JPH03174473A - Production of can with joint coated - Google Patents

Abstract

PURPOSE:To produce a can having the cut edge of a joint perfectly coated and an excellent processability and corrosion resistance by coating the inside of a joint of a can body having the joint on the side with a specific coating material and then baking the coating film under a specific condition. CONSTITUTION:A method for coating the inside of a joint or the neighbouring part thereof a can body having the joint on the side with a coating material and baking the resulting coating film to cover the joint with the coating film, wherein the coating material used comprises 95-25 pts.vol. dispersion medium comprising a soln. of a thermoset resin and 5-75 pts.vol. disperse phase dispersed therein, having a number-average particle diameter of 1-80mum and a ring-and-ball softening point of 50-300 deg.C, and contg. a carbonyl group bound to the main or side chain. The coating film is baked at a temp. at which the thermoplastic resin softens or melt, and then quickly cooled.

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 fiber side joints and has excellent workability and corrosion resistance, and a method for manufacturing the same.

Conventionally, the manufacturing method for the subassembly was to cut a metal material for a can into a cylindrical shape, fit the two ends of the material together, and then join these parts using means such as welding, adhesive, or solder. The most widely used method is to form a seam by

The cut edge of the material is necessarily exposed on the inner surface of the side seam formed by this method.
Coating the cut edges of this material is extremely important in terms of preventing corrosion of the material and suppressing metal elution into the contents.

Various proposals have been made to cover and protect these seams, especially the cut edges of the material (hereinafter referred to as margins). An effective method within this proposal is to cover and protect the cut edge of the material with adhesive tape such as polyamide, but this method cannot be applied to the production of adhesive seams. Even if it can be obtained, it cannot be used in rows when the seam is exposed to extremely high temperatures, such as in welded seamless cans.

As a method of coating and protecting the joints in welded joints, it is known to apply a solution or powder paint to the inner surface of the joint of the connected body after the bottom shape. It lacks the combination of properties such as corrosion resistance, barrier properties against corrosive components, and workability such as double seaming, and is still unsatisfactory for the purpose of completely covering stepped cut edges at seams.

For example, although coating materials made from thermoplastic resins have excellent processability, thermoplastic resins lack adhesion to seams and have poor barrier properties as described above, and seams coated with thermoplastic resins However, depending on the contents, etc., defects such as corrosion and blackening due to sulfide can easily occur.

On the other hand, paints made from thermosetting resins have excellent adhesion to seams and barrier properties against corrosive components, but on the other hand, they lack workability. - It is observed that metal leaching frequently occurs from the double-sealed parts of the joints.

Furthermore, when using any of these resins, these paints flow in a solution or molten state to fill the level difference that exists at the seam, so the paint film may or may not break at the corner of the cut edge. However, the coating film becomes extremely thin, and air bubbles tend to form in the coating film at the stepped portions, making it almost impossible to form a complete coating on the cut edges of the material.

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 can, but also significantly impair the flavor of the contents.

The present inventors have discovered that when applying a paint of a specific composition using a thermosetting resin bath liquid as a dispersion medium and a specific thermoplastic resin particle as a dispersoid to a seam of a can, the corners of the cut edges present at the seam 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

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 edge 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. Coating equipment can be used with special modifications.

According to the present invention, a subassembly having a joint on a side surface and a resin coating layer covering at least the inner surface side of the joint,
The resin coating layer consists of a continuous phase consisting of a thermosetting resin and a dispersed phase consisting of thermoplastic resin particles f), wherein the thermoplastic resin particles have a number average particle size of 1 to 80 microns and a
Provided is a seam-coated can having a ring and ball softening point of from 300°C to 300°C, wherein the thermosetting resin and the thermoplastic resin are present in a volume ratio of 95:5 to 25:75. be done.

According to the present invention, a resin paint is applied to the inner side seam or the vicinity thereof of a fiber braid having a side seam, and then the coating is baked to form a coating film covering the seam. In the method for manufacturing a can coated with A paint comprising a dispersoid of thermoplastic resin particles having a ring and ball softening point of °C, and the thermosetting resin and thermoplastic resin in the paint are present in a volume ratio of 95:5 to 25:75. and the said paint is 2
At 5℃, drop a sample amount of % 0-2 mm on the glass plate.
The joint is coated by baking the thermoplastic resin into a coating film having a contact angle of 18.5 to 45 degrees when measured after 10 minutes, and baking the coating film under conditions in which the thermoplastic resin melts or melts. A method for manufacturing a can is provided.

The present invention can be advantageously applied to cans in which the cut edge of the seam must be coated after the seam is formed, and in particular to cleaning cans and beaks. Therefore, although the present invention will be explained below with reference to a row of welded cans, the effect of the present invention of forming a completely coated coating film with excellent workability and corrosion resistance on the cut edge of the seam is not limited to welded cans. It should be understood that this is similarly achieved in the case of jointed cans, such as adhesive or solder cans.

