Recycled polyester raw material and recycled polyester film

Abstract

To provide a recycled polyester raw material obtained by fully removing the functional layers of laminated polyester film.SOLUTION: Recycled polyester raw material has a relaxation time obtained by pulse NMR method, of 0.0104 ms or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a recycled polyester raw material and a recycled polyester film.

Background Art

[0002] Conventionally, waste plastics have been treated by landfilling, ocean dumping, incineration, etc. However, it is becoming difficult to secure landfill sites, and ocean dumping has become a problem in terms of the environment because plastics do not decompose. In addition, although it can be used as heat by incineration, there is a problem that it leads to global warming due to the emission of carbon dioxide gas.

[0003] Therefore, due to the recent increase in environmental problems, recycling such as reuse and recycling of waste plastics is required, and research and development for this purpose are being actively conducted. In addition, since many plastics are produced from fossil fuels, the construction of a recycling method is also required from the viewpoint of effective use of resources.

[0004] In particular, in Japan, efforts to recycle PET bottles have been underway since the 1990s, and currently, PET bottles have a high recycling rate.

[0005] PET bottle recycled raw materials are reused for bottles (bottle to bottle) and films (bottle to film). As a technology related to the use of such PET bottle recycled raw materials, for example, Patent Document 1 discloses a biaxially oriented polyethylene terephthalate film obtained by using a PET bottle recycled raw material.

[0006] A polyester film, which is a kind of plastic film, is useful as a base film and is often used as a laminated film in which various functional layers are laminated on one or both sides. As functional layers, there are various functional layers such as a hard coat layer, an adhesive layer, a decorative layer, a light-shielding layer, a polarizing layer, an ultraviolet shielding layer, etc. A laminated film in which a material corresponding to the functional layer is laminated on a polyester film is used.

[0007] Recycling of such polyester films is also carried out. For example, Patent Document 2 discloses a method for cleaning a release film having a base film and a release layer formed on the base film, the method including a removing step of contacting the release film having foreign matter in the release layer with a solution containing an alkaline substance and alcohol and then contacting with an organic solvent to remove the release layer from the base film.

[0008] However, recycling of such laminated films has not been widespread so far. Such laminated films are hardly reused after use and are discarded, incinerated, etc.

[0009] On the other hand, although it is conceivable to directly remelt and recycle the laminated film with the functional layer, since the material constituting the functional layer is mixed into the molten polymer, it generates a strange odor during extrusion, or the melt viscosity of the polymer decreases, which causes breakage during film formation. Moreover, even if film formation can be achieved, deterioration in quality due to coloring of the obtained film is inevitable.

[0010] Therefore, for example, Patent Document 3 discloses a method for recycling waste films, more specifically, a method of pulverizing waste films into flakes, pelletizing them, and then making them into films, and a technique of adding a colorant to hide yellowing of the films. Also, Patent Document 4 discloses a polyester film with less yellowing coloring even when using a film provided with a coating layer as a recycled raw material.

Prior Art Documents

Patent Documents

[0011] Patent Document 1 Japanese Patent Application Laid-Open No. 2014-065282 Patent Document 2 Japanese Patent Application Laid-Open No. 2009-291690 Patent Document 3 Japanese Patent Application Publication No. 2013-517157 Patent Document 4 Japanese Patent Application Laid-Open No. 2009-220311 Summary of the Invention Problems to be Solved by the Invention

[0012] By the way, polyester films are used in various fields such as industrial materials, optical materials, electronic component materials, and battery packaging materials, and in recent years, the quality requirements have been extremely high. Therefore, in the recycling methods that do not remove the functional layer as in Patent Documents 3 and 4 above, problems of contamination of the recycled raw materials occur. Also, in the recycling method disclosed in Patent Document 2 above, there is a risk of damage to the base film, and a slight amount of the release layer component remains, leaving a problem of contamination of the recycled raw materials.

[0013] Therefore, the present invention has been made in view of the above circumstances, and the problem to be solved is to provide a recycled polyester raw material obtained by sufficiently removing the functional layer of a laminated polyester film. Means for Solving the Problems

[0014] As a result of intensive studies, the present inventors have found that, for example, the degree of damage to the polyester film by peeling and washing can be grasped by the relaxation time obtained by the pulse NMR method of the recycled polyester raw material after removing the functional layer, and by setting the relaxation time to a specific value or more, a recycled polyester raw material with the functional layer sufficiently removed can be obtained. The present invention has been completed based on such findings and has the following aspects.

[0015] [1] A recycled polyester raw material obtained by the pulsed NMR method, having a relaxation time of 0.0104 ms or more. [2] The recycled polyester raw material according to [1] above, wherein the relaxation time is 0.0150 ms or less. [3] The recycled polyester raw material according to [1] or [2] above, having an intrinsic viscosity (IV) of 0.45 to 0.65 dl / g. [4] The recycled polyester raw material according to any one of [1] to [3] above, wherein the total amount of titanium content and antimony content is 250 to 450 ppm. [5] The recycled polyester raw material according to [4] above, wherein the antimony content is 450 ppm or less. [6] The recycled polyester raw material according to any one of [1] to [5] above, which is polyethylene terephthalate. [7] A recycled polyester film comprising a polyester layer containing the recycled polyester raw material according to any one of [1] to [6] above. [8] The recycled polyester film according to [7] above, having a laminated structure of at least two layers or more. [9] The recycled polyester film according to [7] or [8] above, wherein the thickness of the polyester layer containing the recycled polyester raw material is 50% or more of the total thickness of the recycled polyester film. [Effect of the Invention]

[0016] According to the present invention, it is possible to provide a recycled polyester raw material obtained by sufficiently removing the functional layer of a laminated polyester film. Since the functional layer of the recycled polyester raw material of the present invention is sufficiently removed, when formed into a film, a recycled polyester film with few foreign substances can be obtained. Therefore, the recycled polyester raw material and the recycled polyester film of the present invention can not only improve the recyclability of the polyester film, but also suppress the formation of new foreign substances, and are applicable to display applications and the like where foreign substance management is extremely strict. [Brief Description of the Drawings]

[0017]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0018] Hereinafter, an example of an embodiment of the present invention will be described in detail. However, the present invention is not limited to the embodiment examples described below, and can be arbitrarily modified and implemented without departing from the gist of the present invention.

