film

Abstract

This method suppresses quality degradation caused by polypropylene in films in which polypropylene is dispersed in polyethylene. [Solution] In the film, a dispersed phase is dispersed in a matrix phase. The film comprises a matrix phase containing polyethylene and a dispersed phase containing polypropylene and inorganic material particles. The dispersed phase includes at least a flattened phase oriented in the MD direction, and the average aspect ratio of the flattened phase is 30 or more. The content of the inorganic material particles in the film is 10% by mass or more and 60% by mass or less.

Description

[Technical Field]

[0001] This invention relates to a film containing polyethylene. [Background technology]

[0002] Technologies for recycling polyethylene film are known (see, for example, Patent Document 1). The technology described in Patent Document 1 involves a special washing process to thoroughly wash away mud and other contaminants adhering to used polyethylene film, such as that used in fields, thereby enabling its regeneration as new polyethylene film.

[0003] Furthermore, a technology is known for recycling waste resin films, which are primarily composed of resins other than polyethylene, as a component of polyethylene film (see, for example, Patent Document 2). In this technology, the amount of virgin polyethylene used in the manufacture of polyethylene film can be reduced by the amount of waste resin film used. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2002-052532 [Patent Document 2] Japanese Patent Publication No. 2004-182957 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Because absorbent items such as diapers and sanitary napkins contain many parts made of resin, recycling waste from absorbent items is of great importance. However, when polypropylene, which is abundant in absorbent items, is used as a component of polyethylene film, it tends to impair the quality of the polyethylene film in terms of strength, elongation, and smoothness of texture.

[0006] The object of the present invention is to suppress the deterioration of quality due to polypropylene in a film in which polypropylene is dispersed in polyethylene. [Means for solving the problem]

[0007] In a film according to one embodiment of the present invention, a dispersed phase is dispersed in the matrix phase. The above film comprises a matrix phase containing polyethylene and a dispersed phase containing polypropylene and inorganic material particles. The above-mentioned dispersed phase includes at least a flattened phase oriented in the MD direction, and the average aspect ratio of the flattened phase is 30 or more. The inorganic material particles in the above film are contained in an amount of 10% by mass or more and 60% by mass or less.

[0008] In a method for producing a film in which a dispersed phase is dispersed in a matrix phase according to one embodiment of the present invention, a kneaded mixture is formed into a film by kneading together a first raw material containing polyethylene and constituting the matrix phase, a second raw material containing polypropylene as a component of the dispersed phase, and a third raw material containing inorganic material particles as a component of the dispersed phase. The ratio of the viscosity ηB of the polypropylene contained in the second raw material to the viscosity ηA of the first raw material at the molding temperature during the above film formation, ηB / ηA, is 0.015 or more and less than 1. The inorganic material particles in the film obtained by the above film molding process are 10% by mass or more and 60% by mass or less. [Effects of the Invention]

[0009] According to the present invention, it is possible to suppress the deterioration of quality due to polypropylene in a film in which polypropylene is dispersed in polyethylene. [Brief explanation of the drawing]

[0010] [Figure 1] This figure schematically shows a partial cross-section of a film according to one embodiment of the present invention. [Figure 2]This is a flowchart showing the method for manufacturing the above film. [Figure 3] This is a TEM image obtained by imaging the MD cross-section of the film obtained in the film forming process.

Embodiments for Carrying out the Invention

[0011] A film and a method for manufacturing the same according to an embodiment of the present invention will be described.

[0012] [Configuration of the Film] The film according to this embodiment has a matrix phase and a dispersed phase, and has a configuration in which the dispersed phase is dispersed in the matrix phase. The matrix phase contains polyethylene as a main component. The dispersed phase contains polypropylene and inorganic material particles. The dispersed phase contains polypropylene as a main component and includes a flat phase oriented at least in the MD direction. In this embodiment, the "main component" refers to a component in which the resin content in each phase of the film is 50% by mass or more. In the film according to this embodiment, in order to obtain surface smoothness due to the action of the inorganic material particles, the specific gravity is preferably 0.95 g / cm 3 or more, more preferably 1.00 g / cm 3 or more.

[0013] In FIG. 1, the left-right direction of the paper surface corresponds to the MD direction (Machine Direction: the flow direction of resin molding) of the film, the depth direction of the paper surface corresponds to the TD direction (Transverse Direction: the direction perpendicular to MD) of the film, and the up-down direction of the paper surface corresponds to the thickness direction of the film. FIG. 1 schematically shows the dispersion state of the flat phase and the inorganic material particles constituting the dispersed phase in the matrix phase.

