JP2018145221A - Production method of polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a polyester that is an aliphatic/aromatic polyester obtained by using in combination an aliphatic diol component as a diol component such as PBAT and so on and an aliphatic dicarboxylic acid component and an aromatic dicarboxylic acid component as a dicarboxylic acid component, has a small content of THF and oligomer, and has excellent color tone.SOLUTION: A production method of a polyester, which includes: an esterification and/or ester exchange reaction step of reacting an aliphatic diol component, an aliphatic dicarboxylic acid component and an aromatic dicarboxylic acid component; a pelletizing step of pelletizing a polyester obtained via the esterification and/or the ester exchange reaction step; and a contact treatment step of contacting a polyester pellet that is obtained by the pelletizing step and has a tetrahydrofuran content of 10 mass ppm or higher and a mixed liquid containing ethanol and water, in which the mixed liquid contains 10 mass% or larger and 99 mass% or smaller relative to an entirety of the mixed liquid.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for producing a polyester mainly comprising an aliphatic diol component, an aliphatic dicarboxylic acid component and an aromatic dicarboxylic acid component. More specifically, the present invention relates to a method for producing an aliphatic aromatic polyester having a good color tone with a low content of impurities such as tetrahydrofuran (THF) and oligomers.

  Various materials such as paper, plastic, and aluminum foil are used for various foods, medicines, miscellaneous liquids and granules, solid packaging materials, agricultural materials, and building materials. . Among them, plastics are excellent in strength, water resistance, moldability, transparency, cost, etc., and are therefore used in a wide range of applications as molded articles such as bags and containers. Currently, plastics widely used for applications such as bags and containers include polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate. However, molded articles made of the above-mentioned plastics do not biodegrade or hydrolyze in the natural environment, or the degradation rate is extremely slow, so when they are buried after use, they remain in the soil or are dumped. If this happens, the scenery may be damaged. Moreover, even when incinerated, there are problems such as generating harmful gases and damaging the incinerator.

  Biodegradable resins have been attracting attention as environmentally friendly plastics that solve these problems. Since the film formed by molding the biodegradable resin is decomposed in the soil by embedding in the soil after use, it is possible to prevent global warming and soil and air pollution. Therefore, in recent years, many biodegradable resin films are being used for garbage bags, shopping bags, and the like.

  However, since many of these biodegradable resin films are generally inferior in mechanical properties, many studies have been made to improve mechanical properties while maintaining good biodegradability. As a polyester having both properties, mechanical properties and moldability, an aliphatic diol such as 1,4-butanediol is used as the diol component, and an aliphatic dicarboxylic acid such as adipic acid and an aromatic such as terephthalic acid are used as the dicarboxylic acid component. An aliphatic aromatic polyester such as polybutylene adipate terephthalate (PBAT) obtained by using an aliphatic dicarboxylic acid in combination has been proposed (for example, Patent Document 1).

  However, aliphatic aromatic polyesters such as PBAT have a large content of tetrahydrofuran (THF) and oligomers by-produced in the production process, and when this polyester is molded into a sheet or film, the oligomers bleed out, Product quality may be impaired. In addition, THF volatilizes during the molding of polyester and may adversely affect the environment. Furthermore, conventional aliphatic aromatic polyesters, particularly PBAT, have a case where the color tone is reddish, and there are cases where the molded product using the same is reddish. No technology has been proposed to solve these problems peculiar to aliphatic aromatic polyesters.

  In Patent Document 2, in order to remove a cyclic dimer by-produced in a polyester production process, which is contained in an aliphatic polyester mainly composed of an aliphatic diol represented by polybutylene succinate and an aliphatic dicarboxylic acid. Describes that the obtained polyester pellets are washed with a mixed solution containing ethanol and water. However, in this Patent Document 2, the above-mentioned problem regarding the aliphatic aromatic polyester such as PBAT has not been studied, and THF by washing and the cyclic dimer to be removed in Patent Document 2 are structures. There is no mention of the reduction of the different oligomers and the improvement of the color tone.

Japanese National Patent Publication No. 10-508640 JP 2012-92310 A

  An object of the present invention is to provide a method for producing an aliphatic aromatic polyester such as PBAT as a high-quality aliphatic aromatic polyester having a low content of THF, oligomers and the like and having a good color tone.

  As a result of intensive studies to solve the above problems, the present inventors have undergone an esterification and / or transesterification reaction step in which an aliphatic diol component, an aliphatic dicarboxylic acid component, and an aromatic dicarboxylic acid component are reacted. Polyester pellets obtained by pelletizing the obtained polyester and an ethanol / water mixture are contact-treated, preferably by further drying, thereby efficiently removing oligomers and THF contained in the polyester and adjusting the color tone. The present inventors have found that it can be improved and have completed the present invention.

  That is, the gist of the present invention resides in the following [1] to [8].

[1] An esterification and / or transesterification reaction step of reacting an aliphatic diol component with an aliphatic dicarboxylic acid component and an aromatic dicarboxylic acid component, and a polyester obtained through the esterification and / or transesterification reaction step A method for producing a polyester comprising a pelletizing step for pelletization, a polyester pellet having a tetrahydrofuran content of 10 mass ppm or more obtained in the pelletizing step, and a contact treatment step for contacting a mixed solution containing ethanol and water And the manufacturing method of polyester in which this liquid mixture contains 10 mass% or more and 99 mass% or less of water with respect to the whole liquid mixture.

  [2] The method for producing a polyester according to [1], wherein a temperature at which the polyester pellet is brought into contact with the mixed solution is 25 ° C. or more and not more than a melting point of the polyester.

  [3] The method for producing a polyester according to [1] or [2], including a drying step of drying and removing the mixed solution from the polyester pellet after the contact treatment step.

  [4] The method for producing a polyester according to any one of [1] to [3], wherein an oligomer extracted into the liquid mixture by contact between the polyester pellets and the liquid mixture is used as a raw material for the polyester.

  [5] Intrinsic viscosity is 1.0 dL / g or more and 2.0 dL / g or less, and based on Ministry of Health and Welfare Notification No. 370 “Standards for Foods, Additives, etc.” The method for producing a polyester according to any one of [1] to [4], wherein a polyester having an elution residue evaporation residue of 10 μg / mL or less measured under elution conditions at 60 ° C. for 30 minutes is produced.

  [6] The polyester according to any one of [1] to [4], which produces a polyester having an intrinsic viscosity of 1.0 dL / g or more and 2.0 dL / g or less and a tetrahydrofuran content of less than 10 ppm by mass. Manufacturing method.

  [7] Intrinsic viscosity is 1.0 dL / g or more and 2.0 dL / g or less, and based on Ministry of Health and Welfare Notification No. 370 “Standards for Foods, Additives, etc.” Any one of [1] to [4], which produces a polyester having an evaporation residue amount of 10 μg / mL or less and a tetrahydrofuran content of less than 10 ppm by mass measured under elution conditions at 60 ° C. for 30 minutes. A process for producing the polyester according to claim 1.

  [8] The method for producing a polyester according to any one of [1] to [7], wherein a polyester having a color tone (YI) of 40 or less is produced.

  According to the present invention, it is possible to produce an aliphatic aromatic polyester having a very low content of impurities such as oligomers and THF and having a good color tone, and to provide a high-quality molded product using this polyester. Can do.

