JP2020045412A - Stretched porous film - Google Patents

Abstract

To provide a stretched porous film which has excellent touch feeling such as flexibility and feeling, suppresses generation of an uncomfortable sound generated when the film is rubbed, and is also excellent in air permeability, moisture permeability, strength and heat resistance.SOLUTION: A stretched porous film is formed of a resin composition (Z) containing 25-54 mass% of a thermoplastic resin and 46-75 mass% of an inorganic filler (A), in which tanδ(=E''/E') that is a ratio of storage elastic modulus (E') and loss elastic modulus (E'') calculated by dynamic viscoelasticity measurement of the resin composition (Z) at -20°C is 0.100 or more and the film has a crystal melting peak (Pm1) at 140-200°C.SELECTED DRAWING: None

Description

  The present invention relates to a stretched porous film that has excellent touch feeling such as flexibility and texture, suppresses generation of unpleasant sound generated when the film is rubbed, and is excellent in breathability, moisture permeability, strength, and heat resistance. More specifically, hygiene products such as disposable diapers and feminine sanitary products; work clothes, jumpers, jackets, medical garments, and chemical protective clothing; and other breathable and breathable masks, covers, drapes, sheets, and wraps. The present invention relates to a stretched porous film having an excellent feeling in use that can be suitably used for applications that require.

  Conventionally, by stretching a resin composition containing a thermoplastic resin such as a polyolefin-based resin and an inorganic filler, interfacial separation occurs between the thermoplastic resin and the inorganic filler, resulting in a large number of voids (microporous). Are known. In particular, a stretched porous film made of a resin composition containing a polyolefin-based resin and an inorganic filler has a high permeability and a high moisture permeability because the internal micropores form communication holes. It is used as a moisture-permeable waterproof film that suppresses odors.In particular, sanitary materials such as disposable diapers and feminine hygiene products, work clothes, jumpers, jackets, medical clothing, chemical protective clothing and other clothing, masks, covers, drapes, Widely used for applications requiring breathability and moisture permeability such as sheets and wraps.

  Since porous films used in these applications are often used directly in contact with human skin, it is important that the film has an unpleasant sound or feel, such as rough or rough, in activities while wearing it. It becomes a factor that hinders the feeling. For this reason, the porous film is required to have good texture and flexibility and good touch, and to suppress unpleasant noise.

  To solve these problems, for example, the inorganic filler is contained in an amount of 50 to 300 parts by weight with respect to 100 to 100 parts by weight of the total amount of the ethylene / α-olefin copolymer 65 to 90% by weight and the thermoplastic elastomer 35 to 10% by weight. A resin comprising a porous film (Patent Document 1) and 20 to 100 parts by weight of a crystalline low density polyethylene containing 12% by weight or more of an α-olefin comonomer having 4 to 8 carbon atoms and 80 to 0 parts by weight of polyethylene A moisture-permeable film containing 50 to 400 parts by weight of an inorganic filler with respect to 100 parts by weight of a component (Patent Document 2) is disclosed.

  Further, aeration containing 50 to 300 parts by mass of an inorganic filler and 1 to 30 parts by mass of a plasticizer with respect to 100 parts by mass of a total of 30 to 70 parts by mass of a polyethylene resin and 70 to 30 parts by mass of an olefin elastomer. Film component (Patent Document 3), 100 parts by mass of a resin component including 40 to 90 parts by mass of a polyethylene resin, 5 to 30 parts by mass of a propylene homopolymer, and 5 to 30 parts by mass of a propylene / ethylene copolymer elastomer, and the resin component Moisture-permeable film containing 100 to 200 parts by mass of an inorganic filler and 1 to 20 parts by mass of a plasticizer (Patent Document 4), and a moisture-permeable film containing a polyethylene resin composition, an inorganic filler and a styrene-based elastomer (Patent Document 5) Further, 30 to 85 parts by mass of linear low-density polyethylene, 5 to 20 parts by mass of low-density polyethylene by high-pressure polymerization, metallocene-based Moisture permeable film containing a resin component containing 10 to 50 parts by mass of a styrene / α-olefin copolymer, and 100 to 200 parts by mass of an inorganic filler and 1 to 20 parts by mass of a plasticizer based on 100 parts by mass of the resin component (Patent Document 6) are disclosed.

JP-A-7-228719 JP-A-2000-1557 JP, 2017-31292, A JP 2015-229720 A WO 2014/088065 pamphlet WO 2015/186808 pamphlet

However, Patent Documents 1 and 2 disclose an ethylene / α-olefin copolymer having a melting point of 60 to 100 ° C. and a crystalline low-density polyethylene containing 12% by weight or more of an α-olefin comonomer having 4 to 8 carbon atoms. Since the film is a main component, the film is rich in flexibility, but may be melted under high temperature conditions generated in a step of bonding other members, and the dimensional stability and heat resistance are insufficient.
Specifically, sanitary materials such as disposable diapers are generally manufactured by laminating a porous film and a nonwoven fabric by hot melt lamination, and at that time, the hot melt adhesive is heated to 100 to 200 ° C. Since the film is heated and melted and sprayed onto the porous film, if the heat resistance of the porous film is insufficient, the film is broken and productivity is significantly impaired. Therefore, it is very important that the porous film has sufficient heat resistance.

In Patent Documents 3 to 6, olefin-based elastomers, propylene / ethylene copolymerized elastomers, styrene-based elastomers, metallocene-based ethylene / α-olefin copolymers, etc. are contained in a composition containing a polyethylene-based resin and an inorganic filler. By containing the soft resin of (1), a film having flexibility and elasticity and excellent in texture and touch can be obtained.
On the other hand, in applications where these porous films are used, further improvement in usability is required, and further improvement in tactile sensation such as flexibility and texture, and generation of unpleasant sound generated when the film is rubbed Therefore, it is necessary to suppress the above. However, Patent Literatures 3 to 6 do not mention a technical design guideline regarding suppression of unpleasant noise.

  The present invention has been made in view of the above problems, and has excellent touch feeling such as flexibility and texture, suppresses generation of unpleasant sound generated when the film is rubbed, and has breathability, moisture permeability, strength, and heat resistance. An object of the present invention is to provide a stretched porous film having excellent properties.

  As a result of intensive studies, the present inventors have succeeded in obtaining a stretched porous film that can solve the above-mentioned problems of the conventional technology, and have completed the present invention. That is, the object of the present invention is achieved by the following stretched porous film (hereinafter, also referred to as “stretched porous film of the present invention”).

That is, an object of the present invention is a stretched porous film comprising a resin composition (Z) containing 25% by mass to 54% by mass of a thermoplastic resin and 46% by mass to 75% by mass of an inorganic filler (A),
Tan δ (= E ″ / E ′), which is the ratio of the storage elastic modulus (E ′) and the loss elastic modulus (E ″) calculated from the dynamic viscoelasticity measurement of the resin composition (Z), is −20. The problem is solved by a stretched porous film having a crystal melting peak (Pm1) at 140 ° C. to 200 ° C. of 0.100 or more at 100 ° C.

  According to the present invention, a stretched porous film having excellent touch feeling such as flexibility and texture, suppressing generation of unpleasant sound generated when the film is rubbed, and having excellent breathability, moisture permeability, strength, and heat resistance Therefore, it can be suitably used for applications requiring air permeability and moisture permeability.

  Hereinafter, the stretched porous film of the present invention as an example of an embodiment of the present invention will be described. However, the scope of the present invention is not limited to the embodiments described below. Here, the stretched porous film is a porous film stretched at least in a uniaxial direction.

  In addition, in this specification, a "main component" means a component which occupies the largest mass ratio in the constituent composition, and is preferably 45% by mass or more, more preferably 50% by mass or more, and 55% by mass. The above is more preferred. Further, when described as “X to Y” (X and Y are arbitrary numbers), “preferably larger than X” and “preferably smaller than Y” together with “X or more and Y or less” unless otherwise specified. Is included.

1. Stretched porous film The stretched porous film of the present invention is a stretched porous film comprising a resin composition (Z) containing 25% by mass to 54% by mass of a thermoplastic resin and 46% by mass to 75% by mass of an inorganic filler (A). Tan δ (= E ″ / E ′) which is a ratio of storage elastic modulus (E ′) and loss elastic modulus (E ″) calculated from the dynamic viscoelasticity measurement of the resin composition (Z). Is a stretched porous film having a crystal melting peak (Pm1) at 140 ° C. to 200 ° C. which is 0.100 or more at −20 ° C.

  The stretched porous film of the present invention is the ratio of the storage modulus (E ′) to the loss modulus (E ″) calculated from the dynamic viscoelasticity measurement of the resin composition (Z) constituting the stretched porous film. It is important that tan δ (= E ″ / E ′) is 0.100 or more at −20 ° C., preferably 0.110 or more, more preferably 0.120 or more, and 0 .130 or more. The upper limit of tan δ of the resin composition (Z) constituting the stretched porous film is not particularly limited, but is preferably 1.000 or less at −20 ° C. from the viewpoint of dimensional stability. When tan δ (= E ″ / E ′) is 0.100 or more at −20 ° C., as described later, a sound absorption coefficient (vibration damping rate) for suppressing unpleasant sound generated when the film is rubbed. And a film excellent in touch feeling such as flexibility and texture can be obtained.

