JP2019104812A - Method for producing resin composition and moisture-permeable sheet - Google Patents

Abstract

To provide a method for producing a moisture-permeable sheet capable of producing a moisture-permeable sheet in which occurrence of pin holes is suppressed with high productivity, and a method for producing a resin composition which is suitably used for production of the moisture-permeable sheet.SOLUTION: A method for producing a resin composition includes mixing a resin composition containing 1-30 pts.mass of polyester of a polybasic acid, a polyhydric alcohol, and a monobasic acid having 14-22 carbon atoms and/or a monohydric alcohol having 12-22 carbon atoms, and 0.5-5 pts.mass of an aliphatic acid or its metal salt, with respect to 100 pts.mass of a polyolefin resin component containing 25-55 mass% of a polyolefin resin and 45-75 mass% of an inorganic filler. A mixing time is adjusted so that the resin composition has the Froude number of 0.1 or more and 0.6 or less and variation in a bulk density of the resin composition is within ±2% with respect to the average value of the bulk density.SELECTED DRAWING: Figure 1

Description

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

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

For example, Patent Document 1 discloses a polyolefin resin component including 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 a polyester with a polyhydric alcohol and a fatty acid or a metal salt thereof is subjected to a stretching treatment to double or more the area by uniaxial or biaxial stretching method, and the basis weight is 10 to 25 g A method of manufacturing a moisture-permeable sheet, wherein m ² / m ² , is described.

JP, 2008-163153, A

  However, in the moisture-permeable sheet produced by the method of Patent Document 1, depending on the forming conditions and stretching conditions of the film, a large hole to which water can permeate may be generated, that is, a pinhole may occur. The occurrence of pinholes causes the occurrence of liquid leakage, and it is necessary to discard the moisture-permeable sheet in which pinholes are generated as a defective product, etc. to reduce the productivity of the permeable sheet and absorbent articles using the permeable sheet. There was also a possibility that they would be connected.

Also, as a general method, when the film is manufactured to have a basis weight of more than 30 g / m ^2, although the productivity of the transmission sheet and the like is unlikely to decrease due to the generation of pinholes, the transmission sheet itself This results in a decrease in the flexibility and moisture permeability of the material, making it very difficult to apply to absorbent articles from the viewpoint of the comfort of the user.

  Accordingly, an object of the present invention is to improve the method of manufacturing a moisture-permeable sheet, and to suppress the generation of pinholes in the moisture-permeable sheet.

The present invention has a polybasic acid, a polyhydric alcohol, and a carbon number of 14 to 22 per 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 a polyester with a monobasic acid and / or a monohydric alcohol having 12 to 22 carbon atoms and 0.5 to 5 parts by mass of a fatty acid or its metal salt is mixed Method,
In the resin composition, the fluid number is 0.1 or more and 0.6 or less, and the variation in bulk density of the resin composition is within ± 2% of the average value of the bulk density. It is providing the manufacturing method of a resin composition which adjusts mixing time.

In the present invention, a resin composition is produced, and then the resin composition is molded to obtain a sheet, and the sheet is subjected to uniaxial or biaxial stretching method to stretch the area twice or more to have a basis weight of 10 g An object of the present invention is to provide a method of manufacturing a moisture-permeable sheet having a density of at least ² m ^{2 and at most} 25 g / m ² .

  ADVANTAGE OF THE INVENTION According to this invention, the moisture-permeable sheet which suppressed generation | occurrence | production of a pinhole can be manufactured by 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 of the moisture-permeable sheet in Example 1 and Comparative Example 4.

  The present invention will be described below based on its preferred embodiments. The resin composition of the present invention comprises a polyolefin resin component including a polyolefin resin and an inorganic filler, a polyester, and a fatty acid or a metal salt thereof. The details of each component and the amount contained in the resin composition will be described later.

  Heretofore, in order to mix resin compositions, for example, a mixing apparatus such as a Henschel mixer or a super mixer has been used. However, as described above, there are inconveniences such as the occurrence of pinholes and the decrease in productivity of the transmission sheet and the like due to the generation of the pinholes. As a result of intensive investigations by the inventor, it was unexpectedly found that the Froude number, which is a non-dimensional 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 produced in the moisture-permeable sheet produced therefrom, according to the present inventor. The findings were very surprising.

