JP4651609B2 - Method for producing moisture permeable sheet - Google Patents

Description

  The present invention relates to a method for producing a moisture-permeable sheet that is liquid-impermeable but water-vapor permeable. More specifically, the moldability at low temperatures is good, and so-called eyes, burns, resin gelation, etc. are generated. The present invention relates to a method for producing a suppressed moisture-permeable sheet.

  Various liquid-impervious and water vapor-permeable moisture-permeable sheets made of polyolefin resins are known (see Patent Document 1). This type of moisture-permeable sheet is manufactured by melt-forming a resin composition containing a filler by various molding methods such as a T-die method and an inflation method, and at least uniaxially stretching.

  During melt film formation, the components in the resin composition adhere to the die lip, or the resin composition stays in the cylinder of the extruder, screw, single tube, etc., so-called eyes, a substance called burnt blisters, A substance that hinders molding, such as a gelled resin, is generated, and this substance may inhibit stable molding. The generation of such a substance is more remarkable as the film forming temperature is higher. When the occurrence of such substances frequently occurs, it is necessary to discontinue the molding and to disassemble and clean the extruder and the die, which causes a decrease in productivity.

JP 2001-261868 A

  Accordingly, an object of the present invention is to provide a method for producing a moisture permeable sheet that has good moldability and suppresses the generation of burnt chips, resin gels, and the like in the so-called eyes.

  The present inventors have found that the object can be achieved by using a resin composition having specific flow characteristics and molding at a lower temperature than normal molding conditions.

The present invention has been made on the basis of the above knowledge, and includes 100 to 300 parts by weight of an inorganic filler with respect to 100 parts by weight of a polyolefin resin, and a melt flow rate (load 21.18N) at 190 ° C. is 6 to 25 g / 10 min. A polyolefin-based resin composition having a melt flow ratio at 190 ° C. (ratio of a melt flow rate with a load of 98.07 N and a melt flow rate with a load of 9.81 N) of 85 or less , wherein the polyolefin-based resin is And ethylene and an α-olefin having 3 to 8 carbon atoms, which are manufactured using a metallocene catalyst, having a melt flow rate of 2.5 to 4.5 g / 10 min, a density of 0.920 to 0.930 g / cm ³ , and 80 to 99% by weight of a linear low density polyethylene comprising a copolymer of the above and a melt flow rate of 7 to 12 g / 10 min A polyolefin resin composition containing 1 to 20% by weight of a branched low density polyethylene having a density of 0.915 to 0.925 g / cm ³ is formed into a film by a T-die method at a molding temperature of 180 to 210 ° C. The object is achieved by providing a method for producing a moisture-permeable sheet which is formed into a film and then stretched at least uniaxially by 1.5 to 4 times .

Further, the present invention comprises a polyolefin resin composition containing 100 to 300 parts by weight of an inorganic filler with respect to 100 parts by weight of a polyolefin resin , and is at least uniaxially stretched by 1.5 to 4 times, and has a total light transmittance. Is a moisture permeable sheet having a moisture permeability of 4000 to 8400 g / (m ² · 24 h) and a basis weight of 10 to 50 g / m ² ,
The polyolefin resin composition has a melt flow rate (load 21.18N) at 190 ° C. of 6 to 25 g / 10 min, a melt flow ratio at 190 ° C. (melt flow rate of load 98.07N and load of 9.81N). The ratio to the melt flow rate) is 85 or less,
The polyolefin resin is a melt flow rate 2.5 to 4.5 g / 10min, was prepared using a metallocene catalyst is a density 0.920-.930 g / cm ^3, ethylene and 3 carbon A branched low-density polyethylene 80-99% by weight comprising a copolymer of 8 α-olefin and a melt flow rate of 7-12 g / 10 min and a density of 0.915-0.925 g / cm ^3. there is provided a moisture-permeable sheet comprising a low density polyethylene 20 wt%.

