JPH037502B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a metal lid fastening flange at the opening of a polyester container.

BACKGROUND OF THE INVENTION In recent years, beverage containers molded from thermoplastic synthetic resins have been used instead of containers molded from glass or metal sheets. Containers are known in which a metal lid is wrapped around the opening of a cylindrical body made of thermoplastic synthetic resin (see, for example, Japanese Patent Publication No. 41-20276 and Japanese Utility Model Publication No. 48-782). However, in the above-mentioned known container, the flange portion formed at the opening of the cylinder to tighten the metal lid is integrally formed with the cylinder by injection molding or vacuum forming. Therefore, since the flange part in particular is not molecularly oriented, it has insufficient strength, gas barrier properties, etc., and also has disadvantages in physical properties such as whitening when heated. On the other hand, a can-shaped container is known in which end plates made of synthetic resin or metal are welded and sealed to the upper and lower openings of a cylinder made of polyethylene terephthalate that is biaxially stretched into a linear cylinder shape. -Refer to Publication No. 18355). However, since the above-mentioned known can-shaped container has end plates sealed by welding, polyethylene terephthalate is melted in the welded portion, and the toughness imparted by biaxial stretching is lost, making it brittle. However, there are disadvantages such as a decrease in gas barrier properties and a decrease in the storage stability of the contents.

If a flange is formed at the opening of the above-mentioned biaxially stretched polyethylene terephthalate cylinder, and a metal lid is to be wrapped around this flange, the cylinder has high rigidity, so it will not work at room temperature or lower. In this case, it is not possible to complete the seaming, and the pressure resistance of the seaming portion becomes low, so the seaming must be done while the flange is heated to a high temperature. However, it is not easy to heat the flange to a desired high temperature in a short time, and especially when the filling is at an extremely low temperature such as carbonated drinks, it is difficult to quickly raise the temperature of the flange after filling. There is a problem in that it is difficult and impossible to tighten.

As a result of intensive research in order to solve the above problems, the present inventors have discovered that the opening of the container body, whose molecules have been oriented by stretching, is heated to an appropriate high temperature to form a flange. It was discovered that the lid could be easily tightened at low temperatures, and based on this knowledge, the present invention was achieved.

That is, this application includes two inventions, and the first invention is:
When forming a flange for wrapping a metal lid around the opening of a cylindrical container body made by melt extruding and stretching a thermoplastic polyester mainly composed of ethylene terephthalate repeating units, the flange-forming portion is made of the polyester. This is a method for flange forming a polyester container, which is characterized by heating to a temperature in the range of not less than the glass transition temperature and less than the melting temperature.

A second invention is a method for forming a flange for a polyester container, characterized in that when forming the flange of the first invention, a surface pressure of 1 kg/cm ² or more in the thickness direction is applied to the flange.

The thermoplastic polyester in this invention includes, in addition to polyethylene terephthalate homopolymer,
At least ethylene terephthalate repeating units
It is a polyester copolymer of 80 mol% and other ester repeating units. Other acid components forming ester repeating units include isophthalic acid, diphenyl ether-4,4'-dicarboxylic acid, naphthalene-1,4- or 2,6-dicarboxylic acid, adipic acid, sebacic acid, decane-1 , 10-dicarboxylic acid, hexahydroterephthalic acid, etc.
In addition, glycol components include propylene glycol, 1,4-butanediol, neobentyl glycol, diethylene glycol, 1,6-hexylene glycol, cyclohexanedimethanol, 2,2-bis(4-hydroxyphenyl)propane, , 2-bis(4-hydroxyethoxyphenyl)propane, and other ester repeating units such as p-oxybenzoic acid, p-oxybenzoic acid,
- Includes esters of oxyacids such as hydroethoxybenzoic acid. Furthermore, as a thermoplastic polyester, 80 mol% of ethylene terephthalate units
It may be a mixture of polyethylene terephthalate and other thermoplastic polyester in the above proportions.

