JP5428425B2 - Polyester manufacturing method - Google Patents

Description

  The present invention relates to a method for producing polyester. Specifically, a long-term stable continuous production method of a polyester using at least a dicarboxylic acid component having at least an aliphatic dicarboxylic acid and / or an aliphatic dicarboxylic acid alkyl ester as a main component and a diol component having an aliphatic diol as a main component as raw materials About.

Polyesters obtained by diesterification and polycondensation reaction using dicarboxylic acid and diol as raw materials are used in various applications such as films, fibers, and containers. Among them, aliphatic polyesters typified by polybutylene succinate are required to be derived from plant resources, and have good physical properties and biodegradability. Therefore, agricultural materials, civil engineering materials, vegetation materials, etc. It is being processed into products such as packaging materials and is being widely used.
In general, the polycondensation reaction of polyester is performed by a batch method, a continuous method, or a method combining a batch method and a continuous method. Among these, when mass-producing industrially, the continuous method is advantageous in terms of productivity, quality stability, economy, etc., and those that are mass-produced such as polyethylene terephthalate and polybutylene terephthalate depend on the continuous method. There are overwhelmingly many things.

In addition, as an economically advantageous polyester production method, an ester low polymer is produced by a direct esterification reaction between a dicarboxylic acid and a diol, or an ester exchange reaction between an alkyl ester of a dicarboxylic acid and a diol. A method for producing a polyester having a high degree of polymerization by performing a lower polycondensation reaction and distilling off the produced diol from the reaction system has been known for a long time, and a catalyst is usually used for the polycondensation reaction.
As a method for producing an aliphatic polyester mainly composed of an aliphatic dicarboxylic acid and / or an aliphatic dicarboxylic acid alkyl ester and an aliphatic diol, for example, a polycondensation reaction is performed using an organic alkoxy metal compound such as tetrabutyl titanate as a catalyst. And a method of increasing the molecular weight by adding diisocyanate or diphenyl carbonate as a chain extender to extend the polymer chain length has been proposed (see, for example, Patent Document 1).

  Further, as an improvement of a method for producing an aliphatic polyester by polycondensation reaction using a titanium compound catalyst, for example, a polybutylene succinate or polybutylene adipate polyester is produced by allowing a magnesium compound to coexist with a titanium catalyst. Specifically, a polybutylene succinate is batch-wise prepared by dissolving a titanium compound and a magnesium compound in 1,4-butanediol and adding them to the esterification reaction product, followed by polymerization at elevated temperature. The method of manufacturing by a method is described (for example, refer patent document 2).

JP-A-4-189822 JP 2001-98065 A

However, according to the study by the present inventors, in a continuous process for producing a polyester mainly composed of an aliphatic dicarboxylic acid and / or an aliphatic dicarboxylic acid alkyl ester and an aliphatic diol, these catalysts are brought into a solution state. When continuously added to the reaction system through the piping, it was found that the catalyst was solidified and the piping was blocked, making the continuous addition difficult, and causing problems in the physical properties of the resulting polyester.
The present invention has been made in view of the above problems, and it is possible to add a catalyst to a reaction system in a continuous production operation of a polyester mainly composed of an aliphatic dicarboxylic acid and / or an aliphatic dicarboxylic acid alkyl ester and an aliphatic diol. An object of the present invention is to provide a method for stably producing a polyester having good quality for a long period of time and stably for a long period.

As a result of intensive studies to solve the above problems, the present inventors have identified a polycondensation catalyst in the production of a polyester mainly composed of an aliphatic dicarboxylic acid and / or an aliphatic dicarboxylic acid alkyl ester and an aliphatic diol. By adding to the reaction system under conditions, it was found that the catalyst could be stably added for a long period of time, and the performance of the resulting polyester was stably improved for a long period of time.
That is, the gist of the present invention is to esterify at least (1) a dicarboxylic acid component having an aliphatic dicarboxylic acid and / or an aliphatic dicarboxylic acid alkyl ester as a main component and (2) a diol component having an aliphatic diol as a main component. In a method for producing a polyester by subjecting a polyester low polymer to a polycondensation reaction using a polycondensation catalyst by a polyester and / or transesterification reaction, (a) esterification and / or The transesterification reaction is performed using a single stage or a plurality of continuous esterification reaction tanks, (b) the polycondensation reaction is continuously performed using a multistage polycondensation reaction tank, and (c) polycondensation in a solvent. The catalyst solution in which the reaction catalyst is dissolved is continuously added to the reaction liquid from the last stage esterification reaction tank to the first stage polycondensation reaction tank at a temperature of the melting point of the polyester to 200 ° C. It consists in the production method of a polyester which comprises adding to.

  According to the method of the present invention, it is possible to stably add the polycondensation catalyst to the reaction system, and as a result, it is possible to continuously produce a polyester having stable quality for a long period of time.

It is the schematic which shows one Embodiment of an esterification reaction process. It is the schematic which shows one Embodiment of a melt polycondensation reaction process. It is the schematic which shows one Embodiment of the Y-shaped valve for catalyst addition. It is the schematic which shows one Embodiment of the injection valve for catalyst addition.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the description of constituent elements described below is an example (representative example) of an embodiment of the present invention, and is not specified by these contents.
The present invention comprises at least (1) esterification of a dicarboxylic acid component mainly comprising an aliphatic dicarboxylic acid and / or an aliphatic dicarboxylic acid alkyl ester, and (2) a diol component mainly comprising an aliphatic diol. Alternatively, a polyester low polymer is obtained by transesterification, and a polyester is produced by polycondensation reaction of the obtained polyester low polymer using a polycondensation catalyst.

<Dicarboxylic acid component>
Examples of aliphatic dicarboxylic acids include chain aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid; 1,2-cyclohexanedicarboxylic acid, 1,3 -Cyclohexanedicarboxylic acid, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, etc. can be mentioned. Acid is preferred. The succinic acid and adipic acid can be derived from plants. Two or more of these may be used in combination.

