Methods for manufacturing granules and methods for manufacturing optical films

Abstract

The method for manufacturing the granules of the present invention includes: preparing a resin comprising one or more resins selected from (meth)acrylic resins and cyclic olefin resins, with a bulk density of 0.01 to 0.25 g / cm³. 3 The process involves crushing the material; and melting the crushed material using frictional heat at (50–Tg) °C (Tg is the glass transition temperature of the resin) to obtain a bulk density of 0.26–0.45 g / cm³. 3 The process of granulating materials.

Description

Technical Field

[0001] This invention relates to methods for manufacturing granules and methods for manufacturing optical films. Background Technology

[0002] Polarizers are commonly used in displays such as liquid crystal displays (LCDs), organic OLEDs, and μLEDs. A polarizer consists of a polarizer and an optical film that protects the polarizer and provides optical compensation.

[0003] In the manufacturing process of such optical films, ears with slits at the ends and non-standard parts are sometimes produced. From the viewpoint of effectively utilizing these materials and reducing waste to improve the manufacturing efficiency of optical films, research is being conducted on the reuse of films (recycled materials) that become ears with slits and non-standard parts during film manufacturing.

[0004] However, broken materials such as membranes are difficult to process due to their low bulk density (apparent specific gravity). Therefore, they are sometimes granulated (granulated) for use.

[0005] As a method of granulation, similar to the method for manufacturing granules for new products, methods such as melting crushed materials at a high temperature of around 250°C and granulating crushed materials using frictional heat are known. In Patent Document 1, a method is proposed that granulates (or melts) crushed materials such as recycled film using frictional heat to obtain granules with a bulk density reduced to the same level as granules for new products (see Patent Document 1).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 54-45365 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] However, optical films are required to have high optical stability (delayed humidity dependence) and dimensional stability (dimensional humidity dependence). Films containing cycloolefin resins and (meth)acrylic resins have better delayed humidity dependence and dimensional humidity dependence compared to conventional films containing cellulose ester resins, and are therefore being used more and more.

[0011] However, the fragments of membranes containing these resins are larger (bulky) than the fragments of conventional membranes containing cellulose ester resins, making them difficult to handle (difficult to transfer and store). Furthermore, if these membrane fragments are granulated under the conditions shown in Patent Document 1 (granulation by generating frictional heat at a high temperature of approximately 200°C), the resin in the granulated material is prone to thermal degradation.

[0012] Furthermore, due to the small aspect ratio of the resulting granules, the bulk density of the granules increases, or insufficient melting prevents complete granulation, making it easy for the granules to adhere to the inner wall of the piping during pneumatic conveying. When using such piping and fabricating membranes with different materials, the components of the granules adhering to the inner wall of the piping can easily become contaminated as foreign matter.

[0013] The present invention was made in view of the above-mentioned actual situation, and its purpose is to provide a method for manufacturing granules that suppresses heat-induced material deterioration and foreign matter contamination, while having excellent processability, and a method for manufacturing optical films using the same.

[0014] Methods for solving problems

[0015] The present invention relates to a method for manufacturing the following granules and a method for manufacturing an optical film using the same.

[0016] The method for manufacturing the granules of the present invention includes: preparing a resin comprising one or more resins selected from (meth)acrylic resins and cyclic olefin resins, with a bulk density of 0.01 to 0.25 g / cm³. 3 The process involves crushing the material; and melting the crushed material using frictional heat at a temperature of (50–Tg) °C (Tg being the glass transition temperature of the resin) to obtain a bulk density of 0.26–0.45 g / cm³. 3 The process of granulating materials.

[0017] The method for manufacturing the optical film of the present invention includes: a step of obtaining granules using the method for manufacturing granules of the present invention; and a step of melting or dissolving the granules in a solvent to obtain a film.

[0018] Invention Effects

[0019] According to the present invention, a method for manufacturing granules that suppresses heat-induced material degradation and foreign matter contamination, while exhibiting excellent processability, and a method for manufacturing optical films using the same are provided. Attached Figure Description

[0020] Figure 1 A cross-sectional view showing the structure of the crushing and granulation device.

[0021] Figure 2 for Figure 1 Enlarged view of the main parts. Detailed Implementation

[0022] As mentioned above, films containing cyclic olefin resins and (meth)acrylic resins are more difficult to cut (less prone to breakage) than films containing cellulose ester resins, and the broken pieces tend to become fluffy. The reason for this is unclear, but it is believed to be due to the higher toughness and lower polarity of cyclic olefin resins and (meth)acrylic resins compared to cellulose ester resins, which makes them more prone to generating static electricity.

[0023] In response, it was found that by 1) using frictional heat to melt and granulate the broken parts of the film while keeping the temperature below a certain level; and 2) further adjusting the melting and granulation conditions in a way that does not excessively reduce the bulk density of the resulting granules, the thermal degradation of the resin in the granules and the introduction of foreign matter during product switching can be suppressed.

[0024] Although the cause is still unclear, it is believed to be as follows.

[0025] Granulation utilizing frictional heat differs from conventional granulation utilizing melting. Because heat is applied locally at the contact points between the fragments, the entire fragment is less likely to reach high temperatures. Furthermore, by appropriately lowering the melting temperature generated by frictional heat (below the resin's Tg), the heat applied to the fragments can be kept at the minimum level required for granulation. This suppresses the decrease in resin molecular weight and discoloration caused by thermal degradation. Additionally, by achieving a higher bulk density than before, the granules are less likely to adhere to the inner wall of piping during empty transport, thus suppressing foreign matter contamination caused by granules adhering to the inner wall of piping during product switching. It should be noted that melting utilizing frictional heat preferably refers to bringing the material to a semi-molten state at a temperature lower than its melting point.

