JPH09208730A - Porous film and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a porous film useful as a back sheet for paper diaper, etc., having no reduction in bond strength, etc., with time, while maintaining handle, moisture permeability, thickness accuracy, etc., by adding a specific ocatadecadienoic acid glyceride to a resin composition. SOLUTION: In melting and forming a resin composition comprising (A) (i) 25-70wt.% of a polyolefin resin and (ii) 75-30wt.% of an inorganic filler into a film and orientating the film at least one direction, (B) 0.5-10 pts.wt. of an ocatadecadienoic acid glyceride containing a conjugated diene bond is added to 100 pts.wt. of the component A. Preferably the component (i) is a (linear) low-density polyethylene, the component (ii) is either calcium carbonate or barium sulfate and the component B is an ester of ocatadecadienoic acid and glycerol and the draw ratio of 1.2-5 times.

Description

Detailed Description of the Invention

[0001]

[0001] 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 having improved adhesiveness while maintaining thickness accuracy and the like in the same manner as conventional ones, 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 acid having 10 to 22 carbon atoms, which is a constituent component of the above fatty alcohol fatty acid ester, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid are mentioned. Acid, ricinoleic acid, etc. are exemplified, and among these, ricinoleic acid is described as being most preferable. In addition, examples of the aliphatic alcohol having 1 to 12 carbon atoms include methyl alcohol, ethyl alcohol, butyl alcohol, ethylene glycol, propylene glycol, glycerin, pentaerythritol, and sorbitol. Of these, glycerin is most preferable. It is stated that. Then, as a preferred embodiment, it is described in Examples that refined castor oil containing 85% or more of glycerin triricinoleate was used.

[0005]

However, the porous film obtained by using the refined castor oil as the third component described in the above publication has an adhesive layer having an adhesive layer such as a fastening tape. When the tape is attached to the surface of the porous film through the adhesive layer, castor oil migrates to the adhesive layer over time through the surface of the porous film,
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 3 parts by weight is added to 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. It is a problem that causes leakage of human urine and the like.

The object of the present invention is to solve the above-mentioned problems and to maintain the soft feeling and texture of cloth, moisture permeability, thickness accuracy, etc. at the same level as the conventional products, while the third component is the surface of the porous film. It is an object of the present invention to provide a porous film that does not stand out to lower the adhesiveness and the like, and a method for producing the same.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that by using a specific amount of a drying oil containing octadecadienoic acid glyceride having a conjugated diene bond as a main component as a third component, The inventors have found that the above objects can be achieved 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, Resin composition 1
It is a porous film comprising 0.5 to 10 parts by weight of octadecadienoic acid glyceride having a conjugated diene bond with respect to 00 parts by weight, and a method for producing the same.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The porous film of the present invention is a film obtained by melt-molding a resin composition containing a specific amount of a polyolefin resin, an inorganic filler and octadecadienoic acid glyceride having a conjugated diene bond, and stretching the film in at least uniaxial direction. It can be manufactured by

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 from 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 in order to improve the dispersibility with the polyolefin 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 porous film of the present invention is characterized in that a resin composition containing a polyolefin resin and an inorganic filler further contains, as a third component, a specific amount of octadecadienoic acid glyceride having a conjugated diene bond. . The amount of octadecadienoic acid glyceride having a conjugated diene bond is determined by the dispersibility of the polyolefin resin and the inorganic filler,
Affects film formability, thickness uniformity, and stretchability. When the addition amount of octadecadienoic acid glyceride having a conjugated diene bond is small, good dispersibility between the polyolefin resin and the inorganic filler cannot be obtained, and uniform stretching becomes difficult particularly at low magnification because uniform stretching is difficult. It becomes difficult to obtain a film, and the uniformity of the film thickness is reduced. On the other hand, if the addition amount is large, the extrusion moldability of the film is deteriorated, the extrusion molding becomes unstable, and the continuous productivity and the uniformity of the film thickness tend to be deteriorated, which is not preferable. Considering this point, the addition amount of octadecadienoic acid glyceride having a conjugated diene bond is
Resin composition 1 containing polyolefin resin and inorganic filler
It is preferably 0.5 to 10 parts by weight with respect to 00 parts by weight.

