Polyester-based resin, polyester-based container, polyester-based film, polyester-based fiber, and method for producing polyester-based resin

Abstract

The present invention provides a resin as a polyester resin having excellent mechanical recyclability and optical characteristics without deteriorating mechanical characteristics even if a binder is included in a mechanical recycling step. A polyester resin which is a reactant of a polyester (A) having a glass transition temperature of 30 DEG C or more and less than 140 DEG C and a polyester (B1) having a glass transition temperature of-80 DEG C or more and less than 30 DEG C.

Description

Technical Field

[0001] This invention relates to polyester resins, polyester containers, polyester films, polyester fibers, and methods for manufacturing polyester resins. More specifically, it relates to methods for manufacturing polyester resins, polyester containers, polyester films, polyester fibers, and polyester resins that do not degrade the mechanical properties of the resin and have excellent mechanical recyclability and optical properties. Background Technology

[0002] In recent years, due to problems such as environmental pollution and depletion of petroleum resources, there has been a strong desire for the recycling of polyester resin molded products such as polyester containers, polyester films, and polyester fibers.

[0003] For the recycling of polyester resin molded products, mechanical recycling and chemical recycling are known. From a cost perspective, mechanical recycling has become the mainstream.

[0004] The mechanical recycling typically refers to breaking used polyester resin molded products into granules or flakes, heating and melting them to homogenize the whole, and then using the resulting recycled resin as raw material for polyester resin molded products again.

[0005] Generally, polyester containers such as polyethylene terephthalate (PET) bottles have adhesive labels with various information affixed to their surfaces. Additionally, adhesive tapes based on PET film typically have an adhesive layer on top of the PET film.

[0006] When mechanically recycling polyester resin molded articles with adhesives, the adhesive acts as a foreign substance, reducing the mechanical properties of the resin and thus causing problems with recyclability and optical properties. Therefore, mechanically recycling polyester resin molded articles with adhesives requires an extremely complex operation of peeling off and removing the adhesive.

[0007] For example, Patent Document 1 discloses an adhesive label having a coating on one side of a polyester resin substrate that can be peeled off from the substrate by cleaning and impregnation with an alkaline aqueous solution and has printability, and a polyester adhesive layer on the opposite side, wherein the polyester resin substrate is compatible with a polyester container as the adhered object.

[0008] In addition, Patent Document 2 discloses an adhesive label that enables the recycling of polyester containers without peeling them off, and that can detach (peel off) the printed part in a short time in an alkaline aqueous solution at a low temperature (around 70°C).

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2000-10489

[0012] Patent Document 2: Japanese Patent Application Publication No. 2023-69194 Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] While the print layer exhibits excellent detachability in Patent Documents 1 and 2, issues remain regarding the recyclability and optical properties of polyester resin molded articles. Therefore, to improve the mechanical recyclability of polyester resin molded articles, there is a need for the diversification of adhesive materials and improvements in the recyclability of the adhesive itself.

[0015] Generally, acrylic adhesives are widely used in polyester molded products. However, acrylic adhesives become foreign matter when polyester is mechanically recycled, thus reducing mechanical properties, mechanical recyclability, and optical properties.

[0016] Therefore, in this context, the present invention provides a polyester resin and a method for manufacturing the polyester resin that do not suffer from reduced mechanical properties even when an adhesive is included in the mechanical recycling process, and that exhibit excellent mechanical recyclability and optical properties.

[0017] Solution for solving the problem

[0018] However, the inventors have discovered that the mechanical properties of polyester-based resins, which are reactants of polyester (A) with a glass transition temperature of 30°C or higher and less than 140°C and polyester (B1) with a glass transition temperature of -80°C or higher and less than 30°C, are not reduced, and that they have excellent mechanical recyclability and optical properties.

[0019] That is, the present invention is based on the following [1] to

[23] .

[0020] [1] A polyester resin, which is a reactant of a polyester (A) with a glass transition temperature of 30°C or higher and less than 140°C and a polyester (B1) with a glass transition temperature of -80°C or higher and less than 30°C.

[0021] [2] According to the polyester resin of [1], wherein the nitrogen atom content in the polyester resin is 0.1ppm to 1000ppm.

[0022] [3] The polyester resin according to [1] or [2], wherein the content of the structural units derived from polyester (B1) in the polyester resin is less than 10% by mass.

[0023] [4] The polyester resin according to any one of [1] to [3], wherein the glass transition temperature of the polyester resin is 30°C or higher.

[0024] [5] The polyester resin according to any one of [1] to [4], wherein the weight-average molecular weight of the polyester resin is 5,000 to 300,000.

[0025] [6] The polyester resin according to any one of [1] to [5], wherein the acid value of the polyester resin is less than 5 mg KOH / g.

[0026] [7] The polyester resin according to any one of [1] to [6], wherein the polyester resin has structural units derived from polycarboxylic acids and structural units derived from polyols, and the content of structural units derived from aromatic dicarboxylic acids in the polyester resin is 10% to 90% by mass.

[0027] [8] The polyester resin according to any one of [1] to [7], wherein the haze is 5% or less when the polyester resin is made into a sheet with a thickness of 50 μm.

[0028] [9] The polyester resin according to any one of [1] to [8], wherein the polyester (A) has structural units derived from terephthalic acid and structural units derived from ethylene glycol.

[0029]

[10] The polyester resin according to any one of [1] to [9], wherein the polyester (A) has structural units derived from recycled thermoplastic polyester (A1).

[0030]

[11] The polyester resin according to any one of [1] to

[10] , wherein the polyester (B1) has structural units derived from aromatic dicarboxylic acids.

[0031]

[12] The polyester resin according to any one of [1] to

[11] , wherein the content of aromatic dicarboxylic acids in the structural units of the polyester (B1) derived from polycarboxylic acids (Ba) is 10 mol% to 100 mol%.

[0032]

[13] The polyester resin according to any one of [1] to

[12] , wherein the content of aliphatic diols with 1 to 5 carbon atoms in the structural units of the polyester (B1) is 10 mol% to 100 mol%.

[0033]

[14] The polyester resin according to any one of [1] to

[13] , wherein the heat of fusion of the polyester (B1) is less than 10 J / g.

[0034]

[15] The polyester resin according to any one of [1] to

[14] , wherein the polyester (B1) is a crosslinked compound.

[0035]

[16] The polyester resin according to any one of [1] to

[15] , wherein the gel fraction of the crosslinked polymer of the polyester resin (B1) is 10% to 100%.

[0036]

[17] A polyester container comprising a polyester resin according to any one of [1] to

[16] .

[0037]

[18] A polyester film comprising any one of the polyester resins according to [1] to

[16] .

[0038]

[19] A polyester fiber comprising a polyester resin according to any one of [1] to

[16] .

[0039]

[20] A method for manufacturing a polyester resin, comprising a step of reacting a polyester (A) with a glass transition temperature of 30°C or higher and less than 140°C with a polyester (B1) with a glass transition temperature of -80°C or higher and less than 30°C.

[0040]

[21] The method for manufacturing polyester resin according to

[20] , wherein the process is carried out under a nitrogen atmosphere.

[0041]

[22] The method for manufacturing polyester resin according to

[20] or

[21] , wherein the process is carried out under vacuum conditions of 0.1 Torr to 50 Torr.

[0042]

[23] The method for manufacturing polyester resin according to any one of

[20] to

[22] , wherein, in the process, the resin is heated to 160°C to 280°C and melted.

[0043] Invention Effects

[0044] In this invention, a polyester with a glass transition temperature of 30°C or higher and less than 140°C reacts with a polyester in a polyester-based adhesive that has a glass transition temperature of -80°C or higher and less than 30°C. Therefore, there is no need to remove the adhesive, the mechanical properties of the resin are not reduced, and the mechanical recyclability and optical properties are excellent. Detailed Implementation

[0045] The present invention will now be described based on examples of methods for carrying out the invention. However, the present invention is not limited to the embodiments described below.

[0046] It should be noted that in this specification, "X and / or Y (X and Y can be any configuration)" refers to at least one of X and Y, and specifically refers to X only, Y only, or X and Y.

[0047] Furthermore, in this specification, when expressed as "X~Y" (where X and Y are arbitrary numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less", and also includes the meaning of "preferably greater than X" or "preferably less than Y".

[0048] Furthermore, when expressed as "X or above" (where X is any number) or "Y or below" (where Y is any number), it also implies "preferably greater than X" or "preferably less than Y".

[0049] In this specification, "membrane" refers to and also includes the meanings of "belt" and "sheet".

[0050] Furthermore, in this specification, the term "class" following the name of a compound refers to the concept of including not only the compound but also its derivatives. For example, the term "carboxylic acid class" refers to carboxylic acid derivatives such as carboxylate salts, carboxylic anhydrides, carboxylic acid halides, and carboxylic acid esters, in addition to carboxylic acids.

