JP2008017749A - Weed proofing sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoplastic filament nonwoven fabric having low environmental impact because of comprising aliphatic polyester as the main ingredient, and having characteristics suitable for using as a weed proofing sheet. <P>SOLUTION: The weed proofing sheet is made of the thermoplastic filament nonwoven fabric. The weed proofing sheet comprises thermoplastic filament obtained by blending aliphatic polyester with polyamide. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a herbicidal sheet comprising a thermoplastic filament nonwoven fabric, and includes a thermoplastic filament comprising a blend polymer of an aliphatic polyester and a polyamide.

  Conventionally, a thermoplastic filament nonwoven fabric produced by the so-called spunbond method has been widely used as a herbicidal sheet because of the advantage that high strength can be obtained by thermal bonding or needle punching, and is mainly composed of polyethylene terephthalate. Is used. However, the conventional herbicidal sheet has a big problem in disposal when it becomes unnecessary. For example, when a landfill treatment is performed, the herbicidal sheet is chemically stable and is not easily disintegrated in form, so that there is a problem that the shape is kept for a long period of time. Further, when incinerated, there is a problem that the incinerator is damaged or black smoke is generated due to the high calorific value at the time of combustion.

For example, Patent Document 1 is composed of a synthetic fiber long fiber that is pressure-bonded and bonded, the constituent fibers have an average fineness of 3 to 10 denier, a basis weight of 100 to 500 g / m ² , and a nonwoven fabric density of 0.3 g / cm ^3. As described above, a herbicidal sheet characterized by comprising a synthetic fiber long fiber nonwoven fabric having a projected plane porosity of 0.01 to 0.1% and a penetration resistance of 8 kg or more has been proposed. However, since the herbicidal sheet is a fiber obtained from polyester, polyamide, polypropylene, or a copolymer thereof obtained from an organic synthetic polymer having fiber-forming ability, the disposal problem after use cannot be solved.

  Therefore, in recent years, along with an increase in environmental orientation, aliphatic polyester fibers having various biodegradability, and further nonwoven fabrics made of the same have been proposed. Non-woven fabric with biodegradability is chemically decomposed by the action of sunlight, ultraviolet rays, heat, water, enzymes, microorganisms, etc. in natural environments, and further morphologically collapses, so there is no need for incineration treatment. It can be disposed of by landfill or left outdoors. Even if incineration is performed, the biodegradable resin has a merit that the incinerator is not damaged during incineration because the amount of combustion heat is generally lower than that of polyester and the like used in conventional nonwoven fabrics.

  In addition, among the biodegradable resins, so-called non-petroleum raw materials such as polylactic acid are not derived from petroleum. For example, polylactic acid can be synthesized using starch as the main raw material. It has the merit that it can prevent the increase of carbon dioxide emission to the atmosphere due to. However, non-woven fabrics mainly composed of polylactic acid and other aliphatic polyesters are often inferior in heat resistance and strength compared to non-woven fabrics made of general polyethylene terephthalate or nylon, and are used as a herbicidal sheet. There has never been a combination of sufficient strength, dimensional stability, heat resistance, processing stability, and the like.

For example, Patent Document 2 proposes a herbicidal sheet formed of a nonwoven fabric made of a thermoplastic aliphatic polyester fiber having biodegradability, and in this document, work for laying a sheet on the soil surface From the viewpoint of properties, it is described that the tensile strength when converted to a nonwoven fabric basis weight of 100 g / m ² is preferably 5 kg / 5 cm width or more. Furthermore, Patent Document 3 discloses a biodegradable herbicidal sheet with limited penetration resistance by an iron shaft, assuming a grown reed weed having a shaft diameter of 8.4 mm, a shaft length of 3 cm, and a shaft cutting angle of 45 degrees. In this document, it is described that the penetration resistance needs to be in the range of 0.1X−8 to 0.1X + 5 (X: basis weight) from the viewpoint of the effect on weeds with strong budding power. ing. However, none of these documents describes a strong elongation product when dry or wet, so it is stable against wind and rain after laying a grass-proof sheet, and the force applied by people and cars. It was not able to withstand.
Japanese Examined Patent Publication No. 4-52727 Japanese Patent No. 3573612 JP-A-2005-102600

  In view of the above-mentioned problems of the prior art, the present invention contains a resin that is excellent in mechanical strength and that can be synthesized from non-petroleum raw materials such as aliphatic polyesters, particularly polylactic acid, as a main component. Even so, we will provide a grass protection sheet with low environmental impact.

  The present invention employs the following means in order to solve such problems.

That is,
(1) A herbicidal sheet comprising a thermoplastic filament nonwoven fabric, comprising a thermoplastic filament comprising a blend polymer of aliphatic polyester and polyamide.

(2) The single filament fineness of the thermoplastic filament made of the blend polymer is 1 to 15 dtex, the basis weight of the nonwoven fabric is 50 to 300 g / m ² , and the high elongation product per basis weight when dry and wet Both are 40-300, The weedproof sheet of the said (1) description characterized by the above-mentioned.

  (3) The thermoplastic filament made of the blend polymer contains 0.1 to 5.0 wt% of aliphatic bisamide and / or alkyl-substituted aliphatic monoamide. (1) to (2) The grass prevention sheet | seat in any one of.

  (4) The weedproof sheet according to any one of (1) to (3) above, wherein a weight ratio of aliphatic polyester: polyamide of the blend polymer is 20:80 to 95: 5.

(5) In the cross-sectional direction of the thermoplastic filament made of the blend polymer, the polyamide component is finely dispersed at an average single fiber fineness of 1 × 10 ⁻⁷ to 1 × 10 ⁻³ dtex, (1) The herbicidal sheet according to any one of to (4).

