JP2002102967A - Tapelike resin film covering method to can barrel joint part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly stick a tapelike resin film to a joint part, fill up the step difference of the joint part without a gap to sufficiently cover the metal exposure face, and prevent the gas barrier property of the tapelike resin film itself from being deteriorated more than necessity, in covering the inner face side of the joint part of a can barrel. SOLUTION: As the tapelike resin film 2, a double-layered film provided with a lower layer of a thermoplastic resin having a melting point of 175-225 deg.C to become a sticking face to the can barrel, and a upper layer of the biaxially oriented thermoplastic resin having the melting point of 195-255 deg.C, wherein the melting point of the upper layer resin is higher by 20-60 deg.C than the melting point of the lower lager resin, and the thickness of the lower layer resin exceeds the 60% of the total thickness of the film, is used to preheat the joint part of the can barrel 1. The heating temperature in this process is not within a temperature range from the adhesion start temperature to the melting point of the lower layer resin, and the heating temperature in the process of post-heating of the joint part of each can barrel 1 stuck with the tapelike resin film 2 is set at the temperature or higher than the melting point of the lower layer resin and less than the melting point of the upper layer resin, and the post-heating process is conducted in a state of nonpressing against the stuck tapelike resin film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating the inner surface of a joint of a welded can body with a thermoplastic resin film in the form of a tape, and more particularly, to a method for covering a step in the joint by melting the resin film. The present invention relates to a method for coating a tape-shaped resin film on a can body joint, which can sufficiently cover the gap caused by the gap and prevent gas barrier properties of the tape-shaped resin film itself from being impaired.

[0002]

2. Description of the Related Art In a welding can body formed into a cylindrical body by joining both ends of a metal plate blank by resistance seam welding, usually, a metal plate is printed or painted in a flat state. Although it is cut into blanks for one can and formed into a cylindrical body, printing or painting up to the joints of the blank will not be able to conduct electricity during welding, and resistance seam welding will be performed. Since it is no longer possible to print or paint the part to be joined and its vicinity, the joint and its vicinity are protected against the welding can body formed from the blank into the tubular body by welding. It becomes necessary to apply painting.

[0003] However, the joining portion of the welding can body is a superposed portion in which both ends of the blank are overlapped.
In that part, a step (for example, when the thickness of the blank is 0.18
mm, a step of 0.072 mm) is formed, and in a large-sized thick can, such a step is larger (for example, when the thickness of the blank is 0.32 mm,
In any case, if the metal surface of the joint having such a step is covered by painting, filling this step with paint requires a considerably thick coating. .

[0004] For this reason, it is necessary to devise the paint itself so that the thick paint does not flow, or to prevent bubbles from being generated inside the paint film, so that the paint cost and equipment cost increase. No matter how thick it is applied, the coating will be thinner at the part where the metal surface at the corner of the step protrudes,
In particular, on the inner surface side of the can that is always in contact with the contents, there is a possibility that the metal surface is exposed at the corners of the step and corroded.

Therefore, in order to solve such a problem, a protective film is applied uniformly and thickly by attaching a tape of a thermoplastic resin film which is relatively thicker than the coating film to the joint. Various techniques have been proposed in the past.

That is, for example, Japanese Patent Publication No. 62-4913
In Japanese Patent Publication No. 2, a tape-shaped resin film (correction film) is continuously pressure-bonded to a joint portion of a plurality of can bodies conveyed in tandem by a sticking roll of an elastic body and a support roll.
Regarding the method of cutting with a cutter, laser or melting of film between can bodies, the distance between adjacent can bodies is made shorter than the length of the contact part between the adhering roll and the support roll, and the joining part of the preceding can body is cut. While the tail end is pressed between the application roll and the support roll, the head end of the joining portion of the subsequent can body is caused to enter between the application roll and the support roll, so that the application roll A technique is disclosed in which a can body is constantly brought into contact with the can body.

Further, in the above-mentioned publication, a tape-like resin film having a multilayer structure including a heat-sealing layer and a barrier layer is used, and a can-body joining before attaching the tape-like resin film is performed. The part is heated to a temperature (160 to 200) higher than the softening point of the resin of the tape-shaped resin film by high-frequency induction heating.
C), and a technique of post-heating the can body joint after applying the tape-shaped resin film to a temperature (270-280 ° C.) higher than the melting point of the resin of the tape-shaped resin film. ing.

Japanese Unexamined Patent Publication (Kokai) No. 61-74742 discloses a can preheated to a temperature higher than the melting temperature of a tape-shaped resin film while continuously transporting the can body with the joints aligned on a straight line. A tape-shaped resin film automatically fed out by the transport action of the can body, on the inner surface side of the body joint,
After bonding by a pair of upper and lower pressing rolls arranged inside and outside the can body, the joint is reheated at a temperature lower than the preheating temperature. The conveying speed from the resin film pasting process to the completion of the reheating process is slightly reduced to shorten the interval between the can bodies at the time of film adhering, and the heating speed of the can body after the reheating is completed is reheated. Faster than the transfer speed to completion,
There is disclosed a technique in which a tape-shaped resin film in a connected state is automatically cut by forcibly increasing a can body interval.

[0009] In Japanese Patent Publication No. 2-32060,
In a pressing state in which the entire length of the tape-shaped resin film is pressed inside the joining portion (welded portion) of the can body by a pressing bar, the temperature of the tape-shaped resin film is set to a softening temperature + 20 ° C. or more in the first step, and the first step After the second step, the pressing state is maintained, the softening temperature is set to + 20 ° C. or lower in the second step, and after the second step, the above-mentioned pressed state is released in the third step.

Japanese Patent Application Laid-Open No. 63-192525 discloses a technique suitable for manufacturing a relatively large welding can having a diameter of 150 mm or more. A welding step of forming, a heat bonding step of heat bonding the tape-shaped resin film to the joint of the welding can body, a heating step of heating the heat-bonded tape-shaped resin film in a pressed state, In a manufacturing process including a cooling step of cooling the tape-shaped resin, a technique of repeatedly pressing the tape-shaped resin with a pressing body (roll) many times in the heating step has been disclosed. Using a multilayer film composed of a heat-sealing layer and a barrier layer as a tape-like resin film, or setting the temperature at the time of heat sticking to 230 ° C. which is equal to or higher than the melting point of the resin of the heat-sealing layer, and thereafter Heating It has also been disclosed that heating from 230 ° C. in a heating step by Le until descends 100 ° C..

