JP3166279B2 - Porous film or sheet and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a porous film or sheet and a method for producing the same. Specifically, due to the synergistic action between the modification by the radical generator and the plasticizer, the surface strength and tearing degree are high, and there is no stretching unevenness of the film.
The present invention relates to a porous film or sheet and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, a porous synthetic resin film, which does not allow water droplets to pass through but has fine pores enough to allow a gas such as water vapor to pass, has been used in the field of clothing and the medical field. This has the effect of preventing stuffiness and preventing the liquid from leaking out. More specifically, it is often used in diapers, raincoats, sheets and the like.

A typical method for producing this porous film or sheet having air permeability is to add an inorganic filler to a synthetic resin,
For example, there is a method in which calcium carbonate, talc, clay, or the like is mixed, formed into a film, and then stretched to generate fine cracks in the film. The porous film or sheet thus obtained is anisotropic, especially in the longitudinal direction (stretching direction).
There was a problem in physical properties such as balance of tensile strength in the lateral direction and surface strength. Some of the present inventors have previously solved the above problems by molding and stretching a composition comprising a specific amount of linear polyethylene, branched low-density polyethylene, a radical generator and a filler. A method for manufacturing a film or sheet was proposed (US Pat. No. 5,015,015).
521).

[0004]

DISCLOSURE OF THE INVENTION The present inventors have made intensive studies to provide a film or sheet having further improved tear strength, uneven stretching and unevenness in film thickness.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted various studies on the composition, molding method, etc. in order to solve the above-mentioned problems. As a result, it has been found that a special plasticizer is added and a radical generator is used. As a result, they have found that the problem can be solved, and have completed the present invention.

That is, the gist of the present invention is that the density is 0.93.
0 g / cm ³ or less, a melt index 2 g / 10 minutes or less of the polyolefin resin (A) 100 parts by weight of filler (B) 100 to 400 parts by weight, molecular weight of 100 or more having an ester bond or amide bond in the molecule, normal pressure A composition comprising a plasticizer (C) 1 to 100 parts by weight, which is a compound having a boiling point of 200 ° C. or higher and a melting point of 100 ° C. or lower, and 0.0001-0.1 part by weight of a radical generator (D). A porous film or sheet obtained by inflation molding and obtained by uniaxially stretching the obtained film or sheet in a take-off direction, and a method for producing the same.

Hereinafter, the present invention will be described in more detail. The polyolefin resin (A) is made of a homopolymer of ethylene or propylene or a copolymer of ethylene or propylene and another comonomer (a compound having at least one double bond having 4 or more carbon atoms in the molecule).
930 g / cm ³ or less, melt index (MI) 2 g
/ 10 minute or less polyolefin-based thermoplastic resin, for example, low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ultra-low-density polyethylene having a density of 0.910 or less, polypropylene, ethylene-propylene copolymer, Ethylene-propylene-diene copolymer, ethylene-methacrylic acid ester or a mixture thereof may be used.
-0.95 g / cm ³ linear low density polyethylene 50-1
Ethylene-α having a density of less than 0.91 g / cm ³ and a weight of 00 parts by weight
- Density 0.930 g / cm ³ consisting of an olefin copolymer 50-0 parts by weight or less, in particular, from 0.900 to 0.92
It is a polyolefin-based thermoplastic resin of 5 g / cm ³ and MI 2 or less, particularly 0.1 to 1.5.

[0008] The linear low-density polyethylene is a copolymer of ethylene and another α-olefin, for example, ethylene and about 4 to 17% by weight, preferably about 5 to 15% by weight of 1-butene, 1-hexene, 1-octene, 1
It is produced by copolymerizing with other α-olefins such as -decene, 4-methyl-1-pentene and the like using a Ziegler type catalyst or a Phillips type catalyst used for the production of high-density polyethylene at medium and low pressures.

