JP6063721B2 - Method for producing microporous film - Google Patents

Description

  The present invention relates to a microporous film. Specifically, there is no powder falling off, excellent hygiene, and evenly communicating holes with high water vapor permeability required for sterilization, etc., with uniform appearance, and sharp objects such as injection needles and catheters. The present invention relates to a microporous film that is useful for a lid material or the like in a package such as a medical blister package that has sufficient puncture strength to wrap.

  Conventionally, medical instruments such as disposable syringes and injection needles are sterilized by irradiation with high-pressure steam, ethylene oxide gas, or radiation after being housed in a packaging body such as blister packaging. Since the medical packaging material is subjected to the sterilization treatment, sufficient air permeability is required particularly in the highly versatile ethylene oxide gas sterilization. Specifically, a porous film that allows gas necessary for sterilization and water vapor having a diameter of 0.0004 μm to pass through is effective as a medical packaging material. Also, many medical devices directly touch the human body, and the packaging material must be able to be used in a very hygienic manner so as not to affect the human body. Furthermore, when packaging sharp objects such as injection needles and catheters, puncture strength is required so as not to be broken along the way.

  Conventionally, so-called air-permeable porous films that do not transmit water but transmit gases such as air and water vapor have been used for back sheets of paper diapers, packaging of hygroscopic agents and oxygen scavengers, and the like. As a manufacturing method thereof, as described in Patent Document 1, a composition comprising a resin and a filler, and in some cases, a composition obtained by adding a wax-like hydrocarbon polymer to a film is formed and stretched. Some of them cause microvoids to be generated inside the film, thereby exhibiting air permeability. However, porous films such as these easily stretch at low stress and physically generate microvoids between the filler and the resin, so that various microvoid sizes occur from small to large. There was a problem of disturbing the uniformity of the degree.

  In addition, when the conventional porous film as described above uses an inorganic filler such as calcium carbonate or barium sulfate as a filler (for example, Patent Document 1), the shape of the filler is non-uniform and the phase with the resin There are problems that uniform physical properties cannot be expected due to poor solubility, and that the surface does not become smooth and irregularities occur, so that powder falls off due to contact with the film. In addition, these fillers have poor chemical resistance and may be eluted in an acid such as acetic acid, so that there are limitations on the applications that can be used.

  On the other hand, as a method for producing a porous film, research and development using a polyolefin such as polyethylene and polypropylene as a matrix is actively conducted. For example, Patent Document 2 describes a method for producing a thermoplastic resin porous body in which a sheet made of a polar thermoplastic resin and a nonpolar thermoplastic resin is rolled and then stretched. The interface between the two kinds of resins is pulled away by stretching the sheet, and pores are generated to make a porous film. As the thermoplastic resin, polyethylene, polyvinyl chloride, styrene resin, or the like is used.

  A method for producing a porous film having a polyolefin as a matrix by the stretching method in this manner is useful as a method for producing a porous film. This production method is further described in Patent Document 3, Patent Document 4, Patent Document 5, and the like. It is also described in. For example, Patent Document 3 discloses the production of a porous film by a stretching method using a thermoplastic resin A such as polypropylene and a thermoplastic resin B that is poorly compatible with the resin A and has a melting point of at least 20 ° C. A method is described.

  However, in these methods in which the matrix resin and the dispersion resin are kneaded, formed into a film, and stretched, since the pores are formed by stretching in the stretching direction, not in the thickness direction of the film, the pores communicate with the film. It is generally difficult to obtain a film excellent in air permeability. Furthermore, in these conventional examples, since the matrix resin and the dispersion resin are poorly compatible, it is difficult to disperse the dispersion resin satisfactorily. However, it is difficult to form through-holes in the film, and the air permeability of the obtained film was limited. Therefore, as a method for producing a porous film that transmits gas necessary for sterilization and water vapor having a diameter of 0.0004 μm, It was inadequate.

  Furthermore, even if a certain degree of air permeability can be imparted to the film by such a method, unevenness occurs during stretching, resulting in variations in thickness and air permeability, and uniform communication holes are formed in the stretching direction. It was difficult.

JP-A-60-229731 Japanese Patent Publication No.49-86458 JP 58-198536 A JP-A-63-270748 Japanese Patent Application Laid-Open No. 64-26655

  The object of the present invention is to eliminate the defects of the above-mentioned conventional porous film, to have excellent hygiene without powder falling off, and to have a high degree of air permeability required for sterilization treatment uniformly without unevenness in appearance, and The object is to obtain a microporous film having a sufficient puncture strength for packaging sharp objects such as injection needles and catheters.

