Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/66—Electroplating: Baths therefor from melts
  • C25D3/665—Electroplating: Baths therefor from melts from ionic liquids
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/34—Pretreatment of metallic surfaces to be electroplated
  • C25D5/42—Pretreatment of metallic surfaces to be electroplated of light metals
  • C25D5/44—Aluminium

Definitions

• the invention relates to a process for the electrochemical deposition of aluminum and also an electrolyte which can be used in this process.
• Aluminum is an important material which is used predominantly in vehicle and aircraft construction and also in mechanical engineering, in building or construction and as packaging material. Electrolysis plays an important role both in the production of aluminum and in its purification.
• the conventional process for the industrial production of aluminum is based on the Hall-Heroult process in which aluminum oxide in the form of bauxite is dissolved and aluminum is cathodically deposited by means of direct current from a melt at temperatures of about 1000° C.
• One process for the electrochemical deposition of aluminum is the SIGAL process in which a highly reactive, pyrophoric organoaluminum compound is handled in a flammable base electrolyte. Such organoaluminum compounds decompose spontaneously in air by reaction with atmospheric oxygen and moisture, resulting in flame formation. Such decomposition in the presence of readily flammable toluene or xylene electrolytes can lead to serious industrial accidents through to destruction of the plant.
• a disadvantage of the use of electrolytes based on ionic liquids is the poor surface finish which is at present achieved at industrially relevant current densities of >200 A/m 2 .
• a poor surface finish is a rough, dendritic surface which does not cover the electrode or the substrate onto which it is deposited over the entire area. From decorative and corrosion protection points of view, an even deposit which is shiny or has a matt finish is desirable.
• a dense layer is indispensable for appropriate corrosion protection.
• EP 0 084 816 discloses organometallic electrolytes for the electrochemical deposition of aluminum, which are said to have a high throwing power combined with good electrical conductivity.
• a further object of the present invention is to provide a process for the electrochemical deposition of aluminum from ionic liquids by means of which matt or shiny dense aluminum layers can be obtained.
• the additive of the general formula (I) is a compound of the general formula (I),
• X 1 and X 2 are each, independently of one another, N or CH,
• X 3 is NR 1 , O or S,
• n is an integer from 0 to 4,
• X 1 , X 2 and X 3 are heteroatoms selected from among N, O and S, and
• R 1 is selected from the group consisting of H, alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl, where the alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl groups are optionally substituted by one or more substituents and the alkyl and cycloalkyl groups are optionally interrupted by from 1 to 3 heteroatoms or functional groups, and
• the radicals R 2 are each, independently of one another, H, alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl or heterocyclyl, where the alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl groups are optionally substituted by one or more substituents and the alkyl and cycloalkyl groups are optionally interrupted by from 1 to 3 heteroatoms or functional groups.
• the additive of the general formula (II) is a compound of the general formula (II),
• R 3 is H, alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl or heterocyclyl, where the alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl groups are optionally substituted by one or more substituents and the alkyl and cycloalkyl groups are optionally interrupted by from 1 to 3 heteroatoms or functional groups, and
• the radicals R 4 are each, independently of one another, H, alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl or heterocyclyl, where the alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl groups are optionally substituted by one or more substituents and the alkyl and cycloalkyl groups are optionally interrupted by from 1 to 3 heteroatoms or functional groups, and Hal is selected from the group consisting of fluorine, chlorine, bromine and iodine.
• the additive of the general formula (III) is a compound of the general formula (III),
• R 5 is alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl or heterocyclyl, where the alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl groups are optionally substituted by one or more substituents and the alkyl and cycloalkyl groups are optionally interrupted by from 1 to 3 heteroatoms or by functional groups, and M + is Na + or K + .
• the substituents are selected independently from the group consisting of fluorine, chlorine, bromine, iodine, optionally substituted alkyl, optionally substituted aryl, optionally substituted heterocyclyl, optionally substituted aralkyl, alkoxy, nitro, carboalkoxy, cyano, alkylmercaptyl, trihaloalkyl, carboxyalkyl, —(C 1 -C 7 )-alkyl, —O—(C 1 -C 7 )-alkyl, —N((C 1 -C 4 )-alkyl) 2 , —CO—N((C 1 -C 4 )-alkyl) 2 .
