JP2023072724A - Conductive tarpaulin and method for manufacturing the same - Google Patents

Abstract

To provide a new conductive tarpaulin which has conductivity on both surfaces, and can lower surface resistivity.SOLUTION: There is provided a conductive tarpaulin in which both surfaces of a base fabric composed of a woven and knit fabric are covered with a resin layer, wherein both of the resin layers include a resin layer which contains an ethylenic copolymer as a main component resin and contains no conductive material, and a resin layer which contains an ethylenic copolymer as a main component resin outside in a front-back direction and contains a conductive material, and surface resistivities of both of the surfaces are 103 Ω-1010 Ω.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a conductive tarpaulin (also referred to as "conductive tarpaulin" in the present invention) and a method for producing the same.

Flexible containers, which are widely used for the transportation and storage of granular materials, generally consist of tarpaulin whose base fabric is covered with synthetic resin such as rubber, ethylene-vinyl acetate copolymer, and polyvinyl chloride. It is
Tarpaulin used to mean a waterproof sheet made of canvas coated with tar, which was used as a sailor's outerwear and a waterproof sheet on a ship in the old days. It shall broadly mean a laminated sheet having a structure covered with a resin layer.

Depending on the properties of the powder and granules stored in the flexible container, vibrations and impacts during storage, discharge, and transportation of the granules may cause damage between the granules, or between the granules and the flexible container. It has been known that static electricity is generated by friction with the sides of flexible containers, accumulates on the walls of flexible containers, and in some cases causes dust explosions. Furthermore, the problem of generation and accumulation of static electricity in flexible containers, such as generated static electricity attracting dust and causing contamination of granular materials, has been an important problem to be solved.
In order to solve such problems, a conductive flexible container composed of a conductive tarpaulin, in which the surface of a base fabric is coated with a rubber layer to which carbon black is kneaded to give conductivity, has been proposed and put into practical use. .

Furthermore, with regard to conductive tarpaulins, for example, in Patent Document 1, in a tarpaulin having excellent conductivity in which both sides of a woven or knitted base fabric are coated with a resin layer, one resin layer of the base fabric contains at least ethylene and vinyl acetate. and the other resin layer of the base fabric is composed of a resin layer containing a polyolefin resin layer containing conductive carbon black. ing.

Patent Document 2 discloses a flexible container composed of a tarpaulin having a conductive resin layer and a non-conductive resin layer and having a bag main body provided with a cylindrical pouring/discharging port, in which the conductive resin layer is arranged inside the container. and a grounding mechanism that conducts from the conductive resin layer to the outside of the container is provided, and all parts of the inner surface of the container and the grounding terminal are electrically connected. A container is disclosed.

Patent Document 3 discloses a flexible container composed of a tarpaulin having a conductive resin layer and a non-conductive resin layer and having a bag-like main body with a cylindrical pouring/discharging port. A conductive flexible container is disclosed in which a resin layer is electrically connected to a conductive suspension.

JP-A-2001-191433 JP-A-2002-337980 JP-A-2003-26284

There are two types of flexible containers: round and square. Square containers can be loaded onto trucks and containers without any gaps, so they can be loaded more efficiently and have a larger volume. can.
As shown in Figs. 3 and 4, a rectangular flexible container is configured to hold a rectangular shape by obliquely attaching members called "partitions" to each of the four corners inside the container. Common. As shown in FIG. 4, the partition has openings in the wall surface, and the corners of the partition are filled with fillers through the openings. be in contact.

The JIS standard for conductive flexible containers (JIS C 61340 4-4) stipulates that the materials that come into contact with the filling must have conductive performance. is required to have conductivity on both sides.
However, a conductive tarpaulin having conductivity on both sides has not been known in the past.

Therefore, when a conductive film was laminated on both sides of a tarpaulin formed by coating both sides of a base fabric with a resin layer, it was found that the surface resistivity increased. This is because when the laminated original is turned over and laminated again, the carbon (conductive material) in the conductive film settles due to heat, and the concentration of the conductive material on the surface decreases, resulting in an increase in surface resistivity. It is considered to be

An object of the present invention is to provide a new conductive tarpaulin having conductivity on both the front and back surfaces and a low surface resistivity, and a method for producing the same.

The present invention relates to a conductive tarpaulin comprising a base fabric made of woven and knitted fabric and both sides of which are coated with a resin layer,
Each of the resin layers contains an ethylene-based copolymer as a main component resin, and a resin layer that does not contain a conductive material (referred to as a “non-conductive resin layer”) and an ethylene-based copolymer A resin layer (referred to as a "conductive resin layer") containing coalescence as a main component resin and containing a conductive material,
We propose a conductive tarpaulin having a surface resistance of 10 ³ Ω to 10 ⁸ Ω on both sides.

In the present invention, both the front and back surfaces of the base fabric made of woven and knitted fabric are coated with a resin layer containing an ethylene-based copolymer as a main component resin and containing no conductive material (referred to as a "non-conductive resin layer"). A method for producing a conductive tarpaulin, characterized in that a conductive resin sheet containing an ethylene copolymer as a main component resin and containing a conductive material is laminated and adhered to the outer side of the laminated sheet in the front and back directions. Suggest.

The conductive tarpaulin proposed by the present invention has conductivity on both the front and back surfaces and can keep the surface resistivity low.