[0051] In this specification, "main component" refers to a component that has a significant impact on the properties of the object, and the content of this component is usually 50% by mass or more in the object, preferably 55% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and may also be 100% by mass.

[0052] Furthermore, regarding the numerical ranges described in stages in this specification, the upper or lower limit of a numerical range for a certain stage can be arbitrarily combined with the upper or lower limit of numerical ranges for other stages. Additionally, the upper or lower limit of the numerical range described in this specification can also be replaced with the values ​​shown in the embodiments.

[0053] The polyester resin of one embodiment of the present invention (hereinafter, sometimes referred to as "this polyester resin") is a reactant of a polyester (A) with a glass transition temperature of 30°C or higher and less than 140°C and a polyester (B1) with a glass transition temperature of -80°C or higher and less than 30°C. Hereinafter, "polyester (A) with a glass transition temperature of 30°C or higher and less than 140°C" will sometimes be referred to as "polyester (A)". "Polyester (B1) with a glass transition temperature of -80°C or higher and less than 30°C" will sometimes be referred to as "polyester (B1)".

[0054] The polyesters (A) and (B1) can be used as recycled waste, such as used products, waste generated during manufacturing, and unused products.

[0055] The shape of the polyester (A) is not particularly limited, but resin is preferred. Specific examples of resin include molded articles, containers such as liquid bottles, and substrate films such as tapes.

[0056] Furthermore, from the perspective of the excellent mechanical recyclability of polyester (A), the polyester (B1) is preferably included in a polyester-based adhesive (B) used for affixing labels to containers containing polyester (A) or as an adhesive layer of tape using a film containing polyester (A) as a substrate.

[0057] The following is a description of each component.

[0058] <Polyester (A)>

[0059] The glass transition temperature of the polyester (A) is above 30°C and below 140°C.

[0060] As for the polyester (A), from the perspectives of excellent formability, strength, heat resistance, and mechanical recyclability with polyester (B1), it is preferable that the molecule contains structural units derived from polycarboxylic acids (Aa) and structural units derived from polyols (Ab). Such a polyester (A) is usually obtained by forming ester bonds between polycarboxylic acids (Aa) and polyols (Ab).

[0061] Examples of the aforementioned polycarboxylic acids (Aa) include, for example, terephthalic acid, isophthalic acid, 2-chloroterephthalic acid, 2,5-dichloroterephthalic acid, 2-methylterephthalic acid, 4,4-stilbene dicarboxylic acid, 4,4-biphenyl dicarboxylic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, anthracene dicarboxylic acid, 4,4-diphenyl ether dicarboxylic acid, 4,4-diphenoxyethane dicarboxylic acid, sodium 5-sulfonic acid isophthalate, and other aromatic dicarboxylic acids, adipic acid, and sebacic acid. Azelaic acid derivatives, dodecanoic acid derivatives, malonic acid derivatives, succinic acid derivatives, glutaric acid derivatives, trimethyl adipic acid derivatives, pimelic acid derivatives, 3-methylglutaric acid derivatives, 2,2-dimethylglutaric acid derivatives, 1,9-nonanedicarboxylic acid derivatives, dimer acids derived from the dimerization of unsaturated monocarboxylic acids such as oleic acid, linoleic acid, linolenic acid, and erucic acid, as well as hydrogenated dimer acids obtained by hydrogenation of dimer acids, aliphatic dicarboxylic acids such as fumaric acid, maleic acid, and itaconic acid, 1,3-cyclohexanedicarboxylic acid derivatives, and 1,4-cyclohexanedicarboxylic acid derivatives, etc. These can be used alone or in combination of two or more.

[0062] Among them, aromatic dicarboxylic acids are preferred in terms of excellent formability, strength, heat resistance and mechanical recyclability, and terephthalic acid, isophthalic acid and phthalic acid are preferred in terms of better mechanical recyclability and optical properties, with terephthalic acid being more preferred.

[0063] Examples of polyols (Abs) include, for example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, neopentanediol, 3-methyl-1,5-pentanediol, 2-ethyl-2-butylpropanediol, aliphatic diols such as dimer diols derived from the dimerization of unsaturated monocarboxylic acids such as oleic acid, linoleic acid, linolenic acid, and erucic acid, alicyclic diols such as cyclohexanediol, difunctional alcohols such as terephthalic acid, bisphenol A, tetrabromobisphenol A, tetrabromobisphenol A-bis(2-hydroxyethyl ether), and trifunctional or higher alcohols such as glycerol, trimethylolpropane, and pentaerythritol. These can be used alone or in combination of two or more.

[0064] Among them, aliphatic diols are preferred in terms of excellent formability, strength, heat resistance and mechanical recyclability, and aliphatic diols with 1 to 5 carbon atoms are preferred in terms of better mechanical recyclability and optical properties, and ethylene glycol is even more preferred.

[0065] Furthermore, the polycarboxylic acids (Aa) and polyols (Ab) are preferably made from recycled thermoplastic polyesters (A1), such as unused molded polyester (A), substances obtained by pulverizing residues from the manufacturing of molded polyester (A) products, or recycled products obtained by recycling and cleaning waste. From an environmental perspective, recycled products are preferred. These are substances that can be obtained commercially after washing, drying, granulation, or flake formation.

[0066] The polyester (A) can be manufactured by polycondensation of a polymeric component containing a polycarboxylic acid (Aa) and a polyol (Ab) in the presence of a catalyst using a known method. During the polycondensation reaction, esterification and / or transesterification reactions are performed first, followed by polycondensation. Furthermore, when using recycled thermoplastic polyester (A1) as the polycarboxylic acid (Aa) and polyol (Ab), it is sufficient that the polymeric component contains the recycled thermoplastic polyester (A1) as is, and the resulting polyester resin (A) has structural units derived from the recycled thermoplastic polyester (A1).

[0067] Furthermore, the polyester (A) is preferably obtained using a polyol (Ab) having a molar ratio of 1.01 or more hydroxyl groups per mole of the carboxyl group relative to the polycarboxyl group (Aa), wherein the molar ratio is more preferably 1.05 to 2.5, more preferably 1.1 to 2.0, and even more preferably 1.2 to 1.7. That is, if the molar ratio is too small, there is a tendency for the esterification reaction and / or transesterification reaction to become incomplete. Furthermore, if the molar ratio is too large, there is a tendency for excessive diol to be distilled off, resulting in poor economic efficiency.

[0068] Specific examples of polyesters (A) include polyethylene terephthalate resins, propylene terephthalate resins, butylene terephthalate resins, polyethylene isophthalate resins, polyethylene naphthalate resins, butylene naphthalate resins, polyethylene terephthalate / polyethylene isophthalate resins, polyethylene glycol / neopentyl terephthalate resins, polybutylene succinate resins, and 3-hydroxybutyrate / 3-hydroxyhexanoate polymers.

[0069] Among them, the polyester (A) is preferably composed of structural units derived from terephthalic acid and structural units derived from ethylene glycol, from the perspectives of formability, strength, heat resistance and mechanical recyclability. More preferably, it is a polyethylene terephthalate resin, and even more preferably, it is a recycled polyethylene terephthalate resin.

[0070] The polyester (A) may also have structural units derived from other polycarboxylic acids (Aa) besides those constituting the basic structure and / or from other polyols (Ab) besides those constituting the basic structure, within a range of less than 50% by mass of the structural units.

[0071] The content of structural units derived from aromatic dicarboxylic acids in the polyester (A) is typically 10% to 90% by mass, preferably 30% to 85% by mass, more preferably 40% to 80% by mass, further preferably 50% to 75% by mass, and most preferably 60% to 70% by mass. If the content of structural units derived from aromatic polycarboxylic acids is within the aforementioned range, there is a tendency for excellent formability, strength, heat resistance, mechanical recyclability, and optical properties.

[0072] The content of structural units derived from aliphatic diols having 1 to 5 carbon atoms in the polyester (A) is typically 10% to 90% by mass, preferably 15% to 70% by mass, more preferably 20% to 60% by mass, further preferably 25% to 50% by mass, and most preferably 30% to 40% by mass. If the content of structural units derived from aliphatic diols having 1 to 5 carbon atoms is within the aforementioned range, there is a tendency for excellent formability, strength, heat resistance, mechanical recyclability, and optical properties.

[0073] Furthermore, when using recycled thermoplastic polyester (A1) as the polymerization component, the content of structural units derived from recycled thermoplastic polyester (A1) in the polyester (A) is generally preferably 10% by mass or more, more preferably 20% by mass to 100% by mass, further preferably 30% by mass to 90% by mass, and most preferably 40% by mass to 80% by mass. If the content of structural units derived from recycled thermoplastic polyester (A1) is within the above range, there is a tendency for excellent mechanical recyclability, optical properties, and environmental impact reduction.

