JPH09309541A - Bag body for bag-in-box - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bag body for a bag-in-box provided with the innermost film, which does neither spoil an excellent flexibility and a toughness in a low temperature condition nor arises mutual adhesion between films owing to the heating charge. SOLUTION: A multiple bag is a bag body B for a bag-in-box provided with a grommet G. The bag body B is constituted of two or more films. In this case, the innermost film FL of the multiple bag is a multi-layer film having three or more layers which are polymerized with a single site catalyst and formed by the coextrusion of two or more kinds of ethylene-α olefin copolymer (S-PE). And the multi-layer film having three or more layers is a coextrusion film constituted of the outermost layer 3, an intermediate layer 2 composed of one or more layers, and the innermost layer 1. The density of the intermediate resin layer 2 is lower than the resin density of the outermost layer 3 and the innermost layer 1. And further, the thicknes of the intermediate layer 2 is equal to 50-90% of the whole thickness of the multi-layer film, in the bag body for bag-in-box.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material of the bag body of a bag-in-box which is filled with a liquid in a flexible material and stored in cardboard or the like for distribution, storage and use.

[0002]

2. Description of the Related Art FIG. 2 is a conceptual diagram showing a bag-in-box, showing a state in which a flap of a box P is opened.
FIG. 3 is a partially enlarged view of the heat-sealed bag body. The bag-in-box is a container for commercial use such as mineral water, vinegar, sake, mirin and taste liquid, beverages such as soy sauce or sauce, seasoning, pure water, developing solution and fixing solution,
It is used as a reagent such as liquid chemicals or as an industrial liquid container, and its volume size is mainly about 5 to 20 liters. The bag-in-box as a container for business use such as the beverage and the seasoning is used as the packaging container for the beverage or the seasoning in which the flavor of the content is emphasized, and the bag B is 2 A portion other than the peripheral portion seal S for forming the bag body of one or more films and the seal portion for attaching the grommet G is not bonded to each other, that is, a so-called multiple bag. The film used as the multiple bag is used both as a single film and as a composite film, and as the innermost film thereof, ethylene-vinyl acetate copolymer (hereinafter referred to as EVA), low density polyethylene (hereinafter referred to as LDPE) In most cases, it was composed of a single layer film such as medium density polyethylene (hereinafter referred to as MDPE) and linear low density polyethylene (hereinafter referred to as LLDPE). For example, concrete 2
Examples of the material composition of the heavy bag are Example 1 (outer bag) ON / DL / LDPE, (inner bag) LDPE, Example 2 (outer bag) ON / LDPE / AL / LDPE / LLDPE, (inner bag) LLDPE , Etc. are used in combination. {The abbreviations are ON: Biaxially stretched nylon film, DL: Dry lamination, AL: Aluminum foil}.

The LDPE film usually used has been widely used as the innermost film of a bag-in-box due to its good film-forming property and good heat-adhesiveness. However, as a material which causes less pinholes due to bending than the LDPE, EVA or LL
A film made of a material such as DPE may be used. By using EVA or LLDPE instead of LDPE, the bending resistance is improved and the occurrence of pinholes is suppressed, but the elements derived from these materials including LDPE may adversely affect the taste of the contents. is there. For example, the resin odor itself may be transferred to the contents, or the taste may be deteriorated due to the adsorption of components in the contents. Further, these resins can be heat-sealed in a low temperature region, but on the other hand, the innermost film, the intermediate film, and the outer film may be fused due to the heat of the contents to be heated and filled. . That is, the films in the double bag and the triple bag are heat-sealed with each other to form a single layer, which increases the rigidity of the film in the heat-sealed portion and causes bending due to vibration during transportation. It is easy to generate holes. As a result, it may cause a leak accident. Furthermore, although LDPE is a resin that melts at a relatively low temperature, the thickness of the seal heat-bonding portion H becomes thin during pressurization and heating by the heat-seal bar HS in bag making. A part near the end of the wearing part may exhibit a phenomenon of thinning (FIG. 3). This portion is referred to as a seal thin portion D, and when a strong impact is applied to the bag-in-box container, the seal thin portion D may be broken and a large liquid leakage may occur. Therefore, in the bag-making process, paying attention to the sealing state, the bag-making process is performed under working conditions with a narrow temperature range.

Therefore, as a measure for heat adhesion between films due to deterioration of taste and heat filling, medium density polyethylene is used.
By making the (MDPE) film the innermost film,
Although the above-mentioned problems can be solved, the rigidity of the film becomes too large and the film is weak in bending resistance, so that pinholes were generated.