The intrinsic viscosity of the thermoplastic polyester is 0.55 or more, preferably 0.6 or more, more preferably
It ranges from 0.7 to 1.4. In addition, the above-mentioned intrinsic viscosity is
A solution of polyester dissolved in a mixed solvent of phenol/tetrachloroethane (mixed weight ratio 6/4) was
This is a value measured at 30℃.

Additives such as colorants, ultraviolet absorbers, antistatic agents, thermal and oxidative deterioration inhibitors, antibacterial agents, lubricants, and inorganic fillers can be mixed with the thermoplastic polyester in appropriate proportions as necessary. .

The above thermoplastic polyester is melted and usually
The tubular product is extruded in an annular shape from an annular die, adjusted (heated or cooled) to a temperature suitable for stretching polyester, for example, preferably 90 to 120°C for polyethylene terephthalate, and then pressurized while stretching in the length direction if necessary. A tube is formed by blow-stretching by blowing gas. Then, if necessary, from a temperature of 120℃ or higher to the polyester melting point.
Excellent heat resistance is imparted by heat setting at a temperature lower than 20°C. This heat fixing may be performed on the blow-stretched long tube as it is, or after the blow-stretched long tube is cut into arbitrary lengths.

The above-mentioned polyester pipe may be a double-laminated pipe having a synthetic resin layer with excellent gas barrier properties such as metaxylylene group-containing polyamide, polyvinylidene chloride, acrylonitrile/styrene copolymer, etc. on its outer circumferential surface; A triple laminated pipe with a shape of Alternatively, a multilayer tube may be coated with a water-resistant resin on the outer surface. In the case of the above-mentioned multi-layer tube, additives such as colorants and ultraviolet absorbers are preferably incorporated into the outer layer and/or the intermediate layer. Further, the multi-layered tube may not only be a layered structure of different resins as described above, but also may have a multi-layered structure of polyester.

The above polyester pipe is cut to a predetermined length to form a cylindrical container body, and flanges for fastening and tightening the peripheral edge of the metal plate are formed at the openings at both ends of the container body.

Next, a specific example of the flange forming apparatus will be explained with reference to FIG.

Openings 3 formed from thermoplastic polyester are formed on the outer circumferential surface of the trunk holder 2, which is driven and rotated by a motor 1 and has a collar 2a at the lower part.
A cylindrical container main body 3 having portions a and 3b is fitted and fixed so that the lower end opening 3b of the container main body 3 comes into contact with the flange 2a. A flange molding die 4 for molding a flange 3c on the upper end opening 3a of the container body 3 has a body 4a and a flange molding part 4b with a curved bottom surface, the upper part of which is connected to the body holder 2.
It is rotatably attached via a bearing 6 to the tip of a piston 5a that is moved up and down in a mold cylinder 5 located above the axis of the mold. Further, on the outside of the container body 3 fitted and fixed to the body holder 2, several blow-off nozzles 7 are arranged at equal intervals to blow out hot air toward the upper end opening 3a of the container body 3. has been done. Furthermore, the above-mentioned trunk holder 2
A pressure roller 8 that presses the outer surface of the flange 3c formed by the flange molding die 4 in the thickness direction of the flange 3c is disposed on the outside of the container body 3 which is fitted and fixed to the container body 3. The pressure roller 8 is rotatably attached to the tip of the piston 9a of the pressure cylinder 9.

A flange 3 is attached to the upper end opening 3a of the container body 3.
c, the container body 3 is rotated together with the rotation of the body part holder 2, and the mold cylinder 5 is operated to move the body part 4a of the flange forming mold 4 into the container body 3.
Insert it into the upper end opening 3a and apply pressure. At this time, the flange forming portion near the upper end opening 3a of the container body 3 is rotated, and its outer surface is heated by the hot air jetted from the blowing nozzle 7, and the upper end opening 3a
The flange 3c is easily formed.

