JPH06316044A - Plastics made cover material - Google Patents

Abstract

PURPOSE:To provide a cover material which can improve an oxygen barrier property without any fusion in a heat sealing part a packaging container. CONSTITUTION:A cover material 13 is composed of polycarbonate 1 as an uppermost layer, an ethylene-vinylalcohol copolymer layer 4, a polyolefin layer 2, and an adhesive layer 3 as an intermediate layer, and a polyolefin sealant layer 5 as a lowermost layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic lid member which is heat-sealed to a flange portion of a packaging container.

[0002]

2. Description of the Related Art Conventionally, there has been known a sealing container in which a plastic packaging container is filled with fruits, jelly liquid and the like, and the packaging container is sealed with a plastic lid material.

Of these, the packaging container has a container body and a flange portion provided at the upper end opening of the container body, and the packaging container is obtained by thermoforming a plastic laminate. On the other hand, the lid member is composed of a heat-sealing portion that overlaps the flange portion of the packaging container and a drop lid portion that covers the opening of the packaging container, and is obtained by thermoforming a plastic laminate in the same manner. Further, the heat-sealing portion of the lid member is heat-sealed to the flange portion of the packaging container.

[0004]

However, as described above, the lid member can be obtained by thermoforming a plastic laminate, and such a lid member is required to have gas barrier properties and to be formed with the flange portion. It is required to maintain high seal strength between them. Further, the lid material is required to have easy opening property. As a material satisfying the easy opening property, for example,
JP-B-63-45304, JP-B-63-4530
Publication No. 5, Publication No. 63-45306 and Publication No. 6
The thing described in the 3-45307 gazette is known. However, in fact, the lid materials described in these publications do not take much consideration especially on the gas barrier property.

The present invention has been made in consideration of the above points, and provides a plastic lid material which has an excellent gas barrier property, maintains a high sealing strength with a flange portion, and is easily opened. The purpose is to provide.

[0006]

The present invention comprises a heat-resistant polyester layer as the uppermost layer, an ethylene-vinyl alcohol copolymer layer and a polyolefin layer as the intermediate layer,
A plastic lid material comprising a polyolefin sealant layer as the lowermost layer, and a heat-resistant polyester layer as the uppermost layer, an ethylene-vinyl alcohol copolymer layer as an intermediate layer, and a polyolefin as the lowermost layer. This is a plastic lid material.

[0007]

According to the present invention, since the heat-resistant polyester layer is arranged as the uppermost layer, defective root cutting of the lid material (fusing not only the lid material seal layer but also the base material layer to the packaging container side) is prevented. Further, since the ethylene-vinyl alcohol copolymer layer is arranged as the intermediate layer, the gas barrier property of the lid material can be improved.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. First, a sealed container including a packaging container and a lid member will be described with reference to FIGS. 2 to 4. As shown in FIG. 2, the packaging container 12 is filled with the fruit 14 and the jelly 15, and the packaging container 12 is sealed with the lid member 13 to form the sealed container 11.

The packaging container 12 comprises a container body 12a and a flange portion 12b provided at the upper end opening of the container body 12a. On the other hand, the lid member 13 includes a heat seal portion 13b overlapping the flange portion 12b of the packaging container 12 and a drop lid portion 13 connected to the inside of the heat seal portion 13b.
It consists of a and. The dropping lid 13a is the body 12a of the container.
Which covers the upper opening of the heat seal portion 13b.
It is set down from below.

The packaging container 12 is made of polypropylene (hereinafter P
P) / adhesive layer (hereinafter referred to as AD) / ethylene-
Vinyl alcohol copolymer (hereinafter referred to as EVOH) / A
It is produced by thermoforming a laminated body made of D / PP. On the other hand, the lid member 13 is made of a gas barrier laminate as described later.

Next, the heat sealing work between the flange portion 12b of the packaging container 12 and the heat sealing portion 13b of the lid member 13 will be described with reference to FIG. As shown in FIG.
First, the packaging container 12 filled with the fruit 14 and the jelly 15 is housed in the retainer 21. Next, the packaging container 1
The heat-sealing portion 1 of the lid member 13 on the flange portion 12b of 2
Stack 3b. Thereafter, the seal head 22 is lowered with respect to the retainer 21, the pressing portion 24 of the seal head 22 is pressed against the heat seal portion 13b of the lid member 13, and the heat seal portion 13b of the lid member 13 and the flange portion of the packaging container 12 are pressed. Heat sealing work is performed with 12b.

