Environment-friendly lubricating grease for steel cable

文档序号：914104 发布日期：2021-02-26 浏览：39次中文

阅读说明：本技术 用于钢缆的环保润滑脂 (Environment-friendly lubricating grease for steel cable ) 是由 B·迈尔霍费尔 M·埃尔哈德 P·维特迈尔 S·希梅耶于 2019-07-09 设计创作，主要内容包括：本发明涉及一种用于钢缆(特别是镀锌的钢缆)的环保润滑脂,其包含：a)50重量％至90重量％的可生物降解的基础油,特别是作为基础油的可生物降解的酯,b)3重量％至25重量％和/或7重量％至20重量％的选自以下物质的增稠剂：b1)3重量％至12重量％的可生物降解的钙皂,b2)3重量％至25重量％和/或3.5重量％至20重量％和/或4重量％至12重量％的膨润土,b3)及其混合物,c)4重量％至40重量％,优选7重量％至40重量％的添加剂,所述添加剂包含c1)1重量％至12重量％和/或4重量％至12重量％的热解二氧化硅和/或聚四氟乙烯和其混合物,c2)2重量％至45重量％和/或2重量％至25重量％的聚合物,所述聚合物选自聚异丁烯,聚异丁烯/丁烯共聚物,聚甲基丙烯酸酯,聚酯,优选复合酯,特别是由新戊二醇/二聚酸/2-乙基己醇组成的复合酯及其混合物,和c3)0.5重量％至20重量％和/或1重量％至10重量％的固体润滑剂。(The invention relates to an environmentally friendly grease for steel cables, in particular galvanized steel cables, comprising: a) from 50 to 90% by weight of a biodegradable base oil, in particular a biodegradable ester as base oil, b) from 3 to 25% by weight and/or from 7 to 20% by weight of a thickener selected from the group consisting of: b1)3 to 12% by weight of biodegradable calcium soap, b2)3 to 25% by weight and/or 3.5 to 20% by weight and/or 4 to 12% by weight of bentonite, b3) and mixtures thereof, c)4 to 40% by weight, preferably 7 to 40% by weight, of additives comprising c1)1 to 12% by weight and/or 4 to 12% by weight of fumed silica and/or polytetrafluoroethylene and mixtures thereof, c2)2 to 45% by weight and/or 2 to 25% by weight of polymers selected from polyisobutenes, polyisobutene/butene copolymers, polymethacrylates, polyesters, preferably complex esters, in particular complex esters consisting of neopentyl glycol/dimer acid/2-ethylhexanol and mixtures thereof, and c3)0.5 to 20% by weight and/or 1 to 10% by weight of a solid lubricant.)

1. An environmentally friendly grease comprising:

a) from 50% to 90% by weight of a biodegradable base oil, in particular a biodegradable ester as base oil,

b)3 to 25% and/or 7 to 20% by weight of a thickener selected from:

b1)3 to 12% by weight of a biodegradable calcium soap,

b2)3 to 25% by weight and/or 3.5 to 20% by weight and/or 4 to 12% by weight of bentonite,

b3) and mixtures thereof,

c) from 4 to 40% by weight, preferably from 7 to 40% by weight, of an additive comprising:

c1)1 to 12% by weight and/or 4 to 12% by weight of pyrogenic silica and/or polytetrafluoroethylene and/or mixtures thereof,

c2) from 2% to 45% by weight and/or from 2% to 25% by weight of a polymer selected from polyisobutenes, polyisobutene/butene copolymers, polymethacrylates, polyesters, preferably complex esters, in particular complex esters consisting of neopentyl glycol/dimer acid/2-ethylhexanol and mixtures thereof,

c3)0.5 to 20% by weight and/or 1 to 10% by weight of a solid lubricant.

2. Grease according to claim 1, characterized in that the dropping point according to standard DIN ISO 2176 exceeds 150 ℃.

3. Grease according to claim 1 or 2, characterised in that the maximum service temperature (OGT) according to standard DIN 58397 part 1 is at least 150 ℃.

4. Grease according to one or more of the preceding claims, characterised in that the grease and/or the ester a) has a thermal stability of 150 ℃ to 200 ℃ determinable via TGA (DIN 51006) and/or a volatility of <10 wt.%, preferably <5 wt.%, measured according to DIN 58397 and/or a TAN increase of 0.0mg KOH/g to 20mg KOH/g measured according to DIN ASTM D-2619 (with an extended running time of 400 hours), and/or an acid content (TAN) of less than 5mg KOH/g.

