JP2016124935A - Method for producing polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aliphatic polyester that has a high molecular weight and less discoloration, has good processability, and has less foreign matter such as fish eyes, by suppressing the formation of gels or non-molten materials in the production thereof.SOLUTION: Provided is a method for producing polyester by obtaining a polyester from a raw-material having a dicarboxylic acid component and a diol component composed mainly of 1,4-butane diol, by polycondensation reaction, and producing a polyester by letting the polyester obtained by the polycondensation reaction, go through an exit of a polycondensation reaction tank and a filter unit, and in which the shear rate (γ2) of polyester in molten state in the filter unit is 1 sor more and 20 sor less.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for producing a polyester, and more particularly to a method for producing a polyester that can be suitably used as a raw material for films, monofilaments, fibers, etc., by suppressing the formation of gels and insolubles in the production of aliphatic polyesters.

Polyester is excellent in mechanical properties, chemical stability, thermal stability, etc., and is used in various applications. Conventionally, aromatic polyesters such as polyethylene terephthalate and polybutylene terephthalate have been the mainstream, but in recent years there has also been growing environmental awareness, and aliphatic polyesters such as biodegradable polylactic acid and polybutylene succinate are widely used. It has come to be.
However, aliphatic polyesters have poor polymerizability and thermal stability as compared with aromatic polyesters, and are difficult to obtain highly polymerized products. For this reason, the aliphatic polyester generally has a molecular weight by introducing a chain extender such as a diisocyanate compound or a polyfunctional branching agent (a trifunctional or higher component) such as malic acid or citric acid after the polycondensation reaction step or polycondensation reaction. Raising is done. In particular, when a polyfunctional branching agent is used, the melt tension and melt elasticity of the resin are improved, which is effective for improving moldability.

However, when such a polyfunctional component is used, a gel component may be generated during the transesterification reaction and the polycondensation reaction.
It is known that when gel is present in polyester, it remains as a foreign substance (fish eye or the like) in the obtained molded product, leading to deterioration of the appearance and physical properties of the product. Further, since the gel tends to stay in the molding machine, it was a cause of deterioration and coloring of the molded body.
For example, as a method for removing gels and foreign substances in an aromatic polyester resin, passing the molten resin after the polycondensation reaction through a polymer filter is performed (for example, see Patent Document 1).

JP 2013-35182 A

According to the study by the present inventors, even when an aliphatic polyester is produced, even if a polymer filter is installed as in Patent Document 1, gels and unmelted materials in the aliphatic polyester cannot be sufficiently removed. In addition, it has been found that there is a problem that the amount of terminal carboxyl groups, which is one of the indicators of polymer quality, increases.
The present invention has been made in view of the above problems, and in the production of aliphatic polyester, it suppresses the formation of gels and the formation of non-melted materials, has a high molecular weight, has little coloration, has good moldability, and is a film. It is an object of the present invention to provide an aliphatic polyester with little foreign matter such as fish eyes.

As a result of studying the above problems, the present inventors have found that the formation of gel is suppressed when the shear rate (γ2) of the molten polyester in the filtration device is within a specific range, and the present invention has been achieved. It was. That is, the gist of the present invention is as follows.
[1] A polyester having a dicarboxylic acid component and a diol component mainly composed of 1,4-butanediol as raw materials is obtained by a polycondensation reaction, and the polyester obtained by the polycondensation reaction is filtered at the outlet of the polycondensation reaction tank. In the method for producing polyester through an apparatus, the method for producing polyester, wherein the shear rate (γ2) of the molten polyester in the filtration device is 1 s ⁻¹ or more and 20 s ⁻¹ or less.
[2] Ratio of the shear rate (γ2) of the melted polyester in the filtration device to the shear rate (γ1) of the melted polyester in the transfer pipe from the outlet of the polycondensation reaction tank to the filtration device (γ2 / γ1) The method for producing a polyester according to [1], wherein is 0.1 or more and 15 or less.
[3] The process for producing a polyester according to [1] or [2], wherein the dicarboxylic acid component is mainly composed of succinic acid.
[4] The method for producing a polyester according to [1] to [3], wherein the polyester contains a trifunctional or higher functional oxycarboxylic acid component, a trifunctional or higher functional alcohol component, or a trifunctional or higher functional carboxylic acid component.
[5] The method for producing a polyester according to [4], wherein the polyester contains a malic acid component.

  The polyester produced by the production method of the present invention is excellent in thermal stability since the amount of terminal carboxyl groups is small, and is suitable as a raw material for films, monofilaments, fibers, etc. because there are few gels and unmelted materials in the polyester. Can be used. The effect of the present invention is particularly remarkable in the production of aliphatic polyester.

It is explanatory drawing of an example of the esterification reaction process employ | adopted by this invention. It is explanatory drawing of an example of the polycondensation process employ | adopted by this invention.

Embodiments of the present invention will be described in detail below, but the following descriptions are examples (representative examples) of embodiments of the present invention and are not limited to these contents.
In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
Further, in this specification, the “structural unit” refers to a structural unit derived from a monomer in polyester.
Further, in this specification, “main component” refers to occupying 70 mol% or more of the component. For example, “a diol compound containing 1,4-butanediol as a main component” means that 70 mol% or more of all diol components is 1,4-butanediol.

[1] Polyester raw material The polyester targeted by the production method of the present invention has a structure in which a structural unit derived from a dicarboxylic acid component and a structural unit derived from a diol component are ester-bonded. Here, the dicarboxylic acid component means dicarboxylic acid and / or an ester-forming derivative thereof as a raw material for producing polyester, and the diol component means diol and / or a derivative thereof as a raw material for producing polyester.

  The method for producing a polyester of the present invention is more effective especially in the production of an aliphatic polyester from the viewpoint that gel formation during the production process can be suppressed. The polyester in the present invention is obtained by subjecting a dicarboxylic acid component and a diol component mainly composed of 1,4-butanediol (hereinafter referred to as BG) to an esterification reaction and / or a transesterification reaction, and then a polycondensation reaction. can get. Hereinafter, the present invention will be described by taking aliphatic polyester as an example, but the present invention is not limited thereto.

