JP2013198881A - Protective mat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective mat which has high protective performance, light weight and excellent workability and further which can reduce outflow risk of liquid contaminants because of high water absorbing performance though the mat is invented with a background of conventional techniques.SOLUTION: A protective mat is obtained by integrating: a nonwoven fabric layer A containing a water swelling polymer material of 25 wt.% or more; and a nonwoven fabric layer B consisting essentially of polyolefin polymer fiber or polyester polymer fiber and having mass per unit area of 100 to 800 g/m.

Description

  The present invention is a protective function that prevents the diffusion and leakage of pollutants in facilities and sites that temporarily or for long-term storage / preservation of liquid pollutants such as biodegradable waste and radioactive pollutants. Concerning mats with. More specifically, by absorbing liquid contaminants and preventing or suppressing external outflow, protecting the water shielding sheet as part of the water shielding work, or using a polymer material that swells due to water absorption in some cases. The present invention relates to a protective mat that can also function as a water leakage retarding material or a water shielding material.

  Short fiber non-woven fabric, long fiber non-woven fabric, or geotextile combined with bentonite is used as a cushioning protective material such as a water-impervious sheet to prevent environmental pollution from various disposal sites and illegal dumping materials, and impact cushioning materials. (For example, see Patent Documents 1 and 2).

Bentonite-based materials have been used suitably when there is a possibility that liquid contaminants may flow out because they have not only a function as a protective material for the water shielding sheet but also an effect of suppressing the outflow of contaminated water. However, there are many cases where the basis weight is 5 kg / m ² or more, and there are many cases where heavy machinery is required for construction. Moreover, the joint part of a some sheet | seat is joined by manual work using a granular material and a semi-solid substance, and while construction takes time, it is not easy to aim at perfect water-blocking also regarding a water leak function.

  Short fiber nonwoven fabrics and long fiber nonwoven fabrics are widely used because they are lighter and easier to handle than bentonite, and the thickness is relatively thin, so the construction period can be shortened and the processing or storage capacity can be increased. Has been.

  Moreover, in a waste disposal site, in order to prevent the watertightness fall by the damage of the impermeable sheet in a impermeable structure, it is proposed to use a self-repairing impermeable sheet (for example, refer patent document 3). . As the self-healing water-impervious sheet, a water-swellable sheet containing water-absorbing swellable fibers that swell when moisture is absorbed is used.

  The emergence of materials that can shorten the construction period is expected as an emergency measure such as the treatment of rubble and illegal dumping caused by the recent earthquakes. Further, not only a simple protective function but also a demand for a sheet that adsorbs or absorbs contaminants is increasing. In particular, for contaminated water containing radioactive substances, a higher level of control than other pollutants is desired, and there is an increasing demand for more highly functional water barriers and protective materials.

JP 2004-181393 A JP-A-6-108436 JP 11-291370 A

  The present invention has been made against the background of the prior art, and it is an object of the present invention to provide a protective mat that is lightweight, easy to handle, shortens the work period, and reduces the risk of spillage of liquid contaminants.

  As a result of diligent research to solve the above problems, the inventors have made a composite material using a special material, which is lightweight and easy to handle, and can easily shorten the work period because it is easy to join multiple sheets. In addition, the inventors have found that a protective mat capable of reducing the risk of spillage of liquid contaminants can be obtained, and the present invention has been completed.

That is, the present invention is as follows.
1. Integrated protection of a nonwoven fabric layer A containing 25% by weight or more of a water-swellable polymer material and a nonwoven fabric layer B having a basis weight of 100 to 800 g / m ² and mainly composed of polyolefin-based or polyester-based polymer fibers mat.
2. A protective mat in which the nonwoven fabric layer C containing 20% by weight or more of water-absorbing fibers is integrated with the protective mat 1 described above.
3. The above 1 or 2 wherein the water-swellable polymer material contained in the nonwoven fabric layer A is an acrylic fiber or a modacrylic fiber having a fineness of 2.2 to 13 dtex and capable of absorbing water and seawater by 50% or more of its own weight. Protective mat as described in.
4). 4. The protective mat according to any one of 1 to 3, wherein the water-swellable polymer material in the nonwoven fabric layer A and / or the water-absorbing fiber in the nonwoven fabric layer C adsorbs or absorbs 0.09 g or more of cesium per 1 g.