It is the schematic which shows one Embodiment of the esterification reaction process employ | adopted by this invention. It is the schematic which shows one Embodiment of the polycondensation process employ | adopted by this invention. It is the schematic which shows one Embodiment of the contact processing process employ | adopted by this invention. It is the schematic which shows one Embodiment of the drying process employ | adopted by this invention.

  Hereinafter, embodiments of the present invention will be described in detail. The description of the constituent requirements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these contents unless it exceeds the gist.

  In the present specification, “mass%”, “mass ppm” and “part by mass” and “wt%”, “weight ppm” and “part by weight” have the same meaning, respectively.

  The polyester production method of the present invention is obtained by pelletizing polyester obtained through an esterification and / or transesterification reaction step in which at least an aliphatic diol component, an aliphatic dicarboxylic acid component and an aromatic dicarboxylic acid component are reacted. It is a manufacturing method of the polyester which has a contact treatment process which makes a polyester pellet and the liquid mixture containing ethanol and water contact, Comprising: This liquid mixture contains 10 mass% or more and 99 mass% or less of water with respect to the whole liquid mixture It is characterized by doing.

  Here, the “aliphatic dicarboxylic acid component” is a general term for aliphatic dicarboxylic acids used as polyester raw materials such as aliphatic dicarboxylic acid and aliphatic dicarboxylic acid derivatives such as aliphatic dicarboxylic acid alkyl ester, and “aromatic dicarboxylic acid”. “Component” is a general term for aromatic dicarboxylic acids that are used as polyester raw materials, such as aromatic dicarboxylic acid and aromatic dicarboxylic acid derivatives such as aromatic dicarboxylic acid alkyl esters. Hereinafter, the polyester produced by the method for producing a polyester of the present invention may be referred to as “polyester of the present invention”.

  The production method of the present invention includes an esterification and / or transesterification step in which at least an aliphatic diol, an aliphatic dicarboxylic acid component and an aromatic dicarboxylic acid component are reacted as main raw materials. "The main raw material is an aromatic dicarboxylic acid component and an aromatic dicarboxylic acid component" means that the diol component used as a raw material is mainly composed of an aliphatic diol component, and the dicarboxylic acid component used as a raw material is It means that the main component is an aliphatic dicarboxylic acid component and an aromatic dicarboxylic acid component.

  Here, “having an aliphatic diol component as a main component” means “the total molar ratio of the aliphatic diol component is the largest among the raw material diol components”. Among these, from the viewpoint of physical properties and biodegradability of the polyester, the total of the aliphatic diol components is preferably 50 mol% or more, more preferably 60 mol% or more, and still more preferably based on the total of the raw material diol components. It is 70 mol% or more, and particularly preferably 90 to 100 mol%.

  Further, in the present invention, “mainly using an aliphatic dicarboxylic acid component and an aromatic dicarboxylic acid component” means at least one of aliphatic dicarboxylic acid derivatives such as aliphatic dicarboxylic acid and aliphatic dicarboxylic acid alkyl ester. And at least one of aromatic dicarboxylic acid derivatives such as aromatic dicarboxylic acid and aromatic dicarboxylic acid alkyl ester, and the like, “aliphatic dicarboxylic acid and aliphatic dicarboxylic acid alkyl ester, etc. The total molar ratio of the aliphatic dicarboxylic acid derivative and the aromatic dicarboxylic acid derivative such as aromatic dicarboxylic acid and aromatic dicarboxylic acid alkyl ester is the largest among the raw material dicarboxylic acid components.

  In the present invention, each reaction step in producing the polyester can be carried out by a batch method or a continuous method. From the viewpoint of stabilization of quality and energy efficiency, the raw materials are continuously supplied and continuously. A so-called continuous method for obtaining polyester is preferred.

<Diol component>
As the diol component used in the present invention, as described above, at least the aliphatic diol component is used, and if the total molar ratio is most frequently used in the raw material diol, those usually used for the polyester raw material are used without particular limitation. can do.

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 -Oxygen such as heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, alkylene diol such as neopentyl glycol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol Examples thereof include cycloalkylene diols such as alkylene diol, 1,2-cyclohexane diol, 1,4-cyclohexane diol, 1,2-cyclohexane dimethanol, and 1,4-cyclohexane dimethanol. In view of the physical properties of the polyester to be produced, an alkylene diol having 6 or less carbon atoms such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, or a cyclohexane having 6 or less carbon atoms such as 1,4-cyclohexanedimethanol. Alkylene diols are preferable, and 1,4-butanediol is particularly preferable. Two or more of these may be used in combination. When 1,4-butanediol is used as the aliphatic diol component, the amount of 1,4-butanediol used is the total aliphatic diol from the viewpoint of the melting point (heat resistance), biodegradability, and mechanical properties of the resulting polyester. The amount is preferably 50 mol% or more, more preferably 70 mol% or more, particularly preferably 90 to 100 mol%, based on the components.
Among the aliphatic diol components, ethylene glycol, 1,3-propanediol, and 1,4-butanediol can be derived from plant materials.

<Dicarboxylic acid component>
As the dicarboxylic acid component used in the present invention, those usually used as raw materials for polyesters can be used without particular limitation.

Among the dicarboxylic acid components, 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, undecadicarboxylic acid. Examples include aliphatic dicarboxylic acids such as acid, dodecadicarboxylic acid and dimer acid, and hydrides of aromatic dicarboxylic acids such as hexahydrophthalic acid, hexahydroisophthalic acid and hexahydroterephthalic acid. From the viewpoint of physical properties, aliphatic dicarboxylic acids such as succinic acid, succinic anhydride, adipic acid, and sebacic acid, or derivatives thereof such as alkyl esters thereof are preferable. Depending on the use, adipic acid is particularly preferable from the viewpoint of mechanical properties. Is preferred. Two or more of these may be used in combination.
Among these aliphatic dicarboxylic acid components, succinic acid, succinic anhydride, adipic acid and the like can be derived from plant raw materials.

  When adipic acid is used as the aliphatic dicarboxylic acid component, the amount of adipic acid used is 50 moles relative to the total aliphatic dicarboxylic acid component from the viewpoint of the melting point (heat resistance), biodegradability and mechanical properties of the resulting polyester. % Or more, more preferably 70 mol% or more, and particularly preferably 90 to 100 mol%.

  Examples of the aromatic dicarboxylic acid component include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, derivatives thereof such as alkyl esters thereof, and the like, and terephthalic acid is preferred from the viewpoint of the physical properties of the resulting polyester. These may be used alone or as a mixture of two or more.

  When terephthalic acid is used as the aromatic dicarboxylic acid component, the amount of terephthalic acid used is 50 moles relative to the wholly aromatic dicarboxylic acid component from the viewpoint of the melting point (heat resistance), biodegradability and mechanical properties of the resulting polyester. % Or more, more preferably 70 mol% or more, and particularly preferably 90 to 100 mol%.

  The ratio of the aliphatic dicarboxylic acid component and the aromatic dicarboxylic acid component in the total dicarboxylic acid component used in the present invention is aliphatic with respect to a total of 100 mol% of the aliphatic dicarboxylic acid component and the aromatic dicarboxylic acid component. The dicarboxylic acid component is preferably 30 to 70 mol%, and the aromatic dicarboxylic acid component is preferably 70 to 30 mol%, particularly the aliphatic dicarboxylic acid component is 40 to 60 mol%, and the aromatic dicarboxylic acid component is 60 to 40 mol%. % Is preferable from the viewpoints of heat resistance, biodegradability, mechanical properties, and moldability.

