JPH07108561B2 - Heat-sealable waterproof sheet and its sewing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sealable waterproof sheet, and more particularly to a heat-sealable waterproof sheet having excellent stain resistance and weather resistance, and a sewing method using the same.

[0002]

2. Description of the Related Art Conventionally, for example, a flexible sheet having a soft vinyl chloride (PVC) resin layer on one or both sides of a fibrous base fabric has been used for a large tent such as an air dome.
Such a sheet has advantages peculiar to PVC in terms of processability, economical efficiency, flameproofness, etc. On the other hand, since such a tent is exposed to the outdoors for a long time,
Even if the stabilizers, etc. to be blended are thoroughly examined, the resin gradually decomposes over the years, or the plasticizer migrates to the surface and the surface gradually becomes sticky.
In addition, there is a serious defect that dust or the like adheres to the surface and is contaminated.

As a countermeasure against this, an acrylic resin film layer is formed on the upper surface of the PVC layer to cover the drawbacks of the conventional laminated product having only the PVC layer and obtain a predetermined effect. However, depending on the condition of use of the laminated product, cracking may occur in the acrylic resin film layer under conditions such as strong rubbing, resulting in a marked reduction in the useful life of the laminated product. Has not yet reached.

However, the surface of such a laminated sheet is constituted by sticking a film made of vinylidene fluoride resin / acrylic resin / PVC resin, and the vinylidene fluoride resin layer is used as the outer surface, A method for improving weather resistance and stain resistance was found. When such a waterproof sheet is sewn with a sewing machine, water leaks from the seams, and because the sewing efficiency of the sewing machine is poor, high-frequency or hot air is often used to perform heat-sealing. However, even if it is attempted to join the laminated sheet having the vinylidene fluoride resin layer as the outer surface by using the heat-sealing method, the vinylidene fluoride resin layer does not adhere, and therefore this sheet is also required to be further improved. By the way.

[0005]

DISCLOSURE OF THE INVENTION The present invention is a very useful waterproof sheet having excellent antifouling property and weather resistance, capable of being heat-sealed and having a durable antifouling property. Is to provide. The present invention also seeks to provide a method for sewing such a waterproof sheet.

[0006]

According to the present invention, there is provided a heat-sealable waterproof sheet, which comprises natural rubber, synthetic rubber or In a waterproof sheet having a waterproof layer made of synthetic resin, a vinylidene fluoride resin layer is formed as the outermost layer on the upper surface, and a polyurethane resin is formed as the outermost layer on the lower surface.
It is characterized in that a layer is formed.

According to the present invention, the vinylidene fluoride resin layer as the outermost upper surface of the waterproof sheet and the polyurethane resin layer as the outermost lower surface of the waterproof sheet are superposed and bonded by heat fusion. A thermal fusion stitching method is provided. An example of the waterproof sheet of the present invention will be described with reference to FIG.

In the embodiment of the waterproof sheet of the present invention shown in FIG. 1, waterproof layers 2 and 2'made of natural rubber, synthetic rubber or synthetic resin are formed on both front and back surfaces of a fibrous base cloth 1, and the waterproof layer 2 is formed. A vinylidene fluoride resin layer 3 is formed on the outermost layer of the upper surface on the side. If necessary, an acrylic resin layer, a polyurethane resin layer, or a cyanoethylated ethylene-vinyl alcohol copolymer layer is formed between these waterproof layer 2 and vinylidene fluoride resin layer 3 continuously with these layers. May be. On the other hand, a polyurethane resin layer 4 is formed on the outermost lower surface of the waterproof layer 2 ', which is continuous with the waterproof layer 2'.

In another aspect of the waterproof sheet of the present invention,
Omitting the such waterproof layer 2, 2 ', Polyurethane resin
A layer can be directly formed on the front and back surfaces of the fibrous base fabric 1 to form a waterproof layer. Alternatively, it is also possible to form any other layers between the waterproof layer 2 and the port Li <br/> urethane resin layer and the waterproof layer 2 'and any other between the polyurethane resin layer 4 Layers can also be formed. Further, the waterproof layer 2'may be omitted, or the waterproof layer 2'may be omitted,
Instead of this, another arbitrary layer may be formed.

