Sulfur-free dispersant polymers for industrial applications

Abstract

The present invention relates to lubricants comprising small amounts of dispersant polymers and their use in industrial mechanical equipment to avoid particle formation and deposits.

Description

[0001] The present invention relates to lubricants comprising small amounts of dispersant polymers and their use in industrial mechanical equipment to avoid particle formation and deposits.

[0002] The present invention relates to the preparation of (meth)acrylate statistical copolymers that can be used in industrial lubricant applications and are more resistant to aging. When lubricants and oil formulations are used, they will oxidize and darken due to long-term exposure to high temperatures and oxygen. If the oil's sensitivity to this aging process increases, the service life of the oil formulation will drop sharply, thereby increasing the cost of the equipment due to the need for increased servicing. The aging process not only darkens the oil but also forms oxidative by-products that can cause undesirable sludges or varnishes, which can accumulate and damage machine components. Using polymer additives that tend to cause sludges or varnishes will require shorter service intervals and oil changes, thus increasing the cost to the user. Being able to extend the service interval is valuable to consumers and is a general industrial need.

[0003] An object of the present invention is to provide an additive for industrial oil formulations, preferably compressor oils, turbine oils, hydraulic oils or gear oils, more preferably compressor oils, which additive is capable of dispersing particles generated during the use of the equipment, such as particles generated due to oil aging, and keeping them dispersed in the oil, avoiding particle separation and avoiding the formation of sludges, gums and varnishes.

[0004] Common compressors belong to the group of rotary or reciprocating machines. They compress various gases, such as air, carbon dioxide, other chemical gases or other refrigerants. Small refrigeration compressors are used in household refrigerators, and larger compressors are used, for example, in cooling warehouses.

[0005] Additives are well known in the lubricant industry and can provide performance benefits such as wear and corrosion protection, improved oxidation stability or solving seal problems.

[0006] Particularly poly(meth)acrylates are commonly used. Poly(meth)acrylates are well-known additives for different applications such as engine oils, transmission oils, gear oils, hydraulic oils, shock absorber oils and greases.

[0007] To date, the use of dispersant poly(meth)acrylates as additives in compressor oils to avoid particle formation and deposits has not been reported.

[0008] WO 2022 / 139687 A1 relates to a soot dispersant comprising an A-B type block copolymer. The A block is a soot-anchoring unit and comprises an N-dispersant monomer and styrene or benzyl methacrylate.

[0009] US2006 / 0189490 A1 relates to a lubricating oil composition comprising a friction-modifying additive. Such a friction-modifying additive is a block copolymer.

[0010] EP 4 015 604 A1 relates to acrylate-olefin copolymers and their use as lubricant additives or synthetic base fluids.

[0011] Surprisingly, it has been found that low molecular weight (meth)acrylate statistical copolymers having a sulfur content of less than 50 ppm (so-called sulfur-free (meth)acrylate copolymers) and containing at least 1000 ppm nitrogen allow the formulation of fluids with better oxidation stability and corrosion stability. The aim of the polymers of the present invention in the formulation is to disperse the particles generated during the use of the equipment, such as the particles generated by oil aging, and to keep them dispersed in the oil, avoiding particle separation and the formation of sludge, gum and lacquer films. This property is improved in the absence of sulfur, and the sulfur-free products of the present invention also meet the other requirements as described above. DETAILED DESCRIPTION OF THE INVENTION

[0013] A first object of the present invention relates to a method for avoiding the formation of particles and deposits in industrial oil formulations, the method comprising the following steps:

[0014] (i) Preparing a sulfur-free (meth)acrylate statistical copolymer, which copolymer comprises:

[0015] (a) 41 wt% to 99 wt%, preferably 46 wt% to 99 wt%, more preferably 48.5 wt% to 99 wt% of (meth)acrylate C8-18 alkyl esters, preferably (meth)acrylate C10-15 alkyl esters;

[0016] (b) 1 wt% to 10 wt%, preferably 1 wt% to 5 wt%, more preferably 2.5 wt% to 3.5 wt% of N-dispersing monomers or hydroxy-substituted (meth)acrylate C2-4 alkyl esters;

[0017] (c) 0 wt% to 2 wt% of methyl methacrylate; and

[0018] (d) 0 wt% to 49 wt% of α-olefins comprising C8-16 carbon atoms,

[0019] wherein the (meth)acrylate copolymer has a weight average molecular weight Mw of 5,000 g / mol to 50,000 g / mol;

[0020] (ii) Adding 0.05 wt% to 1.0 wt% of the sulfur-free (meth)acrylate copolymer prepared in step (i) to a base oil or a base oil mixture;

[0021] (iii) Optionally, add one or more additional additives; and

[0022] (iv) Apply the industrial oil preparation prepared in step (ii) or (iii) to a compressor, turbine, hydraulic press or industrial gear, preferably to a compressor.

[0023] The contents of components (a), (b), (c) and (d) are based on the total composition of the (meth)acrylate statistical copolymer. In a specific embodiment, the proportions of components (a), (b), (c) and (d) total 100 wt%.

[0024] Another object relates to the method further mentioned above, wherein the sulfur-free (meth)acrylate statistical copolymer comprises:

[0025] (a) 88 wt% to 99 wt%, preferably 93 wt% to 99 wt%, more preferably 94.5 wt% to 97.5 wt% of C8-18 alkyl (meth)acrylate, preferably C10-15 alkyl (meth)acrylate;

[0026] (b) 1 wt% to 10 wt%, preferably 1 wt% to 5 wt%, more preferably 2.5 wt% to 3.5 wt% of an N-dispersing monomer or a hydroxy-substituted C2-4 alkyl (meth)acrylate, preferably an N-dispersing monomer; and

[0027] (c) 0 wt% to 2 wt% of methyl methacrylate.

[0028] Another object relates to the method further mentioned above, wherein the sulfur-free (meth)acrylate statistical copolymer comprises:

[0029] (a) 90 wt% to 99 wt%, preferably 95 wt% to 99 wt%, more preferably 96.5 wt% to 97.5 wt% of C8-18 alkyl (meth)acrylate, preferably C10-15 alkyl (meth)acrylate;

[0030] (b) 1 wt% to 10 wt%, preferably 1 wt% to 5 wt%, more preferably 2.5 wt% to 3.5 wt% of an N-dispersing monomer or a hydroxy-substituted C2-4 alkyl (meth)acrylate, preferably an N-dispersing monomer; and

[0031] (c) 0 wt% to 2 wt% of methyl methacrylate.