5. Grease according to one or more of the preceding claims, characterized in that the viscosity of the ester a) is at least 50mm²In seconds.

6. Grease according to one or more of the preceding claims, characterised in that the degradable calcium soap b1) is selected from calcium soaps of fatty acids, in particular calcium 12-hydroxystearate.

7. Grease according to one or more of the preceding claims, characterized in that the fumed silica (c1) is chosen from those having a specific surface area of 90 to 130m²Per gram of silica.

8. Grease according to one or more of the preceding claims, characterised in that the polymer of component c2) has a viscosity of at least 600mm measured according to DIN 51562 part 1 at 100 ℃²/s and/or at least 4000mm²Viscosity in/s.

9. Grease according to one or more of the preceding claims, characterized in that it is contained as a groupA preservative according to component C5), preferably selected from alkaline earth metal oxides, in particular calcium oxide and/or magnesium oxide, and calcium sulfonate, magnesium sulfonate and/or sodium sulfonate or C₈To C₂₀Calcium, magnesium and/or sodium salts of dicarboxylic acids, in particular disodium sebacate.

10. Use of the grease according to one or more of the preceding claims for coating steel cables, in particular for coating galvanized steel cables.

Technical Field

The invention relates to an environmentally friendly grease for steel cables, in particular galvanized steel cables. The invention also relates to a method for producing a grease and to the use thereof.

Background

The lubricant for the steel cable serves to separate the individual cable strands from one another by means of a lubricating film, i.e. to lubricate them and thus to reduce wear, and to protect the entire steel cable from corrosion. Depending on the respective field of application, lubricants must also fulfill various additional tasks. Thus, for example, in the field of the marine industry and the oil and gas industry, it is necessary that lubricants not only exhibit good lubricating effect, but also are usable over a large temperature range and in the presence of water. If galvanized steel cables are used, the lubricant must not have any adverse effect on the zinc layer of the steel cable.

Furthermore, there is an increasing demand in principle for environmentally friendly lubricants, which in particular meet the requirements according to the 2013 vessel universal license annex a for environmentally friendly lubricants (EAL ═ environmentally acceptable lubricants) and which can furthermore also be used for parts which can come into contact with seawater. Environmentally friendly lubricants must be biodegradable and have only minimal toxicity and no bioaccumulation.

Various lubricants for steel cables are described in the literature.

CH 540331 a describes a lubricant for steel cables, which comprises as a main component a saturated or unsaturated fatty acid having 5 to 30 carbon atoms or an ester of such an acid or a mixture thereof.

EP 0108536 a1 describes an anti-corrosion composition comprising a corrosion inhibitor, a thickener and a thixotropic gel. The corrosion protection composition is useful for treating multi-strand electrical conductors, wire ropes or cables.

US 4589990 a describes a lubricant composition comprising a mixture of specific synthetic esters, namely polyol esters, trimellitates and polymerized fatty acid esters, and polyisobutylene polymers having different molecular weights. The lubricant composition may also be used to treat wire ropes.

US 4486319 a describes a microporous lubricating composition comprising an ionomer polymer and a liquid lubricant. The ionomer polymer may be combined with other polymers, and the composition may include various additives to modify the properties and properties of the resulting composition. The molded compositions are useful for lubricating mechanical parts, including wire ropes and bearings, such as sliding bearings.

CA 2364200 describes a lubricating composition for lubricating a wire rope comprising: (a) between 50% and 95% by volume of a base liquid; (b) between 1 and 8 volume percent of a low acid lubricant; (c) between 0.2% and 5.0% by volume of a low acidity corrosion inhibitor; (d) between 0.1 and 10 volume percent of an extreme pressure medium; and (e) between 0.1% and 10% by volume of an anti-wear agent.