In FIG. 1 showing the narrow part of the seamless covered can of the present invention, the can metal material 1 cut to a predetermined size is formed into a cylindrical shape, the edges of which are overlapped, and this overlapping part is welded. This forms a seam 2. The inner surface of this fiber braid may be coated with a resin protective coating of 1°, except for the above-mentioned seam 2 or the vicinity thereof.

At the joint 2 located on the inner side of this fiber braid, there is a cut edge 3 of the material or a melted protrusion portion 4 of the gold FJ and the material during welding. This joint 2 is provided with a resin /i15 that covers this portion.

An important feature of the present invention is that the coated resin pigeon 5 is formed from a continuous phase 6 of thermosetting resin and a dispersed layer 7 of thermoplastic resin particles.

Although thermosetting resins have excellent adhesion to seams and barrier properties against corrosive components, they lack processability, and while thermoplastic resins have excellent processability, they have poor adhesion and barrier properties. The lack of sex is already mentioned above.

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. However, by incorporating thermoplastic resin particles in the form of a dispersed phase into the coating film, we have been able to provide workability that can withstand double seaming processing, bead processing, etc. It is.

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; The adhesion of joints, especially cut edges, is reduced, and the barrier properties are also reduced, making metal corrosion such as sulfide blackening easier to occur.

Moreover, if a paint with a thermosetting resin as a continuous phase (dispersion medium) and a thermoplastic resin as a dispersed phase (dispersoid) is used, the coating film will completely cover the cut edges 3 of the seam, especially the corners 8 of the cut edges. It has been found that the unexpected effect of forming a . That is, when a thermosetting resin solution alone is applied to the seam, this solution flows out to the step part of the cut edge 3 or the protruding part 4, and
This causes defects such as the coating film being cut or becoming thinner at the corners 8 of the cut edge, but by incorporating thermoplastic resin particles in a fixed amount ratio into the thermosetting resin solution, the seam 2 When coating on the surface, the thermoplastic resin particles 7 applied near the stepped portion retain the thermosetting resin solution on the surface, and the thermosetting resin solution flows into the gap between the steps, resulting in a smooth coating film. It suppresses the tendency to change. Thus, using a coating of the form of the invention,
Even at the corners 8 of the cut edge, it is possible to maintain a coating film of approximately the same thickness as that applied, 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 the baking conditions, and the mutual adhesion between the thermosetting resin phase and the thermoplastic resin phase is also complete. It is 0, which has even better mechanical strength, impact resistance, workability, etc. Furthermore, by perfecting the mutual adhesion between the two, the barrier properties against the above-mentioned corrosive acids and the like are also significantly improved.

The thermoplastic resin particles used in the present invention range from 0.1 to 80□
micron, especially a number average particle size of 0.5 to 50 microns;
It is also important to have a ball softening point of 50 to 800°C, particularly 90 to 270°C, in view of the above-mentioned objective of the present invention. That is, when the particle size of the dispersed particles is smaller than the above range, the grain boundary area per unit coating film volume becomes as large as 1), resulting in a decrease in the barrier properties of the coating film and the loss of content. Corrosion such as sulfide blackening due to oxidation tends to progress easily, and the workability of the coating film after curing also deteriorates. Furthermore, if the particle size exceeds the above range, it becomes difficult to uniformly form a structure consisting of a continuous phase of thermosetting resin and a dispersed phase of thermoplastic resin in the coating film. There is a tendency for the complete coverage of cut edges, workability, and corrosion resistance to decrease significantly.

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 ability to cover cut edges will also decrease.
Workability and corrosion resistance are 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 invention1, 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 may be used in combination at a volume ratio of 95:5 to 25:75, particularly preferably a volume ratio of 90:10 to 80 near 0. This is also extremely important in achieving the objectives mentioned above.

That is, if the blending ratio of the thermoplastic resin is lower than the above range, it becomes difficult to completely cover the cut edge, making it difficult to avoid corrosion in this area. Furthermore, the processability of the formed coating film is also reduced. -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, making it difficult to completely cover the rough cut edges. In addition, the corrosion resistance of the coating film itself is significantly reduced.

In the present invention, it is desirable that the thermosetting resin and the thermoplastic resin particles are selected so that as strong an adhesive surface as possible is formed at the grain boundaries in the paint. From this point of view, in the present invention, , thermoplastic resins such as carboxylic acids, carboxylates, carboxylic anhydrides, carboxylic esters, carboxylic acid ions, ketones, carbonic esters, urea, urethanes, etc.
-) is preferably used in the main chain or side chain. 12 to 1400 carbonyl groups
The best results in terms of processability and corrosion resistance are obtained when using thermoplastic polymers containing a concentration of 7100 g of mgq(□Liquiparen), especially 50 to 1200 meq/1009 of polymer. It will be done.

