JP7795772B2 - Liquid storage bag - Google Patents

Description

The present invention relates to a liquid storage bag for storing liquids such as detergents, and in particular to a liquid storage bag that is highly convenient and recyclable.

Conventionally, liquid detergents for household use have been sold in synthetic resin containers, but when the detergent in the container runs out, the empty container has to be refilled with detergent refills contained in synthetic resin bags.

However, when refilling an empty container with refill detergent as described above, the refilling process requires holding a flexible synthetic resin bag in one's hand, which makes the position of the bag's opening unstable. This makes it difficult to align the opening of the container with the opening of the bag, which can lead to the problem of detergent spilling out of the container.

To solve this problem, for example, as shown in Patent Document 1, a known system involves placing a synthetic resin bag (liquid storage bag) containing refill detergent inside an empty container that has a pump member at the top of the container that serves as a liquid outlet and a suction needle that protrudes downward from the pump member, piercing the bag with the suction needle, and then moving the pump member up and down to remove the detergent from the bag through the suction needle.

In the liquid storage bag shown in Patent Document 1, not only the part where the suction needle is pierced, but the entire bag is made of a laminate film made by laminating a stretched nylon film and a polyolefin film. Stretched nylon film has the property of being easily torn when a force is applied in a tearing direction by the tip of the suction needle due to the force applied when the suction needle is pierced.

However, in the liquid storage bag shown in Patent Document 1, the polyolefin film laminated to the stretched nylon film also moves in sync with the stretched nylon film due to the force exerted when the suction needle is pierced into the bag, causing a tear in the laminated film at the tip of the suction needle. As a result, air enters the bag through the tear around the hole where the suction needle penetrates. As a result, when the amount of detergent inside the bag becomes small, operating the pump member causes air to be sucked in through the suction needle, making it impossible to remove all of the detergent from the bag. Another problem is that if the container falls over, the detergent inside the bag leaks into the container through the tear, contaminating the inside of the container and even causing detergent to leak outside the container.

As a means for solving the above problem, for example, Patent Document 2 discloses a liquid storage bag in which a liquid such as detergent is stored, characterized in that the entire bag has a layer made of a barrier material, and in at least a portion of the bag, a layer of laminate film made by laminating and bonding an unstretched nylon film and a polyolefin film is provided over the barrier layer without being adhered to it. With the liquid storage bag disclosed in Patent Document 2, the detergent inside the bag can be removed to the last drop without causing tears in the laminate film.

Patent No. 3526626 Patent No. 2527529

However, with liquid storage bags such as those shown in Patent Document 2, it is difficult to separate the individual layers (unstretched nylon film, polyolefin film, and barrier layer) after use. As a result, liquid storage bags such as those shown in Patent Document 2 that are collected after use are not suitable for recycling, and are not actively recycled at present.

The present invention aims to solve the above problems by providing a liquid storage bag in which a needle protruding downward from the container's liquid outlet pierces the bottom of the bag, allowing the liquid inside the bag to be removed to the last drop, preventing the liquid inside the bag from leaking even if the container falls over, and offering excellent recyclability.

In order to solve the above problem, the liquid storage bag of the present invention is a liquid storage bag that stores liquid inside and is placed upside down inside a container that has a liquid outlet at its upper end, and a needle that protrudes downward from the liquid outlet is inserted into the bottom of the bag, the bottom of the bag being formed from a base material made of a polyethylene resin film, the base material having at least a base layer and a water-stopping layer, the base layer having a breaking elongation in at least one of the longitudinal and transverse directions of 300% or less, the water-stopping layer having tear strengths of 3N or more in both the longitudinal and transverse directions, and the ratio of tear strengths in the longitudinal and transverse directions (longitudinal/transverse) being 0.5 or more and 2 or less.

The effects of the present invention are as follows: Even when a needle from a container with a liquid outlet is pierced into the bottom of the liquid storage bag of the present invention, the needle piercing portion of the bag does not tear and adheres tightly to the needle, preventing air from entering the bag. As a result, even when the amount of liquid inside the bag is small, the bag can be maintained in a vacuum state, making it possible to remove almost all of the liquid inside the bag. Furthermore, even if the container is toppled, the liquid inside the bag will not leak inside the container. Furthermore, a liquid storage bag made of polyethylene-based resin has excellent recyclability.