US 6329073B 1 describes a steel article treated with an anti-corrosion and anti-adhesion composition, wherein the composition comprises: A) an oil or waxy carrier as a carrier for the active ingredient, and B) an active ingredient comprising: B1) corrosion inhibitors in the form of class IIA sulfonates; B2) a co-corrosion inhibitor selected from: (a) one or more fatty acids having 6 to 24 carbon atoms, aromatic acids and naphthenic acids, wherein the acids have a free acid form or a salt form; (b) one or more imidazoline derivatives having a C6-24 alkyl unit; and (C) one or more C6-24 alkyl succinic anhydride compounds; and (d) a mixture of one or more compounds defined by (a), (b) and (c) or a mixture of compounds in various forms defined by (a), (b) and (c); C) possible compounds are selected from the following: C1) a hydrophobizing agent; C2) synthetic esters derived from C1 to 10 alcohols having 1 to 12 hydroxyl groups and C6-24 fatty acids; and C3) a C6-18 alcohol; and C4) mixtures of one or more compounds defined by C1), C2) and C3) or mixtures of compounds defined by C1), C2) and C3) in the form of a plurality; wherein the elongated steel object is a hard drawn wire.

US 6010985 a describes a non-toxic lubricant, fat or gel composition comprising a combination of: at least one base oil in an amount from about 45 wt% to about 90 wt%; and at least one polymer from about 10% to about 20% by weight that is at least partially miscible with the at least one base oil; and about 1 wt% to about 50 wt% of at least one silicate thickener comprising at least one compound selected from the group consisting of aluminum silicate, magnesium silicate, sodium silicate, calcium silicate, potassium silicate, lithium silicate, and ammonium silicate.

CN 102102047 a describes a protective grease composition for high temperature resistant steel wire ropes and a production method thereof. The grease composition is made from a base oil (high viscosity mineral oil or synthetic oil), a thickener, an additive and a covering agent. The grease for steel wire ropes is made by thickening a base oil with a solid hydrocarbon thickener. The thickener is bentonite. The macromolecular tackifier and the grease serving as the solid filler are used for improving the performance, the high temperature resistance and the adhesion strength of the bentonite lubricating grease. The protective grease of the steel wire rope is specially used for protecting the steel wire rope in an extreme high-temperature environment.

CN 102618371 a describes a steel rope grease with high dropping point and its processing method. The steel wire rope lubricating grease comprises the following components (in percentage by weight): 65% to 85% of base oil, 5% to 20% of thickening agent, 2% to 15% of adhesive, 1% to 6% of antirust agent, 0% to 5% of antioxidant, 0% to 5% of polar additive and 0.5% to 6% of solid lubricant.

CN 102827678A describes a steel rope grease composition which, in addition to lubrication, provides corrosion protection. The composition consists of the following components: 51.0% to 72.5% of calcium sulfonate complex grease No. 2, 25.0% to 38.0% of base oil, 0.2% to 1.0% of diphenylamine, 1.3% to 5.5% of colloidal graphite and 1.0% to 4.5% of olivine. The product is suitable for lubricating and protecting various steel wire ropes under the marine climate conditions, such as harbors, sea ships, offshore drilling platforms and the like.

However, the above lubricants do not satisfy all of the above requirements, i.e., the requirements of the environmentally friendly lubricant (EAL ═ environmentally acceptable lubricant) in 2013 vessel universal license annex a, in addition to having a good lubricating effect over a wide temperature range and in the presence of water.

Disclosure of Invention

It is therefore an object of the present invention to provide a lubricant which meets the above requirements.

The object is achieved by an environment-friendly grease comprising:

a) from 50% to 90% by weight of a biodegradable base oil, especially a biodegradable ester, as base oil;

b)3 to 25% and/or 7 to 20% by weight of a thickener selected from:

b1)3 to 12% by weight of a biodegradable calcium soap,

b2)3 to 25% by weight and/or 3.5 to 20% by weight and/or 4 to 12% by weight of bentonite,

b3) and a mixture thereof, and a process for the preparation of,

c) from 4 to 40% by weight, preferably from 7 to 40% by weight, of an additive comprising:

c1)1 to 12% by weight and/or 4 to 12% by weight of pyrogenic silica and/or polytetrafluoroethylene and/or mixtures thereof,

c3)0.5 to 20% by weight and/or 1 to 10% by weight of a solid lubricant.

The applicant has found, in extensive tests, that the use of a grease of the above composition makes it possible to provide an environmentally friendly lubricant which has excellent lubricating properties when used on steel cables, in particular galvanized steel cables, and which has usability in combination with a wide temperature range in the presence of water.

