JPH0374627B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a waterproof sheet that can be sewn by heat sealing, particularly a waterproof sheet that has excellent stain resistance and weather resistance, and can be sewn by heat sealing, and a sewing method using the same. BACKGROUND ART Conventionally, flexible sheets having, for example, a fibrous base fabric and a soft vinyl chloride (PVC) resin layer on one or both sides have been used in large tents such as air domes. Such sheets have the unique advantages of PVC in terms of processability, economic efficiency, flame resistance, etc. However, on the other hand, since such tents are exposed outdoors for long periods of time, the stability of the compound is Even if the agent, etc. has been carefully examined, the resin will gradually decompose over many years, the plasticizer will migrate to the surface, and the surface will gradually become sticky, and dust will adhere to the surface. It had serious drawbacks such as contamination. As a countermeasure to this problem, an acrylic resin film layer is formed on the top surface of the PVC layer to cover the drawbacks of the conventional laminate product with only a PVC layer and to obtain the desired effect. However, depending on the usage conditions of the laminate, if the acrylic resin film layer is subjected to strong rubbing or other conditions, cracks may occur in the acrylic resin film layer, resulting in a significant shortening of the service life of the laminate, so this countermeasure is not sufficient. This has not yet been achieved. Therefore, the surface of such a laminated sheet is constructed by pasting a film made of vinylidene fluoride resin/acrylic resin/PVC resin,
We have discovered a method to improve weather resistance and stain resistance by using a vinylidene fluoride resin layer on the outer surface. When such waterproof sheets are sewn using a sewing machine, water leaks from the seams, and machine sewing also has low work efficiency, so high frequency waves or hot air are often used to heat-seal the sheets. However, even if an attempt was made to join the laminated sheets having the vinylidene fluoride resin layer as the outer surface using heat-sealing sewing, the vinylidene fluoride resin layer would not adhere, and therefore, further improvement of this sheet is desired. This is where I am. Problems to be Solved by the Invention The present invention provides an extremely useful waterproof sheet that has excellent stain resistance and weather resistance, can be sewn with heat fusion, and has durable stain resistance. This is what we are trying to provide. The present invention also provides a method for sewing such a waterproof sheet. Means for Solving the Problems According to the present invention, there is provided a waterproof sheet that can be sewn by heat-sealing, and this sheet has natural rubber, synthetic rubber or synthetic rubber on the surface or both front and back surfaces of the fibrous base fabric. In a waterproof sheet having a waterproof layer made of resin, a vinylidene fluoride resin layer is formed as the outermost layer on the upper surface, while an acrylic resin layer, a polyurethane resin layer, or a cyanoethylated ethylene-vinyl alcohol layer is formed as the outermost layer on the lower surface. It is characterized by forming a polymer layer. According to the present invention, the vinylidene fluoride resin layer as the outermost layer on the upper surface of the waterproof sheet and the acrylic resin layer, polyurethane resin layer, or cyanoethylated ethylene-vinyl alcohol copolymer layer as the outermost layer on the lower surface are superimposed, and Provided is a heat-sealing sewing method characterized by joining by heat-sealing. An example of the waterproof sheet of the present invention will be explained with reference to FIG. In the embodiment of the waterproof sheet of the present invention shown in FIG. A vinylidene fluoride resin layer 3 is formed on the outermost layer of the upper surface. If necessary, these waterproof layer 2 and vinylidene fluoride resin layer 3
An acrylic resin layer, a polyurethane resin layer, or a cyanoethylated ethylene-vinyl alcohol copolymer layer may be formed continuously between these layers. On the other hand, the outermost layer on the lower surface of the waterproof layer 2' side has an acrylic resin layer continuous to the waterproof layer 2'.
