JP7326342B2 - anti-fingerprint coating - Google Patents

Description

The present invention is a novel method for coating a metal substrate, especially a chrome substrate, with an anti-fingerprint coating, by coating the metal substrate using a silicone coating mixture, and coating said metal substrate. The use of said silicone coating mixture for

Chromium and other metals are used, for example, in automotive parts, both for the interior of the vehicle and for the exterior of the vehicle, white goods such as refrigerators, stoves, washing machines, and dishwashers, and appliances such as mobile phones. , sanitary ware, and classical chromium layers contained, for example, in corrosion-resistant coatings used for decorative equipment, have found widespread use as decorative materials in multiple applications. All of these surfaces can be adversely affected in their unsightly appearance by the adhering of dirt, particularly fatty or greasy contaminants, to them. The latter type of stain cannot be easily removed using wet cleaners and therefore will strongly affect the appearance of the metal coated article. Fingerprints frequently appear on decorative surfaces as a result of manual handling during everyday use. Due to the inherent fatty substances contained in human exudates, such fouling of decorative surfaces is frequently experienced in decoratively designed parts.

In most cases mechanical removal of stains is used to restore the original good appearance of the decorative surface. When those surfaces contaminated with fingerprints are subsequently mechanically cleaned to remove this contamination, the fatty substances of the fingerprints are diffused across the surface. When mechanical removal is applied to such surfaces, diffusion of the contamination will result and will generally be sufficient to restore the good optical appearance that the surface had prior to contamination.

Matte metal surfaces are more prone to decorative failure due to fatty or greasy contaminants than shiny metal surfaces, and dark metal surfaces are likewise more susceptible than bright metal surfaces. It has been determined that such disorders are likely to occur. Although having the same surface roughness, the surface of a chromium coating deposited from a Cr(III)-containing plating composition exhibits more fingerprints than the surface of a chromium coating deposited using a Cr(VI)-containing plating composition. More susceptible to such disturbances of cause. This different behavior is due to the fact that chromium surfaces produced using Cr(III)-containing plating compositions are darker than chromium surfaces produced using Cr(VI)-containing plating compositions. is. This problem is even more acute on the surface of chromium deposits produced by using chloride-containing Cr(III)-containing plating compositions. In this latter case, fingerprints are more susceptible to damage because their surfaces are relatively dark.

Recent trends caused by environmental concerns and occupational health and safety reasons have led to the need to remove Cr(VI) species in the formation of chromium deposits. However, this results in problems encountered in the manual handling of parts coated with chromium coatings, as fingerprints and other fatty or greasy contamination make such contamination even more prominently visible. worsens.

Various attempts have been made to overcome these problems.

U.S. Patent Application Publication No. 2008/0131706 A1 discloses polysilazanes as permanent coatings on metal surfaces, stainless steel, aluminum, or chromium-plated surfaces, for example, to prevent fingerprint sensitivity. teach the use of Polysilazanes have the general formula -(SiR'R''-NR''') _n -[wherein R', R'', R''' are independently H, optionally substituted an alkyl, aryl, vinyl, or (trialkoxysilyl)alkyl group, where n is an integer such that the polysilazane has a number average molecular weight of 150 to 150,000 g/mol in the solvent; is in the form of a mixture of

Furthermore, DE 102005018740 A1 teaches a fluorine-free hydrophobic protective coating for metal surfaces to prevent the formation of fingerprints. The protective coating comprises (a) 50-65% by weight tetraalkoxy compounds of silicon, titanium, and zirconium; (b) _20-30 % by weight _{methyltrialkoxysilane} ; 20% by weight of an alkyltrialkoxysilane; (d) 2-5% by weight of a hydrolyzate and condensate of a polyalkylene oxide trialkoxysilane.

In addition to these prior art documents, documents have been published relating to coatings based on silicon-containing compounds. Two documents are discussed as follows.

U.S. Pat. No. 6,251,989 (B1) teaches oligomerized polyorganosiloxane cocondensates that can be obtained in part by mixing the indicated water-soluble aminofunctional organosilanes with at least one of Do: fluorofunctional organosilanes, and one of the various types of organosilanes.

U.S. Pat. No. 8,889,812 (B2) teaches aqueous compositions based on trissilylated amino-functional silicon compounds, which are substantially free of organic solvents and contain no alcohol, even during the crosslinking process. Practically no release.

It is possible to mechanically remove fingerprints from metal surfaces, particularly chromium surfaces, which has been shown to remove metal surfaces prior to exposure to fingerprints, as described in US Patent Application Publication No. 2008/0131706 (A1) and Germany. It has become apparent that post-treatment with agents described in National Patent Application Publication No. 102005018740 (A1) may facilitate. However, the metal surfaces provided so far have still proven susceptible to exposure to fingerprints, in that fingerprints are significantly visible. Moreover, the effort required to completely remove fingerprints is relatively high with conventional post-treatments of metal surfaces.

U.S. Patent Application Publication No. 2008/0131706(A1) DE 102005018740 (A1) U.S. Patent No. 6,251,989(B1) U.S. Patent No. 8,889,812(B2) EP 1101787(B1) EP 0675128(B1)

Law and Zhao, Surface Wetting-Characterization, Contact Angle and Fundamentals, Springer Verlag (2016) ISBN 9783319252124

It is therefore an object of the present invention to provide a means for producing a metal surface, preferably a chromium surface, most preferably a chromium coating, produced by using a Cr(III)-containing plating composition. Yes, this surface is largely unaffected by fingerprint generation, and any fingerprints that are generated are then easily removed mechanically.

It is a further object of the present invention to provide a metal surface with the true optical appearance provided upon its production, i.e. its native tint, morphology such as a given roughness or other properties that affect the appearance of the metal surface. It is an object of the present invention to provide a metal surface, preferably a chromium surface, most preferably a chromium coating produced by using a Cr(III)-containing plating composition, with a coating that retains its properties perfectly.

It is a further object of the present invention to provide a coating on a metal surface that is easy to produce, preferably a chromium surface, most preferably a chromium coating produced by using a Cr(III)-containing plating composition. . More specifically, the method for preparing metal surfaces to achieve anti-fingerprint properties is very easy, can be integrated into plating lines without special equipment, and is labor intensive. shall be unnecessary.

DEFINITIONS The term “alkyl” as used herein refers to saturated alkyl groups of 1 to 12 carbon atoms (C ₁ -C ₁₂ ), preferably 1 to 6 carbon atoms (C ₁ -C ₆ ). Refers to a straight or branched chain monovalent or divalent hydrocarbon group, wherein one or more hydrogen atoms of the alkyl group are optionally substituted with the respective number of substitutions described below. It may be independently substituted with groups. Examples of alkyl groups include, but are not limited to, methyl ( _-CH3 ), ethyl ( _-CH2CH3 ), 1-propyl ( _{-CH2CH2CH3 )} , 2-propyl _{( -CH} ( _CH3 ) ₂ ), 1- _butyl (-CH2CH2CH2CH3) _, 2-methyl-1 _- propyl ( _-CH2CH ( _CH3 ) ₂ ), 2-butyl (-CH _{( CH3} ) _CH2CH3 ), 2-methyl-2-propyl ( _-C ( _CH3 ) ₃ ) _, 1-pentyl ( _{-CH2CH2CH2CH2CH3 )} , 2 _{- pentyl} (-CH( _CH3 ) _CH2CH2CH3 ), 3-pentyl ( _-CH ( _{CH2CH3 ) 2 )} , 2 _- methyl-2 _- butyl (-C( _CH3 ) _2CH2CH3 ), 3-methyl-2 -butyl (-CH( _{CH3 ) CH} ( _CH3 ) ₂ ), 3-methyl-1-butyl (-CH2CH2CH( _CH3 ) ₂ ), 2-methyl-1-butyl ( _-CH2CH ( _{CH3 ) CH2CH3} ), 1 _{- hexyl} ( _{-CH2CH2CH2CH2CH2CH3 ) , 2} -hexyl _{( -CH} ( _{CH3 )} CH2CH2CH2CH3), ₃ -hexyl (-CH( _CH2CH3 )( _{CH2CH2CH3 )} ), 2 _- methyl-2-pentyl ₍ -C _{( CH3} ) _{2CH2CH2CH3 )} , 3-methyl _- 2- Pentyl (-CH( _CH3 )CH( _CH3 ) _CH2CH3 ), 4-methyl-2-pentyl ₍ -CH( _CH3 ) _CH2CH ( _CH3 ) ₂ ), 3-methyl-3-pentyl (-C( _CH3 )( _{CH2CH3 ) 2} ), 2-methyl-3-pentyl (-CH( _{CH2CH3 )} CH( _CH3 ) ₂ ), 2,3-dimethyl-2-butyl ( -C( _CH3 ) _2CH ( _CH3 ) ₂ ), 3,3-dimethyl-2-butyl (-CH( _CH3 )C( _CH3 ) ₃ ), 1-heptyl, 1-octyl and the like. Alkyl also includes, but _is not limited to, methylene ( _-CH2- ), ethylene ( _-CH2CH2- ), propylene ( _-CH2CH2CH2- ), and _{the like} .

