DE2420982A1 - READY FOR USE LUBRICATED CAN SHEET - Google Patents

Description

DR. HANS ULRICH MAY

D β MCMCHEN t, OTVOSTRhSSE la

TELEGRAMS: MAYPATENT MONKS

TELEPHONE CO81O 593682

N-8-P-1/1277 Munich, April 30, 1974

72 735 Dr M./cs

National Steel Corporation in Pittsburgh, Pennsylvania, USA

Ready-to-use, lubricated tin can

Brief ■ abstract (Abstract) of the invention The invention relates to ready-lubricated doses sheets as well as the means and methods · According to the invention used for their preparation are lubricated with citric acid esters of metal cans ^ · sheets. The lubricated can sheets are distinguished by the fact that they are very easily wettable and that organic paints in general and especially epoxy resin paints adhere very well. The citric acid esters used as lubricants are pharmacologically harmless and can be applied easily and cheaply by electrostatic deposition and other methods currently used for applying lubricants and aluminum sheet strip, each with the thickness _f suitable for cans and as a lubricant, citric acid esters of the following structural formula are used according to the invention:

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C ",

CH ₂ -COR ₁

O
ι n

R-O-C-C-O-Rg

in which R-, R ₂ and R _{3 can be} identical or different and each represent hydrogen or an alkyl radical containing 1-18 carbon atoms, at least one of the radicals R ₁ , R ₂ and R _{3 being} an alkyl radical and R _{4 being} hydrogen or is a carboxylic acid radical having 1-18, preferably 1-10, carbon atoms. According to the invention, a new method for applying an organic coating to lubricated can plates is also specified.

Background and Description of the Invention;

The invention relates generally to improved lubricated can sheets made of metal in strip or sheet form and a new method for producing the same as well as a method for applying a organic coating on lubricated can plates.

A thin film of lubricant is applied to the surfaces of most metal can sheets made in the United States. The lubricant is necessary to facilitate the handling of the sheet metal and to protect the surfaces against abrasion, scratching and to some extent against corrosion. If a film of lubricant is not applied, the individual panels will stick together and cannot be handled well in subsequent manufacturing steps, where automatic machines are used for applying organic coatings, lithographic printing and for making cans and containers.

The amount of lubricant applied is quite small and must

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be kept within a relatively narrow critical range. Applying too little lubricant gives rise to some extent to the above-mentioned disadvantages as in the absence of lubricants. If too much lubricant is applied, there will be excessive slippage and the stacking and handling of the individual sheets will be difficult. An excess of lubricant (oil) can also affect the application of organic coatings _for lithographic printing, labeling and other subsequent steps. The lubricant is usually present in an amount of from about O ₅ 05 to 1.0 g per applied "base box". The term "base box" (cheese box) is used in the art to mean a lot of can sheet having a total surface, ie the surface of the two sides, of approximately 4NC / f? Ni ^z (62,720 square inches) . The term "base box" is used hereinafter to simplify the description of the invention and refers to a total surface area of 62720 square inches on which the lubricant is applied.

Lubricants can be applied to a metal can sheet according to various Methods are applied such as bran ^ brushing, dipping in a solution of the lubricant in a solvent and subsequent evaporation of the solvent, and electrostatic separation «, Electrostatic deposition is a process that involves the application of the small amounts of lubricants noted above in the form of a thin, uniform film at high throughput speeds enables. In the production of can plates, these speeds can range from 76.2 to 609 m / min. (250 to 2000 feet / min) and the method of applying the lubricant Even with these high and variable throughput speeds, the amount of lubricant applied must be regulated

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enable. For technic: he-n AnveMiaigr nraG the selected lubricant therefore be able to be applied by electrostatic separation.

A lubricant for metal sheets must have a very special combination of properties. If any of these properties are lacking, the lubricant is not entirely satisfactory. As a result, only a very small percentage of the many possible lubricants are satisfactory. The selection of a suitable lubricant is made more difficult by the fact that tests on a laboratory scale usually fail to predict ₉ whether a certain substance is suitable, and the lubricant in question must actually be tested and selected under technical conditions ",

Some of the more important qualities of a truly satisfying one Lubricants for Doseiibleeh® made of metal are the following:

1 ο Pur electrostatic separation must be the lubricant easily on a finely divided dispersion in a gaseous medium, like air, let it atomize. A carefully controlled amount of the lubricant particles present in the resulting gaseous dispersion must develop electrostatically in the form of a thin film on a can sheet moving at high speed Let metal deposit *