[0032] The contents of components (a), (b) and (c) are based on the total composition of the (meth)acrylate statistical copolymer. In a specific embodiment, the proportions of components (a), (b) and (c) total 100 wt%.

[0033] Another object relates to the method further mentioned above, wherein the sulfur-free (meth)acrylic acid alkyl ester statistical copolymer comprises:

[0034] (a) 94.5 wt% to 97.5 wt%, preferably 96.5 wt% to 97.5 wt% of (meth)acrylic acid C8-18 alkyl ester, preferably (meth)acrylic acid C10-15 alkyl ester;

[0035] (b) 2.5 wt% to 3.5 wt% of N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm); and

[0036] (c) 0 wt% to 2 wt% of methyl methacrylate,

[0037] wherein the (meth)acrylic acid alkyl ester copolymer has a weight average molecular weight Mw of 10,000 g / mol to 30,000 g / mol w .

[0038] The contents of components (a), (b) and (c) are based on the total composition of the (meth)acrylic acid alkyl ester statistical copolymer. In a specific embodiment, the proportions of components (a), (b) and (c) total 100 wt%.

[0039] In the context of the present invention, the term "sulfur-free" (meth)acrylic acid alkyl ester statistical copolymer means that the (meth)acrylic acid alkyl ester copolymer comprises less than 300 ppm, preferably less than 100 ppm, more preferably less than 50 ppm of sulfur.

[0040] The weight average molecular weight Mw of the (meth)acrylic acid alkyl ester statistical copolymer according to the present invention w is preferably in the range of 10,000 g / mol to 30,000 g / mol, more preferably 15,000 g / mol to 30,000 g / mol.

[0041] Mw w is determined by size exclusion chromatography (SEC) using commercially available polymethyl methacrylate standards. The determination is carried out by gel permeation chromatography with THF as the eluent.

[0042] The term "(meth)acrylate" means esters of acrylic acid and esters of methacrylic acid. According to the present invention, methacrylates are preferred.

[0043] The (meth)acrylic acid C8-18 alkyl ester used according to the present invention is an ester of (meth)acrylic acid and a straight-chain or branched-chain alcohol having 8 to 18 carbon atoms. The term "(meth)acrylic acid C8-18 alkyl ester" includes the individual (meth)acrylic acid esters with alcohols of a specific length, as well as mixtures of (meth)acrylic acid esters with alcohols of different lengths.

[0044] Suitable C8-18 alkyl (meth)acrylates include, for example, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, 2-propylheptyl (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, heptadecyl (meth)acrylate, and octadecyl (meth)acrylate.

[0045] The C10-15 alkyl (meth)acrylates used according to the present invention are esters of (meth)acrylic acid with linear or branched alcohols having 10 to 15 carbon atoms. The term "(meth)acrylate C10-15" includes the individual (meth)acrylates with alcohols of a specific length, as well as mixtures of (meth)acrylates with alcohols of different lengths.

[0046] Suitable C10-15 alkyl (meth)acrylates include, for example, decyl (meth)acrylate, isodecyl (meth)acrylate, 2-propylheptyl (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, and pentadecyl (meth)acrylate.

[0047] Preferably, at least 30 wt% of the C10-15 alkyl (meth)acrylates are esters of (meth)acrylic acid with branched alcohols having 10 to 15 carbon atoms.

[0048] The N-dispersing monomers used according to the present invention are selected from the group consisting of N,N-dimethylaminoethyl methacrylate (DMAEMA), N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm), and N-vinylpyrrolidone (NVP); preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm).

[0049] The hydroxy-substituted C2-4 alkyl (meth)acrylates used according to the present invention are selected from the group consisting of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate (HEMA), 2-hydroxypropyl acrylate, and 2-hydroxypropyl methacrylate; preferably 2-hydroxyethyl methacrylate (HEMA).

[0050] Another object relates to a method as further mentioned above, wherein the sulfur-free (meth)acrylic acid alkyl ester statistical copolymer is selected from the group consisting of:

[0051] Polymer 1, which consists of a mixture of 97 wt% of C12-C15 alkyl methacrylates and 3 wt% of an N-dispersing monomer, preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm),

[0052] Polymer 2, which consists of a mixture of 99 wt% of C12-C15 alkyl methacrylates and 1 wt% of an N-dispersing monomer, preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm),

[0053] Polymer 3, which consists of a mixture of 95 wt% of C12-C15 alkyl methacrylates and 5 wt% of an N-dispersing monomer, preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm),

[0054] Polymer 4, which consists of a mixture of 96.8 wt% of C12-C15 alkyl methacrylates, 0.2 wt% of methyl methacrylate (MMA), and 3 wt% of an N-dispersing monomer, preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm),

[0055] wherein the (meth)acrylic acid alkyl ester copolymer has a weight-average molecular weight Mw of 15,000 g / mol to 30,000 g / mol w .

[0056] Another object relates to a method as further mentioned above, wherein the sulfur-free (meth)acrylic acid alkyl ester statistical copolymer is selected from the group consisting of:

[0057] Polymer 1, which consists of a mixture of 97 wt% of C12-C15 alkyl methacrylates and 3 wt% of an N-dispersing monomer, preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm), and has a weight-average molecular weight Mw in the range of 18,160 g / mol ± 20%, i.e., in the range of 27,240 g / mol to 24,970 g / mol.

[0058] Polymer 2, which consists of a mixture of 99 wt% of C12-C15 alkyl methacrylates and 1 wt% of an N-dispersing monomer, preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm), and has a weight-average molecular weight Mw in the range of 25,520 g / mol ± 20%, i.e., in the range of 20,416 g / mol to 30,624 g / mol.

[0059] Polymer 3, which consists of a mixture of 95 wt% of C12-C15 alkyl methacrylates and 5 wt% of an N-dispersing monomer, preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm), and has a weight-average molecular weight Mw in the range of 24,900 g / mol ± 20%, i.e., in the range of 19,920 g / mol to 29,880 g / mol.

