CN118514311A

CN118514311A - Method for producing stretched film

Info

Publication number: CN118514311A
Application number: CN202410140881.0A
Authority: CN
Inventors: 荻野真悠子; 中原步梦
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2023-02-17
Filing date: 2024-02-01
Publication date: 2024-08-20
Also published as: JP2024117372A; KR20240128575A

Abstract

The invention provides a method for producing a stretched film, which can inhibit bubbles from generating in a resin film even if the resin film is made of a regenerated material, and can produce the stretched film with the expected characteristics. The method for producing a stretched film according to an embodiment of the present invention comprises the steps of: a step of forming a resin film from a raw material and a regenerated material, wherein both ends in the width direction of the resin film are formed from the regenerated material, and a main body portion located therebetween is formed from the raw material; cutting the resin film, separating the first end film and forming a film; and stretching the film. The regenerated material is prepared from a regenerated resin material having a moisture content of less than 1.0 mass%.

Description

Method for producing stretched film

Technical Field

The present invention relates to a method for producing a stretched film.

Background

Stretched films widely used in various industrial products are produced by stretching a resin film. For example, a method of producing a stretched film has been proposed in which a resin film is stretched in a direction intersecting a longitudinal direction while holding both ends of a long resin film in a width direction with a jig (for example, refer to patent document 1).

In recent years, from the viewpoint of reducing environmental load, recycling of waste generated in the production of various industrial products has been desired. Therefore, there has been studied a method of producing a stretched film by producing a resin film from a recycled material recycled from waste of a resin product and then stretching the resin film. However, when a resin film is formed using a recycled material, bubbles may be generated in the resin film, and as a result, desired properties may not be imparted to the stretched film.

Prior art literature

Patent literature

Patent document 1: japanese patent No. 7096940

Disclosure of Invention

Technical problem to be solved by the invention

The present invention has been made to solve the above-described problems of the prior art, and a main object thereof is to provide a method for producing a stretched film, which can suppress the generation of bubbles in a resin film even when the resin film is produced using a recycled material, and as a result, can produce a stretched film having desired characteristics.

Means for solving the technical problems

[1] The method for producing a stretched film according to an embodiment of the present invention comprises the steps of: a step of preparing a raw material containing a first resin and a regenerated material containing a second resin and a mixed component; a step of forming a long resin film from the raw material and the regenerated material, wherein both ends in the width direction of the resin film are formed from the regenerated material, and a main body portion located between both ends in the width direction of the resin film is formed from the raw material; cutting the resin film, and separating the resin film into a first end film including an end in a width direction of the resin film and a film including the main body portion; and stretching the produced film in a direction intersecting the longitudinal direction. The regenerated material is prepared from a regenerated resin material having a water content of less than 1.0 mass%.

[2] The method for producing a stretched film according to item [1] above, wherein the recycled resin material may contain a first end film.

[3] The method for producing a stretched film according to [1] or [2] above, further comprising a step of cutting both ends of the stretched film in the width direction to obtain a second end film.

[4] The method for producing a stretched film according to item [3], wherein the recycled resin material may contain a second end film.

Effects of the invention

According to the embodiment of the present invention, even if the resin film is made of a recycled material, generation of bubbles in the resin film can be suppressed, and as a result, a stretched film having desired characteristics can be produced.

Drawings

Fig. 1 is a schematic plan view of a resin film according to a method for producing a stretched film according to an embodiment of the present invention.

Fig. 2 is a schematic plan view of a stretched film obtained by stretching a produced film obtained from the resin film of fig. 1.

Sign description

3. Resin film

31. End of the resin film in the width direction

32. Body part

4. Film formation

5. Stretched film

6. First end film

7. Second end film

Detailed Description

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. In addition, although the width, thickness, shape, and the like of each portion are schematically shown in the drawings in comparison with the embodiments for the sake of clarity of description, the present invention is not limited to the explanation of the present invention, but is merely an example.

(Definition of terms and symbols)

The terms and symbols in the present specification are defined as follows.

(1) Refractive index (nx, ny, nz)

"Nx" is the refractive index in the direction in which the in-plane refractive index becomes maximum (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.

(2) In-plane phase difference (Re)

"Re (lambda)" is the in-plane retardation measured at 23℃by light of wavelength lambda nm. For example, "Re (550)" is the in-plane retardation measured at 23℃by light having a wavelength of 550 nm. Re (λ) is represented by the following formula when the thickness of the layer (film) is d (nm): re (λ) = (nx-ny) ×d.

(3) Angle of

When referring to an angle in the present specification, unless otherwise specified, the angle includes an angle in both directions of clockwise rotation and counterclockwise rotation.

A. outline of a method for producing stretched film

FIG. 1 is a schematic plan view of a resin film according to a method for producing a stretched film according to an embodiment of the present invention; fig. 2 is a schematic plan view of a stretched film obtained by stretching a produced film obtained from the resin film of fig. 1.

The method for producing a stretched film according to the embodiment of the present invention includes a preparation step, a film production step, a first cutting step, and a stretching step in this order.

