Biodegradable lubricant composition

Abstract

The present invention relates to a biodegradable lubricant composition comprising at least one vegetable oil with a polyunsaturated fatty acid content from 30 to 70% by weight, at least one ester of C5-C22 fatty acids with monoalcohols, and at least one surfactant belonging to the sorbitan class, which is particularly suitable for use as a penetrating lubricant.

Description

[0001] BIODEGRADABLE LUBRICANT COMPOSITION

[0002] The present invention relates to a biodegradable lubricant composition comprising at least one vegetable oil with a polyunsaturated fatty acid content from 30 to 70% by weight, at least one C5-C22 fatty acid ester with monoalcohols, and at least one surfactant belonging to the sorbitan class, which is particularly suitable for use as a penetrating lubricant.

[0003] Penetrating lubricants are products formulated from a range of base oils and chemical additives and are widely used to reduce friction and wear between metal surfaces in close contact. These lubricants are typically characterised by a high degree of penetration and impart wear and corrosion protection to the metal to which they are applied.

[0004] Depending on the nature of the base oil, the main component of lubricants, these can be classified as mineral (of petroleum origin), or synthetic (for example polyalphaolefins, polyalkylene glycols, synthetic esters, silicones, etc.) or as biolubricants.

[0005] Mineral lubricants are a complex mixture of paraffinic (linear / branched), olefinic, naphthenic and aromatic hydrocarbons with 20 to 50 carbon atoms and are currently the most commonly used commercial lubricants. However, mineral lubricants have poor renewability and biodegradability. If not handled properly, they can leak into the environment, for example through seepage, leakage or overflow, and cause severe environmental damage.

[0006] Synthetic lubricants have advantages over mineral lubricants in that they are more environmentally friendly, have a higher viscosity index, lower pour points and greater stability to oxidation. However, synthetic lubricants are more expensive and less effective than mineral lubricants.

[0007] Biolubricants, typically produced from vegetable oils, are more expensive than mineral lubricants, but are nevertheless a promising alternative to mineral and synthetic lubricants. They possess good properties, such as a high viscosity index, good lubricity, superior anti-corrosive properties, high biodegradability and renewability, and low toxicity in water.

[0008] However, many vegetable oils possess some undesirable characteristics, such as a high pour point and low thermo-oxidative and hydrolytic stability. These limitations can however be mitigated by chemically modifying vegetable oils to achieve a desirable level of performance without increasing their cost.

[0009] Document CN 102199480 describes a method of preparing a lubricant based on palm oil with a high saturated fatty acid content, chemically modified to increase its performance at low temperatures. In addition, the document emphasises the need to use vegetable oils with a low unsaturated content, which cause poor stability to oxidation and a short service life for lubricants containing them. Patent application WO 2003 / 106599 describes a penetrating lubricating oil based on vegetable oil blended with an organic solvent, an antioxidant, a wear inhibitor, an anti-corrosion agent and an emulsifier. The document reiterates the need to reduce the polyunsaturated fatty acid content in vegetable oils, preferring oils with a high oleic acid content.

[0010] Document CN 102851006 describes a lubricating oil for drilling processes consisting of a base oil and a surfactant, where the base oil can be one of: biodiesel, a methyl ester of a fatty acid, a mixture of biodiesel and a mineral white oil, a mixture of a methyl ester of a fatty acid and a mineral white oil, a mixture of a mineral white oil and a vegetable oil.

[0011] There remains, however, the need to find a penetrating lubricant based on vegetable oils that is not only renewable and biodegradable, but also possesses excellent penetrating action and oxidation stability, and is able to provide excellent corrosion protection to many types of metal to which it can be applied.

[0012] The Applicant has now surprisingly found that the addition of at least one surfactant belonging to the class of sorbitans to a composition comprising at least one vegetable oil and at least one C5-C22 fatty acid ester with monoalcohols makes it possible to obtain a biodegradable lubricant that is stable to oxidation, has a high penetrating action and can provide excellent corrosion protection for different types of metal to which it is applied.

[0013] Even more surprisingly, the Applicant has found that the use of vegetable oils with a polyunsaturated fatty acid content of more than 8% by weight and less than 80% by weight, preferably from 8 to 70% by weight, even more preferably from 30 to 70% by weight, allows greater protection from corrosion to be obtained for the metals to which the composition is applied.

