, which has a KV index of 46 cSt. 40 And 106 VI. The pour point of this fluid is -30℃.

[0168] Another object of the present invention relates to a method for improving the energy efficiency of an air compressor, as further outlined above, wherein the compressor oil has a pour point of -33°C or lower. Attached Figure Description

[0169] Figure 1 An exemplary test setup is provided for determining the effect on energy consumption in an air compressor. Detailed Implementation

[0170] The invention is further illustrated by the following non-limiting examples and comparative examples (reference oil). The following examples are used to further illustrate preferred embodiments of the invention but are not intended to limit the invention.

[0171] Experimental Section

[0172] abbreviation

[0173] Alkylated naphthalene base oil, derived from ExxonMobil, has a KV of 29 cSt. 40

[0174] Naphthenic base oil, derived from Total, with a KV of 2.3 cSt. 40 and about 45% C N value

[0175] KV kinematic viscosity as measured by ASTM D445

[0176] KV 40 Kinematic viscosity measured at 40°C according to ASTM D445

[0177] KV 100 Kinematic viscosity measured at 100°C according to ASTM D445

[0178] M n Number average molecular weight

[0179] M w weight average molecular weight

[0180] NS3 is a naphthenic base oil derived from Nynas, with a KV of 2.9 cSt. 40 and about 57% of C N value

[0181] PAO6 Group IV base oil, with a KV of 6 cSt. 100

[0182] PAO8 Group IV base oil, with a KV of 8 cSt 100

[0183] PDI (Polydispersity Index)

[0184] PP Pour Point

[0185] T3 cycloalkane base oil, derived from Nynas, has a KV of 3.6 cSt. 40 and about 52% of C N value

[0186] T9 cycloalkane base oil, derived from Nynas, has a KV of 9.1 cSt. 40 and about 45% C N value

[0187] VI viscosity index

[0188] Test methods

[0189] The polymers based on polyalkyl methacrylate according to the present invention are characterized with respect to their weight-average molecular weight.

[0190] Compressor oils comprising the polymethyl methacrylate-based polymers according to the present invention and comparative examples, regarding their kinematic viscosity (kV) at 40°C according to ASTM D445.40 ) and kinematic viscosity at 100°C (KV) 100 They are characterized according to the viscosity index (VI) of ASTM D2270, their pour point according to ASTM D5950, their flash point according to ASTM D92, and their viscosity shear loss.

[0191] Determine the effectiveness of energy consumption for a household or residential refrigeration unit.

[0192] A standardized performance test bench measures the power consumption of a compressor under specified rated conditions. It ensures identical operating conditions for multiple tests. Additionally, performance testing includes calculating the coefficient of performance (COP; the ratio of cooling power to electric drive power) and volumetric efficiency under specified rated conditions, i.e., the ratio of actual volumetric flow rate to geometrically possible volumetric flow rate. The latter indicates the sealing performance of the compressor's working chamber.

[0193] The test bench is designed for performance testing of small-capacity refrigerant compressors according to ASHRAE Standard 23.1 (2010) or DIN EN 13771-1 (2017). Based on a standard vapor compression cycle, the test bench includes a calorimeter evaporator and a flow meter to determine the refrigerant mass flow rate. In addition to major components such as the compressor, condenser, and electronic expansion device, the cycle is further equipped with an oil separator, filter dryer, observation window, and accumulator.

[0194] The compressor is an Embraco VEMX 7C hermetically sealed reciprocating piston compressor, using R600a (isobutane) as the refrigerant. The compressor operates at three speeds: 50Hz, 100Hz, and 150Hz. CECOMAF (Comitéeuropéen desconstructeurs de matériel frigorifique) conditions are applied: suction-side gas temperature = 32°C, suction-side dew point = -25°C, pressure-side dew point = +55°C, ambient temperature = 35±2°C.

[0195] The general processing of data obtained in this experiment follows the European compressor evaluation standard (DIN EN 13771-1, 2017).

[0196] Table 1: Formulations of the refrigeration compressor oil of the present invention and the comparative refrigeration compressor oil, and the results obtained therefrom.