[0019] [Recycled Polyester Raw Material] The recycled polyester raw material of the present invention (hereinafter, also referred to as "this raw material") is characterized in that the relaxation time obtained by the pulse NMR method is 0.0104 ms or more. Note that this raw material may be in the form of a film, or may be in the form of flakes obtained by pulverizing a polyester film and / or chips formed by chipping the flakes.

[0020] NMR (nuclear magnetic resonance absorption method) is generally well-known as a method for analyzing the structure of molecules from chemical shifts, while the pulse NMR method is a method for evaluating molecular mobility from relaxation time. When a magnetic field is applied to a sample as a pulse, the nuclear spins of the protons in the sample become an excited state with aligned directions. The process until this returns to the original random ground state is called relaxation, and the time required for this process is called the relaxation time. Thus, the relaxation time is determined by the magnitude of the interaction between protons in the sample placed in the magnetic field. When the molecular mobility is high, the influence of neighboring protons becomes small, so the interaction becomes small and relaxation takes time. That is, the relaxation time of a sample with high molecular mobility becomes long.

[0021] In the present invention, for example, when the functional layer is removed from a laminated polyester film having a functional layer on the surface of a polyester film using a cleaning agent, it is presumed that molecular chain scission occurs on the surface of the polyester film as the base material by peeling cleaning, and the molecular chains become smaller and soften, resulting in events such as increased mobility and longer relaxation time. That is, it is considered that the degree of damage to the polyester film due to the peeling cleaning history can be grasped from the relaxation time obtained by the pulse NMR method.

[0022] In the conventional method, as described above, fearing damage to the base film (polyester film), sufficient cleaning could not be performed, and the peeling layer (functional layer) components remained, inevitably contaminating the recycled raw material. In contrast, in the present invention, since the degree of damage to the polyester film can be grasped by the relaxation time, a recycled polyester raw material with the functional layer sufficiently removed can be obtained. Therefore, the present invention serves as an index for obtaining a recycled polyester raw material with the functional layer sufficiently removed.

[0023] From such a perspective, it is essential that the relaxation time of this raw material obtained by the pulse NMR method is 0.0104 ms or more. When the relaxation time is 0.0104 ms or more, the functional layer can be sufficiently removed, that is, a recycled polyester raw material with fewer impurities derived from the functional layer can be obtained. From the same perspective, the relaxation time of the recycled polyester raw material of the present invention is preferably 0.0105 ms or more, more preferably 0.0106 ms or more. On the other hand, from the perspective of preventing excessive damage to the polyester film due to the peeling cleaning history, the relaxation time is preferably 0.0150 ms or less, more preferably 0.0140 ms or less, still more preferably 0.0130 ms or less, and particularly preferably 0.0120 ms or less.

[0024] In addition, the ratio of the relaxation time (T1) of this raw material to the relaxation time (T2) of an untreated laminated polyester film (hereinafter also referred to as the "blank ratio", i.e., T1 / T2) is preferably 1.05 or more and 1.50 or less. When the blank ratio is 1.05 or more, the functional layer can be sufficiently removed, and a recycled polyester raw material with few impurities derived from the functional layer can be obtained. Also, when the blank ratio is 1.50 or less, the damage to the polyester film due to peeling and cleaning does not become excessive. From the above viewpoints, the blank ratio is more preferably in the range of 1.06 to 1.35, and even more preferably in the range of 1.07 to 1.20.

[0025] <Intrinsic viscosity of this raw material> Also, the intrinsic viscosity (IV) of this raw material is preferably 0.45 to 0.65 dl / g. The lower limit is more preferably 0.48 dl / g or more, and even more preferably 0.50 dl / g or more. The upper limit is more preferably 0.62 dl / g or less, and even more preferably 0.60 dl / g or less. Within such a range, since the extrusion moldability and drawability are excellent, film formation is possible.

[0026] <Ti and Sb contents of this raw material> The total amount of the titanium content and the antimony content contained in this raw material is preferably 250 to 450 ppm. The lower limit is more preferably 275 ppm or more, and even more preferably 300 ppm or more. The upper limit is more preferably 425 ppm or less, and even more preferably 400 ppm or less. Among them, the antimony content is preferably 450 ppm or less, more preferably 425 ppm or less, and even more preferably 400 ppm or less. The lower limit is not particularly limited and is 0 ppm. If the total amount of titanium content and antimony content and the antimony content are below the upper limit value, when formed into a film, foreign matters derived from the polymerization catalyst formed by recrystallization on the film surface can be reduced. On the other hand, if the total amount of titanium content and antimony content is above the lower limit value, film formation becomes possible. Incidentally, the titanium compound and the antimony compound are those generally used as a polymerization catalyst for polyester.

[0027] <Removal rate of the functional layer of this raw material> When the functional layer has a siloxane skeleton (Si-O-Si) (for example, a silicone release layer), the removal rate of the functional layer of this raw material can be evaluated by the method described in the examples, and it is preferable that the removal rate is 70% or more. If the removal rate of the functional layer of this raw material is 70% or more, a recycled polyester raw material with few impurities derived from the functional layer can be obtained. Therefore, from this viewpoint, the removal rate of the functional layer is more preferably 80% or more, and even more preferably 90% or more. The upper limit value is 100%.

[0028] <Manufacturing method of this raw material; Step (1)> The manufacturing method of this raw material according to an example of the embodiment of the present invention preferably has a step (step (1)) of preparing a polyester film from which the functional layer has been removed using a cleaning agent from a laminated polyester film.

