JP2001226506A - Porous film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a porous film excellent in transparency, homogeneous stretchability, adhesive property and intercepting property. SOLUTION: This porous film is formed by melt molding a composition comprising a polyolefin resin, a filler and a third component, and then stretching the film to obtain the objective porous film, where the third component is a mixture comprising a hydrogenated castor oil, a polyhedric alcohol having at least 4 carbons and a fatty acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous film used for sanitary materials, medical materials, architectural materials and the like.

[0002]

2. Description of the Related Art As a method for producing a porous film, conventionally, a method of melt-molding a raw material composition containing a polyolefin resin and a filler to generate a film and a void is generally used. Disposable diapers,
When used as a material for sanitary products, it is particularly required to have the ability to pass only moisture without leaking human urine or blood. Moreover, it is difficult to obtain a material having a supple feel from a raw material composition comprising only a polyolefin resin and a filler. Therefore, in order to improve the performance of the porous film, many methods have been proposed in which a raw material composition is blended with a third component other than a polyolefin resin and a filler. As the third component, a mixture of a monoester and a polyester (JP-A-62-280234)
), Hardened castor oil (Japanese Patent Application Laid-open No. Hei 4-227538), dehydrated castor oil (Japanese Patent Application Laid-Open No. 9-208730), and a mixture of hardened castor oil + dehydrated castor oil (Japanese Patent Application Laid-Open No. 9-221560)
No.) are known.

[0003]

There are other problems with the porous film. For example, in use, it is necessary that the adhesive tape such as a fastening tape has good adhesion to the film. When a porous film with poor adhesion is used as a backsheet for disposable diapers, it is difficult to fix the disposable diaper with fastening tape when attaching it to the human body, which may cause leakage of human urine etc. Become. Furthermore, at that time, there is a problem that the components contained in the adhesive tape migrate to the porous film, the shielding property is impaired, and the opaque part is transparent and the inside can be seen through. However, with the above-mentioned known method, there has been no method capable of simultaneously solving the above-mentioned problems of adhesiveness and shielding while maintaining sufficient air permeability.

[0004]

SUMMARY OF THE INVENTION In view of the above problems, the present inventors have maintained the air permeability at the same level or higher as that of conventional products.
As a result of intensive studies to provide a porous film having excellent adhesion and shielding properties, and having good flexibility and good texture, the use of a raw material composition containing a specific third component makes it possible to obtain a desired porosity. The inventors have found that a functional film can be obtained, and have reached the present invention. That is, the present invention is a porous film obtained by melt-forming a composition containing a polyolefin resin, a filler and a third component to form a film, and then stretching the film, wherein the third component is A porous film characterized by being a mixture of hardened castor oil, a polyester comprising a polyhydric alcohol having 4 or more carbon atoms and a fatty acid.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. As the polyolefin resin used in the present invention, ethylene, propylene, and those mainly containing a monoolefin polymer and copolymer such as butene, for example, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polypropylene , Ethylene propylene random or block copolymer, polybutene, ethylene vinyl acetate copolymer and mixtures thereof. Among them, linear low-density polyethylene is preferred because it is flexible and tough.

The polyolefin resin used in the present invention is
And particularly preferred are linear density polyethylene and branched low-density polyethylene.
It is a mixture of high density polyethylene. Linear low density polyethylene
Ren is an α-olefin having a molecular skeleton having 3 to 8 carbon atoms.
It is a copolymer of ethylene and ethylene. Linear low density polyethylene
Len has a density of 0.910 to 0.940 g / cm
^ThreeHaving a melt index of 0.5 to 5 g / 10 minutes
Is preferred. Density 0.910g / cm^ThreeLess than
Uniform stretchability decreases, 0.940 g / cm^ThreeExceeds
The softness of the stretched film is impaired. Also, Mel Toy
When the index is less than 0.5 g / 10 minutes, the film
A film with a uniform thickness due to abnormal flow during extrusion
It is difficult to obtain.
Elongation deteriorates.

[0007] The branched low-density polyethylene is obtained by polymerizing ethylene by a known high-pressure method, and has a melt index of 0.1 to 2 g / 10 min.
Those having a density of 0.915 to 0.925 g / cm ³ are preferred. When the melt index is less than 0.1 g / 10 minutes, the mixing with the former linear low-density polyethylene is poor, and when it exceeds 2 g / 10 minutes, a film having a uniform thickness cannot be obtained. If the density exceeds 0.925, it becomes difficult to obtain a film having a uniform thickness.

[0008] The mixing ratio of the polyethylene resin in the above, linear low density polyethylene is usually 75 to 98
%, Preferably 85 to 96% by weight, and the branched low density polyethylene is usually 25 to 2% by weight, preferably 15 to 96% by weight.
4% by weight. If the amount of the branched low-density polyethylene exceeds 25% by weight, the elongation of the film in a molten state is reduced, and it is difficult to process the film. On the other hand, if it is less than 2% by weight, it is difficult to obtain a film having a uniform thickness.