[0060] Polymer 4, which consists of 96.8 wt% of a mixture of C12-C15 alkyl methacrylates, 0.2 wt% of methyl methacrylate (MMA), and 3 wt% of an N-dispersing monomer, preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm), and has a weight-average molecular weight Mw in the range of 22,300 g / mol ± 20%, i.e., in the range of 17,840 g / mol to 26,760 g / mol.

[0061] The second object of the present invention relates to an industrial oil formulation, which comprises:

[0062] (A) 85 wt% to 99.95 wt% of a base oil;

[0063] (B) 0.05 wt% to 1.0 wt%, preferably 0.05 wt% to 0.5 wt%, more preferably 0.1 wt% to 0.5 wt% of a sulfur-free (meth)acrylic acid alkyl ester statistical copolymer, which comprises:

[0064] (a) 41 wt% to 99 wt%, preferably 46 wt% to 99 wt%, more preferably 48.5 wt% to 99 wt% of (meth)acrylic acid C8-18 alkyl esters, preferably (meth)acrylic acid C10-15 alkyl esters;

[0065] (b) 1 wt% to 10 wt%, preferably 1 wt% to 5 wt%, more preferably 2.5 wt% to 3.5 wt% of an N-dispersing monomer or a hydroxy-substituted (meth)acrylic acid C2-4 alkyl ester;

[0066] (c) 0 wt% to 2 wt% of methyl methacrylate; and

[0067] (d) 0 wt% to 49 wt% of an α-olefin comprising C8-16 carbon atoms,

[0068] wherein the (meth)acrylic acid alkyl ester copolymer has a weight-average molecular weight Mw of 5,000 g / mol to 50,000 g / mol; and

[0069] (C) 0 wt% to 15 wt% of one or more additional additives.

[0070] The contents of each of the components (A), (B), and (C) are based on the total composition of the industrial oil preparation. In a specific embodiment, the proportions of components (A), (B), and (C) total 100 wt%.

[0071] The contents of each of the components (a), (b), (c), and (d) are based on the total composition of the (meth)acrylate statistical copolymer. In a specific embodiment, the proportions of components (a), (b), (c), and (d) total 100 wt%.

[0072] Another second object of the present invention relates to an industrial oil preparation as further mentioned above, wherein the (meth)acrylate statistical copolymer (B) comprises:

[0073] (a) 88 wt% to 99 wt%, preferably 93 wt% to 99 wt%, more preferably 94.5 wt% to 97.5 wt% of C8-18 alkyl (meth)acrylate, preferably C10-15 alkyl (meth)acrylate;

[0074] (b) 1 wt% to 10 wt%, preferably 1 wt% to 5 wt%, more preferably 2.5 wt% to 3.5 wt% of an N-dispersing monomer or a hydroxy-substituted C2-4 alkyl (meth)acrylate, preferably an N-dispersing monomer, more preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm); and

[0075] (c) 0 wt% to 2 wt% of methyl methacrylate.

[0076] Another second object of the present invention relates to an industrial oil preparation as further mentioned above, wherein the (meth)acrylate statistical copolymer (B) comprises:

[0077] (a) 90 wt% to 99 wt%, preferably 95 wt% to 99 wt%, more preferably 96.5 wt% to 97.5 wt% of C8-18 alkyl (meth)acrylate, preferably C10-15 alkyl (meth)acrylate;

[0078] (b) 1 wt% to 10 wt%, preferably 1 wt% to 5 wt%, more preferably 2.5 wt% to 3.5 wt% of an N-dispersing monomer or a hydroxy-substituted C2-4 alkyl (meth)acrylate, preferably an N-dispersing monomer, more preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm); and

[0079] (c) 0 wt% to 2 wt% of methyl methacrylate.

[0080] The contents of components (a), (b), and (c) are based on the total composition of the (meth)acrylic acid alkyl ester statistical copolymer. In a specific embodiment, the proportions of components (a), (b), and (c) total 100 wt%.

[0081] Another second object of the present invention relates to an industrial oil formulation as further mentioned above, which industrial oil formulation comprises:

[0082] (A) 85 wt% to 99.95 wt% of a base oil;

[0083] (B) 0.05 wt% to 1.0 wt% of a sulfur-free (meth)acrylic acid alkyl ester statistical copolymer, which comprises:

[0084] (a) 94.5 wt% to 97.5 wt%, preferably 96.5 wt% to 97.5 wt% of a C10-15 alkyl (meth)acrylate;

[0085] (b) 2.5 wt% to 3.5 wt% of N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm); and

[0086] (c) 0 wt% to 2 wt% of methyl methacrylate,

[0087] wherein the (meth)acrylic acid alkyl ester copolymer has a weight average molecular weight Mw of 10,000 g / mol to 30,000 g / mol w ; and

[0088] (C) 0 wt% to 15 wt% of one or more additional additives.

[0089] The contents of components (A), (B), and (C) are based on the total composition of the industrial oil formulation. In a specific embodiment, the proportions of components (A), (B), and (C) total 100 wt%.

[0090] The contents of components (a), (b), and (c) are based on the total composition of the (meth)acrylic acid alkyl ester statistical copolymer. In a specific embodiment, the proportions of components (a), (b), and (c) total 100 wt%.

[0091] A third object of the present invention relates to a sulfur-free (meth)acrylic acid alkyl ester statistical copolymer, which comprises:

[0092] (a) 88 wt% to 99 wt%, preferably 90 wt% to 99 wt% of a C10-15 alkyl (meth)acrylate;

[0093] (b) 1 wt% to 10 wt% of an N-dispersing monomer; and

[0094] (c) 0 wt% to 2 wt% of methyl methacrylate,

[0095] wherein the (meth)acrylic acid alkyl ester copolymer has a weight average molecular weight M of 5,000 g / mol to 50,000 g / mol w .

[0096] The contents of components (a), (b) and (c) are based on the total composition of the (meth)acrylic acid alkyl ester copolymer. In a specific embodiment, the proportions of components (a), (b) and (c) total 100 wt%.

[0097] Another third object of the present invention relates to a sulfur-free (meth)acrylic acid alkyl ester statistical copolymer, which comprises:

[0098] (a) 93 wt% to 99 wt%, preferably 95 wt% to 99 wt% of C10-15 alkyl (meth)acrylate;

[0099] (b) 1 wt% to 5 wt% of N-dispersing monomer; and

[0100] (c) 0 wt% to 2 wt% of methyl methacrylate,

[0101] wherein the (meth)acrylic acid alkyl ester copolymer has a weight average molecular weight M of 5,000 g / mol to 50,000 g / mol w .

