Method for producing polyester

Abstract

To provide a method for producing polyester capable of obtaining PEF having sufficient mechanical characteristics using a material out of product of polyethylene furanoate (PEF) generated when producing a polymer molding as a raw material.SOLUTION: A method for producing a polyester includes the steps of: melting and kneading a molding of a polyester having a structural unit derived from 2,5-furandicarboxylic acid, and a structural unit derived from an aliphatic diol; and performing solid phase polymerization of a polyester obtained by the step of melting and kneading.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a polyester having structural units derived from 2,5-furandicarboxylic acid and structural units derived from an aliphatic diol. [Background technology]

[0002] In recent years, the demand for polyesters made from plant-derived raw materials has been increasing from the viewpoint of environmental consideration. Plant-derived raw materials for polyesters include dicarboxylic acids such as succinic acid, glutaric acid, sebacic acid, ferulic acid, caffeic acid, and 2,5-furandicarboxylic acid. Diols include ethanediol, propanediol, butanediol, and isosorbite. Among these, 2,5-furandicarboxylic acid has attracted attention as an alternative raw material to terephthalic acid. Polyesters using 2,5-furandicarboxylic acid include polyalkylene furanoates such as polybutylene furanoate, polytrimethylene furanoate, and polyethylene furanoate. Of these, polyethylene furanoate (PEF) is expected to be an alternative polyester to polyethylene terephthalate (PET), which is used in a variety of industrial applications.

[0003] For example, Patent Document 1 discloses a preform containing PEF for producing a plastic container by a stretch blow molding method. Specifically, it describes that a container with high mechanical strength and barrier properties can be obtained by producing a preform having a viscosity of 0.75 dL / g to 0.9 dL / g and a water content of less than 50 ppm.

[0004] Thus, PEF has attracted attention from the perspective of its mechanical strength, barrier properties, etc., but deriving 2,5-furandicarboxylic acid from plant-derived raw materials increases costs, making it difficult to use as a polyester substitute for PET.

[0005] Meanwhile, as a method for reducing the cost of thermoplastic resins, a production method is known in which polymer molded articles or waste products generated during the production of polymer molded articles are used as raw materials. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2018-510800 Summary of the Invention [Problem to be solved by the invention]

[0007] When the present inventors used PEF from polymer molded products or from non-products generated during the manufacture of polymer molded products as raw materials, they found that the PEF did not have sufficient mechanical properties due to its low molecular weight. Therefore, the object of the present invention is to provide a method for producing polyester that can obtain PEF with sufficient mechanical properties from non-products of PEF generated during the manufacture of polymer molded products as raw materials. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above problems, and as a result have found that a specific process is effective in solving the above problems. That is, the gist of the present invention lies in the following [1] to [6].

[0009] [1] A method for producing a polyester, comprising: a step of melt-kneading a molded product of a polyester having structural units derived from 2,5-furandicarboxylic acid and structural units derived from an aliphatic diol; and a step of solid-phase polymerizing the polyester obtained in the melt-kneading step. [2] The method for producing a polyester according to the above [1], wherein the polyester molded body contains a titanium compound and / or a germanium compound. [3] The method for producing a polyester according to the above [1] or [2], wherein the melt-kneading temperature is 220°C or higher and 320°C or lower. [4] The method for producing a polyester according to any one of the above [1] to [3], wherein the temperature of the solid-phase polymerization is 100° C. or higher and 250° C. or lower. [5] The method for producing a polyester according to any one of the above [1] to [4], wherein the solid-phase polymerization time is 0.5 hours or more and 60 hours or less. [6] The method for producing a polyester according to any one of the above [1] to [5], wherein a molded product of the polyester has an intrinsic viscosity of 0.6 dL / g or more and 2.0 dL / g or less. Effect of the Invention

[0010] According to the manufacturing method of the present invention, even if non-productive PEF generated during the production of polymer molded articles is used as a raw material, a polyester having structural units derived from 2,5-furandicarboxylic acid and structural units derived from an aliphatic diol and having excellent mechanical properties can be obtained. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The following describes in detail the embodiments of the present invention. Note that the following description is an example (representative example) of the embodiment of the present invention, and the present invention is not limited to the contents thereof as long as it does not deviate from the gist of the present invention.

[0012] In this specification, the term "structural unit derived from ..." refers to a structural unit derived from the monomer and incorporated into the polyester polymer. Hereinafter, the term "structural unit derived from ..." will be referred to simply as "unit" or "structural unit", and for example, a "structural unit derived from diol" may be referred to as a "diol unit" or "diol structural unit", a "structural unit derived from dicarboxylic acid" may be referred to as a "dicarboxylic acid unit" or "dicarboxylic acid structural unit", a "structural unit derived from 2,5-furandicarboxylic acid" may be referred to as a "2,5-furandicarboxylic acid unit" or "2,5-furandicarboxylic acid structural unit", and a "structural unit derived from aliphatic diol" may be referred to as an "aliphatic diol unit" or "aliphatic diol structural unit".

[0013] In addition, in this specification, the term "main structural unit" refers to a structural unit that occupies the largest proportion among the "structural units" and is usually a structural unit that occupies 50 mol % or more, preferably 70 mol % or more, more preferably 80 mol % or more, and even more preferably 90 to 100 mol % of the structural units.