Next, examples of the filler include calcium carbonate, 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 size of such an inorganic filler is usually 20 μm or less, preferably 10 μm or less, particularly preferably 0.5 to 5 μm. In addition, the inorganic filler,
In order to improve the dispersibility in the resin, it is desirable to coat the surface of the inorganic filler with a surface treatment agent to make it hydrophobic, and as such a surface treatment agent, for example, stearic acid, higher fatty acids such as lauric acid or the like. Examples thereof include metal salts thereof.

[0010] The porous film of the present invention is obtained by adding a polyolefin resin as described above and a resin composition containing an inorganic filler,
The third component is characterized in that it contains a mixture of hydrogenated castor oil, a polyester composed of a polyhydric alcohol having 4 or more carbon atoms and a fatty acid. The present inventors have studied various glycerin esters and found that only hydrogenated castor oil has a specific shielding property, while similar ester compounds such as refined castor oil (castor oil), dehydrated castor oil, hydrogenated tallow oil, It was confirmed that the effect was hardly seen with the ethylene oxide adduct of bean oil or hardened castor oil.
In the present invention, the hardened castor oil is an ester of glycerin with a fatty acid mixture containing 12-hydroxyoctadecanoic acid as a main component, which is a saturated fatty acid obtained by hydrogenating a double bond of ricinoleic acid. The ester includes a monoester, a diester and a triester. These may be used alone or in a mixture, but those containing a triester as a main component are preferable. The content of 12-hydroxyoctadecanoic acid in the fatty acid mixture is 70% by weight or more, and the content of other fatty acids having about 12 to 22 carbon atoms such as hexadecanoic acid and octadecanoic acid is less than 30% by weight. Thus, the shielding property of the porous film surface can be prevented from decreasing with time.
Such hydrogenated castor oil is industrially produced by hydrogenating castor oil, which is a non-drying oil, and commercially available products include, for example, Ito Oil Co., Ltd., hydrogenated castor oil, trade name: Custer wax, etc. Can be mentioned.

On the other hand, the polyester used in the present invention composed of a polyhydric alcohol having 4 or more carbon atoms and a fatty acid (hereinafter sometimes referred to as “specific polyester”) has a hydroxyl group and a carbonyl group terminal in the molecule. However, it is desirable to use a compound which has a high ratio of being blocked in the form of an ester group. As such polyester,
Examples include trioctyl trimellitate, pentaerythritol tetrastearate, dipentaerythritol hexaoctanoate, and diglycerin tetrastearate.

The porous film of the present invention is produced from the above resin composition containing a polyolefin resin, an inorganic filler, a hardened castor oil and a specific polyester. As the composition of the resin composition in this case, the polyolefin resin is usually 25 to 50 parts by weight, preferably 35 to 45 parts by weight, and the inorganic filler is 75 to 50 parts by weight, preferably 65 to 50 parts by weight.
The range is 55 parts by weight. When the amount of the inorganic filler is less than 50 parts by weight, adjacent voids formed by peeling off the interface between the polyolefin resin and the inorganic filler are not communicated with each other, and it is difficult to obtain air permeability. On the other hand, when the amount exceeds 75 parts by weight, elongation of the film at the time of stretching is lost and stretching becomes difficult.

The addition of the hardened castor oil and the specific polyester to the resin composition has a great influence on the uniformity of the thickness of the film, the stretchability, the texture of the film, the moldability of the film, the adhesiveness of the film and the like. If the added amount is too large, these bleed out from the film, and the adhesiveness is deteriorated. On the other hand, if the addition amount is too small, the film will be hard, the texture will be poor, and the uniformity in thickness will be poor. Considering this point, the total amount of the hardened castor oil and the polyester is preferably 0.5 to 5 parts by weight based on 100 parts by weight of the total amount of the polyolefin resin and the inorganic filler. The weight ratio of polyester to hardened castor oil is usually desirably in the range of 0.1 to 10. If the ratio of the polyester to the hardened castor oil is less than 0.1, the stretchability and flexibility tend to decrease, and if it exceeds 10, the shielding properties tend to decrease. In addition, in the resin composition, in addition to the above essential components, additives generally used for the resin composition, for example, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, neutralizers , An anti-fogging agent, an anti-blocking agent, an antistatic agent, a slip agent, a coloring agent and the like may be blended within a range that does not impair the properties of the porous film.

