EP3947773A1

EP3947773A1 - Phosphate-free cleaner for metallic surfaces with reduced pickling erosion

Info

Publication number: EP3947773A1
Application number: EP20732490.6A
Authority: EP
Inventors: Andre SCHAUS; Dominic WEIL
Original assignee: Chemetall GmbH
Current assignee: Chemetall GmbH
Priority date: 2019-04-04
Filing date: 2020-03-20
Publication date: 2022-02-09
Also published as: BR112021019237A2; MX2021012076A; KR20210149116A; JP2022527547A; CN113646467A; WO2020200838A1; US20220162760A1

Abstract

The present invention relates to a water-based, alkaline cleaner concentrate for producing a cleaner for metallic surfaces containing a) at least one (meth)acrylic acid homopolymer having a weight-average molar mass in the range from 3000 to 19 000 g/mol and b) at least one (meth)acrylic acid copolymer having a weight-average molar mass in the range from 50 000 to 100 000 g/mol, wherein the at least one (meth)acrylic acid copolymer is at least one linear copolymer of (meth)acrylic acid and at least one monomer having a vinyl group and at least two acid groups selected from the group consisting of carboxylic acid groups and sulfonic acid groups, and to a corresponding cleaner for metallic surfaces with reduced pickling erosion, which eschew the use of phosphates. The invention further relates to a process for anticorrosive treatment of metallic surfaces, comprising a corresponding cleaning step, to a metallic surface obtainable by said process and to the use thereof in the field of metalworking industries.

Description

Phosphate-free cleaner for metallic surfaces with reduced

Pickling removal

The present invention relates to a water-based, alkaline cleaner concentrate and a corresponding cleaner for metallic surfaces with reduced pickling removal, which does not require the use of phosphates, and a method for the anti-corrosion treatment of metallic surfaces, which includes a corresponding cleaning step, a metallic surface, obtainable by said process, as well as its use in the field of the metalworking industries. Phosphate-containing cleaning products have long been used as standard products in industrial metal cleaning because of their degreasing-accelerating effect. In addition to their degreasing effect, phosphates also have the advantage of acting as complexing agents for interfering ions such as magnesium or calcium. In the anti-corrosion pretreatment of metal strips and metallic components - for example in vehicle construction or in general industry - aqueous cleaning systems and conversion solutions are used, which have a pH value in the clearly acidic or alkaline range.

During the cleaning process, a so-called pickling attack occurs which, in addition to oxide films, can also attack the base material and negatively influence its morphology. This can have an effect on the subsequent deposition of a conversion coating, which in turn can lead to reduced adhesion of subsequent coatings, in particular cathodic electrodeposition paints, and thus impair the protection against corrosion. For this reason, the standard products containing phosphate were often combined with silicate compounds as corrosion inhibitors in order to protect sensitive materials such as galvanized steels, aluminum or aluminum-containing substrates from excessive stress during the cleaning process.

Silicate compounds such as potassium and sodium silicate as well as potash and soda waterglass, however, tend to precipitate at a pH value of less than 11 and thus their activity to lose, and can also lead to encrustation of the cleaning baths or to subsequently difficult to remove and visually disturbing drying on the metal surfaces to be treated. For this reason they are nowadays only reluctantly used as pickling inhibitors in alkaline cleaning systems. Boron compounds such as boric acid, sodium or potassium borate are now used as a replacement for silicate compounds, especially for aluminum and galvanized steels.

For some years now, however, there has been an increasing trend towards safer and more sustainable cleaning compositions. The driving force behind this is, on the one hand, legal regulations that increasingly prohibit the use of certain ingredients in various countries (e.g. China) or areas - these include phosphates and complexing agents such as EDTA - and on the other hand the increasing ecological and safety-conscious thinking of the users.

Since this trend is also evident in conversion systems, organosilane-based thin-film systems such as Oxsilan ^® (Chemetall GmbH, Germany) are moving more into focus. These act like zinc phosphating as an aqueous conversion system, but have clear advantages especially with regard to more sustainable products, ecological thinking and raw material bans, e.g. of nickel or phosphate. Thus, nowadays aqueous cleaners not only have to be highly compatible with well-known conversion processes such as trication phosphating, but also with nickel-free zinc phosphating and, above all, with the aforementioned thin-film systems, which means that the metal surface must be optimally prepared for any type of conversion treatment. No. 9,567,552 B2 describes a phosphate-free cleaner in which long-chain polyacrylates are used as corrosion inhibitors. The cleaner is suitable for the treatment of aluminum / aluminum alloys, but not for multi-metal systems such as are common in the automotive industry. The compatibility of the cleaner with a subsequent organosilane-based thin film coating or a trication phosphate is not shown. The object of the present invention was therefore to provide a water-based cleaner concentrate and a corresponding water-based cleaner for metallic surfaces, which on the one hand manages without the use of phosphates and still combines a balanced pickling attack with good cleaning performance, and on the other hand the metal surface optimally for each Type of conversion treatment prepared.

This object is achieved by a water-based, alkaline cleaner concentrate for the production of a cleaner for metallic surfaces, which a) at least one (meth) acrylic acid homopolymer with a weight average molar mass in the range from 3,000 to 19,000 g / mol and

b) contains at least one (meth) acrylic acid copolymer with a weight average molar mass in the range from 50,000 to 100,000 g / mol, the at least one (meth) acrylic acid copolymer being at least one copolymer of (meth) acrylic acid and at least one monomer which has a vinyl group and at least two acid groups selected from the group consisting of carboxylic acid groups and sulfonic acid groups.

The polymers of components a) and b) are used in the present case as a phosphate substitute in the cleaning concentrate according to the invention described. It has surprisingly been found that none of the polymers alone can achieve the performance of a phosphate-containing standard cleaner. Rather, comparable results can only be achieved with a polymer mixture of components a) and b).

The polymers of component a) are rather short-chain (meth) acrylic acid homopolymers which combine an inhibition of the pickling attack with an average cleaning effect. In contrast, the polymers of component b) are special long-chain (meth) acrylic acid copolymers and, due to their highly complexing properties and the associated strong pickling attack, act as cleaning enhancers, with their cleaning performance corresponding to the phosphates used as standard. The weight-average molar mass of the polymers of components a) and b) was always determined in the present case by means of GPC (gel permeation chromatography) with aqueous eluents. The columns were calibrated using polystyrene sulfonates with a narrow molar weight distribution. Definitions:

In the present case, “water-based” is to be understood as meaning that a corresponding composition, which can contain both dissolved and dispersed components, for example a cleaning concentrate or cleaner, consists of at least 50% by weight, preferably at least 55% by weight, of water. The terms “detergent” and “detergent composition” are used synonymously here. The cleaner or the cleaner composition can in particular be a cleaner solution.

