JP7263762B2 - Flexible container and its manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a flexible container formed by joining together tarpaulins having a non-conductive resin layer formed on the front surface and a conductive resin layer formed on the back surface, and a method for manufacturing the same.

Flexible containers, which are widely used for transportation and storage of granular materials, may be affected by vibrations and impacts during transportation, when the granular materials are injected and discharged from the inlet and outlet, and depending on the properties of the stored granular materials. It is known that static electricity is generated by friction between particles or between particles and the inner surface of a flexible container.

In order to release static electricity to the ground, the surface of the base fabric of the flexible container is coated with a layer of conductive rubber material (including thermoplastic resin material) mixed with carbon black. used. Also, a flexible container is used in which a tongue-like ground wire connecting portion is provided by extending a part of the tarpaulin, and the ground wire connecting portion can be clamped by a clip at the tip of the ground wire.

FIG. 5 is a schematic side view of a commercially available flexible container (with the left half cut away), and FIG. 6 is an enlarged view of the VI portion of FIG. Also, FIG. 7 is a cross section of the same portion as FIG. 6, showing a state in which the ground wire connecting portion is deteriorated.

The flexible container 1 includes a substantially cylindrical peripheral wall portion 2, an upper lid portion 3 covering the upper end side of the peripheral wall portion 2, a lower lid portion 4 covering the lower end side of the peripheral wall portion 2, and a an injection port 5 provided in the container, a discharge port 6 provided in the lower lid portion 4, a ground wire connection portion 7' provided on the outer surface of the flexible container 1, and the like. The injection port 5 and the discharge port 6 each have a substantially cylindrical shape with a smaller diameter than the peripheral wall portion 2 . The injection port 5 extends upward from the center of the upper lid portion 3 , and the discharge port 6 extends downward from the center of the A ground wire connection portion 7 ′ is provided on the lower outer peripheral surface of the peripheral wall portion 2 .

Each part of the flexible container 1 is made of a conductive tarpaulin. As illustrated, the conductive tarpaulin is formed by forming a conductive resin layer 11 on one side of a base fabric and forming a non-conductive resin layer on the other side. This conductive tarpaulin is arranged with the conductive resin layer on the inner side of the flexible container 1 . 5 to 7, the base fabric and the non-conductive resin layer are integrally illustrated and denoted by reference numeral 10. As shown in FIG.

As shown in FIG. 6, the outer peripheral portion 4a of the conductive tarpaulin forming the lower lid portion 4 wraps around the lower outer peripheral surface of the peripheral wall portion 2 and is joined to the lower outer peripheral surface by high-frequency welding or the like.

The ground wire connecting portion 7' is formed of a tongue-shaped piece extending from the outer peripheral portion 4a of the conductive tarpaulin. When the granular material is stored in the flexible container 1, the earth wire connection portion 7' is clamped by an earth clip (see FIG. 4, not shown in FIGS. 5 and 6) at the tip of the earth wire to be grounded.

JP 2012-250753 A

The ground wire connecting portion 7' is originally intended to ground the flexible container 1 by sandwiching it with the ground clip at the tip of the ground wire as described above. However, during actual work, an operator may grasp the ground wire connection portion 7' and pull the ground wire connection portion 7' in the direction of arrow F in FIG. When the ground wire connection portion 7' is pulled in this way, a strong tensile force is applied to the conductive resin layer 11, and as shown in FIG. may occur, and the electrical resistance between the conductive resin layer 11 of the ground wire connecting portion 7' and the conductive resin layer 11 of the flexible container 1 may increase. JIS C 61340-4-4 stipulates that the resistance between the ground terminal and the ground is less than 1×10 ⁸ Ω.

SUMMARY OF THE INVENTION An object of the present invention is to provide a flexible container in which the conductive resin layer of the ground wire connecting portion has excellent durability, and a method for manufacturing the flexible container.

