JP2003340992A - Laminated film for heat seal and packaging bag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film for heat seal which does not spoil releasability even when seal temperature is fluctuated in some extent. <P>SOLUTION: In a laminated film for heat seal obtained by co-extrusion of at least two layers in which at least one layer is a heat seal layer, the heat seal layer is composed of a composition comprising 94-55 wt.% linear low density polyethylene with a density of 0.900-0.940 g/cm<SP>3</SP>, 30-5 wt.% 1-butene homopolymer or 1-butene copolymer comprising at least 90 wt.% isotactic 1- butene polymer, and 1-15 wt.% ethylene-α-olefin copolymer with a density of ≤0.900 g/cm<SP>3</SP>. It is possible to realize a releasable seal in a wide range of sealing temperature by incorporating the ethylene-α-olefin copolymer. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a laminated film for heat sealing and a packaging bag, which can be suitably used as a film for an interior bag used in a bag in carton or a bag in box.

[0002]

BACKGROUND ART Conventionally, a so-called bag-in-carton or bag-in-box is used as a packaging form for a liquid such as a beverage and a gel-like semi-solid body such as butter and cream. This bag-in-carton or bag-in-box consists of a resin inner bag that stores a liquid or a semi-solid body and prevents leakage to the outside of the package, and a corrugated cardboard that prevents the inner bag from being broken by a force acting from the outside. And an exterior body formed of the same.

In the inner bag used for such bag-in-carton and bag-in-box, as an inner bag for storing liquid such as wine and juice, a spout is provided in a part of the inner bag made of resin such as polypropylene and polyethylene. It is widely known that a pouch is integrally provided with a screw cap and can be attached to the spout. On the other hand, the internal bag for storing semi-solids such as butter and cream cannot be pulled out from the spout by tilting the container like liquid, so when using it, you should break the internal bag and take out the stored items. I have to.

As a film which can easily break the inner bag during use, there is proposed a film or sheet capable of peelable seal as shown in Japanese Patent No. 2746644. This film or sheet is made of a material in which polyethylene and polybutene-1 are blended in the heat-sealing layer portion, and by blending polybutene-1, the sealing strength becomes smaller than the normal heat-sealing strength, and peelability is improved. Is improved, the bag is easily broken at the heat seal portion, and the opening property is improved.

[0005]

However, in the film disclosed in the above publication, since the seal temperature region in which peelability is exhibited is narrow, peelability cannot be realized unless the sealing temperature during heat sealing is strictly controlled. There is a problem.

An object of the present invention is to provide a laminated film for heat sealing and a packaging bag which do not impair peelability even if the sealing temperature varies to some extent.

[0007]

The present inventors have found that linear low density polyethylene and 1-butene homopolymer or 1
-In the heat-sealing layer made of a composition containing a butene copolymer, by adding a predetermined amount of ethylene-α-olefin copolymer, based on the knowledge that the seal temperature region expressing peelability is expanded, The invention was conceived.
Specifically, the heat-sealing laminated film according to the present invention is a heat-sealing laminated film having at least one layer as a heat-sealing layer and obtained by coextrusion molding two or more layers, Has a density of 0.900 g /
cm ^{3 to} 0.940 g / cm ³ linear low-density polyethylene 9
4 wt% to 55 wt%, 1-butene homopolymer or 1-butene copolymer containing 90 wt% or more of isotactic 1-butene polymer, 30 wt% to 5 wt%, and density 0.9
The composition is characterized in that it is composed of a composition consisting of 1 wt% to 15 wt% of an ethylene-α-olefin copolymer of 00 g / cm ³ or less.

[0008] The linear low density polyethylene, it is preferable to adopt a density of ^{0.900g / cm 3 ~0.940g / cm 3} , more preferably a density 0.900 g /
cm ^{3 to} 0.930 g / cm ³ is preferable, and MFR (Melt F
A low ratio of 0.2 g / 10 minutes to 10 g / 10 minutes is preferable. The 1-butene homopolymer or 1-butene copolymer has a density of 0.900 g / cm ^{3 to} 0.919.
It is preferred to employ those g / cm ^3, more preferably, to adopt a density of ^{0.900g / cm 3 ~0.910g / cm 3} , MFR is, 0.2 g / 10 min to 10 g / 10 It is preferable to adopt the minute one.

