JP2002249622A - Porous film and preparation method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a porous film having an excellent strain elongation strength along a mechanical stress, excellent flexibility and good touch feeling. SOLUTION: The porous film is prepared by molding a resin composition consisting of 25-55 wt.% of a polyolefin-based resin and 75-45 wt.% of an inorganic filler, where the polyolefin-based resin contains 10-70 wt.% of at least one kind of resin selected from high-density polyethylenes and polypropylenes each having a density of 0.930-0.975, 88-15 wt.% of a linear low-density polyethylene having a density of 0.905-0.930 and 2-15 wt.% of a branched low-density polyethylene.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a porous film and a method for producing the same. More specifically, the present invention relates to a porous film which has low mechanical strain and high elongation strength, is suitable for constant pitch printing, has good moisture permeability, and has good texture, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a film in which an inorganic filler and various oils, waxes, etc. are added to a polyolefin resin is stretched in at least one axial direction, and voids are generated due to interfacial separation between the inorganic filler and the polyolefin. Many methods have been proposed for producing porous films. Since these porous films have a large number of minute voids inside, they do not allow liquid to permeate while having high moisture permeability. Taking advantage of this property, it is widely used in sanitary materials such as disposable diapers, building materials, reflective films, battery separators, and the like.

[0003] In disposable diapers, porous films which have been subjected to various printings in recent years have been used. Printing is preferably performed on a specific portion of the diaper, and for that purpose, it is necessary that the printing pitch does not shift. The printing pitch deviation is apt to occur when the film is stretched too much in the machine direction during printing, and a film with little stretching is required.

[0004] Conventionally, as a porous film used as a material for disposable diapers, linear low-density polyethylene has been exclusively used as a polyolefin resin from the viewpoint of improving flexibility. However, although such a film is excellent in flexibility, it has a drawback that the film stretches during printing. Further, a small heat shrinkage in the machine direction also has a good effect on the pitch deviation.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to have the same level of moisture permeability as a conventional product, to have excellent low strain elongation in the machine direction, to be flexible, and to have a good feeling. To provide a porous film suitable for printing at a constant pitch.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that, when producing a porous film containing a polyolefin resin and an inorganic filler, the polyolefin resin (1) has a high specific density. It is possible to solve the above problem by using at least one kind of high-density polyethylene and polypropylene, (2) a linear low-density polyethylene of a specific density, and (3) a branched low-density polyethylene of three kinds of specific amounts. Heading, the present invention has been reached.

That is, the present invention relates to a porous film formed from a resin composition containing 25 to 55% by weight of a polyolefin resin and 75 to 45% by weight of an inorganic filler, wherein the polyolefin resin has a density of 0.1%. 930-0.9
10 to 70% by weight of at least one resin selected from high-density polyethylene and polypropylene having a density of 0.
905 to 0.930 linear low density polyethylene 88-1
It is a porous film containing 5% by weight and 2 to 15% by weight of a branched low-density polyethylene.

In a preferred embodiment of the porous film according to the present invention, 0.5 to 5 parts by weight of at least one dispersant selected from hardened castor oil and dehydrated castor oil is contained with respect to 100 parts by weight of the resin composition. The porous film, which contains 0.5 to 5 parts by weight of a liquid ethylene-α-olefin oligomer based on 100 parts by weight of the resin composition, and the resin composition 100
The porous film contains 0.5 to 10 parts by weight of at least one lubricant selected from ethylene bisstearic acid amide and methylene bisstearic acid amide with respect to parts by weight.

The porous film according to the present invention has at least 5% of the machine direction of 18 g / 25 mm / (g / m ² ).
Elongation strength and at least 27 g / 25 mm / (g /
m ² ) having at least one property selected from a 10% elongation strength in the machine direction, and a rigidity in the machine direction of 2.
7 mm / (g / m ² ) or less, moisture permeability 1500 g / m ² ·
The basis weight is 10 to 35 g / m ² for 24 hours or more. Further, the heat shrinkage in the machine direction is more preferably 3% or less.

The porous film according to the present invention having the above properties is obtained by forming the resin composition into a film, stretching the obtained film at least 1.5 to 3 times in the machine direction to form a porous film, , 90-120 ° C, and heat-set for at least 0.004 minutes while controlling the shrinkage in the machine direction at 10-25%.

