JP2009084740A - Water-barrier sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an economical and environmentally friendly water-barrier sheet containing 25 mass% or more of biomass-derived polymer as compared with a petroleum-derived polymer. <P>SOLUTION: The water-barrier sheet contains 25-60 mass% of the biomass-derived polymer, and having a tensile tenacity of 980-2,940 N/3 cm, an elongation at the maximum load based on JIS-L-1096 of 8-45%, and a CF (cover factor) of a base fabric of 500-2,200 in the water-barrier sheet wherein the base fabric is subjected to a resin finish. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a water shielding sheet containing a biomass-derived polymer in an amount of 25 to 60% by mass of the total weight, and is a waste final disposal site (general waste disposal site, industrial waste disposal site, etc.) or a roofing material It relates to a water shielding sheet used for such as.

  Most of the conventional synthetic fibers are made from limited fossil fuel resources such as oil, but in recent years, the fossil fuel resources are not only concerned with the remaining reserves but also carbon dioxide generated during incineration disposal. Is also becoming a major social problem as an inducer of global warming. Therefore, there is an urgent need to search and develop new resources that can solve the above-mentioned problems. Among them, biomass-derived substances are attracting attention as resources that do not produce extra carbon dioxide even after disposal. This is because, even if the materials produced from biomass-derived substances are combusted, the carbon dioxide generated at that time was originally in the atmosphere, and in the time scale of human industrial activities, This is based on the idea that the macro balance of carbon dioxide does not increase. This is called carbon neutral and tends to be regarded as important.

  For example, plastic products manufactured from biomass-derived substances have features such as less environmental impact and no loss of carbon dioxide balance compared to petroleum-based plastic products. The recognition that it contributes to the conservation of fuel resources and the preservation of the natural environment is becoming socially established. In addition, in order to promote the spread of biomass-derived plastic products, the Japan Bioplastics Association, a voluntary private organization, proposed the “Biomass Plastic Identification and Labeling System” as a system for distinguishing from existing petroleum-based plastic products. Among them, the inclusion of 25.0% by mass or more of the biomass-derived polymer component is the certification standard.

  Here, focusing on the water shielding sheet, as a polymer having a low environmental load, for example, an industrial material woven fabric or polylactic acid fiber manufactured from a copolymer of polylactic acid or lactic acid and other hydroxycarboxylic acid is used. A water shielding sheet is disclosed (for example, see Patent Documents 1 and 2). However, these disclosed technologies are mainly intended for biodegradability and are rooted in a technical idea including a monomer component derived from petroleum. There is no description for the purpose of using biomass.

  In addition, as a form of use of the biomass-derived polymer, a composite yarn in which a polylactic acid resin is a core and an aromatic polyester resin is arranged in a sheath is disclosed (for example, Patent Documents 3, 4 and 5). However, details about specific applications are not described, and the required performance of each material is not mentioned, and there is no specific technology to manufacture a water shielding sheet using environmentally friendly biomass. It has not been issued.

  On the other hand, biomass-derived polymers have a problem in that they are not cheap because the production amount of biomass-derived polymers is smaller than that of general-purpose resins.

Japanese Patent Application Laid-Open No. 6-0665835 JP 2001-303426 A JP 2004-353161 A JP 2005-187950 A JP 2005-232627 A

  The present invention has been made in view of such a current situation, and is environmentally friendly, such as reducing the amount of carbon dioxide generated by containing 25 to 60% by mass of a biomass-derived polymer, and maintains good required performance. However, the present invention provides a water shielding sheet that can be produced economically by using it together with a petroleum polymer.

  As a result of intensive studies to solve such problems, the present inventors have made a biomass-derived polymer of 25 to 60% by mass with respect to the total mass of the impermeable sheet in the impermeable sheet formed by resin processing on the base fabric. The inventors have found that a water-impervious sheet that is environmentally friendly and inferior in physical properties can be obtained by containing in a range, and the present invention has been achieved.

