JPS58177448A - Welded can body using tin coated steel plate - Google Patents

Abstract

PURPOSE:To develop a welded can body for canning using a tin coated steel plate which has excellent resistance to corrosion and compatibility of contents by providing a protective coating layer consisting of specific resin paint on the inside surface side of the can body. CONSTITUTION:In the stage of manufacturing a can for canning by welding, an Sn plating layer of 0.5-1.7g/m<2> Sn as a whole is formed on the inside surface of a can by plating an Sn-Fe alloy layer contg. 0.35-1.60g/m<2> Sn and Sn layer contg. 0.10-1.35g/m<2> Sn thereon. A protective film of thermosetting epoxy resin paint contg. a phenolic resin contg. >=65wt% resol type phenolic resin formed of bisphenol A and a bisphenol type epoxy resin of 1,400-7,000 number average mol.wt. at 50:50-5:95 weight ratio is painted thereon at 2-10mu thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a welded can body that uses a tin-plated steel plate as a can body member and has a resin protective coating layer on at least the inner surface of the can body, and has excellent corrosion resistance and suitability for contents.

Conventionally, Ushida cans, seam cans, etc. have been used as food or beverage cans, but recently welded cans have also come into practical use. As the can material for 6-1*m cans, tin steel plate (tinplate material) and 9-7 Lee steel are used.

Among these, the tin steel sheet used is one conventionally used in solder cans, and the amount of tin plating is as large as 2.8 gβ or more because of the need to maintain so-called solderability. Recently, due to tin resource issues, consideration has been given to the practical application of tin metal *sn+i: with a small amount of tin plating, and application to welded cans is also being considered, but in general, tin metal with a small amount of tin plating is being considered. If a steel plate is used, even if a protective coating layer is provided on the inner surface of the can, if the contents are filled and stored, corrosion or blisters may occur under the protective coating layer. Changes in color and flavor are likely to occur.

Special K: If an anchor material with a tin material of 1622β or less (so-called thinned tin material) is used, the above-mentioned problem is likely to occur. There are many reasons for this, but one reason is that tin and iron are mixed in the lower layer of the tin plating layer during the heating baking process such as painting and printing, which coats or prints the inner and outer surfaces of the tin-plated steel plate. This is thought to be because as alloying progresses, the tin-iron alloy layer increases, and the tin layer, which has a large protective effect on the iron surface of the can material, becomes thinner, and the protective effect of the narrow layer decreases. In addition, other causes are thought to be that the resin protective coating layer provided on the thin steel sheet is defective, or that it is not suitable for the protective coating of the thin steel sheet.

In addition, as a method for manufacturing a welded can body, after rolling the can material, stacking both ends together, passing the electrode through an electrode plug with or without an electrode wire, and observing the current under pressure. However, in this method, the tin-iron alloy layer increases and the tin layer decreases in the pre-processing process described in Section III. When tin-steel plates are used as can stock for welded cans, not only does the above-mentioned problem occur, but the tin-iron alloy layer has a higher melting point than the base steel plate and tin, so it is not only difficult to weld but also hard. In the electrical resistance welding method under pressure as described above, the tin-iron alloy layer of the material increases and the tin layer of the soft material with a low melting point decreases.
The welding electrode roll or wire electrode cannot be sufficiently pressed against the tin-plated steel plate scrapped as can material, reducing the contact area, and due to the side seam, the overlapping ends of the welding electrodes come into close contact with each other, resulting in poor contact. decreases, leading to an increase in contact resistance and locally causing poor contact.

Moreover, how can we avoid such welding defects? 11-4
It is necessary to increase the welding pressure, but when doing this, it is easy to over-weld, causing spatter and voids to occur at the weld joint, and the appearance of the joint becomes poor. Correcting the coverage of the area becomes difficult.

Therefore, in industrial manufacturing, it is difficult to set appropriate can-making conditions for continuously and stably manufacturing good welded cans, resulting in the production of welded cans of poor quality.

The inventors of the present invention have carried out studies to solve the above-mentioned problems that occur when using a tin-plated steel sheet with a small amount of tin as a can member of a welded can. In order to obtain a welded can body using a tinned steel plate with a tin content of 0.5 to 1.7 g/-, the tin colored layer of the tinned steel plate to be used is prepared in advance. By appropriately setting the composition of the paint applied to the structure and inside of the can, the tin-plated steel plate of the can body after the welded can body is formed has a tin content of at least 0.55 to 1 on the base steel plate. The structure has two layers in this order: a tin-iron alloy layer with .609β and a tin layer with a tin content of 0.10 to 1.5 sp7, and the resin on the inner surface of the can body.
It is recommended that the welded can be provided with a protective coating layer, at least the innermost layer in contact with the tinned steel plate, consisting of a thermosetting epoxy resin paint.Can body welding I1110
0 There are no welding defects, and even when filled with various contents and stored, there is no corrosion or blistering of the can material, and there is no quality deterioration such as discoloration or deterioration of flavor of the filled contents, such as food cans, beverage cans, etc. The present invention was completed after discovering that a welded can with excellent can quality could be obtained as a can body.

