JPH03226319A - Manufacture of metallic can - Google Patents

Abstract

PURPOSE:To improve the printing aptitude and the flavor keeping property while eliminating a degrease washing after drawing by applying a saturated hydrocarbon system lubricating agent uniformly on the surface of organic resin film of a blank material and drawing the blank material after applying the above lubricant. CONSTITUTION:The lubricating agent 4a, 4b of the saturated hydrocarbon system is applied on the surface of the organic resin film 3a, 3b of the blank material 2. The saturated hydrocarbon lubricating agent acts as a fluid lubrication or the lubricating function similar to the fluid lubrication, and the strength of oil film is high. Further, by heating the can obtained by drawing in such a way and removing most of the stuck lubricating agent by evaporation, the printing aptitude of the surface of can is remarkably improved, and the adhesiveness of printing ink or finishing varnish is also improved remarkably.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for manufacturing metal cans by drawing forming from a metal material on which an organic resin film is formed, and more specifically relates to a method for manufacturing metal cans by drawing forming from a metal material on which an organic resin film is formed. This invention relates to a method for improving printability while omitting cleaning.

(Conventional technology) Traditionally, side seamless cans.

Manufacturing methods include metal materials such as aluminum plate, tin plate, or nine-free steel plate.

It is widely practiced that the can be subjected to at least one drawing process between a drawing die and a punch, and then formed into a can from a side portion with no seam and a bottom portion seamlessly joined to the body. It is being said.

Painting cans after drawing and forming is a cumbersome operation, and there is also the problem of environmental pollution due to solvent volatilization during spray painting, so we recommend laminating resin films or painting with organic resin paints. For example, it is widely practiced to apply an organic resin coating to the surface of a metal material in advance. In addition, in order to prevent damage to the film during molding, it is essential to apply a lubricant to the surface of the material.

In Japanese Patent Publication No. 1-36519 proposed by the present inventor, when drawing an organic resin-coated metal material, an oil-in-water aqueous emulsion from liquid glyceride, ethanol, and a nonionic surfactant is uniformly spread over the coated surface. It is described that the cans should be applied to the cans and then washed with warm water after being drawn and formed.

(Problems to be Solved by the Invention) When a normal lubricant is applied to an organic resin-coated metal material to improve its drawability, it is difficult to remove the lubricant on the coating. There is a problem in that the lubricant remaining on the coating tends to spoil the flavor of drinks etc. that rely on delicate flavors, whereas the above-mentioned prior art
It can be said to be significant as it improves degreasing and cleaning properties while improving drawability.

However, the conventional method described above requires two steps: degreasing and washing the can after drawing and drying after washing, which requires a large number of steps and is unsatisfactory from the standpoint of consuming water resources and thermal energy. It's not satisfactory.

It is also possible to select a lubricant with excellent flavor retention to reduce the burden of degreasing and cleaning as much as possible, but in this case, the lubricant remaining on the coating surface may cause printing on the outside of the can. The adhesion of the ink layer to the can is significantly impaired and the adhesion of the ink layer to the can is reduced.

Therefore, the technical problem of the present invention is to eliminate the drawbacks of the above-mentioned conventional method when manufacturing metal cans by drawing from an organic resin-coated metal material, and to improve printability and flavor retention while omitting the AN cleaning after drawing. The goal is to provide ways to improve sexual performance.

(Means for Solving the Problems) According to the present invention, when manufacturing a metal can by subjecting a metal material on which an organic resin film has been formed in advance to a first to several multistage drawing process, a saturated hydrocarbon-based A lubricant is uniformly applied onto the organic resin coating surface of the material, the material after application is subjected to drawing forming, and the can obtained by drawing forming is heated to volatilize most of the lubricant adhering to the can. let

Further, the saturated hydrocarbon lubricant may be a branched chain-containing hydrocarbon lubricant, and the branched chain may have at least one branched chain for every 2 to 10 carbon atoms in the main chain. Furthermore, the branched chain may be characterized in that 70% or more of the branched chains have one carbon atom relative to the entire branched chain.

(Function) In the present invention, a saturated hydrocarbon-based lubricant, especially a branched saturated hydrocarbon-based lubricant, is selected from among various lubricants, and this lubricant is applied to the organic resin-coated surface of the material. The reasons for selecting a saturated hydrocarbon type, especially a branched-chain saturated hydrocarbon type, are as follows: 1. This substance has heating volatility, that is, it volatilizes by heating and is easy to remove;
2. It can impart excellent drawing formability (press formability) to the organic resin-coated metal material; 3. It has excellent flavor retention and does not give off taste or odor to the contents even if it remains on the coating; 4. This is because it has excellent hygienic properties, which is also recognized as a food additive.