  As described above in detail, according to the method for producing a moisture-permeable sheet of the present invention, the moldability is good, and so-called eyes, the occurrence of burnt chips, resin gels, and the like are suppressed. Moreover, the moisture-permeable sheet manufactured by the manufacturing method of the present invention has high transparency while maintaining high moisture permeability. High strength and flexibility. Therefore, this moisture-permeable sheet is particularly suitably used as a back sheet for absorbent articles.

  Hereinafter, the present invention will be described based on preferred embodiments thereof. In the method for producing a moisture permeable sheet of the present invention, a polyolefin resin composition containing a polyolefin resin and an inorganic filler is used as a raw material. In the present invention, one of the characteristics is to use a polyolefin resin composition having specific flow characteristics. Specifically, the polyolefin resin composition has a melt flow rate at 190 ° C. (hereinafter also referred to as MFR) within a specific range and a specific melt flow ratio at 190 ° C. (hereinafter also referred to as MR). The one in the range is used. Conventionally, there are many examples in which optimization of a moisture permeable sheet was examined from the viewpoint of MFR of the polyolefin resin itself, but examination from the viewpoint of MFR of the resin composition has not been made. In particular, the relationship between the MFR of the resin composition and the molding temperature (particularly the molding temperature in the T-die method) has not been studied.

  The MFR of the polyolefin resin composition is 6 to 25 g / 10 min, preferably 7 to 20 g / 10 min, and more preferably 8 to 18 g / 10 min. The MFR in this range is higher than the general MFR of the polyolefin resin composition that is a raw material for the moisture-permeable sheet. By using such a high MFR polyolefin-based resin composition and molding by a T-die method at a low molding temperature, which will be described later, generation of so-called eyes, burns, resin gelation, etc. is suppressed during molding, Also, the moldability is improved. Specifically, if the MFR of the polyolefin resin composition is less than 6 g / 10 min, the fluidity is poor and molding at low temperature is impossible, so it is necessary to mold at high temperature. The occurrence will increase. If it exceeds 25 g / 10 min, the melt tension becomes low, draw resonance occurs, and the thin film moldability at high speed deteriorates. Further, the neck-in at the die outlet becomes large, and a desired sheet width cannot be obtained, resulting in poor productivity. The MFR of the polyolefin resin composition is measured under the conditions of a temperature of 190 ° C. and a load of 21.18 N according to the method defined in ASTM D-1238-57T (E).

  In the polyolefin-based resin composition used in the method of the present invention, MR is also an important physical property that serves as an index of flow characteristics, like the MFR described above. MR is defined as the ratio of the melt flow rate with a load of 98.07 N at 190 ° C. to the melt flow rate with a load of 9.81 N at the same temperature. MR is an index of the shear rate dependency of the polyolefin resin composition. Specifically, the closer the MR value is to 1, the smaller the change in shear rate even if the shear stress of the polyolefin resin composition changes. As a result of studies by the present inventors, it has been found that MR is a factor that becomes an index of formability, particularly when forming by the T-die method. In the method of the present invention, it is necessary to use a polyolefin resin composition having an MR of 85 or less. When a polyolefin resin composition having an MR of more than 85 is used, the change in fluidity increases with respect to the change in shear rate in the extruder, in a single pipe, in a T die, or the like. As a result, burnout due to resin stagnation increases and uneven thickness occurs in the width direction, resulting in a sheet with poor appearance. The preferred range of MR is 10-75, especially 15-70.

  The method for measuring the melt flow rate of loads 98.07N and 9.81N at 190 ° C. used for calculating MR is in accordance with the method prescribed in ASTM D-1238-57T (E). The reason why the load values of the two melt flow rates used for calculating MR were 98.07 N and 9.81 N, respectively, is that the shear rate in a general extruder-T die is approximately this melt flow rate. This is because the load falls within the range of the load. When the load is 98.07N, the values of the melt flow rate itself at 190 ° C. of the loads 98.07N and 9.81N are preferably 60 to 120 g / 10 min, particularly 70 to 110 g / 10 min, and the load 9.81 N. In this case, 0.5 to 5 g / 10 min, particularly 1 to 4.5 g / 10 min is preferable. If the value of the melt flow rate at each load is within this range, the change in the fluidity of the resin within the range of the shear rate is small, and the moldability is good.

