JP3468649B2 - Porous film and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a porous film and a method for producing the same. Specifically, the moisture permeability, texture,
The present invention relates to a porous film that maintains thickness accuracy and the like at the same level as conventional ones and has improved adhesiveness, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, many methods have been proposed for producing a porous film by stretching a film containing a polyolefin resin and an inorganic filler uniaxially or biaxially to generate voids communicating with the film. . This porous film is used for various purposes such as sanitary materials, medical materials, clothing materials, building materials, and battery separators. However, a porous film having a supple texture cannot be obtained with a compounding system of only a polyolefin resin and an inorganic filler, and it cannot be used in a field in which a cloth-like soft feeling, a supple texture, etc. are required. As a method of improving such a problem, a method of adding an additive such as a fatty acid ester as a third component to a compounding system of a polyolefin resin and an inorganic filler has been proposed.

For example, in Japanese Patent Laid-Open No. 62-18435, a film made of a composition of 42 to 87% by volume of a polyolefin resin and 58 to 13% by volume of an inorganic filler is stretched in at least one axial direction to provide air permeability. In producing a film, an aliphatic alcohol fatty acid ester, which is a compound of a fatty acid having 10 to 22 carbon atoms and an aliphatic alcohol having 1 to 12 carbon atoms, is added to the composition in an amount of 3 parts by weight per 100 parts by weight of the composition. Disclosed is a method for producing a breathable film, which comprises blending 25 to 25 parts by weight.

In the publication, as the fatty acids having 10 to 22 carbon atoms, lauric acid, myristic acid, palmitic acid,
Stearic acid, oleic acid, linoleic acid, linolenic acid,
Ricinoleic acid and the like are exemplified, and among these, it is described that ricinoleic acid is most preferable. As the aliphatic alcohol having 1 to 12 carbon atoms, methyl alcohol, ethyl alcohol, butyl alcohol, ethylene glycol, propylene glycol, glycerin,
Pentaerythritol, sorbitol and the like are exemplified, and it is described that glycerin is most preferable among these. Then, as a preferred embodiment, it is described in Examples that refined castor oil containing 85% or more of glycerin triricinoleate was used.

Further, in Japanese Patent Application Laid-Open No. 4-227738, (a) α-containing 6 or more carbon atoms with a density of 0.910 to 0.945 g / cm ³ and a melt flow rate of 0.01 to 20 g / 10 min. A linear low-density polyethylene copolymer having a boiling normal hexane extraction amount of 20% by weight or less, containing 1 to 20% by weight of an olefin or diolefin as a simple substance, (b) having an average particle size of 10 μm or less and having a bulk density 0.
1 to 0.7 g / cm ³ of a granular inorganic filler, and (c) a saturated or unsaturated fatty acid ester having 9 to 40 carbon atoms, each component (a) being 20 to 80% by weight and (b)
(C) to 100 parts by weight of the component of 80 to 20% by weight
Disclosed is a filler-containing stretched film, which comprises a resin composition in which the components are mixed in a proportion of 0.1 to 15 parts by weight and has a tear strength MD of 10 g or more.

As the component (c), glyceryl hydroxystearate, particularly glyceryl-12-hydroxystearate, is preferable as the saturated fatty acid ester, and glyceryl ricinoleate is preferable as the unsaturated fatty acid ester. There is. In the examples, caster wax is used in the amount of 2 to 3 parts by weight as the former and castor oil is used in the amount of 1 to 3% by weight as the latter.

[0007]

However, according to the findings of the present inventors, a porous film obtained by using the refined castor oil described in JP-A-4-227738 as the third component. For example, when an adhesive tape having an adhesive layer such as a fastening tape is attached to the surface of the porous film through the adhesive layer, castor oil adheres to the surface of the porous film over time. Move to the drug layer,
As a result, it was found that the adhesive strength of the adhesive layer was reduced and the adhesive tape was peeled off from the porous film. Further, it has been found that this phenomenon cannot be solved even when 1 part by weight is blended with 100 parts by weight of the resin composition, which is the lower limit of the use range described in the publication.

Therefore, when the porous film produced by the above method is used as a back sheet of a disposable diaper, for example, it is difficult to fix the disposable diaper with a fastening tape or the like when the disposable diaper is attached to a human body. This is a cause of leakage of human urine and the like, which is a problem.