[0014] The object of the present invention is therefore a biodegradable lubricant composition comprising: a) at least one vegetable oil with a polyunsaturated fatty acid content from 30 to 70% by weight, b) at least one C5-C22 fatty acid ester with monoalcohols, c) at least one sorbitan ester with one or more C8-C18 fatty acids, in which the weight ratio between component a) and component b) varies from 5:95 to 60:40. The present invention will be described in more detail below.

[0015] The composition according to the invention comprises at least one vegetable oil (component a)). Vegetable oil is understood to be either the unmodified pressed product or an oil that has undergone chemical or physico / chemical modifications such as purification treatments or enzyme enrichment. These vegetable oils are chosen from: soybean oil, sunflower oil, palm oil, coconut oil, Brassicaceae oil, maize oil, peanut oil, cottonseed oil, olive oil, safflower oil, thistle oil, castor oil, jojoba oil, Lesquerella oil, Jatropha oil, Cuphea oil, Limnanthaceae oil and mixtures thereof. Sunflower, safflower, thistle oils and their mixtures are preferred. Safflower, thistle oils and their mixtures are particularly preferred. Oils with an unsaturated fatty acid content of more than 50% by weight, preferably more than 60% by weight are preferred. Vegetable oils with a polyunsaturated fatty acid content of more than 8% by weight and less than 80% by weight, preferably from 8 to 70% by weight, even more preferably from 30 to 70% by weight, are preferred. According to the present invention, polyunsaturated fatty acids are fatty acids with 2 or 3 unsaturation, preferably 2.

[0016] The use of vegetable oils with such an unsaturated fatty acid content in compositions according to the invention surprisingly allows greater protection from corrosion to be obtained for the metals to which the composition is applied.

[0017] The composition according to the invention comprises at least one C5-C22 fatty acid ester with mono-alcohols (component b)). Said C5-C22 fatty acid ester with mono-alcohols preferably comprises or consists of a mixture of fatty acid methyl esters. Said mixture preferably comprises 50 to 80% by weight of methyl oleate.

[0018] This mixture preferably also comprises 20 to 40% by weight of polyunsaturated fatty acid methyl esters.

[0019] In the composition according to the invention, the weight ratio between component a) and component b) is advantageously 5:95 to 60:40, preferably 10:90 to 50:50.

[0020] Lower component ratios lead to a decrease in corrosion protection.

[0021] Higher component ratios result in a higher viscosity of the composition and make application by spraying and mixing with any additives more difficult.

[0022] The composition according to the invention comprises, with respect to the sum of components a)-c), 1-10% by weight, preferably at least 3% by weight, at least 4% by weight, at least 5% by weight, even more preferably 5 to 8% by weight, of at least one sorbitan ester with one or more C8-C18 fatty acids, preferably C12-C18 (component c)). Preferred are sorbitan monoesters. Even more preferred are sorbitan monoesters with oleic acid.

[0023] In addition, the composition according to the invention may comprise one or more additives chosen from: anti-oxidising agents, anti-wear agents, extreme pressure agents, corrosion inhibitors and deactivators of metals other than the sorbitan ester with one or more C8-C18 fatty acids (component c)), hydrolysis inhibitors, pour point depressants, viscosifying agents, detergents, dispersants, defoamers, emulsifiers or de-emulsifiers. Any type of antioxidant agent, anti-wear agent, extreme pressure agent, corrosion inhibitor and metal deactivator other than sorbitan ester with one or more C8-C18 fatty acids (component c)), hydrolysis inhibitor, pour point depressant, viscosifying agent, detergent, dispersant, antifoaming agent, emulsifier, demulsifier, commercially available from a variety of suppliers and manufacturers, can be used in the composition according to the invention.

[0024] Said additives may be added, individually or as a mixture, each in quantities of 0.01% to 10% by weight, more preferably 0.02% to 8% by weight, by weight of the lubricant composition.