To further explain this point, the above-mentioned saturated hydrocarbon lubricant is characterized in that excellent drawability can be obtained with a significantly smaller amount of application than other lubricants, and this is because the saturated hydrocarbon lubricant used in the present invention This is thought to be because the oil provides fluid lubrication or a lubricating action similar to it, and the strength of the oil film is also quite high. Since the amount of coating is small, it is easy to remove after drawing, and there is little effect of remaining, for example, on printability.

In addition, when compared with the same molecular weight, saturated hydrocarbons are more volatile than polar compounds, and they also have less absorption into organic resin coatings and less swelling effects, so they can be heated for a short time. It exhibits the effect of being able to volatilize and remove. This tendency is particularly noticeable in branched chain-containing hydrocarbon lubricants. In branched chain-containing hydrocarbon lubricants, there are tertiary carbon atoms, and this carbon atom causes branch chain cleavage, resulting in lower molecular weight, which makes volatilization more likely. This seems to be one of the causes. These effects are
This is particularly noticeable when the organic resin coating is composed of a resin film, particularly a polyester film.

In the present invention, the organic resin-coated metal material coated with the above-mentioned saturated hydrocarbon lubricant is subjected to drawing forming by means known per se. Let the parts evaporate. By volatilizing and removing most of the lubricant, the printability of the can surface is significantly improved, and the adhesion of printing ink and finishing varnish is also significantly improved. In other words, many lubricants for drawing molding have a mold release agent effect, and this lubricant acts to provide releasability between the organic resin film and the printing ink layer. The saturated hydrocarbon lubricant used in the invention is easily removed by heating, and most of it is removed, so the above-mentioned effects are extremely small.

Further, even if a small amount of saturated hydrocarbon lubricant remains, this lubricant has a smaller mold release effect than other lubricants and has an extremely small effect on printability.

Thus, according to the present invention, it is possible to omit the degreasing and cleaning step which is indispensable in the conventional drawing method.

This offers a number of advantages, such as saving water resources, reducing the burden of cleaning wastewater treatment, and preventing metal rusting that occurs during degreasing and cleaning.

In addition, heating a can requires only sensible heat to raise the can to a predetermined temperature, which has a small specific heat, and latent heat to volatilize a very small amount of lubricant, compared to drying a can with water droplets. This makes it possible to significantly save thermal energy. This heating also has the advantage of alleviating the strain remaining in the organic resin coating after drawing and improving its adhesion and strength.

(Preferred Embodiment) In FIG. 1, which shows the cross-sectional structure of a metal material to be press-formed, the metal material 1 for forming has a metal substrate 2 made of an aluminum plate, tin-free steel, tinplate, etc., and a metal substrate 2 on both surfaces of the substrate. It consists of organic resin coatings 3a and 3b provided.

In the present invention, on the surfaces of these organic resin coatings 3a and 3b,
Prior to pressing, a layer of saturated hydrocarbon lubricant 4a
, 4b are applied uniformly.

As the saturated hydrocarbon lubricant, any known per se can be used. Such lubricants include paraffin wax, microcrystalline wax, liquid paraffin, petrolatum, polyethylene wax, polypropylene wax, ethylene-propylene wax, and the like.

In the present invention, it is desirable that the branched chain-containing hydrocarbon lubricant, particularly, that at least one branched chain exists in the length of 2 to 10 carbon atoms in the main chain. Furthermore, most of the branched chains are 1-carbon, and the 1-carbon branched chains account for 70% or more, especially 90% or more of the number of branched chains present in the entire lubricant. It is desirable that the area be occupied by In such branched chain-containing hydrocarbon lubricants, tertiary carbon atoms are appropriately present in the main chain, and simple branched chains are broken at such carbon atoms, resulting in lower molecular weight. , it is thought that volatilization is more likely to occur.

Petrolatum, especially white petrolatum (petrolatum), is particularly suitable as such a lubricant.

The melting point of this lubricant is preferably in the range of 35°C to 80°C, particularly 38°C to 60°C, depending on the oxidation state etc., and the molecular weight (weight average) is in the range of 150 to 700. It is better.

It is a remarkable advantage that the amount of the lubricant applied to the organic coating surface of the material is extremely small, and the drawability can be improved.
．． Satisfactory results are obtained with a coating weight of 0 mg/m2. If the coating amount is less than the above range, the lubricating performance will be insufficient, and if it is greater than the above range, a long time will be required for volatilization.