A porous film obtained by using an ester which is solid at room temperature as a third component, such as castor wax, has a small decrease in adhesive strength with time, but the obtained porous film is flexible. The sex becomes poor.

Incidentally, Japanese Patent Application Laid-Open No. 62-32136 discloses that
(A) Melt index (MI) is 0.1 to 100 g
/ 10 minutes, 5 to 50% by weight of an ethylene-α-olefin copolymer having a density of 0.86 to 0.94 g / cm ³ .
(B) 0.1 to 15% by weight of esters consisting of a polyhydric alcohol and a saturated and / or unsaturated aliphatic monobasic acid having 2 to 24 carbon atoms and a hydroxy acid, and (c) an inorganic filler 30. A highly filling composition consisting of ˜90% by weight is disclosed.

However, the present invention has been made for the purpose of increasing the mass per unit area by adding an inorganic filler in a high concentration in order to impart a sound insulating effect to a backing material for an automobile carpet or a tile carpet. The invention is a completely different technical field from the porous film of the present invention, which is useful for a disposable diaper application or the like in which the adhesive strength of a fastening tape or the like is a problem.

The polyhydric alcohol and the carbon number of 2 to 2
Nothing is disclosed about what kind of mixing ratio the plural esters consisting of the saturated and / or unsaturated aliphatic monobasic acid and the hydroxy acid of 4 should be used.
Further, nothing is disclosed that a porous film having appropriate flexibility and excellent adhesiveness can be obtained by mixing and containing the esters in a specific ratio with respect to the polyolefin resin. Absent.

In view of the above problems, however, the object of the present invention is to maintain the softness and texture of the cloth, moisture permeability, thickness uniformity, etc., while maintaining the third component porous. It is an object of the present invention to provide a porous film that does not stand out on the surface of the film and reduce the adhesiveness and the like, and a method for producing the same.

[0014]

As a result of intensive studies, the present inventors achieved the above object by using dehydrated castor oil (a) and hydrogenated castor oil (b) together in a specific amount range. The inventors finally found the present invention and finally reached the present invention.

That is, the present invention is a porous film obtained by stretching at least uniaxially a film obtained from a resin composition containing 25 to 70% by weight of a polyolefin resin and 75 to 30% by weight of an inorganic filler, The resin composition contains 0.5 to 10 parts by weight of dehydrated castor oil (a) and 0.01 to 5 parts by weight of hydrogenated castor oil (b) with respect to a total of 100 parts by weight of the polyolefin resin and the inorganic filler. Including,
Moreover, the porous film is characterized in that the component (a) is 20 to 95% by weight with respect to the total amount of the components (a) and (b), and a method for producing the same.

The porous film provided by the present invention has a cloth-like soft feeling and texture equivalent to those of the conventionally known ones, moisture permeability, uniformity of thickness and the like.
Since the dehydrated castor oil (a) and the hydrogenated castor oil (b) added as the third component do not stand out on the surface of the porous film, the adhesive strength and the like do not decrease with time. Therefore, it can be suitably used in the fields of sanitary materials, medical materials, clothing materials, building materials, packaging materials and the like. In particular, it can be suitably used as a material for a product that is fixed and attached using a fastening tape or the like such as a disposable diaper. Further, it is also suitable for use in laminating with other materials using an adhesive or the like.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The porous film of the present invention is obtained by melt-molding a resin composition containing a specific amount of a polyolefin resin, an inorganic filler, dehydrated castor oil (a) and hydrogenated castor oil (b) into a film, the film being at least uniaxially formed. It can be manufactured by stretching in the direction.

The polyolefin resin used in the present invention is composed mainly of a monoolefin polymer such as ethylene, propylene and butene and a copolymer thereof, and includes low density polyethylene, linear low density polyethylene (ethylene -Α-olefin copolymer), polyethylene resin such as medium density polyethylene, high density polyethylene, polypropylene, polypropylene resin such as ethylene-polypropylene copolymer, poly-4-methylpentene, polybutene, ethylene-vinyl acetate copolymer Included are coalesce and mixtures thereof. These polyolefin resins may be resins produced using a Ziegler catalyst or resins produced using a single-site catalyst such as a metallocene catalyst. Of these, polyethylene-based resins are preferable, and linear low-density polyethylene resin, which is an ethylene-α-olefin copolymer, and low-density polyethylene are most preferable. Also, the formability of the film,
Considering stretchability and the like, the melt index of the polyolefin resin is preferably about 0.5 to 5 g / 10 min.

