Cr(iii)-based improved passivation for zinc-aluminum coated steels

Abstract

The present application relates to an aqueous passivation composition for treating zinc or zinc alloy coatings, the composition having a pH of 6.5 to 9 and comprising, based on the weight of the composition: 5 to 60 wt.-% of a) at least one base polymer selected from the group consisting of acrylic polymers and non-ionic polyurethane polymers; 0.1 to 2.5 wt.-% of b) trivalent Cr(III) ions, calculated as Cr; c) ascorbic acid; 0.1 to 2.5 wt.-% of d) at least one aluminum compound selected from the group consisting of aluminum hydroxide; aluminum metahydroxide; aluminum trichloride; aluminum alcoholate; aluminum glycolate; tris(beta-keto)aluminum; tris(beta-ketoester)aluminum; aluminum soaps; and aluminum carboxylates; and up to 10 wt.-% of e) at least one finely divided wax, wherein the composition is characterized in that it is essentially free of nitrate anions and essentially free of hexavalent chromium (Cr(VI)).

Description

Technical Field

[0001] This invention relates to an aqueous passivation composition comprising ascorbic acid. More specifically, this invention relates to an aqueous passivation composition characterized by comprising ascorbic acid, a film-forming polymer, and a trivalent chromium compound. Background Technology

[0002] The application of metals (such as zinc) to base metal substrates for decorative finishing and / or corrosion protection is a well-established practice in the art. Naturally, quality control standards for coated and plated substrates can be stringent, and consumers will therefore closely examine the finish and appearance of the treated surfaces. Given the protective coatings based on zinc and zinc alloys, a surface condition known as "wet storage stain" can be unsightly and may impair further plating or coating on the substrate. This is also referred to as "white rust" or "black rust" (for...). The white film (stain) on the coating can be attributed to the formation of zinc oxide and zinc hydroxide, and is produced when the deposited zinc or zinc alloy is exposed to atmospheric oxygen and moisture.

[0003] Techniques for removing a white film from freshly galvanized substrates are known, and particularly include: the application of double coatings or powder coatings; the application of waxes and oils, especially for base metal substrates in the form of sheets, beams, and wires; and passivation treatments. This invention relates to treating zinc coatings or platings with a passivation composition that, in addition to providing corrosion resistance, also provides coatings in various colors (including blue, yellow, olive, or black) and a substrate effective for subsequent dyeing and coating operations.

[0004] Existing passivation compositions are primarily based on acidic aqueous solutions of chromates. When the acidic chromate passivation solution is applied to a zinc-coated or electroplated substrate, surface zinc atoms are oxidized to effectively form an interfacial layer of hydrated basic chromium chromate (Cr₂O₃CrO₃·xH₂O) and the hydrated oxides of both chromium and zinc. However, because the acid is consumed in the oxidation reaction, the pH at the surface-liquid interface increases: this reduces the binding force of chromium in the aqueous phase and leads to the precipitation of a gel-like film containing chromium hydroxide and complexes of chromium ions with zinc. This film continues to accumulate until acid protons can no longer contact the zinc metal, thus stopping the surface redox reaction: the resulting gel-like film can then be hardened.

[0005] Traditionally, hexavalent chromium (Cr) is used in passivation compositions. 6+Alternatively, Cr(VI) can be used to provide chromium present in the passivation film or conversion coating. However, the toxicological properties of chromium(VI) are problematic, especially since EC Directive 2000 / 53 / EC strongly restricts the use of chromium(VI)-containing passivation treatments. Therefore, there has been some interest in the art in treating zinc surfaces with passivation compositions in which chromium is at least partially in a trivalent state: in this regard, the following archival disclosures may be referenced: U.S. Patent No. 2,559,878; U.S. Patent No. 3,932,198; U.S. Patent No. 3,647,569; U.S. Patent No. 3,501,352; U.S. Patent No. 4,359,345; U.S. Patent No. 4,359,346; U.S. Patent No. 4,359,347; U.S. Patent No. 4,359,348; U.S. Patent No. 4,349,392; U.S. Patent No. 4,367,099; German Patent No. DE 2526832; and British Patent No. GB ​​1,461,244. The Cr(III) used in these cited references is non-toxic, and the removal of associated Cr(III) waste is not as expensive as that of hexavalent chromium.

[0006] The chromium (III) passivation compositions described in the aforementioned patent almost invariably use peroxide-type oxidants, such as H₂O₂, as an essential bath component. These oxidants, and similar oxidants (e.g., persulfates), can promote the conversion of some trivalent chromium to hexavalent chromium during the formation of the conversion coating. Another related problem is the high consumption rate and loss of peroxide or persulfate oxidants, which necessitates their frequent replenishment and careful control of the composition's pH to avoid accompanying pH elevation. The consumption of peroxide (and persulfate) compounds is partly due to the presence of various activating metal ions (present in solution as additives or contaminants) that tend to catalyze the decomposition of the oxidants. The frequent replenishment of peroxide and persulfate compounds represents the economic and effort costs of carrying out this passivation or conversion process.

[0007] Of course, chromate(III)-based passivation compositions are known in the art that do not use peroxides or persulfate-type oxidants. For example, U.S. Patent No. 4,578,122A (Crotty) describes a peroxide-free acidic aqueous solution used in a method for treating a receiving metal surface to impart a chromium passivation film thereon. The described aqueous solution contains: chromium ions, substantially all of which are in the trivalent state; hydrogen ions to provide a pH of about 1.2 to about 2.5; at least one additional metal ion selected from iron, cobalt, nickel, molybdenum, manganese, lanthanum, cerium, and lanthanides, said ions being present in an amount that effectively activates the formation of the chromate passivation film; and nitrate ions as an essential oxidant, said nitrate ions being present in an amount that provides a molar ratio of at least 4:1 of nitrate ions to the sum of chromium ions and activated metal ions. The amount of nitrate ions should further be sufficient to activate hydrated trivalent chromium to form a chromate film on the substrate. The acidic aqueous solution may optionally further contain controlled amounts of: sulfate ions; halide ions; organic carboxylic acids; bath-soluble and compatible silicate compounds; and at least one wetting agent.

[0008] The presence of nitrates in the compositions of U.S. Patent No. 4,578,122 is considered highly undesirable. These salts are converted to NO during spontaneous decomposition or during the intended oxidative activity. x And the NO x It diffuses into the atmosphere as a pollutant.

[0009] Furthermore, low-pH passivation compositions may also be detrimental in certain applications. In particular, low pH is thought to destabilize any aqueous polymeric lactide included in the composition as a film-forming component through particle aggregation. Additionally, low-pH passivation compositions can promote significant etching of the substrate surface and can provide an unstable passivation bath.

[0010] Therefore, there remains a need in the art to develop passivation compositions containing film-forming components with low acidity, which are particularly suitable for steel surfaces coated with zinc or zinc alloys, wherein the levels of compounds such as chromates (VI), peroxides, persulfates and nitrates can be minimized, but wherein the reduction of these compounds in such compositions cannot be compensated for by a decrease in the performance of the composition. Summary of the Invention

[0011] According to a first aspect of the invention, an aqueous passivation composition for treating zinc or zinc alloy coatings is provided, the composition having a pH of 6.5 to 9, and comprising, based on the weight of the composition:

[0012] 5 to 60% by weight of a) at least one base polymer selected from acrylic polymers and nonionic polyurethane polymers;

[0013] b) Trivalent Cr(III) ions, calculated as Cr, from 0.1 to 2.5% by weight;

[0014] c) Ascorbic acid;

[0015] 0.1 to 2.5% by weight of d) at least one aluminum compound selected from the group consisting of: aluminum hydroxide, aluminum metahydroxide, aluminum trichloride, aluminum alcohol, aluminum glycolate, tri(β-keto)aluminum, tri(β-keto ester)aluminum, aluminum soap, and aluminum carboxylate; and

[0016] e) at least one finely crushed wax, up to 10% by weight

[0017] The composition is characterized in that it is substantially free of nitrate anions and substantially free of hexavalent chromium (Cr(VI)). Preferably, the composition is further characterized in that it is substantially free of peroxides and persulfates.

[0018] For example, an aqueous passivation composition for treating zinc or zinc alloy coatings is provided, the composition having a pH of 7.0 to 8.5, preferably 7.0 to 8.0, and comprising, based on the weight of the composition:

[0019] 15 to 40% by weight, preferably 20 to 35% by weight, of at least one base polymer selected from acrylic polymers and nonionic polyurethane polymers as described in a);

[0020] 0.1 to 2.0 wt%, preferably 0.1 to 1.5 wt%, of the Cr(III) ions described in b), calculated as Cr;

[0021] c) Ascorbic acid, 0.1 to 1.0% by weight, preferably 0.1 to 0.5% by weight;

[0022] 0.1 to 2.0% by weight, preferably 0.2 to 1.0% by weight of at least one aluminum compound selected from the group consisting of: aluminum hydroxide, aluminum metahydroxide, aluminum trichloride, aluminum alcohol, aluminum glycolate, tri(β-keto)aluminum, tri(β-keto ester)aluminum, aluminum soap and aluminum carboxylate;

[0023] 1 to 8% by weight, preferably 1 to 5% by weight of the wax described in e); and

[0024] 10 to 50% by weight, preferably 10 to 40% by weight, of water.

[0025] The composition is characterized in that it is substantially free of nitrate anions and substantially free of hexavalent chromium (Cr(VI)).

[0026] The trivalent chromium ions mentioned above can be provided directly in the composition by salts selected from the following: chromium sulfate (Cr2(SO4)3), chromium alum (KCr(SO4)2), chromium chloride (CrCl3) and chromium bromide (CrBr3), and mixtures thereof.

[0027] Alternatively or additionally, trivalent chromium ions are obtained by reducing chromium (VI) provided as one or more hexavalent chromium compounds: the composition then contains at least one reducing agent in an amount sufficient to ensure complete reduction of hexavalent chromium to trivalent chromium. In some embodiments, the source of hexavalent chromium ions (Cr(VI)) may be selected from: chromium trioxide (CrO3), lithium chromate (Li2CrO4), lithium dichromate (Li2Cr2O7), sodium chromate (Na2CrO4), sodium dichromate (Na2Cr2O7), potassium chromate (K2CrO4), potassium dichromate (K2Cr2O7), ammonium chromate ((NH4)2CrO4), ammonium dichromate ((NH4)2Cr2O7), magnesium chromate (MgCrO4), magnesium dichromate (MgCr2O7), calcium chromate (CaCrO4), calcium dichromate (CaCr2O7), zinc chromate (ZnCrO4), zinc dichromate (ZnCr2O7), and mixtures thereof. In this embodiment, ascorbic acid should be included in the composition to allow complete conversion to trivalent Cr(III), and should preferably be included in an amount such that the molar ratio of ascorbic acid to chromium is 1:3 to 4:5.

[0028] Preferably, d) the at least one aluminum compound is selected from aluminum tricarboxylate (Al(OOCR)3), aluminum monohydroxy dicarboxylate (RCOO)2Al(OH) and aluminum dihydroxy monocarboxylate (RCOOAl(OH)2), wherein R is a C1-C8 alkyl group.