In the preparation step, the raw material and the regenerated material are prepared. The raw material contains a first resin. The recycled material comprises a second resin and a blend component. The regenerated material is prepared from a regenerated resin material having a moisture content of less than 1.0 mass%. The moisture content in the regenerated resin material is preferably 0.8 mass% or less, more preferably 0.5 mass% or less. The lower limit of the moisture content in the regenerated resin material is typically 0.01 mass%. In addition, the water content in the regenerated resin material can be measured by the karl fischer method.

In the film forming step, a long resin film 3 (see fig. 1) is formed from a raw material and a regenerated material. More specifically, the two widthwise ends 31 of the resin film 3 are formed of a recycled material, and the main body portion 32 located between the two widthwise ends 31 of the resin film 3 is formed of an original material. In the resin film 3, the main body portion 32 is integrally continuous with both end portions 31 in the width direction. In the first cutting step, the cut resin film 3 is separated into a first end film 6 including the widthwise end 31 of the resin film 3 and a finished film 4 including the main body portion. In the stretching step, the produced film 4 is stretched in a direction intersecting the longitudinal direction (see fig. 2).

The present inventors have studied to manufacture a stretched film (particularly an optical film) by stretching a resin film made of a recycled material and a virgin material in combination. Then, it was found that bubbles may be generated in the resin film made of the recycled material and the raw material, and that unevenness may be generated in the appearance and/or characteristics of the produced stretched film due to the bubbles of the resin film. Accordingly, as a result of intensive studies on a recycled material, it has been found that when the recycled material is used at both ends in the width direction of a resin film in the film formation of the resin film, and the water content of the recycled resin material, which is a raw material of the recycled material, is adjusted, bubbles in the resin film can be suppressed. Specifically, a reclaimed material is first prepared (prepared) from a reclaimed resin material having a water fraction smaller than the upper limit described above. And, the raw material is additionally prepared. Next, 1 sheet of resin film 3 was produced so that both end portions 31 in the width direction of the resin film 3 were formed from the recycled material and the main body portion 32 of the resin film 3 was formed from the raw material. Even if the resin film 3 is made of recycled material, the generation of bubbles in the resin film 3 can be suppressed, and as a result, the stretched film 5 having desired characteristics can be stably produced.

The recycled resin material is obtained by recycling waste resin products or waste generated during the production of the resin products. Examples of the resin product include an optical film such as a retardation film; packaging materials made of thermoplastic resins such as polyethylene terephthalate (PET) and nylon. Among these resin products, an optical film is preferable, and a retardation film is more preferable. That is, the recycled material is preferably produced from an optical film (typically, a retardation film) and/or waste generated during the production of the optical film. In the method for producing a stretched film according to the embodiment of the present invention, the end film (first end film and/or second end film) produced as a by-product can be preferably used as a recycled resin material in the production of a recycled material. In addition, the regenerated resin material may be regenerated a plurality of times. That is, the recycled material may be prepared from a resin product (typically, an optical film) produced from the recycled resin material and/or waste generated at the time of production of the resin product.

Details of each step of the method for producing a stretched film are described below.

B. preparation step

In the preparation step, the raw material and the regenerated material are prepared, respectively, as described above.

B-1. Raw materials

The starting material is a synthetic resin material containing no regenerated resin material. Examples of the shape of the raw material include a discharged pellet shape and a powder shape. In one embodiment, the starting material is prepared as a starting pellet. The case where the raw material is a raw pellet will be described in detail below.

The raw pellet has any suitable shape and size. The raw charge particles typically have a cylindrical shape. The average maximum length of the raw pellets is, for example, 1.0mm or more and 5.0mm or less. The mass of each 1 of the raw pellets is, for example, 5mg or more and 25mg or less.

The raw pellet (raw material) contains the first resin and is substantially free of other components. The content of the first resin in the raw pellet is, for example, 99.0 mass% or more, preferably 99.2 mass% or more, more preferably 99.5 mass% or more, and typically 100 mass% or less. That is, the content of the other components in the raw pellet is, for example, 1.0 mass% or less, preferably 0.8 mass% or less, more preferably 0.5 mass% or less, still more preferably 0.2 mass% or less, particularly preferably 0.09 mass% or less, particularly preferably 0.05 mass% or less, and typically 0 mass% or more.

The first resin is arbitrarily and appropriately selected according to the use of the stretched film.

Examples of the first resin include polycarbonate resins, polyvinyl acetal resins, cycloolefin resins, (meth) acrylic resins, cellulose ester resins, cellulose resins, polyester carbonate resins, olefin resins, and urethane resins. The (meth) acrylic resin means an acrylic resin and/or a methacrylic resin. These first resins may be used alone or in combination.

Among the first resins contained in the raw pellets, polycarbonate (PC) resins, cycloolefin (COP) resins, (meth) acrylic resins, and polyester resins (typically polyethylene terephthalate (PET)) are preferable, and PC resins are more preferable. When the first resin is such a resin material, desired properties can be stably imparted to the stretched film (particularly, the optical film).