The term "fluoroalkyl" as used herein refers to saturated alkyl groups of 1 to 12 carbon atoms (C ₁ -C ₁₂ ), preferably 1 to 6 carbon atoms (C ₁ -C ₆ ). Refers to a straight or branched chain monovalent hydrocarbon group, wherein one or more hydrogen atoms of the alkyl group of fluoroalkyl is replaced by a respective number of fluorine atoms. A fluoroalkyl is a perfluoroalkyl when all hydrogen atoms of the alkyl group are replaced by fluorine. Hereinafter, the same definitions and examples as given above for the term "alkyl" apply mutatis mutandis to fluoroalkyl.

The term "fluoroalkylalkyl" as used herein refers to a fluoroalkyl having a perfluoroalkyl moiety and an alkyl moiety, wherein the perfluoroalkyl moiety, in a first alternative, is a monovalent group and _the alkyl moiety can also form a divalent moiety, ie it can have the chemical formula _{CnF2n -1} - _CnH2n- . In _a second alternative, the perfluoroalkylalkyl can also form a divalent perfluoroalkyl moiety and a monovalent alkyl moiety, i.e. it has the chemical formula _{CnH2n -1} - _CnF2n- can also

Alkyl can be optionally substituted, wherein one or more of its hydrogen atoms is optionally aryl, heteroaryl, OR, NR'R'', COOR, CONR'R'' , R, R′, and R″ may be independently substituted with any radical group such as ] independently selected from hydrogen, alkyl, aryl, and heteroaryl. Heteroaryl is a monovalent radical that includes an aromatic ring system containing at least one N, S, and O, such as pyridyl, pyryl, thiophenyl, furanyl, and the like.

“Aryl” means 6 to 20 carbon atoms (C ₆ -C ₂₀ ) is a monovalent or divalent aromatic hydrocarbon radical. Aryl also includes bicyclic radicals comprising an aromatic ring fused to an aromatic carbocyclic ring. Typical aryl groups include, but are not limited to, groups derived from benzene (phenyl), substituted benzene, naphthalene, and the like. One or more hydrogen atoms of the aryl may optionally be independently substituted with the respective number of substituents described herein below.

Unless otherwise defined in the general chemical formulas detailed herein, for aryl, one or more of its hydrogen atoms are optionally independently substituted with a respective number of substituents. optionally, wherein at least one hydrogen atom of the aryl moiety is halo, alkyl, aryl, heteroaryl, OR, NR'R'', COOR, CONR'R'' [wherein R, R', and R″ are independently selected from hydrogen, alkyl, aryl, and heteroaryl].

The term "halogen" or "halo" as used herein refers to fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).

The term "siloxane" as used herein refers to a silicon Refers to a compound in which R and R' denote H, alkyl, aryl, including substituted alkyl and aryl, typically forming a [-O-Si]-backbone. In these compounds, the terminal portion may differ from the definition of R, R'.

In a first aspect of the present invention, these objects are a method for coating metal substrates, such as chromium, nickel or stainless steel substrates, in particular chromium substrates, with an anti-fingerprint coating, comprising:
(a) providing a metal substrate, preferably a chromium substrate;
(b) the following:
(i) at least one first silicone compound selected from the group consisting of mono- or oligo(aminoalkyl)-fluoroalkylsilicones;
(ii) at least one second silicone compound selected from the group consisting of aminoalkylsilicones;
(iii) at least one acidifying agent, and
(iv) providing a silicone coating mixture containing water;
(c) treating the metal substrate with the silicone coating mixture by contacting the metal substrate with the silicone coating mixture;
(d) curing the treated metal substrate at a predetermined temperature.

For example, in oligo(aminoalkyl)-fluoroakyl silicones, when the term "oligo" is used, oligo is interpreted as 2 to 8, preferably 2 to 6, more preferably 2 or 3. or as a synonym for a small number of units interpreted as dimers, trimers, tetramers, . . . octamers.

Aminoalkyl in mono or oligo(aminoalkyl) moieties is preferably -N(R')-alkyl [wherein R' is preferably H, alkyl, more preferably C1 _{- C6} alkyl, aryl, more preferably C ₆ -aryl, arylalkyl, alkylaryl, or alkylarylalkyl]. _{Most preferably} R' = ethyl ( _-CH2CH2- ) and/or _propyl ( _-CH2CH2CH2- ).

The fluoroalkyl of the at least one first silicone compound _is preferably perfluoroalkylalkyl and more preferably has the chemical formula _{CnF2n -1} - _CnH2n- . Furthermore, the fluoroalkyl of the at least one first silicone compound is preferably perfluoroC ₂ -C ₅ -alkylalkyl. Most preferably, the fluoroalkyl of at least one first silicone compound is preferably perfluoroC ₂ -C ₅ -alkyl-C ₁ -C ₄ -alkyl.

The silicone coating mixture may contain one mono- or oligo(aminoalkyl)-fluoroalkylsilicone or multiple mono- or oligo(aminoalkyl)-fluoroalkylsilicones, wherein these silicones are mono- or At least one of the chain lengths of the oligo(aminoalkyl) moieties may be different from each other, and the meaning of aminoalkyl includes, for example, the meaning of R' in -N(R')- and the meaning of fluoroalkyl. .

The aminoalkyl of the at least one second silicone compound is preferably R'R''N-alkyl [wherein R' and R'' are independently preferably H, alkyl, preferably C ₁ ~ C ₆ alkyl, aryl, preferably C ₆ -aryl, arylalkyl, alkylaryl, or alkylarylalkyl]. Most preferably R'=R''=H.

The silicone coating mixture may contain one aminoalkylsilicone or a plurality of aminoalkylsilicones, wherein the silicones may differ from each other in at least one of the chain lengths of the silicone chains; The meaning of aminoalkyl includes, for example, the meaning of R' and R'' in R'R''N-alkyl.

In a second aspect of the invention these objects are solved by using a silicone coating mixture for coating a metal substrate with an anti-fingerprint coating. The silicone coating mixture is selected from the group consisting of (i) at least one first silicone compound selected from the group consisting of mono- or oligo(aminoalkyl)-fluoroalkylsilicones, (ii) aminoalkylsilicones. (iii) at least one acidifying agent; and (iv) water.

By coating a metal substrate with an anti-fingerprint coating, an excellent finish of the metal surface is achieved which is highly resistant to fingerprint formation and to fouling with fatty or greasy materials, where any Fingerprint smudges are also easily removed mechanically from the surface. Such removal may be performed using, for example, a microfiber cloth. Anti-fingerprint coatings do not alter their color tone or surface morphology, thus ensuring maintenance of the original appearance of the metal surfaces as prepared. Furthermore, the treatment of metal surfaces according to the present invention with silicone coating mixtures is very easy and does not require time-consuming, labor-intensive and energy-intensive processes; Allows rapid processing at processing temperatures. In preferred embodiments of the invention, the chemicals used are water soluble and they will not require organic solvents as solubilizers. The use of standard functional alkoxysilanes would require the use of organic solvents with known health, safety, and environmental disadvantages when VOCs are used. Unlike standard functional alkoxysilanes, no alcohol is released upon hydrolysis. Therefore, it is not necessary to add an organic solvent. Alternatively, a completely aqueous liquid may be used, ie the silicone coating mixture preferably contains no added organic solvents. Therefore, it is also preferable not to use water-insoluble or poorly water-soluble silicone compounds such as alkylalkoxysilanes or derivatives thereof, since it is necessary to use an organic solvent.

Without being limited by theory, the compounds contained in the silicone coating mixture adsorb to the metal substrate and undergo chemical reactions during the curing process to form a very thin, invisible and mechanically resistant topcoat thereon. can be considered. The method of the present invention is a sol-gel process based on the adsorption of silicon-containing compounds from a mixture of various organofunctional silicon compounds and optionally at least one polyether siloxane copolymer surfactant in solution. It is believed that there is. Due to the overcoat, the surface energy of the substrate is reduced compared to the uncoated state. Therefore, it is possible to monitor the formation of the coating by measuring the contact angle.