<Diol component>
In the present invention, BG used as a raw material diol component may be used in combination with succinic acid produced by either a petrochemical method or a production method having a fermentation process derived from biomass resources, or those production methods.
In the present invention, the proportion of BG in the total diol component used for producing the polyester is 80 mol% or more based on the total aliphatic diol from the viewpoint of the melting point (heat resistance), biodegradability, and mechanical properties of the polyester. It is preferable that it is 90 mol% or more.

(Diol components other than BG)
The raw material diol component used in the present invention may contain a diol component other than BG.
Examples of diol components other than BG that can be used in the present invention include ethylene glycol, diethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3-propanediol, polypropylene glycol, polytetramethylene glycol, dibutylene glycol, 1, Linear aliphatic diols such as 5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,8-octanediol; 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexane Cycloaliphatic diols such as dimethylol, 1,4-cyclohexanedimethylol, isosorbide; xylylene glycol, 4,4′-dihydroxybiphenyl, 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxy) Phenyl ) Aromatic diols such as sulfones;
In addition, ethylene glycol, 1,3-propanediol, isosorbite and the like are not limited to those derived from petroleum, but those derived from biomass resources can be used. From the viewpoint of the physical properties of the resulting polyester, the other diol component is preferably ethylene glycol or 1,3-propanediol. These diol components can be used alone or as a mixture of two or more.

<Dicarboxylic acid component>
The dicarboxylic acid component used in the present invention is a dicarboxylic acid and / or an ester-forming derivative thereof obtained by either a petrification method or a production method having a fermentation process derived from biomass resources, and the above dicarboxylic acids may be used in combination. I can do it. As ester-forming derivatives of dicarboxylic acids, ester-forming derivatives such as acid anhydrides and acid chlorides are preferred in addition to lower alcohol esters of dicarboxylic acids. Here, the lower alcohol usually refers to a linear or branched alcohol having 1 to 4 carbon atoms.

(Aliphatic dicarboxylic acid component)
In the method for producing a polyester of the present invention, the aliphatic dicarboxylic acid component as a raw material may contain other dicarboxylic acids as long as the main component is aliphatic dicarboxylic acid, or a plurality of fats. A group dicarboxylic acid may be mixed and used. As the aliphatic dicarboxylic acid, usually, a chain or alicyclic hydrocarbon group having 2 to 40 carbon atoms in which two carboxyl groups are bonded is used. Specifically, for example, succinic acid, succinic anhydride, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecadicarboxylic acid, dodecadicarboxylic acid, dimer acid, hexahydrophthalic acid, hexa Examples include hydroisophthalic acid and hexahydroterephthalic acid. Of these, aliphatic dicarboxylic acids having 4 to 12 carbon atoms in the molecule are preferred from the viewpoint of the physical properties of the resulting polyester, and more specifically, succinic acid, succinic anhydride, adipic acid, and sebacic acid. Are preferred, succinic acid and succinic anhydride are more preferred, and succinic acid is most preferred. In addition, these may be used independently or may use 2 or more types together by arbitrary combinations.
The amount of succinic acid or succinic anhydride to be used is preferably 70 mol% or more based on the total aliphatic dicarboxylic acid from the viewpoint of the melting point (heat resistance), biodegradability and mechanical properties of the aliphatic polyester obtained. % Or more is more preferable.

(Other dicarboxylic acid components)
Moreover, you may use together aromatic dicarboxylic acid as dicarboxylic acid components other than aliphatic dicarboxylic acid. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and diphenyldicarboxylic acid. These may be used alone or in combination of two or more in any combination.

<Other copolymer components>
In the present invention, examples of the copolymer component that is another component of the polyester include lactic acid, glycolic acid, hydroxybutyric acid, hydroxycaproic acid, 2-hydroxy-3,3-dimethylbutyric acid, and 2-hydroxy-3-methyl. Oxycarboxylic acids such as butyric acid, 2-hydroxyisocaproic acid, malic acid, maleic acid, citric acid, and fumaric acid, and esters, lactones, and oxycarboxylic acid polymers of these oxycarboxylic acids; glycerin, trimethylolethane, trimethylol Trifunctional or higher polyhydric alcohols such as propane and pentaerythritol; trifunctional or higher polyhydric carboxylic acids such as propanetricarboxylic acid, pyromellitic acid, trimellitic acid, benzophenonetetracarboxylic acid and their anhydrides, or the like Is mentioned.

  Add a small amount of trifunctional or higher functional oxycarboxylic acid, trifunctional or higher alcohol, trifunctional or higher carboxylic acid, copolymer component that has a double bond and becomes a polyfunctional group when it becomes a copolymer component. This makes it easier to obtain a highly viscous polyester. Among these, oxycarboxylic acids such as malic acid and citric acid and fumaric acid having a double bond are preferable, among which tri- or higher functional oxycarboxylic acids are more preferable, and malic acid is particularly preferable.

  The amount of the trifunctional or higher polyfunctional compound is usually 0.001 mol% or more, preferably 0.05 mol% or more, based on the total dicarboxylic acid component, while the upper limit is usually 5 mol% or less, preferably 0.5 mol% or less. If the amount of the trifunctional or higher polyfunctional compound is too large, a gel or an insoluble material tends to be generated, and if it is too small, a polyester having a sufficient viscosity tends to be difficult to obtain. Further, a chain extender such as an isocyanate compound or a carbonate compound may be contained for the purpose of further increasing the molecular weight.

