JP2001294695A - Polyolefin-based porous film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a polyolefin-based porous film having a high water vapor permeability, also excellent in liquid impermeability, rich in flexibility, having a good touch feeling and excellent in its appearance. SOLUTION: This polyolefin-based porous film obtained by stretching a polyolefin composition dispersed with inorganic filler particles for making it porous is characterized by having a relationship between the water vapor permeability of the film (A) and its thickness (B) as 2,000<=A<=1,929.7×exp0.0273B, 20-45 μm film thickness range and 0.03-0.20 μm peak top hole diameter range in measuring the hole diameter distribution of the film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polyolefin-based porous film. More specifically, the present invention relates to a polyolefin porous film having good moisture permeability and good liquid impermeability, and good appearance and feel.

[0002]

2. Description of the Related Art Polyolefin-based porous films are used in a variety of applications because they have good air permeability and moisture permeability as well as liquid impermeability.

[0003] As one of the methods for producing the polyolefin-based porous film, a film obtained by melt-molding a polyolefin composition in which an inorganic filler is dispersed is used, and the film is stretched uniaxially or biaxially to form an inorganic filler. 2. Description of the Related Art A method for producing a porous film by causing interfacial separation between a filler and a polyolefin to generate voids has been conventionally known.

In the above production method, when the film is stretched to generate voids, if the stretching ratio is too high,
Since the molecular orientation of the resin is high, the rigidity of the film is high, the flexibility of the film is impaired, the voids are large, and the diameter of the communication hole penetrating the film tends to be large. On the other hand, if the stretching ratio is too low, unevenness occurs in the generation of voids due to stretching, so that the uniformity of the thickness is reduced or a phenomenon that sufficient air permeability or moisture permeability tends to not be obtained is also known. I have.

On the other hand, polyolefin-based porous films are used as medical materials. When used as a material for a disposable surgical gown or a disposable sanitary product in the above-mentioned applications, it is required to have a performance that does not leak blood and allows only moisture to pass through.

That is, in recent years, the problem of hospital-acquired infections at medical sites has become a social phenomenon. In particular, there is a concern that infection of doctors and nurses with bacteria and viruses due to blood adhesion during surgery may occur. From the viewpoints of comfort, safety, and cost during the operation of the surgeon, disposable surgical clothes made of non-woven fabric are used in such applications. However, due to such a problem, more excellent liquid impermeability (bloodproofness) is used. Is required. Also, sanitary products are required to have blood impermeability to blood during menstruation.

However, since blood has a lower surface tension than water, human urine, etc., it has the property of having high permeability to a polyolefin-based porous film. Further, some disposable sanitary products may cause a trace amount of a surfactant to dissolve due to absorbed blood or the like. As a result,
There is a problem that blood easily leaks from the polyolefin porous film.

As a method for solving the above problem, Japanese Patent Laid-Open No.
JP-A-158305 proposes adding at least one selected from ethylenebisstearic acid amide, methylenebisstearic acid amide and methylenebisoleic acid amide to a polyolefin composition containing an inorganic filler. ing. However, although air permeability and flexibility are recognized as effective, liquid impermeable properties to highly permeable liquids such as blood have not been satisfactory.

As a method for solving the above-mentioned problems, control of manufacturing conditions and the like has been studied. However, due to the phenomenon in the above-described filling and stretching method, blood permeability and flexibility are maintained while blood permeability and flexibility are maintained. It has been difficult to impart liquid impermeability to such highly permeable liquids.

[0010]

As described above, in the conventional polyolefin-based porous film, a liquid having a high permeability and a surface tension of about 32 mN / m, such as blood, has a liquid content of 10 minutes or less. It had only impermeability or had a moisture permeability of less than 2000 g / m ² · 24 hr.

Therefore, it has good moisture permeability of 2000 g / m ² · 24 hr or more, and has a surface tension of 32
For liquids of about mN / m, it has good liquid impermeability for 20 minutes or more, and has good texture with good flexibility.
There has been a demand for a polyolefin-based porous film having an excellent appearance.

