Method for manufacturing a stretch film

Abstract

Provided is a method for manufacturing a stretched film, which can suppress the generation of bubbles in a resin film even when the resin film is made of a recycled material, and as a result, can manufacture a stretched film having desired properties. The method for manufacturing a stretched film according to an embodiment of the present invention includes the following steps: a step of forming a resin film from a raw material and a recycled material, in which the both end portions in the width direction of the resin film are formed from the recycled material, and a main body portion located between the both end portions is formed from the raw material; a step of cutting the resin film and separating it into a first end portion film and a manufactured film; and a step of stretching the manufactured film. The recycled material is prepared from a recycled resin material having a moisture content of less than 1.0 mass%.

Description

Technical Field

[0001] This invention relates to a method for manufacturing stretch film. Background Technology

[0002] Stretch films, widely used in various industrial products, are made from stretch resin films. For example, a method for manufacturing stretch films has been proposed in which the resin film is stretched in a direction intersecting the length direction while the two ends of the strip-shaped resin film are held in the width direction by a clamp (see, for example, Patent Document 1).

[0003] In recent years, from the perspective of reducing environmental impact, there has been a growing expectation for the reuse of waste generated during the manufacture of various industrial products. Therefore, the production of stretched membranes has been explored using recycled materials derived from resin product waste to create resin films. However, when using recycled materials to create resin films, air bubbles are generated within the resin film, resulting in situations where the stretched membrane cannot acquire the desired properties.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 7096940 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] This invention was made to solve the above-mentioned problems in the prior art. Its main objective is to provide a method for manufacturing a stretch film that can suppress the generation of air bubbles in the resin film even when using recycled materials, thereby producing a stretch film with desired properties.

[0009] Means for solving technical problems

[0010] [1] The method for manufacturing a stretch film according to an embodiment of the present invention includes the following steps: a step of preparing a raw material comprising a first resin and a recycled material comprising a second resin and an incorporation component; a step of forming a strip-shaped resin film from the raw material and the recycled material, wherein the recycled material forms two ends in the width direction of the resin film, and the raw material forms a main body portion located between the two ends in the width direction of the resin film; a step of cutting the resin film to separate it into a first end film comprising the ends in the width direction of the resin film and a finished film comprising the main body portion; and a step of stretching the finished film in a direction intersecting the length direction. The recycled material is prepared from a recycled resin material with a moisture content of less than 1.0% by mass.

[0011] [2] In the method for manufacturing the stretch film described in [1] above, the recycled resin material may include a first end film.

[0012] [3] The method for manufacturing the stretch film described in [1] or [2] above may further include the step of cutting off the two ends of the stretch film in the width direction to obtain a second end film.

[0013] [4] In the method for manufacturing the stretch film described in [3] above, the recycled resin material may include a second end film.

[0014] Invention Effects

[0015] According to embodiments of the present invention, even when using recycled materials to make resin films, the generation of bubbles in the resin films can be suppressed, resulting in the manufacture of stretch films with desired properties. Attached Figure Description

[0016] Figure 1 This is a schematic top view of the resin film involved in the method for manufacturing a stretch film according to one embodiment of the present invention.

[0017] Figure 2 To be by Figure 1 A schematic top view of a stretched film obtained by stretching a resin film.

[0018] Symbol Explanation

[0019] 3. Resin film

[0020] 31. End of the resin film in the width direction

[0021] 32 Main Body

[0022] 4. Fabrication of membrane

[0023] 5. Stretch film

[0024] 6 First end membrane

[0025] 7 Second end membrane Detailed Implementation

[0026] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments. Furthermore, in order to make the description clearer, the width, thickness, shape, etc., of various parts are sometimes schematically shown compared to the embodiments, but these are merely examples and do not limit the interpretation of the present invention.

[0027] (Definitions of terms and symbols)

[0028] The terms and symbols used in this manual are defined as follows.

[0029] (1) Refractive index (nx, ny, nz)

[0030] “nx” is the refractive index in the direction where the refractive index is greatest (i.e., the slow axis direction), “ny” is the refractive index in the direction orthogonal to the slow axis (i.e., the fast axis direction), and “nz” is the refractive index in the thickness direction.

[0031] (2) In-plane phase difference (Re)

[0032] “Re(λ)” is the in-plane phase difference measured at 23°C using light with a wavelength of λnm. For example, “Re(550)” is the in-plane phase difference measured at 23°C using light with a wavelength of 550nm. Re(λ) is obtained by using the formula: Re(λ) = (nx - ny) × d when the thickness of the layer (film) is set to d (nm).

[0033] (3) Angle

[0034] Unless otherwise specified, when referring to angles in this specification, the angles include angles in both clockwise and counterclockwise directions.

[0035] A. An overview of the manufacturing method of stretch film

[0036] Figure 1 A schematic top view of the resin film involved in the method for manufacturing a stretch film according to one embodiment of the present invention; Figure 2 To be by Figure 1 A schematic top view of a stretched film obtained by stretching a resin film.

[0037] The method for manufacturing a stretch film according to an embodiment of the present invention includes, in sequence, a preparation step, a film forming step, a first cutting step, and a stretching step.

[0038] The preparation process involves preparing raw materials and recycled materials. The raw materials comprise a first resin. The recycled materials comprise a second resin and blending components. The recycled materials are prepared from recycled resin materials with a moisture content of less than 1.0% by mass. The moisture content of the recycled resin materials is preferably 0.8% by mass or less, more preferably 0.5% by mass or less. The lower limit of the moisture content in the recycled resin materials is representatively 0.01% by mass. Furthermore, the moisture content of the recycled resin materials can be determined using the Karl Fischer method.