  Another object of the present invention is to provide a lid for a package using the microporous film that can be suitably used for medical blister packaging.

As a result of intensive studies in view of the above problems, the present inventors have stretched a biaxially oriented thermoplastic resin having a sea-island structure having a polypropylene resin as a matrix component and a polyolefin / polystyrene elastomer resin as a domain component. The inventors have found that the above object can be achieved and completed the present invention.
That is, the present invention
(1) A sea part which is formed of a thermoplastic resin composition containing 25 to 75 parts by mass of a polyolefin / polystyrene elastomer with respect to 100 parts by mass of a polypropylene resin and contains the polypropylene resin as a main component, and the polyolefin / polystyrene. system elastomers have a sea-island structure composed of an island portion which includes as a main component, the 230 ° C. polyolefin polystyrene-based elastomer, a melt flow rate of 2.16kg load is not more than 1.0 g / 10 min, the AMA Prefecture interface between the island portion, and a microporous film holes are formed in the sea portion, a thickness of 50μm or more 500μm or less, air permeability of Ru der 200 sec / 100 cc or less and 20 seconds or more / 100 cc, A method for producing a microporous film,
The microporous material is biaxially stretched 1.1 times or more in the temperature range of 0 ° C. to 60 ° C. in the longitudinal direction, 1.5 times or more in the temperature range of 70 ° C. to 170 ° C. and 2 times or more in the transverse direction. For producing a conductive film .
(2) The method for producing a microporous film according to (1), wherein the polyolefin / polystyrene elastomer has a styrene content of 1 to 40% by mass.
(3) The method for producing a microporous film according to any one of (1) and (2), wherein a particle size of an island part containing the polyolefin / polystyrene elastomer as a main component is 0.01 to 10 μm.
(4) The method for producing a microporous film according to any one of (1) to (3), wherein the puncture strength is 400 gf or more.

According to the present invention, a lid material such as a medical blister pack mainly having high piercing strength, which has sufficient breathability for sterilization treatment and does not fall off powder because it does not contain an inorganic filler, and has high puncture strength. A microporous film suitable for the above can be provided.
Furthermore, according to this invention, the cover material for package bodies using the said microporous film suitable for cover materials, such as a medical blister package body, can be provided.

  Hereinafter, the microporous film of the present invention and the lid for packaging (hereinafter referred to as “the film of the present invention” and “the lid of the present invention”, respectively) will be described in detail.

<Polypropylene resin>
The polypropylene resin used for the film of the present invention is homopropylene (propylene homopolymer), or propylene and ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-octene, Examples thereof include random copolymers or block copolymers with α-olefins such as nonene and 1-decene. Among these, homopolypropylene is more preferable from the viewpoint of maintaining the air permeability and mechanical strength of the microporous film. A polypropylene resin is used individually by 1 type or in mixture of 2 or more types. The polypropylene resin may have any crystallinity and melting point, and two or more kinds of polypropylene resins having different properties can be mixed at any blending ratio depending on the properties and applications of the resulting microporous film. It may be blended with.

  The polypropylene resin is selected from those having a melt flow rate (MFR) at 230 ° C. and a load of 2.16 kg, preferably in the range of 0.1 to 100 g / 10 minutes, more preferably in the range of 0.1 to 50 g / 10 minutes. it can. When the MFR is in the above range, when the polypropylene resin and the polyolefin / polystyrene elastomer are mixed, the dispersibility of the polyolefin / polystyrene elastomer is improved, or the film is difficult to break when processed into a film. It is preferable from the viewpoint of isoformability.

  The polypropylene resin is a known modified polypropylene as described in JP-A-44-15422, JP-A-52-30545, JP-A-6-313078, or JP-A-2006-83294. Resin may be used. Furthermore, the polypropylene resin used in the present invention may be a mixture of any proportion of the above polypropylene resin and modified polypropylene resin.

<Polyolefin / polystyrene elastomer>
The polyolefin / polystyrene elastomer used for the film of the present invention is not particularly limited as long as it is an olefin-based or styrene-based polymer or copolymer and exhibits rubber-like elasticity at around room temperature. Specifically, styrene-olefin block copolymers such as styrene-hydrogenated isoprene block copolymers, styrene-olefin-styrene block copolymers such as styrene-ethylene-butylene-styrene block copolymers, styrene-butadiene-styrene block copolymers, styrene- Examples include isoprene-styrene block copolymer. Among these, styrene-hydrogenated isoprene-styrene block copolymer and styrene-ethylene-butylene-styrene block copolymer are preferably used.