That is, the gist of the present invention is as follows.
(A). A water-impervious sheet formed by subjecting a base fabric to resin processing, containing 25 to 60 mass% of a biomass-derived polymer, tensile strength of 980 to 2940 N / 3 cm, and elongation at maximum load based on JIS-L-1096 Is 8 to 45%, and the cover factor (CF: the following formula (1)) of the base fabric is 500 to 2200.
(B). The water shielding sheet according to (a), wherein the base fabric is composed of a core-sheath type composite fiber in which a biomass-derived polymer is disposed in a core part and a petroleum-based polymer is disposed in a sheath part.
(C). The biomass-derived polymer described in (b) is polylactic acid, and the petroleum-derived polymer is polyethylene terephthalate.

CF = Td · (Ts / pt) ^1/2 + Yd · (Ys / py) ^1/2 (1)
Td: Vertical weave density (main / 2.54cm)
Yd: Horizontal weave density (main / 2.54cm)
Ts: Warp yarn fineness (decitex)
Ys: Weft yarn fineness (decitex)
pt: specific gravity of the warp yarn material (g / cm ³ )
py: specific gravity of the weft material (g / cm ³ )

  Since the water-impervious sheet of the present invention contains 25 to 60% by mass of the biomass-derived polymer, compared to the conventional water-impervious sheet composed of petroleum-based polymers, the atmospheric dioxide dioxide is also used for incineration and disposal. The degree of increasing carbon is small, and it has the effect of reducing global warming.

  In addition, the water-impervious sheet of the present invention contains 25 to 60% by mass of a biomass-derived polymer rich in aliphatic components as a constituent component, and has excellent performance in terms of mechanical properties and workability required as a water-impervious sheet. Holding.

  The water shielding sheet of the present invention can be suitably used as a waste final disposal site (general waste disposal site, industrial waste disposal site, etc.) or a roofing material.

Hereinafter, the present invention will be described in detail.
The water-impervious sheet of the present invention has a form formed by subjecting a base fabric to resin processing, and includes a base fabric and a resin processed portion applied to the base fabric.

  As a water-impervious sheet of this invention, it is necessary to contain a biomass origin polymer 25-25 mass% with respect to the total mass of a water-impervious sheet, and it is preferable to contain 30-55 mass%. When the content of the biomass-derived polymer is less than 25% by mass, for example, the content of the conventional general-purpose polymer such as polyethylene terephthalate is increased, and therefore, the mechanical properties of the water shielding sheet tend to be favorable. However, it is not suitable for the environmental impact reduction and carbon neutral viewpoints that are the gist of the present invention, and is not applicable to bioplastics certification. On the other hand, when the content rate of the biomass-derived polymer exceeds 60% by mass, for example, when the biomass-derived polymer is an aliphatic polyester and is used for fibers constituting the base fabric, the mechanical strength of the obtained water shielding sheet or Characteristics required for weather resistance cannot be maintained.

  The biomass-derived polymer in the present invention is not particularly limited as long as it can be melt-spun. Specifically, polymers obtained by chemically polymerizing monomers derived from biomass such as PLA (polylactic acid), PTT (polytrimethylene terephthalate), and PBS (polybutylene succinate), and PHA (polyhydroxybutyrate) such as polyhydroxybutyric acid. And microbial production systems such as alkanoates). Polylactic acid that is stable in heat resistance and relatively mass-produced is preferable. Examples of polylactic acid include poly D-lactic acid, poly L-lactic acid, poly D-lactic acid which is a copolymer of poly D-lactic acid and poly L-lactic acid, and a mixture of poly D-lactic acid and poly L-lactic acid (stereo Complex), a copolymer of poly D-lactic acid and hydroxycarboxylic acid, a copolymer of poly L-lactic acid and hydroxycarboxylic acid, poly D-lactic acid or poly L-lactic acid, aliphatic dicarboxylic acid and aliphatic diol Or a blend of these.

  In addition, when polylactic acid is used, it is one in which D-lactic acid and L-lactic acid are used alone or in combination as described above. Among them, the melting point is 120 ° C. or higher, and the heat of fusion is 10 J. / G or more is preferable. For example, poly L-lactic acid and poly D-lactic acid, which are homopolymers of polylactic acid, have a melting point of about 180 ° C., but in the case of a copolymer of D-lactic acid and L-lactic acid, If it is about 10 mol%, the melting point will be about 130 ° C. Furthermore, when any component is 18 mol% or more, the melting point is less than 120 ° C., the heat of fusion is less than 10 J / g, and almost completely amorphous properties are obtained. When such an amorphous polymer is used, it becomes difficult to heat-stretch particularly during the production process, and it becomes difficult to obtain high-strength fibers, and even if fibers are obtained, heat resistance, abrasion resistance Since it becomes inferior in property, it is not preferable. Therefore, as polylactic acid, L / D or D / which is the content ratio (molar ratio) of L-lactic acid or D-lactic acid represented by the content ratio of L-lactic acid or D-lactic acid when polymerizing using lactide as a raw material. L is preferably 82/18 or more, more preferably 90/10 or more, and even more preferably 95/5 or more.

