WO2024177005A1

WO2024177005A1 - Polyester resin and polyester resin production method

Info

Publication number: WO2024177005A1
Application number: PCT/JP2024/005759
Authority: WO
Inventors: 佑山本; 珠世佐々井
Original assignee: 東洋紡株式会社
Priority date: 2023-02-20
Filing date: 2024-02-19
Publication date: 2024-08-29

Abstract

The purpose of the present invention is to provide a polyester resin that includes ethylene glycol and a polycarboxylic acid having a furan backbone, that has a sufficient molecular weight and excellent thermal stability, and that can maintain a high crystallization rate even after being re-melted. A polyester resin according to the present invention contains, as structural components, a polycarboxylic acid component and a polyhydric alcohol component, and is characterized by satisfying the following (1)-(4). (1) Contains a polycarboxylic acid having a furan backbone as the polycarboxylic acid component, and ethylene glycol as the polyhydric alcohol component. (2) During the second temperature increase, the temperature of the cold crystallization peak is within the range of 145-185°C, and the heat generation amount is 5 J/g or more, as measured by differential scanning calorimetry (DSC) at a temperature increase rate of 2°C/min. (3) Has a reduced viscosity of 0.50 dl/g or more. (4) Contains at least one metal element selected from antimony, aluminum, titanium, and germanium, and the total contained amount of the metal element is 350 mass ppm or less.

Description

Polyester resin and method for producing polyester resin

The present invention relates to a polyester resin having a furan skeleton and a method for producing a polyester resin having a furan skeleton.

In recent years, polyethylene furanolate (PEF), which uses biomass-derived 2,5-furandicarboxylic acid (FDCA), has been attracting attention as an environmentally friendly or sustainable material. In addition to having mechanical strength and thermal properties equivalent to polyethylene terephthalate (PET), PEF also has gas barrier properties that are better than those of PET, so it is expected to be used in a wide range of applications beyond just bottles, films, and fibers, which are existing alternatives to PET.

However, compared to PET, PEF has a slower crystallization rate, which is cited as an issue in the manufacture of molded products. As with PET, PEF can also be used to increase its molecular weight through solid-state polymerization (SSP), but if the crystallinity is insufficient, resin blocking can occur during the SSP process, degrading product quality. To avoid blocking, a method of annealing before SSP is known, but this is undesirable from the perspective of environmental impact and manufacturing costs in terms of LCA (Life Cycle Assessment).

For example, as disclosed in Patent Document 1, attempts have been made to improve the crystallization rate by adjusting the reduced viscosity and terminal acid value of polyesters using crystal nucleating agents, but the results have not been sufficient.

Also, as disclosed in Non-Patent Document 1, there is a case where a cold crystallization peak of PEF was confirmed by differential scanning calorimetry (DSC) at a heating rate of 10°C/min. However, because a large amount of catalyst was used, a decrease in molecular weight due to thermal decomposition was observed in the thermal history during the first heating, and the thermal stability was low.

JP 2013-155388 A

If the thermal stability is low, the resin may deteriorate due to heat during processing, resulting in a decrease in resin properties, a decrease in molecular weight, and discoloration of the resin. Also, if the molecular weight is low, it is possible to speed up the crystallization rate, but the strength of the molded product may be insufficient. If the molecular weight is high, it is difficult to maintain the crystallization rate of the polyester resin when it is melted again during processing such as melt molding.

The present invention was devised to solve the problems of the prior art, and aims to provide a polyester resin containing a polycarboxylic acid having a furan skeleton and ethylene glycol, which has a sufficient molecular weight and excellent thermal stability and can maintain a high crystallization rate even after remelting, and a method for producing the polyester resin.

The polyester resin according to one embodiment of the present disclosure contains a polycarboxylic acid having a furan skeleton as a polycarboxylic acid component and ethylene glycol as a polyhydric alcohol component. The polyester resin has a cold crystallization peak temperature during the second heating step, measured by differential scanning calorimetry (DSC) at a heating rate of 2°C/min, within the range of 145 to 185°C, a heat generation amount of 5 J/g or more, a reduced viscosity of the polyester resin of 0.50 dl/g or more, and contains at least one metal element selected from antimony, aluminum, titanium, and germanium, and the total content of the metal elements is 350 mass ppm or less. After extensive investigations, the inventors have found that a high crystallization rate can be maintained even after remelting by satisfying the above conditions for the cold crystallization peak temperature and heat generation amount during the second heating step, measured by differential scanning calorimetry (DSC) at a heating rate of 2°C/min. The inventors then discovered that by optimizing the amount of the metal elements in the polyester resin and satisfying the above conditions for the temperature and heat generation amount of the cold crystallization peak during the second heating step, it is possible to provide a polyester resin having a furan skeleton that maintains a high crystallization rate even after remelting, even if the molecular weight is high, and has excellent thermal stability, thereby completing the present invention.

A method for producing a polyester resin according to another embodiment of the present disclosure is a method for producing a polyester resin containing a polycarboxylic acid having a furan skeleton as a polycarboxylic acid component and containing ethylene glycol as a polyhydric alcohol component. The production method includes a step of applying a shear stress to a molten composition of the reaction product obtained in the polycondensation reaction step. The inventors have found that applying a shear stress fixes the orientation of molecules in the polyester resin, and that the molecular orientation remains fixed without being canceled even after remelting, allowing a high crystallization rate to be maintained even after remelting.

That is, the present invention comprises the following:
Item 1. A polyester resin comprising a polyvalent carboxylic acid component and a polyhydric alcohol component as constituent components, the polyester resin being characterized in that it satisfies the following (1) to (4).
(1) The polycarboxylic acid component contains a polycarboxylic acid having a furan skeleton, and the polyhydric alcohol component contains ethylene glycol.
(2) The temperature of the cold crystallization peak during the second heating step, as measured by differential scanning calorimetry (DSC) at a heating rate of 2° C./min, is in the range of 145 to 185° C., and the calorific value is 5 J/g or more.
(3) The reduced viscosity is 0.50 dl/g or more.
(4) At least one metal element selected from antimony, aluminum, titanium, and germanium is contained, and the total content of the metal elements is 350 ppm by mass or less.
Item 2. The polyester resin according to Item 1, comprising 0.1 to 5 mol % of diethylene glycol relative to 100 mol % in total of the polyhydric alcohol components.
Item 3. The polyester resin according to item 1 or 2, containing 0.001 to 4 mass % of a crystal nucleating agent.
Item 4. The polyester resin according to any one of Items 1 to 3, containing 80 mol % or more of units composed of a polyvalent carboxylic acid component having a furan skeleton and an ethylene glycol component.
Item 5. The polyester resin according to any one of items 1 to 4, wherein the change in reduced viscosity before and after heat treatment at 280° C. for 1 hour is 0.15 dl/g or less.
Item 6. The polyester resin according to any one of items 1 to 5, having a melting point of 200° C. or higher.
Item 7. A polyester resin pellet comprising the polyester resin according to any one of items 1 to 6.
Item 8. A bottle formed from the polyester resin according to any one of items 1 to 6, or the polyester resin pellets according to item 7.
Item 9. A film formed from the polyester resin according to any one of items 1 to 6, or the polyester resin pellets according to item 7.
Item 10. A fiber formed from the polyester resin according to any one of items 1 to 6, or the polyester resin pellets according to item 7.
Item 11. A method for producing a polyester resin having a polycarboxylic acid component and a polyhydric alcohol component as constituent components, the method comprising: a step of polycondensing the polycarboxylic acid component and the polyhydric alcohol component; and a step of applying a shear stress to a molten composition of the reaction product obtained in the polycondensation reaction step, the polycarboxylic acid component including a polycarboxylic acid component having a furan skeleton, and the polyhydric alcohol component including ethylene glycol.
Item 12. The method for producing a polyester resin according to Item 11, wherein a shear stress of 0.15 MPa or more is applied in the step of applying a shear stress.
Item 13. The method for producing a polyester resin according to Item 11 or 12, wherein in the step of applying a shear stress, the shear stress is applied by a twin-screw extruder.
Item 14. A method for producing polyester resin pellets, comprising the steps of discharging the polyester resin obtained by the production method according to any one of items 11 to 13 in a molten state, cooling the polyester resin, and cutting the polyester resin pellets.
Item 15. A method for producing polyester resin pellets, comprising a step of further solid-phase polymerizing the polyester resin pellets obtained by the method for producing polyester resin pellets according to item 14.

