JP2005290366A - Porous polypropylene film for filter and filter using the same, mask and filter unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film suitable for a filter, a mask, or a filter unit which prevents from passing pollen, dust, or germ and having few deformation or closure of pores when sterilized or used as a filter, a mask using the filter, a film for a filter unit. <P>SOLUTION: The porous polypropylene film for a filter comprises a polypropylene having ≥30% of β crystal fraction, wherein a microporous polypropylene film having practically non-nucleated pore penetrated between a surface and a rear surface, and having at least one melting point at 140-175°C. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a porous polypropylene film for a filter and a filter, a mask and a filter unit using the same. Specifically, as a filter film used in filter units and masks, it prevents the passage of pollen, dust, and germs, and is suitable for filter units and masks due to less sterilization and micropore deformation and closure during use. The present invention relates to a porous polypropylene film and a filter, mask and filter unit using the same.

  Conventionally, fiber woven fabrics and nonwoven fabrics are often used for filters used in masks and filter units. These filters have coarse eyes and it is difficult to prevent the passage of fine particles contained in the air such as pollen, dust, aerosols, and bacteria. Also, fiber woven fabrics and non-woven fabrics are not suitable for use in workplaces such as semiconductor engineering, precision machining, and food processing because fiber waste is generated.

  Therefore, the nonwoven fabric etc. which suppressed generation | occurrence | production of dust using the long fiber are developed (for example, patent document 1). However, it is difficult for the nonwoven fabric to completely eliminate the generation of dust.

In addition, a filter and a mask using a film having a porous structure having fine through holes have been developed (for example, Patent Document 2). However, when particles are added to form a porous structure, the particles may fall off during use, and when used as a mask, the dropped particles may be inhaled. In addition, when no particles are added, micropores may be deformed or closed during processing such as sterilization or during use, and the effect of capturing fine particles may be reduced, or air permeability and moisture permeability may be reduced. .
JP-A-5-261163 (Claim 1) JP 2003-206564 A (Claims 1 to 5)

  The present invention prevents the passage of pollen, dust, pathogens, etc. as a filter film used in filter units and masks, and is suitable for filter units and masks with less micropore deformation and closed pores during sterilization and use. An object is to provide a porous polypropylene film for a filter and a filter, a mask and a filter unit using the same.

  In order to solve the above-described problems, the present invention mainly has the following configuration. That is, the present invention relates to a porous polypropylene film for a filter which is composed of a microporous polypropylene film having substantially non-nuclear fine holes penetrating the front and back and having at least one melting point at 140 to 175 ° C. It is.

  The polypropylene is a polypropylene having a β crystal fraction of 30% or more. In a preferred embodiment, the polypropylene is a porous polypropylene film for a filter containing 0.01 to 10% by weight of a crystal nucleating agent.

  A preferred embodiment is a porous polypropylene film for a filter having a porosity of 50% or more and a deterioration of Gurley air permeability after heat treatment at 120 ° C. for 30 minutes is 10% or less.

  As a preferred embodiment, the average pore diameter of the fine pores is 0.02 to 3 μm, more preferably 0.03 to 3 μm, and the sum of the elastic modulus in the longitudinal direction and the width direction of the film is 500 MPa or more. A porous polypropylene film for a filter, a filter comprising the same, a mask and a filter unit using the filter.

  According to the present invention, as described below, a porous polypropylene film having excellent characteristics for a filter can be provided.

  (1) It has many substantially non-nuclear fine holes penetrating the front and back, exhibits high porosity, high air permeability, and small deterioration in air permeability after heat treatment at 120 ° C. for 30 minutes. Thus, processing such as heat sterilization can be performed, and when used for a filter unit or a mask, difficulty in supplying and exhausting air and difficulty in breathing can be prevented.

  (2) Having at least two types of crystal forms, polypropylene exhibits a β crystal fraction of a certain ratio or more, and the crystals are formed by adding a certain ratio of a crystal nucleating agent, thereby being substantially non-nuclear and fine. As a result, a porous film free from dust and falling particles can be obtained.

  (3) By setting the average pore diameter of the fine pores within a specific range, it is possible to prevent the passage of fine particles contained in the air such as pollen, dust, aerosols and bacteria without inhibiting air permeation. .

  (4) The use of chemically stable polypropylene as the resin makes it suitable for use in environments where chemicals are used, such as those for the pharmaceutical field, industrial use, and electronic parts.

  (5) By having a high elastic modulus and being thermally stable, it is possible to prevent deformation and closing of the micropores during wearing or processing.

  Hereinafter, the best mode for obtaining the film of the present invention and the mode of application of the porous polypropylene film of the present invention to filters, masks and filter units will be described.

  The porous polypropylene film for a filter of the present invention needs to have a substantially non-nuclear fine hole penetrating the front and back, and to have at least one melting point at 140 to 175 ° C. It is more preferable to have at least one melting point at 140 to 172 ° C., particularly preferably 140 to 165 ° C., in order to prevent deformation of fine pores. If all melting temperatures are 140 or less, fine holes may be clogged by heat during processing or sterilization, and if all melting temperatures exceed 175 ° C, the film is easily broken during stretching and film-forming properties deteriorate. There is a risk. Furthermore, the porous polypropylene film for a filter of the present invention preferably has at least two melting points from the viewpoint of the formation efficiency of fine pores, and at least 1 in the range of 140 to 160 ° C. and 160 to 175 ° C., respectively. More preferably, it has at least one melting point in the range of 142 to 155 ° C and 163 to 172 ° C.

  In the present invention, penetration through the front and back means that fine holes are continuous from the surface to the opposite surface, and the holes have connecting portions, and 1 ml of liquid paraffin (primary) is dropped from the surface of the film. The liquid paraffin passes through the inside of the film and then the hole is filled, and the optical density defined in JIS Z8120 of the dropping part is lowered.

