JP2730891B2 - Aluminum degreasing cleaning method - Google Patents

Abstract

Aluminium containers are cleaned using alkaline cleaning solns., in which the alkaline cleaning is preceded by a precleaning with an aq. acidic soln. and followed by rinsing with an aq. soln. wherein at least a part of the rinsing soln. is employed in the precleaning step. A soln. of pH from 4 to less than 7, pref. 4.5-5.5 is employed in the precleaning step. The soln. contains 0.005-5 g/l, pref. 0.1-1 g/l, of a tensile, and has a temp. of less than 65.6 deg.C, esp. 32.2-54.4 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to a method for degreasing and cleaning an aluminum surface, and more specifically,
The present invention relates to a method of using an aqueous alkali degreasing detergent for degreasing and cleaning the surface of an aluminum container to be preliminarily cleaned prior to contact with an aqueous alkali degreasing cleaning solution. The invention is particularly suitable for degreasing cleaning of drawn and ironed (DI) aluminum containers of the type used as food and beverage packages. The cup-shaped or dish-shaped bottom of such containers holds a portion of the various degreasing and rinsing solutions during processing, and these are retained if a line stop occurs during the degreasing cycle. The liquid causes local rust on the surface of the container. By using an aqueous alkaline degreasing and cleaning solution whose composition has been adjusted as described in pending US Patent Application No. 669491 filed November 8, 1984 entitled "Alkaline Degreasing Method", Eliminate defects due to local rust,
It has been known that a clean aluminum container of a quality that is industrially satisfactory can be provided. In such a degreasing cleaning cycle, a portion of the degreasing cleaning solution is usually flowed into the first pre-cleaning step and brought into contact with the next aqueous alkaline degreasing cleaning solution to be used. As a result, lubricants and organic pollutants gradually accumulated in the alkaline solution for pre-cleaning, and as a result, it was found that sticky substances and sludge adhered to pipes, screens, tank walls, etc. Was. The method of the present invention, i.e., using an acidic pre-cleaning solution prior to the alkaline degreasing step,
It has been found that the gradual accumulation of lubricating oil and organic contaminants in the pre-cleaning stage is eliminated and that the next degreasing and cleaning cycle allows more effective and efficient degreasing of the aluminum container surface. [Summary of the Invention] In the degreasing cleaning cycle of the aluminum container surface,
Prior to the next alkaline degreasing cleaning, pre-washing with an acid solution removes contaminants that have been dissolved and / or emulsified and are present in the pre-cleaning stage, and that the surface of the part that is operating in the pre-cleaning stage is cleaned. The discovery that sludge formation is substantially reduced and the redeposition of organic contaminants on the aluminum surface being degreased and washed is substantially eliminated is the basis of the present invention. According to the present invention,
By controlling the acidity of the pre-wash solution to less than about neutral, ie, a pH of about 7, the emulsion is disrupted, and organic contaminants float on the pre-wash aqueous solution surface, resulting in a DI
Lubricating oil used in the manufacture of aluminum containers and remaining on the surface of the container is removed from the surface of the container in a pre-cleaning stage and tends to separate from the pre-cleaning aqueous solution surface. It was found that this separated product could be removed by scooping, decanting, or the like. The acid used to acidify the pre-cleaning aqueous solution may be any compatible acid, of which sulfuric acid is a preferred component. The acidification is performed so that the pH of the pre-wash solution is in the range of about 4 to less than about 7. According to the method of the present invention, the surface of the aluminum container is
Following the preliminary cleaning, an alkaline aqueous degreasing cleaning process is performed,
Subsequently, one or more washing processes are performed. Usually, it is preferable to further perform a treatment for applying the corrosion-resistant chemical conversion coating on the surface of the aluminum container, for enhancing the transportability of the aluminum container, and for increasing the adhesion of the lacquer, following the water washing treatment. . Other features and advantages of the invention will be apparent from the description below. When the method of the present invention is carried out especially on DI aluminum containers, the aluminum containers transferred from the body making and trimming device will remove the aluminum fines or smut formed on the surface of the aluminum containers during DI processing. It is transferred to a multi-stage degreasing washing step to be performed.
