JPH09132270A - Internal bag for bag-in-box - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal bag of which the slidability is favorable and by which an odor is not transferred to the content by a method wherein for an internal bag for bag-in-box wherein the side of a film which comes into contact with a liquid, is made of an ethylene-olefine copolymer which is obtained by a polymerization with a single site catalyst, the surface roughness of the film is specified. SOLUTION: A bag-in-box is constituted of an internal member which is a film bag and an external member which is a corrugated fiberboard box, and especially the internal bag is made of an enthylene-αolefine copolymer which is obtained by a polymerization with a single site catalyst. For such a bag-in-box, the internal bag is formed of a film of which the surface roughness is made 1-5μm. Also, as the α olefine, one kind or more are selectively applied from butene-1, hexene-1, 4-methylpentene-l, and octene-1, and the ethylene-α olefine copolymer is blended so that the density may become 0.90-0.94g/cm<3> . By this method, the internal bag of which the slidability is favorable, by which an odor is not transferred to the content, and which is functionally favorable, is obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a bag-in-box, and more particularly to a bag-in-box in which the inner bag of the back-in-box is made of an ethylene-α-olefin copolymer obtained by polymerization with a single-site catalyst. Regarding inner bag for box.

[0002]

2. Description of the Related Art A bag-in-box is one of liquid packaging containers. A bag-in-box is a liquid container of a composite type that consists of a thin-walled molded container with a spout or a film bag interior and a cardboard box exterior, and is lightweight, strong and durable, convenient to carry, and easy to dispose of. It is widely used because of its many features, such as ease of use, low distribution cost, chemical stability, excellent hygiene such as aseptic packaging, no need to collect containers, and commerciality.

Conventionally, as the inner bag of the bag-in-box, a thin molded container or a film bag made of low density polyethylene or ethylene-α-olefin copolymer is used because it is easy to mold or heat seal. Further, in order to prevent the contents from leaking during storage, the thickness of the thin-walled molded container is increased, and the film bag is used as a double bag or a triple bag. The content is mainly liquid, specifically, water, juice, coffee, oolong tea, soup sauce, soy sauce, milk shake, cream, edible oil, food applications such as syrup, shampoo, rinse, development. There are applications other than foods such as liquids, and the volume is widely used mainly for business, from 2 liters to 1000 liters.

However, when low-density polyethylene is used as the inner bag of the bag-in-box, the low molecular weight component contained in the low-density polyethylene is transferred to the contents in the bag-in-box, and the taste of the contents changes. There is. Especially the contents are mineral water, juice,
In the case of coffee, oolong tea, dashi soup, etc., it becomes a big problem.

Further, when an ethylene-α-olefin copolymer obtained by polymerizing with a Ziegler catalyst having a plurality of active sites as a multi-site catalyst (conventional catalyst) is used, slipperiness is poor. In particular, if the comonomer component is increased to increase the flexibility, the amount of low molecular weight components increases and the slipperiness decreases,
If it is left as it is, it will cause problems during film forming or bag making. In particular, when the bag is made, if slipperiness is poor, wrinkles are likely to occur, and liquid leakage is likely to occur due to poor appearance and poor heat sealing.

Further, ethylene-α obtained by polymerizing with a metallocene catalyst which is a single site catalyst having a single active site
When an olefin copolymer is used, compared to an ethylene-α olefin copolymer obtained by polymerizing with the above-mentioned multi-site catalyst, the slipperiness is improved because the low molecular weight component is less, but the surface of the film If it is a smooth surface, the slipperiness is poor, and if it is left as it is, it will cause trouble during film forming or bag making.

Therefore, when a lubricant is added to improve the slipperiness, there is a problem that the lubricant migrates to the contents to change the taste and components of the contents, and the lubricant transferred to the film surface lowers the heat seal strength. is there.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve these problems, and its object is to provide good slipperiness, no odor transfer to the contents, and An object is to provide an inner bag for bag-in-box which is sensually good.

[0009]

In order to solve this problem, the present invention has an inner bag for a back-in box, wherein the liquid contact side of the film is composed of an ethylene-α-olefin copolymer obtained by polymerization with a single-site catalyst. In the above, there is provided an inner bag for a bag-in-box, characterized in that the film has a surface roughness of 1 to 5 μm (Ra) on both sides. The α-olefin is at least one selected from butene-1, hexene-1, 4-methylpentene-1, and octene-1, and the density of the ethylene-α-olefin copolymer is 0. .9
Provided is an inner bag for a bag-in-box, which is 0 to 0.94 g / cm ³ .

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The inner bag for a bag-in-box according to the present invention comprises an ethylene-α-olefin copolymer obtained by polymerization with a single-site catalyst, and the surface roughness of the film is 1 A film having a matt surface of ˜5 μm (Ra) is used as an inner bag for a bag-in-box.