Such thermoplastic polymers are produced by incorporating monomers having the aforementioned functional groups into the main chain of the polymer by means such as polymerization or copolymerization, or by graft polymerization or terminal treatment. υ is obtained by bonding it to a thermoplastic polymer. Further, in the case of a hydrocarbon polymer such as an olefin resin, by oxidizing the polymer, it can be made into a thermoplastic resin containing a carbonyl group in the range described in [7] above.

Suitable examples of such thermoplastic polymers include, but are not limited to:

(α) General formula 1l -6-0-R, -0-R, -C+---(R3 in formula 21
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. A polyester comprising a repeating unit represented by the following.

For example, polyethylene adipate, polyethylene separate, polyethylene terephthalate, polytetramethylene inphthalate, polyethylene terephthalate/inphthalate, polytetramethylene terephthalate, polyethylene/2-tramethylene terephthalate, polyethylene/oxybenzoate.

+b1 - 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.
) and olefins or copolymers of 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/methacrylic ester/acrylic acid copolymer, acrylic ester/vinyl chloride copolymer, acrylic ester grafted polyethylene, methacrylic ester/vinyl chloride copolymer, styrene/methacrylic ester/butadiene copolymer Coalescence, methacrylic acid ester/acrylonitrile copolymer.

(C1-formation formula, R3 is a hydrogen atom, an alkyl group, or a phenyl group.) A copolymer of a vinyl ester and an olefin or other vinyl monomer, or a partially saponified product thereof.

For example, partially saponified ethylene-vinyl 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 a copolymer of an ionomer olefin and an unsaturated carboxylic acid or another vinyl monomer with an alkali metal, an alkaline earth metal, or an organic base.

For example, Boleyn products are commercially available from DuPont in the United States.

(gl Copolymer of maleic anhydride and other vinyl monomers or maleic anhydride-modified polyolefin.

For example, anhydrous mullein! #/Styrene copolymer, maleic anhydride-modified polypropylene, maleic anhydride-modified polyethylene.

(b) - Formation % formula % (41 In the formula, R6 has 8 to 1 carbon atoms. Polycarbonate represented by.

For example, poly-p-xylene glycol biscarbonate, poly-dioxydiphenyl-methane carbonate,
Poly-dioxydiphenylethane carbonate, poly-
dioxydiphenyl 2.2-) O ban carbonate,
Poly-dioxydiphenyl 1,1-ethane carbonate.

(gl - formation %formula% fNH-CCH2)n-C+　　---(51 or In the formula, n is a number from 3 to 13, usually a number from 4 to 11. Polyamides consisting of repeating units represented by

For example, poly-ω-aminocaproic acid, poly-ω-aminohebutanoic acid, poly-ω-aminocaprylic acid, poly-ω
- aminoperadaic acid, poly-ω-aminodecanoic acid, poly-ω-aminoundecanoic acid, poly-ω-aminodecanoic acid, poly-ω-aminotridecanoic acid, polyhexamethylene adipamide, polyhexamethylene dodecamide, Polyhexamethylene dodecamide, polyhexamethylene tridecamide, polydecamethylene azibakudo, polydecamethylene dodecamide, polydecamethylene dodecamide, polydecamethylene tridecamide, polytetramethylene azibakudo,
Polytetramethylene sevacagide, polydodecamethylene dodeca(de), polydodecamethylene tridecamide, polytridecamethylene adipamide, polytridecamethylene adipamide, polytridecamethylene dodecamide, polytridecamethylene tri Decamide, polyhexamethylene azelavide, polydecamethylene azelagudo, polydecamethylene dodecamide, boritridecamethylene azelamide.

(hl - formula % formula % (71) wherein each of R7 and R5 is an alkylene group having 1 to 18 carbon atoms. A polyurea derived from a repeating unit represented by:

For example, polyhexamethylene urea, polyhebutamethylene urea, polyundecamethylene urea, polynonamethylene urea.

(i) General Formula In the formula, Ro is an alkylene group having 3 to 24 carbon atoms, a polyether residue, or a polyester residue; R10 is an alkylene group having 3 to 24 carbon atoms or an arylene group; R1 is a carbon number 1 to 18 alkylene group or arylene group; is 0
or the number of l: A polyurethane or polyureaurethane represented by:

For example, polytetramethylene hexamethylene urethane,
Polyhexamethylenetetramethyleneurethane, polyureaurethane obtained by chain-extending isonanate-terminated polyester or polyether with water.

0) 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 purposes of this invention are, in order of importance, polyesters, polycarbonates, polyamides, ionomers, and acid-modified polyolefins.