That is, the essential requirements for the waterproof sheet of the present invention are that it has a fibrous base fabric as an inner layer, that a waterproof layer exists, and that a vinylidene fluoride resin layer is formed as an outermost layer on the upper surface. , And a polyurethane resin layer is formed as the outermost layer on the lower surface. Hereinafter, the present invention will be described more specifically.

The fibrous base fabric used in the waterproof sheet of the present invention includes natural fibers such as cotton and hemp, inorganic fibers such as glass fibers, carbon fibers and metal fibers, regenerated fibers such as viscose rayon. , Cupra and the like, semi-synthetic fibers such as di- and tri-acetate fibers and synthetic fibers such as polyamide (nylon 6,
(Nylon 66 etc.) fiber, polyester (polyethylene terephthalate etc.) fiber, aromatic polyamide fiber, acrylic fiber, polyvinyl chloride fiber, polyolefin fiber and the like.
The fibers in the base fabric may have any shape such as short fiber spun yarn, long fiber yarn, split yarn, tape yarn, etc., and the base fabric may be a woven fabric, a knitted fabric, a non-woven fabric or a composite thereof. It may be any of cloth. Generally, the fiber used in the waterproof sheet of the present invention is preferably a polyester fiber, which is a long fiber (filament).
It is preferable that it is in the shape of, and it is preferable that a plain woven fabric is formed. Further, a woven fabric formed by stacking warp yarns and weft yarns arranged in parallel so as to intersect each other and pressing them with a twine yarn is particularly preferable. The fibrous base fabric is useful for maintaining the mechanical strength of the obtained tarpaulin at a high level.

In the present invention, a waterproof sheet is formed by forming a waterproof layer on the front surface or both front and back surfaces of the fibrous base cloth, and the material of this waterproof layer is natural rubber, neoprene rubber, chloroprene rubber, silicone. Rubber, synthetic rubber such as Hypalon, PVC resin, ethylene-vinyl acetate copolymer (EVA) resin, acrylic resin, silicone resin, urethane resin, polyethylene (PE) resin, polypropylene (PP) resin, polyester resin,
Fluorine resin and other synthetic resins can be used. The waterproof layer made of such a material has a thickness sufficient to give desired waterproofness, flame retardancy and mechanical strength to the resulting waterproof sheet, for example, 0.05 mm or more, preferably 0.
It has a thickness of 05-2.0 mm.

These waterproof layers are formed by a known method such as a topping, calendering, coating or dipping method using a film, solution, paste or straight film of the above rubber or resin.
It can be formed on a fibrous base fabric. These rubbers or resins may contain a plasticizer, a stabilizer, a colorant, an ultraviolet absorber, and other function-imparting agents.

On the upper surface of the waterproof sheet according to the present invention, a vinylidene fluoride resin layer is formed as the outermost layer. As the vinylidene fluoride resin, in addition to vinylidene fluoride homopolymer, vinylidene fluoride is contained in an amount of 70 mol% or more, and a monomer copolymerizable therewith, for example, tetrafluoroethylene, trifluoroethylene, fluorine. A copolymer obtained by copolymerizing at least one monomer selected from vinyl chloride, trifluoroethylene chloride, fluorochlorovinylidene, and vinylidene hexafluoride is used. In some cases, a mixture containing other resins having good compatibility with these homopolymers or copolymers can be used. Examples of the resin having good compatibility with such vinylidene fluoride resin include, for example, a polymer or copolymer mainly composed of methyl methacrylate or methyl acrylate, a polyurethane resin or a cyanoethylated ethylene-vinyl alcohol copolymer. is there. However, it is preferable that these other resin components be within 30 PHR of the constituent resin amount.

