JP2010195989A - Manufacturing method of aliphatic polyester - Google Patents

Abstract

The present invention provides a method for producing an aliphatic polyester having high CD extraction efficiency with alcohol, little physical property deterioration during extraction, and reduced CD content.
SOLUTION: Using an aliphatic diol and an aliphatic dicarboxylic acid as main raw materials, an aliphatic polyester obtained through an esterification reaction step and a polycondensation reaction step is pelletized, and the resulting polyester pellet has a water ratio of 13 mass. % Or more and 95 mass% or less of isopropanol / water mixed solution, The manufacturing method of aliphatic polyester characterized by the above-mentioned.
[Selection figure] None

Description

  The present invention relates to a method for producing an aliphatic polyester. More specifically, the present invention relates to a method for producing an aliphatic polyester having a low oligomer content such as a cyclic dimer.

  Aliphatic polyesters typified by polybutylene succinates can be derived from plant resources, and have good physical properties and biodegradability. Agricultural materials, civil engineering materials, vegetation materials, packaging It is processed into products such as wood and is expected to be widely used.

  However, when the molded article of the above aliphatic polyester is left for a certain period after molding, there is a problem that the surface gloss is lost due to cloudiness (synonymous with bleed-out and whitening phenomenon). These problems are due to the fact that during the production of aliphatic polyester, a cyclic dimer (referred to as CD) produced simultaneously with the production of polyester precipitates as a white product on the surface of the molded product after a certain period of time has elapsed after molding. Is. For this reason, methods for removing cyclic dimers from aliphatic polyesters have been studied.

  Patent Document 1 describes a method for reducing CD by treating an aliphatic polyester with acetone. However, excessive equipment such as a separate water treatment step is required due to the problem of off-flavor caused by acetone remaining in the pellet after extraction. There is a problem that requires. Patent Document 2 describes a CD reduction treatment method using aliphatic polyester in the form of powder, pellets or molded products, with alcohol alone and a water / alcohol mixture containing alcohol as a main component. In the case of methanol and isopropanol, the effect of reducing CD is not always satisfactory. Although there is also a description of a water / alcohol mixture containing water as a main component, it is used for the purpose of inactivating a small amount of residual chain extender (HMDI) and preventing an increase in molecular weight. Are low and the processing time is long.

  In addition, there is a method of increasing the processing temperature to efficiently reduce CD, but in that case, hydrolysis during the contact processing is large, and there is a problem that physical properties such as molecular weight decrease are impaired.

JP 2004-107457 A. JP-A-7-316276.

  In view of the above problems, an object of the present invention is to provide a method for producing an aliphatic polyester, which has a high CD extraction efficiency with alcohol, a small decrease in physical properties during extraction, and a reduced CD content.

  As a result of studying the above problems, the present inventors have found that an isopropanol / water mixture is excellent as a liquid for efficiently extracting CD contained in an aliphatic polyester, and reached the present invention. . That is, the gist of the present invention is that an aliphatic polyester and aliphatic dicarboxylic acid as main raw materials are used to pelletize an aliphatic polyester obtained through an esterification reaction step and a polycondensation reaction step. Is in contact with an isopropanol / water mixture of 13% by mass to 95% by mass.

  An aliphatic polyester having a reduced CD content can be efficiently obtained by the production method of the present invention.

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 reaction process employ | adopted by this invention. It is explanatory drawing of an example of the isopropanol / water liquid mixture contact treatment process employ | adopted by this invention.

  The present invention uses an aliphatic diol and an aliphatic dicarboxylic acid as main raw materials, pelletizes an aliphatic polyester obtained through an esterification reaction step and a polycondensation reaction step, and contacts the resulting polyester pellet with an isopropanol / water mixture. It is the manufacturing method of the aliphatic polyester made to make. Each reaction can be carried out by a batch process or a continuous process, but from the viewpoints of quality stabilization and energy efficiency, a so-called continuous process in which a raw material is continuously supplied to continuously obtain a polyester is preferable.

  The aliphatic dicarboxylic acid and the aliphatic diol are the main raw materials of the aliphatic polyester of the present invention, respectively, and 50 mol% or more of all the dicarboxylic acid components constituting the polyester of the present invention are aliphatic dicarboxylic acids. It is preferable that 50 mol% or more of the total diol component constituting the polyester of the invention is an aliphatic diol.

<Dicarboxylic acid>
Specific examples of the aliphatic dicarboxylic acid component include oxalic acid, malonic acid, succinic acid, succinic anhydride, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, Decadicarboxylic acid, dodecadicarboxylic acid, dimer acid, hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, and the like. Among these, succinic acid, succinic anhydride are used from the viewpoint of physical properties of the obtained polyester. Acid, adipic acid and sebacic acid are preferred. In particular, succinic acid and succinic anhydride are preferable. Two or more of these may be used in combination. Succinic acid is preferably 50 mol% or more, more 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 resulting aliphatic polyester. Most preferably, it is 90 mol% or more.

  In addition, as the dicarboxylic acid component other than the aliphatic dicarboxylic acid, an aromatic dicarboxylic acid may be used in combination. Specific examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, and the like. These may be used alone or as a mixture of two or more thereof in addition to the aliphatic dicarboxylic acid. In addition, succinic acid, succinic anhydride, adipic acid, etc. can be derived from plant raw materials.

<Diol>
Specific examples of the aliphatic diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6- Hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, neopentyl glycol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, 1 , 2-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol and the like. From the viewpoint of the physical properties of the polyester obtained in these, ethylene glycol, 1 , 3-prop Diol, 1,4-butane diol, 1,4-cyclohexane dimethanol and the like are preferable. Two or more of these may be used in combination. 1,4-butanediol is preferably 50 mol% or more, more preferably 70 mol% or more based on the total aliphatic diol from the viewpoint of the melting point (heat resistance), biodegradability and mechanical properties of the aliphatic polyester obtained. More preferably, it is 90 mol% or more especially preferably. Further, ethylene glycol, 1,3-propanediol, 1,4-butanediol and the like can be derived from plant raw materials.