[0014] Furthermore, in this specification, a polyester having a structural unit derived from 2,5-furandicarboxylic acid, a structural unit derived from an aliphatic diol, and a titanium compound and / or a germanium compound may be referred to as the "raw material polyester in the present invention" or "raw material polyester", a polyester obtained by melt-kneading pellets of the raw material polyester or the like may be referred to as the "polyester obtained by melt-kneading" or "melt-kneaded polyester", and a polyester obtained by solid-phase polymerization of the polyester obtained by melt-kneading may be referred to as the "polyester obtained by solid-phase polymerization" or "solid-phase polymerized polyester".

[0015] [Manufacturing method of polyester] The method for producing a polyester of the present invention includes a step of melt-kneading a molded product of a polyester having structural units derived from 2,5-furandicarboxylic acid and structural units derived from an aliphatic diol, and a step of solid-phase polymerizing the polyester obtained in the melt-kneading step.

[0016] <Polyester Molding> The method for producing a polyester of the present invention (hereinafter sometimes referred to as the "production method of the present invention") includes a step of melt-kneading a molded product of a polyester having structural units derived from 2,5-furandicarboxylic acid and structural units derived from an aliphatic diol (hereinafter sometimes simply referred to as a "polyester molded product"). In the production method of the present invention, the polyester molded product is a raw material, and the molded product refers to a form having a solid shape at room temperature. Examples of the molded product include films, bottles, fibers, plates, pellets, flakes, etc., and also includes non-products of PEF generated during the production of polymer molded products. The manufacturing method of the present invention includes a step of melt-kneading a polyester molded body, and the shape of the molded body may be changed according to the melt-kneading step. For example, a film or a bottle can be made into a shape suitable for melt-kneading by pulverizing it into flakes or powder using a pulverizer.

[0017] <Step of melt-kneading polyester molded body> Examples of the process for melt-kneading a polyester molded body (hereinafter, sometimes referred to as the "melt-kneading process") include a method of melt-kneading using a conventional kneading machine such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, a roll mixer, a Brabender plastograph, or a kneader blender. The melt-kneading temperature in the melt-kneading step is usually 220° C. or higher, preferably 230° C. or higher, and most preferably 240° C. or higher. Also, it is usually 320° C. or lower, preferably 300° C. or lower, and most preferably 280° C. or lower. By setting the temperature within the above range, the polyester can be sufficiently melt-kneaded in the extruder, and polyester with reduced coloration can be obtained.

[0018] The preferred range of the screw rotation speed in the melt-kneading step varies depending on the type of kneader and the screw shape, but is usually 10 rpm or more, preferably 30 rpm or more, and most preferably 50 rpm or more. Also, it is usually 500 rpm or less, preferably 300 rpm or less, and most preferably 200 rpm or less. By setting it in the above range, the polyester can be sufficiently melt-kneaded in the extruder, and a polyester with reduced coloring can be obtained.

[0019] The polyester obtained by the melt-kneading step is preferably extracted in a molten state in the form of a strand, cooled, and then cut into pellets. By forming the polyester into a uniform pellet shape, it is possible to reduce the error in intrinsic viscosity in the subsequent solid-phase polymerization step.

[0020] <Step of solid-phase polymerization of polyester obtained by melt kneading> The method for producing a polyester of the present invention includes a step of solid-phase polymerizing a polyester obtained by a step of melt-kneading a molded body of a polyester having structural units derived from 2,5-furandicarboxylic acid and structural units derived from an aliphatic diol (hereinafter, sometimes referred to as a "solid-phase polymerization step"). Generally, the intrinsic viscosity of polyester obtained by melt kneading is reduced by thermal decomposition or hydrolysis in the melt kneading process, and therefore the intrinsic viscosity may be insufficient for applications requiring high mechanical properties. In view of this, it is important in the present invention to include a process of increasing the intrinsic viscosity by solid-phase polymerization of the polyester obtained by melt kneading.

[0021] As the method of solid-phase polymerization, any conventionally known method for solid-phase polymerization of polyester can be used, and one example thereof will be illustrated below. Examples of the method include a method in which the polyester obtained by melt kneading in pellet form or powder form is heated under an inert gas atmosphere or under reduced pressure. The reaction may be carried out with the pellets or powder in a stationary state or with stirring. When stirring, stirring blades installed in a reaction vessel may be used, or the reaction vessel may be moved to stir.

[0022] The reaction temperature of the solid-state polymerization is preferably 100° C. or higher and 250° C. or lower. In this temperature range, the solid-state polymerization proceeds sufficiently and there are no problems such as coloration. In particular, it is preferable to raise the temperature stepwise from a low temperature to a high temperature, and examples of the method include heating at 110-130° C. for 0.5-2 hours, at 140-160° C. for 0.5-2 hours, at 170-190° C. for 2-4 hours, and at 195-240° C. for 3-5 hours. The reaction time of the solid-state polymerization is usually 0.5 hours or more, preferably 1 hour or more, more preferably 2 hours or more. On the other hand, it is preferably 60 hours or less, more preferably 50 hours or less, and even more preferably 45 hours or less. By using a long reaction time, the polyester obtained by solid-state polymerization tends to have a higher molecular weight and excellent mechanical properties. By using a short reaction time, the polyester obtained by solid-state polymerization tends to be less likely to be discolored.

[0023] It is also preferable to carry out preliminary crystallization as a step prior to solid-state polymerization. Preliminary crystallization is, for example, a process of heating at about 110 to 130°C for 2 to 4 hours, cooling to room temperature, loosening the fused raw materials such as pellets, heating at about 140 to 160°C for 2 to 4 hours, cooling to room temperature, and loosening the fused raw materials such as pellets.

