JPS6326796B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for forming a metal beverage container, and more specifically, it is free from problems such as metal elution into the contents and corrosion of the container, has excellent flavor retention of the contents, and has a squeezing rate. The present invention relates to a method for manufacturing a metal beverage container with high processability and good processing workability. Metal containers for beverages are made by deep-drawing or drawing-ironing a metal material such as aluminum or tin to form a pot-shaped case with a flange, and double-sealing this with a can lid. A two-piece can, or a cup-shaped lower body with a cup-shaped spout and a cup-shaped upper body with a spout, are manufactured by press-working the above-mentioned material, and these lower and upper bodies are formed with a circumferential opening. A pin-shaped container is used by overlapping and joining the ends. In this drawing or pressing process, it is recommended to provide an organic coating film on the metal material before processing, in terms of drawing processability and workability.
It is also advantageous in that it does not require the trouble of painting the housing after processing, but the following drawbacks still occur when attempting to deep draw a coated metal material through several stages of press working. In other words, known coated metal materials have a certain drawing limit, and if this drawing limit is exceeded, the material is likely to break at the head or flange. It becomes difficult to manufacture. In addition, when the drawing ratio increases during this press processing, coating defects such as peeling, breakage, cracks, and pinholes are likely to occur in the coating film on the material, and metal elution into the contents (especially iron elution) and can Corrosion such as pitting corrosion on the body becomes more likely to occur. Furthermore, it may be possible to improve the drawing processability by applying a known lubricant on the paint film, but in this case, it becomes difficult to degrease the lubricant on the paint film, and the lubricant remaining on the paint film may A fatal drawback is that the lubricant tends to spoil the flavor of the beverage, which relies on a delicate flavor. The present inventors applied a lubricant mainly consisting of triglyceride, which is composed of glycerin and a saturated fatty acid having 2 to 18 carbon atoms, and the total carbon number of the saturated fatty acids is 10 to 25, to the coating surface of a painted metal material in a solution. It has been found that when applied in the form of , and prior to drawing, a metal container for beverages is obtained in which all of the above-mentioned disadvantages are eliminated. That is, an object of the present invention is to provide a method for molding metal beverage containers in which the above-mentioned drawbacks are eliminated. Another object of the present invention is to provide a method for molding metal beverage containers that has a significantly improved drawing limit compared to conventional molding methods. Still other objects of the present invention are that the coating film on the material does not become defective during the drawing process, that it is easy to degrease and clean after molding, and that even when lubricant remains on the coating film, the contents can be removed. To provide a method for molding metal containers for beverages that hardly impairs flavor. According to the present invention, in a method of forming a metal material on which an organic coating film is formed by relative axial movement of a punch and a die into a metal container by cold multi-stage press working, glycerin and a carbon number A liquid lubricant mainly composed of triglycerides, which consists of 2 to 18 saturated fatty acids and the total number of carbon atoms in the saturated fatty acids is 10 to 25, is applied in the form of a solution to the organic coating surface of the material at room temperature. A method for forming a metal beverage container is provided, which comprises forming a lubricant layer and then subjecting the material to press working. The invention will be explained in detail below. In FIG. 1 showing the cross-sectional structure of a metal material to be press-formed, the metal material 1 for forming includes a metal substrate 2 made of an aluminum plate, tinplate, etc., an organic coating 3a provided on both surfaces of the substrate, It consists of 3b. An important feature of the present invention is that these organic coating films 3a,
3b, prior to pressing, a solution layer 4a, 4 of a liquid lubricant mainly composed of triglyceride, which is composed of glycerin and a saturated fatty acid having 2 to 18 carbon atoms, and the total number of carbon atoms in the saturated fatty acid is 10 to 25.
b is uniformly provided. That is, the lubricant used in the present invention is mainly composed of triglycerides like ordinary animal and vegetable fats and oils, but the fatty acids constituting the triglycerides are saturated fatty acids having 2 to 18 carbon atoms, and the total amount of these saturated fatty acids is It is significantly different from these oils and fats in that the number of carbon atoms is in the range of 10 to 35. First, although this triglyceride is composed of saturated fatty acids, it is a liquid having an appropriate viscosity in relation to having the above-mentioned number of carbon atoms. Therefore, this liquid lubricant is retained on the organic coating surface of the material and forms a lubricating surface with a high oil film strength, preventing stress concentration on specific parts, such as the head and flange, even when machining with a high drawing ratio. This has the advantage of improving drawing workability and significantly improving the drawing limit. Furthermore, since the lubricant on the coating film is essentially liquid, it has the advantage that degreasing is easier than with solid lubricants. Furthermore, since the fatty acids that make up triglycerides are saturated fatty acids, they are tasteless and odorless compared to those made from unsaturated fatty acids.