  The tan δ is preferably 0.100 or more at −20 ° C. to −10 ° C., more preferably 0.100 or more at −20 ° C. to 0 ° C., and 0.100 or more at −30 ° C. to 0 ° C. More preferably, it is more preferably 0.100 or more at -30 ° C to 10 ° C, even more preferably 0.100 or more at -30 ° C to 20 ° C, and -30 ° C to 30 ° C. Most preferably, it is 0.100 or more at ° C. As described later, by increasing the temperature range where tan δ calculated from the dynamic viscoelasticity measurement of the resin composition (Z) constituting the stretched porous film of the present invention is 0.100 or more, various frequencies of Unpleasant noise can be suppressed.

Further, the porosity of the stretched porous film of the present invention is preferably 15% to 80%. The porosity is more preferably from 20% to 80%, even more preferably from 25% to 80%.
When the porosity is 15% or more, as will be described later, the chance of energy loss of sound propagating in the voids of the stretched porous film increases, and unpleasant sound can be sufficiently suppressed. When the porosity is 80% or less, a film strength that can be used practically can be ensured, and furthermore, the waterproofness becomes sufficient and the leakage of the liquid material in contact with the film is hardly caused.

Sound is a vibration wave of air generated when an object moves or rubs. When a sound collides with an object as an incident sound, the incident sound is divided into three sounds, a transmitted sound that passes through the object, a reflected sound that reflects the object, and an absorbed sound that is absorbed by the object, from the relation of the law of conservation of energy. Decomposed. That is, when the incident sound collides with the object and the proportion of the absorbed sound absorbed by the object is large, the object is considered to be an object having a high sound absorption coefficient.
The stretched porous film of the present invention is a film having a void communicating with the inside of the resin composition (Z). That is, when sound propagates in the stretched porous film of the present invention, the sound propagates by vibrating the resin composition (Z) forming the solid part as the film, and propagates through the communicating voids formed inside the film. This shows two ways of sound transmission. Therefore, in suppressing the sound, it is necessary to consider the suppression of the sound that propagates by vibrating the resin composition (Z) and the suppression of the sound that propagates through the communicating gap.

In the stretched porous film of the present invention, it is considered that the suppression of sound that propagates by vibrating the resin composition (Z) is effectively attenuated by the vibration source or the medium. In a viscoelastic body such as a resin, a sound absorbing effect can be obtained by losing vibration energy to heat energy. Therefore, tan δ, which is the ratio between the storage elastic modulus (E ′) and the loss elastic modulus (E ″), is considered to be a necessary element for exhibiting this sound absorbing effect. Therefore, in the present invention, it is preferable that the peak value of tan δ of the resin composition (Z) constituting the stretched porous film is large.
In addition, the peak position of tan δ of the resin composition (Z) constituting the stretched porous film of the present invention is related to the attenuation at the ambient temperature at which the sound is generated, and from the viewpoint of the temperature-time conversion law, the attenuation relative to the frequency. Related. Therefore, in order not to absorb or generate unpleasant sounds having various frequencies, it is preferable that the peak width of tan δ is wide.
Therefore, tan δ (the ratio of the storage elastic modulus (E ′) to the loss elastic modulus (E ″) calculated from the dynamic viscoelasticity measurement of the resin composition (Z) constituting the stretched porous film of the present invention) = E ″ / E ′) is at least 0.100 at −20 ° C., which is important for suppressing the generation of unpleasant noise that occurs when the film is rubbed. As described above, it is preferable that the temperature range in which tan δ is 0.100 or more be widened because unpleasant sounds at various frequencies can be suppressed.

In addition, it is considered that the porosity of the porous film also contributes to the suppression of propagating sound. By increasing the porosity, the number of collisions between the sound propagating in the air and the object increases, and it is thought that the effect of suppressing the sound propagating through the communicating voids formed inside the film is obtained. I have.
Therefore, the porosity of the stretched porous film is preferably 15% or more in order to increase the chance of energy loss of sound propagating in the gap of the film.

It is important that the stretched porous film of the present invention has a crystal melting peak (Pm1) at 140 ° C to 200 ° C. In addition, the crystal melting peak (Pm1) preferably has a temperature of 150 ° C to 190 ° C, more preferably 160 ° C to 180 ° C. Having a crystal melting peak (Pm1) at 140 ° C. or higher is important because sufficient heat resistance can be imparted when bonding and laminating the stretched porous film with other members. Further, by having a crystal melting peak (Pm1) at 200 ° C. or lower, it is not necessary to extremely raise the extrusion temperature in forming a stretched porous film, so that deterioration of the resin does not easily occur and productivity is improved. Therefore, it is preferable.
In order to have the crystal melting peak (Pm1), the resin composition (Z) constituting the stretched porous film of the present invention contains a thermoplastic resin having a melting point of 140 ° C. to 200 ° C., whereby the crystal falls within the above range. It can be adjusted to have a melting peak (Pm1).

In addition, in the stretched porous film of the present invention, the crystal melting enthalpy (ΔHm1) calculated from the crystal melting peak (Pm1) is preferably 1 J / g to 10 J / g. The crystal melting enthalpy (ΔHm1) is more preferably 1 J / g to 8 J / g, further preferably 2 J / g to 6 J / g. When the crystal melting enthalpy (ΔHm1) is 1 J / g or more, it is preferable to have a sufficient crystal component for imparting heat resistance to the stretched porous film. In addition, since the crystal melting enthalpy (ΔHm1) is 10 J / g or less, generation of unpleasant sound described later can be suppressed.
By adjusting the mixing ratio of the thermoplastic resin having a melting point of 140 ° C. to 200 ° C. in the resin composition (Z) constituting the stretched porous film of the present invention, the crystal melting enthalpy (ΔHm1) is adjusted to the above range. Can be.

The stretched porous film of the present invention preferably further has a crystal melting peak (Pm2) at 30 ° C to 130 ° C. Further, it is preferable that the crystal melting enthalpy (ΔHm2) calculated from the crystal melting peak (Pm2) is 10 J / g to 45 J / g. The crystal melting enthalpy (ΔHm2) is more preferably from 12 J / g to 43 J / g, even more preferably from 14 J / g to 41 J / g. When the crystal melting enthalpy (ΔHm2) is 10 J / g or more, heat resistance and dimensional stability of the stretched porous film can be secured. In addition, when the crystal melting enthalpy (ΔHm2) is 45 J / g or less, generation of unpleasant sound described later can be suppressed.
In order to have the crystal melting peak (Pm2), the resin composition (Z) constituting the stretched porous film of the present invention contains a thermoplastic resin having a melting point of 30 ° C to 130 ° C, and the mixing ratio is adjusted. Thereby, the crystal melting peak (Pm2) and the crystal melting enthalpy (ΔHm2) can be adjusted to the above ranges.

As a method of suppressing the unpleasant sound generated when the stretched porous films are rubbed together, it is considered that the suppression of the above-described propagated sound and the suppression of the generation of sound from the sound source are effective. The generation of sound is the vibration of the elastic body, and no sound is generated unless there is an object that causes the vibration (= sound source).
Focusing on the thermoplastic resin contained in the resin composition (Z) constituting the stretched porous film of the present invention, the thermoplastic resin is a viscoelastic body having both elastic properties and viscous properties. That is, by reducing the ratio of the elastic property of the thermoplastic resin, when an external force of rubbing the film is applied, the amount of the elastic component that vibrates in response to the external force is reduced, and the generation of sound is suppressed. The index indicating the ratio between the elastic property and the viscous property is the above-mentioned tan δ, and it is considered that reducing the ratio of the elastic property from the macro viewpoint and the micro viewpoint is effective in reducing the unpleasant sound. The macroscopic elastic property is the storage elastic modulus (E ′) calculated from the dynamic viscoelasticity measurement of the resin composition (Z) constituting the above-described stretched porous film of the present invention, and the elasticity from the microscopic viewpoint. The characteristic property is a crystal component of the resin described later.

First, from the viewpoint of reducing elastic properties from a macro viewpoint, the storage elastic modulus (E ′) calculated from the dynamic viscoelasticity measurement of the resin composition (Z) constituting the stretched porous film of the present invention is 20 ° C. Is preferably 8.0 × 10 ⁸ Pa or less. It is more preferably 7.0 × 10 ⁸ Pa or less, and still more preferably 6.0 × 10 ⁸ Pa or less. When the storage elastic modulus (E ′) is 8.0 × 10 ⁸ Pa or less at 20 ° C., the stretched porous film becomes excellent in touch feeling such as texture and flexibility, and suppresses generation of unpleasant sound. Is preferred because The lower limit is not particularly limited, but is preferably 1.0 × 10 ⁷ Pa or more at 20 ° C. from the viewpoint of handling of the stretched porous film.

In the dynamic viscoelasticity measurement of the resin composition (Z) constituting the stretched porous film of the present invention, a strip-shaped sample piece cut into a width of 4 mm and a length of 35 mm was measured at a frequency of 10 Hz and a strain of 0.1%. The measurement is performed while increasing the temperature at a temperature increasing rate of 3 ° C./min from a chuck distance of 25 mm and a measurement temperature of −100 ° C. At this time, from the obtained temperature-dependent profile of dynamic viscoelasticity, the storage elastic modulus (E ′), the loss elastic modulus (E ″), and the storage elastic modulus (E ′) and the loss elastic modulus (E) at each temperature are obtained. Tan δ (= E ″ / E ′) which is a ratio of E ″) is calculated.
In the dynamic viscoelasticity measurement, the thickness of the sample piece is measured in advance, and the values of the thickness of the sample piece and the width of the sample piece are input to a measuring device, whereby the cross-sectional area of the sample piece is calculated, and each value is calculated. Is calculated.
In the stretched porous film of the present invention, since pores are formed in the resin composition (Z), when the porous body is measured as it is, the calculated storage elastic modulus (E ′) and loss elastic modulus (E ″) are calculated. ) And tan δ tend to have errors. Therefore, in order to obtain the storage elastic modulus (E ′), the loss elastic modulus (E ″), and the tan δ specified in the present invention, the unstretched film of the resin composition (Z) constituting the stretched porous film is required. It is preferable to perform dynamic viscoelasticity measurement on a strip-shaped sample piece cut out into a MD of 4 mm and a TD of 35 mm. However, after the stretched porous film is heated to a temperature equal to or higher than the melting point to melt the film and eliminate pores, a press sample is prepared, and a strip-shaped sample piece is cut out from the press sample to perform dynamic viscoelasticity measurement. In this way, the storage elastic modulus (E ′), the loss elastic modulus (E ″), and tan δ defined by the present invention can be calculated. In the present invention, any measurement method can be adopted.

