JPS5938140B2 - Can with covered seams - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a seam-coated can and a method for manufacturing the same.
More specifically, the present invention relates to a can in which a resin coating is formed that completely covers the side seam of the can body and has excellent workability and corrosion resistance, and a method for manufacturing the same.

Conventionally, the manufacturing method for can bodies is to cut a metal material for a can into a cylindrical shape, overlap the two ends of the material, and join these parts using means such as welding, adhesive, or solder. The most widely used method is to form a seam using The cut edge of the material, that is, the cut edge, is always exposed on the inner side of the side seam can formed by this method.Coating the cut edge of this material prevents corrosion of the material and protects the contents. This is extremely important in suppressing metal elution into materials.

Various proposals have been made to cover and protect this seam, particularly the cut edge of the material.

Among these proposals, a fairly effective method is the force method in which the cut edges of the material are covered and protected in advance with an adhesive tape such as polyamide, but this method is not suitable for manufacturing adhesive-seamed cans. Even if it can be applied, it cannot be applied in cases where the seam is exposed to extremely high temperatures, such as in welded seam cans. As a method of coating and protecting the seams in welded seam cans, it is known to apply a solution or powder paint to the inner surface of the seam of the molded case. However, it lacks a combination of properties such as barrier properties against corrosive components and workability such as double seaming, and is still unsatisfactory for the purpose of completely covering cut edges with stepped seams.

For example, although a coating material made of thermoplastic resin has excellent processability, thermoplastic resin lacks adhesion to seams and also has poor barrier properties as described above, so seams coated with thermoplastic resin Depending on the contents, etc., it can easily cause defects such as corrosion and blackening due to sulfurization.On the other hand, paints made of thermosetting resins have excellent adhesion to seams and barrier properties against corrosive components. On the other hand, the disadvantage is that it lacks workability, and in cases where the joints are covered with thermosetting resin, metal elution frequently occurs from the double-sealed parts. When using these paints, these paints flow in a solution or molten state to fill the level difference in the seam, so the paint film may be cut at the corner of the cut edge, or even if it is not, the paint film may be significantly damaged. It is nearly impossible to form a complete coating on the cut edges of the material, as the coating becomes thin and air bubbles are likely to form in the coating on the stepped portions.

Depending on the type of contents, if there are exposed metal parts, the can may be perforated.
This will not only cause serious defects in the hydrogen-expanded canister, but also significantly impair the flavor of the contents.

The present inventors have discovered that when applying a paint of a specific composition containing a thermosetting resin solution as a dispersion medium and specific thermoplastic resin particles as a dispersoid to the joint of a can, the corners of the cut edges present at the joint are It is possible to perform painting and baking to completely cover the cut edges, and the coating film thus formed has excellent processability such as complete coverage of cut edges, corrosion resistance, and double seaming. I found out that there is.

That is, an object of the present invention is to provide a seam-coated can that has an excellent combination of complete coverage of the cut edges of the seam, workability, and corrosion resistance, and a method for manufacturing the same.

Another object of the present invention is that when powder coatings or films are used, conventional solution-type coating equipment cannot be used and new equipment is required. The coating equipment can be used as is without any special changes. According to the present invention, the can body includes a can body having a seam on the side surface, and a resin coating layer that covers at least the inner surface side of the seam, and the resin coating layer includes a continuous phase made of a thermosetting resin and thermoplastic resin particles. The thermoplastic resin particles have a number average particle size of 0.1 to 80 microns and a dispersed phase consisting of
The seam-covered can has a ring and ball softening point of 0 to 800°C, and the thermosetting resin and the thermoplastic resin are present in a volume ratio of 95:5 to 25:75. provided.

According to the present invention, the seam is further provided by applying a resin paint to or near the inner seam of a can body having a seam on the side surface, and then baking this paint to form a coating film covering the seam. In the method for producing a coated can, the resin coating includes a dispersion medium consisting of a solution of a thermosetting resin that is to become a continuous phase in a film-formed state, and a 0.00% 0.000000.
It is a paint consisting of a dispersoid of thermoplastic resin particles having a number average particle size of 1 to 80 microns and a ring and ball softening point of 50 to 300°C, and which is to become a dispersed phase in the film-formed state, and It is assumed that the thermosetting resin and the thermoplastic resin are present in a volume ratio of 95:5 to 25:75, and the paint is dropped onto a glass plate in a sample volume of 0.2 m71 at 25°C.
A seam-coated can having a contact angle of 18.5 to 45 degrees when measured after 10 minutes, and the formed coating film is baked under conditions in which the thermoplastic resin softens or melts. The present invention can be particularly advantageously applied to cans, particularly welded joints, in which the seam cut edges must be coated after the seam is formed.

Therefore, the present invention will be explained below using the example of a welded can. It should be understood that the same effect can be achieved with other jointed cans, such as welded cans and soldered cans. In FIG. 1 showing the main parts of the seam-covered can of the present invention, a metal material 1 for a can cut to a predetermined size is formed into a cylindrical shape, the end edges of which are overlapped, and this overlapping part is welded. A seam 2 is formed.

The inner surface of the can body may be coated with a resin protective coating 10 except for the above-mentioned seam 2 or the vicinity thereof.
At the joint 2 located on the inner side of the can body, there is a cut edge 3 of the material or a melted protrusion portion 4 of the metal material during welding.

