JP7167580B2 - Stretched porous film - Google Patents

Description

The present invention relates to a stretched porous film that has excellent tactile sensations such as flexibility and texture, suppresses the generation of unpleasant sounds that occur when the film is rubbed, and is also excellent in air permeability, moisture permeability, strength, and heat resistance. More specifically, sanitary products such as disposable diapers and sanitary products for women; clothes such as work clothes, jumpers, jackets, medical clothes, and chemical protective clothing; other breathable and moisture-permeable items such as masks, covers, drapes, sheets, and wraps. The present invention relates to a stretched porous film excellent in use feeling, which can be suitably used for applications requiring

Conventionally, by stretching a resin composition containing a thermoplastic resin such as a polyolefin resin and an inorganic filler, interfacial peeling occurs between the thermoplastic resin and the inorganic filler, resulting in a large number of voids (microporous). is known. In particular, the stretched porous film made of a resin composition containing a polyolefin resin and an inorganic filler has internal micropores that form continuous pores, so it has high air permeability and moisture permeability, but it is permeable to liquids. It is used as a moisture-permeable waterproof film that suppresses , especially sanitary materials such as disposable diapers and feminine hygiene products, work clothes, jumpers, jackets, medical clothes, chemical protective clothing, masks, covers, drapes, etc. It is widely used in sheets, wraps, and other applications that require breathability and moisture permeability.

Since the porous films used for these purposes are often used for applications that come into direct contact with the human skin, it is not acceptable for the film to have an unpleasant sound or feel, such as rough or rough, during activities while wearing the film. It becomes a factor that interferes with feeling. For this reason, the porous film is required to have good texture, flexibility, and feel, and to suppress unpleasant noise.

In order to solve these problems, for example, 50 to 300 parts by weight of an inorganic filler is included with respect to 100 parts by weight of the total amount of 65 to 90% by weight of an ethylene/α-olefin copolymer and 35 to 10% by weight of a thermoplastic elastomer. A porous film (Patent Document 1) or a resin composed of 20 to 100 parts by weight of 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 components is disclosed (Patent Document 2).

In addition, ventilation 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 the total amount of 30 to 70 parts by mass of polyethylene resin and 70 to 30 parts by mass of olefin elastomer 100 parts by mass of a resin component containing a flexible film (Patent Document 3), 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 Permeable film containing 100 to 200 parts by mass of inorganic filler and 1 to 20 parts by mass of plasticizer (Patent Document 4), moisture permeable film containing polyethylene resin composition, inorganic filler and styrene elastomer (Patent Document 5) Furthermore, a resin component containing 30 to 85 parts by mass of linear low-density polyethylene, 5 to 20 parts by mass of high-pressure polymerization low-density polyethylene, and 10 to 50 parts by mass of a metallocene-based ethylene/α-olefin copolymer , a moisture-permeable film containing 100 to 200 parts by mass of an inorganic filler and 1 to 20 parts by mass of a plasticizer with respect to 100 parts by mass of a resin component (Patent Document 6).

JP-A-7-228719 JP-A-2000-1557 JP 2017-31292 A JP 2015-229720 A International Publication No. 2014/088065 pamphlet International Publication No. 2015/186808 pamphlet

However, in Patent Documents 1 and 2, crystalline low-density polyethylene containing 12% by weight or more of an ethylene/α-olefin copolymer having a melting point of 60 to 100° C. or an α-olefin comonomer having 4 to 8 carbon atoms is disclosed. Since it is a film that is the main component, it is highly flexible, but it may melt under high-temperature conditions that occur in the process of bonding other members together, resulting in insufficient dimensional stability and heat resistance.
Specifically, sanitary materials such as disposable diapers are generally produced by laminating porous films and nonwoven fabrics by hot-melt lamination. Since it is heated, melted, and sprayed onto the porous film, if the heat resistance of the porous film is insufficient, the film will tear, resulting in a significant reduction in productivity. Therefore, it is very important that the porous film has sufficient heat resistance.

Further, in Patent Documents 3 to 6, an olefin elastomer, a propylene/ethylene copolymer elastomer, a styrene elastomer, a metallocene-based ethylene/α-olefin copolymer, etc. are added to a composition containing a polyethylene resin and an inorganic filler. By containing the soft resin, it is possible to obtain a film that has flexibility and stretchability and is excellent in texture and touch.
On the other hand, in the applications where these porous films are used, there is a demand for further improvements in the feeling of use. It is necessary to suppress the However, Patent Documents 3 to 6 do not mention technical design guidelines for suppressing unpleasant sounds.

The present invention has been made in view of the above problems, and has excellent tactile sensations such as flexibility and texture, suppresses the generation of unpleasant sounds that occur when the film is rubbed, and has breathability, moisture permeability, strength, and heat resistance. To provide a stretched porous film having excellent properties.

As a result of intensive studies, the present inventors succeeded in obtaining a stretched porous film capable of solving the above-described problems of the prior art, and 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 made of 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),
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) is tan δ (=E″/E′) of −20. °C is 0.100 or more and is resolved by a stretched porous film having a crystalline melting peak (Pm1) between 140°C and 200°C.

According to the present invention, a stretched porous film that has excellent tactile sensations such as flexibility and texture, suppresses the generation of unpleasant sounds that occur when the film is rubbed, and is also excellent in air permeability, moisture permeability, strength, and heat resistance. can be obtained, it can be suitably used for applications that require air permeability and moisture permeability.

Hereinafter, the stretched porous film of the present invention will be described as one example of embodiments of the present invention. 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 uniaxially.

In this specification, the "main component" refers to a component that accounts for the largest mass ratio in the constituent composition, preferably 45% by mass or more, more preferably 50% by mass or more, and 55% by mass. The above is more preferable. In addition, when described as "X to Y" (X and Y are arbitrary numbers), unless otherwise specified, "X or more and Y or less", "preferably larger than X" and "preferably smaller than Y" ” is included.

1. Stretched porous film The stretched porous film of the present invention is a stretched porous film made of 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). and tan δ (=E''/E'), which is the ratio of the storage modulus (E') to the loss modulus (E'') calculated from the dynamic viscoelasticity measurement of the resin composition (Z) is 0.100 or more at -20°C, and the stretched porous film has a crystal melting peak (Pm1) between 140°C and 200°C.

The stretched porous film of the present invention is 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. 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 0.130 or more is more preferable. The upper limit of tan δ of the resin composition (Z) constituting the stretched porous film is not particularly limited, but from the viewpoint of dimensional stability, it is preferably 1.000 or less at -20°C. When tan δ (=E″/E′) is 0.100 or more at −20° C., as will be described later, a sound absorption coefficient (vibration damping rate) for suppressing unpleasant sounds generated when the film is rubbed can be improved, and the film is excellent in tactile sensation such as flexibility and texture.

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 at -30°C to 0°C. 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. It is most preferably 0.100 or more in °C. By widening the temperature range in which 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, as described later, various frequencies Unpleasant sound can be suppressed.

