EP0283912A2 - Process for the formation of metal sheets in the presence of cooling and lubricating agents - Google Patents

Abstract

In the forming of metal sheets, coolants and lubricants have hitherto been used which had to be carefully removed before coating of the resulting products. The novel process is intended to allow simplified forming with subsequent coating. The forming of metal sheets is carried out in the presence of a coolant and lubricant which is an aqueous emulsion or solution of a binder or binder mixture, which produces a paint film. The film thus produced on the formed product can be cured or dried immediately afterwards. Manufacture of cans.

Description

A process is described for forming sheet metal, in particular iron and aluminum sheet, in the presence of a coolant and lubricant. In this process, an aqueous emulsion or solution of a paint film-forming binder or binder mixture is used as the coolant and lubricant, the film on the formed product from the aqueous emulsion or solution being cured or dried immediately after the forming process. The method has the advantage that the coolant and lubricant emulsion remaining on the metal surface after the forming process does not have to be washed off, but rather can be cured, for example by heating in the heat, to form a lacquer film.

In the production of metallic molded parts, a lubricant is used for a low degree of deformation, and a coolant and lubricant for a high degree of deformation, which has the task of minimizing tool wear and, in the case of extreme forming such as deep drawing and stripping, dissipating the forming heat and cold welding prevent between material and tool. If the parts shaped in this way are then intended for use in a corrosive environment, the surface of the moldings must be freed of lubricant and then painted. The higher the adhesion to the paint, the more important it is to clean or pretreat the metal surface.

Probably the most intensive cleaning of the metal surface is necessary in the manufacture of cans for the beverage and food sector, in particular in the manufacture of deep-drawn / ironed two-part cans.

Today's technology works like this:
A sheet metal strip is greased with about 1 g / m² of coolant and lubricant emulsion or solution (K + S emulsion or solution) before punching out and drawing the cup. When the bowl is stretched into a can, the K + S emulsion is used to cool the tools and cans in excess (∼10 l / min.).

The K + S dripping-wet can is cut to the correct height and cleaned inside and outside in a washing machine with water and dried as quickly as possible. The can runs upside down between two conveyor belts in different flow zones. In it, cleaning liquid, rinsing liquid, passivation liquid and rinsing liquid are sprayed in succession with a powerful jet. The further processing is then carried out with external painting and internal painting by roller or spray application. Coolant and lubricant emulsions based on mineral oils and polyglycols are known (DE-PS 29 10 496, EP-A-158 306, DE-OS 34 06 427). The K + S emulsion is removed by saponification at 40 ° C to 80 ° C (EP-A-154 950). The procedural complexity of the cleaning agent is extremely high. If traces of the cleaning agent remain on the metal surface, there will be problems with the properties of the coatings applied later. When painting with water-borne paints, pinholes and craters can occur if the metal surface is contaminated with mineral oils or drawing greases.

The object and invention is to provide a method and a means by which the problematic cleaning treatment of metal substrates following the forming treatment is avoided and an immediate coating of the formed products obtained is made possible. This object is achieved by the method described in the patent claims and the means for carrying out this method, which form the subject of the invention.

Surprisingly, it has been shown in the context of the invention that this object can be achieved by using lacquer binders in the form of aqueous emulsions and / or solutions as coolants or lubricants in the shaping of the metal substrates, acid functions being contained in these binders, for example (e.g. 2 to 250 mg KOH per g solid resin). The binders can then be cured directly to a coating.

The present invention thus creates a coolant and lubricant system which can remain on the metal surface after the shaping work and cutting work and cures during drying either alone or after overcoating with, for example, a water-dilutable paint to form a protective film.

An advantage of the method according to the invention is that the metal surface intended for sheet metal forming comes into contact only with those reagents which can be cured to form an effective protective lacquer. The saponification of the oil-water emulsion or polyglycol-water emulsion previously used as a coolant and lubricant, with subsequent cleaning and drying, is no longer necessary. The procedure according to the invention has a particularly favorable effect on the ironing treatment of a sheet metal substrate in the production of cans. This is always a new one Metal surface formed, which is protected against corrosion by the use of a binder emulsion according to the invention in the "Statu nascendi" and provided with the curable coating.