Thus, in a preferred embodiment of the present invention, the grease has a dropping point of more than 150 ℃, e.g. from 150 ℃ to 300 ℃ and/or from 170 ℃ to 300 ℃ and/or from 200 ℃ to 290 ℃, according to DIN ISO 2176 standard. In another preferred embodiment of the invention, the grease has a maximum use temperature (OGT) according to the first part of standard DIN 58397 of at least 150 ℃, for example from 150 ℃ to 200 ℃ and/or 150 ℃.

According to the present invention, the grease has preferably at least 75 wt.%, such as 75 wt.% to 100 wt.%, more preferably at least 80 wt.%, such as 80 wt.% to 100 wt.% and/or 85 wt.% to 100 wt.% and/or 75 wt.% to 90 wt.% of biodegradable and non-toxic components. The grease may also contain up to 25 wt.% of non-biodegradable components, provided that these components are not bioaccumulable and/or have only minimal toxicity. Thus, the grease according to the present invention complies with the standard for environmentally friendly lubricants (EAL ═ environmentally acceptable lubricants) according to 2013, annex a of universal ship licenses. This means that the grease can also be used in applications where contact with seawater is possible.

It has furthermore been found that the components a) to c) have no negative effect on the zinc layer of the galvanized steel cable and in particular do not react with the zinc layer.

As component a), the grease comprises at least 50 wt.%, for example from 50 wt.% to 90 wt.%, more preferably at least 60 wt.%, for example from 60 wt.% to 80 wt.%, and in particular from 65 wt.% to 75 wt.% of a biodegradable base oil, in particular a biodegradable ester, as base oil. The proportion of component a) is based on the total amount of the grease.

According to the present invention, biodegradable base oils or biodegradable esters are understood as being biodegradable base oils and/or esters according to the OECD 301A-F or OECD 306 standard. According to the invention, it is also possible to use mixtures of different base oils and/or different esters. In order for the lubricant to meet the requirements for EAL, the base oil or ester must also be non-toxic.

According to the invention, a large number of biodegradable base oils, and in particular biodegradable esters, can be used as component a), provided they have sufficient thermal stability. Preferred biodegradable base oils are base oils, and especially esters, having a thermal stability above 150 ℃, e.g. in the range of 150 ℃ to 200 ℃, as determined by TGA (DIN 51006; evaporation loss of more than 1 wt% indicates thermal instability).

The base oils and especially the esters preferably also have a rather low volatility. Thus, preferred biodegradable base oils are base oils and in particular esters having a volatility measured according to DIN 58397 at 7d, 150 ℃ of <10 wt.%, preferably <5 wt.%.

Preferably, the grease also has a relatively low volatility. Thus, a preferred grease is one having a volatility of <10 wt.%, preferably <5 wt.%, measured according to DIN 58397 at 7d, 150 ℃.

In addition, the base oils, and especially the esters, preferably exhibit high hydrolytic stability. Thus, a preferred biodegradable base oil is a base oil and/or ester having a TAN Delta (acid content variation) of from 0.0mg KOH/g to 20mg KOH/g, more preferably from 0.0mg KOH/g to 15mg KOH/g, as measured according to DIN ASTM D-2619 (at 93 ℃ C., with an extended run time of 400 h).

Finally, the base oils, and in particular the esters, preferably have a low acid content (TAN) according to DIN EN 12634, wherein the preferred biodegradable base oils, and in particular the esters, have an acid content (TAN) of less than 5mg KOH/g, such as from 0.01mg KOH/g to 5mg KOH/g, more preferably less than 1mg KOH/g, such as from 0.01mg KOH/g to 1mg KOH/g.

The viscosity of the biodegradable base oil is preferably at least 18mm, each measured according to DIN EN ISO 3104 at 40 ℃²S, e.g. 18mm²S to 1200mm²/s and/or at least 100mm²S, e.g. 100mm²S to 1200mm²S and/or 120mm²S to 500mm²S and/or 120mm²S to 300mm²/s。

Preferred mixtures composed of base oils have a viscosity of at least 18mm, measured in accordance with DIN 51562 part 1 at 40 ℃²S, e.g. 18mm²S to 1200mm²/s and/or 18mm²S to 500mm²/s and/or 18mm²S to 200mm²/s。

The viscosity of the preferred biodegradable esters is preferably at least 50mm, each measured according to DIN EN ISO 3104 at 40 ℃²S, e.g. 50mm²S to 1000mm²S and/or 50mm²S to 1200mm²S, more preferably at least 100mm²S, e.g. 100mm²S to 1000mm²S and/or 100mm²S to 1200mm²S, in particular 130mm²S to 1000mm²S and/or 130mm²S to 1200mm²/s，。

