JPS6357236B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention comprises at least one container made of polyethylene terephthalate and at least one lid material having a heat-sealable resin layer on the lid material. This relates to a pair of packaging bodies. [Prior art] A container body is made of a thermoplastic such as polypropylene or polyethylene terephthalate, and a lid is made of a heat-sealing resin layer on a base material such as metal foil. Packaging bodies that are sealed by heat sealing between a heat-sealing resin layer and a heat-sealing resin layer have been widely used in the field of food packaging and the like. This heat-sealable resin layer is not only heat-sealed to form a heat-sealed structure with excellent sealing reliability, but also has easy-to-open properties, that is, when opened,
It must be strong enough to be easily peeled off by hand. Specifically, in order to achieve both sealing and easy-opening properties, a peel angle of 90° and a tensile speed of 30° are required.
Adhesive strength measured in mm/min ranges from 0.8 to 2.2
Must be Kg/cm. In order to satisfy this requirement, heat-sealing resins based on polypropylene or polyethylene (for example,
JP-A-57-77465) or those using polyester copolymers have been widely used. However, all such conventional heat-sealing resins have the following drawbacks because they are melted and fused by heat. Due to the pressure applied during bonding, the molten resin flows and wraps around the bonded end, making it difficult to open the package because the force required to begin opening is greater than during opening. When opening the package, the peeling surface is not fixed and the peeling surface becomes extremely rough, resulting in poor appearance and texture. Since it is necessary to heat the resin to a high temperature to melt it, the sealing speed cannot be increased. [Object of the Invention] The object of the present invention is to solve the above-mentioned drawbacks, to increase the sealing speed during heat sealing, to make it possible to increase the sealing speed, to apply uniform force to open the seal, and to prevent the unsealing surface from being almost rough when the seal is opened. The purpose is to provide an easy-to-open package that does not contain [Structure of the Invention] The present invention consists of a container body made of polyethylene terephthalate and a lid having a heat-sealing resin layer on the base material, and the polyethylene terephthalate surface of the container body and the lid are heat-sealed. The package body is sealed by heat sealing between the heat sealable resin layer and the heat sealable resin layer.
Easy-to-open resin composition consisting of 60 to 95 wt% of polybutylene terephthalate resin, of which 90 mol% is terephthalic acid, and 40 to 5 wt% of polyethylene terephthalate resin, of which 80 mol% or more of the dicarboxylic acid component is terephthalic acid. It is characterized by a heat-sealed package. The polyethylene terephthalate used for the container body in the present invention means that 95 mol% or more of the acid component is terephthalic acid, and 95 mol% of the alcohol component is terephthalic acid.
Refers to polyesters in which mol% or more is ethylene glycol. In addition, in addition to the polyethylene terephthalate shown above, polyester other than polyethylene terephthalate in an amount of 10wt% or less without impairing its properties.
Alternatively, it may be added with a known resin such as polyethylene or ionomer. Containers made of polyethylene terephthalate refer to various molded containers whose heat-sealed portions are made of polyethylene terephthalate. Of course, this container may be a blow molded container, an injection molded container, a pressure molded container, a vacuum molded container, etc. made of polyethylene terephthalate alone, or it may be a container having a laminated structure with other resins. The birefringence of polyethylene terephthalate in the heat-sealed part is 6×10 ^-3 or less, preferably 2×
It is preferable to use substantially non-oriented polyethylene terephthalate having a particle size of 10 ⁻³ or less. When the birefringence is within the above range, adhesion in a state that is not sufficiently melted as described in the present invention is easier,
Furthermore, the adhesive force is improved and the sealing performance becomes a preferable value. The base material in the present invention is not particularly limited, and includes various materials such as metal, synthetic resin, and paper. Specifically, lids made of these base materials include metal foils such as aluminum foil, tin foil, copper foil, and tin foil, stretched films such as polyethylene terephthalate and nylon, various papers, or each of these materials. A laminate is preferable, and the surface of the lid may be subjected to surface treatment such as anchor coating treatment or corona discharge treatment as necessary. The heat sealable resin layer provided on the base material is a resin composition mainly composed of polybutylene terephthalate resin and polyethylene terephthalate resin. The polybutylene terephthalate resin used for this heat-sealable resin layer is a dicarboxylic acid component.