[0026] The melting temperature generated by frictional heat can be adjusted by any method. For example, the melting temperature can be achieved through methods described later. Figure 1 The width and length of the flow path (gap between the screw and the inner wall of the barrel) of the friction-heat-utilizing melting zone (compression section B, conveying section C), the cooling process (during melting), and the feed rate (processing speed) of the crushed material in the crushing and granulation device 10 can be adjusted. The bulk density of the granules can be adjusted, for example, by the melting temperature generated by frictional heat and the aspect ratio of the granules.

[0027] This invention relates to a method for manufacturing granules using recycled resin film. Therefore, the recycled resin film, which becomes the raw material for granulation, will be described first.

[0028] 1. Regarding recycled materials

[0029] Recycled materials include end pieces and non-standard parts cut off during the manufacturing process of resin films such as optical films. In the manufacturing process of optical films, defective products are sometimes generated due to cut-off ends, disordered winding, etc. Although these are not finished products, they are not defective in terms of material and can therefore be reused.

[0030] The optical film contains cyclic olefin resins or (meth)acrylic resins.

[0031] (Cyclic olefin resins)

[0032] Cycloolefin resins are polymers containing structural units derived from norbornene monomers. Norbornene monomers are represented by the following formula (1).

[0033] [Chemistry 1]

[0034] Equation (1)

[0035]

[0036] R in equation (1) 1 ~R 4 Each represents a hydrogen atom, a halogen atom, a hydrocarbon group, or a polar group.

[0037] Examples of halogen atoms include fluorine atoms, chlorine atoms, etc.

[0038] The hydrocarbon group is a hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 4, more preferably 1 or 2. Examples of hydrocarbon groups include alkyl groups such as methyl, ethyl, propyl, and butyl. The hydrocarbon group may further have a divalent linker containing an oxygen atom, nitrogen atom, sulfur atom, or silicon atom (e.g., carbonyl, imino, ether bond, silyl ether bond, thioether bond, etc.).

[0039] Examples of polar groups include carboxyl, hydroxyl, alkoxy, alkoxycarbonyl, aryloxycarbonyl, amino, amide, and those linked via methylene groups (-(CH2)). n - (n is an integer greater than or equal to 1) groups that bind these groups together. Among them, alkoxycarbonyl and aryloxycarbonyl are preferred, and alkoxycarbonyl is more preferred.

[0040] Among them, R 1 ~R 4 At least one of the components is preferably a polar group. Cycloolefin resins containing structural units from norbornene monomers having polar groups are readily soluble in solvents when film is formed using solution casting, for example, which readily increases the glass transition temperature of the resulting film. On the other hand, in melt casting, cycloolefin resins that do not contain structural units from norbornene monomers having polar groups can be used.

[0041] Additionally, R 1 ~R 4 In the middle, R 1 and R 2 These two (or R) 3 and R 4 Both of these can be hydrogen atoms.

[0042] In equation (1), p represents an integer from 0 to 2. From the viewpoint of improving the heat resistance of the optical film, p is preferably 1 to 2.

[0043] Among the norbornene monomers represented by formula (1), in the example of norbornene monomers with polar groups, the following monomers are included.

[0044] [Chemistry 2]

[0045]

[0046] Examples of norbornene monomers without polar groups include the following monomers.

[0047] [Chemistry 3]

[0048]

[0049] The content of structural units derived from norbornene monomers can be 50–100 mol, relative to all structural units constituting cyclic olefin resins.

[0050] Cycloolefin resins may further comprise structural units from other monomers that can copolymerize with structural units from norbornene monomers. Examples of other copolymerizable monomers include (in the case that the aforementioned norbornene monomers have polar groups) norbornene monomers without polar groups, cyclobutene, cyclopentene, cycloheptene, dicyclopentadiene, and other cycloolefin monomers that do not have a norbornene skeleton.

[0051] There are no particular limitations on the weight-average molecular weight (Mw) of the cyclic olefin resin, but it is preferably 20,000 to 300,000, more preferably 30,000 to 250,000, and even more preferably 40,000 to 200,000. If the Mw of the cyclic olefin resin is within the above range, it will not impair the molding processability and can improve the mechanical properties of the film.

[0052] The molecular weight (Mw) of cyclic olefin resins can be determined by gel permeation chromatography (GPC). Specifically, an HLC8220 GPC manufactured by Tosoh Corporation can be used for determination under the following conditions.

[0053] (Measurement conditions)

[0054] Elution buffer: THF

[0055] Column: TSKgel GMHXL made by Tosoh Corporation × 2 pieces

[0056] Flow rate: 1.0 mL / min

[0057] Sample concentration: 0.1% by mass

[0058] Injection volume: 100μL

[0059] Detector: RI

[0060] Calibration curve: Standard polystyrene

[0061] Column temperature: 40℃

[0062] The glass transition temperature (Tg) of cycloolefin resins is generally preferably above 110°C, more preferably 110–350°C, and even more preferably 120–250°C. If the Tg of the cycloolefin resin is above 110°C, sufficient heat resistance can be easily obtained, and if it is below 350°C, thermal degradation of the cycloolefin resin during molding and processing can be suppressed.

[0063] Tg can be determined using DSC (Differential Scanning Colorimetry) according to JIS K 7121-2012 or ASTM D 3418-82.

[0064] ((meth)acrylic resin)

[0065] (Meth)acrylic resins are preferably polymers containing structural units derived from methyl methacrylate. The polymer may further contain structural units derived from monomers that can copolymerize with methyl methacrylate.

[0066] Examples of other monomers that can copolymerize with methyl methacrylate include alkyl methacrylates with 1 to 18 carbon atoms other than methyl methacrylates such as 2-ethylhexyl methacrylate; α,β-unsaturated acids such as methacrylic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; styrene derivatives such as styrene and α-methylstyrene; maleic anhydride; maleimide derivatives such as maleimide and N-phenylmaleimide; and glutaric anhydride.

[0067] The content of structural units derived from methyl methacrylate is preferably 50% by mass or more, more preferably 70% by mass or more, relative to all structural units constituting the polymer.