<Other copolymer components>
Examples of the copolymer component that is another constituent 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 -Oxycarboxylic acids such as hydroxyisocaproic acid, malic acid, maleic acid, citric acid, fumaric acid, and esters, lactones, oxycarboxylic acid polymers of these oxycarboxylic acids, glycerin, trimethylolpropane, pentaerythritol, etc. Or a trifunctional or higher polyhydric alcohol, or a trifunctional or higher polyhydric carboxylic acid such as propanetricarboxylic acid, pyromellitic acid, trimellitic acid, benzophenonetetracarboxylic acid, and their anhydrides, or the like. . Further, tri- or higher-functional oxycarboxylic acid, tri- or higher-functional alcohol, tri- or higher-functional carboxylic acid, and the like 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. The trifunctional or higher polyfunctional compound is preferably 0.001 to 5 mol%, more preferably 0.05 to 0.5 mol%, based on the total dicarboxylic acid component. If the upper limit of this range is exceeded, gel (unmelted product) is likely to be formed, and if it is less than the lower limit, the effect of increasing the viscosity is difficult to obtain.

<Manufacture of polyester>
The polyester production method of the present invention will be described below by taking a continuous production method as an example.
In the method for producing an aliphatic polyester of the present invention, polyester pellets are continuously obtained through an esterification reaction step and a melt polycondensation reaction step in a plurality of reaction vessels in which an aliphatic dicarboxylic acid and an aliphatic diol are continuous. Can adopt a conventionally known polyester production method. In the present invention, the resulting pellet is treated with an isopropanol / water mixture to extract CD contained in the pellet.

<Esterification reaction process>
The esterification reaction between the dicarboxylic acid component and the diol component can be performed in a plurality of continuous reaction tanks, but can also be performed in one tank. The lower limit of the reaction temperature is 215 ° C, preferably 218 ° C, and the upper limit is 240 ° C, preferably 235 ° C, more preferably 233 ° C. If it is less than the lower limit, the esterification reaction rate is slow, requiring a long reaction time, and undesirable reactions such as dehydration decomposition of aliphatic diols increase. If the upper limit is exceeded, the aliphatic diol and the aliphatic dicarboxylic acid will be decomposed more, and the amount of scattered matter will increase in the reaction tank, causing foreign matter to be easily 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 50 kPa to 200 kPa, the lower limit is preferably 60 kPa, more preferably 70 kPa, and the upper limit is preferably 130 kPa, more preferably 110 kPa. If it is less than the lower limit, the amount of scattered matter in the reaction tank increases, the haze of the reaction product increases, and it is easy to cause an increase in foreign matter, and the distillation of the aliphatic diol to the outside of the reaction system increases and the polycondensation reaction rate tends to decrease. . If the upper limit is exceeded, 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.

  The molar ratio of the aliphatic diol component to the aliphatic dicarboxylic acid component performing the esterification reaction is based on the aliphatic dicarboxylic acid and the esterified aliphatic dicarboxylic acid present in the gas phase and reaction liquid phase of the esterification reaction tank. It represents the molar ratio between the aliphatic diol and the esterified aliphatic diol, and does not include aliphatic dicarboxylic acids, aliphatic diols and their decomposition products that are decomposed in the reaction system and do not contribute to the esterification reaction. The fact that it is decomposed and does not contribute to the esterification reaction does not include, for example, those in which 1,4-butanediol, which is an aliphatic diol, is decomposed into tetrahydrofuran, in this molar ratio. In the present invention, the lower limit of the molar ratio is 1.10, preferably 1.12, more preferably 1.15, and particularly preferably 1.20. The upper limit is 2.00, preferably 1.80, more preferably 1.60, particularly preferably 1.55. If it is less than the lower limit, the esterification reaction tends to be insufficient, and the polycondensation reaction which is a reaction in the subsequent step is difficult to proceed, and it is difficult to obtain a polyester having a high degree of polymerization. Exceeding the upper limit is not preferable because the decomposition amount of the aliphatic diol and the aliphatic dicarboxylic acid increases. In order to keep this molar ratio within a preferable range, it is a preferable method to appropriately supplement the esterification reaction system with an aliphatic diol.

In the present invention, an esterification reaction product having an esterification rate of 80% or more is subjected to a polycondensation reaction. In the present invention, the polycondensation reaction means a high molecular weight reaction of polyester performed at a reaction pressure of 50 kPa or less, the esterification reaction is 50 to 200 kPa, usually performed in an esterification reaction tank, and the polycondensation reaction is 50 kPa or less, preferably It is carried out in a polycondensation reaction tank at 10 kPa or less. 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−acid value) / saponification value) × 100
The esterification rate of the esterification reaction product subjected to the polycondensation reaction is preferably 85% or more, more preferably 88% or more, and particularly preferably 90% or more. If it is less than the lower limit, the polycondensation reactivity, which is a reaction in the subsequent step, is deteriorated. Further, the amount of scattered matter during the polycondensation reaction increases, adheres to the wall surface and solidifies, and further, this scattered matter falls into the reactant and becomes a cause of haze deterioration (foreign matter generation). The upper limit is preferably 99% for the polycondensation reaction, which is a post-process reaction, but is usually 99%.

  In the present invention, the haze is reduced by conducting a continuous reaction with the molar ratio of the dicarboxylic acid and the diol in the esterification reaction, the reaction temperature, the reaction pressure, and the reaction rate within the above ranges and continuously subjecting to a polycondensation reaction. A high-quality aliphatic polyester with few foreign substances can be obtained efficiently.

