JP6908512B2 - Method for manufacturing resin composition and moisture permeable sheet - Google Patents

Description

The present invention relates to a method for producing a resin composition. The present invention also relates to a method for producing a moisture permeable sheet using a resin composition.

For absorbent articles such as disposable diapers and sanitary napkins, a water vapor permeable and water permeable moisture permeable sheet is used. The moisture permeable sheet has fine pores in order to prevent the permeation of water while allowing water vapor to permeate. It is known that such a moisture permeable sheet can be produced by using a resin kneaded product containing an inorganic filler as a raw material, molding the resin kneaded product into a film shape, and then uniaxially stretching or biaxially stretching the film.

For example, Patent Document 1 describes a polyolefin resin component containing a polyolefin resin and an inorganic filler, a polybasic acid, a polyhydric alcohol, a monobasic acid having 14 to 22 carbon atoms, and / or one of 12 to 22 carbon atoms. A sheet obtained by molding a resin composition containing polyester with a valent alcohol and a fatty acid or a metal salt thereof is stretched by a uniaxial or biaxial stretching method to double the area or more, and the basis weight is 10 to 25 g. A method for producing a moisture permeable sheet having a value of / m ^{2 is described.}

Japanese Unexamined Patent Publication No. 2008-163153

However, the moisture-permeable sheet produced by the method of Patent Document 1 may have large holes, that is, pinholes, to which water can permeate, depending on the molding conditions and stretching conditions of the film. The occurrence of pinholes causes liquid leakage, and the moisture-permeable sheet with pinholes must be discarded as a defective product, resulting in a decrease in the productivity of transparent sheets and absorbent articles that use transparent sheets. Could also be connected.

Further, as a general method, when the film is manufactured so that the basis weight of the film exceeds 30 g / m ² , the productivity of the transparent sheet or the like due to the occurrence of pinholes is unlikely to decrease, but the transparent sheet itself. As a result, the flexibility and moisture permeability of the film are reduced, which makes it very difficult to apply it to an absorbent article from the viewpoint of user comfort.

Therefore, an object of the present invention is to improve a method for producing a moisture permeable sheet, and to suppress the occurrence of pinholes in the moisture permeable sheet.

In the present invention, polybasic acid, polyhydric alcohol, and 14 to 22 carbon atoms are used with respect to 100 parts by mass of the polyolefin resin component containing 25 to 55% by mass of the polyolefin resin and 45 to 75% by mass of the inorganic filler. Production of a resin composition in which a resin composition containing 1 to 30 parts by mass of polyester and 0.5 to 5 parts by mass of a fatty acid or a metal salt thereof is mixed with a monobasic acid and / or a monovalent alcohol having 12 to 22 carbon atoms. It ’s a method,
The resin composition so that the Froude number is 0.1 or more and 0.6 or less, and the variation in the bulk density of the resin composition is within ± 2% with respect to the average value of the bulk density. It is an object of the present invention to provide a method for producing a resin composition, which adjusts the mixing time.

Further, in the present invention, a resin composition is produced, and then the resin composition is molded to obtain a sheet, and the sheet is stretched by a uniaxial or biaxial stretching method to double the area or more to increase the basis weight by 10 g. It is an object of the present invention to provide a method for producing a moisture permeable sheet having a temperature of / m ² or more and 25 g / m ^{2 or less.}

According to the present invention, a moisture permeable sheet in which the occurrence of pinholes is suppressed can be produced with high productivity.

FIG. 1 is a graph showing the relationship between the variation in bulk density of the resin composition and the number of pinholes in the moisture permeable sheet in Example 1 and Comparative Example 4.

Hereinafter, the present invention will be described based on its preferred embodiment. The resin composition of the present invention contains a polyolefin-based resin component containing a polyolefin resin and an inorganic filler, polyester, and a fatty acid or a metal salt thereof. Details of each component and amount contained in the resin composition will be described later.

Conventionally, a mixing device such as a Henschel mixer or a super mixer has been used to mix the resin composition. However, as described above, there have been inconveniences such as the occurrence of pinholes and the resulting decrease in productivity of the transparent sheet and the like. As a result of diligent studies by the inventor, it was surprisingly found that the Froude number, which is a dimensionless number often used in the field of chemical engineering, correlates with the degree of occurrence of these defects. In the art, it has been considered that there is no correlation between the degree of mixing of the resin composition and the number of pinholes generated in the moisture permeable sheet produced from the resin composition. The findings were very surprising.