These resins should have at least a sufficient molecular weight to form a film, and these resin particles may optionally contain compounding agents known per se, such as UV absorbers, stabilizers, lubricants, oxidants, etc. Inhibitors, pigments, dyes, antistatic agents, etc. can be blended according to known formulations.

To form the thermoplastic resin into a powder having the above-mentioned particle size, any means known per se can be used. For example, in the case of an addition polymer, the constituent monomers are subjected to emulsion polymerization or suspension polymerization. By doing so, resin particles having a predetermined particle size can be obtained.

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 as 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 thereof are phenol-formaldehyde resins, 7-ran-formaldehyde resins, xylene-formaldehyde resins, ketone-formaldehyde resins, urea-formaldehyde resins,
Melamine-formaldehyde resin, alkyd resin, unsaturated polyester resin, epoxy resin, bismaleimide resin, triallyl sheaslate resin, thermosetting acrylic resin, silicone resin, oil-based resin, etc., these may be used alone or in combination of two or more. Can be used in combination.

Thermosetting resins suitable for adhesion to seams and copper corrosion resistance include epoxy resin components and at least one thermosetting resin selected from the group consisting of phenolic resins, urea resins, melamine resins, and thermosetting acrylic resins. In combination with curable resins, these film-forming resins are used in the paint in the form of a mixture or in the form of 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 functional ethers such as tetrahydro-7rane and dioxane glazes and cellosolve;
Esters such as ethyl acetate and butyl acetate are 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 was measured at a temperature of 25°C with a sample amount of 0-2 m'' on a glass plate 1 minute after dropping.
Having a contact angle of 5 to 45 degrees, particularly a contact angle of 19.0 to 43 degrees, is particularly desirable in order to enable thick coatings that completely cover the cut edges. The solid content aK in the paint is generally in the range of 5 to 50%, and an appropriate concentration may be selected depending on the combination of resins so that appropriate workability and thick coating properties can be obtained.

The metal materials that make up the bell body include, in addition to untreated steel plates (black plates), 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. Chemical conversion treated steel sheets such as treated steel sheets or electrolytic chromic acid treated steel sheets can be mentioned.
Furthermore, a light metal plate such as an aluminum plate can also be used.

The formation of the side seam is preferably carried out by electric resistance welding, and the process of forming the side seam into a cylindrical shape is to mold the metal material into a cylindrical shape, and then place the formed overlapping part between a pair of electrode rotors. or through the electrode wire
This is done by passing it between a pair of electrode rollers. At this time, the welding operation is performed in an inert atmosphere, and the atmosphere in the casing where the surface temperature of the welded part is reduced to 550°C is an inert atmosphere, so that a porous metal hydroxide layer is formed on the outer surface of the joint. It is desirable to prevent this and improve the adhesion of protective coatings. 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 airflow of the above-mentioned inert gas, 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 (tin-free steel), these should be Remove non-conductive coating.

The width of the side seam of this welded part varies depending on the diameter of the can, but it can be relatively small, such as 0.2 to 1-211. One of the notable advantages is that it can be reduced. The thickness of the housing and seams can vary from 2 times to 1.2 times the material thickness.

In other words, this welding method reduces the thickness of the seam by pressing the overlapping part with high pressure during welding, thereby making it possible to reduce the difference in level between the seam and other areas during double seaming. This is an advantage.

Application of the paint to the fiber joint or its vicinity can be carried out by means known per se such as roller application, spray application, brush application, flow coat dip application, etc., and requires special means such as powder coating. It is a significant advantage of the present invention that conventional equipment can be utilized without having to do so.

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 the coating specified in the present invention should be used. Then, it is very easy to form such a coating film.

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 fire, hot oven,
A hot air oven, induction heating, resistance heating, infrared heating, etc. can be used. The curing conditions used were such that the thermosetting resin became reticulated by crosslinking and sufficient adhesion occurred at the grain boundaries between the thermosetting resin and the thermoplastic resin.
Appropriate conditions are selected from a temperature range of 0 to 400°C and a time period of 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, and in this case, the coating film should be The baking temperature of the resin is at least 10°C higher than the crystallization temperature of the resin.
Rapid cooling to a low temperature, particularly within 10 seconds, preferably within 1 second, is desirable from the viewpoint of processability and barrier properties (corrosion resistance due to good adhesion at grain boundaries). Such rapid cooling can be easily achieved by bringing the baked paint film into contact with a cooling medium such as cooling water, a stream of liquefied nitrogen, or cold air, or by bringing the seam after the paint film into contact with a cooling mechanism such as a cooling roller. can be done.

