JP2009183878A - Method for laying capping sheet and capping sheet to be used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a failure from being generated when the adjacent capping sheets are thermally melt-stuck to each other. <P>SOLUTION: The capping sheet 6 is used at installation sites such as a waste disposal site and is produced by arranging protective layers 7, 7, each of which consists of a nonwoven fabric comprising a core-sheath conjugate fiber having a core component and a sheath component having the melting point lower than that of the core component, on both sides of a microporous film 8 having air permeability and water barrier properties. The method for laying the capping sheet comprises the steps of: laying a plurality of capping sheets 6; and melting the sheath component of the core-sheath conjugate fiber to thermally melt-stick the adjacent capping sheets 6, 6 to each other. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capping sheet laying method and a capping sheet used in the method, for example, a capping sheet laying method used for sealing an upper part of a disposal site when closing a waste disposal site, and a capping sheet used in the method. About.

  When the amount of waste at the waste disposal site becomes the upper limit of allowable amount and the disposal site is closed, a water-permeable and air-permeable microporous film is used to seal the upper part of the disposal site (Patent Document 1). . Since this microporous film is very weak and easily damaged by itself, for example, it is sandwiched between nonwoven fabrics having high cushioning and high strength from both sides. The nonwoven fabric used here is generally a nonwoven fabric of long fibers or short fibers, and most are composed of single component fibers such as polyester and polypropylene.

When installing a capping sheet in a waste disposal site, it is necessary to reliably manifest the waste sealing effect by welding adjacent capping sheets together, for example, by heat. In that case, if the welding is incomplete or if the microporous film is damaged by heat, the waste and the external environment will be insufficiently cut off, so work with great care. It is necessary.
JP 2005-81222 A

  In the conventional capping sheet, as described above, since the microporous film is sandwiched between the nonwoven fabrics composed of single-component fibers from both sides, it is very difficult to control the temperature at the time of thermal welding between the capping sheets, and workability is improved. Remarkably reduced.

  Then, this invention aims at preventing generation | occurrence | production of the malfunction when heat-welding adjacent capping sheets.

In order to achieve the above object, the present invention has the following gist.
(1) A method for laying a capping sheet used in a place to be installed such as a waste disposal site, wherein the capping sheet is formed on both sides of a microporous film having air permeability and water impermeability, and a core component and the core component A non-woven fabric protective layer including a core-sheath composite fiber having a cross-sectional structure with a sheath component having a lower melting point, and laying a plurality of capping sheets and end portions of adjacent capping sheets A method for laying a capping sheet, wherein the sheath components are thermally bonded to each other by melting them.

  (2) A capping sheet used in the laying method of (1) above, comprising a core component and a sheath component having a melting point lower than that of the core component on both sides of a microporous film having air permeability and water shielding properties. A capping sheet comprising a protective layer made of a nonwoven fabric containing a core-sheath composite fiber having a cross-sectional structure.

  (3) The capping sheet according to (2), wherein the fibers constituting the nonwoven fabric are entangled three-dimensionally with each other.

  (4) The capping sheet according to (2) or (3), wherein the core component is polyester and the sheath component is polyethylene.

(5) The microporous film is a polyolefin resin film having a moisture permeability of 500 to 10000 g / m ² · 24 hr and an air permeability of 50 to 10000 seconds / 100 cc, any of (2) to (4) A capping sheet.

  In the present invention, a protective layer made of a nonwoven fabric sandwiching a microporous film from both sides is formed of a nonwoven fabric including a core-sheath composite fiber having a cross-sectional structure including a core component and a sheath component having a melting point lower than that of the core component. Therefore, it is possible to prevent the occurrence of problems at the time of capping sheet welding by performing thermal welding under a temperature condition in which the sheath component melts and the core component does not melt.

