Water-dilutable VOC-free cleaning composition

Abstract

The present invention relates to a cleaning composition comprising: 40 to 90 wt.-% of a glycol monoalkyl ether (A) selected from the group consisting of a monoalkylene glycol monoalkyl ether (A1), a dialkylene glycol monoalkyl ether (A2), a trialkylene glycol monoalkyl ether (A3), and a tetraalkylene glycol monoalkyl ether (A4); 10 to 60 wt.-% of a hydroxycarboxylic acid (B); 0 to 10 wt.-% of a surfactant (C); and 0 to 10 wt.-% of a further component (D) different from (A), (B) and (C); all of the aforementioned components have a vapor pressure of less than 0.01 kPa at 20 DEG C, and / or an initial boiling point of greater than 250 DEG C at a pressure of 101.3 kPa; and all wt.-% values are based on the total weight of the cleaning composition, and the combined amount of all ingredients is 100 wt.-%. The invention further relates to a method for removing uncured aqueous coating material from a surface using such a cleaning composition or a diluent thereof in an aqueous medium. Furthermore, the invention relates to the use of the cleaning composition or a diluent thereof in an aqueous medium for cleaning a substrate to which an uncured aqueous coating material is adhered.

Description

[0001] The present invention relates to cleaning compositions based on a mixture of one or more water-soluble organic solvents and one or more hydroxycarboxylic acids and free of volatile organic solvents. These compositions are easy to use for removing uncured aqueous coating materials from surfaces. The present invention further relates to the use of said cleaning compositions for cleaning surfaces to which uncured aqueous coating materials are adhered. Background Art

[0002] The challenges of climate change, combined with the need to continuously increase productivity by improving process times and costs, force the automotive industry to find optimal solutions to improve any process step in the overall manufacturing process of automotive bodies or their parts.

[0003] One process step in the treatment of automotive bodies or their parts involves the step of applying an anti-corrosion coating material thereto by dip coating. Such a step includes bringing the automotive body or its parts into contact with an aqueous coating material, most often in an electro-deposition coating process. However, in the case of newly developed dip coating compositions, a dip coating process without electro-deposition is also possible.

[0004] In particular, the cathodic electro-deposition coating process is effectively used to protect the metal surfaces, edges and cavities or hard-to-reach areas of automotive bodies and their parts from corrosion. The coating materials used in such processes are aqueous and typically based on epoxy resins or acrylic resins.

[0005] Although dip coating is effective, it requires the use of a dip coating tank and, in the special case of electro-deposition coating, a so-called electro-deposition tank. Such tanks, devices and equipment must be cleaned regularly. This requires the optimal removal of the dip coating paint adhering to the surfaces, outer surfaces, but also the floors, etc. of such tanks, devices and equipment.

[0006] Therefore, there is a need to provide a very efficient paint cleaning technology that includes efficient cleaning compositions for cleaning the surfaces of such tanks and associated devices that come into contact with the coating material. These cleaning compositions should be easy to use to gently remove paint residues from various metal substrates such as stainless steel, coated steel (such as galvanized steel), etc. without damaging the equipment.

[0007] In addition to high cleaning efficiency and cleaning ability, there is a need to provide environmentally compatible cleaning compositions that are substantially free of volatile organic compounds (VOCs). These cleaning compositions are not only easy to clean dip tanks, but also easy to clean the external and internal parts of dip coating devices and equipment that have come into contact with coating materials. Effective cleaning should be achievable by dissolving paint residues adhering to the surfaces of tanks, devices (such as pipes), and equipment, especially and even when the cleaning composition is highly diluted (if diluted in an aqueous medium), not only cleaning the visible parts of such devices, but also the invisible parts. In the context of the present invention, the term "VOC-free" should be understood in accordance with EU Directive 2010 / 75 / EU (for substances that are VOC-free, a vapor pressure less than 0.01 kPa at 20 °C is required) and / or Chinese Standard GB 38508-2020 (for substances that are VOC-free, an initial boiling point greater than 250 °C at a standard pressure of 101.3 kPa is required). Summary of the Invention

[0008] The object of the present invention is achieved by providing a cleaning composition comprising:

[0009] a. 40 to 90 wt.-% of one or more glycol monoalkyl ethers (A), selected from the group consisting of monoalkylene glycol monoalkyl ethers (A1), dialkylene glycol monoalkyl ethers (A2), trialkylene glycol monoalkyl ethers (A3), and tetraalkylene glycol monoalkyl ethers (A4);

[0010] b. 10 to 60 wt.-% of one or more hydroxycarboxylic acids (B);

[0011] c. 0 to 10 wt.-% of one or more surfactants (C); and

[0012] d. 0 to 10 wt.-% of one or more additional components (D) different from (A), (B), and (C) and selected from the group consisting of secondary amines, tertiary amines, and dicarboxylic acids;

[0013] All of the above components have

[0014] i. a vapor pressure less than 0.01 kPa at 20 °C, and / or

[0015] ii. an initial boiling point greater than 250 °C at a pressure of 101.3 kPa;

[0016] All wt.-% values are based on the total weight of the cleaning composition, and the combined amount of all components is 100 wt.-%.

[0017] The above-mentioned cleaning composition and its preferred embodiments as described below are also referred to as "the cleaning composition according to the present invention", "the cleaning composition of the present invention", or "the cleaning composition of the invention".

[0018] "Vapor pressure at a temperature of 20 °C" means the pressure exerted by the vapor in a closed system that is in thermodynamic equilibrium with its condensed phase (solid or liquid) at a given temperature. The corresponding vapor pressure value is determined as described in the experimental part of the present invention. This vapor pressure must be understood as used in EU Directive 2010 / 75 / EU.