2, The lubricant must be on the tin plate for an acceptable period Time to be recovered in sufficient quantity to lubricate the surface *

3 «The lubricant must then be applied to the lubricated Can plate applied, for protection and / or jewelry or for identification serving organic coatings and the wettability by such coatings and their adhesion to the sub-

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position not or only in a favorable sense 4 * The lubricant is allowed to become when heated or hardened of the lubricated Do not discolor the tin plate at a temperature sufficient to harden the organic coatings »

5. The lubricant film should be resistant to oxidation and over does not lose its lubricating properties and does not harden for a reasonable time.

6. The lubricant must be used in the quantities used and in the quantities that occur Conditions of use to be free of undesirable taste and odor *

7. The lubricant must be pharmacological in the quantities used Be harmless and non-toxic as lubricated tin plates are often used to make cans and containers for preservation and storage used by food.

A number of naturally occurring vegetable oils and synthetic esters of carboxylic acids are known for use as lubricants for metal can trays.Vegetable oils, such as cottonseed oil, palm oil and the like, tend to oxidize to form a solid film which is no longer a good lubricant after a relatively short storage period · A number of synthetic esters do not exhibit this disadvantage as lubricants _/ and, as a result and because of other advantages, several esters of sebacic acid have been used as lubricants Lubricants Widely Used “While dioctyl sebacate is one of the best synthetic ester lubricants available to date, it has some drawbacks in response to recent requirements. For example, a significant proportion of metal can sheets made in the United States receive one

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cathodic dichromate treatment as described in U.S. Patents 3,278,401 and 3 296 106 described * This treatment is used to increase the ro * c corrosion resistance. If so treated tin cans with dioctyl sebacate or other known lubricants »there is often imperfect wetting or the appearance of picks or eyes ("eyeholing"). This phenomenon is particularly evident when applying coatings from epoxy paints and certain other advanced organic coatings. As a result of this disadvantage, a suitable lubricant has long been sought which the above requirements regardless of the type of subsequently applied organic coating and regardless from a previous cathodic dichromate treatment. However, such a lubricant has not been available until now Disposal.

It is now an object of the invention to provide an improved lubricant for this purpose and to create improved lubricated metal can plates, which were originally free-flowing organic coating materials, which often cause wetting problems, such as epoxy paints, are easily wettable «

Furthermore, a new method for lubricating can plates is to be found can be created using a citric acid ester as a lubricant.

In addition, a new method for attaching an organic Coating can be created on lubricated can sheets, the lubricated surface being slightly flowable through an initially organic coating material becomes wetted and stains and pitting and other Ißi perfections in the finished cured organic Coating must be kept to a minimum.

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Further details and advantages of the invention result from the following, in detail §ehead @ i} description length "

According to zvsr Löswig of the task is proposed to use as a lubricant for geschildertes Dosenblseh eineiCitronensäureester with the following structural formula?

i 9

v-G ^ C

«J · I

wherein R «., R ₂ , and R _{3 are} identical or different xma hydrogen or an alkyl radical with -1-18, preferably 1« »10 carbon atoms, but at least one of the radicals R ^ ,. E ₀ and R "are such an alleyl radical and R. is hydrogen or a calcium carbonate radical and 1-1S _9, preferably 1-10 carbon atoms"

Citroneas esters in which R ^, I ₂ and Ra are alkyl radicals with 1-4 carbon atoms and R ^ are hydrogen or a carboxylic acid radical with 1-4 carbon atoms are particularly preferred.

Examples of preferred citric acid esters are triethyl citrate and acetyl triethyl citrate "tributyl citrate, acetyl tributyl citrate, acetyl tri-2" ethylhexyl citrate and mixtures thereof. Acetyl tributyl citrate often gives the best results

The citric acid esters according to the invention are used as lubricants according to the invention in an amount of about 0.05 to 1.0 g per Srundhoxs, ie about 0.05 to 1.0 g per / (62720 squareinchesj of the lubricated surface and with subsequent application of an organic coating the can sheet is preferably applied in an amount of about 0.15 to 0.40 g per base box.