[0102] The contents of components (a), (b) and (c) are based on the total composition of the (meth)acrylic acid alkyl ester statistical copolymer. In a specific embodiment, the proportions of components (a), (b) and (c) total 100 wt%.

[0103] Another third object of the present invention relates to a sulfur-free (meth)acrylic acid alkyl ester statistical copolymer, which comprises:

[0104] (a) 94.5 wt% to 97.5 wt%, preferably 96.5 wt% to 97.5 wt% of C10-15 alkyl (meth)acrylate;

[0105] (b) 2.5 wt% to 3.5 wt% of N-dispersing monomer; and

[0106] (c) 0 wt% to 2 wt% of methyl methacrylate,

[0107] wherein the (meth)acrylic acid alkyl ester copolymer has a weight average molecular weight M of 10,000 g / mol to 30,000 g / mol w .

[0108] The contents of each of the components (a), (b), and (c) are based on the total composition of the (meth)acrylate copolymer. In a specific embodiment, the proportions of components (a), (b), and (c) total 100 wt%.

[0109] Another third object relates to sulfur-free (meth)acrylate statistical copolymers selected from the group consisting of:

[0110] Polymer 1, which consists of a mixture of 97 wt% of C12-C15 alkyl methacrylates and 3 wt% of an N-dispersing monomer, preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm),

[0111] Polymer 2, which consists of a mixture of 99 wt% of C12-C15 alkyl methacrylates and 1 wt% of an N-dispersing monomer, preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm),

[0112] Polymer 3, which consists of a mixture of 95 wt% of C12-C15 alkyl methacrylates and 5 wt% of an N-dispersing monomer, preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm),

[0113] Polymer 4, which consists of a mixture of 96.8 wt% of C12-C15 alkyl methacrylates, 0.2 wt% of methyl methacrylate (MMA), and 3 wt% of an N-dispersing monomer, preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm),

[0114] wherein the (meth)acrylate copolymer has a weight-average molecular weight Mw of from 15,000 g / mol to 30,000 g / mol w .

[0115] Another object of the present invention relates to sulfur-free (meth)acrylate statistical copolymers selected from the group consisting of:

[0116] Polymer 1, which consists of a mixture of 97 wt% of C12-C15 alkyl methacrylates and 3 wt% of an N-dispersing monomer, preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm), and has a weight-average molecular weight Mw in the range of 18,160 g / mol ± 20%, i.e., in the range of 27,240 g / mol to 24,970 g / mol.

[0117] Polymer 2, which consists of a mixture of 99 wt% of C12-C15 alkyl methacrylates and 1 wt% of an N-dispersing monomer, preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm), and has a weight-average molecular weight Mw in the range of 25,520 g / mol ± 20%, i.e., in the range of 20,416 g / mol to 30,624 g / mol.

[0118] Polymer 3, which consists of a mixture of 95 wt% of C12-C15 alkyl methacrylates and 5 wt% of an N-dispersing monomer, preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm), and has a weight-average molecular weight Mw in the range of 24,900 g / mol ± 20%, i.e., in the range of 19,920 g / mol to 29,880 g / mol.

[0119] Polymer 4, which consists of a mixture of 96.8 wt% of C12-C15 alkyl methacrylates, 0.2 wt% of methyl methacrylate (MMA), and 3 wt% of an N-dispersing monomer, preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm), and has a weight-average molecular weight Mw in the range of 22,300 g / mol ± 20%, i.e., in the range of 17,840 g / mol to 26,760 g / mol.

[0120] According to the present invention, the sulfur-free (meth)acrylic acid alkyl ester statistical copolymer is prepared by a method comprising at least the following steps:

[0121] (i) providing a monomer composition as described above, and

[0122] (ii) initiating radical polymerization of the monomer composition.

[0123] The radical polymerization of the present invention can be carried out in the absence (working examples) or presence (comparative examples) of one or more sulfur-free chain transfer agents as described above.

[0124] Standard radical polymerization is described in detail especially in Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition. Generally, polymerization initiators and optionally chain transfer agents are used for this purpose.

[0125] For the synthesis of (meth)acrylate copolymers, the above monomer mixture can be polymerized by any known method. Conventional free radical initiators can be used to carry out free radical polymerization. These initiators are well-known in the art. Non-limiting examples of these free radical initiators are azo initiators such as 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2-methylbutyronitrile), and 1,1-azobiscyclohexanecarbonitrile; peroxide compounds such as methyl ethyl ketone peroxide, acetylacetone peroxide, dilauryl peroxide, tert-butyl 2-ethylhexanoate peroxide, tert-amyl 2-ethylhexanoate peroxide, methyl isobutyl ketone peroxide, cyclohexanone peroxide, benzoyl peroxide, tert-butyl benzoate peroxide, tert-butyl isopropyl carbonate peroxide, 2,5-bis(2-ethylhexanoyl-peroxy)-2,5-dimethylhexane, tert-amyl 3,5,5-trimethylhexanoate peroxide, tert-butyl 3,5,5-trimethylhexanoate peroxide, dicumyl peroxide, 1,1-bis(tert-butylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, cumene hydroperoxide, and tert-butyl hydroperoxide.

[0126] Poly(meth)acrylates with lower molecular weights can be obtained by using a chain transfer agent. This technique is generally known and practiced in the polymer industry and is described in Odian, Principles of Polymerization, 1991.

[0127] In addition, new polymerization techniques such as ATRP (atom transfer radical polymerization) and / or RAFT (reversible addition fragmentation chain transfer) can be applied to obtain useful polymers derived from alkyl esters. These methods are well-known. The ATRP reaction method is 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). In addition, patent applications WO96 / 30421, WO 97 / 47661, WO 97 / 18247, WO 98 / 40415, and WO 99 / 10387 disclose variants of ATRP as explained above, which are specifically cited for the purpose of disclosure. The RAFT method is extensively presented, for example, in WO 98 / 01478, which is expressly cited for the purpose of disclosure.