[0019] The term "initial boiling point at a pressure of 101.3 kPa" means the boiling temperature (if there is a distinct boiling point); and, if there is a boiling range, the temperature at the start of boiling. The initial boiling point must be understood as used in Chinese Standard GB / T 38597-2020. The corresponding initial boiling point value is determined as described in the experimental part of the present invention.

[0020] Another subject of the present invention is a method for removing uncured aqueous coating material from a surface, the method comprising the following steps

[0021] 1. bringing a surface to which uncured aqueous coating material adheres into contact with the cleaning composition according to the present invention or a dilution thereof in an aqueous medium; and agitating the cleaning composition or its dilution in an aqueous medium while the uncured aqueous coating material dissolves and / or disperses therein,

[0022] 2. removing from the surface the cleaning composition or its dilution in an aqueous medium and the coating material dissolved and / or dispersed therein, and

[0023] 3. rinsing the surface with an aqueous medium.

[0024] The above-mentioned method for removing uncured aqueous coating material and its preferred embodiments as described below are also referred to as "the method according to the present invention", "the method of the present invention", or "the method of the invention".

[0025] Yet another subject of the present invention is the use of the cleaning composition of the present invention for cleaning a surface to which uncured aqueous coating material adheres.

[0026] The above-mentioned use and its preferred embodiments as described below are also referred to as "the use according to the present invention", "the use of the present invention", or "the use of the invention". Detailed Description

[0027] The cleaning composition of the present invention

[0028] The cleaning composition of the present invention contains one or more of the above-mentioned glycol monoalkyl ethers (A) in an amount of 40 to 90 wt.-%, one or more of the above-mentioned hydroxycarboxylic acids (B) in an amount of 10 to 60 wt.-%, one or more of the above-mentioned surfactants (C) in an amount of 0 to 10 wt.-%; and one or more of the above-mentioned additional components (D) different from (A), (B), and (C) in an amount of 0 to 10 wt.-%; all wt.-% values are based on the total weight of the cleaning composition, and the combined amount of all components is 100 wt.-%. Any one of the foregoing (A), (B), (C), and (D) has a vapor pressure of less than 0.01 kPa at 20 °C and / or an initial boiling point of greater than 250 °C at a pressure of 101.3 kPa. Preferably, the requirements i. and ii. regarding the vapor pressure and the initial boiling point also apply to the cleaning composition.

[0029] The cleaning composition of the present invention is water-dilutable, in particular water-soluble and / or water-dispersible.

[0030] Hereinafter, the components of the cleaning composition are described in more detail.

[0031] Glycol monoalkyl ether (A)

[0032] The glycol monoalkyl ether (A) is selected from the group consisting of monoalkylene glycol monoalkyl ethers (A1), dialkylene glycol monoalkyl ethers (A2), trialkylene glycol monoalkyl ethers (A3), and tetraalkylene glycol monoalkyl ethers (A4), and they have a vapor pressure of less than 0.01 kPa at 20 °C and / or an initial boiling point of greater than 250 °C at a pressure of 101.3 kPa.

[0033] Preferably, these glycol monoalkyl ethers have at least a vapor pressure (VP) of less than 0.01 kPa at 20 °C, and more preferably, they have both a vapor pressure (VP) of less than 0.01 kPa at 20 °C and an initial boiling point (IBP) of greater than 250 °C at a pressure of 101.3 kPa.

[0034] The one or more glycol monoalkyl ethers (A) are contained in the cleaning composition of the present invention in an amount of 40 to 90 wt.-% or 50 to 90 wt.-%, preferably 55 to 85 wt.-%, more preferably 60 to 80 wt.-%, and most preferably 65 to 75 wt.-% based on the total weight of the cleaning composition of the present invention.

[0035] Monoalkylene glycol monoalkyl ether (A1)

[0036] The monoalkylene glycol monoalkyl ether is preferably selected from those having the formula HO-R-O-R aEthylene glycol monoalkyl ethers and propylene glycol monoalkyl ethers, where R-O is an ethylene oxide residue or a propylene oxide residue, preferably an ethylene oxide residue, and R a is a straight-chain or branched-chain alkyl residue having 6 to 10 carbon atoms, preferably 6 to 8 carbon atoms and most preferably 6 carbon atoms.

[0037] Therefore, the most preferred monoalkylene glycol monoalkyl ethers are ethylene glycol monohexyl ether (VP: 0.007 kPa; IBP: 208 °C) and propylene glycol monohexyl ether.

[0038] Dialkylene glycol monoalkyl ether (A2)

[0039] The dialkylene glycol monoalkyl ethers are preferably selected from the diglycol monoalkyl ethers and dipropylene glycol monoalkyl ethers having the formula HO-(R-O-)2R b where the two R-O residues are independently of each other an ethylene oxide or propylene oxide residue, and R b is a straight-chain or branched-chain alkyl residue having 4 to 10 carbon atoms, preferably 4 to 8 carbon atoms and most preferably 4 to 6 carbon atoms. Preferably, the two residues R-O are the same, and even more preferably, both residues R-O are ethylene oxide residues.

[0040] Therefore, the most preferred dialkylene glycol monoalkyl ethers are diglycol monobutyl ether (VP: <0.01 kPa; IBP: 224 °C), diglycol monopentyl ether, diglycol monohexyl ether (VP: <0.001 kPa; IBP: 240 °C), dipropylene glycol monobutyl ether (VP: 0.006 kPa; IBP: 229 °C), dipropylene glycol monopentyl ether and dipropylene glycol monohexyl ether. Diglycol monobutyl ether, diglycol monopentyl ether, diglycol monohexyl ether are even more preferred.