• Alkyl is a saturated aliphatic hydrocarbon group which may be linear or branched and can have from 1 to 20 carbon atoms in the chain. Preferred alkyl groups can be linear or branched and have from 1 to 10 carbon atoms in the chain. Branched means that a lower alkyl group such as methyl, ethyl or propyl is attached to a linear alkyl chain.
• Alkyl is, for example, methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methyl-1-propyl (isobutyl), 2-methyl-2-propyl (tert-butyl), 1-pentyl, 2-pentyl, 3-pentyl, 2-methyl-1-butyl, 3-methyl-1-butyl, 2-methyl-2-butyl, 3-methyl-2-butyl, 2,2-dimethyl-1-propyl, 1-hexyl, 2-hexyl, 3-hexyl, 2-methyl-1-pentyl, 3-methyl-1-pentyl, 4-methyl-1-pentyl, 2-methyl-2-pentyl, 3-methyl-2-pentyl, 4-methyl-2-pentyl, 2-methyl-3-pentyl, 3-methyl-3-pentyl, 2,2-dimethyl-1-butyl, 2,3-dimethyl-1-butyl, 3,3-dimethyl-1-butyl, 2-e
• Substituted alkyl means that the alkyl group is substituted by one or more substituents selected from among alkyl, optionally substituted aryl, optionally substituted aralkyl, alkoxy, nitro, carboalkoxy, cyano, halo, alkylmercaptyl, trihaloalkyl and carboxyalkyl.
• Cycloalkyl is an aliphatic ring which has from 3 to above 10 carbon atoms in the ring. Preferred cycloalkyl groups have from 4 to about 7 carbon atoms in the ring.
• Aryl is phenyl or naphthyl.
• Aralkyl is an alkyl group which is substituted by an aryl radical. “Substituted aralkyl” and “substituted aryl” means that the aryl group or the aryl group of the aralkyl group is substituted by one or more substituents selected from among alkyl, alkoxy, nitro, carboalkoxy, cyano, halo, alkylmercaptyl, trihaloalkyl and carboxyalkyl.
• Alkoxy is an alkyl-O group in which “alkyl” is as defined above. Lower alkoxy groups are preferred. Examples of groups include methoxy, ethoxy, n-propoxy, i-propoxy and n-butoxy.
• “Lower alkyl” is an alkyl group having from 1 to about 7 carbon atoms.
• Alkoxyalkyl is an alkyl group as described above which is substituted by an alkoxy groups as described above.
• Halogen is chlorine (chloro), fluorine (fluoro), bromine (bromo) or iodine (iodo).
• Heterocyclyl is an about 4- to about 10-membered ring structure in which one or more of the ring atoms is an element other than carbon, for example N, O or S. Heterocyclyl can be aromatic or nonaromatic, i.e. it can be saturated, partially unsaturated or fully unsaturated.
• Substituted heterocyclyl means that the heterocyclyl group is substituted by one or more substituents, with substituents including: alkoxy, aryl, carboalkoxy, cyano, halo, heterocyclyl, trihalomethyl, alkylmercaptyl and nitro.
• Alkoxycarbonyl is an alkoxy-C ⁇ O group.
• Alkoxycarbonyl is an aralkyl-O—C ⁇ O group.
• Aryloxycarbonyl is an aryl-O—C ⁇ O group.
• Carboalkoxy is a carboxyl substituent esterified by an alcohol of the formula C n H 2n+1 OH, where n is from 1 to about 6.
• Alkoxyalkyl is an alkyl group as described above which is substituted by an alkoxy group as described above.
• radicals R 1 , R 2 , R 3 and R 4 are in principle all heteroatoms which are able to formally replace a —CH 2 —, —CH ⁇ , —C ⁇ or ⁇ C ⁇ group. If the radical comprises heteroatoms, preference is given to oxygen, nitrogen, sulfur, phosphorus and silicon. As preferred groups, mention may be made of, in particular, —O—, —S—, —SO—, —SO 2 —, —NR′—, —N ⁇ , —PR′—, —PR′ 2 and —SiR′ 2 —, where the radicals R′ are in each case the remaining part of the radical.