<Other copolymer components>
The polyester of the present invention may be copolymerized with other components other than the aliphatic diol component, the aliphatic dicarboxylic acid component, and the aromatic dicarboxylic acid component. Copolymerization components that can be used in this case include lactic acid, glycolic acid, hydroxybutyric acid, hydroxycaproic acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxyiso Oxycarboxylic acids such as caproic acid, malic acid, maleic acid, citric acid, and fumaric acid, and esters, lactones, and oxycarboxylic acid polymers of these oxycarboxylic acids, or trifunctional groups such as glycerin, trimethylolpropane, and pentaerythritol The above polyhydric alcohols, or trifunctional or higher polyvalent carboxylic acids such as propanetricarboxylic acid, pyromellitic acid, trimellitic acid benzophenone tetracarboxylic acid, and anhydrides thereof, or the anhydride thereof can be used.

  Of these, tri- or higher-functional oxycarboxylic acids, tri- or higher-functional alcohols, tri- or higher-functional carboxylic acids, and the like can be easily obtained by adding a small amount of polyester. Of these, oxycarboxylic acids such as malic acid, citric acid, and fumaric acid are preferable, and malic acid is particularly preferably used.

  In the case of using a trifunctional or higher polyfunctional compound, the amount used 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 in the obtained polyester, and if it is less than the lower limit, it is possible to increase the viscosity of the resulting polyester (usually by using a polyfunctional compound). ) Is difficult to obtain.

<Production method of polyester>
Below, the continuous manufacturing method is taken as an example, and the manufacturing method of the polyester pellet used for the contact process in this invention is described. In the following, a method for producing a polyester by an esterification reaction step using an aliphatic diol, an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid will be exemplified, but this reaction step may be a transesterification step, It may be a step of performing both esterification reaction and transesterification reaction.

  In the continuous production method, the polyester pellets used for the contact step according to the present invention are, for example, aliphatic dicarboxylic acid and aromatic dicarboxylic acid and aliphatic diol, using a plurality of continuous reaction vessels, esterification reaction step, melting Although it is manufactured by a method of continuously obtaining polyester pellets through a polycondensation reaction step, it is not limited to a continuous method as long as the effects of the present invention are not hindered, and a conventionally known polyester manufacturing method is adopted. be able to. The produced polyester pellets are contact-treated with a mixed solution containing ethanol and water, and then dried.

<Esterification reaction process>
The polyester pellet used in the contacting step of the present invention is produced through an esterification reaction step in which at least a dicarboxylic acid component and a diol component are reacted. The esterification reaction step and other subsequent steps can be carried out in a plurality of continuous reaction tanks or in a single reaction tank, but in order to reduce fluctuations in the physical properties of the resulting polyester, It is preferable to carry out in the reaction tank.

  The reaction temperature in the esterification reaction step is not particularly limited as long as it is a temperature at which the esterification reaction can be performed, but is preferably 200 ° C. or higher, more preferably 210 ° C. in that the reaction rate can be increased. In order to prevent the coloring of the polyester and the like, it is preferably 250 ° C. or lower, more preferably 245 ° C. or lower, and particularly preferably 240 ° C. or lower. If the reaction 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 reaction temperature is too high, the decomposition of aliphatic diol, aliphatic dicarboxylic acid and aromatic dicarboxylic acid will increase, and the amount of scattered matter will increase in the reaction tank, which may cause foreign matter and become turbid in the reaction product ( Haze) is likely to occur. 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 preferably an inert gas atmosphere such as nitrogen or argon.

  The reaction pressure is preferably 50 kPa to 200 kPa, more preferably 60 kPa or more, further preferably 70 kPa or more, more preferably 130 kPa or less, and still more preferably 110 kPa or less. If the reaction pressure is less than the above lower limit, the amount of scattered matter in the reaction tank increases, the haze of the reaction product becomes high and foreign substances increase easily, and the distillation of aliphatic diol to the outside of the reaction system increases and the polycondensation reaction rate increases. It tends to cause a decline. When the reaction pressure exceeds the above upper limit, the aliphatic diol is dehydrated and decomposed easily, and the polycondensation reaction rate tends to decrease.

  The reaction time is preferably 1 hour or longer, and the upper limit is preferably 10 hours or shorter, more preferably 4 hours or shorter.

  The reaction molar ratio of the aliphatic diol to the total of the aliphatic dicarboxylic acid and aromatic dicarboxylic acid to be subjected to the esterification reaction is determined based on the aliphatic dicarboxylic acid and aromatic dicarboxylic acid present in the gas phase and reaction liquid phase of the esterification reaction tank. And an aliphatic dicarboxylic acid that represents a molar ratio of an aliphatic diol and an esterified aliphatic diol to an esterified aliphatic dicarboxylic acid and an aromatic dicarboxylic acid, and that is decomposed in the reaction system and does not contribute to the esterification reaction, Aromatic dicarboxylic acids, aliphatic diols and their degradation products are not included. Examples of those that are decomposed and do not contribute to the esterification reaction include those in which 1,4-butanediol, which is an aliphatic diol, is decomposed into tetrahydrofuran, and tetrahydrofuran is not included in this molar ratio. In the present invention, the lower limit of the reaction molar ratio is usually 1.5 or more, preferably 1.7 or more, more preferably 1.8 or more, and particularly preferably 2.0 or more. The upper limit is usually 5.0 or less, preferably 4.0 or less, more preferably 3.0 or less, and particularly preferably 2.5 or less. When the reaction molar ratio is less than the above lower limit, terephthalic acid is not dissolved and the esterification reaction tends to be insufficient, and the polycondensation reaction, which is a reaction in the subsequent step, hardly proceeds, and it is difficult to obtain a polyester having a high degree of polymerization. When the reaction molar ratio exceeds the above upper limit, the decomposition amount of aliphatic diol, aliphatic dicarboxylic acid, and aromatic dicarboxylic acid tends to increase. In order to keep this reaction molar ratio within a preferable range, it is a preferable method to appropriately replenish the esterification reaction system with an aliphatic diol.

In the present invention, an esterification reaction product having an esterification rate of 80% or more obtained in the esterification reaction step is preferably 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 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 step is preferably 85% or more, more preferably 88% or more, and particularly preferably 90% or more. When the esterification rate is less than the lower limit, the polycondensation reactivity in the polycondensation reaction 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 reaction product, which causes deterioration of haze (foreign matter generation) of the obtained polyester. The upper limit of the esterification rate is preferably higher for polycondensation reactivity in the polycondensation step, but is usually 99%.

  In the present invention, a continuous reaction is carried out with the reaction molar ratio of the dicarboxylic acid component and the diol component in the esterification reaction step, the reaction temperature, the reaction pressure, and the esterification reaction rate within the above ranges, and the esterification reaction product is continuously superposed. By using the condensation reaction step, a polyester having a high degree of polymerization can be obtained efficiently.

<Polycondensation reaction step>
In the production of the polyester pellets used in the contacting step of the present invention, it is preferable to carry out the polycondensation reaction in the polycondensation reaction step following the esterification reaction step.

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

  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 reaction temperature is less than the above lower limit, 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 reaction temperature exceeds the above 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, and the upper limit is usually 15 hours, preferably 10 hours, more preferably 8 hours. 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

  A polyester having a desired intrinsic viscosity can be obtained by controlling the polycondensation reaction temperature and time and the reaction pressure.