[0014] Each flattened phase of the film according to this embodiment has a flattened shape with an aspect ratio of 5 or more, is oriented at least in the MD direction in the in-plane direction, and preferably is also oriented in the TD direction. Furthermore, the average aspect ratio of the flattened phases, defined as the average value of the aspect ratios of the flattened phases of the film according to this embodiment, is 30 or more, preferably 35 or more. Moreover, from the viewpoint of maintaining good heat sealability, the average aspect ratio of the flattened phases of the film according to this embodiment is preferably 100 or less, more preferably 80 or less, even more preferably 60 or less, and even more preferably 55 or less. Each flattened phase is preferably extended in all directions in the in-plane direction, but may be formed in a strip or needle shape extending only in the MD direction.

[0015] To measure the aspect ratio of each dispersed phase, TEM images taken using a transmission electron microscope (TEM) are used. The film to be observed is processed into ultrathin sections using an ultramicrotome and stained with a heavy metal (ruthenium tetroxide) so that the presence states of the matrix phase and the dispersed phase can be observed. The observation surface of the film sample is taken as the MD cross-section formed by cutting parallel to the MD direction. The observation magnification is set to 2500 times or more so that a rectangular field of view with a dimension of 14.3 μm in the in-plane direction and a dimension of 14.3 μm in the thickness direction can be obtained, and TEM images in the film sample are obtained. In each TEM image, when a line segment connecting a point on the contour of the dispersed phase to a point on the contour of the dispersed phase is drawn in the MD direction, the longest line segment is taken as the major axis. Also, when a line segment connecting a point on the contour of the dispersed phase to a point on the contour of the dispersed phase is drawn perpendicular to the major axis, the shortest line segment is taken as the minor axis. When the contour of the dispersed phase does not fit within the rectangular field of view, the major axis and minor axis are determined using the line segment up to the edge of the field of view. Then, the ratio of the length of the major axis to the length of the minor axis (length of major axis / length of minor axis) is defined as the aspect ratio. The aspect ratio of all the dispersed phases in the rectangular field of view of each TEM image is measured, and those with an aspect ratio of 5 or more are regarded as flat phases. The average of the aspect ratios of all the measured flat phases is defined as the average aspect ratio of the flat phases. HT7820 (manufactured by Hitachi High-Tech Corporation) is used for the transmission electron microscope (TEM), and the acceleration voltage is set to 100 kV.

[0016] In the film according to this embodiment, any flat phase is interrupted in the in-plane direction, so that the matrix phase is continuous in the thickness direction. That is, the configuration in which the flat phase is dispersed in the matrix phase in the film according to this embodiment is different from the laminated structure in which the matrix phase and the flat phase are alternately laminated in the thickness direction as a series of layers in the in-plane direction.

[0017] In this embodiment, since the dimension of each flattened phase relative to the film thickness is small in each MD cross-section, the influence of the physical properties of each flattened phase on the overall physical properties of the film is minimal. Furthermore, in the film according to this embodiment, because the thin flattened phase is widely distributed in the in-plane direction, the polypropylene constituting the flattened phase is widely dispersed in the in-plane direction. As a result, the influence of polypropylene does not affect the film locally, and uniform physical properties can be easily obtained along the in-plane direction. Moreover, in the film according to this embodiment, by having polypropylene as a flattened phase, the influence of polypropylene on the tactile feel is minimized, and the inherent smooth feel of polyethylene can be easily obtained.

[0018] Therefore, in the film according to this embodiment, the properties of the polyethylene constituting the matrix phase are dominant, regardless of the properties of the polypropylene constituting the flattened phase. In other words, in the film according to this embodiment, high strength, high elongation, and a smooth feel comparable to a film composed solely of polyethylene can be easily obtained, regardless of the presence of polypropylene. In the film according to this embodiment, it is preferable that the proportion of the flattened phase to the total dispersed phase is large. From this viewpoint, in the film according to this embodiment, it is preferable that the ratio of the total cross-sectional area of ​​the flattened phase to the total cross-sectional area of ​​the dispersed phase in the TEM image is 60% or more.

[0019] Therefore, the film according to this embodiment can recycle waste containing polypropylene derived from various articles as one of its components. As a result, the amount of virgin polyethylene used in the film according to this embodiment can be reduced, thereby reducing the environmental burden associated with its manufacture.