[0005]

A bag for box-in-bag having an innermost film which does not impair excellent flexibility, toughness under low temperature conditions, etc. and does not cause fusion between films due to heat filling. The purpose is to provide the body.

[0006]

[Means for solving the problem]

1. A bag-in-box bag, wherein the bag is a multiple bag composed of two or more films, and the innermost film of the multiple bag is ethylene polymerized using a single-site catalyst. -A multi-layer film having three or more layers obtained by co-extruding an α-olefin copolymer, wherein the multi-layer film having three or more layers is at least an outermost layer, an intermediate layer, and an innermost layer. The density of the resin of the intermediate layer is a resin having a lower density than the density of the resin of the outermost layer, the innermost layer, and the ratio of the thickness of the intermediate layer is 50 to the total thickness of the multilayer film. 90
% Is included.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 1 (1-1) is a plan view of a bag body for bag-in-box according to the present invention, and (1-2) is (1-).
1) is a sectional view taken along line XX, (1-3) is an enlarged sectional view of the Y portion in (1-2), and FIG. 2 is a conceptual view of a bag-in-box.
Further, FIG. 3 is an enlarged cross-sectional view of the seal portion. The bag body B for bag-in-box is a so-called double bag or triple bag in which only the flange portion of the grommet G and the bag body seal portion S are adhered, and inside the box P made of cardboard or plastic as the outermost bag. It is stored in and used (Fig. 2). Since the content K of the bag is a liquid, a distribution stage such as transportation and storage after filling, removal of the content,
It is required that there is no risk of leakage until the use stage such as preservation of residual liquid is completed. Further, the bag body filled with the content such as the beverage targeted in the present invention is required not to impair the taste of the content. Further, the film used for the bag body needs to be a material capable of stable work in the steps of film forming, bag making, and the like.
The present invention has been made in order to solve the above-mentioned many problems.
Focusing on the innermost film of the heavy bag and the triple bag, the innermost film FL is a three-layer formed by co-extruding an ethylene-α-olefin copolymer (S-PE) polymerized using a single-site catalyst. The above multilayer film was used. In addition, the multi-layered film having three or more layers is a coextruded film including an outermost layer 3, an intermediate layer 2 composed of one layer or multiple layers, and an innermost layer 1, and the resin density of the intermediate layer 2 is the outermost layer. 3. A resin having a density lower than that of the resin of the innermost layer 1 was used.
Specifically, if the density of the S-PE used as the outermost layer 3 and the innermost layer 1 is 0.910 to 0.965, and the density of the S-PE used as the intermediate layer 2 is selected within the range of 0.890 to 0.920. Good, but by using S-PE whose S-PE in the middle layer is lower than the S-PE in the outermost layer and the innermost layer, it has flexibility as a bag body for bag-in-box, and LDPE and LLDPE
When the above is used, the low molecular weight component may be eluted into the contents through the innermost layer and the taste may be deteriorated. Therefore, S-PE containing no low molecular weight component as described above is used. Also, since the density is as low as 0.890 to 0.920, it has flexibility,
It also has an effect of preventing the bag body from being damaged by vibration or the like. Further, a bag body for a bag-in-box was prepared in which the ratio of the thickness of the intermediate layer 2 was 50 to 90% of the total thickness of the innermost film. In the present invention, the densities of polyethylene and S-PE and their expressions are as follows. Low density 0.890 to 0.925 Medium density 0.926 to 0.940 High density 0.941 to 0.965

[0008] LLDPE, LLDPE, and MDPE deteriorate in physical properties such as flexibility under low temperature conditions below the chilled temperature. Especially MD
Although PE has a high density and has the above-mentioned heat resistance, it is inferior in pinhole resistance and puncture suitability due to its rigidity, and these physical properties are further deteriorated under low temperature conditions. When these materials are used as the innermost film, a pinhole may be easily generated due to vibration during transportation, or a bag may be broken by a slight impact during work in a cold region. In the present invention, the innermost film is a coextruded multilayer film having three or more layers, and low-density S-PE is used as an intermediate layer thereof,
By setting the thickness of the intermediate layer to be 50 to 90% of the thickness of the innermost film, flexibility under the low temperature condition is ensured. Further, the intermediate layer may have a multi-layer structure of two or more layers in the range of the resin having a lower density than the resins of the outermost layer and the innermost layer as long as there is no problem in solving the problem of the present invention. In order to impart flexibility under low temperature conditions and excellent puncture strength and impact strength, it is desirable to make the intermediate layer of S-PE having a low density as thick as possible. While maintaining the characteristics of the intermediate layer, a seal suitable as a bag body for a bag for box-in-box, the outermost layer so as not to block with an outer film, etc. of the intermediate layer in the innermost layer.
S-PE having a higher density than that of S-PE was laminated (by a coextrusion method).