  Examples of the polypropylene resin having at least one melting point at 140 to 175 ° C. include homopolypropylene or propylene and a second component other than propylene, such as ethylene or α-olefin, ethylene, butene, hexene, octene, etc. A weight% random or block copolymerized one can be used. Moreover, linear low density polyethylene (m-LLDPE), low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), ethylene vinyl acetate (EVA) by the metallocene catalyst method to the above polypropylene resin. , Ethylene-α-olefin copolymer such as ethylene-ethacrylate (EEA), ethylene-methyl methacrylate (EMMA), ethylene-propylene-diene copolymer (EPDM), isoprene rubber (IR), styrene copolymer, styrene -Copolymerize elastomer components such as butadiene rubber (SBR), hydrogenated styrene butadiene rubber (HSBR), styrene-butylene-styrene copolymer (SBS), styrene-ethylene-butylene-styrene copolymer (SEBS) or It can be pressurized. When the elastomer component is copolymerized or added to the polypropylene resin, the copolymerization amount or addition amount is 0.1 to 15% by weight, which improves workability by imparting flexibility, reduces discomfort during wearing, and It is preferable for improving the uniformity of the holes. If the copolymerization amount and the addition amount are less than 0.1% by weight, the addition effect cannot be exhibited. If the copolymerization amount exceeds 15% by weight, dispersion failure occurs, gel-like protrusions are formed, and heat resistance decreases. Deterioration of workability and hole deformation or closing may occur during sterilization.

  In the present invention, the melting point means that a polypropylene film is heated to 250 ° C. at a rate of 10 ° C./min in a nitrogen atmosphere in accordance with a plastic transition heat measurement method (JIS K7122). For 5 minutes, and then cooled to 10 ° C. at a cooling rate of 10 ° C./min. When the temperature was raised again at a rate of 10 ° C./min, The peak temperature of the endothermic peak that appears.

  The polypropylene resin used in the present invention needs to be a polypropylene containing 30% or more of β crystals as a crystal form in order to form many fine pores. More preferably, the ratio of β crystals is 40% or more, more preferably 50% or more, from the viewpoint of uniform pore formation. If the β crystal ratio is less than 30%, pore formation may be insufficient. The upper limit of the β crystal ratio is not particularly limited as long as the effect of the present invention is exhibited, but is preferably 95% or less from the viewpoint of preventing the strength of the film and the enlargement of the pores.

Here, the β crystal ratio of polypropylene in the film of the present invention means that the porous polypropylene film of the present invention is measured by a scanning differential calorimeter (DSC) in accordance with a plastic transition heat measurement method (JIS K7122). In a nitrogen atmosphere, a 5 mg sample was heated to 250 ° C. at a rate of 10 ° C./min and held for 5 minutes, then cooled to 10 ° C. at a cooling rate of 10 ° C./min, and again at a rate of 10 ° C./min. The heat of fusion of the endothermic peak (ΔHu-1) that appears at least once due to the melting of polypropylene-derived β crystals having a peak in the range of 140 ° C. or more and less than 160 ° C. And the heat of fusion (ΔHu−2) of the endothermic peak that appears when one or more crystals derived from polypropylene other than the β crystal having a peak at 160 ° C. or higher are melted:
β crystal ratio (%) = {ΔHu−1 / (ΔHu−1 + ΔHu−2)} × 100.
Is obtained by

  In the polypropylene resin of the present invention, particularly polypropylene, there are methods for increasing the β crystal ratio to 30% or more, such as adding a β crystal nucleating agent or slowing down the crystallization rate. Therefore, it is preferable to add a β crystal nucleating agent. The addition amount of the β crystal nucleating agent depends on the β crystal forming effect of the β crystal nucleating agent to be used, but is preferably 0.01 to 10% by weight for controlling the β crystal ratio. More preferably, it is 0.03 to 5% by weight, and further preferably 0.05 to 2% by weight, from the viewpoint of formation of β crystals and economy. When the amount added is less than 0.01% by weight, it is difficult to make the β crystal ratio 30% or more, and when it is 10% by weight or more, the economic efficiency deteriorates.

Examples of the β crystal nucleating agent used in the present invention include dibasic acid aliphatic compounds, group 2 alkaline earth metal oxides, aniline derivatives, amide compounds, and the like. Specifically, alkali or alkaline earth metal salts of carboxylic acids such as sodium benzoate, potassium 1.2-hydroxystearate, magnesium succinate, di- or triesters of di- or tribasic carboxylic acids, benzenesulfonic acid Oxidation of aromatic sulfonic acid compounds such as sodium, phthalocyanine pigments such as phthalocyanine blue, aliphatic and alicyclic aromatic amic acid diamides and organic dibasic acid components and Group IIA metals on the periodic table And those composed of components which are substances, hydroxides or salts. These β crystal nucleating agents may be used alone or in combination of two or more. As the β crystal nucleating agent, in particular, the following formula:
R ₁ —NHCO—R ₂ —CONH—R ₃ (1)
It is preferable to use one or more kinds of amide compounds of the general formula represented by the formula shown below in order to achieve a high β crystal generation effect.

Here, R ₁ in the formula represents a saturated or unsaturated aliphatic, alicyclic or aromatic dicarboxylic acid residue having _{1 to} 28 carbon atoms, or an amino acid residue, and R ₂ and R ₃ are the same. And / or a different cycloalkyl group having 3 to 18 carbon atoms and a cycloalkenyl group.

  Examples of the amide compound in the general formula (1) include adipic acid dianilide, speric acid dianilide, N, N′-dicyclohexyl terephthalamide, N, N′-dicyclohexyl-1,4-cyclohexanedicarboxamide, N, N ′. -Dicyclohexyl-2,6-naphthalenedicarboxamide, N, N'-dicyclohexyl--4,4'-biphenyldicarboxamide, N, N'-bis (p-ethylphenyl) hexanediamide, N, N'- Examples thereof include bis (4-cyclohexylphenyl) hexanediamide, p- (N-cyclohexanecarbonylamino) benzoic acid cyclohexylamide, and δ- (N-benzoylamino) -N-valeric acid anilide. In particular, from the viewpoint of the effect of forming β crystals and dispersibility, the amide compound is preferably N, N′-dicyclohexyl-2,6-naphthalenedicarboxamide.