  Other dicarboxylic acids include terephthalic acid, isophthalic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyl ether dicarboxylic acid, 4,4′-benzophenone dicarboxylic acid, and 4,4′-diphenoxyethanedicarboxylic acid. Aromatic dicarboxylic acids such as 4,4′-diphenylsulfone dicarboxylic acid and 2,6-naphthalenedicarboxylic acid are listed. From the viewpoints of mechanical properties, wide range of uses, availability of raw materials, etc., terephthalic acid, isophthalic acid Acid is preferred.

  These dicarboxylic acid components can be subjected to the reaction as a dicarboxylic acid, as a dicarboxylic acid anhydride, or as an alkyl ester of a dicarboxylic acid, preferably as a dialkyl ester, and may be a mixture of a dicarboxylic acid and a dicarboxylic acid alkyl ester. There are no particular restrictions on the alkyl group of the dicarboxylic acid alkyl ester, but if the alkyl group is long, the boiling point of the alkyl alcohol produced during the transesterification reaction is high and it is difficult to volatilize from the reaction liquid phase, resulting in polymerization as a terminal stopper. In order to inhibit, an alkyl group having 4 or less carbon atoms is preferable, and a methyl group is particularly preferable.

  The dicarboxylic acid component of the present invention has an aliphatic dicarboxylic acid and / or an aliphatic dicarboxylic acid alkyl ester as a main component, but "the main component is an aliphatic dicarboxylic acid and / or an aliphatic dicarboxylic acid alkyl ester" It means “the sum of the aliphatic dicarboxylic acid and the aliphatic dicarboxylic acid alkyl ester is the largest among the raw material dicarboxylic acids”. Among these, from the viewpoint of physical properties and biodegradability of the polyester, the total of the aliphatic dicarboxylic acid and the aliphatic dicarboxylic acid alkyl ester is preferably 50 mol% or more based on the total of the raw material dicarboxylic acids, and more preferably 60 mol% or more, more preferably 70%, particularly preferably 90% or more.

<Diol component>
Aliphatic diols include ethylene glycol, diethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, polypropylene glycol, polytetramethylene glycol, dibutylene glycol, 1,5 -Chain aliphatic diols such as pentanediol, neopentyl glycol, 1,6-hexanediol, 1,8-octanediol; 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol And alicyclic diols such as 1,4-cyclohexanedimethylol. In addition, ethylene glycol, 1,3-propanediol, 1,4-butanediol and the like can be derived from plant raw materials. Of these, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like are preferable from the viewpoint of the physical properties of the polyester obtained. Two or more of these may be used in combination.

Other diols include aromatic diols such as xylylene glycol, 4,4′-dihydroxybiphenyl, 2,2-bis (4-hydroxyphenyl) propane and bis (4-hydroxyphenyl) sulfone; isosorbide, isomannide, isoide And diols derived from plant materials such as erythritan.
The diol component of the present invention contains an aliphatic diol as a main component, and “having an aliphatic diol as a main component” means “the total of the aliphatic diols is the largest among the raw material diols”. From the viewpoint of physical properties and biodegradability of the polyester, the total of aliphatic diols is preferably 50 mol% or more, more preferably 60 mol% or more, still more preferably 70%, based on the total of raw material diols. %, Particularly preferably 90% or more.

  Of the above, 1,4-butanediol is preferable from the viewpoint of the melting point (heat resistance), biodegradability, and mechanical properties of the resulting polyester. In this case, 1,4-butanediol is based on the total aliphatic diol. Is preferably 50 mol% or more, more preferably 70 mol% or more, and particularly preferably 90 mol% or more.

<Other raw material compounds>
Examples of other constituents (copolymerization components) of the polyester of the present invention include lactic acid, glycolic acid, hydroxybutyric acid, hydroxycaproic acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxyisocaproic acid, malic acid, maleic acid, citric acid, fumaric acid and other oxycarboxylic acids, and esters, lactones, oxycarboxylic acid polymers of these oxycarboxylic acids, glycerin, trimethylolpropane, pentaerythritol Trifunctional or higher polyhydric alcohols such as propanetricarboxylic acid, pyromellitic acid, trimellitic acid benzophenone tetracarboxylic acid and anhydrides thereof, and the like. . A trifunctional or higher polyfunctional compound such as a trifunctional or higher functional oxycarboxylic acid, a trifunctional or higher alcohol, or a trifunctional or higher functional carboxylic acid can be easily added to obtain a highly viscous polyester. Of these, oxycarboxylic acids such as malic acid, citric acid, and fumaric acid are preferable, and malic acid is particularly preferably used.
Other raw material compounds are usually used in a proportion of 0.001 mol% or more, preferably 0.05 mol% or more, and usually 5 mol% or less, preferably 0.5 mol% or less, based on the total dicarboxylic acid component. Is done. If the amount is too large, a gel (unmelted product) is likely to be formed.

<Polyester>
The melting point of the polyester of the present invention cannot be generally specified depending on the type of raw material, the ratio of the raw material used, and the reaction conditions, but the melting point is usually 200 ° C. or lower, preferably 190 ° C. or lower, more preferably 160 ° C. or lower. It is. Moreover, from the relationship with the addition temperature of the catalyst solution mentioned later, it is 200 degrees C or less normally, Preferably it is 180 degrees C or less, More preferably, it is 160 degrees C or less. Examples of the polyester having a melting point of 200 ° C. or lower include aliphatic dicarboxylic acid components such as succinic acid, adipic acid, and sebacic acid, ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,4-cyclohexane. Polyesters containing diol components such as dimethylol as the main component; The dicarboxylic acids containing aliphatic dicarboxylic acid components such as succinic acid, adipic acid and sebacic acid as the main component, and further containing aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid Examples thereof include an acid component and a polyester copolymerized with the diol component. Of these, polyester (polybutylene succinate) of succinic acid and 1,4-butanediol is preferable from the viewpoint of the properties of the resulting polyester.
Moreover, the intrinsic viscosity (IV) of the polyester of the present invention is usually 1.0 to 2.5. In addition, intrinsic viscosity (IV) is measured by the method as described in the below-mentioned Example.