The single-site catalyst is characterized in that it has a single polymerization active site (single site), and has characteristics which cannot be obtained by the conventional multi-site catalyst. Typical examples are metallocene catalysts, so-called Kaminsky catalysts.

This single-site catalyst is a catalyst composed of a metallocene-based transition metal compound and an organoaluminum compound, and examples of the metallocene-based transition metal compound include zirconium-based compounds, titanium-based compounds, and silica-based compounds. There is no particular limitation.

Examples of the organoaluminum compound include alkylaluminum and chain or cyclic aluminoxane, but they are not particularly limited.

The polymerization method may be a solution polymerization method, a gas phase polymerization method, a slurry polymerization method or the like, but is not particularly limited.

The α-olefin which is a comonomer copolymerizable with ethylene includes butene-1, hexene-1, 4
-Methyl pentene-1 and octene-1. These α-olefins may be used alone or 2
A mixture of more than one kind may be used.

The mixing ratio of ethylene and α-olefin is 2 to
20% by weight is preferred, polymerized ethylene-alpha olefin
The density of the copolymer is 0.90 to 0.94 g /
cm ^ThreeIs desirable. This is 0.90 g / cm^ThreeLess than
Has a large amount of comonomer components, and cannot obtain good slipperiness.
0.94 g / cm^ThreeThe greater the flexibility of the film
And the likelihood of pinholes increasing.
U.

The molecular weight is 1 × 10 ³ to 1 ×.
10 ⁶ , melt flow rate (MFR) 0.1
-20 g / 10 min is preferred. In addition, various antioxidants, ultraviolet absorbers, antistatic agents, flame retardants, inorganic and inorganic fillers, dyes, pigments and the like may be appropriately added to the ethylene-α-olefin copolymer.

As a method for molding an inner bag for a bag-in-box made of an ethylene-α-olefin copolymer polymerized by these single-site catalysts, a thin-walled molding container is
There are a vacuum forming method in which a sheet is vacuum formed and welded, and a blow molding method in which a parison extruded from an extruder is cut while being blown in advance and the die is clamped and formed. In the case of a film bag, a film is formed by T-die molding or inflation molding, and is laminated on a double bag or a triple bag with a bag-making machine and heat-sealed on four sides by heat sealing or impulse sealing to form a bag. There is a way to

The interior bag for bag-in-box of the present invention is
Of the above molding methods, it is particularly suitable for a method of stacking films and heat-sealing them. Further, the ethylene-α olefin copolymer polymerized with a single-site catalyst has a small heat of fusion,
Since the sealing can be performed with a small amount of heat, there is also an advantage that the bag-making speed can be increased.

The inner bag for bag-in-box of the present invention is a film bag and is composed of a double bag or a triple bag. The film on the side in contact with the contents is the inner bag and the film on the outer side is the film. When used as an outer bag, the inner bag for a bag-in-box of the present invention is composed of an ethylene-α-olefin copolymer obtained by polymerizing at least the inner bag with a single-site catalyst, and the surface roughness of the film is either front or back. 1-5 μm
(Ra) An inner bag for a bag-in-box, which is made of a film having a matte surface.

As a method of processing the film used for the inner bag, for example, a resin obtained by melting an ethylene-α-olefin copolymer polymerized by a single-site catalyst by a T-die molding method and a cooling roll having a matte surface and a nip roll are used. A method of forming a matte surface of the film by pressure bonding between them to cool and solidify, or passing the inflation-molded film through two heating rolls whose surface is a matte surface,
There is also a method of making the surface of the film a matte surface.

At this time, each of the cooling roll, the nip roll, and the heating roll has a surface roughness of 1 to 5 μm (Ra). If it is less than 1 μm (Ra), good slipperiness cannot be obtained, and if it is more than 5 μm (Ra), the roll-releasing property at the time of film molding becomes poor. The maximum height is preferably 1 to 10 μm. The surface roughness is measured according to the JIS standard "JIS B0601-1976".
Stipulated. Examples of the material of the cooling roll, the nip roll, and the heating roll include metal, ceramic, silicon rubber, urethane rubber, and Teflon.

The film thickness used for these is 40
-200 micrometers is preferable and 50-150 micrometers is desirable.

Further, depending on the use of the contents, oxygen,
EVOH is used as an oxygen barrier material in order to impart various barrier properties such as water vapor and fragrance, and functions such as impact resistance.
PVDC, AL foil, biaxially stretched polyamide film or biaxially stretched polyester film deposited with AL or silicon oxide, polyolefin (including cyclic polyolefin) as water vapor barrier material, PAN as aroma barrier barrier material, and As the impact material, a film obtained by laminating two or more kinds of resins such as biaxially stretched polyamide may be used. The laminating method includes a co-extrusion method, a knee ram method, an extrusion laminating method, and a dry laminating method, but is not particularly limited.