BRIEF DESCRIPTION OF THE DRAWINGS It is the cross-sectional schematic which showed typically the cross-sectional structural example of the electroconductive tarpaulin which concerns on an example of this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram conceptually showing an example of a method for manufacturing a conductive tarpaulin according to an example of the present invention; 1 is a schematic cross-sectional view schematically showing a structural example of a square flexible container; It is the front view which showed an example of the partition material. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partially cut-away enlarged vertical cross-sectional view schematically showing a structural example of a flexible container according to an example of the present invention; BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic cross-sectional view schematically showing a cross-sectional configuration example of a single-sided conductive tarpaulin constituting a flexible container according to an example of the present invention. It is a cross-sectional schematic diagram for demonstrating the manufacturing method of the flexible container which concerns on an example of this invention. It is a cross-sectional schematic diagram for demonstrating the manufacturing method of the flexible container which concerns on another example of this invention. It is the cross-sectional schematic which showed roughly the other structural example of a square flexible container. FIG. 10 is a front view showing another example of the partition wall material;

Next, an example of an embodiment of the invention will be described in detail. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

<< this tarpaulin >>
As shown in FIG. 1, a conductive tarpaulin (referred to as "this tarpaulin") 1 according to an embodiment of the present invention is constructed by coating both the front and back surfaces of a base fabric 2 made of a woven or knitted fabric with a resin layer 3. is provided. From a different point of view, the base fabric 2 is embedded in the resin layer 3, and the resin penetrates into the mesh of the base fabric 2 to unite the base fabric 2 and the resin layer 3 together.

<Base fabric>
The base fabric 2 of the tarpaulin 1 may be woven or knitted. That is, any cloth body made of a woven fabric or a knitted fabric of fibers may be used.
As the structure of the base fabric 2, for example, a cloth body made of a fabric obtained by weaving fibers in a plain weave, a twill weave, a satin weave, or the like can be mentioned. However, there are no particular restrictions on the type and structure of the knitted fabric.

Fibers constituting the base fabric 2 include natural fibers such as cotton and hemp, and synthetic fibers such as polyester fibers, polyamide fibers, polyolefin fibers, polyacrylic fibers and vinylon fibers. These fibers may be filaments or stipes, either alone or in combination of two or more.

The fibers of the woven fabric preferably have a thickness of 200 to 1500 denier, more preferably 250 denier or more or 1000 denier or less, and more preferably 500 denier or more or 1000 denier or less. Among them, from the viewpoint of maintaining the strength as a flexible container, it is particularly preferable that it is 700 denier or more or 1000 denier or less.
Plain woven fabrics with a fiber count per unit area of 10 to 30 fibers/inch are preferable, among which 12 fibers/inch or more or 28 fibers/inch or less, among which 15 fibers/inch or more or 25 fibers/inch or less. A plain weave fabric of

<Resin layer>
In the present tarpaulin 1, the resin layers 3, 3 on both the front and back sides of the base fabric 2 both contain an ethylene-based copolymer as a main component resin and do not contain a conductive material ("non-conductive resin layer"). ) 4 and a resin layer 5 containing an ethylene-based copolymer as a main component resin and containing a conductive material (hereinafter referred to as a "conductive resin layer") 5 on the outer side in the front and back direction.

Preferably, as shown in FIG. 1, both the front and back surfaces of the base fabric 2 are covered with the non-conductive resin layers 4, 4, respectively, and the conductive resin layers 5, 5 are laminated on the outside in the front and back direction, respectively. It has a configuration. From a different point of view, the base fabric 2 is embedded in a single non-conductive resin layer 4, and conductive resin layers 5, 5 are formed on the outside of the non-conductive resin layer 4 in the front and back directions, respectively. It has a laminated structure.

The non-conductive resin layer 4 and the conductive resin layer 5 are preferably directly laminated, for example, preferably fused together.

<Non-conductive resin layer>
The non-conductive resin layer 4 is a layer that contains an ethylene-based copolymer as a main component resin and does not substantially contain a conductive material.

In this case, the “main component resin” means a resin having the highest content ratio by mass among the resins constituting each layer, and is 50% by mass or more, especially 60% by mass or more, of the resins constituting each layer. It can be assumed that it accounts for 70% by mass or more, among them 80% by mass or more, among them 90% by mass or more (including 100% by mass). The same applies to the main component resin in other layers.
In addition, "substantially free" means that it is not intentionally blended, and includes the meaning of allowing the case where it is unavoidably included.

(Ethylene-based copolymer)
The ethylene-based copolymer may be a copolymer of ethylene and a monomer other than ethylene (referred to as a "comonomer").
Examples of the ethylene-based copolymer include ethylene-α-olefin-based resins, ethylene-acrylic acid ester-based resins, and ethylene-methacrylic acid ester-based resins. Specifically, for example, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ultra-low-density polyethylene (ULDPE) and other ethylene/α-olefin copolymers, or copolymers with acrylic acid esters Ethylene-acrylic ester copolymers such as ethylene-methyl acrylate copolymer (EMA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-vinyl acetate copolymer (EVA), etc. can be mentioned.

Among them, an ethylene-based copolymer containing a copolymerizable monomer having an easily polarized functional group as a copolymerization component is preferable because high-frequency welding is possible. From this point of view, preferred specific examples of the ethylene copolymer include EVA (ethylene/vinyl acetate copolymer), EMA (ethylene/methyl acrylate copolymer), and EMMA (ethylene/methacrylic acid copolymer). Any one or two or more of these can be mentioned. All of these are resins capable of high-frequency welding.