Examples of the inorganic filler include calcium carbonate, barium sulfate, calcium sulfate, barium carbonate,
Magnesium hydroxide, aluminum hydroxide, zinc oxide,
Examples thereof include magnesium oxide, titanium oxide, silica, talc, etc. Among these, barium sulfate and calcium carbonate are preferable.

The composition ratio of the polyolefin resin and the inorganic filler affects the moldability and stretchability of the film, the air permeability and the moisture permeability of the resulting film. When the amount of the inorganic filler is small, adjacent voids obtained by interfacial peeling between the polyolefin resin and the inorganic filler do not communicate with each other, and a porous film having good air permeability and moisture permeability cannot be obtained. Further, if the amount of the inorganic filler is large, a molding defect may occur when the film is molded, or the stretchability may be deteriorated to prevent sufficient stretching, which is not preferable. From this viewpoint, the composition ratio of the polyolefin resin and the inorganic filler is 25 to 70% by weight for the polyolefin resin and 7 for the inorganic filler.
It is preferably 5 to 30% by weight. More preferably, the polyolefin resin is 30 to 60% by weight and the inorganic filler is 70 to 40% by weight. The average particle size of the inorganic filler is preferably 20 μm or less, more preferably 10 μm.
m or less, and 0.5 to 5 μm is most preferable.

The inorganic filler is preferably surface-treated to improve dispersibility with the polyolefin resin. The surface treatment agent is preferably one which can make the surface hydrophobic by coating the surface of the inorganic filler, and examples thereof include higher fatty acids such as stearic acid and lauric acid, and metal salts thereof.

The porous film of the present invention comprises a resin composition containing a polyolefin resin and an inorganic filler and, as a third component, dehydrated castor oil (a) and hydrogenated castor oil (b).
It is characterized in that both components are included in specific amounts. The amounts of the dehydrated castor oil (a) and the hydrogenated castor oil (b) added are such that the dispersibility of the polyolefin resin and the inorganic filler, the film moldability,
It affects thickness uniformity, stretchability, flexibility, and adhesion with adhesive tape.

When the added amount of dehydrated castor oil (a) is small,
Good dispersibility between the polyolefin resin and the inorganic filler cannot be obtained, and it becomes difficult to obtain a uniformly stretched film, particularly at low magnification, and it becomes difficult to obtain a uniformly stretched film. . In addition, the obtained film has poor flexibility, which is not preferable. On the contrary, if the addition amount is large, the moldability of the film decreases and the molding becomes unstable, and the continuous productivity and the uniformity of the thickness of the film tend to decrease, and the adhesive force with the adhesive tape decreases. It shows a tendency to decrease with time. Considering this point, the amount of the dehydrated castor oil (a) added is 0.5 with respect to 100 parts by weight of the resin composition containing the polyolefin resin and the inorganic filler.
10 to 10 parts by weight.

On the other hand, when the amount of hydrogenated castor oil (b) added is large, the flexibility of the obtained film is poor and the film becomes hard. On the other hand, if the amount is too small, good dispersibility between the polyolefin resin and the inorganic filler cannot be obtained, and it becomes difficult to uniformly stretch, especially at a low magnification, and it becomes difficult to obtain a uniformly stretched film. Furthermore, the thickness uniformity tends to decrease. Considering this point, the amount of hydrogenated castor oil (b) added is 0.01 to 5 parts by weight per 100 parts by weight of the resin composition containing the polyolefin resin and the inorganic filler. It is preferably 0.1 to 5 parts by weight.

Dehydrated castor oil (a) and hydrogenated castor oil (b)
The compounding ratio of and has an effect on the rigidity of the obtained porous film, the adhesive force with the adhesive tape, and the like. That is, if the ratio of the dehydrated castor oil (a) is too low, the obtained porous film has poor flexibility and becomes a hard film. On the contrary, if it is too high, the adhesive strength tends to decrease. From this perspective,
(A) component 20 relative to the total amount of (a) and (b) components
Up to 95% by weight. It is preferably 30 to 95% by weight.