Even if this substance remains on the paint film, the contents may have an unpleasant taste or
This has the advantage of not giving off any unpleasant odor.
In addition, triglycerides formed from saturated fatty acids having the above-mentioned number of carbon atoms have outstanding uniformity and wettability on the organic coating surface of materials. By applying it to the coating surface, even more excellent wettability or uniform application can be obtained. Moreover, as a result of the combination of the various advantages mentioned above, according to the present invention, even when the amount of triglyceride-based liquid lubricant applied is extremely small, high-level drawing processing can be performed very smoothly and at high speed. The advantage of becoming more efficient is also achieved. In the present invention, it is also important that the total carbon number of the saturated fatty acids constituting the triglyceride is in the range of 10 to 25, particularly 15 to 25. When this total carbon number is smaller than the above range, the above-mentioned No advantage is achieved, whereas if it is larger than the above range, it becomes disadvantageous both in terms of lubrication performance and also in terms of degreasing performance. The three saturated fatty acids constituting the triglyceride used in the present invention may be the same or different from each other within the range that satisfies the above requirements. Moreover, although this saturated fatty acid is preferably a straight chain fatty acid, it can also be a branched chain fatty acid. Examples of suitable constituent fatty acids are acetic acid, butyric acid, caproic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, etc. Suitable examples of triglycerides include, but are not limited to: Tributin, tricaproin, tricaprylin, 1,2-diaceto-3-palmitine, 1,2-diaceto-3-stearin, 1,2-diaceto-3-myristin, 1,2-dilacto-3-laurin, 1,2 -dilacto-3-myristin, 1-aceto-2-lacto-3-laurin. In the present invention, as the liquid lubricant, one consisting of the above-mentioned saturated fatty acid triglyceride alone is preferably used, but this lubricant contains more than 50% by weight, especially 70% by weight or more of saturated fatty acid triglyceride. It is also possible to use it in combination with other lubricants, provided that it is entirely liquid. Lubricants that can be used in combination include other fatty acid glycerides, fatty acids, fatty acid esters,
Examples include fatty acid amides, higher alcohols, paraffins, and the like. These liquid lubricants are applied in the form of solutions to organic coatings on materials. The solvent for forming the solution is one that substantially dissolves the liquid lubricant but does not dissolve or swell the organic coating, such as lower alcohols such as methanol and ethanol; methyl ether and ethyl ether. and hydrocarbon solvents such as benzene, toluene, and xylene; however, the solvents that can be used are of course not limited to these. The concentration of liquid lubricant in the solution is generally in the range from 1 to 20% by weight, in particular from 1 to 10% by weight, to give satisfactory results in terms of spreadability and lubricity. The amount of liquid lubricant solution applied to the organic coating surface of the material is:
One of the advantages of the present invention is that a remarkable effect can be obtained with a significantly small ^{amount .} Satisfactory results can be obtained with the amount of application. If the coating amount is less than the above range, the lubrication performance will be unsatisfactory, and on the other hand, the degreasing operation will be more burdensome than the above range, which is likely to be disadvantageous in terms of economy and flavor characteristics. In the present invention, the liquid lubricant solution is applied to the coating surface by means known per se, such as roller coating, spray coating, dip coating, and foam coating. The coated metal materials used in the present invention are known per se. Examples of the metal materials include untreated steel plates (black plates), various surface-treated steel plates, such as tin-plated steel plates (tin plate), galvanized steel plates, Plated steel sheets such as aluminized steel sheets and chrome-plated steel sheets; electrolytically treated steel sheets such as electrolytic chromic acid treated steel sheets; chemically treated steel sheets such as phosphoric acid and/or chromic acid treated steel sheets, light metal sheets such as aluminum, or composite materials thereof. be done. Suitable metal materials include rolled aluminum materials made of pure aluminum or aluminum alloys, which generally have a diameter of 0.15 to 0.80 mm, although they differ depending on the drawing conditions and purpose.
It is especially used in material thicknesses of 0.17 to 0.50 mm. Other suitable metal materials include those having a tin content, i.e. pounds of tin per base box, of 0.1 to 1.0, especially 0.15.