  In the production method of the present invention, one of the features is that the polyolefin resin composition having the above-mentioned MFR and MR is used, and yet another feature is that the polyolefin resin has a specific linear low This is to use a combination of a density polyethylene (hereinafter also referred to as LLDPE) and a specific branched low-density polyethylene (hereinafter also referred to as LDPE). When a moisture-permeable sheet is produced using such a polyolefin-based resin, generation of burnt chips, resin gelation, and the like are further suppressed during molding, and moldability is further improved. Moreover, the moisture-permeable sheet obtained becomes high strength and flexible. Furthermore, surprisingly, the inventors have found that the resulting moisture-permeable sheet has high moisture permeability and also high transparency.

LLDPE has a melt flow rate of 2 . The thing of 5-4.5 g / 10min is used. The range of this MFR is higher than the MFR of a polyolefin resin that has been conventionally used as a raw material for moisture-permeable sheets. By using such a high MFR LLDPE, the fluidity is improved and the moldability is improved. Moreover, a moisture-permeable sheet with high moisture permeability is obtained. Specifically, when the MFR is less than 2.5 g / 10 min, the fluidity is low and sheet molding becomes difficult. If it exceeds 4.5 g / 10 min, the holes are likely to be opened at the time of stretch opening, resulting in frequent occurrence of holes that cause problems in leakage prevention. The MFR of LLDPE is measured under the conditions of a temperature of 190 ° C. and a load of 21.18 N according to the method defined in ASTM D-1238-57T (E), similarly to the MFR of the polyolefin resin composition.

LLDPE has a density of 0 . 920 to 0.930 g / cm ³ . By using LLDPE having a density in this range, the moisture permeability is sufficiently high, the strength such as longitudinal crack strength and CD fracture strength is high, the flexibility is high, the heat resistance against hot melt coating is high, and the sheet on the appearance A moisture-permeable sheet with little stretching unevenness can be obtained. Specifically, when the density is less than 0.920 g / cm ³ , the moisture permeability becomes low and the moisture permeable sheet has low heat resistance. If it exceeds 0.930 g / cm ³ , the flexibility is low, the sheet is unevenly stretched in appearance, and the moisture-permeable sheet is not good in appearance. The density is measured based on JIS K 7112 method D (measurement method using a density gradient tube).

LLDPE is Ru der those prepared using metallocene catalysts. As a result, a moisture-permeable sheet having a balance between moldability and sheet physical properties, particularly moisture permeability, strength and flexibility can be obtained. In this case the LLDPE, Ru copolymer der with α- olefin of ethylene and 3-8 carbon atoms.

  A commercially available LLDPE can also be used. Examples of such LLDPE include UMERIT2540F and UMERIT2525F manufactured by Ube Industries, Ltd., and Harmolex NC479A and NC564A manufactured by Nippon Polyolefin Co., Ltd.

As LDPE which is the other component of the polyolefin-type resin used in this invention, a thing with MFR of 7-12 g / 10min is used. The range of this MFR is higher than the MFR of a polyolefin resin that has been conventionally used as a raw material for moisture-permeable sheets. By using such a high MFR LDPE, the fluidity is improved and the moldability is improved. Moreover, a moisture-permeable sheet with high moisture permeability is obtained. Specifically, when the MFR is less than 7 g / 10 min, the formability is poor, the thickness is uneven in the width direction, the sheet looks poor in appearance, and the moisture permeability is low. If it exceeds 12 g / 10 min, the holes are likely to be opened at the time of stretch opening, resulting in frequent occurrence of holes that cause problems in leakage prevention. The MFR of LDPE is measured under the conditions of a temperature of 190 ° C. and a load of 21.18 N according to the method defined in ASTM D-1238-57T (E), similarly to the MFR of the polyolefin resin composition.