[0020] Examples of waste containing polypropylene include waste derived from absorbent products such as sanitary napkins, baby diapers, and adult diapers. Examples of waste derived from absorbent products include used absorbent products, absorbent products deemed defective before shipment, and scraps generated during the manufacturing process of absorbent products.

[0021] Examples of polypropylene-containing waste recoverable from absorbent articles include resin fibers and resin films. The technology according to this embodiment expands the possibilities of recycling by enabling the effective reuse of waste containing resin fibers and resin films as resin films with high strength and elongation, and a smooth texture. Furthermore, since the resin contained in absorbent articles often has a higher melting point than polyethylene, high heat resistance can be easily obtained by incorporating waste derived from absorbent articles, and this effect can be expected to increase as the aspect ratio of the flattened phase increases.

[0022] The film according to this embodiment may contain a flattened phase mainly composed of a material other than polypropylene as the dispersed phase. Furthermore, the film according to this embodiment may contain a phase other than the flattened phase and inorganic material particles as the dispersed phase. This makes it possible to improve the quality of the film according to this embodiment by using a dispersed phase other than the flattened phase and inorganic material particles.

[0023] For example, the film according to this embodiment may contain other resins besides the main component polypropylene as a dispersed phase. These other resins may be commercially available resins not derived from waste, but from the viewpoint of reducing environmental impact, they are preferably various resins contained in waste. These resins preferably include at least one of polyethylene terephthalate, nylon, polyurethane, styrene elastomer, ethylene-α-olefin copolymer (including those in which ethylene exists as a comonomer), olefin resins with introduced polar groups, and styrene resins with introduced polar groups. From the viewpoint of reducing environmental impact, these resins are more preferably recycled resins derived from waste. These phases contribute to improving the tensile elongation, tensile strength, and tear strength of the film because they assist in dispersion and enhance the performance of the resins. In the film according to this embodiment, the content of the resin constituting this phase is preferably 0.5% by mass or more and 15% by mass or less. Methods for introducing polar groups include graft polymerization, which uses an electron beam to bond monomers in a grafted manner, using monomers containing polar groups during polymer synthesis, plasma treatment, and corona treatment.

[0024] As described above, the film according to this embodiment contains inorganic material particles composed of an inorganic material as a dispersed phase. The inorganic material particle content in the film according to this embodiment is 10% by mass or more and 60% by mass or less. From the viewpoint of reducing the surface roughness of the film and improving the heat seal strength, the inorganic material particle content in the film is preferably 15% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, and even more preferably 30% by mass or more, and from the viewpoint of improving the tensile elongation, it is preferably 55% by mass or less.

[0025] Average particle size D of inorganic material particles 50 The average particle size D of the inorganic material particles is preferably between 0.5 μm and 3.0 μm. 50From the viewpoint of improving tensile strength and tear strength by ensuring that the inorganic material particles are small enough to be dispersed in the dispersed phase, the average particle size D of the inorganic material particles is more preferably 1.0 μm to 2.5 μm, and even more preferably 1.5 μm to 2.2 μm. 50 This refers to the cumulative particle size by weight at 50% mass, as measured by laser diffraction scattering particle size distribution analysis.

[0026] Furthermore, in the manufacturing process of the film according to this embodiment, the resin components contained in the dispersed phase, such as polypropylene, are crushed by inorganic material particles during the kneading process. As a result, in the film according to this embodiment, the arithmetic mean roughness Ra on the surface is reduced without increasing the molding temperature during film formation, resulting in a smooth appearance and feel. In the film according to this embodiment, the arithmetic mean roughness Ra on the surface is preferably 1.5 μm or less, more preferably 1.3 μm or less, even more preferably 1.2 μm or less, and even more preferably 1.1 μm or less, and from the viewpoint of suppressing an increase in frictional resistance, it is preferably 0.8 μm or more.

[0027] Furthermore, in the manufacturing process of the film according to this embodiment, the resin components contained in the dispersed phase, such as polypropylene, are crushed and made finer by the inorganic material particles during the kneading process, making it easier for the film to deform into a flat shape during molding. As a result, the film according to this embodiment is more likely to maintain a high aspect ratio of the flattened phase. Therefore, in the film according to this embodiment, the above effect of the flattened phase is more effectively obtained, and the arithmetic mean roughness Ra on the surface is further reduced.

[0028] In addition, in films containing fibrous resin, the fibrous resin acts as a nucleus, causing the surrounding area to stretch and thin, and further tearing, making it easier for holes (pinholes) to form. In this respect, in the film according to this embodiment, the fibrous resin is finely crushed by inorganic material particles, which suppresses its function as a nucleus for hole formation, thus making it difficult for holes to form. In the film according to this embodiment, when a fibrous resin is included, it is preferable that the longitudinal dimension of the fibrous resin is 2 mm or less.