Next, the crystal component of the resin is considered as the elastic property from the micro viewpoint. Thermoplastic resins are classified into amorphous resins and crystalline resins in terms of crystals. The amorphous resin is a thermoplastic resin having a structure in which the molecular chains are relatively bulky, and thus the molecular chains cannot be folded regularly and have no crystalline portion. On the other hand, a crystalline resin is a thermoplastic resin in which a molecular chain is regularly folded and has a high-density crystal part therein. However, even in the case of crystalline resins, there is no crystalline resin in which the molecular chains are crystallized to 100%, and both the amorphous part where the molecular chains are randomly arranged and the crystal part where the molecular chains are regularly folded are used. Have.
The amorphous portion of the crystalline resin is capable of micro-Brownian motion in a temperature range equal to or higher than the glass transition temperature, and is in a state of high mobility. On the other hand, in the crystal part of the crystalline resin, the molecular chain is constrained as a crystal in a temperature range from the glass transition temperature to the melting point but below the melting point. Therefore, when the degree of crystallinity of the crystalline resin is low, the number of crystal parts having a high elastic modulus is reduced, so that it is considered that a component which rebounds and vibrates when an external force is applied is small, and a sound generated is also small.
Therefore, the crystal melting enthalpy is an index of the crystal component ratio in the stretched porous film of the present invention, and the crystal melting enthalpy (ΔHm1) is preferably 1 J / g to 10 J / g. Further, the crystal melting enthalpy (ΔHm2) is preferably from 10 J / g to 45 J / g.

The crystal melting peak (Pm) and the peak temperature (Tm) of the stretched porous film of the present invention were measured by a differential scanning calorimeter (DSC) by heating the stretched porous film of the present invention from −40 ° C. to a high holding temperature. After raising the temperature at a rate of 10 ° C./min, hold for 1 minute, then lower the temperature from the high temperature holding temperature to −40 ° C., cool at a cooling rate of 10 ° C./minute, hold for 1 minute, and further from −40 ° C. to the above high temperature holding temperature. These are the crystal melting peak (Pm) that appears when the temperature is raised again at a heating rate of 10 ° C./min, and the temperature (Tm) at which that peak appears.
The crystal melting enthalpy (ΔHm) is calculated from the peak area of the crystal melting peak (Pm) that appears when the temperature is raised again. At this time, the high-temperature holding temperature can be arbitrarily selected in a range of Tm + 20 ° C. or more and Tm + 150 ° C. or less with respect to the highest crystal melting peak temperature (Tm) of the thermoplastic resin to be used.
Note that the crystal melting enthalpy (ΔHm) in the present invention is calculated from the crystal melting peak generated in the reheating process even when cold crystallization as seen in a semicrystalline resin occurs in the reheating process. ΔHm is applied. That is, the crystallization enthalpy (ΔHc) calculated from the exothermic peak area in the cold crystallization generated in the reheating process is not subtracted from ΔHm obtained in the reheating process.

Further, when the stretched porous film of the present invention is laminated with another layer, if the laminate is directly subjected to DSC measurement, ΔHm derived from the stretched porous film may be underestimated. Therefore, when the stretched porous film of the present invention is a laminate, the stretched porous film of the present invention can be peeled off, and ΔHm of the porous layer can be measured. When peeling is difficult, the ΔHm of the stretched porous film of the present invention in the entire laminate is calculated by DSC measurement, and the lamination ratio of the porous layer in the whole laminate is calculated. ΔHm can be calculated. The calculation of the lamination ratio is not particularly limited, but is preferably calculated by cross-sectional observation using an optical microscope, an electron microscope, or the like.
ΔHm (J / g) in the present invention = ΔHm (J / g) of the stretched porous film in the whole laminate / lamination ratio (%) / 100 (%) of the porous layer in the whole laminate

  Further, it is important that the stretched porous film of the present invention has a crystal melting peak (Pm1) at 140 ° C. to 200 ° C., as long as it has at least one crystal melting peak at 140 ° C. to 200 ° C. Or two or more. When there are two or more crystal melting peaks at 140 ° C. to 200 ° C., the crystal melting enthalpy (ΔHm1) is the total value of the crystal melting enthalpies calculated from the two or more crystal melting peaks.

  Further, the crystal melting peak (Pm2) preferably has at least one crystal melting peak at 30 ° C. to 130 ° C., but may have two or more. When there are two or more crystal melting peaks at 30 ° C. to 130 ° C., the crystal melting enthalpy (ΔHm2) is the total value of the crystal melting enthalpies calculated from the two or more crystal melting peaks.

  Further, when the thermoplastic resin contained in the resin composition (Z) constituting the stretched porous film of the present invention is a polyolefin-based resin, the crystal melting onset temperature is slightly higher than the crystal melting peak temperature (Tm) by 30 ° C. or more. Melts gradually and often shows a broad peak. Therefore, by raising the temperature of the differential scanning calorimetry (DSC) from −40 ° C., the baseline can be clarified, and a more accurate crystal melting enthalpy (ΔHm) can be calculated.

  In summary, the present invention provides a tan δ which is a ratio of a storage modulus (E ′) to a loss modulus (E ″) calculated from a dynamic viscoelasticity measurement of a resin composition (Z), and a crystal. By setting the temperature at which the melting peak (Pm1) occurs in a suitable range, not only is the touch feeling such as flexibility and texture excellent, but also the sound absorption coefficient (vibration damping rate) for suppressing the unpleasant sound generated when the film is rubbed. This improves the heat resistance required of the stretched porous film.

The porosity of the stretched porous film of the present invention is determined by measuring the specific gravity (W1) of the stretched porous film by cutting out the stretched porous film into a size of 50 mm in the longitudinal direction (MD) and 50 mm in the transverse direction (TD). . Next, the specific gravity (W0) of the resin composition (Z) constituting the stretched porous film of the present invention is measured. In the measurement of the specific gravity (W0) of the resin composition (Z), the unstretched film of the stretched porous film of the present invention is cut into a size of 50 mm in the longitudinal direction (MD) and 50 mm in the transverse direction (TD), Specific gravity measurement can be performed. When it is difficult to collect an unstretched sheet, the stretched porous film of the present invention is heated to a temperature equal to or higher than the melting point to melt the stretched porous film and eliminate pores. , A vertical direction (MD): 50 mm and a horizontal direction (TD): 50 mm, and the specific gravity can be measured.
The specific gravity (W1) of the stretched porous film and the specific gravity (W0) of the resin composition (Z) were measured at three points at random, and the arithmetic average value was used. From the specific gravity (W1) of the obtained stretched porous film and the specific gravity (W0) of the resin composition (Z), the porosity was calculated from the following equation.
Porosity (%) = [1- (W1 / W0)] × 100

The basis weight of the expanded porous films of the present invention is preferably from ^{10g / m 2 ~50g / m 2} , more preferably from ^{12g / m 2 ~40g / m 2} . When the basis weight is 10 g / m ² or more, it is easy to sufficiently secure mechanical strength such as tensile strength and tear strength. Further, when the basis weight is 50 g / m ² or less, a sufficient lightweight feeling can be easily obtained.
Here, the grammage is obtained by measuring the mass (g) of a sample (vertical direction (MD): 250 mm, lateral direction (TD): 200 mm) with an electronic balance and multiplying the numerical value by 20 to obtain the grammage.

The air permeability of the stretched porous film of the present invention is preferably 1 second / 100 mL to 5000 seconds / 100 mL, more preferably 10 seconds / 100 mL to 4000 seconds / 100 mL, and more preferably 100 seconds / 100 mL to 3000 seconds / 100 mL. More preferably, it is 100 mL. When the air permeability is 1 second / 100 mL or more, it is easy to sufficiently secure water resistance and liquid permeability. Further, when the air permeability is 5000 seconds / 100 mL or less, it indicates that a sufficient communication hole is provided.
Here, the air permeability is the number of seconds during which 100 mL of air passes through a piece of paper, which is measured according to the method specified in JISP8117: 2009 (Gurley tester method). (Oken type air permeability meter EGO1-55). In the present invention, a sample is randomly measured at 10 points, and the arithmetic average value is defined as the air permeability.

Moisture permeability ^{1000g / (m 2 · 24h)} ~15000g / (m 2 · 24h) is preferably in the expanded porous films of the present invention, more ^{preferably, 1500g / (m 2 · 24h} ) ~12000g / (m 2 · 24h ). By moisture permeability is 15000g ^/ (m 2 · 24h) or less, suggesting that it has a water-resistant. Further, water vapor permeability by at 1000g ^/ (m 2 · 24h) or more, the pores has sufficient communicability is suggested.
Here, the moisture permeability conforms to the various conditions of JISZ0208 (Moisture Permeability Test Method for Moisture-Proof Packaging Materials (Cup Method)). Using 15 g of calcium chloride as a hygroscopic agent, the measurement was performed under a constant temperature and constant humidity environment at a temperature of 40 ° C. and a relative humidity of 90%. The sample was measured at two points at random, and the arithmetic mean value was calculated.

