JP2755277B2 - Bag-in-box and bag used for it - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a back-in-box and a bag used for the same, and more particularly, to a heat-sealing portion at the time of hot filling in a bag using an ethylene vinyl alcohol copolymer intermediate layer. The present invention relates to an improvement in a bag that prevents retreat and peeling of the bag and prevents edge breakage due to a drop impact or the like.

[0002]

2. Description of the Related Art A bag-in-box in which a content filling bag formed of a plastic film or a laminate made of the film is contained in a carton box, seals various liquid contents. It is widely used at the distribution stage as a packaging container for packaging and transporting, and has the advantage that packaging costs are relatively low and disposal is easy.

[0003] The carton box is a rectangular parallelepiped. Therefore, it is desired that the content-filling bag also has a substantially rectangular parallelepiped shape that fits (fits into) the content-filled bag. In addition, it is desired that the bag has oxygen permeability in view of the storage stability of the contents.

From these requirements, as a film material constituting a bag, a multilayer film in which a heat-sealing resin, particularly an olefin resin inner and outer layer is laminated on an ethylene-vinyl alcohol copolymer intermediate layer having excellent oxygen permeability is used. This multilayer film is used as a bag after being made into a bag by heat sealing.

[0005]

A bag in which an ethylene vinyl alcohol copolymer is used as an intermediate layer and a heat-sealing resin is laminated on both sides of the intermediate layer is used for preserving the contents due to the excellent gas permeability resistance of the copolymer. Although it has excellent properties, it is still unsatisfactory in the combination of heat resistance and heat sealing strength as a bag for a box-in-box.

That is, most of bag-in-boxes are shipped with liquid contents weighing several to several tens of kilograms from the viewpoint of reducing distribution costs. Large gravitational force acts on the seal part, especially the seal part at the bottom, and there is a problem in particular that the bag may break due to a drop or a shock due to vibration during transportation.

In small packaging containers such as cans, bottles, and pouches, the hot filling method of contents is widely used from the viewpoint of improving the storage stability of the contents. There is a strong demand for improving the preservability of the contents by filling between them. However, in this case, there is still a problem that must be solved to the heat resistance of the heat seal portion of the bag.

[0008] Ethylene vinyl alcohol copolymer has mechanical properties such that the rigidity is high but the elasticity is low as compared with the olefin resin used for heat sealing, and the thermal conductivity is low. There is a problem that acts in a way. For this reason, at the time of heat sealing, while the heat sealing resin layer on the side in contact with the heat sealing bar becomes considerably high temperature, the heat sealing is performed while the heat sealing resin layer on the side opposite to the heat sealing bar is still relatively low temperature. Will be. This tendency is remarkable in a bag-in-box bag filled with a heavy load because the thickness of the multilayer film becomes large.

[0009] For this reason, the heat sealing resin is formed by heat sealing using a resin having a relatively low heat sealing temperature and a temperature range as wide as possible. Since the temperature of the layer is too high, the mechanical strength of the edge of the heat seal portion, particularly the drop impact strength, becomes weak, and so-called edge breakage or the like occurs when the layer is dropped.

Further, even if the sealing strength of the heat sealing portion is satisfactory at room temperature, when the above-described hot filling is performed on the bag-in-box bag, the heat sealing portion is retracted, that is, the sealing portion. However, it is still unsatisfactory in terms of heat resistance, such as peeling off. In addition, as the characteristics required for the resin used for bag-in-box bags,
Examples include slipperiness and waist strength. That is, bag-in-box bags are generally manufactured by heat-sealing and gusset folding a resin film. However, if the resin film is weak and lacks slipperiness, poor folding occurs, and furthermore, the contents of the bag are reduced. When it is stored in a cardboard box after filling, it slips on the inner surface of the box and the workability is poor. For example, conventionally, linear low density polyethylene (LLDPE)
However, it is often used as a heat-sealing material for a heat-sealing multilayer film because it has excellent mechanical properties, especially toughness, good pinhole resistance, and heat resistance among polyethylene. This is due to the fact that the sealing conditions are not narrow. Nevertheless, in the case of a bag for a bag-in-box in combination with an ethylene vinyl alcohol copolymer, the edge is cut off due to a drop impact, etc. Cutting has occurred, and application to this application has not yet been successful. On the other hand, if the ethylene-α-olefin copolymer elastomer is used for the purpose of modifying linear low-density polyethylene, it should be satisfactory in terms of strength against drop impact, etc. In the case of space filling, peeling or receding of the seal portion occurs, and a difficulty still remains in terms of sealing reliability. Further, a bag using a large amount of this elastomer has no stiffness and is inferior in commercial value to a bag using a conventional ordinary olefin resin.