The polyester resin of the present invention has a high molecular weight, good thermal stability, and can maintain a high crystallization rate even after remelting, so that the crystallization rate during melt molding processing can be improved and productivity can be improved. In addition, a polyester resin having a furan skeleton that can suppress thermal decomposition during processing and has high strength can be provided.
Therefore, the polyester resin of the present invention can be suitably used as a material for various molded products such as films, fibers, beverage bottles, and optical products.

FIG. 1 is a graph showing the results of Example 1, with the horizontal axis representing the shear rate [sec ⁻¹ ] and the vertical axis representing the melt viscosity [Pa·s].

Below, we will explain in detail typical embodiments of the present invention, but the present invention is not limited to the following embodiments as long as they do not exceed the gist of the invention.

The polyester resin of the present invention is a polyester resin whose constituent components are a polycarboxylic acid component and a polyhydric alcohol component. It contains a polycarboxylic acid having a furan skeleton as the polycarboxylic acid component, and ethylene glycol as the polyhydric alcohol component. The polyester resin of the present invention preferably contains 80 mol% or more of units consisting of a polycarboxylic acid having a furan skeleton and ethylene glycol, more preferably 85 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may even contain 100 mol%.

The polyester resin of the present invention contains a polycarboxylic acid having a furan skeleton as a polycarboxylic acid component. Examples of the furan skeleton include furan and furan substitution products (i.e., furan in which one or two hydrogen atoms are substituted with any substituent; the substituent does not include a carboxy group). Examples of the substituent introduced into the furan substitution product include an alkyl group having 1 to 10 carbon atoms, an aromatic group having 6 to 18 carbon atoms, a halogen, an alkoxy group having 1 to 10 carbon atoms, etc. A furan substitution product substituted with an alkyl group having 1 to 4 carbon atoms or unsubstituted furan is preferred, and unsubstituted furan is more preferred.

As a polyvalent carboxylic acid component having a furan skeleton, furandicarboxylic acid having two carboxy groups is preferred. There are furandicarboxylic acids having carboxy groups at the 2nd and 3rd positions, the 2nd and 4th positions, the 2nd and 5th positions, or the 3rd and 4th positions of the furan ring that can react with other monomers, and 2,5-furandicarboxylic acid, which is a furandicarboxylic acid having carboxy groups at the 2nd and 5th positions, is particularly preferred in terms of heat resistance. As a raw material monomer for producing polyester resin, furandicarboxylic acid and its derivatives can be used. Examples of derivatives include alkyl esters having 1 to 4 carbon atoms, and among these, methyl ester, ethyl ester, n-propyl ester, isopropyl ester, etc. are preferred, and methyl ester is more preferred. These may be used alone or in combination of two or more.

The polyvalent carboxylic acid component having a furan skeleton that constitutes the polyester resin of the present invention may be a petroleum-derived raw material or a biomass-derived raw material, but from an environmental perspective, it is preferable to use a biomass-derived raw material.

The ratio of the polycarboxylic acid component having a furan skeleton to 100 mol% of all polycarboxylic acid components constituting the polyester resin is not particularly limited, but is usually preferably 95 mol% or more, more preferably 96 mol% or more, even more preferably 97 mol% or more, and may be 98 mol% or more, or may be 99 mol% or more. It is also a preferred embodiment that the polycarboxylic acid component is composed only of polycarboxylic acid components having a furan skeleton.

The polyester resin of the present invention may contain an aliphatic polycarboxylic acid component as the polycarboxylic acid component. As the aliphatic polycarboxylic acid component, an aliphatic dicarboxylic acid having two carboxy groups is preferable. Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, and dimer acid. Among them, an aliphatic dicarboxylic acid having 2 to 12 carbon atoms is preferable.
The aliphatic polycarboxylic acid component may be either a saturated aliphatic dicarboxylic acid or an unsaturated dicarboxylic acid, but is preferably a saturated aliphatic dicarboxylic acid.
The aliphatic polycarboxylic acid component may be a linear aliphatic dicarboxylic acid or a branched aliphatic dicarboxylic acid, but is preferably a linear aliphatic dicarboxylic acid. As a raw material monomer for producing the polyester resin, an aliphatic dicarboxylic acid and its derivatives can be used. The derivatives are the same as those described above.

The aliphatic polycarboxylic acid component is preferably a linear saturated aliphatic dicarboxylic acid having 2 to 12 carbon atoms, more preferably a linear saturated aliphatic dicarboxylic acid having 2 to 10 carbon atoms, and even more preferably a linear saturated aliphatic dicarboxylic acid having 3 to 7 carbon atoms.
The amount of the aliphatic polycarboxylic acid component relative to 100 mol% of the total polycarboxylic acid components constituting the polyester resin is preferably 5 mol% or less, more preferably 4 mol% or less, and even more preferably 3 mol% or less. In addition, the aliphatic polycarboxylic acid component may not be contained, but if it is contained, it is preferably 0.1 mol% or more, more preferably 0.7 mol% or more, and even more preferably 1.5 mol% or more.
When the polyester resin of the present invention contains an aliphatic polycarboxylic acid within the above range, the decrease in heat resistance due to the copolymerization component can be suppressed, and the crystallization rate can be improved. The reason is not clear, but it is thought that the molecular mobility of the polyester resin is increased by containing a flexible aliphatic polycarboxylic acid component within the above optimal range, and the molecules are oriented so that crystals can be formed. If the copolymerization amount of the aliphatic polycarboxylic acid component is larger than the above range, the molecular mobility is increased, but the chain length of the block consisting of the polycarboxylic acid component having a furan skeleton and the polyhydric alcohol component becomes shorter, making it difficult to form crystals.

The aliphatic polyvalent carboxylic acid component that constitutes the polyester resin of the present invention may be a petroleum-derived raw material or a biomass-derived raw material, but from an environmental standpoint, it is preferable to use a biomass-derived raw material.

The polyester resin of the present invention may contain, as the polycarboxylic acid component, other carboxylic acid components than the polycarboxylic acid component having a furan skeleton and the aliphatic polycarboxylic acid component, and may be a dicarboxylic acid component or a trivalent or higher polycarboxylic acid component, as long as the effect of the present invention is not impaired. Examples of the other carboxylic acid components include aromatic polycarboxylic acids and their esters, or alicyclic polycarboxylic acids and their esters, and the polyester may be a mixture of one or more of these.

Examples of aromatic polycarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, diphenic acid, 5-hydroxyisophthalic acid, trimellitic acid, pyromellitic acid, methylcyclohexene tricarboxylic acid, oxydiphthalic dianhydride (ODPA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), 2,2'-bis[(dicarboxyphenoxy)phenyl]propane dianhydride (BSAA), etc. Other examples include aromatic dicarboxylic acids having a sulfonic acid group or a sulfonate salt group, such as sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, 5-(4-sulfophenoxy)isophthalic acid, sulfoterephthalic acid, and their metal salts and ammonium salts.

Examples of alicyclic polycarboxylic acids include alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid and their anhydrides. These other carboxylic acid components may be used alone or in combination of two or more. They may also be ester-modified.