[0039] In the film-making process, a long strip of resin film 3 (refer to) is made from raw materials and recycled materials. Figure 1More specifically, the resin film 3 has two ends 31 in the width direction formed from recycled material, and a main body portion 32 located between the two ends 31 in the width direction formed from virgin material. In the resin film 3, the main body portion 32 is integrally continuous with the two ends 31 in the width direction. In the first cutting step, the resin film 3 is cut to separate it into a first end film 6 containing the ends 31 in the width direction of the resin film 3 and a finished film 4 containing the main body portion. In the stretching step, the finished film 4 is stretched in a direction intersecting the length direction (see reference). Figure 2 ).

[0040] The inventors have explored the production of stretched films (particularly optical films) by forming resin films from recycled and virgin materials and stretching these resin films. It was discovered that air bubbles sometimes form in resin films made from recycled and virgin materials, leading to uneven appearance and / or properties in the resulting stretched films. Therefore, further research into recycled materials revealed that by using recycled materials at both ends of the resin film in its width direction and adjusting the moisture content of the recycled resin material used as the raw material, air bubbles in the resin film can be suppressed. Specifically, recycled materials are first prepared from recycled resin materials with a moisture content less than the aforementioned upper limit. Virgin materials are then prepared separately. Next, a resin film 3 is formed with the recycled materials forming both ends 31 in the width direction and the virgin materials forming the main body 32. Thus, even when using recycled materials to form the resin film 3, air bubbles can be suppressed, resulting in the stable production of stretched films 5 with the desired properties.

[0041] Recycled resin materials are obtained by recycling waste resin products or waste generated during the manufacture of resin products. Examples of resin products include optical films such as retardation films; and packaging materials made of thermoplastic resins such as polyethylene terephthalate (PET) and nylon. Among these resin products, optical films are preferred, and retardation films are more preferred. That is, recycled materials are preferably prepared from optical films (represented by retardation films) and / or waste generated during the manufacture of optical films. Details will be described later. In the method for manufacturing stretch films according to embodiments of the present invention, end films (first end films and / or second end films) generated as byproducts can preferably be used as recycled resin materials in the preparation of recycled materials. Furthermore, recycled resin materials can be recycled multiple times. That is, recycled materials can be prepared from resin products (represented by optical films) manufactured from recycled resin materials and / or waste generated during the manufacture of said resin products.

[0042] The following details the process of manufacturing stretch film.

[0043] B. Preparation process

[0044] In the preparation process, raw materials and recycled materials are prepared as described above.

[0045] B-1. Raw materials

[0046] The raw material is a synthetic resin material that does not contain recycled resin. Examples of the form of the raw material include granules and powder. In one embodiment, the raw material is prepared as raw granules. The case where the raw material is raw granules will be described in detail below.

[0047] The raw feed pellets have any suitable shape and size. The raw feed pellets are typically cylindrical. The average maximum length of the raw feed pellets is, for example, 1.0 mm or more and 5.0 mm or less. The mass of each raw feed pellet is, for example, 5 mg or more and 25 mg or less.

[0048] The raw material granules (raw material) contain a first resin and substantially no other components. The content of the first resin in the raw material granules is, for example, 99.0% by mass or more, preferably 99.2% by mass or more, more preferably 99.5% by mass or more, and representatively 100% by mass or less. That is, the content of other components in the raw material granules is, for example, 1.0% by mass or less, preferably 0.8% by mass or less, more preferably 0.5% by mass or less, further preferably 0.2% by mass or less, particularly preferably 0.09% by mass or less, especially preferably 0.05% by mass or less, and representatively 0% by mass or more.

[0049] The first resin is selected arbitrarily and appropriately according to the intended use of the stretch film.

[0050] Examples of first resins include polycarbonate resins, polyvinyl acetal resins, cycloolefin resins, (meth)acrylic resins, cellulose ester resins, cellulose resins, polyester resins, polyester carbonate resins, olefin resins, and polyurethane resins. Furthermore, (meth)acrylic resins refer to acrylic resins and / or methacrylic resins. These first resins can be used alone or in combination.

[0051] The first resin contained in the raw material granules preferably includes polycarbonate (PC) resins, cyclic olefin (COP) resins, (meth)acrylic resins, and polyester resins (typically polyethylene terephthalate (PET)), with PC resins being more preferred. When the first resin is such a resin material, the desired properties can be stably imparted to the stretched film (especially optical film).

[0052] Examples of PC-based resins include PC-based resins containing structural units derived from dihydroxy compounds. Specific examples of dihydroxy compounds include 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 9,9-bis(4-hydroxy-3-ethylphenyl)fluorene, 9,9-bis(4-hydroxy-3-n-propylphenyl)fluorene, 9,9-bis(4-hydroxy-3-isopropylphenyl)fluorene, 9,9-bis(4-hydroxy-3-n-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-sec-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-tert-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-cyclohexylphenyl)fluorene, 9,9-bis(4-hydroxy-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, and 9,9-bis(4-( 2-Hydroxyethoxy)-3-methylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isopropylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isobutylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-cyclohexylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3,5-dimethylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butyl-6-methylphenyl)fluorene, 9,9-bis(4-(3-hydroxy-2,2-dimethylpropoxy)phenyl)fluorene. In addition to the structural units derived from dihydroxy compounds mentioned above, PC resins may also contain structural units derived from dihydroxy compounds such as isosorbide, isomannitol, isoidulitol, spirodiol, dioxanediol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanediethanol (CHDM), tricyclodecanediethanol (TCDDM), and bisphenols.

