Recycled Polyester Film and Method for Manufacturing the Same

Abstract

To provide a recycled resources-derived polyester film that is obtained by using a raw material derived from the recycled resources recovered from a polyester film substantially by 100%, and has high strength.SOLUTION: A recycled resources-derived polyester film is formed of a material containing a raw material derived from the recycled resources recovered from a polyester film, the raw material derived from the recycled resources contains two or more polyesters with different inherent viscosities (IV), and at least one of the polyesters has an inherent viscosity (IV) of 0.80 dl / g or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a recycled polyester film obtained from recycled resources recovered from a polyester film.

Background Art

[0002] Polyester films are excellent in transparency, dimensional stability, mechanical properties, heat resistance, electrical properties, etc. For example, a release film having a biaxially stretched polyester film as a base material and a release layer mainly composed of a silicone resin or the like is used in many fields.

[0003] On the other hand, in recent years, due to resource reuse and environmental issues, attempts have been made to recover and reuse polyester raw materials generated during use or in the manufacturing process.

[0004] For example, Patent Document 1 discloses a laminated polyester film characterized by using a recycled raw material of a polyester bottle for at least one layer.

[0005] Further, Patent Document 2 discloses a heat-shrinkable polyester-based film containing 25% by weight or more of a PET bottle recycled raw material in the film, having a heat shrinkage rate in the main shrinkage direction of 30% or more when immersed in warm water at 80°C for 10 seconds and pulled up, a heat shrinkage rate in a direction orthogonal to the main shrinkage direction of 10% or less, and performing a tensile test on a direction orthogonal to the main shrinkage direction after storing the film in an atmosphere of 30°C and 85% relative humidity for 28 days, and having a ratio of the number of test pieces broken with an elongation of 5% or less to the total number of test pieces of 25% or less.

[0006] However, in the polyester films disclosed in Patent Documents 1 and 2, the ratio of the recycled raw material is 75% or less.

[0007] Further, Patent Document 3 discloses a biaxially oriented polyethylene terephthalate film using a PET bottle recycled raw material, having a melt specific resistance at a temperature of 285°C of 1.0×10 8A biaxially oriented polyester film is disclosed, characterized in that it is within Ω·cm and the sodium and potassium content in the film is greater than 0 ppm and 150 ppm or less. In this polyester film, the recycled material ratio has been increased to nearly 95%, but still, a polyester film obtained from 100% recycled materials is not disclosed. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 07-323511 [Patent Document 2] Japanese Patent Publication No. 2007-2008 [Patent Document 3] Japanese Patent Publication No. 2014-65282 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] In recycled polyester films, the recycled raw materials recovered from polyester films have undergone thermal history during the manufacturing process, resulting in low intrinsic viscosity (IV). This presents a problem in that a film with high strength cannot be obtained when using 100% recycled raw materials.

[0010] Furthermore, recycled raw materials recovered from PET bottles exhibit significant viscosity variations, making it impossible to obtain a high-strength film using 100% recycled raw materials.

[0011] Furthermore, increasing the proportion of recycled raw materials recovered from polyester products leads to a problem where the color turns yellow, making the product unusable.

[0012] Thus, the manufacture of film products using recycled raw materials still requires the use of virgin raw materials, and there is a strong desire for the development of film products that can be obtained from virtually 100% recycled materials.

[0013] Therefore, one of the objectives of the present invention is to provide a recycled resource-derived polyester film that is obtained using substantially 100% recycled resource-derived raw materials recovered from polyester film and has high strength. Furthermore, one of the objectives of the present invention is to provide a recycled polyester film that is obtained using substantially 100% recycled raw materials recovered from polyester film and has improved color tone. [Means for solving the problem]

[0014] The inventors have found that the above problems can be solved by the means described below, and have completed the present invention.

[0015] In other words, the present invention has the following configuration.

[0016] [1] The recycled resource-derived polyester film of the present invention is formed from a material containing recycled resource-derived raw materials recovered from a polyester film, wherein the recycled resource-derived raw materials contain two or more polyesters with different intrinsic viscosities (IV), and at least one of the polyesters has an intrinsic viscosity (IV) of 0.80 dl / g or more.