<Manufacture of polyester>
Hereinafter, the polyester production method of the present invention is an example of producing polybutylene succinate using succinic acid as an aliphatic dicarboxylic acid, 1,4-butanediol as an aliphatic diol, and malic acid as another component. Although shown, 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 as a main raw material and a transesterification method using succinic acid dialkyl ester, preferably dimethyl succinate as a main raw material. In the former, water is mainly generated in the initial esterification reaction, and in the latter, alcohol is mainly generated in the initial transesterification reaction. However, the reaction distillate is easily processed and the raw material intensity is high. From this viewpoint, a direct polymerization method is preferable.

(Esterification or transesterification)
The esterification reaction and / or transesterification reaction between the dicarboxylic acid component and the diol component can be carried out in a plurality of continuous reaction tanks, but can also be carried out 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 and polybutylene succinate is continuously obtained is preferable. In the present invention, a continuous method is adopted.

  The lower limit of the charged molar ratio of 1,4-butanediol to succinic acid is usually 0.95, preferably 1.00, more preferably 1.05, and the upper limit is usually 2.00, preferably 1.80. Preferably it is 1.60. If the charged molar ratio is too small, the reaction rate tends to decrease, and if it is too large, the color tone of the resulting polyester tends to deteriorate. Moreover, when it is desired to increase the melt viscosity such as film use, it is preferable to add a polyfunctional compound, and examples of the polyfunctional compound include malic acid. The charged mol% of malic acid with respect to succinic acid is preferably 0.05 to 0.50 mol%. If the ratio is too small, there is no effect of increasing the viscosity, and if the ratio is too large, if it exceeds 0.50 mol%, foreign matter due to gelation is generated, which is not preferable. The esterification reaction can be performed in one esterification reaction tank or a plurality of continuous reaction tanks.

  The lower limit of the esterification reaction temperature is usually 150 ° C., preferably 180 ° C., more preferably 200 ° C., and the upper limit is 260 ° C., preferably 250 ° C., more preferably 240 ° C. If the temperature is too low, the esterification reaction rate is slow, requiring a long reaction time, and undesirable reactions such as dehydration decomposition of aliphatic diols increase. If the temperature is too high, the aliphatic diol and the aliphatic dicarboxylic acid are decomposed more, and the amount of scattered matter increases in the reaction tank, and foreign matter is likely to be generated, 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, more preferably 70 kPa, and the upper limit is preferably 130 kPa, more preferably 110 kPa. If the pressure is too low, the amount of scattered matter increases in the reaction tank, causing haze of the reaction product to increase, resulting in an increase in foreign matter, and distilling out of the aliphatic diol to the outside of the reaction system increases. Easy to invite. If the pressure is too large, 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.

  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, a temperature of usually 110 ° C. to 260 ° C., preferably 140 to 245 ° C., particularly preferably 180 to 220 ° C., and usually 10 to 133 kPa, preferably 13 It is carried out under a pressure of ˜120 kPa, particularly preferably 60 to 101 kPa, for 0.5 to 5 hours, preferably 1 to 3 hours.

(Polycondensation reaction)
Next, the obtained esterification reaction product (polyester low polymer) or transesterification reaction product (polyester low polymer) is withdrawn from the final-stage esterification reaction tank and passed through the first-stage polycondensation. Transferred to reaction vessel. The polycondensation reaction is usually performed under reduced pressure, and is performed using a plurality of continuous reaction vessels. The reaction pressure of the polycondensation reaction tank has a lower limit of usually 0.01 kPa or more, preferably 0.03 kPa or more, and an upper limit of usually 3.5 kPa or less, preferably 3.0 kPa or less. The pressure is reduced as the time goes. From this point, the upper limit of the final stage is 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, preferably 220 ° C, and the upper limit is usually 270 ° C, preferably 260 ° C. If the 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 also a high power stirrer is required, which is economically disadvantageous. On the other hand, if the temperature is too high, thermal decomposition of the polyester during production tends to be caused, which tends to make it 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 the thermal decomposition of the polyester becomes remarkable, the mechanical properties of the molded product tend to be inferior, and the terminal amount of the carboxyl group that adversely affects the durability of the polyester is thermally decomposed. May increase due to

<Polycondensation catalyst and catalyst addition>
The esterification reaction and polycondensation reaction are promoted by using a reaction catalyst. In the esterification reaction, a sufficient reaction rate can be obtained without an esterification reaction catalyst. However, in the polycondensation reaction in the present invention, a catalyst is used for promoting the reaction.
As the polycondensation reaction catalyst, a compound containing at least one of the metal elements of Groups 1 to 14 of the periodic table is generally used. Specific examples of metal elements include scandium, yttrium, samarium, titanium, zirconium, vanadium, chromium, molybdenum, tungsten, tin, antimony, cerium, germanium, zinc, cobalt, manganese, iron, aluminum, magnesium, calcium, Examples include strontium, sodium and potassium. Among them, scandium, yttrium, titanium, zirconium, vanadium, molybdenum, tungsten, zinc, iron, and germanium are preferable, and titanium, zirconium, tungsten, iron, and germanium are particularly preferable. Furthermore, in order to reduce the polyester terminal density | concentration which affects the thermal stability of polyester, among the said metals, the periodic table 3-6 metal element which shows Lewis acidity is preferable. Specifically, scandium, titanium, zirconium, vanadium, molybdenum, and tungsten are preferable, and titanium and zirconium are particularly preferable from the viewpoint of availability, and titanium is more preferable from the viewpoint of reaction activity.

  The titanium compound used as the catalyst is preferably a tetraalkyl titanate or a hydrolyzate thereof. Specifically, tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetra-t-butyl titanate, tetra Examples include phenyl titanate, tetracyclohexyl titanate, tetrabenzyl titanate and mixed titanates thereof, and hydrolysates thereof. In addition, titanium (oxy) acetylacetonate, titanium tetraacetylacetonate, titanium (diisoproxide) acetylacetonate, titanium bis (ammonium lactate) dihydroxide, titanium bis (ethylacetoacetate) diisopropoxide, titanium (triethanolaminate) ) Isopropoxide, polyhydroxytitanium stearate, titanium lactate, titanium triethanolamate, butyl titanate dimer and the like are also preferably used.

