Classifications

• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies
  • Y02W30/80—Packaging reuse or recycling, e.g. of multilayer packaging

Definitions

• the present invention relates to a heat-shrinkable polyester film that uses recycled polyester such as recycled PET bottle materials, has high shrinkability, exhibits little deterioration in performance due to aging, and is suitable for use in heat-shrinkable labels, and to packaging using the labels.
• stretched films made of polyvinyl chloride resin, polystyrene resin, polyester resin, etc. have been widely used for label packaging, cap seals, and stacked packaging that protect glass bottles and PET bottles and display products.
• polyvinyl chloride films have problems such as low heat resistance, generating hydrogen chloride gas when burned, and being a source of dioxin.
• polystyrene films have poor solvent resistance, require the use of ink with a special composition when printing, and must be incinerated at high temperatures, which causes problems such as the generation of large amounts of black smoke accompanied by an unpleasant odor when incinerated.
• polyester heat-shrinkable films which are highly heat-resistant, easy to incinerate, and have excellent solvent resistance, have been widely used as shrink labels, and their usage tends to increase along with the increase in the distribution volume of PET containers (PET bottles).
• the main recycling techniques include mechanical recycling, chemical recycling, and thermal recycling, of which mechanical recycling is the most widespread, in which used containers are sorted, crushed, and washed, and then turned into resin chips again in an extruder, after which they are processed into PET bottles or fibers or films for reuse.
• the polyester contained in used PET bottles has been broken down to the monomer level, and the resulting polyester obtained by repolymerization is called chemically recycled polyester, which is then processed again into PET bottles, fibers, films, etc. for use.
• Heat-shrinkable polyester film labels can also contribute to the life cycle of PET, from production to use and disposal, by using some of the recycled PET bottle materials as described above, and can help reduce the environmental impact.
• Patent Document 1 discloses the use of mechanically recycled polyester in heat-shrinkable polyester film. To achieve heat-shrink performance, it is important that the raw polyester material has high amorphousness, but the polyester raw material used in PET bottles is highly crystalline to ensure the thermal stability of the container, so the challenge is to ensure high amorphousness, i.e. high shrink performance, while still using recycled raw materials.
• crystalline polyester raw material is mixed with amorphous polyester, and in order to reduce the fusion enthalpy ( ⁇ Hm), an index of crystallinity, the material is melt-extruded in an extruder while efficiently undergoing transesterification, thereby further reducing the crystalline component and achieving shrinkage performance.
• ⁇ Hm fusion enthalpy
• the kneading of the resin is increased, and at the same time as the amorphous component increases, the low molecular weight component also increases.
• Heat-shrinkable films are generally not used immediately after production, but are often used after aging (long-term storage) during storage and transportation processes. Because heat-shrinkable films are films that shrink when exposed to heat, their performance deteriorates during aging even at room temperature, resulting in poor shrink finish.
• long-chain molecules are used to suppress deterioration of shrink performance after aging, so it is believed that the performance deterioration during aging is caused by low-molecular-weight components (i.e., short-chain molecules). Therefore, the use of recycled raw materials in heat-shrinkable films is disadvantageous in ensuring shrink performance after aging, as low molecular weight components also increase as mentioned above.
• the objective of the present invention is to provide a heat-shrinkable polyester film that overcomes the above problems, suppresses deterioration of shrink finish caused by performance degradation after aging, and contains a larger amount of recycled polyester raw materials, which is useful for reducing the environmental impact.
• a heat-shrinkable polyester film made of a polyester composition containing 1% by mass or more and 50% by mass or less of mechanically recycled and/or chemically recycled polyester,
• the shrinkage stress is 3.0 MPa or more and 15.0 MPa or less
• the intrinsic viscosity is 0.58 dl/g or more and 0.75 dl/g or less
• the area ratio of a region having a molecular weight of 1,000 or less is 1.0% or more and 6.0% or less of the total peak area
• a heat-shrinkable polyester film characterized in that the heat shrinkage rate in the main shrinkage direction when the heat-shrinkable polyester film is immersed in warm water at 90° C.
• the polyester composition "contains 1% by mass or more and 50% by mass or less of mechanically recycled polyester and/or chemically recycled polyester"
• this expression means that the total content of both is 1% by mass or more and 50% by mass or less.
• the polyester composition contains mechanically recycled polyester and does not contain chemically recycled polyester
• this expression means that the content of mechanically recycled polyester is 1% by mass or more and 50% by mass or less.
• the polyester composition does not contain mechanically recycled polyester and contains chemically recycled polyester, this expression means that the content of chemically recycled polyester is 1% by mass or more and 50% by mass or less.
• polyester composition "contains mechanically recycled polyester and/or chemically recycled polyester, and the total content of mechanically recycled polyester and chemically recycled polyester is 1% by mass or more and 50% by mass or less".
• shrinkage stress is the maximum shrinkage stress in the main shrinkage direction at 90°C.
• the polyester composition comprises mechanically recycled polyester; 2.
• the heat-shrinkable polyester film according to 1. characterized in that in a molecular weight distribution curve obtained by gel permeation chromatography, the area ratio of a region having a molecular weight of 1,000 or less is 2.0% or more and 6.0% or less.
• the heat-shrinkable polyester film according to 1. wherein the polyester composition contains a chemically recycled polyester, and the area ratio of a region having a molecular weight of 1,000 or less in a molecular weight distribution curve obtained by gel permeation chromatography is 1.0% or more and 5.5% or less. 4.
• the heat-shrinkable polyester film according to any one of 1. to 4., characterized in that, after aging for 672 hours under a 30°C/85% RH atmosphere, the aged heat-shrinkable polyester film is immersed in 70°C warm water for 10 seconds, and the decrease in heat shrinkage in the main shrinkage direction is 15.0% or less compared to before aging, and the amount of enthalpy relaxation after the aging is 4.0 J/g or less.
• the aging decrease rate is the absolute value of the difference between the 70°C heat shrinkage rate in the main shrinkage direction of a heat-shrinkable film and the 70°C heat shrinkage rate in the main shrinkage direction of a heat-shrinkable film aged at 30°C and 85% RH for 672 hours.
• the present invention also relates to the following 6. and/or 7.
• a heat-shrinkable label comprising the heat-shrinkable polyester film according to any one of 1. to 5. above.
• 7. A package in which at least a portion of the outer periphery of an object to be packaged is covered with the heat-shrinkable label according to 6.
• the present invention also preferably has the following configuration.
• 8. The heat-shrinkable polyester film according to any one of the above configurations, which is uniaxially stretched.
• 10. The heat-shrinkable polyester film according to any one of the preceding configurations, wherein the polyester composition comprises mechanically recycled polyester.