In a preferred embodiment of the invention, the biodegradable ester is a synthetic ester. Furthermore, the esters are particularly preferably based on renewable esters. Particularly preferred esters according to the invention are polyol esters, in particular (trimethylolpropane) esters, pentaerythritol esters, mixtures thereofAnd/or a complex ester. Particularly preferred (trimethylolpropane) esters are trimethylolpropane and branched or unbranched and saturated or unsaturated C₁₀To C₂₂Esters of carboxylic acids. The acid may be a monocarboxylic acid and/or a dicarboxylic acid. If a dicarboxylic acid is used, a complex ester can be obtained. Particularly preferred pentaerythritol esters are pentaerythritol with branched or unbranched and saturated or unsaturated C₁₀To C₂₂Esters of carboxylic acids. More particularly preferred esters are trimethylolpropane or pentaerythritol with a saturated or unsaturated branched C₁₈Carboxylic acids, especially esters with oleic acid, isostearic acid mixtures and/or complex esters thereof. Also particularly preferred are esters of trimethylolpropane with saturated or unsaturated, branched or unbranched C₈To C₂₀Carboxylic acid and/or C₁₀To C₂₂Esters of carboxylic acids, in particular with sebacic acid, stearic acid and isostearic acid, mixtures and/or complex esters thereof.

Also particularly preferred are esters of trimethylolpropane with saturated, branched or unbranched C₈To C₂₀Carboxylic acid and/or C₁₀To C₂₂Carboxylic acids, in particular complex esters with sebacic, stearic and isostearic acids and/or mixtures thereof. Also particularly preferred are esters of trimethylolpropane with at least two saturated or unsaturated, branched or unbranched C₈To C₂₀Carboxylic acid and/or C₁₀To C₂₀Complex esters of mixtures of carboxylic acids, in which at least one of the first acids is a saturated or unsaturated, branched or unbranched C₈To C₂₀Dicarboxylic acids and/or C₁₀To C₂₂The dicarboxylic acid and the at least one second dicarboxylic acid being saturated or unsaturated, branched or unbranched C₈To C₂₀Carboxylic acid and/or C₁₀To C₂₂A carboxylic acid. Likewise particularly preferred esters are trimethylolpropane and at least two saturated, branched or unbranched C₈To C₂₀Carboxylic acid and/or C₁₀To C₂₂Complex esters of mixtures of carboxylic acids, in which at least one first carboxylic acid is a saturated, unbranched C₈To C₁₂Dicarboxylic acids, especially sebacic acid, andat least one second acid being saturated, branched or unbranched C₁₅To C₂₀Carboxylic acids, in particular stearic acid, isostearic acid or mixtures thereof.

In a preferred embodiment of the invention, component a) is not a triglyceride, since triglycerides have unsatisfactory hydrolytic and oxidative or chemical stability, at least in certain applications.

Also suitable as biodegradable base oils are polyalphaolefins and/or polyethylene glycols.

Particularly preferred biodegradable polyalphaolefins have a maximum of 6mm measured according to DIN 51562 part 1 at 100 ℃²Viscosity in/s, e.g. 2mm²S to 6mm²S and/or 2mm²S to 5mm²S and/or 2mm²S to 4mm²Viscosity in/s.

A particularly preferred biodegradable polyethylene glycol is an oil soluble polyethylene glycol. These polyethylene glycols preferably have a maximum of 150mm measured according to DIN 51562 part 1 at 40 ℃²Viscosity in/s, e.g. 18mm²S to 150mm²/s and/or 18mm²S to 68mm²/s and/or 18mm²S to 46mm²Viscosity in/s.

As component b), the grease comprises a thickener selected from the group consisting of: biodegradable calcium soap (b1)), in an amount of 3 to 12 wt.%, more preferably 4 to 10 wt.%, in particular 4 to 7 wt.%; bentonite (b2)) in an amount of from 3 to 25% by weight and/or from 3.5 to 20% by weight and/or from 4 to 12% by weight, more preferably from 4 to 10% by weight; and mixtures thereof. According to the invention, the proportion of thickener is 3 to 25% by weight and/or 7 to 20% by weight. The proportion of component b) is based on the total amount of the grease.