  In particular, when a titanium compound is used, it is preferable to use an alkaline earth metal compound in combination as a polycondensation catalyst. Alkaline earth metal compounds include magnesium acetate, magnesium oxide, magnesium hydroxide, magnesium alkoxide, magnesium carbonate, calcium oxide, calcium hydroxide, calcium acetate, calcium carbonate and other alkali metal acetates, oxides, hydroxides , Alkoxides, carbonates, etc., among which magnesium compounds are preferred, and magnesium acetate is particularly preferred. The ratio of the alkaline earth metal compound to the titanium compound is usually 0.1 / 1 to 10/1, preferably 0.5 / 1 to 2/1, as alkaline earth metal / Ti (molar ratio). .

  A catalyst obtained by previously mixing a titanium compound, an alkaline earth metal compound, and a phosphorus compound is also effective. Examples of phosphorus compounds include orthophosphoric acid, polyphosphoric acid, trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris (triethylene glycol) phosphate, ethyl diethyl phospho Pentavalent phosphorus compounds such as phosphoric acid esters such as nonacetate, methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, monobutyl phosphate, dibutyl phosphate, triethylene glycol acid phosphate, and Phosphoric acid, hypophosphorous acid, diethyl phosphite, trisdodecyl phosphite, trisnonyl decyl phosphite, tri Trivalent phosphorus compound such as E alkenyl phosphite, and the like. The ratio of the phosphorus compound to the titanium compound is usually 0.1 / 1 to 10/1, preferably 0.5 / 1 to 2/1 as P / Ti (molar ratio).

  Among catalysts obtained by premixing titanium compounds and alkaline earth metal compounds, and phosphorus compounds, catalysts obtained by using acidic phosphate esters (partial esters of phosphoric acid) as phosphorus compounds are polymerized. The activity is high, the productivity is good, and the physical properties of the resulting polyester are preferred. In this case, the ratio of the alkaline earth metal compound to the titanium compound and the ratio of the acidic phosphate ester to the titanium compound are the same as the above alkaline earth metal / Ti (molar ratio) and P / Ti (molar ratio). is there.

  When mixing the catalyst components, a solvent is usually used. The solvent is not particularly limited as long as the titanium compound, alkaline earth metal compound, and acidic phosphate ester compound can be made into a homogeneous solution, but alcohol is preferably used. Specific examples include monohydric alcohols such as methanol, ethanol, butanol, propanol, and 2-ethylhexanol, and dihydric alcohols such as glycol. Of these, monovalent alcohols are preferably used because of the solubility of the compounds and ease of handling. These alcohols may be used alone or in combination of two or more. Among the above alcohols, titanium compounds, alkaline earth metal compounds, acidic phosphoric acid ester compounds are particularly highly soluble, and as described later, the catalyst solution obtained by mixing these is used in a concentrated manner. Since ethanol has a low boiling point and is easy to remove, ethanol is preferable.

It is also possible to use a liquid material obtained by mixing a titanium compound, an alkaline earth metal compound, and a phosphate ester compound with an alcohol as it is as a catalyst, but this is concentrated to distill off the alcohol. What is obtained is preferable.
The production method includes (i) a step of mixing, dissolving, and reacting an alcohol, a titanium compound, an alkali metal compound and an acidic phosphate ester compound, and (ii) removing alcohol from the reaction solution obtained in step (i). The method of manufacturing by the process of advancing reaction further while performing concentration by distilling, and obtaining a viscous liquid catalyst, a solid catalyst, or these mixtures is mentioned. The reaction (i) is usually carried out by mixing for a period of time during which each component dissolves at about room temperature. At this time, the alcohol used does not participate in the reaction and is considered to function only as a solvent.

  In addition, it is based on the degree of concentration that the form of the catalyst obtained differs from a viscous liquid catalyst, a solid catalyst, or these mixtures in the form of the obtained catalyst. The catalyst obtained in step (ii) can be easily recovered after it is dissolved or dissolved in glycol such as 1,4-butanediol or ethylene glycol. In addition, what is distilled off at the time of concentration is an alcohol, an organic acid, or the like by-produced by a reaction between an alcohol used as a solvent, a titanium compound, an alkaline earth metal compound, and an acidic phosphate compound.

The weight of the catalyst thus obtained is always less than the total weight of the raw materials excluding the alcohol used as the solvent. The ratio W1 between the weight W1 of the catalyst obtained and the sum W0 of the weight of the titanium compound, alkaline earth metal compound, and acidic phosphate compound used for mixing, that is, mixed with alcohol in the step (i) / W0 is usually 0.45 or more and 0.85 or less. This ratio varies depending on the type of raw material compound used and the composition ratio.
In addition, the amount of alcohol used as a preparation solvent remaining in the liquid catalyst obtained by distilling off alcohol etc. in the above step (ii) or concentrating, or a solid catalyst, or a mixture thereof is 5 wt% or less. Yes, preferably 1 wt% or less, most preferably 0.2 wt% or less. When the amount of residual alcohol is more than 5 wt%, the load on the polymerization distillation system tends to increase.

  Among the polycondensation catalysts, tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, titanium (oxy) acetylacetonate, titanium tetraacetylacetonate, titanium bis (ammonium lactate) dihydroxide, polyhydroxy Preferred are titanium compounds such as titanium stearate, titanium lactate and butyl titanate dimer, and liquids obtained by mixing titanium compounds, alkaline earth metal compounds, acidic phosphate compounds and alcohols, or concentrates thereof. , Tetra-n-butyl titanate, polyhydroxytitanium stearate, titanium (oxy) acetylacetonate and titanium tetraacetylacetonate, and titanium compounds, alkaline earth metallization Things, the liquid product obtained by mixing the acidic phosphate ester compound and an alcohol or its concentrate are preferred.

  The amount of these polycondensation catalysts added is usually 0.1 ppm by weight or more, preferably 0.5 ppm by weight or more, more preferably 1 ppm by weight or more, usually 3000 wt. ppm or less, preferably 1000 ppm by weight or less, more preferably 250 ppm by weight or less, and particularly preferably 130 ppm by weight or less. If too much catalyst is used, it is not only economically disadvantageous, but the reason is not yet clear, but the carboxyl group terminal concentration in the polyester may increase, so the carboxyl group terminal amount and residual catalyst concentration. The increase in the temperature may reduce the thermal stability and hydrolysis resistance of the polyester. 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.