  The isotactic index (II) of the polypropylene of the present invention is preferably 90% or more, more preferably 95% or more from the viewpoint of film formation stability and film strength. In addition, the melt flow rate (MFR) of the polypropylene is preferably 1 to 20 g / 10 min at 230 ° C. and 2.16 kg from the viewpoint of extrusion moldability and uniform formation of fine pores.

  In addition, the porous polypropylene film of the present invention needs to have substantially non-nucleated fine pores. For the formation of fine pores, when incompatible resin or inorganic or organic particles that become the core of the pores are added, the resin or particles become the core and the pores can be stably formed. Large pores are formed due to poor dispersibility or agglomeration of the agent, and the trapping ability of fine particles such as pollen, dust, aerosols and bacteria deteriorates. There is a possibility that particles may fall off, impairing the dust-free property, and hindering the health of workers and wearers.

Here, having substantially non-nuclear holes means that the cross section of the film is 1000 μm ² using a cross-sectional photograph taken by magnifying the cross section of the film 8000 times using a scanning electron microscope manufactured by Hitachi, Ltd. The number of holes, which are single bubbles having all the boundary lines present in the middle, and the shape of a circle, polygon, or the like that is the core of the hole, other than dust attached to the sample, inside the single bubbles A value obtained by counting the number of holes in which grains exist and dividing the number of voids having nuclei by the total number of voids is assumed to have 5% or less of substantially non-nucleated holes. In the cross-sectional observation of the film, ten cross-sectional photometers arbitrarily selected from different measurement visual fields were used.

  In the polypropylene of the present invention, an ultraviolet absorber, an antioxidant, a heat stabilizer, an antistatic agent, a lubricant, an antiblocking agent, a filler, and the like are blended as necessary as long as nuclei are not formed in the pores. be able to.

  In the present invention, the term “porous” means that the solid part and the void are mixed, and when the cross section of the film is magnified 8000 times, the hole part and the solid part are mixed and exist. Point to.

  The porous polypropylene film of the present invention preferably has a porosity of 50% or more from the viewpoint of air permeability. More preferably 55 to 90%, still more preferably 60 to 80%, from the viewpoint of air permeability, capture of fine particles contained in air such as pollen and dust, aerosol, bacteria, and film strength. preferable. When the porosity is 50% or less, there is a risk of causing difficulty in intake / exhaust and breathing difficulty when used as a filter unit or mask, and clogging is likely to occur when a large number of fine particles are trapped. There is a risk.

  In addition, the average pore diameter of the micropores in the porous polypropylene film of the present invention is 0.02 to 3 μm, more preferably 0.03 to 3 μm, ensuring air permeability, pollen, dust, aerosol and bacteria. It is preferable for capturing fine particles contained in the air. More preferably 0.03 to 2.5 μm, still more preferably 0.03 to 2 μm, and particularly preferably 0.03 to 1.5 μm from the viewpoint of air permeability and fine particle capturing performance. . If the average pore diameter is 0.02 μm or less, air permeability may be hindered, resulting in difficulty in intake / exhaust and breathing difficulty. If the average pore diameter is 3 μm or more, the major axis and / or minor axis may be pores. Capturing ability of fine dust, aerosols, bacteria, etc. that are less than the diameter decreases.

  The porous polypropylene film of the present invention has a 10% or less deterioration in Gurley air permeability after heat treatment at 120 ° C. for 30 minutes. It is preferable from the viewpoint of prevention. More preferably, it is 8% or less, and more preferably 6% or less. If the Gurley permeability deteriorates by 10% or more after heat treatment at 120 ° C. for 30 minutes, it becomes difficult to form the film into the target filter shape, target mask shape, or filter unit shape, and the film is sterilized. It cannot be processed and cannot be adapted to applications that require sterilization such as medical use. Here, the Gurley air permeability refers to the time (seconds) required for 100 cc of air to pass through the test piece, measured by the Gurley method according to JIS P8117. Further, the deterioration of the Gurley air permeability means that the numerical value of the Gurley air permeability after the heat treatment is larger than the numerical value of the Gurley air permeability before the heat treatment. Here, although the Gurley air permeability of the film before the heat treatment varies depending on the form to be used, when used for a filter that is a constituent element of a mask, from the viewpoint of preventing sufficient particulate capturing performance and respiration inhibition 1 to 400 seconds / 100 cc, more preferably 1 to 300 seconds / 100 cc, and particularly preferably 1 to 200 seconds / 100 cc. However, depending on the shape of the mask, it may be preferable to be 10 to 400 seconds / 100 cc, more preferably 20 to 300 seconds / 100 cc, and particularly preferably 50 to 200 seconds / 100 cc. Further, when used for a filter as a constituent element of a filter unit, from the viewpoint of capturing performance of fine particles and intake / exhaust, 1 to 500 seconds / 100 cc, more preferably 1 to 400 seconds / 100 cc, particularly preferably 1 to 300. It is preferable that it is second / 100cc. However, depending on the shape of the filter unit, it may be preferable to be 10 to 500 seconds / 100 cc, more preferably 20 to 400 seconds / 100 cc, and particularly preferably 50 to 300 seconds / 100 cc. Moreover, when it is set as the filter which can be used in common with a mask and a filter unit, it is 1 to 400 seconds / 100 cc, More preferably, 1 to 300 seconds from a viewpoint which does not inhibit fine particle capture performance and intake / exhaust, and respiration. / 100 cc, particularly preferably 1 to 200 seconds / 100 cc. However, depending on the shape of the mask or the filter unit, it may be preferable to be 10 to 400 seconds / 100 cc, more preferably 20 to 300 seconds / 100 cc, and particularly preferably 50 to 200 seconds / 100 cc. If the Gurley air permeability is too small, the trapping ability of the fine particles may not be sufficient, and if the Gurley air permeability is too large, breathing and intake / exhaust may be difficult.