[0011]

Among the above-mentioned conventional methods of coating a tape-shaped resin film on a joint portion of a can body, Japanese Patent Publication No. 62-49132 and Japanese Unexamined Patent Publication No.
In the method disclosed in Japanese Patent Application Laid-Open No. 1-74742, the heating temperature of the can body joint is set to be higher after heating the film than before heating. In either case, the heating temperature before attaching is higher than the heating temperature after attaching the film, once the temperature is higher than the melting point of the tape-shaped resin film (composed of a heat-sealing resin layer and a barrier resin layer. Is heated to a temperature higher than the melting point of the resin of the barrier resin layer).

Although the step of the can body joint can be filled without forming a large gap by melting the resin of the tape-shaped resin film, the tape-shaped resin film which is elongated and biaxially stretched can be filled. If the axis orientation is eliminated, and if a barrier layer made of a metal foil is not provided, the gas barrier properties of the tape-shaped resin film will be reduced.

On the other hand, according to the method disclosed in Japanese Patent Publication No. 2-32060, the temperature for heating the can body joint is set to a temperature higher than the melting point of the resin in contact with this joint, and to a temperature lower than that. It is supposed that any of the cases of temperature may be used, but in any case, it is a method of sticking the tape-shaped resin film to the can body joint by the pressing bar,
Since the tape-shaped resin film is intermittently adhered to the joint portion of the can body, it is an impractical method to continuously perform the actual can-making process.

In the method disclosed in Japanese Patent Application Laid-Open No. 63-192525, after a tape-shaped resin film is adhered to a joint portion of a can body, the resin adhered to the joint portion is still in a molten state. In the meantime, a joint having a step is repeatedly and repeatedly pressed by a pressing body (pressing roll) (the pressing force sometimes acts obliquely due to the step). It has been found that there is a problem that the tape-shaped resin film is easily shifted from the position where the tape-like resin film is attached.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems. Specifically, when covering the inner surface of the joining portion of a can body with a tape-like resin film, the tape-like resin film is joined. Not only can be properly adhered to the part, but also the gap of the joint part can be filled without gaps, and the metal exposed surface can be sufficiently covered, and the gas barrier property of the tape-shaped resin film itself is not unnecessarily impaired It is an object to do so.

[0016]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method in which a welding can body formed in a cylindrical body is continuously conveyed at predetermined intervals in a line in the axial direction of the can body. ,
A step of preheating the joint of the can body, a step of continuously applying a series of supplied tape-like resin films to the inner surface side of the joint of each can body by a pressure roll, and a series of tape-like resin. After performing the step of removing the excess portion connected between the respective can bodies of the film, further, by performing the step of post-heating the joint portion of each can body to which the tape-shaped resin film is adhered, In the method of coating the inner surface side of the can body joint with a tape-shaped resin film, as a tape-shaped resin film,
A lower layer made of a thermoplastic resin having a melting point of 175 to 225 ° C., which serves as a surface to be bonded to the can body joint, and an upper layer made of a biaxially oriented thermoplastic resin having a melting point of 195 to 255 ° C. Is 20 to 60 ° C. higher than the melting point of the lower resin,
Using a multilayer film in which the thickness of the lower layer resin exceeds 60% of the total thickness of the film, the heating temperature in the step of preheating the joint of the can body is calculated from the adhesion starting temperature of the lower layer resin to the melting point. The heating temperature in the step of post-heating the joint portion of each can body to which the tape-shaped resin film is adhered is set to a temperature equal to or higher than the melting point of the lower resin and lower than the melting point of the upper resin. At the same time, the step of heating is performed in a non-pressed state on the attached tape-shaped resin film.

In carrying out the above method, the can diameter is 40 mm to 100 mm and the plate thickness is 0.10 m
For a can body of a small can having a size of m to 0.25 mm, it is effective to use a tape-shaped resin film having a width of 5 to 15 mm and a total thickness of 15 to 40 μm,
Can diameter is 100mm ~ 400mm and thickness is 0.25mm ~
For a can body of a large can that is 0.40 mm, the width is 15
It is effective to use a tape-like resin film having a thickness of up to 35 mm, an overall thickness of 40 to 70 μm, and a thickness of the lower layer resin exceeding 80% of the total thickness of the film.

According to the above-described method of coating the tape-shaped resin film on the joint portion of the can body, the tape-shaped resin film has a multilayer structure, and the melting point of the upper resin is higher than that of the lower resin. When a tape-shaped resin film is thermally bonded to a can-body joint, the resin film adheres to the pressure-bonding roll and hinders workability even if the resin film is easily adhered to the can-body joint. If the resin film adheres and adheres to the pressure bonding roll, the resin film is peeled off from the joint portion of the can body.).

In the step of thermally bonding the tape-shaped resin film to the joint of the can body, the tape-shaped resin film is not melted (the lower layer having a low melting point is not melted).
By removing excess portions connected between the can bodies of the tape-shaped resin film in the next step, the tape-shaped resin film is cut well, and the molten resin film is cut. The cut ends are not unsightly (for example, due to the fact that the molten resin extends to pull the yarn) as in the case where the cutting is performed.

In the step of post-heating the joint portion of each can body to which the tape-shaped resin film has been adhered, the upper surface of the tape-shaped resin film can be adhered to the can body joint portion without being melted. By melting only the lower layer, the step of the can body joint can be filled without gaps by melting the lower layer resin, and the adhesion between the tape-shaped resin film and the can body joint can be improved. As a result, the joint of the can body can be sufficiently covered.

In the subsequent heating step, since the temperature of the upper layer resin has not reached its melting point, the biaxial orientation of the biaxially stretched upper layer resin can be maintained as it is, The gas barrier property of the resin film is not unnecessarily reduced. In addition, since there is no step of pressing the tape-shaped resin film with a roll after the lower layer resin is melted, the tape-shaped resin film is displaced from the position where the tape is once adhered, and the joint portion is displaced. Is not incomplete.