[0011] Therefore, an object of the present invention is to provide an excellent heat sealing property at the time of bag making, and that the formed heat sealed portion has mechanical strength, impact resistance and heat resistance enough to withstand hot filling. Another object of the present invention is to provide a bag-in-box in which the bag has both slipperiness and stiffness, and a bag used therefor.

Another object of the present invention is to provide a heat-sealing portion having an excellent heat-sealing property and an impact resistance of a heat-sealing portion while having a laminated structure in which an ethylene-vinyl alcohol copolymer is used as an intermediate layer and an olefin-based resin is used as an inner and outer layer. An object of the present invention is to provide a bag for a box-in-box that has a combination with heat resistance, and also has both slipperiness and waist strength.

[0013]

[Means for solving the problems]

According to the present invention, there is provided a laminated film comprising a paper box and a resin film bag accommodated in the box, wherein the bag comprises an inner and outer layer of an olefin resin and an intermediate layer of an ethylene-vinyl alcohol copolymer. A linear ultra-low density having a density of 0.915 g / cm ³ or less and a melting point of 110 ° C. or more in at least one of the inner and outer layers, which is formed by heat sealing, and at least one of the inner and outer layers to be heat sealed. Polyethylene and density 0.915g / cm
50:50 with linear low density polyethylene larger than ³
A bag-in-box, wherein the bag-in-box is formed of a resin composition containing the resin composition in a weight ratio of about 95: 5.

According to the present invention, the laminated film comprising the inner and outer layers of the olefin resin and the intermediate layer of the ethylene-vinyl alcohol copolymer is formed by heat-sealing the laminated film, and the inner and outer layers have a density of 0.915 g / cm ³ or less. And a linear ultra-low density polyethylene having a melting point of 110 ° C. or higher and a density of 0.1.
A layer formed of a resin composition containing a linear low-density polyethylene having a weight ratio of more than 915 g / cm ³ and a weight ratio of 50:50 to 95: 5. One side piece and a second side piece, two pieces each inward from the edges of the first side piece and the second side piece and between the first side piece and the second side piece. The bag comprises a third side piece and a fourth side piece which are folded and formed with a small space between each bent portion, and the bag has a first side piece and a second side piece at the center at upper and lower ends. The first heat sealing portion formed between the side pieces and the second side piece formed continuously over the first side piece and the third side piece and the fourth side piece and the second side piece. A back-in-box bag characterized by having a heat seal portion.

[0016]

[Function] The bag-in-box bag of the present invention
It is formed by heat-sealing a laminated film of an olefin-based resin inner and outer layer and an ethylene vinyl alcohol copolymer intermediate layer. The layer to be a heat-sealing layer has a density of 0.915 g / cm ³ or less, particularly 0.912
g / cm ³ or less, and a linear ultra low density polyethylene having a melting point of 110 ° C. or more and a linear low density polyethylene having a density of more than 0.915 g / cm ³ from 50:50 to 95: 5.
It is a remarkable feature that it is formed of a resin composition containing a weight ratio.

In the present invention, by forming the heat seal layer with a resin composition containing linear ultra-low density polyethylene and linear low density polyethylene in a predetermined compounding ratio, excellent heat sealability and heat seal portion are obtained. It has been found from a number of experimental results that a bag-in-box bag having a combination of impact resistance and heat resistance and also having both slipperiness and waist strength can be obtained. There are many unknown points, but the following are considered. That is, the linear ultra-low-density polyethylene used in the present invention is a copolymer of ethylene and an α-olefin, like a normal linear low-density polyethylene, and has a substantially linear polymer structure. Although it has a very low density, it is crystalline like ordinary linear low density polyethylene. Therefore, the resin composition containing the linear ultra-low density polyethylene and the ordinary linear low-density polyethylene has excellent mechanical strength and excellent mechanical strength in the heat-sealed portion formed as in the case of the ordinary linear low-density polyethylene alone. It seems to provide heat resistance. In addition, this linear ultra-low density polyethylene seems to have more comonomer segment structures and a random sequence than ordinary linear low-density polyethylene. Therefore, the resin composition containing a normal linear low-density polyethylene and a linear ultra-low-density polyethylene at a predetermined compounding ratio is a resin composition containing only a normal linear low-density polyethylene (Comparative Examples 1 and 7 described later) It is considered that this randomness is higher than that of ()). This increase in randomness is considered to be the reason that the heat sealing conditions can be broadened and excellent heat sealing properties can be imparted, and the impact resistance of the heat sealed portion can be improved, as compared with conventional ones.