The flexible container of the present invention is a flexible container formed by joining a peripheral wall portion, a lower lid portion, and an upper lid portion made of conductive tarpaulin, wherein the conductive tarpaulin has a non-conductive resin layer formed on the front surface and A conductive resin layer is formed on the conductive tarpaulin, and the conductive tarpaulin is disposed so that the conductive resin layer is on the inner side of the flexible container. In a flexible container in which an outer peripheral portion extends along the outer peripheral surface of the peripheral wall portion and is joined to the outer peripheral surface of the peripheral wall portion, a conductive material is provided between the outer peripheral portion of the lower lid portion or the upper lid portion and the peripheral wall portion. The base of the ground wire connecting portion made of elastic tarpaulin is sandwiched and joined to the outer peripheral portion and the peripheral wall portion, and the conductive resin layer of the ground wire connecting portion is positioned on the outer peripheral side. and

In one aspect of the present invention, an extension portion is provided that extends from the outer peripheral edge of the outer peripheral portion along the ground wire connection portion.

In one aspect of the present invention, the ground wire connection portion other than the lower portion is a free piece extending from the outer peripheral portion, and the extension length of the free piece is equal to the extension length of the extension portion. Greater than length.

In one aspect of the present invention, the lateral width of the base end side of the ground wire connection portion and the lateral width of the extension portion are substantially equal.

The flexible container manufacturing method of the present invention is a method of manufacturing the flexible container of the present invention, wherein the conductive tarpaulin forming the peripheral wall portion and the outer peripheral portion of the conductive tarpaulin forming the lower lid portion or the upper lid portion It has a step of sandwiching the base of the ground wire connecting portion between them and high-frequency welding the conductive tarpaulins of the peripheral wall portion, the ground wire connecting portion, and the lower lid portion or the upper lid portion.

In the flexible container provided by the present invention, by arranging the conductive resin layer in the ground wire connection portion so as to face the outer peripheral portion, the ground wire connection is achieved near the base end of the ground wire connection portion. A conductive layer having a total thickness of the conductive resin layer of the portion and the conductive resin layer of the upper lid portion or the lower lid portion is formed. This increases the tensile strength of the conductive layer, suppresses the occurrence of cracks in the conductive layer when the ground wire connecting portion is pulled, and provides sufficient grounding.

The ground wire connection portion overlaps the extension portion, and the conductive resin layer of the ground wire connection portion and the conductive resin layer of the extension portion overlap to establish an electrically conductive state. Therefore, even if the operator repeatedly pulls the ground wire connection portion and the conductive resin layer cracks on the base end side of the ground wire connection portion, the conductive resin layer of the ground wire connection portion extends. Since the conductive resin layer of the entire flexible container is electrically connected to the conductive resin layer of the entire flexible container with low resistance through the conductive resin layer of the portion, sufficient grounding can be achieved.

It is a cross-sectional perspective view of the vicinity of the ground wire connecting portion of the flexible container according to the embodiment. It is a cross-sectional perspective view of the vicinity of the ground wire connecting portion of the flexible container according to the embodiment. FIG. 1B is a sectional view taken along the line IIA-IIA of FIG. 1A; FIG. 1B is a cross-sectional view taken along the line IIA-IIA of FIG. 1B; FIG. 1B is a sectional view taken along line III-III of FIGS. 1A and 1B; FIG. 3 is a cross-sectional view of the same portion as FIG. 2 showing a state in which an earth clip is connected to the earth wire connecting portion; 1 is a side view of a conventional flexible container; FIG. FIG. 6 is an enlarged view of the VI portion of FIG. 5; FIG. 4 is a cross-sectional view showing a deteriorated state of a conductive resin layer;

Embodiments will be described below with reference to FIGS. 1A to 4. FIG. 1A and 2A show an embodiment in which the extending portion 8 is not provided, and FIGS. 1B and 2B show an embodiment in which the extending portion 8 is provided.