[0053] Detailed information about the aforementioned PC-based resins is described, for example, in Japanese Patent Application Publication No. 2012-67300 and Japanese Patent No. 3325560. The descriptions in these patent documents are incorporated herein by reference.

[0054] The melt viscosity A of the raw material (raw material) is appropriately varied depending on the type of the first resin. The melt viscosity A of the raw material is, for example, 300 Pa·s or more, preferably 500 Pa·s or more, more preferably 1000 Pa·s or more, and for example, 3000 Pa·s or less, preferably 2500 Pa·s or less. Furthermore, the melt viscosity of the material can be determined, for example, using a method based on JIS K 7199.

[0055] Raw pellets can be prepared by any suitable method. The preparation method for raw pellets can be wire cutting or thermal cutting. Details of the raw pellet preparation method are described, for example, in Japanese Patent Application Publication No. 2013-181105. The description in that patent document is incorporated herein by reference.

[0056] B-2. Recycled Materials

[0057] The recycled material is prepared from a recycled resin material having the aforementioned moisture content. Examples of the form of the recycled material include granules and powder. In one embodiment, the recycled material is prepared as recycled granules. The case where the recycled material is recycled granules will be described in detail below.

[0058] The shape and size of the recycled granules can be described in the same way as the original granules. The recycled granules contain the second resin and the admixtures mixed into the second resin. The second resin contained in the recycled granules (recycled material) is representatively the same as the first resin contained in the original granules (original material).

[0059] In one embodiment, in the recycled granules, the second resin serves as the matrix resin to form a continuous phase, and the mixed components form a dispersed phase dispersed in the continuous phase as particles.

[0060] The maximum size of the dispersed phase is, for example, 1500 nm or less, preferably 1000 nm or less, more preferably 500 nm or less, further preferably 350 nm or less, particularly preferably 250 nm or less, especially preferably 200 nm or less, most preferably 100 nm or less, and for example, 1 nm or more, preferably 10 nm or more, more preferably 30 nm or more, and further preferably 50 nm or more. If the maximum size of the dispersed phase is below the above-mentioned upper limit, unevenness (uneven resin flow) in the resin film can be suppressed. If the maximum size of the dispersed phase is above the above-mentioned lower limit, recycled materials can be manufactured smoothly. Furthermore, the maximum size of the dispersed phase can be determined, for example, by cross-sectional observation using a scanning electron microscope.

[0061] The proportion of the second resin in the recycled material granules is, for example, 40.0% by mass or more, preferably 50.0% by mass or more, more preferably 70.0% by mass or more, and even more preferably 90.0% by mass or more, and for example, 99.1% by mass or less.

[0062] The proportion of the mixed components in the recycled material pellets is, for example, 60.0% by mass or less, preferably 50.0% by mass or less, more preferably 30.0% by mass or less, and even more preferably 10.0% by mass or less. The lower limit of the proportion of the mixed components in the recycled material pellets is, for example, 0.3% by mass, also for example, 0.5% by mass, and also for example, 0.9% by mass.

[0063] In the recycled granules, the mass ratio of the mixed component to the second resin (mixed component / second resin) is, for example, 0.01 or more, and for example, 1.5 or less, preferably 1.0 or less. When the mixed component / second resin is within the above range, the non-uniformity in the resin film can be stably reduced.

[0064] The inclusion of foreign matter is a typical characteristic of the mixture. Foreign matter is a solid component that is different from the resin component.

[0065] Examples of foreign substances include amide-based foreign substances and fibrous foreign substances. Foreign substances can be mixed into recycled material particles, either alone or in combination.

[0066] The proportion of foreign matter mixed into the component is, for example, more than 1% by volume and less than 100% by volume, or more than 10% by volume and less than 50% by volume.

[0067] The largest foreign object in the mixed component has a maximum size of, for example, less than 3 mm, preferably less than 1 mm. If the maximum size of the largest foreign object is less than the above-mentioned upper limit, the unevenness generated in the resin film can be more stably suppressed. In addition, the maximum size of the foreign object can be determined, for example, by observation and analysis using an optical microscope, or by using a particle counter.

[0068] In one embodiment, the foreign object comprises a first foreign object with a maximum size of 500 μm or more but less than 1 mm and a second foreign object with a maximum size of less than 500 μm. The foreign object may also comprise a third foreign object with a maximum size of more than 1 mm.

[0069] The proportion of the first foreign substance in the mixed component is, for example, 5% or more by volume, and for example, 50% or less by volume, preferably 40% or less by volume.

[0070] The proportion of the second foreign substance in the mixed-in component is, for example, 50% or more by volume, preferably 60% or more by volume, and for example, 95% or less by volume.

[0071] If the proportions of the first and / or second foreign matter are within the above range, unevenness in the resin film can be suppressed more stably.

[0072] In addition to foreign matter, the mixed components may also include resin components that are different from the second resin.

[0073] As a resin component, examples include the same components as the first resin described above. The blended components may comprise one or more resin components. In one embodiment, the resin component comprises an olefin-based resin (typically polyethylene).

[0074] The proportion of resin component mixed into the composition is, for example, 0% or more and 99% or less by volume, or 50% or more and 90% or less by volume.

