JPH101930A - Sheet for preventing water evaporation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase durability by stacking a skin layer having excellent reflecting properties to visible rays or ultraviolet rays onto a surface on the atmospheric air side of a suspension layer consisting of a foamed sheet. SOLUTION: A sheet 1 for preventing water evaporation is composed of integrally stacking a skin layer 1a located on the atmospheric air side and a suspension layer 1b located on the water side. The skin layer 1a is formed of a plastic sheet having metallic luster such as a polyester film sheet plated with porous oriented polytetrafluoroethylene or aluminum or a metallic foil such as an aluminum foil, and the suspension layer 1b is formed of a foamed sheet material floated on water. The sheet 1 is floated on the water surface of a storage reservoir A, etc., and the water surface is covered while the sheet 1 is fixed by a weight 2, etc., and the evaporation of water is inhibited, and deterioration by ultraviolet rays, etc., of the sheet 1 is prevented by the skin layer la. When an ecosystem in water must be considered, a large number of small-diametral through-holes are formed to the whole surface of the sheet 1. Accordingly, weather resistance can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet for preventing water from evaporating, for example, irrigation water or drinking water stored in a dam or a reservoir.

[0002]

2. Description of the Related Art In the above-mentioned reservoirs, especially in the reservoirs on the southern islands, there is a demand to prevent any water loss due to evaporation from the water surface. As a countermeasure, it has been proposed to install a water evaporation preventing sheet on the water surface of the reservoir.

For example, Japanese Patent Application Laid-Open No. 50-97130 discloses that a floatable rod is provided on a back surface of a seat curtain having so-called durability such as deterioration resistance, weather resistance, heat resistance, etc. It is proposed that the sheet curtain be opened and floated so as to cover the water surface by mounting at intervals or by stretching a material having a low specific gravity such as a synthetic resin foam over the entire back surface. I have. It is disclosed that the sheet curtain is strong and suitable for conditions such as deterioration resistance, weather resistance, heat resistance, etc., and the specific kind of material is not mentioned. Also, the invention focuses on minimizing spontaneous evaporation due to solar heat and wind power, and makes no mention of effects on aquatic ecosystems.

Further, Japanese Patent Laid-Open No. 4-131417 discloses
It has been proposed to cover the water surface using a sheet of foamed polyethylene or the like as the sheet for preventing water evaporation as described above. The invention cites foamed polyethylene as a concrete sheet curtain material, and the foamed polyethylene itself is lightweight and floats in water, is resistant to alteration, and has semi-permanent durability.
It emphasizes that it is suitable for use as a water evaporation prevention sheet because of its advantages such as being impermeable to air, being flexible and easy to handle, and the like. That is, it has been proposed to use a foamed sheet material typified by foamed polyethylene as it is as a water evaporation prevention sheet. Since such a water evaporation prevention sheet itself is lightweight and flexible, it can be handled when the sheet curtain is stretched. It emphasizes the effects that are easy.

[0005]

The technical problems that have not yet been solved in these prior arts are as follows. For example, the UV durability and weather resistance of ordinary foam materials typified by foamed polyethylene are not so good as to withstand long-term outdoor use. Therefore, how to improve the durability of the sheet curtain itself has been a technical problem to be solved in the water evaporation preventing sheet. The present invention solves the above-mentioned problem of the conventional technique of improving the durability of a foamed sheet material used as such a floating material against ultraviolet rays. That is, the present invention provides a water evaporation preventing sheet in which the durability of a foamed sheet material used as a floating material against ultraviolet rays is improved.

[0006]

SUMMARY OF THE INVENTION The present invention solves the problem of the prior art of improving the durability of a water evaporation preventing sheet. That is, the present invention, in order to solve this technical problem, as described below, an excellent weather resistance itself as a skin layer on the atmosphere side surface of the foam sheet material, a film material excellent in reflection of light rays or ultraviolet rays. By laminating and fixing on the surface of the foamed sheet material, the foamed sheet material having inferior UV durability is protected and the weather resistance as the water evaporation preventing sheet is improved. Further, the present invention provides a stretched porous polytetrafluoroethylene (eP) as a film material which is itself excellent in weather resistance and excellent in light or ultraviolet ray reflection.
TFE. It should be noted that PTFE simply means polytetrafluoroethylene. ) It is shown that a film or a plastic sheet having a metallic luster, for example, a polyester film sheet plated with aluminum or a metal foil such as an aluminum foil is suitable as a material for the skin layer.