  Further, when the polylactic acid used is a mixture (stereocomplex) of poly D-lactic acid and poly L-lactic acid as described above, the melting point is as high as 200 to 230 ° C. and is not easily affected by frictional heat or the like. Therefore, it is particularly preferable. Further, when the polylactic acid used is a copolymer of polylactic acid and hydroxycarboxylic acid, specific examples of hydroxycarboxylic acid include glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxypentanoic acid hydroxyheptane Examples thereof include acid, hydroxyoctanoic acid, etc. Among them, it is preferable from the viewpoint of cost to use hydroxycaproic acid or glycolic acid. In the case of a copolymer of polylactic acid, aliphatic dicarboxylic acid and aliphatic diol, the aliphatic dicarboxylic acid and aliphatic diol include sebacic acid, adipic acid, dodecanedioic acid, trimethylene glycol, 1,4-butane. Diol, 1,6-hexanediol, etc. are mentioned. Moreover, when copolymerizing another component with such polylactic acid, it is preferable to make polylactic acid 80 mol% or more. If the polylactic acid is less than 80 mol%, the crystallinity of the copolymerized polylactic acid tends to be low, and the melting point is less than 120 ° C. and the heat of fusion is less than 10 J / g.

  The molecular weight of polylactic acid is 1 to 100 (g / 10 min) as measured by a temperature of 210 ° C. and a load of 2160 g according to ASTM D-1238 method used as an index of molecular weight. More preferably, it is 5-50 (g / 10min). By setting the melt flow rate within this range, the strength, wet heat decomposability and wear resistance are further improved.

  For the purpose of enhancing the durability of polylactic acid, a terminal blocking agent such as an aliphatic alcohol, a carbodiimide compound, an oxazoline compound, an oxazine compound, or an epoxy compound may be added to polylactic acid. Furthermore, as long as it does not impair the object of the present invention, it is necessary to add a heat stabilizer, crystal nucleating agent, matting agent, pigment, light-proofing agent, weathering agent, lubricant, antioxidant, antibacterial agent in polylactic acid. Perfumes, plasticizers, dyes, surfactants, flame retardants, surface modifiers, various inorganic and organic electrolytes, and other similar additives may be added.

  The polymer other than the biomass-derived polymer used in the water shielding sheet of the present invention is not particularly limited, but is preferably a petroleum-derived polymer that can be melt-spun when used as a base fabric. . Specifically, polyesters typified by polyalkylene terephthalates such as polyethylene terephthalate (PET), polybutylene terephthalate, polytrimethylene terephthalate: nylon 6, nylon 66, nylon 46, nylon 11 and nylon 12 Polyamide: Polyolefins typified by polypropylene and polyethylene: Polychlorinated polymers typified by polyvinyl chloride and polyvinylidene chloride: Polytetrafluoroethylene and copolymers thereof, fluorinated fibers typified by polyvinylidene fluoride, etc. Can be mentioned. Polyester and polyamide polymer, which are low cost, are preferable. More preferably, since the biomass polymer has a large amount of an aliphatic polyester polymer, a polyester polymer is preferable in terms of compatibility. Particularly preferred is polyethylene terephthalate in view of cost and handleability.

  In view of viscosity, thermal characteristics, and compatibility, the polyester polymer may be copolymerized with other monomer components. For example, examples of the acid component include aromatic dicarboxylic acids such as isophthalic acid and 5-sulfoisophthalic acid: aliphatic dicarboxylic acids such as adipic acid, succinic acid, suberic acid, sebacic acid, and dodecanedioic acid, and alcohol components. Examples thereof include aliphatic diols such as ethylene glycol, propylene glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol. Also, a hydroxycarboxylic acid such as glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxypentanoic acid, hydroxyheptanoic acid, hydroxyoctanoic acid, or an aliphatic lactone such as ε-caprolactone may be copolymerized. .