[0041] Trialkylene glycol monoalkyl ether (A3)

[0042] The trialkylene glycol monoalkyl ethers are preferably selected from the triglycol monoalkyl ethers and tripropylene glycol monoalkyl ethers having the formula HO-(R-O-)3R c where the three R-O residues are independently of each other an ethylene oxide or propylene oxide residue, and R c is a straight-chain or branched-chain alkyl residue having 1 to 10 carbon atoms, preferably 2 to 8 carbon atoms and most preferably 4 to 6 carbon atoms. Preferably, all the residues R-O are the same, and even more preferably, all the residues R-O are ethylene oxide residues.

[0043] Accordingly, the most preferred trialkylene glycol monoalkyl ethers are triethylene glycol monomethyl ether (VP: 0.001 kPa; IBP: 245 °C), triethylene glycol monoethyl ether (VP: <0.001 kPa; IBP: 255 °C), triethylene glycol monopropyl ether, triethylene glycol monobutyl ether (VP: <0.001 kPa; IBP: 300 °C), and tripropylene glycol monobutyl ether (VP: <0.001 kPa; IBP: 274 °C).

[0044] Tetraalkylene glycol monoalkyl ether (A4)

[0045] The tetraalkylene glycol monoalkyl ethers are preferably selected from tetraethylene glycol monoalkyl ethers and tetrapropylene glycol monoalkyl ethers having the formula HO-(R-O-)4R d wherein the four R-O residues are each independently an ethylene oxide or a propylene oxide residue, and R d is a straight-chain or branched-chain alkyl residue having 1 to 10 carbon atoms, preferably 2 to 8 carbon atoms and most preferably 4 to 6 carbon atoms. Preferably, all the residues R-O are the same, and even more preferably, all the residues R-O are ethylene oxide residues.

[0046] Accordingly, the most preferred tetraalkylene glycol monoalkyl ethers are tetraethylene glycol monomethyl ether (VP: <0.001 kPa; IBP: 280 °C), and tetraethylene glycol monobutyl ether (VP: <0.001 kPa; IBP: 300 °C).

[0047] The one or more glycol monoalkyl ethers (A) are included in the cleaning composition of the present invention in an amount of 40 to 90 wt.-% or 50 to 90 wt.-%, preferably 55 to 84.9 wt.-%, more preferably 60 to 79.8 wt.-% and most preferably 65 to 75.6 wt.-% based on the total weight of the cleaning composition of the present invention.

[0048] Among the above glycol monoalkyl ethers (A), the monoalkylene glycol monoalkyl ethers (A1), the dialkylene glycol monoalkyl ethers (A2), the trialkylene glycol monoalkyl ethers (A3); and mixtures thereof are most preferred; and among the foregoing, in the case of (A2) and (A3), the monobutyl ether and the monohexyl ether are particularly preferred, and in the case of (A1), the monohexyl ether is particularly preferred.

[0049] Even more preferred among the above glycol monoalkyl ethers (A) are the monoethylene glycol monoalkyl ethers (A1), the diethylene glycol monoalkyl ethers (A2), the triethylene glycol monoalkyl ethers (A3); and mixtures thereof; and among the foregoing, in the case of (A2) and (A3), the monobutyl ether and the monohexyl ether are particularly preferred, and in the case of (A1), the monohexyl ether is particularly preferred.

[0050] Most preferably, the one or more of the above-mentioned glycol monoalkyl ethers (A) include monoalkylene glycol monoalkyl ethers (A1) and dialkylene glycol monoalkyl ethers (A2); and mixtures thereof or consisting thereof; and among the foregoing, in the case of (A2), the monobutyl ether and the monohexyl ether are particularly preferred, and in the case of (A1), the monohexyl ether is particularly preferred.

[0051] Even more preferably, the one or more of the above-mentioned glycol monoalkyl ethers (A) include monoethylene glycol monoalkyl ether (A1) and diethylene glycol monoalkyl ether (A2); and mixtures thereof or consisting thereof; and among the foregoing, the monobutyl ether and the monohexyl ether are particularly preferred.

[0052] As the one or more of the above-mentioned glycol monoalkyl ethers (A), particularly preferred is a mixture containing at least two of the following or consisting of at least two of the following: monoethylene glycol monohexyl ether (A1), diethylene glycol monohexyl ether (A2), and diethylene glycol monobutyl ether (A2). Among the foregoing glycol monoalkyl ethers (A), diethylene glycol monohexyl ether (A2) and diethylene glycol monobutyl ether (A2) are most preferred, and thus the glycol monoalkyl ether (A) preferably contains a mixture of diethylene glycol monohexyl ether (A2) and diethylene glycol monobutyl ether (A2) or consists thereof. If the glycol monoalkyl ether (A) consists of a mixture of monoethylene glycol monohexyl ether (A1), diethylene glycol monohexyl ether (A2), and diethylene glycol monobutyl ether (A2), the combined amount of the latter two ethers (A2) is preferably in the range of 50 to 100 wt.-% based on the total amount of the glycol monoalkyl ether (A), more preferably in the range of 60 to 99 wt.-%, even more preferably in the range of 70 to 98.5 wt.-% and most preferably in the range of 80 to 98 wt.-%, and the amount of ether (A1) in the mixture is the difference from 100 wt.-% based on the total amount of the glycol monoalkyl ether (A).

[0053] Hydroxycarboxylic acid (B)

[0054] Although acetic acid and formic acid do not have effective cleaning properties, the inventors of the present invention have found that hydroxycarboxylic acids, especially monomeric hydroxycarboxylic acids, containing at least one, preferably one COOH and at least one, preferably one OH group and having a vapor pressure of less than 0.01 kPa at 20 °C, if combined with the glycol monoalkyl ether (A) as described above, are most efficient in the cleaning compositions of the present invention.

