JPH057261B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a polyester container formed by double-sealing a thermoplastic polyester container body and a metal lid. This invention relates to a polyester container with an excellent seaming part. (Prior art) A plastic container body is formed from polyester such as polyethylene terephthalate (PET).
A polyester container is already known in which this container and a metal lid are secured together at their engaging ends (Japanese Patent Laid-Open Publication No. 3915/1983). However, even when resins such as polyester are bent and deformed, it is difficult to maintain this deformed state stably, and furthermore, the rigidity is significantly lower than that of metals, so in the polyester container described above,
The strength of the double seam portion between the container body and the metal lid is a problem. For this reason, attempts have been made to improve the strength of the seamed portion by stretching the flange portion of the plastic container body or by thermal crystallization to improve the rigidity and impact resistance. (Problems to be solved) Therefore, the two parts of the plastic container body and the metal lid.
During heavy seaming, in the flange portion of the container body, a tensile force is applied to the outer surface of the bent portion, and a compressive force is applied to the inner surface of the bent portion in the circumferential direction. Therefore, if the flange of a plastic container body is merely made rigid by the commonly used stretching process, the material of the flange will be resistant to the circumferential tensile and compressive forces generated during seaming. It cannot absorb that force in the circumferential direction. As a result, residual stress remains in the seamed part, and the seamed part of the plastic container body plastically deforms over time, causing problems such as the metal lid slipping off due to internal pressure, etc., especially in pressure-resistant containers. Therefore, sufficient pressure-tight sealing performance cannot be obtained for a long time. Therefore, the technical problem of the present invention is to provide a polyester container consisting of a polyester container body and a metal lid with sustained pressure-tight sealing properties. (Means for Solving the Problems) According to the present invention, it is made of thermoplastic polyester mainly containing ethylene terephthalate units, has an open end at one or both ends, and is wound around the open end. Polyester consisting of a container body on which a tightening flange is formed, a container lid made of metal and whose periphery is a seaming end, and a seaming part formed between the container body and the container lid. In the container, a polyester container preform is stretched 1.3 to 4 times in the axial direction of the container, including the part that will become the flange, and then stretched to 2 times or less in the circumferential direction of the container, excluding the part that will become the flange. The flange is formed by drawing and then heat-setting the flange, and the radial orientation degree () measured by polarized fluorescence method after heat-setting is 0.18 or more, and the circumferential orientation degree is 0.18 or more. (m) is smaller than 0.18, and the orientation ratio (/m) of both is larger than 1.0 and is in the range of 3.5 or less, and the density (20
Provided is a polyester container with excellent seaming properties, characterized in that the molecules are oriented so that the temperature (°C) is 1.36 g/cc or more. (Function) According to the present invention, the degree of radial orientation () of the root portion of the seaming flange of the polyester container body is 0.18.
Due to the molecular orientation as described above, a certain strength is imparted to the flange portion. In addition, since the degree of circumferential orientation (m) is 0.18 or less, the flange part has the ability to follow the tensile force and compressive force in the circumferential direction during seaming, and plastic deformation due to residual stress It becomes possible to effectively prevent this. In other words, when the degree of circumferential orientation (m) is greater than 0.18, the resistance of the flange portion to the circumferential tensile force and compressive force during seaming increases, making it difficult for body hooks to appear. It becomes difficult to tighten. Even if the container is successfully tightened, the flange portion will plastically deform over time due to residual stress, resulting in the inconvenience that the metal lid may easily slip off due to the internal pressure of the container. In the present invention, the orientation ratio (/m) is also
It is also important that it is in the range of 1.0 to 3.5. In other words, if the degree of radial orientation () becomes too large compared to the degree of circumferential orientation (m) and /m exceeds 3.5, the flange part will not be able to follow the tensile force and compressive force in the circumferential direction during seaming. It is impossible to avoid plastic deformation due to residual stress. Also, as mentioned above, the degree of radial orientation () is 0.18
Since the above and the circumferential orientation degree (m) is 0.18 or less, in the present invention, the orientation degree ratio (/
