MXPA97007196A - Cleaning agent protector of the corrosion paraacero chapado de est - Google Patents

Abstract

The present invention relates to an aqueous anticorrosive solution for tin-plated steel, in particular for tin-plated steel cans, the solution contains complex fluorides of the boron, titanium, zirconium and hafnium elements, nonionic surfactants, and anticorrosives. having a pH within the range of 3 to 6. The invention also relates to an aqueous concentrate for preparing the solution by means of dilution with water and a method of cleaning tin-plated cans using the solution

Description

CLEANING AGENT CORROSION PROTECTOR FOR ACERQ PLATED TIN This invention relates generally to the cleaning and corrosive testing of tin-plated steel; more particularly food and drink cans of this material, the well-known "tin cans", between the formation and the enamel, stages of the can manufacturing process.

Tin cans are usually produced by preliminary formation, drawing and intense polishing. They have a desirable glossy surface so that after coating them with an opaque or transparent organic enamel or impression of the outer surface, they remain as an attractive package. The sequence of the steps of the process carried out in the production of tin cans usually comprise the wrapping of a tin strip provided with a layer of protection oil from the roll, applying drafting lubricants; in a preliminary way forming a vessel and stretching and polishing intensively until the final form. In the steps of intense drawing and polishing, cooling lubricants such as water or aqueous emulsions are usually also used to facilitate the deep drawing process. After the formation, the residues of the protective oil and lubricants are removed for deep drainage, as well as the metal powder in a cleaning stage. After the cleaning step, the containers pass through one or more water rinsing steps and by decorative printing of the outer surface. Therefore, the surface of the metal must be of such quality that the lacquer or enamel has sufficient adhesive and allows reliable protection against corrosion.

However, in the production of this type of cans it has been found that oxidized spots can develop during or before drying, particularly if the cans are cleaned with an acid medium (pH 3-5) too much water accumulates in certain areas , or if during the suspension of the production line the individual process steps are not finished fast enough. In this way, oxidized spots can develop. They are visible through the enamel and favor a poor adhesion of the enamel, so that the product packed in such a container is not suitable for consumption.

In accordance with the information in ED-B-1 667, the problem can be solved in unstained steel cans, known as black plate cans, by means of the can treatment after the actual cleaning step with an aqueous anti-corrosive solution. containing from 10 to 5,000 ppm (parts per million) of aluminum ions, 10 to 200 ppm of fluoride ions from at least one of the titanium, zirconium and / or hafnium metals and having a pH value of 2 to 5.5 The problem to which the present invention was directed was to provide a treatment solution, a concentrate for its preparation and a treatment process with which the tin cans can be cleaned, and to provide a surface protected against corrosion in a single step. of treatment, so that the corrosion of the surface before the enamel could be prevented and the adhesion of a firm lacquer would be favored.

In a first embodiment, the present invention relates to an aqueous treatment solution for tin-plated steel containing: 110 to 400 ppm of complex fluorides of the boron, titanium, zirconium, and / or hafnium elements; 100 to 2,000 ppm nonionic surfactants; 100 to 1,000 ppm anticorrosive; and regarding the balance, water or an aqueous solution of other active or auxiliary ingredients and that have a pH value in the field of 3 to 6.

The following concentration fields are particularly preferred for the individual active ingredients: 150 to 300 ppm of complex fluorides of the boron, titanium, zirconium and / or hafnium elements; 300 to 1, 000 ppm of non-ionic surfactants 150 to ppm of corrosive It has been found that the addition of aluminum ions to the cleaning solution in an approximate concentration of 50 to 300 ppm, and preferably, approximately 80 to 200 ppm has positive effects.

A soluble aluminum salt in the mentioned concentration range is preferably used as a source of aluminum ions. For example, those which are suitable for this purpose are aluminum nitrate and in particular aluminum sulfate, the least preferred in the interest of corrosion control is aluminum chloride.