This seam 2 is provided with a resin layer 5 that covers this portion. An important feature of the present invention is that the coating resin layer 5 is formed from a continuous phase 6 made of a thermosetting resin and a dispersed phase 7 made of thermoplastic resin particles. Although thermosetting resins have excellent adhesion to seams and barrier properties against corrosive components, they lack processability, while thermoplastic resins have excellent processability but have poor adhesion and barrier properties. As mentioned above, the lack of According to the present invention, adhesion to seams and barrier properties against corrosive components (e.g., water, acids, oxygen, hydrogen sulfide, etc.) are improved by containing thermosetting resin in the form of a continuous phase in the coating film. Furthermore, by incorporating thermoplastic resin particles in the form of a dispersed phase into the coating film, it has been able to provide processability that can withstand double seaming processing, bead processing, etc. .

In this case, it is also extremely important that the thermosetting resin exists as a continuous phase and the thermoplastic resin particles as a dispersed phase, and if both exist in a homogeneous dispersion form or the opposite dispersion form, the seam In particular, the adhesion to the cut edges decreases,
Furthermore, the barrier properties are also deteriorated, and metal corrosion such as sulfide blackening easily occurs.

Moreover, when using a paint containing a thermoplastic resin as a continuous phase (dispersion medium) and a thermoplastic resin as a dispersed phase (dispersoid), a coating film that completely covers the cut edges 3 of the seam, especially the corners 8 of the cut edges, can be created. It has now been found that an unexpected effect can be achieved.

That is, when the thermosetting resin solution alone is applied to the seam, this solution flows out onto the stepped portion of the cut edge 3 or the protruding portion 4, thereby causing the coating film to form at the corner portion 8 of the cut edge. However, when the thermosetting resin solution contains thermoplastic resin particles at a fixed ratio and is applied to the seam 2, the The thermoplastic resin particles 7 retain the thermosetting resin solution on their surfaces, suppressing the tendency of the surrounding thermosetting resin solution to flow into the gaps between the steps and smoothing out the coating film. Thus, when the paint of the present invention is used, it is possible to maintain a coating film of approximately the same thickness as when it was applied, even on the corner portions 8 of the cut edge, and it is possible to completely cover the entire cut edge 8. Moreover, this state is maintained even when the coating film is baked, and the thermoplastic resin as the dispersed particles softens or melts under baking conditions, forming a thermosetting resin phase and a thermoplastic resin phase. The mutual adhesion between the two becomes perfect, resulting in even better mechanical strength, impact resistance, workability, etc. Also, by perfecting the mutual adhesion between the two, the corrosive components mentioned above, etc. The thermoplastic resin particles used in the present invention have a particle size of 0.1 to 80 microns, particularly 0.1 to 80 microns.
Number average particle size of 5 to 50 microns and temperature of 50 to 300℃
It is also extremely important for the above-mentioned purpose of the present invention that it has a ring and ball softening point, especially from 90 to 270°C.

That is, if the particle size of the dispersed particles is smaller than the above range, the grain boundary area per unit volume of a coating film becomes too large, resulting in a decrease in the barrier properties of the coating film and sulfidation caused by the contents. Corrosion such as blackening easily progresses, and the workability of the cured coating film also deteriorates. Furthermore, if the particle size exceeds the above range, it will be difficult to form a uniform structure consisting of a continuous phase of thermosetting resin and a dispersed phase of thermoplastic resin in the direction of the coating film. There is a tendency for the complete coverage of the cut edges, workability and corrosion resistance to be significantly reduced. Furthermore, if the softening point of the thermoplastic resin is lower than the above range, both resins will become a homogeneous mixture, making it difficult to obtain the dispersion form of the present invention, and the coating ability of the cut edge will be affected, as well as workability and durability. Corrosivity is also reduced.

On the other hand, if this softening point is higher than the above range, the processability will be inferior to that within the range of the present invention, and mutual adhesion at grain boundaries will become difficult, resulting in a decrease in barrier properties. I come to do it. In the present invention, the thermosetting resin and the thermoplastic resin are further provided in a volume ratio of 95:5 to 25:75,
It is also extremely important to use them in combination, particularly preferably at a volume ratio of 90:10 to 30:70, in order to achieve the above-mentioned objective. In other words, if the blending ratio of the thermoplastic resin is lower than the above range, it becomes difficult to completely cover the cut edge.
It becomes difficult to avoid corrosion in this part. Furthermore, the processability of the formed coating film is also reduced. On the other hand, if the blending ratio of the thermosetting resin is lower than the above range, it will be difficult to make the thermosetting resin exist in the form of a continuous phase in the coating film, and it will also be difficult to completely cover the η edge portion. The corrosion resistance of the coating film itself also comes to be significantly reduced. In the present invention, the thermosetting resin and the thermoplastic resin particles are desirably selected so as to form as strong an adhesive surface as possible at the grain boundaries in the paint. From this point of view, in the present invention, , carboxylic acids, carboxylates as thermoplastic resins,
Thermoplastic polymers containing a carbonyl group (-C-) in the main chain or side chain based on carboxylic acid anhydride, carboxylic acid ester, carboxylic acid amide, ketone, carbonate ester, area, urethane, etc. can be used. desirable.