<Reaction catalyst>
The reaction can be promoted by using a reaction catalyst for the esterification reaction and the polycondensation reaction.

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 group 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.
Here, the periodic table refers to a long-period periodic table (Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005).

  The catalyst is preferably a liquid at the time of polymerization or a compound that dissolves in a low ester ester polymer or a polyester because the polymerization rate increases when it is in a molten or dissolved state during the polymerization. The polycondensation is preferably carried out without a solvent. Alternatively, a small amount of solvent may be used to dissolve the catalyst. Examples of the solvent for dissolving the catalyst include alcohols such as methanol, ethanol, isopropanol, and butanol, diols such as ethylene glycol, butanediol, and pentanediol, ethers such as diethyl ether and tetrahydrofuran, and nitriles such as acetonitrile. , Hydrocarbon compounds such as heptane and toluene, water and mixtures thereof.

  In particular, in the present invention, the reaction is preferably carried out using a titanium compound and a magnesium compound in combination as a catalyst.

The titanium compound used in the present invention is preferably a tetraalkyl titanate, specifically, tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetra-t-butyl titanate, tetraphenyl titanate, tetra Examples thereof include cyclohexyl titanate, tetrabenzyl titanate, and mixed titanates thereof. Of these, tetra-n-propyl titanate, tetraisopropyl titanate, and tetra-n-butyl titanate are particularly preferable.
Two or more of these titanium compounds may be used in combination. The addition amount of the titanium compound is 10 to 200 ppm by mass, preferably 20 to 130 ppm by mass, and particularly preferably 30 to 110 ppm by mass with respect to the produced polyester as an addition amount in terms of Ti.

Examples of the magnesium compound used in the present invention include magnesium acetate, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium alkoxide, magnesium hydrogen phosphate, etc., preferably magnesium acetate or magnesium hydroxide, and particularly the polymerization rate. Magnesium acetate is preferable in terms of solubility in 1,4-butanediol (foreign matter generation) and the like. Two or more of these magnesium compounds may be used in combination.
The addition amount of the magnesium compound is preferably 0.5 to 5.0 in terms of an addition molar ratio (Mg / Ti molar ratio) in terms of Mg with respect to the addition amount in terms of Ti of the titanium compound. When Mg / Ti <0.5, the improvement in the polymerization rate is small, and the terminal carboxyl group amount (acid value) of the resulting polyester is high, which is not preferable. When Mg / Ti> 5.0, the polymerization rate is lowered, and the hydrolysis resistance and color tone of the produced polyester are also deteriorated. The Mg / Ti ratio is more preferably 0.7 to 4.0, still more preferably 0.85 to 3.0.

  The titanium compound may be added at the start of transesterification, during the esterification reaction, after the esterification reaction, at the time of polycondensation, etc., but is divided at the start of the esterification reaction or at the start of the esterification reaction and before the polycondensation reaction. Are preferably added. The addition timing of the magnesium compound may be at the start of the esterification reaction, during the esterification reaction, after the esterification reaction, at the time of polycondensation, etc., but it is added at the end of the esterification reaction and before the start of polymerization such as polymerization activity and color tone. This is preferable.

  The titanium compound and the magnesium compound are preferably added as a catalyst solution having a concentration of about 0.05 to 2% by mass using the aforementioned solvent for dissolving the catalyst. However, the titanium compound is added and mixed in advance in the raw material slurry. You can also keep it.

<Reaction tank>
As the esterification reaction tank used in the present invention, known ones 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 receiver, a shaft, and a stirring blade, a turbine stator type high-speed rotary stirrer, a disk mill type stirrer, a rotor mill type stirrer, etc. 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.

<Pelletization>
The polyester obtained through the polycondensation reaction is pelletized and contact-treated with a mixed solution containing ethanol and water in the form of pellets.

  The pelletizing method is a strand cutting method in which molten polyester is extruded from a nozzle hole of a die head using a gear pump or an extruder, and cooled or solidified with water or the like while being cut with a cutter. An underwater hot cut method that cuts immediately in a molten state is widely used. In the polyester of the present invention, underwater hot cut because there are few chips in the pellet, the angle of repose of the resulting pellet is low, the pellet transport stability, and the stability of the feed to the molding machine during molding are good A method is preferably employed. The lower limit of the cooling water temperature in the underwater cut method is preferably 10 ° C or higher, more preferably 20 ° C or higher, and the upper limit is preferably 70 ° C or lower, more preferably 60 ° C or lower, and further preferably 50 ° C or lower.

  As the size of the nozzle holes, those having a hole diameter of 1 mm to 30 mm are usually used. The shape of the opening is not particularly limited, but a shape such as a circle, an ellipse, an oval, a square, or a star is used. The discharge amount per opening is usually 5 to 100 kg / hour, preferably 10 to 70 kg / hour, more preferably 20 to 50 kg / hour.

  The shape of the pellet includes a spherical shape, a cylindrical shape, an elliptical columnar shape, a long cylindrical shape, a prismatic shape, a jasper shape, etc., and those in which these are flattened. The underwater hot cut method often has a spherical shape, a jade shape and a flat shape thereof. Although the size is not particularly limited, the mass per pellet is 1 to 50 mg, preferably 3 to 40 mg, more preferably 5 from the viewpoints of washing efficiency by contact treatment, drying efficiency in the drying process, pellet transfer operability, and the like. ~ 30 mg. A larger pellet surface area per mass is preferable from the viewpoint of cleaning efficiency in the contact treatment step.

<Contact treatment process>
(Mixture containing ethanol and water)
In the present invention, the obtained polyester pellet is contacted with a mixed solution containing ethanol and water, and tetrahydrofuran (THF) and oligomer contained in the pellet are extracted to the mixed solution side to extract the pellet. While reducing the THF and oligomer content, improve the color tone. The contact treatment step is usually performed continuously after pelletization, but the obtained pellets may be temporarily stored in a storage tank and then contact-treated.

  The proportion of water relative to the total of the mixed liquid containing ethanol and water to be brought into contact with the polyester pellets (hereinafter sometimes referred to as “contact treatment liquid”) is usually 10% by mass or more, preferably 20% by mass or more. Preferably it is 25 mass% or more. Moreover, it is 99 mass% or less normally, Preferably it is 95 mass% or less, More preferably, it is 90 mass% or less, Most preferably, it is 85 mass% or less.

  When the mixing ratio of water is decreased (the ratio of ethanol is increased), the quality of the polyester tends to decrease due to a decrease in molecular weight due to alcohol decomposition. Also, if the mixing ratio of water is decreased and the mixing ratio of ethanol is increased, the handling risk is required from the viewpoint of safety, such as the risk of explosion of the liquid in use and the gas generated from the liquid increases. On the other hand, if the proportion of water is too high, the removal of THF and oligomers is not sufficient, the content of THF and oligomers cannot be sufficiently reduced, and the color tone cannot be sufficiently improved, resulting in a polyester of desirable quality. There may not be.

  The contact treatment liquid used in the present invention can contain isopropanol in addition to water and ethanol, and the oligomer reduction effect can be improved by mixing isopropanol. When isopropanol is contained in the contact treatment liquid, the content is usually 20% by mass or less, preferably 15% by mass or less, and more preferably 10% by mass or less. When the isopropanol content exceeds the above upper limit, THF and oligomer removal and color tone improvement are not sufficient, and a polyester having a desired quality may not be obtained.

