stretchable film

Abstract

To provide a stretchable film that has excellent elasticity, with a surface layer laminated on the surface of an elastomer layer.SOLUTION: A stretchable film 1 includes an elastomer layer 5 including thermoplastic elastomer, and surface layers 6, 7 laminated on the surface of the elastomer layer 5. The surface layers 6, 7 are composed of an olefinic resin composition containing an olefinic resin and an inorganic filler. The hysteresis loss is 40% or less.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Stretch films are used in a wide range of fields such as sanitary products, sports products, and medical supplies to improve handling properties, wearing comfort (fit), etc. For example, they are used in clothes such as underwear, the waistband of paper diapers, side panels, leg gathers, incontinence products, sanitary napkins, bandages, surgical drapes, tightening bands, hats, swim trunks, sports supporters, medical product supporters, and adhesive plasters.

[0003] Here, in a stretch film using an elastic elastomer, there is a problem that stickiness due to the properties of the elastomer is strong, and particularly in the case of a thin film such as a film, handling becomes difficult.

[0004] Therefore, in order to prevent stickiness caused by the elastomer, a stretch film provided with a surface layer formed of a resin with little stickiness on the surface of the elastomer has been proposed. More specifically, for example, a stretch film provided with an olefin resin layer laminated on at least one surface of an elastomer layer has been proposed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Generally, the elasticity of a film is evaluated by its permanent strain (the strain that remains on the film even after an external force is applied and then removed). However, relying solely on permanent strain evaluation makes it difficult to obtain a stretchable film with elasticity that approximates an ideal elastic material like rubber.

[0007] Therefore, the present invention has been made in view of the above problems, and aims to provide a stretchable film having excellent stretchability, comprising a surface layer laminated on the surface of an elastomer layer. [Means for solving the problem]

[0008] To achieve the above objective, the stretchable film of the present invention comprises an elastomer layer containing a thermoplastic elastomer and a surface layer laminated on at least one surface of the elastomer layer, wherein the surface layer is made of an olefin resin composition containing an olefin resin and an inorganic filler, and is characterized in that the following hysteresis loss is 40% or less.

[0009] (Hysteresis Loss) From the stretchable film, a strip-shaped test piece measuring 100 mm in one direction and 25 mm in the direction perpendicular to that direction is cut. This test piece is fixed to the grips of the testing machine with a distance of 25 mm between the grips. The test piece is stretched in the longitudinal direction of the test piece at a speed of 254 mm / min until the strain (elongation) calculated by equation (1) below reaches 100%, and the integral area of ​​the stress-strain curve (SS curve) at this time is defined as S1. Immediately after stretching, the test piece is contracted at the same speed until the load on the test piece (N / 25 mm) becomes 0, and the integral area of ​​the stress-strain curve (SS curve) at this time is defined as S2. The hysteresis loss [%] is then calculated from equation (2) below.

[0010] Distortion [%] = (L1 - L0) / L0 × 100 (1) Hysteresis loss [%] = S / S1 × 100 (2)

[0011] However, L0 is the distance between the grips before stretching (mm), and L1 is the distance between the grips after stretching (mm). Also, S1 is the integral area of ​​the stress-strain curve when the strain is stretched from 0% to 100%, S2 is the integral area of ​​the stress-strain curve when the strain is contracted from 100% to 0%, and S is the integral area of ​​the stress-strain curve (S1-S2) obtained by subtracting the integral area S2 from the integral area S1. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a stretchable film having a surface layer laminated on the surface of an elastomer layer, and having excellent stretchability. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view showing a stretchable film according to an embodiment of the present invention. [Figure 2] This is a plan view showing an expandable film according to an embodiment of the present invention. [Figure 3] This figure shows the integral area S1 in the stress-strain curve when the material is stretched from 0% to 100% strain. [Figure 4] This figure shows the integral area S2 in the stress-strain curve when the material is contracted from 100% strain to 0% stress. [Figure 5] This figure shows the integral area in the stress-strain curve when the integral area S2 is subtracted from the integral area S1. [Figure 6] This figure shows the integral area S in the stress-strain curve when the integral area S2 is subtracted from the integral area S1 in Example 1 and Comparative Example 2. [Modes for carrying out the invention]

[0014] Hereinafter, the stretchable film of the present invention will be specifically described. The present invention is not limited to the following embodiments, and can be appropriately modified and applied without changing the gist of the present invention.

[0015] FIG. 1 is a cross-sectional view showing a stretchable film according to an embodiment of the present invention. As shown in FIG. 1, the stretchable film 1 of the present embodiment includes an elastomer layer 5 and surface layers 6 and 7 laminated on the surface of the elastomer layer 5.