With regard to the removal of an extra portion connected between the can bodies of a series of tape-shaped resin films, in the case of a small-can can body that can be welded at a high speed, the conveying speed is set to 50 m / min. At higher speeds, conventional cutters and laser cutting are difficult in terms of timing, and cutting by forcibly enlarging the can body interval by changing the transport speed makes it possible to cut neatly at the edge of the can body. Although edge processing is necessary in the post-process, the method as described in the above-mentioned claim 3 employs a method as described in claim 3 above, so that an extra tape-shaped resin film can be removed from between the can bodies even at high speed. Parts can be removed cleanly.

On the other hand, in the case of a large can having a welding speed of 30 m / min or less, a conventional cutter or laser cutting can be used in terms of timing. Because of using a resin film, it is practically difficult to cut at once along the front and rear edges of the can body. It is desirable to adopt a method as described in claim 3 above.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a method for coating a tape-shaped resin film on a can body joint according to the present invention will be described in detail with reference to the drawings. FIG. 1 schematically shows a can body manufacturing line for carrying out the method of the present embodiment, and FIG. 2 shows a tape removing step in a film removing step of the can body manufacturing line. Each of the steps (A) to (C) for removing an excess portion of the resin film is shown in FIG. 3, and FIG. 3 shows (A) a cross-sectional structure of the tape-like resin film, and (B) affixing to a can body joint. (C) shows the state of the film adhered to the can body joint after the post-heating.

The method of this embodiment is carried out in a can body manufacturing line in which each can body is continuously conveyed at predetermined intervals in a line in the axial direction of the can body. As shown in FIG. 1, from a can body welding step of forming a substantially cylindrical blank into a welded body 1 of a cylindrical body by seam welding using a pair of welding rolls 3 and 4, in a traveling direction of a can body conveying path. Along the joint of the can body 1, the high frequency induction heating device 5
A pre-heating step of heating by heating, and a film attaching step of continuously applying a heat to a series of supplied tape-shaped resin films 2 on the inner surface side of a joint portion of each can body 1 by a pair of pressure rolls 6 and 7. Each can body 1 of a series of tape-shaped resin films 2
The excess part connected between the two is cut off by the heat pressing roll 8 and the pressing roll 9, and the scraper 10 and the suction device 1 are separated.
And a film removing step for eliminating in step 1.

In addition, guide rollers 12 and 13 for guiding the tape-shaped resin film 2 fed from a bobbin (not shown) are provided on the transport path leading to the pair of pressure rolls 6 and 7, Holding rolls 14 and 15 for holding the can body 1 are provided in a transport path extending downstream from the roll 8 and the pressing roll 9.

In each step of such a can body production line,
First, a can body blank formed into a substantially cylindrical shape (cylindrical or square cylindrical shape) and both ends thereof are overlapped is overlapped by a guide arm (not shown) so that the overlapping portion of each can body blank is aligned on the same line in the transport direction. Are continuously supplied to welding rolls (electrode rolls) 3 and 4 at a certain interval from each other, and the can body blanks are welded by the welding rolls 3 and 4 in the can body welding step. The overlapping portion is seam-welded to form a cylindrical can body 1.

The can body 1 having the overlapped portion seam-welded is transported by a belt from both sides (not shown) to each can body 1.
Of the high-frequency induction heating device (high-frequency induction heating coil) 5 are continuously conveyed at a constant speed in a state of being spaced apart from each other by a joint portion (weld seam portion) in the conveying direction. In the preheating step when passing below,
The joint of the can body 1 and the vicinity thereof are heated by induction heating by the high-frequency induction heating device 5.

In the case of a can body of a small can such as a 190 g can or a 350 g can, the conveyance speed of the can body 1 (ie, the welding speed) should be 50 m / min or more. However, in the case of a large can body such as a gallon can, the speed is 30 m / min or less.

On the other hand, a state in which a series of tape-shaped resin films 2 fed from a bobbin not shown are continuously fed at substantially the same speed as the transport speed of the can body 1 and guided by guide rolls 12 and 13. And is guided to the inner surface side of the joint portion of the can body 1.

Although not shown, a series of tape-shaped resin films 2 fed out from the bobbin are, for example, as described in Japanese Patent Publication No. 5-49373, a substantially cylindrical can body. A guide roll axially supported by the downstream end of the guide arm in the transport direction through a groove formed along the transport direction at the bottom of the guide arm formed in the transport path of the blank and the seam-welded can body. The guide roller 12 is guided from the guide roll 12 to the vicinity of a joint portion of the can body 1 via a guide roll 13 located at an upper portion in the can body.

In the film sticking step using a pair of pressure rolls 6 and 7 on the inner side and the outer side of the can body 1,
The tape-shaped resin film 2 guided to the vicinity of the junction is bonded to the inner surface side of the junction of the can bodies 1 that are continuously conveyed at intervals by the pressing rolls 6 and 7 to be heated. After being adhered, each of the can bodies 1 is connected to each other by the heat-pressing roll 8, the pressing roll 9, the scraper 10, and the suction device 11 while the respective can bodies 1 are connected to each other by the tape-shaped resin film 2. The tape-like resin film is transported to a film removing step for cutting off and removing an excess portion.

The pressing force of each of the pair of pressing rolls 6 and 7 and the heating and pressing rolls 8 and 9 is 100 to 200 N.
7 and the pressing roll 9 are not heated, and the heat-pressing roll 8 is in a temperature range from a temperature exceeding the melting point of the lower resin to a temperature not exceeding the melting point of the upper resin (specifically, the melting point of the lower resin + 1).
(0 ° C.).

In the film removing step for removing an excess portion of the tape-shaped resin film, a heat-pressing roll 8 made of metal and heated and a heat-resistant elastic material such as rubber, synthetic rubber or synthetic resin are used. An excess portion of the tape-shaped resin film connected between the can bodies 1 is cut off by the formed pressing roll 9, and then the separated resin film piece cut and adhered to the heat-pressing roll 8 is scraped by a scraper. It is removed by peeling it off at 10 and sucking it with a suction device 11.