[0024] In the case where the solid-state polymerization is carried out in an inert gas atmosphere, for example, nitrogen, argon, etc. can be used as the inert gas, and is not particularly limited as long as it does not adversely affect the solid-state polymerization. Nitrogen is preferred from the viewpoints of ease of handling and production costs. When solid-phase polymerization is carried out in a reduced pressure atmosphere, the pressure may be about 0.01 to 10 kPa, preferably about 0.05 to 1 kPa, and there are no particular limitations as long as the solid-phase polymerization proceeds within this range.

[0025] [Physical properties of polyester molded body] <Intrinsic viscosity (IV)> In the production method of the present invention, the intrinsic viscosity (IV) is an important factor as a physical property of the polyester molded product used as the raw material. Specifically, the intrinsic viscosity (IV) of the polyester molded article is preferably 0.6 dL / g or more, more preferably 0.8 dL / g or more, even more preferably 0.9 dL / g or more, and most preferably 0.95 dL / g or more. On the other hand, the intrinsic viscosity of the polyester molded article is preferably 2.0 dL / g or less, more preferably 1.5 dL / g or less, and most preferably 1.3 dL / g or less. By setting the intrinsic viscosity to the preferred range described above, the polyester finally obtained by solid-phase polymerization has a low melt viscosity, making it easy to mold and enabling the mechanical strength of the molded article to be increased.

[0026] [Physical properties of polyester obtained by melt blending] <Intrinsic viscosity (IV)> The intrinsic viscosity (IV) of the polyester obtained by the melt kneading of the present invention is preferably 0.3 dL / g or more, more preferably 0.4 dL / g or more, even more preferably 0.5 dL / g or more, and most preferably 0.6 dL / g or more. On the other hand, the intrinsic viscosity of the polyester obtained by the melt kneading of the present invention is preferably 1.5 dL / g or less, more preferably 1.0 dL / g or less, and most preferably 0.8 dL / g or less. By making the intrinsic viscosity to be the preferred value as described above, the polyester finally obtained by the solid-phase polymerization has a low melt viscosity, which makes it easy to mold and increases the mechanical strength of the molded product.

[0027] [Physical properties of polyester obtained by solid-state polymerization] <Intrinsic viscosity (IV)> The intrinsic viscosity (IV) of the polyester obtained by the solid-state polymerization of the present invention is preferably 0.7 dL / g or more, more preferably 0.8 dL / g, even more preferably 0.9 dL / g, and most preferably 1.0 dL / g or more. On the other hand, the intrinsic viscosity of the polyester obtained by the solid-state polymerization of the present invention is preferably 1.5 dL / g or less, more preferably 1.3 dL / g or less, and most preferably 1.2 dL / g or less. By setting the intrinsic viscosity to the above-mentioned preferable range, the melt viscosity is low, the polyester is easy to mold, and the mechanical strength of the molded product can be increased.

[0028] <Enthalpy of fusion> The polyester obtained by the solid-state polymerization of the present invention is sufficiently crystallized, so that it can be prevented from melting in a hopper when used as a raw material for melt extrusion. The degree of crystallization can be quantified by the enthalpy of fusion (ΔHm) measured by differential scanning calorimetry (DSC). The melting enthalpy of the polyester obtained by solid-phase polymerization is preferably 20 mJ / mg or more, more preferably 30 mJ / mg or more, still more preferably 40 mJ / mg or more, and most preferably 50 mJ / g or more. On the other hand, the melting enthalpy of the polyester obtained by solid-phase polymerization is preferably 100 mJ / mg or less, more preferably 90 mJ / mg or less, still more preferably 80 mJ / mg or less, and most preferably 70 mJ / mg or less. By setting the melting enthalpy to the above-mentioned preferred value, a crystallization state suitable for molding can be obtained.

[0029] Hereinafter, the polyester molded body, which is a raw material in the production method of the present invention, will be described in detail. The polyester molded body is obtained by molding the polyester described below, and in the present invention, it is described as "raw material polyester" as described above. 〔Raw material polyester〕 The raw material polyester in the present invention is a molded body in which 2,5-furandicarboxylic acid units are the main structural units of all dicarboxylic acid units constituting the polyester, and aliphatic diol structural units are the main structural units of all diol units constituting the polyester.

[0030] <Dicarboxylic acid structural unit> The raw material polyester in the present invention contains a structural unit derived from 2,5-furandicarboxylic acid as a dicarboxylic acid structural unit. By including a structural unit derived from 2,5-furandicarboxylic acid, the glass transition temperature increases, the heat resistance becomes good, and furthermore, the gas barrier property also becomes good. The raw material polyester of the present embodiment preferably has a structural unit derived from 2,5-furandicarboxylic acid as the main dicarboxylic acid unit. That is, the structural unit derived from 2,5-furandicarboxylic acid is usually contained in 50 mol% or more, preferably 70 mol% or more, more preferably 80 mol% or more, and still more preferably 90 to 100 mol% in 100 mol% of all dicarboxylic acid structural units.