[0016] (Elastomer layer) The elastomer layer 5 is a layer that imparts stretchability to the stretchable film 1, and may be a single layer or a multi-layer of two or more layers. This elastomer layer 5 contains a thermoplastic elastomer.

[0017] <Thermoplastic elastomer> "Thermoplastic elastomer" means a polymer or polymer blend that has properties similar to those of vulcanized rubber at the use temperature, the properties disappear at the processing temperature, can be easily processed, and exhibit the original properties again when returned to the use temperature.

[0018] Examples of the thermoplastic elastomer include olefin-based elastomers and styrene-based elastomers. From the viewpoint of being able to gently stretch the film with low stress, olefin-based elastomers are preferred, and from the viewpoint of the film being difficult to stretch and having high dimensional stability during conveyance, styrene-based elastomers are preferred.

[0019] For example, the olefin-based elastomer used in the present invention includes copolymers mainly composed of olefins having 3 or more carbon atoms.

[0020] More specifically, examples include 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, and α-olefin copolymers such as propylene-1-butene copolymers. Alternatively, elastomers in which the above-mentioned elastomers are dispersed in a crystalline polyolefin matrix may be used. Among these, propylene-based elastomers such as propylene-ethylene copolymers are preferred due to their higher elasticity.

[0021] Examples of styrene-based elastomers used in the present invention include styrene-isoprene-styrene copolymer (SIS elastomer), styrene-isoprene block copolymer, styrene-butadiene-styrene block copolymer (SBS elastomer), styrene-butadiene block copolymer, hydrogenated styrene-isoprene-styrene block copolymer (styrene-ethylene-propylene-styrene block copolymer (SEPS elastomer)), and hydrogenated styrene-butadiene-styrene block copolymer (styrene-ethylene-butylene-styrene block copolymer (SEBS elastomer)). Among these, SIS elastomer and SEBS elastomer are preferred due to their higher elasticity.

[0022] Thermoplastic elastomers are generally composed of a hard segment that governs basic physical properties such as mechanical properties and a soft segment that governs rubber-like properties such as elasticity. When the hard segment of an olefin-based elastomer is made of polypropylene, it is called a propylene-based elastomer. Examples of soft segments of olefin-based elastomers include EPDM, EPM, EBM, IIR, hydrogenated styrene-butadiene rubber (HSBR), NBR, and acrylic rubber (ACM). In addition, an example of a hard segment of a styrene-based elastomer is polystyrene, and examples of soft segments of styrene-based elastomers include polybutadiene, polyisoprene, polyethylene, or hydrogenated versions thereof.

[0023] Furthermore, in the case of propylene-based elastomers, the propylene unit content relative to the total units is preferably 70% to 95% by mass, and more preferably 80% to 90% by mass. For example, in the case of propylene-ethylene copolymers, the propylene unit content relative to the total units is preferably 70% to 95% by mass (i.e., the ethylene unit content is 5% to 30% by mass). If the propylene unit content of the hard segment is 70% by mass or more, the strength is improved, resulting in excellent moldability, and if it is 95% by mass or less, the elasticity of the soft segment provides excellent stretchability.

[0024] Furthermore, the MFR of the propylene-based elastomer is preferably 0.5 to 10 g / 10 min, and more preferably 2.0 to 8.0 g / 10 min. If the MFR of the propylene-based elastomer is greater than 10 g / 10 min, the melt viscosity may be too low, making it difficult to control the thickness during film molding. Also, if the MFR of the propylene-based elastomer is less than 0.5 g / 10 min, melt fracture may occur during film molding, resulting in a rough film surface. Furthermore, if the MFR of the propylene-based elastomer is less than 2.0 g / 10 min, the melt viscosity is high, and the film may break if extruded at high speed during film molding.

[0025] Furthermore, the density of the propylene-based elastomer is 0.900 g / cm³. 3 Less than 0.900 g / cm³ is preferable. 3 In the above cases, the elasticity of the film may decrease.

[0026] Furthermore, in the case of styrene-based elastomers, the styrene unit content relative to the total units of the styrene-based elastomer is preferably 30% by mass or less, and more preferably 20% by mass or less. If the styrene unit content of the styrene-based elastomer is greater than 30% by mass, styrene has poor elasticity, which can lead to a large hysteresis loss (described later) and a decrease in the elasticity of the stretchable film.