  FIG. 1 shows an example of a cross-sectional structure of a treatment pond in a waste disposal site. Here, 1 is earth and sand, for example, the processing pond 2 is formed by digging up this earth and sand from the ground surface. A water-impervious sheet 3 is installed at the bottom or slope of the treatment pond 2. A protective mat 4 is laid between the rear surface side of the water shielding sheet 3, that is, between the water shielding sheet 3 and the surface of the earth and sand 1. As shown in phantom lines in FIG. 1, the protective mat 4 can be laid so as to cover the surface of the water shielding sheet 3.

  As shown in FIG. 1, in order to seal the upper part of the treatment pond in which the waste 5 is accumulated when the treatment pond is closed, the amount of waste charged into the treatment pond shown in FIG. The capping sheet 6 is covered. As shown in FIG. 2, the capping sheet 6 is obtained by sandwiching a microporous film 8 from both sides with a protective layer 7 made of nonwoven fabric.

  A plurality of capping sheets 6 having a predetermined size are laid. The configuration of the joint portion between the adjacent capping sheets 6 and 6 can be, for example, as shown in FIG. That is, as shown in the figure, the end portions of the adjacent capping sheets 6 and 6 are overlapped with each other, and the overlapping portion 9 can be thermally bonded to integrate them. Reference numeral 10 denotes the thermal bonding portion. Thermal bonding can be performed by using a hot iron or a hot air generator such as a hot air dryer. In addition to the illustrated embodiment, for example, the end portions of the capping sheets 6 and 6 are butted against each other, a contact member in which the capping sheet 6 is formed in a tape shape is overlapped on the abutting portion, and the overlapping portion is thermally bonded. Can be joined together.

  The nonwoven fabric which comprises the protective layer 7 uses the core-sheath composite fiber in which the melting point of the core component and the sheath component is different, and the sheath component has a lower melting point. The difference in melting point between the core component and the sheath component is preferably 20 ° C. or higher, and more preferably 50 ° C. or higher. When the melting point difference is small, the core component polymer is melted when the capping sheets 6 and 6 are bonded together by melting the sheath component and heat melting, and the intended effect of the present invention cannot be obtained.

  Polymers used for the fibers constituting the nonwoven fabric as the protective layer 7 are used for fibers such as polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyolefins such as polyethylene and polypropylene, and polyamides such as nylon 6 and nylon 66. The polymer group may be selected, and is not particularly specified.

  As a typical example of the combination of the core component and the sheath component, there can be mentioned one in which the core component is polyester, for example, polyethylene terephthalate, and the sheath component is polyethylene. In this case, the melting point difference between the core component and the sheath component can be set at, for example, 100 ° C. or more, and the core component polyethylene terephthalate has a high strength among polymers. Even if the components are sufficiently melted, the core component can be reliably maintained without melting the core component.

  The mixing ratio of the core component and the sheath component is a volume ratio, and the core component: sheath component = 30: 70 to 70:30 is appropriate. By being in this range, it is possible to combine required adhesion performance and fiber form maintenance performance.

  In addition to the core-sheath composite fiber, the nonwoven fabric constituting the protective layer 7 can contain single-phase or other cross-sectional form fibers. The ratio of the mixed fibers needs to be set to such an extent that the function of thermal bonding by melting the sheath component of the core-sheath composite fiber is not hindered. For example, when a single-phase fiber is included, the melting point of the polymer constituting the fiber needs to be higher than the melting point of the sheath component of the core-sheath composite fiber. This is to prevent the fibers from melting and losing the fiber form during thermal bonding.

  The method for producing the fiber may be a known melt spinning method, and is not limited at all, but it should be avoided that the fiber is inappropriate for making a nonwoven fabric. For example, the nonwoven fabric for the capping sheet of the present invention can be produced by a needle punch method using a nonwoven web. In this case, the fiber length is suitably more than 30 mm. In that case, when the fiber length is 30 mm or less, it is difficult to produce a nonwoven fabric by the needle punch method. Moreover, it is preferable that the fiber diameter is in the range of 10 to 100 μm. If the fiber diameter is out of the range, the needle punch processing is similarly difficult to perform, and the nonwoven fabric performance may be hindered.