The seam coating &lI 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 resin solution 70 parts of an epoxy resin with an average molecular iL of 2900, which is a condensation product of bisphenol A and epichlorohydrin, and 30 parts of a butyl ether urea formaldehyde resin, respectively (I) 50 parts of dioxane, 15 parts of xylene, and 15 parts of cyclohexanone. parts, 10 parts of methyl ethyl ketone, 1 part of toluene
(4) 50 g of methyl ethyl ketone, and 50 parts of toluene to obtain a solution with a solid content of 25%. Solution (I) is used in Example 1 and solution (II) as paste paint in Examples 1.3 and 5.

(2) Epoxy/phenol type enteric coating flI
5 moles of O. and 0.5 moles of p-cresol are dissolved in 1.5 moles of 37% formaldehyde aqueous solution, 0.15 moles of ammonia is added as a catalyst, and the mixture is reacted at 95° C. for 3 hours. The reaction product is extracted with a mixed solvent consisting of ketones, alcohols, hydrocarbons, etc., washed with water, the aqueous layer is removed, a small amount of remaining water is removed using an azeotropic method, and the product is cooled to produce a resol type phenolic resin. Obtain a 30% solution of. A condensation product of bisphenol A and epichlorohydrin obtained by dissolving the above resol type phenol resin solution in advance in a mixed solvent consisting of ketones, esters, alcohols, hydrocarbons, etc., and 30% of the epoxy resin with an average molecular weight of i2900.
Mix with the solution. The weight ratio of phenolic resin and epoxy resin is 40:60. This mixture is pre-condensed under reflux for 2 hours to give an epoxy phenolic resin solution (Il) which is used as a paste paint in Examples 2 and 4.

The method for manufacturing the welded can body is as described below.

For welded tin cans, the plate thickness (0.28 mm) and the amount of tin plating are 25 mm.
1b/B, B (tin layer thickness approx. 0.6 μm) tin plate, apply epoxyphenol paint (a mixture of epoxy resin and phenol resin at a ratio of 1:1) to the seam area of the can body. The margins were painted so that the film thickness after baking was 5 microns on the inner surface and 8 microns on the outer surface.
Bake hardening for 10 minutes in a hot air drying oven at 0°C. next,
The painted tin plate was used as a No. 7 can body blank (blank length 206-4mm1 blank hide IG4).
．． Cut this blank into 5) pieces using a roll former.
After making it into a cylindrical shape with the short side facing the axial direction and fixing it by overlapping it at a welding station, the two
Using a commercially available seam welding machine consisting of several roll electrodes,
A pressing force (40kFl/mx2
) in a nitrogen gas stream at a can making speed of 30 m/
Bait welded can body (211 diameter, internal volume 318.2
m/No. 7 can) is obtained. Overlapping width before welding is 0.3m
m, and the overlapping width after welding is 0.4U.

On the other hand, for TFS welded cans, TFS with a plate thickness of 0.28 mark is coated with margins in the same manner as the tin cans, and then the above-mentioned ? 'F S painted board body blank for No. 7 can (Frank length 2064, Frank High) 104.5m
m). Next, the width of both sides of the overlapping part near the cut nip of the joint is approximately I from the cut nip.
Nip cleaning is performed using a cutting method to remove surface chromium and chromium oxide layers across the IRM. After the nip cleaning, the blanks were stacked on a roll former and fixed in a cylindrical shape with the short side oriented in the axial direction at a welding station.
Using a commercially available seam welding machine that uses a roll electrode,
A pressing force (45 kq/rtrx2
), and can making speed 80 m/in nitrogen gas stream.
A welded can body (No. 17 can with a 211 diameter internal volume of 31 & 2 m) was obtained at min. The overlap width before welding was 0.3 mm, and the overlap width after welding was 0.4 mm.

In the present invention, evaluation of actual can test blocks, physical property evaluation of paint, and structural evaluation and physical property evaluation of the paint film near the can seam are performed as follows.

(1) Micro 5lide Glass as a contact angle glass plate
(grade 1, thickness 0.9 to 1.2 y+m) was immersed in a chromium mixed acid for a day and night, thoroughly washed with pure water, dried, and stored in a desiccator to be absolutely dry before use.

The measurement is carried out in a constant temperature room at 25° C. In an air atmosphere, a predetermined paint is dropped onto a glass plate over a distance of 0.2 m using a microsyringe, 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 mm. This sample 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 microtome so as to obtain a cross section perpendicular to the can joint.