[2] Polyester production method <Polyester production>
Hereinafter, the polyester production method of the present invention will be shown as an example of polybutylene succinate using succinic acid as an aliphatic dicarboxylic acid, 1,4-butanediol as an aliphatic diol, and malic acid as another component. However, the present invention is not limited to this.
The polybutylene succinate can be roughly divided into a so-called direct polymerization method using succinic acid or succinic anhydride and 1,4-butanediol as main raw materials, a succinic acid dialkyl ester, preferably succinic acid dimethyl ester and 1 There is a transesterification method using 4-butanediol as a main raw material. In the former, water is mainly produced as a by-product in the initial esterification reaction, and in the latter, alcohol is mainly produced as a by-product in the initial transesterification reaction. From the viewpoint of height, a direct polymerization method is preferred. The esterification reaction or transesterification reaction between the dicarboxylic acid component and the diol component can be performed in a plurality of continuous esterification reaction tanks, but can also be performed in one tank. Moreover, from the viewpoint of stabilization of quality and energy efficiency, a so-called continuous method in which raw materials are continuously supplied to obtain polybutylene succinate continuously is preferable. In this specification, the continuous method will be described as an example.

(Esterification reaction conditions)
As an example of the direct polymerization method, the charged molar ratio of 1,4-butanediol to succinic acid is usually 0.95 to 2.0, preferably 1.0 to 1.7, more preferably 1.05 to 1. 40. Moreover, as for the preparation mol% of malic acid with respect to succinic acid, 0.05-0.50 mol% is preferable. The esterification reaction can be performed in one esterification reaction tank or a plurality of continuous reaction tanks. The lower limit of the reaction temperature is usually 215 ° C or higher, preferably 218 ° C or higher, and the upper limit is usually 240 ° C or lower, preferably 235 ° C or lower, more preferably 233 ° C or lower. If the esterification reaction temperature is too low, the esterification reaction rate is slow and a long reaction time is required, and there is a tendency for undesired reactions such as dehydration and decomposition of aliphatic diols to increase, and if too high, aliphatic diols and aliphatic dicarboxylic acids. In addition, the decomposition of the reaction product increases, and the amount of scattered matter increases in the reaction tank, which can easily cause foreign matters, and the reaction product tends to become cloudy (haze).

  The esterification temperature is preferably a constant temperature. The esterification rate is stabilized due to the constant temperature. The constant temperature is a set temperature ± 5 ° C., preferably ± 2 ° C. The reaction atmosphere is usually an inert gas atmosphere such as nitrogen or argon. The reaction pressure is usually 50 kPa to 200 kPa, and the lower limit is preferably 60 kPa or more, more preferably 70 kPa or more, and the upper limit is preferably 130 kPa or less, more preferably 110 kPa or less. If the reaction pressure is too low, the amount of scattered matter in the reaction vessel increases, the haze of the reaction product increases, and it is easy to increase foreign matter, and the distillation of aliphatic diols to the outside of the reaction system increases and the polycondensation reaction rate decreases. Tend to invite. If the reaction pressure is too high, the dehydration decomposition of the aliphatic diol increases, and the polycondensation rate tends to decrease. The reaction time is usually 1 hour or longer, and the upper limit is usually 10 hours or shorter, preferably 4 hours or shorter.

(Transesterification reaction conditions)
On the other hand, as an example of the transesterification method, the dicarboxylic acid ester component mainly composed of a dialkyl ester of succinic acid and the diol component mainly composed of 1,4-butanediol are transesterified in one or more stages. In the reaction vessel, preferably in the presence of a transesterification catalyst, usually 110 to 260 ° C, preferably 140 to 245 ° C, more preferably 180 to 220 ° C, and usually 10 to 133 kPa, preferably 13 to 120 kPa. More preferably, it is carried out under a pressure of 60 to 101 kPa, usually for 0.5 to 5 hours, preferably 1 to 3 hours.

(Polycondensation reaction conditions)
Next, the obtained esterification reaction product (sometimes referred to as an oligomer) is transferred to the first polycondensation reaction tank through the piping after the final esterification reaction tank. The polycondensation reaction is usually performed under reduced pressure. The polycondensation reaction is performed under reduced pressure using a plurality of continuous reaction vessels.

  The lower limit of the reaction pressure of the final polycondensation reaction tank is usually 0.01 kPa or more, preferably 0.03 kPa or more, and the upper limit is usually 1.4 kPa or less, preferably 0.4 kPa or less. If the pressure during the polycondensation reaction is too high, the polycondensation time will be prolonged, and accordingly, the molecular weight will be lowered or colored due to thermal decomposition of the polyester, which tends to make it difficult to produce a polyester exhibiting practically sufficient characteristics. On the other hand, the method of producing using an ultra-high vacuum polycondensation facility is a preferred embodiment from the viewpoint of improving the polycondensation reaction rate, but it is economically disadvantageous because it requires an extremely expensive equipment investment.

The lower limit of the reaction temperature is usually 215 ° C or higher, preferably 220 ° C or higher, and the upper limit is usually 270 ° C or lower, preferably 260 ° C or lower. If the reaction temperature is too low, the polycondensation reaction rate is slow, and not only does it take a long time to produce a polyester with a high degree of polymerization, but a high power stirrer is also required, which tends to be economically disadvantageous. On the other hand, if the reaction temperature is too high, thermal decomposition of the polyester during production tends to be caused, and it tends to be difficult to produce polyester having a high degree of polymerization.

  The lower limit of the reaction time is usually 1 hour or longer, and the upper limit is usually 15 hours or shorter, preferably 8 hours or shorter, more preferably 6 hours or shorter. If the reaction time is too short, the reaction is insufficient and it is difficult to obtain a polyester having a high degree of polymerization, and the mechanical properties of the molded product tend to be inferior. On the other hand, if the reaction time is too long, the molecular weight drop due to thermal decomposition of the polyester becomes remarkable, and not only the mechanical properties of the molded product tend to be inferior, but also the terminal amount of carboxyl groups that adversely affect the durability of the polyester. May increase due to degradation. In addition, gel formation is facilitated.

<Catalyst and additive>
The transesterification reaction and the polycondensation reaction are promoted by using a catalyst. In the esterification reaction, a sufficient reaction rate can be obtained without an esterification reaction catalyst. In addition, if an esterification reaction catalyst is present during the esterification reaction, water generated by the esterification reaction may cause a precipitate that is insoluble in the reaction product, which may impair the transparency of the resulting polyester (ie, increase haze). In addition, since the catalyst may become a foreign substance, it is preferable not to add the catalyst during the esterification reaction. Further, when the catalyst is added to the gas phase part of the reaction vessel, the haze may be increased, and the catalyst may be converted into a foreign substance. Therefore, it is preferable to add the catalyst to the reaction solution.