In the present invention, in particular, the polycondensation catalyst as a catalyst solution dissolved in a solvent is used in the reaction solution from the final stage esterification reaction tank to the first stage polycondensation reaction tank, at a temperature not lower than the melting point of the polyester and not higher than 200 ° C. Must be added continuously.
By adding the polycondensation catalyst to the reaction solution as a catalyst solution dissolved in a solvent, the polymerization rate can be increased. The catalyst solution need not be a complete solution in which a part of the catalyst component is dispersed as long as it is liquid, but is preferably a uniform solution for the stable supply of the catalyst.

  Solvents for dissolving the polycondensation catalyst include monohydric alcohols such as methanol, ethanol, isopropanol and butanol, aliphatic diols such as ethylene glycol, butanediol and pentanediol, and ethers such as diethyl ether and tetrahydrofuran. , Nitriles such as acetonitrile, hydrocarbon compounds such as heptane and toluene, water and mixtures thereof. Of these, the use of the same diol as the diol component of the polyester as the solvent is preferable in that the distillation impurities can be reduced.

  The upper limit value of the polycondensation catalyst concentration in the catalyst solution is usually 10% by weight, preferably 3% by weight, more preferably 1.5% by weight, particularly preferably 0.5% by weight, as the catalyst metal concentration. The lower limit is usually 0.01% by weight, preferably 0.05% by weight, and more preferably 0.1% by weight as the catalyst metal concentration. If the catalyst metal concentration is too high, the catalyst is likely to precipitate in the solution, making it difficult to stably supply the catalyst.If the catalyst metal concentration is too low, a large amount of diluting solvent will be sent to the reactor. Or the load on the polycondensation equipment such as a reactor, a decompression device, or a heating device tends to increase.

  As long as the catalyst solution is added to the reaction solution from the final stage esterification reaction tank to the first stage polycondensation reaction tank, the reaction liquid in the first stage polycondensation reaction tank is the reaction liquid in the esterification reaction tank. It may be added to any of the reaction solution between the final stage esterification reaction tank and the first stage polycondensation reaction tank, and in particular, the final stage esterification reaction tank and the first stage weight It is preferable to add continuously in the reaction liquid between condensation reaction tanks. Therefore, by supplying the pipe for transferring the esterification reaction product from the final stage esterification reaction tank to the first stage polycondensation reaction tank, between the final stage esterification reaction tank and the first stage polycondensation reaction tank. It is preferably added to the reaction solution.

  If a polycondensation catalyst is present during the esterification reaction, the polycondensation catalyst generates insoluble precipitates in the reaction product due to water generated by the esterification reaction, and transparency is impaired when the resulting polyester is formed into a molded article such as a film ( That is, the haze is increased), and foreign matters are formed in the polyester. In addition, when a polycondensation catalyst is added to the gas phase part of the polymerization reaction tank, the haze of the resulting polyester becomes high or the polycondensation catalyst becomes foreign, so it is added in the reaction liquid (in the liquid phase). Preferably, from this point of view, it is added as a catalyst solution to the reaction solution at the stage preceding the first stage polycondensation reaction tank.

  The esterification rate of the reaction solution at the time of adding the catalyst is preferably 80% or more, more preferably 85% or more, and still more preferably 88% or more. In the present invention, the esterification rate indicates the ratio of the esterified acid component to the total acid component in the esterification reaction product sample, and is represented by the following formula.

  Esterification rate (%) = (saponification value−oxidation) / saponification value) × 100

If the esterification rate of the reaction solution at the time of catalyst addition is low, the residual dicarboxylic acid and the catalyst may react to form foreign matter.
In the present invention, the temperature of the catalyst solution added to the reaction solution is not lower than the melting point of the finally obtained polyester and not higher than 200 ° C. The lower limit of the temperature of the catalyst solution is preferably (polyester melting point + 5) ° C., more preferably (polyester melting point + 10) ° C., and the upper limit is preferably 180 ° C., more preferably 160 ° C. When the temperature of the catalyst solution is too low, the reaction solution is solidified around the addition port, and it becomes difficult to stably add the catalyst solution. If the temperature of the catalyst solution is too high, the catalyst component is altered in the catalyst solution and precipitates, causing piping clogging, making it difficult to add the catalyst. Moreover, the performance of polyester will be inferior, for example, the fish eye will increase when the resulting polyester is used as a film.

The temperature of the catalyst solution can be adjusted by controlling the temperature of the catalyst solution storage tank, controlling the temperature of the catalyst solution addition pipe, or the like. Specifically, the storage tank or the piping can be provided with a jacket, and the temperature-controlled heating medium can be circulated in the jacket.
When the catalyst solution is added to the reaction solution through a pipe, the linear velocity in the pipe of the catalyst solution when adding to the reaction solution is usually 0.01 m / s or more, preferably 0 from the viewpoint of preventing the addition pipe from being blocked. 0.03 m / s or more, more preferably 0.05 m / s or more, and particularly preferably 0.1 m / s or more.

<Example of production line>
Hereinafter, preferred embodiments of a method for producing a polyester using succinic acid as an aliphatic dicarboxylic acid, 1,4-butanediol as an aliphatic diol, and malic acid as a polyfunctional compound will be described, but the present invention is not limited thereto. Is not to be done.
Hereinafter, preferred embodiments of the method for producing a polyester of the present invention 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, FIG. 2 is an explanatory diagram of an example of a polycondensation step employed in the present invention, and FIG. 3 is an example of a Y-type valve for adding a catalyst solution. FIG. 4 is a view of an example of an injection valve for adding a catalyst.
In FIG. 1, succinic acid and malic acid as raw materials are usually mixed with 1,4-butanediol (may be referred to as BG) in a raw material mixing tank (not shown), and slurry is supplied from the raw material supply line (1). Or it is supplied to the esterification reaction tank (A) in a liquid 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), passed through the pump (D), and partly from the BG recirculation line (2) to the esterification reaction tank (A). And a 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 light 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). Can be stored. A part of the light boiling components collected in the tank (F) is returned to the rectification column (C) through 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) via the extraction pump (B) and the extraction line (4) of the esterification reaction product. .