[0031] The raw material polyester of the present embodiment may have a dicarboxylic acid (also referred to as "other dicarboxylic acid") structural unit other than the 2,5-furandicarboxylic acid unit as a dicarboxylic acid unit. Examples of the other dicarboxylic acid include aliphatic dicarboxylic acids and aromatic dicarboxylic acids. Examples of the aliphatic dicarboxylic acid include chain aliphatic dicarboxylic acids such as oxalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dimer acid, and dodecanedioic acid; and cyclic aliphatic dicarboxylic acids such as 1,6-cyclohexanedicarboxylic acid. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and diphenyldicarboxylic acid. Among these dicarboxylic acids, aliphatic dicarboxylic acids are preferred because of their excellent flexibility, and chain aliphatic dicarboxylic acids are more preferred.

[0032] In the case where the dicarboxylic acid structural unit contains another dicarboxylic acid structural unit, the other dicarboxylic acid structural unit may be only one type, or may contain two or more types in any combination and ratio. In the case where the polyester of the present embodiment contains another dicarboxylic acid structural unit, the content is preferably low in terms of easily obtaining the above-mentioned effects due to the inclusion of the 2,5-furandicarboxylic acid structural unit. On the other hand, in terms of excellent flexibility, etc., it is preferable that the content is high. Therefore, in the case where the other dicarboxylic acid structural unit is contained, the content is usually 10 mol% or more, preferably 20 mol% or more, more preferably 30 mol% or more in 100 mol% of the total dicarboxylic acid structural units, and the upper limit is usually 50 mol%. The dicarboxylic acid structural unit can be introduced into the polyester by using a dicarboxylic acid component such as a dicarboxylic acid, a dicarboxylic acid anhydride, a lower alkyl ester of a dicarboxylic acid (the alkyl group has 1 to 4 carbon atoms), or a dicarboxylic acid chloride as a raw material for producing the raw material polyester of this embodiment.

[0033] <Diol structural unit> The raw material polyester in the present invention contains an aliphatic diol structural unit as a diol structural unit. Examples of the aliphatic diol structural unit include 1,2-ethanediol, 2,2'-oxydiethanol, 2,2'-(ethylenedioxy)diethanol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, ethylene glycol, diethylene glycol, triethylene glycol, and isosorbide. Among these, from the viewpoint of improving heat resistance and gas barrier properties, aliphatic diols such as 1,2-ethanediol, 1,3-propanediol, and 1,4-butanediol are preferred, and 1,2-ethanediol is particularly preferred. From the viewpoint of improving heat resistance and gas barrier property, the aliphatic diol structural unit is preferably contained in an amount of usually 50 mol % or more, preferably 70 mol % or more, more preferably 80 mol % or more, still more preferably 90 mol % or more, and particularly preferably 100 mol %, based on 100 mol % of all diol structural units contained in the polyester.

[0034] The raw material polyester in the present invention may have a structural unit other than an aliphatic diol unit as a diol structural unit. Examples of diols other than aliphatic diols include aromatic diols. For example, xylylene glycol, 4,4'-dihydroxybiphenyl, 2,2-bis(4'-hydroxyphenyl)propane, 2,2-bis(4'-β-hydroxyethoxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, bis(4-β-hydroxyethoxyphenyl)sulfone, etc. may be mentioned. When the starting polyester of the present embodiment contains another diol structural unit, the other diol may be contained alone or in any combination and ratio of two or more kinds.

[0035] <Other copolymer components> The raw material polyester in the present invention may contain structural units derived from other copolymerization components other than the dicarboxylic acid and the diol. Examples of the other copolymerization components include compounds containing three or more functional groups.

[0036] Examples of compounds having three or more functional groups include trifunctional or higher polyhydric alcohols, trifunctional or higher polyvalent carboxylic acids (or their anhydrides, acid chlorides, or lower alkyl esters), trifunctional or higher hydroxycarboxylic acids (or their anhydrides, acid chlorides, or lower alkyl esters), trifunctional or higher amines, etc.

[0037] Examples of trifunctional or higher polyhydric alcohols include glycerin, trimethylolpropane, pentaerythritol, etc. These may be used alone or in any combination and ratio of two or more.

[0038] Examples of trifunctional or higher polyvalent carboxylic acids or anhydrides thereof include trimesic acid, propanetricarboxylic acid, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic anhydride, cyclopentatetracarboxylic anhydride, etc. These may be used alone or in any combination and ratio of two or more.

[0039] Examples of trifunctional or higher functional hydroxycarboxylic acids include malic acid, hydroxyglutaric acid, hydroxymethylglutaric acid, tartaric acid, citric acid, hydroxyisophthalic acid, hydroxyterephthalic acid, etc. These may be used alone or in any combination and ratio of two or more.

[0040] When the raw material polyester in the present invention contains a structural unit derived from a compound having three or more functional groups, the content is preferably low in order that the crosslinking of the polyester in the present embodiment proceeds moderately, strands can be easily extracted stably, and moldability, mechanical properties, etc. are easily improved. Therefore, the content is preferably usually 5 mol % or less, particularly 4 mol % or less, and especially 3 mol % or less, based on 100 mol % of the total of all structural units constituting the polyester, and a binary polyester having no other copolymerization components is most preferred.

[0041] <Catalyst> As the catalyst for producing the raw material polyester in the present invention, any catalyst that can be used for producing polyester can be selected, but metal compounds such as germanium, titanium, zirconium, hafnium, antimony, tin, magnesium, calcium, zinc, aluminum, cobalt, lead, cesium, manganese, lithium, potassium, sodium, copper, barium, and cadmium are preferred. Among them, germanium compounds, titanium compounds, antimony compounds, magnesium compounds, tin compounds, zinc compounds, and lead compounds are preferred from the viewpoint of high activity. Furthermore, titanium compounds, germanium compounds, and antimony compounds are more preferred from the viewpoint of high solid-phase polymerization activity after melt kneading in the production method of the present invention, and titanium compounds and germanium compounds are most preferred.