  The base fabric in the present invention is not particularly limited, and can be handled by a woven fabric or a knitted fabric. In a field where strength is required, a woven fabric in which the strength of the raw yarn is easily reflected is preferable. When a coarse mesh such as a grid is required, a weft insertion Russell knitting may be used. The woven fabric is not particularly limited, and various forms can be taken depending on the use. The texture of the woven fabric can be selected as appropriate depending on the raw yarn and the conditions of use.

However, as the base fabric in the present invention, the cover factor (CF) of the woven fabric needs to be 500 to 2200, and preferably 700 to 1300. Formula (1) shows the formula for calculating the cover factor (CF).
CF = Td · (Ts / pt) ^1/2 + Yd · (Ys / py) ^1/2 (1)
Td: Vertical weave density (main / 2.54cm)
Yd: Horizontal weave density (main / 2.54cm)
Ts: Warp yarn fineness (decitex)
Ys: Weft yarn fineness (decitex)
pt: specific gravity of the warp yarn material (g / cm ³ )
py: specific gravity of the weft material (g / cm ³ )

  If the above CF is less than 500, the porosity is too large as a fabric constituting the resin processing, so that the surface becomes uneven, and the resin-coated coating layer becomes thin at the convex portion. It is easily affected by the environment and cracks are likely to occur. On the other hand, when the CF is larger than 2200, there is no gap between the base fabric yarns, and the anchoring effect on the base fabric is reduced, resulting in poor adhesion between the base fabric and the resin or between the resins. Preferably it is 700-1300.

  In the water shielding sheet of the present invention, the biomass-derived polymer is used in the base fabric, but the method is not particularly limited. Specifically, a method of using a fiber made of a petroleum-derived polymer and a fiber made of a biomass-derived polymer in a twisted manner, a method of weaving separately in the weft direction of the fabric, and a petroleum-based origin at predetermined intervals A method of setting and using a fiber made of a polymer and a biomass-derived polymer, a method of covering a fiber made of a biomass-derived polymer with a fiber made of a petroleum-derived polymer, and using a petroleum-derived polymer and a biomass-derived polymer The method using the used composite fiber and the method by these combination can be mentioned. Among these, the method using as a composite fiber is preferable from the point that the mechanical property and thermal property of the fiber which consists of a petroleum origin polymer, and a biomass origin polymer differ. In addition, the composite fiber can be appropriately selected from forms such as a modified cross-section type composite fiber, a side-by-side type composite fiber, and a core-sheath composite fiber, but is a core-sheath composite fiber in the application of the water-shielding sheet of the present invention. It is preferable. Furthermore, the core-sheath conjugate fiber is a concentric core-sheath conjugate fiber in which the core part and the sheath part are arranged substantially concentrically, because it is difficult for spots to occur in mechanical properties and thermal properties, preferable. By setting it as such a structure, the effect which distributes a general purpose polymer uniformly to a sheath part can be show | played. When it exists on an eccentricity, a thin part will arise in the general-purpose polymer layer of a sheath part, and when the general-purpose polymer layer is thin and contraction occurs during resin processing, it will be eccentric and cause misalignment and wrinkles. Such a core-sheath composite fiber can be produced by a known technique.

  Furthermore, the core-sheath composite fiber preferably has a structure in which a biomass-derived polymer is disposed in the core and a polymer other than biomass is disposed in the sheath. Furthermore, it is more preferable that the core part is polylactic acid which is a biomass-derived polymer, and the sheath part is ethylene terephthalate which is a petroleum-based polymer.

  Moreover, as a core-sheath ratio (mass ratio) in the said core-sheath composite fiber, it is preferable that it is core part / sheath part = 50 / 50-90 / 10. When the ratio of the core part using the biomass-derived polymer is less than 50, the amount of the biomass-derived polymer used is small, so that it is not suitable for the purpose of the present invention. In addition, when the ratio of the core part exceeds 90, the thickness of the sheath part for maintaining the mechanical properties and weather resistance is reduced, so that the required physical properties of the obtained water shielding sheet tend not to be maintained, which is not preferable. .