A polyurethane resin layer or a cyanoethylated ethylene-vinyl alcohol copolymer layer 4 is formed. In another embodiment of the waterproof sheet of the present invention, the waterproof layers 2, 2' as described above are omitted, and the acrylic resin layer,
A polyurethane resin layer or a cyanoethylated ethylene-vinyl alcohol copolymer layer can be directly formed on the front and back surfaces of the fibrous base fabric 1 to serve as a waterproof layer. Alternatively, any other layer may be formed between the waterproof layer 2 and the acrylic resin layer, polyurethane resin layer, or cyanoethylated ethylene-vinyl alcohol copolymer layer, or between the waterproof layer 2' and the acrylic resin layer. , the polyurethane resin layer or the cyanoethylated ethylene-vinyl alcohol copolymer layer 4, any other arbitrary layer may also be formed. Further, the waterproof layer 2' may be omitted, or the waterproof layer 2' may be omitted and any other layer may be formed in its place. 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, that a vinylidene fluoride resin layer is formed as the outermost layer on the upper surface, and that the lower surface In this case, an acrylic resin layer, a polyurethane resin layer, or a cyanoethylated ethylene-vinyl alcohol copolymer layer is formed as the outermost layer. The present invention will be explained in more detail below. 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 fiber, carbon fiber, and metal fibers, and recycled fibers such as viscose rayon and Kyupura. , semi-synthetic fibers such as di- and tri-acetate fibers, and synthetic fibers,
For example, polyamide (nylon 6, nylon 66
etc.) fibers, polyester (polyethylene terephthalate, etc.) fibers, aromatic polyamide fibers, acrylic fibers, polyvinyl chloride fibers, polyolefin fibers, and the like. The fibers in the base fabric may be in any form such as short fiber spun yarn, long fiber yarn, split yarn, or tape yarn, and the base fabric may be a woven fabric, a knitted fabric, a nonwoven fabric, or a composite fabric thereof. It may be either. Generally, the fibers used in the waterproof sheet of the present invention are preferably polyester fibers, preferably in the form of long fibers (filaments), and preferably in the form of a plain woven fabric. Further, a woven fabric constructed by stacking parallel warp and weft yarns so as to cross each other and pressing them with leno yarns is particularly preferable. The fibrous base fabric is useful for maintaining the mechanical strength of the resulting tarpaulin sheet at a high level. In the present invention, a waterproof layer is formed on the surface or both front and back surfaces of a fibrous base fabric to form a waterproof sheet. Materials for this waterproof layer include natural rubber, neoprene rubber, chloroprene rubber, silicone rubber, and hypalon. Other synthetic rubber or 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 material has a thickness sufficient to provide the resulting waterproof sheet with the desired waterproof properties, flame retardance and mechanical strength, for example, 0.05 mm or more, preferably 0.05 to 2.0 mm. It has a thickness. These waterproof layers are coated on the fibrous base fabric by known methods such as topping, calendering, coating, and dipping using rubber or resin films, solutions, pastes, or straights as described above. can be formed into These rubbers or resins may contain plasticizers, stabilizers, colorants, ultraviolet absorbers, and other functional 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. Vinylidene fluoride resins include, in addition to vinylidene fluoride monopolymers, monomers that contain 70 mol% or more of vinylidene fluoride and are copolymerizable with it, such as tetrafluoroethylene, trifluoroethylene, A copolymer obtained by copolymerizing one or more monomers selected from vinyl chloride, chloroethylene trifluoride, fluorochlorovinylidene, vinylidene hexafluoride, etc. is used. In some cases, a mixture of these homopolymers or copolymers with other resins having good compatibility with them may also be used. Examples of resins having good compatibility with such vinylidene fluoride resins include methyl methacrylate, polymers or copolymers mainly composed of methyl acrylate, polyurethane resins, and cyanoethylated ethylene-vinyl alcohol copolymers. be. However, the amount of these other resin components is preferably within 30 PHR of the constituent resin amount. This vinylidene fluoride resin layer may contain processing aids such as stabilizers and lubricants and UVA, if necessary. In particular, the addition of UVA prevents photodeterioration of these resins near the bonding surface with the acrylic resin layer, polyurethane resin layer, or cyanoethylated ethylene-vinyl alcohol copolymer layer formed below, if necessary. It is preferable because it means However, the amount of UVA that is compatible with the vinylidene fluoride resin in a homogeneous phase is not very large, and is generally 3% or less. In addition, since the vinylidene fluoride resin layer is generally extremely thin,
It cannot be expected that this layer of UVA alone will completely protect the waterproof layer. However, since the vinylidene fluoride resin layer protects only the surface layer of the sheet, it has a thickness of 0.3 to 10 μm.