  Further, the porous polypropylene film of the present invention preferably has a sum of elastic modulus in the longitudinal direction and the width direction of 500 MPa or more in order to prevent deformation of micropores during wearing or processing. When the sum of the elastic moduli is 500 MPa or less, since the pores are substantially non-nucleated, the pore diameter is enlarged by deformation of the micropores during wearing or processing, and the trapping ability of fine particles such as pollen, dust, aerosol, bacteria, etc. May get worse. In addition, the upper limit of the sum of the elastic modulus is not particularly limited in the porous polypropylene film of the present invention, but from the viewpoint of reduction in discomfort when worn when used as a mask, and workability when used for a mask or filter unit. It is preferable that it is 3000 MPa or less.

  The porous polypropylene film of the present invention can have a laminated structure in which layers having different average pore diameters are stacked for the purpose of improving particle capturing properties and preventing clogging. The laminated structure may be formed before stretching, or may be formed after stretching uniaxially or biaxially.

  Next, although an example is demonstrated about the manufacturing method of the porous polypropylene film for filters of this invention, this invention is not limited only to this example.

  In the single layer film of the porous polypropylene film of the present invention, a polypropylene resin containing 0.01 to 10% by weight of a crystal nucleating agent is supplied to an extruder heated to 180 to 300 ° C. and melted. Extrusion is performed with a die die to obtain a molten sheet. This molten sheet is extruded onto a drum maintained at a surface temperature of 100 to 130 ° C. and brought into intimate contact to be cooled and solidified to produce an unstretched film. The cooling and solidification may be performed only by extrusion onto the drum or may be performed while blowing hot air. At this time, since the drum temperature is high, a film having a high porosity after biaxial stretching can be obtained. Next, in order to form holes in the film, the unstretched laminated sheet is guided to a roll group or an oven heated to 80 to 160 ° C., the film temperature is set to 80 to 150 ° C., and the surface temperature is set to 80 to 140. A pair of nip rolls (stretching rolls) of hard chrome-plated metal roll and rubber roll kept at ℃, and a pair of nip rolls (cooling rolls) of hard chrome-plated metal roll and rubber roll kept at a surface temperature of 30-130 ℃ The film is stretched 3 to 7 times in the longitudinal direction (longitudinal direction, that is, the traveling direction of the film) by a difference in peripheral speed between the stretching roll and the cooling roll, and cooled or heat-treated with a roll group of 30 to 130 ° C. Subsequently, the both ends of the film stretched in the longitudinal direction are guided to a tenter while being gripped by clips, and are perpendicular to the longitudinal direction (width direction) in an atmosphere heated to 110 to 190 ° C. (film temperature: 90 to 165 ° C.). To 5 to 12 times. The area ratio (longitudinal stretch ratio × lateral stretch ratio) is preferably 15 to 84 times, and preferably 30 to 50 times in view of film formation stability. When the area magnification is less than 15 times, formation of the obtained pores is insufficient, and the characteristics of the film of the present invention cannot be obtained, and when the area magnification exceeds 84 times, the film tends to be broken during stretching. .

  In order to complete the crystal orientation of the biaxially stretched film thus obtained and to impart flatness and dimensional stability, it is subsequently subjected to heat treatment at 140 to 170 ° C. for 1 to 30 seconds in the tenter, and thereafter The porous film of the present invention can be obtained by uniformly cooling and then cooling to room temperature and winding. In addition, in the said heat processing process, you may perform a 3-12% relaxation process in a horizontal direction or a vertical direction as needed. Biaxial stretching may be either sequential biaxial stretching or simultaneous biaxial stretching, and may be re-stretched in either the longitudinal or lateral direction after biaxial stretching.

  Moreover, when it is set as a laminated structure, as a lamination | stacking method of a skin layer, in the composite film forming apparatus which has an extruder (a) and an extruder (b), each heats the polypropylene resin from which (beta) crystal ratio differs to 180-240 degreeC. The extruded extruder (a) and the extruded machine (b) are fed and melted and introduced into a T-die composite die, respectively, and the polymer of the extruded machine (b) is the surface layer (one side) of the polymer of the extruded machine (a). Or it laminate | stacks so that it may come to both surface layers (both surfaces), and it coextrudes in a sheet form, and obtains a fusion | melting lamination sheet. This melt-laminated sheet is closely cooled and solidified on a drum maintained at a surface temperature of 100 to 130 ° C. to produce an unstretched laminated film.

  Further, as another method for laminating the skin layers, it is possible to carry out transverse stretching after extrusion lamination on a longitudinally stretched film.

  The microporous film of the present invention thus obtained can also improve the capturing ability of fine particles such as pollen, dust and bacteria by electret treatment or surface treatment.

  The filter of the present invention is characterized in that it contains at least one porous polypropylene film for a filter as a component for capturing fine particles.

  The mask of the present invention is characterized in that it contains at least one of the filters as a component for capturing fine particles.

  Even if the filter of the present invention is composed of the above-described porous polypropylene film for a filter alone, it does not impair the object of the present invention, and the mesh or support composed of known gauze, non-woven fabric, metal, ceramic, plastic, etc. It is good also as a structure laminated | stacked in combination with the body.

  When the film of the present invention is used alone, it may be used alone or several layers may be used. In addition, when the film of the present invention is used in combination with gauze, non-woven fabric, net, etc., the gauze may be sandwiched between the films, the film may be sandwiched with the gauze, etc. as long as the object of the present invention is not impaired. May be used one by one or several at a time. In addition, when a film and gauze are used in an overlapping manner, the film and one or more types of gauze, non-woven fabric, net, and the like can be used in a configuration necessary for achieving the intended performance. When the film of the present invention alone or two or more films and a gauze are used in an overlapping manner, they may be used in direct contact with each other or may be used with a space between them. However, when using a gauze or non-woven fabric that may generate dust during use, the film of the present invention should have a surface layer on both the front and back sides of the laminated structure that needs to ensure dust-free properties. In order to prevent generation of dust during use, it is preferable that the film of the present invention is used in a bag or a gauze or nonwoven fabric is inserted into the bag. In addition, when the film of the present invention is used in combination with a support, the film may be attached to the support or may be sandwiched between the supports within the range that does not impair the object of the present invention. The support may be inserted into the bag.

