JPH09165047A - Bag for liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bag for liquid, which is excellent in flexibility, whose wear, fold and heat resistances are improved and further in which a blocking resistance is improved. SOLUTION: A bag for liquid is formed by heat-sealing circumferential portions of a double-layer film comprising an inside film and an outside film. The inside film and the outside film comprise an inner layer, an outer layer and an intermediate layer provided therebetween, respectively, and the inner layer and the outer layer are both made of a blended resin composed of 100 pts.wt. of a polypropylene resin and 40-150 pts.wt. of a high-density polyethylene resin, while the intermediate layer is made of a polypropylene resin. The polypropylene resin in each of the inner layer, the outer layer and the intermediate layer has 80,000-5,000,000 of a weight-average molecular weight and is the resin whose quantity of elution in the cross fractionation process is 40-70wt.% at 0-10 deg.C, 8-30wt.% at 10-70 deg.C and 15-35wt.% at 70-120 deg.C for the total weight of the polypropylene resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid bag used as a container for drinking water, vinegar, soy sauce, juices, chemicals, agricultural chemicals, etc. More specifically, it has excellent flexibility and heat resistance. The present invention relates to an inner bag of a liquid container with a spout having excellent wear resistance, bending resistance, moldability, and blocking resistance, or a liquid bag used for a bag-in-box.

[0002]

2. Description of the Related Art Containers made of synthetic resin for liquids having a capacity of 5 liters or more include a molded type container and a heat sealable film container.

In recent years, a bag-in-box in which a bag made of a heat-sealable film is placed in a cardboard box has been widely used in view of disposal problems. In this case, the film used has excellent flexibility,
It is required that the strength of the film and the strength of the heat-sealed portion be large and that the disposal be easy.

Conventionally, as a film used for a bag-in-box, a film containing a polyethylene resin as a main component has been widely used because of its price and ease of heat sealing.

However, the bag-in-box made by using only the conventional polyethylene resin film is difficult in heat resistance, abrasion resistance and crease resistance, and particularly in terms of heat resistance, the filling temperature is 80-100. In the case of a boil pack at ℃, there was a problem that the sealing strength of the heat-sealed portion is lowered and blocking occurs in the non-heat-sealed portion of the inner film and the outer film.

Further, the outer cardboard box and the film bag were rubbed during transportation and the bag was worn, or the film bag was cracked and pinholes were generated, which caused liquid leakage.

[0007]

In order to prevent such liquid leakage due to abrasion, conventionally, the thickness of the film is increased, the number of laminated films is increased, the slippage of the film is improved, and other problems occur. Attempts have been made to compensate for the above drawbacks by combining with a resin film.

However, these techniques lead to a new problem that the cost of the obtained film increases and the film manufacturing process becomes long.

In order to solve these problems, for example, Japanese Utility Model Application Laid-Open No. 2-69839 proposes to emboss at least one surface of a plurality of films constituting both sides of the bag.

Further, Japanese Patent Publication No. 3-49820 discloses that
A film in which a low-density polyethylene-based resin and a styrene-butadiene copolymer are mixed in a specific ratio to form a multilayered high-density polyethylene-based resin layer has been proposed.

Further, Japanese Patent Publication No. 4-78467 proposes a multilayer film composed of a film molded from a composite resin composition and a film molded from a low density polyethylene resin.

[0012] However, even if these films can improve the sliding and impact resistance, the abrasion resistance and the fold resistance are not sufficiently improved, and the heat resistance is poor, and the cost of the product bag is high. There is also a problem of causing problems, and a liquid bag that fully satisfies the market demand has not yet been realized.

The present invention has been made to solve the above-mentioned problems, and is a liquid having excellent flexibility, improved abrasion resistance, fold resistance, and heat resistance, as well as good blocking resistance. The purpose is to provide a bag.

[0014]

A liquid bag according to the present invention is a liquid bag formed by heat-sealing peripheral portions of a multilayer film composed of an inner film and an outer film. The outer film is composed of an inner layer, an outer layer and a middle layer between them, and the inner layer and the outer layer are each made of polypropylene resin 10
It is composed of a blended resin of 0 parts by weight and 40 to 150 parts by weight of a high-density polyethylene resin, the middle layer is composed of a polypropylene resin, and the polypropylene resin used for the inner layer, the outer layer and the middle layer is a weight average. The molecular weight is 80,000 to 500,000, and the elution amount in each temperature range by the cross fractionation method is 40 to 70% by weight at 0 to 10 ° C and 10 to 70 ° C with respect to the total weight of the polypropylene resin. 8-30% by weight, 15-35% by weight at 70 ° C-120 ° C
The resin is a resin.