[0017] [2] The present invention provides a method for producing a recycled resource-derived polyester film, comprising the following steps (1) to (4). (1) Process for preparing recycled raw materials recovered from polyester film. (2) A process to produce a recycled resource-derived raw material (a) containing polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more by solid-phase polymerization of polyester contained in the recycled resource-derived raw material and making the intrinsic viscosity (IV) of the polyester 0.80 dl / g or more. (3) Step of producing a recycled resource-derived raw material (b) containing polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less, recovered from a polyester film (4) Step of melt-kneading the mixed raw materials of (a) and (b) and then molding them into a film shape

Advantages of the Invention

[0018] The recycled resource-derived polyester film of the present invention is formed from a substantially 100% recycled resource-derived raw material recovered from a polyester film, and has the advantage of having the same strength as a polyester film obtained using a conventional virgin raw material.

[0019] In addition, the recycled resource-derived polyester film of the present invention contains a fluorescent whitening agent, and has the advantage that, although it is formed from a substantially 100% recycled resource-derived raw material recovered from a polyester film, its color tone is improved as compared with conventional recycled products.

Modes for Carrying Out the Invention

[0020] <Recycled Resource-Derived Polyester Film> The recycled resource-derived polyester film of the present invention (hereinafter also referred to as "this film") is formed from a recycled resource-derived raw material recovered from a polyester film, more specifically, a recycled resource-derived raw material recovered from a step of manufacturing a used polyester film product and / or a polyester film (hereinafter, both are collectively or individually referred to as "this recycled resource film").

[0021] (Configuration of this film) This film can adopt either a single-layer or a laminated structure having two or more layers (laminated film), and in particular, it is preferable to have a laminated structure of three or more layers.

[0022] When the film has a laminated structure with two or more layers, a three-layer structure consisting of A / B / C, which is composed of a base layer B and surface layers A and C, and A / B / A, which is composed of a base layer B and surface layer A, is preferred.

[0023] (raw materials derived from recycling) "Recycled resource-derived raw materials" refers to materials such as polyester that have been melted at least once after production has occurred. Furthermore, it is preferable that this resource film is formed from self-recoverable recycled resource-derived raw materials generated during the process of manufacturing polyester film. By using self-recovering recycled raw materials, it is possible to accurately understand the characteristics of recycled raw materials and provide recycled polyester film with stable quality. Furthermore, the term "film" is a concept that includes sheets, and when referring to "film," it includes "sheets," and when referring to "sheets," it includes "film."

[0024] Furthermore, it is preferable that this film be formed from substantially 100% recycled raw materials. "Substantially" means intentionally not using virgin polyester raw materials, but rather allowing for unavoidable inclusion during the manufacturing process, etc. More specifically, in the present invention, "substantially 100% recycled raw materials" means that 99% or more, preferably 99.5% or more, are recycled raw materials.

[0025] Therefore, this film does not need to be formed from raw materials derived from 100% recycled resources, but rather from a material containing 99% or more, preferably 99.5% or more, raw materials derived from recycled resources.

[0026] As mentioned above, the recycled resource-derived raw materials are recovered from this resource film, and the recovered polyester film is reused by crushing, re-pelletizing, etc.

[0027] Because the aforementioned recycled resource-derived raw materials have undergone thermal history during the manufacturing process, etc., when reused, they have a low intrinsic viscosity (IV), making it difficult to ensure sufficient strength. Therefore, it is preferable that the recycled resource-derived raw material contains two or more polyesters with different intrinsic viscosities (IV), and at least one of the polyesters has an intrinsic viscosity (IV) of 0.80 dl / g or more. From this viewpoint, it is preferable that at least one of the polyesters has an intrinsic viscosity (IV) of 0.82 dl / g or more, and most preferably 0.85 dl / g or more. Intrinsic viscosity (IV) refers to the viscosity measured at 30°C using an Uperohde viscometer with a solvent ratio of phenol:tetrachloroethane = 1:1.

[0028] In order to obtain polyester with an intrinsic viscosity (IV) of 0.80 dl / g or higher from raw materials recovered and reused from this resource film, it is preferable to solid-state polymerize the reused polyester raw material. As for the solid-phase polymerization method, known methods can be used, and either a continuous or batch method may be employed.

[0029] Furthermore, the recycled raw material preferably contains two or more polyesters with different intrinsic viscosities (IV), and at least one of the polyesters preferably has an intrinsic viscosity (IV) of 0.60 dl / g or less. By using recycled raw materials containing polyester with an intrinsic viscosity (IV) of 0.60 dl / g or less, it is possible to maintain the productivity and cost of the film, among other benefits.

[0030] By using at least two types of polyesters—one with an intrinsic viscosity (IV) of 0.80 dl / g or higher and the other with an intrinsic viscosity (IV) of 0.60 dl / g or lower—from the raw materials recovered and reused from this resource film, it is possible to suppress film breakage during production due to a decrease in polyester film strength, which is a concern when using recovered and reused raw materials, and to achieve strength equivalent to that of polyester films obtained using conventional virgin raw materials.