The 1-butene copolymer preferably contains at least 90 wt% or more, preferably 97 wt% or more, more preferably 98 wt% or more isotactic polymer. For example, 1-butene is a main chain. It is preferable to employ an ethylene copolymer of Further, if the 1-butene homopolymer or 1-butene copolymer exceeds 30 wt%, the heat sealing strength at the time of tight sealing by raising the sealing temperature cannot be ensured and is not suitable as a film for packaging heavy goods. On the other hand, 1-butene homopolymer or 1
-If the butene copolymer is less than 5 wt%, peelability does not appear even if the sealing temperature is lowered.

The ethylene-α-olefin copolymer has a density of 0.900 g / cm ³ or less, preferably 0.1.
890 g / cm ³ or less is preferably adopted, and for example, an ethylene-butene-1 copolymer having ethylene as a main chain or an ethylene-propylene copolymer can be adopted. In addition, the ethylene-α-olefin copolymer is 5
If it is less than wt%, the region of the seal temperature at which peelability develops is not sufficiently expanded, which is not practical. On the other hand, when the ethylene-α-olefin copolymer exceeds 30 wt%, the seal temperature range where peelability is exhibited becomes too wide, and the seal temperature range where tight sealing can be performed becomes narrow, resulting in sufficient heat seal strength. Unable to manufacture secured packaging bags.

Layers other than the seal layer of the heat-sealing laminated film described above can be functional layers having a gas barrier property or the like, if necessary. For example, nylon, HDPE (Hi
gh Density PolyEthylene) or the like. Further, although such a laminated film is obtained by coextrusion molding, either T die extrusion molding or inflation molding using a circular die can be adopted.

According to the present invention as described above, since the seal temperature region of the heat seal exhibiting peelability is expanded, the stability of the peelable seal is significantly increased. Further, since the peelable seal can be stably performed, the packaging bag partially formed with the peelable seal can be closed at a high speed by the peelable seal to realize high-speed filling of the stored items. .

The packaging bag of the present invention is characterized in that it is formed by welding the sealing layers of the above-described laminated film for heat-sealing, and preferably comprises a plurality of heat-sealing portions having different heat-sealing temperatures. It is characterized by
Specifically, in the packaging bag of the present invention, a part of the packaging bag is welded at a sealing temperature that provides a tight seal to ensure the sealing property and sealing strength of the packaging bag, and the other part has a sealing temperature that provides a peelable seal. It is characterized in that the opening property is secured by welding with.

Specifically, such a packaging bag is preferably used as an interior bag for a bag-in-box, bag-in-carton or the like. As an inner bag for bag-in-box and bag-in-carton, for example, both ends of a tubular film formed by inflation molding are folded inward to form a gusset, and one end in the extending direction of the tubular film is sealed with a tight seal. However, it is conceivable that after filling a semi-solid storage item such as butter or cream, the other end is sealed with a peelable seal. After sealing with a peelable seal, the package in which the stored items are sealed may be stored in an exterior body such as a corrugated board.

[0015]

EXAMPLES The present invention will be described in more detail with reference to examples and specific examples, but the present invention is not limited thereto. I. Material composition [Examples 1 to 4] A sealing layer in which the compounding ratio of LLDPE, polybutene, and an ethylene-α-olefin copolymer was changed, and an HDPE layer were subjected to coextrusion inflation molding to form a tubular shape having a folding width of 1500 mm. It was produced as a film. Specific blending ratios are shown in Table 1. [Comparative Examples 1 to 4] As Comparative Example 1, a sealing layer made of a resin composition composed of LLDPE and polybutene, and an HDPE layer,
A tubular film having a folding width of 1500 mm was produced by coextrusion inflation molding. Also, as Comparative Example 2, LL excluding polybutene and ethylene-α-olefin resin
A DPE-only seal layer and an HDPE layer were produced by coextrusion inflation molding as a tubular film having a folding width of 1500 mm. Furthermore, as Comparative Example 3 and Comparative Example 4, L
A sealing layer made of a resin composition obtained by further adding ethylene-α-olefin copolymer to a resin composition obtained by adding 35 wt% of polybutene to LDPE, and an HDPE layer are subjected to coextrusion inflation molding to form a tubular film having a folding width of 1500 mm. Manufactured. Table 1 shows specific mixing ratios of Comparative Examples 1 to 4.