  In the transesterification reaction and the polycondensation reaction, the reaction is difficult to proceed without a catalyst, and a catalyst is preferably used. As the catalyst, a compound containing at least one kind of metal elements of Groups 1 to 14 of the periodic table (hereinafter sometimes referred to as “metal element compound”) is generally used. Specific examples of the metal element include scandium, yttrium, samarium, titanium, zirconium, vanadium, chromium, molybdenum, tungsten, tin, antimony, cerium, germanium, zinc, cobalt, manganese, iron, aluminum, magnesium, Examples include calcium, strontium, sodium and potassium. Among these, scandium, yttrium, titanium, zirconium, vanadium, molybdenum, tungsten, zinc, iron, and germanium are preferable, and titanium, zirconium, tungsten, iron, and germanium are more preferable.

  Furthermore, in order to reduce the carboxyl group terminal density | concentration which affects the thermal stability of polyester, among the said metal elements, the periodic table 3-6 metal element which shows Lewis acidity is preferable. Specific examples include scandium, titanium, zirconium, vanadium, molybdenum, tungsten, and the like. In particular, titanium and zirconium are preferable from the viewpoint of availability, and titanium is more preferable from the viewpoint of reaction activity.

In the present invention, as a catalyst, a compound containing an organic group such as a carboxylate salt, an alkoxy salt, an organic sulfonate salt, or a β-diketonate salt containing these metal elements, and the above-described metal oxide, halide, etc. Inorganic compounds and mixtures thereof are preferably used.
The catalyst is preferably a compound that is liquid at the time of polymerization or is soluble in an ester low polymer or polyester because the polymerization rate is increased when it is in a molten or dissolved state at the time of polymerization. A small amount of solvent may be used to dissolve the catalyst.
Examples of the solvent for dissolving the catalyst include alcohols such as methanol, ethanol, isopropanol and butanol, diols such as ethylene glycol, butanediol and pentanediol, ethers such as diethyl ether and tetrahydrofuran, and nitriles such as acetonitrile. , Hydrocarbon compounds such as heptane and toluene, water and mixtures thereof. The amount used is such that the catalyst concentration is usually 0.0001% by mass or more and 99% by mass or less.

Specifically, examples of the titanium compound include tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetra-t-butyl titanate, tetraphenyl titanate, tetracyclohexyl titanate, and tetrabenzyl titanate. Tetraalkyl titanates and their hydrolysates, titanium (oxy) acetylacetonate, titanium tetraacetylacetonate, titanium (diisoproxide) acetylacetonate, titanium bis (ammonium lactate) dihydroxide, titanium bis (ethylacetoacetate) diiso Propoxide, titanium (triethanolamate) isopropoxide, polyhydroxytitanium stearate, titanium lactate, titanium triethanolamate, Titanate dimer and the like.
Among these, tetraalkyl titanates and hydrolysates thereof are preferred.
These titanium compounds may be used alone or in combination of two or more in any combination.
Moreover, it is preferable to use a titanium compound as a liquid obtained by mixing the solvent mentioned above, the periodic table group 2 metal compound, and the phosphate ester compound.

  The amount of catalyst added in the case of using a metal compound as these polycondensation catalysts, the lower limit is usually 0.1 mass ppm or more, preferably 0.5 mass ppm or more, more preferably 1 mass ppm, as the amount of metal relative to the polyester to be produced. The upper limit is usually 3000 mass ppm or less, preferably 1000 mass ppm or less, more preferably 250 mass ppm or less, and particularly preferably 130 mass ppm or less. If too much catalyst is used, it is not only economically disadvantageous, but also the carboxyl group terminal concentration in the polyester may increase, so the thermal stability of the polyester is increased by increasing the carboxyl group terminal amount and residual catalyst concentration. And hydrolysis resistance tends to decrease. On the other hand, when the amount is too small, the polymerization activity is lowered, and accordingly, thermal decomposition of the polyester is induced during the production of the polyester, and it tends to be difficult to obtain a polyester having practically useful physical properties.

  The position of addition of the catalyst to the reaction system is not particularly limited as long as it is before the polycondensation reaction step, and may be added at the time of charging the raw material, but the catalyst is used in a situation where a lot of water is present or generated. If it coexists, the catalyst is deactivated and foreign matter may be precipitated, which may impair the quality of the product. Therefore, it is preferably added after the esterification reaction step.

<Example of production line>
Hereinafter, preferred embodiments of a method for producing an aliphatic polyester will be described with reference to the accompanying drawings. FIG. 1 is an explanatory diagram of an example of an esterification reaction step employed in the present invention, and FIG. 2 is an explanatory diagram of an example of a polycondensation step employed in the present invention.

(Esterification)
In FIG. 1, succinic acid as a raw material is usually mixed with 1,4-butanediol (sometimes referred to as BG) in a raw material mixing tank (not shown), and is supplied as a slurry or liquid from a raw material supply line (1). It is supplied to the esterification reaction tank (A) in the form. Moreover, when adding a catalyst at the time of esterification reaction, after making it a solution of BG with a catalyst adjustment tank (not shown), it is made by supplying a solution to BG supply line (3). In FIG. 1, the BG supply line (3) is connected to the recirculation line (2) of the recirculated 1,4-butanediol, mixed and then supplied to the liquid phase part of the esterification reaction tank (A). showed that.
The gas distilled from the esterification reaction tank (A) is separated into a high-boiling component and a low-boiling component in the rectifying column (C) through the distillation line (5). Usually, the main component of the high-boiling component is 1,4-butanediol, and the main component of the low-boiling component is tetrahydrofuran (sometimes referred to as THF) which is a decomposition product of water and BG.