[0029] In one important embodiment, the passivation composition as defined above and in the appended claims can be obtained by mixing a portion of hexavalent chromium dissolved in water as component b) with a molar excess of ascorbic acid according to component c), preferably wherein the molar ratio of ascorbic acid to chromium is in the range of 1:3 to 4:5; and then adding components a), d) and e) to the mixture.

[0030] According to a second aspect of the invention, a method is provided to impart a chromate passivation film to a substrate on at least one surface of which a zinc or zinc alloy coating has been applied, the method comprising contacting the at least one coated surface of the substrate with an aqueous composition as defined above and in the appended claims for a period of time sufficient to form a passivation film thereon at a temperature of 20°C to 90°C.

[0031] According to a third aspect of the invention, a passivated substrate is provided, which is obtained by the methods defined in the foregoing and appended claims. The passivated substrate has been shown to provide effective corrosion resistance.

[0032] definition

[0033] As used in this article, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly indicates otherwise.

[0034] As used herein, the terms “comprising,” “comprises,” and “comprised of” are synonymous with “including,” “includes,” “containing,” or “contains,” and are inclusive or open-ended, not excluding additional non-referenced members, elements, or method steps. The phrase “consisting of,” if used, is closed and excludes all additional elements. Furthermore, the phrase “substantially constitutes” excludes additional material elements but allows the inclusion of non-material elements that do not substantially alter the nature of the invention.

[0035] When quantities, concentrations, dimensions, and other parameters are expressed in the form of ranges, preferred ranges, upper limits, lower limits, or preferred upper and lower limits, it should be understood that, regardless of whether the obtained range is explicitly mentioned in the context, any range that can be obtained by combining any upper or preferred value with any lower or preferred value is also specifically disclosed.

[0036] The terms “better,” “preferred,” “especially,” “particularly,” and “ideally” are generally used herein to refer to embodiments of the present disclosure that may provide particular benefits in certain circumstances. However, the enumeration of one or more better, preferred, particularly, or ideal embodiments does not imply that other embodiments are not useful, and is not intended to exclude those other embodiments from the scope of the present disclosure.

[0037] As used throughout this application, the word “may” is used in a permissive sense, meaning that there is a potential for…, rather than in a mandatory sense.

[0038] As used in this article, the room temperature was 23℃±2℃.

[0039] As used herein, number-average molecular weight (Mn) and weight-average molecular weight (Mw) were determined by gel permeation chromatography (GPC) with tetrahydrofuran (THF) as the eluent, according to DIN 55672-1:2007-08. The term polydispersity (PD) was derived from Mw and Mn and calculated as (Mw / Mn).

[0040] If specified, the hydroxyl value is analyzed according to the standard test method ASTM D4274-11.

[0041] The viscosity of the composition can be measured using a Brookfield viscometer (model RVT) under standard conditions of 20°C and 50% relative humidity (RH). The viscometer is calibrated using silicone oil of known viscosity (which varies between 5,000 cps and 50,000 cps). A set of RV rotors connected to the viscometer is used for calibration. Measurements of the passivated composition are performed by using a No. 6 rotor at 20 rpm for 1 minute until the viscometer is balanced. The viscosity corresponding to the balanced reading is then calculated using the calibration.

[0042] As used herein, the glass transition temperature (Tg) is determined according to DIN 53 765 by differential scanning calorimetry using a heating rate of 20 K / min and a midpoint measurement.

[0043] As used in this article, “d” 50 "Particle size" refers to a particle size distribution such that at least 50% by weight of the particles have a particle diameter smaller than a specified value. Unless otherwise stated, particle size is determined by laser diffraction.

[0044] As defined herein, the terms “conversion coating” or “conversion treatment” refer to a surface treatment of a substrate that chemically transforms the surface material into a different material.

[0045] The term "passivation" refers to a surface treatment of a substrate that forms a barrier layer against corrosive conditions on the surface, but without forming a cohesive film with chemical bonds between the surface and the passivation layer. As used herein, the term "passivation composition" refers to a composition that actually contacts a zinc-coated or zinc alloy-coated substrate. As is known in the art, such contact occurs in a so-called "bath," the shape, size, and arrangement of which allow at least a portion of the substrate to be immersed. Furthermore, the size of the passivation bath should allow the composition to move around and throughout the loaded substrate, movement which can be further enhanced by recirculation and / or ultrasound. The pH of the composition in the bath, the temperature of the bath, and the contact time with the substrate are variables that determine the outcome and should be monitored manually or automatically whenever possible.

[0046] Unless otherwise stated, when molar ratios are given herein with respect to chromium, this refers to the total chromium content in the composition, regardless of the oxidation state of the metal.

[0047] As used herein, the term "alloy" refers to a substance composed of two or more metals or of metals and nonmetals, which are typically bonded together by melting them together and dissolving in each other during melting. Thus, the term "zinc alloy" indicates an alloy in which zinc metal is a constituent component, and on a metal basis, zinc typically constitutes at least 40% by weight, more typically at least 50% by weight, or at least 60% by weight of the alloy. Metals that can be alloyed with zinc include, but are not limited to, aluminum, tin, nickel, titanium, and cobalt. In this document, for zinc / aluminum alloys, it is preferred that zinc constitutes at least 40% by weight of the alloy on a metal basis, and conversely, that aluminum constitutes at most 60% by weight of the alloy on a metal basis.

[0048] As used in this article, “mineral acid” refers to an acid derived from one or more inorganic compounds. Mineral acids are not organic, and all mineral acids release hydrogen ions when dissolved in water.

[0049] As used herein, “phosphoric acid” refers to orthophosphoric acid having the formula H3PO4, which is typically obtained as an aqueous solution of H3PO4 with a concentration of up to 75% by weight. As used herein, “phosphonic acid” refers to an oxoacid of phosphorus having the formula H3PO3, which consists of a single pentavalent phosphorus covalently bonded to a single hydrogen atom and two hydroxyl groups via a single bond and covalently bonded to oxygen via a double bond.

[0050] As used herein, the term "α-hydroxycarboxylic acid" refers to a carboxylic acid having at least one hydroxyl functional group, wherein the hydroxyl functional group occupies the α-position (the carbon adjacent to the carboxylic acid functional group) of the acid. The presence of hydroxyl groups occupying positions in the molecule other than the α-position on the acid is not excluded. The α-hydroxycarboxylic acid is included in the compositions of the present invention as a free acid.

[0051] As used herein, the term "monomer" refers to a substance that can undergo polymerization to contribute structural units to the chemical structure of a polymer. As used herein, the term "monofunctional" refers to a substance having one polymerizable moiety. As used herein, the term "polyfunctional" refers to a substance having more than one polymerizable moiety.

[0052] As used herein, the term "olefinic unsaturated monomer" refers to any monomer containing a terminal double bond that can be polymerized under normal conditions of free radical addition polymerization.

[0053] As used herein, the term "active hydrogen compound" refers to a compound comprising at least one hydrogen atom that is readily dissociable in an aqueous environment. Preferably, the hydrogen atom is attached to a nitrogen atom, an oxygen atom, a phosphorus atom, or a sulfur atom.

[0054] As used in this article, "nonionic polyurethane" refers to polyurethane that does not contain hydrophilic ionizable groups.

[0055] As used herein, “(meth)acryloyl” is an abbreviation for “acryloyl” and / or “methacryloyl”. Therefore, the term “(meth)acrylate” refers to both acrylates and methacrylates.

[0056] "Hydrocarbon group" is used herein in its common sense as is known to those skilled in the art.

[0057] As used in this article, "C1-C" n An alkyl group is a monovalent group containing 1 to n carbon atoms; it is a group of alkanes and includes both straight-chain and branched organic groups. Accordingly, "C1-C..." 30 An "alkyl" group refers to a monovalent group containing 1 to 30 carbon atoms, which is an alkane group and includes both straight-chain and branched organic groups. Examples of alkyl groups include, but are not limited to: methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, and 2-ethylhexyl. In this invention, such alkyl groups may be unsubstituted or may be substituted with one or more halogens. Where applicable, preferences for given substituents will be noted in the specification. Typically, conditions "C1-C2" are stated... 30 In the case of "alkyl", it should be noted that alkyl groups containing 1 to 18 carbon atoms (C1-C4) are preferred. 18 Alkyl groups, such as alkyl groups containing 1 to 12 carbon atoms (C1-C4). 12 Alkyl groups or alkyl groups containing 1 to 6 carbon atoms (C1-C6 alkyl groups).

[0058] As used in this article, the term "C1-C" 18 "Hydroxyalkyl" refers to a HO-(alkyl) group having 1 to 18 carbon atoms, wherein the substituent is connected by an oxygen atom and the alkyl group is as defined above.

[0059] "Alkoxy" refers to a monovalent group represented by –OA, where A is an alkyl group; non-limiting examples are methoxy, ethoxy, and isopropoxy. As used herein, the term "C1-C" is used in conjunction with other related terms. 18 "Alkoxyalkyl" refers to an alkyl group having an alkoxy substituent as defined above, wherein the (alkyl–O–alkyl) portion contains a total of 1 to 18 carbon atoms: such groups include methoxymethyl (–CH2OCH3), 2–methoxyethyl (–CH2CH2OCH3), and 2–ethoxyethyl.

[0060] As used herein, the term “C2-C4 alkylene” is defined as a saturated divalent hydrocarbon group having 2 to 4 carbon atoms.

[0061] The term "C3–C" 30"Cycloalkyl" should be understood to mean a saturated, monocyclic, bicyclic, or tricyclic hydrocarbon group having 3 to 30 carbon atoms. In this invention, such cycloalkyl groups may be unsubstituted or may be substituted with one or more halogens. Generally, it should be noted that cycloalkyl groups containing 3 to 18 carbon atoms (C3-C4) are preferred. 18 Cycloalkyl groups. Examples of cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, adamantane, and norcamphene.

[0062] As used herein, "C6-C" is used alone or as part of a larger portion (as in "araneyl") 18 The term "aryl" refers to monocyclic, bicyclic, and tricyclic systems, wherein the monocyclic system is aromatic, or at least one ring in the bicyclic or tricyclic system is aromatic. Bicyclic and tricyclic systems comprise benzofused 2- to 3-membered carbon rings. In this invention, such aryl groups may be unsubstituted or may be substituted with one or more halogens. Exemplary aryl groups include: phenyl; (C1-C4)alkylphenyl, such as tolyl and ethylphenyl; indenyl; naphthyl, tetrahydronaphthyl, tetrahydroindenyl; tetrahydroanthrayl; and anthracel. Note may be given to the preference for phenyl groups.

[0063] As used in this article, "C2-C" 20 "Alkenyl" refers to a hydrocarbon group having 2 to 20 carbon atoms and at least one alkene-bonded unsaturated unit. The alkenyl group can be straight-chain, branched, or cyclic, and can optionally be substituted with one or more halogens. As will be understood by those skilled in the art, the term "alkenyl" also includes groups having "cis" and "trans" configurations, or "E" and "Z" configurations. However, it should generally be noted that groups containing 2 to 10 carbon atoms... 2-10 ) or 2 to 6 (C 2-6 The preference for unsubstituted alkenyl groups on the carbon atom. Examples of the C2-C6 alkenyl groups include, but are not limited to: –CH=CH2; –CH=CHCH3; –CH2CH=CH2; –C(=CH2)(CH3); –CH=CHCH2CH3; –CH2CH=CHCH3; –CH2CH2CH=CH2; –CH=C(CH3)2; –CH2C(=CH2)(CH3); –C(=CH2)CH2CH3; –C(CH3)=CHCH3;

[0064] –C(CH3)CH=CH2; –CH=CHCH2CH2CH3; –CH2CH=CHCH2CH3;

[0065] –CH2CH2CH=CHCH3; –CH2CH2CH2CH=CH2; –C(=CH2)CH2CH2CH3;

[0066] –C(CH3)=CHCH2CH3; –CH(CH3)CH=CHCH; –CH(CH3)CH2CH=CH2;

[0067] –CH2CH=C(CH3)2; 1-cyclopent-1-alkenyl; 1-cyclopent-2-alkenyl; 1-cyclopent-3-alkenyl; 1-cyclohexyl-1-alkenyl; 1-cyclohexyl-2-alkenyl; and 1-cyclohexyl-3-alkenyl.