  (6) The weedproof sheet according to any one of (1) to (5), wherein the aliphatic polyester is polylactic acid and the polyamide is nylon 6.

  (7) The weedproof sheet according to any one of (1) to (6) mp, wherein the nonwoven fabric is a spunbond nonwoven fabric.

  (8) The weedproof sheet according to any one of (1) to (7), wherein fibers constituting the nonwoven fabric are mechanically entangled.

  ADVANTAGE OF THE INVENTION According to this invention, the herbicidal sheet which has the outstanding mechanical strength can be provided, including aliphatic polyester as one of the main components.

  The herbicidal sheet of the present invention is composed of a thermoplastic filament nonwoven fabric, and contains a thermoplastic filament composed of a blend polymer in which an aliphatic polyester and a polyamide are blended as a thermoplastic filament constituting the thermoplastic filament nonwoven fabric. It is.

  The aliphatic polyester is not particularly limited as long as it is a biodegradable aliphatic polyester. For example, polylactic acid, polyglycolic acid, polyhydroxybutyrate, polyhydroxybutyrate valerate, or a copolymer or modified product thereof. Can be used alone or in combination. Of these, polylactic acid is most preferable because it has good spinnability and mechanical properties, and can be synthesized from plant-derived starch, and therefore has little environmental impact. As such polylactic acid, poly (D-lactic acid), poly (L-lactic acid), a copolymer of D-lactic acid and L-lactic acid, or a blend thereof (including a stereo complex) is preferable. . The weight average molecular weight of the polylactic acid resin is preferably 50,000 to 300,000, more preferably 100,000 to 300,000. When the weight average molecular weight is less than 50,000, the strength of the fiber tends to be low, and when the weight average molecular weight exceeds 300,000, the spinnability of the polymer extruded from the nozzle is poor because the viscosity is high, It becomes difficult to draw at high speed, and ultimately it becomes an undrawn state, and there is a tendency that sufficient fiber strength cannot be obtained.

  Further, the aliphatic polyester used in the present invention is preferably one in which a part or all of the carboxyl groups at the molecular chain terminals are end-capped with a terminal blocking agent. When a part or all of the carboxyl groups at the end of the molecular chain of the aliphatic polyester are end-capped, a decrease in strength of the filament and further the sheet due to hydrolysis is suppressed. The terminal carboxyl group concentration of the aliphatic polyester is preferably 0 to 20 equivalents / ton, more preferably 0 to 15 equivalents / ton, and more preferably 0 to 10 equivalents / ton by adding a terminal blocking agent. Is more preferable. Here, the carboxyl group end concentration of the aliphatic polyester was determined by dissolving a precisely weighed sample in o-cresol (5% water), adding an appropriate amount of dichloromethane to this solution, and then using 0.02 N KOH methanol solution. It can be determined by titration.

  The endblocker for the aliphatic polyester used in the present invention is not limited at all, but carbodiimide compounds and glycidyl-modified compounds having isocyanuric acid as a basic skeleton are preferable. The addition amount of these end-capping agents is preferably in the range of 0.05 to 10 wt%, more preferably in the range of 0.1 to 7 wt%, with respect to the aliphatic polyester.

Although it does not specifically limit as a carbodiimide compound used as a terminal blocker of aliphatic polyester in this invention, When a monocarbodiimide compound is used, 5% weight reduction temperature (henceforth T5 _% is shown. ) Is preferably a monocarbodiimide compound having a temperature of 170 ° C. or higher, and more preferably, T _5% is a monocarbodiimide compound having a temperature of 190 ° C. or higher. When T _5% of the monocarbodiimide compound is less than 170 ° C., the monocarbodiimide compound is decomposed and / or vaporized during spinning, which tends to increase yarn breakage and deteriorate product quality, which is not preferable. Furthermore, the monocarbodiimide compound is not preferable because it does not effectively react and act on the carboxyl group terminal of the aliphatic polyester and a sufficient effect of improving hydrolysis resistance cannot be obtained. Here, the 5% weight loss temperature is a sample weight of about 10 mg measured by a “TG-DTA2000S” TG-DTA measuring machine manufactured by MACSCIENCE, at a temperature rising rate of 10 ° C./min in a nitrogen atmosphere. This is the temperature obtained as the temperature when the weight is reduced by 5% with respect to the sample weight before the start of measurement.

  Examples of the monocarbodiimide compound that can be used as a terminal blocking agent in the present invention include, for example, N, N′-di-2,6-diisopropylphenylcarbodiimide, N, N′-di-2,6-di-tert. . -Butylphenylcarbodiimide, N, N'-di-2,6-diethylphenylcarbodiimide, N, N'-di-2-ethyl-6-isopropylphenylcarbodiimide, N, N'-di-2-isobutyl-6 Isopropylphenylcarbodiimide, N, N′-di-2,4,6-trimethylphenylcarbodiimide, N, N′-di-2,4,6-triisopropylphenylcarbodiimide, N, N′-di-2,4 Examples thereof include 6-triisobutylphenyl carbodiimide. The monocarbodiimide compound used as the end-capping agent may be a single type or a mixture of a plurality of types, but N, N in terms of heat resistance and reactivity and affinity with aliphatic polyesters. '-Di-2,6-diisopropylphenylcarbodiimide (hereinafter referred to as TIC) is preferable. When a plurality of types of monocarbodiimide compounds are used in combination, 50% or more of the total amount of monocarbodiimide compounds used as the end-capping agent is TIC. It is preferable that

  As a method of blocking the terminal carboxyl group with the monocarbodiimide compound, it can be obtained by reacting an appropriate amount of the monocarbodiimide compound as a terminal blocking agent in the molten state of the aliphatic polyester. From the viewpoint of suppressing low molecular weight substances, it is preferable to add and react the monocarbodiimide compound after completion of the polymerization reaction of the polymer. Examples of the mixing and reaction of the above-described monocarbodiimide compound and aliphatic polyester include, for example, a method of adding a monocarbodiimide compound to a molten aliphatic polyester immediately after the completion of the polycondensation reaction, stirring and reacting, and an aliphatic polyester chip. A method of adding and mixing a monocarbodiimide compound and then kneading and reacting with a reactor or an extruder, etc., a method of continuously adding a liquid monocarbodiimide compound to aliphatic polyester with an extruder, kneading and reacting, It can be carried out by a method of kneading and reacting a blend chip obtained by mixing a concentration-containing aliphatic polyester master chip and an aliphatic polyester homochip with an extruder or the like.