  The polyolefin / polystyrene elastomer used in the film of the present invention has a melt flow rate (MFR) measured at 230 ° C. under a load of 2.16 kg of 0.5 to 1.0 g / 10 min, preferably 0.1 to 0.1 g. 0.5 g / 10 min, more preferably 0-0.1 g / 10 min. By setting the viscosity within the above range, the polyolefin / polystyrene elastomer can be uniformly dispersed in a spherical manner in the polypropylene resin, and it becomes easy to make it porous by stretching.

  The styrene content of the polyolefin / polystyrene elastomer used in the film of the present invention is preferably 1% by mass to 40% by mass, more preferably 1% by mass to 35% by mass, and still more preferably 5% by mass to 35% by mass, particularly. Preferably it is 10 mass%-35 mass%. If the styrene content of the polyolefin / polystyrene elastomer is in the above range, the resulting molded product is not too flexible, and the porosity during stretching, which will be described in detail later, is preferable.

  The content of the polypropylene resin and polyolefin / polystyrene elastomer in the film of the present invention is preferably 30 to 70 parts by mass of polyolefin / polystyrene elastomer, more preferably 100 parts by mass of polypropylene resin. The amount of polyolefin / polystyrene elastomer is 40 to 65 parts by mass with respect to 100 parts by mass. If the content ratio of the polyolefin / polystyrene elastomer is within the above range, it is preferable because the stretchability, air permeability, and puncture strength of the resulting film can be obtained in a balanced manner.

  The mixture of the polypropylene resin and the polyolefin / polystyrene elastomer used in the film of the present invention is composed of a sea part mainly composed of a polypropylene resin and an island part principally composed of a polyolefin / polystyrene elastomer in a sheet state before stretching. It is preferable to have a sea-island structure consisting of Furthermore, it is preferable that the particle size of the island part is in the range of 0.01 μm to 10 μm. When the sheet state before stretching has the sea-island structure, the film of the present invention is preferable because air permeability becomes better while maintaining high piercing strength.

  In addition to the above components, the film of the present invention has known film additives such as antioxidants, heat stabilizers, antistatic agents, slip agents, antiblocking agents, polyterpene resins, petroleum resins, and fillers. You may make it contain to such an extent that it does not reduce.

  The film of the present invention preferably has a film thickness of preferably 50 to 500 μm, more preferably 50 to 200 μm. When the film thickness is 50 μm or more, it is preferable that the film is not stretched by the tension, vertical wrinkles are generated, or the film is not broken in the film forming step and the secondary processing step.

  The film of the present invention has an air permeability of preferably 50 seconds / 100 cc to 1000 seconds / 100 cc, more preferably 40 seconds / 100 cc to 500 seconds / 100 cc, still more preferably 20 seconds / 100 cc to 200 seconds / 100 cc. . If the air permeability is in the above range, it is preferable because a film having high water vapor permeability required for sterilization treatment and the like can be obtained.

  The film of the present invention has a puncture strength of preferably 400 gf or more, more preferably 500 gf or more, and further preferably 600 gf or more. If the puncture strength is within the above range, it is preferable because sufficient strength can be obtained for packaging sharp objects such as injection needles and catheters.

<The manufacturing method of the film of this invention>
The film production method of the present invention can be produced by a method comprising the following steps (A) and (B). According to this method, the microporous film having good permeability and a sea-island structure Can be manufactured.
(A) A cold stretching step of stretching a thermoplastic resin composition containing 25 to 75 parts by mass of a polyolefin / polystyrene elastomer to 100 parts by mass of a polypropylene resin at a temperature of 0 ° C. or more and less than 60 ° C.
(B) A hot stretching step of stretching the thermoplastic resin composition at a temperature of 70 ° C. or higher and lower than 170 ° C. after the cold stretching step.

In the film of the present invention, first, raw materials are mixed, and a substantially unstretched sheet is produced by an extrusion method.
Various known methods such as a single or twin screw extruder, a Banbury mixer, a mill, a kneader blender, etc. can be adopted as the raw material mixing method. The processed material may be used for extrusion molding, or may be melt-mixed and directly extruded.
As the extrusion method, various molding methods such as T-die extrusion molding, inflation molding, calender molding, and Skyf's method can be adopted. Among these, from the viewpoint of physical properties and applications required for the film of the present invention, T-die extrusion Molding is preferred.