[0025] Examples of antioxidant agents are sterically encumbered phenols that can be variously substituted, for example 2,6-di-t-butylphenol, 2,6-di-t-butyl-p-cresol and butylhydroxyanisole; t-butyl hydroquinone and all variously substituted derivatives with one or more functional groups; aromatic amines such as variously substituted diphenylamines, for example octylated and butylated diphenylamine, phenyl naphthylamines such as variously substituted alphanaphthylamine (PANA) and phenyl beta-naphthylamine (PBNA) metal alkylaryl dithiophosphates, such as variously substituted zinc dithiophosphate; metal dialkyldithiocarbamates, such as zinc and molybdenum dithiocarbamates; ashless dialkyldithiocarbamates such as alkylenebis(dialkyldithiocarbamates) and the like; sulfurated phenols, such as phenol thioesters and phenol and alkyl thioethers; disulfides, such as diaryldisulfides; trialkyl and triaryl phosphates and phosphites, such as tris(di-t-butyl phenyl phosphite); variously substituted tolyltriazoles.

[0026] Examples of anti-wear and extreme-pressure agents are olefins; vegetable oils; sulfur esters; chlorinated paraffins; metal alkylaryl-dithiophosphates, such as variously substituted zinc dithiophosphate; metal dialkyldithiocarbamates, such as zinc, antimony and molybdenum dithiocarbamates; ashless dialkyldithiocarbamates such as alkylene bis(dialkyldithiocarbamates) and similar phosphorothionates, such as butyltriphenyl phosphoro thionate; esters derived from dithiophosphoric acid in salt or acid form, such as dibutyl [[bis[(2-ethylhexyl)oxy]phosphinothio]thio] succinate, phosphate esters such as tricresyl phosphate or other esters of phosphoric acid and aliphatic alcohols whether or not neutralised with amines; variously substituted phosphite esters such as di-n-octyl phosphite, dibutyl phosphite or tri-lauryl phosphite, isodecyl diphenyl phosphite or tris(2,4-di-t-butyl- phenyl)phosphite; variously substituted boric acid esters; sulfides and disulfides, such as diaryldisulfides; complex esters or esters of high molecular weight polyols; 2,5-dimercapto- 1,3,4-thiadiazole derivatives; molybdenum carboxylates; molybdenum disulfide; sulfurised oleins; sulfurised isobutylene; amides from fatty acids such as oleylamide. Examples of corrosion inhibitors and metal deactivators other than the sorbitan ester with one or more C8-C18 fatty acids (component c)) are alkylsuccinic acid derivatives; ethoxylated phenols; fatty amines; fatty acid and amine salts; ethoxylated fatty acids and fatty alcohols; natural or synthetic waxes; variously substituted phosphate ester salts; variously substituted alkyl and alkylaryl metal or ammonium sulfonates, such as calcium salts of benzene sulfonic acid or variously substituted alkylnaphthalene sulfonic acid; polymeric sulfonate salts; amides and various derivatives such as sarcosine polycarboxylates; imidazoline derivatives; esterified amino acids; imidazoline derivatives; triazole derivatives; 2,5-dimercapto-l,3,4-thiadiazole derivatives; 4 fatty acid derivative of 5-dihydro-lH-imidazole.

[0027] Hydrolysis inhibitors include, for example, monomeric and polymeric carbodiimides, or even glycidyl esters that act as acid scavengers.

[0028] Examples of pour point depressants are alkylated polystyrene or polyalkyl methacrylate.

[0029] Examples of viscosifiers are poly(alkyl methacrylates), olefin copolymers, styrene butadiene copolymers, complex esters or esters of high- viscosity polyols.

[0030] Examples of metal deactivators are benzotriazoles, 2-mercaptobenzothiazoles, variously substituted thiadiazoles and tolyl triazole derivatives.

[0031] Examples of detergents are phenates, alkyl, alkylaryl and naphthene sulfonates of barium, calcium and sodium, phosphate esters such as neutral or suprabasic long-chain alkylarylsulfonic acids, calcium and magnesium metal salts of alkylphenols and neutral or suprabasic alkyl sulfides, metal salts of alkyl salicylates, phosphates, thiophosphates and thiophosphonates obtained by the reaction of phosphorus pentasulfide with polyisobutenes (PIBs), olefins, fatty alcohols and esters neutralised after hydrolysis with metal hydroxide.

[0032] Examples of dispersants are polyisobutenyl succinimide, polyisobutenyl succinate ester, Mannich dispersants, olefin copolymers, polymethacrylates.

[0033] Examples of defoamers are oxirane polymers, poly siloxanes, polydimethylsiloxanes and acrylate polymers.