  The resin composition of the present invention can be produced by mixing the above-mentioned components using a mixing apparatus or the like, but the components in the resin composition having different specific gravities are uniformly mixed, and the resin composition In order to effectively suppress the occurrence of pinholes in the moisture-permeable sheet manufactured using the above method, the fluid number is mixed to 0.1 or more, preferably 0.3 or more, and the upper limit thereof is 0.6 Hereinafter, mixing is preferably performed so as to be 0.57 or less. Specifically, mixing is performed so that the Froude number is 0.1 or more and 0.6 or less. It is preferable to mix so that it may be 0.3 or more and 0.57 or less.

Here, the Froude number is expressed by the following equation, where V is the circumferential speed (m / s), D is the radius (m) from the rotation center to the circumference of the rotating object, and g is the gravitational acceleration (m / s ² ). It is a value calculated by the following equation (1). When the mixing device provided with the main wing and the crushing blade is used for mixing the resin composition, the circumferential velocity V and the radius D are to be those of the main wing.
Froude number = V ² / (D × g) (1)

  In addition, the "pinhole" in this specification refers to the through-hole which has the magnitude | size which can permeate | transmit water among the holes which exist in a moisture-permeable sheet, The magnitude | size of this through-hole is 0.5 mm in width , Those with a length of 0.5 mm or more. Whether or not a pinhole is present in the moisture-permeable sheet can be determined or detected, for example, by a pinhole inspection machine by CCD camera detection. The method of detecting pinholes will be described in detail in the embodiments described later.

  In the mixing of the components constituting the resin composition, the resin composition is mixed so that the bulk density thereof is preferably 0.3 g / mL or more, more preferably 0.4 g / mL or more, and the upper limit thereof Are 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 so that the bulk density of the resin composition 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 measuring method of bulk density is explained in full detail by the example mentioned later. By mixing the resin composition of the present invention so as to have such a range of bulk density, heating and kneading of the resin composition described later can be performed uniformly.

  In the resin composition of the present invention, the variation (fluctuation) of the bulk density of the resin composition is within ± 2% with respect to the average value of the bulk density of the resin composition, provided that the above-mentioned Froude number is satisfied. As described above, the mixing time is adjusted, and preferably adjusted to be within ± 1.5%. By setting the dispersion of the bulk density of the resin composition to such a range, each component in the resin composition having different specific gravities 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 composition so as to cause such variation in bulk density, for example, the mixing can be achieved by mixing for a predetermined time using a mixing apparatus described later. The method of calculating the average value and the variation of the bulk density will be described in detail in the examples described later, together with the method of measuring the bulk density.

  The inventors have found that it is preferable to use, for example, a low shear stirring-type mixing apparatus in order to mix the resin composition so that the variation in the fluid number and the bulk density of the resin composition falls within the above-described specific range. . The low shear stirring type mixing device refers to a mixing device which does not give strong shear to the composition at the time of mixing when mixing the resin composition, and the resin composition is not easily consolidated. As a low shear stirring type mixing apparatus used for this invention, a tumbler mixer, a ribbon mixer, a V-type mixer etc. are mentioned, for example. In particular, these low shear stirring-type mixing devices are preferable because the mixing of the resin composition with low shear can be easily achieved in the specification of the mixing device. In addition, even if it is a mixing apparatus which can give high shear to a resin composition, it can be used if it is a mixing apparatus which can reduce and operate a shear force by setting of operation conditions etc.

  Another way of achieving low shear mixing can also be achieved by setting the number of revolutions of the mixing device or the number of revolutions of the mixing blades provided in the mixing device to a low value.

  Similarly, when a ribbon mixer is used as the mixing device, the number of revolutions of the mixing blade 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 Is preferably 50 rpm or less. Specifically, the number of revolutions 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 number of rotations of the mixing blades refers to the number of rotations of the main blades. 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 manufactured using the resin composition can be suppressed.