[0075] The bubble rate of the recycled material particles is, for example, 10% by volume or less, preferably 3% by volume or less, and more preferably 0% by volume. Furthermore, the bubble rate can be determined by observation and analysis using a microscope. If the bubble rate of the recycled material particles is below the aforementioned upper limit, the generation of bubbles in the resin film can be stably suppressed.

[0076] The melt viscosity C of the recycled granules (recycled material) is appropriately varied depending on the type of the second resin and the mixed components. The melt viscosity C of the recycled granules is, for example, 200 Pa•s or more, preferably 350 Pa•s or more, and for example, 2800 Pa•s or less, preferably 2300 Pa•s or less.

[0077] The melt viscosity of the raw pellets (raw material) and the melt viscosity of the recycled pellets (recycled material) satisfy, for example, the following formula (1), preferably the following formula (2).

[0078] [Mathematical Expression 1]

[0079]

[0080] [Mathematical Expression 2]

[0081]

[0082] (In equations (1) and (2), A represents the melt viscosity of the original material [Pa•s] and C represents the melt viscosity of the recycled material [Pa•s].)

[0083] The absolute value of the difference in melt viscosity between the original and recycled particles relative to the melt viscosity A of the original particles (|(CA) / A|) is more preferably 0.08 or more, further preferably 0.55 or less, particularly preferably 0.45 or less, especially preferably 0.35 or less, and most preferably 0.25 or less. When |(CA) / A| is within the above range, the non-uniformity in the resin film can be sufficiently reduced.

[0084] B-2-1. Preparation method of recycled pellets

[0085] The recycled granules can be prepared from the aforementioned recycled resin material using any suitable method. The preparation method of the recycled granules can be wire cutting or thermal cutting. In one embodiment, the method for preparing the recycled granules includes: a step of melting a recycled resin material having the aforementioned moisture content (melting step); and a step of extruding the molten recycled resin material (extrusion molding step).

[0086] To adjust the moisture content of the recycled resin material to the aforementioned range, any suitable method can be employed. Examples of methods for adjusting the moisture content of the recycled resin material include storing it in a moisture-proof bag and storing it in a container and then depressurizing the container (typically by vacuuming). Among these methods, storing the recycled resin material in a moisture-proof bag is preferred.

[0087] Moisture-proof bags can have any suitable composition. For example, a packaging material with aluminum fused to the inner lining can be considered as a moisture-proof bag. The moisture permeability of the moisture-proof bag is, for example, 10 g / m³. 2 • Less than 24 hours, preferably 5g / m 2 • Less than 24 hours, preferably 3g / m 2 • Less than 24 hours. Water permeability can be measured, for example, using the cup method.

[0088] The storage time is, for example, 2 hours or more, preferably 12 hours or more, and for example, 72 hours or less, preferably 36 hours or less. With this method, even if the recycled resin material is stored for the above-mentioned time, the moisture content of the recycled resin material can be stably maintained within the above-mentioned range.

[0089] The storage temperature is, for example, above 0°C and below 30°C, and the storage humidity is, for example, above 0%RH (relative humidity) and below 60%RH (relative humidity).

[0090] In the melting process, the aforementioned recycled resin material is heated to melt it. Typically, the recycled resin material is fed into a cylinder equipped with a screw, where it is heated and melted while being mixed using the screw.

[0091] The heating temperature and heating time can be set arbitrarily and appropriately according to the type of recycled resin material. The heating temperature is, for example, above 80°C and below 150°C. The heating time (retention time) is, for example, above 6 hours and below 48 hours.

[0092] The screw rotation speed is, for example, 5 rpm or more, preferably 10 rpm or more, more preferably 20 rpm or more, and even more preferably 40 rpm or more, and for example, 200 rpm or less, preferably 100 rpm or less, and more preferably 80 rpm or less. If the screw rotation speed is at or above the aforementioned lower limit, the maximum size of the dispersed phase in the recycled material particles can be stably adjusted to below the aforementioned upper limit. If the screw rotation speed is at or above the aforementioned lower limit, the incorporation of air bubbles into the recycled material particles can be suppressed.

[0093] The ratio of the screw length L to the screw diameter D (L / D) is, for example, 15 or more, preferably 20 or more, and for example, 60 or less, preferably 40 or less.

[0094] Thus, a molten recycled resin material (hereinafter referred to as molten resin) is obtained.

[0095] In one embodiment, the molten resin is passed through a filter before being fed to the extrusion molding process. This removes large foreign matter contained in the molten resin.

[0096] The filter can take any suitable configuration. Examples of filters include screens and disc filters, with screens being preferred.

[0097] The mesh size of the screen is, for example, 2.6 mm or less (8 mesh), preferably 2.0 mm or less (10 mesh), more preferably 0.60 mm or less (30 mesh), and even more preferably 0.15 mm or less (100 mesh), and for example, 0.034 mm or more (400 mesh), preferably 0.045 mm or more (300 mesh), and more preferably 0.060 mm or more (250 mesh). If the mesh size is below the upper limit mentioned above, large foreign objects can be smoothly removed from the molten resin, especially when the mesh size is less than 1.0 mm, large foreign objects with a maximum size exceeding 1 mm can be removed from the molten resin. If the mesh size is above the lower limit mentioned above, the molten resin can pass through smoothly.

[0098] In the extrusion molding process, molten resin is ejected from the die and then cooled to solidify. This produces recycled granules.