[0068] The heat resistance (Tg) of the (meth)acrylic resin is preferably 90°C or higher, more preferably 100–150°C. If the Tg of the (meth)acrylic resin is within the above range, the heat resistance of the optical film can be easily improved. The Tg of the (meth)acrylic resin can be determined using the same method as described above.

[0069] The Mw of the (meth)acrylic resin is preferably 400,000 to 3,000,000, more preferably 500,000 to 2,000,000. If the Mw of the (meth)acrylic resin is within the above range, sufficient mechanical strength can be imparted to the film. The Mw of the (meth)acrylic resin can be determined using the same method as described above.

[0070] The content of cyclic olefin resin or (meth)acrylic resin is preferably 50% by mass or more, and more preferably 70% to 99% by mass, relative to the optical film.

[0071] (Other ingredients)

[0072] Optical films may further include other components as needed. Examples of other components include rubber particles, matting agents, antioxidants, and UV absorbers.

[0073] Rubber particles impart flexibility to the film. The rubber particles are graft copolymers comprising a rubber-like polymer (crosslinked polymer). Examples of rubber-like polymers include butadiene-based crosslinked polymers, (meth)acrylic acid-based crosslinked polymers, and organosiloxane-based crosslinked polymers. From the viewpoint of having a small refractive index difference with methacrylic acid resins and minimizing the risk of impairing the transparency of the optical film, (meth)acrylic acid-based crosslinked polymers are preferred, and acrylic acid-based crosslinked polymers (acrylic rubber-like polymers) are more preferred.

[0074] Matting agents can create irregularities on the surface of optical films, imparting slip properties. Matting agents can be inorganic particles, resin particles, etc. Examples of inorganic particles include microparticles such as silica, titanium dioxide, alumina, zirconium oxide, and calcium carbonate, with silica particles being preferred.

[0075] There are no particular restrictions on antioxidants; for example, hindered phenolic antioxidants can be used.

[0076] (thickness)

[0077] There are no particular limitations on the thickness of the optical film, for example, it is 5 to 100 μm, preferably about 5 to 40 μm.

[0078] Secondly, the method for manufacturing granules using the aforementioned recycled materials will be explained.

[0079] 2. Method for manufacturing granules

[0080] The method for manufacturing granules according to the present invention includes: 1) a step of preparing crushed material containing the above-mentioned resin; 2) a step of melting the obtained crushed material by using frictional heat to obtain granules.

[0081] Regarding the process in 1),

[0082] In this process, crushed material containing the above-mentioned resin is prepared.

[0083] Regarding the resin-containing shredded material, as described above, it is preferable to shredded material from recycled resin films such as optical films. The thickness of the recycled material is the same as the thickness of the optical film.

[0084] The resin membrane is preferably broken up under conditions where the breaking occurs and the heat received by the broken material is reduced, i.e., the bulk density of the resulting membrane is moderately reduced.

[0085] Specifically, the bulk density of the obtained crushed material is preferably 0.01–0.25 g / cm³. 3 If the bulk density of the obtained crushed material is 0.25 g / cm³ 3 The following (i.e., larger fragments) reduces the load during crushing and the resulting heat generation, making it easier to suppress the heat-induced deterioration and discoloration of the fragments. If the bulk density of the fragments is 0.01 g / cm³... 3 Since the crushed material is not too large, it is easy to granulate. Based on the above considerations, the bulk density of the obtained crushed material is more preferably 0.07–0.18 g / cm³. 3 about.

[0086] The bulk density of the crushed material can be determined using the following methods.

[0087] A 100 mL container was filled with crushed material, and the mass of the filled crushed material (or granules) was measured. This measurement was performed 10 times, and the average bulk density was calculated from the relationship with the volume. Note that no tapping was performed when filling the container.

[0088] The size of the crushed material is not particularly limited as long as its bulk density meets the above-mentioned range. A roughly square (or a rectangle with the same area) with one side length of approximately 2-8 mm is preferred. If one side length of the crushed material is 2 mm or more, it is easier to reduce the bulk density, thus making it easier to adjust the bulk density to the above-mentioned range. If one side length of the crushed material is 8 mm or less, since the crushed material is not too large, subsequent melting using frictional heat is easier. From the above perspective, a roughly square (or a rectangle with the same area) with one side length of approximately 3-7 mm is more preferable.

[0089] There is no particular limitation on the percentage (%) of crushed material separated when sieved for 2 minutes using a sieve with an average mesh size of 1 mm. For example, it can be 10% by mass or less relative to the total amount of crushed material before sieving. Crushed material with a separation rate of 10% by mass or less is crushed under gentle conditions, with a moderately low load during crushing, thus easily suppressing thermal degradation of resin caused by heat generated during crushing. From the above perspective, a separation rate (%) of crushed material relative to the total amount of crushed material before sieving is more preferably 5% by mass or less.

[0090] The bulk density, size, and fractionation rate of the crushed material can be adjusted by adjusting the crushing conditions. In order to make the bulk density, size, and fractionation rate of the crushed material fall within the above range, it is preferable to reduce the heat generated during crushing (reduce the heat received by the return material during crushing). Specifically, this involves reducing the load during crushing or removing heat to reduce the heat generated during crushing.

[0091] The resin film can be broken up using any method. For example, the resin film can be broken up by clamping the recycled material between a fixed blade and a rotating blade.

[0092] Regarding process 2):

[0093] Next, frictional heat is generated in the resulting fragments, and this heat is used to melt or fuse the fragments.

[0094] The melting using frictional heat is preferably carried out at (50~Tg)℃ (Tg is the glass transition temperature of the resin). If the melting temperature using frictional heat is 50℃ or higher, the crushed material can be made into a semi-molten state, thus easily obtaining granules with reduced bulk density. When the melting temperature is below Tg℃, the crushed material does not become excessively hot, which can suppress the thermal degradation of the resin, and can suppress the decrease in the molecular weight of the resin and the coloring of the granules. In addition, from the viewpoint of further suppressing yellowing of the regenerated film obtained by using the granules, the melting temperature is more preferably 50~100℃, and more preferably 60~100℃.