That is, in this film removing step, as shown in FIG. 2A, each can body 1 in which the tape-shaped resin film 2 is adhered to the inner surface of the joint by the pressure rolls 6 and 7 is provided. The tape-shaped resin film 2 between the can body 1B and the preceding can body 1A is first cut off while being pressed against the rear end edge of the preceding can body 1A by the pressing roll 9, and the pressing roll 9 By being pressed against the heat-pressing roll 8, it is stuck to the heat-pressing roll 8 by heat.

Next, the heat pressing roll 8 and the pressing roll 9
2B and the advance of each can body 1A, 1B, as shown in FIG. 2B, each can body 1A, 1
In a state where most of the portion between B is pasted on the heat-pressing roll 8, the tape-shaped resin film 2 between the can bodies 1A and 1B is pressed against the front end edge of the succeeding can body 1B by the pressing roll 9. It is separated in the state where it was done.

The extra tape-shaped resin film piece 2a cut off from the space between the can bodies 1A and 1B and attached to the heating and pressing roll 8 is shown in order from FIG. 2 (C) to FIG. 2 (A). As described above, the heating and pressing roll 8 is carried to the position of the scraper 10 by the rotation of the heating and pressing roll 8, and is peeled off from the heating and pressing roll 8 by the scraper 10 as shown in FIG. Be eliminated.

On the other hand, in the can body 1B from which the tape-shaped resin film 2 between the preceding can body 1A and the tape-shaped resin film piece 2a has been removed, as shown in FIG. As a result, the adhesiveness of the tape-shaped resin film 2 press-bonded to the bonding portion with the bonding portion of the can body 1 </ b> B is strengthened by the heat of the heating and pressing roll 8 and the pressing of the heating and pressing roll 8 and the pressing roll 9. The Rukoto.

The can body 1B in which the adhesiveness of the tape-shaped resin film 2 is strengthened as described above is such that the tape-shaped resin film 2 between the subsequent can body 1C and the preceding can body 1A as described above. After being removed in the same manner as in the case of the tape-shaped resin film 2 between them, as shown in FIG. 1, the opposite side of the joining portion of the can body is carried out of the apparatus while being held by the can body holding rolls 14 and 15. Is done.

In the film removing step, 19
When the welding speed (conveying speed) is set to 50 m / min or more in a can body of a small can such as a 0 g can or a 350 g can, cutting by a cutter or a laser cannot be performed in a timely manner. When the welding speed (transport speed) is 30 m / min or less in a can body of a large can such as a gallon can, cutting with a cutter or a laser is possible in terms of timing. However, as described later, by using a tape-shaped resin film having a large width and a large thickness, it becomes difficult to cut it neatly at a time, so it is desirable to employ the above method. .

In the can body manufacturing line on the downstream side of the film removing process in the transporting direction, furthermore, although the specific arrangement of the apparatus is not shown, a printing lot mark (manufacturing factory name, manufacturing The line name, the date of manufacture and the time of 10 minutes or less) on the outer surface of the can body joint by ink-jet printing, and the outer surface of the can body joint from a thermosetting resin known by a spray coating device. A step of applying a transparent paint consisting of, and heating with hot air in an oven, drying the coating film applied on the outer surface side of the can body joint, and a tape-like attached to the inner surface of the can body joint A step of post-heating the resin film and a step of rapidly cooling the joint of each can body after the post-heating are sequentially provided.

In each step on the downstream side of the transfer,
Each can body which was printed on the outer surface side of the joint in the printing process and spray-coated with transparent paint on the outer surface side of the joint in the painting process,
While being transported upward by the transport conveyor and placed directly on the net conveyor from a single row of transport paths in the can body axis direction up to that time, while being introduced into the oven in that state, while being transported in the upright state In order to dry the coating film on the outer surface side of the can body joint and to melt the lower layer resin of the tape-shaped resin film on the inner surface side of the can body joint, it is heated in an oven by hot air and then taken out of the oven Each can body was
By immediately blowing cold air (20 ° C. or lower, preferably 15 ° C. or lower), the lower resin is rapidly cooled to a temperature lower than the melting point.

The method for coating the tape-shaped resin film of the present embodiment, which is carried out in the can body production line by the above steps, firstly includes a blank for forming a can body,
The tape-shaped resin film itself for covering the inner surface side of the joining portion (weld seam portion) of the welding can body formed from such a blank will be described below.

The blank for the can body supplied to the can body welding step is a blank in which a polyester resin film such as polyethylene terephthalate is adhered to both sides of a portion except a portion to be welded and a portion in the vicinity thereof. As a polyester resin film to be attached to the blank for the body, a printing ink layer, which is repeatedly printed in the longitudinal direction with a trademark design, is attached on one side of the film at intervals of 1 to 10 mm in the width direction, and is adhered thereon. In a state in which the agent layer is applied, a polyester resin film having a multilayer structure in which a plurality of strips are formed with a width slightly smaller than the circumferential width of the can body and a thermosetting coating layer is formed on the other surface. Along with the preparation, a polyester resin film having only one side coated with an adhesive is prepared.

Then, the strip-shaped ultra-thin tin-plated steel sheet is heated in advance to a temperature slightly higher than the thermal bonding temperature of the adhesive applied to the polyester resin film, and one side of the steel sheet is bonded to the printing ink layer. The adhesive layer side was turned to the steel sheet while cutting and removing the non-printing film portion having a width of 1 to 10 mm where the printing ink layer or the like was not applied to the polyester resin film having a multilayer structure having an agent layer. In this state, a set of sticking rolls is used to press and adhere to the steel sheet, and further, on the other surface of the steel sheet, a polyester resin film coated with only an adhesive is 1 to 10 mm.
While the width portion is being cut and removed, the steel sheet is pressed and bonded to the steel sheet by a pair of sticking rolls with the adhesive side facing the steel sheet. At this time, the two non-sticking portions of the polyester resin film are adjusted so that the non-sticking portions coincide with the back of the steel sheet in the front and the sticking.

The steel sheet having the polyester resin film adhered on both sides as described above is cut into a size for each can in a cutting step to form a blank for the can body. The ink layer is supplied to the can body welding step in a state of being formed into a substantially cylindrical shape (cylindrical or rectangular cylindrical shape) such that both ends thereof are overlapped so that the surface with the ink layer is on the outside.