[0012]

Means for Solving the Problems The present inventors have intensively studied to solve the above problems. As a result, the inventors have found that the above object can be achieved by a polyolefin-based porous film in which the moisture permeability, thickness, and pore size of the film have a special relationship, and have completed the present invention.

That is, the present invention relates to a polyolefin film in which a polyolefin composition in which an inorganic filler is dispersed is made porous by stretching.
And the thickness (B) (μm) is 2000 ≦ A ≦ 192
9.7 × exp ^0.0273B and the film thickness is 2
0 to 45 μm, and the peak top pore diameter in the pore diameter distribution measurement of the film is 0.03 to 0.20 μm
Is a polyolefin-based porous film.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

In the polyolefin porous film of the present invention, the relationship between the moisture permeability (A) and the thickness (B) (μm) is 200.
0 ≦ A ≦ 1929.7 × exp ^0.0273B , the film thickness (B) is 20 to 45 μm, and the peak top pore size in the pore size distribution measurement of the film is 0.03 to 0.20 μm. Is required. When these requirements are met, a blood-like surface tension of 32
It has good liquid impermeability to liquids with high permeability of about mN / m.

The relationship between the moisture permeability (A) and the thickness (B) is A> 1.
When it is 929.7 × exp ^0.0273B, it is not preferable because sufficient liquid impermeability is not exhibited. On the other hand, A <200
A value of 0 is not preferable because the moisture permeability is not sufficient.

Considering that sufficient moisture permeability and liquid impermeability are exhibited, the lower limit of A is 2300 ≦ A
Is preferable, and it is more preferable that 2600 ≦ A. The upper limit of A varies depending on the relationship with the thickness, but is preferably 5000 or less, more preferably 4 or less.
000 or less.

The moisture permeability in the present invention is determined by sampling a circular portion having a diameter of 40 mm from a film at five arbitrarily positions and measuring the temperature at 40 ° C. and a humidity of 60% for each circular portion.
Water evaporation permeation amount for 24 hours was measured under the conditions of, m ²
It is the average value of each measured value converted to moisture permeability in units.

Further, the thickness of the polyolefin porous film of the present invention is 20 to 45 μm, and in consideration of exhibiting sufficient moisture permeability and liquid impermeability, the thickness is 25 to 4 μm.
0 μm is preferred. If the thickness is out of the above range, it is not preferred because it is rich in flexibility and good in texture, and cannot have moisture permeability and liquid impermeability.

In the present invention, the peak top pore size in the pore size distribution measurement of the film is 0.03 to 0.20 μm.
m, preferably 0.04 to 0.15 μm, more preferably 0.05 to 0.10 μm. When the peak top pore diameter is smaller than 0.03 μm, it is not preferable because sufficient moisture permeability is not exhibited. On the other hand, when the peak top pore diameter is larger than 0.20 μm, the liquid impermeability is undesirably reduced.

In the present invention, the peak top pore size in the pore size distribution measurement is a value measured only for through holes in the film by the following method.

First, a circular portion having a diameter of 50 mm is arbitrarily sampled from a film, sufficiently immersed in a petri dish containing a liquid having a high permeability and a low volatility, and the porous portion in the film is filled with the liquid. . Here, methanol, ethanol, a fluorine-based inert liquid, or the like can be used as the liquid having a high permeability and a low volatility, and among them, a fluorine-based inert liquid is preferably used for a long-time measurement.

At the beginning of the measurement, the liquid is held in the film by capillary tension. However, when the air pressure difference is gradually applied between both surfaces of the sample, the liquid flows from the through hole having the largest diameter in the through hole at a certain pressure. It is eliminated, and thereafter, it is sequentially drained from the larger pores. In this way, the flow rate with respect to the gas pressure of the wet sample and the flow rate with respect to the gas pressure of the dry sample (in a state in which the liquid is excluded in all the through holes) are measured. The pore size distribution in this measurement is obtained by calculating the pressure at a point where a curve having a slope of 1/2 of the wetting flow rate curve and the dry flow rate curve intersects, and using the following equation (1). further,
In the pore diameter distribution, the pore diameter range is divided into discrete sections, the limit value of each section is selected, and each pressure is obtained by the following equation (1). Then, data points at the pressure limit are determined from the wet flow rate curve and the dry flow rate curve. From the numerical values, the pore size distribution of the through holes of the porous film can be obtained by the following equations (2) and (3). Here, the point at which the flow rate occurs first was defined as the maximum pore size, and the pore size of the portion having the highest strength in the pore size distribution was defined as the peak top pore size.