<Polycondensation reaction step>
The polycondensation reaction can be carried out under reduced pressure using a plurality of continuous reaction vessels. Regarding the reaction pressure of the final polycondensation reaction tank, the lower limit 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 preferable embodiment from the viewpoint of improving the polycondensation reaction rate, but it is economically disadvantageous because it requires an extremely expensive facility 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 it is less than the lower limit, the polycondensation reaction rate is slow, and not only a long time is required for producing a polyester having a high degree of polymerization, but also a high power stirrer is required, which is economically disadvantageous. On the other hand, if the amount exceeds the upper limit, 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 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

<Reaction catalyst>
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. In addition, if an esterification reaction catalyst is present during the esterification reaction, the catalyst may cause insoluble precipitates in the reaction product due to water generated by the esterification reaction, which may impair the transparency of the resulting polyester (ie, increase haze). Moreover, since it may become a foreign material, it is preferable not to use the reaction catalyst during the esterification reaction. Further, when the catalyst is added to the gas phase part of the reaction tank, the haze may be increased, and the catalyst may be converted into a foreign substance.

  In the polycondensation reaction, it is difficult to proceed without a catalyst, and it is preferable to use a catalyst. 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.

  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 further, an oxide or halide of the above-described metal, etc. Inorganic compounds and mixtures thereof are preferably used.

  In the present invention, the catalyst is preferably a liquid at the time of polymerization or a compound that dissolves in an ester low polymer or polyester because the polymerization rate is increased when the catalyst is in a melted or dissolved state at the time of polymerization. The polycondensation is preferably carried out without a solvent. Alternatively, a small amount of solvent may be used to dissolve the catalyst. Solvents for dissolving the catalyst include alcohols such as methanol, ethanol, isopropanol and butanol, the above-mentioned 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, and the like. The amount used is usually such that the catalyst concentration is 0.0001 wt% or more and 99 wt% or less.

  As the titanium compound, tetraalkyl titanate and a hydrolyzate thereof are preferable. Specifically, tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetra-t-butyl titanate, tetraphenyl titanate, Examples include 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.

  Moreover, the liquid substance obtained by mixing alcohol, an alkaline-earth metal compound, a phosphate ester compound, and a titanium compound is also used. Among these, tetra-n-propyl titanate, tetraisopropyl titanate and tetra-n-butyl titanate, titanium (oxy) acetylacetonate, titanium tetraacetylacetonate, titanium bis (ammonium lactate) dihydroxide, polyhydroxytitanium stearate Preferred is a liquid obtained by mixing rate, titanium lactate, butyl titanate dimer, and alcohol, alkaline earth metal compound, phosphate ester compound, and titanium compound. Tetra-n-butyl titanate, titanium (oxy) Acetyl acetonate, titanium tetraacetyl acetonate, polyhydroxy titanium stearate, titanium lactate, butyl titanate dimer, alcohol, alkaline earth metal compound, phosphate ester More preferred are liquids obtained by mixing tellurium compounds and titanium compounds, especially tetra-n-butyl titanate, polyhydroxytitanium stearate, titanium (oxy) acetylacetonate, titanium tetraacetylacetonate and alcohol. A liquid material obtained by mixing an alkaline earth metal compound, a phosphate ester compound, and a titanium compound is preferred.

  Specific examples of zirconium compounds include zirconium tetraacetate, zirconium acetylate hydroxide, zirconium tris (butoxy) stearate, zirconyl diacetate, zirconium oxalate, zirconyl oxalate, potassium potassium oxalate, and polyhydroxyzirconium. Examples include stearate, zirconium ethoxide, zirconium tetra-n-propoxide, zirconium tetraisopropoxide, zirconium tetra-n-butoxide, zirconium tetra-t-butoxide, zirconium tributoxyacetylacetonate and mixtures thereof. Among these, zirconyl diacetate, zirconium tris (butoxy) stearate, zirconium tetraacetate, zirconium acetate acetate, zirconium ammonium oxalate, zirconium potassium oxalate, polyhydroxyzirconium stearate, zirconium tetra-n- Propoxide, zirconium tetraisopropoxide, zirconium tetra-n-butoxide, zirconium tetra-t-butoxide are preferred, zirconyl diacetate, zirconium tetraacetate, zirconium acetate acetate hydroxide, zirconium tris (butoxy) stearate, sulphate Zirconium ammonium acid, zirconium tetra-n-propoxide, zirconium tetra-n-butoxide are more preferred, Preferred for reasons of zirconium tris (butoxy) stearate is easily obtained polyester having a high degree of polymerization without colored.

  Specific examples of the germanium compound include inorganic germanium compounds such as germanium oxide and germanium chloride, and organic germanium compounds such as tetraalkoxygermanium. From the viewpoint of price and availability, germanium oxide, tetraethoxy gel and mu and tetrabutoxy germanium are preferable, and germanium oxide is particularly preferable.

  Other metal-containing compounds include scandium carbonate, scandium acetate, scandium chloride, scandium compounds such as scandium acetylacetonate, yttrium carbonate, yttrium chloride, yttrium acetate, yttrium acetate such as yttrium acetylacetonate, vanadium chloride, and vanadium trichloride. Oxides, vanadium acetylacetonate, vanadium compounds such as vanadium acetylacetonate oxide, molybdenum compounds such as molybdenum chloride, molybdenum acetate, tungsten compounds such as tungsten chloride, tungsten acetate, tungstic acid, cerium chloride, samarium chloride, ytterbium chloride, etc. Examples include lanthanoid compounds.

  The amount of catalyst added in the case of using a metal compound as these polycondensation catalysts, the lower limit is usually 0.1 ppm or more, preferably 0.5 ppm or more, more preferably 1 ppm or more, as the amount of metal relative to the produced polyester. The upper limit is usually 3000 ppm or less, preferably 1000 ppm or less, more preferably 250 ppm or less, and particularly preferably 130 ppm 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, if 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, making it 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.

<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 number of polycondensation reaction tanks can be one, or a plurality of tanks of the same or different types can be connected in series. It is preferable to select a horizontal stirring polymerization machine having a thin film evaporation function excellent in renewability, plug flow property, and self-cleaning property.