With respect to the tape-shaped resin film for covering the inner surface of the joint portion of the welding can body, polyolefin resins such as polyethylene, modified polyethylene, polypropylene, and modified polypropylene can be used as the resin to be used. When a polyester resin such as polyethylene terephthalate is used as the inner protective film as described above, it is preferable to use a polyester resin.

The usable polyester resin is a saturated polyester comprising a dicarboxylic acid component and a diol component. Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid and naphthalenedicarboxylic acid. Aliphatic carboxylic acids such as adipic acid, sebacic acid and azelaic acid;
As the diol component, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, decamethylene glycol, neopentyl glycol, 1.4-
Cyclohexanedimethanol can be mentioned.

In the method of this embodiment, a 190 g can
For small cans such as 0g cans, can diameter is 40mm-100m
For a can body having a sheet thickness of 0.10 mm to 0.25 mm in m, a tape-like resin film having a film thickness of 15 to 40 μm and a film width of 5 to 15 mm is used,
For large cans such as gallon cans, with a can diameter of 100mm to 40mm
For a can body having a thickness of 0 mm and a plate thickness of 0.25 mm to 0.40 mm, a tape-shaped resin film having a film thickness of 40 to 70 μm and a film width of 15 to 35 mm is used.

As shown in FIG. 3A, the resin film has a lower layer 21 made of a thermoplastic resin having a melting point of 175 to 225 ° C. and an upper layer 21 made of a biaxially oriented thermoplastic resin having a melting point of 195 to 255 ° C. 22 having a two-layer structure, wherein the melting point of the upper resin 22 is lower than that of the lower resin 21.
The lower layer 21 which is 20 to 60 ° C. higher than the melting point of the film 2 and serves as a surface to be adhered to the inner surface side of the can body joint is so formed that its thickness exceeds 60% of the total thickness of the film 2. Especially, for a can body of a large can such as a gallon can, the thickness of the lower layer 21 is 80% of the total thickness of the film 2.
It is formed so as to exceed.

The melting point of the upper resin 22 and the melting point of the lower resin 21 need to be different from each other by 20 to 60 ° C. In particular, it is easy to control the temperature in pre-heating and post-heating, and moreover, From the viewpoint of facilitating the adhesion of the resin film, facilitating the cutting of the resin film, and improving the adhesiveness of the resin film, the difference in the melting point between the resins in both layers is 30 to 50.
C. is preferred.

Regarding the melting point of the resin, polyester (an alcohol having two alcohol components [—OH groups]
Resin formed by polymerizing a carboxylic acid having two carboxylic acid components [-COOH group]) has a specific melting point,
By slightly changing the structure of a single resin (homopolymer) such as polyethylene terephthalate (containing ethylene terephthalate) or polybutylene terephthalate (containing butylene terephthalate), the melting point of the resin can be improved. Can be changed.

For example, a polyethylene terephthalate resin containing ethylene terephthalate as a sole component has a melting point of about 255 ° C.
% Polyethylene terephthalate / isophthalate copolymer having a melting point of 2%.
35 ° C., and when the constitutional ratio of the copolymer becomes 80:20, the melting point becomes 211 ° C., and further, the constitutional ratio becomes 70:30.
, The melting point becomes 170 ° C.

The melting point of the polybutylene terephthalate resin containing butylene terephthalate as a sole component is about 225 ° C., but a polybutylene terephthalate / isophthalate copolymer having 90% butylene terephthalate and 10% isophthalate is used. The melting point is 208 ° C., and the melting point is 190 ° C. if the constituent ratio of the copolymer is 80:20. Further, in the case of the polyethylene terephthalate / adipate copolymer, the melting point is 238 ° C. if the constituent ratio of ethylene terephthalate and ethylene adipate is 90:10, and the melting point is 180 ° C. if the constituent ratio is 70:30. Become.

Incidentally, the biaxial orientation of the upper layer resin of the tape-shaped resin film is usually controlled when a film is produced from a crystalline resin in order to maintain a uniform thickness, a small thickness and a predetermined strength. Is stretched (stretched) in the machine direction and the transverse direction at a temperature lower than the melting point and at or above the glass transition point, so that it is inevitably biaxially stretched. In the tape-shaped resin film, both the upper and lower layers are naturally biaxially oriented. However, since the method of the present invention does not specify the method of manufacturing the tape-shaped resin film, regardless of the orientation of the lower layer, the upper layer is What is necessary is just to be biaxially oriented.

The method for coating a tape-shaped resin film of the present embodiment by using the tape-shaped resin film having a two-layer structure as described above will be described below. In the pre-heating step of heating the part, the heating temperature is within the temperature range from the adhesion start temperature (softening start temperature) of the lower resin of the tape-shaped resin film to the melting point. In the film removing step of heating, the temperature of the heat-pressing roll 8 is set to a temperature range from a temperature exceeding the melting point of the lower layer resin to a temperature range not exceeding the melting point of the upper layer resin, and further, for each of the can bodies to which the tape-shaped resin film is adhered. In the post-heating step of heating the joint with hot air in an oven, the heating temperature is set to a temperature not lower than the melting point of the lower resin of the tape-shaped resin film and lower than the melting point of the upper resin. It is set to.

That is, specifically, the melting point of the lower layer of the tape-shaped resin film is 175 to 225 ° C. (Specific example is 205
° C), the lower layer has an adhesion initiation temperature of 130 to 190 ° C (a specific example is 165 ° C), the upper layer has a melting point of 195 to 255 ° C (a specific example is 245 ° C), and the melting point of the upper layer resin is lower than the melting point of the lower layer resin. In the pre-heating step, the temperature of the can body joint is 130 to 225 ° C. (specific example is 185 ° C.). Heating, and in the post-heating step, the temperature of the can body joint is 175-175.
Heating is performed to 255 ° C. (a specific example is 225 ° C.).

According to the tape-like resin film coating method of the present embodiment based on the above-described tape-like resin film having a two-layer structure and the heating conditions in each step, the tape-like resin film has a two-layer structure, By making the melting point higher than the melting point of the lower layer resin, when the resin film is thermally adhered to the can body joint, it is easy to thermally adhere to the can body joint and hard to adhere to the pressure roll. It is possible that the resin film adheres to the pressure roll and hinders workability (when the resin film sticks and adheres to the pressure roll, the resin film is peeled off from the joint of the can body). It can prevent getting up.