• Possible functional groups are in principle all functional groups which can be bound to a carbon atom or a heteroatom. Suitable examples are ⁇ O (in particular as carbonyl group) and —CN (cyano). Functional groups and heteroatoms can also be directly adjacent, so that combinations of a plurality of adjacent atoms such as —O— (ether), —S— (thioether), —COO— (ester) or —CONR′— (tertiary amide) are also comprised, for example di(C 1 -C 4 -alkyl)amino, C 1 -C 4 -alkyloxycarbonyl or C 1 -C 4 -alkoxy.
• R 1 is selected from among methyl, ethyl, 1-propyl, 1-butyl, 1-pentyl and 1-hexyl. In a particularly preferred embodiment of the invention, the radical R 1 is methyl.
• R 2 is H and m is 4.
• the compound of the general formula (I) is N-methylbenzotriazole.
• the compound of the general formula (I) is one or more compound(s) selected from among N-methylbenzodiazole, N-ethylbenzodiazole, benzoxazole, benzisooxazole, benzisothiazole and benzothiazole.
• R 3 is a linear, saturated aliphatic hydrocarbon group having from 5 to 20 carbon atoms in the chain, particularly preferably from 10 to 18 carbon atoms in the chain.
• the radicals R 4 are identical or different and are selected from among H, methyl, ethyl, 1-propyl and 2-propyl.
• the compound of the general formula (II) is one or more compounds(s) selected from among hexadecyltrimethylammonium bromide and hexadecyltrimethylammonium chloride.
• R 5 is a linear, saturated aliphatic hydrocarbon group having from 5 to 20 carbon atoms in the chain, particularly preferably from 10 to 15 carbon atoms in the chain.
• the compound of the general formula (III) is sodium lauryl sulfate.
• the current density at which the process of the invention is carried out is at least 50 A/m 2 , and can vary within a wide range.
• the electric current density is for the present purposes defined as the ratio of current to effective electrode area in the electrolysis.
• the electric current density is preferably at least 100 A/m 2 , more preferably at least 200 A/m 2 and in particular at least 400 A/m 2
• Ionic liquids are suitable electrolytes for the deposition of aluminum.
• the electrolytes are typically salt melts having a water content of less than 0.1% by weight, based on the total amount of the electrolyte.
• the anion of the ionic liquid is tetrachloroaluminate.
• dialkylimidazolium cations preference is given to using dialkylimidazolium cations in which the two alkyl groups can be identical or different, branched or unbranched, unsubstituted or substituted by one or more phenyl groups and have from 1 to 6 carbon atoms.
• the ionic liquid very particularly preferably has a formula KaCl ⁇ n AlCl 3 , where Ka is one of the abovementioned imidazolium cations and n is from 1.4 to 2.0, more preferably 1.4 to 1.7, in particular 1.5.
• ionic liquids are described, for example, in DE-A 10 2005 017 733.
• radicals R and R 1 to R 9 possible heteroatoms are in principle all heteroatoms which are able formally to replace a —CH 2 — group, a —CH ⁇ group, a —C ⁇ group or a ⁇ C ⁇ group.
• the carbon-comprising radical comprises heteroatoms, preference is given to oxygen, nitrogen, sulfur, phosphorus and silicon.
• Preferred groups are, in particular, —O—, —S—, —SO—, —SO 2 —, —NR′—, —N ⁇ , —PR′—, —PR′ 2 and —SiR′ 2 —, where the radicals R′ are the remaining part of the carbon-comprising radical.
• the radicals R 1 to R 9 in the abovementioned formulae (IV) are bound to a carbon atom and (not to a heteroatom), these can also be bound directly via the heteroatom.
• Possible functional groups are in principle all functional groups which can be bound to a carbon atom or a heteroatom.
• suitable functional groups are ⁇ O (in particular as carbonyl group) and —CN (cyano).