  Further, the filter of the present invention is not limited to the purpose of the present invention, such as sewing, pressure bonding, bonding with an adhesive, molding, fitting or pinching to a frame of one or more metals, plastics, ceramics, etc. A desired structure can be formed by the method.

  Moreover, the known gauze and nonwoven fabric used together with the film of the present invention and the film of the present invention can improve the symptom of hay fever, as long as the holes do not interfere with the purpose of the present invention. In order to impart an effect such as a relaxation effect, essential oil or the like may be used while being held on a part or the whole of the filter by a method such as injection, impregnation, or spraying.

  With this configuration, while having air permeability, moisture permeability, and particulate capturing properties, it is excellent in mechanical strength, and further, it is possible to impart effects such as improvement of symptoms of hay fever.

  Next, the mask using the filter of the present invention is appropriately cut into a shape suitable for the shape of the target mask. To cover the mouth and nose, the shape of the filter that becomes the mask body part is a rectangle, ellipse, etc., a rectangle or ellipse that is folded into a pleated shape, to cover only the nose, The shape may be a shape necessary to achieve the purpose, such as a shape that is the same or similar to the nose, or a shape that is the same or similar to the nasal cavity for insertion into the nose. The mask may have a shape that directly contacts the nose and / or mouth, or may have a shape that does not directly contact the nose and / or mouth by molding, frame attachment, or fitting into the frame. The mask of the present invention may be composed of only a mask filter or may be fixed using rubber, string, band, band or the like. When the mask body is composed of only a mask filter, the mask body can be fixed by cutting both ends of the mask body to match the shape of the ear to form an integral shape, or one or two ends of the mask body. There are methods such as the above-described string shape or belt shape, which can be fixed by tying both ends together to form an integral shape.

  Moreover, the filter unit using the filter of the present invention is used by appropriately processing the filter into a shape suitable for the form of the intended filter unit. The shape of the filter incorporated in the filter unit may be any shape as long as it does not hinder the characteristics of the filter of the present invention, but the viewpoint of increasing the surface area per unit volume and reducing pressure loss. Therefore, it is preferable that the filter cut into a shape such as a rectangle or an ellipse is folded into a depth suitable for the shape of the target filter unit and formed into a pleat shape. In the case of a pleated shape, the shape of the pleat is within a range that does not impede the characteristics of the filter of the present invention, such as a shape that folds and folds from above and below at regular intervals, and a shape that folds and folds a shape such as a diamond shape. Any shape is acceptable.

[Measurement and evaluation method of characteristics]
The characteristic value of this invention is calculated | required with the following evaluation method and evaluation criteria.

(1) Heat of fusion and β-crystal ratio The heat of fusion is measured with a plastic resin and polypropylene film using a scanning differential calorimeter RDC220 (DSC) manufactured by Seiko Denshi Kogyo Co., Ltd. (JIS K7122). In conformity, a 5 mg sample was heated to 250 ° C. at a rate of 10 ° C./min and held for 5 minutes in a nitrogen atmosphere, then cooled to 10 ° C. at a cooling rate of 10 ° C./min, and again 10 ° C. / When the temperature is raised at a rate of minutes, when the temperature is raised again, the heat of fusion of an endothermic peak (ΔHu) that appears one or more due to melting of polypropylene-derived β crystals having a peak in the range of 140 ° C. or more and less than 160 ° C. -1) and the heat of fusion (ΔHu-2) of the endothermic peak that appears by melting one or more crystals derived from polypropylene other than the β crystal having a peak at 160 ° C. or higher. . The β crystal ratio is expressed by the following formula:
β crystal ratio (%) = {ΔHu−1 / (ΔHu−1 + ΔHu−2)} × 100
I asked for.

(2) Melting point Melting point is a nitrogen atmosphere in accordance with a method for measuring the transition heat of plastic (JIS K7122) using a polypropylene film with a scanning differential calorimeter RDC220 (DSC) manufactured by Seiko Denshi Kogyo Co., Ltd. 5 mg sample was heated up to 250 ° C. at a rate of 10 ° C./min and held for 5 minutes, then cooled to 10 ° C. at a cooling rate of 10 ° C./min, and again heated at a rate of 10 ° C./min. At that time, the peak temperature of the endothermic peak accompanying the melting of the resin during the temperature rise was defined as the melting point (Tm).

(3) Film thickness Using a dial gauge thickness gauge (JIS B-7509, measuring element 5 mmφ flat type), 10 points were measured at 10 cm intervals in the longitudinal direction and the width direction of the film, and the average value was obtained.

(4) Specific gravity and porosity The specific gravity of the film is obtained by substituting a sample sample obtained by cutting the film into a size of 30 mm × 40 mm using a high-precision electronic hydrometer SD-120L manufactured by Mirage Trading Co., Ltd. It was measured according to (Method A of JIS K-7112). The measurement was performed under conditions of a temperature of 23 ° C. and a relative humidity of 65%. Further, the apparent specific gravity (d1) of the film obtained by the above method is measured. Further, this film was thermally melted and compressed by a hot press at 280 ° C. to prepare a sheet from which pores were completely eliminated, and the apparent specific gravity (d2) of the sheet which was rapidly cooled by being immersed in water at 30 ° C. Measure in the same way. The porosity of the film is the following formula:
Porosity (%) = (1−d1 / d2) × 100
I asked for.

(5) Air permeability The air permeability is based on a paper and paperboard-air permeability test method-Gurley tester method (JIS P-8117) using a B-type densometer manufactured by Tester Sangyo Co., Ltd. Ten different points were measured under an environment of 25 ° C., and the average value was taken as the air permeability of the film.