[0095] Melting temperature can be determined as the atmosphere temperature during melting, which utilizes frictional heat. For example, as described later... Figure 1 In the crushing and granulation apparatus 10, the atmosphere temperature can be measured downstream of the melting process utilizing frictional heat (for granulation) (see below). Figure 2 ).

[0096] Regarding the melting temperature, it can be adjusted, for example, by the magnitude of friction applied to the crushed material, the duration of friction application (residence time), and cooling treatment. When using the crushing and granulation apparatus 10 described later, the melting temperature can be adjusted by the feed rate of the crushed material, the width and length of the flow paths in the compression section B and the transfer section C, and the degree of cooling or slow heating (cooling temperature) using the temperature regulating unit (cooling means). When lowering the melting temperature, for example, it is preferable to make the width of the flow paths in the compression section B and the transfer section C of the crushing and granulation apparatus 10 moderately large and the length moderately short. In addition, it is preferable to lower the cooling temperature generated by the temperature regulating unit (cooling means) inside and outside the apparatus, or to lower the feed rate of the crushed material. In particular, it is preferable to use the temperature regulating unit (cooling means) to cool the crushed material so that its melting temperature is within the aforementioned range.

[0097] In addition, the fragments melted by frictional heat can be further cut into specified sizes (or lengths).

[0098] (Physical properties of granules)

[0099] The bulk density of the granulated material is preferably higher than that of the crushed material. Specifically, the bulk density of the granulated material is preferably higher than that of the crushed material, and lower than that of virgin (not recycled) granules (e.g., less than 80% of the bulk density of virgin granules). Specifically, the bulk density of the granulated material is preferably 0.26–0.45 g / cm³. 3 If the bulk density of the granules is 0.26 g / cm³ 3 The above methods facilitate empty delivery and storage, improving processability. If the bulk density of the granulated material is 0.45 g / cm³... 3 In this way, excessive heat is not applied during granulation, thus suppressing the thermal degradation of the resin in the granulated material and inhibiting the decrease in molecular weight and discoloration of the resin constituting the granulated material. Furthermore, the regenerated film obtained using such granulated material maintains good mechanical and optical properties. From the above perspective, the bulk density of the granulated material is more preferably 0.35–0.45 g / cm³. 3 The bulk density of granules can be determined using the same method as that used for crushed materials.

[0100] The bulk density of the granules can be about 150 to 1500% of the bulk density of the crushed material.

[0101] The bulk density of the granules can be adjusted by the melting temperature and the aspect ratio of the granules. In order to moderately reduce the bulk density of the granules, it is preferable to moderately reduce the melting temperature and more preferably to moderately increase the aspect ratio of the granules.

[0102] The aspect ratio of the granules can be appropriately set in such a way that the bulk density of the granules meets the above-mentioned range and according to the required processability. The aspect ratio of the granules is preferably, for example, 4 to 50. If the aspect ratio is 4 or higher, for example, it is difficult to adhere to the inner wall of the piping during empty transport, and it is easy to suppress the contamination of foreign matter during product switching. If it is 50 or lower, the bulk density of the granules does not increase excessively, and therefore it is less likely to impair the processability of transfer and storage. From the above viewpoint, the aspect ratio of the granules is more preferably 4 to 20. The aspect ratio of the granules refers to the average ratio of the length of the major axis to the length of the minor axis of the granules (average aspect ratio).

[0103] The aspect ratio of the granules can be determined using the following methods.

[0104] First, for any 100 granules, the lengths of the major and minor axes of the granules are measured using images taken with a camera, and the aspect ratio (length of major axis / length of minor axis) is calculated. The major axis is the line segment connecting the two furthest points in the outline of the granule image in the photographed image, and the minor axis is the longest line segment connecting the intersection of a line perpendicular to the major axis and the outline. The average of the obtained aspect ratios is then used as the "aspect ratio".

[0105] The aspect ratio of the granules can be adjusted by the cutting length and diameter (or the inner diameter of the extrusion port 22 of the crushing and granulating device 10) of the strip of resin extruded from the crushing and granulating device 10.

[0106] From the viewpoint of reducing the coloration of the obtained film, it is preferable that the YI of the granules is small. Specifically, the YI of the granules is preferably 1.0 or less, and more preferably 0.6 or less.

[0107] The YI of the granules can be measured using a spectrophotometer (such as the Konica Minolta CM-3700d spectrophotometer) with D65 (color temperature 6504K) as the light source and a viewing angle of 10°.

[0108] Frictional heating granulation can be carried out using any method. For example, frictional heating granulation can be carried out using an extrusion device, such as one with a screw.

[0109] The processes 1) and 2) described above can be performed separately in different devices or in a single, continuous device. For example, a device similar to the one described in Japanese Patent Application Publication No. 54-45365 can be used as a single, continuous device. In the following embodiments, an example of performing the processes 1) and 2) described above in a single, continuous device is shown.

[0110] Figure 1 A cross-sectional view showing the configuration of the crushing and granulation apparatus 10 in this embodiment.

[0111] Figure 2 for Figure 1 Enlarged view of the main parts.

[0112] like Figure 1 As shown, the crushing and granulation device 10 includes: a barrel 20, a screw 30 rotatably disposed therein, a cutting section 40, a separating section 50, and a temperature regulating section 60.

[0113] The barrel 20 has a supply port 21 for supplying recycled material 70 such as resin film, and an extrusion port 22 for extruding the recycled material 70 compressed in the barrel 20.

[0114] The screw 30 includes: a rotating shaft 31, a cutting screw 32A, a mixing screw 32B, and a conveying screw 32C arranged around it. In other words, with regard to the crushing and granulation apparatus 10, along the screw 30, from the supply port 21 side, there are sequentially: a crushing section A (the area corresponding to the cutting screw 32A) for crushing the recycled material 70, a compression section B (the area corresponding to the mixing screw 32B) for compressing the crushed material to generate frictional heat, and a conveying section C (the area corresponding to the conveying screw 32C) for melting and conveying the recycled material using frictional heat.