[0011] The porous film of the present invention has the same level of moisture permeability as conventional products, is excellent in low strain elongation in the machine direction, is rich in flexibility, and has good texture.
Therefore, it is useful as a material for sanitary articles worn on human skin such as disposable diapers and sanitary pads.
In particular, because of its excellent low strain elongation strength in the machine direction,
When performing printing or the like on the sanitary article, a clear pattern or the like can be obtained without shifting the printing pitch.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. When the porous film of the present invention is used to produce a porous film containing a polyolefin resin and an inorganic filler, at least one of (1) high-density polyethylene and polypropylene having a specific density is used as the polyolefin resin.
Using a specific amount of three types of resins, (2) linear low-density polyethylene having a specific density and (3) branched low-density polyethylene, and forming a resin composition in which an inorganic filler is added thereto, into a film. The film is produced by stretching the obtained film at least in the machine direction to form a porous film, and then heat-setting.

The high-density polyethylene used in the present invention is a homopolymer of ethylene and has a density of 0.930 to 0.97.
0 g / cm ³ . Commercial products are Mitsui Chemicals, Inc.
Product name: HIZEX 3300F [Density: 0.95
4 g / cm ³ , melt index (hereinafter referred to as MI): 1.1 g / 10 min], and Hyzex 500
0SF [density: 0.959 g / cm ³ , MI: 0.65 g
/ 10 min].

The polypropylene is a homopolymer of propylene or a copolymer of propylene and another α-olefin, having a density of 0.900 to 0.940 g / cm
³ , MI is 0.1 to 30.0 g / 10 min. Commercially available polypropylene, manufactured by Grand Polymer Co., Ltd., trade name: F103WH (density: 0.910
g / cm ³ , MI: 2.4 g / 10 min).

In the present invention, at least one resin of the above-mentioned high-density polyethylene and polypropylene, that is,
High-density polyethylene or polypropylene may be used alone or a mixture of both. The amount of the high-density polyethylene and polypropylene used affects the low strain elongation strength, stiffness, texture, and the like of the obtained porous film. If these amounts are large, the softness increases, and when touched by hand, a rough sound is made and the texture becomes poor. Conversely, if the amount is small, the low strain elongation strength decreases. With this in mind,
The amount of at least one resin selected from high-density polyethylene and polypropylene is preferably 10 to 70% by weight of the total amount of the polyolefin-based resin.

The linear low-density polyethylene has a density of 0.905 to 0.930 g / cm ³ and an MI of 0.1 to 2
What is 0.0g / 10min is used. Commercially available linear low-density polyethylene is available from Mitsui Chemicals, Inc.
Product name: Ultzex UZ2021L (density: 0.9
20 g / cm ³ , MI: 2.1 g / 10 min), Evolu SP2540 (density: 0.925 g / cm ³ , M
I: 4.0 g / 10 min). The amount of the linear low-density polyethylene used affects the strength and rigidity of the obtained porous film. If the amount is large, the strength is reduced. Conversely, if less, the flexibility increases. Considering this point, the amount of the linear low-density polyethylene is preferably 88 to 15% by weight of the total amount of the polyolefin-based resin.

As the branched low-density polyethylene, density
Is 0.910 to 0.940 g / cm ^Three, MI is 0.1 ~
What is 20.0 g / 10min is used. Commercially available
Mitsui Chemicals, Inc.
Product name: Mirason F967 (density: 0.918 g /
cm^Three, MI: 1.0 g / 10 min), Mirason 10
2 (density: 0.919 g / cm^Three, MI: 0.35 g /
10 min). Branched low density polyethylene
The amount of ren used is the uniform thickness of the resulting porous film.
Affects gender. If the amount used is small, the thickness uniformity is poor
Become From such a viewpoint, the branched low-density polyethylene
The amount used is 2 to 15 weight of the total amount of the polyolefin resin.
%.

The polyolefin resin used in the present invention may be a resin produced using a multi-site catalyst such as a Ziegler catalyst or a resin produced using a single-site catalyst such as a metallocene catalyst. You may.