Depending on the condition of the surface of the cans before being cleaned, the additional presence of the cleaning solution of one or more monobasic, dibasic or tribasic hydroxycarboxylic acids containing from 4 to 7 carbon atoms in the molecule (the sum total of the hydroxyl and carboxyl groups which are at least 3) as an additional or auxiliary active ingredient in a concentration of 200 to 800 ppm may have favorable effects. The hydroxycarboxylic acid (s) are preferably selected from monobasic, dibasic or tribasic hydroxycarboxylic acids containing β carbon atoms and at least 4 hydroxyl groups. Gluconic acid is particularly preferred. It does not matter whether the acids are used in this manner or in the form of soluble salts in the aforementioned concentration field, more particularly in the form of their sodium salts. The acids will be partially present in the pH value of the cleaning solution in the field of 3 to ß in their acid form and partly as carboxylate anions, depending on their acid constants.

The complex fluorides of the boron, titanium, zirconium and / or hafnium elements can also be used in the form of their acids, for example tetrafluoruroborated acid or the hexafluoride acids of titanium, zirconia and hafnium, or in the form of soluble salts in the mentioned concentration field, for example the alkali metal salts. Since these complex fluorides represent anions of strong acids, they will be widely presented as ionic in the pH range of 3 to 6.

In a preferred embodiment, the cleaning solution contains complex boron fluorides in addition to the complex fluorides of at least one of the titanium, zirconium and hafino metals, particularly zirconium. A particularly preferred cleaning solution contains complex boron and zirconium fluorides in a weight ratio of 4: 1 to 1: 1 and more particularly in a weight ratio of 3: 1 to 1: 5: 1.

The nonionic surfactants are the surfactants or mixtures of surfactants having a cloud point of less than about 40 to about 45 ° C. The cleaning solution in this way can be applied by spraying at a working temperature of approximately 50 to 70 ° C without excessive or annoying foam. Suitable surfactants are in particular the ethoxylates and ethoxylates / propoxylates of alkanols containing approximately 10 to 18 carbon atoms. The ethoxylates and / or the ethoxylates / propoxylates can also be encapsulated and can occur, for example, as butyl ether. Preferably, the ethoxylates contain from 4 to 12 ethylene oxide groups, and more particularly, from about 6 to 10 β-ethylene oxide groups while the preferred ethoxylates / propoxylates contain from 3 to 7 ethylene oxide groups and from 2 to 6 ethylene oxide groups. to 6 propylene oxide groups, preferably 4 to 6 ethylene oxide groups and 3 to 5 propylene oxide groups. The alkanol component can be a pure compound having a chain extension of certain carbons. However, the alkanol component can be a mixture of fatty alcohol containing 12 to 14 carbon atoms or an oxoalcohol containing 12 to 15 carbon atoms. A particularly preferred mixture of surfactant contains both ethoxylates and alkanol atosylates / propoxylates, for example in a weight ratio of 1: 3 to 1: 1.

The anticorrosive must be selected, for example, from a mono, di, or triethanolamine of aromatic carboxylic acids, pyridine or pyrimidine derivatives and diethyl thiolurea. Among ethanolamines, triethanolamine is particularly preferred for toxicology reasons (the formation of nitrosamine is avoided). Particularly suitable aromatic carboxylic acids are methyl benzoic acids, nitrobenzoic acids, aminobenzoic acids, for example anthranilic acid or p-aminobenzoic acid, and hydroxybenzoic acids, for example salicylic acid. If the treated cans are to be used for meals, the least preferred ones are those derived from pyridines or pyrimidines and thiolurea diethylca. An example of a suitable inhibitor combination is a mixture of trielanolamine and benzoic acid, for example in a radium by weight of 3: 1 to 1: 3, However, triethanolamine can also be used as the sole anticorrosive.

If complex fluorides are used in the form of their acids in the preparation of the cleaning solution, it would be necessary to increase the pH value of the required field from about 3 to about 6, preferably, from about 4 to about 5 by the sum of one base. Basic alkali metal compounds, for example hydroxics or carbonates, are suitable for this purpose. However, ammonia is preferably used to adjust the pH value.