[0027] Furthermore, thermoplastic elastomers may be used individually or in combination of two or more. For example, styrene-isoprene-styrene copolymer may be used alone, or a blend of styrene-isoprene-styrene copolymer and styrene-ethylene-butylene-styrene block copolymer may be used. Alternatively, a blend of propylene-ethylene copolymer and styrene-ethylene-butylene-styrene block copolymer may be used.

[0028] <Other ingredients> The elastomer layer 5 may contain other components besides the thermoplastic elastomer described above, as long as they do not impair the effects of the present invention. Examples of other components include other resins besides thermoplastic elastomers such as olefin resins, amide antiblocking agents (such as amide stearate), plasticizers, ultraviolet absorbers, antioxidants, weather stabilizers, antistatic agents, colorants, antifogging agents, metal soaps, waxes, antifungal agents, antibacterial agents, nucleating agents, flame retardants, lubricants, and the like. The other components may also be added to the material for stretchable film after being formed into a masterbatch.

[0029] (Surface layer) The surface layers 6 and 7 are layers that prevent the elastomer layer from becoming sticky and suppress the occurrence of blocking in the stretchable film 1. The surface layers are provided on at least one or both of the first and second surfaces of the elastomer layer, but from the viewpoint of sufficiently suppressing the occurrence of blocking in the stretchable film 1, it is preferable that they be provided on both the first and second surfaces of the elastomer layer 5, as shown in Figure 1. The surface layers 6 and 7 may be of the same type or different types.

[0030] Each of the surface layers 6 and 7 is formed from an olefin resin composition containing an olefin resin and an inorganic filler. Furthermore, the surface layers 6 and 7 may optionally contain other components as described above, to the extent that they do not impair the effects of the present invention.

[0031] <Olefin resin> As for the olefin resin, one that is compatible with the thermoplastic elastomer in the elastomer layer 5 is preferred, for example, polyethylene resins and polypropylene resins are preferred. Furthermore, from the viewpoint of improving the elasticity of the surface layers 6 and 7, polyethylene resins are preferred, and from the viewpoint of improving the heat resistance of the surface layers 6 and 7, polypropylene resins are preferred.

[0032] For example, polyethylene resins include low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE). Of these, low-density polyethylene (density: 0.910~0.930 g / cm³) is used from the viewpoint of suppressing the stickiness of the elastomer component. 3 ) is preferred, and from the viewpoint of improving elasticity, linear low-density polyethylene (density: 0.910~0.920 g / cm³) is preferred. 3 ) is preferable.

[0033] Furthermore, examples of polypropylene resins include random polypropylene (R-PP) obtained by copolymerizing propylene with ethylene, and propylene-ethylene copolymers and other propylene-based elastomers. Of these, random polypropylene (ethylene unit content: 5% by mass or less, melting point: 135-150°C) is preferred from the viewpoint of improving flexibility and heat resistance compared to polyethylene resins, as ethylene copolymerization reduces stereoregularity and lowers the degree of crystallinity. Propylene-based elastomers (propylene unit content: 70% by mass to 95% by mass, ethylene unit content: 5-30% by mass) are preferred from the viewpoint of improving elasticity.

[0034] Furthermore, olefin resins may be used individually or in combination of two or more types. For example, from the viewpoint of improving elasticity, random polypropylene and linear low-density polyethylene may be blended and used. Also, from the viewpoint of suppressing the occurrence of blocking in the elastomer component, propylene elastomer and low-density polyethylene may be blended and used.

[0035] Furthermore, the content of olefin resin relative to the entire surface layer 6 (or surface layer 7) (i.e., the entire olefin resin composition) is preferably 30% by mass or more and 85% by mass or less, when the entire surface layer is considered to be 100% by mass. This is because if it is less than 30% by mass, the content of inorganic filler in the surface layer increases, which may reduce elasticity, and if it is greater than 85% by mass, the content of inorganic filler in the surface layer decreases, which may cause blocking.

[0036] <Inorganic fillers> The inorganic filler is a component that provides slipperiness to the surface of surface layers 6 and 7, further suppressing the occurrence of blocking in the stretchable film 1.

[0037] Examples of inorganic fillers include calcium carbonate, zeolite, silica, titanium dioxide, calcium oxide, magnesium oxide, zinc oxide, clay, mica, barium sulfate, and magnesium hydroxide. Note that one or more inorganic fillers may be used individually or in combination.

[0038] Furthermore, the inorganic filler content relative to the entire surface layer 6 (or surface layer 7) (i.e., the entire olefin resin composition) is preferably 15% by mass or more and 70% by mass or less, when the entire surface layer is considered to be 100% by mass. This is because if it is less than 15% by mass, the inorganic filler content in the surface layer decreases, which may cause blocking, and if it is greater than 70% by mass, the inorganic filler content in the surface layer increases, which may reduce elasticity.