[0099] When preparing recycled granules using a wire cutting method, molten resin is extruded from a die in filament form and then cooled to obtain strands composed of recycled resin material. These strands are then cut to a specified size to obtain recycled granules.

[0100] When the recycled granules are prepared by thermal cutting, molten resin is ejected from the die head in a filamentous form and immediately sheared to obtain recycled granules.

[0101] C. Film-making process

[0102] like Figure 1 As shown, in the film-making process, a long strip of resin film 3 is made from the above-mentioned raw material particles and recycled material particles. More specifically, the two ends 31 in the width direction of the resin film 3 are formed from the recycled material particles, and the main body 32 of the resin film 3 is formed from the raw material particles, thus forming one resin film 3.

[0103] Detailed descriptions of the resin film preparation method are provided, for example, in Japanese Patent Application Publication No. 2006-315275. The descriptions in that patent document are incorporated herein by reference. More specifically, in the method for manufacturing a brittle resin film described in Japanese Patent Application Publication No. 2006-315275, virgin granules are used as brittle resin A, and recycled granules are used as toughening resin B, thereby producing a resin film 3.

[0104] The resin film 3 obtained in the film-forming process can have any suitable configuration. As described above, the resin film 3 is elongated. The dimensions of the resin film 3 in each direction can be any suitable value. The width of the resin film 3 (the dimension in the direction orthogonal to the length direction) is, for example, 500 mm or more, preferably 700 mm or more, and for example, 2500 mm or less, preferably 2000 mm or less. The thickness of the resin film 3 is, for example, 40 μm or more, preferably 60 μm or more, and for example, 200 μm or less, preferably 180 μm or less.

[0105] D. First cutting process

[0106] In the first cutting process, the two ends 31 of the resin film 3 in the width direction are cut off respectively.

[0107] In the example shown, two cutting lines 33 are formed in the resin film 3. The cutting lines 33 extend along the length direction of the resin film 3. The two cutting lines 33 are formed at a predetermined interval from each other in the width direction of the resin film 3, and the two cutting lines 33 are formed at a predetermined interval from the edge of the resin film 3 in the width direction.

[0108] Thus, the resin film 3 is separated into two first end films 6 containing an end 31 in the width direction of the resin film 3 and a finished film 4 containing a main body portion 32. The two first end films 6 and the finished film 4 are each elongated strips.

[0109] The width of the first end film 6 is, for example, 1% or more, preferably 5% or more, more preferably 10% or more, and for example, 50% or less, preferably 30% or less, when the width of the stretch film 3 is 100%. The width of the first end film 6 is, for example, 10 mm or more, preferably 50 mm or more, more preferably 100 mm or more, and for example, 1000 mm or less, preferably 600 mm or less. When the width of the first end film is at or above the aforementioned lower limit, the portion from the recycled material particles can be sufficiently included in the first end film. When the width of the end film is at or below the aforementioned upper limit, an improvement in the yield rate of the stretch film can be achieved.

[0110] The first end film 6 can be recycled using any suitable method. The recycled first end film 6 is preferably used as a recycled resin material in the above-described method for preparing recycled granules. That is, the recycled resin material may include the first end film 6. In this case, the first end film 6 is recycled immediately after the first cutting step, and the moisture content is adjusted to less than 1.0% using the above-described moisture content adjustment method. Then, it is fed to the above-described melting step.

[0111] E. Stretching process

[0112] like Figure 2 As shown, in the stretching process, the elongated film 4 is stretched in a direction intersecting the length direction. Any suitable stretching method can be used. Various stretching methods, such as free-end stretching and fixed-end stretching, can be used individually, simultaneously, or sequentially. Fixed-end uniaxial stretching is a preferred stretching method.

[0113] Fixed-end uniaxial stretching is typically performed using a stretching device equipped with clamps capable of holding the width-direction ends of the film 4. A typical stretching device is a tenter frame stretching device. With the clamps holding (typically clamping) both width-direction ends of the film 4, the stretching device stretches the film 4 in a direction intersecting the length direction. The stretching direction can be substantially orthogonal to the length direction of the film 4 (e.g., 90° ± 1° relative to the length direction), or it can be a direction intersecting both the length and width directions of the film 4.

[0114] Details of the stretching process are described, for example, in Japanese Patent No. 7096940, Japanese Unexamined Patent Publication No. 2004-226686, and International Publication No. 2007 / 111313. The descriptions in these patent documents are incorporated herein by reference.

[0115] Thus, it was created as Figure 2 The elongated stretch film 5 shown. The stretch ratio in the width direction during the stretching process (width of the stretch film / width of the finished film) is, for example, 1.1 or more, preferably 1.5 or more, and for example, 6.0 or less, preferably 4.0 or less.

[0116] The stretched film 5 is characterized by having a slow axis in the aforementioned stretching direction and is constructed as a phase retardation film. The refractive index of the stretched film 5 shows a relationship of nx > ny.

[0117] In one embodiment, the stretch membrane 5 functions as a λ / 4 plate. When the stretch membrane functions as a λ / 4 plate, the in-plane phase difference Re(550) of the stretch membrane 5 is, for example, 100 nm to 180 nm, preferably 135 nm to 155 nm.

[0118] In another embodiment, the stretch membrane 5 functions as a λ / 2 plate. When the stretch membrane functions as a λ / 2 plate, the in-plane phase difference Re(550) of the stretch membrane is, for example, 230 nm to 310 nm, preferably 250 nm to 290 nm.

