Purification of metal objects in the presence of a liquid and a phyllosilicate

Abstract

The invention relates to a process for purifying a metal object comprising an oil adsorption step in the presence of a liquid and a layered silicate component.

Description

TECHNICAL FIELD

[0001] The present invention relates to a process for purifying a metal object comprising an oil adsorption step in the presence of:

[0002] - a liquid, and

[0003] - a layered silicate component. BACKGROUND

[0004] After production of metal objects such as screws, nuts or bolts, these metal objects comprise impurities. Typical impurities are an oxide layer on the surface of the metal object, such as rust or scale, and oil / grease. If the impurities are not removed, the metal object does not function according to the standard. To improve properties such as performance and corrosion inhibition, further processing steps are required, such as further metallization or coating of the metal object. However, to obtain the best results, the impurities must be removed from the metal object before this processing is performed.

[0005] In the literature, methods are described to remove said impurities.

[0006] The removal of oil, fat, grease, etc. is often referred to as degreasing. Sometimes the term deoiling is used instead.

[0007] Metal oxides such as rust or scale can be removed chemically or mechanically. Chemical treatment, usually by an acid such as hydrochloric acid or sulfuric acid, is referred to as pickling. Mechanical removal is usually performed by abrasive methods such as sandblasting, shot blasting or wet blasting.

[0008] The degreasing and pickling steps can be performed simultaneously or sequentially.

[0009] DE2507059 describes a process for single-bath degreasing and pickling of metal articles consisting of iron or containing iron, by treating the metal articles with an aqueous solution containing, in addition to acid, wetting agent and / or emulsifier, as oxidizing agent, a water-soluble aromatic nitro compound. The process is used to clean oil, fat, resin and coking residues from the surface of, for example, screws and sheet material. The surface can be further treated directly, such as by electroplating.

[0010] CN203700531U discloses a rust removal and cleaning system for screws / nuts. The system consists of different devices, such as an acid pickling rust removal device and an alkali degreasing device. The focus is on neutralization of the waste stream.

[0011] CN110270797 discloses a method for treating a spring compressor. The method comprises the step of producing screws, followed by the steps of cleaning, degreasing, pickling and blackening.

[0012] KR20190072768 discloses a method for removing scale and improving surface cleanliness of a screw part of a vehicle fastener such as a bolt, a screw and a nut, the method comprising: a surface cleaning step of improving surface cleanliness by soaking in a fastener degreasing liquid maintained at 15 to 25 ppm of alkali concentration point (ppm) and a temperature of 60 to 80 degrees Celsius for 5 to 15 minutes to remove organic and inorganic matter and vinylidene chloride resin coating adhered to the surface by rapid removal; a first pickling step of allowing scale and burrs of the fastener for a vehicle to be first dissolved by generating a first Fe ion (Fe2 + ) and a negative electrode reaction of water by soaking in a scale pickling solution for 30 to 180 seconds; and a second pickling step.

[0013] WO2011020540 discloses a method for cleaning / removing scale of a metal strip, wherein water is first applied and then ice crystals, such as liquid nitrogen, are applied.

[0014] Furthermore, the prior art discloses several methods comprising a composition with clay as one of several components and / or a number of process steps.

[0015] In the experimental section, WO2017197665 discloses a degreasing anticorrosive rust preventive agent comprising sodium hydroxide, sodium chlorate, triethylenetriamine, hydrochloric acid, phosphoric acid and a small amount of an unspecified clay. CN105331992 discloses an aluminum surface degreasing agent comprising not less than 16 components, such as cerium nitrate, polyvinyl alcohol, molybdenum disulfide and a small amount of an unspecified clay. DE2022763 discloses a method for purifying a mixed waste stream comprising organic solvents or basic emulsifiers by an unspecified clay (<20 pm) and inorganic salts.

[0016] US 2003 / 0119689 A1 relates to a hard surface cleaning, optionally silicate-containing, composition for removing cooking, baking or burning food soils from cookware and tableware, the composition comprising a smectite-type clay thickening agent and a hydrophobically modified polyacrylate polymer.