• Functional groups and heteroatoms can also be directly adjacent, so that combinations of a plurality of adjacent atoms such as —O— (ether), —S— (thioether), —COO— (ester) or —CONR′— (tertiary amide) are also comprised, for example di(C 1 -C 4 -alkyl)amino, C 1 -C 4 -alkyloxycarbonyl or C 1 -C 4 -alkyloxy.
• halogens mention may be made of fluorine, chlorine, bromine and iodine.
• the radical R is preferably
• the radical R is particularly preferably unbranched and unsubstituted C 1 -C 18 -alkyl, for example methyl, ethyl, 1-propyl, 1-butyl, 1-pentyl, 1-hexyl, 1-heptyl, 1-octyl, 1-decyl, 1-dodecyl, 1-tetradecyl, 1-hexadecyl, 1-octadecyl, in particular methyl, ethyl, 1-butyl and 1-octyl, or CH 3 O—(CH 2 CH 2 O) n —CH 2 CH 2 — and CH 3 CH 2 O—(CH 2 CH 2 O) n —CH 2 CH 2 — where n is from 0 to 3.
• radicals R 1 to R 9 each being, independently of one another,
• C 1 -C 18 -Alkyl which is optionally substituted by functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles is preferably methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methyl-1-propyl (isobutyl), 2-methyl-2-propyl (tert-butyl), 1-pentyl, 2-pentyl, 3-pentyl, 2-methyl-1-butyl, 3-methyl-1-butyl, 2-methyl-2-butyl, 3-methyl-2-butyl, 2,2-dimethyl-1-propyl, 1-hexyl, 2-hexyl, 3-hexyl, 2-methyl-1-pentyl, 3-methyl-1-pentyl, 4-methyl-1-pentyl, 2-methyl-2-pentyl, 3-methyl-2-pentyl, 4-methyl-2-pentyl, 2-methyl-3-penty
• C 6 -C 12 -Aryl which is optionally substituted by functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles is preferably phenyl, tolyl, xylyl, ⁇ -naphthyl, ⁇ -naphthyl, 4-diphenylyl, chlorophenyl, dichlorophenyl, trichlorophenyl, difluorophenyl, methylphenyl, dimethylphenyl, trimethylphenyl, ethylphenyl, diethylphenyl, isopropylphenyl, tert-butylphenyl, dodecylphenyl, methoxyphenyl, dimethoxyphenyl, ethoxyphenyl, hexyloxyphenyl, methylnaphthyl, isopropylnaphthyl, chloronaphth
• C 5 -C 12 -Cycloalkyl which is optionally substituted by functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles is preferably cyclopentyl, cyclohexyl, cyclooctyl, cyclododecyl, methylcyclopentyl, dimethylcyclopentyl, methyl-cyclohexyl, dimethylcyclohexyl, diethylcyclohexyl, butylcyclohexyl, methoxycyclohexyl, dimethoxycyclohexyl, diethoxycyclohexyl, butylthiocyclohexyl, chlorocyclohexyl, dichlorocyclohexyl, dichlorocyclopentyl, C n F 2(n ⁇ a) ⁇ (1 ⁇ b) H 2a ⁇ b where n ⁇ 30, 0 ⁇ a ⁇ n and
• a five- or six-membered, oxygen-, nitrogen- and/or sulfur-comprising heterocycle which is optionally substituted by functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles is preferably furyl, thiophenyl, pyrryl, pyridyl, indolyl, benzoxazolyl, dioxolyl, dioxyl, benzimidazolyl, benzthiazolyl, dimethylpyridyl, methylquinolyl, dimethylpyrryl, methoxyfuryl, dimethoxypyridyl or difluoropyridyl.
• two adjacent radicals together form an unsaturated, saturated or aromatic ring which is optionally substituted by functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles and may optionally be interrupted by one or more oxygen and/or sulfur atoms and/or one or more substituted or unsubstituted imino groups
• the two radicals together are preferably 1,3-propylene, 1,4-butylene, 1,5-pentylene, 2-oxa-1,3-propylene, 1-oxa-1,3-propylene, 2-oxa-1,3-propylene, 1-oxa-1,3-propenylene, 3-oxa-1,5-pentylene, 1-aza-1,3-propenylene, 1-C 1 -C 4 -alkyl-1-aza-1,3-propenylene, 1,4-buta-1,3-dienylene, 1-aza-1,4-buta-1,3-dienylene or 2-
• radicals comprise oxygen and/or sulfur atoms and/or substituted or unsubstituted imino groups
• the number of oxygen and/or sulfur atoms and/or imino groups is not subject to any restrictions. There will generally be no more than 5 in the radical, preferably no more than 4 and very particularly preferably no more than 3.