[0197]

[0198] *) As a performance package, a commercially available zinc-free performance package is used to protect the compressor. This zinc-free performance package contains at least anti-wear agents, anti-corrosion agents, and antioxidants.

[0199] **) KV 40 The value is 4.12 mm. 2 / s, slightly below the range defined in ISO VG 5; not defined in ISO VG 4.

[0200] Polymer 1 consists of 13% by weight methyl methacrylate and 86.5% by weight C methacrylate. 10-16 Alkyl ester and 0.5% by weight of methacrylic acid C 11-18 Alkyl ester composition (M) w =77,000 g / mol, 80% of the solids are dissolved in highly refined mineral oil.

[0201] As a comparative example 1 (CE 1), KV was used. 40 It is 4.90mm 2 Commercially available alkylbenzene base oil at / s (corresponding to ISO VG 5). Comparative Example 2 (CE 2) is a KV... 40 It is a mixture of different cycloalkane base oils of approximately 7 (corresponding to ISO VG 7). The comparative example does not contain any poly(meth)acrylate alkyl esters.

[0202] Working Examples 1-3 (Ex 1-3) are also based on cycloalkane base oils and polymer 1 as a poly(meth)acrylate alkyl ester. Ex 1-3 was formulated into KV... 40 4mm 2 / s(Ex 1), 5mm 2 / s(Ex 2) and 7mm 2 / s(Ex 3), which correspond to ISO "VG 4", VG 5 and VG 7 respectively.

[0203] in conclusion:

[0204] The oils of this invention exhibit improved volumetric efficiency and coefficient of performance at all drive speeds (50 / 100 / 150 Hz). Compressor oils with high VI show good compatibility with the refrigerant (no harmful separation or buildup observed) and are able to improve equipment performance.

[0205] The effect of measuring the energy efficiency of air compressors

[0206] Another aspect of the invention is to improve the efficiency of air compressors.

[0207] Compressor oils with VI of 140 and higher were tested in a Kaeser SX4 screw compressor and compared with commercially available Kaeser mineral oil-based single-stage fluids with VI of 106.

[0208] A second, larger air compressor, the Atlas Copco GA75VSD, was used to determine the energy efficiency benefits.

[0209] Figure 1 The test setup used is described.

[0210] Characterization of the air compressor used in the relevant test procedures:

[0211] (1) KAESER SX4

[0212] Production date: September 2019

[0213] Manufacturer: Kaeser

[0214] Compressed medium: Air

[0215] Reference frequency: 50Hz

[0216] Maximum air volumetric flow rate: 0.36 m³ 3 / min

[0217] Pressure level: 1

[0218] Maximum discharge pressure: 11 bar

[0219] Motor capacity: 3.0kW

[0220] (2)Atlas Copco GA75VSD PA 13MK5

[0221] Production date: January 2019

[0222] Manufacturer: Atlas Copco

[0223] Compressed medium: Air

[0224] Reference frequency /

[0225] Lower limit frequency: 73 / 20Hz

[0226] Maximum air volumetric flow rate: 14.76 m³ / h 3 / min

[0227] Pressure level: 1

[0228] Maximum discharge pressure: 13 bar

[0229] Motor capacity: 75kW

[0230] Measure the following parameters: oil pan temperature, air temperature on the intake and exhaust sides, ambient air temperature, pressure, and humidity; air pressure on the intake and exhaust sides, airflow rate, and power requirements of the equipment. On the exhaust side, use a condenser air dryer to maintain the dried air with a water content of less than 0.1% compared to compressed air.

[0231] Adjust steady-state operating conditions with two different oil temperatures and four different air pressures. Airflow and power requirements result in specific power requirements in W / (bar·L / min).

[0232] Table 2 below shows the formulations of the air compressor oil of the present invention and the comparative air compressor oil, and the results obtained therefrom.

[0233] Table 2: Formulations of the air compressor oil of the present invention and comparative air compressor oils (AirEx and AirCE) and the results obtained therefrom.

[0234]

[0235] *) As a performance package, a commercially available zinc-free performance package is used to protect the compressor, the zinc-free performance package containing at least an anti-wear agent, an anti-corrosion agent, and an antioxidant.

