JPH021746B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyolefin-coated metal can, and more particularly to a polyolefin-coated metal can having a polyolefin coating formed on the inner surface and having side joints and double seams with excellent airtightness and joint strength. A metal can whose inner surface is coated with polyolefin in advance to store contents such as sulfuric acid aqueous solution and alkaline liquid detergent, which are relatively corrosive and do not want to be contaminated with metal ions eluted due to corrosion. It is preferable to use a metal can made of a plate from the viewpoints of ensuring corrosion resistance and economy. Such polyolefin-coated metal sheets include electrolytic chromic acid treated steel sheets, (tein-free steel),
On one side of a metal plate (usually in the form of a strip) such as a tin-plated steel plate, a phosphate-treated steel plate, or an aluminum (alloy) plate,
A polyolefin film is heat-bonded using a suitable adhesive (for example, containing acid-modified polyolefin powder and epoxy resin), and a baked coating is applied to the other side (for example, epoxy urea, epoxy ester, epoxy phenol, epoxy acrylic, acrylic).・Produced by forming a baked coating film of amino, polyester, modified alkyd, alkyd/amino paint, etc. In order to form a side joint of the body of a metal can made of a polyolefin-coated metal plate as described above, when the opposing side edges are seamed or overlapped, a lock seam part 1 as shown in FIG. 1a is formed. , or a wrap seam 2 as shown in FIG. 1b is obtained. In the figure, 3 is a polyolefin-coated metal plate, 4 is a metal plate, 5 is a polyolefin coating, and 6 is a baked coating, and the polyolefin coating 5 is bonded to the metal plate 4 via an adhesive layer (not shown). In the case of FIG. 1a, when the lock seam part 1 is heated to a temperature higher than the melting point of the polyolefin forming the polyolefin coating 5, the part a' where the polyolefin coatings 5 are in contact with each other is fused, but the polyolefin coating 5 and the part a' are baked. The b' portion where the coatings 6 are in contact with each other and the c' portion where the baked coatings 6 are in contact with each other are not fused and have almost no bonding strength. Therefore, the bonding strength of the lock seam portion 1 after the above-mentioned heat treatment is not sufficient, and the seam portion 1 is likely to peel off due to a drop impact, etc., resulting in troubles such as leakage of the liquid content. Further, since the fusion is performed only at the a' portion, there is a problem that the airtightness is not sufficient.
On the other hand, in the case of FIG. 1b, the polyolefin coating 5 and the baked coating 6 are only in contact with each other at the lap seam portion 2, so even if the lap seam portion 2 is heated to a level greater than the fusion of the polyolefin, no fusion will occur. Therefore, almost no bonding strength can be obtained and it cannot be put to practical use. Figure 2 shows a double seam portion 9 between the can body 7 and the end plate 8 made of a polyolefin-coated metal plate; in this case, the double seam portion 9 is also heated above the melting point of the polyolefin. By doing this, parts d' and e' where the polyolefin films 5 are in contact with each other are fused together, but parts f' where the polyolefin film 5 and the baked-on film 6 are in contact with each other and the baked-on films 6 are fused together. The contacting portion g' is not fused and has almost no bonding strength. Therefore, 2 after the above heat treatment
There is a problem in that the joint strength and airtightness of the heavy seaming portion 9 are insufficient. It is an object of the present invention to solve the problems of the prior art described above. In order to achieve the above object, the present invention is made of a polyolefin-coated metal plate in which the surface that is to become the inner surface of the can is coated with a polyolefin film, and the surface that is to become the outer surface of the can is coated with a baked coating film. In a polyolefin-coated metal can in which the body has a side joint and an end plate is joined to the body by a double seam, the baked coating film is made of synthetic resin 100 having excellent adhesion to the metal plate. It is formed by applying and baking a paint containing 1 to 20 parts by weight of modified polyolefin powder, and the side joints and double seams are coated with the polyolefin coating and the baked coating. The present invention provides a polyolefin-coated metal can characterized in that a heat-sealed portion is formed therein. Furthermore, the present invention provides a metal plate formed of a polyolefin-coated metal plate in which the surface that is to become the inner surface of the can is coated with a polyolefin coating, and the surface that is to become the outer surface of the can is coated with a baked coating film, and the body is formed of a lock seam portion. In a polyolefin-coated metal can having a joint portion and an end plate joined to the body portion by a double seam portion, the baked coating film is made of 100 parts by weight of a synthetic resin with excellent adhesiveness to the metal plate. It is formed by applying and baking a paint containing 1 to 20 parts by weight of modified polyolefin powder to the side joints and the second