The flexible container according to the embodiment of FIGS. 1A, 2A, 1B, and 2B also has a peripheral wall portion 2, an upper lid portion 3, a lower lid portion 4, an injection port 5, and an exhaust port, similarly to the flexible container 1 shown in FIG. It has an outlet 6 and a ground wire connection portion 7 (the upper lid portion 3, the inlet 5, and the outlet 6 are not shown in FIGS. 1 to 4). An outer peripheral portion 4a of the lower lid portion 4 rises along the outer peripheral surface of the peripheral wall portion 2 and is joined to the outer peripheral surface of the peripheral wall portion 2 by high-frequency welding or the like. Note that a joining method other than high-frequency welding may be employed.

Also in these embodiments, the peripheral wall portion 2, the upper lid portion 3 and the lower lid portion 4 are all made of conductive tarpaulin. The conductive resin layer 11 of the peripheral wall portion 2 is located on the inner surface side of the flexible container, the conductive resin layer 11 of the upper lid portion 3 is located on the lower surface side of the upper lid portion 3, and the conductive resin layer 11 of the lower lid portion 4 is located. is positioned on the upper surface side of the lower lid portion 4 .

In these embodiments, the ground wire connecting portion 7 is made of a conductive tarpaulin formed separately from the conductive tarpaulins forming the peripheral wall portion 2 and the lower lid portion 4 .

The conductive tarpaulin constituting the ground wire connecting portion 7 is, for example, approximately rectangular with a horizontal width of 20 to 200 mm and a vertical length of 30 to 100 mm, but the shape and dimensions are not limited to this. The conductive tarpaulin constituting the ground wire connection portion 7 is arranged so that the conductive resin layer 11 is on the outer peripheral portion 4a side and the non-conductive resin layer 10 is on the peripheral wall portion 2 side.

The lower portion (base portion) of the ground wire connection portion 7 is sandwiched between the outer peripheral portion 4a of the lower lid portion 4 and the lower portion of the peripheral wall portion 2, and is joined to both the outer peripheral portion 4a and the peripheral wall portion 2 by high-frequency welding or the like. It is

The ground wire connecting portion 7 has a free piece shape extending upward from the outer peripheral portion 4a except for the lower portion thereof. The free piece portion of the ground wire connecting portion 7 is not joined to the peripheral wall portion 2 . Furthermore, it is not joined to an extension portion 8, which will be described later.

1A and 2A, the extending portion 8 is not provided. In FIGS. 1B and 2B, the extending portion 8 extends from a portion of the outer peripheral edge of the outer peripheral portion 4a of the conductive tarpaulin forming the lower lid portion 4, which overlaps with the ground wire connecting portion 7. As shown in FIG. The lateral width of the extending portion 8 is substantially the same as the lateral width of the ground wire connecting portion 7, but it may be slightly longer than that. The extension length of the extension portion 8 is preferably about 3 to 50 mm, particularly about 5 to 20 mm, but is not limited to this.

Other configurations of the flexible container shown in FIGS. 1A, 2A, 1B, and 2B are the same as the flexible container 1 shown in FIGS.

Also in the flexible container according to these embodiments, grounding is achieved by attaching a grounding clip 9 (FIG. 4) at the tip of the grounding wire so as to sandwich the free piece portion of the grounding wire connecting portion 7 .

Also in these embodiments, the operator may pull the ground wire connection portion 7 . If the operator repeatedly pulls the ground wire connection portion 7, the conductive resin layer 11 may crack at the base end side of the ground wire connection portion 7, as in FIG.

In the embodiments of FIGS. 1A, 2A, 1B and 2B, the conductive resin layer 11 of the ground wire connection portion 7 is disposed on the outer peripheral portion 4a side, thereby A conductive layer having a total thickness of the conductive resin layer 11 of the ground wire connecting portion 7 and the conductive resin layer 11 of the upper lid portion 3 or the lower lid portion 4 is formed near the end portion. As a result, the tensile strength of the conductive layer is increased, and the occurrence of cracks in the conductive layer when the ground wire connecting portion 7 is pulled is suppressed. Therefore, even when the ground clip sandwiches only the ground wire connecting portion 7, sufficient grounding can be achieved.