The inorganic filler is, for example, calcium carbonate,
Examples thereof include barium sulfate, calcium sulfate, barium carbonate, magnesium hydroxide, aluminum hydroxide, zinc oxide, magnesium oxide, titanium oxide, silica, and talc. Of these, calcium carbonate and barium sulfate are particularly preferred. The average particle diameter of the inorganic filler is preferably 20 μm or less, more preferably 10 μm or less,
Most preferably, the thickness is 0.5 to 5 μm. Further, it is more preferable that the inorganic filler has been subjected to a surface treatment in order to improve the dispersibility with the resin. As the surface treatment agent, those capable of rendering the surface hydrophobic by coating the surface of the inorganic filler are preferable, and examples thereof include higher fatty acids such as stearic acid and lauric acid, and metal salts thereof.

The composition ratio of the polyolefin resin to the inorganic filler is 25 to 55% by weight of the polyolefin resin and 75 to 45% by weight of the inorganic filler. Preferably, the content of the polyolefin resin is 30 to 50% by weight, and the content of the inorganic filler is 70 to 50% by weight. 4 inorganic fillers
When the amount is less than 5 parts by weight, adjacent voids formed by peeling off the interface between the polyolefin resin and the inorganic filler become difficult to communicate with each other, and the air permeability deteriorates. On the other hand, if it exceeds 75 parts by weight, elongation during stretching of the film is lost, and stretching becomes difficult.

The porous film of the present invention is characterized in that it is produced from the above resin composition. As a method for improving the uniformity of the thickness, a method of adding 0.5 to 5 parts by weight of (1) hardened castor oil, dehydrated castor oil, or a mixture thereof to 100 parts by weight of the resin composition;
(2) a method of adding 0.5 to 5 parts by weight of a liquid ethylene-α-olefin oligomer, and (3) a method of adding 0.5 to 10 parts of ethylenebisstearic acid amide, methylenebisstearic acid amide, or a mixture thereof. It is effective to include the parts by weight. The methods (1) and (2) also have the effect of improving the flexibility of the porous film.

Here, the hardened castor oil is an ester of a fatty acid mixture containing at least 70% by weight of 12-hydroxyoctadecadienoic acid and glycerin. As a commercial product,
Ito Oil Co., Ltd., trade name: Custer wax. Dehydrated castor oil is defined as a mixture of glycerin and a fatty acid mixture containing at least 30% by weight of 9,11-octadecadienoic acid, at least 30% by weight of 9,12-octadecadienoic acid, and at least 70% by weight of both acids in total. It is an ester. As a commercially available product, DCO manufactured by Ito Oil Co., Ltd. may be used.

The liquid ethylene-α-olefin oligomer is obtained by copolymerizing ethylene and α-olefin, and has a kinematic viscosity at 40 ° C. (JIS K2283) of 50 to 100000 mm ² / s. . Further, an ethylene-α-olefin copolymer modified with an acid by introducing a polar group such as a maleic acid group is also preferably used. Commercially available ethylene-α-olefin oligomers include Lucant HC600 (trade name, manufactured by Mitsui Chemicals, Inc.).

Further, other additives used in ordinary resin compositions may be blended. Such additives include, for example, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, neutralizers, lubricants, antifoggants, antiblocking agents, antistatic agents, slip agents, colorants, and the like. Is mentioned.

The porous film of the present invention is produced by the following method. After mixing the polyolefin resin and the inorganic filler, and other additives as necessary, a Henschel mixer,
The mixture is mixed using a mixer such as a super mixer or a tumbler type, and then kneaded by a usual single-screw or twin-screw extruder or a tandem-type kneading extruder to form pellets. Next, the pellets are molded at a temperature equal to or higher than the melting point of the polyolefin resin, preferably equal to or higher than the melting point + 20 ° C. and lower than the decomposition temperature, by a known molding method such as an extruder equipped with a T-die or the like or an inflation molding machine equipped with a circular die. Melting and film formation using a machine. In some cases, it is also possible to form a film directly with a molding machine without pelletizing.