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, Also optionally be used in each case with a ahromhaltigen Beschichtiang _/ as well as aluminum sheet as can sheet 2 <ann invention & ß Weißolech or black plate of corresponding thickness. The can sheets are usually in the form of plates or endless belts, but can also be any other for the manufacture of cans, for example. Containers have a suitable shape. Can sheets suitable for this purpose are described in numerous publications and US patents. For example, such black plates and tin plates are described in the book "The Making, Shaping and Treating of Steel", 7 A ^- Uflage, publisher United States Steel Corporation, while Alosninium »» can plates are described / ^6S Ali2minium ^Sf , published by the American Society for Metals s where Sand 3, Chapter 23 _{9 is} particularly relevant. Black plate with eineüi chromium-containing coating is described in U.S. Patent Ho. 3316 160g 3 526 486 $ 3 567 599 uad 3475 295. US Patent No. 3,526,486 describes black plate with the Eisenmetallobsrfläche isunitteibar contacting metallic chromium containing coating \ ma an overlying non-metallic chromium-containing film which is cathodically deposited from an aqueous electrolyte containing hexavalent chromium. Reference is expressly made to the prior art known from these publications.

The can sheets provided with a lubricant can previously be subjected to an electrochemical treatment day in an aqueous electrolyte containing a water-soluble chromium compound in order to deposit a chromium-containing film on the sheet which increases the corrosion resistance. The US-PS 3,278,401 describes a process for the electrochemical deposition of a chiwn-containing film on tinplate, which preferably, however, is not un-

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is conditionally with flow gloss varsekenes electrolyte tinplate. The chromium-containing film is cathodically deposited on the tinplate from an aqueous electrolyte bath containing hexavalent chromium. Cathodic dichromate treatment is usually preferred. US Pat. No. 3,296,106 describes the treatment of various metallic substrates for the purpose of electrochemical deposition of a chromium-containing film on them. Improvement of the corrosion resistance »The metallic substrates are treated cathodically in an aqueous electrolyte containing 6-valent Cteom, and the treatment is effective _. ferrous metal coated with an iron-tin alloy ₉ tinplate and other tin plates. The deposition of a non-metallic chromium-containing film on Schwarzbleeh, which is coated with metallisch® "öhrom" is describe might in US Patent No. 3,526,486, _s "rora ^ yf is also expressly made. It should notice ₉ 'that-XJQsesibleehe before applying the lubricant Einei? electrochemical treatment, as described above, or other fesksamtea treatments for the purpose of increasing the corrosion resistance od @ 3? sis? Errsiehimg other desirable properties subjected w @ s? d @ a graining ₀

486 manufactured products

ata? often preferred. the i@rad.ttel are with these

According to US Pat. No. 3,278,401 and

are particularly desired © Can:

particularly effective *

The Git ^ oa ^ asaiarasster-Setoiiermittel according to the invention can after any known method in the form of a thin substantially uniform film can be applied to the can sheets. Examples of known processes are electrostatic deposition, bran abrasion, Applying a solution of the lubricant in one

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volatile solvent vad subsequent evaporation of the solvent, application of an aqueous emulsion of the lubricant and

subsequent evaporation of the water and application of the lubricant itself directly to the can sheet using metering rollers, spraying or the like, if the lubricant is sufficiently fluid. Electrostatic deposition is usually preferred for the manufacture of bosan sheets on an industrial scale. The citric acid esters used in accordance with the invention are easy to apply electrostatically and have the desirable properties mentioned above. In addition, the synthetic citric acid est © 3? the wettability ü <bt gesefamierte "surface by an initially flowable organic coating agent and reduce Obe ^ area error" wis spots or holes in the coating. Furthermore, the adhesion is improved, and the finished cured or vulcanized organic coatings produced close to the coating process according to the invention show excellent adhesion. ttel weMsa ä ± m should occasionally occur Bsnet & ungsprobleias aaeSi Iz & thsälBdh & T ¹ Offer © aat-Beliandluag "ψοη Weißbleeli and other aa Ifetailsi ^ st ^ af ^ iv @ 3? iti <3d @ n»

Ffe di © BsseMchtiiag dkss according to the invention? Any known flowable organic coating material such as varnishes, paints and oils for can metal sheets can be used. Specific examples of organic BesöhieatumgsstoJffen are Εψ @ $ ψ ~ modified phenolic "- _s modifisiebte Fh <sr & ol ^ _D ^ Acs RL, lodifiaierte acrylic.