Carbonyl groups at a concentration of 12 to 1400 meq/1009 polymer, especially 50 to 120
The best results in terms of processability and corrosion resistance are obtained when thermoplastic polymers containing a concentration of 0 meq/1009 polymer are used.
A monomer having the above-mentioned functional group is incorporated into the main chain of the polymer by a method such as polymerization or copolymerization, or is bonded to a thermoplastic polymer by a method such as graft polymerization or terminal treatment. It can be obtained by

Further, in the case of a hydrocarbon polymer such as an olefin resin, by oxidizing this polymer, it can be made into a thermoplastic resin containing carbonyl groups in the above-mentioned range. Suitable examples of such thermoplastic polymers include, but are not limited to:

(a) In the general formula or formula, R1 is an alkylene group having 2 to 6 carbon atoms, and R2 is an alkylene group or arylene group having 2 to 24 carbon atoms.
polyester consisting of repeating units coated with

For example, polyethylene adipate, polyethylene separate, polyethylene terephthalate, polytetramethylene isophthalate, polyethylene terephthalate/isophthalate, polytetramethylene terephthalate, polyethylene/tetramethylene terephthalate, polyethylene/oxybenzoate. (b) General Formula In the formula, R3 is a hydrogen atom or a lower alkyl group, and R4 is a hydrogen atom or an alkyl group having 1 to 12 carbon atoms.

A homopolymer or copolymer of the monomer of (2), or the above (2)
) and olefins or copolymers with other vinyl monomers or acrylic-modified polyolefins.

For example, polyacrylic ester, polymethacrylic ester, ethylene/acrylic ester copolymer, acrylic ester/acrylic acid copolymer, ethylene/acrylic ester/acrylic acid copolymer, ethylene/acrylic acid copolymer , styrene/methacrylate ester/acrylic acid copolymer, acrylate ester/vinyl chloride copolymer, acrylate ester grafted polyethylene, methacrylate ester/vinyl chloride copolymer, styrene/
Methacrylic acid ester/butadiene copolymer, methacrylic acid ester/acrylonitrile copolymer.

(c) A copolymer of a vinyl ester of the general formula in which R5 is a hydrogen atom, an alkyl group, or a phenyl group and an olefin or other vinyl monomer, or a partially saponified product thereof.

For example, partially saponified ethylene monovinyl acetate copolymer,
Ethylene-vinyl propionate copolymer, ethylene/vinyl acetate copolymer, acrylic ester/vinyl acetate copolymer, vinyl chloride/vinyl acetate copolymer.

(d) A resin obtained by neutralizing an unsaturated carboxylic acid such as an ionomer olefin, or a copolymer with another vinyl monomer, with an alkali metal, an alkaline earth metal, or an organic base.

For example, Surlyn products are commercially available from Deh Hong Co., Ltd. in the United States.

(e) Copolymer of maleic anhydride and other vinyl monomer or maleic anhydride-modified polyolefin 0 For example,
Maleic anhydride/styrene copolymer, maleic anhydride-modified polypropylene, maleic anhydride-modified polyethylene.

(f) A polycarbonate represented by the general formula in which R6 is a hydrocarbon group having 8 to 15 carbon atoms.

For example, poly-p-xylene glycol biscarbonate, polydiokidiphenyl-methane carbonate,
Polydioxydiphenyl ethane carbonate, polydioxydiphenyl 2,2-propane carbonate, polydioxydiphenyl 1,1-ethane carbonate.

Polyamides consisting of repeating monomers represented by the general formula or formula in which n is a number from 3 to 13 and m is a number from 4 to 11.

For example, poly-ω-aminocaproic acid, poly-ω-aminoheptanoic acid, poly-ω-aminocaprylic acid, poly-ω-aminocaprylic acid,
- aminopelagoic acid, poly-ω-aminodecanoic acid, poly-ω-aminoundecanoic acid, poly-ω-aminododecanoic acid, poly-ω-aminotridecanoic acid, polyhexamethylene adipamide, polyhexamethylene sebacamide, Polyhexamethylene dodecamide, polyhexamethylene tridecamide, polydecamethylene adipamide, polydecamethylene sebamide, polydecamethylene dodecamide, polydecamethylene tridecamide, polydodecamethylene adipamide, polydodecamethylene Cebamide, polydodecamethylene dodecamide, polydodecamethylene tridecamide, polytridecamethylene adipamide, polytridecamethylene sebacamide, polytridecamethylene dodecamide, polytridecamethylene tridecamide, polyhexa Methylene azeramide, polydecamethylene azeramide, polydodecamethylene azeramide, polytridecamethylene azeramide. 1
) A polyurea in which R7 and R8 each consist of a repeating unit having 1 to 13 carbon atoms.

For example, polyhexamethylene urea, poly\putamethylene urea, polyundecamethylene urea, polymethylene urea.