  The tensile breaking strength in the stretching direction of the stretched porous film of the present invention is preferably 7 N / 25 mm or more, and more preferably 10 N / 25 mm or more. When the tensile breaking strength is 7 N / 25 mm or more, practically sufficient mechanical strength and flexibility can be secured. The upper limit is not particularly limited, but is preferably 35 N / 25 mm or less in consideration of stretchability. Here, the tensile breaking strength in the stretching direction was 100 mm in the stretching direction and 25 mm in the perpendicular direction to the stretching direction in accordance with JIS K7127 to prepare a sample, and at a temperature of 23 ° C. and a relative humidity of 50%, the tensile speed was 200 m / m. This is the tensile strength at break when the sample is broken using a triple tensile tester under the conditions of min and a distance between chucks of 50 mm. In the present invention, an arithmetic average of the tensile strength at break calculated by performing the measurement three times was used.

The tensile elongation at break in the stretching direction of the stretched porous film of the present invention is preferably from 40% to 400%, more preferably from 80% to 300%. When the tensile elongation at break is 40% or more, when the stretched porous film of the present invention is used for a disposable diaper and a sanitary article such as a moisture-permeable waterproof back sheet such as a sanitary treatment article, it has a good touch and excellent wearing comfort. Is obtained. Further, when the tensile elongation at break is 400% or less, the film has moderate rigidity and tensile strength and excellent mechanical properties, and the film has small elongation and strain during printing, slitting and winding, and has excellent mechanical suitability in a production line. Is obtained.
Here, the tensile elongation at break in the stretching direction was set to 100 mm in the stretching direction and 25 mm in the perpendicular direction to the stretching direction in accordance with JIS K7127 to prepare a sample, and the tensile speed was 200 m in an environment of 23 ° C. and 50% relative humidity. / Min, the tensile elongation at break when the sample was broken using a triple tensile tester under the conditions of a chuck-to-chuck distance of 50 mm. In the present invention, the arithmetic average value of the tensile elongation at break calculated by performing the measurement three times is used.

The total light transmittance of the stretched porous film of the present invention is preferably 18% to 60%. When the total light transmittance is 18% or more, when the stretched porous film of the present invention is used for sanitary articles such as a back sheet for moisture permeability and waterproofing such as a disposable diaper, it is recognized even if an indicator agent indicating that urination is applied is applied. it can. When the total light transmittance is 60% or less, the film is white and rich in concealment.
Here, the total light transmittance is obtained by measuring five points at random using a haze meter based on JIS K7361 and calculating an arithmetic average value thereof.

The film breakage heat resistance temperature of the stretched porous film of the present invention is preferably 120 ° C or higher, more preferably 140 ° C or higher, and further preferably 160 ° C or higher. When the film-breaking heat resistance temperature is 120 ° C. or higher, the stretched porous film of the present invention is bonded to another member, without laminating the film due to the heat of a hot melt adhesive or the like. It can be determined that heat resistance has been imparted.
Here, the rupture resistance temperature is determined by sandwiching a sample (100 mm x 100 mm) between two stainless steel plates (100 mm x 100 mm x 2 mm (thickness)) whose center is punched out into a circle with a diameter of 50 mm, and fixing the four sides with clips. After heating for 2 minutes in a convection oven at a temperature of 120 ° C. in the bath, the sample at the circular punched portion of the stainless steel plate was melted and visually checked for holes to see if any Those having no opening are set to a heat resistance temperature of 120 ° C. or higher. When the temperature in the tank was changed to 140 ° C. and 160 ° C., and the same evaluation was performed, those having no breakage or perforation were set to a heat-resistant temperature of 140 ° C. or higher and 160 ° C. or higher, respectively.

  Hereinafter, after describing the resin composition (Z) constituting the stretched porous film of the present invention, a method for producing the stretched porous film will be described.

2. Resin composition (Z)
It is important that the stretched porous film of the present invention comprises a resin composition (Z) containing 25% by mass to 54% by mass of a thermoplastic resin and 46% by mass to 75% by mass of an inorganic filler (A).

2-1. Inorganic filler (A)
Examples of the inorganic filler (A) include fine particles and minerals such as calcium carbonate, calcium sulfate, barium carbonate, barium sulfate, titanium oxide, talc, clay, kaolinite, and montmorillonite. Calcium carbonate and barium sulfate can be suitably used due to advantages such as high expression, high versatility, low price and abundant brands.

  The average particle diameter of the inorganic filler (A) is preferably 0.1 to 10 μm, more preferably 0.3 to 5 μm, and still more preferably 0.5 to 3 μm. When the average particle diameter is 0.1 μm or more, poor dispersion and secondary agglomeration of the inorganic filler (A) can be suppressed, and the inorganic filler (A) can be uniformly dispersed in the resin composition (Z). On the other hand, when the average particle diameter is 10 μm or less, generation of large voids can be suppressed when the film is made thinner, and sufficient strength and water resistance can be ensured for the film. Further, for the purpose of improving dispersibility and mixing with the resin, it is preferable to coat the inorganic filler with a fatty acid, a fatty acid ester, or the like in advance, so that the surface of the inorganic filler is easily compatible with the resin, and is used in the present invention. In the inorganic filler (A) to be used, a surface-treated inorganic filler can be used.

2-2. Thermoplastic resin As the thermoplastic resin, polyolefin resin, polystyrene resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, chlorinated polyethylene resin, polyester resin, polycarbonate resin, polyamide resin Resin, ethylene / vinyl alcohol copolymer, ethylene / vinyl acetate copolymer, polymethylpentene resin, polyvinyl alcohol resin, cyclic olefin resin, polylactic acid resin, polybutylene succinate resin, polyacrylonitrile Resin, polyethylene oxide resin, cellulose resin, polyimide resin, polyurethane resin, polyphenylene sulfide resin, polyphenylene ether resin, polyvinyl acetal resin, polybutadiene resin, polybutene resin Fat, polyamideimide resin, polyamidebismaleimide resin, polyarylate resin, polyetherimide resin, polyetheretherketone resin, polyetherketone resin, polyethersulfone resin, polyketone resin, polysulfone resin , Aramid resin, fluorine resin, polyacetal resin and the like. Among them, from the viewpoint of heat resistance, examples of the thermoplastic resin include polyolefin-based resins, ethylene-vinyl alcohol-based resins, polymethylpentene-based resins, polylactic acid-based resins, polyketone-based resins, fluorine-based resins, and polyacetal-based resins. Preferably, the thermoplastic resin is particularly preferably a polyolefin resin from the viewpoints of flexibility, heat resistance, formation of communication holes, environmental hygiene, odor and the like.
The thermoplastic resin may be one type or two or more types. When the thermoplastic resin is composed of two or more kinds, the sum thereof becomes the mass of the thermoplastic resin, and the mass ratio of the thermoplastic resin in the resin composition (Z) is calculated.

  The polyolefin resin is a resin containing an olefin monomer as a main monomer component. The main monomer component refers to a monomer component occupying 50 mol% or more and 100 mol% or less in the resin. Examples of the olefin monomer include ethylene, propylene, and α-olefins such as 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene, and dienes, isoprene, butylene, and butadiene. Or a multi-component copolymer obtained by copolymerizing two or more kinds. Further, those obtained by copolymerizing vinyl acetate, (meth) acrylic acid, (meth) acrylic acid ester, glycidyl (meth) acrylate, vinyl alcohol, ethylene glycol, maleic anhydride, styrene, diene, and cyclic olefin may be used. Among them, from the viewpoint of imparting flexibility and texture, ethylene homopolymer, branched low-density polyethylene, propylene homopolymer, ethylene • (α-olefin copolymer), propylene • (α-olefin copolymer), Preferred are an ethylene / vinyl acetate copolymer, a styrene / ethylene / propylene copolymer, and a styrene / ethylene / butylene copolymer.

  When the thermoplastic resin is a polyolefin-based resin, one type or two or more types may be used as long as the resin is mainly composed of an olefin monomer. When the polyolefin-based resin is composed of two or more types, the total thereof is the mass of the polyolefin-based resin.

When the thermoplastic resin is a polyolefin-based resin, the density of the polyolefin-based resin is preferably 0.850 g / cm ³ or more and 0.940 g / cm ³ or less. Further, as the polyolefin resin, a polyethylene resin (B) having a density of 0.910 g / cm ³ or more and 0.940 g / cm ³ or less, and a density of 0.850 g / cm ³ or more and less than 0.910 g / cm ³ It is preferable to have a soft polyolefin resin (C) and a polypropylene resin (D), respectively.

<Polyethylene resin (B)>
The polyethylene resin (B) is a resin having a density of 0.910 g / cm ³ or more and 0.940 g / cm ³ or less and containing ethylene as a main monomer component. The main monomer component refers to a monomer component occupying 50 mol% or more and 100 mol% or less in the resin. Therefore, the polyethylene resin (B) may be an ethylene homopolymer, or a copolymer containing ethylene as a main monomer component and containing other monomers. Examples of the copolymer include ethylene / propylene copolymer, ethylene / (1-butene) copolymer, ethylene / (1-hexene) copolymer, and ethylene / (4-methyl-1-pentene) copolymer. Polymers, ethylene / (α-olefin) copolymers such as ethylene / (1-octene) copolymer, and ethylene / vinyl acetate copolymer, ethylene / (meth) acrylic acid copolymer, (Meth) acrylate copolymer, ethylene / glycidyl (meth) acrylate, ethylene / vinyl alcohol copolymer, ethylene / ethylene glycol copolymer, ethylene / maleic anhydride copolymer, ethylene / styrene copolymer , An ethylene / diene copolymer and an ethylene / cyclic olefin copolymer. A multi-component copolymer containing two or more of the above-mentioned monomer components such as an ethylene-propylene- (1-butene) copolymer may be used.
Among them, ethylene homopolymer and ethylene / (α-olefin) copolymer are preferred from the viewpoint of dimensional stability.