According to the present invention, when a resin composition containing a linear ultra-low density polyethylene and a linear low-density polyethylene in a predetermined weight ratio is used, the heat sealing property is improved, and the mechanical strength and impact resistance of the heat sealed portion are improved. Although the improvement in heat resistance and heat resistance is sufficient, the slipperiness and waist strength required for a bag-in-box bag are also improved. That is, when the heat seal layer is composed of only the linear ultra-low density polyethylene (Comparative Example 4 ′ described later),
On the contrary, the film is weak and lacks slipperiness,
Since the elongation at high temperature is large, the range of manufacturing conditions as a bag, such as poor folding or an elongated heat-sealed portion in a gusset-folded bag, is narrowed.
The reason why the strength of the waist and the slipperiness decrease in this way is
It is considered that ultra-low density polyethylene has lower crystallinity than ordinary low-density polyethylene. Thus, by containing the linear ultra-low density polyethylene and the normal linear low-density polyethylene within the above amount range, for the first time,
While maintaining excellent heat sealability and heat resistance, the bag can be given the necessary slipperiness and can have a firm back.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION (Laminate Film) In FIG. 1 showing an example of the laminate of the present invention, the laminate film 1 has an intermediate layer 2 mainly composed of an ethylene vinyl alcohol copolymer, an adhesive resin It is composed of surface olefin resin layers 3, 4 laminated via layers 2a, 2b. At least one of the surface olefin resin layers 3, 4 to be heat-sealed, preferably both layers, comprises a layer containing linear ultra-low density polyethylene.

I. Ethylene vinyl alcohol copolymer In the present invention, the ethylene vinyl alcohol copolymer is used as a gas barrier resin because it has an excellent oxygen permeability coefficient and can be thermoformed. Examples of the ethylene-vinyl alcohol copolymer include an ethylene-vinyl acetate copolymer having an ethylene content of 20 to 60 mol%, particularly 25 to 50 mol%.
A saponified copolymer obtained by saponifying so as to have a saponification degree of 96 mol% or more, particularly 99 mol% or more is used. The ethylene vinyl alcohol copolymer should have a molecular weight sufficient to form a film, and is generally 0.01 dl / measured in a mixed solvent of phenol: water at a weight ratio of 85:15 at 30 ° C. g or more, especially 0.0
It is desirable to have a viscosity of 5 dl / g or more.

As the intermediate layer, it is preferable to use an ethylene-vinyl alcohol copolymer alone.
Polyester, acid-modified olefin resin and the like may be blended and used.

II. Linear ultra-low-density polyethylene The linear ultra-low-density polyethylene used in the present invention is similar to linear low-density polyethylene (LLDPE) and ethylene-α-olefin copolymer elastomer in that it is composed of an ethylene-α-olefin copolymer. However, the linear low-density polyethylene is generally 0.920 g / cm ³ or more, especially 0.1 g / cm ³ .
Having a density of less than or equal to 925 g / cm ³ , and ethylene-α-olefin copolymer elastomers having a density generally less than 0.900 g / cm ³ and being amorphous, Scanning calorimetry (DSC)
The linear ultra-low-density polyethylene is different in that it does not have a clear crystal melting peak, whereas the linear ultra-low density polyethylene still has a clear crystal melting peak. Although there is no strict definition of the density, a density of 0.915 g / cm ³ or less is generally referred to as an ultra-low density in many cases. It is important to use a linear ultra-low density polyethylene having the above density and melting point. That is, those having a density exceeding the range of the present invention are ordinary linear low-density polyethylenes.However, if only this is used, as already pointed out, the multilayer film when used as a bag-in-box is used. The heat sealability is reduced, the impact resistance of the heat seal portion is unsatisfactory, and the heat seal portion tends to be easily cut off the edge. On the other hand, when the melting point is lower than the range of the present invention, the heat-sealing portion has unsatisfactory heat resistance with respect to hot filling.

The linear ultra low density polyethylene used in the present invention is a copolymer of ethylene and α-olefin,
Consisting of a substantially linear polymer chain, this polymer has short branches based on α-olefins. The branched chains suppress crystallization of polyethylene, and the density is kept in the above-mentioned low range. Generally, the crystallinity by X-ray diffraction is preferably 20 to 55%, more preferably 25%.
Linear ultra-low density polyethylene in the range of ~ 50% is used.