[0074] When the polyester (A) has structural units derived from aromatic dicarboxylic acids, the content of structural units derived from aromatic dicarboxylic acids relative to structural units derived from polycarboxylic acids (Aa) is preferably 20 mol% or more, more preferably 40 mol% or more, further preferably 60 mol% or more, particularly preferably 80 mol% or more, and most preferably 90 mol% or more. If the content of structural units derived from aromatic dicarboxylic acids is within the specified range, there is a tendency for excellent formability, strength, heat resistance, mechanical recyclability, and optical properties.

[0075] When the polyester (A) has structural units derived from aliphatic dicarboxylic acids, the content of structural units derived from aliphatic dicarboxylic acids relative to structural units derived from polycarboxylic acids (Aa) is preferably 80 mol% or less, more preferably 60 mol% or less, further preferably 40 mol% or less, particularly preferably 20 mol% or less, and most preferably 10 mol% or less. If the content of structural units derived from aliphatic dicarboxylic acids is within this range, there is a tendency for excellent formability, strength, heat resistance, mechanical recyclability, and optical properties.

[0076] When the polyester (A) has structural units derived from aliphatic diols having 1 to 5 carbon atoms, the content of structural units derived from aliphatic diols having 1 to 5 carbon atoms relative to structural units derived from polyols (Ab) is preferably 20 mol% or more, more preferably 40 mol% or more, further preferably 60 mol% or more, particularly preferably 80 mol% or more, and most preferably 90 mol% or more. If the content of structural units derived from aliphatic diols having 1 to 5 carbon atoms is within this range, there is a tendency for excellent formability, strength, heat resistance, mechanical recyclability, and optical properties.

[0077] The glass transition temperature (Tg) of the polyester (A) is 30°C or higher and less than 140°C, preferably 40°C to 130°C, more preferably 50°C to 120°C, and even more preferably 60°C to 100°C. If the glass transition temperature (Tg) is within the range described above, it tends to have excellent formability, strength, heat resistance, mechanical recyclability, and optical properties.

[0078] From the perspective of excellent formability, strength, and heat resistance, the polyester (A) may also have a melting point. The melting point (Tm) of the polyester (A) is typically above 60°C, preferably 100°C to 300°C, more preferably 150°C to 280°C, and even more preferably 200°C to 260°C. If the melting point (Tm) is within the above range, there is a tendency for excellent formability, strength, and heat resistance.

[0079] From the perspective of excellent formability, strength, and heat resistance, the polyester (A) may also have a heat of fusion. The heat of fusion of the polyester (A) is typically below 100 J / g, preferably 0.1 J / g to 80 J / g, more preferably 1 J / g to 60 J / g, 3 J / g to 40 J / g, and even more preferably 5 J / g to 35 J / g. If the heat of fusion is within this range, there is a tendency for excellent formability, strength, and heat resistance.

[0080] The glass transition temperature (Tg), melting point (Tm), and heat of fusion of the crystal were measured using a differential scanning calorimeter (DSC, e.g., TA Instruments Q20). It should be noted that the measurement temperature range was -90°C to 200°C, and the temperature rise rate was 10°C / minute.

[0081] The weight-average molecular weight of the polyester (A) is typically 5,000 to 300,000, preferably 10,000 to 150,000, more preferably 20,000 to 100,000, and even more preferably 30,000 to 75,000. If the weight-average molecular weight is within the range described above, it tends to have excellent formability, strength, heat resistance, and mechanical recyclability.

[0082] The weight-average molecular weight was obtained by converting the molecular weight of standard polystyrene, and was determined by using two columns in a high-performance liquid chromatograph (TOSOH, "HLC-8320 GPC"): TSKgel SuperMultipore HZ-M (exclusion limit molecular weight: 2 × 10⁻⁶). 6 Theoretical plate number: 16000 plates / tube, packing material: styrene-divinylbenzene copolymer, packing particle size: 4μm) were used in series for determination.

[0083] The ester bond concentration of the polyester (A) is typically 1 mmol / g to 14 mmol / g, preferably 4 mmol / g to 13 mmol / g, more preferably 8 mmol / g to 12 mmol / g, and even more preferably 9 mmol / g to 11 mmol / g. If the ester bond concentration is within this range, it tends to exhibit excellent formability, strength, heat resistance, and mechanical recyclability.

[0084] The ester bond concentration (mmol / g) refers to the number of moles of ester bonds in 1g of polyester (A), which can be calculated, for example, based on the charge amount. This calculation method involves dividing the smaller mole count of the polycarboxylic acid (Aa) and polyol (Ab) by the total weight. An example of the calculation formula is shown below. It should be noted that the calculation method may be appropriately modified when using substances with both carboxyl and hydroxyl groups as monomers, or when polyesters are made from materials such as caprolactone.

[0085] <Cases where polycarboxylic acids (Aa) are less than polyols (Ab)>

[0086] Ester bond concentration (mmol / g) = [(D1 / d1×m1 + D2 / d2×m2 + D3 / d3×m3……) / Z]×1000

[0087] D: The amount of polycarboxylic acid (Aa) in the feed (g).

[0088] d: Molecular weight of polycarboxylic acids (Aa).

[0089] m: The number of carboxylic acid groups per molecule of a polycarboxylic acid (Aa).

[0090] Z: Finished product weight (g).

[0091] <Cases where polyols (Ab) are less than polycarboxylic acids (Aa)>

[0092] Ester bond concentration (mmol / g) = [(E1 / e1×n1 + E2 / e2×n2 + E3 / e3×n3……) / Z] × 1000

[0093] E: The amount of polyols (Ab) in the feed (g).

[0094] e: Molecular weight of polyols (Ab).

[0095] n: The number of hydroxyl groups per molecule of a polyol (Ab).

[0096] Z: Finished product weight (g).

[0097] In addition, the ester bond concentration can also be determined using known methods such as NMR (Nuclear Magnetic Resonance).

[0098] Methods for adjusting the concentration of the ester bond include, for example, selecting polyols with 4 or fewer carbon atoms as polyols (Ab), increasing the content of straight-chain alkyl aliphatic dicarboxylic acids as polycarboxylic acids (Aa), and combining the two.

[0099] The acid value of the polyester (A) is typically below 5 mg KOH / g, preferably below 4.5 mg KOH / g, more preferably below 4 mg KOH / g, further preferably below 3.5 mg KOH / g, particularly preferably below 3 mg KOH / g, and most preferably below 1 mg KOH / g. If the acid value is within this range, it tends to exhibit excellent hydrolysis resistance, heat resistance, mechanical recyclability, and optical properties. The acid value is determined based on JIS K0070 and by neutralization titration.

[0100] <Polyester Adhesives (B)>

[0101] The polyester-based adhesive (B) contains polyester (B1) as the main component, has adhesive properties at 25°C, and can be used as an adhesive for bonding materials.

[0102] The adhesiveness refers to the following: at 25°C, according to JIS Z0237:2009, a tilted rolling ball adhesiveness test is conducted with an inclined plate angle of 30°, and the result is that the ball number is 1 or higher.

[0103] From the perspective of mechanical recyclability and optical properties, the polyester adhesive (B) preferably contains polyester (B1) having structural units derived from polycarboxylic acids (Ba) and structural units derived from polyols (Bb), and more preferably contains aromatic dicarboxylic acids as structural units derived from polycarboxylic acids (Ba) and aliphatic diols with 1 to 5 carbon atoms as structural units derived from polyols (Bb).

[0104] [Polyester (B1)]

[0105] The glass transition temperature of the polyester (B1) is above -80°C and below 30°C.

[0106] The polyester (B1) is obtained by copolymerizing (condensing) polymers containing polycarboxylic acids (Ba) and polyols (Bb) as constituent raw materials, thereby having structural units derived from polycarboxylic acids (Ba) and structural units derived from polyols (Bb) as its resin composition.

[0107] [Polycarboxylic acids (Ba)]

[0108] As the polycarboxylic acid (Ba), examples include dicarboxylic acids and ternary or higher polycarboxylic acids. From the perspective of stably obtaining polyester (B1), dicarboxylic acids are preferred. These polycarboxylic acids (Ba) can be used alone or in combination of two or more.

[0109] Examples of dicarboxylic acids include, for example, terephthalic acid, isophthalic acid, 2-chloroterephthalic acid, 2,5-dichloroterephthalic acid, 2-methylterephthalic acid, 4,4-stilbene dicarboxylic acid, 4,4-biphenyl dicarboxylic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, anthracene dicarboxylic acid, 4,4-diphenyl ether dicarboxylic acid, 4,4-diphenoxyethane dicarboxylic acid, sodium 5-sulfonic acid isophthalate, etc., as well as aromatic dicarboxylic acids, adipic acid, sebacic acid, and nonyl phthalate. Dicarboxylic acids, including dodecanoic acid, malonic acid, succinic acid, glutaric acid, trimethyl adipic acid, pimelic acid, 3-methylglutaric acid, 2,2-dimethylglutaric acid, 1,9-nonanedicarboxylic acid, dimer acids derived from the dimerization of unsaturated monocarboxylic acids such as oleic acid, linoleic acid, linolenic acid, and erucic acid, as well as hydrogenated dimer acids obtained by hydrogenation of dimer acids, aliphatic dicarboxylic acids such as fumaric acid, maleic acid, and itaconic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid, etc., and alicyclic dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid.