The polyethylene-based resin (B) may have a density of 0.910 g / cm ³ or more and 0.940 g / cm ³ or less, and may be a single resin as long as it is a resin containing ethylene as a main monomer component. Two or more types may be used. When the polyethylene-based resin (B) is composed of two or more types, the total thereof is the mass of the polyethylene-based resin (B).
By including the polyethylene resin (B) having a density of 0.910 g / cm ³ or more and 0.940 g / cm ³ or less, the stretched porous film has air permeability, moisture permeability, dimensional stability, liquid leakage resistance, concealment, The appearance can be satisfied. The density of the polyethylene resin (B) is more preferably at most 0.910 g / cm ³ or more 0.937 g / cm ^3, not more than 0.910 g / cm ³ or more 0.935 g / cm ^3, especially preferable. Here, the density is a density measured by a pycnometer method (JIS K7112B method). Also, the density of the resin described later is a value measured similarly.

  The polyethylene resin (B) may be linear or branched. The method for producing the polyethylene resin (B) is not particularly limited, and a known polymerization method using a known olefin polymerization catalyst, for example, a multisite catalyst represented by a Ziegler-Natta type catalyst, a metallocene catalyst, or the like. And a polymerization method using a single-site catalyst.

  It is preferred that at least one of the polyethylene resins (B) is a branched low-density polyethylene. It is preferable that at least one kind of the polyethylene resin (B) is a branched low-density polyethylene because the melt tension of the resin composition (Z) increases and moldability is improved. The branched low-density polyethylene has a value of tan δ (= E ″ / E ′) which is a ratio of a storage elastic modulus (E ′) and a loss elastic modulus (E ″) calculated from dynamic viscoelasticity measurement. However, since it shows a large value at 0 to 30 ° C., it is preferable that at least one of the polyethylene resins (B) is a branched low-density polyethylene.

The melting point of the polyethylene resin (B) is preferably from 110 to 135 ° C, more preferably from 110 to 130 ° C. It is preferable that the melting point of the polyethylene resin (B) is 110 to 135 ° C. because the dimensional stability of the stretched porous film can be improved.
Here, the melting point was measured by using a differential scanning calorimeter (DSC) to raise about 10 mg of the resin from -40 ° C to 200 ° C at a heating rate of 10 ° C / min, hold at 200 ° C for 1 minute, and then cool at a cooling rate of 10 ° C. It is a crystal melting peak temperature (Tm) (° C.) determined from a thermogram measured when the temperature was lowered to −40 ° C. at a rate of 10 ° C./min, and again increased to 200 ° C. at a heating rate of 10 ° C./min. The melting point of the resin described below is a value measured in the same manner.

The polyethylene resin (B) preferably has a melt flow rate (MFR) of 0.1 to 20 g / 10 minutes, more preferably 0.5 to 10 g / 10 minutes. It is preferable to set the MFR to 0.1 g / 10 min or more because the moldability of the stretched porous film can be sufficiently maintained. In addition, it is preferable to set it to 20 g / 10 minutes or less because the strength of the stretched porous film can be sufficiently maintained.
Here, the MFR is a value measured according to JIS K7219, and the measurement conditions are 190 ° C. and a load of 2.16 kg.

<Soft polyolefin resin (C)>
The soft polyolefin-based resin (C) is a resin having a density of 0.850 g / cm ³ or more and less than 0.910 g / cm ³ and containing an olefin monomer as a main monomer component. The main monomer component refers to a monomer component occupying 50 mol% or more and 100 mol% or less in the resin. Examples of the olefin monomer include ethylene, propylene, and α-olefins such as 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene, and dienes, isoprene, butylene, and butadiene. Or a multi-component copolymer obtained by copolymerizing two or more kinds. Further, those obtained by copolymerizing vinyl acetate, (meth) acrylic acid, (meth) acrylic acid ester, glycidyl (meth) acrylate, vinyl alcohol, ethylene glycol, maleic anhydride, styrene, diene, and cyclic olefin may be used. Among them, from the viewpoint of imparting flexibility and texture, ethylene homopolymer, branched low-density polyethylene, ethylene / (α-olefin copolymer), ethylene / vinyl acetate copolymer, styrene / ethylene / propylene copolymer And a styrene / ethylene / butylene copolymer.

The soft polyolefin-based resin (C) may be a single resin as long as the resin has a density of 0.850 g / cm ³ or more and less than 0.910 g / cm ³ and has an olefin monomer as a main monomer component. Or two or more types. When the soft polyolefin-based resin (C) is composed of two or more kinds, the total thereof is the mass of the soft polyolefin-based resin (C). By including the soft polyolefin-based resin (C) having a density of 0.850 g / cm ³ or more and less than 0.910 g / cm ³ , the flexibility and texture of the stretched porous film can be improved, and the satisfaction of the touch can be improved. Further, the density of the flexible polyolefin resin (C) is preferably less than 0.855 g / cm ³ or more 0.910 g / cm ^3, less than 0.860 g / cm ³ or more 0.910 g / cm ³ Is more preferred.

  The soft polyolefin-based resin (C) preferably has a melt flow rate (MFR) of 0.1 to 20 g / 10 minutes, more preferably 0.5 to 10 g / 10 minutes. It is preferable to set the MFR to 0.1 g / 10 min or more because the moldability of the stretched porous film can be sufficiently maintained. In addition, it is preferable to set it to 20 g / 10 minutes or less because the strength of the stretched porous film can be sufficiently maintained.

  Further, tan δ (= E ″ / E ′), which is a ratio of the storage elastic modulus (E ′) and the loss elastic modulus (E ″), calculated from the dynamic viscoelasticity measurement of the soft polyolefin-based resin (C). The peak is preferably in the range of -50 to 50C. When the peak of tan δ of the soft polyolefin-based resin (C) is in the range of −50 to 50 ° C., it is preferable because it contributes to suppression of unpleasant sounds such as rough and rough sounds.

  Further, tan δ (= E ″ / E ′) which is a ratio of the storage elastic modulus (E ′) and the loss elastic modulus (E ″) calculated from the dynamic viscoelasticity measurement of the soft polyolefin resin (C). Is preferably 0.100 or more, more preferably 0.200 or more, and even more preferably 0.300 or more. When the peak value of tan δ of the soft polyolefin resin (C) is 0.100 or more, it is preferable because it contributes to suppression of unpleasant sounds such as rough and rough sounds.

<Polypropylene resin (D)>
Polypropylene resin (D) is preferably a density less than 0.890 g / cm ³ or more 0.910 g / cm ^3. Further, the melting point is preferably from 140 ° C to 170 ° C. Further, the MFR is preferably 10 to 50 g / 10 min. Here, the MFR of the polypropylene resin (D) is a value measured according to JIS K7210 condition M, and the measurement conditions are 230 ° C. and a load of 2.16 kg.

The thermoplastic resin is a polyolefin resin, and the polyolefin resin is a polyethylene resin (B) having a density of 0.910 g / cm ³ or more and 0.940 g / cm ³ or less, and a density of 0.850 g / cm ³ or more. When the resin has a soft polyolefin resin (C) and a polypropylene resin (D) of less than 0.910 g / cm ³ , respectively, the polyethylene resin (B), the soft polyolefin resin (C), and the polypropylene resin (D) ) Is (B) / (C) / (D) = 1 mass% to 25 mass% / 50 mass% to 98 mass% / 1 mass% to 25 mass% (however, (A) and (B) ) And (C) are preferably 100% by mass.), And (B) / (C) / (D) = 5% to 20% by mass / 60% to 90% by mass. / 5 mass% to 2 It is more preferably 0% by mass (provided that the total mass% of (A), (B) and (C) is 100% by mass).

In the mixing composition ratio of the polyethylene resin (B), the soft polyolefin resin (C), and the polypropylene resin (D), the mixing composition ratio of the polypropylene resin (D) is equal to or more than the lower limit in the preferable range described above. When it is, it becomes easy to express sufficient heat resistance to the stretched porous film.
In addition, when the mixing composition ratio of the polyethylene resin (B) is equal to or more than the lower limit in the above preferable range, molding of the resin composition becomes easy, and there is no problem in productivity.
Further, the mixture composition ratio of the polypropylene resin (D) is equal to or less than the upper limit in the above-described preferred range, and the mixture composition ratio of the polyethylene resin (B) is equal to or less than the upper limit in the above-described preferred range, and When the mixed composition ratio of the soft polyolefin-based resin (C) is equal to or more than the lower limit in the above-described preferred range, a good touch such as flexibility and texture is obtained, and uncomfortable sound generated when the film is rubbed is easily suppressed. .

2-3. Other Components Further, the stretched porous film of the present invention preferably contains 0.1% by mass to 8.0% by mass of the plasticizer (E) in the resin composition (Z). When the plasticizer (E) is contained in an amount of 0.1% by mass or more, the value of tan δ of the resin composition (Z) increases, and the peak width of tan δ of the resin composition (Z) is further increased. Can be. In addition, the crystal melting enthalpy (ΔHm) of the stretched porous film can be reduced. On the other hand, when the plasticizer (E) is 8.0% by mass or less, bleed-out of the plasticizer can be suppressed, blocking when the stretched porous film is wound into a roll, or poor printing at the time of printing. Can be suppressed.