The binders used in the aqueous emulsions according to the invention are preferably those with an acid number of up to 250, measured as mgKOH per g of binder (solid resin). The acid number is at least 2, so that a range of 2 to 250 results according to the invention. The acid number is preferably 2 to 150 or 3 to 100 and particularly preferably 5 to 75.

For the treatment of cans intended for food or beverages, amine-neutralized epoxy resin-phosphoric acid esters, acrylate resins and / or polyesters with an acid number of 2 to 150 are used, optionally combined with melamine and / or phenolic resins, the baked films of which are physiologically harmless and are neutral in taste. Because the K + S emulsion according to the invention has good corrosion protection properties, this system can be used at an earlier stage in sheet metal strip treatment than before. In the case of tinplate, for example, chrome passivation and / or DOS pre-greasing can be dispensed with.

Suitable base binders are, for example, epoxy, acrylate, polyester and alkyd resins with acid functions. The acid functions such as carboxyl groups, phosphoric acid or sulfonic acid residues can be introduced in a manner known per se. Examples of usable epoxy resin phosphoric acid esters are described in DE-OS 27 57 733. Also suitable are polyesters modified with phenolic resin, as described, for example, in DE-OS 26 38 464 and EP-A-62 786. Further examples of resins which can be used are those in DE-OS 27 21 822 and DE-OS 27 21 823 and graft polymers of epoxy resins described in EP-A-17 911.

Combinations of different binders can also be used, for example combinations of epoxy resin-acrylic acid graft polymers with epoxy resin-phosphoric acid esters, as described in EP-A-144 872 and EP 174 628. Further examples are graft polymers on epoxy resin phosphoric acid esters, as are described, for example, in EP-A-122 603 or EP 164 589.

Specific examples of binders that can be used are as follows:

1. A fatty acid-free, acidic phosphoric acid ester with an acid number of 10 to 40, made from an epoxy group-containing polyglycidyl ether and / or polyglycidyl (meth) acrylate resin with more than 1.3 epoxy groups per molecule by reaction with 0.2 to 1.0 mol of 70 to 90% orthophosphoric acid per epoxy group at 110 to 130 ° C if necessary in the pressure vessel in the presence of some water.

It is naturally possible to use combinations of two or more of the compounds mentioned. It is preferred to use compounds with a relatively low acid number, for example 15 to 35, in a mixture with compounds with a higher acid number, for example 35 to 100. Under certain circumstances, compounds with a very low acid number are not readily soluble in water. However, sufficient miscibility is achieved by mixing with compounds with a high acid number. Sufficient miscibility with water in the case of compounds with a low acid number of, for example, 20 to 40 can also be achieved by adding a relatively high OH number to these components game gives 100 to 200. A mixture of 40 to 80% by weight of a fatty acid-free, acidic epoxy resin-phosphoric acid ester with a low acid number of 10 to 30 and 20 to 60% by weight of a phenolic resin-modified, carboxyl group-containing, oil-free polyester with a higher acid number of 35 to 70 is preferred .

mit

verstanden, wobei
Rʹ = -C_mH_2m+1 und/oder bevorzugt -H,
R⁴ = -SO₂-, -O-, bevorzugt -CR³₂-,
R² = -(CR¹₂)_m-, bevorzugt -CH₂-,
R³ = Halogen oder Rʹ
n = 0 bis 15, bevorzugt 6 bis 13, und
m = 1 bis 8, bevorzugt 1 ist.Polyglycidyl ether in the context of this invention preferably includes resins of the general idealized formula

With

understood, whereby
Rʹ = -C _m H _{2m + 1} and / or preferably -H,
R⁴ = -SO₂-, -O-, preferably -CR³₂-,
R² = - (CR¹₂) _m -, preferably -CH₂-,
R³ = halogen or Rʹ
n = 0 to 15, preferably 6 to 13, and
m = 1 to 8, preferably 1.