[0031] Based on the above, it is preferable that the film contains 50% by mass or less of polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more, more preferably 30% by mass or less, and most preferably 25% by mass or less.

[0032] Furthermore, it is preferable that the film contains 50% by mass or more of polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less, more preferably 60% by mass or more, and most preferably 70% by mass or more.

[0033] (Other ingredient 1; fluorescent whitening agent) When a film is formed from virtually 100% recycled raw materials, the polymer degrades, causing the color to turn yellow, making it difficult to use as a finished product. Therefore, it is preferable that this film contains a fluorescent whitening agent as a component other than the recycled resource-derived raw materials mentioned above. By adding a fluorescent whitening agent, the yellowing of the film can be improved.

[0034] Furthermore, since the fluorescent whitening agent is excited when exposed to ultraviolet light and emits blue visible light, it can also serve as a marker indicating that this film is a recycled product.

[0035] Examples of the aforementioned fluorescent whitening agents include those with structures such as stilbene, coumarin, oxazole, imidazole, and naphthalimide. Specifically, 4,4'-bis(benzoxazole-2-yl)stilbene, 2,5-bis(5-t-butyl-2-benzoxazolyl)thiophene, 1,2-di(5-methyl-2-benziazolyl)ethylene, 1,2-bis(5-methyl-2-benzoxazole)ethylene, 2,2'-(4,4'-diphenolvinyl)dibenzoxazole, 1,1'-biphenyl-4,4'-bis-benzoxazole, 2,5-bis(benzoxazole-2-)thiophene, 4-4'-bis(5- Examples include methyl-2-benzoxazole)ethylene, 1,4-bis(benzoxazollyl-2-yl)ethylene, 1,4-bis(benzoxazollyl-2-yl)naphthalene, 4-4'-bis[(4-amino-6-morpholino-1,3,5-triazine-2-yl)amino]stilbenn-disulfonate, and 2,2'-(1,4-naphthalenediyl)bis-benzoxazole. One of these can be used alone, or two or more can be used in combination.

[0036] The content of the fluorescent whitening agent in this film is preferably 0.01 to 1.0% by mass, and more preferably 0.02 to 0.08% by mass. If the fluorescent whitening agent content exceeds 1.0% by weight, not only will the color improvement effect saturate, but problems such as excessive bleeding of the fluorescent whitening agent out onto the film surface will occur, negatively impacting its use.

[0037] (Other ingredients 2: particles) From the viewpoint of providing slipperiness and scratch resistance, it is preferable that this film contains particles as a component other than the recycled resource-derived raw material.

[0038] Examples of the aforementioned particles include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide, as well as crosslinked polymers such as crosslinked silicone resin particles, crosslinked acrylic resin particles, crosslinked styrene-acrylic resin particles, and crosslinked polyester particles, and organic particles such as calcium oxalate and ion exchange resins.

[0039] The content of the particles in this film is preferably 0.001 to 1.0% by mass, and more preferably 0.01 to 0.08% by mass.

[0040] (This is a recyclable film.) This resource film is made by molding polyester or a polyester-containing composition into a film, and its main component is polyester. Furthermore, "main constituent component" refers to a component that accounts for 50% or more by mass of the components that make up the film, and preferably 70% or more by mass.

[0041] (a) Polyester The aforementioned polyester refers to a polymer compound having ester bonds continuously in its main chain, and may be either a homopolyester or a copolymerized polyester. Specifically, examples include polyesters obtained by polycondensation reaction of a dicarboxylic acid component and a diol component.

[0042] In this invention, it is preferable to use a polyester that contains more than 50% aromatic dicarboxylic acid or aliphatic dicarboxylic acid when the dicarboxylic acid component is considered to be 100 mol%.

[0043] Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, and 4,4'-diphenylsulfondicarboxylic acid, as well as aliphatic dicarboxylic acids such as adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedionic acid, cyclohexanedicarboxylic acid, and their ester derivatives.

[0044] Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-hexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis(4-hydroxyethoxyphenyl)propane, isosorbate, and spiroglycol.

[0045] When the above polyester consists of a homopolyester, it is preferable to obtain one obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. Examples of the aforementioned aromatic dicarboxylic acids include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of aliphatic glycols include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical examples of polyesters include polyethylene terephthalate (PET) and polyethylene-2,6-naphthalenedicarboxylate (PEN). Among these, polyethylene terephthalate (PET) is particularly preferred.