• the heat-shrinkable polyester film according to any one of the above configurations, wherein the mechanically recycled polyester is mechanically recycled polyethylene terephthalate. 12.
• the heat-shrinkable polyester film according to any one of the above configurations, wherein the chemically recycled polyester is chemically recycled polyethylene terephthalate. 16.
• the heat-shrinkable polyester film according to any one of the above configurations, wherein the content of mechanically recycled and/or chemically recycled polyester in the polyester composition is 3% by mass or more, or 5% by mass or more. 19.
• the heat-shrinkable polyester film according to any one of the above configurations wherein the content of mechanically recycled and/or chemically recycled polyester in the polyester composition is 48% by mass or less or 46% by mass or less.
• 20. The heat-shrinkable polyester film according to any one of the above configurations, which has a shrinkage stress of 4.0 MPa or more or 5.0 MPa or more.
• 21. The heat-shrinkable polyester film according to any one of the above configurations, which has a shrinkage stress of 14.0 MPa or less or 13.0 MPa or less. 22.
• the heat-shrinkable polyester film according to any one of the above configurations wherein the area ratio of a region having a molecular weight of 1,000 or less in a molecular weight distribution curve is 1.5% or more or 2.0% or more.
• 23. The heat-shrinkable polyester film according to any one of the above configurations, wherein the area ratio of a region having a molecular weight of 1,000 or less in a molecular weight distribution curve is 2.5% or more or 3.0% or more.
• 24. The heat-shrinkable polyester film according to any one of the above configurations, wherein the area ratio of a region having a molecular weight of 1,000 or less in a molecular weight distribution curve is 5.8% or less or 5.5% or less. 25.
• the heat-shrinkable polyester film according to any one of the above configurations wherein the area ratio of a region having a molecular weight of 1,000 or less in a molecular weight distribution curve is 5.3% or less or 5.1% or less. 26.
• a heat-shrinkable polyester film according to any one of the above configurations wherein the main shrinkage direction of the heat-shrinkable polyester film after aging when the heat-shrinkable polyester film is immersed in warm water at 27.70°C for 10 seconds is the width direction of the heat-shrinkable polyester film.
• the polyester composition comprises a fossil fuel-derived polyester.
• the fossil fuel-derived polyester has ethylene terephthalate units.
• the fossil fuel-derived polyester contains a neopentyl glycol component, i.e., the fossil fuel-derived polyester is a polyester in which at least neopentyl glycol is polymerized.
• the heat-shrinkable polyester film according to any one of the above configurations wherein the polyester composition contains the mechanically recycled and/or chemically recycled polyester and the fossil fuel-derived polyester in a total amount of 80% by mass or more, or 90% by mass or more. 33. The heat-shrinkable polyester film according to any one of the above configurations, wherein the polyester composition contains the mechanically recycled and/or chemically recycled polyester and the fossil fuel-derived polyester in a total amount of 95% by mass or more, or 97% by mass or more. 34. The heat-shrinkable polyester film according to any one of the above configurations, which is a single-layer film. 35.
• 36. A package comprising an object to be packaged, at least a part of the outer periphery of which is covered with the heat-shrinkable label according to any one of the above configurations.
• 37. A package comprising an object to be packaged and a heat-shrinkable label according to any one of the above configurations, the heat-shrinkable label covering at least a portion of the outer periphery of the object to be packaged.
• the heat-shrinkable polyester film of the present invention reduces the environmental impact and exhibits characteristics that cause little deterioration in performance due to aging. Therefore, even when using recycled polyester, packaging products with excellent shrink finish can be obtained, regardless of whether they are aged or not.
• thermal shrinkage rate may be referred to as “shrinkage rate.”
• Poly may be referred to as “polyester resin.”
• the heat-shrinkable polyester film of the present invention contains mechanically recycled polyester and/or chemically recycled polyester, which reduces the environmental impact.
• Used polyester products may be in the form of bales, flakes, or pellets, for example. Used polyester products are preferably used PET bottles.
• the moles of the isophthalic acid component content is preferably 10 mole% or less, more preferably 8 mole% or less, even more preferably 5 mole% or less, and even more preferably 3 mole% or less.
• the moles of the isophthalic acid component content is preferably 0.1 mole% or more, more preferably 1 mole% or more, and even more preferably 2 mole% or more.
• the mechanically recycled PET may contain one or more types of isophthalic acid components that satisfy such a suitable mole number of the isophthalic acid components.
• the intrinsic viscosity of the mechanically recycled polyester is preferably 0.58 dl/g or more, more preferably 0.60 dl/g or more, and even more preferably 0.62 dl/g or more. If it is 0.58 dl/g or more, the area ratio of the region with a molecular weight of 1000 or less in the mechanically recycled polyester, i.e., the amount of low molecular weight components, can be reduced, so that the deterioration of the shrinkage rate of the heat-shrinkable polyester film after aging can be further reduced.
• the area ratio of the region of the mechanically recycled polyester with a molecular weight of 1000 or less, i.e., the low molecular weight component (measurement method described later), is preferably 2.0% or more and 6.0% or less. If it is less than 2.0%, the shrinkage stress increases. If it is more than 6.0%, the shrinkage performance after aging decreases significantly.
• the low molecular weight component of the mechanically recycled polyester is preferably 2.1% or more and 5.7% or less, and more preferably 2.2% or more and 5.5% or less.
• the mechanically recycled polyester may contain one or more types of such suitable low molecular weight components.
• Chemically recycled polyester is polyester obtained by breaking down polyester contained in used polyester products to the monomer or oligomer level and then polymerizing it again. Because chemically recycled polyester is produced using polyester contained in used polyester products as the raw material, it reduces the environmental impact.
• the used polyester product may be, for example, in the form of bales, flakes, or pellets. Used PET bottles are preferred as used polyester products.
• One method for breaking down polyester to the monomer level is to crush and wash PET bottle bales, add at least ethylene glycol (EG) and a catalyst to the flakes, and heat them to break them down into bis-2-hydroxyethyl terephthalate (BHET) (hereinafter sometimes referred to as the "BHET method") (see Patent Document 3, i.e., JP 2000-169623 A).
• Another method for breaking down polyester to the monomer level is the method described in Patent Document 4 (JP 2000-302707 A).
• polyester may be broken down to the monomer or oligomer level by methods other than those exemplified here.
• chemically recycled polyester examples include chemically recycled polyethylene terephthalate (hereinafter sometimes referred to as "chemically recycled PET”), chemically recycled polybutylene terephthalate, and chemically recycled polyethylene-2,6-naphthalate. These may contain copolymer components. Chemically recycled PET is preferred because it is easy to obtain and has excellent mechanical properties and heat resistance. These may be used alone or in combination of two or more types.
• the chemically recycled polyester may be copolymerized with other components.