[0029] Furthermore, in the film according to this embodiment, the specific heat of the inorganic material particles at 25°C is lower than that of the matrix phase, preferably 1.40 kJ / (kg·K) or less, more preferably 1.00 kJ / (kg·K) or less, and even more preferably 0.85 kJ / (kg·K) or less. As a result, the heat dissipation of the film according to this embodiment is improved, and the film cools down rapidly after film formation. Therefore, the film hardens after formation while maintaining a high aspect ratio due to the rapid cooling. Consequently, in the film according to this embodiment, the above effect of the flattened phase is more effectively obtained, and the arithmetic mean roughness Ra on the surface is further reduced.

[0030] Furthermore, the film according to this embodiment has improved low-temperature heat sealability due to improved thermal conductivity, meaning that high heat seal strength can be easily obtained even when heat sealing in the low-temperature range. In the film according to this embodiment, it is preferable that the heat seal strength on the surface is 0.08 N / cm or higher.

[0031] In this embodiment, the arithmetic mean roughness Ra of the film surface is measured using a white light interferometry laser microscope (VK-X3000 / 3100, manufactured by Keyence Corporation) under the following conditions: The objective lens is set to 10x magnification, autofocus is enabled, and in the built-in image processing software, the "multiple line settings" are set to "5 lines around the periphery, skipping 4 lines at intervals, line selection No. 6," and the "line roughness measurement settings" are set to "measurement line type: roughness, cutoff λc 0.8 mm, with termination effect correction enabled." The arithmetic mean roughness Ra of the film surface is measured at three points as described above, and the average value is used.

[0032] In this embodiment, the heat seal strength of the film is measured as follows. Two films are prepared, each measuring 20 mm in width and 50 mm in length. Next, the two films are placed on top of each other and sealed using a heat sealing machine (product name: Heat Seal Tester (TP-701-C), manufactured by Tester Sangyo Co., Ltd.) under the following conditions: set temperature: 160°C (top and bottom), press pressure: 0.15 MPa, and press time: 0.7 s, by pressing 20 mm in width and 10 mm in length. Subsequently, the two sealed films are gripped by a tensile testing machine (product name: AG-1S, manufactured by Shimadzu Corporation) so that the distance between the chucks in the length direction is 30 mm, and the average value of five measurements taken at a rate of 600 mm / min is normalized by the film width to determine the heat seal strength of the film.

[0033] In this embodiment, the specific gravity of the film is measured as follows: Fifty 50mm x 50mm films are prepared. The prepared films are measured using a specific gravity measuring device (product name: AUW220D, manufactured by Shimadzu Corporation) by the liquid immersion method.

[0034] In the film according to this embodiment, as the inorganic material constituting the inorganic material particles, for example, metal salts such as calcium carbonate, metal oxides such as aluminum oxide and titanium oxide, minerals such as talc, and metals such as aluminum can be used. In the film according to this embodiment, from the viewpoint of obtaining the above effects, it is preferable to use at least one selected from metal salts and metal oxides as the inorganic material particles, and it is more preferable to use metal salts and metal oxides. In the film according to this embodiment, from the viewpoint of obtaining the above effects and being able to obtain them at low cost, it is even more preferable to use at least one selected from calcium carbonate and titanium oxide as the inorganic material particles, and it is even more preferable to use calcium carbonate and titanium oxide.

[0035] In the film according to this embodiment, when calcium carbonate and titanium dioxide are used as the inorganic materials constituting the inorganic material particles, the ratio G2 / G1 of the mass content G2 of calcium carbonate to the mass content G1 of titanium dioxide is preferably 0.5 to 25.0, more preferably 1.0 to 23.0, even more preferably 3.0 to 20.0, even more preferably 5.0 to 18.0, and even more preferably 6.0 to 15.0, from the viewpoint of improving tensile elongation, tensile strength, and tear strength.

[0036] In the film according to this embodiment, from the viewpoint of reducing manufacturing costs, it is preferable to use as much as possible components that are included together with polypropylene in waste materials to constitute the phases other than the flattened phase and inorganic material particles in the dispersed phase. However, in the film according to this embodiment, any of these materials may be added separately from polypropylene.

[0037] The applications of the film according to this embodiment are not particularly limited. For example, the film according to this embodiment can be used as a packaging film for various products. Examples of products suitable for use as a packaging film according to this embodiment include sanitary products, baby diapers, adult diapers, and household goods.