Examples of the plasticizer (E) include the following ester plasticizers. Those having a polar structure, for example, a monovalent carboxylic acid ester-based plasticizer (butanoic acid, isobutanoic acid, hexanoic acid, 2-ethylhexanoic acid, heptanoic acid, octylic acid, 2-ethylhexanoic acid, lauric acid, etc. And a polyhydric alcohol such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, or glycerin, which is obtained by a condensation reaction. Ethylene glycol di 2-ethyl hexanoate, triethylene glycol diisobutanoate, triethylene glycol hexanoate, triethylene glycol di 2-ethyl butanoate, triethylene glycol dilaurate, ethylene glycol di 2-ethyl Xanoate, diethylene glycol di 2-ethyl hexanoate, tetraethylene glycol di 2-ethyl hexanoate, tetraethylene glycol diheptanoate, PEG # 400 di 2-ethyl hexanoate, triethylene glycol mono 2-ethyl hexano Ethyl, glycerin tri-2-ethylhexanoate, pentaerythritol tetrastearate, dipentaerythritol hexaoctanoate, diglycerin tetrastearate, diglycerin distearate, etc.), polycarboxylic acid ester plasticizer (adipin) Polycarboxylic acids such as acid, succinic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid and trimellitic acid, and methanol, ethanol, butanol, hexanol and 2-ethylbutanol And compounds obtained by a condensation reaction with a monohydric alcohol having 1 to 12 carbon atoms such as heptanol, octanol, 2-ethylhexanol, decanol, dodecanol, butoxyethanol, butoxyethoxyethanol, and benzyl alcohol. For example, dihexyl adipate, di-2-ethylhexyl adipate, diheptyl adipate, dioctyl adipate, di-2-ethylhexyl adipate, di (butoxyethyl) adipate, di (butoxyethoxyethyl) adipate, monoadipate (2-ethylhexyl), dibutyl phthalate, dihexyl phthalate, di (2-ethylbutyl) phthalate, dioctyl phthalate, di (2-ethylhexyl) phthalate, benzylbutyl phthalate, didodecyl phthalate, Trioctyl rimette), hydroxycarboxylic acid ester-based plasticizer (monohydric alcohol ester of hydroxycarboxylic acid; methyl ricinoleate, ethyl ricinoleate, butyl ricinoleate, methyl 6-hydroxyhexanoate, ethyl 6-hydroxyhexanoate, 6 -Butyl hydroxyhexanoate, polyhydric alcohol ester of hydroxycarboxylic acid; ethylene glycol di (6-hydroxyhexanoate) ester, diethylene glycol di (6-hydroxyhexanoate) ester, triethylene glycol di (6-hydroxyhexanoate) ester 3-methyl-1,5-pentanediol di (6-hydroxyhexanoate) ester, 3-methyl-1,5-pentanediol di (2-hydroxybutyrate) ester, 3-methyl-1,5-pentene Diol di (3-hydroxybutyrate) ester, 3-methyl-1,5-pentanediol di (4-hydroxybutyrate) ester, triethylene glycol di (2-hydroxybutyrate) ester, glycerin tri (ricinoleate) ester, L- Appropriate materials such as di (1- (2-ethylhexyl) tartrate), castor oil and the like, and polyester plasticizers can be used.
Castor oils include ordinary castor oil, refined castor oil, hardened castor oil, dehydrated castor oil, and the like. Examples of the hardened castor oil include hardened castor oil mainly containing triglyceride composed of 12-hydroxyoctadecanoic acid and glycerin.

  In addition to the above raw materials, depending on the intended use, other resin raw materials, recycled resin generated from trimming loss of ears, etc., compatibilizers, processing aids, melt viscosity improvers, antioxidants, antioxidants , Heat stabilizer, light stabilizer, weather resistance stabilizer, ultraviolet absorber, neutralizer, nucleating agent, cross-linking agent, lubricant, anti-blocking agent, slip agent, anti-fog agent, antibacterial agent, deodorant, difficult A flame retardant, an antistatic agent, a colorant, a pigment and the like may be appropriately added to the resin composition (Z) constituting the stretched porous film of the present invention.

3. Method for Producing Stretched Porous Film The method for producing the stretched porous film of the present invention is not particularly limited, and can be produced by a conventionally known method, but is preferably stretched in at least one direction.
Here, the “film” has a meaning encompassing from a thick sheet to a thin film. The film may be flat or tubular, but is preferably flat from the viewpoint of productivity (a number of products can be cut in the width direction of the raw sheet) and printing on the inner surface. . As a method for producing a flat film, for example, a film (unstretched) obtained by melting the resin composition using an extruder, extruding the resin composition from a die into a film, and cooling and solidifying with a cooling roll, air cooling, or water cooling. After stretching the film in at least one direction, the film may be wound by a winder to obtain a film.

  As a method for obtaining the unstretched film, it is preferable to mix and melt-knead the composition (Z) constituting the stretched porous film of the present invention. Specifically, after mixing with a mixer such as a tumbler mixer, a mixing roll, a Banbury mixer, a ribbon blender, and a super mixer for an appropriate time, an extruder such as a bidirectional twin screw extruder or a bidirectional twin screw extruder is used. Used to promote uniform distribution of the composition. The obtained resin composition can be formed into a film by connecting a die such as a T die or a round die to the tip of the extruder. Also, a strand die is connected to the tip of the kneading machine, and once pelletized by a method such as strand cutting or die cutting, the obtained pellets (along with an additional composition in some cases) are introduced into a single screw extruder or the like. Alternatively, a die such as a T-die or a round die may be connected to the end of the extruder to form a film. In forming into a film, a film forming method such as inflation molding, tubular molding, or T-die molding is preferable. The extrusion temperature is preferably about 180 to 260 ° C, more preferably 190 to 250 ° C. It is also effective to control the dispersion state of the material by optimizing the extrusion temperature and the state of shearing, so that the above-mentioned various physical and mechanical properties of the film are set to desired values.

  The stretched porous film of the present invention can be produced by stretching the unstretched film. For example, a resin is melted using an extruder, extruded from a T-die or a round die, cooled and solidified with a cooling roll, and roll-stretched in a longitudinal direction (film flow direction, MD) or a lateral direction (film flow direction). The film is stretched in at least a uniaxial direction by a tenter stretching in a direction perpendicular to the TD, for example. Moreover, after extending | stretching in a longitudinal direction, you may extend | stretch in a horizontal direction and may extend | stretch in a longitudinal direction after extending | stretching in a horizontal direction. Further, the film may be stretched two or more times in the same direction. Furthermore, after extending | stretching in a longitudinal direction, you may extend | stretch in a horizontal direction and may extend | stretch further in a longitudinal direction. Further, the film may be simultaneously stretched in the vertical and horizontal directions by a simultaneous biaxial stretching machine. Further, the tubular unstretched film may be radially stretched by an internal pressure by tubular molding. Furthermore, after stretching the tube-shaped unstretched film obtained by inflation molding in a folded state, the ears of the folded tube-shaped stretched porous film are cut out, divided into two pieces, and wound up. Alternatively, the ears of the folded unstretched film may be cut, divided into two unstretched films, and then stretched and wound.

  In the present invention, it is preferable to perform stretching at least once in the longitudinal direction, and it is also possible to perform stretching twice or more in the longitudinal direction in consideration of stretching unevenness and air permeability. The stretching temperature is preferably from 0 ° C to 90 ° C, more preferably from 20 ° C to 70 ° C. The stretching ratio is preferably 1.5 times to 6.0 times in total, more preferably 2.0 times to 5.0 times. When the stretching ratio is 1.5 times or more in total, a stretched porous film that is uniformly stretched and has an excellent appearance can be obtained. On the other hand, when the stretching ratio is 6.0 times or less in total, breakage of the film can be suppressed.

  If necessary, a heat treatment or a relaxation treatment at a temperature of 50 ° C. or more and 120 ° C. or less can be performed after stretching for the purpose of improving various physical properties. When performing stretching by roll stretching, heat treatment can be performed by bringing the stretched film into contact with a heated roll (annealing roll) between the stretching step and the winding step. In addition, the relaxation treatment can be performed by lowering the speed of the next contacting roll to be lower than the annealing roll speed while heating with the annealing roll. These heat treatments and relaxation treatments can also be performed in another step after stretching the unstretched film and winding the stretched porous film. If the temperature of the heat treatment or the relaxation treatment is too low, the shrinkage of the film is hardly reduced, and if the temperature is too high, there is a possibility that the film is wound around a roll or the formed micropores are closed. Therefore, it is preferable to perform heat treatment or relaxation treatment at a temperature of 50 ° C. or more and 120 ° C. or less. These heat treatments and relaxation treatments may be performed a plurality of times.

  In addition, the stretched porous film of the present invention can be subjected to surface treatment or surface processing such as slitting, corona treatment, printing, application of an adhesive, coating, vapor deposition, etc., as necessary.

4. Use The stretched porous film of the present invention is formed in a large number of fine pieces penetrating the front and back sides, and has excellent air permeability. Therefore, hygiene products such as disposable diapers and feminine sanitary products; clothing such as work clothes, jumpers, jackets, medical clothing, and chemical protective clothing; and breathability and moisture permeability such as masks, covers, drapes, sheets, and wraps. Can be suitably used for applications requiring.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In addition, the measurement value and evaluation shown in an Example were performed as follows. In the examples, the direction of film flow is described as a "longitudinal" direction (or MD), and the direction perpendicular thereto is described as a "lateral" direction (or TD).