Examples of the PC resin include PC resins containing a structural unit derived from a dihydroxy compound. As a specific example of the dihydroxy compound, examples thereof include 9, 9-bis (4-hydroxyphenyl) fluorene, 9-bis (4-hydroxy-3-methylphenyl) fluorene, 9-bis (4-hydroxy-3-ethylphenyl) fluorene, 9-bis (4-hydroxy-3-n-propylphenyl) fluorene 9, 9-bis (4-hydroxy-3-isopropylphenyl) fluorene, 9-bis (4-hydroxy-3-n-butylphenyl) fluorene, 9-bis (4-hydroxy-3-sec-butylphenyl) fluorene, 9-bis (4-hydroxy-3-tert-butylphenyl) fluorene 9, 9-bis (4-hydroxy-3-isopropylphenyl) fluorene, 9-bis (4-hydroxy-3-n-butylphenyl) fluorene 9, 9-bis (4-hydroxy-3-sec-butylphenyl) fluorene, 9-bis (4-hydroxy-3-tert-butylphenyl) fluorene, 9, 9-bis (4- (2-hydroxyethoxy) -3-cyclohexylphenyl) fluorene, 9-bis (4- (2-hydroxyethoxy) -3-phenylphenyl) fluorene, 9-bis (4- (2-hydroxyethoxy) -3, 5-dimethylphenyl) fluorene, 9-bis (4- (2-hydroxyethoxy) -3-tert-butyl-6-methylphenyl) fluorene, 9-bis (4- (3-hydroxy-2, 2-dimethylpropoxy) phenyl) fluorene. The PC-based resin may contain, in addition to the structural unit derived from the above-mentioned dihydroxy compound, structural units derived from a dihydroxy compound such as isosorbide, isomannide, isoidide, spiroglycol, dioxanediol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanedimethanol (CHDM), tricyclodecanedimethanol (TCDDM), bisphenols and the like.

Details of the PC-based resin are described in, for example, japanese patent application laid-open No. 2012-67300 and japanese patent No. 3325560. The descriptions of the patent documents are incorporated by reference into the present specification.

The melt viscosity a of the raw pellet (raw material) is appropriately changed according to the type of the first resin. The melt viscosity A of the raw pellets is, for example, 300 Pa.s or more, preferably 500 Pa.s or more, more preferably 1000 Pa.s or more, and is, for example, 3000 Pa.s or less, preferably 2500 Pa.s or less. The melt viscosity of the pellets can be measured, for example, by a method based on JIS K7199.

The starting pellets may be prepared by any suitable method. The preparation method of the raw material grains can be a stranded wire cutting mode or a hot cutting mode. Details of the method for producing the raw pellets are described in, for example, japanese patent application laid-open No. 2013-181105. The description of said patent document is incorporated by reference into the present specification.

B-2. Regenerated material

The recycled material is prepared from a recycled resin material having the above moisture content. Examples of the shape of the regenerated material include a discharged granular shape and a powder shape. In one embodiment, the recycled material is prepared as recycled pellets. The case where the regenerated material is regenerated pellets will be described in detail below.

The shape and size of the reclaimed pellet can be described in the same manner as the original pellet. The reclaimed material particles contain the second resin and a blending component blended into the second resin. The second resin contained in the reclaimed pellet (reclaimed material) is typically the same as the first resin contained in the original pellet (original material).

In one embodiment, in the reclaimed material particles, the second resin forms a continuous phase as a matrix resin, and the blending component forms a dispersed phase that is dispersed in the continuous phase in a particulate form.

The maximum size of the dispersed phase is, for example, 1500nm or less, preferably 1000nm or less, more preferably 500nm or less, still more preferably 350nm or less, particularly preferably 250nm or less, particularly preferably 200nm or less, most preferably 100nm or less, and is, for example, 1nm or more, preferably 10nm or more, more preferably 30nm or more, still more preferably 50nm or more. When the maximum size of the dispersed phase is equal to or less than the upper limit, occurrence of unevenness (resin flow unevenness) in the resin film can be suppressed. When the maximum size of the dispersed phase is not less than the lower limit, the regenerated material can be produced smoothly. The maximum size of the dispersed phase can be measured, for example, by cross-sectional observation using a scanning electron microscope.

The content of the second resin in the reclaimed material particles is, for example, 40.0 mass% or more, preferably 50.0 mass% or more, more preferably 70.0 mass% or more, still more preferably 90.0 mass% or more, and for example, 99.1 mass% or less.

The content of the mixed component in the reclaimed material particles is, for example, 60.0 mass% or less, preferably 50.0 mass% or less, more preferably 30.0 mass% or less, and still more preferably 10.0 mass% or less. The lower limit of the content ratio of the mixed component in the reclaimed material particles is, for example, 0.3 mass%, still more preferably 0.5 mass%, still more preferably 0.9 mass%.

In the reclaimed material pellet, 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 mixing component/second resin is within the above range, unevenness in the resin film can be stably reduced.

The mixed component typically contains foreign matter. The foreign matter is a solid component different from the resin component.

Examples of the foreign matter include amide-based foreign matter and fiber-based foreign matter. The foreign matter may be mixed into the reclaimed material particles alone or in combination.

The content of the foreign matter to be mixed into the component is, for example, 1% by volume or more and 100% by volume or less, and also, for example, 10% by volume or more and 50% by volume or less.

The maximum size of the largest foreign matter among the foreign matters contained in the mixed components is, for example, less than 3mm, preferably less than 1mm. If the maximum size of the largest foreign matter is smaller than the upper limit, generation of unevenness in the resin film can be more stably suppressed. The maximum size of the foreign matter can be measured by observation and analysis using an optical microscope, for example, or can be measured using a particle counter, for example.