[0038] The film according to this embodiment preferably has desirable properties as a packaging film. For example, in order to obtain high durability as a packaging film, the film according to this embodiment preferably has high tensile elongation, tensile strength, and tear strength. Specifically, in the film according to this embodiment, the tensile elongation is preferably 700% or more, more preferably 900% or more. In addition, in the film according to this embodiment, the tensile strength per unit cross-sectional area is preferably 0.23 N / (g / m²). 2 (cm) or more, more preferably 0.30 N / (g / m²) 2 The thickness is 0.05 N / (g / m²) or more. Furthermore, in the film according to this embodiment, the tear strength per unit thickness is preferably 0.05 N / (g / m²). 2 ) or more, more preferably 0.075 N / (g / m³)2 )That's all.

[0039] In this embodiment, the tensile elongation and tensile strength of the film are measured as follows. The film to be measured is punched out to make a dumbbell-shaped No. 3 sample so as to match the direction of the tensile test. Measure the weight of the sample to obtain the basis weight C (g / m 2 ). Fix the punched sample to a tensile testing machine (trade name: AG-1S, manufactured by Shimadzu Corporation) with the distance between chucks set to 50 mm. After fixing, set the load read by the tensile testing machine to zero, and extend the sample at a deformation rate of 300 mm / min until it breaks. The tensile elongation and tensile strength are read from the obtained data for the elongation amount A (mm) and load B (N) in the elongation process, and are calculated as follows together with the previously measured basis weight C (g / m 2 ). The tensile elongation and tensile strength of the film are obtained as the average values of three samples for each of the MD direction and the TD direction. Tensile elongation (%) = 100×A (mm) / 20 mm Tensile strength (N / (g / m 2 ·cm)) = B (N) / 0.5 cm / C (g / m[[ID=​​​​​​​​​​)) is calculated. The tear strength of the film is determined as the average value of three samples in the MD direction.

[0041] The film according to this embodiment may have text, designs, etc., representing the product name or product information printed on its surface as a packaging film. In this regard, it is preferable that the film according to this embodiment has a surface wettability of 40 mN / m or more by applying a surface treatment such as corona treatment in order to obtain high printability on the surface. Wettability is evaluated as surface energy. Specifically, to evaluate the wettability of the film, several centimeters of 40 mN / m DynePen ink are applied to the film and it is observed whether the state is maintained for 2 to 4 seconds. Specifically, the wettability of the film is determined to be 40 mN / m or more if the above observation is performed three times and the applied state is maintained without forming droplets all three times.

[0042] [Film manufacturing method] An example of a film manufacturing method according to this embodiment will be described below with reference to Figure 2, but the film manufacturing method according to this embodiment is not limited to the example shown in Figure 2. The film manufacturing method shown in Figure 2 includes a raw material preparation step (step S01), a kneading step (step S02), and a film forming step (step S03).

[0043] (Step S01: Raw material preparation) In step S01, the raw materials for the film according to this embodiment are prepared. Specifically, in step S01, a first raw material, a second raw material, and a third raw material are prepared. The first raw material is virgin polyethylene that constitutes the matrix phase. The second raw material is recycled material containing polypropylene that constitutes the flattened phase of the dispersed phase. The third raw material is inorganic material particles that constitute the dispersed phase.

[0044] The first raw material can be prepared, for example, as commercially available polyethylene pellets. The second raw material can be prepared, for example, as pellets obtained by repelling waste containing polypropylene. The repelling conditions for the second raw material can be appropriately determined according to the physical properties of the components constituting the waste. The third raw material can be prepared, for example, as commercially available inorganic material powder.

[0045] The first raw material may contain inorganic material particles that constitute the dispersed phase. The second raw material may contain polyethylene that constitutes the matrix phase and at least one of the inorganic material particles that constitute the dispersed phase. Furthermore, the second raw material may contain at least one of polyethylene terephthalate, nylon, polyurethane, styrene-based elastomer, ethylene-α-olefin copolymer, olefin-based resin with polar groups introduced, and styrene-based resin with polar groups introduced. In addition, the first raw material may contain components other than polyethylene, and the third raw material may contain components other than inorganic material particles.

[0046] The viscosity ηA of the first raw material, which is composed of polyethylene, is adjusted according to the viscosity ηB of the polypropylene contained in the second raw material. More specifically, the viscosity ηA of the first raw material is adjusted so that the ratio of viscosity ηB to viscosity ηA at the molding temperature during film formation in step S03, ηB / ηA, is 0.015 or more and less than 1.