Furthermore, the porosity of the stretched porous film of the present invention is preferably 15% to 80%. The porosity is more preferably 20% to 80%, even more preferably 25% to 80%.
When the porosity is 15% or more, as will be described later, the chance of energy loss of sound propagating through the pores of the stretched porous film increases, and unpleasant sound can be sufficiently suppressed. Further, when the porosity is 80% or less, it is possible to ensure the film strength to the extent that it can be used practically, and furthermore, the waterproof property is sufficient, and the liquid substance that comes into contact with the film hardly leaks.

Sound is vibration waves in the air that occur when objects move or rub against each other. When sound collides with an object as incident sound, the incident sound is divided into three types of sound: transmitted sound transmitted through the object, reflected sound reflected by the object, and absorbed sound absorbed by the object, according to the law of conservation of energy. decomposed. That is, when incident sound collides with an object, if the ratio of absorbed sound absorbed by the object is large, the object is considered to have a high sound absorption coefficient.
The stretched porous film of the present invention is a film having voids 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 portion of the film, and the sound propagates through the interconnected voids formed inside the film. It shows two ways of transmitting sound. Therefore, for the suppression of sound, it is necessary to consider the suppression of sound propagating by vibrating the resin composition (Z) and the suppression of sound propagating through the interconnected voids.

In the stretched porous film of the present invention, damping of the vibration source or medium of the sound is considered effective for suppressing the sound that propagates by vibrating the resin composition (Z). In a viscoelastic body such as resin, a sound absorbing effect can be obtained by losing vibrational energy to thermal energy. Therefore, tan δ, which is the ratio of the storage elastic modulus (E′) to the loss elastic modulus (E″), is considered to be a factor necessary for exhibiting this sound absorbing effect. Therefore, in the present invention, the peak value of tan δ of the resin composition (Z) constituting the stretched porous film is preferably as large as possible.
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 temperature of the atmosphere where the sound is generated, and from the viewpoint of the temperature-time conversion rule, the attenuation with respect to frequency. Related. Therefore, in order to absorb or not generate unpleasant sounds having various frequencies, it is preferable that the peak width of tan δ is wide.
Therefore, tan δ ( =E''/E') being 0.100 or more at -20°C is important for suppressing the generation of unpleasant noise that occurs when the film is rubbed. As described above, it is preferable to widen the temperature range in which tan δ is 0.100 or more because it is possible to suppress unpleasant sounds of various frequencies.

In addition, it is considered that the porosity of the porous film also contributes to the suppression of propagating sound. As the porosity increases, the number of collisions between sound propagating in the air and objects increases. there is
Therefore, it is preferable that the stretched porous film has a porosity of 15% or more in order to increase the chances of energy loss of sound propagating through the pores of the film.

It is important that the stretched porous film of the present invention has a crystalline melting peak (Pm1) at 140°C to 200°C. The crystal melting peak (Pm1) is preferably at 150°C to 190°C, more preferably at 160°C to 180°C. Having a crystalline melting peak (Pm1) at 140° C. or higher is important because sufficient heat resistance can be imparted when the stretched porous film is adhered or laminated to another member. In addition, by having a crystal melting peak (Pm1) at 200 ° C. or less, it is not necessary to raise the extrusion temperature extremely in forming a stretched porous film, so resin degradation products are less likely to occur, and productivity is improved. Therefore, it is preferable.
In order to have the crystalline 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. It can be adjusted to have a melting peak (Pm1).

Further, the stretched porous film of the present invention preferably has a crystal melting enthalpy (ΔHm1) calculated from the crystal melting peak (Pm1) of 1 J/g to 10 J/g. The crystal melting enthalpy (ΔHm1) is more preferably 1 J/g to 8 J/g, even more preferably 2 J/g to 6 J/g. The crystal melting enthalpy (ΔHm1) of 1 J/g or more is preferable because it has sufficient crystal components for imparting heat resistance to the stretched porous film. Further, when the crystal melting enthalpy (ΔHm1) is 10 J/g or less, it is possible to suppress the generation of an unpleasant sound, which will be described later.
The crystalline melting enthalpy (ΔHm1) is adjusted to the above range 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. can be done.

The stretched porous film of the present invention preferably further has a crystalline melting peak (Pm2) at 30°C to 130°C. Further, the crystal melting enthalpy (ΔHm2) calculated from the crystal melting peak (Pm2) is preferably 10 J/g to 45 J/g. The crystal melting enthalpy (ΔHm2) is more preferably 12 J/g to 43 J/g, even more preferably 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 ensured. Further, by setting the crystal melting enthalpy (ΔHm2) to 45 J/g or less, it is possible to suppress the generation of an unpleasant sound, which will be described later.
In order to have the crystalline melting peak (Pm2), the resin composition (Z) constituting the stretched porous film of the present invention should contain a thermoplastic resin having a melting point of 30° C. to 130° C., and the mixing ratio should be adjusted. The crystal melting peak (Pm2) and the crystal melting enthalpy (ΔHm2) can be adjusted within the above ranges.

In addition to suppressing the above-described transmitted sound, it is considered effective to suppress the generation of sound from the sound source as a method of suppressing the unpleasant sound generated when the stretched porous films are rubbed together. The generation of sound is the vibration of an elastic body, and no sound is generated unless there is something that causes 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 proportion of the elastic property of the thermoplastic resin, when an external force is applied to rub the films together, the elastic component that repels the external force and vibrates is reduced, thereby suppressing the generation of sound. The above-mentioned tan δ is an index that indicates the ratio of elastic properties to viscous properties, and we believe that reducing the ratio of elastic properties from a macroscopic and microscopic point of view is effective in reducing unpleasant noise. The macroscopic elastic property is 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 described above, and the microscopic elasticity. The physical property is the crystalline component of the resin, which will be described later.

First, from the viewpoint of reducing the elastic properties from a macroscopic point of view, 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, 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 has excellent tactile sensation such as texture and flexibility, and suppresses the generation of unpleasant noise. It is preferable because Although the lower limit is not particularly limited, it 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 measurement frequency of 10 Hz and a measurement strain of 0.1%. , the distance between chucks is 25 mm, and the temperature is raised from the measurement temperature of -100°C at a rate of temperature rise of 3°C/min. At this time, from the temperature dependence profile of the dynamic viscoelasticity obtained, the storage elastic modulus (E') at each temperature, the loss elastic modulus (E''), and the storage elastic modulus (E') and the loss elastic modulus ( E'') ratio tan δ (=E''/E') is calculated.
In the dynamic viscoelasticity measurement, the thickness of the sample piece is measured in advance, and the values of the thickness and width of the sample piece are input into the measuring device, the cross-sectional area of the sample piece is calculated, and each value is Calculated.
Since the stretched porous film of the present invention has pores 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'' ), and tan δ are prone to errors. Therefore, in order to obtain the storage elastic modulus (E′), loss elastic modulus (E″), and tan δ specified in the present invention, an unstretched film of the resin composition (Z) constituting the stretched porous film is It is preferable to perform dynamic viscoelasticity measurement on a strip-shaped sample piece cut out to MD 4 mm and TD 35 mm using the above. However, after heating the stretched porous film to the melting point or higher to melt the film and eliminate the pores, a press sample is produced, and a strip-shaped sample piece is cut out from the press sample and subjected to dynamic viscoelasticity measurement. Also, the storage elastic modulus (E′), loss elastic modulus (E″) and tan δ specified in the present invention can be calculated. Any measuring method can be employed in the present invention.