Next, to explain the present invention in more detail, firstly, in the present invention, the amount of tin plating is 0. B~1.79/II tin steel plate is used as the can stock, but the ζ0 can stock is enriched with the below-mentioned protective coating and is not subject to the necessary coating, heat treatment, etc. when applying printing. After undergoing heat treatment in the normal can manufacturing process, the tin layer on the surface of the final can body has a tin content of 0.10 to 1.
The thickness of one layer is less than 559 mm thick (the thickness of one layer is expressed as the tin content per unit area m), and the tin-iron alloy layer below it has a thickness of 0.55 to 1.1597 mm in terms of tin content. Thickness: The thickness of the tin-iron alloy layer is expressed in terms of tin content per unit area.

) It is necessary to use a tin-plated steel plate in advance.

Generally, welded cans are made by applying the desired coating and printing to the inner and outer surfaces of tin-plated steel plates with multiple can bodies, except for the parts to be welded, and then cutting the can bodies into tin-sized pieces, which are then rolled and rolled using a known method. A can body is formed by welding the side surfaces of the can body together using a welding machine, and after coating and correcting the exposed iron surface of the joint and its vicinity, a 7-turn process is applied to the end of the can body.
This can be obtained by seaming the can and, if desired, applying correction coating or the like to the inner surface of the can body. For this reason, the tin-plated steel sheets used for can manufacturing are painted and printed over a period of time to protect or decorate the can material, and are heated at temperatures ranging from 160°C to 200°C. During heat treatment under temperature conditions exceeding ℃, alloying of tin and iron progresses in the intermediate layer between the tin layer and the base steel sheet, forming a tin-iron alloy layer that is generally 1 e 8 n@. increases,
The tin layer decreases.

This tendency varies depending on the composition of the tin plating layer of the tin-plated steel sheet, which is the unpainted original sheet, especially the thickness of the alloy layer, the thickness of the tin layer, and the manufacturing conditions of the tin-plated steel sheet, but it depends on the can manufacturing process. In the original plate before being subjected to various heat treatments, sometimes in the painting and printing process, the tinned layer is coated with a fine 9! The tin-iron alloy layer is relatively thick (for example, o, i, 1 or more).
If the tin-iron alloy layer is formed, the increase in the tin-iron alloy layer due to the heat treatment part of the painting and printing process will be as small as 0.2 to 0.39/d, but if the tin-iron alloy layer is hardly formed, for example, the tin-iron alloy layer In the case of a tin steel sheet having 0.1 gβ or less, the heat treatment causes the tin-iron alloy layer to form as much as 0.4 to 0.69/d, and the tin layer is greatly reduced.

Moreover, the configuration of the tin layer and the tin-iron alloy layer of the tin metal layer is closely related to the weldability of the can material and the quality of the can after melting. In other words, it is necessary to have an appropriate tin-iron alloy layer and a somewhat thick tin layer to avoid WJW defects and to improve the corrosion resistance and content resistance of the can body. If the structure of the tin layer and the tin-iron alloy layer is inappropriate, various problems arise in terms of can manufacturing and can quality.

In particular, in the case of the tin-plated steel sheet used in the present invention, which originally has a small amount of tin plating, the growth of the tin-iron alloy layer due to heat treatment such as the painting printing process leads to a relatively significant reduction in the tin layer. In the case of , or -b can stock, the effect of the tin layer as described above is hardly expected.

In the present invention, tin plating 0.5 to 1.79/lrl
A tin-plated steel plate is used, but when the can body is finally formed through a heat treatment process such as a painting and printing process, the tin plating layer on the can body has a tin layer of 0.10 to 1.3! 19/m", it is necessary that the tin-iron alloy layer is formed with a thickness of 0.s5 to 1.601 in terms of tin content. In the following, the original effect of tin plating is not expected at all, and if it is 1.7 g/11 m' or more, it is sufficient to treat it in the same way as a so-called conventional tin-plated steel sheet, which is outside the scope of the present invention. .