The high-boiling components separated in the rectification column (C) are extracted from the extraction line (6) and pump (D
) Is partly circulated from the BG recirculation line (2) to the esterification reactor (A) and part is returned from the circulation line (7) to the rectification column (C). Further, the surplus is extracted outside from the extraction line (8). On the other hand, the low-boiling components separated in the rectification column (C) are extracted from the gas extraction line (9), condensed in the condenser (G), and temporarily passed through the condensate line (10) to the tank (F). Accumulated. Part of the low-boiling components collected in the tank (F) is returned to the rectification column (C) via the extraction line (11), the pump (E) and the circulation line (12), and the remainder is extracted. It is extracted outside through the line (13). The condenser (G) is connected to an exhaust device (not shown) via a vent line (14). The esterification reaction product generated in the esterification reaction tank (A) is supplied to the first polycondensation reaction tank (a) in FIG. 2 via the extraction pump (B) and the extraction line (4) of the esterification reaction product. Is done.

In the process shown in FIG. 1, the BG supply line (3) is connected to the recirculation line (2), but both may be independent. Moreover, the raw material supply line (1) may be connected to the liquid phase part of the esterification reaction tank (A).
In the case of adding a catalyst to the esterification reaction product before the polycondensation tank, it is adjusted to a predetermined concentration in a catalyst preparation tank (not shown), and then passed through the catalyst supply line (L7) in FIG. ), And further diluted with BG, and then supplied to the esterification reaction product extraction line (4) shown in FIG.

(Polycondensation)
Next, the esterification reaction product supplied to the first polycondensation reaction tank (a) from the extraction line (4) of the esterification reaction product through the filter (p) is polycondensed under reduced pressure to reduce the polyester low weight. Thereafter, they are combined and then supplied to the second polycondensation reaction tank (d) through the extraction gear pump (c), the extraction line (L1) serving as the outlet channel, and the filter (q). In the second polycondensation reaction tank (d), the polycondensation reaction usually proceeds further at a lower pressure than in the first polycondensation reaction tank (a). The obtained polycondensate is supplied to the third polycondensation tank (k) via the extraction gear pump (e), the extraction line (L3) serving as the outlet channel, and the filter (r). The third polycondensation reaction tank (k) is the final polycondensation tank of the present invention in this example. The polycondensation reaction product introduced into the third polycondensation reaction tank (k) from the second polycondensation reaction tank (d) through the extraction line (L3) is further subjected to a polycondensation reaction.

(Removal pelletization)
After the completion of the polycondensation reaction, the polymer as the reaction product is continuously discharged from the outlet of the polycondensation reaction tank (k) through the transfer pipe, but on the way through the gear pump (m) and the filtering device (s), the base (g The polymer is extracted in the form of a strand from The extracted polyester is cut by a rotary cutter (h) or pelletized after cooling or while cooling.

  Here, from the polycondensation reaction tank (k) outlet, the extraction gear pump (m), the filtration device (s), the transfer pipe connecting the base (g), and the device are preferably managed at the lowest possible temperature. The piping and device from the polycondensation reaction tank (k) outlet to the base (g) can be heated with a heat medium, steam, electric heater, etc., from the polycondensation reaction tank outlet to the filtration device (s). Piping, filtration device (s), and piping from the filtration device (s) to the base (g) can be adjusted separately. The temperature from the polycondensation reaction tank (k) outlet to the base (g) and the temperature of the apparatus are usually controlled at the melting point of the polyester to 250 ° C. The heating temperature of the preferable piping is 130 ° C. or higher and 240 ° C. or lower, more preferably 150 ° C. or higher and 220 ° C. or lower, and particularly preferably 170 ° C. or higher and 200 ° C. or lower. If the piping temperature is too high, the thermal decomposition and thermal deterioration of the polyester become remarkable, causing an increase in the terminal acid value and a decrease in viscosity (molecular weight), which tends to be unfavorable in terms of quality. If the piping temperature is too low, excessive pressure is applied to the piping and the filtration device, so that the durability of the device tends to decrease. Further, since the polyester is solidified and clogged in the pipe, it tends to be unfavorable in terms of operation.

  Moreover, it is preferable that the transfer piping connecting the gear pump (m), the filtering device (s), and the base (g) from the outlet of the polycondensation reaction tank (k) is as short as possible. The residence time of the polyester from the polycondensation reaction tank (k) outlet to the die (g) is usually within 50 minutes, preferably within 40 minutes, more preferably within 30 minutes, particularly preferably within 20 minutes, Most preferably, it is within 15 minutes. If the residence time of the polyester from the polycondensation reaction tank outlet to the die is too long, the thermal decomposition and thermal deterioration of the polyester will become remarkable, causing an increase in the terminal acid value and a decrease in viscosity (molecular weight), which tends to be unfavorable in terms of quality. is there.

  On the other hand, the residence time of the polyester in the filtration device (s) is usually within 10 minutes, preferably within 8 minutes, and more preferably within 5 minutes. If the residence time of the polyester in the filtration device (s) is too long, gel formation increases and the effects of the present invention tend not to be obtained.

Moreover, the shear rate (γ1) of the molten polyester in the transfer pipe from the polycondensation reaction tank (k) outlet to the filtration device (s) is usually from 0.1 s ^{−1 to} 10 s ⁻¹ , and the upper limit is , Preferably 8 s ⁻¹ or less, more preferably 5 s ⁻¹ or less, still more preferably 4 s ⁻¹ or less, particularly preferably 3 s ⁻¹ or less. The lower limit is preferably 0.15s ^-1 or more, more preferably 0.2 s ^-1 or more, more preferably 0.5 s ^-1 or higher, particularly preferably ^{1s -1} or less.

  If the shear rate (γ1) is too high, excessive pressure is applied to the piping, and the durability of the apparatus is reduced. In addition, thermal decomposition and thermal degradation due to shear heat generation of polyester become remarkable, causing an increase in terminal acid value and a decrease in viscosity (molecular weight), which tends to be unfavorable in terms of quality. When the shear rate (γ1) is too low, there is a tendency that the gel cannot be sufficiently removed from the molten polyester supplied into the filtration device.