[0128] The polymerization can be carried out at atmospheric pressure, reduced pressure or elevated pressure. The polymerization temperature ranges from -20 °C to 200 °C, preferably from 60 °C to 120 °C, without any limitation expected therefrom. The polymerization can be carried out with or without a solvent. The term "solvent" should be understood broadly herein. According to a preferred embodiment, the polymer can be obtained by polymerization in Group I, II or III mineral oils of the API or in Group IV synthetic oils of the API.

[0129] According to the present invention, poly(alkyl methacrylate) copolymers are preferably prepared without using any sulfur-containing chain transfer agent. However, when a sulfur-containing CTA such as dodecyl mercaptan or 2-mercaptoethanol is used in the free radical polymerization of the monomer composition, its content should be less than 0.05 wt% based on the total weight of the monomer composition.

[0130] Preferably, the sulfur-containing chain transfer agent is not included in the monomer composition of the present invention, or is not used or added in the free radical polymerization of the monomer composition to obtain the sulfur-free poly(alkyl methacrylate) of the present invention.

[0131] The recovered copolymer is a statistical copolymer.

[0132] The base oils used in industrial oil formulations include oils of lubricating viscosity. Such oils include natural oils and synthetic oils, oils derived from hydrocracking, hydrogenation and hydrorefining, unrefined, refined, re-refined oils or mixtures thereof.

[0133] The base oils can also be defined according to the provisions of the American Petroleum Institute (API) (see the April 2008 version of "Appendix E - API Base Oil Interchangeability Guidelines for Passenger Car Motor Oils and Diesel Engine Oils", section 1.3 Subheading 1.3. "Base Stock Categories").

[0134] The API currently defines five groups of lubricant base stocks (API 1509, Annex 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, which are classified according to the amount of saturates and sulfur they contain and according to their viscosity index; Group IV is polyalphaolefins; and Group V is all others, including, for example, ester oils. The following table illustrates these API classifications.

[0135]

[0136] The kinematic viscosity (KV 100 ) of a suitable base oil for preparing an industrial oil formulation according to the present invention as determined by ASTM D445 at 100 °C is preferably in the range of 0.7 mm 2 / s to 20 mm 2 / s, more preferably in the range of 2 mm 2 / s to 10 mm 2 / s.

[0137] A particularly preferred industrial oil formulation of the present invention comprises at least one base oil selected from API Group II oils, API Group III oils, API Group IV oils, and mixtures thereof.

[0138] Other base oils that can be used according to the present invention are Group II - III Fischer - Tropsch derived base oils.

[0139] Fischer - Tropsch derived base oils are known in the art. The term "Fischer - Tropsch derived" means that the base oil is a synthetic product of the Fischer - Tropsch process or is derived from a synthetic product of the Fischer - Tropsch process. Fischer - Tropsch derived base oils may also be referred to as GTL (Gas - To - Liquids) base oils. Suitable Fischer - Tropsch derived base oils that can be conveniently used as base oils in the industrial oil formulations of the present invention are, for example, those disclosed in EP 0 776 959, EP 0668 342, WO 97 / 21788, WO 00 / 15736, WO 00 / 14188, WO00 / 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.

[0140] The industrial oil preparation used according to the present invention may also contain one or more additional additives selected from pour point depressants, dispersants, defoamers, detergents, demulsifiers, antioxidants, antiwear additives, extreme pressure additives, friction modifiers, corrosion inhibitors, metal deactivators and metal passivators and mixtures thereof; preferably antiwear additives, corrosion inhibitors and antioxidants.

[0141] The industrial oil preparation used according to the present invention may preferably contain up to 2.5 wt%, preferably 0.5 wt% to 1.5 wt% of a performance package which contains at least an antiwear agent, a corrosion inhibitor and an antioxidant.

[0142] This performance package is preferably a zinc-free performance package and more preferably completely ashless.

[0143] Preferred pour point depressants are, for example, selected from alkylated naphthalenes and phenolic polymers, polyalkyl methacrylates different from those of the present invention, maleate copolymer esters and fumarate copolymer esters, which can be conveniently used as effective pour point depressants. The industrial oil preparation may contain 0.1 wt% to 0.5 wt% of a pour point depressant. Preferably, not more than 0.3 wt% of a pour point depressant is used.

[0144] Suitable dispersants include poly(isobutene) derivatives such as poly(isobutene) succinimide (PIBSI), including borated PIBSI; and ethylene-propylene oligomers having N / O functional groups. Based on the total weight of the industrial oil preparation, the industrial oil preparation may contain up to 5 wt% of at least one dispersant.

[0145] Suitable defoamers include, for example, silicone oils, fluorosilicone oils and fluoroalkyl ethers. Based on the total weight of the industrial oil preparation, the industrial oil preparation may contain 0.01 wt% to 0.02 wt% of at least one defoamer.

[0146] The detergents include metal-containing compounds such as phenates; sulfonates; thiophosphonates, especially thiopyrophosphonates, thiophosphonates and phosphonates; sulfonates and carbonates. These compounds may preferably be used in neutral or overbased form.

[0147] Preferred demulsifiers include alkylene oxide copolymers and (meth)acrylate esters comprising polar functional groups.

[0148] 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, 4,4'-methylenebis(2,6 - di - tert - butylphenol); aromatic amines, especially alkylated diphenylamines, N - phenyl - 1 - naphthylamine (PNA), N,N'-diphenyl - p - phenylenediamine, polymeric 2,2,4 - trimethyldihydroquinone (TMQ); "OOS triesters" = reaction products of dithiophosphoric acid with activated double bonds from olefins, cyclopentadiene, norbornadiene, α - pinene, polybutene, acrylate, maleate (ash - free on combustion); organophosphorus compounds such as triaryl phosphites and trialkyl phosphites; organic copper compounds and overbased calcium - and magnesium - based phenates and salicylates. Based on the total weight of the industrial oil formulation, the industrial oil formulation may contain from 0.05 wt% to 5 wt% of at least one antioxidant.

[0149] Preferred anti - wear and extreme - pressure additives include phosphorus compounds such as trialkyl phosphates, triaryl phosphates such as tricresyl phosphate, amine - neutralized monoalkyl and dialkyl phosphates, ethoxylated monoalkyl and dialkyl phosphates, phosphites, phosphonates or phosphines. Based on the total weight of the industrial oil formulation, the industrial oil formulation may contain from 0.05 wt% to 3 wt% of at least one anti - wear agent and extreme - pressure additive.