[0039] Furthermore, 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 larger, secondary aggregation of the inorganic filler is suppressed, resulting in good dispersibility in the resin and improved slipperiness. If it is 10 μm or smaller, the texture becomes smoother.

[0040] <Method for manufacturing stretchable film> Next, the method for manufacturing the stretchable film of the present invention will be described in detail.

[0041] The stretchable film of the present invention is manufactured by forming a film from raw materials containing the above-mentioned thermoplastic elastomer, olefin resin, and inorganic filler using an extruder.

[0042] More specifically, first, a thermoplastic elastomer and, if necessary, other components mentioned above are mixed in a predetermined ratio, and the mixture is extruded into strands using a twin-screw extruder equipped with a strand die and then cut to obtain pellets for forming the elastomer layer. Similarly, an olefin resin, an inorganic filler, and, if necessary, other components are mixed in a predetermined ratio, and the mixture is extruded into strands using a twin-screw extruder equipped with a strand die and then cut to obtain pellets for forming the surface layer.

[0043] Next, using an extruder equipped with a T-die, pellets for forming the elastomer layer and pellets for forming the surface layer are extruded at a predetermined temperature to obtain a raw film before stretching, having an elastomer layer, a first surface layer provided on the first surface of the elastomer layer (for example, surface layer 6 in Figure 1), and a second surface layer provided on the second surface of the elastomer layer (for example, surface layer 7 in Figure 1), by the cast-fill process method.

[0044] Then, by performing a uniaxial stretching process on the raw film, the raw film is stretched, and the stretchable film 1 shown in Figures 1 and 2 is manufactured. The stretching method is not particularly limited and examples include gear stretching, roll stretching, tenter stretching, etc.

[0045] For example, gear stretching can be performed using a pair of shaping rolls arranged opposite each other with a predetermined clearance such that the grooves between the protrusions of the first shaping roll and the protrusions of the second shaping roll interlock, and the grooves between the protrusions of the first shaping roll and the protrusions of the second shaping roll interlock.

[0046] Then, while rotating the first shaping roll and the second shaping roll, the raw film before gear stretching is passed between the first shaping roll and the second shaping roll, thereby forming stretched and unstretched regions between the protrusions of the first shaping roll and the protrusions of the second shaping roll.

[0047] In gear stretching, the stretching ratio can be adjusted by adjusting the width W of the top of the ridge on the shaping roll, the height H of the ridge, the distance P between the tops of adjacent ridges, and the engagement depth D between the ridges of the first and second shaping rolls. Furthermore, the stretching ratio in gear stretching can be easily calculated using the Pythagorean theorem based on the stretching principle.

[0048] Furthermore, the uniaxial stretching process described above is a stretching process performed in either the direction of the machine axis (longitudinal direction) of the stretchable film shown in Figure 2 (hereinafter also referred to as "MD") or in the direction perpendicular to the machine axis (hereinafter also referred to as "TD"). Alternatively, biaxial stretching, which stretches in both the MD and TD directions, may also be performed.

[0049] Furthermore, the stretching temperature in uniaxial stretching is typically room temperature (23±2°C). This is because stretching at room temperature removes residual strain that remains after film formation, thereby reducing permanent strain. Stretching at temperatures higher than room temperature can increase permanent strain because orientation progresses in the stretching direction.

[0050] Furthermore, the stretching ratio in uniaxial stretching is between 1.5 and 9 times. This is because if the stretching ratio is less than 1.5 times, residual strain remaining after film formation may not be removed. Also, if it is greater than 9 times, the film may break when stretched. Here, "stretching ratio" refers to the multiple of the length of the stretched film to the length of the film before stretching, in the stretching direction. In the case of gear stretching, it refers to the multiple of the length of the stretched region of the film to the length of the film before stretching. For example, if the distance between the top of the ridge of the first shaping roll and the top of the ridge of the second shaping roll (the width of the stretched portion of the film before gear stretching) is 1 mm and the meshing depth is √3 mm, then the width of the stretched portion of the film will be 2 mm, and the stretching ratio will be 2 times.

[0051] Furthermore, the stretchable film of this embodiment manufactured by the method described above has a hysteresis loss of 40% or less. Therefore, in the stretchable film 1 in which surface layers 6 and 7 are laminated on the surface of the elastomer layer 5, it is possible to prevent a decrease in the stretchability of the surface layers 6 and 7, and as a result, it is possible to obtain a stretchable film 1 with excellent stretchability. The hysteresis loss is preferably 35% or less, and more preferably 25% or less.