In the second invention, after the flange 3c is formed, the pressure cylinder 9 is operated to apply surface pressure to the outer surface of the flange 3c using the pressure roller 8.

To form a flange on the lower end opening 3b of the container body 3, the container body 3 is removed, turned upside down, and fitted into the body holder 2, and the same operation as above is performed.

FIG. 2 shows the work of tightening the metal lid to the flange, with the right side A showing the work before tightening, and the left side B showing the work after tightening. The curved portion 10a of the peripheral edge of the metal lid 10 is
A bent portion 1 which has an outward opening shape along the flange 3c of the container body 3, extends from the curved portion 10a, and is double bent downward from the flange 3c of the container body 3.
It has 0b. After inserting the metal lid 10 into the upper part of the container body 3 as shown on the right side A, the flange 3c of the container body 3 and the metal lid 10 are inserted.
By tightening the bent portion 10b, the peripheral edge of the metal lid 10 is double tightened and fixed as shown on the left side B. Note that the metal lid 10
The container may be equipped with an opening tool commonly used for metal containers.

The temperature at which the flange forming portion of the container body described above is heated is in the range of not less than the glass transition temperature of polyester and less than the melting temperature, preferably from a temperature of 15 degrees Celsius or more than the glass transition temperature of polyester to 10 degrees Celsius or more than the melting temperature of the polyester. ℃ or below, particularly preferably 20 to below the glass transition temperature.
The temperature range is 170℃ higher. If the heating temperature is lower than the glass transition temperature, the molecular orientation of the flange will not be relaxed and the rigidity will not be reduced, resulting in a large number of defective wrapping products and poor pressure resistance. Furthermore, if the heating temperature is higher than the melting temperature, the molecular orientation of the body also disappears, resulting in a significant decrease in toughness.

To heat the flange forming part of the container body,
It is preferable to insert the flange forming mold downward into the upper end of the container body to form the flange, as this makes forming the flange easier. good.

The heating means described above is not particularly limited, and may be, for example, a contact heating method, an infrared irradiation heating method, an electromagnetic induction heating method, an ultrasonic heating method, or the like.

By heating the flange forming portion of the container body as described above, a sufficient effect can be obtained even when the metal lid is tightened at a low temperature. When the gas pressure of a carbonated drink or the like filled in the container is high, the gas may leak from the seamed portion and the quality of the filling may deteriorate.

The second invention of this application solves the problem of the first invention, and the outer surface of the flange is applied with a pressure roller to a surface pressure of 1 kg/cm ² or more, preferably 2 to 5 kg/cm ² in the thickness direction. It pressurizes it. Surface pressure is 1Kg/
If it is less than ^cm2 , no improvement in the pressure resistance effect of the seamed portion will be obtained. Pressure by the pressure roller may be performed simultaneously with the heating of the flange, or may be performed after the flange is heated. It is effective for the pressure to be applied at a temperature above the glass transition temperature of the flange, particularly preferably within the heating temperature range of the above-mentioned flange forming part and below the melting temperature, and if necessary, a heating means may be provided on the pressure roller. It's okay. The above-mentioned pressure disturbs the plane orientation in the axial direction and the circumferential direction, thereby preventing peeling and the like, and enables seaming with excellent pressure resistance.

The flange of the container body formed according to the present invention does not lose its pressure resistance and gas barrier properties even if it is tightened at room temperature or below. Therefore, the polyester container obtained according to the present invention is particularly suitable for filling and storing carbonated beverages such as beer, cola, and cider. Furthermore, since the polyester container of this invention does not undergo thermal deformation even at high temperatures, it can of course be used for high-temperature beverages such as youth, coffee, and alcoholic beverages. agent,
It can also be used as containers for various products such as medicines, chemicals, tennis balls, and luxury goods, and has excellent storage stability.

Examples of the present invention will be described below.