The copolymerization ratio of the monomer that copolymerizes with ethylene in the ethylene-based copolymer (referred to as “comonomer”) in the non-conductive resin layer 4 is preferably 6 to 30% by mass, especially 10% by mass or more. Alternatively, it is more preferably 25% by mass or less.
For example, when the ethylene-based copolymer in the non-conductive resin layer 4 is an ethylene-vinyl acetate copolymer, the component polymerization mass ratio of ethylene and vinyl acetate is ethylene:vinyl acetate=94:6 to 70:30. It is preferable to have If the proportion of vinyl acetate is 6% by mass or more, high-frequency welding can be performed, and if it is 30% by mass or less, heat resistance can be maintained, which is preferable. From this point of view, it is more preferable that the component polymerization ratio of ethylene and vinyl acetate is 90:10 to 75:25.

At this time, the copolymerization ratio of the monomer that copolymerizes with ethylene in the ethylene copolymer in the non-conductive resin layer 4 (referred to as "comonomer") is determined from the viewpoint of maintaining the suitability for high-frequency welding. It is preferably higher than the copolymerization ratio of the copolymerization monomer of the ethylene-based copolymer in the resin layer 5 .
From this point of view, the copolymerization ratio of the copolymerization monomer of the ethylene copolymer in the non-conductive resin layer 4 is 120 to 600% of the copolymerization ratio of the copolymerization monomer of the ethylene copolymer in the conductive resin layer 5. , more preferably 150% or more or 400% or less, and even more preferably 150% or more or 200% or less.

When the ethylene-based copolymer in the non-conductive resin layer 4 is an ethylene-vinyl acetate copolymer, the melt flow rate (MFR) measured in accordance with JIS K7210 under the conditions of a temperature of 190° C. and a load of 2.16 kgf is 0.1 to 5.0 g/10 minutes is preferable, and 0.5 g/10 minutes or more or 3.0 g/10 minutes or less is particularly preferable.

When two or more types of ethylene-based copolymers are used in the non-conductive resin layer 4, the copolymerization ratio and MFR of the above-mentioned copolymerization monomers should be within the above range, taking into consideration the mass content of each of the copolymerization monomers. .

(Other resins)
The non-conductive resin layer 4 may contain other resins than the ethylene-based copolymer, if necessary.
Examples of the above-mentioned "other resins" include rubber components such as EPR, EPDM, SBS and SEBS in order to impart flexibility to the tarpaulin.

(other ingredients)
The non-conductive resin layer 4 can contain components other than the resin, if necessary.
Other components include known additives such as lubricants, antioxidants, antistatic agents, light stabilizers, ultraviolet absorbers, antiblocking agents, slip agents, flame retardants, coloring agents, fillers, and the like. .

<Conductive resin layer>
The conductive resin layer 5 is a layer containing an ethylene-based copolymer as a main component resin and containing a conductive material.

(Ethylene-based copolymer)
As the ethylene copolymer for the conductive resin layer 5, the same ethylene copolymer as for the non-conductive resin layer 4 can be used.
At this time, the ethylene copolymer of the conductive resin layer 5 and the ethylene copolymer of the non-conductive resin layer 4 may be the same resin or different resins. Considering the adhesiveness between the layers, especially the heat-sealing property, it is preferable that the resins are of the same type.

However, it is said that the copolymerization ratio of the copolymerization monomer of the ethylene copolymer in the non-conductive resin layer 4 is preferably higher than the copolymerization ratio of the copolymerization monomer of the ethylene copolymer in the conductive resin layer 5. From the point of view, the copolymerization ratio of the copolymerization monomer of the ethylene copolymer in the conductive resin layer 5 is preferably 5 to 20% by mass, more preferably 8% by mass or more or 15% by mass or less. 9% by mass or more or 13% by mass or less is more preferable.

When the ethylene-based copolymer in the conductive resin layer 5 is an ethylene-vinyl acetate copolymer, the melt flow rate (MFR) measured at a temperature of 190° C. and a load of 2.16 kgf is 0 according to JIS K7210. .1 to 5.0 g/10 minutes is preferable, and 0.5 g/10 minutes or more or 3.0 g/10 minutes or less is particularly preferable.

When two or more types of ethylene-based copolymers are used in the conductive resin layer 5, the copolymerization ratio and MFR of the above-mentioned copolymerizable monomers should be within the above-mentioned range, taking into account the respective masses contained therein.

(Conductive material)
Examples of the conductive material contained in the conductive resin layer 5 include conductive polymers such as polythiophene, polyaniline, polyacetylene, polyphenylene vinylene, and polynaphthalene, and tin oxide-based, antimony oxide-based, indium oxide-based, and zinc oxide-based materials. and ionic compounds such as alkali metal salts, organic cation-anion salts, carbon materials such as acetylene black, ketjen black, natural graphite, artificial graphite, and titanium black. can be done. These can be used singly or in combination of two or more.
Among them, acetylene black, ketjen black, furnace black, channel black, natural graphite, Carbon materials such as artificial graphite are preferred, and among them, carbon blacks such as acetylene black, ketjen black, and furnace black are preferred.

When the average surface area of the conductive material is relatively small, a large amount of the conductive material is used, which may deteriorate the fluidity when forming a film or reduce the strength of the film. Therefore, the average surface area is preferably 30 m ² /g or more, more preferably 100 m ² /g or more.