(Contact temperature)
The lower limit of the temperature of the contact liquid for bringing the polyester pellets into contact with the contact treatment liquid is 25 ° C, preferably 30 ° C, more preferably 35 ° C, and particularly preferably 40 ° C. The upper limit is usually the melting point of the polyester, preferably 95 ° C, more preferably 90 ° C, and particularly preferably 85 ° C. If the contact temperature between the polyester pellets and the contact treatment liquid is less than the above lower limit, a long time is required for the treatment time, which is not only economically disadvantageous, but also due to a decrease in THF and oligomer removal effect, color tone improvement effect, The desired polyester may not be obtained. On the other hand, when the contact temperature exceeds the above upper limit, the decrease in viscosity becomes large due to hydrolysis and alcohol decomposition, which not only impairs the quality, but also causes problems in terms of operation such as fusion between pellets and poor pellet extraction.

(Contact time)
The lower limit of the time for contacting the polyester pellet and the contact treatment liquid is usually 0.1 hour, preferably 1 hour, more preferably 3 hours. The upper limit is usually 24 hours, preferably 18 hours, and more preferably 10 hours. When the contact time is less than the above lower limit, the effect of removing THF and oligomers and the effect of improving the color tone are not sufficient, and a polyester having a desired quality may not be obtained. On the other hand, when the contact time exceeds the above upper limit, the decrease in viscosity increases due to hydrolysis and alcohol decomposition, which may impair quality.

(Ratio of polyester pellets and contact treatment liquid)
The lower limit of the ratio of the polyester pellets to be contacted and the contact treatment liquid (treatment liquid / pellet ratio) is usually 1.0 or more, preferably 1.5 or more, and more preferably 2.0 or more in terms of mass ratio. The upper limit is usually 50 or less, preferably 30 or less, more preferably 20 or less. If the mass ratio of the pellet to be contacted and the contact treatment liquid is less than the above lower limit, the THF and oligomer removal effect and color tone improvement effect are reduced due to an increase in the concentration of impurities such as THF and oligomer in the contact treatment liquid during treatment, and desirable quality May not be obtained. On the other hand, if the mass ratio of the pellet to be brought into contact with the liquid exceeds the above upper limit, it is disadvantageous in terms of process and cost, such as an increase in the size of equipment due to the large amount of contact treatment liquid used and an increase in the cost of the contact treatment liquid.

(Contact method)
As an aspect which makes a polyester pellet and a contact processing liquid contact, there exist a batch type and a continuous type, and any aspect is employable.

As a batch-type aspect in this invention, the method of extracting after putting a pellet and a contact processing liquid into a processing tank and carrying out contact processing at predetermined temperature and time is mentioned. While the pellets and the contact treatment liquid are contact-treated, the contact treatment liquid can be circulated or non-circulated.
As a continuous mode in the present invention, the pellets are continuously supplied to the pipe or the treatment tank, and the contact treatment liquid at a predetermined temperature is brought into contact with the flow of the pellets in parallel or countercurrent, and the predetermined contact is made. There is a method of continuously extracting pellets while maintaining time.

  In the present invention, the contact treatment liquid after the contact treatment can be recovered by distillation and recycled. The extracted oligomers can be separated from the contact treatment solution by cooling or the like, or concentrated and then supplied to an esterification reaction step or a polycondensation reaction step to be used as a polyester raw material. It is a preferable method to return the recovered oligomers to the esterification reaction tank of the esterification reaction step or the raw slurry preparing tank of aliphatic dicarboxylic acid and aromatic dicarboxylic acid and aliphatic diol.

  After the contact treatment, the extracted contact treatment liquid can be circulated and reused as is, or a part of the extracted contact treatment liquid can be discarded and a new amount of contact treatment liquid added to the discarded amount. It can also be recycled.

  After the contact treatment, the oligomers separated from the contact treatment liquid by distillation concentration and / or cooling etc. are once melted or made into a solution dissolved in an aliphatic diol as a raw material and then recovered as a polyester raw material. Can do. 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 1st polycondensation reaction tank (a) illustrated in FIG. Moreover, it can also supply to the raw material slurry preparation tank (not shown) of aliphatic dicarboxylic acid and aromatic dicarboxylic acid, and aliphatic diol.

<Drying process>
Since the polyester pellets after the contact treatment with the contact treatment liquid contain a contact treatment liquid such as ethanol and water, they are preferably dried in a drying step in order to remove them.

  The dryer used in the drying process circulates an inert gas such as heated air or heated nitrogen as a drying gas, a shelf-type dryer, a band dryer, a horizontal cylindrical rotary dryer, a horizontal dryer with rotary blades, There are vertical dryers with rotating blades (so-called hopper dryer type dryers), moving bed type vertical dryers, fluidized bed type dryers, and the like. In addition, as a dryer different from the above gas distribution method, there are a double cone type rotary vacuum dryer, a tumbler type rotary vacuum dryer, a microwave dryer and the like.

  These can be carried out batch-wise, semi-batch-wise or continuously, but the continuous method is preferred for mass production from the viewpoint of production efficiency. In addition, since the facilities do not become complicated, a moving bed type vertical dryer or one in which a plurality of stages thereof are continuously used can be preferably used.

  The lower limit of the drying temperature as the gas temperature is 25 ° C, preferably 30 ° C, more preferably 35 ° C, and particularly preferably 40 ° C. The upper limit is usually the melting point of the polyester, preferably the melting point of the polyester minus 5 ° C, more preferably the melting point of the polyester minus 8 ° C, and particularly preferably the melting point of the polyester minus 10 ° C. If the drying temperature is less than the above lower limit, a long time is required for drying, which is economically disadvantageous. On the other hand, when the drying temperature exceeds the above upper limit, it may be difficult to operate, such as fusing the pellets together or causing defective extraction when the pellets are extracted from the dryer. The dry gas that has passed through the drier contains contact treatment liquid components such as water and ethanol, and the contact treatment liquid components can be reduced by cooling or adsorption of the dry gas and reused as the dry gas.

  The drying time is usually 0.1 to 100 hours, preferably 1 to 80 hours, more preferably 5 to 50 hours. In the case of a moving bed type, the flow rate of the drying gas is usually 0.05 to 1.0 m / sec (superficial velocity).

  The pellet after drying has an upper limit of ethanol content of usually 1000 ppm by mass, preferably 800 ppm by mass, more preferably 500 ppm by mass. When there is much ethanol contained, the fall of the melt viscosity at the time of melt molding of this pellet will be remarkable, and there exists a tendency for a moldability to become poor. The lower the lower the better, the better, but the concentration that is reasonably obtained industrially is usually 50 ppm by mass. Usually, the moisture content of the pellets after drying is less than the ethanol content. The moisture content of the pellet is usually 1000 ppm by mass or less, preferably 500 ppm by mass or less, more preferably 250 ppm by mass or less. When there is a lot of moisture, the inherent viscosity is significantly lowered due to hydrolysis at the time of melt molding of the pellet, resulting in molding failure, and the physical properties of the resulting molded product tend to decrease.

<Example of manufacturing process>
Hereinafter, based on the drawings, adipic acid as an aliphatic dicarboxylic acid, terephthalic acid as an aromatic dicarboxylic acid, 1,4-butanediol as an aliphatic diol, and a method for producing a polyester using malic acid as a polyfunctional compound are preferable. Although an embodiment is described, the present invention is not limited to this.

  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 a contact treatment employed in the present invention. FIG. 4 is an explanatory diagram of an example of a drying process employed in the present invention.

