JPS60180833A - Easy-open heat-seal package - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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]

It consists of a container body made of thermoplastic plastic such as polypropylene or polyethylene terephthalate, and a lid with a heat-sealable resin layer on a base material such as metal foil. BACKGROUND ART Packaging bodies that are sealed with a resin layer by heat sealing have been widely used in the field of food packaging and the like.

゛This heat-sealing resin layer is not only heat-sealed to form a heat-sealed structure with excellent sealing reliability, but also has an easy-to-open sealing structure, that is, can be easily peeled off by hand when opening. At the same time it has a degree of strength.

It must have a smooth peeling interface without surface roughness or feathering. In order to satisfy this requirement, heat-sealing resins based on polyglopylene and polyethylene (for example,
Attempts have been made to use JP-A-57-77465) or polyethylene terephthalate/isophthalate copolymers. However, such a conventional heat-sealable resin layer has the disadvantage that all is rare.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks and provide a package that is smooth and easy to open.

[Structure of the invention]

The present invention consists of a container body made of polyethylene terephthalate as a constituent material, and a lid body having a heat-sealing resin layer on the base material. In the package which is sealed by heat sealing, the heat sealable resin layer is (-) a polyethylene terephthalate resin in which 75 or more moles of dicarboxylic acid is terephthalic acid, and/or a polyethylene terephthalate resin in which 75 or more moles of dicarboxylic acid is 80 or more moles of dicarboxylic acid. Polybutylene terephthalate resin whose mole fraction is terephthalic acid is 10 to 40 (b) Polybutylene terephthalate resin whose dicarboxylic acid is 50 to 75 mole fraction is terephthalic acid is 90 to 6
9. A resin composition comprising 10 to 30 parts by weight of the polyolefin resin (c) based on 100 parts by weight of the blend of (a) and (b). Cooling down crystallization temperature T of resin (a).

eA is the cooling crystallization temperature Tm of resin (b) (2 from IB).
This is an easy-to-open package characterized by a temperature higher than 0°0.

The polyethylene terephthalate used for the container body in the present invention refers to a polyester in which 95 moles or more of the acid component is terephthalic acid and 95 moles or more of the alcohol component is ethylene glycol.

In addition to the polyethylene terephthalate shown above, polyesters other than polyethylene terephthalate with a weight of 10% less than the polyethylene terephthalate within a range that does not impair 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 in which the heat-sealed portion is made of the above-mentioned 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 the polyethylene terephthalate in the heat-sealed portion is preferably 6×10 2 or less, preferably 2×10 −5 or less, and is preferably made of substantially non-oriented polyethylene terephthalate. When the birefringence is within the above range, adhesion becomes easier and adhesive strength is improved, resulting in favorable sealing performance.

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 preferred, and the surface of the lid may be subjected to a surface treatment such as anchor coating treatment or corona discharge treatment as necessary.

The resin (-) used in the heat sealable resin layer is a single substance or a mixture of polyethylene terephthalate resin and/or polybutylene terephthalate resin described below.

Polyethylene terephthalate resin is composed of 75 or more moles of dicarboxylic acid, preferably 80 or more moles of terephthalic acid! The diol component is mainly composed of ethylene glycol. Furthermore, this resin (a
) is preferably a saturated polyester having an intrinsic viscosity (hereinafter abbreviated as IV) of at least 0.50 as measured in 0-chloroenol at 25°C. Dicarboxylic acids other than terephthalic acid include isophthalic acid and sebacic acid.

Aromatic and aliphatic dicarboxylic acids such as adipic acid, azelaic acid, etc. can be used. Ethylene glycol is used as the diol component, but 1,4-butanediol, diethylene glycol, neopentyl glycol, 1,4-cyclohexane dimetatool, 1,6
Copolymerization of other diol components such as hexanediol within a range (preferably 0 to 20 mol %) that does not impair the properties of the polyethylene terephthalate resin can be used. Specific examples of these polyethylene terephthalate resins include polyethylene terephthalate (PET
), polyethylene terephthalate/inphthalate (
PET/I), polyethylene terephthalate sebacate (PET/S), polyethylene terephthalate adipate (PET/A), and the like.

9. Polybutylene terephthalate and rate resins are those in which 80 or more moles of the dicarboxylic acid component, preferably 85 or more moles, are terephthalic acid. And as a diol component, 1
．． The resin is mainly composed of 4-butanediol, and this resin is preferably a saturated polyester having an IV of at least 0.50. As a dicarboxylic acid other than terephthalic acid.

Aromatic and aliphatic dicarboxylic acids such as isophthalic acid, sebacic acid, adipic acid, azelaic acid can be used. As a diol component.