[0052] Furthermore, the term "hysteresis loss" used here refers to the value calculated using the following method.

[0053] From the stretchable film, a strip-shaped test piece measuring 100 mm in one direction and 25 mm in the direction perpendicular to that direction is cut, and this test piece is fixed to the grips of a testing machine (for example, Shimadzu Corporation's Autograph AG-5000A) with a grip distance of 25 mm. Then, under the condition that the test piece is stretched in the longitudinal direction at a speed of 254 mm / min so that the strain (elongation) calculated by the following equation (1) becomes 100%, the integral area of ​​the stress-strain curve (SS curve) is taken as S1, and immediately after stretching, the test piece is contracted at the same speed until the load on the test piece (N / 25 mm) becomes 0, and the integral area of ​​the stress-strain curve (SS curve) is taken as S2, and the hysteresis loss [%] is calculated from the following equation (2).

[0054] Distortion [%] = (L1 - L0) / L0 × 100 (1) Hysteresis loss [%] = S / S1 × 100 (2)

[0055] However, L0 is the distance between the grips before stretching (mm), and L1 is the distance between the grips after stretching (mm). Also, S1 is the integral area of ​​the stress-strain curve when the strain is stretched from 0% to 100%, S2 is the integral area of ​​the stress-strain curve when the strain is contracted from 100% to 0%, and S is the integral area of ​​the stress-strain curve obtained by subtracting the integral area S2 from the integral area S1 (i.e., S = S1 - S2).

[0056] In other words, the hysteresis loss can be calculated by subtracting the integral area S2 of the stress-strain curve (shown in Figure 4) obtained when the strain is reduced from 100% to 0% stress, from the integral area S1 of the stress-strain curve (shown in Figure 3) when the strain is extended from 0% to 100%, and then dividing the resulting integral area (i.e., the integral area S shown in Figure 5) by the integral area S1, using the above equation (2).

[0057] Furthermore, since the stretchable film of this embodiment has a permanent strain of 10% or less in the stretching direction, it is possible to obtain excellent stretchability. The permanent strain is preferably 7% or less, and more preferably 5% or less.

[0058] Furthermore, the term "permanent deformation" as used here refers to the amount calculated by the following method.

[0059] From the stretchable film, a strip-shaped test piece measuring 100 mm in one direction and 25 mm in the direction perpendicular to that direction is cut. This test piece is fixed to the grips of a testing machine (for example, Shimadzu Autograph AG-5000A) with a grip distance of 25 mm. The test piece is then stretched in the longitudinal direction at a speed of 254 mm / min until the strain (elongation) calculated by formula (1) below reaches 100%, and then immediately contracted at the same speed. The permanent strain [%] is then calculated from formula (3) below.

[0060] Distortion [%] = (L1 - L0) / L0 × 100 (1) Permanent strain [%] = (L2 - L0) / L0 × 100 (3)

[0061] However, L0 is the distance between the grips before stretching (mm), L1 is the distance between the grips after stretching (mm), and L2 is the distance between the grips when the load on the test piece (N / 25mm) becomes 0 during contraction (mm).

[0062] Furthermore, from the viewpoint of transportability of the stretchable film, it is preferable that the test force (test force at 10% stretch) used to stretch the MD so that the strain (elongation) calculated by formula (1) above becomes 10% is 0.5 N or more, more preferably 0.8 N or more, and even more preferably 1.5 N or more.

[0063] The thickness of the base film is preferably 20 to 80 μm, more preferably 20 to 60 μm, and even more preferably 30 to 50 μm. If the thickness of the base film is 20 μm or more, it has excellent elasticity. If the thickness of the base film is 80 μm or less, the stretchable film can be made thinner, resulting in lower rigidity and excellent elasticity.

[0064] Furthermore, the thickness of the elastomer layer 5 in the base film is preferably 10 to 60 μm, and more preferably 20 to 40 μm. If the thickness of the elastomer layer 5 is 10 μm or more, sufficient elasticity can be obtained in the stretchable film 1, and it can be stably wound onto a roll during film molding. Also, if the thickness of the elastomer layer 5 is 60 μm or less, the stress on the stretchable film 1 will not become too high, so the stretchable film 1 can be stretched with a weak force.