[0017] US 3,966,432 relates to an abrasive composition in liquid form for cleaning hard surfaces for domestic or industrial use.

[0018] US 9,782,804 B1 relates to a method of passivating a substrate surface by removing surface contaminants.

[0019] DE 0 117 599 A1 relates to a method of pre-treating a metal surface comprising a pre-treatment bath comprising bentonite.

[0020] JP 2015 110760 A relates to a composition for washing and cleaning containing humus substance-containing fulvic acid and clay.

[0021] CN 107059028 B relates to an aluminum alloy cleaner with corrosion inhibition.

[0022] JPH 10130691 A relates to a detergent composition.

[0023] It is known to use an abrasive for shaping or finishing a workpiece. Exemplarily, Wiener Kalk shall be referred to as a powder abrasive, i.e. an abrasive without additional cleaning agents. Wiener Kalk comprises crushed dolomite, i.e. a calcium magnesium carbonate rock CaMg(C03)2. A workpiece is rubbed with Wiener Kalk and rust / oxidation is removed. In contrast to e.g. phyllosilicates, Wiener Kalk is a solid material comprising an inner structure only to a very small extent. Its ability to adsorb e.g. organic molecules is rather limited. Thus, the treatment is mainly based on mechanical wear.

[0024] The adsorptive properties of bentonite are known. Thus, bentonite is used in the wine making process to remove excess proteins in white wine. Further, bentonite is used in various pet care products such as cat litter to absorb odors and to surround feces. It is also used to absorb oil and grease.

[0025] Invention Objectives

[0026] It is an object of the present invention to provide a process for degreasing a metal object.

[0027] It is a further object of the present invention to provide a process for removing an oxidation layer from a metal object.

[0028] It is a further object to provide a process which reduces the amount of waste water.

[0029] It is a further object to provide a process which has a limited number of process steps.

[0030] It is a further object to minimize interruptions / physical separations of steps to avoid any unnecessary oxidation. SUMMARY

[0031] The above objects are solved by providing a process for purifying a metal object, the process comprising an oil adsorption step in the presence of:

[0032] - a liquid, and

[0033] - a phyllosilicate component.

[0034] The above objects are further solved by providing a process for purifying a metal object, the process further comprising a grinding step,

[0035] While both steps are performed separately or simultaneously, preferably simultaneously; preferably

[0036] further comprising a grinding step with a grinding material,

[0037] While both steps are performed separately or simultaneously, preferably simultaneously. DETAILED DESCRIPTION

[0038] Purification:

[0039] Within the framework of the present invention, purification in its broadest sense describes the removal of one or more of the following substances from the surface of a metal object:

[0040] - an oxide layer, such as rust or scale and / or

[0041] - oil.

[0042] The removal can be partial or complete.

[0043] The impurities are a result of the respective production process. If the impurities are not removed, the metal object has a non-standardized functionality. In order to improve properties such as performance and corrosion inhibition, further processing steps such as further metallization or coating of the metal object are required. However, in order to achieve the best results, the impurities must be removed from the metal object before this processing is carried out.

[0044] Removal of rust / scale:

[0045] According to the prior art, metal oxides such as rust or scale can be removed by chemical or mechanical methods. Chemical treatment, usually by an acid such as hydrochloric acid or sulfuric acid, is known as pickling. Mechanical removal is usually carried out by abrasive methods such as sandblasting, shot blasting or wet sandblasting.

[0046] Removal of oil:

[0047] As used herein, the term 'oil' includes fatty oils, fats, synthetic oils, mineral oils, silicone oils, semi-synthetic oils, substituted oils, greases or mixtures thereof.

[0048] The term 'fatty oil' generally refers to lipids with short and / or unsaturated fatty acid chains which are liquid at room temperature, whereas 'fats' specifically refer to lipids which are solid at room temperature.

[0049] The term'synthetic oil' describes a lubricant composed of compounds manufactured by man. Synthetic lubricants can be manufactured using chemically modified petroleum components rather than whole crude oil, but can also be synthesized from other raw materials. However, the base material is still predominantly crude oil which is distilled and then physically and chemically modified.