[0150] Examples of metal deactivators include triazoles, thiadiazoles and salicylidene - type, such as N,N′ - disalicylidene - 1,2 - diaminopropane.

[0151] Rust inhibitors are widely used. Common chemicals are carboxylic acid esters such as succinic acid semi - esters, sulfonic acid esters, alkyl amines and phosphate esters, such as amine - neutralized phosphate esters.

[0152] The friction modifiers used may include mechanically active compounds such as molybdenum disulfide, graphite (including fluorinated graphite), poly(trifluoroethylene), polyamides, polyimides; compounds that form an adsorbed layer such as long - chain carboxylic acids, fatty acid esters, ethers, alcohols, amines, amides, imides; compounds that form a layer through tribochemical reactions such as saturated fatty acids, phosphoric and thiophosphoric acid esters, xanthates (esters), sulfurized fatty acids; compounds that form a polymer - like layer such as ethoxylated dicarboxylic acid partial esters, dialkyl phthalates, methacrylates, unsaturated fatty acids and sulfurized olefins.

[0153] The additives described in detail above are described in particular in T. Mang, W. Dresel (eds.): "Lubricants and Lubrication", Wiley-VCH, Weinheim 2001; R.M. Mortier, S.T. Orszulik (eds.): "Chemistry and Technology of Lubricants".

[0154] The present invention is further illustrated by the following non-limiting examples and comparative examples. The following examples are used to further explain the preferred embodiments according to the present invention, but are not intended to limit the present invention.

[0155] Experimental section

[0156] Abbreviations

[0157] BV100 Kinematic bulk viscosity measured at 100 °C according to ASTM D445

[0158] DMAPMAm N-(3-Dimethylaminopropyl)methacrylamide

[0159] KV100 Kinematic viscosity measured at 100 °C according to ASTM D445

[0160] LIMA Mixture of C12-C15 alkyl methacrylates (average carbon number = 13.4), 60% branched

[0161] M n Number-average molecular weight

[0162] M w Weight-average molecular weight

[0163] nDDM n-Dodecyl mercaptan

[0164] PDI Polydispersity index, molecular weight distribution calculated via Mw / Mn

[0165] Test methods:

[0166] Molecular weight

[0167] The (meth)acrylate copolymers according to the present invention and the comparative examples are characterized by their molecular weights and PDI.

[0168] The molecular weight was determined by size exclusion chromatography (SEC) using a commercially available polymethyl methacrylate (PMMA) standard. For polymers without N-dispersed monomers (e.g., CE1), the molecular weight was determined by gel permeation chromatography using THF as the eluent (flow rate: 1 mL / min; injection volume: 100 μl) under the following conditions:

[0169] Columns: 5 SDV columns, 8 x 300 mm, 8 x 50 mm (PSS, Mainz)

[0170] 1 solvent-peak separation column 8 x 100 mm (Shodex)

[0171]

[0172] Instrument: Agilent 1100Series Pump G1310A

[0173] PSS SECcurity Inline-Degaser 409-0024

[0174] Agilent 1260Series Autosampler G1329B

[0175] Agilent 1260Series UV-Detector G1314B

[0176] Agilent 1100Series RI-Detector G1362A

[0177] Agilent 1100Series Control-Module G1323B

[0178] Techlab Column oven K-5oven: Temperature 35 °C

[0179] Eluent: Tetrahydrofuran

[0180] The eluent was continuously distilled and recycled by the pump

[0181] Flow rate: 1 ml / min

[0182] Injection volume: 100 μl

[0183] Detection: RI: Temperature 35 °C

[0184] UV: Wavelength 239 nm

[0185] Delay volume: 0.175 ml (between UV- and RI-signals)

[0186] Software: PSS WinGPC-Software

[0187] Sample solution concentration: 2 g / L (Mw > 10 6 : 1 g / L...0.5 g / L)

[0188] Standard: PMMA (e.g., PSS (Mainz) or Polymer Laboratories) Standard solution concentration: 1 g / l (for Mw > 10 6 : 0.5 g / l, Mw > 2 * 10 6 : 0.25 g / l) (narrow distribution)

[0189] Internal standard: 1,2-dichlorobenzene → 0.2 μL to 99.8 μL of sample

[0190] For polymers that truly contain N-dispersed monomers (such as Examples 1-4 and CE2-5 of the present invention), the molecular weight was determined by gel permeation chromatography using THF + 0.02 Mol 2-(diethylamino)ethylamine as the eluent (flow rate: 1 mL / min; injection volume: 100 μl) under the following conditions:

[0191] Columns: 5 SDV columns 8 x 300 mm, 8 x 50 mm (PSS, a company in Mainz)

[0192]

[0193] Instrument: Agilent 1100Series Pump G1312A

[0194] PSS SECcurity Inline-Degaser 409-0024

[0195] Agilent 1100Series Autosampler G131313A

[0196] Agilent 1260Series RI-Detector G1362A

[0197] Agilent 1200Series Control-Module G4208A

[0198] PSS SECurity Column oven TCC6000

[0199] Oven: Temperature 35 °C

[0200] Eluent: Tetrahydrofuran + 0.02 Mol DEAEA (2-(diethylamino)ethylamine)

[0201] Flow rate: 1 ml / min

[0202] Sample injection volume: 100 μl

[0203] Detection: RI: Temperature 35 °C

[0204] UV: Wavelength 239 nm

[0205] Delay volume: 0.175 ml (between UV- and RI-signals)

[0206] Software: PSS WinGPC-software

[0207] Sample solution concentration: 2 g / L (Mw > 10 6 : 1 g / L…0.5 g / L)

[0208] Standard: PMMA (ReadyCal from PSS Mainz)

[0209] Standard solution concentration: 1 g / L (for Mw > 10 6 : 0.5 g / L, Mw > 2*10 6 : 0.25 g / L)

[0210] (Narrow distribution)

[0211] Internal standard: 1,2-dichlorobenzene → 0.2 μL to 99.8 μL sample

[0212] Sulfur content and nitrogen content

[0213] Use the molecular formulas of the monomers and chain transfer agents used for polymer synthesis and calculate the sulfur and nitrogen contents by using the masses of the added components. Round the values to the nearest 100 ppm.

[0214] Viscosity

[0215] (Meth)acrylate copolymers according to the invention and comparative examples are received as compositions in oil, and the oil compositions are characterized by kinematic volume viscosity at 100 °C according to ASTM D445.