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 this embodiment, the catalyst solution is added to the reaction solution between the esterification reaction vessel and the first stage polycondensation reaction vessel. In the illustrated example, the catalyst solution is added to the reactant extraction line (4) of FIG. 2 through the catalyst supply line (L7). Various known valves can be used for the catalyst solution addition section, but a globe valve, a Y-type valve and an injection valve capable of adjusting the addition flow rate of the catalyst solution are preferable, and a Y-type valve and an injection valve are more preferable. Most preferred is an injection valve with less stagnation and backflow of catalyst solution around it. A type as shown in FIG. 3 is exemplified as the Y-type valve, and a type as shown in FIG. 4 is exemplified as the injection valve.

  3 and 4, the esterified product extracted from the esterification reaction tank is supplied in the direction of 31 through the pipe, while the catalyst solution is supplied in the direction of 32 from the Y-type valve or the injection valve connected to the pipe. Supplied. At this time, the supply amount of the catalyst solution can be adjusted by moving the stem 35 with the handle 36 to change the opening of the flow path. The piping in FIG. 3 and the Y-type valve and the piping and injection valve in FIG. 4 are kept warm by the reaction medium transfer piping heat medium jacket 33 and the catalyst solution addition section heat medium jacket 34, and the catalyst addition temperature is reduced. The adjustment is made by adjusting the jacket temperature of the pipe of the catalyst addition unit, and specifically by adjusting the temperature of the heat medium flowing through the jacket laid on the pipe and the valve. For example, in FIGS. 3 and 4, the temperature of the catalyst solution refers to the temperature of the heat medium flowing through the heat medium jacket 34.

  In the above piping, the esterification reaction product (polyester low polymer) to which the catalyst solution has been added is polycondensed under reduced pressure and polycondensation proceeds. Then, it is supplied to the second polycondensation reaction tank (d) through the extraction gear pump (c) and the extraction line (L1). 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) through the extraction gear pump (e) and the extraction line (L3). 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 extracted after the polycondensation reaction is further advanced here. After being extracted from the die (r) in the form of a melted strand through the gear pump (n) and the extraction line (L5), cooled with water, etc., and then cut with a rotary cutter (u) Become. Reference numerals (L2), (L4), and (L6) denote vent lines of the first polycondensation reaction tank (a), the second polycondensation reaction tank (d), and the third polycondensation reaction tank (k), respectively. . In line (4), L1, L3, and L5, a filter can be appropriately installed in the middle of each line in consideration of the foreign matter removing effect and the operation stability as necessary.

<Reaction tank>
As the esterification reaction tank used in the present invention, a known one can be used, and any of a vertical stirring complete mixing tank, a vertical heat convection mixing tank, a tower type continuous reaction tank, etc. may be used. A single tank or a plurality of tanks in which similar or different tanks are connected in series may be used. Among them, a reaction tank having a stirrer is preferable. As a stirrer, in addition to a normal type including a power unit, a bearing, a shaft, and a stirring blade, a turbine stator type high-speed rotating stirrer, a disk mill type stirrer, a rotor mill type stirrer, and the like The type that rotates at a high speed can also be used.

There is no limitation on the form of stirring, and in addition to the normal stirring method in which the reaction liquid in the reaction tank is directly stirred from the top, bottom, side, etc. of the reaction tank, a part of the reaction liquid is piped outside the reaction tank, etc. It is possible to take a method of circulating the reaction liquid by taking it out with a line mixer and the like.
Known types of stirring blades can be selected, and specific examples include propeller blades, screw blades, turbine blades, fan turbine blades, disk turbine blades, fouller blades, full zone blades, Max blend blades, and the like.

  There is no restriction | limiting in particular in the type of the polycondensation reaction tank used for this invention, For example, a vertical stirring polymerization tank, a horizontal stirring polymerization tank, a thin film evaporation type polymerization tank etc. can be mentioned. The polycondensation reaction tank can be a plurality of tanks in which a plurality of tanks of the same type or different types are connected in series, but in the latter stage of the polycondensation in which the viscosity of the reaction solution increases, the interface renewability, plug flow property, and self-cleaning property It is preferable to select a horizontal stirring polymerization machine having an excellent thin film evaporation function.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited at all by the following examples. In addition, the physical property and the measuring method of an evaluation item performed below are as follows.
<Analysis of metal elements in catalyst>
A sample of 0.1 g of a sample obtained by wet decomposition with hydrogen peroxide in the presence of sulfuric acid in a Kjeldahl flask and then with a constant volume of distilled water was used. Plasma emission spectroscopic analyzer (ICP-AES ULTRACE JY-138U type manufactured by JOBIN YVON) ) And converted to the metal content (mass%) in the catalyst.

<PH analysis of catalyst solution>
Using an automatic titrator (AUT-301 type) manufactured by Toa DKK, the pH electrode was immersed in the catalyst solution and measured in the atmosphere.

<Esterification rate>
It calculated from the acid value and the saponification value by the following calculation formula (1). The acid value was determined by titration using a 0.1N KOH / methanol solution after dissolving the sample in benzyl alcohol. The saponification value was determined by hydrolyzing the sample with a 0.5N KOH / ethanol solution and titrating with 0.5N hydrochloric acid.

    Esterification rate = ((saponification value−acid value) / saponification value) × 100 (1)

<Melting point>
Using a differential scanning calorimeter [Metler Toledo Co., Ltd., model DSC822e], a polymer amount of about 5 mg was heated from room temperature to 200 ° C. at a heating rate of 10 ° C./min under a nitrogen atmosphere. The temperature was lowered from 200 ° C. to 40 ° C. at a rate of 10 ° C. per minute, held at 40 ° C. for 3 minutes, and finally heated again from 40 ° C. to 200 ° C. at a rate of 10 ° C. per minute. . The endothermic peak temperature at the time of the final temperature rise was taken as the melting point.

<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 polymer solution having a concentration of 0.5 g / dL and the solvent at 30 ° C., the following formula (2) I asked more.
IV = ((1 + 4K _H η _SP ) ^0.5 −1) / (2K _H C) (2)
(Where η _SP = η / η ₀ −1, η is the polymer solution falling seconds, η ₀ is the solvent dropping seconds, C is the polymer solution concentration (g / dL), and K _H is the Huggins constant. Yes, K _H is 0.33.)