More specifically, the water evaporation preventing sheet of the present invention is a plastic sheet having a metallic luster such as a pure white ePTFE film or an aluminum-plated polyester film sheet, or a metal foil such as an aluminum foil. As a skin layer having excellent reflectivity to visible rays or ultraviolet rays, is laminated and fixed on the air side of the foamed sheet material, which is a floating layer, by means such as adhesion or fusion.

[0008] In the present invention, the above-mentioned skin layer contains ePT.
An FE film sheet, a plastic sheet having a metallic luster, or a metal foil is used as the most suitable one. The material of the foam sheet used for the floating layer is not particularly specified as long as it does not react with water (for example, swell) and has a bulk density of 1 or less (that is, floats on the water surface). A foamed sheet made of a homopolymer resin such as polyethylene, polypropylene, polyolefin such as polybutene, polyvinyl acetate, polyester such as polyethyl acrylate, polyacrylic acid, polyurethane, and polyethermelamine, or a sheet constituting these resins A foamed sheet made of a copolymer composed of a combination of two or more of a monomer and another monomer is used as a typical example.

[0009]

A plastic sheet having a metallic luster, such as an ePTFE film or an aluminum-plated polyester film sheet, or a metal foil such as an aluminum foil is laminated on the surface of a floating layer made of a foam sheet as a skin layer. Durability can be improved. This is because the whiteness of the ePTFE film and the metallic luster of a metal foil such as an aluminum-plated polyester film sheet or an aluminum foil reflect ultraviolet light, and its shielding effect significantly reduces ultraviolet light deterioration of the foam sheet. ePTFE is a unique fine fibrous structure as will be described later, and its surface area is very large, so that it has a large effect of totally reflecting light rays including ultraviolet rays, and as a result, protects the lower foam sheet material from ultraviolet rays. The effect becomes particularly large.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A water evaporation preventing sheet according to the present invention will be specifically described below with reference to the embodiment shown in the drawings. FIG. 1 is a longitudinal sectional view showing a state in which a sheet for preventing water evaporation according to the present invention is installed in a reservoir, and FIG. 2 is an enlarged sectional view of a part of the sheet for preventing water evaporation.

In the figure, reference numeral 1 is a water evaporation preventing sheet installed on the water surface of a reservoir A, and the sheet 1 comprises a skin layer 1a located on the atmosphere side and a floating layer 1b located on the water side. The skin layer 1a is a plastic film having a metallic luster such as an ePTFE film or a polyester film sheet plated with aluminum, or a metal foil such as an aluminum foil.

In particular, the ePTFE film is excellent in flexibility and light in weight, can be easily laminated with a foamed sheet material by adhesion, fusion or the like, and can be colored. It is the most preferred material for the layer.

The above-mentioned ePTFE film is produced by a production method described in, for example, JP-B-53-39719 and JP-B-51-18991, and the fine structure thereof is also known together with the production method. Specifically, the ePTFE film is basically a mixture of PTFE fine powder and a lubricating aid such as petroleum naphtha. A paste molding is extruded through a die, and the obtained tape-shaped extrudate is heated. After the lubricant aid is removed by evaporation, it is produced by uniaxially or biaxially stretching at a high temperature below the melting point of PTFE. In addition, in order to fix the microstructure generated by stretching and improve dimensional stability, a baking treatment may be performed in which after stretching, heating is performed at a temperature equal to or higher than the melting point of PTFE while the stretched state is fixed, followed by cooling. . However, in the ePTFE film of the present invention, the final baking treatment is not always essential.

The ePTFE film produced in this manner is a pure white film having a marshmallow-like feel and a very soft feel. When the film is observed with an electron microscope, it is found that both the surface and the inside are formed of fibrils (small fibers) and nodes (nodules) connecting them, and have a unique fibrous porous body structure. In ePTFE, a space called a "hole" partitioned by these fibrils and nodes exists inside the structure,
Since these spaces (holes) are continuous from the front surface to the back surface of the film, they have air permeability. The structural form of the fibril / node structure changes depending on the stretching direction and the stretching ratio. For example, when stretched in the uniaxial direction, the fibrils are formed into a comb shape oriented in one direction, and the nodes connecting the fibrils are observed as elongated islands perpendicular to the stretching direction. On the other hand, when stretched in the biaxial direction, the fibrils spread radially, and the nodes connecting them are observed as fine particles rather than islands. In addition, when the draw ratio is increased, the fibril becomes longer and the node shape becomes relatively smaller,
Ultimately, it becomes a so-called nodeless structure consisting of only fibrils. The bulk density of ePTFE film is pure P
It is smaller than the density of the TFE solid body and depends on the porosity, but is often smaller than the density of water. Therefore, when the ePTFE film is used as the water evaporation preventing sheet of the present invention, there is an advantage that the buoyancy of the floating layer is not impaired.