[0042] The titanium compound used as the catalyst is not particularly limited, and preferred examples include organic titanium compounds such as tetraalkoxy titanates such as tetrapropyl titanate, tetrabutyl titanate, tetraethyl titanate, tetrahydroxyethyl titanate, tetraphenyl titanate, etc. Among these, tetrapropyl titanate, tetrabutyl titanate, etc. are preferred in terms of cost and availability, and the most preferred catalyst is tetrabutyl titanate in terms of high activity.

[0043] Examples of germanium compounds include germanium dioxide, germanium tetrachloride, germanium tetraethoxide, etc. Among them, germanium dioxide is preferred from the viewpoints of polymerization catalyst activity, physical properties of the resulting polyester resin, and cost.

[0044] These catalysts may be used alone or in combination of two or more.

[0045] The amount of catalyst used is the amount of metal in the catalyst relative to the polyester produced, and the lower limit is preferably 0.0001% by mass, more preferably 0.0005% by mass, and even more preferably 0.001% by mass. The upper limit is preferably 1% by mass, more preferably 0.5% by mass, and even more preferably 0.1% by mass. By using an amount of catalyst that is equal to or greater than the lower limit, the polymerization reaction rate can be increased, and by using an amount that is equal to or less than the upper limit, the production cost related to the catalyst can be suppressed, and the catalyst residue can be reduced, so that the stability of the polyester obtained tends to be improved.

[0046] The timing of adding the catalyst is not particularly limited as long as it is before the start of the depressurization reaction, and the catalyst may be added when the raw materials are charged, or when the depressurization starts. The catalyst may be added separately when the raw materials are charged and when the depressurization starts.

[0047] <Chain extender> In producing the raw material polyester of this embodiment, a chain extender such as a carbonate compound, a diisocyanate compound, a dioxazoline, a silicate ester, etc. may be used. For example, a polyester carbonate can be obtained by using a carbonate compound such as diphenyl carbonate in an amount of preferably 20 mol % or less, more preferably 10 mol % or less, based on 100 mol % of all structural units of the polyester.

[0048] In this case, specific examples of the carbonate compound include diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, ethylene carbonate, diamyl carbonate, dicyclohexyl carbonate, etc. In addition, carbonate compounds consisting of the same or different hydroxy compounds derived from hydroxy compounds such as phenols and alcohols can also be used.

[0049] Specific examples of the diisocyanate compound include known diisocyanates such as 2,4-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

[0050] Specific examples of the silicate ester include tetramethoxysilane, dimethoxydiphenylsilane, dimethoxydimethylsilane, and diphenyldihydroxysilane. These may be used alone or in any combination and ratio of two or more.

[0051] <End-capping agent> In addition, in this embodiment, the terminal groups of the polyester may be blocked with a carbodiimide, an epoxy compound, a monofunctional alcohol, a carboxylic acid, etc. When a terminal blocking agent is used, the content thereof is preferably 20 mol % or less, and more preferably 10 mol % or less, relative to 100 mol % of all structural units of the polyester.

[0052] In this case, the carbodiimide compound of the terminal blocking agent may be a compound having one or more carbodiimide groups in the molecule (including polycarbodiimide compounds).Specific examples of the monocarbodiimide compound include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, and N,N'-di-2,6-diisopropylphenylcarbodiimide. These may be used alone or in any combination and ratio of two or more. In addition, in the production of the polyester of this embodiment, various additives such as a heat stabilizer, an antioxidant, a hydrolysis inhibitor, a flame retardant, an antistatic agent, a release agent, and an ultraviolet absorber may be used as long as the properties of the polyester are not impaired, in the same manner as in the polyester composition of this embodiment described later.

[0053] As described above, the raw material polyester in the present invention may contain structural units other than the structural units derived from 2,5-furandicarboxylic acid and the structural units derived from an aliphatic diol. Even in this case, the total amount of the structural units derived from 2,5-furandicarboxylic acid and the structural units derived from an aliphatic diol is preferably 80 mol % or more, and more preferably 90 mol % or more, relative to 100 mol % of all structural units of the polyester.

[0054] The raw material used in the production of the raw material polyester in the present invention may be a petroleum-derived raw material or a biomass-derived raw material. From the viewpoint of environmental protection, it is preferable to use a biomass-derived raw material, and it is more preferable to use a biomass-derived raw material as the main structural unit. Examples of the biomass-derived raw material include dicarboxylic acid components such as 2,5-furandicarboxylic acid, succinic acid, glutaric acid, adipic acid, and sebacic acid, and diol components such as 1,3-propanediol, 1,4-butanediol, and 1,2-ethanediol.

[0055] <Manufacturing method of raw polyester> The method for producing the raw material polyester in the present invention can be carried out by carrying out an esterification reaction or transesterification reaction step using 2,5-furandicarboxylic acid, an aliphatic diol, and other copolymerization components used as necessary, followed by a polycondensation reaction step. The esterification reaction or transesterification reaction step and the polycondensation reaction step are also referred to as the polyester raw material production step. In the reaction, the above-mentioned chain extender or terminal blocking agent may be used as necessary. In order to increase the intrinsic viscosity, it is preferable to further carry out a solid-phase polymerization step after the polycondensation reaction step in the polyester raw material production step.