  The protective mat of the present invention has high water absorption, light weight, and good handleability, so it is suitable for shortening the construction period of highly urgent construction, and it is possible to absorb liquid contaminated parts and prevent loss to the outside. Become.

  Examples of the water-swellable polymer material used for the nonwoven fabric layer A of the present invention include super water-absorbing polymer powder, water-swellable acrylic fiber and modacrylic fiber. These water-swellable polymer materials can absorb water about 30 to 200 times their own weight, and the water swells to increase the volume. In the case of a nonwoven fabric, about 70 to 90% of the space is normally a space in which fibers do not exist, but an effect of suppressing water permeation is expected by filling the space with a swollen polymer material. When the nonwoven fabric layer A contains 25% by weight or more of the water-swellable polymer material, high water absorption performance can be expected, and when it is 50% by weight or more, water stoppage and water leakage delay can be imparted. In particular, when the water-swellable polymer material is contained in an amount of 65% by weight or more, it becomes possible to capture or stop the liquid that has flowed from the top with a very high probability without flowing downward.

  Super water-absorbing polymer powder, water-swelling acrylic fiber and modacrylic fiber have much higher water absorption performance than bentonite, and can swell about 70% of equilibrium water absorption in about 10 seconds. Even if it flows in, the possibility of causing leakage can be reduced. Since bentonite requires a water absorption time of one day or more, the difference is very large.

  The water-swellable polymer material may be in the form of powder, but it is easy to cause problems such as the powder falling off from the cross section of the mat and the swollen and softened powder being pushed out of the sheet edge by earth pressure. is necessary. When water-swellable acrylic fiber modacrylic fiber is used as the water-swellable polymer material, some water-swelling acrylic fibers and modacrylic fibers have fibers with a core-sheath structure, and the core part swells too much. There is a fiber made of a resin that adsorbs water, and the sheath part is made of a resin that gives a stable mechanical strength without using it. Using these fibers, it is possible to enhance the contaminant outflow function as the protective mat of the present invention. Especially preferred.

  When the water-swellable polymer material is in the form of powder, it is necessary to prevent it from falling off by being sandwiched between a plurality of nonwoven fabrics. After the heat-adhesive powder and water-swellable polymer powder are uniformly mixed, the heat-adhesive powder is melted by a heat treatment such as an air-through method and then uniformly applied to the non-woven fabric as the base material. It is one of the preferred forms to prevent the particles from falling off by attaching them.

  Moreover, in this invention, modifiers, such as an antioxidant, a light-resistant agent, a coloring agent, an antibacterial agent, a flame retardant, a hydrophilizing agent, can be added as needed within the range which does not reduce a characteristic.

  The fineness of the water-swellable fiber that can be suitably used for the nonwoven fabric layer A of the present invention is preferably 2.2 to 13 dtex, more preferably 3.3 to 11 dtex. If the fineness is less than 2.2 dtex, the entanglement of the fibers will be weak, and the strength and penetration resistance of the protective mat will be inferior, resulting in insufficient durability. In addition, the thickness may be reduced and the cushion function as the protective mat may be reduced. On the other hand, if it exceeds 13 dtex, the number of fiber components is reduced, the density of the nonwoven fabric structure is lowered, and the water absorption and water leakage delay as the structure may be lowered. Acrylic fibers and modacrylic fibers are relatively easy to introduce functional groups by chemically modifying the surface functional groups. By selecting the functional groups to be introduced, it is possible to effectively adsorb cesium and the like. .

  In the present invention, if the ratio of the water-swellable polymer material to the surface of the protective mat is too high, care must be taken because the space existing inside the protective mat and the remaining water-swellable polymer material cannot be used. When the ratio of the water-swellable polymer material to the surface of the protective mat is high, non-hygroscopic fibers can be arranged by needle punching or the like so as to penetrate the nonwoven fabric layer A, and water can be diffused from the portion. is necessary. In addition, providing a layer for diffusing moisture in the uppermost layer is also one preferred mode.