1 is an exploded perspective view of a container for accommodating a liquid storage bag according to the present invention; 1 is a perspective view of a container for accommodating a liquid storage bag according to the present invention; 1 is a perspective view of a liquid storage bag according to the present invention; This is an oblique view illustrating the arrangement of the laminated film for the body material (the laminated film on the front and rear walls that will become the body material) and the laminated film for the bottom material when manufacturing the liquid storage bag of the present invention.

The following describes a liquid storage bag 10 according to an embodiment of the present invention. However, the present invention is not limited to these embodiments as long as they do not deviate from the gist of the present invention. Figure 1 is an exploded perspective view of a container 20 that houses a liquid storage bag 10 according to the present invention. Figure 2 is a perspective view of a container 20 that houses a liquid storage bag 10 according to the present invention. Figure 3 is a perspective view of a liquid storage bag 10 according to the present invention. Figure 4 is a perspective view illustrating the arrangement of the laminated film for the body material 15 (the laminated film on the front and rear walls that will become the body material) and the laminated film for the base material 14 when manufacturing a liquid storage bag 10 according to the present invention.

As shown in Figures 1 and 2, the liquid storage bag 10 is placed upside down inside a container 20 that has a liquid outlet at its top. More specifically, the liquid storage bag 10 is placed in the container body 21 with the bottom 13 facing upward so that the bottom 13 is at the top, and the lid 22 is fitted onto the container body 21 from above, thereby placing the liquid storage bag inside the container 20.

A pump member 23, which serves as a liquid outlet, is attached to the lid 22. The pump member 23 is provided with a needle 24 that protrudes downward. The needle 24 is inserted into the liquid storage bag 10 so that its tip pierces the bottom 13 of the liquid storage bag 10 placed in the container body 21 and is positioned near the bottom end of the liquid storage bag 10.

As shown in Figure 3, the liquid storage bag 10 is a stand-up pouch having a body 12 with heat-sealed seals 11 on two opposing sides, and a bulging bottom 13 at the bottom. As shown in Figure 4, the liquid storage bag 10 is manufactured, for example, by heat-sealing a folded base material 14 and two separate body materials 15 at predetermined locations.

The body material 15 that forms the body portion 12 is made of a polyethylene-based resin film. Similarly, the base material 14 that forms the bottom portion 13 is made of a polyethylene-based resin film. In this way, the liquid storage bag 10 is made of a polyethylene-based resin film.

The base material 14 has at least a substrate layer and a water-stopping layer.

The base material layer used in the base material 14 of the present invention has a breaking elongation of 300% or less in at least one of the longitudinal and transverse directions. If the breaking elongation of the base material layer of the base material 14 exceeds 300%, when the liquid-extracting needle 24 attached to the container 20 is pierced into the bottom 13, the film constituting the base material 14 will stretch, preventing the needle 24 from piercing the bottom 13.

To ensure that the breaking elongation of the base layer of the base material 14 is 300% or less, it is preferable that the film that makes up the base material 14 be stretched. The stretching process for the film that makes up the base material 14 may be uniaxial or biaxial, with biaxial stretching being more preferable. Biaxial stretching of the film increases the film's rigidity. Furthermore, in printing, laminating, or bag-making processes, the film is not stretched by tension during the thermal process of drying the ink or adhesive, improving processability. In addition, in the case of uniaxial stretching, it is preferable that the film be stretched in the machine direction, which increases the rigidity against tension during processing.

The stretching ratio of the base layer of the base material 14 in the longitudinal and transverse directions is preferably 2 to 10 times in the case of uniaxial stretching, and the product of the longitudinal and transverse stretching ratios (area ratio) is preferably 4 to 16 times in the case of biaxial stretching. By setting the stretching ratio of the base layer of the base material 14 in the longitudinal and transverse directions to 2 times or more (in the case of uniaxial stretching) or 4 times or more (in the case of biaxial stretching), the breaking elongation of the base layer of the base material 14 can be set to 300% or less, and strength and heat resistance can be further improved. Furthermore, if the stretching ratio of the base layer of the base material 14 in the longitudinal and transverse directions exceeds 10 times (in the case of uniaxial stretching) or 16 times (in the case of biaxial stretching), the base layer of the base material 14 is prone to breakage during film production and is therefore not practical.