The ethylene-α-olefin copolymer polymerized with the above single-site catalyst is compared with the ethylene-α-olefin copolymer polymerized with the conventional multi-site catalyst,
The polymer has a narrow molecular weight distribution (Mw / Mn = 3 or less), shows a uniform composition distribution, and has an ordered molecular structure, and has a low amount of low molecular weight components, and the surface of the film made of these resins is a matte surface. Therefore, it becomes physically uneven, the contact area is small, and the sliding property between the films and the sliding property between the film and the roll of the bag-making machine are excellent, so wrinkles do not occur during bag-making, so heat sealing is easy. .

Further, since it can be used without adding a lubricant or an anti-blocking agent, it is an excellent interior bag for a bag-in-box, which does not have a problem of odor or a decrease in heat seal strength due to the lubricant or the anti-blocking agent. Is obtained.

[0027]

[Example] A solution polymerization method using a single-site catalyst
Obtained density 0.902 g / cm ^ThreeEthylene-octet
Extrusion of styrene-1 copolymer (MI = 3) by T-die molding method
Melted at a temperature of 240 ° C and cooled with a surface roughness of 2 μm (Ra)
Cooling and solidification using a cooling roll and a silicon nip roll
The front and back surfaces are mat-shaped and the film thickness is 75 μm
Create a film for the interior bag for the bag-in-box that becomes clear
did.

Comparative Example 1 The ethylene-octene-1 copolymer of Example 1 was cooled and solidified using a cooling roll having a surface roughness of 2 μm (Ra) and a Teflon nip roll having a surface roughness of 0.1 μm (Ra). Thus, a film of an inner bag for a bag-in-box having a film thickness of 75 μm, the front and back surfaces of which are mat-like and smooth, was prepared.

<Comparative Example 2> In Comparative Example 1, an ethylene-octene-1 copolymer and a lubricant (fatty acid amide type) of 0.
A film thickness of 75 μm in which the front and back surfaces are mat-shaped and smooth-shaped, in the same manner as in Comparative Example 1 except that 07% by weight and 0.7% by weight of an anti-blocking agent (diatomaceous earth type) were melt mixed and used.
The film of the inner bag for the bag-in-box of was produced.

<Comparative Example 3> In Comparative Example 2, a density of 0.919 obtained by a solution polymerization method using a multisite catalyst.
g / cm ³ ethylene-octene-1 copolymer (MI =
6), a lubricant (fatty acid amide type) 0.07% by weight and a blocking resistance agent (diatomaceous earth type) 0.7% by weight were melt-mixed and used in the same manner as in Comparative Example 1 so that the front and back surfaces were matte. A film of an inner bag for a bag-in-box having a film thickness of 75 μm, which is a flat shape and a smooth shape, was prepared.

Next, in order to evaluate the slipperiness of these films, based on the JIS standard "JIS-K-7125",
The coefficient of static friction and the coefficient of dynamic friction of each film were measured. It is shown in Table 1.

[0032]

[Table 1]

Next, in order to evaluate the odor of these films, sensory evaluation based on the taste of water was performed. The method of sensory evaluation of water taste is to heat seal each film,
A bag of 200 × 300 mm in size, which was filled with 300 cc of mineral water at 0 ° C. and sealed, was prepared. After storing this for 7 days at an ambient temperature of 40 ° C, a panel of 10
Sensory evaluation by name was performed. Table 2 shows the sensory evaluation results.

[0034]

[Table 2]

As is clear from Table 1 and Table 2, the film of Example 1 according to the present invention is excellent in slipperiness and is also excellent in odor according to the sensory evaluation of water taste.

[0036]

INDUSTRIAL APPLICABILITY The inner bag for bag-in-box of the present invention has a matte film surface on the front and back sides, and therefore has excellent slipperiness during film formation or bag formation, and requires a lubricant or an antiblocking agent. Therefore, the heat-sealing property and low odor characteristic of the ethylene-α-olefin copolymer polymerized by the single-site catalyst can be maximized.

Front page continuation (72) Inventor Ken Takahara 1-5-1 Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd.

Claims (3)

[Claims] 1. An inner bag for a back-in-box, wherein the liquid contact side of the film is composed of an ethylene-α-olefin copolymer obtained by polymerization with a single-site catalyst, and the surface roughness of the film is shown on both front and back sides. An inner bag for a bag-in-box, which is made of a film having a thickness of 1 to 5 μm (Ra). 2. The α-olefin is selected from at least one selected from butene-1, hexene-1, 4-methylpentene-1, and octene-1. Interior bag for bag-in-box. 3. The inner bag for a bag-in-box according to claim 1, wherein the ethylene-α olefin copolymer has a density of 0.90 to 0.94 g / cm ³ .