50 to 90 mol%, preferably 60 to 85 mol% of the resin is composed of terephthalic acid, and the diol component is mainly 1,4-butanediol. Preferably, the polyester is a saturated polyester having an intrinsic viscosity (abbreviated as IV) of at least 0.60 as measured in chlorophenol. As dicarboxylic acids other than terephthalic acid, aromatic and aliphatic dicarboxylic acids such as isophthalic acid, sebacic acid, adipic acid, and azelaic acid can be used in an amount of 10 to 50 mol%, preferably 15 to 40 mol%. Especially isophthalic acid
It is preferable to use 15 to 40 mol% from the viewpoint of heat sealability and peelability. As a diol component, 1,4
-Butanediol is used, but ethylene glycol, diethylene glycol, neopentyl glycol, 1,4 cyclohexanedimethanol, 1,
Copolymerization of other diol components such as 6-hexanediol within a range (preferably 0 to 20 mol %) that does not impair the properties of the polybutylene terephthalate resin can be used. Specific examples of these polybutylene terephthalate resins include polybutylene terephthalate (PBT), polybutylene terephthalate isophthalate (PBT/I), polybutylene terephthalate sebacate (PBT/S), and polybutylene terephthalate adipate (PBT/I). A), polybutylene/ethylene terephthalate, and the like. If the terephthalic acid content is less than 50 mol%, the composition will become too soft and the peeling surface will become dirty, which is not preferable. The blending ratio of polybutylene terephthalate resin is based on the mixture of polybutylene terephthalate resin and polyethylene terephthalate resin.
60 to 95 wt%, preferably 70 to 90 wt%, and 1
It may be of different types, or it may be a mixture of two or more types of resin. In particular, from the viewpoint of achieving both sealability and ease of opening, it is preferable to use PBT/I (65 mol % of terephthalic acid) alone or a resin composition containing this resin as a main component. If the blending ratio of the polybutylene terephthalate resin is less than 60 mol%, the sealing performance will be poor, which is not preferable. Moreover, if it exceeds 95 wt%, it is not preferable because it is necessary to raise the sealing temperature, which makes it impossible to increase the sealing speed and also reduces the ease of opening. In addition, the polyethylene terephthalate resin used for the heat-sealable resin layer has a dicarboxylic acid component of 80 to 100 mol%, preferably 90 to 100 mol% of terephthalic acid, and a diol component that is mainly ethylene glycol. and
Note that this resin is preferably a saturated polyester having an IV of at least 0.50. Dicarboxylic acids other than terephthalic acid include isophthalic acid,
Aromatic and aliphatic dicarboxylic acids such as sebacic acid, adipic acid, azelaic acid, etc. can be used. In particular, a copolymer of 98 mol% or more of terephthalic acid or 10 mol% or less of isophthalic acid is preferred from the viewpoint of sealability and easy opening. As the diol component, ethylene glycol is used, but other diols such as diethylene glycol, butanediol, 1,4 cyclohexanedimethanol, 1,6 hexanediol, etc. are used within a range that does not impair the properties of the polyethylene terephthalate resin (preferably). 0 to 20 mol%) can be used. Specific examples of these polyethylene terephthalate resins include polyethylene terephthalate (PET), polyethylene terephthalate isophthalate (PET/I), and polyethylene terephthalate sebacate (PET/I).
S), polyethylene terephthalate adipate (PET/A), etc. If the terephthalic acid component is less than 80 mol%, processability during heat sealing will be poor and the peeled surface will be rough, which is not preferable. The blending ratio of polyethylene terephthalate resin is as follows:
It is 40 to 5 wt%, preferably 30 to 10 wt%, and may be one type or a mixture of two or more types of resin. If the blending ratio of the polyethylene terephthalate resin exceeds 40 wt%, it is not preferable because the sealing performance will be lost. Also, on the other hand, 5wt
If it is less than %, sealing performance cannot be obtained unless the sealing temperature is raised, which is not preferable because easy opening properties are lost and the peeling interface becomes rough. The present invention relates to an easily openable heat-sealable package characterized by having the above-mentioned resin composition as a heat-sealable resin layer. Additives such as stabilizers, ultraviolet absorbers, viscosity modifiers, plasticizers, nucleating agents, organic lubricants, and pigments can be dispersed and blended. In addition, 0 to 20 parts, preferably 3 to 10 parts of inorganic fine particles such as titanium oxide and mica are added to 100 parts of the resin composition.
