Alkaline reaction rinse liquor for decorative autophoretic coatings

Abstract

The present invention relates to an aqueous rinsing composition having a pH of 8 to 12 obtained by forming a mixture comprising: i) at least one inorganic base; ii) at least one water-soluble compound according to general formula (IIA) or a water-soluble salt thereof, where R1, R2 and R3 are independently selected from H or C1-C6 alkyl, and / or at least one water-soluble compound according to general formula (IIB) or a water-soluble salt thereof, where R4 is selected from H or C1-C6 alkyl; iii) at least one water-soluble polyphosphonic acid or a water-soluble salt thereof wherein the polyphosphonic acid has the general formula (III) wherein n is at least 2 and Z is an organic linking moiety having an effective valence of n, further wherein the polyphosphonic acid is characterized in that at least two phosphonic acid groups are separated by an alkylene bridge having 1 or 2 carbon atoms (C1-C2 alkylene); and iv) water. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to aqueous rinse compositions for treating autodeposition coatings on active metal substrates. More specifically, the present invention relates to aqueous rinse compositions having a pH of 8 to 12 for treating uncured autodeposition coatings on ferrous metal substrates. Background Art

[0002] Autodeposition has been used commercially on ferrous metal substrates such as steel for over thirty years and is now well established. The autodeposition process is often contrasted with electrodeposition: although each of the methods can produce an adherent film on a substrate with similar performance characteristics, the dispersions used in the methods and the mechanisms of depositing the film are significantly different. Electrodeposition requires that the metal or other article to be coated be connected to a DC power source in order to be coated: in autodeposition no such external current is used, which offers the advantage of a simpler and generally cheaper operation compared to methods requiring the application of a voltage, and also enables more efficient coating of the edges and cavities of the target substrate.

[0003] The autodeposition composition is generally a weakly acidic aqueous solution, suspension, emulsion or dispersion of a resin or polymer. The composition is generally placed in a bath where it is stable to precipitation or flocculation of the resin or polymer without contact with an active metal. However, when a substrate having an active metal surface is inserted into the bath, those surfaces become coated with an adherent resin or polymer film. For completeness, the term "active metal" is defined herein as a metal that spontaneously begins to dissolve at a substantial rate when introduced into an autodeposition composition. More specifically, for an active ferrous metal substrate, a weakly acidic bath reacts with the ferrous substrate to produce positively charged iron ions at the substrate surface; these cations react with negatively charged latex particles in the bath to form a deposit on the surface of the steel. The deposited wet film is adhesive but porous, allowing the acid and iron ions to continue to diffuse and form additional coatings. Since the process is diffusion controlled, coverage is fairly uniform across the workpiece. The longer the metal remains in the bath, the more the film thickness increases, but eventually the wet film solids tightly bind to the point where no more ion diffusion occurs and the reaction ceases.

[0004] After removal from the coating bath, the adhered film is typically thermally cured. The peak metal temperature (PMT) characterizes the thermal curing process. Higher peak metal temperatures, greater than 200°C, can provide cured coatings with favorable chemical and thermal resistance, but there are obviously concomitant tradeoffs associated with the energy consumption required to reach these high temperatures. Conversely, compositions cured at low peak metal temperatures (e.g., 130°C or less) may be characterized by poor thermal stability, poor storage stability, poor corrosion resistance, and poor chemical resistance.

[0005] Guidance on self-deposition can be found in the following documents, among others: U.S. Pat. No. 3,063,877; U.S. Pat. No. 3,585,084; U.S. Pat. No. 3,592,699; and EP 0624182A1 (Henkel Corporation). In addition, exemplary epoxy-based self-deposition coating systems are described in U.S. Pat. No. 4,180,603; U.S. Pat. No. 4,289,826; U.S. Pat. No. 5,500,460; U.S. Pat. No. 7,388,044; U.S. Patent Application Publication No. 2003 / 0068498A1 (Weller et al.); U.S. Patent Application Publication No. 2018 / 0304306A1; and International Patent Application Publication No. WO 00 / 71337.

[0006] Faced with the need to optimize the corrosion resistance, functionality and / or appearance of self-deposited films, the authors have developed three main strategies: (i) chemical pretreatment of the substrate surface before forming the coating film; (ii) purposefully selecting a specific resin to form the coating film; and (iii) chemical post-treatment of the uncured coating film. The present disclosure relates to the last of these strategies.

[0007] US2002 / 102356A1 (Agarwal et al.) discloses a method for improving the corrosion resistance of a metal surface having a cured autodeposition coating adhered thereto, the method comprising contacting an uncured autodeposition coating present on the metal surface with an acidic aqueous rinse solution comprising an amount of at least one source of metal cations selected from Group IIA or Group IIB metal cations and at least one phosphate source.

[0008] CA 2,199,983A1 (Henkel Corporation) discloses a method for providing a metal substrate with a protective coating comprising an organic binder, the method comprising the steps of: (a) contacting the metal substrate with a liquid autodeposition composition for a time sufficient to form a wet adherent film comprising an organic binder deposited from the autodeposition composition on the surface of the metal substrate; (b) removing the substrate having the wet adherent film formed in step (b) from further contact with the autodeposition composition and contacting the wet adherent film with an aqueous liquid rinsing solution comprising water and anions, the anions consisting of: (i) at least four fluorine atoms and (ii) atoms of at least one element selected from titanium, zirconium, hafnium, silicon and boron, and optionally (iii) one or more oxygen atoms; and (c) separating the substrate having the wet adherent film modified by the contact in step (B) from the aqueous liquid rinsing solution used in step (B), and subsequently drying the wet film on the substrate in situ to form a dry film.