[0065] Furthermore, the thickness of the surface layers 6 and 7 in the raw film is preferably 0.5 to 7 μm, and more preferably 1 to 4 μm. If the thickness of the surface layers 6 and 7 is 0.5 μm or more, the occurrence of blocking in the stretchable film 1 after stretching treatment can be sufficiently suppressed. Also, if the thickness of the surface layers 6 and 7 is 7 μm or less, sufficient stretchability can be obtained in the stretchable film 1. Note that the surface layers 6 and 7 may have the same thickness or different thicknesses.

[0066] Furthermore, the thickness of the stretched film 1 after stretching is 85-95% of the original film when stretched at room temperature. In the case of gear stretching, the unstretched portion is the same thickness as the original film, and the stretched portion is 85-95% of the original film.

[0067] Furthermore, even in stretchable film 1 where the thickness ratio of the surface layers 6 and 7 to the total thickness of the stretchable film is small, from the viewpoint of improving stretchability, it is preferable that the thickness ratio of the surface layer 7 (or surface layer 8) to the elastomer layer 5 in the base film be surface layer:elastomer layer = 1:4 to 1:30, and more preferably 1:9 to 1:18.

[0068] By the method described above, in this embodiment, excellent stretchability can be obtained in the stretchable film 1 in which surface layers 6 and 7 are laminated on the surface of the elastomer layer 5.

[0069] The stretchable film may be a single layer or a multi-layered film of two or more layers. If the stretchable film is multi-layered, the composition and thickness of each layer may be the same or different. The thickness of a multi-layered stretchable film refers to the total thickness of the multi-layered film. [Examples]

[0070] 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 and altered in accordance with the spirit of the invention; such modifications do not exclude them from the scope of the invention.

[0071] The materials used to produce the stretchable film are listed below. (1) Propylene elastomer (manufactured by ExxonMobil, trade name: Vistamaxx(registered trademark) 6102FL, propylene-ethylene copolymer, ethylene unit content: 16% by mass, density: 0.862 g / cm³) 3 (MFR: 3.0g / 10 minutes) (2) LDPE: Low-density polyethylene, density: 0.922 g / cm³ 3 MFR: 0.3g / 10min (manufactured by Sumitomo Chemical Co., Ltd., product name: Sumikasen, F101-1) (3) R-PP: Random polypropylene, density: 0.90 g / cm³ 3 MFR: 6.7g / 10 minutes (Prime Polymer Co., Ltd., product name: F227) (4) LLDPE: Linear low-density polyethylene, melting point: 120°C, density: 0.913 g / cm³ 3 MFR: 2.0g / 10 minutes (manufactured by Tosoh Corporation, product name: Nipolon-Z ZF220) (5) Inorganic filler: Calcium carbonate (manufactured by Shiraishi Calcium Co., Ltd., product name: PO-150B-10) (6) Ethylene-based elastomer (manufactured by Dow Chemical, trade name: Infuse9007, ethylene-octene copolymer) (7) SIS Elastomer 1 (manufactured by Zeon Corporation, product name: Quintac3390, styrene unit content: 48% by mass) (8) SIS Elastomer 2 (Manufactured by Zeon Corporation, Product name: Quintac3290, Styrene unit content: 35% by mass) (9) SIS Elastomer 3 (Manufactured by Zeon Corporation, Product name: Quintac3440, Styrene unit content: 18% by mass) (10) SIS Elastomer 4 (manufactured by Zeon Corporation, product name: Quintac3620, styrene unit content: 14% by mass) (11) SBS elastomer (manufactured by Asahi Kasei Chemikells, product name: Toughprene A, styrene unit content: 40% by mass) (12) SEBS elastomer (manufactured by Asahi Kasei Chemikells, product name: ToughTec H1221, styrene unit content: 14% by mass)

[0072] (Example 1) <Fabrication of stretchable film> First, the materials shown in Table 1 were mixed to prepare the elastomer layer-forming material and the surface layer-forming material for Example 1, having the composition (parts by mass) shown in Table 1. Next, these materials were extruded into strands and cut at 200°C using a twin-screw extruder equipped with a strand die (manufactured by JSW, product name: TEX28V-42CW-4V) to obtain elastomer layer-forming pellets and surface layer-forming pellets.

[0073] Next, using an extruder equipped with a T-die (manufactured by Labotec), pellets for forming the elastomer layer and pellets for forming the surface layer were extruded at 200°C. A film having an elastomer layer, a first surface layer provided on the first surface of the elastomer layer, and a second surface layer provided on the second surface of the elastomer layer was formed by the cast film process method, and the raw film before stretching was obtained by winding the film on a winding roll.