The ePTFE is made of pure PTFE, and both the fibrils and nodes characterizing the structure are PTFE. PTFE is a chemically very stable resin, and has weather resistance, UV resistance, heat resistance, cold resistance,
It is well known as a material excellent in water resistance and the like. Therefore,
ePTFE is essentially PTFE itself, has excellent chemical stability, is not oxidized by air, and is resistant to ultraviolet light. Also,
Since PTFE is not synthesized in nature, it is not eroded by bacteria.

Moreover, ePEFE has an outstanding pure white color and has an excellent shielding effect against ultraviolet rays.
It is considered that this is due to the total reflection phenomenon derived from the microporous structure of ePTFE. On the other hand, the solid PTFE film has a transparent or ground glass-like milky white color, and thus easily transmits ultraviolet light, and is therefore inferior to the ePTFE film in the ultraviolet light shielding effect.

Further, PTFE has no affinity with other substances and is generally considered to be a material that is difficult to adhere to.
Since PTFE has a porous structure, it can be easily adhered and fused by the so-called anchor effect.

Further, the ePTFE film has a marshmallow-like feel and has a strong plastic property that can conform to the shape of another object in contact in any manner. PTFE
Is generally a rigid polymer, but the flexible nature of ePTFE is believed to be due to its unique fibrous structure. Therefore, even if the ePTFE film and the foamed sheet material are laminated, the expansion and contraction of the foamed sheet can be easily followed and curling hardly occurs. However, since its fibrous structure is a network structure consisting of a unitary structure in which all nodes are connected by fibrils, it also has an elastic recovery force that is extremely gentle against deformation, which makes it easy to perform appropriate lamination processing. It also causes

In the present invention, the thickness of the skin layer 1a is 3 to 3
It is desirable to be in the range of 00 μm. This is determined based on the case where an ePTFE film is used for the skin layer, but considering the cost balance with the productivity as a water evaporation preventing sheet and the actual effects such as ultraviolet ray shielding property and durability. , More preferably 10 to 150 μm, and further preferably 20 to 100 μm. In addition, when this thickness is defined particularly in the case of ePTFE film, the average thickness measured with a dial gauge (when measured using a 1/1000 mm dial thickness gauge manufactured by Technolock Co., Ltd., without applying a load other than the main body spring load) ). When the thickness is less than 3 μm, sufficient mechanical strength and durability cannot be obtained, and lamination processing becomes difficult. Conversely, if it exceeds 300 μm, the productivity is poor and the material cost is high, so that it cannot be said that the cost is appropriate.

The color tone of the skin layer 1a may be appropriately selected from the viewpoint of aesthetics or environmental atmosphere. Generally, white or metallic colors reflect sunlight and ultraviolet rays better than dark colors,
It is considered preferable that the surface temperature of the evaporation prevention sheet can be kept relatively low even in the summer, so that the thermal deterioration of the floating layer 1b can be reduced. E as the skin layer 1a
When a PTFE film is used, this film is pure white and reflects well sunlight and ultraviolet rays. Even in summer, the surface temperature of the sheet for preventing evaporation is suppressed to around 60 ° C, and water evaporation is effectively suppressed to reduce the foaming sheet material. Deterioration can be prevented.

In the case where pure white or stimulating color of metallic luster or appearance is disliked from the viewpoint of environmental atmosphere, colored ePT
An FE film may be used. As a method of coloring ePTFE, a pigment is mixed in advance at the time of mixing an auxiliary agent into PTFE fine powder for ePTFE production, and ePTFE is mixed.
A method of burying a pigment in pores of ePTFE, a method of burying a pigment in pores of ePTFE by applying a solvent-based pigment by applying a solvent-based pigment after forming a film, Examples thereof include a method of dipping in a bath and immersing the pigment in the pores of the film.

Next, as the floating layer 1b, any foam sheet material that floats on water can be used as appropriate, but a single layer such as polyethylene, polypropylene, polybutene, polyvinyl acetate, polyethyl acrylate, polyacrylic acid, polyurethane or melamine can be used. Examples thereof include a foamed sheet made of a resin composed of a polymer or a copolymer composed of a monomer constituting the resin and another monomer. Above all, polyolefin foam sheets such as polyethylene and polypropylene are excellent in water resistance and inexpensive,
Most preferred.