This thin piece was immersed in a blue dye (methyl violet) aqueous solution for 10 minutes at room temperature to selectively stain only the thermoset coating [7] After washing well with water, the structure was examined using an optical microscope, especially the thermoplastic resin particles. Observe by paying attention to the state of dispersion. 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) Copper redness of the joint part (α) Current value during constant voltage electrolysis The can joint part, which is baked and hardened after applying the specified paint, has a width of 2 cm.
A specimen is cut out over fn and sealed with vinyl tape except for a portion 3 mm wide in the direction perpendicular to the seam and 100+ am in the parallel direction to prepare a trial piece. After immersing this test piece in an electrolytic solution of 3% saline solution at 25°C for 3 minutes, using a carbon rod as a counter electrode, constant voltage decomposition was performed at a voltage of 1αOV for 10 seconds, and the average current flowing at that time was calculated. Measure.

For each sample, the arithmetic mean value of the measured values of 5 test specimens is adopted as the result.
Immerse it in a 0% sulfuric acid steel aqueous solution (containing about 5% hydrochloric acid) for 5 minutes, and count the number of copper spots deposited near the can joint using a microscope. Measurements were made on 5 test pieces for each sample, and on average, 111 (○) showed no copper precipitation, and 1 to 1 copper was measured.
In the table below, those in which 10 points were precipitated are designated as ---(Δ), and those in which 11 or more points were deposited are designated as -(X).

(4) Processing Resistance A test piece is cut out from the joint part of the can, which is coated with a specified paint and cured by baking, to a width of 40 mm and a length of 60 mm, centering on the joint part. Bending test is JIS K540
0.6.16 bending resistance.

After folding, the test piece was sealed with vinyl tape, except for a 3-width area around the seam and a 6-inch area around the bending tip in the direction parallel to the seam (under the same conditions as 81). Conduct constant voltage electrolysis and copper sulfate test@.In both cases, the average of 5 test pieces is adopted as the result.In the copper sulfate test, 111 (○) indicates that no copper precipitation is observed, and 1 to 5 copper Those with point precipitation---(Δ), those with 6 or more points precipitation---(X)
as shown in the table below.

(5) Evaluation method of actual can test results (cL) Amount of hydrogen generated When the can is opened, the gas content in the can is sampled, and the water Xi is examined by gas chromatography, and the arithmetic average value of the 10 cans is shown. In addition, regarding the expansion can, it indicates that it is the 11th expansion can.

(b) Condition of can Miff with perforation and can inner surface joint part is 3
After being stored at 7℃ for one year, for cans that are visually observed to have leaked the contents (liquid), the correction area near the joint after opening the can is observed under a microscope, and those with through holes are considered as perforated cans. It is expressed as the ratio of perforated cans to the total number of test cans. After opening the can, check the corrosion state by visually or microscopically observing the corrected area near the joint. The number of cans subjected to storage trials was 100, and 50 randomly selected cans were examined for corrosion status.

EXAMPLES Here, the epoxy urea resin solution (I[) was used as the thermosetting paint except for Sample No. 463.

In sample A68, the epoxy urea resin solution (I) having a different solvent composition was used. As the thermoplastic resin, polybutylene terephthalate (PBT)-polybutylene isophthalate (CPBI) copolymer CPBT80mo
L%, carbonyl group concentration 917 meq, equivalent weight 710
0g, softening point 205°C by ring and ball method). Hawk 1
In samples No. 3 and 3, the resin pellets were freeze-pulverized using liquefied nitrogen and used as a powder with an average particle size of 25 μm.

On the other hand, a sample of 1,464 having an average particle size of 0.8 μm was obtained by dissolving the resin pellets in a solvent at a high temperature, and then gradually lowering the temperature of the solution to cause the particles to precipitate and settle. These resin powders are added to the above paint so that the volume fraction of the solid content is 2.
Mix each at a concentration of 5% and mix with a high-speed mixer for 20%.
The mixture was stirred for a minute to disperse it, and a seam correction paint was obtained. In addition, Taka 2 sample contains the above resin powder! No resin solution (I) Part 1
Table 1 shows the contact angles of these paints measured by the method described above using No. 1.

Next, using an air spray gun, spray paint on the inner and outer surfaces of the seam of the can body using the tinplate material obtained by welding each of the above-mentioned phase paints using the method described above. While maintaining the temperature between 40 and 70 degrees Celsius, the cans were spray-painted to a width of approximately 10 mg and a dry coating thickness of 40 to 60 μm, and then baked in a hot air drying oven at 220 degrees Celsius for 8 minutes to cover the seams. I got the torso. 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 examined by current values during constant voltage electrolysis and copper sulfate test.

Next, the can body with the joints obtained by the above method was subjected to 7-lung processing, and then a tin lid for a can with a nominal inner diameter of 65.8+U having an epoxy/phenol coating on the inner and outer surfaces was double-sealed. Two types of boiled salmon and tomato sauce were packed in the resulting empty cans, and the same tin lids as above were double-sealed using a vacuum seaming machine. Each of these cans is 11
After heat sterilization at 8℃ for 90 minutes and storage at 37℃ for 1 year, the amount of hydrogen was measured in 10 randomly extracted cans out of 100 cans for each sample, and 50 randomly extracted cans were opened and the cans The state of corrosion at the joints of the shell was investigated. The results are shown in Table 1.