[0110] In addition, examples of the three or more polycarboxylic acids include trimellitic acid, pyromellitic acid, adamantane tricarboxylic acid, and pyromellitic acid.

[0111] Among the polycarboxylic acids (Ba), aromatic dicarboxylic acids are preferred due to their superior hydrolysis resistance, heat resistance, mechanical recyclability, and optical properties of polyesters (B1). Furthermore, among the aromatic dicarboxylic acids, terephthalic acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, and furan dicarboxylic acid are more preferred for their superior mechanical recyclability. And isophthalic acid, phthalic acid, and furan dicarboxylic acid are further preferred for their superior ability to adjust the crystallinity, viscosity, and adhesiveness of polyester resins.

[0112] Furthermore, as a polycarboxylic acid (Ba), aliphatic dicarboxylic acids containing 4 or more carbon atoms (including carbons with carboxyl groups) are preferred. Among them, aliphatic dicarboxylic acids containing 6 to 12 carbon atoms (including carbons with carboxyl groups), such as adipic acid, pimelic acid, azelaic acid, and sebacic acid, are more preferred from the perspective of excellent adhesive strength, mechanical recyclability, and optical properties.

[0113] [Polyols (Bb)]

[0114] Examples of polyols (Bb) include diols and polyols with three or more nucleotides. These polyols (Bb) can be used alone or in combination of two or more.

[0115] Examples of such diols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, neopentanediol, 3-methyl-1,5-pentanediol, 2-ethyl-2-butylpropanediol, dimer diols derived from dimer acids derived by dimerizing unsaturated monocarboxylic acids such as oleic acid, linoleic acid, linolenic acid, and erucic acid, 2,4-diethyl-1,5-pentanediol, and 2,2,4-trimethyl- Aliphatic diols such as 1,3-pentanediol; alicyclic diols such as 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, spirocyclodiol, tricyclodecanediol, adamantanediol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol; aromatic diols such as 4,4'-thiodiphenol, 4,4'-methylenediphenol, 4,4'-dihydroxybiphenyl, o-dihydroxybenzene, m-dihydroxybenzene, p-dihydroxybenzene, 2,5-naphthol, terephthalic acid diol, and their ethylene oxide adducts and propylene oxide adducts.

[0116] Among them, from the perspective of excellent mechanical recyclability with polyester (A), aliphatic diols are preferred, aliphatic diols with 1 to 5 carbon atoms are more preferred, and ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 2,2-dimethyl-1,3-propanediol (neopentyl glycol) are even more preferred.

[0117] In addition, examples of polyols with three or more components include pentaerythritol, dipentaerythritol, tripentaerythritol, glycerol, trimethylolpropane, trimethylolethane, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6-hexanetriol, 1,3,6-hexanetriol, adamantanetriol, etc.

[0118] Among the polyols (Bb), diols with hydrocarbon side chains are preferred from the perspective of increasing branching points and disrupting crystallinity. Examples of such diols with hydrocarbon side chains include 1,2-propanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol, 2-methyl-1,3-propanediol, neopentyl glycol, 2-methyl-2-ethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1,3-butanediol, 3-methyl-1,5-pentanediol, and 2,2,4-trimethyl- Branched aliphatic diols include 1,6-hexanediol, dimer diols derived from the dimerization of unsaturated monocarboxylic acids such as oleic acid, linoleic acid, linolenic acid, and erucic acid, as well as 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, spirocyclodiol, tricyclodecanediol, adamantanediol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol.

[0119] Among them, aliphatic diols with 1 to 5 carbon atoms in the side chain are preferred as diols with hydrocarbon groups in order to maintain mechanical strength, heat resistance and not easily cause crystallization. 2-methyl-1,3-propanediol and neopentyl glycol are more preferred in terms of excellent mechanical recyclability.

[0120] Furthermore, from the viewpoint of adjusting the glass transition temperature (Tg) of polyester (B1), aliphatic diols with a straight-chain structure are preferred as polyols (Bb), more preferably aliphatic diols with a straight-chain structure having 1 to 10 carbon atoms, and even more preferably ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. Among these, 1,4-butanediol is most preferred from the viewpoint of lowering the glass transition temperature (Tg) of polyester (B1).

[0121] Furthermore, from the perspective of forming reaction sites with the crosslinking agent described later in the polyester (B1) and improving cohesiveness, polyols with three or more components can also be used as polyols (Bb). Among these, trimethylolpropane, trimethylolethane, glycerol, pentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, and 1,2,6-hexanetriol are preferred. Among these, trimethylolpropane is preferred from the perspective of being less prone to gel formation.

[0122] The polyester (B1) can be manufactured by arbitrarily selecting the polycarboxylic acids (Ba) and polyols (Bb) and carrying them to polycondensation in the presence of a catalyst using known methods. In the polycondensation reaction, esterification and / or transesterification reactions are carried out first, followed by polycondensation.

[0123] There are no particular restrictions on the ratio of polycarboxylic acids (Ba) to polyols (Bb), but from the viewpoint that the weight-average molecular weight and yield can be arbitrarily adjusted, the amount of polyol (Bb) is preferably 1.01 or more per 1 equivalent of polycarboxylic acid (Ba), more preferably 1.05 to 2.5 equivalents, even more preferably 1.1 to 2.0 equivalents, and most preferably 1.2 to 1.7 equivalents.

[0124] In the case of the polyester (B1) obtained in this way, from the perspective of mechanical recyclability, mechanical properties and transparency, structural units derived from aromatic dicarboxylic acids are preferred as structural units derived from polycarboxylic acids (Ba).

[0125] When the polyester (B1) has structural units derived from aromatic dicarboxylic acids, its content is preferably 10 mol% to 100 mol% of structural units derived from polycarboxylic acids (Ba), more preferably 15 mol% to 95 mol%, further preferably 25 mol% to 90 mol%, particularly preferably 35 mol% to 85 mol%, especially preferably 45 mol% to 80 mol%, and most preferably 55 mol% to 75 mol%. If the content of structural units derived from aromatic dicarboxylic acids is within the above range, there is a tendency for excellent hydrolysis resistance, heat resistance, mechanical recyclability, and optical properties.

[0126] Furthermore, when the polyester (B1) has structural units derived from aromatic dicarboxylic acids, their content is typically 1% to 70% by mass of the polyester (B1), preferably 5% to 60% by mass, more preferably 10% to 55% by mass, further preferably 15% to 50% by mass, particularly preferably 20% to 45% by mass, and most preferably 25% to 40% by mass. If the content of structural units derived from aromatic dicarboxylic acids is within the aforementioned range, there is a tendency for excellent mechanical recyclability and optical properties.

[0127] When the polyester (B1) has structural units derived from aliphatic dicarboxylic acids, its content is preferably 95 mol% or less of structural units derived from polycarboxylic acids (Ba), more preferably 5 mol% to 85 mol%, further preferably 10 mol% to 75 mol%, particularly preferably 15 mol% to 65 mol%, especially preferably 20 mol% to 55 mol%, and most preferably 25 mol% to 45 mol%. If the content of structural units derived from aliphatic dicarboxylic acids is within the above range, there is a tendency for excellent adhesive strength, tackiness, mechanical recyclability, and optical properties.

[0128] Furthermore, when the polyester (B1) has structural units derived from aliphatic dicarboxylic acids, their content is typically 1% to 70% by mass of the polyester (B1), preferably 3% to 55% by mass, more preferably 5% to 45% by mass, further preferably 10% to 35% by mass, and most preferably 15% to 30% by mass. If the content of structural units derived from aliphatic dicarboxylic acids is within the aforementioned range, there is a tendency for excellent adhesive strength, tackiness, mechanical recyclability, and optical properties.

[0129] From the perspectives of adhesion, tackiness, mechanical recyclability, and optical properties, the polyester (B1) preferably has structural units derived from aliphatic diols with 1 to 5 carbon atoms as structural units derived from polyols (Bb).

[0130] When the polyester (B1) has structural units derived from aliphatic diols with 1 to 5 carbon atoms as structural units derived from polyols (Bb), the content of such structural units is preferably 10 mol% to 100 mol%, more preferably 30 mol% to 95 mol%, and even more preferably 50 mol% to 90 mol%. If the content of structural units derived from aliphatic diols with 1 to 5 carbon atoms is within the above range, there is a tendency for excellent mechanical recyclability and optical properties.