The structure of the liquid bag according to the present invention will be described in detail below.

The thickness of each inner layer and outer layer of the inner film and the outer film is preferably in the range of 1/3 to 1/10 of the total thickness of each of the inner film and the outer film.

The thickness of each of the inner film and the outer film is usually 50 to 150 μm. This thickness is 5
When the thickness is 0 μm or less, the mechanical strength of the film may be insufficient, and when the thickness is 150 μm or more, the film may lack flexibility.

In the present invention, the weight average molecular weight of the polypropylene resin used for the inner layer, the middle layer and the outer layer of the inner film and the outer film is, for example, high temperature GPC.
(Gel Permeation Chromatography, 150V, WAT
ERS).

The weight average molecular weight of the polypropylene resin used in the present invention is 80,000 to 500,000, preferably 150,000 to 350,000.

When the weight average molecular weight of the polypropylene resin is less than 80,000, the viscosity of the molten resin is too low, the film-forming property is poor in the extrusion molding method by the usual method, and the strength of the obtained film is insufficient. However, if the viscosity exceeds 500,000, the viscosity of the molten resin is too high and the film-forming property is poor in extrusion molding by the usual method, and the film obtained is Is likely to become cloudy.

In the present invention, the cross fractionation method adopted as an index for identifying the polypropylene resin is as follows.

First, the polypropylene resin is heated at 140 ° C. or at a temperature at which the polypropylene resin is completely dissolved.
-Dissolving in dichlorobenzene, then cooling this solution at a constant rate to produce a thin polymer layer on the surface of the previously prepared inert carrier in order of increasing crystallinity and increasing molecular weight. Next, the temperature of the polymer layer is continuously or stepwise increased, and the concentration of the eluted components is detected to measure the component distribution (crystallinity distribution). This is the temperature rising elution fractionation.
This is a method called actionation; TREF). at the same time,
The high temperature GPC (Size Exclusion Chr
omatograph (SEC) to determine the molecular weight and molecular weight distribution. In the present invention, a cross fractionation chromatograph device (CFC manufactured by Mitsubishi Chemical Co., Ltd.) equipped with both the above-mentioned temperature rising elution fractionation part and high temperature type GPC part as a system.
-T150A type) was used for the measurement.

The polypropylene resin used in the present invention has an elution amount of 40 to 70 at 0 to 10 ° C. relative to the total amount of polypropylene resin measured by the cross fractionation method.
It is not more than 50% by weight, preferably 50 to 60 parts by weight. When the amount eluted is 40% by weight or less, the obtained film lacks flexibility, and the bending resistance is impaired.
When it exceeds 0% by weight, the film becomes too flexible and the strength is significantly lowered, so that the obtained film is not practical.

The polypropylene resin has an elution amount of 8 to 30% by weight at 10 to 70 ° C. with respect to the total amount of polypropylene resin measured by the cross fractionation method.

The polypropylene resin has an elution amount of 15 to 35% by weight, preferably 20 to 30% by weight, at 70 to 120 ° C. with respect to the total amount of polypropylene resin measured by the cross fractionation method. If this elution amount is less than 15% by weight, the heat resistance of the obtained film is insufficient, and conversely, if it exceeds 35% by weight, the flexibility of the film is lowered and the folding resistance may be impaired. .

In the polypropylene resin used in the present invention, the elution amount and the weight average molecular weight in each temperature range are within the above ranges, that is, flexibility, heat resistance, abrasion resistance,
It is important for obtaining a film having excellent bending resistance.

The polypropylene resin used in the present invention is produced, for example, by the multistage polymerization method as shown below.

First, in the first step, a propylene monomer is homopolymerized in the presence of a titanium compound catalyst component and an organoaluminum compound catalyst component, or a propylene monomer is copolymerized with an ethylene monomer or an α-olefin monomer. , Propylene homopolymer, propylene-ethylene copolymer, propylene
A first polypropylene resin made of an α-olefin copolymer or the like is obtained.

Then, in the second step, a reaction solution containing a titanium compound catalyst component, an organoaluminum compound catalyst component, the above homopolymer or copolymer, for example, a reaction after producing the above homopolymer or copolymer. Propylene / ethylene copolymer, propylene / α-olefin copolymer, ethylene / α-olefin copolymer, etc. can be obtained by adding propylene monomer, ethylene monomer and / or α-olefin monomer to the liquid and copolymerizing To obtain a second polypropylene resin.