The protective mat of the present invention is preferably optimized so that 3 kg / m ² or more of purified water or seawater can be absorbed into the protective mat, and particularly preferably 6 kg / m ² or more can be absorbed.

  The water absorbed by the protective mat can also be expected to play a role in reducing the leakage of radiation to the outside when radiation is generated from materials stored at the disposal site or illegal dumping.

In the nonwoven fabric layer A of the present invention, the other material combined with the water-swellable polymer material is not particularly limited, but it is possible to use a general-purpose thermoplastic resin with a low price such as polyester or polyolefin. Recommended. Polyester fibers are particularly preferable. By using a polyester fiber, it becomes easy to obtain excellent mechanical properties (tensile strength and tear strength) and strength at the time of thermal bonding using a lyster.
Examples of usable polyesters include homopolymers such as polyethylene terephthalate (PET) and polylactic acid (PLA), and copolyesters thereof. In particular, when core-sheath type fiber with isophthalic acid-based copolymer polyester as the sheath component and PET as the core component is used in combination with the water-swellable polymer material, thermal bonding is performed using a lyster or the like to join multiple mats. When it is performed, the workability is good and the risk of water leakage at the joint can be reduced.
Moreover, there is no problem in terms of physical properties even when PET using biologically derived ethylene glycol as a component is used as a polyester monomer.

It is preferable that the fabric weight of the nonwoven fabric layer a of this invention is 150-600 g / m < ² >. If it is less than 150 g / m ² , the water absorption is insufficient, and if it is more than 600 g / m ² , the handleability is lowered, which is not preferable.

The nonwoven fabric layer b of the present invention is preferably a nonwoven fabric having a basis weight of 100 to 800 g / m ² mainly composed of fibers made of polyolefin or polyester resins.
The fiber may be a solid fiber of polyethylene terephthalate (pet) fiber or polypropylene (pp) fiber alone, but includes a composite fiber containing two components of low melting point pet and pet, or two components of polyethylene and pet. One of the preferred embodiments is a composite fiber. The form of the composite fiber may be a core-sheath structure or a side-by-side structure. When it is desired to increase the thickness of the nonwoven fabric layer b, it is also a preferred embodiment to use a fiber having a hollow core-sheath structure or a hollow side-by-side structure.
When using a composite fiber for the purpose of setting adhesive strength and bulkiness to desired values, the fineness of the fiber is preferably 2.2 to 8.9 dtex, more preferably 3.3 to 6.7 dtex. preferable.

The nonwoven fabric layer B of the present invention may be composed of a short fiber nonwoven fabric, or may be a polyester long fiber nonwoven fabric having a high tensile strength and high penetration resistance. A composite of long fiber nonwoven fabric and short fiber nonwoven fabric is also preferable.
Short fiber nonwoven fabrics have excellent cushioning properties, so that high protection performance can be obtained when they come into contact with foreign matter or protrusions. General short fiber nonwoven fabrics are excellent in bulkiness, but have many cut ends of fibers, and therefore often have poor mechanical properties and penetration resistance compared to long fiber nonwoven fabrics or composites of long fiber nonwoven fabrics / short fiber nonwoven fabrics. .

The basis weight of the nonwoven fabric layer B of the present invention greatly affects the penetration resistance. Therefore, the preferable basis weight of the nonwoven fabric layer B is 100 to 800 g / m ² . A more preferable basis weight is 200 to 500 g / m ² , and most preferably 250 to 330 g / m ² . When the basis weight is less than 100 g / m ² , the penetration resistance of the protective mat becomes low. When the basis weight exceeds 800 g / m ² , good workability due to weight reduction is hindered.

In the present invention, it is also preferable that a nonwoven fabric layer C containing 20% by weight or more of water-absorbing fibers is combined and integrated with a protective mat in which the nonwoven fabric layer A and the nonwoven fabric layer B are integrated.
The nonwoven fabric layer c may be bonded to one side of the composite of the nonwoven fabric layer a and the nonwoven fabric layer b, or may be bonded between the nonwoven fabric layer a and the nonwoven fabric layer b.