D = C · γ / P (1) Q = (wet flow rate × h) / (dry flow rate × h) − (wet flow rate × i) / (dry flow rate × i) (2) D = (Q− QL) / (dL-d) (3) (d: pore diameter (μm), γ: surface tension of liquid (mN /
m), P: differential pressure, C: pressure constant, Q: filter flow rate percentage, h: high pressure limit, i: low pressure limit, D: pore size distribution, L: leading value, d: pore size)

In the above method, the pressure increasing speed may be appropriately set according to the film strength and the speed required for measuring the flow rate, and the pressure increasing speed may be determined in advance by an experiment. Usually, the pressure increasing speed is preferably in the range of 0.1 to 10 kPa.

Other physical properties of the polyolefin porous film of the present invention are not particularly limited,
Taking into account the liquid impermeability, it is preferable to have the following physical properties.

That is, the peak half width of the peak top pore diameter in the pore diameter distribution measurement is 0.01 to 0.10 μm.
m is preferable, and 0.02 to 0.05 μm is particularly preferable. Further, the maximum pore size in the pore size distribution measurement is 0.1
To 1.5 μm, and preferably 0.2 to 0.7 μm. Furthermore, 0.25μ in pore size distribution measurement
The through-hole component amount of m or more is preferably less than 1% of the whole, and particularly preferably less than 0.25%.
The porosity of the film is preferably from 10 to 60%,
~ 45% is more preferred.

The method for producing the polyolefin-based porous film of the present invention is not particularly limited, and a conventionally known filling and stretching method using a polyolefin in which an inorganic filler is dispersed may be appropriately employed so as to satisfy the requirements of the present invention. Good. For example, a typical manufacturing method is as follows.

The polyolefin used in the present invention includes:
There is no particular limitation, and ethylene, propylene, 1-butene, 4
Homopolymers of α-olefins such as -methyl-1-pentene, copolymers of two or more α-olefins, copolymers of α-olefins and other monomers copolymerizable with α-olefins, and these A mixture of polymers and the like can be used.

Among these, high-density polyethylene, low-density polyethylene, and linear low-density polyethylene are preferable. Considering that the requirements defined in the present invention are easily achieved, a copolymer of ethylene and α-olefin is preferred. More preferred is a mixture of certain linear low density polyethylene and low density polyethylene. Specific examples of the linear low-density polyethylene include ethylene and 1-butene, 1-hexene,
4 to 4 carbon atoms such as -methyl-1-pentene and 1-octene
8 with an α-olefin. The density of the polyolefin is not particularly limited, but may be 0.91.
It is preferably from 0 to 0.935 g / cm ³ . The melt index at 190 ° C. is 0.5 to 1
It is preferably 0 g / 10 minutes.

The inorganic filler used in the present invention is not particularly limited, and may be calcium carbonate, barium sulfate, calcium sulfate, barium carbonate, magnesium hydroxide, aluminum hydroxide, zinc oxide, magnesium oxide, titanium oxide,
Inorganic substances such as clay, silica and talc, or organic metal salts mainly composed of inorganic substances may be used. Among these, calcium carbonate is particularly preferred in view of easily achieving the requirements specified in the present invention.

The average particle diameter of the inorganic filler is preferably 5 μm or less, more preferably 3 μm or less, and considering that the requirements defined in the present invention are easily achieved, 0.2 to 1.5 μm. Are particularly preferred. When the average particle size of the inorganic filler is larger than 5 μm, the maximum pore size developed in the stretched film tends to be too large, and the denseness of the pores tends to be reduced. As a result, the requirements defined in the present invention are satisfied. It tends to be impossible. On the other hand, when the average particle size is smaller than 0.2 μm, due to poor dispersion of the inorganic filler, the moldability of the film becomes poor, or a uniform porous film tends to be obtained due to stretching unevenness, As a result, the requirements defined in the present invention tend not to be satisfied.