In the present context, “(meth) acrylic acid” always means methacrylic acid, acrylic acid or both. In addition, the deprotonated form, i.e. the conjugate base of methacrylic acid or acrylic acid, should also always be included.

Correspondingly, a “(meth) acrylic acid homopolymer” can be a polymer that contains only methacrylic acid, only acrylic acid or both methacrylic acid and acrylic acid as monomer units - but has no further monomer units. The same applies to a “meth (acrylic) acid copolymer”: This can only contain methacrylic acid, only acrylic acid or both methacrylic acid and acrylic acid as monomer units - but also always has other monomer units that are not methacrylic acid or acrylic acid. In the case of the at least one monomer which has a vinyl group and at least two acid groups, all deprotonated forms of the corresponding acid groups should also be included.

If “calculated as X” is used in connection with weight concentrations (% by weight), where X is a specific, specifically specified chemical compound, this is to be understood as follows: If an alternative chemical compound is used (not X ), it should be in such a molar concentration can be used, as calculated for X, taking into account its molar mass, from the specific weight concentration (% by weight) specified in each case.

The at least one (meth) acrylic acid homopolymer of component a) of the cleaner concentrate according to the invention preferably comprises at least one acrylic acid homopolymer.

Preferably includes, more preferably the at least one

(Meth) acrylic acid homopolymer of component a) at least one (meth) acrylic acid homopolymer with a weight average molar mass in the range from 5,000 to 15,000 g / mol, particularly preferably from 6,000 to 12,000 g / mol and very particularly preferably from 7,000 to 9,000 g / mol - calculated as polyacrylic acid.

Calculated as polyacrylic acid ”is to be understood as follows: Even if the at least one (meth) acrylic acid homopolymer of component a) is not or not exclusively polyacrylic acid, it is nevertheless assumed for the purpose of calculating the concentration that all monomer units (100 mol- %) of the at least one (meth) acrylic acid homopolymer of component a) would be acrylic acid.

Particularly preferably, the at least one (meth) acrylic acid homopolymer of component a) is at least one acrylic acid homopolymer with a weight-average molecular weight in the range from 5,000 to 15,000 g / mol, particularly preferably from 6,000 to 12,000 g / mol and very particularly preferably from 7,000 up to 9,000 g / mol - calculated as polyacrylic acid.

The at least one (meth) acrylic acid homopolymer of component a) is added to the cleaning concentrate preferably as a salt, more preferably as an alkali metal salt and particularly preferably as a sodium salt. The sodium salt, in particular, is advantageous due to the resulting alkalinity of the cleaning concentrate.

Particularly suitable polyacrylic acid, for example, having a weight average molecular weight of about 8,000 g / mol (available as Sokalan ^® PA 30 CL from BASF SE, Germany) The at least one (meth) acrylic acid copolymer of component b) of the cleaning concentrate according to the invention is at least one, preferably linear, copolymer of (meth) acrylic acid and at least one monomer which has a vinyl group and at least two acid groups selected from the group consisting of carboxylic acid groups and Has sulfonic acid groups.

The (meth) acrylic acid units on the one hand and the monomer units with the at least two acid groups on the other hand are preferably arranged in an alternating sequence. Corresponding block copolymers and statistical copolymers are also suitable in principle. The at least one (meth) acrylic acid copolymer preferably does not contain any other monomer units, in particular no vinyl acetate or vinyl alcohol units, and in particular no vinyl acetate units.

The (meth) acrylic acid units make up preferably 35 to 65 mol%, particularly preferably 40 to 50 mol% and very particularly preferably 45 to 55 mol% of the at least one (meth) acrylic acid copolymer of component b), while the monomer units with the at least two acid groups make up preferably 65 to 35 mol%, particularly preferably 60 to 40 mol% and very particularly preferably 55 to 45 mol% of the at least one (meth) acrylic acid copolymer of component b), the aforementioned mol% Preferably add% to each 100.

According to a first preferred embodiment, the at least one (meth) acrylic acid copolymer of component b) comprises at least one - preferably alternating - copolymer of (meth) acrylic acid and at least one, preferably exactly one, monomer containing a vinyl group and at least two, preferably has exactly two carboxylic acid groups.

The at least one monomer which has a vinyl group and at least two carboxylic acid groups is preferably selected from the group consisting of vinyl dicarboxylic acids, in particular consisting of maleic acid and fumaric acid, more preferably maleic acid. When “maleic acid” is mentioned here, maleic anhydride or a mixture of maleic acid and maleic anhydride should also be included. In particular, however, it is maleic acid, which is formed from maleic anhydride by hydrolysis in an aqueous medium.

According to a second preferred embodiment, the at least one (meth) acrylic acid copolymer of component b) comprises at least one - preferably alternating - copolymer of (meth) acrylic acid and at least one, preferably exactly one, monomer that has a vinyl group and at least two, preferably has exactly two sulfonic acid groups.

The monomer which has a vinyl group and at least two sulfonic acid groups is preferably selected from the group consisting of vinyl disulfonic acids.

Preferably, the at least one (meth) acrylic acid copolymer of component b) is at least one (meth) acrylic acid copolymer with a weight average molecular weight in the range from 55,000 to 90,000 g / mol, particularly preferably from 60,000 to 80,000 g / mol and very particularly preferred from 65,000 to 75,000 g / mol - calculated as poly (acrylic acid e-maleic acid).

"Calculated as poly (acrylic acid-a / f-maleic acid)" is to be understood accordingly as follows: Even if the at least one (meth) acrylic acid copolymer of component b) is not or not exclusively "poly (acrylic acid-a / f- maleic acid) ”, for the purpose of calculating the concentration it is nevertheless assumed that one half (50 mol%) of the monomer units of the at least one (meth) acrylic acid copolymer of component b) would be acrylic acid and the other half (50 mol%) would be maleic acid.

