JPH0243382A - Metal can for filling - Google Patents

Abstract

PURPOSE: To provide a filling metallic can that is formed by coating the outside surface of the rim of the bottom a can with a nontoxic hydrophobic oily, greasy or waxy material, and is capable of effectively preventing the secondary corrosion from the outside to the can for mainly food, for drinks in particular.

CONSTITUTION: The rim of the bottom of a metallic can consisting of Al (alloy), steel, etc., is provided with the coating of a nontoxic hydrophobic and colorless oily, greasy or waxy material on its outer surface. This coating material may be mineral plant or animal fats and oils and may be any fats and oils, insofar as the se fats and oils are admitted to be used in contact with food. Such materials include, for example, petrolactum, aliphat. hydrocarbon mixture, cetyl alcohol, silicones, etc. The graph of Fig indicates that the coated can described above has the corrosive parts fewer than the objective parts of the non-coated can.

COPYRIGHT: (C)1990,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a filled metal can, typically of tin or aluminum, of the type in which the lid is sealed to the side walls to protect the contents from external attack. Such cans are very widely used for storing and transporting food and beverages. Inevitably, small portions of such cans will leak as a result of handling damage. The present invention is concerned with the problem of secondary corrosion attacks on adjacent ends by fluids exiting such secondary leak canisters. Therefore, unlike secondary corrosion, secondary corrosion attack begins on the outside of the can.

Beverage irons, whether made of steel or aluminum,
Requires internal coating with a protective lacquer to prevent interaction between the beverage and unprotected metals. In practice, a high integrity, single-stage coating can be easily applied to aluminum, whereas a two-layer coating is generally required for steel.

In addition to internal protection, it is also necessary to protect the entire external surface of the steel to prevent atmospheric corrosion (rust).

Aluminum, on the other hand, does not require such external protection because its raw alloy is highly resistant to normal moisture conditions due to the presence of its natural oxide film. Only the riding edge (i.e. bottom rim) of the can
It is usually coated, primarily in the form of auxiliaries to provide mobility during both manufacturing and filling steps.

For aluminum cans under certain conditions, a form of localized secondary corrosion can occur. This is caused by a primary leakage from one can (most often due to mechanical failure), which causes the contents to attack and sometimes puncture the exposed outer surfaces of adjacent cans. Sometimes. If a leaking can is located at the top of a pile of cartons, a cascade of corrosion can occur which can adversely affect a large number of cans in a relatively short period of time.

Steel iron is also negatively affected. Although it generally takes longer for the holes to open, the formation of rust can quickly reduce the commercial value of the can in terms of its exterior.

These problems have existed since cans were first used as food and beverage containers, approximately 16 years for aluminum and longer for steel. One of the UK's leading fillers of aluminum potable irons has sold 1,000 pieces to 1,000 pieces, roughly due to secondary corrosion.
In other words, it is estimated that hundreds of thousands of cans are lost each year. G
, Win d au 8, et al.
In the May 1977 issue of J.R. Rundschau, the May 1977 issue describes severe secondary corrosion failure of both filter steel and aluminum beer cans exported to the Middle East.

A typical aluminum beverage tin has a bottom consisting of a domed concave central region, a riding edge (the bottom edge, i.e., the edge that contacts the surface on which the can rests when it is erected) and the rider edge joins the side walls. tilted chine
). It is primarily in this area of the rim that secondary corrosion occurs. Previous attempts to reduce this problem have mainly focused on the following two directions (
It was aimed at a) and (b).

(a) After drawing the can and removing the drawing lubricant, the inner and outer surfaces are coated with a zirconium-containing pretreatment agent, such as rAldine 404, which acts as a sufficient anchoring layer for the organic coating reservoir that is then applied. J (trademark: Amchem Products). Apply lacquer to the inner surface of the can and also to the outer riding edge/chachin area. The purpose of this external lacquering is primarily to improve the movement of the cans on the production line. The idea of reducing corrosion by applying several layers of lacquer to the riding edge/chine area has been tried but has not been shown to be very effective. Abrasion due to contact with conveyor systems etc. may cause the pre-treatment layer to be removed before lacquer application, in which case the lacquer will not adhere to the underlying metal, or abrasion may cause thick lacquer coatings. will be removed as easily as a thin lacquer coating.

(b) The electrochemical behavior of aluminum alloys is well understood, and in fact "Aluminum and Aluminum Alloys in the Food Industry"
(Department of Scientific and Industrial Research, Special Report A 50 It is known that corrosion is significantly accelerated when contaminated with iron or iron.Cans and copper-containing materials,
It is a good practice to avoid contact as much as possible, especially with the dead plates of conveyor equipment.

In mixed filling lines (i.e., lines used to fill both aluminum cans and steel iron), especially at the palletized load release equipment and end crimpers,
It is a good practice to remove as much iron/tin fines as possible.

However, in production facilities that handle 600 to 1000 cans per minute, it is difficult to avoid wear and contact between aluminum and other metals.

The present invention adopts a completely different solution, in one aspect of the invention a filled metal can having a bottom including a rim, the rim having a non-toxic hydrophobic coating on its outer surface. A metal can is provided, characterized in that it has a coating of an oily, greasy or waxy substance. It is, of course, well known to use oily, greasy or waxy substances to prevent corrosion under other circumstances. However, applying such substances to the outside of the filling can is completely contrary to the conventional wisdom of the club industry, which has always sought to provide consumers with a beautiful, clean outside surface of the can without the risk of contaminating the contents. It is something.