The ethylene-α-olefin copolymer is usually a copolymer of ethylene and an α-olefin having 3 or more carbon atoms, and has a density of 0.91 g / cm ^3.
Is preferably less than 0.85 and more preferably less than 0.85-0.
It is 90 g / cm ³ . As the α-olefin having 3 or more carbon atoms to be copolymerized with ethylene, propylene, 1-
Butene, 1-pentene, 1-hexene, 4-methyl-1
-Pentene; and non-conjugated dienes such as 1,4-hexadiene, dicyclopentadiene, and ethylidene norbornene.

[0010] The ethylene-α-olefin copolymer is prepared by using a Ziegler-type catalyst, particularly a catalyst comprising a vanadium compound such as vanadium oxytrichloride or vanadium tetrachloride and an organoaluminum compound to obtain ethylene and α-olefin.
-The copolymer can be produced by copolymerizing an olefin, the ethylene content in the copolymer is in the range of 40 to 90 mol%, and the α-olefin content is 10 to 60 mol%.
It is desirably in the range of mol%. The above ethylene-α-
Commercially available olefin copolymers include, for example, CdF
Chimie E. P. NORSOFLEX (FW
1600, FW1900, MW1920, SMW244
0, LW2220, LW2500, LW2550); Nippon Unicar Flex Resin (DFDA1137,
DFDA1138, DEFD1210, DEFD904
2); Tuffmer (A4085, A40) of Mitsui Petrochemical Company
90, P0180, P0480), Nippon Synthetic Rubber J
SR-EP (EP02P, EP07P, EP57P) and the like.

When the density (ρ) of the polyolefin resin (A) alone or as a mixture is larger than 0.930 g / cm ³ , the synergistic effect of the plasticizer and the radical generator is small, and the tear strength is not improved. If the MI is more than 2 g / 10 minutes, the tear strength of the film decreases, and the molding stability decreases.

In the method of the present invention, the melt index (MI) is J, which is a reference standard of JIS K 6760.
It is a value measured based on the condition 4 of Table 1 of IS K7210. In addition, a heat stabilizer, an ultraviolet stabilizer, a pigment, an antistatic agent, a fluorescent agent, and the like may be added to the polyolefin resin according to a conventional method.

Next, inorganic and organic fillers are used as the filler of the component (B). Inorganic fillers include calcium carbonate, talc, clay, kaolin, silica, diatomaceous earth, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, aluminum hydroxide, zinc oxide, magnesium hydroxide, calcium oxide, magnesium oxide , Titanium oxide, alumina, mica, asbestos powder, glass powder, shirasu balloon, zeolite, silicate clay, etc., and calcium carbonate, talc, clay, silica, diatomaceous earth, barium sulfate and the like are particularly preferable.

As the organic filler, cellulosic powders such as wood powder and pulp powder are used. These may be used alone or as a mixture. The average particle size of the filler is 30
μm or less, more preferably 10 μm or less, and most preferably 0.7 to 5 μm. If the particle size is too large, the denseness of the pores of the stretched product will be poor. If the particle size is too small, dispersibility in the resin will be poor and moldability will be poor.

The surface treatment of the filler is preferably carried out in view of the dispersibility in the resin and the stretchability, and the treatment with a fatty acid or a metal salt thereof gives preferable results. The plasticizer of the component (C) has an ester bond or an amide bond in the molecule and has a molecular weight of 100 or more, preferably 150 or more.
Above, especially, the boiling point at 200 to 1000 normal pressure is 200 ° C.
Or more, preferably 250 ° C. or more, particularly 250 to 70
It is a compound having a melting point of 0 ° C. and a melting point of 100 ° C. or lower, preferably 50 ° C. or lower, particularly −100 to 10 ° C.

For example, there may be mentioned an ester of a carboxylic acid having 6 or more carbon atoms and an alcohol having 5 or more carbon atoms or an aliphatic amide having 10 to 25 carbon atoms, which satisfies the above physical properties. Among them, esters of aromatic carboxylic acids and aliphatic alcohols having 6 or more carbon atoms, preferably esters of aromatic dicarboxylic acids or aromatic tricarboxylic acids and aliphatic alcohols having 6 to 18 carbon atoms, particularly aromatic dicarboxylic acids Esters of acids and aliphatic alcohols having 8 to 15 carbon atoms, and esters of aromatic tricarboxylic acids and aliphatic alcohols having 6 to 10 carbon atoms are preferred.