<Isopropanol / water mixture contact treatment process>
The aliphatic polyester obtained through the polycondensation reaction is pelletized and subjected to a contact treatment with an isopropanol / water mixture in the pellet state. The isopropanol / water mixed solution contact treatment may be performed in the pelletizing step, or may be performed after the pellet is transferred out of the step.

  A mixed liquid of isopropanol and water is useful because of ease of properties as a dangerous substance of isopropanol and expansion of possibility of selection of extraction conditions (temperature, contact time, recovery conditions, etc.). For example, when contacting only aliphatic polyester and isopropanol, it is not only economically disadvantageous because it requires handling for handling hazardous materials and facilities necessary for preventing explosions, etc. There is a need to limit extraction conditions, such as loss of quality due to viscosity reduction due to decomposition. On the other hand, when the aliphatic polyester is brought into contact with water alone, the oligomer removal is not sufficient, so that not only the polyester of the target quality can not be obtained, but also the polyester pellet having a high terminal acid value has an intrinsic viscosity due to hydrolysis ( IV) There is a need to limit the quality of pellets subjected to the contact treatment, such as a significant decrease. On the other hand, when the aliphatic polyester pellets are brought into contact with the isopropanol / water mixture, the danger during handling is alleviated, handling is improved, and oligomer removal is performed without impairing quality such as IV degradation. There is an advantage that the selection possibility of the extraction condition is expanded, such as being able to efficiently perform.

  The lower limit of the ratio of water in the treatment liquid (isopropanol / water mixture) to be brought into contact with the aliphatic polyester pellets is 13% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, and particularly preferably 50%. It is at least mass%, most preferably at least 60 mass%. The upper limit is 95% by mass or less, preferably 90% by mass or less, and particularly preferably 85% by mass or less. When the proportion of water used is small (the proportion of isopropanol is increased), the quality tends to be impaired due to a decrease in molecular weight due to alcohol decomposition. In addition, the increase in the alcohol use ratio increases the risk of explosion of the liquid composition and gas composition during use, and handling is difficult from the viewpoint of safety. Furthermore, there are cases where the amount of remaining isopropanol after drying the pellet tends to increase, and there are cases where restrictions are imposed on the application or molding process conditions. On the other hand, if the ratio of water exceeds the upper limit, oligomer removal may not be sufficient, and an aliphatic polyester having a desired quality may not be obtained.

  The lower limit of the temperature at which the aliphatic polyester pellets and the treatment liquid are brought into contact is 40 ° C. or higher, preferably 45 ° C. or higher, more preferably 50 ° C. or higher, and particularly preferably 55 ° C. or higher. The upper limit is usually not higher than the melting point of the aliphatic polyester, preferably not higher than 95 ° C, more preferably not higher than 90 ° C, particularly preferably not higher than 85 ° C. When the contact temperature is less than the lower limit, a long treatment time is required, which is not only economically disadvantageous, but a desirable aliphatic polyester may not be obtained due to a decrease in the oligomer removal effect. On the other hand, when the contact temperature exceeds the upper limit, the viscosity decreases greatly due to hydrolysis and alcohol decomposition, which not only impairs the quality, but also causes difficulty in operation, such as causing fusion between pellets and defective pellet extraction.

  The lower limit of the time for contacting the pellet and the treatment liquid is usually 0.1 hour or longer, preferably 1 hour or longer, more preferably 3 hours or longer. The upper limit is usually 24 hours or less, preferably 18 hours or less, more preferably 10 hours or less. If the contact time is less than the lower limit, oligomer removal may not be sufficient, and an aliphatic polyester having a desired quality may not be obtained. On the other hand, when the contact time exceeds the upper limit, the decrease in viscosity increases due to hydrolysis and alcohol decomposition, which may impair quality.

  The ratio between the pellets to be contacted and the treatment liquid (pellet / liquid ratio) is mass ratio, and the lower limit is usually 1.0 or more, preferably 1.5 or more, and more preferably 2.0 or more. The upper limit is usually 50 or less, preferably 30 or less, more preferably 20 or less. If the mass ratio of the pellets to be brought into contact with the liquid is less than the lower limit, the oligomer removal effect is lowered due to an increase in the concentration of oligomers in the liquid during the treatment, and an aliphatic polyester having a desired quality may not be obtained. On the other hand, if the mass ratio of the pellets to be brought into contact with the liquid exceeds the upper limit, it is disadvantageous in terms of process and cost such as an increase in size of equipment due to a large amount of processing liquid used and an increase in cost of the processing liquid.

  As an aspect which makes an aliphatic polyester pellet and a process liquid contact, there exist a batch type and a continuous type, and any aspect can be taken. As a batch-type aspect in this invention, the method of extracting after putting a pellet and a processing liquid into a processing tank and carrying out contact processing for predetermined temperature and time is mentioned. During the contact treatment between the pellet and the treatment liquid, the treatment can be performed under circulation of the treatment liquid or can be performed under non-circulation. As a continuous mode in the present invention, while a pellet is continuously supplied to a pipe or a processing tank, a processing liquid at a predetermined temperature is brought into contact with the flow of the pellet in parallel or countercurrent, and a predetermined contact time. There is a method of continuously pulling out the pellets while holding.

  In the present invention, the treatment liquid after the contact treatment can be recovered by distillation and recycled. The extracted oligomer containing cyclic dimer is separated from the treatment liquid by cooling or the like, or concentrated, and then returned to the esterification reaction step or polycondensation reaction step to obtain an aliphatic polyester raw material. Can be used as Returning to the esterification reaction tank in the esterification reaction step or the slurry tank of aliphatic dicarboxylic acid and aliphatic diol is a preferable method.

  After the contact treatment, the extracted treatment liquid can be circulated and reused as it is, or a part of the extracted treatment liquid can be discarded, and a new treatment liquid can be added in the discarded amount. Further, the extracted treatment liquid can be purified by distillation and reused, and only an amount not recovered as a concentrated liquid can be added as an isopropanol / water mixture.

