Stretchable Film

Abstract

To provide a stretchable film that can suppress a manufacturing cost and achieve both excellent stretchability and air permeability.SOLUTION: A stretchable film comprises a thermoplastic elastomer, a polyethylene-based resin, and an inorganic filler, has an air permeability, as determined with an Oken-type air permeability tester, of 500 s / 100 cc to 10,000 s / 100 cc, and has a permanent strain in at least one direction of 30% or less. The average stretch ratio of a belt-like first region which extends along the machine axis direction of the stretchable film and has a broken surface is 1.8 times or more and 3.0 times or less, and the average stretch ratio of a belt-like second region which is adjacent to the first region, is less stretchable than the first region, and extends along the machine axis direction is 1.0 time or more and 1.8 times or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a stretch film. [Background technology]

[0002] Stretch films are used in a wide range of fields, including hygiene products, sporting goods, and medical products, to improve handling, wearing comfort (fit), etc. For example, they are used in garments such as underwear, waistbands of disposable diapers, side panels, leg gathers, incontinence products, sanitary napkins, bandages, surgical drapes, tightening bands, hats, swimming trunks, sports supports, medical supporters, and adhesive bandages.

[0003] For example, a stretch film containing a polymer component including a propylene-based elastomer and a filler and produced by stretching an unstretched film has been proposed. It is described that this type of structure can provide a stretch film with excellent stretchability and breathability (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-204625 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the stretch film described in Patent Document 1, the stretching process is carried out at a temperature higher than the actual use temperature (e.g., 60°C) in order to ensure breathability, which has the problem that the elastomer is prevented from returning to its original state, maintaining the open pores and resulting in poor stretchability.

[0006] Furthermore, the stretching process in Patent Document 1 involves stretching in the machine axis (longitudinal) direction (hereinafter also referred to as "MD") of the stretch film, so when raw film obtained by extrusion molding is used, the film is oriented in the MD to some extent and cannot be stretched until sufficient breathability is achieved. Therefore, transverse stretching in the direction perpendicular to the machine axis (hereinafter also referred to as "TD") is necessary, but transverse stretching by the commonly used tenter method or inflation molding requires large equipment, which poses a problem of increased production costs, particularly for disposable products such as disposable diapers.

[0007] Therefore, the present invention has been made in consideration of the above problems, and aims to provide a stretch film that can reduce manufacturing costs and has both excellent stretchability and breathability. [Means for solving the problem]

[0008] In order to achieve the above object, the stretch film of the present invention is a stretch film containing a thermoplastic elastomer, a polyethylene resin, and an inorganic filler, and has an air permeability of 500 s / 100 cc or more and 10,000 s / 100 cc or less as measured by an Oken air permeability tester, a permanent set in at least one direction of 30% or less, and has alternating band-shaped first regions with destroyed surfaces extending along the mechanical axis direction of the stretch film and band-shaped second regions adjacent to the first regions and extending along the mechanical axis direction which are less stretchable than the first regions, and is characterized in that the average elongation ratio of the first regions is 1.8 times or more and 3.0 times or less, and the average elongation ratio of the second regions is 1.0 times or more and 1.8 times or less.

[0009] (Permanent deformation of stretch film) A strip-shaped test piece measuring 100 mm in one direction of the film and 25 mm in the direction perpendicular to that direction is cut from the stretch film, and this test piece is fixed to the gripping jaws of the testing machine so that the distance between the jaws is 25 mm. The test piece is stretched in the longitudinal direction of the test piece at a speed of 254 mm / min so that the elongation (elongation ratio) calculated by the following formula (1) becomes 100%, and then the test piece is immediately contracted at the same speed, and the permanent set [%] is calculated using the following formula (2).

[0010] Elongation [%] = (L1 - L0) / L0 × 100 (1)

[0011] Permanent set [%] = (L2-L0) / L0 × 100 (2)

[0012] where L0 is the distance between the grips (mm) before stretching, L1 is the distance between the grips (mm) after stretching, and L2 is the distance between the grips (mm) when the load on the test piece (N / 25mm) becomes 0 when contracting.

[0013] (Average elongation magnification) A strip-shaped test piece measuring 50 mm in the mechanical axis direction of the first and second regions and 100 mm in the direction perpendicular to the mechanical axis direction is cut from the stretch film. The test piece is fixed to the grips of the testing device so that the distance between the grips is 30 mm. The test piece is stretched in the direction perpendicular to the mechanical axis direction of the first and second regions at a speed of 100 mm / min so that the elongation calculated by equation (3) below is 100%. The elongation ratio (times) is calculated using equation (4) below. The elongation ratios are calculated at five randomly selected locations in both the first and second regions, and the average value is calculated.

[0014] Elongation [%] = (L1 - L0) / L0 × 100 (3)

[0015] Elongation ratio [times] = R1 / R0 (4)

[0016] where L0 is the distance between the grippers (mm) before stretching, L1 is the distance between the grippers (mm) after stretching, R0 is the length (μm) of the first region or the second region in the direction perpendicular to the mechanical axis direction before stretching, and R1 is the length (μm) of the first region or the second region in the direction perpendicular to the mechanical axis direction after stretching (however, R0 and R1 are measured at the same point in the same region).

[0017] Another stretch film of the present invention is a stretch film comprising an elastomer layer containing a thermoplastic elastomer, a polyethylene resin, and an inorganic filler, and a surface layer laminated on at least one side of the elastomer layer, wherein the air permeability measured using an Oken air permeability tester is 500 s / 100 cc or more and 10,000 s / 100 cc or less, the permanent set in at least one direction is 30% or less, and the stretch film has alternating band-shaped first regions with destroyed surfaces extending along the mechanical axis of the stretch film and band-shaped second regions adjacent to the first regions and extending along the mechanical axis, which are less stretchable than the first regions, and the average elongation ratio of the first regions is 1.8 times or more and 3.0 times or less, and the average elongation ratio of the second regions is 1.0 times or more and 1.8 times or less.

[0018] (Permanent deformation of stretch film) A strip-shaped test piece measuring 100 mm in one direction of the film and 25 mm in the direction perpendicular to that direction is cut from the stretch film, and this test piece is fixed to the gripping jaws of the testing machine so that the distance between the jaws is 25 mm. The test piece is stretched in the longitudinal direction of the test piece at a speed of 254 mm / min so that the elongation (elongation ratio) calculated by the following formula (1) becomes 100%, and then the test piece is immediately contracted at the same speed, and the permanent set [%] is calculated using the following formula (2).

[0019] Elongation [%] = (L1 - L0) / L0 × 100 (1)

[0020] Permanent set [%] = (L2-L0) / L0 × 100 (2)

[0021] where L0 is the distance between the grips (mm) before stretching, L1 is the distance between the grips (mm) after stretching, and L2 is the distance between the grips (mm) when the load on the test piece (N / 25mm) becomes 0 when contracting.

[0022] (Average elongation magnification) A strip-shaped test piece measuring 50 mm in the mechanical axis direction of the first and second regions and 100 mm in the direction perpendicular to the mechanical axis direction is cut from the stretch film. The test piece is fixed to the grips of the testing device so that the distance between the grips is 30 mm. The test piece is stretched in the direction perpendicular to the mechanical axis direction of the first and second regions at a speed of 100 mm / min so that the elongation calculated by equation (3) below is 100%. The elongation ratio (times) is calculated using equation (4) below. The elongation ratios are calculated at five randomly selected locations in both the first and second regions, and the average value is calculated.