Specific examples of these compounds include, for example, stearic acid amide, oleic acid amide, triisodecyl trimellitate, trioctyl trimellitate,
Diisodecyl phthalate, dioctyl phthalate and the like. Most preferred are trioctyl trimellitate and diisodecyl phthalate.

If the melting point is higher than 100 ° C., the effect of improving the tear strength by modification with a radical generator is small, and if the boiling point is lower than 200 ° C., the formability and stretchability deteriorate due to smoking and foaming during molding. On the other hand, if the molecular weight is small, bleeding of the plasticizer from the film is unfavorably fast.

Next, as the radical generator of the component (D) used in the present invention, the decomposition temperature at which the half life is 1 minute is 1
Those having a temperature in the range of 30 to 300 ° C., preferably 160 to 260 ° C. are preferable, for example, dicumyl peroxide, 2,
5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-bis (t-butylperoxy) -3-hexyne, α, α′-bis (t-butylperoxy) Peroxides such as (isopropyl) benzene, dibenzoyl peroxide, and di-t-butyl peroxide 2,5-dimethylhexane-2,5-dihydroperoxide. Most preferably, 2,5-dimethyl-2,5-bis (t-butylperoxy) -3-hexyne is used.

In the present invention, 100 to 40 parts by weight of the polyolefin resin (A) and 100 to 40 parts of the filler (B) are used.
0 parts by weight, preferably 120 to 300 parts by weight, in particular,
130 to 250 parts by weight, 1 to 100 parts by weight of plasticizer (C), preferably 2 to 50 parts by weight, particularly 2 to 30 parts by weight, and 0.0001 to 0.1 part by weight of radical generator (D) It is preferably used in the range of 0.0005 to 0.07 parts by weight, particularly 0.005 to 0.05 parts by weight. If the proportion of the filler (B) is less than 100 parts by weight, pores are not sufficiently formed in the stretched film, and the degree of porosity is low. On the other hand, when the proportion of the filler exceeds 400 parts by weight, kneading properties, dispersibility, film or sheet formability are inferior, and the surface strength of the stretched product is further reduced.

If the plasticizer (C) is less than 1 part by weight,
There is no effect of improving the tear strength, if more than 100 parts by weight,
The kneading property and the dispersing property are deteriorated, and the film formability is lowered and the stretchability cannot be secured.

The radical generator (D) is 0.0001 to
It is selected from the range of 0.1 parts by weight, and if less than this range, improvement in tear strength due to a synergistic effect with a plasticizer cannot be obtained, and if it is more than this range, the melt index is too low, It is not preferable because the film is likely to be cut during the film formation and the surface of the film becomes rough.

In the present invention, the polyolefin resin (A), the filler (B), the plasticizer (C), and the radical generator (D) are usually used in the above amounts by the following method I or II, for example. After mixing at a ratio and then kneading to form a pellet, inflation molding is performed to obtain an unstretched film.
Method I: A polyolefin resin, a filler, a plasticizer, and a radical generator are mixed, kneaded using a kneader such as an extruder or a Banbury mixer, and then pelletized, and the pellets are used for inflation molding. Method II: A large amount of radical generator 0.3 to 2% in polyolefin resin
(3000 to 20,000 ppm), and a master batch is prepared in advance by melting and kneading at a temperature at which the radical generator hardly reacts with the polyolefin and at a temperature equal to or higher than the melting point of the polyolefin to form a pellet. The mixture is mixed with a polyolefin resin, a filler and a plasticizer, kneaded and then pelletized, and the pellets are used for inflation molding.