[0050] The term'mineral oil' describes any of various colorless, odorless, light mixtures of higher alkanes from mineral sources, especially petroleum distillates.

[0051] The term'silicone oil' describes any liquid polymeric siloxane with organic side chains.

[0052] The term'semi-synthetic oil' describes a mixture of mineral oil and synthetic oil.

[0053] The term'substituted oil' describes an oil comprising atoms other than carbon, oxygen and / or hydrogen, for example chlorinated oil.

[0054] The term 'grease' generally refers to a solid or semi-solid lubricant which generally comprises a thickening soap mixed (e.g. emulsified) with oil.

[0055] Metallic object:

[0056] The metallic object is made of metal, i.e. the metallic object consists mainly, i.e. more than 80 wt.%, preferably more than 90 wt.% of metal.

[0057] The metal is preferably selected from the group consisting of iron, copper, zinc, titanium, nickel, aluminium, magnesium and mixtures / alloys of each, for example steel, in particular stainless steel, brass, bronze and Monel.

[0058] The metallic object has a size of 0.005 m to 2 m, preferably 0.01 m to 1 m, more preferably 0.02 m to 0.5 m, even more preferably 0.05 m to 0.25 m, particularly preferably 0.05 m to 0.20 m.

[0059] The size is thus defined as the average length of the largest dimension of the defined number of metallic objects.

[0060] Preferred metallic objects are fasteners, for example screws, bolts, nuts and nails. More preferred are screws or nuts.

[0061] Oil adsorption step:

[0062] The oil adsorption step is performed as a step in which the oil of the metallic object is removed by adsorbing the oil on a solid substance which is insoluble in the liquid. Thus, the phyllosilicate component is preferably a solid.

[0063] The preferred liquid comprises water. The more preferred liquid comprises water in an amount of at least 50 wt.% (weight of water: weight of total liquid), the even more preferred liquid comprises water in an amount of at least 80 wt.%, the even more preferred liquid comprises water in an amount of at least 90 wt.%, the even more preferred liquid comprises water in an amount of at least 95 wt.%. The most preferred liquid consists of water.

[0064] Preferably, the water is the only solvent in the entire oil adsorption step.

[0065] According to the present application, the solid oil adsorbing substance is a phyllosilicate component. Thus, the oil adsorbing step preferably utilizes a dispersion for purifying metal objects, which comprises said liquid and said phyllosilicate component.

[0066] Phyllosilicate component:

[0067] Phyllosilicates, alternative terms are sheet silicates or phyllosilicates, are silicates formed from silicate tetrahedra with parallel sheets of Si2O5.

[0068] Examples are Serpentine Subfamily such as antigorite - Mg3Si2O5(OH)4, chrysotile - Mg3Si2O5(OH)4, lizardite - Mg3Si2O5(OH)4; Clay Mineral Group such as halloysite - Al2Si2O5(OH)4, kaolinite - Al2Si2O5(OH)4, illite - (K,H3O)(Al,Mg,Fe)2(Si,Al)4O 10 (OH)2,(H2O)], montmorillonite - (Na,Ca) 0.33 (Al,Mg)2Si4O 10 (OH)2»nH2O, vermiculite - (MgFe,Al)3(Al,Si)4O 10 (OH)2»4H2O, talc - Mg3Si4O 10 (OH)2, sepiolite - Mg4Si6O 15 (OH)2»6H2O, palygorskite (or sepiolite) - (Mg,Al)2Si4O 10 (OH)»4(H2O), pyrophyllite - Al2Si4O 10 (OH)2; Mica Group such as biotite - K(Mg,Fe)3(AlSi3)O 10 (OH)2, chromium mica - K(Al,Cr)2(AlSi3O 10 )(OH)2, white mica - KAl2(AlSi3)O 10 (OH)2, phlogopite - KMg3(AlSi3)O 10 (OH)2, lepidolite - K(Li,Al) 2–3 (AlSi3)O 10 (OH)2, margarite - CaAl2(Al2Si2)O 10 (OH)2, glaukophan - (K,Na)(Al,Mg,Fe)2(Si,Al)4O 10 (OH)2; Chlorite Group such as chlorite - (Mg,Fe)3(Si,Al)4O 10(OH)2 · (Mg,Fe)3(OH)6.