In preferred embodiments of the invention, the silicone coating mixture is a liquid, more preferably an aqueous liquid, and most preferably an aqueous solution or aqueous sol (colloidal solution).

In a further preferred embodiment of the invention the metal substrate is produced in a conventional manner. The metal substrate may be in the form of any work piece made from any material and coated with any deposit of metal. The work material may preferably be plastic, metal, glass, ceramic material or any other material. Typically, depending on the intended use, the work piece exhibits any automotive parts, or sanitary parts, or any parts for building installations, or parts for electronic or audiovisual equipment, or exhibits decorative properties. It can be provided as any other part. The metal deposit is preferably a nickel or stainless steel coating, or most preferably a chromium coating.

Accordingly, in a further preferred embodiment of the invention, the metal substrate is a chromium substrate, more preferably a chromium metal layer forming the substrate deposited on the workpiece. In this latter case, the chromium substrate is produced by depositing a chromium metal layer on the workpiece. In this case, a primer is generally first produced on the work piece before depositing the chromium metal layer thereon. Such a primer may consist of multiple metal layers to provide optimum decorative (horizontal, gloss) and functional (corrosion resistance) properties of the overall metal coating. The undercoat consists, for example, of a base copper metal layer and one or more nickel metal layers placed directly beneath the chromium metal layer. These metal layers are generally electroplated by using the proper plating composition. Such sandwich metal coatings and methods for their deposition are well known to those skilled in the art.

Depositing the chromium metal layer comprises providing a work piece and an electroplating solution containing at least one chromium plating species, more preferably Cr(III) plating species, and at least one chromium plating species. and more specifically electroplating a chromium metal layer onto the work piece by using an electroplating solution containing a Cr(III) plating species. A chromium coating can be produced by conventional methods. In an even more preferred embodiment of the invention, when the chromium metal layer is produced using an electroplating method, the electroplating is chromium(III) chloride, chromium(III) sulfate or basic chromium(III) sulfate It is carried out by using an electroplating solution (composition) containing Cr(III) species such as. Such electroplating solutions typically contain one or more buffers such as boric acid and carbonic acid, conductive salts such as ammonium sulfate, sodium sulfate, potassium sulfate, and potassium halides, carbonic acid and amino acids. and one wetting agent such as a sulfosuccinate. If a dark chromium metal layer is desired, darkening agents may be added. Such liquids are available and those skilled in the art are familiar with the use of such liquids to produce chromium coatings on electroplated work pieces.

In an even more preferred embodiment of the present invention, the Cr(III) plating species containing liquid does not contain chloride species.

In a further preferred embodiment of the present invention, the at least one first silicone compound selected from the group consisting of mono- or oligo(aminoalkyl)-fluoroalkylsilicones comprises mono- or oligo(aminoalkyl)silicones and (fluoro It is a water-soluble statistical copolymer of alkyl)alkylsilicones.

In a further preferred embodiment of the invention, the at least one first silicone compound comprises at least two monomers selected from the group consisting of mono- or oligoaminoalkyltrihydroxysilane compounds and fluoroalkylalkyltrihydroxysilane compounds. derived from the aqueous cocondensation of units,
Aminoalkyltrihydroxysilane compounds have the following general chemical formula (I):
(HO) _3Si- ( _CH2 ) _x- [NH( _CH2 ) _y ] _z - _NH2 (I)
[In the formula,
x is 1-8, preferably 1-6, more preferably 1-4,
y is 1-6, preferably 1-4, more preferably 1-2,
z is 0-8, preferably 0-6, more preferably 0-4, most preferably 1 or 2]
has
The fluoroalkylalkyltrihydroxysilane compound has the following general formula (II):
₍ HO) _3Si- ( _CH2 ) _a- ( _CF2 ) _bCF3 (II)
[In the formula,
a is 1-8, preferably 1-6, more preferably 1-4,
b is 0-20, preferably 0-10, more preferably 0-5, most preferably 2-5]
have

The molar relation of aminoalkyltrihydroxysilane compound to fluoroalkylalkyltrihydroxysilane compound preferably ranges from 1:10 to 10:1.

The first silicone compound derived from aqueous cocondensation is most preferred, the aminoalkyltrihydroxysilane compound being (HO) _3Si- ( _CH2 ) _3- [NH( _CH2 ) ₂ ] ₂ - _NH2. , _the fluoroalkylalkyltrihydroxysilane compound is (HO) _3Si- ( _CH2 ) _2- ( _CF2 ) _5CF3 .

In a further preferred embodiment of the invention, the average molecular weight of the at least one first silicone compound is between 200 and 3,000 g/mol, more preferably between 300 and 2,000, as determined by gel permeation chromatography against polyethylene oxide standards. g/mol, most preferably 400-1,000 g/mol.

Such compounds are available. For example, Dynasylan® SIVO 112 (CAS No. 1222158-90-8) and Dynasylan® F 8815 available from Evonik, WASF-1511 available from Gelest Inc. are combined with at least one It may be used as one of the first silicone compounds. Methods of producing these above compounds are described, for example, in U.S. Pat. No. 8,889,812 (B2), U.S. Pat. incorporated into the specification. This compound has been found to be largely responsible for the low surface energy of the metal substrate.

In a further preferred embodiment of the invention, the at least one second silicone compound is a water-soluble polymer derivable from the aqueous condensation of at least one monomeric unit selected from the group consisting of aminoalkyltrihydroxysilane compounds. An aminoalkyl silicone compound of
Aminoalkyltrihydroxysilane compounds have the following general chemical formula (III):
(HO) _3Si- ( _CH2 ) _x- [NH( _CH2 ) _y ] _z - _NH2 (III),
[In the formula,
x is 1-6, preferably 1-4, more preferably 1-3,
y is 1-6, preferably 1-4, more preferably 1-2,
z is 0-6, preferably 0-4, more preferably 0-2]
have

A second silicone compound derived from aqueous condensation is most preferred and the aminoalkyltrihydroxysilane compound is (HO) ₃ Si--(CH ₂ ) ₃ --NH ₂ .

Such compounds are available. For example, Dynasylan® SIVO 160 (CAS No. 1443627-61-9) and Dynasylan® 1151 (CAS Nos. 58160-99-9, 29159-37-3) available from Evonik, Gelest Inc. 3-Aminopropyl-Silantriol (CAS No. 58160-99-9) available from Momentive Performance Materials Inc., Silquest® A 1106 (CAS No. 58160-99-9) available from Power Chemical SiSiB® PC1106 (CAS No. 58160-99-9) available from Corporation may be used as one of the at least one second silicone compound. Methods of producing these above compounds are described, for example, in EP 0675128 (B1), which is incorporated herein. This compound plays the most important role in forming the polymer network matrix and is therefore effective as an anti-fingerprint coating at low temperatures.

In a further preferred embodiment of the invention the at least one acidifying agent can be any organic or inorganic acid. More preferably, at least one acidifying agent is selected from the group comprising formic acid, oxalic acid, sulfuric acid, methacrylic acid, methanesulfonic acid and acetic acid. Additionally, lactic acid, malic acid, glyceric acid, orthophosphoric acid, tartaric acid, and succinic acid have in principle all proven acceptable for use. However, these latter acids are less preferred than formic acid, oxalic acid, sulfuric acid, methacrylic acid, methanesulfonic acid, and acetic acid because they can lead to deterioration of the optical appearance of the chromium surface. Most preferably acetic acid, formic acid and sulfuric acid are used.

In a further preferred embodiment of the invention, the silicone coating mixture has a preferred pH of 3.5-4.5, more preferably about 3.5 (±0.2). A pH of 4.5 will result in the lowest surface energy of the coated metal substrate and thus provide excellent anti-fingerprint properties to the metal substrate. However, a lower pH promotes better optical finish of the anti-fingerprint coating. During the use of silicone coating mixtures, anti-fingerprint coatings produced outside the preferred pH range of 3.5-4.5 of the mixtures used lead to poor fingerprint test results. Also, if the pH is below 3 or above 4.5, a shortened life of the silicone coating mixture may be observed.

In a further preferred embodiment of the invention, the silicone coating mixture additionally contains at least one siloxane polymer. At least one siloxane polymer functions as a surfactant, hereinafter also referred to as SURF.