The aluminum fine particles adhere together with the lubricant used at the time of forming the aluminum container. Aluminum containers with such contaminating particulates and lubricants on the surface are first pre-cleaned to remove particulates and organic contamination from the surface, thereby reducing the accumulation of contaminants in the next alkaline degreasing cleaning step. The acidification of the pre-wash aqueous solution can be carried out using any one or a mixture of various acidic components, of which sulfuric acid is preferred. According to a preferred embodiment of the present invention, the acidified rinsing liquid flows directly into the pre-cleaning tank from the rinsing step following the alkaline degreasing step, or
Alternatively, it is performed by adding an acid to the pre-washing step. According to the teachings of the above-mentioned U.S. Patent Application No. 669,491 and further described herein below, brown rust on the aluminum container body as a result of the line shutdown in the rinsing stage is less than pH 7.5, preferably less than 7.5. It has been found that the use of a mildly acidified wash liquor to a pH of from 6.5 to less than 7 is substantially mitigated or eliminated. According to another finding of the applicant, the use of a highly acidified aqueous base washing solution with a pH below 6.5 and above 1.5 in the washing step following the alkaline degreasing main washing step further enhances aesthetics, It has also been found that the degree of transport of the aluminum containers moved along the rails and transport equipment of the high-speed transport can line is increased, that is, the productivity is increased. Flowing the acidified aqueous rinsing solution directly into the pre-wash tank from the rinsing step can provide some or all of the required acidity in the pre-wash solution. If necessary to achieve the desired pH, an acidifying agent such as sulfuric acid may be supplemented separately. As a result of the fragmentation of the emulsion by using the pre-washing solution acidified as described above, organic dirt and lubricating oil tend to separate from the solution, and the organic dirt and the like can be scooped or drained from the tank weir. This method has the advantage that the accumulation of organic contaminants during the long-term use of the pre-cleaning solution is reduced because the pre-cleaning solution can be immediately removed from the surface of the processing tank by a method such as flowing out. The pre-cleaning solution may further contain one or a combination of two or more surfactants effective for improving the removal of organic contaminants from the surface of the aluminum container. Surfactants which can be used satisfactorily for this purpose are anionic, cationic or non-ionic surfactants. A typical example of such a surfactant is Tergitol Anionic-08 (Un
ion Carbide anionic surfactant, presumably sodium 2-ethylhexyl sulfate), Triton DF-16 (Rohm
& Haas modified polyethoxylated non-ionic surfactants that appear to be linear alcohols), Polytergent S-505 L
F (a nonionic surfactant that appears to be a modified polyethoxylated linear alcohol from Olin), Surfonic LF-17 (Jeffe
rson Chemical Inc., a nonionic surfactant believed to be an alkyl polyethoxylated ether), Plurac RA-30 (BAS
F Wyandotte, a non-ionic surfactant that appears to be a modified oxyethylated linear alcohol), Plurac D-25 (BASF
Wyandotte's modified oxyethylated non-ionic surfactant, which may be a linear alcohol, Triton X-102 (Rohm
And non-ionic surfactants that seem to be octylphenoxy polyethoxy alcohols from Hass), Antarox BL 330
(A non-ionic surfactant presumably GAF alkyl poly (ethylphenoxy) ethanol), Pluronic L61
(BASF Wyandotte's nonionic surfactant, which is thought to contain only ethylene oxide and propylene oxide chains), Triton CF-10 (Rohm & Hass, Inc., a carbon chain with 14 carbon atoms and 16 moles of ethoxy) Surfactant AR 150 (a nonionic surfactant that is believed to be a 15 mole ethoxylated ethoxylated abietic acid derivative from Hercules), Antarox LF-330 (G
AF's non-ionic surfactant, which may be an alkyl poly (ethyleneoxy) ethanol, Renex 20 (ICIUn
nonionic polyoxyethylene esters of mixed fatty acids and resin acids from ited States), Pegosperse 700-T0
(Nonionic surfactant from Glyco Chemicals, which is likely to be an abietic ester containing 14 to 16 moles of ethoxy groups), Igepal Ca-630 (Nonionic surfactant which appears to be alkylphenoxypoly (ethyleneoxy) ethanol from GAF) Surfactant, Trycol LF-1 (Emery Indust-rie
(nonionic surfactants which are considered to be alkylpolyethers of S. Co.). If a surfactant as described above is used, its usable concentration in the prewash solution is generally in the range of 0.005 to 5 grams per liter, preferably 0.1 g / 1.