The thickness is preferably 1 to 5 μm, and 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,
The thickness of these layers 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 preferably a resin whose main component is a polymer or copolymer whose main monomer is an ester of C ₁ to C ₄ alcohol of acrylic acid or methacrylic acid. . The main constituent monomers of such acrylic ester resins are specifically methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, and butyl methacrylate, particularly methyl acrylate and methyl acrylate. Methacrylate is preferred. In addition, examples of comonomers to be copolymerized with these main constituent monomers include:
Monomers include esters of _C1 - _C12 alcohols of acrylic acid or methacrylic acid, vinyl fluoride, vinylidene fluoride, vinyl chloride, vinylidene chloride, vinyl acetate, styrene, acrylonitrile, methacrylonitrile, butadiene. These copolymers are not limited to random copolymers, but may also be graft copolymers. For example, a polymer obtained by adding vinylidene fluoride to a methyl methacrylate polymer and then grafting the same can also be used. Although acrylates containing amino groups, imino groups, ethyleneimine residues, and alkylene diamine residues can also be used, particularly preferred results are obtained when using acrylates containing aziridinyl groups. The acrylic resin layer may contain a small amount of other resin having 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 can be said of the cyanoethylated ethylene-vinyl alcohol copolymer.
Furthermore, ultraviolet absorbers (UVA) may be added to these resin layers in order to provide durable weather resistance. The amount of UVA to be added is preferably determined so as to block approximately 50% or more of incident ultraviolet rays. The amount of UV blocking is determined by the concentration of UVA in these resin layers containing UVA and the thickness of this layer, but if the UVA concentration is too low, it is necessary to increase the thickness of these resin layers. Therefore, the UVA concentration of these resin layers should preferably be 0.3% or more, more preferably 1.0% or more. However, if the UVA concentration in this resin layer is too high, it may bleed to the interface with the vinylidene fluoride resin layer constituting the outermost layer on the upper surface and reduce the adhesive strength with this layer, which is not preferable. Of course, the compatibility with these resins and vinylidene fluoride resin varies depending on the type of UVA, so the upper limit of its concentration varies, but even benzotriazole-based UVA, which has a relatively high affinity for vinylidene fluoride resin, If it exceeds 30PHR, it becomes easy to peel off at the interface of both layers, so 30PHR
It is preferable to keep the amount below. UVA includes not only benzotriazole type, but also
Any of benzophenone type, salicylic acid ester type, or copolymerization of these and other resins can be used, and there is no particular limitation. When manufacturing the waterproof sheet of the present invention, for example, a sheet with a waterproof layer formed on the surface or both front and back surfaces of a fibrous base fabric is first manufactured, and then an acrylic resin, a polyurethane resin, or a cyanoethylated ethylene-vinyl alcohol copolymer is used. Vinylidene fluoride resin may be coated or not, and as an alternative, vinylidene fluoride resin or vinylidene fluoride resin/acrylic resin, polyurethane resin, or cyanoethylated ethylene may be coated on the top surface. - A laminated film of vinyl alcohol copolymer may be attached. If the thickness of the laminated film of vinylidene fluoride resin or vinylidene fluoride resin/acrylic resin is thin and causes problems in workability, the thickness should be 30 to 50 μm.
Vinylidene fluoride resin/acrylic resin using a preferably waterproof base material such as PVC film as a support.
Polyurethane resin or cyanoethylated ethylene
It is also possible to make a laminated film made of vinyl alcohol copolymer/PVC resin or the like and attach it to the above sheet. Although the production of such a laminated film is not particularly limited, the resin of each layer is made to flow in a composite manner from a composite T-die or a composite cylindrical die, and a flat sheet or cylindrical product is coextruded and then taken off by a normal method. From the viewpoint of interlayer adhesion and productivity, it is desirable to carry out a heat treatment as necessary. In the waterproof sheet of the present invention, the acrylic resin layer, polyurethane resin, or cyanoethylated ethylene-vinyl alcohol copolymer layer constituting the outermost layer on the lower surface has a thickness similar to that described above for these resin layers on the upper surface. Materials can be selected. In this case, since the lower surface is less exposed to direct sunlight, it is not necessary to incorporate UVA as much as the upper surface, and UVA can be omitted. Further, this layer can be formed not only by adhering a film as described above but also by coating. Further, other copolymers and other processing agents may be added to this layer as long as they do not impair adhesion. Further, in order to promote adhesion with the waterproof layer, for example, when a PVC waterproof layer is formed, measures such as mixing PVC into this layer can be taken. The polyurethane resin used in the present invention can be freely selected in terms of its use form, and plasticizers, stabilizers, colorants, lubricants, and various other tactile agents can be freely added within known ranges. Examples of polyurethane resins, particularly thermoplastic polyurethane elastomer resins useful in the present invention are shown below. As the polyurethane elastomer, one obtained by reacting an organic polyisocyanate with a polymeric polyol and, if necessary, a chain extender is used. Organic polyisocyanates include aliphatic, cycloaliphatic or aromatic polyisocyanates, such as hexamethylene diisocyanate, lysine diisocyanate, cyclohexylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, Examples include diphenylmethane diisocyanate (MDI), biphenylene diisocyanate, and naphthylene diisocyanate. Among these, MDI or an organic diisocyanate mainly composed of MDI is preferred. Examples of the polymer polyol include polyether polyols, polyester polyols, polyether ester polyols, polymer polyols, and mixtures of two or more thereof.