Particularly preferably, the at least one (meth) acrylic acid copolymer of component b) comprises at least one - preferably alternating - copolymer of (meth) acrylic acid and at least one, preferably exactly one, monomer which has a vinyl group and at least two, preferably exactly two carboxylic acid groups has, with a weight-average molecular weight in the range from 55,000 to 90,000 g / mol, particularly preferably from 60,000 to 80,000 g / mol and very particularly preferably from 65,000 to 75,000 g / mol - calculated as poly (acrylic acid-a / f-maleic acid). The at least one (meth) acrylic acid comopolymer of component b) is added to the cleaning concentrate preferably as a salt, more preferably as an alkali metal salt and particularly preferably as a sodium salt. The sodium salt, in particular, is advantageous due to the resulting alkalinity of the cleaning concentrate. For example, poly (acrylic acid-a / f-maleic acid) with a weight-average molar mass of approx. 70,000 g / mol (available as Sokalan® CP 5 from BASF SE, Germany) is very particularly suitable.

Accordingly, as the inventive polymer mixture of components a) and b), for example, the combination of polyacrylic acid with a weight-average molar mass of approx. 8,000 g / mol (available as Sokalan® PA 30 CL from BASF SE, Germany) and poly (acrylic acid-a / f-maleic acid) with a weight average molar mass of approx. 70,000 g / mol (available as Sokalan® CP 5 from BASF SE, Germany) is particularly suitable.

The at least one (meth) acrylic acid homopolymer of component a) is preferably in a concentration of at least 1.0% by weight, particularly preferably at least 1.5% by weight and very particularly preferably at least 1.7% by weight , but preferably of at most 2.5% by weight, more preferably of at most 2.0% by weight - calculated as polyacrylic acid and based on the total cleaner concentrate - before, while the at least one (meth) acrylic acid copolymer of component b) in a concentration of at least 0.5% by weight, particularly preferably of at least 0.7% by weight and very particularly preferably of at least 0.9% by weight, but preferably of at most 1.5% by weight - calculated as poly (acrylic acid-a / f-maleic acid) and based on the total cleaning concentrate. The at least one (meth) acrylic acid homopolymer of component a) and the at least one (meth) acrylic acid homopolymer of component b) in the cleaning concentrate according to the invention are preferably in a weight ratio in the range from 1.0: 1 to 2.5: 1, more preferably 1 , 3: 1 to 2.0: 1, particularly preferably from 1.5: 1 to 1.9: 1 and very particularly preferably from 1.7: 1 to 1.8: 1 - calculated as polyacrylic acid: poly (acrylic acid- a / f-maleic acid) - before. By choosing a weight ratio of components a) and b) in the preferred ranges mentioned above, the performance - good cleaning performance with a balanced pickling attack - of the cleaning agent obtainable from the cleaning concentrate according to the invention can be brought even closer to the performance of a phosphate-containing standard cleaning agent or even exceed it.

The cleaning concentrate according to the invention is preferably phosphate-free, i. by definition, no phosphates were added to it during manufacture. However, it is possible, albeit undesirable, for the raw materials used to have low levels of phosphate contamination and the cleaning concentrate therefore also contains a small amount of phosphate. More preferably, however, the cleaning concentrate contains less than 100 ppm, more preferably less than 10 ppm, particularly preferably less than 1 ppm and very particularly preferably less than 0.1 ppm of phosphate. The cleaning concentrate is preferably free of silicate compounds, i. that no silicate compounds were added to it during manufacture. It is possible, however, that the raw materials used have a low level of silicate contamination and the cleaning concentrate therefore also contains a small amount of silicate compounds. More preferably, however, the cleaner concentrate contains less than 100 ppm, more preferably less than 10 ppm, particularly preferably less than 1 ppm and very particularly preferably less than 0.1 ppm of silicate compounds.

This is because, as already explained above, silicate compounds tend to precipitate at a pH value of less than 11 and thus lose their activity as pickling inhibitors. They can also lead to encrustation of the cleaning baths or to optically disruptive drying on the metal surfaces to be treated.

The cleaning concentrate according to the invention preferably additionally contains at least one water-soluble boron compound c), which is preferably selected from the group consisting of boric acid and alkali metal borates, in particular consisting of boric acid, sodium borate and potassium borate. Surprisingly, this allows the aggressiveness, ie the pickling attack of the medium, to be precisely controlled for each metallic surface to be cleaned - even for sensitive materials such as aluminum and galvanized and / or pre-phosphated steels. This in turn leads to an improved multimetal capability of the cleaner obtainable from the cleaner concentrate according to the invention, ie to an improved multimetal treatment in which different metallic substrates such as steel, aluminum, galvanized steels and pre-phosphated steels are cleaned simultaneously or one after the other in the same bath.

In the present case, galvanized steels can in particular be hot-dip galvanized or electrolytically galvanized steels or steels that are coated with a zinc-magnesium alloy. The galvanized steels can also be pre-phosphated. When "aluminum" is mentioned, aluminum alloys should always be included.

The at least one water-soluble boron compound c) is preferably in a concentration of at least 7.5% by weight, more preferably at least 10.0% by weight, more preferably at least 10.5% by weight, particularly preferably at least 12.5% by weight and very particularly preferably at least 14.0% by weight, but preferably at most 25.0% by weight, more preferably at most 20.0% by weight, particularly preferably at most 17 , 0% by weight and very particularly preferably not more than 16.0% by weight - calculated as boric acid and based on the total cleaning concentrate - before. By adhering to the aforementioned lower limits for the concentration of the at least one water-soluble boron compound c), the multimetal capability of the corresponding cleaner can be further improved - especially when diluted 1:50 from the concentrate - while the upper limits are based on the pH-dependent solubility of the water-soluble ones Result in boron compounds.

The cleaning concentrate according to the invention is alkaline, ie it has a pH of greater than 7. Its pH is preferably in the range from 9.5 to 14.0, particularly preferably from 10.5 to 14.0 and very particularly preferably from 11.5 to 14.0. The alkalinity can be adjusted, for example, by adding an appropriate amount of sodium or potassium hydroxide and / or sodium or potassium carbonate to the cleaning composition according to the invention. The cleaning concentrate preferably also contains at least one salt which, together with its conjugate acid formed in situ, forms a buffer system and ensures a stable pH value for the concentrate according to the invention and the cleaning agent obtainable therefrom, primarily by counteracting a carbon dioxide entry from the ambient air Lowering the pH value takes effect. The at least one salt is preferably sodium carbonate, sodium hydrogen carbonate, potassium carbonate and / or potassium hydrogen carbonate. The advantage of the particularly preferred use of sodium and / or potassium carbonate is that the required alkalinity can be set at the same time.