[0047] The viscosity ηA of the first raw material and the viscosity ηB of the polypropylene contained in the second raw material are measured as follows: The resin is filled into the barrel of a capillograph (product name: CAPIROGRAPH 1B, manufactured by Toyo Seiki Seisakusho Co., Ltd.) that has been preheated to the measurement temperature, and the viscosity value (Pa·s) is read from the load when the resin is extruded by a piston at a speed of 10 mm / min in the "Capillary Flow Test" mode of the program "Capirograph of Windows (registered trademark)". A nozzle with a diameter of φ1 mm and a length of 10 mm is used, and a barrel with a diameter of 9.55 mm is used.

[0048] (Step S02: Mixing) In step S02, a mixture is prepared by kneading the first raw material, second raw material, and third raw material prepared in step S01. In step S02, a single-screw extruder or a twin-screw extruder can be used to knead the first raw material, second raw material, and third raw material, or a single-screw extruder and a twin-screw extruder can be used in combination.

[0049] In step S02, the first raw material, the second raw material, and the third raw material are mixed to obtain a kneaded product in which the dispersed phase is dispersed in the matrix phase. In addition, during the process of step S02, the inorganic material particles contained in the third raw material crush the polypropylene contained in the second raw material and any fibrous resins that may be contained in the second raw material.

[0050] In step S02, the kneaded mixture is formed in a spherical shape with a low aspect ratio. In this embodiment, in step S03, during the process of forming the mixture into a film, the polypropylene-based dispersed phase is transformed into a flattened phase with an aspect ratio of 5 or more.

[0051] In the film according to this embodiment, as described above, by making the dispersed phase mainly composed of polypropylene a flattened phase, the polypropylene is widely dispersed in the in-plane direction. Therefore, in this embodiment, there is little need to improve the dispersibility of the dispersed phase mainly composed of polypropylene at a very fine level during the kneading in step S02.

[0052] Therefore, in step S02, it is preferable to use a single-screw extruder rather than using advanced kneading technology such as a twin-screw extruder, from the viewpoint of reducing the number of steps. As a result, the manufacturing cost of the film according to this embodiment can be reduced.

[0053] Furthermore, in step S02, it is advantageous to have a low viscosity ratio between polyethylene and polypropylene and low interfacial tension between the matrix phase and the dispersed phase in order to finely divide the dispersed phase. From this viewpoint, it is preferable that the kneading temperature in step S02 be between 200°C and 300°C. In step S02, it is preferable that the temperature in all areas through which the raw materials pass, excluding the raw material supply port, during the kneading process in the extruder is within the above range, but the temperature in some areas may be outside the above range.

[0054] (Step S03: Film Forming) In step S03, the kneaded material prepared in step S02 is rolled out thinly to form a film. The viscosity ηA of the first raw material is adjusted so that the ratio of viscosity ηB to viscosity ηA at the molding temperature ηB / ηA is 0.015 or more and less than 1, so that the dispersed phase mainly composed of polypropylene becomes a flattened phase during the rolling of the kneaded material.

[0055] In other words, in this embodiment, by keeping the ratio ηB / ηA at the molding temperature within the above range, the matrix phase is stretched without being affected by the polypropylene, and at the same time, the dispersed phase mainly composed of polypropylene is deformed in accordance with the deformation of the matrix phase. As a result, the dispersed phase mainly composed of polypropylene, which is stretched thinly together with the matrix phase, becomes a flattened phase.

[0056] Figure 3 shows an example of a TEM image of the MD cross-section of the film obtained in step S03. Figure 3 shows the state in which the flattened phase and inorganic material particles are dispersed in the matrix phase. In addition, in the TEM image shown in Figure 3, a considerably thin area is observed in the flattened phase, and furthermore, the flattened phase appears to be torn (see, for example, the enclosed region R in Figure 3). This is thought to be due to the polypropylene being finely crushed by the inorganic material particles in step S02.

[0057] In the film manufacturing method according to this embodiment, it has been found that by setting the molding temperature of the kneaded material in step S03 to a relatively high level, the ratio of viscosity ηB to viscosity ηA at the molding temperature, ηB / ηA, tends to remain below 1. Furthermore, a high molding temperature is advantageous in suppressing the force that causes the deformed flattened phase to return to a spherical shape due to interfacial tension. However, raising the molding temperature too high can lead to problems such as deterioration of moldability and degradation of the resin. From these viewpoints, the molding temperature of the kneaded material in step S03 is preferably 200°C to 300°C, and more preferably 200°C to 280°C. In addition, if the raw materials include polyethylene terephthalate, nylon, and / or polyurethane, it is preferable to set the molding temperature to be above the highest melting point of polyethylene terephthalate, nylon, and / or polyurethane, and to melt them once. This allows the polyethylene terephthalate, nylon, and / or polyurethane to be spherical or flattened.