• dicarboxylic acid components as copolymerization components include isophthalic acid, naphthalenedicarboxylic acid, 4,4-diphenyldicarboxylic acid, adipic acid, sebacic acid, and ester-forming derivatives thereof.
• diol components as copolymerization components include diethylene glycol, hexamethylene glycol, neopentyl glycol, and cyclohexanedimethanol.
• polyoxyalkylene glycols such as polyethylene glycol and polypropylene glycol can also be mentioned. These may be used alone or in combination.
• isophthalic acid is generally copolymerized with the PET that constitutes PET bottles to improve moldability into bottles, it is preferable that the chemically recycled PET contains at least an isophthalic acid component as a copolymerization component.
• the moles of the copolymerization components are preferably 10 mole% or less, more preferably 8 mole% or less, even more preferably 5 mole% or less, and even more preferably 3 mole% or less.
• the moles of the copolymerization components are preferably 0.1 mole% or more, more preferably 1 mole% or more, and even more preferably 2 mole% or more.
• the chemically recycled polyester may contain one or more types of copolymerization components that satisfy such suitable mole numbers.
• the chemically recycled polyester is chemically recycled PET
• the moles of isophthalic acid components are preferably 10 mole% or less, more preferably 8 mole% or less, even more preferably 5 mole% or less, and even more preferably 3 mole% or less.
• the moles of isophthalic acid components are preferably 0.1 mole% or more, more preferably 1 mole% or more, and even more preferably 2 mole% or more.
• the chemically recycled PET may contain one or more types of isophthalic acid components that satisfy such a suitable mole number of the isophthalic acid components.
• the intrinsic viscosity of the chemically recycled polyester is preferably 0.58 dl/g or more, more preferably 0.60 dl/g or more, and even more preferably 0.62 dl/g or more. If it is 0.58 dl/g or more, the area ratio of the region with a molecular weight of 1000 or less in the chemically recycled polyester, i.e., the amount of low molecular weight components, can be reduced, so that the deterioration of the shrinkage rate after aging of the heat-shrinkable polyester film can be further reduced.
• the intrinsic viscosity of the chemically recycled polyester is preferably 0.90 dl/g or less, more preferably 0.85 dl/g or less, and even more preferably 0.80 dl/g or less. If it is 0.90 dl/g or less, the shrinkage stress of the heat-shrinkable polyester film can be suppressed, so that when used as a label, sink marks at the time of shrinkage finishing can be further reduced, and as a result, a label with good shrinkage finishing can be obtained.
• the chemically recycled polyester may contain one or more types that satisfy such a suitable intrinsic viscosity.
• the area ratio of the region of molecular weight of 1000 or less in chemically recycled polyester, i.e., low molecular weight components, is 1.0% or more and 5.5% or less. If it is less than 1.0%, the shrinkage stress increases. If it is more than 5.5%, the shrinkage performance after aging decreases significantly.
• the low molecular weight components of chemically recycled polyester are preferably 1.1% or more and 5.3% or less, and more preferably 1.2% or more and 5.1% or less. Chemically recycled polyester is more preferable because it has less low molecular weight components compared to mechanically recycled polyester. Note that chemically recycled polyester may contain one or more types of such suitable low molecular weight components.
• Fossil fuel-derived polyester The heat-shrinkable polyester film may contain fossil fuel-derived polyester, i.e., virgin polyester.
• Fossil fuel-derived polyester is a polyester obtained by condensation polymerization of a fossil fuel-derived diol compound and a fossil fuel-derived dicarboxylic acid compound.
• the fossil fuel-derived polyester preferably has ethylene terephthalate units, and preferably has ethylene terephthalate as the main constituent.
• the main constituent refers to 50 mol% or more of the total ester components (100 mol%) that make up the fossil fuel-derived polyester.
• the fossil fuel-derived polyester preferably has one or more units derived from monomers that can become amorphous components. A description of these units will be omitted here, as they overlap with the description below.
• the total content of the mechanically recycled and/or chemically recycled polyester and the fossil fuel-derived polyester is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 97% by mass or more.
• polyesters of the heat-shrinkable polyester-based film contains polyester as described above.
• This polyester i.e., the polyester of the heat-shrinkable polyester-based film, contains mechanically recycled and/or chemically recycled polyester as described above.
• the polyester of the heat-shrinkable polyester-based film may further contain fossil fuel-derived polyester as described above.
• the "polyester of the heat-shrinkable polyester-based film" may be referred to as the "polyester used in the heat-shrinkable polyester-based film.”
• the polyester used in the heat-shrinkable polyester film of the present invention preferably has an ethylene terephthalate unit, and preferably has ethylene terephthalate as the main component.
• the main component refers to 50 mol% or more of the total ester components (100 mol%) that make up the polyester.
• the heat-shrinkable polyester film of the present invention contains a polyester that can be an amorphous component in order to ensure heat shrinkability, and specific examples of the monomer include neopentyl glycol, 1,4-cyclohexanedimethanol, 1,4-butanediol, isophthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, 2,2-isopropyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, and hexanediol.
• the monomer include neopentyl glycol, 1,4-cyclohexanedimethanol, 1,4-butanedi
• the polyester in the heat-shrinkable polyester film preferably has units derived from one or more monomers that can become amorphous components.
• the units (total amount) derived from one or more monomers that can become amorphous components are preferably 6 mol% to 30 mol% of the total polyester resin components (100 mol%).
• the monomers that can become amorphous components are preferably 6 mol% to 30 mol% of the 100 mol% polyhydric alcohol components or 100 mol% polycarboxylic acid components that constitute the polyester of the heat-shrinkable polyester film. If the amorphous components are less than 6 mol%, the heat shrinkage properties will be inferior.
• the monomers that can become amorphous components are preferably 8 mol% to 25 mol% of the 100 mol% polyhydric alcohol components or 100 mol% polycarboxylic acid components in the total polyester resin.
• the polyester resin that constitutes the film will contain a mixture of constituent units consisting of terephthalic acid and neopentyl glycol, constituent units consisting of isophthalic acid and neopentyl glycol, and constituent units consisting of isophthalic acid and ethylene glycol.
• the constituent unit consisting of isophthalic acid and neopentyl glycol is a constituent unit derived from neopentyl glycol, and is also a constituent unit derived from one or more monomers that can become amorphous components. Therefore, in the present invention, the content of the constituent unit consisting of isophthalic acid and neopentyl glycol is counted as a constituent unit derived from neopentyl glycol, and as a constituent unit derived from one or more monomers that can become amorphous components.
• the content of the constituent unit derived from neopentyl glycol is the total content of the constituent unit consisting of isophthalic acid and neopentyl glycol and the content of the constituent unit consisting of terephthalic acid and neopentyl glycol.