The amount of the above-mentioned other carboxylic acid components relative to 100 mol% of all polycarboxylic acid components constituting the polyester resin of the present invention is preferably 3 mol% or less in total, more preferably 2 mol% or less, and even more preferably 1 mol% or less. It is also a preferred embodiment that does not contain the above-mentioned other carboxylic acid components, that is, the polycarboxylic acid component consists only of polycarboxylic acid components having a furan skeleton and aliphatic polycarboxylic acid components. It is also a preferred embodiment that the polycarboxylic acid component consists only of polycarboxylic acid components having a furan skeleton.

The polyhydric alcohol component constituting the polyester resin of the present invention includes ethylene glycol. The proportion of ethylene glycol in the total polyhydric alcohol components constituting the polyester resin of the present invention is not particularly limited, but is usually preferably 80 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, and particularly preferably 95 mol% or more. It is also a preferred embodiment that the polyhydric alcohol component consists only of ethylene glycol. Furthermore, it is also preferable that it is 99.5 mol% or less, even more preferably 99 mol% or less, and even more preferably 98 mol% or less.

The ethylene glycol that constitutes the polyester resin of the present invention may be a petroleum-derived raw material or a biomass-derived raw material, but from an environmental perspective, it is preferable to use a biomass-derived raw material.

The polyester resin of the present invention may also contain diethylene glycol as a polyhydric alcohol component. The ratio of diethylene glycol to 100 mol% of all polyhydric alcohol components constituting the polyester resin of the present invention is preferably 5 mol% or less, more preferably 3 mol% or less, and even more preferably 2 mol% or less. The ratio of diethylene glycol to 100 mol% of all polyhydric alcohol components is preferably 0.1 mol% or more, more preferably 0.5 mol% or more, and even more preferably 1 mol% or more.

When the polyester resin of the present invention contains diethylene glycol as a polyhydric alcohol component, it may be a by-product of condensation of ethylene glycol, or it may be added as a raw material. In order to suppress the amount of diethylene glycol by-product, for example, a basic compound can be added as a diethylene glycol inhibitor. Examples of basic compounds include tertiary amines such as triethylamine and tri-n-butylamine, and quaternary ammonium salts such as tetraethylammonium hydroxide.

The polyester resin of the present invention may also contain a polyhydric alcohol component other than ethylene glycol or diethylene glycol, and may be a dihydric alcohol component or a trihydric or higher polyhydric alcohol component. The polyhydric alcohol component other than ethylene glycol or diethylene glycol is preferably selected from aliphatic polyhydric alcohols, alicyclic polyhydric alcohols, ether bond-containing polyhydric alcohols, and aromatic-containing polyhydric alcohols, and may be a mixture of one or more of these. Examples of aliphatic polyhydric alcohols include 1,2-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 2-ethyl-2-butylpropanediol, hydroxypivalic acid neopentyl glycol ester, dimethylolheptane, 2,2,4-trimethyl-1,3-pentanediol, glycerin, pentaerythritol, trimethylolethane, trimethylolpentane, and trimethylolpropane.

Examples of the alicyclic polyhydric alcohol include 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, tricyclodecanediol, tricyclodecanedimethylol, spiroglycol, hydrogenated bisphenol A, and ethylene oxide and propylene oxide adducts of hydrogenated bisphenol A.
Examples of the ether bond-containing polyhydric alcohol include diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, neopentyl glycol ethylene oxide adduct, and neopentyl glycol propylene oxide adduct, which may also be used if necessary.
Examples of aromatic polyhydric alcohols include glycols obtained by adding 1 to several moles of ethylene oxide or propylene oxide to two phenolic hydroxyl groups of bisphenols, such as paraxylene glycol, metaxylene glycol, orthoxylene glycol, 1,4-phenylene glycol, an ethylene oxide adduct of 1,4-phenylene glycol, bisphenol A, an ethylene oxide adduct of bisphenol A, and a propylene oxide adduct of bisphenol A. These may be used alone or in combination of two or more.

The polyester resin of the present invention contains at least one metal element selected from antimony, aluminum, titanium, and germanium, and the total content of the metal elements is 350 mass ppm or less. Preferably, the total content is 300 mass ppm or less, and more preferably, 250 mass ppm or less. In this case, the polyester resin of the present invention has excellent thermal stability. If the polyester resin contains a large amount of the metal elements, it may promote the thermal decomposition reaction of the polyester resin at high temperatures, which may cause a decrease in reduced viscosity, coloration of the resin, and thermal degradation.

The polyester resin of the present invention may contain a crystal nucleating agent. Examples of the crystal nucleating agent include inorganic materials such as talc, boron nitride, silica, and layered silicate, and organic materials such as ester oligomer, polyethylene wax, and polypropylene wax. Talc and ester oligomer are preferred. These may be used alone or in combination of two or more. The polyester resin of the present invention has a cold crystallization peak in the range of 145 to 185°C during the second heating step, as measured by differential scanning calorimetry (DSC) at a heating rate of 2°C/min, and has a heat generation rate of 5 J/g or more. By including a crystal nucleating agent in the polyester resin, the crystallization rate can be further improved and a high crystallization rate can be maintained. In addition, it is also a preferred embodiment that the polyester resin contains a crystal nucleating agent and has a history of being subjected to high shear stress in a molten state.

When a crystal nucleating agent is contained, the preferred content is 0.001% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.1% by mass or more, based on the polyester resin. The upper limit of the crystal nucleating agent content is 4% by mass, more preferably 3% by mass, even more preferably 2% by mass, and most preferably 1% by mass. If the content of the crystal nucleating agent is less than the lower limit, the effect of promoting crystallization cannot be fully obtained, and if it is more than the upper limit, the mechanical properties of the polyester resin may decrease, and flexibility may be impaired.

When the nucleating agent is an inorganic material, the smaller the particle size, the better for the nucleating effect. The preferred average particle size of the nucleating agent is 5 μm or less, more preferably 3 μm or less, even more preferably 1 μm or less, and most preferably 0.5 μm or less. The lower limit of the average particle size of the nucleating agent is preferably 0.1 μm.

The method for producing the polyester resin of the present invention preferably includes a step of polycondensing a polycarboxylic acid component containing a polycarboxylic acid having a furan skeleton with a polyhydric alcohol component containing ethylene glycol, and a step of applying a shear stress to the molten composition of the reaction product obtained in the polycondensation reaction step.

The method for producing the polyester resin of the present invention can be carried out using a method including known steps, except that a polycarboxylic acid having a furan skeleton is used as the polycarboxylic acid component, ethylene glycol is used as the polyhydric alcohol component, and a polycondensation reaction step is included.

In the method for producing the polyester resin of the present invention, the molar ratio of the polyvalent carboxylic acid component containing a polyvalent carboxylic acid having a furan skeleton and the polyhydric alcohol component containing ethylene glycol at the time of charging is not particularly limited as long as the polyester resin of the present invention can be produced. However, in terms of facilitating the production of a polyester resin with a high molecular weight, the diol is preferably 0.9 mol or more, more preferably 1.0 mol or more, and even more preferably 1.2 mol or more, per 1.0 mol of the dicarboxylic acid component. On the other hand, it is preferably 4.0 mol or less, more preferably 3.0 mol or less, and even more preferably 2.5 mol or less.

The method for producing the polyester resin of the present invention includes a step of polycondensation reaction. When polycondensing the polyester resin of the present invention, it is preferable to use a polymerization catalyst. The timing and amount of the catalyst to be added may be appropriately adjusted. That is, the polymerization catalyst may be added when the raw materials are charged, or may be added during the production process. Also, the polymerization catalyst may be added when the raw materials are charged and during the production process.
The catalyst may be charged as a simple polymerization catalyst or in a state of being dissolved or dispersed in water, alcohol, or glycol such as ethylene glycol.