When the polyolefin resin is kneaded with a radical generator under heating (preferably at a temperature not lower than the temperature at which the half-life of the radical generator is 10 minutes) according to the method described in the above I or II, the crosslinking by the radical generator A reaction occurs, and polyolefins are intermolecularly coupled to increase the high molecular weight component, thereby obtaining a modified polymer having a reduced melt index. This modified polymer is more likely to be oriented in the transverse direction at the time of inflation molding than the polymer before modification, and the film thus obtained, when subjected to a stretching treatment, has significantly improved tensile strength and impact strength. .

To mix the polyolefin resin, plasticizer, radical generator and filler, a drum, a tumbler type mixer, a ribbon blender, a Henschel mixer, a super mixer, etc. are used. A mixer of a mold is desirable, and the polyethylene is preferably supplied in the form of a powder of usually 10 to 150 mesh, especially 20 to 60 mesh. The kneading of the obtained mixture is carried out using a well-known kneading device such as a screw extruder, a twin-screw extruder, a mixing roll, a Banbury mixer, a twin-screw kneader and the like.

In the present invention, an unstretched film having a thickness of 10 to 200 μm or an unstretched sheet having a thickness of 200 to 400 μm is usually formed from the composition obtained above by an inflation method. Is stretched. Inflation molding is usually performed at a blow-up ratio (BUR) of 2 to 8.

Preferably, the blow-up ratio is 3 to 6, and the height of the frost line is 2 to 5 times the diameter of the annular slit of the die.
Make it 0 times. More preferably, it is carried out under the condition that the height of the frost line is in the range of 5 to 20 times the diameter of the annular slit of the die. When the blow-up ratio is lower than the above range, the tensile strength and impact strength of the film are reduced, and when the blow-up ratio is higher than the above range, the molding stability of the bubble is lowered. When the height of the frost line is lower than the above range, the tensile strength of the film decreases, and when the height is higher than the above range, the molding stability of the bubble decreases.

The unstretched film or sheet formed by the inflation method is then uniaxially stretched in the machine direction (the direction in which the film is taken off). The uniaxial stretching is usually performed by a roll stretching method, but may be a tubular stretching method in which the uniaxial direction (drawing direction) is emphasized. The stretching may be performed in one stage or in two or more stages.

The stretching treatment is performed at 100 ° C. from the melting point of the resin composition.
It is preferably carried out in a temperature range from a low temperature to 20 ° C. lower than the melting point, particularly in a range from 90 ° C. lower than the melting point of the resin composition to 50 ° C. lower than the melting point. Occurs, and at temperatures above this range the porosity of the film tends to decrease.

The stretching ratio is preferably 1.2 to 8 times. In addition, if heat treatment is performed after uniaxial stretching, the dimensional accuracy of the film can be stabilized, and a known corona treatment,
Surface treatment such as frame treatment can also be performed. The porous film or sheet of the present invention thus obtained has a high surface strength and a high tear strength and has no stretching unevenness, so that it can be suitably used. In particular, in the case of a porous film having a thickness of 100 μ or less, preferably 15 to 50 μ, both the softness in the longitudinal direction and the horizontal direction are 50 mm or less, preferably 10 to 10 μm.
In 35mm, moisture permeability of 1500g / m ² · 24hr or more,
Preferably, 2500 to 5000 g / m ² · 24 hr
And the surface strength is the following formula (1)

[0031]

## EQU3 ## Surface strength [kg] ≧ 35 × film thickness [mm] (1) Preferably, formula (1 ′),

[0032]

(4) The surface strength [kg] ≧ 50 × film thickness [mm] (1 ′) is satisfied and the tear strength is expressed by the following formula (2).

[0033]

[Mathematical formula-see original document] Tear strength [g / sheet] ≥ 1500 x film thickness [mm] (2)

[0034]

## EQU6 ## It is preferable because a film satisfying the following formula is satisfied: tear strength [g / sheet] ≧ 1800 × film thickness [mm] (2 ′).

[0035]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which, however, are not intended to limit the scope of the present invention.