The formed film is formed by a known roll method,
By stretching method such as tenter method and gear stretching method, 1
The film is stretched in a temperature range of 0 ° C. or higher and lower than the softening point of the resin (a value measured by a method specified in JIS K-6760). In each method, the moisture permeability is controlled by changing the stretching ratio. The stretching direction is
The film is stretched in a direction including at least the machine direction (hereinafter, referred to as the MD direction). Biaxial stretching may be performed in the MD direction and a direction perpendicular to the MD direction (hereinafter, TD direction). In that case,
It may be performed in one stage or may be performed in multiple stages. The stretching ratio is about 1.5 to 3 times. If the stretching ratio is less than 1.5 times, sufficient moisture permeability cannot be obtained. If it exceeds three times, the heat shrinkage tends to be poor.

As a method of suppressing the heat shrinkage of the film, there is a method of heat setting the stretched film. Here, the heat setting means that after the stretching step, heat is applied to the film in advance to shrink the film intentionally, thereby suppressing the shrinkage of the formed film. As a method of heat setting, a method in which the stretched film is heated by a roll to which heat is applied (annealing roll) is used. If the temperature is too low, the heat shrinkage of the film increases, and if the temperature is too high, there occurs a problem that the film is caught on a roll and wound around. Considering this point, the heat setting temperature is 9
0-120 ° C is preferred.

The heat setting time refers to the time during which the film is in contact with the annealing roll. Number of annealing rolls is 1
The number of books may be two or more, and in the case of two or more, the heat setting time is the sum of the time when the film is in contact with each roll. If the heat setting time is not more than 0.004 minutes, the heat setting becomes insufficient, and the heat shrinkage rate deteriorates. The upper limit of the heat setting time is
It depends on the temperature of the annealing roll (heat setting temperature),
About one hour is sufficient in the above temperature range. Also,
At the time of heat setting, the annealing rate (shrinkage rate) of the film is determined by the speed difference between the annealing roll and the subsequent roll (cooling roll), but is preferably 10 to 25%. The annealing rate can be represented by {1- (cooling roll speed / annealing roll speed)} × 100. If the annealing rate is too low, the heat shrinkage of the film will increase, and if the annealing rate is too high, the film will sag during production and production will not be stable. The annealing roll is desirably made of metal to efficiently transmit heat to the film.

[0029] The porous film of the present invention can be used as described above.
The main properties are at least 18 g /
25 mm / (g / m^Two) 5% elongation strength in the machine direction and
At least 27 g / 25 mm / (g / m^Two) Machine direction
At least one property selected from 10% elongation strength
And the rigidity in the machine direction is 2.7 mm / (g / m
^Two) Below, the moisture permeability is 1500 g / m^Two・ Above 24h
Injury 10 to 35 g / m ^TwoIt is. Also, heat collection in the machine direction
More preferably, the shrinkage ratio is 3% or less.

As described above, the porous film of the present invention has a 5% elongation strength in the machine direction and / or a 10% elongation strength in the machine direction.
Since the% elongation strength is the above value, when performing printing or the like, a clear pattern or the like can be obtained without deviation of the printing pitch. In addition, since the rigidity in the machine direction is the above value, a rough sound is not generated when touched with a hand or the like, and the texture is good.

EXAMPLES Examples will be given below to describe the present invention more specifically. Note that the present invention is not limited to these examples. The moisture permeability, stiffness, strength and elongation shown in the examples are values measured by the following methods.

(1) Moisture Permeability (g / m ² · 24 hr) A sample (10 cm × 10 cm) was taken from a porous film.
Samples are taken and measured under the conditions of a temperature of 40 ° C., a relative humidity of 60% and a pure water method in accordance with the method specified in ASTME-96, and the average value is calculated. The measurement time is 24 hours. The distance between the water surface and the sample at the beginning of the measurement is 8 mm.

(2) Stiffness in machine direction (mm) Measured according to the method (cantilever method) specified in JIS-L1096. <Preparation of sample> 200m width
m, length (MD direction) 300 mm, basis weight 20 g / m ²
After wrapping a porous film of
Pull out the gold scale. The obtained flat scroll (width 25 mm,
(Length: 300 mm) is pressed back and forth once by a roller weighing 1 kg to obtain a sample.