[0131] Furthermore, when the polyester (B1) has structural units derived from aliphatic diols having 1 to 5 carbon atoms, the content of such units is typically 10% to 70% by mass of the polyester (B1), preferably 15% to 60% by mass, and more preferably 25% to 45% by mass. If the content of structural units derived from aliphatic diols having 1 to 5 carbon atoms is within this range, there is a tendency for excellent mechanical recyclability and optical properties.

[0132] When the polyester (B1) has structural units derived from ternary or higher polyols, there is no particular limitation on its content. From the viewpoints of crosslinking efficiency, mechanical recyclability, optical properties, and production efficiency, it is preferable to have 10 mol% or less of structural units derived from polyols (Bb), more preferably 0.1 mol% to 5 mol%.

[0133] Furthermore, when the polyester (B1) has structural units derived from ternary or higher polyols, their content is typically 0.1% to 10% by mass of the polyester (B1), preferably 0.3% to 5% by mass, and more preferably 0.5% to 3% by mass. If the content of structural units derived from ternary or higher polyols is within the aforementioned range, there is a tendency for excellent crosslinking efficiency, mechanical recyclability, and optical properties.

[0134] Here, the proportions (composition ratios) of the structural units derived from each component of the polyester (B1) can be determined, for example, by nuclear magnetic resonance (NMR).

[0135] The weight-average molecular weight of the polyester (B1) is preferably 2,000 to 500,000, more preferably 10,000 to 300,000, further preferably 20,000 to 200,000, particularly preferably 30,000 to 150,000, especially preferably 50,000 to 130,000, and most preferably 70,000 to 110,000. If the weight-average molecular weight is within the range described above, it tends to exhibit excellent adhesive strength, holding power, heat resistance, and mechanical recyclability. The weight-average molecular weight of the polyester (B1) can be determined using the same method as that used for polyester (A).

[0136] The glass transition temperature (Tg) of the polyester (B1) is -80°C or higher and less than 30°C, more preferably -70°C to 20°C, further preferably -60°C to 15°C, particularly preferably -50°C to 10°C, especially preferably -40°C to 5°C, and most preferably -25°C to 3°C. If the glass transition temperature is within this range, it tends to exhibit excellent adhesive strength, mechanical recyclability, and optical properties. The glass transition temperature of the polyester (B1) can be determined using the same method as that of the polyester (A).

[0137] The heat of fusion of polyester (B1) measured using differential scanning calorimetry is preferably below 10 J / g, more preferably below 5 J / g, further preferably below 3 J / g, particularly preferably below 1 J / g, and most preferably without a crystallization peak (0 J / g). If the heat of fusion is within this range, it tends to have excellent viscosity and adhesive strength. The heat of fusion refers to the energy consumed when heating and melting a crystallized substance, and can be measured by differential scanning calorimetry (DSC).

[0138] Methods for adjusting the heat of fusion of the crystal include, for example, using polycarboxylic acids with alkyl side chains or diols with hydrocarbon side chains; and using comonomers with 3 or more components, preferably 4 or more components.

[0139] The acid value of the polyester (B1) is typically below 30 mg KOH / g, preferably below 20 mg KOH / g, more preferably below 10 mg KOH / g, further preferably below 5 mg KOH / g, and most preferably below 1 mg KOH / g. If the acid value is too high, there is a tendency for reduced resistance to damp heat, mechanical recyclability, and optical properties. The acid value of the polyester (B1) is determined based on JIS K0070 and by neutralization titration.

[0140] To adjust the acid value, methods such as increasing the ratio of polyols or adjusting reaction conditions during esterification or transesterification reactions can be cited. It should be noted that the lower limit of the acid value is typically 0 mg KOH / g.

[0141] From the perspective of excellent mechanical recyclability and optical properties, the polyester (B1) content in the polyester adhesive (B) is usually 80% by mass or more, preferably 85% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0142] From the perspective of excellent adhesion, tack, holding power and heat resistance, the polyester adhesive (B) is preferably a cross-linked product formed by cross-linking with a cross-linking agent, and more preferably a cross-linked product formed by cross-linking the polyester (B1) with a cross-linking agent.

[0143] [Cross-linking agent]

[0144] Examples of crosslinking agents include polyisocyanate compounds, polyepoxy compounds, polyoxazoline compounds, and polycarbodiimide compounds, which have functional groups that react with at least one of the hydroxyl and carboxyl groups contained in the polyester (B1). Furthermore, polyfunctional acrylic monomers and urethane acrylate oligomers that improve cohesiveness even without reacting with the polyester (B1) can also be used. Among these, polyisocyanate compounds and polycarbodiimide compounds are preferred, and polyisocyanate compounds are particularly preferred, considering their ability to achieve a good balance between initial adhesive strength and mechanical strength, heat resistance, and excellent thermal decomposition and mechanical recyclability. These crosslinking agents can be used alone or in combination of two or more.

[0145] Examples of such polyisocyanate compounds include toluene diisocyanate compounds such as 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, xylene diisocyanate compounds such as 1,3-xylene diisocyanate, diphenylmethane compounds such as diphenylmethane-4,4'-diisocyanate, and naphthalene diisocyanate compounds such as 1,5-naphthalene diisocyanate, as well as aromatic isocyanate compounds; isophorone diisocyanate, 1,4-cyclohexane... Alicyclic isocyanate compounds such as alkyl diisocyanates, 4,4'-dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate, 1,3-diisocyanate-methylcyclohexane, and norbornene diisocyanate; aliphatic isocyanate compounds such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; and adducts, biuret forms, and isocyanurate esters of the aforementioned isocyanate compounds. It should be noted that the polyisocyanate compounds may also be compounds formed by end-capping the isocyanate portion with phenol, lactam, or the like.

[0146] Examples of polycarbodiimide compounds include those obtained by decarboxylation condensation of diisocyanates. Examples of such diisocyanates include 4,4'-diphenylmethane diisocyanate, 3,3'-dimethoxy-4,4'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 3,3'-dimethyl-4,4'-diphenyl ether diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and tetramethylphenyldimethyl diisocyanate. These can be used alone or in combination of two or more. It should be noted that the polycarbodiimide compounds can also be compounds formed by capping the terminal isocyanate portion with an alcohol or the like.

[0147] The content of the crosslinking agent can be appropriately selected according to the molecular weight of the polyester (B1) and the intended use. Generally, it is preferred that the crosslinking agent contains a crosslinking agent in a ratio of 0.1 equivalent to 10 equivalents relative to 1 equivalent of hydroxyl and / or carboxyl groups contained in the polyester (B1), more preferably 0.2 equivalents to 5 equivalents, further preferably 0.3 equivalents to 3 equivalents, and particularly preferably 0.5 equivalents to 1.5 equivalents. If it is set within the above equivalent range, it is preferred from the viewpoint of cohesion, mechanical recyclability, and optical properties.

[0148] Furthermore, the content of the crosslinking agent relative to 100 parts by weight of polyester (B1) is preferably 0.01 to 15 parts by weight, more preferably 0.1 to 10 parts by weight, even more preferably 0.3 to 6 parts by weight, particularly preferably 0.5 to 4 parts by weight, especially preferably 0.75 to 3 parts by weight, and most preferably 1 to 2 parts by weight. Setting it within the above-mentioned range of parts by weight is preferred from the viewpoints of adhesive strength, cohesive strength, mechanical recyclability, and optical properties.

[0149] In addition to the polyester (B1) and crosslinking agent, the polyester adhesive (B) may also contain additives such as hydrolysis inhibitors, urethane esterification catalysts, antioxidants, tackifying resins, softeners, ultraviolet absorbers, stabilizers, and antistatic agents, as well as inorganic or organic fillers, powders such as metal powders and pigments, and compounding agents in powder or particulate form, within a range that does not impair the effects of the present invention (e.g., typically 20% by mass or less, preferably 10% by mass or less of the polyester adhesive (B)). These can be used alone or in combination of two or more. Furthermore, the polyester adhesive (B) may also contain small amounts of impurities contained in the raw materials used to manufacture the constituent components.

[0150] The gel fraction of the crosslinked polyester (B1) [polyester adhesive (B)] is preferably 10% to 100%, more preferably 15% to 80%, further preferably 20% to 70%, particularly preferably 25% to 60%, and most preferably 30% to 50%. If the gel fraction is within the range described above, there is a tendency for excellent adhesion, holding power, heat resistance, mechanical recyclability, and optical properties.

[0151] The gel fraction is an indicator of the degree of crosslinking, calculated for example by the following method: Polyester (B1) [polyester adhesive (B)] is wrapped in a 200-mesh SUS metal mesh and impregnated in toluene at 23°C for 24 hours. The mass percentage of the insoluble polyester (B1) [polyester adhesive (B)] remaining in the impregnated metal mesh relative to the mass of the polyester (B1) [polyester adhesive (B)] before impregnation is taken as the gel fraction.