Example 1 Polyethylene terephthalate (intrinsic viscosity 0.75,
Polyester RT-543 (trade name, manufactured by Nippon Unipet Co., Ltd.) was melted at 275°C, and the outer diameter was 18.6 mm and the inner diameter was 13.6 mm.
Extruded into a tubular shape with a wall thickness of 2.5 mm from an annular die of 95 mm.
℃, blow stretched at a pressure of 2Kg/ ^cm2 to a thickness of 0.3mm,
A polyester stretched tube with an outer diameter of 53 mm was manufactured, and this stretched tube was heated at 150℃ in a mold with an internal pressure of 2 kg/cm ² .
Heat set for 15 seconds, length 140mm after heat set.
A cylindrical container body was obtained by cutting into pieces. The end of the container body was heated to 100°C using the apparatus shown in Fig. 1 above to form flanges on the upper and lower openings, and then a hand seamer (Osaka Can Manufacturing Co., Ltd.) was attached to one opening. At room temperature, an aluminum lid is rolled and fixed using a plastic wrapper (manufactured by
After filling with a gas volume of carbonated water containing carbon dioxide gas, the other openings were sealed by wrapping in the same manner as above. When 1,000 of these filled containers were stored at 50°C for 24 hours, no leakage of internal pressure gas was observed.
The internal pressure of the container at this time was 4.0 Kg/cm ² .

Furthermore, when filled with carbonated water containing 4 gas volumes of carbon dioxide gas and stored at 50°C, 30 out of 1000 gas leaked during storage. The internal pressure of the container at this time was 8.5 Kg/cm ² .

Example 2 When forming the flange of the container body in Example 1 while heating, the bottom surface of the flange was further heated to 90°.
Pressure was applied with a surface pressure of 2.5 kg/cm ² using a pressure roller heated to ℃. The opening of this container body was sealed with an aluminum lid in the same manner as in Example 1, and carbonated water containing carbon dioxide gas in an amount of 4 gases was filled and sealed. When 1000 of these filled containers were stored in the same manner as in Example 1, no leakage of internal pressure gas was observed. The internal pressure of the container at this time was 8.5 Kg/cm ² .

Comparative Example In Example 1 above, the outer surface of the flange was not heated or pressurized when forming the flange, and the flange was heated to 90°C when tightening the aluminum lid to the opening.
The container was heated to a temperature of 100.degree. C., and then filled with carbonated water containing carbon dioxide gas having the above-mentioned 2 gas volumes and sealed. In this case, gas leakage was observed in 400 out of 1000 pieces during the same storage as in Example 1.

[Brief explanation of the drawing]

FIG. 1 is a vertically cut front view of a flange forming apparatus according to the present invention, and FIG. 2 is a vertically cut front view showing states A and B before and after tightening a metal lid to a container. 3: container body, 3a, 3b: opening, 3c: flange, 10: metal lid.

Claims (1)

[Claims] 1. When forming a flange for wrapping a metal lid onto the opening of a cylindrical container body made by melt-extruding and stretching thermoplastic polyester mainly containing ethylene terephthalate repeating units, A method for forming a flange for a polyester container, which comprises heating the flange forming portion to a temperature above the glass transition temperature and below the melting temperature of the polyester. 2. The method of forming a flange for a polyester container according to claim 1, wherein the heating temperature of the flange forming portion is 20 to 170°C higher than the glass transition temperature. 3. When forming a flange for wrapping a metal lid around the opening of a cylindrical container body made by melt-extruding and stretching a thermoplastic polyester mainly composed of ethylene terephthalate repeating units, the flange-forming portion is made of the above-mentioned polyester. 1. A method for forming a flange for a polyester container, the method comprising: heating the flange to a temperature above the glass transition temperature and below the melting temperature, and applying a surface pressure in the wall thickness direction of 1 Kg/cm ² or above to the flange. 4 The heating temperature of the flange is 20° below the glass transition temperature.
Claim 3, which is a temperature range of ~170°C higher
A method for flange forming a polyester container as described in Section 1.