(6) Average pore diameter The average pore diameter is determined by POROUS MATERIALS. Using an Automated Capillary Flow Porometer manufactured by INC, Fluorinert FC-40 manufactured by Sumitomo 3M Limited was measured as a test solution. The measurement was performed at three different points, and the average value of the average pore diameter at each point was defined as the average pore diameter of the film.

(5) Elastic modulus The elastic modulus was measured at 25 ° C. using Tensilon (tensile tester) manufactured by Orientec. The measurement was performed by obtaining the sum of the elastic moduli obtained from the average values obtained by measuring the elastic modulus (MPa) in the film longitudinal direction and the width direction at 10 points, respectively, with a pulling speed of 300 mm / min, a width of 10 mm, and a sample length of 50 mm.

(6) Heat resistance The film was heat-treated with a sample width of 100 mm and a sample length of 100 mm using a gear oven at 120 ° C. for 30 minutes. The rate of change due to the heat treatment of the film, the polypropylene film, the film before and after the heat treatment, measured the air permeability 10 points each to determine the average value,
Following formula:
Change rate (%) = [(air permeability before heat treatment−air permeability after heat treatment) / air permeability before heat treatment] × 100
Calculated by The method of judging heat resistance is
◯: Change rate of less than 8% Δ: Change rate of 8% or more and less than 10% ×: Change rate of 10% or more

  The present invention will be described with reference to the following examples, but the present invention is not limited thereto.

(Example 1)
As the resin composition of the porous film, 99.8% by weight of highly crystalline polypropylene (manufactured by Idemitsu Petrochemical Co., Ltd., F300SV, MFR: 3 g / 10 min), and N, N′-dicyclohexyl- 2,6-Naphthalene dicarboxyamide (manufactured by Shin Nippon Rika Co., Ltd., NU-100) 0.2% by weight was added and mixed, fed to a twin screw extruder, melted and mixed at 280 ° C, and then gut-shaped. Extruded, cooled by passing through a 20 ° C. water bath, cut to 3 mm length with a chip cutter, and dried at 100 ° C. for 2 hours. The β crystal ratio of the β crystal nucleating agent-added polypropylene was 77%. Next, the β crystal PP is supplied to an extruder heated to 200 ° C., melted, extruded into a sheet through a T die die, and brought into close contact with a cast drum heated to a surface temperature of 120 ° C. Cooled and solidified to produce an unstretched film. Next, the unstretched film was introduced into an oven heated and held at 120 ° C., preheated, stretched four times in the longitudinal direction (longitudinal direction, that is, the film traveling direction), and cooled with a roll at 100 ° C. Subsequently, the film stretched in the MD direction is guided to a tenter while holding both ends of the film with clips, and stretched 9 times in the direction perpendicular to the MD direction (lateral direction) in an atmosphere heated to 135 ° C. (area magnification: longitudinal stretching) (Magnification x transverse stretch ratio = 36 times), and then in order to complete the crystal orientation of the biaxially oriented white film and to impart flatness and dimensional stability, a relaxation heat treatment of 5% in the transverse direction at 155 ° C in a tenter After uniform cooling, the product was cooled to room temperature and wound up. The resulting film had a large number of substantially nucleus-free voids, good heat resistance, and high porosity and air permeability. It was successfully used as a filter. The properties of the obtained film are shown in Table 1.

(Example 2)
The resin composition of the porous film is 99.92% by weight of highly crystalline polypropylene (manufactured by Idemitsu Petrochemical Co., Ltd., F300SV, MFR: 3 g / 10 min), and N, N′-dicyclohexyl- as the β crystal nucleating agent. Add 0.08% by weight of 2,6-naphthalenedicarboxamide (manufactured by Shin Nippon Rika Co., Ltd., NU-100), supply it to a twin-screw extruder, melt and mix at 280 ° C. Extruded, cooled by passing through a 20 ° C. water bath, cut to 3 mm length with a chip cutter, and dried at 100 ° C. for 2 hours. The β crystal ratio of the β crystal nucleating agent-added polypropylene was 73%. Next, the β crystal PP is supplied to an extruder heated to 220 ° C., melted, extruded into a sheet through a T die die, and brought into close contact with a cast drum heated to a surface temperature of 120 ° C. Cooled and solidified to produce an unstretched film. Next, the unstretched film was introduced into an oven heated and maintained at 130 ° C., preheated, stretched 4 times in the longitudinal direction (longitudinal direction, that is, the traveling direction of the film), and cooled with a roll at 110 ° C. Subsequently, the film stretched in the MD direction is guided to a tenter while holding both ends of the film with clips, and stretched 9 times in the direction perpendicular to the MD direction (lateral direction) in an atmosphere heated to 135 ° C. (area magnification: longitudinal stretching) (Magnification x transverse stretching ratio = 36 times), and then in order to complete the crystal orientation of the biaxially oriented white film and to provide flatness and dimensional stability, a relaxation heat treatment of 5% in the transverse direction at 160 ° C in a tenter After uniform cooling, the product was cooled to room temperature and wound up. The resulting film had a large number of substantially nucleus-free voids, good heat resistance, and high porosity and air permeability. It was successfully used as a filter. The properties of the obtained film are shown in Table 1.