The base material layer of the base material 14 can be an unstretched film of high-density polyethylene or medium-density polyethylene, or a stretched film of high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, or the like.

Furthermore, the base layer of the base material 14 may be formed by mixing two or more of the above polyethylenes. For example, by blending linear low-density polyethylene with high-density polyethylene, it is possible to form a film that has excellent film-forming properties, high film rigidity, and excellent transparency, making it suitable for use as a film for the base layer of the base material 14.

The water-stopping layer used in the base material 14 of the present invention preferably has a tear strength of 3N or more in at least one of the longitudinal or transverse directions, and the ratio of tear strength in the longitudinal direction to that in the transverse direction (longitudinal direction/transverse direction) is 0.5 or more and 2 or less.

If the tear strength of the water-stopping layer of the base material 14 in both the vertical and horizontal directions is less than 3N, the film of the base material 14 will tear when pierced with the needle 24 of the container 20, resulting in liquid leakage and air intrusion. As a result, it will not be possible to maintain a vacuum inside the liquid storage bag 10, a feature of the present invention, and the contents of the liquid storage bag 10 will not be able to be sucked out to the last drop.

Furthermore, by setting the ratio of tear strength in the longitudinal direction to the transverse direction (longitudinal direction/transverse direction) of the water-stopping layer of the base material 14 to 0.5 or more and 2.0 or less, a base material 14 with excellent water-stopping properties can be obtained.

In other words, in the present invention, the water-stopping properties of the base material 14 are achieved when the needle 24 of the container 20 pierces the bottom 13 of the liquid storage bag 10, and the film of the base material 14 stretches and wraps evenly around the needle 24 of the container 20. It has been found that when this happens, the film of the base material 14 stretches evenly around the circumference, resulting in improved water-stopping properties. When the ratio of the tear strength in the longitudinal direction to the lateral direction (longitudinal direction/lateral direction) of the water-stopping layer of the base material 14 falls within the scope of the present invention, which is between 0.5 and 2.0, the film of the base material 14 stretches evenly, resulting in excellent water-stopping properties.

However, if the tear strength ratio (longitudinal/lateral) of the water-stopping layer of the base material 14 is less than 0.5 or exceeds 2.0, the film will be more likely to tear in one direction, resulting in uneven, circumferential elongation. Furthermore, tearing of the film will also suppress elongation in the direction of higher tear strength, resulting in less elongation overall and variations in elongation. This results in a shorter wrapping length in areas with less elongation, making the water-stopping properties of those areas insufficient and causing liquid leakage from those areas. More preferably, the ratio of tear strength (longitudinal/lateral) of the length to the width of the water-stopping layer of the base material 14 is 0.7 or more and 1.5 or less; the closer to 1.0 it is, the better the water-stopping properties will be.

The water-stopping layer of the base material 14 can be made of unstretched films such as medium-density polyethylene, low-density polyethylene, and linear low-density polyethylene. Unstretched films of low-density polyethylene and linear low-density polyethylene are particularly preferred, and an unstretched film made of linear low-density polyethylene and produced by inflation molding is even more preferred.

In general, linear low-density polyethylene films produced by inflation molding have a higher tear strength than linear low-density polyethylene films produced by the T-die method because the molecular weight of the polyethylene used as the raw material is higher. Furthermore, because it is possible to reduce the anisotropy caused by the flow of the resin, the film has the high tear strength and a ratio of longitudinal to transverse strength close to 1 required for the water-stopping layer of the base material 14 of the present invention, making it suitable for use as the water-stopping layer of the base material 14 of the present invention.

When laminating the base material 14 of the present invention, the well-known dry lamination method, solventless lamination method, or extrusion lamination method can be used, with extrusion lamination being more preferred.

The polyethylene resin typically used in extrusion lamination has a lower molecular weight than the polyethylene resin used in the base layer and water-stopping layer of the base material 14 of the present invention. Therefore, by using extrusion lamination, the polyethylene resin layer used in extrusion lamination acts as a buffer layer to prevent the water-stopping layer of the base material 14 from tearing along with the base layer of the base material 14 when the needle 24 of the container 20 is pierced into the bottom 13 of the liquid storage bag 10. This also reduces the contamination of adhesive, which could become a foreign substance, when the liquid storage bag 10 is recycled.