  The coating resin for applying resin processing to the base fabric in the present invention is preferably a polyethylene resin in consideration of chemical resistance, weather resistance and mechanical properties. The polyethylene resin may be any one of high density, medium density, low density, and ultra-low density. In consideration of workability and the like, it is preferable to use a low-density one from the viewpoint of flexibility and mechanical properties.

  In order to impart rubber elasticity, an unsaturated hydrocarbon rubber material may be added as a third component, and in consideration of weather resistance and mechanical properties, pigments such as UV absorbers and carbon black are added to the resin. May be added.

  Furthermore, in the water-impervious sheet of the present invention, it is necessary to cover at least one surface of the synthetic fiber with the coating resin in consideration of water shielding. In addition, as a method of coating, in accordance with a normal method, laminating a film, calendar coating for extruding and coating, or knife coating for applying a liquid using a knife or the like can be employed. Among these, in consideration of the quality of the water-impervious sheet obtained and processing costs, it is desirable to employ extrusion coating with a calendar.

  The waterproof sheet of the present invention requires a tensile strength of 980 to 2940 N / 3 cm, and preferably 1200 to 2500 N / 3 cm. When the tensile strength is less than 980 N / 3 cm, the mechanical strength is insufficient when laying as a waterproof sheet such as a roofing, and the durability is insufficient when embedded in soil such as a final disposal site. . On the other hand, when the tensile strength exceeds 2940 N / 3 cm, there are problems in workability such as dimensional adjustment during construction, and additional processing is required to increase the strength, which is uneconomical.

  As the water shielding sheet of the present invention, the elongation at the maximum load based on JIS-L-1096 needs to be 8 to 45%, and preferably 15 to 35%. If the elongation is less than 8%, it will cause tearing to the mechanical load at the time of construction. If the elongation exceeds 45%, elongation will occur when laid and laid and workability will be reduced. Deteriorate.

  Moreover, as a water-impervious sheet of this invention, it is preferable that the tensile strength retention after irradiation for 250 hours at 63 degreeC with a WS type | mold accelerated exposure apparatus is 60% or more. Thereby, when using as a water-impervious sheet, durability will be guaranteed.

  Furthermore, as a water-proof sheet | seat of this invention, it is preferable that thickness is 1-5 mm, and it is more preferable that it is 1.5-5 mm. When the thickness is less than 1 mm, it is not preferable because there is no cushioning property, mechanical properties for applications are inferior, and breakage easily occurs.

  The biomass-derived polymer and the petroleum-based polymer constituting the water-impervious sheet of the present invention can be added with various additives, thickeners, and known additives that are effective as crystal nucleating agents as necessary. . Specifically, carbon black, calcium carbonate, silicon oxide and silicate, zinc white, high-site clay, kaolin, basic magnesium carbonate, mica, talc, quartz powder, diatomaceous earth, dolomite powder, titanium oxide, zinc oxide , Antimony oxide, barium sulfate, calcium sulfate, alumina, calcium silicate, boron nitride, behenic acid amide and other aliphatic amide compounds, aliphatic urea compounds, benzylidene sorbitol compounds, crosslinked polymer polystyrene, rosin metal salts And glass fiber and whiskers. The substance may be added as it is, or may be added after processing necessary as a nanocomposite. In order to achieve a good price and good physical property balance, an inorganic filler is preferably blended. Moreover, the compounding of a crystal nucleating agent is preferable.