The shear rate can be calculated from the following formula (1).
_{γ = 4Q / (π · (} D 1/2) 3) ··· (1)
γ: Shear rate (1 / s)
Q: Volume flow rate (m ³ / s)
D ₁ : Pipe diameter (m)

On the other hand, the shear rate (γ2) of the molten polyester in the filtration device (s) is 1 s ⁻¹ or more and 20 s ⁻¹ or less, and the upper limit is preferably 18 s ⁻¹ or less, more preferably 16 s ⁻¹ or less. Particularly preferably, it is 15 s ^-1 or less. The lower limit is preferably 1.5 s ⁻¹ or more, more preferably 2 s ⁻¹ or more, and particularly preferably 3 s ⁻¹ or more. If the shear rate (γ2) is too high, excessive pressure is applied in the filtration device, and the durability of the device is reduced. In addition, thermal decomposition and thermal deterioration due to shear heat generation in the filtration device become remarkable, causing an increase in the amount of terminal carboxyl groups and a decrease in viscosity (molecular weight), and polyester which is undesirable in terms of quality is produced. When the shear rate (γ1) is too low, the gel in the polyester is not sufficiently removed.

Moreover, the shear rate in a filtration apparatus shall be calculated from following formula (2).
γ = 4Q / (n · π · (D 2/2) 3) ··· (2)
γ: Shear rate (1 / s)
Q: Volume flow rate (m ³ / s)
D ₂ : filter opening (m)
n: Number of openings The number of openings (n) was calculated from the following formula (3).
n = filtration area / (filtration accuracy) ² (3)
In addition, the filtration precision in this invention is calculated | required by JISB8356-8 (ISO16889) and JISB8356-9.

  Further, the shear rate (γ2) of the molten polyester in the filtration device (s) and the shear rate (γ1) of the molten polyester in the transfer pipe from the outlet of the polycondensation reaction tank (k) to the filtration device (s). ) Ratio (γ2 / γ1) is usually 0.1 or more and 15 or less, preferably 0.2 or more and 10 or less, more preferably 0.3 or more and 8 or less, and further preferably 0.4 or more and 6 or less. . When it is in the above range, gel removal can be performed efficiently, and the effects of the present invention can be easily obtained.

In the present invention, when the shear rate (γ2) of the molten polyester in the filtration device is within the specified range, the formation of gels and non-melting materials is suppressed, and the aliphatic polyester is high in molecular weight and less colored. Although the details are not clear regarding the fact that it was able to be manufactured, it is considered as described below.
Since the inventors of the present invention generate a large number of gels and insoluble matter generated in the aliphatic polyester during the transfer through the piping as compared with the melt polycondensation tank, the gel and the insoluble matter are not sheared in the molten state. It was estimated that insoluble matter was formed. The reason is that when shearing is not applied, an aliphatic polyester having a plurality of active sites or an unreacted branching agent reacts with a branching agent or the like, and a high molecular weight gel or insoluble matter is generated in the aliphatic polyester. It is guessed.
For this reason, the inventors can suppress the generation of high molecular weight components such as gels generated in the polyester by providing a shearing portion in the transfer pipe, and can also unravel the generated high molecular weight components by shearing. Various studies have been made under the assumption that the configuration and effect of the present invention have been achieved.

  Further, the filters (filtering devices) p, q, and r before the final polycondensation tank are not necessarily installed, and r is not installed in the examples described later. In the present invention, in order to remove foreign substances such as gel generated after the final polycondensation reaction tank, it is essential to install a filtration device (s) at least from the final polymerization tank to the die.

  As a filtration device, a filter that can filter a fluid having a melt viscosity of about several tens to 100 poises, and a filter that can filter a fluid having a melt viscosity of several thousand poises or more coming out from the outlet of the polyester extraction die is generally known. Can be used. As the filter media, for example, several fine meshes that determine filtration accuracy, reinforcing meshes, and protective meshes are stacked, and a laminated metal mesh that is completely integrated by sintering, or a stainless metal fiber felt is laminated. And sintered metal nonwoven fabrics.

Examples of the shape of the filter include a basket type, a disk type, a leaf disk type, a tube type, a flat cylindrical type, and a pleated cylindrical type. These filters can be appropriately selected and used according to the conditions such as the viscosity, pressure and temperature of the fluid at the installation location, but when installing a low polymer having a low melt viscosity at the location to be filtered, the washing properties, etc. Tube type or flat cylindrical type is preferable from the viewpoint of, and when installing polyester with high melt viscosity in the place to filter, leaf disk type or pleated cylindrical type from the viewpoint of pressure resistance and processing flow rate per unit area Is preferred.
The absolute filtration accuracy of these filters is usually 0.5-100 μm, preferably 1-80 μm, more preferably 2-60 μm from the viewpoint of filtration efficiency, etc., and a low polymer having a low melt viscosity. In the case of filtration, the range is 0.5 to 30 μm, and in the case of filtration of polyester having a high melt viscosity, it is usually 5 to 100 μm, preferably 8 to 90 μm.

<Physical properties of aliphatic polyester>
The intrinsic viscosity of the aliphatic polyester obtained by the production method of the present invention is determined by the measurement conditions described in the examples. The intrinsic viscosity of the aliphatic polyester is usually 1.0 dL / g or more, preferably 1.3 dL / g or more, more preferably 1.6 dL / g or more, and the upper limit is usually 2.8 dL / g or less, preferably 2. It is 5 dL / g or less, More preferably, it is 2.3 dL / g or less. When the intrinsic viscosity is less than the lower limit, it tends to be difficult to obtain sufficient mechanical strength when formed into a molded product. If the intrinsic viscosity exceeds the upper limit, the melt viscosity is high during molding and the molding tends to be difficult.

  The terminal carboxyl group amount (AV) of the aliphatic polyester is usually 100 equivalents / ton or less, preferably 50 equivalents / ton or less, more preferably 25 equivalents / ton or less, while the lower limit is not particularly limited, but usually 1 equivalent. / Ton or more, preferably 5 equivalents / ton or more. If the amount of the terminal carboxyl group of the aliphatic polyester is high, the thermal stability is poor and thermal decomposition tends to increase during molding.