The present invention provides a polyolefin-coated metal can characterized in that a heat-sealed portion of the polyolefin coating, the polyolefin film, or either one of the polyolefin coating and the baked coating is formed in the heavy seam portion. The present invention will be described below with reference to drawings showing embodiments. 10 in FIG. 3 is a polyolefin-coated metal can (hereinafter referred to as metal can), 17 is a body, 1
8a is a cover plate, 18b is a bottom plate (in this specification, the cover plate and the bottom plate are referred to as an end plate), and 19 is 2
The heavy seaming part, 20 shows the side joint part. A polyolefin coating 15 is formed on the inner surface of the polyolefin-coated metal plate 13 forming the body 17 via an adhesive (not shown), and a baked coating 16 is formed on the outer surface (see FIG. 4). Similarly, cover plate 1
A polyolefin coating 1 is applied to the inner surface of the polyolefin coated metal plate 13 forming the bottom plate 18a and the bottom plate 18b.
5 is formed via an adhesive layer (not shown),
A baked coating film 16 is formed on the outer surface. (5th
(see figure). Polyolefin here refers to ethylene,
Refers to homopolymers or copolymers of olefin monomers such as propylene and 1-butene, such as low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene, ethylene-propylene random copolymer, ethylene-propylene block. Copolymers, ethylene-1-butene copolymers, mixtures thereof, etc., including these alone or those containing colorants, light and heat stabilizers, flame retardants, lubricants, etc. The thickness of the polyolefin coating 15 is usually 30 to 70 μm. The baked coating film 16 is a paint in which modified polyolefin powder is dispersed in a synthetic resin paint (for example, an epoxy/urea resin paint, an epoxy/phenol resin paint, an epoxy ester resin paint) that has excellent adhesion to the metal plate 14. It is formed by coating and baking, and its thickness is usually 3 to 10 μm. The modified polyolefin powder herein refers to a powder prepared by grafting a polyolefin with an unsaturated carboxylic acid or a derivative thereof, and the polyolefin is of the same type as the polyolefin forming the polyolefin coating 5 (for example, a low The side joints 20 and 2
This is desirable in order to ensure high bonding strength due to thermal fusion between the polyolefin coating 15 and the baked coating 16 that are in contact with each other in the heavy seam portion 19 . The particle size distribution of the modified polyolefin powder is such that 50% or more of the weight fraction is
It is desirable that the thickness be 10 μm or less, more preferably 5 μm or less. The baked coating film 16 is mainly formed as an external coating film for protection such as corrosion prevention and rust prevention of the metal plate 14, but on the other hand, aesthetic appearance is also important in order to increase the commercial value of the metal can 10. However, the weight fraction of particles with the above particle size exceeding 10 μm is 50%.
If this happens, after baking (baking conditions usually follow those of the synthetic resin paint), the powder portion will protrude significantly and the baked coating surface will become rough, impairing its appearance. In the baked coating film 16, the synthetic resin
It is desirable that the modified polyolefin be contained in an amount of 1 to 20 parts by weight, more preferably 3 to 10 parts by weight, per 100 parts by weight. If the amount exceeds 20 parts by weight, the surface of the baked coating film 16 will become rough, lose its luster, and spoil its appearance.
On the other hand, if it is less than 1 part by weight, the polyolefin coating 1
This is because the bonding strength between 5 and the baked coating film 16 is lost. Note that the synthetic resin is particularly preferably an epoxy/urea resin. This is because it has excellent adhesion to the metal plate 14 and modified polyolefin. In Fig. 4a, the side joint 20 is connected to the lock seam 2.