Although 1,4-butanediol is used, other diol components such as ethylene glycol, diethylene glycol, neopentyl glycol, 1.4 cyclohexane dimetatool, and 1°6 hexane diol are used without impairing the properties of the polybutylene terephthalate resin. Within the range (preferably 0
~20 molar ratio) can be used.

Specific examples of these polybutylene terephthalate resins include polybutylene terephthalate (P B T ),
Polybutylene terephthalate/isophthalate (PB,
T/I) Polybutylene terephthalate sebacate (P
BT/S), polybutylene terephthalate adipes) (PBT/AL polybutylene ethylene terephthalate, etc.).

The resin (a) is a single substance or a mixture of the polyethylene terephthalate resin and/or polybutylene terephthalate resin described above.

10-40% by weight for the heat-sealable resin layer, preferably
Add 20-60% by weight. If the resin (a) is added in excess of 40% by weight, the sealing performance will be poor, which is not preferable. Furthermore, if resin (a) is added in an amount of 10% less, the change in opening force over time will increase, and a portion of the heat-sealable resin layer will be torn off at the peeling interface, resulting in poor smoothness. Lost.

This is not desirable because it becomes dirty.

9. The resin (b) used in the heat-sealable resin layer has a dicarboxylic acid component in which 50 to 75 moles, preferably 60 to 70 moles, of the dicarboxylic acid component is terephthalic acid. As a diol component, 1.
It is mainly composed of 4-butanediol, and IV
is preferably at least 0.50. 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.

As the diol component, 1,4-butanediol is used, but ethylene glycol, diethylene glycol:r-k
, Neohair f/l/f IJ call, 1.4
Copolymerization of other diol components such as cyclohexane dimetatool and 1,6 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 isophthalate (PBT/I
), polybutylene terephthalate sebacate (PB
T/S), polybutylene terephthalate-adipate (PBT/A).

Examples include butylene ethylene terephthalate.

The polybutylene terephthalate resin (b) preferably has a weight ratio of 90 to 60 with respect to the heat sealable resin layer.
Add 0% by weight. If more than 90 parts by weight is added, the sealability after retorting and processing becomes poor and the smoothness of the peeling interface becomes poor, which is not preferable. If the amount is less than 60 parts by weight, the sealing performance will deteriorate, which is not preferable.

Polyolefin resin (C
) means a copolymer with melt index refinement measured at 190'a, a copolymer of melt measured at 260°C, a melt index force D measured at 190'a,
Polypoor which is 05-200 g/10 minutes ;”M
A/Product polybutene polymers, modified polyolefin fibers, ionomers, and mixtures of these polyolefin resins can be used. The modified olefin mentioned above is obtained by graft polymerizing polyolefin with at least one monomer selected from α, β-ethylenically unsaturated basic acids and their acid anhydrides, esters, amides, and imides at a grafting ratio of 20 molar or less. This is what I did.

Examples include polyethylene grafted with maleic anhydride. The ionomer referred to in the present invention is a copolymer of an α-olefin and an ionic salt of an α,β-unsaturated carboxylic acid containing a mono- to trivalent metal ion. As an example, mention may be made of partial metal salts of copolymers of ethylene and methacrylic acid. These polyolefin resins (c) were added in an amount of 10-60 parts by weight based on 3100 parts by weight of ((a)+(b)).

Add 15 to 25 parts by weight of Koshikake. If the amount of the polyolefin resin added is less than 10 parts by weight, the ease of opening will be poor and the peeling surface will be extremely rough, which is not suitable. As these polyolefin resins, polyethylene, ionomer, and ethylene grafted with maleic anhydride are preferable, and among them, polyethylene is particularly preferable.

However, ethylene/vinyl acetate copolymer is easy to open.

Unpleasant in terms of odor.

The cooling crystallization temperature in the present invention refers to the crystallization peak temperature when the melt is cooled at a constant cooling rate, and is considered to be a measure of the ease with which the resin crystallizes. When the cooling crystallization temperature of resin (a) is TmcA and the cooling crystallization temperature of resin (b) is TmaB + TmaA≧TmQB+20
℃ is necessary in order to obtain a uniform peeling interface. If 7m0A≧TmcB+25°C.

This is preferable because it further improves the uniformity of the peeled interface.

It is not clear why the peeling characteristics are improved when the cooling crystallization temperatures of resin (a) and resin (b) have the above relationship, but it is not clear why the peeling characteristics are improved, but after melt-extruding the heat-sealed resin layer, it is cooled. In this process, resin (a) is first crystallized, and resin (b), which is the main component, is crystallized.
It is presumed that the resin (b), which acts as a nucleating agent during the crystallization of ), becomes fine crystals, improving the releasability and stability of oral adhesion.