[0068] As used herein, “alkylaryl” means an alkyl-substituted aryl group, and “substituted alkylaryl” means an alkylaryl group further comprising one or more substituents (e.g., halogen, nitro, cyano, amide, amino, sulfonyl, sulfinyl, sulfanyl, sulfoxy, urea, thiourea, aminesulfonyl, sulfonamide, and hydroxyl). Furthermore, as used herein, “aralkyl” means an alkyl group substituted with an aryl group as defined above.

[0069] As used herein, the term "hetero" refers to a group or part containing one or more heteroatoms such as N, O, Si, and S. Thus, for example, "heterocyclic" refers to a cyclic group having, for example, N, O, Si, or S as part of its ring structure. The moiety "heteroalkyl," "heterocycloalkyl," and "heteroaryl" are alkyl, cycloalkyl, and aryl groups as defined above, respectively, containing N, O, Si, or S as part of their structure.

[0070] The compositions of this invention are defined herein as "substantially free" of certain compounds, elements, ions, or other similar components. The term "substantially free" is intended to mean that the compound, element, ion, or other similar component is not intentionally added to the composition and is present at most in trace amounts, which have no (adverse) effect on the desired properties of the coating. An exemplary trace amount is less than 1000 ppm by weight of the composition. The term "substantially free" covers embodiments in which the specified compounds, elements, ions, or other similar components are completely absent from the composition or are not present in any amount measurable by techniques commonly used in the art. Detailed Implementation

[0071] A: Basic polymer

[0072] The compositions of the present invention comprise 5 to 60% by weight of a) at least one base polymer selected from acrylic polymers and nonionic polyurethane polymers. Preferably, component a) constitutes 15 to 40% by weight of the composition, for example, 20 to 35% by weight.

[0073] (A1): Acrylic emulsion polymer

[0074] In one embodiment, one or more acrylic polymers may be included as the base polymer of the composition. Preferably, the included acrylic polymer is characterized by at least one of the following: a glass transition temperature (Tg) of 30°C to 60°C; and a weight-average molecular weight of 50,000 to 500,000 Daltons.

[0075] There is no particular intention to limit the composition of the monomers from which the acrylic polymers are derived. However, it is preferred that, based on the total weight of the monomers, at least 70% by weight, preferably at least 80% by weight, of the monomers from which the polymers are derived are (meth)acrylate monomers. In particular, the (meth)acrylate monomers can be defined according to definitions a1) to a3) given below.

[0076] a1) Aliphatic and alicyclic (meth)acrylate monomers

[0077] In one embodiment, the polymer may comprise a1) at least one (meth)acrylate monomer represented by formula I:

[0078] H2C = CGCO2R 1 (I)

[0079] in:

[0080] G is hydrogen, halogen, or C1-C4 alkyl; and

[0081] R 1 Selected from: C1-C 30 Alkyl; C2-C 30 Heteroalkyl; C1-C 18 Hydroxyalkyl; C3-C 30 Cycloalkyl; C2-C8 heterocycloalkyl; C2-C 20 alkenyl; and C2-C 12 Alkyne group.

[0082] For example, R 1 Can be selected from C1-C 18 Alkyl, C2-C 18 Heteroalkyl, C1-C 18 Hydroxyalkyl, C3-C 18 Cycloalkyl, C2-C8 heterocycloalkyl, C2-C8 alkenyl, and C2-C8 alkynyl. Ideally, the monomer a1) is characterized by R 1 Selected from C1-C 12 Alkyl, C1-C6 hydroxyalkyl and C3-C 12 Cycloalkyl.

[0083] Examples of (meth)acrylate monomers according to formula (I) include, but are not limited to: methyl (meth)acrylate; ethyl (meth)acrylate; butyl (meth)acrylate; hexyl (meth)acrylate; 2-ethylhexyl (meth)acrylate; dodecyl (meth)acrylate; lauryl (meth)acrylate; cyclohexyl (meth)acrylate; isobornyl (meth)acrylate; 2-hydroxyethyl (meth)acrylate (HEMA); 2-hydroxypropyl (meth)acrylate; ethylene glycol monomethyl ether (meth)acrylate; ethylene glycol monoethyl ether (meth)acrylate; ethylene glycol monododecyl ether (meth)acrylate; diethylene glycol monomethyl ether (meth)acrylate; trifluoroethyl (meth)acrylate; and perfluorooctyl (meth)acrylate.

[0084] a2) Aromatic (meth)acrylate monomers

[0085] In another embodiment, which is not mutually exclusive with the embodiments given above, the polymer may comprise a2) at least one (meth)acrylate monomer represented by Formula II:

[0086] H2C=CQCO2R 2 (II)

[0087] in:

[0088] Q can be hydrogen, halogen, or C1-C4 alkyl; and

[0089] R 2 Can be selected from C6-C 18 Aryl, C1-C9 heteroaryl, C7-C 18 Alkyl and C7-C 18 Aryl group.

[0090] According to the exemplary (meth)acrylate monomer a2) of formula (II), it can be used alone or in combination, including but not limited to: benzyl (meth)acrylate; phenoxyethyl (meth)acrylate; phenoxydiethylene (meth)acrylate; phenoxypropyl (meth)acrylate; and phenoxydipropylene glycol (meth)acrylate.

[0091] a3)(meth)acrylate functionalized oligomers

[0092] In yet another embodiment, which is not intended to be mutually exclusive with aliphatic and alicyclic monomers (a1) and aromatic monomers (a2), the polymer may comprise (a3) ​​at least one (meth)acrylate-functionalized oligomer. The oligomer may have one or more acrylate and / or methacrylate groups attached to the oligomer backbone, these (meth)acrylate functional groups being located at terminal positions on the oligomer and / or distributed along the oligomer backbone.

[0093] Preferably, the at least one (meth)acrylate functionalized oligomer has: i) two or more (meth)acrylate functional groups per molecule; and / or ii) a weight-average molecular weight (Mw) of 300 to 1000 Daltons.

[0094] Examples of such oligomers that can be used alone or in combination include, but are not limited to: (meth)acrylate-functionalized urethane oligomers, such as (meth)acrylate-functionalized polyester urethane and (meth)acrylate-functionalized polyether urethane; (meth)acrylate-functionalized polyepoxide resins; (meth)acrylate-functionalized polybutadiene; (meth)acrylate polyol (meth)acrylate; polyester (meth)acrylate oligomers; polyamide (meth)acrylate oligomers; and polyether (meth)acrylate oligomers. Such (meth)acrylate functionalized oligomers and methods for their preparation are particularly disclosed in: U.S. Patent Nos. 4,574,138; 4,439,600; 4,380,613; 4,309,526; 4,295,909; 4,018,851; 3,676,398; 3,770,602; 4,072,529; 4,511,732; 3,700,643; 4,133,723; 4,188,455; 4,206,025; and 5,002,976. Among the above-mentioned polyether (meth)acrylate oligomers, specific examples include, but are not limited to: PEG 200DMA (n≈4); PEG 400DMA (n≈9); PEG 600DMA (n≈14); and PEG 800DMA (n≈19), wherein the specified number (e.g., 400) represents the weight-average molecular weight of the diol portion of the molecule.

[0095] This invention does not exclude polymers a) derived from olefinically unsaturated nonionic monomers that do not conform to the definitions of a1), a2), and a3). This invention is not intended to limit the invention; other such olefinically unsaturated nonionic monomers may include: silicone (meth)acrylate monomers, such as those taught and claimed in U.S. Patent No. 5,605,999 (Chu); α,β-olefinically unsaturated monocarboxylic acids containing 3 to 5 carbon atoms, such as acrylic acid, methacrylic acid, and crotonic acid; C1-C of crotonic acid. 18 Alkyl esters; α,β-olefinic unsaturated dicarboxylic acids containing 4 to 6 carbon atoms, and their anhydrides, monoesters, and diesters; vinyl esters, such as vinyl acetate, vinyl propionate, and VEOVA available from Shell Chemical Company. TMMonomers of the series; vinyl halides and vinylidene halides; vinyl ethers, such as vinyl ethyl ether; vinyl ketones, including alkyl vinyl ketones, cycloalkyl vinyl ketones, aryl vinyl ketones, arylalkyl vinyl ketones, and arylcycloalkyl vinyl ketones; aromatic or heterocyclic aliphatic vinyl compounds; poly(meth)acrylates of alkane polyols, such as ethylene glycol di(meth)acrylate, propylene glycol di(methyl)acrylate, butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, etc. Poly(meth)acrylates, glycerol tri(meth)acrylates and pentaerythritol tetra(meth)acrylates; poly(meth)acrylates of oxyalkane polyols, such as diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dibutyl glycol di(meth)acrylate, di(pentanediol) dimethacrylate; polyethylene glycol di(meth)acrylates; and bisphenol A di(meth)acrylates, such as ethoxylated bisphenol A (meth)acrylate (“EBIPMA”).

[0096] Representative examples of other olefinically unsaturated polymerizable nonionic monomers include, but are not limited to: ethylene glycol dimethacrylate (EGDMA); fumaric anhydride, maleic anhydride, and itaconic anhydride, and monoesters and diesters with C1-C4 alcohols (e.g., methanol, ethanol, propanol, isopropanol, butanol, isobutanol, and tert-butanol). Representative examples of vinyl monomers include, but are not limited to, compounds such as: vinyl acetate; vinyl propionate; vinyl ethers, such as vinyl ethyl ether; and vinyl ethyl ketone. Representative examples of aromatic or heterocyclic aliphatic vinyl compounds include, but are not limited to, compounds such as: styrene, α-methylstyrene, vinyltoluene, tert-butylstyrene, 2-vinylpyrrolidone, 5-ethylidene-2-norbornene, and 1-, 3-, and 4-vinylcyclohexene.

[0097] As is known in the art, acrylic-based polymers can be prepared from starting monomers by aqueous emulsion polymerization in the presence of a water-soluble free radical initiator and under appropriate heating. The polymerization medium may include water and water-miscible liquids, such as C1-C4 alkanols, but preferably consists only of water. The polymerization temperature can be in the range of 30°C to 120°C, for example, 50°C to 100°C: this temperature does not need to be kept constant but can be increased during emulsion polymerization.