In one embodiment, the foreign matter includes a first foreign matter having a maximum size of 500 μm or more and less than 1mm and a second foreign matter having a maximum size of less than 500 μm. The foreign matter may further comprise a third foreign matter having a largest dimension exceeding 1 mm.

The content of the first foreign matter in the foreign matter contained in the component is, for example, 5% by volume or more and, for example, 50% by volume or less, preferably 40% by volume or less.

The content of the second foreign matter in the foreign matter contained in the component is, for example, 50% by volume or more, preferably 60% by volume or more, and 95% by volume or less.

When the content ratio of the first foreign matter and/or the second foreign matter is within the above range, generation of unevenness in the resin film can be more stably suppressed.

The mixed component may contain a resin component different from the second resin in addition to the foreign matter.

Examples of the resin component include the same components as the first resin. The mixed component may contain a single resin component or 2 or more resin components. In one embodiment, the resin component includes an olefinic resin (typically polyethylene).

The content of the resin component to be mixed into the component is, for example, 0% by volume or more and 99% by volume or less, and also, for example, 50% by volume or more and 90% by volume or less.

The bubble ratio of the reclaimed material particles is, for example, 10% by volume or less, preferably 3% by volume or less, and more preferably 0% by volume. In addition, the bubble ratio can be measured by observation and analysis using a microscope. When the bubble ratio of the reclaimed material particles is equal to or less than the upper limit, the occurrence of bubbles in the resin film can be stably suppressed.

The melt viscosity C of the reclaimed material particles (reclaimed material) is appropriately changed according to the type of the second resin and the mixed component. The regenerated pellet has a melt viscosity C of, for example, 200 Pa.s or more, preferably 350 Pa.s or more, and 2800 Pa.s or less, preferably 2300 Pa.s or less.

The melt viscosity of the raw pellet (raw material) and the melt viscosity of the reclaimed pellet (reclaimed material) satisfy, for example, the following formula (1), and preferably satisfy the following formula (2).

[ Mathematics 1]

[ Math figure 2]

(In the formulae (1) and (2), A represents the melt viscosity [ Pa.s ] of the starting material, and C represents the melt viscosity [ Pa.s ] of the regenerated material.)

The difference in melt viscosity between the raw pellets and the reclaimed pellets is more preferably 0.08 or more, still more preferably 0.55 or less, particularly preferably 0.45 or less, particularly preferably 0.35 or less, and most preferably 0.25 or less, relative to the absolute value of the melt viscosity A of the raw pellets (i (C-A)/A). When the ratio of (C-A)/A is within the above range, unevenness in the resin film can be sufficiently reduced.

Preparation method of B-2-1 regenerated material particles

The reclaimed material particles can be produced from the above reclaimed resin materials by any suitable method. The preparation method of the regenerated material particles can be a stranded wire cutting mode or a hot cutting mode. In one embodiment, a method of making reclaimed feed particles comprises: a step (melting step) of melting the regenerated resin material having the water content; and a step of extrusion molding the regenerated resin material in a molten state (extrusion molding step).

In order to adjust the water fraction of the regenerated resin material to the above range, any suitable method may be employed. Examples of the method for adjusting the moisture content of the regenerated resin material include a method in which the regenerated resin material is stored in a moisture-proof bag and a method in which the regenerated resin material is stored in a container and then the container is depressurized (typically, evacuated). Among such water fraction adjustment methods, a method of storing a regenerated resin material in a moisture-proof bag is preferable.

The moisture barrier bag may have any suitable composition. Examples of the moisture-proof bag include a packing material in which aluminum is fusion-bonded to the inner bag. The moisture permeability of the moisture-proof bag is, for example, 10g/m ².multidot.24 hours or less, preferably 5g/m ².multidot.24 hours or less, and preferably 3g/m ².multidot.24 hours or less. The moisture permeability can be measured, for example, by a cup method.

The storage time is, for example, 2 hours or more, preferably 12 hours or more, and is, for example, 72 hours or less, preferably 36 hours or less. In this method, even when the regenerated resin material is stored for the above-described period of time, the water content of the regenerated resin material can be stably maintained in the above-described range.

The storage temperature is, for example, 0 ℃ to 30 ℃, and the storage humidity is, for example, 0% RH (relative humidity) to 60% RH (relative humidity).

In the melting step, the regenerated resin material is heated and melted. Typically, a regenerated resin material is supplied into a cylinder equipped with a screw, and kneaded by the screw while being heated and melted.

The heating temperature and the heating time are set arbitrarily and appropriately according to the type of the regenerated resin material. The heating temperature is, for example, 80 ℃ to 150 ℃. The heating time (residence time) is, for example, 6 hours to 48 hours.

The rotation speed of the screw is, for example, 5rpm or more, preferably 10rpm or more, more preferably 20rpm or more, still more preferably 40rpm or more, and is, for example, 200rpm or less, preferably 100rpm or less, more preferably 80rpm or less. When the rotational speed of the screw is not less than the lower limit, the maximum size of the dispersed phase in the reclaimed material particles can be stably adjusted to not more than the upper limit. If the rotational speed of the screw is not less than the lower limit, the incorporation of bubbles into the reclaimed material particles can be suppressed.