[0046] On the other hand, if the polyester is a copolymerized polyester, it is preferable that it is a copolymer containing 30 mol% or less of a third component. Examples of dicarboxylic acid components in copolymerized polyesters include one or more types such as isophthalic acid, terephthalic acid phthalate, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acids. Examples of glycol components in copolymerized polyesters include one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, and neopentyl glycol.

[0047] Furthermore, the polyester is preferably composed of 80 mol% or more, more preferably 90 mol% or more, of polyethylene terephthalate units, such as polyethylene terephthalate, or polyethylene-2,6-naphthalate units, such as polyethylene-2,6-naphthalate.

[0048] (b) Polyester polycondensation catalyst Examples of polycondensation catalysts used when polycondensing the above-mentioned polyester include antimony compounds, germanium compounds, aluminum compounds, and titanium compounds, but it is particularly preferable to use polyester obtained using an antimony compound.

[0049] (c) Particles This resource film may be formed from a polyester composition containing particles. The particles described above can be used as appropriate.

[0050] (d) Fluorescent whitening agent This resource film may be formed from a polyester composition containing a fluorescent whitening agent. Furthermore, the above-mentioned fluorescent whitening agents can be used as appropriate.

[0051] (e) Additives This resource film may be formed from a polyester composition containing various additives such as antioxidants, lightfastness agents, gelation inhibitors, organic wetting agents, antistatic agents, ultraviolet absorbers, and surfactants.

[0052] (Format of this film) This film may be an unoriented film, a uniaxially oriented film, or a biaxially oriented film. In particular, from the viewpoint of film strength, a biaxially oriented film is preferred.

[0053] (Release layer) This film can also be used in a form having a release layer on at least one side, that is, in the form of a release film. Furthermore, it is particularly preferable that the release layer also be made from recycled materials.

[0054] (Particularly preferred embodiment 1) (1) The film has a multilayer structure comprising at least three layers A / B / A, wherein layer A is the outermost layer and is formed from recycled raw materials recovered from polyester film, and the recycled raw materials for forming layer A (A-1) contain polyester with an intrinsic viscosity (IV) of 0.60 dl / g or less, and layer B is formed from recycled raw materials recovered from polyester film, and the recycled raw materials for forming layer B (B-1) contain polyester with an intrinsic viscosity (IV) of 0.80 dl / g or more. (2) In (1) above, the recycled resource-derived raw material (B-1) for forming the B layer is in a form in which the B layer contains 30% by mass or less of polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more. (3) In (1) or (2) above, the recycled resource-derived raw material (B-1) for forming the B layer further comprises polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less. (4) In (3) above, the recycled resource-derived raw material (B-1) for forming the B layer contains 50% by mass or more of polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less in the B layer. (5) In any of (1) to (4) above, the B layer further contains a fluorescent whitening agent. (6) In any of (1) to (5) above, the A layer further contains particles. (7) In any of the above (1) to (6), the film is a biaxially oriented film. (8) In any of (1) to (7) above, the recycled resource-derived raw material (B-1) for forming the B layer includes a recycled resource-derived raw material (b-1) recovered from a polyester film having a coating layer. (9) In any of (1) to (8) above, the recycled resource-derived raw material (A-1) for forming the A layer is in a form that substantially does not contain the recycled resource-derived raw material (b-1). (10) A form of the main film having a release layer on at least one side of any of the above (1) to (9).

[0055] According to the particularly preferred embodiment 1 described above, the recycled resource-derived raw material (B-1) for forming the B layer contains polyester with an intrinsic viscosity (IV) of 0.80 dl / g or more, thereby providing the film with excellent strength. Furthermore, the recycled resource-derived raw material (B-1) used for forming the B layer contains polyester with an intrinsic viscosity (IV) of 0.60 dl / g or less, which offers advantages such as maintaining the mechanical strength of the film while also maintaining its productivity and cost.

[0056] Furthermore, from the viewpoint of suppressing film breakage during production, the recycled resource-derived raw material (B-1) for forming the B layer preferably contains 30% by mass or less, and more preferably 25% by mass or less, of polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more.

[0057] Furthermore, from the same viewpoint as above, the recycled resource-derived raw material (B-1) for forming the B layer preferably contains 50% by mass or more of polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less, and more preferably 70% by mass or more.

[0058] Furthermore, the inclusion of a fluorescent whitening agent in layer B has the advantage of preventing the fluorescent whitening agent from bleeding out to the outermost layer.

[0059] In addition, by including particles in layer A, the film can be given slipperiness and scratch resistance.