Examples of polymerization catalysts include titanium compounds (tetra-n-butyl titanate, tetraisopropyl titanate, titanium oxyacetylacetonate, etc.), antimony compounds (tributoxyantimony, antimony trioxide, etc.), germanium compounds (tetra-n-butoxygermanium, germanium oxide, etc.), zinc compounds (zinc acetate, etc.), and aluminum compounds (aluminum acetate, aluminum acetylacetate, etc.). When using an aluminum compound as a polymerization catalyst, it is preferable to use a phosphorus compound in combination as a co-catalyst. The above polymerization catalysts may be used alone or in combination. In terms of reactivity in polycondensation, antimony compounds, aluminum compounds, titanium compounds, and germanium compounds are preferred, and in consideration of the effect on the coloring of the resin, aluminum compounds and germanium compounds are more preferred.

Phosphorus compounds can be added in the polyester resin manufacturing process. There are no particular limitations on the phosphorus compound, but phosphonic acid compounds and phosphinic acid compounds are preferred because they have a large effect of improving catalytic activity, and of these, phosphonic acid compounds are more preferred because they have a particularly large effect of improving catalytic activity.

The amount of the polymerization catalyst used is preferably large in terms of a high polycondensation reaction rate and high production efficiency. On the other hand, if the polyester resin contains a large amount of metal elements, the polyester resin may be discolored or thermally deteriorated due to the promotion of thermal decomposition reaction at high temperatures.
Even if the polymerization catalyst is placed in a reduced pressure environment during the polycondensation of the polyester resin, almost 100% of the amount initially added to the system as a catalyst remains in the copolymerized polyester resin produced by polycondensation. That is, since the amount of the polymerization catalyst is almost unchanged before and after polycondensation, the amount of the polymerization catalyst added to the polyester resin produced is specifically 1 mass ppm or more, more preferably 3 mass ppm or more, and even more preferably 5 mass ppm or more. On the other hand, it is preferably 350 mass ppm or less, more preferably 300 mass ppm or less, and even more preferably 250 mass ppm or less.

In the method for producing the polyester resin of the present invention, from the viewpoint of the thermal stability of the polyester resin, it is preferable to produce the polyester resin using a polymerization catalyst containing an aluminum compound and a phosphorus compound.

When the polyester resin of the present invention contains a phosphorus compound, it preferably contains 20 to 250 ppm by mass of phosphorus element, more preferably 30 to 200 ppm by mass, even more preferably 40 to 150 ppm by mass, and particularly preferably 50 to 120 ppm by mass. If the phosphorus element is less than 20 ppm by mass, there is a risk of reduced polymerization activity and increased amounts of foreign matter. On the other hand, if it exceeds 250 ppm by mass, catalyst costs will increase and polymerization activity may decrease.

When the phosphorus compound, which functions as a catalyst together with the aluminum compound, is placed in a reduced pressure environment during the polycondensation of the copolymerized polyester resin, a portion (about 10 to 40%) of the amount initially added to the system as a catalyst is generally removed from the system, and this removal rate varies depending on the molar ratio of phosphorus element added to aluminum element, the basicity or acidity of the aluminum compound-containing glycol solution or phosphorus compound-containing glycol solution added, the method of adding the aluminum compound-containing solution or phosphorus compound-containing solution (whether they are added as a single liquid or added separately), etc. Therefore, it is preferable to add 20 to 250 ppm by mass of phosphorus element to the polyester resin to be produced, more preferably 30 to 200 ppm by mass, and even more preferably 40 to 150 ppm by mass.

In the polyester resin of the present invention, the molar ratio of phosphorus element to aluminum element is preferably 1.1 to 2.8, more preferably 1.3 to 2.6, and even more preferably 1.5 to 2.5. As described above, the aluminum element and phosphorus element in the polyester resin are derived from the aluminum compound and phosphorus compound used as polymerization catalysts for the polyester resin, respectively. By using these aluminum compounds and phosphorus compounds in combination in a specific ratio, a complex having catalytic activity in the polycondensation system is functionally formed, and sufficient polymerization activity can be exhibited. If the content ratio of phosphorus element to aluminum element is less than 1.1, there is a risk of reduced thermal stability and thermal oxidation stability, and an increase in the amount of foreign matter. On the other hand, if the content ratio of phosphorus element to aluminum element exceeds 2.8, the amount of phosphorus compound added becomes too large, and the catalyst cost increases.

As mentioned above, when the phosphorus compound is placed in a reduced pressure environment during the polycondensation of polyester resin, a portion (about 10 to 40%) of the amount initially added to the system as a catalyst is generally removed from the system, so the molar ratio of phosphorus element added to aluminum element is preferably 1.3 to 2.5, more preferably 1.5 to 2.3, and even more preferably 1.7 to 2.2.

In the method for producing the polyester resin of the present invention, the esterification reaction can be, for example, a direct esterification method in which a polycarboxylic acid having a furan skeleton is directly reacted with ethylene glycol, and if necessary, other copolymerization components, water is distilled off to carry out the esterification reaction, and then a polycondensation reaction is carried out under normal pressure or reduced pressure. The transesterification reaction can be, for example, a production method in which 2,5-dimethyl furandicarboxylate is reacted with ethylene glycol, and if necessary, other copolymerization components, methyl alcohol is distilled off to carry out the esterification reaction, and then a polycondensation reaction is carried out under normal pressure or reduced pressure.

The conditions of temperature, time, pressure, etc. in the esterification reaction and transesterification reaction can be within the ranges of conventionally known polyester resin manufacturing methods. The reaction temperature is usually 100°C or higher, and preferably 120°C or higher. Also, it is usually 300°C or lower, preferably 290°C or lower, and more preferably 280°C or lower. By keeping the temperature within these ranges, the reaction can proceed efficiently. The reaction atmosphere is usually an inert gas atmosphere such as nitrogen or argon. The reaction pressure is usually -0.05 MPa to 0.3 MPa in gauge pressure. The reaction time is usually 1 hour or more, and on the other hand, it is usually 10 hours or less, preferably 8 hours or less.

The conditions for the polycondensation reaction, such as temperature, time, and pressure, can be within the ranges of conventionally known polyester manufacturing methods. The polycondensation reaction temperature is preferably 230°C or higher, more preferably 235°C or higher, and even more preferably 240°C or higher. On the other hand, it is preferably 300°C or lower, more preferably 290°C or lower, and even more preferably 280°C or lower. The absolute pressure is preferably 150 Pa or lower, more preferably 100 Pa or lower, and even more preferably 50 Pa or lower. The reaction time is preferably 10 hours or less, more preferably 7 hours or less, and even more preferably 5 hours or less. By setting the reaction time within this range, the polycondensation reaction rate is sufficiently ensured, and thermal decomposition, coloration, side reactions, etc. are suppressed, resulting in a polyester resin with a high molecular weight.

In any of these methods, the esterification reaction or transesterification reaction may be carried out in one step or in multiple steps. The polycondensation reaction may be carried out in one step or in multiple steps.

The apparatus for producing the polyester resin of the present invention may be of either a batch type or a continuous type.

The method for producing the polyester resin of the present invention can include a step of applying shear stress to the molten composition of the reaction product obtained by the polycondensation reaction.

The process of applying shear stress may, for example, be a method in which a reaction product obtained by a polycondensation reaction between a polycarboxylic acid component containing a polycarboxylic acid having a furan skeleton and a polyhydric alcohol component containing ethylene glycol is supplied to a device that applies shear stress, and shear stress is applied to the molten composition.

As a device for applying shear stress, a twin-screw extruder, a resin kneading device such as a gear pump, a passing device such as a die, a compression device such as a heat press or a roll press, etc. can be used, but it is preferable to use a twin-screw extruder.