(1) In the general formula or formula, R9 is an alkylene group having 3 to 24 carbon atoms, a polyether residue, or a polyester residue; RlO is an alkylene group or arylene group having 3 to 24 carbon atoms; Rll is an alkylene group having 3 to 24 carbon atoms; Rll is an alkylene group having 3 to 24 carbon atoms; alkylene group or arylene group, k is O
or a number of 1. For example, polytetramethylenetetramethyleneurethane, polyhexamethylenehexamethyleneurethane, polyureaurethane obtained by chain-extending isocyanate-terminated polyester or polyether with diamine or water.

(J) Resin particles obtained by oxidizing particles of polyethylene, polypropylene, or crystalline ethylene propylene copolymer with oxygen oxidation, ozone oxidation, or other oxidizing agents.

Particularly desirable resins for the purposes of this invention are, in order of importance, polyesters, polycarbonates, polyamides, atomizers, and acid-modified polyolefins.

These resins have at least a molecular weight sufficient to form a film, and if desired, these resin particles may contain compounding agents known per se, such as ultraviolet absorbing agents, stabilizers, Lubricants, antioxidants, pigments, dyes, antistatic agents, and the like can be blended according to known formulations. Any means known per se can be used to form the thermoplastic resin into a powder having the above-mentioned particle size.

For example, in the case of an addition polymer, resin particles of a predetermined particle size can be obtained by emulsion polymerization or suspension polymerization of the constituent monomers. Alternatively, there are methods in which the resin is pulverized under cooling, a method in which a solution in which the resin is dissolved at a high temperature is cooled to precipitate the resin in the form of particles, or a method in which the resin solution is brought into contact with a non-solvent to coagulate and precipitate in the form of particles. Alternatively, a method in which a resin solution is sprayed into an air stream and deposited in the form of particles can be adopted. The obtained resin powder is sieved if necessary to obtain resin particles of a predetermined particle size. As the thermosetting resin, all thermosetting resins conventionally used for paint applications can be used.

Suitable examples are phenol formaldehyde resins,
Furan-formaldehyde resin, xylene-formaldehyde resin, ketone-formaldehyde resin, urea-formaldehyde resin, melamine-formaldehyde resin,
Alkyd resin, unsaturated polyester resin, epoxy resin, hismaleimide resin, triallyl cyanurate resin,
These include thermosetting acrylic resins, silicone resins, oil-based resins, etc., and these can be used alone or in combination of two or more. Thermosetting resins suitable for adhesion to seams and corrosion resistance include an epoxy resin component and at least one thermosetting resin selected from the group consisting of phenolic resins, urea resins, melamine resins, and thermosetting acrylic resins. These coating film-forming resins are
It is used in paints in the form of a mixture or as a precondensate.
The paint used in the present invention can be easily obtained by dissolving the above-mentioned thermosetting resin in a suitable organic solvent and dispersing thermoplastic resin particles in this solution.

At this time, a solvent is selected that dissolves the thermosetting resin but does not dissolve the thermoplastic resin. In general,
Aromatic solvents such as xylene and toluene; Ketone solvents such as acetone, methyl ethyl ketone, and cyclohexanone; Alcohol solvents such as ethanol and butanol; cyclic or linear ethers such as tetrahydrofuran, dioxane, and various cetanol; ethyl acetate, butyl acetate These esters can be used alone or in combination of two or more. The thermoplastic resin particles may be added to the thermosetting resin solution in the form of a dispersion. The paint used in the present invention is heated at a temperature of 25°C.
A contact angle of 18.5 to 45 degrees, especially 19.0 to 4 when measured 1 minute after dropping a sample of 0.2 m 7 d on a glass plate.
A contact angle of 3 degrees is particularly desirable in order to enable a thick coating that completely covers the cut edges.

The solid content concentration in the paint may be selected from a range of generally 5 to 50%, depending on the combination of resins, so as to provide suitable workability and thick coating properties. In addition to untreated steel plates (black plates), the metal materials that make up the housing include electroplated or hot-dip plated steel plates such as tinplate, galvanized plates, and chrome plated plates, or chemically treated steel plates with chromic acid, phosphoric acid, etc. For example, a chemical conversion treated steel plate such as a steel plate or an electrolytic chromic acid treated steel plate can be used, and a light metal plate such as an aluminum plate can also be used.

The side seam is suitably formed by electric resistance welding. In the commercial resistance welding of the side seam, the can material is formed into a cylindrical shape, and the overlapped portion is placed between a pair of electrode rollers. or pass the electrode wire through the upper and lower 1
This is done by passing it between a pair of electrode rollers. At this time, performing the welding operation in an inert atmosphere and keeping the atmosphere inert until the surface temperature of the welded part drops to 550°C will allow a porous metal oxide layer to form on the outer surface of the joint. desirable to prevent this and improve the adhesion of protective paints. As the inert atmosphere, nitrogen, argon, neon, hydrogen, carbon dioxide, etc. can be used. Although it is preferable to carry out the work while holding the welded joint in the above-mentioned inert gas flow, the work may also be carried out in a closed container filled with the above-mentioned gas. If a non-conductive protective film is formed on the surface of the metal material, such as electrolytic chromic acid-treated steel sheet (tain-free steel), remove these non-conductive layers from the overlapping area prior to electrical resistance welding. Remove the sexual coating.

Although the width of the side seam of this welded can differs depending on the diameter of the can, it can be relatively small such as 0.2 to 1.2WL1L, and according to this seam formation method, the width of the side seam of the can can is One of the notable advantages is that the amount can be reduced.