[0115] The cutting screw 32A in the crushing section A can be, for example, a rotating blade formed in the shape of a screw. On the inner wall surface of the barrel 20 corresponding to the cutting screw 32A, a plurality of fixed blades 23 are arranged such that their tips are close to the cutting screw 32A. Furthermore, the return material 70 supplied into the barrel 20 is cut by the fixed blades 23 and the cutting screw 32A.

[0116] In the compression section B, the barrel 20 corresponding to the mixing screw 32B is formed into a cone shape, with its inner diameter decreasing along the conveying direction. The mixing screw 32B is formed into a cone shape together with the barrel 20, and for example, multiple screws may be present. Furthermore, the return material 70 is compressed during its flow path between the barrel 20 and the mixing screw 32B, generating frictional heat.

[0117] The transfer screw 32C in the transfer section C is formed into multiple screws, for example, in a shape that reduces heat generation. Furthermore, a certain pushing force is applied to the return material 70 conveyed from the mixing screw 32B in a semi-molten state, and it is extruded into a strip shape from the extrusion port 22.

[0118] That is, process 1) above can be performed in crushing section A, and the melting using frictional heat in process 2) above can be performed in compression section B and transfer section C. Furthermore, in this invention, the melting temperature during the melting using frictional heat in process 2) above is adjusted to the aforementioned range, i.e., 50 to Tg (°C). Figure 1 In the crushing and granulation apparatus 10 shown, the melting temperature can be measured using a thermocouple 24 positioned near the extrusion port 22 (see reference). Figure 2 ).

[0119] Regarding the melting temperature, as described above, it can be adjusted by, for example, the feed rate of the crushed material (screw speed, etc.), the angle of the cone of the compression section B, the width W1 (or W2) of the flow path between the mixing screw 32B (or conveying screw 32C) in the compression section B (or the transfer section C) and the inner wall surface of the barrel 20, the length L1 (or L2) in the conveying direction, and cooling inside and outside the device. When lowering the melting temperature, it is preferable to reduce the feed rate of the crushed material, preferably reduce the angle of the cone of the barrel 20, preferably increase the width C1 (or C2) of the gap between the screw 32B (or 32C) and the inner wall surface of the barrel 20, and preferably shorten the length L1 (or L2) of the gap in the conveying direction. Furthermore, it is also preferable to use the temperature regulating unit 60, described later, to regulate the temperature of the barrel 20 and the screw 30 (for cooling).

[0120] The cutting section 40 is located near the extrusion port 22 of the barrel 20 and cuts the extruded strip of recycled material 72 into a specified length. There are no particular limitations on the cutting section 40, for example, it may have a cutting blade 41.

[0121] The separation section 50 separates the product from the re-fusion of the granules obtained from the cutting section 40. There are no particular limitations on the separation section 50, which includes a cooling or air supply means 51 such as a cooling blower and a rotating circular plate 52 with blades.

[0122] The temperature regulating unit 60 may be a cooling device for adjusting the barrel 20 and screw 30 to an appropriate temperature. The temperature regulating unit 60 includes, for example, a cooling jacket 61 that functions from the outside of the barrel 20, and a water-passing means 62 that functions from the inside of the screw 30.

[0123] In the crushing and granulation apparatus 10 configured in this way, recycled material 70, such as resin film, is fed into the barrel 20 from the recycled material supply section 1. In the crushing section A, the recycled material 70 is cut into shreds by the cutting screw 32A (rotating blade) and the fixed blade 23 of the barrel 20 and then fed into the compression section B.

[0124] The recycled material 70 (crushed material) sent to the compression section B is mixed under conditions of compression as it passes through the gap between the tapered barrel 20 and the mixing screw 32B, generating moderate frictional heat. Utilizing this frictional heat, the recycled material 70 (crushed material) becomes semi-molten and is sent to the transfer section C.

[0125] The return material 70, which is fed to the transfer section C in a semi-molten state, moves in the gap between the barrel 20 and the transfer screw 32C while being moderately fused, and is extruded from the extrusion port 22 at the front end of the barrel 20 in a semi-molten state.

[0126] To explain, in the compression section B and the transfer section C, the granulation conditions (size and length of the gap between the screw and the inner wall of the barrel 20), the feed rate of the return material 70, and the cooling generated by the temperature control section 60 are performed in such a way that the melting temperature measured by the thermocouple 24 is within the above-mentioned range.

[0127] The extruded strip of recycled material 70 is cut into granules of a specified length (length-to-diameter ratio) using the cutting section 40, becoming granules. The resulting granules are sometimes remelted using heat and separated by blowing cooling air through the separation section 50. Thus, granules with a suitable bulk density can be continuously recovered from the discharge port 53.

[0128] Secondly, the method for manufacturing optical films (recycled products) using the obtained granules will be explained.

[0129] 3. Manufacturing methods for optical films

[0130] The method for manufacturing the optical film of the present invention includes: 2-1) a step of obtaining granules by the above manufacturing method; and 2-2) a step of obtaining a film by using the obtained granules.

[0131] Regarding process 2-1)

[0132] The granules were obtained using the above manufacturing method.

[0133] Regarding process 2-2):

[0134] The obtained granules are used to obtain a film. The film can be obtained by any method, including melt casting and solution casting.

[0135] (Melting casting method)

[0136] In the melt casting method, the hot melt stream of granules is delayed and then cooled and solidified to obtain a cast film. Specifically, it can be obtained by a step of delaying and cooling the hot melt stream of granules to solidify, and optionally by a step of stretching the obtained film.

[0137] In process A1), the prepared granules are melt-mixed using a twin-screw extruder, etc., and then cast from a casting die. When the glass transition temperature of the resin is set to Tg, the hot melt temperature in the melt casting process can be (Tg+30)~(Tg+70)℃.