[0119] There are no particular limitations on the wavelength dependence of the stretched film 5. The stretched film 5 preferably exhibits an anti-dispersion wavelength dependence. The Re(450) / Re(550) of the stretched film 5 is preferably 0.8 or more and less than 1.0, more preferably 0.8 to 0.95. In addition, the Re(550) / Re(650) of the stretched film 5 is preferably 0.8 or more and less than 1.0, more preferably 0.8 to 0.97.

[0120] The absolute value of the photoelastic coefficient of the stretched film 5 is, for example, 2 × 10⁻⁶. -12 (m) 2 / N) ~100×10 -12 (m) 2 / N), preferably 5×10 -12 (m) 2 / N) ~50×10 -12 (m) 2 / N).

[0121] F. Second cutting process

[0122] In one embodiment, the manufacturing of the stretch film further includes a second cutting step. In the second cutting step, both ends of the stretch film 5 in the width direction are cut off.

[0123] In the example shown, two cutting lines 55 are formed in the stretch film 5. The cutting lines 55 extend along the length direction of the stretch film 5. The two cutting lines 55 are formed at a predetermined interval between each other in the width direction of the stretch film 5, and the two cutting lines 55 are formed at a predetermined interval from the edge of the stretch film 5 in the width direction.

[0124] During the stretching process, when uniaxial stretching is performed at the fixed end, clamping marks 51 may sometimes form at both ends of the stretching membrane 5 in the width direction. The clamping marks 51 are harder and more brittle than the rest of the stretching membrane 5.

[0125] Furthermore, the slow axis of the stretch film 5 may deviate in the width direction. More specifically, the direction of the slow axis of the stretch film 5 is prone to deviate from the desired angle at its width-direction ends. This axial deviation is typically not substantial in the central portion of the stretch film 5 in the width direction, but becomes larger closer to the width-direction ends. In the stretch film 5 illustrated in the figure, in the central portion of the width direction, the slow axis is substantially parallel to the aforementioned stretching direction (e.g., axial deviation less than 0° ± 1°). However, at the width-direction ends of the stretch film 5, the slow axis may intersect with the aforementioned stretching direction (e.g., axial deviation of 1° to 3°).

[0126] Therefore, if the second cutting process is performed, the gripping marks 51 of the clamp and / or the portion of the stretch film with a relatively large axial deviation can be removed from the stretch film 5. In addition, two second end films 7 corresponding to the two ends of the stretch film 5 in the width direction are obtained from the stretch film 5.

[0127] The second end film 7 in the illustration includes clamping marks 51. Furthermore, the stretched film 2, after being cut from the two second end films 7, is constituted as the product film 8. That is, in the second cutting process, the stretched film 5 is representatively separated into two second end films 7 and the product film 8. The product film 8 is representatively constituted as the aforementioned phase difference film.

[0128] The width of the second end film 7, when the width of the stretched film 5 is 100%, is for example 0.5% or more, preferably 1.0% or more, more preferably 5.0% or more, and even more preferably 10.0% or more, and for example 30% or less, preferably 25% or less, and even more preferably 20% or less. The width of the second end film 7 is for example 10 mm or more, preferably 20 mm or more, more preferably 100 mm or more, and even more preferably 200 mm or more, and for example 600 mm or less, preferably 500 mm or less, and even more preferably 300 mm or less.

[0129] When the width of the second end film is above or above the aforementioned lower limit, the second end film can stably contain the entire clamping marks of the fixture, and the second end film can stably contain the portion of the stretch film with relatively large axial deviation. As a result, residual clamping marks of the fixture in the product film can be suppressed, and axial deviation in the product film can be reduced. When the width of the second end film is below or above the aforementioned upper limit, the yield rate of the product film can be improved.

[0130] The second end film 7 can be recycled using any suitable method. The recycled second end film 7 is preferably used as a recycled resin material in the above-described method for preparing recycled granules. That is, the above-described recycled resin material may include the second end film 7. In this case, the second end film 7 is recycled immediately after the second cutting step, and the moisture content is adjusted to less than 1.0% using the above-described moisture content adjustment method. Then, it is fed into the above-described melting step.

[0131] Example

[0132] The present invention is specifically illustrated below using examples, but the invention is not limited to these examples. The methods for measuring each characteristic are described below. Furthermore, unless otherwise specified, "parts" and "%" in the examples and comparative examples refer to quality standards. Additionally, the methods for measuring each characteristic in the examples and comparative examples are described below.

[0133] (1) Determination of the melt viscosity of raw and recycled particles

[0134] Using a method based on JIS K 7199, at a shear rate of 100 sec -1 The melt viscosity of the original and recycled granules used in the examples and comparative examples was determined at a temperature of 24°C. The results are shown in Tables 1-3.

[0135] (2) Determination of the maximum size of the dispersed phase in recycled material particles

[0136] The maximum size of the dispersed phase in the recycled material particles used in the examples and comparative examples was determined by observation using a scanning microscope. The results are shown in Tables 1-3.

[0137] (3) Determination of the maximum size of foreign matter contained in recycled material particles and determination of the content ratio of each component in the foreign matter.

[0138] The maximum size of foreign matter in the recycled material particles used in the Examples and Comparative Examples was determined using a particle counter. The foreign matter included a first foreign matter with a maximum size x of 500 μm or more but less than 1 mm and / or a second foreign matter with a maximum size x of less than 500 μm. In addition to the first and second foreign matter, the foreign matter in Example 14 also included a third foreign matter with a maximum size x of 1 mm or more. The proportions (volume %) of the first, second, and third foreign matter were calculated using an optical microscope. The results are shown in Tables 1-3.