<Film Fish Eye>
After drying the polyester pellets in an inert oven at 80 ° C. for 10 hours in a nitrogen atmosphere, a film quality testing system (Optical Control Systems type FS-5) was used to form a film having a thickness of 30 μm and a width of 110 mm at a molding temperature of 190 ° C. T-die molding was performed at a cooling roll temperature of 30 ° C., and the number of fish eyes was measured in-line after molding was stabilized, and the number of fish eyes having a size of 200 μm or more per 1 m 2 of film area was determined.

[Reference Example 1]
[Preparation of catalyst solution]
Into 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, 122.0 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 a reduced pressure of 5 Torr to obtain a viscous liquid catalyst. The metal elemental analysis value of the obtained catalyst was as follows: titanium atom content was 10.3 mass%, magnesium atom content was 6.8 mass%, phosphorus atom content was 7.8 mass%, The ratios were titanium / phosphorous = 0.78 and magnesium / phosphorous = 1.0. This liquid catalyst was dissolved in 1,4-butanediol to prepare a titanium atom content of 3.36% by mass. The storage stability of this catalyst solution in 1,4-butanediol was good, and no precipitate was observed in the catalyst solution stored at 40 ° C. in a nitrogen atmosphere for at least 40 days. The catalyst solution had a pH of 6.3.

[Example 1]
Through the esterification reaction step shown in FIG. 1 and the polycondensation reaction step shown in FIG. 2, polyester was produced in the following manner.
First, a slurry of 60 ° C. mixed at a ratio of 1.30 mol of 1,4-butanediol and 0.0033 mol of malic acid with respect to 1.00 mol of succinic acid is passed through the raw material supply line (1). The mixture was continuously supplied to an esterification reaction tank (A) having a screw type stirrer in which a polyester low polymer having an esterification rate of 99% was melt-filled in advance so as to be 42 kg / h. At the same time, the bottom component of the rectifying column (C) at 100 ° C. (98% by mass or more was 1,4-butanediol) was supplied at 3.0 kg / h from the recirculation line (2).

  The internal temperature of the reaction vessel (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 the rectification column (C) It separated into a high boiling component and a low boiling component. The high-boiling component at the bottom of the column after the system is stabilized is 98% by mass or more of 1,4-butanediol, and the extraction line (8) so that the liquid level of the rectifying column (C) is constant. A part of it was extracted outside. On the other hand, a low boiling component mainly composed of water and tetrahydrofuran is withdrawn in the form of gas from the top of the column, condensed with a condenser (G), and an extraction line (13) so that the liquid level in the tank (F) becomes constant. More extracted outside.

  The esterification reaction product produced in the reaction vessel (A) is continuously extracted from the esterification reaction product extraction line (4) using the pump (B), and the reaction product in the reaction vessel (A) is agglutinated. The liquid level was controlled so that the average residence time in terms of acid unit was 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 reaction vessel (A) was 90.6%.

The catalyst solution prepared in Reference Example 1 was further diluted with 1,4-butanediol to supply a solution in which the total concentration of titanium atoms, magnesium atoms and phosphorus atoms was 0.41% by mass. FIG. 2 (L7) Was supplied to the extraction line (4) of the esterification reaction product through 1.0 kg / h.
The injection solution of the type shown in FIG. 4 was used for the catalyst solution addition portion, and a heat medium of 150 ° C. was passed through the heat medium jacket 34 and a heat medium of 250 ° C. was passed through the heat medium jacket 33 to keep the temperature. In this experiment, the catalyst solution addition temperature was the same as the temperature of the heat medium circulated through the heat medium jacket (34).

The internal temperature of the first polycondensation reaction tank (a) was 250 ° C., the pressure was 2.7 kPa, and the liquid level was controlled so that the residence time was 120 minutes. 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 reaction tank (d).
The internal temperature of the second polycondensation reaction tank (d) is 250 ° C., the pressure is 400 Pa, the liquid level is controlled so that the residence time is 60 minutes, and a vent line (L4) connected to a decompressor (not shown). ), Polycondensation reaction was further carried out while extracting water, tetrahydrofuran and 1,4-butanediol. 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 250 ° C., the pressure was 130 Pa, the residence time was 60 minutes, and the polycondensation reaction was further advanced. The reaction product after the polycondensation reaction is extracted from the third polycondensation reaction tank (k) through the line (L5), and then the extracted strand is cooled with cooling water through the gear pump (n) and then through the die (r). Then, cutting was performed with a rotary cutter (u) to obtain a polyester chip.
Clogging of the catalyst addition part did not occur for one year, and continuous production was possible. A sample for evaluation was taken 48 hours after the start of continuous operation. The melting point of the obtained polyester chip was 120 ° C., and film fish eye evaluation was performed using this chip. The results are shown in Table-1.

[Example 2]
The same procedure as in Example 1 was performed except that the temperature of the heat medium flowing through the heat medium jacket 34 was changed to 170 ° C. Film fish eye evaluation was performed with the obtained polyester chip. The results are shown in Table-1. On the 250th day from the start of continuous operation, the catalyst addition section was clogged and production was stopped. Analysis of the obstruction revealed magnesium and phosphorus as catalyst components.

[Comparative Example 1]
The same procedure as in Example 1 was performed except that the temperature of the heat medium flowing through the heat medium jacket 34 was changed to 230 ° C. Film fish eye evaluation was performed with the obtained polyester chip. The results are shown in Table-1. On the third day from the start of continuous operation, the catalyst addition section was clogged and production was stopped. Analysis of the obstruction revealed magnesium and phosphorus as catalyst components.

[Comparative Example 2]
<Continuous production of polybutylene terephthalate>
Through the esterification step shown in FIG. 1 and the polycondensation step shown in FIG. 2, polybutylene terephthalate (PBT) was produced in the following manner. First, a 60 ° C. slurry mixed at a ratio of 1.80 moles of 1,4-butanediol with respect to 1.00 moles of terephthalic acid is passed through a raw material supply line (1) from a slurry preparation tank in advance with an esterification rate of 99. % Was continuously fed to a reactor (A) for esterification having a screw type stirrer packed with low PBT polymer at a rate of 40 kg / h. At the same time, the bottom component of the rectification tower (C) at 185 ° C. (98% by weight or more is 1,4-butanediol) is supplied at 18.4 kg / h from the recirculation line (2), and the titanium catalyst supply line From (3), a 6.0 wt% 1,4-butanediol solution of tetrabutyl titanate at 65 ° C. was fed at 127 g / h as a catalyst. The moisture in the catalyst solution was 0.2% by weight.