[0060] Furthermore, from the viewpoint of securing recycled raw materials, it is preferable that the recycled raw material (B-1) for forming layer B includes recycled raw material (b-1) recovered from a polyester film having a coating layer, and from the same viewpoint, it is preferable that the recycled raw material (A-1) for forming layer A substantially does not contain the recycled raw material (b-1). Furthermore, "substantially" means intentionally excluding the recycled resource-derived raw material (b-1), and specifically, the content of the recycled resource-derived raw material (b-1) in layer A is less than 5% by mass, and more preferably less than 1% by mass.

[0061] The aforementioned coating layer refers to a layer obtained by preparing a coating solution containing a solvent, binder resin, and crosslinking agent, which has various functions such as easy adhesion, applying the coating solution to a film, and then drying it.

[0062] Examples of binder resins used in the coating solution include acrylic resins, urethane resins, polyester resins, olefin resins, fluororesins, vinyl resins, chlorine resins, styrene resins, epoxy resins, silicone resins, and mixtures of these resins.

[0063] <Method of manufacturing this film> The following describes a method for manufacturing a biaxially oriented film as an example of the manufacturing method for this film. First, the above-mentioned recycled resource-derived raw materials, such as recycled polyester chips, are supplied to a melt extruder by known methods, heated above the melting point of each polymer, the molten polymer is extruded from the die, and cooled and solidified on a rotating cooling drum to a temperature below the glass transition point of the polymer, thereby obtaining a substantially amorphous, unoriented sheet.

[0064] Next, the unoriented sheet is stretched in one direction using a roll or tenter type stretcher. In this case, the stretching temperature is usually 25 to 120°C, preferably 35 to 100°C, and the stretching ratio is usually 2.5 to 7 times, preferably 2.8 to 6 times.

[0065] Next, it extends in a direction perpendicular to the extension direction of the first stage. In this case, the stretching temperature is usually 50 to 140°C, and the stretching ratio is usually 3.0 to 7 times, preferably 4.5 times or more, and more preferably 4.5 to 5.0 times.

[0066] Then, by continuing the heat-fixation treatment at a temperature of 180-220°C under tension or under relaxation of 30% or less, the polyester film as a biaxially oriented film can be obtained. Furthermore, in the aforementioned extension, a method can be adopted in which the extension is carried out in two or more stages in one direction.

[0067] (Particularly preferred embodiment 2) (1) A method for manufacturing this film having the following steps A to D. A. Process for preparing recycled raw materials recovered from polyester film. B. A process to produce a recycled resource-derived raw material (a) containing polyester with an intrinsic viscosity (IV) of 0.80 dl / g or more by solid-phase polymerization of polyester contained in the recycled resource-derived raw material and making the intrinsic viscosity (IV) of the polyester 0.80 dl / g or more. C. Process for producing recycled resource-derived raw material (b) containing polyester recovered from polyester film with an intrinsic viscosity (IV) of 0.60 dl / g or less. D. A process of melting and kneading the mixed raw materials of (a) and (b) above, and then forming them into a film. (2) In the above (1), step D is a molding step in which the mixed raw materials are melted and kneaded, then melted and extruded, and cooled to form a film. (3) The configuration of (1) or (2) above, wherein the following step E is performed after step D. E. Stretching process that extends in the longitudinal and / or widthwise directions.

[0068] As described above, according to the particularly preferred manufacturing method of this film, by using recycled resource-derived raw material (a) with an intrinsic viscosity (IV) adjusted to 0.80 dl / g or higher, and recycled resource-derived raw material (b) with an intrinsic viscosity (IV) of 0.60 dl / g or lower, it is possible to obtain a film that is substantially made from 100% recycled resource raw materials while possessing excellent strength.

[0069] Furthermore, by incorporating a fluorescent whitening agent into the film, the color tone of the film can be improved, and it also becomes possible to identify that the film was obtained from recycled materials.

[0070] In step A described above, for example, the recovered polyester film is crushed using a pulverizer to produce polyester flakes, and these polyester flakes are extruded using an extruder and then rapidly cooled and solidified to obtain recycled polyester pellets, i.e., raw materials derived from recycled resources.

[0071] In step B described above, the recycled resource-derived raw material is solid-phase polymerized at 220°C under vacuum to increase its intrinsic viscosity (IV) to 0.80 dl / g or higher, thereby obtaining a recycled resource-derived raw material (a) containing polyester with an intrinsic viscosity (IV) of 0.80 dl / g or higher.