In the linear ultra-low density polyethylene, the α-olefin copolymerized with ethylene is generally an α-olefin having 4 to 10 carbon atoms, particularly 4 to 8 carbon atoms, specifically 1-butene, -Pentene, 1-hexene, 4-
Methyl-1-pentene, 1-octene, 1-decene or a mixture thereof, with 1-butene, 1-hexene and 1-octene being particularly preferred. These α-olefins are present in an amount of from 10 to 25% by weight, in particular 1%, per copolymer.
It may be copolymerized in an amount of 2 to 20% by weight.

Further, the linear ultra low density polyethylene is 0.1 to 50 g / 10% in terms of processability into a multilayer film.
min, preferably not more than 30 g / 10 min. If the melt index is less than 0.1 g / 10 min, the flow characteristics and dispersibility are poor, and the film formability is reduced. On the other hand, if it exceeds 50 g / 10 min, the mechanical strength tends to decrease, so that the strength as a bag-in-box bag tends to decrease.

III. Resin Composition In the present invention, the linear ultra-low density polyethylene is preferably contained at least 50% by weight in the heat seal resin layer.

In the present invention, the linear ultra low density polyethylene (A) and the linear low density polyethylene (B) having a density of more than 0.915 g / cm ³ are mixed with 50:50 to 95:
5, especially a resin composition containing 50:50 to 90:10 by weight is used as the heat sealing resin layer. That is, linear low-density polyethylene, compared to other olefin resins, has good familiarity with the linear ultra-low-density polyethylene, and the mechanical strength of the multilayer film, particularly the tensile strength,
It is a component that improves tear strength, toughness, and the like, and further provides the multilayer film with the waist strength and slipperiness required for a bag for a bag-in-box. Of course, in the present invention,
As long as the above-mentioned compounding conditions are satisfied, the resin composition of the linear ultra-low density polyethylene and the ordinary linear low-density polyethylene may further contain another resin. Other resins that may be included in the resin composition include, for example, low density, medium density or high density polyethylene, linear low density polyethylene, crystalline polypropylene, ethylene-propylene copolymer, ethylene-propylene-butene -Olefin resins such as copolymers, ionomers, ethylene-vinyl acetate copolymers and ethylene-ethyl acrylate copolymers.

In this resin composition, even if the amount of the linear low-density polyethylene falls below the above range, the above-mentioned properties, particularly the slipperiness and the strength of the waist, are not sufficiently improved. Is exceeded, the object of the present invention is not sufficiently achieved.

The linear low-density polyethylene (B) used in the present invention is also similar to the linear ultra-low-density polyethylene (A).
It is a copolymer of ethylene and an α-olefin, but they are different in density. Also, the crystallinity by the X-ray diffraction method is different, and the crystallinity is generally 56%.
乃至 80%.

In this linear low-density polyethylene (B), the α-olefin to be copolymerized with ethylene may be the same as described above for the linear ultra-low-density polyethylene, and specifically has 3 to 10 carbon atoms, especially Α-olefins of 4 to 8, preferably 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-
Decene or a mixture thereof, particularly preferably 1-butene, 1-hexene and 1-octene. These α-olefins are preferably copolymerized in an amount of 3 to 15% by weight, especially 3 to 10% by weight, based on the copolymer.

When the amount of the linear ultra-low density polyethylene is less than the above range, the heat sealability, the mechanical strength of the heat seal portion, the impact resistance and the heat resistance are insufficiently improved. When the amount of the low-density polyethylene is less than the above range, the slipperiness as a bag,
They also tend to lack waist strength.

The resin or resin composition used for forming the inner and outer layers in the present invention may contain a compounding agent known per se, for example, a lubricant,
One or more kinds of stabilizers, antioxidants, ultraviolet absorbers, antiblocking agents, coloring agents, and the like can be blended according to a known formulation.

IV. Adhesive layer If there is no adhesiveness between the intermediate layer of ethylene vinyl alcohol copolymer and the inner and outer surface layers, between both resin layers,
Acid-modified olefin resins such as maleic anhydride, acrylic acid, methacrylic acid, ethylenically unsaturated carboxylic acids such as itaconic anhydride, or low-, medium-, high- or linear low-grafts modified with their anhydrides. Density polyethylene,
It is preferable to interpose an adhesive layer such as polypropylene. Instead of interposing the adhesive layer, the above-described resin can be contained in at least one of the intermediate layer and the inner and outer surface layers.

The laminated film or sheet used in the bag of the present invention is produced by melt-kneading each of the above resins in a corresponding extruder, and simultaneously extruding the melt through a multilayer multiple die. For the film formation, a T-die method or an inflation film formation method is used, and the film or sheet may be unstretched or may be uniaxially or biaxially stretched.