[0009] U.S. Pat. No. 5,248,525A (Siebert) discloses a method for forming a self-depositing organic coating on a metal portion of a surface of an object, the method comprising the following steps: i) contacting the metal surface to be coated with a liquid self-depositing composition to produce an uncured intermediate coating thereon; ii) before drying the uncured intermediate coating, contacting it with an aqueous solution having a pH between about 7 and about 11 and containing about 0.05 wt. % to about 5 wt. % of anions of a polyfunctional organic acid selected from 1,1-diphosphonic acid, citric acid, tartaric acid and oxalic acid; and iii) drying the uncured intermediate coating to produce a final self-depositing organic coating.

[0010] When the coated surface is removed from the autodeposition bath and rinsed with water, the coating remains permeable: this permeability is believed to be caused by iron that is not bound to the latex particles within the autodeposition coating. Most of the above chemical rinses aim to remove or precipitate the iron, thereby sealing the coating film. However, these methods may not be completely effective, and residual uncomplexed iron (particularly uncomplexed Fe 3+ ) can adversely affect the color and appearance of the coating after it cures. Such discoloration can be noticeable when the coating film is to be finished with a clear coat or a light-colored coating. One of ordinary skill in the art will recognize that finishing with a colored coating can mitigate the discoloration caused by the presence of iron, but this may not be appropriate in many applications.

[0011] Therefore, it is considered desirable to provide a novel rinse composition which can effectively remove uncomplexed iron from autodeposition coatings on ferrous metal substrates without compromising the stability of the uncured coating film and the adhesion and corrosion resistance of the cured film obtained therefrom. Summary of the invention

[0012] According to a first aspect of the present invention, there is provided an aqueous rinse composition having a pH of 8 to 12 obtained by forming a mixture comprising:

[0013] i) at least one inorganic base;

[0014] ii) at least one water-soluble compound according to the general formula (IIA) or a water-soluble salt thereof:

[0015]

[0016] Where: R 1 , R 2 and R 3 are the same or different and are independently selected from H or C1-C6 alkyl; and / or

[0017] At least one water-soluble compound according to the general formula (IIB) or a water-soluble salt thereof:

[0018]

[0019] Where: R 4 Selected from H or C1-C6 alkyl;

[0020] iii) at least one water-soluble polyphosphonic acid or a water-soluble salt thereof, wherein the polyphosphonic acid has the general formula (III):

[0021]

[0022] Where: n is at least 2; and

[0023] Z is an organic linking moiety with an effective valence of n,

[0024] Further wherein the polyphosphonic acid is characterized in that at least two phosphonic acid groups are separated by an alkylene bridge having 1 or 2 carbon atoms (C1-C2 alkylene); and

[0025] iv) Water.

[0026] In an important embodiment, the aqueous rinse composition has a pH of 9 to 11 and is obtained by forming a mixture comprising, based on the total weight of the composition:

[0027] 5-20 wt. %, preferably 5-15 wt. %, more preferably 5-10 wt. % of i) the at least one inorganic base;

[0028] 10-50 wt. %, preferably 15-40 wt. %, more preferably 20-40 wt. % of component (part) ii);

[0029] 5-30 wt. %, preferably 5-15 wt. %, more preferably 10-15 wt. % of iii) at least one water-soluble polyphosphonic acid of general formula (III) or a water-soluble salt thereof; and

[0030] 30-80 wt. %, preferably 40-70 wt. %, more preferably 40-60 wt. % iv) water.

[0031] In an illustrative embodiment, the aqueous rinse composition has a pH of 9 to 11 and is obtained by forming a mixture comprising, based on the total weight of the composition:

[0032] 5-20 wt. %, preferably 5-15 wt. %, more preferably 5-10 wt. % of i) the at least one inorganic base;

[0033] 10-50 wt. %, preferably 15-40 wt. %, more preferably 20-40 wt. % of ii) at least one substituted amine compound according to formula (IIA) or a water-soluble salt thereof;

[0034] 5-30 wt. %, preferably 5-15 wt. %, more preferably 10-15 wt. % of iii) at least one water-soluble polyphosphonic acid of general formula (III) or a water-soluble salt thereof; and

[0035] 30-80 wt. %, preferably 40-70 wt. %, more preferably 40-60 wt. % iv) water.

[0036] It will be clear to those skilled in the art that in certain embodiments a neutralization reaction will occur within the mixture between the base (component i)) and any free acid added in component iii). However, the molar concentrations of the added components of the mixture must be selected to meet the alkaline pH conditions of the aqueous rinse composition.

[0037] Without intending to be bound by theory, it is believed that: at the pH, one or more of the compounds of ingredient ii) (hydroxylamine, substituted hydroxylamine, nitroguanidine, substituted nitroguanidine, and mixtures thereof) act to reduce the Fe(III) ions present in the autodeposition film on the iron-containing metal substrate: the Fe(II) ions obtained can then be complexed by the polyphosphonate anions present in the aqueous rinse composition. The complex formed is stable and can be washed out of the film to achieve the desired appearance.

[0038] Preferably, the at least one inorganic base of i) of the mixture is selected from the group consisting of: sodium carbonate; potassium carbonate; sodium hydroxide; potassium hydroxide; sodium metasilicate; and potassium metasilicate. Particularly preferably, component i) of the mixture comprises or consists of sodium hydroxide.

[0039] Independently or in addition to these preferred statements about the base, it is preferred that component ii) of the mixture consists of at least one compound selected from the group consisting of hydroxylamine (NH2-OH); N-methylhydroxylamine; N,N-dimethylhydroxylamine; N-isopropylhydroxylamine; N,N-diethylhydroxylamine; nitroguanidine; 1-methyl-3-nitroguanidine; and 1-ethyl-3-nitroguanidine. It is particularly preferred that component ii) comprises hydroxylamine (NH2-OH), nitroguanidine, or a mixture thereof, or consists of hydroxylamine (NH2-OH), nitroguanidine, or a mixture thereof.