(Example 3)
As the resin composition of the porous film, a polypropylene resin (manufactured by Sumitomo Chemical Co., Ltd., type: FS2016, MFR: 2.1 g / 10 min.) 49.95% by weight and a β crystal nucleating agent-added polypropylene resin, SUNOCO “Bepol” (type: B-022-SP, MFR: 1.8 g / 10 min) 50% by weight and N, N′-dicyclohexyl-2,6-naphthalenedicarboxyamide (new) as β crystal nucleating agent Nippon Rika Co., Ltd., NU-100) was added and mixed at 0.05% by weight, supplied to a twin screw extruder, melted and mixed at 280 ° C, then extruded into a gut shape, and passed through a 20 ° C water tank. It was cooled, cut to 3 mm length with a tip cutter, and dried at 100 ° C. for 2 hours. The β crystal ratio of the β crystal nucleating agent-added polypropylene was 72%. Next, the β crystal PP is supplied to an extruder heated to 200 ° C., melted, extruded into a sheet through a T die die, and brought into close contact with a cast drum heated to a surface temperature of 118 ° C. Cooled and solidified to produce an unstretched film. Next, the unstretched film was introduced into an oven heated and held at 120 ° C., preheated, stretched 4 times in the longitudinal direction (longitudinal direction, that is, the film traveling direction), and cooled with a roll at 40 ° C. Subsequently, the film stretched in the MD direction is guided to a tenter while grasping both ends with a clip, and stretched 10 times in the direction perpendicular to the MD direction (lateral direction) in an atmosphere heated to 145 ° C. (area magnification: longitudinal stretching) (Magnification x transverse stretching magnification = 40 times), and then in order to complete the crystal orientation of the biaxially oriented white film and to impart flatness and dimensional stability, a relaxation heat treatment of 8% in the transverse direction at 145 ° C in a tenter After uniform cooling, the product was cooled to room temperature and wound up. The resulting film had a large number of substantially nucleus-free voids, good heat resistance, and high porosity and air permeability. It was successfully used as a filter. The properties of the obtained film are shown in Table 1.

Example 4
As the resin composition of the porous film, polypropylene resin (Mitsui Chemicals Co., Ltd., type: F107BV, MFR: 7 g / 10 min.) 94.9% by weight and linear low density polyethylene obtained with a metallocene catalyst 5% resin (Mitsubishi Chemical Co., Ltd., “Kernel” KS560, MFR: 17 g / 10 min) and N, N′-dicyclohexyl-2,6-naphthalenedicarboxyamide (Shin Nippon Rika) as β crystal nucleating agent NU-100 manufactured by Co., Ltd. was added and mixed at 0.1 wt%, supplied to a twin screw extruder, melted and mixed at 280 ° C, then extruded into a gut, cooled through a 20 ° C water bath, and cooled. It was cut into 3 mm length with a chip cutter and dried at 100 ° C. for 2 hours. The β crystal ratio of the β crystal nucleating agent-added polypropylene was 72%. Next, the β crystal PP is supplied to an extruder heated to 220 ° C., melted, extruded into a sheet through a T die die, and brought into close contact with a cast drum heated to a surface temperature of 120 ° C. Cooled and solidified to produce an unstretched film. Next, the unstretched film was introduced into an oven heated and held at 120 ° C., preheated, stretched 4 times in the longitudinal direction (longitudinal direction, that is, the film traveling direction), and cooled with a roll at 40 ° C. Subsequently, the film stretched in the MD direction is guided to a tenter while holding both ends of the film with a clip, and stretched 8 times in the direction perpendicular to the MD direction (lateral direction) in an atmosphere heated to 145 ° C. (area magnification: longitudinal stretching) (Magnification x transverse draw ratio = 32 times), and then in order to complete the crystal orientation of the biaxially oriented white film and to provide flatness and dimensional stability, a relaxation heat treatment of 8% in the transverse direction at 145 ° C in a tenter After uniform cooling, the product was cooled to room temperature and wound up. Although the obtained film was somewhat inferior in heat resistance, a large number of substantially non-nucleated voids were formed, and it had high porosity and good air permeability. It was successfully used as a filter. The results of the obtained film are shown in Table 1.

(Example 5)
As the resin composition of the porous film, 99.92% by weight of polypropylene (manufactured by Idemitsu Petrochemical Co., Ltd., F300SV, MFR: 3 g / 10 min), and N, N′-dicyclohexyl-2, 6-naphthalene dicarboxyamide (manufactured by Shin Nippon Rika Co., Ltd., NU-100) 0.08 wt% was added and mixed, fed to a twin screw extruder, melted and mixed at 280 ° C, and then extruded into a gut shape. The mixture was cooled by passing through a 20 ° C. water tank, cut to a length of 3 mm with a chip cutter, and dried at 100 ° C. for 2 hours. The β crystal ratio of the β crystal nucleating agent-added polypropylene was 73%. Next, the β crystal PP is supplied to an extruder heated to 220 ° C., melted, extruded into a sheet through a T die die, and brought into close contact with a cast drum heated to a surface temperature of 100 ° C. Cooled and solidified to produce an unstretched film. Next, the unstretched film was introduced into an oven heated and held at 120 ° C., preheated, stretched four times in the longitudinal direction (longitudinal direction, that is, the film traveling direction), and cooled with a roll at 100 ° C. Subsequently, the film stretched in the MD direction is guided to a tenter while holding both ends of the film with clips, and stretched 9 times in the direction perpendicular to the MD direction (lateral direction) in an atmosphere heated to 135 ° C. (area magnification: longitudinal stretching) (Magnification × lateral stretching ratio = 36 times), and then the crystal orientation of the biaxially oriented white film was completed, followed by a relaxation heat treatment of 135% in the transverse direction at 135 ° C. in the tenter. Cooled and wound up. The resulting film had a large number of substantially non-nucleated voids and had high porosity and air permeability, but had poor heat resistance, but was used as a filter. . The properties of the obtained film are shown in Table 1.