Next, let us consider the crystalline component of the resin as an elastic property from a microscopic point of view. Thermoplastic resins are classified into amorphous resins and crystalline resins in terms of crystallinity. Amorphous resins are thermoplastic resins that have relatively bulky molecular chains and therefore cannot be regularly folded and do not have crystalline portions. On the other hand, a crystalline resin is a thermoplastic resin in which the molecular chains are regularly folded and which has a high-density crystalline portion inside. However, even if it is a crystalline resin, there is no such thing as a crystalline resin in which the molecular chains are 100% crystallized. 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 crystalline part of the crystalline resin, the molecular chains are constrained as crystals in the temperature range between the glass transition temperature and the melting point, and the elastic modulus is very high. Therefore, when the degree of crystallinity of the crystalline resin is low, the number of crystal parts with a high elastic modulus is reduced, so it is thought that there are few components that repel and vibrate when an external force is applied, and the generated sound is also reduced.
Therefore, the crystalline melting enthalpy is an index of the crystalline component ratio in the stretched porous film of the present invention, and the crystalline melting enthalpy (ΔHm1) is preferably 1 J/g to 10 J/g. Further, the crystal melting enthalpy (ΔHm2) is preferably 10 J/g to 45 J/g.

The crystalline melting peak (Pm) of the stretched porous film of the present invention and its peak temperature (Tm) were measured by a differential scanning calorimeter (DSC), and the stretched porous film of the present invention was heated from −40° C. to a high temperature holding temperature. After the temperature was raised at a rate of 10°C/min, the temperature was maintained for 1 minute, then the temperature was lowered from the high temperature holding temperature to -40°C at a cooling rate of 10°C/min, the temperature was maintained for 1 minute, and further from -40°C to the high temperature holding temperature. The crystal melting peak (Pm) that appears when the temperature is reheated at a heating rate of 10° C./min, and the temperature (Tm) at which the 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 reheated. At this time, the high-temperature holding temperature can be arbitrarily selected within the range of Tm+20° C. or higher and Tm+150° C. or lower with respect to the highest crystalline melting peak temperature (Tm) of the thermoplastic resin to be used.
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 such as that seen in semi-crystalline resins occurs in the reheating process. ΔHm is applied. That is, the enthalpy of crystallization (ΔHc) calculated from the exothermic peak area in cold crystallization occurring in the reheating process is not subtracted from ΔHm obtained in the reheating process.

Furthermore, when the stretched porous film of the present invention is laminated with other layers, if the DSC measurement is performed on the laminate as it is, 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 the ΔHm of this 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 entire laminate is calculated. ΔHm at can be calculated. Although the calculation of the lamination ratio is not particularly limited, it is preferably calculated by cross-sectional observation with 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 entire laminate/lamination ratio (%) of the porous layer in the entire laminate/100 (%)

In addition, it is important that the stretched porous film of the present invention has a crystal melting peak (Pm1) at 140°C to 200°C. , may be two or more. Further, 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 crystal melting enthalpies calculated from two or more crystal melting peaks.

Also, with respect to the crystalline melting peak (Pm2), it is preferable to have at least one crystalline melting peak at 30° C. to 130° C., but it may be two or more. Further, 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 crystal melting enthalpies calculated from 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 resin, the crystalline melting start temperature is at least 30°C lower than the crystalline melting peak temperature (Tm). They melt one by one and often show broad peaks. Therefore, by raising the temperature from −40° C. in differential scanning calorimetry (DSC), the baseline can be clarified and the crystal melting enthalpy (ΔHm) can be calculated more accurately.

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

For the porosity of the stretched porous film of the present invention, the stretched porous film is cut into a size of 50 mm in the machine direction (MD) and 50 mm in the transverse direction (TD), and the specific gravity (W1) of the stretched porous film is measured. . 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 machine direction (MD) and 50 mm in the transverse direction (TD), Specific gravity measurements can be made. In addition, when it is difficult to collect an unstretched sheet, the stretched porous film of the present invention is heated to the melting point or higher to melt the stretched porous film and eliminate the pores, and then a press sample is prepared. , longitudinal direction (MD): 50 mm, transverse 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 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 formula.
Porosity (%) = [1-(W1/W0)] x 100

The basis weight of the stretched porous film of the present invention is preferably 10 g/m ² to 50 g/m ² , more preferably 12 g/m ² to 40 g/m ² . When the basis weight is 10 g/m ² or more, it is easy to sufficiently ensure mechanical strength such as tensile strength and tear strength. Further, when the basis weight is 50 g/m ² or less, it is easy to obtain a sufficiently light feeling.
Here, the basis weight is obtained by measuring the mass (g) of a sample (vertical direction (MD): 250 mm, transverse direction (TD): 200 mm) with an electronic balance and multiplying the value by 20.

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 100 seconds/100 mL to 3000 seconds/100 mL. More preferably 100 mL. When the air permeability is 1 sec/100 mL or more, it is easy to sufficiently secure water resistance and liquid permeation resistance. It also suggests that the air permeability is 5000 seconds/100 mL or less, which means that the material has sufficient communication holes.
Here, the air permeability is the number of seconds for 100 mL of air measured according to the method specified in JISP8117: 2009 (Gurley test method) to pass through a piece of paper. It can be measured using Oken type air permeability measuring machine EGO1-55 type). In the present invention, 10 samples are randomly measured, and the arithmetic average value is taken as the air permeability.

The moisture permeability of the stretched porous film of the present invention is preferably 1000 g/(m ² ·24 h) to 15000 g/(m ² ·24 h), more preferably 1500 g/(m ² ·24 h) to 12000 g/(m ² ·24 h). ). A moisture permeability of 15000 g/(m ² ·24 h) or less suggests that the material has water resistance. In addition, it is suggested that the water vapor permeability of 1000 g/(m ² ·24 h) or more indicates that the pores have sufficient communication properties.
Here, the moisture permeability complies with the conditions of JISZ0208 (Method for testing moisture permeability of 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 with a temperature of 40° C. and a relative humidity of 90%. Samples were randomly measured at two points, and the arithmetic mean value was obtained.

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, more preferably 10 N/25 mm or more. When the tensile strength at break is 7 N/25 mm or more, practically sufficient mechanical strength and flexibility can be ensured. Although the upper limit is not particularly limited, it is preferably 35 N/25 mm or less in view of stretchability. Here, the tensile breaking strength in the stretching direction is measured in accordance with JISK7127 by preparing a sample cut into 100 mm in the stretching direction × 25 mm in the direction perpendicular to the stretching direction, and under an environment of 23 ° C. and a relative humidity of 50%, at a tensile speed of 200 m / It is the tensile breaking strength when broken using a triple tensile tester under the conditions of min and a distance between chucks of 50 mm. In the present invention, the arithmetic mean value 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 40% to 400%, more preferably 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 sanitary products such as disposable diapers and moisture-permeable waterproof backsheets such as sanitary treatment products, it feels good on the skin and is excellent in comfort. is obtained. In addition, when the tensile elongation at break is 400% or less, it has moderate rigidity and tensile strength, excellent mechanical properties, small elongation and distortion of the film during printing, slitting, and winding processing, and excellent mechanical suitability in the production line. is obtained.
Here, the tensile elongation at break in the stretching direction is measured by preparing a sample cut into 100 mm in the stretching direction × 25 mm in the direction perpendicular to the stretching direction in accordance with JISK7127, and pulling it at a tensile speed of 200 m under an environment of 23 ° C. and a relative humidity of 50%. /min and the distance between chucks of 50 mm. In the present invention, the arithmetic mean value of the tensile elongation at break calculated by measuring three times is used.