Next, the substantially unstretched film produced by the extrusion method is stretched to obtain the film of the present invention. As the stretching method, various methods such as rolls, tenters, tubulars, autographs, etc. can be adopted, but as the stretching method of the film of the present invention, a longitudinal stretching process by rolls and a horizontal stretching process by tenters are combined, It is preferable to employ sequential biaxial stretching.
Furthermore, the manufacturing method of the film of this invention performs the stretching process of 2 steps | paragraphs of (A) cold stretching process and (B) hot stretching process in a longitudinal stretching process. By performing the longitudinal stretching process in two stages, the resulting porous film has high air permeability. Also, the film appearance is excellent. Hereinafter, the method for producing the microporous film of the present embodiment will be described with an example, but the present embodiment is not limited to this example.

<Sheet forming process>
By supplying a resin composition comprising a mixture of a specific range of polypropylene resin and polyolefin / polystyrene elastomer resin to an extruder, and melt-kneading at a temperature of 190 ° C. to 240 ° C., preferably 200 ° C. to 210 ° C., A polyolefin / polystyrene elastomer is dispersed in a polypropylene resin, extruded into a sheet form from a T-shaped die, and the sheet is cast on a roll at 90 to 130 ° C., preferably 100 to 120 ° C., and cooled and solidified.

<(A) Cold drawing process>
Next, the sheet obtained in the molding step is 0 ° C. or more and less than 60 ° C., preferably 10 ° C. or more and less than 40 ° C., and 1.1 times or more and less than 3.0 times, preferably 1.2 times in the machine direction. Uniaxial stretching is performed in the range of at least twice and less than 2.0 times. When stretched at 0 ° C. or lower, the film tends to break, and when stretched at 60 ° C. or higher, the resulting stretched film tends to have low porosity and high air permeability. In addition, since the permeability of the microporous film obtained in the present embodiment is improved, the sheet obtained in the sheet forming step is subjected to a certain temperature range before the stretching step (step (A)) is performed. The heat treatment may be performed for a certain time.

<(B) Thermal stretching process>
Next, the stretched sheet is at a temperature of 70 ° C. or higher and lower than 170 ° C., preferably 90 ° C. or higher and lower than 120 ° C., in the machine direction 1.5 times or more and less than 5.0 times, preferably 1.5 times or more and 3.0 times. In the range of uniaxial stretching. When stretched at 70 ° C. or lower, the film tends to break, and when stretched at 170 ° C. or higher, the resulting stretched film tends to have low porosity and high air permeability. Further, from the viewpoint of physical properties and applications required for the microporous film of the present embodiment, it is preferable to stretch two or more steps under the above-described conditions. If the stretching process is one stage, the stretched film obtained may not satisfy the required physical properties.

  Surprisingly, it has been found that good permeability can be imparted to the microporous film obtained in the present embodiment by stretching two or more stages under the conditions described above. In a thermoplastic resin composition film that has been heat-stretched in one stage as shown in JP-A-8-34872, although pores are formed in the film, permeability in the film thickness direction can be obtained. Can not. On the other hand, if two or more stages are stretched under the above-described conditions, voids are formed and good communication holes are formed (the holes are three-dimensionally connected to form through holes in the film thickness direction). It was found that Furthermore, for example, for the purpose of improving dimensional stability, the obtained microporous film may be heat-set at a temperature of 120 to 170 ° C.

<Horizontal stretching process>
Next, the end of the stretched sheet uniaxially stretched by (A) cold stretching step and (B) hot stretching step is held by a tenter clip, and in the tenter oven, the stretching temperature is 90 ° C. or more and less than 170 ° C. in the width direction. Stretching is preferably performed in the range of 120 ° C. or more and less than 150 ° C., and in the range of draw ratio of 2 to 5 times, preferably in the range of 2 to 4 times to obtain the microporous film of the present embodiment. In addition to the above-described stretching steps, a stretching step can be further added.

<Lid of the present invention>
The film of the present invention has no sagging, excellent hygiene, high puncture strength, uniform and sufficient level of high air permeability required for sterilization treatment, and is therefore a lid for medical blister packaging. Suitable as a material.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited only to these Examples.