  Moreover, it is also possible to use a plasticizer together with the resin composition constituting the composite fiber in the present invention as long as the effects of the present invention are not impaired. By using a plasticizer, it is possible to reduce the melt viscosity during heat processing, especially during extrusion processing, and to suppress a decrease in molecular weight due to shear heating, etc.In some cases, an improvement in crystallization speed can also be expected. Furthermore, when a film or sheet is obtained as a molded product, extensibility and the like can be imparted. Although there is no limitation in particular as a plasticizer, the following can be illustrated. As the plasticizer for the aliphatic polyester-based biodegradable polyester, ether-based plasticizers, ester-based plasticizers, phthalic acid-based plasticizers, phosphorus-based plasticizers, and the like are preferable, and ether-based plasticizers are excellent in compatibility with polyesters. A plasticizer and an ester plasticizer are more preferable. Examples of ether plasticizers include polyoxyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Examples of ester plasticizers include esters of aliphatic dicarboxylic acids and aliphatic alcohols. Examples of aliphatic dicarboxylic acids include oxalic acid, succinic acid, sebacic acid, and adipic acid. Aliphatic alcohols such as monohydric alcohols such as methanol, ethanol, n-propanol, isopropanol, n-hexanol, n-octanol, 2-ethylhexanol, n-dodecanol, stearyl alcohol, ethylene glycol, 1,2-propylene Dihydric alcohols such as glycol, 1,3-propylene glycol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, neopentyl glycol, polyethylene glycol, and glycerin Trimethylolpropane, it may be mentioned polyhydric alcohols such as pentaerythritol.

Furthermore, in the composite fiber according to the present invention, if necessary, colorants such as pigments and dyes, odor absorbers such as activated carbon and zeolite, fragrances such as vanillin and dextrin, stabilizers such as antioxidants and ultraviolet absorbers. , Lubricants, mold release agents, water repellents, antibacterial agents and other secondary additives.

Next, although an Example demonstrates this invention concretely, it is not limited to this. The obtained water shielding sheet was evaluated by the following method.
(1) Thickness: The thickness of each water shielding sheet was measured according to JIS-L-1096.
(2) Fineness and number of filaments: measured according to JIS-L-1013.
(3) Strength (yarn): Measured according to JIS-L-1013.
(4) Cutting elongation (yarn): Measured according to JIS-L-1013.
(5) Fabric density: measured in accordance with JIS-L-1096.
(6) Tensile strength: measured according to JIS-L-1096.
(7) Elongation at maximum load: Elongation at maximum load when measuring tensile strength according to JIS-L-1096 was measured.

(8) Tensile strength retention after irradiation for 250 hours at 63 ° C. by a WS type accelerated exposure device: The WS type accelerated exposure device (using a sunshine weather meter) was irradiated under conditions of 63 ° C. × 250 hours. Thereafter, the tensile strength was measured by the method (6) to measure the holding ratio.
(9) Tensile strength retention after alkali treatment: After dipping in a saturated calcium hydroxide aqueous solution (PH12) at 70 ° C. for 250 hours, the tensile strength was measured by the method of (6) and the retention rate was measured.
(10) Workability: A sheet of 2 m wide sample was placed in a 20 m × 20 m site (a site in which about 5 kg / piece of rock was laid), and the workability was confirmed by bonding the sheets with a puff.
(11) Testing with heavy machinery: Covering about 30 cm on the sheet installed in (8), reciprocating 10 times at 5 kg / h with a 10 t dump truck (6 cm ³ sediment loading) and a 15 t class bulldozer, The soil covering was removed, and the appearance change was visually confirmed.

Example 1 Polylactic acid having a melting point of 170 ° C., a heat of fusion of 38 J / g, a content ratio of L-lactic acid and D-lactic acid of 98.5 / 1.5 (manufactured by Nature Works), and aromatic polyester As follows, 15 mol% isophthalic acid copolymerized PET having a melting point of 217 ° C. was used, each chip was dried under reduced pressure, and then supplied to a concentric core-sheath type compound melt spinning apparatus for melt spinning. At this time, melt-spinning was performed at a spinning temperature of 240 ° C. with a copolymer ratio of 50/50 and a composite ratio (core-sheath mass ratio) of copolymer PET as a sheath and polylactic acid as a core. The obtained composite fiber had a round cross-sectional shape with a fineness of 940 dtex 140 filament, a tensile strength of 6.3 cN / dtex, and a cut elongation of 26.0%.
This raw yarn was woven in a plain weave structure at a weaving density of 19.0 yarns / 2.54 cm and a weft density of 20.0 yarns / 2.54 cm on a rapier loom. (The raw yarn specific gravity was calculated as (1.27 + 1.38) /2=1.325 because the core-sheath mass ratio was 50/50.) LDPE (for example, trade name: Sumikasen manufactured by Sumitomo Chemical Co., Ltd.) was coated so as to be 25 g / m ² to produce a water shielding sheet of Example 1 shown in Table 1.