The stretched porous film of the present invention preferably has a total light transmittance of 18% to 60%. Since the total light transmittance is 18% or more, when the stretched porous film of the present invention is used for sanitary products such as moisture-permeable waterproof backsheets such as disposable diapers, even if an indicator agent for urinating is applied, it can be recognized. can. In addition, since the total light transmittance is 60% or less, the film is white and has excellent opacity.
Here, the total light transmittance is obtained by randomly measuring 5 points using a haze meter conforming to JISK7361 and calculating the 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 even more preferably 160° C. or higher. When the film breakage heat resistance temperature is 120° C. or higher, when the stretched porous film of the present invention is adhered or laminated to other members, the film does not break due to the heat of a hot melt adhesive or the like. It can be judged that heat resistance is imparted.
Here, the film rupture heat resistance temperature was measured by sandwiching the sample (100 mm × 100 mm) between two stainless steel plates (100 mm × 100 mm × 2 mm (thickness)) punched out in a circular shape of Φ 50 mm at the center and fixing the four sides with clips. , After heating for 2 minutes in a convection oven with an internal temperature of 120 ° C, the sample at the circular punched part of the stainless steel plate melted and visually judged whether there was a hole or not. The membrane rupture heat resistance temperature of 120° C. or higher is defined as those with no opening. In addition, when the temperature inside the tank is changed to 140° C. and 160° C., and the same evaluation is performed, those with no tear or hole are defined as 140° C. or higher and 160° C. or higher, respectively.

The resin composition (Z) constituting the stretched porous film of the present invention will be described below, and then the 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% to 54% by mass of a thermoplastic resin and 46% 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 preferably used because of their advantages such as expression, high versatility, low price, and abundant brands.

The inorganic filler (A) preferably has an average particle size of 0.1 to 10 μm, more preferably 0.3 to 5 μm, still more preferably 0.5 to 3 μm. If the average particle size is 0.1 μm or more, poor dispersion and secondary aggregation of the inorganic filler (A) are suppressed, and the inorganic filler can be uniformly dispersed in the resin composition (Z), which is preferable. On the other hand, if the average particle size is 10 μm or less, the generation of large voids can be suppressed when the film is thinned, and sufficient strength and water resistance of the film can be ensured. In addition, for the purpose of improving the dispersibility and mixability with the resin, it is preferable to coat the inorganic filler with fatty acid, fatty acid ester, etc. in advance to make the surface of the inorganic filler more compatible with the resin. A surface-treated inorganic filler can also be used as the inorganic filler (A).

2-2. Thermoplastic resin Examples of thermoplastic resins include polyolefin resins, polystyrene resins, acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, chlorinated polyethylene resins, polyester resins, polycarbonate resins, and polyamide resins. Resins, ethylene/vinyl alcohol copolymers, ethylene/vinyl acetate copolymers, polymethylpentene resins, polyvinyl alcohol resins, cyclic olefin resins, polylactic acid resins, polybutylene succinate resins, polyacrylonitrile resin, polyethylene oxide resin, cellulose resin, polyimide resin, polyurethane resin, polyphenylene sulfide resin, polyphenylene ether resin, polyvinyl acetal resin, polybutadiene resin, polybutene resin, polyamideimide resin, polyamide bis Maleimide resins, polyarylate resins, polyetherimide resins, polyetheretherketone resins, polyetherketone resins, polyethersulfone resins, polyketone resins, polysulfone resins, aramid resins, fluorine resins, A polyacetal-based resin and the like are included. Among them, from the viewpoint of heat resistance, the thermoplastic resins include polyolefin-based resins, ethylene-vinyl alcohol-based resins, polymethylpentene-based resins, polylactic acid-based resins, polyketone-based resins, fluorine-based resins, polyacetal-based resins, and the like. From the viewpoints of flexibility, heat resistance, formation of communicating pores, environmental sanitation, odor, etc., the thermoplastic resin is particularly preferably a polyolefin resin.
The thermoplastic resin may be of one type or two or more types. When the thermoplastic resin is composed of two or more types, the total is the mass of the thermoplastic resin, and the mass ratio of the thermoplastic resin in the resin composition (Z) is calculated.

A polyolefin resin is a resin containing an olefin monomer as a main monomer component. The main monomer component means a monomer component that accounts for 50 mol % or more and 100 mol % or less in the resin. Examples of olefin monomers include ethylene, propylene, α-olefins such as 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene, dienes, isoprene, butylene, and butadiene. may be a homopolymer, or a multi-component copolymer obtained by copolymerizing two or more kinds. It may also be a copolymer of vinyl acetate, (meth)acrylic acid, (meth)acrylic acid ester, glycidyl (meth)acrylate, vinyl alcohol, ethylene glycol, maleic anhydride, styrene, diene, and cyclic olefin. Among them, ethylene homopolymer, branched low density polyethylene, propylene homopolymer, ethylene (α-olefin copolymer), propylene (α-olefin copolymer), Ethylene/vinyl acetate copolymers, styrene/ethylene/propylene copolymers, and styrene/ethylene/butylene copolymers are preferred.

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

Further, when the thermoplastic resin is a polyolefin resin, the polyolefin resin preferably has a density of 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 of soft polyolefin-based resin (C) and polypropylene-based resin (D).

<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 means a monomer component that accounts for 50 mol % or more and 100 mol % or less in the resin. Therefore, the polyethylene-based resin (B) may be an ethylene homopolymer or a copolymer containing ethylene as a main monomer component and other monomers. Examples of copolymers 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) copolymers, ethylene/vinyl acetate copolymers, ethylene/(meth)acrylic acid copolymers, ethylene/ (Meth)acrylic acid ester copolymer, ethylene/glycidyl (meth)acrylate, ethylene/vinyl alcohol copolymer, ethylene/ethylene glycol copolymer, ethylene/maleic anhydride copolymer, ethylene/styrene copolymer , ethylene/diene copolymers, and ethylene/cyclic olefin copolymers. It may be a multi-element copolymer containing two or more of the above monomer components, such as an ethylene/propylene/(1-butene) copolymer.
Among these, ethylene homopolymers and ethylene/(α-olefin) copolymers are preferred from the viewpoint of dimensional stability.