The resin composition of the present invention can be produced by mixing each of the above-mentioned components using a mixing device or the like, and the resin composition is uniformly mixed with each component in the resin compositions having different specific densities. In order to effectively suppress the occurrence of pinholes in the moisture permeable sheet produced using the above, the Froude number is mixed to 0.1 or more, preferably 0.3 or more, and the upper limit thereof is 0.6. Hereinafter, the mixture is preferably mixed so as to be 0.57 or less. Specifically, they are mixed so that the Froude number is 0.1 or more and 0.6 or less. It is preferable to mix them so as to be 0.3 or more and 0.57 or less.

Here, the Froude number is when the peripheral speed (m / s) is V, the radius (m) from the center of rotation to the circumference of the rotating object is D, and the gravitational acceleration (m / s ² ) is g. It is a value calculated by the following formula (1). When a mixing device including a main wing and a crushing wing is used for mixing the resin composition, the values of the main wing are used for the peripheral speed V and the radius D.
Froude number = V ² / (D × g) ・ ・ ・ (1)

The term "pinhole" as used herein refers to a through hole having a size that allows water to permeate among the holes existing in the moisture permeable sheet, and the size of the through hole is 0.5 mm in width. , The length is 0.5 mm or more. Whether or not a pinhole is present in the moisture permeable sheet can be determined or detected by, for example, a pinhole inspection machine detected by a CCD camera. The pinhole detection method will be described in detail in Examples described later.

In mixing each component constituting the resin composition, the resin composition is mixed so that its bulk density is preferably 0.3 g / mL or more, more preferably 0.4 g / mL or more, and its upper limit thereof. Is mixed so as to be 0.6 g / mL or less, more preferably 0.55 g / mL or less. Specifically, it is preferable to mix the resin composition so that the bulk density is 0.3 g / mL or more and 0.6 g / mL or less, and 0.4 g / mL or more and 0.55 g / mL or less. It is more preferable to mix. The method for measuring the bulk density will be described in detail in Examples described later. By mixing the resin composition of the present invention so as to have such a bulk density range, heat kneading of the resin composition described later can be uniformly performed.

The resin composition of the present invention has a variation (fluctuation) in the bulk density of the resin composition within ± 2% of the average value of the bulk density of the resin composition, provided that the above-mentioned Froude number is satisfied. The mixing time is adjusted so as to be preferably within ± 1.5%. By setting the variation in bulk density of the resin composition within such a range, each component in the resin composition having a different specific gravity can be uniformly mixed, and as a result, the occurrence of pinholes in the moisture permeable sheet is effectively suppressed. can do. In order to mix the resin compositions so as to have such variations in bulk density, it can be achieved by mixing for a predetermined time using, for example, a mixing device described later. The method of calculating the average value and the variation of the bulk density will be described in detail in Examples described later together with the method of measuring the bulk density.

The present inventor has found that, for example, in order to mix the resin composition so that the variation in the Froude number and the bulk density of the resin composition is within the above-mentioned specific range, it is preferable to use, for example, a low shear stirring type mixing device. .. The low-shear stirring type mixing device refers to a mixing device that does not give strong shear to the composition at the time of mixing when the resin composition is mixed, and the resin composition is difficult to consolidate. Examples of the low shear stirring type mixer used in the present invention include a tumbler mixer, a ribbon mixer, a V type mixer and the like. In particular, these low-shear stirring type mixing devices are preferable because the mixing of the resin composition at low shear can be easily achieved due to the specifications of the mixing device. Even a mixing device capable of imparting high shear to the resin composition can be used as long as it can be operated by reducing the shearing force by setting operating conditions or the like.

Another method of achieving mixing at low shear can also be achieved by setting the rotation speed of the mixing device or the rotation speed of the mixing blade provided in the mixing device to be low.

Similarly, when a ribbon mixer is used as the mixing device, the rotation speed of the mixing blades of the ribbon mixer is preferably 5 rpm or more, more preferably 10 rpm or more, and the upper limit thereof is 60 rpm or less. It is preferably present, and more preferably 50 rpm or less. Specifically, the rotation speed of the mixing blade is preferably 5 rpm or more and 60 rpm or less, and more preferably 10 rpm or more and 50 rpm or less. When the mixing device is provided with a plurality of mixing blades, the rotation speed of the mixing blade refers to the rotation speed of the main blade. By mixing the resin composition at such a rotation speed, the resin composition can be uniformly mixed, and the occurrence of pinholes in the moisture permeable sheet produced by using the resin composition can be suppressed.