  From the viewpoint of achieving both improvement of processing efficiency in production of a resin composition and suppression of generation of pinholes of a moisture-permeable sheet produced 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 for such time, variation in bulk density of the resin composition can be further reduced. As a result, it is possible to further suppress the occurrence of pinholes in the moisture-permeable sheet manufactured using the resin composition.

  The volume of the resin composition provided for mixing in the mixing device is preferably 60% to 100% of the effective volume of the device for mixing the resin composition, and the volume of the effective volume of the device for mixing the resin composition is It is more preferable to set it as 70% or more and 90% or less. By mixing the resin composition in such a volume range, the respective components of the resin composition having different specific gravities can be uniformly mixed without separation, and the variation in bulk density of the resin composition is further reduced. be able to. As a result, it is possible to further suppress the occurrence of pinholes in the moisture-permeable sheet manufactured using the resin composition.

  Next, the manufacturing method of the moisture-permeable sheet using the above-mentioned resin composition is demonstrated. The moisture-permeable sheet of the present invention can be produced by forming a resin composition produced by the above-mentioned production method of the resin composition to obtain a sheet, and then subjecting the sheet to a stretching treatment.

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

  Next, the resin composition in a molten state is molded using a molding apparatus described later to obtain a sheet of the resin composition. The melt flow rate (MFR) of the resin composition in a molten state is preferably 1 g / 10 min or more, and more preferably 2 g / 10 min or more, from the viewpoint of improving the production efficiency. The upper limit thereof is preferably 8 g / 10 min or less, 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. In addition, MFR can be measured by performing heating and load application according to the kind of polyolefin resin according to the method prescribed | regulated to ASTMD-1238-57T (E). For example, when polypropylene is used as the polyolefin resin, the temperature is measured at 190 ° C. under a load of 21.18 N.

  As a shaping | molding apparatus which shape | molds the resin composition of a molten state in a sheet form, well-known shaping | molding apparatuses, such as a T-die shaping | molding apparatus and an inflation molding apparatus, can be used, for example. The heating temperature during molding is not particularly limited as long as the resin composition can melt at least, but from the viewpoint of simplicity of molding and prevention of thermal decomposition of components in the resin composition, the melting point of the resin composition is When M (° C.), it is preferable that the temperature is [M + 20] ° C. or more and [M + 60] ° C. or less. When the resin composition is composed of a plurality of resins, the highest melting point of the constituent resins is taken as the melting point M of the resin composition.

  Finally, the sheet obtained in the above-mentioned process is subjected to a stretching treatment by a uniaxial or biaxial stretching method to obtain the 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 do not allow water to permeate while allowing water vapor to permeate.

  As a method of stretching the sheet, for example, a roll method or a tenter method is used. In addition, when performing the stretching process, it is preferable to heat the sheet to be subjected to the stretching process 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 more and 100 ° C. or less. The method for heating the sheet is not particularly limited, and examples thereof include a method in which the sheet is brought into contact with a heated roll, and a method in which heating is performed by hot air or a heater.

  The stretching ratio of the sheet to be stretched by uniaxial or biaxial stretching method is at least twice the area of the sheet from the viewpoint of securing the strength and water impermeability of the moisture-permeable sheet, and the flexibility and moisture permeability. It is preferable to stretch by 2.2 times or more. The upper limit thereof is preferably 4 times or less, and more preferably 3 times or less of the area of the sheet. Specifically, the stretching ratio of the sheet is preferably 2 to 4 times the area of the sheet, and more preferably 2.2 to 3 times.

In stretching the sheet, it is preferable to perform stretching so that the basis weight of the moisture-permeable sheet after stretching is 10 g / m ² or more, from the viewpoint of securing the strength and water impermeability of the moisture-permeable sheet, It is more preferable to conduct stretching so as to be 15 g / m ² or more, and it is further preferable to conduct stretching so as to be 17 g / m ² or more. Further, from the viewpoint of securing flexibility and moisture permeability, it is preferable to conduct stretching so that the basis weight of the moisture-permeable sheet is 25 g / m ² or less, and stretching so as to be 23 g / m ² or less More preferable. Specifically, it is preferable to conduct stretching 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 stretching so as to be 15 g / m ² or more and 25 g / m ² or less The stretching treatment is more preferably 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 draw ratio of the sheet to be subjected to the drawing treatment to the above-mentioned range.