Polyether polyols include those obtained by polymerizing or copolymerizing (block or random) alkylene oxides (ethylene oxide, propylene oxide, butylene oxide, etc.), heterocyclic ethers (tetrahydrofuran, etc.),
Examples include polyethylene glycol, polypropylene glycol, polyethylene-propylene (block or random) glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, polyoctamethylene ether glycol, and mixtures of two or more thereof. As polyester polyol,
Dicarboxylic acids (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-octamethylene diol, neopentyl glycol, bishydroxymethylcyclohexane, bishydroxyethylbenzene, alkyl dialkanolamine, etc.), such as polyethylene adipate, poly Examples include butylene adipate, polyhexamethylene adipate, polyethylene/propylene adipate, polylactone diols such as polycaprolactone diols, and mixtures of two or more thereof. As the polyether ester polyol, ether group-containing diols (the above-mentioned polyether diols, diethylene glycol, triethylene glycol, dipropylene glycol, etc.) or mixtures of these and other glycols are combined with the above-mentioned dicarboxylic acids or dicarboxylic acid anhydrides (phthalic anhydride, etc.). acid, maleic anhydride, etc.) and alkylene oxide, such as poly(polytetramethylene ether) adipate. In addition, as the polymer polyol, ethylenically unsaturated monomers (acrylonitrile, styrene, etc.) and those obtained by polymerizing them. The average molecular weight of the polymer polyol (by hydroxyl value titration) is usually 500 to 5000, preferably 700 to 5000.
4000, particularly preferably 2000 to 3500. As the chain extender, low-molecular polyols with a molecular weight of less than 500, such as ethylene glycol, propylene glycol, 1,4-butanediol,
1,6-hexanediol, diethylene glycol, triethylene glycol, thiodiglycol (thiodiethanol, etc.); polyamines, e.g.
Aliphatic diamines such as ethylene diamine, propylene diamine, butylene diamine, and hexamethylene diamine; alicyclic polyamines such as piperazine, 1,4-diaminopiperazine, 1,3-cyclohexylene diamine, and dicyclohexylmethane diamine; diphenylmethane diamine; Aromatic polyamines such as diamine, phenylene diamine, aromatic-aliphatic polyamines such as xylylene diamine, hydrazine and monoalkylhydrazine; alkanolamines such as ethanolamine, propanolamine; and mixtures of two or more thereof. It will be done. Among these, preferred are low molecular diols (especially ethylene glycol). However, it is not limited to the above examples, and any other thermoplastic polyurethane resin can be used, and it is not limited to ester-based, ether-based, etc. ) You can use anything that can be worn. The waterproof sheet thus obtained has excellent stain resistance and weather resistance, and can be sewn by heat fusion. That is, overlap these two waterproof sheets,
The outermost vinylidene fluoride resin layer on the top surface and the outermost acrylic resin layer, polyurethane resin layer, or cyanoethylated ethylene-vinyl alcohol copolymer layer on the bottom surface are brought into contact with each other, and fused by ultrasonic heating, high-frequency heating, or hot air. They are joined together. When heat-sealing is performed in this way, the adhesive strength is 0 for sheets that do not have an acrylic resin layer, a polyurethane resin layer, or a cyanoethylated ethylene-vinyl alcohol copolymer layer formed on the lower surface like conventional waterproof sheets. However, 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 the practically required value of about 5 Kg/3 cm.
Although it is conceivable to sandwich a film made of resin that provides favorable adhesive strength between the two sheets and fuse them together during such heat-fusion sewing, in this case, the adhesion to the waterproof sheet would be lacking. Therefore, the adhesive strength is about 3 to 4 kg/3 cm, and it is difficult to position the required part during the fusion work, which is not favorable for work. It is also possible to partially form these resin layers on the bottom surface instead of the continuous outermost layer on the bottom surface, but in this case, the work of applying these resin layers during sewing is cumbersome and reduces workability. degrading and harming the working environment.