A value in the range of 0.75 to 0.75 is used. This tin plating layer may be a no-reflow board (matte board) that has been electrolytically plated, or may be a reflow board (bright board) in which the electrolytically plated layer has been heat-melted. The thickness of the base plate is generally 0.15 to 0.5mm, especially 0.15mm.
A material in the range of 0.35 mm to 0.35 mm is used. On the other hand, the protective coatings include any protective coatings made of thermosetting and thermoplastic resins; for example, modified epoxy coatings such as phenolic epoxy coatings and amino-epoxy coatings; for example, vinyl chloride-vinyl acetate copolymers, vinyl chloride-acetic acid copolymers, etc. Vinyl or modified vinyl paints such as partially saponified vinyl copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, epoxy-modified, epoxyamino-modified, or epoxyphenol-modified vinyl resin paints; acrylic resin paints; Synthetic rubber paints such as styrene-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 enamel or lacquer, or in the form of aqueous dispersions or solutions, in the form of roll coating, spray coating, dip coating, electrostatic coating, electrophoretic coating, etc. Apply. Of course, if the resin paint is thermosetting, the paint may be baked if necessary. These organic coatings generally have a thickness of 2 to 30 μm, particularly 3 to 30 μm, from the viewpoint of preventing corrosion and improving drawing workability.
It is desirable to have a thickness (dry state) of 20 μm. According to the present invention, as shown in FIG. 2, a painted metal material 10 coated with a liquid lubricant is held down by a wrinkle presser 11 between a punch 12 and a die 13 that are relatively movable in the axial direction. It is pressed and formed into a seamless cup with a bottom. At this time, the solution layer of the liquid lubricant may be dried and then subjected to press processing, but in general, the solution layer after application is It is preferable to press it in its original form, that is, in a wet state. In the present invention, press working is performed several times while gradually decreasing the diameter of the punch and die until the desired shape and desired height/diameter ratio are achieved. At this time, the drawing ratio defined by the following formula: Drawing ratio = Diameter before processing / Diameter after processing is 1.20 in one press processing.
to 2.10, especially 1.30 to 1.90, and the overall aperture ratio to 1.50 to 3.00, especially 1.80.
It is desirable to do this so that the ratio is between 2.70 and 2.70. After the drawn cup is trimmed, it is subjected to a degreasing operation known per se, such as hot water washing, solvent washing, and fluorocarbon gas washing, and is then used for subsequent can manufacturing operations. In other words, in a normal deep-drawn can with a two-piece structure,
If necessary, neck-in processing and flange processing are performed, and after filling with the contents, the can is double-sealed with the can lid to form the can. In addition, in the case of a bottle-shaped metal container having a circumferential side seam, a lower body 2 consisting of a bottomed cup shown in FIG. 3 and an upper body 21 consisting of an inverted cup with an opening are formed, As shown in FIG. 4, these two pieces are overlapped and bonded via the adhesive layer 22 to form a bottle-shaped container. The invention is illustrated by the following example. Example 1 Modified vinyl paint was applied to the inner and outer surfaces of an aluminum plate (3004H19 material) with a base thickness of 0.23 mm, and the total coating amount was
Tricaprylin [symbol L-1] after coating and baking to give 150 mg/dm ² and 60 mg/dm ²
A liquid lubricant prepared by diluting (fatty acid carbon number 8, total fatty acid carbon number 24) with ethanol to a concentration of 5% by weight is applied to the inner and outer coating surfaces at room temperature using a roll method to give a concentration of 35mg/ ^m2 . It was applied evenly. After that, it was punched into a disc with a diameter of 250 mm, and drawn using normal press processing so that the total drawing ratio was 2.26. After forming a cup with an inner diameter of 110.6 mm at the edge of the joint, it was further subjected to multi-stage press processing. An upper body having a spout with a diameter of 30 mm in the center was manufactured. On the other hand, a painted plate coated with the same liquid lubricant was drawn with a total drawing ratio of 2.26 similar to the upper body, and the outside diameter of the joint edge was further reduced by a netting process.
The lower body was made to have a diameter of 110.6 mm. Afterwards, both parts were spray washed with hot water (70°C) and then dried in an oven. The upper body and the lower body were heat-bonded using a heat-sealing adhesive to produce a metal beverage container with a capacity of about 2. In the process of manufacturing these metal containers, we evaluated their press formability, and after filling them with synthetic carbonated beverages, we sealed the spouts, sterilized them at 62°C for 10 minutes, and left them at room temperature for 3 months to evaluate metal elution. The amount was measured and the flavor was evaluated. Table 1 shows the results.