[0072] In step C described above, for example, a recovered polyester film having an intrinsic viscosity (IV) of 0.60 dl / g or less is crushed in a pulverizer to produce polyester flakes, and these polyester flakes are extruded in an extruder and then rapidly cooled and solidified to obtain recycled polyester pellets, i.e., recycled resource-derived raw material (b). Furthermore, using recycled raw materials (b) offers advantages such as maintaining the mechanical strength of the film while also maintaining its productivity and cost.

[0073] In step D described above, the material can be formed into a film by, for example, a co-extrusion method which includes a step of feeding the raw materials for each layer into separate extruders and melt-extruding them into a sheet from a T-die, or by a method in which the materials are melted separately in multiple extruders and the extruded films are laminated together from the die outlet. In particular, a method of forming the material into a film by co-extrusion is preferred.

[0074] In step E described above, a stretched film can be obtained by stretching the unstretched film produced in step D using a roll or tenter type stretcher in one direction and / or perpendicular thereto.

[0075] More specifically, in the stretching process described above, the unstretched sheet is stretched in one direction in the longitudinal direction (longitudinal direction (MD)) using a roll or tenter type stretching machine. The stretching temperature in this case is usually 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is usually 2.0 to 7.0 times, preferably 2.5 to 5.0 times.

[0076] Next, the material is stretched in a direction perpendicular to the stretching direction of the first stage (lateral direction (TD)). In this case, the stretching temperature is usually 70 to 170°C, and the stretching ratio is usually 3.0 to 7.0 times, preferably 3.5 to 6.0 times. Then, the film is heat-treated at a temperature of 180-270°C under tension or under relaxation of 30% or less to obtain a biaxially oriented film.

[0077] In the above extension process, a method can also be employed in which the extension is carried out in two or more stages in one direction. In that case, it is preferable to carry out the process so that the stretching ratios in both directions ultimately fall within the above-mentioned ranges.

[0078] (Application) This film can be used for optical filters such as AR film, NIR film, and EMI film, as well as optical films such as diffusion film and prism film, and general industrial materials such as card materials, label materials, electronic materials, packaging materials, graphic materials (photographic materials), printing plates, magnetic recording media, various process papers, and OHP films. Since it is composed of virtually 100% recycled raw materials, it has a high degree of environmental contribution and can help reduce environmental impact.

[0079] (Explanation of terms, etc.) In this invention, when "X~Y" (where X and Y are any numbers) is written, unless otherwise specified, it means "X or greater and Y or less," and also includes the meaning of "preferably greater than X" or "preferably less than Y."

[0080] Furthermore, when "X or greater" (where X is any number) is written, unless otherwise specified, it includes the meaning of "preferably greater than X," and when "Y or less" (where Y is any number) is written, unless otherwise specified, it also includes the meaning of "preferably less than Y." [Examples]

[0081] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0082] <Manufacturing of raw materials derived from recycled resources> a) Production of recycled polyester pellets (1) A self-recovering polyester film without a coating layer was crushed and processed to obtain recycled polyester pellets (a) with an intrinsic viscosity (IV) of 0.57 dl / g. (2) A self-recovering polyester film without a coating layer was crushed and processed to obtain recycled polyester pellets (b1) with an intrinsic viscosity (IV) of 0.54 dl / g. (3) A self-recovering polyester film having a coating layer is crushed and processed to obtain an intrinsic viscosity (I A recycled polyester pellet (c) with a concentration of 0.58 dl / g (V) was obtained. (4) Recycled polyester pellets (b1) with an intrinsic viscosity (IV) of 0.54 dl / g were subjected to solid-phase polymerization under vacuum at 220°C to obtain recycled polyester pellets (b2) with an intrinsic viscosity (IV) of 0.85 dl / g.

[0083] b) Manufacturing of recycled polyester As raw materials for the front and back layers, recycled polyester pellets (a), recycled polyester pellets (b1), and virgin raw material silica particles (x1) with an average particle size of 2.7 μm are mixed so that their content in the resulting film is (a) 16.48% by mass, (b1) 4.08% by mass, and (x1) 0.04% by mass, respectively. As raw materials for the intermediate layer, recycled polyester pellets (c), recycled polyester pellets (b2), and recycled polyester pellets (b1) are mixed. (x2) The virgin raw material was mixed with the fluorescent whitening agent (4,4'-Bis(2-benzoxazolyl)stilbene) so that the content in the resulting film was (c) 52.93% by mass, (b2) 23.41% by mass, (b1) 3.01% by mass, and (x2) 0.05% by mass, respectively. These mixtures were supplied to two twin-screw extruders with vents, melted and kneaded at 280°C, and extruded using a multi-layer T-die to achieve a composition ratio of A / B / A = 3 / 32 / 3. The mixture was rapidly cooled and solidified on a casting drum set to a surface temperature of 28°C to obtain an unstretched film consisting of two types and three layers. Next, the film was stretched 3.40 times in the longitudinal direction (vertical direction) at 87°C, then guided into a tenter, stretched 4.04 times in the width direction (transverse direction) at 120°C, and then heat-treated at 233°C to relax by 4.76% in the transverse direction, resulting in a biaxially oriented film with a thickness of 38 μm. Next, the obtained biaxially oriented film was slit at a position 255 mm from both ends. Any excess material generated during the slitting process was collected as slitting edges, which were then crushed and processed to obtain recovered polyester (d). Furthermore, the intrinsic viscosity (IV) of the recovered polyester (d) is calculated to be 0.60.