If necessary, the vinylidene fluoride resin layer may contain a stabilizer, a processing aid such as a lubricant, and UVA. In particular, the addition of UVA is
In some cases, it is preferable from the viewpoint of preventing photodegradation of these resins in the vicinity of the joint surface with the acrylic resin layer, polyurethane resin layer or cyanoethylated ethylene-vinyl alcohol copolymer layer formed thereunder. However, the amount of UVA that is compatible with the vinylidene fluoride resin in a uniform phase is not so large, and is generally 3% or less. In addition, since the vinylidene fluoride resin layer is generally extremely thin, it cannot be expected that UVA of this layer completely protects the waterproof layer.

However, since the vinylidene fluoride resin layer protects only the surface layer of the sheet, 0.3 to 10
It preferably has a thickness of μm, more preferably 1 to 5 μm. In the present invention, it is preferable to form an acrylic resin layer, a polyurethane resin layer or a cyanoethylated ethylene-vinyl alcohol copolymer layer immediately below the uppermost outermost vinylidene fluoride resin layer, and the thickness of these layers is The thickness is preferably 0.5 to 30 μm, more preferably 2 to 20 μm, and is generally larger than the thickness of the vinylidene fluoride resin layer.

The acrylic resin constituting the acrylic resin layer useful in the present invention is mainly composed of a polymer or copolymer having an ester of C _{1 to} C ₄ alcohol of acrylic acid or methacrylic acid as a main constituent monomer. Resins are preferred. The main constituent monomers of such an acrylic ester resin are specifically methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate and butyl methacrylate, and particularly methyl acrylate and methyl acrylate. Methacrylate is preferred. Examples of comonomers copolymerized with these main constituent monomers include esters of C _{1 to} C ₁₂ alcohols of acrylic acid or methacrylic acid, vinyl fluoride, vinylidene fluoride, vinyl chloride, vinylidene chloride, vinyl acetate, styrene. , Acrylonitrile, methacrylonitrile and butadiene. These copolymers are not limited to random copolymers and may be graft copolymers. For example,
It is also possible to use a polymer obtained by adding vinylidene fluoride to a methyl methacrylate polymer and then graft-polymerizing this. An acrylate containing an amino group, an imino group, an ethyleneimine residue, or an alkylenediamine residue can be used, but particularly preferable results are obtained when an acrylate containing an aziridinyl group is used.

The acrylic resin layer may contain a small amount of another resin having a good compatibility with the acrylic resin. In particular, PVC resin, polyurethane resin, and vinylidene fluoride resin are all useful because they have good compatibility with acrylic resin. The same applies to the cyanoethylated ethylene-vinyl alcohol copolymer. Further, an ultraviolet absorber (UVA) may be added to these resin layers in order to impart durable weather resistance. It is preferable that the compounding amount of UVA is determined so that the incident ultraviolet light can be blocked by about 50% or more. This UV blocking amount depends on the concentration of UVA in these resin layers containing UVA and the thickness of this layer.
If the concentration is too low, it is necessary to increase the thickness of these resin layers, so the UVA concentration of these resin layers should preferably be 0.3% or more, more preferably 1.0% or more. is there. However, if the UVA concentration in this resin layer is too high, bleeding may occur at the interface with the vinylidene fluoride resin layer forming the outermost upper surface, and the adhesive strength with this layer may be reduced, which is not preferable. Of course, UVA
Since the compatibility of these resins and vinylidene fluoride resin differs depending on the type of the above, the upper limit of the concentration is different, but even with a benzotriazole-based UVA having a relatively high affinity for vinylidene fluoride resin, 30 PHR can be obtained. If it exceeds 30%, peeling easily occurs at the interface of both layers.
It is preferable to limit it to about PHR or less. As the UVA, not only benzotriazole-based UVA, but also benzophenone-based, salicylate-based UVA, or those obtained by copolymerizing these with other resins is not particularly limited. .