ersetzt werden, wobei R = H oder ein niedriger, gege­benenfalls mit verschiedenen Substituenten versehener Alkylrest ist und q = 2 bis 6 und p = 3 bis 50 bedeutet. Beispiele sind Reaktionsprodukte von Epichlorhydrin mit Polypropylenglykol oder Polybutylenglykol verschiedenen Molekulargewichtes. Die Epoxidharze können durch Reaktion von längerkettigen Dicarbonsäuren wie Isophthalsäure, Cyclohexandicarbonsäure, Adipinsäure oder Sebacinsäure mit langkettigen Polyalkoholen wie Hexandiol-1,6 , Glycerin, Monoanhydropentaerythrit, Polytetrahydro­furandiol, Polycaprolactondiol, Polycaprolactamdiol oder Polybutadiendiol, sowie NCO-terminisierten Reaktions­produkten aus Polyalkoholen und Polyisocyanaten oder halbblockierten Diisocyanaten modifiziert sein oder stufenweise hergestellt werden. Es werden etwa 0.5 bis 3 Gew.-% Orthophosphorsäure mit 100 g Epoxidharz umgesetzt. Für die Verdünnbarkeit ist außerdem der An­teil Wasser maßgebend, der für die Addition an die Oxirangruppe und zur Hydrolyse der gebildeten Phosphor­säuredi- und triester dient.Examples are reaction products of different molecular weights from dihydroxy-diphenylpropane (bisphenol A) or dihydroxy-diphenylmethane (disphenol F) and epichlorohydrin and / or methylepichlorohydrin. Products with higher molecular weights can also be produced by other processes, for example by reacting low polyepoxides with bisphenol A. These polyglycidyl ethers have an epoxy equivalent of 180 to 5000, especially 2000 to 4000. They can be partially or completely hydrogenated or in Mixtures with different epoxy equivalent or with different structure can be used. Polyglycidyl ethers of phenolic novolak resins are also suitable, as a result of which the functionality can be increased from 2 to about 6 glycidyl groups per molecule. The functionality of the resins can also be reduced by reaction with monofunctional (alkyl) phenols or monocarboxylic acids, preferably α-branched monocarboxylic acids. For elasticization, part of the polyglycidyl ether described can be aliphatic polyglycidyl ether of the formula

are replaced, where R = H or a lower alkyl radical, optionally provided with different substituents, and q = 2 to 6 and p = 3 to 50. Examples are reaction products of epichlorohydrin with polypropylene glycol or polybutylene glycol of different molecular weights. The epoxy resins can be obtained by reacting longer-chain dicarboxylic acids such as isophthalic acid, cyclohexanedicarboxylic acid, adipic acid or sebacic acid with long-chain polyalcohols such as 1,6-hexanediol, glycerol, monoanhydropentaerythritol, polytetrahydrofuranediol, polycaprolactonediol, polycaprolactam diol Polybutadiene diol and NCO-terminated reaction products made from polyalcohols and polyisocyanates or semi-blocked diisocyanates can be modified or produced in stages. About 0.5 to 3% by weight of orthophosphoric acid are reacted with 100 g of epoxy resin. The proportion of water which is used for the addition to the oxirane group and for the hydrolysis of the phosphoric acid di- and triester formed is also decisive for the dilutability.

Resins containing epoxy groups can also be poly (meth) acrylate resins which, in addition to (meth) acrylic acid esters with C₁ to C₁₅ alcohol residues and / or optionally substituted vinylaromatics, contain copolymerized epoxy-containing unsaturated monomers. Suitable for this are glycidyl ethers of (meth) acrylic acid and maleic and / or fumaric acid, glycidyl ethers of unsaturated alcohols such as vinyl alcohol, allyl alcohol and / or hydroxyalkyl (meth) acrylate. Glycidyl compounds of (meth) acrylamide, maleic and / or fumaric acid diamide or maleimide. The resins are produced by radical solution polymerization at temperatures from 60 to 160 ° C.

2. A fatty acid-free, acidic epoxy resin carboxylic acid ester with an acid number of 30 to 50 is prepared by reacting an epoxy group-containing resin with more than 1.3 epoxy groups per molecule and an epoxy equivalent of 180 to 2500 with mono (alkyl) phenols and / or excess multinuclear phenols and subsequent reaction of the epoxy group-free reaction product thus obtained with cyclic carboxylic anhydrides. The epoxy equivalent of the compound used is preferably 400 to 2000.

These basic binders are not modified with linear saturated or unsaturated fatty acids. These are epoxy resins as described above and which have been reacted with saturated or unsaturated aliphatic, cycloaliphatic and / or aromatic polycarboxylic acids and / or their anhydrides, such as adipic acid, sebacic acid, isophthalic acid, cyclohexanedicarboxylic acid, tetrahydrophthalic anhydride, trimellitic anhydride. The reaction can also be carried out with hydroxycarboxylic acids such as dimethylolpropionic acid or hydroxybenzoic acid. Resins whose ester groups are difficult to saponify are particularly suitable.