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

Thereby, a regenerated resin material in a molten state (hereinafter referred to as a molten resin) is obtained.

In one embodiment, the molten resin is passed through a filter before being fed to the extrusion process. Thus, coarse foreign matters contained in the molten resin can be removed from the molten resin.

The filter may take any suitable form. Examples of the filter include a mesh and a disc filter, and preferably a mesh.

The mesh size of the screen is, for example, 2.6mm or less (8 mesh), preferably 2.0mm or less (10 mesh), more preferably 0.60mm or less (30 mesh), still more preferably 0.15mm or less (100 mesh), and is, for example, 0.034mm or more (400 mesh), preferably 0.045mm or more (300 mesh), still more preferably 0.060mm or more (250 mesh). When the mesh size of the screen is not more than the upper limit, coarse foreign matters can be removed smoothly from the molten resin, and particularly when the mesh size is less than 1.0mm, coarse foreign matters having a maximum size exceeding 1mm can be removed from the molten resin. If the mesh size of the screen is not less than the lower limit, the molten resin can pass smoothly.

In the extrusion molding step, the molten resin is discharged from a die, and then cooled to be solidified. Thereby preparing regenerated pellets.

When the method for producing the regenerated strand is a strand cutting method, the molten resin is discharged in a strand form from a die and cooled to obtain a strand made of a regenerated resin material. Thereafter, the strands were sheared to a predetermined size to obtain reclaimed pellets.

When the method for producing the reclaimed granular material is a thermal cutting method, the reclaimed granular material is obtained by immediately shearing a molten resin after the molten resin is discharged in a filament form from a die.

C. Film forming process

As shown in fig. 1, in the film forming step, a long resin film 3 is formed from the raw pellets and the reclaimed pellets. More specifically, the two widthwise ends 31 of the resin film 3 are formed from reclaimed pellets, and the main body portion 32 of the resin film 3 is formed from virgin pellets, thereby producing 1 sheet of resin film 3.

Details of a method for forming a resin film are described in, for example, japanese patent application laid-open No. 2006-315275. The description of said patent document is incorporated by reference into the present specification. More specifically, in the method for producing a brittle resin film described in japanese patent application laid-open No. 2006-315275, raw pellets are used as the brittle resin a, and reclaimed pellets are used as the ductile resin B, so that the resin film 3 can be produced.

The resin film 3 obtained in the film forming step may have any suitable structure. The resin film 3 has an elongated shape as described above. The dimensions of the resin film 3 in each direction may take any appropriate values. The width (dimension in the direction perpendicular to the longitudinal direction) of the resin film 3 is, for example, 500mm or more, preferably 700mm or more, and is, for example, 2500mm or less, preferably 2000mm or less. The thickness of the resin film 3 is, for example, 40 μm or more, preferably 60 μm or more, and is, for example, 200 μm or less, preferably 180 μm or less.

D. First cutting process

In the first cutting step, both ends 31 in the width direction of the resin film 3 are cut.

In the example of the figure, 2 cut lines 33 are formed in the resin film 3. The cutting line 33 extends along the longitudinal direction of the resin film 3. The 2 cutting lines 33 are formed at predetermined intervals from each other in the width direction of the resin film 3, and the 2 cutting lines 33 are formed at predetermined intervals from the edges of the resin film 3 in the width direction.

Thereby, the resin film 3 is separated into 2 first end films 6 including the end portions 31 in the width direction of the resin film 3 and the produced film 4 including the main body portion 32. The 2 first end films 6 and the finished film 4 each have an elongated shape.

The width of the first end film 6 is, for example, 1% or more, preferably 5% or more, more preferably 10% or more, and is, for example, 50% or less, preferably 30% or less, when the width of the stretched film 3 is set to 100%. The width of the first end film 6 is, for example, 10mm or more, preferably 50mm or more, more preferably 100mm or more, and is, for example, 1000mm or less, preferably 600mm or less. When the width of the first end film is equal to or greater than the lower limit, the portion from which the reclaimed material particles originate may be sufficiently contained in the first end film. When the width of the end film is equal to or less than the upper limit, the yield of the stretched film can be improved.

The first end membrane 6 may be recovered using any suitable method. The recovered first end film 6 can be preferably used as a recycled resin material in the above-described method for producing recycled pellets. That is, the regenerated resin material may contain the first end film 6. At this time, the first end film 6 is recovered immediately after the first cutting step, and the moisture content is adjusted to less than 1.0% by the moisture content adjustment method described above. Then, the molten material is fed to the above-mentioned melting step.

E. Stretching step

As shown in fig. 2, in the stretching step, the long produced film 4 is stretched in a direction intersecting the longitudinal direction. Any suitable method may be used for the stretching method. The stretching methods such as free end stretching and fixed end stretching may be used alone or simultaneously or sequentially. In the stretching method, the fixed-end uniaxial stretching is preferably exemplified.

The fixed-end uniaxial stretching is typically performed by a stretching apparatus including a clamp capable of holding the widthwise end portion of the film 4. The stretching device is typically a tenter stretching device. The stretching device stretches the produced film 4 in a direction intersecting the longitudinal direction while holding (typically clamping) both ends of the produced film 4 in the width direction by a clamp. The stretching direction may be a direction substantially orthogonal to the longitudinal direction of the produced film 4 (for example, 90 ° ± 1 ° with respect to the longitudinal direction), or may be a direction intersecting both the longitudinal direction and the width direction of the produced film 4.