The polyethylene-based resin (B) may be of one type as long as it has a density of 0.910 g/cm ³ or more and 0.940 g/cm ³ or less and 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 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 improved air permeability, moisture permeability, dimensional stability, liquid leakage resistance, concealment, It becomes possible to satisfy appearance and the like. The density of the polyethylene resin (B) is more preferably 0.910 g/cm ³ or more and 0.937 g/cm ³ or less, and particularly 0.910 g/cm ³ or more and 0.935 g/cm ³ or less. preferable. Here, the density is the density measured by the pycnometer method (JIS K7112 B method). In addition, the density of the resin described later is also the value when measured in the same manner.

The polyethylene-based 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, such as a multisite catalyst represented by a Ziegler-Natta type catalyst, or a metallocene catalyst A polymerization method using a single-site catalyst represented by

At least one of the polyethylene-based resins (B) is preferably branched low-density polyethylene. When at least one of the polyethylene-based resins (B) is a branched low-density polyethylene, the melt tension of the resin composition (Z) is increased, and moldability is improved, which is preferable. In addition, the branched low-density polyethylene has a value of 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. However, since it shows a large value at 0 to 30° C., it is preferable that at least one of the polyethylene-based resins (B) is branched low-density polyethylene.

The polyethylene resin (B) preferably has a melting point of 110 to 135°C, more preferably 110 to 130°C. If the melting point of the polyethylene-based resin (B) is 110 to 135° C., the dimensional stability of the stretched porous film can be improved, which is preferable.
Here, using a differential scanning calorimeter (DSC), about 10 mg of the resin was heated to -40°C to 200°C at a heating rate of 10°C/min, held at 200°C for 1 minute, and then cooled at a rate of 10°C. It is the crystalline melting peak temperature (Tm) (°C) obtained from the thermogram measured when the temperature was lowered to −40° C. at a heating rate of 10° C./min and then raised to 200° C. at a heating rate of 10° C./min. Also, the melting point of the resin described later is a value when 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. An MFR of 0.1 g/10 minutes or more is preferable 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, MFR is a value measured according to JIS K7219, and the measurement conditions are 190° C. and 2.16 kg load.

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

The flexible polyolefin-based resin (C) may be of one type as long as it 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. , may be two or more. When the soft polyolefin resin (C) is composed of two or more types, the total is the mass of the soft polyolefin resin (C). By including the soft polyolefin 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 tactile sensation can be improved. Further, the density of the soft polyolefin resin (C) is preferably 0.855 g/cm ³ or more and less than 0.910 g/cm ³ , and is 0.860 g/cm ³ or more and less than 0.910 g/cm ³ is more preferred.

The soft polyolefin 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. An MFR of 0.1 g/10 minutes or more is preferable 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.

In addition, 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 soft polyolefin resin (C), The peak is preferably in the range of -50 to 50°C. When the soft polyolefin resin (C) has a tan δ peak in the range of −50 to 50° C., it is preferable because it contributes to suppressing unpleasant sounds such as rustling and burping.

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

<Polypropylene resin (D)>
The polypropylene resin (D) preferably has a density of 0.890 g/cm ³ or more and less than 0.910 g/cm ³ . Also, the melting point is preferably 140°C to 170°C. Also, MFR is preferably 10 to 50 g/10 min. Here, the MFR of the polypropylene resin (D) is a value measured according to JISK7210 condition M, and the measurement conditions are 230° C. and 2.16 kg load.

The thermoplastic resin is a polyolefin resin, 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 soft polyolefin-based resin (C) and the polypropylene-based resin (D) each have an amount of less than 0.910 g/cm ³ , the polyethylene-based resin (B), the soft polyolefin-based resin (C), the polypropylene-based resin (D ) is (B) / (C) / (D) = 1% by mass to 25% by mass / 50% by mass to 98% by mass / 1% by mass to 25% by mass (however, (A) and (B The total mass% of ) and (C) is 100 mass%. /5% by mass to 20% by mass (where the total mass% of (A), (B) and (C) is 100% by mass) is more preferable.

In the mixed composition ratio of the polyethylene-based resin (B), the soft polyolefin-based resin (C), and the polypropylene-based resin (D), the mixed composition ratio of the polypropylene-based resin (D) is at least the lower limit of the preferred range described above. When it is, it becomes easy to develop sufficient heat resistance in a stretched porous film.
Moreover, when the mixing composition ratio of the polyethylene-based resin (B) is equal to or higher than the lower limit of the preferred range described above, molding of the resin composition becomes easy, and there is no problem with productivity.
Furthermore, the mixed composition ratio of the polypropylene resin (D) is equal to or less than the upper limit in the preferred range described above, and the mixed composition ratio of the polyethylene resin (B) is equal to or less than the upper limit in the preferred range described above, and When the mixed composition ratio of the soft polyolefin-based resin (C) is equal to or higher than the lower limit of the preferred range described above, a pleasant touch feeling such as flexibility and texture can be obtained, and unpleasant noise generated when the film rubs can be 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 a plasticizer (E) in the resin composition (Z). When the plasticizer (E) is contained in an amount of 0.1% by mass or more, the tan δ value of the resin composition (Z) increases, and the tan δ peak width of the resin composition (Z) widens. can be done. In addition, the crystalline melting enthalpy (ΔHm) of the stretched porous film can be reduced. On the other hand, if the plasticizer (E) is 8.0% by mass or less, bleeding out of the plasticizer can be suppressed, blocking when the stretched porous film is wound into a roll, and printing defects during printing. can be suppressed.

Examples of the plasticizer (E) include the following ester plasticizers. Those having a polar structure, such as monovalent carboxylic acid ester plasticizers (butanoic acid, isobutanoic acid, hexanoic acid, 2-ethylhexanoic acid, heptanoic acid, octylic acid, 2-ethylhexanoic acid, lauric acid, etc.) with polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, and glycerin. Ethylene glycol di-2-ethylhexanoate, triethylene glycol diisobutanoate, triethylene glycol-hexanoate, triethylene glycol di-2-ethylbutanoate, triethylene glycol dilaurate, ethylene glycol di-2-ethylhexanoate, diethylene glycol Di-2-ethylhexanoate, tetraethylene glycol di-2-ethylhexanoate, tetraethylene glycol diheptanoate, PEG#400 di-2-ethylhexanoate, triethylene glycol mono-2-ethylhexanoate, glycerin tri-2-ethylhexanoate, pentaerythritol tetrastearate, dipentaerythritol hexaoctanoate, diglycerin tetrastearate, diglycerin distearate, etc.), polyvalent carboxylic acid ester plasticizers (adipic acid, succinate acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid and other polyvalent carboxylic acids, and methanol, ethanol, butanol, hexanol, 2-ethylbutanol, heptanol, octanol, 2-ethylhexanol, Examples include compounds obtained by condensation reaction with monohydric alcohols having 1 to 12 carbon atoms such as decanol, dodecanol, butoxyethanol, butoxyethoxyethanol, benzyl alcohol, etc. Specific examples of compounds include dihexyl adipate and adipic acid. di-2-ethylhexyl, diheptyl adipate, dioctyl adipate, di-2-ethylhexyl adipate, di(butoxyethyl) adipate, di(butoxyethoxyethyl) adipate, mono(2-ethylhexyl) adipate, dibutyl phthalate, Dihexyl phthalate, di(2-ethylbutyl) phthalate, dioctyl phthalate, di(2-ethylhexyl) phthalate, benzyl butyl phthalate, didodecyl phthalate, trioctyl limetate, etc.), hydroxycarboxylic acid ester plasticizers (monohydric alcohol esters of hydroxycarboxylic acids; methyl ricinoleate, ethyl ricinoleate, butyl ricinoleate, methyl 6-hydroxyhexanoate, ethyl 6-hydroxyhexanoate, 6 - butyl hydroxyhexanoate, polyhydric alcohol esters of hydroxycarboxylic acids; ethylene glycol di(6-hydroxyhexanoic acid) ester, diethylene glycol di(6-hydroxyhexanoic acid) ester, triethylene glycol di(6-hydroxyhexanoic acid) ester , 3-methyl-1,5-pentanediol di(6-hydroxyhexanoic acid) ester, 3-methyl-1,5-pentanediol di(2-hydroxybutyric acid) ester, 3-methyl-1,5-pentanediol Di(3-hydroxybutyric acid) ester, 3-methyl-1,5-pentanediol di(4-hydroxybutyric acid) ester, triethylene glycol di(2-hydroxybutyric acid) ester, glycerin tri(ricinoleic acid) ester, L- Appropriate ones such as di(1-(2-ethylhexyl)) tartarate, castor oils, etc.) and polyester plasticizers can be used.
Castor oils include common castor oil, refined castor oil, hydrogenated castor oil and dehydrated castor oil. Examples of hardened castor oil include hardened castor oil mainly composed of triglyceride composed of 12-hydroxyoctadecanoic acid and glycerin.