[0029] <Laminated polyester film> The laminated polyester film refers to, for example, a laminated polyester film that is waste material, and more specifically, a film in which a functional layer such as a resin layer is laminated on the surface of a polyester film that is a base film. The polyester film (base film) may have a single-layer structure or a multilayer structure. In the case of a multilayer structure, it may have a two-layer structure, a three-layer structure, etc., or may be a multilayer of four layers or more, and the number of layers is not particularly limited. Also, the polyester film may be a stretched film such as a biaxially stretched film or an unstretched film. The polyester constituting the polyester film is not particularly limited, and those commercially available can be appropriately used. Specifically, polyesters formed by polycondensing dicarboxylic acids and diols can be mentioned. As the dicarboxylic acid, aromatic dicarboxylic acids are preferred, and as the diol, aliphatic glycols are preferred.

[0030] Examples of the above aromatic dicarboxylic acids include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, phthalic acid, etc. Examples of the above aliphatic glycol component include ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, 1,4-cyclohexanedimethanol, neopentyl glycol, etc. The polyester may be a homopolyester or a copolyester. Further, the polyester may contain a third component other than aromatic dicarboxylic acids and glycols as a copolymer component. Specific examples of the polyester include polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, polybutylene-2,6-naphthalate, etc. Among these, polyethylene terephthalate is preferred. Also, these may be copolymer polyesters. For example, polyethylene terephthalate may have dicarboxylic acid units other than terephthalic acid units at about 30 mol% or less of the dicarboxylic acid units, and may also have diol units other than ethylene glycol units at about 30 mol% or less of the diol units.

[0031] The components of the functional layer are not particularly limited, but from the viewpoint of being removed by a cleaning agent, it is preferably composed of a resin. Examples of the functional layer include a hard coat layer, an adhesive layer, a release layer, a decorative layer, a light-shielding layer, an ultraviolet shielding layer, an easy adhesion layer (primer layer), an antistatic layer, a refractive index adjustment layer, an oligomer sealing layer, etc.

[0032] The hard coat layer is a layer provided to impart scratch resistance and the like to the polyester film. The material for forming the hard coat layer is not particularly limited, and examples thereof include cured products of monofunctional (meth)acrylates, polyfunctional (meth)acrylates, reactive silicon compounds such as tetraethoxysilane, and the like.

[0033] The adhesive layer is a layer provided for adhesion to other devices and the like. The material constituting the adhesive layer is not particularly limited, and for example, known pressure-sensitive resins such as acrylic, rubber, and silicone can be used.

[0034] The release layer is a layer provided to impart releasability to the polyester film. For example, it is a layer provided on a release film used for a process paper for forming a green sheet used in the manufacture of ceramic electronic components, an adhesive separator for an optical member used in the manufacture of flat panel displays such as a polarizing plate and an optical filter. The material constituting the release layer is not particularly limited, and examples thereof include those mainly composed of a curable silicone resin, or a modified silicone resin obtained by graft polymerization with a urethane resin, an epoxy resin, etc., a long-chain alkyl group-containing compound, a fluorine compound, a hydrocarbon wax, and the like.

[0035] The decorative layer is a layer provided to impart design properties. The material constituting the decorative layer is not particularly limited, and examples thereof include polyurethane-based resins, vinyl-based resins, polyamide-based resins, polyester-based resins, acrylic-based resins, polyvinyl acetal-based resins, and the like. Pigments, dyes, etc. are added to these resins for decoration.

[0036] The light-shielding layer or ultraviolet-shielding layer is a layer provided to protect the contents from ultraviolet rays, visible light, etc. The material constituting the light-shielding layer or ultraviolet-shielding layer is not particularly limited, and examples thereof include various resins described in the decorative layer, and inorganic fillers such as calcium carbonate, talc, clay, kaolin, silica, diatomaceous earth, barium sulfate, etc., organic fillers such as wood powder, pulp powder, and cellulose powder.

[0037] The easy - adhesion layer (primer layer) is a layer provided for adhering other layers or films onto the polyester film. Although not particularly limited, examples include polyurethane - based resins, vinyl - based resins, polyamide - based resins, polyester - based resins, acrylic - based resins, polyvinyl acetal - based resins, etc., as well as various cross - linking agents, particles, and the like.

[0038] The antistatic layer is a layer provided to prevent static electricity generated by contact or peeling with other materials. The antistatic agents used in the antistatic layer are not particularly limited, and examples include non - ionic, cationic, anionic, amphoteric surfactants, conductive polymers such as polypyrrole, polyaniline, poly(3,4 - ethylenedioxythiophene), poly(4 - styrenesulfonate), metal oxide fillers such as SnO2 (Sb - doped), In2O3 (Sn - doped), ZnO (Al - doped), and carbon compounds such as graphene, carbon black, carbon nanotubes (CNT). These may be used alone or in combination of two or more. Also, the antistatic layer may be formed from a resin composition containing an antistatic agent. Examples of the resin contained in the resin composition include polyester resins, acrylic resins, and urethane resins.

[0039] The refractive index adjustment layer is a layer provided to adjust the refractive index. The materials constituting the refractive index adjustment layer are not particularly limited, and examples include polyester resins, acrylic resins, urethane resins, polycarbonate resins, epoxy resins, alkyd resins, urea resins, fluorine resins, and metal oxides such as zirconium oxide and titanium oxide. These may be used alone or in combination of two or more.

[0040] The oligomer - sealing layer is a layer provided to prevent film whitening and foreign matters after the heating process. Although not particularly limited, for example, materials constituting the oligomer - sealing layer include amine - based compounds, ionic resins, etc. Also, the oligomer - sealing layer may be a highly cross - linked coating film or the like.

[0041] These functional layers may be single layers or two or more types of layers may be laminated. When two or more types of layers are laminated, it is preferable that at least one layer is a layer composed of a resin.

[0042] <Detergent> From the viewpoint of making the relaxation time of the raw material 0.0104 ms or more and reducing impurities derived from the functional layer, the detergent preferably comprises a combination of (a) an alkalizing agent, (b) a compound having at least one hydroxyl group, and (c) a compatibilizer.

[0043] (Alkalizing agent) The detergent preferably contains (a) an alkalizing agent. The alkalizing agent makes the detergent alkaline and can also be called an alkali agent. The alkalizing agent may be an inorganic alkalizing agent or an organic alkalizing agent, but from the viewpoints described later, it is preferably an inorganic alkalizing agent.