Details of the stretching step are described in, for example, japanese patent application laid-open No. 7096940, japanese patent application laid-open No. 2004-226686, and International publication No. 2007/111313. The description of said patent document is incorporated by reference in the present specification.

Thus, a long stretched film 5 as shown in fig. 2 was produced. The stretching ratio in the width direction (width of stretched film/width of film to be formed) in the stretching step is, for example, 1.1 or more, preferably 1.5 or more, and is, for example, 6.0 or less, preferably 4.0 or less.

The stretched film 5 typically has a slow axis in the stretching direction, and is configured as a retardation film. The refractive index of the stretched film 5 shows the relationship of nx > ny.

In one embodiment, the stretched film 5 functions as a lambda/4 plate. When the stretched film functions as a lambda/4 plate, the in-plane retardation Re (550) of the stretched film 5 is, for example, 100nm to 180nm, preferably 135nm to 155nm.

In another embodiment, the stretched film 5 functions as a lambda/2 plate. When the stretched film functions as a lambda/2 plate, the in-plane retardation Re (550) of the stretched film is, for example, 230nm to 310nm, preferably 250nm to 290nm.

The wavelength dependence of the stretched film 5 is not particularly limited. The stretched film 5 preferably exhibits a wavelength dependence of the inverse dispersion. 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. 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.

The absolute value of the photoelastic coefficient of the stretched film 5 is, for example, 2X 10 ^-12(m²/N)～100×10^-12(m²/N), preferably 5X 10 ^-12(m²/N)～50×10^-12(m²/N.

F. Second cutting step

In one embodiment, the manufacturing of the stretched film further includes a second cutting step. In the second cutting step, both ends of the stretched film 5 in the width direction are cut.

In the example of the figure, 2 cut lines 55 are formed in the stretched film 5. The cut line 55 extends along the longitudinal direction of the stretched film 5. The 2 cutting lines 55 are formed at predetermined intervals in the width direction of the stretched film 5, and the 2 cutting lines 55 are formed at predetermined intervals from the edges of the stretched film 5 in the width direction.

When the fixed-end uniaxial stretching is performed in the stretching step, grip marks 51 of the jigs may be formed at both ends in the width direction of the stretched film 5, respectively. The grip trace 51 of the jig is harder and more brittle than the portion of the stretched film 5 other than the grip trace 51.

In addition, the slow axis of the stretched film 5 may deviate from the axis in the width direction. More specifically, the direction of the slow axis of the stretched film 5 tends to deviate from a desired angle at the widthwise end. The axial deviation is not substantially exhibited in the widthwise central portion of the stretched film 5, but becomes larger as it approaches the widthwise end portions. In the stretched film 5 illustrated in the drawing, the slow axis is substantially parallel to the stretching direction (for example, the axis is deviated by less than 0 ° ± 1 °) in the widthwise central portion. In addition, the slow axis may intersect the stretching direction (for example, the axis may deviate from 1 ° to 3 °) at the widthwise end of the stretched film 5.

Therefore, when the second cutting step is performed, the grip mark 51 of the jig and/or the portion of the stretched film where the axis is relatively greatly deviated can be removed from the stretched film 5. In addition, 2 second end films 7 corresponding to both ends in the width direction of the stretched film 5 were obtained from the stretched film 5.

The second end film 7 of the illustrated example contains the grip trace 51 of the jig. The stretched film 2 obtained by cutting 2 second end films 7 is formed as a product film 8. That is, in the second cutting process, the stretched film 5 is typically separated into 2 second end films 7 and a product film 8. The product film 8 is typically formed as the above-described retardation film.

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

When the width of the second end film is equal to or greater than the lower limit, the second end film may include the entire grip trace of the jig and the second end film may include a portion of the stretched film in which the axis is relatively greatly deviated. As a result, the holding trace of the remaining jig in the product film can be suppressed, and the shaft deviation in the product film can be reduced. When the width of the second end film is equal to or less than the upper limit, the yield of the product film can be improved.

The second end membrane 7 may be recovered using any suitable method. The recovered second end film 7 can be preferably used as a regenerated resin material in the above-described method for producing regenerated pellets. That is, the regenerated resin material may include the second end film 7. At this time, the second end film 7 is recovered immediately after the second cutting step, and the moisture content is adjusted to less than 1.0% by the moisture content adjustment method described above. Then, the molten material is fed to the above-mentioned melting step.

Examples

The present invention will be specifically described below by way of examples, but the present invention is not limited to these examples. The measurement method of each characteristic is as follows. Unless otherwise specified, "parts" and "%" in examples and comparative examples are mass standards. The measurement methods of the characteristics in examples and comparative examples are as follows.

(1) Determination of melt viscosity of raw and regenerated pellets

The melt viscosities of the raw pellets and the reclaimed pellets used in examples and comparative examples were measured by a method based on JIS K7199 under conditions of a shear rate of 100sec ^-1 and a measurement temperature of 24 ℃. The results are shown in tables 1 to 3.