A common method is the reaction of the epoxy groups with monocarboxylic acids that form difficult-to-saponify esters, or with (C₁ to C₁₅ alkyl) phenols. The reaction takes place in the melt or by azeotropic condensation at temperatures from 100 to 220 ° C., preferably 130 to 180 ° C., optionally with the addition of suitable basic catalysts, such as triphenylphosphine, tetramethylammonium chloride or suitable metal salts, such as chromium-III-ethylhexanoate complex . Examples of phenols are substituted monophenols, such as tert-butylphenol, and bisphenol A, which, when used in excess, breaks off the polymer chain. Saponification-stable esters are prepared by reaction with acrylic monocarboxylic acid, such as benzoic acid or tert-butylbenzoic acid, or with linear α-branched C₂ to C₂₀-alkane monocarboxylic acids, such as Versatic acid®. A prerequisite for the increased saponification stability of the resin is that all epoxy groups have been converted, if possible. By linking two molecules of this intermediate with preferably C₄ to C₁₈ alkanedicarboxylic acids, a hydrolysis-stable elastification is achieved.

In a second reaction step, cyclic anhydrides are attached to the secondary hydroxyl groups at reaction temperatures from 100 to 160 ° C. to form a relatively stable acidic half-ester. As cyclic anhydrides are preferably used succinic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride or tricarboxylic acid anhydrides, the carboxyl group of which is esterified with a linear or branched C₂ to C₂₀ monoalcohol. Resins of this type are described in DE-A-23 54 607 (US-A-3,862,914) or DE-C-27 47 818. The acid number of the resins is 25 to 100. In order to achieve good sterilization strength, it should be as low as possible, preferably below 40, particularly preferably below 35.

3. A phenol resin-modified, carboxyl-containing, oil-free polyester with an acid number of 35 to 110 and an OH number of 15 to 175, made from polyols or hydroxyl-containing polyesters or polyethers with preferably 2 to 6 OH groups per molecule with higher molecular weight hydroxyl-containing phenol ethers at 60 to 160 ° C.

In order to achieve optimal properties, the polyester resins used must have an average molecular weight Mn have at least 1500 and each contain 0.3 to 3, preferably 0.8 to 2 hydroxyl and carboxyl equivalents per 1000 g of polyester. In a known manner, the polyester unsaturated fatty acids are not produced from polyalcohols such as 1,6-hexanediol, neopentyl glycol, cyclohexanedimethanol, trimethylolpropane, glycerol and / or pentaerythritol, and polycarboxylic acids such as adipic acid, isophthalic acid, cyclohexane-1,4-dicarboxylic acid or trimellitic anhydride contain. These oil-free polyesters are used in the absence of acidic catalysts or polynuclear phenols, especially alkylphenols and with aldehydes at 60 to 160 ° C, especially 100 to 130 ° C, implemented. Preferred phenols are monoalkylphenols, such as p-tert-butylphenol, p-cumylphenol, nonylphenol, phenylphenol or bisphenol A (1.1-bis-4-hydroxy-phenyl-propane), which are incorporated in amounts of 0.5 to 50% by weight . Particularly favorable results with regard to the resistance properties of the baked films against aggressive solvents are achieved with partial or complete replacement of the phenols mentioned by phenolcarboxylic acids. Suitable for this are, for example, 4,4-bis- (4-hydroxyphenyl) pentanoic acid, glycolic acid derivatives of diphenols, such as 2- (4-hydroxyphenyl) -2- (carbethoxyphenyl) propane, or salicylic acid. As usual in phenol resin chemistry, formaldehyde is preferably added as an aldehyde in an amount of 0.5 to 3 moles per mole of phenolic hydroxyl group. According to another process, such condensation products can be prepared by reacting an isolated resol made from mono- and / or polynuclear phenols with carboxyl-containing polyesters at 80 to 240 ° C, which have an average molecular weight Mn from 300 to 1500 and an acid number from 50 to 150 mg KOH / g solid resin. The phenolic resin-modified polyester preferably contains an acid number of 30 to 110, particularly preferably 40 to 90.