[0055] Most preferably, the hydroxycarboxylic acid is an α-hydroxycarboxylic acid, which is also denoted as α-hydroxy acid (AHA) in the literature. The α-hydroxycarboxylic acid preferably contains one or two hydroxyl groups and one, two or three carboxylic acid groups, where at least one of these hydroxyl groups is in the α-position of at least one of these carboxylic acid groups.

[0056] Among these α-hydroxy acids, monohydroxy monocarboxylic acids, monohydroxy dicarboxylic acids, monohydroxy tricarboxylic acids, dihydroxy monocarboxylic acids, dihydroxy dicarboxylic acids, and dihydroxy tricarboxylic acids are particularly preferred; even more preferred are monohydroxy monocarboxylic acids, monohydroxy dicarboxylic acids, monohydroxy tricarboxylic acids, and dihydroxy dicarboxylic acids.

[0057] Preferred examples of monohydroxy monocarboxylic acids are lactic acid, glycolic acid, and mandelic acid, among which glycolic acid and mandelic acid, and especially glycolic acid, are preferred. Preferred examples of monohydroxy dicarboxylic acids are tartronic acid and malic acid. Preferred examples of monohydroxy tricarboxylic acids are citric acid and isocitric acid. A preferred example of dihydroxy dicarboxylic acid is tartaric acid.

[0058] However, it has been particularly found that glycolic acid has high efficiency in the cleaning compositions of the present invention.

[0059] The one or more hydroxycarboxylic acids (B) are included in the cleaning composition of the present invention in an amount of 10 to 60 wt.-% or 10 to 50 wt.-%, preferably 15 to 44.9 wt.-%, more preferably 20 to 39.8 wt.-%, and most preferably 25 to 35.6 wt.-% based on the total weight of the cleaning composition of the present invention.

[0060] Surfactant (C)

[0061] Preferably, one or more surfactants (C) are present in the cleaning composition of the present invention.

[0062] Typical surfactants (C) that may be part of the cleaning composition include foam control agents (C1), such as defoamers and foam inhibitors; and wetting and / or dispersing agents (C2).

[0063] The one or more surfactants (C) are included in the cleaning composition of the present invention in an amount of 0 to 10 wt.-%, preferably 0.1 to 8 wt.-%, more preferably 0.2 to 6 wt.-%, and most preferably 0.4 to 4 wt.-% based on the total weight of the cleaning composition of the present invention.

[0064] Foam control agent (C1)

[0065] Among the foam inhibitors, substances such as polysiloxanes, especially dimethylpolysiloxane; polyglycols; any of the aforementioned substances containing hydrophobic groups, such as hydrophobic silica and hydrophobic urea; and 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD; VP: 0.0007 kPa, IBP: 255 °C) are preferred.

[0066] Wetting additive and / or dispersing additive (C2)

[0067] Among the wetting and / or dispersing additives (C2), nonionic amphiphilic surfactants such as alcohol polyethoxylates are preferred. The alcohols of these alcohol polyethoxylates are preferably aromatic or aliphatic saturated or unsaturated straight-chain or branched-chain monohydric alcohols. Aliphatic saturated or unsaturated straight-chain or branched-chain monohydric alcohols are preferred and preferably contain 6 to 20 carbon atoms.

[0068] Further components (D)

[0069] Amine (D1)

[0070] The further components (D) are different from components (A), (B) and (C). Such further amines (D1) are preferably secondary and tertiary amines, such as triethanolamine (VP: <0.001 kPa, IBP: 360 °C) and methyldiethanolamine (VP: 0.0013 kPa, IBP: 243 °C) and octyldiethanolamine.

[0071] The one or more further components (D) are included in the cleaning composition according to the invention in an amount of 0 to 10 wt.-%, preferably 0 to 8 wt.-%, more preferably 0 to 6 wt.-% and most preferably 0 to 5 wt.-% based on the total weight of the cleaning composition according to the invention.

[0072] Dicarboxylic acids (D2)

[0073] The further components may also be dicarboxylic acids, such as oxalic acid, malonic acid, succinic acid, glutaric acid and adipic acid. Since the further components (D) must be different from components (A), (B) and (C), the dicarboxylic acids (D) should not be classified under the hydroxycarboxylic acids (B).

[0074] Amounts of components in the cleaning composition

[0075] The following amount ranges, preferred amount ranges, more preferred amount ranges and most preferred amount ranges of the components included in the cleaning composition according to the invention also apply to the preferred components and groups of components.

[0076] The cleaning composition according to the invention comprises:

[0077] · one or more glycol monoalkyl ethers (A) in an amount of 40 to 90 wt.-% or 50 to 90 wt.-%, preferably 55 to 84.9 wt.-%, more preferably 60 to 79.8 wt.-% and most preferably 65 to 74.6 wt.-%,

[0078] · one or more hydroxycarboxylic acids (B) in an amount of 10 to 60 wt.-% or 10 to 50 wt.-%, preferably 15 to 44.9 wt.-%, more preferably 20 to 39.8 wt.-% and most preferably 25 to 34.6 wt.-%;

[0079] · from 0 to 10 wt.-%, preferably from 0.1 to 8 wt.-%, more preferably from 0.2 to 6 wt.-% and most preferably from 0.4 to 4 wt.-% of one or more surfactants (C); and

[0080] · from 0 to 10 wt.-%, preferably from 0 to 8 wt.-%, more preferably from 0 to 6 wt.-% and most preferably from 0 to 5 wt.-% of one or more additional components (D);

[0081] All wt.-% values are based on the total weight of the cleaning composition, and the combined amount of all components is 100 wt.-%.