From 1g / 1. The pre-cleaning solution is applied to the aluminum
゜ F (16 ° C) to 200 ° F (93 ° C), preferably 150 ° F (6
5 ° C), for example in the range of 90 ° F (32 ° C) to 130 ° F (54 ° C). The contact between the aluminum surface to be degreased and cleaned and the pre-cleaning solution can be performed by immersion, spraying, etc., particularly in the case of an aluminum container, since the shape is complicated. Spraying is a preferred method because it is evenly distributed on the inner and outer surfaces of the surface. According to a preferred embodiment of the present invention, a portion of the prewash solution is continuously withdrawn and transferred to a disposal site after appropriate treatment. Replenishment water with moderate acidity, with or without surfactant addition, is added to the solution in the pre-wash tank to maintain the desired acidity and volume. Subsequent to the pre-cleaning step, the pre-degreased and cleaned aluminum container is transferred to a degreasing and cleaning step including an aqueous alkaline solution. A preferred degreasing cleaning composition of this solution is described in pending US Patent Application No. 669,491. A typical suitable degreasing aqueous cleaning solution is one that contains an amount of an alkaline agent that can achieve sufficient removal of residual aluminum particulates on the container surface without causing unwanted etching of the aluminum surface. Generally, the pH of the alkaline degreasing cleaning solution is at least in the range of about 10 to about 13. The alkali agent contains an alkali metal hydroxide and / or an alkali metal carbonate together with a suitable complexing agent, and the amount of the complexing agent is such that if it does not complex, it forms an insoluble precipitate such as sludge or hard scales. This is the amount required to effectively complex metal ions in the prone solution. Particularly useful complexing agents for this purpose are organic acids and their salts,
Examples include sodium gluconate and sodium citrate, and the complexing agent is used in combination with one or a mixture of surfactants effective for removing organic dirt from the container surface. It is optional for the alkaline degreasing solution to contain a foam inhibitor. The type and concentration of such foam inhibitors will depend to some extent on the particular type and concentration of surfactant used in the degreasing cleaning solution. Such foam inhibitors are used at a concentration sufficient to prevent unwanted foaming of the degreasing cleaning solution, especially when applied by spraying. According to a preferred embodiment, the pH of the alkaline degreasing cleaning solution is controlled between 10 and 13, preferably between 11.5 and 12.5. To achieve a pH in these ranges, an alkaline agent such as sodium hydroxide and / or sodium carbonate is used at a concentration of 0.05 g / 1 to 10 g / 1. The concentration of the complexing agent used in the alkaline degreasing washing solution is generally in the range from 0.01 g / 1 to 3 g / 1, typically in the range from 0.05 g / 1 to 1 g / 1. Further, gluconic acid, citric acid and its salts, glucoheptanoic acid, ED
TA, tartaric acid and the like can be used, and salts and mixtures thereof which are soluble and compatible with the bath can also be used. Furthermore, the alkaline degreasing cleaning solution contains, as an essential component, at least one or a combination of surfactants usually selected from the group of alkoxylated hydrocarbon surfactants. These surfactants, preferably individually or in combination, have a hydrophilic-lipophilic balance (HLB), i.e., a hydrophilic (affinity or polar to water) in the molecule and a lipophilic (oil to oil). (Affinity or non-polar)
It has an HLB ratio of 2, preferably 12 to 15.