The at least one salt is preferably in a concentration of at least 5% by weight, more preferably at least 7% by weight and particularly preferably in the range from 8 to 12% by weight - calculated as potassium carbonate and based on the total cleaning concentrate - in front. The cleaning composition preferably also has at least one complexing agent that can complex interfering foreign ions, in particular Ca, Mg and Zn cations, and thus keep them in solution so that they do not have a negative effect on the overall process, i.e. Do not pollute the baths in the form of crusts and thus lead to increased cleaning effort and do not reduce the performance of the system through reaction with cleaning agents. The at least one complexing agent preferably comprises gluconate, which was added to the cleaning composition, preferably as sodium and / or potassium gluconate.

The at least one complexing agent is preferably in a concentration of at least 1.0% by weight, more preferably at least 2.0% by weight and particularly preferably in the range from 2.5 to 3.5% by weight - calculated as sodium gluconate and based on the total cleaner concentrate.

According to a particularly preferred embodiment, the cleaning concentrate according to the invention contains the following components: a) at least 1, 0 wt .-%, calculated as polyacrylic acid, one

(Meth) acrylic acid homopolymer with a weight average molar mass in the range from 3,000 to 19,000 g / mol,

b) at least 0.5% by weight, calculated as poly (acrylic acid-a / f-maleic acid), of a copolymer of (meth) acrylic acid and at least one

Vinyl dicarboxylic acid with a weight average molar mass in the range from 50,000 to 100,000 g / mol,

c) at least 10.0% by weight, calculated as boric acid, of sodium and / or potassium borate,

d) at least 8% by weight, calculated as potassium hydroxide, of sodium and / or potassium hydroxide,

e) at least 5% by weight, calculated as potassium carbonate, of sodium and / or potassium carbonate,

f) at least 1.5% by weight, calculated as sodium gluconate, of one

Complexing agent and

g) at least 50% by weight of water, the (meth) acrylic acid homopolymer and the copolymer of (meth) acrylic acid and at least one vinyl dicarboxylic acid being present in a weight ratio of 2.0: 1 to 1.5: 1 and the aforementioned wt .-% to each add 100% by weight. The present invention also relates to a water-based, alkaline cleaner for metallic surfaces, which a) at least one (meth) acrylic acid homopolymer with a weight-average molar mass in the range from 3,000 to 19,000 g / mol,

b) at least one (meth) acrylic acid copolymer with a weight average molar mass in the range from 50,000 to 100,000 g / mol and

h) contains at least one surfactant, the at least one (meth) acrylic acid copolymer being at least one copolymer of (meth) acrylic acid and at least one monomer which has a vinyl group and at least two acid groups selected from the group consisting of carboxylic acid groups and sulfonic acid groups , and in the case that it is a fresh cleaner, the component a) in a concentration of at most 0.65 g / l, preferably in the range from 0.1 to 0.50 g / l - calculated as polyacrylic acid - and component b) in a concentration of at most 0.35 g / l, preferably in the range from 0.05 to 0.30 g / l - calculated as poly (acrylic acid-a / f-maleic acid) - is present.

If the specified maximum concentrations of components a) and b) are exceeded, the cleaning performance is satisfactory, but the pickling attack is too strong.

In the present case, a “fresh cleaner” is understood to mean one that has not yet been brought into contact with a metallic surface. In contact with a metallic surface, ions are released from it and oils and fats are removed from it, which accumulate in the cleaning bath. One then speaks of bath aging. This reduces the pickling attack of the cleaner, which makes it possible to use component a) in a concentration of up to 1.0 g / l and component b) in a concentration of up to 0.55 g / l and nevertheless none To obtain excessive pickling removal.

The cleaner according to the invention can be obtained from the cleaner concentrate according to the invention by

1) Dilution, preferably in water and preferably by a dilution factor in the range from 1:20 to 1: 100 (corresponding to 10 to 50 g of concentrate for 1.0 l of cleaner),

2) by adding at least one surfactant, preferably in the concentration range from 0.3 to 10 g / l - based on the cleaner - and

3) optionally by adjusting the pH with at least one acid or base.

The dilution factor in step 1) is particularly preferably in the range from 1:40 to 1:60 and very particularly preferably from 1:45 to 1:55. The concentration of the at least one surfactant in step 2), however, is particularly preferably in the range of 0.4 to 5 g / l and very particularly preferably from 0.5 to 3.5 g / l - based on the cleaner. The at least one surfactant serves to remove any organic contamination such as mineral oils and fats within the cleaning process, and must therefore necessarily be added to the diluted concentrate. The at least one surfactant is in particular at least one nonionic, anionic and / or cationic surfactant.

The following are particularly suitable as nonionic surfactants:

- Alkylphenol alkoxylates, in particular alkylphenol ethoxylates, with C6 to C14 alkyl chains and a degree of alkoxylation of 5 to 30 mol per mol of phenol,

- Alkyl polyglucosides which have an alkyl chain length of C8 to C22, preferably C10 to C18 and contain 1 to 20, preferably 1 to 5 glucoside units,

- Fatty acid amide alkoxylates, fatty acid alkanolamide alkoxylates, N-alkylglucamides or block copolymers consisting of ethylene, propylene and / or butylene oxide and

- Alkoxylated C8 to C22 alcohols such as fatty alcohol alkoxylates, oxo alcohol alkoxylates and Guerbet alcohol alkoxylates, it being possible for the alkoxylation to take place with ethylene oxide, propylene oxide, butylene oxide and / or a mixture of these as a block copolymer or a random copolymer. The alcohols preferably have 8 to 18 carbon atoms; the degree of alkoxylation is usually between 2 to 50 mol, preferably 3 to 20 mol, of at least one of the alkylene oxides mentioned per mole of alcohol. The alkylene oxide head group can furthermore contain the following so-called end group closures as a modification: benzyl, methyl and / or t-butyl closure.

Depending on the application, the following anionic surfactants are mainly used:

- Fatty alcohol sulfates with alkyl chain lengths of 8 to 22, preferably 10 to 18, carbon atoms such as lauryl sulfate, cetyl sulfate, myristyl sulfate, palmityl sulfate or stearyl sulfate,

- Alkyl ether sulfates with alkyl chain lengths of 8 to 22, preferably 10 to 18, carbon atoms and - Linear C8 to C20 alkylbenzenesulfonates or alkanesulfonates and soaps, such as sodium or potassium salts of C8 to C24 carboxylic acids.