[0098] Suitable free radical initiators (which are typically used in amounts between 0.05 and 5% by weight based on the total weight of the monomers used) include: hydrogen peroxide; alkyl hydroperoxides, such as tert-butyl hydroperoxide and cumene hydroperoxide; persulfates, such as ammonium persulfate, potassium persulfate, and sodium persulfate; organic peroxides, such as acyl peroxides, including benzoyl peroxide; dialkyl peroxides, such as di-tert-butyl peroxide; peroxide esters, such as tert-butyl perbenzoate; and azo-functionalized initiators, such as azobis(isobutyronitrile) (AIBN), 2,2'-azobis(2-methylbutanenitrile) (ANBN), and 4,4'-azobis(4-cyanopentanoic acid).

[0099] The aforementioned peroxide initiator compounds can be advantageously combined with suitable reducing agents in certain situations to form redox systems. Suitable reducing agents include: sodium metabisulfite; potassium metabisulfite; sodium bisulfite; potassium bisulfite; acetone bisulfite; hydroxymethanesulfinic acid; and isoascorbic acid. Metal compounds such as Fe·EDTA can also be used as part of redox initiator systems.

[0100] Those skilled in the art can select a suitable method for adding the initiator to the polymerization vessel during free radical aqueous emulsion polymerization. It can be introduced entirely into the polymerization vessel or used continuously or in stages depending on its consumption during the free radical aqueous emulsion polymerization process. Preferably, a portion is fed initially, with the remainder supplied according to the consumption during polymerization.

[0101] Aqueous polymerization is typically carried out in the presence of an emulsifier at a total weight of 0.1 to 5.0 wt% based on the monomers. Nonionic emulsifiers are preferred, optionally used in combination with anionic emulsifiers. Suitable nonionic emulsifiers include linear or branched polyoxyethylene alcohols having 5 to 50 ethylene oxide (EO) units. Suitable anionic emulsifiers include C1-C... 18 Alkyl sulfates, C1-C 18 Alkyl sulfonates and phosphate esters.

[0102] In the emulsion polymerization according to the invention, an aqueous dispersion of the polymer with a solids content greater than 60% by weight is typically obtained. Furthermore, the acrylic emulsion polymer should be obtained with a unimodal particle size distribution, characterized in that the average particle size (d50) of the polymer particles in the aqueous dispersion is 50 to 400 nm, for example, 50 to 200 nm. The obtained aqueous dispersion may be further processed, or may be directly mixed with other components to form an aqueous coating composition.

[0103] A2: Nonionic polyurethane emulsion polymer

[0104] In another alternative, and as is known in the art, a suitable nonionic polyurethane can be obtained by reacting the following substances: i) at least one polyol; ii) optionally other active hydrogen compounds; and iii) at least one polyisocyanate compound. The equivalence ratio of the active hydrogen to the NCO groups of the reactants should be selected to ensure the absence of free NCO groups: thus the equivalence ratio can be at least 1:1, preferably 1:1 to 1.2:1.

[0105] As used herein, “polyol” refers to any compound containing two or more hydroxyl groups; therefore, the term is intended to include diols, triols, and compounds containing four or more –OH groups. Furthermore, the at least one reactant polyol herein should be selected from polyester polyols, polyether polyols, and polycarbonate polyols. The polyol should preferably have a number-average molecular weight (Mn) of 1000 to 50,000 g / mol, for example, 1000 to 25,000 g / mol. As an alternative or additional measure to this molecular weight characterization, the hydroxyl value of the reactant polyol should preferably be 20 to 850 mg KOH / g, for example, 25 to 500 mg KOH / g.

[0106] Polycarbonate diols can be obtained by reacting a carbonate derivative with a diol. Exemplary carbonate derivatives are diaryl carbonates, including but not limited to diphenyl carbonate, di(C1-C6)alkyl carbonates, and phosgene. Exemplary diols include but are not limited to: ethylene glycol; 1,2-propanediol; 1,3-propanediol; 1,3-butanediol; 1,4-butanediol; 1,5-pentanediol; 1,6-hexanediol; cyclohexanediol; diethylene glycol; dipropylene glycol; neopentanediol; and mixtures thereof.

[0107] Polyester diols can be obtained by reacting the diol with aliphatic, aromatic, or alicyclic dicarboxylic acids, or in some cases with their corresponding anhydrides: the reaction may optionally be carried out in the presence of an esterification catalyst. Examples of suitable dicarboxylic acids include, but are not limited to: adipic acid; glutaric acid; pimelic acid; octanoic acid; nonanedicarboxylic acid; decanedicarboxylic acid; succinic acid; maleic acid; sebacic acid; azelaic acid; terephthalic acid; isophthalic acid; phthalic acid; tetrahydrophthalic acid; hexahydrophthalic acid; trimellitic acid; and 1,4-cyclohexanedicarboxylic acid. Examples of suitable anhydrides include succinic anhydride, phthalic anhydride, and trimellitic anhydride. It is noteworthy that various commercially available saturated (hydrogenated) or unsaturated forms of dimer fatty acids can also be used as dicarboxylic acids. Examples of suitable diols for preparing polyester diols include: ethylene glycol; diethylene glycol, triethylene glycol, or tetraethylene glycol; 1,2-propanediol; dipropylene glycol, tripropylene glycol, tetrapropylene glycol; 1,3-propanediol; 1,4-butanediol; 1,3-butanediol; 2,3-butanediol; 1,6-hexanediol; 1,5-pentanediol; 2,2-dimethyl-1,3-propanediol (neopentylene glycol); 1,4-dihydroxycyclohexane; 1,4-dimethylcyclohexane; 1,8-octanediol; 1,10-decanediol; 1,12-decanediol; 2,2,4- and / or 2,4,4-trimethyl-1,3-pentanediol; and mixtures thereof.

[0108] Other useful polyester glycols are those that can be obtained from the polymerization of glycols containing 2 to 12 carbon atoms of hydroxycarboxylic acids or their lactones. Hydroxycarboxylic acids can be saturated or unsaturated, linear or branched, and examples include: glycolic acid; lactic acid; 5-hydroxyvalerate; 6-hydroxyhexanoate; ricinoleic acid; 12-hydroxystearic acid; 12-hydroxydodecanoic acid; 5-hydroxydodecanoic acid; 5-hydroxydecanoic acid; and 4-hydroxydecanoic acid. Suitable lactones are β-propiolactone, δ-valerate, (C1-C6)alkylvalerate, ε-caprolactone, and (C1-C6)alkyl-ε-caprolactone.

[0109] In addition, it is preferred that the polyol from which the polyurethane is derived is a polyether polyol, particularly a polyether polyol with a polydispersity (PD) of less than 2, preferably less than 1.5, and more preferably less than 1.3. For completeness and for the purposes of this invention, "polyether" is understood to be a polymer in which the repeating unit contains ether functional groups C–O–C in the main chain. Therefore, polymers with side ether groups, such as cellulose ethers, starch ethers, and vinyl ether polymers, as well as polyacetals, are not covered by this definition. Ideally, the polyether polyol is a polyoxyethylene, particularly a polyoxy(C2-C3) olefin.

[0110] In particular, as described in U.S. Patent Nos. 3,905,929 and 3,920,598, the presence of polyoxy(C2-C3) olefin chains in the reactant polyol can stabilize nonionic polyurethanes in aqueous dispersions. This can minimize or eliminate the need to include emulsifiers in the dispersion to provide external stability for the nonionic polyurethane.

[0111] It is worth noting that at least one monool can preferably be used as a further active hydrogen reactant (ii) in the synthesis of nonionic polyurethanes. For example, a monofunctional hydrophilic polyoxyethylene (e.g., polyethylene oxide or polypropylene oxide) can be incorporated into the polyurethane as a means of altering latex properties and improving its emulsion-forming ease. When present, the monool is present in an amount of 0.1 to 5% by weight based on the weight of reactants (i) to (iii).

[0112] As used herein, “polyisocyanate” refers to a compound containing at least two –N=C=O functional groups, such as 2 to 5 or 2 to 4 –N=C=O functional groups. Suitable polyisocyanates include aliphatic, alicyclic, aromatic and heterocyclic isocyanates, their dimers and trimers, and mixtures thereof.

[0113] Aliphatic and alicyclic polyisocyanates may contain 6 to 100 carbon atoms linked in a straight chain or cyclically, and have at least two isocyanate reactive groups. Examples of suitable aliphatic isocyanates include, but are not limited to, straight-chain isocyanates such as ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI), octamethylene diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, 1,6,11-undecane triisocyanate, 1,3,6-hexamethylene triisocyanate, bis(isocyanoethyl) carbonate, and bis(isocyanoethyl) ether. Exemplary alicyclic polyisocyanates include, but are not limited to, dicyclohexylmethane 4,4′-diisocyanate (H... 12 MDI), 1-isocyanomethyl-3-isocyano-1,5,5-trimethyl-cyclohexane (isophorone diisocyanate, IPDI), cyclohexane 1,4-diisocyanate, hydrogenated xylene diisocyanate (H6XDI), 1-methyl-2,4-diisocyano-cyclohexane, m- or p-tetramethylxylene diisocyanate (m-TMXDI, p-TMXDI), and dimer fatty acid diisocyanates.

[0114] The term “aromatic polyisocyanate” is used herein to describe organic isocyanates in which the isocyanate group is directly attached to a ring of a mononuclear or polynuclear aromatic group. A mononuclear or polynuclear aromatic group refers to a substantially planar cyclic hydrocarbon moiety of a conjugated double bond, which may be a single ring or may include multiple condensed (fused) or covalently linked rings. The term aromatic also includes alkylaryl. Typically, the hydrocarbon (main) chain comprises 5, 6, 7, or 8 main chain atoms in a ring. Examples of such planar cyclic hydrocarbon moiety include, but are not limited to, cyclopentadienyl, phenyl, naphthyl,

[10] cycloalkenyl–(1,3,5,7,9-cyclodecaptenyl–),

[12] cycloalkenyl–, [8]cycloalkenyl–, benzo[a]naphthalene (phenaene), 1,9-dihydropyrene, (1,2-benzophenanthrene). Examples of alkylaryl moiety are benzyl, phenethyl, 1-phenylpropyl, 2-phenylpropyl, 3-phenylpropyl, 1-naphthylpropyl, 2-naphthylpropyl, 3-naphthylpropyl and 3-naphthylbutyl.

[0115] Exemplary aromatic polyisocyanates include, but are not limited to: all isomers of toluene diisocyanate (TDI), in the form of pure isomeric forms or mixtures of several isomers; naphthalene-1,5-diisocyanate; diphenylmethane 4,4′-diisocyanate (MDI); diphenylmethane 2,4′-diisocyanate, and mixtures of diphenylmethane 4,4′-diisocyanate with 2,4′ isomers or mixtures thereof with oligomers of higher functionality (so-called crude MDI); xylene diisocyanate (XDI); diphenyl dimethylmethane 4,4′-diisocyanate; dialkyl and tetraalkyl diphenylmethane diisocyanates; dibenzyl 4,4′-diisocyanate; phenylene 1,3-diisocyanate; and phenylene 1,4-diisocyanate.

[0116] Where necessary, polyisocyanates can be biuretized and / or isocyanurate-esterified by methods generally known (e.g., those described in UK Patent No. 889,050). It should also be noted that the term "polyisocyanate" is intended to include prepolymers formed by the partial reaction of the aforementioned aliphatic, alicyclic, aromatic, and heterocyclic isocyanates with polyols to obtain isocyanate-functionalized oligomers, which can be used alone or in combination with free isocyanates.