[0236] **) The mixture of Group III oils totaled 81.4% by weight.

[0237] Polymer 2 consists of 13% by weight methyl methacrylate and 87% by weight C methacrylate. 10-16 Alkyl ester composition (M) w =56,000 g / mol, 74% of the solids are dissolved in highly refined mineral oil.

[0238] Polymer 3 consists of 11.3 wt% methyl methacrylate and 88.3 wt% C-methacrylate. 10-18 Alkyl ester and 0.4% by weight of C methacrylate 20-22 Alkyl ester composition (M) w =375,000 g / mol, 42% solids dissolved in highly refined mineral oil.

[0239] Polymer 4 consists of 0.2% by weight methyl methacrylate and 99.8% by weight isocyanate methacrylate. 12-15 Alkyl ester composition (M) w =13,800 g / mol).

[0240] As a comparative example 1 (AirCE 1), KV was used. 40 46mm 2Original fluid (available commercially from Kaeser) at / s (corresponding to ISO VG 46). It contains no poly(meth)acrylates.

[0241] Working Examples 1-6 (AirEx 1-6) are based on different Group III base oils and contain poly(meth)acrylates. AirEx 1-5 is formulated into KV. 40 Approximately 46mm 2 / s, corresponding to ISO VG 46; AirEx 6 is configured as KV 40 Approximately 55mm 2 / s,

[0242] The effects on energy consumption in air compressors obtained by using the compressor oil according to the present invention are summarized in Tables 3a, 3b and 3c below.

[0243] Table 3a: Pressure p in the range of 8.39 to 9.43 bar 空气 The following describes the effect of using the compressor oil according to the invention on energy consumption and efficiency in an air compressor.

[0244]

[0245] Table 3b: Pressure p in the range of 7.06 to 7.67 bar 空气 The following describes the effect of using the compressor oil according to the invention on the energy consumption and efficiency of the air compressor.

[0246]

[0247] Table 3c: Pressure p in the range of 4.89 to 5.15 bar 空气 The following describes the effect of using the compressor oil according to the invention on the energy consumption and efficiency of the air compressor.

[0248]

[0249] p 空气 Air pressure at the exhaust port

[0250] T 油 Compressor oil temperature

[0251] P 总 Total power requirement of the compressor

[0252] Airflow rate: Airflow rate on the exhaust side (at p) 空气 (dry air below)

[0253] P 比： Power requirement of compressor unit divided by air flow rate

[0254] Power ratio: The power requirement of the compressor unit divided by (air flow rate × air discharge pressure)

[0255] Efficiency improvement is achieved by P 比 The following parameters were calculated: inhalation pressure and various compression ratios (correction factors) under test conditions relative to reference conditions:

[0256]

[0257] Additional testing was conducted on an Atlas Copco GA75VSD. The oil temperature was controlled at 90°C. Three different exhaust air pressures were investigated at 8 bar, 10 bar, and 12.5 bar.

[0258] Table 4 below shows the results obtained using the Atlas Copco GA75VSD.

[0259] Table 4: Results obtained using Atlas Copco GA75VSD

[0260]

[0261] Table 5: Shear loss of oil during the test procedure after 1 day of testing under various conditions:

[0262]

[0263] in conclusion:

[0264] After reaching steady-state operating conditions under various discharge pressures and oil temperatures, measure the power demand for at least 15 minutes.

[0265] The power ratio is defined as the ratio of measured power demand to output power, and is measured by multiplying the air volumetric flow rate (expressed in liters per minute) by the pressure on the compressor discharge side. Constant and repeatable environmental conditions are achieved by operating the equipment in a controlled, air-conditioned room.