[0040] Likewise, independently or in addition to the preferred statements for components i) and ii) of the mixture, it is preferred that the at least one water-soluble polyphosphonic acid of iii) is selected from the group consisting of: aminotri(methylenephosphonic acid) (ATMP); 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP); hexamethylenediaminetetra(methylenephosphonic acid) (HDTMP); diethylenetriaminepenta(methylenephosphonic acid); and diethylenetriaminepenta(methylenephosphonic acid) (DTPMP). It is particularly preferred that component iii) comprises or consists of 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP).

[0041] According to a second aspect of the present invention there is provided the use of an aqueous rinse composition as defined above and in the appended claims for rinsing a coating film applied to a ferrous metal substrate.

[0042] The present invention also provides a method of providing a ferrous metal substrate with a protective coating comprising an organic binder, the method comprising:

[0043] contacting the ferrous metal substrate with a liquid autodeposition composition for a time sufficient to form an adherent film coating comprising a curable organic binder deposited from the autodeposition composition on at least one surface of the substrate;

[0044] separating the coated ferrous metal substrate from the liquid autodeposition composition;

[0045] subjecting the adhesive film coating to a rinsing phase, wherein the rinsing phase comprises at least one rinsing step using an aqueous rinsing composition as defined above and in the appended claims; and

[0046] The organic binder contained in the rinsed adhesive film coating is cured.

[0047] The rinsing phase may consist of a single rinsing step or of multiple rinsing steps. However, although more than one rinsing liquid may be used in a multi-step process, it is essential that at least one rinsing step using an aqueous rinsing composition of the present invention is performed. For the final step of a multi-step rinsing phase, it is particularly preferred to use an aqueous rinsing composition of the present invention.

[0048] In an important embodiment, a method of providing a ferrous metal substrate with a protective coating comprising an organic binder comprises the steps of:

[0049] pretreating the ferrous metal substrate to remove foreign matter from its surface;

[0050] contacting the ferrous metal substrate with a liquid autodeposition composition for a time sufficient to form an adherent film coating comprising a curable organic binder deposited from the autodeposition composition on at least one surface of the substrate;

[0051] separating the coated ferrous metal substrate from the liquid autodeposition composition;

[0052] subjecting the adhesive film coating to a rinsing phase having a plurality of rinsing steps, wherein the rinsing phase comprises at least one rinsing step using an aqueous rinsing composition as defined above and in the appended claims, and wherein the rinsing phase is further characterized in that the rinsing step using the aqueous rinsing composition as defined constitutes the final step of the phase; and

[0053] The organic binder contained in the rinsed adhesive film coating is cured.

[0054] A final aspect of the present invention provides a ferrous metal substrate obtainable according to a coating process as defined hereinabove and in the appended claims.

[0055] definition

[0056] As used herein, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise.

[0057] As used herein, the terms "comprising / comprises / comprised of" are synonymous with "including / includes" or "containing / contains," are inclusive or open-ended, and do not exclude additional unrecited members, elements, or method steps. If used, the phrase "consisting of is closed-ended and excludes all additional elements. Furthermore, the phrase "consisting essentially of excludes additional essential elements, but allows for the inclusion of insubstantial elements that do not materially change the nature of the invention.

[0058] When amounts, concentrations, sizes 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 any range that can be obtained by combining any upper limit or preferred value with any lower limit or preferred value is also specifically disclosed, regardless of whether the obtained range is explicitly mentioned in the context.

[0059] The words "preferable / preferred / preferably", "particularly / especially", and "desired" and their synonyms are generally used herein to refer to embodiments of the present disclosure that may provide particular benefits in certain circumstances. However, the recitation of one or more preferred, preferred, particular, or desired embodiments does not mean that other embodiments are not useful, and is not intended to exclude those other embodiments from the scope of the present disclosure.

[0060] As used throughout this application, the words "may" are used in a permissive sense (ie, meaning having the potential to), rather than in a mandatory sense.

[0061] As used herein, the phrase "and / or" should be understood to mean "either or both" of the elements so connected (i.e., elements that exist in conjunction in some cases and separately in other cases). The expressions "at least one" and "one or more" are also intended to be both conjunctive and separate in the operation of this document.

[0062] For a given part of the mixture or composition, the term "comprising at least one of", "consisting of at least one of", followed by a listing of items, does not mean that each item in the listing is required. Instead, it means that one or more of the listed items may constitute the specified part. For example, if it is the part "A comprises at least one of compounds a, b and c", it means: (i) A may comprise a; (ii) A may comprise b; (iii) A may comprise c; (iv) A may comprise a and b; (v) A may comprise a and c; (vi) A may comprise b and c; or (vii) A may comprise a, b and c. Similarly, the statement "A comprises at least one compound selected from a, b and c" means: (i) A may comprise a; (ii) A may comprise b; (iii) A may comprise c; (iv) A may comprise a and b; (v) A may comprise a and c; (vi) A may comprise b and c; or (vii) A may comprise a, b and c.

[0063] In the context of reference to the periodic table and its groups, this is intended to mean https: / / iupac.org / what-we- do / periodic-table-of-elements / Table shown.

[0064] As used herein, room temperature is 23°C ± 2°C.

[0065] As used herein, the number average molecular weight (Mn) and weight average molecular weight (Mw) are determined by gel permeation chromatography (GPC) according to DIN 55672-1:2007-08 with tetrahydrofuran (THF) as eluent. The term polydispersity (PD) is derived from Mw and Mn and is calculated as (Mw / Mn).