The present invention relates to an easily openable heat-sealable package characterized by having a resin composition as described above as a heat-sealable resin layer.

Additives such as antioxidants, heat stabilizers, ultraviolet absorbers, viscosity modifiers, plasticizers, organic lubricants, pigments, etc. are dispersed and added as necessary.
Can be blended. It is preferable to add 0 to 20 parts, preferably 3 to 10 parts, of inorganic fine particles such as titanium oxide or mica to 100 parts of the resin composition, since the sealing properties and peelability can be further improved.

Next, a method for manufacturing a package according to the present invention will be described, but the method is not limited thereto. Resin (a), (b).

After (C) is mixed by triblending, this composition is fed to an extruder and made into a film by a known method such as a T-die method or an inflation method. Of course, chips obtained by kneading these resins in advance using a pelletizer or the like may also be used. The film thus obtained is adhered onto a substrate using heat or an adhesive. If necessary, an anchor coating treatment may be performed on the base material, or, of course, melt extrusion lamination may be performed directly on the base material. Using the lid provided with the heat-sealable resin layer obtained in this manner.

Various types of containers whose heat-sealed portion is made of polyethylene terephthalate are heat-sealed using a heat sealing method, a high-frequency induction heating method, or the like. The thickness of the heat-sealable resin layer provided on the base material varies depending on its purpose and usage.

Although not particularly limited, generally 5 to 100 μm, particularly 1
0 to 50 μm is preferable.

The easy-open heat-sealed package of the present invention can be used as a container for various contents including 9 foods.

Of course, since the peeling interface after opening is good, it is suitable for use in applications where the peeling surface directly contacts the mouth, such as containers for soft drinks such as juice and alcoholic beverages.

〔Effect of the invention〕

In the present invention, the heat-sealable resin layer is made of a blend of two or more specific polyester copolymers and polyolefin, and thus the following excellent effects can be obtained.

(a) There is virtually no change in opening force over time.

(b) No feathering at the peeling interface,
The roughness of the interface becomes fine and the appearance of peeling is good.

Show your mouth.

[Method of measuring characteristics, evaluation criteria]

The characteristics measurement method and evaluation criteria in the present invention are as follows.

(1) Cooling crystallization temperature: PerkinElmer DS
'Measure at C. The resin dried under predetermined conditions is melted at a temperature of its melting peak temperature (in the case of a mixture of various polymers, its highest melting peak temperature) +30°C, and held at that temperature for 15 minutes.

Thereafter, the temperature was lowered at a cooling rate of 10°0/min, and the temperature at which the heat generation due to crystallization peaked was defined as the cooling crystallization temperature. When a large number of exothermic peaks occur, a weighted average of the peak area S of the cooling crystallization curve was taken, and this was taken as the cooling crystallization temperature. Then, the difference between TmcA and -08 was expressed as ΔTmQ.

(2) An unstretched polyethylene terephthalate film with a thickness of 150μ is used as the heat-sealed part of the unsealed polyethylene terephthalate container body, and an aluminum plate anchor-coated with urethane resin is used as the base material to ensure heat sealability between the two. Sandwich the resin layer.

Heat for 1 second with a heat sealer heated to the specified temperature,
Glued. The sample obtained in this way was 1CI1
It was cut into 1-width strips and stretched at a peeling angle of 180° C. with a Tensilon manufactured by Toyo Baldwin Co., Ltd. at a peeling speed of 10 mm/sea, and the peel strength at that time (the opening force was approximately 0).

The opening force evaluated in this way is 0.8 to 2.0 bags/bag/
■ If it is, the state where both sealability and easy opening are compatible is "○".
and the others were designated as rXJ.

(3) Opening after a few days The opening force was expressed after being left in an atmosphere of 50° C. for one month.

(4) Peeling surface: Judgment was made based on the surface condition of the polyethylene terephthalate film after measuring the adhesive strength. The peeling surface is smooth and there is no feathering.
"○", those with slightly poor smoothness were marked "△", and those with no smoothness and feathering were marked "x".

〔Example〕

Embodiments of the present invention will be described below based on Examples, and will be indicated using the following abbreviations.

P B T / I = (α/β) 1.4 butanediol is used as the diol component. Terephthalic acid and isophthalic acid are used as acid components, with α molar amount of terephthalic acid and β molar amount of isophthalic acid.

PET/I=(α/β) Ethylene glycol is used as the diol component. The acid component is the same as above.

Examples 1-4. Comparative examples 1 to 3 Polyethylene terephthalate (Tm.