In a further preferred embodiment of the invention, the at least one siloxane polymer has the following general formula (IV):

[In the formula,
(x+y) is 1-60, x is 1-30, y is 0-30,
n is 3 to 4;
a is from 0 to 30;
b is from 0 to 30;
R is hydrogen or an alkyl group of 1 to 4 carbon atoms]
is selected from the group consisting of compounds having

Preferably, (x+y) is 1-20, x is 1-10, y is 0-10, and at least one of a and b is not 0, a is 0-15; b is 0-15; (a+b) is 1-30.

In a further preferred embodiment of the invention, the at least one siloxane polymer is a siloxane block copolymer selected from the group consisting of polyether siloxane-siloxane copolymers, wherein (x+y) is from 2 to 60; x is 1 to 30, y is 1 to 30, more preferably (x+y) is 1 to 20, x is 1 to 10, y is 1 to 10 a is 0-15; b is 0-15; and (a+b) is 1-30, such that at least one of a and b is not 0.

The silicone coating mixture may contain one siloxane polymer or multiple siloxane polymers, wherein the polymers may differ from each other in at least one of the parameters a, b, and n.

The siloxane polymer preferably has a molecular weight between 1,000 and 30,000 g/mol, preferably between 5,000 and 15,000 g/mol.

Such compounds are available. For example, TEGO® Wet 280 (CAS No. 68938-54-5), TEGO® Wet 240 (CAS No. 67674-67-3) available from Evonik®, TEGO® ) Wet 250 (CAS No. 27306-78-1), and TEGO® Wet 270 (CAS No. 68938-54-5), dimethylsiloxane-(50-55% ethylene oxide) blocks available from Gelest Inc. Copolymer (CAS No. 68938-54-5), Silwet® L 7600 (CAS No. 68938-54-5) and Silwet® L 77 (CAS No. 27306-5) available from Momentive Performance Materials Inc. 78-1), Metolat® 342 (CAS No. 27306-78-1) available from Munzing Chemie GmbH may be used as one of the at least one siloxane polymer. This compound is a wetting agent and further lowers the surface energy of the coated metal substrate. It facilitates drying of the coated metal substrate.

In a further preferred embodiment of the invention, the silicone coating mixture contains at least one first silicone compound and at least one second silicone compound in a predetermined weight ratio, and all first silicone compounds to all second silicone compounds is preferably 1.0 to 4.0, more preferably 1.0 to 1.0, most preferably 3.0 to 4.0.

In a further preferred embodiment of the invention, the concentration of the at least one first silicone compound in the silicone coating mixture is between 0.05g/l and 5.00g/l, preferably between 0.10g/l and 2.50g/l, most It is preferably 0.30 g/l to 1.50 g/l.

In a further preferred embodiment of the invention the concentration of the at least one second silicone compound in the silicone coating mixture is from 0.05 g/l to 10.00 g/l, preferably from 0.10 g/l to 3.00 g/l, most It is preferably 0.40 g/l to 1.00 g/l.

In a further preferred embodiment of the invention, the concentration of at least one siloxane polymer in the silicone coating mixture is between 0.02g/l and 5.00g/l, preferably between 0.05g/l and 1.00g/l, most preferably 0.10 g/l to 0.30 g/l.

In a further preferred embodiment of the invention, the step of contacting the metal substrate with the silicone coating mixture is performed at a temperature of 10°C to 90°C, more preferably 20°C to 70°C, most preferably about 50°C (±5°C). It is carried out at the temperature of the mixture.

In a further preferred embodiment of the present invention, the exposure time of the metal substrate to the anti-fingerprint coating solution is 0.5 minutes to 60 minutes, more preferably 1 minute to 20 minutes, most preferably 1 minute to 2 minutes.

In a further preferred embodiment of the invention the curing of the coated metal substrate is carried out from 20° C. to It is carried out at a temperature of 100°C, more preferably 40°C to 90°C, most preferably 60°C to 80°C.

To coat a metal substrate with an anti-fingerprint coating, it is brought into contact (treated) with a silicone coating mixture. In a first alternative form of the method, the treated metal substrate is partially dried to remove excess silicon coating mixture on the geometrically unfavorable parts to avoid optical defects, It is then rinsed with water (wet-in-wet rinsing method). The processed and rinsed metal substrate is finally cured. In a second alternative of the method, the treated metal substrate is dried without rinsing (dry withdrawal method) and finally cured. The first alternative is quick and easy to implement. However, in this case some of the adsorbed silicone species are desorbed again in the rinse step. A second alternative overcomes this drawback by achieving a homogeneous distribution of the coating over the entire surface area of the metal substrate. However, several application parameters must be controlled to achieve good optical finish. In a further preferred embodiment of the method, the metal substrate is brought into contact with the silicone coating mixture by immersing it in the coating mixture and allowing it to remain therein for a period of time. Afterwards, either the substrate (coating by substrate withdrawal) or the silicone coating mixture (coating by draining) is removed from the plating bath. More preferably, the application of the coating is performed with a constant (linear) withdrawal or drain rate. Even more preferably, the withdrawal/drainage rate is at least 1 mm/min, more preferably at least 50 mm/min, and most preferably at least 10 mm/min. Further, the withdrawal speed is preferably up to 1000 cm/min, more preferably up to 500 cm/min and most preferably up to 100 cm/min.

In principle, silicone coating mixtures can be used in the plating industry, i.e. in dip tanks as described above or in conveyorized processing where the workpiece to be treated is conveyed from one treatment station to the next. It may be applied using conventional methods in the plant. Since the method of the present invention essentially comprises the steps of treating a metal substrate with a silicone coating mixture, and curing, and optionally further rinsing (contacting the metal substrate with water), the conveyorized plant can A first station for treating the substrate with the silicone coating mixture and an optional second station where the metal substrate is rinsed and optionally a third station where the coated metal substrate is cured. station.

The anti-fingerprint action of an anti-fingerprint coating will have an effect on the surface energy of the coated metal substrate. Surface energy can be measured indirectly by measuring the contact angle of the test liquid brought into contact with the coated metal substrate. Methods for measuring contact angles are well known and described, for example, in Law and Zhao, Surface Wetting-Characterization, Contact Angle and Fundamentals, Springer Verlag (2016) ISBN 9783319252124.

Another approach for determining the effectiveness of anti-fingerprint coatings on metal substrates is the ability of the coated metal substrate to resist fouling of its surface by human exudates and/or human sebum, and/or a contaminated surface. is to evaluate the ability to overcome such fouling when attempting to mechanically clean the . Correspondingly, exemplary test conditions may be set to investigate the effectiveness of anti-fingerprint coatings produced by the method of the present invention. For example, an artificial exudate specimen containing a given composition is applied in a reproducible manner by stamping it with a given force onto a metal substrate surface, for example with a silicone stamp. Mechanical removal of exudate/sebum is likewise wiping off artificial fingerprints with a fabric of a given quality, e.g. a microfiber cloth, with a given force, a given wiping speed and movement, e.g. a circular motion. may be reproducibly tested for a set number of wiping events. The effect and removal efficiency of contamination on the metal substrate surface may finally be determined by determining and comparing the color difference using L/a/b coordinates with a spectrophotometer before and after applying the test. A smaller difference between initial and final color indicates a less sensitive surface to fingerprints. For example, ΔL values greater than 2.5 units and/or Δb values greater than 1.75 units on test points are readily discernible by the human eye as flakes, whereas smaller values are less likely to be detected under normal lighting conditions. Then you won't be able to see much.

The invention will now be described by way of example. These examples do not constitute any limitation on the scope of the invention, which is defined in the appended claims.