• radicals comprise heteroatoms
• radicals R 1 to R 9 each being, independently of one another,
• radicals R 1 to R 9 each being, independently of one another, hydrogen or C 1 -C 18 -alkyl, for example methyl, ethyl, 1-butyl, 1-pentyl, 1-hexyl, 1-heptyl, 1-octyl, phenyl, 2-cyanoethyl, 2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl, 2-(n-butoxycarbonyl)ethyl, N,N-dimethylamino, N,N-diethylamino, chlorine or CH 3 O—(CH 2 CH 2 O) n —CH 2 CH 2 — or CH 3 CH 2 O—(CH 2 CH 2 O) n —CH 2 CH 2 — where n is from 0 to 3.
• pyridinium ions IVa
• imidazolium ions mention may be made of 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1-(1-butyl)-3-methylimidazolium, 1-(1-butyl)-3-ethylimidazolium, 1-(1-hexyl)-3-methylimidazolium, 1-(1-hexyl)-3-ethylimidazolium, 1-(1-hexyl)-3-butylimidazolium, 1-(1-octyl)-3-methylimidazolium, 1-(1-octyl)-3-ethylimidazolium, 1-(1-octyl)-3-butylimidazolium, 1-(1-dodecyl)-3-methylimidazolium, 1-(1-dodecyl)-3-ethylimidazolium, 1-(1-dodecyl)-3-methylimi
• IVI very particularly preferred imidazolinium ions
• IVt very particularly preferred imidazolidinium ions
• ammonium ions IVu
• tertiary amines from which the quaternary ammonium ions of the general formula (IVu) are derived by quaternization with the abovementioned radicals R are diethyl-n-butylamine, diethyl-tert-butylamine, diethyl-n-pentylamine, diethylhexylamine, diethyloctylamine, diethyl(2-ethylhexyl)amine, di-n-propylbutylamine, di-n-propyl-n-pentylamine, di-n-propylhexylamine, di-n-propyloctylamine, di-n-propyl(2-ethylhexyl)-amine, diisopropylethylamine, diisopropyl-n-propylamine, diisopropylbutylamine, diisopropylpentylamine, diisopropylhexyl
• Preferred tertiary amines (IVu) are diisopropylethylamine, diethyl-tert-butylamine, diiso-propylbutylamine, di-n-butyl-n-pentylamine, N,N-di-n-butylcyclohexylamine and tertiary amines derived from pentylisomers.
• tertiary amines are di-n-butyl-n-pentylamine and tertiary amines derived from pentylisomers.
• a further preferred tertiary amine which has three identical radicals is triallylamine.
• cholinium ions in which R 3 is selected from among hydrogen, methyl, ethyl, acetyl, 5-methoxy-3-oxapentyl, 8-methoxy-3,6-dioxa-octyl, 11-methoxy-3,6,9-trioxaundecyl, 7-methoxy-4-oxaheptyl, 11-methoxy-4,8-dioxa-undecyl, 15-methoxy-4,8,12-trioxapentadecyl, 9-methoxy-5-oxanonyl, 14-methoxy-5,10-oxatetradecyl, 5-ethoxy-3-oxapentyl, 8-ethoxy-3,6-dioxaoctyl, 11-ethoxy-3,6,9-trioxaundecyl, 7-ethoxy-4-oxaheptyl, 11-
• IIIx Very particularly preferred phosphonium ions (IVx) are those in which
• heterocyclic cations preference is given to the pyridinium ions, pyrazolinium ions, pyrazolium ions and the imidazolinium and imidazolium ions. Ammonium ions are also preferred.