1B and 2B, as shown in FIG. 4, the free piece portion of the ground wire connection portion 7 hangs downward when the ground clip 9 is connected, overlaps the extension portion 8, and the ground wire The conductive resin layer 11 of the connecting portion 7 and the conductive resin layer 11 of the extending portion 8 are overlapped and electrically connected. Therefore, even if a crack occurs in the conductive resin layer 11 on the base end side of the free piece portion of the ground wire connection portion 7 , the conductive resin layer 11 of the ground wire connection portion 7 is not the conductive resin of the extension portion 8 . Through the layer 11, the conductive resin layer 11 of the entire flexible container is electrically connected with low resistance, and sufficient grounding can be achieved.

The thickness of the conductive resin layer 11 of the conductive tarpaulin is preferably 0.01 to 1 mm, particularly 0.02 to 0.1 mm, and the thickness of the non-conductive resin layer 12 is 0.1 to 3 mm, particularly It is preferably 0.2 to 1 mm.

[Material, etc.]
Examples of materials for the conductive tarpaulin forming each part of the flexible container 1 include the following, but are not limited to these.

Examples of base fabrics for conductive tarpaulins include woven fabrics made of natural fibers such as cotton and hemp, and synthetic fibers such as polyester fibers, polyamide fibers and vinylon fibers. The base fabric may be a filament or stile made of these fibers alone or in combination of two or more. In addition, the woven fabric means a woven fabric or knitted fabric obtained by weaving these fibers in plain weave, twill weave, satin weave, etc. The type and structure of the woven fabric are those that do not hinder the flexibility of the conductive tarpaulin. There are no particular restrictions.

As the woven fabric constituting the base fabric, a plain weave fabric having a fiber thickness of 500 to 1000 denier and a yarn count of 15 to 30 per inch is suitable. When a woven fabric made of polyester fiber or polyamide fiber is used, the woven fabric is preferably a plain weave fabric having a fiber thickness of 750 denier and a number of stitches of 20×20 per inch. Such a woven fabric generally has a thickness of 0.2 to 2 mm and a width of about 0.5 to 3 m.

The non-conductive resin layer is preferably made of a thermoplastic resin composition, and particularly preferably made of a resin layer containing a copolymer layer of ethylene and vinyl acetate. The resin layer including a copolymer layer of ethylene and vinyl acetate includes a resin layer consisting of a single layer of a copolymer layer of ethylene and vinyl acetate, and a copolymer layer of ethylene and vinyl acetate and other layers. It may be a multilayer resin layer in which resin layers are laminated. Other resins forming the resin layer include polyvinyl chloride-based resins such as polyvinyl chloride and vinyl chloride-based copolymers containing vinyl chloride as a main component, and polyethylenes such as low-density polyethylene, high-density polyethylene, and chlorinated polyethylene. resin, ethylene-acrylic acid copolymer such as ethylene-methyl acrylate copolymer (EMA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), polyurethane , polyvinyl acetate, and the like, but are not limited thereto.

As the ethylene-vinyl acetate copolymer, those having a component polymerization ratio of ethylene and vinyl acetate of 90:10 to 70:30 are suitable. If the proportion of vinyl acetate is less than 10% by mass, high-frequency welding becomes difficult, and if it exceeds 30% by mass, heat resistance deteriorates, both of which are not preferred. A particularly preferred range for the component polymerization ratio of ethylene and vinyl acetate is 85:15 to 75:25. The ethylene-vinyl acetate copolymer has a melt flow rate (MFR) measured in accordance with JIS K7210 at a temperature of 190° C. and a load of 21.28 N (2.16 kgf) in the range of 0.1 to 5.0. are preferred, and those in the range of 0.5 to 2.0 are particularly preferred.