  The water-absorbing fiber contained in the nonwoven fabric layer C of the present invention is a fiber that can absorb water about 0.5 to 3 times its own weight, and a part of acrylic fiber (for example, n manufactured by Toyobo Co., Ltd.). -38) and cellulosic fibers (part of cotton, rayon, polynosic fibers) having a relatively low crystallinity.

It is preferable that the fabric weight of the nonwoven fabric layer C of this invention is 100-500 g / m < ² >. If it is less than 100 g / m ² , the amount of water absorption will be small, and if it is greater than 500 g / m ^{2, the} workability during laying will be reduced.

The protective mat of the present invention preferably has a thickness of 4 mm or more at a load of 7 g / cm ² . More preferably, it is 6 mm-20 mm. When the thickness exceeds 20 mm, the handleability decreases.

The method for controlling the thickness at a load of 7 g / cm ² to a desired value is not particularly limited. However, when the needle punch method is used for manufacturing the nonwoven fabric layer, the piercing density is increased or the piercing depth is increased. Measures such as can be taken. When the air-through method is used for the production of the nonwoven fabric layer, it is possible to increase the processing temperature, increase the circulating air speed, or perform heat treatment while sandwiched between nets.

  It is also an effective method to contact with a heating roll. An appropriate thickness can be achieved by providing a clearance between the opposing heating rolls. Alternatively, by using a roll on one side made of resin or rubber, it is possible to prevent the thickness from becoming too small due to being crushed without setting a clearance. Moreover, it becomes easy to control thickness by setting hardnesses, such as a resin roll and a rubber roll, appropriately. Although the thickness controllability is inferior, it is also possible to take a method such as indirect heating with a far-infrared heater or the like or contact with a heated bar or plate.

  In needle punching when manufacturing a protective mat or each nonwoven fabric layer, in general, mechanical properties such as tensile strength and tear strength are desired by increasing the piercing density to some extent or increasing the piercing depth. However, it should be noted that if an appropriate condition is exceeded, other problems such as generation of dust and a decrease in strength due to fiber cutting often occur.

  Further, when a calendar roll is used to perform the thermal bonding process, it is considered that the thickness can be easily increased by setting the processing temperature low, increasing the processing speed, or providing a clearance.

Since the Great East Japan Earthquake, the treatment and storage of soil, sediments, and rubble containing radioactive materials has become a problem, and it has become important to reduce the risk of liquid pollutants flowing out from them.
Therefore, it is preferable that the water-swellable polymer material in the nonwoven fabric layer A and / or the water-absorbing fiber in the nonwoven fabric layer C constituting the protective mat of the present invention adsorb or absorb 0.09 g or more of cesium chloride per 1 g. . According to the inventor's study, some of the acrylic fibers or modacrylic fibers have a high function of selectively adsorbing cesium, and furthermore, the higher the water absorption rate, the harder it is to release the trapped contaminants. Therefore, by using these as a material for a protective mat that satisfies the requirements of the present invention, it is possible to carry out the decontamination process more safely.

  The penetration resistance of the protective mat of the present invention is preferably 500 N or more, and more preferably 800 N or more. If the penetration resistance is less than 500 N, the function as a protective mat for the water-impervious work may be deteriorated. Moreover, in the range of examination of this inventor, there existed a tendency for the water stop function to become high, so that a sheet | seat with a high penetration resistance.

The tensile strength of the protective mat of the present invention is preferably 900 to 1500 N / 5 cm, and more preferably 950 to 1200 N / 5 cm.
Moreover, it is preferable that elongation rate is 30% or more, and it is more preferable that it is 50% or more.

An example of a preferred method for producing the protective mat of the present invention will be described below, but the present invention is not particularly limited to this example.
The nonwoven fabric layer A is generally manufactured by a card method and needle punching. When the nonwoven fabric layer A is composed of water-swellable acrylic fiber or modacrylic fiber and a heat-adhesive core-sheath composite fiber, it is preferable to subsequently form a partial heat-bonded portion by an air-through method. The process of the air-through method is particularly suitable as the method for producing the reinforcing material of the present invention because the partial adhesion point can be increased without reducing the thickness. In the case of a heat-bondable core-sheath composite polyester fiber, the processing temperature is preferably about 90 to 150 ° C., and it is possible to obtain a suitable adhesion state by performing heat treatment for 30 to 40 seconds. Become. The setting of the processing temperature can be controlled by the melting point and the mixing ratio of the low melting point component of the thermoadhesive core-sheath composite fiber.