[0069] Preferred layered silicates are Clay Mineral Group those of the group of 10 [(OH)2,(H2O)], montmorillonite-(Na,Ca) 0.33 (Al,Mg)2Si4O 10 (OH)2 · nH2O, vermiculite-(MgFe,Al)3(Al,Si)4O 10 (OH)2 · 4H2O, talc-Mg3Si4O 10 (OH)2, sepiolite-Mg4Si6O 15 (OH)2 · 6H2O, palygorskite (or attapulgite)-(Mg,Al)2Si4O 10 (OH) · 4(H2O), pyrophyllite-Al2Si4O 10 (OH)2.

[0070] Preferably, in the process of the present application, the layered silicate component comprises montmorillonite.

[0071] More preferred is the process of the present application, wherein the layered silicate component comprises silica and alumina, wherein preferably, in the layered silicate component, the amount of silica and alumina together is 85 wt.% or more, preferably 87 wt.% or more, more preferably 89 wt.% or more, even more preferably 91 wt.% or more, most preferably 93 wt.% or more, based on the total weight of the layered silicate component.

[0072] Clay minerals can be classified as 1 : 1 or 2: 1, since they are essentially composed of tetrahedral silicate sheets and octahedral hydroxide sheets. 1 : 1 clays consist of one tetrahedral sheet and one octahedral sheet, and examples are kaolinite and serpentine. 2: 1 clays consist of an octahedral sheet sandwiched between two tetrahedral sheets, and examples are talc, vermiculite and montmorillonite.

[0073] Clay minerals include the following groups:

[0074] • the kaolin group, which includes the minerals kaolinite, dickite, halloysite and nacrite (polymorphs of Al2Si2O5(OH)4).

[0075] o Some sources include the kaolinite-serpentine group due to structural similarities.

[0076] • the group of the green earths, which includes dioctahedral green earths such as montmorillonite, nontronite and beidellite and trioctahedral green earths such as saponite.

[0077] • the group of the illites, which includes clay mica. Illite is the only mineral that is commonly found.

[0078] • the group of the chlorites includes a wide variety of similar minerals with considerable chemical variation.

[0079] • there are other 2:1 clay types, such as sepiolite or palygorskite, clays with long water channels inside their structure.

[0080] Particularly preferred are montmorillonites and mixtures thereof with other phyllosilicates, such as bentonite, which is a naturally occurring phyllosilicate. In addition to montmorillonite, bentonite can also contain quartz, mica, feldspar, pyrite, calcite, illite and / or kaolinite.

[0081] Bentonite is preferably selected from sodium bentonite, calcium bentonite, potassium bentonite or a mixture of two or more of these.

[0082] Different soils can also be classified according to the particle size:

[0083] The particle size of clay is less than 2 micrometres, that of silt is greater than 2 micrometres but less than 63 micrometres; the particle size of sand is greater than 63 micrometres.

[0084] Mixtures of these species are known, such as loam. Depending on the composition, these are referred to as, for example, clay loam, sandy loam, sandy clay loam, silty loam, silty clay loam.

[0085] Amount and ratio:

[0086] The typical amount of metal objects is from 4 kg to 400 kg, preferably from 20 kg to 150 kg.

[0087] The typical amount of liquid is from 100 kg to 5 000 kg, preferably from 150 kg to 2 000 kg.

[0088] Typically, the amount of metal objects and the amount of liquid are within a certain ratio.

[0089] The preferred ratio (metal objects) : (liquid) is from 0.005:1 (by weight) to 0.1 :1 (by weight), more preferably from 0.01 :1 (by weight) to 0.06:1 (by weight).

[0090] The amount of phyllosilicate component depends on the amount of metal objects to be purified. If too little phyllosilicate component is applied, its oil absorption capacity is reached too quickly.