• the content of the constituent unit derived from one or more monomers that can become amorphous components is the total content of the constituent units derived from one or more monomers that can become all amorphous components, including the content of the constituent unit consisting of isophthalic acid and neopentyl glycol and the content of the constituent unit consisting of isophthalic acid and ethylene glycol.
• dicarboxylic acid components constituting the polyester of the present invention include aromatic dicarboxylic acids such as orthophthalic acid; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid; and alicyclic dicarboxylic acids.
• an aliphatic dicarboxylic acid e.g., adipic acid, sebacic acid, decanedicarboxylic acid, etc.
• the content is preferably less than 3 mol % (out of 100 mol % of the dicarboxylic acid component).
• Heat-shrinkable polyester films obtained using polyesters containing 3 mol % or more of these aliphatic dicarboxylic acids have insufficient film stiffness when applied at high speed. Note that aliphatic carboxylic acids may be used alone or in combination to satisfy these preferred contents.
• the polyester does not contain trivalent or higher polyvalent carboxylic acids (e.g., trimellitic acid, pyromellitic acid, and anhydrides thereof). Heat-shrinkable polyester films obtained using polyesters containing these polyvalent carboxylic acids will have difficulty achieving the required high shrinkage rate.
• trivalent or higher polyvalent carboxylic acids e.g., trimellitic acid, pyromellitic acid, and anhydrides thereof.
• polyhydric alcohol components that make up the polyester include aromatic diols such as bisphenol A and diethylene glycol.
• the polyester used in the present invention is preferably a polyester whose glass transition point (Tg) is adjusted to 50 to 80°C by appropriately selecting the amount of neopentyl glycol or a monomer that can become an amorphous component.
• the glass transition point (Tg) of the polyester in the heat-shrinkable polyester film is preferably 50 to 80°C.
• the polyester does not contain diols having 8 or more carbon atoms (e.g., octanediol, etc.) or polyhydric alcohols having three or more valences (e.g., trimethylolpropane, trimethylolethane, glycerin, diglycerin, etc.). Heat-shrinkable polyester films obtained using polyesters containing these diols or polyhydric alcohols have difficulty in achieving the required high shrinkage rate. It is also preferable that the polyester does not contain triethylene glycol or polyethylene glycol as much as possible.
• additives such as waxes, antioxidants, antistatic agents, crystal nucleating agents, viscosity reducers, heat stabilizers, coloring pigments, color inhibitors, UV absorbers, etc.
• waxes antioxidants, antistatic agents, crystal nucleating agents, viscosity reducers, heat stabilizers, coloring pigments, color inhibitors, UV absorbers, etc.
• fine particles as a lubricant to the resin forming the heat-shrinkable polyester film of the present invention to improve the workability (slipperiness) of the film.
• Any fine particles can be selected, but examples of inorganic fine particles include silica, alumina, titanium dioxide, calcium carbonate, kaolin, barium sulfate, etc., and organic fine particles include acrylic resin particles, melamine resin particles, silicone resin particles, cross-linked polystyrene particles, etc.
• the average particle size of the fine particles can be appropriately selected as needed within the range of 0.05 to 3.0 ⁇ m (measured with a Coulter counter).
• the above particles can be blended into the resin that forms the heat-shrinkable polyester film at any stage in the production of the polyester resin, but it is preferable to add the particles as a slurry dispersed in ethylene glycol or the like at the esterification stage or after the completion of the transesterification reaction and before the start of the polycondensation reaction, and then proceed with the polycondensation reaction. It is also preferable to blend a slurry of particles dispersed in ethylene glycol or water or the like with the polyester resin raw material using a vented kneading extruder, or to blend dried particles with the polyester resin raw material using a kneading extruder.
• the polyester resin raw material referred to here includes fossil fuel-derived polyester, chemically recycled polyester, and mechanically recycled polyester.
• the recycled polyester contained in the heat-shrinkable polyester film of the present invention may be either one of mechanically recycled polyester and chemically recycled polyester, or both may be used in combination.
• the content of recycled polyester is preferably 1% by mass or more and 50% by mass or less when the entire film is taken as 100% by mass. That is, when the polyester composition of the heat-shrinkable polyester film is taken as 100% by mass, the content of recycled polyester in the polyester composition is preferably 1% by mass or more and 50% by mass or less. If it is 1% by mass or less, the contribution to reducing the environmental load is extremely small.
• the mass% ratio of the polyester of a specific composition that exhibits heat shrinkability in the entire film layer decreases, and a sufficient shrinkage rate cannot be obtained.
• the content of recycled polyester is preferably 3% by mass or more and 48% by mass or less, and more preferably 5% by mass or more and 46% by mass or less.
• one or more kinds of recycled polyester may be used as long as they satisfy these suitable contents.
• the intrinsic viscosity of the heat-shrinkable polyester film of the present invention is 0.58 dl/g or more, preferably 0.60 dl/g or more, and more preferably 0.62 dl/g or more.
• the intrinsic viscosity of the heat-shrinkable polyester film is 0.75 dl/g or less, more preferably 0.73 dl/g or less, and even more preferably 0.71 dl/g or less.
• the intrinsic viscosity of 0.75 dl/g or less it is possible to reduce the shrinkage stress of the heat-shrinkable polyester film, and therefore it is possible to prevent or reduce the occurrence of sink marks when a label made of the heat-shrinkable polyester film is shrunk and finished.
• the area ratio of the region of molecular weight of 1000 or less is 1.0% to 6.0% of the total peak area.
• the present inventors have newly found that by making it 6.0% or less, that is, by setting an upper limit on the content of components having a molecular weight of 1,000 or less (i.e., low molecular weight components), it is possible to suppress the deterioration of the performance of the heat-shrinkable polyester film after aging.
• the present inventors have also found that the preferable numerical range of the area ratio is different between mechanically recycled polyester and chemically recycled polyester.
• this area ratio is preferably 2.0% or more and 6.0% or less. If it is less than 2.0%, the extrusion temperature must be lowered, which can result in unmelted resin and increased shrinkage stress. Therefore, 2.0% or more is preferable, 2.5% or more is preferable, and 3.0% or more is more preferable. If it is more than 6.0%, the amount of enthalpy relaxation increases and performance after aging deteriorates. Therefore, 6.0% or less is preferable, 5.8% or less is preferable, and 5.5% or less is more preferable.
• the mechanically recycled polyester may contain one or more types that satisfy these suitable low molecular weight components.
• the content is preferably 1.0% or more and 5.5% or less. It is known that chemically recycled polyester has less heat history than mechanically recycled polyester, and therefore has a relatively small amount of low molecular weight components. If it is less than 1.0%, the extrusion temperature must be lowered, which can result in unmelted resin and an increase in shrinkage stress. Therefore, 1.0% or more is preferable, 1.5% or more is preferable, and 2.0% or more is more preferable. If it is more than 5.5%, the amount of enthalpy relaxation increases and the performance after aging deteriorates. Therefore, 5.5% or less is preferable, 5.3% or less is preferable, and 5.1% or less is more preferable.