  The nonwoven fabric layer B may be produced by a dry short fiber nonwoven fabric production method or a spunbond method. Alternatively, a short fiber web may be laminated on a long fiber nonwoven fabric by the spunbond method, and then composited by a knee pan processing machine.

  As a joining method of the nonwoven fabric layer A and the nonwoven fabric layer B, a method using a needle punch method, a curtain spray method, a thermal laminating method using a film, and a method of hot pressing by inserting a thermal adhesive fiber nonwoven fabric or a film can be considered.

  When compounding by the needle punch method, it is possible to increase the water stop effect by the water-swellable fiber so that the needle penetrates from the nonwoven fabric layer A side regardless of the nonwoven fabric as the composite partner. Is preferable.

  When the non-woven fabric layer C is further combined, it is also one of preferable modes that the non-woven fabric layer B is first combined with the non-woven fabric layer A by the needle punch method and then combined with the non-woven fabric layer B.

  Among the nonwoven fabric layers constituting the protective mat, the width of the nonwoven fabric layer containing the heat-adhesive fibers is made wider than the width of the other nonwoven fabric layers, and when the nonwoven fabric layers containing the heat-adhesive fibers are thermally bonded, A high water stop effect can be obtained. As a heat bonding method, heating may be performed with a gas burner or the like, or a self-propelled bonding machine (leister) may be used. Also, two-component urethane, asphalt, modified asphalt, other adhesives, etc. may be sprayed or applied to the joint. It is also preferable to use a waterproof tape or the like.

  Moreover, it is one of the preferable forms that the film layer which carried out the slightly adhesion process is stuck on the upper surface of the protection mat of this invention, and it removes after completion of laying. Even if there is a sudden rain during laying work at the site, the swelling of the water-swellable polymer material due to rain can be suppressed, and only the water that contains the pollutant, which is the original purpose, can be absorbed efficiently. This is preferable because it can be performed.

Hereinafter, the present invention will be described more specifically with reference to examples, conventional examples, and comparative examples, but the present invention is not limited to these examples. In addition, the evaluation method used by the Example and comparative example of this invention was performed with the following method.
(1) Fineness [dtex]
Five arbitrary points of the sample were selected, and the single fiber diameter was measured at n = 20 using an optical microscope, and the total average value (D) was obtained. Subsequently, the fineness is expressed by dtex by converting the average single fiber cross-sectional area and the average specific gravity into a weight per 10,000 m.
(2) Weight per unit [g / m ² ]
It was measured according to JIS L 1913 (2010) 6.2 “mass per unit area”.
(3) Thickness [mm]
According to JIS L 1913 (2010) 6.1.1 “Thickness A method”, measurement was performed under a load of 7 g / cm ² .
(4) Tensile strength [N / 5cm] and elongation [%]
Measured according to JIS L 1913 (2010) 6.3.1 “Tensile strength and elongation”.
(5) Penetration resistance (N)
Measured according to ASTM D-4833.
(6) Shading rate (%)
Measured according to JIS L 1055 (2009) Method A.
(7) Cesium adsorption amount (g / g-sample)
100 mg of a sample was added to a solution obtained by adding 100 mg of cesium chloride to 100 ml of pure water, and the mixture was stirred with a stirrer for 24 hours. The liquid was filtered, and the Cs concentration of the residual liquid was measured by a high frequency inductively coupled plasma method (ICP method) emission spectrometry (using a CIROS-120 RIGAKU apparatus). The concentration was measured using a calibration curve prepared in advance, and the adsorption amount per 1 g of the sample was measured from the difference from the initial concentration.
(8) Water absorption rate (%)
Filter paper was laid on a flat sandbox not exposed to direct sunlight to prevent the sand from adhering to the protective mat, and a 1 m square protective mat was laid on the flat sand pit so as not to bend. 6 kg of seawater was poured into a substantially central portion of the protective mat with a bucket, and the increase in the weight of the mat was measured after 3 hours. It was measured how much of the seawater that flowed into the bottom filter paper or sand layer.
The water absorption was calculated by the following formula.
Water absorption (%) = (Protective mat weight after 3 hours−Original protective mat weight) / 6 kg × 100