[0091] Furthermore, the amount of the phyllosilicate component further depends on the amount of the liquid. If too much phyllosilicate component is applied, handling problems can occur.

[0092] Therefore, the preferred amount of the phyllosilicate component is 5 kg to 1 500 kg, more preferably 100 kg to 400 kg.

[0093] The preferred ratio (phyllosilicate component) : (metal object) is 0.05 : 1 (by weight) to 5 : 1 (by weight), more preferably 0.2 : 1 (by weight) to 1 : 1 (by weight).

[0094] The preferred ratio (phyllosilicate component) : (liquid) is 0.05 : 1 (by weight) to 0.6 : 1 (by weight), more preferably 0.1 : 1 (by weight) to 0.4 : 1 (by weight).

[0095] Very preferred is the process of the present application, wherein

[0096] - the phyllosilicate component has a total amount in the range of 10 wt.% to 40 wt.%, preferably in the range of 14 wt.% to 35 wt.%, more preferably in the range of 18 wt.% to 31 wt.%, even more preferably in the range of 21 wt.% to 28 wt.%, most preferably in the range of 23 wt.% to 26 wt.%, based on the total weight of the combination of liquid, phyllosilicate component and abrasive material;

[0097] and / or

[0098] - the abrasive material has a total amount in the range of 0.5 wt.% to 15 wt.%, preferably in the range of 1 wt.% to 12 wt.%, more preferably in the range of 2 wt.% to 10 wt.%, even more preferably in the range of 3 wt.% to 8 wt.%, most preferably in the range of 4 wt.% to 6 wt.%, based on the total weight of the combination of liquid, phyllosilicate component and abrasive material.

[0099] Even without surfactants, the adsorption of the oil at the phyllosilicate component reduces the formation of a lipophilic liquid phase. Therefore, the prior art process of micelle / emulsion formation by surfactants can be completely replaced by the process of the present application. However, surfactants can be used in the process of the present application to facilitate the purification of the metal object. However, since the presence of surfactants leads to problems such as water pollution, it is preferred to carry out the process of the present application in the absence of surfactants.

[0100] In a preferred embodiment, the process is carried out in an ultrasonic field.

[0101] In a preferred embodiment, the oil adsorption step is performed in a non-abrasive manner. The term "non-abrasive" means that the metal object and the phyllosilicate component are contacted in such a way that abrasion of the metal object surface only occurs to a very small extent, if at all.

[0102] The adsorption process can be influenced by several parameters.

[0103] In principle, the process can be performed at various pH values. However, it has been found that the process works best in the absence of strong acids or strong bases. Preferably, the process is performed at a pH of 4 to 10.6, more preferably, the process is performed at a pH of 5 to 9.

[0104] Similarly, the process can be performed at various temperatures. Preferably, the process is performed at a temperature of 10 °C to 50 °C, preferably 20 °C to 40 °C.

[0105] The process can be supported by stirring the mixture of the metal object, the liquid and the phyllosilicate component. This can be achieved by bubbling air through the mixture or by suitable mechanical mixing or by a circulation pump.

[0106] Preferably, the inventive process is performed in an immersion or barrel apparatus, a drum washing apparatus, a spraying apparatus and / or a spraying apparatus.

[0107] The test for the removal of oil from the metal object was as follows:

[0108] - The cleaned metal object was immersed in a slightly acidic copper sulphate solution and the regularity / homogeneity of the copper immersion deposit was determined (copper sulphate test);

[0109] - The surface tension was measured by a test pen as commercially available from the company Dyne (http: / / www.dynetechnology.co.uk / measurement-equipment / dyne-test-pens / ).

[0110] - Surface fluorescence test: a test method that makes use of fluorescence (https: / / www.sita-process.com / products / fluorescence-measuring-and-testing-devices / sita- cleanospector / ).

[0111] The copper sulphate test is preferred. The sample passes the test if the copper layer is visually dense. This particularly means that no defects larger than 0.1 mm2can be determined.

[0112] When the process is performed for the first time, the metal object is periodically removed from the process and tested. This allows to determine the time needed for the metal object to be sufficiently free of oil to meet the required specifications for any selected treatment, but not limited to electroplating, post-treatment or any other application.