From the viewpoint of improving the treatment efficiency in the production of the resin composition and suppressing the occurrence of pinholes in the moisture permeable sheet produced by using the resin composition, the resin composition is mixed for 3 minutes or more and 5 minutes or more. It is preferable to mix. By mixing the resin composition over such a time, the variation in the bulk density of the resin composition can be further reduced. As a result, the occurrence of pinholes in the moisture permeable sheet produced by using the resin composition can be further suppressed.

The volume of the resin composition to be mixed in the mixing device is preferably 60% or more and 100% or less of the effective volume of the device for mixing the resin composition, and is the effective volume of the device for mixing the resin composition. It is more preferably 70% or more and 90% or less. By mixing the resin composition within such a volume range, each component of the resin composition having a different specific gravity can be uniformly mixed without being separated, and the variation in the bulk density of the resin composition is further reduced. be able to. As a result, the occurrence of pinholes in the moisture permeable sheet produced by using the resin composition can be further suppressed.

Next, a method for producing a moisture permeable sheet using the above-mentioned resin composition will be described. The moisture-permeable sheet of the present invention can be produced by molding a resin composition produced by the above-mentioned production method to obtain a sheet, and then stretching the sheet.

First, the mixing time is adjusted so that the variation in the Froude number and bulk density of the resin composition is within the above-mentioned specific range, and then the resin composition is heat-kneaded by a uniaxial or twin-screw extruder to be in a molten state. The resin composition of. The heating temperature in the heat kneading may be set according to the type of the polyolefin resin. For example, in the case of a polyethylene-based resin, the temperature can be 130 ° C. or higher and 190 ° C. or lower. For example, in the case of polypropylene-based resin, the temperature can be 150 ° C. or higher and 210 ° C. or lower.

Next, a molten resin composition is molded using a molding apparatus described later to obtain a sheet of the resin composition. The melt flow rate (MFR) of the molten resin composition is preferably 1 g / 10 min or more, and more preferably 2 g / 10 min or more, from the viewpoint of improving production efficiency. The upper limit thereof is preferably 8 g / 10 min or less, and more preferably 5 g / 10 min or less. Specifically, it is preferably 1 g / 10 min or more and 8 g / 10 min or less, and more preferably 2 g / 10 min or more and 5 g / 10 min or less. The MFR can be measured by heating and loading according to the type of polyolefin resin according to the method specified in ASTM D-1238-57T (E). For example, when polypropylene is used as the polyolefin resin, it is measured under the conditions of a temperature of 190 ° C. and a load of 21.18 N.

As a molding apparatus for molding the molten resin composition into a sheet, for example, a known molding apparatus such as a T-die molding apparatus or an inflation molding apparatus can be used. The heating temperature during molding is not particularly limited as long as the resin composition can be melted, but the melting point of the resin composition is set from the viewpoint of ease of molding and prevention of thermal decomposition of the components in the resin composition. When M (° C.), it is preferably [M + 20] ° C. or higher and [M + 60] ° C. or lower. When the resin composition is composed of a plurality of resins, the highest melting point of the constituent resins is defined as the melting point M of the resin composition.

Finally, the sheet obtained in the above step is stretched by a uniaxial or biaxial stretching method to obtain a moisture permeable sheet of the present invention. By performing the stretching treatment, interfacial peeling between the resin contained in the resin composition of the present invention and the inorganic filler can be generated, and the sheet can be made porous. As a result, it is possible to obtain a moisture permeable sheet having pores that allow water vapor to permeate but not water to permeate.

As a method for stretching the sheet, for example, a roll method or a tenter method is used. Further, when performing the stretching treatment, it is preferable to heat the sheet to be stretched from the viewpoint of uniformly stretching the sheet by taking advantage of the thermoplastic property of the polyolefin resin contained in the resin composition. It is more preferable to heat at 50 ° C. or higher and 100 ° C. or lower. The method for heating the sheet is not particularly limited, and examples thereof include a method of contacting with a heated roll and a method of heating with hot air or a heater.