  The carbodiimide compound used as a hydrolysis inhibitor in the present invention is not particularly limited, but when a polycarbodiimide compound is used, [Chemical Formula 1]

4,4'-dicyclohexylmethane diisocyanate represented by the formula:

And isophorone diisocyanate represented by the formula:

It is preferably a polycarbodiimide compound derived from at least one tetramethylxylylene diisocyanate represented by the formula, having two or more carbodiimide groups in the molecule, and having the isocyanate terminal sealed with a carboxylic acid. .

  The polycarbodiimide compound is a 4,4′-dicyclohexylmethane diisocyanate (hereinafter abbreviated as HMDI) represented by the above formula 1, or an isophorone diisocyanate (hereinafter abbreviated as “IPDI”) represented by the above formula 2, or the above A carbodiimide derived from any one of tetramethylxylylene diisocyanate (hereinafter abbreviated as TMXDI) represented by Formula 3, or a carbodiimide derived from any mixture of the above compounds or any of the three mixtures. The main component is one having 2 or more carbodiimide groups in the molecule, preferably 5 or more carbodiimide groups. The upper limit of carbodiimide groups in polycarbodiimide is 20. Such a carbodiimide can be produced by a carbodiimidization reaction accompanied by a decarbonation reaction using HMDI, IPDI, TMXDI, a mixture of the above two compounds, or a mixture of the three compounds as a raw material. Of these, carbodiimide using 50% by weight or more of HMDI is preferable and carbodiimide using 80% by weight or more of HMDI is more preferable because the obtained fiber has excellent mechanical properties.

  In addition, as the polycarbodiimide compound used in the present invention, even if an unreacted polycarbodiimide compound is present in the aliphatic polyester resin, since it is excellent in thermal stability, the spinnability deteriorates when it is made into a filament. Since generation | occurrence | production of an irritating gas can be suppressed, it is necessary for the isocyanate terminal to be the terminal sealed using carboxylic acid. The carboxylic acid preferably used is a monocarboxylic acid, such as cyclohexane carboxylic acid, benzoic acid, trimellitic anhydride, 2-naphthoic acid, nicotinic acid, isonicotinic acid, 2-fluic acid, propionic acid, butyric acid, isobutyric acid, Examples include methacrylic acid, palmitic acid, stearic acid, oleic acid, cinnamic acid, glyceric acid, acetoacetic acid, benzylic acid, and anthranilic acid. Among these, cyclohexanecarboxylic acid is most preferred.

  In order to reduce the amount of pyrolysis gas generated by thermal degradation of the unreacted polycarbodiimide compound, the amount of polycarbodiimide compound added is equal to or less than twice the total carboxyl group terminal amount of the aliphatic polyester as the carbodiimide group equivalent. It is preferable to do. The addition amount of the polycarbodiimide compound is more preferably 1.5 times equivalent or less, more preferably 1.2 times equivalent or less of the total carboxyl group terminal amount.

  The glycidyl-modified compound having isocyanuric acid as a basic skeleton used as an endblocker for aliphatic polyesters in the present invention is represented by the following [Chemical Formula 4].

(Here, at least one of R _{1 to} R ₃ is a glycidyl ether or a glycidyl ester, and the rest are functional groups such as hydrogen, an alkyl group having 1 to 10 carbon atoms, a hydroxyl group, and an allyl group).
The glycidyl-modified compound having isocyanuric acid as a basic skeleton used as a terminal blocking agent in the present invention is not particularly limited as long as it is a compound represented by the above [Chemical Formula 4]. Any one of R ₁ to ₃ is a glycidyl group, the remaining two are allyl groups, diallyl monoglycidyl isocyanurate, or any _one of R _{1 to} R _{3 in} the above [Chemical Formula 4] is a glycidyl group. Monoallyl diglycidyl isocyanurate, one of which is an allyl group, and tris (2,3-epoxypropyl) isocyanurate in which all of R _{1 to} R _{3 in} the above [Chemical Formula 4] are glycidyl groups are preferably used. In addition, a crystal nucleating agent, a matting agent, a pigment, an antifungal agent, an antibacterial agent, a flame retardant, an antistatic agent, a hydrophilic agent, and the like may be added to the aliphatic polyester as long as the effects of the present invention are not impaired. .

  In the present invention, nylon 6, nylon 66, nylon 6-10, nylon 12, or a copolymer or a modified product thereof can be used alone or blended as the polyamide constituting the blended polymer with the aliphatic polyester. . In selecting the polyamide, it is preferable to select a polyamide having a small melting point difference from the aliphatic polyester. In addition, a crystal nucleating agent, a matting agent, a pigment, an antifungal agent, an antibacterial agent, a flame retardant, an antistatic agent, a hydrophilic agent, and the like may be added to the polyamide as long as the effects of the present invention are not impaired.

  The most preferred blend polymer in the present invention is one using the above-mentioned polylactic acid as the aliphatic polyester and nylon 6 as the polyamide. Nylon 6 is particularly preferable because it has a melting point of 220 ° C. and a melting point of 170 ° C. of polylactic acid with a small difference in melting point, high affinity, and good spinnability when combined spinning. Furthermore, since one polymer does not melt excessively when heat-bonded with a small difference in melting point and the flexibility of the sheet is not impaired, it is also possible to obtain a herbicidal sheet excellent in workability during laying. preferable.