(Example 2) Melt spinning was performed in the same manner as in Example 1 to obtain a composite fiber having a round cross-sectional shape of 830 dtex 96 filaments, a tensile strength of 7.0 cN / dtex, and a cut elongation of 12.0%. Using this raw yarn, weaving and processing was carried out in the same manner as in Example 1 to obtain a water shielding sheet of Example 2.
(Example 3) Melt spinning was carried out in the same manner as in Example 1 to obtain a composite fiber having a round sectional shape of 1670 dtex 140 filaments, a tensile strength of 8.2 cN / dtex, and a cut elongation of 10.0%. However, since the core-sheath ratio was 30/70, the specific gravity was calculated as (1.27 × 0.3 + 1.38 × 0.7) = 1.347. This raw yarn was woven in a plain weave structure at a weaving density of warp density of 14.0 yarns / 2.54 cm and weft density of 14.0 yarns / 2.54 cm on a rapier loom. The subsequent steps were carried out in the same manner as in Example 1 to obtain the water shielding sheet of Example 3.

(Comparative Example 1) Melt spinning was carried out in the same manner as in Example 1 to obtain a composite fiber having a round cross-sectional shape of 940 dtex 140 filaments, a tensile strength of 4.0 cN / dtex, and a cut elongation of 40.0%. Using this raw yarn, weaving and processing was performed in the same manner as in Example 1 to obtain a water shielding sheet of Comparative Example 1.
(Comparative Example 2) The composite fiber obtained in Example 1 was used for weaving and processing in the same manner as in Example 1 except that the weaving density of warps and wefts was 6 / 2.54 cm. A good water shielding sheet could not be obtained.

(Comparative Example 3) As aromatic polyester, PET copolymerized with 15 mol% of isophthalic acid having a melting point of 217 ° C was dried under reduced pressure, and then supplied to a melt spinning apparatus to perform melt spinning at a spinning temperature of 240 ° C. The obtained fiber had a round cross-sectional shape with a fineness of 1100 dtex192 filament, a tensile strength of 7.7 cN / dtex, and a cut elongation of 19.0%. Using this raw yarn, weaving and processing was performed in the same manner as in Example 1 except that the warp density was 20.0 pieces / 2.54 cm and the weft density was 20.0 pieces / 2.54 cm. Got.

  Table 1 shows the physical property measurement results for each example and comparative example.

From the results of Table 1, Examples 1 to 3 were satisfactory in all items, and had physical properties equivalent to those of conventional materials. However, Comparative Example 1 using a polymer derived from biomass was an environmentally friendly material, but due to its high elongation, elongation occurred during laying, resulting in poor workability. The damaged part was confirmed, and it was not practically endurable as a water shielding sheet. Further, in Comparative Example 2, since the cover factor of the base fabric was too low, a high-quality water-impervious sheet could not be obtained, and it did not withstand subsequent evaluation. In Comparative Example 3, since the base fabric is composed only of polyethylene terephthalate, the required values of each physical property are satisfied, but the biomass-derived polymer is not used, and therefore, it is not suitable for the purpose of the present invention.

Claims (3)

A water-impervious sheet formed by subjecting a base fabric to resin processing, containing 25 to 60 mass% of a biomass-derived polymer, tensile strength of 980 to 2940 N / 3 cm, and elongation at maximum load based on JIS-L-1096 Is 8 to 45%, and the cover factor (CF: the following formula (1)) of the base fabric is 500 to 2200.

CF = Td · (Ts / pt) ^1/2 + Yd · (Ys / py) ^1/2 (1)
Td: Vertical weave density (main / 2.54cm)
Yd: Horizontal weave density (main / 2.54cm)
Ts: Warp yarn fineness (decitex)
Ys: Weft yarn fineness (decitex)
pt: specific gravity of the warp yarn material (g / cm ³ )
py: specific gravity of the weft material (g / cm ³ )
The water shielding sheet according to claim 1, wherein the base fabric is constituted by a core-sheath type composite fiber in which a biomass-derived polymer is disposed in a core part and a petroleum-based polymer is disposed in a sheath part. 3. The water shielding sheet according to claim 2, wherein the biomass-derived polymer is polylactic acid and the petroleum-based polymer is polyethylene terephthalate.