  In FIG. 1, the raw materials adipic acid, terephthalic acid and malic acid are usually mixed with 1,4-butanediol in a raw material mixing tank (not shown), and in the form of slurry or liquid from the raw material supply line (1). It supplies to an esterification reaction tank (A). Moreover, when adding a catalyst at the time of esterification, after making it the solution of 1, 4- butanediol in a catalyst adjustment tank (not shown), a catalyst solution is supplied from a catalyst supply line (3). In FIG. 1, the catalyst supply line (3) is connected to the recirculation line (2) of the recirculated 1,4-butanediol, and both are 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 point component is 1,4-butanediol, and the main component of the low boiling point component is water and tetrahydrofuran (THF) which is a decomposition product of 1,4-butanediol.

  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 recirculation line (2) to the esterification reaction tank (A). It is circulated and part is returned from the circulation line (7) to the rectification column (C). Further, the surplus is extracted outside from the extraction line (8). On the other hand, the 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) passes through the extraction pump (B) and the extraction line (4) of the esterification reaction product, and the first polycondensation reaction tank (a) shown in FIG. To be served.

  In the process shown in FIG. 1, the catalyst 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).

  When adding a catalyst to the esterification reaction product before the polycondensation tank, a catalyst solution is prepared to a predetermined concentration in a catalyst preparation tank (not shown), and then passed through a catalyst supply line (L7) in FIG. (L8), further diluted with 1,4-butanediol, and then supplied to the esterification reaction product extraction line (4).

  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 become a polyester low polymer, Then, it is supplied to the second polycondensation reaction tank (d) through the extraction gear pump (c), the extraction line (L1), 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 reaction 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.

  In the pelletizing step, molten polyester is discharged in the form of strands melted from the die head (g) through the extraction gear pump (m), the outlet channel filter (s) and the extraction line (L5). After drawing out and cooling with water etc., it cut | disconnects with a rotary cutter (h) and obtains a polyester pellet. Moreover, it can also extract in the form of a strand in water without extracting in air | atmosphere, and it can also cut | disconnect with a rotary underwater cutter to make a pellet. The polyester pellets are fed from the pellet supply line (103) to the contact treatment tank (III) in FIG.

  Reference numerals (L2), (L4), and (L6) in FIG. 2 denote vents of the first polycondensation reaction tank (a), the second polycondensation reaction tank (d), and the third polycondensation reaction tank (k), respectively. Line. 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 operation stability.

  In the contact treatment step shown in FIG. 3, the temperature of the ethanol / water mixture as the contact treatment liquid is controlled from the circulation tank (I) by the pump (IX) via the heat exchanger (II), and the contact treatment liquid supply line ( 101) is supplied to the contact treatment tank (III). The contact treatment liquid is countercurrently contacted with the pellets in the contact treatment tank (III), then withdrawn from the withdrawal line (102), and collected into the circulation tank (I) through the fine powder remover (IV). The

  The pellets used for the contact treatment are continuously supplied from the pellet supply line (103), and after contact treatment with the ethanol / water mixture for a predetermined time, the extraction line (104) while adjusting the extraction amount with the rotary valve (V). ) More continuously extracted. The contact treatment liquid extracted along with the pellets is separated by the preliminary solid-liquid separator (VI), passes through the collection tank (VII), and then is supplied by the pump (X) to the supply line (105) and the collection line (106). ) Through the fine powder remover (IV), and then recovered into the circulation tank (I). The contact treatment liquid is continuously extracted from the circulation tank (I) through the extraction line (107). Further, an ethanol / water mixed solution corresponding to the amount of the contact treatment liquid extracted from the supply line (108) is supplied. The pellets continuously extracted are separated from the entrained contact treatment liquid in the preliminary solid-liquid separator (VI), and then passed through the solid-liquid separator (VIII) and from the extraction line (109), It supplies continuously to the drying process of FIG.

  The drying process of FIG. 4 includes two drying towers (H) and (K).

  The polyester pellets after the contact treatment step are continuously supplied from the extraction line (109) to the first drying tower (H) through the pellet supply line (201). Heated dry nitrogen gas is continuously introduced into the first drying tower (H) from the drying gas supply line (208) and discharged from the drying gas recovery line (207). The discharged gas is heated by the heat exchanger (N) through the condenser (L), and circulated and used to the first drying tower (H) through the dry gas supply line (208). The contact treatment liquid condensed by the condenser (L) and the heat exchanger (M) is extracted from the condensate extraction line (210). New dry nitrogen gas is supplied from the new dry gas supply line (209). The pellets are continuously sent from the first drying tower (H) to the cooling tower (J) through the rotary valve (O). Dry air is introduced into the cooling tower (J) from the cooling gas supply line (212) and discharged from the cooling gas extraction line (211).

  Pellets cooled in the cooling tower (J) to a temperature lower than the drying temperature of the first drying tower (H) pass through the pellet extraction line (204), the rotary valve (P), and the pellet supply line (205), and then the second. Supplied to the drying tower (K). A drying gas (normal air) is supplied to the second drying tower (K) through the heat exchanger (S) and the drying gas supply line (214), and is discharged from the drying gas extraction line (213).

  The air temperature supplied to the second drying tower (K) is usually lower than the nitrogen gas temperature supplied to the first drying tower (H). For example, the nitrogen gas temperature is 50 to 100 ° C. (for example, 80 ° C.), and the air temperature is 40 to 80 ° C. (For example, 50 ° C.).

  The polyester pellets after drying are continuously or intermittently extracted through a rotary valve (Q) and a pellet extracting line (206), and become a product through a storage tank, a fine powder remover, a packaging machine, and the like. The storage tank can also be used as the second drying tower (K). In this figure, the storage tank and the subsequent parts are not shown.

<Physical properties of polyester>
(Polyester before contact treatment process)
In the present invention, the physical properties of polyester (hereinafter, sometimes referred to as “polyester before treatment”) of the polyester pellets subjected to the contact treatment step are as follows.

  The lower limit of the intrinsic viscosity (IV) of the polyester before treatment is preferably 1.2 dL / g, particularly preferably 1.3 dL / g. Further, the upper limit of the intrinsic viscosity of the polyester before treatment is preferably 2.5 dL / g, more preferably 2.0 dL / g, and particularly preferably 1.8 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 amount of terminal carboxyl groups of the pre-treated polyester is usually 80 (equivalent / ton) or less, preferably 60 (equivalent / ton) or less, more preferably 40 (equivalent / ton) or less, particularly preferably 25 (equivalent / ton). Ton) or less. When the amount of the terminal carboxyl group of the polyester before the treatment exceeds the above upper limit, a decrease in viscosity due to hydrolysis becomes remarkable, and the quality may be significantly impaired. The lower the terminal carboxyl group amount, the better the thermal stability and hydrolysis resistance, but it is usually 5 (equivalent / ton) or more.

  The pre-treatment polyester obtained by the production method of the present invention contains THF and oligomers by-produced in the production process, and the THF content is usually 10 mass ppm or more, and may be 50 mass ppm or more. May be 100 ppm by mass or more.

  In addition, due to the inclusion of oligomers, the pre-treated polyester has a distillation residue amount of 5 μg / mL or more, usually 10 μg / mL or more when the pre-treated polyester is immersed in heptane at 25 ° C. for 60 minutes. In some cases.