[0044] Examples of the inorganic alkalizing agent include hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide; hydroxides of alkaline earth metals such as calcium hydroxide and barium hydroxide; carbonates of alkali metals such as sodium carbonate and potassium carbonate; phosphates of alkali metals such as trisodium phosphate, sodium pyrophosphate, sodium tripolyphosphate, sodium tetrapolyphosphate, tripotassium phosphate, potassium pyrophosphate, and potassium tripolyphosphate; silicates of alkali metals such as sodium orthosilicate, sodium metasilicate, and potassium silicate; and ammonia.

[0045] Among the inorganic alkalizing agents in the detergent, hydroxides of alkali metals are preferable, sodium hydroxide and potassium hydroxide are more preferable from the viewpoint of easy availability, and potassium hydroxide is particularly preferable from the viewpoint of detergency.

[0046] As the inorganic alkalizing agent in the detergent, one kind can be used alone, or two or more kinds can be used in combination. In particular, it is preferable to use a combination of potassium hydroxide and sodium hydroxide from the viewpoints of effect and handleability.

[0047] Examples of the organic alkalizing agent include organic amine compounds such as N,N-bis(2-hydroxyethyl)-N-cyclohexylamine, diazabicycloundecene, diazabicyclononene, monomethylamine, dimethylamine, trimethylamine, monoethanolamine, diethanolamine, triethanolamine, morpholine, 2-(dimethylamino)ethanol, 2-(diethylamino)ethanol, 1-amino-2-propanol, and triisopropanolamine. In addition, as the organic alkalizing agent ((a) component in the present invention), a compound having at least one hydroxyl group ((b) component in the present invention) may be included. If the acidity constant (pKa) of the compound is 30 or more, it is handled as the alkalizing agent ((a) component).

[0048] Among the organic alkalizing agents in the detergent, monoethanolamine, diethanolamine, and triethanolamine are preferable from the viewpoint of versatility, monoethanolamine and diethanolamine are more preferable from the viewpoint of easy availability, and monoethanolamine is particularly preferable from the viewpoint of detergency.

[0049] Also, the content of the (a) alkalizing agent in the whole detergent is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 3 to 10% by mass. When it is within the above range, sufficient effects as a detergent can be obtained.

[0050] (Compound having at least one hydroxyl group) From the perspective of effectively removing the functional layer, it is preferable that the cleaning agent contains (b) a compound having at least one hydroxyl group in addition to (a) an alkalizing agent. Regarding the mechanism by which the functional layer can be effectively removed by using the components (a) and (b) in combination, it is not clear, but it is presumed as follows. (b) An ester exchange reaction occurs at the ester bond part of the functional layer and / or the base material by the alkoxide generated from the hydroxyl group of the compound having at least one hydroxyl group, and a low molecular weight compound is obtained. Next, a saponification reaction proceeds by a nucleophilic attack of the hydroxyl group ionized from the alkalizing agent on the ester bond of the low molecular weight compound to obtain a carboxylate. It is presumed that the functional layer elutes (swells and peels off) thereby.

[0051] Examples of the compound (b) having at least one hydroxyl group include alcohols and phenols.

[0052] Examples of the alcohols include monohydric alcohols such as hexafluoro-2-propanol, methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, benzyl alcohol, ethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether; dihydric alcohols such as ethylene glycol, diethylene glycol, and propylene glycol; and polyhydric alcohols such as glycerin.

[0053] Examples of the phenols include phenol, xylenol, salicylic acid, picric acid, naphthol, catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, dibutylhydroxytoluene, bisphenol A, cresol, estradiol, eugenol, gallic acid, guaiacol, phenolphthalein, serotonin, dopamine, adrenaline, noradrenaline, thymol, tyrosine, hexahydroxybenzene, etc.

[0054] These may be used alone or in combination of two or more kinds. Among these, alcohols are preferable from the viewpoint of maintaining detergency without impairing the alkalinity of the detergent.

[0055] In addition, a dihydric alcohol or a polyhydric alcohol may be used in combination with the above-mentioned preferable alcohols.

[0056] In the detergent, the content of the compound (b) having at least one hydroxyl group is preferably 10 to 90% by mass, more preferably 20 to 75% by mass, still more preferably 30 to 65% by mass, and particularly preferably 35 to 50% by mass. Within the above range, in addition to the alkalizing agent, the amount of the compatibilizer can also be made appropriate, so that the quality of the recycled polyester raw material and the recycled polyester film can be maintained. Moreover, when making it an aqueous system, a certain amount or more of water can also be contained.

[0057] (Compatibilizer) The detergent preferably further contains (c) a compatibilizer. The (c) compatibilizer has a function of assisting the elution of the functional layer from the laminated polyester film and also has a function of solubilizing the above-mentioned components (a) and (b) and other optionally added additives, etc. Thereby, impurities derived from the functional layer can be reduced to the limit. In addition, by containing the (c) compatibilizer, even when the detergent contains water as one component, the compatibility between the components (a) and (b) becomes good.

[0058] There is no particular limitation on the (c) compatibilizer, and any of anionic compatibilizers, cationic compatibilizers, nonionic compatibilizers, and amphoteric compatibilizers can be used. Since the compatibilizer includes a compound corresponding to the above-mentioned alkalizing agent, when using the (c) compatibilizer in combination with the above-mentioned components (a) and (b), a different one from the components (a) and (b) is used.

[0059] Examples of anionic compatibilizers include alkylsulfonic acid, alkylbenzenesulfonic acid, alkylcarboxylic acid, aromatic carboxylic acid, alkylnaphthalenesulfonic acid, α-olefinsulfonic acid, dialkylsulfosuccinic acid, α-sulfonated fatty acid, N-methyl-N-oleyltaurine, petroleum sulfonic acid, alkyl sulfuric acid, sulfated oil, polyoxyethylene alkyl ether sulfuric acid, polyoxyethylene styrenated phenyl ether sulfuric acid, alkyl phosphoric acid, polyoxyethylene alkyl ether phosphoric acid, polyoxyethylene alkyl phenyl ether phosphoric acid, naphthalenesulfonic acid formaldehyde condensate, salts thereof, and the like.