In addition to the above raw materials, depending on the purpose of use, other resin raw materials, recycled resins generated from trimming loss such as ears, compatibilizers, processing aids, melt viscosity improvers, antioxidants, anti-aging agents , heat stabilizers, light stabilizers, weather stabilizers, UV absorbers, neutralizers, nucleating agents, cross-linking agents, lubricants, anti-blocking agents, slip agents, anti-fogging agents, antibacterial agents, deodorants, A retardant, an antistatic agent, a coloring agent, 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 it can be produced by a conventionally known method, but it is preferred that the film is stretched at least uniaxially.
Here, the term "film" is meant to include thick sheets to thin films. The film may be either planar or tubular, but planar is preferred from the viewpoint of productivity (several units can be taken as a product in the width direction of the original sheet) and the ability to print on the inner surface. . As a method for producing a planar film, for example, the resin composition is melted using an extruder, extruded into a film form from a die, and cooled and solidified by cooling rolls, air cooling, or water cooling to obtain a film (unstretched Film) is stretched at least uniaxially and then wound up with a winder to obtain a film.

As a method for obtaining the unstretched film, it is preferable to mix the composition (Z) constituting the stretched porous film of the present invention and then melt-knead the mixture. Specifically, after mixing for an appropriate time with a mixer such as a tumbler mixer, mixing roll, Banbury mixer, ribbon blender, and super mixer, extruders such as counter-rotating twin-screw extruders and co-rotating twin-screw extruders are used. used to promote uniform distribution of the composition. The obtained resin composition can be molded into a film by connecting a die such as a T-die or a round die to the tip of the extruder. In addition, a strand die is connected to the tip of the kneader, and after pelletization is performed 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 round die can be connected to the tip of the extruder to form a film. Film-forming methods such as inflation molding, tubular molding, and T-die molding are preferred for film-forming. The extrusion temperature is preferably about 180-260°C, more preferably 190-250°C. Controlling the dispersion state of the material by optimizing the extrusion temperature and shearing conditions is also effective in setting the various physical and mechanical properties of the film to desired values.

The stretched porous film of the present invention can be produced by stretching the unstretched film. For example, the resin is melted using an extruder, extruded from a T-die or a round die, cooled and solidified with a cooling roll, roll-stretched in the vertical direction (film flow direction, MD), or in the horizontal direction (film flow direction). It is stretched at least uniaxially, such as by tenter stretching in the direction perpendicular to the film (TD). Further, after stretching in the longitudinal direction, the film may be stretched in the horizontal direction, or after stretching in the horizontal direction, it may be stretched in the vertical direction. Moreover, you may extend|stretch in the same direction twice or more. Furthermore, the film may be stretched in the longitudinal direction, then stretched in the transverse direction, and then stretched in the longitudinal direction. Alternatively, the film may be stretched simultaneously in the machine direction and the transverse direction by a simultaneous biaxial stretching machine. Alternatively, a tubular unstretched film may be radially stretched by internal pressure in tubular molding. Furthermore, after stretching the tubular unstretched film obtained by inflation molding in a folded state, the edges of the folded tubular stretched perforated film are cut, divided into two sheets, and each wound up. Alternatively, the edges of the folded unstretched film may be cut off and divided into two unstretched films, each of which may be stretched and wound up.

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

If necessary, heat treatment or relaxation treatment can be performed at a temperature of 50° C. or more and 120° C. or less after stretching for the purpose of improving various physical properties. When the film is stretched 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 making the speed of the next contacting roll slower than the speed of the annealing roll while heating with the annealing roll. Moreover, these heat treatments and relaxation treatments can also be carried out in separate steps after stretching the unstretched film and winding up the stretched porous film. If the temperature of the heat treatment or relaxation treatment is too low, the shrinkage rate of the film will be difficult to reduce. Therefore, it is preferable to perform heat treatment or relaxation treatment at a temperature of 50° C. or higher and 120° C. or lower. These heat treatments and relaxation treatments may be performed in multiple divided steps.

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

4. Applications The stretched porous film of the present invention has a large number of fine pores penetrating through the front and back, and has excellent air permeability. Therefore, sanitary goods such as paper diapers and sanitary products for women; clothes such as work clothes, jumpers, jackets, medical clothes, and chemical protective clothing; It can be suitably used for applications that require.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Measured values and evaluations shown in Examples were performed as follows. In the examples, the direction of film flow is referred to as the "longitudinal" direction (or MD), and the direction perpendicular thereto is referred to as the "transverse" direction (or TD).

(1) Measurement of dynamic viscoelasticity of the resin composition (Z) constituting the stretched porous film In the following examples and comparative examples, an unstretched film of the resin composition (Z) constituting the stretched porous film was used. , MD4 mm, and TD35 mm using a strip-shaped sample piece, dynamic viscoelasticity measurement is performed according to the method described above, and the storage elastic modulus (E'), loss elastic modulus (E''), and storage elastic modulus A tan δ (=E''/E'), which is the ratio of (E') to the loss modulus (E''), was calculated. In Table 1, when tan δ is 0.100 or more at −20° C., it is indicated as “◯”, and when tan δ is less than 0.100 at −20° C., it is indicated as “x”.
Furthermore, Table 1 summarizes E′ (unit: ×10 ⁸ Pa) at 20°C and tan δ values 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 method described above.

(3) Porosity of Stretched Porous Film According to the method described above, the porosity of the stretched porous film was calculated.