The porous film of the present invention is obtained by mixing the above resin composition using a Henschel mixer, a super mixer, a tumbler type mixer or the like, and then kneading with a single-screw or twin-screw extruder, a kneader or the like to form a pellet. I do.
Next, the pellets are melted above the melting point of the polyethylene resin,
Preferably, at a temperature not lower than the melting point + 20 ° C. and lower than the decomposition temperature, melting and film formation are performed by 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, the film can be directly formed by a molding machine without pelletizing.

[0015] The wound film may be formed at a temperature from room temperature to the softening point (J) of the resin by a known method such as a roll method or a tenter method.
(Measured value according to IS K6760), the film is stretched in at least one axial direction to cause interfacial separation between the polyolefin resin and the inorganic filler to obtain a porous film. Stretching may be performed in one step or in multiple steps. Further, since the stretching ratio relates to tearing of the film during stretching, air permeability of the obtained film, softness of the film, and the like, it is not preferable that the ratio is too high or too low. From such a viewpoint, the stretching ratio in the present invention is usually 1.2 to 5 times, preferably 1.5 to 3 times. When biaxially stretching, first uniaxially stretching in the machine direction or in a direction perpendicular to it, then a method of stretching the second axis in a direction perpendicular to this direction, and machine direction, and perpendicular to it And simultaneously biaxially stretching in the direction of After the stretching, a heat setting treatment may be performed, if necessary, in order to stabilize the form of the obtained opening. The thickness of the porous film of the present invention is not particularly limited, but is usually about 10 to 100 μm. If it is less than 10 μm, the film is easily broken,
If it exceeds 100 μm, the film becomes hard, and it is difficult to obtain a porous film having a cloth-like soft feeling and a good texture, which is not preferable.

[0016]

The present invention will now be described more specifically with reference to the following examples. Note that the present invention is not limited to these examples. The adhesive strength after aging shown in the examples is a value measured by the following method. (1) Air permeability Measured according to JIS-P8117 (unit: sec / 5
0cc). (2) Stretchability The uniform stretchability of the stretched film was visually evaluated according to the following criteria. ：: Stretching unevenness was hardly recognized. Δ: Stretching unevenness was observed. X: Stretching unevenness was significantly observed.

(3) Flexibility Evaluation was made according to the following criteria by touch feeling. ：: No rustling sound even when the film was bent, and the feel was very good. ：: No rustling sound even when the film was bent, and the feel was good. Δ: The film does not make a rustling sound even when bent, but is slightly hard and uncomfortable. ×: A crunchy sound was produced even when the film was bent, and the film was hard and uncomfortable. (4) Stickiness Evaluated according to the following criteria by finger touch. ：: When the film surface is slid with a finger, it is not sticky and smooth. Δ: The film surface is slightly sticky when slid on the film surface with a finger. ×: When the film surface is slid with a finger, the film is sticky.

(5) Shielding A 25 mm wide double-sided adhesive tape (trade name: KOKUYO T-225) is adhered to one surface of the film to form a sample, and the remaining release paper is peeled off to obtain a total light transmittance T1. It was measured. Also, one side of a double-sided adhesive tape having a width of 25 mm (trade name: KOKUYO T-225) was adhered to one surface of the film to form a sample. The sample was left in a constant temperature and humidity of 40 ° C. and 75% for one week, and then left at room temperature. The sample was peeled off and the remaining release paper was peeled off, and the total light transmittance of the sample was measured as T2. Then, the difference in total light transmittance (T (%) = T1−T2 (%)) was measured and evaluated according to the following criteria. ：: T is less than 10% ：: T is 10% or more and less than 20% Δ: T is 20% or more and less than 30% ×: T is 30% or more The measurement of total light transmittance was based on JIS-K6718. Haze meter (NDH-20 manufactured by Nippon Denshoku Co., Ltd.)
0) was used.

(6) Adhesion One side of a double-sided adhesive tape (trade name: KOKUYO T-225) having a width of 25 mm is adhered to one surface of the porous film to prepare a sample, and the sample is placed in a constant temperature and high humidity atmosphere at 40 ° C. and 75%. After standing for one week, the temperature is returned to room temperature, the remaining release paper is peeled off, the gauze is adhered, and the peeling stress when the adhesive and the gauze are peeled off using a Tensilon tensile tester is peeled by 180 degrees as specified in JIS-Z0237. It measured by the method and judged with the following criteria. ◎: Adhesive strength of 150 g / 25 mm or more ：: Adhesive strength of 100 g / 25 mm or more and 150 g / 25
mm: △: Adhesion strength of 50 g / 25 mm or more and 100 g / 25 m
m: ×: adhesive strength of less than 50 g / 25 mm