  The weight ratio of aliphatic polyester: polyamide blended in the present invention is preferably in the range of 20:80 to 95: 5, more preferably 40:60 to 90:10, and most preferably 50:50 to 85:15. If the weight ratio of the polyamide exceeds 80, the effect of reducing the environmental impact by blending the aliphatic polyester is reduced, which is not preferable. If the weight ratio of the polyamide is 5 or more, the nonwoven fabric tends to have sufficient strength and heat shrinkage characteristics, which is preferable.

The thermoplastic filament made of the blend polymer in the present invention is preferably formed by finely dispersing polyamide in the cross-sectional direction at an average single fiber fineness of 1 × 10 ⁻⁷ to 1 × 10 ⁻³ dtex. If the average single fiber fineness of the polyamide is finely dispersed within the above range, the nonwoven fabric tends to have sufficient strength and heat shrinkage characteristics, which is preferable. The average single fiber fineness of the finely dispersed polyamide is more preferably 2 × 10 ^{−7 to} 5 × 10 ⁻⁴ dtex, and most preferably in the range of 9 × 10 ⁻⁷ to 4 × 10 ⁻⁴ dtex. In addition, the average single fiber fineness of the polyamide component in this invention is calculated | required with the following method. That is, 10 small sample samples are randomly collected from a sample, embedded in an epoxy resin, cut out as an ultrathin section in a cross-sectional direction, and 40,000 to 100,000 using a transmission electron microscope (TEM, for example, Hitachi H7100FA type). Take a photo at double magnification. The average value is calculated by measuring the size of the cross-sectional area of the polyamide component from each sample by 20 pieces in total, calculating a mean value, converting this to the fiber diameter of the circular fiber, and correcting the polymer density. is there. If it is difficult to distinguish between polyamide and aliphatic polyester in TEM observation, the sample may be appropriately stained.

In the present invention, as a method for finely dispersing the polyamide in the aliphatic polyester, it is preferable to knead by a melt kneading extruder, a stationary kneader or the like. In addition, as a method for improving kneadability, the combination of polyamide and aliphatic polyester is also important, and it is preferable to optimize the compatibility of the combined polymer. As a compatibility index, the difference in solubility parameter (SP value) between polyamide and aliphatic polyester is preferably 1 to 9 (MJ / m ³ ) ^1/2 . Here, the SP value is a parameter reflecting the cohesive strength of a substance defined by (evaporation energy / molar volume) ^1/2 . For example, “Plastic Data Book” Asahi Kasei Amidus Co., Ltd./Plastics Editorial Department, 189 It is described on the page. If the SP value difference between the polyamide and the aliphatic polyester is in the range of 1 to 9 (MJ / m ³ ) ^1/2 , the compatibility between the polymers will be improved, so that the dispersibility of the polyamide will be improved and the spinning stability will be improved. This is a preferable direction because the tendency to improve the property is also improved. For example, the above-mentioned combination of polylactic acid and nylon 6 has a difference in SP value of 2 (MJ / m ³ ) ^1/2 and is preferable from the viewpoint of compatibility.

Furthermore, it is preferable that the melt viscosity of the polyamide is lower than that of the aliphatic polyester. It is preferable that the melt viscosity of the polyamide is lower than that of the aliphatic polyester because the polyamide is easily deformed by shearing force and easily dispersed.
Although the said blend polymer is used as a raw material polymer of a thermoplastic filament nonwoven fabric, when manufacturing a thermoplastic filament nonwoven fabric by the spun bond method mentioned later, you may perform a blend and spinning continuously. Moreover, thermoplastic filaments other than the thermoplastic filament which consists of blend polymers may be included.

  Moreover, it is preferable that the single fiber fineness of the thermoplastic filament which consists of a blend polymer in this invention is 1-15 dtex. If the single fiber fineness of the filament is less than 1 dtex, the spinnability tends to deteriorate, which is not preferable. If the single fiber fineness of the filament exceeds 15 dtex, it is not preferable because spinning of the yarn becomes insufficient during spinning and the spinning stability tends to deteriorate. A more preferable range of the single fiber fineness is 2 to 12 dtex. In addition, the single fiber fineness referred to here is a sample of 10 small pieces taken at random from a sample, photographed 500 to 3000 times with a scanning electron microscope or the like, and 10 fibers from each sample, a total of 100 fibers. The fiber diameter calculated by rounding off the average of those values and rounding to the nearest 0.01 μm is corrected with the density of the polymer, and the first decimal place is rounded off. Furthermore, the cross-sectional shape of the filament is not limited at all, and a round shape, an oval shape, a hollow round shape, a flat shape, or an irregular shape such as an X shape, a Y shape, or a multileaf shape is preferably used. .

The basis weight of the thermoplastic filament nonwoven fabric in the present invention is preferably 50 to 300 g / m ² . If the basis weight is less than 50 g / m ² , it tends to be difficult to obtain sufficient strength for use as a weedproof sheet, and if the basis weight exceeds 300 g / m ² , workability when laying the weedproof sheet is not preferable. Deteriorates and is not preferable in terms of cost. More preferred nonwoven basis weight 60~250g / ^{m 2,} more preferably in the range of 70~200g / ^{m 2.} Here, the basis weight is obtained by the following method. In other words, three samples with a size of 50 cm in length x 50 cm in width are taken and each weight is measured, and the average value of the obtained values is converted per unit area and calculated by rounding off the first decimal place. It is.