  After the contact treatment, the oligomer containing CD separated from the treatment liquid by distillation concentration and / or cooling or the like is once melted or dissolved in an aliphatic diol as a raw material, and then aliphatic polyester. Can be recovered as a raw material. The recovered oligomers can be directly supplied to the esterification reaction tank, or can be supplied to the aliphatic diol recycle line (2) and the esterification reaction product extraction line (4) illustrated in FIG. it can. Moreover, it can also supply to the polycondensation tank (a) illustrated in FIG. Moreover, it can also supply to the slurry tank of aliphatic dicarboxylic acid and aliphatic diol.

  In the present invention, the lower limit of the intrinsic viscosity (IV, dL / g) of the aliphatic polyester pellet to be contact-treated with the isopropanol / water mixture is preferably 1.4 dL / g, particularly preferably 1.6 dL / g. g. The upper limit is preferably 2.8 dL / g, more preferably 2.5 dL / g, and particularly preferably 2.3 dL / g. When the intrinsic viscosity is less than the lower limit, it is 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 molding is difficult.

  In the present invention, the terminal carboxyl group concentration (equivalent / ton) of the aliphatic polyester contacted with the isopropanol / water mixture is usually 80 or less, preferably 60 or less, more preferably 40 or less, and particularly preferably 25 or less. is there. The lower the lower, the better the thermal stability and hydrolysis resistance, but it is usually 5. When the upper limit is exceeded, in the step of contact treatment with the isopropanol / water mixture, the viscosity is significantly reduced due to hydrolysis, and the quality may be significantly impaired.

<Example of production line>
Hereinafter, a preferred embodiment of a method for producing an aliphatic 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. It is not limited.

  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. 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) 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.

  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 a horizontal reaction tank composed of a plurality of stirring blade blocks and equipped with a biaxial self-cleaning type stirring blade. The polycondensation reaction product introduced from the second polycondensation reaction tank (d) to the third polycondensation reaction tank (k) through the extraction line (L3) is further pelletized after the polycondensation reaction is further advanced here. It is transferred to the process.

<Pelletization process>
In the pelletizing step, the material is extracted into the atmosphere in the form of a melted strand from the die head (g) through the extraction gear pump (m), the extraction line (L5) as the outlet channel and the filter (s), After cooling with water or the like, it is cut with a rotary cutter (h) to form polyester pellets. Alternatively, it can be extracted in the form of a strand into the water without being extracted into the atmosphere, and cut into a pellet by a rotary underwater cutter. 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. . The filters p, q, r, and s are not necessarily all installed, and can be appropriately installed in consideration of the foreign matter removing effect and the operation stability.

  The obtained aliphatic polyester pellet is subjected to a treatment of contacting with an isopropanol / water mixture. FIG. 3 is an explanatory diagram of an example of an isopropanol / water mixed solution contact treatment step employed in the present invention. The temperature of the isopropanol / water mixture as the contact liquid is controlled from the circulation tank (I) via the heat exchanger (II) by the pump (IX) and supplied to the treatment tank (III) from the supply line (a). After making counter-current contact with the pellets in the treatment tank, the pellets are extracted from the extraction line (A) and collected in the circulation tank (I) via the fine powder remover (IV). The pellets used for contact treatment are continuously supplied from the supply line (c), and after contact treatment with the isopropanol / water mixture for a predetermined time, from the extraction line (d) while adjusting the extraction amount with the rotary valve (V). Extract continuously. The contact liquid extracted along with the pellets is separated by the preliminary solid-liquid separator (VI), passes through the recovery tank (VII), and then passes through the supply line (e) by the pump (X) to the recovery line (capacity). Return to). The contact liquid is continuously extracted from the circulation tank from the extraction line (K). An isopropanol / water mixture corresponding to the amount of contact liquid extracted from the supply line (ku) is supplied. The pellets continuously extracted are separated from the contact liquid entrained by the preliminary solid-liquid separator, and then continuously supplied to the drying process via the solid-liquid separator (VIII). Drying is performed by sending atmospheric air at 70 ° C. and drying the resin for a predetermined time. After drying, the aliphatic polyester resin of the present invention is obtained.

<Polyester>
The lower limit of the intrinsic viscosity (IV, dL / g) of the aliphatic polyester after contact treatment with the isopropanol / water mixture obtained in the present invention is preferably 1.4 dL / g, particularly preferably 1.6 dL / g. g. The upper limit is preferably 2.8 dL / g, more preferably 2.5 dL / g, and particularly preferably 2.3 dL / g. When the intrinsic viscosity is less than the lower limit, it is 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 molding is difficult. The percentage of the ratio of the intrinsic viscosity (dL / g) after the contact treatment with the isopropanol / water mixture to the intrinsic viscosity (dL / g) before the contact treatment is preferably 98.0% or more, and more preferably 98 .5% or more.

  The terminal carboxyl group concentration (equivalent / ton) of the aliphatic polyester after contact treatment with the isopropanol / water mixture obtained in the present invention is usually 80 or less, preferably 60 or less, more preferably 40 or less, particularly preferably 25 or less. It is. The lower the lower, the better the thermal stability and hydrolysis resistance, but it is usually 5. If the upper limit is exceeded, the thermal stability is poor and thermal decomposition increases during molding.

  The cyclic dimer content of the aliphatic polyester after the contact treatment with the isopropanol / water mixture obtained in the present invention is usually 6,000 mass ppm or less, preferably 5,000 mass ppm or less, more preferably It is 4,000 mass ppm or less, More preferably, it is 3,500 mass ppm or less, Most preferably, it is 3,000 mass% or less. When the upper limit is exceeded, if it is left for a certain period of time after molding, the original purpose cannot be achieved such as cloudiness (synonymous with bleed-out or whitening phenomenon) on the surface and loss of surface gloss.