(2) Determination of maximum size of dispersed phase in reclaimed Material particles

The maximum size of the dispersed phase in the reclaimed material particles used in examples and comparative examples was measured by observation with a scanning microscope. The results are shown in tables 1 to 3.

(3) Measurement of maximum size of foreign matter contained in reclaimed material particles and measurement of content ratio of each component in foreign matter

The maximum size of foreign matter in the reclaimed material particles used in examples and comparative examples was measured by a particle counter. The foreign matter includes a first foreign matter having a maximum dimension x of 500 μm or more and less than 1mm and/or a second foreign matter having a maximum dimension x of less than 500 μm. The foreign matter of example 14 includes, in addition to the first foreign matter and the second foreign matter, a third foreign matter having a maximum dimension x of 1mm or more. The content (vol%) of each of the first foreign matter, the second foreign matter, and the third foreign matter was calculated by observation and analysis using an optical microscope. The results are shown in tables 1 to 3.

(4) Moisture fraction of end film

The water fraction of the end film (regenerated resin material) immediately before the production process of the regenerated pellet in examples and comparative examples was measured by the karl fischer method. The results are shown in tables 1 to 3.

(5) Air bubbles in resin film

The presence or absence of bubbles in the resin films prepared in examples and comparative examples was confirmed by an optical microscope. The results are shown in tables 1 to 3.

Preparation of tip film

Preparation examples 1 to 6 >

A resin film made of a PC-based resin was produced in the same manner as in production example 9 of japanese patent application laid-open No. 2022-150732, and the resin film was stretched to produce a stretched film made of a PC-based resin. The thickness of the stretched film was 48. Mu.m.

Then, both ends of the stretched film in the width direction were cut by a cutter (cutting device) to obtain 2 end films (number of times of regeneration: 1 time). The respective widths of the 2 end films were 250mm.

Then, the end film obtained was washed with water. Thereafter, the end film was dried at 100℃for 10 minutes (number of times of washing: 1 time).

Next, the end film was placed in a moisture-proof bag (trade name: moisture-proof package sheet, manufactured by mountain packaging industry company) under the environment shown in table 1 or 3, and was kept for 24 hours.

PREPARATION EXAMPLE 7

An end film was prepared and stored in the same manner as in preparation example 1, except that the moisture-proof bag was changed to a non-moisture-proof bag (trade name: inner bag, manufactured by mountain packaging industry Co.).

Preparation examples 8 to 13

Using the end film obtained in production example 1, a resin film was produced from the raw pellets and the regenerated pellets (production process) in the same manner as in example 1 described later, the resin film was cut, the produced film was separated into a first end film and a produced film (first cutting process), the produced film was stretched (stretching process), and the stretched film was cut and separated into a second end film and a product film (second cutting process). Next, using the obtained second end film, the preparation step, the film formation step, the first cutting step, the stretching step, and the second cutting step were repeated until the number of regenerations shown in table 1 or 3 was reached. Thus, an end film (second end film) of the number of regenerations shown in table 1 or 3 was prepared. Subsequently, the end film was stored in the same manner as in preparation example 1.

PREPARATION EXAMPLES 14 to 16

Next, a Polyethylene (PE) film (thickness: 48 μm) as a protective film was adhered to the surface of the stretched film via an acrylic pressure-sensitive adhesive layer. Thereafter, both ends in the width direction of the laminate film of the stretched film and the protective film were cut by a cutter (cutting device), respectively, to obtain 2 end films (number of times of regeneration: 1 time). The respective widths of the 2 end films were 250mm.

Then, the end film obtained was washed with water. Thereafter, the end film was dried at 100℃for 10 minutes (number of times of washing: 1 time). Thereafter, the end film was stored in the same manner as in preparation example 1.

PREPARATION EXAMPLE 17

An edge film was prepared and stored in the same manner as in preparation example 14, except that the thickness of the PE film as the protective film was changed to 96 μm.

PREPARATION EXAMPLE 18

An end film was prepared and stored in the same manner as in preparation example 1, except that washing and drying of the end film were repeated 5 times.

Preparation example 19 and 20 >

An end film was prepared and stored in the same manner as in preparation example 1, except that the resin film made of a PC-based resin was changed to a resin film made of PET (model "50U48", manufactured by Toray corporation). Further, the thickness of the stretched film obtained by stretching the resin film was 50 μm.

Preparation example 21 >

The preparation process, the film-forming process, the first cutting process, the stretching process, and the second cutting process were repeated in the same manner as in preparation example 8, except that the end film obtained in preparation example 1 was used instead of the end film obtained in preparation example 19, until the number of regenerations shown in table 2 was reached. Thus, an end film (second end film) of the number of regenerations shown in table 2 was prepared. Subsequently, the obtained end film was stored in the same manner as in preparation example 1.

PREPARATION EXAMPLE 22

An end film including a PE film was prepared and stored in the same manner as in preparation example 14, except that the resin film made of a PC-based resin was changed to a resin film made of PET (model "50U48", manufactured by Toray corporation). Further, 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.

Preparation example 23 and 24 >

An end film was produced and stored in the same manner as in production example 1, except that the resin film made of a PC-based resin was changed to a resin film made of an acrylic-based resin (manufactured by Kaneka corporation, product name "HTX-Z"). Further, the thickness of the stretched film obtained by stretching the resin film was 40 μm.