Shown below. Examples 2 to 5 Tributylene [symbol L-2] as liquid lubricant
(fatty acid carbon number 4, fatty acid total carbon number 12), tricaproin [symbol L-3] (fatty acid carbon number 6, fatty acid total carbon number 18), 1,2-dilacto-3-laurin [symbol L-4] (fatty acid 80% by weight of tricaprylin (fatty acid carbon number 8, fatty acid total carbon number 24), 1,2
- Same as Example 1 except that a 20% by weight mixture of diaceto-3-olein (containing unsaturated fatty acid component) [symbol L-5] was diluted with ethanol to a concentration of 5% by weight and applied to the coating surface. A metal container was produced by performing multi-stage press forming. Table 1 shows the evaluation results of these press formability, amount of metal elution, and flavor. Comparative Examples 1 to 3 For comparison, as liquid lubricants, triacetin [symbol L-6] (fatty acid carbon number 2, fatty acid total carbon number 6), trilaurin [symbol L-7] (fatty acid carbon number 12, fatty acid total carbon number 36), 1,2-diaceto-3-olein [symbol L-8] were prepared in the same manner as in Example 1, and after coating them on a painted plate, they were subjected to a cold multistage press to form beverage metals. A container was made. These containers were also filled with contents in the same manner as in Example 1, and each characteristic was evaluated. The results are shown in Table 1. Example 6 Epoxy paint was applied to the inner and outer surfaces of a tin-plated steel plate (tinplate material, plating amount #25/25, tempered T-2) with a base plate thickness of 0.20 mm, each with a total coating amount of 100 mg/
Using the same liquid lubricant as in Example ¹ , except that the coating and baking were performed so that the lubricant was 50 mg/dm ² ,
Press molding was performed to evaluate the press formability of the upper and lower bodies and their properties as metal containers. As a result, even in the case of tin-plated steel sheets coated with epoxy paint, the forming method for forming the liquid lubricant of the present invention not only improves press formability but also improves metal elution and flavor. It was found that there were no abnormalities and that good metal beverage containers similar to Examples 1 to 5 were obtained.

[Evaluation of metal containers]

In the above Examples and Comparative Examples, the metal containers were evaluated according to the method described below. (a) Paint film damage A metal container was filled with a 1% aqueous sodium chloride solution, a voltage of 7V was applied, and the current value (mA) that flowed at that time was evaluated. Ten pieces of each were measured, and their arithmetic mean value was used as the result. (b) Metal elution Fill a metal container with synthetic carbonated drink and let it cool for 30 minutes at room temperature.
After several months, the amount of eluted metal was measured by atomic absorption spectrometry. Ten pieces of each were measured, and their arithmetic mean value was used as the result. (c) Flavor test Fill a metal container with synthetic carbonated beverage and heat it at room temperature for 30 minutes.
After several months, a flavor test was conducted by a panel of 20 people. The results will be evaluated using a 5-point system.
It was indicated as (good) to 1 (bad).

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the structure of a metal material subjected to press forming, Fig. 2 is a sectional view illustrating the drawing process of the metal material, and Figs. 3 and 4 are illustrating the press forming method according to the present invention. 1 is a diagram illustrating a specific example of a metal container for storage, in which reference numeral 1 is a metal material, 2 is a metal substrate, 3a,
3b is an organic coating film, 4a and 4b are liquid lubricant solution layers, 10 is a painted metal material, 11 is a wrinkle suppressor, 12
13 is a punch, 20 is a lower body, 21 is an upper body, 22 is an adhesive layer, and 23 is a joint edge.

Claims (1)

[Scope of Claims] 1. A method for forming a metal material on which an organic coating film is formed by relative axial movement between a punch and a die into a metal container by cold multi-stage press working,
A liquid lubricant mainly composed of triglyceride, which is composed of glycerin and a saturated fatty acid with a carbon number of 2 to 18, and the total carbon number of the saturated fatty acids is 10 to 25, is applied in the form of a solution to the organic coating surface of the material at room temperature. A method for forming a metal beverage container, which comprises forming a uniform lubricant layer and then subjecting the material to press working. 2. A method according to claim 1, wherein the liquid lubricant solution is applied to the organic coating surface of the material in an amount of 5 to 70 mg/m ² based on non-volatile components.