[0060] Examples of cationic compatibilizers include quaternary ammonium, tetraalkylammonium, trialkylbenzylammonium, alkylpyridinium, 2-alkyl-1-alkyl-1-hydroxyethylimidazolinium, N,N-dialkylmorpholinium, polyethylene polyamine fatty acid amide, urea condensate of polyethylene polyamine fatty acid amide, quaternary ammonium of urea condensate of polyethylene polyamine fatty acid amide, salts thereof, and the like.

[0061] Examples of nonionic compatibilizers include polyoxyalkylene ethers such as polyoxyethylene alkyl ethers and polyoxyethylene-polyoxypropylene alkyl ethers; polyoxyethylene alkyl phenyl ethers, polyoxyethylene polystyryl phenyl ethers, polyoxyethylene-polyoxypropylene glycols, partial esters of polyhydric alcohol fatty acids, partial esters of polyoxyethylene polyhydric alcohol fatty acids, polyoxyethylene fatty acid esters, polyglycerin fatty acid esters, polyoxyethylenated castor oil, fatty acid diethanolamides, monomethylamine, dimethylamine, trimethylamine, monoethanolamine, diethanolamine, triethanolamine, morpholine, 2-(dimethylamino)ethanol, 2-(diethylamino)ethanol, 1-amino-2-propanol, triisopropanolamine, polyoxyethylene alkylamines, partial esters of triethanolamine fatty acids, and organic amine compounds such as trialkylamine oxides.

[0062] Examples of amphoteric compatibilizers include betaines such as N,N-dimethyl-N-alkyl-N-carboxymethylammonium betaine, N,N,N-trialkyl-N-sulfoalkyleneammonium betaine, N,N-dialkyl-N,N-bis(polyoxyethylene)ammonium sulfate ester betaine, and 2-alkyl-1-carboxymethyl-1-hydroxyethylimidazolinium betaine; and aminocarboxylic acids such as N,N-dialkylaminoalkylene carboxylates.

[0063] Note that as the compatibilizer, the compound having at least one hydroxyl group in (b) may be included. However, alkanolamine compounds, alkanolamide compounds, and hydroxy compounds having 12 or more carbon atoms corresponding to the following are treated as (c) compatibilizers. Examples of alkanolamine compounds include monoethanolamine, diethanolamine, and triethanolamine, etc. Examples of alkanolamide compounds include monoethanolamide, diethanolamide, and triethanolamide, etc. In addition, examples of the hydroxy compound having 12 or more carbon atoms include polyoxyethylene alkyl ether-based, thioether-based, polyoxyalkylene glycol-based, acetylene glycol-based, ester-based, and glycoside-based hydroxy compounds having 12 or more carbon atoms.

[0064] Among the (c) compatibilizers in the detergent, from the viewpoints of compatibility and handleability, the use of aromatic sulfonates and amine compounds containing a hydroxyl group is preferred. Specific compounds include sodium benzenesulfonate, sodium toluenesulfonate, sodium 2,4-dimethylbenzenesulfonate, sodium 2-naphthalenesulfonate, alkanolamines such as monoethanolamine, diethanolamine, and triethanolamine. Among these, from the viewpoint of raising the upper limit of the heating temperature of the detergent, the use of the above aromatic sulfonates having a high boiling point is more preferred. Here, as described above, it is premised that a compound different from the (a) alkalizing agent is used.

[0065] In addition, in the detergent, it is preferable to use an inorganic alkalizing agent as the (a) alkalizing agent, alcohols and / or phenols as the (b) compound having at least one hydroxyl group, and at least one selected from aromatic sulfonates and amine compounds containing a hydroxyl group as the (c) compatibilizer. Among them, a combination of at least one inorganic alkalizing agent of sodium hydroxide and potassium hydroxide, alcohols and / or phenols, and an aromatic sulfonate such as sodium 2,4-dimethylbenzenesulfonate is preferred. In addition, a combination of at least one inorganic alkaline agent such as sodium hydroxide and potassium hydroxide, alcohols and / or phenols, and at least one hydroxyl group-containing amine compound selected from monoethanolamine, diethanolamine, triethanolamine, morpholine, 2-(dimethylamino)ethanol, 2-(diethylamino)ethanol, 1-amino-2-propanol, and triisopropanolamine is preferred. Among these, a combination of at least one inorganic alkaline agent selected from sodium hydroxide and potassium hydroxide, alcohols and / or phenols, and at least one hydroxyl group-containing amine compound selected from monoethanolamine and diethanolamine used in combination is particularly preferred.

[0066] Also, from the perspective of comprehensively dissolving various additives in the detergent, two or more types of the solubilizing agent may be used in combination. Moreover, the content of the solubilizing agent in the detergent is preferably in the range of 1 to 30% by mass. When within the above range, sufficient detergency can be obtained. From the above perspective, the content of the solubilizing agent in the detergent is more preferably in the range of 5 to 25% by mass, and even more preferably in the range of 8 to 20% by mass.

[0067] The detergent is preferably an aqueous detergent. The aqueous detergent is obtained by dissolving the components (a) to (c) etc. in water and diluting them. The aqueous detergent is advantageous in that it can raise the flash point and is relatively safe.

[0068] In addition, the detergent can contain various additives other than the components (a) to (c), for example, antioxidants, rust inhibitors, pH adjusters, preservatives, viscosity adjusters, defoamers, etc. can be added.

[0069] As a method for removing the functional layer using the cleaning agent, for example, an immersion method of immersing in a cleaning tank containing the cleaning agent, a coating method of applying the cleaning agent in a solution state, a spraying method of spraying the cleaning agent in a solution state or a vaporized cleaning agent, etc. can be used. Among these, from the viewpoint of the penetrability of the cleaning agent into the functional layer, the immersion method is preferable.