Next, examples of the lid member according to the present invention will be described. FIG. 1 is a diagram showing an embodiment of a plastic lid member according to the present invention. In FIG. 1, the lid material of the present invention is a polycarbonate (hereinafter referred to as PC) layer 1 as an uppermost layer, and a polyolefin (hereinafter referred to as PO) as an intermediate layer.
It comprises layers 2, 2 ', adhesive layers 3, 3', EVOH layer 4 and PO sealant layer 5 as the bottom layer.

Thus, in the present invention, the PC layer 1 is laminated in order to impart properties such as moldability, heat resistance and shape retention property to the lid material, and its thickness is preferably 15 to 150 μm, and 15 μm. In the following cases, pinholes and holes are formed in the corners of the molded product, the shape retention is deteriorated, and the shape of the lid cannot be maintained, which is not preferable. On the other hand, when it is 150 μm or more, it is not preferable because heat is extremely difficult to be transferred during heat sealing, heat sealing tends to be defective, and cost is increased.

Next, the EVOH layer 4 is laminated in order to give an oxygen barrier property to the lid material, and preferably has a thickness of 10 to 50 μm. When it is 10 μm or less, pinholes and holes are formed at corners during molding. However, since the barrier effect is lost, it is not preferable, and when it is 50 μm or more, the moldability is deteriorated.

Except for the PC layer, PO / AD / EVOH / A
The PO layer 2, which is made by coextrusion with the composition of D / PO / PO sealant and adheres to the PC layer, is subjected to corona treatment. The PO layers 2 and 2'are laminated in order to give rigidity to the lid material, and the total thickness including the AD layers 3 and 3'is preferably 150 μm or less, and when the thickness is 150 μm or more, at the time of heat sealing. It is not preferable because heat is difficult to be transmitted and heat sealing tends to be poor.

For the layers other than the PC layer, a normal film may be produced by dry lamination.
The O layers 2 and 2 ′ are not necessarily provided as described later. The resin used for the PO layers 2 and 2'includes propylene-based resins such as isotactic polypropylene, ethylene-propylene copolymer, propylene-butene-1 copolymer, ethylene-propylene-butene-
One copolymer or the like can be used alone or in combination of two or more kinds. Other than this, it is also possible to use other crystalline olefin polymers such as high-density, medium-density or low-density polyethylene, and two or more kinds of ethylene / vinyl acetate copolymers and polymethylpentene resin mixtures. it can. In particular, a propylene-based resin is a low water-absorbing thermoplastic resin and is preferably used because it has rigidity, transparency (contact clearness) and other characteristics. In addition, a crushed product such as an edge loss at the time of manufacturing the co-pressed sheet or a defective product may be mixed as a recovered resin.

The adhesive layers (AD) 3, 3'are mainly composed of an adhesive polyolefin resin. Examples of the adhesive polyolefin resin used for the AD layers 3 and 3'include polyethylene (hereinafter referred to as PE), ethylene-α / olefin copolymers, α / polyolefins such as polypropylene, polybutyne, and polyisobutylene, and polybutadiene and polyisoprene. Carbonyl groups based on carboxylic acids, carboxylic acid salts, carboxylic acid anhydrides, carboxylic acid esters, carboxylic acid amides or imides, aldehydes, ketones or the like, or cyano groups; hydroxy groups; ether groups; oxiranes A copolymer with one or more ethylenically unsaturated monomers having a combination with groups and the like can be used.

More specifically, A. Ethylenically unsaturated carboxylic acids: acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid, 5-norbornene-2,3-dicarboxylic acid, etc., B.I. Ethylenically unsaturated carboxylic acid anhydride: acrylic acid anhydride,
Citraconic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, tetrahydrophthalic anhydride and the like, C.I. Ethylenic unsaturated ester: ethyl acrylate, ethyl methacrylate, 2-ethylhexyl acrylate,
Monoethyl or diethyl maleate, vinyl acetate, vinyl propionate, propyl γ-hydroxymethacrylate, ethyl β-hydroxyacrylate, glycidyl acrylate, glycidyl methacrylate, β-N-ethylaminoethyl acrylate, etc., D.I. Ethylenically unsaturated amides or imides: acrylamide, methacrylamide, maleimide, etc. E. Ethylenically unsaturated aldehydes or ketones: Copolymers of acrolein, methacrolein, vinyl ethyl ketone, vinyl butyl ketone and the like with ethylenically unsaturated monomers can be used.