LDPE has a density of 0 . 915 to 0.925 g / cm ³ . By using LDPE having a density in this range, the moisture permeability is sufficiently high, the strength such as longitudinal crack strength and CD fracture strength is high, the flexibility is high, the heat resistance against hot melt coating is high, and the sheet on the appearance A moisture-permeable sheet with little stretching unevenness can be obtained. Specifically, when the density is less than 0.915 g / cm ³ , the moisture permeability becomes low and the moisture permeable sheet has low heat resistance. If it exceeds 0.925 g / cm ³ , the flexibility is low, the sheet is unevenly stretched in appearance, and it becomes a moisture-permeable sheet with poor appearance.

  A commercially available LDPE can also be used. Examples of such LDPE include J1019 manufactured by Ube Industries, Ltd. and JH606N manufactured by Nippon Polyolefin Co., Ltd.

  In the present invention, the blending ratio of LLDPE and LDPE is also important. Specifically, the blending amount of LLDPE in the polyolefin resin is 80 to 99% by weight, preferably 85 to 99% by weight, and more preferably 85 to 95% by weight. On the other hand, the blending amount of LDPE in the polyolefin resin is 1 to 20% by weight, preferably 1 to 15% by weight, and more preferably 5 to 15% by weight. When the blending amount of each resin is within such a range, a moisture-permeable sheet having good sheet formability, little thickness unevenness in the width direction and flow direction, and good appearance can be obtained. Further, a moisture permeable sheet having an excellent balance between moisture permeability, strength and flexibility can be obtained.

  The inorganic filler used together with the polyolefin-based resin is used for making the moisture-permeable sheet of the present invention porous and imparting moisture permeability. Examples of inorganic fillers include calcium carbonate, gypsum, talc, clay, kaolin, silica, diatomaceous earth, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium phosphate, aluminum hydroxide, zinc oxide, titanium oxide, alumina, mica , Zeolite, carbon black, aluminum powder, iron powder and the like. These can be used alone or in combination of two or more. These inorganic fillers preferably have an average particle size of 0.3 to 8 μm and a maximum particle size of 20 μm or less from the viewpoint of ensuring the strength of the moisture-permeable sheet obtained and preventing sheet breakage during production. More preferably, the particle size is 0.5-5 μm and the maximum particle size is 15 μm or less.

Of the various inorganic fillers described above, calcium carbonate or barium sulfate is preferably used, and calcium carbonate is particularly preferably used. When calcium carbonate is used, a sheet having a specific surface area of 16000 to 24000 cm ² / g, particularly 18000 to 22000 cm ² / g, is a sheet with high moisture permeability and high water resistance, that is, a large number of dense holes are opened. In view of this, the liquid is less likely to bleed and a sheet having sufficient strength is obtained.

  The inorganic filler is used in an amount of 100 to 300 parts by weight, preferably 100 to 200 parts by weight, more preferably 120 to 200 parts by weight, based on 100 parts by weight of the polyolefin resin. If the amount of the inorganic filler is less than 100 parts by weight, the moisture permeability of the resulting sheet will be insufficient. If it exceeds 300 parts by weight, the water resistance of the sheet decreases, the liquid tends to bleed, the strength decreases, and the moldability also deteriorates.

  In the polyolefin resin composition used in the method of the present invention, in addition to the above-described polyolefin resin and inorganic filler, in order to give a supple texture, reduction of squealing, slipperiness, and improve stretchability, Three components can be added. As the third component, a plasticizer or a lubricant that is usually mixed with rubber or plastic can be used. For example, a monoester composed of a fatty acid and an aliphatic alcohol, or a monoester composed of an aromatic carboxylic acid and an aliphatic alcohol. Ester or polyester, polyester comprising aliphatic polycarboxylic acid and polyalcohol, monocarboxylic acid and / or polyester comprising polycarboxylic acid and monoalcohol and / or polyalcohol, alcohol and / or a part of carboxylic acid is left Esters or polyesters, aliphatic amides, aromatic amides, fatty acid metal soaps, aromatic carboxylic acid metal soaps, butadiene oligomers, butene oligomers, isobutylene oligomers, isoprene oligomers, petroleum resins, coumarone resins, ketone resins, chlorinated paraffins , Hi Shea oil, silicone oil, liquid paraffin, polyethylene wax. Among these, it is particularly preferable to blend a specific polyester as the third component. This polyester is a polyester of a polybasic acid, a polyhydric alcohol, a monobasic acid having 14 to 22 carbon atoms, and / or a monohydric alcohol having 12 to 22 carbon atoms. By blending this polyester, the flow characteristics of the polyolefin resin composition can be further desired. As a result, the generation of burnt chips, resin gelation, etc., is further suppressed during molding, and the moldability is further improved. The combination of each component constituting the polyester is selected in consideration of the number of ester groups in a certain weight of the polyester and the degree of branching of the hydrocarbon chain from the balance of the affinity with the polyolefin resin and the inorganic filler.