[0056] <Esterification or transesterification reaction step> The esterification or transesterification reaction is usually carried out by charging a dicarboxylic acid component, a diol component, and other copolymerization components used as necessary into a reaction vessel equipped with a stirrer and a distillation tube, and stirring the mixture under reduced pressure in an inert gas atmosphere, preferably in the presence of a catalyst, while distilling off by-products such as moisture generated by the reaction. The ratio of raw materials used, that is, the molar ratio of the total of diol components to the total of dicarboxylic acid components, is usually 1.0 to 3.0 times by mole. A larger amount of diol components is preferable in that the esterification reaction is easily advanced and a polyester having fewer carboxyl ends than hydroxyl ends is easily obtained by the polycondensation reaction. On the other hand, a smaller amount of diol components is preferable in that the generation of an ether structure due to a side reaction derived from the aliphatic diol component is unlikely to occur. Therefore, the lower limit of the molar ratio is preferably 1.25 times by mole, more preferably 1.30 times by mole. On the other hand, the upper limit is preferably 2.5 times by mole, more preferably 2.0 times by mole.

[0057] <Polycondensation reaction process> The polycondensation reaction step is usually carried out under reduced pressure following the esterification or transesterification reaction step. The polycondensation reaction is preferably carried out at a lower pressure starting temperature since by-products are less likely to be produced. The reaction temperature is preferably set to be equal to or higher than the melting point of the polyester obtained and equal to or lower than melting point + 100°C. The relationship between the reaction temperature and the melting point of the polyester obtained can be confirmed to be within this preferred range by predicting the approximate melting point of the polyester obtained, reacting the polyester, and then measuring the melting point of the polyester obtained. Specifically, the reaction temperature is preferably 230°C or higher, more preferably 240°C or higher. On the other hand, it is preferably 280°C or lower, more preferably 270°C or lower. By setting the reaction temperature within these ranges, the reaction can be carried out at a sufficiently fast speed in a state where coloration due to thermal decomposition or side reactions is unlikely to occur.

[0058] The reaction pressure begins to be reduced when the desired temperature is reached. The final pressure is usually 0.01×10 3 Pa or more, preferably 0.05×10 3 Pa or more. Also, it is usually 1.4×10 3 Pa or less, preferably 0.6×10 3 Pa or less, more preferably 0.3×10 3 It is preferable that the reaction pressure is set to 0.1 Pa or less. When the reaction pressure is low, the polymerization proceeds in a short time, and the polyester is less likely to undergo a decrease in molecular weight or coloration due to thermal decomposition, making it easier to obtain a polyester that exhibits sufficient properties for practical use. On the other hand, it is preferable that the reaction pressure is high in order to avoid the need to use expensive equipment. The reaction time is usually 1 hour or more and 15 hours or less. It is preferably 10 hours or less, and more preferably 8 hours or less. When the reaction time is long, the reaction proceeds sufficiently, and it is easy to obtain a polyester with a high degree of polymerization and excellent mechanical properties. On the other hand, when the reaction time is short, the polyester is less likely to undergo a decrease in molecular weight due to thermal decomposition, and it is easy to obtain a polyester with excellent mechanical properties. After the polycondensation reaction is completed, the polyester is generally drawn off in a molten state in the form of a strand, cooled, and then cut into pellets.

[0059] <Production of Molded Product> The polyester (pellets) obtained as described above is melted and molded into a film or the like in a conventional manner, or a molded article is produced by injection molding using a mold or the like. The raw material of the present invention is a non-product generated during the production of a molded article, or a used molded article, etc. EXAMPLES

[0060] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples as long as it does not depart from the gist of the present invention.

[0061] The methods for measuring the various physical properties and evaluation items are as follows. <Intrinsic viscosity (IV) (dL / g)> The viscosity was determined using an Ubbelohde viscometer as follows: A mixed solvent of phenol / tetrachloroethane (mass ratio 1 / 1) was used, and the number of seconds it took for a polyester composition solution with a concentration of 0.5 g / dL and the solvent alone to fall at 30° C. was measured, and the viscosity was determined from the following formula (1). IV=((1+4K H η SP ) 0.5 -1) / (2K H C) (1)

[0062] Where, η SP = η / η 0 -1, η is the time it takes for the sample solution to fall, η 0 is the time it takes for the solvent to fall, C is the concentration of the sample solution (g / dL), and K H is Huggins' constant. K H The value used was 0.32.

[0063] [Example 1] <Production of polyester obtained by solid-state polymerization> <Melt polymerization> A reaction vessel equipped with a stirrer, a nitrogen inlet, a heater, a thermometer, and a pressure reduction port was charged with the following raw materials: 85.7 parts by mass of 2,5-furandicarboxylic acid (manufactured by V&V PHARMA INDUSTRIS), 68.2 parts by mass of ethylene glycol (manufactured by Mitsubishi Chemical), and 0.03 parts by mass of a 35% by mass aqueous solution of tetraethylammonium hydroxide, and the inside of the reaction vessel was filled with a nitrogen atmosphere. Next, the reaction vessel was placed in an oil bath, stirring was started, and the temperature was raised to 210° C. The mixture was reacted at 210° C. for 3.5 hours to recover the distillate. Next, 0.71 parts by mass of an ethylene glycol solution in which 5% by mass of titanium tetrabutylate was dissolved (50 ppm as titanium in the produced polyester) was added. The temperature was then raised to 260°C over 1 hour and 30 minutes, and the pressure was gradually reduced to about 130 Pa. After 3 hours and 40 minutes had elapsed since the start of the pressure reduction, the stirring was stopped, the pressure was restored, and the polycondensation reaction was terminated. The product was taken out as a strand, cooled, and then cut to obtain pellets of polyester (A-1) of about 2 to 3 mm square. The intrinsic viscosity (IV) was 0.72 dL / g.