[0082] The cleaning composition of the present invention preferably indeed contains in total at least 80 wt.-%, more preferably 85 wt.-%, even more preferably at least 90 wt.-% and most preferably at least 95 wt.-%, such as 100 wt.-% of components (A), (B), (C) and (D).

[0083] If other organic components are also present in the cleaning composition of the present invention in addition to (A), (B), (C) and (D), the requirements i. and ii. regarding the vapor pressure and the initial boiling point should equally preferably apply to these components.

[0084] Among the above ranges, it is most preferred to combine the "preferred" range, the "more preferred" range and the "most preferred" range.

[0085] Particularly preferred embodiments of the cleaning composition of the present invention comprise:

[0086] · from 50 to 90 wt.-% of one or more glycol monoalkyl ethers (A), the one or more glycol monoalkyl ethers (A) being selected from monoalkylene glycol monoalkyl ethers (A1), dialkylene glycol monoalkyl ethers (A2), trialkylene glycol monoalkyl ethers (A3),

[0087] · from 10 to 50 wt.-% of an α-hydroxycarboxylic acid (B), which is preferably selected from monohydroxy monocarboxylic acids, monohydroxy dicarboxylic acids, monohydroxy tricarboxylic acids, dihydroxy monocarboxylic acids, dihydroxy dicarboxylic acids and dihydroxy tricarboxylic acids;

[0088] · from 0 to 10 wt.-% of one or more surfactants (C), the one or more surfactants (C) being selected from the group consisting of foam control agents (C1), wetting and / or dispersing agents (C2); and

[0089] · from 0 to 10 wt.-% of one or more additional components (D);

[0090] All wt.-% values are based on the total weight of the cleaning composition, and the combined amount of all components is 100 wt.-%.

[0091] Another particularly preferred embodiment of the cleaning composition of the present invention comprises:

[0092] · 55 to 84.9 wt.-% of one or more glycol monoalkyl ethers (A), the one or more glycol monoalkyl ethers (A) being selected from ethylene glycol monohexyl ether, propylene glycol monohexyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monopentyl ether and dipropylene glycol monohexyl ether, (A2), trialkylene glycol monoalkyl ether (A3),

[0093] · 15 to 44.9 wt.-% of an α-hydroxycarboxylic acid (B), which is selected from lactic acid, glycolic acid, mandelic acid, tartronic acid, malic acid, citric acid, isocitric acid and tartaric acid;

[0094] · 0.1 to 8 wt.-% of one or more surfactants (C), the one or more surfactants (C) being selected from polysiloxanes, polyglycols, any of the aforementioned substances containing hydrophobicity, 2,4,7,9-tetramethyl-5-decyne-4,7-diol and alcohol polyethoxylates; and

[0095] · 0 to 8 wt.-% of one or more additional ingredients (D);

[0096] All wt.-% values are based on the total weight of the cleaning composition, and the combined amount of all ingredients is 100 wt.-%.

[0097] A highly preferred embodiment of the cleaning composition of the present invention comprises:

[0098] · 60 to 79.8 wt.-% of one or more glycol monoalkyl ethers (A), the one or more glycol monoalkyl ethers (A) being selected from ethylene glycol monohexyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether and diethylene glycol monohexyl ether,

[0099] · 20 to 39.8 wt.-% of glycolic acid (B);

[0100] · 0.2 to 6 wt.-% of one or more surfactants (C), the one or more surfactants (C) being selected from polysiloxanes, polyglycols, any of the aforementioned substances containing hydrophobicity, 2,4,7,9-tetramethyl-5-decyne-4,7-diol and alcohol polyethoxylates; and

[0101] · 0 to 6 wt.-% of one or more additional ingredients (D);

[0102] All wt.-% values are based on the total weight of the cleaning composition, and the combined amount of all ingredients is 100 wt.-%.

[0103] Method for removing uncured aqueous coating material from a surface

[0104] The present invention further relates to a method for removing uncured aqueous coating material from a surface, the method comprising the following steps

[0105] 1. contacting a surface to which uncured aqueous coating material is adhered with the cleaning composition according to the invention or a dilution thereof in an aqueous medium; and agitating the cleaning composition or its dilution in an aqueous medium while the uncured aqueous coating material dissolves and / or disperses therein,

[0106] 2. removing from the surface the cleaning composition or its dilution in an aqueous medium and the coating material dissolved and / or dispersed therein, and

[0107] 3. rinsing the surface with an aqueous medium.

[0108] Uncured aqueous coating material

[0109] The uncured aqueous coating material to be removed from the surface by using the method according to the invention is preferably a dip-coated coating material, particularly preferably an electrodeposited coating material, even more preferably a cathodic electrodeposited coating material.

[0110] Such cathodic electrodeposited coating materials typically contain amino-functional binders which are converted into a water-dilutable form by carboxylic acids (such as formic acid) for the coating process. During the deposition process, the positively charged coating material particles migrate and diffuse to the workpiece connected as the cathode, react with hydroxide ions, and deposit on the workpiece as a water-insoluble polyamine. The binders used typically include adducts of epoxy resins and polyamines, or amino-functional poly(meth)acrylates; both typically crosslink with blocked polyisocyanates at elevated temperatures.

[0111] The electrodeposited coating material preferably has a solids content of about 20 to 40 wt.-% based on the weight of the coating material. However, the solids content in the deposited coating film is typically 80 to 90 wt.-% based on the weight of the wet coating film. In addition to the positively charged binder typically contained in an amount of 10 to 15 wt.-%, the cathodic electrodeposited coating material also contains pigments and a small proportion of organic solvents as solubilizers. It further contains additives and water. The electrodeposited coating material for primer coatings is mostly grey or black and contains anticorrosive pigments.