[0023] Elongation [%] = (L1 - L0) / L0 × 100 (3)

[0024] Elongation ratio [times] = R1 / R0 (4)

[0025] where L0 is the distance between the grippers (mm) before stretching, L1 is the distance between the grippers (mm) after stretching, R0 is the length (μm) of the first region or the second region in the direction perpendicular to the mechanical axis direction before stretching, and R1 is the length (μm) of the first region or the second region in the direction perpendicular to the mechanical axis direction after stretching (however, R0 and R1 are measured at the same point in the same region). [Effects of the Invention]

[0026] According to the present invention, it is possible to provide a stretch film that can reduce production costs and has both excellent stretchability and breathability. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a plan view illustrating a stretchable film according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view showing an example of a pair of shaping rolls. [Figure 3] FIG. 4 is a cross-sectional view illustrating a stretchable film according to a second embodiment of the present invention. [Figure 4] FIG. 4 is a plan view illustrating a stretchable film according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] The stretch film of the present invention will be specifically described below. Note that the present invention is not limited to the following embodiments, and can be appropriately modified and applied within the scope of the present invention.

[0029] (First embodiment) The stretch film of this embodiment is a film-like molded article containing a thermoplastic elastomer, low-density polyethylene, and an inorganic filler. The stretch film of this embodiment has alternating strip-shaped first regions extending along the mechanical axis (longitudinal) direction (i.e., MD) of the stretch film and strip-shaped second regions extending along the MD adjacent to the first regions and less stretchable than the first regions, and has a plurality of through holes formed therein.

[0030] <Thermoplastic elastomer> "Thermoplastic elastomer" means a polymer or polymer blend that has properties similar to those of vulcanized rubber at use temperatures, loses these properties at processing temperatures, is easily processed, and regains its original properties when returned to use temperatures.

[0031] Examples of the thermoplastic elastomer include olefin elastomers, styrene elastomers, urethane elastomers, and polyester elastomers.

[0032] For example, the olefin-based elastomer used in the present invention may be a copolymer or homopolymer mainly composed of an olefin having 3 or more carbon atoms, or a copolymer mainly composed of ethylene and an olefin having 3 or more carbon atoms.

[0033] More specifically, examples of the elastomer include (1) α-olefin homopolymers such as propylene homopolymers and 1-butene homopolymers having low stereoregularity, (2) α-olefin copolymers such as propylene-ethylene copolymers, propylene-ethylene-1-butene copolymers, 1-butene-ethylene copolymers, 1-butene-propylene copolymers, 4-methylpentene-1-propylene copolymers, 4-methylpentene-1-1-butene copolymers, 4-methylpentene-1-propylene-1-butene copolymers, propylene-1-butene copolymers, ethylene-propylene copolymers, ethylene-hexene copolymers, and ethylene-octene copolymers, and (3) ethylene-α-olefin-diene terpolymers such as ethylene-propylene-ethylidenenorbornene copolymers, ethylene-propylene-butadiene copolymers, and ethylene-propylene-isoprene copolymers. Furthermore, elastomers in which the above-mentioned elastomers are dispersed in a crystalline polyolefin matrix may also be used. The olefin-based elastomers may be used alone or in combination of two or more.

[0034] Thermoplastic elastomers are generally composed of hard segments that govern basic physical properties such as mechanical properties, and soft segments that govern elasticity, a rubber-like property. Olefin-based elastomers whose hard segments consist of polypropylene are called propylene-based elastomers, while those whose hard segments consist of polyethylene are called ethylene-based elastomers. Examples of soft segments in olefin-based elastomers include EPDM, EPM, EBM, IIR, hydrogenated styrene-butadiene rubber (HSBR), NBR, and acrylic rubber (ACM). Examples of hard segments in styrene-based elastomers include polystyrene, while examples of soft segments in styrene-based elastomers include polybutadiene, polyisoprene, polyethylene, or hydrogenated versions of these.

[0035] In the case of a propylene-based elastomer, the content of propylene units relative to all units is preferably 70% by mass to 95% by mass, more preferably 80% by mass to 90% by mass. If the content of propylene units, which are hard segments, is 70% by mass or more, strength is improved, resulting in excellent moldability, while if it is 95% by mass or less, excellent stretchability is obtained due to the elasticity of the soft segments.

[0036] Furthermore, from the viewpoint of obtaining excellent stretchability, the content of the thermoplastic elastomer in the entire stretch film is preferably 20% by mass to 50% by mass, and more preferably 35% by mass to 45% by mass, of 100% by mass of the stretch film. If the content of the thermoplastic elastomer is within the above range, excellent stretchability can be obtained due to the elasticity of the soft segment contained in the elastomer.

[0037] <Polyethylene resin> The polyethylene resin is preferably one that is compatible with the thermoplastic elastomer described above, and examples of the polyethylene resin that can be used include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and ultra-low-density polyethylene (ULDPE). One type of polyethylene resin may be used alone, or two or more types may be used in combination.

[0038] Furthermore, from the viewpoint of improving breathability by contributing to the fixation of pores, the content of polyethylene resin in the entire stretch film is preferably 10% by mass or less out of 100% by mass of the stretch film. This is because if it is more than 10% by mass, the stretchability of the film may be significantly reduced since ordinary polyethylene itself is not stretchable.

[0039] From the viewpoint of improving air permeability, it is preferable to use low-density polyethylene as the polyethylene-based resin, and to set the content of low-density polyethylene to 10% by mass or less relative to the entire stretch film.

[0040] <Inorganic fillers> The inorganic filler is a component that forms through-holes by making the film porous. By performing a stretching process while the film contains this inorganic filler, the stretchable film of this embodiment can exhibit excellent breathability.

[0041] Examples of the inorganic filler include calcium carbonate, zeolite, silica, titanium oxide, calcium oxide, magnesium oxide, zinc oxide, clay, mica, barium sulfate, magnesium hydroxide, etc. The inorganic fillers may be used alone or in combination of two or more.

[0042] The inorganic filler content of the entire stretch film is preferably 50% by mass to 70% by mass, and more preferably 50% by mass to 60% by mass, of 100% by mass of the stretch film. If the inorganic filler content is within the above range, the stretching treatment will promote porosity.

[0043] The average particle size of the inorganic filler is preferably 0.8 to 15 μm. If the average particle size of the inorganic filler is 0.8 μm or more, secondary aggregation of the inorganic filler is suppressed and dispersibility in the resin is improved, and if it is 15 μm or less, holes due to drawdown during extrusion are not generated and moldability is excellent.

[0044] The term "average particle size" used herein refers to the particle size of 50% of the particles in the particle size distribution measured by a particle size distribution analyzer.

[0045] <Other ingredients> The stretch film may contain components other than the thermoplastic elastomers described above, as long as the stretchability of the stretch film is not impaired.

[0046] Other components include amide antiblocking agents (such as stearic acid amide), plasticizers, ultraviolet absorbers, antioxidants, weather stabilizers, antistatic agents, colorants, antifogging agents, metal soaps, waxes, mildew inhibitors, antibacterial agents, nucleating agents, flame retardants, lubricants, etc. The other components may be made into a masterbatch and added to the material for the stretch film.

[0047] <First and second areas> Fig. 1 is a plan view showing a stretchable film of the present embodiment. As shown in Fig. 1, stretchable film 1 of the present embodiment has a first region 2, which is a portion of the surface that is stretch-broken when the film before gear stretching is stretched into stripes by gear stretching, which will be described later, and a second region 3, which is a portion of the surface that is not stretch-broken when the film before gear stretching is stretched into stripes by gear stretching, which will be described later.