In another embodiment, the present invention relates to the use of the cleaning solution previously characterized by cleaning, anticorrosive and / or improving the adhesion of the enamel to tin-plated steel articles; more particularly in cans for food or drinks. This process has as an advantage over the conventional process that the control of cleaning and temporary corrosion can be achieved in a single step of the treatment. Corrosion control prevents corrosion of metal surfaces before enamelling, as it should occur for example in the case of factory break. At the same time, both the enamel adhesion and the corrosion control after the enamel are improved without the need for additional treatment after the cleaning step. After treatment with the cleaning solution, the lates are normally rinsed with water, dried at high temperatures and then enameled.

The present invention also relates to a process for cleaning, anticorrosion and / or improving enamel adhesion in tin-plated steel articles, more particularly in food or beverage cans, in which cans are treated with a cleaning solution described above for a period of about 30 to about 150 seconds at a temperature in the range of about 50 to about 70 ° C. The treatment can be carried out by spraying the cans with the cleaning solution or by bathing them in this cleaning solution, the cleaning spray is preferred.

In principle, the cleaning solution according to the invention can be prepared by mixing the individual components together in situ in the aforementioned concentration fields. However, in practice these solutions are normally marketed in the form of aqueous concentrates that could be adjusted to the concentration field required by the user in situ by dilution with water. Accordingly, the present invention also relates to water-based concentrates that when mixed with water in a concentration of approximately 0.5 to 2.5% by weight, the cleaning solution according to the invention is formed. In addition to water and an aqueous solution of other active or auxiliary ingredients, this concentrate preferably contains; 1 to 4% by weight of complex fluorides of the boron, titanium, zirconium and / or hafnium elements; 1 to 20% by weight of nonionic surfactants; 1 to 10% by weight of anticorrosive Preferably, the concentrate comprises as active ingredients: 1.5 to 3% by weight of complex fluorides of the boron, titanium, zirconium and / or hafnium elements; 0. 5 to 3% by weight of aluminum ions; and 3 to 10% by weight of nonionic surfactants; 1. 5 to 5% by weight of anticorrosive A concentrate containing aluminum preferably contains from 2 to 8% by weight of one or more monobasic, dibasic or tribrabic hydrocarboxylic acids containing from 4 to 7 carbon atoms in the molecule (the sum of hydroxyl and carboxyl TS groups at least 3) as additional active or auxiliary ingredients.

The above observations apply to the preferred choice of the individual components. To facilitate the preparation of the concentrate and increase its storage stability, in addition to the actual active ingredients, one or more soluble substances are preferably present in the concentration range of about 1 to approx. 10 by weight and more preferably in a concentration range of about 3 to about 7% by weight. Suitable soluble substances are, for example, xylene sulphonates, alkaline phosphates (for example Triton® H66, a product of Union Carbide) and, in particular, sulphonated curaene. These anionic soluble substances are preferably used in the form of alkali metal salts, for example, sodium and / or potassium salts.

EXAMPLES Example 1 A cleaning concentrate according to the invention was prepared with the following composition by mixing individual components in the following order: water 70.8% by weight fluorophoric acid 1.1% by weight potassium hexafluorozirconium 0.7% by weight aluminum sulfate 17 H20 12.4% by weight 3.3% sodium gluconate by weight fatty alcohol C12 / 14 x 5 ethyl oxide x 4 propyl oxide 3.7% by weight oxoalcohol Ci2-? sx 8 ethyl oxide 1.2% by weight cumene sulfonate Na (40% solution) 4.3% by weight triethanolamine 2.5% by weight Aqueous cleaning solutions with a pH value of 4 to 4.5 were prepared from this concentrate in various concentrations and were used to clean the tin cans that were soiled with the residues of the anticorrosive oils and the deep drawn lubricants. by means of several periods of spraying at a temperature of 63 ° C. The cleaning effect was evaluated by means of visual advice of the surface area free of water (0: no cleaning, 100%: good cleaning). The results are set forth in Table 1.