Cationic surfactants used are, depending on the application, in particular:

- Quaternary mono- and di- (C7-C25-alkyl) dimethylammonium compounds,

- Esterquats, especially quaternary esterified mono-, di- and trialkanolamines which are esterified with C8 to C22 carboxylic acids, and

- C7- to C25-alkylamines, N, N-dimethyl-N- (hydroxy-C7-C25-alkyl) ammonium salts and / or imidazoline quats.

Preferably comprises, more preferably the at least one surfactant is at least one nonionic surfactant. In most applications, anionic surfactants have too high a tendency to foam, whereas cationic surfactants often attach to the metallic surface and can thus create problems within the conversion layer deposition. Nonionic surfactants do not have these disadvantages.

When the cleaning concentrate according to the invention is diluted, a pH value suitable for use in a multimetal pretreatment system (“ready-to-use” pH) is achieved even without setting the pH value, so that at least one acid or Base must be added.

The cleaner of the invention is preferably phosphate-free, i. no phosphates were added to it. However, it is possible - albeit undesirable - for the raw materials used to have low levels of phosphate contamination and the cleaning concentrate and the cleaning agent made from it therefore also contain a small amount of phosphate. A small amount of phosphate in the cleaner can also be caused by detachment from the cleaned metallic surfaces, especially if the surfaces are pre-phosphated. More preferably, however, the cleaner contains less than 200 ppm, particularly preferably less than 20 ppm and very particularly preferably less than 2 ppm of phosphate.

The cleaner is preferably free from silicate compounds, ie no silicate compounds were added to it during manufacture. However, it is possible that the raw materials used have low levels of silicate contamination and the cleaner therefore also contains a small amount of silicate compounds. More preferably, however, the cleaner contains less than 100 ppm, more preferably less than 10 ppm, particularly preferably less than 1 ppm and very particularly preferably less than 0.1 ppm of silicate compounds.

The cleaner according to the invention preferably additionally contains at least one water-soluble boron compound c), which is preferably selected from the group consisting of boric acid and alkali metal borates, in particular consisting of boric acid, sodium borate and potassium borate. The at least one water-soluble boron compound c) is preferably in a concentration of at least 0.15% by weight, more preferably at least 0.20% by weight, more preferably at least 0.21% by weight, particularly preferably at least 0.25% by weight and very particularly preferably at least 0.28% by weight, but preferably at most 0.50% by weight, more preferably at most 0.40% by weight, particularly preferably at most 0 , 34% by weight and very particularly preferably at most 0.32% by weight - calculated as boric acid and based on the total cleaning concentrate. By adhering to the aforementioned lower limits for the concentration of the at least one water-soluble boron compound c), the multi-metal capability of the cleaner can be further improved, while the upper limits are increased by the pH-dependent solubility of the water-soluble boron compounds in the corresponding concentrate - especially with a 1:50 dilution of the Cleaner from the concentrate - result.

Further advantageous embodiments and features of the cleaner according to the invention have already been described above in connection with the cleaner concentrate according to the invention.

The present invention also relates to a method for the anti-corrosion treatment of a metallic surface, in which the surface is brought into contact successively with the following compositions: i) at least one water-based, alkaline cleaner for metallic surfaces, which a) at least one (meth) acrylic acid homopolymer with a weight average molecular weight in the range from 3,000 to 19,000 g / mol, b) at least one (meth) acrylic acid copolymer with a weight average molecular weight in the range of 50,000 to 100,000 g / mol and h) contains at least one surfactant, the at least one (meth) acrylic acid copolymer being at least one copolymer of (meth) acrylic acid and at least one monomer which has a vinyl group and at least two acid groups selected from Group consisting of carboxylic acid groups and sulfonic acid groups, and in the event that it is a fresh cleaner, component a) in a concentration of at most 0.65 g / l, preferably in the range from 0.10 to 0.50 g / l - calculated as polyacrylic acid - and component b) in a concentration of at most 0.35 g / l, preferably in the range from 0.05 to 0.30 g / l - calculated as poly (acrylic acid-a / f-maleic acid) - is present,

ii) a first water-based rinse composition,

iii) optionally a second water-based rinsing composition, iv) a water-based acidic conversion composition,

v) optionally a third water-based rinsing composition and vi) a water-based composition containing a (meth) acrylate- and / or epoxy-based cathodic or anodic dip paint and / or a water- or solvent-based wet or powder paint.

The fact that the metallic surface is brought into contact one after the other with the compositions i) to vi) should not exclude that it is before, after or in between with at least one further, preferably water-based composition, for example an activation composition or a passivation composition - as below in the phosphating process - or brought into contact with another rinsing composition or that it is subsequently subjected to at least one drying process - for example in a drying oven - or provided with further layers of paint such as filler, topcoat and clearcoat (automotive paintwork). The method according to the invention is characterized in that it manages without the use of a phosphate-containing cleaning composition, and it nevertheless leads to corrosion protection and paint adhesion results which are comparable to those obtained when using a phosphate-containing cleaning composition.

By bringing the metallic surface into contact with the at least one cleaning agent according to the invention in step i), which combines a balanced pickling attack with good cleaning performance, the metallic surface is optimally prepared for any type of conversion treatment. Thus, the acidic conversion composition in step iv) can be not only one for trication phosphating but also one for nickel-free zinc phosphating, one for applying an organosilane-based thin film coating or a passivation composition.

The at least one cleaner in step i) preferably additionally contains at least one water-soluble boron compound c), which is preferably selected from the group consisting of boric acid and alkali metal borates, in particular consisting of boric acid, sodium borate and potassium borate. As already stated above, this allows the aggressiveness for each metallic surface to be cleaned and subsequently coated - also for sensitive materials - to be precisely controlled. The metallic surface therefore preferably comprises at least one sensitive material selected from the group consisting of aluminum, galvanized steels and pre-phosphated steels.

The addition of at least one water-soluble boron compound c) leads - as also already stated - to an improved multimetal capability. The metallic surface therefore preferably comprises at least two metallic materials selected from the group consisting of steel, aluminum, galvanized steels and pre-phosphated steels, in particular selected from the group consisting of aluminum, galvanized steels and pre-phosphated steels. The metallic surface further preferably comprises both aluminum and at least one galvanized and / or pre-phosphated steel, particularly preferably both aluminum as well as at least one galvanized and at least one pre-phosphated steel.