The lubricant is conveniently applied, for example, by spraying or electrostatically atomizing the lubricant in a liquid state onto the organic resin-coated metal material, but it can also be applied by roller application or the like.

In the present invention, various surface-treated steel plates and light metal plates such as aluminum are used as the metal material.

Surface-treated steel sheets are obtained by subjecting cold-rolled steel sheets to secondary cold rolling after annealing, followed by one or more surface treatments such as galvanizing, tin plating, nickel plating, electrolytic chromic acid treatment, and chromic acid treatment. can be used. An example of a suitable surface-treated steel sheet is:

It is an electrolytic chromic acid-treated steel sheet, and is particularly equipped with a metal chromium layer of 12/12 and a chromium oxide layer of 1 to 50 mg/m2 (metal chromium equivalent) per 10 to 200 m, which has excellent paint film adhesion. Excellent combination of corrosion resistance and corrosion resistance. Other examples of surface treated steel sheets are 0.5 to 11.21/d
It is a hard tin plate with a tin plating amount of . This tin plate has a chromium content of 1 to 30Il1 in terms of metal chromium.
It is desirable that the chromic acid treatment or the chromic acid/phosphoric acid treatment be performed so that the chromic acid/phosphoric acid treatment is performed.

Further, as another example, an aluminum-coated steel plate plated with aluminum, aluminum pressure-welded, etc. is used.

As the light metal plate, an aluminum alloy plate is used in addition to a so-called pure aluminum plate. Aluminum alloy plates with excellent corrosion resistance and workability have n: 0.2 to 1.5.
% by weight, Mg: 0.8 to 5% by weight, Zn: 0.25 to 0.3% by weight, Cu: 0.15 to 0.25% by weight, and the balance is A1. These light metal plates also have a chromium content of 20 to 30 in terms of metal chromium.
It is desirable that chromic acid treatment or chromic acid/phosphoric acid treatment be performed so that 0+ag/i2.

The base thickness (TB) of the metal plate varies depending on the type of metal and the shape and size of the container, but it is generally good to have a thickness of 0.10 to 0.50+am, and within this range, surface-treated steel plate In the case of
It is preferable to have a thickness of mm.

Further, in the present invention, examples of the organic resin film coated on the metal plate include various resin films and various resin paints. Thermoplastic resin films include polyethylene, polypropylene, ethylene-propylene copolymer,
Olefin system #I such as ethylene-'# dinylic acid copolymer, ethylene-acrylic ester copolymer, and ionomer
Fat film; polyester such as polyethylene terephthalate, polybutylene terephthalate, ethylene terephthalate/isophthalate copolymer; nylon 6, nylon 6.6. Nylon 11. Examples include polyamides such as nylon 12; polyvinyl chloride; polyvinylidene chloride, and the like.

In the present invention, the thermoplastic resin coating layer also contains an inorganic filler (JI
) can be included.

Inorganic fillers include rutile-type or anatase-type titanium dioxide, zinc white, inorganic white raw materials such as gloss white; pallite, precipitated pallite sulfate, calcium carbonate,
White extender pigments such as gypsum, precipitated silica, aerosil, talc, fired or unfired ray, barium carbonate, alumina white, synthetic or natural mica, synthetic calcium silicate, magnesium carbonate; black colors such as carbon black and magnetite. Raw materials; red pigments such as Benkara; yellow pigments such as sienna; and blue pigments such as #back and cobalt blue. These inorganic fillers are added in an amount of 10 to 5 per resin.
00% by weight, especially 10 to 300% by weight.

Coating the metal plate with the coating resin film is carried out by a heat fusion method, dry lamination, extrusion coating method, etc. If the adhesiveness (heat fusion property) between the coating resin and the metal plate is poor, 1. For example, urethane adhesives, epoxy adhesives, acid-modified olefin resin adhesives, copolyamide adhesives,
A copolyester adhesive can be interposed.

Furthermore, the thickness of the crystalline thermoplastic resin is generally 3 to 50 mm.
It is desirable that the thickness be in the range of .mu.m, particularly 5 to 40 .mu.I.

In the case of heat fusion using a film, it may be unstretched or stretched.

On the other hand, the protective coatings include any protective coatings made of thermosetting and thermoplastic resins; for example, modified epoxy coatings such as phenol-epoxy coatings, amino-epoxy coatings; for example, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate copolymers, etc. Vinyl or modified vinyl paints such as partially saponified copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, epoxy-modified, epoxyamino-modified, or epoxyphenol-modified vinyl resin paints; acrylic resin paints; styrene - Synthetic rubber coatings such as butadiene copolymers may be used alone or in combination of two or more.