Even if other surfactants are used, it is possible to effectively purify the alkaline degreasing cleaning solution.However, if a surfactant characterized by having the above-mentioned HLB is used, a high-capacity, high-speed container washing machine cannot be used. The tendency for white rust on the aluminum surface in the case of frequent line stops is substantially reduced or eliminated. Such a line is stopped for about 1/2 minute to 1 hour, and the problem of white rust may occur when the degreasing cleaning solution remains on the container surface. This problem of white rust is substantially eliminated by using a surfactant having a suitable HLB. Therefore, even if a line stop occurs, the occurrence of white rust in the aluminum container due to the line stop is suppressed, and the degree of container transfer (productivity) is accordingly increased. As in the case of the pre-cleaning solution, the alkaline aqueous solution for degreasing cleaning can be applied by immersion or, preferably, spraying for a sufficient time to perform degreasing cleaning on the surface of the container. Generally, an alkaline aqueous solution for degreasing and washing is
From less than 150 ゜ F (about 65.6 ℃ C) to 60 ゜ F (about 16 ℃ C)
Preferably, it is used at a temperature in the range of 90 ° F (about 32 ° C) to 130 ° F (about 54 ° C). Subsequent to washing with the degreasing alkaline solution, the remaining degreasing alkaline solution is removed from the vessel surface, preferably in a multi-stage washing stage of a conveyor type washer. By maintaining the pH of the aqueous washing solution below 7.5, preferably between pH 6.5 and 7, brown rust develops on the container body by the method described in pending US Patent Application No. 669,491. The tendency can be further reduced. If the pH of the rinsing liquid rises above 7.5 due to the introduction of the alkaline degreasing cleaning solution, there is a tendency for brown rust to form on the surface of the aluminum container, especially when the line stops during the rinsing step. It becomes big. After degreasing and washing the above aluminum with water,
Using a zirconium-based processing solution with or without heavy metal phosphate or tannic acid,
It is common to subject a container to a chemical conversion treatment. Examples of conversion treatments suitable for use in the method of the present invention are described in U.S. Pat.
No. 334, 4,054,446 and 4,338,140. These patents are cited. The degreased washed and chemically treated container is then dried and applied in a conventional manner with one or more of lacquer coating, decorative coating, ink, etc., after which the container is filled with a suitable food or beverage and the container Perform sealing. Hereinafter, the present invention will be described with reference to examples, but these examples do not limit the present invention. Example 1 A DI aluminum container body in which a body-forming lubricant and aluminum fine particles that are industrially used remained were subjected to a multistage cleaning cycle of a spray-type can cleaning tester.