[0117] To facilitate their inclusion in the compositions of the present invention, the at least one nonionic polyurethane may initially be provided in the form of an aqueous dispersion, wherein the particles of the dispersion may preferably have a dm of less than 1 micrometer, for example 50 to 400 nm. 50 The particle size distribution (e.g., measured by dynamic light scattering) is characterized by a single-peak particle size distribution.

[0118] The formation of a polyurethane dispersion in water is preferably achieved by: i) first forming a prepolymer with free NCO groups from the above reactants under anhydrous conditions or in the presence of an organic solvent; and ii) dispersing the prepolymer in an aqueous phase in a continuous process, exemplified by a high internal ratio (HIPR) process, or in a batch process, exemplified by a reversed phase process. Reaction i) can be carried out under catalysis and at a temperature, for example, between 25 and 100 °C. The resulting prepolymer should preferably be characterized by at least one of the following: i) an NCO content of 5 to 30 wt%, preferably 10 to 25 wt%, based on the weight of the prepolymer; ii) an NCO functionality of 2.2 to 3.0, preferably 2.2 or 2.4 to 2.9; iii) a viscosity at 20°C of 300 to 35,000 mPa·s, preferably 1,000 to 10,000 mPa·s; and iv) a number-average molecular weight (Mn) of 500 to 30,000, for example 500 to 15,000, or 500 to 10,000 g / mol. For completeness, these characteristics i) to iv) are not intended to be mutually exclusive: in fact, the prepolymer may satisfy one, two, three, or four of these characteristics.

[0119] Standard polyurethane catalysts known in the art include: stannous salts of carboxylic acids, such as stannous octoate, stannous oleate, stannous acetate, and stannous laurate; dialkyltin dicarboxylic acids, such as dibutyltin dilaurate and dibutyltin diacetate; tertiary amines; alkanolamine compounds; 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine; tetraalkylammonium hydroxide; alkali metal hydroxides; alkali metal alkoxides; tin alkyloxides, such as dibutyldimethoxytin, dibutyldiphenoxytin, and dibutyldiisopropoxytin; tin oxides, such as dibutyltin oxide and dioctyltin oxide; reaction products of dibutyltin oxide and phthalates; tin thiolates; alkyl titanates; organoaluminum compounds, such as aluminum triacetylacetonate, aluminum triethylacetoacetate, and... Aluminum diisopropoxyethylacetoacetate; chelating compounds, such as zirconium tetraacetylacetonate and titanium tetraacetylacetonate; organosilicon titanium compounds; bismuth tri-2-ethylhexanoate; acidic compounds, such as phosphoric acid and p-toluenesulfonic acid; triphenylborane; triphenylphosphine; 1,8-diazabicycloundec-7-ene (DBU); 1,5-diazabicyclo[4.3.0]non-5-ene; 1,4-diazabicyclo[2.2.2]octane; 4-dimethylaminopyridine; 1,5,7-trizabicyclo[4.4.0]dec-5-ene; 7-methyl-1,5,7-trizabicyclo[4.4.0]dec-5-ene; 1,8-bis(tetramethylguanidinyl)naphthalene; and 2-tert-butyl-1,1,3,3-tetramethylguanidine. Depending on the nature of the isocyanate, the amount of catalyst used is typically in the range of 0.005 to 10% by weight of the catalyzed mixture.

[0120] As previously stated, the prepolymer can optionally be prepared in the presence of a solvent, and the solvent is at least partially and preferably completely removed before or after the preparation of the aqueous dispersion. Examples of solvents that do not react with isocyanates when used include: ketones, such as acetone and butanone; ethers, such as tetrahydrofuran, dioxane, and dimethoxyethane; ether esters, such as methoxypropyl acetate; (cyclic)amides and ureas, such as dimethylformamide and dimethylacetamide; N,N′-dimethyl-2,5-diazopentanone; N-methylpyrrolidone; and terminally capped glycol ethers. Such solvents can be added at any stage of prepolymer preparation.

[0121] Preferably, the prepolymer described above is extended using a chain extender. As known to those skilled in the art, typical chain extenders have a weight-average molecular weight (Mw) of 18 to 500 g / mol and have at least two active hydrogen-containing groups. In particular, polyamines and / or water can be used as chain extenders, with mixtures of water and polyamines being particularly preferred. Examples of exemplary polyamines that can be used alone or in combination include: amination of polypropylene glycol, such as Jeffamine D-400, available from Huntsman Chemical Company; hydrazine; piperazine; aminoethylpiperazine; 2-methylpiperazine; 1,5-diamino-3-methylpentane; isophorone diamine; ethylenediamine; diaminobutane; hexamethylenediamine; hexamethylenediamine; tetramethylenetetramine; aminoethylpropyltrimethoxysilane; diethylenetriamine; triethylenetetramine; triethylenepentamine; ethanolamine; and lysine.

[0122] In preparing the nonionic polyurethane polymer of the present invention, a chain extender other than water (as a dispersion medium) is used, and the equivalence ratio of the active hydrogen provided by the chain extender to the NCO groups of the prepolymer should be selected to ensure that there are no free NCO groups in the final polyurethane: therefore, the equivalence ratio can be at least 1:1, preferably 1:1 to 1.2:1.

[0123] B: Trivalent chromium

[0124] Based on the weight of the composition, the compositions of the present invention contain 0.1 to 2.5 wt% Cr(III) ions, calculated as Cr. Preferably, the composition will contain 0.1 to 2.0 wt%, for example, 0.1 to 1.5 wt% of the Cr(III) ions.

[0125] Trivalent chromium ions can be directly introduced into the passivation composition in the form of bath-soluble and compatible chromium(III) compounds, with salts such as chromium sulfate (Cr2(SO4)3), chromium alum (potassium chromium sulfate, KCr(SO4)2), chromium chloride (CrCl3), and chromium bromide (CrBr3) being particularly suitable for this purpose.

[0126] In a preferred alternative, chromium(III) ions are introduced into the composition by reducing hexavalent chromium ions in the aqueous phase with ascorbic acid. Exemplary water-soluble hexavalent chromium compounds that can be used alone or in combination include: chromium trioxide (CrO3); lithium chromate (Li2CrO4); lithium dichromate (Li2Cr2O7); sodium chromate (Na2CrO4); sodium dichromate (Na2Cr2O7); potassium chromate (K2CrO4); potassium dichromate (K2Cr2O7); ammonium chromate ((NH4)2CrO4); ammonium dichromate ((NH4)2Cr2O7); magnesium chromate (MgCrO4); magnesium dichromate (MgCr2O7); calcium chromate (CaCrO4); calcium dichromate (CaCr2O7); zinc chromate (ZnCrO4); and zinc dichromate (ZnCr2O7). Preferred compounds include chromium trioxide (CrO3), sodium chromate (Na2CrO4), sodium dichromate (Na2Cr2O7), potassium chromate (K2CrO4), and potassium dichromate (K2Cr2O7). Good results are particularly obtained when using chromium trioxide, a compound that is alternatively referred to in the art as anhydrous chromic acid.

[0127] C: Ascorbic acid

[0128] As used herein, the term "ascorbic acid" is intended to include enantiomeric forms of compounds or mixtures thereof. The compositions of the present invention contain ascorbic acid, which must be added to chromium (Cr), wherein it is required that all hexavalent chromium introduced into the aqueous composition be converted to Cr(III). However, for the appearance of treated zinc or zinc alloy coated steel surfaces, it is preferred herein that the molar ratio of ascorbic acid to aluminum in the composition for treating zinc or zinc metal coatings is not greater than 1:1, more preferably not greater than 1:2, particularly preferably not greater than 1:3, but preferably at least 1:10, more preferably at least 1:5, wherein the amount of aluminum preferably originates from d) at least one aluminum compound of the composition according to the invention, and thus from component D as further specified below.

[0129] Therefore, in some embodiments, the composition may also be characterized by containing 0.1 to 1.0% by weight of ascorbic acid, based on the weight of the composition. Preferably, the composition will contain 0.1 to 0.5% by weight of ascorbic acid.

[0130] For completeness, the present invention does not exclude the presence of inorganic reducing agents in the composition; in fact, this may help ensure the complete reduction of the added Cr(VI). Suitable inorganic reducing agents include, but are not limited to: alkali metal iodides; tin(II) compounds, such as SnSO4 and SnCl2·2H2O; antimony(III) compounds; ferrous salts, such as ferrous sulfate heptahydrate (HH), ferrous sulfate monohydrate (MH), and ferrous ammonium sulfate; sulfur dioxide; and alkali metal sulfites, bisulfites, and metabisulfites.

[0131] D: Aluminum compound

[0132] The compositions of the present invention comprise 0.1 to 2.5% by weight of at least one aluminum compound, said aluminum compound being selected from: aluminum hydroxide; aluminum metahydroxide; aluminum trichloride; aluminum alkoxide (aluminum alkoxide); aluminum glycolate; tri(β-ketone)aluminum; tri(β-ketone ester)aluminum; aluminum soap; and aluminum carboxylate. Preferably, the compositions comprise 0.1 to 2.0% by weight, for example 0.2 to 1.0% by weight of said at least one aluminum compound.

[0133] Exemplary alcohol compounds that can be used as ligands for alcohol compounds include: C1-C8 alkyl alcohols, such as methanol, ethanol, propanol, isopropanol, butanol, sec-butanol, isobutanol, tert-butanol, pentanol, isopentanol, and tert-pentanol; and C1-C8 ether alcohols, such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-methoxy-1-methylethanol, 2-methoxy-1,1-dimethylethanol, 2-ethoxy-1,1-dimethylethanol, 2-isopropoxy-1,1-dimethylethanol, 2-butoxy-1,1-dimethylethanol, 2-(2-methoxyethoxy)-1,1-dimethylethanol, 2-propoxy-1,1-diethylethanol, 2-sec-butoxy-1,1-diethylethanol, and 3-methoxy-1,1-dimethylpropanol.

[0134] Exemplary diol compounds that can form glycolate ligands are C2-C8 diol compounds, including: 1,2-ethylene glycol; 1,2-propanediol; 1,3-propanediol; 2,4-hexanediol, 2,2-dimethyl-1,3-propanediol; 2,2-diethyl-1,3-propanediol; 1,3-butanediol; 2,4-butanediol; 2,2-diethyl-1,3-butanediol; 2-ethyl-2-butyl-1,3-propanediol; 2,4-pentanediol; 2-methyl-1,3-propanediol; 2-methyl-2,4-pentanediol; 2,4-hexanediol; and 2,4-dimethyl-2,4-pentanediol.

[0135] Regarding the aforementioned tri(β-ketone)aluminum, exemplary β-diketone compounds that can form ligands include: C1-C8 alkyl-substituted β-ketones, such as acetylacetone, hexane-2,4-diketone, 5-methylhexane-2,4-diketone, heptane-2,4-diketone, 2-methylheptane-3,5-diketone, and 2,6-dimethylheptane-3,5-diketone; and fluoroalkyl-substituted β-diketones, such as 1,1,1-trifluoropentane-2,4-diketone, 1,1,1-trifluoro-5,5- Dimethylhexane-2,4-dione, 1,1,1,5,5,5-hexafluoropentane-2,4-dione and 1,3-diperfluorohexylpropane-1,3-dione; and C1-C8 ether-substituted β-diones, such as 1,1,5,5-tetramethyl-1-methoxyhexane-2,4-dione, 2,2,6,6-tetramethyl-1-methoxyheptane-3,5-dione and 2,2,6,6-tetramethyl-1-(2-methoxyethoxy)heptane-3,5-dione.