In the present invention, the dehydrated castor oil (a) is usually a fatty acid mixture containing octadecadienoic acid as a main component, in which hydroxyl groups and hydrogen groups of ricinoleic acid are eliminated, and the number of double bonds is increased, and glycerin. Is an ester of. This fatty acid mixture contains 30% by weight of 9,11-octadecadienoic acid.
Above, and 30% by weight of 9,12-octadecadienoic acid
It is preferable that the above content is included, and the total content of both is 70 wt% or more.

Examples of fatty acids other than octadecadienoic acid contained in this fatty acid mixture include other fatty acids having about 12 to 22 carbon atoms such as hexadecanoic acid, octadecanoic acid and octadecaenoic acid. It is preferable that the content of the other fatty acid be 30% by weight or less in order to prevent the ester from bleeding out on the surface of the porous film with time and to prevent the decrease in the adhesive strength. Esters of a fatty acid mixture containing octadecadienoic acid as a main component and glycerin include monoesters, diesters and triesters, but they may be used alone or in a mixture. The thing which has a triester as a main component is preferable.

The dehydrated castor oil (a) used in the present invention is
It is industrially produced by converting castor oil, which is a non-drying oil, into a drying oil by a chemical reaction. Examples of commercially available products thereof include dehydrated castor oil manufactured by Ito Oil Co., Ltd.,
Product name: DCO etc. can be mentioned.

In the present invention, hydrogenated castor oil (b) is usually a fatty acid mixture containing 12-hydroxyoctadecanoic acid as a main component and glycerin as a saturated fatty acid obtained by hydrogenating the double bond part of ricinoleic acid. And the ester. The content of 12-hydroxyoctadecanoic acid in this fatty acid mixture is preferably 70% by weight or more. Other fatty acids contained in this fatty acid mixture include fatty acids having about 12 to 22 carbon atoms such as hexadecanoic acid and octadecanoic acid. It is preferable that the content of the other fatty acid is 30% by weight or less in order to prevent the ester from bleeding out on the surface of the porous film over time and to prevent the decrease in adhesive strength.

Esters of a fatty acid mixture containing 12-hydroxyoctadecanoic acid as a main component and glycerin include monoesters, diesters and triesters, and these may be used alone or as a mixture. The thing which has a triester as a main component is preferable.

The hydrogenated castor oil (b) used in the present invention is
It is industrially produced by hydrogenating castor oil, which is a non-drying oil. Examples of commercially available products thereof include Ito Oil Co., Ltd., hydrogenated castor oil, trade name: castor wax, and the like.

The dehydrated castor oil (a) migrates to the surface of the porous film containing the polyolefin resin and the inorganic filler,
It is not clear why it does not float and the adhesiveness of the film is suppressed, but refined castor oil is a non-drying oil, whereas octadecadienoic acid glyceride is a dry oil. Therefore, it is presumed that the film absorbs oxygen in the air and changes into a solid, so that it is more difficult to migrate to the surface of the film as compared with refined castor oil or the like which remains in a liquid state.

Further, the reason why the hardened castor oil (b) does not migrate to the surface of the porous film containing the polyolefin resin and the inorganic filler, does not rise, etc., and suppresses the deterioration of the adhesiveness of the film is as follows. 12-
Since hydroxystearic acid glyceride is solid at room temperature, it is presumed that it will be more difficult to migrate to the surface of the film as compared to refined castor oil or the like that is liquid at room temperature.

The porous film of the present invention may contain other additives such as a stabilizer, an antioxidant, a colorant and an ultraviolet absorber within the range not impairing the object of the present invention.