When producing the base material 14 of the present invention, it is sufficient to have at least a two-layer structure of substrate layer/waterstop layer, and it is also possible to laminate a separate layer with functionality such as a sealant layer, for example, a substrate layer/waterstop layer/sealant layer structure.

When the base material 14 is a substrate layer/waterstop layer, the waterstop layer also serves as a sealant layer. However, if there is little difference in melting point between the substrate layer and the waterstop layer, the substrates are more likely to fuse together or develop heat wrinkles during the bag-making process. In such cases, it is preferable to provide a separate sealant layer, such as a substrate layer/waterstop layer/sealant layer.

In this case, there are no particular restrictions on the film's breaking elongation or tear strength for the sealant layer of the base material 14, and any sealant film can be used, but an ultra-low-temperature linear low-density polyethylene film produced by inflation molding is preferred.

In the present invention, the lamination strength between the base layer and the water-stopping layer of the base material 14 is preferably 3.0 N/15 mm or less, and more preferably 2.0 N/15 mm or less.

By setting the lamination strength between the base material layer and the water-stopping layer of the base material 14 to 3.0 N/15 mm or less, when the needle 24 of the container 20 is pierced into the bottom 13 of the liquid storage bag 10, the base material layer and the water-stopping layer of the base material 14 are bonded together when the tip of the needle 24 penetrates the bottom 13. However, as the needle 24 penetrates the base material 14, the base material layer and the water-stopping layer of the base material 14 delaminate as the needle 24 penetrates the bottom 13. This allows the water-stopping layer of the base material 14 to stretch without tearing, forming a water-stopping band of the base material 14 that wraps around the needle 24, resulting in excellent water-stopping properties.

If the lamination strength between the base layer and the water-stopping layer of the base material 14 exceeds 3.0 N/15 mm, the water-stopping layer of the base material 14 may be easily torn when the needle 24 of the container 20 is pierced into the bottom 13 of the liquid storage bag 10, resulting in poor water-stopping properties, which is undesirable.

Furthermore, there is no particular lower limit to the lamination strength between the base material layer and the water-stopping layer of the base material 14, but it is preferable that it be 1.5 N/15 mm or more in order to facilitate processing and prevent peeling due to external forces such as dropping or application of pressure during use.

To achieve a lamination strength of 3.0 N/15 mm between the base layer and water-stopping layer of the base material 14, for example, in the case of dry lamination or solventless lamination, it is possible to use a two-component curing polyether urethane adhesive or reduce the amount of adhesive applied. In the case of extrusion lamination, this can be achieved by adjusting the temperature and MFR (molecular weight) of the extruded resin.

The liquid storage bag 10 according to the present invention has a polyethylene resin content of 80% by mass or more, and preferably 90% by mass or more. In the liquid storage bag 10, the base material 14 forming the bottom 13 is made of a polyethylene resin film, and the body material 15 forming the body 12 is made of a polyethylene resin film, thereby achieving a polyethylene resin content of 80% by mass or more. This allows the polyethylene resin film forming the base material 14 and body material 15 to be suitably utilized when recycling the liquid storage bag 10. If the polyethylene resin content were less than 80%, the polyethylene resin film forming the base material 14 and body material 15 would have to be treated with a compatibilizer, dispersant, etc. when recycling the liquid storage bag 10, which would increase costs and make it difficult to obtain good quality.

Furthermore, as long as the properties of the present invention are not impaired, each layer of the base material 14 (substrate layer, water-stopping layer) can contain additives, such as crosslinking agents, antioxidants, antiblocking agents, slip agents, UV absorbers, light stabilizers, fillers, reinforcing agents, and antistatic agents.

Furthermore, to impart light-blocking or barrier properties to the liquid storage bag 10, the base material 14 and body material 15 can be coated, printed, or vapor-deposited. For example, light-blocking properties can be imparted to the liquid storage bag 10 by coating it with a coating agent containing titanium oxide or carbon black. Methods for imparting barrier properties to the liquid storage bag 10 include coating it with a polyvinyl alcohol (PVAL), vinyl acetate (PVAc), ethylene vinyl alcohol copolymer (EVOH), or polyvinylidene chloride (PVDC) coating agent. Furthermore, vapor deposition can impart light-blocking or barrier properties to the liquid storage bag 10 by vapor-depositing inorganic oxides such as silica, alumina, zinc oxide, or magnesium oxide, or metals such as aluminum or tin.