[0113] Typically, the time is in the range of 5 minutes to 60 minutes, preferably in the range of 10 minutes to 20 minutes.

[0114] The process further comprises a polishing step:

[0115] In a preferred embodiment of the present invention, the process further comprises a polishing step, while both steps are performed separately or simultaneously, preferably simultaneously. In the polishing step, a polishing material is utilized.

[0116] By'simultaneously' is in particular meant that both steps take place in the same apparatus, but not necessarily at the same location of said apparatus.

[0117] In the polishing step, the metal object is in contact with the polishing material, which is preferably provided in the form of a slurry.

[0118] In principle, the polishing material can be any material having a sufficient hardness to remove the scale. Known polishing materials are e.g. silicon carbide, silicon oxide, tungsten carbide, garnet, corundum (a-Al203, crystalline phase of aluminum oxide), quartz and quartz sand. More preferred is the process of the present invention, wherein the polishing material comprises aluminum oxide, most preferably corundum.

[0119] Even more preferred is the process of the present invention, wherein the phyllosilicate component and the polishing material comprise aluminum oxide.

[0120] Preferred are polishing materials which remove the scale but at the same time have no or only a small impact on the metal of the metal object itself (i.e. no or only a small notch effect). Thus, preferred polishing materials are selected from the group consisting of glass, garnet and steel, in particular stainless steel, and mixtures thereof, preferably applied as small beads ("shot").

[0121] Preferably, the polishing material comprises at least particles having a particle size of less than 500 micrometer, preferably less than 300 μm, more preferably less than 150 μm, most preferably less than 100 μm. More preferably, the polishing material comprises at least particles having a particle size in the range of 10 μm to 100 μm, preferably 25 μm to 90 μm, most preferably 40 μm to 80 μm. Most preferably, more than 50 wt% of the total amount of polishing material utilized in the polishing step comprises particles having a particle size in the range of 10 μm to 100 μm, preferably 25 μm to 90 μm, most preferably 40 μm to 80 μm.

[0122] If shot blasting is chosen as the method in the grinding step, the gas flow rate is preferably in the range of 300 L / min to 1 000 L / min.

[0123] If wet sanding is chosen as the method in the grinding step, the flow rate of the respective slurry is preferably in the range of 500 L / h to 10 000 L / h.

[0124] The grinding step is preferably carried out in the presence of a liquid, preferably at least partly in the presence of the liquid utilized in the oil adsorption step. This most preferably provides the slurry.

[0125] The use of a liquid in the grinding step has several advantages, such as reduced dust and / or gentler treatment of the metal object.

[0126] It is particularly preferred to partly transfer the supernatant of the oil adsorption step to the grinding step. This preferably means that at least part of the liquid utilized in the oil adsorption step is transferred (i.e. also used for) the grinding step.

[0127] An advantage of this transfer is that the use of e.g. fresh water can be avoided, which makes the process more benign environmentally and economically.

[0128] The oil adsorption step and the grinding step are carried out separately:

[0129] If the oil adsorption step and the grinding step are carried out separately, the scale removed from the metal object in the grinding step has to be tested. This can be done by the same methods as described above. Preferred is the copper sulfate test.

[0130] When the process is first carried out, metal objects are periodically removed from the process and tested. This allows to determine the time required for the metal object to be sufficiently free of scale to meet the required specifications for any selected treatment (but not limited to electroplating, post-treatment or any other application).

[0131] A typical time is in the range of 0.5 min to 15 min, preferably in the range of 5 min to 10 min.

[0132] The oil adsorption step and the grinding step are carried out simultaneously:

[0133] If the oil adsorption step and the grinding step are carried out simultaneously, the oil adsorption step is time-limited.

[0134] Thus, for simultaneous treatment, a typical time is in the range of 5 min to 60 min, preferably in the range of 10 min to 20 min.

[0135] Removal after purification (with or without grinding step):

[0136] After sufficient purification, the purified metal object is removed.

[0137] In a further embodiment of the application, the process comprises one or more subsequent washing steps.