[0066] As used herein, “d 50 "Particle size" means a particle size distribution such that at least 50% by weight of the particles have a particle diameter less than the specified value. Unless otherwise stated, particle size is determined by laser diffraction.

[0067] As used herein, the term "aqueous rinse composition" refers to the composition that actually contacts the metal substrate. As is known in the art, such contact can occur in a so-called "bath", which is shaped, sized, and arranged so that at least a portion of the substrate can be immersed therein. In addition, the bath should be sized to allow the aqueous rinse composition to move around and throughout the loaded substrate, which movement 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 of the substrate are variables that have an impact on the result (result effective variable), which should be monitored manually or automatically as much as possible.

[0068] As used herein, "pH" refers to a measure of the effective concentration of hydrogen ions in a solution: pH = -log [H + ]. pH can be measured by a standard pH meter comprising a glass electrode connected to an electronic meter; the pH meter is calibrated using aqueous standard pH buffers.

[0069] As used herein, the term "alloy" refers to a substance composed of two or more metals, or of a metal and a non-metal, which have been intimately combined (usually by melting together and dissolving in each other when melted). Thus, the term "X alloy" refers to an alloy in which metal X is the major constituent component, and in which X will typically comprise at least 40 weight percent, more typically at least 50 weight percent, or at least 60 weight percent of the alloy, based on the metal.

[0070] As used herein, “C1-C n"Alkyl" refers to a monovalent group containing 1 to n carbon atoms, which is a radical of an alkane and includes straight-chain and branched organic radicals. Thus, "C1-C 18 "Alkyl" refers to a monovalent group containing 1-18 carbon atoms, which is a radical of an alkane and includes 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 the present invention, such alkyl groups may be unsubstituted or may be substituted with one or more halogens. When applicable to a given portion (R), the specification will indicate the tolerance for one or more non-halogen substituents in the alkyl group.

[0071] As used herein, the term "alkylene" is defined as a saturated divalent hydrocarbon radical. Generally, in the present disclosure, such alkylene groups may be unsubstituted or may be substituted with one or more halogens.

[0072] As used herein, the term "base" refers to a substance that is capable of abstracting a proton in a polar or nonpolar solvent; or that is capable of donating a hydroxide anion (OH - ).

[0073] The term "amine" is used according to its ordinary meaning in the art, and broadly refers to a compound containing a nitrogen atom with a lone pair of electrons.

[0074] In this context, the viscosity of the composition is determined under standard conditions of 25° C. and 50% relative humidity (RH). In this context, the viscosity is measured using a PhysicaRheometer MCR 300 measuring system featuring a PP 20 spindle and a measuring gap of 0.2 mm.

[0075] The compositions of the present invention may be defined herein as being "substantially free of" certain compounds, elements, ions, or other similar components. The term "substantially free of" is intended to mean that the compounds, elements, ions, or other similar components are not intentionally added to the composition, and are present at most in trace amounts that will 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 of" encompasses the term "free of", which latter term represents those embodiments in which the specified compounds, elements, ions, or other similar components are not present in the composition at all, or are not present in any amount measurable by techniques commonly used in the art. DETAILED DESCRIPTION

[0076] i) Base

[0077] When forming the aqueous rinse composition of the present invention, the prepared mixture contains at least one inorganic base. The one or more inorganic bases should be included in an amount such that the pH of the aqueous rinse composition is from 8 to 12, especially from 9 to 11. Subject to this pH characteristic, the mixture may also be characterized by containing 5-20 wt %, preferably 5-15 wt % i) of the at least one inorganic base, based on the weight of the composition.

[0078] In embodiments, the mixture may contain ammonia (NH3) as a base, either independently or in combination with one or more other inorganic bases. For the sake of completeness, the composition weight of the ammonia contained in the mixture will be calculated based on NH3. Unreacted ammonia will be present in the aqueous composition of the present invention as an ammonia solution NH3(aq), which encompasses a weakly alkaline solution of ammonia in water, which may be referred to in the art as ammonium hydroxide, ammonia water, ammonia liquor, liquid ammonia (aqua ammonia), aqueous ammonia (aqueous ammonia), or simply ammonia. Although the term "ammonium hydroxide" refers to an aqueous ammonia solution having a composition of [NH4 + ][OH - ] base, but it is practically impossible to separate NH4OH samples because these ions do not constitute a significant part of the total amount of ammonia in the ammonia solution, except in the case of extremely dilute ammonia solutions.

[0079] In another embodiment, which is not intended to be mutually exclusive with the embodiments given above, the mixture may comprise at least one inorganic base having the following general formula:

[0080] (Z1 x- ) m (Z2 y+ ) n (I)

[0081] Wherein: Z2 represents a metal selected from Groups 1 to 13 of the Periodic Table of Elements;

[0082] Z1 x- Indicates selected from CO3 2- OH - 、HCO3 2- 、SiO3 - 、HPO4 2- PO4 3- and B4O7 2- anion of anion;

[0083] x is 1, 2, or 3;

[0084] y is 1, 2, 3, or 4;

[0085] m and n independently represent 1, 2, 3, or 4; and

[0086] n*y=m*x.

[0087] Regarding the formula (I), it is preferred that: Z2 represents a metal selected from Group 1 and Group 2 of the Periodic Table of Elements; Z1 x- Indicates selected from CO3 2- OH - and SiO3 2- an anion of an ion; x is 1; y represents 1 or 2; m and n independently represent 1 or 2; and n*y=m*x.

[0088] Exemplary but non-limiting inorganic bases that may be present alone or in combination include: sodium carbonate; potassium carbonate; sodium hydroxide; potassium hydroxide; sodium metasilicate; and potassium metasilicate. The use of sodium hydroxide may be mentioned as preferred.