[0058] The method for forming the film of the kneaded material according to this embodiment is not limited to a specific method, but it is preferable to use an inflation molding method. In the inflation molding method, the material can be efficiently stretched not only in the MD direction but also in the TD direction, so the influence of polypropylene can be suppressed not only in the MD direction but also in the TD direction.

[0059] The film forming machine used in the inflation molding method can be configured, for example, to be integrated with an extruder used for kneading, and to receive the kneaded material directly from the extruder. The molding temperature in inflation molding refers to the temperature of the kneaded material at the time it is discharged from the die. In inflation molding, it is preferable that the temperature of the kneaded material is between 200°C and 300°C, and more preferably between 200°C and 280°C, throughout the entire process from the time the kneaded material is discharged from the extruder until the molding is completed. However, in inflation molding, the temperature of the kneaded material may be outside the above range at any point other than the time the kneaded material is discharged from the extruder.

[0060] [Other embodiments] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the present invention.

[0061] For example, the film manufacturing method according to this embodiment may include steps other than those described above, as needed. For instance, a surface treatment may be applied to modify the surface of the film after the film forming process. An example of such a surface treatment is corona treatment to improve the wettability of the film surface. Alternatively, slits may be formed or bag-making processes may be performed after the film forming process.

[0062] Furthermore, in the film manufacturing method according to this embodiment, a kneaded mixture obtained by kneading recycled material with other materials may be used as the second raw material. Moreover, in the film manufacturing method according to this embodiment, recycled material is not required as the second raw material; for example, virgin polypropylene or a kneaded mixture obtained by kneading virgin polypropylene with other materials may be used. In addition, in the film manufacturing method according to this embodiment, the first raw material may not be virgin material but recycled waste material containing polyethylene. Furthermore, in the film according to this embodiment, the third raw material may be recycled waste material containing inorganic material particles. Moreover, in the film manufacturing method according to this embodiment, other materials may be added and kneaded separately from the first raw material, second raw material, and third raw material during the kneading process.

[0063] [Examples and Comparative Examples] The following describes examples and comparative examples of the above embodiments, but the present invention is not limited to the configurations of the following embodiments.

[0064] (raw materials) For the first raw material, the following linear low-density polyethylene (LLDPE) products with mutually different melt flow rates (MFRs) were used as virgin polyethylene (PE) materials. In Tables 1-3 below, the MFR is shown without units to distinguish each polyethylene (PE) product. The MFR values ​​for polyethylene (PE) shown are the manufacturer's catalog values ​​(190°C, 2.16 kg load) for each product. • Evolu SP0510 (manufactured by Prime Polymer, MFR: 1.2g / 10min) • Evolu SP2510 (manufactured by Prime Polymer, MFR: 1.5g / 10min)

[0065] The recycled material, which is the second raw material and mainly consists of polypropylene (PP), is made by pelletizing scraps generated when the crotch area is cut during the manufacturing process of Merries® Pants Sarasa Air Through L size (2023 model), a baby diaper manufactured by Kao Corporation, using a single-screw extruder. The average composition of the recycled material is 95.4% by mass of polypropylene (PP), 3.6% by mass of styrene elastomer, and 1.0% by mass of polyurethane (PU).

[0066] Calcium carbonate and titanium dioxide were used as inorganic material particles. Calcium carbonate was prepared as a calcium carbonate masterbatch (manufactured by Samprack Industries, Ltd., 30% LLDPE, 70% calcium carbonate). Titanium dioxide was prepared as a titanium dioxide masterbatch (TET1TA538WHT-FD (manufactured by Toyo Color Co., Ltd.), 60% titanium dioxide). A propylene-based elastomer (Vistamaxx Performance Polymer 7050BF (manufactured by ExxonMobil)) was used as a dispersion aid.

[0067] Tables 1-3 below show the composition of each raw material as a mass ratio. Tables 1-3 also show the ratio of viscosity ηB to viscosity ηA at the molding temperature (ηB / ηA), the ratio of the mass content of calcium carbonate G2 to the mass content of titanium dioxide G1 (G2 / G1), and the mass ratio of recycled material to all resin components contained in the film.