The moisture-permeable sheet of the present invention produced through the above steps has a moisture permeability of preferably 3600 g / (m ² · 24 h) or more, more preferably 4000 g / (m ² · 24 h) or more Preferably, it is 5000 g / (m ² · 24 h) or more. The upper limit is preferably 8400 g / (m ² · 24 h) or less. Specifically, the moisture permeability of the moisture-permeable sheet of the present invention is preferably 3600 g / (m ² · 24 h) or more and 8400 g / (m ² · 24 h) or less, more preferably 4000 g / (m ² · 24 h ) 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 accordance with JIS Z 0208 under conditions of temperature 30 ° C. ± 0.5 ° C. and humidity 90 ± 2% RH.

  The moisture-permeable sheet of the present invention has moisture permeability that allows water vapor to permeate while being water-impermeable, since generation of pinholes that allow water to permeate is suppressed. Such a moisture-permeable sheet is used, for example, as a sanitary material, a medical material, a clothing material, and the like. The moisture-permeable sheet of the present invention can also be used as the above-mentioned material in the form of a composite sheet in which the sheet is bonded as it is or with a fiber sheet such as a nonwoven fabric on one surface thereof. Furthermore, when the moisture-permeable sheet of the present invention is used as a composite sheet, it can be used as a constituent material of absorbent articles such as disposable diapers, sanitary napkins, incontinence pads, panty liners, etc. The occurrence of rash and the like on the skin of the wearer can be effectively prevented.

  Next, components contained in the above-described resin composition will be described. The resin composition of the present invention comprises 1 to 30 parts by mass of polyester and fatty acid or metal thereof per 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. It contains 0.5 to 5 parts by mass of a salt.

  Polyolefin resin is a material used as a raw material of a liquid-impermeable moisture permeable sheet. Examples of the polyolefin resin used in the present invention include polymers containing ethylene, propylene, butene and the like, and resins containing these copolymers as a main component. Specific examples thereof 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 combination of two or more. From the viewpoint of achieving both the flexibility and the durability of the transmission 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 pores in the moisture-permeable sheet produced from the resin composition of the present invention to impart moisture permeability. As the inorganic filler, for example, 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, Powdered particles such as mica, zeolite, carbon black, aluminum powder, iron powder and the like can be mentioned. These can be used alone or in combination of two or more. Among these inorganic fillers, calcium carbonate and barium sulfate are preferably used, and calcium carbonate is particularly preferably used.

  From the viewpoint of maintaining the durability of the moisture-permeable sheet, the average particle diameter of the inorganic filler is preferably 0.3 μm to 8 μm, and more preferably 0.5 μm to 5 μm. In addition, on the condition that the average particle size of the inorganic filler satisfies the above-mentioned range, the maximum particle size is preferably 20 μm or less, and more preferably 15 μm or less. The particle size of the inorganic filler can be measured, for example, using a laser diffraction type particle size distribution analyzer (LA950V2, manufactured by Horiba, Ltd.).

From the viewpoint of achieving both the moisture permeability and durability of the transmission sheet, the inorganic filler preferably has a brane specific surface area of 20000 cm ² / g or more and 22000 cm ² / g or less, and 20500 cm ² / g or more and 22000 cm ² / g or less It is more preferable that The brane specific surface area of the inorganic filler can be measured according to JIS R 5201 using, for example, a brane air permeation particle size measurement device (Braen air permeation particle size measurement device, manufactured by Tsutsui Rika Chemical Co., Ltd.).

  The content of the polyolefin resin is 25% by mass or more, preferably 30% by mass or more, and more preferably 35% by mass or more in the polyolefin resin component, and the upper limit thereof is 55% by mass or less, The content is preferably 50% by mass or less, more preferably 45% by mass or less. Specifically, the content of the polyolefin resin is 25 to 55% by mass, preferably 30 to 50% by mass, and more preferably 35 to 45% by mass in the polyolefin resin component. By having the content of the polyolefin resin, it is possible to manufacture a moisture permeable sheet having moisture permeability, water resistance, and durability.