[0138] In the process of A2), stretching can be performed according to the required optical properties, preferably in one or more of the following directions: width direction (TD direction), transport direction (MD direction), and tilt direction.

[0139] The stretching ratio is set according to the required optical performance; for example, from the viewpoint of functioning as a film with low phase difference, it can be set to 1.01 to 1.3 times. The stretching ratio is defined as (the magnitude of the stretching direction of the film after stretching) / (the magnitude of the stretching direction of the film before stretching). The stretching temperature (the drying temperature during stretching) is preferably (Tg-20) to (Tg+30) °C.

[0140] (Solution casting method)

[0141] In solution casting, a solution (solvent) in which granules are dissolved in a solvent is cast and then dried to obtain a cast film. Specifically, it can be manufactured by a step of B1) preparing a solvent containing granules, a step of B2) casting the obtained solvent on a support, drying and peeling it to obtain a film, and optionally a step of B3) stretching the obtained film.

[0142] In step B1), the granules are dissolved in a solvent to prepare a paste. The solvent used must contain at least an organic solvent (good solvent) capable of dissolving cyclic olefin resins. Examples of good solvents include chlorinated organic solvents such as dichloromethane; and non-chlorinated organic solvents such as methyl acetate, ethyl acetate, acetone, and tetrahydrofuran, with dichloromethane being preferred. From the viewpoint of improving the peelability of the cast film from the support, the solvent used may further include undesirable solvents such as aliphatic alcohols with 1 to 4 carbon atoms, such as methanol and ethanol.

[0143] In step B2), the obtained adhesive paste is discharged from, for example, a casting mold and cast onto a support. Then, the solvent is evaporated from the adhesive paste cast on the support, and the paste is peeled off to obtain a film.

[0144] In step B3), the resulting film is stretched. The stretching ratio and stretching temperature can be the same as in step A2).

[0145] The optical film obtained in this way can be preferably used as a protective film for polarizers (including phase retardation films, etc.).

[0146] (Properties of optical films)

[0147] The total light transmittance of the optical film is not particularly limited as long as it has sufficient light transmittance, but is preferably 80% or more, more preferably 85% or more, and even more preferably 88% or more. The total light transmittance of the optical film can be measured according to JIS K 7361-1:1997.

[0148] The difference in YI before and after regeneration of the optical film is preferably less than 0.1, more preferably less than 0.05, and even more preferably less than 0.03. The difference in YI before and after regeneration of the optical film can be calculated as the difference (YI1-YI0) between the YI0 of the optical film before regeneration (recycled material) and the YI1 of the regenerated optical film (made using granules). YI can be measured using the same method as described above.

[0149] Example

[0150] The present invention will be specifically described below through examples, but the present invention is not limited thereto.

[0151] 1. Materials for optical films (recycled materials)

[0152] (1) Resin

[0153] Cycloolefin resins (COP):

[0154] Cycloolefin resins containing the following structural units (Tg: 165℃, Mw: 150,000)

[0155] [Chemistry 4]

[0156]

[0157] (Meth)acrylic resins (Acr):

[0158] MMA / N-phenylmaleimide / 2-ethylhexyl acrylate copolymer (Tg: 120℃, Mw: 2 million)

[0159] The Tg and Mw of the resin were determined using the following method.

[0160] (Tg)

[0161] The Tg of the resin was determined using DSC (Differential Scanning Colorimetry) according to JIS K 7121-2012.

[0162] (Mw)

[0163] The Mw of the resin was determined using gel permeation chromatography (HLC8220GPC manufactured by Tosoh Corporation) under the following conditions.

[0164] (Measurement conditions)

[0165] Elution buffer: THF

[0166] Column: TSKgel GMHXL made by Tosoh Corporation × 2 pieces

[0167] Flow rate: 1.0 mL / min

[0168] Sample concentration: 0.1% by mass

[0169] Injection volume: 100μL

[0170] Detector: RI

[0171] Calibration curve: Standard polystyrene

[0172] (2) Rubber particles

[0173] Rubber particles (Korea M210 manufactured by Kaneka Co., Ltd., average primary particle size R: 200 nm)

[0174] (3) Additives

[0175] Irganox 1076 (manufactured by BASF Japan) (antioxidant)

[0176] 2. Fabrication of optical films (recycled materials)

[0177] <Preparation of Membrane A-1>

[0178] (Preparation of additive solution)

[0179] 95 parts by weight of dichloromethane were added to a sealed container, and 0.00145 parts by weight of Irganox 1076 (manufactured by BASF Japan) (antioxidant) were added while stirring. The mixture was then stirred in a dissolver for 50 minutes. The resulting mixture was passed through a high-pressure dispersion device (trade name: M110-E / H ultra-high pressure homogenizer, manufactured by Microfluidics Corporation), treated once at 175 MPa, and then filtered through a FINEMET NF filter manufactured by Nippon Seisen Co., Ltd., to obtain an additive solution (antioxidant content: 0.0015% by weight).

[0180] (Preparation of adhesive paste)

[0181] Next, a paste with the following composition was prepared. First, dichloromethane and ethanol were added to a pressure dissolving vessel. Then, in a pressure dissolving tank, granules of a cyclic olefin resin (COP-1) were added while stirring, followed by the additive solution prepared above, which was then completely dissolved or dispersed while stirring. The resulting solution was filtered using an SHP150 filter manufactured by Rokitekino Co., Ltd., to obtain a paste with the following composition.

[0182] Cycloolefin resin (COP): 100 parts by weight

[0183] Dichloromethane: 220 parts by weight

[0184] Ethanol: 35 parts by weight

[0185] Additive solution: 200 parts by weight

[0186] (Membrane fabrication)

[0187] On a stainless steel strip support, the solvent is evaporated until the residual solvent content in the cast adhesive reaches 30% by mass. Then, it is peeled from the stainless steel strip support at a peel tension of 128 N / m to obtain a film (the residual solvent content of the film at peeling is 30% by mass). While the peeled film is transported by multiple rollers, the resulting film is stretched 30% in the width direction using a tenter frame at (Tg+15) °C (140 °C in this example). The residual solvent content of the film at the start of stretching is 10% by mass. Then, while being transported by rollers, it is further dried at (Tg-20) °C to obtain film A-1 (cyclic olefin resin film) with a thickness of 40 μm. Film A-1 is slit using a laser cutter to obtain recycled material.