In the case of using the above calcium carbonate, considering that the requirements specified in the present invention are easily achieved, it is preferable to use calcium carbonate surface-treated with a chain carboxylic acid having 3 to 6 carbon atoms. Particularly preferred.
Here, as the calcium carbonate to be subjected to the surface treatment, any of heavy calcium carbonate and light calcium carbonate can be used without any limitation.

The above-mentioned chain carboxylic acid may be not only a straight-chain carboxylic acid but also one having a branched chain, and not only a monocarboxylic acid but also one having a plurality of carboxyl groups. Specific examples include saturated monobasic acids such as propionic acid, butyric acid, valeric acid, and caproic acid; saturated dibasic acids such as succinic acid and adipic acid; and unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and pentenoic acid. And unsaturated dicarboxylic acids such as maleic acid. Among them, in view of easily achieving the requirements specified in the present invention, unsaturated carboxylic acids having a polymerizable unsaturated group such as acrylic acid and methacrylic acid are preferable, and acrylic acid is particularly preferable.

The above-mentioned chain carboxylic acid reacts on the surface by surface treatment of calcium carbonate to form a chain calcium carboxylate. Then, the produced chain-type calcium carboxylate adheres firmly to the surface of the calcium carbonate, thereby improving the adhesive strength with the polyolefin. In addition, such surface-treated calcium carbonate has excellent dispersibility and interfacial peeling effect inherently possessed by calcium carbonate.

The above-mentioned surface treatment may be performed by any known method without any particular limitation, and among them, it is preferable to perform the surface treatment within a range that does not impair the interfacial releasability from polyolefin during film stretching. The amount of the chain carboxylic acid used for the surface treatment varies depending on the particle size of the calcium carbonate used and the type of the chain carboxylic acid used. 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, per part.

The surface treatment method is not particularly limited, and a method of spraying a chain carboxylic acid while stirring calcium carbonate with a super mixer or the like, a method of mixing a chain carboxylic acid with an aqueous suspension of calcium carbonate, and stirring. And a method of drying.

The surface treatment time depends on the type of chain carboxylic acid,
Although it depends on the temperature conditions, it is preferably 10 minutes to 12 hours, more preferably 30 minutes to 5 hours. Further, the surface treatment temperature is preferably 0 to 100 ° C, more preferably 20 to 80 ° C, and still more preferably 30 to 60 ° C.

In order to impart other properties to the calcium carbonate surface-treated with the above-mentioned chain carboxylic acid or to improve the dispersibility in polyolefin, the surface-treated calcium carbonate is treated with a treating agent such as a fatty acid. For secondary surface treatment.

As the above fatty acid, a higher saturated fatty acid having 8 to 24 carbon atoms is suitable, and more preferably, a higher saturated fatty acid having 10 to 24 carbon atoms.
~ 14 higher saturated fatty acids. Specifically,
Examples thereof include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and arachidic acid, and among them, stearic acid is particularly preferable. The higher saturated fatty acid may be a fatty acid salt as long as it can be sufficiently adsorbed on the surface of calcium carbonate.

In consideration of further improving the dispersibility, the higher saturated fatty acid salt is adsorbed on the surface of the secondary surface-treated calcium carbonate, or the higher saturated fatty acid salt is separately blended with polyolefin. Is preferred. Among the above higher saturated fatty acid salts, zinc salts are preferred in terms of imparting a particularly high dispersibility improving effect to calcium carbonate.

The composition comprising the polyolefin and the inorganic filler used in the present invention contains components other than the above components, for example, an antioxidant, a weathering agent, a pigment, a plasticizer, as long as the effects of the present invention are not impaired. Additives such as an antistatic agent and silicone oil or wax may be blended to obtain uniform stretchability.

In the present invention, a method for producing a composition for obtaining a polyolefin-based porous film in which an inorganic filler is dispersed is not particularly limited, and a known method may be employed. For example, there is a method in which the above-mentioned components are preliminarily mixed with a super mixer, a Henschel mixer or the like, then melt-kneaded with a high kneading type twin screw extruder or the like, and then pelletized.