[0048] The surface of the first region 2 is stretch-broken, and the surface of the second region 3 is not stretch-broken, so the second region 3 is less likely to stretch than the first region 2, and the first region 2 is more likely to stretch than the second region 3.

[0049] Here, "the second region is less stretchable than the first region (or the first region is more stretchable than the second region)" means that when the stretch film is stretched in a direction perpendicular to the mechanical axis direction of the first and second regions (i.e., TD), the elongation (%) of the second region is smaller than the elongation (%) of the first region (or the elongation (%) of the first region is greater than the elongation (%) of the second region).

[0050] Furthermore, there are no particular limitations on the width of the first region 2 and the width and length of the second region 3, and these may be determined appropriately depending on the intended use of the stretch film 1. For example, the width W1 of the first region 2 may be set to 1.5 to 2.5 mm, and the width W2 of the second region 3 may be set to 0.2 to 0.4 mm.

[0051] <Through hole> 1, the stretchable film 1 of this embodiment has a plurality of through holes 4 formed therein. As will be described later, the through holes 4 are formed by performing a stretching process on the raw film before it is made porous.

[0052] The stretchable film 1 of this embodiment is configured to be porous by performing a stretching process on the raw film while it contains the inorganic filler 5 described above.

[0053] 1, the through holes 4 are formed in the first region 2, but they may also be formed in the second region 3. Whether the through holes 4 are formed in the first region 2 or the second region 3, breakage originating from the through holes 4 is unlikely to occur when the stretch film 1 is stretched.

[0054] Furthermore, since the surface of the first region 2 is broken, it can be stretched with low stress. Therefore, the stress applied to the periphery of the through-hole 4 is also small, and breakage during stretching is unlikely to occur. On the other hand, since the surface of the second region 3 is not broken, it has high rigidity and is unlikely to deform during stretching, and therefore is unlikely to break.

[0055] When the stretchable film 1 is manufactured by the manufacturing method of the present invention described below, most of the through holes 4 are formed in the first region 2.

[0056] The diameter of the through holes 4 is preferably 1 μm to 100 μm. If the diameter is 1 μm or more, the holes will not be clogged even in a stretchable material such as an elastomer, and excellent breathability can be obtained, and if the diameter is 100 μm or less, waterproofness can be obtained. The diameter of the through holes 4 is the average value of the opening diameters of through holes 4 at 50 randomly selected locations.

[0057] <Stretch film manufacturing method> Next, an example of a method for manufacturing the stretch film of this embodiment will be described in detail.

[0058] When manufacturing the stretch film of this embodiment, first, a raw material containing the above-mentioned thermoplastic elastomer, polyethylene resin, and inorganic filler is molded into a film using an extruder to produce a raw film before being made porous.

[0059] More specifically, first, a thermoplastic elastomer, a polyethylene resin, an inorganic filler, and, if necessary, the other components described above are mixed in a predetermined blending ratio, and the mixture is extruded into strands using a co-rotating twin-screw extruder equipped with a strand die or the like, and then cut to obtain pellets.

[0060] Next, the pellets are melt-extruded in a single-screw extruder equipped with a T-die to form a film, and the film is taken up on a take-up roll to obtain a raw film before being made porous.

[0061] Then, the raw film is subjected to uniaxial stretching (TD gear stretching) to stretch the raw film into a striped shape and make it porous, producing an elastic film 1 having alternating first regions 2 and second regions 3 and having multiple through holes 4 formed therein, as shown in Figure 1.

[0062] From the viewpoint of improving breathability, a biaxial stretching process in which stretching is performed in both MD and TD may be performed. For example, the raw film may be subjected to roll stretching in MD, and then the MD-stretched film may be subjected to gear stretching in TD.

[0063] Gear stretching is performed using a first shaping roll having multiple ridges extending circumferentially or axially and a second shaping roll having multiple ridges extending in the same direction as the ridges of the first shaping roll, arranged opposite each other so that the ridges of one shaping roll intermesh with the grooves between the ridges of the other shaping roll.

[0064] 2 is an enlarged view showing an example of a pair of shaping rolls. A first shaping roll 20 having a plurality of ridges 24 extending in the circumferential direction on the peripheral surface of a cylindrical roll body 22 and a second shaping roll 30 having a plurality of ridges 34 extending in the circumferential direction on the peripheral surface of a cylindrical roll body 32 are arranged opposite to each other with a predetermined clearance provided so that the ridges 24 of the first shaping roll 20 and the grooves 36 between the ridges 34 of the second shaping roll 30 mesh with each other, and so that the grooves 26 between the ridges 24 of the first shaping roll 20 and the ridges 34 of the second shaping roll 30 mesh with each other.

[0065] Then, while rotating the first shaping roll 20 and the second shaping roll 30, the film before the above-mentioned gear stretching (i.e., the original film in the case of uniaxial stretching, or the film after MD stretching in the case of biaxial stretching) is passed between the first shaping roll 20 and the second shaping roll 30, thereby forming a stretched first region 2 and an unstretched second region 3 between the convex ribs 24 of the first shaping roll 20 and the convex ribs 34 of the second shaping roll 30.

[0066] 2, the film before gear stretching passing between them is pushed downward by the ridges 24 of the first shaping roll 20 and upward by the ridges 34 of the second shaping roll 30. Therefore, the film before gear stretching is partially stretched in an oblique vertical direction by the adjacent ridges 24 of the first shaping roll 20 and the ridges 34 of the second shaping roll 30, forming the first region 2. At this time, cracks can be generated at the interface between the inorganic filler 5 and the resin in the stretched portion, resulting in sufficient breathability.

[0067] On the other hand, in the film before gear stretching, the portion in contact with the top of the convex rib 24 of the first shaping roll 20 or the top of the convex rib 34 of the second shaping roll 30 is not stretched and therefore becomes the second region 3.

[0068] The direction in which the film before gear stretching is partially stretched by the pair of shaping rolls in Fig. 2 is TD, and therefore gear stretching by the pair of shaping rolls in Fig. 2 is also called TD gear stretching. According to TD gear stretching, as shown in Fig. 1, strip-shaped first regions 2 extending in MD and strip-shaped second regions 3 extending in MD are alternately formed in TD.

[0069] Gear stretching is usually performed at room temperature, but not limited to gear stretching, and stretching at room temperature can remove residual strain that remains during molding, thereby having the effect of reducing permanent strain. Furthermore, when performing biaxial stretching, in which stretching is performed in both the MD and TD directions, the stretching temperature in the MD stretching process is 20°C or higher and lower than 70°C.

[0070] In gear stretching, the stretching ratio can be adjusted by adjusting the width W of the top of the convex stripes of the shaping roll, the height H of the convex stripes, the spacing P between the tops of adjacent convex stripes, and the meshing depth D between the convex stripes 24 of the first shaping roll 20 and the convex stripes 34 of the second shaping roll 30.

[0071] Furthermore, when the raw film is subjected to uniaxial stretching (gear stretching in TD), the stretching ratio is 4 to 9. This is because a stretching ratio of 4 or more promotes porosity through the stretching process, further improving the moisture permeability of the stretchable film 1, but if it is greater than 9, the film may break when stretched. Note that the "stretching ratio" here refers to the multiple, in the stretching direction, of the length of the film after stretching relative to the length of the film before stretching.

[0072] Furthermore, when a biaxial stretching process is performed in which stretching is performed in both the MD and TD directions, the stretching ratio of the gear stretching in TD can be adjusted in accordance with the stretching ratio in MD from the viewpoint of preventing the film from breaking during gear stretching in TD.