[0070] The temperature of the cleaning agent in the immersion method is preferably room temperature (20 ° C) or higher. When it is room temperature (20 ° C) or higher, the viscosity of the cleaning agent is low and it easily penetrates into the functional layer, so good detergency can be obtained. From the above viewpoints, the temperature of the cleaning agent in the immersion method is more preferably 40 ° C or higher, further preferably 50 ° C or higher, and particularly preferably 60 ° C or higher. Also, as the upper limit value of the temperature of the cleaning agent, when the cleaning agent is used in a solution state, a temperature below the boiling point is preferable. In the case of the aqueous cleaning agent which is a preferred embodiment of the present application, 100 ° C or lower is preferable, and 90 ° C or lower is more preferable. In addition, even in cases other than the immersion method, the temperature of the cleaning agent during cleaning is the same as above. Also, in the peeling cleaning by the immersion method, microwave irradiation may be performed for the purpose of promoting the hydrolysis reaction.

[0071] The pH of the cleaning agent is preferably 12 or higher, and more preferably 13 or higher from the viewpoint of detergency.

[0072] Regarding the immersion time, it is preferably adjusted as appropriate as follows depending on the type of the object to be cleaned.

[0073] When the laminated polyester film provided with an acrylic adhesive layer as the functional layer is the object to be cleaned, 1 second or more and 30 minutes or less is preferable. When it is 1 second or more, the cleaning agent can sufficiently penetrate into the functional layer and the detergency can be exhibited. On the other hand, when it is within 30 minutes, the polyester film as the base material will not be excessively dissolved. From the above viewpoints, 15 seconds or more and 20 minutes or less is more preferable, 30 seconds or more and 15 minutes or less is further preferable, and 1 minute or more and 10 minutes or less is particularly preferable.

[0074] When the laminated polyester film provided with an acrylic hard coat layer as a functional layer is the object to be cleaned, it is preferably for 1 second or more and 30 minutes or less. When it is 1 second or more, the cleaning agent can sufficiently penetrate into the functional layer and the detergency can be exhibited. On the other hand, when it is within 30 minutes, the polyester film as the base material will not be excessively dissolved. From the above viewpoints, it is more preferably 15 seconds or more and 30 minutes or less, further preferably 30 seconds or more and 25 minutes or less, and particularly preferably 1 minute or more and 20 minutes or less.

[0075] When the laminated polyester film provided with a silicone release layer as a functional layer is the object to be cleaned, it is preferably for 1 second or more and 30 minutes or less. When it is 1 second or more, the cleaning agent can sufficiently penetrate into the functional layer and the detergency can be exhibited. On the other hand, when it is within 30 minutes, the polyester film as the base material will not be excessively dissolved. From the above viewpoints, it is more preferably 15 seconds or more and 20 minutes or less, further preferably 30 seconds or more and 10 minutes or less, and particularly preferably 1 minute or more and 5 minutes or less.

[0076] <The manufacturing method of this raw material; Step (2)> Moreover, after the step (1), it preferably has a step (step (2)) of pulverizing the polyester film to obtain a raw material in which flakes and / or the flakes are chipped into chips. In the step (2), as a method for obtaining flakes, a conventionally known method can be used, and an example is a method of pulverizing a polyester film with a pulverizer to obtain flakes. Also, as a method for chipping the flakes, a conventionally known method can be used. For example, after melting and extruding the flakes, a method of obtaining a chipped raw material by cutting the strand-like melt extrudate can be mentioned.

[0077] <Other raw materials> This raw material may contain recycled raw materials obtained from the following (A) to (C), etc. (A) Films that do not become products when manufacturing polyester films (for example, film ends cut and removed from products, etc.) (B) Film that broke during film formation (C) Film that did not reach the product due to poor quality, etc. Regarding the method for producing the recycled raw material obtained from the above (A) to (C), etc., there are no particular restrictions, but it is preferable to pulverize the film into flakes and / or chip the flakes to obtain a raw material.

[0078] Also, this raw material may contain a recycled raw material derived from bottles.

[0079] [Recycled polyester film] The recycled polyester film of the present invention (hereinafter also referred to as "this film") preferably has a polyester layer containing this raw material. In addition, this film may contain virgin raw materials.

[0080] This film may have a single-layer structure or a multi-layer structure, but from the viewpoints of particle design on the film surface and maintaining film strength, a multi-layer structure is preferable. In the case of a multi-layer structure, at least two or more laminated configurations are sufficient, and the number of layers is not particularly limited. Also, this film may be a stretched film such as a biaxially stretched film or an unstretched film, but from the viewpoints of balance of mechanical properties, flatness, and thinning of the film, it is preferably a biaxially stretched film.

[0081] The content ratio of this raw material in the polyester layer containing this raw material is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more. The upper limit is 100% by mass. Within such a range, the recyclability of the polyester film is excellent. In addition, when this film has a plurality of layers with different content ratios of this raw material, the content ratio of this raw material in the polyester layer containing this raw material means the content ratio of the entire polyester layer containing this raw material.

[0082] Also, the thickness of the polyester layer containing this raw material is preferably 50% or more of the total thickness of this film, more preferably 70% or more, and even more preferably 80% or more. The upper limit is 100% (a laminated structure in which this raw material is included in a single layer or all layers). However, when this film has a multilayer structure composed of at least two or more laminated layers including a polyester layer containing this raw material and a polyester layer not containing this raw material, the upper limit of the thickness is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less.

[0083] <Method for manufacturing a recycled polyester film> Regarding the method for manufacturing this film, there is no particular limitation, and it can be formed into a film in the same manner as a normal polyester film. An example of the method for manufacturing this film will be specifically described, but it is not limited to the following description.