Next, the method for producing the porous film of the present invention will be illustrated. For example, the above-mentioned polyolefin resin, inorganic filler, dehydrated castor oil (a) and hydrogenated castor oil (b),
If necessary, other additives are mixed using a Henschel mixer, a super mixer, a tumbler type mixer, etc., and then kneaded using a single or twin screw type extruder to form pellets. Then, the pellets are molded at a temperature not lower than the melting point of the polyolefin resin, preferably not lower than the melting point + 20 ° C. and lower than the decomposition temperature, by a known molding method such as an extrusion molding machine equipped with a T-die or an inflation molding machine equipped with a circular die. Melting and film formation using a machine. In some cases, the film may be directly formed by a molding machine without pelletizing. The formed film may be formed by a known method such as a roll method or a tenter method at room temperature to the softening point of the resin (JIS.
At a value measured by the method defined in K-6760), stretching is performed in at least uniaxial direction to cause interfacial peeling between the polyolefin resin and the inorganic filler to produce a porous film. Stretching may be performed in one step or may be performed in multiple steps. The stretching ratio is not preferable if the stretching ratio is too high or too low, because it is related to film breakage during stretching, air permeability of the obtained film, moisture permeability and the like. From this viewpoint, the draw ratio is preferably 1.2 to 5 times in at least the uniaxial direction. More preferably, it is 1.2 to 4 times. When biaxially stretching, a method of first uniaxially stretching in a machine direction or a direction perpendicular to the machine direction, and then stretching a second axis in a direction perpendicular to the machine direction, and a machine direction and There is a method of biaxially stretching simultaneously in the directions forming a right angle. Either method can be applied. Further, after stretching, if necessary, heat setting treatment may be performed in order to stabilize the shape of the obtained pores.
Examples of the heat setting treatment include a method of heat treatment for 0.1 to 100 seconds at a temperature equal to or higher than the softening point of the resin and lower than the melting point.

The thickness of the porous film of the present invention is not particularly limited, but the usual thickness is about 5 to 100 μm.
It is preferably 10 to 70 μm. If it is less than 5 μm, the film tends to be broken, and if it exceeds 100 μm, the film becomes hard and it is difficult to form a porous film having a cloth-like soft feeling and a good texture, which is not preferable.

The porous film of the present invention produced as described above is JIS-Z0208 (40 ° C., 90%, C
The water vapor permeability measured by the method defined in (aCl ₂ method conditions) is in the range of 1000 to 20000 g / m ² · 24 hr.

In addition, the porous film of the present invention has the dehydrated castor oil (a) and the hardened castor oil (b) transferred and floated on its surface even after being stored or stored for a long period of time after being manufactured. There is nothing to put out. It is preferable that the adhesive strength (measurement method will be described in detail in Examples described later), which is a parameter indicating the migration and the floating property of the components (a) and (b), is at least 600 g / 25 mm. By having an adhesive strength of at least 600 g / 25 mm, for example, when used as a back sheet of a disposable paper diaper, the obtained paper diaper can be firmly fixed with a fastening tape or the like. The upper limit of the adhesive strength is not particularly limited, but the breaking strength of the film is the upper limit according to the measuring method described later.

The rigidity of the porous film of the present invention is 80 mm
It is below, and has moderate flexibility. Therefore, it is preferably used as an application requiring flexibility, for example, as a back sheet of a disposable diaper. The lower limit of the rigidity is not particularly specified, but is usually about 20 mm.

The porous film having such properties has appropriate breathability, moisture permeability, texture, and excellent mechanical properties and aging adhesion. Therefore, disposable diapers, pads for absorbing body fluids, sanitary materials such as bed sheets, surgical clothes, medical materials such as base materials for hot compresses, jumper, clothing materials such as rain clothes, wallpaper, roof waterproofing materials, house wraps, etc. It can be preferably used in the fields of building materials, desiccants, dehumidifiers, deoxidants, insect repellents, disposable body warmers, packaging materials such as freshness-keeping packaging, food packaging, and battery separators. Since it has excellent adhesive properties over time, it is used as a fastening tape (pressure-sensitive adhesive tape) such as disposable diapers and pads for absorbing body fluids.
It is particularly suitable as a material for articles that are mounted and fixed in. Also, the adhesiveness when laminated with other materials by the adhesive is also good.