[0073] For example, when the MD stretching ratio is 2 times, the TD gear stretching ratio can be adjusted to 3 to 7 times, and when the MD stretching ratio is 3 to 4 times, the TD gear stretching ratio can be adjusted to 2 to 6 times.

[0074] Furthermore, the stretching ratio in gear stretching can be easily calculated using Pythagoras' theorem based on the principles of stretching. For example, if the distance between the top of the ridge 24 of the first shaping roll 20 and the top of the ridge 34 of the second shaping roll 30 (the width of the stretched portion of the film before gear stretching) is 1 mm and the meshing depth is √3 mm, the width of the stretched portion of the film will be 2 mm, and the stretching ratio will be 2 times. If the permanent set of this film is 30%, the width of the stretched portion will change from 1 mm before stretching to 1.3 mm.

[0075] In this way, in this embodiment, a pair of shaping rolls shown in Figure 2 is used to perform gear stretching in the TD on the raw film, so unlike the conventional technology described above, it is possible to avoid increasing the size of the equipment and reduce manufacturing costs.

[0076] Furthermore, the stretch film of this embodiment produced by the above-described method has an air permeability of 500 s / 100 cc or more and 10,000 s / 100 cc or less as measured by an Oken air permeability tester, making it possible to obtain excellent breathability. The air permeability is preferably 7,500 s / 100 cc or less, more preferably 5,000 s / 100 cc or less, and even more preferably 2,000 s / 100 cc or less.

[0077] Furthermore, the stretch film of this embodiment has a permanent set of 30% or less in at least one of the MD and TD directions, making it possible to obtain excellent stretchability.

[0078] The term "permanent strain" used herein refers to a value calculated by the following method.

[0079] A rectangular test piece measuring 100 mm in one direction of the film and 25 mm in the direction perpendicular to the one direction was cut from the stretch film, and this test piece was fixed to the grippers of a precision universal testing machine (Shimadzu Corporation, Autograph AG-5000A) with a distance between the grippers of 25 mm. The test piece was then stretched in the longitudinal direction at a speed of 254 mm / min until the elongation (elongation ratio) calculated by the following formula (1) reached 100%, and then immediately contracted at the same speed. The permanent set [%] was then calculated using the following formula (2).

[0080] Elongation [%] = (L1 - L0) / L0 × 100 (1)

[0081] Permanent set [%] = (L2-L0) / L0 × 100 (2)

[0082] where L0 is the distance between the grips (mm) before stretching, L1 is the distance between the grips (mm) after stretching, and L2 is the distance between the grips (mm) when the load on the test piece (N / 25mm) becomes 0 when contracting.

[0083] From the viewpoint of improving stretchability, the permanent set in TD where gear stretching is performed is preferably 15% or less, more preferably 10% or less.

[0084] Furthermore, from the viewpoint of stretching the stretch film with a weak force, the test force (test force at 100% elongation) when stretching in TD so that the elongation (elongation ratio) calculated by the above formula (1) is 100% is preferably 2 N or less. This test force is more preferably 1.2 N or less, even more preferably 1 N or less, and particularly preferably 0.5 N or less.

[0085] Furthermore, in the stretch film 1 of this embodiment produced by the above-mentioned gear stretching, the average elongation ratio of the first region 2 is 1.8 times or more and 3.0 times or less, and the average elongation ratio of the second region 3 is 1.0 times or more and 1.8 times or less, making it possible to obtain excellent stretchability.

[0086] The term "average elongation ratio" used herein refers to a value calculated by the following method.

[0087] A strip-shaped test piece measuring 50 mm in the mechanical axis direction (i.e., MD) of the first and second regions and 100 mm in the direction perpendicular to the mechanical axis direction (i.e., TD) is cut from the stretch film. The test piece is fixed to the grips of the testing device so that the distance between the grips is 30 mm. The test piece is stretched in the direction perpendicular to the mechanical axis direction of the first and second regions at a speed of 100 mm / min so that the elongation calculated by equation (3) below is 100%. The elongation ratio (times) is calculated using equation (4) below. The elongation ratios are calculated at five randomly selected locations in both the first and second regions, and the average is calculated.

[0088] Elongation [%] = (L1 - L0) / L0 × 100 (3)

[0089] Elongation ratio [times] = R1 / R0 (4)

[0090] where L0 is the distance between the grippers (mm) before stretching, L1 is the distance between the grippers (mm) after stretching, R0 is the length (μm) of the first region or the second region in the direction perpendicular to the mechanical axis direction before stretching, and R1 is the length (μm) of the first region or the second region in the direction perpendicular to the mechanical axis direction after stretching (however, R0 and R1 are measured at the same point in the same region).

[0091] If the average elongation ratio of the first region 2 is 1.8 times or more, the first region 2 will elongate preferentially when the stretch film 1 is stretched, thereby improving the overall stretchability of the stretch film 1. Furthermore, if the average elongation ratio of the first region 2 is 3.0 times or less, appropriate stretchability will be obtained.

[0092] Furthermore, if the average elongation ratio of the second region 3 is 1.0 times or more and 1.8 times or less, the permanent set will be small, and the stretchability of the entire stretch film will be good.

[0093] Furthermore, if the average elongation ratio of the second region 3 is 1.0 to 1.8 times, and the average elongation ratio of the first region 2 is 1.8 times or more, the first region 2, whose surface is destroyed, will elongate preferentially when the stretch film 1 is stretched. This reduces the stress around the through-holes, making breakage less likely to occur during stretching. Furthermore, the second region 3, whose surface is not destroyed, has high rigidity and undergoes little deformation when the stretch film 1 is stretched, making breakage less likely to occur.

[0094] The width of the first region 2 and the width of the second region 3 before stretching are not particularly limited, and may be determined appropriately depending on the stretchability, breathability, flexibility, etc. required for the stretch film 1.

[0095] The thickness of the raw film before stretching is preferably 10 to 80 μm, more preferably 20 to 60 μm. If the thickness of the raw film is 10 μm or more, handling properties such as wrinkles during winding and trimming ease during slitting can be ensured. If the thickness of the raw film is 80 μm or less, the stretch film after stretching can have sufficient breathability.

[0096] The thickness of the stretched film after stretching is 40-60% of the original film when stretched at room temperature, and 85-95% of the original film when stretched at room temperature. In the case of gear stretching, the unstretched portion has the same thickness as the original film, and the stretched portion is 85-95% of the original film.

[0097] By the above method, in this embodiment, it is possible to reduce production costs and obtain a stretch film that has both excellent stretchability and breathability.

[0098] The stretch film may be a single layer or may be a multi-layer film consisting of two or more layers. When the stretch film is a multi-layer film, the composition and thickness of each layer may be the same or different. When the stretch film is a multi-layer film, the thickness refers to the total thickness of the multi-layer film.

[0099] (Second embodiment) Next, a second embodiment of the present invention will be described. Note that components similar to those in the first embodiment are given the same reference numerals and descriptions thereof will be omitted.

[0100] Fig. 3 is a cross-sectional view showing a stretch film according to a second embodiment of the present invention. As shown in Fig. 3, stretch film 10 of this embodiment includes elastomer layer 6 made of a stretch film containing thermoplastic elastomer, low-density polyethylene, and inorganic filler as described in the first embodiment above, and surface layers 7 and 8 laminated on the surface of elastomer layer 6.

[0101] The elastomer layer 6 may contain other components as explained in the first embodiment above, as long as the stretchability of the stretch film 10 is not impaired.