=186℃, IV=C1,61L PET/I (8
5/15) (T, ., = 139'O, IV = 0.65)
, PBT/I (85/15) (T, 0.=158°O
, Iv=0.96).

On the other hand, as resin (b) PBT/I (65/35)
(TmcB=”'°0.IV=1.02).

The resin (C) is low-density polyethylene (melt flow index measured at 190°C is 12 g/10 minutes).

density 0.927) (hereinafter abbreviated as LDPE). These resins were kneaded in the proportions shown in Table 1 by the triblend method. These blend raw materials were passed through a 40 mmφ extruder with a T-die (L/D=22. Compression ratio=4.[],
15 μm thick aluminum foil coated with 50 μm thick aluminum foil anchor-coated with urethane adhesive.
It was laminated by melt extrusion.

The thus obtained laminate of aluminum foil and heat-sealable resin was bonded to an unstretched polyethylene terephthalate film with the resin layer inside at a bonding temperature of 160°0°180°C and a heat-sealing pressure of 1 kv'- Hot glue in Step 2. In this way, the opening force of the obtained sample before and after aging and the condition of the peeled surface after peeling were determined, and the ΔT process was performed. It is shown in Table 1. As shown in Table 1, Examples 1 to 4 had good opening force before and after oral administration, showed excellent ease of opening with virtually no change after oral administration, and had an excellent resin layer with a smooth peeling surface. Compared to Comparative Examples 1 to B, the adhesive strength decreased significantly over time and the smoothness of the peeled surface was poor.

Example 5. Comparative Examples 4 to 6 PET/I (85/15) (T
m, -139°C, IV, = 0.65), PET/I
(60/40) ("no maA, rv=0.66). On the other hand, as resin (b) PBT/I (85/15
) (TmoB-158°C.

IV=0.96), PBT/I (75/25)(T,
. B=141'a, IV=0.96), PBT/I (
65/35) (TmcB = 111°O, ■v=1.
02'). Also, LDPE is selected as the resin (C). These resins were kneaded using the triblend method in the proportions shown in Table 1. These blended raw materials are extruded into a film from a T-die in the same manner as in Example 1, and laminated by melt extrusion to a thickness of 20 μm on a 50 μm thick aluminum foil anchor-coated with a urethane adhesive.

Opening force, peeling surface and ΔT□ of the thus obtained laminate.

The results are shown in Table 1. Example 5 shows good ease of opening and a smooth peeling surface, but when no polyolefin is added (Comparative Example 4), the peeling force is high but the peeling surface is rough. on the other hand.

When a large amount of polyolefin is added (Comparative Example 5),
Although the peeling surface is good, the adhesive force (unsealing force) is too low and the contents may leak, so it cannot be put to practical use. On the other hand, when a large amount of resin (-) to be the core is added (Comparative Example 6),
The adhesive force is too low to be of practical use. Further, in the case of amorphous PET/I (Comparative Example 7) in which the amount of isophthalic acid is as high as 40 mol, a good peeling surface cannot be obtained at all because it cannot become a crystal nucleus.

Example 6 A cup-shaped container having a capacity of 180 mt was made from an unstretched sheet of polyethylene terephthalate having a thickness of 120 μm by vacuum forming using a conventional method. This container was filled with sake, covered with a lid made from the laminate of Example 1 (with the heat-sealing resin layer surface aligned with the container), and heat-sealed at 180° C. using a round heat sealer. A leak test was performed by inverting the container, but no abnormality was found.

Next, when the lid was opened by hand, it was easily opened.

Moreover, the peeled surface was smooth. Also, 50 filled containers
After being left for 1 month, the unsealability and peeling surface were similarly examined, and both were found to be good.

Claims (1)

[Claims] (1) Consists of a container body made of polyethylene terephthalate and a lid with a heat-sealable resin layer on the base material, and the ethylene terephthalate surface of the container body and the heat-sealable resin layer of the lid. In a package sealed by heat sealing between the two, the heat sealable resin layer is made of (-) a polyethylene terephthalate resin in which 75 moles or more of dicarboxylic acid is terephthalic acid, and/or 80 moles of dicarboxylic acid. (b) Polyethylene terephthalate resin in which terephthalic acid accounts for 50 to 40 moles of dicarboxylic acid. Polybutylene terephthalate resin in which terephthalic acid accounts for 50 to 75 moles of dicarboxylic acid has a weight proportion of 90 to 6.
0 weight ratio (0) The polyolefin resin is a resin composition consisting of 10 to 60 parts by weight per 100 parts by weight of the blend of the above (-) and (b), the cooling crystallization temperature T of the resin (a)
m6A is the cooling crystallization temperature of resin (b) -0B 92
An easy-to-open package characterized by a temperature higher than 0°C.