(4) Air Permeability of Stretched Porous Film According to the method described above, the air permeability of the stretched porous film was calculated. As the air permeability measuring device, 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 method described above, the moisture permeability of the stretched porous film was calculated.

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

(7) Tensile Elongation at Break in Stretching Direction of Stretched Porous Film According to the method described above, the tensile elongation at break in the stretching direction (MD in this example and comparative example) of the stretched porous film was calculated.

(8) Total Light Transmittance of Stretched Porous Film According to the method described above, the total light transmittance of the stretched porous film was calculated.

(9) Crystal melting peak (Pm) and crystal melting enthalpy (ΔHm) of stretched porous film
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 using a differential scanning calorimeter (DSC), and 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 heated 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) in the heating process and the crystal melting peak (Pm) in the reheating process.
At this time, the presence or absence of a crystal melting peak (Pm1) at 140°C to 200°C was confirmed. Also, the peak temperature (Tm1) and crystal melting enthalpy (ΔHm1) were calculated from the above (Pm1).
Similarly, the presence or absence of a crystalline melting peak (Pm2) at 30°C to 130°C was confirmed. Also, the peak temperature (Tm2) and crystal melting enthalpy (ΔHm2) were calculated from the above (Pm2).

(10) Membrane rupture heat resistance temperature of stretched porous film The membrane rupture heat resistance temperature was evaluated according to the method described above. The evaluation was carried out by setting the internal temperature of the convection oven to 120°C, 140°C, and 160°C, and visually evaluating the state after standing in the tank for 2 minutes and heating according to the following criteria.
◯: There is no break or hole in the sample at the circular punched portion of the stainless steel plate.
x: The sample at the circular punched portion of the stainless steel plate melted and had a hole.

(11) Flexibility of Stretched Porous Films The stretched porous films obtained in the following examples and comparative examples were cut into pieces of 1000 mm in the longitudinal direction (MD) and 200 mm in the transverse direction (TD), touched by hand, and measured according to the criteria below. ,evaluated.
◯: The film has a soft texture.
x: Hardness is felt in the film.

(12) Uncomfortable sound measurement of stretched perforated film Unpleasant sound measurement of stretched perforated film was conducted in a private room (in an environment with little external noise) about 3m wide, 4m long, and 3m high. A normal sound level meter NL-42 manufactured by Rion Co., Ltd. was used, and the frequency weighting characteristic was A characteristic and the time weighting characteristic was F characteristic.
First, stretched porous films obtained in the following examples and comparative examples were cut into 400 mm in the machine direction (MD) and 200 mm in the transverse direction (TD), folded once at the center in the longitudinal direction, and folded in two. After that, both TD end portions of the stretched porous films that were overlapped were clamped, and the distance between the clamped TD end portions was adjusted to 100 mm.
Furthermore, after adjusting the distance between the sandwiched stretched porous film and the microphone (sound collection part) of the ordinary sound level meter to be 100 mm, the sandwiched stretched porous film MD and TD and the direction perpendicular to (thickness direction) ), the film was rubbed against each other by vibrating the clamped ends three times per second, and the time-average sound level (LAeq) was measured for a measurement time of 10 seconds, and evaluated according to the following criteria.
The time-average sound level (LAeq) was 26 dB for a measurement time of 10 seconds in a state in which the film was not vibrated (non-operating state).
◎: 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) Comprehensive Evaluation Considering the evaluations shown in (1) to (12) above, comprehensive evaluation was performed according to the following criteria.
A: It is a film suitable for applications requiring breathability and moisture permeability, which has excellent tactile sensation such as flexibility and texture, suppresses the generation of unpleasant sounds generated when the film is rubbed, and has sufficient heat resistance. It is a film that combines
B: The film has excellent tactile sensations such as flexibility and texture, and suppresses the generation of unpleasant sounds that occur when the film is rubbed, and is suitable for applications requiring breathability and moisture permeability, but insufficient heat resistance is.
C: The film is excellent in air permeability and moisture permeability, but the film does not give a tactile sensation such as flexibility or texture, and produces an unpleasant sound.
D: The film is insufficient in physical properties such as breathability and moisture permeability required for stretched porous films.

The raw materials used in each example and comparative example are as follows.
<Inorganic filler (A)>
· Bihoku Funka Kogyo Co., Ltd., heavy calcium carbonate “Ryton BS-0” (average particle size 1.1 μm, surface-treated with stearic acid). Hereinafter, it will be abbreviated as "A-1".
<Polyethylene resin (B)>
· Nippon Polyethylene Co., Ltd., linear low-density polyethylene "Novatec LL UF230" (density 0.921 g/cm ³ , MFR 1.0 g/10 minutes, melting point 121°C). Hereinafter, it will be abbreviated as "B-1".
- Branched low-density polyethylene "Novatec LD LF441" manufactured by Nippon Polyethylene Co., Ltd. (density 0.918 g/cm ³ , MFR 2.3 g/10 minutes, melting point 113°C). Hereinafter, it will be abbreviated as "B-2".
<Soft polyolefin resin (C)>
・Metallocene ethylene/(α-olefin) copolymer “Kernel KF360T” manufactured by Nippon Polyethylene Co., Ltd. (density 0.898 g/cm ³ , MFR 3.5 g/10 minutes, melting point 90° C.). Hereinafter, it will be abbreviated as “C-1”.
Ethylene/(1-butene) copolymer “Tafmer A1050S” manufactured by Mitsui Chemicals, Inc. (density 0.862 g/cm ³ , MFR 1.2 g/10 minutes, melting point 45° C.). Hereinafter, it will be abbreviated as “C-2”.
Ethylene-octene block copolymer “Infuse D9107” manufactured by Dow Chemical Co. (density 0.866 g/cm ³ , MFR 1 g/10 minutes, melting point 119° C.). Hereinafter, it will be abbreviated as “C-3”.
<Polypropylene resin (D)>
· Nippon Polypro Co., Ltd., polypropylene "Novatec PP SA03" (density 0.900 g/cm ³ , MFR 30 g/10 minutes, melting point 165°C). Hereinafter, it is abbreviated as "D-1".
<Plasticizer (E)>
· Hydrogenated castor oil "HCO-P3" manufactured by KEF Trading Co., Ltd. Hereinafter, it is abbreviated as "E-1".
<Antioxidant>
· BASF Japan Co., Ltd., antioxidant "Irganox B225". Hereinafter, it is abbreviated as "F-1".
<Other resins>
· Mitsui Chemicals, Inc., α-olefin copolymer “Absotomer EP-1001” (density 0.84 g/cm ³ , MFR 10 g/10 minutes (230° C. 2.16 kg load)). Hereinafter, it will be abbreviated as "G-1".