The advantage of using calcium soap as thickener is that it increases the resistance to water, especially when used in combination with component c 2).

According to the invention, biodegradable calcium soap is understood to mean calcium soap biodegradable according to OECD 301A-F and/or OECD 306 standards. In order for the lubricant to meet EAL requirements, the lime soap must also be non-toxic or only minimally toxic. Preferred calcium soaps are water-resistant, in particular according to DIN 51807T1, which have a static water resistance. According to the present invention, lime soap is more preferable than bentonite because lime soap has higher thickening effect and better biodegradability. Mixtures of different lime soaps or bentonites may also be used.

Particularly preferred are calcium soaps of fatty acids, especially C₈To C₂₆Fatty acids, in particular calcium 12-hydroxystearate.

In principle, mixtures of lime soaps and bentonite may also be used. However, this embodiment is less preferred, at least in the case of galvanized steel cables, because the corrosion of zinc is more severe than when using calcium soap or bentonite alone.

It is conceivable that the base oil comprises 1 to 40% by weight of additives as component c). According to the invention, the base oil comprises from 4 to 40 wt%, more preferably from 5 to 40 wt%, even more preferably from 7 to 40 wt% and especially from 10 to 35 wt% of additives. The proportion of component c) is based on the total amount of the grease.

According to the invention, the additive of component c) comprises 1 to 12% by weight and/or 4 to 12% by weight, preferably 4 to 10% by weight, of pyrogenic silica and/or polytetrafluoroethylene as component c 1). The proportion of component c1) is based on the total amount of the grease.

In a particularly preferred embodiment of the invention, the pyrogenic silica is selected from fumed silicas having a specific surface area of 90m²G to 130m²Per gram of silica. Preference is likewise given to hydrophobicized pyrogenic silicas, in particular silicic acids hydrophobicized with the aid of dichlorodimethylsilane.

Component c1) contributes to improving the dropping point of the grease and thus to increasing its heat resistance in terms of increasing the maximum service temperature (OGT). In addition, component c1) has the advantage that it acts as a co-thickener and can thus help to stabilize the thickener system.

As component c2), the additives of component c) according to the invention comprise polymers selected from the group consisting of polyisobutenes, polyisobutene/butene copolymers, polymethacrylates, polyesters, preferably complex esters, in particular complex esters of neopentyl glycol/dimer acid/2-ethylhexanol and mixtures thereof. According to the invention, complex esters are understood to mean polyesters which are obtained by reacting polyols with dicarboxylic acids and possibly monocarboxylic acids. The proportion of component c2) is from 2 to 45% by weight, preferably from 2 to 25% by weight, even more preferably from 5 to 20% by weight, in particular from 7 to 17% by weight, based in each case on the total amount of the grease.

The polymers of component c2) preferably have a particle size, measured according to DIN 51562 part 1 at 100 ℃, of at least 600mm²S, more preferably at least 800mm²/s and/or at least 1000mm²/s and/or at least 1500mm²/s and/or at least 4000mm²S, e.g. 4000mm²S to 10000mm²/s and/or 4000mm²S to 6000mm²S, in particular 4000mm²S to 4700mm²Viscosity in/s. A high viscosity is advantageous because it allows the use of low amounts. Particularly preferred according to the invention are polyisobutenes and/or polyisobutene/butene copolymers, since they are inexpensive raw materials and are free from hydrolysable groups, such as ester groups. Biodegradable polymers are also preferred.

The use of component c2) is advantageous because it acts as a toxicologically harmless adhesion promoter, which can improve the adhesion between grease and steel cable, measured according to ASTM D4049, with a loss of <50 wt.%, for example <30 wt.%, more preferably <25 wt.%.

Thus, according to the present invention, the grease preferably has a weight loss of less than 50 wt.%, such as less than 30 wt.%, more preferably less than 25 wt.%, in a water spray test according to ASTM D4049.

As component c3), the additive of component c) according to the invention comprises from 0.5 to 20% by weight and/or from 1 to 10% by weight, more preferably from 1 to 9% by weight, and in particular from 1.5 to 8% by weight of a solid lubricant, preferably selected from alkaline earth metal salts, in particular calcium carbonate, calcium stearate, graphite, melamine cyanurate, zinc sulfide (ZnS), molybdenum sulfide (MoS2) and mixtures thereof. The proportion of component c3) is based on the total amount of the grease.