According to a first preferred embodiment, the acidic conversion composition in step iv) is a composition for nickel-free zinc phosphating which, in addition to zinc ions and manganese ions, also contains phosphate ions and to which no nickel ions have been added.

In the case of nickel-free zinc phosphating as well as in the case of trication phosphating, in which zinc, manganese and nickel ions and phosphate ions are used, the metallic surface is usually also brought into contact with an aqueous activation composition, which is preferably particles, before step iv) contains zinc and / or titanium phosphate crystals. This facilitates the deposition of a phosphate crystal layer in step iv).

After the phosphating in step iv), the metallic surface can also be brought into contact with an aqueous passivation composition. This can be of particular advantage for surfaces which contain areas containing zinc and / or iron as well as areas containing aluminum. In this way, corrosion protection and paint adhesion of the painted surface can be further improved. Said passivation composition preferably contains at least one titanium, zirconium and / or hafnium compound, in particular at least one fluorocomplex of the elements mentioned, and more preferably also at least one organosilane - including its hydrolysis and condensation products.

According to a second preferred embodiment, the acidic conversion composition in step iv) is a composition for applying an organosilane-based thin film system which, in addition to at least one organosilane - including its hydrolysis and condensation products - optionally also at least one titanium, zirconium and / or Contains hafnium compound.

Unlike in the case of phosphating, the cleaning composition according to the invention in combination with an organosilane-based thin film system even leads to better corrosion protection results than a Standard cleaner containing phosphate, especially if the cleaner composition is phosphate-free. The at least one inventive cleaner in step i) and accordingly also the inventive cleaner concentrate are therefore preferably phosphate-free, particularly when an organosilane-based thin-film system is subsequently applied.

According to a third preferred embodiment, the acidic conversion composition in step iv) is a passivation composition which, in addition to at least one titanium, zirconium and / or hafnium compound, in particular at least one fluorocomplex of the elements mentioned, optionally also at least one organol silane - its hydrolysis and condensation products included - contains.

Advantageous embodiments and features of the cleaner according to the invention used in step i) have already been described above in connection with the cleaner concentrate according to the invention and the cleaner according to the invention.

The present invention also relates to a metallic surface treated to protect against corrosion, which can be obtained with the method according to the invention, and its use in the field of metalworking industries in which conversion processes are used for pretreatment, in particular in the field of the automotive, automotive supplier or general industry.

The present invention is to be illustrated below by exemplary embodiments and comparative examples, which are not to be understood as restrictive.

Examples

/) Determination of the pickling removal:

Measuring principle:

The pickling rate indicates the weight loss of the bare metal during a cleaning step. For this purpose, a defined standard sheet of aluminum quality AA6014 with the dimensions 105 x 190 mm (Gardobond® test sheet, Chemetall GmbH, Germany) is immersed in the solution to be tested - here the corresponding cleaning solution. The mass loss is then determined gravimetrically using an analytical balance. It was limited to aluminum surfaces, as these are the most sensitive to pickling.

Preparation of the test panels:

The test panels were first pre-degreased with petroleum spirit in order to remove any kind of organic contamination. In this way, the direct attack of the test solution on the base substrate itself can be assessed and compared.

Measurement of the pickling removal:

The mass of the respective pre-degreased test sheet was determined on an analytical balance. Immediately thereafter, the test sheet was immersed for 10 min at 55 ° C. in a 3 l beaker which contained the corresponding test solution. A 40 mm magnetic stirrer bar at the bottom of the beaker was used to stir at a speed of 500 rpm.

After 10 minutes, the test panel was removed from the test solution, rinsed with fully demineralized (DI) water and dried with compressed air. The weight loss was then determined on the analytical balance.

In order to be able to compare the values obtained, a reference was always checked in parallel.

//) Determination of the minimum cleaning time:

Measuring principle:

The minimum cleaning time (MRZ) indicates the minimum duration of a cleaning step that is required to clean a standard sheet of steel quality 1 .0312 with the dimensions 105 x 190 mm (test sheet) under constant conditions of organic To rid impurities. The quality of the cleaning must reach a certain minimum value, which is determined on the basis of the percentage of water wetting of the metal surface. The focus here is exclusively on steel surfaces, as these are usually the most difficult surfaces to degrease.

Preparation of the test panels:

Test panels were used which had a constant oil layer (1.7 +/- 0.2 g / m ² ). This served to compare the results.

Measurement of the minimum cleaning time:

To determine the minimum cleaning time, the respective test panel was immersed for 1 min at 55 ° C. in a 3 l beaker which contained the appropriate cleaning solution. A 40 mm magnetic stirrer bar at the bottom of the beaker was used to stir at a speed of 500 rpm. The test panel was then rinsed with lifting movements (approx. 15 strokes) in the immersed sink, the panel always being pulled completely out of the rinsing water and held vertically for assessment after 10 s (to rule out false wetting).

The minimum cleaning time is reached when the water wetting of the surface is at least 95%, i.e. there is a closed film of water. If this condition is not met, the test panel is immersed in the cleaning solution for a further minute as described above and then rinsed in the immersion sink. This is repeated until the condition is met.

The number of repetitions is added up and an identical and oiled test panel is left in the cleaning solution for the entire time as a check. This is necessary because the rinsing steps in between improve the cleaning performance. If the sheet is at least 95% wetted after the added time, this time is noted as MRZ. If this is not the case, cleaning and rinsing is carried out again in 1 minute steps until the surface is at least 95% wettable with water without any rinsing steps in between. This is then the MRZ. / ^' / ^' / ^' ) Investigation of different Reiniaerlösunaen:

In order to test the effect of various polymers with regard to pickling removal and MRZ, a standard cleaning concentrate (VB1) with a pH value of 12.9 was initially used as a reference, which, in addition to deionized water, contained the following components:

By adding the following polymers to this standard, various cleaning concentrates were obtained (VB2 to VB6 and B1):

In addition, a standard cleaning concentrate containing phosphate (VB7) with a pH value greater than 11.5 was used as a reference, which, in addition to deionized water, contained the following components:

All cleaner concentrates were then diluted by a factor of 1:50 (corresponding to 20 g concentrate for 1.0 l cleaner) with deionized water and mixed with 2 g / l of an ethylene / propylene oxide fatty alcohol, i.e. a nonionic surfactant, added.