  As the monobasic acid in the polyester, a long-chain hydrocarbon monocarboxylic acid having 14 to 22 carbon atoms or the like is used. As the polybasic acid, dicarboxylic acid, tricarboxylic acid, tetracarboxylic acid and the like are used. As the monohydric alcohol, a long-chain hydrocarbon monoalcohol having 12 to 22 carbon atoms is used. As the polyhydric alcohol, diols, trimethylolpropane, pentaerythritol, dipentaerythritol, sorbitol, sucrose and the like are used. When the carbon number of monobasic acid is 12 or less, or the carbon number of monohydric alcohol is 10 or less, the balance of affinity for polyolefin resin and inorganic filler is shifted, and polyester is partially concentrated during film molding. Unevenness may occur during stretching, and the vertical tear strength may decrease.

  The polyester is a polyester obtained by dehydrating and condensing a polybasic acid and a polyhydric alcohol. When the terminal is a carboxylic acid, most of the polyester is a long-chain hydrocarbon monoester such as stearyl alcohol, oleyl alcohol, or gerbe alcohol. It is preferably esterified with alcohol. In the case where the terminal is an alcohol, most of the terminal is preferably an end-capped polyester esterified with a monocarboxylic acid of a long chain hydrocarbon such as stearic acid, hydroxystearic acid, oleic acid, and isostearic acid. However, even in these cases, not all ends need to be blocked. More preferred are esters containing branched acids or alcohols as ester constituents.

  Examples of preferred specific polyesters are polyesters in which the carboxylic acid or alcohol at both ends of the polyester of diethylene glycol and dimer acid is partially or completely blocked with stearyl alcohol or stearic acid, 1,3-butanediol and adipic acid Polyester having both ends of the polyester blocked with hydroxystearic acid, hexaester composed of trimethylolpropane-adipic acid-stearic acid, octaester composed of pentaerythritol-adipic acid-stearic acid, dipentaerythritol-adipic acid-stearin Dodecaester consisting of acid, polyester using dimer acid or hydrogenated dimer acid instead of adipic acid, which is a component of the polyester, and isostearic acid instead of stearic acid It was a polyester or the like.

  The polyester is blended in an amount of 1 to 30 parts by weight, particularly 5 to 20 parts by weight, based on 100 parts by weight of the polyolefin-based resin. Good flowability at the time of molding, supple texture, reduction of noise, slipperiness, It is preferable from the viewpoint of improvement of stretchability.

  In the polyolefin resin composition used in the method of the present invention, stearic acid can be blended for the purpose of improving dispersibility in the polyolefin resin composition. Stearic acid is preferably blended in an amount of 0.5 to 3 parts by weight, particularly 0.8 to 2 parts by weight, based on 100 parts by weight of the inorganic filler.

  In addition to the above-described components, the polyolefin resin composition used in the present invention may be blended with a plasticizer, a stabilizer, an antioxidant, an ultraviolet absorber, etc. within a range not impeding the effects of the present invention. .

  The method of the present invention includes a step of at least uniaxially stretching the above-described polyolefin-based resin composition as a raw material, melt-forming the film into a film by a T-die method, and the like. Specifically, each component constituting the polyolefin-based resin composition is premixed using a Henschel mixer or a supermixer, and then kneaded with a single or twin screw extruder to be pelletized. Next, the obtained pellet is used to form a film by a T-die type molding machine. The obtained film is uniaxially or biaxially stretched to cause interfacial peeling between the resin and the inorganic filler to make it porous. A roll method or a tenter method is used for stretching. In this way, a moisture permeable sheet is obtained.