In the present invention, the mixing ratio of the polyolefin and the inorganic filler is preferably in a weight ratio of polyolefin: inorganic filler = 30: 70 to 60:60 in consideration of easily achieving the requirements specified in the present invention. 40 is preferred,
40:60 to 55:45 is more preferred.

If the compounding ratio of the inorganic filler is less than 40% by weight, sufficient porosity may not be generated at the time of stretching the film. There is a possibility that a defect may occur or the stretchability may decrease, and as a result, it becomes difficult to easily achieve the requirements specified in the present invention.

In the present invention, the method of forming the composition into a sheet is not particularly limited, and generally, an inflation molding method or a T-die molding method is used.

In the present invention, the method for stretching the above-mentioned sheet material is not particularly limited, and a known stretching method is employed.
For example, uniaxial stretching by a roll, a tenter stretching machine after uniaxial stretching, sequential biaxial stretching by a stretching mandrel, or the like, or simultaneous biaxial stretching may be mentioned, and among these, the requirements defined in the present invention are easily achieved. In consideration of the above, sequential biaxial stretching is preferable from the viewpoint of controlling the pore size and controlling the moisture permeability.

As for the stretching conditions, considering that the requirements defined in the present invention are easily achieved, the uniaxial stretching temperature is set at 2 ° C.
It is preferably carried out at a temperature of from 0 ° C. to (a temperature 35 ° C. lower than the melting point of the polyolefin).
0 ° C. to (a temperature 40 ° C. lower than the melting point of the polyolefin). If the uniaxial stretching temperature is lower than 20 ° C., the stretching load increases, and uniform stretching cannot be performed. If the uniaxial stretching temperature exceeds a temperature lower by 35 ° C. than the melting point of the polyolefin, the interface between the inorganic filler and the polyolefin is lowered. Peeling is unlikely to occur, making it difficult to easily achieve the requirements specified in the present invention.

In the present invention, the melting point of the polyolefin is the temperature at the apex of the maximum peak measured by a differential scanning calorimeter (DSC).

The stretching ratio is preferably from 1.1 to 5 times, more preferably from 1.3 to 3 in terms of area ratio, in view of the fact that the sheet is favorably porous at the above stretching temperature without breaking the sheet. 0.5 times. If the area magnification is smaller than 1.1 times, the film cannot be stretched uniformly, and it is difficult to make the film porous. On the other hand, when the area magnification is larger than 5 times, the film is easily broken. Among the above conditions, it is particularly preferable that the film is stretched at least 1.5 to 3.5 times in the uniaxial direction. In view of easily achieving the requirements defined in the present invention, the film is further orthogonal to the uniaxial direction. It is particularly preferable that the film is weakly stretched in a direction not exceeding the area magnification.

The polyolefin porous film of the present invention may be produced by appropriately selecting the above-mentioned raw materials and the production method so as to satisfy the requirements specified in the present invention.

Among them, ethylene and α-
A linear low-density polyethylene which is a copolymer with an olefin and a resin composition with the low-density polyethylene;
And a calcium carbonate surface-treated with a chain carboxylic acid having a weight ratio of 30:70 to 60:40 (weight ratio) of resin composition: surface-treated calcium carbonate in a blending ratio, and stretching conditions. The stretching temperature is 20 ° C
(A temperature lower by 40 ° C. than the melting point of the polyolefin), a method of stretching 1.5 to 3.5 times in a uniaxial direction, and then weakly stretching in a direction perpendicular to the uniaxial direction within a range not exceeding the area magnification. Is particularly preferred in view of achieving the requirements defined in the present invention very easily.

The polyolefin porous film of the present invention has excellent appearance, good texture, high moisture permeability and high liquid impermeability. Therefore, it can be used as an extremely useful material as a sanitary material such as disposable disposable diapers and sanitary articles, and a medical material such as a surgical gown and a base material for a hot compress, and further, a building material, rainy clothing, and a battery. It can also be suitably used as a material such as a separator for use.

[0054]

EXAMPLES The present invention will be described below in more detail with reference to examples. Note that the present invention is not limited to these examples. The measured physical properties shown in Examples and Comparative Examples were measured by the following methods.