• the chemically recycled polyester may contain one or more of these suitable low molecular weight components.
• the area percentage of the region with a molecular weight of 1000 or less multiple types of recycled polyesters may be used as the recycled polyester from among mechanically recycled polyesters and one or more other types of recycled polyesters including chemically recycled polyesters, and in such cases, the area percentage of the region with a molecular weight of 1000 or less is not limited to the preferred range described above.
• Hot water heat shrinkage rate ⁇ (length before shrinkage - length after shrinkage) / length before shrinkage ⁇ x 100 (%)
• the heat shrinkage rate at 90°C is preferably 20.0% or more and 80.0% or less.
• the shrinkage rate at 90°C is more preferably 25.0% or more, and more preferably 30.0% or more. On the other hand, if the shrinkage rate at 90°C exceeds 80.0%, the shrinkage stress becomes high.
• the shrinkage rate at 90°C is preferably 79.0% or less, and more preferably 78.0% or less.
• the "heat shrinkage rate at 90°C” can be expressed as the heat shrinkage rate in the main shrinkage direction when the heat-shrinkable polyester film is immersed in 90°C hot water, i.e., 90°C hot water, for 10 seconds. More specifically, the "heat shrinkage rate at 90°C” can be expressed as the heat shrinkage rate in the main shrinkage direction when a heat-shrinkable polyester film is immersed in 90°C warm water for 10 seconds under no load, and then the heat-shrinkable polyester film is immediately immersed in water at 25°C ⁇ 0.5°C for 10 seconds after being removed from the warm water.
• the heat shrinkage rate at 70°C is preferably 10.0% or more and 40.0% or less.
• the shrinkage amount at low temperatures is small, and when used as a label, the label after heat shrinkage may move upward (jump up).
• the shrinkage rate at 70°C is more preferably 11.0% or more, and more preferably 12.0% or more.
• the shrinkage rate at 70°C exceeds 40.0%, the label after shrinkage may be distorted.
• the shrinkage rate at 70°C is preferably 39.0% or less, and more preferably 38.0% or less.
• the "heat shrinkage rate at 70°C" can be expressed as the heat shrinkage rate in the main shrinkage direction when the heat-shrinkable polyester film is immersed in 70°C hot water, i.e., 70°C hot water, for 10 seconds.
• the "heat shrinkage rate at 70°C” can be expressed as the heat shrinkage rate in the main shrinkage direction when a heat-shrinkable polyester film is immersed in warm water at 70°C for 10 seconds under no load, and then the heat-shrinkable polyester film is immediately immersed in water at 25°C ⁇ 0.5°C for 10 seconds after being removed from the warm water.
• the main shrinkage direction is preferably the width direction of the heat-shrinkable polyester film.
• ⁇ Film shrinkage rate after aging> A heat-shrinkable polyester film aged at 30°C and 85% RH for 672 hours is immersed in 70°C hot water for 10 seconds without load, and the film is immediately immersed in water at 25°C ⁇ 0.5°C for 10 seconds.
• the heat shrinkage rate at 70°C in the main shrinkage direction of the film is calculated from the length before and after shrinkage using the above formula 1.
• the heat shrinkage rate is sometimes referred to as the shrinkage rate of the film after aging or the shrinkage rate after aging.
• the shrinkage rate after aging is preferably 10.0% or more and 40.0% or less.
• the shrinkage amount at low temperatures is small, and when used as a label, the label after heat shrinkage may move to the top (jump up). If it is more than 40.0%, the label after shrinkage may be distorted.
• the shrinkage rate after aging is preferably 11.0% or more and 39.0% or less, and more preferably 12.0% or more and 38.0% or less.
• the aging reduction rate can be determined by the following method.
• a heat-shrinkable film i.e., a heat-shrinkable polyester film
• a heat-shrinkable film aged at 30°C and 85% RH for 672 hours are immersed in warm water at 70°C for 10 seconds under no load to cause heat shrinkage, then immersed in water at 25°C ⁇ 0.5°C for 10 seconds, pulled out of the water, and the dimensions of the film in the longitudinal and transverse directions are measured, and the heat shrinkage rate is determined according to formula 1.
• the direction in which the heat shrinkage rate is greater in each film is defined as the main shrinkage direction (width direction).
• the difference (absolute value) between the shrinkage rate of the heat-shrinkable film and the shrinkage rate in the main shrinkage direction of the film after aging treatment is defined as the aging reduction rate (%). That is, the aging reduction rate (%) is the absolute value of the difference between the 70°C heat shrinkage rate in the main shrinkage direction of a heat-shrinkable film and the 70°C heat shrinkage rate in the main shrinkage direction of a heat-shrinkable film aged at 30°C and 85% RH for 672 hours.
• the aging reduction rate is preferably 15.0% or less, more preferably 14.5% or less, and more preferably 14.0% or less. If it is more than 15.0%, the shrinkage characteristics after aging are deteriorated, and there is a risk of slackening when used as a label.
• the aging reduction rate may be, for example, 10.0% or less, 8.0% or less, or 7.0% or less. Also, 0.0% or more is preferable. At present, a technical level of 1.0% or more is sufficient for practical use.
• the shrinkage stress of the heat-shrinkable polyester film of the present invention (not placed in an aging atmosphere) is preferably 3.0 MPa or more and 15.0 MPa or less, more preferably 4.0 MPa or more and 14.0 MPa or less, and even more preferably 5.0 MPa or more and 13.0 MPa or less.
• the shrinkage stress is the maximum shrinkage stress in the main shrinkage direction at 90° C.
• the maximum shrinkage stress in the main shrinkage direction at 90° C. is usually observed within 10 seconds after the start of measurement of the shrinkage stress.
• the heat-shrinkable polyester film of the present invention (not placed in an aging atmosphere) preferably has a maximum shrinkage stress in the main shrinkage direction (hereinafter, width direction) measured in hot air at 90° C., usually observed within 10 seconds after the start of measurement of 3.0 MPa to 15.0 MPa, preferably 4.0 MPa to 14.0 MPa, more preferably 5.0 MPa to 13.0 MPa.
• width direction the main shrinkage direction measured in hot air at 90° C.
• the label is tightly wrapped around the bottle to suppress the thermal expansion of the bottle, thereby preventing the label from loosening after cooling the bottle, but if the maximum shrinkage stress at 90° C. in the film width direction is less than 3.0 MPa, the above effect may be insufficient.