[0034] Examples of demulsifiers are polyalkoxylated phenols, polyalkoxy polyols, and poly alkoxy lated poly amines.

[0035] The composition according to the invention advantageously imparts wear protection to the materials to which it is applied, which, when tested according to ASTM D4172, undergo wear of less than 0.5 mm.

[0036] The composition according to the invention is resistant to extreme pressures exceeding 160 kgf (measured according to ASTM D2783). The composition according to the invention advantageously protects metals to which it is applied from corrosion in corrosive acidic water for a period of more than 6 days. Such metals are, for example, brass, copper, cast iron, soft iron, steel or aluminium.

[0037] In one embodiment, the composition according to the invention, applied to soft iron specimens for a time of 30 minutes to 3 hours, protects them from corrosion for more than 6 days when said specimens are immersed in corrosive water (pH=l) in closed glass jars and held at 50°C. In particular, the soft iron specimen showed no signs of oxidation after at least 15 days in corrosive water.

[0038] In a further embodiment, the composition according to the invention, applied for 3 hours to metals such as tin-plated steel, steel, aluminium, cast iron, brass and copper, protects them from corrosion when immersed in corrosive water for 7 days at 25°C. In particular, after 7 days in corrosive water at 25°C, said metals are not stained and show no traces of pitting.

[0039] The following examples illustrate the present invention for non-limiting purposes.

[0040] EXAMPLES

[0041] Compositions

[0042] Three penetrating lubricant compositions were prepared as shown in Table 1.

[0043] The high oleic sunflower oil (HOSO)_used in comparative Example 1 had a polyunsaturated fatty acid content of 6.25%.

[0044] The thistle oil used in Examples 2 and 3 had a polyunsaturated fatty acid content of 59%. Protection against corrosion

[0045] Soft iron samples were immersed in each of the compositions in Examples 1-3 for 30 minutes. After this time, they were drained and immersed in corrosive water at pH=l, in closed glass jars and held at 50°C until ferric oxide formed. The results are shown in Table 2.

[0046] The results shown in Table 2 demonstrate that the composition according to the invention, applied to soft iron specimens subsequently placed in corrosive acidic water, protects the metal from corrosion for a period of at least 15 days. These results are comparable to those obtainable with a non-biodegradable reference product for this application. Furthermore, when thistle oil with a polyunsaturated fatty acid content higher than 30% by weight is used in the composition (Examples 2 and 3), the performance is definitely better than when using a sunflower oil with a high content of oleic acid (HOSO, Comparative Example 1)(.

Claims

CLAIMS1) Biodegradable lubricant composition comprising: a) at least one vegetable oil with a polyunsaturated fatty acid content from 30 to 70% by weight; b) at least one ester of C5-C22 fatty acids with monoalcohols, c) at least one ester of sorbitan with one or more C8-C18 fatty acids, in which the weight ratio between component a) and component b) varies between 5:95 and 60:40.2) Biodegradable lubricant composition according to claim 1, comprising 1-10% by weight of component c),with respect to the sum of components a)-c).3) Biodegradable lubricant composition according to either of claims 1-2, where component a) is chosen from: safflower oil, thistle oil and mixtures thereof.4) Biodegradable lubricant composition according to one or more of claims 1-3, in which component a) has an unsaturated fatty acid content of more than 50% w / w.5) Biodegradable lubricant composition according to one or more of claims 1-4, in which component b) consist of a mixture of fatty acid methyl ethers.6) Biodegradable lubricant composition according to claim 5, in which said mixture comprises 50 to 80% by weight of methyl oleate.7) A biodegradable lubricant composition according to claim 5, in which said mixture comprises 20 to 40% by weight of polyunsaturated fatty acid methyl esters.8) Biodegradable lubricant composition according to one or more of claims 1-7, in which component c) comprises sorbitan monoesters.9) Biodegradable lubricant composition according to one or more of claims 1-8, comprising one or more additives selected from among: antioxidising agents, anti-wear agents, extreme pressure agents, corrosion inhibitors and metal deactivators other than sorbitan ester with one or more C8-C18 fatty acids (component c)), hydrolysis inhibitors, pour point depressants, viscosity depressants, detergents, dispersants, anti-foaming agents, emulsifiers or de-emulsifiers.

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