(3) Low strain elongation strength [g / 25 mm /
(G / m ² )] From a porous film with a basis weight of 20 g / m ² , a width of 25 m
Cut out a sample with a length of 150 mm in the MD direction (MD direction). According to ASTM D882, distance between chucks 50m
m, pulling in the MD direction at a pulling speed of 500 mm / min.
m) The strength (stress) in the MD direction when stretched by 10% (5 mm) is measured.

(4) Heat shrinkage (%) in the machine direction Sample (MD: 20 cm, TD: 1c)
m) are sampled, and marked lines are inserted in the MD direction so that the distance between the marked lines is 10 cm. After leaving for 1 hour at a temperature of 60 ° C. and cooling to room temperature, the distance between the marked lines is measured with a steel measure. It is calculated by the following equation (1). S = {(N ₀ −N ₁ ) / N ₀ } × 100 (1) where S: shrinkage, N ₀ : distance between marked lines before heating, N ₁ :
Marked distance after heating.

(5) Thickness uniformity Three samples (machine direction: 21 cm, direction perpendicular to the machine direction: 5 cm) were collected from a porous film having a basis weight of 20 g / m ² , and a total of 60 samples were taken at 1 cm intervals in the vertical direction. Regarding the measurement points, use a thickness measuring device (UPACHI, manufactured by PEACOCK).
T DIALGAUGE NO. 25), the average thickness (X), the maximum thickness (MAX), and the minimum thickness (MIN) are determined, and [(MAX) − (MIN)] /
Calculate (X) and use this as the uniformity of the film thickness.

(6) Crispy sound The feeling when the film is bent. ：: There is almost no rustling sound. ：: There is a slight rustling sound.
Δ: A rustling sound is heard. ×: The rustling sound is severe.

(7) Comprehensive evaluation ：: Water vapor permeability of 1500 g / m ² · 24 hr or more, 5% elongation strength of 18 g / 25 mm / (g / m ² ) or more, and / or
Or, the 10% elongation strength is 27 g / 25 mm / (g / m ² )
As described above, the rigidity in the machine direction is 2.7 mm / (g / m ² ) or less. X: These characteristics are other than the above.

Example 1 High-density polyethylene (manufactured by Mitsui Chemicals, Inc., trade name: HIZEX 3300F, density: 0.954 g / cm ³ , M
I: 1.1 g / 10 min) 13 parts by weight (32.5% by weight in polyolefin resin), linear low density polyethylene (manufactured by Mitsui Chemicals, Inc., trade name: Evolue SP254)
0, density: 0.925 g / cm ³ , MI: 4.0 g / 1
0 min) 25 parts by weight (62.
5%), branched low-density polyethylene (Mitsui Chemicals, Inc.)
Product name: Mirason F967, density: 0.918 g /
cm ³ , MI: 1.0 g / 10 min) 2 parts by weight (5% in polyolefin resin) and 60 parts by weight of calcium carbonate (trade name: SST-40, manufactured by Dowa Calfine Co., Ltd.) using a tumbler mixer. After that, the mixture was uniformly kneaded at 230 ° C. using a tandem-type kneading extruder, and processed into pellets. The pellets were melt-formed at 240 ° C. by using an extruder equipped with a T-die.
1. between a preheated roll heated to 0 ° C. and a stretch roll;
The film is uniaxially stretched in the machine direction at a stretch ratio of 0 at a line speed of 20 m / min, and subsequently, a heat fixing roll (diameter 30)
cm) using two pieces (heat fixing time: 0.047 minutes), 85
Thermal fixation at 8 ° C and an annealing rate of 8%.
² porous films were obtained. Table 1 shows the composition of the resin composition and annealing conditions, and Table 2 shows the obtained results.

Example 2 The high-density polyethylene of Example 1 was replaced with polypropylene (manufactured by Grand Polymer Co., Ltd., trade name: F103WH, density: 0.910 g / cm ³ , MI: 2.4 g / 10 mi).
A porous film was obtained in the same manner as in Example 1 except that n) was changed. Table 1 shows the composition of the resin composition and the annealing conditions, and Table 2 shows the obtained results.