It is even more preferable to add 10% of the above-mentioned compound, since it is possible to further improve the sealing property and the peeling interface. Further, a known resin may be added for the same purpose as the above-mentioned additive in an amount not exceeding 20 parts per 100 parts of the composition. It should be noted that the term "easy-openability" as used in the present invention refers to having adhesive strength to the extent that it can be easily peeled off by hand. Specifically, it refers to an adhesive strength of 0.8 to 2.2 Kg/cm when measured at a peel angle of 90° and a tensile speed of 300 mm/min. Next, a method for manufacturing the package of the present invention will be explained. After the polybutylene terephthalate resin and the polyethylene terephthalate resin are mixed by dry blending, this composition is fed to an extruder and formed into a film by a known method such as an inflation method or a T-die method. Of course, chips prepared by kneading these resins in advance using a pelletizer or the like may also be used. This film is bonded to a base material such as aluminum foil to form a heat-sealable resin layer. Note that an anchor coat may be applied to the base material as necessary, or the heat-sealable resin layer may be directly melt-extruded laminated onto the base material. The material provided with the heat-sealable resin layer thus obtained is formed into a lid shape to form a lid body (however, the base material may be previously processed into a lid shape). The lid provided with the heat-sealable resin layer thus obtained and various containers whose heat-sealed portion is polyethylene terephthalate are heat-sealed by a heat-sealing method, high-frequency induction heating, or the like. The thickness of the heat-sealable resin layer provided on the base material varies depending on the purpose and method of use, but is 5 to 100 μm, preferably 10 to 50 μm.
m is desirable. It goes without saying that the easy-open heat-sealed packaging of the present invention can be used as a container for a variety of containers including food, but unlike when polyolefin resins are used, there is almost no inherent odor.
Suitable for packaging contents where flavor is important, such as alcoholic beverages. In addition, since the peeling interface after opening is good, it is preferable to use it in applications where the peeling surface comes into direct contact, for example, containers for soft drinks such as youth and alcoholic beverages. [Operations and Effects of the Invention] As described above, the present invention provides an easy-to-open heat-sealable container body comprising a container body made of polyethylene terephthalate as a component and a lid body provided with a heat-sealable resin layer made of a specific resin composition. Since it is a package, by sealing it at a temperature below the melting point of the heat-sealable resin,
The following excellent effects were obtained. Since the heat sealing temperature is low, it can be sealed at high speed. The opening force is stable. That is, there is almost no difference between the force required to start opening and the force required to open the package while peeling is progressing. There is no feathering at the peeled interface, and the peel shows a good appearance. The resin-specific odor does not transfer to the contents. Next, a method for measuring characteristics and evaluation criteria in the present invention will be explained. (1) Sealing performance Adhesive strength was used as an indicator. Specifically, a 50 μm thick anchor coated with vinyl chloride/vinyl acetate copolymer primer
A heat-sealable resin sheet is sandwiched between ^an aluminum foil of Seal it. The adhesive strength [Kg/cm] of the obtained sample was measured using Tensilon manufactured by Toyo Baldwin Co., Ltd. at a peel angle of 90° and a tensile speed of 300 mm/min. In this case, if the adhesive strength during stable peeling was 0.8 Kg/cm or more, the sealing performance was good, and if it was less than 0.8 Kg/cm, it was considered poor. (2) Openability The ratio of the adhesive strength at the start of peeling to the adhesive strength in a stable peeling state and the absolute value of the adhesive strength in a stable peeling state were used as indicators. Specifically, the adhesive strength was measured in the same manner as in (1), and the adhesive strength at the start of peeling was divided by the adhesive strength at stable peeling, and the value was 1.5 or less.
If there was an adhesion temperature at which the adhesive strength during stable peeling was 2.2 kg/cm or less, the resin was considered to have good unsealability. If even one of the above conditions was not met, the product was considered to have poor unsealability. (3) Peelability A laminate of aluminum foil, heat-sealed resin sheet, and unstretched polyethylene terephthalate film obtained by heat-pressing in the same manner as in (1) at the lowest bonding temperature at which an adhesive strength of 1 kg/cm can be obtained. was peeled off using Tensilon manufactured by Toyo Baldwin Co., Ltd. at a tensile speed of 300 mm/min. Those with small variations in peeling force and good peeling interface condition are marked with "○", those with large variations in peeling force and severe feathering are marked with "x", and those in between are marked with "△". (4) High-speed sealability The adhesive strength when bonded using the method described in (1)
The lowest bonding temperature showing 0.8Kg/cm is higher than the melting peak temperature of polybutylene terephthalate resin.