FIG. 4 shows contact angle values for samples treated in solutions of single compounds. For comparison, a standard composition (Std: silicone coating mixture according to the invention) is included in the graph (CMPD B/CMPD A/SURF 0.9/0.3/0.2 g/l). FIG. 3 shows fingerprint test results for samples OA-OE measured before and after fingerprint application and cleaning in the form of ΔL/Δa/Δb values. FIG. 4 shows contact angle values for samples treated in silicone coating mixtures containing CMPD B and CMPD A with and without a surfactant (SURF). Fingerprint test results for samples treated in silicone coating mixtures containing CMPD B and CMPD A, with and without a surfactant (SURF), were measured before and after application and cleaning of the fingerprints. It is a figure shown in the form of a /Δb value. FIG. 4 shows contact angle values for samples treated in silicone coating mixtures at different pHs. pH was adjusted by adding acetic acid. FIG. 2 shows fingerprint test results for samples processed in solutions of different pH. FIG. 4 shows contact angle values for samples treated in silicone coating mixtures containing different types of acids for pH adjustment. FIG. 3 shows contact angle values for samples treated in silicone coating mixtures containing CMPD B and CMPD A in different combinations. FIG. 2 shows a diagram representing fingerprint test results for samples treated in silicone coating mixtures containing CMPD B and CMPD A in different combinations. FIG. 4 shows contact angle values for various chrome substrates after treatment with a silicone coating mixture. FIG. 3 shows fingerprint test results for various chrome substrates after treatment with a silicone coating mixture. FIG. 4 shows contact angle values for samples treated in silicone coating mixtures at different temperatures. FIG. 4 shows the contact angle values of samples treated with a silicone coating mixture and continuously cured at 70° C. for various curing durations. FIG. 4 shows fingerprint test results of samples treated with a silicone coating mixture and continuously cured at 70° C. for various curing durations. FIG. 4 shows contact angle values for samples pulled from silicone coating mixtures at various speeds. FIG. 3 shows fingerprint test results for samples pulled from the silicone coating mixture at various speeds. FIG. 2 shows a schematic workflow for fingerprint testing;

substrate:
A 7 cm x 10 cm copper Hull Cell plate was used as the substrate for all measurements. Hull Cell plates were prepared using the following procedure:
i. Satin Ni deposition in a Satilume® Plus (trademark of Atotech Deutschland GmbH) bath (12-15 μm coating thickness);
ii. Deposition of chromium from a trivalent chromium bath Trichrome® Plus (trademark of Atotech Deutschland GmbH) (coating thickness 0.4-0.6 μm).

The Satilume® Plus bath is an electroplating bath for depositing satin nickel coatings. It is based on _NiSO4 , _NiCl2 , and boric acid as main ingredients and organic additives to create a satin appearance. Nickel was deposited under the following conditions: T: 51° C., pH: 4.1, current density: 4 A/dm ² , plating time 15 minutes. The trivalent chromium bath Trichrome® Plus is a chloride-containing electroplating bath for depositing thin chromium coatings. It is based on basic chromium sulphate, boric acid as buffer, carboxylic acid-based complexing agent, and halide-based conductive salt as main components. Chromium is electrodeposited using this bath according to the following plating conditions: T: 35° C., pH: 2.8, current density: 10 A/dm ² , plating time 2 minutes.

Other baths Cr843 (Cr(IV)=Hex Cr), Trichrome® ICE, Trichrome® Smoke 2, Trichrome® Graphite ( All Cr(III) electroplating baths) were likewise used according to the technical data sheet (TDS).

Cr843 is based on _CrO3 and a sulfate and _SiF6 containing catalyst. Chromium is electrodeposited using this bath according to the following plating conditions: T: 40° C., current density: 10 A/dm ² , plating time 3 minutes.

Trichrome® ICE is based on basic chromium sulfate, boric acid as a buffer, a carboxylic acid-based complexing agent, and a sulfate-based conductive salt. Chromium is electrodeposited using this bath according to the following plating conditions: T: 55° C., pH: 3.5, current density: 5 A/dm ² , plating time 10 minutes.

Trichrome® Smoke 2 is based on basic chromium sulfate, boric acid as a buffer, carboxylic acid-based complexing agents, and halide-based conductive salts, and sulfur-containing darkening agents. . Chromium is electrodeposited using this bath according to the following plating conditions: T: 35° C., pH: 2.8, current density: 10 A/dm ² , plating time 5 minutes. Trichrome® Graphite is based on basic chromium sulfate, boric acid as a buffer, carboxylic acid-based complexing agents, and halide-based conductive salts, and sulfur-containing darkening agents. Chromium is electrodeposited using this bath according to the following plating conditions: T: 35° C., pH: 3.2, current density: 10 A/dm ² , plating time 5 minutes.

Silicone coating mixture:
A standard composition of a silicone coating mixture contains the following ingredients:
- 0.9g/l CMPD B
- 0.3g/l CMPD A
- 0.2g/l SURF
- pH 3.5 (adjusted with acetic acid)

CMPD A is a first silicone-based composition derived from an aqueous co-condensation of at least two monomer units selected from the group consisting of aminoalkyltrihydroxysilane compounds and fluoroalkylalkyltrihydroxysilane compounds, ,
Aminoalkyltrihydroxysilane compounds have the following general chemical formula (I):
(HO) _3Si- ( _CH2 ) _x- [NH( _CH2 ) _y ] _z - _NH2 (I),
[Where x is 3, y is 2, and z is 2]
has
The fluoroalkylalkyltrihydroxysilane compound has the following general formula (II):
₍ HO) _3Si- ( _CH2 ) _a- ( _CF2 ) _bCF3 (II)
[wherein a is 2 and b is 5]
have

This silicone compound is used in the form of a 15% by weight solution of this compound in water acidified to pH 4 with formic acid.

CMPD B is a second silicone-based compound and is a water-soluble polymeric aminoalkylsilicone compound derived from the aqueous condensation of at least one monomer unit selected from the group consisting of aminoalkyltrihydroxysilane compounds. There is
Aminoalkyltrihydroxysilane compounds have the following general chemical formula (III):
(HO) _3Si- ( _CH2 ) _x- [NH( _CH2 ) _y ] _z - _NH2 (III)
[where x is 3 and z is 0]
have

This second silicone compound is used in the form of a 10% by weight solution of this compound in water acidified to pH 4 with formic acid.

A siloxane polymer (SURF) is used as a siloxane block copolymer (CAS number 68938-54-5) in the form of a 10% by weight solution of this compound in water.

Unless otherwise specified, the temperature of the silicone coating mixture during the process of treating the metal substrate was fixed at 25°C.

Application method:
Before the sol-gel application, the substrate is cleaned in a cathodic degreaser UniClean® 256 (trademark of Atotech Deutschland GmbH, Germany; alkaline degreaser) for 1 min at 10 ASD (A/dm ² ), followed by Rinse thoroughly with deionized water. A wet substrate was immersed in the silicone coating mixture in a 500 ml glass beaker.

Immersion and withdrawal of the samples were performed with the aid of a dip-coating robot that made it possible to control the immersion and withdrawal speeds (immersion speed: 100 cm/min; immersion time: 1 min; immersion depth: 8 cm (below the liquid level). lower edge of the specimen); withdrawal speed: 5 cm/min (unless otherwise stated)).

After withdrawing the sample from the silicone coating mixture, the dried sample was cured in an oven (ambient air). Standard settings for curing were t _oven = 30 minutes, T _oven = 70°C. These settings were also varied in a specific set of experiments to investigate the effect of curing parameters.

Contact angle measurement:
Contact angle measurements were performed after storing the samples in ambient air for a minimum of 24 hours. Measurements were made by detecting the contact angle of 3 μl of water on a modified substrate (substrate with anti-fingerprint coating). Angle evaluation was performed with the Laplace-Young method (Law and Zhao, Surface Wetting-Characterization, Contact Angle and Fundamentals, Springer Verlag (2016) ISBN 9783319252124).

The contact angle of water deposited on the as-prepared samples or the samples coated with each anti-fingerprint coating was measured. All measurements were performed at 25° C. and 40-60% relative humidity. All contact angle values given below consist of the average of 5 measurements. Contact angles were determined with a constant drop volume of 3.0 μl.

Fingerprint test:
Fingerprint testing was performed on a selected set of samples. The test was performed with an in-house developed procedure (see Appendix: Fingerprint test method). Basically, the color change (Δ color = ΔL/Δa/Δb) of the surface is measured by measuring the color in L/a/b color space using a spectrophotometer (colorimeter), artificial It was detected before and after applying and cleaning a typical fingerprint.

The color impression of the samples was measured with a colorimeter and the colors were described in the L ^* a ^* b ^* color space system (introduced in 1976 by the International Commission on Illumination). The value L ^* indicates lightness and a ^* and b ^* indicate color direction. A positive value of a ^* of 25 indicates red, while a negative value of a ^* means green. A positive value of b ^* indicates a yellow color and a negative value of b ^* means a blue color. If the absolute values of a ^* and b ^* increase, the color saturation also increases. The value of L ^* ranges from 0 to 100, where 0 indicates black and 100 means white.

On fingerprint-sensitive surfaces, the difference between measured L/a/b values before and after testing (ΔL/Δa/Δb) is usually due to the large amount of residual fat deposited by artificial fingerprints. turned out to be large. The easy-to-clean surfaces (obtained with the method according to the invention) had lower ΔColor values.

Details of the test procedure are provided in the appendix "Fingerprint Test Method" at the end of this specification.

Test results and considerations First set of experiments/Experiments OA to OF/Influence of a single component
(Comparative example)
Table 1 shows the set parameters for generating the test samples.