Therefore, as in the waterproof sheet of the present invention, if these resin layers are formed as a continuous layer over the entire lower surface from the beginning, the waterproof sheet itself can be manufactured at low cost and easily, and can be easily sewn. It has the advantage that it can be carried out wherever it is needed. Examples Hereinafter, the present invention will be further explained with reference to Examples. Example 1 A vinylon fiber canvas having the following structure, density 20/3 x 20/4/45 x 38, and basis weight 360 g/m ² was used as a base fabric, which was then boiled and dried. Next, this base fabric was prepared with 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 of toluene (solvent)...After immersing in a processing solution consisting of 130 parts by weight, it was squeezed between rollers until the adhesion amount was 100%, dried at 90°C for 1 minute, and then heated to 180°C.
The PVC was gelled and fixed by heat treatment at ℃ for 1 minute to create a waterproof sheet. The thickness of the waterproof layer of this tarpaulin sheet was 0.3 mm. On the upper surface of this waterproof sheet, a KFC sheet manufactured by Kureha Chemical Industry Co., Ltd. [vinylidene fluoride resin (2-3 μm)/acrylic resin (2-4 μm)/PVC
The PVC side of the resin (45 μm) was attached to the waterproof sheet surface using heat. Further, an acrylic resin film (25 μm) manufactured by Mitsubishi Rayon Co., Ltd. was heat-adhered to the lower surface of this waterproof sheet to obtain a product sheet (). Separately, coat the bottom surface of this waterproof sheet with polyurethane resin to a thickness of 7 μm to form a product sheet ().
I made it. The conditions for applying the polyurethane resin are as follows. Resin composition Nitsuporan 3022 (solid content 35%) 100 parts by weight Coronate L 15 parts by weight (all of the above are products for urethane processing by Nippon Urethane Co., Ltd.) Processing conditions 60 mesh gravure coat, 25 g/m ² and dried at 100°C for 1 minute. For comparison, a conventional sheet () was manufactured in exactly the same manner as above except that these resin films were not formed on the back surface. For each of these three samples, the end portions of 3 cm were overlapped as described in the text above, and this overlapped portion was subjected to high-frequency treatment for 3 seconds using a high-frequency oscillator with an output of 2 kW and a frequency of 40.68 MHz. The average peel strength of the joint portion of the heat-sealed sewn sheet obtained in this way was determined by the sheet of the present invention ().
and (), respectively 8.5Kg/3cm and 8.4Kg/3
cm, and in the case of comparison sheet () 0.5Kg/3cm
It was hot. That is, the sheet of the present invention had a bonding strength sufficient for practical use, but the bonding strength of the comparative sheet was not practical. In addition, the parts to be joined of the sheets are stacked facing each other, and using a Leister hot air welding machine, a nozzle with a flat hot air outlet with a width of 3 cm is inserted between the stacked parts, and the nozzle is waterproofed along the sheet surface. from the nozzle while moving the sheet in the sewing direction.
Hot air at 400℃ was applied to melt the resin in a width of approximately 3cm. Following this melting operation, the overlapping portions were pressed with a pressure roller and fused and sewn. The peeling strength of the fusion-sewn sheets thus obtained was almost the same as that of the sheets obtained by high-frequency welder sewing. Example 2 The same base fabric used in Example 1 was coated with a Hypalon resin waterproof layer, a silicone resin waterproof layer, and a silicone resin waterproof layer, respectively.
EVA resin waterproof layer, acrylic resin waterproof layer and urethane resin waterproof layer are formed on the top surface of Sony
Vinylidene fluoride resin (4 μm)/cyanoethylated ethylene-vinyl alcohol copolymer (10 μm) using acrylic adhesive SC462 manufactured by Chemical Co., Ltd.
A film consisting of was attached (). Similarly,
A film consisting of vinylidene fluoride resin (4 μm)/polyurethane resin (10 μm) was attached (). In addition, KFC film was attached in the same manner (). Further, adhesive SC462 was applied to the back side to a thickness of 5 μm to create a waterproof sheet (A group) according to the present invention. Further, a cyanoethylated ethylene-vinyl alcohol copolymer having a thickness of 5 μm was applied thereon to prepare a waterproof sheet (Group B) according to the present invention. Separately, also apply adhesive SC462 to the back side.