The use of the abovementioned solid lubricants, in particular calcium carbonate, graphite, melamine cyanurate and calcium stearate, as component c3) is particularly advantageous, since these compounds are toxicologically harmless and can significantly improve the friction properties of the steel cable.

Less preferred solid lubricants according to the invention are dithiocarbamates, in particular ashless dithiocarbamates, bis-stearoyl-ethylenediamine and mixtures thereof. In practical tests it was found that the use of these compounds has a negative effect on the corrosion of the zinc layer. This is also disadvantageous from an environmental point of view, since zinc oxide is toxic to aquatic organisms, which is produced when zinc is corroded.

It is also conceivable that the grease comprises 0.5% by weight, in particular 0.5 to 2.8% by weight, of a succinic acid derivative as first corrosion inhibitor, in particular amidated succinic acid half-esters as component c 4). The proportion of component c4) is based on the total amount of the grease. Component c4) preferably has a neutralization Number (NZ) of from 70mg KOH/g to 100mg KOH/g (DIN 53402).

The use of succinic acid derivatives is advantageous because they are biodegradable and have a high corrosion protection effect.

In a preferred embodiment of the invention, the grease comprises as component C5) a second corrosion protection agent, which is preferably selected from the group consisting of alkaline earth metal oxides, in particular calcium oxide and/or magnesium oxide, and sulfonates or C of calcium, magnesium and/or sodium₈To C₂₀Salts of dicarboxylic acids, especially disodium sebacate. The advantage of the aforementioned components is that they provide good protection against corrosion and are non-toxic. Magnesium oxide, disodium sebacate and/or mixtures thereof are particularly preferred. In another preferred embodiment of the invention, component c5) has a particle size distribution d10 of from 1 μm to 10 μm, more preferably from 3 μm to 8 μm, even more preferably from 4 μm to 6 μm and in particular 5 μm, and/or from 10 μm to 30 μm, more preferably 1 μmA particle size distribution d50 of from 3 μm to 22 μm, even more preferably of from 15 μm to 20 μm and in particular of 17 μm, and/or a particle size distribution d90 of from 30 μm to 50 μm, even more preferably of from 35 μm to 45 μm and in particular of 40 μm. In a particularly preferred embodiment of the present invention, component c5) has a particle size distribution d50 of less than 25 μm, for example from 5 μm to 25 μm and/or from 5 μm to 20 μm.

The advantage of using component c5) is that it can be used as a basic reserve in addition to improving the corrosion protection properties of the grease. In addition, in practical tests, magnesium oxide was found to act synergistically as component c5) in combination with c 4).

The proportion of component c5) is preferably in the range from 0.3 to 5% by weight, more preferably from 0.5 to 2.5% by weight, in particular from 1 to 2.3% by weight. The proportion of component c5) is based on the total amount of the grease.

The grease may also contain other conventional additives, such as antioxidants, as long as these additives do not negatively affect the environmental properties of the grease. Thus, in a preferred embodiment of the present invention, the grease comprises an antioxidant as component c 6). This is preferably selected from non-toxic or only slightly toxic antioxidants. The proportion of the antioxidant is preferably in the range of 0.3 to 3% by weight, more preferably 0.5 to 2% by weight, and in particular 0.8 to 1.5% by weight. The proportion of component c6) is based on the total amount of the grease.

Particularly preferred antioxidants according to the invention are phenolic and/or aminic antioxidants.

In a preferred embodiment of the present invention, the grease comprises:

a)50 to 90% by weight of a biodegradable ester as a base oil;

b)7 to 20% by weight of a thickener selected from the group consisting of:

b1)3 to 12% by weight of a biodegradable calcium soap,

b2)4 to 12% by weight of bentonite,

c) from 4 wt% to 40 wt% of an additive comprising:

c1)4 to 12% by weight of fumed silica and/or polytetrafluoroethylene and/or mixtures thereof,

c2) from 2 to 25% by weight of a polymer selected from the group consisting of polyisobutylene, polyisobutylene/butene copolymer, polymethacrylates, complex esters of neopentyl glycol/dimer acid/2-ethylhexanol, and mixtures thereof,

c3)1 to 10% by weight of a solid lubricant.