TABLE 1 Effects of cleaning the concentrate of Example 1 mixed in various concentrations: Concentration Spray time% of free area of (% by weight) (seconds) periods of water outside within 0.7 45 60-65 / 100 90 85-90 / 100 t 60 75/100 0. 9 45 75 / 85-90 60 85-90 / 100 ^ 90 100/100 1. 2 45 90/100 60 100/100 Example 2 To verify the effects of the anticorrosive, concentrates were prepared according to Example 1 without the anticorrosive, the triethanolamine or as a complete or partial substitute thereof. Differences were made in the composition with water. The concentrates were diluted with water to obtain a concentration of 1.2% by weight and a ready-to-use cleaning solution was sprayed onto the cans for 60 seconds at a temperature of 63 ° C. The cans were then left in the spray cabinet for 10 minutes without being sprayed. The formation of the thin corrosion film was evaluated visually on the scoring scale: 6 = very poor, 1 = very good. The results of the scoring are set forth in Table 2.

TABLE 2 EFFECT OF ANTICORROSIVE Anticorrosive in the Concentrate Evaluation of the (% by weight) Score None 6 2. 5 Triethanolamine 3 0.83 Triethanolamine + 0.83 benzoic acid 3.5 1.67 Triethanolamine + 1.67 benzoic acid 2 1.67 Triethanolamine + 1.67 benzoic acid + 0.8 thiourea dithilic 1.5 2.5 Benzoic acid 3.5 1. 5 Trietanolamj na + 1.5 d < = salicylic acid 2 Example 3 To verify the long-term effect of the corrosive after enamelling, the tin cans were cleaned with various solutions, rinsed for 15 seconds under running water and with deionized water, dried in a drying cabinet 170 ° C and enameled once (in normal practice two coats of enamel are applied). Correspondingly, two hundred and eighty eight (288) treated cans were filled with Coca Cola® (Coke®) and stored for 4 months. In this way it was possible to determine the determined number of oxidized cans. The results are set forth in Table 3.

TABLE 3 • CORROSION VERIFICATION (288 COCA COLA® FILLED CANS) Cleaning * Perforated cans Comp. 1 40 Comp. 2 20 Example 1 14 * Comp 1: only running water Comp. 2: commercial alkaline spray cleaner based on NaOH, gluconate, non-ionic surfactants, anticorrosive agents. They were used following the instructions. Example 1 the concentrate of Example 1, 1.2% by weight in water, temperature of 63 ° C, pH 4.3, sprayed for 60 seconds.

Example 4 A cleaning concentrate according to the invention was prepared with the following composition by mixing the individual components in the following order. water 68.1% by weight fluorophoric acid (49% solution) 1.1% by weight potassium hexafluorozirconium 0.7% by weight aluminum sulfate 18 H2O 12.4% by weight 3.3% sodium gluconate by weight C12 / 14 x 5 fatty alcohol ethyl alcohol x 4 propyl oxide 3.7% by weight oxoalcohol C12-1S x 8 ethyl oxide 1.2% by weight cumene sulphonate Na (40% solution) 5.3% by weight triethanolamine 4.2% by weight Of this concentrate, 1.1% by weight was prepared of aqueous solution with a pH value of 4.6. The cans were cleaned with this solution by rolling them for one minute at 60 ° C and rinsing for 15 seconds with tap water and deionized water, drying in a drying cabinet at 170 ° C and enamelling twice. After the test was carried out ) adhesion of the enamel both on the side and on the neck of the cans. For this the cans were placed in a detergent solution boiling at 1% for 30 seconds, rinsed with water and dried. Then the enamel was cross-cut and an adhesive tape (Scotch tape No. 610) was applied and it was exfoliated. The adhesion of the enamel is usually finished without counting a few cases in which it was completely finished.