• the maximum shrinkage stress at 90° C. exceeds 15.0 MPa, it is not preferable because the label cannot shrink slowly and is likely to be distorted after heat shrinkage.
• the heat-shrinkable polyester film of the present invention preferably has an enthalpy relaxation amount of 4.0 J/g or less after aging for 672 hours under an atmosphere of 30° C. and 85% RH.
• an endothermic peak observed near the glass transition point indicates enthalpy relaxation.
• the amount of enthalpy relaxation can be obtained by integrating the peak area of the endothermic peak. A detailed measurement method will be described later.
• the enthalpy relaxation is the result of a decrease in the free volume of the amorphous part, and since the molecular chain becomes less mobile by that amount, it appears as an endothermic peak during the DSC temperature rise process.
• the amount of enthalpy relaxation after aging is preferably 4.0 g/J or less.
• the amount of enthalpy relaxation after aging is more preferably 3.8 g/J or less, and even more preferably 3.5 g/J or less.
• the enthalpy relaxation amount of a film that has not been aged under the above conditions is 0.1 g/J or less.
• the heat-shrinkable polyester film of the present invention is not particularly limited, but the thickness is preferably 10 ⁇ m or more and 200 ⁇ m or less, more preferably 20 ⁇ m or more and 100 ⁇ m or less.
• the haze value is preferably 2.0% or more and 13.0% or less. If the haze value exceeds 13.0%, the transparency becomes poor, and the appearance may become poor when making a label, which is not preferable.
• the haze value is more preferably 11.0% or less, and particularly preferably 9.0% or less. The smaller the haze value, the better, but considering that a certain amount of lubricant must be added to the film in order to impart the slipperiness required for practical use, the lower limit is about 2.0%.
• the heat-shrinkable polyester film of the present invention can also be subjected to corona treatment, coating treatment, flame treatment, etc. to improve the adhesion of the film surface.
• the heat-shrinkable polyester film of the present invention can be a single layer or a laminate of two or more layers.
• the manufacturing process of the heat shrinkable polyester film of the present invention is (1) mixing and supplying raw materials, (2) melt extrusion, (3) casting process of unstretched sheet, (4) transverse stretching process, and (5) final heat treatment process.
• Heat shrinkable films generally require amorphous components as raw materials, but the heat shrinkable polyester film of the present invention uses PET bottle recycled raw material chips, so it is necessary to use at least two or more types of raw material chips including PET bottle recycled raw material.
• a blending method is generally used as the method, and is also adopted in the present invention.
• the recycled PET bottle material and the amorphous material are melt-mixed in the extruder to carry out transesterification and turn them into polyester in a random copolymer state, which is important for increasing amorphousness.
• Transesterification is affected by the mixing condition of the resin in the extruder, temperature, time, etc.
• the melt extruder is mainly composed of a cylinder and a screw, but it is preferable to use a twin-screw extruder with two screws. This is because the rotation of the two screws promotes distributive mixing of the molten resin, increasing the interfacial area between resins of different components, and efficiently carrying out transesterification.
• the distributive mixing capacity is small, and in order to promote transesterification, it is necessary to raise the resin temperature or extend the residence time in the extruder. However, raising the temperature or extending the residence time also promotes the thermal decomposition of the resin, which is undesirable because it increases the amount of low-molecular components.
• multi-screw extruders can have screws that rotate in the same direction or in opposite directions, but it is preferable to use screws that rotate in the same direction. This is also to increase the distributive mixing capacity as mentioned above.
• a single start screw is not preferable because it has weak shear and does not promote transesterification.
• a three start screw is preferable from the viewpoint of promoting transesterification, but it has a smaller resin transport capacity, which can become a bottleneck in film production, which is becoming increasingly faster. Therefore, it is most preferable to use a screw with two starts.
• kneading discs In the melt mixing section near the middle of the extruder, it is preferable to use kneading discs as screw elements.
• kneading discs There are various types of kneading discs, including types with forward feeding capability (forward feed), types with return capability (reverse feed), and types without forward feeding capability (neutral), but it is more preferable to use a combination of each of these types.
• the residence time of the resin inside the extruder is determined by the shape of the screw, the rotation speed, etc., but is preferably between 60 and 300 seconds. If it is less than 60 seconds, unmelted components, especially unmelted recycled polyethylene terephthalate and polyester derived from fossil fuels, will be generated, putting a strain on the extruder. If it exceeds 300 seconds, decomposition of the resin will progress and low molecular weight components will increase, which is not preferable. More preferably, it is between 80 and 280 seconds, and even more preferably, it is between 100 and 260 seconds.
• the ratio (Q/N) of the discharge rate of the extruder to the screw rotation speed, represented by formula (2), is called the filling rate, and is preferably 1.0 to 5.0.
• Q is the discharge rate (kg/h)
• N is the screw rotation speed (rpm).
• the filling rate exceeds 5.0, the resins are not mixed sufficiently, and the transesterification is not promoted, so that the crystallinity cannot be reduced.
• the filling rate is less than 1.0, the resin is easily deteriorated, which is not preferable because it causes the generation of low molecular weight components and foreign matter. More preferably, it is 1.2 to 4.8, and even more preferably, it is 1.4 to 4.6.
• Filling rate discharge rate (kg/h) ⁇ screw rotation speed (rpm) ... formula (2)
• the extruder is divided into a feed section, a melt mixing section, and an extrusion section from the raw material supply side, and the cylinder temperature in each section is preferably 200°C or more and 270°C or less in the feed section. If it is less than 200°C, a part of the resin (especially the PET bottle recycled raw material) is not melted completely, which is not preferable. If it exceeds 270°C, it is not preferable because it tends to wrap around the screw (especially highly amorphous raw materials). More preferably, it is 210°C or more and 260°C or less.
• the melt mixing section is preferably 260°C or more and 330°C or less.
• the transesterification reaction is not promoted, which is not preferred. If it exceeds 330°C, the decomposition of the resin proceeds and low molecular weight components are generated, which is not preferred. More preferably, it is 270°C or more and 310°C or less.
• the extrusion section is preferably 255°C or more and 300°C or less. If it is less than 230°C, the melt viscosity is too high, which increases the resin pressure and causes failure of the subsequent piping and foreign matter filter, which is not preferred. If it exceeds 300, the melt viscosity is low, which causes defects such as pulsation during subsequent extrusion from the die, which is not preferred.
• the extruder may be a multi-screw extruder having two or more screws. Specifically, a four-screw extruder, an eight-screw extruder, a sixteen-screw extruder, or the like can be suitably used.
• the unstretched sheet is extruded into a sheet using existing methods such as the T-die method and the tubular method.
• the sheet melt-extruded by the extruder is then quenched to obtain an unstretched film.