Also, the thickness of the seam can vary from 2 times to 1.2 times the material thickness. In other words, by pressing the overlapping part with high pressure during welding, the thickness of the seam can be reduced, thereby making it possible to reduce the level difference between the joint part and other parts during double seaming. This is the advantage of the law. The coating can be applied to the housing joints or the vicinity thereof by means known per se, such as roller coating, spray coating, brush coating, and flow coat dip coating, or by special methods such as powder coating. It is a significant advantage of the present invention that conventional equipment can be used without any modification.

In order to completely cover the corners of the cut edges of the seam, it is desirable that the coating thickness at the corners of the cut edges after baking be in the range of 2 to 50 microns, and when using the coating specified in the present invention, Forming such a coating film is extremely easy.

According to the present invention, the coating film thus formed is heated to a temperature equal to or higher than the softening point or melting point of the thermoplastic resin to cure the coating film.

Heating methods include direct flame, hot oven, hot air oven,
Induction heating, resistance heating, infrared heating, etc. can be used. The curing conditions used are 150 to 400' so that the thermosetting resin becomes reticulated by crosslinking and sufficient adhesion occurs at the grain boundaries between the thermosetting resin and the thermoplastic resin.
Appropriate conditions are selected from the range of temperature C and 1 second to 20 minutes. From the point of view of the mechanical strength of the coating film, it is desirable that the thermoplastic resin used be crystalline; in this case,
In order to suppress the crystallization of the thermoplastic resin in the coating film, the coating film is rapidly cooled from the baking temperature to a temperature at least 10°C lower than the crystallization temperature of the resin, particularly within 10 seconds, preferably 1 second. Processability and barrier properties (
Desirable for its corrosion resistance (due to good adhesion at grain boundaries).

Such rapid cooling can be achieved by contacting the baked paint film with a cooling medium such as cooling water, nitrogen gas, or cold air, or by bringing the seam after the paint film into contact with a cooling mechanism such as a cooling roller. It can be done easily. The seam-covered can according to the present invention can be used in various fields, such as vacuum cans for retort sterilization of contents, internal pressure cans for filling carbonated drinks, etc., and aerosol cans.

The invention is illustrated by the following example.

The thermosetting resin solution used in the examples of the present invention is prepared by the method described below.

(1) Epoxy urea thread resin solution 70 parts of an epoxy resin with an average molecular weight of 2900, which is a condensation product of bisphenol A and epichlorohydrin, and 30 parts of a butyl ether urea formaldehyde resin (
1) 50 parts of dioxane, 15 parts of xylene, 15 parts of cyclohexanone, 10 parts of methyl ethyl ketone, 10 parts of toluene
(H) in a mixed solvent consisting of 50 parts of methyl ethyl ketone and 50 parts of toluene to obtain a solution with a solid content of 25%.

Solution 18 (1) is Example 1, Solution (H) is Example 1, 3
and 5 as a base paint. (2) Epoxy/phenol thread resin solution 0.5 mol of carbolic acid and 0.5 mol of p-cresol at 37%
Dissolve in 1.5 mol of formaldehyde aqueous solution, add 0.15 mol of ammonia as a catalyst, and react at 95°C for 3 hours.

The reaction product is extracted with a mixed solvent consisting of ketones, alcohols, hydrocarbons, etc., washed with water, and the aqueous layer is removed.
Furthermore, a small amount of remaining water is removed by an azeotropic method, and the mixture is cooled to obtain a 30% solution of resol type phenolic resin. 30% of an epoxy resin with an average molecular weight of 2900, which is a condensation product of bisphenol A and epichlorohyrin, obtained by dissolving the above resol type phenolic resin solution in advance in a mixed solvent consisting of ketones, esters, alcohols, hydrocarbons, etc. %
Mix with the solution. The weight ratio of phenolic resin and epoxy resin was 40:60. This mixture is precondensed under reflux for 2 hours to obtain epoxy-phenolic resin solution 1.
This solution is used as a paint in Examples 2 and 4. The method for manufacturing a welded can body is as follows.
For welded tin cans, the plate thickness (0.23m77!) and the amount of tin plating are 251b/B. After baking, apply epoxy phenol thread paint (a mixture of epoxy thread resin and phenol resin at a ratio of 1:1) to the tin plate B (tin layer thickness approximately 0.6 μm), except for the seam area of the can body. Paint the margins so that the film thickness is 5 microns on the inner surface and 3 microns on the outer surface.
Bake hardening for 10 minutes in a hot air drying oven at 200°C. Next, the painted tin plate was used as a body blank for a No. 7 can (
Blank length 206.4mm, black bite 10
This blank is cut into a cylindrical shape with the short side facing the axial direction using a roll former, and after being stacked and fixed at a welding station, the blank is cut into 2 roll electrodes via a wire electrode. A pressing force (40 kg/Md) was applied to the overlapping part of the molded bodies using a commercially available seam welding machine.
and welded the can body (211 diameter, internal volume 318.2 m, No. 17 can) at a can making speed of 30 min in a nitrogen gas stream.
get. The overlap width before welding is 0.3 mm, and the overlap width after welding is 04 dragon. On the other hand, with TFS welded cans,
After margin-coating TFS with a thickness of 0.23 mm (:l) in the same manner as the tin can, the TFS coated plate was used as a No. 7 can body blank (blank length 206).