Conventionally, the innermost film of the bag for the box-in-box is a single layer film such as LDPE, LLDPE, etc. However, if the innermost film of these materials is used, the contents should be hot-packed (heat filled). As a result, the films may cause heat fusion (blocking) between the innermost film and the intermediate film. When blocking between films in multiple bags, the rigidity of the film increases, and due to stress concentration on the blocking part (heat fusion part), the film at a specific part bends due to vibration during transportation and pinholes. In some cases, liquid leakage occurred as a result. In the present invention, the resin forming the outermost layer of the innermost film has a higher density than the intermediate layer.
By using S-PE, blocking between films due to heat filling and the like could be prevented. The thickness of the S-PE having a higher density than that of the intermediate layer 2 used as the outermost layer may be such that the blocking can be prevented. When the innermost film is a single layer of LDPE, LLDPE or the like, a seal thinning phenomenon may occur during heating and pressing with a heat seal bar during bag making. The thinning of the seal is a phenomenon that occurs when a resin that melts at a low temperature such as LDPE and LLDPE is used. Occasionally, accidents such as breakage and bag breakage occurred. In the innermost film FL of the present invention, since S-PE having a higher density than that of the intermediate layer 2 is used for the innermost layer 1, the low-density S-PE of the intermediate layer 2 is melted during heat sealing and excessive Controls the occurrence of seal thinning without causing fluidity. Therefore, it is effective in reducing bag breakage due to impact. The thickness of the S-PE having a higher density than that of the intermediate layer 2 used for the innermost layer provides an appropriate heat seal strength when used as a bag for a bag-in-box,
Any thin film may be used as long as it does not cause the seal thinning D. In addition, the innermost film FL of the present invention is a coextruded film, and on the outside of the coextruded film,
It is conceivable that other films are laminated by a laminating method or a coating method, but it can be carried out within a range not impeding the intention of the present invention.

As described above, the innermost film FL of the bag-in-box bag body has the low density S-PE as the intermediate layer, and the outermost layer and the innermost layer are higher in density than the intermediate layer S-PE. By using S-PE, punching for attaching the grommet G when manufacturing the bag body
In the process, since the film has rigidity, there is an advantage that it becomes a stable drawing process, and the slippage of the film surface is better than that of lower density S-PE or PE.

When a single layer film such as LDPE or LLDPE is used as the innermost film, the resin odor caused by the low molecular weight components contained in these films is transferred to the contents,
On the contrary, it sometimes adsorbs a specific component in the content. As a result, it may have a sensory adverse effect on the contents in which the taste and flavor are particularly important. S-PE
Has a uniform molecular weight compared to LDPE, LLDPE, etc., and in particular, it contains less low-molecular weight components, so it has less resin odor and relatively less adsorption of contents components. Therefore, the taste of the content is less deteriorated, and it is suitably used as a liquid contact material suitable for transporting and storing the content that attaches importance to delicate flavor.

The innermost film of the bag-in-box bag of the present invention is composed of three or more layers of multi-layered film obtained by coextrusion of two or more kinds of S-PE, and the thickness of the intermediate layer of the multi-layered film is the above-mentioned. Various experiments have revealed that it has a great influence on the solution of the problem. The ratio of the thickness of the intermediate layer in the present invention is 50 to 90% with respect to the total thickness of the innermost film FL. When the ratio of the thickness of the intermediate layer is less than 50% with respect to the total thickness of the innermost film FL, the film is inferior in flexibility required as a bag body for bag-in-box, and the flexibility is improved. Focusing on the above,
When the ratio of the thickness of the intermediate layer exceeds 90% with respect to the total thickness of the innermost film FL, the seal thinning prevention effect is lost, and there is a risk that the contents will be fused between the films by hot packing. Occurs. As the innermost film FL that secures flexibility, it is better to make the intermediate layer as thick as possible, but the thicknesses of the innermost layer and the outermost layer as measures against the seal thinning and the blocking are the minimum thickness in an appropriate range. And

[0013]