Example 1 (1) Linear low-density polyethylene Melt index (MI): 1.0 g / 10 min, flow ratio: 19, density (ρ): 0.921 g / cm ³ , copolymer component: 1 -Butene, copolymerization amount: 10% by weight, melting point: 120 ° C., pulverized into a 40-mesh powder, and 80 parts by weight of ethylene-propylene copolymer (EPR, manufactured by Nippon Synthetic Rubber Co., Ltd.)
P07P, MI: 0.4 g / 10 min, ρ: 0.86 g /
cm ³ ) was also ground into 40 mesh powder, and 20 parts by weight was stirred and mixed in a Henschel mixer. The MI of the obtained polymer composition was 0.8 g / 10 min, and the density was 0.909 g / cm ³ . Next, 4 parts by weight of dioctyl phthalate as a plasticizer and 0.02 parts by weight of a radical generator 2,5-dimethyl-2,5-bis (t-butylperoxy) -3-hexyne were added and mixed with stirring. Furthermore, calcium carbonate (average particle size 1.2 μm,
Fatty acid treatment) was added and mixed by stirring.

The mixture thus obtained is mixed with a twin-screw kneader D
SM-65 (Double Screen Mixer,
The mixture was kneaded and granulated using Nippon Steel Works Co., Ltd.). This was blown formed by a 40 mmφ extruder to form a film having a thickness of 70 μm. Extrusion conditions are as follows. Cylinder temperature: 170-190-210-230 ° C Head and die temperature: 200 ° C Die diameter: 100mm Take-up speed: 8m / min Blow-up ratio: 3 Frost line height: 700mm Folding diameter: 471mm

The film thus obtained was slit in the take-off direction and uniaxially stretched by a roll stretching machine. The stretching conditions were as follows. Stretching temperature: 60 ° C Stretching ratio: 2.0 times Speed after stretching: 11.0 m / min Film thickness after stretching: 30 μm

The physical properties were evaluated as follows and the results are shown in Table 1.
It was shown to. 1) Moisture permeability: according to ASTM E26-66 (E). 2) Tear strength: The tearing direction of the film is measured according to JIS P 8116, and the strength per sheet is obtained in g. 3) Surface strength: A film sample is cut into a square of 100 mm x 100 m, and is fixed by sandwiching between two donut-shaped pressing rings having an inner diameter of 80 mm. The thickness is 2 in the center of the film
A 0 mm round bar is used to push a hemispherical plunger with a radius of 10 mm at the tip at a speed of 500 mm / min. The pressing distance when the film breaks is defined as elongation, and the strength at that time is defined as surface strength. 4) Moldability: Visually determined according to the following criteria. ：: Bubble stable, no die line ○: Bubble stable, die line present Δ: Film width variation ×: Molding not possible 5) Flexibility: Hand feel was determined according to the following criteria. ：: Extremely soft ○: Soft △: Slightly hard ×: Hard 6) Stretchability ：: No cutting, uniform stretching, no stretching unevenness ○: No cutting, stretching unevenness, almost none △: No cutting, stretching unevenness, slightly × : Large cutting or stretching unevenness

Example 2 80 parts by weight of the linear low-density polyethylene used in Example 1,
Ethylene-butene-rubber (manufactured by Mitsui Petrochemical Co., Ltd., Tuffmer A4085, MI: 3.6 g / 10 min, ρ: 0.88
g / cm ³ ) (Tuffmer is a trade name) in an amount of 20 parts by weight (the density of the composition when these are mixed is 0.913 g / cm ³ ).
^{At 3} , MI is 1.3 g / 10 min. ), 6 parts by weight of trioctyl trimellitate as a plasticizer, 0.03 parts by weight of 2,5-dimethyl-2,5-bis (t-butylperoxy) -3-hexyne as a radical generator, and calcium carbonate 200 parts by weight were used. A film was obtained in the same manner as in Example 1 except that the frost line height was 800 mm among the molding conditions. Table 1 shows the evaluation results.