[0136] Regarding the aforementioned tri(β-ketoester)aluminum, suitable ligands include, but are not limited to, C1-C8 alkylmalonates and C1-C8 alkylpyruvates. Aluminum soaps include, but are not limited to, aluminum monolaurate, aluminum dilaurate, aluminum trilaurate, aluminum monomyristate, aluminum dimyristate, aluminum trimyristate, aluminum monopalmitate, aluminum dispalmitate, aluminum tripalmitate, aluminum monostearate, aluminum distearate, and aluminum tristearate.

[0137] Suitable aluminum carboxylate options include aluminum tricarboxylate (Al(OOCR)3), aluminum monohydroxy (mono)dicarboxylate (RCOO)2Al(OH), and aluminum dihydroxy (di)monocarboxylate (RCOOAl(OH)2), where R is a C1-C8 alkyl group. Specific, but non-limiting, examples include aluminum monoformate, aluminum diformate, aluminum triformate, aluminum monoacetate, aluminum diacetate, aluminum triacetate, aluminum monopropionate, aluminum dipropionate, aluminum tripropionate, and aluminum trioctanoate.

[0138] In a preferred embodiment, the passivation composition comprises 0.1 to 2.5% by weight of at least one aluminum carboxylate, selected from aluminum triformate, aluminum triacetate, aluminum tripropionate, and aluminum trioctanoate, based on the weight of the composition. It may be noted that aluminum triacetate is preferred.

[0139] E: Wax

[0140] The compositions of the present invention comprise at most 10% by weight of at least one finely ground wax, based on the weight of the composition. For example, the composition may contain 1 to 8% by weight, such as 1 to 5% or 2 to 5% by weight of the wax, based on the weight of the composition.

[0141] The term "wax" is known to those skilled in the art and can be referenced to the definition in Ullmann's Encyclopedia of Industrial Chemistry, 6th Edition, Electronic Release (1998). However, this is not intended to limit the invention, and exemplary waxes include: paraffin wax [CAS No. 8002-74-2]; polyethylene wax [CAS No. 9002-88-4]; polyethylene-polypropylene wax; copolymerized polyethylene wax, such as copolymers of ethylene with at least one monomer selected from (meth)acrylic acid, maleic anhydride, vinyl acetate and vinyl alcohol, which can be obtained, for example, by CAS Nos. 38531-18-9, 104912-80-3 and 219843-86-4; polybutene wax; Fischer-Tropsch waxes; oxidized waxes, such as oxidized polyethylene wax [CAS No. 68441-17-8]; polar modified polypropylene waxes; microcrystalline waxes, such as microcrystalline stone wax [CAS No. 63231-60-7]; lignite waxes and lignite wax raffinate; lignite acid and its salts and esters; fatty acid amides, such as sinigrinamide [CAS No. 112-84-5], oleamide [CAS No. 301-02-0] and 1,2-vinylbis(stearamide) [CAS No. 110-30-5]; and carnauba wax.

[0142] Preferably, any wax contained in this composition satisfies at least one of the following conditions: i) an acid value of less than 200 mg KOH / g, preferably less than 100 mg KOH / g; ii) a melting point of 40 to 200 °C, preferably 60 to 180 °C; and iii) a number-average molecular weight (Mn) of at least 200 g / mol, preferably at least 400 g / mol. For completeness, these conditions are not mutually exclusive: a wax may satisfy one, two, or three of these conditions.

[0143] It is noteworthy that at least one wax selected from polyethylene wax, oxidized polyethylene wax, polypropylene wax, oxidized polypropylene wax and ethylene or propylene-based copolymer waxes is particularly preferred as the main monomer, wherein the at least one wax is further characterized by a number average molecular weight (Mn) of 400 to 30,000 g / mol, preferably 1,000 to 25,000 g / mol.

[0144] To facilitate their inclusion in the compositions of the present invention, waxes can be provided in the following forms: i) in the form of fine powder, particularly in the form characterized by d as measured by laser diffraction. 50 The micronized form with a particle size of less than 5 micrometers; and / or ii) in the form of an aqueous dispersion, wherein the particles of the dispersion are desirablely characterized by a dm of less than 1 micrometer, for example, 20 to 500 nm, as measured by dynamic light scattering. 50 Particle size.

[0145] F: Auxiliary ingredients

[0146] The compositions of the present invention typically further comprise auxiliary materials, which are necessarily minor components but can still impart improved properties to these compositions. The total amount of auxiliary materials in the composition is 0 to 10% by weight, preferably 0.1 to 10% by weight or 0.1 to 7.5% by weight, based on the total weight of the composition. The desired viscosity of the composition generally determines the total amount of auxiliary materials added, but the pH of the passivating composition described above may determine the amount of auxiliary acidic components added.

[0147] Included in such auxiliary materials are: ammonia; mineral acids; divalent metals; water-soluble or water-dispersible fluoroacids or their salts; corrosion inhibitors, such as dialkylthiourea, copper sulfate, and copper sulfate; adhesion promoters; wetting agents; defoamers; chelating agents; lubricants; and mixtures thereof. As further exemplary corrosion inhibitors, the following commercial materials may be mentioned: The series is available from JMN Specialties, Inc. and Henkel Corporation; The series is available from Clariant AG; and The series is available from Akzo Nobel Surfactants LLC.

[0148] As previously stated, the compositions of the present invention may optionally include ammonia (NH3). Preferably, based on the weight of the composition, the composition will contain up to 2% by weight, for example, 0.1 to 2% by weight, or 0.2 to 1% by weight, of ammonia. For completeness, the weight of the ammonia composition is calculated based on NH3. Ammonia will be present in the aqueous compositions of the present invention in the form of an ammonia solution NH3 (aqueous), which comprises a weakly alkaline solution of ammonia in water, and may be referred to in the art as ammonium hydroxide, ammonia water, liquid ammonia, aqua ammonia, aqueous ammonia, or simply ammonia. Although the term "ammonium hydroxide" implies a form having [NH4+] + ][OH - The base is composed of NH4OH, but it is practically impossible to separate the NH4OH sample because these ions do not constitute a large part of the total ammonia in ammonia solution, except in the case of extremely dilute ammonia solution.

[0149] Regarding the optional addition of mineral acids, the use of nitric acid is not excluded, but it is not preferred; instead, the addition of at least one of phosphoric acid, phosphonic acid, sulfurous acid, sulfuric acid, hydrochloric acid, and hydrobromic acid is considered particularly suitable. It may be mentioned that the use of at least one of phosphoric acid, phosphonic acid, sulfurous acid, and sulfuric acid is particularly preferred.

[0150] The passivation composition may further comprise at least one divalent metal cation (M 2+ In a preferred embodiment, the at least one divalent metal cation (M) is selected from: Mg 2+ Ca 2+ Mn 2+ Co 2+ Ni 2+ 、Sr 2+ Ba 2+ and Zn 2+ The aforementioned metal ions or mixtures thereof are most conveniently introduced into the composition in the form of metal oxides, metal hydroxides, and / or soluble and compatible metal salts (including, but not limited to, sulfates and halide salts). However, nitrates and fluoride salts are not preferred for this purpose.

[0151] In some embodiments of the present invention, the passivation composition comprises magnesium (Mg) 2+ ) and / or manganese (Mn 2+ It is desirable to introduce this magnesium and manganese into the aqueous passivation composition in one or more of the following forms: manganese chloride, manganese sulfate, magnesium oxide, magnesium hydroxide, magnesium sulfate, and magnesium chloride. A preference for magnesium oxide or magnesium hydroxide is noted.

[0152] When present, the divalent metal cations (M) in the aqueous composition, based on the weight of the composition, are... 2+ The total amount of ) should not exceed 5% by weight, preferably not exceeding 2.5% by weight.

[0153] The passivation composition may optionally contain at least one water-soluble or water-dispersible fluoroacid or a salt thereof, wherein the fluoroacid is defined by the following empirical general formula (II):

[0154] H p T q F r O s (II) Wherein:

[0155] Each of q and r represents an integer from 1 to 10;

[0156] Each of p and s represents an integer from 0 to 10; and

[0157] T represents an element selected from Ti, Zr, Hf, Si, Sn, Al, Ge, and B.

[0158] Preferred fluoroacids of empirical formula (II) include compounds in which: T is selected from Ti, Zr or Si; p is 1 or 2; q is 1; r is 2, 3, 4, 5 or 6; and s is 0, 1 or 2.

[0159] The exemplary fluoroacids used in this invention can be selected from: fluorotitanic acid (H2TiF6); fluorozirconic acid (H2ZrF6); fluorosilicic acid (H2SiF6); fluoroboric acid (HBF4); fluorostannic acid (H2SnF6); fluorogermanic acid (H2GeF6); fluorohafnium acid (H2HfF6); and fluoroaluminic acid (H3AlF6). Preferred fluoroacids are: fluorotitanic acid (H2TiF6) and fluorozirconic acid (H2ZrF6).

[0160] Under conditions where the salt is water-soluble or water-dispersible, one or more H atoms of the aforementioned fluoroacids can be replaced by suitable cations (e.g., ammonium, alkaline earth metal cations, or alkali metal cations). Salts of alkali metal cations and ammonium are preferred herein, and therefore the following examples of suitable fluoroacid salts can be mentioned: (NH4)2ZrF6, H(NH4)ZrF6, (NH4)2TiF6, H(NH4)2TiF6, Na2ZrF6, K2ZrF6, Li2ZrF6, Na2TiF6, K2TiF6, and Li2TiF6.

[0161] This salt can be added directly to the composition, or it can be generated in situ in an aqueous passivation composition by partially or completely neutralizing the acidic fluoride or acidic fluoride oxide with a suitable base. It is noteworthy that the base can be organic or inorganic in nature: for example, ammonium bicarbonate and hydroxylamine can be used.

[0162] When both fluoroacids and mineral acids are present, the fluoroacid or its salt is typically included in the composition such that the molar ratio of the mineral acid to the metal (T) of the fluoroacid is in the range of 10:1 to 2:1, preferably 9:1 to 3:1, and more preferably 8:1 to 4:1. When the level of the mineral acid is outside the above range, the stability of the formulation decreases: at lower levels of mineral acid within the range, the accompanying loss of formulation stability can be mitigated by increasing the amount of divalent metal cations in the composition. When the level of metal (T) drops below the said molar range, the stability of the composition may be substantially affected, but a performance degradation may be observed in neutral salt spray (NSS).

[0163] In alternative, but not mutually exclusive, expressions, the fluoroacid or its salt shall be included in the passivating composition in an amount of 1 to 5% by weight, for example, 1 to 2.5% by weight, based on the weight of the composition.