The content of the conductive material in each conductive resin layer 5 is preferably 1 to 40 parts by mass with respect to 100 parts by mass of the ethylene copolymer that is the main component resin. If the content of the conductive material is 1 part by mass or more, the surface specific resistance can be kept low. On the other hand, if it is 40 parts by mass or less, the flexibility of the tarpaulin can be maintained. From this point of view, the content of the conductive material in each conductive resin layer 5 is preferably 1 to 40 parts by mass with respect to 100 parts by mass of the ethylene-based copolymer that is the main component resin, especially 15 parts by mass or more. Alternatively, it is 35 parts by mass or less, more preferably 25 parts by mass or more or 35 parts by mass or less.

(Other resins)
The conductive resin layer 5 may contain other resins than the ethylene-based copolymer, if necessary.
Examples of the above-mentioned "other resins" include resins having an ethylene skeleton such as EVOH, EPR and EPDM.

(other ingredients)
The conductive resin layer 5 can contain components other than the resin, if necessary.
Examples of other components include known additives such as lubricants, antioxidants, antistatic agents, light stabilizers, ultraviolet absorbers, antiblocking agents, slip agents, flame retardants, colorants, and dispersants. can.

<Other resin layers>
The resin layer 3 can also include resin layers other than the non-conductive resin layer 4 and the conductive resin layer 5 . In other words, each resin layer 3 may have a multi-layer structure of three or more layers. However, even in that case, it is preferable to dispose the conductive resin layer 5 so as to be the outermost layer.

<Thickness>
The thickness of the entire tarpaulin 1 is preferably 0.2 mm to 1.5 mm.
If the thickness of the entire tarpaulin 1 is 1.5 mm or less, it is possible to prevent deterioration of the folding workability, and if it is 0.2 mm or more, it is possible to prevent the strength of the tarpaulin from being lowered. ,preferable.
From this point of view, the thickness of the entire tarpaulin 1 is preferably 0.2 mm to 1.5 mm, more preferably 0.4 mm or more or 1.2 mm or less, and more preferably 0.6 mm or more or 1.0 mm or less. .

The thickness of each layer of the conductive resin layer 5 is preferably 20 μm to 300 μm.
If the thickness of each layer of the conductive resin layer 5 is 20 μm or more, the durability of the conductive resin layer can be maintained when the present tarpaulin is used to form a flexible container. is preferred because it does not impair the flexibility of the tarpaulin.
From this point of view, the thickness of each layer of the conductive resin layer 5 is preferably 20 μm to 300 μm, more preferably 30 μm or more or 200 μm or less, and more preferably 40 μm or more or 100 μm or less.

The ratio of the total thickness of the conductive resin layers 5, 5 to the thickness of the entire tarpaulin 1 is preferably 2.5% or more from the viewpoint of durability of the conductive layer, especially 5% or more, and especially 10%. % or more is more preferable. On the other hand, from the viewpoint of high-frequency weldability, it is preferably 50% or less, more preferably 30% or less, and more preferably 20% or less.

<Surface resistivity>
In the present tarpaulin 1, the surface resistance of both the front and back surfaces is preferably 10 ³ Ω to 10 ⁸ Ω.
When the tarpaulin 1 is used as a partition wall material placed in a conductive flexible container, it is necessary to suppress the surface resistance of both the front and back sides of the tarpaulin 1 (JIS C 61340 4-4). The surface resistance of both the front and back surfaces is preferably 10 ³ Ω to 10 ⁸ Ω, especially 2×10 ³ Ω or more or 10 ⁵ Ω or less, especially 3×10 ³ Ω or more or 10 ⁴ Ω or less, especially In particular, 4×10 ³ Ω or more or 9×10 ³ Ω or less is more preferable.

<Manufacturing method>
This tarpaulin 1 is made by preparing or preparing a laminated sheet 6 in which both the front and back sides of a base fabric 2 made of a woven or knitted fabric are covered with a non-conductive resin layer 4, and on the outer side of the laminated sheet 6 in the front and back direction, respectively. It can be obtained by stacking and laminating conductive resin sheets 7, 7 containing a polymer as a main component resin and containing a conductive material.
At this time, the conductive resin sheets 7, 7 are laminated on the outside of the laminated sheet 6 in the front and back direction, respectively, and may be laminated and bonded at the same time or sequentially, but it is preferable to perform them substantially at the same time on the same production line.
However, the manufacturing method of the present tarpaulin is not limited to such a manufacturing method.

The laminated sheet 6, that is, the laminated sheet 6 in which both the front and back surfaces of the base fabric 2 made of woven and knitted fabric are coated with the non-conductive resin layers 4, 4 can be manufactured by a known method.
For example, a topping method in which the film for the non-conductive resin layer is heat-laminated on each side of the base fabric 2 at the same time as the film for the non-conductive resin layer is molded, or a laminator is used after the film for the non-conductive resin layer is single-layered. For example, two sheets of non-conductive resin layer films are heat-pressed at once to sandwich the base fabric 2 .
For example, the resin composition for forming a non-conductive resin layer is melt-extruded into a film or sheet by calendering or a molding machine equipped with a T die or an annular die, preferably an inverted L-shaped calendering molding machine. A non-conductive resin layer film is prepared by using a laminator, and then this non-conductive resin layer film is thermocompression bonded to both sides of the base fabric 2 by a laminator to prepare the laminated sheet 6. . At this time, the front and back non-conductive resin layers 4, 4 are partially thermally melted and bridged through the voids of the base fabric 2 to exhibit an anchor effect.
However, the method for producing the laminated sheet 6 is not limited to the above method.