[0152] <Manufacturing Method of Polyester Resins>

[0153] Next, the manufacturing method of this polyester resin will be described.

[0154] The method for manufacturing this polyester resin includes a step of reacting a polyester (A) with a glass transition temperature of 30°C or higher and less than 140°C with a polyester (B1) with a glass transition temperature of -80°C or higher and less than 30°C. Furthermore, this manufacturing method can yield a polyester resin composition containing this polyester resin.

[0155] As described above, the polyester (A) and the polyester-based adhesive (B) containing the polyester (B1) can be used from used products, waste generated during the manufacturing process, unused products, etc., which are collected as resource waste.

[0156] The polyester (A) and the polyester-based adhesive (B) containing polyester (B1) can be pulverized into granules or flakes as needed, and cleaned by known cleaning methods such as alkaline cleaning or warm water cleaning to remove dirt and foreign matter remaining on the surface of the pulverized granules or flakes. Furthermore, the cleaned granules or flakes can be dried as needed.

[0157] In this method of manufacturing polyester resin, it is only necessary to heat and melt the polyester (A) and the polyester (B1) contained in the polyester adhesive (B) and react them.

[0158] Regarding the mass ratio of polyester (A) to polyester (B1) during the reaction, the amount of polyester (B1) is typically 0.1 to 10 parts by mass relative to 100 parts by mass of polyester (A), preferably 0.2 to 8 parts by mass, more preferably 0.3 to 8 parts by mass, and most preferably 0.5 to 5 parts by mass. If the mass ratio of polyester (A) to polyester (B1) is within this range, there is a tendency for excellent formability, strength, heat resistance, mechanical recyclability, and optical properties.

[0159] Furthermore, when reacting polyester (A) with polyester (B1), a known antioxidant is typically included in an amount of 0.01 to 10 parts by mass, preferably 0.05 to 5 parts by mass, more preferably 0.1 to 3 parts by mass, and even more preferably 0.3 to 1.5 parts by mass, relative to a total of 100 parts by mass of polyester (A) and polyester (B1). If the antioxidant content is within the aforementioned range, there is a tendency for excellent formability, strength, heat resistance, mechanical recyclability, and optical properties.

[0160] Examples of antioxidants include phenolic antioxidants, hindered phenolic antioxidants, amine antioxidants, hindered amine antioxidants, sulfur-based antioxidants, and phosphoric acid antioxidants. Preferably, at least one of hindered phenolic antioxidants, hindered amine antioxidants, and phosphoric acid antioxidants is selected, and more preferably, a hindered phenolic antioxidant is used.

[0161] As hindered phenolic antioxidants, examples include antioxidants with a hindered phenolic structure in which at least one of the carbon atoms adjacent to the carbon atom on the aromatic ring bonded to the hydroxyl group of the phenol is bonded with a sterically hindered group such as tert-butyl.

[0162] When the polyester (A) reacts with the polyester (B1), from the perspectives of formability, strength, heat resistance, mechanical recyclability, and optical properties, it is preferable to carry out the reaction under an inert gas atmosphere, and more preferably under a nitrogen atmosphere.

[0163] When the polyester (A) reacts with the polyester (B1), from the perspective of formability, strength, heat resistance, mechanical recyclability, and optical properties, it is preferably carried out under a vacuum of 0.1 Torr to 50 Torr, more preferably 0.3 Torr to 40 Torr, even more preferably 0.5 Torr to 30 Torr, particularly preferably 1 Torr to 20 Torr, and especially preferably 3 Torr to 10 Torr. If the vacuum conditions are within the range described above, there is a tendency to suppress the oxidative degradation of the polyester (A) and polyester (B1) and to achieve excellent formability, strength, heat resistance, mechanical recyclability, and optical properties.

[0164] From the perspective of mechanical recyclability, the heating and melting temperature is preferably 160℃~280℃, more preferably 180℃~275℃, further preferably 200℃~270℃, and most preferably 220℃~265℃. If the heating and melting temperature is within the range described above, the transesterification reaction between polyester (A) and polyester (B1) proceeds effectively, exhibiting a tendency towards excellent mechanical recyclability and optical properties.

[0165] Furthermore, from the perspectives of mechanical recyclability and transparency, the heating time is preferably 1 hour to 24 hours, and more preferably 2 hours to 10 hours.

[0166] By reacting under such reaction conditions, an ester exchange reaction occurs between polyester (A) and polyester (B1) to obtain the polyester-based resin as their reactant.

[0167] The content of polyester (B1)-derived structural units in this polyester-based resin is preferably 10% by mass or less, more preferably 8% by mass or less, further preferably 6% by mass or less, particularly preferably 4% by mass or less, and most preferably 2% by mass or less. When the content of polyester (B1)-derived structural units is within the above range, there is a tendency for excellent formability, strength, heat resistance, mechanical recyclability, and optical properties.

[0168] This polyester resin contains structural units derived from polycarboxylic acids and structural units derived from polyols. The content of aromatic dicarboxylic acid structural units in the polyester resin is preferably 10% to 90% by mass, more preferably 30% to 85% by mass, further preferably 40% to 80% by mass, particularly preferably 50% to 75% by mass, and most preferably 60% to 70% by mass. When the content of aromatic dicarboxylic acid structural units is within the aforementioned range, the resin tends to exhibit excellent formability, strength, heat resistance, mechanical recyclability, and optical properties.

[0169] Furthermore, the content of structural units derived from aliphatic diols having 1 to 5 carbon atoms in this polyester resin is typically 10% to 90% by mass, preferably 15% to 70% by mass, more preferably 20% to 60% by mass, particularly preferably 25% to 50% by mass, and most preferably 30% to 40% by mass. When the content of structural units derived from aliphatic diols having 1 to 5 carbon atoms is within the aforementioned range, there is a tendency for excellent formability, strength, heat resistance, mechanical recyclability, and optical properties.

[0170] From the perspective of excellent mechanical recyclability and optical properties, the content of the polyester resin in the polyester resin composition is generally 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more.

[0171] Furthermore, within a range that does not impede the effects of the present invention (e.g., less than 10% by mass, preferably less than 5% by mass of the polyester resin composition), the polyester resin composition may be combined with crystallizing nucleating agents, antioxidants, chain extenders, hydrolysis inhibitors, anti-coloring agents, pigments, dyes, ultraviolet absorbers, release agents, slip agents, flame retardants, antistatic agents, inorganic particles and / or organic particles, etc., depending on its use.

[0172] Furthermore, the polyester resin composition may also contain additives derived from molded articles containing polyester (A), additives derived from polyester (B1), and compounding agents, to the extent that it does not impede the effects of the present invention.

[0173] In addition, other resins besides this polyester resin may also be mixed into the polyester resin composition, but the other resins are preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, even more preferably 1% by mass or less, particularly preferably 0.1% by mass or less, and most preferably 0% by mass.

[0174] The moisture content of the polyester resin composition is preferably 0.5% or less, more preferably 0.3% or less, even more preferably 0.1% or less, particularly preferably 0.05% or less, especially preferably 0.03% or less, and most preferably 0.01% or less. If the moisture content is within the range described above, it tends to exhibit excellent moldability, strength, heat resistance, and mechanical recyclability. The moisture content of this resin composition is determined using a Karl Fischer moisture analyzer.

[0175] <Polyester Resins>

[0176] The nitrogen content in this polyester resin is preferably 0.1 ppm to 1000 ppm, more preferably 1 ppm to 750 ppm, further preferably 3 ppm to 500 ppm, particularly preferably 5 ppm to 300 ppm, especially preferably 10 ppm to 200 ppm, and most preferably 20 ppm to 100 ppm. If the nitrogen content is within the above range, it tends to have excellent mechanical recyclability, mechanical properties, and optical properties. The nitrogen content can be determined by a trace total nitrogen analyzer.

[0177] It should be noted that the nitrogen atoms contained in this polyester resin refer to the nitrogen atoms contained in the case where an isocyanate compound is used as a crosslinking agent for the polyester (B1) or a carbodiimide compound is used as a hydrolysis inhibitor, wherein nitrogen atoms derived from isocyanate groups are preferred.

[0178] The glass transition temperature (Tg) of this polyester resin is preferably 30°C or higher, more preferably 40°C to 140°C, even more preferably 50°C to 120°C, and most preferably 60°C to 100°C. If the glass transition temperature (Tg) is within this range, it tends to exhibit excellent moldability, strength, and heat resistance. The glass transition temperature of this polyester resin can be determined using the same method as that used for polyester (A).