• the metal cations [M 1 ] + , [M 2 ] + , [M 3 ] + , [M 4 ] 2+ and [M 5 ] 3+ mentioned in the formulae (IIIa) to (IIIj) are in general metal cations of groups 1, 2, 6, 7, 8, 9, 10, 11, 12 and 13 of the Periodic Table. Suitable metal cations are, for example, Li + , Na + , K + , Cs + , Mg 2+ , Ca 2+ , Ba 2+ , Cr 3+ , Fe 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , Ag + , Zn 2+ and Al 3+ .
• the anion [Y] n ⁇ of the ionic liquid is, for example, selected from
• R a , R b , R c and R d are each, independently of one another, hydrogen, C 1 -C 30 -alkyl, C 2 -C 18 -alkyl which is optionally interrupted by one or more nonadjacent oxygen and/or sulfur atoms and/or one or more substituted or unsubstituted imino groups, C 6 -C 14 -aryl, C 5 -C 12 -cycloalkyl or a five- or six-membered, oxygen-, nitrogen- and/or sulfur-comprising heterocycle, where two of the radicals may together form an unsaturated, saturated or aromatic ring which is optionally interrupted by one or more oxygen and/or sulfur atoms and/or one or more unsubstituted or substituted imino groups, where the radicals mentioned may in each case also be substituted by functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles.
• C 1 -C 18 -alkyl which is optionally substituted by functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles is, for example, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, 2,4,4-trimethylpentyl, decyl, dodecyl, tetradecyl, heptadecyl, octadecyl, 1,1-dimethylpropyl, 1,1-dimethylbutyl, 1,1,3,3-tetramethylbutyl, benzyl, 1-phenylethyl, ⁇ , ⁇ -dimethylbenzyl, benzhydryl, p-tolylmethyl, 1-
• C 2 -C 18 -Alkyl which is optionally interrupted by one or more nonadjacent oxygen and/or sulfur atoms and/or one or more substituted or unsubstituted imino groups is, for example, 5-hydroxy-3-oxapentyl, 8-hydroxy-3,6-dioxaoctyl, 11-hydroxy-3,6,9-trioxaundecyl, 7-hydroxy-4-oxaheptyl, 11-hydroxy-4,8-dioxaundecyl, 15-hydroxy-4,8,12-trioxapentadecyl, 9-hydroxy-5-oxanonyl, 14-hydroxy-5,10-oxatetradecyl, 5-methoxy-3-oxapentyl, 8-methoxy-3,6-dioxaoctyl, 11-methoxy-3,6,9-trioxaundecyl, 7-methoxy-4-oxaheptyl, 11
• radicals can be, for example as fused-on building block, 1,3-propylene, 1,4-butylene, 2-oxa-1,3-propylene, 1-oxa-1,3-propylene, 2-oxa-1,3-propenylene, 1-aza-1,3-propenylene, 1-C 1 -C 4 -alkyl-1-aza-1,3-propenylene, 1,4-buta-1,3-dienylene, 1-aza-1,4-buta-1,3-dienylene or 2-aza-1,4-buta-1,3-dienylene.
• the number of nonadjacent oxygen and/or sulfur atoms and/or imino groups is not restricted in principle or is restricted automatically by the size of the radical or the ring building block. In general, there will be no more than 5 in the respective radical, preferably no more than 4 and very particularly preferably no more than 3. Furthermore, there is generally at least one carbon atom, preferably at least two carbon atoms, between each two heteroatoms.
• Substituted and unsubstituted imino groups can be, for example, imino, methylimino, isopropylimino, n-butylimino or tert-butylimino.
• the term “functional groups” refers, for example, to the following: carboxy, di(C 1 -C 4 -alkyl)amino, C 1 -C 4 -alkyloxycarbonyl, cyano or C 1 -C 4 -alkoxy.
• C 1 -C 4 -alkyl is methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl or tert-butyl.