  As described above, the nonwoven fabric used for the capping sheet of the present invention is optimally manufactured by the needle punch method, but if necessary, resin bonding or heat bonding can be further added.

  When producing a nonwoven fabric by a manufacturing method other than the needle punch method, it is necessary to select the basis weight, strength, etc. of the nonwoven fabric so as to have a function of preventing damage to the microporous film.

When producing a nonwoven fabric by the above-mentioned manufacturing method, the mass per unit area of the nonwoven fabric, that is, the basis weight, is not particularly limited, but is preferably 50 g / m ² or more, particularly 300 g / m ² or more. If it is less than 50 g / m ² , the effect of protecting the microporous film is poor, and there is a possibility that the microporous film may be melted and damaged when bonded by heat sealing.

The microporous film used in the capping sheet of the present invention is made of a polyolefin resin such as polyethylene or polypropylene, and has a moisture permeability of 500 to 10,000 g / m ² · 24 hr and an air permeability of 50 to 10,000 seconds / 100 cc. Is preferred. Those outside this range may have insufficient waterproof performance to prevent rainwater from penetrating into the disposal site, and may prevent gas from leaking inside the disposal site.

  The method for laminating the nonwoven fabric and the microporous film is not particularly limited as long as it does not lose the moisture permeability and waterproof performance of the microporous film. As a specific method, thermal lamination or resin bonding is conceivable. In the case of thermal lamination, it is necessary to select conditions so that the microporous film does not melt. In the case of resin bonding, it is necessary to select conditions that do not cover the entire surface of the microporous film. .

  The capping sheet thus prepared is, for example, a speed condition of 1.0 m / min to 2.0 m / min under a temperature condition of 150 ° C. to 190 ° C. using a TWINNY type hot air welding machine manufactured by Leister. It is possible to have the performance that the adhesive strength when bonded together is 8 kN / m or more and the water pressure resistance of the bonded portion is 5 kPa or more.

Next, examples and comparative examples of the present invention will be described.
In the following examples and comparative examples, test methods for various properties were as follows.

  Bonding condition: visually observed.

  Bond strength at the joint: A sample with a width of 5 cm and a length of 30 cm is prepared so that the bonded portion comes to the center of the sample. According to the tensile strength test method specified in JIS L1906, the grip interval is 20 cm and the pulling speed is 10 cm / min. A tensile test was conducted to obtain the maximum load at that time and determined the adhesive strength.

  Water pressure resistance of joints: Stainless steel to prevent sample expansion in accordance with JIS L-1092 hydrostatic pressure method A (low water pressure method) according to the situation where the capping sheet is buried in the soil at the actual laying site. Measurement was performed after setting the mesh.

  Air permeability: Measured according to JIS L-1096 B method (Gurley method).

  Moisture permeability: Measured according to JIS L-1099 A-1 method (calcium chloride method).

Example 1
A polyethylene terephthalate having a melting point of 255 ° C. was used as the core component, and a polyethylene having a melting point of 125 ° C. was used as the sheath component, and a web composed only of core-sheath composite long fibers was prepared by a spunbond method known as a method for producing long fiber nonwoven fabrics. The core-sheath composite fiber constituting the nonwoven web had a volume ratio of 1: 1 between the core component and the sheath component, and a fiber diameter of 25 μm. In addition, a mild thermocompression treatment was performed so as to be suitable for the needle punch in the next step. That is, by using a heat embossing roll, by adjusting the surface temperature to be equal to or lower than the melting point of the sheath component polyethylene, it is adjusted so that the adhesion between the fibers becomes light, and the adhesion between the fibers is easily released by physical impact. It was.

Subsequently, the core-sheath composite long fiber nonwoven web was needle punched to obtain a nonwoven fabric having a mass per unit area, that is, a basis weight of 300 g / m ² . The needle punching conditions were a 40th needle made by FOSTER, a punch density of 60 P / square inch, and a needle depth of 9 mm.