[0089] ii) water-soluble hydroxylamine, substituted hydroxylamine, nitroguanidine, or substituted nitroguanidine

[0090] The mixture preferably comprises 10-50 wt%, such as 15-40 wt%, or 20-40 wt%, based on the weight of the composition, of component ii), consisting of:

[0091] ii) a) at least one substituted amine compound according to formula (IIA) or a water-soluble salt thereof

[0092]

[0093] Where: R 1 , R 2 and R 3 may be the same or different and are independently selected from H or C1-C6 alkyl; and / or ii) b) at least one water-soluble compound according to formula (IIB) or a water-soluble salt thereof

[0094]

[0095] Where: R 4 Selected from H or C1-C6 alkyl.

[0096] In an embodiment, the component ii) consists of at least one substituted amine compound according to formula (IIA) or a water-soluble salt thereof.

[0097] Exemplary salts of the compound of formula (IIA) include, but are not limited to: hydrochloride (NR 1 R 2 (OR 3 ).HCl); sulfate; and phosphate. With respect to formula (IIA), it is preferred that R 1 , R 2 and R 3is independently selected from H or C1-C4 alkyl. 3 is H, and R 1 and R 2 In a particularly preferred embodiment, R 1 , R 2 and R 3 Each is H.

[0098] Exemplary compounds according to formula (IIA) include: hydroxylamine (NH2-OH); N-methylhydroxylamine; N,N-dimethylhydroxylamine; N-isopropylhydroxylamine; and N,N-diethylhydroxylamine, which can be added individually or in combination to form a mixture from which the aqueous rinse composition is obtained. Note that the presence of hydroxylamine in the aqueous rinse composition is particularly preferred.

[0099] Regarding formula (IIB), it is preferred that R 4 is selected from H or C1-C4 alkyl. In an embodiment, R 4 is selected from H or C1-C2 alkyl. In a particularly preferred embodiment, R 4 It is H or methyl.

[0100] Exemplary compounds according to formula (IIB) include: nitroguanidine; 1-methyl-3-nitroguanidine; and 1-ethyl-3-nitroguanidine, which can be added individually or in combination to form a mixture from which the aqueous rinse composition is obtained.

[0101] iii) polyphosphonic acid or its water-soluble salt

[0102] Another essential component of the mixture of the present invention is iii) at least one water-soluble polyphosphonic acid or a water-soluble salt thereof, wherein the polyphosphonic acid has the general formula (III):

[0103]

[0104] in:

[0105] n is at least 2; and

[0106] Z is an organic linking moiety with an effective valence of n,

[0107] The polyphosphonic acids are characterized in that at least two phosphonic acid groups are separated by an alkylene bridge having 1 or 2 carbon atoms (C1-C2-alkylene).

[0108] In a particular embodiment, n is an integer from 2 to 5, or preferably 2 or 3. Most desirably, the polyphosphonic acid is selected from the group consisting of: aminotri(methylenephosphonic acid) (ATMP); 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP); hexamethylenediaminetetra(methylenephosphonic acid) (HDTMP); diethylenetriaminepenta(methylenephosphonic acid); diethylenetriaminepenta(methylenephosphonic acid) (DTPMP); and mixtures thereof. It should be noted that 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) is particularly preferred.

[0109] Suitable water-soluble salts of the above polyphosphonic acids include sodium, potassium, calcium, magnesium, ammonium, triethanolammonium, diethanolammonium and monoethanolammonium salts.

[0110] The polyphosphonic acid or a water-soluble salt thereof is preferably included in the mixture in an amount of 5-30 wt%, such as 5-15 wt%, or 10-15 wt%, based on the weight of the composition.

[0111] Auxiliary ingredients

[0112] The aqueous rinse compositions of the present disclosure may also contain adjuvants and additives that can impart improved properties to these compositions. The adjuvants and additives may, for example, impart one or more of: reduced drying time; reduced corrosivity; improved stability; and longer shelf life of the composition.

[0113] Such additives and adjuvants may include, for example: corrosion inhibitors, such as dialkylthioureas, gallstones, and copper sulfate; defoamers; water-miscible cosolvents; chelating agents; surfactants; and mixtures thereof. As further exemplary corrosion inhibitors, the following commercial materials may be mentioned: series; available from Clariant AG series; and available from Akzo Nobel Surfactants LLC series.

[0114] Additives and adjuvants may be mixed with components i) to iv) simultaneously to form the above mixture, and thus may be present during any neutralization reaction occurring within the mixture. Alternatively, additives or adjuvants may be added after mixing of components i) to iii) and, if applicable, the neutralization reaction. In the case where the neutralization reaction is exothermic, the solution formed may be allowed to cool before mixing the additive or adjuvant.

[0115] The adjuvants and additives may be used in such combinations and proportions as desired, provided that they do not adversely affect the characteristics and essential properties of the composition. Although exceptions may exist in some cases, these adjuvants and additives should not total more than 5% by weight of the total weight of the aqueous rinse composition.

[0116] Exemplary Aqueous Rinse Composition Formulations

[0117] In a first exemplary embodiment, which is not intended to limit the present invention, there is provided an aqueous rinse composition having a pH of 9 to 11 obtained by forming a mixture, the mixture comprising, based on the total weight of the composition:

[0118] 5-15 wt. %, preferably 5-10 wt. % of i) at least one inorganic base selected from sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, sodium metasilicate and potassium metasilicate;

[0119] 15-40% by weight, preferably 20-40% by weight, of ii) at least one compound selected from hydroxylamine (NH2-OH), N-methylhydroxylamine, N,N-dimethylhydroxylamine, N-isopropylhydroxylamine, N,N-diethylhydroxylamine, nitroguanidine, 1-methyl-3-nitroguanidine and 1-ethyl-3-nitroguanidine;

[0120] 5 to 15% by weight, preferably 10 to 15% by weight, of iii) at least one water-soluble polyphosphonic acid selected from aminotri(methylenephosphonic acid) (ATMP), 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), hexamethylenediaminetetra(methylenephosphonic acid) (HDTMP), diethylenetriaminepenta(methylenephosphonic acid) and diethylenetriaminepenta(methylenephosphonic acid) (DTPMP); and

[0121] iv) 40-70% by weight, preferably 40-60% by weight, of water.