[0102] <Surface layer> The surface layers 7 and 8 are layers for suppressing the occurrence of blocking in the stretch film 10. As shown in Figure 3, the surface layers 7 and 8 are provided on either or both of the first and second surfaces of the elastomer layer 6, but from the viewpoint of sufficiently suppressing the occurrence of blocking in the stretch film 10, it is preferable that the surface layers 7 and 8 be provided on both the first and second surfaces of the elastomer layer 6. Note that the surface layers 7 and 8 may be the same type of surface layer or different types of surface layers.

[0103] The surface layers 7 and 8 contain a thermoplastic resin (excluding a thermoplastic elastomer) and preferably further contain an inorganic filler. The surface layers 7 and 8 may also contain other components as needed, provided that the effects of the present invention are not impaired.

[0104] <Thermoplastic resin> The thermoplastic resin is preferably one that is compatible with the thermoplastic elastomer in the elastomer layer 6, and is, for example, a polyethylene-based resin or a polypropylene-based resin. In addition, from the viewpoint of excellent hot melt properties, a polyethylene-based resin is preferred, and from the viewpoint of excellent heat resistance, a polypropylene-based resin is preferred.

[0105] Examples of polyethylene-based resins include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE). Examples of polypropylene-based resins include homopolypropylene (H-PP) obtained by polymerizing propylene alone, random polypropylene (R-PP) obtained by copolymerizing ethylene and propylene, and block polypropylene (B-PP) obtained by polymerizing homopolypropylene and then copolymerizing ethylene and propylene in the presence of the homopolypropylene. One type of thermoplastic resin may be used alone, or two or more types may be used in combination.

[0106] Furthermore, from the viewpoint of obtaining excellent stretchability, the content of the thermoplastic resin in the entire surface layer is preferably 30% by mass or more and 60% by mass or less, and more preferably 40% by mass or more and 50% by mass or less, of 100% by mass of the surface layer.

[0107] <Inorganic fillers> The inorganic filler is a component that imparts slipperiness to the surfaces of the surface layers 6, 7, and further suppresses the occurrence of blocking in the stretch film 10. It is also a component that forms the through holes 4 by making the film porous, and by performing a stretching process in a state containing this inorganic filler, the stretch film of this embodiment can exhibit excellent breathability.

[0108] Examples of the inorganic filler include calcium carbonate, zeolite, silica, titanium oxide, calcium oxide, magnesium oxide, zinc oxide, clay, mica, barium sulfate, magnesium hydroxide, etc. The inorganic fillers may be used alone or in combination of two or more.

[0109] The content of the inorganic filler in the entire surface layer is preferably 40% by mass or more and 70% by mass or less, and more preferably 50% by mass or more and 60% by mass or less, of 100% by mass of the surface layer. If the content of the inorganic filler is within the above range, the porosity is promoted by performing a stretching treatment.

[0110] The average particle size of the inorganic filler is preferably 0.8 to 10 μm. If the average particle size of the inorganic filler is 0.8 μm or more, secondary aggregation of the inorganic filler is suppressed and dispersibility in the resin is improved, and if it is 10 μm or less, the feel is improved.

[0111] <Other ingredients> Other components include amide antiblocking agents (such as stearic acid amide), plasticizers, ultraviolet absorbers, antioxidants, weather stabilizers, antistatic agents, colorants, antifogging agents, metal soaps, waxes, mildew inhibitors, antibacterial agents, nucleating agents, flame retardants, lubricants, etc. The other components may be made into a masterbatch and added to the material for the stretch film.

[0112] <First and second areas> Figure 4 is a plan view showing the stretchable film of this embodiment. As shown in Figure 4, the stretchable film 10 of this embodiment has a first region 20, which is a portion of the surface layers 7, 8 that was stretch-broken when the film before gear stretching was stretched into stripes by the above-mentioned gear stretching, and a second region 30, which is a portion of the surface layers 7, 8 that was not stretch-broken when the film before gear stretching was stretched into stripes by the above-mentioned gear stretching.

[0113] In the first region 20, although the surface layers 7 and 8 remain, the surface layers 7 and 8 have been stretched to destruction, so that the stretchability is close to that of the elastomer layer alone.

[0114] In the second region 30, the surface layers 7, 8 are not broken by stretching, that is, the non-stretchable surface layers 7, 8 remain on the surface of the elastomer layer, so the stretchability is somewhat insufficient.

[0115] Furthermore, the width of the first region 20 and the width and length of the second region 30 are not particularly limited and may be determined appropriately depending on the intended use of the stretch film 10. For example, the width W3 of the first region 20 may be set to 1.5 to 2.5 mm, and the width W4 of the second region 30 may be set to 0.2 to 0.4 mm.

[0116] <Through hole> As shown in Figure 4, the stretchable film 10 of this embodiment has a plurality of through holes 4 formed therein. As will be described later, these through holes 4 are formed by stretching the raw film before it is made porous. The stretchable film 10 of this embodiment is configured so that the raw film is made porous by stretching it while it contains the inorganic filler 5 described above.

[0117] 4, the through holes 4 are formed in the first region 20, but they may also be formed in the second region 30. Whether the through holes 4 are formed in the first region 20 or the second region 30, breakage originating from the through holes 4 is unlikely to occur when the stretch film 10 is stretched.

[0118] Furthermore, the first region 20 stretches with low stress because the surface layers 7 and 8 are destroyed. Therefore, the stress acting around the through-hole 4 is also small, making it less likely to break when stretched. On the other hand, the second region 30 has high rigidity because the surface layers 7 and 8 are not destroyed, making it less likely to deform when stretched and therefore less likely to break.

[0119] When the stretchable film 10 is manufactured by the manufacturing method of the present invention described below, most of the through holes 4 are formed in the first region 20 .

[0120] As described above, the porous structure can be enhanced during the stretching process by including an inorganic filler in the surface layers 7 and 8. The diameter of the through holes 4 is preferably 1 μm to 100 μm, as in the first embodiment.

[0121] <Stretch film manufacturing method> Next, an example of a method for manufacturing the stretch film of this embodiment will be described in detail.

[0122] In the stretch film of this embodiment, similar to the first embodiment described above, a thermoplastic elastomer, a polyethylene resin, an inorganic filler, and optionally other components are mixed in a predetermined mixing ratio, extruded into strands using a co-rotating twin-screw extruder equipped with a strand die, and cut to obtain pellets for forming the elastomer layer. Similarly, a thermoplastic resin, optionally inorganic filler, and other components are mixed in a predetermined mixing ratio, extruded into strands using a co-rotating twin-screw extruder equipped with a strand die, and cut to obtain pellets for forming the surface layer.

[0123] Next, using an extruder equipped with a T-die, the pellets for forming the elastomer layer and the pellets for forming the surface layer are extruded at a predetermined temperature, and a cast film process is used to obtain a raw film before being made porous, which has an elastomer layer, a first surface layer provided on a first surface of the elastomer layer, and a second surface layer provided on a second surface of the elastomer layer.

[0124] Then, the raw film is subjected to a uniaxial stretching process (TD gear stretching) using a pair of shaping rolls as shown in Figure 2 at the same stretching temperature and stretching ratio as in the first embodiment described above, stretching the raw film into a striped shape to make it porous, thereby producing an elastic film 10 as shown in Figure 4, which has alternating first regions 20 and second regions 30 and has multiple through holes 4 formed therein.