Furthermore, the pH value of all cleaning concentrates was adjusted to 10.5 by adding boric acid or potassium hydroxide solution. The cleaning solutions obtained were then as above - cf. i) and ii) - described with regard to pickling removal and MRZ tested. The results obtained in this way are summarized in Tab. 1 (mean values of at least 3 sheets in each case, i.e. n> 3).

Table 1 :

*) Weight ratio of the two polymers

The test results show that the cleaning performance (see MRZ) can be greatly improved by adding a polymer - polyacrylic acid or poly (acrylic acid-a / f-maleic acid) (VB2 to VB6 and B1 vs. VB1). At the same time, the aggressiveness of the medium increases Aluminum increased (see pickling removal). It can be seen that with polyacrylic acid, with increasing chain length, ie molar mass of the Influence of the addition of polymer in relation to pickling attack and MRZ increases (VB2 to VB4).

It was also shown that no polymer alone can achieve the performance of a standard cleaner containing phosphate in terms of stain removal and MRZ. Only the cleaning solution according to the invention (B1), which has a special mixture of two polymers, is able, with a generally low use concentration and a balanced pickling attack - pickling removal up to 0.8 g / m ² - the cleaning performance of a phosphate-containing cleaner (VB7) - MRZ below 4 min - to be achieved and even surpassed. However, if you double the concentration of the two polymers, the cleaning performance is still satisfactory, but the pickling attack is too strong (VB6). iv) Determination of the multimetal capability:

The multimetal capability of the various solutions was also determined using the two measurement principles already described, pickling removal (see Tab. 2: n> 3) and MRZ (see Tab. 3: n> 3), but a special VDA 230-213 test apparatus was used for each has been. The corresponding tests were carried out on the following four substrates found in the automotive industry: cold-rolled steel (CRS), hot-dipped-galvanized steel (HDG), pre-phosphated electrolytically galvanized steel (ZEP) and aluminum in automotive quality (AA6014).

Table 2:

*) Weight ratio of the two polymers Table 3:

*) Weight ratio of the two polymers

As can be seen in Tab. 2, the pickling attack with the cleaning agent solution (B1) according to the invention is somewhat higher compared to a cleaning agent containing phosphate (VB7). In contrast to a cleaning solution based on only one polymer with a lower polymer concentration (VB8), values are also obtained on aluminum (AA6014) which are acceptable for a running process, which proves the multi-metal capability of the cleaning solution according to the invention.

Tab. 3 shows that with the cleaning solution (B1) according to the invention the minimum cleaning time (MRZ), i.e. the cleaning performance is better, especially in comparison to a phosphate-containing cleaner (VB7) but also to a cleaning solution based on only one polymer with a lower polymer concentration (VB8) on each of the substrates used in a multimetal process.

By using the special VDA 230-213 test apparatus, the resulting pickling and MRZ results are higher compared to the manually determined results in Table 1, which is due to the lower circulation / bath movement within the apparatus.

In the cleaning solution B1 according to the invention, the borate concentration was also varied in order to determine the optimum with regard to the pickling attacks within a multimetal process. The cleaning solutions produced in this way (B1-1 to B1- 3) were then used as above - cf. i) - described with regard to their pickling removal, tested on the following three substrates occurring in the automotive industry: aluminum in automotive quality (AA6014), hot-dip galvanized steel (hot-dipped- galvanized steel = HDG) and electrolytically galvanized steel (MBZE). The metal sheets used for this purpose were each pre-degreased with an aqueous surfactant solution.

The results obtained in this way are summarized in Tab. 4 (mean values of at least 3 sheets in each case, i.e. n> 3). Table 4:

*) Weight ratio of the two polymers

As the examination of the test results of the cleaning agent solution B1 according to the invention and its variants B1 -1 to B1 -3 shows, the pickling attack on aluminum (AA6014) is at a concentration of 14.5 and 16.5% by weight boric acid in the concentrate - i.e. from 0.29 or 0.33% by weight at a dilution of 1:50 in the cleaning solution - in the desired low range. In this way, all tested substrates - including aluminum - can be optimally treated as a composite. v) Compatibility with conversion treatments:

The compatibility of the cleaning solution (B1) according to the invention with known conversion treatments was checked on the basis of an organosilane-based thin-film coating and a trication phosphating. In order to investigate the influence of the cleaning solution (B1) according to the invention, the corresponding polymers were added to the two conversion baths (B2 and B3) in larger quantities than usual in the process - as they can get into a conversion bath through a carryover of cleaning medium through components. The substrates used in the automotive industry were cold-rolled steel (CRS), hot-dipped-galvanized steel (HDG) and aluminum (AA6014) in one

Standard treatment process - organosilane and zirconium compound or zinc-manganese-nickel-phosphate (phosphating time: 180 s) after prior activation with zinc phosphate (activation time: 60 s) - pretreated. The influence of the polymers was assessed by means of layer weight (SG) determination by means of X-ray fluorescence analysis (XRF) and scanning electron microscope (SEM) images of the surface structure of the conversion layer. The layer weights determined - calculated as zirconium metal (Zr) - are summarized for the organosilane-based thin-film coating in Tab. 5 (n> 3). Table 5:

*) Weight ratio of the two polymers The deviations obtained within the different variants (VB9, B2 and B3) are within the possible error tolerance of the SG determination. The SEM images of the surface structure of the conversion layer did not show any abnormalities. Thus, the polymers used according to the invention do not have any negative influences on the optimal layer formation of an organosilane-based thin film system, and are therefore compatible with the latter.

The layer weights determined - each calculated as Zn3 (P0 ₄ ) ₂ 4 FO - are summarized for the zinc phosphate activation and for the subsequent trication phosphating in Tab. 6 and Tab. 7 (each n> 3). Table 6:

Table 7:

The layer weights obtained show that the two polymers show no influence at all on zinc phosphate activation (cf. Tab. 6) and only slight effects on trication phosphate (cf. Tab. 7) (B4 and B5 vs. VB10), which occur during the ongoing process Adjustment of the phosphating parameters are compensated can. The SEM images of the surface structure of the trication conversion layer show no abnormalities.