0a, in which the polyolefin coatings 15 are bonded to each other in portion a, the polyolefin coating 15 and baked coating film 16 are bonded to each other in portion b, and the baking coating 16, polyolefin film 21, and baked coating film 16 are bonded together in portion c. The coating films 16 are brought into contact with each other to form a heat-sealed portion and are airtightly joined. It is desirable that the polyolefin forming the polyolefin film 21 be of the same type as the polyolefin forming the modified polyolefin contained in the baked coating film 16 in order to achieve strong bonding strength. In Fig. 4b, the side joint part is the wrap seam part 20b.
In this example, the polyolefin film 15 and the baked coating film 16 are in contact with each other to form a thermally fused portion and are airtightly joined. FIG. 5 shows an example of the double-sealed portion 19, where a portion d shows the polyolefin film 15 and a portion f the baked coating 16 and the polyolefin film 2.
1, polyolefin film 15, part g is baked coating 16, polyolefin film 21, baked coating 1
6. The polyolefin coating 15 is in contact with the portion e, forming a heat-sealed portion, and is airtightly joined. The metal can 10 having the lock seam portion 20a and the double seam portion 19 is manufactured, for example, as follows. Usually, a tape-like material is applied on one side edge 22a and both end edges 22b of the baked coating film 16 side of the fuselage blank 22, which is formed by cutting a strip-shaped polyolefin-coated metal plate 13 to a predetermined size. As shown in FIGS. 6 and 7, the polyolefin film 21 is thermally bonded using a thermal bonding roll (not shown). The width of the polyolefin film 21 is usually 3 to 20 mm, and the thickness is 30 to 100 μm. Next, after corner cutting, the polyolefin film 21 is cut so that the polyolefin coating 15 is on the inner surface.
The side edge 22a to which is thermally bonded is the lock seam portion 2.
0a (however, in the case of FIG. 4a, it may be placed inside), mold a can body molded body by a conventional method, and heat the lock seam part 20a above the melting point of the polyolefin. After cooling, flanges are formed at both open ends to form the body 17. Next, the bottom plate 18b having a peripheral curl portion formed from the polyolefin-coated metal plate 13 so that the polyolefin coating 15 is on the inner surface is double-sealed to the body 17, and the double-sealed portion 19 is attached to the melting point of the polyolefin. Heat fusion is performed by heating to the above temperature. Next, a lid plate 18a having a structure similar to that of the bottom plate 18b (usually provided with a mouthpiece not shown) is double-sealed to the can body, and the double-sealed portion 19 is heated to a temperature higher than the melting point of the polyolefin. Then perform heat fusion. When the side joint part consists of a lap seam part 20b, a polyolefin film 2 is placed on the side edge 22a.
1 may be thermally bonded, but it is not necessarily necessary to thermally bond. The present invention is not limited to the above embodiments, but when forming a lock seam portion,
It is not necessary to thermally bond the polyolefin film 21 onto the side edge 22a. Even in this case, portion c is not heat-sealed, but portion b is coated with polyolefin coating 1.
5 and the baked coating film 16 are formed.
A side joint portion 20 having far superior airtightness and joint strength than the conventional seaming portion 1 can be obtained. Alternatively, the polyolefin film 21 may be thermally bonded to both side edges 22a. Furthermore, it is not necessary to thermally bond the polyolefin film 21 onto the edge 22b. Even in this case, it is only the portion g that is not heat-sealed, and the heat-sealed portion of the polyolefin coating 15 and the baked coating film 16 is formed on the portion f, so that it is better than the conventional double-sealed portion 9. A double-sealed part with far superior airtightness and bonding strength can be obtained. Furthermore, as shown in FIGS. 8 and 9, a lock seam portion 2 is formed from a fuselage blank with polyolefin film 21 thermally bonded to both side edges 22a and both end edges 22b.