[0125] As in the first embodiment, a biaxial stretching process in which stretching is performed in both MD and TD may be performed to improve breathability. For example, the raw film may be roll-stretched in MD, and then the MD-stretched film may be gear-stretched in TD.

[0126] Furthermore, in the stretch film 10 of this embodiment manufactured by the above-mentioned method, as in the case of the first embodiment described above, the air permeability measured using an Oken air permeability tester is 500 s / 100 cc or more and 10,000 s / 100 cc or less, and the permanent strain in at least one direction is 30% or less, making it possible to obtain a stretch film that can achieve both excellent stretchability and breathability.

[0127] Furthermore, in the stretch film 10 of this embodiment manufactured by the gear stretching described above, as in the first embodiment described above, the average elongation ratio of the first region 20 is 1.8 times or more and 3.0 times or less, and the average elongation ratio of the second region 30 is 1.0 times or more and 1.8 times or less, making it possible to obtain excellent stretchability.

[0128] The thickness of elastomer layer 6 in the raw film is preferably 10 to 80 μm, and more preferably 20 to 60 μm. If the thickness of elastomer layer 6 is 10 μm or more, sufficient test force in the MD can be ensured in stretch film 10 after stretching, and wrinkles and dimensional changes can be prevented, ensuring ease of handling. If the thickness of elastomer layer 5 is 80 μm or less, sufficient breathability can be achieved in stretch film 10 after stretching.

[0129] Furthermore, the thickness of the surface layers 7, 8 in the raw film is preferably 1 to 6 μm, and more preferably 2 to 4 μm. If the thickness of the surface layers 7, 8 is 1 μm or more, the occurrence of blocking in the stretchable film 10 after stretching can be sufficiently suppressed and the breathability of the stretchable film 10 can be improved. If the thickness of the surface layers 7, 8 is 6 μm or less, the stretchability of the stretchable film 10 can be sufficiently obtained. Note that the surface layers 7, 8 may have the same thickness or different thicknesses.

[0130] Furthermore, the thickness of the stretchable film 10 after stretching is 40 to 60% of the original film when stretched at room temperature, and 85 to 95% of the original film when stretched at room temperature. In the case of gear stretching, the unstretched portion has the same thickness as the original film, and the stretched portion has a thickness of 85 to 95% of the original film.

[0131] Furthermore, from the viewpoint of improving breathability, even in stretch films 10 in which the thickness ratio of the surface layers 7, 8 to the entire stretch film is small, it is preferable that the thickness ratio of the surface layer 7 (or surface layer 8) of the raw film and stretch film 10 to the elastomer layer 5 is surface layer:elastomer layer = 1:10 to 1:30, and more preferably surface layer:elastomer layer = 1:15 to 1:20.

[0132] By the above method, in this embodiment, as in the first embodiment described above, it is possible to reduce manufacturing costs and obtain a stretch film that has both excellent stretchability and breathability.

[0133] The stretch film may be a single layer or may be a multi-layer film consisting of two or more layers. When the stretch film is a multi-layer film, the composition and thickness of each layer may be the same or different. When the stretch film is a multi-layer film, the thickness refers to the total thickness of the multi-layer film. [Example]

[0134] The present invention will be described below based on examples. However, the present invention is not limited to these examples, and these examples can be modified or changed based on the spirit of the present invention, and such modifications are not excluded from the scope of the present invention.

[0135] The materials used to prepare the stretch film are listed below. (1) Inorganic filler: calcium carbonate (manufactured by Shiraishi Calcium Co., Ltd., product name: PO-150B-10) (2) HDPE: High-density polyethylene, density: 0.951 g / cm 3MFR: 9.1 g / 10 min (manufactured by Asahi Kasei Corporation, product name: Hizex2110JH) (3) R-PP: Random polypropylene, density: 0.90 g / cm 3 MFR: 6.7 g / 10 min (Prime Polymer Co., Ltd., product name: F227) (4) Propylene-based elastomer (Vistamaxx (registered trademark) 6102FL (manufactured by ExxonMobil, propylene-ethylene copolymer, ethylene unit content: 16% by mass) (5) LDPE: Low-density polyethylene, density: 0.922 g / cm 3 , MFR: 0.3 g / 10 min (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumikasen, F101-1)

[0136] Example 1 <Preparation of stretchable film> First, the materials shown in Table 1 were mixed to prepare a material for Example 1 having the composition (parts by mass) shown in Table 1. Next, this material was extruded into a strand shape at 200°C using a co-rotating twin-screw extruder (manufactured by JSW Corporation, product name: TEX28V-42CW-4V) equipped with a strand die, and cut to obtain pellets.

[0137] Next, these pellets were formed into a film by melt extrusion (extrusion temperature: 200°C) using a single-screw extruder (manufactured by Nagata Seisakusho) equipped with a T-die, and the film was taken up on a take-up roll to obtain a raw film before being made porous.

[0138] Then, this raw film was subjected to gear stretching in the TD using a pair of shaping rolls shown in Figure 2 under the conditions of the stretching temperature and stretching ratio shown in Table 1, thereby stretching the raw film into a striped shape to make it porous, and producing an elastic film with multiple through holes.

[0139] <Air permeability measurement> Next, the air permeability of the prepared stretched film was measured using an Oken type air permeability meter (s / 100cc) (manufactured by Asahi Seiko Co., Ltd., product name: EG01-6-1MR). Films that did not exhibit air permeability in this measurement were expressed as 99999 (s / 100cc). The results are shown in Table 1.

[0140] <Measurement of permanent deformation> From the prepared stretch film, strip-shaped test specimens measuring 100 mm in one direction and 25 mm in the direction perpendicular to the one direction were cut. These test specimens were fixed to the grips of a precision universal testing machine (Shimadzu Corporation, Autograph AG-5000A) with a distance between the grippers of 25 mm. The test specimens were then stretched in the longitudinal direction at a rate of 254 mm / min until the elongation (elongation ratio) calculated by the above formula (1) reached 100%, and then immediately retracted at the same rate. The permanent set [%] in MD and TD was calculated using the above formula (2). The test was conducted at room temperature (23°C ± 2°C). The results are shown in Table 1. The test force [N] at 100% elongation in MD and TD obtained during the permanent set measurement is also shown in Table 1.

[0141] <Measurement of average elongation ratio> From the prepared stretch film, strip-shaped test pieces measuring 50 mm in the mechanical axis direction of the first and second regions and 100 mm in the direction perpendicular to the mechanical axis direction were cut. The test pieces were fixed to the grippers of a precision universal testing machine (Shimadzu Corporation, Autograph AG-5000A) with a distance between the grippers of 30 mm. The test pieces were then stretched in the direction perpendicular to the mechanical axis direction of the first and second regions at a speed of 100 mm / min until the elongation (elongation ratio) calculated by the above formula (3) was 100%. The elongation ratio (times) was then calculated using the above formula (4). The elongation ratios were calculated at five randomly selected locations in both the first and second regions, and the average was calculated. The results are shown in Table 1.

[0142] <Waterproofness evaluation> A4 size test pieces were cut out from the prepared stretch film, and the ends of the test pieces were fixed, and 50 ml of water was dropped onto the test pieces from above. At this time, the presence or absence of water droplets or other moisture on the back surface of the test pieces was visually confirmed, and the test pieces were evaluated according to the following evaluation criteria.

[0143] No water droplets or other moisture were found on the back of the test piece: 〇 Water droplets or other moisture were observed on the back of the test piece: ×

[0144] Example 2 Except for changing the conditions of the stretching ratio in the stretching process to those shown in Table 1, the raw film having the thickness shown in Table 1 was stretched in the same manner as in Example 1 described above to produce a stretchable film.