Example 3 80 parts by weight of the linear low-density polyethylene used in Example 1 was mixed with ultra-low-density polyethylene (CDF Chemie).
E. FIG. P. FW1900, MI: 1.0 g / 10
Ρ: 0.900 g / cm ³ ) and 20 parts by weight (the density of the composition when these are mixed is 0.917 g / cm ³ ,
MI is 1.0 g / 10 min. ), 3 parts by weight of diisodecyl phthalate as a plasticizer, 0.02 parts by weight of the same radical generator as in Example 1, and 200 parts by weight of calcium carbonate. Among the molding conditions, set the frost line height to 1
Example 1 except that the drawing magnification was 2.1 times and the drawing magnification was 2.1 times.
A film was obtained in the same manner as described above. Table 1 shows the evaluation results.

Example 4 As a linear low-density polyethylene (MI: 0.5 g / 10
Min, flow ratio: 20, density: 0.921 g / cm ³ , copolymerization component: 1-butene, copolymerization amount: 10% by weight, melting point: 12
80 parts by weight), 20 parts by weight of ethylene-butene-rubber used in Example 2 (the density of the composition when these are mixed is 0.909 g / cm ³ and the MI is 0.5 g /
10 minutes. ), 4 parts by weight of diisodecyl phthalate as a plasticizer and 0.04 of the same radical generator as in Example 1.
3 parts by weight and 200 parts by weight of calcium carbonate were used. A film was obtained in the same manner as in Example 1, except that the frost line height was 800 mm and the stretching ratio was 2.5 times. Table 1 shows the evaluation results.

Example 5 80 parts by weight of the linear low-density polyethylene used in Example 4 and 20 parts by weight of the ethylene-butene rubber used in Example 2 (the density of the composition when these were mixed) Is 0.913 g / cm ³ and MI is 0.7 g / 10 min.), 4 parts by weight of oleamide as a plasticizer, 0.02 parts by weight of the same radical generator as in Example 1, and 200 parts by weight of calcium carbonate. Parts by weight were used. A molding film was obtained in the same manner as in Example 1 except that the stretching ratio was 2.2. Table 1 shows the evaluation results.

Example 6 The same linear low-density polyethylene as used in Example 1 was used.
0 parts by weight, 4 parts by weight of trioctyl trimellitate as a plasticizer, the same radical generator as used in Example 1.
03 parts by weight and 200 parts by weight of calcium carbonate were used. A film was obtained in the same manner as in Example 1 except that the frost line height was set to 600 mm among the molding conditions. Table 1 shows the evaluation results.

Example 7 A film was obtained in the same manner as in Example 1 except that the radical generator was 2,5-dimethyl-2,5 di (t-butylperoxy) hexane. Table 1 shows the evaluation results. Comparative Example 1 A film was obtained in the same manner as in Example 1 except that no plasticizer was used. Table 1 shows the evaluation results. Comparative Example 2 A film was obtained in the same manner as in Example 1 except that the radical generator was not used. Table 1 shows the evaluation results.

Comparative Example 3 A film was obtained in the same manner as in Example 2 except that no plasticizer was used. Table 1 shows the evaluation results. Comparative Example 4 A film was obtained in the same manner as in Example 2 except that the radical generator was not used. Table 1 shows the evaluation results. Comparative Example 5 A film was obtained in the same manner as in Example 2 except that the plasticizer and the radical generator were not used. Table 1 shows the evaluation results.

Comparative Example 6 A film was obtained in the same manner as in Example 6, except that 120 parts by weight of the plasticizer was used and the frost line height under the molding conditions was 700 mm. Table 1 shows the evaluation results. Comparative Example 7 A film was obtained in the same manner as in Example 1, except that 4 parts by weight of ethylenebisstearylamide (melting point: 145 ° C) was used as a plasticizer. Table 1 shows the evaluation results. Comparative Example 8 A film was obtained in the same manner as in Example 1, except that 4 parts by weight of dimethylformamide (boiling point: 153 ° C) was used as a plasticizer. Table 1 shows the evaluation results.