1) Moisture permeability (g / m ² · 24 hr) JIS Z0 under conditions of a temperature of 40 ° C. and a relative humidity of 60%.
The amount of water evaporation was measured according to Method 208.

2) Thickness (μm) The thickness was measured using a thickness measuring instrument in accordance with JIS K6734.

3) Pore size distribution (μm) Measured according to the ASTM F316 method using a Palm Porometer APP-1200AEIFX device manufactured by PMI under the following conditions. Permeate: Florinert (manufactured by 3M) Measurement mode: Pore size distribution measurement (Wet UP, Dry)
UP) Boosting speed: 5kPa

4) Liquid Permeation Test (Leakage) A 15 cm square polyolefin porous film was used as a sample, and a surfactant solution (Rikemar B205, manufactured by Riken Vitamin Co., Ltd .; 005% by weight solution: surface tension was 32 mN / m). In order to determine the liquid permeability, a small amount of Red No. 2 was added to color the liquid. A horizontal sample table with a transparent top plate (made of acrylic resin, a box type table with a height of 30 cm and a height of 10 cm)
20cm square filter paper (0.1mm thick)
And place it on it so that the sample film does not protrude. Further, a square filter paper of 10 cm in length and width is placed, and 10 ml of the above solution is dropped on the filter paper with a dropper. When the solution has penetrated the filter paper, 10cm in height and 10cm in height
A weight of 10 m and a weight of 10 kg is put on the filter paper and the time is measured. The test solution was observed by a mirror placed under the sample stand to see if the test solution had penetrated from the filter paper, and the time during which red color appeared on the filter paper was recorded as “leakage”.

5) Particle size measurement (μm) Laser diffraction particle size distribution analyzer (Shimadzu Corporation S
ALD2000) was used to measure the particle size distribution of calcium carbonate. The average particle diameter was a particle diameter (μm) at a relative particle amount of 50%.

Example 1 100 parts by weight of heavy calcium carbonate having an average particle size of 0.8 μm was put into a super mixer, and stirred at 50 ° C. for 1 hour while spraying 1.5 parts by weight of acrylic acid little by little from a small nozzle. . The resulting surface-treated calcium carbonate was further surface-treated with 1 part by weight of stearic acid. Melting point 125 ° C
47 parts by weight of linear low density polyethylene (Idemitsu Petrochemical Co., Ltd.)
234CL) and 3 parts by weight of low-density polyethylene having a melting point of 110 ° C. (Mirason 16P manufactured by Mitsui Chemicals, Inc.), a composition comprising 50 parts by weight of the surface-treated calcium carbonate and 1 part by weight of zinc stearate were mixed by a super mixer. Thereafter, the mixture was melt-kneaded at a cylinder temperature of 220 ° C. using a twin screw kneading extruder having a diameter of 50 mm, and processed into pellets. Using an inflation extruder, the pellets were heated at a cylinder temperature of 185 ° C., a die temperature of 175 ° C., and a take-up speed of 11 m / m.
After forming a cylindrical film having a sheet thickness of 80 μm and a folded diameter of 420 mm under the conditions of “in”, the film was longitudinally stretched 1.8 times in the longitudinal direction at 30 ° C.
The film is stretched 1.3 times in the transverse direction in an atmosphere of 0 ° C. and has a thickness of 35 μm.
m of polyolefin-based porous film was obtained. Various properties of the obtained polyolefin-based porous film were measured by the above methods, and are shown in Table 2.

Example 2 An extruded sheet having a thickness of 99 mm was stretched 1.8 times in length and 1.3 times in width to obtain a sheet having a thickness of 43 mm.
A porous film was obtained in the same manner as in Example 1, except that a μm porous film was obtained. Table 2 shows the properties of the obtained porous film.

Example 3 A sheet having a thickness of 53 mm was extruded and stretched 1.8 times in length and 1.3 times in width to obtain a sheet having a thickness of 2 mm.
A porous film was obtained in the same manner as in Example 1, except that a 3 μm porous film was obtained. Table 2 shows the properties of the obtained porous film.