[0145] Then, the air permeability, permanent set, and average elongation ratio were measured, and the waterproofness was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0146] Example 3 First, a raw film before being porous was obtained in the same manner as in Example 1. Next, this raw film was roll-stretched in MD under the conditions of the stretching temperature and stretching ratio shown in Table 1, and then gear-stretched in TD using a pair of shaping rolls shown in Figure 2, thereby stretching the raw film into a stripe shape to make it porous, and a stretchable film having a plurality of through-holes was produced.

[0147] Then, the air permeability, permanent set, and average elongation ratio were measured, and the waterproofness was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0148] Example 4 Except for changing the conditions of the stretching ratio in the stretching process to those shown in Table 1, the raw film having the thickness shown in Table 1 was stretched in the same manner as in Example 1 described above to produce a stretchable film.

[0149] Then, the air permeability, permanent set, and average elongation ratio were measured, and the waterproofness was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0150] (Examples 5 to 7) Except for changing the conditions of the stretching ratio in the stretching process to those shown in Table 1, the raw film having the thickness shown in Table 1 was stretched in the same manner as in Example 3 described above to produce a stretchable film.

[0151] Then, the air permeability, permanent set, and average elongation ratio were measured, and the waterproofness was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0152] Example 8 Except for changing the composition (mass parts) of the stretch film to the conditions shown in Table 1, a raw film having the thickness shown in Table 1 was stretched in the same manner as in Example 1 described above to produce a stretch film.

[0153] Then, the air permeability, permanent set, and average elongation ratio were measured, and the waterproofness was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0154] Example 9 <Preparation of stretchable film> First, the materials shown in Table 1 were mixed to prepare a material for forming an elastomer layer and a material for forming a surface layer of Example 9 having the composition (parts by mass) shown in Table 1. Next, these materials were extruded into strands at 200°C using a co-rotating twin-screw extruder (manufactured by JSW Corporation, product name: TEX28V-42CW-4V) equipped with a strand die, and then cut to obtain pellets for forming an elastomer layer and pellets for forming a surface layer.

[0155] Next, using an extruder equipped with a T-die (manufactured by Sumitomo Heavy Industries Modern Co., Ltd.), the pellets for forming the elastomer layer and the pellets for forming the surface layer were extruded at 200°C, and a film having an elastomer layer, a first surface layer formed on a first surface of the elastomer layer, and a second surface layer formed on a second surface of the elastomer layer was formed by a cast film process.The film was then wound up on a take-up roll to obtain a raw film before being made porous.

[0156] Then, this raw film was subjected to gear stretching in the TD using a pair of shaping rolls shown in Figure 2 under the conditions of the stretching temperature and stretching ratio shown in Table 1, thereby stretching the raw film into a striped shape to make it porous, and producing an elastic film with multiple through holes.

[0157] Then, the air permeability, permanent set, and average elongation ratio were measured, and the waterproofness was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0158] Example 10 Except for changing the composition (mass parts) of the surface layer to the conditions shown in Table 1, a raw film having the thickness shown in Table 1 was stretched in the same manner as in Example 9 above to produce a stretchable film.

[0159] Then, the air permeability, permanent set, and average elongation ratio were measured, and the waterproofness was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0160] (Comparative Example 1) Except for changing the conditions of the stretching ratio in the stretching process to those shown in Table 2, the raw film having the thickness shown in Table 2 was stretched in the same manner as in Example 1 described above, in an attempt to produce the stretch film of Comparative Example 1. However, in Comparative Example 1, because the stretching ratio in the TD gear stretching was very high, the film broke during stretching, and it was not possible to produce a stretch film.

[0161] Therefore, in Comparative Example 1, it was not possible to measure the air permeability, permanent set, and average elongation ratio, and to evaluate the waterproofness.

[0162] (Comparative Examples 2 to 5) Except for changing the conditions of the stretching ratio in the stretching process to those shown in Table 2, the raw film having the thickness shown in Table 2 was stretched in the same manner as in Example 3 described above to attempt to produce a stretchable film. However, in Comparative Examples 2 to 5, the stretching ratio in the gear stretching in TD was higher than the stretching ratio in MD, so the film broke during stretching and it was not possible to produce a stretchable film.

[0163] Therefore, in Comparative Examples 2 to 5, it was not possible to measure the air permeability, permanent set, and average elongation ratio, and to evaluate the waterproofness.

[0164] (Comparative Example 6) Raw films having the thicknesses shown in Table 2 were prepared in the same manner as in Example 1 above, except that no stretching treatment was carried out.

[0165] The air permeability, permanent deformation, and waterproofness were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0166] (Comparative Examples 7 to 8) Except for changing the composition (mass parts) of the stretch film to the conditions shown in Table 2, a raw film having the thickness shown in Table 2 was stretched in the same manner as in Example 1 described above to produce a stretch film.

[0167] The air permeability, permanent deformation, and waterproofness were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0168] Comparative Example 9 First, a raw film before being made porous was obtained in the same manner as in Example 1. Next, this raw film was stretched and made porous by roll stretching in the MD under the conditions of the stretching temperature and stretch ratio shown in Table 2, thereby producing a stretchable film having a plurality of through holes.

[0169] Then, the air permeability, permanent deformation, and waterproofness were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0170] (Comparative Example 10) Except for changing the conditions of the stretching ratio in the stretching process to those shown in Table 2, the raw film having the thickness shown in Table 2 was stretched in the same manner as in Comparative Example 9 described above to produce a stretchable film.

[0171] Then, the air permeability, permanent deformation, and waterproofness were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0172] [Table 1]

[0173] [Table 2]

[0174] As shown in Table 1, the stretch films of Examples 1 to 10 have an air permeability of 500 s / 100 cc or more and 10,000 s / 100 cc or less, measured using an Oken air permeability tester, a permanent set in at least one of the MD and TD directions of 30% or less, an average elongation ratio in the first region of 1.8 times or more and 3.0 times or less, and an average elongation ratio in the second region of 1.0 times or more and 1.8 times or less, and therefore it can be seen that excellent stretchability and breathability can be achieved at the same time.

[0175] On the other hand, as shown in Table 2, in Comparative Example 6, since no stretching treatment was performed, no through holes were formed by porosity, and the fabric exhibited no breathability at all (air permeability was displayed as 99999 s / 100 ml).

[0176] Furthermore, in Comparative Example 7, since no inorganic filler was blended, no through holes were formed due to porosity, and it was found that the material exhibited no breathability at all (air permeability was displayed as 99999 s / 100 ml).

[0177] Furthermore, in Comparative Example 8, since LDPE is not blended, separation between the resin and the inorganic filler is unlikely to occur, and it is clear that the material exhibits no breathability at all (air permeability is displayed as 99999 s / 100 ml).

[0178] In addition, in Comparative Example 9, only the stretching treatment (room temperature) in MD was performed, and gear stretching in TD was not performed, so it is understood that the breathability was poor (air permeability was greater than 10000 s / 100 ml).