[0084] For example, when manufacturing a biaxially stretched film, a polyester raw material (including this raw material) is put into an extruder, extruded as a molten sheet from a die, and rapidly cooled and solidified on a rotating cooling drum to a temperature below the glass transition temperature to first obtain an unstretched sheet. In this case, in order to improve the flatness of the unstretched sheet, it is preferable to enhance the adhesion between the molten sheet and the rotating cooling drum, and the electrostatic printing adhesion method and / or the liquid coating adhesion method are preferably adopted. Next, the obtained unstretched sheet is stretched in one direction by a roll or tenter-type stretching machine. The stretching temperature is usually 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Then, it is stretched in a direction perpendicular to the first stretching direction at a temperature of usually 70 to 170°C, and the stretching ratio is usually 3.0 to 7 times, preferably 3.5 to 6 times. And then, a heat treatment is continuously performed at a temperature of 180 to 270°C under tension or with a relaxation of within 30% to obtain a biaxially stretched film. In the above stretching, a method of performing unidirectional stretching in two or more steps can also be adopted. In that case, it is preferable to finally perform biaxial stretching ratios within the above ranges respectively.

[0085] Also, when manufacturing a biaxially stretched film, a simultaneous biaxial stretching method can be adopted. The simultaneous biaxial stretching method is a method of simultaneously stretching the above-mentioned unstretched sheet in the machine direction and the width direction while controlling the temperature to be usually 70 to 120°C, preferably 80 to 110°C. As the stretching ratio, the area ratio is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times. Then, subsequently, heat treatment is performed at a temperature of 170 to 270°C under tension or under relaxation within 30% to obtain a biaxially stretched film. Regarding the simultaneous biaxial stretching device, conventionally known stretching methods such as a screw method, a pantograph method, and a linear drive method can be adopted.

[0086] Also, as a method of charging the recycled polyester raw material, there are two methods. One is a method of directly charging the flaky recycled polyester raw material, and the other is a method of melt-extruding the flaky recycled polyester raw material and charging the pelletized product. Among these, from the viewpoint of suppressing thermal degradation, the method of directly charging the flaky recycled polyester raw material is preferable.

[0087] <<Explanation of terms>> In the present invention, when referring to a "film", it includes a "sheet", and when referring to a "sheet", it includes a "film". In the present invention, when described as "X to Y" (X and Y are arbitrary numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less" and also the meaning of "preferably greater than X" or "preferably less than Y". In addition, when it is described as "X or more" (X is an arbitrary number), unless otherwise specified, it includes the meaning of "preferably greater than X", and when it is described as "Y or less" (Y is an arbitrary number), unless otherwise specified, it also includes the meaning of "preferably less than Y".

Examples

[0088] Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

[0089] <Evaluation method> (1) Functional layer removal (cleaning) experiment The following cleaning agents 1 to 3 were placed in a 30 ml container, and a laminated polyester film with a size of 3 × 10 cm was immersed therein. Note that the immersion conditions for cleaning agents 1 and 2 were 80°C, 1 minute, and 3 minutes, and the immersion condition for cleaning agent 3 was 3 minutes at room temperature (25°C). When using cleaning agent 3, after the immersion, it was further immersed in xylene at room temperature (25°C) for 1 minute.

[0090] (Cleaning agent 1) (a) Component: 5 parts by mass of potassium hydroxide (b) Component: 41 parts by mass of benzyl alcohol (c) Component: 18 parts by mass of sodium 2,4-dimethylbenzenesulfonate Other components: 36 parts by mass of water

[0091] (Cleaning agent 2) 100 parts by mass of water

[0092] (Cleaning agent 3) (a) Component: 10 parts by mass of potassium hydroxide (b) Component: 45 parts by mass of ethanol Other components: 45 parts by mass of water

[0093] (2) Measurement of the intrinsic viscosity (dl / g) of polyester 1 g of polyester from which other polymer components and pigments incompatible with the polyester were removed was precisely weighed, 100 ml of a mixed solvent of phenol / tetrachloroethane = 50 / 50 (mass ratio) was added and dissolved, and the measurement was carried out at 30°C.

[0094] (3) Pulse NMR method - Measurement of relaxation time The measurement was carried out under the following apparatus and conditions. Apparatus: mq20 manufactured by Bruker Biospin Temperature: 40°C Observation frequency: 20 MHz 90° pulse width: 2.74 μs Pulse repetition time: 2.0 s Pulse mode: Solido Echo method

[0095] For the measurement, the films of the examples, comparative examples, and reference examples (3×10 cm) were rolled up and packed into a glass tube with an outer diameter of 10 mm. 1 The spin-spin relaxation time of the H nucleus was determined. The measurement was started after the film was put into the apparatus and kept warm for 15 minutes.

[0096] In addition, for the obtained data, the relaxation time was evaluated by the exponential single relaxation model of the following formula (1). In formula (1), M is the magnetization intensity (%), y0 is the initial value of the magnetization intensity (%), A l is a constant, x is the measurement time, and T2 represents the relaxation time.

[0097]

Equation

[0098] (4) Measurement of titanium content and antimony content For the films of the examples, comparative examples, and reference examples, quantitative analysis of Ti element and Sb element was carried out using a fluorescent X-ray analyzer (XRF, "EDX-8000" manufactured by Shimadzu Corporation). The surface on which the functional layer was applied was used as the measurement surface.

[0099] (5) Evaluation of functional layer removal rate The surfaces of the films of the examples, comparative examples, and reference examples were quantitatively analyzed for Si element using a fluorescent X-ray analyzer (XRF, "EDX-8000" manufactured by Shimadzu Corporation). The surface on which the functional layer was applied was used as the measurement surface. In this evaluation, the removal rate (%) of the functional layer was calculated by setting the Si element amount on the surface of the functional layer of the non-pretreated laminated polyester film (Reference Example 1) to 100% and the Si element amount of the plain film without the functional layer of the laminated polyester film to 0%.

[0100] <Materials Used> [Laminated Polyester Film] Laminated polyester film having a silicone release layer; commercially available product ("MHA25" manufactured by Mitsubishi Chemical Corporation), thickness; 25 μm

[0101] (Example 1) The laminated polyester film was washed with Detergent 1 and evaluated by the above method.

[0102] (Comparative Example 1) The laminated polyester film was washed with Detergent 2 and evaluated by the above method.

[0103] (Comparative Example 2) The laminated polyester film was washed with Detergent 3 and xylene and evaluated by the above method.