The thickness of the floating layer 1b is preferably in the range of 1 to 50 mm, taking a polyethylene foam sheet as an example. 2-10mm considering workability, cost, etc.
Are preferred. If it is less than 1 mm, the buoyancy and mechanical strength are insufficient, and if it exceeds 50 mm, it is flexible,
It is not preferable because it is inferior in portability and increases in cost and weight.

Although the expansion ratio of the polyethylene foam sheet is not particularly limited, it is 5 to 50 times, and more preferably 1 to 50 times.
It is suitable from the viewpoint of required buoyancy, that is 0 to 40 times. If the expansion ratio is too small, the layer becomes too hard, winding becomes difficult, and continuous lamination processing becomes difficult. When the expansion ratio is increased, the production becomes difficult, and the handling becomes difficult due to insufficient mechanical strength. Considering these, it is preferable that the expansion ratio of the polyethylene foam sheet is 10 to 40 times.

As for the lamination of the skin layer 1a and the floating layer 1b, an evaporation preventing sheet can be appropriately used whether it is a bonding process or a fusing process as long as the skin layer 1a and the floating layer 1b can be completely integrated. Is used in an extremely severe environment exposed to water and exposed to the natural environment, so that an adhesive-free fusion process is more preferable. Since a frame bonding process can be applied to a foamed sheet, the fusion bonding process is easy. Further, if an ePTFE film is used as the skin layer 1a, there is an advantage that flame bonding with a foam sheet material can be easily performed.

Polyethylene foam sheet and ePTFE
Taking the case of fusing the film by frame bonding processing as an example, immediately after the polyethylene foam sheet is annealed by a flame, the flame annealed surface of the polyethylene foam sheet and the ePTFE film are pressure-bonded to each other so that they are melted by a flame. The so-called anchor effect, in which the polyethylene resin enters into the micropores of the ePTFE film and a part of the polyethylene resin penetrates into the structure of the ePTFE, so-called anchor effect, maintains a tightly and stably bonded state for a long time. It will be.

When it is necessary to consider aquatic organisms such as fish and microorganisms and aquatic ecosystems such as plants, a water evaporation preventing sheet having a large number of small through holes is used or is not provided. In such a case, the through-hole may be formed by an appropriate means. The opening ratio of these through holes to the sheet surface may be appropriately selected depending on the usage environment of the evaporation preventing sheet, but is practically 80% or less, more preferably 50% or less, and further preferably 30% or less. It is desirable.
If the porosity exceeds 80%, the mechanical strength becomes insufficient,
The handling and construction become difficult, and the permeation of water vapor becomes large, so that the object of the present invention cannot be achieved.
In short, the porosity is determined within a range where there is no effect on the aquatic ecosystem and within a range in which water vapor transmission can be effectively reduced based on a balance between the water vapor transmission rate and the air transmission rate.

Next, an example of a specific form of use or a method of using the water evaporation preventing sheet according to the present invention will be described. Sheet 1 for preventing water evaporation, which comprises the skin layer 1a and the floating layer 1b
Although the overall planar shape and size are appropriate, for example, the water evaporation preventing sheet 1 is formed in a rectangular shape having a predetermined size in advance and arranged vertically and horizontally on the water surface of the reservoir. Alternatively, the water vaporization prevention sheet 1 may be provided with a predetermined width (for example, 1
(Approximately 10 m) to form a long strip, cut it into a predetermined length according to the length of the reservoir, etc., and arrange a plurality of them in the width direction so as to cover almost the entire surface of the reservoir. What should I do?

By installing the water evaporation preventing sheet 1 formed by integrally joining the skin layer 1a and the floating layer 1b on the water surface of the reservoir A as shown in FIGS. By the buoyancy of the floating layer 1b made of a material, the water evaporation preventing sheet 1 covers the water surface in a state where it is always floating above the water surface, and evaporation from the water surface can be reduced. Also,
By providing the weather-resistant skin layer 1a on the upper surface of the floating layer 1b, it is possible to prevent the skin layer 1a as well as the floating layer 1b from being deteriorated or damaged by ultraviolet rays from the sun. In particular, when an ePTFE film is used as the skin layer 1a as in the above embodiment, it has various excellent properties such as UV resistance, heat resistance, cold resistance, water resistance, and flexibility as well as weather resistance as described above. Accordingly, the present invention provides a water-evaporation-preventing sheet having good durability irrespective of weather, temperature, and the like in an area where the apparatus is installed.