  Moreover, in the thermoplastic filament nonwoven fabric in this invention, it is preferable that both the strong elongation products per basis weight at the time of drying and wetness are 40-300. When the strength / elongation product is less than 40 per unit weight when dry or wet, the strength of the nonwoven fabric becomes insufficient, and the sheet may be torn due to wind and rain after laying, people, cars, etc. In particular, when wet, nonwoven fabrics generally made of aliphatic polyester resins tend to have low strength, and when a weedproof sheet is laid on the slope, the weight of the sheet increases due to moisture and tears occur from the fixing parts of the sheet. From the standpoint of ease, the product of strong elongation per unit weight is preferably 40 or more. On the other hand, when the product of strong elongation per unit area exceeds 300, the texture of the nonwoven fabric becomes too hard and the workability during laying tends to deteriorate. A more preferred strength elongation product per unit weight is in the range of 50 to 250.

In addition, the strong elongation product per basis weight of the nonwoven fabric in the present invention indicates the relationship between the basis weight of the nonwoven fabric, the tensile strength, and the elongation. The tensile strength and elongation are obtained by the following methods. That is, for each of the longitudinal direction (sheet length direction) and the lateral direction (sheet width direction) of the nonwoven fabric, 10 test pieces having a length of 30 cm and a width of 5 cm are collected. The test piece is subjected to a tensile test with a constant speed extension type tensile tester at a grip interval of 20 cm and a tensile speed of 10 ± 1 cm / min, and the strength (N) at the maximum load until breakage is about 0.1N. To obtain a tensile strength (N / 5 cm). Further, the elongation (cm) at the maximum load is obtained to the order of 0.1 cm, this is divided by the test length (20 cm), and the second decimal place is rounded off to obtain the elongation (%). The total average value of the total 20 points of the obtained tensile strength and elongation in the machine direction and the transverse direction is obtained by rounding off the first decimal place, and these are taken as the tensile strength and elongation of the nonwoven fabric. The basis weight is obtained by the above-described method. Here, the strong elongation product per basis weight is obtained by dividing the product of the tensile strength and the elongation by the basis weight and rounding off the first decimal place. In addition, the strong elongation product per basis weight at the time of drying is obtained from a non-woven fabric having a moisture content of 0.5 to 4 wt%, while the strong elongation product per basis weight when wet is a moisture content of 250 to 300 wt%. It is obtained from the non-woven fabric.
Moreover, in the thermoplastic filament nonwoven fabric in this invention, it is preferable that the stress at the time of 5% elongation per basis weight is 0.6-1.4, and it is further more preferable that it is 0.7-1.3. . If the stress at 5% elongation per unit weight exceeds 1.4, the texture of the nonwoven fabric is hard, the surface is inferior in unevenness, and laying workability may be deteriorated. On the other hand, when the stress at the time of 5% elongation per basis weight is less than 0.6, it is not preferable because the strength of the nonwoven fabric is reduced.

  In addition, the stress at the time of 5% elongation per basis weight of the nonwoven fabric in the present invention indicates the relationship between the basis weight of the nonwoven fabric and the stress at 5% elongation. For the stress at 5% elongation, a tensile test is performed under the same conditions as those for obtaining the tensile strength and elongation at the time of drying. The strength (N) when the elongation is 5% is obtained to the order of 0.1N, and this is defined as the stress at 5% elongation. The total average value is obtained by rounding off the first decimal place, and this is defined as the 5% elongation stress of the nonwoven fabric. Further, the 5% elongation stress of the obtained nonwoven fabric is divided by the basis weight, and the second decimal place is rounded off to obtain the 5% elongation stress per basis weight.

  In the present invention, the thermoplastic filament constituting the thermoplastic filament nonwoven fabric preferably contains 0.1 to 5.0 wt% of aliphatic bisamide and / or alkyl-substituted aliphatic monoamide. By containing 0.1 wt% or more of aliphatic bisamide and / or alkyl-substituted aliphatic monoamide, the frictional resistance of the filament surface is reduced, and the texture of the nonwoven fabric becomes flexible. It tends to be improved and is preferable, and by setting the content to 5.0 wt% or less, it is preferable that deterioration of spinnability hardly occurs. A more preferable content range is 0.1 to 3.0 wt%, and a most preferable range is 0.3 to 2.0 wt%. In the present invention, aliphatic bisamides or alkyl-substituted aliphatic monoamides may be used singly or in combination.

The aliphatic bisamide used in the present invention is not particularly limited, and examples thereof include saturated fatty acid bisamides, unsaturated fatty acid bisamides, and aromatic fatty acid bisamides, such as methylene bis stearamide, ethylene bis stearamide, Examples thereof include ethylene bisvalmitic acid amide and ethylene bisoleic acid amide, and a plurality of these may be used in combination.
Examples of the alkyl-substituted aliphatic monoamide used in the present invention include compounds having a structure in which an amide hydrogen such as a saturated fatty acid monoamide or an unsaturated fatty acid monoamide is substituted with an alkyl group, and N-lauryl lauric acid amide and N-palmityl Examples thereof include palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, and a plurality of these may be used in combination.

  In order to contain the aliphatic bisamide and / or the alkyl-substituted aliphatic monoamide in the thermoplastic filament, there are methods such as applying to the surface of the thermoplastic filament, but a method of adding to the blend polymer as a raw material is preferable. The method of adding the aliphatic bisamide and / or the alkyl-substituted aliphatic monoamide to the blend polymer as a raw material for spinning is not limited at all, but the raw resin and the substance to be added are previously heated and melt mixed. The most preferable method is to prepare a master chip and add the necessary amount to the raw material resin during spinning to adjust the amount of the added substance.