Here, as an example of the method for producing the present tarpaulin, as shown in FIG. 4B is prepared, and the non-conductive resin layer film 4B is thermocompressed to the base fabric 2 by a laminator or the like to prepare a laminated sheet 6, and the conductive resin sheet is attached to the outer side of the laminated sheet 6 in the front and back direction. A method of stacking 7 and 7 and laminating and adhering them at the same time can be mentioned.
On the other hand, after laminating the conductive resin sheet 7 on one surface of the laminated sheet 6, if necessary, it is turned over and the conductive resin sheet 7 is laminated on the other surface of the laminated sheet 6 at successive timings. Since the resin softens due to heat, the conductive material in the conductive resin settles and the concentration of the conductive material on the surface decreases, resulting in an increase in surface resistivity. On the other hand, as described above, by stacking the conductive resin sheets 7 and 7 on the outside of the laminated sheet 6 in the front and back direction and simultaneously laminating and bonding them, the sedimentation of the conductive material is prevented and the surface resistivity is improved. The rise can be suppressed, and the surface resistance on both the front and back surfaces can be adjusted as described above.

<Application>
Since the tarpaulin 1 has conductivity on both sides, it is particularly suitable as a material for members that may come into contact with the filling on both sides, for example, partition walls arranged in a flexible container.
Therefore, next, a flexible container using the tarpaulin 1 as a partition wall material will be described.

<<This flexible container>>
A flexible container 10 according to an example of an embodiment of the present invention (hereinafter referred to as "the present flexible container") is a flexible container provided with a partition member 12 formed from the present tarpaulin 1. As shown in FIG.

The shape of the flexible container 10 is arbitrary. For example, it may be round, square, or any other shape. A rectangular container will be described here.

As shown in FIG. 3, the flexible container 10 includes a bag body 11 which has a substantially square shape when viewed from the top and which is open at least at the top, and partition walls attached obliquely to the four corners of the interior of the container, that is, the bag body when viewed from the top. 12,12,12,12.

The bag body 11 has a substantially square shape when viewed from above and has a bottom portion and side surfaces. For example, as shown in FIG. , a lower wall portion 15 covering the lower end side of the peripheral wall portion 13, an inlet 16 provided in the upper wall portion 14, an outlet 17 provided in the lower wall portion 15, and a ground wire connection portion 18. It has However, the shape of the bag 11 is arbitrary.

The bag body 11 may have a single-layered structure, a double-layered structure, or a further multiple-layered structure. The material is preferably formed of a single-sided conductive tarpaulin with the conductive layer on the inside.

In this case, the single-sided conductive tarpaulin preferably has a conductive resin layer laminated on one side of the base fabric and a non-conductive resin layer laminated on the other side, and the conductive resin layer is placed on the inside of the flexible container, and the single-sided conductive tarpaulins constituting each part are joined to each other and processed into a predetermined shape. At this time, as a joining method, for example, a high-frequency welding method, a thermal welding method, a hot plate press working method, a hot air welding method, an ultrasonic welding method, or the like can be mentioned.
Since the inside of the single-sided conductive tarpaulin is the surface that comes into contact with the contents, the conductive resin layer must be electrically connected to the ground wire connecting portion 18 .

The ground wire connecting portion 18 functions to discharge static electricity accumulated in the flexible container 10 to the outside of the container by connecting the ground wire.
The ground wire connection portion 18 is made of (a) a metal wire, a cloth made by twisting a metal wire into fibers, a string, a cloth or a string made by twisting carbon fibers into other fibers, and (b) a conductive material such as carbon black or metal particles. Sheets and tapes made by kneading elastic materials into resin, strings processed from these, (c) woven and knitted tapes woven or knitted with metal wires, carbon fibers, conductive threads, carbon black on woven fabrics, metal particles It can be formed by attaching a member such as a conductive tape-like material such as a sheet or tape coated with a resin or rubber kneaded with the above to each part of the bag body 11 .
The ground wire connecting portion 18 can be attached by (a) a method of attaching the upper wall and the lower wall to the upper and lower sides of the large-diameter tubular body of the flexible container at the same time, and (b) a method of attaching the inner surface of the tubular flexible container. A method of attaching to the inner surface at the same time when attaching the cylindrical pouring/discharging port to the upper and lower walls, (c) a method of attaching to the inner surface by sewing during or after making the flexible container, (d) A method of attaching by heat welding can be used.
Among them, the ground wire connecting portion 18 in the flexible container 10 is formed by forming the single-sided conductive tarpaulin 20 or the tarpaulin 1 described later in a belt-like or strip-like shape, and one end side of this longitudinal direction is connected to each portion of the bag 11, for example, the upper wall portion. It is formed by joining, preferably welding, to the upper surface of the lower wall, the lower surface of the lower wall, the outer peripheral surface of the discharge port, etc., or by ejecting a part of the lower surface or the upper surface into a terminal shape (Reference: Japanese Patent Application 2018- 238470) is preferred.
Note that the number and arrangement of the ground wire connection portions 18 are not limited to this.
All of the conductive resin layer of the single-sided conductive tarpaulin 20 and the conductive resin layer of the tarpaulin 1 must be electrically connected to the ground connecting portion 18 .