[0122] In a second exemplary embodiment, which is not intended to limit the present invention, there is provided an aqueous rinse composition having a pH of 9 to 11 obtained by forming a mixture, the mixture comprising, based on the total weight of the composition:

[0123] 5-15 wt. %, preferably 5-10 wt. % of i) at least one inorganic base selected from sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide;

[0124] 15-40 wt %, preferably 20-40 wt % of ii) at least one of hydroxylamine (NH2-OH) and nitroguanidine;

[0125] 5 to 15% by weight, preferably 10 to 15% by weight, of iii) at least one water-soluble polyphosphonic acid selected from aminotri(methylenephosphonic acid) (ATMP), 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), hexamethylenediaminetetra(methylenephosphonic acid) (HDTMP), diethylenetriaminepenta(methylenephosphonic acid) and diethylenetriaminepenta(methylenephosphonic acid) (DTPMP); and

[0126] iv) 40-70% by weight, preferably 40-60% by weight, of water.

[0127] In particular, good results have been obtained using aqueous rinse compositions having a pH of 9 to 11 obtained by forming a mixture comprising, based on the total weight of the composition:

[0128] 5-10 wt. % i) sodium hydroxide;

[0129] 20-40 wt. % of ii) hydroxylamine (NH2-OH);

[0130] 10-15 wt. % of iii) 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP); and

[0131] iv) 40-60 wt. % water.

[0132] Preparation of aqueous compositions

[0133] The aqueous composition is prepared by simply mixing the ingredients. If desired, the composition can be prepared long before its application. However, in an interesting alternative embodiment, a concentrated composition can first be obtained by mixing ingredients i) to iii) with only a portion of the water that will be present in the applied composition: the concentrated composition can then be diluted with the remaining water shortly before its use. It is believed that such concentrated compositions can be prepared and stored as a single-pack concentrate (which can be converted by diluting with water alone) or as a multi-part concentrate (two or more of which must be combined and diluted to form a complete working composition according to the present invention). Any dilution can be achieved simply by adding water (particularly deionized water and / or demineralized water) under mixing. The composition can also be prepared in a rinse stream, whereby one or more streams of one or more concentrates are injected into a continuous stream of water.

[0134] It is not particularly intended to limit the amount of water contained in the aqueous composition, preferably, the composition comprises 30-80 wt. %, preferably 40-70 wt. %, more preferably 40-60 wt. % of water, based on the weight of the composition. In an alternative but not mutually exclusive characterization, the aqueous composition can be defined by a viscosity of 5 to 1000 mPa.s, for example 5 to 500 mPa.s, measured at 25° C. and 50% relative humidity.

[0135] Methods and Applications

[0136] The use of the aqueous rinsing composition of the present invention will be described in terms of autodeposition coatings of active ferrous metal substrates. As will be appreciated by those skilled in the art, prior to applying an autodeposition coating to an active ferrous metal substrate, it is generally advisable to pretreat the relevant surface to remove foreign matter therefrom: if applicable, this step can facilitate subsequent adhesion of the composition thereto. Such treatments are known in the art and can be performed in a single-stage or multi-stage manner consisting of, for example, the use of one or more of the following: etching treatment with an acid suitable for the substrate and an optional oxidizing agent; ultrasonic treatment; plasma treatment, including chemical plasma treatment, corona treatment, atmospheric pressure plasma treatment and flame plasma treatment; immersion in an aqueous alkaline degreasing bath; treatment with an aqueous cleaning emulsion; treatment with a cleaning solvent (such as acetone, carbon tetrachloride or trichloroethylene); and water rinsing, preferably with deionized or demineralized water. In those cases where an aqueous alkaline degreasing bath is used, any degreasing agent remaining on the surface should desirably be removed by rinsing the substrate surface with deionized or demineralized water.

[0137] After any pretreatment(s) that may have been applied, the active ferrous metal substrate is contacted with a liquid autodeposition coating composition containing a curable organic binder, optionally with one or more autodeposition promoters, for a time sufficient to form an adherent film coating comprising a curable organic binder on at least one surface of the substrate. Such contact is typically performed in an operating bath as described above: such a bath is prepared, and the liquid autodeposition composition is applied to the substrate by, but not limited to, immersion and dipping. The contact time with the autodeposition coating composition is not critical, but should be sufficient to allow the temperature of the ferrous metal substrate to equilibrate with the temperature of the composition in the operating bath: exemplary contact times are from 1 minute to 15 minutes, for example, from 2 minutes to 10 minutes. In alternative but non-mutually exclusive characterizations of this contact step, the duration of contact between the one or more active metal surfaces and the liquid autodeposition coating composition should be sufficient to produce a wet film thickness of 10-100 microns, for example, 10-50 microns.

[0138] Alternative techniques that may be used to apply the liquid autodeposition coating composition to a single surface or multiple surfaces of a ferrous metal substrate include, but are not limited to: painting; brushing; pouring; rolling; wiping; air atomizing spraying; air-assisted spraying; airless spraying; high volume, low pressure spraying; and air-assisted airless spraying.