m) is necessarily 1.0 or more. According to the present invention, the density (at 20°C) of the flange root portion is 1.36 g/cc or more, that is, it is heat-set in a molecularly oriented state, so that the shape is stably maintained and fixed in the tightened state. This makes it possible. (Preferred Embodiment of the Invention) In FIG. 1 showing a cross section of essential parts of a polyester container of the present invention, there is a seaming portion generally indicated by 3 between a container body 1 made of thermoplastic polyester and a metal lid 2. It is formed. The polyester container body 1 has a downwardly directed body hook 4 in which the flange portion 20 of the polyester container body shown in FIGS. 2 and 3 together with the seaming edge 6 of the metal lid 2 It is formed by being forcibly bent downward. On the other hand, the metal lid 2 has a lid hook 7 that faces upward in the tightened state, and has an outer peripheral part 8 on the outer peripheral side of the lid hook 7 and an inner peripheral part 9 on the inner peripheral side of the lid hook 7. The lid hook 7 and the outer circumferential part 8 are connected via a connecting part 10 at the seaming bottom, and the outer circumferential part 8 and the inner circumferential part 9
and are connected to each other via a connecting portion 11 at the top of the seaming portion. Thus, the body hook 4 of the polyester container is held between the lid hook 7 and the outer periphery 8 of the metal lid, and the straight top 12 of the polyester container is held between the lid hook 7 and the inner periphery 9 of the metal lid. It is clear that there are. Container body material In the polyester container of the present invention, the thermoplastic polyester whose main repeating unit is ethylene terephthalate used as the container body material is usually 80 mol% or more of the acid component, preferably 90 mol% or more of terephthalic acid, and glycol It means a polyester in which 80 mol%, preferably 90 mol% or more of the component is ethylene glycol, and the remaining acid components 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, and as other glycol components propylene glycol, 1,4 -butanediol,
Neopentyl glycol, diethylene glycol, 1,6-hexylene glycol, cyclohexanedimethanol, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyethoxyphenyl)propane, or oxyacid It means a polyester containing P-oxybenzoic acid, P-hydroethoxybenzoic acid, etc. Further, a polyfunctional component having trifunctionality or more may be copolymerized within a range that does not impair moldability. Further, it may be a mixed polyester of two or more types such that polyethylene terephthalate is mixed with another thermoplastic polyester so that the content of ethylene terephthalate is 80 mol% or more. In addition, the polyester in the present invention can contain additives such as colorants, ultraviolet absorbers, antistatic agents, thermal oxidative deterioration inhibitors, antibacterial agents, lubricants, and inorganic fillers in appropriate proportions as necessary. . The thermoplastic polyester used in the present invention needs to have an intrinsic viscosity of 0.55 or more, preferably 0.6 or more, and more preferably 0.7 to 1.4. The intrinsic viscosity is the intrinsic viscosity measured at 30°C of a solution of polyester dissolved in a mixed solvent of phenol/tetrachloroethane (6/4 weight ratio). Polyester container body In the present invention, the polyester container body is made of the above-mentioned thermoplastic polyester, and is made of the polyester and other resins such as metaxylylene group-containing polyamide, polyvinylidene chloride, acrylonitrile styrene copolymer, and ethylene vinyl alcohol copolymer. It may also be made of a laminated cylinder or a coated polyester cylinder with a resin having better gas barrier properties. In addition, the polyester container body may be a cylindrical body with both ends open and a metal lid wrapped around both open ends (Figure 2), or it may have a bottom with an open end only at one end. It may also have a pot-like structure (FIG. 3). In the present invention, the flange portion of the polyester container body has a radial orientation degree () of 0.18 or more, a circumferential orientation degree (m) of 0.18 or less, and an orientation degree ratio (/
The molecular orientation is such that m) is in the range of 1.0 to 3.5, and the density (at 20°C) is 1.36 g/cc or more. As a result, as described above, sustained pressure-tight sealing performance and shape retention are achieved at the seamed portion with the metal lid. Manufacture of container body In the present invention, a container body having a flange portion with the above-mentioned molecular orientation is produced by imparting uniaxial molecular orientation to a container forming material such as a pipe or cup, and then fixing the end portion. It is formed by blow molding and flanging the rear end. For example, in order to form a cylindrical container body with openings at both ends as shown in FIG. 2, referring to FIG. 4-A showing the manufacturing process, the polyester described above is subjected to a known extrusion or injection molding process. The pipe 50 obtained by this process is subjected to a uniaxial stretching operation and both ends are cut to obtain a pipe 51 whose molecules are uniaxially oriented as a whole including the flange forming portion (both ends) (step A). This pipe forming may be performed, for example, by uniaxially pulling the pipe during pipe extrusion, or by sizing the pipe at 100°C during pipe extrusion.
Once the temperature reaches a certain level, pipe forming may be performed while uniaxially stretching using a draw cone. Next, by gripping both ends and performing blow molding, a biaxially stretched cylinder 52 having a predetermined shape except for both ends is obtained (Step B). This improves the mechanical strength of the body. In addition, this blow molding is similar to the uniaxial stretching described above, where the temperature is higher than the glass transition point.
Stretching is carried out at an appropriate stretching temperature of 150°C or less. In addition, if the container body is to be able to withstand high temperatures such as high temperature liquid filling or high temperature sterilization, a heat setting operation is performed at the same time as blow molding. Both ends of the cylindrical body 52 having a predetermined shape are then formed into flanges to obtain a polyester container body 53 having a flange formed therein (step C). The flanging is performed by drawing, for example, as shown in FIG.