<Example 1>
As non-woven fabric layer A, water-swellable acrylic fiber Runseal FK (Toyobo Co., Ltd., cesium chloride adsorption amount 0.40 g / g-sample) having a fineness of 3.9 dtex and 5.5 dtex low melting point polyester composite short fiber TE5 A 200 g / m ² short fiber nonwoven fabric obtained by needle punching a web mixed with Toyobo Co., Ltd. at a weight ratio of 70:30 and a nonwoven fabric layer C as a water absorbent acrylic with a fineness of 4.4 dtex. Fiber 50-50 by weight ratio of fiber N-38B (Toyobo Co., Ltd., cesium adsorption amount 0.51 g / g-sample) and 5.5 dtex hollow acrylic short fiber (Toyobo Co., Ltd.) A needle-punched 200 g / m ² basis weight non-woven fabric obtained by needle punching a mixed web is used to make a needle protrusion using an FPD1-40S needle manufactured by Organ. The needle punch composite processing was performed at a stab density (projection density) of 45 / cm ² and a needle depth of 10 mm to obtain a two-layered nonwoven fabric. Next, as the nonwoven fabric layer B, a polyester long fiber nonwoven fabric 9201HB (made by Toyobo Co., Ltd., containing 0.3% carbon as a colorant) having a basis weight of 200 g / m ² is joined to the nonwoven fabric layer A side by the curtain spray method (olefin type). A protective mat made of a non-woven fabric having a three-layer structure made of 10 g / m ^{2 of} hot melt fiber was prepared.
The evaluation results using the obtained protective mat are shown in Table 1.
Example 1 was a protective mat satisfying the requirements of the present invention and having excellent mechanical properties. The water absorption was 100%.

<Example 2>
As the nonwoven fabric layer A, a water-swellable acrylic fiber run seal FJ (manufactured by Toyobo Co., Ltd., cesium chloride adsorption amount 0.46 g / g-sample) having a fineness of 5.6 dtex and a low-melting-point polyester composite short fiber TE5 having 5.5 dtex a short fiber nonwoven fabric mixed web to be 35:65 by weight ratio (Toyobo Co., Ltd.) needle punch processed having a basis weight of 300 g / ^{m 2,} as a non-woven fabric layer B, a basis weight of 300 g / ^{m 2} Polyester long fiber nonwoven fabric 9301HB (manufactured by Toyobo Co., Ltd., containing 0.3% carbon as a colorant) joined by curtain spray method (using olefin-based hot melt fiber 10 g / m ² ), a protective mat comprising a two-layer nonwoven fabric It was created.
The evaluation results using the obtained protective mat are shown in Table 1.
Example 2 was a protective mat that satisfied the requirements of the present invention and had excellent mechanical properties. The water absorption was 100%.

<Example 3>
As the nonwoven fabric layer A, a weight ratio of polyethylene resin powder and water-swellable hygiene hot melt powder (both particle size is about 1 mm) to 100 g / m ² short fiber nonwoven fabric made of polyester fiber with a fineness of 5.6 dtex The mixture was uniformly mixed so as to be 60:40 and sprayed so that the spray amount was 200 g / m ² . Next, as a non-woven fabric layer C, water-absorbing acrylic fiber N-38B having a fineness of 4.4 dtex (produced by Toyobo Co., Ltd., cesium adsorption amount 0.51 g / g-sample) and 5.5 dtex of hollow acrylic short 100 g / m ² basis weight, which is a needle punched web mixed with fibers (manufactured by Toyobo Co., Ltd.) at a weight ratio of 50:50, is overlaid with short fiber nonwoven fabric and heated at a temperature of 160 ° C. with a felt calender machine. Processed and integrated. Furthermore, as the nonwoven fabric layer B, a protection comprising a nonwoven fabric having a three-layer structure in which a polyester long fiber nonwoven fabric 9301HB having a basis weight of 300 g / m ² is joined to the nonwoven fabric layer A side by curtain spray method (using 10 g / m ² of olefin-based hot melt fiber). Made a mat.
The evaluation results using the obtained protective mat are shown in Table 1.
Example 3 was a protective mat satisfying the requirements of the present invention and having excellent mechanical properties. The water absorption was 100%.