Examples 1 to 3 and Comparative Examples 1 and 2 In 37 parts by weight of a polyethylene resin, a linear low-density polyethylene [manufactured by Nippon Polychem Co., Ltd., trade name: FW20G, density: 0.921 g / cm ³ , MI 1 g / 10 min] 32
Parts by weight (95% by weight in polyethylene resin), branched low-density polyethylene [manufactured by Nippon Polychem Co., Ltd., trade name: LF441, density: 0.919 g / cm ³ , MI:
2 g / 10 min], 5 parts by weight of calcium carbonate (trade name: Ryton U-26, manufactured by Shiraishi Industry Co., Ltd., average particle size 1.2 μm)
m, fatty acid treatment) 63 parts by weight and the respective third component compounds shown in Table 1 were mixed in a tumbler mixer, and then uniformly kneaded at 220 ° C. using a tandem kneading extruder.
It was processed into a pellet. The pellets were melt-formed at 200 ° C. using an extruder equipped with a circular die, and then stretched at a stretch ratio of 2.0 times between a preheated roll and a stretch roll heated to 60 ° C. at a line speed of 20 m / m. In one minute, the film was uniaxially stretched in the machine direction to obtain a porous film having a thickness of 25 μm. Table 2 shows the results of measuring various properties of the obtained porous film.

Example 4, Comparative Example 3 Pellets obtained by the same method as in Example 1 were melt-formed at 200 ° C. using an extruder equipped with a T-die, and then heated to 60 ° C. The film was uniaxially stretched in the machine direction with a draw ratio of 2.1 times and a line speed of 20 m / min with respect to the stretched preheating roll stretching roll to obtain a porous film having a thickness of 25 µm. Table 2 shows the results of measuring various properties of the obtained porous film.

[0022]

[Table 1]

The third component in Table 1 is as follows. DPEHO Mitsubishi Chemical Corporation's trade name: dipentaerythritol hexaoctanoate D-600 DGDS Sakamoto Pharmaceutical Co., Ltd. trade name: diglycerin distearate IS-202 DGTS Sakamoto Pharmaceutical Co., Ltd. trade name: Diglycerin tetrastearate IS-204 Hardened castor oil Made by Ito Oil Co., Ltd. Trade name: Hardened castor oil Castor wax Dehydrated castor oil Made by Ito Oil Co., Ltd. Product name: Dehydrated castor oil DCO

[0024]

[Table 2]

[0025]

As described above, the porous film of the present invention can maintain the air permeability, uniform stretchability and the like at the same level or higher as those of the conventional product.
It has good adhesion and shielding properties, and has good flexibility and good texture. Therefore, sanitary materials such as disposable paper diapers, body fluid absorbing pads, bed sheets, etc., medical materials such as surgical gowns, base materials for hot compresses, clothing materials such as jumpers and rainwear, wallpaper, roof waterproof materials, etc. It can be very suitably used as a packaging material such as a material for use, a desiccant, a desiccant, an oxygen scavenger, a disposable body warmer, a packaging for keeping freshness, a food packaging, and a separator for a battery.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F071 AA14 AB21 AB24 AB26 AC09 AC10 AH04 AH19 BA01 BB06 BB07 BB09 BC01 BC17 4F074 AA00 AA16 AA20 AA98 AC19 AC20 AC21 AC26 AC32 AD11 AG01 CA01 CA02 CA03 DA10 DA33 DA38 DA53 DA59 DA59 BB031 BB032 BB061 BB121 BB151 BB171 BP021 DE066 DE076 DE106 DE136 DE146 DE236 DG046 DG056 DJ016 DJ046 EH047 EH057 EH147 FD016 FD207 GB01 GL00

Claims (5)

[Claims] 1. A porous film obtained by melt-forming a composition containing a polyolefin resin, a filler and a third component to form a film, and then subjecting the film to a stretching treatment, wherein the third component is cured. A porous film, which is a mixture of castor oil, a polyester comprising a polyhydric alcohol having 4 or more carbon atoms and a fatty acid. 2. The porous film of claim 1, wherein the weight ratio of polyester to hydrogenated castor oil is 0.1 to 10. 3. The porous film according to claim 1, wherein the hardened castor oil is an ester of a fatty acid mixture containing 12-hydroxyoctadecanoic acid as a main component and glycerin. 4. A polyolefin resin having a density of 0.910
~ 0.940 g / cm ^Three, Melt index 0.5 ~
5 g / 10 min linear density polyethylene 75-98 wt%
And melt index of 0.1 to 2 g / 10 min, density
0.915 to 0.925 g / cm^ThreeBranched low density poly
2. A mixture comprising 25 to 2% by weight of ethylene.
The porous film according to any one of Items 1 to 3. 5. A hardened castor oil containing 25 to 50 parts by weight of a polyolefin resin (A) and 75 to 50 parts by weight of an inorganic filler (B), and 100 parts by weight of (A) and (B). The porous film according to any one of claims 1 to 4, further comprising 0.5 to 5 parts by weight of a mixture of a polyester composed of a polyhydric alcohol having 4 or more carbon atoms and a fatty acid.