PREPARATION EXAMPLE 25

The preparation process, the film-forming process, the first cutting process, the stretching process, and the second cutting process were repeated in the same manner as in preparation example 8, except that the end film obtained in preparation example 1 was used in place of the end film obtained in preparation example 23, until the number of regenerations shown in table 2 was reached. Thus, an end film (second end film) of the number of regenerations shown in table 2 was prepared. Subsequently, the obtained end film was stored in the same manner as in preparation example 1.

PREPARATION EXAMPLE 26

An end film including a PE film was prepared and stored in the same manner as in preparation example 14, except that the resin film made of a PC-based resin was changed to a resin film made of an acrylic resin (manufactured by Kaneka corporation, product name "HTX-Z"). Further, the thickness of the stretched film obtained by stretching the resin film was 80 μm, and the thickness of the PE film as the protective film was 80 μm.

PREPARATION EXAMPLE 27 and 28

An end film was prepared and stored in the same manner as in preparation example 1, except that the resin film made of the PC-based resin was changed to a resin film made of the COP-based resin (model "ZF16" manufactured by Zeon corporation). Further, the thickness of the stretched film obtained by stretching the resin film was 40 μm.

PREPARATION EXAMPLE 29

The preparation process, the film-forming process, the first cutting process, the stretching process, and the second cutting process were repeated in the same manner as in preparation example 8, except that the end film obtained in preparation example 1 was used instead of the end film obtained in preparation example 27, until the number of regenerations shown in table 2 was reached. Thus, an end film (second end film) of the number of regenerations shown in table 2 was prepared. Subsequently, the obtained end film was stored in the same manner as in preparation example 1.

Preparation example 30

An end film including a PE film was prepared and stored in the same manner as in preparation example 14, except that the resin film made of a PC-based resin was changed to a resin film made of a COP-based resin (model "ZF16" manufactured by Zeon corporation). Further, the thickness of the stretched film obtained by stretching the resin film was 40 μm, and the thickness of the PE film as the protective film was 40 μm.

Examples 1 to 30 and comparative examples 1 to 3

The end film after storage obtained in each production example was supplied as a regenerated resin material to a pellet production apparatus (strand cutting system) provided with the filters shown in tables 1 to 3. In the pellet production apparatus, the end film was heated to 270 ℃ and melted, and passed through the filters shown in tables 1 to 3. Thereafter, pellets were produced by extrusion molding under extrusion conditions (screw speed, compression ratio and effective length) shown in tables 1 to 3. The mass ratio of the mixed component/the second resin in the reclaimed material pellet is shown in tables 1 to 3.

Further, raw pellets are produced by melt extrusion according to a method described in Japanese unexamined patent publication No. 2013-181105. The raw pellets contained the first resins shown in tables 1 to 3. The content of the first resin in the raw pellet was 100 mass%.

Next, a resin film is produced from the raw pellets and the reclaimed pellets. More specifically, according to the embodiment of japanese patent application laid-open No. 2006-315275, both widthwise ends of a resin film are formed from reclaimed pellets, and a main body portion located between both widthwise ends of the resin film is formed from virgin pellets. The width of the resin film was 800mm. The thickness of the resin film was 200. Mu.m.

Next, the resin film is cut by a cutter (cutting device), and separated into a first end film including an end in the width direction of the resin film and a produced film including a main body portion. The respective widths of the 2 first end films were 60mm (7.5% when the widths of the resin films were set to 100%).

Next, according to production example 9 of japanese patent application laid-open No. 2022-150732, the produced film is stretched in the width direction. Thereby obtaining a stretched film. The stretch ratio was 3.0 times. The width of the stretched film was 2000mm.

Next, the stretched film was cut by a cutter (cutting device), and separated into 2 second end films and a product film. The respective widths of the 2 second end films were 250mm (12.5% when the widths of the resin films were set to 100%). The width of the product film was 1500mm.

TABLE 1

* 50% Of foreign matters having a particle diameter of 100 μm are captured in Table 2

TABLE 2

TABLE 3

[ Evaluation ]

As is clear from tables 1 to 3, when the water content of the regenerated resin material as the raw material of the regenerated pellet was adjusted to be less than 1.0 mass%, air bubbles in the resin film were suppressed.

Industrial applicability

The method for producing a stretched film of the present invention is preferably used for producing a stretched film which can be used for various industrial products, particularly for producing an optical film (specifically, a retardation film).

Claims

1.A method for producing a stretched film, comprising the steps of:

A step of preparing a raw material containing a first resin and a regenerated material containing a second resin and a mixed component;

a step of forming a long resin film from the raw material and the regenerated material, wherein both ends in the width direction of the resin film are formed from the regenerated material, and a main body portion located between both ends in the width direction of the resin film is formed from the raw material;

Cutting the resin film, and separating the resin film into a first end film including an end in a width direction of the resin film and a film including the main body portion; and

And stretching the produced film in a direction intersecting the longitudinal direction, wherein the regenerated material is produced from a regenerated resin material having a water content of less than 1.0 mass%.

2. The method for producing a stretched film according to claim 1, wherein,

The recycled resin material includes a first end film.

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

4. The method for producing a stretched film according to claim 3, wherein,

The recycled resin material includes a second end film.