In producing the waterproof sheet of the present invention, for example, a sheet in which a waterproof layer is formed on the front surface or both front and back surfaces of a fibrous base fabric is first produced, and then an acrylic resin, a polyurethane resin or cyanoethylated ethylene-vinyl alcohol. The copolymer may or may not be coated and a vinylidene fluoride resin may be formed by coating. Alternatively, a vinylidene fluoride resin or a vinylidene fluoride resin / acrylic resin, a polyurethane resin, or a separately manufactured vinylidene fluoride resin may be formed on the upper surface of the resin. A laminated film of a cyanoethylated ethylene-vinyl alcohol copolymer may be attached. When the laminated film of this vinylidene fluoride resin or vinylidene fluoride resin / acrylic resin has a small thickness and causes a problem in workability, a waterproof group such as a PVC film having a thickness of 30 to 50 μm is preferably used. A laminated film made of vinylidene fluoride resin / acrylic resin, polyurethane resin, cyanoethylated ethylene-vinyl alcohol copolymer / PVC resin or the like can be prepared using the material as a support, and this can be attached to the above sheet. The production of such a laminated film is not particularly limited, but the resin of each layer is subjected to a composite flow from a composite T die or a composite cylindrical die, a flat sheet or a cylinder is coextruded, and drawn by an ordinary method. From the viewpoint of the interlayer adhesiveness and the productivity, it is preferable that the heat treatment is performed and then heat treatment is performed if necessary.

[0020] In the waterproof sheet of the present invention, polyurethane resins constituting the outermost layer of the lower surface is substantially in the same manner as described above for these resin layers of the upper surface, it is possible to select the thickness and material. In this case, the lower surface is less likely to be exposed to direct sunlight, and thus UVA need not be compounded as much as the upper surface, and compounding can be omitted. Further, this layer can be formed not only by sticking the film as described above but also by coating. Further, other copolymers and other processing agents can be added to this layer as long as the adhesion is not impaired. Further, for the purpose of promoting adhesiveness with the waterproof layer, for example, when a PVC waterproof layer is formed, measures such as mixing PVC with this layer can be taken.

The polyurethane resin used in the present invention is freely selected with respect to its use form, and includes a plasticizer, a stabilizer,
Colorants, lubricants and other various additives can be freely added within the known range. An example of the polyurethane resin useful in the present invention, particularly the thermoplastic polyurethane elastomer resin, is shown below.

As the polyurethane elastomer, one obtained by reacting an organic polyisocyanate with a polymer polyol and, if necessary, a chain extender is used. As the organic polyisocyanate, aliphatic, alicyclic or aromatic polyisocyanate, for example, hexamethylene diisocyanate, lysine diisocyanate, cyclohexylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, diphenylmethane. Diisocyanate (MDI), biphenylene diisocyanate,
Examples include naphthylene diisocyanate. Among these, MDI or an organic diisocyanate mainly containing MDI is preferable.

As the polymer polyol, polyether polyol, polyester polyol, polyether ester polyol, polymer polyol and these two
Mention may be made of mixtures of more than one species. Polyether polyols include alkylene oxides (ethylene oxide, propylene oxide, butylene oxide, etc.),
Those obtained by polymerizing or copolymerizing (block or random) a heterocyclic ether (tetrahydrofuran etc.), for example, polyethylene glycol, polypropylene glycol, polyethylene-propylene (block or random) glycol, polytetramethylene ether glycol, polyhexa Mention may be made of methylene ether glycol, polyoctamethylene ether glycol and mixtures of two or more thereof. As the polyester polyol, dicarboxylic acid (adipic acid, succinic acid,
Sebacic acid, glutaric acid, maleic acid, fumaric acid, phthalic acid, etc.) and glycols (ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octamethylenediol, neopentyl glycol) , Bishydroxymethylcyclohexane, bishydroxyethylbenzene, alkyl dialkanolamine, etc.), such as polyethylene adipate, polybutylene adipate, polyhexamethylene adipate, polyethylene / propylene adipate; polylactone diols such as poly Caprolactone diol; and mixtures of two or more thereof. As the polyether ester polyol, an ether group-containing diol (the above-mentioned polyether diol, diethylene glycol, triethylene glycol, dipropylene glycol, etc.) or a mixture thereof with another glycol is used as the above-mentioned dicarboxylic acid or dicarboxylic acid anhydride (anhydrous phthalate). Acid, maleic anhydride, etc.)
And those obtained by reacting with alkylene oxides, such as poly (polytetramethylene ether) adipate.