Next, the liquid storage bag 10 of the present invention, which is manufactured using the body material 15 and base material 14 films described above, will be specifically described using examples and comparative examples.

(Creation of body material 15)
A non-oriented linear low-density polyethylene film (40 μm) made of linear low-density polyethylene with a density of 0.932 g/ ^cm3 and produced by a T-die method was used as the base layer of the body material 15. A non-oriented linear low-density polyethylene film (40 μm) made of linear low-density polyethylene with a density of 0.912 g/ ^cm3 and produced by an inflation method was used as the sealant layer of the body material 15. The base layer film of the body material 15 and the sealant layer film of the body material 15 were bonded together by a dry lamination method using a two-component curing polyester urethane adhesive (application amount when dried: 3.5 g), and then aged at 40°C for 24 hours to obtain the body material 15.

(Creation of base material 14)
A biaxially oriented polyethylene film (40 μm) made of linear low-density polyethylene was used as the base layer of the base material 14. The breaking elongation of the film was 260% in the longitudinal direction and 100% in the transverse direction. The breaking elongation of the film was determined in accordance with "JIS K7127:1999 (ISO527-3:1995) Plastics - Test methods for tensile properties - Part 3: Test conditions for films and sheets" (note that the breaking elongation of the film described below was also determined in the same manner).

The waterproof layer of the base material 14 was an unstretched linear low-density polyethylene film (80 μm) produced by the inflation method. The breaking elongation of the film was 650% in the longitudinal direction and 750% in the transverse direction. The tear strength of the film was 6.0 N in the longitudinal direction and 10.4 N in the transverse direction, and the longitudinal/transverse ratio of the film's tear strength (longitudinal/transverse) was 0.58. The tear strength of the film was determined in accordance with JIS K7128-3:1998 "Testing Method for Tear Strength of Plastic Films and Sheets" (note that the tear strength of the file described below was also determined using the same method).

The base layer film and water-blocking layer film were bonded together using an extrusion lamination method with LDPE (low-density polyethylene) to create the base material 14. The LDPE extrusion temperature was 320°C, and the thickness was 15 μm.

(Creation of liquid storage bag 10)
The liquid storage bag 10 was made using the obtained base material 14 and body material 15. The outer dimensions of the liquid storage bag 10 were 145 mm wide and 240 mm long, and the width of the bottom gusset portion, i.e., the length from the bottom edge of the liquid storage bag 10 to the folded-back portion of the film of the base material 14, was 45 mm.

The resulting liquid storage bag 10 was filled with 500 ml of water and placed with the bottom 13 facing upward in a container 20 equipped with a pump member 23 (liquid outlet) at the top end. When the liquid outlet needle 24 attached to the container 20 was pierced into the bottom 13, the needle 24 was easily inserted.

With the needle 24 pierced into the bottom 13, the pump member 23, which serves as the liquid outlet, was operated to eject water until the liquid storage bag 10 was empty. No air entered the liquid storage bag 10, and the amount of water remaining in the liquid storage bag 10 was 5.6 g.

In Example 2, a liquid storage bag 10 of Example 2 was prepared in the same manner as in Example 1, except that a non-oriented linear low-density polyethylene film (40 μm) produced by the inflation method was used as the water-stopping layer of the base material 14. The film had a breaking elongation of 650% in the longitudinal direction and 750% in the transverse direction, a tear strength of 3.0 N in the longitudinal direction and 5.2 N in the transverse direction, and a longitudinal/transverse ratio of tear strength of the film was 0.58. A discharge test was conducted on the liquid storage bag 10 of Example 2, with no problems with the piercing ability of the needle 24 in the bottom 13 (base material 14) or the discharge ability of the pump member 23. The amount of water remaining in the liquid storage bag 10 was 4.8 g.