(Comparative Example 1)
The resin composition of the porous film is 96.92% by weight of highly crystalline polypropylene (manufactured by Idemitsu Petrochemical Co., Ltd., F300SV, MFR: 3 g / 10 min), and N, N′-dicyclohexyl- as the β crystal nucleating agent. 2,6-Naphthalenedicarboxyamide (manufactured by Shin Nippon Rika Co., Ltd., NU-100) 0.08% by weight, cross-linked particles of polymethyl methacrylate having an average particle size of 2.5 μm (manufactured by Nippon Shokubai Co., Ltd., type MA) -1002) Add 3% by weight, feed to twin screw extruder, melt and mix at 280 ° C, extrude into gut, cool through 20 ° C water bath, cut to 3mm length with chip cutter And dried at 100 ° C. for 2 hours. The β crystal ratio of the β crystal nucleating agent-added polypropylene was 69%. Next, the β crystal PP is supplied to an extruder heated to 220 ° C., melted, extruded into a sheet through a T die die, and brought into close contact with a cast drum heated to a surface temperature of 100 ° C. Cooled and solidified to produce an unstretched film. Next, the unstretched film was introduced into an oven heated and held at 120 ° C., preheated, stretched 5 times in the longitudinal direction (longitudinal direction, that is, the traveling direction of the film), and cooled with a roll at 100 ° C. Subsequently, the film stretched in the MD direction is guided to a tenter while holding both ends of the film with clips, and stretched 9 times in the direction perpendicular to the MD direction (lateral direction) in an atmosphere heated to 135 ° C. (area magnification: longitudinal stretching) (Magnification × lateral stretching magnification = 45 times), and then the crystal orientation of the biaxially oriented white film was completed, followed by a relaxation heat treatment of 135% in the transverse direction at 135 ° C. in the tenter. Cooled and wound up. The resulting film had a large number of voids and had a high porosity and air permeability, but had a large number of nuclei in the pores, so that the nuclei dropped when used as a filter. Besides being concerned, it was inferior in heat resistance. The properties of the obtained film are shown in Table 1.

(Comparative Example 2)
As the resin composition of the porous film, 30% by weight of calcium carbonate (trade name: Star Piggot 15A, manufactured by Shiraishi Calcium Co., Ltd., average particle size 0.15 μm), polypropylene (manufactured by Sun Allomer Co., Ltd., PM671A, MFR: 7 g / 10) ) 69.8% by weight and 0.2% by weight of N, N′-dicyclohexyl-2,6-naphthalenedicarboxamide (manufactured by Shin Nippon Rika Co., Ltd., NU-100) as β crystal nucleating agent Add and mix, feed to twin screw extruder, melt and mix at 280 ° C, extrude into gut shape, pass through 20 ° C water bath, cool and cut to 3mm length with chip cutter, dry at 100 ° C for 2 hours did. Next, the β-crystal polypropylene is supplied to an extruder heated to 240 ° C., melted, extruded into a sheet through a T die die, and brought into close contact with a cast drum heated to a surface temperature of 100 ° C. Cooled and solidified to produce an unstretched film. The obtained raw film was stretched about 5 times at a stretching temperature of 110 ° C. by a tenter stretching machine to obtain a porous film. The resulting film showed a high porosity, but the air permeability was low, the pore diameter exceeded the measurement limit of the instrument, and there were many nuclei in the pores. Since the calcium carbonate particles dropped out of the film during film formation, there was concern about the possibility of the particles falling off when used as a filter. The properties of the obtained film are shown in Table 1.

(Comparative Example 3)
As the resin composition of the porous film, 99.92% by weight of an ethylene-propylene random copolymer (manufactured by Sun Allomer Co., Ltd., type = PC540R, MFR = 5 g / 10 min) as a resin, and N, 0.08% by weight of N′-dicyclohexyl-2,6-naphthalenedicarboxamide (manufactured by Shin Nippon Rika Co., Ltd., NU-100) was added and mixed, supplied to a twin screw extruder, and melt mixed at 280 ° C. Thereafter, it was extruded in a gut shape, passed through a 20 ° C. water bath, cooled, cut into a 3 mm length with a chip cutter, and dried at 100 ° C. for 2 hours. The β crystal ratio of the β-crystal nucleating agent-added ethylene-polypropylene random copolymer was 12%. Next, the β crystal PP is supplied to an extruder heated to 220 ° C., melted, extruded into a sheet through a T die die, and brought into close contact with a cast drum heated to a surface temperature of 100 ° C. Cooled and solidified to produce an unstretched film. Next, the unstretched film was introduced into an oven heated and held at 90 ° C., preheated, stretched 4 times in the longitudinal direction (longitudinal direction, that is, the traveling direction of the film), and cooled with a roll at 100 ° C. Subsequently, the film stretched in the MD direction is guided to a tenter while gripping both ends with a clip, and stretched 8 times in the direction perpendicular to the MD direction (lateral direction) in an atmosphere heated to 135 ° C. (area magnification: longitudinal stretching) (Magnification × lateral stretching ratio = 32 times), and then the crystal orientation of the biaxially oriented white film was completed, followed by a relaxation heat treatment of 5% in the transverse direction at 155 ° C. in the tenter, and after uniform cooling to room temperature Cooled and wound up. Although the obtained film was formed with substantially non-nucleated voids, it had poor heat resistance, low porosity and low air permeability, and the average pore diameter exceeded the detection limit of the instrument. It was not used as a filter. The properties of the obtained film are shown in Table 1.

The porous polypropylene film of the present invention prevents passage of pollen, dust, germs, etc. as a filter, a mask using the filter, and a filter unit film, and has little micropore deformation and closed pores during sterilization and use. It can be used for porous polypropylene films for filters suitable for filters, masks and filter units, and filters, masks and filter units using the same.

Claims (9)

A microporous polypropylene film having substantially non-nuclear fine holes penetrating the front and back surfaces and having at least one melting point at 140 to 175 ° C., and having a β crystal fraction of 30% or more A porous polypropylene film for a filter, comprising: 2. The porous polypropylene film for a filter according to claim 1, comprising 0.01 to 10% by weight of a crystal nucleating agent. 3. The porous polypropylene film for a filter according to claim 1, wherein the porosity is 50% or more, and the deterioration of the Gurley air permeability after heat treatment at 120 ° C. for 30 minutes is 10% or less. The porous polypropylene film for a filter according to any one of claims 1 to 3, wherein an average pore diameter of the fine pores is 0.02 to 3 µm. The porous polypropylene film for a filter according to any one of claims 1 to 3, wherein an average pore diameter of the fine pores is 0.03 to 3 µm. The porous polypropylene film for a filter according to any one of claims 1 to 5, wherein the sum of the elastic modulus in the longitudinal direction and the width direction of the film is 500 MPa or more. The filter which uses the porous polypropylene film for filters in any one of Claims 1-6 for at least one part. A mask comprising at least a part of the filter according to claim 7. A filter unit comprising at least a part of the filter according to claim 7.