As the polymer polyol, a high molecular weight polyol (the above-mentioned polyether polyol, polyester polyol, and / or polyether ester polyol) or a mixture of these with a medium to low molecular weight diol is used. Examples thereof include those obtained by polymerizing acrylonitrile and styrene).
Average molecular weight of polymer polyol (by hydroxyl value titration)
Is usually 500 to 5000, preferably 700 to 400
0, particularly preferably 2000 to 3500.

As the chain extender, a low molecular weight polyol having a molecular weight of less than 500, for example, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-
Hexanediol, diethylene glycol, triethylene glycol, thiodiglycol (thiodiethanol, etc.); polyamines, for example, ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine and other aliphatic diamines, piperazine, 1,4-diaminopiperazine, 1, Alicyclic polyamines such as 3-cyclohexylenediamine and dicyclohexylmethanediamine, aromatic polyamines such as diphenylmethanediamine, tolylenediamine and phenylenediamine, aromatic-aliphatic polyamines such as xylylenediamine, hydrazine and monoalkylhydrazine; alkanolamines , Ethanolamine, propanolamine; and mixtures of two or more thereof. Of these, preferred are low molecular weight diols (especially ethylene glycol).

However, the present invention is not limited to the above examples, and any other thermoplastic polyurethane resin can be used, and it is not limited to an ester type, an ether type, or the like, and is melted by heat and heat-pressed. Any material that can be welded (welded) can be used. The waterproof sheet thus obtained has excellent antifouling properties and weather resistance, and can be heat-sealed. That is, two sheets of this waterproof sheet are superposed, the uppermost outermost vinylidene fluoride resin layer and the lowermost outermost polyurethane resin layer are brought into contact with each other, and fusion-bonded by ultrasonic heating, high-frequency heating or hot air. . When heat fusion stitching is performed in this way, polyurethane resin is applied to the lower surface like a conventional waterproof sheet.
Adhesion in a sheet formed with no layer 0~3kg
Although it was extremely small as / 3 cm, in the case of the waterproof sheet of the present invention, the adhesive strength is 6 to 10 kg / 3 cm, which is a preferable value exceeding about 5 kg / 3 cm which is practically required. Although it is conceivable that a film made of a resin that gives a preferable adhesive force at the time of such heat fusion sewing is sandwiched between two sheets to perform fusion bonding,
In this case, since the adhesiveness to the waterproof sheet is lacking, the adhesive strength is about 3 to 4 kg / 3 cm, and there is a difficulty in positioning a necessary portion during the fusion work, which is not preferable in terms of work.
Further, it is possible to partially form these resin layers on the lower surface instead of the outermost continuous layer on the lower surface, but in this case, the work of applying these resin layers at the time of sewing is troublesome and the workability is reduced. It lowers and harms the working environment. Therefore, if these resin layers are formed as a continuous layer on the entire lower surface from the beginning like the waterproof sheet of the present invention, the waterproof sheet itself can be manufactured inexpensively and easily,
Further, there is an advantage that the sewing can be performed at any portion that requires sewing.

[0027]

EXAMPLES The present invention will be further described below with reference to examples. Example 1 A vinylon fiber canvas having the following structure and a density (20/3 × 20/4) / (45 × 38) basis weight of 360 g / m ² was used as a base fabric, which was blanched and dried. Next, this base cloth was subjected to the following composition: PVC resin: 80 parts by weight butylbenzyl phthalate: 68 parts by weight Epoxidized soybean oil: 7 parts by weight Calcium carbonate: 20 parts by weight Cadmium barium stabilizer: 3 parts by weight Pigment: 8 parts by weight Part Toluene (solvent) ... After being immersed in a working fluid consisting of 130 parts by weight, the amount of adhesion between rollers is 10
It was squeezed to 0%, dried at 90 ° C. for 1 minute, and then heat-treated at 180 ° C. for 1 minute to gel and adhere PVC to prepare a waterproof sheet. The waterproof layer of this waterproof sheet had a thickness of 0.3 mm.