Claims (13)

1. The use of an aqueous solution with a pH value of 3 to 6 that contains: 110 to 400 ppm of complex fluorides of the boron, titanium, zirconium, and / or hafnium elements, based on the complex fluorides of the elements; 100 to 2,000 ppm nonionic surfactants; 100 to 1, 000 ppm anticorrosive; and like the balance, the water or an aqueous solution of other active or auxiliary ingredients selected from the aluminum ions, hydroxycarboxylic acids and soluble substances for cleaning, anticorrosive and / or improved enamel adhesives for the plated steel of tin.

2. The use claimed in Claim 1, characterized in that the solution contains: 150 to 300 ppm of complex fluorides of the boron, titanium, zirconium and / or hafnium elements; 50 to 300 ppm of aluminum ions; and 300 to 1,000 ppm of nonionic surfactants; 200 to 700 ppm corrosive

3. The use claimed in Claim 1 or 2, or both, characterized in that the solution contains: 200 to 800 ppm one or more monobasic, dibasic or tribasic hydroxycarboxylic acids containing from 4 to 7 carbon atoms in the molecule, the sum of the hydroxyl and carboxyl groups are at least 3, as additional active or auxiliary ingredients.

4, The use claimed in claim 3, characterized in that the hydroxycarboxylic acid (s) is selected from monobasic or diabasic hydroxycarboxylic acids, contains 5 carbon atoms and at least 4 hydroxyl groups.

5. The use claimed in one or more of Claims 1 to 4, characterized in that the solution contains boron and zirconium complex fluorides in a weight ratio of 4: 1 to 1: 1.

6. The claimed use as claimed in one or more of claims 1 to 5, characterized in that the nonionic surfactants are selected from alkanol ethoxylates and ethoxylate / alkanole propoxylates containing from 10 to 18 carbon atoms and from 4 to 12 groups of ethyl oxide in the case of alkanol ethoxylates and from 3 to 7 ethyl oxide groups and from 2 to 6 propyl oxide groups in the case of ethoxylates / propoxylates.

7. The use claimed in one or more of Claims 1 to 6, characterized in that the corrosives are selected from mono-, di- or tri-ethanolamine, aromatic carboxylic acids, pyridine or pyrimidine derivatives and diethyl thiourea.

8. The claimed use in one or more of the Claims 1 to 7 for cleaning, anticorrosion and / or improving the enamel adhesion of tin-plated steel cans for food or beverages.

9. A process for cleaning, anticorrosion and / or improving the adhesion of the enamel, characterized in that the cans are treated with a cleaning solution for use in accordance with one or more of the claims of Ia a la 7 for 30 to 150 seconds at a temperature of 50 to 70 ° C, spraying the cans with a cleaning solution or immersing the cans in the cleaning solution.

10. An aqueous cleaning solution for tin-plated steel containing: 150 to 300 ppm of complex fluorides of the boron, titanium, zirconium and / or hafnium elements, based on the fluorides of the elements 50 to 300 ppm of aluminum ions; Y 300 to 1,000 ppm of non-ionic tensioactive agents; 200 to 700 ppm corrosive and as to the balance, water or an aqueous solution of other active or auxiliary ingredients selected from hydrocarboxylic acids and soluble substances and having a pH value in the range of 3 to 6.

11. A water-based concentrate for preparing the cleaning solution claimed in Claim 10 by dilution with water, characterized in that it contains: 1.5 to 3% by weight of complex fluorides of the boron, titanium, zirconium and / or hafnium elements, based on the complex fluorides of the elements; 0.5 to 2% by weight of aluminum ions; 3 to 10% by weight of nonionic tencioctivos agents; 1.5 to 5% by weight of corrosive and as to the balance, water or an aqueous solution of other ingredients or active auxiliaries selected from hydroxyarbamate acids and soluble substances.

12. A water-based concentrate as claimed in claim 11, characterized in that it contains: 2 to 8% by weight of one or more monobasic, dibasic or tribasic hydroxycarboxylic acids containing from 4 to 7 carbon atoms in the molecule; the sum of the hydroxyl and carboxyl groups is at least 3; as additional active or auxiliary ingredients.

13. An aqueous concentrate as claimed in one or both of Claims 11 and 12, characterized in that it also contains: 1 to 10% by weight of a soluble substance.