The nonwoven fabric obtained as described above is coated on both sides of a polyethylene microporous film (thickness 100 μm, water pressure resistance 100 kPa, water vapor transmission rate 6000 g / m ² · 24 hr, air permeability 500 seconds / 100 cc). The adhesive was used to adhere by curtain spray lamination method. Thus, a capping sheet of Example 1 of the present invention was obtained.

  With respect to the obtained capping sheet, an overlapping portion similar to that shown in FIG. 2 is formed, and the wrap width of the material is set to about 10 cm. Using a hand hot air blower TWINNY manufactured by Leister, the temperature is in the range of 180 to 190 ° C. The adhesion test was performed under the condition of an adhesion speed of 1 m / min. As a result, only the low melting point component, that is, the sheath component of the constituent fibers of the nonwoven fabric melted, and a good adhesion state could be obtained.

About the heat bonding part of the capping sheet, the bonding state was observed, and a joint tensile test and a joint water pressure resistance test were performed. The results are shown in Table 1.
As shown in Table 1, the bonding state of the matching portion was good, and the bonding strength and bonding water pressure resistance were satisfactory.

(Example 2)
A core-sheath composite short fiber was prepared by a known melt spinning method using polyethylene terephthalate having a melting point of 255 ° C. as the core component and polyethylene having a melting point of 125 ° C. as the sheath component. The composite ratio of the core component and the sheath component was 1: 1 by volume ratio. The fiber diameter of the obtained core-sheath composite short fiber was 25 μm. The fiber length was 51 mm, and the number of crimps was 11/25 mm.

Next, the core-sheath composite short fiber was passed through a card machine to produce a web having a mass per unit area, that is, a basis weight of about 300 g / m ² . In creating the web, the core-sheath composite short fiber was made 100%, and the short fibers of other materials were not mixed.

The obtained web was subjected to needle punching in the same manner as in Example 1 to obtain a nonwoven fabric having a mass per unit area, that is, a basis weight of 300 g / m ² .
And the obtained nonwoven fabric was adhere | attached on both surfaces of the microporous film by the method similar to Example 1, and the capping sheet of Example 2 was obtained.

  With respect to the obtained capping sheet, an overlapping portion similar to that shown in FIG. 2 is formed, and the wrap width of the material is set to about 10 cm, using a hand hot air blower TWINNY manufactured by Leister, in a temperature range of 150 to 170 ° C. The adhesion test was performed under the condition of an adhesion speed of 1 m / min. As a result, only the low melting point component of the constituent fibers of the nonwoven fabric melted, and a good adhesion state could be obtained.

About the heat bonding part of the capping sheet, the bonding state of the bonding part was observed, and a bonding part tensile test and a bonding part water pressure resistance test were performed. The results are shown in Table 1.
As shown in Table 1, the bonding state of the bonded portion was good, and the bonded portion bonding strength and the bonded portion water pressure resistance were satisfactory.

(Example 3)
Compared to Example 2, the core component was changed to polypropylene having a melting point of 170 ° C., and the sheath component was polyethylene having a melting point of 125 ° C. Otherwise, the capping sheet of Example 3 was obtained in the same manner as Example 2.

  With respect to the obtained capping sheet, an overlapping portion similar to that shown in FIG. 2 is formed, and the wrap width of the material is set to about 10 cm. Using a hand hot air blower TWINNY manufactured by Leister, a temperature range of 140 to 160 ° C. The adhesion test was performed under the condition of an adhesion speed of 1 m / min. As a result, only the low melting point component, that is, the sheath component of the constituent fibers of the nonwoven fabric melted, and a good adhesion state could be obtained.

About the heat bonding part of the capping sheet, the bonding state of the bonding part was observed, and a bonding part tensile test and a bonding part water pressure resistance test were performed. The results are shown in Table 1.
As shown in Table 1, the bonding state of the bonded portion was good, and the bonded portion bonding strength and the bonded portion water pressure resistance were satisfactory.