4m7! Cut into L, black bite 104.5mm).

Next, both sides of the overlapping part near the cut edge of the general part are separated by a width of about 1 mm from the cut edge, and edge cleaning is performed using a cutting method to remove the cucum layer and chromium oxide layer on the surface. The edge-cleaned blank was formed into a cylindrical shape with the short side oriented in the axial direction using a roll former, and after being superimposed and fixed on a welding station, a commercially available blank consisting of two roll electrodes connected via a wire electrode was formed. Using a beam welder, a pressing force (45 kg/M7i) was applied to the overlapping part of the molded bodies, and a can body (No. 17 can of 211 radial volume 318.2 m) was welded at a speed of 30 m/min in a nitrogen gas flow. Obtained. The overlap width before welding was 0.3 mm, and the overlap width after welding was 0.4 mm. In the present invention, the actual can test 1 evaluation, the physical property evaluation of the paint, the structural evaluation of the paint film near the can joint, and the enclosure evaluation are performed as follows. (1) Using MicroOSlldeGlass (grade 1, thickness 0.9 to 1.2 mm) as a contact angle glass plate, soak it in chromium mixed acid for a day and night, wash it thoroughly with pure water, dry it, and then place it in a desiccator to dry it completely. Save and use.

The measurement is carried out in a constant temperature room at 25° C., and 0.2 ml of the specified paint is dropped onto a glass plate using a microsyringe in an air atmosphere, and the contact angle is directly measured using a goniometer after 1 minute has elapsed.

(2) Observation of the dispersed state. Peel off the cured coating film at the joint part of the can, and apply a 2-width strip parallel to the joint.
Cut out a test piece with a length of 15 dragons.

This Test 1 test piece is embedded and solidified in epoxy resin, and a thin piece with a thickness of about 15 μm is cut out using a stainless steel microdome so as to obtain a cross section perpendicular to the can joint. This thin piece was placed in an aqueous solution of blue dye (methyl violet) for 10 minutes at room temperature.
After being immersed for a minute to selectively dye only the thermoset coating film, it is thoroughly washed with water and its structure is observed using an optical microscope, paying particular attention to the dispersion state of the thermoplastic resin particles. At this time, the average particle size of the particles present in the field of view is also measured after taking a photograph. In the following, the number average particle size will be used as the average particle size, and in this case it will simply be referred to as the particle size or average particle size. (3) Coverage property of the joint part (a) Current value during constant voltage electrolysis The can joint part, which is baked and hardened after applying the specified paint, is 2C wide.
Cut across the TIL and cut a width of 3 in the direction perpendicular to this seam.
m77! , 100m77 in parallel direction! Seal the sample with vinyl tape except for the part marked , and use it as a test piece.

After immersing this test piece in an electrolytic solution of 3% saline at 25°C for 3 minutes, a carbon rod was used as a counter electrode, and a voltage of 100V was applied to the test piece.
Constant voltage electrolysis is performed for 0 seconds, and the average current value flowing at that time is measured. For each sample, the arithmetic mean value of the measured values of 5 tests and 1 test piece is adopted as the result. (b) Copper sulfate test Using the same test piece as used in (a) above,
The sample was immersed in a 0% copper sulfate aqueous solution (containing about 5% hydrochloric acid) for 5 minutes, and the number of copper spots deposited near the can joint was counted using a microscope.

Measurements were made on 5 test pieces for each sample, and on average no copper precipitation was observed (○), copper was 1 to 1.
In the table below, those in which 10 points were precipitated are shown as (△), and those in which 11 or more points were precipitated are shown as (x). (4) Processing Resistance From the seam part of the can, which was coated with a specified paint and cured by baking, a test piece was cut out from the seam part to a width of 40 mm and a length of 60 mm.

The analytical bending test 1 test is JISK54OOl6. 16 bending resistance. The test piece after pre-bending is 3m1L wide around the joint, and 6 mm in the direction parallel to the joint with the tip of the pre-bending centering on the joint.
Seal with vinyl tape except for the door part, and perform constant voltage electrolysis and copper sulfate tests under the same conditions as in (3).

In each case, the average of 5 test pieces was adopted as the result, and in the copper sulfate test, no copper precipitation was observed...
(0), copper precipitated at 1 to 5 points... (Δ)
, Those with 6 or more precipitated points are indicated as (×) in the table below. (5) Evaluation method of actual can test (a) Hydrogen generation amount When the can is opened, the gas in the direction of the can is sampled, and the amount of hydrogen is determined by gas chromatography, and the arithmetic mean value of the 10 cans is shown.

In addition, an expansion can is simply an expansion can. (b) Condition of perforations and can-facing joints For canned goods that have been stored at 37°C for one year and are found to have leaked a container-friendly product (liquid) after being visually observed, check the condition of cans near the can joint after opening. The correction part is observed under a microscope, and those with through holes are considered perforated cans, and the ratio of perforated cans to the total number of test cans is shown.