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Vinyl, modified Viayl, Allcyil and polyurethane lacquers, paints and / or enamels. For the purposes of the invention, well-known lithographic or printing inks are also to be regarded as organic coating agents, which are suitable for use on boseneck plates for marking and ornamental purposes or indirect printing or lithographic printing can be applied _/ and can range from soft pastes to % u flowable liquids »j © according to the type of application chosen« The initially flowable organic coating material is dried or hardened after application ₉ for example by evaporation of the solvent or E & » Mtz @ n »to produce the finished organic coating» When applying the originally flowable organic coating and then hardening the finished organic coating, known methods can be used «The Bosenblec to be coated According to the invention, however, it must be coated with a citric acid ester. The citric acid ester used as a lubricant ensures essentially immediate wetting of the surface by the initially flowable organic coating material licks wetting · In addition, the finished dried, cured or vulcanized organic coatings adhere more firmly to the surface described with citric acid ester without the occurrence of defects such as spots, holes and the like. The invention therefore eliminates the previous problems in the operation of coating apparatuses with high

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. ₁₂ - 2420382

Work on throughput _{speed /} and in particular avoid the difficulties encountered when using organic coating mixes that are difficult to wet.

The invention is further illustrated by the following exemplary embodiments:

A tinned sheet metal strip supplied from a known electrolytic tinning machine at a line speed in excess of 305 m / min (1000 feet / min) is continuously passed through a flow brightening zone where it is flow brightened and then quenched with water and followed by a Diehromat cathodic treatment according to US Pat. No. 3,278,401. The sheet metal product obtained is rinsed, dried and passed through an electrostatic lubricating zone at a speed corresponding to that of the tinning device. Acetyl tributyl citrate is sprayed into a fine gaseous suspension which is passed through an ionization zone where the suspended particles of the acetyl tributyl citrate lubricant acquire an electrical charge. A stream of the gaseous suspension of ionized lubricant particles was directed onto the electrically grounded continuous tape and electrostatically deposited thereon in the form of a thin uniform film. The lubricated tinplate tape withdrawn from the electrostatic lubrication zone had 0.26 g / base box (HOfti *? = 62720 square ± ncbe $) of tributylci occurred on its surface.

The lubricated blank tinplate tape was cut into sheets, which are in automatic. Equipment handled without undesirable abrasion or scratching, and the product was used in the following Examples used

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Example 2:

A second run was carried out as in Example 1, except that the acetyl tributyl citrate was used as the lubricant Dioctyl sebacate was used. The product obtained was 0.27 g / Basic box of dioctyl sebacate lubricant on the plate surfaces

Samples of the lubricated tinplate from Examples 1 and 2 were stored for four months under the same conditions to determine the amount of to determine lubricant lost during this time "

The product of Example 1 was initially 0.26 g and after four months Storage 0.20 g per basic box of acetyl tributyl citrate on its Surface. The product of Example 2 initially had 0.27 g per basic box of dioctyl sebacate and after four months only 0.17 g / basic box on its surface. So obviously the ratio is or the rate of loss of acetyl tributyl citrate during the storage is significantly lower than that of dioctyl sebacate, which is very surprising since dioctyl sebacate than in this regard is assessed extremely well.

Example 4:

Samples of lubricated tinplate from Examples 1 and 2 were taken below same conditions with diluted paints tested to the respective Determine wettability. One part of the paint was mixed with six parts of solvent, and one drop of the resulting Mixture was applied to the surface of a sample of each of Examples 1 and 2 lying horizontally on a flat surface upset. The drops of the diluted varnish were allowed to air dry and then heated to fix the result. The flowing surface (wetted area) was in each case in cm (square inch)

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measured and the received '. Excellent result

In one test, one part by volume was epoxy paint with six parts by volume Isophorone diluted and the mixture used for the specified test. A wetting area of 1.548 cm (0.24 cm) was obtained square inch) for the tinplate lubricated with dioctyl sebacate and 15.48 cm (2.4 square inches) for the one with acetyl tributyl citrate lubricated tinplate.

In a further test, one part of Eppxylack was diluted with six parts of diacetone alcohol. This mixture provided the aforementioned Tested on tinplate lubricated with dioctyl sebacate to have a wetting area of 1.097 cm (0.17 square inch) and on with acetyl tributylci stepped greased tinplate 6.129 cm (0.95 square inch).

In another test, one part of epoxy resin was diluted with six parts by volume of ethylene glycol monoethyl ether acetate and used for the mentioned test used. The mixture showed up with dioctyl sebacate lubricated tinplate has a wetting area of 3.99 cm (0.62 in square inch) and on tinplate lubricated with acetyl tributyl citrate an area of 13.55 cm (2.1 square inches).