  The color b value in the Hunter color coordinates of the aliphatic polyester pellets is usually 0.0 or more, and the upper limit is usually 3.0 or less, preferably 2.5 or less. If the color b value of the aliphatic polyester is too high, a yellowish color is produced when formed into a molded product, which may be undesirable.

<Use of aliphatic polyester>
Since the aliphatic polyester obtained by the method of the present invention has practical physical properties such as thermal stability, tensile strength, and tensile elongation, the film can be formed by a general-purpose plastic molding method such as an injection molding method, a hollow molding method, and an extrusion molding method. Can be used for molded products such as laminated film, sheet, plate, stretched sheet, monofilament, multifilament, non-woven fabric, flat yarn, staple, crimped fiber, striped tape, split yarn, composite fiber, blow bottle, foam is there.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example at all unless the summary is exceeded. In addition, the values of various production conditions and evaluation results in the following examples have meanings as preferable values of the upper limit or the lower limit in the embodiment of the present invention, and the preferable range is the value of the upper limit or the lower limit. It may be a range defined by a combination of values of the following examples or values of the examples.
In addition, the measuring method of the physical property and evaluation item which were employ | adopted in the following examples is as follows.

<Intrinsic viscosity (IV)>
It calculated | required in the following way using the Ubbelohde type viscometer. That is, using a mixed solvent of phenol / tetrachloroethane (mass ratio 1/1) and measuring the number of seconds of dropping only the sample solution having a concentration of 0.5 g / dL and the solvent at 30 ° C., the following formula (3) I asked more.
IV = ((1 + 4K _H η _sp ) ^0.5 −1) / (2K _H C) (3)
(Where η _sp = η / η ₀ −1, η is the sample solution falling seconds, η ₀ is the solvent dropping seconds, C is the sample solution concentration (g / dL), and K _H is the Huggins constant. .K _H adopted the 0.33.)

<Terminal carboxyl group concentration (AV) of esterification reaction product>
0.3 g of a sample was put in 40 mL of benzyl alcohol, heated at 180 ° C. for 20 minutes, cooled for 10 minutes, and then titrated with a 0.1 mol·L ⁻¹ KOH / methanol solution to obtain the esterification reaction product. It was expressed in terms of equivalent concentration / ton of carboxyl group based on the total amount of
Since aliphatic polyester having a high amount of carboxyl groups has low thermal stability, a resin having a low terminal carboxyl group is generally preferably used.

<Number of fish eyes (FE)>
The polyester pellets were dried at 80 ° C. for 8 hours under a nitrogen atmosphere, and a film forming machine (model ME-20 / 26V2) manufactured by Optical Control Systems was used to obtain a film having a thickness of 50 μm. The cylinder and die temperatures were 190 ° C. The number of fish eyes per 1 m ^{2 of the} film was measured using Film Quality Testing System [Optical Control Systems, Inc., Type FS-5].

Example 1
[Preparation of polymerization catalyst]
To a glass eggplant-shaped flask equipped with a stirrer, 100 parts by mass of magnesium acetate tetrahydrate was added, and 1500 parts by mass of absolute ethanol (purity 99% by mass or more) was further added. Furthermore, 65.3 parts by mass of ethyl acid phosphate (mixing mass ratio of monoester and diester was 45:55) was added and stirred at 23 ° C. After confirming that magnesium acetate was completely dissolved after 15 minutes, 122 parts by mass of tetra-n-butyl titanate was added. Stirring was further continued for 10 minutes to obtain a uniform mixed solution. This mixed solution was transferred to an eggplant-shaped flask and concentrated under reduced pressure by an evaporator in an oil bath at 60 ° C. After 1 hour, most of ethanol was distilled off to obtain a translucent viscous liquid. The temperature of the oil bath was further raised to 80 ° C., and further concentrated under reduced pressure of 5 Torr (666.5 Pa) to obtain a viscous liquid. This liquid catalyst was dissolved in 1,4-butanediol (BG) to prepare a titanium atom content of 3.36% by mass. The catalyst solution had a pH of 6.3.

[Production of aliphatic polyester]
In accordance with the manufacturing process shown in FIGS. 1 and 2, an aliphatic polyester resin was manufactured in the following manner. First, a slurry was prepared so that the amount of 1,4-butanediol was 1.30 mol and malic acid was 0.0033 mol with respect to 1.00 mol of succinic acid containing 0.15% by mass of malic acid. Added to the bath and mixed at 40 ° C.
Next, an ester having a stirrer filled with an aliphatic polyester low molecular weight substance (esterification reaction product) having an esterification rate of 99% by mass in a nitrogen atmosphere from a slurry preparation tank (not shown) through a raw material supply line (1). Into the chemical reaction tank (A) at a rate of 58.8 kg / h.

  The internal temperature of the esterification reaction tank (A) is 230 ° C., the pressure is 101 kPa, and the produced water, tetrahydrofuran and excess 1,4-butanediol are distilled from the distillation line (5), and a rectifying column ( In C), a high-boiling component and a low-boiling component were separated. A part of the high boiling point component at the bottom of the column after the system was stabilized was extracted to the outside through an extraction line (8) so that the liquid level of the rectification column (C) was constant. On the other hand, a low boiling point component mainly composed of water and THF is extracted in the form of gas from the top of the column, condensed in a condenser (G), and the extraction line (13) so that the liquid level in the tank (F) is constant. More extracted outside. At the same time, the total amount of the bottom component (98% by mass or more of 1,4-butanediol) of the rectification column (C) at 100 ° C. from the BG recirculation line (2), and 1% from the BG supply line (3) , 4-butanediol was supplied together, and the molar ratio of 1,4-butanediol supplied to the amount of succinic acid supplied per unit time into the esterification reaction tank was adjusted to 1.50. The supply amount was 4.5 kg / h in total for the recirculation line (2) and the BG supply line (3).