In the present invention, octadecadienoic acid glyceride having a conjugated diene bond is a compound represented by the following formula (1) having a conjugated diene bond in which the hydroxyl group and hydrogen group of ricinoleic acid are eliminated and the number of double bonds is increased by one. Chemical 3]

[0017]

Embedded image Is an ester of glycerin and the acid having octadecadienoic acid as a constituent fatty acid. That is, it is a drying oil containing octadecadienoic acid glyceride having a conjugated diene bond of the formula (1) as a main component. The octadecadienoic acid glyceride having a conjugated diene bond of the formula (1) includes monoesters, diesters and triesters, and these may be used alone or as a mixture. Examples of these commercially available products include dehydrated castor oil manufactured by Ito Oil Co., Ltd., trade name: DCO, and the like.

The octadecadienoic acid glyceride having a conjugated diene bond does not migrate to the surface of the porous film containing the polyolefin resin and the inorganic filler, does not float, etc., and suppresses the deterioration of the adhesiveness of the film. Although the reason is not clear, refined castor oil or the like is a non-drying oil, whereas octadecadienoic acid glyceride is a drying oil, and absorbs oxygen in the air in the film to change into a solid. It is presumed that it may be more difficult to transfer to the surface of the film, as compared with refined castor oil or the like that remains liquid.

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.

The porous film of the present invention is prepared by, for example, mixing the above-mentioned polyolefin resin, inorganic filler and dehydrated castor oil and, if necessary, other additives with a Henschel mixer, super mixer, tumbler type mixer or the like. The mixture is kneaded into pellets using a single-screw or twin-screw extruder. Next, the pellets are melted at or above the melting point of the polyolefin resin, preferably above the melting point + 20 ° C.,
At a temperature lower than the decomposition temperature, melting and film formation are performed using a known molding machine such as an extruder equipped with a T die or the like, or an inflation molding machine equipped with a circular die. In some cases, it is possible to form a film directly with 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 or higher at a softening point of the resin (JIS
Below a value measured by the method defined in K-6760), the film is stretched 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 the 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 10 to 100 μm. It is preferably 15 to 70 μm. If it is less than 10 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.

Further, the octadecadienoic acid glyceride having a conjugated diene bond on the surface of the porous film of the present invention may migrate and float even after being stored or stored for a long period of time after being manufactured. Absent. The adhesion strength after aging, which is a parameter showing the migration and the floating property of octadecadienoic acid glyceride having a conjugated diene bond (the measuring method will be described in detail in Examples described later), is 500 g.
/ 25 mm or more. By having an adhesive strength after aging of 500 g / 25 mm or more, 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. is there.

The porous film having such properties has appropriate breathability, moisture permeability, texture, and excellent mechanical properties. Therefore, disposable paper diapers, pads for absorbing body fluids, hygiene materials such as bed sheets, medical materials such as surgical clothes, base materials for hot compresses, clothing materials such as jumpers and rain clothes, wallpaper, roof waterproofing materials, etc. It can be used very suitably as a material, a desiccant, a dehumidifying agent, an oxygen scavenger, an insect repellent, a disposable body warmer, a packaging material for freshness-keeping packaging, food packaging and the like, and a material such as a battery separator.

[0025]

EXAMPLES Examples will be shown below in order to more specifically describe the present invention. Note that the present invention is not limited to these examples. The melt index (hereinafter referred to as MI), the moisture permeability, the adhesive strength after aging and the uniformity of the film thickness shown in the examples are values measured by the following methods.

(1) Melt index (g / 10 mi
n) Measured at a temperature of 190 ° C. and a load of 2160 g by the method specified in ASTM D-1238-57T (E).

(2) Water vapor transmission rate (g / m ² · 24 hr) JIS-Z-0 at a temperature of 40 ° C. and a relative humidity of 90%
It is measured by the method specified in 208 (CaCl ₂ method) (measurement time: 2 hours).

(3) Adhesive strength after aging (g / 25 mm) A 25 mm wide PP tape (manufactured by Toyo Kagaku Co., Ltd., trade name: KALARIAN PP, with adhesive layer) was attached to one surface of the porous film. After leaving this sample in an oven at 60 ° C. for 48 hours, a Tensilon tensile tester (manufactured by Toyo Baldwin Co., Ltd., trade name: Tensilon) was used.
The peeling stress when peeling the PP tape is JIS-Z023.
It is measured by the 180-degree peeling method specified in 7.