[0216] To determine the thickening of the polymer product, the kinematic viscosity (KV100) at 100 °C was measured for blends of 25 wt% of the examples in Group I oils. The Group I oils had an initial viscosity of 5.4 cSt at 100 °C. The blends were prepared by blending 25 g of the example and 75 g of Group I oil at 80 °C for 30 minutes. Then KV100 was measured according to ASTM D445.

[0217] Sediment test / Aging test

[0218] The aging test was carried out by blending 0.5 wt% of the polymer into ISO 220 fluid. 10 g of the mixture was placed in a test tube and stored in an oven at 150 °C without a lid for 30 days. After 30 days, the liquid was taken out and the color change was visually observed. After recording the color / darkening of the observed fluid, the fluid was passed through a filter paper to check for sludge formation. The amount of sludge formed was recorded using the grades of no sediment, minimal sediment, moderate sediment, or heavy sediment.

[0219] Preparation of Example 1:

[0220] 100 g of Shellsol A150 ND was placed in a 1 L four-necked round-bottom flask. In a separate beaker, the reaction mixture was prepared by placing 485 g of LIMA, 15 g of DMAPMAm, and 15 g of tert-butyl peroxy-2-ethylhexanoate. The round-bottom flask containing 100 g of Shellsol A150 ND was heated to 115 °C, mixed using a C-stirrer, and inerted with nitrogen. Once the reactor reached the set-point temperature, the reaction mixture was fed into the reactor at a rate of 1.7 g / min. After the reaction mixture was completely added to the reactor, the reactor was maintained at 110 °C for 60 minutes.

[0221] Since all the monomers used as starting materials were mixed together before the polymerization began, the recovered polymer was a statistical copolymer.

[0222] Examples 2, 3, and 4 were prepared in the same manner as Example 1, except that the weight ratios of the reaction components were changed according to Table 1 below.

[0223] Table 1: Amounts of monomers used to prepare Examples 1-4

[0224]

[0225] Preparation of Comparative Example 1:

[0226] 485 g of LIMA, 15 g of DMAPMAm, and 2.75 g of nDDM were placed in a 1 L four-necked round-bottom flask. The reactor was heated to 120 °C, mixed using a C-stirrer, and inerted with nitrogen. Once the reactor reached the set-point temperature, 2.25 g of tert-butyl peroxy-2-ethylhexanoate was fed into the reactor using the following feeding scheme: 0.15 g in the first 60 minutes, 0.3 g in the next 60 minutes, and 0.9 g in the next 60 minutes. The reaction was continued with stirring for 1 hour, and then the final 0.9 g of initiator was fed into the reactor. The reactor was maintained at 110 °C for 60 minutes.

[0227] Since all the monomers used as starting materials are mixed together before polymerization starts, the recovered copolymer is a statistical copolymer.

[0228] Comparative Examples 2 - 4 were prepared in the same manner as Comparative Example 1, except that the weight ratios of the reaction components were changed according to Table 2 below.

[0229] Table 2: Net composition of examples and comparative examples

[0230]

[0231] "CE" means Comparative Example

[0232] Examples 1 - 4 are according to the present invention and are sulfur - free. They contain nitrogen in the range of 1600 ppm to 8200 ppm and are prepared in the absence of any sulfur - containing regulator.

[0233] Comparative Examples 1 - 5 do not contain any nitrogen (CE1) and / or are prepared in the presence of the sulfur - containing regulator nDDM (CE2 - CE5).

[0234] The values of sulfur and nitrogen are calculated based on the raw material data.

[0235] The characterization data such as molecular weight, PDI, kinematic viscosity, and KV100 are summarized in Table 3 below.

[0236] Table 3: Characteristic data

[0237]

[0238] "CE" means Comparative Example

[0239] The weight - average molecular weight of the (meth)acrylate copolymer according to the present invention is in the range of 20,000 g / mol to 30,000 g / mol. Their kinematic viscosity at 100 °C is in the range of 190 mm 2 / s to 210 mm 2 / s, and the KV100 data is between 12 mm 2 / s and 13 mm 2 / s.

[0240] The results of the aging test are listed in Table 4 below.

[0241] Table 4: Results of the aging test

[0242]

[0243] "CE" means Comparative Example

[0244] Examples 1 - 3 show that the use of polymers containing <50 ppm sulfur and at least 1000 ppm nitrogen can significantly reduce oil aging. Aging tests conducted with these polymers showed no deposit formation after a 30-day aging cycle and no visible deposits on the filter paper test.

[0245] Comparative Example 1 does not contain any nitrogen-containing monomers, and although the deposits are small, the oil shows sensitivity to aging through a drastic change in color.

[0246] Comparative Examples 2 - 5 contain different amounts of sulfur and nitrogen, and all show severe darkening of the fluid and a large amount of deposits formed.

[0247] Table 5 below also shows the aging of ISO VG 220 fluid without any polymer additives.

[0248] Table 5: Untreated oil vs. Treated oil

[0249]

[0250] The ISO VG 220 oil darkens rapidly to brown within 4 weeks, while the oil treated with Example 1 of the present invention only darkens to a light amber color. The fluid treated with Comparative Example 2 darkens the most and also has visible sludge formed.

Claims

1. A method for avoiding the formation of particles and deposits in industrial oil formulations, the method comprising the following steps: (i) Preparing a sulfur-free (meth)acrylic acid alkyl ester statistical copolymer, the copolymer comprising: (a) 93 wt% to 99 wt%, preferably 95 wt% to 99 wt% of C10-15 alkyl (meth)acrylate; (b) 1 wt% to 5 wt% of an N-dispersing monomer; and (c) 0 wt% to 2 wt% of methyl methacrylate, wherein the (meth)acrylic acid alkyl ester copolymer has a weight-average molecular weight Mw of 5,000 g / mol to 50,000 g / mol, preferably 10,000 g / mol to 30,000 g / mol, more preferably 15,000 g / mol to 30,000 g / mol; (ii) Adding 0.05 wt% to 1.0 wt% of the sulfur-free (meth)acrylic acid alkyl ester copolymer prepared in step (i) to a base oil or a base oil mixture; (iii) Optionally adding one or more additional additives; and (iv) Applying the industrial oil formulation prepared in step (ii) or (iii) to a compressor, a turbine, a hydraulic press or an industrial gear, preferably to a compressor.