On the upper surface of this waterproof sheet, a KFC sheet [vinylidene fluoride resin (2
.About.3 .mu.m) / acrylic resin (2 to 4 .mu.m) / PVC resin (45 .mu.m)] was adhered by heat with the PVC surface facing the waterproof sheet surface. Further, a polyurethane resin was applied to the lower surface of the waterproof sheet to a thickness of 7 μm to prepare a product sheet (I). The application conditions of the polyurethane resin are as follows. Resin composition Nipporan 3022 (solid content 35%) 100
Weight part Coronate L 15
Parts by weight (These are all products for urethane processing of Nippon Urethane Co., Ltd.) Processing conditions A 60 mesh gravure coat was applied at a rate of 25 g / m ² and dried at 100 ° C. for 1 minute.

For comparison, a comparative sheet (II) as a conventional product was manufactured in exactly the same manner as above except that no polyurethane resin was applied to the back surface. For each of these three samples, overlap the end 3 cm as described in the text above, and output 2 k at this overlap.
High-frequency treatment was performed for 3 seconds using a high-frequency oscillator with W and a frequency of 40.68 MHz. The average peel strength of the joint portion of the heat-sealed sewn sheet thus obtained is 8.4 kg / 3 cm in the case of the sheet (I) of the present invention, and the comparative sheet (II)
In the case of, it was 0.5 kg / 3 cm. That is, although the sheet of the present invention had a bonding strength sufficient for practical use, the bonding strength of the comparative sheet was not practical.

Further, the portions to be joined of the sheets are overlapped with facing each other, and using a Leister hot air welding machine, a nozzle having a flat hot air outlet having a width of 3 cm is inserted between the overlapping portions, and the nozzle is placed on the sheet surface. While moving along the seaming direction of the waterproof sheet, apply hot air of 400 ℃ from the nozzle,
The resin was melted in a width of approximately 3 cm. Following this melting operation, the overlapping portion is pressed by a pressure roller,
Fused and sewn. The peel strength of the fusion-bonded sewn sheet thus obtained was almost the same as that of the sheet obtained by high-frequency welder sewing.

Example 2 The same base fabric as used in Example 1 was applied to each of the Hypalon resin waterproof layer, the silicone resin waterproof layer, the EVA resin waterproof layer,
Acrylic resin waterproof layer and urethane resin waterproof layer are formed,
Acrylic adhesive S made by Sony Chemicals on the surface
Vinylidene fluoride resin (4 μm) / cyanoethylated ethylene-vinyl alcohol copolymer (1
A film composed of 0 μm) was attached (I). Similarly, a film made of vinylidene fluoride resin (4 μm) / polyurethane resin (10 μm) was attached (II). Also, a KFC film was attached in the same manner (III). Moreover, the adhesive SC462 is applied to the back surface to a thickness of 5 μm,
Further by sticking a urethane resin film (10 [mu] m) on this to prepare a waterproof sheet (A group) according to the present invention. In addition, for comparison, a sheet without these layers formed on the back side was prepared, and a comparison sheet (Group B )
And Each of these sheets was subjected to the same high frequency welder sewing as described in Example 1. As a result, the peel strength (kg / 3 cm) was as follows. Surface composition of waterproof layer A group B group Hypalon resin I 7.8 0.3 II 9.2 0.3 III 9.0 0.2 ─────────────────── ───────── Silicone Resin I 7.2 0 II 7.4 7.4 III III 7.2 0.1 ───────────────────── ─────── EVA resin I 7.4 0.9 II 9.4 0.8 III 8.2 8.2 1.0 ───────────────────── ─────── Acrylic resin I 8.4 8.9 II 9.6 9.2 III 9.4 9.4 ──────────────────── ─────── Urethane resin I 8.2 8.4 II 9.4 9.4 III 9.0 9.2 ──────────────────── ───────

[0032]

As can be seen from the above, since the waterproof sheet according to the present invention has a protective layer of vinylidene fluoride resin, it retains excellent antifouling property, weather resistance and durability while it has a reverse surface. Since it has a polyurethane resin layer , its industrial value is extremely great as a sheet that can be easily and inexpensively heat-sealed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing an example of the waterproof sheet of the present invention.