These paints can be applied to metal materials in the form of organic solvent solutions such as enamels or lacquers, or in the form of aqueous dispersions or solutions, in the form of roller coating, spray coating, dip coating, electrostatic coating, electrophoretic coating, etc. Apply in advance. Of course, if the resin paint is thermosetting, the paint may be baked if necessary.

These organic coatings preferably have a thickness (dry state) of generally 2 to 30 .mu.m, particularly 3 to 20 .mu.m, from the viewpoint of preventing corrosion and improving drawability.

According to the present invention, as shown in FIG. 2, the punch 12 and the die 13 are movable in the axial direction while holding the organic resin-coated metal material 1o coated with a specific lubricant with the wrinkle presser 11. The cup is then pressed between the cup and molded into a seamless cup with a bottom.

In the present invention, pressing is performed several times while gradually reducing the punch and die diameters until the desired shape and desired height/diameter ratio are achieved.

At this time, the drawing ratio defined by the following formula: Diameter drawing ratio before processing = diameter after processing should be 1.20 to 2.10, especially 1.30 to 1.90 in - stage press processing. ,
Also, the overall aperture ratio is 1.50 to 3.00.
It is particularly desirable to set the value between 1.80 and 2.70. In addition, in the final deep drawing step, the side wall portion is bent and stretched so that the ratio of TB /TV (TB is the bottom wall thickness and Tl11 is the side thickness) is 1.0 to 1.60. It is also possible to make the portion thinner.

After forming, the can is trimmed, necked in, flanged, etc. to make it into a double seam can.

In the present invention, the can is heated to volatilize the lubricant at any stage after drawing and before printing on the outside of the can. The temperature at which the can is heated varies depending on the type of lubricant and the type of organic resin coating, but it is generally 100 to 240°C, especially 15°C.
The temperature ranges from 0 to 230°C and is lower than the melting point or softening point of the resin. The heating is such that most of the lubricant can be volatilized and, depending on the amount of lubricant applied, is generally on the order of 0.5 to 15 minutes, particularly 1 to 10 minutes. The heating atmosphere is generally a heat transfer atmosphere; for example, as a heating method, forced air drying using an oven or the like is advantageously used.

(Effects of the Invention) According to the present invention, a saturated hydrocarbon lubricant is uniformly applied on the organic resin surface of an organic resin-coated metal material in advance, and the material after application is subjected to drawing forming. High lubrication performance can be obtained during draw forming by adjusting the amount of application, and the can can be simply heated after forming.

Most of the lubricant can be removed.

For this reason, it is possible to significantly improve printability and flavor retention while omitting the degreasing and cleaning process and subsequent drying process that were indispensable in conventional methods, saving water and energy resources, and reducing pollution. It is also significantly superior in terms of prevention.

The invention is illustrated by the following example.

The evaluation method for the metal containers used in the following specific examples is as follows.

(Volatilization amount evaluation) Fill a molded metal container with diethyl ether,
Store at room temperature for an hour to extract the lubricant.

Concentrate this extract using a rotary evaporator.1. The rIL was solidified and dissolved in hexane.

In the case of branched paraffin, this solution was quantitatively analyzed by gas chromatography to determine the amount of branched paraffin remaining, and the difference from the amount applied was determined as the amount of volatilization.

In the case of palm oil, a sodium methoxide-methanol/boron fluoride-methanol glyceride decomposition methyl esterification method was used, and the residual amount of palm oil was determined by gas chromatography, and the volatile amount was determined from the difference from the applied amount.

(Flavor Evaluation) A metal container was filled with distilled water and left at 37° C. for one month, after which a flavor test was conducted by a panel of 20 people. As for the results, cases in which there was a change in flavor were indicated by an X, and cases in which there was no change were indicated by an O.

Example 1 A steel plate with a base thickness of 0.18 mm and subjected to electrolytic chromic acid treatment was laminated with PET film on the inner and outer surfaces.
The coating amount of branched paraffin (on average, there is a branch chain for every 4 carbon atoms in the main chain, 90% or more of which have 1 carbon in the branch chain, and the melting point is 45°C) is 1, OB/d + a2. It was applied evenly. Thereafter, a metal container was obtained by drawing by normal press working so that the total drawing ratio was 2.7 and the outer diameter was 66 mm.

In the process of producing this metal container, press workability was evaluated.