2. The method according to claim 1, wherein the sulfur-free (meth)acrylic acid alkyl ester statistical copolymer comprises: (a) 94.5 wt% to 97.5 wt% of C10-15 alkyl (meth)acrylate; (b) 2.5 wt% to 3.5 wt% of an N-dispersing monomer; and (c) 0 wt% to 2 wt% of methyl methacrylate, wherein the (meth)acrylate copolymer has a weight-average molecular weight M of 10,000 g / mol to 30,000 g / mol w .

3. The method according to claim 1, wherein the sulfur-free (meth)acrylic acid alkyl ester statistical copolymer comprises: (a) 96.5 wt% to 97.5 wt% of C10-15 alkyl (meth)acrylate; (b) 2.5 wt% to 3.5 wt% of an N-dispersing monomer; and (c) 0 wt% to 2 wt% of methyl methacrylate, wherein the (meth)acrylic acid alkyl ester copolymer has a weight-average molecular weight M of 10,000 g / mol to 30,000 g / mol w .

4. The method according to claim 1, 2 or 3, wherein the N-dispersing monomer is selected from the group consisting of N,N-dimethylaminoethyl methacrylate (DMAEMA), N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm) and N-vinylpyrrolidone (NVP); preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm).

5. The method according to claim 1, 2, 3 or 4, wherein at least 30 wt% of the C10-15 alkyl (meth)acrylate in component (a) is branched.

6. An industrial oil formulation comprising: (A) 85 wt% to 99.95 wt% of a base oil selected from the group consisting of API Group II, Group III and Group IV oils and mixtures thereof; (B) 0.05 wt% to 1.0 wt%, preferably 0.05 wt% to 0.5 wt%, more preferably 0.1 wt% to 0.5 wt% of a sulfur-free (meth)acrylic acid alkyl ester statistical copolymer, which comprises: (a) 93 wt% to 99 wt%, preferably 95 wt% to 99 wt% of C10-15 alkyl (meth)acrylate; (b) 1 wt% to 5 wt% of an N-dispersing monomer; and (c) 0 wt% to 2 wt% of methyl methacrylate, wherein the alkyl (meth)acrylate copolymer has a weight-average molecular weight Mw of 5,000 g / mol to 50,000 g / mol, preferably 10,000 g / mol to 30,000 g / mol, more preferably 15,000 g / mol to 30,000 g / mol; and (C) 0 wt% to 15 wt% of one or more additional additives.

7. The industrial oil formulation according to claim 6, wherein the statistical copolymer (B) of alkyl (meth)acrylate comprises: (a) 94.5 wt% to 97.5 wt% of C10-15 alkyl (meth)acrylate; (b) 2.5 wt% to 3.5 wt% of an N-dispersing monomer, more preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm); and (c) 0 wt% to 2 wt% of methyl methacrylate, wherein the (meth)acrylate copolymer has a weight-average molecular weight M of 10,000 g / mol to 30,000 g / mol w .

8. The industrial oil formulation according to claim 6, wherein the statistical copolymer (B) of alkyl (meth)acrylate comprises: (a) 96.5 wt% to 97.5 wt% of C10-15 alkyl (meth)acrylate; (b) 2.5 wt% to 3.5 wt% of an N-dispersing monomer, more preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm); and (c) 0 wt% to 2 wt% of methyl methacrylate, wherein the (meth)acrylate copolymer has a weight-average molecular weight M of 10,000 g / mol to 30,000 g / mol w .

9. The industrial oil formulation according to claim 7 or 8, wherein the N-dispersing monomer of component (b) is selected from the group consisting of N,N-dimethylaminoethyl methacrylate (DMAEMA), N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm), and N-vinylpyrrolidone (NVP); preferably N-(3-(dimethylamino)propyl)-methacrylamide (DMAPMAm).

10. The industrial oil formulation according to claim 6, 7, 8 or 9, wherein the industrial oil formulation is selected from compressor oil, turbine oil, hydraulic oil and gear oil; preferably compressor oil.

11. A sulfur-free statistical copolymer of alkyl (meth)acrylate, which comprises: (a) 93 wt% to 99 wt% of C10-15 alkyl (meth)acrylate; (b) 1 wt% to 5 wt% of an N-dispersing monomer; and (c) 0 wt% to 2 wt% of methyl methacrylate, wherein the (meth)acrylate copolymer has a weight average molecular weight M of 5,000 g / mol to 50,000 g / mol, preferably 10,000 g / mol to 30,000 g / mol, more preferably 15,000 g / mol to 30,000 g / mol w .

12. The sulfur-free statistical copolymer of alkyl (meth)acrylate according to claim 16, which comprises: (a) 95 wt% to 99 wt% of C10-15 alkyl (meth)acrylate; (b) 1 wt% to 5 wt% of an N-dispersing monomer; and (c) 0 wt% to 2 wt% of methyl methacrylate.

13. The sulfur-free (meth)acrylic acid alkyl ester statistical copolymer according to claim 11 or 12, wherein the N-dispersing monomer is selected from the group consisting of: N,N-dimethylaminoethyl methacrylate, N-(3-(dimethylamino)propyl)-methacrylamide, and N-vinylpyrrolidone; preferably N-(3-(dimethylamino)propyl)-methacrylamide.

14. The sulfur-free (meth)acrylic acid alkyl ester statistical copolymer according to claim 11, 12 or 13, comprising: (a) 94.5 wt% to 97.5 wt% of a C10-15 alkyl (meth)acrylate; (b) 2.5 wt% to 3.5 wt% of an N-dispersing monomer; and (c) 0 wt% to 2 wt% of methyl methacrylate, wherein the (meth)acrylic acid alkyl ester copolymer has a weight-average molecular weight M of 10,000 g / mol to 30,000 g / mol w .

15. The sulfur-free (meth)acrylic acid alkyl ester statistical copolymer according to claim 11 or 12, comprising: (a) 96.5 wt% to 97.5 wt% of a C10-15 alkyl (meth)acrylate; (b) 2.5 wt% to 3.5 wt% of an N-dispersing monomer; and (c) 0 wt% to 2 wt% of methyl methacrylate, wherein the (meth)acrylate copolymer has a weight-average molecular weight M of 10,000 g / mol to 30,000 g / mol w .

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