  The thermoplastic filament nonwoven fabric used as the herbicidal sheet in the present invention is preferably a long-fiber nonwoven fabric composed of continuous filaments, and is a long length obtained by the spunbond method from the viewpoint of high production efficiency and excellent mechanical strength and dimensional stability. A fiber nonwoven fabric is most preferred. The spunbond method of the present invention is to extrude a melted raw material polymer from a nozzle, suck and stretch it with a high-speed suction gas to form a filament, charge and open it, and deposit and collect it on a moving conveyor to form a fiber web. This fiber web is a method of forming a sheet integrated by thermal bonding, mechanical entanglement, or a combination of these methods. In the present invention, the temperature at which the raw polymer is melted is preferably 30 to 90 ° C higher than the melting point of the aliphatic polyester, more preferably 40 to 80 ° C, and most preferably 50 to 70 ° C. When the difference between the melting temperature and the melting point of the aliphatic polyester is less than 30 ° C., the melt viscosity of the raw material becomes too high, and the spinnability tends to become unstable, which is an undesirable direction. When the difference between the melting temperature and the melting point of the aliphatic polyester exceeds 90 ° C., the thermal decomposition of the aliphatic polyester tends to be particularly severe, which is not preferable. Furthermore, the spinning speed at which the filament is drawn by suction is preferably 1500 to 6000 m / min. When the spinning speed is less than 1500 m / min, the filament strength may be insufficient due to insufficient stretching, which is not preferable. When the spinning speed exceeds 6000 m / min, the spinning stability tends to deteriorate, which is not preferable. A more preferable spinning speed range is 2000 to 5000 m / min.

  In addition, as a method of integrating the fiber web, thermal bonding, mechanical entanglement, or a combination of these methods is preferable. What is made partially in the range of 5 to 50% with respect to the total area is preferable. As a method of thermally bonding the fibers partially, a heat embossing process using a pair of embossing rolls or a heat embossing process using an embossing roll and a flat roll is preferable. In the partial thermal bonding, when the ratio of the bonding area is less than 5% with respect to the total area of the nonwoven fabric, the strength of the nonwoven fabric tends to be insufficient, which is not preferable. When the ratio of partial thermal bonding exceeds 50% with respect to the total area of the nonwoven fabric, the nonwoven fabric feels too hard, and the workability during laying tends to deteriorate, which is not preferable. A more preferable ratio of partial thermal bonding is 8 to 30%. Furthermore, the temperature of these thermal bonding is preferably 5 to 70 ° C., more preferably 10 to 60 ° C. lower than the melting point of the aliphatic polyester constituting the filament. When the temperature difference between the thermal bonding temperature and the melting point of the aliphatic polyester is less than 5 ° C., the thermal bonding tends to be too strong, which is not preferable. When the temperature exceeds 70 ° C., thermal bonding may be insufficient, which is an undesirable direction.

In addition, the mechanical entanglement in the present invention is preferably a needle punch process in which filaments are entangled with needles having protrusions, or a water jet punch process in which filaments are entangled with a columnar water flow. In the case of the needle punching treatment, those treated at a needle density of 20 to 200 times / cm ² are preferable. When the needle density is less than 20 times / cm ² , the entanglement is insufficient and the strength tends to be low, which is not preferable. When the needle density exceeds 200 times / cm ² , the entanglement is sufficient, but the filament is severely damaged and the strength of the nonwoven fabric tends to decrease, which is not preferable. A more preferable needle density is 30 to 150 times / cm ² . In the case of the water jet punching treatment, it is preferable to treat each of the front and back surfaces at least once with a water pressure of 5 to 20 MPa. When the treatment water pressure is in the range of 5 to 20 MPa, the entanglement is appropriately performed and the strength of the nonwoven fabric tends to be sufficient. Nonwoven fabrics mechanically entangled by these methods are preferable in that the constituent fibers are entangled three-dimensionally, so that the texture becomes flexible and the workability during laying is excellent.

In addition, as described above, thermal bonding and mechanical entanglement are preferable as a method for integrating the fiber web in the present invention, but a combination of these is also preferable. For example, a method in which a mechanical entanglement is imparted by a needle punch and then a part is thermally bonded, or a part is thermally entangled and then entangled while loosening a thermal bonding point to impart flexibility to the sheet. A method and the like are also preferable.
The herbicidal sheet of the present invention is a method of laying on the ground to prevent the growth of weeds, a method of preventing the growth of weeds by laying around vegetation trees, and the method of promoting the growth of vegetation trees, and the ground of parks, etc. It is suitably used for a construction method in which soil is further put on a laid grass protection sheet to grow plants such as turf and green.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. Moreover, the evaluation method used in the Example and its measurement conditions are demonstrated below.

(1) Polymer melt viscosity (poise)
The melt viscosity of the polymer was measured with a capillarograph 1B manufactured by Toyo Seiki Seisakusho. The polymer storage time from sample introduction to measurement start was 10 minutes.

(2) Melting point (° C)
Using a Perkin Elmer DSC-7, the peak top temperature indicating the melting of the polymer at 2nd run was taken as the melting point of the polymer. The temperature rising rate at this time was 20 ° C./min, and the sample amount was 10 mg.

(3) Weight average molecular weight The weight average molecular weight of polylactic acid was calculated | required with the following method. Tetrahydrofuran was mixed with the chloroform solution of the sample to obtain a measurement solution, which was measured at 25 ° C. using a gel permeation chromatograph (GPC) Waters 2690 manufactured by Waters, and the weight average molecular weight was determined in terms of polystyrene. Three measurements were performed for each sample, the average value was calculated, and the weight average molecular weight was rounded off to the nearest thousand.

(4) Single fiber fineness (decitex)
Ten small sample samples are taken at random from the nonwoven fabric, photographed at 500 to 3000 times with a scanning electron microscope or the like, 10 from each sample, the diameter of 100 fibers in total, and the average value thereof. The fiber diameter calculated by rounding off the 0.01 μm position was corrected by the polymer density, and the first decimal place was rounded off.