[0266] Studies on an air compressor test bench clearly demonstrate the efficiency advantage of compressor oils with a VI of at least 140 and high shear stability. Significant efficiency improvements were observed under all studied operating conditions. At an oil temperature of approximately 75°C, when the compressor oil was changed from AirCE1 to AirEx4 (which contains polymer 2 and has a VI of 200), the power ratio decreased from 1.15 (W·min) / (bar·L) to 1.10 (W·min) / (bar·L). At oil temperatures of 92 to 94°C, even stronger improvements were observed, from 1.26 (W·min) / (bar·L) for AirCE1 to 1.18 (W·min) / (bar·L) for AirEx4. The corresponding efficiency improvement was calculated to be 4.3%. AirEx5, containing polymer 3 and with a VI of 200, also demonstrated improved efficiency. At oil temperatures above 90°C and air discharge pressures of approximately 9 bar, the improvement was approximately 1.5%. Compared to compressor oil AirEx4, AirEx5 uses polymers with higher molecular weights and lower shear stability. Higher shear stability is beneficial for efficiency improvement and oil lifespan. The fluid of this invention exhibits 40% of its maximum KV in a 40-minute acoustic shear test according to ASTM D5621. 100 Shear loss. According to ASTM D5621, a minimum shear loss of 20% is preferred, and more preferably less than 10%.

[0267] Table 5 shows the oil viscosity before and after testing on the compressor test bench. The viscosity of AirEx3 and AirEx4 did not change over time during the test; however, under actual life conditions, the viscosity of AirEx5, containing polymer 3, decreased by more than 10%. Polymer 3 has a relatively high molecular weight and insufficient shear stability to achieve long-term efficiency improvements in the air compressor.

[0268] The compressor fluid according to the invention has a pour point of -33°C or lower. High VI, low pour point, and high shear stability are achieved by blending Group II, Group III, or PAO base oils with a viscosity index improver based on polymethyl methacrylate according to the invention (having a defined composition and a molecular weight of up to 400,000 g / mol, preferably less than 200,000 g / mol, and more preferably less than 100,000 g / mol). It is recognized that the equipment can operate at lower temperatures using lubricants with higher VI and better shear stability. When using more efficient fluids, it is necessary to block the cooling unit to achieve the higher oil operating temperature level of 90°C required for test operation.

[0269] Studies have shown that overheating can be avoided by using the compressor oil according to the invention, since more efficient air compressors tend to operate at lower temperatures.

Claims

1. A method for improving the energy efficiency of an air compressor, the method comprising operating the air compressor with compressor oil, wherein the compressor oil comprises: (i) 1% to 30% by weight of a viscosity index improver based on polyalkyl methacrylate, comprising: (a) 0% to 25% by weight of methyl methacrylate; (b) 75% to 100% by weight of linear or branched (meth)acrylic acid C 10-18 Alkyl esters; and (c) 0% to 2% by weight of (meth)acrylic acid linear or branched C 5-9 Alkyl esters or (meth)acrylic acid straight-chain or branched C 20-24 Alkyl esters, of which The weight-average molecular weight (M) of the viscosity index improver based on poly(meth)acrylate is... w Within the range of 5,000 g / mol to 400,000 g / mol; (ii) 70% to 99% by weight of base oils selected from API Groups II, III, IV and V and mixtures thereof; and (iii) An optional performance package of up to 2.5% by weight, which contains one or more additional additives. The compressor oil has a viscosity index of at least 140.

2. The method of claim 1, wherein the compressor oil has a viscosity index of at least 160.

3. The method of claim 1, wherein the compressor oil has a viscosity index of at least 180.

4. The method of claim 1, wherein the viscosity index improver based on alkyl polymethacrylate comprises: (a) 0.2% to 25% by weight of methyl methacrylate; (b) 75% to 99.8% by weight of methacrylic acid C 10-18 Alkyl esters; and (c) 0% to 2% by weight of (meth)acrylic acid linear or branched C 5-9 Alkyl esters or (meth)acrylic acid straight-chain or branched C 20-24 Alkyl esters.

5. The method of claim 4, wherein the viscosity index improver based on alkyl polymethacrylate comprises: (a) 4% to 16% by weight of methyl methacrylate; (b) 84% to 96% by weight of methacrylic acid C 10-18 Alkyl esters; and (c) 0% to 2% by weight of (meth)acrylic acid linear or branched C 5-9 Alkyl esters or (meth)acrylic acid straight-chain or branched C 20-24 Alkyl esters.