The thickness of the ethylene vinyl alcohol copolymer layer in the laminated film is generally 2 to 30 μm,
The thickness is particularly preferably in the range of 4 to 15 μm, and the thickness of the linear ultra-low density polyethylene-containing resin layer serving as the heat seal layer is 30 to 150 μm, particularly 50 to 120 μm.
And the total thickness is 70 to 220 μm.
m, especially in the range of 100 to 300 μm.
It is preferred that the inner and outer surface layers are both made of linear ultra-low density polyethylene-containing resin layers having the same thickness. Further, in the laminated film or sheet, a scrap resin or the like can be provided as a layer between the intermediate layer and the inner and outer surface layers.

(Bag) The bag of the present invention can be produced by laminating two pieces of the above-mentioned multilayer film or sheet and heat-sealing their side edges. A nozzle with a cap for filling and pouring out the contents can be provided by heat sealing or the like at a portion near the side edge of one of the films or sheets.

The preferred bag of the present invention, in the empty bag state, has the first side piece and the second side piece located on the outside and the edges of the first side piece and the second side piece respectively. From the third side piece and the fourth side piece inwardly folded into two pieces between the first side piece and the second side piece and having a small space between each bent portion. The bag has a first heat seal portion formed between the first side piece and the second side piece at the center at the upper and lower ends, and the first side piece and the third And a second heat seal portion formed over the fourth side piece and the second side piece.

In FIG. 2 (perspective view) and FIG. 3 (side view) showing a preferred example of the bag-in-box of the present invention, the bag-in-box is used for filling a carton box 10 and contents contained therein. And a bag 20. The carton box 10 has a rectangular parallelepiped shape, and includes four side walls 11, a bottom 12, and an openable top cover 13. The content-filled bag 20 includes a bag body 21,
It comprises an opening 22 for filling and unloading the contents, and a cap 23 which is provided so as to be able to be sealed and removed from the opening 22.

The bag body 21 is formed of the above-mentioned multilayer plastic film or sheet, and has a shape and a size that fits inside the carton box 10 when the contents are filled.

In FIG. 4 (perspective view) and FIG. 5 (cross-sectional view) showing the bag body in an empty bag state, the bag body 21 is shown.
Is composed of a first side piece 24 and a second side piece 25, and a third side piece 27 and a fourth side piece 28 which are folded inward from the edge 26 of these side pieces into two pieces. Made up of A bent portion 29 exists between the third side piece 27 and the fourth side piece 28, and a small interval is formed between the opposed bent portions 29, 29.

The bag body 21 may be a tube-shaped body having no seam on the side, or a single film may be folded.
Although it is possible to have one side seam overlapped and sealed at the side edges, preferably, two film or sheets are overlapped and two side seams 30a overlapped and sealed at both side edges, Those having 30b are preferred.

This bag body is heat-sealed at the top and bottom of the above-mentioned folded structure to form an upper heat-sealing portion 31 and a bottom heat-sealing portion 32. The contents-filling bag 21 spreads in a rectangular parallelepiped shape in the contents-filled state, fits tightly into the rectangular parallelepiped carton box, and has no gaps. Therefore, damage caused by misalignment between the bag and the box during transportation, etc. There is an advantage that generation of pinholes is prevented.

The weakest portion of the above bag against drop impact is a heat-sealed portion at the bottom, particularly a portion where both sides are folded inward and the inside bent edges are heat-sealed. When a drop impact is applied in a state filled with, tensile stress locally concentrates on the portion,
Although cracks and pinholes are generated and heat seal breakage occurs, causing problems such as leakage. However, according to the present invention, since the heat seal portion is made of the linear ultra-low-density polyethylene-containing resin described above, drop impact It is possible to prevent the bag from being locally broken at the bottom due to the like. In particular, the effect tends to be more remarkable as the content of the bag-in-box increases. When the capacity coefficient (g / cm) is defined by the ratio of the actual internal capacity (g) of the bag converted to water and the total heat seal length (cm), the drop impact resistance is 10 or more, especially 20 or more. A remarkable effect was observed on the properties, and the same tendency was observed with respect to the retreat and breakage of the heat-sealed portion during hot filling with water or the like. It is considered that as the capacity coefficient increases, the stress caused by the shock wave applied to the vicinity of the seal portion increases drastically when dropped, and the creep force applied to the seal portion increases remarkably in heat resistance.