[0139] It should be noted here that the present application is particularly useful in the case where the liquid autodeposition coating is an aqueous composition comprising a dispersed acrylate resin. As a non-limiting example, EP 0624182A1 (Henkel Corporation) discloses an aqueous autodeposition coating composition having a pH of 1.6 to 5.0, comprising: a) a water-dispersible or water-soluble organic film-forming resin selected from urethane resins, epoxy resins, polyester resins and resins containing a group of at least one monomer selected from methyl acrylate, ethyl acrylate or butyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycidyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, ethylene, styrene, vinyl chloride, vinylidene chloride, vinyl acetate, acrylic acid and methacrylic acid; b) fluoride ion or at least one of fluoride ion and complex fluoride ion; c) additional at least one metal ion selected from zinc, cobalt, manganese, nickel, iron and aluminum; d) at least one of tungstate ion and molybdate ion; and e) water. As another important example, US2003 / 0068498 A1 (Weller et al.) discloses a self-deposition composition comprising: (a) water; (b) at least one epoxy resin in dispersed form; (c) at least one acrylic resin in dispersed form; and (d) at least one epoxy curing agent. The disclosure of the pigment-free self-deposition coating compositions (CL, N and O) of the examples of Table I of EP 0624182 A1 and the disclosure of the examples of US2003 / 0068498 A1 are expressly incorporated herein by reference.

[0140] The active metal substrate having thereon a film coating of an uncured organic binder is then separated from the autodeposition coating composition and subjected to a rinsing phase comprising at least one rinsing step with an aqueous rinsing composition according to the invention. For the sake of safety, it should be noted that if it is necessary to remove adsorbed but otherwise unadhered components of the curable film coating, the rinsing phase may comprise a plurality of rinsing steps and with a plurality of different rinsing agents, but at least one rinsing step must be with an aqueous rinsing composition as defined. However, it is preferred that no rinsing with tap water, demineralized water or deionized water is performed after rinsing with the aqueous composition according to the invention, since this would reduce the positive effect of the composition.

[0141] The method of rinsing the substrate is not particularly intended to be limited: for each rinse agent, the substrate can be independently, for example: dipped or immersed in a bath thereof; roller coated with the rinse agent; sprayed with the rinse agent; treated with a mist of the agent; or a combination of said treatments can be applied. Good results have been obtained by immersing the substrate in the aqueous rinse composition of the present invention. Based on the contact time, the total duration of the rinsing phase (whether performed as one step or in multiple steps) will generally be 5-600 seconds, for example 10-300 seconds or 30-300 seconds. When relatively small concentrations of active compounds are used in the aqueous rinse composition, the contact time will necessarily be much longer than when a composition containing relatively high concentrations of said compound is used.

[0142] During the rinse process, the or each rinse agent should be maintained at a temperature of 20-100° C., for example 25-75° C. or 30-70° C. Although there are attendant energy costs to raising the temperature of the aqueous rinse composition of the invention above room temperature, coating edge coverage is generally improved by increasing the rinse temperature.

[0143] After the rinsing treatment, the organic binder applied to the ferrous metal substrate can be cured. Curing can be performed in any known manner, but will generally be achieved by heating. The choice of a specific curing temperature will depend, inter alia, on the type of binder resin, crosslinking agent and any coalescing agent used for the autodeposition coating. In addition, the surface temperature of the metal substrate should be controlled during heating: the peak metal temperature (PMT) need not exceed 300°C, and in particular should be in the range of 65 to 200°C, for example 75 to 150°C.

[0144] In general, the heating of the ferrous metal substrate may be carried out for a duration of 5 to 60 minutes, such as 10 to 50 minutes. It is contemplated that the heating itself may be performed in multiple stages, if desired. For example, in a first stage lasting 5-15 minutes, the coated substrate is heated to a peak temperature of 55° C. to 65° C. to flash off most of the residual water in the coating; and in a second stage lasting 15-55 minutes, the coated substrate is heated to a peak temperature of 65-300° C., such as 75-150° C. Preferably, the peak temperature is reached no more than 10 minutes after the first heating stage has been completed.

[0145] The above treatment should produce a cured coating on the ferrous metal substrate, the coating preferably having a coating thickness of 1 to 50 g / m 2 , preferably 1 to 40 g / m 2 or 5 to 40g / m 2 weight.

[0146] It is not intended to limit the base ferrous metal substrate to which the above-described coating method can be applied. Thus, suitable base ferrous metal substrates can include, but are not limited to: iron; alloys of iron with an element selected from boron, carbon, cerium, chromium, cobalt, copper, manganese, molybdenum, nickel, silicon, titanium, uranium, or vanadium; Elinvar (iron-nickel-chromium); Fernico (iron-nickel-cobalt); Kovar (iron-nickel-cobalt); Kanthal (iron-chromium-aluminum); and steel. Illustrative steel substrates include: cold-rolled steel; hot-rolled steel; steel plated with zinc metal, zinc compounds, or zinc alloys, such as electrogalvanized steel; hot-dip galvanized steel; galvanealed steel; and steel plated with zinc alloys. In addition, the following ferrous metal substrates comprising or consisting of steel may be specifically mentioned: galvanized steel and galvanealed steel meeting the requirements of ASTM Designation A653; A 55% Al / 43.4% Zn / 1.6% Si alloy coated steel sheet available from Bethlehem Steel Corporation; and A 5% Al / 95% Zn alloy coated steel sheet available from Weirton Steel Corporation.

[0147] The initial form of the substrate to which the above treatment method is applied need not be limited. Conventional raw material forms in which the ferrous metal substrate may be provided include: sheets; plates; cuboids; spheres; rings; solid cylinders; tubes; and wires, although more complex shapes and prefabricated forms are certainly not excluded.