[0139] (4) Moisture content of the end membrane

[0140] The moisture content of the end-film (recycled resin material) in the Examples and Comparative Examples prior to the manufacturing process of the recycled granules was determined using the Karl Fischer method. The results are shown in Tables 1-3.

[0141] (5) Air bubbles in the resin film

[0142] The presence of air bubbles in the resin films prepared in the examples and comparative examples was confirmed using an optical microscope. The results are shown in Tables 1-3.

[0143] <<Preparation of End-Membranes>>

[0144] <Preparation Examples 1-6>

[0145] A resin film made of PC-based resin was prepared in the same manner as Manufacturing Example 9 of Japanese Patent Application Publication No. 2022-150732, and the resin film was stretched to prepare a stretched film made of PC-based resin. The thickness of the stretched film was 48 μm.

[0146] Next, the two ends of the stretched film in the width direction are cut off using a cutter (cutting device) to obtain two end films (regeneration times: 1). The width of each of the two end films is 250mm.

[0147] Next, the resulting end membrane was washed with water. Then, the end membrane was dried at 100°C for 10 minutes (washing times: 1).

[0148] Next, place the end film in a moisture-proof bag (product name: moisture-proof packaging bag sheet moisture-proof type, made by Yamaguchi Packaging Industry Co., Ltd.) under the conditions shown in Table 1 or 3 and store for 24 hours.

[0149] <Preparation Example 7>

[0150] Except for changing the moisture-proof bag to a non-moisture-proof bag (product name: inner bag almi bag, manufactured by Yamaguchi Packaging Industry Co., Ltd.), the end film was prepared and stored in the same manner as in Preparation Example 1.

[0151] <Preparation Examples 8-13>

[0152] Using the end-cap film obtained in Preparation Example 1, recycled granules were manufactured using the same method as in Example 1 described later (preparation step). A resin film was then formed from the original granules and recycled granules (film forming step). The resin film was cut to separate a first end-cap film and a finished film (first cutting step). The finished film was then stretched (stretching step). The resulting stretched film was cut to separate a second end-cap film and a product film (second cutting step). Next, using the obtained second end-cap film, the preparation step, film forming step, first cutting step, stretching step, and second cutting step were repeated until the number of regenerations shown in Table 1 or 3 was reached. Thus, an end-cap film (second end-cap film) with the number of regenerations shown in Table 1 or 3 was prepared. The obtained end-cap film was then stored in the same manner as in Preparation Example 1.

[0153] <Preparation Examples 14-16>

[0154] A resin film made of PC-based resin was prepared in the same manner as Manufacturing Example 9 of Japanese Patent Application Publication No. 2022-150732, and the resin film was stretched to prepare a stretched film made of PC-based resin. The thickness of the stretched film was 48 μm.

[0155] Next, a polyethylene (PE) film (thickness: 48 μm) as a protective film is adhered to the surface of the stretch film via an acrylic adhesive layer. Then, the two ends of the laminated film, consisting of the stretch film and the protective film, are cut in the width direction using a cutter (cutting device) to obtain two end films (recycling times: 1). Each of the two end films has a width of 250 mm.

[0156] Next, the obtained end-film was washed with water. Then, the end-film was dried at 100°C for 10 minutes (washing times: 1). Afterward, the end-film was stored in the same manner as in Preparation Example 1.

[0157] <Preparation Example 17>

[0158] Except that the thickness of the PE film used as a protective film is changed to 96 μm, the end film is prepared and stored in the same manner as in Preparation Example 14.

[0159] <Preparation Example 18>

[0160] Except for repeatedly washing and drying the end membrane five times, the end membrane was prepared and stored in the same manner as in Preparation Example 1.

[0161] <Preparation Examples 19 and 20>

[0162] Except that the resin film made of PC-based resin was replaced with a resin film made of PET (Toray Corporation, model "50U48"), the end film was prepared and stored in the same manner as in Preparation Example 1. Furthermore, the thickness of the stretched film obtained by stretching the resin film was 50 μm.

[0163] <Preparation Example 21>

[0164] Except that the end film obtained in Preparation Example 19 was used instead of the end film obtained in Preparation Example 1, the preparation process, film-making process, first cutting process, stretching process, and second cutting process were repeated in the same manner as in Preparation Example 8 until the number of regenerations shown in Table 2 was reached. Thus, an end film (second end film) with the number of regenerations shown in Table 2 was prepared. Next, the obtained end film was stored in the same manner as in Preparation Example 1.

[0165] <Preparation Example 22>

[0166] Except that the resin film made of PC-based resin was replaced with a resin film made of PET (Toray Corporation, model "50U48"), the end film containing the PE film was prepared and stored in the same manner as in Preparation Example 14. Furthermore, the thickness of the stretched film obtained by stretching the resin film was 50 μm, and the thickness of the PE film was 50 μm.

[0167] <Preparation Examples 23 and 24>

[0168] Except that the resin film made of PC-based resin was replaced with a resin film made of acrylic resin (manufactured by Kaneka Corporation, product name "HTX-Z"), the end film was prepared and stored in the same manner as in Preparation Example 1. Furthermore, the thickness of the stretched film obtained by stretching the resin film was 40 μm.