The conductive resin layer 11 is preferably made of a thermoplastic resin composition containing conductive carbon black, and particularly made of a resin layer containing conductive carbon black and an ethylene-vinyl acetate copolymer layer as a main component. is preferred. A resin layer containing conductive carbon black and an ethylene-vinyl acetate copolymer layer as a main component is a single layer of an ethylene-vinyl acetate copolymer layer (polyolefin resin layer) as a main component containing conductive carbon black. In addition to the resin layer, it may be a multilayer resin layer in which another resin layer is laminated on this layer. Other resin layers Examples of resins that form the resin layer include polyethylene resins such as low-density polyethylene, high-density polyethylene, and chlorinated polyethylene; polypropylene resins such as polypropylene and propylene-ethylene copolymer; and ethylene-methyl acrylate copolymer. polymers, and ethylene-acrylic copolymers such as ethylene-methyl methacrylate copolymers and ethylene-ethyl acrylate copolymers. In addition, the other resin layer may include a thermoplastic resin layer containing a specific amount of conductive carbon black.

The conductive carbon black to be blended in the conductive resin layer is not particularly limited, but when the average surface area of the conductive carbon black is relatively small, the amount of the conductive carbon black to be used becomes large. Disadvantages such as deterioration of fluidity when the thermoplastic resin is formed into a film and an extreme decrease in the strength of the film become conspicuous. From the viewpoint of physical properties, the conductive carbon black preferably has an average surface area of 30 m ² /g or more, and particularly preferably has an average surface area of 100 m ² /g or more.

The amount of the conductive carbon black blended into the thermoplastic resin, preferably the resin containing the ethylene-vinyl acetate copolymer, is preferably 0.1 to 25 parts by mass with respect to 100 parts by mass of the thermoplastic resin. If the content of the conductive carbon black is less than 0.1 part by mass, the surface resistivity of the conductive resin layer 11 increases, making it difficult to improve the conductivity, which is not preferable. If the amount of the conductive carbon black blended exceeds 25 parts by mass, the surface resistivity of the conductive resin layer 11 will decrease and the conductivity will be improved, but the flexibility of the tarpaulin will be impaired, and high-frequency welding will be difficult. This is not preferable because it increases the risk of sparks occurring in the A particularly preferred blending amount of the conductive carbon black with respect to 100 parts by mass of the thermoplastic resin is 3 to 15 parts by mass.

In order to manufacture the flexible container of the present invention, when the conductive tarpaulin of the peripheral wall portion 2 and the outer peripheral portion 4a of the conductive tarpaulin of the lower lid portion 4 are welded by high frequency, between the upper portion of the peripheral portion 4a and the peripheral wall portion 2, The peripheral wall portion 2, the lower portion of the ground wire connection portion 7, and the outer peripheral portion 4a may be high frequency welded with the lower portion of the ground wire connection portion 7 interposed therebetween.

When the lower portion of the ground wire connection portion 7 is sandwiched between the peripheral wall portion 2 and the outer peripheral portion 4a and the high-frequency welding is performed in this way, the thickness of the portion sandwiching the ground wire connection portion 7 (from the inner surface of the peripheral wall portion 2 to the outer peripheral portion thickness to the outer surface of the portion 4a) is increased. Then, as shown in FIG. 3, a step is formed between the portion sandwiching the ground wire connection portion 7 and the surroundings thereof. In order to reduce this step, it is preferable to make the thickness of the tarpaulin forming the ground wire connection portion 7 smaller than the thickness of the tarpaulin forming the peripheral wall portion 2 and the lower lid portion 4 .

The above-described embodiment is an example of the present invention, and the present invention may be in forms other than those shown in the drawings. For example, in the above-described embodiment, the ground wire connection portion 7 has a substantially rectangular shape, but it may have a shape such as a trapezoid whose width decreases toward the tip of the free piece portion. In the present invention, when the ground-to-ground resistance of the ground wire connection portion 7 increases, the ground wire connection portion 7 and the extension portion 8 may be overlapped and repaired by high-frequency welding.

In the above embodiment, the ground wire connection portion 7 is arranged between the lower lid portion 4 and the peripheral wall portion 2, but the ground wire connection portion may be arranged between the upper lid portion 3 and the peripheral wall portion 2. good. The configuration in this case is vertically symmetrical in FIGS.