0'a and a metal can having a double seam 19'. In this case, there is an advantage that the joint strength is even greater than that of the lock seam portion 20a and double seam portion 19 shown in FIGS. 4a and 5. The polyolefin-coated metal can of the present invention has excellent airtightness and bonding strength at the side joints and double seams, and also has high corrosion resistance on the inside of the can, and has moderate corrosion resistance on the outside of the can due to the baked coating. It also has the effect of having an excellent appearance. Examples will be described below. Example 1 On one side of a 0.32 mm thick stain-free steel,
Apply a roll coat of modified polypropylene powder-dispersed epoxy/urea paint with the following composition, and
Baking was performed at 250°C for 1 minute. The dry film thickness is
The diameter was 5 μm, and the surface was smooth. Paint composition: Epoxy/urea resin (epoxy/
Uriya (weight ratio) = 90/10): 100 parts by weight Maleic anhydride-modified polypropylene powder: 5 parts by weight (manufactured by Toyo Ink Manufacturing Co., Ltd.,
Product name: Liosene, particle size: 5μm or less
80% by weight) Solvent: Ethyl cellosolve: 75 parts by weight Diacetone alcohol: 13 parts by weight Methyl isobutyl Carbitol: 12 parts by weight: 40 parts by weight Next, on the other side, apply an epoxy/urethane paint with the following composition dispersed in modified polypropylene powder as an adhesive and bake. (ambient temperature 250℃ x 1 minute, dry film thickness
6 μm). Paint composition: Epoxy/urethane resin (epoxy/urethane (weight ratio) = 70/30):
100 parts by weight Maleic anhydride modified polypropylene powder: 70 parts by weight (manufactured by Toyo Ink Manufacturing Co., Ltd.,
(Product name: LIOTHEN) Solvent MIBK 30 parts by weight Cyclohexanone 20 parts by weight Toluene 20 parts by weight Cellosolve Acetate 30 parts by weight: 40 parts by weight Next, keep the temperature of the tain-free steel at 150°C and attach a 60 μm thick polypropylene film to the above adhesive. A polypropylene-coated metal plate 13 was manufactured by thermally adhering the metal plate 13 through the wafer and then heating it to 200° C. for thermal fusion bonding. A fuselage blank 22 of 914.4 mm x 353.3 mm was formed from the metal plate 13, and a square cover plate with rounded corners and a bottom plate with a side length of 243 mm were formed with the polypropylene coating facing the inner surface. .
As shown in FIG. 6, a polypropylene tape 21 having a thickness of 60 μm and a width of 10 mm was thermally bonded onto the baked coating surfaces of one side edge 22a and both end edges 22b of the fuselage blank 22 using a pressure roll. Next, after cutting the corners of the fuselage blank 22, it is formed into a square shape (square cross section with rounded corners), and the side edges 22 are pasted with tape 21.
A lock seam portion 20a of the type shown in FIG. 4a was formed with point a on the outside, and the lock seam portion 20a was heated to 200° C. using a direct gas burner to heat-seal the lock seam portion 20a. A bottom plate was double-sealed to the obtained body 17, and the double-sealed portion was heated to 200° C. to be heat-sealed. A lid plate with a cap part is double-sealed to this, and the double-sealed part is heated to 200℃ and heat-sealed.
Metal can 10 (18 liter can) was produced. The bonding strength and airtightness of the metal can 10 manufactured as described above were tested as follows,
In addition, the appearance was evaluated as follows. Similar tests and determinations were conducted for Examples 2 and 3 and Comparative Examples. (1) Joint strength: The lock seam part and double seam part should be at right angles to the tensile direction.
Cut into strips of 20 mm width and test them at a tensile speed of 40 using a tensile tester.
The maximum tensile strength was measured by pulling at mm/min. (2) Airtightness test: A metal can was submerged in water, compressed air of 0.2 kg/cm ² (gauge pressure) was blown into the can from the mouthpiece, and leakage was checked by the generation of air bubbles. The number of test cans is 100, and the number of cans in which leakage occurred is shown. (3) Appearance: Good for practical use. ×...The film surface lacks gloss and cannot be put to practical use. The test results are shown in Table 1.