In a further test, one part of epoxy paint was diluted with six parts of ethylene glycol monoethyl ether and the mixture was tested as above. It showed a wetting area of 3.87 cm ² (0.6 square inch) on tinplate lubricated with dioctyl sebacate and an area of 12.26 cm (1.9 square inches) on tinplate lubricated with acetyl tributyl citrate.

These test results clearly show that the tinplate lubricated with acetyl tributyl citrate according to the invention through the various diluted epoxy lacquer was wetted much more easily than is known

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te, with dioctyl sebaca ': climmed thin sheet.

Example Sc ₁

Individual test runs are carried out using the lubricated Products of Example 1 and Example 2 in a plant for painting operating at high throughput speeds and lithographically printing the plates. That in both test runs The organic coating agent used was an epoxy paint with a tendency to peck (hole) formation and poor wetting properties

With regard to Pleeken-CLoch-) formation and wetting resulted no difficulties with the lubricated product of the invention of Example 1, ie the tinplate lubricated with acetyl tributyl citrate. The lubricated product of Example 2, i.e. that tinplate lubricated with dioctyl sebacate, however, showed formation of spots and holes and poor wetting and was therefore in this Not satisfactory. The cured films of the epoxy paint also adhered better to the product of Example 1 than to that of example 2.

In further test runs the same as those of Examples 1 to 5 with regard to the lubrication level, except that the tinplate is replaced by blackplate, blackplate with a chromium-containing coating and aluminum sheet is replaced, comparable results are obtained. In each case, the can plate lubricated with acetyl tributyl chloride shows better wetting properties and better adhesion of the hardened organic coating films as-the products where dioctyl sebacate is the lubricant »

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Claims (8)

Claims that thin, having ι Iy processing Ready-lubricated sheet metal cans, characterized in that on at least one of its faces a substantially uniform film of a lubricant "of at least one citric acid ester having the following structural formula R ₄ -OCCOR ₂ 0
CH ₂ - (SOR ₃ contains where R ₁ , R ₂ and R _{3 are} identical or different and are hydrogen or an alkyl radical having 1 to 18, preferably 1 to 10 carbon atoms, but at least one of the radicals R ₁ , R ₂ and R _{3 are} such an alkyl radical and R- is hydrogen or a carboxylic acid radical with 1 to 18, preferably 1 to 10, carbon atoms. 2. Can plate according to claim 1, characterized in that R ₁ , R ₂ and R, alkyl radicals with 1 to 4 carbon atoms and / or R _{4 are} hydrogen or a carboxylic acid radical with 1 to 4 carbon atoms. 3. Can sheet according to claim 1 or 2, characterized in that the lubricant is present on its surface in an amount of about 0.05 to 1.0 g per W ₁ W _m ² (62720 inch ² ) of the lubricated surface. 4. Can plate according to one of claims 1 to 3, characterized in that that the lubricant consists essentially of the citric acid ester or the citric acid esters. 509846/0897 ~ 2420382 5. Can plate according to one of claims Ί to 4, characterized in that that the citric acid ester contains acetyl tributylate and in an amount of 0.15-0.4 g per ^ / 0.47 m of the lubricated Surface is present. 6. Can plate according to one of claims 1 to 5, characterized in that that the sheet metal is tinplate or blackplate, tinplate or blackplate with a chromium-containing coating, or an aluminum sheet, each with the thickness suitable for the tin plate. 7. Ready-to-use, lubricated can sheet, characterized in that that it is coated with a layer of organic paint, varnish or enamel * 8. Use of at least one citric acid ester for lubrication of metal sheets that can be used for the production of cans and containers, where the citric acid ester (s) correspond to the following structural formula: H ₂ -COR ₁ Rv-OCCOR ₂ CH ₂ -COR ₃ wherein R *, R ₂ and R _{3 are} identical or different and are hydrogen or particularly preferably 1 to 4 is an alkyl radical with 1 to 18, preferably 1 to 10, / u atoms, but at least one of the radicals R ₁ , R ₂ and R _{3 is} such an alkyl radical and R. is hydrogen or a carboxylic acid radical with 1 to 18 , preferably 1 to 10 carbon atoms, particularly preferably 1 to 4 carbon atoms . 509846/0897