• C 6 -C 14 -Aryl which is optionally substituted by functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles is, for example, phenyl, tolyl, xylyl, ⁇ -naphthyl, ⁇ -naphthyl, 4-diphenylyl, chlorophenyl, dichlorophenyl, trichlorophenyl, difluorophenyl, methylphenyl, dimethylphenyl, trimethylphenyl, ethylphenyl, diethylphenyl, isopropylphenyl, tert-butylphenyl, dodecylphenyl, methoxyphenyl, dimethoxyphenyl, ethoxyphenyl, hexyloxyphenyl, methylnaphthyl, isopropylnaphthyl, chloronap
• C 5 -C 12 -Cycloalkyl which is optionally substituted by functional groups, aryl, alkyl, aryloxy, halogen, heteroatoms and/or heterocycles is, for example, cyclopentyl, cyclohexyl, cyclooctyl, cyclododecyl, methylcyclopentyl, dimethylcyclopentyl, methylcyclohexyl, dimethylcyclohexyl, diethylcyclohexyl, butylcyclohexyl, methoxycyclohexyl, dimethoxycyclohexyl, diethoxycyclohexyl, butylthiocyclohexyl, chlorocyclohexyl, dichlorocyclohexyl, dichlorocyclopentyl or a saturated or unsaturated bicyclic system such as norbornyl or norbornenyl.
• a five- or six-membered, oxygen-, nitrogen- and/or sulfur-comprising heterocycle is, for example, furyl, thiophenyl, pyryl, pyridyl, indolyl, benzoxazolyl, dioxolyl, dioxyl, benzimidazolyl, benzthiazolyl, dimethylpyridyl, methylquinolyl, dimethylpyryl, methoxyfuryl, dimethoxypyridyl, difluoropyridyl, methylthiophenyl, isopropylthiophenyl or tert-butylthiophenyl.
• Preferred anions are selected from the group of halides and halogen-comprising compounds, the group of carboxylic acids, the group of sulfates, sulfites and sulfonates and the group of phosphates.
• Preferred anions are chloride, bromide, iodide, SCN ⁇ , OCN ⁇ , CN ⁇ , acetate, C 1 -C 4 -alkylsulfates, R a —COO ⁇ , R a SO 3 ⁇ , R a R b PO 4 ⁇ , methanesulfonates, tosylate, C 1 -C 4 -dialkylphosphates, hydrogensulfate or tetrachloroaluminate.
• dialkylimidazolium cations in which the two alkyl groups can be identical or different, branched or unbranched, unsubstituted or substituted by one or more phenyl groups and have from 1 to 6 carbon atoms.
• an electrolysis apparatus which has at least one anode and at least one cathode in an electrolysis space is provided.
• the at least one anode and the at least one cathode are connected in an electrolytically conductive fashion by the electrolyte, which is an ionic liquid.
• anode it is possible to use one anode, but a plurality of anodes can also be employed. These can have the same composition or different compositions. The same applies to the cathode(s).
• the anode functions as sacrificial anode comprising primary aluminum.
• the at least one anode preferably comprises aluminum in a proportion by weight of at least 95% by weight, preferably 99% by weight, more preferably at least 99.5% by weight, based on the total weight of the at least one anode.
• the at least one cathode present in the electrolysis apparatus can be selected from among various conductive materials.
• the at least one cathode comprises a material or a plurality of materials selected from among metals, alloys, graphite, electrically conductive plastics or polymers and steels.
• the material of the cathode is selected from among metals, alloys and steels, in particular from among steel, Ni alloys, Cu alloys, Zn alloys and Al alloys.
• cathode materials are stainless steel, nickel-based alloys, graphite, copper and particularly preferably aluminum.
• the electrolyte is agitated at the surface of the cathode, e.g. by means of stirring, recirculation or agitation of the whole apparatus.
• the shapes of the anode and of the cathode can in principle be selected freely. Preference is given to selecting arrangements known in the prior art.
• the cathode is a workpiece such as a vehicle bodywork part on which aluminum is deposited.
• the process of the invention is carried out at a temperature in the range from 20 to 200° C., preferably at a temperature in the range from 20 to 120° C., particularly preferably at a temperature in the range from 60 to 90° C., very particularly preferably at a temperature of about 90° C.