  In addition, when the pre-treated polyester is immersed in a 20% by mass ethanol aqueous solution at 60 ° C. for 30 minutes, the amount of the distillation residue of the eluate is usually 5 μg / mL or more and sometimes 10 μg / mL or more.

  In addition, when the pre-treated polyester is immersed in a 4% by mass acetic acid aqueous solution at 60 ° C. for 30 minutes, the amount of distillation residue of the eluate is usually 5 μg / mL or more, and may be 10 μg / mL or more.

  Moreover, when the pre-treatment polyester is immersed in water at 60 ° C. for 30 minutes, the amount of distillation residue of the eluate is usually 10 μg / mL or less.

  Further, the polyester before treatment in the present invention has a red to pink color tone, and the yellowness (YI) is usually 40 or more, sometimes 50 or more, and sometimes 60 or more.

(Polyester after contact treatment)
In the present invention, the pre-treatment polyester having physical properties as described above is treated in the aforementioned contact treatment step, preferably in the aforementioned contact treatment step and drying step, thereby reducing the contained THF and oligomers. , Improve its color tone.

  In the present invention, the polyester of the present invention obtained through the above contact treatment step, preferably the above contact treatment step and the drying step, has an intrinsic viscosity of 1.0 dL / g or more and 2.0 dL / g or less. It is preferable that (YI) is 40 or less, particularly 30 or less, and the THF content is less than 10 mass ppm, particularly 5 mass ppm or less. When the intrinsic viscosity, the color tone, and the THF content are in the above ranges, it can be a raw material for a good polyester molded product without impairing the quality of the molded product.

  Further, the amount of distillation residue of the eluate when the polyester of the present invention is immersed in heptane at 25 ° C. for 60 minutes is preferably 10 μg / mL or less, more preferably 5 g / mL or less.

  Moreover, the distillation residue amount of the eluate when the polyester of the present invention is immersed in a 20% by mass aqueous ethanol solution at 60 ° C. for 30 minutes is preferably 10 μg / mL or less, more preferably 5 μg / mL or less.

  The amount of the distillation residue of the eluate when the polyester of the present invention is immersed in a 4% by mass acetic acid aqueous solution at 60 ° C. for 30 minutes is preferably 10 μg / mL or less, more preferably 5 μg / mL or less.

  For any eluate, if the amount of distillation residue exceeds the above upper limit, it does not meet the standards for equipment and containers / packaging among the standards for food additives, etc., so application to containers and packaging for food is not permitted. .

  Furthermore, the distillation residue amount of the eluate when the polyester of the present invention is immersed in water at 60 ° C. for 30 minutes is usually 5 μg / mL or less.

  The intrinsic viscosity, the THF content, the yellowness (YI), and the amount of distillation residue from each eluate are values measured by the methods shown in the Examples section described later.

<Polyester composition>
You may mix | blend aliphatic polyester, aliphatic oxycarboxylic acid, etc. with the polyester of this invention. Furthermore, carbodiimide compounds, fillers, plasticizers, and other biodegradable resins that are used as necessary, such as polycaprolactone, polyamide, polyvinyl alcohol, cellulose ester, etc. 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, anti-blocking 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 products. Further, a modifier, a crosslinking agent, etc. may be included.

  The method for producing the polyester composition from the polyester of the present invention is not particularly limited, but is a method in which raw material chips of the blended polyester are melt mixed in the same extruder, a method in which each is melted and mixed in separate extruders, Examples thereof include mixing by kneading using a normal kneader such as a single screw extruder, twin screw extruder, Banbury mixer, roll mixer, Brabender plastograph, kneader blender, and the like. 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 measurement method of the physical property and evaluation item which were employ | adopted in the following examples is as follows.

<Measurement of intrinsic viscosity (IV)>
It calculated | required in the following way using the Ubbelohde type viscometer. That is, using a mixed solvent of phenol / tetrachloroethane (weight ratio 1/1), at 30 ° C., the sample solution having a concentration of 0.5 g / dL and the number of falling seconds of the solvent alone were measured and obtained from the following formula.
IV = ((1 + 4K _H η _sp ) ^0.5 −1) / (2K _H C)
However, a _{η sp = η / η 0 -1} , η is the sample solution drop seconds, eta ₀ is falling seconds of the solvent, C is a sample solution concentration (g / dL), is _{K H} is a Huggins constant. K _H adopted the 0.33.

<Measurement of yellowness (YI)>
It measured based on the method of JISK7373.

<Measurement of evaporation residue by dissolution test>
It was measured based on Ministry of Health and Welfare Notification No. 370 “Standards for Foods, Additives, etc.”. As the eluent, heptane, 20% by mass ethanol aqueous solution, 4% by mass acetic acid aqueous solution, or water was used, and the elution test conditions were 25 ° C. or 60 ° C. for 30 minutes.

<Measurement of THF content>
About 0.3 g of the sample was weighed into a head space vial, and 1.0 mL of the gas phase gas when heated at 125 ° C. for 30 minutes was injected into the gas chromatography, and GC / MS (Agilent 7890 / 5977A) measurement was performed. For the calibration curve, prepare a standard solution with acetone as the solvent and a tetrahydrofuran concentration of 5000, 1000, 500, 250, 100, 50 μg / mL, inject 1 μL of the standard solution into a headspace vial, and perform the same measurement. Go and created.

  A polyester was produced according to the present invention by the following procedure.

[Preparation of Mg catalyst solution]
A magnesium catalyst solution was prepared by dissolving magnesium oxide tetrahydrate in 1,4-butanediol to a concentration of 0.64% by mass.

[Production of polyester]
A polyester was produced as follows by the esterification step shown in FIG. 1 and the polycondensation step shown in FIG. First, 53 mol% and 47 mol% of adipic acid and terephthalic acid, respectively, 0.35 mol% of trimethylolpropane and 1.5 times mol of 1,4-butanediol with respect to both acids, and Ti of 0.1%. A slurry at 50 ° C., in which tetra-n-butyl titanate was mixed so as to be 013 mol%, was passed in advance from a slurry preparation tank (not shown) through a raw material supply line (1) (Ti addition amount to production polyester 30 mass ppm). In a nitrogen atmosphere, it was continuously fed to an esterification reaction tank (A) having a stirrer filled with a low molecular weight polyester (esterification reaction product) having an esterification rate of 99 mass% so as to be 47 kg / hour ( 34 kg / hour as polymer).

  The esterification reaction tank (A) is set to an internal temperature of 230 ° C. and a pressure of 101 kPa, and water, tetrahydrofuran and surplus 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, low-boiling components mainly composed of water and tetrahydrofuran are extracted from the top of the tower in the form of gas through the line (9), condensed in the condenser (G), and the liquid level in the tank (F) becomes constant. It extracted outside from the extraction line (13). At the same time, the total amount of the bottom component of the rectification column (C) at 100 ° C. from the recirculation line (2) (98% by mass or more is 1,4-butanediol) and the polymer from the raw material supply line (1) Adipic acid and terephthalic acid in the esterification reaction tank (A) are supplied together with 1,4-butanediol according to the production amount, tetrahydrofuran generated in the esterification reaction tank and equimolar 1,4-butanediol. The molar ratio of 1,4-butanediol to was adjusted to 2.2.

  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 adipic acid and terephthalic acid units 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 90% (acid value 950 eq / t).

  The Mg catalyst solution prepared in advance was continuously supplied from the catalyst preparation tank (not shown) through the supply line (L8) to the extraction line (4) of the esterification reaction product at 2 kg / hour (Mg here) The addition amount is 2.8 times mol with respect to the Ti addition amount).