In the present invention, when the tin layer is 0.5 to 1.79β, the structure of the tin layer and the tin-iron alloy layer as described above is desirable, and when the tin layer is 0.12 to less than 0.5, welding Not only will the properties deteriorate, but also the corrosion resistance and content resistance will decrease. In addition, as in the present invention, the tin stoichiometric amount is 0.5 to 1.7 Mm' (in the D tin steel sheet, the tin iron alloy layer is 0.1 g β at the stage of the original plate).
Even if it is below, a tin-iron alloy layer grows during heat treatment such as a painting printing process in a normal can manufacturing process, and usually Q becomes 55 gβ or more, and the tin layer does not become 1.55 gβ or more.

However, the presence of an appropriate tin-iron alloy layer is expected to improve the adhesion of the tin plating layer to the base steel plate and provide corrosion protection for the base steel plate. A tin-iron alloy layer of i5 to 1.69 mm, preferably 0.40 mm, op.

To obtain a can body with a tin-iron layer having the above structure, even if the tin-iron alloy layer grows in the heat treatment step of the can-making process, the tin layer and the tin-iron alloy layer do not remain as the tin layer with the above-mentioned structure. It is necessary to use a tin steel sheet as the base plate, which is designed to fall within the range of the carbon layer.
Preferably, at the stage of the original plate before painting and printing, the tin plating amount of the tin plating layer is 0.5 to 1.7 g, and the tin layer is 0.
．． A tin steel sheet having a structure of 5 to 1.49/m' and a tin-iron alloy layer of 0 to 1.22 is suitable.

Generally, the tin-iron alloy layer that constitutes the plating layer of a tin-plated steel sheet is not evenly covered with the outer tin layer, and the tin-iron alloy layer and the base steel sheet may be exposed locally. The extent of this varies depending on the manufacturing method, etc. even with the same tin-iron alloy layer and tin layer thickness, so-called no-rif 0-type tin steel sheets tend to have less exposed alloy layers than reflow type ones. In the present invention, a no-rif 0-type tin-plated steel sheet in which the tin-iron alloy layer is less exposed is preferred. Furthermore, in the case of ordinary tinned steel sheets, an extremely thin chromate layer is provided on the surface, but the chromate layer is extremely thin compared to the tin plating layer, and the thin plating layer of the present invention In the present invention, there is no problem even if a conventional chromate layer is provided since it does not particularly affect the effect.

The tin-plated steel sheet of the present invention has a lower amount of tin electrolyte than the tin steel sheet used for conventional solder cans, welding cans, etc.
This decreases the protective effect of the base steel plate and the effect of preventing iron elution into the contents, so A
In the third step, at least the surface of the tin-plated steel plate corresponding to the inner surface of one can is protected from the contents to be filled into the can,
In addition, it is extremely important to provide an appropriate resin protective coating layer for the purpose of preventing the contents from discoloring and reducing the 7-lever value due to elution of the can material.

As such a resin protective coating layer, a single coating layer or a protective coating layer consisting of a plurality of coating layers using the same or different types of paints is used. As such, it is necessary to use a thermosetting epoxy resin paint, and a thermosetting epoxy phenol resin paint is particularly suitable, especially one containing approximately 6s weight or more of resol IjIl phenol resin carved from bisphenol A. A phenol resin and a bisphenol distilled epoxy resin having a number average molecular weight of 1,400 to 7,000 were mixed in a s o/s
o~5/95 weight ratio, preferably 50/70~1
A thermosetting coating material containing it in a weight ratio of 0/90 is suitable.

If a paint other than a thermosetting epoxy resin paint is used as the paint constituting the protective coating layer, the adhesion to the tin base layer with a small amount of tin, corrosion resistance, discoloration of the contents, etc.
It is inappropriate to use it without expecting a preventive effect. Among the thermosetting epoxy resin paints, which are difficult paint systems, the above-mentioned thermosetting epoxy phenol resin paints are particularly suitable, but if the molecular weight of the epoxy resin used is too low or the phenol resin If the resol formed from bisphenol A in the coating film has a phenolic resin content of less than 65% by weight, and the ratio of phenolic resin to epoxy resin falls outside the range of 50150 to 5/9S weight ratio, the paint film will deteriorate. It is not preferable because the hardenability, monolayer property, workability, etc. of the material are deteriorated, and in practical terms, the corrosion resistance and the effect of preventing iron elution into the contents are reduced.

Such thermosetting epoxy resin paints are usually used as solvent-based paints in which the resin component is dissolved in a solvent, but if necessary, a solvent-soluble or insoluble resin component may be added as a modifying component.
A curing agent, a curing catalyst, or an inorganic component can be used.