(1) Measurement of Dynamic Viscoelasticity of Resin Composition (Z) Constituting Stretched Porous Film In Examples and Comparative Examples shown below, unstretched films of resin composition (Z) constituting a stretched porous film were used. , MD4mm, TD35mm, using a strip-shaped sample piece, the dynamic viscoelasticity was measured according to the above method, and the storage elastic modulus (E '), the loss elastic modulus (E''), and the storage elastic modulus Tan δ (= E ″ / E ′), which is the ratio between (E ′) and the loss modulus (E ″), was calculated. In Table 1, when tan δ is 0.100 or more at −20 ° C., the result is indicated by “○”, and when tan δ is less than 0.100 at −20 ° C., the result is indicated by “×”.
Further, Table 1 summarizes E ′ (unit: × 10 ⁸ Pa) at 20 ° C. and values of tan δ at −30 ° C., −20 ° C., −10 ° C., and 0 ° C.

(2) Basis Weight of Stretched Porous Film The basis weight of the stretched porous film was calculated according to the above method.

(3) Porosity of Stretched Porous Film The porosity of the stretched porous film was calculated according to the above method.

(4) Air permeability of the stretched porous film The air permeability of the stretched porous film was calculated according to the method described above. As an air permeability measuring device, an Oken type air permeability measuring device EGO1-55 manufactured by Asahi Seiko Co., Ltd. was used.

(5) Moisture Permeability of Stretched Porous Film According to the above method, the moisture permeability of the stretched porous film was calculated.

(6) Tensile Rupture Strength in the Stretching Direction of Stretched Porous Film According to the method described above, the tensile rupture strength in the stretching direction (MD in this example and comparative example) of the stretched porous film was calculated.

(7) Tensile breaking elongation in the stretching direction of the stretched porous film According to the method described above, the tensile breaking elongation in the stretching direction of the stretched porous film (MD in the present example and the comparative example) was calculated.

(8) Total light transmittance of the stretched porous film The total light transmittance of the stretched porous film was calculated according to the method described above.

(9) Crystal melting peak (Pm) and crystal melting enthalpy (ΔHm) of the stretched porous film
Using a differential scanning calorimeter (DSC), the stretched porous films obtained in the following Examples and Comparative Examples were heated from −40 ° C. to 200 ° C. at a heating rate of 10 ° C./min, and then held for 1 minute. Then, the temperature was lowered from 200 ° C. to −40 ° C. at a cooling rate of 10 ° C./min, held for 1 minute, and further raised from −40 ° C. to 200 ° C. at a heating rate of 10 ° C./min. The crystal melting enthalpy (ΔHm) of the stretched porous film was calculated from the peak area of the crystal melting peak (Pm) during the temperature rising process and the peak area of the crystal melting peak (Pm) during the reheating process.
At this time, the presence or absence of a crystal melting peak (Pm1) at 140 ° C to 200 ° C was confirmed. Further, the peak temperature (Tm1) and the enthalpy of crystal melting (ΔHm1) were calculated from (Pm1).
Similarly, the presence or absence of a crystal melting peak (Pm2) was confirmed at 30 ° C to 130 ° C. Further, the peak temperature (Tm2) and the enthalpy of crystal melting (ΔHm2) were calculated from the above (Pm2).

(10) Breaking heat resistance temperature of the stretched porous film According to the method described above, the breaking heat resistance temperature was evaluated. In the evaluation, the temperature in the convection oven tank was set to 120 ° C., 140 ° C., and 160 ° C., and the state after standing and heating in the tank for 2 minutes was visually evaluated according to the following criteria.
：: The sample at the circular punched portion of the stainless steel plate has no tear or hole.
×: The sample at the circular punched portion of the stainless steel plate was melted and a hole was opened.

(11) Flexibility of Stretched Porous Film The stretched porous films obtained in the following Examples and Comparative Examples are cut out in a longitudinal direction (MD) of 1000 mm and a transverse direction (TD) of 200 mm, touched by hand, and according to the following criteria. ,evaluated.
：: The film has a soft texture.
X: The film has hardness.

(12) Discomfort Sound Measurement of Stretched Porous Film The unpleasant sound measurement of the stretched porous film is performed in a measurement room of about 3m in width, about 4m in length, and about 3m in height (in an environment where the influence of external noise is small). Using an ordinary sound level meter NL-42 manufactured by Rion Co., Ltd., the frequency weighting characteristic was set to the A characteristic and the time weighting characteristic was set to the F characteristic.
First, the stretched porous films obtained in the following Examples and Comparative Examples were cut out in a machine direction (MD) of 400 mm and a machine direction (TD) of 200 mm, folded once in the center in the machine direction, and folded in two. Thereafter, both ends of the TD of the laminated stretched porous film were sandwiched, and the distance between both ends of the sandwiched TD was adjusted to be 100 mm.
Further, after adjusting the distance between the sandwiched stretched porous film and the microphone (sound collecting unit) of the ordinary sound level meter to be 100 mm, the MD and TD of the sandwiched stretched porous film are perpendicular to the thickness direction (thickness direction). ), The film was rubbed by vibrating the sandwiched end portion three times in 1 second, and the time average sound level (LAeq) was measured for 10 seconds in the measurement time, and evaluated according to the following criteria.
The time-average sound level (LAeq) for a measurement time of 10 seconds in a state where the film was not vibrated (no operation state) was 26 dB.
◎: Time average sound level (LAeq) is 26 dB or more and less than 35 dB ：: Time average sound level (LAeq) is 35 dB or more and less than 45 dB ×: Time average sound level (LAeq) is 45 dB or more

(13) Overall evaluation In view of the evaluations described in the above (1) to (12), an overall evaluation was performed based on the following criteria.
A: A film having excellent touch feeling such as flexibility and texture, and suppressing generation of unpleasant sound generated when the film is rubbed, suitable for applications requiring breathability and moisture permeability, and sufficient heat resistance. It is a film having both.
B: A film having excellent touch feeling such as flexibility and texture, and suppressing generation of unpleasant sound generated when the film is rubbed, and suitable for applications requiring air permeability and moisture permeability, but insufficient heat resistance. It is.
C: A film that is excellent in air permeability and moisture permeability, but does not have a tactile sensation such as flexibility or texture, and also has an unpleasant sound.
D: A film having insufficient physical properties required for a stretched porous film such as air permeability and moisture permeability.

The raw materials used in each of Examples and Comparative Examples are as follows.
<Inorganic filler (A)>
-Heavy calcium carbonate "Ryton BS-0" manufactured by Bihoku Powder Chemical Industry Co., Ltd. (average particle diameter 1.1 µm, surface-treated stearic acid). Hereinafter, it is abbreviated as “A-1”.
<Polyethylene resin (B)>
Japan Polyethylene Co., Ltd., linear low density polyethylene "Novatec LL UF230" (density 0.921g ^/ cm 3, MFR1.0g ^/ 10 min, melting point 121 ° C.). Hereinafter, it is abbreviated as “B-1”.
Japan Polyethylene Co., Ltd., branched low density polyethylene "NOVATEC LD LF441" (density 0.918g ^/ cm 3, MFR2.3g ^/ 10 min, melting point 113 ° C.). Hereinafter, it is abbreviated as “B-2”.
<Soft polyolefin resin (C)>
A metallocene-based ethylene / (α-olefin) copolymer “Kernel KF360T” (density 0.898 g / cm ³ , MFR 3.5 g / 10 min, melting point 90 ° C.) manufactured by Japan Polyethylene Corporation. Hereinafter, it is abbreviated as “C-1”.
Mitsui Chemicals Co., Ltd., ethylene (1-butene) copolymer "TAFMER A1050S" (density 0.862g ^/ cm 3, MFR1.2g ^/ 10 min, melting point 45 ° C.). Hereinafter, it is abbreviated as “C-2”.
Dow Chemical Co., an ethylene-octene block copolymer "Infuse D9107" (density 0.866g ^/ cm 3, MFR1g ^/ 10 min, melting point 119 ° C.). Hereinafter, it is abbreviated as “C-3”.
<Polypropylene resin (D)>
-Polypropylene "Novatech PP SA03" (manufactured by Nippon Polypropylene Co., Ltd.) (density 0.900 g / cm3, MFR ³⁰ g / 10 min, melting point 165 ° C). Hereinafter, it is abbreviated as “D-1”.
<Plasticizer (E)>
-Hardened castor oil "HCO-P3" manufactured by KY Trading Co., Ltd. Hereinafter, it is abbreviated as “E-1”.
<Antioxidant>
-An antioxidant "Irganox B225" manufactured by BASF Japan Ltd. Hereinafter, it is abbreviated as "F-1".
<Other resins>
-Α-olefin copolymer “Absortmer EP-1001” manufactured by Mitsui Chemicals, Inc. (density 0.84 g / cm ³ , MFR 10 g / 10 min (230 ° C. 2.16 kg load)). Hereinafter, it is abbreviated as “G-1”.