  The molding temperature is 180 to 220 ° C., which is lower than the molding temperature of the conventional polyolefin moisture-permeable sheet. By combining this molding temperature using the T-die method with the above-mentioned polyolefin resin composition, the generation of so-called eyes, burns, resin gels, etc. during molding is suppressed, and the moldability is improved. . Even if inflation molding is performed using the polyolefin-based resin composition as a raw material under the same molding temperature conditions, the moldability is not good. The molding temperature is preferably 180 to 210 ° C., particularly 190 to 210 ° C. from the viewpoint of further suppressing the generation of substances that hinder molding and further improving moldability. The molding temperature is the temperature at the T die.

To obtain a total light transmittance and moisture permeability desired will be described later, as the stretching conditions, 1 in a uniaxial direction. 5-4 times, preferably stretched 1.5 to 3.5 times.

Since the moisture permeable sheet thus obtained is made from the polyolefin resin composition described above, its total light transmittance is preferably a high value of 50% or more. Despite exhibiting such a high total light transmittance, moisture-permeable sheet becomes high as the moisture permeability of ^{4000 ~8400g / (m 2 · 24h} ), preferably from 5 000~8400g / (m ² · 24h ) Thus, the moisture-permeable sheet has a high total light transmittance and a high moisture permeability that could not be achieved at the same time. In the present invention, the total light transmittance is measured according to JIS K 7105 using a haze / transmission / reflectometer HR-100 manufactured by Murakami Color Research Laboratory. The moisture permeability is measured in accordance with JIS Z 0208 in an environment of a temperature of 30 ° C. ± 0.5 ° C. and a humidity of 90 ± 2% RH.

Moisture permeable sheet basis weight is preferably 10 to 50 g / m ^2. As will be described later, the basis weight of the moisture-permeable sheet is more preferably 10 to 35 g / m ² , more preferably 15 to 30 g in the form of a composite sheet bonded to a fiber sheet such as a nonwoven fabric on one surface. / M ² . When the basis weight is within this range, the balance of sheet strength, water resistance, flexibility and moisture permeability is good.

  The moisture-permeable sheet thus obtained is used as, for example, a sanitary material, a medical material, or a clothing material. Moreover, a moisture-permeable sheet | seat can also be used as said material with the form of the composite sheet bonded together with the fiber sheets, such as a nonwoven fabric, on the one surface. In particular, since the moisture permeable sheet has high moisture permeability as described above, it is used as a constituent material of absorbent articles such as disposable diapers and sanitary napkins as it is or as a composite sheet bonded with a fiber sheet. When used, it is possible to prevent an increase in humidity in the dress and effectively prevent rash from occurring on the wearer's skin. These absorbent articles generally include a liquid-permeable top sheet, a liquid-impermeable back sheet, and a liquid-retaining absorbent disposed between both sheets. The composite sheet formed by bonding is used as the back sheet.

  In the following examples, “parts” means “parts by weight” unless otherwise specified.

[Examples 1 to 5 and Comparative Examples 1 and 2]
(1) Preparation of polyolefin-based resin composition The materials shown in Table 1 below were blended in the composition shown in Table 2, premixed with a 100-liter Henschel mixer, and then melt-kneaded with a twin-screw extruder to be pelletized. A resin composition was obtained. The twin screw extruder was Ikegai PCM-45-33.5, and the screw diameter was 45 mm. The set temperature was 160 ° C., the screw rotation speed was 150 rpm, and the extrusion rate was 25 kg / h.
(2) Molding of moisture-permeable sheet Using a T-die film molding apparatus comprising a single-screw extruder (L / D = 28) with a diameter of 50 mm and a T-die with a width of 500 mm (die lip clearance 1.5 mm) The resulting polyolefin resin composition was molded to obtain a film having a thickness of 35 μm and a width of 400 mm. The set temperature of the T die was 200 ° C., and the molding speed was 10 m / min. The obtained film was stretched in the longitudinal direction using a roll uniaxial stretching machine to obtain a moisture permeable sheet. The draw ratio was as shown in Table 2. The preheating temperature was 80 ° C., the stretching temperature was 50 ° C., and the annealing temperature was 80 ° C. The return rate in annealing was 13%.