[0164] The presence of other complexed fluoride anions in the passivation composition is not excluded; in this regard, fluoroindium salts (e.g., InF4) can be mentioned. -1 ); Fluorophosphates (e.g., PF6) -1 ); Fluoroarsenates (e.g., AsF6) -1 ); Fluoroantimonates (e.g., SbF6) -1 ); Fluorobismuthates (e.g., BiF6)-1 ); Fluorosulfate (e.g., SF6) -2 ); Fluorose selenates (e.g., SeF6) -2 ); Fluorotellurates (e.g., TeF6) -2 Or TeOF5 -1 ); Fluorocopperates (e.g., CuF3) -1 ); fluorosilverate; fluorozincate (e.g., ZnF4) -2 ); fluorovanadates (e.g., VF7) -2 ); Fluoroniobates (e.g., NbF7) -2 ); Fluorotantalates (e.g., TaF7) -2 ); Fluoromolybdates (e.g., MoF6) -3 ); fluorotungstates (e.g., WF6) -1 ); Yttrium fluorophosphates (e.g., YF6) -3 ); fluorolanthanates (e.g., LaF6) -3 ); ceric fluorophosphates (e.g., CeF6) -3 or CeF6 -2 ); Fluoromanganate (e.g., MnF6) -2 ); Fluoroferrates (e.g., FeF6) -3 ); fluoronickelates; and fluorocobaltates. Such anions may be included in the form of water-soluble or water-dispersible salts (particularly ammonium, alkaline earth metal, or alkali metal salts). When present, the complexed fluoride anion should be included in the composition in an amount of up to 0.1 mol / L, for example, up to 0.05 mol / L.

[0165] It is also possible that the passivation composition contains uncomplexed free fluoride ions, as fluoride anions can act as promoters in the formation of the passivation coating and are present at the interface between the conversion coating and the metal substrate. Such free fluoride anions can be included by adding substances such as hydrofluoric acid, alkali metal fluorides (e.g., sodium fluoride), alkali metal hydrofluorides (e.g., sodium hydrogen fluoride, ammonium fluoride), and ammonium hydrogen fluoride to the passivation composition.

[0166] In addition, the presence of free fluoride ions (not bound in a complexed form) is undesirable. Although fluoride species are used in passivation compositions, the environmental release of fluorides is problematic, as documented at https: / / www.cdc.gov / niosh / . Therefore, it is preferable that the passivation composition is substantially free of free fluoride anions.

[0167] Based on the weight of the composition, the passivation composition may include up to 2.5% by weight, for example, 0.1 to 2.5% by weight of a nonionic surfactant. While other nonionic surfactants may be useful in this invention, it is worth mentioning that fatty alcohol ethoxylates are particularly preferred, examples of which include ethoxylated lauryl alcohol, stearyl alcohol, behenyl alcohol, and oleyl cetyl alcohol.

[0168] Furthermore, the compositions of the present invention may optionally comprise at least one α-hydroxycarboxylic acid represented by the following general formula (III):

[0169] R1CH(OH)COOH(III) where: R1 represents a hydrogen atom, C1-C4 alkyl, C2-C6 alkenyl, C1-C6 alkoxy, C3-C6 cycloalkyl, or C6-C 10 Aryl group. Where applicable, R1 may optionally be substituted with one or more groups selected from the following: halogen; oxo group; or –COOH.

[0170] Suitable α-hydroxycarboxylic acids include, but are not limited to: glycolic acid; lactic acid (2-hydroxypropionic acid); 2-hydroxybutyric acid; 2-hydroxyvalerate; 2-hydroxyhexanoic acid; glucuronic acid; citric acid; mandelic acid; galacturonic acid; ribonucleic acid (2,3,4,5-tetrahydroxyvalerate); gluconic acid (2S,3S,4R,5S)-2,3,4,5,6-pentahydroxyhexanoic acid; malonic acid; tartaric acid; and malic acid.

[0171] In one embodiment, the at least one α-hydroxycarboxylic acid is selected from: glycolic acid; gluconic acid; lactic acid (2-hydroxypropionic acid); 2-hydroxybutyric acid; 2-hydroxyvalerate; and 2-hydroxyhexanoic acid. More particularly, the α-hydroxycarboxylic acid of the coating composition should include or consist of gluconic acid.

[0172] For completeness, it is noted again that the pH of the passivation composition, as described above, determines to some extent the amount of this α-hydroxycarboxylic acid added. When added within this pH limit, the α-hydroxycarboxylic acid should generally be included in the aqueous passivation composition at a maximum of 0.1 mol / L, for example, a maximum of 0.05 mol / L.

[0173] It is believed that the corrosion resistance of the disclosed passivation compositions and the resulting passivation films can be enhanced by incorporating transition metal salts and / or transition metal complexes therein. Salts or complexes of transition metals selected from Ce, Ni, Co, V, Fe, Zn, Zr, Mn, Mo, W, Ti, Zr, Hf, Bi, and the lanthanides are considered particularly useful in this regard.

[0174] Although the transition metals may be present as complexed fluoride anions mentioned above, these transition metals are alternatively or additionally included in the composition in the form of complexes with other ligands and / or as salts with other anions, provided that the salts are at least partially soluble in water. Examples of anions may include: oxides; hydroxides; sulfates; chlorides; iodides; citrates; lactates; succinates; formates; oxalates; malonic acids; and acetates. Exemplary ligands for transition metal complexes may include: ethylenediaminetetraacetic acid (EDTA); diethylenetriaminepentaacetic acid (DTPA); hydroxyethylethylenediaminetriacetic acid (HEDTA); nitrotriacetic acid (NTA); and methylglycine diacetic acid (MGDA).

[0175] Preparation of passivation composition

[0176] Aqueous passivation compositions are formulated by simply mixing various components and any auxiliary ingredients. While the order of mixing the components is not limited, an aqueous dispersion of the base polymer and / or wax can be carefully formed first before mixing the dispersion with other components. In this case, an aqueous dispersion of acrylic polymer, nonionic polyurethane, and wax can be prepared, for example, with a solids content of 45 to 60% by weight. Furthermore, a preliminary step can be carefully performed by mixing any hexavalent chromium (Cr(VI)) source dissolved in water with ascorbic acid: this precursor solution containing Cr(III) ions obtained through reduction can be mixed with other original dispersed or dissolved components to form the final aqueous composition.

[0177] If desired, the composition can be well prepared prior to its application. However, in an interesting alternative embodiment, a concentrated passivation composition can be obtained first by mixing the components with only a portion of the water that would be present in the applied passivation composition; the concentrated passivation composition can then be diluted with the remaining water shortly before its application. It is believed that such a concentrated composition can be prepared and stored either as a single-package concentrate (which can be converted by dilution with water alone) or as a multi-component concentrate (two or more of which must be mixed and diluted to form the complete working composition according to the invention). Any dilution can be achieved simply by adding water (particularly deionized water and / or softened water) under mixing. The composition can also be prepared in a rinsing stream, thereby injecting one or more concentrated streams into a continuous water flow.

[0178] Where there is no particular intention to limit the amount of water contained in the passivation composition, it is preferred that the composition contains 10 to 50 wt%, preferably 10 to 40 wt%, and more preferably 20 to 40 wt% water, based on the weight of the composition. In alternative but non-exclusive characterization, the passivation composition may be defined by a viscosity of 0.005 to 1 Pa·s (50 cps to 1000 cps) measured using a Brookfield viscometer at 25°C.

[0179] Methods and Applications

[0180] While this invention relates to the passivation of surfaces of zinc or zinc alloys, it is not intended to limit the base substrates to which zinc or zinc alloys may have been applied, nor is it intended to limit the methods of such application. Therefore, suitable base metal substrates may include, but are not limited to, iron, nickel, copper, aluminum, and their alloys; substrates comprising or composed of steel may be specifically mentioned. These metals and alloys may be provided in various forms, including sheets, plates, cubes, spheres, rings, solid cylinders, tubes, and wires; however, this does not preclude the provision of substrates in more complex, shaped forms (obtained through conventional techniques such as bending, punching, casting, forging, rolling, and welding). Moreover, zinc or zinc alloy plating or coatings may be applied to these base substrates by methods such as electroplating; galvanizing, including hot-dip galvanizing and hot-diffusion galvanizing; and galvanizing treatment. By way of example only, the passivation compositions and methods of this invention can be used to treat: galvanized and galvanized diffusion-treated steel that meets the requirements of ASTM Designation A653; A steel sheet coated with a 55% Al / 43.4% Zn / 1.6% Si alloy, available from Bethlehem Steel Corporation; and A steel sheet coated with a 5% Al / 95% Zn alloy, available from Weirton Steel Corporation.

[0181] According to the method of the invention, it is often desirable to remove foreign matter from a coated or plated metal substrate by cleaning and degreasing the relevant surface. Such treatment is known in the art and can be carried out in a single-stage or multi-stage manner, for example by using one or more of the following: an aqueous alkaline degreasing bath; an aqueous cleaning emulsion; a cleaning solvent, such as carbon tetrachloride or trichloroethylene; and water rinsing, preferably deionized or softened water. In those cases using an aqueous alkaline degreasing bath, any degreasing agent remaining on the surface should ideally be removed by rinsing the substrate surface with deionized or softened water. Regardless of the cleaning agent or degreasing agent applied, the substrate thus treated should not undergo an intermediate drying step before passivation treatment or any subsequent pretreatment step prior to said passivation treatment.

[0182] Therefore, as implied above, the present invention does not exclude pretreatment of the zinc or zinc alloy surface, unrelated to the implementation of cleaning and / or degreasing steps. Such pretreatment is known in the art, and references can be made to: German Patent Application No. DE 19733 972A1; German Patent Application No. DE 10 2010 001 686A1; German Patent Application No. DE 10 2007021364A1; and US Patent Application No. 2014 / 360630. In particular, the surface may be treated with a primer to promote the subsequent adhesion of the passivation film.

[0183] Following the cleaning, degreasing, and / or pretreatment steps, the passivation composition is applied to the substrate. The passivation composition can be applied at ambient temperature, or the temperature of the passivation composition can be raised to, for example, a temperature in the range of 30°C to 90°C, such as 30°C to 70°C, before application.

[0184] For the production of double-sided coated plates, commercially, it is conventional to prepare the operating bath as described above, and apply the passivation composition to the substrate by, but not limited to, immersion, overflow, air atomization spraying, air-assisted spraying, airless spraying, high-volume low-pressure spraying, and air-assisted airless spraying. The minimum contact time between the composition and the substrate is broadly defined as the time sufficient to form the desired passivation film thereon: in the case where the metal to be cold-worked is being passivated or converted, the contact time can be as short as 1 second or as long as 15 minutes; however, depending on the pH and concentration of the applied solution, a contact time of 5 to 300 seconds, for example 5 to 50 seconds, is more typical.

[0185] In some cases, it is only necessary to form a passivation film on a single surface of the substrate. In the context of this invention, the passivation film can be applied only to the electroplated surface of a steel substrate that will form the inside of the fuel tank, i.e., the side in contact with the fuel stored therein: forming a passivation film on both the inner and outer surfaces of such an electroplated steel substrate may be detrimental to the subsequent solderability of the substrate. Techniques for applying the passivation composition only to a single surface include, but are not limited to: painting; brushing; roller coating; wiping; air atomization spraying; air-assisted spraying; airless spraying; high-volume low-pressure spraying; and air-assisted airless spraying.

[0186] At the end of the application step, the article is dried using methods such as ambient air drying, circulating warm air, forced air drying, or infrared heating. The surface temperature of the substrate is controlled during drying: the peak metal temperature (PMT) does not need to exceed 100°C, and more specifically, it should be in the range of 20 to 90°C, for example, 50 to 75°C.