[0068] (Evaluation method) The methods for measuring the average aspect ratio of the flattened phase, the specific gravity, the tensile elongation and tensile strength, the tear strength, the arithmetic mean roughness Ra, and the heat seal strength are as described in the above embodiment.

[0069] (Example 1 and Comparative Example 1) As Example 1 and Comparative Example 1, films were prepared using the manufacturing conditions and raw materials shown in Table 1. In both Example 1 and Comparative Example 1, a single-screw extruder was used for kneading, and the inflation molding method was used for molding. The film according to Comparative Example 1 differs from the configuration of the above embodiment in that it does not contain inorganic material particles.

[0070] Table 1 shows the evaluation results for the films of Example 1 and Comparative Example 1. The film of Example 1, which contained inorganic material particles, had a higher average aspect ratio of the flattened phase than the film of Comparative Example 1, which did not contain inorganic material particles. This confirmed that the average aspect ratio of the flattened phase in the film can be increased by the action of inorganic material particles.

[0071] [Table 1]

[0072] (Examples 2-4 and Comparative Example 2) In Examples 2-4 and Comparative Example 2, films were prepared using the manufacturing conditions and raw materials shown in Table 2. In all of Examples 2-4 and Comparative Example 2, a single-screw extruder was used for kneading, and the inflation molding method was used for molding. The film according to Comparative Example 2 differs from the configuration of the above embodiments in that the total content of inorganic material particles is less than 10% by mass.

[0073] Table 2 shows the evaluation results for the films of Examples 2-4 and Comparative Example 2. In all cases, the films of Examples 2-4 showed better results than the film of Comparative Example 2 in terms of tensile elongation, arithmetic mean roughness Ra, and heat seal strength. Furthermore, in the films of Comparative Examples 2-4, there was a tendency for the arithmetic mean roughness Ra to improve and the tensile elongation to decrease with increasing specific gravity. However, even the film of Example 2, which had the highest specific gravity, showed better tensile elongation than the film of Comparative Example 2.

[0074] [Table 2]

[0075] (Examples 5-7) In Examples 5-7, films were prepared using the manufacturing conditions and raw materials shown in Table 3. In all of Examples 5-7, a single-screw extruder was used for mixing, and the inflation molding method was used for molding.

[0076] Table 3 shows the evaluation results for the films of Examples 5 to 7. In all of the films of Examples 5 to 7, good results were obtained for tensile elongation, tensile strength, and tear strength. In all of the films of Examples 5 to 7, although the total content of inorganic material particles was the same, a tendency was observed for tensile elongation, tensile strength, and tear strength to improve as the ratio of the mass content of calcium carbonate G2 to the mass content of titanium dioxide G1 (G2 / G1) increased.

[0077] [Table 3]

Claims

1. A film in which a dispersed phase is dispersed in a matrix phase, It comprises a matrix phase containing polyethylene and a dispersed phase containing polypropylene and inorganic material particles, The dispersed phase includes at least a flattened phase oriented in the MD direction, and the average aspect ratio of the flattened phase is 30 or more. The inorganic material particles in the film are 10% by mass or more and 60% by mass or less. film.

2. The inorganic material particles include at least one selected from calcium carbonate and titanium dioxide. The film according to claim 1.

3. The inorganic material particles contain calcium carbonate and titanium dioxide, and the ratio of the mass content G2 of calcium carbonate to the mass content G1 of titanium dioxide, G2 / G1, is 0.5 or more and 20.0 or less. The film according to claim 1 or 2.

4. Waste derived from absorbent materials is used as part of the raw materials. The film according to claim 1 or 2.

5. The dispersed phase further comprises a fibrous resin. The film according to claim 1 or 2.

6. The arithmetic mean surface roughness Ra is between 0.8 μm and 1.5 μm. The film according to claim 1 or 2.

7. A method for manufacturing a film in which a dispersed phase is dispersed in a matrix phase, A kneaded mixture is formed into a film by kneading together a first raw material containing polyethylene and constituting the matrix phase, a second raw material containing polypropylene as a component of the dispersed phase, and a third raw material containing inorganic material particles as a component of the dispersed phase. The ratio ηB / ηA of the viscosity of polypropylene contained in the second raw material at the molding temperature to the viscosity ηA of the first raw material at the molding temperature during the film formation is 0.015 or more and less than 1. The inorganic material particles in the film obtained by the aforementioned film molding are 10% by mass or more and 60% by mass or less. A method for manufacturing film.

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