  The liquid level was controlled so that the internal temperature of the first polycondensation reaction tank (a) was 240 ° C., the pressure was 2.7 kPa, and 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., a pressure of 400 Pa, liquid level control 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 liquid level was controlled so that the internal temperature of the third polycondensation reactor (k) was 240 ° C., the pressure was 130 Pa, and the residence time was 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 L6). The obtained polyester was continuously extracted in the form of a strand from the die head (g), and cut with a rotary cutter (h) into water pellets while cooling with water.

  The pellets are columnar and the mass per pellet is about 20-30 mg. This pellet was reddish.

  The esterification reaction and polycondensation reaction were carried out for 7 consecutive days, and polyester pellets obtained by sampling after 16 hours from the start of the reaction were used as polyester pellets before contact treatment.

[Polyester pellet contact treatment]
The obtained polyester pellets were subjected to contact treatment by the contact treatment step shown in FIG. The mixed liquid of ethanol and water used as the contact treatment liquid is controlled to 70 ° C. from the circulation tank (I) via the heat exchanger (II) by the pump (IX), and from the supply line (101) to the treatment tank ( To III). The ratio of ethanol and water in the contact treatment liquid was 90% by mass of water and 10% by mass of ethanol with respect to the entire contact treatment liquid. The mass ratio of the contact treatment liquid and pellets in the contact treatment tank (III) was 5 (treatment liquid / pellet ratio).

  The contact treatment liquid is brought into counter-current contact with the pellets in the contact treatment tank (III), then withdrawn from the withdrawal line (102), and from the recovery line (106) through the fine powder remover (IV) to the circulation tank ( Recovered to I). Pellets to be subjected to the contact treatment were continuously supplied from the supply line (103), brought into contact with the contact treatment liquid for 8 hours, and then continuously extracted from the extraction line (104) by the rotary valve (V).

  The contact treatment 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 (105) by the pump (X) to the recovery line (106). Returned to. The contact treatment liquid was continuously extracted from the circulation tank (I) through the extraction line (107), and the amount thereof was set to 1/20 (flow rate ratio) of the total circulation flow rate of the contact treatment liquid. From the supply line (108), a mixed liquid of ethanol and water in an amount corresponding to the contact treatment liquid extracted was supplied to the circulation tank (I).

  The pellets continuously extracted are separated from the contact treatment liquid entrained by the preliminary solid-liquid separator (IV), and then continuously from the solid-liquid separator (VIII) via the extraction line (109) to the drying process. Supplied to.

[Drying of pellets]
Drying after the contact treatment with the mixed solution containing ethanol and water was performed by the drying step shown in FIG.

  In the first drying tower (I), a dry nitrogen gas having a purity of 99% or more (dew point minus 40 ° C.) is used. The gas temperature is 80 ° C., the gas (empty) speed is 0.125 m / sec, and the pellet residence time is 15 hours. In the second drying tower (K), drying is performed under the conditions using a dry air (dew point minus 40 ° C.) at a temperature of 50 ° C., a gas (superficial velocity) of 0.125 m / sec, and a pellet residence time of 24 hours. Went.

  Table 1 shows the results of measuring the intrinsic viscosity, the yellowness (YI), the evaporation residue amount, and the THF content of the polyester pellets before the contact treatment and the polyester pellets after the contact treatment and the drying treatment, respectively.

  From Table 1, it can be seen that according to the present invention, high-quality aliphatic aromatic polyesters with low THF and oligomer contents and good color tone can be obtained efficiently.

  By the production method of the present invention, it is possible to efficiently obtain a high-quality aliphatic aromatic polyester having a low THF and oligomer content and a good color tone, and molding with high commercial value using this aliphatic aromatic polyester. Goods can be provided.

DESCRIPTION OF SYMBOLS 1 Raw material supply line 2 Recirculation line 3 Catalyst supply line 4 Extraction line of 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 Pump E Pump F Tank G Capacitor L1, L3, L5 Polycondensation reaction product extraction line L2, L4, L6 Vent line L7 Catalyst supply line L8 Raw material supply line a First polycondensation reaction tank d Second polycondensation 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 Contact treatment tank IV Fine powder remover V Rotary valve VI Preliminary solid-liquid separator V II Recovery tank VIII Solid-liquid separator IX Pump X Pump 101 Contact processing liquid supply line 102 Extraction line 103 Pellet supply line 104 Extraction line 105 Supply line 106 Recovery line 107 Extraction line 108 Supply line 109 Extraction line H 1st Drying tower J Cooling tower K Second drying tower L Condenser M Heat exchanger N Heat exchanger O Rotary valve P Rotary valve Q Rotary valve R Blower S Heat exchanger 201 Pellet supply line 202 Pellet extraction line 203 Pellet supply line 204 Pellet Extraction line 205 Pellet supply line 206 Pellet extraction line 207 Dry gas recovery line 208 Dry gas supply line 209 New dry gas supply line 210 Condensate extraction line 211 Cooling gas extraction line 212 Retirement gas supply line 213 dry gas extraction line 214 dry gas supply line

Claims (8)

  An esterification and / or transesterification reaction step of reacting an aliphatic diol component with an aliphatic dicarboxylic acid component and an aromatic dicarboxylic acid component, and a polyester obtained through the esterification and / or transesterification reaction step are pelletized. A method for producing a polyester comprising a pelletizing step, and a contact treatment step of contacting a polyester pellet having a tetrahydrofuran content of 10 mass ppm or more obtained in the pelletizing step with a mixed solution containing ethanol and water, The method for producing a polyester, wherein the mixed solution contains 10% by mass to 99% by mass of water with respect to the entire mixed solution.   The manufacturing method of the polyester of Claim 1 whose temperature which makes the said polyester pellet and the said liquid mixture contact is 25 degreeC or more and below melting | fusing point of this polyester.   The manufacturing method of the polyester of Claim 1 or Claim 2 which has a drying process which dries and removes the said liquid mixture from the said polyester pellet after the said contact treatment process.   The method for producing a polyester according to any one of claims 1 to 3, wherein an oligomer extracted into the mixed liquid by contact between the polyester pellets and the mixed liquid is used as a raw material of the polyester.   Intrinsic viscosity is 1.0 dL / g or more and 2.0 dL / g or less, and based on Ministry of Health and Welfare Notification No. 370 “Standards for Foods, Additives, etc.” The method for producing a polyester according to any one of claims 1 to 4, wherein a polyester having an evaporation residue amount of 10 µg / mL or less measured under an elution condition of 30 minutes is produced.   The method for producing a polyester according to any one of claims 1 to 4, wherein a polyester having an intrinsic viscosity of 1.0 dL / g or more and 2.0 dL / g or less and a tetrahydrofuran content of less than 10 ppm by mass is produced. .   Intrinsic viscosity is 1.0 dL / g or more and 2.0 dL / g or less, and based on Ministry of Health and Welfare Notification No. 370 “Standards for Foods, Additives, etc.” The polyester according to any one of claims 1 to 4, wherein a polyester having an evaporation residue amount of 10 µg / mL or less and a tetrahydrofuran content of less than 10 ppm by mass measured under an elution condition of 30 minutes is produced. Polyester production method.   The method for producing a polyester according to any one of claims 1 to 7, wherein a polyester having a color tone (YI) of 40 or less is produced.

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