In addition, after opening the can, the state of corrosion is examined by visually or microscopically observing the corrected area near the joint. The number of cans subjected to the storage test was 100 cans, and 50 randomly selected cans were examined for corrosion status. Example 1 Here, except for sample 3, the epoxy urea thread resin solution 1 was used as the thermosetting paint.

Sample E. In Example 3, the epoxy urea thread resin solution 1 having a different solvent composition was used. As the thermoplastic resin, a polybutylene terephthalate (PBT) polybutylene isophthalate (PBI) copolymer (PBT8OmOe%, carbonyl group concentration 917 meq. equivalent/1009, softening point 205° C. by ring and ball method) was used. ? In samples 1 and 3, the resin pellets were freeze-pulverized using liquefied nitrogen and used as powders with an average particle size of 25 μm. on the other hand,. II).
Sample No. 4 with an average particle size of 0.08μ was obtained by dissolving the above resin pellets in a solvent at high temperature, and then gradually lowering the temperature of this solution to allow the particles to precipitate. They were mixed in the above paint so that the volume fraction of the solid content was 25%, and stirred for 20 minutes using a high speed mixer to disperse them, thereby preparing a seam correction paint. Note that for samples ▲2, the contact angles of these paints are shown in Cloth 1, which were measured by the method described above using the resin solution 1 that does not contain the resin powder as it is.
Next, an air spray gun was used to spray the paint at a temperature of 40 to 70°C on the inner and outer surfaces of the seam of the tin can body obtained by welding the various paints by the method described above. The can body was spray-coated to a width of 10 mm and a dry coating thickness of 40 to 60 μm, and then baked in a hot air drying oven at 220° C. for 3 minutes to obtain a can body with the seam covered. Subsequently, the dispersion state of the thermoplastic resin powder in this cured coating film was observed by the method described above, and the coating properties and workability were further investigated by the current value during constant voltage electrolysis and the copper sulfate condensation test. Next, after flanging the can body with the seam covered by the above method, a tin lid for a can with a nominal inner diameter of 65.3 mm having an epoxy/phenol thread coating on the inner and outer surfaces was double-sealed. Two types of boiled salmon and tomato sauce were placed in the empty cans, and the same tin lids as above were double-sealed using a vacuum seaming machine.

Each of these cans was heat sterilized at 118°C for 90 minutes and stored at 87°C for one year.
The amount of hydrogen was investigated in 10 arbitrarily extracted cans, and 50 arbitrarily extracted cans were opened to examine the state of corrosion at the can body joint. The results are shown in Table 1. Example 2 Here, the epoxy phenol thread resin solution 1 was used as a thermosetting coating.

As a thermoplastic resin, polybutylene terephthalate (
PBT) (carbonyl group concentration 917 meq. equivalent/10
09, softening point of 222°C by ring and ball method) was used. Resin powders having each average particle weight shown in Table 2 were created by the above method. In other words, a sample with an average particle size of 15μ or more (sample 6
, 7, 8, and 10), the above-mentioned resin pellets were freeze-pulverized using liquefied nitrogen to obtain resin powders. On the other hand, for Samples 5 and 9, resin powders having the respective average particle sizes were obtained by the same method as for the samples of Examples 1 to 4. Table 2 shows the average particle size of each sample. Next, these resin powders were mixed into the above coating material so that the volume fraction in the solid content was 20%, and the mixture was stirred and dispersed using a high speed mixer for 20 minutes to obtain a seam correction coating material.

Table 2 shows the contact angles of these paints on a 25°C glass plate. Next, an air spray gun is applied to the facing and outer surfaces of the seam of the can body made of tin material obtained by welding the above various paints using the method described above. After spray painting to a thickness of 60 μm, the can body was baked for 3 minutes in a hot air drying oven at 220° C. to obtain a can body with the seam portion covered.

Subsequently, the state of dispersion of the thermoplastic resin powder in this cured coating film was observed by the method described above, and the coating properties and workability were further investigated by the current value during constant voltage electrolysis and a copper sulfate test.
Next, after flanging the can body with the seam covered by the above method, the can body was coated with epoxy phenol thread on the inner and outer surfaces and had a nominal inner diameter of 65.3 m77! Double-tighten the tin lid for the can, and pour boiled salmon and tomato sauce into the empty can.
Each type was packed, and the same tin lids as above were double-sealed using a vacuum seaming machine.

Each of these canned goods was heat sterilized at 118°C for 90 minutes and stored at 37°C for one year. After that, the amount of hydrogen was measured in 10 cans randomly extracted from each sample of 100 cans, and then 50 randomly extracted cans were opened. The cans were then inspected for corrosion at the can body joints. The results are shown in Table 2. Example 3 Here, the epoxy area thread resin solution was used as a thermosetting coating.

As the thermoplastic resin, polycarbonate (sample 11
), maleic anhydride-modified polypropylene (same, Rei 12)
, zinc-containing ionomer (Ibid., E.l3), polyethylene terephthalate (Ibid., Boiled 14), and as a comparative example, ethylene-propylene copolymer (ethylene 50m01%) (Ibid., E.). 15), polytetrafluoroethylene (same, ?
16), maleic anhydride-modified polyethylene (same, boiled 17)
) was used. For each sample, a pellet or chip sample was frozen and crushed using liquefied nitrogen to obtain a resin powder. The softening point (melting point) of these resins measured by the ring and ball method and
Table 3 shows the average particle diameter and carbonyl group concentration of the resin powder.
Shown below. The thermoplastic resin powders were mixed in the dispersion medium so that the volume fraction in the solid content of the paint was 30%, and the mixture was stirred and dispersed for 20 minutes using a high-speed mixer to obtain a seam correction paint.