[0138] In a more preferred embodiment, the slurry is at least partially transferred to the oil adsorption step.

[0139] Most preferably, the application relates to a process for purifying a metal object, comprising an oil adsorption step in the presence of:

[0140] - a liquid, and

[0141] - a phyllosilicate component,

[0142] wherein,

[0143] - the process is carried out in the absence of surfactants, and

[0144] - the ratio of the phyllosilicate component and the liquid is 0.05:1 to 0.6:1, both by weight.

[0145] Generally, but especially in the preferred process of the application, it is important that the phyllosilicate component is present in a total amount sufficient to largely act as an oil adsorption component. Thus, the phyllosilicate component is present in an amount that significantly provides sufficient oil adsorption capacity. In other words, the amount of the phyllosilicate component is generally only exceeded by a small amount, which is often used to modify the rheological characteristics. This also means that in the context of the present application, the phyllosilicate component is present in this amount such that it can reasonably act as an oil adsorbent in the oil adsorption step. This additionally leads to the fact that the advantageous effects of utilizing surfactants can preferably be omitted in the process of the present application. Since the oil adsorption capacity is sufficiently high, the oil, grease, etc. from the metal object is effectively adsorbed on the phyllosilicate component, often without the help of any surfactants. It remains on the phyllosilicate component without the need for further dissolving it with surfactants. This has a great impact on the recycling / disposal of the phyllosilicate component after use. Since the oil (and oily substances) is completely adsorbed on the phyllosilicate component, it can easily be separated from the liquid. The liquid is most preferably reused or disposed of. Since it does not contain surfactants, expensive or complex waste water treatment is not required. The oil-containing phyllosilicate component is very compact but still contains a large amount of oil. This provides a great advantage in terms of storage capacity compared to surfactant-containing liquids that contain comparable amounts of oil. BRIEF DESCRIPTION OF DRAWINGS

[0146] Figure 1 The effect as described in Example 1 is demonstrated.

[0147] Figure 2 Examples showing embodiments of the process of the application.

[0148] (1): mixture of liquid / phyllosilicate component

[0149] (2): loading (metal objects)

[0150] (3): drum washing apparatus

[0151] (4): removal (metal objects)

[0152] (5): agitation (here: air bubbling)

[0153] (6): spray (for milling step)

[0154] (7): transfer line of mixture of liquid / layer silicate component to spray (6)

[0155] Figure 3 An example of an embodiment of the inventive process according to Figure 1 with a subsequent washing step is shown.

[0156] Examples

[0157] Example 1 : Oil adsorption capacity

[0158] According to the following table, mixtures of 5 g of clay (W05-25 Sibelco), 20 g of water and different amounts of oil (15W-40 motor oil) were prepared (samples 1a to 1e). The lid was put on and then the mixture was shaken thoroughly by hand for 10 minutes. The mixture was allowed to settle. A photo was taken. These can be found in Figure 1 In all cases only one liquid phase was produced.

[0159]

Claims

1. A process for purifying a metal object, comprising an oil adsorption step in the presence of: - a liquid, and - a phyllosilicate component, wherein - the process is carried out in the absence of a surfactant, and - the phyllosilicate component and the liquid have a ratio of 0.1 : 1 to 0.4 : 1, both by weight.

2. The process according to claim 1, wherein the liquid comprises water.

3. The process according to claim 1, wherein the liquid consists of water.

4. The process according to any one of the preceding claims 1 to 3, wherein the phyllosilicate component comprises a smectite.

5. The process according to any one of the preceding claims 1 to 3, wherein the process is carried out at a pH of 4 to 10.

6.

6. The process according to any one of the preceding claims 1 to 3, wherein the process is carried out at a pH of 5 to 9.

7. The process according to any one of the preceding claims 1 to 3, wherein the process is carried out at a temperature of 10 °C to 50 °C.

8. The process according to any one of the preceding claims 1 to 3, wherein the process is carried out at a temperature of 20 °C to 40 °C.