4. Carboxyl-containing acrylate resins with an acid number from 20 to 120 and a hydroxyl number from 0 to 200 can be used as non-yellowing resins. When using a resin with a low acid number, a high hydroxyl number is to be used and vice versa. For example, a soluble product can be produced with an acid number of 25 and a hydroxyl number of 150. Such resins are known in the art Technique preferably by radical solution polymerization at temperatures from 60 to 160 ° C from α, β-unsaturated mono- and dicarboxylic acids and their esters with linear or branched aliphatic and cycloaliphatic mono- and polyalcohols, the polyalcohols being only esterified with one hydroxyl group and the remaining hydroxyl groups remain as potential crosslinking sites. Examples of monomers containing carboxyl groups are acrylic acid, methacrylic acid, crotonic acid, maleic acid (anhydride) or fumaric acid, or maleic or fumaric acid monoesters. The (meth) acrylic acid esters and / or maleic acid and / or fumaric acid dialkyl esters include, for example, n-butyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, isopropyl methacrylate, stearyl methacrylate, cyclohexyl acrylate, benzyl acrylate and / or corresponding crotonic acid. Unsaturated ethers such as ethoxyethyl methacrylate or tetrahydrofury acrylate can also be used. The copolymerizable monomers also include vinyl esters of α-branched C₂ to C₂₀ alkane carboxylic acids, such as the vinyl ester of Versatic acid®. The monomers with hydroxyl groups include allyl alcohol, monovinyl ethers of polyols, such as monovinyl ethers of ethylene glycol and butanediol, and hydroxyl-containing allyl ethers or esters, such as 2,3-dihydroxyallyl ether, trimethylolpropane monoallyl ether or 2,3-dihydroxypropanoic acid allyl ester. (Meth) acrylic acid hydroxyalkyl esters, such as β-hydroxypropyl methacrylate, hydroxyethyl acrylate, butanediol 1,4-monoacrylate, 2,3-dihydroxypropyl methacrylate, polypropylene glycol monoacrylate or fumaric acid di-hydroxyalkyl ester, are particularly suitable.

Corresponding monomers can also be prepared via (meth) acrylamides, such as hydroxyethyl acrylamide or 2-hydroxypropyl methacrylamide. Particularly elastic properties are obtained when using a reaction product of hydroxyalkyl (meth) acrylate with ε-caprolactone.

The binders are neutralized with the neutralizing agents individually or in a mixture and, if appropriate, diluted with deionized or distilled water in the presence of solvents. Easily volatile amines, such as ammonia, lower primary, secondary or tertiary alkylamines, which easily leave the film when baked, serve as neutralizing agents. However, volatile amines and / or amino alcohols can also be used if they have the ability to react firmly into the film dressing by means of suitable substituents, such as hydroxyl groups. Examples of amines are diethylamine, triethylamine, n-butylamine, morpholine, N-methylmorpholine, aminoethanol, diisopropanolamine, 2-dimethylamino-2-methylpropanol, 2-amino-2-methyl-1-propanol, tris- (hydroxymethyl) aminomethane, methyldiethanolamine , Triethanolamine. The pH of the K + S emulsions is preferably between 7.0 and 9.0.

Systems used for the coating of metal objects, such as cans, which are intended for the intake of food, use amines which comply with the health regulations, such as the FDA of the USA and the BGA of the Federal Republic of Germany; an example of this is dimethylaminomethylpropanol (DMAMP).

Aldehyde condensation resins can be chemically incorporated into the binders for the K + S emulsions and / or admixed before or after the emulsion preparation. Will the Once the K + S emulsion has been overpainted again after forming, it is often practical to use the K + S emulsion without a crosslinking agent and then apply a lacquer with a crosslinking agent over it.

One or more aldehyde condensation resins, for example, can serve as thermal crosslinking agents for the acid-functional binders. They are added to the base binders in an amount of, for example, 2 to 30% by weight, in particular 10 to 30% by weight, based on the base binder. The weight ratio of parent binder to crosslinking agent is preferably about 80:20. Aldehyde condensation resins are understood as thermal crosslinking agents: amine and phenol-formaldehyde condensation resins as they correspond to the prior art, but also copolymers which can react via built-in reactive monomers. These crosslinking agents are generally dispersible in the binders according to the invention. To improve solubility, they can optionally contain an acid number of up to about 80 mg KOH per g solid resin.