• the aluminum is generally supplied to the process of the invention in the form of a metal salt selected from the group consisting of AlCl 3 , AlBr 3 , AlI 3 and AlF 3 . Preference is given to AlCl 3
• the invention further provides for the use of additives having the general formulae (I), (II) and (III) in a process for the electrochemical deposition of aluminum.
• the invention further provides an electrolyte for the electrochemical deposition of aluminum from an ionic liquid comprising an ionic liquid comprising anions and cations and also one or more metal salts, one or more additives of the general formulae (I), (II) and (III) and also, if appropriate, one or more solvents.
• the electrolyte of the invention in combination with one or more additives of the general formulae (I), (II) and (III) is found to be very progressive from an electroplating point of view, i.e. it fulfills the requirements which an electrolyte has to meet for an industrially widely usable and economical aluminum deposition process to a far higher extent than has hitherto been possible.
• a further advantage of the electrolyte of the invention is that when it is used in the electrochemical deposition of aluminum, it leads to an even deposit of aluminum having a shiny or matt finish on the cathode.
• the composition of the electrolyte of the invention can generally vary over a wide range; thus, the electrolyte of the invention comprises from 0.1 to 10% by weight of additive and from 99.9 to 90% by weight of ionic liquid and from 0 to 50% by weight, preferably from 10 to 30% by weight, of one or more organic solvent(s).
• the organic solvent is generally selected from the group consisting of aromatics and heteroaromatics.
• the solvent is selected from among toluene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,3-dichlorobenzene, trichlorobenzene and xylene.
• the polarity is then reversed again and aluminum is deposited on the cathode over a further 286 minutes at 95° C. and a current density of 40 mA/cm 2 , with the anode simultaneously being consumed as a sacrificial anode.
• the terminal voltage drops from 991 to 801 mV.
• the electrodes are removed from the electrolyte and successively rinsed with 40 ml of acetonitrile, stirred in 100 ml of water for 15 minutes and rinsed with isopropanol. They are finally dried at 105° C. for one hour. From the cathodic mass difference, the current yield is determined as 97.3%. The appearance of the cathode deposit is matt and dense.
• the terminal voltage drops from 974 to 850 mV.
• the electrodes are removed from the electrolyte and successively rinsed with 40 ml of acetonitrile, stirred in 100 ml of water for 15 minutes and rinsed with isopropanol. They are finally dried at 105° C. for one hour. From the cathodic mass difference, the current yield is determined as 95.8%. The appearance of the gray cathode deposit is matt and dense.
• the polarity is then reversed again and aluminum is deposited on the cathode over a further 141 minutes at 95° C. and a current density of 80 mA/cm 2 , with the anode simultaneously being consumed as a sacrificial anode.
• the terminal voltage drops from 1812 mV to 1626 mV.
• the electrodes are removed from the electrolyte and successively rinsed with 40 ml of acetonitrile, stirred in 100 ml of water for 15 minutes and rinsed with isopropanol. They are finally dried at 105° C. for one hour. From the cathodic mass difference, the current yield is determined as 91.3%. The appearance of the cathode deposit is shiny and silvery.
• Aluminum is deposited on the cathode over a period of 15 minutes at 90° C. and a current density of 40 mA/cm 2 , with the anode simultaneously being consumed as a sacrificial anode. During the course of the experiment, the terminal voltage increases from 1.2 to 1.3 V. After the electrolysis is complete, the electrodes are removed from the electrolyte and washed with 50 ml of acetonitrile. The appearance of the cathode deposit is silvery-matt and dense.
• the mild steel cathode was electrolytically degreased beforehand by means of the Metex Cleaner System from MacDermid, rinsed with water, pickled with concentrated hydrochloric acid for 10 seconds and rinsed with acetone.
• Aluminum is deposited on the cathode over a period of 15 minutes at 90° C. and a current density of 40 mA/cm 2 , with the anode simultaneously being consumed as a sacrificial anode.
• the terminal voltage increases from 1.3 to 1.5 V.
• the electrodes are removed from the electrolyte and washed with 50 ml of acetonitrile.
• the appearance of the cathode deposit is silvery and dense.

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• 2010
  • 2010-03-16 EP EP10708571A patent/EP2419551A2/de not_active Withdrawn
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