9. The process according to any one of the preceding claims 1 to 3, wherein the process is carried out in a soaking or barrel apparatus, a drum washing apparatus, a spraying apparatus and / or a spraying apparatus.

10. The process according to any one of the preceding claims 1 to 3, further comprising a grinding step with a grinding material, wherein the oil adsorption step and the grinding step are carried out separately or simultaneously.

11. The process according to claim 10, wherein the supernatant of the oil adsorption step is partially transferred to the grinding step.

12. The process according to any one of the preceding claims 1 to 3, wherein the process comprises one or more subsequent washing steps.

13. The process according to claim 12, wherein a slurry is at least partially transferred to the oil adsorption step.

14. The process according to claim 10, wherein the grinding material comprises aluminum oxide.

15. The process according to claim 10, wherein the grinding material comprises corundum.

16. The process according to claim 14, wherein the phyllosilicate component and the grinding material comprise aluminum oxide.

17. The process according to any one of the preceding claims 1 to 3, wherein the phyllosilicate component comprises silicon dioxide and aluminum dioxide.

18. The process according to any one of preceding claims 1 to 3, wherein the phyllosilicate component comprises silica and alumina, wherein, In the phyllosilicate component, the amount of silicon dioxide and aluminum dioxide together is 85% by weight or more, based on the total weight of the phyllosilicate component.

19. The process according to any one of the preceding claims 1 to 3, wherein the phyllosilicate component comprises silicon dioxide and aluminum dioxide, wherein, In the phyllosilicate component, the amount of silicon dioxide and aluminum dioxide together is 87% by weight or more, based on the total weight of the phyllosilicate component.

20. The process according to any one of preceding claims 1 to 3, wherein the phyllosilicate component comprises silica and alumina, wherein, In the phyllosilicate component, the amount of silicon dioxide and aluminum dioxide together is 89% by weight or more, based on the total weight of the phyllosilicate component.

21. The process according to any one of preceding claims 1 to 3, wherein the phyllosilicate component comprises silica and alumina, wherein, In the phyllosilicate component, the amount of the silica and the alumina together is 91% by weight or more, based on the total weight of the phyllosilicate component.

22. The process according to any one of preceding claims 1 to 3, wherein the phyllosilicate component comprises silica and alumina, wherein, In the phyllosilicate component, the amount of the silica and the alumina together is 93% by weight or more, based on the total weight of the phyllosilicate component.

23. The process according to claim 10, wherein - the phyllosilicate component has a total amount range of 10% to 40% by weight, based on the combined total weight of the liquid, the phyllosilicate component and the abrasive material; and / or - the abrasive material has a total amount range of 0.5% to 15% by weight, based on the combined total weight of the liquid, the phyllosilicate component and the abrasive material.

24. The process according to claim 23, wherein the phyllosilicate component has a total amount range of 14% to 35% by weight, based on the combined total weight of the liquid, the phyllosilicate component and the abrasive material.

25. The process according to claim 23, wherein the phyllosilicate component has a total amount range of 18% to 31% by weight, based on the combined total weight of the liquid, the phyllosilicate component and the abrasive material.

26. The process according to claim 23, wherein the phyllosilicate component has a total amount range of 21% to 28% by weight, based on the combined total weight of the liquid, the phyllosilicate component and the abrasive material.

27. The process according to claim 23, wherein the phyllosilicate component has a total amount range of 23% to 26% by weight, based on the combined total weight of the liquid, the phyllosilicate component and the abrasive material.

28. The process according to claim 23, the abrasive material has a total amount range of 1% to 12% by weight, based on the combined total weight of the liquid, the phyllosilicate component and the abrasive material.

29. The process according to claim 23, the abrasive material has a total amount range of 2% to 10% by weight, based on the combined total weight of the liquid, the phyllosilicate component and the abrasive material.

30. The process according to claim 23, the abrasive material has a total amount range of 3% to 8% by weight, based on the combined total weight of the liquid, the phyllosilicate component and the abrasive material.

31. The process according to claim 23, the abrasive material has a total amount range of 4% to 6% by weight, based on the combined total weight of the liquid, the phyllosilicate component and the abrasive material.

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