All treatment compositions were prepared as shown in Table 1, with the addition of each component to 1 L and the balance being water. T _sol was the temperature of the silicone coating mixture during the test. t _oven was at curing temperature. Speed [mm/min] was the speed at which the sample was removed from the silicone coating mixture. The parameter "substrate" represents the particular plating bath for depositing the top chromium substrate.

In this experimental setup, the effect of single components on coating quality was investigated. A completely new sample (OA) was immersed in water only. The samples did not contain any other substances. In the following experiments, each component of the silicone coating mixture containing acetic acid was dissolved separately in water and used in the respective respective texts (OB-OE). After bath immersion, all samples were processed according to standard procedures. The modification of the surface by providing an anti-fingerprint coating was tested by contact angle measurements and fingerprint testing. Water contact angle values for the set of samples for experiments OE-OA are shown in Table 2. The results are illustrated in FIG.

According to the results of the contact angle measurements, treatment with acetic acid alone, alternatively with a given concentration of SURF alone, did not result in a significant change in the surface energy of the chromium substrate. On the other hand, CMPD A and CMPD B have a relatively small but noticeable effect on surface energy. The lowest surface energy is obtained after treatment in CMPD B solution, resulting in a contact angle of 55.5°. CMPD A yielded contact angles of only approximately 30°, even though this component contains fluorinated functional groups that are expected to yield low surface energies. Without being bound by theory, it is believed that CMPD A cannot adequately adsorb to surfaces when this component is not supported on other organosilicon compounds that strongly anchor it to chromium surfaces.

Table 3 lists the results from fingerprint measurements.

The results of fingerprint testing are shown in FIG. Basically, the test results are based on contact angle measurements. A more hydrophobic surface will not accept dirt and is easier to clean. As a result, the L/a/b values deviate less from the primary color after applying the artificial fingerprint. The deviation is more pronounced for the L and b values, while the a values are less affected in this test. The untreated sample (OA) shows deviations of -4.0 and 2.3 units in L and b values, respectively. Similar ΔL/Δb values were measured for samples treated in acetic acid (OB) and SURF (OE) solutions. Color shift was smaller after treatment in CMPD A (OC) and CMPD B (OD) solutions. Treatment with a standard composition containing all components resulted in ΔL/Δa/Δb values of −2.4/0.2/1.6, respectively.

Second set of experiments/Experiments 1 and 2/Influence of surfactant (experiments according to the invention)
In this set of experiments, the surfactant SURF was omitted from the coating mixture.
Table 4 shows the set parameters for generating the samples for this set of experiments. Again, as described for the first set of experiments, all treatment compositions were prepared with the addition of each component to 1 L, with the balance being water, as shown in this table. did. Table 5 lists the results from the contact angle measurements for these samples. Table 6 lists the results from this experimental set of fingerprint measurements. Figure 3 shows the contact angle values measured on the relevant samples.

First, the silicone coating mixture resulted in a lower surface energy (larger contact angle) compared to the single component. Contact angle values of 75-90° were achieved by treatment in the silicone coating mixture.

Second, the addition of the surfactant SURF did not significantly change the surface energy. However, its addition results in a significantly more uniform coating, as deduced from the lower standard deviation of the contact angles. The addition of surfactants also positively impacted the optical appearance of the coatings by eliminating flakes, discoloration, and other types of defects that otherwise occurred. Please note.

A fingerprint test (Figure 4) showed that the standard composition containing surfactant had the best score.

Third set of experiments/Experiments 3a-c/Effect of pH of coating mixture
(Experiments according to the present invention)
The pH of the silicone coating mixture makeup was originally 4.3-4.4 before any acid was added. At this pH, amino-functional organosilicon molecules are most stable in water with the highest hydrolysis kinetics. However, it was found that the anti-fingerprint coating produced at this pH was non-uniform, resulting in some optical drawbacks. Therefore, pH adjustments were made to improve homogeneity and optical properties.

Table 7 shows the set parameters, including pH values, for generating the samples of this set of experiments. Again, as described for the first set of experiments, all treatment compositions were prepared with the addition of each component to 1 L, with the balance being water, as shown in this table. did. Table 8 lists the results from the contact angle measurements for these samples. Table 9 lists the results from this experimental set of fingerprint measurements. The pH of the silicone coating mixture was adjusted by adding acetic acid.

There was a tendency for the contact angle value to gradually decrease as the pH decreased (Fig. 5). Fingerprint test results correlated with contact angle measurements (FIG. 6).

Fourth set of experiments/Experiments 4a-e/Effect of acid type for pH adjustment
(Experiments according to the present invention)
In previous experiments (third set of experiments, Examples 3a-d), lowering the pH from 4.4 to lower values improved the uniformity and optical properties of the coating without significantly changing the surface energy of the coating. It has been shown to be found to help improve appearance. Besides acetic acid, other commonly used acids were tested in this set of experiments. Testing was performed by adjusting the bath pH to 3.5 using the given acid.

Table 10 shows the set parameters for generating the samples for this set of experiments. Again, as described for the first set of experiments, all treatment compositions were prepared with the addition of each component to 1 L, with the balance being water, as shown in this table. did. Table 11 lists the results from contact angle measurements for these samples. Table 12 lists the results from this experimental set of fingerprint measurements.

As can be clearly seen from Figure 7, at a given pH, neither acid has a superior effect on the coating surface energy compared to acetic acid. On the other hand, some negative effects on optical properties were observed with some acids, especially when a post-rinse was applied after the substrate was withdrawn from the coating mixture. Previous studies found that siloxane condensation/gelation on the substrate occurred only after the sol film was completely dried. If the substrate was rinsed with water before being completely dried, the siloxane molecules diffused into the rinse water in a hydrolyzed state while the rinsed areas remained uncovered. Basically, these exposed areas locally reduced the anti-fingerprint effect on the substrate without forming visible defects on and around them. However, the use of orthophosphoric acid, glyceric acid, and malic acid softened the white, hazy color of such rinsed areas. Therefore, it was assessed that the use of these acids in silicone coating mixtures should be avoided. Similar behavior was observed with tartaric acid and lactic acid as well.

Acetic acid, formic acid, and sulfuric acid were shown not to cause any discoloration on the surface, even when post-rinsed. Of these acids, acetic acid and formic acid resulted in slightly lower coating surface energies. Acetic acid was preferred due to its easier handling.

Fifth set of experiments/Experiments 5a-f/Influence of component ratios
(Experiments according to the present invention)
As shown above (experimental sets OA-OE), the two main silicone compounds in the coating mixture (CMPD B and CMPD A) do not perform well without the other. The combination of these two compounds has been shown to give much better results than each used without the other. Different mixing ratios of these compounds were tested in this set of experiments.

Table 13 shows the set parameters for generating the samples for this set of experiments. Again, as described for the first set of experiments, all treatment compositions were prepared with the addition of each component to 1 L, with the balance being water, as shown in this table. did. Table 14 lists the results from the contact angle measurements for these samples. Table 15 lists the results from this experimental set of fingerprint measurements.

The remarkable difference in surface energy of coatings resulting from different combinations of CMPD B and CMPD A is clearly visible in FIG. By keeping the CMPD B concentration constant and increasing the CMPD A concentration in the coating mixture (Std: 0.9 g/l CMPD B/silicone coating mixture containing 0.3 g/l CMPD A), the surface energy gradually increased. to Using the standard coating mixture, the average contact angle measured on the coating surface was 89°. Using a combination of 0.9 g/l CMPD B/1.5 g/l CMPD A (which contained 4 times more CMPD A compared to the standard composition) resulted in an average contact angle of 107°. Starting from this point, by further reducing the CMPD B content to approximately half this amount (0.5 g/l CMPD B/1.5 g/l CMPD A), the surface energy of the coating is reduced to a maximum of 114°. further decreased to Interestingly, further reducing the CMPD B content had a negative effect, increasing the surface energy, as observed with 0.2 g/l CMPD B/1.5 g/l CMPD A.

Similar results were obtained using fingerprint testing as shown in FIG. Best results were obtained with 0.5 g/l CMPD B in combination with 1.5 g/l CMPD A.

Experiments 5b and 5e used different total concentrations, but the coating mixtures commonly contained CMPD A at 50% of the total silicone compound amount. Experiments 5b and 5e yielded the same surface energies with the combinations 0.9 g/l CMPD B/1.5 g/l CMPD A and 0.5 g/l CMPD B/0.8 g/l CMPD A.