In the case of thermosetting epoxyphenol paints, which are suitable paints for the present invention, phenoxy resins may be used in combination, aminoplus resins such as urea resins may be used as curing agents, and solvent-insoluble thermosetting resins or thermosetting resins may be used in combination. can be used in combination with dispersion of cured resin powder. The amount of such modifying component is preferably 50 or less based on the amount of resin in the paint.

As a method for forming a protective coating layer on the tin layer on the inner surface of a can using the thermosetting epoxy resin paint of the present invention, use the paint of the present invention and apply appropriate coating using a roll coater or the like. By placing the can body in multiple pieces, the inner surface of the can and the 1kh side of the tin steel plate were coated with paint, except for the weld joints, and after baking, the can body was made into a planter, and the welded can body was welded using a welding machine. Alternatively, after producing a can body using a tinless steel sheet as a can body blank, and then spraying the paint on the inner surface of the can body before or after attaching At to one end of the can body. Although methods such as coating and baking may be mentioned, the former method is preferable in terms of actual workability.

Here, the protective coating layer can be used as a multilayer by further applying the same or different type of paint on the coating film already formed before or after forming the can body and baking and drying. . The suitable coating thickness for such a protective coating layer is 2 to 1011 mm.For multi-layer protective coating layers such as coating or multiple coatings, the thickness of the protective coating layer is from thermosetting epoxy resin paint. A suitable thickness is 2 to 7 seconds. If the thickness of the protective coating layer is less than 2 μm, the effectiveness of the can material cannot be expected, and if it is more than 10 parts, the workability of the coating will be poor, and it will be difficult to tighten the can material when attaching the contents by II spring tightening after filling. If processing defects occur in the processed portion and the contents are filled and stored, that portion will corrode, which is undesirable. In particular, when the thermosetting epoxy phenol resin paint is used as the paint for forming the protective coating layer of the present invention, a similar or different type of paint may be applied over the pre-formed paint film. Even if you do not take any measures to improve the quality by creating a multi-layer coating by overcoating R-Le Coat or Spray Coat IIIfi, you can apply it with just one coat! It is possible to sufficiently cover and protect the can material with a relatively thin film of ~7μ, especially 5~77m, which is particularly suitable.

In addition, in the present invention, the outside distance of the can stock is 11K.

Except for the welded joints, wear m-wear for protection or decoration as appropriate.
Printing is slowed down.

The can bodies of the present invention thus obtained have excellent can quality and are suitable as cans for canning various contents, especially foods and beverages. Hereinafter, the description will be given with reference to Examples, but the parts by weight will be explained. Also, the amount of tin plating on the tin steel sheet in the Examples, the amount of tin in the surface tin layer,
Measuring the tin content in the tin-iron alloy layer is carried out by J-K8 G3301.
(Electrolytic foil koji method).

Comparative Example-1 For a picture with a plate thickness of 0.22mm and a tinned steel plate CIt14 on both sides having the structure shown in Table 1, 75 parts of y-cresol was added as a paint. Alcohol-based, ketone-based,
Obtained by dissolving in a mixed solvent consisting of Nissil and aromatic organic solvents
℃) 40 seconds using a phenol-sum based paint (paint), excluding the weld seam, margin painting with a roll coater, baking for 205"C x 10 minutes, film thickness 5. A cured coating film with a thickness of 2μ was formed.Next, anti-static acrylic resin white paint was applied to the weld seam on the outer surface of the can body, and baked at 190°C for XIO minutes to form a white coating film. Print on top 160
Baking was carried out at 175°C for 10 minutes, and a finishing varnish was applied thereon and baking was carried out at 175°C for 10 minutes to obtain a coated plate in which both sides of the tin-plated steel plate were painted and printed. This coated steel sheet is cut into can body blanks for 250 g beverage cans, and is welded using a known welding machine that performs pressurized seam welding with an electrode p-ler through a copper electrode wire at a can making speed of s50 cans per minute. The side parts of the can body were welded together in an active gas atmosphere to form a can body. Next, we coated and corrected the weld seam on the inner side of the can body and its vicinity using correction paint, applied 7-lunge processing to both ends of the can body, and attached an internally painted aluminum lid to one end! The attached 2509 can body was obtained by heavy seaming, and the results of various evaluations performed using the obtained painted plate, can body, and can body are shown in the attached table.

From this result, in this comparative example, there were localized welding defects in the welded joints of the can body, and the electrical conductivity was poor.

In addition, in actual can storage tests, corrosion was observed on the inner surface of the can body, and the iron content in the contents increased.