[0179] The weight-average molecular weight of this polyester resin is preferably 5,000 to 300,000, more preferably 10,000 to 150,000, even more preferably 20,000 to 100,000, and particularly preferably 30,000 to 75,000. If the weight-average molecular weight is within the range described above, it tends to exhibit excellent moldability, strength, heat resistance, and mechanical recyclability. The weight-average molecular weight of this polyester resin can be determined using the same method as that used for polyester (A).

[0180] The intrinsic viscosity of this polyester resin is preferably 0.3 dL / g to 1.5 dL / g, more preferably 0.4 dL / g to 1.3 dL / g, even more preferably 0.5 dL / g to 1.1 dL / g, particularly preferably 0.6 dL / g to 1.0 dL / g, especially preferably 0.65 dL / g to 0.9 dL / g, and most preferably 0.7 dL / g to 0.8 dL / g. If the intrinsic viscosity is within the range described above, it tends to exhibit excellent moldability, strength, heat resistance, and mechanical recyclability. The intrinsic viscosity of this polyester resin was determined based on JIS K7367.

[0181] The acid value of this polyester resin is preferably below 5 mg KOH / g, more preferably below 4.5 mg KOH / g, further preferably below 4 mg KOH / g, particularly preferably below 3.5 mg KOH / g, especially preferably below 3 mg KOH / g, and most preferably below 1 mg KOH / g. If the acid value is within the specified range, it tends to exhibit excellent hydrolysis resistance, heat resistance, mechanical recyclability, and optical properties. The acid value of this polyester resin can be determined by neutralization titration based on JIS K0070.

[0182] When this polyester resin is used to produce sheets with a thickness of 50 μm, the haze is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less. If the haze is below these values, there is a tendency for excellent optical properties. The haze is measured based on JIS K7136.

[0183] This polyester resin, and polyester resin compositions containing this polyester resin, are preferably used as molded articles such as polyester containers, polyester films, and polyester fibers.

[0184] The molding method of the molded article is not particularly limited, and examples include injection molding, extrusion molding, blow molding, and in-mold molding.

[0185] For example, the polyester resin or polyester resin composition can be extruded into sheets, and the sheets can be shaped into desired shapes by vacuum forming or the like to form containers. These are useful as beverage bottles, bottle caps, trays, containers, etc., for fried foods, side dishes, etc. Furthermore, the sheets can be stretched into films, etc., for use as protective films on the inner and outer surfaces of food packaging materials, trays, and containers.

[0186] The polyester container, polyester film, and polyester fiber may contain only the polyester resin. For example, they may be formed solely from the polyester resin or a polyester resin composition, or they may be formed by laminating the polyester resin, the polyester resin composition, and other resins.

[0187] Example

[0188] The following examples illustrate the present invention in further detail, but the present invention is not limited to these examples as long as it does not conform to its spirit. It should be noted that in the examples, "parts" and "%" refer to mass standards.

[0189] First, polyester (A) and polyester-based adhesive (B) are prepared as described below.

[0190] [Polyester (A)]

[0191] [Preparation of Polyester (A-1)]

[0192] In a reaction vessel equipped with a heating device, thermometer, stirrer, distillation column, nitrogen inlet pipe and vacuum device, 323 parts of isophthalic acid as a polycarboxylic acid (Aa), 60.3 parts of ethylene glycol as a polyol (Ab), 243 parts of neopentyl glycol, and 373.7 parts of recycled polyethylene terephthalate (256.9 parts of recycled terephthalic acid and 116.8 parts of recycled ethylene glycol) and 0.1 parts of zinc acetate as a catalyst were added. The temperature was slowly raised to 260°C and the esterification reaction was carried out for 4 hours.

[0193] Then, 0.05 parts of tetrabutyl titanate were added as a catalyst, and polycondensation reaction was carried out at an internal temperature of 260°C and reduced to 1.33 hPa for 3 hours to obtain polyester (A-1).

[0194] The obtained polyester (A-1) has a glass transition temperature (Tg) of 68℃ and a weight-average molecular weight (Mw) of 38,000. Other physical properties are shown in Table 1 below.

[0195] Furthermore, in terms of the proportions of the finished product components, as a polycarboxylic acid (Aa), isophthalic acid / recycled terephthalic acid = 50 mol% / 50 mol%, and as a polyol (Ab), recycled ethylene glycol / ethylene glycol / neopentyl glycol = 39 mol% / 18 mol% / 45 mol%, the content of structural units derived from recycled polyethylene terephthalate in the polyester (A-1) is 42%.

[0196] [Polyester-based adhesives (B)]

[0197] [Preparation of Polyester (B1-1)]

[0198] In a reaction vessel equipped with a heating device, thermometer, stirrer, distillation column, nitrogen inlet pipe, and vacuum device, 96.1 parts of isophthalic acid (Ba), 467.8 parts of sebacic acid (Ba), 271 parts of neopentyl glycol (Bb), 130.3 parts of 1,4-butanediol, 29.7 parts of 1,6-hexanediol, 5 parts of trimethylolpropane, and 0.1 parts of zinc acetate (catalyst) were added. The mixture was slowly heated to an internal temperature of 260°C and carried out the esterification reaction over 4 hours.

[0199] Subsequently, 0.05 parts of tetrabutyl titanate were added as a catalyst, and the polycondensation reaction was carried out at an internal temperature of 260°C and reduced to 1.33 hPa for 3 hours to obtain polyester (B1-1).

[0200] The obtained polyester (B1-1) has a glass transition temperature (Tg) of -48℃ and a weight-average molecular weight (Mw) of 84,000. Other physical properties are shown in Table 2 below.

[0201] In addition, regarding the proportions of the finished product components, as a polycarboxylic acid (Ba), isophthalic acid / sebacic acid = 20 mol% / 80 mol%, and as a polyol (Bb), neopentyl glycol / 1,4-butanediol / 1,6-hexanediol / trimethylolpropane = 59 mol% / 34 mol% / 6 mol% / 1 mol%.

[0202] [Preparation of polyester (B1-2) and polyester (B1-3)]

[0203] In the preparation of the polyester (B1-1), the proportions of the polycarboxylic acid (Ba) and polyol (Bb) in the finished product are as described in Table 2 below. Otherwise, polyester (B1-2) and polyester (B1-3) are obtained in the same manner.

[0204] The obtained polyester (B1-2) has a glass transition temperature (Tg) of -32℃ and a weight-average molecular weight (Mw) of 88,000. Other physical properties are shown in Table 2 below.

[0205] Furthermore, the obtained polyester (B1-3) has a glass transition temperature (Tg) of 1°C and a weight-average molecular weight (Mw) of 94,000. Other physical properties are shown in Table 2 below.

[0206] [Preparation of acrylic resin (B1'-1)]

[0207] In a four-necked round-bottom flask equipped with a reflux condenser, a stirrer, a nitrogen inlet, and a thermometer, 919 parts of butyl acrylate, 80 parts of acrylic acid, 1 part of 2-hydroxyethyl methacrylate, and 800 parts of ethyl acetate were added. After heating to reflux, 5 parts of azobisisobutyronitrile (AIBN) were added as a polymerization initiator. After reacting for 7 hours at the reflux temperature of ethyl acetate, the mixture was diluted with ethyl acetate to obtain an acrylic resin (B1'-1) solution.

[0208] The resulting acrylic resin (B1'-1) has a glass transition temperature of -48°C and a weight-average molecular weight of 280,000. It should be noted that the glass transition temperature was calculated using the Fox formula, and the weight-average molecular weight was determined using the same method as for the polyester (B1).

[0209] [Polyester-based adhesives (B)]

[0210] [Preparation of polyester adhesive (B-1)]

[0211] The polyester (B1-1) obtained above was diluted with ethyl acetate to a solids concentration of 50%. 2 parts (solids) of a polyisocyanate compound [Takenate D101E (trimethylolpropane adduct of toluene diisocyanate: nitrogen content 12.8%), manufactured by Mitsui Chemicals Co., Ltd.] and 0.1 parts of an antioxidant (IRGANOX 1010, manufactured by BASF Co., Ltd.) were added to the polyester (B1-1) (100 parts by solids) as a crosslinking agent, and the mixture was stirred and mixed to obtain a polyester-based adhesive composition.

[0212] The obtained polyester adhesive composition was applied to a 38 μm thick PET release film (Mitsui Chemicals Tohcello, SP-PET-03-BU) using an applicator and dried at 120°C for 4 minutes to obtain an adhesive sheet with a single-sided release film and an adhesive composition layer thickness of 50 μm.

[0213] Next, the surface of the adhesive composition layer of the single-sided adhesive sheet with release film was covered with a 38 μm thick PET release film (Mitsui Chemicals Tohcello, SP-PET-01-BU), and cured at 40°C for 4 days. The release films on both sides were then peeled off to obtain the polyester adhesive (B-1). Table 3, described later, shows the composition and gel fraction of the polyester adhesive (B-1).