Comparative Example 9 In Example 2, no linear low-density polyethylene was used.
Example 2 was repeated except that 100 parts by weight of ethylene-butene-rubber was used, 4 parts by weight of trioctyl trimellitate was used as a plasticizer, 0.03 part by weight of a radical generator was used, and the height of the frost line was 700 mm. A film was obtained in the same manner. Table 1 shows the evaluation results.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

Industrial Applicability The porous film of the present invention is particularly excellent in tear strength and surface strength, and has little stretching unevenness, and can be advantageously used in applications such as diapers, raincoats, and sheets.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ identification code FIB29L 7:00 C08L 23:00 (58) Investigated field (Int.Cl. ⁷ , DB name) C08J 9/00 B29C 55/04 B29C 55/28

Claims (10)

(57) [Claims] 1. 100 parts by weight of a polyolefin resin (A) having a density of 0.930 g / cm ³ or less and a melt index of 2 g / 10 minutes or less, 100 to 400 parts by weight of a filler (B), and an ester bond or an amide bond in the molecule. 1-100 parts by weight of a plasticizer (C) which is a compound having a molecular weight of 100 or more, a boiling point at normal pressure of 200 ° C. or more and a melting point of 100 ° C. or less, and a radical generator (D) 0.0001-0.1
A porous film or sheet obtained by inflation-molding a composition comprising the following components by weight, and uniaxially stretching the obtained film or sheet in the take-off direction. 2. A porous film having a thickness of not more than 90 μm, having a softness in both longitudinal and transverse directions of not more than 50 mm, a moisture permeability of not less than 1500 g / m ² · 24 hr, and a surface strength of not more than (1) Formula (1) Surface strength [kg] ≧ 35 × Film thickness [mm] (1) and tear strength of the following formula (2) Formula (2) Tear strength [g / sheet] ≧ 1500 × film thickness [mm] (2). The porous film according to claim 1, wherein: 3. The plasticizer (C) has a molecular weight of 200 to 1000 having an ester bond or an amide bond in the molecule.
Boiling point at normal pressure is 250-700 ° C and melting point is -10
The porous film or sheet according to claim 1, which is a compound at 0 to 10C. 4. A plasticizer (C) having an ester bond or an amide bond in the molecule and having a molecular weight of 100 or more, a boiling point at normal pressure of 200 ° C. or more, and a melting point of 100 ° C. or less and a carbon number of 6 or more. The porous film or sheet according to claim 1, which is an ester of an acid and an alcohol having 5 or more carbon atoms or an aliphatic amide having 10 to 25 carbon atoms. 5. The porous film or sheet according to claim 4, wherein the ester is an ester of an aromatic carboxylic acid and an aliphatic alcohol having 6 or more carbon atoms. 6. The porous film or sheet according to claim 4, wherein the ester is an ester of an aromatic dicarboxylic acid or an aromatic tricarboxylic acid with an aliphatic alcohol having 6 to 18 carbon atoms. 7. The porous film or sheet according to claim 4, wherein the ester is trioctyl trimellitate or diisodecyl phthalate. 8. The porous film or sheet according to claim 1, wherein the decomposition temperature at which the half-life of the radical generator (D) is 1 minute is 130 to 300 ° C. 9. The porous film according to claim 1, wherein the radical generator (D) is 2,5-dimethyl-2,5-bis (t-butylperoxy) -3-hexyne. Sheet. 10. 100 parts by weight of a polyolefin resin (A) having a density of 0.930 g / cm ³ or less and a melt index of 2 g / 10 minutes or less, 100 to 400 parts by weight of a filler (B), and an ester bond or an amide bond in the molecule. A plasticizer (C) having a molecular weight of at least 100, a boiling point at normal pressure of at least 200 ° C. and a melting point of at most 100 ° C.
0 parts by weight, and a radical generator (D) 0.0001-
0.1 parts by weight, after passing the conditions under which the radical generator decomposes, or while inflation molding at a blow-up ratio of 2 to 8, the resulting film or sheet in the direction of its take-off Stretch ratio 1.2 ~
A method for producing a porous film or sheet, wherein the film is stretched uniaxially by 8 times.