A waterproof sheet (Group C) according to the present invention was prepared by applying the coating to a thickness of 5 μm and further adhering a urethane resin film (10 μm) thereon. In addition, for comparison, sheets without these layers formed on the back side were created, and a comparison sheet (D group) was created.
And so. Each of these sheets was subjected to high frequency welding in the same manner as described in Example 1. As a result, the peel strength (Kg/3cm) was as follows.

[Table] Comparative examples use resin as a waterproof layer.
Effects of the Invention As can be seen from the above, the waterproof sheet according to the present invention has a protective layer of vinylidene fluoride resin, so it maintains excellent stain resistance, weather resistance, and durability, and also has an acrylic resin on the back side. Since it has a polyurethane resin layer or a cyanoethylated ethylene-vinyl alcohol copolymer layer, its industrial value is extremely great as a sheet that can be easily and inexpensively sewn.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view schematically showing an example of the waterproof sheet of the present invention. 1... Fibrous base fabric, 2,2'... Waterproof layer, 3...
...vinylidene fluoride resin layer, 4...acrylic resin, polyurethane resin, or cyanoethylated ethylene-vinyl alcohol copolymer layer.

Claims (1)

[Claims] 1. Natural rubber on the surface or both front and back surfaces of the fibrous base fabric,
In a waterproof sheet having a waterproof layer made of synthetic rubber or synthetic resin, a vinylidene fluoride resin layer is formed as the outermost layer on the upper surface, while an acrylic resin layer, a polyurethane resin layer, or a cyanoethylated ethylene layer is formed on the lower surface as the outermost layer. - A waterproof sheet that can be sewn by heat-sealing and is characterized by forming a vinyl alcohol copolymer layer. 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. The waterproof sheet according to claim 1 or 2, wherein an acrylic resin layer, a polyurethane resin layer, or a cyanoethylated ethylene-vinyl alcohol copolymer layer is formed on the waterproof layer on the lower surface. 4. The waterproof sheet according to claim 1, wherein the acrylic resin layer, the polyurethane resin layer, or the cyanoethylated ethylene-vinyl alcohol polymer layer forms the waterproof layer. 5. The waterproof sheet according to any one of claims 1 to 4, wherein the waterproof layer has a thickness of 0.05 to 2.0 mm. 6. Claims 1 to 5, wherein the acrylic resin layer is made of a resin whose main component is a polymer or copolymer whose main monomer is an ester of a _C1 to _C4 alcohol of acrylic acid or methacrylic acid.
A tarpaulin sheet as described in any of the paragraphs. 7. The waterproof sheet according to any one of claims 1 to 6, wherein the acrylic resin layer, polyurethane resin layer, or 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 layer has a thickness of 2 to 20 μm. 9. According to any one of claims 1 to 8, the vinylidene fluoride resin layer is made of a resin whose main component is a vinylidene fluoride monopolymer or a copolymer containing 70 mol% or more of vinylidene fluoride. tarpaulin. 10 The vinylidene fluoride resin layer has a thickness of 0.3 to 10 μm
The waterproof sheet according to any one of claims 1 to 9, having a thickness of . 11 The thickness of the vinylidene fluoride resin layer is 1 to
The waterproof sheet according to claim 10, which has a thickness of 5 μm. 12 A waterproof sheet having a waterproof layer made of natural rubber, synthetic rubber or synthetic resin on the front or both sides of a fibrous base fabric, with a vinylidene fluoride resin layer formed as the outermost layer on the top surface, and a vinylidene fluoride resin layer formed on the bottom surface. For this purpose, a waterproof sheet having an acrylic resin layer, a polyurethane resin layer, or a cyanoethylated ethylene-vinyl alcohol copolymer layer formed on the outermost layer is used, and the upper surface of the waterproof sheet has the outermost vinylidene fluoride resin layer and the lower surface. Outermost acrylic resin layer, polyurethane resin layer or cyanoethylated ethylene
A heat-fusion sewing method characterized by overlapping vinyl alcohol copolymer layers and joining them by heat-fusion. 13. The method according to claim 12, wherein the means for thermal fusion is high frequency heating. 14. The method according to claim 12, wherein the means for thermal fusion is heating with hot air. 15. The method according to claim 12, wherein the means for thermal fusion is ultrasonic heating.