In the step of applying the shear stress, it is preferable to apply a shear stress of 0.15 MPa or more. More preferably, it is 0.25 MPa or more, even more preferably, it is 0.35 MPa or more, and particularly preferably, it is 0.45 MPa or more. If the shear stress is more than this, it is believed that a sufficient shear stress can be applied to the resin, the molecules become more likely to be oriented so that crystals can be formed, and a high crystallization rate can be maintained even after remelting.

Here, the shear stress τ is expressed by the following formula (1) where γ is the shear rate and μ is the melt viscosity.
τ=μγ Formula (1)
It is expressed as:

For example, in the case of a twin-screw extruder, when the screw outer diameter is D, the screw rotation speed is N, and the tip clearance is h, the shear rate γ is calculated by the following formula (2):
γ=πDN/h Formula (2)
It is expressed as:

In a preferred embodiment, the melt viscosity of the composition when the shear stress is applied is preferably 300 to 3000 Pa·s, more preferably 600 to 2000 Pa·s, the extrusion temperature is preferably 180° C. or higher, more preferably 190° C. or higher, the shear rate is preferably 1500 sec ⁻¹ or lower, more preferably 1000 sec ⁻¹ or lower, and it is preferable to knead and extrude the polyester resin at the above shear rate.

In the method for producing the polyester resin of the present invention, the molecules are more easily oriented by including a step of applying shear stress to the molten composition of the reaction product obtained in the polycondensation reaction step. In addition, it is believed that the oriented molecules are fixed and can maintain a high crystallization rate even after remelting. This can improve the productivity of molded bodies during melt molding processing.

In the method for producing polyester resin of the present invention, the reactants obtained in the polycondensation reaction process may be supplied to the device that applies shear stress by, for example, directly connecting the polymerization device and the device that applies shear stress. In this case, the reactants obtained in the polycondensation reaction process can be transported in a molten state and supplied to the device that applies shear stress, allowing continuous production. Alternatively, the reactants may be discharged once in chip form from the polymerization device and then supplied to the device that applies shear stress. From the viewpoint of production efficiency, it is preferable to directly connect the polymerization device and the device that applies shear stress.

The polyester resin obtained in the manufacturing process that includes the step of applying shear stress has a high crystallization rate and can maintain an oriented molecular state, so crystallization can be easily promoted even after melting. Therefore, the degree of crystallization can be sufficiently increased in melt molding processes such as injection molding and melt film forming, and molded products with excellent operational stability during melt molding and high mechanical strength can be obtained.

The polyester resin pellets of the present invention can be produced by a conventional pellet production method. For example, the polyester resin obtained in the shear stress application step can be discharged from the device in the form of strands, which can then be cut by a cutter while being cooled with water or the like.

If necessary, the polyester resin obtained in the shear stress application process may be polymerized further by solid-phase polymerization to increase the molecular weight. In this case, the molecular weight of the polyester resin after the polycondensation reaction process can be further increased.

The method of the solid-phase polymerization is not particularly limited, but examples include a method of heating the polyester resin obtained in the above-mentioned step of applying shear stress, or the polyester resin pellets obtained in the above-mentioned method of manufacturing polyester resin pellets, in an inert gas atmosphere or under reduced pressure. The reaction may be carried out with the polyester resin pellets or powder left to stand, or with stirring. When stirring, stirring may be carried out by installing a stirring blade in the reaction vessel, or by moving the reaction vessel.

The solid-phase polymerization reaction temperature is preferably below the melting point. The reaction temperature is preferably 180°C or higher, and more preferably 190°C or higher. On the other hand, it is preferably 260°C or lower, and more preferably 250°C or lower. The heating time is preferably 1 hour or longer, and more preferably 3 hours or longer. On the other hand, since discoloration is less likely to occur, it is preferably 50 hours or shorter, more preferably 40 hours or shorter, and even more preferably 30 hours or shorter.

The solid-phase polymerization process makes it possible to increase the molecular weight of the polyester resin of the present invention, resulting in the production of molded products with high strength.

The cold crystallization peak measurement and the calorimetry of fusion by differential scanning calorimetry (DSC) are described below.
In general, DSC changes the temperature of the sample section, which consists of a sample and a reference material, at a constant rate and measures the temperature difference between the sample and the reference material. By analyzing the sample's melting, glass transition, crystallization, hardening, and other thermal history, various measurements such as specific heat and purity are possible.
In the first heating in DSC measurement, when the temperature is gradually increased from room temperature (e.g., 20°C), the glass transition temperature is reached and a shift in the baseline occurs. If the temperature is further increased, a cold crystallization peak, which is an exothermic peak resulting from the crystallization of the polymer, is obtained. Generally, the crystallization behavior of a polymer is evaluated by the cold crystallization peak temperature and the amount of heat generated (heat of cold crystallization), which are indicators of the polymer crystallization rate. In particular, during the first heating, the crystallization rate is obtained that includes the influence of the manufacturing process, such as pretreatment and thermal history of the polymer. If the temperature is further increased, the polymer begins to melt and heat is absorbed. The melting peak temperature is the melting point, and the amount of heat absorbed when the temperature is increased to above the melting point and the polymer is completely melted indicates the heat of fusion of the polymer. The heat of cold crystallization is the amount of crystals newly generated during heating, and the difference between the heat of fusion and the heat of cold crystallization corresponds to the amount of crystals that the polymer possessed before the start of the first heating. For example, if the heat of cold crystallization is 10 J/g and the heat of fusion is 30 J/g, it is understood that a polymer with crystals of the difference of 20 J/g was subjected to DSC measurement. The temperature is then lowered to room temperature and cooled. If the cooling rate is slow during this cooling process, the molten polymer will begin to crystallize, generate heat, and recrystallization can be confirmed. At this time, crystals with the original arrangement of the polymer are obtained. On the other hand, if the cooling rate is fast, an amorphous polymer can be obtained without recrystallization.
In the second heating step, the amorphous polymer obtained by quenching from the molten state in the first heating step is gradually heated again from room temperature to above the melting point. In the heating process, a cold crystallization peak is obtained again. The amount of heat generated by the cold crystallization obtained here is generally the inherent crystallization rate of the polymer, which cancels the effects of the manufacturing process, such as the pretreatment and thermal history of the polymer. In other words, a high inherent crystallization rate of the polymer means that the cold crystallization peak temperature in the second heating step is low, and the amount of heat generated by the cold crystallization is high. If the temperature is further increased, the polymer will melt again.

The cold crystallization peak of the polyester resin of the present invention refers to the cold crystallization peak during the second heating, which is measured by melting the polyester resin during the first heating step, then amorphizing it by rapid cooling, and then performing differential scanning calorimetry (DSC) at a heating rate of 2°C/min. The cold crystallization peak temperature during the second heating step is in the range of 145 to 185°C. It is preferably 150 to 183°C, and more preferably 155°C to 180°C. The heat generated by cold crystallization during the second heating step in the polyester resin of the present invention is 5 J/g or more. It is preferably 8 J/g or more, more preferably 10 J/g or more, and even more preferably 15 J/g or more. In this case, the polyester resin of the present invention exhibits a high crystallization rate even after the remelting process, and by improving the crystallization rate during melt molding of the polyester resin, the productivity of the molded body can be improved.

The heat of fusion of the polyester resin of the present invention during the first heating step, measured by differential scanning calorimetry (DSC) at a heating rate of 10°C/min, is not particularly limited, but is preferably 6 J/g or more, more preferably 8 J/g or more. The upper limit of the heat of fusion during the first heating step is not particularly limited, but is, for example, 40 J/g or less, and preferably 30 J/g or less. The heat of fusion during the second heating step, measured by differential scanning calorimetry (DSC) at a heating rate of 2°C/min, is preferably 10 J/g or more, more preferably 15 J/g or more, and even more preferably 20 J/g or more. The upper limit of the heat of fusion during the second heating step is not particularly limited, but is, for example, 60 J/g or less, and preferably 45 J/g or less.