The washer consisted of three stages, each stage containing a total of 3 liters of solution. As cleaning, 105 ± 5 ゜ F (approximately 40.6
(± 2.8 ° C.) for a period of 9 to 18 seconds, followed by a degreasing wash with an aqueous alkaline solution at 125 ° F. (about 51.7 ° C.) for a period of 1 minute. Thereafter, the degreased and cleaned cans are stored at 48 to 75 ° F (about 8.9 to 23.9 ° C), pH
7 washes with water. The preparation of the alkaline aqueous solution for degreasing and washing is carried out by first, on a weight basis, 60% sodium hydroxide, 10% sodium gluconate, 20% soda ash, 5% Tergitol 15-S-9 surfactant (HLB = 13.5) , Quakerol Additi as defoamer
Prepare a mixture containing ve DFB and 2% sodium citrate and add 20 g at the concentration of this mixture to 19 liters of water to make the alkaline aqueous degreasing solution used for testing. During the degreasing and washing operation, a part of the alkaline aqueous solution for degreasing and washing in the second degreasing and washing step was flowed into the pre-washing step to make a pre-washing solution with a pH of 10.5. Observation of the pre-cleaning solution shows that the lubricant gradually builds up due to over-emulsification of the fuselage molding lubricant, and that the lubricant is redeposited on the container, the walls, screens and nozzles of the pre-cleaning equipment. I understood. Example 2 The degreasing cleaning cycle of Example 1 was repeated, but in this example, the temperature was 120 ±
Warm water of 5 ° F (about 48.9 ° C ± 2.8 ° C) was used. However,
The alkaline aqueous solution for primary degreasing cleaning was not counter-flowed from the cleaning stage to the pre-cleaning stage. The pH of the pre-wash solution was 8. When the aluminum container body was cleaned in the degreasing cleaning stage, the cleaning in the pre-cleaning stage was inadequate. Had been redeposited. Example 3 The degreasing cleaning cycle described in Example 1 was used again, except that sulfuric acid was added to the water used in the pre-cleaning step to bring the pH to 6. Following the pre-cleaning step, the vessel was again subjected to primary alkaline degreasing and then water washing as described above. During the operation of the degreasing cleaning cycle, the use of an acidified pre-cleaning solution breaks the emulsion of lubricant dirt and separates from the surface of the aluminum container body, causing the lubricant to float and rise to the surface. The material was easily removed in the form of a floating film by overflowing or scooping in the treatment tank. The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Carl A. Corynec               United States, Michigan 48098, G               Roy, Cheltenham 5389                (56) References JP-A-50-77440 (JP, A)                 JP-A-50-155434 (JP, A)                 Tokiko Sho 53-28245 (JP, B2)                 Tokiko 56-33470 (JP, B2)

Claims (1)

(57) [Claims] The aluminum container is degreased and washed to remove fine particles and residual organic contaminants on the surface of the aluminum container.
Less than a pre-cleaning aqueous solution, and then contact the pre-cleaned aluminum container with a degreasing cleaning alkaline aqueous solution for a time sufficient to remove all of the aluminum fine particles and residual organic waste remaining on the surface thereof, Contacting the degreased and washed aluminum container with at least one of water-based cleaning solutions to remove the remaining alkaline degreased cleaning solution in the solution. 2. 2. The method of claim 1, further comprising adjusting the pH of the pre-cleaning solution to a range of 4.5 to less than 5.5. 3. The method according to claim 1, further comprising the step of: acidifying the water-based cleaning solution; and flowing at least a part of the acidified water-based cleaning solution into the pre-cleaning solution and mixing. 2. The method for degreasing and cleaning aluminum according to claim 1. 4. 2. The method according to claim 1, wherein said pre-cleaning solution further contains a surfactant. 5. 2. The method of claim 1, further comprising the step of adjusting the concentration of the surfactant to a range of 0.005 g / 1 to 5 g / 1. 6. 5. The method according to claim 4, further comprising the step of adjusting the concentration of the surfactant to a range of 0.1 g / 1 to 1 g / 1. 7. The temperature of the pre-cleaning solution is increased from 60 ° F (about 16 ° C) to 200 ° C.
2. The method of claim 1, further comprising the step of adjusting the temperature to a range of ゜ F (about 93.3 ° C.). 8. Raise the temperature of the pre-cleaning solution from 90 ° F (about 32.2 ° C) to 2 ° C.
The method of claim 1, further comprising the step of adjusting the temperature to a range of 00 ° F (about 93.3 ° C). 9. 2. The method of claim 1, wherein the step of contacting the surface of the aluminum container with the pre-cleaning solution is performed by spraying. 10. 2. The method of claim 1, further comprising the step of contacting the surface of the aluminum container, which has been degreased and washed, with a water-based cleaning solution, to a chemical conversion treatment solution. 11. 11. The method for degreasing and cleaning aluminum according to claim 10, further comprising a step of bringing the surface of the chemical conversion-treated aluminum container into contact with a water washing solution to remove a remaining treatment solution from the surface.