[0104] (Comparative Example 3) Using a hot air circulation oven, the laminated polyester film was heat-treated and evaluated by the above method. The temperature of the oven was set at 80°C for the treatment.

[0105] (Reference Example 1) Using the non-pretreated laminated polyester film (untreated), it was evaluated by the above method.

[0106] (Reference Example 2) Using the non-pretreated polyethylene terephthalate film ("T100" manufactured by Mitsubishi Chemical Corporation, thickness; 25 μm), it was evaluated by the above method.

[0107] In the examples and comparative examples, the treatment was carried out at the temperature and for the time described in Table 1. However, in Comparative Example 2, as described above, after being immersed in Detergent 3 at room temperature (25°C) for 3 minutes, it was further immersed in xylene at room temperature (25°C) for 1 minute. For convenience, the treatment method in Table 2 is washing (Detergent 3), and the treatment time is set to 3 minutes.

[0108] The evaluation results of the examples, comparative examples, and reference examples are shown in Table 1. Also, graphs showing the relaxation time and the blank ratio are shown in FIGS. 1 and 2.

[0109]

Table 1

[0110] The blank ratio in Table 1 and FIG. 2 refers to the relaxation time of each example, comparative example, and reference example with respect to the relaxation time of Reference Example 1, and was calculated by the following formula. (Blank ratio) = (Relaxation time of each example, comparative example, and reference example) / (Relaxation time of Reference Example 1)

[0111] From the results of Example 1, it can be seen that the recycled polyester raw material of the present invention has the functional layer sufficiently removed. Also, from Table 1, FIGS. 1 and 2, it can be seen that the relaxation time became longer due to the damage history of removing the functional layer (peeling wash). This is considered to be related to the heat conduction efficiency. In the film subjected to peeling wash, since it is considered that molecular chain scission has occurred, a high heat conduction efficiency that cannot be achieved simply by immersing the film in warm water or applying heat to the film (see Comparative Example 1 and Comparative Example 3) is obtained, and it is considered that the molecular motion was activated by heat and the relaxation time became longer. Furthermore, it can be seen that the relaxation time did not become longer under the washing conditions where sufficient removal of the functional layer could not be performed for fear of damaging the polyester film (see Comparative Example 2).

[0112] In addition, in Example 1, it can also be seen that the relaxation time increased with the damage history. From this, the invention of the present application is considered to be an index for obtaining a recycled polyester raw material from which the functional layer has been sufficiently removed. That is, it can be said that if the relaxation time is 0.0104 ms or more, a recycled polyester raw material from which the functional layer has been sufficiently removed can be obtained.

Industrial Applicability

[0113] The recycled polyester raw material of the present invention has a sufficiently removed functional layer, and when formed into a film, it can be made into a recycled polyester film with few foreign matters. Therefore, the recycled polyester raw material and the recycled polyester film of the present invention are applicable also to display applications where foreign matter management is extremely strict. In addition, since the functional layer of the recycled polyester raw material and the recycled polyester film of the present invention has been sufficiently removed and they are of high quality, it can be expected that they can withstand multiple recycling cycles, leading to an improvement in the recyclability of polyester films.

Claims

The manufacturing method of recycled polyester raw material for removing a functional layer from a laminated polyester film having a functional layer on the surface of the polyester film using a cleaning agent, wherein the spin-spin relaxation time of the 1H nucleus of the film after removing the functional layer evaluated by the exponential single relaxation model of the following formula (1) is 0.0104 ms or more, measured by the pulsed NMR method under the conditions of 40 ° C., an observation frequency of 20 MHz, a 90 ° pulse width of 2.74 μm, a pulse repetition time of 2.0 s, and a pulse mode of Solid Echo method, is used as an index. 【Equation 1】 (In formula (1), M is the magnetization intensity (%), y0 is the initial value of the magnetization intensity (%), Al is a constant, x is the measurement time, and T2 represents the relaxation time.) The manufacturing method of recycled polyester raw material for removing a functional layer from a laminated polyester film having a functional layer on the surface of the polyester film using a cleaning agent, wherein the spin-spin relaxation time of the 1H nucleus evaluated by the exponential single relaxation model of the following formula (1) satisfies the following formula (2), measured by the pulsed NMR method under the conditions of 40 ° C., an observation frequency of 20 MHz, a 90 ° pulse width of 2.74 μm, a pulse repetition time of 2.0 s, and a pulse mode of Solid Echo method, is used as an index. 【Equation 2】 (In formula (1), M is the magnetization intensity (%), y0 is the initial value of the magnetization intensity (%), Al is a constant, x is the measurement time, and T2 represents the relaxation time.) T1 / T2 = 1.05 to 1.50... (2) T1: Relaxation time of the film after removing the functional layer T2: Relaxation time of the film before removing the functional layer

3. The manufacturing method of recycled polyester raw material according to claim 1 or 2, wherein the relaxation time of the film after removing the functional layer is 0.0150 ms or less.

4. The method for producing a recycled polyester raw material according to any one of claims 1 to 3, wherein the intrinsic viscosity (IV) of the recycled polyester raw material is 0.45 to 0.65 dl / g.

5. The method for producing a recycled polyester raw material according to any one of claims 1 to 4, wherein the total amount of titanium content and antimony content contained in the recycled polyester raw material is 250 to 450 ppm.

6. The method for producing a recycled polyester raw material according to claim 5, wherein the antimony content contained in the recycled polyester raw material is 450 ppm or less.

7. The method for producing a recycled polyester raw material according to any one of claims 1 to 6, wherein the recycled polyester raw material is polyethylene terephthalate.

8. A method for producing a recycled polyester film, comprising a polyester layer containing a recycled polyester raw material obtained by the production method according to any one of claims 1 to 7.

9. The method for producing a recycled polyester film according to claim 8, comprising a laminated structure of at least two layers or more.

10. The method for producing a recycled polyester film according to claim 8 or 9, wherein the thickness of the polyester layer containing the recycled polyester raw material is 50% or more of the total thickness of the recycled polyester film.

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