JPS58153624A - Treating method for opening of cylinder of polyester container - Google Patents

Abstract

PURPOSE:To obtain the titled flange of opening without the decrease of pressure resistance and gas blanketing preformance in the case of sealing a metal lid by double seaming, by a method wherein the flange of the opening is formed by heating at a suitable high temperature, and pressuring the opening of container main body molecularly orientated with stretching. CONSTITUTION:The opening of cylinder of container main body melt-extruded in a tublar state from thermal plastic polyester composed of ethylene terephthalate repeated base unit as main body and stretched, is heated at a temperature within the range of the glass transition temperature of polyester and over upto the melting temperature. The opening of the cylinder is applied with a pressure of not less than 1kg/cm<2> to the direction of the wall thickness at the same time. Thus, the molecular orientation of the formed flange is relieved, the rigidity being decreased, while the number of the products defective in double seaming process is decreased, and the pressure resistance of the acceptable products is not deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating the opening of a cylindrical body of a polyester container.

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 cylindrical body for tightening the metal lid is integrally formed with the cylindrical body by injection molding or vacuum forming. In particular, the flange portion is not molecularly oriented, so it has insufficient strength, gas barrier properties, etc., and also has drawbacks 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 straight cylinder shape (1986). (Refer to Publication No.-18855).

However, since the above-mentioned known can-shaped containers have end plates sealed by welding, polyethylene terephthalate is melted in the welded portions, and the toughness imparted by biaxial stretching is lost, resulting in brittleness. There are drawbacks 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. Since it is not possible to completely tighten the seams and the withstand pressure of the first seam is low, the flanges must be seamed at a high temperature.

However, it is not easy to heat the flange to a desired high temperature in a short period of time, and especially when the filling is at an extremely low temperature such as carbonated drinks, it is difficult to rapidly 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 extensive 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 and pressurized prior to flange forming, thereby creating a metal lid. They discovered that it was possible to easily sew the material at low temperatures, and based on this knowledge, they were able to achieve this invention.

That is, in this invention, prior to forming a flange for winding a metal lid at the opening of a cylinder that becomes a container body made by melt-extruding and stretching a thermoplastic polyester mainly composed of ethylene terephthalate repeating units, A polyester characterized in that the opening of the cylinder is heated in advance to a temperature above the glass transition temperature of the polyester and below the melting temperature, and a surface pressure of 1 kq/cd or more in the thickness direction is applied to the opening of the cylinder. This is a method for treating the opening of a cylindrical body of a container.

The thermoplastic polyester in this invention includes polyethylene terephthalate homopolymer as well as polyethylene terephthalate homopolymer.

It is a polyester copolymer containing at least 80 mole % of ethylene terephthalate repeating units and other ester repeating units. Among the acid components forming other ester repeating units, °”isophthalic acid, diphenyl ether/I/-
4,4'-dicarboxylic acid, naphthalene □No 1
．． Examples of glycol components include propylene glycol, 1,4-butanediol, pentyl glycol, diethylene glycol,
1.6-hexylene glycol, cyclohexane dimetatool, 2.2-? 'nu(4-hydroxyphenyl/
) propane, 2,2-bis(4-hydroxyethoxyphenyl)propane, and other ester repeating units include esters of oxyacids such as p-oxybenzoic acid and p-hydroethoxybenzoic acid. Furthermore, the thermoplastic polyester may be a mixture of polyethylene terephthalate and another thermoplastic polyester in such a proportion that the ethylene terephthalate units are 80 mol % or more.

The intrinsic viscosity of the thermoplastic polyester is 0.55 or more, preferably 0.6 or more, and more preferably 0.7 to
It is in the range of 1.4. In addition, the above-mentioned intrinsic viscosity is the polyester mixed solvent of pheno-/L//tetrachloroethane (
This is the value measured at 30°C for a solution dissolved in a mixture weight ratio of 6/4).

Thermoplastic polyester may contain colorants, ultraviolet absorbers, antistatic agents, heat/oxidative deterioration inhibitors, antibacterial agents,
Additives such as lubricants and inorganic fillers can be mixed in appropriate proportions.

The above thermoplastic polyester is melted and usually extruded into a tubular shape through an annular die, and the tubular product is adjusted (heated or cooled) to a temperature suitable for stretching the polyester, for example, preferably 90 to 120°C for polyethylene terephthalate, and then In some cases, the tube is formed by blow-stretching, which involves blowing pressurized gas while stretching in the length direction. Excellent heat resistance is then imparted by heat setting, if necessary, at a temperature ranging from 120°C or more to a temperature 20"C or more lower than the melting point of the polyester.
The blow-stretched long tube may be used as it is, or the blow-stretched long tube may be cut to an arbitrary length.

The polyester pipe has metaxylylene group-containing polyamide and polyvinylidene chloride on its outer peripheral surface.

It may be a double-laminated tube having a synthetic resin layer with excellent Ganu barrier properties such as acrylonitrile/styrene copolymer, or it may be a sandwich-like triple-laminated tube. Alternatively, a multilayer tube may be provided with a water-resistant resin layer on its 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 of the casing.

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 heat-set polyester tube is cut to a predetermined length to form a cylindrical container body, and flanges for securing the peripheral edge of the metal plate are formed in the openings at both ends of the container body. Ru.