[0074] Then, by performing a gear stretching treatment (stretching ratio: 7.4 times) on this raw film roll at room temperature (23℃±2℃), a stretchable film was produced.

[0075] <Measurement of hysteresis loss> From the fabricated stretchable film, strip-shaped test pieces measuring 100 mm in one direction (TD) and 25 mm in the direction perpendicular to that direction (MD) were cut. These test pieces were fixed to the grips of a precision universal testing machine (Shimadzu Corporation, Autograph AG-5000A) with a grip distance of 25 mm. Then, under the condition of stretching the test piece in the longitudinal direction at a speed of 254 mm / min, the integral area of ​​the stress-strain curve (SS curve) when the strain (elongation) calculated by equation (1) above reached 100% was defined as S1. Immediately after stretching, the test piece was contracted at the same speed until the load on the test piece (N / 25 mm) became 0. The integral area of ​​the stress-strain curve (SS curve) when the test piece was contracted until the load on the test piece (N / 25 mm) became 0 was defined as S2. The hysteresis loss [%] was calculated from equation (2) above. The results are shown in Table 1.

[0076] <Measurement of permanent deformation> From the fabricated stretchable film, strip-shaped test pieces measuring 100 mm in one direction (TD) and 25 mm in the direction perpendicular to the TD (MD) were cut. These test pieces were fixed to the grips of a precision universal testing machine (Shimadzu Corporation, Autograph AG-5000A) with a grip distance of 25 mm. The test piece was then stretched in the longitudinal direction at a speed of 254 mm / min until the strain (elongation) calculated by equation (1) above reached 100%, and immediately contracted at the same speed. The permanent strain [%] in TD was then calculated from equation (3) above. The test was conducted at room temperature (23℃ ± 2℃). The results are shown in Table 1.

[0077] <Overall evaluation as an elastic material> The fabricated stretched film was subjected to a comprehensive evaluation as an elastic material. More specifically, the hysteresis loss mentioned above was evaluated and scored according to the following criteria.

[0078] Hysteresis loss of 25% or less... 3 points Hysteresis loss greater than 25% but less than or equal to 35%... 2 points Hysteresis loss greater than 35% but less than or equal to 40%... 1 point Hysteresis loss is greater than 40%... 0 points

[0079] Furthermore, the permanent deformations mentioned above were evaluated according to the following criteria.

[0080] Permanent distortion of 5% or less... 3 points Permanent deformation greater than 5% but less than or equal to 7%... 2 points Permanent deformation greater than 7% but less than or equal to 10%... 1 point Permanent deformation is greater than 10%... 0 points

[0081] The combined scores of the hysteresis loss and permanent strain evaluations were rated as follows: 5-6 points for ◎, 2-4 points for ○, and 0-1 point for ×. Furthermore, regardless of the combined scores of the hysteresis loss and permanent strain evaluations, a hysteresis loss score of 3 points was rated as ◎, and a score of 0 points was rated as ×. The results are shown in Table 1.

[0082] <Test force at 10% elongation> From the fabricated stretchable film, strip-shaped test pieces measuring 100 mm in one direction (MD) and 25 mm in the direction perpendicular to that direction (TD) were cut. These test pieces were fixed to the grips of a precision universal testing machine (Shimadzu Corporation, Autograph AG-5000A) with a grip distance of 25 mm. The test piece was then stretched in the longitudinal direction at a speed of 254 mm / min so that the strain (elongation) calculated by formula (1) above was 10%. Table 1 shows the results of the test force [N] at 10% elongation in the MD direction.

[0083] (Examples 2-12, Comparative Examples 1-12) Except for changing the composition (parts by mass) of the surface layer, the composition (parts by mass) of the elastomer layer, and the thickness ratio of the surface layer to the elastomer layer to the conditions shown in Tables 1 and 2, 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 stretchable film.

[0084] Then, hysteresis loss and permanent strain were measured in the same manner as in Example 1 described above. The results are shown in Tables 1 and 2.

[0085] Figure 6 shows the integral area S (i.e., S1-S2) in the stress-strain curve obtained by subtracting the integral area S2 from the integral area S1 in Example 1 and Comparative Example 2.

[0086] As shown in Figure 6, the stretchable film of Example 1 has a smaller integrated area S and lower hysteresis loss (i.e., superior stretchability) compared to the stretchable film of Comparative Example 2.

[0087] [Table 1]

[0088] [Table 2]

[0089] As shown in Table 1, the stretchable films of Examples 1 to 12 exhibit excellent stretchability because the hysteresis loss is 40% or less. In particular, the stretchable films of Examples 7, 9 to 10 exhibit extremely excellent stretchability because the styrene unit content of the SIS elastomer blended into the elastomer layer is 20% by mass or less (18% by mass).