The additive components in the above-mentioned second stage may be added once or dividedly in plural times. That is, this polymerization reaction may be a multi-step polymerization of three or more steps as a whole.

Hereinafter, the copolymerization reaction may be carried out at any stage depending on the purpose. The feature of this production method is that the polymerization is not completed in one step, but multi-step polymerization of two or more steps is performed. This allows the creation of multiple types of polymers, producing blend-type copolymers at the molecular level that are quite different from conventional polymer blends.

Examples of actual resins obtained by the above manufacturing method include "PER" manufactured by Tokuyama Corporation and "Cataloy" manufactured by Highmont Corporation.

Each of the inner and outer layers of the inner film and the outer film is made of polypropylene resin 100.
It is composed of a blended resin of 40 parts by weight and 40 to 150 parts by weight of high-density polyethylene resin.

When the content of the high-density polyethylene resin is less than 50 parts by weight, the additive elution from the film layer is large in the 70 ° C. water filling dissolution test, and when the content of the high-density polyethylene resin exceeds 150 parts by weight, it is obtained. The flexibility of the obtained film is deteriorated and the folding resistance is impaired.

The resins used in the present invention include stabilizers such as ultraviolet absorbers, antioxidants and stabilizing aids, plasticizers, lubricants, precipitated barium sulfate and talc to the extent that the effects of the present invention are not impaired. Fillers such as calcium carbonate, mica and titanium oxide, and additives such as colorants can be added.

The film may be colorless and transparent, colored and transparent, or colored and non-transparent.

The method for molding the film is not particularly limited, but the inner layer, the middle layer and the outer layer are separately molded by, for example, the T-die extrusion molding method or the inflation extrusion molding method, and these three layers are laminated by a laminator or the like. It may be laminated using a laminating device, or may be formed into a film for the intermediate layer, and then laminated with an inner layer and an outer layer by a dry laminating method or an extrusion laminating method, and further,
You may manufacture the laminated body which consists of an inner layer, a middle layer, and an outer layer at once by coextrusion molding methods, such as a T die coextrusion molding method and an inflation coextrusion molding method.

As described above, in the liquid bag according to the present invention, since the specific polypropylene resin is used for each inner layer, middle layer and outer layer of the inner film and the outer film, heat resistance, abrasion resistance and resistance It is possible to provide a liquid bag in which breakability and strength are remarkably improved and appropriate heat sealability and seal strength are secured.

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described more specifically below with reference to Examples.

Example 1 As a raw material resin for each inner layer and outer layer of the inner film and the outer film, a polypropylene resin (manufactured by Highmont Co., "Cataloy KS081P", MFR = 0.8,
Density = 0.895 g / cm ³ ) 100 parts by weight and high-density polyethylene resin (Mitsubishi Chemical Corporation, “HF110”, M
FR = 0.04, density = 0.925 g / cm ³ ) 100
A blended resin of parts by weight is prepared, and polypropylene resin (“Cataloy KS081P” manufactured by Highmont Co., Ltd., MFR =) is used as each middle layer of the inner film and the outer film.
0.8, density = 0.895 g / cm ³ ) was prepared.

Then, using the above-mentioned raw material resin, a laminated film having an interlayer ratio of outer layer / middle layer / inner layer = 1/3/1 and a total thickness of 90 μm was prepared by a coextrusion inflation method.

An inner film and an outer film were produced from this laminated film, and the peripheral portion of the multilayer film obtained by combining these films was heat-sealed to obtain a liquid bag.

Example 2 A laminated film was produced in the same manner as in Example 1 except that the blending ratio of the polypropylene resin and the high-density polyethylene resin was 100 parts by weight of the former and 50 parts by weight of the latter. , A liquid bag was obtained.

Comparative Example 1 As an inner layer, an inner layer and an outer layer of each of the inner film and the outer film, a polypropylene resin (manufactured by Himont Co., "Cataloy KS081P", MFR = 0.
No. 8, density = 0.895 g / cm ³ ) was used to produce a laminated film in the same manner as in Example 1 to obtain a liquid bag. Comparative Example 2 As a raw material resin for each inner layer and outer layer of the inner film and the outer film, a polypropylene resin (manufactured by Highmont Co., "Cataloy KS081P", MFR = 0.8,
100 parts by weight of density = 0.895 g / cm ³ and polypropylene resin (“EG8” manufactured by Mitsubishi Chemical Corporation, MFR = 0.
7. Density = 0.90 g / cm ³ ) In the same manner as in Example 1 except that 100 parts by weight of the blended resin was used,
A laminated film was produced to obtain a liquid bag. Comparative Example 3 As each inner layer and outer layer (two-layer structure) of the inner film and the outer film, a linear low-density polyethylene (“UA421” manufactured by Mitsubishi Chemical Co., MFR = 0.7, density =)
A laminated film was produced in the same manner as in Example 1 except that 0.923 g / cm ³ ) was used to obtain a liquid bag.