(Comparative Example 1)
Instead of the core-sheath composite long fiber of Example 1, single-phase long fibers made of polyethylene terephthalate having a melting point of 255 ° C. and having a fiber diameter of 25 μm were used. Other than that was the same as Example 1, and a capping sheet of Comparative Example 1 was obtained.

  The obtained capping sheet was subjected to a thermal adhesion test using a hand hot air blower TWINNY manufactured by Leister Co. As a result, it was not possible to bond at 150 to 220 ° C., and it was easy to make holes partially when bonded at 270 ° C. or higher. The sheet was difficult to handle.

About the heat bonding part of the capping sheet, the bonding state of the bonding part was observed, and a bonding part tensile test and a bonding part water pressure resistance test were performed. The results are shown in Table 1.
As shown in Table 1, the bonding state of the bonded portion was poor because it was perforated, and the bonding strength of the bonded portion was satisfactory, but the bonded portion did not have any water pressure resistance because of the perforation.

(Comparative Example 2)
A core-sheath composite short fiber was produced in the same manner as in Example 2. In addition, single-phase short fibers made of polyethylene terephthalate having a melting point of 255 ° C., having a fiber diameter of 25 μm, a fiber length of 51 mm, and a crimp number of 11/25 mm were produced.

Then, in the production of the nonwoven fabric, the core-sheath composite short fiber and the polyethylene terephthalate short fiber were mixed so that the mass ratio was 50%: 50%, and other than that, in the same manner as in Example 2, the basis weight was 300 g / A non-woven fabric of m ² was obtained.

The obtained nonwoven fabric was adhered to both surfaces of the microporous film in the same manner as in Example 1 to obtain a capping sheet of Comparative Example 2.
With respect to the obtained capping sheet, an overlapping portion similar to that shown in FIG. 2 is formed, and the wrap width of the material is set to about 10 cm. Using a hand hot air blower TWINNY manufactured by Leister, at a temperature of 150 to 220 ° C. The adhesion test was performed under the condition of an adhesion speed of 1 m / min.

About the heat bonding part of the capping sheet, the bonding state of the bonding part was observed, and a bonding part tensile test and a bonding part water pressure resistance test were performed. The results are shown in Table 1.
Since the blending ratio of the polyethylene terephthalate short fibers was too high, as shown in Table 1, adhesion was possible, but there were some areas where adhesion was weak, and adhesion was insufficient. Further, neither the bonding strength of the bonded portion nor the water pressure resistance of the bonded portion was satisfactory.

It is a figure which shows the outline of the laying method of the capping sheet | seat of embodiment of this invention. It is a figure which shows the heat bonding part of the capping sheets in FIG.

Explanation of symbols

6 Capping sheet 7 Non-woven protective layer 8 Microporous film 10 Thermal bonding part

Claims (5)

  A method of laying a capping sheet used in a place to be installed such as a waste disposal site, wherein the capping sheet is disposed on both sides of a microporous film having air permeability and water-imperviousness with a core component and lower than the core component. With a configuration in which a protective layer made of a nonwoven fabric including a core-sheath composite fiber having a cross-sectional structure with a melting point sheath component is provided, and laying a plurality of capping sheets, and end portions of adjacent capping sheets, A capping sheet laying method, wherein the sheath component is thermally bonded by melting the sheath component.   A capping sheet used in the laying method according to claim 1, comprising a core component and a sheath component having a melting point lower than that of the core component on both sides of a microporous film having air permeability and water shielding properties. A capping sheet comprising a non-woven protective layer including a core-sheath composite fiber having a structure.   The capping sheet according to claim 2, wherein the fibers constituting the nonwoven fabric are entangled three-dimensionally with each other.   The capping sheet according to claim 2 or 3, wherein the core component is polyester and the sheath component is polyethylene. The microporous film is a polyolefin resin film having a moisture permeability of 500 to 10,000 g / m ² · 24 hr and an air permeability of 50 to 10,000 seconds / 100 cc. Capping sheet.

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