[0041]

EXAMPLES Examples will be shown below in order to more specifically describe the present invention. The present invention is not limited to these examples. Melt index (hereinafter referred to as MI), moisture permeability, adhesive strength,
Uniformity of film thickness and rigidity are values measured by the following methods. (1) Melt index (g / 10 min) Measured according to the method specified in ASTM D-1238-57T (E) under conditions of a temperature of 190 ° C. and a load of 2160 g. (2) Water vapor transmission rate (g / m ² · 24 hr) JIS-Z02 at a temperature of 40 ° C and a relative humidity of 90%
08 (CaCl ₂ method). (3) Adhesive strength (g / 25 mm) A pressure-sensitive adhesive polypropylene tape having a width of 25 mm (manufactured by Toyo Kagaku Co., Ltd., trade name: Kalarian PP, with an adhesive layer) is attached to one surface of the porous film in the machine direction of the film. The sample is attached so that is in the peeling direction. This sample is 6
After standing in an oven at 0 ° C for 48 hours, a Tensilon tensile tester (manufactured by Toyo Baldwin Co., Ltd., trade name: Tensilon) is used to define 180 according to JIS-Z0237.
According to the peeling-off method, the polypropylene tape is peeled from one surface of the porous film, and the peel stress at that time is measured.

(4) Uniformity of Film Thickness Three samples [machine direction (hereinafter referred to as longitudinal direction): 101 cm, machine direction (hereinafter referred to as lateral direction): 5 cm] were taken from the porous film, Thickness measuring machine (PE
UPRIGHT DIAL GUAG manufactured by ACOCK
E NO. 25) is used to measure the thickness, the average thickness (X), the maximum thickness (MAX) and the minimum thickness (MIN) are obtained, and [(MAX)-(MIN)] / (X) is calculated, and this is calculated. Uniformity of film thickness. (5) Rigidity (mm) Measured according to the method (cantilever method) specified in JIS-L1096. <Preparation of sample> 200m width
m, length 300 mm, thickness 40 μm, width 25
After winding around a mm scale, the scale is removed. Weight of the obtained flat roll (width 25 mm, length 300 mm) is 1 k.
The sample is pressed back and forth once with the roller g.

Example 1 Linear low density polyethylene (manufactured by Mitsui Petrochemical Industry Co., Ltd.,
Product name: Ultzex 2510F, density: 0.925
g / cm ³ , melt index (MI): 1.3 g /
10 min) 40 parts by weight calcium carbonate (manufactured by Dowa Calfine Co., Ltd., trade name: SST-40, average particle diameter: 1.0 μm) 60 parts by weight, dehydrated castor oil (manufactured by Ito Oil Co., Ltd., product Name: DCO) 1.5 parts by weight and hydrogenated castor oil (Ito Oil Co., Ltd., trade name: Castor wax) 1.5 parts by weight with a tumbler mixer, and then 200 using a tandem extruder. The mixture was uniformly kneaded at 0 ° C and processed into pellets. Using an extruder equipped with a T-die, the pellets were subjected to melt film formation at 240 ° C., and then, in a machine direction at a draw ratio of 2.0 times between a preheating roll heated to 70 ° C. and a drawing roll. Uniaxially stretched,
A 40 μm thick porous film was obtained. The adhesive strength, moisture permeability, thickness uniformity and rigidity of the obtained porous film after aging were measured by the above methods. The obtained results are shown in [Table 1].

Examples 2 to 7, 9 to 12, Comparative Examples 1 to 9 Linear low density polyethylene, calcium carbonate, dehydrated castor oil, hydrogenated castor oil, and other additives (third component) compounding ratio (parts by weight) ), And the draw ratio was changed as shown in [Table 1] or [Table 2], and a porous film was produced in the same manner as in Example 1. In Example 7, barium sulfate (manufactured by Barite Industry Co., Ltd., trade name: HD, average particle size: 0.95 μm) was used as the inorganic filler. Each property of the obtained porous film was evaluated in the same manner as in Example 1, and the obtained results are shown in [Table 1] and [Table 2].

Example 8 Low density polyethylene (manufactured by Mitsui Petrochemical Co., Ltd., trade name: Mirason F312, density: 0.925 g / cm ³ ,
A porous film was produced in the same manner as in Example 1 except that the melt index (MI): 2 g / 10 min) was used. Each property of the obtained porous film was evaluated in the same manner as in Example 1, and the obtained results are shown in [Table 1].