The polyester resin of the present invention preferably has a melting point of 200°C or higher, more preferably 205°C or higher, from the viewpoint of increasing the mechanical strength of the molded body obtained from the polyester resin. Furthermore, in the case of a solid-phase polymerization process, the processing temperature can be set high, so that productivity can be improved. There is no particular upper limit to the melting point, and it is, for example, 240°C or lower, and preferably 230°C or lower.

The lower limit of the reduced viscosity of the polyester resin of the present invention is 0.50 dl/g or more. It is preferably 0.55 dl/g or more, and more preferably 0.60 dl/g or more. The upper limit of the reduced viscosity is preferably 1.20 dl/g or less, more preferably 1.10 dl/g or less, even more preferably 1.00 dl/g or less, particularly preferably 0.90 dl/g or less, and most preferably 0.80 dl/g or less. By having a reduced viscosity of the above or more and a sufficient crystallization rate, the polyester resin of the present invention has high strength and excellent thermal stability, and can improve productivity.

The polyester resin of the present invention preferably has a small change in reduced viscosity before and after the thermal decomposition test. That is, the change in reduced viscosity after heat treatment at 280°C for 1 hour is preferably 0.15 dl/g or less, more preferably 0.14 dl/g or less, and even more preferably 0.13 dl/g or less. If the change in reduced viscosity exceeds the above range, discoloration or thermal degradation of the resin may occur. There is no particular lower limit to the change in reduced viscosity, and it is, for example, 0.03 dl/g or more, and preferably 0.05 dl/g or more.

In the polyester resin of the present invention, the acid value after the polycondensation reaction process is preferably 100 eq/ton or less, more preferably 50 eq/ton or less, and even more preferably 25 eq/ton or less. In this case, it is possible to prevent the acid value of the polyester resin in the subsequent process from becoming too high. As a result, it is possible to prevent the deterioration of the thermal stability of the polyester resin, prevent discoloration of the polyester resin during processing and a decrease in molecular weight, and obtain a molded product with high strength. There is no particular lower limit for the acid value after the polycondensation reaction process, and it is, for example, 3 eq/ton or more, and preferably 7 eq/ton or more.

The copolymer polyester resin of the present invention can contain various antioxidants as appropriate. The method of blending with the polyester resin is not particularly limited, and examples include adding the antioxidant when the raw materials for producing the polyester resin are charged, adding the antioxidant during the polyester resin production process, and dry blending with the polyester resin after production. Examples of antioxidants include known antioxidants such as phenol-based antioxidants, phosphorus-based antioxidants, amine-based antioxidants, sulfur-based antioxidants, nitro compound-based antioxidants, and inorganic compound-based antioxidants. Phenol-based antioxidants, which have relatively high heat resistance, are preferred, and it is preferable to include 0.05 to 0.5 parts by mass per 100 parts by mass of the resulting polyester resin.

In addition to the antioxidant, various additives such as heat stabilizers, hydrolysis inhibitors, flame retardants, antistatic agents, release agents, and ultraviolet absorbers may be added to the polyester resin of the present invention, so long as the properties of the resin are not impaired. These additives may be added when the raw materials used to manufacture the polyester resin are charged, or may be added during the manufacturing process of the polyester resin, or may be dry-blended with the polyester resin after manufacture.

The polyester resin of the present invention is preferably formed into polyester resin pellets, which are easily handled. These can be used to form molded articles. The polyester resin pellets of the present invention have a high crystallization rate, which makes it possible to prevent resin blocking, and to obtain excellent operational stability during melt molding and stable supply to the molding machine.

The polyester resin of the present invention can be molded into bottles, films, fibers, etc. using known molding methods.

This application claims the benefit of priority based on Japanese Patent Application No. 2023-024348, filed on February 20, 2023. The entire contents of the specification of Japanese Patent Application No. 2023-024348, filed on February 20, 2023, are incorporated by reference into this application.

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.
Moreover, each physical property was measured by the following methods.

Melt viscosity (μ) measurement;
The melt viscosity in the step of applying a shear stress was measured by the following method.
A capillary die having a diameter of 1 mm, a capillary length of 10 mm, and a furnace diameter of 9.55 mm was used in a Toyo Seiki Co., Ltd. Capillograph 1B. A dried resin sample (polyester resin after polycondensation) was filled into a cylinder kept at a predetermined temperature, and after melting for about 1 minute, the melt viscosity (Pa s) at a predetermined shear rate was measured.

shear rate γ;
In the step of applying a shear stress, the following twin-screw extruder was used, and the shear rate γ was calculated from the following formula 3.
・Technovel KZW15TW-45/60MG-NH (-2200)
・Screw outer diameter: 15.21 mm
Clearance: 0.22 mm
Shear rate γ (sec ⁻¹ ): γ=πD(N/60)/h (Formula 3)
(D: screw outer diameter (mm), N: screw rotation speed (rpm), h: clearance (mm))

Shear stress (MPa);
The shear stress was calculated from the following formula 4 using τ, the melt viscosity μ, and the shear rate γ.
Shear stress τ (MPa) = μγ (Equation 4)

Reduced viscosity measurement;
0.10 g of the polyester resin was dissolved in a mixed solvent of phenol/1,1,2,2-tetrachloroethane (6/4 (mass ratio)), and the viscosity was measured at 30° C. using an Ubbelohde viscometer and expressed in dl/g.

Measurement of the change in reduced viscosity before and after thermal decomposition test;
5 g of the polyester resin was placed in a glass container and dried in a vacuum at 140° C. for 16 hours to produce a dried polyester resin with a moisture content of 150 ppm or less. The glass container was then filled with nitrogen and heat-treated in a salt bath at 280° C. for 1 hour. The reduced viscosity after the treatment was measured in the same manner as above, and the amount of change in reduced viscosity before and after the thermal decomposition test was calculated using the following formula.
(Change in reduced viscosity before and after thermal decomposition test)=(reduced viscosity before heat treatment)−(reduced viscosity after heat treatment) (Equation 5)

Polyester resin composition:
20 mg of the polyester resin was dissolved in 0.6 ml of a mixed solvent of trifluoroacetic acid/deuterated chloroform (15/85 (volume ratio)) and centrifuged. The supernatant was then collected and subjected to H-NMR measurement, and the composition of the polyester resin was identified from the NMR spectrum.
H-HMR measurements were carried out using the following equipment and conditions.
Apparatus: Fourier transform nuclear magnetic resonance apparatus (AVANCE NEO600, manufactured by BRUKER)
・^1H resonance frequency: 600.13MHz
Lock solvent: deuterated chloroform Flip angle: 30°
Data acquisition time: 4 seconds Delay time: 1 second Measurement temperature: 30°C
・Number of times of accumulation: 128 times

Metal element content in polyester resin;
The polyester resin was weighed in a platinum crucible, carbonized on an electric stove, and then incinerated in a muffle furnace at 550°C for 8 hours. The incinerated sample was dissolved in 1.2M hydrochloric acid to prepare a sample solution. The prepared sample solution was measured under the following conditions, and the concentrations of antimony, aluminum, titanium, and germanium in the polyester resin were determined by high-frequency inductively coupled plasma emission spectrometry.
・Apparatus: SPECTRO CIROS-120
Plasma output: 1400W
Plasma gas: 13.0 L / min
Auxiliary gas: 2.0 L/min
Nebulizer: Crossflow nebulizer Chamber: Cyclone chamber Measurement wavelength: 167.078 nm
Phosphorus element content in polyester resin;
The polyester resin was subjected to wet decomposition with sulfuric acid, nitric acid, and perchloric acid, and then neutralized with ammonia water. Ammonium molybdate and hydrazine sulfate were added to the prepared solution, and the absorbance at a wavelength of 830 nm was measured using an ultraviolet-visible absorption spectrophotometer (Shimadzu Corporation, UV-1700). The concentration of phosphorus element in the polyester resin was determined from a calibration curve prepared in advance.