It is desirable that the water evaporation preventing sheet 1 installed on the water surface of the reservoir as described above is provided with an appropriate fixing means so as not to be moved by wind or waves. 1 and 2 use a weight 2 such as a concrete block as the fixing means. The weight 2 is sunk at a desired position on the bottom of the reservoir A, and the weight 2 and a sheet for preventing water evaporation are provided. 1
Are connected by a rope 3 such as a wire rope.

The lower end of the cord 3 is connected to an inverted U-shaped locking rod 2a embedded in the weight 2 as shown in FIG. 3, and the upper end of the cord 3 is water vaporized via a stopper 4. It is fixed to the prevention sheet 1. 1 to 3, the stopper 4 is formed in a rivet shape having a flange portion 4a at an upper portion, and the shaft portion 4b is pierced into the water evaporation preventing sheet 1, and the shaft portion 4b is formed.
The cord 3 is inserted into and connected to the locking hole 4c formed in 1. Reference numeral 4d is a concave-convex shape that is formed on the shaft portion 4b to prevent slipping off.

The shape and the like of the above-mentioned stopper 4 can be appropriately changed. For example, as shown in FIG. 4, a lightening hole 4e may be formed in the flange portion 4a. Further, for example, as shown in FIG. 5, an eye nut-shaped receiver 5 having a flange portion 5a at one end and a locking hole 5b for the cord 3 at the other end may be used together with the stopper 4 configured substantially the same as above. Good. The receiver 5 is
A receiving hole 5c of the stopper 4 is formed at an upper portion, and a shaft 4b of the stopper 4 is inserted into the receiving hole 5c to thereby form a flange 4c.
This is a configuration in which a sheet 1 for preventing water evaporation is sandwiched between a and 5a.

Further, for example, as shown in FIG. 6, a male screw 4f is formed on the shaft portion 4b of the stopper 4 and screwed into a cylindrical nut 6 having a flange 6a to thereby form both flanges 4a and 6a.
The water evaporating prevention sheet 1 may be sandwiched between the nuts a, and an eyebolt 7 may be screwed into the lower end of the nut 6 to connect the rope 3 to a locking hole 7a of the eyebolt 7.

When the water vaporization prevention sheet 1 is to be transported to the site, for example, in the case of the above-mentioned rectangular sheets, it is sufficient to transport them in a state of stacking a plurality of sheets. For example, the sheet 1 may be transported to the site in a state of being wound up in a roll shape, and the sheet 1 wound up in a roll shape may be placed while being sequentially fed out onto the water surface.

Further, in moving the water evaporation preventing sheet 1 on the water surface of the reservoir, when the reservoir is large in area and installation from the land is difficult, for example, as shown in FIG. 7, the boat B is towed. You can set it up. 8 in the figure
Is a rope for towing, and 9 is a bracket for connecting the rope 8 to the sheet 1 for preventing water evaporation.
As shown in FIG. 8, the water evaporation preventing sheet 1 is sandwiched between a pair of upper and lower attachment plates 91 and 92, and is fastened and fixed with bolts 93 and nuts 94 with flanges.

The water evaporation preventing sheets 1 arranged on the water surface of the reservoir as described above are connected and fixed to each other by an appropriate connecting means so that no gap is formed between the adjacent sheets and the sheets do not overlap each other. Is desirable. The connecting means is appropriate. For example, as shown in FIG. 9 and FIG.

Example 1 As the floating layer 1b of the water evaporation preventing sheet according to the present invention, a closed cell polyethylene foam sheet (30 times foamed product, thickness 10 mm, cream color) manufactured by Furukawa Electric Co., Ltd. was used. In addition, the skin layer 1a
As an uncolored, white ePTFE film (thickness 6
0 μm, maximum pore size 0.2 μm) was used.

In order to obtain the sheet for preventing water evaporation according to the present invention, an ePTFE film constituting the skin layer 1a was laminated and fixed to the polyethylene foam sheet constituting the floating layer 1b by frame bonding. That is, the polyethylene foam sheet was burned with a flame, and the two layers were fused and fixed by pressing an ePTFE film on the surface burned with the flame. The processing speed was 5 m / min.

The ePTFE film used in this example was measured for UV shielding rate by the unified evaluation method for the processing effect of UV blocking materials (Japan Chemical Fiber Inspection Association).
It was 6%.