Example 2 Here, the epoxy-phenol resin solution fIl was used as a thermosetting paint. As a thermoplastic resin,
Polyethylene terephthalate (PBT) (carbonyl group concentration 91'1 meq-equivalent/100 g, softening point 222° C. by ring and ball method) was used. Resin powders having each average particle size shown in Table 2 were created by the following method. In other words, a sample with an average particle size of 15μ or more (sample/166.7.8.10)
Then, each of the above resin pellets was freeze-pulverized using liquefied nitrogen to obtain resin powder. On the other hand, samples /165 and 9 were processed in the same manner as the practical sample 17164.
Resin powders having respective average particle sizes were obtained. In Table 2,
The average particle size of each sample is shown.

Next, these resin powders are mixed into the above paint so that the volume fraction in the solid content is 20%, and the resin powders are mixed at high speed.
The mixture was stirred and dispersed for 20 minutes to obtain a seam correction paint. Table 2 shows the contact angles of these paints on a 25°C glass plate.

Next, an air spray gun was applied to the inner and outer surfaces of the seam of the can body made of tin material obtained by welding the above various paints by the method described above to a width of about 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 in a hot air drying oven at 220° C. for 3 minutes to obtain a can body with the joint portion 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 test noise.

Next, the can body with the seam covered by the above method was subjected to 7-lung processing, and then a tin lid for a can with a nominal inner diameter of 65-8 mm, which had an epoxy/phenol coating on the inner and outer surfaces, was double-sealed. Two types of boiled salmon and tomato sauce were packed in the resulting empty cans, and the same tin lids as above were double-sealed using an X-air seaming machine. These canned goods each cost 118
After heat sterilization at ℃ for 90 minutes and storage at 37℃ for 1 year, the amount of hydrogen was measured in 10 randomly extracted cans out of 100 cans for each sample, and 50 randomly extracted cans were opened and the can body joints were examined. The corrosion status of the parts was investigated. Table 2 shows each result.
Shown below.

Example a Here, the epoxy-urea resin solution (II) was used as a thermosetting paint. The thermoplastic resins include polycarbonate (sample Al l), maleic anhydride-modified polypropylene (PL, %12), zinc-containing ionomer (sample AlB), and polyethylene terephthalate (sample Al).
Same, Al4), ethylene-propylene copolymer (ethylene 50mol1%) (PI, /%1) as a comparative example
5), polytetrafluoroethylene (same, A16),
Maleic anhydride-modified polyethylene (Ibid., /1617) was used. For each sample, a pellet or chip sample was freeze-pulverized using liquefied nitrogen to obtain a resin powder. Softening grooves of these resins measured by ring and ball method, (Is!li point)
Table 3 shows the average particle size and carbonyl group concentration of the resin powder.

The thermoplastic resin powders were mixed in the dispersion medium so that the volume fraction in the solid content of the paint was 80%, and the mixture was stirred and dispersed using a high-speed mixer for 20 minutes 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 of the can body made of TFS material obtained by welding the above various paints using the method previously described were sprayed with an air spray gun to a width of about 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 220° C., and the can body with the seam portion covered was preset. Subsequently, 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 processability were also investigated using the current value during constant voltage electrolysis and copper sulfate trial testing.

Next, after flanging the can body with the seam covered by the above method, a TFS lid for a can with a nominal diameter of 65.3 mm and having an epoxy-phenol coating layer on the inner and outer surfaces was double-sealed. Two types of boiled salmon and tomato sauce were each packed in the resulting empty cans, and a TFS lid similar to the above was double-sealed using an X air-sealing machine. These canned goods each cost 118
After heat sterilization at ℃ for 90 minutes and storage at 37℃ for 1 year, the amount of hydrogen was measured in 100 cans arbitrarily extracted from 100 cans for each sample, and the 500 cans randomly extracted were opened and the can body joints were examined. The corrosion status of the parts was investigated. The results are shown in Table 3.

Here, the epoxy-phenol resin solution (Il) was used as the thermosetting paint.As the thermoplastic resin,
Polybutylene terephthalate (softening point measured by ig method 222℃ carbonyl group concentration 9l7mgq equivalent/10
The above resin pellets were freeze-pulverized using liquefied nitrogen to obtain a powder with an average particle size of about 25 μm, and this was added to the above coating material so that the volume ratio of the solid content of thermoplastic resin and thermosetting resin was adjusted. They were mixed so as to obtain the values shown in Table 4, and stirred for 20 minutes using a high-speed mixer to disperse and obtain seam correction paint f. Table 4 shows the contact angles of these paints on a glass plate at 25° C. as measured by the method described above.