As for the stretching ratio of the sheet to be stretched by the uniaxial or biaxial stretching method, the area of the sheet is stretched more than twice from the viewpoint of ensuring the strength and water impermeableness of the moisture permeable sheet, as well as flexibility and moisture permeability. It is preferable to stretch it by 2.2 times or more. Further, the upper limit thereof is preferably that the area of the sheet is stretched 4 times or less, and more preferably 3 times or less. Specifically, as the stretching ratio of the sheet, it is preferable to stretch the area of the sheet to 2 times or more and 4 times or less, and more preferably 2.2 times or more and 3 times or less.

In the stretching treatment of the sheet, from the viewpoint of ensuring the strength and water impermeableness of the moisture permeable sheet, it is preferable to stretch the ^{sheet so that the basis weight of the moisture permeable sheet after the stretching treatment is 10 g / m 2 or more.} The stretching treatment is more preferably 15 g / m ² or more, and further preferably the stretching treatment is ^{17 g / m 2 or more.} Further, from the viewpoint of ensuring flexibility and moisture permeability, it is preferable to perform stretching treatment so that the basis weight of the moisture permeable sheet is 25 g / m ² or less, and it is possible to perform stretching treatment so that ^{the basis weight of the moisture permeable sheet is 23 g / m 2} or less. More preferred. Specifically, the moisture-permeable sheet is preferably stretched so that the basis weight of the moisture-permeable sheet is 10 g / m ² or more and 25 g / m ² or less, and 15 g / m ² or more and 25 g / m ² or less. It is more preferable, and it is further preferable to carry out the stretching treatment so as to be ^{17 g / m 2} or more and 23 g / m ^{2 or less.} The basis weight of such a moisture-permeable sheet can be achieved by setting the stretching ratio of the sheet to be subjected to the stretching treatment within the above range.

More moisture-permeable sheet of the process the present invention manufactured through the, the moisture permeability is preferably at 3600g ^/ (m 2 · 24h) or more, more preferably 4000g ^/ (m 2 · 24h) or higher, further preferably at 5000g ^/ (m 2 · 24h) or more. The upper limit is preferably 8400g ^/ (m 2 · 24h) or less. Specifically, moisture-permeable sheet of the present invention, the moisture permeability is preferably 3600g ^/ (m 2 · 24h) or 8400g ^/ (m 2 · 24h) or less, more preferably 4000g ^/ (m 2 · 24h ) or 8400g ^/ (m 2 · 24h) or less, still more preferably 5000g ^/ (m 2 · 24h) or 8400g ^/ (m 2 · 24h) or less. The moisture permeability can be measured in a temperature of 30 ° C. ± 0.5 ° C. and a humidity of 90 ± 2% RH environment according to JIS Z 0208.

Since the moisture permeable sheet of the present invention suppresses the generation of pinholes that allow water to permeate, it has moisture permeability that allows water vapor to permeate while being impermeable to water. Such a moisture permeable sheet is used, for example, as a sanitary material, a medical material, a clothing material, or the like. Further, the moisture permeable sheet of the present invention can be used as the above-mentioned material as it is or in the form of a composite sheet in which a fiber sheet such as a non-woven fabric is bonded to one surface thereof. Further, when the moisture permeable sheet of the present invention is used as a constituent material of an absorbent article such as a disposable diaper, a sanitary napkin, an incontinence pad, and a panty liner in the form of a composite sheet, it is possible to prevent an increase in humidity in the clothing. It is possible to effectively prevent a rash or the like from occurring on the wearer's skin.

Next, the components contained in the above-mentioned resin composition will be described. The resin composition of the present invention comprises 1 to 30 parts by mass of polyester and 1 to 30 parts by mass of polyester and a fatty acid or a metal thereof with respect to 100 parts by mass of a polyolefin resin component containing 25 to 55% by mass of a polyolefin resin and 45 to 75% by mass of an inorganic filler. It contains 0.5 to 5 parts by mass of salt.

The polyolefin resin is a material that is a raw material for a liquid-impermeable moisture-permeable sheet. Examples of the polyolefin resin used in the present invention include polymers such as ethylene, propylene and butene, and those containing a copolymer thereof as a main component. Specific examples include linear low density polyethylene (LLDPE), branched low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene, ethylene-propylene copolymer, polybutene and the like. These polyolefin resins may be used alone or in admixture of two or more. From the viewpoint of achieving both flexibility and durability of the transparent sheet, it is preferable to use LLDPE as the polyolefin resin used in the present invention.