[0112] To apply an electrodeposition coating material on a conductive substrate, the workpiece is immersed in a bath of the electrodeposition coating material. A DC field is applied between the workpiece and a counter electrode, and the ionized coating material discharges and coagulates on the workpiece. As already stated above, the deposited paint film typically has a solids content in the range of 80 to 90 wt.-%, and is no longer dilutable with water, such that the adhering bath liquid can be rinsed off with water. The final coating is formed by curing the deposited coating material at a temperature typically in the range of 120 °C to 180 °C.

[0113] The tank containing the coating material bath, the devices in such a tank, and the equipment must be thoroughly cleaned from time to time, i.e., the adhering coating material in liquid or dried-on form but not cured must be removed from the respective surfaces of these tanks, the devices associated therewith, and the equipment used, as well as from outer surfaces and floors etc. that may have been splashed.

[0114] Step 1

[0115] In step 1, the surface to which uncured aqueous coating material adheres is brought into contact with the cleaning composition of the present invention or preferably a dilution thereof in an aqueous medium.

[0116] The terms "non-cured" or "uncured" mean that the coating material is in liquid form and / or in dried-on form, but not crosslinked or cured according to the requirements of the coated workpiece.

[0117] The surface to which uncured aqueous coating material adheres can be any surface that has come into contact with uncured aqueous coating material, especially dip coating material, more especially electrodeposition coating material, and even more especially cathodic electrodeposition coating material, as described above.

[0118] The surface can be, for example, the surface of a dip coating tank (especially an electrodeposition dip coating tank), the surface of any device associated with the dip coating tank (such as the surface of a skid for transporting the workpiece to be coated through the coating material), and also the surface of pipes etc. through which the coating material is transported. In addition, outer surfaces and equipment surfaces in contact with the coating material, as well as floors etc.

[0119] Preferably and typically, the surface to which uncured aqueous coating material adheres is a metal surface, but this is not essential, since floors etc. (which may be made of other materials) can also be cleaned.

[0120] The contact with the surface to which uncured aqueous coating material adheres can be achieved by any means, such as brushing, dipping, spraying, or filling the tank with the cleaning composition of the present invention or a dilution thereof in an aqueous medium.

[0121] While the cleaning composition of the present invention can be used in an undiluted (i.e., pure) form, in most cases, it is not necessary to use the concentrate, or it is even preferred to use the cleaning composition of the present invention in the form of its dilution in an aqueous medium. As used herein, the term "aqueous medium" means any medium that is water-based and contains water as its main component and does not interfere with the purpose of the present invention to provide cleaning without using VOC-containing compounds.

[0122] Therefore, the "aqueous medium" does not contain organic components having a vapor pressure of 0.01 kPa or higher at 20 °C. Preferably, the "aqueous medium" is water, and even more preferably deionized water.

[0123] A suitable dilution of the cleaning composition in an aqueous medium, preferably in water, preferably contains at least 0.5 wt.-% of the cleaning composition according to the present invention. Depending on the purpose and the degree of contamination, different concentrations are sufficient or different concentrations are required.

[0124] Typical concentration ranges of the cleaning composition of the present invention in an aqueous medium, preferably in water, are from 0.5 to 50 wt.-%, which is also the range for cleaning outer surfaces and floors. For cleaning an uncured electrocoating apparatus, such as a tank, pipeline, exchanger or other apparatus, preferably a concentration of the cleaning composition of the present invention in an aqueous medium in the range of 0.5 to 2.0 wt.-% is used. To remove uncured electrocoating from an apparatus (such as a pendulum rod, fastener or other apparatus), typically a concentration of the cleaning composition of the present invention in an aqueous medium in the range of 2.0 to 40 wt.-%, more preferably 3.0 to 30 wt.-%, such as 10 to 25 wt.-% is preferably used.

[0125] The contact time depends on the thickness of the layer of uncured coating material adhered to the surface, and is preferably at least 1 minute, but can also be, for example, up to 7 days. Typically, the contact time is in the range of 5 minutes to 4 days, more preferably in the range of 15 minutes to 3 days, such as in the range of 30 minutes to 2 days.

[0126] The contact temperature, i.e., the temperature of the cleaning composition of the present invention or its dilution in an aqueous medium (preferably water), preferably ranges from 10 °C to 60 °C, more preferably 20 °C to 50 °C.

[0127] While in contact with the surface to which an uncured aqueous coating material is adhered, the cleaning composition of the present invention or its dilution in an aqueous medium is agitated (such as stirred or oscillated) to enhance the contact and promote the dissolution and / or dispersion of the coating material so as to remove it from the surface. A particular type of agitation is to repeatedly circulate the cleaning composition, preferably the water-diluted cleaning composition, by using a process pump.

[0128] Step 2

[0129] After Step 1, the cleaning composition or a dilution thereof in an aqueous medium, together with the coating material dissolved and / or dispersed therein, is removed from the surface, i.e., separated from the surface. This can be accomplished by any known means, such as pouring into a trough, pumping out the used cleaning composition, etc.

[0130] Step 3

[0131] After Step 2, the surface thus cleaned is rinsed with an aqueous medium, preferably water. The rinsing in Step 3 can be carried out in one step or several consecutive steps. For example, by removing a first rinse liquid containing the main residue of the cleaning composition and the coating material dissolved and / or dispersed therein, followed by one or more further rinses until the aqueous medium is as clean as desired. The rinsing can of course be carried out by any known means. In particular, the first rinse and sometimes the second rinse can be carried out with an aqueous medium, preferably water, under high pressure, while the subsequent rinses can be carried out by simply recycling the aqueous medium using a process pump.