Further, in the step of thermally bonding the tape-shaped resin film to the joint portion of the can body, since the tape-shaped resin film is not melted (the lower layer having a low melting point is not melted), When removing the excess part connected between the can bodies of the resin film, the tape-shaped resin film can be cut well, as in the case of cutting the molten resin film. (For example,
The cut ends are not unsightly (such as due to the fact that the molten resin stretches the yarn).

In the film removing step for removing an excess portion of the tape-shaped resin film, the tape-shaped resin film is sandwiched between the heat-pressing roll and the pressing roll. By heating the resin from a temperature exceeding the melting point of the resin to a temperature not exceeding the melting point of the upper resin, while not heating the pressing roll, the lower resin in contact with the heat-pressing roll is melted, and the upper resin contacting the pressing roll is melted. Can be prevented from melting, and an excess portion of the resin film can be securely adhered to the heat-pressing roll without adhering the resin film to the pressing roll.

On the other hand, in the step of post-heating the joint portion of each can body to which the tape-shaped resin film has been adhered, the upper surface of the tape-shaped resin film can be adhered to the can-body joint portion without melting the upper layer. By melting only the lower layer, the state shown in FIG. 3 (B) is changed to the state shown in FIG. 3 (C). It can be filled without gaps, and can improve the adhesion between the tape-shaped resin film and the can body joint,
The exposed metal surface of the can body joint can be sufficiently covered.

In such a post-heating step, since the temperature of the upper resin does not reach its melting point, the biaxial orientation of the biaxially stretched upper resin can be maintained as it is. Without reducing the gas barrier properties of the tape-shaped resin film more than necessary, and
Since the tape-shaped resin film is not pressed by a roll or the like, even if the resin in the lower layer is melted, the tape-shaped resin film does not shift from the position where the tape-shaped resin film is stuck.

In this embodiment, a 190 g can or 35 g
For a can body for a small can such as a 0 g can, the overall thickness of the tape-shaped resin film is set to 15 to 40 μm, and the entire resin film is prevented from being too thick when the joint of the can body is covered. Although the thickness is suppressed, the lower layer of the resin film is made to be more than 60% of the total thickness,
The step at the joint portion of the can body can be sufficiently filled with the molten lower layer resin.

On the other hand, for a can body for a large can such as a gallon can, the total thickness of the tape-shaped resin film is 40 to
By setting the thickness to 70 μm, even if the plate thickness is large and the step of the can body joint is large, it is possible to sufficiently fill the step of the can body joint with one press bonding, and further, the By setting the thickness to be more than 80% of the thickness of the entire film, it is possible to more reliably fill the steps with the molten lower layer resin, and to increase the thickness of the entire resin film. Also, when removing an excess portion of the resin film, the resin film is easily cut. In FIGS. 3 (B) and 3 (C), the ratio of the thickness of the resin film to the thickness of the can body is different from the actual one for easy understanding in the drawings.

Further, in the method of the present embodiment, after the step of post-heating the joint portion of each can body to which the tape-shaped resin film is attached, a step of rapidly cooling the joint portion of each can body is provided. By this, the melted lower resin is rapidly cooled to become amorphous, thereby further improving the adhesiveness of the resin film to the can body joint.

Further, according to the method of the present embodiment, in the can body manufacturing line, the excess portion of the tape-shaped resin film connected between the can bodies is cut off by using a heat-pressing roll arranged in the conveying path of the can body. With the use of a press roll, even for small cans, even if the speed of conveying the can body is increased to a speed of 50 m / min or more, there is no need for timing, and the extra portion of the resin film can be cleaned at once. All can be removed, and even for a large-sized can, even if the width and thickness of the tape-shaped resin film to be used are large, the excess portion of the resin film can be completely and completely removed at once.

That is, since an extra portion of the tape-shaped resin film is adhered to the heat-pressing roll by pressing the pressing roll, the resin film is applied at each of the start time and the end time of the application to the heat-pressing roll. Since it is cut while being pressed against the edge of the can body by the pressing roll, the excess portion of the resin film is cut and cut in a clean state without adversely affecting the adhesion of the resin film to the can body. be able to.

In this regard, in a conventionally known method of coating a tape-shaped resin film on a can body joint, a series of tape-shaped resin is applied to the can body joint while continuously transporting a plurality of can bodies. After attaching the film, cut the resin film with a cutter or laser to remove the excess part of the tape-shaped resin film connected between the can bodies, or increase the transport speed of the can body after attaching the film. Various methods are employed, such as cutting the resin film with a vacuum, or vacuum-sucking an excess portion of the softened resin film after adhering the film between the can bodies.

However, the method of cutting with a cutter or a laser is such that the conveying speed of the can body is 30 m / min.
This is a method that can be used when the material is intermittently conveyed at a low speed of m / min. In the case of a high-speed can-making machine in which the conveying speed of the can body is 50 m / min or more, 450 g / min.
Since cans must be cut at a rate of 380 times / min or more in the direction perpendicular to the direction of transport of the can body, it is difficult to take timing and it is difficult to perform cutting. In this case, cutting is performed at substantially the center of the can body interval, and it is necessary to perform edge processing for cutting and aligning the tape-shaped resin film in accordance with the end (edge) of the can body in a later step.

Even if the speed of transporting the can body is low, when the tape-shaped resin film is wide and thick, it is practical to cut at one time along the front and rear edges of the can body. The upper part is difficult and cannot be completely cut out without protruding from the can body edge, so that an edge treatment for cutting and aligning the tape-shaped resin film in accordance with the can body edge in a later step is required.

On the other hand, in the method of cutting by increasing the transport speed of the can body after the film is attached, the tape-like resin film is pulled to tear off the tape-like resin film, which adversely affects the attachment to the can body. There is a possibility that the tape-shaped resin film is cut at some point in the space between the can bodies, so that the edge treatment of the tape-shaped resin film is necessary in the post-process. Also, for the method of vacuum suction of the excess portion of the softened resin film after the film is adhered between the can bodies, the softened tape-shaped resin film is eventually torn off by suction at the end of the can body. When the tape-shaped resin film is clean, it is not cut.