The resin composition of the present invention contains an inorganic filler. The inorganic filler is used to form a pore in a moisture permeable sheet produced from the resin composition of the present invention and impart moisture permeability. Examples of the inorganic filler 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, and the like. Granules such as mica, zeolite, carbon black, aluminum powder, and iron powder can be mentioned. These can be used alone or in combination of two or more. Among these inorganic fillers, it is preferable to use calcium carbonate or barium sulfate, and it is particularly preferable to use calcium carbonate.

From the viewpoint of maintaining the durability of the moisture permeable sheet, the average particle size of the inorganic filler is preferably 0.3 μm or more and 8 μm or less, and more preferably 0.5 μm or more and 5 μm or less. Further, the maximum particle size of the inorganic filler is preferably 20 μm or less, more preferably 15 μm or less, provided that the average particle size of the inorganic filler satisfies the above range. The particle size of the inorganic filler can be measured using, for example, a laser diffraction type particle size distribution meter (LA950V2 manufactured by HORIBA, Ltd.).

From the viewpoint of satisfying both moisture permeability and durability of the transmission sheet, Blaine specific surface area of the inorganic filler is preferably not more than 20000 cm ² / g or more ^{22000cm 2 / g, 20500cm 2 /} g or more 22000cm ² / g or less Is more preferable. The brain specific surface area of the inorganic filler can be measured according to JIS R 5201 using, for example, a brain air permeation powder degree measuring device (Brain air permeation powder degree measuring device manufactured by Tsutsui Rika Chemical Instruments Co., Ltd.).

The content ratio of the polyolefin resin is 25% by mass or more, preferably 30% by mass or more, more preferably 35% by mass or more, and the upper limit thereof is 55% by mass or less. It is preferably contained in an amount of 50% by mass or less, and more preferably 45% by mass or less. Specifically, the content ratio of the polyolefin resin is preferably 25 to 55% by mass, preferably 30 to 50% by mass, and more preferably 35 to 45% by mass in the polyolefin resin component. When the polyolefin resin has this content ratio, a moisture permeable sheet having moisture permeability, water resistance and durability can be produced.

Similarly, the content ratio of the inorganic filler is 45% by mass or more, preferably 50% by mass or more, more preferably 55% by mass or more, and the upper limit thereof is 75% by mass. It contains the following, preferably 70% by mass or less, and more preferably 65% by mass or less. Specifically, the content ratio of the inorganic filler is preferably 45 to 75% by mass, preferably 50 to 70% by mass, and more preferably 55 to 65% by mass in the polyolefin resin component. When the content of the inorganic filler is this, a moisture permeable sheet having moisture permeability, water resistance and durability can be produced.

The resin composition used in the present invention contains polyester. This polyester is a polyester containing a polybasic acid, a polyhydric alcohol, and a monobasic acid having 14 to 22 carbon atoms and / or a monohydric alcohol having 12 to 22 carbon atoms. By including polyester in the resin composition, the appearance and moisture permeability of the moisture permeable sheet produced by using the resin composition can be improved.

As the polybasic acid contained in polyester, dicarboxylic acid, tricarboxylic acid, tetracarboxylic acid and the like are used. As the multivalent alcohol, diols, trimethylolpropane, pentaerythritol, dipentaerythritol, sorbitol and the like are used. As the monobasic acid, a long-chain hydrocarbon monocarboxylic acid having 14 to 22 carbon atoms is used. As the monohydric alcohol, a long-chain hydrocarbon monoalcohol having 12 to 22 carbon atoms is used.

Polyester is obtained by dehydration condensation of a polybasic acid and a polyhydric alcohol. When the end of the polyester is a carboxylic acid derived from another basic acid, it is preferable that most of the polyester is esterified with a monoalcohol of a long-chain hydrocarbon such as stearyl alcohol, oleyl alcohol, and gelve alcohol. When the terminal is an alcohol, it is preferable that the terminal-sealed polyester is mostly esterified with a monocarboxylic acid of a long-chain hydrocarbon such as stearic acid, hydroxystearic acid, oleic acid, or isostearic acid. In this case, not all ends of the polyester need to be esterified.