[0148] Various features and embodiments of the disclosure are described in the following examples, which are intended to be representative and not limiting.

Claims

1. An aqueous rinse composition having a pH of 8 to 12 obtained by forming a mixture comprising: i) at least one inorganic base; ii) at least one water-soluble compound according to the general formula (IIA) or a water-soluble salt thereof: in: R 1 , R 2 and R 3 is independently selected from H or C1-C6 alkyl; and / or At least one water-soluble compound according to the general formula (IIB) or a water-soluble salt thereof: Where: R 4 Selected from H or C1-C6 alkyl; iii) at least one water-soluble polyphosphonic acid or a water-soluble salt thereof, wherein the polyphosphonic acid has the general formula (III): Where: n is at least 2; and Z is an organic linking moiety with an effective valence of n, Further wherein the polyphosphonic acid is characterized in that at least two phosphonic acid groups are separated by an alkylene bridge having 1 or 2 carbon atoms (C1-C2 alkylene); and iv) Water.

2. The aqueous rinse composition according to claim 1, having a pH of 9 to 11, obtained by forming a mixture, based on the total weight of the composition, comprising: 5-20 wt % of i) at least one inorganic base; 10-50 wt. % of ii) at least one compound according to formula (IIA) or a water-soluble salt thereof and / or at least one compound according to formula (IIB) or a water-soluble salt thereof; 5-30 wt% of iii) at least one water-soluble polyphosphonic acid of general formula (III) or a water-soluble salt thereof; and iv) 30-80 wt. % water.

3. The aqueous rinse composition according to claim 2, having a pH of 9 to 11, obtained by forming a mixture, based on the total weight of the composition, comprising: 5-15 wt. %, preferably 5-10 wt. % of i) the at least one inorganic base; 15-40 wt. %, preferably 20-40 wt. % of ii) the at least one compound according to the general formula (IIA) or a water-soluble salt thereof and / or the at least one compound according to the general formula (IIB) or a water-soluble salt thereof; 5-15 wt. %, preferably 10-15 wt. % of iii) at least one water-soluble polyphosphonic acid of the general formula (III) or a water-soluble salt thereof; as well as iv) 40-70% by weight, preferably 40-60% by weight, of water.

4. An aqueous rinse composition according to any one of claims 1 to 3, wherein i) the at least one inorganic base is selected from: sodium carbonate; potassium carbonate; sodium hydroxide; potassium hydroxide; sodium metasilicate; and potassium metasilicate.

5. An aqueous rinse composition according to claim 4, wherein component i) consists of sodium hydroxide.

6. An aqueous rinse composition according to any one of claims 1 to 5, wherein: R in the general formula (IIA) 1 , R 2 and R 3 is independently selected from H or C1-C4 alkyl; and R in the general formula (IIB) 4 It is H or C1-C2 alkyl.

7. An aqueous rinse composition according to claim 6, wherein component ii) of the mixture consists of at least one compound selected from the group consisting of: Hydroxylamine (NH2-OH); N-methylhydroxylamine; N,N-dimethylhydroxylamine; N-isopropylhydroxylamine; N,N-diethylhydroxylamine; nitroguanidine; 1-methyl-3-nitroguanidine; and 1-ethyl-3-nitroguanidine.

8. An aqueous rinse composition according to claim 7, wherein component ii) consists of hydroxylamine (NH2-OH), nitroguanidine, or a mixture thereof.

9. The aqueous rinse composition according to any one of claims 1 to 8, wherein n in the general formula (III) is an integer from 2 to 5, and is preferably 2 or 3.

10. An aqueous rinse composition according to any one of claims 1 to 9, wherein iii) the at least one water-soluble polyphosphonic acid is selected from: aminotri(methylenephosphonic acid) (ATMP); 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP); hexamethylenediaminetetra(methylenephosphonic acid) (HDTMP); diethylenetriaminepenta(methylenephosphonic acid); and diethylenetriaminepenta(methylenephosphonic acid) (DTPMP).

11. An aqueous rinse composition according to claim 10, wherein component iii) consists of 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP).

12. Use of an aqueous rinse composition according to any one of claims 1 to 11 for rinsing a coating film applied to a ferrous metal substrate.

13. A method of providing a ferrous metal substrate with a protective coating comprising an organic binder, the method comprising: contacting the ferrous metal substrate with a liquid autodeposition composition for a time sufficient to form an adherent film coating comprising a curable organic binder deposited from the autodeposition composition on at least one surface of the substrate; separating the coated ferrous metal substrate from the liquid autodeposition composition; subjecting the adhesive film coating to a rinsing phase, wherein the rinsing phase comprises at least one rinsing step using an aqueous rinsing composition as defined in any one of claims 1 to 11; as well as The organic binder contained in the rinsed adhesive film coating is cured.

14. The method according to claim 13, comprising the steps of: pretreating the ferrous metal substrate to remove foreign matter from its surface; contacting the ferrous metal substrate with a liquid autodeposition composition for a time sufficient to form an adherent film coating comprising a curable organic binder deposited from the autodeposition composition on at least one surface of the substrate; separating the coated ferrous metal substrate from the liquid autodeposition composition; subjecting the adhesive film coating to a rinsing phase having a plurality of rinsing steps, wherein the rinsing phase comprises at least one rinsing step using an aqueous rinsing composition as defined in any one of claims 1 to 11, and wherein the rinsing phase is further characterized in that the rinsing step using the aqueous rinsing composition as defined constitutes the final step of the phase; and The organic binder contained in the rinsed adhesive film coating is cured.

15. A ferrous metal substrate obtainable according to a method as defined in claim 13 or claim 14.

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