In producing the bag of the present invention, it is a remarkable advantage that the heat sealing can be performed under a rather wide range of conditions, but it is generally at 180 to 270 ° C., especially at 210 to 2 ° C.
It is preferably carried out at a temperature of 50 ° C. It is also an advantage of the present invention that the heat sealing can be performed using a heat sealing bar having a temperature difference between the front and back. Of course, heat sealing,
It can also be performed by ultrasonic heat sealing, dielectric heat sealing, laser heat sealing, or the like.

[0045]

EXAMPLES The present invention will be described specifically with reference to the following examples. Example 1 In an extruder for an outer layer, an ethylene / butene-1 copolymer (LLD) was used.
PE-, density 0.905 g / cm ³ , melting point 120 ° C,
MFR 0.5g / 10min) and ethylene butene
1 copolymer (LLDPE-, density 0.920 g / cm
³ , a melting point of 121 ° C. and a MFR of 0.8 g / 10 min) in a weight ratio of 70:30, and a saponified ethylene-vinyl acetate copolymer (ethylene content of 40 mol%, saponification degree) 99%) was converted to a maleic anhydride graft-modified resin (density 0.920, melting point 104 ° C., M
FR (1.3 g / 10 min), and co-extruded using a multilayer inflation die and air-cooled to obtain an inner layer (I) / adhesive layer (I) / intermediate layer / adhesive layer (II) / outer layer (II). = 82/4/8/4/82 (μm)
Then, a three-layer, five-layer film having a total thickness of 180 μm was formed (used in the present invention 1). For comparison, LLDPE-simple (Comparative Example 1) and LLDPE-
70 parts of ethylene-based elastomer (density 0.8
85 g / cm ³ , melting point not measured, softening point 65 ° C, M
FR (3 g / 10 min) (Comparative Example 2), a film having the same film thickness was produced in the same manner.

Next, for these films, the width 57
After piercing the upper film, attaching a filling nozzle, folding it in a gusset shape, heat-sealing both side edges, and heat-sealing and cutting the top and bottom parts. , Flat size, width 41cm, length 57
A gusset bag for an internal volume of 20 liters per cm (actual internal volume 20.45 liters, volume coefficient 72) was prepared. Here, a hot plate seal having a seal width of 10 mm was used for heat sealing. The upper set temperature is a)
210 ° C, b) 230 ° C, c) 250 ° C, all below 7
Performed at 0 ° C., surface pressure 5.2 kg / cm ² , time 1.5 seconds,
Cooling was performed at room temperature, a surface pressure of 4.5 kg / cm ² , and a time of 1.5 seconds.

The bag produced as described above was evaluated for the container performance described below. As the heat resistance of the bag, after filling each 20 liter bag with hot water of 90 ° C., the gusset bag was kept standing for about 1 hour, and the presence or absence of receding of the seal portion and the presence or absence of leakage were inspected. Table 1 shows the number of leaks in the evaluation of 10 bags for each condition, or the average value of the maximum seal retreat width in the case of no leak (mm).
Shows the evaluation results of the bag heat resistance. On the other hand, as a drop impact resistance of the bag, water of 5 ° C. was filled in each 20 liter bag, and then stored in a special cardboard carton having an outer width of 32 cm, a length of 29 cm, and a height of 30 cm, and was stored at 5 ° C. for 48 hours.
Those stored for a time were dropped from a height of 90 cm onto a concrete surface such that the bottom of the carton was horizontal, and the occurrence of leakage was examined. Table 1 shows the number of leaked bags in the test of 10 bags under each condition.

As a result, in the case of a bag whose outer layer resin is made of LLDPE alone, a heat-resistant heat seal can be obtained at a high heat seal temperature, but there is a lot of leakage due to drop at any heat seal temperature. All the seals leaked, and there were no favorable conditions (Comparative Example 1). Also, the addition of a soft elastomer to LLDPE- significantly improves the drop impact resistance,
There is no heat-sealing condition for obtaining sufficient heat resistance, and leakage or retreat of the seal is remarkable under any of the conditions (Comparative Example 2).
When E- was used as the main component of the outer layer resin, stable bag performance satisfying both heat resistance and drop impact resistance was achieved under a wide range of heat sealing conditions.