[Explanation of symbols]

1 ... fibrous fabric 2,2 '... waterproof layer 3 ... polyvinylidene fluoride layer 4 ... polyurethane resins layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B29K 627: 12 633: 04

Claims (17)

[Claims] 1. A waterproof sheet having a fibrous base cloth having a waterproof layer made of natural rubber, synthetic rubber or synthetic resin on the front surface or both front and back surfaces thereof, wherein a vinylidene fluoride resin layer is formed as an outermost layer on the upper surface of the waterproof sheet. A heat-sealable waterproof sheet having a polyurethane resin layer as the outermost layer on its lower surface. 2. The waterproof sheet according to claim 1, wherein an acrylic resin layer, a polyurethane resin layer or a cyanoethylated ethylene-vinyl alcohol copolymer layer is formed under the vinylidene fluoride resin layer on the upper surface. 3. A said lower surface, waterproof sheet according to claim 1 or 2, wherein Po Caixaforum <br/> Tan resin layer on the waterproof layer is formed. 4. A tarpaulin according to claim 1, wherein the front Kipo polyurethane resin layer forms the waterproof layer. 5. The waterproof sheet according to claim 1, wherein the waterproof layer has a thickness of 0.05 to 2.0 mm. 6. The waterproof according to claim 2, wherein the acrylic resin layer is made of a resin containing a polymer or a copolymer having a C _{1 to} C ₄ alcohol ester of acrylic acid or methacrylic acid as a main constituent monomer as a main component. Sheet. 7. The waterproof sheet according to claim 2 , wherein the acrylic resin layer, the polyurethane resin layer or the cyanoethylated ethylene-vinyl alcohol copolymer layer has a thickness of 0.5 to 30 μm. 8. The waterproof sheet according to claim 7, wherein the thickness of the layer is 2 to 20 μm. 9. waterproof sheet according to claim 1 wherein the vinylidene fluoride resins is a copolymer containing at least 70 mol% of vinylidene fluoride homopolymer or a vinylidene fluoride. 10. The vinylidene fluoride resin layer is fluorinated.
Compatibility of vinylidene resin and this vinylidene fluoride resin
10. The resin composition according to claim 9, wherein the resin composition is a mixed resin with another resin having good
Tarpaulin. 11. Compatibility with the vinylidene fluoride resin
Other resins with good Methyl methacrylate or methyl
Polymer or copolymer mainly composed of acrylate,
Polyurethane resin or cyanoethylated ethylene-vinyl
The waterproof sheet according to claim 10, which is an alcohol resin. 12. The vinylidene fluoride resin layer has a thickness of 0.3.
Waterproof sheet according to any one of claims 1 to 11 having a thickness of 10 .mu.m. 13. The waterproof sheet according to claim 12 , wherein the vinylidene fluoride resin layer has a thickness of 1 to 5 μm. 14. A waterproof sheet having a waterproof layer made of natural rubber, synthetic rubber or synthetic resin on the front surface or both front and back surfaces of a fibrous base fabric, wherein a vinylidene fluoride resin layer is formed as an outermost layer on the upper surface thereof. On the other hand, a waterproof sheet having a polyurethane resin layer as the outermost layer is used on the lower surface thereof, and the vinylidene fluoride resin layer of the uppermost outermost layer of this waterproof sheet and the polyurethane resin layer of the lowermost outermost layer are superposed, A heat-sealing sewing method, characterized in that these are joined by heat-sealing. 15. The method according to claim 14 , wherein the means for heat fusion is high frequency heating. 16. The method according to claim 14 , wherein the means for heat fusion is heating with hot air. 17. The method according to claim 14 , wherein the means for heat fusion is ultrasonic heating.