In Example 3, a liquid storage bag 10 was prepared in the same manner as in Example 1, except that a biaxially oriented polyethylene film (20 μm) made of linear low-density polyethylene was used as the base layer of the base material 14, and a discharge test was conducted. The breaking elongation of the film base layer of the base material 14 was 228% in the longitudinal direction and 46% in the transverse direction. The liquid storage bag 10 of Example 3 had no problems with the piercing ability of the needle 24 into the bottom 13 (base material 14) or the discharge ability of the pump member 23, and the amount of water remaining in the liquid storage bag 10 was 6.1 g.

(Comparative Example 1)
In Comparative Example 1, a liquid storage bag was obtained in the same manner as in Example 1, except that an unstretched linear low-density polyethylene film (40 μ) produced using a T-die method, with a film breaking elongation of 620% in the longitudinal direction and 760% in the transverse direction, was used as the base material layer of the base material.

The liquid storage bag obtained in Comparative Example 1 was filled with water, and the liquid storage bag was placed with its bottom facing up in a container 20 equipped with a pump member 23 (liquid outlet) at its upper end. When the liquid outlet needle 24 attached to the container 20 was pierced into the bottom of the liquid storage bag, the base material stretched, making it impossible to pierce the needle 24 into the bottom (base material) of the liquid storage bag.

(Comparative Example 2)
In Comparative Example 2, a liquid storage bag for hearing was obtained in the same manner as in Example 1, except that a non-oriented linear low-density polyethylene film (30 μm) produced by an inflation method, in which the film had a breaking elongation of 650% in the longitudinal direction and 750% in the transverse direction, a tear strength of 2.3 N in the longitudinal direction and 3.9 N in the transverse direction, and a longitudinal/transverse ratio of the tear strength of the film was 0.59, was used as the water-stopping layer of the base material.

When the obtained liquid storage bag of Comparative Example 2 was subjected to a discharge test in the same manner as in Example 1, air was sucked in through the needle 24 puncture opening at the bottom of the liquid storage bag, and it was not possible to suck out all of the water inside the liquid storage bag.

When the needle 24 puncture hole at the bottom of the liquid storage bag in Comparative Example 2 was observed, it was confirmed that the film of the water-stopping layer of the base material had not stretched sufficiently, resulting in the creation of a gap.

(Comparative Example 3)
In Comparative Example 3, a linear low-density polyethylene film was used as the water-stopping layer of the base material, with a film breaking elongation of 760% in the longitudinal direction and 830% in the transverse direction, a film tear strength of 1.8 N in the longitudinal direction and 5.6 N in the transverse direction, and a film tear strength longitudinal/transverse ratio of 0.32.

When the obtained liquid storage bag of Comparative Example 3 was subjected to a discharge test in the same manner as in Example 1, air was sucked in through the needle 24 puncture opening at the bottom of the liquid storage bag, and it was not possible to suck out all of the water inside the liquid storage bag.

When the needle 24 puncture hole at the bottom of the liquid storage bag in Comparative Example 3 was observed, it was confirmed that the film of the water-stopping layer of the base material had not stretched sufficiently, resulting in the creation of a gap.

The liquid storage bag of the present invention is ideal for storing liquids such as detergents, as it does not require refilling and the contents can be used almost entirely without coming into contact with air.After use, the liquid storage bag can be recycled as polyethylene, making it an ideal liquid storage bag that reduces environmental impact.

10 Liquid storage bag 13 Bottom 14 Base material 20 Container 23 Pump member (liquid outlet)
24 Needle

Claims (2)

A liquid storage bag that is placed upside down inside a container that stores a liquid therein and has a liquid outlet at its upper end, and a needle that protrudes downward from the liquid outlet pierces the bottom of the bag,
The bottom of the bag is made of a base material made of a polyethylene resin film,
The base material has at least a base layer and a water-stopping layer,
The base material layer has a breaking elongation of 300% or less in at least one of the longitudinal direction and the transverse direction,
The liquid storage bag is characterized in that the tear strength of the water-stopping layer is 3N or more in both the longitudinal and transverse directions, and the ratio of the tear strength in the longitudinal direction to the transverse direction (longitudinal direction/transverse direction) is 0.5 or more and 2 or less. 2. The liquid storage bag according to claim 1, wherein the body of the bag is made of a body material made of a polyethylene resin film.