  The aliphatic polyester obtained after the contact treatment with the isopropanol / water mixture obtained in the present invention has an intrinsic viscosity of 1.4 dL / g or more and a cyclic dimer content of 5,000 mass ppm or less. Will not be damaged. It can be a raw material for good polyester molded products.

<Aliphatic polyester composition>
You may mix | blend aromatic-aliphatic copolyester, aliphatic oxycarboxylic acid, etc. with the aliphatic polyester of this invention. In addition to carbodiimide compounds, fillers, and plasticizers used as necessary, other biodegradable resins, such as polycaprolactone, polyamide, polyvinyl alcohol, cellulose ester, and the like, as long as the effects of the present invention are not impaired, starch Cellulose, paper, wood powder, chitin / chitosan, animal / plant substance fine powder such as coconut shell powder, walnut shell powder, or a mixture thereof can be blended. Furthermore, additives such as heat stabilizers, plasticizers, lubricants, antiblocking agents, nucleating agents, inorganic fillers, colorants, pigments, ultraviolet absorbers, light stabilizers, etc., are used for the purpose of adjusting the physical properties and processability of the molded product. Further, a modifier, a crosslinking agent, etc. may be included.

  The method for producing the aliphatic polyester composition of the present invention is not particularly limited, but is a method in which raw material chips of the blended aliphatic polyester are melt-mixed in the same extruder, and a method in which each is melted and mixed in separate extruders. , A single screw extruder, a twin screw extruder, a Banbury mixer, a roll mixer, a Brabender plastograph, a kneader blender and the like, and mixing by kneading. In addition, it is possible to obtain a molded body at the same time as preparing a composition by directly supplying each raw material chip to a molding machine.

  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 measuring method of the physical property and evaluation item which were employ | adopted in the following examples is as follows.

<Intrinsic viscosity (IV) dL / g>
It calculated | required in the following way using the Ubbelohde type viscometer. That is, a mixed solvent of phenol / tetrachloroethane (mass ratio 1/1) was used, and at 30 ° C., the polymer solution having a concentration of 0.5 g / dL and the number of falling seconds of the solvent alone were measured, and the following formula (1) I asked more.
IV = [(1 + 4KH ηSP) 0.5 −1] / (2KH C) (1)
(Where ηSP = η / η0 −1, η is the sample solution drop seconds, η0 is the solvent drop seconds, C is the sample solution concentration (g / dL), and KH is the Huggins constant. 0.33 was adopted.)

<Polyester carboxyl group concentration (AV) equivalent / ton>
After pulverizing the pelletized polyester, it was dried for 15 minutes at 140 ° C. in a hot air dryer, and 0.1 g was accurately weighed from a sample cooled to room temperature in a desiccator, and 3 mL of benzyl alcohol was added. Then, it was dissolved in 195 ° C. for 3 minutes while blowing dry nitrogen gas. Subsequently, 5 cm 3 of chloroform was gradually added and cooled to room temperature. Add 1 to 2 drops of phenol red indicator to this solution and titrate with 0.1 mol·L-1 sodium benzyl alcohol solution with stirring while blowing dry nitrogen gas. Ended. Moreover, the same operation was implemented as a blank, without adding a polyester sample, and the amount of terminal carboxyl groups (acid value) was computed by the following formula | equation (2).
Terminal carboxyl content (equivalent / ton) = (ab) × 0.1 × f / W (2)
Here, a is the amount (μL) of 0.1 mol·L-1 sodium benzyl alcohol solution required for titration, and b is 0.1 mol·L-1 water required for titration with a blank. The amount (μL) of sodium oxide in benzyl alcohol, w is the amount (g) of polyester sample, and f is the titer of 0.1 mol·L−1 sodium hydroxide in benzyl alcohol.

The titer (f) of a benzyl alcohol solution of 0.1 mol·L-1 sodium hydroxide was determined by the following method.
Collect 5 cm 3 of methanol in a test tube, add 1-2 drops as an indicator of an ethanol solution of phenol red, Titration to a discoloration point with 0.4 cm 3 of benzyl alcohol solution of 1 mol·L-1 sodium hydroxide, then 0.2 cm 3 of 0.1 mol·L-1 aqueous hydrochloric acid solution with known titer was taken as a standard solution and added, Again, the solution was titrated with a 0.1 mol·L-1 sodium benzyl alcohol solution to the discoloration point (the above operation was performed while blowing dry nitrogen gas). And titer (f) was computed by the following formula | equation (3).
Titer (f) = titer of 0.1 mol·L-1 hydrochloric acid aqueous solution x amount of 0.1N hydrochloric acid aqueous solution collected (µL) / titration of 0.1 mol·L-1 sodium hydroxide in benzyl alcohol solution Amount (μL) (3)

<Measurement of cyclic dimer content in pellet>
0.5 g of the sample was precisely weighed, 10 mL of chloroform was added, and after dissolution at room temperature, 30 mL of an ethanol / water mixture (volume ratio 4/1) was slowly added dropwise with stirring to precipitate the polymer component. After 15 minutes, the stirring was stopped and the separation was performed for 90 minutes. Next, 2 mL of the supernatant was collected and evaporated to dryness, and then 2 mL of acetonitrile was added and dissolved. After filtering with a 0.45 μm filter, Shimadzu liquid chromatography “LC-10” was used, the mobile phase was acetonitrile / water (volume ratio = 4/6), and the column was “SHISEIDOCAPELL PAK C- Quantification using “18 TYPE MG”.