  The internal temperature of the reactor (A) is 230 ° C., the pressure is 78 kPa, and the produced water, tetrahydrofuran and excess 1,4-butanediol are distilled from the distillation line (5), and the rectification column (C) It separated into a high boiling component and a low boiling component. The high-boiling component at the bottom of the column after the system has been stabilized is 98% by weight or more of 1,4-butanediol, and the extraction line (8) so that the liquid level of the rectifying column (C) is constant. A part of it was extracted outside. On the other hand, a low boiling component mainly composed of water and THF is extracted in the form of gas from the top of the column, condensed by a condenser (G), and an extraction line (13) so that the liquid level of the tank (F) becomes constant. More extracted outside.

A certain amount of the esterification reaction product generated in the reactor (A) is extracted from the esterification reaction product extraction line (4) using the pump (B), and the terephthalic acid unit in the reactor (A) internal solution. The liquid level was controlled so that the average residence time in terms of conversion was 3 hours. The esterification reaction product extracted from the extraction line 4 was continuously supplied to the first polycondensation reactor (a). After the system was stabilized, the esterification rate of the esterification reaction product collected at the outlet of the reactor (A) was 97.3%.
The catalyst solution prepared in Reference Example 1 was further diluted with 1,4-butanediol to supply a solution in which the total concentration of titanium atoms, magnesium atoms and phosphorus atoms was 0.41% by mass. FIG. 2 (L7) Was supplied to the extraction line (4) of the esterification reaction product through 1.0 kg / h.

An injection valve of the type shown in FIG. 4 was used for the catalyst addition section, the temperature of the heat medium flowing through the heat medium jacket 34 was 190 ° C., and the temperature of the heat medium flowing through the heat medium jacket 33 was 250 ° C.
The internal temperature of the first polycondensation reactor (a) was 246 ° C., the pressure was 2.4 kPa, and the liquid level was controlled so that the residence time was 120 minutes. 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 reactor (d) is 239 ° C., the pressure is 150 Pa, the liquid level is controlled so that the residence time is 130 minutes, and a vent line (L4) connected to a decompressor (not shown). ), Polycondensation reaction was further carried out while extracting water, tetrahydrofuran and 1,4-butanediol. The obtained polymer was continuously supplied to the third polycondensation reactor (k) via the extraction line (L3) by the extraction gear pump (e). The internal temperature of the third polycondensation reactor (k) was 238 ° C., the pressure was 130 Pa, the residence time was 70 minutes, and the polycondensation reaction was further advanced. The reaction product after the polycondensation reaction is extracted from the third polycondensation reaction tank (k) through the line (L5), and then the extracted strand is cooled with cooling water through the gear pump (n) and then through the die (r). Then, cutting was performed with a rotary cutter (u) to obtain a polybutylene terephthalate chip. The melting point was 220 ° C.

  One day after the start of continuous operation, the catalyst addition section was clogged, and the production was stopped. When the plug was analyzed, it was a low polymer of polybutylene terephthalate.

  According to the present invention, operational stability in continuous production of a polyester mainly composed of an aliphatic dicarboxylic acid and / or an aliphatic dicarboxylic acid alkyl ester and an aliphatic diol is improved, and a polyester having good quality can be obtained.

1: Raw material supply line 2: Recirculation line 4: Extraction line for esterification reaction product 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 A: Esterification reaction tank B: Extraction pump C: Rectification tower D, E: Pump F: Tank G: Capacitors L1, L3, L5 : Reactant extraction line L2, L4, L6: Decompression line L7: Catalyst supply line a: First polycondensation reaction tank d: Second polycondensation reaction tank k: Third polycondensation reaction tank c, e, n: Extraction Output gear pump r: Die u: Rotary cutter 31: Flow of esterified product 32: Flow of catalyst solution 33: Heat medium jacket for reaction liquid transfer pipe 34: Heat medium jacket for catalyst solution addition part 35: Stem of valve 36: Valve Closed handle

Claims (8)

  Esterification and / or transesterification reaction of at least (1) a dicarboxylic acid component mainly comprising an aliphatic dicarboxylic acid and / or an aliphatic dicarboxylic acid alkyl ester and (2) a diol component mainly comprising an aliphatic diol In the method of producing a polyester by subjecting the obtained polyester low polymer to a polycondensation reaction using a polycondensation catalyst, the polyester low polymer is obtained by (a) performing esterification and / or transesterification in one step or continuously. A catalyst solution in which (b) a polycondensation reaction is continuously performed using a plurality of polycondensation reaction tanks, and (c) a polycondensation reaction catalyst is dissolved in a solvent. Is continuously added to the reaction solution from the final stage esterification reaction tank to the first stage polycondensation reaction tank at a temperature not lower than the melting point of the polyester and not higher than 200 ° C. Process for producing a polyester to be. The method for producing a polyester according to claim 1, wherein a trifunctional or higher polyfunctional compound is further used as a raw material. The method for producing a polyester according to claim 1, wherein the catalyst solution is added at a melting point of the polyester to 180 ° C. or less. The method for producing a polyester according to any one of claims 1 to 3, wherein the solvent of the catalyst solution is a main component diol. The method for producing a polyester according to any one of claims 1 to 4, wherein the polycondensation catalyst contains a titanium compound. The method for producing a polyester according to any one of claims 1 to 5, wherein a catalyst obtained by previously mixing a titanium compound, an alkaline earth metal compound and a phosphorus compound is used as the polycondensation catalyst. 7. A catalyst obtained by mixing a titanium compound, an alkaline earth metal compound, an acidic phosphate compound and an alcohol as a polycondensation catalyst, and concentrating the mixture. A process for producing the polyester according to item 1.   The catalyst solution addition temperature is adjusted by the jacket temperature of the catalyst addition pipe.
The method for producing a polyester according to any one of claims 1 to 7.

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