[0064] <Solid-state polymerization> Pre-crystallization was performed on polyester (A-1) by heating while introducing nitrogen gas at a flow rate of 30 L / min. Specifically, 5 g of polyester (A-1) was placed in an inert oven (manufactured by Yamato Scientific Co., Ltd., "DN411I"), heated at 120°C for 3 hours, cooled to room temperature (25°C), and then the fused pellets were loosened. The pellets were heated once more at 150°C for 3 hours, cooled to room temperature (25°C), and then the fused pellets were loosened. Next, 5 g of this pre-crystallized polyester (A-1) was placed in the inert oven described above, and in a state where nitrogen gas was introduced at a flow rate of 30 L / min, solid-phase polymerization was carried out by heating at 120°C for 1 hour, 150°C for 1 hour, 180°C for 3 hours, and 200°C for 4 hours in that order to obtain raw material polyester (A-2). The intrinsic viscosity of raw material polyester (A-2) was 0.83 dL / g. In the present invention, the raw material polyester is a non-finished product during the production of a molded body of PEF or a molded body of PEF. In this embodiment, the polyester (A-2) was used instead of the molded body to demonstrate the effects of the present invention as follows.

[0065] <Melt mixing> Using a small kneader (Xplore series MC15 manufactured by Xplore Instruments), 15 g of polyethylene furanoate, which is the raw material polyester (A-2), was fed from a hopper and kneaded at a rotation speed of 100 rpm, 260°C, and nitrogen atmosphere for 3 minutes, and then the kneaded resin was recovered from a purge hole to obtain polyester strands. The obtained polyester strands were cut by a pelletizer to obtain pellets of polyester (A-3).

[0066] <Solid-state polymerization of melt-kneaded polyester> Polyester (A-3) was solid-phase polymerized in the same manner as in the solid-phase polymerization process for polyester (A-2), except that the solid-phase polymerization time at 200°C was 5 hours, to obtain "solid-phase polymerized polyester." The intrinsic viscosity of the obtained polyester (A-4) was 0.88 dL / g, and it was a polyester with a sufficiently high intrinsic viscosity.

[0067] [Example 2] A "solid-phase polymerized polyester" was obtained in the same manner as in Example 1, except that the solid-phase polymerization time of polyester (A-3) at 200°C was changed to 20 hours. The intrinsic viscosity of the obtained polyester was 1.13 dL / g, which was a polyester with a sufficiently high intrinsic viscosity.

[0068] [Example 3] A "solid-phase polymerized polyester" was obtained in the same manner as in Example 1, except that the solid-phase polymerization time of polyester (A-3) at 200°C was changed to 30 hours. The intrinsic viscosity of the obtained polyester was 1.20 dL / g, and it was found to be a polyester with a sufficiently high intrinsic viscosity.

[0069] [Example 4] A reaction vessel equipped with a stirrer, a nitrogen inlet, a heater, a thermometer, and a pressure reduction port was charged with the following raw materials: 85.7 parts by mass of 2,5-furandicarboxylic acid (manufactured by V&V PHARMA INDUSTRIS), 68.2 parts by mass of ethylene glycol (manufactured by Mitsubishi Chemical), 5.4 parts by mass of a 0.8% aqueous solution of germanium dioxide (300 ppm in the produced polyester as germanium), and 0.44 parts by mass of a 5% aqueous solution of magnesium acetate tetrahydrate (25 ppm in the produced polyester as magnesium), and the inside of the reaction vessel was filled with a nitrogen atmosphere. Next, the reaction vessel was placed in an oil bath, stirring was started, and the temperature was raised to 190°C. The reaction was carried out at 190°C for 3.5 hours, and the distillate was collected. The temperature was then raised to 260°C over 1 hour and 30 minutes, and the pressure was gradually reduced to about 130 Pa. After 4 hours and 30 minutes had elapsed since the start of the pressure reduction, the stirring was stopped, the pressure was restored, and the polycondensation reaction was terminated. The product was taken out as a strand, cooled, and then cut to obtain pellets of polyester (B-1) of about 2 to 3 mm square. The intrinsic viscosity (IV) was 0.73 dL / g.

[0070] For the obtained polyester (B-1), a raw material polyester (B-2) was obtained in the same manner as in the process for obtaining polyester (A-2) in Example 1, except that the solid-phase polymerization time was changed to 4 hours. The intrinsic viscosity of the obtained polyester was 0.82 dL / g.

[0071] Melt kneading was carried out in the same manner as in Example 1, except that polyester (B-2) was used, to obtain pellets of polyester (B-3).

[0072] Using polyester (B-3), a "solid-phase polymerized polyester" was obtained in the same manner as in Example 1. The intrinsic viscosity of the obtained polyester was 0.78 dL / g, and a polyester with a sufficiently high intrinsic viscosity was obtained.