<Evaluation method>
(1) Gurley Air Permeability Based on JIS P8117, it was measured with Oken type air permeability tester EGO1 type (manufactured by Asahi Seiko).

(2) Puncture strength Using a universal tester AGS-X manufactured by Shimadzu, measurement was performed under the conditions of a needle diameter of 1.0 mm and an indentation speed of 300 mm / min, and the maximum load when the membrane was broken was puncture strength (needle penetration Strength).

(3) Powder fall test The front and back surfaces of the sample cut into 10 cm squares were rubbed 10 times with 5 cm square black foamed chloroprene rubber (product number C-4205, manufactured by Inoac Corporation), and visually evaluated.
-Evaluation criteria (circle): Powder fall did not arise. X: Powder fall-off occurred.

<Raw materials>
The raw materials used in each example and comparative example are as follows. The indications in parentheses for each elastomer are abbreviations.
(Polypropylene resin)
PP: Product name “Novatec PP FY6HA” manufactured by Nippon Polypro Co., Ltd.
MFR = 2.4 g / 10 min, melting point = 158 ° C.
(Polyolefin resin)
PO1: Product name “Hi-Zex 3300F” manufactured by Prime Polymer Co., Ltd.
MFR = 1.1 g / 10 min, melting point = 132 ° C.
PO2: Product name “NOVATEC SF240” manufactured by Japan Polytechnic Co., Ltd.
MFR = 2.0 g / 10 min, melting point = 126 ° C.
(Polyolefin / polystyrene elastomer)
EL1: Product name “Septon 1001” manufactured by Kuraray Co., Ltd.
Styrene-hydrogenated isoprene block copolymer (SEP)
EL2: Kuraray product name “Septon 2006”
Styrene-hydrogenated isoprene-styrene block copolymer (SEPS)
EL3: Kuraray product name “Septon 8004”
Styrene-ethylene-butylene-styrene block copolymer (SEBS)
EL4: Kuraray product name “Septon 8006”
Styrene-ethylene-butylene-styrene block copolymer (SEBS)
EL5: Product name “Tuftec L605” manufactured by Asahi Kasei Chemicals
Styrene-ethylene-butylene-styrene block copolymer (SEBS)
EL6: Product name “Tough Tech L606” manufactured by Asahi Kasei Chemicals
Styrene-ethylene-butylene-styrene block copolymer (SEBS)
(Olefin elastomer)
EL7: Product name “Toughmer P0480” manufactured by Mitsui Chemicals, Inc.
Ethylene-propylene copolymer (EPM)
EL8: Product name “engage 8480” manufactured by Dow Chemical Japan
Ethylene-octene copolymer (EOM)
(filler)
Filler 1: Barium sulfate, average particle size = 1.1 μm

Table 1 shows the physical properties of each elastomer.

（ＭＦＲ測定条件）
スチレン系エラストマー ：２３０℃、２．１６ｋｇ
オレフィン系エラストマー：１９０℃、２．１６ｋｇ Table 1

(MFR measurement conditions)
Styrene elastomer: 230 ° C., 2.16 kg
Olefin-based elastomer: 190 ° C, 2.16 kg

Example 1
As a polypropylene resin, PP is blended at 100 parts by mass, and polyolefin / polystyrene elastomer as EL1 is blended at a ratio of 43 parts by mass. , Diameter = 25 mmφ, L / D = 40), melt-kneaded, extruded from a T-die having a die temperature of 210 ° C., a die width of 300 mm, and a lip gap of 1 mm, and cast at a casting temperature of 110 ° C., width = A sheet having a thickness of 280 mm and an average thickness of 300 μm was obtained.
Next, the obtained raw sheet is stretched in a longitudinal direction in a roll stretching machine at a stretching temperature of 20 ° C. and a stretching ratio of 1.5 times, and further stretched at a stretching temperature of 120 ° C. and a stretching ratio of 2 times. Next, the end of the longitudinally stretched film was held with a tenter clip, and stretched in the tenter oven in the transverse direction at a stretching temperature of 145 ° C. and a stretching ratio of 3 times to obtain a microporous film having a thickness average of 100 μm. . This was evaluated. The results are shown in Table 2.

(Example 2)
In Example 1, the thickness average was obtained in the same manner as in Example 1 except that the addition amount of the polypropylene resin “PP” was 100 parts by mass and the addition amount of the polyolefin / polystyrene elastomer EL1 was 67 parts by mass. A 108 μm microporous film was obtained. This was evaluated. The results are shown in Table 2.