[0084] [Example 1] As raw materials for the front and back layers, recycled polyester pellets (a), recycled polyester pellets (b1), and virgin raw material silica particles (x1) with an average particle size of 2.7 μm are mixed so that their content in the resulting film is (a) 13.47% by mass, (b1) 3.33% by mass, and (x1) 0.03% by mass, respectively. As raw materials for the intermediate layer, recycled polyester pellets (c), recycled polyester pellets (b2), recycled polyester pellets (b1), and (x2) virgin raw material fireflies The photowhitening agent (4,4'-Bis(2-benzoxazolyl)stilbene) and the recovered polyester (d) were mixed so that their content in the resulting film was (c) 43.24% by mass, (b2) 19.13% by mass, (b1) 2.46% by mass, (x2) 0.04% by mass, and (d) 18.30% by mass, respectively. These mixtures were supplied to two twin-screw extruders with vents, melted and kneaded at 280°C, and then extruded using a multi-layer T-die in a composition ratio of A / B / A = 3 / 32 / 3. The mixtures were rapidly cooled and solidified on a casting drum set to a surface temperature of 28°C to obtain an unstretched film consisting of two types and three layers. Next, the film was stretched 3.40 times in the longitudinal direction (vertical direction) at 87°C, then guided to a tenter, stretched 4.04 times in the width direction (transverse direction) at 120°C, and then heat-treated at 233°C to relax by 4.76% in the transverse direction, yielding a recycled resource-derived polyester film 1 with a thickness of 38 μm. The recycled resource-derived polyester film 1 is formed from a material containing 99.93% by mass of recycled resource-derived raw materials. Furthermore, the color tone of the recycled polyester film 1 was improved. Furthermore, in layer A, the polyester content with an intrinsic viscosity (IV) of 0.60 dl / g or less is 99.80% by mass, and in layer B, the polyester content with an intrinsic viscosity (IV) of 0.60 dl / g or less is 76.96% by mass, and the polyester content with an intrinsic viscosity (IV) of 0.80 dl / g or more is 23.00% by mass.

[0085] [Example 2] A recycled resource-derived polyester film 2 was obtained in the same manner as in Example 1, except that it was a 50 μm thick film with a composition ratio of A / B / A = 4 / 42 / 4. The recycled resource-derived polyester film 2 is formed from a material containing 99.93% by mass of recycled resource-derived raw materials. Furthermore, the recycled polyester film 2 showed improved color tone. Furthermore, in layer A, the polyester content with an intrinsic viscosity (IV) of 0.60 dl / g or less is 99.80% by mass, and in layer B, the polyester content with an intrinsic viscosity (IV) of 0.60 dl / g or less is 76.96% by mass, and the polyester content with an intrinsic viscosity (IV) of 0.80 dl / g or more is 23.00% by mass.

[0086] The various physical properties of recycled resource-derived polyester films 1 and 2, prepared in Examples 1 and 2, are shown in Table 1.

[0087] [Table 1]

[0088] The tensile strength (MPa) was measured as follows.

[0089] (Tensile strength) Polyester films 1 and 2 derived from recycled resources were cut into rectangles with a width of 15 mm, and stretched in a tensile testing machine with a section length of 50 mm at a tensile speed of 200 mm / min to determine the tensile strength, i.e., the stress at fracture.

[0090] Furthermore, the recycling rate refers to the percentage of recycled raw materials used in the total materials constituting the recycled polyester film, and the unit is mass%.