Comparative Example 1 Instead of the surface-treated calcium carbonate, heavy calcium carbonate having an average particle diameter of 2.0 μm, which had not been subjected to a surface treatment with acrylic acid, was used. A porous film was obtained in the same manner as in Example 1 except that a 22-μm-thick porous film was obtained by stretching twice. Table 2 shows the properties of the obtained porous film. The porous film of Comparative Example 1 was not satisfactory in liquid impermeability.

Comparative Example 2 Instead of the surface-treated calcium carbonate, heavy calcium carbonate having an average particle size of 2.0 μm and not subjected to surface treatment with acrylic acid was used, and the stretching ratio was 2.1 times in length and 1.4 times in width. A porous film was obtained in the same manner as in Example 1, except that a porous film having a thickness of 35 μm was obtained by performing double stretching. Table 2 shows the properties of the obtained porous film. The porous film of Comparative Example 2 was not satisfactory in liquid impermeability.

Comparative Example 3 A porous film was obtained in the same manner as in Example 1 except that the stretching temperature was changed to 95 ° C. Table 2 shows the properties of the obtained porous film. The porous film of Comparative Example 3 was
The moisture permeability was not satisfactory.

Example 4 The mixing ratio of the polyolefin resin and the surface-treated calcium carbonate was changed to 60/40 as shown in Table 1, and the thickness was 67 μm.
A porous film was obtained in the same manner as in Example 1 except that a 35 μm-thick porous film was obtained by stretching the m-shaped sheet material 1.6 times in length and 1.2 times in width.
Table 2 shows the properties of the obtained porous film.

Example 5 As shown in Table 1, the mixing ratio of the polyolefin resin and the surface-treated calcium carbonate was changed to 35/65 and the thickness was changed to 105/65.
A porous film was obtained in the same manner as in Example 1, except that a 35-μm-thick porous film was obtained by stretching a μm sheet-like material 2.3 times in length and 1.3 times in width. Table 2 shows the properties of the obtained porous film.

Example 6 Using a surface-treated calcium carbonate having an average particle size of 2.0 μm, a sheet having a thickness of 96 mm was 2.0 times in length and 1.times. In width.
A porous film was obtained in the same manner as in Example 1 except that a porous film having a thickness of 37 μm was obtained by stretching three times. Table 2 shows the properties of the obtained porous film.

[0069]

[Table 1]

[0070]

[Table 2]

[0071]

Industrial Applicability The polyolefin porous film of the present invention is a porous film which is excellent in appearance and moisture permeability and has a very good liquid impermeability and good texture.
Therefore, it can be effectively used for various materials such as medical materials and sanitary materials which require liquid impermeability, especially for liquids having high moisture permeability and permeability, and can be suitably used particularly as disposable surgical wear materials and sanitary products.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI theme coat ゛ (reference) A41D 13/12 A61F 13/18 320 A61F 13/15 F term (reference) 3B011 AA01 AA02 AB06 AC08 AC18 3B029 BC03 BC06 4C003 CA06 4F074 AA16 AA20 AC26 CA03 CA04 CA06 CC02Y DA10 DA23 DA24 DA38 4J002 BB001 BB031 BB051 BB121 DE076 DE106 DE136 DE146 DE236 DG046 DG056 DJ016 DJ036 DJ046 FB086 FD016 GB00 GK00

Claims (3)

[Claims] 1. A polyolefin film in which a polyolefin composition in which an inorganic filler is dispersed is made porous by stretching, and the moisture permeability (A) and the thickness (B) (μm) of the film are obtained.
2000 ≦ A ≦ 1929.7 × exp ^0.0273B , the film thickness is in the range of 20 to 45 μm, and the peak top pore diameter in the pore diameter distribution measurement of the film is 0.03 to 0.20 μm. A polyolefin-based porous film, characterized in that: 2. The polyolefin porous film according to claim 1, wherein the blending ratio of the polyolefin and the inorganic filler is 30 to 60% by weight of the polyolefin, and the inorganic filler is 70 to 40% by weight. 3. A disposable surgical gown comprising the polyolefin-based porous film according to claim 1.