Incidentally, with respect to the tape-like resin film having a two-layer structure used in the method of the present embodiment as described above, a polyester resin (homopolymer) obtained by polymerizing various dicarboxylic acid components and diol components as described above. And a copolymer), and shown in Table 1 below for a can body for a small can having a plate thickness of 0.18 mm and a can body for a large can having a plate thickness of 0.30 mm. For each of the group of resin films for small cans and the group of resin films for large cans shown in Table 2 below, biaxially oriented films of various two-layer configurations having different melting points between the upper resin and the lower resin ( No. 1 to No. 18) were created for each group.

[0073]

[Table 1]

[0074]

[Table 2]

The adhesion start temperature in the above Tables 1 and 2 means that the film surfaces of the same resin are overlapped, a pressure (about 100 MPa) is applied, the temperature is increased, and the T-peel of the overlap surface is increased. This is the temperature at which the strength becomes 10 N / 15 mm or more.

The two-layer films of each group shown in Tables 1 and 2 (Nos.
o18), an experiment was conducted to cover the joint of the welded can body. In this experiment, as a condition for coating the two-layer film with respect to the welded can body joint, the can body joint was heated to the median temperature between the melting point of the lower resin of the two-layer film and the adhesion initiation temperature. In the group shown in Table 1, the can body was 6
While conveying at a speed of 0 m / min, and in the group shown in Table 2, while transporting the can body at a speed of 20 m / min, each of the groups of tape-shaped 2 The layer film is adhered to the can body junction, the portion of the two-layer film connected between the can bodies is cut and removed, and then the junction is heated with hot air to a temperature above the melting point of the lower resin of the two-layer film. After heating for 90 seconds to a temperature lower than the melting point of the upper resin (approximately the median between the melting point of the lower resin and the melting point of the upper resin), immediately
It was quenched with cold air of 20 ° C.

As a result (the result of observing the joint of ten can bodies for each film), similar results were obtained in the group of Table 1 and the group of Table 2, and the results of both groups were obtained. Are summarized in Tables 3 and 4 below.

[0078]

[Table 3]

Incidentally, the film sticking property in the above Table 3 means
It is an evaluation at the time of film sticking and the state of sticking. Regarding the temperature suitability, it was determined whether or not there was an appropriate temperature range for sticking. That is,
If the difference in melting point between the upper layer and the lower layer of the two-layer film is small and the temperature at the time of sticking (the pre-heating temperature of the bonding portion) is high, the pressure roll disposed on the inner side of the can body due to the adhesion of the upper layer film The upper film adheres to the film, and the film cannot be stuck to the joint. On the other hand, when the temperature at the time of sticking is lowered, the film does not stick to the joint portion of the can body. Therefore, the temperature at which the upper layer of the two-layer film does not adhere to the pressure bonding roll and the lower layer adheres to the can body joint is the appropriate temperature. Regarding the cut property, the degree of the length of the film remaining on the can body was evaluated after cutting and removing the excess film connected between the can bodies. ○ is within 0.5 mm, Δ is 0.5 to 1.0 m
In m, x is 1 mm or more. For wrinkles,
When the film is cut and removed, a case where wrinkles are generated on the film by the pressing roll (lower layer cohesive failure) is indicated by x.
And no wrinkles were evaluated as ○.

[0080]

[Table 4]

The performance of the coated film shown in Table 4 is an evaluation after the can body joint is post-heated. Regarding the step embedding property, the film covering state of the welding step after the post-heating was obtained by embedding the welded portion in an epoxy resin, cutting in a direction perpendicular to the welded portion, and then polishing to observe the embedded state of the stepped portion. ○ indicates that the welding step is completely covered, Δ indicates that there is an intermittent gap between the welding step and the film, and X indicates that there is a continuous gap between the welding step and the film. Regarding upper layer shrinkage, the degree to which the upper layer film shrinks during post-heating was evaluated. This becomes more remarkable as the difference in melting point between the upper resin and the lower resin increases. ○ indicates shrinkage of 0 to 0.5 mm, Δ indicates shrinkage of 0.5 to 1.0 mm, and X indicates shrinkage of 1.0 mm or more. Regarding the adhesiveness, a cellophane tape peeling test was performed in which a crosscut was made on the film surface with a cutter after post-heating, a cellophane tape was attached, and then peeled off. The case where there was no peeling was rated as “○”, and the case where there was partial or full peeling was rated as “x”. Regarding workability,
Two-stage neck processing was performed on the can body having the joint portion covered with a film, and the case where the film of the processed portion was cracked or the film floated from the steel plate was evaluated as x, and the others were evaluated as ○.
For retortability, put in a retort pot and
The film was subjected to heating and pressurizing treatment for 30 minutes, and the presence or absence of peeling or whitening of the film was checked. Regarding the corrosion resistance, the bottom lid was wrapped around a can body whose joint was covered with a film, and then the can was filled with a 1% aqueous solution of malic acid, citric acid and salt, and the top lid was wrapped and sealed. After storing in a constant temperature bath at 38 ° C. for one week, the can was opened and the corrosion state of the can body joint was observed. No corrosion was evaluated as 、, and corrosion was evaluated as ×.

In view of the experimental results shown in Tables 3 and 4, in each of the films in the groups shown in Table 1 and Table 2, the difference in melting point between the upper resin and the lower resin in the film was observed. Is, from the viewpoint of temperature suitability and cutability,
It is found that the temperature is preferably 20 ° C. or more, while the temperature is preferably 60 ° C. or less from the viewpoint of reducing the shrinkage of the upper layer, and the melting point of the lower layer resin is suitable for temperature, cutting property, retort property, corrosion resistance, and wrinkle. From the viewpoint of preventing generation, the melting point of the upper layer resin is preferably from 195 to 255 from the viewpoint of retort properties and corrosion resistance.
It turns out that C is preferable.

Further, as for the thickness of the whole film, in the group (for small cans) shown in Table 1, from the viewpoint of cutability, step embedding property, workability and corrosion resistance, it is necessary that the thickness be larger than 10 μm and smaller than 50 μm. Required, especially 15-40μ
m is preferable, and the thickness of the lower layer is required to be 12 μm or more from the viewpoint of step embedding property, adhesion and corrosion resistance, and it is preferable that the thickness is more than 60% of the thickness of the entire film.