A PO resin, particularly polyethylene, can be contained in the adhesive layers 3, 3'containing such an adhesive polyolefin resin. In this case, the content of the adhesive polyolefin resin in the adhesive layers 3 and 3'is preferably 30% by weight or more. If the content of the adhesive polyolefin-based resin is less than 30% by weight, the adhesiveness with the EVOH layer 4 is deteriorated, which is not preferable. The thickness of such adhesive layers 3, 3'is preferably about 5 to 10 m. In this specification, the heat-resistant polyester layer can also be coextruded, but since the adhesive for coextrusion has adhesiveness with polyester and does not have heat resistance sufficient to withstand sterilization, it is usually manufactured by lamination.

The polyolefin sealant layer 5 functions as a heat seal layer and has a thickness of 10 to 10.
100 μm is preferable, and when it is 10 μm or less, the peel strength after heat fusion becomes less than the practical strength, which is not preferable.
When it is more than 00 μm, not only the cost increases but also the film-forming property is extremely deteriorated, which is not preferable. Also, 100 μm
In the above case, stringing and fluffing can be seen on the flange portion of the packaging container after opening, which is not preferable.

The polyolefin sealant layer 5 is usually a PE-PP blend polymer for PP containers. The sealant may be two coextruded layers with a PE backing layer. The blending ratio of PE and PP is preferably 7: 3 to 3: 7. When the PE amount becomes large and the blending ratio becomes 7: 3 or more, cohesive failure does not occur and interfacial peeling occurs, and the heat seal strength is It is not preferable because it fluctuates and is unstable. On the other hand, when the amount of PP increases and the blend ratio becomes 3 to 7 or less, complete fusion occurs,
It is not preferable because the easy opening property is lost. In addition, PE-P
Since P-blended polymer film does not contain low molecular weight substances, it has a low odor and is suitable for fruit packaging. Moreover, as for the polyolefin sealant layer 5, the product in which the PP layer on the sealing side of the packaging container 12 is a blend specification with PE is a product other ethylene-vinyl acetate copolymer (hereinafter referred to as EV
A), linear low density polyethylene (hereinafter LL
DPE), low density polyethylene (hereinafter referred to as LDPE), etc., or a mixed resin of two or more thereof can be used as the sealant layer.

In the above embodiment, P is used as the uppermost layer.
Although the example using the C film 1 is shown, any film may be used as long as it is a thermoplastic polyester having a melting point of 200 ° C. or higher (hereinafter referred to as heat resistant polyester). Examples of such heat-resistant polyesters include crystalline polyesters such as polyethylene terephthalate (hereinafter PE).
T), polybutylene terephthalate (PBT),
Examples include polyethylene naphthalate (PEN). Also,
As the non-crystalline polyester, there are polyarylate (PAR) and the like in addition to the above PC.

Thus, the uppermost layer has a melting point of 200 ° C.
By using the above heat resistant polyester film,
The uppermost layer can be left without being melted even at the time of heat sealing by heating from the seal head 22. Therefore, the lid material 13
Defective root cutting (the entire lid material is fused to the packaging container side)
Can be reliably prevented.

According to the present embodiment, it is possible to provide a lid member which can be easily opened with an appropriate peel strength without causing stringing or fluffing on the flange surface of the packaging container. Moreover, since the thickness of the lid material is such that the heat of the seal head 22 can be sufficiently transmitted to the sealing surface through the lid material, it is possible to provide a lid material that does not cause a sealing failure. Further, since the lid material contains the ethylene-vinyl alcohol copolymer film having excellent gas barrier properties, the gas barrier property of the entire lid material can be improved.

(Specific Example 1) Next, a specific example of the present invention will be described. First, in the following layer structure, a heat resistant polyester layer was dry-laminated using an isocyanate-based adhesive, and this laminated body was vacuum / pressure air molded to form a lid material. PC 30 μm / dry lamination (hereinafter referred to as LMD) / PP 90 μm / adhesive layer (AD) 5 μm / EVO
H20 μm / AD5 μm / PE-PP blend sealant 30 μm In this case, PE-PP blend polymer film is PE
HDPE with a density of 0.97 and MI = 8 is used as PP
As 50% by weight random copolymer, density 0.90, M
The one with I = 6.0 was used.

Next, the oxygen transmission rate of this lid material was measured. This lid member has a 70 mm square and a height of 10 mm, and has a volume of about 49 cc. Measurement of oxygen permeability is OX
TRAN (Modern Controls. Inc.
(Manufactured by Mitsui Chemicals, Inc.) was used and the measurement was performed under the conditions of 20 ° C. and 90% RH.