<Example 1>
After weighing each raw material at the composition ratio shown in Table 1, it was charged into a Henschel mixer, mixed and dispersed for 5 minutes, and then melt-kneaded at a set temperature of 200 ° C. using a bidirectional twin screw extruder. The resin composition was extruded with a T-die connected to the tip of the same-direction twin-screw extruder, taken up with a casting roll set at 50 ° C., and solidified by cooling to obtain an unstretched film having a thickness of 35 μm. The obtained unstretched film was subjected to dynamic viscoelasticity measurement.
Thereafter, the obtained unstretched film is subjected to (S)-(T) between the roll (S) set at 60 ° C, the roll (T) set at 60 ° C, and the roll (U) set at 60 ° C. ) The MD was stretched by a total of 4.0 times by multiplying the draw ratio by 100% (stretching ratio: 2.0 times) and the draw ratio (T)-(U) by 100% (stretching ratio: 2.0 times). Next, a stretched porous film was obtained by performing a heat treatment / relaxation treatment with a roll (V) set at 90 ° C. Various evaluations were performed on the obtained stretched porous film. The results are summarized in Table 1.

<Example 2>
An unstretched film having a thickness of 35 μm was collected in the same manner as in Example 1 except that the raw materials were changed to the composition ratios shown in Table 1. The obtained unstretched film was subjected to dynamic viscoelasticity measurement. Thereafter, the obtained unstretched film was stretched, heat-treated and relaxed in the same manner as in Example 1 to obtain a stretched porous film. Various evaluations were performed on the obtained stretched porous film. The results are summarized in Table 1.

<Example 3>
An unstretched film having a thickness of 35 μm was collected in the same manner as in Example 1 except that the raw materials were changed to the composition ratios shown in Table 1. The obtained unstretched film was subjected to dynamic viscoelasticity measurement. Thereafter, the obtained unstretched film was stretched, heat-treated and relaxed in the same manner as in Example 1 to obtain a stretched porous film. Various evaluations were performed on the obtained stretched porous film. The results are summarized in Table 1.

<Example 4>
An unstretched film having a thickness of 35 μm was collected in the same manner as in Example 1 except that the raw materials were changed to the composition ratios shown in Table 1. The obtained unstretched film was subjected to dynamic viscoelasticity measurement. Thereafter, the obtained unstretched film was stretched, heat-treated and relaxed in the same manner as in Example 1 to obtain a stretched porous film. Various evaluations were performed on the obtained stretched porous film. The results are summarized in Table 1.

<Example 5>
An unstretched film having a thickness of 35 μm was collected in the same manner as in Example 1 except that the raw materials were changed to the composition ratios shown in Table 1. The obtained unstretched film was subjected to dynamic viscoelasticity measurement. Thereafter, the obtained unstretched film was stretched, heat-treated and relaxed in the same manner as in Example 1 to obtain a stretched porous film. Various evaluations were performed on the obtained stretched porous film. The results are summarized in Table 1.

<Comparative Example 1>
An unstretched film having a thickness of 50 μm was collected in the same manner as in Example 1 except that the raw materials were changed to the composition ratios shown in Table 1. The obtained unstretched film was subjected to dynamic viscoelasticity measurement. Thereafter, the obtained unstretched film was stretched, heat-treated and relaxed in the same manner as in Example 1 to obtain a stretched porous film. Various evaluations were performed on the obtained stretched porous film. The results are summarized in Table 1.

<Comparative Example 2>
An unstretched film having a thickness of 50 μm was collected in the same manner as in Example 1 except that the raw materials were changed to the composition ratios shown in Table 1. The obtained unstretched film was subjected to dynamic viscoelasticity measurement. Thereafter, the obtained unstretched film was stretched, heat-treated and relaxed in the same manner as in Example 1 to obtain a stretched porous film. Various evaluations were performed on the obtained stretched porous film. The results are summarized in Table 1.

<Comparative Example 3>
An unstretched film having a thickness of 30 μm was collected in the same manner as in Example 1 except that the raw materials were changed to the composition ratios shown in Table 1. The obtained unstretched film was subjected to dynamic viscoelasticity measurement. Thereafter, the obtained unstretched film was stretched, heat-treated and relaxed in the same manner as in Example 1 to obtain a stretched porous film. Various evaluations were performed on the obtained stretched porous film. The results are summarized in Table 1.

<Comparative Example 4>
An unstretched film having a thickness of 35 μm was collected in the same manner as in Example 1 except that the raw materials were changed to the composition ratios shown in Table 1. The obtained unstretched film was subjected to dynamic viscoelasticity measurement. Thereafter, the obtained unstretched film was stretched, heat-treated and relaxed in the same manner as in Example 1 to obtain a stretched porous film. Various evaluations were performed on the obtained stretched porous film. The results are summarized in Table 1.

The stretched porous films obtained in Examples 1 to 5 were excellent in air permeability and moisture permeability, and had suitable tensile strength at break, tensile elongation at break, and total light transmittance. Further, the time-average sound level (LAeq) when the stretched porous films obtained in Examples 1 to 5 were rubbed with each other showed a low value, and no unpleasant sound was felt. Further, in the film rupture heat test, no film rupture was observed at 120 ° C., 140 ° C., and even at 160 ° C.
This result shows that the tan δ calculated from the dynamic viscoelasticity measurement of the resin composition (Z) constituting the stretched porous film of the present invention and the appearance temperature of the crystal melting peak satisfy the range specified by the present invention. It is thought to be. Specifically, the tan δ calculated from the dynamic viscoelasticity measurement of the resin composition (Z) constituting the stretched porous films of Examples 1 to 5 is 0.100 or more at −20 ° C. It is considered that the sound that propagates by vibrating the resin composition (Z) is attenuated and contributes to suppression of unpleasant noise. Further, since the stretched porous films obtained in Examples 1 to 5 had a crystal melting peak at 140 ° C to 200 ° C, it was shown to have high heat resistance.
On the other hand, since the films obtained in Comparative Examples 1 and 2 did not satisfy tan δ defined by the present invention, they were insufficient for suppressing unpleasant sound, and showed high values of the time-average sound level (LAeq). . In addition, the film obtained in Comparative Example 3 is a film in which the crystal melting peak is not in the temperature range defined by the present invention, and thus is a film in which the unpleasant sound is suppressed, but the heat resistance required for the stretched porous film is low. It turns out to be insufficient.
Further, in Comparative Example 4, although the film contains an α-olefin copolymer having a density of less than 0.850 g / cm ^{3, the} film does not satisfy tan δ defined in the present invention, and thus is insufficient for suppressing unpleasant noise. Met. That is, in order to achieve both the imparted heat resistance required for the stretched porous film and the suppression of unpleasant noise generated when the film is rubbed, the above-described tan δ, and both the temperature at which the crystal melting peak appears, the present invention It is understood that it is important to satisfy the specified range.

  Although the present invention has been described in connection with the most practical and preferred embodiments at this time, the invention is not limited to the embodiments disclosed herein. Without departing from the scope of the invention, which can be read from the claims and the entire specification, or the scope of the invention, it is possible to appropriately change the stretched porous film with such a change, which is also included in the technical scope of the present invention. Must be understood as

  The stretched porous film of the present invention has excellent touch feeling such as flexibility and texture, suppresses generation of unpleasant sound generated when the film is rubbed, and is excellent in breathability, moisture permeability and strength. Accordingly, sanitary articles such as disposable diapers and feminine sanitary articles provided with a stretched porous film; garments such as work clothes, jumpers, jackets, medical garments, and chemical protective suits; and further, masks, covers, drapes, sheets, and wraps It can be suitably used for applications requiring air permeability and moisture permeability.

Claims (12)

A stretched porous film comprising a resin composition (Z) containing 25% to 54% by mass of a thermoplastic resin and 46% to 75% by mass of an inorganic filler (A),
Tan δ (= E ″ / E ′), which is the ratio of the storage elastic modulus (E ′) and the loss elastic modulus (E ″) calculated from the dynamic viscoelasticity measurement of the resin composition (Z), is −20. A stretched porous film having a crystal melting peak (Pm1) of at least 0.100 at 140 ° C. and 140 ° C. to 200 ° C.   The stretched porous film according to claim 1, wherein the crystal melting enthalpy (ΔHm1) calculated from the crystal melting peak (Pm1) is 1 J / g to 10 J / g.   The crystal melting peak (Pm2) further at 30 ° C to 130 ° C, and the crystal melting enthalpy (ΔHm2) calculated from the crystal melting peak (Pm2) is 10 J / g to 45 J / g. The stretched porous film according to the above. The resin composition (Z) storage modulus calculated from the dynamic viscoelasticity measurement of (E '), according to claim 1 or less 8.0 × 10 8 ^Pa at 20 ° C. Stretched porous film.   The stretched porous film according to any one of claims 1 to 4, wherein the porosity is 15% to 80%.   The stretched porous film according to any one of claims 1 to 5, wherein the thermoplastic resin is a polyolefin-based resin. The stretched porous film according to claim 6, wherein the density of the polyolefin-based resin is 0.850 g / cm ³ or more and 0.940 g / cm ³ or less. As the polyolefin resin, density 0.910 g / cm ³ or more 0.940 g / cm ³ or less of the polyethylene resin (B) a density of 0.850 g / cm ³ or more 0.910 g / cm ³ less than the flexible polyolefin The stretched porous film according to claim 6, comprising a resin (C) and a polypropylene resin (D), respectively.   The mixing ratio of the polyethylene resin (B), the soft polyolefin resin (C), and the polypropylene resin (D) is (B) / (C) / (D) = 1 mass% to 25 mass% / 50. The stretched porous material according to claim 8, wherein the amount is from 100% by mass to 98% by mass / 1% by mass to 25% by mass (provided that the total mass% of (B), (C), and (D) is 100% by mass). the film.   The stretched porous film according to any one of claims 1 to 9, wherein the resin composition (Z) contains 0.1% to 8.0% by mass of a plasticizer (E).   A sanitary article comprising the stretched porous film according to claim 1.   Clothing provided with the stretched porous film according to any one of claims 1 to 10.