Example 3 The polyolefin resin of Example 1 was replaced with polypropylene (trade name: F103WH, manufactured by Grand Polymer Co., Ltd.).
Density: 0.910 g / cm ³ , MI: 2.4 g / 10 m
in) 18 parts by weight (45% in polyolefin resin),
Linear low-density polyethylene (manufactured by Mitsui Chemicals, Inc., trade name:
Evolu SP2540, density: 0.925 g / c
m ³ , MI: 4.0 g / 10 min) 20 parts by weight (50% in polyolefin resin), branched low-density polyethylene (manufactured by Mitsui Chemicals, Inc., trade name: Mirason F967, density: 0.918 g / cm ³⁾ , MI: 1.0 g / 10 mi
n) 2 parts by weight (5% in polyolefin resin), composition 1 comprising polyolefin resin and calcium carbonate
A porous film was obtained in the same manner as in Example 1, except that 2 parts by weight of hardened castor oil and 1 part by weight of dehydrated castor oil were added to 00 parts by weight. Table 1 shows the composition of the resin composition and the annealing conditions, and Table 2 shows the obtained results.

Example 4 The hardened castor oil of Example 3 (trade name, manufactured by Ito Oil Co., Ltd.)
A porous film was obtained in the same manner as in Example 3, except that dehydrated castor oil was removed from 2 parts by weight of caster wax and 1 part by weight of dehydrated castor oil (trade name: DCO, manufactured by Ito Oil Co., Ltd.). Table 1 shows the composition of the resin composition and the annealing conditions.
Table 2 shows the obtained results.

Example 5 The hardened castor oil of Example 3 (trade name, manufactured by Ito Oil Co., Ltd.)
2 parts by weight of caster wax) and 1 part by weight of dehydrated castor oil (trade name: DCO, manufactured by Ito Oil Co., Ltd.)
A porous film was obtained in the same manner as in Example 3, except that 1 part by weight of C600 (manufactured by Mitsui Chemicals, Inc.) was used. Table 1 shows the composition of the resin composition and the annealing conditions, and Table 2 shows the obtained results.

Example 6 The hardened castor oil of Example 3 (trade name, manufactured by Ito Oil Co., Ltd.)
2 parts by weight of caster wax) and 1 part by weight of dehydrated castor oil (trade name: DCO, manufactured by Ito Oil Co., Ltd.) were mixed with ethylene bisstearic acid amide (trade name, manufactured by Nippon Kasei Co., Ltd., trade name: ethylene bisstearic acid amide Srivac) E) A porous film was obtained in the same manner as in Example 3 except that the amount was changed to 2 parts by weight. Table 1 shows the composition of the resin composition and the annealing conditions, and Table 2 shows the obtained results.

Example 7 The polyolefin resin of Example 3 was replaced with a high-density polyethylene (trade name: HIZEX 3300, manufactured by Mitsui Chemicals, Inc.).
F) 8 parts by weight (20% by weight in polyolefin resin, polypropylene (manufactured by Grand Polymer Co., Ltd., trade name: F
103 WH, density: 0.910 g / cm ³ , MI: 2.
4 g / 10 min) 9 parts by weight (22.5% in polyolefin resin), linear low-density polyethylene (manufactured by Mitsui Chemicals, Inc., trade name: Evolue SP2540, density:
0.925 g / cm ³ , MI: 4.0 g / 10 min)
21 parts by weight (52.5% in polyolefin resin), branched low-density polyethylene (manufactured by Mitsui Chemicals, Inc., trade name:
Mirason F967, density: 0.918 g / cm ³ , M
I: 1.0 g / 10 min) A porous film was obtained in the same manner as in Example 3, except that 2 parts by weight (5% in polyolefin resin) was used. Table 1 shows the composition of the resin composition and the annealing conditions, and Table 2 shows the obtained results.

Example 8 The annealing conditions in Example 3 were changed to a heat fixing roll (diameter 3).
0cm) using two (heat fixation time 0.047 minutes), 10
A porous film was obtained in the same manner as in Example 3, except that the heat setting was performed at 5 ° C. and an annealing rate of 15%.
Table 1 shows the composition of the resin composition and the annealing conditions, and Table 2 shows the obtained results.

Comparative Example 1 The polyolefin resin of Example 1 was replaced with polypropylene (manufactured by Grand Polymer Co., Ltd., trade name: F103WH).
Density: 0.910 g / cm ³ , MI: 2.4 g / 10 m
in) 40 parts by weight (100% in polyolefin resin)
A porous film was obtained in the same manner as in Example 1, except that Table 1 shows the composition of the resin composition and the annealing conditions, and Table 2 shows the obtained results.