[Example 1]
A flexible container shown in FIGS. 1 to 3 was manufactured in which the peripheral wall portion 2 and the lower lid portion 4 were made of tarpaulin with a thickness of 0.80 mm, and the ground wire connecting portion 7 was made of tarpaulin with a thickness of 0.60 mm. The ground wire connection portion 7 was a square with a side of 50 mm, and was sandwiched between the outer peripheral portion 4a and the peripheral wall portion 2 in a range of 10 mm on the base end side and was welded by high frequency.

The extending portion 8 has a lateral width of 50 mm and a height of 10 mm.

This ground wire connection portion 7 was pulled ten times at 294 N (30 kg) or 392 N (40 kg) in a direction perpendicular to the outer peripheral portion 4a (direction F in FIG. 5) (a load was applied at a speed of 500 N/min, One pull was completed when it was reached). Before and after the pulling, an earth clip was attached to the earth wire connection portion 7 to measure the resistance between grounds. Table 1 shows the results.

[Example 2]
The same flexible container as in Example 1 was manufactured, and the tensile direction during the tensile test was the direction in which the ground wire connection portion 7 and the extension portion 8 were folded back 180° along the outer peripheral portion 4a (the vertically downward direction in FIG. 2). A tensile test was carried out as above to measure the ground-to-ground resistance. Table 1 shows the results.

[Comparative Example 1]
The same tensile test as in Example 2 was performed, except that the ground wire connecting portion was configured as shown in FIG. 6 (width 50 mm, projection length 40 mm). Table 1 shows the results.

[Discussion]
As shown in Table 1, in Examples 1 and 2, even if the ground wire connecting portion is repeatedly pulled, the ground-to-ground resistance does not increase or hardly increases. On the other hand, in Comparative Example 1, it is recognized that the resistance between the grounds increases due to the pulling, and in particular, the resistance between the grounds increases when the folding angle of the ground wire connecting portion increases.

REFERENCE SIGNS LIST 1 flexible container 2 peripheral wall 3 upper lid 4 lower lid 5 inlet 6 outlet 7, 7' ground wire connector 8 extension 9 ground clip 10 base fabric and non-conductive resin layer 11 conductive resin layer

Claims (4)

A flexible container formed by joining a peripheral wall portion, a lower lid portion, and an upper lid portion made of conductive tarpaulin,
The conductive tarpaulin has a non-conductive resin layer formed on the front surface and a conductive resin layer formed on the back surface,
The conductive tarpaulin is arranged so that the conductive resin layer is the inner side of the flexible container,
In a flexible container in which the outer peripheral portion of the conductive tarpaulin constituting the lower lid portion or the upper lid portion extends along the outer peripheral surface of the peripheral wall portion and is joined to the outer peripheral surface of the peripheral wall portion,
Between the outer peripheral portion and the peripheral wall portion of the lower lid portion or the upper lid portion, a base portion of a ground wire connecting portion made of conductive tarpaulin is sandwiched and joined to the outer peripheral portion and the peripheral wall portion,
The conductive resin layer of the ground wire connecting portion is located on the outer peripheral portion side ,
A flexible container , wherein an extension portion is provided that extends from the outer peripheral edge of the outer peripheral portion along the ground wire connecting portion . Of the ground wire connection portion, portions other than the base portion are free pieces extending from the outer peripheral portion,
A flexible container according to claim 1, characterized in that the length of extension of said free piece is greater than the length of extension of said extension portion. 3. The flexible container according to claim 1, wherein the lateral width of the base end of the ground wire connecting portion and the lateral width of the extending portion are substantially equal. A method for manufacturing a flexible container according to any one of claims 1 to 3 ,
The base portion of the ground wire connection portion is sandwiched between the conductive tarpaulin forming the peripheral wall portion and the outer peripheral portion of the conductive tarpaulin forming the lower lid portion or the upper lid portion, and the peripheral wall portion, the ground wire connection portion and the lower lid are provided. A method for manufacturing a flexible container, comprising a step of high-frequency welding each conductive tarpaulin with a part or an upper lid part.

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