Examples of the polyester contained in the resin composition of the present invention include polyesters in which the carboxylic acids or alcohols at both ends of the polyester of diethylene glycol and dimeric acid are partially or wholly sealed with stearic acid or stearic acid, 1,3. Polyester with hydroxystearic acid at both ends of the polyester of butanediol and adipic acid, hexaester consisting of trimethylpropan-adipic acid-stearic acid, pentaerythritol-octaester consisting of adipic acid-stearic acid, dipenta Dodecaester composed of erythritol-adipic acid-stearic acid, polyester using dimeric acid or hydrogenated dimeric acid instead of adipic acid, which is a component of the polyester, polyester using isostearic acid instead of stearic acid, etc. Can be mentioned.

The polyester contained in the resin composition of the present invention preferably contains 1 part by mass or more and 2 parts by mass or more with respect to 100 parts by mass of the polyolefin resin component, and the upper limit thereof includes 30 parts by mass or less and 20 parts by mass. It is preferable to include parts by mass or less. Specifically, the polyester preferably contains 1 to 30 parts by mass and 2 to 20 parts by mass with respect to 100 parts by mass of the polyolefin resin component. By including polyester in this range, flexibility and stretchability can be imparted to the moisture permeable sheet produced by using the resin composition.

The resin composition of the present invention contains a fatty acid or a metal salt thereof. The fatty acid or a metal salt thereof is for uniformly dispersing the inorganic filler in the resin composition. Examples of the fatty acid or the metal salt thereof used in the present invention include stearic acid, magnesium stearate, calcium stearate and the like.

The fatty acid or the metal salt thereof is preferably contained in the resin composition in an amount of 0.5 part by mass or more and 1.0 part by mass or more with respect to 100 parts by mass of the polyolefin resin component, and the upper limit thereof is 5. It contains 0 parts by mass or less, preferably 4.0 parts by mass or less, and more preferably 3.0 parts by mass or less. Specifically, it contains 0.5 to 5 parts by mass, preferably 0.5 to 4.0 parts by mass, and more preferably 1.0 to 3.0 parts by mass.

In addition to the above-mentioned components, the resin composition used in the present invention may contain additives as long as the effects of the present invention are not impaired. Examples of additives include plasticizers, stabilizers, antioxidants, UV absorbers and the like.

Hereinafter, the present invention will be described in more detail by way of examples. However, the scope of the present invention is not limited to such examples.

[Example 1]
Using each of the materials shown below, 3.9 parts by mass of polyester was added to 100 parts by mass of the polyolefin resin component containing 39.2% by mass of polyolefin resin and 60.8% by mass of calcium carbonate as an inorganic filler. , 0.8 parts by mass of the fatty acid was mixed using a ribbon mixer (radius from the center of rotation to the circumference of the rotating object: 490 mm) to obtain a resin composition. The mixing conditions (froude number and mixing time) of the ribbon mixer were as shown in Table 1.

[Material of resin composition]
-Polyolefin resin (LLDPE): Made by Prime Polymer Co., Ltd., "UZ2520F (trade name)"
-Inorganic filler (calcium carbonate): "Escalon # 2000 (trade name)" manufactured by Sankyo Seiko Co., Ltd.
-Polyester: "Exepearl (registered trademark) TM20-AS (trade name)" manufactured by Kao Corporation
-Fatty acid: "Lunac (registered trademark) S-40 (trade name)" manufactured by Kao Corporation

Next, the obtained resin composition was melt-kneaded by a pellet manufacturing apparatus equipped with a twin-screw extruder to obtain resin-kneaded pellets. The resin kneaded pellets were molded into a sheet using an inflation molding apparatus to obtain a sheet. Subsequently, the obtained sheet was stretched 2.4 times in the transport direction of the sheet using a uniaxial stretching machine to produce a moisture permeable sheet having a basis weight of ^{18 g / m 2.}

[Example 2]
A resin composition and a moisture permeable sheet were produced in the same manner as in Example 1 except that the mixing time with the ribbon mixer was changed to 3 minutes.

[Comparative Examples 1 and 2]
A resin composition and a moisture permeable sheet were produced in the same manner as in Example 1 except that the mixing time with the ribbon mixer was changed as shown in Table 1.

[Comparative Example 3]
A resin composition and a moisture permeable sheet were produced in the same manner as in Example 1 except that the Froude number of the ribbon mixer was changed to 0.09.