These results indicate that more CMPD A can be added to the coating mixture to lower the surface energy. However, it was shown that the CMPD B concentration should be maintained above a critical value, ideally above 0.3 g/l. It is conceivable that this would fully support the co-adsorption of CMPD A. It has been found that the surface energy of the coating remains constant regardless of film thickness once a compact coating is formed. Theoretically, film thickness increased with increasing total silicone concentration in the coating mixture.

Sixth set of experiments/Experiments 6a-d/Effect of chromium substrate
(Experiments according to the present invention)
The method of the present invention was tested on different chromium substrates to investigate whether silicone adsorption would be beneficial to a particular type of chromium surface. Substrates were prepared in different electroplating chromium baths, all of which had the same anti-fingerprint coating applied.

Table 16 shows the set parameters for generating the samples for this set of experiments. Again, as described for the first set of experiments, all treatment compositions were prepared with the addition of each component to 1 L, with the balance being water, as shown in this table. did. Table 17 lists the results from the contact angle measurements for these samples. Table 18 lists the results from this experimental set of fingerprint measurements.

According to the contact angle (Fig. 10) and fingerprint test (Fig. 11) results, darker chrome layers such as TC Shadow and TC Graphite are more sensitive than lighter chrome layers such as TC Plus and TC ICE. It does not have much obvious effect of repelling water and dirt. Considering that darker chromium deposits contain more alloying elements, sol-gel film formation can become more difficult to achieve on such complex surfaces. On the other hand, even if the same coating quality should be achieved on light and dark surfaces, a larger color shift would be expected on darker surfaces after surface contamination due to optical effects. be.

Seventh set of experiments / Experiments 7a-g / Effect of coating mixture temperature
(Experiments according to the present invention)
The temperature of the coating mixture proved to be an important parameter indicating not only the kinetic activity of the components, but also its drying rate after withdrawal of the substrate from the silicone coating mixture. In this set of experiments, the temperature of the coating mixture was gradually increased to investigate its effect on coating quality.

Table 19 shows the set parameters for generating the samples for this set of experiments. Again, as described for the first set of experiments, all treatment compositions were prepared with the addition of each component to 1 L, with the balance being water, as shown in this table. did. Table 20 lists the results from the contact angle measurements for these samples.

Delta color values were not measured for these samples.

Looking at the contact angle results in FIG. 12, a strong effect of the temperature of the silicone coating mixture on the quality of the coating was observed. It has been found that the surface energy of anti-fingerprint coatings decreases when the temperature increases, making them more hydrophobic and dirt-repellent. Furthermore, the high bath temperature allows the substrate to be removed from the silicone coating mixture without the formation of optical defects such as puddles, which essentially occur after slow drying of the solution accumulated in geometrically unfavorable areas. It was possible to withdraw faster.

Eighth set of experiments/Experiments 8a-f/Effect of cure duration
(Experiments according to the present invention)
It has been found that the cross-linking of the adsorbed anti-fingerprint coating is accelerated by curing the dry coating at elevated temperatures. For this set of experiments, the curing temperature was fixed at 70°C. This temperature was the maximum allowable temperature for the polymeric ABS support. Experimental sets 8a-f varied the duration of post-curing at 70°C.

Table 21 shows the set parameters for generating the samples for this set of experiments. Again, as described for the first set of experiments, all treatment compositions were prepared with the addition of each component to 1 L, with the balance being water, as shown in this table. did. Table 22 lists the results from contact angle measurements for these samples. Table 23 lists the results from this experimental set of fingerprint measurements.

The positive impact of curing on coating tightness and consequently hydrophobic effect was observed by the contact angle values plotted in FIG. The contact angle was shown to be greater with longer curing duration. Jumping was observed at 45-60 minutes. However, beyond 60 minutes, a slight increase in hydrophobicity was found.

The fingerprint test results (Figure 14) also suggest two regions of cure duration below 60 minutes and above 60 minutes. Above 60 minutes, the artificial fingerprint was shown to be easier to remove and leave less residue behind as estimated from the ΔL/Δa/Δb values.

Ninth set of experiments/Experiments 9a-i/Influence of withdrawal speed
(Experiments according to the present invention)
At the end of the immersion time, the substrate was withdrawn from the coating mixture at a specified speed. The withdrawal speed was shown to have a direct effect on the speed of drying and, consequently, the quality of the anti-fingerprint coating formed. In this set of experiments, the withdrawal speed was varied to investigate its effect on the sol-gel process.

Table 24 shows the set parameters for generating the samples for this experimental set. Again, as described for the first set of experiments, all treatment compositions were prepared with the addition of each component to 1 L, with the balance being water, as shown in this table. did. Table 25 lists the results from the contact angle measurements for these samples. Table 26 lists the results from this experimental set of fingerprint measurements.

Generally, lower withdrawal speeds have been found to be advantageous in aqueous coatings, especially to control the drying process. Interestingly, it was observed that as the withdrawal speed increased, a more hydrophobic and dirt-repellent coating was formed (Figures 15 and 16). This behavior is believed to be due to thick coatings formed at high withdrawal speeds, which was proposed theoretically by Landau and Levich in 1942 and confirmed experimentally.

where h is the thickness of the liquid layer adhering to the drawn substrate [m], U is the drawing speed [m/s], c is a constant (0.944 for Newtonian fluids), η is the liquid viscosity of the liquid [Pa s], γ is the surface tension of the liquid against air [N/m], ρ is the density of the liquid [kg/m ³ ], and g is , is the gravitational acceleration [m/s ² ]].
According to the Landau-Levich equation (equation 1), the film thickness increases with withdrawal rate, which would not be intuitively expected. It is believed that at higher speeds, the breaking of capillary forces causes the volume of silicone solution present per unit area to be greater than before gelation occurred. As a result, the silicone concentration is enhanced at the surface, thus forming a thicker film.

On the other hand, we have observed that a very slow withdrawal speed (10mm/min) gives better results than a slightly higher speed (20mm/min). At first glance, this result could be considered experimental error. However, there are several studies in the literature consistent with our findings that reveal this behavior by the existence of two film formation regimes on the substrate during extraction: (i ) capillary regime and (ii) drainage regime. The drainage regime follows the Landau-Levich equation, which does not consider film formation by evaporation. In the capillary regime evaporation of the solvent (in this case water) occurs at the triple point. The film thickness increases with the evaporation rate, which is higher with respect to the withdrawal speed if the substrate is moved very slowly, but is higher with respect to the withdrawal speed if the substrate is moved faster. lower. Assuming below a certain thickness, film thickness and hydrophobicity are directly correlated to each other. Good agreement is therefore found between the proposed theory and the results of this study.

CONCLUSION The influence of various parameters on the application and quality of the method of the invention has been investigated. The following conclusions are drawn from the validated data.

Coating quality can be tested by measuring the contact angle. Fingerprint test results are usually consistent with contact angle results. However, contact angle measurements are more reproducible and much easier to apply.

Single-component solutions do not exhibit the expected coating quality. Best performance is achieved when CMPD B, CMPD A, and SURF are mixed.

CMPD B is believed to behave as a matrix for anti-fingerprint coatings. By providing a sufficient amount of CMPD B, the other major component CMPD A is better anchored to the chromium surface and better incorporated into the coating network.

CMPD A is believed to be the main hydrophobizing agent in the formulation. Increasing amounts of CMPD A form a more hydrophobic, dirt-repellent coating.

Film thickness appears to be decisive for coating stability and leveling effect, especially on rough surfaces. Therefore, thicker membranes appear to be more advantageous. If desired, CMPD A can be added separately to the coating mixture to improve the repellency of the coating.

The surfactant SURF improves film uniformity and reduces the number of optical defects on the coating.

It is necessary to add some acid to the bath to adjust the bath pH. At the original pH of the coating mixture (without any added acid) more defects were observed on the coating. At pH 3.5, the number of defects was greatly reduced. Adjusting the pH to a more acidic value resulted in better coating quality, but a lower pH value reduced the rate of hydrolysis and increased the rate of condensation of dissolved silicone compounds. , had a negative impact on the stability of the coating mixture.

For adjusting pH, acetic acid was found to be the best compound to use. Alternatively, formic acid and sulfuric acid can also be employed. Other tested acids such as phosphoric acid, malic acid, and glyceric acid work mostly well, but they can cause surface discoloration under certain circumstances.

The method of the present invention performs better on light-colored chromium deposits than on dark-colored chromium deposits. As the deposit contains more alloying elements and becomes darker, it becomes less hydrophobic and less effective at repelling dirt.

Coating quality improves significantly with increasing temperature of the coating mixture. Another great advantage of the high temperature of the coating mixture is that the dip coating dries faster, allowing for faster withdrawal speeds.