[0132] If in some cases there is a persistent adhesion of the coating material to the surface, then of course the method can be repeated, if necessary, with a higher concentration of the cleaning composition of the present invention in an aqueous medium and / or with a longer contact time and / or a higher contact temperature and / or enhanced agitation.

[0133] In the method according to the present invention, any general or specific embodiment of the cleaning composition according to the present invention or a dilution thereof in an aqueous medium can be used.

[0134] Use of the cleaning composition of the present invention for cleaning a surface

[0135] Another subject of the present invention is the use of the cleaning composition of the present invention for cleaning a surface to which an uncured aqueous coating material has adhered.

[0136] These surfaces are preferably the same as those described for the method according to the present invention, and these uncured aqueous coating materials are preferably the same as those described above.

[0137] In the use according to the present invention, any general or specific embodiment of the cleaning composition according to the present invention or a dilution thereof in an aqueous medium can be used.

[0138] Hereinafter, the present invention will be illustrated by working examples.

[0139] Examples

[0140] Determination of Parameters

[0141] At 20 °C Determination of the vapor pressure

[0142] This vapor pressure was determined using the gas saturation method in accordance with OECD / OCDE Guideline 104 (OECD / OCDE Guidelines for the testing of Chemical 104) (adopted on March 23, 2008) for chemical testing.

[0143] Determination of the initial boiling point at 101.3 kPa

[0144] This initial boiling point was determined using the dynamic method in accordance with OECD / OCDE Guideline 103 (OECD / OCDE Guidelines for the testing of Chemical 103) (adopted on July 27, 1995) for chemical testing.

[0145] Preparation of the cleaning composition and its dilution in water

[0146] The cleaning composition is obtained by mixing the ingredients shown in Table 1:

[0147] Table 1

[0148] Component Type Amount [wt.-%] Diethylene glycol monobutyl ether <![CDATA[Alkyl glycol monoether (A) 1 > 65 Diethylene glycol monohexyl ether <![CDATA[Alkyl glycol monoether (A) 1 > 3 Monoethylene glycol hexyl ether <![CDATA[Alkyl glycol monoether (A) 2 > 2 Glycolic acid Hydroxycarboxylic acid (B) 30 TMDD <![CDATA[Surfactant (C) 3 > 1

[0149] 1 Dialkylene glycol monoalkyl ether (A2)

[0150] 2 Monoalkylene glycol monoalkyl ether (A1)

[0151] 3 Foam control agent (C1)

[0152] Method for cleaning a surface with the cleaning composition

[0153] Cleaning an electro-deposition dip tank

[0154] First, empty the electro-deposition dipping tank into the storage tank. In a second step, manually pre-clean the tank under high pressure to remove large paint particles from the facility. Subsequently, fill the tank with deionized water to 80% and add the cleaning composition of Table 1 to reach a concentration of 0.8% (v / v). Fill the tank with deionized water until the working level (100%) is reached. Then, remove the 5 or 10 μm multi-layer filter to facilitate recirculation. Subsequently, open the valve to allow the maximum recirculation flow. Start the recirculation and carry out for about 48 hours. Then stop the recirculation and remove the diluted cleaning composition containing dissolved and dispersed paint residues. After that, manually clean again with high-pressure water to remove dissolved paint particles from the facility. Reinstall the filter and fill the tank with deionized water, and recirculate the deionized water for about 2 hours. Remove the water and refill the tank again with fresh deionized water for a second rinse. Check the filter and replace it with a new one.

[0155] Finally, the tank is ready to be refilled again with electro-deposition dipping material, which is transferred back from the storage tank to the electro-deposition dipping tank. This cleaning procedure shows very good results.

[0156] Cleaning an organic dip tank

[0157] In laboratory experiments, the cleaning composition of Table 1 was diluted with water to reach a final concentration of 10 wt.-% based on the total weight of the water-diluted cleaning composition.

[0158] A small stainless-steel tank was coated with an organic dipping material and dried at room temperature for 120 hours. Subsequently, fill the tank with a 10 wt.-% solution of the formulation in Table 1 in water and keep stirring at room temperature for 60 minutes. After that, remove the water-diluted cleaning composition and rinse the tank with water. The dissolution rate is very high, and the cleaning shows good to very good results.

[0159] Further experiments

[0160] Similar experiments were carried out on other surfaces such as conventional steel, plastic parts, and composite materials (glass fiber, glass) with a conventional organic dipping material or a cathodic electro-deposition coating material adhered thereto. Use a process pump to recirculate the water-diluted cleaning composition for 1 to 2 days under different conditions (such as lower and higher concentrations and temperatures). Typically, the temperature used is room temperature (about 23 °C). Similarly, the dissolution rate is very high, and the cleaning shows good to very good results.

[0161] As a comparative example, a similar solution using acetic acid instead of glycolic acid was used. In such a case, only average results at most were obtained.

Claims

1. A cleaning composition comprising: a. 40 to 90 wt.-% of one or more glycol monoalkyl ethers (A) selected from the group consisting of monoalkylene glycol monoalkyl ethers (A1), dialkylene glycol monoalkyl ethers (A2), trialkylene glycol monoalkyl ethers (A3) and tetraalkylene glycol monoalkyl ethers (A4); b. 10 to 60 wt.-% of one or more hydroxycarboxylic acids (B); c. 0 to 10 wt.-% of one or more surfactants (C); and d. 0 to 10 wt.-% of one or more further components (D) selected from secondary amines, tertiary amines and dicarboxylic acids different from (A), (B) and (C); All of the above ingredients have i. A vapor pressure of less than 0.01 kPa at 20°C, and / or ii. an initial boiling point greater than 250°C at a pressure of 101.3 kPa; All wt.-% values are based on the total weight of the cleaning composition and the combined amount of all ingredients is 100 wt.-%.