[0073] [Example 5] A "solid-phase polymerized polyester" was obtained in the same manner as in Example 4, except that the solid-phase polymerization time of polyester (B-3) at 200°C was changed to 20 hours. The intrinsic viscosity of the obtained polyester was 0.98 dL / g, which was a polyester with a sufficiently high intrinsic viscosity.

[0074] [Example 6] A "solid-phase polymerized polyester" was obtained in the same manner as in Example 4, except that the solid-phase polymerization time of polyester (B-3) at 200°C was changed to 30 hours. The intrinsic viscosity of the obtained polyester was 1.04 dL / g, and it was found to be a polyester with a sufficiently high intrinsic viscosity.

[0075] [Example 7] A reaction vessel equipped with a stirrer, a nitrogen inlet, a heater, a thermometer, and a pressure reduction port was charged with the following raw materials: 85.7 parts by mass of 2,5-furandicarboxylic acid (manufactured by V&V PHARMA INDUSTRIS), 68.2 parts by mass of ethylene glycol (manufactured by Mitsubishi Chemical), 0.03 parts by mass of a 35% by mass aqueous solution of tetraethylammonium hydroxide, and 0.036 parts by mass of diantimony trioxide (300 ppm as antimony in the produced polyester), and the inside of the reaction vessel was filled with a nitrogen atmosphere. Next, the reaction vessel was placed in an oil bath, stirring was started, and the temperature was raised to 210°C. The reaction was carried out at 210°C for 3.5 hours, and the distillate was collected. The temperature was then raised to 260°C over 1 hour and 30 minutes, and the pressure was gradually reduced to about 130 Pa. Six hours after the start of pressure reduction, the stirring was stopped, the pressure was restored, and the polycondensation reaction was terminated. The product was taken out as strands, cooled, and cut to obtain polyester (C-1) pellets of about 2 to 3 mm square. The intrinsic viscosity (IV) was 0.72 dL / g.

[0076] For the obtained polyester (C-1), a raw material polyester (C-2) was obtained in the same manner as in the process for obtaining polyester (A-2) in Example 1, except that the solid-phase polymerization time was changed to 9 hours. The intrinsic viscosity of the obtained polyester was 0.83 dL / g.

[0077] Kneading was carried out in the same manner as in Example 1, except that polyester (C-2) was used, to obtain pellets of polyester (C-3).

[0078] Using polyester (C-3), a "solid-phase polymerized polyester" was obtained in the same manner as in Example 1. The intrinsic viscosity of the obtained polyester was 0.88 dL / g, and a polyester with a sufficiently high intrinsic viscosity was obtained.

[0079] [Example 8] A "solid-phase polymerized polyester" was obtained in the same manner as in Example 7, except that the solid-phase polymerization time of polyester (C-3) at 200°C was changed to 20 hours. The intrinsic viscosity of the obtained polyester was 0.90 dL / g, which was a polyester with a sufficiently high intrinsic viscosity.

[0080] [Example 9] A "solid-phase polymerized polyester" was obtained in the same manner as in Example 7, except that the solid-phase polymerization time of polyester (C-3) at 200°C was changed to 30 hours. The intrinsic viscosity of the obtained polyester was 0.91 dL / g, which was a polyester with a sufficiently high intrinsic viscosity.

[0081] [Comparative Examples 1 to 3] The intrinsic viscosities of polyester (A-3), polyester (B-3), and polyester (C-3) when the solid-phase polymerization process was not performed after the melt-kneading process were 0.75 dL / g, 0.71 dL / g, and 0.74 dL / g, respectively, making them difficult to use in applications requiring high mechanical properties.

[0082] [Table 1] [Industrial Applicability]

[0083] According to the production method of the present invention, even when off-product polyethylene furanoate generated during the production of polymer molded articles is used as a raw material, a polyester having structural units derived from 2,5-furandicarboxylic acid and structural units derived from an aliphatic diol and having excellent mechanical properties can be obtained. Polyethylene furanoate (PEF) is a polyester made from plant-derived raw materials. It is a promising material from an environmental perspective and is expected to be an alternative polyester to polyethylene terephthalate (PET), which is used in a variety of industrial applications. Furthermore, according to the production method of the present invention, PEF having excellent mechanical properties can be obtained using aftermarket or recycled polyethylene furanoate as a raw material, and this is a technology of great industrial value.

Claims

1. A method for producing a polyester, comprising: a step of melt-kneading a molded product of a polyester having structural units derived from 2,5-furandicarboxylic acid and structural units derived from an aliphatic diol; and a step of solid-phase polymerizing the polyester obtained in the melt-kneading step.

2. The method for producing a polyester according to claim 1 , wherein the molded article of the polyester contains a titanium compound and / or a germanium compound.

3. The method for producing a polyester according to claim 1 or 2, wherein the melt kneading temperature is 220° C. or higher and 320° C. or lower.

4. The method for producing a polyester according to any one of claims 1 to 3, wherein the temperature of the solid-state polymerization is 100°C or higher and 250°C or lower.

5. The method for producing a polyester according to any one of claims 1 to 4, wherein the solid-state polymerization time is 0.5 hours or more and 60 hours or less.

6. The method for producing a polyester according to any one of claims 1 to 5, wherein the molded product of the polyester has an intrinsic viscosity of 0.6 dL / g or more and 2.0 dL / g or less.

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