  Similarly, the content of the inorganic filler is 45% by mass or more, preferably 50% by mass or more, and more preferably 55% by mass or more, in the polyolefin resin component, and the upper limit thereof is 75% by mass. It is preferable to contain 70% by mass or less, and more preferable to contain 65% by mass or less. Specifically, the content ratio of the inorganic filler is 45 to 75% by mass, preferably 50 to 70% by mass, and more preferably 55 to 65% by mass in the polyolefin resin component. By the content ratio of the inorganic filler, it is possible to manufacture a moisture permeable sheet having moisture permeability, water resistance and durability.

  The resin composition used in the present invention contains a polyester. This polyester is a polyester of 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 using the resin composition can be improved.

  As polybasic acid contained in polyester, dicarboxylic acid, tricarboxylic acid, tetracarboxylic acid etc. are used. As the polyhydric 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 and the like are used. As the monohydric alcohol, a long-chain hydrocarbon monoalcohol having 12 to 22 carbon atoms, or the like is used.

  The polyester is obtained by dehydration condensation of a polybasic acid and a polyhydric alcohol. When the terminal of the polyester is a carboxylic acid derived from another basic acid, it is preferable that the majority of the ester is esterified with monoalcohol of long chain hydrocarbon such as stearyl alcohol, oleyl alcohol and Guerbet alcohol. When the end is an alcohol, the end-capped polyester is preferably esterified with a monocarboxylic acid of a long chain hydrocarbon such as stearic acid, hydroxystearic acid, oleic acid and isostearic acid. In this case, all ends of the polyester may not be esterified.

  Examples of the polyester contained in the resin composition of the present invention include polyesters in which the carboxylic acid or alcohol at both ends of the polyester of diethylene glycol and dimer acid is partially or wholly blocked with stearyl alcohol or stearic acid, 1, 3 -A polyester obtained by blocking both ends of a polyester of butanediol and adipic acid with hydroxystearic acid, hexaester consisting of trimethylolpropane-adipic acid-stearic acid, octaester consisting of pentaerythritol-adipic acid-stearic acid, dipenta Dodecaester consisting of erythritol-adipic acid-stearic acid, polyester using dimer acid or hydrogenated dimer acid instead of adipic acid which is a component of the polyester, and substitution of stearic acid Polyester or the like using isostearic acid.

  The polyester contained in the resin composition of the present invention is contained in an amount of 1 part by mass or more, preferably 2 parts by mass or more, and preferably 30 parts by mass or less, with respect to 100 parts by mass of the polyolefin resin component. It is preferable to include by mass or less. Specifically, the polyester is contained in an amount of 1 to 30 parts by mass, preferably 2 to 20 parts by mass, with respect to 100 parts by mass of the polyolefin resin component. By containing polyester in this range, it is possible to impart flexibility and stretchability to a moisture-permeable sheet produced using a resin composition.

  The resin composition of the present invention contains a fatty acid or a metal salt thereof. The fatty acid or the metal salt thereof is for uniformly dispersing the inorganic filler in the resin composition. Examples of fatty acids or metal salts 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 contained in the resin composition in an amount of 0.5 parts by mass or more, preferably 1.0 parts by mass or more, with respect to 100 parts by mass of the polyolefin resin component. It is preferable to contain 0 mass part or less, and to contain 4.0 mass part or less, and it is more preferable to contain 3.0 mass part or less. Specifically, 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 components described above, the resin composition used in the present invention can contain an additive within a range that does not impair the effects of the present invention. Examples of additives include plasticizers, stabilizers, antioxidants, ultraviolet light 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 embodiments.