It was thus possible to demonstrate not only the compatibility of the cleaning solution according to the invention with organosilane-based thin-film coatings but also with tri-cation phosphating. vi) Corrosion behavior in the case of orcianosilane-based thin-film coating:

In order to investigate the influence of the cleaning solution B1 according to the invention on the corrosion behavior, the HDG material in sheet form was treated within a standardized process. Process: 1.) Splash cleaning, 60 seconds

2.) Immersion cleaning, 180 seconds

3.) Immersion rinse, 30 seconds

4.) Immersion conversion, 180 seconds

5.) Immersion rinse, 30 seconds

6.) Drying with compressed air

The cleaning steps 1.) and 2.) were carried out with the aid of the phosphate-free cleaning solution B1 according to the invention at a dilution of 1:50 from the concentrate and with 2 g / l of an ethylene / propylene oxide fatty alcohol. As a comparison, two phosphate-containing standard cleaners (VB11 and VB12) were also tested. An organosilane-based thin film system (Chemetall, Germany) was used for the conversion in step 4.). After step 6), the treated sheets were tested for corrosion and paint adhesion by means of a cyclical corrosion test (VDA 621-415) that is customary in the automotive industry.

The results of the corrosive infiltration and the paint adhesion after falling rocks are summarized in Tab. 8 (each n> 3).

It can be seen that the inventive phosphate-free cleaning solution B1 in combination with an organosilane-based conversion system significantly improves both the corrosion behavior and the paint adhesion properties of the surface compared to a standard cleaning agent containing phosphate (VB11 and VB12). Table 8:

Claims

Expectations

1. Water-based, alkaline cleaner concentrate for the production of a cleaner for metallic surfaces, characterized in that it a) at least one (meth) acrylic acid homopolymer with a weight-average molar mass in the range from 3,000 to 19,000 g / mol and

b) contains at least one (meth) acrylic acid copolymer with a weight-average molecular weight in the range from 50,000 to 100,000 g / mol, the at least one (meth) acrylic acid copolymer being at least one linear copolymer of (meth) acrylic acid and at least one monomer, which has a vinyl group and at least two acid groups selected from the group consisting of carboxylic acid groups and sulfonic acid groups.

2. Detergent concentrate according to claim 1, characterized in that the at least one (meth) acrylic acid homopolymer of component a) has at least one (meth) acrylic acid homopolymer with a weight average molecular weight in the range from 5,000 to 15,000 g / mol, preferably from 6,000 to 12,000 g / mol - calculated as polyacrylic acid - includes.

3. detergent concentrate according to claim 1 or 2, characterized in that the at least one (meth) acrylic acid copolymer of component b) at least one - preferably alternating - copolymer of (meth) acrylic acid and at least one, preferably exactly one monomer that has a vinyl group and at least has two, preferably exactly two, carboxylic acid groups.

4. detergent concentrate according to any one of the preceding claims, characterized in that the at least one (meth) acrylic acid copolymer of component b) is at least one (meth) acrylic acid copolymer with a weight average molecular weight in the range from 55,000 to 90,000 g / mol, preferably from 60,000 to 80,000 g / mol - calculated as poly (acrylic acid-a / f-maleic acid) -.

5. cleaning concentrate according to any one of the preceding claims, characterized in that the at least one (meth) acrylic acid homopolymer of component a) in a concentration of at least 1, 0 wt .-%, preferably of at least 1.5% by weight, but preferably at most 2.5% by weight, more preferably at most 2.0% by weight - calculated as polyacrylic acid - is present, while the at least one (meth) acrylic acid copolymer of component b ) is present in a concentration of at least 0.5% by weight, preferably of at least 0.7% by weight, but preferably of at most 1.5% by weight - calculated as poly (acrylic acid e-maleic acid) .

6. detergent concentrate according to one of the preceding claims, characterized in that the at least one (meth) acrylic acid homopolymer of component a) and the at least one (meth) acrylic acid homopolymer of component b) in a weight ratio in the range from 1.0: 1 to 2, 5: 1, more preferably from 1.3: 1 to 2.0: 1, particularly preferably from 1.5: 1 to 1.9: 1 and very particularly preferably from 1.7: 1 to 1.8: 1 - calculated as polyacrylic acid: poly (acrylic acid-a / f-maleic acid) - are present.

7. cleaning concentrate according to one of the preceding claims, characterized in that it is phosphate-free.

8. cleaning concentrate according to any one of the preceding claims, characterized in that it additionally contains at least one water-soluble boron compound c), which is preferably selected from the group consisting of boric acid and alkali metal borates.

9. cleaning concentrate according to claim 8, characterized in that the at least one water-soluble boron compound c) in a concentration of at least 10.5 wt .-%, preferably of at least 12.5 wt .-%, but preferably of at most 25.0 wt .-%, more preferably of at most 20.0% by weight - calculated as boric acid - is present. 10. Water-based, alkaline cleaner for metallic surfaces, which a) at least one (meth) acrylic acid homopolymer with a weight-average molar mass in the range from 3,000 to 19,000 g / mol,

h) at least one preferably nonionic surfactant contains, wherein the at least one (meth) acrylic acid copolymer is at least one copolymer of (meth) acrylic acid and at least one monomer which has a vinyl group and at least two acid groups selected from the group consisting of carboxylic acid groups and sulfonic acid groups, and wherein for the If it is a fresh cleaner, component a) in a concentration of at most 0.65 g / l, preferably in the range of 0,

10 to 0.50 g / l - calculated as polyacrylic acid - and component b) in a concentration of at most 0.35 g / l, preferably in the range from 0.05 to 0.30 g / l - calculated as poly (acrylic acid -a / f-maleic acid) - is present.

11. A method for the anti-corrosion treatment of a metallic surface, characterized in that the surface is successively brought into contact with the following compositions: i) at least one water-based, alkaline cleaner according to claim 10, ii) a first water-based rinsing composition,

12. The method according to claim 11, characterized in that the acidic conversion composition in step iv) is a composition for nickel-free zinc phosphating which, in addition to zinc ions and manganese ions, also contains phosphate ions and to which no nickel ions have been added.

13. The method according to claim 11, characterized in that the acidic conversion composition in step iv) is a composition for applying an organosilane-based thin-film system which, in addition to at least one organosilane - including its hydrolysis and condensation products - optionally also at least one titanium -, zirconium and / or hafnium compound.

14. A metallic surface treated to protect against corrosion, characterized in that it can be obtained using a method according to any one of claims 11 to 13.

15. Use of the metallic surface according to claim 14 in the field of the metalworking industries.