A feature of the present invention is that, prior to forming the flange, the outer surface of the opening of the cylindrical body that will become the container body is heated and pressurized in advance. The temperature at which the opening of the cylindrical body 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°C or more than the glass transition temperature of polyester to a temperature of 10°C or less than the melting temperature. The temperature range is particularly preferably 20 to 170°C higher than the glass transition temperature. If the heating temperature is lower than the glass transition temperature, the molecular orientation of the molded flange will not be relaxed and the rigidity will not be reduced, resulting in a large number of defective seaming 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.

The surface pressure when pressurizing the outer surface of the housing opening in the thickness direction is 1 kq/c- or more, preferably 2 to 5 kq/cd.
It is. If the surface pressure is less than 1 kq/d, the pressure resistance effect of the seamed portion cannot be improved.

The above-mentioned heating and processing are performed after cutting the tubular object to the desired length of the container body. may be treated at the same time.

The heating and pressurizing means are not particularly limited. The core material is inserted into the cylindrical body, and the outer surface of the cylindrical opening is heated by blowing hot air, contact with a heating element, infrared irradiation, etc. while rotating relatively. ,
Further, it is preferable to apply pressure using a pressure roller or the like. Furthermore, if a heated pressurizing row 7 is used, the heating means described above becomes unnecessary.

A flange molding die is inserted into the opening of the cylinder and pressed to form a flange in which the end of the cylinder curves and protrudes outward.
A metal lid is placed on the flange, the peripheral edge of which has a shape that opens outward along the flange, and has a bent portion that extends from the flange of the container body and is double bent downward from the flange, and By tightening the bent portion of the flange and the metal lid, the peripheral edge of the metal lid is double-sealed and fixed.

As explained above, the cylindrical opening of the container body according to the present invention is heated and pressurized in advance before flange forming to relax the molecular orientation and reduce the rigidity to some extent.
Pressure resistance and gas barrier properties are not impaired even if flange forming and metal lid seaming are performed at or below room temperature.

Therefore, the polyester container obtained by this invention is
It is particularly suitable for filling and storing carbonated beverages such as beer, cola, and cider. The polyester container of the present invention does not undergo thermal deformation even when heated to high temperatures, so it can of course be used for high-temperature beverages such as juice, coffee, and alcoholic beverages.
Food, grease, glue, pharmaceuticals, chemicals, tennis balls.

It can also be used as a container for various products such as luxury items, and has excellent storage stability.

This invention will be explained in detail below.

Example 1 Polyethylene terephthalate) (i-eyesperm [0,75° trade name Polyester RT-5481 Nippon Univetsu) Company fM
) was melted at 275°C, with an outer diameter of 13.51 nl and an inner diameter of 18
．． It was extruded into a tubular shape with a wall thickness of 2.5 mm through a 6 mm annular die, and blow-stretched at 95 mm and a pressure of 2/C- to a thickness of 0.5 mm.
A polyester stretched tube of 81 m11 and an outer diameter of 53 al was manufactured, and this stretched tube was heat-set at 150°C for 15 seconds in a mold under an internal pressure of 2 kg/cd, and cut into lengths of 140 mm after heat-setting. A cylindrical container body was obtained.

Next, the cylindrical opening of the container body is rotated, and pressure is applied in the wall thickness direction at a pressure of 3 kti/Cd with a pressure roller that is rotatably attached to the tip of the cylinder and heated to 90°C. did. After that, a flange is formed on the opening of the cylinder,
Then, using a hand seamer (manufactured by Osaka Can Seiki Co., Ltd.), seal an aluminum lid to one opening at room temperature to form a bottom, and fill this container with carbonated water containing 4 gas volumes of carbon dioxide gas. Thereafter, the other openings were sealed in the same manner as above. When this filled container was 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 8.5 kti/c-.

Comparative Example In the above Example
After 4 hours of storage, 10% of the samples tested had leakage of internal pressure gas.

In addition, in the above embodiment, the cylindrical opening 1 of the container body!
:When heating to 90°C with hot air without pressurizing, 4% of the test pieces leaked due to internal pressure after storage.

Furthermore, in the above example, if the flange was heated to 9 (l) when sealing the aluminum lid without heating and pressurizing the cylindrical opening of the container body, 8% of the test pieces would be defective after storage. there were.

Patent applicant: Toyobo Co., Ltd. Sorin Beer Co., Ltd. Agent: Patent Attorney Takeo Sakano

Claims (1)

[Scope of Claims] [1] Thermoplastic polyester mainly consisting of ethylene terephthalate repeating units t is melt-extruded and stretched into a tubular shape, and a flange for winding a metal lid is attached to the opening of the cylindrical body that becomes the container body. Prior to molding, the opening of the cylinder is heated in advance to a temperature above the glass transition temperature of polyester and below the melting temperature, and 1 kq/kg is heated to the opening of the cylinder.
A method for treating the opening of a cylindrical body of a polyester container, characterized by applying surface pressure in the wall thickness direction of CD or more. [2] The heating temperature of the opening of the cylinder is 20° below the glass transition temperature.
The method for treating a cylindrical opening of a polyester container according to claim 1, wherein the temperature range is ~170°C higher.