Next, this seam correction paint was welded using the method described above, and the dried paint film was sprayed onto the circular and outer surfaces of the seam area of the TFS material using an air spray gun. After spray painting to a thickness of 40 to 60 μm, the can body was abraded for 3 minutes in a hot ML drying oven at 220° C. to obtain a can body with the joint portion covered. The dispersion state of the thermoplastic resin powder in this cured coating film was observed using the method shown above, and the coating properties and workability were further examined using the current value during constant voltage electrolysis and the copper sulfate test 1iVc! I looked into it.

Furthermore, after performing 7-lung processing on 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 coating film on the inner and outer surfaces was double-sealed. Two kinds of boiled salmon and tomato sauce were packed in the empty cans, and the TFSM was 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 1 year, after which 10 out of 100 cans were arbitrarily extracted from each sample and hydrogen i
Furthermore, 50 randomly selected cans were opened and the state of corrosion at the can body joint was examined. The respective results are shown in Table 4.

Example 5 The above epoxy urea resin solution (
It) and nylon 12 with an average particle size of 80μ obtained by freeze-pulverizing pellets in advance as a thermoplastic resin (softening point 178 ° C by ring and ball method carbonyl group concentration 5O8 mgq
Right! / 100 g) were mixed so that the volume fraction of the thermoplastic resin in the solid content was 20%, and the mixture was stirred and dispersed for 20 minutes using a high-speed ξ mixer to produce a seam correction paint.

When the contact angle of this paint on a glass plate was measured, it was found that 27
．． It was 8 degrees.

Next, a tin plate with a thickness of 0.28111 was coated with epoxy urea paint (a mixture of epoxy resin and butyl ether urea formaldehyde resin in a weight ratio of 8:1) and baked in the same manner as described above. Blank length of board 206-40! I11 plank length 1) 125.4
It was cut into zero-strength body blanks, and a welded tin can body was made according to the method described above. The above paint was spray-coated on the circular surface and outer surface of the joint portion of the obtained can body in the same manner as in the previous example and baked to obtain a can body with the joint portion covered.

When the cross-sectional structure of this coated coating film was observed using the method described in Reference Example 8-+11, it was observed that the nylon 12 particles were dispersed in an extremely orderly manner without blocking in the epoxy urea cured coating film. It was done. Next, we examined the covering properties and processability of this coating using the same method as in the previous comparative example, and found that the unprocessed parts and bent parts were completely covered, and there were no cracks or cracks caused by processing. I couldn't see it at all.

Furthermore, the can body obtained by the above method was flanged by a conventional method, and then coated with a nominal inner diameter of 65.8 tny, having an epoxy urea coating on the inner and outer surfaces, a tin lid for the can, and an epoxy-phenol coating on the inner and outer surfaces. Double-tighten each eyelid with a membrane, back the resulting empty aerosol can with DiGlas Cleaner and Washing Step 9 using the usual method, attach a mounting cup, and store at 50°C for 3 and 6 months. After that, each can was opened and the presence or absence of corrosion at the seam of the can 111i1 was observed.

As a result, no corrosion was observed in the joints in any of the above cases, and the results were extremely good.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view of the main parts of the seam-coated can of the present invention, in which 1 is a metal layer for sealing, 2 is a seam, 5 is a protective material, 6 is a thermosetting resin, and 7 is a seam-covered container. Thermoplastic resin particles are shown respectively.

Claims (1)

[Claims] 1. A seam formed by applying a resin paint to or near the inner seam of a can body that has a seam on the side, and then baking this paint to form a coating film that covers the seam. In the method for producing a can coated with
and a dispersoid of thermoplastic resin particles having a ring and ball softening point of The paint was applied on a glass plate at 25°C with a temperature of 0.2
It is characterized in that it has a contact angle of 19 to 45 degrees when measured 1 minute after dropping with a sample amount of mm^3, and that the formed coating film is baked under conditions in which the thermoplastic resin softens or melts. A method of manufacturing cans with covered seams. 2. The thermoplastic resin is a carboxylic acid, a carboxylate,
Carbonyl group based on carboxylic acid anhydride, carboxylic acid ester, carboxylic acid amide, ketone, carbonate ester, urea, urethane, etc. in main chain or side chain 12 to 1400
2. The method of manufacturing a seam-coated welded can as claimed in claim 1, wherein the resin has a concentration of meq/100g of polymer. 3. The method for manufacturing a welded can according to claim 1 or 2, wherein the thermoplastic resin is polyester, polycarbonate, polyamide, ionomer, or acid-modified polyolefin. 4. The thermosetting resin according to any one of claims 1 to 3, wherein the thermosetting resin comprises 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. Method for manufacturing welded cans.