[Performance evaluation]
About the moisture-permeable sheet | seat obtained by the Example and the comparative example, the moldability (sheet moldability and thickness nonuniformity) was evaluated with the following method. Further, the moisture permeability and the total light transmittance were measured by the method described above. Further, the basis weight, tear strength and breaking strength were measured by the following methods. These results are shown in Table 3 below.

[Sheet formability]
The state during molding was observed and evaluated according to the following criteria.
○: A thin sheet was stably formed.
Δ: Molding was slightly unstable.
X: The thin film sheet could not be stably formed.

[Thickness unevenness]
The thickness unevenness of the moisture permeable sheet was evaluated according to the following criteria.
(Double-circle): There was no thickness nonuniformity and the external appearance was also very favorable.
○: Almost no thickness unevenness and good appearance.
(Triangle | delta): There was thickness nonuniformity and the external appearance was a little bad.
X: Thickness unevenness was large and the appearance was bad.

[Basis weight]
The moisture permeable sheet was cut into a size of 10 cm × 10 cm, and the weight thereof was measured and converted to an area of 1 m ² .

(Tear strength)
The tear strength in the machine direction (MD) was measured in accordance with JIS K 7128-2 Elmendorf tear method.

〔Breaking strength〕
The breaking strength in the machine direction (MD) and the width direction (CD) was measured in accordance with JIS K 7127.

As is apparent from the results shown in Table 3, it can be seen that the moisture-permeable sheets of the examples have good moldability and no thickness unevenness is observed. Further, it can be seen that the moisture permeability is as high as 4460 g / (m ² · 24 h) or more and the total light transmittance is as high as 51% or more while maintaining sufficient tear strength and breaking strength. On the other hand, in the moisture-permeable sheet of the comparative example, it can be seen that the molding is unstable and the occurrence of uneven thickness is large. Further, it is understood that the total light transmittance is lowered when the moisture permeability is increased, and the moisture permeability is decreased when the total light transmittance is increased.

Claims (3)

It contains 100 to 300 parts by weight of an inorganic filler with respect to 100 parts by weight of a polyolefin resin, has a melt flow rate (load 21.18N) at 190 ° C. of 9.6 to 15.4 g / 10 min, and melt at 190 ° C. A polyolefin resin composition having a flow ratio (ratio of a melt flow rate with a load of 98.07 N to a melt flow rate with a load of 9.81 N) of 85 or less, wherein the polyolefin resin has a melt flow rate of 2.5 in ~ 4.0 g / 10min, a density 0.920~0.930g / cm ^3, consisting of a copolymer of which has been produced using a metallocene catalyst, and α- olefin of ethylene and 3-8 carbon atoms linear low density polyethylene 80 to 99 wt% and a melt flow rate 7~ 10.5 g / 10min, a density from 0.915 to 0 The polyolefin resin composition comprising a branched low density polyethylene 1-20 wt% is 925 g / cm ^3, was formed into a film by T-die method under a molding temperature of 180-210 ° C., and then 1.5 A method for producing a moisture permeable sheet that is at least uniaxially stretched by 4 times.   The polyolefin resin composition is a polybasic acid, a polyhydric alcohol, a monobasic acid having 14 to 22 carbon atoms and / or a monohydric alcohol having 12 to 22 carbon atoms with respect to 100 parts by weight of the polyolefin resin. The manufacturing method of the moisture-permeable sheet | seat of Claim 1 which further contains 1-30 weight part of polyester.   The method for producing a moisture-permeable sheet according to claim 1, wherein the molding temperature is 190 to 210 ° C, and the stretching is 1.5 to 3.5 times.