(5) Weight per unit area (g / m ² )
Three samples each having a size of 50 cm in length and 50 cm in width were collected from the nonwoven fabric, and each weight was measured. The average value of the obtained values was converted per unit area, and the first decimal place was rounded off.

(6) Dispersion state of polyamide component (average single fiber fineness: decitex)
Ten small piece samples are randomly collected from the nonwoven fabric, embedded in an epoxy resin, cut in the cross-sectional direction, cut into ultrathin sections, and cut into 40,000 to 100,000 with a transmission electron microscope (TEM: H7100FA type manufactured by Hitachi). Photos were taken at double magnification. Measure the cross-sectional area of the polyamide component from each sample, 20 in total, 200 in total, calculate the average value thereof, convert this to the fiber diameter of the circular fiber, and correct it with the polymer density to obtain the polyamide component The single fiber fineness was determined. In TEM observation, when it was difficult to distinguish between polyamide and aliphatic polyester, the sample was appropriately stained.

(7) Ten test pieces of 5 cm × 30 cm are collected for each of the longitudinal direction (sheet length direction) and the lateral direction (sheet width direction) of the high elongation product nonwoven fabric per basis weight when dried and wet. The test piece is subjected to a tensile test with a constant speed extension type tensile tester at a grip interval of 20 cm and a tensile speed of 10 ± 1 cm / min, and the strength (N) at the maximum load until breakage is about 0.1N. To obtain a tensile strength (N / 5 cm). Further, the elongation (cm) at the maximum load is obtained to the order of 0.1 cm, this is divided by the test length (20 cm), and the second decimal place is rounded off to obtain the elongation (%). The total average value of the total 20 points of the obtained tensile strength and elongation in the machine direction and the transverse direction is obtained by rounding off the first decimal place, and these are taken as the tensile strength and elongation of the nonwoven fabric. The product of strong elongation per unit weight was obtained by dividing the product of tensile strength and elongation by the basis weight obtained by the method of (5) above, and rounding off the first decimal place.
Here, the strength elongation product per unit weight at the time of drying is obtained from a non-woven fabric that is left in an atmosphere at a temperature of 20 ° C. and a relative humidity of 65% for 24 hours, and the moisture content is adjusted to 0.5 to 4 wt%. The strength elongation product per basis weight was determined from a nonwoven fabric that was impregnated in water at a temperature of 20 ° C. and then nipped with a pair of mangle rolls, and the moisture content was adjusted to 250 to 300 wt%.

(8) Stress at 5% elongation per unit weight Tensile test was performed under the same conditions as those for determining the product of strength per unit area when dried according to the above (7). The strength (N) when the elongation is 5% is obtained to the order of 0.1N, and this is defined as the stress at 5% elongation. The total average value was calculated by rounding off the first decimal place, and this was taken as the stress at 5% elongation of the nonwoven fabric. Further, the 5% elongation stress of the obtained nonwoven fabric was divided by the basis weight obtained by the method of (5) above, and the second decimal place was rounded off to obtain a 5% elongation stress per basis weight.

(Example 1)
Melt viscosity 570 poise (240 ° C., shear rate 2432 sec ⁻¹ ), melting point 220 ° C. nylon 6 (40 wt%), weight average molecular weight 120,000, melt viscosity 300 poise (240 ° C., shear rate 2432 sec ⁻¹ ), melting point 170 ° C. Poly (L-lactic acid) (optical purity of 99.5% or higher) (60% by weight) was kneaded at 240 ° C. with a twin-screw extruder kneader to obtain a blend polymer chip.

Using this blend polymer chip as a raw material, the raw material is melted by an extruder at 240 ° C., spun from a round pore at a spinning temperature of 245 ° C., and then spun at a spinning speed of 4200 m / min by an ejector. Using a embossing roll and a flat roll, the roll temperature is 140 ° C., the linear pressure is applied to the web obtained by opening the yarn with a fiber device and collecting it on the moving conveyor. Thermal bonding was performed under the condition of 50 kg / cm to obtain a spunbonded nonwoven fabric having a single fiber fineness of 2 dtex and a basis weight of 100 g / m ² , and used as a herbicidal sheet. The average single fiber fineness of the polyamide component was 9 × 10 ⁻⁵ dtex.

(Example 2)
To the blend polymer chip used in Example 1, 0.5 wt% of ethylenebisstearic acid amide was added, melted in an extruder at 240 ° C., spun from a round pore at a spinning temperature of 245 ° C., and then ejector An embossing roll that spins at a spinning speed of 4000 m / min, opens the yarn with a known opening device, and collects the web collected on the moving conveyor with a crimping area ratio of 16%. And a flat roll, heat-bonding was performed under the conditions of a roll temperature of 135 ° C. and a linear pressure of 40 kg / cm to obtain a nonwoven fabric having a single fiber fineness of 1 dtex and a basis weight of 150 g / m ² , which was used as a herbicidal sheet. The average single fiber fineness of the polyamide component was 1 × 10 ⁻⁴ dtex.

(Example 3)
Under the same conditions as in Example 1, only the weight ratio of nylon 6: poly (L-lactic acid) was changed to 20:80 to obtain a blend chip. To this blend polymer chip, 0.5% by weight of ethylenebisstearic acid amide was added, the raw material was melted at 240 ° C with an extruder, spun from a round pore at a spinning temperature of 240 ° C, and then spun with an ejector. An embossing roll and a flat roll that are spun at a speed of 3500 m / min, opened the yarn with a known opening device, and collected on a moving conveyor, with a crimping area ratio of 13% Was used for heat-bonding under the conditions of a roll temperature of 145 ° C. and a linear pressure of 50 kg / cm to obtain a nonwoven fabric having a single fiber fineness of 3 dtex and a basis weight of 80 g / m ² , which was used as a herbicidal sheet. The average single fiber fineness of the polyamide component was 9 × 10 ⁻⁵ dtex.