Claims

1. A method for producing a recycled polyester film formed from a material containing two or more recycled raw materials having different intrinsic viscosities (IV), wherein at least one of the recycled raw materials has an intrinsic viscosity (IV) of 0.80 dl / g or more, and the method for producing a recycled polyester film comprising the following steps. The process of preparing raw materials derived from recycled resources recovered from polyester film. A process for producing a recycled resource-derived raw material containing polyester with an intrinsic viscosity (IV) of 0.80 dl / g or more, by making the intrinsic viscosity (IV) of the polyester contained in the recycled resource-derived raw material 0.80 dl / g or more. A process for producing a recycled resource-derived raw material containing polyester with an intrinsic viscosity (IV) of 0.60 dl / g or less, recovered from polyester film. A step of mixing a recycled resource-derived raw material containing polyester with an intrinsic viscosity (IV) of 0.80 dl / g or more obtained in the above step with a recycled resource-derived raw material containing polyester with an intrinsic viscosity (IV) of 0.60 dl / g or less obtained in the above step, melt-kneading the mixture, and then forming it into a film.

2. The method for producing a polyester film derived from recycled resources according to claim 1, wherein the recycled resource-derived raw material consists of self-recovered raw material generated in the polyester film manufacturing process.

3. The method for producing a recycled resource-derived polyester film according to claim 1 or 2, wherein the material contains a fluorescent whitening agent.

4. A method for producing a recycled resource-derived polyester film according to any one of claims 1 to 3, wherein the polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more is solid-phase polymerized.

5. A method for producing a recycled resource-derived polyester film according to any one of claims 1 to 4, having a laminated structure of two or more layers.

6. A method for producing a recycled resource-derived polyester film according to claim 5, wherein a fluorescent whitening agent is contained in layers other than the outermost layer.

7. A method for producing a recycled resource-derived polyester film according to claim 5 or 6, wherein one of the two or more layers is layer A formed from a recycled resource-derived raw material (A-1) containing polyester with an intrinsic viscosity (IV) of 0.60 dl / g or less, and one of the two or more layers is layer B formed from a recycled resource-derived raw material (B-1) containing polyester with an intrinsic viscosity (IV) of 0.80 dl / g or more.

8. The method for producing a recycled resource-derived polyester film according to claim 7, wherein the recycled resource-derived raw material (B-1) contains 30% by mass or less of polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more.

9. The method for producing a recycled resource-derived polyester film according to claim 7 or 8, wherein the recycled resource-derived raw material (B-1) further includes a polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less.

10. The method for producing a recycled resource-derived polyester film according to any one of claims 7 to 9, wherein the recycled resource-derived raw material (B-1) further contains 50% by mass or more of polyester having an intrinsic viscosity (IV) of 0.60 dl / g or less.

11. A method for producing a recycled resource-derived polyester film according to any one of claims 7 to 10, wherein the film has a multilayer structure comprising at least three layers of A / B / A.

12. A method for producing a recycled resource-derived polyester film according to any one of claims 1 to 11, wherein the material contains 99% by mass or more of raw materials derived from recycled resources.

13. A method for producing a recycled polyester film according to any one of claims 1 to 12, wherein the two or more polyesters are all homopolyesters.

14. A method for producing a recycled polyester film, comprising the step of providing a release layer on at least one side of the recycled polyester film according to any one of claims 1 to 13.

15. The method for producing a recycled resource-derived polyester film according to any one of claims 1 to 14, wherein the step of forming the film is a molding step of melting and kneading the mixed raw materials, then melting and extruding them, and cooling them to form a film.

16. A method for producing a recycled resource-derived polyester film according to any one of claims 1 to 15, comprising a stretching step of stretching in the longitudinal direction and / or width direction after the step of forming it into a film.

17. A recycled resource-derived polyester film having a laminated structure of two or more layers formed from a material containing recycled resource-derived raw materials recovered from polyester film, A recycled polyester film comprising two or more layers, wherein one of the layers is layer A, formed from recycled raw material (A-1) containing polyester with an intrinsic viscosity (IV) of 0.60 dl / g or less, and one of the two or more layers is layer B, formed from recycled raw material (B-1) containing polyester with an intrinsic viscosity (IV) of 0.60 dl / g or less and polyester with an intrinsic viscosity (IV) of 0.80 dl / g or more, and the layer B contains 50% by mass or more of polyester with an intrinsic viscosity (IV) of 0.60 dl / g or less.

18. The recycled resource-derived polyester film according to claim 17, wherein the recycled resource-derived raw material (B-1) contains 30% by mass or less of polyester having an intrinsic viscosity (IV) of 0.80 dl / g or more.

19. A recycled resource-derived polyester film according to claim 17 or 18, having a multilayer structure comprising at least three layers of A / B / A.

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