[0187] After drying, the article may be subjected to: at least one water rinse to remove any residual passivating composition; and / or a rinse with a dilute silicate solution. The rinsed substrate may be dried after one or more rinsing steps or after each rinsing solution (if applicable).

[0188] The above treatment should desirablely produce a protective passivation monolayer on zinc or zinc alloy, the monolayer having a concentration of 25 to 500 mg / m³. 2 Preferred concentration: 25 to 250 mg / m³ 2 Or 25 to 100 mg / m 2 The membrane weight. If the membrane charge is less than 25 mg / m³ 2 If the passivation film is insufficient, it may impart inadequate corrosion resistance. If the film thickness exceeds 500 mg / m³, further action may be necessary. 2 If the passivation film does not adhere well to the surface, the coating may peel off during further processing of the substrate.

[0189] The compositions according to the invention produce a passivation film that is colorless, blue, or olive-colored, with a smooth to glossy finish. The exact nature of this finish is determined primarily by the base substrate, the zinc or zinc alloy coating, and the immersion time in the conversion coating composition. The zinc or zinc alloy coating passivated according to the invention exhibits corrosion protection for at least 250 hours before the observed onset of white rust corrosion, as defined in ASTM B-201. Alternatively or additionally, when treated with neutral salt spray (NSS, 5 wt% NaCl, 95 wt% H2O) under steady-state conditions according to ASTM B-117, the zinc or zinc alloy coating passivated according to the invention exhibits corrosion protection for at least 250 hours before the observed onset of white rust corrosion (as defined in ASTM B-201).

[0190] This invention does not preclude the application of a supplemental conversion coating to the passivation film obtained according to the invention; in fact, such a supplemental coating can further extend the corrosion protection of the final article. Reference may be made to silicate-based inorganic coatings and epoxy resin-based organic conversion coatings as non-limiting examples of supplemental conversion coatings: in particular, reference can be made to U.S. Patent Nos. 5,743,971 (Inoue) and 5,855,695 (McMillen). These supplemental conversion coatings can be applied by any suitable method known in the art, such as dip coating, spray coating, roll coating, electrocoating, or powder coating.

[0191] Various features and embodiments of this disclosure are described in the following examples, which are intended to be representative and not restrictive.

[0192] Example

[0193] The following commercial and principal products representing compositions according to the invention were used in Example 1: Ammonia solution: a solution of 25% ammonia in water; Acrylic emulsion: Acrystar HP Cresta, purchased from EOC Tailor Made Polymers India Ltd.; Wetting agent / coupling agent: Rhodoline WA 40, purchased from Solvay Group.

[0194] Polyethylene wax: Aquaslip 671, purchased from The Lubrizol Corporation

[0195] Antibacterial agent: BYK 331, purchased from BYK Altana Group

[0196] Defoamer: Timet W 288S

[0197] Aqueous passivation compositions were prepared by mixing the components given in Table 1 below:

[0198] Table 1

[0199]

[0200] In addition, as a comparative example, the commercial formulation QUALAC obtained from GTZ India Private Ltd. is provided. TM 3732. This composition is based on a chromium(III) compound and a styrene-acrylate copolymer aqueous emulsion: this commercial formulation does not contain ascorbic acid.

[0201] Standard test plate preparation The Advanced Coating Technology (ACT) G-90 hot-dip galvanized steel specimens were mechanically cut into 4cm × 4cm squares. Each obtained plate was treated with an alkaline cleaner at 55°C for 10 seconds, rinsed with tap water at room temperature, and then dried by scraping. Each passivation composition selected for evaluation was applied to one surface of the plate using a roller coater: nine plates were prepared from the aqueous passivation compositions according to the invention; four plates were prepared for each reference passivation composition. The resulting coated test plates were then baked to the peak metallographic temperature (PMT) given in Table 2 below. The coating weights of the obtained test plates were determined on a metallographic basis and are also given in Table 2.

[0202] Based on these aqueous compositions used to make the table, the following tests were performed using the aqueous passivation composition of the present invention and a reference composition.

[0203] Friction coefficient test: Where applicable, test this parameter on (coated) plates according to ASTM G115, the Standard Guide for Measuring and Reporting Friction Coefficients. Uncoated G-90 hot-dip galvanized steel (μ) plates have a friction coefficient of 0.35 to 0.4.

[0204] Neutral Salt Spray (NSS): This test is performed according to ASTM B117 using a 5% NaCl solution at 35°C (https: / / www.astm.org / Standards / B117). Coated panels are placed in a spray chamber (ERICHSEN 606 / 400L type) at 15–30° to the vertical for 96 hours, and if applicable, for 500 hours. The test panels must not come into contact with other surfaces in the chamber, and cross-contamination of condensate or corrosion products on their surfaces is not permitted. The test panels are photographed every 24 hours. After exposure, the test panels are rinsed in deionized water to remove salt deposits from their surfaces and then dried immediately. The coated panels are visually inspected after 500 hours.

[0205] Table 2

[0206] test Comparative Example Example 1 Appearance Green to blue liquid Green to blue liquid pH 6.3 7.5 Solid content (%) 35.0 29.5 Specific gravity (23℃) 1.06 1.03 Peak temperature of metal (°C) 80–85 80–85 Coefficient of friction (μ) 0.11 0.11 <![CDATA[Total coating weight (gm -2 / side)]]> 1.5–1.8 1.5–1.8 NSS (96 hours) Some white rust and observed spots No white rust, no observed spots NSS (500 hours) Stop using Less than 5% rust by area

[0207] In view of the foregoing description and embodiments, those skilled in the art will understand that equivalent modifications may be made thereto without departing from the scope of the claims.

Claims

1. An aqueous passivation composition for treating a zinc or zinc alloy coating, the composition having a pH of 6.5 to 9 and comprising, based on the weight of the composition: 5 to 60 wt.% of a) at least one base polymer selected from the group of acrylic polymers and non-ionic polyurethane polymers; 0.1 to 2.5 wt.% of b) trivalent Cr(III) ions, calculated as Cr; c) ascorbic acid; 0.1 to 2.5 wt.% of d) at least one aluminum compound selected from the group of aluminum hydroxide, aluminum meta-hydroxide, aluminum trichloride, aluminum alcoholate, aluminum glycolate, aluminum tris(beta-keto), aluminum tris(beta-keto ester), aluminum soaps and aluminum carboxylates; and up to 10 wt.% of e) at least one finely divided wax, wherein the composition is characterized in that it is essentially free of nitrate anions and essentially free of hexavalent chromium (Cr(VI)).

2. The composition according to claim 1 having a pH of 7.0 to 8.5 and comprising, based on the weight of the composition: 15 to 40 wt.% of a) the at least one base polymer selected from the group of acrylic polymers and polyurethane polymers; 0.1 to 2.0 wt.% of b) the Cr(III) ions, calculated as Cr; 0.1 to 1.0 wt.% of c) ascorbic acid; 0.1 to 2.0 wt.% of d) the at least one aluminum compound selected from the group of aluminum hydroxide, aluminum meta-hydroxide, aluminum trichloride, aluminum alcoholate, aluminum glycolate, aluminum tris(beta-keto), aluminum tris(beta-keto ester), aluminum soaps and aluminum carboxylates; 1 to 8 wt.% of e) the wax; and 10 to 50 wt.% of water, wherein the composition is characterized in that it is essentially free of nitrate anions and essentially free of hexavalent chromium (Cr(VI)).

3. The composition according to claim 1 or 2, wherein the acrylic polymer is characterized by at least one of the following: a glass transition temperature of -30 °C to 60 °C or a weight average molecular weight (Mw) of 50000 to 500000 Dalton.

4. The composition according to claim 1 or 2, wherein the at least one base polymer is dispersed in the composition and has a monomodal particle size distribution, characterized by The average particle size (d 50 ) of the polymer particles in the aqueous dispersion is from 50 to 400 nm.

5. The composition according to claim 1 or 2, wherein the chromium(III) ions are obtained by reducing chromium(VI) provided as one or more hexavalent chromium compounds.

6. The composition according to claim 5, wherein the provided hexavalent chromium compound is selected from the group of chromium trioxide (CrO3), lithium chromate (Li2CrO4), lithium dichromate (Li2Cr2O7), sodium chromate (Na2CrO4), sodium dichromate (Na2Cr2O7), potassium chromate (K2CrO4), potassium dichromate (K2Cr2O7), ammonium chromate ((NH4)2CrO4), ammonium dichromate ((NH4)2Cr2O7), magnesium chromate (MgCrO4), magnesium dichromate (MgCr2O7), calcium chromate (CaCrO4), calcium dichromate (CaCr2O7), zinc chromate (ZnCrO4), zinc dichromate (ZnCr2O7) and mixtures thereof.

7. The composition according to claim 5, wherein the provided hexavalent chromium compound is selected from the group of chromium trioxide (CrO3), sodium chromate (Na2CrO4), sodium dichromate (Na2Cr2O7), potassium chromate (K2CrO4), potassium dichromate (K2Cr2O7) and mixtures thereof.

8. The composition according to claim 1 or 2, wherein the molar ratio of ascorbic acid : aluminum is not more than 1 :

1.

9. The composition according to claim 8, wherein the molar ratio of ascorbic acid : aluminum is not more than 1 :

2.

10. The composition according to claim 8, wherein the molar ratio of ascorbic acid : aluminum is not more than 1 :

3.

11. The composition according to claim 8, wherein the amount of aluminum is derived from d) the at least one aluminum compound of the composition.

12. The composition according to claim 1 or 2, wherein d) the at least one aluminum compound is selected from the group of aluminum tricarboxylates (Al(OOCR)3), aluminum monohydroxydicarboxylates ((RCOO)2Al(OH)) and aluminum dihydroxymonocarboxylates (RCOOAl(OH)2), wherein R is a C1-C8 alkyl group.

13. The composition according to claim 1 or 2, wherein e) the wax fulfils at least one of the following conditions: an acid value of less than 200 mg KOH / g; a melting point of 40 to 200 °C; and a number average molecular weight (Mn) of at least 200 g / mol.

14. The composition according to claim 13, wherein the acid value is less than 100 mg KOH / g.

15. The composition according to claim 13, wherein the number average molecular weight (Mn) is at least 400 g / mol.

16. The composition according to claim 1 or 2, wherein e) the wax is provided in micronized form or as an aqueous dispersion, the micronized form being characterized by a d 50 particle size of less than 5 microns, the particles of the dispersion being characterized by a d 50 particle size of less than 1 micron.

17. The composition according to claim 1 or 2, wherein the composition is characterized by being essentially free of peroxide and persulfate compounds.

18. The composition according to claim 1 or 2, which is obtained in the following way: mixing a fraction comprising hexavalent chromium dissolved in water as component b) with ascorbic acid according to component c); and thereafter; adding the components a), d) and e) to the mixture.

19. A method of imparting a chromate passivation film to a substrate, wherein the substrate has been applied with a zinc or zinc alloy coating on at least one of its surfaces, the method comprising contacting the at least one coated surface of the substrate with an aqueous composition as defined in one of claims 1 to 18 at a temperature of 20 °C to 90 °C for a period of time sufficient to form a passivation film thereon.

20. A passivated substrate obtained by the method as defined in claim 19.

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