Comparative Example 4 Polypropylene resin (“Cataloy KS081P” manufactured by Highmont Co., Ltd., MFR = 0.8, density = 0.8) was used as each inner layer and outer layer of the inner film and the outer film.
95 g / cm ³ ) 100 parts by weight and low density polyethylene resin (Mitsubishi Chemical Co., Ltd., “LF-325M”, MFR =
1.3, density = 0.924 g / cm ³ ) A laminated film was produced in the same manner as in Example 1 except that 100 parts by weight of the blended resin was used to obtain a liquid bag.

Comparative Example 5 Polypropylene resin (“Cataloy KS081P” manufactured by Highmont Co., MFR = 0.8, density = 0.8) was used as each inner layer and outer layer of the inner film and the outer film.
95 g / cm ³ ) 100 parts by weight and linear low-density polyethylene (Mitsubishi Chemical Co., Ltd., “UF421”, MFR = 0.
7. Density = 0.923 g / cm ³ ) A laminated film was produced in the same manner as in Example 1 except that 100 parts by weight of the blended resin was used to obtain a liquid bag.

Table 1 shows the laminated films of the liquid bags produced in Examples and Comparative Examples.

[0048]

[Table 1] Performance Evaluation In order to evaluate the performance of the laminated films of the liquid bags produced in Examples and Comparative Examples, the following items were tested.

(1) Breaking strength and breaking elongation Measured in accordance with JIS Z 1702.

(2) Tear strength The tear strength was measured according to JIS Z 1702.

(3) Static friction coefficient Measured in accordance with JIS Z7215.

(4) Abrasion resistance It was measured according to JIS L 0849.

(5) Folding strength Measured according to JIS P 8115.

(6) Heat resistant temperature The fusion temperature was measured.

(7) The number of pinholes was measured in accordance with Gelboflex ASTM F392.

(8) Appearance evaluation test The liquid bag was filled with hot water having a water temperature of 90 ° C., and the appearance of the liquid bag was visually observed.

(9) Elution with high-temperature water filling Hot water having a water temperature of 90 ° C. was filled in a liquid bag, and the presence or absence of elution of additives from the liquid bag was visually observed.

(10) High-temperature water filling vibration test A liquid bag was filled with hot water having a water temperature of 90 ° C.
G was vibrated under conditions of 1 inch and 30 minutes, and the presence or absence of water leakage was visually observed.

(11) Drop test with high temperature water Filling the liquid bag with hot water having a water temperature of 90 ° C.
It was dropped onto a concrete floor from a height of 0 m and 0.7 m, and the appearance of the liquid bag, such as a bag, was observed.

The test results obtained are summarized in Table 2.

[0061]

[Table 2] As is clear from Table 2, it is recognized that the laminated films obtained in the examples show good results in all items.

[0062]

EFFECTS OF THE INVENTION Since the present invention is constructed as described above, it provides a liquid bag having excellent flexibility, improved abrasion resistance, fold resistance, and heat resistance, as well as good blocking resistance. can do.

Claims (1)

[Claims] 1. A liquid bag formed by heat-sealing peripheral portions of a multilayer film composed of an inner film and an outer film, wherein the inner film and the outer film are inner layers, respectively.
The outer layer and the middle layer between them are composed of 100 parts by weight of the polypropylene resin and 40 to 15 parts of the high-density polyethylene resin.
0 parts by weight of a blended resin, the middle layer is made of a polypropylene resin, and the polypropylene resin used for the inner layer, the outer layer and the middle layer each have a weight average molecular weight of 80,000 to 500,000, and The elution amount in each temperature range by the fractionation method was 4 at 0 to 10 ° C with respect to the total weight of the polypropylene resin.
0 to 70% by weight, 8 to 30% by weight at 10 to 70 ° C, 7
A bag for liquid, which is 15 to 35% by weight of resin at 0 ° C to 120 ° C.