Comparative Example 1 Further, as Comparative Example 1, a PC
30 μm / LMD / PP 90 μm / AD 5 μm / EVO
A lid member was formed by vacuum / pressure forming from a laminate having a layer structure of H20 μm / AD5 μm / PE-PP blend sealate 30 μm. The oxygen permeability of the lid member of Comparative Example 1 was measured. The results are shown in Table 1. Comparative Example 1
The PE-PP blend sealate is the same as that shown in Example 1 of the present invention. As is clear from Table 1, the lid material according to the present invention has an excellent oxygen barrier property.

[0028]

[Table 1]

(Specific Example 2) Next, as the lid material of the present invention,
Films having different layer configurations as described below were dry-laminated with each other using an isocyanate-based adhesive, and this laminated body was vacuum / pressure-formed to form four types of lid materials. Regarding the following, a laminate was prepared by molding LDPE-PP blend polymer and co-extrusion of LLDPE and LDPE blend sealant except for the PC layer, and molded.

20 μm PET / unstretched PP (hereinafter C
PP) film 150 μm / EVOH 20 μm /
PE-PP blend polymer (hereinafter referred to as PE-PP)
Film 30μm PC 20μm / CPP film 150μm / EVO
H 20 μm / PE-PP film 30 μm PC 120 μm / EVOH 20 μm / PE-PP film 30 μm PC 30 μm / LMD / LDPE-PP blend layer 50 μm / AD 5 μm / EVOH 10 μm / AD 5 μm
/ LDPE-PP blend layer 50 μm / LLDPE-L
DPE blend sealant 30μm

Comparative Example 2 Similarly as Comparative Example 2, a lid member having the following layer structure was formed. CPP 180 μm / EVOH 20 μm / PE-PP film 30 μm In addition, the PE-PP films of the present invention and Comparative Example 2 use HDPE having a density of 0.97 as PE and MI = 8 and a random copolymer of 60 wt% as PP. , Density 0.90, MI = 6.0 was used. Also, of the present invention does not include unstretched polypropylene film.
Then, put these lids into a plastic packaging container.
Heat sealing was performed under the condition of 2 seconds at ˜210 ° C. for 2 seconds (total sealing pressure 80 kg). After the heat-sealed surface was sufficiently cooled, the lid material was opened, and the appearance of the peeled surface after opening was confirmed. The results are shown in Table 2.

[0032]

[Table 2] (The numbers in the table indicate the layer thickness μm, and ◎, ○, △, and × are as shown below) ◎: Good appearance of release surface ○: Normal appearance of release surface △: Appearance of release surface ×: Appearance of the peeling surface is defective in root cutting. As is clear from Table 2, in the case of the lid materials of the present invention,
It is possible to reliably prevent the root material of the lid from breaking,
A good release surface can be obtained.

[0033]

As described above, according to the present invention, it is possible to prevent the root material of the lid member from being cut off. Therefore, the peeled surface after the lid member is peeled from the packaging container is kept clean. be able to. Moreover, since the oxygen barrier property of the lid member can be improved, the storability of the contents in the packaging container can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a lid member according to the present invention.

FIG. 2 is a sectional view of a hermetically sealed container including a packaging container and a lid material.

FIG. 3 is an enlarged view of FIG. 3A.

FIG. 4 is a diagram showing heat sealing work.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polycarbonate layer 2, 2'Polyolefin layer 3, 3'Adhesive layer 4 Ethylene-vinyl alcohol copolymer layer 5 Polyolefin sealant layer 11 Sealed container 12 Packaging container 12a Container body 12b Flange portion 13 Lid material 13a Dropping lid portion 13b Heat Seal part 14 Fruit 15 Jelly liquid 21 Retainer 22 Seal head 24 Pressing part

Claims (3)

[Claims] 1. A plastic lid material comprising a heat-resistant polyester layer as an uppermost layer, an ethylene-vinyl alcohol copolymer layer and a polyolefin layer as an intermediate layer, and a polyolefin sealant layer as a lowermost layer. . 2. The heat-resistant polyester layer has a thickness of 15 to 1
50 μm, the thickness of the ethylene-vinyl alcohol copolymer layer of the intermediate layer is 10 to 50 μm, the thickness of the polyolefin layer is 150 μm or less, and the thickness of the lowermost polyolefin sealant layer is 10 to 100 μm. The plastic lid member according to claim 1. 3. A plastic lid material comprising a heat-resistant polyester layer as an uppermost layer, an ethylene-vinyl alcohol copolymer layer as an intermediate layer, and a polyolefin sealant layer as a lowermost layer.