Comparative Example 2 The polyolefin resin of Example 1 was replaced with a high-density polyethylene (trade name: HIZEX 3300, manufactured by Mitsui Chemicals, Inc.).
F, density: 0.954 g / cm ³ , MI: 1.1 g / 1
0 min) 40 parts by weight (100 in polyolefin resin)
%), Except that the porous film was obtained in the same manner as in Example 1. Table 1 shows the composition of the resin composition and the annealing conditions.
Table 2 shows the obtained results.

Comparative Example 3 The polyolefin resin of Example 1 was replaced with polypropylene (manufactured by Grand Polymer Co., Ltd., trade name: F103WH,
Density: 0.910 g / cm ³ , MI: 2.4 g / 10 m
in) 33 parts by weight (82.5 in polyolefin resin)
%), Linear low density polyethylene (manufactured by Mitsui Chemicals, Inc., trade name: Evolue SP2540, density: 0.925 g /
cm ³ , MI: 4.0 g / 10 min), 5 parts by weight (12.5% in polyolefin resin), branched low-density polyethylene (manufactured by Mitsui Chemicals, Inc., trade name: Mirason F96)
7,) A porous film was obtained in the same manner as in Example 1, except that 2 parts by weight (5% in the polyolefin resin) was used.
Table 1 shows the composition of the resin composition and the annealing conditions, and Table 2 shows the obtained results.

Comparative Example 4 The polyolefin resin of Example 1 was replaced with a linear low-density polyethylene (manufactured by Mitsui Chemicals, Inc., trade name: Evolu SP2)
540, density: 0.925 g / cm ³ , MI: 4.0 g
/ 10 min) 40 parts by weight (1 in polyolefin resin)
00%) and 2 parts by weight of hardened castor oil (manufactured by Ito Oil Co., Ltd .; trade name: Custer Wax) and 1 part by weight of dehydrated castor oil (manufactured by Ito Oil Co., Ltd., trade name: DCO) were added. A porous film was obtained in the same manner as in Example 1. Table 1 shows the composition of the resin composition and the annealing conditions, and Table 2 shows the obtained results.

Comparative Example 5 The polyolefin resin of Example 1 was replaced with a linear low-density polyethylene (trade name: EVOLUE SP2 manufactured by Mitsui Chemicals, Inc.)
540, density: 0.925 g / cm ³ , MI: 4.0 g
/ 10 min) 38 parts by weight (9 in polyolefin resin)
5%), branched low-density polyethylene (Mitsui Chemicals, Inc.)
Product name: Mirason F967, density: 0.918 g /
cm ³ , MI: 1.0 g / 10 min) 2 parts by weight (5% in polyolefin resin), 2 parts by weight of hardened castor oil (trade name: Castor wax, manufactured by Ito Oil Co., Ltd.), and dehydrated castor oil (Ito Oil ( A porous film was obtained in the same manner as in Example 1 except that 1 part by weight of DCO) was added. Table 1 shows the composition of the resin composition and the annealing conditions, and Table 2 shows the obtained results.

[0052]

[Table 1]

<Description of Symbols in Table 1> A: High-density polyethylene (trade name, manufactured by Mitsui Chemicals, Inc.)
HiSex 3300F), B: polypropylene (Grand Polymer Co., Ltd., trade name: F103WH), C: linear low density polyethylene (Mitsui Chemicals, trade name: Evolu SP2540), D: linear low density polyethylene (Mitsui) Chemical Co., Ltd., trade name: Ultzex 2021L),
E: branched low-density polyethylene (manufactured by Mitsui Chemicals, Inc., trade name: Mirason F967), F: hardened castor oil (manufactured by Ito Oil Co., Ltd., trade name: caster wax), G: dehydrated castor oil (Ito Oil Co., Ltd.) ), Trade name: DCO), H: ethylene-α-olefin oligomer (Mitsui Chemicals, Inc.)
Manufactured by Nippon Kasei Co., Ltd., trade name: ethylene bisstearic acid amide Srivac E)
J: calcium carbonate (manufactured by Dowa Calfine Co., Ltd., trade name: SST-40)