Acid number;
20 mg of polyester resin was dissolved in 0.6 ml of a mixed solvent of deuterated hexafluoroisopropanol/deuterated chloroform (1/9 (volume ratio)) and centrifuged. The supernatant was then collected and 10 μL of deuterated pyridine was added, followed by H-NMR measurement in the same manner as in identifying the composition of the polyester resin described above, and the acid value was determined from the NMR spectrum.

Temperature of cold crystallization peak (°C), heat of cold crystallization peak (J/g), melting point (°C), heat of fusion (J/g);
Using a Hitachi High-Tech Science Corporation differential scanning calorimeter "DSC7000", 5 mg of polyester resin was placed in an aluminum pan and the lid was pressed down to seal. Next, the temperature was raised to 250°C at 10°C/min and held at 250°C for 3 minutes to completely melt the crystals, and a DSC curve was obtained at the 1st temperature rise. Then, the temperature was lowered from 250°C to 25°C at 50°C/min, and the temperature was raised again to 250°C at 2°C/min to obtain a DSC curve at the 2nd temperature rise. The temperature of the cold crystallization peak was determined from the exothermic peak temperature of the DSC curve at the 2nd temperature rise, and the heat generation amount of the cold crystallization peak was determined from the integral value obtained from the intersection of the exothermic curve generated by crystallization at the 2nd temperature rise and the extrapolated baseline. The melting point was determined from the endothermic peak temperature of each of the DSC curves during the first heating and the second heating, and the heat of fusion was determined from the integral value obtained from the intersection of each of the endothermic curves generated by the changes during melting during the first heating and the second heating with the extrapolated baseline.

The preparation of the aluminum-containing ethylene glycol solution and the phosphorus-containing ethylene glycol solution used as the catalyst will be described below.
<Preparation of Aluminum-Containing Ethylene Glycol Solution s>
A 20 g/L aqueous solution of basic aluminum acetate and an equal amount (volume ratio) of ethylene glycol were charged into a blending tank and stirred at room temperature (23° C.) for several hours. After that, water was distilled off from the system while stirring at 50 to 90° C. under reduced pressure (3 kPa) for several hours, to prepare an aluminum-containing ethylene glycol solution s containing 20 g/L of an aluminum compound.
<Preparation of phosphorus-containing ethylene glycol solution t>
As a phosphorus compound, Irganox 1222 (manufactured by BASF) was charged into a mixing tank together with ethylene glycol, and heat-treated at 175° C. for 150 minutes while stirring under nitrogen substitution to prepare a phosphorus-containing ethylene glycol solution t containing 50 g/L of the phosphorus compound.

Example 1
In a 2-liter stainless steel autoclave equipped with an electric wire heater, 2,5-furandicarboxylic acid (100 mol%) as a polycarboxylic acid component and ethylene glycol (200 mol%) in an amount twice the molar amount of the polycarboxylic acid component as a polyhydric alcohol component were charged. The amounts of these raw material monomers were such that the resin composition was as shown in Table 1. Note that diethylene glycol contained in the resin composition was not intentionally added, but was obtained by condensation of ethylene glycol. Furthermore, 0.3 mol% of triethylamine was added relative to the polycarboxylic acid component, and an esterification reaction was carried out for 120 minutes at 240°C under normal pressure while distilling water out of the system, to obtain an ester oligomer with an esterification rate of 95%.
Antimony trioxide was added as a catalyst to the obtained ester oligomer so that the antimony element was 250 ppm by mass relative to the mass of the obtained polyester resin.
Then, the temperature of the system was raised to 270°C in 1 hour, during which the pressure of the system was gradually reduced to 0.15 kPa, and under these conditions, a polycondensation reaction was carried out to reach the target melt viscosity. The resin was then fed to a twin-screw extruder (barrel temperature 215°C, screw rotation speed 150 rpm), and melt extruded while applying shear stress to the polyester resin at an actual resin temperature of 216°C, and the discharged strand was quenched in a water bath and pelletized with a cutter to obtain a polyester resin. The results of the obtained polyester resin are shown in Table 1. The temperature dependency of the melt viscosity of the obtained polyester resin is also shown in Figure 1.

Example 2
In the same manner as in Example 1, an ester oligomer having an esterification rate of 95% was obtained.
The same treatment as in Example 1 was carried out, except that the aluminum-containing ethylene glycol solution s and the phosphorus-containing ethylene glycol solution t prepared by the above-mentioned method were added as catalysts to the obtained ester oligomer to prepare a one-component mixture in such amounts of aluminum element and phosphorus element relative to the mass of the obtained polyester resin as shown in Table 1. The results of the obtained polyester resin are shown in Table 1.

Example 3
The same treatment as in Example 1 was carried out, except that the catalyst was changed to tetra-n-butoxytitanium, and the titanium element was added in an amount relative to the mass of the obtained polyester resin shown in Table 1. The results of the obtained polyester resin are shown in Table 1.

Example 4
The same treatment as in Example 1 was carried out, except that the catalyst was changed to germanium dioxide and the germanium element was added in an amount shown in Table 1 relative to the mass of the obtained polyester resin. The results of the obtained polyester resin are shown in Table 1.

Example 5
The same treatment as in Example 1 was carried out, except that the barrel temperature of the twin-screw extruder was changed to 230° C. The results of the obtained polyester resin are shown in Table 1.

Example 6
The same treatment as in Example 1 was carried out, except that the barrel temperature of the twin-screw extruder was changed to 200° C. The results for the obtained polyester resin are shown in Table 1. Note that, since it became impossible to measure the melt viscosity at 200° C. using a capillograph, it is noted in Table 1 that "measurable" was not possible.

(Example 7)
The same treatment as in Example 1 was carried out, except that after the target melt viscosity was reached in the polycondensation reaction, a PBT oligomer (Polysizer A-55: manufactured by DIC Corporation) was added as a crystal nucleating agent to the polyester resin in an amount of 1 mass %. The results of the obtained polyester resin are shown in Table 1.

(Example 8)
The same treatment as in Example 7 was carried out, except that talc (SG-95: manufactured by Nippon Talc Co., Ltd.) was used as the crystal nucleating agent. The results of the obtained polyester resin are shown in Table 1.

Example 9
The same treatment as in Example 1 was carried out, except that the barrel temperature of the twin-screw extruder was changed to 250° C. The results of the obtained polyester resin are shown in Table 1.

Example 10
The polyester resin obtained in Example 1 was dried in a vacuum dryer at 80° C. for 200 hours, and 10 g of the dried resin was placed in a glass container, kept at a vacuum of 1 Torr or less, and subjected to solid-phase polymerization for 6 hours in an oil bath at 200° C. The results of the obtained polyester resin are shown in Table 1.

(Example 11)
The polyester resin obtained in Example 1 was dried in a vacuum dryer at 80° C. for 200 hours, and 10 g of the dried resin was placed in a glass container, kept at a vacuum of 1 Torr or less, and subjected to solid-phase polymerization for 12 hours in an oil bath at 200° C. The results of the obtained polyester resin are shown in Table 1.

Example 12
The same treatment as in Example 1 was carried out except that the polybasic carboxylic acid component was changed to 2,5-furandicarboxylic acid (98 mol %) and succinic acid was changed to 2 mol %. The results of the obtained polyester resin are shown in Table 1.