[0188] <Preparation of Membrane A-2>

[0189] Except for changing the amount of casting, a film A-2 (cyclic olefin resin film) with a thickness of 15 μm was obtained in the same way as film A-1.

[0190] <Preparation of Membrane A-3>

[0191] (Preparation of rubber particle dispersion)

[0192] 11.3 parts by weight of rubber particles R1 and 200 parts by weight of dichloromethane were stirred and mixed in a dissolver for 50 minutes, and then dispersed in a micro-disperser (manufactured by Taihei Kiko Co., Ltd.) at 1500 rpm to obtain a rubber particle dispersion.

[0193] (Preparation of adhesive paste)

[0194] Next, a mortar with the following composition was prepared and used. In addition, a membrane A-3 ((meth)acrylic resin membrane) with a thickness of 40 μm and its recycled material were obtained by the same method as membrane A-1.

[0195] (Meth)acrylic resin: 100 parts by weight

[0196] Dichloromethane: 220 parts by weight

[0197] Ethanol: 35 parts by weight

[0198] Rubber particle dispersion: 200 parts by weight

[0199] 3. Manufacturing and evaluation of granules

[0200] <Experiment 1>

[0201] (Crushing of recycled materials)

[0202] The obtained recycled materials Figure 1 The crushing section A of the crushing and granulation device 10 crushes the material to obtain a particle size of 2mm square (2mm×2mm) and a bulk density of 0.10g / cm³. 3 The membrane (fragments).

[0203] (Melting and granulation using frictional heat)

[0204] exist Figure 1 The compression section B and conveying section C of the crushing and granulation device 10 utilize frictional heat to melt (granulate) the crushed material. Granulation (melting) is performed simultaneously with cooling (water cooling) via the temperature regulating section 60. The melting temperature generated by frictional heat is set at... Figure 1 The K-type thermocouple (thermocouple 24) is arranged near the extrusion port 22 of the crushing and granulation device 10 for measurement.

[0205] Next, the resin extruded in strip form from the crushing and granulation device 10 is cut into a specified length such that the bulk density of the granules is the value shown in Table 1, thereby obtaining granules.

[0206] <Experiments 2-6>

[0207] By changing the cooling temperature (water temperature) generated by the temperature regulating unit 60, the granulation conditions (melting temperature generated by frictional heat) are changed as shown in Table 1. Otherwise, granulation is performed in the same manner as in Experiment 1.

[0208] <Experiments 7 and 8>

[0209] Except for changing the granulation conditions (processing speed) as shown in Table 1, the granulation was performed in the same manner as in Experiment 1.

[0210] <Experiments 9, 10 and 12>

[0211] Except for changing the cutting length so that the aspect ratio of the granules is the value shown in Table 1, the granulation was performed in the same manner as in Experiment 4.

[0212] <Experiment 11>

[0213] Except for changing the cutting length so that the aspect ratio of the granules is the value shown in Table 1, the granulation was performed in the same manner as in Experiment 1.

[0214] <Experiment 13>

[0215] Except for changing the type of recycled material (film thickness) to the type shown in Table 1, the granulation was performed in the same manner as in Experiment 4.

[0216] <Experiment 14>

[0217] Except for changing the type of recycled material (type of resin) and granulation conditions (melt temperature) to the values ​​shown in Table 1, granulation was performed in the same manner as in Experiment 4. The melt temperature was adjusted by changing the cooling temperature generated by the temperature control unit 60.

[0218] <Experiment 15>

[0219] Except for changing the granulation conditions (melt temperature) and the aspect ratio of the granules as shown in Table 1, granulation was performed in the same manner as in Experiment 14. The melt temperature was adjusted by changing the cooling temperature generated by the temperature control unit 60.

[0220] <Evaluation>

[0221] The following methods were used to evaluate the bulk density before and after granulation, the aspect ratio of the granules, the molecular weight of the resin, and the characteristics of the films made using the granules (coloration, presence or absence of foreign matter) used in experiments 1–15.

[0222] (1) Bulk density

[0223] A 100 mL container was filled with crushed material (or granules), and the mass of the filled material (or granules) was measured. This measurement was performed 10 times, and the average bulk density was calculated from the relationship with the volume. Note that no tapping was performed when filling the container.

[0224] (2) Aspect ratio of granules

[0225] The aspect ratio of the granules was determined using the following steps.

[0226] First, for any 100 granules, the lengths of the major and minor axes of the granules are measured using images taken with a camera, and the aspect ratio (length of major axis / length of minor axis) is calculated. The major axis is the line segment connecting the two furthest points in the outline of the granule image in the photographed image, and the minor axis is the longest line segment connecting the intersection of a line perpendicular to the major axis and the outline. The average of the obtained aspect ratios is then used as the "aspect ratio".

[0227] (3) The molecular weight of the resin in the granulated product

[0228] The Mw of the granulated resin was determined in the same manner as that of the resin before granulation.

[0229] Then, the evaluation is based on the following criteria.

[0230] ○: The decrease in Mw (relative to Mw before granulation) is less than 20%.

[0231] ×: The decrease in Mw (relative to Mw before granulation) is more than 20%.

[0232] (4) Membrane properties

[0233] (Production of recycled membrane)

[0234] Using the obtained granules as resin, a regenerated membrane with a thickness of 40 μm was obtained in the same manner as that used in the manufacture of membranes A-1 to A-3.