<Example 1>
After weighing each raw material at the composition ratio shown in Table 1, it is put into a Henschel mixer, mixed and dispersed for 5 minutes, and melt-kneaded at a set temperature of 200 ° C. using a co-rotating twin-screw extruder. A resin composition was extruded with a T-die connected to the tip of a co-rotating twin-screw extruder, taken up with a casting roll set at 50° C., and solidified by cooling to obtain an unstretched film with a thickness of 35 μm. A dynamic viscoelasticity measurement was performed on the obtained unstretched film.
After that, the obtained unstretched film is placed between the roll (S) set at 60 ° C., the roll (T) set at 60 ° C., and the roll (U) set at 60 ° C., (S) - (T ) A draw ratio of 100% (stretching ratio of 2.0 times) and a (T)-(U) draw ratio of 100% (stretching ratio of 2.0 times) were applied, and the MD was stretched a total of 4.0 times. Then, a stretched porous film was obtained by performing heat treatment and 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 obtained in the same manner as in Example 1, except that the composition ratio of the raw materials was changed as shown in Table 1. A dynamic viscoelasticity measurement was performed on the obtained unstretched film. Thereafter, the obtained unstretched film was subjected to stretching, heat treatment and relaxation treatment 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 obtained in the same manner as in Example 1, except that the composition ratio of the raw materials was changed as shown in Table 1. A dynamic viscoelasticity measurement was performed on the obtained unstretched film. Thereafter, the obtained unstretched film was subjected to stretching, heat treatment and relaxation treatment 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 obtained in the same manner as in Example 1, except that the composition ratio of the raw materials was changed as shown in Table 1. A dynamic viscoelasticity measurement was performed on the obtained unstretched film. Thereafter, the obtained unstretched film was subjected to stretching, heat treatment and relaxation treatment 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 obtained in the same manner as in Example 1, except that the composition ratio of the raw materials was changed as shown in Table 1. A dynamic viscoelasticity measurement was performed on the obtained unstretched film. Thereafter, the obtained unstretched film was subjected to stretching, heat treatment and relaxation treatment 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 obtained in the same manner as in Example 1, except that the composition ratio of the raw materials was changed as shown in Table 1. A dynamic viscoelasticity measurement was performed on the obtained unstretched film. Thereafter, the obtained unstretched film was subjected to stretching, heat treatment and relaxation treatment 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 obtained in the same manner as in Example 1, except that the composition ratio of the raw materials was changed as shown in Table 1. A dynamic viscoelasticity measurement was performed on the obtained unstretched film. Thereafter, the obtained unstretched film was subjected to stretching, heat treatment and relaxation treatment 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 obtained in the same manner as in Example 1, except that the composition ratio of the raw materials was changed as shown in Table 1. A dynamic viscoelasticity measurement was performed on the obtained unstretched film. Thereafter, the obtained unstretched film was subjected to stretching, heat treatment and relaxation treatment 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 obtained in the same manner as in Example 1, except that the composition ratio of the raw materials was changed as shown in Table 1. A dynamic viscoelasticity measurement was performed on the obtained unstretched film. Thereafter, the obtained unstretched film was subjected to stretching, heat treatment and relaxation treatment 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 films having excellent air permeability and moisture permeability, and suitable tensile strength at break, tensile elongation at break, and total light transmittance. In addition, the time-average sound level (LAeq) when the stretched porous films obtained in Examples 1 to 5 were rubbed together showed a low value, and no unpleasant sound was felt. Furthermore, in the membrane rupture heat resistance test, the membrane did not rupture at 120°C, 140°C and even 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 crystalline melting peak satisfy the range defined by the present invention. It is considered to be for 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 was 0.100 or more at -20°C. This is thought to be because the vibration of the resin composition (Z) attenuates the sound that propagates and contributes to the suppression of the unpleasant sound. In addition, the stretched porous films obtained in Examples 1 to 5 had a crystal melting peak at 140°C to 200°C, indicating that they had high heat resistance.
On the other hand, the films obtained in Comparative Examples 1 and 2 do not satisfy the tan δ defined by the present invention, so they are insufficient for suppressing unpleasant sounds, and the time average sound level (LAeq) shows a high value. . In addition, the film obtained in Comparative Example 3 does not have a crystal melting peak within the temperature range defined by the present invention. It turns out to be insufficient.
Furthermore, in Comparative Example 4, although the film contains an α-olefin copolymer with a density of less than 0.850 g/cm ³ , it does not satisfy the tan δ specified by the present invention, so it is insufficient for suppressing unpleasant sounds. Met. That is, in order to achieve both the necessary heat resistance imparted to the stretched porous film and the suppression of unpleasant noise generated when the film is rubbed, both the above-mentioned tan δ and the temperature at which the crystal melting peak appears should be adjusted according to the present invention. It can be seen that it is important to satisfy the specified range.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, the invention is not limited to the embodiments disclosed herein. However, it can be changed as appropriate within the scope not contrary to the gist of the invention read from the claims and the entire specification, or the idea, and the stretched porous film accompanying such changes 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 tactile sensations such as flexibility and texture, suppresses the generation of unpleasant sounds that occur when the film is rubbed, and is also excellent in air permeability, moisture permeability and strength. Therefore, sanitary products such as disposable diapers and sanitary products for women with stretched perforated films; garments such as work clothes, jumpers, jackets, medical clothing, chemical protective clothing; and masks, covers, drapes, sheets, and wraps. It can be suitably used for applications that require air permeability and moisture permeability such as.

Claims (12)

A stretched porous film made of 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),
As the thermoplastic 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 soft polyolefin resin having a density of 0.850 g/cm ³ or ^more and less ^than 0.910 g/cm ³ Each has a resin (C) and a polypropylene resin (D),
The mixed composition ratio of the soft polyolefin resin (C) is 50% by mass to 98% by mass (provided that the total mass% of (B), (C) and (D) is 100% by mass),
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) is tan δ (=E″/E′) of −20. A stretched porous film having a crystalline melting peak (Pm1) of 0.100°C or more at 140°C to 200°C. The mixed composition ratio of the polyethylene-based resin (B), the soft polyolefin-based resin (C), and the polypropylene-based resin (D) is (B)/(C)/(D)=1% by mass to 25% by mass/50. % to 98% by mass/1% to 25% by mass (provided that the total mass% of (B), (C) and (D) is 100% by mass). the film. 3. The stretched porous film according to claim 1, wherein at least one of the polyethylene resins (B) is branched low-density polyethylene . The stretched porous film according to any one of claims 1 to 3, wherein the crystal melting enthalpy (ΔHm1) calculated from the crystal melting peak (Pm1) is 1 J/g to 10 J/g. It further has a crystal melting peak (Pm2) 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 any one of the above. 6. The resin composition (Z) according to any one of claims 1 to 5 , wherein the resin composition (Z) has a storage elastic modulus (E′) calculated from dynamic viscoelasticity measurement of 8.0×10 ⁸ Pa or less at 20°C. Stretched perforated film. The stretched porous film according to any one of claims 1 to 6 , which has a porosity of 15% to 80%. The stretched porous film according to any one of claims 1 to 7 , wherein the thermoplastic resin is a polyolefin resin. The stretched porous film according to claim 8 , wherein the polyolefin resin has a density of 0.850 g/cm ³ or more and 0.940 g/cm ³ or less. The stretched porous film according to any one of claims 1 to 9, wherein the resin composition (Z) contains 0.1% by mass to 8.0% by mass of the plasticizer (E). A sanitary product comprising the stretched porous film according to any one of claims 1 to 10. A garment comprising the stretched perforated film according to any one of claims 1-10.