Comparative Example-2 The configuration of the tin-metallic layer of the tin-metallic steel plate before painting and printing (total amount of tin-metal, tin layer, tin-iron alloy layer) is except for using a fine-gained steel plate with the configuration shown in the table. A painted steel plate, a can body, and a can body were prepared in the same manner as Comparison M-1, and various evaluations were performed.

As a result, as shown in the attached table, the tin layer in the tin layer in the can body after can body formation is reduced compared to the original sheet before painting and printing, as shown in the attached table. The number of tin-iron alloy 5 layers has been increased 9, and like the can body of Comparison No. 1, the WI adhesion is poor, and even in the actual storage test, slight corrosion was observed on the inner surface 11 of the can body, and the iron in the contents was The content also increased slightly.

Example 1 A painted copper plate was prepared in the same manner as in Comparative Example 1, except that a tin steel plate having the structure shown in the table below was used. , can bodies and can bodies were constructed and various evaluations were conducted.

As shown in the attached table, the welded seam of the can body of this example formed a good welded seam even under the same conditions as those in Comparative Example-1 where welding defects locally occurred. In the actual storage test, only slight corrosion was observed, and the amount of iron leached into the contents was smaller than that of Comparative Example-1.

Implementation f1-2 Using a tin-plated steel plate with the structure of the anchor layer on the tin-plated steel plate as shown in the table before painting and printing, bisphenol was applied as a paint to the inner surface of the can body of the steel plate. Obtained by dissolving 20 parts of a resol type phenol resin obtained by reacting A with formaldehyde in the presence of an ammonia catalyst and BO part of a bisphenol type epoxy resin with a number average molecular weight of 10 in a mixed solvent. %, viscosity (P
Painted steel sheets, can bodies, and can bodies were prepared in the same manner as Comparative Example-1, except that 40110 thermosetting type xyphenol paint (0 paint) was used, and various evaluations were performed. .

As a result, as shown in the attached table, the welded joint of the can 11iWh of this embodiment was in good condition with no defective sand batter leaking, and it was possible to cover it with the correction paint with good results. In addition, no corrosion was observed on the inner surface of the can body in actual storage tests.
There was no I#1IIIB inside, which was good.

Example-S~6 Using tin-plated steel plates with different tin-plated color layer compositions before painting and printing, the paint used in Example-2 was used as the paint to be applied to the inner surface of the can body. A coated steel plate, a can body, and a can body were prepared in the same manner as in Comparative Example 1, and various evaluations were performed. As shown in the attached table, the results are as follows.
The can body and can body using the tin-plated steel plate and paint of this example had good weldability, and good results were obtained in the actual storage test after filling the contents.

261 (Qin 1) The composition of the tin plating layer (inner surface side of the can) of the original plate before painting and printing was measured using the above-described method.

(*2) Cut a test piece from the M section of an empty can and measure the structure of the tin plating layer using the above-described method.

(Qin i) Judging the joint state of the weld joint of the can body by visual observation (SL microscopic observation) K (inner coating correction carried out).

◎Extremely good, ○Good, ∆There is no bonding defect, but the appearance is poor and it is difficult to correct the coating. ×If the welding conditions are changed due to poor bonding, spatter occurs frequently, and the appearance is poor (*4) Filling an empty can with milk coffee, The container was sealed using painted tin, sterilized in a retort at 135°C for 50 minutes, and stored at 50°C for 2 months. Measure the amount of iron eluted and make a 7-lever judgment.

◎ indicates no abnormality.

Claims (1)

[Scope of Claims] L A welded can body in which the can body is formed by overlapping and welding both side edges of tin steel plates, and a resin protective coating layer is provided on at least the inner surface of the can body, wherein the welding The tin steel plate that forms the can body has a tin content of 0. S ~ 1.79A', on the base steel plate - at least o, is ~ in terms of tin content
1.6Q9βO tin iron alloy layer and tin amount 0.10 to 1.315
g/@' and a tin layer in this order, and the resin protective coating layer is a protective coating in which at least the innermost layer in contact with the tinned steel plate of the can body is made of a thermosetting epoxy resin paint. A welded can body using a tinned steel plate characterized by a layered structure.
・2 The thermosetting epoxy resin paint contains 65% of the Resor A/W1 phenolic resin formed by bisphenol A.
The paint contains a phenolic resin having a weight ratio of 50/sO to 5/9s, and a bisphenol A type epoxy resin having a number average molecular weight of 1,400 to 1,400 to 5/9s, and the resin protective coating layer formed by the paint. Claim 1, characterized in that the film thickness is 2 to 1 aμ.
A welded can body using the tinned steel plate described in 1.