The partition wall 12 is formed from the tarpaulin 1, and as shown in FIGS. 3 and 4, is a substantially rectangular sheet member having a predetermined height from the bottom of the container. has an opening 12A at an appropriate location.
The partition walls 12 are fixed at both left and right ends to the side surfaces of the inner wall of the container at each of the four corners in the container, and are attached at each corner so as to cross obliquely when viewed from the top. The shape of the mold can be retained.
The shape and arrangement of the partition walls 12 are arbitrary. For example, as shown in FIGS. It may be shaped with edges, or the openings may be arranged such that one partition 12 is placed over the two corners for a total of two partitions 12, as shown in FIGS. The two wall surfaces may be connected via a central surface portion, and fixed edge portions may be provided on both left and right sides of each wall surface.

The single-sided conductive tarpaulin constituting each part of the bag 11 and the ground wire connecting part 18 has a conductive resin layer laminated on one side of the base fabric and a non-conductive resin layer on the other side, as described above. It is preferably formed from a single-sided conductive tarpaulin laminated with .
Among them, as a preferable example of the single-sided conductive tarpaulin, from the viewpoint of the weldability with the present tarpaulin 1 described above, both the front and back surfaces of the base fabric 21 made of woven and knitted fabrics contain an ethylene-based copolymer as a main component resin, and are conductive. coated with a resin layer (referred to as a "non-conductive resin layer") 22 containing no conductive material, and containing an ethylene-based copolymer as a main component resin only on the outer side of one non-conductive resin layer 22 in the front and back direction, A single-sided conductive tarpaulin 20 having a resin layer (referred to as “conductive resin layer”) 23 containing a conductive material can be mentioned.

The base fabric 21 in the single-sided conductive tarpaulin 20, the ethylene copolymer as the main component resin of the non-conductive resin layer 22, the ethylene copolymer as the main component resin of the conductive resin layer 23, and the conductive resin layer The conductive materials 23 are respectively an ethylene-based copolymer that is the main component resin of the base fabric 2 and the non-conductive resin layer 4 in the tarpaulin 1, and an ethylene-based copolymer that is the main component resin of the conductive resin layer 5. , is the same as the conductive material of the conductive resin layer 5 . However, they may be of the same type or of different types.

In the flexible container 10, the entire inner surface of the inner wall material of the bag 11 and the partition wall 12 are electrically connected to each other, so that static electricity can be eliminated with a smaller number of grounding mechanisms. Therefore, the conductive resin layer 23 of the single-sided conductive tarpaulin 20 forming the inner wall material of the bag body 11 and the conductive resin layer 5 of the tarpaulin 1 forming the partition wall 12 are directly welded without an adhesive or the like. It is preferable to
At this time, when the two are bonded with an adhesive, the peel strength of the bonded portion is weak, so if a rectangular flexible container having partition walls is formed, there is a possibility that the flexible container will peel off during use.

Examples of the welding method at this time include thermal welding such as iron welding, hot plate welding and hot air welding, as well as high frequency welding and ultrasonic welding. In particular, high-frequency welding (high-frequency Welding by a welder is preferred. However, since sparks may occur, it is preferable to weld as follows.

For example, as shown in FIG. 7, the inner surface of the single-sided conductive tarpaulin 20 forming the bag body 11 of the flexible container 10, that is, the conductive resin layer 23, is overlapped with the constant width portions of both ends of the tarpaulin 1 forming the partition wall 12. Then, in this overlapped portion, a metal mold (electrode) 32 of a high-frequency welding machine 31 is brought into contact with the surface of the conductive resin layer 5 of the tarpaulin 1 constituting the partition wall 12 through an insulating sheet 30 to perform high-frequency welding. is preferably carried out to weld the conductive resin layer 23 of the single-sided conductive tarpaulin 20 forming the bag 11 and the conductive resin layer 5 of the tarpaulin 1 forming the partition wall 12 .
Such welding can prevent the generation of sparks.

At this time, as the insulating sheet 30, a known insulating sheet having electromagnetic wave insulating properties can be appropriately used. Examples include sheets of polyimide, epoxy resin, polyurethane, polyethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, and the like. However, it is not limited to these.

For example, as shown in FIG. 8, the inner surface of the single-sided conductive tarpaulin 20 forming the bag body 11 of the flexible container 10, that is, the conductive resin layer 23, has a constant width portion at both ends of the tarpaulin 1 forming the partition walls 12. are overlapped, and a metal mold (electrode) 32 of a high-frequency welder 31 is applied to the outer surface of the single-sided conductive tarpaulin 20 constituting the bag 11, that is, the surface of the non-conductive resin layer 22 at the overlapped portion. It is preferable to weld the conductive resin layer 23 of the single-sided conductive tarpaulin 20 forming the bag 11 and the conductive resin layer 5 of the tarpaulin 1 forming the partition wall 12 by welding.
Such welding can also prevent the generation of sparks.

The conditions for high-frequency welding (high-frequency welder) are not particularly limited. Generally, the frequency is in the range of 10 to 100 MHz and the welding time is 1 to 60 seconds.

In the flexible container 10, the resistance between all the ground wire connection parts 18 and all the partition walls 12 and between the ground wire connection parts 18 and the inner surface of the bag body 11, that is, the inner wall material of the bag body 11, is Both are preferably 1×10 ¹⁰ Ω or less, and more preferably less than 1×10 ⁸ Ω.
By setting the resistance between them within the above range, even if static electricity is generated, it can be eliminated by grounding, which is preferable.
In order to adjust the resistance between them within the above range, the resistance on both sides of the partition wall 12 and the resistance on the surface of the inner wall material of the bag body 11 are adjusted, and then the two are welded without an adhesive as described above. do it. However, it is not limited to this method.