[Comparative Example 4]
A resin composition and a moisture-permeable sheet were produced in the same manner as in Example 1 except that the resin composition was obtained by mixing using a Henschel mixer instead of the ribbon mixer. The Henschel mixer corresponds to a high-shear stirring type mixing device due to its structure.

[Measurement and variation of bulk density]
The resin compositions mixed in Examples and Comparative Examples were sampled, and the resin composition was dropped from the funnel opening and filled in the cup through a funnel having a diameter of 10 mm in which a 100 mL cup was arranged at the bottom of the funnel opening. Next, the resin composition filled in the cup was frayed in parallel along the open end of the cup, and the mass (g) of the resin composition filled in the cup was measured. The bulk density (g / mL) was calculated by dividing the measured mass (g) of the resin composition by the volume of the cup (100 mL). The variation (%) in bulk density is calculated by calculating the average value of bulk density as an arithmetic mean from five resin composition samples obtained by sampling the mixed resin composition from an arbitrary location and arithmetically averaging the standard deviation. It was calculated by multiplying the divided value by 100. The measurement results are shown in Table 1 below.

[Evaluation of bulk density variation]
For the resin compositions mixed in Examples and Comparative Examples, the mixed products in the tank were evaluated according to the following criteria. The results are shown in Table 1 below.
◯: Among the mixed resin compositions, those in which the value calculated by [Measurement of bulk density] in the previous step was within ± 2% were regarded as a uniform mixed state.
X: In the mixed resin composition, a value calculated by [Measurement of bulk density] in the previous step of + 2% or more or -2% or less was regarded as a non-uniform mixed state.

[Appearance evaluation of resin composition]
The appearance of the resin compositions mixed in Examples and Comparative Examples was evaluated according to the following criteria. The results are shown in Table 1 below.
◯: The mixed resin composition has a uniform appearance with no large lumps of resin or inorganic filler observed.
X: In the mixed resin composition, large lumps of resin and inorganic filler and uneven mixing are observed, resulting in a non-uniform appearance.

[Evaluation of the number of pinholes in the transparent sheet]
For the transmissive sheets obtained in Example 1 and Comparative Example 4, the number of pinholes existing per ^{1 m 2 of} the transmissive sheet was measured by dividing the number of pinholes detected by the CCD camera by the sheet area. The results are shown in Table 1 below.

It can be seen that the resin compositions produced in Examples 1 and 2 have less variation in bulk density and can be mixed uniformly as compared with the resin compositions produced in Comparative Examples 1 to 4. Further, the number of pinholes in the transparent sheet of Example 1 is smaller than the number of pinholes in the transparent sheet of Comparative Example 4, which is sufficient for a moisture-permeable sheet used for an absorbent article or the like that requires water impermeability. It turns out that it can be used.

Claims (5)

Polyolefin resin, polyhydric alcohol, monobasic acid having 14 to 22 carbon atoms, and 100 parts by mass of the polyolefin resin component containing 25 to 55% by mass of the polyolefin resin and 45 to 75% by mass of the inorganic filler. / Or a method for producing a resin composition in which a resin composition containing 1 to 30 parts by mass of polyester and 0.5 to 5 parts by mass of a fatty acid or a metal salt thereof is mixed with a monovalent alcohol having 12 to 22 carbon atoms. ,
The resin composition so that the Froude number is 0.1 or more and 0.6 or less, and the variation in the bulk density of the resin composition is within ± 2% with respect to the average value of the bulk density. A method for producing a resin composition, which adjusts the mixing time. The method for producing a resin composition according to claim 1, wherein the resin composition is mixed using a low-shear stirring type mixing device. The method for producing a resin composition according to claim 1 or 2, wherein the resin composition having a volume of 60% or more and 100% or less of the effective volume of the device for mixing the resin composition is charged into the device and mixed. The method for producing a resin composition according to claim 3, wherein the resin composition is mixed for a time of 3 minutes or more. A resin composition is produced by the production method according to any one of claims 1 to 4, and then the resin composition is molded to obtain a sheet, and the sheet is uniaxially or biaxially stretched to have an area of 2 A method for producing a moisture-permeable sheet, which is stretched more than twice to have a basis weight of 10 g / m ² or more and 25 g / m ^{2 or less.}

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