In a preferred embodiment of the present invention, the grease comprises:

a) from 50% to 90% by weight, more preferably from 60% to 80% by weight, even more preferably from 65% to 75% by weight of pentaerythritol esters, in particular pentaerythritol esters consisting of pentaerythritol and isostearic acid, as base oil,

b)3 to 25% by weight of a thickener selected from the group consisting of:

b1)3 to 12% by weight, more preferably 4 to 10% by weight, even more preferably 4 to 7% by weight of calcium 12-hydroxystearate,

c) from 4 to 40 wt%, more preferably from 5 to 40 wt%, even more preferably from 7 to 40 wt%, more preferably from 10 to 35 wt% of an additive comprising:

c1)1 to 12% by weight and/or 4 to 12% by weight, preferably 4 to 10% by weight, of pyrogenic silica,

c2) from 2 to 45% by weight and/or from 2 to 25% by weight, more preferably from 5 to 20% by weight and in particular from 7 to 17% by weight, of polyisobutene,

c3)0.5 to 20% by weight and/or 1 to 10% by weight, more preferably 1 to 9% by weight and in particular 1.5 to 8% by weight of calcium carbonate as solid lubricant.

In another preferred embodiment of the present invention, the grease comprises:

b)3 to 25% by weight of a thickener selected from the group consisting of:

b1)3 to 12% by weight, more preferably 4 to 10% by weight, even more preferably 4 to 7% by weight of calcium 12-hydroxystearate,

c) from 4 to 40 wt%, more preferably from 5 to 40 wt%, even more preferably from 7 to 40 wt%, more preferably from 10 to 35 wt% of an additive comprising:

c1)1 to 12% by weight and/or 4 to 12% by weight, preferably 4 to 10% by weight, of pyrogenic silica,

c2) from 2 to 45% by weight and/or from 2 to 25% by weight, more preferably from 5 to 20% by weight and in particular from 7 to 17% by weight, of polyisobutene,

c3)0.5 to 20% by weight and/or 1 to 10% by weight, more preferably 1 to 9% by weight and in particular 1.5 to 8% by weight of calcium carbonate as solid lubricant,

c5) from 0.3 to 5% by weight, more preferably from 0.5 to 2.5% by weight and in particular from 1 to 2.3% by weight, of magnesium oxide as anticorrosive agent,

c6)0.3 to 3% by weight, more preferably 0.5 to 2% by weight and in particular 0.8 to 1.5% by weight of phenolic antioxidants.

In another preferred embodiment of the present invention, the grease comprises:

a)50 to 90% by weight, more preferably 60 to 80% by weight, even more preferably 65 to 75% by weight of a complex ester, in particular of trimethylolpropane and at least two saturated or unsaturated, branched or unbranched C₈To C₂₀Complex esters of mixtures of carboxylic acids, in which at least one first carboxylic acid is a saturated or unsaturated, branched or unbranched C₈To C₂₀A dicarboxylic acid, and at least one second acid which is saturated or unsaturated, branchedOr unbranched C₈To C₂₀The carboxylic acid, as a base oil,

b)3 to 25% by weight of a thickener selected from the group consisting of:

b1)3 to 12% by weight, more preferably 4 to 10% by weight, even more preferably 4 to 7% by weight of calcium 12-hydroxystearate,

c) from 4 to 40 wt%, more preferably from 5 to 40 wt%, even more preferably from 7 to 40 wt%, more preferably from 10 to 35 wt% of an additive comprising:

c1)1 to 12% by weight and/or 4 to 12% by weight, preferably 4 to 10% by weight, of pyrogenic silica,

c2) from 2 to 45% by weight and/or from 2 to 25% by weight, more preferably from 5 to 20% by weight and in particular from 7 to 17% by weight, of polyisobutene,

c3)0.5 to 20% by weight and/or 1 to 10% by weight, more preferably 1 to 9% by weight and in particular 1.5 to 8% by weight of calcium carbonate as solid lubricant.

In another preferred embodiment of the present invention, the grease comprises:

a)50 to 90% by weight, more preferably 60 to 80% by weight, even more preferably 65 to 75% by weight of a complex ester, in particular of trimethylolpropane and at least two saturated or unsaturated, branched or unbranched C₈To C₂₀Complex esters of mixtures of carboxylic acids, in which at least one first carboxylic acid is a saturated or unsaturated, branched or unbranched C₈To C₂₀Dicarboxylic acid, and at least one second acid being saturated or unsaturated, branched or unbranched C₈To C₂₀The carboxylic acid, as a base oil,