[Table] Example 2 A metal can was manufactured in the same manner as in Example 1, except that polypropylene tape 21 was attached to both side edges 22a and both end edges 22b of the body blank 22. The test results for this metal can are shown in Table 1. Example 3 Side edge 22a and end edge 22 of fuselage blank 22
A metal can was manufactured in the same manner as in Example 1, except that the polypropylene tape 21 was not attached to b. The test results for this metal can are shown in Table 1. Comparative Example 1 A metal can was produced in the same manner as in Example 2, except that maleic anhydride-modified polypropylene powder was not added to the epoxy-urea paint applied to the surface that was to become the outer surface. The test results for this metal can are shown in Table 1. Comparative Example 2 A metal can was manufactured in the same manner as in Example 1, except that the amount of maleic anhydride-modified polypropylene powder was 0.5 parts by weight in the epoxy-urea paint applied to the surface that was to become the outer surface. . The test results for this metal can are shown in Table 1. Comparative Example 3 A metal can was manufactured in the same manner as in Example 1, except that the amount of maleic anhydride-modified polypropylene added to the epoxy area paint applied to the surface that was to become the outer surface was 23 parts by weight. . The outer surface of this metal can was rough and lacked luster, making it unattractive as a product. The test results are shown in Table 1.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the side joint for comparison; FIG. 1a shows the lock seam part, and FIG.
2 is a longitudinal sectional view of the double seam portion for comparison, FIG. 3 is a perspective view of an embodiment of the metal can of the present invention, and FIG. 4 is a view showing the lap seam portion. −
FIG. 4A is a cross-sectional view taken along line V-V in FIG. 3; FIG. 4B is a view showing a lap seam portion; FIG. 6 is a plan view of an example of a body blank used for manufacturing the metal can of FIG. 1, FIG. 7 is a longitudinal sectional view taken along the line - in FIG. 6, and FIG. 8 is a lock seam of the metal can of the present invention. A cross-sectional view showing another example of the section,
FIG. 9 is a longitudinal cross-sectional view showing another example of the double-sealed portion of the metal can of the present invention. DESCRIPTION OF SYMBOLS 10...Polyolefin coated metal can, 13...Polyolefin coated metal plate, 14...Metal plate, 15...Polyolefin coating, 16...Baked coating film, 17...Body part, 19, 19'...Double seam part, 20...Side joint part, 20a, 20'a...lock seam part, 20b
...Lapseam part, 21...Polyolef in film.

Claims (1)

[Scope of Claims] 1. It is formed from a polyolefin-coated metal plate in which the surface that is to become the inner surface of the can is coated with a polyolefin film, and the surface that is to become the outer surface of the can is coated with a baked coating film, and the body is joined to the sides. In a polyolefin-coated metal can having a double seam and an end plate joined to the body by a double seam, the baked coating film is made of 100 parts by weight of a synthetic resin that has excellent adhesion to the metal plate. On the other hand, it is formed by applying and baking a paint containing 1 to 20 parts by weight of modified polyolefin powder. 1. A polyolefin-coated metal can characterized by having a bonded part formed therein. 2. The polyolefin-coated metal can according to claim 1, wherein the side joint portion is a lock seam portion. 3. The polyolefin-coated metal can according to claim 1, wherein the side joint portion is a lap seam portion. 4. A metal plate made of a polyolefin-coated metal plate whose surface that is to become the inner surface of the can is coated with a polyolefin coating, and whose surface that is to become the outer surface of the can is coated with a baked coating film, and whose body has a side joint part consisting of a lock seam part. In the polyolefin-coated metal can in which the end plate is joined to the body part by a double seam part, the baked coating film is made of a synthetic resin with excellent adhesiveness to the metal plate.
1 to 100 parts by weight of modified polyolefin powder
It is formed by applying and baking a paint containing 20 parts by weight, and the side joint part and the double seam part are coated with the polyolefin coating and/or the polyolefin film and the heat of the baked coating film. A polyolefin-coated metal can characterized by having a fused portion formed therein.