Furthermore, this metal container was heated for 22 hours using a normal gas oven.
A heat treatment was performed at 0° C. for 4 minutes. Then, the amount of volatilization of the lubricant in this metal container was measured.

Curved surface printing was performed on this metal container, and printing suitability such as ink adhesion and repellency was evaluated. Additionally, flavor tests were conducted on these metal containers.

These results are summarized in Table 1.

Example 2 A metal container was produced and evaluated in the same manner as in Example 1, except that the amount of branched paraffin applied was (1.6 B/dm2).

The results regarding press workability, lubricant volatilization amount, printability, and flavor are shown in Table 1.

Example 3 A metal container was produced and evaluated in the same manner as in Example 1, except that the heat treatment conditions were that it was held at 215° C. for 8 minutes.

The results regarding press processing ff, lubricant volatilization amount, printability, and flavor are shown in Table 1.

Example 4 Epoxy/phenol paint was applied and baked on the inner and outer surfaces of a steel plate with a base thickness of 0.18 mm so that the total coating amount was 150 mg/dm2, and then monobranched paraffin was applied in an amount of 150 mg/dm2. A metal container was produced in the same manner as in the example by uniformly applying the solution to a concentration of 1.0 mg/da2.

Then, these metal containers were subjected to heat treatment at 220° C. for 4 minutes.

The amount of lubricant volatilization, printability, and flavor were evaluated. These evaluation results are shown in Table 1.

As a result, as shown in Examples 1 to 4, good results were obtained in all cases. In particular, it showed excellent properties in terms of printability and flavor after heat treatment, demonstrating the superiority of producing metal containers using the method of the present invention.

Comparative Example 1 For comparison, the same plate material as in Example 1 was coated with the same coating amount as in Example 1, except that polyethylene glycol (molecular weight 400) was used as the lubricant. The coating was applied uniformly to achieve OB/dm2, and subjected to drawing forming in the same manner as in Example 1. However, the can body broke during the pressing process, and a metal container could not be obtained.

Comparative Example 2 Branched paraffin is used as a lubricant, coating amount is 0.3 m
Except for applying it evenly so that g/d+*2.
It was subjected to drawing forming in the same manner as in Example 1. However, one part of the can jl broke during the pressing process, and a metal container could not be obtained.

Comparative Example 3 Branched paraffin was used as a lubricant, and the coating amount was 10.0
The coating was applied uniformly so as to achieve +H/da2, and drawing was performed in the same manner as in Example 1 to obtain a metal container. These metal containers were subjected to heat treatment at 220° C. for 4 minutes, and then the amount of lubricant volatilization was measured and printability was evaluated. As a result, it was found that ink repellency was large and printing suitability was poor.

Comparative Example 4 Refined palm oil was used as a lubricant, and the application amount was 2.0mz
/dm2, and drawing was performed in the same manner as in Example 1 to obtain a metal container. These metal containers were subjected to heat treatment at 220° C. for 4 minutes, and then the amount of lubricant volatilization was measured, and the printability and flavor were evaluated. As a result, some repellency was observed in the printing, and it was found that the flavor was poor.

The results of Comparative Examples 1 to 4 above are summarized in Table 2. From this, it was found that the conditions of Comparative Examples 1 to 4 were significantly inferior to the conditions of Examples 1 to 4 in moldability, printability, and flavor, and were difficult to apply to containers.

[Brief explanation of drawings]

FIG. 1 is a new view showing the cross-sectional structure of the metal material used in the method of the present invention, and FIG. 2 is an explanatory view (cross-sectional view) illustrating the drawing process of the metal material. 1 is a metal material for molding, 2 is a metal substrate, and 3a. 3b is an organic resin coating, and 4a and 4b are saturated hydrocarbon lubricant layers.

Claims (3)

[Claims] (1) In a method for manufacturing a metal can by subjecting a metal material on which an organic resin film has been formed in advance to a first to several multi-stage drawing process, a saturated hydrocarbon lubricant is applied onto the organic resin film surface of the material. A method for producing metal cans, which comprises uniformly applying a lubricant, subjecting the coated material to drawing forming, and heating the can obtained by drawing to volatilize most of the lubricant adhering to the can. (2) The saturated hydrocarbon lubricant is a hydrocarbon lubricant containing branched chains, and the branched chain has at least one branched chain for every 2 to 10 carbon atoms in the main chain. The method for manufacturing a metal can according to item 1. (3) The method for manufacturing a metal can according to claim 2, wherein in the branched chains, branched chains having one carbon number account for 70% or more of the total number of branched chains.