2. The cleaning composition according to claim 1, wherein The one or more glycol monoalkyl ethers (A) are selected from Ethylene glycol monoalkyl ethers (A1) and propylene glycol monoalkyl ethers (A1) having the formula HO-R-O-R a , where R a is a straight-chain or branched-chain alkyl residue having 6 to 10 carbon atoms; Diethylene glycol monoalkyl ethers (A2) and dipropylene glycol monoalkyl ethers (A2) having the formula HO-(R-O-)2R b wherein R b is a linear or branched alkyl residue having 4 to 10 carbon atoms; Having the formula HO-(R-O-)3R c Triethylene glycol monoalkyl ethers (A3) and tripropylene glycol monoalkyl ethers (A3), where R c is a straight-chain or branched-chain alkyl residue having 1 to 10 carbon atoms; and tetraethylene glycol monoalkyl ether (A4) and tetrapropylene glycol monoalkyl ether (A4) having the formula HO-(R-O-)4R d wherein R d is a straight-chain or branched-chain alkyl residue having 1 to 10 carbon atoms; And wherein in any of these glycol monoalkyl ethers (A1), (A2), (A3) and (A4), the residues RO are independently of one another ethylene oxide or propylene oxide residues.

3. The cleaning composition according to claim 1 or claim 2, characterized in that, These glycol monoalkyl ethers (A) are selected from the group consisting of monoalkylene glycol monoalkyl ethers (A1), dialkylene glycol monoalkyl ethers (A2), trialkylene glycol monoalkyl ethers (A3); and mixtures thereof.

4. The cleaning composition according to any one or more of claims 1 to 3, characterized in that These glycol monoalkyl ethers (A) are selected from the group consisting of monoethylene glycol monoalkyl ether (A1), diethylene glycol monoalkyl ether (A2), triethylene glycol monoalkyl ether (A3); and mixtures thereof.

5. The cleaning composition according to any one or more of claims 1 to 4, characterized in that, These glycol monoalkyl ethers (A) are selected from the group consisting of monoalkylene glycol monohexyl ether (A1) and dialkylene glycol monohexyl ether (A2) and dialkylene glycol monobutyl ether (A2).

6. The cleaning composition according to any one or more of claims 1 to 5, characterized in that, The hydroxycarboxylic acid (B) is glycolic acid.

7. The cleaning composition according to any one or more of claims 1 to 6, characterized in that These surfactants (C) are selected from the group consisting of foam control agents (C1) and wetting and / or dispersing agents (C2).

8. The cleaning composition according to claim 7, characterized in that These foam control agents (C1) are selected from the group consisting of: polysiloxanes and polyglycols, and any of the aforementioned hydrophobic substances; and 2,4,7,9-tetramethyl-5-decyne-4,7-diol; and / or These wetting and / or dispersing agents (C2) are chosen from nonionic amphoteric surfactants.

9. The cleaning composition according to any one or more of claims 1 to 8, characterized in that, These further components (D) are chosen from tertiary amines.

10. The cleaning composition according to any one or more of claims 1 to 9, characterized in that The composition comprises 55 to 84.9 wt.-% of one or more of these glycol monoalkyl ethers (A), 15 to 44.9 wt.-% of one or more of these hydroxycarboxylic acids (B); 0.1 to 8 wt.-% of one or more of these surfactants (C); and 0 to 8 wt.-% of one or more of these further ingredients (D); All wt.-% values are based on the total weight of the cleaning composition and the combined amount of all ingredients is 100 wt.-%.

11. The cleaning composition according to any one or more of claims 1 to 10, characterized in that, The composition comprises 60 to 79.8 wt.-% of one or more glycol monoalkyl ethers (A), said one or more glycol monoalkyl ethers (A) being selected from ethylene glycol monohexyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether and diethylene glycol monohexyl ether; 20 to 39.8 wt.-% of glycolic acid (B); 0.2 to 6 wt.-% of one or more surfactants (C), said one or more surfactants (C) being selected from polysiloxanes, polyglycols, any of the aforementioned hydrophobic-containing substances, 2,4,7,9-tetramethyl-5-decyne-4,7-diol and alcohol polyethoxylates; and 0 to 6 wt.-% of one or more additional components (D); All wt.-% values are based on the total weight of the cleaning composition, and the combined amount of all components is 100 wt.-%.

12. A method for removing uncured aqueous coating material from a surface, the method comprising the following steps 1. contacting a surface to which an uncured aqueous coating material is adhered with the cleaning composition according to any one or more of claims 1 to 11 or a dilution thereof in an aqueous medium; and agitating the cleaning composition or its dilution in an aqueous medium while the uncured aqueous coating material dissolves and / or disperses therein, 2. removing from the surface the cleaning composition or its dilution in an aqueous medium and the coating material dissolved and / or dispersed therein, and 3. rinsing the surface with an aqueous medium.

13. The method according to claim 12, characterized in that the uncured aqueous coating material is a liquid and / or dry-adhered dip coating material selected from electrodeposition coating materials and other dip coating materials; and / or the aqueous medium is water; and / or the dilution of the cleaning composition according to any one or more of claims 1 to 11 in an aqueous medium contains at least 0.5 wt.-% of the cleaning composition.

14. The method according to claim 12 or 13, characterized in that the contact of the surface to which the uncured aqueous coating material is adhered with the cleaning composition or its dilution in an aqueous medium is carried out for at least 1 minute; and / or the cleaning composition or its dilution in an aqueous medium has a temperature in the range of 10 °C to 60 °C.

15. Use of the cleaning composition according to any one or more of claims 1 to 11 or a dilution thereof in an aqueous medium for cleaning a substrate to which an uncured aqueous coating material is adhered.