1 to form the connecting part 19, and then a flange die 63 consisting of a connecting chuck 62a and a flanging ring 62b.
This can be done by pressing against the flange portion 20 to form the flange portion 20. In this drawing process, molecular orientation in the circumferential direction is imparted to the flange portion 20, thus obtaining a polyester container body having a flange portion in which molecules are preferentially oriented in the radial direction. Further, the cup-shaped container body shown in Fig. 3 is made by molding a cup-shaped material 70 obtained by injection molding a specified polyester at a temperature of 65 to 120°C, with reference to Fig. 4-B showing the manufacturing process. Uniaxial molecular orientation is imparted by ironing (step a). Next, cut the opening tip (step b),
The tip is fixed and subjected to a blow molding process known per se (step c) to obtain a container body having a body and a bottom of a predetermined shape. During this blow molding, it is preferable to perform heat setting at the same time to impart heat resistance to the body. Next, flanging is performed on the open end of this container body in the same manner as described above (step d) to obtain a container body having a flange 20 with molecules preferentially oriented in the radial direction. In order to impart the above-mentioned molecular orientation to the flange portion of the polyester container body, it is necessary to stretch it in the axial direction and then in the circumferential direction except for the portion that will become the flange, but each of these stretching methods is known in the art. This can be carried out depending on the stretching operation and stretching conditions. The stretching ratio is preferably 1.3 to 4 times in the axial direction of the container, and 2 times or less in the circumferential direction of the container. A container body having a flange portion with molecular orientation as described above is subjected to a heat-setting operation of the flange portion, and is then subjected to tightening with a metal lid. By performing such heat fixation, the density of the polyester in the flange (at 20°C) is 1.36 g/cc or more.
Generally, it is in the range of 1.360 to 1.395 g/cc, and mechanical properties such as heat resistance and impact resistance are improved. The heat setting conditions are generally 0.5 to 250 seconds at a temperature of 100 to 230°C, particularly 140 to 200°C for 1 second.
It is desirable that the time is between 120 seconds and 120 seconds. Of course, even within the above conditions, when the temperature is high, a short time is sufficient, and when the temperature is low, a long time is required. This heat setting is substantially transparent, which is a significant difference from thermal crystallization. Further, this heat fixing may be performed by high-frequency induction heating after the container body and metal lid are seamed together as described above. Metal Lid In the present invention, the metal lid includes a tin-plated steel plate,
It is made of various surface-treated steel sheets such as tain-free steel (electrolytic chromic acid treated steel sheets) and light metals such as aluminum, and the surface is coated with epoxy-phenol paints, epoxy-urea paints, epoxy-acrylic paints, and epoxy-vinyl paints. based paint, vinyl
A coating with a protective coating such as phenol paint is used. A circumferential groove is provided around the can lid for engagement with the seaming end of the container body, and the groove is lined with a sealing rubber composition. The center panel portion of the can lid can be provided with a known easy-to-open mechanism. Figure 6 shows a suitable example of the can lid,
An annular rim portion 2 is provided around the center panel portion 26.
A circumferential tightening groove 28 is provided through the groove 7, and a lining layer 29 of a sealing rubber composition is provided within this groove. The center panel portion 26 is provided with a score 31 that defines a portion 30 that should be opened.
An opening piece 32 is attached to this portion 30 to be opened via a fixing part 33 such as a rivet. For the double seaming of the polyester container body and the metal lid, a seamer conventionally used for seaming metal cans can be used. (Effects) The polyester container of the present invention has a double seam portion between the polyester container body and the metal lid, which has excellent instantaneous pressure resistance, continuous sealing performance, and impact resistance. Useful as a container. Example 1 and Comparative Examples 1 and 2 When polyethylene terephthalate (PET) with an intrinsic viscosity of 0.95 is formed into a melt-extruded pipe, it is uniaxially stretched (stretching ratio: 2 times) in the extrusion direction using a draw cone, and the inner diameter is 52.5 mm and the thickness is 0.4 mm. A pipe with a length of 150 mm with both ends open was formed. Next, the parts of this pipe, excluding 10 mm at each end, are heated to approximately 105°C using infrared rays, and then using a split mold set at 150°C that can grip and seal both ends, pressurized air is blown from one end in the radial direction. A hollow tube with an outer diameter of 70 mm and both ends open was formed (stretching ratio approximately 1.3 times), and immediately heated to 10°C.
It was inserted into a split mold of the same shape as the split mold set at 150° C. and cooled by blowing pressurized air from the end. 10 mm of both ends of this hollow space were rapidly heated to 100℃ using infrared rays, and flanges were formed using a flange die to form seaming flanges at both ends.