<Conventional example>
Table 1 shows the evaluation results using a polyester long fiber nonwoven fabric 9551HB (manufactured by Toyobo Co., Ltd.) having a basis weight of 550 g / m ² as a protective mat.
The conventional example was a protective mat excellent in mechanical properties, but the water absorption was 8%, and most of the water flowed out to the filter paper and sandy layer, so that the object of the present invention was not satisfied.

<Comparative Example 1>
Results obtained by performing the same evaluation as in Example 1 using a commercially available bentonite sheet having a basis weight of 5600 g / m ² (catalog value) (polypropylene non-woven fabric with a skin attached, cesium adsorption amount 0.087 g / g-sample) Table 1 shows.
In Comparative Example 1, the water absorption was 45%, which was mainly due to water flowing out from the end of the mat, the lower filter paper was not wet, and there was no permeation of seawater. Because of its heavy weight, it took time to lay and there was concern about water leakage at the connecting surface of multiple sheets.

<Comparative example 2>
Runseal FJ of water-swellable acrylic fiber with a fineness of 3.9 dtex (Toyobo Co., Ltd., cesium adsorption amount 0.46 g / g-sample) and 5.5 dtex low melting point polyester composite short fiber TE5 (Toyobo Co., Ltd.) ) And a short fiber nonwoven fabric having a basis weight of 200 g / m ² and a water-absorbing acrylic fiber N-38B having a fineness of 3.3 dtex (Toyobo Co., Ltd.) Made of cesium chloride adsorbed by 0.51 g / g-sample) and 5.5 dtex hollow acrylic short fiber (manufactured by Toyobo Co., Ltd.) at a weight ratio of 50:50. 200 g / m ² of short fiber nonwoven fabric, needle piercing density (protrusion density) of 45 / A needle punch composite process was performed at cm ² and a needle depth of 10 mm to obtain a two-layered nonwoven fabric. Next, a three-layer structure in which a white polyester long fiber nonwoven fabric 9201H (manufactured by Toyobo Co., Ltd.) with a basis weight of 200 g / m ² is joined to the nonwoven fabric layer A side by curtain spray method (using olefin-based hot melt fibers 10 g / m ² ). A protective mat made of non-woven fabric was prepared.
The evaluation results using the obtained protective mat are shown in Table 1.
Comparative Example 2 was a protective mat excellent in mechanical properties, but the water absorption was 38%.

  The protective mat of the present invention has good water absorption and water shielding sheet protection performance, is lightweight and has excellent workability, and can further contribute to reducing the risk of liquid contaminants flowing out. It can also be used as a sheet for storage and storage of rubble containing liquid contaminants in which radioactive substances are suspended.

Claims (4)

Integrated protection of a nonwoven fabric layer A containing 25% by weight or more of a water-swellable polymer material and a nonwoven fabric layer B having a basis weight of 100 to 800 g / m ² and mainly composed of polyolefin-based or polyester-based polymer fibers mat.   A protective mat in which a nonwoven fabric layer C containing 20% by weight or more of water-absorbing fibers is integrated with the protective mat according to claim 1.   The water-swellable polymer material contained in the nonwoven fabric layer A is an acrylic fiber or modacrylic fiber having a fineness of 2.2 to 13 dtex and capable of absorbing water and seawater by 50% or more of its own weight. 2. The protective mat according to 2.   The protective mat according to any one of claims 1 to 3, wherein the water-swellable polymer material in the nonwoven fabric layer A and / or the water-absorbing fibers in the nonwoven fabric layer C adsorb or absorb 0.09 g or more of cesium per 1 g.