[0214] [Preparation of polyester adhesives (B-2) and (B-3)]

[0215] By changing the polyester (B1-1) used in the polyester adhesive (B-1) to polyester (B1-2) and polyester (B1-3), respectively, polyester adhesive (B-2) and polyester adhesive (B-3) are obtained in the same manner. The composition and gel fraction of polyester adhesive (B-2) and polyester adhesive (B-3) are shown in Table 3 below.

[0216] [Preparation of acrylic adhesive (B'-1)]

[0217] The obtained acrylic resin (B1'-1) was diluted with ethyl acetate to a solids concentration of 50%. 0.5 parts (solids) of a polyisocyanate crosslinking agent (Takenate D101E, manufactured by Mitsui Chemicals) and 0.1 parts of an antioxidant (IRGANOX 1010, manufactured by BASF) were added relative to 100 parts of the acrylic resin (B1'-1) and the mixture was stirred and mixed to obtain an acrylic adhesive composition.

[0218] The obtained acrylic adhesive composition was applied to a 38 μm thick PET release film (Mitsui Chemicals Tohcello, SP-PET-03-BU) using an applicator and dried at 120°C for 4 minutes to obtain an adhesive sheet with a single-sided release film and an adhesive composition layer thickness of 50 μm.

[0219] Next, the adhesive composition layer of the single-sided adhesive sheet with release film was covered with a 38 μm thick PET release film (Mitsui Chemicals Tohcello, SP-PET-01-BU), and cured at 40°C for 4 days. The release films on both sides were then peeled off to obtain the acrylic adhesive (B'-1). Table 3, described later, shows the composition and gel fraction of the acrylic adhesive (B'-1).

[0220] <Example 1>

[0221] In a reaction vessel equipped with a heating device, thermometer, stirrer, distillation column, nitrogen inlet pipe, and vacuum device, 500 parts of the obtained polyester resin (A-1), 5 parts of polyester binder (B-1), and 0.5 parts of antioxidant (IRGANOX 1010, manufactured by BASF) were added, and the reaction vessel was purged with nitrogen. Then, the temperature was raised to 260°C, the pressure was reduced to 7.5 Torr, and the mixture was heated and stirred for 5 hours to obtain the polyester resin composition of Example 1, which was mechanically recycled.

[0222] <Examples 2-6, Comparative Example 1>

[0223] By changing the types and amounts of polyester (A) and polyester adhesive (B) used in Example 1 to the proportions described in Table 4 below, the polyester resin compositions of Examples 2 to 6 and Comparative Example 1 were obtained in the same manner.

[0224] The polyester resin compositions obtained in Examples 1 to 6 and Comparative Example 1 were used to evaluate their optical properties (haze) and mechanical recyclability. The evaluation results are shown in Table 4 below.

[0225] [Optical properties (haze)]

[0226] The polyester resin compositions of Examples 1 to 6 and Comparative Example 1 were diluted with toluene / methyl ethyl ketone at a ratio of 70 / 30 (mass ratio) to a solids concentration of 40% to obtain polyester resin composition solutions. The obtained polyester resin composition solutions were coated onto PET release films (Mitsui Chemicals Tohcello, SP-PET-03-BU) using a coater and dried at 120°C for 5 minutes. The release films were then peeled off to obtain films with a thickness of 50 μm.

[0227] The obtained membrane was cut into 30mm × 50mm pieces at 23°C and 50% RH to prepare test pieces. The haze of these test pieces was measured using a HAZE MATER NDH2000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.), and evaluated according to the following evaluation criteria.

[0228] (Evaluation Criteria)

[0229] ◎ (Excellent) ... below 2.5.

[0230] 〇 (very good) ... greater than 2.5 and less than 3.5.

[0231] △ (good) ... greater than 3.5 and less than 5.

[0232] × (poor) ... greater than 5.

[0233] [Mechanical recyclability]

[0234] The polyester resin compositions obtained in Examples 1 to 6 and Comparative Example 1 were diluted with toluene / methyl ethyl ketone at a ratio of 70 / 30 (mass ratio) to a solids concentration of 40% to obtain polyester resin composition solutions. 500 g of the obtained polyester resin composition solutions were filtered using a nylon mesh filter (Nylon 250T: average mesh size 59 μm, opening ratio 33%, wire diameter 43 μm, thickness 78 μm), and evaluated according to the following evaluation criteria.

[0235] (Evaluation Criteria)

[0236] ◎ (Excellent) ... It can filter.

[0237] × (Poor) ... The filter is clogged with foreign objects and cannot filter.

[0238]

[0239]

[0240]

[0241]

[0242] According to the results in Table 4, the resins of the polyester resin compositions of Examples 1 to 6, which contain polyester resins as reactants of polyester (A) and polyester (B1), do not have reduced mechanical properties, have excellent mechanical recyclability, and also have excellent optical properties.

[0243] On the other hand, the polyester resin composition of Comparative Example 1, which uses an acrylic adhesive as an adhesive, has poor mechanical recyclability and optical properties.

[0244] The embodiments described illustrate specific aspects of the invention, but are merely examples and not intended to be limiting. It is intended that various modifications, readily apparent to those skilled in the art, fall within the scope of the invention.

[0245] Industrial availability

[0246] This polyester resin does not suffer from reduced mechanical properties and has excellent mechanical recyclability and optical properties, making it a preferred raw material for molding containers, membranes, and fibers.

Claims

1. A polyester resin, which is a reactant of a polyester (A) with a glass transition temperature of 30°C or higher and less than 140°C and a polyester (B1) with a glass transition temperature of -80°C or higher and less than 30°C.

2. The polyester resin according to claim 1, wherein, The nitrogen atom content in the polyester resin is 0.1ppm to 1000ppm.

3. The polyester resin according to claim 1 or 2, wherein, The content of structural units derived from polyester (B1) in the polyester resin is less than 10% by mass.

4. The polyester resin according to any one of claims 1 to 3, wherein, The glass transition temperature of the polyester resin is above 30°C.

5. The polyester resin according to any one of claims 1 to 4, wherein, The weight-average molecular weight of the polyester resin is 5,000 to 300,000.

6. The polyester resin according to any one of claims 1 to 5, wherein, The acid value of the polyester resin is below 5 mg KOH / g.

7. The polyester resin according to any one of claims 1 to 6, wherein, The polyester resin has structural units derived from polycarboxylic acids and structural units derived from polyols, and the content of structural units derived from aromatic dicarboxylic acids in the polyester resin is 10% to 90% by mass.

8. The polyester resin according to any one of claims 1 to 7, wherein, When the polyester resin is made into a sheet with a thickness of 50 μm, the haze is less than 5%.

9. The polyester resin according to any one of claims 1 to 8, wherein, The polyester (A) has structural units derived from terephthalic acid and structural units derived from ethylene glycol.

10. The polyester resin according to any one of claims 1 to 9, wherein, The polyester (A) has structural units derived from recycled thermoplastic polyester (A1).

11. The polyester resin according to any one of claims 1 to 10, wherein, The polyester (B1) has structural units derived from aromatic dicarboxylic acids.

12. The polyester resin according to any one of claims 1 to 11, wherein, The content of aromatic dicarboxylic acids in the structural units of the polyester (B1) derived from polycarboxylic acids (Ba) is 10 mol% to 100 mol%.

13. The polyester resin according to any one of claims 1 to 12, wherein, The polyester (B1) contains 10 mol% to 100 mol% aliphatic diols with 1 to 5 carbon atoms in the structural units of polyols (Bb).

14. The polyester resin according to any one of claims 1 to 13, wherein, The heat of fusion of the polyester (B1) crystals is below 10 J / g.

15. The polyester resin according to any one of claims 1 to 14, wherein, The polyester (B1) is a crosslinked compound.

16. The polyester resin according to any one of claims 1 to 15, wherein, The gel fraction of the crosslinked polyester resin (B1) is 10% to 100%.

17. A polyester container comprising a polyester resin according to any one of claims 1 to 16.

18. A polyester film comprising a polyester resin according to any one of claims 1 to 16.

19. A polyester fiber comprising a polyester resin according to any one of claims 1 to 16.

20. A method for manufacturing a polyester resin, comprising a step of reacting a polyester (A) with a glass transition temperature of 30°C or higher and less than 140°C with a polyester (B1) with a glass transition temperature of -80°C or higher and less than 30°C.

21. The method for manufacturing polyester resin according to claim 20, wherein, The process is carried out under a nitrogen atmosphere.

22. The method for manufacturing a polyester resin according to claim 20 or 21, wherein, The process is carried out under vacuum conditions of 0.1 Torr to 50 Torr.

23. The method for manufacturing the polyester resin according to any one of claims 20 to 22, wherein, In the process described, the material is heated to 160°C to 280°C until it melts.

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