Example 1
3.9 parts by mass of polyester with respect to 100 parts by mass of a polyolefin resin component containing 39.2% by mass of a polyolefin resin and 60.8% by mass of calcium carbonate as an inorganic filler, using each material shown below A resin composition was obtained by mixing 0.8 parts by mass of a fatty acid with a ribbon mixer (radius from the center of rotation to the circumference of the rotating object: 490 mm). 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): manufactured by Prime Polymer Co., Ltd., "UZ2520F (trade name)"
· Inorganic filler (calcium carbonate): Sanko Seimitsu Co., Ltd., "ESKALON 2000 2000 (trade name)"
-Polyester: Kao Co., Ltd., "EXCEPEARL (registered trademark) TM 20-AS (trade name)"
-Fatty acid: Kao Co., Ltd. product, "Lunack (registered trademark) S-40 (trade name)"

Subsequently, the obtained resin composition was melt-kneaded by a pellet production 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 sheet conveying direction 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 by 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 by 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 using a Henschel mixer instead of the ribbon mixer to obtain a resin composition. The Henschel mixer, by its structure, corresponds to a mixing apparatus of high shear stirring type.

[Measurement of bulk density and variation]
The resin composition mixed in the example and the comparative example was sampled, and the resin composition was dropped from the funnel port and filled into the cup through a funnel with a diameter of 10 mm in which a 100 mL cup was placed at the bottom of the funnel port. Next, the resin composition filled in the cup was scraped off in parallel along the open end of the cup, and the mass (g) of the resin composition filled in the cup was measured. Bulk density (g / mL) was calculated by dividing the measured mass of the resin composition (g) 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 any place, and calculating the standard deviation thereof by arithmetic mean It was calculated by multiplying the divided product by 100. The measurement results are shown in Table 1 below.

[Evaluation of bulk density variation]
With respect to the resin compositions mixed in the examples and the comparative examples, the in-tank mixed product was evaluated based on the following criteria. The results are shown in Table 1 below.
○: A mixed resin composition in which the value calculated by [Determination of bulk density] in the previous stage is within ± 2% was brought into a homogeneous mixed state.
X: In the mixed resin composition, the one having a value of + 2% or more or -2% or less calculated by [Measurement of bulk density] in the previous stage was brought into a non-uniform mixed state.

[Appearance evaluation of resin composition]
The appearances of the resin compositions mixed in the examples and comparative examples were evaluated based on the following criteria. The results are shown in Table 1 below.
○: Large lumps of resin and inorganic filler are not observed in the mixed resin composition, and the appearance is uniform.
X: Large lumps and mixing unevenness of resin and inorganic filler are observed in the mixed resin composition, and the appearance is uneven.

[Evaluation of the number of pinholes of the transmission sheet]
For transmitting sheet obtained in Example 1 and Comparative Example 4, by dividing the number of pins holes which are detected by the CCD camera at a sheet area, the number of pinholes present in the permeable sheet 1 m ² per measured. The results are shown in Table 1 below.

It can be seen that the resin compositions produced in Examples 1 and 2 have smaller variations in bulk density and can be uniformly mixed as compared with the resin compositions produced in Comparative Examples 1 to 4. In addition, the number of pinholes of the transmission sheet of Example 1 is smaller than the number of pinholes of the transmission sheet of Comparative Example 4, and is sufficient for the moisture-permeable sheet used for absorbent articles etc. It turns out that it is usable.

Claims (5)

A polybasic acid, a polyhydric alcohol, a monobasic acid having 14 to 22 carbon atoms, and 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 And / or a method for producing a resin composition in which a resin composition containing 1 to 30 parts by mass of a polyester with a monohydric alcohol having 12 to 22 carbon atoms and 0.5 to 5 parts by mass of a fatty acid or its metal salt is mixed. ,
In the resin composition, the fluid number is 0.1 or more and 0.6 or less, and the variation in bulk density of the resin composition is within ± 2% of the average value of the bulk density. The manufacturing method of the resin composition which adjusts mixing time.   The manufacturing method of the resin composition of Claim 1 mixed using a low shear stirring type | mold mixing apparatus.   The method for producing a resin composition according to claim 1 or 2, wherein the resin composition having a volume of 60% to 100% of the effective volume of the apparatus for mixing the resin composition is charged into the apparatus 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 subjected to an area of 2 or more by uniaxial or biaxial stretching. moisture permeable sheet manufacturing method of the basis weight by stretching more than doubled to 10 g / ^{m 2} or more 25 g / ^{m 2} or less.

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