(4) Uniformity of Film Thickness Three samples [machine direction (hereinafter referred to as longitudinal direction): 100 cm, machine direction (hereinafter referred to as lateral direction): 5 cm] were taken from the porous film, Thickness measuring machine (PE
ACOCK, UPLIGHT DIAL GUAG
E NO. 25), the average thickness (X), the maximum thickness (MAX), and the minimum thickness (MIN) are obtained, and [(MAX) − (MIN)] / (X) is calculated. Uniformity of film thickness.

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 parts by weight to 40 parts by weight of calcium carbonate (manufactured by Dowa Calfine Co., Ltd., trade name: SST-40, average particle size: 1.0 μm), 60 parts by weight, and dehydrated castor oil (made by Ito Oil Co., Ltd.) , (Trade name: DCO) were mixed in a tumbler mixer, and then uniformly kneaded at 200 ° C. using a tandem type extruder to form 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 to obtain a porous film having a thickness of 40 μm. The adhesive strength, moisture permeability and uniformity of thickness of the obtained porous film after aging were measured by the above methods. The results obtained are shown in [Table 1].

Examples 2 to 7, Comparative Examples 1 to 4 Other than changing the blending ratio (parts by weight) of linear low density polyethylene, calcium carbonate and dehydrated castor oil, and the draw ratio as shown in [Table 1]. A porous film was produced in the same manner as in Example 1. Incidentally, in Example 7,
Barium sulfate (Barite Industry Co., Ltd.) as an inorganic filler
(Manufactured by, trade name: HD, average particle size: 0.95 μm). Further, in Comparative Example 1, instead of dehydrated castor oil, refined castor oil (manufactured by Ito Oil Co., Ltd., trade name: rhombus special A) 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].

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].

[0033]

[Table 1]

[0034]

EFFECTS OF THE INVENTION The porous film of the present invention maintains the texture, moisture permeability, thickness accuracy and the like of the conventional product, while the dehydrated castor oil added as the third component migrates to the surface of the porous film and floats. Since it is not squeezed out, the adhesive strength etc. does not decrease with time. Therefore, in the field of hygiene materials, medical materials, clothing materials, and the like, it can be suitably used as a material for products that are fixed and attached using a fastening tape or the like such as disposable paper diapers.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tsutomu Iseki 2-1-1 Tangodori, Minami-ku, Aichi Prefecture Mitsui Toatsu Chemical Co., Ltd. (72) Inventor Toshiyuki Enomoto 2-chome, Tangodori, Minami-ku, Aichi Prefecture No. 1 Mitsui Toatsu Chemical Co., Ltd.

Claims (12)

[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. A porous film comprising 0.5 to 10 parts by weight of octadecadienoic acid glyceride having a conjugated diene bond with respect to parts by weight. 2. The porous film according to claim 1, wherein the polyolefin resin is linear low density polyethylene or 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. Octadecadienoic acid glyceride having a conjugated diene bond is represented by the formula (1) [Chemical Formula 1] The porous film according to claim 1, which is an ester of octadecadienoic acid and glycerin represented by: 5. The porous film according to claim 1, wherein the stretching ratio is 1.2 to 5 times. 6. The moisture permeability of the porous film is 1000 to 2
0000 g / m ² · 24 hr, The porous film according to any one of claims 1 to 5, which is characterized in that: 7. A method for producing a porous film in which a resin composition containing 25 to 70% by weight of a polyolefin resin and 75 to 30% by weight of an inorganic filler is melt-molded to form a film, and the film is stretched in at least uniaxial direction. The method for producing a porous film is characterized by adding 0.5 to 10 parts by weight of octadecadienoic acid glyceride having a conjugated diene bond to 100 parts by weight of the resin composition. 8. The method for producing a porous film according to claim 7, wherein the polyolefin resin is linear low density polyethylene or low density polyethylene. 9. The method for producing a porous film according to claim 7, wherein the inorganic filler is at least one compound selected from calcium carbonate and barium sulfate. 10. An octadecadienoic acid glyceride having a conjugated diene bond is represented by the formula (1) [Chemical Formula 2] The method for producing a porous film according to claim 7, which is an ester of octadecadienoic acid and glycerin represented by: 11. The method for producing a porous film according to claim 7, wherein the draw ratio is 1.2 to 5 times. 12. The water vapor permeability of the porous film is from 1000 to 1000.
It is 20000 g / m < ² > * 24 hr, The manufacturing method of the porous film in any one of Claims 7-11 characterized by the above-mentioned.