• a method for quenching the molten resin a method can be suitably adopted in which the molten resin is cast from a die onto a rotating drum and quenched and solidified to obtain a substantially unoriented resin sheet.
• the film is preferably stretched in a transverse uniaxial stretching manner only in the width direction.
• a method of performing longitudinal stretching in a process prior to the transverse stretching this is not preferred because the production machine becomes long and large.
• the unstretched sheet obtained as described above is introduced into a tenter device capable of holding both ends of the sheet with clips and heating it, and the film is heated to a predetermined temperature by hot air, and then stretched by widening the distance between the clips while conveying it in the longitudinal direction.
• the film temperature during the transverse stretching is preferably Tg+5°C or more and Tg+40°C or less.
• the stretching force becomes too high, which is not preferred because the risk of breakage increases. If the film temperature exceeds Tg+40°C, the stretching force is too low, which is not preferred because sufficient shrinkage cannot be imparted to the film.
• the stretching ratio is preferably 3 times or more and 7 times or less. If it is less than 3 times, the required shrinkage rate cannot be obtained or stretching unevenness becomes large, which is not preferred. Stretching at a ratio of more than 7 times is not preferred because the risk of breakage is high. More preferably, it is from 3.5 to 6.5 times, and further preferably from 4 to 6 times.
• the shrinkage rate decreases significantly when the final product is stored at room temperature, which is not preferable. If the relaxation rate is less than 0.5%, the relaxation of the molecular orientation of the low molecular weight components in the width direction is not performed sufficiently, which is not preferable. If the relaxation ratio is more than 20%, not only the orientation of the low molecular weight component but also the orientation of the high molecular weight component is reduced, which is undesirable since it reduces the shrinkage characteristics.
• the relaxation ratio is preferably 1.0% or more and 18.0% or less, and more preferably 1.5% or more and 16.0% or less. This allows the heat-shrinkable polyester film of the present invention to be obtained.
• the heat-shrinkable polyester film of the present invention can be labeled by a conventional method.
• a heat-shrinkable polyester film cut to a desired width is appropriately printed, and the left and right ends of the film are overlapped and bonded using the above-mentioned solvent composition to produce a tube film.
• This tube film is then cut to an appropriate length to produce a tube-shaped label.
• the label is placed on a PET bottle, and the PET bottle is placed on a belt conveyor or the like and passed through a shrink tunnel that blows steam (steam tunnel) or a shrink tunnel that blows hot air (hot air tunnel).
• the label thermally shrinks as it passes through these tunnels, and the label is attached to the bottle container, such as a PET bottle.
• the packaging of the present invention is preferably made from the heat-shrinkable polyester film of the present invention, and is formed by covering at least a part of the outer periphery of an object to be packaged with a label, preferably having a perforation or notch, and then heat-shrinking the label.
• objects to be packaged include PET bottles for beverages, various bottles, cans, plastic containers for sweets and lunch boxes, and paper boxes.
• a label made from a heat-shrinkable polyester film is heat-shrunk to cover such objects to be packaged, the label is usually heat-shrunk by about 5 to 70% to be adhered to the packaging.
• the label to be covered on the object to be packaged may or may not be printed.
• ⁇ Content of terephthalic acid and isophthalic acid components A sample (specifically, raw polyester and heat-shrinkable polyester film) was dissolved in a solvent in which chloroform D (manufactured by Eurisopp) and trifluoroacetic acid-D1 (manufactured by Eurisopp) were mixed at a volume ratio of 10:1. Proton NMR was measured for this sample solution using a nuclear magnetic resonance (NMR) spectrometer ("GEMINI-200" manufactured by Varian) under measurement conditions of a temperature of 23°C and an accumulation number of 64. In this NMR measurement, the peak intensity of a predetermined proton was calculated, and then the content (mol %) of the terephthalic acid component and the isophthalic acid component in 100 mol % of the acid component was calculated.
• NMR nuclear magnetic resonance
• GPC gel permeation chromatography
• the area outside the calibration curve is generally excluded from the calculation range of the GPC analysis.
• the GPC chromatogram area i.e., the total peak area
• Heat shrinkage rate and heat shrinkage rate after aging The heat shrinkable film or the film aged for 672 hours at 30°C and 85% R.H. was cut into a 10 cm x 10 cm square and immersed in warm water of a specified temperature ⁇ 0.5°C for 10 seconds under no load to cause heat shrinkage, then immersed in water at 25°C ⁇ 0.5°C for 10 seconds and pulled out of the water to measure the longitudinal and lateral dimensions of the film, and the heat shrinkage rate was calculated according to the following formula 1. The direction with the largest heat shrinkage rate was determined as the main shrinkage direction (width direction).
• Heat shrinkage rate ⁇ (length before shrinkage - length after shrinkage) / length before shrinkage ⁇ x 100 (%)
• the heat shrinkage rate measured using a heat-shrinkable film is the shrinkage rate before aging
• the heat shrinkage rate measured using a film aged at 30° C. and 85% RH for 672 hours is the shrinkage rate after aging.
• ⁇ Aging decrease rate> The heat shrinkable film and the film aged at 30°C and 85% RH for 672 hours were cut into 10 cm x 10 cm squares, immersed in 70°C warm water for 10 seconds without load to allow heat shrinkage, immersed in 25°C ⁇ 0.5°C water for 10 seconds, and pulled out of the water to measure the longitudinal and transverse dimensions of the film, and the heat shrinkage rate was calculated according to formula 1.
• the direction with the larger heat shrinkage rate was determined as the main shrinkage direction (width direction).
• ⁇ Enthalpy relaxation amount> Using a temperature modulated differential scanning calorimeter (DSC) "Q100" (manufactured by TA Instruments), 4.0 mg of a film sample after aging for 672 hours under an atmosphere of 30°C and 85% RH was weighed into a hermetic aluminum pan, and measurement was performed in MDSC (registered trademark) heat only mode at an average heating rate of 2.0°C/min and a modulation period of 50 seconds. The peak area of the enthalpy relaxation portion near the glass transition point of the non-reverse heat flow obtained was taken as the enthalpy relaxation amount (J/g). Furthermore, in the reverse heat flow obtained by measuring in the same manner as the non-reverse heat flow described above, a baseline shift occurred near the Tg without any disturbance, confirming that the non-reverse heat flow measurement was also performed normally.
• DSC temperature modulated differential scanning calorimeter
• ⁇ Shrinkage stress> A sample having a length of 200 mm in the main shrinkage direction and a width of 20 mm was cut out from a heat-shrinkable film that had not been placed in an aging environment (unless otherwise specified, the term "heat-shrinkable film” hereinafter refers to a heat-shrinkable film that had not been placed in an aging environment), and was measured using a heating furnace-equipped strength and elongation measuring instrument (Tensilon (registered trademark of Orientec Co., Ltd.)). The heating furnace was preheated to 90°C, and the distance between the chucks was 100 mm.