[0090] On the other hand, as shown in Table 2, the stretchable film of Comparative Example 1 has poor elasticity (hysteresis loss is greater than 40%) because an ethylene-based elastomer is incorporated into the elastomer layer.

[0091] Furthermore, in the stretchable films of Comparative Examples 2 to 8, the elastomer layer contains SIS elastomer with a styrene unit content greater than 30% by mass (35% by mass or 48% by mass), resulting in poor stretchability (hysteresis loss greater than 40%).

[0092] Furthermore, in the stretchable films of Comparative Examples 9 and 10, the elastomer layer contains SBS elastomer with a styrene unit content greater than 30% by mass (40% by mass), resulting in poor elasticity (hysteresis loss greater than 40%).

[0093] Furthermore, in Comparative Example 11, the thickness ratio of the surface layer to the elastomer layer of the base film was surface layer:elastomer layer = 1:9. Compared to Example 12, where the composition (parts by mass) of the surface layer and the elastomer layer were the same (thickness ratio of the surface layer to the elastomer layer of the base film = 1:18), the larger proportion of the surface layer resulted in a larger proportion of resin components with low elastomer properties, indicating poor elasticity (hysteresis loss greater than 40%).

[0094] Furthermore, in Comparative Example 12, the thickness ratio of the surface layer to the elastomer layer of the base film was surface layer:elastomer layer = 1:4. Compared to Examples 7-8, where the composition (parts by mass) of the surface layer and the elastomer layer were the same (thickness ratio of the surface layer to the elastomer layer of the base film = 1:18 or 1:9), the larger proportion of the surface layer resulted in a larger proportion of resin components with low elastomer properties, leading to poor elasticity (hysteresis loss greater than 40%). [Industrial applicability]

[0095] As described above, the present invention is suitable for stretchable films used in clothing such as underwear, diaper waistbands, side panels, leg gathers, incontinence products, sanitary napkins, bandages, surgical drapes, compression bands, hats, swimming trunks, sports supports, medical supports, adhesive bandages, etc. [Explanation of symbols]

[0096] 1. Stretchable film 5. Elastomer layer 6,7 Surface layer

Claims

1. An elastomer layer containing a thermoplastic elastomer, A surface layer laminated on at least one surface of the elastomer layer and A stretchable film comprising, The surface layer is made of an olefin resin composition containing an olefin resin and an inorganic filler. The thermoplastic elastomer is at least one of an olefin-based elastomer and a styrene-based elastomer. The styrene unit content relative to the total units of the styrene-based elastomer is 30% by mass or less. In MD, the test force (test force at 10% elongation) used to stretch the material so that the strain (elongation) calculated by the following formula (1) becomes 10% is 0.6 N or more and 3.9 N or less. The thickness is 17 to 60 μm. A stretchable film characterized by having a hysteresis loss of 40% or less. (Hysteresis Loss) From the stretchable film, a strip-shaped test piece measuring 100 mm in one direction and 25 mm in the direction perpendicular to that direction is cut. This test piece is fixed to the grips of the testing machine with a distance of 25 mm between the grips. The test piece is stretched in the longitudinal direction of the test piece at a speed of 254 mm / min until the strain (elongation) calculated by formula (1) below reaches 100%, and the integrated area of ​​the stress-strain curve (S-S curve) at this time is defined as S1. Immediately after stretching, the test piece is contracted at the same speed until the load on the test piece (N / 25 mm) becomes 0, and the integrated area of ​​the stress-strain curve (S-S curve) at this time is defined as S2. The hysteresis loss [%] is then calculated from formula (2) below. Distortion [%] = (L1 - L0) / L0 × 100 (1) Hysteresis loss [%] = S / S1 × 100 (2) However, L0 is the distance between the grips before stretching (mm), and L1 is the distance between the grips after stretching (mm). Also, S1 is the integral area of ​​the stress-strain curve when the strain is stretched from 0% to 100%, S2 is the integral area of ​​the stress-strain curve when the strain is contracted from 100% to 0%, and S is the integral area of ​​the stress-strain curve (S1-S2) obtained by subtracting the integral area S2 from the integral area S1.

2. The stretchable film according to claim 1, characterized in that the content of the olefin resin relative to the entire olefin resin composition is 30% by mass or more and 85% by mass or less, and the content of the inorganic filler relative to the entire olefin resin composition is 15% by mass or more and 70% by mass or less.

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