[0235] (evaluate)

[0236] (4-1)YI

[0237] YI0 of the membrane before regeneration (new membrane) and YI1 of the membrane after regeneration (regenerated membrane) were measured using a Konica Minolta CM-3700d spectrophotometer with D65 (color temperature 6504K) as the light source and a viewing angle of 10°.

[0238] Then, the evaluation is based on the following criteria.

[0239] ◎: The increase in YI (YI1-YI0) is less than 0.03.

[0240] ○: The increase in YI (YI1-YI0) is greater than 0.03 and less than 0.05.

[0241] △: The increase in YI (YI1-YI0) is greater than 0.05 and less than 0.1.

[0242] ×: The increase in YI (YI1-YI0) is 0.1 or more.

[0243] If it is △ or above, then it is within the allowable range.

[0244] (4-2) Foreign matter contamination

[0245] (Preparation of membrane B)

[0246] Except for the absence of an antioxidant, membrane B with a thickness of 40 μm and its recycled material were obtained in the same manner as membranes A-1 to A-3.

[0247] (Crushing and granulation of recycled materials)

[0248] The recycled material was crushed using the same method and conditions as in Experiment 1. Frictional heat was used to melt the crushed material and granulate it. Otherwise, the granules were obtained using the same method and conditions as in Experiment 1.

[0249] (Preparation of Regenerated Membrane B)

[0250] (1) Piping cleaning

[0251] After cleaning the piping through which the granules from membrane A-1 are sent, the granules from membrane B are sent through the same piping. Otherwise, regenerated membrane B-1 is produced in the same manner as regenerated membrane A-1.

[0252] (2) Cleaning without piping

[0253] The piping from which the granules of membrane A-1 were emptied was not cleaned. Instead, the granules from membrane B were emptied through the same piping. Otherwise, regenerated membrane B-2 was produced in the same manner as regenerated membrane A-1.

[0254] (evaluate)

[0255] YI1 of the regenerated membrane B-1 (with piping cleaning) and YI2 of the regenerated membrane B-2 (without piping cleaning) were measured using the same method as described above. Then, the impact of foreign matter contamination was evaluated based on the following criteria.

[0256] ◎: The increase in YI (YI2-YI1) is less than 0.03.

[0257] ○: The increase in YI (YI2-YI1) is greater than 0.03 and less than 0.05.

[0258] △: The increase in YI (YI2-YI1) is greater than 0.05 and less than 0.1.

[0259] ×: The increase in YI (YI2-YI1) is 0.1 or more.

[0260] If it is △ or above, then it is within the allowable range.

[0261] The evaluation results of the granules obtained in experiments 1–15 are shown in Table 1.

[0262] [Table 1]

[0263]

[0264] As shown in Table 1, it can be seen that the melting process using frictional heat was carried out at a low temperature below Tg, and the bulk density of the granules was adjusted to 0.6 g / cm³. 3 The granules from Tests 2-5, 8-10, and 13-14 (relative to 80% of the granules for new products) can reduce the decrease in molecular weight and coloring of the resin caused by thermal degradation, and can also suppress the introduction of foreign matter during product switching.

[0265] In contrast, it is known that melting using frictional heat is carried out at temperatures exceeding Tg, and the bulk density of the granules is adjusted to exceed 0.6 g / cm³. 3 The granules from Tests 1, 11 (Test 11 is equivalent to the conditions in Patent Document 1) and 15 (90% relative to the granules of the new product) not only resulted in a decrease in the molecular weight of the resin and coloring due to thermal degradation, but also resulted in the introduction of foreign matter during product switching.

[0266] It should be noted that the reason for the foreign matter contamination in Experiment 6 is still unclear. It is believed that the reason is that the granulation temperature was too low, and part of the crushed material remained in the state of the crushed material before granulation. The crushed material adhering to the inner wall surface of the piping, etc., was mixed in.

[0267] This application claims priority based on Japanese Patent Application 2020-216666, filed on December 25, 2020. All contents described in and accompanying drawings of that application are incorporated herein by reference.

[0268] Explanation of reference numerals in the attached figures

[0269] 10 Crushing and Granulating Unit

[0270] 20 barrel

[0271] 21 Supply Port

[0272] 22 Extrusion Port

[0273] 23 fixed blade

[0274] 24 thermocouples

[0275] 30 screw

[0276] 31 rotating axis

[0277] 32A Cutting Screw

[0278] 32B Hybrid Screw

[0279] 32C Transmission Screw

[0280] 40 cutting section

[0281] 41 Cutting Blade

[0282] 50 Separation Section

[0283] 51 Cooling blower

[0284] 52 Rotating Circular Plate

[0285] 60 Temperature Control Unit

[0286] 61 Cooling Jacket

[0287] 62. Water supply methods

[0288] 70 recycled materials

[0289] A. Fragmentation section

[0290] B Compression Section

[0291] C Transfer Department

[0292] The widths of W1 and W2 (flow paths)

[0293] Lengths of L1 and L2 (flow paths)

Claims

1. A method for manufacturing granules, comprising: The optical film, with a bulk density of 0.01–0.25 g / cm³, is prepared by crushing recycled material containing one or more resins selected from (meth)acrylic and cycloolefin resins. 3 The process of crushing materials; The crushed material was melted using frictional heat at 50℃~100℃ to obtain a bulk density of 0.26~0.45g / cm³. 3 The process of granulating materials with an aspect ratio of 4 to 50; and The process of melting the granules or dissolving the granules in a solvent to obtain a film.

2. The method for manufacturing granules according to claim 1, wherein, The aspect ratio of the granules is 4 to 20.

3. A method for manufacturing an optical film, comprising: The process of obtaining granules using the manufacturing method of granules according to claim 1 or 2; and The process of melting the granules or dissolving the granules in a solvent to obtain a film.

4. The method for manufacturing the optical film according to claim 3, wherein, The process for obtaining the membrane includes: The process of dissolving the granules in a solvent to obtain a paste; and The process of casting the adhesive onto a support, drying it, and peeling it off to obtain a film.

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