Amine-formaldehyde condensation resins are formed by the reaction of aldehydes with urea, N-alkylurea, dicyandiamide, various triazines, such as melamine, benzoguanamine and acetoguanamine or their mixtures. Aldehydes can be monofunctional, but also polyfunctional. Examples include formaldehyde and its polymerization products, such as paraformaldehyde, polyoxymethylene, trioxane, or aliphatic and cyclic aldehydes, such as glyoxal, acetaldehyde, acrolein, propionaldehyde, butyraldehyde and furfural. Depending on the reaction conditions and degree of methylolation, resins with different molecular weights and different reactivity are obtained. The condensation with formaldehyde, furfural, paraformaldehyde, polyoxymethylene or trioxane is generally added of weak acids or bases as a catalyst. Strong acids are used for the codification with acrolein, glyoxal, acetaldehyde, propionaldehyde or butyraldehyde. The primary reaction product is neutralized, then aldehyde is added and further reaction is carried out with the addition of weak acids or bases. The preferred aldehyde is formaldehyde. The alcohol, preferably methylol, of the aldehyde condensation products are partially or preferably completely etherified with alcohols. Preferred amine-formaldehyde resins are those whose main amount of methylol groups has been reacted with monoalcohols or mixtures thereof. Methanol, ethanol, propanol, butanol, heptanol, benzyl alcohol and other aromatic alcohols, cyclic alcohols, such as cyclohexanol, or monoethers of ethylene glycols, such as ethoxyethanol or butoxyethanol, are particularly preferred. If alcohols with more than 4 carbon atoms are to be incorporated, the methylol group is first etherified with a lower alcohol and then the higher alcohol is introduced by transetherification. The preferred alcohols are lower aliphatic monoalcohols, such as methanol and / or butanol. Melamine resins which are reacted with 3 to 6 moles of formaldehyde and then completely etherified with methanol are particularly preferred. The resins are manufactured according to the state of the art and offered by many companies as sales products. When etherified with hydroxycarboxylic acids such as hydroxybenzoic acid, salicylic acid or dimethylolpropionic acid, carboxyl group-containing melamine resin types are formed which are unsaturated when using hydroxyalkyl (meth) acrylates or allyl alcohol.

The preferred phenolic resins are reaction products of phenol or substituted phenols with various aldehydes in molar excess in the presence of alkaline catalysts (resol type). Examples of phenolic compounds are phenol, cresol, xylenol, resorcinol and substituted phenols such as p-tert-butylphenol, p-tert-amyl phenol, p-phenylphenol, isothymol, cardanol or polynuclear phenols such as dihydroxy-diphenyl-propane (bisphenol A) or dihydroxy-diphenylmethane (bisphenol F). Phenolic novolak resins are also used as the starting material, which are optionally defunctionalized with monocarboxylic acids, preferably α-branched monocarboxylic acids, monophenols, which are particularly substituted with C₂ to C₁₈ alkyl groups or also monoepoxides such as α-monoepoxyalkanes, monoglyceride ethers or monoglyceride esters. Formaldehyde and its polymerization products such as paraformaldehyde, trioxymethylene, polyformaldehyde or also hexamethylenetetramine are used as aldehydes. Acetaldehyde, paraldehyde and metaldehyde, butyraldehyde or furfural are particularly suitable. The methylol groups are partially or preferably completely etherified with methanol, ethanol, propanol and / or butanol. Resins are preferred which are reacted per phenolic OH group with excess formaldehyde, ie about 1.1 to 2.5 mol of formaldehyde in an alkaline medium. Resins based on bisphenol A, which are reacted with about four formaldehyde molecules and are completely etherified with butanol, are particularly preferred. Both water-insoluble and carboxyl-containing phenolic resins of different molecular weights can be used. Suitable phenol carboxylic acids for this are, for example, 4,4-bis (4-hydroxyphenyl) pentanoic acid, glycolic acid derivatives of bisphenols, such as 2- (4-hydroxyphenyl) -2 (carbethoxyphenyl) propane, or salicylic acid. If necessary, very low molecular weight, optionally unsaturated, methylolphenol ethers can also be used, such as trimethylol phenol allyl ether (Methylonharze ®).