[0016]

[Table 1]

In Table 1, the following materials were used for LLDPE, HDPE, polybutene, and ethylene-α-olefin copolymer. Also, the density of the following materials can be measured by J
MFR (Melt Flow Ra) according to ISK7112
The measurement of tio) was performed according to JIS K7210. (1) LLDPE: Idemitsu Petrochemical Co., Ltd. MORET
EC IDEMITSUL 0138H (Density 0.91
7 g / cm ³ , MFR 1.3 g / 10 min) (2) HDPE: Idemitsu Petrochemical Co., Ltd. IDEMIT
SU HD (density 0.947 g / cm ³ , MFR 0.21
g / 10 minutes)

(3) Polybutene: manufactured by Mitsui Chemicals, Inc. Toughmer BL BL-3110 (density 0.910 g / c)
m ³ , MFR 1.0 g / 10 min) (4) Ethylene-α-olefin copolymer: Mitsui Chemicals, Inc. Tufmer A-4085 (density 0.880 g / cm
³ , MFR 3.6g / 10 minutes)

II. Heat-sealing method The laminated film obtained in Example 1 was cut into strips having a width of 15 mm, and two test pieces were laminated with the sealing layers, and the heat-sealing temperature of the superposed portions was 105 ° C, 110 ° C.
C., 115.degree. C., 120.degree. C., 130.degree. C., 140.degree. Specimens were prepared in the same procedure for Examples 2 to 4 and Comparative Examples 1 to 4.

III. Evaluation method Both ends of the film of the test samples of Examples and Comparative Examples were gripped and pulled by a universal testing machine such as Tensilon, and the load at which the heat-sealed portion was broken was measured. The test results are shown in Table 2. In addition, at that time, the seal thinness of the heat-sealed portion was also evaluated. Δ in Table 2 indicates that the appearance after sealing such as seal thin is not preferable, and × indicates that the film is fused to the seal bar and sealing is difficult. Yes, the tensile test could not be performed.

[0021]

[Table 2]

IV. Evaluation Results As shown in Examples 1 to 4, it was confirmed that according to the present invention, a peelable seal can be developed in a wide sealing temperature range of 110 ° C to 115 ° C. On the other hand, in the case of Comparative Example 1, the peelable seal can be developed only at around 120 ° C., and in order to obtain the peelable seal, the seal temperature must be controlled with high accuracy. I understand.

Further, as can be seen from the comparison with Comparative Example 2,
It is understood that the tight seal can be performed at a low sealing temperature by adding polybutene. In Table 2, the seal strength is 9.81 N / 15 mm width (1000 gf
(/ 15 mm width converted to SI unit)) or more means that the film itself stretched and the seal strength did not increase any more, and the heat-sealed portion did not break. Further, as can be seen from Comparative Example 3 and Comparative Example 4, when polybutene was added in an excessive amount of 35 wt%, the sealing strength at the time of tight sealing was too weak, and it was used as a packaging bag for heavy-weight packages such as bag-in-box. Turns out to be impractical.

[0024]

EFFECTS OF THE INVENTION According to the present invention as described above, since the sealing temperature range of the heat seal which exhibits peelability is expanded,
The stability of the peelable seal is greatly increased. Further, since the peelable seal can be stably performed, the packaging bag partially formed with the peelable seal can be closed at a high speed by the peelable seal to realize high-speed filling of the stored items. .

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3E035 AA03 BA01 BA08 BC02 BD04                       CA07                 3E064 AB11 BA21 BA24 BA25 BB03                       BC18 EA07 EA21 FA03 HN05                 4F100 AK05B AK09A AK09J AK62A                       AK63A AL01A AL05A AT00B                       BA02 BA10A BA10B BA13                       EH20 GB16 JA13A JL12A                       JL14 YY00A

Claims (4)

[Claims] 1. At least one layer is a heat seal layer,
A laminated film for heat sealing obtained by coextrusion molding two or more layers, wherein the heat sealing layer has a density of 0.9.
A 1-butene copolymer containing 00 g / cm ^{3 to} 0.940 g / cm ³ of linear low-density polyethylene 94 wt% to 55 wt% and 1-butene homopolymer or 90 wt% or more isotactic 1-butene polymer. 30 wt% to 5 wt% of polymer,
A laminated film for heat sealing, comprising a composition comprising 1 wt% to 15 wt% of an ethylene-α-olefin copolymer having a density of 0.900 g / cm ³ or less. 2. A packaging bag formed by welding the sealing layers of the laminated film for heat sealing according to claim 1. 3. The packaging bag according to claim 2, comprising a plurality of heat-sealing portions having different heat-sealing temperatures. 4. The packaging bag according to claim 2 or 3, which is an interior bag for a bag-in-box or a bag-in-carton.