The esterification reaction product produced in the esterification reaction tank (A) is continuously extracted from the extraction line (4) of the esterification reaction product using the extraction pump (B), and the esterification reaction tank (A). The liquid level was controlled so that the average residence time of the internal liquid in terms of succinic acid unit was 4.3 hours. The esterification reaction product extracted from the extraction line (4) was continuously supplied to the first polycondensation reaction tank (a). After the system was stabilized, the esterification rate of the esterification reaction product collected at the outlet of the esterification reaction tank (A) was 92.7%, and the terminal carboxyl concentration was 853 equivalent / ton.

A catalyst solution prepared in advance by the above-described method was prepared by diluting a catalyst solution diluted with 1,4-butanediol so that the concentration as titanium atoms was 0.1% by mass in a catalyst preparation tank. L2) and the supply line (L8) were continuously supplied to the esterification reaction product extraction line (4) at 2.15 kg / h (the catalyst was added to the liquid phase of the reaction solution). The supply was stable during the operation period.
The liquid level was controlled so that the internal temperature of the first polycondensation reaction tank (a) was 240 ° C., the pressure was 1.6 kPa, and the residence time was 2 hours. An initial polycondensation reaction was performed while extracting water, tetrahydrofuran, and 1,4-butanediol from a vent line (L2) connected to a decompressor (not shown). The extracted reaction liquid was continuously supplied to the second polycondensation reactor (d).
The internal temperature of the second polycondensation reaction tank (d) is 245 ° C., the pressure is 0.36 kPa, the liquid level is controlled so that the residence time is 3.5 hours, and it is connected to a decompressor (not shown). The polycondensation reaction was further advanced while extracting water, tetrahydrofuran and 1,4-butanediol from the bent line (L4). The obtained polyester was continuously supplied to the third polycondensation reaction tank (k) via the extraction line (L3) by the extraction gear pump (e). The internal temperature of the third polycondensation reaction tank (k) was 240 ° C., the pressure was 0.16 kPa, the residence time was 3 hours, and the polycondensation reaction was further advanced.

The polyester increased to a predetermined viscosity was continuously extracted in a strand form from the die head (g) through the filtration device from the outlet of the third polycondensation reaction tank, and cut into pellets by a rotary cutter (h). The product acquisition amount was 43 kg / hr.
The diameter of the transfer pipe from the reaction vessel outlet to the filtration device was 0.04 m, and the shear rate γ1 was 1.8 s ⁻¹ . A pleated cylindrical type was used for the filtration device. A laminated metal mesh with a filtration accuracy of 20 μm was used as the filter medium, and the filtration area was 0.4 m ² . The shear rate γ2 in the filtration device was 14.5 s ⁻¹ .
The ratio γ2 / γ1 between the shear rate (γ1) of the polyester in the transfer pipe and the shear rate (γ2) in the filtration device was determined to be 8.0. The obtained polyester had good film properties. The measurement results are shown in Table 1.

(Example 2)
A polyester was produced in the same manner as in Example 1 except that the amount of slurry supplied to the esterification reaction tank (A) was continuously supplied so as to be 75.2 kg / h. The product acquisition amount was 55 kg / hr. The measurement results are shown in Table 1.

Example 3
A polyester was produced in the same manner as in Example 1 except that a laminated metal mesh having a filtration accuracy of 100 μm was used as the filter of the filtration device. The product acquisition amount was 43 kg / hr. The measurement results are shown in Table 1.

(Comparative Example 1)
A polyester was produced in the same manner as in Example 1 except that the filtration area of the filter of the filtration device was 0.2 m ² . The obtained polyester had low IV and high AV due to thermal degradation. Also, film FE increased. The product acquisition amount was 43 kg / hr. The measurement results are shown in Table 1.

(Comparative Example 2)
A polyester was produced in the same manner as in Example 1 except that no polymer filter was installed. The polyester film FE obtained was high. The product acquisition amount was 43 kg / hr. The measurement results are shown in Table 1.

  According to the present invention, it is possible to suppress the formation of gel in the production of polyester, and to obtain a polyester with less defects such as fish eyes when molded, and in a molded product such as a film using the same, there is less foreign matter such as fish eyes. A molded product can be obtained.

1: Raw material supply line
2: BG recirculation line
3: BG supply line
4: Esterification reaction product extraction line
5: Distillation line
6: Extraction line
7: Circulation line
8: Extraction line
9: Gas extraction line
10: Condensate line
11: Extraction line
12: Circulation line
13: Extraction line
14: Vent line
15: Supply line
16: Supply line A: Esterification reaction tank
B: Extraction pump
C: Rectification tower
D, E: Pump
F: Tank
G: Capacitor
L1, L3, L5: Polycondensation reaction product extraction line
L2, L4, L6: Vent line
L8: BG supply line
L7: Catalyst supply line
a: First polycondensation reaction tank
d: Second polycondensation reaction tank k: Third polycondensation reaction tank
c, e, m: gear pump for extraction
g: Base
h: Rotary cutter
p, q, r, s: filtration device (filter)

Claims (5)

A polyester obtained from a dicarboxylic acid component and a diol component mainly composed of 1,4-butanediol as a raw material is obtained by a polycondensation reaction, and the polyester obtained by the polycondensation reaction is subjected to a polycondensation reaction tank outlet and a filtration device. The method for producing polyester, wherein the shear rate (γ2) of the molten polyester in the filtration device is 1 s ⁻¹ or more and 20 s ⁻¹ or less.   The ratio (γ2 / γ1) of the shear rate (γ2) of the molten polyester in the filtration device to the shear rate (γ1) of the molten polyester in the transfer pipe from the outlet of the polycondensation reaction tank to the filtration device is 0. The method for producing a polyester according to claim 1, which is 1 or more and 15 or less.   The method for producing a polyester according to claim 1, wherein the dicarboxylic acid component is mainly composed of succinic acid.   The method for producing a polyester according to any one of claims 1 to 3, wherein the polyester contains a trifunctional or higher functional oxycarboxylic acid component, a trifunctional or higher functional alcohol component, or a trifunctional or higher functional carboxylic acid component.   The method for producing a polyester according to claim 4, wherein the polyester contains a malic acid component.

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