Reactive copolymers which can crosslink with carboxyl groups or hydroxyl groups of the binders are produced by copolymerization of N-methylol ethers of the (meth) acrylamides or methacrylamidoglycolate methyl esters. In addition to these reactive monomers, there are also (meth) acrylic acid esters, hydroxylalkyl (meth) acrylates or optionally substituted vinyl aromatics. N-methylol ethers can also be incorporated by polymer-analogous reaction of polymerized (meth) acrylamide with formaldehyde and monoalcohols. The resins are generally prepared by solution polymerization with a solids content of 60 to 90% by weight with the addition of free radical initiators.

Within the scope of the invention it has surprisingly been found that aqueous emulsions of water-dilutable binders can take on the function of lubricant and coolant emulsions in the processing of metal substrates, such as metal sheets. Aqueous emulsions are used which, when neutralized with amines, are not tacky and can therefore perform the lubricant and coolant functions. It has been shown that this function is achieved in particular with the acid numbers defined above. Without wanting to make a binding statement, it can be assumed that the part of the emulsions that gets between the tool and the material creates a hydrodynamic lubricating film that prevents the so-called cold welding.

The binder emulsions can contain customary additives, for example ionic or non-ionic emulsifiers, defoamers, leveling additives, waxes, lubricants and other customary liquid additives.

The emulsions according to the invention have solids concentrations of 1 to 10% by weight. These concentrations can vary depending on the application. When applied to the metal substrate, for example the sheet, before the shaping treatment, there are preferably solid concentrations of 0.2 to 20% by weight. During the cutting, pressing or deep-drawing processes, for example in the cup press or the ironing press, for example Kon concentrations of 5 to 20 wt .-% may be preferred. The solids concentration in the emulsions also depends on the desired coating obtained by hardening after the shaping process. Such a coating can serve, for example, as a primer or as a final top coating.

The method according to the invention can be applied to all metal substrates which are subjected to a shaping treatment in which metal surfaces are released, such as pressing, deep drawing, drawing, cutting and / or punching. It can be applied particularly favorably to the treatment of metal sheets. Any type of sheet metal is suitable, for example steel sheet, tin-plated sheet, galvanized sheet, black sheet or aluminum sheet.

The method according to the invention is particularly suitable for the production of two-part cans, the can body being produced by cup drawing and ironing treatment and the can lid being punched out of sheet metal. The method can also be used particularly advantageously for the production of those can lids in which pouring openings are to be produced according to the sealing plate principle. In this case, the emulsions used according to the invention serve as lubricants or paints for the cut surfaces.

Binders, crosslinking agents and amines which comply with the health regulations of the individual countries (eg FDA and BGA) are used in the manufacture of cans which are intended to contain food and beverages, such as beer. Of particular interest is the process according to the invention for the production of cans from aluminum for the intake of food and beverages. The coating obtained can serve as a final coat.

In the case of critical filling goods, especially for use in steel cans, it may be necessary to repaint or overpaint the inside. It can be overpainted with the same binder systems. However, the lacquer should contain a crosslinking agent in order to achieve the necessary resistance to the contents. Under certain circumstances, the crosslinking agent can also react with the K + S coating if it originally did not contain any crosslinking agent.

EXAMPLE 1 ( cross-linking K + S system) Epoxy resin phosphoric acid ester:

914 g of polyglycidyl ether based on bisphenol A with an epoxy equivalent weight of 2250 are dissolved in 440 g of butoxyethanol while heating to 125 ° C. 19.2 g of 85% orthophosphoric acid are diluted with 100 g of butoxyethanol and added over 30 minutes with vigorous stirring at 125 ° C. This temperature is held for 2 hours until the orthophosphoric acid has reacted completely and then cooled to 115.degree. 10 g of water below the surface are carefully added to the flameproof system, the pressure temporarily increasing slightly. The mixture is then held at 115 ° C. for 2 hours to complete the hydrolysis. The product obtained is diluted with butoxyethanol to a solids content of 60% by weight.
Acidity: approx. 20 (mg KOH per g solid resin).