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

EFFECTS OF THE INVENTION The porous film provided by the present invention maintains the texture, moisture permeability, thickness uniformity and the like as conventional products, while adding the dehydrated castor oil (a) added as the third component and the cured film. Since the castor oil (b) does not migrate to the surface of the porous film and does not float, the adhesive strength and the like with time do not decrease. Therefore, hygiene materials,
It is preferably used in the fields of medical materials, clothing materials, building materials, packaging materials and the like. In particular, it can be suitably used as a material for a product that is fixed and attached using a fastening tape or the like such as a disposable diaper. Furthermore, it is also suitable for use in laminating with other materials using an adhesive.

Front Page Continuation (72) Inventor Toshiyuki Enomoto 2-1, Tango Dori, Minami-ku, Nagoya-shi, Aichi Mitsui Toatsu Chemical Co., Ltd. (56) References JP-A-7-118431 (JP, A) (58) Survey Areas (Int.Cl. ⁷ , DB name) C08J 9/00-9/42 C08L 1/00-101/16

Claims (16)

(57) [Claims] 1. A porous film obtained by stretching at least uniaxially a film obtained from a resin composition containing 25 to 70% by weight of a polyolefin resin and 75 to 30% by weight of an inorganic filler, the resin composition comprising: A total of 100 parts by weight of the polyolefin resin and the inorganic filler, 0.5 to 10 parts by weight of dehydrated castor oil (a) and 0.01 to 5 parts by weight of hydrogenated castor oil (b), and A porous film comprising the component (a) in an amount of 20 to 95% by weight based on the total amount of the components (a) and (b). 2. The porous film according to claim 1, wherein the polyolefin resin is at least one resin selected from linear low density polyethylene and low density polyethylene. 3. The porous film according to claim 1, wherein the inorganic filler is at least one compound selected from calcium carbonate and barium sulfate. 4. The dehydrated castor oil (a) comprises 9,11-octadecadienoic acid in an amount of 30% by weight or more and 9,12-octadecadienoic acid in an amount of 30% by weight or more, and both acids in total of 70% by weight or more. The porous film according to claim 1, which is an ester of a fatty acid mixture containing glycerin. 5. The porous film according to claim 1, wherein the hardened castor oil (b) is an ester of a fatty acid mixture containing 70% by weight or more of 12-hydroxyoctadecanoic acid and glycerin. 6. The stretching ratio is 1.2 to 5 times.
The porous film described. 7. A porous film having a water vapor transmission rate of 1000 to 2
The porous film according to claim 1, having a weight of 0000 g / m ² · 24 hr. 8. The porous film according to claim 1, wherein the porous film has an adhesive strength of at least 600 g / 25 mm and a rigidity of 80 mm or less. 9. A method for producing a porous film, which comprises stretching a film obtained from a resin composition containing 25 to 70% by weight of a polyolefin resin and 75 to 30% by weight of an inorganic filler in at least uniaxial direction, the resin comprising: The composition contains dehydrated castor oil (a) 0.5 to 10 parts by weight and hydrogenated castor oil (b) 0.01 to 5 parts by weight with respect to a total of 100 parts by weight of the polyolefin resin and the inorganic filler. ,and,
20 parts of (a) component with respect to the total amount of (a) and (b) components
The method for producing a porous film is characterized in that the content is ˜95% by weight. 10. The method for producing a porous film according to claim 9, wherein the polyolefin resin is at least one resin selected from linear low-density polyethylene and low-density polyethylene. 11. The method for producing a porous film according to claim 9, wherein the inorganic filler is at least one compound selected from calcium carbonate and barium sulfate. 12. The dehydrated castor oil (a) comprises 30% by weight or more of 9,11-octadecadienoic acid and 30% by weight or more of 9,12-octadecadienoic acid, and the total amount of both acids is 70% by weight. The method for producing a porous film according to claim 9, which is an ester of a fatty acid mixture containing at least 100% by weight and glycerin. 13. The method for producing a porous film according to claim 9, wherein the hydrogenated castor oil (b) is an ester of a fatty acid mixture containing 70% by weight or more of 12-hydroxyoctadecanoic acid and glycerin. 14. The method for producing a porous film according to claim 9, wherein the stretching ratio is 1.2 to 5 times. 15. The moisture permeability of the porous film is from 1000 to 1000.
The method for producing a porous film according to claim 9, which has a weight of 20000 g / m ² · 24 hr. 16. The method for producing a porous film according to claim 9, wherein the porous film has an adhesive strength of at least 600 g / 25 mm and a rigidity of 80 mm or less.