[0049]

[Table 1]

Example 2 As an outer layer resin, as shown in Table 2, the LLD of the present invention 1 was used.
In the case of PE- and-, the mixing ratio was changed, a multilayer film having the same configuration as in Example 1 was formed, bags were produced, and various container performances were evaluated (Comparative Examples 3 and 4). , 3 ', 4', the present invention 3, 4). Further LLDPE
After fixing the compounding ratio of-to 50 parts by weight, the same evaluation was performed for a case where 50 parts of an ethylene / α-olefin copolymer having various melting points and densities were blended as shown below. As ethylene / α-olefin copolymers having various melting points, three types of ethylene / hexene-
1 copolymer (LLDPE-: density 0.900 g / cm
³ , melting point 103 ° C, MFR 0.8g / 10min, LL
DPE-: density 0.900 g / cm ³ , melting point 110
° C, MFR 0.7g / 10min, LLDPE-:
Density 0.900 g / cm ³ , melting point 123 ° C, MFR
0.8 g / 10 min) was used in Comparative Example 5 and the present inventions 6 and 7, respectively. In addition, ethylene with various densities
As the α-olefin copolymer, in addition to the above examples, ethylene / butene-1 copolymer (LLDPE-: density 0.9
10, melting point 121 ° C, MFR 0.6g / 10min)
, Ethylene-octene-1 copolymer (LLDPE-
: Density 0.915, melting point 122 ° C, MFR 0.7g
/ 10 min), ethylene / 4-methylpentene-1 copolymer (LLDPE-: density 0.918, melting point 123)
C., MFR 0.8 g / 10 min) were used in the present inventions 8, 9 and Comparative Example 6, respectively.

As a result, the so-called ultra-low density LLDPE
When the compounding ratio of-is changed, the compounding ratio is 25 wt%
In Comparative Examples (Comparative Examples 3 and 4), the drop impact resistance is remarkably reduced, and a higher heat seal temperature tends to be required to secure the heat resistance of the heat seal. However, it was difficult to find a condition for ensuring both performances. Also, the outer layer resin has an ultra-low density L
When composed of only LDPE (Comparative Example 4 '),
Although sufficient performance was obtained in terms of bag performance, the film was weak and lacked slipperiness, or stretched at high temperatures, causing poor folding in gusset-folded bags and heat The range of manufacturing conditions was narrow, such as a tendency for the seal portion to extend. Furthermore, when the content was filled and stored in a cardboard box, the slip with the inner surface of the carton was poor and the workability tended to be poor. The blending ratio of the ultra-low-density resin is preferably 25 wt% or more, and more preferably 50 wt% or more and less than 90 wt% in consideration of workability and the like.

If the melting point of the ultra low density resin used in the compounding is too low, the heat resistance of the heat seal tends to be impaired. When withstanding 95 ° C. and the density exceeds 0.915 g / cm ³ (Comparative Example 5)
In some cases, it loses its flexibility, resulting in reduced drop impact resistance,
The frequency of leakage due to falling tended to increase.

[0053]

[Table 2]

Example 3 The films used in the present invention 1 and the comparative example 1 of the example 1 are shown in Table 3 as shown in Table 3.
1 liter and 30 liter pillow bags each
A bag was made from the film in the order of filling nozzle piercing, nozzle bonding, backing seal (width 10 mm, 230 ° C.), and both ends seal (same). The capacity coefficients expressed by the ratio of the total heat sealing length (cm) to the actual internal capacity (g) of these bags were 81, 130, and 172 for each size bag.

After filling these bags with the juice heated to 90 ° C., the bags were allowed to cool at room temperature, and after about 6 hours, the seal was receded and inspected for leakage. Furthermore, these bags were stored in a cardboard box of a predetermined size and stored at 5 ° C. for 48 hours. After dropping horizontally with the backing part on the concrete surface lower than the height of 90 cm from the height of 90 cm, leakage was observed. The outbreak was examined. Table 3 shows the results of these tests performed on 10 bags under each condition.

According to this, the outer layer resin is a very common L
When the LDPE is composed of a single substance, as the internal capacity increases and the capacity coefficient increases, the receding and leaking of the seal portion increase, and leakage at the time of dropping (mainly cutting near the seal portion). ) The frequency tended to increase (Comparative Example 7), and the difference from the case where the ultra-low density LLDPE of the present invention 10 was used as the main component was further clarified. It is considered that the larger the capacity, the higher the stress applied to the seal portion, and the stronger the shock wave at the time of the drop. Therefore, the bag-in-box according to the present invention is more suitable for a bag having a large capacity. It is understood that the effect is achieved.