Example 3
In Example 1, except that the polyolefin / polystyrene elastomer was changed to EL2, it was molded in the same manner as in Example 1 to obtain a microporous film having a thickness average of 100 μm. This was evaluated. The results are shown in Table 2.

Example 4
The raw sheet of Example 3 was molded in the same manner as in Example 3 except that the stretch ratio at 20 ° C. was doubled in the longitudinal stretching process using a roll stretching machine, and the microporous material having a thickness average of 90 μm. A film was obtained. This was evaluated. The results are shown in Table 2.

(Example 5)
In Example 1, except that the polyolefin / polystyrene elastomer was changed to EL3, it was molded in the same manner as in Example 1 to obtain a microporous film having a thickness average of 118 μm. This was evaluated. The results are shown in Table 2.

(Example 6)
In Example 1, except that the polyolefin / polystyrene elastomer was changed to EL4, it was molded in the same manner as in Example 1 to obtain a microporous film having a thickness average of 90 μm. This was evaluated. The results are shown in Table 2.

(Example 7)
The raw sheet of Example 6 was molded in the same manner as in Example 3 except that the stretch ratio at 20 ° C. was doubled in the longitudinal stretching step using a roll stretching machine, and the microporous material having an average thickness of 80 μm. A film was obtained. This was evaluated. The results are shown in Table 2.

(Comparative Example 1)
In Example 1, except that the polyolefin / polystyrene elastomer was changed to EL5, it was molded in the same manner as in Example 1, and an attempt was made to produce a microporous film. The sheet was wrinkled, and the sheet was broken in the transverse stretching process, and a microporous film was not obtained. The results are shown in Table 3.

(Comparative Example 2)
In Example 1, except that the polyolefin / polystyrene elastomer was changed to EL6, it was molded in the same manner as in Example 1 and an attempt was made to produce a microporous film, but no good whitening was observed during longitudinal stretching. Since the sheet was wrinkled and good air permeability characteristics were not obtained, the subsequent evaluation was not performed. The results are shown in Table 3.

(Comparative Example 3)
In Example 1, except that the polyolefin / polystyrene elastomer was changed to EL7, it was molded in the same manner as in Example 1 and an attempt was made to produce a microporous film, but no good whitening was observed during longitudinal stretching. Since the sheet was wrinkled and good air permeability characteristics were not obtained, the subsequent evaluation was not performed. The results are shown in Table 3.

(Comparative Example 4)
In Example 1, except that the polyolefin / polystyrene elastomer was changed to EL8, it was molded in the same manner as in Example 1 and an attempt was made to produce a microporous film. Since the sheet was wrinkled and good air permeability characteristics were not obtained, the subsequent evaluation was not performed. The results are shown in Table 3.

(Comparative Example 5)
A raw sheet was prepared in the same manner as in Example 5, and this original sheet was stretched three times at 20 ° C. in the longitudinal direction of the sheet. However, since the sheet broke during stretching, no subsequent evaluation was performed. The results are shown in Table 3.

(Comparative Example 6)
A raw fabric sheet was prepared in the same manner as in Example 5, and this raw fabric sheet was sequentially stretched at a stretching ratio of 3 times at 120 ° C in the machine direction of the sheet and then 3 times at 145 ° C in the transverse direction. Since the film did not show good uniform whitening and good air permeability performance was not obtained, subsequent evaluation was not performed. The results are shown in Table 3.

(Comparative Example 7)
As a polyolefin-based resin, 233 parts by mass of PO2 and 500 parts by mass of filler 1 are blended with respect to 100 parts by mass of PO. In addition, hardened castor oil (trade name “H-COP” manufactured by KF Trading Co., Ltd.) 20 parts by weight, 1.3 parts by weight of antioxidant (BASF, trade name “Irgafos 168”), 0.7 parts by weight of heat stabilizer (BASF, trade name “Irganox 1010”) Then, the same direction twin screw extruder (Toshiba Machine Co., Ltd., caliber = 40 mmφ, L / D = 32) is melted and kneaded at a set temperature of 240 ° C. and extruded from a strand die, and then the strand is cooled in water. The resin composition which solidified, cut the strand with the cutter, and was processed into the pellet form was produced.
The obtained resin composition was extruded in a molten state at 240 ° C. to produce a sheet.
Next, the obtained raw sheet is stretched in a roll stretching machine at a stretching temperature of 20 ° C. and a stretching ratio of 1.5 times in the longitudinal direction, and further stretched at a stretching temperature of 110 ° C. and a stretching ratio of 2 times. Next, the end of the longitudinally stretched film was held with a tenter clip, and stretched in the tenter oven in the transverse direction at a stretching temperature of 100 ° C. and a stretching ratio of 3 times to obtain a microporous film having a thickness average of 150 μm. This was evaluated. The results are shown in Table 3.