[Comparative Example 1] As Comparative Example 1 with respect to Example 1 above, a closed-cell foamed polyethylene foam sheet (30-fold foamed product, thickness: 10 mm, cream color) manufactured by Furukawa Electric Co., Ltd. of the same material as the floating layer 1b Alone was used as a sheet for preventing water evaporation.

The results of comparative evaluation of the weather resistance of Example 1 and Comparative Example 1 according to the present invention are shown below. The test method is JIS
According to an outdoor exposure test based on Z 2381, two samples of the sheet for preventing water evaporation according to Example 1 and Comparative Example 1 were used.
An exposure test was conducted by exposing it outdoors for one year. As a result, 2
Observation of each sheet after one year, the sheet of Comparative Example 1 had a brittle surface, markedly deteriorated resin, and had a remarkable decrease in strength, whereas the laminated sheet of Example 1 had a skin layer 1a. No deterioration was observed in the ePTFE film, the strength of the laminated sheet was slightly decreased, and the laminated sheet was in a good state without peeling.

From the above results, according to the present invention, ePTF
Due to the ultraviolet shielding effect of the skin layer 1a made of the E film, deterioration of the floating layer 1b made of a polyethylene foam sheet due to ultraviolet rays can be favorably prevented, and the weather resistance of the floating layer 1b can be improved to a necessary and sufficient level. It could be confirmed.

[0043]

As described above, the water evaporation preventing sheet of the present invention is an ePT having excellent ultraviolet shielding effect and excellent weather resistance.
A floating layer 1b made of a foamed sheet is laminated and fixed to a skin layer 1a made of a metal foil such as an FE film sheet or an aluminum-plated polyester film sheet having a metallic luster or an aluminum foil by adhesion or fusion. Consisting of The skin layer 1a itself has excellent weather resistance and shields ultraviolet rays, so that it is possible to prevent ultraviolet deterioration of the foam sheet of the lower floating layer 1b, and at the same time provide a water evaporation preventing sheet that can withstand long-term use. .

It should be noted that a large number of through holes having a small hole diameter may be provided on the entire surface of these water evaporation preventing sheets. In this case, it is possible to prevent the loss of water due to evaporation of water resources such as dams and reservoirs while maintaining the survival of the aquatic ecosystem while maintaining a balance between air permeation and water vapor permeation.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view of a water evaporation preventing sheet according to the present invention installed in a reservoir.

FIG. 2 is an enlarged vertical sectional view of a part thereof.

FIG. 3 is a perspective view of an example of fixing means for preventing movement of a water evaporation preventing sheet.

FIG. 4 is a perspective view showing a modified example of a stopper of a fixing cord of a water evaporation preventing sheet.

FIG. 5 is a cross-sectional view showing another modification of the stopper.

FIG. 6 is an exploded view showing still another modification of the stopper.

FIG. 7 is a perspective view of a state in which the water evaporation preventing sheet is towed by a boat or the like.

FIG. 8 is an enlarged view of a part thereof.

FIG. 9 is a perspective view showing an example of means for connecting adjacent water evaporation preventing sheets.

FIG. 10 is an enlarged cross-sectional view of the main part thereof.

[Explanation of symbols]

 1 Water Evaporation Prevention Sheet 1a Skin Layer 1b Floating Layer 2 Weight 3 Rope 4 Stopper A Reservoir

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyofumi Imai 3-2-17 Nishitenma Kita-ku, Osaka City, Osaka Prefecture KFC Co., Ltd.

Claims (6)

[Claims] 1. A water evaporation preventing sheet used for preventing natural evaporation of water by floating on a water surface of a dam, a reservoir, or the like, wherein the skin layer has excellent reflectivity to visible light or ultraviolet light. A sheet for preventing water evaporation, comprising a structure laminated on a floating layer made of a foamed sheet. 2. The water evaporation preventing sheet according to claim 1, wherein the skin layer is a porous stretched polytetrafluoroethylene (ePTFE) sheet. 3. The sheet for preventing water evaporation according to claim 1, wherein the skin layer is a plastic sheet having a metallic luster or a metal foil. 4. The sheet for preventing water evaporation according to claim 3, wherein the plastic sheet having a metallic luster is a polyester film sheet plated with aluminum. 5. The water evaporation preventing sheet has a large number of small through holes on substantially the entire surface thereof.
The water evaporation prevention sheet according to 3 or 4. 6. The water evaporation preventing sheet according to claim 1, further comprising fixing means for preventing the movement of the sheet.
6. The water evaporation preventing sheet according to 4 or 5.