[0169] <Preparation Example 25>

[0170] Except that the end film obtained in Preparation Example 23 was used instead of the end film obtained in Preparation Example 1, the preparation process, film-making process, first cutting process, stretching process, and second cutting process were repeated in the same manner as in Preparation Example 8 until the number of regenerations shown in Table 2 was reached. Thus, an end film (second end film) with the number of regenerations shown in Table 2 was prepared. Next, the obtained end film was stored in the same manner as in Preparation Example 1.

[0171] <Preparation Example 26>

[0172] Except that the resin film made of PC-based resin was replaced with a resin film made of acrylic resin (manufactured by Kaneka Corporation, product name "HTX-Z"), the end film containing the PE film was prepared and stored in the same manner as in Preparation Example 14. In addition, the thickness of the stretched film obtained by stretching the resin film was 80 μm, and the thickness of the PE film as a protective film was 80 μm.

[0173] <Preparation Examples 27 and 28>

[0174] Except that the resin film made of PC-based resin was replaced with a resin film made of COP-based resin (manufactured by Zeon Corporation, Japan, model "ZF16"), the end film was prepared and stored in the same manner as in Preparation Example 1. Furthermore, the thickness of the stretched film obtained by stretching the resin film was 40 μm.

[0175] <Preparation Example 29>

[0176] Except that the end film obtained in Preparation Example 27 was used instead of the end film obtained in Preparation Example 1, the preparation process, film-making process, first cutting process, stretching process, and second cutting process were repeated in the same manner as in Preparation Example 8 until the number of regenerations shown in Table 2 was reached. Thus, an end film (second end film) with the number of regenerations shown in Table 2 was prepared. Next, the obtained end film was stored in the same manner as in Preparation Example 1.

[0177] <Preparation Example 30>

[0178] Except that the resin film made of PC-based resin was replaced with a resin film made of COP-based resin (manufactured by Zeon Corporation, Japan, model "ZF16"), the end film containing the PE film was prepared and stored in the same manner as in Preparation Example 14. In addition, the thickness of the stretched film obtained by stretching the resin film was 40 μm, and the thickness of the PE film as a protective film was 40 μm.

[0179] [Examples 1-30, Comparative Examples 1-3]

[0180] The preserved end-cap membranes obtained in each preparation example were supplied as recycled resin material to a pellet manufacturing apparatus (wire cutting method) equipped with filters shown in Tables 1-3. In the pellet manufacturing apparatus, the end-cap membranes were heated to 270°C and melted, then passed through the filters shown in Tables 1-3. Recycled pellets were then manufactured by extrusion molding under the extrusion conditions (screw speed, compression ratio, and effective length) shown in Tables 1-3. The mass ratio of the mixed component / secondary resin in the recycled pellets is shown in Tables 1-3.

[0181] Furthermore, raw material pellets were manufactured by melt extrusion according to the method described in Japanese Patent Application Publication No. 2013-181105. The raw material pellets contained the first resin shown in Tables 1-3. The content of the first resin in the raw material pellets was 100% by mass.

[0182] Next, a resin film is formed from the virgin granules and the recycled granules. More specifically, according to the embodiment disclosed in Japanese Patent Application Publication No. 2006-315275, the two ends of the resin film in the width direction are formed from the recycled granules, and the main body portion located between the two ends of the resin film in the width direction is formed from the virgin granules. The width of the resin film is 800 mm. The thickness of the resin film is 200 μm.

[0183] Next, the resin film is cut using a cutter (cutting device) to separate it into a first end film containing the end portion of the resin film in the width direction and a finished film containing the main body portion. The width of each of the two first end films is 60 mm (7.5% when the width of the resin film is 100%).

[0184] Next, according to Manufacturing Example 9 of Japanese Patent Application Publication No. 2022-150732, the prepared film was stretched in the width direction. A stretched film was thus obtained. The stretch ratio was 3.0 times. The width of the stretched film was 2000 mm.

[0185] Next, the stretch film is cut using a cutter (cutting device) to separate it into two second end films and a product film. The width of each of the two second end films is 250 mm (12.5% ​​when the width of the stretch film is 100%). The width of the product film is 1500 mm.

[0186]

[0187] Captures 50% of foreign objects up to 100μm in size.

[0188]

[0189]

[0190] [evaluate]

[0191] As shown in Tables 1-3, adjusting the moisture content of the recycled resin material used as raw material for recycled granules to less than 1.0% by mass can suppress air bubbles in the resin film.

[0192] Industrial availability

[0193] The method for manufacturing the stretch film of the present invention is preferably used in the manufacture of stretch films that can be used in various industrial products, especially in the manufacture of optical films (specifically, phase difference films).

Claims

1. A method for manufacturing a stretch film, comprising the following steps: The process of preparing raw materials containing a first resin and recycled materials containing a second resin and mixed components; A process for making a strip-shaped resin film from the original material and the recycled material, wherein the recycled material forms the two ends of the resin film in the width direction, and the original material forms the main body portion located between the two ends of the resin film in the width direction; The process of cutting the resin film to separate it into a first end film containing the width direction end of the resin film and a film forming part containing the main body portion; as well as The process of stretching the formed film in a direction intersecting the length direction, wherein the recycled material is prepared from a recycled resin material with a moisture content of less than 1.0% by mass.

2. The method for manufacturing a stretch film according to claim 1, wherein, The recycled resin material includes a first end membrane.

3. The method for manufacturing a stretch film according to claim 1 or 2, further comprising the step of cutting off both ends of the stretch film in the width direction to obtain a second end film.

4. The method for manufacturing a stretch film according to claim 3, wherein, The recycled resin material includes a second end membrane.

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