[Example] The outermost FLN film was a composite film having a barrier property of KON ¹⁵ / DL / LLDPE ⁶⁰ , and the innermost film FL was
When an 80 μm (inner bag) film was used, six types of bag-in-box bags were prepared using the following six types as the innermost film. (Material) Example 1 S-PE (H) / S-PE (L) / S-PE (M) Thickness ratio 1: 18: 1 (Intermediate layer 90%) Example 2 〃 Thickness ratio 1: 8: 1 (Intermediate layer 80%) Example 3 〃 Thickness ratio 1: 3: 1 (Intermediate layer 60%) Example 4 〃 Thickness ratio 1: 1: 1 (Intermediate layer 33%) Comparative example 1 LLDPE Single layer Comparative example 2 MDPE The materials used for the single layer are as follows. S-PE (H): Dow Chemical AFFINITY HF1030 (MI 2.5 D 0.935) S-PE (L): Dow Chemical AFFINITY FW1650 (MI 3.0 D 0.902) S-PE (M): Dow Chemical AFFINITY PL1845 (MI 3.5 D 0.915) ) LLDPE: Mitsubishi Chemical SF240 (MI 2.0 D 0.920) MDPE: Mitsubishi Chemical SF941 (MI 2.0 D 0.936)

(Heat resistance and cutability) Heat resistance is obtained by applying a load to two test pieces, which are set at a predetermined temperature, and allowed to stand for 1 hour. The load is 700g on a 10 × 10cm iron plate (300g)
Put a weight on it so that the total load is 1 kg (10 g / m ² ). After heating, the blocking strength is measured with a Tensilon tensile tester. The cuttability was measured by an Elmendorf tear tester (JIS K7128). Heat resistance Cutability Test material 90 ℃ 100 ℃ ─────────────────────────────────── Example 1 ○ △ × Example 2 ◎ ○ ○ Example 3 ◎ ◎ ○ Example 4 ◎ ◎ ○ Comparative Example 1 × × ○ Comparative Example 2 ○ △ ○

(Bending resistance to pinholes) A gelbo flex tester was bent 5000 times at a temperature of -10 ° C., and the number of pinholes generated within an area of 300 × 210 mm was counted. . However. The number of measurements was 4 each, and the maximum value was shown. Number of pinholes generated ────────────────── Example 10 0 Example 2 0 〃 Example 3 0 〃 Example 4 5 〃 Comparative Example 1 8 〃 Comparative Example 2 40 〃 (Result) As an evaluation by each of the above test items, a bag body for bag-in-box shows stable properties when the thickness ratio of the middle layer of the three-layer structure of the innermost film is in the range of 50 to 90%. It was found that it is preferably used as.

[0016]

EFFECT OF THE INVENTION Since the innermost film FL of the bag-in-box bag of the present invention is a multi-layer film having three or more layers formed by co-extruding S-PE, LDPE and LL which have been conventionally used have been used.
It has no elution of low molecular weight components such as DPE, is effective in maintaining the taste of the contents, and has a lower density than the S-PE of the outermost layer and the innermost layer of S-PE of the middle layer of the multilayer film. And the ratio of the layer thickness of the intermediate layer is 50 to 90% of the total thickness of the innermost film FL, so that flexibility as a bag body for a bag-in-box is ensured and an appropriate thickness is obtained. Due to the surface layer of high-density S-PE designed in, it is possible to prevent blocking during winding when forming the film.
In heat-sealing during bag making for bag-in-box bags, by reducing the seal thinning, the bag breaking strength is increased, and blocking between the outer surface of the innermost film and the intermediate film etc. during hot packing of contents is possible. It was possible to prevent it, give the film a proper elasticity, and impart good processability and filling suitability.

[Brief description of drawings]

FIG. 1 is a plan view and a partially enlarged cross-sectional view of a bag body for bag-in-box according to the present invention.

[Figure 2] Conceptual diagram of bag-in-box

FIG. 3 is an enlarged sectional view of a seal portion of the bag body.

[Explanation of symbols]

 P box B bag body S bag body seal part G grommet K contents HS heat seal bar H heat fusion part D seal thin part FL innermost film FM intermediate film FN outer film 1 innermost layer 2 of innermost film 2 of innermost film Middle layer 3 Outermost layer of innermost film

Claims (3)

[Claims] 1. A bag-in-box bag, wherein the bag is a multiple bag composed of two or more films, and the innermost film of the multiple bag is ethylene polymerized using a single-site catalyst. A bag body for a bag-in-box, which is a multi-layer film having three or more layers formed by co-extruding an α-olefin copolymer. 2. The multi-layer film having three or more layers is a coextrusion film comprising at least an outermost layer, an intermediate layer and an innermost layer, wherein the resin density of the intermediate layer is equal to that of the outermost layer and the innermost layer. The bag body for bag-in-box according to claim 1, which is a resin having a density lower than the density. 3. The bag body for bag-in-box according to claim 1, wherein the ratio of the thickness of the intermediate layer is 50 to 90% of the total thickness of the multilayer film.