[0054]

[Table 2]

<Consideration of Examples> The porous films obtained in Examples 1 to 8 have high moisture permeability, are excellent in low strain elongation strength in the machine direction, and have high flexibility and good texture. is there. The thickness uniformity is also good. On the other hand, since the porous films obtained in Comparative Examples 1 and 2 do not contain low-density polyethylene, they have poor texture (bending softness and rustling). In addition, since no branched low-density polyethylene is contained, the uniformity of the thickness is not good. In Comparative Example 3,
Since the amount of low-density polyethylene is small, it is better than Comparative Examples 1 and 2, but the texture is poor. In Comparative Example 4, the HD
Since it does not contain PE and PP, the low strain elongation strength is low. Further, the thickness uniformity is not good because no branched low-density polyethylene is contained. In Comparative Example 5, HDP
Since E and PP are not contained, the low-magnification elongation strength is low.

[0056]

Industrial Applicability The porous film of the present invention has the same level of moisture permeability as conventional products, is excellent in low strain elongation in the machine direction, is rich in flexibility, and has good hand. Therefore, it is useful as a material for sanitary articles worn on human skin such as disposable diapers and sanitary pads. In particular, when printing or the like is performed on the above-mentioned sanitary article, the pitch of printing is not shifted, and a clear pattern or the like is obtained because of excellent low strain elongation strength in the machine direction.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 23/10 C08L 23/10 91/00 91/00 // B29K 23:00 B29K 23:00 105: 04 105: 04 B29L 7:00 B29L 7:00 (72) Inventor Toshiyuki Enomoto 2-1 Tango-dori, Minami-ku, Nagoya-shi, Aichi F-term (reference) 4F071 AA16 AA18 AA20 AA71 AC12 AF07Y AF21Y AF26Y BA01 BB06 BB07 BB08 BB09 BC01 4F210 AA05 AA07 AA08 AA11 AB01 AB19 AG01 AG20 AR06 AR11 QC02 QG01 QG18 QW07 4J002 AE05Y BB03W BB03X BB05Z BB12W BB14W EP026 FD010

Claims (7)

[Claims] 1. A polyolefin resin 25 to 55% by weight.
And a porous film formed from a resin composition containing 75 to 45% by weight of an inorganic filler, wherein the polyolefin-based resin is at least one selected from high-density polyethylene and polypropylene having a density of 0.930 to 0.975. A porous film comprising 10-70% by weight of a seed resin, 88-15% by weight of a linear low density polyethylene having a density of 0.905-0.930, and 2-15% by weight of a branched low density polyethylene. 2. The porous material according to claim 1, further comprising 0.5 to 5 parts by weight of at least one dispersant selected from hardened castor oil and dehydrated castor oil, based on 100 parts by weight of the resin composition according to claim 1. Film. 3. The porous film according to claim 1, comprising 0.5 to 5 parts by weight of a liquid ethylene-α-olefin oligomer based on 100 parts by weight of the resin composition according to claim 1. 4. A resin composition according to claim 1, which contains 0.5 to 10 parts by weight of at least one lubricant selected from ethylene bisstearic acid amide and methylene bisstearic acid amide based on 100 parts by weight of the resin composition according to claim 1. Item 4. The porous film according to Item 1, 5. At least 18 g / 25 mm / (g / m
² ) 5% elongation strength in the machine direction of at least 27 g /
It has at least one property selected from 10% elongation strength in the machine direction of 25 mm / (g / m ² ), and has a rigidity in the machine direction of 2.7 mm / (g / m ² ) or less. Humidity of 1500 g / m ² · 24 h or more, basis weight of 10 to 35 g
/ M ² . 6. The porous film according to claim 1, wherein the heat shrinkage in the machine direction is 3% or less. 7. A method for producing a porous film according to any one of claims 1 to 6, wherein the resin composition according to any one of claims 1 to 4 is formed into a film. The resulting film is stretched at least 1.5 to 3 times in the machine direction to form a porous film, and then at 90 to 120 ° C. for at least 0.004 minutes while controlling the shrinkage in the machine direction to 10 to 25%. A method for producing a porous film, comprising heat setting.