<Measurement of residual amount of isopropanol in pellet>
A sample (0.1 g) was weighed and placed in a headspace vial (20-MCB manufactured by Chromacol). After adding 5 mL of 1,2,4-trichlorobenzene, the polymer was dissolved at 120 ° C. for 30 minutes. The vial was placed in a constant temperature bath at 120 ° C., and the gas in the gas phase portion after 30 minutes was collected with a gas tight syringe and introduced into the gas chromatograph inlet. The column tip was cooled to −150 ° C. for 30 seconds from the time of gas injection (CTS2 manufactured by GERSTEL) to condense the gas component, and then rapidly heated to 280 ° C. to be vaporized and introduced into the gas chromatograph. The apparatus is a gas chromatograph: HP 6890 (split ratio 50: 1) manufactured by Hewlett-Packard, and the column is DB-1 (inner diameter: 0.25 mm, length: 60 m, membrane pressure: 1.0 μm) manufactured by J & W. used. The temperature of the injection section and detector was 280 ° C., the column temperature was kept at 40 ° C. for 7 minutes, then the temperature was raised to 250 ° C. at 10 ° C./min, and kept at 250 ° C. for 5 minutes. Helium (1 mL / min) was used as the carrier gas.
The amount of residual isopropanol (mass ppm) in the pellet was calculated by the following method. Prepare gas vials containing 10 μL, 20 μL, 40 μL, 100 μL, 200 μL, and 400 μL of solutions prepared to 800 μg / mL isopropanol in vials containing 5 mL of trichlorobenzene, and perform gas chromatographic analysis in the same manner as above. A calibration curve was created. The amount of isopropanol remaining in the pellet (mass ppm) was calculated from the formula of isopropanol peak area and calibration curve at the time of sample measurement.

Example 1
[Preparation of catalyst for polycondensation]
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 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. 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.

[Production of aliphatic polyester]
By the esterification step shown in FIG. 1 and the polycondensation step shown in FIG. 2, an aliphatic polyester was produced as follows. First, with respect to 1.00 mol of succinic acid containing 0.18% by weight of malic acid, 1.30 mol of 1,4-butanediol and malic acid were mixed at a total amount of 0.0033 mol. A stirrer in which a slurry at 50 ° C. was previously filled with an aliphatic polyester low molecular weight substance (esterification reaction product) having an esterification rate of 99% under a nitrogen atmosphere through a raw material supply line (1) from a slurry preparation tank (not shown). Was continuously fed to the esterification reaction tank (A) having 45.5 kg / h. The esterification reaction tank (A) is set to an internal temperature of 230 ° C. and a pressure of 101 kPa, and water, tetrahydrofuran and excess 1,4-butanediol produced are distilled from the distillation line (5), and a rectifying column (C) It separated into a high boiling component and a low boiling component. A part of the high-boiling 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 component mainly composed of water and tetrahydrofuran is extracted from the top of the tower in the form of gas, condensed in a condenser (G), and the extraction line (13) so that the liquid level in the tank (F) becomes constant. ) Extracted outside. At the same time, the entire bottom component (98% by weight or more of 1,4-butanediol) of the rectification column (C) at 100 ° C. from the BG recirculation line (2) and the ester from the BG supply line (3) Tetrahydrofuran generated in the oxidization reaction tank and equimolar 1,4-butanediol were supplied together, and the molar ratio of 1,4-butanediol to succinic acid in the esterification reaction tank was adjusted to 1.30. . The supply amount of the recirculation line (2) and the BG supply line (3) was 3.8 kg / h. The amount of 1,4-butanediol converted to tetrahydrofuran was 0.042 mol with respect to 1.00 mol of succinic acid. (THF conversion rate: 4.2 mol% vs. succinic acid)

  The esterification reaction product produced in the esterification reaction tank (A) is continuously extracted from the esterification reaction product extraction line (4) using the pump (B), and the liquid in the esterification reaction tank (A). The liquid level was controlled so that the average residence time in terms of succinic 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) in FIG. After the system was stabilized, the esterification rate of the esterification reaction product collected at the outlet of the esterification reaction tank (A) was 92.4%, and the terminal carboxyl concentration was 884 equivalents / ton. After preparing the catalyst solution prepared in advance by the above-mentioned method in a catalyst preparation tank so that the concentration as titanium atoms is 0.12 wt%, the catalyst solution is diluted with 1,4-butanediol, Through L8), the esterification reaction product was continuously fed to the extraction line (4) at 1.4 kg / h (the catalyst was added to the liquid phase of the reaction solution). The supply was stable during the operation period.

  The internal temperature of the first polycondensation reaction tank (a) was 240 ° 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 reactor (d). The second polycondensation reactor (d) has an internal temperature of 240 ° C. and a pressure of 400 Pa. The liquid level is controlled so that the residence time is 120 minutes, and a vent line (not shown) connected to a decompressor (not shown) The polycondensation reaction was further advanced while extracting water, tetrahydrofuran and 1,4-butanediol from L4). The obtained polyester 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 240 ° C., the pressure was 130 Pa, the residence time was 60 minutes, and the polycondensation reaction was further advanced. The obtained polyester was continuously extracted in the form of a strand from the die head (g) and cut with a rotary cutter (h) to obtain pellets. The esterification reaction and polycondensation reaction were carried out for 7 consecutive days, and the physical properties of the aliphatic polyester obtained by sampling every 8 hours after the lapse of 16 hours from the start of the reaction were measured. The average value and the touch width of each sample are shown. The intrinsic viscosity is 1.85 ± 0.02 dL / g, the terminal carboxyl group concentration is 19 ± 1 equivalent / ton, the color b value is 1.9 ± 0.1, and the solution haze is 0.4 ± 0.1%. It was a highly transparent polyester with stable quality.