A PET container body was obtained. The degree of radial orientation (l), degree of circumferential orientation (m) of the flange portion of this container, and 20
The density (d) in °C is shown in Table 1. As Comparative Example 1, a preform with one end open was molded by injection molding using the same material as in Example 1, and then a bottle-shaped container was molded by ordinary heat-set biaxial stretching blowing, and then this bottle-shaped container was molded with a laser. After horizontally cutting the body, a flange was formed using a flange die in the same manner as in Example 1 to obtain a PET container body with a seaming flange formed at one end. Table 1 shows the degree of orientation and density of this container flange. As Comparative Example 2, when forming a pipe using the same material as in Example 1, uniaxial stretching was performed in the extrusion direction using a draw cone, and pressurized air was sucked into the pipe to expand it 2.2 times in the radial direction, thereby increasing the outer diameter. 70mm/thickness
A biaxially stretched medium space of 0.4 mm and length of 150 mm was formed.
After heat-setting this hollow space in a split mold set at 150℃, both ends were heated to 100℃ and flanges were formed using a flange die to obtain a PET container body with seaming flanges formed at both ends. Ta. The degree of orientation of the flange part of this container and the density at 20°C are
Shown in the table. Among the three types of PET containers mentioned above, the containers of Example 1 and Comparative Example 2 have a stain-free steel lid on one end (the surface has a protective coating, and a groove on the periphery of the lid is used for sealing). (with rubber) is double seamed,
The three types of containers thus obtained were filled with four gas volumes of carbonated beverages at a low temperature and then double-sealed with aluminum lids. Table 1 shows the results of storing these three types of filled containers at 20°C and 50°C for one month. Comparative Example 3 The same material as in Example 1 was used, except that instead of the split mold set at 150°C used in Example 1, a split mold set at 20°C was used (no heat setting). A PET container having the same shape as in Example 1 and having flanges formed at both ends was obtained using exactly the same method. This container was used in Example 1, Comparative Examples 1 and 2.
In the same manner as above, the container was filled with 4 gas volume carbonated beverage, double-sealed with metal lids (one is a tain-free steel lid, the other is an aluminum lid), and a storage test was conducted. The degree of radial orientation, degree of circumferential orientation, and density at 20°C of the flange portion of this container are respectively =
0.185, m=0.145, 1.335g/ ^cm3 . As a result of the storage test, no leakage was observed for one month when stored at 20°C, but the lid came off after two weeks when stored at 50°C. Comparative Example 4 Using the same material as in Example 1, a draw cone was used in which the degree of stretching (thickness reduction rate = processing rate) when uniaxially stretching the extruded pipe in the extrusion direction with the draw cone was set lower than in Example 1. A PET container having flanges at both ends was molded by the same method as in Example 1 except for the use of the following. This container was filled with 4-gas volume carbonated beverage in the same manner as in Example 1 and Comparative Examples 1 and 2, the metal lid was double-sealed, and a storage test was conducted. The degree of radial orientation of the flange of this container,
The degree of orientation in the circumferential direction and the density at 20℃ are respectively =
0.17, m=0.15, d=1.37g/ ^cm3 . As a result of the storage test, leakage occurred after one week when stored at 20℃, and leakage occurred after 3 hours when stored at 50℃. 【table】

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the main parts of the plastic container of the present invention, FIGS. 2 and 3 are diagrams showing aspects of the container body used in the plastic container of the present invention, and FIGS. 4-B is a diagram showing the manufacturing process of the container body shown in FIGS. 2 and 3, FIG. 5 is a diagram for explaining the method for forming the flange portion of the container body, and FIG. Figure A and Figure 6-B are diagrams showing an example of a metal lid used in the present invention. 1... Container body, 2... Metal lid, 3... Sealing part, 4... Body hook, 7... Lid hook, 19...
Netsukin processing section, 20... flange section.

Claims (1)

[Scope of Claims] 1. A container made of thermoplastic polyester mainly containing ethylene terephthalate units, having an open end at one or both ends, and having a seaming flange formed around the open end. In a polyester container consisting of a body, a container lid made of metal and having a seaming end around its periphery, and a seaming part formed between the container body and the container lid, polyester container preforming is performed. Stretch the object by 1.3 to 4 times in the axial direction of the container, including the part that will become the flange, and then stretch it by 2 times or less in the circumferential direction of the container, excluding the part that will become the flange, and process the part that will become the flange by drawing. , and then heat-set, and the root part of the flange has a degree of radial orientation () of 0.18 or more and a degree of circumferential orientation (m) of less than 0.18 as measured by a polarized fluorescence method after heat-setting. In addition, the orientation ratio (/m) of both is greater than 1.0 and less than 3.5, and the density (20
A polyester container with excellent seaming properties characterized by molecular orientation such that the temperature (°C) is 1.36 g/cc or more.