Table 3 shows the contact angles of these paints measured by the method described above. Next, the inner and outer surfaces of the seam part of the can body made of TFS material obtained by welding the above various paints by the method described above are sprayed with an air spray gun to a width of about 10 m to a thickness of 40 to 40 mm. After spray painting to a thickness of 60 μm, the can body was baked for 3 minutes in a hot air drying oven at 220° C. to obtain a can body with the seam portion covered.

Subsequently, the state of dispersion of the thermoplastic resin powder in this cured coating film was observed by the method described above, and the coating properties and workability were further investigated by the current value during constant voltage electrolysis and a copper sulfate test.
Next, after flanging the can body with the seam covered by the above method, a TFS lid for a can with a nominal inner diameter of 65.3 mm having an epoxy phenol thread coating film on the inner and outer surfaces was double-sealed. Two types of boiled salmon and tomato sauce were packed in empty cans, and the same TFS lids as above were double-sealed using a vacuum seaming machine.

Each of the canned vegetables was heat sterilized at 118°C for 90 minutes and stored at 37°C for 1 year. After that, the hydrogen content of 10 cans randomly extracted out of 100 cans was examined for each sample. The can was opened and the state of corrosion at the can body joint was examined. The results are shown in Table 3. Example 4 Here, the epoxy phenol thread resin solution 1 was used as a thermosetting coating.

As a thermoplastic resin, polybutylene terephthalate (
Softening point measured by ring and ball method: 222°C Carbonyl group concentration: 9
The resin pellets were freeze-pulverized using liquefied nitrogen to obtain a powder with an average particle size of about 25 μm. They were mixed so that the values were as shown in Table 4, and stirred for 20 minutes using a high-speed mixer to disperse and obtain a seam correction paint. The angles are shown in Table 4. Next, this seam correction paint was welded using the method described above, and the inner and outer surfaces of the seam of the TFS material were sprayed onto the inner and outer surfaces of the seam part of the can body to a width of approximately 10 mm and a dry coating thickness of 40 mm. After spray painting to a thickness of 60 μm to 60 μm, the can body was baked for 3 minutes in a hot air drying oven at about 220° C. to obtain a can body with the seam covered. The dispersion state of the thermoplastic resin powder in this cured coating film was observed using the method described above, and the coating properties and workability were further investigated using the current value during constant voltage electrolysis and a copper sulfate test. Furthermore, after flanging the can body coated with the seam obtained by the above method, a TF for a can with a nominal inner diameter of 65.3 mm having an epoxy phenol thread coating film on the inner and outer surfaces.
The S lid was double-sealed, two types of boiled salmon and tomato sauce were packed in the resulting empty cans, and the TFS lid was double-sealed using a vacuum seaming machine.

Claims (1)

[Scope of Claims] 1. Consists of a can body having a seam on the side surface and a resin coating layer covering at least the inner surface side of the seam, the coating layer comprising a continuous phase made of a thermosetting resin and thermoplastic resin particles. The thermoplastic resin particles have a dispersed phase of 0.1
It has a number average particle size of 80 to 80 microns and a ring and ball softening point of 50 to 300°C, and the thermosetting resin and the thermoplastic resin are present in a volume ratio of 95:5 to 25:75. A can with a characteristic seam coating. 2 The thermoplastic resin is a carboxylic acid, a carboxylate,
12 to 1400 carbonyl groups based on carboxylic anhydride, carboxylic ester, carboxylic acid amide, ketone, carbonate ester, urea, urethane, etc. in the main chain or side chain
The can according to claim 1, which is a resin having a concentration of meq/100g of polymer. 3. The can according to claims 1 and 2, wherein the thermoplastic resin is polyester, polycarbonate, polyamide, ionomer, or acid-modified polyolein. 4. The can according to claims 1 to 3, wherein the thermosetting resin is a combination of an epoxy resin and at least one of a phenol resin, a urea resin, a melamine resin, and a thermosetting acrylic resin. 5. It consists of applying a resin paint to the inner side seam of a can body that has a seam on the side, or at or near the inner side seam of the can body, and then baking this paint to form a coating film that covers the seam. In the method for manufacturing a seam-coated can, the resin coating includes a dispersion medium consisting of a solution of a thermosetting resin that is to become a continuous phase in a film-formed state, and a dispersion medium of 0.1 to 80% Number average particle size of microns and 50 to 30
It is a paint consisting of a dispersoid of thermoplastic resin particles that should become a dispersed phase in a film-formed state and has a ring and ball softening point of 0°C, and the thermosetting resin and thermoplastic resin in the paint are 95%
:5 to 25:75, and the paint has a contact angle of 18.5 to 45 degrees as measured 1 minute after dropping a sample of 0.2 mm^3 on a glass plate at 25°C. 1. A method for manufacturing a can having a seam covered with corners, characterized in that the formed coating film is baked under conditions in which the thermoplastic resin is cured or melted.