<<Description of terms, etc.>>
In the present invention, the term "film" includes the "sheet", and the term "sheet" includes the "film".
In addition, the expression "panel" such as an image display panel, a protective panel, etc. includes a plate, a sheet and a film.

In this specification, when described as "X to Y" (X and Y are arbitrary numbers), unless otherwise specified, "X or more and Y or less" and "preferably larger than X" or "preferably It also includes the meaning of "smaller than Y".
In addition, when described as "X or more" (X is an arbitrary number), it includes the meaning of "preferably greater than X" unless otherwise specified, and is described as "Y or less" (Y is an arbitrary number). If not otherwise specified, it also includes the meaning of "preferably smaller than Y".

Next, the present invention will be described in more detail based on examples. However, the present invention is not limited to the following description examples as long as the gist of the present invention is not exceeded.

The base fabrics, resins and conductive materials used in the following examples and comparative examples are as follows.

Base fabric: 750 denier polyester fiber, 20 × 20/inch plain fabric EVA1: Ethylene-vinyl acetate copolymer, vinyl acetate content of 20% by mass, MFR (JIS K7210, temperature 190 ° C. , load 2.16 kg) 2.0 g/10 minutes EVA2: Ethylene-vinyl acetate copolymer having a vinyl acetate content of 10% by mass, MFR (JIS K7210, temperature 190°C, load 2.16 kg) 2.0 g /10 minutes EVA3: Ethylene-vinyl acetate copolymer with a vinyl acetate content of 8% by mass, MFR (JIS K7210, temperature 190°C, load 2.16 kg) 2.0 g/10 minutes EVA4: ethylene-vinyl acetate A copolymer having a vinyl acetate content of 15% by mass and an MFR (JIS K7210, temperature of 190°C, load of 2.16 kg) of 2.0 g/10 minutes Carbon black: DBP adsorbed oil amount of 180 ml/10 g, specific surface area of 50 m ² / g, particle size 50 nm

[Example 1]
As shown in FIG. 2, the non-conductive resin layer-forming resin composition 4A made of EVA1 is melt-extruded into a sheet by calendering to form a non-conductive resin layer film 4B. The film 4B is thermocompression bonded to the base fabric 2 to form non-conductive resin layers 4, 4 having a thickness of 0.3 mm on both sides of the base fabric 2 in the front and back directions to form a laminated sheet 6. On both sides in the front and back directions, a conductive resin sheet 7 made of a resin composition for forming a conductive resin layer in which 33.3 parts by mass of the carbon black is blended with the EVA 2 (100 parts by mass) is simultaneously laminated and melted. 0.05 mm-thick conductive resin layers 5, 5 were formed on both sides of the laminate sheet 6 in the front and back directions to prepare a double-sided conductive tarpaulin (sample) with a total thickness of 0.85 mm.
The surface resistivity of the conductive resin layers 5 on the front and back sides was 4×10 ⁴ Ω.

[Example 2]
A double-sided conductive tarpaulin (sample) was produced in the same manner as in Example 1, except that EVA2 in Example 1 was changed to EVA3 having a vinyl acetate content of 8%. The surface resistivity of the conductive resin layers 5 on the front and back sides was 4×10 ⁴ Ω.

[Example 3]
A double-sided conductive tarpaulin (sample) was produced in the same manner as in Example 1, except that EVA2 in Example 1 was changed to EVA4 having a vinyl acetate content of 15%. The surface resistivity of the conductive resin layers 5 on the front and back sides was 4×10 ⁴ Ω.

[Comparative Example 1]
A conductive tarpaulin (sample) was produced in the same manner as in Example 1, except that carbon black was not blended. The surface specific resistance of the conductive resin layer 5 on the front and back sides was 1×10 ¹⁵ Ω.

[Comparative Example 2]
A double-sided conductive tarpaulin (sample) was produced in the same manner as in Example 1, except that the amount of carbon black blended in Example 1 was changed to 42.9 parts by mass. The surface resistivity of the conductive resin layers 5 on the front and back sides was 5×10 ² Ω.

<Production of conductive flexible container>
(Production of single-sided conductive tarpaulin)
By calendering, the non-conductive resin layer-forming resin composition made of EVA1 is melt-extruded into a sheet to form a non-conductive resin layer film, and the non-conductive resin layer film is thermocompression bonded to the base fabric. Then, a non-conductive resin layer having a thickness of 0.3 mm is formed on both sides of the base fabric in the front and back direction to form a laminated sheet. A conductive resin layer having a thickness of 0.05 mm was formed from the resin composition for forming a conductive resin layer containing 3 parts by mass of the above, and a single-sided conductive tarpaulin having a total thickness of 0.8 mm was produced. The surface specific resistance of the conductive resin layer surface was 4×10 ⁴ Ω.

Using the single-sided conductive tarpaulin thus produced, the ends of the single-sided conductive tarpaulin constituting each part are welded together by high-frequency welding so that the conductive resin layer is positioned on the inside, as shown in FIG. As shown, a peripheral wall portion 13, an upper wall portion 14 covering the upper end side of the peripheral wall portion 13, a lower wall portion 15 covering the lower end side of the peripheral wall portion 13, and an injection port provided in the upper wall portion 14 16, a discharge port 17 provided in the lower wall portion 15, and a ground wire connection portion 18 were prepared.