On the other hand, the groups shown in Table 2 (for small cans)
From the viewpoint of cutability, step embedding property, workability, and corrosion resistance, it is necessary to be thicker than 30 μm and thinner than 80 μm, and particularly preferable to be 40 to 70 μm. 36μ from the viewpoint of resistance and corrosion resistance
It is understood that a thickness of at least m is necessary, and it is preferable that the thickness be more than about 80% of the thickness of the entire film.

In the above, one embodiment of the method for coating a tape-shaped resin film on a can body joint according to the present invention has been described.
The present invention is not limited only to the above embodiments. For example, a tape-shaped resin film to be used is not limited to a two-layer structure including only an upper layer and a lower layer, and has a layer other than the upper layer and the lower layer. It is also possible to carry out as a multilayer structure, and the can body production line is also limited to a production line having a film removing step of removing a tape-shaped resin film between each can body by a heat-press roll and a press roll. If the welding speed (conveyance speed) of the can body is low, it can be carried out even on a low-speed production line equipped with a process of cutting the tape-shaped resin film between the can bodies with a cutter or laser. Of course, it is needless to say that the present invention can be carried out by omitting the quenching step after the post-heating step.

[0086]

According to the method for coating a tape-shaped resin film on a joint portion of a can body of the present invention as described above, when coating the inner surface of the joint portion of the welded can body with the tape-shaped resin film, When heat bonding the resin film to the bonding portion, the resin film can be satisfactorily bonded to the bonding portion without attaching the resin film to the pressure bonding roll, and
By performing post-heating in the non-pressed state, the lower part of the resin film can be melted at the correct position without shifting the resin film from the joint, filling the gap at the joint without any gap, exposing the metal surface In addition to being able to sufficiently cover the joined portion, it is possible to prevent the gas barrier properties of the tape-shaped resin film itself from being unnecessarily impaired by not melting the upper layer of the resin film throughout the entire process. .

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing an example of a can body production line for carrying out a method for coating a tape-shaped resin film on a can body joint according to the present invention.

FIG. 2 is a sectional side view showing states (A), (B), and (C) of respective stages in a film removing process of the apparatus of the can body manufacturing line shown in FIG.

FIG. 3 shows the tape-shaped resin film used in the method of the present invention, (A) the cross-sectional structure of the film, (B) the state of the film affixed to the joint of the can body before heating, and (C) the can. Sectional drawing which shows the state after the post-heating of the film stuck on the trunk | drum junction part, respectively.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 can body (weld can body) 2 tape-shaped resin film 21 lower layer (of tape-shaped resin film) 22 upper layer (of tape-shaped resin film) 3 welding roll (can body welding process) 4 welding roll (can body welding process) 5 High-frequency induction heating device (preheating step) 6 Pressure roll (film sticking step) 7 Pressure roll (film sticking step) 8 Heat pressure roll (film removing step) 9 Press roll (film removing step) 10 Scraper (film removing step) 11) Suction hood (film removal process)

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Atsushi Kobayashi 5-5-1 Nishihashimoto, Sagamihara-shi, Kanagawa F-term in the Technology Development Center, Yamato Seikan Co., Ltd. 4F211 AD05 AD08 AD20 AH55 TA05 TC06 TC11 TD11 TH06 TJ13 TN02 TQ10 TW06

Claims (5)

[Claims] 1. A step of preheating a joint portion of a can body while continuously conveying a welding can body formed in a cylindrical body at predetermined intervals in a line in an axial direction of the can body, and a series of supplied tapes. The step of heat-bonding the resin film to the inner surface side of the joining portion of each can body by a pressure roll continuously, and the step of removing an extra portion connected between the can bodies of a series of tape-shaped resin films. After performing, further, by performing a step of post-heating the joint portion of each can body to which the tape-shaped resin film is adhered,
A method of coating the inner surface of a can body joint with a tape-shaped resin film, comprising: a tape-shaped resin film; a lower layer made of a thermoplastic resin having a melting point of 175 to 225 ° C., which serves as a bonding surface to the can body joint; And an upper layer made of a thermoplastic resin biaxially oriented at 195 to 255 ° C., wherein the melting point of the upper layer resin is higher by 20 to 60 ° C. than the melting point of the lower layer resin, and the thickness of the lower layer resin is 60 times the thickness of the entire film. %, The heating temperature in the step of pre-heating the joint of the can body should be within the temperature range from the adhesion start temperature of the lower resin to the melting point, and the tape-like resin film The heating temperature in the step of post-heating the joint portion of each can body to which the affixed is applied is set to a temperature equal to or higher than the melting point of the lower layer resin and lower than the melting point of the upper layer resin, and thereafter, the tape to which the step of heating is applied is applied. For resin film Can body tape-like resin film coating method to joint and performing a non-pressed state Te. 2. A can body having a can diameter of 40 mm to 100 mm and a plate thickness of 0.10 mm to 0.25 mm has a width of 5 to 5 mm.
The method according to claim 1, wherein a tape-shaped resin film having a thickness of 15 mm and a total thickness of 15 to 40 m is used. 3. A can body having a can diameter of 100 mm to 400 mm and a plate thickness of 0.25 mm to 0.40 mm has a width of 15 mm.
2. The tape-like resin film according to claim 1, wherein the tape-like resin film has a total thickness of 40 to 70 [mu] m and a thickness of the lower layer resin exceeds 80% of a total thickness of the film. Method of coating a tape-shaped resin film on a joint of a can body. 4. A step of post-heating the joint portion of each can body to which the tape-shaped resin film is attached, and further comprising a step of rapidly cooling the joint portion of each can body. The method for coating a tape-like resin film on a can body joint according to any one of claims 1 to 3. 5. A heating and pressing roll which is located on the outer surface of the can body and which is heated in the step of removing an extra portion connected between the respective can bodies of the series of tape-shaped resin films; By the pressing roll located in, the extra part connected between each can body of a series of tape-shaped resin film,
The method according to claim 1, wherein the pressing is performed by a pressing roll, and the tape is adhered to a heat-pressing roll, thereby separating and removing the can from each can body and strengthening the bonding between the inner surface of the joint portion of each can body and the tape-shaped resin film. 5. The method for coating a tape-like resin film on a can body joint according to any one of 1 to 4.