Table 2

Table 3

  As shown in Table 2, the film of the present invention of Examples has high air permeability and high piercing strength. In addition, a microporous film excellent in hygiene was obtained without the disadvantage of powder falling off.

  On the other hand, as shown in Table 3, when a polyolefin / polystyrene elastomer having a high MFR value, that is, a low viscosity, or a polyolefin elastomer is used as in Comparative Examples 1 to 4, a raw sheet When the film was stretched, uniform whitening was not observed and good air permeability characteristics could not be obtained. In the film production of the present invention, it is necessary that the elastomer as islands is uniformly dispersed in the polypropylene-based resin that is the sea part of the raw sheet, and it has not been seen in these systems. It seems to be the cause. The transmission electron microscope (TEM) images of the cross sections of the original fabric sheets of Example 1 and Comparative Example 4 are shown below (FIGS. 1 and 2). In the dispersion state of FIG. 1 (Example 1), it can be seen that the polyolefin-polystyrene elastomer is uniformly dispersed in a spherical shape in the polypropylene resin, but in the state of FIG. 2 (Comparative Example 4), the olefin elastomer. It can be seen that has been stretched and spread. The film of the present invention is produced by forming a void by concentrating stress on the interface between the polypropylene resin as the sea part and the polyolefin / polystyrene elastomer as the island part during the stretching process of the raw sheet. It is considered possible. Therefore, it can be seen that the structure of the raw sheet is very important in the present invention.

  Further, in Comparative Example 5, when the stretching ratio in the low temperature stretching process at 20 ° C. was increased to 3 times, the sheet was broken. In Comparative Example 6, only the high temperature stretching process at 120 ° C. When trying to produce a microporous film, good air permeability was not exhibited, and a useful microporous film could not be obtained. Thus, this invention can provide a favorable air permeability characteristic by performing the extending process including the cold extending process at low temperature and the hot extending process at high temperature.

  Further, when a film was prepared by adding an inorganic filler as in Comparative Example 7, powder falling off in the powder falling test was conspicuous, and the problem in terms of hygiene could not be solved.

  The microporous film of the present invention is excellent in hygiene without powder falling, has high puncture strength, and has sufficient high air permeability required for sterilization treatment, and is a medical blister packaging It can be suitably used for a body cover material or the like.

2 is a TD cross-sectional view of a transmission electron microscope (TEM) photograph of the raw sheet obtained in Example 1. FIG. TD sectional drawing of the transmission electron microscope (TEM) photograph of the original fabric sheet obtained by the comparative example 4. FIG.

Claims (4)

The sea part containing the polypropylene resin as a main component, and the polyolefin / polystyrene elastomer is formed of a thermoplastic resin composition containing 25 to 75 parts by mass of polyolefin / polystyrene elastomer with respect to 100 parts by mass of polypropylene resin have a sea-island structure composed of an island portion comprising as a main component, the 230 ° C. polyolefin polystyrene-based elastomer, a melt flow rate of 2.16kg load is not more than 1.0 g / 10 min, the island portion and the sea portion surfactants, and a microporous film holes are formed in the sea portion, a thickness of 50μm or more 500μm or less, air permeability of Ru der 200 sec / 100 cc or less and 20 seconds or more / 100 cc, microporous A method of manufacturing a film,
The microporous material is biaxially stretched 1.1 times or more in the temperature range of 0 ° C. to 60 ° C. in the longitudinal direction, 1.5 times or more in the temperature range of 70 ° C. to 170 ° C. and 2 times or more in the transverse direction. For producing a conductive film . The method for producing a microporous film according to claim 1, wherein the polyolefin / polystyrene elastomer has a styrene content of 1 to 40% by mass. 3. The method for producing a microporous film according to claim 1, wherein a particle diameter of an island portion containing the polyolefin / polystyrene elastomer as a main component is 0.01 to 10 μm. The method for producing a microporous film according to any one of claims 1 to 3, wherein the puncture strength is 400 gf or more.

Images