Example 4
To the blend polymer chip used in Example 1, 0.5 wt% of ethylenebisstearic acid amide was added, and further 1 wt% of TIC was added with respect to the content of poly (L-lactic acid). After melting and spinning from the round pores at a spinning temperature of 245 ° C., spinning with an ejector at a spinning speed of 2500 m / min, opening the yarn with a known opening device, and collecting on a moving conveyor The resulting web was thermally bonded using an embossing roll and a flat roll with a crimping area ratio of 16% under the conditions of a roll temperature of 135 ° C. and a linear pressure of 50 kg / cm, and a single fiber fineness of 5 dtex and basis weight. A nonwoven fabric of 130 g / m ² was obtained and used as a herbicidal sheet. The average single fiber fineness of the polyamide component was 2 × 10 ⁻⁴ dtex.

(Example 5)
To the blend polymer chip used in Example 1, 0.5 wt% of ethylenebisstearic acid amide was added, melted in an extruder at 240 ° C., spun from a round pore at a spinning temperature of 240 ° C., and then ejector An embossing roll that spins at a spinning speed of 2800 m / min, opens the yarn with a known opening device, and collects the web collected on the moving conveyor with a crimping area ratio of 16%. And a flat roll, and bonded under the conditions of a roll temperature of 80 ° C. and a linear pressure of 50 kg / cm, a temporary bonded nonwoven fabric having a single fiber fineness of 4 dtex was obtained. This was punched at a rate of 100 times / cm ² with a needle punch machine in which a 1-barb needle was implanted, and the nonwoven fabric was mechanically entangled to obtain a nonwoven fabric with a basis weight of 140 g / m ² to obtain a weedproof sheet. . The average single fiber fineness of the polyamide component was 1 × 10 ⁻⁴ dtex.

(Example 6)
Poly (L-lactic acid) having a melt viscosity of 570 poise (240 ° C., shear rate of 2432 sec ⁻¹ ), a melting point of 220 ° C. nylon 6 and a weight average molecular weight of 120,000, a melt viscosity of 300 poise (240 ° C., shear rate of 2432 sec ⁻¹ ), and a melting point of 170 ° C. ) (Optical purity of 99.5% or more) was mixed and charged into an extruder at 240 ° C. at a weight ratio of 30:70, and spun from a round pore at a spinning temperature of 245 ° C., and then ejected by an ejector. An embossing roll and a flat that have a spun area ratio of 16% are obtained by spinning at a spinning speed of 3000 m / min, opening the yarn with a known opening device, and collecting the web on a moving conveyor. using a roll, roll temperature 140 ° C., and heat-bonding under conditions of a linear pressure 50 kg / cm, single fiber fineness 3 dtex, the spunbonded nonwoven fabric having a basis weight of 100 g / ^{m 2} , It was the Anti-weed sheet. The average single fiber fineness of the polyamide component was 2 × 10 ⁻³ dtex.

  The properties of the obtained nonwoven fabric are as shown in Table 1, but the nonwoven fabrics of Examples 1 to 5 all contain a poly (L-lactic acid) resin that is an aliphatic polyester. It has a high elongation and has excellent properties such as 134 · 107, 111 · 86, 79 · 69, 98 · 95, 109 · 98, respectively. It has excellent properties as a herbicidal sheet.

(Comparative Example 1)
Using the poly (L-lactic acid) resin described in Example 1 as a raw material, the raw material was melted with an extruder at 230 ° C., spun from a round pore at a spinning temperature of 235 ° C., and then a spinning speed of 4500 m / second with an ejector. The web obtained by spinning in min, opening the yarn with a known opening device, and collecting it on the moving conveyor, using an embossing roll and a flat roll with a crimping area ratio of 16% Then, heat bonding was performed under the conditions of a roll temperature of 150 ° C. and a linear pressure of 60 kg / cm to obtain a nonwoven fabric having a single fiber fineness of 2 dtex and a basis weight of 120 g / m ² .

  The properties of the obtained nonwoven fabric are as shown in Table 1, but the nonwoven fabric of Comparative Example 1 has a low strength elongation product per unit area of 35/24 when dried and wet, and is preferable as a herbicidal sheet. Did not have.

Claims (8)

A herbicidal sheet comprising a thermoplastic filament nonwoven fabric, comprising a thermoplastic filament comprising a blend polymer of aliphatic polyester and polyamide. The single filament fineness of the thermoplastic filament made of the blend polymer is 1 to 15 dtex, the basis weight of the nonwoven fabric is 50 to 300 g / m ² , and the high elongation product per basis weight when dry and wet is 40 to 40 The weedproof sheet according to claim 1, which is 300. The thermoplastic filament made of the blend polymer contains 0.1 to 5.0 wt% of an aliphatic bisamide and / or an alkyl-substituted aliphatic monoamide. Weedproof sheet. The weedproof sheet according to any one of claims 1 to 3, wherein a weight ratio of aliphatic polyester: polyamide of the blend polymer is 20:80 to 95: 5. The polyamide component is finely dispersed at an average single fiber fineness of 1 × 10 ⁻⁷ to 1 × 10 ⁻³ dtex in the cross-sectional direction of the thermoplastic filament made of the blend polymer. The herbicidal sheet according to crab. The herbicidal sheet according to any one of claims 1 to 5, wherein the aliphatic polyester is polylactic acid and the polyamide is nylon 6. The weedproof sheet according to any one of claims 1 to 6, wherein the nonwoven fabric is a spunbonded nonwoven fabric. The weedproof sheet according to any one of claims 1 to 7, wherein fibers constituting the nonwoven fabric are subjected to mechanical entanglement treatment.