The cooling, lubricating and painting emulsion is made by mixing:
21.3% epoxy resin phosphoric acid ester 60%
3.7% carboxy-functional melamine resin of the HMM type (hexamethoxymethylmelamine) with an acid number of about 30 (mg KOH per g solid resin)
0.9% dimethylaminomethylpropanol (80% in water)
0.1% polysiloxane as leveling agent
and stirring with a dissolver for 30 minutes at 60 ° C. The concentrated material is carefully diluted with 74% deionized water after thorough stirring and filtered.

The emulsion has a solids content of 15% by weight and a pH of 9.0.

The 15% emulsion is used for the bowl drawing, and for the ironing, it is diluted to a solids content of 4.5% by weight with deionized water. The can thus produced using commercially available tools and the coolant and lubricant according to the invention is freed of excess K + S standing upside down for 2 minutes and then baked at 220 ° C. for 3 minutes.

The can surface has a trouble-free, optically perfect, smooth lacquer film with a dry film thickness of 1.8 g / m².

To increase the weight of the paint on the inside of the can, the K + S emulsion can be sprayed on conventionally. For this purpose, 10% butoxyethanol, 1.1% silicone-modified wetting agent are added to the binder mixture instead of the leveling agent and diluted to 33% solids with deionized water.

EXAMPLE 2 (Self- Crosslinking K + S System)

The cooling, lubricating and painting emulsion is made by mixing:
29.5% polyester, modified with phenolic resin (acid number 70 to 90 mg KOH, solids 80% in butoxyethanol)
1.0% dimethylaminomethylpropanol (80% in water)
1.6% silicone modified wetting agent
while stirring with a dissolver for 5 minutes at 30 ° C. Then 68.1% deionized water is slowly added with vigorous stirring and filtered.

The K + S emulsion has a solids content of 15% by weight and a pH of 9.8.
The procedure is then analogous to EXAMPLE 1.

EXAMPLE 3 (external and self-crosslinking K + S system)

Mixing the K + S emulsions of Examples 1 and 2 in a ratio of 1: 5 gives a K + S emulsion with the same result.

EXAMPLE 4

In order to increase the dry film thickness on the finished can, the K + S emulsion from Example 3 can be electrophoretically deposited on the sheet at 25 ° C., 80 volts and 5 seconds in a dipping process and Example 1 further processed. This mainly increases the paint weight in the non-deep-drawn sectors of the can, i.e. in the floor area.

Claims (9)

1. A method for forming sheet metal by ironing in the presence of a coolant and lubricant, characterized in that an aqueous emulsion or aqueous solution of a paint film-forming binder or binder mixture is used as the coolant and lubricant and the film located on the drawn product from the aqueous Emulsion or aqueous solution is cured or dried immediately after the shaping and optionally cutting process. 2. The method according to claim 1, characterized in that an aqueous emulsion or aqueous solution of a binder with acid functions and an acid number of 5 to 250 mg KOH, in particular 5 to 30 mg KOH, the acid functions being neutralized by ammonia, amines and / or amino alcohols are used. 3. The method according to claim 1 or 2, characterized in that an aqueous emulsion of an emulsion polymer is used. 4. The method according to claim 1, 2 or 3, characterized in that an aqueous emulsion or aqueous solution of a thermosetting binder is used. 5. The method according to claim 1, 2, 3 or 4, characterized in that as an aqueous emulsion or aqueous solution of a coating film-forming binder, an aqueous emulsion of an epoxy resin, an acrylate resin, a polyester modified with phenolic resin, a graft polymer of epoxy resin and unsaturated carboxylic acids, one Combination of an epoxy acrylic resin and an epoxy resin Phosphoric acid ester or a combination of graft polymers on epoxy phosphoric acid ester is used. 6. The method according to any one of claims 1 to 5, characterized in that an aqueous emulsion of a thermosetting binder is used which contains a melamine resin, urea resin or phenolic resin as a crosslinking agent. 7. The method according to any one of claims 1 to 6, characterized in that the forming is carried out by stretching to produce metal cans. 8. The method according to any one of claims 1 to 7, characterized in that the forming is carried out on iron, tinned iron or aluminum sheets. 9. The method according to any one of the preceding claims, characterized in that an aqueous emulsion or solution of a paint film-forming binder or binder mixture is used as the coolant and lubricant, which contains no crosslinking agent and the film on the formed product from the aqueous emulsion or solution before or after curing or drying is coated with a coating film-forming binder containing crosslinking agent.