(Production of partition wall material)
Using the double-sided conductive tarpaulin (sample) produced in Examples and Comparative Examples, as shown in FIG. .

(Production of square flexible container)
As shown in FIG. 3, at each of the four corners of the bag body 11, the right and left ends of the partition wall material were fixed to the side surfaces of the container inner wall and obliquely attached in a top view to fabricate a rectangular flexible container.
At this time, as shown in FIG. 7, both ends of the double-sided conductive tarpaulin (sample) forming the partition wall 12 were overlapped on the conductive resin layer 23 of the single-sided conductive tarpaulin 20 forming the bag body 11. At this overlapping portion, a high-frequency welder 31 is applied to the surface of the conductive resin layer 5 of the double-sided conductive tarpaulin (sample) constituting the partition wall 12 via an insulating sheet 30 made of Teflon and having a thickness of 0.2 mm. High-frequency welding (frequency 27 MHz, 7 seconds, welding width 60 mm × 1 m) is performed by applying the mold (electrode) 32 of the conductive resin layer 23 of the single-sided conductive tarpaulin 20 constituting the bag 11 and the partition wall 12 was welded with the conductive resin layer 5 of the double-sided conductive tarpaulin (sample).

<Evaluation method>
In Examples and Comparative Examples, various properties were evaluated by the methods described below.

(1) Surface specific resistance The surface specific resistance of the conductive tarpaulins (samples) produced in Examples and Comparative Examples was measured according to JIS K7194.

(2) High-frequency welding workability As described later, when a single-sided conductive tarpaulin and a double-sided conductive tarpaulin (sample) are high-frequency welded, the peel strength of the welded portion is measured according to JFC007, and is measured according to the following criteria. evaluated.
When the welded portion peel strength was 25 kg or more, it was evaluated as "Good", and when it was less than 20 kg, it was evaluated as "X: Poor".

<Discussion>
From the results of the above Examples and Comparative Examples and the results of the tests conducted by the present inventors so far, both the front and back sides of the base fabric contain an ethylene-based copolymer as a main component resin and do not contain a conductive material. A conductive resin layer containing an ethylene-based copolymer as a main component resin and containing a conductive material is further laminated on the outer side in the front and back direction, and the surface resistance of both the front and back sides is 10 ³ . It was confirmed that if the resistance is between Ω and 10 ⁸ Ω, both surfaces have sufficient conductivity and the surface resistivity can be sufficiently lowered, and high-frequency welding can be performed.
Further, from the viewpoint of maintaining high-frequency welding suitability, the copolymerization ratio of the copolymerization monomer of the ethylene-based copolymer in the non-conductive resin layer is preferably 6 to 30%, and the ethylene-based copolymer in the conductive resin layer. It has been found that the copolymerization ratio of the combined copolymerized monomers is preferably 5 to 20%.
Furthermore, it is also found that the copolymerization ratio of the copolymerization monomer of the ethylene-based copolymer in the non-conductive resin layer is preferably higher than the copolymerization ratio of the copolymerization monomer of the ethylene-based copolymer in the conductive resin layer. rice field.

1 Tarpaulin 2 Base fabric 3 Resin layer 4 Non-conductive resin layer 4A Resin composition for forming non-conductive resin layer 4B Film for non-conductive resin layer 5 Conductive resin layer 6 Laminated sheet 7 Conductive resin sheet 9 Calendering molding machine 10 flexible container 11 bag body 12 partition wall 13 peripheral wall portion 14 upper wall portion 15 lower wall portion 16 inlet 17 outlet 18 ground wire connecting portion 20 single-sided conductive tarpaulin 21 base cloth 22 non-conductive resin layer 23 conductive resin layer 30 insulating sheet 31 high-frequency welder 32 mold (electrode)

Claims (5)

A conductive tarpaulin comprising a woven and knitted base fabric coated with a resin layer on both sides,
Each of the resin layers contains an ethylene-based copolymer as a main component resin, and a resin layer that does not contain a conductive material (referred to as a "non-conductive resin layer") and an ethylene-based copolymer A resin layer (referred to as a "conductive resin layer") containing coalescence as a main component resin and containing a conductive material,
A conductive tarpaulin having a surface resistance of 10 ³ Ω to 10 ⁸ Ω on both sides. The ethylene-based copolymers of the non-conductive resin layer and the conductive resin layer are EVA (ethylene-vinyl acetate copolymer), EMA (ethylene-methyl acrylate copolymer) and EMMA (ethylene-methacrylic acid). copolymer), or two or more thereof. The copolymerization ratio of the monomer that copolymerizes with ethylene in the ethylene-based copolymer in the non-conductive resin layer (referred to as a “comonomer”) is the ratio of the copolymerization monomer of the ethylene-based copolymer in the conductive resin layer. The conductive tarpaulin according to claim 1 or 2, characterized in that it is higher than the copolymerization proportion. The conductive tarpaulin according to any one of claims 1 to 3, wherein said non-conductive resin layer and said conductive resin layer are fused together. Laminated sheet in which both the front and back sides of a base fabric made of woven and knitted fabric are coated with a resin layer containing an ethylene copolymer as a main component resin and not containing a conductive material (referred to as a "non-conductive resin layer"). A method for producing a conductive tarpaulin, characterized in that conductive resin sheets containing an ethylene-based copolymer as a main component resin and containing a conductive material are laminated and adhered simultaneously on the outer sides in the front and back directions.

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