[0179] In addition, in Comparative Example 10, only the stretching treatment (room temperature) in MD was performed, and gear stretching in TD was not performed, so it is found that the breathability is poor (air permeability is greater than 10,000 s / 100 ml) and the stretchability is poor (permanent set in TD is greater than 15%). [Industrial Applicability]

[0180] As described above, the present invention is suitable for stretch films and methods for manufacturing such films that are used in, for example, garments such as underwear, waistbands of disposable diapers, side panels, leg gathers, incontinence products, sanitary napkins, bandages, surgical drapes, tightening bands, hats, swimming trunks, sports supports, medical supporters, adhesive bandages, etc. [Explanation of symbols]

[0181] 1 stretch film 2. First Area 3. The Second Region 4 through holes 5. Inorganic fillers 6 Elastomer layer 7,8 Surface layer 10 Stretch film 20 First Area 30 Second Area

Claims

1. A stretch film containing a thermoplastic elastomer, a polyethylene resin, and an inorganic filler, The air permeability measured by an Oken type air permeability tester is 500 s / 100 cc or more and 10,000 s / 100 cc or less, The following permanent strain in at least one direction is 30% or less, the permanent strain in a direction perpendicular to the mechanical axis direction is 10% or less, The stretch film has alternating band-shaped first regions having a broken surface extending along the mechanical axis direction of the stretch film and band-shaped second regions adjacent to the first regions and extending along the mechanical axis direction, which are less stretchable than the first regions; The first region has an average elongation ratio of 1.8 times or more and 3.0 times or less, The second region has an average elongation ratio of 1.0 to 1.8 times as follows: A stretchable film characterized by: (Permanent deformation of stretch film) A strip-shaped test piece measuring 100 mm in one direction of the film and 25 mm in the direction perpendicular to the one direction was cut from the stretch film, and this test piece was fixed to the gripping tools of the testing machine so that the distance between the gripping tools was 25 mm. The test piece was stretched in the longitudinal direction of the test piece at a speed of 254 mm / min so that the elongation (elongation ratio) calculated by the following formula (1) was 100%, and then the test piece was immediately contracted at the same speed, and the permanent set [%] was calculated using the following formula (2). Elongation [%] = (L1 - L0) / L0 × 100 (1) Permanent set [%] = (L2 - L0) / L0 × 100 (2) where L0 is the distance (mm) between the grippers before stretching, L1 is the distance (mm) between the grippers after stretching, and L2 is the distance (mm) between the grippers when the load (N / 25 mm) on the test piece becomes 0 when contracting. (Average extension ratio) A strip-shaped test piece measuring 50 mm in the mechanical axis direction of the first and second regions and 100 mm in the direction perpendicular to the mechanical axis direction is cut from the stretch film. The test piece is fixed to the grips of the testing device so that the distance between the grips is 30 mm. The test piece is stretched in the direction perpendicular to the mechanical axis direction of the first and second regions at a speed of 100 mm / min so that the elongation calculated by the following formula (3) is 100%. The elongation ratio (times) is calculated using the following formula (4). The elongation ratios are calculated at five randomly selected locations in both the first and second regions, and the average is calculated. Elongation [%] = (L1 - L0) / L0 × 100 (3) Elongation ratio [times] = R1 / R0 (4) where L0 is the distance between the grippers (mm) before stretching, L1 is the distance between the grippers (mm) after stretching, R0 is the length (μm) of the first region or the second region in the direction perpendicular to the mechanical axis direction before stretching, and R1 is the length (μm) of the first region or the second region in the direction perpendicular to the mechanical axis direction after stretching (where R0 and R1 are measured at the same location in the same region).

2. The stretch film of claim 1, characterized in that the content of the thermoplastic elastomer relative to the entire stretch film is 20% by mass or more and 50% by mass or less, the content of the inorganic filler relative to the entire stretch film is 50% by mass or more and 70% by mass or less, and the content of polyethylene-based resin relative to the entire stretch film is 10% by mass or less.

3. 3. The stretchable film according to claim 1, wherein the film has an air permeability of 7500 s / 100 cc or less.

4. A method for producing the stretch film according to any one of claims 1 to 3, preparing a raw film containing the thermoplastic elastomer, the polyethylene resin, and the inorganic filler; a step of gear stretching the raw film in a direction perpendicular to the machine axis direction; A method for manufacturing a stretchable film, comprising at least the steps of:

5. A stretch film comprising an elastomer layer containing a thermoplastic elastomer, a polyethylene resin, and an inorganic filler, and a surface layer laminated on at least one surface of the elastomer layer, The air permeability measured by an Oken type air permeability tester is 500 s / 100 cc or more and 10,000 s / 100 cc or less, The following permanent strain in at least one direction is 30% or less, the permanent strain in a direction perpendicular to the mechanical axis direction is 10% or less, The stretch film has alternating band-shaped first regions having a broken surface extending along the mechanical axis direction of the stretch film and band-shaped second regions adjacent to the first regions and extending along the mechanical axis direction, which are less stretchable than the first regions; The first region has an average elongation ratio of 1.8 times or more and 3.0 times or less, The second region has an average elongation ratio of 1.0 to 1.8 times as follows: A stretchable film characterized by: (Permanent deformation of stretch film) A strip-shaped test piece measuring 100 mm in one direction of the film and 25 mm in the direction perpendicular to the one direction was cut from the stretch film, and this test piece was fixed to the gripping tools of the testing machine so that the distance between the gripping tools was 25 mm. The test piece was stretched in the longitudinal direction of the test piece at a speed of 254 mm / min so that the elongation (elongation ratio) calculated by the following formula (1) was 100%, and then the test piece was immediately contracted at the same speed, and the permanent set [%] was calculated using the following formula (2). Elongation [%] = (L1 - L0) / L0 × 100 (1) Permanent set [%] = (L2 - L0) / L0 × 100 (2) where L0 is the distance (mm) between the grippers before stretching, L1 is the distance (mm) between the grippers after stretching, and L2 is the distance (mm) between the grippers when the load (N / 25 mm) on the test piece becomes 0 when contracting. (Average extension ratio) A strip-shaped test piece measuring 50 mm in the mechanical axis direction of the first and second regions and 100 mm in the direction perpendicular to the mechanical axis direction is cut from the stretch film. The test piece is fixed to the grips of the testing device so that the distance between the grips is 30 mm. The test piece is stretched in the direction perpendicular to the mechanical axis direction of the first and second regions at a speed of 100 mm / min so that the elongation calculated by the following formula (3) is 100%. The elongation ratio (times) is calculated using the following formula (4). The elongation ratios are calculated at five randomly selected locations in both the first and second regions, and the average is calculated. Elongation [%] = (L1 - L0) / L0 × 100 (3) Elongation ratio [times] = R1 / R0 (4) where L0 is the distance between the grippers (mm) before stretching, L1 is the distance between the grippers (mm) after stretching, R0 is the length (μm) of the first region or the second region in the direction perpendicular to the mechanical axis direction before stretching, and R1 is the length (μm) of the first region or the second region in the direction perpendicular to the mechanical axis direction after stretching (where R0 and R1 are measured at the same location in the same region).

6. The stretch film described in claim 5, characterized in that the content of the thermoplastic elastomer relative to the entire elastomer layer is 20% by mass or more and 50% by mass or less, the content of the inorganic filler relative to the entire elastomer layer is 50% by mass or more and 70% by mass or less, and the content of the polyethylene-based resin relative to the entire elastomer layer is 10% by mass or less.

7. 7. The stretchable film according to claim 5, wherein the air permeability is 7500 s / 100 cc or less.

8. A method for producing the stretch film according to any one of claims 5 to 7, preparing a raw film having an elastomer layer containing the thermoplastic elastomer, the polyethylene resin, and the inorganic filler, and a surface layer provided on at least one surface of the elastomer layer; a step of gear stretching the raw film in a direction perpendicular to the machine axis direction; A method for manufacturing a stretchable film, comprising at least the steps of:

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