(Comparative Example 1)
A 2-liter stainless steel autoclave equipped with an electric wire heater was charged with 2,5-furandicarboxylic acid (100 mol%) as a polycarboxylic acid component and ethylene glycol (200 mol%) in an amount twice the molar amount of the polycarboxylic acid component as a polyhydric alcohol component. The amounts of these raw material monomers were such that the resin composition was as shown in Table 1. Furthermore, 0.3 mol% of triethylamine was added relative to the polycarboxylic acid component, and an esterification reaction was carried out for 120 minutes at 240°C under normal pressure while distilling water out of the system, to obtain an ester oligomer with an esterification rate of 95%.
Antimony trioxide was added as a catalyst to the obtained ester oligomer so that the antimony element was 250 ppm by mass relative to the mass of the obtained polyester resin.
The temperature of the system was then raised to 270°C over 1 hour, during which the pressure of the system was gradually reduced to 0.15 kPa, and the polycondensation reaction was carried out under these conditions until the target melt viscosity was reached. The strands discharged from the autoclave were then quenched in a water bath and pelletized with a cutter to obtain a polyester resin. The results of the obtained polyester resin are shown in Table 1.

(Comparative Example 2)
Except for changing the amount of antimony trioxide to 400 ppm by mass, the same treatment as in Comparative Example 1 was carried out. The results of the obtained polyester resin are shown in Table 1.

(Comparative Example 3)
A portion of the polyester resin obtained in Comparative Example 1 was taken out and subjected to the following annealing treatment. The results for the obtained polyester resin are shown in Table 1.

<Annealing treatment>
5 g of the sample was placed in a glass container, pre-dried in vacuum at 80° C. for 3 hours, and then treated at 180° C. for 3 hours to prepare a crystalline polyester.

(Comparative Example 4)
After the target melt viscosity was reached in the polycondensation reaction, a PBT oligomer (Polysizer A-55: manufactured by DIC Corporation) was added as a crystal nucleating agent to the polyester resin in an amount of 1% by mass, but the same treatment as in Comparative Example 1 was carried out. The results of the obtained polyester resin are shown in Table 1.

According to Examples 1 to 12, the temperature of the cold crystallization peak during the 2nd heating is in the range of 145 to 185 ° C., and a polyester resin with a calorific value of 5 J / g or more is obtained. Even if the molecular weight is high, the crystallization rate after remelting is sufficiently maintained, and the thermal decomposition is also high. In addition, Examples 2 to 4 are examples in which the catalyst is changed from Example 1, and all of them obtained good results. Examples 5, 6, and 9 are examples in which the temperature when applying shear stress is changed from Example 1. There is a tendency that the shear stress decreases by increasing the temperature, and the shear stress increases by decreasing the temperature. In Example 6, the shear stress was high and could not be measured, but all of them obtained good results. In particular, since the temperature of the cold crystallization peak during the 2nd heating in Example 6 is relatively low, it can be seen that the crystallization rate is improved when the shear stress is high. Examples 7 and 8 are examples in which a crystal nucleating agent is added. It can be seen that the crystallization rate after remelting is improved by adding a crystal nucleating agent, since the temperature of the cold crystallization peak during the 2nd heating is lower than that of Example 1 by adding a crystal nucleating agent. Examples 10 and 11 are examples of solid-state polymerization. It can be seen that the reduced viscosity is further improved. Example 12 is a polyester resin copolymerized with succinic acid, and it can be seen that the temperature of the cold crystallization peak during the 2nd heating is low and the crystallization rate is improved.
On the other hand, in Comparative Example 1, the process of applying shear stress was not performed, and the cold crystallization peak was not observed during the 2nd heating, so it can be seen that the crystallization rate was not sufficient. Comparative Example 2 is an example in which the amount of catalyst was increased compared to Comparative Example 1. Even without the process of applying shear stress, the temperature of the cold crystallization peak during the 2nd heating was observed in the range of 145 to 185 ° C., the heat generation amount was 5 J / g or more, and an improvement in the crystallization rate was observed, but the amount of change in reduced viscosity before and after the thermal decomposition test was large, and the thermal decomposition property was deteriorated, which is not preferable for practical use. In Comparative Example 3, a high heat of fusion was obtained by performing an annealing treatment on the resin of Comparative Example 1, and the temperature of the cold crystallization peak during the 1st heating was observed in the range of 145 to 185 ° C., the heat generation amount was 3 J / g or more, and an improvement in the crystallization rate during the 1st heating was observed, but the cold crystallization peak during the 2nd heating was not observed, and the progress of crystallization during remelting could not be confirmed. Comparative Example 4 is a case where a crystal nucleating agent was added to the resin of Comparative Example 1, but no cold crystallization peak was observed during the second heating step, indicating that the crystallization rate was insufficient.

The polyester resin having a furan skeleton of the present invention has a sufficient molecular weight and can maintain a high crystallization rate even after remelting. Therefore, the crystallization rate during melt molding processing can be improved, and productivity can be improved. In addition, a polyester resin having a furan skeleton with high strength can be provided, which can suppress thermal decomposition during processing. In addition, it can be suitably used as a material for various molded products such as films, fibers, beverage bottles, and optical applications. This allows the polyester resin to be produced by a simple method, and a polyester resin with reduced CO ₂ emissions from the viewpoint of LCA can be produced. In addition, a polyester resin with a high biomass degree can be produced, and a sustainable polyester resin with consideration for the environment can be produced. In addition, a polyester resin having a high crystallization rate can be obtained by the method for producing a polyester resin of the present invention. By crystallizing quickly, processing troubles such as blocking of pellets can be suppressed, and productivity can be improved.

Claims

A polyester resin comprising a polyvalent carboxylic acid component and a polyhydric alcohol component as constituent components, the polyester resin being characterized in that it satisfies the following (1) to (4).
(1) The polycarboxylic acid component contains a polycarboxylic acid having a furan skeleton, and the polyhydric alcohol component contains ethylene glycol.
(2) The temperature of the cold crystallization peak during the second heating step, as measured by differential scanning calorimetry (DSC) at a heating rate of 2° C./min, is in the range of 145 to 185° C., and the calorific value is 5 J/g or more.
(3) The reduced viscosity is 0.50 dl/g or more.
(4) At least one metal element selected from antimony, aluminum, titanium, and germanium is contained, and the total content of the metal elements is 350 ppm by mass or less.
The polyester resin according to claim 1, which contains 0.1 to 5 mol % of diethylene glycol per 100 mol % of the total of the polyhydric alcohol components.
The polyester resin according to claim 1, containing 0.001 to 4% by mass of a crystal nucleating agent.
The polyester resin according to claim 1, which contains 80 mol% or more of units consisting of a polycarboxylic acid component having a furan skeleton and an ethylene glycol component.
The polyester resin according to claim 1, in which the change in reduced viscosity before and after heat treatment at 280°C for 1 hour is 0.15 dl/g or less.
The polyester resin according to claim 1, having a melting point of 200°C or higher.
　Polyester resin pellets made of the polyester resin described in any one of claims 1 to 6.
A bottle formed from the polyester resin described in any one of claims 1 to 6.
A film formed from the polyester resin described in any one of claims 1 to 6.
Fiber formed from the polyester resin described in any one of claims 1 to 6.
A method for producing a polyester resin having a polycarboxylic acid component and a polyhydric alcohol component as constituent components, the method comprising the steps of polycondensation reacting the polycarboxylic acid component and the polyhydric alcohol component, and applying a shear stress to a molten composition of the reaction product obtained in the polycondensation reacting step, the polycarboxylic acid component including a polycarboxylic acid component having a furan skeleton, and the polyhydric alcohol component including ethylene glycol.
The method for producing a polyester resin according to claim 11, wherein a shear stress of 0.15 MPa or more is applied in the step of applying the shear stress.
The method for producing a polyester resin according to claim 11, wherein the shear stress is applied by a twin-screw extruder in the step of applying the shear stress.
A method for producing polyester resin pellets, comprising the steps of discharging, cooling, and cutting the polyester resin obtained by the method according to any one of claims 11 to 13 in a molten state.
A method for producing polyester resin pellets, comprising a step of further solid-phase polymerizing the polyester resin pellets obtained by the method for producing polyester resin pellets according to claim 14.