[Contact treatment of aliphatic polyester with isopropanol / water mixture]
By the contact treatment process shown in FIG. 3, the contact treatment of the aliphatic polyester resin was performed in the following manner. The isopropanol / water mixture (13% by mass of water) as the contact liquid is controlled from the circulation tank (I) to 40 ° C via the heat exchanger (II) by the pump (IX), and processed from the supply line (a). Feeded to tank (III). The treatment liquid was brought into countercurrent contact with the pellets in the treatment tank, extracted from the extraction line (A), and collected into the circulation tank (I) via the fine powder remover (IV). The pellets for contact treatment are continuously supplied from the supply line (c), contact-treated for 6 hours, and then continuously extracted from the extraction line (d) while adjusting the extraction amount with the rotary valve (V). . The contact liquid extracted along with the pellets is separated by the preliminary solid-liquid separator (VI), passes through the recovery tank (VII), and then passes through the supply line (e) by the pump (X) to the recovery line (capacity). ). The contact liquid was continuously extracted from the circulation tank (I) from the extraction line (ki), and the amount thereof was set to 1/20 (flow rate ratio) of the total circulation flow rate of the contact liquid. An isopropanol / water mixture equivalent to the contact liquid extracted from the supply line (ku) was supplied to the circulation tank (I). Continuously extracted pellets are separated from the contact liquid entrained in the preliminary solid-liquid separator (IV), then continuously from the dehydrator (VIII) via the extraction line (ke) to the drying process. Supplied to Drying was performed for 12 hours in a state where air heated to 70 ° C. was allowed to flow upward from below the drying tank (not shown). Table 1 shows the ratio of the intrinsic viscosity measured with respect to the sample after drying to the intrinsic viscosity before contact treatment (represented by% retention), the cyclic dimer content of the sample after drying, and the amount of residual isopropanol in the pellet. In the table, “IPA” is “isopropanol”.

(Example 2) to (Example 7)
In Example 1, the ratio of water in the isopropanol / water mixture as the contact treatment liquid is changed as shown in Table 1, and the contact treatment liquid temperature and the contact treatment time are changed as shown in Table 1, respectively. In the same manner as in Example 1, the IV retention rate, the CD content, and the amount of residual isopropanol in the pellets were measured, and the results are shown in Table 1.

(Comparative Example 1)
In Example 1, the contact treatment was performed in the same manner as in Example 1 except that the contact treatment solution was changed to isopropanol. The results are shown in Table 1.
(Comparative Example 2)
In Example 1, the contact treatment was performed in the same manner as in Example 1 except that the contact treatment liquid was changed to water. The results are shown in Table 1.

(Comparative Example 3) to (Comparative Example 6)
In Example 1, except that the isopropanol part of the isopropanol / water mixture of the contact treatment liquid was replaced with ethanol (EtOH), methanol (MeOH), acetone (AcMe), and tetrahydrofuran (THF), respectively, and the contact treatment time was changed to 5 hours. The contact treatment was performed in the same manner as in Example 3. The results are shown in Table 2.

(Example 8)
In Example 1, contact treatment was performed in the same manner as in Example 3 except that the catalyst solution prepared to 0.12% by weight was continuously supplied at 2.0 kg / h. The results are shown in Table 3.
Example 9
In Example 1, contact treatment was performed in the same manner as in Example 3 except that the catalyst solution prepared to 0.12% by weight was continuously supplied at 4.2 kg / h. The results are shown in Table 3.
(Comparative Example 7)
In Example 1, the contact treatment was performed in the same manner as in Example 3 except that the catalyst solution prepared to 0.12% by weight was continuously supplied at 4.2 kg / h and the contact treatment liquid was ethanol. . The results are shown in Table 3.

  According to the production method of the present invention, an aliphatic polyester having a reduced CD content can be efficiently obtained, and a polyester that can be used as a molding raw material for a molded product that does not cause fogging on the surface can be provided.

1: Raw material supply line 2: BG recirculation line 3: BG supply 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 15: Supply line A: Esterification reaction tank B: Extraction pump C: Rectification tower D, E: Pump F : Tank G: Capacitors L1, L3, L5: Polycondensation reaction product extraction line L2, L4, L6: Vent line L7: Catalyst supply line L8: BG supply line a: First polycondensation reaction tank d: Second polycondensation reaction Reaction tank k: Third polycondensation reaction tank c, e, m: Extraction gear pump g: Die head h: Rotary cutter p, q, r, s: Filter
I: Circulation tank
II: Heat exchanger
III: Treatment tank
IV: Fine powder remover
V: Rotary valve
VI: Preliminary solid-liquid separator
VII: Collection tank
VIII: Solid-liquid separator
IX: Pump
X: Pump A: Supply line B: Extraction line C: Supply line D: Extraction line E: Supply line C: Collection line K: Extraction line K: Supply line K: Extraction line

Claims (6)

  Using an aliphatic diol and an aliphatic dicarboxylic acid as main raw materials, an aliphatic polyester obtained through an esterification reaction step and a polycondensation reaction step is pelletized, and the resulting polyester pellet has a water ratio of 13% by mass or more and 95% by mass. A method for producing an aliphatic polyester, which comprises contacting with an isopropanol / water mixture of not more than%.   In the production method of an aliphatic polyester having an esterification reaction step, a polycondensation reaction step, and a step of pelletizing the resulting aliphatic polyester using an aliphatic diol and an aliphatic dicarboxylic acid as main raw materials, A method for producing an aliphatic polyester, comprising the step of bringing the aliphatic polyester pellets into contact with an isopropanol / water mixture having a water ratio of 13% by mass to 95% by mass.   The method for producing an aliphatic polyester according to claim 1 or 2, wherein the temperature at which the aliphatic polyester pellet is brought into contact with the isopropanol / water mixture is 40 ° C or higher and not higher than the melting point of the aliphatic polyester.   The oligomer extracted into the isopropanol / water mixture by contact between the aliphatic polyester pellets and the isopropanol / water mixture is used as a part of the raw material of the aliphatic polyester. A method for producing an aliphatic polyester according to one item.   An aliphatic polyester obtained by the production method according to any one of claims 1 to 4, wherein the intrinsic viscosity is 1.40 dL / g or more and the cyclic dimer content is 5,000 mass ppm or less. An aliphatic polyester characterized by being.   6. The ratio of the ratio of the intrinsic viscosity (dL / g) after contact with the isopropanol / water mixture to the intrinsic viscosity (dL / g) before contact is 98.0% or more. Aliphatic polyester.

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