The high-speed sealing property was rated “〇” when the temperature was lower than 15°C, and the other cases were rated “×”. If there are two or more types of polybutylene terephthalate resin, the melting peak temperature of each of them
The melting peak temperature Tm was calculated using the following formula for Ti and the added weight Wi. Tm=(Σ ^j Ti×Wi)/Σ ⁱ Wi [Examples] Next, embodiments of the present invention will be described based on examples. Examples 1 to 3, Comparative Examples 1 and 2 Melting peak temperature (hereinafter abbreviated as Tm) is 165
PBT/I (copolymerization ratio of terephthalic acid and isophthalic acid is 65:35 and IV is 1.00) is
Dry in a hot air oven at 120°C. On the other hand, PET
(IV of 0.62) was dried in a vacuum dryer at 180°C for 3 hours. PET was added to this PBT/I at 0 wt% (Comparative Example 1), 10 wt% (Example 1), 20 wt% (Example 2), 30 wt% (Example 3), and 50 wt% (Comparative Example 2). After adjusting each amount to 100wt%, they are mixed by a dry blending method. Next, using an extruder with a diameter of 65 mm and L/D of 22, the mixture was extruded from a T-die attached to the tip of an extruder using aluminum foil (thickness:
50μm) to a thickness of 20μm. The laminate and unstretched polyethylene terephthalate film were heated at the temperatures shown in Table 1 to determine the unsealability,
The sealability and peelability were investigated, and the results are shown in Table 1. As is clear from Table 1, PBT/
With I alone, sufficient adhesion cannot be obtained unless the bonding temperature is Tm or higher. Further, at 180°C, the sealability is good, but the ease of opening is lost and the condition of the peeling surface is also poor. On the other hand, in Examples 1, 2, and 3 of the present invention in which PET with a high Tm of 270°C was added, the Tm of PBT/I was lower than that of PBT/I.
Sufficient sealing power was obtained even at a low temperature of 140°C, the sealing speed could be increased, and a product with excellent sealing performance and peelability was also obtained. However, in Comparative Example 2, which is outside the scope of the present invention, sufficient sealing force could not be obtained even if the bonding temperature was increased. Example 4, Comparative Example 3 As Example 4, the sample used in Example 1 above was
PBT/I has a Tm of 225°C (copolymerization molar ratio of terephthalic acid and isophthalic acid is 85:15).
, with an IV of 0.70), and as comparative example 3,
PET/I (copolymerization molar ratio of terephthalic acid and isophthalic acid of 70:30, IV of 0.72) with a Tm of 180°C was prepared in the same manner as in Example 1 to a thickness of 20 μm.
Example 1
It was evaluated in the same way. The results are shown in Table 1. As is clear from comparing Example 4 (and Example 1) and Comparative Example 3, Comparative Example 3 in which the terephthalic acid component in PET/I was less than 80 mol% had good sealing performance, but feathering occurred. However, this is not preferable because the peeled surface becomes rough. Examples 5 to 6, Comparative Example 4 As Example 5, PBT/I with Tm of 190°C (copolymerization molar ratio of terephthalic acid and isophthalic acid is 80:20)
(IV is 0.90), and as Example 6, Tm is
PBT/I at 145°C (copolymerization molar ratio of terephthalic acid and isophthalic acid is 55:45, IV is 1.10),
And as Comparative Example 4, PBT/
PBT/
10 wt% of PET was added to each of I in the same manner as in Example 1, and a film was formed and evaluated in the same manner as in Example 1. The results are shown in Table 1. As is clear from comparing Examples 5 and 6 (and Example 1) with Comparative Example 4, when terephthalic acid in PBT/I is 50 mol% or more (Example 1,
5, 6) have good high-speed sealing properties, peelability, unsealability,
Although it has good sealing properties, when the content of terephthalic acid is less than 50 mol % (Comparative Example 4), feathering occurs on the peeled surface and the opening property is also poor. 【table】

Claims (1)

[Claims] 1 Consisting of a container body made of polyethylene terephthalate and a lid with a heat-sealable resin layer on the base material, heat is generated between the polyethylene terephthalate surface of the container body and the heat-sealable resin layer of the lid. In the package sealed by sealing, the heat-sealable resin layer contains 50 to 90 mol% of dicarboxylic acid.
60 to 95 wt% of a polybutylene terephthalate resin whose dicarboxylic acid component is terephthalic acid, and 40 to 5 wt% of a polyethylene terephthalate resin whose dicarboxylic acid component is at least 80 mol% of terephthalic acid. Openable heat-sealed package.