[0057]

[Table 3]

[0058]

According to the present invention, a paper box and a resin film bag housed in the box are provided.
The bag is a bag-in-box formed by heat-sealing a laminated film composed of an olefin-based resin inner and outer layer and an ethylene vinyl alcohol copolymer intermediate layer, and at least one of the inner and outer layers is heat-sealed. Density is 0.915 g / cm ³ or less and melting point is 1
Linear ultra-low density polyethylene of 10 ° C or higher and density of 0.9
By using a layer formed of a resin composition containing a linear low-density polyethylene having a weight ratio of more than 15 g / cm ³ and a weight ratio of 50:50 to 95: 5, excellent heat sealability and impact resistance of the heat seal portion are obtained. In addition to having a combination of heat resistance and heat resistance, slipperiness and waist strength were also obtained.

Further, a bag having a folded seal portion is provided.
Even in the in-box content filling bag, by forming the heat seal portion with the resin composition, even if tensile stress due to a drop impact or the like is concentrated on the bent seal portion, the bag breaks or the edge breaks. Thus, it was possible to effectively prevent the bag from being broken and the bag from leaking. Further, the content was hot-filled, whereby the preservability of the content could be improved, in combination with the fact that the intermediate layer was made of an ethylene vinyl alcohol copolymer. Furthermore, the multilayer film bag of the present invention has other advantages in addition to the properties of the heat seal portion. That is, this bag is excellent in pinhole resistance and shows about twice the resistance as compared with a bag having an ordinary linear low-density polyethylene as an outer surface layer. This may be referred to as an increase in resistance to vibration and shaking during transportation, and long-distance transportation is possible using the bag-in-box of the present invention.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a laminate of the present invention.

FIG. 2 is a perspective view of a preferred example of a bag-in-box of the present invention.

FIG. 3 is a side view of the bag-in-box of FIG. 2;

FIG. 4 is a perspective view showing an example of a content filling bag.

FIG. 5 is a cross-sectional view of an example of a content filling bag.

[Description of Signs] 1 is a laminated film, 2 is an intermediate layer mainly composed of an ethylene-vinyl alcohol copolymer, 2a, 2
b is an adhesive resin layer, 3 and 4 are surface olefin resin layers containing linear ultra-low density polyethylene, 10 is a carton box, 20 is a bag, 21 is a bag body, 24 is a first side piece, and 25 is a first Two side pieces, 26 are their edges, 27 is a third side piece, 28 is a fourth side piece, 29 is a bent portion, and 32 is a bottom seal portion.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-117441 (JP, A) JP-A-2-19276 (JP, A) JP-A-60-120051 (JP, A) JP-A-62-162 130847 (JP, A) JP-A-4-44969 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B65D 30/02 B32B 27/32 B65D 77/06

Claims (3)

(57) [Claims] 1. A paper box and a resin film bag housed in the box, wherein the bag is formed by heat sealing a laminated film comprising an olefin resin inner / outer layer and an ethylene vinyl alcohol copolymer intermediate layer. at least heat-sealed by the layer density of 0.915 g / cm ³ linear ultra low density polyethylene and the density of the melting point of more than 110 ° C. or less of and inner and outer layers are formed by bags than 0.915 g / cm ³ A low-density linear polyethylene having a weight ratio of 50:50 to 95: 5 in a weight ratio of 50:50 to 95: 5. 2. A paper box and a resin film bag housed in the box, wherein the bag is formed by heat sealing a laminated film comprising an inner and outer layer of an olefin resin and an intermediate layer of an ethylene vinyl alcohol copolymer. Formed of a bag and both inner and outer layers have a density of 0.91
A linear ultra-low-density polyethylene having a melting point of 110 ° C. or more at 5 g / cm ³ or less and a linear low-density polyethylene having a density of more than 0.915 g / cm ³ are mixed with 50:50 to 95: 5.
A bag-in-box formed of a resin composition containing a weight ratio. 3. A laminated film comprising an inner and outer layer of an olefin resin and an intermediate layer of an ethylene-vinyl alcohol copolymer, formed by heat-sealing, wherein the inner and outer layers have a density of 0.915 g / cm ³ or less and a melting point of 110 ° C. A layer formed of a resin composition containing the above linear ultra low density polyethylene and the linear low density polyethylene having a density of more than 0.915 g / cm ^{3 in a} weight ratio of 50:50 to 95: 5, The bag is, in the empty bag state, the first side piece and the second side piece located on the outside, and inward from the edges of the first side piece and the second side piece, respectively, and on the first side piece. A third side piece and a fourth side piece which are folded into two pieces between the piece and the second side piece and a small gap is formed between each bent portion, and the bag has upper and lower end portions. In the first part formed between the first side piece and the second side piece at the center A back seal having a heat seal portion and a second heat seal portion formed continuously over the first side piece and the third side piece, and the fourth side piece and the second side piece.・ In-box bag.