The withdrawal speed has a dramatic effect on coating quality. Higher speeds appear to form thicker, more hydrophobic coatings. However, high withdrawal speeds usually create defects at the bottom of the substrate (pools, last drop, etc.).

An applied sol-gel anti-fingerprint coating must be cured to achieve the best performance. Longer curing durations result in denser films. Saturation was found to be reached after 60 minutes.

Contact angle values greater than 115° were not achieved in any of the experiments. This degree of hydrophobicity appears to be the upper limit for coating. Combining two positive effects such as improving both bath temperature and withdrawal speed does not provide any additional benefit.

The coating mixture performs slightly better after heating it. The activation of the coating mixture is maintained for some time even after the coating mixture has cooled again.

Addendum: Fingerprint Test Method To simulate a real fingerprint, a certain amount of artificial skin fat is applied onto the test surface with the help of a silicone stamp. Consequently, the ability to easily clean the surface by removing the applied fingerprints with a microfiber cloth is evaluated.

Sample preparation: The minimum surface area of the sample was 25 ^cm2 . Samples were measured as received unless they were excessively contaminated. Visible dust particles and other soils were gently removed from the surface prior to application of the test. Only dry samples were measured.

Artificial fingerprint application: To evaluate the fingerprint test, the color values of the L/a/b color space (L: lightness, a: green-red, and b: blue-yellow axis) were Measurements were taken with a spectrophotometer on the test points before application (Figure 18: Measurement of initial color). Another color measurement was taken at the end of the test at the same point for comparison (Figure 17: final color measurement). The illumination area for color measurement is fixed within a range of φ10±2 mm using an appropriate aperture. Measurements are performed by pressing the sample firmly towards the spectrophotometer in a vertical position.
All measurement steps were performed at room temperature in ambient environment.

An artificial fingerprint was applied onto the sample surface using a silicone stamp. To prepare the stamps, prior to each measurement, the silicone stamps were cleaned by immersion in isopropanol rather than immersing in isopropanol for a minimum of 10 seconds and then drying.

Artificial sebum (according to BEY, for example commercially available from wfk Testgewebe GmbH) is evenly applied to a felt cloth, which is pressed with a silicone stamp onto the cloth with a force of 4.0N±0.5N for 5 seconds. was transferred to a silicone stamp. A stamp with artificial sebum was pressed onto the test (chrome) surface for 5 seconds by applying a force of 4.0N±0.5N. Finally, the stamp is carefully pulled back, leaving an artificial fingerprint on the surface of the sample (Figure 17: Artificial Fingerprint). A minimum of three different fingerprints were applied onto the test surface following the same procedure.

Sample surface evaluation:
Fingerprint removal ability is assessed by rubbing the stamped area with a microfiber cloth. For manual cleaning procedures, mimic typical cleaning gestures. A cloth was wrapped around the index finger of the preferred hand. Using constant force and velocity, rub the fingerprint in a circular motion. The applied force for rubbing is approximately 5N--the finger force was tested on a laboratory scale targeting a 500g measurement mass during the motion. The speed of rubbing does not significantly affect the test results. Always use an unused microfiber cloth for cleaning. A total of 20 rubbing cycles were applied (Figure 17: Cleaning process with a cloth. 40 circular motion cycles). After 20 cycles, L/a/b values were measured again on the cleaned area. ΔL/Δa/Δb, the difference in color parameters before and after soiling/cleaning, was used to assess ease of cleaning.

Depending on the color difference, the results range from G (good), S (sufficient), or I (poor).

The same evaluation process is applied to all available fingerprints (minimum of 3) on the surface. Finally, average results were obtained to assess the samples globally.

Claims (14)

A method of coating a metal substrate with an anti-fingerprint coating, comprising:
(a) providing a metal substrate;
(b) the following:
(i) at least one first silicone compound selected from the group consisting of mono- or oligo(aminoalkyl)-fluoroalkylsilicones;
(ii) at least one second silicone compound selected from the group consisting of aminoalkylsilicones;
(iii) at least one acidifying agent, and
(iv) providing a silicone coating mixture containing water;
(c) treating the metal substrate with the silicone coating mixture by contacting the metal substrate with the silicone coating mixture;
(d) curing the treated metal substrate at a predetermined temperature, comprising:
The method, wherein the silicone coating mixture has a pH of 3.5-4.5 . The metal substrate is a chromium substrate, the chromium substrate is produced by depositing a chromium metal layer on a work piece, depositing the chromium metal layer comprises a work piece and at least one Cr. (III) providing an electroplating solution containing plating species, and using said electroplating solution containing at least one Cr(III) plating species to deposit said chromium metal layer onto said work piece; 2. The method of claim 1, comprising electroplating. 3. A method according to claim 2, characterized in that the electroplating solution containing at least one Cr(III) plating species is free of chloride species. 4. Any one of claims 1 to 3, characterized in that said at least one first silicone compound is a water-soluble statistical copolymer of mono- or oligo(aminoalkyl)silicones and (fluoroalkyl)alkylsilicones. The method described in . said at least one first silicone compound is derived from an aqueous co-condensation of at least two monomer units selected from the group consisting of mono- or oligoaminoalkyltrihydroxysilane compounds and fluoroalkylalkyltrihydroxysilane compounds;
The mono- or oligo-aminoalkyltrihydroxysilane compound has the following general chemical formula (I):
(HO) _3Si- ( _CH2 ) _x- [NH( _CH2 ) _y ] _z - _NH2 (I)
[In the formula,
x is 1-8, preferably 1-6, more preferably 1-4,
y is 1-6, preferably 1-4, more preferably 1-2,
z is 0-8, preferably 0-6, more preferably 0-4]
has
The fluoroalkylalkyltrihydroxysilane compound has the following general formula (II):
₍ HO) _3Si- ( _CH2 ) _a- ( _CF2 ) _bCF3 (II)
[In the formula,
a is 1-8, preferably 1-6, more preferably 1-4,
b is 0-20, preferably 0-10, more preferably 0-5]
5. A method according to any one of claims 1 to 4, characterized in that it comprises at least one second silicone compound is a water-soluble polymeric aminoalkylsilicone compound derived from aqueous condensation of at least one monomeric unit selected from the group consisting of aminoalkyltrihydroxysilane compounds;
The aminoalkyltrihydroxysilane compound has the following general chemical formula (III):
(HO) _3Si- ( _CH2 ) _x- [NH( _CH2 ) _y ] _z - _NH2 (III)
[In the formula,
x is 1-6, preferably 1-4, more preferably 1-3,
y is 1-6, preferably 1-4, more preferably 1-2,
z is 0-6, preferably 0-4, more preferably 0-2]
6. A method according to any one of claims 1 to 5, characterized in that it comprises 7. Process according to any one of claims 1 to 6, characterized in that said acidifying agent is selected from the group comprising formic acid, sulfuric acid and acetic acid. 8. Method according to any one of the preceding claims, characterized in that the silicone coating mixture additionally contains at least one siloxane polymer. 9. The method of claim 8 , wherein said at least one siloxane polymer is selected from the group consisting of polyethersiloxane-siloxane copolymers. The at least one siloxane polymer has the following general formula (IV):
[In the formula,
(x+y) is 1-60, x is 1-30, y is 0-30,
n is 3 to 4;
a is from 0 to 30;
b is about 0 to 30;
R is hydrogen or an alkyl group of 1 to 4 carbon atoms]
10. A method according to claim 8 or 9 , characterized in that it is selected from the group consisting of compounds having The silicone coating mixture contains the at least one first silicone compound and the at least one second silicone compound in a predetermined mass ratio, wherein all first silicone compounds, all second 11. A process according to any one of claims 1 to 10, characterized in that the weight ratio of to the silicone compound is between 1.0 and 4.0 . The concentration of said at least one first silicone compound in said silicone coating mixture is between 0.05 g/l and 5.00 g/l, and the concentration of said at least one second silicone compound in said silicone coating mixture. is between 0.05 g /l and 5.00 g/l. A method according to any one of claims 1 to 12 , characterized in that the curing of said coated metal substrate is carried out at a temperature between 10°C and 90°C. Use of a silicone coating mixture for coating a metal substrate with an anti-fingerprint coating, said silicone coating mixture comprising:
(i) at least one first silicone compound selected from the group consisting of mono- or oligo(aminoalkyl)-fluoroalkylsilicones;
(ii) at least one second silicone compound selected from the group consisting of aminoalkylsilicones;
(iii) at least one acidifying agent, and
(iv) contains water;
Use having a pH of 3.5 to 4.5 .

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