Although the filling of the can is not critical to the present invention, secondary corrosion problems are primarily limited to food and especially beverage cans. Secondary corrosion problems are associated with steel, but are particularly important when the metal is aluminum. The term "aluminum" herein is intended to include alloys containing aluminum as the main alloy, particularly aluminum alloys commonly used as can materials.

Oily, greasy or waxy substances may come into accidental contact with the contents of the can and therefore need to be non-toxic according to FDA standards, at least when the contents are food or beverages. . To protect metal surfaces from physical contact with corrosive fluids, the coating material needs to be hydrophobic. The material does not form a peelable film. Advantageously, the material has sufficient fluid properties to readily form a continuous coating.

However, its viscosity should be sufficiently high that it does not drip appreciably from the can under the influence of gravity. Preferably, the substance is colorless, translucent or transparent. The substance may be a mineral, vegetable extract or animal fat, such as Martin dill.
dale) [The Extra Pharmacopoeia:
The Extra Pharmacopoeia
may be those listed in Chapter J of ``Barrafins and Simimar Ha-'y-S.''
Examples of preferred coating materials for coating include petrolatum, mixtures of aliphatic hydrocarbons, cetyl alcohol, and the trademark "Molykot Molykot" from Dow Corning Company.
There are silicones such as those sold by El.

These materials provide the required barrier properties, are stable, non-fouling, have good load-carrying properties, and
It is solid or semi-solid at ambient temperatures of ~25°C.

An oily, greasy or waxy substance is applied to the rim VC of the bottom of the can, or, particularly in the case of aluminum cans, to the lighting and surrounding edges. Such materials may be applied over bare metal (--an oxide layer in the case of overlay aluminum) or over a lacquer layer. The amount of such material applied is preferably minimized by limiting the area of application and by limiting the amount of application to selected areas. Coating amount (
The application rate (coating rate per unit area) is not very important and can be suitably on the order of a few grams per square meter of metal surface.

After the food and beverage cans have been filled and optionally sterilized, they are packed into cartons for storage and transportation. In particular, in the case of beverage cans, the carton consists of a horizontal layer of multiple cans placed vertically on the bottom of the packaging material, and a thermoplastic shrink wrap film surrounding them. Consisting of

The bottom of the packaging is typically a low cost paperboard, which is sometimes treated with wax to reduce liquid ingress. The coating of oily, greasy or waxy material according to the invention is preferably applied as a final step to the filling can and then packed into cartons. In another aspect, the invention also relates to a carton containing a number of metal cans packed together, each plate of which is protected as described above.

Example 1 Aluminum cans coated or uncoated with a thin layer of lubricant (Molykote 111, or petrolatum, ie petrolatum) were stored in packaging cartons soaked with a kola-based product. The packages were kept at room temperature for 120 days and periodically soaked with a kola-based product (cola drink).

At approximately monthly intervals, the cans were removed and inspected for corrosion sites. The attack type and depth of the corrosion points were recorded.

The graph in the accompanying figure (Table 1) shows that the coated cans have fewer corrosion sites than the uncoated controls.

Corrosion on coated cans does not penetrate as deeply into the metal as on uncoated cans.

(ll) Example 2 018%Fe, 0.40%S1.0.13%Cu.

A sample of aluminum alloy material with a nominal composition of 11% MnS 1.0% Mg and balance AI is provided with a copper insert, -
This was then placed on a sponge saturated with cola beverage. The opening time for the specimen coated with rMolykote J silicone on the underside was 504 hours compared to 168 hours (hrs) for the uncoated control.

Example 3 Tin beverage tins from a commercial filling line (after filling operation)
[I took it out. The riding edges of those cans showed wear from contact with the conveyor equipment.

The bottom half of each board was coated with petrolatum and the cans were stood bottom down on water-soaked packaging paperboard.

To more clearly see the occurrence of rust, I placed white filter paper under each disc.

After 24 hours, rust stains were evident on the uncoated portions of each board. There was no rust stain on the coated area. Longer exposure times will cause more severe corrosion and eventually lead to leakage.

[Brief explanation of the drawing]

FIG. 1 shows the results of Example 1, and shows the exposure time (
It is a graph in which the pitting frequency (vertical axis) is plotted against the horizontal axis (number of days). △ Control substance ◇ Molycote petrolatum

Claims (1)

[Scope of Claims] 1. A filled metal can having a bottom including a rim, characterized in that the rim has a coating of a non-toxic hydrophobic oily, greasy or waxy substance on its outer surface. The above-mentioned filling can. 2. The can according to claim 1, which is filled with a beverage. 3. The can according to claim 2, wherein the metal is tinplate. 4. The can according to claim 2, wherein the metal is aluminum. 5. The rim consists of a riding edge and a surrounding chain;
5. A can according to claim 4, both of which have a coating. 6. The can according to any one of claims 1 to 5, wherein the hydrophobic substance is colorless and translucent or transparent. 7. The can according to any one of claims 1 to 6, wherein the hydrophobic substance is petrolatum. 8. The can according to any one of claims 1 to 6, wherein the hydrophobic substance is silicone. 9. A carton filled with a large number of filled cans according to any one of claims 1 to 8. 10. The can of claim 9, comprising a plurality of cans disposed in a layer laterally adjacent to each other on the bottom of the packaging material, and a thermoplastic shrink wrap film surrounding the entire can.