6. The method according to any one of claims 1-5, wherein the weight-average molecular weight (M) of the viscosity index improver based on poly(meth)acrylate is... w (In the range of 5,000 g / mol to 200,000 g / mol) 7. The method according to claim 6, wherein the weight-average molecular weight (M) of the viscosity index improver based on poly(meth)acrylate is... w (In the range of 8,000 g / mol to 100,000 g / mol) 8. The method according to claim 6, wherein the weight-average molecular weight (M) of the viscosity index improver based on poly(meth)acrylate is... w (In the range of 10,000 g / mol to 80,000 g / mol) 9. The method according to any one of claims 1-5, wherein the performance package (iii) is a zinc-free performance package that contains at least an anti-wear agent, an anti-corrosion agent, and an antioxidant.

10. The method of claim 9, wherein the performance package (iii) is an ashless performance package.

11. The method according to any one of claims 1 to 5, wherein the compressor oil comprises: (i) 1% to 20% by weight of the aforementioned viscosity index improver based on alkyl polymethacrylate; (ii) 80% to 99% by weight of base oils selected from API Groups II, III, IV and V and mixtures thereof; and (iii) 0% to 2.5% by weight of zinc-free performance packages containing at least anti-wear agents, corrosion inhibitors and antioxidants.

12. The method of claim 11, wherein the compressor oil comprises: (i) 1% to 15% by weight of the viscosity index improver based on polymethyl methacrylate; (ii) 85% to 99% by weight of base oils selected from API Groups II, III, IV and V and mixtures thereof; and (iii) 0% to 2.5% by weight of zinc-free performance packages containing at least anti-wear agents, corrosion inhibitors and antioxidants.

13. The method of claim 11, wherein the compressor oil comprises: (i) 1% to 10% by weight of the viscosity index improver based on polyalkyl methacrylate; (ii) 90% to 99% by weight of base oils selected from API Groups II, III, IV and V and mixtures thereof; and (iii) 0% to 2.5% by weight of zinc-free performance packages containing at least anti-wear agents, corrosion inhibitors and antioxidants.

14. The method of claim 1, wherein the base oil (ii) is selected from API Groups II, III and IV or mixtures thereof, and the compressor oil has a kinematic viscosity at 40°C in the range of 28.8 to 74.8 cSt.

15. The method of claim 1, wherein the method comprises operating the air compressor with compressor oil, wherein the compressor oil comprises: (i) 1% to 20% by weight of a viscosity index improver based on alkyl polymethacrylate, comprising: (a) 0.2% to 25% by weight of methyl methacrylate; (b) 75% to 99.8% by weight of (meth)acrylic acid C 10-18 Alkyl esters; and (c) 0% to 2% by weight of (meth)acrylic acid linear or branched C 5-9 Alkyl esters or (meth)acrylic acid straight-chain or branched C 20-24 Alkyl esters, of which The weight-average molecular weight (M) of the viscosity index improver based on poly(meth)acrylate is... w Within the range of 5,000 to 400,000 g / mol; (ii) 80% to 99% by weight of API Group II, III or IV base oils or mixtures thereof, and (iii) 0% to 2.5% by weight of zinc-free performance packages, which contain at least anti-wear agents, corrosion inhibitors, and antioxidants. The compressor oil described herein has a kinematic viscosity at 40°C in the range of 28.8 to 74.8 cSt and a viscosity index of at least 140.

16. The method of claim 15, wherein the weight-average molecular weight (M) of the viscosity index improver based on alkyl poly(meth)acrylate is... w The range is from 5,000 to 200,000 g / mol.

17. The method of claim 15, wherein the weight-average molecular weight (M) of the viscosity index improver based on alkyl poly(meth)acrylate is... w The range is from 10,000 to 80,000 g / mol.

18. The method of claim 15, wherein the compressor oil has a viscosity index of at least 160.

19. The method of claim 15, wherein the compressor oil has a viscosity index of at least 180.

20. The method of claim 14 or 15, wherein the compressor oil has a pour point of -33°C or lower.

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