• the airflow from the heating furnace was stopped once, the door of the heating furnace was opened, and the sample was attached to the chuck, after which the door of the heating furnace was quickly closed and airflow was resumed.
• the shrinkage stress was measured for 30 seconds or more, and the maximum value during the measurement was used as the maximum shrinkage stress (MPa).
• the filters were installed in the extruder up to the third stage filter so that the mesh size was successively smaller.
• the mesh size of the third stage filter was 50 ⁇ m. In this manner, a mechanically recycled polyester with an intrinsic viscosity of 0.69 dl/g, i.e., polyester A, was obtained.
• PET bottles were crushed in a wet crusher together with a cleaning solution (specifically, a cleaning solution of 1000 liters of water and 500 g of liquid kitchen detergent) while circulating it.
• a gravity separator connected to the wet crusher allowed foreign matter with a high specific gravity, such as metal, sand, and glass, to settle, and flakes were taken out from the upper layer.
• the flakes were rinsed with pure water and centrifuged. The recovered flakes were obtained by this procedure.
• the filtrate was further cooled, and after confirming that the crude BHET was completely dissolved, the filtrate was passed through an activated carbon bed at 50° C. to 51° C. and then through an anion/cation exchange mixed bed for 30 minutes, i.e., a pre-purification treatment was performed.
• the pre-purified solution was charged into a stirring autoclave and heated to distill off excess ethylene glycol at normal pressure, thereby obtaining a molten solution of concentrated BHET.
• the concentrated BHET melt was allowed to cool naturally while stirring under a nitrogen gas atmosphere, and then removed from the stirring autoclave to obtain a block of concentrated BHET flakes.
• the block of fine pieces was heated to 130° C.
• purified BHET 2650 kg of this purified BHET was fed at once to a dissolution tank purged with nitrogen, and after replacing with nitrogen again, dissolution was carried out at a temperature of 150° C. After completion of dissolution, the temperature of the dissolution tank was raised to 230° C. over 30 minutes while stirring.
• 2650 kg of the obtained BHET solution was transferred to a polycondensation reaction tank, and 300 ppm of antimony trioxide, 170 ppm of cobalt acetate, 55 ppm of phosphoric acid, and 0.3 wt % of titanium dioxide were added to the BHET solution relative to the amount of PET obtained (approximately 2000 kg of PET can be obtained from 2650 kg of BHET), and the temperature of the polycondensation reaction tank was gradually raised from 230° C. to 290° C. while stirring at 10 to 40 rpm, and the pressure was reduced to 40 Pa. When a predetermined stirring torque was reached, the polycondensation reaction vessel was purged with nitrogen to return to normal pressure and terminate the polycondensation reaction.
• the resulting mixture was discharged in the form of strands, cooled, and immediately cut to obtain polyester chips.
• the obtained polyester was continuously fed to a crystallizer and crystallized at 150° C., then fed to a dryer and dried at 130° C. for 10 hours.
• the dried polyester B was sent to a preheater and heated to 180° C. before being fed to a solid-state polymerizer.
• a solid-state polymerization reaction was carried out at 190° C. for 24 hours under nitrogen gas to obtain a chemically recycled polyester having an intrinsic viscosity of 0.79 dl/g, i.e., polyester B.
• polyester E is polyethylene terephthalate.
• SiO2 SiO2 (Silysia 266 manufactured by Fuji Silysia Corporation) was added as a lubricant to the polyester during the production of polyester F, and this was used as polyester F.
• Polyesters C and D were synthesized in the same manner as polyester E, except that the polyhydric alcohol components charged in the autoclave were changed according to Table 1.
• TPA is terephthalic acid
• IPA is isophthalic acid
• EG is ethylene glycol
• NPG is neopentyl glycol
• BD is 1,4-butanediol
• DEG is diethylene glycol
• CHDM is 1,4-cyclohexanedimethanol.
• the intrinsic viscosity of each polyester is shown in Table 1. Each polyester was appropriately cut into chips. It should be noted that terephthalic acid, neopentyl glycol, diethylene glycol, and 1,4-cyclohexanedimethanol were not derived from used polyester products, but from fossil fuels.
• a twin-screw extruder was used as the extruder. The screw had a kneading disk, and the number of threads was two. The screw rotation speed was 200 rpm.
• the cylinder temperature of the feed section of the extruder was 215°C
• the cylinder temperature of the melt mixing section was 300°C
• the cylinder temperature of the extrusion section was 265°C.
• a gear pump was installed after the extruder, and the discharge rate was adjusted to 473 kg/h.
• the filling rate was 2.4.
• the resin extruded from the extruder was extruded from a T-die and then quenched to obtain an unstretched film.
• This unstretched film was introduced into a tenter, preheated at a set temperature of 105°C, and then stretched 4.5 times in the width direction at a stretching temperature of 75°C by widening the clip interval. Further, it was introduced into a final heat treatment zone, heat treated at a film temperature of 78°C, and the stretching pattern was narrowed so that the relaxation rate (relaxation rate) in the width direction was 3%, and then cooled.
• the film was obtained by cutting and removing both edges and winding it into a roll with a width of 500 mm.
• the thickness of the film after stretching was 40 ⁇ m.
• the film was continuously wound using a paper tube to obtain a film roll.
• the production method and the evaluation results of the film are shown in Table 2.
• Example 2 The mixing ratio of the raw materials, the discharge amount, the cylinder temperature, and the tenter relaxation rate were variously changed, and films were obtained.
• the film production conditions and evaluation results are shown in Table 2.
• Comparative Examples 1 to 6 Films of Comparative Examples 1 to 6 were prepared under the polyester blend ratios and film-forming conditions shown in Table 2. The results are shown in Table 2.
• the heat-shrinkable polyester film of the embodiment of the present invention is a transversely uniaxially stretched film that contains a specified amount of recycled polyester and has a specified heat shrinkage rate and an area ratio of a region with a molecular weight of 1000 or less.
• the finish of the label is good, there is little deterioration in the heat shrinkage properties after aging, and the shrink finish of the label after aging is also excellent.
• the raw polyester contained CHDM, which caused thermal decomposition during the melting process, resulting in a high area ratio of regions with molecular weights of 1000 or less, a large rate of aging deterioration, and sagging of the label was observed in the shrink finish after aging.
• Comparative Example 6 does not contain recycled polyester, so its contribution to reducing the environmental impact is extremely small.
• the heat-shrinkable polyester film of the present invention has the excellent properties described above, and can therefore be suitably used for labeling bottles and the like.
• Bottles and other packaging products obtained by using the heat-shrinkable polyester film of the present invention as a label have a beautiful appearance.

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